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Biomedical subjects

M B Wheeler

Publications and source records attributed to M B Wheeler.

108 records · Page 6Linked to original sources
PubMed1989

Capacitation of bovine spermatozoa by lysophospholipids and trypsin.

Bovine spermatozoa were incubated in vitro with lysophosphatidylserine (LPS), lysophosphatidylcholine (LPC), lysophosphatidylethanolamine (LPE), lysophosphatidylinositol (LPI), or trypsin. Capacitation of sperm was evaluated by penetration of the zonae pellucidae of dead bovine oocytes. Capacitation times could be shortened to 3 h or less by treatment of spermatozoa with each of these lysophospholipids (LPLs) (P less than .05). The maximum oocyte penetration percentages for individual LPLs were 40% for 10 microM LPS. 24% for 160 microM LPC, 31% for 320 microM LPE, and 19% for 320 microM LPI. Capacitation also was facilitated (P less than .01) by trypsin treatment of spermatozoa. Spermatozoa treated with 250 or 2,500 units/ml of trypsin penetrated more oocytes (17 and 18%) than spermatozoa treated with 0 or 25 units/ml of trypsin (0 and 3%). Spermatozoa treated with increasing concentrations of LPL showed a decrease in both the percentage of intact acrosomes and of progressively motile spermatozoa. Increasing levels of trypsin in the incubation medium also led to a decrease (P less than .05) in the percentages of intact acrosomes and a decrease (P less than .01) in the percentages of progressively motile spermatozoa. Percentages of live, ovulated oocytes fertilized by spermatozoa incubated for 1 h in LPS (86%, 6/7) were not different from those incubated for 24 h in control medium (71%, 5/7). Percentages of oocytes fertilized with both of these capacitation treatments were higher (P less than .05) than for oocytes exposed or killed or uncapacitated sperm. Rapid induction of capacitation and the acrosome reaction can be accomplished by exogenous treatment of bovine sperm with lysophospholipids or trypsin.

Animals↗
PubMed1989

Risk evaluation for bovine embryo transfer services using computer simulation and economic decision theory.

A mathematical model was used to evaluate the dynamics and risks in bovine embryo transfer. Variables included embryo collection, fertilization, and transfer rates, plus overall pregnancy rates. Decision analysis was applied to three sets of 500 simulated flushes to test three strategies: 1) nonsuperovulation, 2) superovulation using follicle stimulating hormone (FSH) and 3) superovulation using pregnant mare serum gonadotropin (PMSG). Model validation involved comparing model performance against standards derived from 39 published studies. The model's repeatability was +/- 0.10 against standards in 93% of cases, and never exceeded +/- 0.13 in all 1500 simulations. Model outcomes were accurate to +/- 3% using average results. No pregnancies occurred in 22% of nonsuperovulated donors, 8% of FSH superovulated donors, and 6% of PMSG superovulated donors. PMSG treatment averaged more pregnancies per flush than FSH treatment (4.4 vs 3.9) but showed greater variation in response (64 vs 51%). Decision analysis suggests that a PMSG-induced flush would net $105 more than an FSH-induced flush, and that either superovulation strategy would yield approximately 10 times the net income of a nonsuperovulated flush. Pricing by response (PMSG) or by transfer (FSH) is optimal for the provider of embryo transfer services.

Journal Article↗
PubMed1989

Gastrin release in obese Zucker rats.

In this study, gastrin release in the obese Zucker rat was investigated by in vivo and in vitro experiments. Obese rats exhibited normal plasma gastrin levels at 3 weeks (preobese), were moderately hypergastrinemic at 3 months and severely hypergastrinemic at 5 months, compared to lean littermates. Following oral peptone, plasma gastrin levels doubled in both lean and obese rats. Basal and vagally stimulated gastrin release from perfused stomachs was greater in obese compared to lean rats and atropine had no effect on basal gastrin release in either group. Basal somatostatin release from the perfused stomach was found not to differ in both groups of animals. Morphological studies revealed an increase in the number of gastrin-containing G-cells in adult obese rats compared to lean littermates, but not in 3-week-old pups compared to lean littermates, indicating a strong correlation between cell number and plasma gastrin levels. These data indicate that the obese Zucker rat exhibits fasting hypergastrinemia in vivo, a condition which appears after weaning and increases in severity with age. Gastrin hypersecretion persists from the vascularly perfused stomach preparation. The basal hypergastrinemia of the obese Zucker rat is independent of a hyperactive postganglionic cholinergic drive but is associated with and probably causally related to an increase in antral G-cell numbers.

Animals↗
PubMed1989

Purification of three forms of chromatographically distinct protein kinase C from the swine ovary.

A calcium-sensitive, lipid-dependent protein kinase (protein kinase C) modulates physiological function in a variety of cells. In certain tissues, multiple forms of this key regulatory enzyme exist. To examine the nature of ovarian protein kinase C, swine luteal cytosol (1000 mg protein) was applied and eluted from DE-52 cellulose. The pooled active fractions were sequentially purified further by threonine- (TS) and phenyl-Sepharose (PS) affinity chromatography in a buffer of 20 mM Tris, 0.5 mM EDTA, 0.5 mM EGTA, 5 mM dithiothreitol and 250 micrograms/l leupeptin. Protein kinase C activity was eluted with NaCl gradients of 0.075-125 M (DE-52), 0.1-1 M (TS) and 0.6-0.0 M (PS). This purification scheme yielded three distinct peaks of highly purified protein kinase C activity and an overall enrichment in protein kinase C activity of approximately 1000-fold. Inasmuch as control of steroidogenesis or peptide hormone production in the ovary via the Ca2+-protein kinase C pathway could occur at several different levels, we postulate that the demonstrated presence of isoforms of this enzyme in ovarian tissue offers a means for selective spatial and temporal compartmentalization of the endocrine stimulus with correspondingly distinct changes in cellular function.

Animals↗
PubMed1989

Facilitative actions of the protein kinase-C effector system on hormonally stimulated adenosine 3',5'-monophosphate production by swine luteal cells.

The exact nature of the interaction(s) between cAMP and calcium-sensitive phospholipid-dependent protein kinase-C effector pathways is not well understood in many tissues, including the ovary. In the present work we have evaluated the ability of protein kinase-C to modulate receptor-and nonreceptor-mediated cAMP generation in acute suspension cultures of swine luteal cells. Cells were exposed to LH (1 micrograms/ml), forskolin (100 microM), cholera toxin (1 microgram/ml), pertussis toxin (100 ng/ml), and/or phorbol ester [12-O-tetradecanoylphorbol-13-acetate (TPA)] for 0-90 min. TPA had no effect on basal cAMP accumulation, but increased (P less than 0.05) LH-, forskolin-, and cholera toxin-activated cAMP formation, with maximal facilitation at 30, 45, and 60 min, respectively. This facilitative effect was robust, as it could be demonstrated in both the presence and absence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (0.5 mM). TPA increased dose-dependent LH (0.1-1 microgram/ml)-, forskolin (3-300 microM-, and cholera toxin (0.3-10 microgram/ml)-stimulated cAMP accumulation. TPA induced a dose-dependent (0.3-30 ng/ml) increase in cAMP accumulation when incubated with the half-maximally effective (ED50) and maximally effective doses of LH (0.8 and 1 microgram/ml, respectively), forskolin (10 and 300 microM), and cholera toxin (0.2 and 3 micrograms/ml). TPA had an ED50 for this functional activation of 6.1 (67% confidence interval, 4.4-9.7) nM. The stimulatory effect of TPA could be mimicked by two synthetic diacylglycerols, 1,2-Dioctanoylglycerol and 1-oleoyl-2-acetylglycerol, but not by inactive phorbol esters. In addition, TPA augmented the stimulatory effect of pertussis toxin when combined with maximally effective doses of LH, forskolin, and cholera toxin. The stimulatory action of TPA on cAMP production was limited to endogenous cellular adenylyl cyclase. Bacterially derived adenylyl cyclase toxin isolated from Bordetella pertussis resulted in a dose-dependent increase in cAMP formation over 60 min, which was not facilitated by phorbol ester. We conclude that stimulatory coupling exists between the calcium-dependent protein kinase-C and cAMP-generating systems in swine luteal cells. This stimulatory coupling is enacted in part at the levels of both the guanine binding and the catalytic subunits of adenylyl cyclase.

Adenylate Cyclase Toxin↗
PubMed1988

Interactions of protein kinase C with receptor- and non-receptor-mediated cyclic AMP generation in swine granulosa cells.

Interactions between signal transducing systems may be important in the integrated control of cellular processes in basal and hormonally regulated cells. The swine granulosa cell provides a model to study the interactions between the cAMP and calcium-lipid-dependent signaling pathways. To this end, porcine granulosa cells were incubated in monolayer culture for 1-4 days in the presence of FSH (200 ng/ml), forskolin (85 microM), or cholera toxin (3 micrograms/ml) with or without an activator of protein kinase C, the phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) (30 ng/ml). TPA had little effect on basal cAMP generation (1-4 days) or on follicle-stimulating hormone (FSH)-stimulated cAMP formation during the first 24 h. Phorbol ester did inhibit cAMP formation on day 2 (by approximately 25%), on day 3 (by approximately 70%) and on day 4 (by greater than 80%). Forskolin-mediated cAMP generation was inhibited (33-56%) on days 1-4, respectively. TPA suppressed dose-dependent FSH (3-300 ng/ml)-stimulated cAMP production on day 2, virtually abolished FSH-provoked cAMP formation on day 4 and inhibited dose-dependent forskolin-stimulated cAMP production on both days. TPA had no effect on the half-maximally effective dose, ED50, of FSH-stimulated cAMP production but did decrease the ED50 of forskolin and the maximal stimulatory effect of FSH and forskolin on days 2 and 4. Similar effects were observed with the synthetic diacylglycerols DOG (1,2-dioctanoylglycerol) and OAG (1-oleoyl-2-acetylglycerol). The TPA effect was limited to the mammalian adenylate cyclase as it had no effect on bacterially derived adenylate cyclase from Bordetella pertussis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Zona pellucida penetration assay for capacitation of bovine sperm.

In vitro capacitation and in vitro zona penetration systems are described for bovine spermatozoa. The criterion for capacitation was penetration by sperm of either 1) the zona pellucida of dead bovine oocytes, or 2) live, intact oocytes in which subsequent development was observed. Sperm were washed free of seminal plasma by centrifugation and incubated in a modified Tyrode's medium (TALP) in a 5% CO2-air atmosphere at 38 degrees C. Dead bovine oocytes were obtained from greater than 1 mm follicles from ovaries stored at -20 degrees C. Spermatozoa at a final concentration of 10(7) ml were coincubated with the oocytes for 3 hr after capacitation treatments. Initial experiments established that: 1) dead bovine oocytes can be penetrated by bovine sperm capacitated in the rabbit reproductive tract; 2) oocytes should be used for the penetration test within 24 hr of thawing; 3) oocytes could be stored for 24 hr at 4 degrees C after penetration before evaluation; and 4) penetration of zonae pellucidae of dead bovine oocytes by sperm is species specific. The percentages of dead oocytes penetrated after incubating frozen-thawed sperm for 0, 6, 12, 24, and 30 hr prior to incubation with oocytes were 17, 24, 34 10, and 0% respectively; the corresponding percentages for fresh semen were 1, 2, 5, 42, and 25%. Addition of 1% bovine seminal plasma to suspensions of washed, capacitated sperm decreased oocyte penetration percentages from 48% for the control (no seminal plasma) to 23%. Spermatozoa capacitated in vitro for 24 hr fertilized 15 of 22 ovulated oocytes (68%) from superovulated cows. Three embryos developed to the morula stage, but no pregnancy resulted after transfer of these embryos to bovine recipients. The present results provide the basis for a reliable (interassay C.V. = 13.4%) in vitro assay system for capacitation based on sperm penetration of the zona pellucida of dead bovine oocytes.

Animals↗
PubMed1987

The effect of total parenteral nutrition (TPN) on gastrin release in the rat.

The effect of short-term (7 days) total parenteral nutrition (TPN) on gastrin release was studied in vivo and in the isolated vascularly perfused rat stomach. The daily plasma gastrin concentration of parenterally fed rats was significantly lower than in ad lib fed control animals (53 +/- 17 pg/ml vs 159 +/- 32 pg/ml, P less than 0.05) as early as day 2 and a similar pattern was observed on days 4 and 6. The fasting plasma gastrin concentration of control animals was 2-fold greater than of the parenterally fed group (P less than 0.05). Following oral peptone, the gastrin response of TPN and control animals doubled although peak gastrin levels were greatly reduced in TPN rats. Basal gastrin release from the perfused stomachs of control rats was 2-fold greater than from TPN rats (P less than 0.05). Electrical stimulation of the vagal trunks resulted in a significantly greater elevation in gastrin secretion from control stomachs compared to TPN animals (4-fold vs. 2.4-fold increase, P less than 0.05). Quantification of the antral G-cell population revealed a significant reduction in the number of G-cell of TPN rats compared to controls (97 +/- 8 cells/mm vs 76 +/- 6 cells/mm, P less than 0.05). These results indicate that luminal nutrient stimulation is necessary for the maintenance of normal G-cell secretory activity in vivo and from the in vitro stomach. G-cell hypoplasia appears to be partially responsible for reduced gastrin output to basal and stimulated conditions after TPN.

Animals↗
PubMed1987

Catalytic and receptor-binding properties of the calcium-sensitive phospholipid-dependent protein kinase (protein kinase C) in swine luteal cytosol.

We have evaluated the catalytic and receptor-binding properties of protein kinase C in swine luteal cytosol using two complementary approaches: assay of catalytic activity assessed as the enzymatic transfer of radiolabeled phosphate to histone III-s acceptor protein in the presence of specific phospholipid, diacylglycerol, or phorbol ester and ionic calcium; and, the high-affinity binding of [3H]phorbol-12,13-dibutyrate ([3H]PDB) to the protein kinase C receptor. Catalytic properties of pig luteal protein kinase C included: absolute dependence on calcium ions for maximal activation (approximate ka = 0.5 microM); synergistic activation by 1,2-sn-diolein, phospholipid and calcium ions; and rank order of specific phospholipid activational potency: phosphatidylserine greater than phosphatidic acid greater than phosphatidylinositol greater than phosphatidylethanolamine greater than phosphatidylcholine. The enzyme was also activated by specific phorbol esters at the following half-maximally effective (ED50) concentrations: 12-O-tetradecanoylphorbol-13-acetate (TPA) 11 nM; phorbol-12,13-dibenzoate (PDBe) 26 nM; phorbol-12,13-dibutyrate (PDBu) 33 nM; mezerein 65 nM; and phorbol-12,13-diacetate (PDA) 130 nM. Phorbol-ester receptor properties of protein kinase C included specific, high-affinity (kd congruent to 19 nM), saturable, low-capacity (congruent to 44 pmol/mg protein) [3H]PDB binding sites. Moreover, the rank order of the equilibrium binding ID50s for various phorbol compounds was similar to that of catalytic ED50s: viz. 3 nM TPA; 8 nM PDBe; 16 nM PDBu; 19 nM mezerein; and 590 nM PDA. Thus, swine luteal cytosol contains catalytically active protein kinase C with specific phospholipid sensitivity, synergistic activation by diacylglycerol, phospholipid and calcium, and a strict dependence on ionic calcium concentrations that is influenced markedly by the presence of diacylglycerol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Application of pattern evoked potential techniques for evaluating infant perceptual systems.

An evoked potential (EP) test was developed to aid in the diagnostic evaluation of a 16-week-old infant of initially unknown pathology and degree of perceptual deficit. Patterned stimuli were presented at two repetition rates to challenge the infant's visual and auditory information processing capabilities. The data were compared to those obtained from a "normal" infant of the same age and sex and, where possible, to normative population data. The EP data indicated the following: (1) the "suspect" infant's occipital response to visual pattern was abnormal in terms of waveform characteristics and in the relationship of its amplitude to spatial frequency of pattern; (2) in comparing brain response to 1 Hz and 6 Hz stimulation rates, the "suspect" infant's occipital EPs were abnormally attenuated for the faster presentation rate when a patterned visual display was part of the stimulus complex; (3) an auditory speech sound produced equivalent EP effects in both infants. These data indicated that the "suspect" infant's perceptual deficit was restricted to the processing of visual pattern information, possibly due to abnormal functioning of the geniculo-striate system. Subsequent tests and the diagnosis of ocular albinism corroborated the results of the abnormalities suggested by the EP procedure.

Auditory Perceptual Disorders↗
PubMed1982

Prolactin response in beef cows and heifers suckling one or two calves.

Blood was collected, at 5-min intervals for 3 h, via jugular cannulation every 14 days during the first 4 months post partum from beef cows and heifers, 4 suckling 2 calves and 4 suckling 1 calf. Calves were isolated from the dams to prevent suckling for approximately 4 h before and 2 1/2 h during sampling to obtain baseline values for prolactin, measured by radioimmunoassay. During the last 30 min of sampling, calves were allowed to suck. Milk samples were also collected at 28-day intervals from 60 females, 30 with twins and 30 with single calves. beginning 2 weeks after calving and continuing until calves were weaned at 180 days of age. No differences were observed between dams with 1 and 2 calves for baseline plasma prolactin level or for prolactin response to the suckling stimulus by 1 or 2 calves. However, milk prolactin concentration was significantly higher (P less than 0.01) for dams with 2 calves, probably reflecting the more frequent suckling that occurs with twins. Milk prolactin value in this study was not highly correlated with the post-partum interval to first ovulation from another study on these animals. It is concluded that prolactin is not significantly higher (P less than 0.01) for dams with 2 calves, probably reflecting the more frequent suckling that occurs with twins. Milk prolactin value in this study was not highly correlated with the post-partum interval to first ovulation from another study on these animals. It is concluded that prolactin is not significantly higher (P less than 0.01) for dams with 2 calves, probably reflecting the more frequent suckling that occurs with twins. Milk prolactin value in this study was not highly correlated with the post-partum interval to first ovulation from another study on these animals. It is concluded that prolactin is not the primary factor controlling the longer post-partum interval to first ovulation in beef cattle with twins.

Animals↗
PubMed1982

Postpartum ovarian function and fertility in beef cattle that produce twins.

A study was conducted to determine the effect of suckling on ovarian function and postpartum reproductive performance in beef cattle induced to produce twins by embryo transfer. This study involved 31 pluriparous Hereford, Angus and Hereford X Angus crossbred cows and 24 Hereford, Angus and Hereford X Angus crossbred heifers. Seventeen of the cows and 16 of the heifers calved twins, and the remainder produced single calves. From 45 d postpartum, the dams were exposed to three Hereford bulls until pregnancy was confirmed. The first postpartum ovulation was estimated from an increase in serum progesterone level. The interval to first postpartum ovulation was slightly, but not significantly longer for dams that calved and suckled twins than for dams that calved and suckled singles or calved twins and suckled singles (50.7 +/- 3.1, 43,5 +/- 3.4, and 37.7 +/- 5.6 d, respectively). This delay, however, did not significantly affect the number of days to conception for dams that suckled or calved twin or single calves. Once estrous cycles were initiated, the interval to conception for dams with twins was similar to that for dams with single calves. Under the management scheme used, postpartum ovulation and conception in beef heifers and cows were not significantly reduced by the production of twins.

Animals↗
PubMed1979

Developmental evaluation in congenital esotropia.

Eleven patients with congenital esotropia were tested with the Bayley Scales of Infant Development (BSID) before surgery and at two and six months after surgery. Eight patients completed all three tests and no obvious changes were found between the first and last test. Of the eight patients, two were considered developmentally normal by the BSID; three had significantly delayed mental and motor scores; one showed significant mental delay; and one had motor delay. Medial rectus muscle recessions were done bilaterally on all patients. Four required a second operation. Orthophoria was obtained in six patients.

Developmental Disabilities↗
PubMedDate not supplied

Correlation of postnatal regression of the anterior vascular capsule of the lens to gestational age.

The AVC of the lens was examined and graded at birth and prospectively at weekly intervals, in 30 preterm infants of gestational age between 27 and 34 weeks. Influence of postnatal age, postnatal nutrition, subsequent development of retinopathy of prematurity as well as intrauterine growth retardation, multiple gestation and prenatal maternal steroid administration on regression of AVC was analyzed. We conclude that examination of the AVC of the lens can reliably be used to estimate gestational age between 27th and 34th weeks, in appropriate as well as small for gestational age infants. Such an examination can be used postnatally, provided that the infant's corrected gestational age is between 27 and 34 weeks. Prenatal steroid administration, postnatal nutritional status or subsequent development of retinopathy of prematurity do not appear to be correlated with the rate of AVC regression.

Birth Weight↗
PubMedDate not supplied

Kestenbaum surgical procedure for torticollis secondary to congenital nystagmus.

The records of 48 patients with congenital nystagmus who required surgery for a significant head turn were reviewed to compare the effectiveness of the surgical techniques. Patients were omitted from the study if the last postoperative visit was less than five months following surgery, or if the surgery was for a vertical head posture. The average preoperative head turn of the 38 patients with horizontal nystagmus was 41.3 degrees with an average postoperative head turn of 11.5 degrees. The net change in head turn was 33.4 degrees. The average duration of time from surgery to final examination was four years and six months. The study was divided into six groups of patients. The first group received the Parks modification of the standard Kestenbaum procedure, the 5-6-7-8 millimeter procedure. The second group received the above procedure plus 1 mm additional surgery. The third group received another modification by Parks of 6.5-8-9-10 millimeters. The fourth group received the Calhoun and Harley modification of 40% augmentation of the original Parks recommendation, and the fifth group received 60% modification. The sixth group required more than one procedure on the horizontal recti for the abnormal head posture. The pre- and postoperative measurements are compared for each of these six groups. In some patients followed for many years, there is a tendency for a gradual return toward the preoperative head posture. In four patients in the study, the gaze preference was shifted to the opposite direction postoperatively.

Adolescent↗