Biomedical subjects

R H Foote

Publications and source records attributed to R H Foote.

At least 127 records · Page 7Linked to original sources

PubMed1987

Dilauroylphosphatidylcholine liposome effects on the acrosome reaction and in vitro penetration of zona-free hamster eggs by bull sperm: I. A fertility assay for fresh semen.

Fresh sperm from five bulls having nonreturn rates ranging from 48% to 77% were treated with 15.7, 21.0, 26.2, 31.5, 36.7, and 42.0 microM dilauroylphosphatidylcholine (PC12) to induce the sperm acrosome reaction (AR). Treated sperm were incubated 3 hr with zona-free hamster eggs at 39 degrees C prior to fixation. The eggs were then stained and examined for sperm penetration. Differences in the percentages of motile sperm and of sperm exhibiting an AR among bulls were small when compared on a within-liposome-concentration basis. Increasing the PC12 concentration from 15.7 microM to 42.0 microM increased the percentage of sperm exhibiting an AR for all bulls. At the lowest lipid concentration (15.7 microM), the percentage of eggs penetrated by sperm from the five bulls was 6% to 36%, with 0% in controls. When sperm were incubated with increasing lipid concentrations, the egg penetration rate increased to over 80%, and the total number of sperm increased to over 100 per 36 eggs in each treatment for every bull. These penetration rates decreased at the highest lipid concentration. A correlation between the PC12 concentration maximizing egg penetration and the nonreturn rate of -.63 was found. The correlation between the PC12 concentration maximizing the total number of penetrated sperm per treatment and the bull nonreturn rate was -.96. It was concluded that PC12 liposomes induce the AR in bull spermatozoa, which enables them to penetrate zona-free hamster eggs. High fertility bulls required less lipid to induce the AR than did lower fertility bulls. Consequently, this assay of fresh semen could provide a laboratory method to estimate the fertility of a bull.

Acrosome↗

PubMed1987

Dilauroylphosphatidylcholine liposome effects on the acrosome reaction and in vitro penetration of zona-free hamster eggs by bull sperm: II. A fertility assay for frozen-thawed semen.

Frozen-thawed sperm from five bulls with fertility rates ranging from 48% to 77% were treated with seven concentrations of dilauroylphosphatidylcholine (PC12) liposomes to induce an acrosome reaction (AR) that enabled sperm to penetrate eggs. Treated sperm were incubated with liposomes for 7 min prior to insemination of zona-free hamster eggs in vitro. Sperm and eggs were incubated 3 hr at 39 degrees C prior to fixation, staining, and examination for sperm penetration and nuclear decondensation. The percentage of motile sperm immediately after thawing as well as after treatment with liposomes had a low correlation with sire fertility (r = .39 and less than or equal to .63, respectively). The percentage of sperm exhibiting an AR was more highly correlated with fertility (r less than or equal to -.85). Similar correlations were found between fertility and the penetration rates of zona-free hamster eggs or the total number of penetrating sperm. When data for two high and for two lower fertility bulls were each grouped to increase information per data point the correlation between the PC12 concentration giving the maximum proportion of eggs penetrated and fertility was r = .92 (P less than .05). The correlation between the PC12 concentration producing the most total sperm penetrating the eggs and fertility r = .97 (P less than .05). It was concluded that PC12 liposomes induced an AR in bull sperm frozen-thawed in egg yolk extender. Frozen-thawed sperm from low fertility bulls require less PC12 to induce the AR and to penetrate zona-free hamster eggs than do sperm from higher fertility bulls. These differences in lipid requirements may help to provide a quick, direct laboratory assay method to estimate the fertility of frozen bull semen.

Acrosome↗

PubMed1987

Homospermic versus heterospermic insemination of zona-free hamster eggs to assess fertility of fluorochrome-labeled acrosome-reacted bull spermatozoa.

Fresh spermatozoa from six bulls, with fertility ranging from 64% to 78%, (based upon 59-day nonreturn rates for 159,448 cows inseminated) were mixed with zona-free hamster eggs in 15 heterospermic pair inseminations. Five of the bulls were used in homospermic insemination studies. Prior to incubation, spermatozoa from each bull were labeled with contrasting fluorescent stains pretested for effects on spermatozoa. Equal numbers of spermatozoa were mixed and treated with liposomes of dilauroylphosphatidylcholine to induce the acrosome reaction. Spermatozoa from split ejaculates within a male competed against each other equally in the hamster egg test, indicating that the staining procedure did not affect egg penetration rates. Bulls differed in their egg penetration rates when their sperm were inseminated either homospermically or heterospermically, but the differences in the homospermic inseminations were not significantly correlated with sire fertility. The number and percentage of sperm which penetrated eggs, and the number of eggs penetrated in the heterospermic competitive tests were highly correlated with fertility (r greater than or equal to 0.86). Therefore, egg penetration rates from heterospermic inseminations appear to be valuable indicators of fertility and much more sensitive predictors than results from homospermic inseminations.

Acrosome↗

PubMed1987

In vitro fertilization and embryo transfer in domestic animals: applications in animals and implications for humans.

Extensive research has been conducted in domestic animals, particularly in cattle, in the reproductive technologies of sperm handling, capacitation, and acrosome reaction, superovulation, and embryo handling, sexing, bisection, cryopreservation, and transfer. Because of the economic importance of cattle these technologies have been tested and improved under clinical conditions. The results of employing these procedures are available on tens of thousands of pregnancies and offspring. This information has implications in applying some of the same technologies in human reproduction. The large number of normal progeny produced in cattle after a long prenatal development period, similar to humans, provides some assurance that these technologies, carefully applied, are safe. The basis for these conclusions is documented in the publications cited in this review.

Animals↗

PubMed1987

Effect of several lipids, fatty acyl chain length, and degree of unsaturation on the motility of bull spermatozoa after cold shock and freezing.

Diluents containing sonicated liposomes of purified phosphatidylserine (PS), phosphatidylcholine (PC) with varying fatty acyl chain lengths and double bonds and cholesterol (CH) alone or in combination, or egg yolk lecithin were evaluated for protection of bull sperm during cold shock produced by rapid cooling from 25 to 0 degrees C and during freezing and thawing. Bull semen was washed twice and diluted to 50 X 10(6) sperm/ml in diluents containing no lipid, 0.5 or 5 mM sonicated lipid or 20% egg yolk and plunged into ice water to cold shock the sperm. Sperm so treated were frozen using conventional methods. The percentage of progressively motile sperm (MS) was estimated prior to cooling, after cold shock, and after freezing and thawing. Lipids with fatty acyl chains of less than 12 carbons were toxic to sperm cells. Phosphatidylserine alone or in combination with PC or CH, but not PC or CH alone, protected sperm from cold shock as well as did egg yolk lecithin liposomes or egg yolk. Liposomes of PS/PC or PS/CH were not better than PS in protecting sperm from cold shock. Lipid concentrations of 0.5 mM were more effective than liposomes at 5 mM in protecting sperm during freezing and thawing. During freezing, PS alone or in combination with PC partially protected sperm, but only PS/CH was as effective as egg yolk in protecting sperm from freeze-thaw damage. It is concluded that defined diluents, particularly those containing PS, may be useful in studies of cryobiology of spermatozoa.

Animals↗

PubMed1987

Penetration of zona-free hamster eggs by liposome-treated sperm from the bull, ram, stallion, and boar.

Spermatozoa from each of four rams, four stallions, and three boars (six semen samples) were treated with dilauroylphosphatidylcholine (PC12) liposomes and compared with control bull sperm to induce the acrosome reaction (AR) and study possible penetration of the sperm into zona-free hamster eggs. Diluted sperm were incubated with several concentrations of PC12 for 7 min at 39 degrees C prior to insemination of the hamster eggs in vitro. The sperm from the bull were diluted to 10(6) cells/ml, as previously studied. Sperm from the ram, stallion, and boar were diluted to 6 X 10(6) and 20 X 10(6) cells/ml. After addition to the eggs, the sperm concentration was reduced by 75 percent. Inseminated eggs were incubated with sperm for 3 h at 39 degrees C prior to being fixed, stained, and observed for sperm penetration. At an initial concentration of 6 X 10(6) cells/ml, bull sperm treated with 36.7 microM PC12 achieved an egg penetration rate of 92%, whereas under nearly identical conditions stallion spermatozoa achieved only 54% egg penetration. Under similar conditions, ram spermatozoa failed to penetrate eggs, but when the initial sperm concentration was increased to 20 X 10(6) cells/ml, sperm incubated with 51.1 microM PC12 achieved 52% egg penetration. Boar spermatozoa treated with PC12 at either sperm concentration failed to exhibit an AR or penetrate hamster eggs. In general, as PC12 concentration increased the percentage of sperm with an AR increased and sperm motility decreased. It is concluded that 1) PC12 liposomes are effective in inducing the AR in sperm from the bull, ram, and stallion, but under conditions tested are ineffective with boar sperm;(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Production of identical twin rabbits by micromanipulation of embryos.

The research was conducted to improve micromanipulation procedures with rabbit embryos, including the production of genetically identical progeny. In the first experiment, embryos in different stages of development were used for micromanipulation by removing half of the blastomeres with a beveled aspirating pipette. Embryos 74-78 h postovulatory, in the late compacted morula or early blastocyst stage, were demonstrated to be best for micromanipulation. When embryos at this stage were halved, 77% (64/83) developed into blastocysts compared to 78% (65/83) for the intact control. In the second experiment, the survival of demi-embryos in original versus foreign zonae was tested. Young born from the demi-embryos transferred within original zonae (33%) were not significantly different (p greater than 0.05) from those transferred in foreign zonae (24%). Significantly more offspring, however, were obtained from intact control embryos (58%, p less than 0.01). In the third experiment, identical monozygotic twins were produced from Day 3 embryos, after modification of the aspirating pipette by further sharpening it to a fine point with a microforge. Thirty-four percent young (11) were obtained after microsurgery compared to 36% for intact control embryos transferred. Among the demi-embryos, a pair of albino and a pair of Dutch-belted young were identical twins.

Animals↗

PubMed1987

Lipids of plasma membrane and outer acrosomal membrane from bovine spermatozoa.

Plasma membrane (PM), primarily from the anterior sperm head, and outer acrosomal membrane (OAM), were isolated from ejaculated bovine spermatozoa, and the major lipid classes were characterized. Whole sperm (WS) lipids were analyzed for comparison. PM was removed by nitrogen cavitation and purified by sucrose density-gradient centrifugation. The OAM was removed by centrifugation through hyperosmotic sucrose and recovered by sucrose density-gradient centrifugation. The PM contained primarily spherical vesicles from the region overlying the OAM and was enriched 9- and 13-fold in 5'-nucleotidase and alkaline phosphatase activity, respectively, compared to the original cavitate. The OAM was recovered as caplike structures with associated ground substance. Protein, phospholipid, and cholesterol (PR, PL, and CH as micrograms/5 x 10(9) sperm) were 300, 467, and 93 for PM and 276, 111, and 25 for OAM, respectively. Corresponding values for WS (mg/5 x 10(9) sperm) were 31.4, 6.63, and 0.72. The PR/PL (w/w) and CH/PL (mol/mol) ratios were 0.66 and 0.38 for PM; 2.48 and 0.26 for OAM; and 4.39 and 0.22 for WS. Cholesterol was the only free sterol detected by gas/liquid chromatography in WS, PM, and OAM, with traces of CH sulfate present in all three preparations. Glycolipid tentatively identified as sulfogalactolipid was detected by thin-layer chromatography (TLC) in PM but not OAM. Phospholipid composition of WS and membranes was determined by TLC. Cardiolipin (3% of total PL) was present in WS only. Choline, ethanolamine, and inositol phosphoglycerides (CP, EP, PI, PIP, PIPP); sphingomyelin (SP); phosphatidylserine (PS); and lysophosphatidylcholine (LPC) were present in WS, PM, and OAM. Approximately 50% of total PL was CP in all preparations; SP was 13% of PL in PM and 17% in OAM (p less than 0.05); EP was 7% of PL in PM and 10% in OAM (p less than 0.05). The differences in composition between PM and OAM is discussed with respect to capacitation and ability of sperm to undergo the acrosome reaction.

5'-Nucleotidase↗

PubMed1987

Relationship of sire fertility to acrosome-reacted and motile spermatozoa after treatment with liposomes.

The relationship between bull non-return rate and percent acrosome-reacted and percent motile sperm treated with 24.8, 34.8, and 44.8 microM dilauroylphosphatidylcholine liposomes was examined. Frozen-thawed spermatozoa from six bulls, with fertility ranging from 64 to 78%, were incubated at 39 degrees C with the liposomes for 0, 7, and 15 min. Bulls differed in percentages of motile sperm, and this decreased over time, especially at the highest concentration of lipids (44.8 microM). Bulls differed initially in their percentage of sperm with intact acrosomes and in their linear rate of increase in percent acrosome-reacted sperm. At 24.8 microM of lipid the rate of increase was nearly linear, whereas at higher concentrations the maximum acrosome reaction was approached during short incubations. The variables 1) decline in percent motile sperm and 2) increase in percent acrosome-reacted sperm, used singly, predicted fertility most accurately when measured on sperm treated with 44.8 and 24.8 microM of lipids, respectively. However, the highest relationship (R2 greater than or equal to .97) was established by combining the acrosome and motility measurements of sperm exposed to 34.8 microM of lipids. Thus, potential fertility of bulls may be predicted by application of this assay to frozen-thawed semen.

Acrosome↗

PubMed1987

Glycerolation and thawing effects on bull spermatozoa frozen in detergent-treated egg yolk and whole egg extenders.

Bull sperm in Experiment 1 were added to a standard egg yolk-Tris extender containing 0, .25, .5, 1.0, 1.5, and 2.0% (vol/vol) of the detergent mixture, sodium and triethanolamine lauryl sulfate. Glycerol was added in one step to the initial extender or in three steps after cooling semen to 4 degrees C. The extended semen was packaged in .5-ml French straws and frozen over static nitrogen vapor. Thawing was at 4, 30, and 60 degrees C. There was little difference due to the method of adding glycerol provided detergent was present. Percentages of motile sperm after freezing in the six concentrations of detergent, in ascending order, were 31, 45, 52, 51, 48, and 36. Percentages of motile sperm following thawing at 4, 30, and 60 degrees C were 36.5, 46.0, and 48.6. Acrosome retention also was better preserved with the higher thaw temperatures. A second experiment, similar in design to the first one, was conducted with whole egg-Tris extender. The best results were in whole egg-Tris containing .125% detergent where post-thaw motile sperm of 70.4% greatly exceeded 30.7% without sodium and triethanolamine lauryl sulfate. Fertility of sperm frozen in yolk-Tris-detergent was equivalent to whole milk used as a control.

Animals↗

PubMed1987

Antibiotics for bull semen frozen in milk and egg yolk extenders.

In six experiments, gentamicin, clindamycin, amikacin, minocin, tylosin, and Linco-Spectin were tested for their effect on motility and fertility of frozen bull spermatozoa and all but clindamycin were used in fertility trials. Antibiotics were added to raw (unextended) semen and nonglycerol portions of the three commonly used semen extenders, whole milk, egg yolk-Tris, and egg yolk-citrate. Semen was frozen in .5-ml straws, stored in liquid nitrogen, and thawed at 37 degrees C for 30 s. Postthaw percentage of motile spermatozoa in antibiotic-treated semen was different for individual bulls in each experiment. Percentage of motile sperm was slightly but significantly depressed at the higher concentrations of clindamycin and Linco-Spectin tested in whole milk and with minocin in the two egg yolk extenders. In general, nonspermicidal concentrations of each antibiotic were established. Of five antibiotics tested for fertility, only gentamicin reduced fertility on the basis of 59-d nonreturn rates.

Animals↗

PubMed1987

Motility and fertility of bull sperm frozen-thawed differently in egg yolk and milk extenders containing detergent.

The purpose of this study was to examine survival and fertility of frozen bull sperm processed in several extenders containing a detergent mixture, sodium, and triethanolamine lauryl sulfate. Addition of .5% (vol/vol) detergent to whole milk was completely spermicidal. When 10% egg yolk (vol/vol) was included in the glycerol or nonglycerol fractions or both fractions of milk, sperm were equally well preserved in the presence of .5% detergent, and sperm survival following thawing at 4 degrees C was dramatically improved by the detergent. This improved result with the 4 degrees C thaw temperature also was obtained by adding .5% detergent to an egg yolk-Tris extender. Thawing temperatures of 30 and 50 degrees C (later for 15 s) were generally superior to 4 degrees C. A fertility trial with whole milk, whole milk-10% yolk, whole milk-10% yolk-.5% detergent, egg yolk-Tris, and egg yolk-Tris-.5% detergent was conducted. The 59-d percent nonreturns, respectively, were 73.4, 65.8, 65.6, 69.5, and 73.4. Whole milk or egg yolk-Tris plus detergent were equally superior to the other extenders for bull semen.

Animals↗

PubMed1987

Reproductive patterns in cyclic and pregnant thyroidectomized mares.

Three Quarter-horse mares were thyroidectomized at about 1.5 years of age. Three similar intact mares served as controls. The study continued through two breeding seasons. The thyroidectomized mares were lethargic, rear limbs were oedematous and hair coats were coarse. They displayed a tranquil oestrous behaviour when exposed to a stallion and were only mildly antagonistic when not in oestrus. Length of oestrous cycles varied but most often they were 19-24 days long. Duration of oestrus (mean +/- s.e.m.) for the control and thyroidectomized mares was 12.9 +/- 2.9 and 11.7 +/- 2.2 days respectively (P greater than 0.05). The peak of LH during oestrus was as high as 60 ng/ml blood serum with no difference between the two groups. Peak progestagen on Day 7 after ovulation for controls was 9.0 +/- 1.6 ng/ml and was not different (P greater than 0.05) from the peak of 6.3 +/- 1.7 ng/ml for thyroidectomized mares on Day 8. Pregnancy was achieved in both groups of mares, including the use of semen from a thyroidectomized stallion. Thyroxine was detectable in one pregnant thyroidectomized mare during the last two-thirds of pregnancy only.

Animals↗

PubMed1986

Measurement of semen quality, fertility, and reproductive hormones to assess dibromochloropropane (DBCP) effects in live rabbits.

Thirty-six sexually mature Dutch rabbits were divided into six equal groups to receive in the drinking water 5 days/week for 10 weeks 0, 0.94, 1.88, 3.75, 7.50, and 15.00 mg of DBCP/kg body wt. General health, body weight, semen quality (four ejaculates per male per week), and libido were measured throughout. Fertility, blood follicle stimulating hormone (FSH), luteinizing hormone (LH), and testosterone were measured the last week and cauda epididymal sperm were examined at sacrifice. There was no effect of DBCP on general health or body weight. There was considerable variation in ejaculate volume, percentage motile sperm, and sperm concentration per milliliter within groups and among weeks. However, between the first 2 weeks and the last 2 weeks of the experiment sperm output had increased by 19% in the three lower DBCP groups and decreased by 16% in the three higher DBCP groups (p less than 0.01). The proportion of sperm with abnormal tails also increased as DBCP dosage increased. Fertility was unaffected. FSH was elevated (p less than 0.01) in the group receiving 15 mg/kg of DBCP, which is consistent with the impairment of spermatogenesis. Libido, LH, and testosterone levels were not affected. Sperm morphology was the most sensitive indicator of a DBCP effect in the live animal, being affected at a daily oral intake greater than or equal to 1.88 mg DBCP/kg body wt.

Animals↗

PubMed1986

Use of quantitative testicular histology to assess the effect of dibromochloropropane (DBCP) on reproduction in rabbits.

Dibromochloropropane (DBCP) was administered orally to 36 sexually mature male Dutch Belted rabbits assigned at random to one of six groups to receive 0, 0.94, 1.88, 3.75, 7.5, or 15.0 mg DBCP per kilogram of body weight daily 5 days per week during a 69-day treatment period. Animals were euthanized and necropsied on Day 70. Body weights and weights of the kidneys, liver, epididymides, and accessory sex glands were not influenced by DBCP treatment. The highest dosage reduced mean paired testes weight to 45% of control values (p less than 0.01). Mean seminiferous tubular diameter was reduced by 15 and 29% with the two highest dosages of DBCP, respectively (p less than 0.01), and the percentage of seminiferous tubules containing elongating and round spermatids, as the most advanced cell type present, was decreased (p less than 0.01). The number of leptotene primary spermatocytes per Sertoli cell, and the numbers of spermatogonia, young and old primary spermatocytes, and Step 1 spermatids per Stage I seminiferous tubular cross section likewise indicated a general depression (p less than 0.01) of spermatogenesis. Based upon the number of Step 1 spermatids per cross section at Day 70, production of sperm at this time by rabbits receiving the highest dose of DBCP was estimated to be less than one-fourth of control values. No significant effect (p greater than 0.05) of 0.94 mg DBCP/kg on any parameters was found, so this could be considered to be the no effect dose. However, the regressions and mean values are interpreted to indicate that the no effect level of DBCP may be less than 0.94 mg DBCP/kg of body weight. It is suggested that the most sensitive tests described here be included in future screening tests for potential effects of agents on male reproduction.

Animals↗

PubMed1986

Fertility of cooled and frozen rabbit sperm measured by competitive fertilization.

The fertility of rabbit sperm that had been cooled to 5 degrees C or frozen and thawed was determined by competitive fertilization. Treatments were identified by labeling sperm with fluorescein isothiocyanate (FITC) or tetramethylrhodamine B isothiocyanate (TRITC). Sperm from different treatments were mixed and used in a competitive insemination experiment. Does were inseminated 5, 10 or 15 h prior to ovulation. Time of ovulation was controlled by injections of luteinizing hormone. The functional sperm transport, as determined by the number of sperm transported to the site of fertilization and capable of fertilizing oocytes, was estimated by counting the total number of differently stained sperm that surrounded or fertilized each oocyte. The fertility of sperm cooled to 5 degrees C was not affected (p less than 0.05) as compared to fertility of uncooled sperm. Functional sperm transport at all times of insemination and fertilization ratio at insemination 10 or 15 h before ovulation were reduced (p less than 0.05) for frozen-thawed vs. cooled sperm. No difference in fertilization ratio (p greater than 0.05) occurred, however, when does were inseminated 5 h before ovulation. While sperm survival and capacitation time appeared to play roles in fertility of frozen-thawed sperm, the most important factor was reduced functional sperm transport. However, fertility of frozen-thawed sperm was improved when the time from insemination to ovulation was reduced.

Animals↗

PubMed1986

Effect of dilauroylphosphatidylcholine on the acrosome reaction and subsequent penetration of bull spermatozoa into zona-free hamster eggs.

Incubation of bull sperm with liposomes made with phosphatidylcholine (PC) containing fatty acyl chains of either 10 (PC10) or 12 (PC12) carbons resulted in greater than 90% of the sperm exhibiting an acrosome reaction (AR) within 15 min. Liposomes of PC10 rapidly destroyed sperm motility while PC12 acrosome-reacted sperm remained motile for several h. Liposomes of PC with greater than or equal to 14-carbon fatty acyl chains had no effect on the AR or motility of sperm. The AR was not induced by lysophospholipids, because lysophospholipids were not detected in the PC liposomes, and the AR did not occur when lysophospholipids were tested at the same concentration as PC12. The concentration of PC12 necessary to induce maximal numbers of acrosome-reacted sperm varied with the concentration of sperm. The effect of PC12 on sperm also varied with the ratio of live to dead sperm in a sample. When 3 X 10(6) bull sperm/ml were treated with 0, 10, 20, and 30 microM PC12 for 7 min prior to addition to zona-free hamster eggs, 6, 6, 98, and 77% of the eggs were penetrated, respectively. Lipid concentrations of 0 microM and 10 microM did not affect the AR, whereas higher levels induced the AR in sperm. This procedure can quickly provide acrosome-reacted bull sperm for use with various in vitro fertilization procedures and for assessment of male fertility.

Acrosome↗

PubMed1986

Effect of oxytocin, prostaglandin F2 alpha and reproductive tract manipulations on uterine contractility in Holstein cows on days 0 and 7 of the estrous cycle.

The influence of various treatments on cattle at the time of natural estrus vs estrus induced by prostaglandin F2 alpha (PGF2 alpha) or at d 7 of the estrous cycle were studied; the latter is when embryo transfer often is performed. Eight lactating and 25 nonlactating, normal cycling cows were tested many times while in estrus and 7 d after estrus. A balloon was positioned in the body of the uterus to record changes in intrauterine pressure following clitoral massage, cervical massage, vaginal distention, electrical stimulation of the cervix and vagina, tailhead rubbing, udder massage and the injection of oxytocin or PGF2 alpha. Blood oxytocin and intramammary pressure were measured. There were no differences between cows in estrus spontaneously or those induced, so these groups were combined. Intravenous oxytocin injections of .5, 1, 2, 4 and 15 IU increased blood levels of oxytocin. Intramammary pressure was increased by all oxytocin doses, but greater than or equal to 2 IU were required to cause substantial changes in uterine contractions. As expected, the peak contractions during control periods for cows in estrus were high, averaging 31 mm Hg vs 11 mm Hg on d 7. None of the manipulations of the reproductive organs caused detectable oxytocin release or increases in intramammary pressure, contrasting to responses to massage of the udder. Clitoral massage increased peak uterine pressure by 32 to 60% in four experiments. It did not induce luteinizing hormone release. The contraction was immediate, was not sustained and could be obtained repeatedly, suggesting a reflex response. Treatment with PGF2 alpha increased intramammary pressure. It increased uterine pressure on d 7, but had no effect at estrus. This contrasts with injected oxytocin, which resulted in the highest amplitude for cows in estrus, although the response on d 7 was greater in proportion to the low activity in controls at that time. It is concluded that manual manipulation of the reproductive tract (other than clitoral massage) has little effect on uterine contractility.

Animals↗