Fluoride resistant acid phosphatase activity in pacinian corpuscles of the cat mesentery. Light microscope

Fluoride-resistant acid phosphatase (extralysosomal) activity has been investigated in Pacinian sensory corpuscles from cat's mesentery. The activity was found in the innermost and intermediate layers of the capsular system, but it is not possible to establish its exact localization. The central axon and the inner core were FRAP negative. The authors discuss the possible functional significance of FRAP activity in sensory corpuscles.     

Electrophoretic analysis of heterogeneous lipopolysaccharides from various strains ofVibrio vulnificus biotypes 1 and 2 by silver staining and immunoblotting

Lipopolysaccharides (LPS) of 11 strains of Vibrio vulnificus biotypes 1 and 2, isolated from an eel farm, and of 10 reference strains, were examined by SDS-polyacrylamide gel electrophoresis coupled with silver staining and immunoblotting. LPS samples were obtained from whole-cell lysates, outer membrane fragments, and extracellular products. By silver staining, only a diffuse band of low-molecular weight could be visualized in all cases except for a biotype 1 strain isolated from water. However, immunoblotting with antisera obtained against strains of biotypes 1 and 2 from eels allowed visualization of multiple O-polysaccharide chains. All biotype 2 strains, independently of their origins, belonged to the same serotype and presented the same LPS profile, whereas eel isolates of biotype 1 were serologically identical and different from the rest of tested strains of biotype 1. This is the first report of LPSs with a ladder-like structure in Vibrio vulnificus.     

Coca chewing for exercise: hormonal and metabolic responses of nonhabitual chewers

Favier, Roland, Esperanza Caceres, Laurent Guillon, BrigitteSempore, Michel Sauvain, Harry Koubi, and Hilde Spielvogel. Cocachewing for exercise: hormonal and metabolic responses of nonhabitualchewers. J. Appl. Physiol. 81(5):1901-1907, 1996.To determine the effects of acute coca use onthe hormonal and metabolic responses to exercise, 12 healthynonhabitual coca users were submitted twice to steady-state exercise(~75% maximal O₂ uptake). Onone occasion, they were asked to chew 15 g of coca leaves 1 h beforeexercise, whereas on the other occasion, exercise was performed after 1 h of chewing a sugar-free chewing gum. Plasma epinephrine,norepinephrine, insulin, glucagon, and metabolites (glucose, lactate,glycerol, and free fatty acids) were determined at rest before andafter coca chewing and during the 5th, 15th, 30th, and 60th min ofexercise. Simultaneously to these determinations, cardiorespiratoryvariables (heart rate, mean arterial blood pressure, oxygen uptake, andrespiratory gas exchange ratio) were also measured. At rest, cocachewing had no effect on plasma hormonal and metabolic levels exceptfor a significantly reduced insulin concentration. During exercise, theoxygen uptake, heart rate, and respiratory gas exchange ratio weresignificantly increased in the coca-chewing trial compared with thecontrol (gum-chewing) test. The exercise-induced drop in plasma glucoseand insulin was prevented by prior coca chewing. These results contrastwith previous data obtained in chronic coca users who display duringprolonged submaximal exercise an exaggerated plasma sympatheticresponse, an enhanced availability and utilization of fat (R. Favier,E. Caceres, H. Koubi, B. Sempore, M. Sauvain, and H. Spielvogel.J. Appl. Physiol. 80: 650-655, 1996). We conclude that, whereas coca chewing might affect glucose homeostasis during exercise, none of the physiological data provided bythis study would suggest that acute coca chewing in nonhabitual userscould enhance tolerance to exercise.

     

Inherited congenital normofunctional testicular hyperplasia and mental deficiency

Summary Three 46,XY unrelated individuals out of 84 postpubertal male inpatients with severe mental deficiency in a psychiatric hospital were found to have megalorchidia and macrogenitosomia. One of the cases had a similarly affected brother. Endocrine studies were performed in two of the cases with similar results. Normal plasma levels of pituitary gonadotropins were found. A normal testicular function was demonstrated by the finding of normal: (a) baseline plasma testosterone levels and a significant rise following human chorionic gonadotropin administration, (b) sperm analysis, and (c) morphology and cell architecture of the testes. These results were compatible with normofunctional testicular hyperplasia confirming previous observations and allowing the definite individualization of a syndrome with mental deficiency probably due to an X-linked recessive mutation.Presented at the III Congreso Latinoamericano de Genética, Montevideo, February 6–12, 1977. Abstract published in: Resum. III Congr. Latinoamer. Genet., p. 14. Montevideo 1977     

Genes Essential for Nod Factor Production and Nodulation Are Located on a Symbiotic Amplicon (AMPRtrCFN299pc60) in Rhizobium tropici

Amplifiable DNA regions (amplicons) have been identified in the genome of Rhizobium etli. Here we report the isolation and molecular characterization of a symbiotic amplicon of Rhizobium tropici. To search for symbiotic amplicons, a cartridge containing a kanamycin resistance marker that responds to gene dosage and conditional origins of replication and transfer was inserted in the nodulation region of the symbiotic plasmid (pSym) of R. tropici CFN299. Derivatives harboring amplifications were selected by increasing the concentration of kanamycin in the cell culture. The amplified DNA region was mobilized into Escherichia coli and then into Agrobacterium tumefaciens. The 60-kb symbiotic amplicon, which we termed AMPRtrCFN299pc60, contains several nodulation and nitrogen fixation genes and is flanked by a novel insertion sequence ISRtr1. Amplification of AMPRtrCFN299pc60 through homologous recombination between ISRtr1 repeats increased the amount of Nod factors. Strikingly, the conjugal transfer of the amplicon into a plasmidless A. tumefaciens strain confers on the transconjugant the ability to produce R. tropici Nod factors and to nodulate Phaseolus vulgaris, indicating that R. tropici genes essential for the nodulation process are confined to an ampliable DNA region of the pSym.     

Electroconvulsive shock does not modify striatal contents of dopamine in MPTP-treated mice

It has been suggested that the therapeutic response to electroconvulsive therapy in depressed patients could be mediated by functional changes in the dopaminergic pathways; a favorable response to electroconvulsive therapy was also observed recently in patients with Parkinson's disease. To study a possible interference of electroconvulsive shock in the course of MPTP-induced parkinsonism in rodents, we measured the striatal content of dopamine in MPTP-treated mice that received electroconvulsive shock at various intervals in the course of MPTP neurotoxicity. Our results showed no immediate or delayed differences in striatal dopamine content of animals that received MPTP and electroconvulsive shock when compared with animals that received only MPTP, thus suggesting that the strong biological effects of MPTP and electroconvulsive shock on the brain may follow different biochemical mechanisms.     

Nodulating ability of Rhizobium tropici is conditioned by a plasmid-encoded citrate synthase

Rhizobium species elicit the formation of nitrogen-fixing root nodules through a complex interaction between bacteria and plants. Various bacterial genes involved in the nodulation and nitrogen-fixation processes have been described and most have been localized on the symbiotic plasmids (pSym). We have found a gene encoding citrate synthase on the pSym plasmid of Rhizobium tropici, a species that forms nitrogen-fixing nodules on the roots of beans (PhasBoius vuigaris) and trees (Leucaena spp.). Citrate synthase is a key metabolic enzyme that incorporates carbon into the tricarboxylic acid cycle by catalysing the condensation of acetyl-CoA and oxalo-acetic acid to form citrate. R. tropici pcsA (the plasmid citrate synthase gene) is closely related to the corresponding genes of Proteobacteria. pcsA inactivation by a Tn5-mob insertion causes the bacteria to form fewer nodules (30–50% of the original strain) and to have a decreased citrate synthase activity in minimal medium with sucrose. A clone carrying the pcsA gene complemented ail the phenotypic alterations of the pcsA mutant, and conferred Rhizobium iegumino-sarum bv. phaseoli (which naturally lacks a plasmid citrate synthase gene) a higher nodulation and growth capacity in correlation with a higher citrate synthase activity. We have also found that pcsA gene expression is sensitive to iron availability, suggesting a possible role of pcsA in iron uptake.     

Functional reconstitution of the glycine receptor

The functional reconstitution of the chloride channel coupled glycine receptor is described. Glycine receptors were purified from the cholate extract of rat spinal cord membranes by affinity chromatography and incorporated into phospholipid vesicles by the addition of phosphatidylcholine and removal of detergent by gel filtration. The reconstituted vesicles showed the same polypeptide composition as the purified receptor (proteins of Mr 48,000 and 58,000). The pharmacological characteristics of the glycine receptor were also preserved in the proteoliposomes, as demonstrated by the displacement of [3H]strychnine binding by several glycinergic ligands and by photoaffinity labeling experiments. In order to observe functional responses (i.e., specific agonist-induced anion translocation), we have developed an assay based on the fluorescence quenching of an anion-sensitive entrapped probe, SPQ [6-methoxy-N-(3-sulfopropyl)quinolinium]. Reconstituted vesicles were loaded with the fluorescent probe during a freeze-thaw-sonication cycle in the presence of added liposomes containing cholesterol. In such a reconstituted system, glycine receptor agonists are able to increase the rate of anion influx into the vesicles. The action of agonists is blocked by the simultaneous presence of strychnine or other glycine antagonists. Our results show that the purified 48,000- and 58,000-dalton polypeptides reconstituted into phospholipid vesicles can bind ligands and promote specific ion translocation in a way similar to the glycine receptor in its native environment.     

Increased Bean (Phaseolus vulgaris L.) Nodulation Competitiveness of Genetically Modified Rhizobium Strains

Rhizobium leguminosarum bv. phaseoli strain collections harbor heterogeneous groups of bacteria in which two main types of strains may be distinguished, differing both in the symbiotic plasmid and in the chromosome. We have analyzed under laboratory conditions the competitive abilities of the different types of Rhizobium strains capable of nodulating Phaseolus vulgaris L. bean. R. leguminosarum bv. phaseoli type I strains (characterized by nif gene reiterations and a narrow host range) are more competitive than type II strains (that have a broad host range), and both types are more competitive than the promiscuous rhizobia isolated from other tropical legumes able to nodulate beans. Type I strains become even more competitive by the transfer of a non-Sym, 225-kilobase plasmid from type II strain CFN299. This plasmid has been previously shown to enhance the nodulation and nitrogen fixation capabilities of Agrobacterium tumefaciens transconjugants carrying the Sym plasmid of strain CFN299. Other type I R. leguminosarum bv. phaseoli transconjugants carrying two symbiotic plasmids (type I and type II) have been constructed. These strains have a diminished competitive ability. The increase of competitiveness obtained in some transconjugants seems to be a transient property.     

Growth, reproduction and recruitment patterns of the wide-eyed flounder, Bothus podas Delaroche (Pisces: Bothidae), from the Azores

The wide-eyed flounder, Bothus podas, occurs in many East Atlantic sub-tropical and temperate inshore areas and is the dominant flatfish in shallow-water areas around the Azores. The aim of this study was to examine the growth, reproductive biology and recruitment patterns of the wide-eyed flounder in the Azores. Adult fish samples were obtained by spear fishing and SCUBA hand netting at Faial Island. Juveniles were obtained from a complementary monthly beach-seining programme undertaken at Porto Pim Bay, Faial. Sex and development stage were determined by macroscopic examination of gonads, whereas age estimates were obtained by counting the number of opaque bands in the otoliths. In the Azores, B. podas reaches 6 years old, which is more than reported for the central Mediterranean, the only other population of this species that has been studied. The studied population has a sex ratio biased to males, which contrasts to a previous observational study, which noted a female-biased sex ratio. Spawning time, as determined from the gonadosomatic ratio and the macroscopic examination of gonads, was between July and September. This time period agrees with behavioural observations in the same area. Sexual maturity was estimated at a total length (TL₅₀) of 14.1 cm and at an age (A₅₀) of 1.7 years. Small juveniles occur on sandy inshore nursery areas for most of the year, but mainly between July and August each year. The presence of small fish throughout most of the year could suggest a protracted settlement period or slow growth on occasions on the shallow-water nursery grounds.