Insertional inactivation of the lpxA gene involved in the biosynthesis of lipid A in Neisseria meningitidis resulted in lpxA/lpxA::aph-3' heterodiploids

The lpxA gene is known to be involved in the biosynthesis of lipid A in Gram-negative bacteria and thought to be an essential gene. However, viable meningococcal lpxA mutants devoid of detectable endotoxin (lipooligosaccharide) have been reported. We characterised such mutants in strains of Neisseria meningitidis belonging to serogroups B and C using molecular and biochemical analysis. While lpxA mutants with no detectable or a low level of lipooligosaccharide could be obtained in N. meningitidis, the simple insertional inactivation of lpxA was not possible. In all mutants, we obtained lpxA/lpxA::aph-3' heterodiploids harbouring one copy of the wild-type lpxA gene and one copy of the inactivated lpxA gene by insertion of the kanamycin resistance cassette, aph-3'. The absence of lipooligosaccharide in these mutants may result from a negative transdominance effect of a truncated LpxA protein on the wild-type LpxA protein.     

Medroxyprogesterone priming and response to the ram effect in Corriedale ewes during the nonbreeding season

The "ram effect" (RE) is an inexpensive technique that allows farmers to obtain out-of-season lambs. Five hundred and ninety-six Corriedale ewes were used in three experiments to determine the effectiveness of different medroxyprogesterone (MAP) treatments associated with the ram effect during the nonbreeding season. The aim of the first experiment was to evaluate the effectiveness of short-term (6-day) MAP priming. We obtained similar results in estrus incidence and fertility after using MAP sponges for 6, 9, and 13 days. In the second experiment, we compared the effect of sponges containing 20, 40, or 60 mg of MAP used in 6-day priming. Estrous behavior and fertility were not affected by dosage. In the third experiment, 2.5mg of MAP was administered in single treatments 0, 1, 3, or 5 days before the introduction of the rams. Medroxyprogesterone administration 1, 3, or 5 days before the introduction of the rams concentrated estrus in ewes 17 to 20 days later.     

Mechanical properties and chemical composition of avian long bones

We have studied the mechanical behaviour of avian long bones as whole structures, by calculating mechanical parameters such as maximum load, stiffness, bending strength and flexural Young's modulus; bones were always tested in three-point bending. Furthermore composition in several chemical elements and amino acids related to collagen content was also analysed. Correlations were established between body mass, mechanical parameters and chemical contents. Both bending strength and Young's modulus were negatively correlated to body mass. Significant correlations were found between nitrogen content and both strength and Young's modulus, with negative slopes in both cases. Magnesium and phosphorus appear to be the most important inorganic elements to the understanding of the mechanical behaviour of avian long bones.     

Dietary alterations in protein,carbohydrates and fat increase liver protein-turnover rate and decrease overall growth rate in the rainbow trout (Oncorhynchus mykiss

We have determined the protein-turnover rates and nucleic-acid concentrations in the liver of trout (Oncorhynchus mykiss) fed on two different isocaloric diets: low-protein/high-fat and non-carbohydrate/high-fat. Compared to controls, the partial replacement of protein with fat significantly decreased the protein accumulation rate and protein-retention efficiency in the liver whilst increasing the fractional protein-synthesis and protein-degradation rates as well as protein-synthesis efficiency. The complete replacement of carbohydrates with fat significantly lowered the protein-accumulation rate and protein-retention efficiency, but enhanced both the protein-synthesis and protein-degradation rates as well as protein-synthesis capacity. The protein:DNA and RNA:DNA ratios decreased considerably on both diets. Total DNA decreased in fish on a low-protein/high-fat diet but did not change in those on a non-carbohydrate/high-fat diet. The absolute protein-synthesis rate registered no significant change under any of the nutritional conditions. Both the experimental diets did however raise the fractional protein-synthesis rate significantly, due to enhanced protein-synthesis efficiency when protein was partially replaced with fat and to enhanced protein-synthesis capacity when carbohydrates were completely replaced with fat. Our results show the capacity of the liver to adapt its turnover rates and conform to different nutritional conditions. They also point to the possibility of controlling fish growth by dietary means.     

Analysis of airborne pollen in the town of Almería (South-East Spain), 1995–1996

The first results are presented of an aerobiological analysis of the atmosphere of the town of Almería, carried out between November 1995 and October 1996. A Lanzoni volumetric spore trap was used for sample collection. The composition and seasonal evolution of the pollen spectrum were determined over a 1-year period in relation to the vegetation and climatic conditions of the study area. Twenty-six pollen types were identified as accounting for >0.05% of the total pollen collected. The main sources of airborne pollen were Palmae (17.76%),Olea (16.10%), Chenopodiaceae/Amaranthaceae (13.99%), Urticaceae (10.18%) and Poaceae (8.64%). The annual pollen variation presented a period of maximum emission from March to June, with a subsequent, less intensive period from August to November. The minimum pollen values were obtained from December to February. The highest concentrations occurred in May, which was also the month which presented the highest pollen diversity, whereas the lowest values were observed in January.     

An α-Tubulin Mutant Destabilizes the Heterodimer: Phenotypic Consequences and Interactions with Tubulin-binding Proteins

Many effectors of microtubule assembly in vitro enhance the polymerization of subunits. However, several Saccharomyces cerevisiae genes that affect cellular microtubule-dependent processes appear to act at other steps in assembly and to affect polymerization only indirectly. Here we use a mutant α-tubulin to probe cellular regulation of microtubule assembly. tub1-724 mutant cells arrest at low temperature with no assembled microtubules. The results of several assays reported here demonstrate that the heterodimer formed between Tub1-724p and β-tubulin is less stable than wild-type heterodimer. The unstable heterodimer explains several conditional phenotypes conferred by the mutation. These include the lethality of tub1-724 haploid cells when the β-tubulin–binding protein Rbl2p is either overexpressed or absent. It also explains why the TUB1/tub1-724 heterozygotes are cold sensitive for growth and why overexpression of Rbl2p rescues that conditional lethality. Both haploid and heterozygous tub1-724 cells are inviable when another microtubule effector, PAC2, is overexpressed. These effects are explained by the ability of Pac2p to bind α-tubulin, a complex we demonstrate directly. The results suggest that tubulin-binding proteins can participate in equilibria between the heterodimer and its components.     

Formation and Function of the Rbl2p–β-Tubulin Complex

The yeast protein Rbl2p suppresses the deleterious effects of excess β-tubulin as efficiently as does α-tubulin. Both in vivo and in vitro, Rbl2p forms a complex with β-tubulin that does not contain α-tubulin, thus defining a second pool of β-tubulin in the cell. Formation of the complex depends upon the conformation of β-tubulin. Newly synthesized β-tubulin can bind to Rbl2p before it binds to α-tubulin. Rbl2p can also bind β-tubulin from the α/β-tubulin heterodimer, apparently by competing with α-tubulin. The Rbl2p–β-tubulin complex has a half-life of ~2.5 h and is less stable than the α/β-tubulin heterodimer. The results of our experiments explain both how excess Rbl2p can rescue cells overexpressing β-tubulin and how it can be deleterious in a wild-type background. They also suggest that the Rbl2p–β-tubulin complex is part of a cellular mechanism for regulating the levels and dimerization of tubulin chains.     

Design,synthesis, and docking of highly hypolipidemic agents: Schizosaccharomyces pombe as a new model for evaluating α-asarone-based HMG-CoA reductase inhibitors

A series of α-asarone-based analogues was designed by conducting docking experiments with published crystal structures of human HMG-CoA reductase. Indeed, synthesis and evaluation of this series showed a highly hypocholesterolemic in vivo activity in a murine model, as predicted by previous docking studies. In agreement with this model, the polar groups attached to the benzene ring could play a key role in the enzyme binding and probably also in its biological activity, mimicking the HMG-moiety of the natural substrate. The hypolipidemic action mechanism of these compounds was investigated by developing a simple, efficient, and novel model for determining HMG-CoA reductase inhibition. The partial purification of the enzyme from Schizosaccharomyces pombe allowed for testing of α-asarone- and fibrate-based analogues, resulting in positive and significant inhibitory activity.