The surface membrane of the small intestinal epithelial cell. I. Localization of adenyl cyclase.

The subcellular distribution of adenyl cyclase was investigated in small intestinal epithelial cells. Enterocytes were isolated, disrupted and the resulting membranes fractionated by differential and sucrose gradient centrifugation. Separation of luminal (brush border) and contra-luminal (basolateral) plasma membrane was achieved on a discontinuous sucrose gradient. The activity of adenyl cyclase was followed during fractionation in relation to other enzymes, notably those considered as markers for luminal and contraluminal plasma membrane. The luminal membrane was identified by the membrane-bound enzymes sucrase and alkaline phosphatase and the basolateral region by (Na+ + K+)-ATPase. Enrichment of the former two enzymes in purified luminal plasma membrane was 8-fold over cells and that of (Na+ + K+)-ATPase in purified bisolateral plasma membranes was 13-fold. F--activated adenyl cyclase co-purified with (Na+ + K+)-ATPase, suggesting a common localization on the plasma membrane. The distribution of K+-stimulated phosphatase and 5'-nucleotidase also followed (Na+ + K+)-ATPase during fractionation.     

Zwergstrauchige Arten der FlechtengattungCaloplaca

The frutescent species of the lichen genusCaloplaca are usually united in sect.Thamnoma, but they do not form a natural group. They are derived from different species groups within sect.Gasparrinia from different parts of the world, presumable from species having scleroplectenchymes in cortex and medulla. The algal cells are concentrated between the scleroplectenchymatic strands in large and dense groups, from where medullary plectenchyme extends to the cortex and forms characteristic pseudocyphellae there.—Most of the species seem to be ornithocoprophilous; they grow on rocks along marine coasts where much fog is induced by cold currents.—Caloplaca cribrosa is endemic in Tasmania and New Zealand,C. regalis and the doubtfulC. ambitiosa belong to the antarctic element.C. fragillima from central Chile seems to be propagated by thallus fragments.C. coralloides andC. thamnodes are endemic to California and Baja California respectively.C. cladodes from the Rocky Mountains deviates in many characteristics from the other species i.a. by it different ontogenetic development, reduced spore septum, and cementing amyloid polysaccharides within the scleroplectenchymatic strands. The African species are characterized by their distinctly dorsiventral lobes and usually possess oil cells in some of the paraphyses.Caloplaca bonae-spei, C. fragillima andC. thamnodes are new to science.

     

The γ subunits of the native GABAA/benzodiazepine receptors

Subunit-specific antibodies to all the γ subunit isoforms described in mammalian brain (γ₁, γ_2S, γ_L, and γ₃) have been made. The proportion of GABA_A receptors containing each γ subunit isoform in various brain regions has been determined by quantitative immunoprecipitation. In all tested regions of the rat brain, the γ₁, and γ₃ subunits are present in considerable smaller proportion of GABA_A receptor than the γ₂ subunit. Immunocytochemistry shows that γ₁ immunoreactivity concentrates in the stratum oriens and stratum radiatum of the CA1 region of the hippocampus. In the dentate gyrus, γ₁ immunoreactivity concentrates on the outer 2/3 of the molecular layer coinciding with the localization of the axospinous synapses of the perforant pathway. In contrast, γ₃ immunoreactivity concentrates on the basket cells and other GABAergic local circuit neurons of the hilus. These cells are also rich in γ_2S. In the cerebellu, γ₁ immunolabeling was localized on the Bergmann glia. The γ_2S and γ_2L subunits are differentially expressed in various brain regions. Thus the γ_2S is highly expressed in the olfactory bulb and hippocampus whereas the γ_2L is very abundant in inferior colliculus and cerebellum, particularly in Purkinje cells, as immunocytochemistry, in situ hybridization and immunoprecipitation techniques have revealed. The γ_2S and γ_2L coexist in some brain areas and cell types. Moreover, the γ_2S and γ_2L subunits can coexist in the same GABA_A receptor pentamer. We have shown that this is the case in some GABA_A receptors expressed in cerebellar granule cells. These GABA_A receptors also have α and β subunits forming the pentamer. Immunoblots have shown that the rat γ₁, γ_2S, γ_2L and γ₃ subunits are peptides of 47, 45, 47 and 44 kDa respectively. Results also indicate that there are aging-related changes in the expression of the γ_2S and γ_2L subunits in various brain regions which suggest the existence of aging-related changes in the subunit composition of the GABA_A receptors which in turn might lead to changes in receptor pharmacology. The results obtained with the various γ subunit isoforms are discussed in terms of the high molecular and binding heterogeneity of the native GABA_A receptors in brain. Special issue dedicated to Dr. Kinya Kuriyama     

Assignment of the human gene for muscle-type phosphofructokinase (PFKM) to chromosome 1 (region cen leads to q32) using somatic cell hybrids and monoclonal anti-M antibody

Human phosphofructokinase (PFK; EC 2.7.1.11) is under the control of three structural loci which encode muscle-type (M), live-type (L), and platelet-type (P) subunits; human diploid fibroblasts and leukocytes express all three loci. In order to assign human PFKM locus to a specific chromosome we have analyzed human x Chinese hamster somatic cell hybrids for the expression of human M subunits, using an anti-human M subunit-specific mouse monoclonal antibody. In 18 of 19 hybrids studied, the expression of the PFKM locus segregated concordantly with the presence of chromosome 1 (discordance rate 0.05) as indicated by chromosome and isozyme marker analysis. The discordance rates for all the other chromosomes were 0.32 or greater, indicating that the PFKM locus is on chromosome 1. For the regional mapping of PFKM, eight hybrids were studied that contained one of five distinct regions of chromosome 1. These results further localize the human PFKM locus to region cen leads to q32 chromosome 1.     

Differential processing of Asn-linked oligosaccharides on pituitary glycoprotein hormones: implications for biologic function

Luteinizing hormone, follicle-stimulating hormone, and thyroid-stimulating hormone from pituitary and chorionic gonadotropin from placenta are a family of glycoproteins, each consisting of an and subunit. Within an animal species, the subunit of all four hormones contains the identical amino acid sequence, while each subunit is distinct and confers biologic specificity to the hormone dimer. Despite sharing common subunits, these hormones bear Asn-linked oligosaccharides which differ in structure. Whereas chorionic gonadotropin contains exclusively neutral and sialylated oligosaccharides, the pituitary hormones bear neutral, sialylated, sulfated, and sialylated/sulfated structures. The sulfated oligosaccharides are unique in structure and are more prevalent on certain pituitary hormones, indicating that the synthesis of these unusual oligosaccharides is tightly regulated. The differences in oligosaccharide structures in conjunction with the highly specific endocrine responses elicited by these hormones, suggest an important functional role for the oligosaccharides, such as metabolic clearance, control of hormone response, modulation of hormone potency, and/or intracellular sorting of hormones into separate secretory granules.     

Recombinant human interleukin 1 alpha: purification and biological characterization

Interleukin 1 (IL 1) is a polypeptide hormone produced by activated macrophages that affects many different cell types involved in immune and inflammatory responses. The cloning and expression of a murine IL 1 cDNA in Escherichia coli encoding a polypeptide precursor of 270 amino acids has been reported, and expression of the carboxy-terminal 156 amino acids of this precursor in E. coli yields biologically active IL 1. By using the murine IL 1 cDNA as a probe, we have isolated its human homolog from cDNA generated to lipopolysaccharide-stimulated human leukocyte mRNA. Nucleotide sequence analysis of this cDNA predicts a protein of analysis of this cDNA predicts a protein of 271 amino acids (termed IL 1 alpha) which shows congruent to 61% homology to its murine counterpart but only 27% homology to a recently characterized human IL 1 precursor (IL 1 beta). We have expressed the carboxy-terminal 154 amino acids of IL 1 alpha in E. coli, purified this protein to homogeneity, and have compared it with pure recombinant murine IL 1 in several different IL 1 assays based on murine and human cells. Recombinant IL 1 is capable of stimulating T cell and fibroblast proliferation and inducing fibroblast collagenase and prostaglandin production, thus proving that a single molecule has many of the activities previously ascribed to only partially purified IL 1 preparations. Our results indicate that there exists a family of at least two human IL 1 genes (alpha and beta) whose dissimilar protein products have similar biological activities.     

Sequentially Deposited versus Conventional Nonfullerene Organic Solar Cells: Interfacial Trap States,Vertical Stratification,and Exciton Dissociation

Bulk heterojunction (BHJ) nonfullerene organic solar cells prepared from sequentially deposited donor and acceptor layers (sq‐BHJ) have recently been shown to be highly efficient, environmentally friendly, and compatible with large area and roll‐to‐roll fabrication. However, the related photophysics at donor‐acceptor interface and the vertical heterogeneity of donor‐acceptor distribution, critical for exciton dissociation and device performance, have been largely unexplored. Herein, steady‐state and time‐resolved optical and electrical techniques are employed to characterize the interfacial trap states. Correlating with the luminescent efficiency of interfacial states and its nonradiative recombination, interfacial trap states are characterized to be about 40% more populated in the sq‐BHJ devices than the as‐cast BHJ (c‐BHJ), which probably limits the device voltage output. Cross‐sectional energy‐dispersive X‐ray spectroscopy and ultraviolet photoemission spectroscopy depth profiling directly visualize the donor–acceptor vertical stratification with a precision of 1–2 nm. From the proposed “needle” model, the high exciton dissociation efficiency is rationalized. This study highlights the promise of sequential deposition to fabricate efficient solar cells, and points toward improving the voltage output and overall device performance via eliminating interfacial trap states.     

Characterization of crystals of genetically engineered human manganese superoxide dismutase

The genetically engineered human manganese superoxide dismutase crystallizes in space group P2(1)2(1)2 with a = 75.51 A, b = 79.00 A, c = 67.95 A. At room temperature the crystals are not stable against radiation, so we cooled them to 90 K and collected a data set to 3 A resolution at this temperature.     

Effect of humidity on the disintegrant property of α-cellulose,Part II: A technical note

Conclusion  The summary is that the high humidity impaired the disintegrant property of α-cellulose in all 3 tablets tested. Tablets of aspirin, which is the more hygroscopic drug, were also more sensitive to the humidity effect, while tablets of chloroquine phosphate, which is a water-soluble drug, were the least sensitive to the humidity effect. The results permit the conclusion that moisture uptake with subsequent gelling of the α-cellulose is the mechanism of impairment of its disintegrant property. The tablets would not normally be stored under an RH as high as 100%, nevertheless, the results of the accelerated stability study have underscored the need to protect tablets containing α-cellulose as disintegrant from moisture. Published: August 10, 2005