Identification of type IV collagenase in rat testicular cell culture: influence of peritubular-Sertoli cell interactions

In the testis, interactions between peritubular cells (mesenchyme) and Sertoli cells (epithelium), together with proteolytic remodeling of the extracellular matrix, may play a central role in testicular development, morphogenesis, and spermatogenesis. In this study we demonstrate that a metalloproteinase of 72 kDa present in rat Sertoli cell and Sertoli-peritubular cell coculture medium is activated by p-aminophenylmercuric acetate (p-APMA) to a lower molecular mass form, indicating that it is likely to be a latent collagenase. Immunoblots using antibodies to three different domains of type IV collagenase show that the 72-kDa protease and a 76-kDa protease are type IV pro-collagenases. Sertoli cells cultured alone produce basal levels of type IV collagenase that can be immunolocalized in the cytoplasm of cultured cells. Peritubular cells cultured alone produce much less type IV collagenase. However, Sertoli and peritubular cells in coculture do produce type IV pro-collagenase, and in cultures consisting predominantly of peritubular cells, the activated form of type IV collagenase was detected by both zymography and immunoblotting. Cells growing during the transitional phase (from cell attachment to confluence) secrete more metalloproteinases than during the confluent phase. In contrast, plasminogen activator levels are unaffected by time in culture. These results show that rat testicular cells in culture produce and secrete type IV collagenase, and that the secretion and activation of this enzyme and other metalloproteases is regulated by the ratio of mesenchymal cells to epithelial cells and time in culture.     

Systematic reinstatement of Schilbe depressirostris (Peters, 1852), based on differences in DNA barcoding and morphology,from Schilbe intermedius Rüppell, 1832 (Siluriformes,Schilbeidae)

Climate change poses an unprecedented threat to biodiversity worldwide. Consequently, unrecognised taxa may not receive adequate conservation attention to survive. We used molecular and morphological data to address the challenge of species delimitation within the genus Schilbe. The presence or absence of an adipose fin and distribution based on east-flowing, conceivably faster-flowing, or west-flowing, probably more slow-flowing, river systems were considered. Distinctive geographic patterns in genetic variation within southern, eastern, and western African populations were revealed. Particularly, the South African population is distinct from those of Namibia, Botswana and Nigeria. No individuals with rudimentary adipose fins were found at any locality, but specimens from three localities either had or did not have adipose fins. These mixed occurrences are suspected to be a result of human interventions, and that the presence of rudimentary adipose fins in the east African species could be an adaptive feature that serves to stabilise these fish in faster currents. In addition, the genetic divergence observed among African silver catfish from geographically isolated river systems is conceivably the result of micro-evolutionary adaptive responses to different environmental conditions. Collectively, these results distinguish S. depressirostris from S. intermedius.     

Living enantiosymmetric and enantioasymmetric polymerization of methylthiirane in homogeneous phase

The polymerization of racemic methylthiirane in homogeneous phase, initiated by bis(isopropyl-S-cysteinato) cadmium is a living process. The resulting polymers are isotactic and optically active at partial conversion. The optical purity of the residual monomer may reach 27% at half conversion. The propagation occurs mainly on one valency of Cd, however oligomers grow slowly on the second valency. The stereoregularity of the polymer chain appears only when the length of the oligomer becomes high enough, making possible a bicoordination of the Cd counterions. The stereoregularity of the polymer is characterized by the molar fraction σ of isotactic diads which varies from 0.5 for atactic chains—formed at the beginning—to about one for isotactic segments formed for longer chains. The stereospecifictity also depends on temperature of propagation and on initiator concentration. The kinetics observed (zero order in monomer and one-half in Cd) are explained by monomer coordination before insertion and dimeric association of the thiolate end groups. The enantioasymmetric process observed results from an unbalance in the number of the two different types of active sites and possibly from a difference in their reactivities. Enantioasymmetry has been found to decrease significantly when the dielectric constant ε of the medium increases.     

Conspecifics and Their Posture Influence Site Choice and Oviposition in the Damselfly Argia moesta

Finding a suitable oviposition site can be costly because of energy and time requirements, and ovipositioning can be dangerous because of the risk of predation and harassment by males. The damselfly Argia moesta oviposits, contact-guarded by her mate, on vegetation in streams. Oviposition aggregations are commonly observed in this species, despite their territorial nature during other behaviors. We conducted experiments in the field to test the hypothesis that aggregations are the result of conspecific attraction. In the first experiment, two oviposition sites (sycamore leaves) were provided, one with models of ovipositing pairs, and one without. In the second experiment, one leaf again had ovipositing models, while the other had models of uncoupled males and females in a resting posture. In both experiments, damselfly pairs preferred the site with ovipositing models. In general, they visited the ovipositing models first more often than expected by chance, stayed longer there, were more likely to oviposit there, and laid a greater total number of eggs there. These results support the hypothesis that conspecific attraction is responsible for ovipositing aggregations in A. moesta and that posture is an important cue for attraction. Using conspecific cues could be a beneficial strategy to save in search costs while taking advantage of the presence of ovipositing conspecifics to dilute the effects of harassment and predation.     

THE EFFECT OF ASSOCIATED SOIL MICROFLORA ON FUSARIUM UDUM BUTL., THE FUNGUS CAUSING WILT OF PIGEON-PEA (CAJANUS CAJAN (L.) MILLSP.)

Inoculation with Fusarium udum Butl. produced more wilt of pigeon-pea in sterilized than in unsterilized soils at the same pH. From unsterilized soils with low disease incidence, nine fungi, Bacillus subtilis and an Actinomyces were isolated. The number of isolations of a particular organism varied from month to month during the cropping season of pigeon-pea in Delhi. Interaction of Fusarium udum and other organisms isolated was studied. Aspergillus niger and A. terreus secreted inhibitory substances in potato-dextrose broth: Bacillus subtilis inhibited growth on solid medium and also produced a toxic substance in potato-dextrose broth. The nature of the medium employed and period of growth were important factors in the production of the inhibitory principle, which is thermostable. The low incidence of pigeon-pea wilt in unsterilized soils may result from the inhibitory activity of the associated microflora in the soil.     

Ferrous iron transport in Streptococcus mutans.

Radioiron uptake from 59FeCl3 by Streptococcus mutans OMZ176 was increased by anaerobiosis, sodium ascorbate, and phenazine methosulfate (PMS), although there was a 10-min lag before PMS stimulation was evident. The reductant ascorbate may have provided ferrous iron. The PMS was reduced by the cells, and the reduced PMS then may have generated ferrous iron for transport; reduced PMS also may have depleted dissolved oxygen. We conclude that S. mutans transports only ferrous iron, utilizing reductants furnished by glucose metabolism to reduce iron prior to its uptake.     

Tritiated Water Vapour Exchange Method for the Evaluation of Whole Plant Diffusion Resistance

Water vapour exchange between plant and atmosphere was studiedby using THO as a tracer. Pulses of THO vapour were brieflyinjected into the airflow of an open circuit plant chamber.Water vapour exchange was calculated from the difference intotal quantity of THO escaping from the plant chamber with andwithout a plant The amount of THO exchanged was closely dependenton the product of total leaf area x mean leaf conductance. Themethod is suitable for measuring on the same plant short termvariations in leaf conductance following changes in environmentalconditions.