Worcester Foundation for Biomedical Research

About: Worcester Foundation for Biomedical Research is a based out in . It is known for research contribution in the topics: Estrone & Estrogen. The organization has 2195 authors who have published 2646 publications receiving 115809 citations. The organization is also known as: Worcester Foundation for Experimental Biology.

Role of cAMP in the reactivation of demembranated ram spermatozoa

Abstract: Ejaculated ram sperm were demembranated with Triton X-100, separated from the detergent-soluble matrix, and reactivated [San Agustin and Witman (1993): Cell Motil. Cytoskeleton 24:264–273]. The percent motility of models prepared from freshly washed sperm was comparable to that of the washed sample before demembranation, regardless of whether cAMP was included in the reactivation medium. However, demembranated models derived from aging or metabolically inhibited sperm exhibited a lower percent reactivation and required cAMP to attain the level of motility of freshly washed sperm. Cyclic AMP was ∼100 times more effective than cGMP. The requirement for cAMP could be bypassed by addition of porcine heart cAMP-dependent protein kinase (PKA) catalytic subunit to the reactivation medium, demonstrating that cAMP was acting via PKA. The cAMP stimulation of reactivation was not affected by inclusion of the PKA inhibitor PKI(5–24) in the reactivation medium, but was decreased when the models were preincubated with PKI(5–24) prior to reactivation. The cytosol-free models retained >90% of the sperm PKA activity; therefore, the PKA appears to be anchored to internal sperm structures. This PKA could not be extracted by cAMP or Triton X-100 alone, but only by cAMP and Triton X-100 in combination. We conclude that cAMP-dependent protein phosphorylation is critical for sperm motility, but that the essential protein phosphate sites turn over slowly under our reactivation conditions, so that the cAMP requirement is apparent only in models prepared from sperm having a low internal ATP or cAMP content. Interestingly, reactivation was rapidly blocked by the peptide arg-lys-arg-ala-arg-lys-glu, which has been reported to be a selective inhibitor of cGMP-dependent protein kinase. © 1994 Wiley-Liss, Inc.

Capacitation of rabbit spermatozoa in the uterus with special reference to the reproductive phases of the female1

Abstract: The capacitation of sperm (spermatozoa undergo a certain physiological change in the female tract before they are capable of fertilization) was investigated by injection of sperm into the uterus of rabbits at various reproductive phases or rabbits treated with gonadotrophin, estrogen or progesterone. Twelve hours later the injected sperm were recovered and then deposited into the top of the fallopian tubes of another rabbit that had ovulated recently. This was done to determine whether sperm so treated could fertilize the ova. Although capacitation was achieved in the uterus of immature and ovariectomized rabbits with or without the treatment of gonadotrophin or estrogen, it could not be achieved in the uterus of pseudopregnant rabbit with or without the treatment of gonadotrophin or estrogen or in the uterus of immature, ovariectomized, or estrous rabbits treated with progesterone. The inhibition of capacitation of sperm in the pseudopregnant uterus or in the uterus of rabbits treated with progesterone w...

Control of torpor and body weight patterns by a seasonal timer in Siberian hamsters

Abstract: Two experiments were designed to assess whether the short-day-induced patterns of shallow daily torpor, body weight, and other seasonal responses (food intake and pelage pigmentation) exhibited by Siberian hamsters (Phodopus sungorus sungorus) are under the control of a "seasonal timekeeping mechanism" that is independent of reproductive status [testosterone, (T)]. We examined whether the patterning and expression of these seasonal responses were altered by decreases in serum T that accompany gonadal regression during the first 8 wk of short-day exposure (i.e., the "preparatory phase" of the torpor season) or by experimental increases in serum T after this phase. Short-day-housed, castrated hamsters bearing T implants had long-day levels of the hormone and did not exhibit torpor. Appropriate seasonal patterns and levels of torpor, body weight, pelage color stage, and food intake were exhibited after T implant removal although serum T was clamped to long-day levels during the preparatory phase. In animals that were gonad intact during the preparatory phase and were subsequently castrated and given T implants, torpor did not occur as long as the implants were in place. However, the patterns and levels of daily torpor, food intake, and body weight rapidly returned to appropriate seasonal values compared with the castrated, blank-implanted controls on T implant removal; these effects occurred whether the T implants were removed when torpor frequency was increasing, at its peak, or decreasing across the torpor season. T did not affect pelage color stage under any condition.(ABSTRACT TRUNCATED AT 250 WORDS)