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Biomedical subjects

J Greenberg

Publications and source records attributed to J Greenberg.

At least 199 records · Page 11Linked to original sources
PubMed1981

Nitrosoguanidine sequential mutagenesis mapping of Mycobacterium tuberculosis genes.

Nitrosoguanidine-induced mutations occur at higher frequencies at the replication region than at other nonreplicating regions of the chromosome. Cultures of Mycobacterium tuberculosis synchronized with phenylethanol were used to determine the order of replication for 10 genes controlling drug resistance. Use of M. tuberculosis provided a 10-h replication map with good resolution because of the slow rate of deoxyribonucleic acid replication. The direction of chromosome replication could not be determined, but this study indicated no pause between rounds of deoxyribonucleic acid replication in a rich medium.

Antibiotics, Antitubercular↗
PubMed1980

Direct effect of phenylethylamine upon isolated rat aortic strip.

Phenylethylamine (PEA) has been implicated in a number of central and peripheral nervous system disorders. Its possible mechanisms of action include stimulation via catecholamine release and direct stimulation by PEA. We have examined the effects of PEA on isolated vascular smooth muscle (VSM) to further explore the mechanism by which PEA produces contraction in this tissue. Helical strips of rat aorta were suspended in a muscle bath. Smooth muscle contractions were recorded via force transducer. PEA elicited a concentration dependent contraction from these strips with a threshold near 10(-6) M and a maximum response at 5 X 10(-3) M. Pretreatment of rats with reserpine dramatically reduced the norepinephrine (NE) content of kidney, heart and spleen of these animals but did not prevent the action of PEA on VSM. The presence of phentolamine (10(-4) M) completely blocked the strip response to PEA. The presence of propranolol (10(-7) or 10(-4) M) altered but did not block the VSM response to PEA. These results argue that the effects of PEA upon the aortic strip preparation involve a direct action of this amine upon VSM.

Animals↗
PubMed1979

The [18F]fluorodeoxyglucose method for the measurement of local cerebral glucose utilization in man.

A method has been developed to measure local glucose consumption in the various structures of the brain in man with three-dimensional resolution. [18F]-2-deoxy-2-fluoro-D-glucose is used as a tracer for the exchange of glucose between plasma and brain and its phosphorylation by hexokinase in the tissue. A mathematical model and derived operational equation are used which enable local cerebral glucose consumption to be calculated in terms of the following measurable variables. An intravenous bolus of [18F]-2-deoxy-2-fluoro-D-glucose is given and the arterial specific activity monitored for a predetermined period of from 30 to 120 minutes. Starting at 30 minutes, the activity in a series of sections through the brain is determined with three-dimensional resolution by an emission tomographic scanner. The method was used to measure local cerebral glucose consumption in two normal volunteers. The values in gray matter structures range from 5.79 mg/100 g per minute in the cerebellar cortex to 10.27 in the visual cortex, whereas, in white matter structures, the values range from 3.64 mg/100 g per minute in the corpus callosum to 4.22 in the occipital lobe. Average values for gray matter, white matter, and whole brain metabolic rates, calculated as a weighted average based on the approximate volume of each structure, are 8.05, 3.80, and 5.90 mg/100 g per minute, respectively. The value of 5.9 mg/100 g per minute compares favorably with values previously reported.

Adult↗
PubMed1979

Acute hydrocephalus in cerebellar infarct and hemorrhage.

Although cerebellar infarction was known at the turn of the century, not until 1956 was it realized that large cerebellar infarctions could cause acute obstructive hydrocephalus. There are many more reports of cerebellar hemorrhages. The clinical differentiation between hemorrhage and infarction was difficult prior to computerized tomography (CT). Cerebellar hemorrhage is a neurosurgical emergency, as are some cerebellar infarctions. We present three patients with acute hydrocephalus resulting from these vascular syndromes; they are first cases to be successfully treated by ventricular drainage and shunting. Four other cerebellar infarcts demonstrate the efficacy of CT.

Acute Disease↗
PubMed1978

The structure of the epididymis, efferent ductules and ductus deferens of the guinea pig: a light microscope study.

In the guinea pig, the narrow part of the epididymis that traverses the upper pole of the testis and passes downward over the entire length of the gonad is composed exclusively of efferent ductules and the initial segment (zone I) of the epididymal duct. At the beginning of zone II, the narrow contour of zone I expands into a large globular region which lies adjacent to the caudal pole of the testis. The globular region of the guinea pig epididymis is commonly referred to as the cauda epididymidis but in the present study, examination with the light microscope reveals that it is composed of five histologically distinct zones (zones III through VII). A detailed histological analysis of the characteristics of the epithelium in the seven zones of the guinea pig epididymis and in the efferent ductules and ductus deferens was udertaken to obtain a better understanding of structure-function relationships in the epididymis of the guinea pig. It was found that each of the zones could be readily distinguished on the basis of its histological features and primarily on the basis of the appearance of the principal cells.

Animals↗
PubMed1978

Resistance relationships in Mycobacterium smegmatis ATCC 607 to phages sensitive or resistant to both chloroform and streptomycin sulphate.

Four of eight mycobacteriophages did not form plaques after they were exposed to chloroform. Phages sensitive to chloroform did not produce plaques when plated on media containing 1000 microgram/ml of streptomycin sulphate. The same concentration of dihydrostreptomycin sulphate did not interfere with plaque formation. Mutants of Mycobacterium smegmatis resistant to each of the eight phages were isolated. Sensitivity or resistance to chloroform and streptomycin sulphate and phage resistant bacterial mutants may provide a basis for classifying the mycobacteriophages.

Adsorption↗
PubMed1978

Modification of methods used in bacteriophage typing of Mycobacterium tuberculosis isolates.

A procedure in which soft agar overlays were used in bacteriophage-typing Mycobacterium tuberculosis is presented. This safer method uses commercially available media, whereas media presently used must be prepared in the laboratory. Single plaque isolations of the phage BG-1 specifying phage type A and B of M. tuberculosis were readily made by using the modified procedures. This purification and the use of prototype strain Myc 1415 as the indicator host strain have significantly enhanced the ability to discriminate among strains of phage types A and B.

Bacteriophage Typing↗
PubMed1978

Alterations in regional cerebral hemodynamics and metabolism produced by focal cerebral ischemia.

Since diffuse changes in blood flow and metabolism occur in the brain following a focal ischemic insult, changes of cerebral blood flow on the side opposite a cerebral infarction were observed. We have examined the course of the cerebral hemodynamic changes occurring in 15 patients with unilateral acute strokes. In 12 of these patients, significant blood flow changes (over 15%) occurred in the nonischemic hemisphere during the period of observation. A similar time course of change was found in the ischemic hemisphere and the flow changes in the two hemispheres appeared parallel to one another (diaschisis). Thus we have demonstrated a significant reduction in flow in the contralateral cortex following a unilateral ischemic insult. This reduction in flow was of the order of 38% from the control value which agrees quite well with the reduction in cortical glucose consumption of the order of 31%. We postulate that these changes are the hemodynamic and metabolic concomitants of diaschisis and may in part be due to a transneuronal depression of function.

Animals↗
PubMed1978

Lysosomal activity in experimental spinal cord trauma: an ultrastructural cytochemical evaluation.

The possible role of lysosomal activity in the early post-trauma phase of severe experimental spinal cord trauma was assessed utilizing an acid phosphatase cytochemical ultrastructural study. The results indicate that there is no evidence for lysosomal alteration prior to the development of cellular degeneration or necrosis. No diffuse cytoplasmic staining was observed. This study indicates that physical lysosomal injury resulting in release of hydrolases into spinal cord cells is not a tenable hypothesis as a primary initiating event in the development of spinal cord necrosis following trauma. However, the data are consistent with the general theory that lysosomal activity is important in the secondary degradation of cells following their being altered beyond recovery.

Acid Phosphatase↗