Movements of Mitochondria Associated with Isolated Egg Cortex

Cortical tragments of Tubifex eggs undergoing ooplasmic segregation were isolated in plastic dishes with an oil droplet separating part of them from the dish. Except at the edges of fragments and at the base of the oil droplet, the nearly entire area of the cortex was firmly attached to the plastic surface. Many mitochondria were associated with the cortical actin lattice. On addition of ATP to the preparations, only nonadhering portions of the cortex exhibited contractions. At the base of oil droplets, some mitochondria moved in the same direction concurrently with cortical contractions. Contractile activities of isolated cortices were completely inhibited by their preincubation with N-ethylmaleimide-modified heavy meromyosin, suggesting the involvement of an actomyosin force-generating mechanism in the cortical contractions during ooplasmic segregation.     

Evidence for the Presence of a Low Molecular Weight Factor in Sera from Various Animals that Induces in vitro Maturation of Fish Oocytes

Studies were made on whether sera from various animals or serum components could induce in vitro maturation of medaka oocytes in the absence of any exogenous hormone. When intra-follicular oocytes were preincubated in medium containing serum of some mammals or chickens, and were then washed, they matured during further incubation in the same medium without the serum. In contrast, no remarkable stimulatory effect on oocyte maturation was recognized in sera from some other mammals and from reptiles, amphibian and fish. A dialysate of rabbit serum collected using a cellulose membrane (mol. wt. retention 3,500) also induced in vitro maturation of intra-follicular oocytes. This activity was stable on treatment with proteolytic enzymes or heat-treatment. Small molecular weight fractions with this activity were obtained by filtering the dialysate through Sephadex G-10. The oocytes matured by the serum factor were capable of developing normally beyond the stage of embryonic body formation.
From these results, it is concluded that the serum of higher vertebrates contains a low molecular weight factor that stimulates in vitro nuclear and cytoplasmic maturation of intrafollicular fish oocytes.     

β-Lactoglobulin Suppresses Melanogenesis in Cultured Human Melanocytes

The effects of whey proteins from bovine milk on melanogenesis in cultured human melanocytes were examined. Among the major protein components of milk whey including β-lactoglobulin (BLG), α-lactalbumin, serum albumin, and IgG, only BLG exhibited the depigmenting effect at a concentration of 1 mg/ml. Also, BLG suppressed the activity of tyrosinase in these cells. Retinol, to which BLG is known to bind, slightly increased the pigmentation of the cells at concentrations in the range of 1–100 nM, and retinoic acid, a metabolite of retinol, exhibited a strong pigmentation-promoting effect within the same concentration range. Treatment of the cells with 1 mg/ml BLG completely abrogated the pigmentation induced by these A vitamins. These results demonstrate a novel biological activity of BLG and suggest that this activity is dependent on its ability to bind retinol.     

Glycoproteins from Teratocarcinomas and Organs of Adult Mice: Analysis by Affinity Chromatography on Lectin-conjugated Agarose1

Glycoproteins were isolated from particulate fraction of four teratccarcinomas and several organs of adult mice by affinity chromatography on lectins conjugated with agarose [concanavalin A (Con A), wheat germ agglutinin (WGA), Ricinus communis agglutinin (RCA), peanut agglutinin (PNA) and Dolichos biflorus agglutinin (DBA)] and were compared by SDS gel electrophoresis. Glycoprotein components were found to be very similar in three lines of solid teratocarcinoma, namely F9, STT-2 and OTT-10A. Teratocarcinoma OTT6050, which is an ascitic form called embryoid bodies, also gave glycoprotein profiles somewhat similar to those of other teratocarcinomas. However, glycoprotein profiles of most adult organs were significantly different from those of teratocarcinomas. The following points were of special interest. 1) RCA receptors from the four teratocarcinomas gave a strong band with an apparent molecular weight 145,000 daltons, which was either weak or absent in the receptors from adult organs. 2) The WGA receptors of all adult organs except muscle and small intestine gave more intense bands than those of the teratocarcinomas. 3) Glycoproteins with molecular weights of more than 240,000 daltons were present in WGA receptors, RCA receptors and PNA receptors of teratocarcinoma OTT 6050, but not in the receptors of other teratocarcinomas.     

Incidence of Enterotoxigenic Clostridium perfringens in Healthy Humans in relation to the Enhancement of Enterotoxin Production by Heat Treatment

Enterotoxin production was greatly enhanced in two of five food poisoning strains of Clostridium perfringens subjected to heat treatment prior to incubation in Duncan and Strong sporulation medium. Heating was carried out on three successive cultures of each strain, the optimum temperature for treatment being 85 °C for one strain and 95 °C for another: on each occasion cultures were heated for 20 min. The triple heat treatment procedure was used in testing strains of Cl. perfringens isolated from faeces of healthy human subjects for production of enterotoxin. Eleven of 35 (31%) individuals were found to be carriers of enterotoxigenic strains, the isolates producing more than 0·1 μ/ml of enterotoxin. Six of the 11 enterotoxigenic strains were killed by heating at 95 °C but one isolate produced more enterotoxin following treatment at this temperature than after heating at 75 °C.     

Detection of Enterotoxin in Faeces and Anti-enterotoxin in Serum after Clostridium perfringens Food-poisoning

Two outbreaks of Clostridium perfringens food-poisoning involving the same person were investigated. In the first, typical symptoms with diarrhoea and abdominal pain were observed. In the second, there were no classical signs of food-poisoning; the victim felt some flatulence and the faeces had a pasty appearance and an unpleasant smell. Counterimmunoelectrophoresis and the reversed passive haemagglutination test were rapid and reliable assay methods for enterotoxin in faeces. In the first outbreak, 13–16 μg enterotoxin/g faeces were detected, and 3–4 μg/g in the second. The detection of enterotoxin in faeces indicates the potential use of enterotoxin tests on diarrhoeal samples for diagnosing C. perfringens food-poisoning. No enterotoxin was detected in serum during the acute stage of the illness, but the antibody titre showed a considerable rise in the first two months after the food-poisoning outbreak.     

Experimental Diarrhoea in Human Volunteers Following Oral Administration of Clostridium perfringens Enterotoxin

Peroral administration of purified enterotoxin to human volunteers provoked diarrhoea and abdominal pain, symptoms identical with those encountered in outbreaks of Clostridium perfringens food poisoning. Eight milligrams of enterotoxin caused diarrhoea in one of two volunteers. All of five subjects given 10 and 12 mg of purified enterotoxin or crude enterotoxin developed the classical symptoms of this food poisoning. Passive haemagglutination anti-enterotoxin titres in serum increased in only 5 of 9 volunteers after exposure to enterotoxin. As such levels of anti-enterotoxin can be detected in normal serum samples, titration of anti-enterotoxin may be of little use in diagnosing Cl. perfringens food poisoning. Enterotoxin was detected in all diarrhoeal faecal specimens, and the enterotoxin level varied from 0·2–16 μg/g. Detection of enterotoxin in diarrhoeal faeces may be the most reliable procedure in diagnosing outbreaks of Cl. perfringens food poisoning.     

INITIATION OF CLEAVAGE IN FISH EGGS BY INJECTION OF FLAGELLA OR MICROTUBULES OF SEA URCHIN SPERMATOZOA

Flagella and their microtubules obtained from sea urchin ( Hemicentrotus pulcherrimus ) spermatozoa were injected into unfertilized eggs of the medaka ( Oryzias latipes ) with a micropipette. Upon activation, some of the eggs began the first cleavage with three or more irregular blastomeres, and developed to the morula stage. It is suggested that sperm flagellar microstubule material is one of the cleavage initiation substances.     

Role of male‐biased dispersal in inbreeding avoidance in the grey‐sided vole (Myodes rufocanus)

Effects of male‐biased dispersal on inbreeding avoidance were investigated in a semi‐natural population of Myodes (formerly Clethrionomys) rufocanus using a large outdoor enclosure (3 ha). Parentage of 918 voles weaned from 215 litters and relatedness of mates were analysed using microsatellite loci, and dispersal distances were obtained from mark–recapture live‐trapping data. Natal and breeding male‐biased dispersal was observed. There remained, however, chances that incestuous mating could occur, because not all males dispersed from their natal site, and 51 matings occurred between relatives (relatedness r > 0). The number of weaned juveniles from inbred litters was significantly smaller than that from non‐inbred litters. Fourteen incestuous matings occurred between close relatives (r ≥ 0.25), most of which were those between non‐littermate maternal half siblings (four cases) and those between paternal half siblings (seven cases). When comparing the observed frequencies to the expected ones generated by combining every oestrous female with a male randomly chosen from her surroundings, the observed values for inbreeding of r ≥ 0.25 were significantly smaller than the expectations, while no difference was observed for inbreeding of 0 < r < 0.25. These results suggest that male‐biased dispersal is partly effective to avoid incestuous mating, but it does not provide complete separation of male and female close relatives. Additional mechanisms such as kin discrimination based on familiarity may work in inbreeding avoidance of the vole.