The effect of repeated administration of insulin on pain threshold and gamma-aminobutyric acid level in mouse brain

In experiments on male Albino-Swiss mice weighing 18-22 g insulin given in doses of 2 i.u./kg caused no change in the time of reaction to pain, while the same dose administered daily for 7 days potentiated the analgesic action of morphine (3 mg/kg s.c.). Glucose caused no change in this effect of insulin. After 14 days of insulin treatment the time of reaction to pain in the animals subjected to the action of morphine returned to its initial value. Twenty-four hours after the last administration of morphine the level of gamma-aminobutyric acid (GABA) was found to be decreased in the animals receiving insulin with glucose. These results suggest that the central action of insulin is dependent not only on hypoglycaemia produced by it, but may be due also to its direct action on the central structures and an indirect action mediated by its effect on other neurotransmitter systems.     

Motor asymmetry of the forelimbs of the rat

Preference was studied of one of the forelimbs during performance of different manipulating movements in white rats. High degree of "handedness" was observed in all studied movements. However it was not absolute--no animals performed all movements by one and the same limb. Degree and character of "handedness" were different for different movements, though the number of "righthanded" rats in most tests as a whole exceeded the number of "lefthanded" ones. The "handedness" depends on the individuality of the animal, the character of the motor task, learning and interference of different motor tasks during training.     

Lipid peroxidation in plumbagin administered rats

Plumbagin was administered to rats at a concentration of 1,2,4,8 and 16 mg per kg body weight. After 24 h lipid peroxide levels were found to decrease in subcellular fractions of liver. Plumbagin inhibited ascorbate and nicotinafde adenine dinucleotide phosphate (reduced) dependent lipid peroxidation but was without any effect on cumene hydroperoxide dependent lipid peroxidation. Injection of 16 mg of plumbagin per kg body weight was found to decrease liver total reduced glutathione and also fcrosomal glucose-6-phosphatase. The results are discussed with reference to the anti- and prooxidant properties of plumbagin.     

Subcellular location of enzymes involved in the N-glycosylation and processing of asparagine-linked oligosaccharides in Saccharomyces cerevisiae

A particulate translation system isolated from the yeast Saccharomyces cerevisiae was shown to translate faithfully in-vitro-transcribed mRNA coding for a mating hormone precursor (prepro-alpha-factor mRNA) and to N-glycosylate the primary translation product after its translocation into the lumen of the microsomal vesicles. Glycosylation of its three potential sugar attachment sites was found to be competitively inhibited by acceptor peptides containing the consensus sequence Asn-Xaa-Thr, supporting the view that the glycan chains are N-glycosidically attached to the prepro-alpha-factor polypeptide. The accumulation in the presence of acceptor peptides of a membrane-specific, unglycosylated translation product (pp-alpha-F0) differing in molecular mass from a cytosolically located, protease-K-sensitive alpha-factor polypeptide (pp-alpha-Fcyt) by about 1.3 kDa, suggests that, in contrast to previous reports, a signal sequence is cleaved from the mating hormone precursor on/after translocation. This conclusion is supported by the observation that the multiply glycosylated alpha-factor precursor is cleaved by endoglucosaminidase H to a product with a molecular mass smaller than the primary translation product pp-alpha-Fcyt but larger than the membrane-specific pp-alpha-F0. Translation and glycosylation experiments carried out in the presence of various glycosidase inhibitors (e.g. 1-deoxynojirimycin, N-methyl-1-deoxynojirimyin and 1-deoxymannojirimycin) indicate that the N-linked oligosaccharide chains of the glycosylated prepro-alpha-factor species are extensively processed under the in vitro conditions of translation. From the specificity of the glycosidase inhibitors applied and the differences in the molecular mass of the glycosylated translation products generated in their presence, we conclude that the glycosylation-competent microsomes contain trimming enzymes, most likely glucosidase I, glucosidase II and a trimming mannosidase, which process the prepro-alpha-factor glycans down to the (Man)8(GlcNAc)2 stage. Furthermore, several arguments strongly suggest that these three enzymes, which apparently represent the full array of trimming activities in yeast, are exclusively located in the lumen of microsomal vesicles derived from endoplasmic reticulum membranes.     

Aortic diastolic caliber changes as a determinant for complete aortic baroreceptor resetting

It is well known that baroreceptors reset to operate at higher pressure in hypertension. The time course and mechanisms responsible for resetting are still unclear. There is a rapid or acute partial resetting that reaches its maximum within the first 5-15 min but changes little within the first hours. This resetting is, however, partial and becomes complete only if the pressure change is held permanently. Resetting is complete when the change in pressure threshold for baroreceptor activation matches the total pressure change. In the rat, complete resetting to hypo- or hypertension occurs in 48 h. The aortic caliber was studied in freely moving rats during the development of sustained hypertension produced by subdiaphragmatic aortic constriction. A striking coincidence was observed between the time taken for the diastolic caliber to reach maximal dilation and the time taken for complete resetting of the aortic baroreceptors. Moreover, during sudden pressure increases, the displacement of the diastolic caliber is much greater than the increase in pulsation, which indicates that in conscious rats the operational level of the resting diastolic caliber is an important factor for aortic baroreceptor distortion.     

Spontaneous mutation of the H-2b-haplotype in C57BL/10SnY mice

A new spontaneous mutation of the H-2b haplotype was found in skin graft tests with BC3 mice derived from B10.R111 (71NS) and C57BL/10SnY outcrossing. The mutation site localized in the F1 test in the H-2Kb gene is nonidentical to and noncomplementary with bm1, bm3, bm4 mutations. The novel mutation is maintained as B10.R111-H-2bm25 strain.     

Binding of chondroitin sulfate, dermatan sulfate and fat-storing cell-derived proteoglycans to rat hepatocytes

1. The interaction of isolated rat hepatocytes with exogenous 3H-labeled chondroitin-4-sulfate and dermatan sulfate and with biosynthetically 35S-labeled proteoglycans secreted by cultured rat liver fat-storing cells has been studied. 2. All ligands are bound by hepatocytes in a concentration-dependent manner. Scatchard-plot analysis of the data revealed the existence of high- and low-affinity binding modes. 3. The cell-bound exogenous [3H]glycosaminoglycans could be displaced by each unlabeled ligand and by heparin, whereas displacement of the endogenous material was less effective. 4. Binding of all ligands to hepatocytes increased with time. For the exogenous glycosaminoglycans the two- to threefold amount was retained at 37 degrees C as compared to 4 degrees C; it was markedly reduced by pretreatment of the cells with trypsin. 5. Degradation of the exogenous ligands could be detected neither for the cell-bound fraction nor for the free glycosaminoglycans in the culture medium. 6. The binding of the ligands to hepatocytes is viewed as a cell-matrix interaction. Its possible pathobiochemical relevance in liver fibrosis or neoplasia is discussed.     

The ATP-dependent interaction of eukaryotic initiation factors with mRNA

The interaction of three protein synthesis initiation factors, eukaryotic initiation factor (eIF)-4A, -4B, and -4F, with mRNA has been examined. Three assays specifically designed to evaluate this interaction are RNA-dependent ATP hydrolysis, retention of mRNAs on nitrocellulose filters, and cross-linking to periodate-oxidized mRNAs. The ATPase activity of eIF-4A is only activated by RNA which is lacking in secondary structure, and the minimal size of an oligonucleotide capable of effecting an optimal activation is 12-18 bases. In the presence of ATP, eIF-4A is capable of binding mRNA. Consistent with the ATPase activity, this binding shows a definite preference for single-stranded RNA. In the absence of ATP, eIF-4F is the only factor to bind capped mRNAs, and this binding, unlike that of eIF-4A, is sensitive to m7GDP inhibition. The activities of both eIF-4A and eIF-4F are stimulated by eIF-4B, which seems to have no specific independent activity in our assays. Evidence from the cross-linking studies indicates that in the absence of ATP, only the 24,000-dalton polypeptide of eIF-4F binds to the 5' cap region of the mRNA. From the data presented in conjunction with the current literature, a suggested sequence of factor binding to mRNA is: eIF-4F is the first initiation factor to bind mRNA ind an ATP-independent fashion; eIF-4B then binds to eIF-4F, if in fact it was not already bound prior to mRNA binding; and finally, eIF-4A binds to the eIF-4F X eIF-4B X mRNA complex and functions in an ATP-dependent manner to allow unwinding of the mRNA.