Age-related differences in muscle activity, stride frequency and heart rate response during walking in water.

This study aimed to examine whether walking in water produces age-related differences in muscle activity, stride frequency (SF), and heart rate (HR) response. Surface electromyography (EMG) was used to evaluate muscle activities in six older and six young subjects while they walked in water immersed to the level of the xiphoid process. The trials in water utilized the Flowmill which consists of a treadmill at the base of a water flume. The measurement of maximal voluntary contraction (MVC) of each muscle was made prior to the gait analysis. The %MVCs, which refer to the surface EMG measures, from the gastrocnemius of the older subjects were significantly lower than those of the young subjects, in every experimental condition (P<0.05). In contrast, the %MVCs from the rectus femoris (P<0.05) and the biceps femoris (P<0.001) of older subjects were significantly greater than those of young subjects in every experimental condition. Moreover, the SFs of older subjects were also significantly greater than those of young subjects (P<0.05), while the HR responses of older and young subjects were similar. In conclusion, the older subjects had increased hip musculature activity and decreased ankle plantar flexor activity while walking in water, compared with the young subjects.     

A toxic substance produced by Nocardia otitidiscaviarum isolated from cutaneous nocardiosis

During our studies on toxic substances from clinically isolated Nocarida, a new isolate identified as Nocardia otitidiscaviarum from cutaneous nocardiosis was found to produce a toxic substance called HS-6 that had strong in vitro as well as in vivo toxicity. The mouse intraperitoneal LD₅₀ value was 1.25 mg/kg and the ED₅₀ value for L1210 cultured cells was 0.3 ng/ml. The structure of HS-6 was determined and found to belong to the 16-membered macrocyclic group with a molecular formula of C₄₃H₆₈O₁₂. HS-6 also showed activity against pathogenic fungi such as Cryptococcus neoformans.     

Mechanism of proline transport in Escherichia coli K12. III. Inhibition of membrane potential-driven proline transport by syn-coupled ions and evidence for symmetrical transition states of the 2H+/proline symport carrier

Specific inhibition of 2H+/proline symport by syn-coupled ions (Na+, Li+, and H+) was investigated using cytoplasmic membrane vesicles prepared from the proline carrier-overproducing strain MinS/ pLC4 -45 of Escherichia coli K12. The 2H+/proline symport driven by the membrane potential generated via respiration with 20 mM ascorbate/Tris, 0.1 mM phenazine methosulfate was specifically inhibited by Na+. The inhibition by Na+ was described by a fully noncompetitive mechanism, and the apparent Ki for Na+ was 15 mM. A linear correlation between the apparent Vmax and the apparent Kd was observed. Li+ stimulated the transport activity 2-fold at 10 mM and inhibited it at concentrations above 50 mM. H+ caused fully noncompetitive inhibition of 2H+/proline symport, and its apparent Ki was 0.6 microM. These results indicate that the concentrations of Na+ and H+ strictly and independently regulate the amount of the active C state carrier responsible for 2H+/proline symport driven by the membrane potential by inhibiting the transition from the C* state carrier which exhibits Na+- and H+-dependent binding of proline and is predominant in nonenergized conditions.     

Induction of chromosomal aberrations in cultured Chinese hamster cells by short-term treatment with cadmium chloride

Inducibility of chromosomal aberrations and cytotoxicity in cultured Chinese hamster cells by cadmium chloride (CdCl2) was investigated under 3 different treatment conditions: (i) 2-h treatment in MEM medium supplemented with 10% fetal bovine serum (MEM + 10% FBS) or (ii) in HEPES-buffered Hanks' solution (HEPES-Hanks), and (iii) continuous treatment for 24 h in MEM + 10% FBS. Two-h treatment with CdCl2 in HEPES-Hanks or continuous treatment for 24 h in MEM + 10% FBS was respectively 2 or 3 times more cytotoxic than 2-h treatment with the metal in MEM + 10% FBS. Continuous treatment for 24 h with a CdCl2 concentration in excess of 5 X 10(-6) M was too toxic to the cells to allow chromosomal analysis, and moreover, only a slight increase in incidence of chromosomal aberrations was observed at a concentration of 5 X 10(-6) M CdCl2. In contrast, a marked and concentration-dependent increase in incidence of chromosomal aberrations was observed after post-treatment culture for 22 h follows 2-h treatment with 1 X 10(-6) M to 5 X 10(-5) M of CdCl2 in both MEM + 10% FBS and HEPES-Hanks. Two-h treatment with cadmium in HEPES-Hanks was approximately 3 times more potent for the induction of chromosomal aberrations than that in MEM + 10% FBS. Types of aberrations induced by CdCl2 mainly consisted of chromatid gaps and breaks, although a few exchanges, dicentrics and fragmentations were observed at high concentrations of cadmium. Increase in incidence of tetraploidy was also observed with a concentration dependency after 2-h treatment with CdCl2. Potency of CdCl2 to induce chromosomal aberrations after 2-h exposure was comparable to that of benzo[a]pyrene activated with S9 at equitoxic concentrations. Two-h treatment with cadmium markedly inhibited incorporation of [3H]thymidine, even at concentrations at which incorporation of [3H]uridine or [3H]leucine was less inhibited. However, the inhibition of [3H]thymidine incorporation by cadmium was reversible and the incorporation restored to the control level during 2-6 h of post-treatment incubation. These findings suggest that restoration of DNA synthesis after cadmium exposure is required for the efficient detection of chromosomal aberrations induced by the metal.     

Coordinate repression of arginine aminopeptidase and three enzymes of the arginine deiminase pathway in Streptococcus mitis

Streptococcus mitis contains two arginine aminopeptidases (I and II) as an arginine-supplying system and the arginine deiminase pathway as an arginine-utilizing system. The levels of arginine aminopeptidase I and three enzymes of the arginine deiminase pathway were suppressed by glucose in an apparently coordinate manner. Enzyme II appeared to be constitutive.     

Structure-function studies on bacteriorhodopsin. VIII. Substitutions of the membrane-embedded prolines 50, 91, and 186: the effects are determined by the substituting amino acids

To study their role in the structure and function of bacteriorhodopsin, three prolines, presumed to be in the membrane-embedded alpha-helices, have been individually replaced as follows: Pro-50 and Pro-91 each by Gly and Ala and Pro-186 by Ala, Gly, and Val. The mutants of Pro-50 and Pro-91 all showed normal chromophore and proton pumping. However, the rates of regeneration of the chromophore in Pro-50----Ala, Pro-91----Ala and ----Gly with all-trans-retinal were about 30-fold slower than that in the wild-type, whereas the chromophore regeneration rate in Pro-50----Gly was 10-fold faster than in the wild-type. While, Pro-186----Ala regenerated the wild-type chromophore, the mutants Pro-186----Val and Pro-186----Gly showed large blue shifts (about 80 nm) in the chromophore regenerated with all-trans-retinal and showed no apparent dark-light adaptation. Pro-186----Gly first regenerated the wild-type chromophore with 13-cis-retinal which was thermally unstable and rapidly converted to the blue-shifted chromophore obtained with all-trans-retinal. High salt concentration restored the wild-type purple chromophore in the Pro-186----Gly mutant. Thus, in this mutant, the protein interconverts between two conformational states. Pro-186----Ala and Pro-186----Gly showed about 65%, whereas Pro-186----Val showed 10-20% of the normal proton pumping.     

Heme O biosynthesis in Escherichia coli: the cyoE gene in the cytochrome bo operon encodes a protoheme IX farnesyltransferase.

The cytochrome bo complex of Escherichia coli is encoded by the cyoABCDE operon and functions as a redox-coupled proton pump. In this study, we have constructed eight cyoE deletion mutants and found that all the mutants were nonfunctional. Spectroscopic and heme analyses of the mutant oxidases revealed that the mutations specifically substituted protoheme IX for heme O present in the high-spin heme binding site. We found also that the overexpression of the cyoE gene in a cyo operon deletion strain resulted in a conversion of protoheme IX to heme O. Since the CyoE protein contains the putative allylic polyprenyldiphosphate binding domain, we concluded that the cyoE gene encodes a novel enzyme, protoheme IX farnesyltransferase, essential for heme O biosynthesis.     

Intergeneric hybridization betweenMonascus anka andAspergillus oryzae by protoplast fusion

Summary To breed industrially useful strains of a slow-growing, red-pigment-producing strain ofMonascus anka, protoplasts ofM. anka MAK1 (arg) andAspergillus oryzae AOK1 (met, thr) were fused. A mixture of protoplasts prepared from mycelia ofM. anka MAK1 treated with 2% Usukizyme and ofA. oryzae AOK1 treated with 2% Usukizyme and 0.2% NovoZym 234 was incubated with 30% (w/v) polyethylene glycol no. 6000. Heterokaryon fusants complementing the auxotrophies of both mutants were isolated on minimal medium, but segregated into red (MAK1) and white (AOK1) sectors after being cultured on a complete medium. After irradiation with UV light, the fusants gave stable heterozygous diploids that formed long white hyphae. These diploids, which had twice as much DNA in the nucleus as their parents, grew more rapidly than the parent strain YZT1, and produced ethanol earlier than the parents. Production of amylase, protease, and kojic acid by the fusants was intermediate in amount between that of the two parents.     

Detection of inactive or less active forms of tyrosine hydroxylase in human adrenals by a sandwich enzyme immunoassay

A sensitive sandwich enzyme immunoassay for tyrosine hydroxylase (TH) from bovine and human adrenals has been developed. Anti-TH antibody was prepared from bovine adrenal TH. The assay system consisted of an antibody F(ab')2 immobilized on polystyrene beads as a solid phase and of beta-D-galactosidase-conjugated antibody. This method was highly sensitive and specific for the assay of TH. Human adrenal TH level was determined by similar sensitivity as bovine adrenal TH, suggesting the presence of common antigenic sites between human and bovine adrenal enzymes. The presence of inactive or less active forms of TH in human adrenals was revealed by purification of the enzyme and monitoring with this enzyme immunoassay as well as with enzyme activity assay.