Morphogenesis of cartilage canals: experimental approach in the rat tibia.

This paper studies the participation of vessels in the canal morphogenesis. The proximal chondroepiphysis of the left tibia of 44 five-day-old rats was exposed and the vessels of the intercondylar fossae, near the attachment of cruciate ligaments, were cauterized. In addition to the vascular lesion this assay induced a perichondral lesion. However, the canal appeared and joined to the secondary ossification center. 36 tibiae of 4-day-old rats were removed under sterile conditions and cultured in a serum-free chemically defined medium. The cultures were carried out for as long as 15 days. A canal lumen structure was found on the first days of culture, and grew in depth to the central region of the chondroepiphysis during the culture. The secondary ossification center was not found. The vessels and mesenchymal cells observed in the control canal were not found in the culture. We suggest that the presence of vessels, perivascular cells or perichondrium does not appear to be necessary in canal morphogenesis.     

Efflux and exchange of glycine by plasma membrane vesicles isolated from glioblastoma cells

The efflux and exchange of glycine were studied in plasma membrane vesicles isolated from cultured glioblastoma cells. The mechanism of glycine translocation has been probed by comparing the ion dependence of net efflux to that of exchange. Dilution-induced efflux requires the simultaneous presence of internal sodium and chloride, while influx is dependent on the presence of these two ions on the outside (Zafra, F. and Giménez, C. (1986) Brain Res. 397, 108-116). Glycine efflux from the membrane vesicles is stimulated by external glycine, this exchange being dependent on external sodium, but not on external chloride. The parallelism observed in influx and efflux processes suggests that glycine is translocated in both directions across the membrane, probably by interacting with the carrier. To account for all the observed effects of external ions, glycine concentrations and membrane potential on glycine influx and efflux, a kinetic model of the Na+/Cl-/glycine cotransport system is discussed.     

Relationship between the cartilage canal and the perichondrium in the rat proximal tibial epiphysis

One of the most widespread hypotheses for chondral canal morphogenesis suggests that the canal is an extension of the perichondrium. To study the possible relation between perichondrium and chondral canal morphology, the proximal epiphyses in the tibias of 42 rats were studied from birth to their 29th day. The study was divided into three periods: from birth to the 4th day before canal appearance; from the 5th day, the moment of canal appearance, until the appearance of the secondary ossification center of the epiphysis on the 9th day; the 3rd ran from this point on the 10th day until its full development. We have also divided the canal into three regions: entrance, neck and bottom. The central portion (lumen) and canal wall were analyzed in each region. Our results show the perichondrium to be a complex structure, composed of a series of cellular layers in a biphasic extracellular matrix (eosinophil and basophil). The canal walls are lined by a layer of elongated cells. In the lumen there are many different cell types: fibroblasts, histiocytes, multinuclear giant cells and multivacuolated cells. Our study of the canal, its walls and lumen show no morphological structure that is reminiscent of the perichondrium. These results suggest that the canal is not itself a continuation of the perichondrium.     

Striatal input from the ventrobasal complex of the rat thalamus

We have analyzed whether caudal regions of the caudate putamen receive direct projections from thalamic sensory relay nuclei such as the ventrobasal complex. To this aim, the delivery of the retrograde neuroanatomical tracer Fluoro-Gold into the caudal caudate putamen resulted in the appearance of retrogradely labeled neurons in the ventral posteromedial and ventral posterolateral thalamic nuclei. These projections were further confirmed with injections of the anterograde tracers biotinylated dextran amine or Phaseolus vulgaris leucoagglutinin into these thalamic nuclei, by showing the existence of axonal terminal fields located in the caudal striatum. These results support the existence of direct projections linking the thalamic ventrobasal complex and the caudal striatum in the rat, probably via collateralization of thalamocortical axons when passing through the caudate putamen, and therefore supporting the putative involvement of the caudal striatum in sensory-related functions.     

Beneficial effects of solar UV‐B radiation on soybean yield mediated by reduced insect herbivory under field conditions

Ultraviolet‐B radiation (UV‐B: 280–315 nm) has damaging effects on cellular components and macromolecules. In plants, natural levels of UV‐B can reduce leaf area expansion and growth, which can lead to reduced productivity and yield. UV‐B can also have important effects on herbivorous insects. Owing to the successful implementation of the Montreal Protocol, current models predict that clear‐sky levels of UV‐B radiation will decline during this century in response to ozone recovery. However, because of climate change and changes in land use practices, future trends in UV doses are difficult to predict. In the experiments reported here, we used an exclusion approach to study the effects of solar UV‐B radiation on soybean crops, which are extensively grown in many areas of the world that may be affected by future variations in UV‐B radiation. In a first experiment, performed under normal management practices (which included chemical pest control), we found that natural levels of UV‐B radiation reduced soybean yield. In a second experiment, where no pesticides were applied, we found that solar UV‐B significantly reduced insect herbivory and, surprisingly, caused a concomitant increase in crop yield. Our data support the idea that UV‐B effects on agroecosystems are the result of complex interactions involving multiple trophic levels. A better understanding of the mechanisms that mediate the anti‐herbivore effect of UV‐B radiation may be used to design crop varieties with improved adaptation to the cropping systems that are likely to prevail in the coming decades in response to agricultural intensification.     

Assessment of phenotypic and genetic diversity in the yeast genusMetschnikowia

The taxonomy of the yeast genusMetschnikowia has undergone profound changes over the past century. Major developments, from the capacity to obtain pure cultures of parasitic species to progress associated with the extensive use of molecular biology tools in yeast systematics, are briefly reviewed. Results from past work and new data are combined to evaluate evolutionary relationships and clarify the classification of both terrestrial and aquatic species. Recent physiological studies, including the utilization of non-conventional carbon and nitrogen sources, and characteristics like lipolytic activity and maximum temperatures for growth, are presented. The assessment of the genetic diversity within the genus by restriction analysis of the mitochondrial DNA and by the production of specific DNA probes has been explored. The results indicate the potential application of the latter in rapid identification procedures.     

Development of a novel fluorescent microbead-based immunoassay and comparison with three enzyme-linked immunoassays for detection of anti-Erysipelothrix spp. IgG antibodies in pigs with known and unknown exposure

A novel fluorescent microbead immunoassay (FMIA) using the recombinant polypeptide SpaA415 was developed for detection of anti-Erysipelothrix spp. IgG in pig sera. The diagnostic performance of the FMIA was evaluated on samples from pigs with known and unknown Erysipelothrix spp. exposure and compared to an in-house enzyme-linked immunosorbent assay (ELISA-1) based on the same capture antigen, and two commercially available ELISAs (ELISA-2 and ELISA-3). Sera from pigs experimentally infected with Erysipelothrix rhusiopathiae serotype 1a (n=60) or 19 (n=12), sera from pigs vaccinated with a commercial attenuated-live vaccine based on serotype 1a (n=12) or a commercial bacterin based on serotype 2 (n=12), and 90 field samples were utilized. The sensitivity on 22 true positive samples collected in the later stages of infection/post-vaccination was 100% for the FMIA and ELISA-1, 63.6% for ELISA-2 and 81.8% for ELISA-3. The earliest antibody response was detected 7days post inoculation with the FMIA (77.8%) and ELISA-1 (11.1%), and at 14days post-vaccination (dpv) with FMIA (50%) and ELISA-1 (50%). On field samples, a higher seroprevalence was found in pigs older than 21days with all four assays. Kappa analysis indicated that the FMIA and ELISA-1 had almost complete agreement whereas the agreement was slight with ELISA-2 and fair with ELISA-3. The sensitivity of both immunoassays based on the rSpaA415 antigen was higher compared to that of the two commercial ELISAs. The rSpaA415 FMIA has great potential as an inexpensive ELISA alternative for detection of antibodies against E. rhusiopathiae in the future.