The cyclophilin multigene family of peptidyl-prolyl isomerases. Characterization of three separate human isoforms.

Cyclophilin (CyP), a major cytosolic protein possessing peptidyl-prolyl cis-trans isomerase activity, has been implicated as the specific receptor of the immunosuppressive drug cyclosporin A (CsA). To identify other potential CsA receptors related to CyP, two human cDNA libraries were screened under low stringency conditions using human CyP cDNA (encoding hCyP1) as a probe. Two cDNAs were identified which encode distinct proteins related to human hCyP1. These two novel proteins, designated hCyP2 and hCyP3, share 65 and 76% amino acid sequence homology with hCyP1, respectively. Both hCyP2 and hCyP3 contain NH2-terminal hydrophobic extensions of 32 and 42 amino acids, respectively. Protein-specific antibodies revealed the predominant association of hCyP2 and hCyP3 with membranes and subcellular organelles, which suggests that the amino-terminal leader sequences of the two CyP isoforms may act as signal peptides. In contrast to the results with hCyP1, Southern blot analysis indicated that both hCyP2 and hCyP3 gene sequences are represented infrequently in the human genome. Northern and Western blot analysis showed that the distribution of mRNA and proteins of the three hCyPs in differing tissues and cell types was similar. Each hCyP protein was expressed in Escherichia coli, purified, and shown to be an active peptidyl-prolyl isomerase. Substrate specificity was examined with 11 synthetic peptides (Suc-Xaa-Yaa-Pro-Phe-4-nitroanilide), and inhibition of the peptidyl-prolyl isomerase activities associated with hCyP1, hCyP2, and hCyP3 was studied with CsA, MeAla6-CsA and MeBm2t1-CsA. From both equilibrium considerations and the results of kinetic characterizations it is proposed that of these three CyP proteins, hCyP1 is the most likely intracellular target for CsA.     

Effects of sequential acute stress exposure on stress-induced pituitary luteinizing hormone and prolactin secretion

The present study was carried out to determine the effects of repetitive acute stress exposure on pituitary secretion of both luteinizing hormone (LH) and prolactin (PRL). Adult male rats were exposed to sequential episodes of acute novel environment stress separated by intervals of either 60 or 120 minutes. Serial blood samples were obtained from animals before, during and after each stress episode via indwelling intra-cardiac cannulas. The imposition of 10 minute episodes of novel environment stress on an hourly basis eventually rendered the hypothalamic-hypophyseal LH axis refractory to the stimulatory effect of stress. If sequential stress was imposed at 120 minute intervals, LH release was significantly enhanced during each exposure. A different pattern of PRL release was observed during the same sequential stress schedule. After an initial increase in hormone release in response to the first hourly stress episode, PRL levels were unaltered during the second and third hourly stress exposures. Thereafter, plasma PRL levels showed a trend toward a progressive increase in release during each successive episode, and were significantly elevated above preceding baseline levels during the fourth and fifth hourly stress exposures. In rats exposed to stress every two hours, a significant increase in PRL levels occurred following the first, but not the second stress episode. Hormone release was again enhanced in response to the third exposure to novel environment. The present results demonstrate that the repetitive exposure to acute novel environment stress results in differential alterations in pituitary LH and PRL secretion over time, and that the timing of repeated episodes is an important determinant of continued responsiveness to stress, particularly with regard to LH release. These findings suggest that the LH and PRL hormonal responses to at least this specific stressor are mediated by independent neural mechanisms.     

Variation in human limb joint articular morphology

Objectives

Synovial joints in human limbs strike a balance between mobility, stability, and articular fit, yet little is known about how these conflicting demands pattern intraspecific variation in articular shape. In this study, we use geometric morphometrics to establish the apportionment and magnitude of morphological variance of the articular surfaces of the human shoulder, elbow, hip, and knee. We hypothesize that variances will be comparable between articulating surfaces within a joint and will be larger in joints with smaller ranges of motion, given their plurality of functional demands.

Materials and Methods

Three-dimensional landmarks were taken on the articular surfaces of the glenohumeral, humeroulnar, acetabulofemoral, and tibiofemoral joints from CT scans of 200 skeletons from the University of Tennessee Donated Skeletal Collection (84 females, 116 males). Root mean-squared distances between articulations calculated from Procrustes shape coordinates were used to determine variance distributions.

Results

We found no difference in variances for each articular surface between the sexes or between left and right articular surfaces. A high range of motion is associated with greater morphological variance; however, this pattern is largely driven by the concave articular surfaces of each joint, which consistently exhibit statistically greater variance than their convex counterparts.

Discussion

The striking pattern of differential variance between articulating morphologies points to potential disparities in development between them. Consistently higher variance in concave surfaces may relate to chondral modeling theory for the formation of joints. Establishing intraspecific morphological variance patterns is a first step in understanding coordinated evolution among articular features.     

Consequences of defaunation for a tropical tree community

Hunting affects a considerably greater area of the tropical forest biome than deforestation and logging combined. Often even large remote protected areas are depleted of a substantial proportion of their vertebrate fauna. However, understanding of the long‐term ecological consequences of defaunation in tropical forests remains poor. Using tree census data from a large‐scale plot monitored over a 15‐year period since the approximate onset of intense hunting, we provide a comprehensive assessment of the immediate consequences of defaunation for a tropical tree community. Our data strongly suggest that over‐hunting has engendered pervasive changes in tree population spatial structure and dynamics, leading to a consistent decline in local tree diversity over time. However, we do not find any support for suggestions that over‐hunting reduces above‐ground biomass or biomass accumulation rate in this forest. To maintain critical ecosystem processes in tropical forests increased efforts are required to protect and restore wildlife populations.     

A bayesian approach to the design of phase II clinical trials

A new strategy for the design of Phase II clinical trials is presented which utilizes the information provided by the prior distribution of the response rate, the costs of treating a patient, and the losses or gains resulting from the decisions taken at the completion of the study. A risk function is derived from which one may determine the optimal Bayes sampling plan. The decision theoretic/Bayesian approach is shown to provide a formal justification for the sample sizes often used in practice and shows the conditions under which such sample sizes are clearly inappropriate.     

Grazing impact of copepod assemblages and gravitational flux in coastal and oceanic waters off central Chile during two contrasting seasons

In evaluating carbon flux in coastal and oceanic waters offcentral Chile (~36°S), the grazing pressure by copepod size-assemblagesand the gravitational flux from the surface layer were estimatedduring two contrasting seasons: spring upwelling (October 1998)and winter (July 1999) periods. Grazing pressure upon phytoplanktonbiomass was small (<5%) during both periods at all stations.It was, however, an important proportion of primary productionat the coast during the spring (17–43%) but minimal inwinter (<5%) while, at the oceanic station, it was significantduring both seasons (13–46%). Similarly, the downwardflux of particulate organic carbon was a significant percentageof primary production at the coast during the spring (31%) andless so in winter (15%); at the oceanic station, it was a higherfraction during both seasons (46–47%). Copepod pelletswere only a minor component of the faecal flux, suggesting thatthey were rapidly recycled in the water column. The seasonaldifferences in these carbon fluxes in the coastal upwellingzone were related directly to the larger quantities of organicmatter in the water column during the spring upwelling period,including higher chlorophyll a concentrations and primary productionrates. During the winter, the particulate organic carbon appearsto be mainly recycled in the water column. In the oceanic zone,in contrast to what is expected, a large percentage of the primaryproduction appears to be exported during both periods, thoughconsumption by copepod assemblages was also important, suggestingsignificant horizontal carbon export from the coast to the openocean.