Effects of 60 Hz electric and magnetic fields on maturation of the rat neopallium

This study was undertaken to determine the effects of extremely low frequency (ELF; 60 Hz) electromagnetic (EM) fields on somatic growth and cortical development, as well as biochemical and morphological maturation, of the rat neopallium. On the fifth day of pregnancy, female rats were put in pairs into plastic cages that were housed in a specially constructed apparatus for irradiation under three separate sets of combination and intensity: 1) 1 kV/m and 10 gauss; 2) 100 kV/m and 1 gauss; and 3) 100 kV/m and 10 gauss. The dams were exposed for 23 h daily, from days 5 through 19 postconception after which they were returned to cages outside the exposure apparatus until they littered. The neonates were culled to eight pups per litter. At 0 (birth), 5, 12, and 19 days postnatally, they were killed for biochemical and morphological studies. Another group of pregnant rats was sham-exposed in an identical apparatus, which was not energized, and the pups were used as controls. The irradiated rats exhibited no physical abnormalities, nor did they show brain deformities such as swelling or herniation following exposure to ELF-EM fields. There was no difference in somatic growth between control and exposed rats, but a small reduction in cortical weight was observed in rats exposed at 1 kV/m and 10 gauss, and 100 kV/m and 1 gauss, respectively. Biochemical measurements of DNA. RNA, protein, and cerebroside concentrations indicated that among the three separate exposures, only the neopallium of rats exposed at 1 kV/m and 10 gauss showed a small reduction in DNA level, as well as small reductions in RNA and protein levels. No changes were noticed in cerebroside levels in any exposed animals, and there were no differences in protein/DNA and cerebroside/DNA ratios between control and exposed rats. Morphological observations did not reveal any detectable alterations in the irradiated rats. These results indicate that exposure to ELF-EM fields caused minimal or no changes in somatic growth and cerebral development of the rat. © 1993 Wiley-Liss, Inc.     

Factors Affecting In Vitro Multiplication of Date Palm

Rapid method of in vitro multiplication of date palm was developed. Shoot tips were cultured on Murashige and Skoog (MS) medium supplemented with 2 mg dm^–3 dimethylaminopurine (2iP) + 1 mg dm^–3 naphthalene acetic acid (NAA). Shoot buds were proliferated from white nodular cultures on hormone free medium. Shoot bud proliferation strongly enhanced when cultured on MS-medium contained 3 mg dm^–3 2iP + 0.5 mg dm^–3 NAA. Culturing on full-strength MS medium showed higher multiplication rate compared with half-strength MS medium. Among four concentrations of sucrose used, 30 g dm^–3 speeded up the bud proliferation more than 10, 20 and 40 g dm^–3. However, the largest shoot buds were observed with 40 g dm^–3 sucrose. Solidification of culture media by 1.75 g dm^–3 Phytagel showed the highest proliferation rate, but the largest buds were observed with 1 g dm^–3 Phytagel.     

Ornithodoros porcinus ticks, bushpigs, and African swine fever in Madagascar

African swine fever (ASF) has recently made its appearance in Madagascar. Ticks of the Ornithodoros moubata group, considered to be O. porcinus Walton, 1962 were formerly known to occur in western Madagascar, but seem to have disappeared from that region. However, three new sites where they occur were found in the humid and cool central highlands of Anatananarivo province. These ticks are known to be efficient reservoirs and vectors of ASF and constitute a considerable complication to the control of the disease. The authors also discuss another potentially complicating factor, the presence of a species of African bushpig, Potamochoerus larvatus.     

Enhanced muscle insulin receptor autophosphorylation with short-term aerobic exercise training

Exercise training improves insulin action in skeletal muscle, but the mechanisms of this effect are not completely understood. In particular, the role of the insulin receptor (IR) is unclear. We examined the IR and an enzyme indicative of oxidative capacity in muscle in relation to improved insulin action in 20 previously sedentary individuals before and after a 7-day program of moderate-intensity cycle ergometry. After training, insulin sensitivity increased 33% (6.20 +/- 0.91 vs. 8.22 +/- 1.12 min. microU(-1). ml(-1) mean +/- SE, pre- vs. posttraining, respectively, P < 0.05). The mitochondrial marker enzyme cytochrome c oxidase (COX) increased in vastus lateralis biopsies by 21% (P < 0.05). After training, IR autophosphorylation, determined by ELISA, was significantly increased by approximately 40% at insulin concentrations from 1 to 100 nM (P < 0.05). The training-induced improvements in IR autophosphorylation were significantly correlated with changes in muscle COX content (r = 0.65, P < 0.05). These studies indicate that, in this model of increased physical activity, improvements in IR function are an early adaptation to exercise in humans, are correlated with increases in muscle oxidative capacity, and likely contribute to the beneficial effects of exercise training on insulin action.     

Effect of the cultivation conditions of Candida species yeast-like fungi on their sensitivity to levorin]

The effect of levorin on yeast-like fungi under (different) cultivation conditions was studied. It was shown that the medium composition and incubation temperature affected the results of determination of the test-culture sensitivity to levorin. There was correlation between the time of the population lag-phase and the critical time of the zone formation and these values depended on the temperature of the test-microbe vegetation. Strain 037 of C. utilis was more sensitive to levorin and had a longer lag-phase as compared to the other species of the yeast-like fungi, which provided favourable conditions for formation of the growth inhibition zones.     

Pulsation of nuclei in insect oocytes is reversibly inhibited by cytochalasin B

Oocyte nuclei of the dipteran insect Heteropeza pygmaea display swift pulsating movements during in vitro follicle formation in the ovaries. Low doses of cytochalasin B (CB) completely inhibit the nuclear movements within a few minutes and cause the nuclei to assume spherical shapes. If the drug is removed, nuclear pulsation is resumed within 5–10 min. Phalloidin and colchicine do not affect the nuclear movements. Actin is shown by indirect immunofluorescence microscopy to be present in considerable amounts all over the cytoplasm of the oocytes. It is concluded that microfilaments are responsible for pulsation of the oocyte nuclei, whereas microtubules are not involved.     

Control of Sodium Transport in Sunflower Roots

Electrochemical potential differences (driving forces) for sodiumdistributed between the outside solution and the exuding sapof water-culture-grown sunflower plants (Helianthus annuius)have been determined. The results indicated that sodium wasmoving from the outside solution to the xylem against the electrochemicalpotential gradient at external concentrations below approximately0.30 mM Na. At higher external concentrations sodium appearedto be actively excluded from the xylem. An electrical potential difference between the exuding sap andthe external solution of approximately 30 mV was observed. Itwas unaffected by the external sodium concentration. Use ofa short-circuiting technique indicated that the trans-root potentialresides at the plasmalemma of the cortical cells. Driving forces on sodium distributed between the external solutionand the root and between the xylem sap and the root were calculated.They indicated that the root is able to accumulate sodium activelyboth from the external solution and the xylem sap. It is concludedthat sodium transport to the xylem in this species is controlledby the balance of these two opposing forces.