Sex steroids modulate rat anterior pituitary and liver iodothyronine deiodinase activities.

In this study, we investigated the sex hormone regulation of 5'-iodothyronine deiodinase activity, which is responsible for enzymatic conversion of thyroxine into the bioactive form, triiodothyronine. Pituitary homogenates and liver microsomes from: 1) ovariectomized rats injected with 17-beta-estradiol benzoate and/or progesterone (0.7 and 250 microg/100 g body weight, respectively, subcutaneously, over 10 days); 2) male castrated rats treated or not with 0.4 mg/100 g body weight testosterone propionate, intramuscular, over 7 days, were assayed for type 1 and type 2 deiodinase activity in the pituitary. Enzyme activities were measured by release of (125)I from deiodination of (125)I reverse triiodothyronine under varying assay conditions. Estrogen stimulated anterior pituitary and liver type 1 deiodinase activity in ovariectomized rats (45 and 30 %, p < 0.05). Progesterone inhibited the liver enzyme (40 %, p < 0.05), and had no effect on the pituitary, but in both tissues, blocked estrogen stimulatory effect on type 1 deiodinase. In males, testosterone normalized the reduced liver type 1 deiodinase of castrated rats. However, in the pituitary, castration increased (50 %) type 1 deiodinase independent of testosterone treatment, suggesting the existence of a inhibitory testicular regulator of pituitary type 1 enzyme. Treatments did not alter pituitary type 2 deiodinase activity. In conclusion, gonads and sex steroids differentially modulate type 1 deiodinase activity in rat pituitary and liver.     

THE FIBRILLAR POLYSACCHARIDES AND THEIR LINKAGE TO ALGAENAN IN THE TRILAMINAR LAYER OF THE CELL WALL OF COELASTRUM SPHAERICUM (CHLOROPHYCEAE)

Methylation and spectroscopical analyses of DMSO-LiCl-solubilized fractions of the fibrillar cell wall of Coelastrum sphaericum Näg. established the presence of cellulose and β-1,4-linked mannan. A small proportion (2–7%) of (1→2) linkages in β-mannan that introduced an interruption in the regular ribbon chain conformation was interpreted as a component that modulated the mechanical strength of the cell wall. The trilaminar layer fractions consisted mostly of algaenan and cellulose. Evidence for ether linkages between glucose C-6 in the β-1,4-glucan and algaenan was obtained.     

Frequency of anti-Toxoplasma gondii antibodies in cats from Valdivia city, Chile

Toxoplasmosis is a parasitic zoonosis. The importance of the cat as related to this parasitosis lies in the fact that it is not only the definite host of the parasite, but responsible for its dissemination through the release of oocysts, which subsequently infect both humans and other animals. The objective of this study was to determine the serological prevalence of Toxoplasma gondii in the feline population of the city of Valdivia (Chile) and to establish the possible epidemiological implications of this prevalence. With these goals in mind the technique of indirect immunofluorescence was implemented to detect anti- T. gondii species--specific IgG. Blood samples from 97 cats (selected using a directed sampling process) from different sectors of Valdivia were collected. The sample included 46 males and 51 females of different ages, Positive and negative control sera obtained from de United States were used to verify the results, observed by UV microscopy. The anti-feline IgG antibody was used as directed by the manufacturer (Sigma). Of the 97 selected cats, 32 were found to be positive with a titre higher than 1:4, a prevalence of 33.0%. The number of infected males as compared to the number of infected females was found to be statistically insignificant, using the chi-square analysis with p less than 0.1. In contrast, a definite correlation between age and seropositivity was found; infection levels were higher in older animals. These results are consistent with those obtained in different studies on this topic that have been performed in different parts of the world. However, they would seem to be in conflict with other, similar studies that have been done recently in Chile; this may be due to the fact that the cats selected for this study were exposed to different climatic conditions than those examined in previous works. In conclusion, it has been determined that in Valdivia exist cats infected by T. gondii, which indicate the presence of the necessary epidemiological conditions for the persistence of this parasitic cycle and the source of infection for humans and other animals.     

MPTP Decreases MT-I mRNA In Mouse Striatum

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a drug that induces parkinsonism in humans and non-human primates. Free radicals are thought to be involved in its mechanism of action. Recently, metallothionein has been proposed to play a role as a scavenger of free radicals. In the present work, we studied the effect of MPTP neurotoxicity on brain metallothionein-I (MT-I) mRNA expression. Male C-57 black mice were treated with MPTP (30 mg/kg, i.p., daily) for 3 or 5 days. All animals were killed by cervical dislocation 7 days after the last MPTP dose. The brains were removed quickly and immediately frozen, and quantitative in situ hybridization was performed using MT-I cDNA probe. MT-I mRNA content in striatum, a region which is known to be highly predisposed and sensitive to MPTP-induced oxidative stress, decreased by 30% (3 days) and 39% (5 days) respectively, after the last MPTP administration. These results suggest that MT-I gene expression is decreased in MPTP neurotoxicity. It is suggested that the reduction of MT, an anti-oxidant and a free radical scavenger, in the striatum by MPTP enables the neurotoxin to exert maximal oxidative damage to the striatum.     

The Atapuerca human fossils

After 20 years of research, the Atapuerca sites have provided a large amount of archaeological and palaeontological remains. Human fossils have been found in three sites: Gran Dolina, galería and Sima de los Huesos. The Early Pleistocene human fossils from Gran Dolina have been ascribed to a new species,Homo antecessor, that represent the last common ancestor of Neandertals and modern humans. The Sima de los Huesos fossils and all the European Middle Pleistocene human fossils are the ancestors exclusively of the Neandertals, which evolved in Europe in conditions of geographic and genetic isolation.     

Genetic variation and migration pathways of maritime pine (Pinus pinaster Ait) in the Iberian peninsula

The genetic variability and migration pathways of Pinus pinaster after glaciation in the Iberian peninsula was studied by means of 18 loci from 12 natural populations of the species. The analysis showed the existence of three groups of populations with different levels of diversity and patterns of recolonization. The southern Iberian group displays a high level of diversity, with a stepping-stone model of variation. The presence of rare alleles in this group and their position in the phylogenetic tree suggest the existence of refugia during glaciations in this zone. The eastern Iberian group also has high levels of diversity but is clearly separate from the first group based on their genetic distances. The Atlantic group displays a low level of diversity that could be interpreted as a rapid recolonization of the entire area by the Eastern group that has not yet developed to a divergence in this area. The southern Iberian range is indicated to be the dispersal centre of the species after the last glaciation. Received: 15 February 1999 / Accepted: 30 April 1999     

Effect of climatic variation on the relative abundance of the red alga Gelidium robustum in Baja California Sur, Mexico

The red alga Gelidium robustum is important,because of its commercial exploitation in Mexico as araw material for the agar industry, providing 10% ofthe world production of agarophytes. In recent years,its annual harvest in Mexico has shownobvious,variations partly because of an increasedharvesting effort, but also because of environmentalchanges. An analysis is presented of the effect thatinterannual variability of the sea surfacetemperature, wind speed, and upwelling index had onthe relative abundance of this alga from 1980 to 1990.The results indicate a close relation betweenenvironmental fluctuations and the relative abundanceof this species. The response of G. robustum tothe different environmental conditions has not alwaysbeen equal. During El Niño 1982–84, the seasurface temperature was the most important factor andthere was a high negative correlation with therelative abundance. A lag period of three monthsshowed a positive correlation with upwelling index andwind speed. Under normal conditions and during LaNiña, the relative abundance of the alga showed apositive correlation with the sea surface temperature. For the upwelling index and wind speed, therelationship was similar to that during El Niño.     

A study on the microbiota from olive-mill wastewater (OMW) disposal lagoons, with emphasis on filamentous fungi and their biodegradative potential

The microbial composition of olive mill wastewater (OMW) from four disposal ponds has been studied. Such OMW samples contained a variable (but high) number of bacteria, yeasts and molds. Among the latest, members of twelve different genera (Acremonium, Alternaria, Aspergillus, Chalara, Fusarium, Lecytophora, Paecilomyces, Penicillium, Phoma, Phycomyces, Rhinocladiella and Scopulariopsis) were found. Members of five genera (Chalara, Fusarium, Paecilomyces, Penicillium and Scopulariopsis) were widely distributed, and they were able to grow efficiently in undiluted OMW as a sole source of nutrients. Strains of Fusarium, Paecilomyces, Penicillium and Scopulariopsis showed a marked capacity for OMW detoxification, depleting its antibacterial activity almost completely.