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Biomedical subjects

M Horowitz

Publications and source records attributed to M Horowitz.

At least 559 records · Page 31Linked to original sources
PubMed1979

Effects of heat acclimation on the secretory products of the submaxillary gland of the rat. An ultrastructural and biochemical study.

Secretory granule area and glycoprotein concentration of the saliva in the submaxillary gland of rats were measured during various stages of acclimation to heat at 34 +/- 1 degrees C. Granule size decreased by 18% during the first five days of heat acclimation (0.025 less than p less than 0.05) after which period it increased to reach 118% of the control levels after 28 days (p less than 0.05). Glycoprotein concentration in the saliva of stimulated glands rose above control levels, reaching a maximum between the 2nd and 5th day of acclimation (p less than 0.05). It was concluded that the initial decrease in granule size reflects a decrease in glycoprotein content following an increase in salivary flow known to occur at high ambient temperatures. The subsequent increase in granule size is considered an adaptation of the gland to continuous stimulation. The rise in salivary glycoprotein concentration suggests increased efficiency of the secretory mechanism.

Adaptation, Physiological↗
PubMed1979

Impact of Event Scale: a measure of subjective stress.

Clinical, field, and experimental studies of response to potentially stressful life events give concordant findings: there is a general human tendency to undergo episodes of intrusive thinking and periods of avoidance. A scale of current subjective distress, related to a specific event, was based on a list of items composed of commonly reported experiences of intrusion and avoidance. Responses of 66 persons admitted to an outpatient clinic for the treatment of stress response syndromes indicated that the scale had a useful degree of significance and homogeneity. Empirical clusters supported the concept of subscores for intrusions and avoidance responses.

Adaptation, Psychological↗
PubMed1979

Plasma water shifts during thermal dehydration.

Changes in body water compartments during acute dehydration before and after acclimation to heat and the role of plasma proteins in body fluid dynamics were studied in the rat. Compartment volumes, plasma and interstitial protein concentrations, and colloid osmotic pressures (COP) were measured in anesthetized (with thiopental sodium) and, if necessary, nephrectomized rats. Albumin outfluxes, total protein mass (TPM), and total albumin mass (TAM) were calculated. Nonacclimated rats conserved plasma volume (PV) as long as dehydration did not exceed 15-16% body weight loss (18.6% total body water loss). This was associated with decreased albumin outflux, elevated plasma COP, and reduced subcutaneous COP. When water loss reached 25,5%, PV and extracellular fluid volume decreased by 45 and 34%, respectively. Albumin outflux recovered, TPM and TAM decreased, and plasma COP remained high. In acclimated dehydrated rats PV remained unchanged, albumin outflux decreased, TPM and COP increased, and interstitial COP decreased. Most of the water loss was intracellular in origin. It was concluded that PV changes during dehydration are related to changes in plasma protein distribution. PV conservation rate is different in rats as compared to desert PV conservers.

Acclimatization↗
PubMed1978

Electron microscopic evidence for splicing of SV40 late mRNAs.

Poly(A)-containing SV40 cytoplasmic RNA was hybridized with linear double-stranded SV40 DNA and formed RNA displacement loops (R loops). The structures visualized in the electron microscope are consistent with the conclusion that the leader sequences at the 5' ends of the 16S and 19S late mRNAs are not coded immediately adjacent to the main portions of the mRNAs. These data are consistent with either segmentation of the leaders or heterogeneity of their lengths. Measurements carried out on the R loop structures have provided the locations, on the physical map of SV40 DNA, for the bodies and leaders of the 16S and 19S late mRNAs, and the lengths of the bodies, leaders and the corresponding intervening DNA sequences.

DNA, Viral↗
PubMed1978

Amylase activity, glycoprotein and electrolyte concentration in rat's submaxillary salivary gland during heat acclimation.

1. Amylase activity, glycoproteins, Na and K concentrations were measured in submaxillary salivary gland of the rat during heat acclimation (34 degrees C). 2. Acclimation resulted in a decrease in glycoprotein concentration and amylase activity, whereas Na and K concentrations and the Na/K ratio increased. 3. It is suggested that heat acclimation results in an increase in glandular activity leading to increased water secretion and depletion of the glycoprotein store. The decrease in amylase activity is probably due to liver atrophy which occurs during prolonged heat exposure.

Acclimatization↗
PubMed1978

Polyoma infected cells contain at least three spliced late RNAs.

Poly(A)-containing polyoma cytoplasmic RNA was hybridized with linear double-stranded polyoma DNA and RNA displacement loops (R-loops) were formed. The structures visualized in the electron microscope are consistent with the conclusion that there are at least three late polyoma specific RNAs and that the leader sequences at the 5' ends of these viral RNAs are not coded immediately adjacent to the bodies of the RNAs. Measurements carried out on the R-loop structures have provided the locations on the physical map of polyoma DNA, for the bodies and leaders of the RNAs and the length of the bodies, leaders and the corresponding intervening DNA sequences.

Microscopy, Electron↗
PubMed1978

Cellular dynamics of rats' submaxillary gland during heat acclimatization.

Male laboratory rats (Rattus norvegicus) ranging between 130 and 160 g were subjected to ambient temperatures of 34.5 degrees C from 0 to 28 days. The submaxillary gland, liver, spleen, and kidney were weighed. The acini size and the mitotic index of the acinar cells after intraperitoneal injection of vinblastine sulfate and colchicine were recorded for the submaxillary and parotid glands. The submaxillary glands showed increased growth rate over the initial 5 days, whereas the growth rate of the other organs decreased. The submaxillary gland enlargement was due to an initial hyperplasia of the acini cells reaching a maximum on the 2nd day. This was followed by hypertrophy of the Acini reaching a maximum on the l0th day. The parotid acini at control values throughout the experiment. It is postulated that the gland enlargement is effected to increase evaporative heat loss during the early stages of acclimatization prior to the lowering of heat production resulting from biochemical adaptation.

Acclimatization↗
PubMed1978

Acute dehydration: body water distribution in acclimated and nonacclimated Psammomys obesus.

Body water distribution after "acute dehydration" treatment (37 degrees C) was studied in Psammonys obesus before and after acclimation at 34 +/- 1 degrees C for 16-18 days. Determinations of water compartment volumes were performed on anaesthetized (thiopental sodium) nephrectomized animals. Plasma volume (PV) and extracellular volume (ECV) were measured by T-1824 and [14C]inulin, respectively. Total body water was determined after desiccating the animals. Albumin outflux was calculated from the half-life (T1/2) of T-1824 and total plasma albumin mass. Nonacclimated animals conserved PV as long as dehydration did not exceed 10-11% loss of body wt. This conservation was at the expense of ECV and was associated with diminished albumin outflux (T1/2 T-1824 approached infinity). With increased dehydration PV retention failed and a resumption of albumin outflux occurred. Acclimation resulted in diminished albumin outflux in both control and dehydrated animals (T1/2 T-1824 approached infinity). Most of the water lost during dehydration was of intracellular origin. It was concluded that reduction in permeability of the capillary bed during dehydration and acclimatization plays an important role in PV and ECV regulation.

Acclimatization↗
PubMed1977

Novel mechanism for RNA maturation: the leader sequences of simian virus 40 mRNA are not transcribed adjacent to the coding sequences.

The 5'-terminal 100-200 ribonucleotides of late simian virus 40 (SV40) mRNAs are not transcribed immediately adjacent to their coding sequences. This conclusion is based on the following observations. The major late SV40 cytoplasmic RNA species, 16S and 19S, were purified from poly(A)-containing cytoplasmic RNA by hybridization to and elution from an SV40 DNA fragment that maps between 0.67 and 0.76. This fragment is remote from the DNA fragments that include the coding sequences. The RNA transcripts from the fragment located between 0.67 and 0.76 were found in abundance. Even though selected on oligo(dT)-cellulose columns, the 5'-terminal sequences did not contain poly(A) tails directly adjacent to their 3' termini. The 5' terminus of the 16S mRNA, as monitored by hybridization of the sequences adjacent to the "cap" structure, was found adjacent to the coding sequences when intact [3H]methyl-labeled RNA was hybridized with restriction fragments. However, after fragmentation, the methyl label of this same RNA hybridized with a fragment that is remote from the coding sequences and maps between 0.67 and 0.73. These results imply a novel mechanism for biosynthesis of SV40 mRNA.

DNA Restriction Enzymes↗
PubMed1977

Arming of macrophages with lymphocytes from mice immunized with tumor tissue.

C57BL/6 macrophages are rendered specifically cytotoxic ("armed") by incubation with spleen cells from C57BL/6 mice sensitized in vivo with allogeneic P-815 mastocytoma cells. Data are presented which suggest that the cytotoxic activity of the macrophages is not due to the adherence of sensitized lymphocytes. The results indicate that it is the T-lymphocyte which is primarily involved in arming. Furthermore it is the cytotoxic and not the proliferating T-cell which is responsible for arming.

Animals↗
PubMed1977

Bactericidal studies of penicillin-gentamicin combinations against group B streptococci.

The bactericidal activity of penicillin-aminoglycoside combinations was studied in 16 strains of Group B streptococci. Minimal inhibitory concentrations (MIC) against kanamycin or gentamicin were greater than 50 microgram/ml, whereas ampicillin or penicillin inhibitory concentrations were uniformly less than 0.1 microgram/ml. Although all strains had bactericidal concentrations (MBC) less than 0.1 microgram penicillin/ml, penicillin at a concentration equal to each strains respective MBC reduced inoculum colony forming units (CFU) 2 logs in only 6 of 16 strains in bactericidal kinetic studies. However, the addition of gentamicin in concentrations of 5.0 or 10.0 microgram/ml to penicillin markedly enhanced bactericidal activity in all strains tested. The addition of lower concentrations of gentamicin (1.0 microgram/ml) had minimal advantage over penicillin alone. No distinct advantage was noted for combinations including either ampicillin or kanamycin. The theoretical advantage of penicillin-aminoglycoside combinations in experimental conditions, suggests that the use of antibiotic combinations in clinical infections due to Group B streptococci, may result in a more rapid eradication of these organisms.

Ampicillin↗
PubMed1976

Acclimatization of rats to moderate heat: body water distribution and adaptability of the submaxillary salivary gland.

Changes in plasma and extracellular fluid volumes were studied in rats during exposure to 35 degree C for 28 days. In addition the adaptability of the submaxillary salivary gland to these conditions was studied by measuring its weight, plasma and extracellular volumes during the acclimatization period. Major changes in parameters studied occurred during the first 10 days of acclimatization. Total plasma volume on day 10 was less than in controls (P = 0.02), but from then on returned to normal values. Extracellular fluid volume was expanded for most of the period. An enlargement of the submaxillary salivary gland was present during the whole period, but maximal enlargement was observed on day 10 (42%). On day 28 the gland was 14% larger. No changes in plasma and extracellular volumes of the gland were observed. It appears that due to redistribution of the blood pool at the beginning of heat exposure, plasma and extracellular volumes remain constant.

Acclimatization↗