Simultaneous analysis of skin response to the different L.E.T. regions of a 55 MeV helium ion beam

Summary Rat tail epidermis was used to analyze the in vivo response of a biological system to heavy particle irradiation. The conical configuration of the rat tail gives rise to a variable energy degradation of the beam thus yielding information on the damage elicited by 2 different L.E.T. regions of the helium beam at different sites on the same sample. Cytochrome oxidase activity and epidermal thickness were used to analyze the metabolic and structural radioinduced response. Quantitative evaluation of radiation damage revealed marked variations within a few micrometers of tissue.     

Differential effects of the destruction of Leydig cells by administration of ethane dimethane sulphonate to postnatal rats

Ethane dimethane sulphonate (EDS) is a cytotoxic drug that selectively destroys Leydig cells in adult testes. This study has examined the effect of a single injection of EDS on the Leydig cell populations present in the testes of rats aged 5, 10, or 20 days. Microscopic examination of the tissue demonstrated that the fetal Leydig cell population was destroyed at all ages, but that subsequent development of the adult population of Leydig cells was not affected. Whilst the destruction of the fetal Leydig cells in this acute phase of EDS on 5-day-old rats was accompanied by a decline in serum testosterone levels, there was no apparent effect on this hormone when EDS administered at 10 or 20 days of age, despite the destruction of fetal Leydig cells in these rats. The long-term effects of EDS on Day 5 of age resulted in proliferation of the intertubular tissue in which more Leydig cells were observed, but serum testosterone and testosterone levels in response to human chorionic gonadotropin stimulation in vitro were normal despite moderate or severe disruption of the seminiferous epithelium. These data show that the fetal Leydig cells of immature testes are sensitive to the cytotoxic effects of EDS in the adult, but the response of the testes differs depending on the age at which the drug is administered.     

Epidemiology of tegumentary leishmaniasis in Mérida, Venezuela. I. Diversity and dispersion of phlebotomine species at 3 altitude levels and its possible role in the transmission of the disease

As part of an epidemiological study on leishmaniasis in Merida, Venezuela, the diversity and dispersion of sandflies species found in 15 localities between 175 m and 1,960 m.a.s.l., are presented. From 7,126 collected sandflies (5,132 female and 1,994 male), 24 species were identified, 10 of them recognized as anthropophilic. The relation species-altitude is presented, and the species composition found in human dwellings, periodomestic and sylvatic areas, are recorded. The possible role of the identified species on the transmission of leishmaniasis in the andean region, is discussed.     

Factors affecting the activity patterns of black-backed jackals Canis mesomelas

Daily activity levels of black-backed jackals Canis mesomelus were determined in southern Africa through direct observation and radio-tracking. Jackals have a bigeminus activity pattern that is closely paralleled by the activity levels of some of their most important prey. Although differences due to sex, age, study area and season of year were found, this activity pattern was most markedly influenced by light conditions during both the crepuscular and the nocturnal periods.     

Killing of Escherichia coli cells modulated by components of the stability system ParD of plasmid R1

Summary The proteins P10 and P12 have been shown to be gene products of a new stability system, ParD, of plasmid R1. It is now shown that an R1 miniplasmid, pAB112, carrying a trans-complementable amber mutation in the gene of the P10 protein, is lethal for the host in the absence of suppression. This lethal effect is suppressed in a supF background and also by deletions in pAB112 that affect the gene of the P12 protein. These data indicate that the P12 protein has a lethal effect on the host and that this effect is neutralized by the P10 protein. The possibility that the stabilization conferred by the ParD system could be due to a counterselection, mediated by P12, of cells that lose the plasmid at cell division, is discussed.     

A new technique for the treatment of palpebral bags

A new technique for the treatment of palpebral bags is presented. The technique consists of returning fat to the orbital cavity and retaining it by means of a continuous suture (with nonabsorbable filament) of the capsulopalpebral fascia to the periosteum of the lower orbital rim. The anatomic basis for the technique, after examination of the relevant literature and dissection on fresh cadavers, is analyzed. The procedure followed and results obtained are described in detail. Evaluation of the results suggests to the authors that this might be the method to be applied in the majority of patients.     

Depletion of the spermatogonia from the seminiferous epithelium of the rhesus monkey after X irradiation

In unirradiated testes large differences were found in the total number of spermatogonia among different monkeys, but the number of spermatogonia in the right and the left testes of the same monkey appeared to be rather similar. During the first 11 days after irradiation with 0.5 to 4.0 Gy of X rays the number of Apale spermatogonia (Ap) decreased to about 13% of the control level, while the number of Adark spermatogonia (Ad) did not change significantly. A significant decrease in the number of Ad spermatogonia was seen at Day 14 together with a significant increase in the number of Ap spermatogonia. It was concluded that the resting Ad spermatogonia are activated into proliferating Ap spermatogonia. After Day 16 the number of both Ap and Ad spermatogonia decreased to low levels. Apparently the new Ap spermatogonia were formed by lethally irradiated Ad spermatogonia and degenerated while attempting to divide. The activation of the Ad spermatogonia was found to take place throughout the cycle of the seminiferous epithelium. Serum FSH, LH, and testosterone levels were measured before and after irradiation. Serum FSH levels already had increased during the first week after irradiation to 160% of the control level. Serum LH levels increased between 18 and 25 days after irradiation. Serum testosterone levels did not change at all. The results found in the rhesus monkey are in line with those found in humans, but due to the presence of Ad spermatogonia they differ from those obtained in non-primates.     

Effect of n-3 and n-6 fatty acids on hepatic microsomal lipid metabolism: a time course study

The present study examines the time dependent effects of n-6 and n-3 polyunsaturated fatty acids on liver microsomal lipid metabolism in FVB mice fed a diet supplemented with a mixture of free fatty acids (mainly 18:3n-6 and 20:5n-3) at 25 mg/g diet. Significant changes in the fatty acid composition of total liver and microsomal lipids were observed after 7 days on the diets. Thereafter, some animals remained on the same diet while others were fed a diet supplemented with hydrogenated coconut oil (HCO). With the exception of 20:5n-3 which showed a slower recovery, establishment of the HCO pattern was rapid indicating that the diet-induced changes could be easily reversed. The unsaturation index, the cholesterol/phospholipid ratio and the microviscosity of the microsomal membranes were not affected by these dietary manipulations. Unsaturated fatty acid supplementation reduced the activity of ⁹ desaturase by 50%. Feeding the HCO diet to mice previously fed the EPA/GLA diet led to a progressive increase in ⁹ desaturase activity, reaching 80% of the day zero values after 14 days. The monoene content of hepatic total lipids reflected, in most cases, the changes in enzyme activity. This study shows that a low dose of a n-3 and n-6 free fatty acid mixture increases the quantities of members of the n-3 family, without loss of n-6 fatty acids in microsomal membranes and modifies the activity of ⁹ desaturase without altering the microsome physicochemical parameters.