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J K Adams

Publications and source records attributed to J K Adams.

10 recordsLinked to original sources
PubMed2001

Colonic production and expression of IL-4, IL-6, and IL-10 in neonatal suckling rats after LPS challenge.

It has been demonstrated that the neonatal suckling rat is more susceptible to endotoxin [lipopolysaccharide (LPS)]-induced colonic damage compared with weaned littermates. There is evidence to suggest that differences in the production of certain cytokines, including interleukin (IL)-4, IL-6, and IL-10, are associated with intestinal inflammation in children. We have examined the production, localization, and mRNA detection of these cytokines in suckling and weaned rat colons after bacterial LPS challenge. Suckling (10 day old) and weaned (25 day old) rats were injected with LPS (3 mg/kg ip). Colon samples were taken up to 4 h after treatment, and cytokines were measured by ELISA. LPS-induced cytokine levels were significantly different in suckling rats compared with weaned rats. Cytokine localization to the colonic mucosa was evident in suckling rats up to 4 h after LPS administration but was not consistently seen in weaned rats. The mRNA for cytokines examined were detected by RT-PCR in suckling but not in weaned rat colons after LPS treatment. Induction of neutropenia via anti-neutrophil serum (ANS) administration did not affect cytokine mRNA detection in neonates after LPS treatment. Weaned animals displayed positive detection of all cytokines examined after ANS. Therefore, we have shown that the suckling rat displays a different production and expression of colonic IL-4, IL-6, and IL-10 compared with weaned littermates after LPS challenge. Furthermore, neutrophils may be implicated in colonic cytokine expression after LPS challenge in rats.

Animals↗
PubMed1998

Response distribution as an explanation of the mirror effect.

Response distribution has recently been proposed as an explanation of the mirror effect in recognition memory. According to the proposal, participants presented with distinctive sets of items (e.g., low- and high-frequency words) vary their responses to give an equal number of positive responses (e.g., the sum of hits and false alarms) to each set. Four experiments tested this proposal. Two experiments showed that the mirror effect is present in the absence of distinctive sets of items. Two experiments showed that the mirror effects is present in the absence of response equalization. Wherever the response distribution hypothesis can be tested, it fails.

Adult↗
PubMed1993

The regularities of recognition memory.

Three regularities in recognition memory are described with supporting data: the mirror effect, the order of receiver operating characteristic slopes, and the symmetry of movement of underlying distributions. The derivation of these regularities from attention/likelihood theory is demonstrated. The theory's central concept, which distinguishes it from other theories, is the following: Ss make recognition decisions by combining information about new and old items, the combination made in the form of likelihood ratios. The central role of the likelihood ratios extends the implications of signal detection theory for recognition memory. Attention/likelihood theory is fitted to data of 2 series of experiments. One series involves yes-no tests and confidence ratings, the other forced-choice experiments. It is argued that the regularities require a revision of most current theories of recognition memory.

Aging↗
PubMed1991

Forgetting and the mirror effect in recognition memory: concentering of underlying distributions.

The mirror effect is a strong regularity in recognition memory: If there are two conditions, A and B, with A giving higher recognition accuracy, then old items in A are recognized as old better than old items in B, and also new items in A are recognized as new better than new items in B. The mirror effect is explained by attention/likelihood theory, which also makes several new, counterintuitive predictions. One is that any variable, such as forgetting, that affects recognition changes the responses to new as well as old stimuli. In terms of underlying distributions, forgetting produces concentering, the bilateral movement of distributions, both new (noise) and old (signal), toward a midpoint. Data from two forced-choice experiments are reported that support the prediction of concentering and other predictions drawn from the theory. It is argued that current theories of memory, which are strength theories, cannot handle these regularities.

Attention↗
PubMed1990

The mirror effect in recognition memory: data and theory.

The mirror effect is a regularity in recognition memory that requires reexamination of current views of memory. Five experiments that further support and extended the generality of the mirror effect are reported. The first two experiments vary word frequency. The third and fourth vary both word frequency and concreteness. The fifth experiment varies word frequency, concreteness, and the subject's operations on the words. The experiments furnish data on the stability of the effect, its relation to response times, its extension to multiple mirror effects, and its extension beyond stimulus variables to operation variables. A theory of the effect and predictions that derive from the theory are presented.

Humans↗
PubMed1983

Effect of several inhibitors of enzymatic DNA methylation on the in vivo methylation of different classes of DNA sequences in a cultured human cell line.

We have previously demonstrated that, while most enzymatic formation of 5-methylcytosine in the DNA of mammalian cells occurs very shortly after strand synthesis, there is also a minor fraction of methylation which occurs in some DNA sequences up to at least several hours after strand synthesis. Using a human cell line, we have examined the effects on these two classes of enzymatic DNA methylation of several compounds which have been reported to be inhibitors of methylation reactions. We have found that cycloleucine, ethionine, and 5'-deoxy-5'-methylthioadenosine (MTA) are all effective as inhibitors of enzymatic DNA methylation, but that there is no differential effect between the delayed and non-delayed methylation reactions. Tubericidin (7-deaza-adenosine) plus homocysteine inhibited delayed DNA methylation much more than non-delayed methylation (by up to 4 times). By contrast, 5-azacytidine produced a higher level of inhibition of DNA methylation at sites in the DNA in which the methylation occurred very shortly after strand synthesis. Also 5-azacytidine was by far the most potent inhibitor of DNA methylation of the compounds tested. S-Adenosyl-homocysteine and caffeine were found to have no effect on DNA methylation. These results are discussed in relation to the number and specificity of DNA methylases in these cells and to the cellular functions of those DNA sequences in which methylation is delayed for some hours after strand synthesis.

5-Methylcytosine↗
PubMed1982

Characteristics of enzymatic DNA methylation in cultured cells of human and hamster origin, and the effect of DNA replication inhibition.

In mammalian cells, inhibitors of DNA replication have been shown to induce chromosomal aberrations, cell death and changes in gene control. Inhibition of DNA synthesis has been reported to induce hypermethylation of mammalian DNA (enzymatic postsynthetic formation of 5-methylcytosine). These 5-methylcytosines in mammalian DNA have variously been suggested to be important in gene control, DNA repair, and control of DNA replication. In establishing the normal characteristics of enzymatic DNA methylation, we have demonstrated that, in asynchronously growing cells of both human and hamster origin, some cytosine methylation is delayed for several hours after strand synthesis and that this delayed methylation is completed before the DNA strand acts as a template for DNA replication in the next S-phase. Further, in testing whether the deleterious effects on mammalian cells of DNA synthesis inhibitors might be mediated via changes in enzymatic DNA methylation, we have found, contrary to some previous findings, no evidence for any change in the level of DNA methylation in DNA strands synthesized during 6 h of treatment of cells of human origin with high concentrations of four different inhibitors of DNA replication or during the 4 h following the 6 h treatment. Almost totally blocking DNA replication had no effect on the small amount of delayed methylation of DNA strands not involved in semi-conservative replication during the time of the experiment. This lack of effect on DNA methylation was obtained when the labelling medium contained normal, undialysed serum. In contrast, if dialysed serum was used in the labelling medium in order to maximize L-[Me-3H]methionine utilization, highly variable, totally irreproducible patterns of apparent DNA hypermethylation were obtained.

5-Methylcytosine↗
PubMed1982

Relationship between aberrant DNA replication and loss of cell viability in Chinese hamster ovary CHO-K1 cells.

We have previously presented evidence that a transient block to DNA replication induces an aberrant form of DNA synthesis. The most feasible explanation for this data is that the block to DNA replication results in some segments of the chromosomal DNA being replicated more than once in a single cell cycle. This form of aberrant DNA synthesis was demonstrated to occur following direct inhibition of DNA replication by 1-beta-D-arabinofuranosylcytosine or 9-beta-D-arabinofuranosyladenine or after indirect inhibition with cycloheximide. We have proposed mechanisms whereby this phenomenon could induce chromosome damage and cell death. In this paper, we present data on the relationship between this aberrant form of DNA replication and the loss of cell viability. Using Chinese hamster ovary CHO-K1 cells growing as monolayer cultures, we have simultaneously monitored the loss of cell viability as measured by colony formation and the relative extent of this aberrant DNA replication induced by 2-hr pulses of a series of concentrations of inhibitors of DNA replication. We have found that, with either direct inhibition of DNA replication with 1 beta-D-arabinofuranosylcytosine or with indirect inhibition, with cycloheximide, pulses of inhibitor administered to Chinese hamster ovary cells at increasing of this aberrant DNA replication which paralleled the increase in cell killing.

Animals↗