Renin release responses to in vitro prostaglandin challenge in the summer-active ground squirrel, Spermophilus lateralis

1. Using a renal cortical slice preparation from the summer-active ground squirrel, Spermophilus lateralis, resting renin release (RR) and tissue cyclic AMP content (TcAMPC) levels were found to be significantly higher and lower, respectively, than those previously reported for its hibernating counterpart. 2. At a 10(-5) M dose, PGE2 but not PGE1, PGF2-alpha or PGA1, significantly stimulated RR in the summer-active ground squirrel (SAGS). 3. Addition of agents which normally increase TcAMPC significantly potentiated the effect of PGE1, while preventing that of PGE2, on RR and TcAMPC. 4. Opposite TcAMPC changes may mediate the in vitro RR responses to PGE1 and PGE2 administration in the SAGS.     

Characterization of DNA sequences that mediate nuclear protein binding to the regulatory region of the Pisum sativum (pea) chlorophyl a/b binding protein gene AB80: identification of a repeated heptamer motif

Two protein factors binding to the regulatory region of the pea chlorophyl a/b binding protein gene AB80 have been identified. One of these factors is found only in green tissue but not in etiolated or root tissue. The second factor (denominated ABF-2) binds to a DNA sequence element that contains a direct heptamer repeat TCTCAAA. It was found that presence of both of the repeats is essential for binding. ABF-2 is present in both green and etiolated tissue and in roots and factors analogous to ABF-2 are present in several plant species. Computer analysis showed that the TCTCAAA motif is present in the regulatory region of several plant genes.     

Nigericin forms highly stable complexes with lithium and cesium

Nigericin is a monocarboxylic polyether molecule described as a mobile K⁺ ionophore unable to transport Li⁺ and Cs⁺ across natural or artificial membranes. This paper shows that the ion carrier molecule forms complexes of equivalent energy demands with Li⁺, Cs⁺, Na⁺, Rb⁺, and K⁺. This is in accordance with the similar values of the complex stability constants obtained from nigericin with the five alkali metal cations assayed. On the other hand, nigericinalkali metal cation binding isotherms show faster rates for Li⁺ and Cs⁺ than for Na⁺, K⁺, and Rb⁺, in conditions where the carboxylic proton does not dissociate. Furthermore, proton NMR spectra of nigericin-Li⁺ and nigericin-Cs⁺ complexes show wide broadenings, suggesting strong cation interaction with the ionophore; in contrast, the complexes with Na⁺, K⁺, and Rb⁺ show only clear-cut chemical shifts. These latter results support the view that nigericin forms highly stable complexes with Li⁺ and Cs⁺ and contribute to the explanation for the inability of this ionophore to transport the former cations in conditions where it catalyzes a fast transport of K⁺>Rb⁺>Na⁺.Part of the results of this paper were presented at the 14th International Congress of Biochemistry in Prague, Czechoslovakia.     

Genetic diversity and population genetic structure of wild banana Musa ornata (Musaceae) in Mexico

The wild banana Musa ornata is an inhabitant of the tropical regions of Mexico characterized by patches of tropical rainforest. The overexploitation of its habitat has caused the extinction of several populations affecting diversity and population genetic structure of remaining ones. We used microsatellite markers to determine the genetic diversity and the population’s genetic structure of all extant populations. The thirty-two microsatellite loci previously characterized for M. acuminata and M. balbisiana were tested in M. ornata. Only twelve amplified. From these seven were polymorphic and were used for genetic analyses. The Nei’s diversity estimator shows low levels of genetic diversity (H _e = 0.263) with a mean of 4.40 alleles per locus. Excess homozygosity was evident in all populations indicating high levels of inbreeding. F _ST pairwise analyses and AMOVA indicated low genetic differentiation. However, 28 % of private alleles were registered, suggesting limited gene flow. Genetic distances, Jaccard’s coefficient and principal component analysis showed a good correspondence to geographical locations. The Mantel test performed was not significant. The results support the hypothesis of recent fragmentation events; therefore, not enough time has passed to detect differences between populations. However, it is also likely that results are caused by factors such as bottleneck, decline in pollinator populations, self-pollination and/or a tendency towards clonal reproduction. It is proposed that the preservation strategy focuses on maintaining all the remaining populations and ensuring their connectivity, so as to maintain gene flow and increase the genetic diversity of this species.     

Studies related to progesterone-induced hamster sperm acrosome reaction

Experiments were designed to characterize the effect of progesterone on the hamster sperm acrosome reaction (AR). Progesterone stimulated exocytosis of previously capacitated spermatozoa in a dose-dependent manner Progesterone-3-(O-carboxymethyl)oxime:BSA conjugate also induced AR when added to capacitated sperm suspensions. EGTA and La³⁺, added 10 min before progesterone, completely abolished the steroid-stimulatory effect. Benzamidine, a trypsin inhibitor, also inhibited AR when added to sperm cells 10 min before progesterone. This effect was avoided when spermatozoa were treated with the Ca2+ ionophore ionomycin. Conversely, the H+ ionophore PCCP, or the Na⁺/K⁺ ionophore nigericin, did not prevent the effect of the inhibitor. Results suggest that progesterone acts on the hamster sperm plasma membrane to stimulate exocytosis, which requires external Ca2+ and presumably Ca2+ influx. In addition, a sperm trypsin like protease may be part of the mechanism by which progesterone stimulates AR. Since the ionomycin-induced AR does not require this proteolytic activity, the possible involvement of such an enzyme in the progesterone-stimulated Ca2+ influx necessary for the occurrence of AR is discussed. © 1996 Wiley-Liss, Inc.     

Role of manganese accumulation in increased brain glutamine of the cirrhotic rat

Cirrhosis promotes increases of both manganese and glutamine in brain. Manganese is a modulator and glutamine is the product of glutamine synthetase. This work studies the relationship between manganese and glutamine synthetase in a model of cirrhosis in the rat. We administered manganese (1 g/L) in the drinking water of sham-operated and bile-duct obstructed rats. We evaluated the manganese and glutamine accumulation and the glutamine synthetase activity in frontal cortex, striatum, and pallidum after 2, 4, and 6 weeks of biliary obstruction or sham surgery. Cirrhotic rats receiving manganese increased their brain content of metal about 400%–600% after 4 weeks of treatment (P < .05) and also remarkably accumulated glutamine through time in the three regions studied (P < .05 at week 6). Interestingly, bile-duct obstructed rats treated with manganese showed no effect on glutamine synthetase activity. Results from this study suggest that manganese induces increases of brain glutamine independently of its synthesis.     

White spot syndrome virus (WSSV) in cultured Penaeus monodon in the Philippines

The prevalence and geographic distribution of white spot syndrome virus (WSSV) infection among cultured penaeid shrimp in the Philippines was determined from January to May, 1999, using PCR (polymerase chain reaction) protocol and Western blot assays. A total of 71 samples consisting of 18 post-larvae (PL) and 53 juvenile/adult shrimp samples (56 to 150 days-of-culture, DOC) were screened for WSSV. Of the 71 samples tested, 51 (72%) were found positive for WSSV by PCR: 61% (31/51) after 1-step PCR and 39% (20/51) after 2-step, non-nested PCR. Of the PL and juvenile/adult shrimp samples tested, 50 and 79% were positive for WSSV, respectively. By Western blot, only 6 of the 51 (12%) PCR-positive samples tested positive for WSSV. Of the 20 samples negative for WSSV by PCR, all tested negative for WSSV by Western blot assay. This is the first report of the occurrence of WSSV in the Philippines.     

ROS-Induced JNK and p38 Signaling Is Required for Unpaired Cytokine Activation during Drosophila Regeneration

Upon apoptotic stimuli, epithelial cells compensate the gaps left by dead cells by activating proliferation. This has led to the proposal that dying cells signal to surrounding living cells to maintain homeostasis. Although the nature of these signals is not clear, reactive oxygen species (ROS) could act as a signaling mechanism as they can trigger pro-inflammatory responses to protect epithelia from environmental insults. Whether ROS emerge from dead cells and what is the genetic response triggered by ROS is pivotal to understand regeneration of Drosophila imaginal discs. We genetically induced cell death in wing imaginal discs, monitored the production of ROS and analyzed the signals required for repair. We found that cell death generates a burst of ROS that propagate to the nearby surviving cells. Propagated ROS activate p38 and induce tolerable levels of JNK. The activation of JNK and p38 results in the expression of the cytokines Unpaired (Upd), which triggers the JAK/STAT signaling pathway required for regeneration. Our findings demonstrate that this ROS/JNK/p38/Upd stress responsive module restores tissue homeostasis. This module is not only activated after cell death induction but also after physical damage and reveals one of the earliest responses for imaginal disc regeneration.