Feeding habits of guanacos<Emphasis Type="Italic">Lama guanicoe</Emphasis> in the high Andes of north-central Chile

The guanacoLama guanicoe Muller, 1776 has a wide distribution along the Andes and Patagonia. We studied the feeding behaviour of a guanaco population that lives over 4100 m altitude in the Andes of north-central Chile. By contrasting the diet of guanacos during a dry year with that of a wet year and comparing it with the plant availabilities in the field, we tested the hypothesis that the guanaco is a generalist herbivore. We predicted that under such extreme habitat conditions guanacos should consume whatever plant species are available in the environment, especially in a dry year, when vegetation is scarcer. In addition, we compared its diet at three different age classes. We estimated the diet through the microhistological analysis of plant remains found in guanaco pellets collected during January of 1997 (ie after a dry year) and 1998 (ie after a wet year; 41 vs 495 mm, respectively). Then, we computed dietary preferences, food niche-breadth, and food-niche overlap between years and among age classes. Vegetation cover and plant species richness were higher during the wet than during the dry year. The most common plants in the environment were perennial graminoids and legumes. Contrary to our prediction, the guanaco preferred a few plant species, showing a relatively narrow diet breadth that changed little between years differing in plant abundances. The diet proportions differed among the three age classes, however. Our data indicate that at least in this high-elevation population, guanacos are selective and non-opportunistic herbivores. This specialized feeding behaviour is puzzling given the energetic demands of living in a harsh environment with low availabilities of resources. The hypothesis that this is due to the lower palatability of the plants not eaten, remains to be tested.     

Estrogen receptor,cyclic adenosine monophosphate,and protein kinase A are involved in the nongenomic pathway by which estradiol accelerates oviductal oocyte transport in cyclic rats

This investigation examined the role of estrogen receptor (ER) on the stimulatory effect of estradiol (E2) on protein phosphorylation in the oviduct as well as on E2-induced acceleration of oviductal oocyte transport in cyclic rats. Estrous rats were injected with E2 s.c. and with the ER antagonist ICI 182 780 intrabursally (i.b.), and 6 h later, oviducts were excised and protein phosphorylation was determined by Western blot analysis. ICI 182 780 inhibited the E2-induced phosphorylation of some oviductal proteins. Other estrous rats were treated with E2 s.c. and ICI 182 780 i.b. The number of eggs in the oviduct, assessed 24 h later, showed that ICI 182 780 blocked the E2-induced egg transport acceleration. The possible involvement of adenylyl cyclase, protein kinase A (PK-A), protein kinase C (PK-C), or tyrosine kinases on egg transport acceleration induced by E2 was then examined. Selective inhibitors of adenylyl cyclase or PK-A inhibited the E2-induced egg transport acceleration, whereas PK-C or tyrosine kinase inhibitors had no effect. Furthermore, forskolin, an adenylyl cyclase activator, mimicked the effect of E2 on ovum transport and E2 increased the level of cAMP in the oviduct of cycling rats. Finally, we measured PK-A activity in vitro in the presence of E2 or E2-ER complex. Activity of PK-A in the presence of E2 or E2-ER was similar to PK-A alone, showing that E2 or E2-ER did not directly activate PK-A. We conclude that the nongenomic pathway by which E2 accelerates oviductal egg transport in the rat requires absolute participation of ER and cAMP and partial participation of PK-A signaling pathways in the oviduct.     

The annual cycle of primary productivity in a tropical estuary: the inner regions of the Golfo de Nicoya, Costa Rica

A one year cycle of primary productivity (PP) was studied using the "light and dark bottle" technique in the Golfo de Nicoya, located at 10 degrees N and 85 degrees W at the Pacific coast of Costa Rica. Samples were always incubated at 0, 1, 2, 3 and 4 m depth for 5 hrs from 8:30 till 13:30. The measurements were performed twice per month, first around high tide and one week later at low tide to account for tidal influences. This routine study was supplemented by special measurements about regional and short-term variations of primary productivity using the 14C-method, which mainly served to account for the shortcomings of the routinely employed incubation technique. The upper Golfo de Nicoya is an extremely productive, phytoplankton dominated estuarine system with an annual gross PP of 1037, a net PP of 610 and a community respiration of 427 g C m(-2) a(-1). Highest monthly PP values occurred during the dry season and at the beginning of the rainy season. Peaks in primary productivity coincided with massive blooms of red tide forming algae. Internal biological dynamics, estuarine circulation and land run-off are the most important nutrient sources. High water turbidity reduces the euphotic layer to 4-5 m depth, making the underwater light regime the rate limiting factor. On an annual basis, 41% of the organic carbon produced in the system is already consumed in the euphotic layer. Considering the entire water column (mean depth at mean tidal water level is around 7.7 m) 79% is consumed in the pelagial. Taking into account the organic material consumed and stored in the sediments the carbon budget of the upper gulf is probably balanced. Since, however, the system receives a considerable amount of organic material from its terrestrial surroundings (especially from the mangrove forests), a surplus of organic carbon is exported from the upper Golfo de Nicoya, which enhances the overall water productivity of the lower gulf and the adjacent area.     

Synthesis and antiparasitic activity of 1H-benzimidazole derivatives

Compounds 1-18 have been synthesized and tested in vitro against the protozoa Giardia lamblia, Entamoeba histolytica and the helminth Trichinella spiralis. Inhibition of rat brain tubulin polymerization was also measured and compared for each compound. Results indicate that most of the compounds tested were more active as antiprotozoal agents than Metronidazole and Albendazole. None of the compounds was as active as Albendazole against T. spiralis. Although only compounds 3, 9 and 15 (2-methoxycarbonylamino derivatives) inhibited tubulin polymerization, these were not the most potent antiparasitic compounds.     

High yield of endoreduplication induced by ICRF-193: a topoisomerase II catalytic inhibitor

Previous studies have demonstrated that phenolic compounds, including genistein (4',5,7-trihydroxyisoflavone) and resveratrol (3,4',5-trihydroxystilbene), are able to protect against carcinogenesis in animal models. This study was undertaken to examine the ability of genistein and resveratrol to inhibit reactive oxygen species (ROS)-mediated strand breaks in phi X-174 plasmid DNA. H(2)O(2)/Cu(II) and hydroquinone/Cu(II) were used to cause oxidative DNA strand breaks in the plasmid DNA. We demonstrated that the presence of genistein at micromolar concentrations resulted in a marked inhibition of DNA strand breaks induced by either H(2)O(2)/Cu(II) or hydroquinone/Cu(II). Genistein neither affected the Cu(II)/Cu(I) redox cycle nor reacted with H(2)O(2) suggest that genistein may directly scavenge the ROS that participate in the induction of DNA strand breaks. In contrast to the inhibitory effects of genistein, the presence of resveratrol at similar concentrations led to increased DNA strand breaks induced by H(2)O(2)/Cu(II). Further studies showed that in the presence of Cu(II), resveratrol, but not genistein was able to cause DNA strand breaks. Moreover, both Cu(II)/Cu(I) redox cycle and H(2)O(2) were shown to be critically involved in resveratrol/copper-mediated DNA strand breaks. The above results indicate that despite their similar in vivo anticarcinogenic effects, genistein and resveratrol appear to exert different effects on oxidative DNA damage in vitro.     

Sternal osteomyelitis and scrofuloderma due to BCG vaccination

BCG vaccine has been used for nearly 100 years in the prevention of tuberculosis. The case of a 13 month-old girl vaccinated as a newborn with BCG is described as presenting a sternal mass with associated periostic erosion. The mass was resected, and histopathological examination revealed a chronic inflammatory reaction with caseous granulomas, and extension to bone and skin. PCR amplifications using specific primers for Mycobacterium tuberculosis on paraffin-embedded tissue were negative. BCG vaccination at birth, the histological appearance and the absence of M. tuberculosis DNA in the resected tissue indicated that osteomyelitis and scrofuloderma were a consequence of BCG. Osteomyelitis is a rarely occurring adverse effect of BCG vaccination, more commonly seen in immunosuppressed patients. In the patient described above, no symptoms of immunodeficiency were seen, however.     

The effects of superior ovarian nerve sectioning on ovulation in the guinea pig

The effects on spontaneous ovulation associated with the unilateral or bilateral sectioning of the superior ovarian nerves (SON) were analyzed in guinea pigs at different time intervals of the estrous cycle. Day 1 of the estrous cycle was defined as the day when the animal presents complete loss of the vaginal membrane (open vagina). Subsequent phases of the cycle were determined by counting the days after Day 1. All animals were autopsied on the fifth day of the estrous cycle after surgery. Sectioning the right, left, or both SONs on day 5 (early luteal phase) resulted in a significant increase in the number of fresh corpora lutea. Ovulation increased significantly when the left SON (L-SON) was sectioned during late follicular phase (day 1) and medium luteal phase (day 8). When surgery was performed on days 1 or 8, neither sectioning the right SON (R-SON) nor sectioning the SON bilaterally had an apparent effect on ovulation rates. Similarly, ovulation rates were not affected when unilateral (right or left) or bilateral sectioning of the SON was performed during late luteal phase two (day 12). Unilateral or bilateral sectioning of the SON performed during the early luteal phase (day 5) was associated with a significant decrease in uterine weight. A comparable effect was observed when the L-SON was sectioned during late follicular phase (day 1), or medium luteal phase (day 8). No effects on uterine weight were observed when unilateral or bilateral sectioning of the SON was performed during late luteal phase. Our results suggest that in the guinea pig the SON modulates ovulation, and that the degree of modulation varies along the estrous cycle. The strongest influence of the SONs on ovulation occurs during early luteal phase, and decrease thereafter, being absent by late luteal phase. In addition, sectioning the left or the right SON caused different responses by the ovaries of adult guinea pigs. This paper discusses the mechanisms by which ovulation increased when the SON was surgically cut.     

Peptides of the liver stage antigen-1 (LSA-1) of Plasmodium falciparum bind to human hepatocytes

Synthetic peptides from the liver stage antigen-1 (LSA-1) antigen sequence were used in HepG2 cell and erythrocyte binding assays to identify regions that could be involved in parasite invasion. LSA-1 protein peptides 20630 ((21)INGKIIKNSEKDEIIKSNLRY(40)), 20637 ((157)KEKLQGQQSDSEQERRAY(173)), 20638 ((174)KEKLQEQQSDLEQERLAY(190)) and 20639 (191KEKLQEQQSDLEQERRAY(207)) had high binding activity in HepG2 assays. Were located in immunogenic regions; peptide cell binding was saturable. Peptide 20630 bound specifically to 48kDa HepG2 membrane surface protein. LSA-1 peptides 20630 ((21)INGKIIKNSEKDEIIKSNLRY(40)) and 20633 ((81)DKELTMSNVKNVSQTNFKSLY(100)) showed specific erythrocyte binding activity and inhibited merozoite invasion of erythrocytes in vitro. A monkey serum prepared against LSA-1 20630 peptide analog (CGINGKNIKNAEKPMIIKSNLRGC) inhibited merozoite invasion in vitro. The data suggest LSA-1 "High Activity Binding Peptides" could play a possible role in hepatic cell invasion as well as merozoite invasion of erythrocytes.     

Cytotoxic activity of flavonoids and extracts from Retama sphaerocarpa Boissier

Seven flavonoids isolated from chloroform, ethyl acetate and butanol extracts, obtained from the aerial parts of Retama sphaerocarpa, have been assessed for cytotoxic activity against three human cancer cell lines: TK-10 (renal adenocarcinoma), MCF-7 (breast adenocarcinoma) and UACC-62 (melanoma), using the SRB assay. All of them, extracts and flavonoids, were actives in, at least, one of the three cell lines at the recommended National Cancer Institute doses. They produce a dose-dependent inhibition of cell growth at concentrations in the 10(-6)-10(-4) M and 25-250 microg/ml range for the flavonoids and extracts respectively, being the flavonol rhamnazin the most cytotoxic.