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S Levy

Publications and source records attributed to S Levy.

At least 271 records · Page 15Linked to original sources
PubMed1982

Beta-methyl[1-11C]heptadecanoic acid: a new myocardial metabolic tracer for positron emission tomography.

We have tagged heptadecanoic acid with C-11 at the carboxyl group and have inserted a methyl radical in the beta position to inhibit beta oxidation of the fatty acid; we have then explored the tracer's potential as an indicator of myocardial metabolism for use with the positron tomograph. In this preliminary evaluation, biodistribution studies were made in rats and dogs, and imaging of normal and infarcted dogs was performed. At 30 min the tissue distribution studies in rats and dogs showed, respectively, 1.9% and 8.3% uptake in the heart. Sequential images of the canine heart exhibited a remarkable uptake, peaking at 16-18 min and retaining the same level of activity over the one-hour study period. Images of the heart after LAD ligation showed an area of diminished uptake corresponding to the region of infarction. Thus this agent has the basic properties required for potential use in the assessment and quantitation of free fatty-acid metabolism in the heart in a manner similar to the measurement of glucose metabolism in the brain with 2-[18F]fluoro-3-deoxy-D-glucose.

Animals↗
PubMed1981

[Cerebral emboli due to subclinical heart disease. Value of thorough investigations (author's transl)].

In a series of 250 cases of cerebral vascular accident, the authors have selected 12 patients whose embolus appeared to have originated in the heart, although this could not be confirmed by clinical examination, ECG, Holter system monitoring and echocardiographic studies. Angiocardiography, complemented or not by His bundle exploration and/or coronary arteriography, revealed the presence of a heart disease likely to produce emboli in 11 cases, and in 8 cases, this was prolapsed mitral valve. These 11 cases represent 4.5% of the whole series and 22% of cases with emboli of suspected cardiac origin. Thorough cardiological studies, therefore, seem to be justified in young adults presenting with stroke. The high incidence of prolapsed mitral valve is in keeping with recently published data.

Adolescent↗
PubMed1981

Monocistronic transcription is the physiological mechanism of sea urchin embryonic histone gene expression.

We have examined histone gene expression during the early stages of sea urchin embryogenesis. The five histone genes expressed at that time are contained in tandem repetitive segments. It has been suggested that adjacent coding regions and their intervening spacer sequences are transcribed into large polycistronic messenger ribonucleic acid (RNA) precursors. We have subcloned into pBR322 deoxyribonucleic acid (DNA) sequences mapping either in the coding region, the 5' spacer, or the 3' spacer of the H2B histone gene. These clones were used to produce radioiodinated hybridization probes. We measured the steady-state quantity of H2B messenger RNA as well as spacer-specific RNA in the total RNA from embryos taken at various stages of development from fertilization to hatching of blastulae (0 to 22 h post-fertilization). Small amounts of RNA hybridizing to both spacer probes could be found. However, we show that these RNAs form mismatched hybrids with the spacer DNA and therefore cannot originate from the spacers present in the histone genes. We conclude that there is no detectable transcription of the spacer regions on either side of the H2B histone gene. The detection limit for RNA complementary to the 5' spacer sequence corresponds to a maximum of about three RNA molecules per cell, an amount shown to be far less than the projected steady-state pool size of a putative polycistronic transcript, if such a precursor were to be the obligatory transcript of the histone genes. (This conclusion was derived by using the known rates of production of H2B mRNA throughout early development [R. E. Maxson and F. H. Wilt, Dev. Biol., in press].) The physiologically relevant transcript of the histone genes in early development is therefore monocistronic and probably identical to the messenger RNA itself.

Animals↗
PubMed1980

Leader sequences of Strongylocentrotus purpuratus histone mRNAs start at a unique heptanucleotide common to all five histone genes.

We have determined the sequence of the untranslated leader nucleotides of all five histone mRNAs from Strongylocentrotus purpuratus by the dideoxy chain termination method. Total polysomal RNA from sea urchin embryos was used as a substrate for cDNA synthesis primed by specific DNA restriction fragments. Each of the primers was derived from the 5'-terminal part of the coding region for a different histone protein. The five histone mRNA leader sequences are different in length and primary structure. The 5' termini of all five histone mRNAs coincide with the unique heptanucleotide Py-Py-A-T-T-C-Pu in genomic DNA. This sequence, which defines the start of the individual histone mRNAs, is preceded by the A+T-rich octanucleotide identified in front of all eukaryotic structural genes where sequences have been determined to date.

Animals↗
PubMed1980

Alternate ventriculoatrial Wenckebach conduction.

Three cases are presented showing retrograde alternate Wenckebach periods. Retrograde alternate Wenckebach periods were defined as 2:1 ventriculoatrial (VA) block in which the conducted beats showed progressive prolongation of conduction (VA) time. The sequence terminates with two or three successively blocked ventricular beats. In one of the three cases the level of block was identified as being in the atrioventricular (AV) node. In the other two the level of block could not be clearly identified. This report provides further evidence for the concept of multilevel block within the AV node. Retrograde alternate Wenckebach periods may explain some instances of variation of atrial depolarization intervals during episodes of ventricular tachycardia and may be clinically significant.

Aged↗
PubMed1980

[Auriculo-Hisian conduction of patients with bundle branch block. Clinical significance].

The clinical and electrophysiological data in 52 consecutive patients with bundle branch block and followed-up for an average period of 20.8 +/- 10.4 months was reviewed. The patients were divided into two groups: Group A with normal AH intervals (36 patients) and Group B with prolonged AH intervals (16 patients). These two groups differed in age, the average being higher in Group B (p < 0.05), in history of syncope (more common in Group A: p < 0.01) and in the duration of PR interval (p < 0.05). On electrophysiological investigation the Wenckebach point was lower in Group B (118 +/- 29 ms) than in Group A (160 +/- 33) (p < 0.001). The effective right atrial refractory period was significantly longer in Group B (321 +/- 111 ms) than in Group A (246 +/- 59 ms) (p < 0.05). The effective refractory period of the atrioventricular node was also significantly longer in Group B (492 +/- 190 ms) than in Group A (333 +/- 125 ms (p < 0.05). On the other hand, there was no significant difference in the HV interval or in the number of patients managed by permanent pacing.

Atrioventricular Node↗
PubMed1979

Rapid purification of biologically active individual histone messenger RNAs by hybridization to cloned DNA linked to cellulose.

We describe a rapid and simple method for the purification of biologically active messenger RNAs. The method allows the isolation in a few hours of specific mRNAs from either whole cell or polysomal RNA even if the RNA represents less than 1% of the starting molecules. We used, as a model, cloned sea urchin (Strongylocentrotus purpuratus) histone gene fragments linked to cellulose by the method of B. E. Noyes & G. R. Stark (1975) Cell 5, 301--310) as hybridization probes to isolate specific histone mRNAs from whole cell and polysomal RNA extracts. RNAs isolated in this manner maintain their biological activity, serving as templates for histone proteins in a wheat-germ, cell-free protein translation system. In addition, radiolabeled histone-specific RNA purified from cleavage stage sea urchin embryos, pulse labeled for short periods of time and analyzed on denaturing polyacrylamide gels, was the same size as mature histone mRNA's.

Animals↗
PubMed1979

Vasectomy as an outpatient procedure.

The technique of vasectomy performed at Groote Schuur Hospital on 250 men under local anesthesia is detailed. The importance and extent of adequate counselling are outlined. The procedure is acceptable, effective and safe, and complications have been minor and transient.

Adult↗
PubMed1979

Normal and benzo(a)pyrene-transformed fetal mouse brain cell. I. Tumorigenicity and immunochemical detection of glial fibrillary acidic protein.

Primary cultures of whole brain and cortex cells origination from 14-day-old A/Jax or C3H mouse fetuses were treated with benzo(a)pyrene (B(a)P) for 24 h. After 7 to 8 passages a malignant transformation was observed in the chemically treated whole brain and cortex cultures. Control cultures of cortex remained non-transplantable during the whole experiment (up to 14 passages) whereas in the control cultures originating from whole brain a spontaneous transformation appeared after 11 passages. With horseradish peroxidase-labelled antibody, the specific glial fibrillary acidic protein (GFAP) was detected in both control and transformed total brain and cortex cultures, and in the tumors initiated by the in vitro transformed cells. This finding shows that glialike cells persisted after a long in vitro maintanance and transformation.

Animals↗