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Biomedical subjects

R Gelfand

Publications and source records attributed to R Gelfand.

At least 37 records · Page 2Linked to original sources
PubMed1981

Synthesis and turnover of mitochondrial ribonucleic acid in HeLa cells: the mature ribosomal and messenger ribonucleic acid species are metabolically unstable.

The synthesis rates and half-lives of the individual mitochondrial ribosomal ribonucleic acid (RNA) and polyadenylic acid-containing RNA species in HeLa cells have been determined by analyzing their kinetics of labeling with [5-3H]-uridine and the changes in specific activity of the mitochondrial nucleotide precursor pools. In one experiment, a novel method for determining the nucleotide precursor pool specific activities, using nascent RNA chains, has been utilized. All mitochondrial RNA species analyzed were found to be metabolically unstable, with half-lives of 2.5 to 3.5 h for the two ribosomal RNA components and between 25 and 90 min for the various putative messenger RNAs. A cordycepin "chase" experiment yielded half-life values for the messenger RNA species which were, in general, larger by a factor of 1.5 to 2.5 than those estimated in the labeling kinetics experiments. On the basis of previous observations, a model is proposed whereby the rate of mitochondrial RNA decay is under feedback control by some mechanism linked to RNA synthesis or processing. A short half-life was determined for five large polyadenylated RNAs, which are probably precursors of mature species. A rate of synthesis of one to two molecules per minute per cell was estimated for the various H-strand-coded messenger RNA species, and a rate of synthesis 50 to 100 times higher was estimated for the ribosomal RNA species. These data indicate that the major portion of the H-strand in each mitochondrial deoxyribonucleic acid molecule is transcribed very infrequently, possibly as rarely as once or twice per cell generation. Furthermore, these results are consistent with a previously proposed model of H-strand transcription in the form of a single polycistronic molecule.

Deoxyadenosines↗
PubMed1981

Return to work after myocardial infarction in a lower socioeconomic population.

A retrospective study of the work status of 45 consecutive male patients who were at least 12 months post myocardial infarction was carried out. The vast majority of patients were in the lower socioeconomic classes. Only 31 percent of those previously working returned to employment. No differences were found in mean age, physical disability, or anxiety; however, those not working were significantly more depressed (P < .05). A major factor related to failure to return to work may be that the majority of this lower socioeconomic group of patients worked as laborers and did not have the education or training to find alternative jobs.

Adult↗
PubMed1980

The tRNA genes punctuate the reading of genetic information in human mitochondrial DNA.

A detailed transcription map of HeLa cell mitochondrial DNA (mtDNA) has been constructed by using the S1 protection technique to localize precisely the sequences coding for the ribosomal RNA (rRNA) and poly(A)-containing species on the physical map of the DNA. This transcription map has been correlated with the positions of the tRNA genes derived from the mtDNA sequence. It has been shown that, with the exception of the D loop and another small segment near the origin of replication, the mtDNA sequences are completely saturated by the rRNAs, poly(A)-containing RNAs and tRNA coded for by the two strands. No evidence for intervening sequences has been found. The sequences coding for the individual poly(A)-containing RNA and rRNA species appear to be immediately contiguous on one side, and most frequently on both sides, to tRNA coding sequences. Furthermore, the H strand sequences coding for the two rRNAs, the poly(A)-containing RNAs and the tRNAs appear to be adjacent to each other, extending from coordinate 2/100 to coordinate 95/100 of the genome relative to the origin taken as 0/100. The results are consistent with a model of transcription of the H strand in the form of a single molecule which is processed into mature RNA species by precise endonucleolytic cleavages, occurring in almost all cases immediately before and after a tRNA sequence. The tRNA sequences may play an important role as recognition signals in the processing of the primary transcripts.

Chromosome Mapping↗
PubMed1980

Psychiatric consultation to a general hospital medical evaluation service.

Psychiatric consultation to a general hospital medical evaluation service was reviewed and compared with consultation patterns for general hospital inpatients and psychiatric emergency service patients. Results of a questionnaire survey indicated nearly 1 in 5 patients admitted to this acute medical service (24-hour maximum stay) required psychiatric consultation. A study of those patients seen by psychiatric consultants is reported. The prevalence of depressive illness as well as the psychiatric hospitalization referral rate was substantially greater than in general hospital inpatient or psychiatric emergency service evaluations. The implications of this relatively new area of consultation-liaison for hospital staffing and medical education are discussed.

Adolescent↗
PubMed1980

Human respiratory control at high ambient pressures and inspired gas densities.

Four men, exposed to the pressure equivalent of 1,200 ft of seawater (37 ATA) for 6 days in a CO2-free, normoxic helium-oxygen environment (Predictive Studies III-1971, Aviation Space Environ. Med. 4: 843-855, 1977), had no evident respiratory distress at work, at rest, or asleep. Ventilatory responses of two men to CO2 were measured in 20-min acute exposures to mixtures of oxygen (173 Torr) with nitrogen, crude neon, and helium over a gas density range of 0.4-22 g/l and a pressure range of 1-37 ATA during stepwise compression of 37 ATA. Analysis of delta V/delta PACO2 as functions of pressure, of density, and of density-to-viscosity ratios shows that increased gas density, but not nitrogen narcosis, is associated with gross diminution of the ventilatory response to CO2. A small ventilatory response to CO2 is predicted for liquid breathing when viscosity is included as a parameter in the analysis. Other findings associated with increased gas densities and progressive elevation of inspired CO2 concentration are disruption of the normal patterns of tidal volume and frequency of breathing and reduction in the range of linear respiratory response to CO2.

Adult↗
PubMed1980

Speech intelligibility at high helium-oxygen pressures.

Word-list intelligibility scores of unprocessed speech (mean of 4 subjects) were recorded in helium-oxygen atmospheres at stable pressures equivalent to 1600, 1400, 1200, 1000, 860, 690, 560, 392, and 200 fsw daring Predictive Studies IV-1975 by wide-bandwidth condenser microphones (frequency responses not degraded by increased gas density). Intelligibility scores were substantially lower in helium-oxygen a 200 fsw than in air at l ATA, but there was little difference between 200 fsw and 1600 fsw. A previously documented prominent decrease in intelligibility of speech between 200 or 600 fsw because of helium and pressure was probably due to degradation of microphone frequency response by high gas density.

Adult↗
PubMed1979

Surreptitious use of warfarin.

The authors present the case of a 61-year-old woman who became increasingly sensitive to her warfarin. When she remained anticoagulated during a 2-month period off of warfarin a plasma analysis detected warfarin indicating she was taking the anticoagulant surreptitiously. This patient demonstrated features of factitious illness including a background of unsatisfactory childhood relationships, average intelligence, a lack of psychosis, and no obvious secondary gain. Surreptitious use of anticoagulants should be considered in all cases of unexplained hemorrhagic symptoms with low prothrombin activity.

Denial, Psychological↗
PubMed1979

Effects of gas density on the frequency response of gas-filled pressure transducers.

The effects of gas density on the frequency responses of four pressure transducers were determined at gas densities from 1.2 to 25.0 g/l. Transducers tested included three sensitive differential types used with pneumotachographs to measure respiratory flow (Validyne DP-45 and DP-103; Medistor P-11) and a transducer commonly used to measure esophageal pressure (Statham P23Dd). Three different responses were obtained. The Validyne DP-103 was overdamped and its response was essentially independent of gas density. The frequency response of this transducer is adequate for use with quiet breathing only. The Validyne DP-45 and Medistor P-11 responses were underdamped. The resonant peaks of these transducers decreased markedly in frequency as the gas density increased. The Statham P23Dd was also underdamped; however, its resonant frequency increased as gas density increased. An esophageal balloon did not alter the frequency response characteristics of this tubing-transducer system. Both increases in length and decreases in diameter of connecting tubing reduced the frequency of resonant peaks of underdamped pressure transducers.

Atmospheric Pressure↗
PubMed1979

Tremor and somatosensory studies during chamber He-O2 compressions to 13.1, 25.2, 37.3, and 49.4 ATA.

Comparison was made between intentional and postural tremor amplitudes with a 2-to 50-Hz bandwidth in four men rapidly compressed from surface to 13.1, 25.2, and 37.3 ATA in 4 h while breathing helium-oxygen mixtures (Predictive Studies IV, University of Pennsylvania). Excursions with compression rates of 20 and 40 ft/min were then made to 49.4 ATA on exposure days 2 and 3, returning to saturation at 37.3 ATA for 6 additional days. During compression from 25.2 to 37.3 ATA, there were increases in tremor amplitudes for both intentional and postural tremor in the 3-to 7-Hz and 8- to 12-Hz ranges. Both types of tremor showed increases in amplitudes at 49.4 ATA on exposure days 2 and 3. Amplitude changes in postural tremor, which occurred only on the fastest compression to 49.4 ATA, were less evident than those in intentional tremor during the remaining dive profile, and adaptation to pressure exposure could be defined by day 8. Intentional tremors did not show adaptation at pressure.

Adult↗
PubMed1978

Visual evoked cortical potentials in men during compression and saturation in He-O2 equivalent to 400, 800, 1200 and 1600 feet of sea water.

Visual evoked cortical potentials and related EEG activity were recorded from subjects during rapid compression and exposure to pressures of 400, 800, 1200 and 1600 fsw. In one phase, subjects made repeated excursions to 1200 fsw from a base at 800 fsw; in the second phase, the saturated base was 1200 fsw with excursions to 1600 fsw. The results included: (1) For the visual evoked potentials, sizeable and significant decreases in amplitude and increases in latency of the response with depth; (2) Changes in the visual evoked potentials which varied systematically with depth but not with related changes in compression rate or decompression. The changes were small but consistent alterations of normal responses to visual stimulation; and (3) Theta activity in discrete EEG recordings increased progressively with depth. With all subjects showed increases in theta activity the pattern of increase varied individually.

Alpha Rhythm↗
PubMed1976

Pneumotachograph for flow and volume measurement in normal and dense atmospheres.

Measurement of ventilatory flow during pulmonary function maneuvers and in severe exercise by the pneumotachograph flow transducer in dense atmospheres is handicapped by the inverse relationship between the linear range of such transducers and gas density. This limitation in the usefulness of the pneumotachograph can be overcome by mounting such flow transducers in parallel and taking into account the reduction in peak ventilatory flow transducers in parallel and taking into account the reduction in peak ventilatory flow which occurs with increasing density. The design of such assemblies, their static performance characteristics, and a drift subtractor, constructed to stabilize the output of the pneumotachograph pressure transducer, are described.

Atmospheric Pressure↗