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Biomedical subjects

L H Cohen

Publications and source records attributed to L H Cohen.

At least 91 records · Page 5Linked to original sources
PubMed1982

Ribosomal protein genes of yeast contain intervening sequences.

From a colony bank of HindIII-generated yeast DNA fragments we have isolated a number of recombinant DNAs carrying genes for ribosomal proteins (e.g., S10, S16A, S20, S24, S31, S33, L16, L25 and L34) of the yeast Saccharomyces carlsbergensis. By electron microscopic analysis of the R-loops formed between various DNA fragments and yeast mRNA, we could locate the ribosomal protein genes on the physical maps of the cloned DNA fragments. The R-loop structures observed indicate that a number of the ribosomal protein genes contain an intervening sequence.

Base Sequence↗
PubMed1982

Peer review of psychodynamic psychotherapy: generous versus restrictive reviewers.

American Psychological Association/CHAMPUS peer reviewers (N=168) evaluated clinical treatment reports that described psychodynamic treatment of middle-aged, depressed outpatients. Descriptive data are reported on the reviewer' recommendations concerning the reimbursement for previous and total (previous plus future) care. In addition, generous and restrictive reviewers are compared on their theorectical orientation, the self-reported factors affecting their review decisions, and their previously reported clinical practice patterns and attitudes toward psychological peer review. The implications of these findings for mental health quality assurance programs are discussed.

Health Benefit Plans, Employee↗
PubMed1982

Peer review of psychodynamic psychotherapy. Experimental studies of the American Psychological Association/CHAMPUS program.

Two factorial experiments examined the effects of reviewer theoretical orientation, documented treatment progress, and patient concurrence data on the peer review of clinical treatment reports that described long-term psychodynamic psychotherapy with a depressed, female outpatient. The experiments employed an unobtrusive methodology; peer reviewers believed that their evaluations would affect the disposition of actual mental health insurance claims. Subjects (n = 105) were American Psychological Association/Civilian Health and Medical Program of the Uniformed Services (CHAMPUS) peer reviewers of a psychodynamic, behavioral, or eclectic theoretical orientation. The psychodynamic reviewers, compared with the behavioral and eclectic reviewers, were more positive in their ratings of treatment and more generous in their future care reimbursement recommendations. Additionally, the data demonstrated that APA/CHAMPUS peer review was sensitive to reported treatment progress, and that reviewers of diverse orientations were equally responsive to documented progress in psychodynamic psychotherapy. The patient concurrence manipulation had little effect on the dependent measures. Implications for mental health quality assurance programs are discussed.

Health Benefit Plans, Employee↗
PubMed1981

Phosphorylation states of different histone 1 subtypes and their relationship to chromatin functions during the HeLa S-3 cell cycle.

The histone 1 (H1) fraction of HeLa S-3 cells contains two principal subtypes, H1A (Mr approximately 21 000) and H1B (Mr approximately 22 000). In G1 cells, the H1 molecules are distributed among several phosphorylation states, most H1A molecules containing 0 or 1 phosphate groups and most H1B molecules containing 0, 1, 2, or 3 phosphate groups. Both subtypes undergo a general increase in phosphorylation levels of approximately 1 P/mol during the S phase and a further increase or 3--4 P/mol during mitosis. These two increases affect most of the H1 molecules and thus reflect phosphorylations occurring widely throughout the chromatin, presumably in association with replication and mitotic chromosome condensation. During all these periods, multiple phosphorylation levels of H1 molecules persist, as does the phosphorylation differential between H1A and H1B. Thus, there appear to be phosphorylation states that only some of the H1 molecules occupy, a fact that may be related to the conformational diversity in interphase and mitotic chromatin. The existence of differences between H1A and H1B phosphorylation states throughout the cell cycle, and within a single cell type, is in accord with the hypothesis that the H1 subtypes are functionally distinct, such that subtype-specific phosphorylations contribute to the control of chromatin organization.

Cell Cycle↗
PubMed1981

Isolation of cloned ribosomal protein genes from the yeast Saccharomyces carlsbergensis.

A colony bank of yeast dna obtained by cloning HindIII-generated fragments of total yeast nuclear DNA in Escherichia coli K-12 with the vector pBR322, was screened with a radioactive RNA probe enriched for a subset of ribosomal protein mRNAs. The selected recombinant DNA molecules were hybridized with poly(A)-containing mRNA under R-loop conditions. From the DNA-RNA hybrids the respective mRNAs were melted off and translated in vitro in a rabbit reticulocyte cell-free system. The translational products were analyzed by immunoprecipitation with antibodies raised against ribosomal proteins. The identity of the ribosomal protein gene products was further established by electrophoresis on two-dimensional gels. At least 15 recombinant DNA molecules were shown to contain ribosomal protein genes. Four of them, i.e. Y65, Y89, Y113 and Y138, have been characterized preliminarily.

DNA, Fungal↗
PubMed1980

Isolation, properties and cellular distribution of D1, a chromosomal protein of Drosophila.

The protein D1 was obtained from nuclei of Drosophila melanogaster embryos and purified by perchloric acid fractionation and preparative gel electrophoresis. In nuclei its amount is approximately 1% of the amount of DNA by weight. D1 is soluble in 5% perchloric acid and extractable from nuclei by solutions of moderate ionic strength (0.35 M NaCl). Amino acid analysis shows that it is rich in both basic (20%) and acidic (27%) aminoacids. In all these properties D1 resembles HMG proteins (high mobility group; Johns et al., 1975) of vertebrates; however, its apparent molecular weight (approximately 50,000) is much higher. The distribution of D1 in salivary gland polytene chromosomes was investigated by immunofluorescence. Two levels of fluorescence intensity were observed: 1) Very bright fluorescence at chromosomal positions 81F, 83E, 101F, 102C and 102F; these sites are shown, by double labeling techniques, to coincide with quinacrine bright sites. 2) Medium to low fluorescence at many sites widely distributed throughout all chromosomes. In order to interpret these results and to relate them to the in vivo distribution of D1, we have investigated the pattern of immunofluorescence staining as a function of the methods of chromosome preparation and salivary gland fixation. The immunological specificity of the anti-D1 serum was studied by comparing its reactivity with D. melanogaster and D. virilis chromosome spreads and whole salivary glands, and by using reagents that minimize non-specific antibody interactions. We conclude that D1 is widely distributed throughout cytoplasm and nucleus, present in many chromomeres but most abundant in chromosomal sites that contain the AT-rich satellite DNA of density 1.672. This distribution, together with available evidence about the nucleotide sequences present in this satellite, suggests that D1 binds preferentially to chromatin containing sequences AATAT and/or AATATAT.

Amino Acids↗
PubMed1980

Control of active proton transport in turtle urinary bladder by cell pH.

The rate of active H+ secretion (JH) across the luminal cell membrane of the turtle bladder decreases linearly with the chemical (delta pH) or electrical potential gradient (delta psi) against which secretion occurs. To examine the control of JH from the cell side of the pump, acid-base changes were imposed on the cellular compartment by increasing serosal[HCO3-] at constant PCO2 or by varying PCO2 at constant [HCO3-]. When serosal [HCO3-] was increased from 0 to 60 mM, cell [H+] decreased, as estimated by the 5,5-dimethyloxazoladine-2,4-dione method. JH was a saturable function of cell [H+], with an apparent Km of 25 nM. When PCO2 was varied between 1 and 20% at various serosal Km of 25 nM. When PCO2 was varied between 1 and 20% at various serosal [HCO3-], the PCO2 required to reach a maximal JH increased with [HCO3-] so that JH was a function of cell [H+] rather than of cell [HCO3-] or CO2. The proton pump was controlled asymmetrically with respect to the pH component of the electrochemical potential for protons, microH. On the cell side of the pump, a delta pH of < 1 U was required to vary JH between maximal and zero values, whereas on the luminal side a delta pH of 3 U was required. Cell [H+] regulates JH by determining the availability of H+ to the pump in a relationship resembling Michaelis-Menten kinetics. Increasing luminal [H+] generates an energy barrier at a luminal pH near 4.4 that equals the free energy (per H+ translocated) of the metabolic driving reaction.

Acid-Base Equilibrium↗
PubMed1979

Pathways for bicarbonate transfer across the serosal membrane of turtle urinary bladder: studies with a disulfonic stilbene.

Bicarbonate is transferred across the serosal (S) membrane of the epithelial cells of the turtle bladder in two directions. Cellular HCO3- generated behind the H+ pump moves this membrane into the serosal solution. This efflux of HCO3- is inhibited by SITS (4-isothiocyano-4'-acetamido-2,2'-disulfonic stilbene). When HCO3- is added to the serosal solution it is transported across the epithelium in exchange for absorbed Cl-. This secretory HCO3- flow traverses the serosal cell membrane in the opposite direction. In this study the effects of serosal addition of 5 x 10(-4) M SITS on HCO3- secretion and Cl- absorption were examined. The rate of H+ secretion was brought to zero by an opposing pH gradient, and 20 mM HCO3- was added to S. HCO3- secretion, measured by pH stat titration, was equivalent to the increase in M leads to S Cl- flux after HCO3- addition. Neither the S leads to M flux of HCO3- nor the M leads to S flux of Cl- were affected by SITS. In the absence of electrochemical gradients, net Cl- absorption was observed only in the presence of HCO3- in the media; under such conditions, unidirectional and net fluxes of Cl- were not altered by serosal or mucosal SITS. H+ secretion, however, measured simultaneously as the short-circuit current in ouabain-treated bladders decreased markedly after serosal SITS. The inhibition of the efflux of HCO3- in series with the H+ pump and the failure of SITS to affect HCO3- secretion and Cl- absorption suggest that the epithelium contains at least two types of transport systems for bicarbonate in the serosal membrane.

Animals↗
PubMed1979

Long-term follow-up of the Hancock bioprosthetic heart valve: a 6-year review.

Clinical experience with the Hancock porcine bioprosthetic heart valve was reviewed in 467 patients (254 men and 213 women, 18--84 years old, average, 56 years) who received 528 valves from January, 1972, to January, 1978. Associated procedures, including coronary bypass graft, ascending aortic aneurysm, and valvuloplasty were done in 102 of the 467 patients (22%). The overall operative mortality was 25/467 (5.6%), 12/226 (5.3%) for aortic valve replacement (AVR), 11/183 (6%) for mitral valve replacement (MVR), and 2/58 (3.4%) for multiple valve replacement. The first 323 patients with a minimum follow-up of 16 months (16--75 months, average 33 months) were analyzed for survival and thromboemboli. Actuarial survival at 66--75 months was 75.7% for AVR, 79% for MVR, and 75.8% for multiple valve replacement. Emboli per 100 patient-years was 0.55 for AVR (no anticoagulants), 3.9 for MVR, and 4.8 for multiple valve replacement (anticoagulants for atrial fibrillation patients only); emboli occurred only in patients with atrial fibrillation. There were seven of 528 primary dysfunctional valves (1.3%): calcification in two, tissue failure in two, and fibrosis in three. A hemodynamic study of four patients with a 21 mm Hancock Modified Orifice aortic valve prosthesis showed improved orifice areas (greater than 1.3 cm2) over the standard aortic valve. The Hancock porcine xenograft bioprosthetic heart valve has been a durable heart valve in excess of 6 years and has a low associated incidence of thromboemboli in patients off anticoagulants except in those with chronic atrial fibrillation.

Adolescent↗
PubMed1979

The bias in psychotherapy research evaluation.

Using a 3 X 3 X 3 factorial design, clinical psychologists' (N = 204) evaluations were obtained of the methodology of a bogus psychotherapy outcome experiment that varied on the outpatient population treated and the results. Three types of neurotic outpatients were treated in the bogus study, and the experiment's results indicated that psychoanalytically oriented therapy was more effective than behavior therapy, behavior therapy was more effective than psychoanalytically oriented therapy, or psychoanalytically oriented therapy and behavior therapy were equally effective. The third independent variable was psychologists' theoretical orientation (psychodynamic, behavioral, or eclectic). A significant Orientation X Results interaction was obtained, and the results suggest that psychodynamic clinicians are biased against outcome research that demonstrates the superiority of behavior therapy.

Attitude of Health Personnel↗
PubMed1978

Two structurally closely related polypeptides encoded by 14-S mRNA isolated from rat lens.

14-S mRNA from rat lens codes for two subunits of alpha-crystallin, A2 (Mr 20 000) and AIns (Mr 24 000, previously referred to as alphaX). Structural relationship between both translation products has been proved by immunoprecipitation with antisera directed against the different crystallin classes. Competition immunoprecipitation showed that the 14-S mRNA translation products are precipitated by common antibodies, specific for the A subunit of alpha-crystallin. Two-dimensional gel electrophoresis and peptide analysis provided further evidence that the 24 000-Mr polypeptide, synthesized in vitro under direction of 14-S mRNA, is identical with native alphaAIns. Although the structures of alphaA2 and alphaAIns are very similar, no precursor-product relationship exists between both 14-S-mRNA-encoded polypeptides.

Animals↗
PubMed1978

Rat alpha-crystallin A chain with an insertion of 22 residues.

Rat lens alpha-crystallin contains, besides the usual alphaA and alphaB subunits, an additional minor chain. This subunit was purified by ion-exchange chromatography and its primary structure studied. It appeared to be an elongated alphaA-like chain, having an insertion of 22 residues between position 63 and 64 of an otherwise normal alphaA2 chain. Therefore this subunit was called alphaAIns, i.e. an alphaA chain with an inserted sequence. This inserted region, which contains three methionyl, five basic and no acidic residues, apparently results in an adequately functioning alphaAIns chain. The alphaAIns chain may be the product of a gene which has originated, after duplication of the alphaA gene, by insertion in one of the copies of a stretch of 66 nucleotides of unknown origin, or alternatively be the result of unusual transcription or processing of precursor mRNA (pre-mRNA), leaving an extra 66 nucleotides internally in the mRNA to be translated.

Amino Acid Sequence↗