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Biomedical subjects

B Levy

Publications and source records attributed to B Levy.

At least 163 records · Page 9Linked to original sources
PubMed1981

Study of relations between arterial oscillation period and heart rate.

This study was performed to determine the relationship between variations of arterial cross-section and cardiac period. Relative section variations were recorded by impedance rheography. In 176 anesthetized adult mongrel dogs, aortic and femoral rheograms, femoral pressure, and ECG were recorded. The cardiac period (Tc) and the interval between the systolic and the dicrotic wave, i.e., the arterial intrinsic period (Ta), were measured and related to each other (Tc/Ta ratio). In 125 dogs, the dicrotic wave appeared spontaneously. In these cases Tc/Ta 1.98 +/- 0.16. In 51 dogs, no dicrotic wave appeared spontaneously. Lengthening of cardiac period was obtained in 25 of these dogs by vagus stimulation. As related to the cardiac period before vagal stimulation Tc/Ta was then 0.98 +/- 0.08. In the remaining 26 dogs, such a lengthening was obtained by inducing a premature ventricular depolarization. In this group, Tc/Ta was 1.00 +/- 0.03. The results of the present study suggest that a constant adaptation exists between ventricular ejection and arterial dynamics. The physiologic implications are discussed.

Animals↗
PubMed1980

The effect of particle size on the osteogenic activity of composite grafts of allogeneic freeze-dried bone and autogenous marrow.

This study was carried out to determine if particle size is a factor to be considered in the evaluation of the osteogenic activity of freeze-dried bone allografts (FDBA) and, if so, whether small particles enhance or inhibit osteogenesis. Small particle FDBA (100-300 microns) plus marrow and large particle FDBA (1000-2000 microns) plus marrow were placed in plexiglass diffusion chambers secured to the femurs of six Rhesus monkeys. Control chambers contained either marrow alone or were left empty. Two animals were given injections of oxytetracycline hydrochloride at 5 and 7 weeks to obtain intravital osseous labeling. All chambers were removed after 8 weeks. Ten chambers were evaluated for new bone formation by fluorescent microscopy. The contents of 15 additional chambers were evaluated by single blind technique for presence or absence of bone resorption and ossification. The results indicated that there was significantly more new bone formation associated with small particle FDBA (100-300 microns) plus autogenous marrow than with large particle FDBA (1000-2000 microns) plus autogenous marrow. In addition, small particle FDBA (100-300 microns) plus autogenous marrow tended to display more resorption than large particle FDBA (1000-2000 microns) plus autogenous marrow. It was concluded that within the parameters of this study, small particles of FDBA enhance osteogenesis. This study also demonstrated that particle size is a variable to be considered when comparing the osteogenic potential of freeze-dried bone allografts.

Animals↗
PubMed1979

Angel dust use in an outpatient setting--clinical profile and implications for treatment.

The study attempts to identify two populations of 20 young people who are self-reporting marijuana use in one group and angel dust in the other. We have examined these populations and evaluated them on a series of variables in an attempt to discover whether there are significant differences between them and, if so, whether there is in fact a clinical profile which may be descriptive of nonacute reactions to angel dust. Results indicate that there are significant differences on variables that distinguish angel dust users in an outpatient setting.

Adolescent↗
PubMed1978

In vitro transcription of heat-shock-specific RNA from chromatin of Drosophila melanogaster cells.

Polyadenylylated RNA synthesized after heat shock was isolated from polysomes of cultured cells of Drosophila melanogaster and used as template to prepare cDNA. An excess of poly(A)-RNA from heat-shocked cells hybridized to 80% of the cDNA, whereas cytoplasmic poly(A)-RNA from cells grown at 25 degrees could drive only half of the cDNA probe into hybrid. These sequences were removed from the cDNA population by annealing to poly(A)-RNA from cells grown at 25 degrees. The unreacted material represented only heat-shock-induced mRNA sequences, as shown by a second cycle of hybridization. Isolated chromatin was transcribed in vitro at 25 degrees with Escherichia coli RNA polymerase, with mercurated UTP as precursor. RNA transcribed from chromatin that was prepared from cells 1 hr after the temperature was shifted to 37 degrees hybridized with 100-fold faster kinetics to the heat-shock-specific cDNA probe than did RNA transcribed from chromatin of cells grown at 25 degrees. Therefore, heat shock results in a change in chromatin structure recognizable by E. coli RNA polymerase.

Cells, Cultured↗
PubMed1978

Seroconversion against Epstein-Barr virus in two nonhuman primate species infected by the oropharyngeal route.

Transforming Epstein-Barr virus (EBV) was inoculated into eight squirrel monkeys (Saimiri sciureus) by spraying of viral concentrates into the nose and throat. Virus was inoculated into three marmosets (two Saguinus oedipus and one Calithrix jacchus jacchus) by direct injection into nasopharyngeal tissue. Two of these squirrel monkeys seroconverted after repeated inoculation as determined by the presence of EBV-specific antibodies to early antigen and viral capsid antigen. One squirrel monkey had antibody to EBV nuclear antigen only. One S. oedipus marmoset also seroconverted. None of the animals developed disease. The results show that seroconversion can be accomplished in squirrel monkeys after spraying of EBV into the nasopharynx, and in marmosets by direct inoculation of the virus into nasopharyngeal tissue.

Aerosols↗
PubMed1978

Partial purification of transcriptionally active nucleosomes from trout testis cells.

Mononucleosomes (MN1) enriched in structural non-histone proteins and transcribed DNA sequences were obtained by limited digestion of trout testis nuclei with micrococcal nuclease followed by selective solubilization in 0.1 M NaCl. These monosomes consist of the four inner histones plus stoichiometric amounts of the non-histone protein H6, of the HMG group, complexed with 140 base pairs of DNA. Hybridization experiments indicate that MN1 DNA is enriched in sequences complementary to cytoplasmic polyadenylated RNA.

Animals↗
PubMed1977

Impedance rheography: a new method for recording spontaneous arterial section variation.

The aim of this work is to define, on the basis of impedance rheography, a method to record arterial section variations without either inertia or the production of wall-strain. High frequency current (2 MHz) is employed to measure the impedance variations of the deforming artery. The modulating envelope is representative of arterial section variations. This method permits the recording of arterial section variations by a peri-arterial method or an external method on superficial arteries (without denudation). A comparison between arterial section variations and arterial pressure variations at the same point shows that the arterial wall behaves as a non-linear pressure gauge: Rheogram-pressure curves are similar to volume-arterial pressure curves. The great precision with which this method describes the chronology of arterial deformations is of great interest in defining viscous properties of the arterial wall and following their evolution during pathologic alterations such as atherosclerosis.

Animals↗
PubMed1977

A hardware device for recognition of P and QRS waves.

A new hardware device has been constructed to detect QRS and P complexes for the purpose of automatic arrhythmia interpretation. This apparatus can operate in noisy conditions and provide synchronized pulses representative of P complex, QRS complex, wide QRS, and premature QRS to different output channels. P wave identification is achieved with a high degree of reliability through a specially designed bipolar electrode catheter. The device could minimize demands on central processor time and core storage computer.

Arrhythmias, Cardiac↗
PubMed1977

Diversity of sequences of polyadenylated cytoplasmic RNA from rainbow trout (Salmo gairdnerii) testis and liver.

We have compared the sequence complexity and diversity of polyadenylated cytoplasmic RNA derived from two differentiated trout tissues: liver and testis. The kinetics of hybridization of polyadenylated RNA from each of these tissues with complementary DNA synthesized by reverse transcriptase revealed three abundance classes for liver RNA, the first comprising 4 sequences, the second 120, and the third, 20 000; in contrast, testis RNA showed only two abundance classes containing 6 and 6100 different RNA sequences, respectively and of average length 6 x 10(5) daltons. The extent of overlapping among those two RNA populations was further studied by performing heterologous annealing reactions between cDNA and a vast excess of mRNA. Liver mRNA was complementary to 80% of the testis cDNA. Conversely, testis mRNA reacted with only 25% of the liver cDNA. Experiments with fractionated cDNA probes indicated that the unshared sequences belonged mainly to the less frequent, most complex, class of mRNAs.

Animals↗
PubMed1977

The efficacy and safety of furosemide and a combination of spironolactone and hydrochlorothiazide in congestive heart failure.

The therapeutic and biochemical effects of two commonly employed diuretic preparations were compared in a double-blind fashion in 32 patients with congestive heart failure. At the doses employed, furosemide and a fixed combination of spironolactone and hydrochlothiazide maintained control of the clinical manifestations of congestive heart failure to about the same degree. However, significant biochemical changes in the renin-aldosterone system were found in patients receiving the spironolactone/thiazide combination therapy. A significant increase in plasma renin activity and a significantly greater increase in aldosterone excretion were found in the spironolactone/thiazide group compared to the furosemide group. No significant differences were observed in serum potassium levels or 24-hour potassium excretion rates in patients treated with the two diuretic preparations.

Adult↗
PubMed1977

Renaturation kinetics of cDNA complementary to cytoplamic polyadenylated RNA from rainbow trout testis. Accessibility of transcribed genes to pancreatic DNase.

We have determined the fraction of polyadenylated cytoplasmic RNA from trout testis complementary to unique and repetitive DNA. Some 21% of the cDNA probe representative of this RNA population renatures with rapid kinetics, characteristics of repetitive sequences. The major proportion of the cDNA renatures with unique sequence DNA. Experiments with fractionated cDNA probes allow us to conclude that, in trout testis, the most abundant polyadenylated mRNAs are not preferentially transcribed from repetitive DNA, as it has shown to be the case in two eukaryotic cell lines. Treatment of trout testis nuclei with DNase I, under conditions in which 10% of the total DNA is digested, preferentially depletes the DNA of sequences being transcribed into polyadenylated mRNA. These data confirm the results of H. Weintraub and M. Groundine [(1976) Science 193, 848-856] and those of A. Garel and R. Axel [(1976) Proc. Natl. Acad. Sci. U.S.A. 73, 3966-3970] and suggest that the conformation of DNA in the active genes of chromatin is such that it is more susceptible to digestion by DNaseI.

Animals↗
PubMed1977

The value of vaginal cultures in general practice.

One hundred and eighty high risk cases in a hospital special treatment centre and 50 low risk cases of vaginal discharge from general practice were investigated by the cultural examination of vaginal secretion. The results show this procedure is of value in diagnosing sexually transmitted diseases.

Adolescent↗