Physiological Control of Molluscan Gill Cilia by 5-Hydroxytryptamine

An examination is made of the hypothesis that endogenous 5-hydroxytryptamine (5-HT) serves as a local hormone regulating ciliary activity in the lamellibranch gill. These cilia are sensitive to exogenous 5-HT and respond to it by a prompt, sustained, and reversible rise in beat frequency; at the same time the carbohydrate metabolism is stimulated, as described elsewhere. Control gill contains small but definite amounts of endogenous 5-HT according to bioassay, fluorometry, and chromatography. The amount can be increased markedly by exposing the isolated gill to the precursor substance 5-hydroxytryptophan but not l-tryptophan. As the tissue level of 5-HT rises, the spontaneous beat frequency also rises. Both remain elevated for hours and perhaps for days. The gill of Mytilus edulis is richer than the gill of Modiolus demissus in both endogenous 5-HT and effective 5-hydroxytryptophan decarboxylase activity. Modiolus gill lacks the 5-hydroxyindole oxidase by which Mytilus gill destroys 5-HT. What if any mechanism exists in Modiolus for degrading 5-HT is not known, but monoamine oxidase is not present. The 5-HT content of Mytilus and Modiolus gill cannot be modified by treatment with reserpine or α-methyl-dopa. Which cells of the gill synthesize and destroy 5-HT has not been established, but these observations support the concept that the physiological activity of lamellibranch gill cilia is controlled by a serotonergic mechanism.     

Some Medical Problems of Chronic Hemodialysis

Chronic intermittent hemodialysis may relieve some medical problems of terminal uremia (for example, azotemia, acidosis, hypertension, neuro-muscular disorders, bleeding, pericarditis) to such a degree that many patients are able to resume their normal activity. There remain, however, problems which are not readily changed by hemodialysis (anemia, peripheral neuropathy, pruritus, sexual impotence, renal osteodystrophy). These, together with medical problems possibly caused by hemodialysis (for example, osmotic disequilibrium, errors in dialysate composition, hepatitis, hemosiderosis, isoimmunization from blood transfusions, shunt problems and psychological problems of dependency upon the artificial kidney) represent a limitation of the present type of hemodialysis therapy.     

Localization of Arbutin in Pyrvs by Means of Alkaline P-Phenylenediamine

A reagent composed of 0.2% p-phenylenediamine in 2 N NH₄OH was used for the cytochemical demonstration of arbutin in plant tissue. Sections of fresh tissue were cut at 25-50 μ, mounted in a drop of the reagent, and allowed to stand uncovered 15-20 min before applying a coverslip. Arbutin stained dark blue to dark purple and was easily distinguished from other constituents of the cell, such as chlorogenic acid, isochlorogenic acid, caffeic acid, and quinic acid, which stained yellow, yellow-green, red or brown in color. The limit of sensitivity of the p-phenylenediamine-arbutin reaction was 1:100,000, as determined by spot-plate tests.     

Heat Shock RNA Levels in Brain and Other Tissues After Hyperthermia and Transient Ischemia

A number of studies have demonstrated increased synthesis of heat shock proteins in brain following hyperthermia or transient ischemia. In the present experiments we have characterized the time course of heat shock RNA induction in gerbil brain after ischemia, and in several mouse tissues after hyperthermia, using probes for RNAs of the 70-kilodalton heat shock protein (hsp70) family, as well as ubiquitin. A synthetic oligonucleotide selective for inducible hsp70 sequences proved to be the most sensitive indicator of the stress response whereas a related rat cDNA detected both induced RNAs and constitutively expressed sequences that were not strongly inducible in brain. Considerable polymorphism of ubiquitin sequences was evident in the outbred mouse and gerbil strains used in these studies when probed with a chicken ubiquitin cDNA. Brief hyperthermic exposure resulted in striking induction of hsp70 and several-fold increases in ubiquitin RNAs in mouse liver and kidney peaking 3 h after return to room temperature. The oligonucleotide selective for hsp70 showed equivalent induction in brain that was more rapid and transient than observed in liver, whereas minimal induction was seen with the ubiquitin and hsp70-related cDNA probes. Transient ischemia resulted in 5- to 10-fold increases in hsp70 sequences in gerbil brain which peaked at 6 h recirculation and remained above control levels at 24 h, whereas a modest 70% increase in ubiquitin sequences was noted at 6 h. These results demonstrate significant temporal and quantitative differences in heat shock RNA expression between brain and other tissues following hyperthermia in vivo, and indicate that hsp70 provides a more sensitive index of the stress response in brain than does ubiquitin after both hyperthermia and ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

Enumeration of anaerobic oxalate-degrading bacteria in the ruminal contents of sheep

Abstract Concentrations of oxalate-degrading anaerobes in ruminal contents of sheep were determined from counts of colonies producing clear zones on a calcium oxalate medium (D agar with 7 mM CaCl₂). Viable counts of oxalate degraders from a 55-kg sheep fed a diet containing 32% halogeton (4.6% oxalate) averaged 2.6 × 10⁶/ g (dry weight). When the halogeton concentration in the diet was reduced to 16%, counts of oxalate degraders decreased nearly 300-fold. Oxalate-degrading isolates from this sheep were similar to OxB, the type strain of Oxalobacter formigenes . When a 45-kg sheep was fed diets containing 2.2, 1.5, and 0.8% oxalate, viable counts of oxalate degraders (enumerated on D agar with 14 mM CaCl₂ and 20% filter-sterilized ruminal fluid) represented 0.85, 0.52, and 0.06% of the total viable population, respectively; total viable counts were essentially unchanges by these concentrations of dietary oxalate. Similar percentages of oxalate degraders were also observed when a 23-kg sheep was fed diets containing 1.5 or 0.8% oxalate. This report presents the first direct measurements of the concentrations of oxalate-degrading bacteria in the rumen and supports the concept that the availability of oxalate in the diet influences the proportion of oxalate-degrading bacteria in the rumen     

Interleukin-1 inhibits PGE2 binding to macrophage-like P388D1 cells by a cyclic AMP-independent process.

The interaction between interleukin IL-1 alpha and PGE2 on P388D1 cells has been investigated. Preincubation of murine macrophage-like cells, P388D1, with IL-1 alpha (0-73 pM) reduced the binding of PGE2 to these cells in a concentration-dependent manner. Scatchard analysis showed that IL-1 alpha decreased the PGE2 binding by lowering both the high and low affinity receptor binding capacities (from 0.31 +/- 0.02 to 0.12 +/- 0.01 fmol/10(6) cells for the high affinity receptor binding sites and from 2.41 +/- 0.12 to 1.51 +/- 0.21 fmol/10(6) cells for the low affinity receptor binding sites). However, the dissociation constants of the receptors of the IL-1 alpha-treated cells remained unchanged. Inhibition of PGE2 binding by IL-1 alpha did not involve changes in either protein phosphorylation or intracellular cyclic AMP levels. Our data clearly show that IL-1 alpha inhibits the binding of PGE2 to monocytes/macrophages and may thereby counter the immunosuppressive actions of PGE2.     

Poly(ethylene oxide)-grafted thermoplastic membranes for use as cellular hybrid bio-artificial organs in the central nervous system

Poly(acrylonitrile-co-vinyl chloride) (PAN/VC) anisotropic membranes were chemically modified with poly(ethylene oxide) (PEO) (5000 and 20,000 g/mol) by one of two aqueous reactions: (a) acid hydrolysis of the nitrile group to a carboxylic acid with which amine-terminated PEO (PEO-NH(2)) reacted or (b) base reduction of the nitrile group to an amine with which PEO-succinimide (PEO-SC) reacted. Approximately 1.3% of the bulk material was modified with PEO-NH(2) whereas 1.8 to 3.5% was modified with PEO-SC as determined by proton nuclear magnetic resonance ((1)H NMR) and attenuated total reflectance Fourier transform infrared (ATR FTIR) spectra. Approximately 50 to 75% less bovine serum albumin (BSA) adsorbed to PEO-grafted single skin fibers than to unmodified PAN/VC. Transport properties of modified and unmodified fibers were compared by passive diffusion, convective nominal molecular weight cutoff, and hydraulic permeability. Neither hydraulic permeability nor nominal molecular weight cutoff of BSA changed appreciably after surface modification with PEO indicating that pore structure was not adversely affected by the chemistry involved in grafting poly(ethylene oxide). However, in the absence of any membrane conditioning, the apparent diffusion of alpha-chymotrypsinogen (24,000 g/mol) was enhanced in PEO-grafted PAN/VC fibers possibly as a result of reduced sorption of the permeating protein. In vivo biocompatibility in the brain tissue of rats was judged by histological assessment of the host's cellular response to fibers implanted for 30 days; biocompatibility of both PAN/VC and PAN/VC-g-PEO was satisfactory but improved slightly with PEO grafting. (c) 1994 John Wiley & Sons, Inc.     

P-type ATPases of eukaryotes and bacteria: Sequence analyses and construction of phylogenetic trees

The amino acid sequences of 47 P-type ATPases from several eukaryotic and bacterial kingdoms were divided into three structural segments based on individual hydropathy profiles. Each homologous segment was (1) multiply aligned and functionally evaluated, (2) statistically analyzed to determine the degrees of sequence similarity, and (3) used for the construction of parsimonious phylogenetic trees. The results show that all of the P-type ATPases analyzed comprise a single family with four major clusters correlating with their cation specificities and biological sources as follows: cluster 1: Ca²⁺-transporting ATPases; cluster 2: Na⁺- and gastric H⁺-ATPases; cluster 3: plasma membrane H⁺-translocating ATPases of plants, fungi, and lower eukaryotes; and cluster 4: all but one of the bacterial P-type ATPases (specific for K⁺, Cd²⁺, Cu²⁺ and an unknown cation). The one bacterial exception to this general pattern was the Mg²⁺-ATPase of Salmonella typhimurium, which clustered with the eukaryotic sequences. Although exceptions were noted, the similarities of the phylogenetic trees derived from the three segments analyzed led to the probability that the N-terminal segments 1 and the centrally localized segments 2 evolved from a single primordial ATPase which existed prior to the divergence of eukaryotes from prokaryotes. By contrast, the C-terminal segments 3 appear to be eukaryotic specific, are not found in similar form in any of the prokaryotic enzymes, and are not all demonstrably homologous among the eukaryotic enzymes. These C-terminal domains may therefore have either arisen after the divergence of eukaryotes from prokaryotes or exhibited more rapid sequence divergence than either segment 1 or 2, thus masking their common origin. The relative rates of evolutionary divergence for the three segments were determined to be segment 2 < segment 1 < segment 3. Correlative functional analyses of the most conserved regions of these ATPases, based on published site-specific mutagenesis data, provided preliminary evidence for their functional roles in the transport mechanism. Our studies define the structural and evolutionary relationships among the P-type ATPases. They should provide a guide for the design of future studies of structure-function relationships employing molecular genetic, biochemical, and biophysical techniques. Correspondence to: M.H. Saier, Jr.