Distribution of albumin in normal and regenerating livers of mice

Summary The conditions affecting the immunohistochemical identification of albumin in livers of male NMRI-mice were investigated by light microscopy. In normal livers albumin is randomly distributed, revealing a pancytoplasmic nearly homogen reaction in groups of hepatocytes or single parenchymal cells. However, combined autoradiographic studies after pulse labelling with ³H-valin and perfusion experiments with human albumin indicate that this distribution is caused by albumin from blood plasma and does not reflect true protein synthesis. After perfusion of the livers followed by immunohistochemical amplification techniques which allowed to dilute the primary antibody up to 1:30,000, albumin could be detected nearly in all liver parenchymal cells as granular deposits decreasing in its density from periportal fields towards the terminal hepatic venules.In regenerating livers due to partial hepatectomy no remarkable differences in granular albumin deposits between G₁- and S-phase of the cell cycle could be detected as was demonstrated by combined immunohistochemistry and ³H-dThd-autoradiography. However, during mitosis the content of albumin was often considerably reduced.Supported by a grant from the Robert-Bosch-Foundation, Stuttgart, Federal Republic of Germany     

Restriction enzyme map for streptomycete plasmid pUC3

A restriction enzyme map for the streptomycete plasmid pUC3 was constructed for the enzymes XhoI, EcoRI, HindIII, PstI, BamH-I, and BglII. The plasmid was isolated from Streptomyces sp. 3022a which produces chloramphenicol and has been referred to as S. venezuelae (Bewick et al., 1976 and Bewick and Williams, 1977, Microbios, 19, 27–35).     

The isolation and properties of pig submandibular kallikrein

The kallikrein from pig submandibular glands was highly purified, with an overall yield of 31%. Affinity chromatography on bovine basic pancreatic trypsin inhibitor linked to Sepharose 4B was an especially effective step in the purification procedure, giving a purification factor of 80. The enzyme is a single-chain molecule, occurring, as does pig urinary kallikrein, as a major B-form of apparent mol.wt. 39600 and minor amounts of an A-form of apparent mol.wt. 35900; the two forms can be separated by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The amino acid composition of pig submandibular kallikrein is very similar to, but not quite identical with, that of the two-chain beta-kallikrein isolated from pig pancreatic autolysates. Submandibular kallikrein contains notably more glucosamine and hexoses than does pancreatic beta-kallikrein. Submandibular kallikrein, and also urinary kallikrein, exhibit an unusual biphasic hydrolysis of substrate esters that is not shared by pancreatic beta-kallikrein. For the submandibular enzyme, the K(m) for the initial reaction phase of the hydrolysis of alpha-N-benzoyl-l-arginine ethyl ester is 0.15+/-0.01mm (mean+/-s.e.m.), but rises to 0.69+/-0.04mm (mean+/-s.e.m.) in the stationary reaction phase; the V(max.) does not differ significantly between the two phases. The esterolytic activities of submandibular and urinary kallikreins on a number of esters of different amino acids resemble each other much more closely than those of pancreatic beta-kallikrein.     

H-2 I alloantigens and recall of memory cytotoxic responses

AQR mice were immunized with H-2K and H-2 I encoded alloantigens presented by (Ax6R)F₁ splenocytes. Spleen cells from these alloimmune mice were subsequently restimulated in vitro with B10.A lymphocytes and/or B10.T(6R) lymphocytes, thus presenting them with the immunizing H-2K and H-2 I alloantigens independently. When stimulated with B10.A lymphocytes, alloimmune lymphocytes develop significant cytotoxicity against the immunizing H-2K target antigens. When stimulated with a similar number of B10.T(6R) spleen cells, alloimmune lymphocytes undergo a prominant proliferative response, but develop little, if any, cytotoxicity against the immunizing H-2 K target antigens. The most efficient restimulation of cytotoxicity occurs when the alloimmune spleen cells are simultaneously restimulated by B10.A and B10.T(6R) lymphocytes. Stimulation with the immunizing H-2 I alloantigens alone is not sufficient for regeneration of detectable cytotoxic responses from alloimmune spleen populations. Stimulation with the immunizing H-2K alloantigens alone appears to be both necessary and sufficient to stimulate alloimmune cytotoxic responses. Although the immunizing H-2 I alloantigens are apparently not required to generate alloimmune cytotoxic responses, they markedly potentiate the cytotoxic responses induced by the immunizing H-2K alloantigens.     

Myoinositol biosynthesis by Sertoli cells, and levels of myoinositol biosynthetic enzymes in testis and epididymis.

Levels of glucose-6-phosphate cyclase (myoinsitol-1-phosphate synthase, EC 5.5.1.4) and myoinositol-1-phosphate phosphatase (myoinositol-1-phosphatase, EC 3.1.3.25) were determined in extracts of testes from10-, 20-, and 30-day-old rats, and in extracts of Sertoli cells, germinal cells, and epididymides. The specific activity of the cyclase was approximately 1/10th that of the phosphatase in all extracts found to contain either enzyme. Among cells in the testis examined, Sertoli cells had highest levels of enzymes required for inositol biosynthesis from glucose, while spermatocytes and round spermatids did not have detectable activity. Spermatozoa from the epididymis also had no detectable cyclase or phosphatase activity. In contrast, extracts of washed epididymides contained exceedingly high specific activities of these enzymes. Primary cultures of Sertoli cells, maintained in a chemically defined medium without added inositol, released inositol into the medium during three successive 24-h periods. The amounts released were greater in cells stimulated by dibutyryl cyclic AMP. Results were interpreted to indicate that inositol in the fluid of seminiferous tubules most probably originates from Sertoli cells, which synthesize inositol from glucose. Additional inositol in the fluid of epididymal tubules could readily be provided by metabolism of glucose by epididymal epithelial cells     

Synapses of optic nerve afferents in the rat suprachiasmatic nucleus

Summary The identification of optic synapses in the rat suprachiasmatic nucleus (Güldner, 1978) has made it possible to study them morphometrically. The measurements followed the check-list introduced by Palay and Chan-Palay (1976). There are several items which could usefully be added to this list. The structure of essential synaptic components varies considerably in what is apparently one synaptic population based on morphological criteria. The possible reasons for the variable sizes of the optic boutons containing different amounts of clear and dense core vesicles are discussed in terms of different activities or metabolic states of the individual boutons and/or different metabolic states of neuronal and glial elements in their vicinity. The active zones of optic synapses are also extremely variable. One optic bouton can form several active zones of very different sizes, or form Gray-type-I (asymmetric), Gray-type-II (symmetric) and intermediate contacts at the same time. The function and/or functional efficiency of a single optic bouton therefore could then be quite different with respect to its various postsynaptic elements. The different appearance of the active zones is discussed mainly in terms of possible regulative influences from neighboring synapses via the postsynaptic neuron.The author wishes to thank Mrs. Bassirat Pirouzmandi for her excellent technical assistance     

Uniparental chromosome elimination at mitosis and interphase in wheat and pearl millet crosses involves micronucleus formation, progressive heterochromatinization, and DNA fragmentation

Complete uniparental chromosome elimination occurs in several interspecific hybrids of plants. We studied the mechanisms underlying selective elimination of the paternal chromosomes during the development of wheat (Triticum aestivum) x pearl millet (Pennisetum glaucum) hybrid embryos. All pearl millet chromosomes were eliminated in a random sequence between 6 and 23 d after pollination. Parental genomes were spatially separated within the hybrid nucleus, and pearl millet chromatin destined for elimination occupied peripheral interphase positions. Structural reorganization of the paternal chromosomes occurred, and mitotic behavior differed between the parental chromosomes. We provide evidence for a novel chromosome elimination pathway that involves the formation of nuclear extrusions during interphase in addition to postmitotically formed micronuclei. The chromatin structure of nuclei and micronuclei is different, and heterochromatinization and DNA fragmentation of micronucleated pearl millet chromatin is the final step during haploidization.     

Evidence for multiple calcium response mechanisms in mammalian olfactory receptor neurons

Olfactory receptor neurons employ a diversity of signaling mechanisms for transducing and encoding odorant information. The simultaneous activation of subsets of receptor neurons provides a complex pattern of activation in the olfactory bulb that allows for the rapid discrimination of odorant mixtures. While some transduction elements are conserved among many species, some species-specificity occurs in certain features that may relate to their particular physiology and ecological niche. However, studies of olfactory transduction have been limited to a relatively small number of vertebrate and invertebrate species. To better understand the diversity and evolution of olfactory transduction mechanisms, we studied stimulus-elicited calcium fluxes in olfactory neurons from a previously unstudied mammalian species, the domestic cat. Isolated cells from cat olfactory epithelium were stimulated with odorant mixtures and biochemical agents, and cell responses were measured with calcium imaging techniques. Odorants elicited either increases or decreases in intracellular calcium; odorant-induced calcium increases were mediated either by calcium fluxes through the cell membrane or by mobilization of intracellular stores. Individual cells could employ multiple signaling mechanisms to mediate responses to different odorants. The physiological features of these olfactory neurons suggest greater complexity than previously recognized in the role of peripheral neurons in encoding complex odor stimuli. The investigation of novel and unstudied species is important for understanding the mechanisms of odorant signaling that apply to the olfactory system in general and suggests both broadly conserved and species-specific evolutionary adaptations.