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D. L. GARBERS and N. L. FIRST

It is the purpose of this study to determine the effect of relative centrifugal force (RCF) × g on various semen characteristics of the bull and boar.

Entire ejaculates of mature Yorkshire boars were collected and separated from the gel fraction by allowing the semen to run through three layers of cheesecloth into a warm thermos. The ejaculate was then placed in 50-ml centrifuge tubes and centrifuged at 1000g for 10 or 15 min to remove the spermatozoa. Part of the first supernatant was kept for further analyses, while the remaining semen was centrifuged at forces and times given in Tables 1, 2 and 3. Bull epididymal fluid was collected by flushing through the vas deferens with a 154 mm-KCl, 10 mm-tris buffer at pH 7·2 according

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D. L. GARBERS and N. L. FIRST

Summary.

Two experiments using twenty-four sows and forty-eight gilts were designed to study ovarian and pituitary functions after treatment with oestradiol-17β (3 mg/day), progesterone (150 mg/day) or ICI 33828 (50 or 100 mg/day). The dose levels were chosen so that oestrus and ovulation would be inhibited.

None of the treatments blocked total synthesis of fsh or lh within the 10-day treatment period. ICI 33828 at 100 mg blocked fsh release early in the cycle but 50 mg did not. Oestrogen also blocked fsh release early in the cycle. All follicle growth greater than 4 mm diameter was effectively inhibited by oestrogen and the corpora lutea were maintained. Both progesterone and ICI 33828 reduced the number of follicles growing larger than 5 mm as compared to the control gilts. All treatments blocked fsh release late in the cycle.

There were increased levels of pituitary lh in ICI 33828-treated gilts compared to progesterone-treated gilts early in the cycle, but none of the treatments caused differences in lh levels from those found in the control gilts early in the cycle. All treatments blocked pituitary lh release late in the oestrous cycle.

The pituitary content of prolactin did not differ significantly between treatments.

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D. L. GARBERS and N. L. FIRST

Summary.

Thirty-five sexually mature gilts were fed either the compound ICI 33828 (100 mg/day) or a control ration on Day 18 of the oestrous cycle (Day 1 = oestrus). At 2, 4 or 6 days after oestrus, gilts were killed and ovarian and pituitary data collected. Treated gilts not showing an oestrus were killed 10 days after treatment was started. Sixty-seven per cent of the treated gilts showed the forthcoming oestrus. A high percentage (75%) of the treated gilts which exhibited oestrus failed to ovulate. The number of follicles was less than would normally be present before ovulation, and pituitary fsh and lh levels were greater in the ICI 33828-treated (non-ovulating) gilts than in controls. Gilts killed 10 days after initiation of treatment had high levels of pituitary fsh and lh, which may explain the occurrence of superovulation in one gilt (> 100 corpora lutea). These gilts, which did not ovulate except for one pig, also had no follicles greater than 6 mm in diameter, indicating that fsh release was blocked by the drug. The lower ovulation rate in the three ICI 33828-treated gilts which ovulated, compared to the controls, was thought to be the result of decreased follicular growth in the treated gilts.

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D. L. GARBERS and N. L. FIRST

Exogenous oestrogens maintain the corpora lutea (cl) in the cycling gilt (Gardner, First & Casida, 1963). The pituitary is required, since oestrogen will not maintain cl in the gilt in which the pituitary stalk has been transected (Anderson, Dyck, Mori, Henricks & Melampy, 1967). Oestrogen blocks pituitary lh and fsh release, and Rothchild (1966) has therefore suggested that increased prolactin release due to oestrogen may maintain the corpora lutea in the intact gilt. Prolactin, however, will not delay cl regression in the hypo-physectomized pig (Du Buisson, Leglise, Anderson & Rombauts, 1964). Since a single oestrogen injection was found to maintain cl in the sow (Nishikawa, 1959), oestrogen may stimulate a single release of a pituitary luteotrophin, induce a constant pituitary release of a luteotrophin, or act directly at the ovarian or uterine levels to effect
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D. L. GARBERS and N. L. FIRST

It has been shown that a dithiocarbamoylhydrazine, ICI 33828, inhibits the milk-ejection reflex in lactating rats without significantly altering milk formation (Benson & Zagni, 1965), and that oxytocin treatment can overcome the milk ejection inhibition caused by ICI 33828 in the sow (Gerrits, Johnson & Kraeling, 1965). Because the site of action of the ICI 33828 compound is believed to be at the pituitary or hypothalamic level, we have directed research effort to establishing the effect of this compound on various pituitary hormones. This brief communication is presented to demonstrate further, using a larger number of sows, that exogenous oxytocin can overcome the inhibitory action of ICI 33828 on milk ejection.

Ten crossbred sows were assigned to this study as pairs dependent on the time of farrowing. One sow in each pair was then assigned

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G. S. Kopf and D. L. Garbers

Summary. A factor associated with sea urchin eggs that increases sperm cyclic nucleotide concentrations and respiration rates was identified as having a low molecular weight. The factor was more potent at elevating cyclic GMP concentrations than cyclic AMP concentrations, and represents the first demonstration of a factor associated with eggs that is capable of causing elevations of sperm cyclic GMP. Concentration—response curves of the crude mixture of egg factors to increase sperm cyclic AMP and cyclic GMP concentrations and respiratory rates were very similar, and comparable losses of these three activities were observed after extensive dialysis and heat treatment of the crude egg factors. The factor was partly purified by ethanol precipitation of a large molecular weight egg jelly component, and by charcoal adsorption and LH-20 chromatography of the resultant ethanol-soluble material. The factor was not extracted into a variety of organic solvents and had an apparent molecular weight of between 1000 and 2000, as estimated by gel filtration.

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R. V. Hyde and D. L. Garbers

Summary. In protein-deficient minimal culture medium, acrosome reactions of motile guinea-pig spermatozoa were first evident after 30 min and maximal by 2 h. Addition of 5% (v/v) of guinea-pig serum filtrate or human plasma filtrate, obtained by passing these fluids through an Amicon UM-2 ultrafiltration membrane, prevented the sperm acrosome reaction during a 4-h incubation, but did not inhibit sperm motility. A similar inhibitory effect was found in porcine epididymal fluid. The factor(s) in porcine epididymal fluid effectively inhibited acrosome reactions if it was added to uncapacitated spermatozoa but failed to decapacitate sperm cells capacitated in Ca2+-free medium. Preliminary characterization of the factor(s) in porcine epididymal fluid indicate that it is a small organic molecule, stable to heat (90°C), soluble in methanol, sparingly soluble in ethanol and insoluble in ether, chloroform or acetone; it also appears to have no net charge at pH values between 4 and 10.

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R. V. Hyne and D. L. Garbers

Summary. The acrosome reaction was induced by jelly coat factors, nigericin, or elevated pH. When spermatozoa were preincubated for 5 min in sea water maintained at pH 7·9 in the presence of 1 mm-phenylmethylsulphonyl-flouride (PMSF), 1 mm-benzamidine, 0·1 mm-1-chloro-3-tosyl-amido-7-amino-2-heptanone (TLCK), 5 mm-diisopropylphosphofluoridate (DFP) or 5 mm-DFP that was previously hydrolysed, only DFP or its hydrolysis product(s) prevented formation of the acrosomal filament induced by jelly coat factors. When incubation with inhibitors was extended to 2 h only TLCK and its hydrolysis products inhibited the jelly-induced acrosome reaction. Only DFP significantly inhibited the acrosome reaction induced by elevated pH (9·0). Nigericin induced acrosome reactions in the presence of DFP or TLCK. These findings do not support the concept of an active role for acrosin in development of an acrosome reaction.

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D. L. Garbers and G. S. Kopf

Summary. Factors released from eggs (FRE) of the sea urchin, Strongylocentrotus purpuratus, caused up to 20-fold increases in sperm cyclic AMP levels after a 1-min incubation. Putative cyclic nucleotide phosphodiesterase inhibitors such as theophylline acted in a synergistic manner with FRE to cause even greater increases in sperm cyclic AMP levels. This effect appeared to be specific for egg factors since various hormones (triiodothyronine, norepinephrine, histamine), nucleosides (adenosine, guanosine), nucleophiles (azide), anaesthetics (procaine), ionophores (X537A, A23187), metals (Mn2+) and neurotransmitters (acetylcholine) did not increase sperm cyclic AMP levels. Various mammalian tissue extracts (serum, uterus, adrenal, ovary, lung) also had no effect.

We suggest that the activity which elevates the cyclic AMP of sea urchin spermatozoa is specifically associated with sea urchin eggs.

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R. B. STAIGMILLER, D. L. GARBERS and N. L. FIRST

Increasing the level of energy intake of gilts has been shown to increase ovulation rate, but the exact hormonal mechanism by which this phenomenon occurs is unknown. Different quantitative changes in the pituitary content of lh and fsh of gilts on high and low energy intakes were reported, however, by Kirkpatrick, Howland, First & Casida (1967). They also noted a higher progesterone content of the corpora lutea from gilts on high energy than from those on low energy intake.

Methallibure (ICI 33828) inhibits the release of pituitary lh and fsh in swine (Garbers & First, 1969). Gilts receiving the compound showed a lower level of luteal progesterone than control gilts on Day 8 but a higher level on Day 16 (Stormshak, Leverage, Kelley & Gerrits, 1970).

The present study was conducted to determine