Nla and Nlb of peanut stripe potyvirus are present in the nucleus of infected cells, but do not form inclusions

We investigated, by immunological and gene-fusion methods, whether the failure of peanut stripe potyvirus (PStV)-encoded nuclear inclusion proteins a (Nla) and b (Nlb) to form nuclear inclusions is due to the lack of their in vivo accumulation or the inability of one or both proteins to be transported into the nucleus Nla domains (Nla-VPg and Nla-proteinase), full-length Nlb, and full-length cylindrical inclusion (CI) protein of PStV were cloned, expressed in Escherichia coli, and used for antisera production. Immunoblot analysis of accumulation of Nla, Nlb, and CI in time course experiments revealed that they accumulated to similar levels in PStV-infected Nicotiana benthamiana. In immunocytochemical studies with electron microscopy, antiserum against Nla-VPg, Nla-Pro, and Nlb specifically labeled Nla and Nlb proteins throughout the nuclei of PStV-infected cells, in the absence of nuclear inclusions. Translational fusions were made between Nla and Nlb to either the green fluorescence protein or the beta-glucuronidase in vectors for transient gene expression or stable expression in transgenic plants respectively. Fusion proteins containing Nla accumulated in the nucleus, whereas fusion proteins containing Nlb accumulated in a punctate pattern in the cytoplasm. These data indicate that at least Nla possesses a nuclear localization signal.

The shocking lung mass: a case report

Two years after implantation of an ICD with epicardial patch leads, a patient presented with hemoptysis. The posterior left ventricular patch was found to have eroded into lingular segmental bronchus. During thoracotomy, the hardware was removed and the bronchus successfully repaired.

BTK as a mediator of radiation-induced apoptosis in DT-40 lymphoma B cells

Bruton's tyrosine kinase (BTK) is a member of the SRC-related TEC family of protein tyrosine kinases (PTKs). DT-40 lymphoma B cells, rendered BTK-deficient through targeted disruption of the btk gene by homologous recombination knockout, did not undergo radiation-induced apoptosis, but cells with disrupted lyn or syk genes did. Introduction of the wild-type, or a SRC homology 2 domain or a plecstrin homology domain mutant (but not a kinase domain mutant), human btk gene into BTK-deficient cells restored the apoptotic response to radiation. Thus, BTK is the PTK responsible for triggering radiation-induced apoptosis of lymphoma B cells, and its kinase domain is indispensable for the apoptotic response.

Roles of the sequence encoding tobacco etch virus capsid protein in genome amplification: requirements for the translation process and a cis-active element

The roles of the capsid protein (CP) and the CP coding sequence of tobacco etch potyvirus (TEV) in genome amplification were analyzed. A series of frameshift-stop codon mutations that interrupted translation of the CP coding sequence at various positions were introduced into the TEV genome. A series of 3' deletion mutants that lacked the CP coding sequence beyond each of the frameshift-stop codon mutations were also produced. In addition, a series of 5' CP deletion mutants were generated. Amplification of genomes containing either frameshift-stop codon insertions after codons 1, 59, 103, and 138 or genomes containing the corresponding 3' deletions of the CP coding sequence was reduced by 100- to 1,000-fold relative to that of the parental genome in inoculated protoplasts. In contrast, a mutant containing a frameshift-stop codon after CP position 189 was amplified to 27% of the level of the parental virus, but the corresponding 3' deletion mutant lacking codons 190 to 261 was nonviable. Deletion mutants lacking CP codons 2 to 100, 2 to 150, 2 to 189, and 2 to 210 were amplified relatively efficiently in protoplasts, but a deletion mutant lacking codons 2 to 230 was nonviable. None of the amplification-defective frameshift-stop codon or deletion mutants was rescued in transgenic cells expressing TEV CP, although the transgenic CP was able to rescue intercellular movement defects of replication-competent CP mutants. Coupled with previous results, these data led to the conclusions that (i) TEV genome amplification requires translation to a position between CP codons 138 and 189 but does not require the CP product and (ii) the TEV CP coding sequence contains a cis-active RNA element between codons 211 and 246. The implications of these findings on mechanisms of RNA replication and genome evolution are discussed.

Site-directed mutagenesis of monocyte chemoattractant protein-1 identifies two regions of the polypeptide essential for biological activity

Monocyte chemoattractant protein-1 (MCP-1) mediates monocyte migration into tissues in inflammatory diseases and atherosclerosis. We have investigated structure-activity relationships for human MCP-1. Mutations were introduced based upon differences between MCP-1 and the structurally related but functionally distinct molecule interleukin-8 (IL-8). Mutant proteins produced using the baculovirus/insect cell expression system were purified and their ability to stimulate monocyte chemotaxis and elevation of intracellular calcium in THP-1 monocytic leukaemia cells was measured. Two regions in MCP-1 were identified as important for its biological activity. One region consists of the sequence Thr-Cys-Cys-Tyr (amino acids 10-13). Point mutations of Thr-10 to Arg and Tyr-13 to Ile greatly lowered MCP-1 activity. The second functionally important region is formed by Ser-34 and Lys-35. Insertion of a Pro between these two residues, or their substitution by the sequence Gly-Pro-His, caused nearly complete loss of MCP-1 activity. Competition binding experiments showed that the mutations that affected activity also lowered the ability to compete with wild-type MCP-1 for receptors on THP-1 cells. Point mutations at positions 8, 15, 30, 37, 38 and 68 had little effect on MCP-1 activity. The important regions that we have identified in MCP-1 correspond with previously identified functionally important regions of IL-8, suggesting that the two molecules bind to their respective receptors by similar contacts.

Reconstitution of the B cell antigen receptor signaling components in COS cells

To elucidate interactions occurring between B cell protein tyrosine kinases and the signaling components of the B cell antigen receptor, we have co-transfected into COS cells individual tyrosine kinases together with chimeric cell surface receptors containing the cytoplasmic domains of Ig alpha or Ig beta. Of the tyrosine kinases transfected (Lyn, Blk, Hck, Syk, Fyn), only Blk was able to phosphorylate and subsequently associate with cotransfected Ig alpha and Ig beta chimeras in vivo. Association between Blk and the Ig alpha and Ig beta cytoplasmic domains was shown by mutational analyses to be the result of an SH2-phosphotyrosine interaction. We identified the tyrosine residues of the Ig alpha and Ig beta cytoplasmic domains was shown by mutational analyses to be the result of an SH2-phosphotyrosine interaction. We identified the tyrosine residues of the Ig alpha and Ig beta cytoplasmic domains phosphorylated by Blk. The enzymatic activity and membrane association of Blk were required for the observed phosphorylation of the Ig alpha and Ig beta chimeras. Sequences within the amino-terminal unique domain of Blk are responsible for recognition and subsequent phosphorylation of the Ig alpha chimera since transfer of the unique region of Blk to Fyn results in the chimeric kinase's ability to phosphorylate the cytoplasmic domain of Ig alpha. These findings indicate that the unique domain of Src family kinases may direct recognition of certain substrates leading to their phosphorylation.

Src family protein tyrosine kinases induce autoactivation of Bruton's tyrosine kinase

Bruton's tyrosine kinase (Btk) is tyrosine phosphorylated and enzymatically activated following ligation of the B-cell antigen receptor. These events are temporally regulated, and Btk activation follows that of various members of the Src family of protein tyrosine kinases, thus raising the possibility that Src kinases participate in the Btk activation process. We have evaluated the mechanism underlying Btk enzyme activation and have explored the potential regulatory relationship between Btk and Src protein kinases. We demonstrate in COS transient-expression assays that Btk can be activated through intramolecular autophosphorylation at tyrosine 551 and that Btk autophosphorylation is required for Btk catalytic functions. Coexpression of Btk with members of the Src family of protein tyrosine kinases, but not Syk, led to Btk tyrosine phosphorylation and activation. Using a series of point mutations in Blk (a representative Src protein kinase) and Btk, we show that Src kinases activate Btk through an indirect mechanism that requires membrane association of the Src enzymes as well as functional Btk SH3 and SH2 domains. Our results are compatible with the idea that Src protein tyrosine kinases contribute to Btk activation by indirectly stimulating Btk intramolecular autophosphorylation.

Temporal differences in the activation of three classes of non-transmembrane protein tyrosine kinases following B-cell antigen receptor surface engagement

We evaluated in WEHI 231 B cells the time-dependent responses of Lyn, Blk, Btk, Syk, and three members of the Jak family of protein tyrosine kinases following antibody-mediated surface engagement of the B-cell antigen receptor. Our results show that the enzyme activities of Lyn and Blk were stimulated within seconds of antigen receptor engagement and correlated with the initial tyrosine phosphorylation of the Ig alpha and Ig beta subunits of the B-cell antigen receptor. Btk enzyme activity was also transiently stimulated and was maximal at approximately 5 min after B-cell receptor surface binding. Syk activity gradually increased to a maximum at 10-30 min following receptor ligation and was found to parallel the association of Syk with the tyrosine phosphorylated Ig alpha and Ig beta subunits of the receptor. While the specific activities of the Jak1, Jak2, and Tyk2 protein tyrosine kinases were unaltered following B-cell receptor ligation, the abundance of Jak1 and Jak2 were increased 3- to 4-fold within 10 min of receptor engagement. These results demonstrate that multiple families of non-transmembrane protein tyrosine kinases are temporally regulated during the process of B-cell antigen receptor-initiated intracellular signal transduction.

Temporal regulation of non-transmembrane protein tyrosine kinase enzyme activity following T cell antigen receptor engagement

We evaluated in Jurkat T cells the time-dependent responses of Fyn, Lck, Syk, and Zap following antibody-mediated cross-linking of the T cell antigen receptor. Our results show that the protein kinase activities of Fyn and Lck were activated within seconds of receptor cross-linking. Fyn activity, as measured by autophosphorylation and tyrosine phosphorylation of an exogenous substrate, was maximal 5 s to 1 min following receptor cross-linking. Lck was also found to be activated within 5 s of antigen receptor cross-linking but differed from Fyn in that Lck activity was elevated for at least 30 min. Syk and Zap protein kinase activities were found to peak between 5 and 10 min following receptor cross-linking, returning to approximately basal activity levels by 60 min. The protein kinase activities of both Syk and Zap were found to parallel their reactivity in immunoblotting experiments with anti-phosphotyrosine antibodies. Both Syk and Zap were found to associate with the tyrosine-phosphorylated zeta subunit of the T cell antigen receptor. These observations imply that T cell antigen receptor signal transduction involves the activation of multiple members of at least two different families of non-transmembrane protein tyrosine kinases.

Effect of BHA on longevity, antioxygenic enzymes and peroxides in Callosobruchus maculatus

Life span and antioxygenic enzyme activities of insects reared on optimal BHA concentration (1 mM) soaked seeds were higher than their respective controls. However, the reproductive potential, peroxides and the level of free radicals declined. The increased longevity with BHA could be attributed to its free radical quenching effect, thereby leading to the decreased peroxide levels and the increased antioxygenic enzyme activities of the insects.

Effect of ascorbic acid on longevity and biochemical alterations in Callosobruchus maculatus F. (Coleoptera: Bruchidae)

Optimal ascorbic acid concentration (1 mM) increased the median (LT(50)) and maximum (LT(100)) life spans, decreased age-independent susceptibility to death (a(0)), reproductive period, number of eggs laid/female but prolonged the post-reproductive period in Callosobruchus maculatus. The activities of respiratory enzymes and the levels of metabolic end-products declined while the activities of antioxygenic enzymes increased. The increased longevity of insects reared on ascorbic acid soaked seeds may be interpreted in terms of conservation of energy by way of decreased reproductive potentiality and the maintenance of a homeostatic balance between pro-oxidant generation and antioxidant defences.

Signal transduction through a biomolecular receptor tyrosine protein kinase composed of a platelet-derived growth factor receptor-CD4 chimera and the nonreceptor tyrosine protein kinase Lck

We have generated a novel "receptor tyrosine kinase" by fusing the extracellular and transmembrane domain of the mouse platelet-derived growth factor receptor (PDGFR) to the cytoplasmic domain of CD4 and coexpressing the construct with the murine cytoplasmic tyrosine protein kinase p56lck. NMuMG cells, which are mouse mammary gland epithelial cells that lack endogenous platelet-derived growth factor (PDGF) receptor expression, were stably transfected with both PDGFR-CD4 and p56lck. The PDGFR-CD4 chimeric protein was expressed at the cell surface and formed a complex with p56lck. Addition of PDGF to these cells led to increased tyrosine phosphorylation of a 56-kDa protein likely to be p56lck and several unidentified cellular proteins. The enzymatic activity of p56lck was increased after treatment with PDGF, indicating that dimerization (or oligomerization) mediated by ligand binding at the cell surface is capable of inducing the activation not only of receptor tyrosine kinases but nonreceptor tyrosine kinases as well. However, the PDGFR-CD4.p56lck complex was, in contrast to the wild type PDGF receptor, not able to induce a PDGF-dependent mitogenic response or DNA synthesis in NMuMG cells. Analysis of several known substrates of the PDGFR-signaling pathway indicates an early block in the transduction of the signal generated by p56lck.

Signal transduction by immunoglobulin is mediated through Ig alpha and Ig beta

Immunoglobulin (Ig) antigen receptors are composed of a noncovalently-associated complex of Ig and two other proteins, Ig alpha and Ig beta. The cytoplasmic domain of both of these Ig associated proteins contains a consensus sequence that is shared with the signaling proteins of the T cell and Fc receptor. To test the idea that Ig alpha-Ig beta heterodimers are the signaling components of the Ig receptor, we have studied Ig mutations that interfere with signal transduction. We find that specific mutations in the transmembrane domain of Ig that inactivate Ca2+ and phosphorylation responses also uncouple IgM from Ig alpha-Ig beta. These results define amino acid residues that are essential for the assembly of the Ig receptor. Further, receptor activity can be fully reconstituted in Ca2+ flux and phosphorylation assays by fusing the cytoplasmic domain of Ig alpha with the mutant Igs. In contrast, fusion of the cytoplasmic domain of Ig beta to the inactive Ig reconstitutes only Ca2+ responses. Thus, Ig alpha and Ig beta are both necessary and sufficient to mediate signal transduction by the Ig receptor in B cells. In addition, our results suggest that Ig alpha and Ig beta can activate different signaling pathways.

Gastric intramucosal acidosis in patients with chronic kidney failure

BACKGROUND

Patients with chronic kidney failure have an increased incidence of gastrointestinal complications, particularly bleeding from the stomach. Diminished mucosal blood flow is thought to be an important etiologic factor for such bleeding.

METHODS

Eleven patients with kidney failure on maintenance dialysis underwent placement of a gastric tonometer for the determination of gastric intramucosal pH (pHi) before and during dialysis. The arterial pH (pHa), calculated pHi, and pHa-pHi differences were compared with the results in a control group of seven normal volunteers.

RESULTS

The patients with chronic kidney failure had a mean (+/- SD) pHa (7.36 +/- 0.04) similar to that found in seven control subjects (7.37 +/- 0.04). However, the gastric mucosal pH in the patients on dialysis (7.20 +/- 0.17) was lower than in the seven control subjects (7.38 +/- 0.06) (p < 0.01). A gastric mucosal pH thought to be predictive of either bleeding from stress ulceration (pHi < 7.32) or mucosal ischemia (pHi-pHa difference > 0.13) was found in nine (82%) of the patients with kidney failure and in only one (14%) of the control subjects (p < 0.001).

CONCLUSIONS

This new preliminary finding suggests that the high incidence of gastric bleeding in chronic kidney failure may be related to mucosal ischemia.

Photosystem II reaction center particle from Spirodela stroma lamellae

A Photosystem II (PSII) reaction center particle from the stroma lamellae of Spirodela oligorrhiza has been isolated. The stroma lamellar PSII reaction center contained the same proteins found in granal PSII reaction centers, namely D1, D2, and cytochrome b559; however, the cytochrome b559 content was half of that in the granal centers. The pigment composition, 77 K fluorescence emission, and excitation spectra of the stroma lamellar reaction centers were determined. Our results indicate a fully functional PSII particle in the stromal lamellae.

Cross-linking of surface immunoglobulin activates src-related tyrosine kinases in WEHI 231 cells

Crosslinking of sIgM on the B cell line WEHI 231 with anti-sIgM antibody induces protein tyrosine phosphorylation, implicating protein tyrosine kinases (PTKs) in sIg-mediated signal transduction. We have analyzed this cell line for members of the src family of PTKs and have evaluated whether these PTKs might be involved in the process of sIgM-mediated signaling. Our results show that Blk, Lyn, Lck, and Hck are detectable in WEHI 231 cells. Addition of antibodies to sIgM were found to variably stimulate the activities of Blk, Lyn, Lck, and Hck as measured by immune-complex protein kinase assays. Autophosphorylation of these src PTKs, as assessed by reaction with anti-phosphotyrosine antibodies, increased over the time course of sIgM-mediated activation. Co-immunoprecipitation studies to investigate the potential physical interaction of src PTKs with the sIgM receptor complex revealed that, under digitonin and Brij 96 lysis conditions Lyn, Lck, Hck, but not Blk associated with sIgM.

Life prolonging effect of butylated hydroxy anisole in Callosobruchus maculatus F. (Coleoptera: Bruchidae)

The present study deals with the effect of butylated hydroxy anisole (BHA), an antioxidant, on longevity and fecundity of insects infesting BHA soaked seeds of Vigna radiata. Median (LT(50)) and maximum (LT(100)) life spans as well as post-reproductive period of the insect reared on optimal concentration (1 mM) of antioxidant soaked seeds were higher than the control. However, the reproductive period of the females and the number of eggs laid/female declined. The results are indicative of the increased life span of the insects on BHA feeding at the cost of the reproductive period.

Conversion of monocyte chemoattractant protein-1 into a neutrophil attractant by substitution of two amino acids

The small cytokine monocyte chemoattractant protein-1 has structural similarity to the neutrophil chemoattractant interleukin-8, but each protein is specific in attracting its own target cell. To investigate the structural basis of this cell type specificity, we have developed an Escherichia coli expression system for the monocyte chemoattractant and mutagenized selected amino acid residues to ones found at the corresponding positions of interleukin-8. We find that a double mutation of tyrosine 28 and arginine 30 to leucine and valine, respectively, causes a drastic decrease in chemotactic activity toward monocytes with the appearance of a novel (interleukin-8-like) neutrophil chemotactic activity. Computer graphic analysis predicts that, with the double substitution, a putative receptor binding groove of the monocyte chemoattractant protein would become topographically similar to that of interleukin-8. We therefore postulate that one or both of these amino acid residues are part of the binding contact of these small cytokines and their receptors.

Morphine-induced modulation of sciatic nerve stimulation evoked blood pressure responses

Effect of i.v. morphine (1-2 mg/kg) on blood pressure changes evoked by sciatic nerve stimulation (SNS) were studied in chloralose anaesthetised cats. SNS gave a depressor, pressor or a biphasic BP response generally linked to the parameters of stimulation. Morphine produced marked attenuation of depressor and some facilitation of pressor response, suggesting a possible reciprocal relationship between depressor and pressor responses. Depressor response has been correlated with deep tissue or visceral pain mediated through A delta fibres and pressor response to cutaneous nociception involving C fibres or non nociceptive input via group II fibres. Involvement of medullary regions in differential modulation of these depressor and pressor response has been suggested.

Isolation, characterization, and host-cell-binding properties of a cytotoxin from Campylobacter jejuni

A 68,000-molecular-weight protein was isolated by polyacrylamide gel electrophoresis from the organism-free filtrate of a fully virulent clinical strain of Campylobacter jejuni. The eluted protein was heat labile, was inactivated at either pH 3.0 or 9.0, was sensitive to trypsin, and was lethal for fertile chicken eggs. It also had toxic effects on chicken embryo fibroblast, Chinese hamster ovary (CHO), and intestinal 407 (Int407) cells. A monoclonal antibody (CETPMAb4) raised to this eluted toxic protein (ETP) from C. jejuni abolished these toxic activities. Homology between C. jejuni ETP and Vibrio cholerae toxin was not observed in that specific antisera to each did not block their respective toxic activities. In enzyme-linked immunosorbent assays, ETP, unlike chlorea enterotoxin, did not bind to GM1 ganglioside. Furthermore, the C. jejuni toxin had cytotoxinlike properties and induced rounding of CHO cells. Binding of ETP to Int407 and primary chicken embryo fibroblast cells was maximal after 2 h as assessed by enzyme-linked immunosorbent assay, and this toxin adherence to host cell membranes was significantly reduced by prior treatment of the cells with proteolytic enzymes, neuraminidase, or glutaraldehyde but not by treatment with beta-galactosidase, lipase, Nonidet P-40, or sodium metaperiodate. In competitive binding assays, sugars, lectins, or GM1 ganglioside did not adversely influence uptake of ETP by these cells. These results suggest that the ETP produced by C. jejuni is a cytotoxin which binds to Int407 cells via a protein- or glycoproteinlike receptor on cell membranes and possesses properties dissimilar to those of V. cholerae toxin.

Variations in the life span, enzymes and lipid peroxide levels in ageing Caryedon serratus (Coleoptera: Bruchidae)

In the bruchid Caryedon serratus, life span of males was longer than that of females. Catalase showed an increasing trend with age in both the sexes but the increase was higher in males. However, an opposite trend was observed for lipid peroxide levels. A rapid decline of NADH and succinate dehydrogenases in females is indicative of early depletion of food reserves due to the higher metabolic rate. Thus, in C. serratus, the factors contributing to relatively higher life span of males are efficient homeostatic defence mechanisms and low oxidative damage in males, early maturity and more reproductive demands in females.

Studies on the purified, lipid-reconstituted (Na+ + Mg2+)-ATPase from Acholeplasma laidlawii B membranes. Dependence of enzyme activity on lipid headgroup and hydrocarbon chain structure

The purified (Na+ + Mg2+)-ATPase from Acholeplasma laidlawii B membranes was successfully reconstituted with a number of different phospho- and glycolipids, and the ability of these lipids to support the function of this enzyme was evaluated by their ability to increase the specific activity of the purified enzyme and by their ability to restore its lipid-phase state-dependent properties which were lost during purification. The incorporation of this ATPase into liposomes composed of the endogenous membrane lipids of the organism, or of zwitterionic phospholipids such as phosphatidylcholine or phosphatidylethanolamine, results in a full reconstitution of its activity and its lipid-phase state-dependent properties. In contrast, anionic phospholipids alone, or in combination with zwitterionic phospholipids at concentrations higher than 10 mol % of the anionic phospholipid, cause an irreversible inhibition of this ATPase. However, when combined with neutral glycolipids, larger amounts of anionic phospholipid can be tolerated without enzyme inhibition. Phosphatidylcholines with acyl chains of 14-24 linear carbon atoms and varying degrees of branching and unsaturation successfully reconstitute the enzyme, in marked contrast to the shorter chain homologues, which were ineffective. Our results indicate that the full expression of the activity of the A. laidlawii B ATPase requires a host lipid bilayer membrane of low to moderate negative surface charge which is predominantly liquid-crystalline and of a minimal bilayer thickness. Once such requirements are met, the enzyme exhibits considerable flexibility regarding the nature of the lipids which can effectively support its function. In particular, the activity of the A. laidlawii B ATPase is not very sensitive to lipid "fluidity" in the liquid-crystalline state.

Virulence of Campylobacter jejuni for chicken embryos

The pathogenicity of Campylobacter jejuni was examined in chicken embryos. In this system, mortality data and histopathological findings induced by organisms and by bacterium-free filtered broth were identical. The absence in chicken embryo tissues both of organisms and of an inflammatory infiltrate suggests a toxin etiology.

Taste acuity and zinc metabolism in captopril-treated hypertensive male patients

Hypogeusia is a reported side effect of captopril. Linkage of hypogeusia to zinc deficiency has been suggested. We objectively assessed taste acuity using Henkin's three-drop stimulus technique and measured plasma zinc (PZn) level and urinary zinc excretion in 31 hypertensive patients. Of these, 11 were long-term, high-dose captopril recipients (more than 6 months, 266 +/- 34 mg/day), six were short-term captopril recipients (less than 6 months, 104 +/- 40 mg/daily dose), and the remaining 14 served as noncaptopril controls. Compared to controls, the long-term captopril group had significantly higher taste detection and recognition thresholds, lower PZn (91 +/- 3 vs. 100 +/- 3 micrograms/dl, P less than 0.05) and higher urinary zinc excretion (1017 +/- 89 vs. 609 +/- 76 micrograms/day, P less than 0.005). The short-term captopril group did not differ significantly from the noncaptopril group except for higher taste-recognition thresholds for NaCl and sucrose (P less than 0.05). Discontinuing captopril improved taste acuity and almost normalized zinc parameters in two patients on long-term captopril. These results suggest that abnormalities of taste are commonly associated with captopril therapy and may be related to changes in zinc metabolism. This is especially true in patients on long-term, high-dose captopril therapy.

Cerulenin inhibition of lipid synthesis and its reversal by exogenous fatty acids in Mycobacterium smegmatis ATCC 607

Cerulenin inhibited the lipid synthesis of Mycobacterium smegmatis ATCC 607 over the range of 0.5-1.8 microgram/mL with complete inhibition at 1.8 microgram/mL, as monitored by [14C]glycerol incorporation into lipids. Exogenous fatty acids failed to restore the lipid synthesis at 1.8 microgram/mL; however, the addition of palmitic acid to the growth medium partially restored the lipid synthesis when cerulenin concentration was decreased to 1.6 microgram/mL. Fatty acid analysis of cerulenin plus palmitic acid supplemented cultures revealed that exogenously supplied fatty acid was incorporated into cellular phospholipids. Further investigations with 1.6 microgram/mL of cerulenin and [14C]acetate and [32P]orthophosphoric acid showed that cerulenin inhibited the synthesis of saturated plus unsaturated fatty acids and phospholipids. Pulse-chase studies with [14C]acetate revealed decreased synthesis and degradation of each of the phospholipid components.

Cerulenin effect on phospholipid metabolism in Mycobacterium smegmatis ATCC 607

Phospholipid metabolism in the presence of a subinhibitory concentration of cerulenin was studied in Mycobacterium smegmatis ATCC 607 by pulse labelling and subsequent chasing of radioactivity in phospholipids using [32P]orthophosphate. Cerulenin inhibited biosynthesis of total phospholipids to a significant level which is reflected equally in all the phospholipid components (phosphatidylethanolamine, phosphatidylinositol mannosides and cardiolipin) within the time of exposure. On chase, alteration in degradation of all phospholipid components was observed on cerulenin treatment, in comparison with control cells. Differences seen in the metabolism of phospholipids in cerulenin-treated and control cells are discussed.

Role of calcium in regulating intracellular pH following the stepwise release of the metabolic blocks at first-meiotic prophase and second-meiotic metaphase in amphibian oocytes

31P-NMR has been used to monitor changes in intracellular pH following the sequential release of the block at first-meiotic prophase by hormones and the block at second-meiotic metaphase by fertilization in Rana eggs and oocytes. The broad phosphoprotein signal was eliminated by a combination of spin-echo and deconvolution techniques. pHi was determined from the pH-dependent separation of intracellular Pi and phosphocreatine resonances. Agents that release the prophase block (progesterone, insulin, D-600, La3+) increased pHi from 7.38 to 7.7-7.8 within 1-3 h. Noninducers such as 17 beta-estradiol were without effect. By second-metaphase arrest (ovulated, unfertilized) the pHi had fallen to 7.1-7.2. pHi underwent a transient increase to about 7.7 within the first 30 min at fertilization, with a slow 0.1-0.2 pH unit oscillation during early cleavage. The progesterone-induced elevation of intracellular pH is not blocked by amiloride and occurs in Na+-free medium. A transient rise in pHi occurs when the prophase-arrested oocyte is transferred to Ca2+-free medium or when ionophore A23187 is added to the Ca2+-containing medium. Agents that inhibit the resumption of the first meiotic division either block the rise in pHi (procaine, PMSF) or shorten the time-course of the rise in pHi (ionophore A23187). Conditions that elevate intracellular Ca2+ levels and/or increase Ca2+ exchange produce an increase in pHi, whereas those conditions that decrease intracellular Ca2+ levels and/or exchange produce a fall in pHi within 1 h. The time-course of the increase in pHi both following release of the prophase block and at fertilization coincide with a fall in intracellular cAMP and release of surface and/or intracellular Ca2+. These results suggest that: (1) pHi is a function of cytosolic free Ca2+ levels and/or Ca2+ exchange across the oocyte plasma membrane, and (2) meiotic agonists (progesterone, insulin, D-600) and mitogens (sperm, ionophore A23187) modulate intracellular and/or membrane Ca2+ with the resulting changes in pHi and cAMP and resumption of the meiotic divisions.

Leukocyte metabolism and function in uremia

Leukocyte metabolism was studied in 13 non-diabetic hemodialysis patients, 8 clinically stable, nondiabetic transplant recipients, and 13 control subjects. Metabolic parameters included rates of oxygen consumption (nmoles/min/10(6) cells), glucose uptake, lactate production (nmoles/hr/10(6) cells), and 14C-l-glucose oxidation to 14CO2 (nmoles/hr/10(6) cells). Granulocyte metabolism was stimulated by phagocytosis of opsonized zymosan (Z) and by the membrane perturbing agent phorbol myristate acetate (PMA). Granulocyte motility in response to zymosan-activated plasma (ZAP) was also studied. Granulocytes from hemodialysis patients showed significantly impaired stimulated oxygen consumption (Z = 2.41 +/- 0.30 vs. 3.73 +/- 0.39; PMA = 2.63 +/- 0.33 vs. 3.67 +/- 0.19), resting glucose uptake (17.7 +/- 2.9 vs. 36.5 +/- 3.5), stimulated glucose uptake (Z = 44.2 +/- 7.1 vs. 71.8 +/- 5.3; PMA = 63.7 +/- 5.5 vs. 92.8 +/- 5.6), stimulated lactate production (Z = 68.4 +/- 5.1 vs. 97.5 +/- 9.3; PMA = 70.7 +/- 4.9 vs. 92.7 +/- 5.4), and ZAP-stimulated granulocyte motility (16 +/- 3 vs. 30 +/- 4 mu). Metabolic responses of granulocytes from transplant recipients were frequently intermediate between those of hemodialysis patients and controls, but not significantly different from controls. Abnormalities of glucose and oxygen metabolism in granulocytes from uremic patients may cause or contribute to granulocyte dysfunction and vulnerability to infection in such patients.

Changes in short-latency somatosensory evoked potentials during hemodialysis in chronic renal failure

Short-latency SEPs were monitored in eight patients undergoing hemodialysis for end-stage renal disease. The peak latencies of EP,N13, and N20 were significantly delayed compared with those of the control group. Because the interpeak latency of N13 - N20 (central conduction time) was not significantly prolonged, there could be no possible subclinical involvement of the ascending sensory fibers in the brainstem. The dialysis did alter the peak latencies of EP,N20, and interpeak latencies of EP-N13 and EP-N20; these changes, however, were not highly significant. The evoked potential changes did not correlate with the routine biochemical data. Monitoring short-latency SEP may lead to early recognition of pathologic involvement of the peripheral nervous system.

An intravasal non-occlusive contraceptive device in rats

An implantable miniature biogalvanic cell was developed to kill the spermatozoa in the vas deferens by an electric current. Experiments in vitro and in vivo showed that a combination of aluminum/silver electrodes connected with platinum wires with the vas deferens fluid as n electrolyte is effective in killing spermatozoa. Female rats paired with males having biogalvanic devices in the vas deferens, which remained patent, did not produce any young.

Histology of the rat vas deferens after injection of a non-occlusive chemical contraceptive

An alternate co-polymer of styrene and maleic anhydride was dissolved in dimethylsulphoxide and injected into the vas deferens of rats. The polymer was retained in the vas deferens and the morphological changes detected were confined to the mucosa. When the polymer was removed by flushing dimethylsulphoxide, the mucosal structure became normal within 2 weeks.