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A New International
(2023)
To reopen educational institutions and return to the classroom, we all need to modify how we act to successfully face the challenges of the new normal resulting from the COVID-19 pandemic and entailing our insights into and the after-effects of the pandemic. More specifically, the new normal might encompass online education we are getting used to during the pandemic and the age-old onsite education as well. Thoughtfully integrated, online and onsite learning combine to create blended learning. However, the pertinent literature reveals that English as a foreign language (EFL) students and teachers differently perceive and react to blended learning in diverse contexts. This study was designed to explore student and teacher perceptions of and reactions to blended learning in the Department of English, Jahangirnagar University in the new normal. Fifty undergraduates of EFL and eight teachers of the department participated in the study. To collect data from them, the Student Questionnaire and the Teacher Questionnaire were used. And the data were processed by applying the SPSS programme module. The findings revealed that the majority of the students and the teachers had mostly positive perceptions of blended learning, although the former did not have sufficient exposure to online learning and the latter lacked adequate insights into online teaching. Further, both the students and the teachers expressed mostly positive reactions to blended learning in the new normal, though the former deemed online examinations inadequately smooth and reliable, and the latter had insufficient experience of online instruction and assessment. The study categorically recommends reforming the curriculum, adopting relevant instructional strategies, developing suitable materials, customizing the assessment, integrating and installing technology, training the teachers, upskilling the students for blended learning, improving the infrastructure, and adjusting the management.
Teaching comprises all types of disciplines and teachers need to look outside the confines of English as a Second Language. The acquisition of knowledge comes in a variety of the learners’ educational potential. English as a Second Language in teaching and learning, focuses on active learner’s involvement and reduction of coercion. Indeed, Gibran’s thoughts remain true that “wisdom leads one to discuss his or her potentials. To realize this, teachers in all educational levels have to portray a less dominant classroom role in accord with the importance of classroom interaction in the teaching learning process.
N.A. Flaunders retorted that “in the average classroom someone is talking for two-thirds of the time, two-thirds of the task is direct influence.” What does this mean? Students’ participation or interaction in the classroom has a significant content to enhance their linguistic competence and its core basis is how to use the language as the most important factor in the classroom. Comprehending the information caters one to establish a fair and well-balanced condition that teachers are facilitators, and the learners are to stay in the frontline.
In today’s classroom setting, the adoption-adaption of teaching strategies focuses on the learners’ ability to have a strong command or fluency of the language. ESL is learned around the globe and the learners’ interests are the primary goals in the teaching and learning process. Colin Blakemore once said that “True knowledge, as Plato argues, must be within us all, and learning consists of solely of discussing what we already know.”
In an ESL classroom, discovery of knowledge is not a new game. Teachers do perform their tasks and the learners serve not as passive listeners but as active recipients in the transformation-sharing of all the five macro skills namely speaking, reading, writing, listening, and viewing. In fact, if commitment, knowledge of subject-matter for independent learning, and management of learning are packaged in one big box, both the teachers and the learners will operate a mutual process of generating a lively culture and quality of educational life.
With the aforementioned views I had experienced in teaching ESL, the teacher’s passion for teaching and attitude in dealing with the learners create a strong impact on the learners cognitive, affective, and psychomotor domains.
The article deals with the notion of internet aggression (cyber aggression). It considers the mentioned term from both psychological and communicative approaches. The paper also provides detailed analyses of the cyber aggression in political discourse. The provided ex-amples are taken from the speeches of politicians during the time of Covid pandemic. The author also identifies several types of cyber aggression.
Deoxyribozymes are artificially evolved DNA molecules with catalytic abilities. RNA-cleaving deoxyribozymes have been recognized as an efficient tool for detection of modifications in target RNAs and provide an alternative to traditional and modern methods for detection of ribose or nucleobase methylation. However, there are only few examples of DNA enzymes that specifically reveal the presence of a certain type of modification, including N6-methyladenosine, and the knowledge about how DNA enzymes recognize modified RNAs is still extremely limited. Therefore, DNA enzymes cannot be easily engineered for the analysis of desired RNA modifications, but are instead identified by in vitro selection from random DNA libraries using synthetic modified RNA substrates. This protocol describes a general in vitro selection stagtegy to evolve new RNA-cleaving DNA enzymes that can efficiently differentiate modified RNA substrates from their unmodified counterpart.
This research paper concentrates on the analysis of the aphoristic potential of G. W. Bush’s presidential rhetoric. Aphorisms are the most ancient laconic forms of expressing original and completed thoughts which reveal the peculiarity of their authors’ world perception and worldview. From this perspective, these units can serve as the means of values codification. Repeatability and widespread use of aphorisms in various communications contribute to transmitting the values and ideas between the generations.
Political aphorisms, which are a combination of aphoristic expressions from political communication and discourse, play an important role in this process. The authors of these expressions are not only politicians, but also philosophers, historians, writers, celebrities of different nationalities and generations. Presidential rhetoric is an integral and significant part of political discourse.
The use of aphorisms as the means of codification of national and common human values in President G. W. Bush’s formal addresses and speeches is intentional. It makes them concise and original, influential and convincing. Aphoristic expressions denoting common human values show the ideas and beliefs of their authors, as well as the politician, about life, justice, equality, freedom, faith, family. Aphorisms defining national values become the means of updating concepts of democracy, unity and diversity, freedom and security, success, and opportunity to fulfill one’s potential in American society. The distinctive feature of G.W. Bush’s rhetoric is the frequent use of aphorisms whose authors are the Founding Fathers.
English language is being taught as a second foreign language in India. For most of the learners in India, English still a foreign language or target language. The study of this language is important to fulfill different kinds of academic and professional requirements. Still, there is a big gulf between demand and supply for which the failure of the system is largely responsible as its main emphasis on to adherence to the foreign curriculum. The government tries to impose this curriculum on English teachers, but, in fact, the curriculum is outdated.
A Case Study of the Basic Learners’ Struggles in Guessing from Context to Retain Words Learned
(2022)
Guessing meaning from context is a challenging strategy for Second Language Learners (SLLs). In using the strategy, research found that poor students or low proficiency learners struggled in their attempts to use it. Mainly, it was reported that it was due to their vocabulary knowledge was limited. In another aspect, retaining vocabulary learnt is also important. Such is essential since learning vocabulary does not mean knowing the definition only. Yet, learners must also be able to use the vocabulary as they engage in language skills such as reading, writing, speaking and listening. The study aims at finding the hindrances faced among poor students’ using contextual clues in retaining vocabulary. The study employed a case study to collect data from two basic students studying at a tertiary level. The study found that their hindrances in guessing meaning contexts were due to their being confused in guessing meaning when reading a sentence. Also, it was found that they were not able to find clues since they lacked vocabulary to guess correctly. The study implied that guessing meaning from context required sizeable vocabulary knowledge. Therefore, more training is necessary to assist basic learners in being successful in guessing from contexts.
The paper focuses on digital discourse. This is a speech-intellectual product of innovative information technologies, a phenomenon, which needs further interdisciplinary and linguistic interpretation. The English-language digital discourse shows how linguistic verbal communication is mediated by digits and to what extent these Signum and Verbum unity reigns over the world.
The paper analyzes the ways and methods of integrated and differential use of verbal and non-verbal sign systems in the English language as compared to programming languages, considering the types of synchronous changes in the socio-cultural dimension of the sign. This research describes the processes of signs transformation during their functioning in programming languages and in the English language, common and distinctive features in the arrangement of grammatical, lexical-semantic, and graphic means of (natural) English and (artificial) programming languages in their projection on different modes of communication in the system Human ↔ Machine.
Programming languages are constituted by verbal means of the English language with additional use of its own semiotic resources, which testifies to their integrative linguistic and mathematical nature. The specific representation of ElDD conveys its reciprocal nature when the English language using its own tools combines them with the elements of the programming languages thus creating an effective toolkit for self-process
The paper analyses specific characteristics of language that influence the development of culture and societies. The problem of the connection between language and culture has occupied the minds of many famous scientists: some believe that language is a part of the culture as a whole; others think that language is only a form of cultural expression. Undoubtedly, language constitutes a vital component of the cultural background underlying social development. Language is an essential means of communication and interaction. However, language is at the same time sovereign about culture as a whole and can be separate from culture or compared to culture as an equal element (i.e., that language is neither a form nor a component of culture).
In the present chapter, an attempt has been made to discuss the need to create Zambian English to address English language variations in Zambia. No language in the world can remain the same after interacting with other languages. The present chapter intends to propose and support the idea of using ‘Zambian English’ for both formal and informal business. Such a measure would create the communicative competence that the majority of the Zambians have always longed for. In Zambia, the purpose of using English language office is to deliberate day to day’s business. On the contrary, this has been found to be an obstacle to those who lack principles of command in the language usage, but are able to construct sentences for communicative purposes yet are deprived in international interactions. The views expressed in this chapter are those of the language experts who were engaged in a conversation with regard to the possibility of creating what would be known as Zambian English (ZamEnglish).
In 3 Maccabees, kingship as a form of rule is addressed on two levels: On the political level the question about a good king is addressed against the background of Hellenistic understandings of kingship, using the example of Ptolemy IV Philopator. This king is portrayed at the beginning of 3 Maccabees as a successful, positive, Hellenistic ruler, but one whose good rule goes off the rails. This analysis of the ideal of Hellenistic rule (cf. 3 Macc. 3:12-29; 6:24-28; 7:1-9) is then taken to a theological level: the God of Israel is portrayed as the true good king, the Soter who saves his people in their time of greatest trial (6:29, 32; 7:16). By these means the many divine epithets that are a striking feature of 3 Maccabees are incorporated into the narrative (cf. 2:2-3). Thereby 3 Maccabees not only thematises the conflict with a Hellenistic king who exploits his power in diverse ways but also focuses in a concentrated way the notion of a good (Hellenistic) king into the notion of God as king and ruler.
Although the Letter of Aristeas mentions the translation of the Jewish nomos into Greek, it is striking that worship is not a fundamental theme of this writing. Nevertheless, six passages present acts of worship, which recount worship from different perspectives: Aristeas prays to God and explains his “Greek” idea of worship (Let. Aris. 17), whereas in Let. Aris. 132-140 the high priest explains the Jewish concept of worship. Sacrifices and prayers at the temple in Jerusalem for the Ptolemaic royal house are told in Let. Aris. 45, while at the Ptolemaic court in Alexandria one of the Jewish scholars prays at the beginning of the symposium (Let. Aris. 184-186). Then the daily prayer of the Jewish scholars are recounted in Let. Aris. 305-306 and finally the Ptolemaic king performs a proskynesis before the law at the end of the letter and thereby accepts the translation (Let. Aris. 317).
"...using different names, as Zeus and Dis" (Arist 16). Concepts of "God" in the letter of Aristeas
(2016)
The “Letter of Aristeas” recounts the translations of the Hebrew Bible into Greek. Probably originating in the 2nd century BCE1, the book tells a legend of how the translation of the Torah into Greek came into being. This shows that translating a holy, canonical text or the first time needed explication. Notably, the translation of the godly nomos (Arist 3) comparatively takes up little space (Arist 301–307). And it has to be noted, that “God” is seldom a topic in the Book of Aristeas. The word (ὁ) θεός “God” is found in only three contexts: in the dialogue between king Ptolemaios and Aristeas (Arist 15–21), in the dialogue of the high priest Eleazar and Aristeas (Arist 121–171; above all 128; 130–141; 155–166; 168) and in the question-and-answer-speech during the symposium at the Ptolemaic royal court between the king and the Jewish scholars (Arist 184–294).
In analysing the different statements regarding God, the frame of the narrative is of decisive importance: In the Book of Aristeas, “Aristeas” (Ἀριστέας), who writes in Greek, presents himself as the author, but he is also part of the story. Accordingly, Aristeas is the narrator, who tells the story from his own point of view, and at the same time, he is a character in the ‘world’ of the text. This Aristeas presents himself as a Greek and a Non-Jew (Arist 16; 121–171), who already wrote a book (Arist 6) and plans further publications (Arist 322). In the double-role as narrator of the text and protagonist in the text, Aristeas has to be differentiated from the (real) writer/author of the Book of Aristeas, who possibly was Jewish. That means that the (real, probably Jewish) author of the Book of Aristeas presents (or invents) “Aristeas” and gives him the role of the narrator of his text.3 The author portrays Aristeas as a Greek, non-Jewish character, who is a servant of the royal court. This differentiation between narrator and writer/author is of crucial importance for the question of the different conceptions of God in the Book of Aristeas.
Starting with a terminological and phenomenological perspective on the question “What is an emotion?”, particularly as developed by Aaron Ben Zeʾev , the kiling scene in the book of Judith (Jdt 12:10–13:9 is analysed. This crucial scene in the book’s plot reports the intense emotions of Holofernes but nothing is said about any emotions on the part of of Judith. The only emotional glimpse occurs in Judith’s short prayers in the killing scene. The highly emotional Holofernes and the unemotional Judith together reveal that Holofernes is already made “headless” by his own emotions, whereas the unemotional Judith, unencumbered by emotions, is able to behead the “headless” Holofernes.
Memory development
(1994)
Hierarchical structures among male individuals in a population are frequently reflected in differences in aggressive and reproductive behaviour and access to the females. In general social dominance requires large investments which in turn may have to be compensated for by high reproductive success. However, this hypothesis has so far only been sufficiently tested in small mating groups due to the difficulties of determining paternity by classical methods using non-molecular markers. DNA fingerprinting overcomes these problems offering the possibility to determine genetic relationships and mating patterns within larger groups. Using this approach we have recently shown (Schartl et al., 1993) that in the poeciliid fish Limia perugiae in small mating groups the dominant male has 100% mating success, while in larger groups its contribution to the offspring unexpectedly drops to zero. The reproductive failure under such social conditions is explained by the inability of the ex-male to protect all the females simultaneously against mating attempts of his numerous subordinate competitors.
Motoneurons played an essential role in establishing the concept of target-mediated support of innervating neurons. However, it took several decades until molecules were identined which trophically support motoneurons in vitro and in vivo. The most potent molecule identined so far is ciliary neurotrophic factor (CNTF). It is expressed as a cytosolic molecule in myelinating Schwann cells rather than in skeletal muscle in the postnatal period and therefore does not qualify as a target-derived neurotrophic factor regulating motoneuron survival during embryonic development. However, the inactivation of CNTF by gene targeting experiments results in progressive atrophy and degeneration of motoneurons, demonstrating that CNTF plays an essential role as a maintenance factor for motoneurons postnatally. Secretory molecules which are expressed in skeletal muscle during embryonic development and which support motoneurons in culture and partially also in vivo include members of the NGF gene family (BDNF, NT-3, NT-4/S) , FGF-S, IGF-I, and UF. The evaluation of the physiological importance of these molecules is under investigation.
An improved 32P-postlabelling assay for detection and quantitation of styrene 7,8-oxide-DNA adducts
(1993)
Using DNA modified with [7-3H]styrene 7,8-oxide (SO) in vitro we have standardized the 32P-postlabelling assay for detecting SO-DNA adducts. Nuclease P 1-enriched adducts were 32P-labelled and purified by high-salt ( 4.0 M ammonium formate, pH 6.1} C1s reverse-phase TLC. After elution from the layer with 2-butoxyethanol:H20 (4:6), adducts were separated by two-dimensional PEI cellulose TLC in non-urea solvents (2.0 M ammonium formate, pH 3.5, and 2.7 M sodium phosphate, pH 5.6). One major, three minor and several trace adducts were detected. The efficiency of the kinase reaction depended on the ATP concentration. Use of standard labelling conditions (['Y· 32P]ATP, <3000 Ci/mmol; <2 Mikromol) resulted in poor ( 4-7%) adduct recovery. An ATP concentration of 40 Mikromol, however, increased the labeJling efficiency by a factor of 5-8 (35-55% based on 3H-SO labelied DNA). The results indicate that the new separation technique is suitable for the relatively polar SO-DNA adducts and that high labelling efficiency can be achieved.
[7-3H)Styrene 7,8-oxide was administered by oral gavage to male CD rats at a dose of 1.3 mg/kg. After 4 h, the forestomach was excised, DNA was isolated, purified to constant specific radioactivity and degraded nzymatically to the 3 '-nucleotides. Highperformance liquid chromatography fractions with the normal nucleotides contained most of the radiolabel, but a minute level of adduct label was also detccted. Using the units of the covalent binding index (micromoles adduct per mole DNA nucleotide)/(millimole chemical administered per kilogram body weight), a DNA binding potency of 1.0 was derived. A comparison of the covalent binding indices and carcinogenic potencies of other genotoxic forestarnach carcinogens showed that the tumorigenic activity of styrene oxide is unlikely to be purely genotoxic. Therefore, styrene oxide was compared with 3-tbutylhydroxyanisole (BHA) with respect to stimulation of cell proliferation in the forestomach. Male Fischer 344 rats were treated for four weeks at three dose levels of styrene oxide (0, 137, 275 and 550 mg/kg, three times per week by oral gavage) and BHA (0, 0.5, 1 and 2% in the diet); the highest doses had been reported to result in 84% and 22% carcinomas in the forestomach, respectively. Cell proliferation was assessed by incorporation of bromodeoxyuridine into DNA and immunohistochemical analysis. An increase in the lablling indexwas found in a11 treated animals. In the prefundic region of the forestomach, the labeHing index increased significantly, from 42% (controls) to 54% with styrene oxide and from 41 to 55% with BHA. Rats treated with BHA also had severe hyperplastic lesions in the prefundic region, i.e., at the location of BHA-induced forestomach carcinomas. The number of cells per millimetre of section length was increased up to 19 fold. Hyperplastic lesions were not seen with styrene oxide, despite the higher tumour incidence reported with this compound. We conclude that the carcinogenicity of styrene oxide to the forestomach most probably involves a mechanism in which marginal genotoxicity is combined with promotion by increased cell proliferation.
A panel of simple repetitive oligonucleotide probes has been designed and tested for multilocus DNA fingerprinting in some 200 fungal, plant and animal species as well as man. To date at least one of the probes has been found to be informative in each species. The human genome, however, has been the major target of many fingerprintins studies. Using the probe (CAC)5 or (GTG)5, individualization of all humans is possible except for monozygotic twins. Paternity analyses are now perfonned on a routine basis by the use of multilocus fingerprints, inctuding also cases of deficiency, i.e. where one of the parents is not available for analysis. In forensie science stain analysis is feasible in all tissue remains containing nuc)eated cells. Depending on the degree of DNA degradation a variety of oligonucleotides are informative, and they have been proven useful in actual case work. Advantages in comparison to other methods including enzymatic DNA amplification techniques (PCR) are evident. Fingerprint patterns of tumors may be changed due to the gain or loss of chromosomes and/or intrachromosomal deletion and amplification events. Locus-specific probes were isolated from the human (CAC)5/( GTG)5 fingerprint with a varying degree of informativeness (monomorphic versus truly hypervariable markers). The feasibility of three different approaches. for the isolation of hypervariable mono-locus probes was evaluated. Finally, one particular mixed simple (gt)n(ga)m repeat locus in the second intron of the HLA-DRB genes has been scrutinized to allow comparison of the extent of exon-encoded (protein-) polymorphisms versus intronie bypervariability of simple repeats: adjacent to a single gene sequence (e.g. HLA-DRB1*0401) many different length alleles were found. Group-specific structures of basic repeats were identified within the evolutionarily related DRB alleles. As a further application it is suggested here that due to the ubiquitous interspersion of their targets, short probes for simple repeat sequences are especially useful tools for ordering genomic cosmid, yeast artificial chromosome and phage banks.
Mechanistic possibilitles responsible for nonlinear shapes of the dose-response relationship in chemical carcinogenesis are discussed. (i) Induction and saturation of enzymatic activation and detoxification processes and of DNA repair affect the relationship between dose and steady-state DNA adduct Ievel; (ii) The fixation of DNA adducts in the form of mutations is accelerated by stimulation of the cell division, for Jnstance due to regenerative hyperplasia at cytotoxic dose Ievels; (iii) The rate of tumor formation results from a superposition of the rates of the individual steps. It can become exponential with dose if more than one step is accelerated by the DNA damage exerted by the genotoxic carcinogen. The strongly sigmoidal shapes often observed for dose-tumor incidence relationships in animal bioassays supports this analysis. A power of four for the dose in the su~linear part of the curve is the maximum observed (formaldehyde). In contrast to animal experiments, epidemiological data ln humans rarely show a slgnificant deviation from linearity. The discrepancy might be explained by the fact that a I arge nu mber of genes contribute to the overall sensitivity of an individual and to the respective heterogeneity within the human population. Mechanistic nonlinearities are flattened out in the presence of genetic and life-style factors which affect the sensitivity for the development of cancer. For a risk assessment, linear extrapolation from the high-dose lncidence to the spontaneaus rate can therefore be approprlate in a heterogeneous population even if the mechanism of action would result in a nonlinear shape of the dose-response curve in a homogeneaus population.
Tbe alkylating potency of unstable N-nitrosamino acids and N-nitrosopeptides was investigated in vitro using 4-(para-nitrobenzyl)pyridine (NBP) as nucleophile. Of the amino acids, Met and those with an aromatic side chain were the most potent. The relative overall alkylating potency was 23:10:5:4:2:1: for Trp, Met, His, 1)rr, Phe and Gly, respectively. The homo-dipeptides were much more potent than the amino acids, with relative potencies of 400:110:100:8:3:1, for Trp-Trp, l)T-'I)T, Met-Met, Asp-Asp, Phe-Phe and Gly, respectively. In the one-phase reaction system (in which NBP is already present durlog the nitrosation reaction at acidic pH), all amino acids tested showed a second-order reaction for nitrite. In the two-phase system (in which NBP is added only after bringing the nitrosation reaction mixture to neutrality), all amino acids tested except one again showed a second-order reaction for nitrite (Phe, His, Asp and the dipeptide artiticial sweetener aspartame); only Met under these conditions bad a reaction order of one for nitrite. This could mean that nitrosation of the side chain of Metproduces a second N-nitroso product which is relatively stable in acid but reacts with NBP under neutral conditions. In the human stomach, this side-chain nitrosation might become more important than the reactions at the primary amino group, firstly because of the greater stability of the product(s) in acid and secondly because of the tirst-order reaction rate for nitrite. A decrease in nitrite concentration from the millimolar concentrations ofthe in-vitro assay to the micromolar concentrations in the stomach reduces the reaction rate by a factor of 1000 for the side-chain nitrosation, whereas a million-fold reduction will be observed for nitrosation of the amino group.
Comprehensive geochemical investigations of rnetabasites yielded constraints for a correlation of, or discrimination between the different tectonic units within the northeast Bavarian crystalline basement. The Münchberg nappe pile consists of at least five large tectonic units which exhibit differences in lithology, in part also in metamorphie grade and in metamorphie history. The metabasites in each of these nappes show their own, significant geochemical characteristics. The lowermost tectonic unit, the Bavarian lithofacies, includes the anchimetamorphie Ordovician Randschieferserie which contains alkaline basalts. In their geochemistry, they are sirnilar to the metabasites of the Fichtelgebirge crystalline complex in the autochthonous Saxo-thuringian. The next higher tectonic unit of the Münchberg nappe pile, the Prasinit-Phyllit-Serie contains metabasites which can be derived from subalkaline basalts with a clear calc-alkaline tendency. There is a striking geochemical resemblance to the metabasites of the Erbendorf Greenschist Zone (EGZ) underscorinq the similar lithology of both allochthonous units which appear to be in a similar tectonic position. The Randamphibolit-Serie higher up in the Münchberg nappe pile consists of metabasites with tholeiitic characteristics and a pronounced differentiation trend. The next higher tectonic unit, the Liegendserie of the Münchberg gneiss cornplex s. str., contains metagabbros to metagabbronorites with a high-Al basaltic composition. The amphibolites and banded hornblende gneisses of the overlying Hangendserie are of subalkaline basaltic character with calc-alkaline affinity. The Zone Erbendorf-Vohenstrauss (ZEV) is currently regarded as an allochthonous unit equivalent to the higher crystalline nappes of the Münchberg pile. However, the geochemical character of the metabasites do not encourage such a correlation. Neither the schistose and striped amphibolites nor the flaseramphibolites of the ZEV with their N-KORB and E-MORB character respectively, find convincing counterparts in the crystalline nappes of the Münchberg pile. However, an interestingly close resemblance exists between the schistose and striped amphibolites in the ZEV, on the one hand, and in the autochthonous Zone Tirschenreuth- Mähring (ZTM) and the adjacent Moldanubian sensu strictu, on the other. Owing to the absence of age criteria, our results cannot be used, so far, to reconstruct the paleogeographical position of the individual tectonic units, based on the geochemical characteristics of their respective metabasites.
Adenosine modulates a variety of physiological functions via membrane-bound receptors. These receptors couple via G proteins to adenylate cyclase and K+channels. The A1 subtype mediates an inhibition of adenylate cyclase and an opening of K+-channels, and the A2 subtype a Stimulation of adenylate cyclase. Both subtypes have been characterized by radioligand binding. This has facilitated the development of agonists and antagonists with more than 1000-fold A1 selectivity. A1-selective photoaffinity labels have been used for the biochemical characterization of A1 receptors and the study of their coupling to adenylate cyclase. Such selective ligands allow the analysis of the involvement of adenosine receptors in physiological functions. Selective interference with adenosine receptors provides new pharmacological tools and eventually new therapeutic approaches to a number of pathophysiological states.
Experimental research on memory development has typically focused on the description of universal development trends across the life span and the identification of major sources of development within this domain. However, there is a lack of studies investigating the preconditions and effects of interindividual variability within age groups across different memory tasks. Similarly, our knowledge about the stability of interindividual differences across the life span as well as the sources and the amount of intraindividual variability across memory tasks is scarce. In the present chapter, we concentrate on these neglected issues. First, theoretical assumptions concerning the interindividual and intraindividual variability of memory development are discussed. Next, empirical evidence is presented that seems suited to document the importance of these neglected issues. While we try to give a representative account of the literature, the emphasis is on more recent studies of memory development in children and elderly adults conducted in our laboratory. The results demonstrate that age-related changes and individual differences in the knowledge base are particularly important for describing and explaining individual differences in memory develoment. In comparison, the rote of stable individual differences in basic memory capacities in explaining variations in memory development is less clear given tbe conflicting empirical evidence. In the final section of the chapter consequences for future research are discussed.
No abstract available
The ligand-binding subunit ofthe A1 adenosine receptor has been identified in membranes with the photoaffinity Iabel R-2-azido-N6-p-hydroxyphenylisopropyladenosine (R-AHPIA). Covalent labelling ofthe A1 receptor can also be achieved in intact cells. The dissociation of the radioiodinated label (1251-AHPIA) from isolated rat fat cells was incomplete after UV irradiation, leaving about 20°/o of irreversible specific binding. Such covalent labelling of the receptor led to a concentration-dependent reduction of cellular cyclic AMP levels. This persistent effect of covalent labeHing occurred with an IC50 value of 9 nM, as compared to an IC50 value of 0.9 nM for the direct reduction of cyclic AMP Ievels by the ligand. The difference in the IC5o values can be explained by assuming spare receptors. This hypothesis was verified in binding studies using [ 3HJPIA as a radioligand. R-AHPIA inhibited binding of [3H)PIA to intact fat cells with a K1 value of about 20 nM, which is about 20 tim es high er than the corresponding IC50 value of cyclic AMP reduction. These data show that the A1 receptor is activated according to the occupancy theory. The high sensitivity of the activation in intact ceJis is due to a large number of spare receptors.
The potential health risk posed by the endogenous formation of N-nitroso compounds (NOC) from nitrosation of dietary ureas, guanidines, amides, amino acids and amanes (primary, secondary and aromatic) was estimated according to the model:
Risk = ( daily intake of precursor] X (gastric concentration of nitrite ]n X [nitrosatability rate constant] X [cilrcinogenicity of derivative].
The daily intakes ofthese compound classes span five orders ofmagnitude (100 g/day amides, top; 1-10 mg/day secondary amines, ureas, bottom); the nitrosation rate constants span seven orders of magnitude (aryl amines, ureas, top; amides, secondary amines, bottom); and the carcinogenicity estimates span a 10 000-fold range from 'very strong' to 'virtually noncarcinogenic'. The resulting risk estimates likewise span an enormous range (nine orders of magnitude ): dietary ureas and aromatic amines combined with high nitrite concentration could pose as great a risk as the intake of preformed N-nitrosodimethylamine in the diet. In contrast, the risk posed by the in-vivo nitrosation of primary and secondary amines is probably negligible. The risk contributed by amides (including protein), guanidines and primary amino acids is intermediate between these two extremes.
Nitrosation of dietary components has been combined with the 4-(para-nitrobenzyl)pyridine (NBP) colorimetric test for screening alkylating agents and with the Ames test for the detection of mutagenic activity. This allowed the investigation of short-hved nitrosation products of dietary components which generate electrophilic degradation products requiring no metabolic activation (natural amino acids and some derivatives, ureas, guanidines, primary alkyl and aryl amines). In a first system, precursor, nitrous acid and NBP were present simultaneously. All amino acids tested, except glutamic acid and glutamine, gave positive results. The reactivities spanned more than three orders of magnitude, with the aromatic amino acids and methionine the most active; two primary amines, tryptamine and histamine, were also strongly reactive. All guanidines tested, except the amino acid arginine, gave negative results. A second system consisted of two phases: NBP was added only after destruction of residual nitrite and adjustment of the pH to neutrality. This system was useful for the study of ureas, which are stable in acid but not in neutral media. The range of responses covered more than two orders of magnitude. Most amino acids and primary amines also gave positive results, but could be assessed only after analysing the kinetics of the competing reactions and choosing appropriate reaction times. In a third system, Salmonella typhimurium strain TA1OO replaced NBP. Representatives of the class of amino acids, ureas, the primary amine tryptamine, and aniline became higbly mutagenic upon nitrosation. Methylguanidine was only weakly mutagenic under the present assay conditions. The results indicate that further studies with unstable nitrosation products of dietary components are required to understand more thoroughly the role of endogenous nitrosation in gastric cancer.
Barbiturates inhibit binding of radioligands to A 1(Ri) adenosine receptors of rat brain membranes. This inhibition is dose-dependent and stereospecific and occurs in the range of pharmacologically active concentrations. The displacement of radiolabelled A1antagonists by barbiturates is not modified by GTP, indicating that barbiturates might act as antagonists at this receptor. This action of barbiturates does not seem to be related to the binding of barbiturates to plasma membranes, as the latter process has different characteristics. Barbiturates also inhibit the binding of radioligands to solubilized A1receptors, and saturation and kinetic experiments suggest that this is due to a competitive antagonism. These results indicate that barbiturates interact with the recognition site of the A1adenosine receptor.
Climate affects both the distribution and abundance of isopods. Humidity and moisture affect their activity and distribution. Survival of juveniles is largely dependent on moisture. The reproductive pattern is affected by temperature and light. Food affects growth and thus, indirectly, also reproduction, as larger females tend to produce larger broods and more frequent broods than smaller ones. Generally in isopods there is little evidence to suggest that food is a very important factor affecting their abundance. Both semelparity and iteroparity are found in isopods and both reproductive strategies are apparently successful. Mortality factors affect the oocytes, the marsupial stages, and most of all the newly released individuals . Apart from climatic factors, predation and, to a lesser extent, parasitism are the main causes of mortality. Longevity of isopods ranges from one to five years. Occasional population explosions ofisopods are known to take place, their cause being unknown.
The methodological implications of a differential psychopharmacology are discussed. It is shown that the technique of stratifying subjects with personality scores depends on one basic assumption: the personality score is not affected by the other experimental factors. Two experiments are reported in which pre- and posttest (after the experiment) scores were measured. The pre-post-differences showed themselves to be affected by the medication. It is argued that in psychopharmacological experimentation an additional step must be included. All non-treatment factors must be examined for their stability in the course of the experiment. If they are stable, usual evaluation may take place. If changes are attributable to the treatment, personality scores must be regarded as dependent variables. They have to be evaluated together with the other observables with a multivariate model. Additionally, a procedure like this yields as "experimental differential psychology" a self-reliant contribution to the problems of differential psychology.