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Biomedical subjects

L H Cohen

Publications and source records attributed to L H Cohen.

At least 73 records · Page 4Linked to original sources
PubMed1986

Relationships among negative life events, physiological reactivity, and health symptomatology.

College undergraduates classified as high (n = 25) and low (n = 25) on recent life stress participated in an experiment involving a novel laboratory stressor. Heart rate and pulse arrival time (PAT) were measured during baseline, anticipation, testing, and recovery periods of the experiment. The results did not replicate those obtained by Pardine and Napoli in that high and low life stress subjects did not show differential physiological reactions. In addition, regression analyses failed to demonstrate that physiological reactivity moderated the relationship between life stress and subsequent self-reported psychiatric or physical health symptomatology. The present findings demonstrated neither the stress-buffering effects of physiological reactivity nor a relationship between life stress and reactivity when the latter was conceptualized as an outcome.

Adult↗
PubMed1985

Measurement of adolescents' life events: the junior high life experiences survey.

The first of these two studies examined the relationship between adolescents' scores on a social desirability questionnaire and scores of negative, positive, and total life events. Only number of positive events was significantly related to social desirability. The second study compared various scoring strategies with respect to their intercorrelation and their ability to predict adolescents' maladjustment (depression, anxiety, and number of missed school days). The results demonstrated that (a) total number of events and readjustment-weighted life change scores were equally predictive of the maladjustment criteria; (b) negative events, but not positive events, however scored, were significantly related to the maladjustment criteria; (c) indices based on psychologist-judges' ratings of event desirability were not more predictive of the maladjustment criteria than were indices based on the adolescents' self-reports; and (d) uncontrollable negative events and controllable negative events were equally predictive of the maladjustment criteria.

Absenteeism↗
PubMed1985

Distribution of histone H1 alpha among cells of the sea urchin embryo.

We have used immunofluorescent staining of sea urchin embryos to study how histone H1 alpha is distributed among progeny cells formed after the cessation of its synthesis. Our results are consistent with H1 alpha being distributed to both daughter cells at mitosis, resulting in it being most concentrated in cells that stop dividing shortly after H1 alpha synthesis ends, while cells that continue to divide dilute their H1 alpha content in proportion to the number of cell divisions. This rules out our earlier suggestion that H1 alpha becomes segregated in dividing cells. In addition, our results show that most dividing cells of the 3-day embryo contain predominantly H1 beta and H1 gamma. Since these subtypes are known not to undergo phosphorylation, this finding has implications regarding the roles of H1 phosphorylation in the cell cycle.

Animals↗
PubMed1984

Embryonal histone H1 subtypes of the sea urchin Strongylocentrotus purpuratus: purification, characterization, and immunological comparison with H1 subtypes of the adult.

The four H1 subtypes utilized during embryonic development of Strongylocentrotus purpuratus were purified. Their amino acid compositions and immunological reactivities show that they have different primary structures. Antisera against them were used to identify the H1 subtypes present in adult tissues. These experiments revealed that adult tissues do not contain detectable levels of the two H1 subtypes expressed in the earliest embryonic stages (H1 cs and H1 alpha) but do contain the two subtypes expressed from the blastula stage on (H1 beta and H1 gamma). In addition, all adult tissues examined contain H1 lambda, a subtype of unusually low apparent molecular weight, which is not found in the embryo prior to the feeding larval stage and is not closely related immunologically to any of the embryonal H1 subtypes.

Animals↗
PubMed1984

Effects of compactin, mevalonate and low-density lipoprotein on 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity and low-density-lipoprotein-receptor activity in the human hepatoma cell line Hep G2.

Compactin, an inhibitor of HMG-CoA (3-hydroxy-3-methylglutaryl-CoA) reductase, decreased cholesterol synthesis in intact Hep G2 cells. However, after the inhibitor was washed away, the HMG-CoA-reductase activity determined in the cell homogenate was found to be increased. Also the high-affinity association of LDL (low-density lipoprotein) to Hep G2 cells was elevated after incubation with compactin. Lipoprotein-depleted serum, present in the incubation medium, potentiated the compactin effect compared with incubation in the presence of human serum albumin. Addition of either mevalonate or LDL prevented the compactin-induced rise in activities of both HMG-CoA reductase and LDL receptor in a comparable manner. It is concluded that in this human hepatoma cell line, as in non-transformed cells, both endogenous mevalonate or mevalonate-derived products and exogenous cholesterol are able to modulate the HMG-CoA reductase activity as well as the LDL-receptor activity.

Animals↗
PubMed1984

Positive life events and social support and the relationship between life stress and psychological disorder.

This study investigated the relationship between negative life events and psychological disorder and the roles of positive life events and received and perceived social support in moderating this relationship. A prospective design was used and statistical analyses were based on a hierarchical regression model. College undergraduates served as subjects. Negative events were significantly related to psychological disorder at each of two measurement periods. This relationship was found even when initial disorder was statistically controlled. The cross-sectional analyses, but not the prospective analyses, provided some support for the stress-buffering (interaction) effects of positive events. There was no support for the stress-buffering effects of received social support, but the cross-sectional and prospective regression analyses provided strong support for the stress-buffering effects of perceived social support.

Female↗
PubMed1984

The alterations in H1 histone complement during mouse spermatogenesis and their significance for H1 subtype function.

The principal histone H1 subtypes of mouse prepachytene spermatocytes were identified as H1a and H1c, proteins that are metabolically unstable and have been postulated to promote extended or flexible chromatin conformations. We suggest that the unusual H1 subtype composition in these cells favors chromatin conformations compatible with the precise chromosomal pairing necessary for genetic recombination and also that it may expedite histone replacement during spermiogenesis.

Aging↗
PubMed1983

Yeast ribosomal protein S33 is encoded by an unsplit gene.

The structure of the gene coding for ribosomal protein S33, - a protein which escapes the coordinate control of ribosomal protein synthesis in rna 2 mutant cells -, was determined by sequence analysis. The gene comprises an uninterrupted coding region of 204 nucleotides encoding a protein of 8.9 kD. Like for other yeast ribosomal protein genes that have been sequenced so far, a relatively strong codon bias was observed. By S1 nuclease mapping the 5' end of the S33 mRNA was shown to be located at 11 to 15 nucleotides upstream from the initiation codon.

Amino Acid Sequence↗
PubMed1983

The histone H1 complements of dividing and nondividing cells of the mouse.

In liver, kidney, and lung of the mouse, two of the major H1 subtypes present at 1 week after birth, H1a and H1b, decline to nearly undetectable levels by 8-16 weeks, and a third subtype, H1d, also diminishes. The amounts of two other H1 subtypes, H1e and H1 degrees, increase markedly and that of another, H1c, also increases. The disappearance of H1a is almost complete by the age of 4 weeks, whereas the decline in H1b occurs largely between 4 and 16 weeks, when most cells are nondividing. A decline in H1a was observed also in cultured mouse embryo fibroblasts after they became quiescent. Furthermore, in the quiescent fibroblasts, the synthesis of H1a and H1b was preferentially reduced. In the thymus, newly formed nondividing cells have as much H1a and H1b as the dividing cells from which they are derived, but circulating lymphocytes have less H1a and H1b and more H1e, indicating that molecules of H1a and H1b are removed from chromatin, and H1e deposited, after cell division ceases. H1 degrees, however, is not present in thymocytes or peripheral blood lymphocytes. Our results indicate that 1) there are no tissue-specific H1 subtypes among the somatic tissues examined; 2) H1a and H1b are synthesized in large amounts only in dividing cells, whereas H1c, H1d, and H1e are synthesized in both dividing and nondividing cells; 3) different H1 subtypes are degraded at different rates in nondividing cells; and 4) H1e always, and H1 degrees sometimes, accumulates in nondividing somatic cells. We conclude that alterations of the H1 composition of chromatin are a general feature of nondividing cell formation; that such alterations are made, in large part, after the nondividing cells are formed and are accomplished both by changes in the pattern of synthesis of the various H1 subtypes and by differential loss of subtypes; and that each H1 subtype differs from the others in some or all of the properties that we have examined, supporting the idea that the individual H1 subtypes differ from each other in some of their functions.

Aging↗
PubMed1983

Locus of control and control perceptions and the relationship between life stress and psychological disorder.

This study tested the effects of life stress and variables hypothesized to moderate these effects using a multivariate hierarchical regression model. College undergraduates served as subjects. The variables of life stress, dispositional locus of control beliefs, perceptions of control over life event outcomes and psychological disorder were measured at two points in time. At both measurement periods, negative life events were significantly related to psychological disorder. This relationship was found even when initial psychological disorder was statistically controlled. Dispositional locus of control beliefs and control perceptions failed to moderate the effects of life events at either measurement period. Control perceptions appeared to be more a function of event characteristics than subjects' dispositional characteristics, given that these perceptions were unrelated to locus of control beliefs and that the outcomes of negative events were consistently viewed as less controllable than those of positive events. The findings support the relationship between life stress and psychological disorder but they call into question the moderating effects of locus of control beliefs and perceptions of control over life event outcomes.

Adaptation, Psychological↗
PubMed1983

"Red herrings," adolescents, and testicular tumors.

Testicular tumors, although rare in the general population, comprise the most common class of solid tumors in males aged 15-34 years. Although commonly appearing as a painless scrotal mass, one-third of testicular tumor cases are accompanied by pain or other atypical symptoms that may confound diagnosis, particularly if the clinician is misdirected by other issues. In this case report of an adolescent male with embryonal cell carcinoma of the right testis, a premorbid history of psychological problems, and immature, complaining behavior led to an improper assessment of the significant clues in the patient's oral history and a delay in diagnosis.

Adolescent↗
PubMed1983

Mental health quality assurance. Development of the American Psychological Association/CHAMPUS program.

In this article, quality assurance efforts in the field of mental health are discussed, especially concerning the reviews of outpatient clinical services. The recently established American Psychological Association APA/CHAMPUS program is described in detail, a national program of peer review that is illustrative of the major conceptual and professional issues inherent in the mental health quality assurance process. Throughout the article, comparisons are made between quality assurance in the medicine and mental health fields.

Community Mental Health Centers↗
PubMed1982

The structure of the gene coding for the phosphorylated ribosomal protein S10 in yeast.

From previous studies on cloned yeast ribosomal protein genes we obtained evidence that a large number of them contain an intron [Bollen et al. (1982) Gene 18, 29-38]. In the temperature-sensitive rna2-mutant transcription of these genes leads to the accumulation of precursor RNAs at the restrictive temperature. These precursor mRNAs are several hundreds of nucleotides longer than the respective mature mRNAs. The split character of one of these ribosomal protein genes, viz. the gene coding for the major phosphorylated small-subunit protein S10, was further established by sequence analysis. The intervening sequence interrupts the coding sequence after the second codon and has a length of 352 nucleotides. Genomic Southern hybridizations with a DNA fragment carrying part of the S10-gene revealed that this gene is duplicated on the yeast genome. The molecular weight of S10 as deduced from the sequence analysis was estimated to be 31462 dal. Comparison of the N-terminal aminoacid sequence of the yeast ribosomal protein S10 with that of ribosomal protein S6 from rat liver revealed a striking homology between both proteins. Moreover, at the C-terminal end of the yeast ribosomal protein the sequence Arg-Ala-Ser-Ser-Leu-Lys is present which is very similar to the phosphorylation site of the rat liver protein S6.

Amino Acid Sequence↗
PubMed1982

The H1 histones and their interphase phosphorylated states in differentiated and undifferentiated cell lines derived from murine teratocarcinomas.

The histone H1 fraction from the murine embryonal carcinoma cell line F9 can be resolved by two-dimensional gel electrophoresis into at least 15 components. Ten of these components incorporate 32P from administered orthophosphate. The digestion of 3H- and 32P-labeled samples with alkaline phosphatase indicates that this cell line has at least five H1 subtypes, three of which have not been observed in the mouse before. Every subtype is phosphorylated to some extent. There are, however, striking differences among them in the degree of phosphorylation in interphase, both in the proportion of molecules present as phosphorylated forms and in the numbers of phosphate groups per molecule. Phosphorylations of two types are discernible; most phosphorylations do not significantly affect the mobility of the protein in sodium dodecyl sulfate-containing gels but one does, probably reflecting a phosphorylation-induced alteration in protein conformation. Four subtypes undergo only the first type of phosphorylation; the other subtype undergoes both types of phosphorylation. The same 5 subtypes are also present in two other independently derived embryonal carcinoma cell lines. In contrast, two differentiated (endoderm-like) cell lines derived from teratocarcinomas lack H1b, and one also lacks H1d. Our results are consistent with the view that the H1 subtypes differ from each other functionally. They also show that neither H1b nor H1d is essential for cell division.

Animals↗