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S L Adams

Publications and source records attributed to S L Adams.

At least 55 records · Page 3Linked to original sources
PubMed1994

Effects of drugs on response duration differentiation. III. Acute variation of reinforced duration.

Rats trained to hold a lever down for at least 1.0 s but less than 1.3 s could differentiate the reinforced response duration on about 50% of the trials. The response duration frequency distribution was a normal distribution with a peak near the minimum reinforced response duration. Dose-effect curves were determined for the effects of phencyclidine (PCP) and methamphetamine. Subsequently, rats continued to be trained for 3 days a week with responses between 1.0 and 1.3 s reinforced, but on days when injections were given either the maximum reinforced duration was increased to 2.3 s, or the minimum reinforced duration was lowered to 0.5. When the maximum duration was increased to 2.3 s, the percentage of reinforced responses increased to 60% and when the minimum reinforced duration was decreased to 0.5 s, the percentage of reinforced responses increased to 89%. Despite the increased percentage of reinforced responses when the time window was widened, the effects of PCP and methamphetamine were not changed. These data suggest that the effects of drugs on response duration differentiation are not greatly influenced by transient changes in reinforcement frequency.

Animals↗
PubMed1994

Molecular characterization of the human EAA5 (GluR7) receptor: a high-affinity kainate receptor with novel potential RNA editing sites.

Several cDNA clones encoding EAA5 receptor polypeptides were isolated from a human fetal brain library. The EAA5 cDNAs demonstrated an 88.7-90.1% nucleotide identity with rat GluR7 cDNAs. The nucleotide sequence of EAA5 would encode a 919-amino acid protein, that has a 97.7-98.9% identity with the rat GluR7 receptor. Two variation of the EAA5 cDNA were identified which result in amino acid substitutions in the predicted extracellular amino-terminal region; Ser310-->Ala and Arg352-->Gln. These variations can be attributed to RNA editing involving T-->G and G-->A substitutions. Both the location (with respect to glutamate receptors), and the nucleotides involved, in this putative RNA editing are novel and may therefore involve novel mechanisms. Ligand binding studies with membranes of transfected COS-1 cells expressing EAA5 polypeptides demonstrate a rank order of ligand affinity similar to that observed with the rat GluR7 receptor, and a dissociation constant for kainate (2.72 +/- 0.12 nM (n = 3)) that is approximately 20- to 30-fold higher than that observed for the rat GluR7 receptor. All of the ligands tested had a higher affinity for the human EAA5 receptor as compared to the rat GluR7 receptor. This report provides another example of pharmacological differences for similar receptors across species.

Amino Acid Sequence↗
PubMed1993

Responsiveness to retinoic acid changes during chondrocyte maturation.

We previously showed that retinoic acid (RA) participates in the regulation of chondrocyte maturation during endochondral ossification, a process involving multiple developmental stages. To assess whether the responsiveness to RA treatment changes during chondrocyte maturation, immature chondrocytes were isolated from the caudal portion of Day 18-19 chick embryo sterna, a portion that remains cartilaginous through early postnatal life but ossifies with age. The immature cells were allowed to reach different stages of maturation by growth for different time in culture. Progression by the cells toward the mature phenotype during culture was confirmed by increases in average cell diameter, proteoglycan synthesis, and alkaline phosphatase (APase) activity. When developmentally immature passage 0 (PO) cultures were treated with RA (10-100 nM) for 72 h, the cells readily became fibroblastic, reduced drastically their proteoglycan synthesis, and failed to activate type X collagen gene expression. When older cultures (P1 and P2) were treated with RA, the cells acquired a characteristic epithelioid shape and increased their APase activity. Moreover, 5-10% of P1 cells and 20-25% of P2 cells activated type X collagen synthesis in response to RA. RA treatment markedly induced expression of the gene encoding the beta isoform of retinoic acid receptor (RAR beta) and also provoked a moderate 2.5-fold increase in RAR alpha gene expression. A similar change in responsiveness to RA was observed during maturation in vivo. Chondrocytes were isolated from the cephalic portion of Day 10, 11, 13, and 16 chick embryo sterna, and were treated with different doses of RA (10-100 nM) for 72 h. The cells from the Day 10 sternum failed to activate type X collagen gene expression in response to RA. In contrast, with increasing age of the embryos, an increasing fraction of cells induced type X collagen gene expression in response to RA. We conclude that responsiveness to RA changes during the early stages of chondrocyte maturation and that maturation depends on interactions between exogenous retinoids and the endogenous developmental program of chondrocytes.

Alkaline Phosphatase↗
PubMed1993

Retinoic acid induces rapid mineralization and expression of mineralization-related genes in chondrocytes.

Numerous studies of experimental hypo- and hypervitaminosis A have long suggested that retinoic acid (RA) is involved in chondrocyte maturation during endochondral ossification and skeletogenesis. However, the specific and direct roles of RA in these complex processes remain unclear. Based on recent studies from our laboratories, we tested the hypothesis that RA induces the expression of genes associated with the terminal mineralization phase of chondrocyte maturation and promotes apatite deposition in the extracellular matrix. Cell populations containing chondrocytes at advanced stages of maturation were isolated from the upper portion of Day 18 chick embryo sterna and grown for 2 weeks in monolayer until confluent. The cells were then treated with low doses (10-100 nM) of RA for up to 6 days in the presence of a phosphate donor (beta-glycerophosphate) but in the absence of ascorbic acid. Within 4 days of treatment, RA dramatically induced expression of the alkaline phosphatase (APase), osteonectin, and osteopontin genes, caused a several-fold increase in APase activity, and provoked massive mineral formation while it left type X collagen gene expression largely unchanged. The mineral had a mean Ca/Pi molar ratio of 1.5; Fourier transform infrared spectra confirmed that it represented hydroxyapatite. Mineralization was completely abolished by treatment with parathyroid hormone; this profound effect confirmed that RA induced cell-mediated mineralization and not nonspecific precipitation. When cultures were treated with both RA and ascorbic acid, there was a slight further increase in APase activity and increased calcium accumulation. The effects of RA were also studied in cultures of immature chondrocytes isolated from the caudal portion of sternum; however, RA only had minimal effects on mineralization and gene expression in these cells. Thus, RA appears to be a rapid, potent, maturation-dependent, ascorbate-independent promoter of terminal maturation and matrix calcification in chondrocytes.

Alkaline Phosphatase↗
PubMed1993

Late onset alcoholism: stress or structure.

We studied 60 men (M age = 63.6 years) from six midwest treatment centers to determine whether stress resulting from loss of social-psychological structures was greater for later onset alcoholics. Each subject completed a modified Veteran's Alcoholism Screening Test (V.A.S.T.; Magruder-Habib, Harris, & Franker, 1982) and the Drinking Practices Survey (Adams, 1990). They were then identified as early onset (problem drinking before age 40) and later onset (problem drinking after age 40). Cross tabulations using the chi-square statistic showed that more early onset alcoholics were married than later onset alcoholics. Of the social-psychological structures, only marital status showed a significant relationship with alcoholism. This seemed to confirm that the onset of problem drinking has less to do with stress than with the loss of a spouse who may serve to regulate the older man's drinking.

Age Factors↗
PubMed1991

Cloning, sequencing and overexpression of the gene for prokaryotic factor EF-P involved in peptide bond synthesis.

A soluble protein EF-P (elongation factor P) from Escherichia coli has been purified and shown to stimulate efficient translation and peptide-bond synthesis on native or reconstituted 70S ribosomes in vitro. Based on the partial amino acid sequence of EF-P, 18- and 24-nucleotide DNA probes were synthesized and used to screen lambda phage clones from the Kohara Gene Bank. The entire EF-P gene was detected on lambda clone #650 which contains sequences from the 94 minute region of the E.coli genome. Two DNA fragments, 3.0 and 0.78 kilobases in length encompassing the gene, were isolated and cloned into pUC18 and pUC19. Partially purified extracts from cells transformed with these plasmids overrepresented a protein which co-migrates with EF-P upon SDS polyacrylamide gel electrophoresis, and also exhibited increased EF-P mediated peptide-bond synthetic activity. Based on DNA sequence analysis of this gene, the EF-P protein consists of 187 amino acids with a calculated molecular weight of 20,447. The sequence and chromosomal location of EF-P establishes it as a unique gene product.

Amino Acid Sequence↗
PubMed1991

The splicing pattern of fibronectin mRNA changes during chondrogenesis resulting in an unusual form of the mRNA in cartilage.

Chondrogenesis, the differentiation of mesenchyme into cartilage, results in a change in composition of the extracellular matrix. The cartilage matrix contains several unique components, including type II collagen and chondroitin sulfate proteoglycan; it also contains fibronectin, a glycoprotein that mediates the interaction of cells with their matrix. We show that chick cartilage fibronectin mRNA contains an unusual pattern of alternatively spliced exons. Specifically, it contains exon IIIB but does not contain exon IIIA whereas fibronectin mRNA from mesenchyme contains both exons IIIB and IIIA. Thus the splicing pattern of the fibronectin mRNA must change from B+A+ to B+A- during chondrogenesis. Most fibronectin mRNA in other mesenchymal tissues contains exon IIIA but little exon IIIB (B-A+). Culturing of chondrocytes (cartilage-producing cells) results in loss of exon IIIB from fibronectin mRNA (B-A-). Manipulation of culture conditions to produce more adhesive chondrocytes (treatment with hyaluronidase, transformation with Rous sarcoma virus, and treatment with retinoic acid) increases the amount of fibronectin mRNA containing exon IIIA. These results suggest that exon IIIB may mediate the interactions of chondrocytes with the unique components of the cartilage matrix and exon IIIA may play a role in chondrocyte adhesion.

Animals↗
PubMed1991

Cell hypertrophy and type X collagen synthesis in cultured articular chondrocytes.

Articular cartilage is a permanent tissue whose cells do not normally take part in the endochondral ossification process. To determine whether articular chondrocytes possess the potential to express traits associated with this process such as cell hypertrophy and type X collagen, chondrocytes were isolated from adult chicken tibial articular cartilage and maintained in long-term suspension cultures. As a positive control in these experiments, we used parallel cultures of chondrocytes from the caudal portion of chick embryo sternum. Both articular and sternal chondrocytes readily proliferated and progressively increased in size with time in culture. Many had undergone hypertrophy by 4-5 weeks. Analysis of medium-released collagenous proteins revealed that both articular and sternal chondrocytes initiated type X collagen synthesis between 3 and 4 weeks of culture; synthesis of this macromolecule increased with further growth. Immunofluorescence analysis of 5-week-old cultures showed that about 15% of articular chondrocytes and 30% of sternal chondrocytes produced type X collagen; strikingly, there appeared to be no obvious relationship between type X collagen production and cell size. The results of this study show that articular chondrocytes from adult chicken tibia possess the ability to express traits associated with endochondral ossification when exposed to a permissive environment. They suggest also that the process of cell hypertrophy and initiation of type X collagen synthesis are independently regulated both in articular and sternal chondrocytes.

Amino Acid Sequence↗
PubMed1991

Retinoic acid treatment induces type X collagen gene expression in cultured chick chondrocytes.

The vitamin A derivative retinoic acid (RA) is widely thought to be involved in cartilage development, but its precise roles and mechanisms of action in this complex process remain unclear. We have tested the hypothesis that RA is involved in chondrocyte maturation during endochondral ossification and, in particular, is an inducer of maturation-associated traits such as type X collagen and alkaline phosphatase. Immature chondrocytes isolated from the caudal region of Day 19 chick embryo sterna were seeded in secondary monolayer cultures and treated either with a high dose (100 nM) or with physiological doses (10-35 nM) of RA for up to 3 days. We found that after an initial lag of about 24 h, physiological doses of RA indeed induced type X collagen gene expression in the immature cells. This induction was not accompanied by obvious changes in expression of the type II collagen and large aggregating proteoglycan core protein genes. As revealed by immunocytochemistry, 30-35% of the cells in cultures treated with RA for 3 days were engaged in type X collagen production. Interestingly, these cells were relatively similar in size to chondrocytes in which no type X collagen was detected, suggesting that chondrocytes can initiate type X collagen production independent of cell hypertrophy. RA treatment also led to increased alkaline phosphatase activity occurring as early as 24 h after the start of treatment. The data in this study indicate that RA may have a role in endochondral ossification as an inducer/promoter of maturation-associated traits during chondrocyte maturation.

Alkaline Phosphatase↗
PubMed1991

Rapid induction of type X collagen gene expression in cultured chick vertebral chondrocytes.

During endochondral ossification, small rapidly proliferating chondrocytes mature into flattened disc-shaped cells and then into large round hypertrophic cells. These morphological changes are accompanied by a decrease in the rate of cell proliferation. Type X collagen synthesis is initiated during chondrocyte maturation and reaches very high levels in the hypertrophic cells. We have analyzed type X collagen gene expression in chick embryo vertebral chondrocytes that were allowed to mature in monolayer culture and were then switched to suspension culture. The resuspended chondrocytes changed in shape from flat to round and decreased the proliferation rate as they do in vivo. These events were accompanied by a rapid, dramatic increase in type X collagen gene expression at the levels of transcription, steady-state mRNA and protein synthesis, as well as an increase in the number of cells producing type X collagen. The amount of type X collagen gene expression in resuspended chondrocytes was comparable to that in mineralizing cartilage in vivo. These results indicate that events accompanying the switch from monolayer to suspension culture (for example, the change from a flat to a round shape and/or the decrease in proliferation rate) may play a role in the induction of type X collagen gene expression during chondrocyte maturation. Thus we have developed an in vitro system that appears to mimic the events occurring during in vivo chondrocyte maturation. This in vitro model may provide an ideal system for further examination of the parameters regulating chondrocyte maturation and type X collagen gene expression.

Animals↗
PubMed1991

Narrow-angle glaucoma presenting as acute, painless visual impairment.

A 42-year-old woman presented with the acute onset of bilateral blurred vision that occurred immediately after bending over. She denied pain or any other associated symptoms. Markedly increased intraocular pressure readings were found. Treatment for acute narrow-angle glaucoma was initiated, and normal vision returned. This case represents an atypical presentation of acute narrow-angle glaucoma, a true ophthalmological emergency. The pathophysiology and treatment options of this disease process are summarized.

Acetazolamide↗
PubMed1991

Human IgE-binding synthetic peptides of bovine beta-lactoglobulin and alpha-lactalbumin. In vitro cross-reactivity of the allergens.

The allergenicity of cow's milk whey proteins, purified by high performance liquid chromatography (HPLC), was examined by the radio-allergosorbent test (RAST) against the sera of children immediately hypersensitive to milk. beta-lactoglobulin and alpha-lactalbumin bound specific IgE in the sera of 63% and 75% of these patients respectively. These allergens were tested for cross reactivity with each other by RAST inhibition. Both inhibited the binding of IgE, in the sera of allergic patients, to the other protein. Two possible determinant peptides, one from beta-lactoglobulin and one from alpha-lactalbumin, were selected by computer prediction of antigenic sites and synthesized by the fluorenylmethoxycarbonyl (FMOC)-polyamide method. The peptides were adsorbed to nitrocellulose discs and used in further RAST studies with sera from the allergic children. Both peptides bound specific IgE in the RAST assay.

Allergens↗
PubMed1991

Ascorbic acid regulates multiple metabolic activities of cartilage cells.

Bones grow in length because of the activities of cartilage cells in the epiphyseal growth plate. We have examined selected events that occur in the growth cartilage by the use of cultured epiphyseal cells; we have also evaluated the influence of ascorbate on these activities. Our studies indicate that 1) ascorbate induces the expression of a unique collagen isoform, type X collagen; 2) ascorbate stimulates alkaline phosphatase activity of maturing chondrocytes; and 3) ascorbate regulates the energy status of the maturing chondrocyte. We have found that in the presence of ascorbate there is a change in oxidative activity. Thus, lactate formation is inhibited, there is an increase in the adenylate energy charge ratio, and there is an elevation in the activity of isocitrate dehydrogenase. The results of these studies point to multiple effects of vitamin C on chondrocyte maturation involving changes in protein synthesis and energy metabolism.

Alkaline Phosphatase↗
PubMed1991

Late onset of alcoholism among older midwestern men in treatment.

60 men were administered a questionnaire to assess whether the prevalence of alcoholism in men over 60 years of age in alcoholism treatment centers parallels the reported rates of late-onset for one-third or more alcoholics. Analysis showed 11% of the subjects were of late onset while 33% were quasilate onset. There were no significant differences in the life stress between alcoholics of early and later onset.

Aged↗
PubMed1991

Comparisons of Purpose in Life scores between alcoholics with early and later onset.

No significant differences were found on Purpose in Life scores of 33 early onset (before age 40) and 27 late onset (after 40 years of age) alcoholic men in alcoholism treatment centers. Differences were found between the later onset group and another group of early onset alcoholics (n = 38) as well as an older nonalcoholic group of 20 tested by Meier and Edwards.

Adult↗
PubMed1991

The effects of Tordon 202c exposure on urethan-induced lung adenoma formation in female CD-1 mice.

Female CD-1 mice were exposed to Tordon 202c, a herbicide containing 2,4-dichlorophenoxyacetic acid and picloram, in the drinking water for 15 w at concentrations ranging from 0 to 0.3% of the product formulation. After 3 w of the 15-w treatment period, the mice received 1.5 mg/g urethan ip. Pulmonary adenoma production was evaluated 12 w later. Tordon 202c exposure produced a dose-dependent increase in tumor number, but had no effect on tumor size. Urethan-induced sleeping times which reflected the rate of urethan metabolism or excretion were altered, but a specific dose-related effect which could be correlated with tumor production was not observed. This suggests that Tordon 202c exposure influences adenoma formation by immunological mechanisms rather than by causing indirect effects on urethan metabolism or excretion.

2,4-Dichlorophenoxyacetic Acid↗
PubMed1990

Identification of a cartilage-specific promoter within intron 2 of the chick alpha 2(I) collagen gene.

Chick cartilages contain type I collagen mRNAs but do not synthesize type I collagen. The 5' end of the mRNA derived from the alpha 2 type I collagen gene (alpha 2(I] in cartilage differs from the 5' end of the mRNA in cells and tissues that actively synthesize alpha 2(I) collagen. This difference in mRNA structure results from the use of a cartilage-specific transcription start site within intron 2 of the alpha 2(I) collagen gene. The use of the cartilage transcription start site replaces exons 1 and 2 with a 96-base exon contained within intron 2. The resulting transcripts contain several small open reading frames, all of which appear out of frame with the collagen coding sequence. The cartilage form of the mRNA no longer encodes alpha 2(I) collagen, thus explaining the absence of alpha 2(I) collagen in cartilage. Transcription of the alpha 2(I) collagen gene initiates at the previously described (bone/tendon) promoter in prechondrogenic limb mesenchyme, which synthesizes alpha 2(I) collagen. Thus, the cessation of alpha 2(I) collagen synthesis which occurs during differentiation of prechondrogenic mesenchymal cells into chondrocytes apparently results from the switch in promoter utilization from the bone/tendon promoter to the cartilage promoter.

Amino Acid Sequence↗