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Biomedical subjects

N L First

Publications and source records attributed to N L First.

At least 127 records · Page 7Linked to original sources
PubMed1983

Chondroitin sulfate facilitates an acrosome reaction in bovine spermatozoa as evidenced by light microscopy, electron microscopy and in vitro fertilization.

Bovine epididymal spermatozoa were incubated for 22 h in a modified Tyrode's medium. The percentages of sperm exhibiting an acrosome reaction were determined morphologically after fixing and staining specimens. The addition of chondroitin sulfate A (CS-A) significantly increased the incidence of acrosome reaction. When observed by electron microscopy, acrosome-reacted sperm had undergone vesiculation of the plasma and outer acrosomal membranes. Sperm incubated in the presence of CS-A demonstrated a significantly higher incidence of vesiculation when compared to the controls. Additionally, rates of in vitro fertilization of bovine oocytes were significantly elevated when sperm and ova were exposed to CS-A. These results suggest that glycosaminoglycans in the female reproductive tract may be responsible for some of the biochemical changes associated with fertilization, and a light microscope procedure can be used to assess occurrence of the acrosome reaction.

Acrosome↗
PubMed1983

Factors affecting successful in vitro fertilization of bovine follicular oocytes.

These experiments were designed to define and optimize the efficiency of a system whereby bovine oocytes could be fertilized in vitro. The frequency of ova penetrated and the stage of fertilization were the end points examined. All experiments utilized cumulus-oocyte complexes from 1- to 5-mm follicles which were matured in vitro prior to fertilization. The experiments were designed to examine the effects of the following factors on fertilization: 1) pretreatment of sperm with ionomycin (a Ca++ ionophore), 2) preincubation of sperm at a high concentration and the presence of hypotaurine and epinephrine during fertilization, 3) the use of either follicle-stimulating hormone (FSH) or cAMP for the induction of cumulus expansion prior to fertilization, and 4) the need for the presence of cumulus cells during fertilization. Sperm exposure to ionomycin or preincubation at high sperm concentrations was not necessary for fertilization. The presence of hypotaurine and epinephrine during fertilization improved (P less than 0.05) the quality of fertilization (i.e., higher frequencies of oocytes with both female and male pronuclei were observed). However, they did not increase the percentage of ova penetrated (P greater than 0.05). Fertilization frequencies were not different (P greater than 0.05) between oocytes with cumulus expansion induced by FSH or cAMP. However, the use of either treatment resulted in higher fertilization rates when compared to untreated controls (P less than 0.05). Finally, while the presence of cumulus cells was not necessary for penetration of ova, increased frequencies of ova with both male and female pronuclei were found when cumuli were present (P less than 0.05).

Animals↗
PubMed1983

In vitro maturation and fertilization of bovine oocytes are temperature-dependent processes.

Effects of temperature on bovine sperm acrosome reaction, oocyte maturation, hyaluronic acid production by cumulus cells and in vitro fertilization were studied. Viability and a true acrosome reaction of bovine spermatozoa were impaired at 40 degrees C. Temperatures lower than 35 degrees C did not enhance the acrosome reaction. However, viability between 30 degrees C-38 degrees C was not altered after 22 h of incubation. The optimal temperature for the acrosome reaction was 38 degrees C. Labeled glucosamine incorporation into glycosaminoglycans was not different among temperatures of 35 degrees C, 37 degrees C or 39 degrees C, whereas 41 degrees C caused a significant reduction (P less than 0.02). Temperatures ranging between 35 degrees C-39 degrees C had no deleterious effects on resumption and completion of meiosis, but at 41 degrees C the frequency of oocytes that progressed to Metaphase II was significantly reduced (P less than 0.0001). Ova matured at 39 degrees C had significantly higher rates of fertilization than at 35 degrees C, 37 degrees C, or 41 degrees C. Killed spermatozoa (control) had no effect on ovum activation at 39 degrees C. From these results it was concluded that events occurring prior to and during fertilization are temperature sensitive.

Acrosome↗
PubMed1983

Role of the adrenals in the maintenance of pregnancy in cows.

On Day 215 of gestation, cows were treated as controls (Group 1), bilaterally ovariectomized (Group 2), bilaterally adrenalectomized (Group 3) or bilaterally adrenalectomized and ovariectomized (Group 4). The mean +/- s.e.m. lengths of gestation (days) were 278 +/- 3 (N = 5), 270 +/- 2 (N = 7), 277 +/- 1 (N = 5) and 219 +/- 1 (N = 3) in Groups 1, 2, 3 and 4 respectively. In Group 4, serum progesterone concentrations declined to undetectable levels within 24 h after surgery and all the cows aborted 3-6 days later. All the cows in Groups 1, 2 and 3, except 1 cow in Group 2, completed gestation and delivered live calves. Progesterone concentrations in Group 2, cows declined to approximately one-third those of cows in Groups 1 or 3. All 3 cows in Group 4 and 7/8 in Group 2 had a retained placenta. At 1 and 2 days after surgery there were no significant differences in plasma levels of oestradiol-17 beta, but by the third day this difference was significant (P less than 0.01). Oestrogen levels were high before parturition in cows in Groups 1 and 3 but were not noticeably elevated in those in Groups 2 and 4. The abrupt termination of pregnancy and negligible concentrations of progesterone in adrenalectomized-ovariectomized cows indicate that the bovine adrenals contribute to progesterone production and are capable of maintaining pregnancy after ovariectomy at 215 days of gestation.

Adrenal Glands↗
PubMed1983

Pregnancy and parturition.

The establishment and maintenance of pregnancy in domestic animals requires interactions between the developing conceptus and the maternal system. These interactions are essential for maintenance of the corpora lutea (CL), conceptus development and placentation, regulation of uterine endometrial secretory activity, placental transport of nutrients and gases, regulation of uterine blood flow, achievement of immunological "privilege" for the conceptus, stimulation of development of the maternal mammary glands and various other effects on the physiology and endocrinology of the maternal and conceptus systems. Interactions between the conceptus and maternal systems are also responsible for initiating parturition. All of these events are discussed, on a comparative basis, with respect to current knowledge obtained from studies of domestic farm animals and, where appropriate, data from laboratory species.

Animals↗
PubMed1982

Preovulatory changes in cumulus-oocyte complex of the hamster.

An orderly series of associations was found between the cumulus and the stages of nuclear development in the hamster oocyte as the oocyte-cumulus complex underwent preovulatory maturation. Ten hours prior to ovulation meiotic resumption was first seen in the oocyte. The onset of cumulus dissociation with corresponding morphological changes in cumulus cells was observed eight hours prior to ovulation. Completion of the first meiotic division in the oocyte and full cumulus dissociation occurred 2 hours prior to ovulation. Cumulus dissociation was found to occur only in vesicular follicles destined to ovulate and not in follicles undergoing atresia. Cells with large vacuolar inclusions with distorted, hyperchromatic nuclei were found in the maturing cumulus.

Animals↗
PubMed1982

Glycosaminoglycans in bovine cumulus-oocyte complexes: morphology and chemistry.

Bovine cumulus-oocyte complexes from small (1-5 mm) follicles were cultured for 24 h in 0.25 ml minimum essential medium supplemented with 10% fetal bovine serum and 20 microCi [3H]glucosamine. Treatment groups consisted of supplementing the culture medium with no hormone (control), 0.5 IU/ml follicle-stimulating hormone (FSH) or 10 mM 8-Br-adenosine cyclic monophosphate (cAMP). After culture, the complexes were fixed for light and scanning electron microscopy. Electron photomicrographs revealed that complexes induced to expand with FSH or cAMP contained a copious glycosaminoglycan (GAG) matrix extending between and around the cumulus cells. Control complexes did not exhibit expansion or an extracellular matrix. The radiolabeled GAG material was isolated for chemical identification. Chemical analyses included: (1) electrophoresis of GAG material, (2) electrophoresis of GAG material after enzyme or nitrous acid treatment, (3) thin-layer chromatography of GAG hydrolysates. The results from electrophoresis showed that the radiolabeled GAG co- migrated with hyaluronic acid. The GAG material was resistant to chondroitinase ABC and nitrous acid degradation but was digested by hyaluronidase. Complexes treated with FSH and cAMP incorporated higher (P less than 0.1 and P less than 0.025 respectively) amounts of [3H]glucosamine into hyaluronic acid than control cultures. Thin-layer chromatography identified the primary amino sugar of the GAG to be glucosamine. These data collectively showed that the radioactive GAG produced by bovine cumulus-oocyte complexes was hyaluronic acid.

Animals↗
PubMed1982

Release of relaxin by a nonluteolytic dose of prostaglandin F2 alpha in pregnant swine.

Ten gilts were infused intravenously for 5 min on Days 105 and 108 of gestation with 50 micrograms prostaglandin F2 alpha (PGF2 alpha) in 10 ml of saline or saline alone. Plasma concentrations of relaxin and progesterone were determined in samples taken 1) immediately before and after infusion, 2) at 10-min intervals throughout the first h postinfusion, 3) at 30-min intervals throughout the next 5 h, and 4) at 12-h intervals from Day 103 of gestation through Day 1 postpartum. Plasma concentrations of relaxin were increased immediately after infusion with PGF2 alpha and peaked within 10 min postinfusion. The peak was followed by a rapid decline in plasma relaxin throughout the remainder of the first hour following infusion. Progesterone values did not change from preinfusion levels for either treatment during this time period and did not differ between treatments for the remainder of the gestation period. When compared to controls, PGF2 alpha-treated animals were not significantly different with respect to length of gestation, duration of parturition or frequency of live births. These results indicate that exogenous PGF2 alpha can stimulate relaxin release from the corpus luteum without inducing luteolysis.

Animals↗
PubMed1982

Proteoglycan production by bovine granulosa cells in vitro is regulated by calmodulin and calcium.

Proteoglycan production by granulosa cells in vitro is regulated by gonadotropins. The objective of this study was to determine if FSH stimulation of proteoglycan synthesis was modulated by calmodulin or calcium. Assay for calmodulin using an ATPase assay dependent on calmodulin yielded concentrations of 7.7 microM. Bovine granulosa cells from follicles 1-9 mm diameter were incubated for 45 minutes in a chemically defined medium containing 5 microCi/ml 3H-glucosamine and various phenothiazine drugs which are inhibitors of calmodulin. In response to oFSH or rFSH at equivalent biological potencies, proteoglycan production decreased with increasing concentrations of phenothiazines from 1 to 50 microM. Addition of EGTA at 0.0, 0.5, 1.0 or 2.0 mM showed decreased proteoglycan production with increased amounts of the chelator. These data suggest that calmodulin and calcium are necessary for proteoglycan production by granulosa cells in response to FSH in vitro.

Animals↗
PubMed1982

Effect of relaxin on parturition and frequency of live births in pigs.

Gilts on Day 105 of gestation were sham ovariectomized (Group C, N = 5); ovariectomized and given i.m. injections of 100 mg progesterone twice daily from Day 105 to 112 (Group OP, N = 5); or ovariectomized and given progesterone and i.m. injections of 1 mg highly purified porcine relaxin 4 times/day from Day 105 until the end of parturition (Group OPR, N = 5). Concentrations of progesterone in peripheral plasma of gilts in Group OP were similar to those in Group C. Relaxin was undetectable in peripheral plasma of gilts in Group OP which also showed prolonged parturition (P less than 0.001) and impaired frequency of live births (P less than 0.001), although onset of lactation was not affected. In Group OPR the duration of parturition and frequency of live births were similar to those observed for gilts in Group C. These results indicate that the ovarian hormone relaxin is necessary for normal duration of parturition and frequency of live births and that the onset of lactation is not prevented by an absence of relaxin.

Animals↗
PubMed1981

Effect of indomethacin dexamethasone-induced parturition in swine.

The hypothesis that corticosteroids induce parturition in swine by stimulating the synthesis of prostaglandins was tested. Twenty Yorkshire sows were treated with indomethacin and(or) dexamethasone or the respective vehicles of the drugs. Only sows treated with dexamethasone alone showed a premature increase in the concentration of prostaglandin F2 alpha-metabolite (PGF2 alpha-M), a decrease in the concentration of progesterone in the peripheral plasma and induction of parturition. Treatment with indomethacin alone or indomethacin plus dexamethasone prolonged gestation and prevented an increase in PGF2 alpha-M and a decrease in progesterone. These results show that the effect of dexamethasone on prepartum luteolysis and induction of parturition is mediated through stimulation of the synthesis or the release of PGF2 alpha.

Animals↗
PubMed1981

Effect of removal of follicles, corpora lutea or ovaries on maintenance of pregnancy in swine.

The effects of the removal of follicles, corpora lutea (CL) or ovaries at day 108 of gestation on maintenance of pregnancy and on concentrations of progesterone, prostaglandin 2 alpha-metabolite (PGF2 alpha-M) and relaxin in maternal plasma were studied in 20 gilts. Controls were subjected to sham surgical procedures. Removal of CL or ovaries decreased progesterone and relaxin and increased PGF2 alpha-M in the maternal circulation and prematurely terminated pregnancy without causing onset of lactation. Progesterone and relaxin decreased to a lower concentration after ovariectomy than after removal of CL, probably because of incomplete extirpation of luteal tissue. Ovariectomy increased the frequency of stillbirths. These results show that the CL are the main source of progesterone and relaxin in pregnant swine and that relaxin may play a role in parturition and the onset of lactation.

Animals↗
PubMed1980

Radiolabeling of mammalian spermatozoa and their use to monitor sperm transport in females.

Radiolabeling of mammalian spermatozoa with 131I, 67Ga, 111In, and 99mTc was investigated. Spermatozoa were labeled with 99mTc for in vivo studies because of a high labeling yield (70 to 90%) combined with the lack of impairment of sperm motility. Ovariectomized sheep were brought into estrus by sequential administration of progesterone and estradiol cyprionate. Sheep were necropsied up to 6 hours after insemination with 99mTc-labeled ram sperm and their reproductive tracts were resected and examined with a rectilinear scanner. Radioactivity was clearly observed in the fallopian tubes, with larger amounts in the vaginas, cervices, and uteri. In contrast, when 99mTc-spermatozoa were replaced with 99mTcO4-, much less radioactivity remained in the reproductive tract at resection and this was evenly distributed. Some label left the 99mTc-spermatozoa in vivo, but radioactivity remained on the cells long enough to consider attempting to monitor sperm transport in vivo in a suitable species.

Animals↗