Chitin utilization by marine bacteria. A physiological function for bacterial adhesion to immobilized carbohydrates

Chitin turnover is essential for recycling carbon and nitrogen in marine ecosystems. A key step in this process is the adhesion of marine bacteria to chitin-containing particulates. Vibrio species were therefore surveyed for their ability to bind to immobilized carbohydrates, and one, Vibrio furnissii, adhered to glycosides of three sugars, N-acetylglucosamine (the preferred ligand), D-mannose, and D-glucose. A single Ca(2+)-requiring lectin is responsible for binding to the three sugars. Cells adhering to the chitin analogue divided at the same rate as cells in liquid culture. The first progeny of adherent cells continued to bind to the beads, but the population gradually shifted to a large fraction of free swimming cells, a process that may be necessary for colonization. Metabolic energy is required for cell adhesion to the glycosides, and transient (or no) adhesion occurred in incomplete growth media. The results were explained by studying met and pro mutants. Both the initiation and maintenance of lectin-mediated adhesion requires continuous protein synthesis; expression of lectin activity is a major priority of these cells and functions under conditions adequate for minimal protein synthesis, but insufficient to support cell growth. The adhesion/deadhesion apparatus is apparently used to continuously monitor the nutrient status of the environment, i.e. as a nutrient sensorium. In incomplete medium, cells deadhere, presumably to migrate to a more favorable environment.

Chitin utilization by marine bacteria. Degradation and catabolism of chitin oligosaccharides by Vibrio furnissii

Chemotaxis of the marine bacterium Vibrio furnissii to chitin oligosaccharides has been described (Bassler, B. L., Gibbons, P. J., Yu, C., and Roseman, S. (1991) J. Biol. Chem. 266, 24268-24275). Some steps in catabolism of the oligosaccharides are reported here. GlcNAc, (GlcNAc)2, and (GlcNAc)3 are very rapidly consumed by intact cells, about 320 nmol of GlcNAc equivalents/min/mg of protein. (GlcNAc)4 is utilized somewhat more slowly. During these processes, there is virtually no release of hydrolysis products by the cells. The oligosaccharides enter the periplasmic space (via specific porins?) and are hydrolyzed by a unique membrane-bound endoenzyme (chitodextrinase) and an exoenzyme (N-acetyl-beta-glucosaminidase; beta-Glc-NAcidase). The genes encoding these enzymes have been cloned and expressed in Escherichia coli. The chitodextrinase cleaves soluble oligomers, but not chitin, to the di- and trisaccharides, while the periplasmic beta-GlcNAcidase hydrolyzes the GlcNAc termini from the oligomers. The end products in the periplasm, GlcNAc and (GlcNAc)2 (possibly (GlcNAc)3) are catabolized as follows. (a) Disaccharide pathway, A (GlcNAc)2 permease is apparently expressed by Vibrio furnissii. Translocated (GlcNAc)2 is rapidly hydrolyzed by a soluble, cytosolic beta-GlcNAcidase, and the GlcNAc is phosphorylated by an ATP-dependent, constitutive kinase to GlcNAc-6-P. (b) Monosaccharide pathway, Periplasmic GlcNAc is taken up by Enzyme IINag of the phosphoenolpyruvate:glycose phosphotransferase system, yielding GlcNAc-6-P, the common intermediate for both pathways. Finally, GlcNAc-6-P----Ac- + GlcNH2-6-P----Fru-6-P + NH3. (GlcNAc)2 is probably the "true" inducer of the chitin degradative enzymes described in this report and, depending on its concentration in the growth medium, differentially induces the periplasmic and cytosolic beta-GlcNAcidases. The disaccharide pathway appears to be the most important when the cells are confronted with low concentrations of the oligomers (e.g. in chemotaxis swarm plates). The relative activities of the induced enzymes suggest that the rate-limiting steps in oligosaccharide catabolism are the glycosidase activities in the periplasm.

Chitin utilization by marine bacteria. Chemotaxis to chitin oligosaccharides by Vibrio furnissii

The adhesion/deadhesion apparatus of the marine bacterium Vibrio furnissii (Yu, C., Lee, A., Bassler, B. L., and Roseman, S. (1991) J. Biol. Chem. 266, 24260-24267) probably catalyzes the first step in colonizing chitin. Evidence is presented here for a second step, chemotaxis to chitin hydrolysis products. V. furnissii swarms toward chitin oligomers (GlcNAc)n, n = 1-6, at initial concentrations as low as 10 microM. A modified capillary assay was used for quantitation; the cells exhibit low level constitutive taxis to GlcNAc but not to the oligosaccharides. A mutant defective in the GlcNAc receptor (IINag of the phosphotransferase system) showed inducible taxis to the oligosaccharides. Two (or more) independently inducible receptors with overlapping specificities recognize (GlcNAc)n, n = 2-4. (GlcNAc)5 and (GlcNAc)6 were inactive in the capillary assay; expression of this receptor(s) apparently require special induction conditions. The (GlcNAc)n, n = 1-4, chemoreceptors of V. furnissii may be the most potent reported for bacteria. L-Amino acids were weak, constitutive attractants; glutamine, not known to be an attractant in other bacteria, was the most effective amino acid. The most potent receptor in Escherichia coli, Tar (aspartate), is not expressed in V. furnissii. The chemotactic responses were greatly affected by growth and induction conditions and the presence of nutrients in the assay media. Taxis to GlcNAc and GlcNAc oligomers was optimally induced by growth in lactate medium containing 0.6 mM sugar, while growth on the sugar per se resulted in poor taxis. Chemotaxis to the sugars increased 2- to 3-fold when the cells were starved. Nutrients in the assay medium, especially compounds that feed into or are part of the Krebs cycle, were potent inhibitors of taxis to the sugars and Gln. With the exception of isocitrate, inhibition of taxis correlated with the rate of oxidation of these compounds. The results suggest a link between catabolism and taxis in this organism, i.e. interactions or "cross-talk" between systems that are regulated by protein phosphorylation (Stock, J. A., Ninfa, A. J., and Stock, A. M. (1989) Microbiol. Rev. 53, 450-490).

Inhibitory effects of anticardiolipin antibodies on lymphocyte proliferation and neutrophil phagocytosis

Anticardiolipin antibodies purified from serum from patients with systemic lupus erythematosus (SLE) by cardiolipin micelles were studied for their effects on lymphocytes and neutrophils. At a concentration of 160 micrograms/ml they markedly suppressed the [3H]thymidine incorporation of mononuclear cells stimulated by phytohaemagglutinin (4.9 (SEM 1.9%) of the control) and pokeweed mitogen (26.7 (10.5%) of the control). In addition, anticardiolipin antibodies changed the cell cycle of phytohaemagglutinin stimulated lymphocytes such that the S and G2+M phases were significantly diminished (G0/G1 = 64.62%, S = 20.59%, G2+M = 14.78% in the presence of normal human IgG v G0/G1 = 86.07%, S = 10.32%, G2+M = 3.59% in the presence of anticardiolipin antibodies). The suppression of lymphocyte proliferation by anticardiolipin antibodies was shown not to be caused by an alteration of T cell subpopulations. However, the interleukin 2 receptors on the cell surface and the soluble interleukin 2 receptors in the supernatant of phytohaemagglutinin stimulated mononuclear cells were decreased in the presence of anticardiolipin antibodies. On the other hand, the phagocytic activity of neutrophils was 40% inhibited at a higher concentration of anticardiolipin antibodies (300 micrograms/ml) through suppression of C3b/C4b and Fc receptors on polymorphonuclear leucocytes. These results suggest that anticardiolipin antibodies exert inhibitory effects on both lymphocytes and phagocytes in addition to the coagulation cascade. These newly found activities of anticardiolipin antibodies were mediated by the non-specific membranotropic property of the antibodies.

Camptothecin overcomes MDR1-mediated resistance in human KB carcinoma cells

In order to understand the high efficacy of camptothecin derivatives against human colon tumor xenografts in nude mice, we have studied the transport properties of camptothecin derivatives across cellular membranes of MDR1-overexpressing cells. MDR1 overexpression was shown to have little effect on camptothecin cytotoxicity; camptothecin was equally cytotoxic to both the drug-sensitive parental cell line, KB 3-1, and its multidrug-resistant derivative, KB V1. The ability of camptothecin to overcome MDR1-mediated resistance is most likely due to unimpaired accumulation of camptothecin in MDR1 cells as suggested from the following experiments: (a) cytotoxicity of camptothecin against KB V1 cells was not altered by the known MDR1-reversing agent, verapamil; (b) camptothecin was ineffective as compared with vinblastine in competing with [3H]azidopine for photoaffinity labeling of MDR1; (c) camptothecin was equally efficient in trapping cellular topoisomerase I molecules on chromosomal DNA in the form of cleavable complexes in both KB 3-1 and KB V1 cells. The mechanism by which camptothecin overcomes MDR1-mediated resistance has been further studied using a number of uncharged and charged camptothecin derivatives. In contrast to the uncharged camptothecin derivatives, such as 9-amino-camptothecin and 10,11-methylenedioxy-camptothecin, the charged camptothecin derivative, topotecan, showed reduced cytotoxicity against MDR1-overexpressing KB V1 cells. The reduced cytotoxicity of topotecan in KB V1 cells was due to the overexpression of MDR1 in KB V1 cells since verapamil restored both topotecan accumulation and cytotoxicity. These results suggest that the charge on camptothecin can affect the drug's sensitivity to MDR1. The possible effect of membrane permeability in determining drug selectivity of MDR1 is discussed.

The conformation of echinomycin in DMSO solution

The conformation of the antibiotic echinomycin in DMSO solution has been determined from two-dimensional NMR and distance geometry calculation with distance constraints. Five converged conformations were calculated with NOE distance constraints followed by restraint energy minimization.

Defective expression of neutrophil C3b receptors and impaired lymphocyte Na(+)-K(+)-ATPase activity in patients with systemic lupus erythematosus

In our previous report, we demonstrated that the functions of phagocytes and lymphocytes were defective in patients with systemic lupus erythematosus (SLE). In an attempt to further clarify the defective mechanisms of these cells, 25 active SLE, 10 bronchial asthma patients (BA) on corticosteroids and 25 age and sex-matched normal individuals were investigated for the expression of membraneous C3b receptors, ionophore-induced 45Ca(2+)-uptake, mitochondrial potentials and phagocytic activity of neutrophils. We found decreased expression of C3b receptors on SLE PMN in both resting (37.2 +/- 3.7% of the normal controls) and FMLP-stimulated (68.3 +/- 7.1% of the normal controls) conditions, whereas the C3b receptor expression on BA-PMN receiving long-term steroid treatment was not different from normal controls. This suggests that the defective phagocytosis of SLE PMN is in the recognition, but not in the ingestion phase because of the normal function of Ca(2+)-influx and mitochondrial activity in SLE PMN. On the other hand, hyporesponsiveness to PHA stimulation (stimulation index: 127.4 +/- 46.3 in SLE vs. 311.2 +/- 30.4 in normals, p = 0.0077) was a distinct cell-mediated immune abnormality in our SLE patients. We measured the membrane potential of individual cells using 3,3'-dihexyloxacarbocyanin and found hyperpolarization in resting SLE lymphocytes. However, the membrane polarization of SLE lymphocytes became lower than that of normal cells after PHA stimulation for 3 days. A similar tendency was also found in Na(+)-K(+)-dependent ATPase activity in SLE lymphocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Common cis-acting region responsible for transcriptional regulation of Bradyrhizobium japonicum hydrogenase by nickel, oxygen, and hydrogen

Bradyrhizobium japonicum expresses hydrogenase in microaerophilic free-living conditions in the presence of nickel. Plasmid-borne hup-lacZ transcriptional fusion constructs were used to study the regulation of the hydrogenase gene. The hydrogenase gene was transcriptionally induced under microaerobic conditions (0.1 to 3.0% partial pressure O2). The hydrogenase gene was not transcribed or was poorly transcribed in strictly anaerobic conditions or conditions above 3.0% O2. Hydrogen gas at levels as low as 0.1% partial pressure induced hydrogenase transcription, and a high level of transcription was maintained up to at least 10% H2 concentration. No transcription was observed in the absence of H2. Hydrogenase was regulated by H2, O2, and Ni when the 5'-upstream sequence was pared down to include base number -168. However, when the upstream sequence was pared down to base number -118, the regulatory response to O2, H2, and Ni levels was negated. Thus, a common cis-acting regulatory region localized within 50 bp is critical for the regulation of hydrogenase by hydrogen, oxygen, and nickel. As a control, the B. japonicum hemA gene which codes for delta-aminolevulinic acid synthase was also fused to the promoterless lacZ gene, and its regulation was tested in the presence of various concentrations of O2 and H2. hemA-lacZ transcription was not dependent on levels of Ni, O2, or H2. Two different hup-lacZ fusions were tested in a Hup- background, strain JH47; these hup-lacZ constructs in JH47 demonstrated dependency on nickel, O2, and H2, indicating that the hydrogenase protein itself is not a sensor for regulation by O2, H2, or nickel.

Ras GTPase-activating protein physically associates with mitogenically active phospholipids

The physical interaction between GTPase-activating protein (GAP) and lipids has been characterized by two separate analyses. First, bacterially synthesized GAP molecules were found to associate with detergent-mixed micelles containing arachidonic but not with those containing arachidic acid. This association was detected by a faster elution time during molecular exclusion chromatography. Second, GAP molecules within a crude cellular lysate were specifically retained by a column on which certain lipids had been immobilized. The lipids able to retain GAP on such columns were identical to those which were shown previously to be most active in blocking GAP activity. The association between lipids and GAP was dependent upon magnesium ions. Lipids unable to inhibit GAP activity were also unable to physically associate with GAP. The tight association of GAP with these lipids was predicted by and helps to rationalize their ability to inhibit GAP activity.

Immunoregulatory effects of phospholipase A2 (PLA2) on the proliferation of human lymphocytes

Extracellular phospholipase A2 (PLA2) is a proinflammatory enzyme found especially in the inflammatory exudate to modulate blood flow to areas of antigen stimulation. In this study we found that PLA2 exerted a biphasic effect on the proliferation of phytohemagglutinin (PHA)-stimulated human mononuclear cells (PHA MNC). At low concentrations range from 0.001 to 1 U/ml, PLA2 enhanced the proliferation of PHA MNC (maximal increase was 37.0 +/- 5.67%). Conversely, at concentrations over 10 U/ml, PLA2 markedly suppressed the PHA-induced MNC proliferation (maximal decrease was 88.86 +/- 2.89%). PLA2 was non-toxic to lymphocytes after three days culture, unless the concentration was higher than 100 U/ml. The membrane polarization of PHA-stimulated lymphocytes was also increased by PLA2 at a low concentration. In addition, PLA2 displayed a similar effect on the proliferation of streptokinase-streptodornase (SK/SD) or allogeneic cell stimulated lymphocytes. The change of lymphocyte proliferation by PLA2, was parallel to the change of percentage of helper T cells. Furthermore--a CD4-rich population was proved more susceptible to PLA2 effect than a CD8-rich population. Para-bromophenacyl bromide (pBPB), an irreversible inhibitor of PLA2, abrogated the biphasic effect of PLA2 on PHA MNC proliferation. These results suggest that PLA2 plays a regulatory role on immune reactions by modulating the percentage of helper T cells.

Calcium, network activity, and the role of NMDA channels in synaptic plasticity in vitro

Functionally effective neuronal circuits are constructed through a competitive process that requires patterned neuronal activity elicited by structured input from the environment. To explore the mechanisms of this activity-dependent synaptic restructuring, we have developed an in vitro preparation of mouse spinal cord neurons maintained in a 3-chambered cell-culture system. Sensory afferents that received chronic electrical stimulation for 3-5 d developed stronger synaptic connections than unstimulated afferents converging onto the same postsynaptic spinal cord neuron. Exposure to 100 microM DL-2-amino-5-phosphonovaleric acid (APV), an antagonist of the NMDA channel, during the stimulation period prevented the competitive advantage associated with electric stimulation. However, when APV was applied with a higher concentration of calcium (3 mM), activity-dependent synaptic plasticity was no longer inhibited by the NMDA receptor antagonist. This reversal of APV block of the plasticity was not impaired by reducing transmitter release with 3 mM magnesium (in addition to 3 mM calcium and APV). A suppressant effect of APV on spontaneous activity was observed, which was attributed to loss of the NMDA component of the EPSP. Activity-dependent plasticity was also blocked if spontaneous activity was suppressed with dilute tetrodotoxin (TTX; 5-10 nM), a dosage that reduces excitability of neurons but is insufficient to block sodium-dependent action potentials. These experiments bring into question how NMDA channel activation is involved in the processes of synaptic remodeling during development. The data suggest that postsynaptic activity is required for synaptic remodeling, but this activity need not involve NMDA receptor activation specifically for activity-evoked synaptic plasticity. Instead, the mechanism for plasticity appears to operate through calcium-dependent processes in general.

Simple bone cysts. The effects of methylprednisolone on synovial cells in culture

Ten years ago, a protocol using Depo-Medrol injections was developed for the treatment of unicameral bone cysts. This concept, designed by tumor surgeons and based on theory, has been cautiously approached. However, reproducible results have gradually increased clinical acceptance. Understanding the healing process has been restricted because of the lack of an experimental model. In an attempt to elucidate this mechanism of healing, a cell culture model was used to investigate the effects of methylprednisolone on synovial cells. Initially, three doses of the drug were tested and maximal changes were noted with the concentration of 40 mg/ml. Changes were then quantified by morphology, DNA assay, cell protein analysis, and electron microscopy. Results suggest that methylprednisolone may have a direct effect on the cellular component of unicameral bone cysts.

Serum stimulation of NIH 3T3 cells induces the production of lipids able to inhibit GTPase-activating protein activity

Quiescent NIH 3T3 cells were stimulated with serum prior to the extraction of total cellular lipids. These lipids were fractionated on thin-layer chromatography plates, and individual fractions were tested for the ability to inhibit GTPase-activating protein (GAP) activity. Two separate GAP inhibitory lipids were produced. One behaved similarly to arachidonic acid during silica gel chromatography, whereas the other was related to a phosphoinositide. Further study of the arachidonic acid-related material indicated that it was produced between 1 and 5 min after serum addition but was never observed in high-density, contact-inhibited cultures. The identity of these lipids is under investigation. The possibility raised by these results, that a metabolite of arachidonic acid is involved in mitogenic signaling, was supported by the finding that several lipoxygenase products of arachidonic acid efficiently inhibited GAP activity. These results provide further support for the hypothesis that lipids, GAP, and ras activity function together in the control of cellular proliferation.

Modulation of lymphocyte proliferation by enzymes that degrade amino acids

In a previous study we demonstrated thirteen amino acids to be essential and two to be partially essential for lymphocyte proliferation. Arginine is one of the essential amino acids, and the highly purified arginase strongly inhibited lymphocyte proliferation. The modulation of lymphocyte growth by various amino acid-degrading enzymes was studied. Peripheral lymphocytes were cultured in RPMI 1640 with or without amino acid-degrading enzyme for 72 h. A total of 17 commercial L-amino acid-degrading enzymes were studied. At 10 micrograms/ml, both lysine decarboxylase and asparaginase completely inhibited lymphocyte proliferation, arginase resulted in 78% inhibition and tyrosinase 57% inhibition. Other enzymes inhibited less than 20% lymphocyte proliferation; they included alanine dehydrogenase, arginine decarboxylase, aspartase, glutamic decarboxylase, glutamic dehydrogenase, glutaminase, histidase, histidine decarboxylase, leucine dehydrogenase, phenylalanine decarboxylase, phenylalanine hydroxylase, tryptophanase, and tyrosine decarboxylase. All four enzymes that strongly inhibited lymphocyte proliferation degraded amino acids that are essential for lymphocyte growth.

A cytoplasmic protein inhibits the GTPase activity of H-Ras in a phospholipid-dependent manner

A cytoplasmic protein has been identified that inhibits the guanosine triphosphatase (GTPase) activity of bacterially synthesized, cellular H-Ras protein. This GTPase inhibiting protein is able to counteract the activity of GTPase activating protein (GAP), which has been postulated to function as a negative regulator of Ras activity. The potential biological importance of the GTPase inhibiting protein is further supported by its interaction with lipids. Phospholipids produced in cells as a consequence of mitogenic stimulation increase the activity of the GTPase inhibiting protein, as well as inhibit the activity of GAP. The interaction of such lipids with each of these two regulatory proteins would, therefore, tend to increase the biological activity of Ras and stimulate cell proliferation.

Two-dimensional NMR studies and secondary structure of cobrotoxin in aqueous solution

The 1H-NMR spectra of cobrotoxin, a neurotoxic protein isolated from Formosan cobra Naja naja atra, have been studied by two-dimensional NMR techniques. Of 62 amino acid residues in cobrotoxin, the complete assignments of 58 residues have been made. The resonances from several of the remaining residues have been identified but not yet specifically assigned. The secondary structure of an antiparallel triple- and double-stranded beta-sheet has also been determined by observing the NOE.

Modulation of human lymphocyte proliferation by amino acids

The amino acids required for phytohaemagglutinin (PHA) induced lymphocyte proliferation were determined by the 3H-thymidine incorporation in amino acid-deficient media. Results indicate that the PHA-stimulated lymphocytes require alanine and serine in addition to 13 other amino acids present in Eagle's minimal essential medium (arginine, cysteine, glutamine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, tyrosine, and valine). The omission of any one of the 13 amino acids would stop almost completely the proliferation of PHA-stimulated lymphocytes. The omission of serine from RPMI 1640 medium caused a mean reduction of 64% of cell proliferation, while the addition of alanine to PRMI 1640 culture medium caused a mean increment of 52%. The lymphocyte proliferation appears to be modulated by amino acids in the culture medium, and for optimal growth of lymphocytes, all these 15 amino acids are essential.

Intrathecal morphine's effect on somatosensory impulses transmission-studied with posterior tibial nerve SSEP

In order to investigate neurotoxic potential of spinally injected morphine solution, somatosensory evoked potential (SSEP) was utilized to detect the change of electrophysiologic activity of spinal neurons after long term application of intrathecal morphine. Eight patients received intrathecal morphine injection regularly after CHEMO-PORT implantation were studied with posterior tibial nerve SSEP. Patients received SSEP examination just before and right after first episode of morphine injection and were followed up at 30 minutes, 60 minutes, 2 hours, 8 hours, and the 7th day and the third month of regularly injection. The results showed that there were no definite change of latencies and amplitudes of impulses generated by lumbar spinal cord (N22) and cortex (P40). We therefore suggest that electrophysiologic activities of spinal cord and cortex are not affected by chronic intrathecal morphine injection. Possible mechanism and proposed pathway of morphine's action were also discussed.

A circulatory model for combined nitroprusside-dopamine therapy in acute heart failure

A computer model was developed to approximate the hemodynamic responses of dopamine and nitroprusside in acute left ventricular pump failure. The model is intended to aid the design of a multiple drug infusion system. A non-linear electrical analog model with baroreflex feedback was used to simulate the circulatory system. Heart failure was represented by a reduction in left ventricular inotropy. Pharmacodynamic relationships between the drugs studied and several elements of the system were incorporated into the model to simulate the overall drug responses which include secondary interactions between vascular components. Despite several shortcomings, the model showed good agreement with experimental and clinical data.

[Influences of 3,4,5-trihydroxystibene-3-beta-mono-D-glucoside on beat rate and injury of cultured newborn rat myocardial cells]

3,4,5-Trihydroxystibene-3-beta-mono-D-glucoside (PD) from Polygonum cuspidatum 0.05-0.45 mmol/L increased beat rate of myocardial cells from 100% to 112-220%. This action of PD 0.15 mmol/L was agonized by nisoldipine 0.1, propranolol 10 and phentolamine 1 mumol/L. PD (0.05, 0.15 mmol/L) decreased the lactate dehydrogenase (LDH) amount liberated by myocardial cells, from 98 +/- 11 IU/ml of deprivation of oxygen and glucose (DOG) to 55 +/- 16, 68 +/- 14 IU/ml (P less than 0.01) 6 h after injury of DOG; 77 +/- 9, 80 +/- 6 IU/ml (P less than 0.01) 9 h after injury of DOG. PD 0.15 mmol/L decreased the LDH amount liberated by myocardial cells, from 311 +/- 34 to 231 +/- 42 IU/ml (P less than 0.05) 9 h after injury of chlorpromazine (CPZ). It is suggested that PD can protect myocardial cells injured by DOG and CPZ.

[Effects of nicardipine on beating rates of cultured myocardial cells]

Nicardipine (Nic) 15 nmol/L had no effects on beating rates of cultured myocardial cells. Nic 75 and 150 nmol/L depressed the beating rates significantly. Rapid standstills occurred earlier and more in 150 nmol/L group than in 75 nmol/L. Both isoproterenol and CaCl2 restored the beating depressed by Nic. However, only CaCl2 prevented the standstill. These results suggest that nicardipine may compete with calcium in excitation-contraction coupling.

[Protective effects of total saponins of semen Ziziphi spinosae on cultured rat myocardial cells]

The effects of total saponins of Semen Ziziphi spinosae (ZS) were observed on cultured neonatal rat myocardial cells injured by deprivation of oxygen and glucose (DOG) or treatment with chlorpromazine (CPZ) and mitomycin C (MMC). The increases of lactate dehydrogenase release from damaged myocardial cells induced by DOG, CPZ and MMC were attenuated by ZS (33 micrograms/ml) except 11 micrograms/ml which showed no effect on MMC (24 h) and CPZ (9 h)-induced injuries. These data suggest that ZS is an effective protective drug for myocardial cells.

[Median nerve somatosensory evoked potential monitoring during carotid endarterectomy-report of one case]

Carotid endarterectomy was performed on a 64 y/o female patient who had been suffering from multiple transient ischemic attacks caused by the stenosis of right common carotid artery at its bifurcation. Median nerve somatosensory evoked potential (SSEP) was utilized for monitoring cerebral function during and after operation. Latency, amplitude and central conduction time (CCT) of bilateral N13 (CV2) and N20 (C3', C4') were measured as an aid for management of anesthesia, surgical procedure and postoperative care. The results showed SSEP which is sensitive for detection of cerebral ischemia and could help the surgeon and anesthesiologist maintaining optimal cerebral perfusion, but yields little information about postoperative hyperperfusion state. Besides evaluating the efficacy of SSEP, we discussed the problems encountered during the SSEP monitoring.

Characterization of murine liver-derived inhibitory protein

Murine liver-derived inhibitory protein (LIP) capable of inhibiting human lymphocyte proliferation was highly purified from liver extract. Its molecular weight determined by gel filtration and SDS-PAGE was 105,000 and 38,400 respectively. LIP moved electrophoretically at the gamma-globulin region. Its activity in inhibiting lymphocyte proliferation was temperature-stable up to 60 degrees C, and pH-stable between 4 and 11. It was not cytotoxic to lymphocytes as shown in 51Cr-release experiments. The purified LIP possessed arginase activity.

Multi-determinate regulation of neuronal survival: neuropeptides, excitatory amino acids and bioelectric activity

Neuronal survival of dorsal root ganglion-spinal cord cultures was determined after treatment with vasoactive intestinal peptide (VIP) and an antagonist to the N-methyl-D-aspartate receptor (NMDA). Blockade of NMDA receptors with 2-amino 5-phosphonovaleric acid (AP5) produced a biphasic response on neuronal survival: low concentrations (0.1 microM) resulting in greater survival and higher concentrations (100 microM) causing cell death. VIP, a substance with demonstrated neurotrophic properties in vitro, prevented the neuronal cell death associated with high concentrations of AP5, while having no additive effect on the survival-promoting action of low levels of AP5. Electrophysiological studies indicated that AP5, although reducing high frequency bursting activity, did not significantly reduce the abundant on-going asynchronous activity present in these cultures of high density neuronal networks. These data indicate that excitatory amino acids have more than one action that can influence neuronal survival during development and that VIP can increase neuronal survival in bioelectrically active cultures when NMDA channels are blocked. Together with previous studies, these data suggest that multiple neurochemical inputs serve to determine the survival of spinal cord neurons during development, perhaps through one final common pathway: intracellular calcium regulation.

Mechanisms involved in activity-dependent synapse formation in mammalian central nervous system cell cultures

Differences in neuronal activity produced by electrical stimulation lead to competition between synapses from sensory afferents converging on a common spinal cord neuron. Studies were performed on neurons dissociated from the mouse spinal cord and grown in culture dishes with three compartments. Synaptic efficacy from stimulated afferents was increased compared with unstimulated convergents, and the number of functional connections was increased by stimulation compared with control cultures. Blocking NMDA channel activation with 100 microM APV in medium containing 1.8 mM calcium inhibited this synaptic plasticity, but plasticity was not blocked by APV in medium in which the calcium concentration was elevated to 3 mM. These experiments support the view that electrical activity differentially influences processes that cause a persistent decrease in synaptic efficacy or lead to synapse elimination and those that increase synaptic strength or lead to synapse augmentation. We interpret our results in terms of a model in which these antagonistic mechanisms are both regulated via changes in calcium levels and second messengers that are modulated by electrical activity. A significant portion of the activity-related calcium influx relevant to synaptic plasticity passes through the NMDA channel, but other sources of calcium are involved. In particular, competitive elimination of synapses appears to occur during blockade of NMDA channels if the extracellular concentration of calcium is elevated moderately. The outcome of competition between the two calcium-dependent but antagonistic processes may depend either on their differential sensitivity to intracellular calcium concentration or separate specificities to NMDA and non-NMDA receptor-linked mechanisms.

Complete sequence of the lamprey fibrinogen alpha chain

The complete amino acid sequence of the lamprey fibrinogen alpha chain has been determined by a combination of peptide sequencing and cDNA and genomic cloning. The chain, which has an apparent molecular weight by dodecyl sulfate-polyacrylamide gel electrophoresis of ca. 100,000, is composed of 961 amino acid residues and has a calculated molecular weight of 96,722. It is distinguished by a large number of 18-residue repeats in a region where mammalian fibrinogens have 13-residue repeats. The data are in accord with our previous finding that the lamprey alpha chain has a distinctive amino acid composition, almost half the residues being glycine, serine, or threonine. The chain differs from mammalian alpha chains in that there are no cysteines in the carboxy-terminal half, and thus no intrachain loop, nor are there any RGD sequences in the lamprey alpha chain. Taken together with previous data on the sequences of the beta and gamma chains, the findings bear significantly on our understanding of fibrin formation. The alpha chain also provides an interesting case of structural convergence during evolution.

The mechanisms of the inhibitory effects of liver extract on lymphocyte proliferation. III. The effects of arginase on DNA polymerase activities

The incorporation of labeled precursors into DNA, RNA and protein in phytohaemagglutinin (PHA)-prestimulated human lymphocytes was maximally inhibited by liver extract (LEx) or arginase at 24 h. The activities of DNA polymerase alpha, beta and gamma were less inhibitable by these agents than was [3H]thymidine incorporation. The inhibition of DNA, RNA and protein syntheses by either LEx or arginase is probably due to arginine depletion by arginase activity, since their syntheses were similarly inhibited when cultured in an arginine-free medium in the absence of arginase. These results indicate that arginase nonspecifically inhibits the activities of DNA polymerase. The inhibition is probably due to arginine depletion.

Synaptic connections in vitro: modulation of number and efficacy by electrical activity

The functional architecture of synaptic circuits is determined to a crucial degree by the patterns of electrical activity that occur during development. Studies with an in vitro preparation of mammalian sensory neurons projecting to ventral spinal cord neurons slow that electrical activity induces competitive processes that regulate synaptic efficacy so as to favor activated pathways over inactive convergent pathways. At the same time, electrical activity initiates noncompetitive processes that increase the number of axonal connections between these sensory and spinal cord neurons.

[Effect of nisoldipine on cultured myocardial cells of neonatal rats]

Nisoldipine 1.5 nmol/L, 0.75, and 1.5 mumol/L depressed the beat rates of myocardial cells. The effects were negatively correlated with dosages. Nisoldipine depressed the beat rates increased by calcium chloride 0.15 mmol/L or isoprenaline 1.5 mumol/L and atropine 20 nmol/L. Conversely, the above drugs reversed the beat rates depressed by nisoldipine. Therefore, the acting nisoldipine may be antagonistic to calcium chloride, isoprenaline and atropine. In addition, nisoldipine 10 nmol/L may significantly aggravated the damage to myocardial cells induced by mitomycin C 5 micrograms/ml in which elevated lactate dehydrogenase appeared.

The effect of GTPase activating protein upon ras is inhibited by mitogenically responsive lipids

Bacterially synthesized c-Ha-ras protein (Ras) was incubated with guanosine triphosphatase (GTPase) activating (GA) protein in the presence of various phospholipids. The stimulation of Ras GTPase activity by GA protein was inhibited in some cases. Among the lipids most active in blocking GA protein activity were lipids that show altered metabolism during mitogenic stimulation. These included phosphatidic acid (containing arachidonic acid), phosphatidylinositol phosphates, and arachidonic acid. Other lipids, including phosphatidic acid with long, saturated side chains, diacylglycerols, and many other common phospholipids, were unable to alter GA protein activity. The interaction of lipids with GA protein might be important in the regulation of Ras activity during mitogenic stimulation.

Defective phagocytosis, decreased tumour necrosis factor-alpha production, and lymphocyte hyporesponsiveness predispose patients with systemic lupus erythematosus to infections

Twenty-three patients with systemic lupus erythematosus (SLE) were studied in order to understand the mechanism of increased susceptibility to infection in SLE patients. We found that phagocytosis by polymorphonuclear leucocytes (PMN) was significantly defective in untreated (24.2 +/- 3.1%) and immunosuppressant-treated SLE patients (30.0 +/- 3.6%) compared with normals (47.9 +/- 0.6%), while the generation of superoxide anion radicals was normal. The defective phagocytosis in SLE could be increased by human recombinant tumour necrosis factor alpha (TNF-alpha). However, the percentages of phagocytosis in SLE before and after TNF-alpha stimulation were 56.6% and 60.7% of the normal values. This indicates that certain populations of PMN in SLE are not only defective as regards phagocytosis but also unresponsive to TNF-alpha stimulation. In an ELISA, TNF-alpha production by phorbol myristate acetate (PMA)-stimulated mononuclear cells from SLE patients was significantly decreased (181.4 +/- 22.7 pg/ml vs. 533.0 +/- 81.9 pg/ml, p = 0.002). In addition, the percentage of phytohaemagglutinin (PHA)-stimulated mononuclear cells in S phase in the cell cycle was deficient in patients with SLE (17.2 +/- 1.8% vs. 29.7 +/- 2.9%, p less than 0.001). These results lead us to propose that defective PMN in spontaneous and TNF-alpha-induced phagocytosis, decreased production of TNF-alpha, and lymphocyte hyporesponsiveness predispose patients with SLE to infections.

Defective helper T cell function in IgM rheumatoid factor synthesis in patients with ankylosing spondylitis

Despite chronic inflammation and the presence of hypergammaglobulinemia, rheumatoid factor (RF) is rarely found in the blood of patients with ankylosing spondylitis (AS). We used ELISA to compare spontaneous and pokeweed mitogen (PWM)-induced IgG, IgM and IgM rheumatoid factor (IgM-RF) production in normals and in patients with rheumatoid arthritis (RA) and AS. The IgG and IgM synthesis in these three groups did not differ. However, the IgM-RF level in PWM-induced mononuclear cell cultured supernatants of AS was significantly decreased, compared with normal and RA patients. Furthermore, mixing experiments by co-culture of normal T or B cells with patient's B or T cells in the presence of PWM revealed a deficiency of the helper T cell function in patients with AS. These results illustrate the cellular mechanism of the seronegativity of the rheumatoid factor in patients with ankylosing spondylitis.

Alteration of mitogenic responses of mononuclear cells by anti-ds DNA antibodies resembling immune disorders in patients with systemic lupus erythematosus

Anti-double-stranded DNA antibodies (anti-DNA) purified from pooled active SLE sera by lambda phage DNA-affinity chromatography was found to affect phytohemagglutinin (PHA) and pokeweek mitogen (PWM)-induced responses of normal mononuclear cells. Anti-DNA at a concentration of 0.25 mg/ml (equivalent to 21 units/ml of DNA binding activity) significantly suppressed the PHA-induced [3H]thymidine incorporation of mononuclear cells in 3 days of culture but had no effect on 5-day and 7-day cultures. In contrast, a biphasic effect of anti-DNA on PWM response was found such that early phase (3-day culture) was inhibited whereas late phase (from 5 days to 9 days of culture) was enhanced by the antibodies. Anti-DNA also increased the immunoglobulin synthesis by PWM-stimulated B cells. The inhibition of PHA response in 3-day culture by anti-DNA is not due to changes in T cell subpopulations. Because interleukin 1 (10 units/ml) could restore the PHA response, it appears that anti-DNA suppressed the IL-1 production by monocyte/macrophage. The biphasic effect of anti-DNA on PWM response is the result of monocyte impairment and B cell stimulation by the antibodies. In the early phase (on day 3) the inhibition would seem to be due to impairment of accessory cell function by anti-DNA, though in late phase (after day 5) the anti-DNA may stimulate B lymphocytes to incorporate more thymidine in the presence of PWM. These biological effects of anti-DNA in vitro resemble the in vivo immunologic disorders in patients with SLE, in that impaired cell-mediated immunity and B cell hyperactivity are frequently observed.

Purification of murine liver-derived inhibitory protein

Murine liver-derived inhibitory protein (LIP) capable of inhibiting human lymphocyte proliferation was separated from liver extract. The steps of purification included ammonium sulfate precipitation, DEAE-cellulose and hydroxylapatite ion exchange chromatographies, and gel filtration. The purified LIP appeared to be highly homogeneous, as verified by polyacrylamide gel electrophoresis (PAGE) and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). There was arginase activity in the LIP Preparation.

Prevention by gamma interferon of fatal infection with Listeria monocytogenes in mice treated with cyclosporin A

The significance of interferons (IFNs) induced by Listeria monocytogenes in the antilisterial defense mechanism was studied in mice. Cyclosporin A (CsA) had no effect on IFN-alpha production that was induced in the bloodstream after intravenous infection of mice with L. monocytogenes, whereas IFN-gamma that was induced in the bloodstreams of control mice 6 h after stimulation with specific antigen in the late phase of infection was suppressed in CsA-treated mice, depending on the dose of the drug injected. The decrease in IFN-gamma production caused an increase in bacterial growth in the spleens and livers of CsA-treated mice. Furthermore, administration of a daily dose of CsA at 80 or 100 mg/kg of body weight resulted in fatal listeriosis, even though the dose was nonlethal for normal mice. The administration of recombinant murine IFN-gamma on day 0 of L. monocytogenes infection prevented CsA-treated mice from developing fatal listeriosis and restored their ability to produce IFN-gamma in the bloodstream, in response to specific antigen in the late phase of infection.

The mechanisms of inhibitory effects of liver extract on lymphocyte proliferation: II. Inhibition of DNA, RNA, and protein synthesis and their relationship to the effects of metabolic inhibitors

The inhibitory effects of liver extract (LEx) on DNA, RNA, and protein synthesis in phytohaemagglutinin (PHA)-stimulated lymphocytes were studied by measuring the incorporation of labelled precursors. DNA, RNA, and protein synthesis were all inhibited by LEx in a dose-related manner. The inhibitory effect of LEx on protein synthesis was additive to the inhibitory effect of puromycin. The inhibitory effect of LEx on DNA synthesis was antagonistic to the inhibitory effect of mitomycin C. In the case of actinomycin D for RNA synthesis, its interactions with LEx were variable, but not additive. LEx may act as an inhibitor of protein synthesis through the mechanism of arginine-depletion.

Cellular ras activity and phospholipid metabolism

Cellular ras activity has been neutralized in 3T3 cells by microinjection of a specific anti-ras monoclonal antibody. The injected antibody efficiently inhibited proliferation in cells treated with a phorbol ester and a calcium ionophore, or with prostaglandin F2 alpha. These treatments were designed to imitate the action of phospholipase C or of phospholipase A2. In addition, the highly efficient mitogenic potential of phosphatidic acid was inhibited by the injected antibody even more efficiently than was serum-induced proliferation. The close reliance of phospholipid-induced mitogenesis upon ras activity suggests that ras proteins are unlikely to function to control the action of a phospholipase.

Calcium agonist (BayK 8644) augments voltage-sensitive calcium currents but not synaptic transmission in cultured mouse spinal cord neurons

The effects of the calcium agonist, BayK 8644, and other agents upon voltage-dependent calcium conductance (VSCC) and evoked synaptic activity were studied in cultured mouse spinal cord and dorsal root ganglion neurons. As expected, BayK 8644 increased the VSCC corresponding to L channels. It had relatively little effect on evoked synaptic activity; the small but statistically significant effect that was noted was a decrease. Nitrendipine had either no effect or an increase with no statistically significant effect being seen with regard to synaptic activity over the population sampled. An increased extracellular Ca++ concentration increased both VSCC and synaptic activity. We conclude that VSCC with L channel properties are probably not involved in transmitter release produced by action potentials in the central synapses occurring in the dissociated mouse spinal cord cell culture system.

Critical role of cellular ras proteins in proliferative signal transduction

In the experiments described above, a neutralizing anti-ras antibody was utilized to study the role of ras protein in normal cell proliferation. Initially, it was demonstrated that the antibody was specific for ras protein, and that ras activity was efficiently inhibited. With the neutralizing antibody, it was first shown that ras activity is required for the proliferation of all normal cell types tested. ras activity was required just prior to initiation of S phase. The transforming activity of several retroviral oncogenes was also blocked following anti-ras injection. This included the tyrosine kinase, plasma-membrane-associated proteins, and an oncogene derived from a growth factor. On the other hand, cytoplasmic oncogenes with serine kinase activity were not dependent on ras activity for expression of the transformed phenotype. These observations form the basis of our model for proliferative signal transduction. We propose that the action of either growth factors, their receptor molecules, or related oncogenes initiate an intracellular signal received by ras proteins and then transferred by ras to cytoplasmic serine kinase oncogenes. This signal transduction system directly regulates cellular proliferation. Although further evidence in support of this model is needed, it appears from our studies that the mechanism of signaling between tyrosine kinases and ras proteins might be at the level of phospholipid metabolism. This observation is based on the fact that the mitogenic lipid molecules tested were remarkably dependent on ras activity, even more so than the growth factors or related oncogenes tested. Finally, our work suggests a fundamental distinction between normal and tumor cells. All the normal cell types tested were efficiently inhibited in proliferation by the injected antibody. Tumor cells, on the other hand, were never completely inhibited by the antibody and often were not inhibited at all. The presence of an activated ras oncogene within the tumor assured at least a partial role for ras activity in the proliferation of the mature tumor line. The significance of the observed distinction between normal and tumor cells is not known. The fact that this distinction involves a protein with an apparently critical role in normal proliferation suggests that the observation might be important.

The sugar-specific adhesion/deadhesion apparatus of the marine bacterium Vibrio furnissii is a sensorium that continuously monitors nutrient levels in the environment

Our earlier studies on cell adhesion to immobilized carbohydrates are extended here to a marine bacterium, Vibrio furnissii. Apparently one lectin mediates the binding of these cells to glycosides of N-acetylglucosamine, mannose, and glucose covalently linked to Agarose beads. Kinetic studies show that protein synthesis is required for initiating and for maintaining adhesion to the glycosides. Furthermore, a pro- mutant binds to GlcNAc-beads at Pro concentrations insufficient to support cell growth. Expression of the functional lectin therefore predominates under conditions of limiting protein synthesis. Thus, cells adhere to the sugars in an environment compatible with protein synthesis, and deadhere when depleted of any required nutrient, presumably to migrate to a more favorable locale. The adhesion-deadhesion apparatus thereby permits constant monitoring of the surrounding environment, comprising a "nutrient sensorium".

Modulation of lymphocyte proliferation by murine liver extract

Murine liver extract (LEx) purified by ammonium sulfate (45-70% saturation) possesses a strong inhibitory effect on human lymphocyte proliferation. We have shown that the inhibitory effect of LEx is not via a cytotoxic effect and that it is proportional to the length of incubation with LEx. Mitogen-prestimulated lymphocytes are more resistant to LEx inhibition than cells not prestimulated. B cells stimulated by PWM are more susceptible to LEx-induced inhibition than PHA- or Con A-stimulated T cells. In Con A cultures, there may be a population of cells more resistant to LEx inhibition. This population is not yet identified. The degree of reversibility of LEx inhibition was different in cells prestimulated by different mitogens. The inhibitory activity of LEx decreased in the presence of an increasing number of cells in the culture.