Role of membrane lipid fatty acids in cold adaptation.

Psychrophilic and psychrotolerant bacteria have evolved various strategies to adapt to low temperature. One important strategy, which is crucial to the survival of the cell at low temperature, relates to the ability of the cell to modulate the fluidity of the membrane. Bacteria in general modulate membrane fluidity by altering their fatty acid composition. But, bacteria could also achieve the same by various other strategies such as by altering the lipid head group, the protein content of the membrane, the type of carotenoids synthesized, the fatty acid chain length and the proportion of cis to trans fatty acids. In addition bacteria have a two-component signal transduction pathway consisting of a membrane-bound sensor and a soluble cytoplasmic response regulator involved in the perception and transduction of low temperature signals. This review on cold adaptation highlights the various strategies by which bacteria modulate the fluidity of the membrane and the process by which it senses and transduces the low temperature signal.     

Role of signaling pathways in regulating the capacitation of mammalian spermatozoa.

Mammalian testicular spermatozoa are immotile and incompetent for fertilization. They acquire motility during epididymal maturation and fertilizing ability during a second phase of maturation in the female reproductive tract, termed as capacitation. Capacitation was discovered independently by Austin and Cang in early 1950s and was defined as the obligate period of residency of spermatozoa in the female reproductive tract, which confers on the spermatozoa the ability to fertilize an oocyte. Over the years, the definition of capacitation has changed and it has been recognized as a complex phenomenon, which is correlated with changes associated with the spermatozoa in the female tract. These alterations in metabolism, intracellular ion concentration, membrane fluidity, intracellular pH, cAMP concentration and concentration of reactive oxygen species, ultimately make the spermatozoa fertilization-competent. The molecular basis of capacitation is poorly understood despite the fact that it is an important event preceding fertilization. This review presents our current understanding of the signaling events involved in the process of capacitation.     

Interaction of seminalplasmin with chlortetracycline, a fluorescent chelate probe of Ca2+

The interaction of seminalplasmin with chlortetracycline, a fluorescent chelate probe of Ca2+, was studied. The results indicate that seminalplasmin binds to chlortetracycline. The binding is not influenced by salt. Both Ca2+ and seminalplasmin probably bind to the same site on chlortetracycline. Seminalplasmin also reduced the Tb3+-associated fluorescence of bovine spermatozoal plasma membrane. These results are discussed in relation to the inhibitory effect of seminalplasmin on the uptake of Ca2+ in bovine spermatozoa.     

Dysbiosis in the Gut Bacterial Microbiome of Patients with Uveitis,an Inflammatory Disease of the Eye

Uveitis (UVT), an inflammatory disease of the eye significantly contributes to vision impairment and blindness. Uveitis is associated with systemic infectious and autoimmune diseases, but in most cases, the aetiology remains unidentified. Dysbiosis in the gut microbiome has been implicated in autoimmune diseases, inflammatory diseases, cancers and mental disorders. In a mice model of autoimmune UVT, it was observed that manipulating the gut microbiome reduces the inflammation and disease severity. Further, alterations in the bacterial gut microbiome and their metabolites were reported in UVT patients from a Chinese cohort. Hence, it is worth comparing the bacterial gut microbiome of UVT patients with that of healthy controls (HC) to ascertain whether dysbiosis of the gut microbiome has implications in UVT. Our analyses showed reduced diversity of several anti-inflammatory organisms including Faecalibacterium, Bacteroides, Lachnospira, Ruminococcus and members of Lachnospiraceae and Ruminococcaceae families, and enrichment of Prevotella (proinflammatory) and Streptococcus (pathogenic) OTUs in UVT microbiomes compared to HC. In addition, decrease in probiotic and antibacterial organisms was observed in UVT compared to HC microbiomes. Heatmap and PCoA plots also indicated significant variations in the microbiomes of UVT versus HC. This is the first study demonstrating dysbiosis in the gut bacterial communities of UVT patients in an Indian cohort and suggests a role of the gut microbiome in the pathophysiology of UVT.     

P NMR study of phosphorus containing metabolites in the uterus of hamster: Changes during the estrous cycle and the effect of hormonal manipulation

Changes in the concentrations of phosphorus containing metabolites were monitored by ³¹P NMR in the uteri of hamsters during the estrous cycle. Concentrations of phosphocreatine (PCr) and ATP were significantly increased in estrus animals compared to diestrus animals. Concentrations of these metabolites were also increased in immature female hamsters and ovariectomized (OVX) adult hamsters treated with estradiol indicating that estradiol was responsible for this effect. However, the steroid hormones progesterone and testosterone did not increase the concentrations of the phosphorus containing metabolites. Further, immature female hamsters also following treatment with estradiol showed an initial decline in phosphomonoester (PME), PCr, ATP and inorganic phosphate but by 24 h of treatment the concentrations returned to control levels. The NMR study also revealed that the intracellular pH of the hamster uterus was around 7.4 all through the estrous cycle.     

Bull sperm plasma and acrosomal membranes: Fluorescence studies of lipid phase fluidity

Bull sperm plasma and outer acrosomal membranes have been isolated by discontinuous sucrose density gradient centrifugation and Ca²⁺-ATPase activity has been determined for both the membranes. Pyrene excimer fluorescence and diphenylhexatriene fluorescence polarization studies show that the lipid phase of the sperm plasma membranes is more fluid than the lipids of the outer acrosomal membranes. Approximately, a three fold increase in the cholesterol content has been found in the outer acrosomal membranes as compared to that in the plasma membranes.     

Proteins implicated in sperm capacitation

Spermatozoa after being deposited in the female reproductive tract spend a considerable time in this foreign environment prior to fertilization of the oocyte. Chang and Austin independently observed1,2 that this time spent by the spermatozoa in the female tract is not consequential but a necessary event in the life cycle of the male gamete, and Austin2 first called this maturation period of spermatozoa as 'Capacitation'. Ever since, attempts have been made to understand and unravel the molecular mechanism of capacitation. Based on the results obtained so far, it is clear that capacitation is guided by novel signal transduction pathways influencing varied aspects of spermatozoa. Capacitation could be, thus, defined as the cumulative molecular, cellular and physiological changes that occur in spermatozoa in the female reproductive tract to achieve the final competence to fertilize the oocyte. This review is structured so as to first understand the key features of capacitation and then to survey the players which bring about these changes during capacitation.     

Semen characteristics, cryopreservation, and successful artificial insemination in the Blue rock pigeon (Columba livia)

The present study was undertaken in the Blue rock pigeon (Columba livia) to evaluate the annual semen characteristics, to identify a suitable extender for semen short-term storage, to determine a protocol for cryopreservation of semen and finally to check whether intracloacal insemination would lead to the birth of a chick. Semen characteristics such as semen volume, sperm concentration, sperm motility, and percentage of normal spermatozoa were maximum during the monsoon season. TALP was observed to be the most suitable semen extender and the sperm survived best at 37 degrees C at a dilution of 1:100 in TALP. Further, cryopreservation studies on pigeon semen indicated that 8% DMSO with or without egg yolk (20%) proved to be a better cryoprotectant compared to glycerol and polyethylene glycol. In addition, the slow freezing protocol was better than the fast-freezing protocol and about 40% of the cryopreserved spermatozoa were motile following thawing. Computer-aided semen analysis indicated that pigeon spermatozoa were extremely active immediately after dilution in TALP and exhibited linear trajectories persisting up to 9h. But, with time there was a time-dependent decrease in the velocity parameters (VAP, VSL, and VCL). Cryopreserved spermatozoa following thawing also exhibited linear trajectories but had reduced velocity as evident from the significant decrease in VAP, VSL, and VCL. Further, artificial inseminations using fresh semen resulted in 45% fertilization and birth of a live chick.