In this paper, we present a model of a delay tolerant network (DTN) and identify that this model ... more In this paper, we present a model of a delay tolerant network (DTN) and identify that this model can be suitably reformulated as a bipartite network and that the major predictions from the former are equivalent to that of the latter. In particular, we show that the coverage of the information dissemination process in the DTN matches accurately with the size of the largest component in the suitably thresholded one-mode projection of the corresponding bipartite network. In the process of this analysis, some of the important insights gained are that (a) arbitrarily increasing the number of agents participating in the dissemination process cannot increase the coverage once the system has reached the stationary state for a given buffer time (i.e., the time for which a message resides in the buffer of the places visited by the agents), (b) the coverage varies inversely with the square of the number of places in the system and directly with the square of the average social participation of the agents and (c) it is possible to design an optimal buffer time for a desired cost of coverage. To the best of our knowledge, this is the first such work that employs the rich theoretical backbone of bipartite networks as a "proxy" for the analysis of the otherwise intractable DTN dynamics thus allowing for various novel analytical estimates.
A sperm motility inhibitor from boar seminal plasma was purified. The purification procedure incl... more A sperm motility inhibitor from boar seminal plasma was purified. The purification procedure included dialysis against 0.1 M Tris-HCI containing 0.1 mM D T and chromatographies on SP-Sephadex C-25 and Phenyl-Sepharose CL-4B. With this procedure, the seminal plasma motility inhibitor (SPMI) preparation was highly purified with a 18% recovery of inhibitory activity. The molecular weight of SPMl in native conditions has been estimated at 50,000 by molecular sieving, but 3 polypeptides with molecular weights of 14,000, 16,000 and 18,000 were observed following polyacrylamide gel electrophoresis in denaturing conditions. SPMl is a thermolabile basic protein that is stable between pH 6 and pH 11. The observations that SPMl effects on motility of demembranated spermatozoa are reversed by Mg.ATP and that SPMl inhibited bull dynein ATPase in a concentrationdependent manner suggest that this protein blocks the motility of demembranated spermatozoa by interfering with dynein arm function.
In any present-day spectrophotometer, the vertical position of the cuvette is fixed. Here, a uniq... more In any present-day spectrophotometer, the vertical position of the cuvette is fixed. Here, a unique developmental work on a spectrophotometer is talked about where vertical movement of the cuvette has been exhibited for determining vertical-motility parameters of sperms. The cuvette holder of the spectrophotometer was replaced with a redesigned electromechanical platform, driven by a software controlled stepper motor, capable of moving the cuvette upward and downward within the light path. Goat spermatozoa (model system) layered at the bottom of the cuvette containing buffer solution swim upward against gravity and enter the light path to cause variation in absorbance value. Continuous change in absorbance as a function of time was acquired using software at varied heights of the cuvette and stored in the attached computer and analyzed by the data analysis software developed for determining various sperm motility parameters using respective mathematical models. Thus, it has huge potential for application in infertility clinics, animal breeding and conservation centres and biological researches
Several studies have been reported on the occurrence of sperm motility inhibiting factors in the ... more Several studies have been reported on the occurrence of sperm motility inhibiting factors in the male reproductive fluids of different mammalian species, but these proteins have not been adequately purified and characterized. A novel sperm motility inhibiting factor (MIF-II) has been purified from caprine epididymal plasma (EP) by Hydroxylapatite gel adsorption chromatography, DEAE-Cellulose ion-exchange chromatography and chromatofocusing. The MIF-II has been purified to apparent homogeneity and the molecular weight estimated by Sephacryl S-300 gel filtration is 160 kDa. MIF-II is a dimeric protein, made up of two subunits each having a molecular mass of 80 kDa as shown by SDS-PAGE. The isoelectric point of MIF-II is 5.1 as determined by chromatofocusing and isoelectric focusing. It is a heat labile protein and maximal active at the pH 6.9 to 7.5. The sperm motility inhibiting protein factor at 2 mg/ml (12.5 nM) level showed maximal motility-inhibiting activity. The observation that the epididymal plasma factor lowered the intracellular cAMP level of spermatozoa in a concentration-dependent manner suggests that it may block the motility of caprine cauda spermatozoa by interfering the cAMP dependent motility function. The results revealed that the purified protein factor has the potential of sperm motility inhibition and may serve as a vaginal contraceptive. The antibody raised against the MIF-II has the potential for enhancement of forward motility of cauda-spermatozoa. This antibody may thus be useful for solving some of the problems of male infertility due to low sperm motility.
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