Rat cell surface antigens: Nonidentity of the H-4 and Ag-F traits

Animals partially congenic to Lewis have been bred that differ at the locus, linked to C., which controls the Ag-F antigenic trait. Skin grafts from these animals, placed on Lewis recipients, were not rejected. This result demonstrates that Ag-F does not mediate skin incompatibility and, thus, is distinct from H-4, which was defined based on a demonstrable incompatibility and which is also linked to C.     

Effect of 2450 MHz microwave exposure on behavioural thermoregulation in mice

1. 1.|The purpose of this study was to determine the threshold specific absorption rate (SAR) during exposure to 2450 MHz continuous wave (CW) microwaves that affected thermoregulatory behaviour in mice.

2. 2.|A Plexiglas shuttle box was placed inside a waveguide imposed with a temperature gradient. The temperature gradient allowed the mice to select a particular section of the shuttle box which was, presumably, related to their state of thermal comfort. Exposing the mice to 2450 MHz inside the waveguide at SARs of 0–5.3 W kg⁻¹ for 1 h caused no significant change in their preferred ambient temperature.

3. 3.|Increasing SAR from 5.3 to 18.1 W kg⁻¹ caused the animals to shift their position to the cooler end of the shuttle box.

4. 4.|Following termination of microwave exposure animals that had selected a cool ambient temperature returned to the warm side of the shuttle box.

5. 5.|It is concluded that for mice exposed to radiation at 2450 MHz the thermoregulatory behaviour is significantly affected at SARs of 5.3 to 9.9 W kg⁻¹.

Differential Responses of the Phosphorylation of Ribosomal Protein S6 to Nerve Growth Factor and Epidermal Growth Factor in PC 12 Cells

Previous studies from this laboratory have shown that the phosphorylation of the S6 protein of the ribosomes is catalyzed by at least two different and separable kinase activities in PC12 cells. One of these activities is increased by treatment of the cells with nerve growth factor, the other by treatment of the cells with epidermal growth factor. The present work shows that these two factors stimulate the phosphorylation of S6 with quite different kinetics, and that both the number of phosphates incorporated into S6 and the phosphopeptide pattern of S6 are different in cells treated with nerve growth factor than in cells treated with epidermal growth factor. The characteristics of the nerve growth factor-sensitive S6 kinase and of the epidermal growth factor-sensitive kinase were also clearly different. Substrate specificity and inhibitor studies indicated that neither was identical to cyclic AMP-dependent kinase, kinase C, or the calcium/calmodulin-dependent kinases. However, two major phosphopeptides produced by S6 phosphorylation in nerve growth factor-treated cells were also seen on phosphorylation of S6 by cyclic AMP-dependent kinase in vitro. In addition, when rat liver 40S ribosomal subunits were pretreated with cyclic AMP-dependent kinase in vitro, the action of the nerve growth factor-sensitive S6 kinase was increased about twofold.     

Preservation of RNA for in situ hybridization: Carnoy's versus formaldehyde fixation.

Tissues fixed with organic solvent fixatives such as Carnoy's solution are known to give poor and erratic results with in situ hybridization, whereas those fixed with paraformaldehyde produce more consistent results. To understand this difference and to improve the utility of Carnoy's-fixed tissue for in situ hybridization, we explored several parameters of RNA integrity and preservation. Carnoy's-fixed, paraffin-embedded livers and paraformaldehyde-fixed, paraffin-embedded livers of mice were compared for RNA extractability, degradation, and hybridizability. In addition, retention of RNA in tissue sections after sequential in situ hybridization treatments was compared. RNA was found to be easily extractable from Carnoy's-fixed liver and was well preserved, with only slight degradation of high molecular weight RNA. Conversely, only a small percentage of the RNA was extractable from paraformaldehyde-fixed liver unless the tissue was digested with protease. The extracted RNA was well preserved, without detectable degradation. Sections of tissue fixed in Carnoy's solution subjected to in situ hybridization retained only about 10% of their original RNA content and gave correspondingly weak in situ hybridization signals. Formaldehyde-fixed tissues retained much more of the RNA (about 45%) and produced strong in situ hybridization signals. Treatment of Carnoy's-fixed tissue sections with vaporous formaldehyde increased retention of RNA and provided in situ hybridization signals comparable with those of paraformaldehyde-fixed tissues.     

Identification of nitroxide radioprotectors.

The nitroxide Tempol, a stable free radical, has recently been shown to protect mammalian cells against several forms of oxidative stress including radiation-induced cytotoxicity. To extend this observation, six additional water-soluble nitroxides with different structural features were evaluated for potential radioprotective properties using Chinese hamster V79 cells and clonogenic assays. Nitroxides (10 mM) were added 10 min prior to radiation exposure and full radiation dose-response curves were determined. In addition to Tempol, five of the six nitroxides afforded in vitro radioprotection. The best protectors were found to be the positively charged nitroxides, Tempamine and 3-aminomethyl-PROXYL, with protection factors of 2.3 and 2.4, respectively, compared with Tempol, which had a protection factor of 1.3. 3-Carboxy-PROXYL, a negatively charged nitroxide, provided minimal protection. DNA binding characteristics as studied by nonequilibrium dialysis of DNA with each of the nitroxides demonstrated that Tempamine and 3-amino-methyl-PROXYL bound more strongly to DNA than did Tempol. Since DNA is assumed to be the target of radiation-induced cytotoxicity, differences in protection may be explained by variabilities in affinity of the protector for the target. This study establishes nitroxides as a general class of new nonthiol radioprotectors and suggests other parameters that may be exploited to find even better nitroxide-induced radioprotection.     

Prostaglandin production in the umbilical and uterine circulations in pregnant sheep at 129-136 days gestation.

Prostaglandins circulating in the maternal and foetal blood have been implicated in important physiological systems. These functions include foetal adrenal function, maintenance of patency of the ductus arteriosus, regulation of uterine and umbilical circulations, and labor and delivery type myometrial contractions. The placenta is a major site of prostaglandin production in pregnancy. Limited data are available which combine measurements of veno-arterial differences across the uterine and umbilical circulations with blood flow in these circulations to enable calculation of umbilical-placental and utero-placental production rates for the prostaglandins. In chronically instrumented pregnant ewes, between 129 and 136 days of gestation, prostaglandin F2 alpha(PGF2 alpha), 13, 14 dihydro-15-keto prostaglandin F2 alpha (PGFM), prostaglandin E2 (PGE2) were measured in the maternal carotid artery and uterine vein. Foetal PGE2, and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) (the major metabolite of prostacyclin) were measured in umbilical venous and foetal descending aorta arterial plasma. Umbilical and uterine blood flow were measured using the diffusion-equilibrium technique. Uterine blood flow was 1693 +/- 137 ml.min-1 (mean +/- SEM); uterine production rates were 480 +/- 88 ng.min-1 for PGF2 alpha, 517 +/- 144 ng.min-1 for PGFM, and 165 +/- 27 ng.min-1 for PGE2. Umbilical blood flow was 147 +/- 17 ml.min-1.kg-1 foetal body weight. Umbilical production rates into the foetal circulation were 11 +/- 2 ng.min-1.kg-1 for PGE2 and 6 +/- 2 ng. ng.min-1.kg-1 foetal body weight for PGI2.     

Using medical genetics applications to educate for computer competence.

This article proposes specific areas of computing competence and illustrates how these skills can be acquired as an integral part of the curriculum of medical genetics. Geneticists are at the forefront in the use of computers for medical care, because of the driving force of the Human Genome Project. Computer searching of international data bases is the most efficient method to keep current with the explosion in molecular genetics data and with its immediate relevance to clinical care. The use of computers in genetics education could go far beyond the use of computer-assisted instruction (CAI) to show how to use computer systems to assist with clinical decisions. The proposed basic computer skills can be obtained using genetics software. The six proposed skills include the use of (1) microcomputers, (2) productivity software, (3) CAI, patient simulations and specific application programs, (4) remote computers, (5) data bases and knowledge bases, and (6) computers to improve the clinical care of patients.     

Seasonal changes in the cytochemical properties of the peritoneal mast cells in rats]

Contents of histamine, 5-hydroxytryptamine, functional state of heparinic proteoglycan have been studied in the rat peritoneal mast cells during various seasons of the year (January-February, May-June, July). In winter the mast cells have a high content of histamine and 5-hydroxytryptamine, heparinic proteoglycan of their granules is stained with both alcian blue and safranin. In summer (July) content of histamine in the mast cells is sharply decreased in comparison with that of 5-hydroxytryptamine and in May-June the content of both amines is decreased nearly to background values. Both during spring and summer periods heparinic proteoglycan of the mast cell granules is stained only with alcian blue and does not take safranin. A suggestion is made on independence of the seasonal changes of annual rhythmical pattern of histamine and 5-hydroxytryptamine contents in the mast cells. A conclusion is made concerning possible participation of the mast cell system of organs and tissues in the seasonal changes of biogenic amine levels in them.