Detection by electron spin resonance of an exchange-coupled Cob(II)alamin...free radical pair species generated by anaerobic photolysis of polycrystalline adenosylcobalamin

Exposure to nitrous oxide (N₂O) $\text{in vivo}$ is accompanied by oxidation of cob[I]alamin to the inactive cob[III]alamin [1] and to loss of methionine synthetase activity [2]. There is a steady increase in thymidylate synthetase activity in marrow collected from rats exposed to N₂O and this returns to normal on restoring the animals to an air environment.     

Regulation of calcium fluxes in rat pancreatic islets: Quinine mimics the dual effect of glucose on calcium movements

The effects of quinine and 9-aminoacridine, two blockers of potassium conductance in islet cells, on ⁴⁵Ca efflux and insulin release from perifused islets were investigated in order to elucidate the mechanisms by which glucose initially reduces ⁴⁵Ca efflux and later stimulates calcium inflow in islet cells. In the absence of glucose, 100 μM quinine stimulated ⁴⁵Ca net uptake, ⁴⁵Ca outflow rate and insulin release. Quinine also dramatically enhanced the cationic and the secretory response to intermediate concentrations of glucose, but had little effect on ⁴⁵Ca net uptake, ⁴⁵Ca fractional outflow rate and insulin release at a high glucose concentration (16.7 mM). The ability of quinine to stimulate ⁴⁵Ca efflux depended on the presence of extracellular calcium, suggesting that it reflects a stimulation of calcium entry in the islet cells. In the absence of extracellular calcium, quinine provoked a sustained decrease in ⁴⁵Ca efflux. Such an inhibitory effect was not additive to that of glucose, and was reduced at low extracellular Na⁺ concentration. At a low concentration (5 μM), quinine, although reducing ⁸⁶Rb efflux from the islets to the same extent as a non-insulinotropic glucose concentration (4.4 mM), failed to inhibit ⁴⁵Ca efflux. In the presence of extracellular calcium, 9-aminoacridine produced an important but transient increase in ⁴⁵Ca outflow rate and insulin release from islets perifused in the absence of glucose. In the absence of extracellular calcium, 9-aminoacridine, however, failed to reduced ⁴⁵Ca efflux from perifused islets. It is concluded that quinine, by reducing K⁺ conductance, reproduces the effect of glucose to activate voltage-sensitive calcium channels and to stimulate the entry of calcium into the B-cell. However, the glucose-induced inhibition of calcium outflow rate, which may also participate in the intracellular accumulation of calcium, does not appear to be mediated by changes in K⁺ conductance.     

A respiration-dependent primary sodium extrusion system functioning at alkaline pH in the marine bacterium Vibrioalginolyticus

The membrane potential generated at pH 8.5 by K⁺-depleted and Na⁺-loaded $\text{Vibrio}\text{alginolyticus}$ is not collapsed by proton conductors which, instead, induce the accumulation of protons in equilibrium with the membrane potential. The generation of such a membrane potential and the accumulation of protons are specific to Na⁺-loaded cells at alkaline pH and are dependent on respiration. Extrusion of Na⁺ at pH 8.5 occurs in the presence of proton conductors unless respiration is inhibited while it is abolished by proton conductors at acidic pH. The uptake of α-aminoisobutyric acid, which is driven by the Na⁺-electrochemical gradient, is observed even in the presence of proton conductors at pH 8.5 but not at acidic pH. We conclude that a respiration-dependent primary electrogenic Na⁺ extrusion system is functioning at alkaline pH to generate the proton conductor-insensitive membrane potential and Na⁺ chemical gradient.     

Human liver aldehyde dehydrogenase in Chinese and Asiatic Indians: Gene deletion and its possible implications in alcohol metabolism

Two separate human liver aldehyde dehydrogenases exist which show differences in substrate specificity, cation inhibition or activation, and molecular weight. In this paper we report a common absence of enzyme 2 in Chinese which may be taken to indicate a gene deletion coding for this enzyme. The possible implication of this gene deletion among Chinese is discussed.     

Formation of heterophile antibodies by human tonsilar lymphocytes: II. In vitro stimulation with allogeneic cells

Short-term cultures of human tonsilar lymphocytes (HTL), 5 × 10⁶ cells/culture, in medium RPMI 1640 supplemented with human group AB serum were studied for the production of plaque-forming cells (PFC) against sheep (SRBC) and bovine (BRBC) red blood cells following in vitro stimulation by various allogeneic lymphoid cells. Of 55 HTL specimens examined, 48 produced a significant number (50–300/culture) of PFC against SRBC and/or BRBC following the in vitro stimulation. The optimal doses of the stimulator HTL and peripheral blood lymphocytes (PBL) were 10⁷ and 5 × 10⁶/culture, respectively. After the stimulation, PFC appeared in significant numbers on the third day, reached the peak number on the sixth day, and decreased sharply in number thereafter. Removal of E-rosetting cells from both stimulator and responder populations abolished the PFC formation. PFC formation against SRBC was inhibited by solubilized Forssman antigen, while PFC formation against BRBC was inhibited strongly by Hanganutziu-Deicher antigen, hardly by Paul-Bunnell antigen and not at all by Forssman antigen. Supernatants of mixed lymphocyte culture of PBL were shown to enhance PFC formation of HTL cultures stimulated by allogeneic lymphocytes. The results of this study indicated that in vivo primed B cells of the HTL were triggered in vitro by allogeneic stimulation for the heterophile antibody formation. Since these antibodies are apparently directed against Forssman and Hanganutziu-Deicher antigens, the “allo” nature of these antigens as well as their relationship to the previously described heterophile transplantation antigens have to be clarified.     

Schistosoma mansoni: Electrophoretic characterization of strains selected for different levels of infectivity to snails

Individual adult Schistosoma mansoni from strains selected for high or low infectivity to specific strains of the snail intermediate host, Biomphalaria glabrata, were subjected to enzyme electrophoresis on starch gels. Fourteen enzyme systems were analyzed in an attempt to find electrophoretic markers associated with genes for infectivity to snails. The S. mansoni strains were selected from different isolates from Puerto Rico in several strains of B. glabrata. Of an estimated 18 loci, 3 were polymorphic and the remainder monomorphic. For 1 of the 3 polymorphic enzyme loci, lactate dehydrogenase (Ldh, EC 1.1.1.27), phenotype frequencies were correlated with infectivity to snails. In schistosome strains of low infectivity, frequencies of the Ldh-N phenotype ranged between 0.56 and 0.69, while in strains of high infectivity, Ldh-N frequencies were typically 0.91 to 1.00. Whether the correlation is accidental or due to some form of association, such as chromosomal linkage, between the locus responsible for variation in lactate dehydrogenase and a gene for infectivity to snails remains to be determined.     

Hormonal stimulation of cAMP-dependent protein kinase in rat pancreas

The phosphorylation of myelin (basic protein) purified from rabbit brain was markedly stimulated by exogenously added calmodulin in the presence of calcium and inhibited by W-7(N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide), a calmodulin interacting agent, in a dose-dependent fashion. However, exogenously added myelin basic protein free from protein kinase activity could not serve as a substrate of this calmodulin dependent protein kinase, suggesting that this kinase catalyzes the phosphorylation of the enzyme-substrate complex. These results suggest that a calmodulin-dependent protein kinase complex with the substrate (basic protein) is located in the myelin membrane of the central nervous system.     

Assignment of the sorbitol dehydrogenase locus to human chromosome 15 pter→q21

The locus for sorbitol dehydrogenase (SORD, E.C. 1.1.1.14) has been shown to segregate with hexosaminidase A and mannose phosphate isomerase in a series of human-Chinese hamster somatic cell hybrids. Cytogenetic analysis supports the assignment to chromosome 15 and further defines the gene locus to the region 15pterq21.This research was supported by the Medical Research Council of Canada (MT 4061), the Children's Hospital of Winnipeg Research Foundation, Inc., and the Department of Health, Province of Manitoba (H.S.W.).     

Trisomic analysis of isozymic loci in tomato species: Segregation and dosage effects

Five isozymic loci were localized in the tomato (Lycopersicon esculentum) genome by trisomic analysis. Results revealed the following locations: Aps-1 on chromosome 6, Est-1 and Prx-2 on chromosome 2, Prx-4 on chromosome 10, and Prx-7 on chromosome 3. Three genes—Aps-1, Prx-2, and Prx-4—showed an arithmetic increase in allozyme concentration in direct proportion to the increase of gene dosage in respective primary trisomics. In contrast, no increase in relative Est-1 isozyme concentration was observed for any primary trisomic type. The phenotypes of the Aps-1, Prx-2, and Est-1 genes showed a pattern of banding intensity proportional to the allelic ratio (+/+/a vs. + /a/a) in primary trisomics; zymotypes of these differential trisomic heterozygotes appeared as converse images of each other.This research was performed under the auspices of NSF Grants BMS75-03024 and DEB77-02248 to C. M. Rick.