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Biomedical subjects

Y Asada

Publications and source records attributed to Y Asada.

At least 289 records · Page 16Linked to original sources
PubMed1977

Staphylococcal scalded skin syndrome I. Purification of exfoliatin and maternal transmission of neutralizing ability against exfoliatin.

Exfoliatin, an exotoxin produced by phage group 2 staphylococci, was separated and was analyzed. The toxin was separated in a single peak by Sephadex G-100 gel filtration and subsequent DEAE Sephadex chromatography. By acrylamide gel disc electrophoresis this single peak was found to contain 2 components both of which posessed exfoliative activity and the same antigenic properties. Their molecular weight, however, differed; the major component had a molecular weight of 30,000 and the minor component had 27,000. The toxin was stable when heated at 60 degrees C for 40 minutes, and labile at 100 degrees C for 20 minutes. The toxin was immunogenic to mice and produced antibody which could be transmitted to neonatal mice to neutralize exfoliative activity of the toxin. Innoculation of the bacteria caused the production of antibodies against both exfoliatin and alpha-hemolysin in mice. The antibodies were also transmitted to neonatal mice to neutralize the exfoliative activity of exfoliatin.

Animals↗
PubMed1977

Staphylococcal scalded skin syndrome. II. Serum level of anti exfoliatin and anti alpha-toxin in patients with staphylococcal scalded skin syndrome or bullous impetigo.

In order to study the differences between staphylococcal scalded skin syndrome (SSSS) and bullous impetigo, the anti exfoliatin level was assessed in the sera from both groups of patients, and no significant difference in the level was found. However a significant difference was noted in the anti alpha-toxin levels in sera from both group of patients; that of SSSS patients was much lower than that of impetigo patients and of children in a control group. Five out of 6 patients with SSSS showed an unchaged level of anti alpha-toxin at the second examination, while an increased anti exfoliatin level was noted in 4 out of 6 SSSS patients.

Age Factors↗
PubMed1976

The existence of three types of acetohydroxy acid synthetase in an isoleucine-requiring mutant of Aerobacter aerogenes.

The synthesis of the three types of acetolactate synthase (EC 4.1.3.18) which are responsible for the biosynthesis os isoleucine and valine, was observed in Aerobacter aerogenes I-12, an isoleucine-requiring mutant, when grown on the four kinds of media. When the cells were grown on isoleucine-rich medium, acetolactate synthase sensitive to feedback inhibition and having an optimum pH at 8.0 was formed. By increasing the amount of potassium phosphate in the medium, the catabolite repression of the enzyme having an optimum pH at 6.0 and which is insensitive to feedback inhibition, was released. In contrast, acetolactate synthase having an optimum pH at 8.0 and insensitive to feedback inhibition was formd when isoleucine was limited, irrespective of phosphate concentrations. Two insensitive enzymes were not regulated by isoleucine, leucine and valine, although sensitive pH 8.0 enzyme was repressed by them. Thus, it may be assumed that the synthesis of insensitive pH 8.0 enzyme were repressed by limiting the amount of isoleucine is still open.

Acetolactate Synthase↗
PubMed1971

Experimental alteration of coupling resistance at an electrotonic synapse.

Adjacent segments of the septate axon of the crayfish Procambarus are electrotonically coupled by junction located in the septa between them (see Pappas et al. 1970. J. Cell Biol.49:173). The coupling resistance at the septa was changed by several experimental treatments. Mechanical injury to an axon increased coupling resistance (more than 7-fold); no recovery of coupling resistance was observed, although the resting potential and resistance of the injured axon could return to near normal levels. Immersion in salines with Na propionate substituted for NaCl increased coupling resistance (mean: 6.1-fold). On return of the preparation to normal saline, coupling resistance recovered virtually completely. Immersion in low Ca(++) solutions moderately increased coupling resistance (3.5-fold or less), but return to normal saline was followed by large increases in coupling resistance (5-100-fold). 60 nM Ca(++) is near the maximum concentration that leads to increased coupling resistance on return to normal saline. Large increases in coupling resistance are associated with separation of junctional membranes (Pappas et al. 1970. Ibid.); calculations show that the separated membranes greatly increase in resistance. Increase in coupling resistance is probably an important response to injury. Mechanisms underlying changes reported here may be relevant to normal physiological processes of coupling and decoupling.

Acetates↗
PubMed1971

Morphological correlates of increased coupling resistance at an electrotonic synapse.

Close appositions between axonal membranes are present in the septum between adjacent axonal segments of the septate or lateral giant axons of the crayfish Procambarus. In sections the closely apposed membranes appear separated by a space or gap. The use of lanthanum indicates that there may be structures connecting the apposed membranes. The apparent gap is actually a network of channels continuous with the extracellular space. Adjacent axonal segments are electrotonically coupled at the septa. The coupling resistance is increased by mechanical injury of an axon, immersion in low Cl(-) solutions, and immersion in low Ca(++) solutions, followed by a return to normal physiological solution. Septa at which coupling resistance had been measured were examined in the electron microscope. The induced increases in coupling resistance are associated with separation of the junctional membranes (with the exception of the moderate increases during immersion in low Ca(++) solutions). Schwann cell processes are present between the separated axonal membranes. When nerve cords in low Cl(-) solutions are returned to normal physiological solution, coupling, i.e., electrotonic synapses. A model of an electrotonic synapse is proposed in which tween axonal membranes are again found. The association between the morphological and physiological findings provides further evidence that the junctions are the sites of electrotonic coupling, i.e., electrotonic, synapses. A model of an electrotonic synapse is proposed in which intercytoplasmic channels not open to the extracellular space are interlaced with a hexagonal network of extracellular channels between the apposed junctional membranes.

Animals↗
PubMedDate not supplied

Photosynthetic accumulation of poly-(hydroxybutyrate) by cyanobacteria--the metabolism and potential for CO2 recycling.

Regulatory mechanism in PHB [poly-(hydroxybutyrate)] accumulation by cyanobacteria, especially by a thermophilic isolate, Synechococcus MA19 was reviewed in comparison with a genetically engineered strain. The strain, MA19 accumulates PHB under nitrogen starved and photoautotrophic conditions (MA19-N). Little PHB synthase activity was detected in crude extracts from the cells grown in nitrogen sufficient conditions (MA19 + N). The activity was detected exclusively in membrane fractions from MA19 + N. The change of the enzyme activity was insensitive to chloramphenicol, which suggests post-translational activation. In vitro, acetyl phosphate activated PHB synthase in membrane fractions from MA19 + N, and the extent of activation depended on the concentration of acetyl phosphate. Phosphotransacetylase which catalyzes the conversion of acetyl-CoA to acetyl phosphate was detected in crude extracts from MA19-N but not in those from MA19 + N. These results suggested that intracellular acetyl phosphate concentration could be controlled, depending on C-N balance and intracellular acetyl-CoA concentration. On the contrary, in genetically-engineered cyanobacterium (transformant with PHB synthesizing genes from Ralstonia eutropha), it did not seem to be PHB synthase but acetyl-CoA flux that limits PHB synthesis. The closer association of PHB granules with thylakoid membranes in MA19 is suggested than that in the genetically-engineered cyanobacterium, which may reflect the difference of distribution of PHB synthase. Transposon-mutagenesis was used to acquire mutants of its altered PHB regulatory mechanism. PHA production by cyanobacteria was considered from the aspects of photobioreactors.

Acyltransferases↗