Variation in genotypic responses and biochemical analysis of callus induction in cultivated wheat.

Wheat is notorious for callus induction, which is a major hindrance in direct gene transfer and consequently for genetic improvement programs. In order to provide a successful platform for gene transformation, good callus quantity and quality is important. We investigated the variation in callus induction capabilities of Pakistani wheat cultivars and measured the reducing sugar content in the induced calluses. Ten elite wheat varieties, developed and cultivated in Pakistan were selected on the basis of agronomic and stress tolerance parameters. Significant differences were found between and among wheat cultivars for callus induction response, shoot length and callus quality. The callus induction responses of Punjab-81, Punjab-96 and Zarghoon-79 were found to be the best among the 10 varieties. The induced calluses were of two types, embryogenic (hard) and non-embryogenic (soft). The seeds gave good germination. The highest reducing sugar concentration was found in cultivar Sutlaj-86, which needs to be tested for stress resistance, a measure of its utility for genetic engineering programs. The relative callus induction rate and reducing sugar content of the wheat cultivars were found to be genotype-dependent.

Interrelationship among testicular cells in wall lizard Hemidactylus flaviviridis (Rüppell): an ultrastructural seasonal and experimental study.

The present study was aimed at investigating ultrastructure of different testicular cells and their interactions through various junctional specializations during different phases of reproductive cycle in wall lizard H. flaviviridis to develop an integrated approach of cell-cell interaction in control of testicular functions. Specialized steroid synthesizing cell organelles such as smooth endoplasmic reticulum (SER) and long slender mitochondria with tubulo-vesicular cristae were predominantly seen in Leydig as well as Sertoli cells during spermatogenically active phase, suggesting their active involvement in steroid biosynthesis. Peritubular cells also exhibited marked seasonal variations. Multi-layered fibroblast-like peritubular cells during regressed phase became single layered myoid-like during spermatogenically active phase. The presence of various types of junctions, including gap and tight junctions (occluding junctions) and adhering junctions such as desmosomes, septate-like junction, ectoplasmic specializations and tubulo-bulbar complexes, were demonstrated among testicular cells in wall lizard H. flaviviridis. However, the nature and degree of junctional (environmental) interaction varied with the reproductive state of the wall lizard. Further, administration of dihydrotestosterone in wall lizards during regressed phase resulted in increase of lipid droplets in Leydig cells and accumulation of germ cell debris in seminiferous tubules. Some of the Sertoli cells were seen darker in response to testosterone treatment probably due to its inhibitory effect on lipid metabolism. These results suggest that testosterone either directly or via inhibiting pituitary basal gonadotropin secretion has suppressive effect on testicular cells.

In vitro effect of FSH and testosterone on Sertoli cell nursing function in wall lizard Hemidactylus flaviviridis (Rüppell).

The present in vitro Sertoli cell-enriched culture study was aimed to understand the precise role of FSH and testosterone either alone or in combination in regulation of Sertoli cell nursing function such as lactate production, which in turn is utilized by the germ cells as an energy substrate. The stimulatory effect of FSH on lactate production by Sertoli cell-enriched culture was significantly enhanced when FSH and dihydrotestosterone were supplemented in the medium either simultaneously or DHT was added 12 h later to FSH (0 h FSH+12 h DHT). On the contrary, DHT alone or added 12 h prior to FSH (0 h DHT+12 h FSH) in the incubation medium, significantly reduced the lactate secretion by Sertoli cells as compared to control or FSH alone/FSH+DHT simultaneously/0 h FSH+12 h DHT, respectively. This provides the conclusive evidence that androgen has additive effect on nursing function of Sertoli cell-enriched clusters only when they are in an activated state in response to gonadotropin.