Catalytic function of a tyrosyl residue in tryptophanase

Tryptophanase has an essential tyrosyl residue/active site which can be modified by tetranitromethane. Pyridoxal 5'-phosphate can prevent this modification efficiently, whereas pyridoxal 5'-phosphate N-oxide cannot, indicating that the free pyridinium N is required for the interaction of the coenzyme with the tyrosyl residue, probably via a hydrogen bond. The weakened binding of the coenzyme to the modified enzyme was confirmed on gel filtration, the modified enzyme being dissociated from the coenzyme seven-fold faster than the native enzyme. Furthermore, absorption spectral analyses demonstrated that the modified enzyme can catalyze the transaldimination step, but fails to abstract the alpha-H of substrates. The tyrosyl residue, therefore, not only participates in coenzyme binding, but also contributes to alpha-H labilization.     

Fungi in bathwater and sludge of bathroom drainpipes

Samples of bathwater from 14 homes and 22 public bathhouses and sludge in drainpipes from 19 house-hold bathrooms were plated out onto potato dextrose agar supplemented with chloramphenicol. Several media were used to study colony morphology of the isolates and the thermotolerance and alkaline tolerance of each isolate were examined.Eleven sludge samples produced 12 isolates of Exophiala jeanselmei, 2 of E. dermatitidis and 1 of E. moniliae. Five household bathwater samples produced 2 isolates of E. jeanselmei, 4 of E. dermatitidis and 1 of E. alcalophila. One isolate of E. jeanselmei, 2 of E. dermatitidis, 3 of E. moniliae and 2 of unidentified Exophiala species were recovered from 6 samples of the bathwater dissolving Chinese medicine in the bathtubs of public bathhouses. One isolate of E. jeanselmei was recovered from the 15 samples of bathwater from public bathhouses. Bathwater and sludge in bathroom drainpipes may be an important habitat of Exophiala species.     

Effect of volume expansion on hemodynamic variables in nephrectomized dogs

We have previously demonstrated that blood pressure elevation by acute blood volume expansion is volume-dependent during the infusion period and resistance-dependent in the post-infusion period in normal anesthetized dogs, and that such an increase in blood pressure is associated with a potentiation of the pressor response to norepinephrine. To evaluate the possible renal contribution to these hemodynamic changes, blood volume expansion was performed for 1 h with dextran dissolved in lactated Ringer's solution (20 ml/kg) in 15 nephrectomized dogs. The mean blood pressure, cardiac output and total peripheral resistance at the end of infusion were 126%, 225% and 60%, respectively; 3 h after volume expansion they were 126%, 151%, and 92% respectively. However, in 4 dogs, there was an increase in mean blood pressure (138%) 3 h after volume expansion. This was thought to result from an increase in the total peripheral resistance (133%) associated with the recovery of cardiac output (106%). The pressor response to norepinephrine (0.5 microgram/kg) was potentiated after volume expansion. These results indicate that the handling of volume by the kidney contributed to the maintenance of an elevated level of cardiac output. However, nephrectomy did not seem to interfere with the hemodynamic switching of the causative factor for blood pressure elevation from increased cardiac output to increased total peripheral resistance. Neither was the potentiation of pressor response to norepinephrine affected.     

Complete deficiency of 20 KDa homologous restriction factor (HRF20) and restoration with purified HRF20

20 KDa homologous restriction factor (HRF20) is a membrane glycoprotein which inhibits formation of membrane attack complexes of homologous complement. Erythrocytes from a patient who is completely deficient in HRF20 were readily hemolyzed by homologous complement activated by sucrose or by acidification as in paroxysmal nocturnal hemoglobinuria (PNH). After incubating PNH erythrocytes (PNH-E) with purified HRF20, the cells were analyzed by flow cytometry using a monoclonal antibody to HRF20 and shown to have the antigen absorbed. These PNH-E acquired resistance to hemolysis by homologous complement suggesting that HRF20 may be successfully used for treatment of these patients.     

Hypoxia-induced fibre type transformation in rat hindlimb muscles Histochemical and electro-mechanical changes

Twelve male Sprague-Dawley rats (21 days old) were randomly assigned into two experimental groups: sea level control (CONT) and hypobaric hypoxia (HYPO). The HYPO rats were kept in an hypobaric chamber maintaining a simulated altitude of 4000 m (61.1 kPa). After 10 weeks of treatment, the rat hindlimb muscles [soleus (SOL) and extensor digitorum longus (EDL)] were subjected to histochemical and electro-mechanical analyses. Results indicated that compared to CONT the HYPO SOL muscle had a significantly greater relative distribution of fast-twitch-oxidative-glycolytic (FOG) fibres (28.9% SEM 2.0 vs 18.3% SEM 1.8, P less than 0.01) with a significant decrease in slow twitch oxidative fibre distribution (69.5% SEM 2.4 vs 82.9% SEM 3.1, P less than 0.01). Compared to CONT the HYPO EDL muscle also manifested a significant increase in FOG fibre distribution (51.6% SEM 0.8 vs 46.6% SEM 1.1, P less than 0.01), but this was accompanied by a significant decrease in fast twitch glucolytic fibres (44.3% SEM 0.9 vs 49.2% SEM 1.7, P less than 0.05). These histochemical fibre type transformations accompanied significant and expected changes in the electro-mechanical parameters tested in situ, e.g. maximal twitch force, maximal rate of force development, contraction time, half relaxation time, force: frequency curve, and fatigability. It was concluded that chronic hypobaric hypoxia could have a potent influence upon the phenotype expression of muscle fibres.     

Studies on detection of Candida antigen in the sera of mice inoculated orally with Candida albicans

Summary The authors succeeded in establishing a murine model of systemic candidiasis being disseminated from the primary gastrointestinal lesions caused by oral inoculation of Candida albicans. Using this model, an attempt was made for detecting the Candida antigen by enzyme-linked immunosorbent assay using avidin-biotin (AB-ELISA) from the serum of infected mice.Gastrointestinal candidiasis was formed in all of the 20 mice treated with the drugs (antibiotics, antineoplastic agents, hydrocortisone, etc.) and inoculated orally with C. albicans. Fourteen of these mice suffered from submucosal candidiasis, and C. albicans was cultured from the visceral organs in 12 of them. The assay by AB-ELISA was able to detect 1.0 ng/ml Candida mannan in the mouse serum. The Candida antigen was detected in the sera of 11 of the 14 mice with submucosal candidiasis. However, the antigen could not be detected in the sera of the 6 mice with intramucosal candidiasis.The assay by AB-ELISA is more sensitive and specific for the diagnosis of systemic candidiasis than other serological assays.     

Cloning and sequencing of a ligninase gene from a lignindegrading basidiomycete,Phanerochaete chrysosporium

Summary A ligninase gene has been cloned from a Phanerochaete chrysosporium genomic DNA library. Nucleotide sequencing of the gene has revealed that the ligninase structural gene contains 1116 bp of the protein-encoding sequence, of which 84 bp encode the signal peptide. The protein-encoding sequence is interrupted by eight introns which conform to the universal G-T/A-G splicing rule observed for the 3 and 5 intron boundaries. The putative eukaryotic regulatory sequences, i.e. CAAT and TATA box-like sequences, are present in the 5 flanking region.     

Effects of hypobaric-hypoxia on the total number and histochemical properties of the soleus muscle fibers and motoneurons in the rat

After 7 weeks of hypobaric-hypoxia adaptation, horseradish peroxidase was injected into the soleus muscle to label motoneurons of the spinal cord in rats. Fiber type distribution in the soleus muscle and oxidative enzyme activity of motoneurons innervating the soleus muscle were examined. Fiber type was converted from slow-twitch-oxidative (SO) to fast-twitch-oxidative-glycolytic (FOG). Oxidative enzyme activity of motoneurons (25-45 micron soma diameter) was increased. However, oxidative capacity of larger motoneurons (greater than or equal to 45 micron soma diameter) was not changed. These data suggest that the lack of increase in oxidative capacity of larger motoneurons (innervating SO units) by hypoxia secondarily causes fiber type shift from SO to FOG.     

Sequence rearrangement in JC virus DNAs molecularly cloned from immunosuppressed renal transplant patients.

From nonimmunocompromised individuals, we have recently identified a possible archetypal JC virus DNA sequence from which various regulatory sequences of JC virus isolates derived from patients with progressive multifocal leukoencephalopathy (PML) could have evolved. In this study, we analyzed the regulatory sequences of JCV DNAs cloned from urine samples of a PML risk group (renal transplant patients on immunosuppressive therapy). A number of JC virus DNAs were molecularly cloned from virions excreted in the urine of eight patients. Furthermore, fragments containing the regulatory region were amplified by the polymerase chain reaction and subsequently molecularly cloned from cell-associated JC virus excreted in the urine of two patients. The regulatory regions in all clones were analyzed with restriction enzymes, and those in representative clones were sequenced. We found that clones with the archetypal regulatory sequence were predominant in all urine samples, but a few clones carried regulatory sequences that diverged from the archetypal sequence by deletion or duplication. The finding that sequence rearrangement in the archetypal regulatory region occurs in the course of infection in immunosuppressed hosts is consistent with the adaptation hypothesis which has been put forward to explain the divergence of the regulatory regions in PML-derived JC virus isolates.