Genetically polymorphic α-l-fucosidase (FUCA1) isozymes detected in blood plasma

The main isozyme patterns of desialylated blood plasma or serum -l-fucosidase (FUCA) were found to be almost identical to those of semen, urine, placental extracts, and leukocyte lysates, when detected by polyacrylamide gel isoelectric focusing, and activity staining using the fluorogenic substrate 4-methylumbelliferyl--l-fucopyranoside. Three phenotypes (1, 2-1, and 2) determined from plasma samples were identical to the phenotypes from urine and leukocyte lysates from the same individuals. A population study of plasma samples collected from 485 Japanese individuals indicated that the frequencies of the FUCA11 ^* and FUCA12 ^* alleles were 0.7505 and 0.2495, respectively. The mean plasma enzyme activities (+SD) of the three phenotypes were 318.8 ± 116.7 nmol/ml per h for type 1, 268.0 ± 108.3 nmol/ml per h for type 2-1, and 233.2 ± 84.4 nmol/ml per h for type 2. The mean activities of types 1 and 2 suggest that, on average, the FUCA11 ^* gene product in plasma has about 1.4 times the activity of FUCA12 ^*.     

The induction of recessive mutations in mouse primordial germ cells with N-ethyl-N-nitrosourea

A specific-locus test was carried out to examine the mutagenic activity of N-ethyl-N-nitrosourea (ENU) on mouse primordial germ cells (PGC). Embryos of C3H/He mice were treated transplacentally with 30 or 50 mg ENU per kg of maternal body weight on day 8.5, 10.5, or 13.5 of gestation (G8.5 day, G10.5 day, or G13.5 day). Male and female mice that had been treated with ENU in embryonic stages were mated with female or male tester PW mice to detect recessive mutations induced in PGC.

ENU induced recessive mutations at a relatively high rate in PGC at these developmental stages. The most sensitive stage was G10.5 day. On G8.5 day, the induced mutation rate in males and females was not significantly different. Cluster mutations, which originate from the limited number of PGC and cell killing, were more frequently induced at an earlier developmental stage. The induced mutation rate per unit dose of ENU (1 mg/kg) was higher in G8.5 and G10.5 day PGC than in stem-cell spermatogonia. It can be concluded that mouse PGC are more sensitive than stem-cell spermatogonia to the induction of recessive mutations by ENU.     

A comparison of sweating responses during exercise and recovery in terms of sweating rate and body temperature

Based on the hypothesis that the relation between sweating rate and body temperature should be different during exercise and rest after exercise, we compared the sweating response during exercise and recovery at a similar body temperature. Healthy male subjects performed submaximal exercise (Experiment 1) and maximal exercise (Experiment 2) in a room at 27° C and 35% relative humidity. During exercise and recovery of 20 min after exercise, esophageal temperature (Tes), mean skin temperature, mean body temperature ( ), chest sweating rate ( ), and the frequency of sweat expulsion (F _SW) were measured. In both experiments, andF _SW were clearly higher during exercise than recovery at a similar body temperature (Tes, ). was similar during exercise and recovery, or a little less during the former, at a similarF _SW. It is concluded that the sweating rate during exercise is greater than that during recovery at the same body temperature, due to greater central sudomotor activity during exercise. The difference between the two values is thought to be related to non-thermal factors and the rate of change in mean skin temperature.     

N-Acetylchitooligosaccharides,biotic elicitor for phytoalexin production,induce transient membrane depolarization in suspension-cultured rice cells

Summary N-acetylchitooligosaccharides (fragments of chitin) elicit the production of phytoalexin in suspension-cultured rice cells. This oligosaccharide elicitor induced rapid and transient membrane depolarization at sub-nanomolar concentrations. Only the oligomers with a certain degree of polymerization were active, while deacetylated chitooligosaccharides caused no effect. Such specificity coincided well with that for the elicitor activity, suggesting possible involvement of this transient change in membrane potential as one of the initial signals in the signal transduction sequence for the activation of defense responses.     

Mos induces the in vitro activation of mitogen-activated protein kinases in lysates of frog oocytes and mammalian somatic cells.

Mitogen-activated protein kinases (MAPKs) are rapidly and transiently activated when both quiescent Go-arrested cells and G2-arrested oocytes are stimulated to reenter the cell cycle. We previously developed a cell-free system from lysates of quiescent Xenopus oocytes that responds to oncogenic H-ras protein by activating a MAPK, p42MAPK. Here, we show that the oncogenic protein kinase mos is also a potent activator of p42MAPK in these lysates. Mos also induces p42MAPK activation in lysates of activated eggs taken at a time when neither mos nor p42MAPK is normally active, showing that the mos-responsive MAPK activation pathway persists beyond the stage where mos normally functions. Similarly, lysates of somatic cells (rabbit reticulocytes) also retain a mos-inducible MAPK activation pathway. The mos-induced activation of MAPKs in all three lysates leads to phosphorylation of the pp90rsk proteins, downstream targets of the MAPK signaling pathway in vivo. The in vitro activation of MAPKs by mos in cell-free systems derived from oocytes and somatic cells suggests that mos contributes to oncogenic transformation by inappropriately inducing the activation of MAPKs.     

Influence of a menhaden oil diet on cercarial penetration of Schistosoma mansoni.

The ability of a menhaden oil (MO) diet to influence cercarial penetration into mouse tail skin was evaluated. Male CD-1 mice 4-6 wk old (15.2 g average weight) were fed a 0, 10%, or 20% MO-supplemented diet for 2 wk. After this time mice were infected with either 65 +/- 3 or 145 +/- 3 [35S]methionine/cysteine-labeled cercariae for 1 hr by tail immersion. Twenty-four hours and 7 days later groups of mice were killed and their tail skin removed and autoradiographed. At 24 hr postinfection, mice fed a 20% MO diet had significantly higher cercarial penetration than controls and 10% MO diets (56% +/- 5.2 vs. 44% +/- 2.9, P = 0.02, 1-tailed t-test). After 7 days mice fed a 20% MO diet retained more radioactive foci than controls or 10% MO diets (21% +/- 2.0 vs. 15% +/- 1.3, P = 0.01, 1-tailed t-test).     

REPRODUCTIVE ISOLATION BY HOST SPECIFICITY IN A PAIR OF PHYTOPHAGOUS LADYBIRD BEETLES

Crossing experiments and food-choice tests show that two sympatric species of phytophagous ladybird beetles, Epilachna niponica and E. yasutomii, are reproductively isolated by host-plant specificity. Adult beetles selected their natural hosts when given choices, though some accepted the host of the other species when no choice was offered. In each species, survival of larvae to the second instar was significantly higher on their own host plant. No evidence for sexual isolation, gametic isolation, hybrid inviability, or reduced hybrid fertility was detected. Reproductive isolation by host specificity is an important prerequisite for certain models of sympatric speciation. Although the present example supports the plausibility of such models, an allopatric origin of host-plant specificity cannot be discounted.     

Cloning and nucleotide sequence of fosfomycin biosynthetic genes of Streptomyces wedmorensis

The biosynthetic pathway for production of the antibiotic fosfomycin by Streptomyces wedmorensis consists of four steps including the formation of a C-P bond and an epoxide. Fosfomycin production genes were cloned from genomic DNA using S. wedmorensis mutants blocked at different steps of the biosynthetic pathway. Four genes corresponding to each of the biosynthetic steps were found to be clustered in a DNA fragment of about 5 kb. Nucleotide sequencing of a large fragment revealed the presence of ten open reading frames, including the four biosynthetic genes and six genes with unknown functions.