Suppressor response in lepromatous leprosy patients: role of Leu 2a cells.

The contribution of non-specific suppressor mechanisms to the overall immunoregulatory defect observed in lepromatous leprosy was evaluated. Con A-induced suppression was assayed using the standard two-stage test in 27 lepromatous leprosy patients, 19 of them during the quiescent stage (LL) and eight during erythema nodosum lepromatosum (ENL). Lymphocytes from normal individuals react in this assay, yielding higher suppression as the numbers of Con A-induced suppressor cells (Leu 2a+ cells) increase. In contrast, two patterns of response were observed in both LL and ENL patients: those giving lower suppression as the number of suppressor cells increased (LL-A and ENL-A) and those responding with the normal pattern (LL-B and ENL-B). The abnormal dose-response profile was not related to the disease stage, as both ENL and LL patients were included in groups with normal or atypical response. Reaction of the potential suppressor cells with anti-Leu 2a antibody abolished suppression in LL-B and normals, whereas Con A-induced suppression was unchanged or higher in ENL-A, ENL-B and LL-A, indicating that in these patients Leu 2a+ cells interfered with the generation of Con A-induced suppression. The contribution of spontaneous suppression was examined and it was shown that suppressor activity in the absence of Con A stimulus was higher in ENL (both ENL-A and ENL-B) and LL-A. Thus, it appears that the occurrence of high spontaneous suppressor activity, probably related to in vivo activation, is associated with a relative inability to generate de novo suppression after Con A stimulation in these patients.     

Postnatal changes in membrane properties of mice trigeminal ganglion neurons

Intracellular recordings from neurons in the mouse trigeminal ganglion (TG) in vitro were used to characterize changes in membrane properties that take place from early postnatal stages (P0-P7) to adulthood (>P21). All neonatal TG neurons had uniformly slow conduction velocities, whereas adult neurons could be separated according to their conduction velocity into Adelta and C neurons. Based on the presence or absence of a marked inflection or hump in the repolarization phase of the action potential (AP), neonatal neurons were divided into S- (slow) and F-type (fast) neurons. Their passive and subthreshold properties (resting membrane potential, input resistance, membrane capacitance, and inward rectification) were nearly identical, but they showed marked differences in AP amplitude, AP overshoot, AP duration, rate of AP depolarization, rate of AP repolarization, and afterhyperpolarization (AHP) duration. Adult TG neurons also segregated into S- and F-type groups. Differences in their mean AP amplitude, AP overshoot, AP duration, rate of AP depolarization, rate of AP repolarization, and AHP duration were also prominent. In addition, axons of 90% of F-type neurons and 60% of S-type neurons became faster conducting in their central and peripheral branch, suggestive of axonal myelination. The proportion of S- and F-type neurons did not vary during postnatal development, suggesting that these phenotypes were established early in development. Membrane properties of both types of TG neurons evolved differently during postnatal development. The nature of many of these changes was linked to the process of myelination. Thus myelination was accompanied by a decrease in AP duration, input resistance (R(in)), and increase in membrane capacitance (C). These properties remained constant in unmyelinated neurons (both F- and S-type). In adult TG, all F-type neurons with inward rectification were also fast-conducting Adelta, suggesting that those F-type neurons showing inward rectification at birth will evolve to F-type Adelta neurons with age. The percentage of F-type neurons showing inward rectification also increased with age. Both F- and S-type neurons displayed changes in the sensitivity of the AP to reductions in extracellular Ca(2+) or substitution with Co(2+) during the process of maturation.     

Caspase-dependent and -independent DNA fragmentation in Sertoli and germ cells from men with primary testicular failure: relationship with histological diagnosis

BACKGROUND: Germ cell elimination and sperm DNA fragmentationin men with primary testiculopathies involve apoptosis-relatedprocesses whose mechanisms are poorly understood. This studyexamines the participation of typical (caspase-dependent) andatypical (caspase-independent) pathways in these processes.METHODS: Caspase activity and DNA fragmentation were evaluatedin Sertoli and germ cells from 63 men with non-obstructive azoospermiaand with different histological diagnoses who were undergoingtesticular biopsy for an assisted reproduction attempt. In eightof these men, phosphatidylserine externalization was also examined.RESULTS: The percentage of Sertoli cells showing caspase activityand DNA fragmentation was low and uniform in all diagnoses.In germ cells that remained tightly associated with Sertolicells despite vigorous mechanical treatment, the incidence ofboth caspase activity and DNA fragmentation was high, particularlyin men with maturation arrest. In Sertoli cell-free germ cells,high incidence of DNA fragmentation contrasted with low incidenceof caspase activity and phosphatidylserine externalization.CONCLUSIONS: In men with primary testicular failure, apoptosisof Sertoli cells is insignificant. Some germ cells undergo caspase-dependentapoptosis, show phosphatidylserine externalization and are tightlyassociated with Sertoli cells. Other germ cells show caspase-independentDNA fragmentation, do not externalize phosphatidylserine andlack a tight association with Sertoli cells.     

Evolution of foot-and-mouth disease virus

Foot-and-mouth disease virus evolution is strongly influenced by high mutation rates and a quasispecies dynamics. Mutant swarms are subjected to positive selection, negative selection and random drift of genomes. Adaptation is the result of selective amplification of subpopulations of genomes. The extent of adaptation to a given environment is quantified by a relative fitness value. Fitness values depend on the virus and its physical and biological environment. Generally, infections involving large population passages result in fitness gain and population bottlenecks lead to fitness loss. Very different types of mutations tend to accumulate in the foot-and-mouth disease virus (FMDV) genome depending on the virus population size during replication. Quasispecies dynamics predict higher probability of success of antiviral strategies based on multivalent vaccines and combination therapy, and this has been supported by clinical and veterinary practice. Quasispecies suggest also new antiviral strategies based on virus entry into error catastrophe, and such procedures are under investigation. Studies with FMDV have contributed to the understanding of quasispecies dynamics and some of its biological implications.     

Purification and properties of a glycoprotein acid phosphatase from the yeast form of Yarrowia lipolytica

An acid phosphatase from derepressed cells of the yeast form of Yarrowia lipolytica was purified 176-fold by ammonium sulfate precipitation, chromatography on DEAE-Sephacel and gel filtration in Biogel A 5-M. The enzyme is a glycoprotein with a sugar content of 60%. The MICHAELIS constant of the enzyme is 5.5 × 10^?4 M for p-nitrophenyl phosphate as substrate; the isoelectric point estimated by electrofocusing is around 4.6 and the optimum pH is 6.2. Phosphatase activity was destroyed by exposure of the enzyme to 40 °C for 30 min or at pH 3 for 30 min. The purified enzyme shows size heterogeneity within a linear concentration gradient of polyacrylamide (4–20%) which indicates an apparent molecular weight in the range of 90,000–200,000 in the presence of sodium dodecyl sulfate. The heterogeneity of the enzyme is due to its carbohydrate content, as can be demonstrated by gel filtration and by treatment with endoglycosidase H. The carbohydrate-depleted protein has a molecular weight of 60,000. Aminoacid analysis revealed a high content of aspartic acid, serine, threonine, glycine and alanine. Antibodies against the protein moiety show cross reactivity with the acid phosphatase of Saccharomyces cerevisiae.