Expression of listeriolysin O by intracellular Listeria monocytogenes following infection of lipopolysaccharide-treated or untreated J774.1 macrophage-like cells

Abstract Listeria monocytogenes replicates in a phagocytic cell following escape into the host cytoplasm. Listeriolysin O, secreted by L. monocytogenes , which belongs to the thiol-activated hemolysin family, is known to play an important role in the escape of the bacterium into the host cytoplasm. In this study, we demonstrated that expression of listeriolysin O by infecting L. monocytogenes was lightly induced in J774.1 macrophage-like cells pretreated with lipopolysaccharide, although the growth of the bacteria was suppressed. The number of viable L. monocytogenes decreased until 4 h post-infection and then increased between 4 and 8 h post-infection in untreated J774.1 host cells, but it decreased until 8 h post-infection in lipopolysaccharide-treated host cells. However, expression of listeriolysin O by L. monocytogenes was not induced in the untreated host cells, while it increased between 0 and 4 h post-infection in the lipopolysaccharide-treated host cells. Expression of listeriolysin O mRNA in the lipopolysaccharide-treated host cells was also induced at 2 h post-infection, suggesting that listeriolysin O was newly synthesized in the macrophage-like cells. These results suggest that macrophage activation induced with lipopolysaccharide could lead to the expression of the listeriolysin O gene and the synthesis of listeriolysin O protein under suppression of the intracellular growth of L. monocytogenes .     

Immunohistochemical localization of Na+-dependent glucose transporter in the rat digestive tract

Summary Glucose is actively absorbed in the intestine by the action of the Na⁺-dependent glucose transporter. Using an antibody against the rabbit intestinal Na⁺-dependent glucose transporter (SGLT1), we examined the localization of SGLT1 immunohistochemically along the rat digestive tract (oesophagus, stomach, duodenum, jejunum, ileum, colon and rectum). SGLT1 was detected in the small intestine (duodenum, jejunum and ileum), but not in the oesophagus, stomach, colon or rectum. SGLT1 was localized at the brush border of the absorptive epithelium cells in the small intestine. Electron microscopical examination showed that SGLT1 was localized at the apical plasma membrane of the absorptive epithelial cells. SGLT1 was not detected at the basolateral plasma membrane. Along the crypt-villus axis, all the absorptive epithelial cells in the villus were positive for SGLT1, whose amount increased from the bottom of the villus to its tip. On the other hand, cells in the crypts exhibited little or no staining for SGLT1. Goblet cells scattered throughout the intestinal epithelium were negative for SGLT1. These observations show that SGLT1 is specific to the apical plasma membrane of differentiated absorptive epithelial cells in the small intestine, and suggest that active uptake of glucose occurs mainly in the absorptive epithelial cells in the small intestine.     

Phosphorylation of Myristoylated Alanine-Rich C Kinase Substrate (MARCKS) by Proline-Directed Protein Kinases and Its Dephosphorylation

Abstract: Excitatory amino acid (EAA) neurotransmitters may play a role in the pathophysiology of traumatic injury to the CNS. Although NMDA receptor antagonists have been reported to have therapeutic efficacy in animal models of brain injury, these compounds may have unacceptable toxicity for clinical use. One alternative approach is to inhibit the release of EAAs following traumatic injury. The present study examined the effects of administration of a novel sodium channel blocker and EAA release inhibitor, BW1003C87, or the NMDA receptor-associated ion channel blocker magnesium chloride on cerebral edema formation following experimental brain injury in the rat. Animals (n = 33) were subjected to fluid percussion brain injury of moderate severity (2.3 atm) over the left parietal cortex. Fifteen minutes after injury, the animals received a constant infusion of BW1003C87 (10 mg/kg, i.v.), magnesium chloride (300 µmol/kg, i.v.), or saline over 15 min (2.75 ml/kg/15 min). In all animals, regional tissue water content in brain was assessed at 48 h after injury, using the wet weight/dry weight technique. In saline-treated control animals, fluid percussion brain injury produced significant regional brain edema in injured left parietal cortex ( p < 0.001), the cortical area adjacent to the site of maximal injury ( p < 0.001), left hippocampus ( p < 0.001), and left thalamus ( p = 0.02) at 48 h after brain injury. Administration of BW1003C87 15 min postinjury significantly reduced focal brain edema in the cortical area adjacent to the site of maximal injury ( p < 0.02) and left hippocampus ( p < 0.01), whereas magnesium chloride attenuated edema in left hippocampus ( p = 0.02). These results suggest that excitatory neurotransmission may play an important role in the pathogenesis of posttraumatic brain edema and that pre- or post-synaptic blockade of glutamate receptor systems may attenuate part of the deleterious sequelae of traumatic brain injury.     

A single amino acid substitution within the mature sequence of ornithine aminotransferase obstructs mitochondrial entry of the precursor.

We describe here evidence of congenital enzyme mistargeting induced not by abnormalities in the signal sequence. We examined the molecular mechanism of hereditary ornithine aminotransferase (OAT) deficiency causing gyrate atrophy of the choroid and retina (GACR). Nucleotide sequencing of OAT cDNA generated from a GACR patient's mRNA revealed a single base change from C to G at position 268, resulting in an amino acid substitution of neutral Gln(CAA) with negatively charged Glu(GAA) at position 90 (Q90E). Immunohistochemical and transient expression analyses suggested expression of a defective labile OAT in the patient's tissues. However, high-level expression and immunocytochemical analyses elucidated that Q90E OAT (the patient's OAT) was localized within the limits of cytoplasmic free ribosomes in precursor form without any mitochondrial entry, indicating that the patient's precursor OAT was synthesized and rapidly degraded because of accumulation in the cytosol. It is interesting that, although the mutation site (Q90E) in this GACR patient's OAT was within the coding sequence of the mature protein, the precursor exhibited loss of mitochondrial targeting function. These findings suggest that not only the signal sequence but a critical part of the mature sequence plays an essential role in mitochondrial entry of the OAT precursor protein.     

Prevention of Vascular Graft Infection by Sisomicin Incorporated into Fibrin Glue

To examine the efficacy of sisomicin (SISO) incorporated into fibrin glue (FG) for the prevention of graft infection in animal models, the susceptibility to infection of Dacron grafts (control) and SISO-FG Dacron grafts following the inoculation of Staphylococcus aureus or S. epidermidis was compared. The results showed that SISO-FG Dacron grafts displayed resistance to graft infection.     

Peroxidation of lipids and growth inhibition induced by UV-B irradiation

Cotyledons excised from dark-grown seedlings of cucumber (Cucumis sativus L.) were cultured in vitro under UV radiation at different wavelengths, obtained by passage of light through cut-off filters with different transmittance properties. Growth and the synthesis of chlorophyll (Chl) in cotyledons were inhibited and malondialdehyde was accumulated upon irradiation at wavelengths below 320 nm. Exogenous application of scavengers of free radicals reversed the growth inhibition induced by UV-B. Measurement of the fluorescence of Chl a suggested that electron transfer in photosystems was affected by UV-B irradiation. On the basis of these results, the involvement is postulated of active species of oxygen in damages to thylakoid membranes and the growth inhibition that are induced by UV-B irradiation.Abbreviations Chl chlorophyll - F_m maximal fluorescence (dark) - F_m maximal fluorescence (light) - F_v variable fluorescence (dark) - F_v variable fluorescence (light) - MDA malondialdehyde - O₂ Superoxide radical - PS photosystem - q_N non-photochemical quenching of fluorescence - q_P photochemical quenching of fluorescence - UV-B_BE biologically effective UV-B radiation - WL(T = 0.5) wavelength at which 50% transmittance occurs     

Phosphatidyl inositol: myo-Inositol exchange enzyme from rat liver: Partial purification and characterization

The enzyme which catalyzes CDP-diglyceride-independent incorporation of myo-inositol into phosphatidyl inositol was solubilized from rat liver microsomes by sodium cholate and was partially purified by ammonium sulfate fractionation and sucrose density gradient centrifugation. Addition of phospholipids during purification and assay procedures prevented irreversible loss of the enzyme activity to some extent. The resulting preparation contained about 3.7% of the protein and 35% of the original activity of the microsomal fraction. The activity of the enzyme preparation was strongly enhanced by addition of phosphatidyl inositol. The enzyme required Mn²⁺ for activity. The K_m for myo-inositol was 4 × 10^?5m. The pH optimum was 7.4. The activity was inhibited by thiol-reactive reagents and also to some extent by inosose-2 but not by scyllitol. Phosphorus-containing acidic substances such as acidic phospholipids and nucleotides were generally inhibitory. It was found that the preparation catalyzed liberation of inositol moiety from phosphatidyl inositol in a manner dependent on the concentration of free myo-inositol and also on Mn². The K_m of this reaction for free myo-inositol was estimated to be 7 × 10^?5m. This result indicates that CDP-diglyceride-independent incorporation, which has been assumed to show inositol exchange reaction, actually represents an exchange reaction between the myo-inositol moiety of phosphatidyl inositol and free myo-inositol. Phosphatidyl choline and phosphatidyl ethanolamine did not play a role as acceptor of the exchange reaction.     

A study on the gustatory effects of tetrodotoxin in rat (author's transl)]

Effects of tetrodotoxin (TTX) on neural responses of the chorda tympani to four basic taste stimuli were investigated electrophysiologically in rats. When the TTX (10 mg/ml) was applied directly to the tongue surface for 3 minutes, magnitude of the integrated responses of the chorda tympani was diminished to about 60% of that of the control response. This diminution of response was recovered within 30 minutes by degrees and the effect of the TTX was antagonized by guanylate. This result gives a suggestion that guanidyl group in the TTX may play an important role for the inhibitory actions to the responses of the chorda tympani. On the other hand, when the TTX (0.25 mg/100 g b. wt.) was applied intravenously, magnitude of the responses of the chorda tympani to four basic taste stimuli decreased gradually to 20 approximately 30% of that of the control responses within 60 minutes and did not recover more than 10 hours. This is assumed due to the blocking of the sodium pump of nerve fibers in the chorda tympani by the TTX.     

Control of the production of orthophosphate repressible extracellular enzymes in Neurospora crassa

Molecular Genetics and Genomics - The abilities of purine- and pyrimidinerequiring mutants to produce six orthophosphate repressible extracellular enzymes, alkaline phosphatase,...