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.     

Aggregatibacter actinomycetemcomitans induces detachment and death of human gingival epithelial cells and fibroblasts via elastase release following leukotoxin‐dependent neutrophil lysis

Aggregatibacter actinomycetemcomitans is considered to be associated with periodontitis. Leukotoxin (LtxA), which destroys leukocytes in humans, is one of this bacterium's major virulence factors. Amounts of neutrophil elastase (NE), which is normally localized in the cytoplasm of neutrophils, are reportedly increased in the saliva of patients with periodontitis. However, the mechanism by which NE is released from human neutrophils and the role of NE in periodontitis is unclear. In the present study, it was hypothesized that LtxA induces NE release from human neutrophils, which subsequently causes the breakdown of periodontal tissues. LtxA‐treatment did not induce significant cytotoxicity against human gingival epithelial cells (HGECs) or human gingival fibroblasts (HGFs). However, it did induce significant cytotoxicity against human neutrophils, leading to NE release. Furthermore, NE and the supernatant from LtxA‐treated human neutrophils induced detachment and death of HGECs and HGFs, these effects being inhibited by administration of an NE inhibitor, sivelestat. The present results suggest that LtxA mediates human neutrophil lysis and induces the subsequent release of NE, which eventually results in detachment and death of HGECs and HGFs. Thus, LtxA‐induced release of NE could cause breakdown of periodontal tissue and thereby exacerbate periodontitis.     

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.     

Scale Arrangement Pattern in a Lepidopteran Wing. 1. Periodic Cellular Pattern in the Pupal Wing of Pieris rapae

In most species of lepidopteran insects, anteroposterior rows formed by scales are arranged at regular intervals in the adult wing; within each row two kinds of scales are alternately arranged. To investigate the cellular basis for the scale arrangement pattern, we examined cell arrangement in the epidermal monolayer of the pupal wing of a small white cabbage butterfly, Pieris rapae , by scanning electron microscopy and light microscopy.
The arrangement of scale precursor cells, closely resembling that of scales in the adult wing, was observed in the wing epidermis of the early pupa. Scale precursor cells are proximodistally elongated and form anteroposterior rows. Within a row two kinds of scale precursor cells are nearly alternately arranged, which is not so precise as the alternation of scales in the adult wing. Individual rows of scale precursor cells are separated by rows of single or double undifferentiated general epidermal cells. Occasionally, arrangement abnormalities occur both in the adult and the pupal wing. The cellular basis for the regular spacing of scale rows is discussed.     

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.     

Changes of DNA methylation level during pre-and postnatal periods in mice

DNA methylation in an adult mammalian body shows tissue-specificity. But when and how the specificity is established in the process of development has not yet been elucidated. Here we have investigated age-dependent changes in the amount of 5-methyldeoxycytidine (5mdC) that DNA of various mouse tissues contains during the late-fetal and postnatal periods, using high-performance liquid chromatography. The tissue-specificity in the 5mdC level was observed in the late-fetal stage, and the level continued to change during the subsequent periods. The most pronounced alterations were observed in brain and liver, where similar biphasic changes were seen, but at different ages. At maturation, the 5mdC levels were high in thymus, spleen and brain, intermediate in lung, and low in liver and sperm. The data demonstrate the importance of the peri- and postnatal periods in establishment of tissue-specificity in 5mdC content.     

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.