Large amplitude photo-voltage transients of bilayer lipid membranes in the presence of chlorophyllin

Large amplitude electrical voltage transients result from the flash illumination of bilayer lipid membranes (BLM) in the presence of chlorophyllin, electron acceptors [FeCl₃ or (NH₄)₂ Ce(NO₃)₆] and an electron donor (FeCl₂). The BLM were prepared from lecithin and oxidized cholesterol, or spinach chloroplast extracts. The photo-voltage waveforms observed may be resolved into three components, which have characteristic times of approximately the flash duration (8 sec), 1 msec, and the BLM resistance-capacitance discharge time. These components are thus comparable to the Components A, B, and D previously reported for BLM and thin lipid membranes (TLM) of the spinach chloroplast extracts in the presence of electron acceptors. Component C of the chloroplast-BLM is extinguished by near trace quantities (1 g/l) of chlorophyllin. Higher concentrations (1 to 20 mg/l) reduce the BLM resistance and stability but under some conditions the Component A response exceeds 200 mV. The inferred peak photo-current exceeds 10 mA/cm². Membrane resistance and stability data suggest that the chlorophyllin bonds within and disrupts the adjacent interface (monolayer), but that it does not permeate the BLM.     

Specific Inhibition of Mammalian Ribonucleic Acid C-Type Virus Deoxyribonucleic Acid Polymerases by Rat Antisera

Inhibition of the ribonucleic acid (RNA)- and deoxyribonucleic acid (DNA)-dependent DNA polymerase activities of mammalian C-type viruses was obtained with sera from rats bearing murine leukemia virus-induced transplant tumors. Polymerase activities of nonmammalian (viper) C-type virus and murine mammary tumor virus were not inhibited by such sera nor by serum from a rat immunized with the DNA polymerase of feline leukemia virus purified by isoelectric focusing. The latter serum appeared to inhibit preferentially the DNA-dependent DNA polymerase activity of mammalian C-type viruses showing no inhibition of RNA-dependent DNA synthesis.     

Spatial and temporal transcellular current patterns during oogenesis.

We have used the two-dimensional vibrating probe to examine spatial and temporal patterns in the transcellular current flow around telotrophic ovarioles of the insect Rhodnius prolixus. We demonstrate a dynamic pattern of currents which correlates with various stages of vitellogenesis. Asymmetries exist in the radial current pattern around intact ovarioles, particularly around the terminal follicle, and may correlate with early developmental axes. The extra-cellular current pattern is largely reflected by a similar, though weaker pattern of currents over the germ cell membranes, indicating that both germ cell and somatic cell membranes are involved in current generation. Current enters previtellogenic oocytes and leaves oocytes entering vitellogenesis. We speculate that current reversal and loss of trophic cord contact may represent an electrophysiological feedback control mechanism during oogenesis.     

Chromosomal location of murine and human IL-1 receptor genes.

The gene for the type I interleukin-1 (IL-1) receptor has been mapped in both mouse and human. In the human genome, a combination of segregation analysis of rodent-human hybrid cells and chromosomal in situ hybridization has placed the gene on the long arm of chromosome 2, at band 2q12. This is near the reported map position of the loci for IL-1 alpha and IL-1 beta (2q13----2q21). The murine gene has been mapped by analysis of restriction fragment length polymorphisms in interspecific backcrosses to the centromeric end of chromosome 1, in a region that is syntenic to a portion of human chromosome 2. The murine Il-1r1 gene has thus been separated from the IL-1 genes, which lie on murine chromosome 2.     

Comets as a possible source of prebiotic molecules

Prebiotic molecules derive from abiotic organic molecules, radicals, and ions that pervade the universe at temperatures as high as several 1000 K. Here we review the role of organic molecules that condensed at low temperatures before or during comet formation in the early history of the Solar System. Recent spacecraft encounters and ground-based observations of carbon-rich volatile and dust components of comet comae provide a broad database for the investigation of these organic molecules. New laboratory data for some potential cometary organics are presented. Probable icy organic constituents of the nucleus and CHON particles as likely candidates for the distributed sources of gas-phase organic species in the coma are discussed. There is broad agreement that many organic molecules observed in the coma originate from the dust that must have existed in the solar nebula at the time and place of comet formation. We conclude that complex organic molecules found in comets may be a source of prebiotic molecules that led to the origins of life.     

Cloning and expression of the human substance K receptor and analysis of its role in mitogenesis.

The primary structure of the human substance K receptor was established from the sequences of complementary DNA clones isolated from a human jejunal complementary DNA library. It consists of 398 amino acids, including seven putative transmembrane regions. The gene for the human substance K receptor was localized to chromosome region 10p13-10q23, a region with frequent chromosomal abnormalities. The human substance K receptor was expressed in transfected NIH-3T3 cells lacking endogenous substance K receptors, and Scatchard analysis of 125I-labeled substance K binding indicates approximately 100,000 receptors/cell with a single dissociation constant of 12 nM. Covalent cross-linking experiments utilizing 125I-substance K and three different chemical cross-linking reagents (disuccinimidyl suberate, disuccinimidyl tartrate, or 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide-HCl) demonstrate an apparent molecular weight of 45,000, consistent with little or no N-linked glycosylation. The binding of substance K to its receptor on transfected cells led to a rapid increase in the production of total inositol phosphates and the release of Ca2+ from internal stores. Growth of the cells transfected with the human substance K receptor is stimulated by the addition of substance K to the medium to a level similar to 10% serum. Therefore, the human substance K receptor can function as a growth factor receptor when expressed in mouse 3T3 cells.     

The gene encoding vasoactive intestinal peptide is located on human chromosome 6p21→6qter

Summary Vasoactive intestinal peptide (VIP) is a regulatory neuropeptide involved in a wide variety of functions, among them vasodilation, smooth muscle relaxation, sweat secretion, gastrointestinal peristalsis, and pancreatic function. A deficient VIP-innervation of sweat glands was recently described as a possible pathogenic factor in sweating of cystic fibrosis (CF) patients. To investigate a possible role for a defective VIP-gene in cystic fibrosis, we have used a panel of rodent-human hybrid cells, retaining defined complements of human chromosomes to localize the VIP-gene to the human chromosome region 6p216qter. As the CF gene was recently mapped to chromosome 7, we conclude that the VIP-gene is not the primary gene defect in this disease.     

Identification of serotonin from rabbit upper stomach as a stimulant of in vitro gallbladder contraction

Using an in vitro rabbit gallbladder bioassay, the distribution and identification of bioactive substances in rabbit gastrointestinal tract were investigated. Comparison of the bioactivities of tissue extracts before and after cholecystokinin was removed by affinity chromatography demonstrated that the distributions of cholecystokinin and non-cholecystokinin substances were different. While cholecystokinin bioactivity per g of tissue was highest in the duodenum, non-cholecystokinin bioactivity was greatest in the upper stomach. The biochemical properties of the non-cholecystokinin substance in the upper stomach could not be distinguished from those of serotonin. These included molecular weights of 176, identical ultraviolet spectra, similar nuclear magnetic resonance spectra, and co-chromatography in HPLC. By weight, serotonin had 1/6th of the bioactivity of cholecystokinin octapeptide. We conclude that the principal gallbladder-contracting substance in rabbit upper stomach is serotonin.