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Biomedical subjects

J H Clark

Publications and source records attributed to J H Clark.

At least 109 records · Page 6Linked to original sources
PubMed1989

Effects of calcium carbonate on ruminal fermentation, nutrient digestibility, and cow performance.

Sixteen Holstein cows were used in a 4 x 4 Latin square design (four replicates) to investigate the effect of feeding calcium carbonate on feed intake, ruminal fermentation, apparent total tract nutrient digestibility, milk yield, and milk composition. Supplementation of calcium carbonate to diets that contained 60% concentrate and 40% corn silage (DM basis) decreased DM intake and milk production and was not effective in altering ruminal fluid pH, ruminal fluid dilution rate or outflow, molar proportions of ruminal fluid VFA, or synthesis of milk fat and milk protein by dairy cows. Calcium carbonate supplementation to the diet tended to improve efficiency of feed utilization (4% FCM/DM intake). The exact site of action of calcium carbonate, if any, is not known. However, these data suggest that calcium carbonate exerts little or no buffering effect in the rumen when the pH is 6 or above regardless of its reactivity rate in strong acid or its mean particle size. This lack of effect is probably because of its low solubility in ruminal fluid at pH above 5.5.

Animals↗
PubMed1989

Effects of prilled fatty acids and calcium salts of fatty acids on rumen fermentation, nutrient digestibilities, milk production, and milk composition.

Lactating Holstein cows averaging 193 d postpartum and fitted with rumen cannulae were used in two experiments to investigate the effects of supplementing Ca salts of fatty acids or prilled fatty acids to the diet on fermentation in the rumen, apparent total tract nutrient digestibility, milk production, and milk composition. Cows were fed ad libitum total mixed diets consisting of 45% concentrate and 55% forage. Treatments in Experiment 1 were: 1) control, 2) control plus 680 g/cow per d of Ca salts of fatty acids, 3) control plus 680 g/cow per d of prilled fatty acids, or 4) control plus 907 g/cow per d of prilled fatty acids. Treatments in Experiment 2 were: 1) control, 2) control plus 553 g/cow per d of Ca salts of fatty acids, or 3) control plus 454 g/cow per d of prilled fatty acids. Data suggest that Ca salts of fatty acids and prilled fatty acids are inert in the rumen and do not greatly alter fermentation in the rumen, apparent total tract digestibilities of DM, organic matter, ADF, NDF, and CP, or milk composition when fed at recommended amounts of 3 to 4% of the DM intake. The fact that milk production was not increased in these experiments by feeding Ca salts of fatty acids and prilled fatty acids may be attributed to the use of medium to low producing cows that were past the peak of milk production. Additional experiments are needed to obtain information about feeding these sources of supplemental fat to high producing cows during the early stages of lactation.

Animals↗
PubMed1989

Production responses of dairy cows fed various amounts of rumen-protected methionine and lysine.

A 3 x 3 factorial response surface design was used to study the effects of feeding rumen-protected methionine and lysine to dairy cows between 22 and 305 d of lactation. A total of 130 dairy cows at three universities were individually fed a corn silage and corn grain-based diet that contained either soybean meal or corn gluten meal and urea. An unsupplemented control diet plus nine treatment combinations of three amounts of rumen-protected DL-methionine (3.4, 7.8, and 12.2 g/d) and three amounts of rumen-protected L-lysine (5.9, 13.5, and 21.1 g/d) were fed at all locations. Plasma concentrations of methionine and lysine were increased when rumen-protected methionine and lysine were supplemented to the diets. Rumen-protected methionine and lysine did not affect feed intake by cows fed either by soybean meal or corn gluten meal and urea based diets. Milk protein percentage was increased, but milk and milk protein yields were not improved when diets containing soybean meal were supplemented with rumen-protected methionine and lysine. In contrast, milk and milk protein yields were improved when a diet that contained corn gluten meal and urea was supplemented with rumen-protected methionine and lysine. Health and reproduction measurements were similar for cows receiving all treatments.

Animal Feed↗
PubMed1989

Effects of source of protein and carbohydrate on ruminal fermentation and passage of nutrients to the small intestine of lactating cows.

Four early lactation multiparous Holstein cows were used in a 4 x 4 Latin square to investigate the effects of source of protein (fish meal or soybean meal) and carbohydrate (corn or barley) on ruminal fermentation, flow of nutrients to the small intestine, and animal performance. The treatments, arranged in a 2 x 2 (protein x carbohydrate) factorial were: 1) corn plus soybean meal; 2) corn plus fish meal; 3) barley plus soybean meal; and 4) barley plus fish meal. Dry matter and starch intakes were greater when corn was fed than when barley was fed. Barley-based diets were more extensively degraded in the rumen than corn-based diets and therefore provided more energy for microbial growth. However, passage of amino acids and starch to the duodenum was greater for corn-based diets than barley-based diets, because of the greater intake and lower ruminal degradability of the corn-based diets. Microbial protein constituted a larger portion of the total N and had a greater influence on the pattern and quantity of amino acids that passed to the duodenum than did protein from fish meal or soybean meal, which escaped ruminal degradation. Feeding corn-based diets increased production of milk and milk protein compared with feeding barley-based diets.

Animals↗
PubMed1988

Keratomas in horses: seven cases (1975-1986).

The diagnosis of keratoma in 7 horses and their treatment and outcome were evaluated. Horses were 2 to 20 years old, of various breeds, and were intact or castrated males. All were lame, and 6 horses had had previous injuries of the affected hoof that had not responded to prior treatments. Only 1 hoof was affected in each horse. Keratomas were beneath the hoof wall (6 horses) or sole (1 horse). Radiographically, a circular or semicircular defect with a discrete margin was present in the distal portion of the third phalanx in 3 horses. Grossly, keratomas were firm solitary masses (1.5 to 5 cm diameter); gray, tan, or yellow; and oval or conical. Keratomas were excised from beneath the hoof wall by removing a section of hoof wall (5 horses) or by undermining the wall beginning at its junction with the sole (1 horse). A keratoma beneath the sole in 1 horse was excised by excavating the sole to the level of the palmar surface of the third phalanx. Keratoma was verified microscopically by the presence of characteristic rings of squamous epithelial cells with abundant keratin. Purulent exudate and inflammatory infiltrate often were present concurrently, reflecting an associated localized infection. Aftercare included daily application of an antiseptic iodine solution and foot bandages, and shoeing with a treatment plate several weeks after surgery. Hoof and sole defects healed completely between 6 months and 1 year. By 1 year after surgery, 6 horses were sound, and keratoma had not recurred.

Animals↗
PubMed1988

Methyl p-hydroxyphenyllactate. An inhibitor of cell growth and proliferation and an endogenous ligand for nuclear type-II binding sites.

We previously described and partially characterized endogenous ligands for nuclear type II sites in normal and malignant tissues. Chromatography of these ligands on Sephadex LH-20 revealed that two peaks with binding activity (alpha and beta) could be resolved. The beta-peak component was present in all normal tissues that we examined, but not in malignant tissues, and it inhibited the growth of MCF-7 human breast cancer cells in vitro. Conversely, the alpha-peak component was found to be present in both normal and malignant tissues, and did not inhibit MCF-7 cell growth. The present studies describe the purification and identification of the alpha-peak and beta-peak components in bovine serum and an assessment of the effects of these compounds on normal and malignant cell growth. Gas chromatography-mass spectroscopy analysis of the purified beta-peak component demonstrated that the compound was methyl p-hydroxyphenyllactate (MeHPLA). Competition analysis revealed that MeHPLA binds to nuclear type II sites with a high binding affinity, while physiological levels of this compound blocked estradiol stimulation of uterine growth in vivo and inhibited the growth of MCF-7 human breast cancer cells in vitro. The alpha-peak component was found to be the corresponding acid, p-hydroxyphenyllactic acid (HPLA). This compound interacted with nuclear type II sites with a relatively low affinity and did not block uterotropic response to estradiol or inhibit MCF-7 cell growth. These studies demonstrate that HPLA and MeHPLA are ligands for nuclear type II sites and that MeHPLA may be a very important regulator of normal and malignant cell growth.

Animals↗
PubMed1988

Bioflavonoid interaction with rat uterine type II binding sites and cell growth inhibition.

Competition analysis with a number of known bioflavonoids demonstrated that these compounds (luteolin, quercetin, pelargonin) compete for [3H]estradiol binding to cytosol and nuclear type II sites in rat uterine preparations. The inhibition of [3H]estradiol binding to type II sites was specific and these bioflavonoids did not interact with the rat uterine estrogen receptor. Since estradiol stimulation of nuclear type II sites in the rat uterus is highly correlated with cellular hypertrophy and hyperplasia, we assessed the effects of these compounds on the growth of MCF-7 human breast cancer cells in culture and on estradiol stimulation of uterine growth in the immature rat. The data demonstrated that addition of quercetin (5-10 micrograms/ml) to MCF-7 cell cultures resulted in a dose-dependent inhibition of cell growth (DNA/flask). This effect was reversible by removal of quercetin from the culture medium, or by the addition of 10 nM estradiol-17 beta to these cell cultures containing this bioflavonoid. Since estradiol-17 beta (10 nM) stimulated nuclear type II sites and proliferation of MCF-7 cells, we believe bioflavonoid inhibition of MCF-7 cell growth may be mediated through an interaction with nuclear type II sites. This hypothesis was confirmed by in vivo studies which demonstrated that injection of luteolin or quercetin blocked estradiol stimulation of nuclear type II sites in the immature rat uterus and this correlated with an inhibition of uterine growth (wet and dry weight). These studies suggest bioflavonoids, through an interaction with type II sites, may be involved in cell growth regulation.

Animals↗
PubMed1988

The effect of immunization against somatostatin on growth and concentration of somatotropin in plasma of Holstein calves.

Holstein calves were used to investigate the effects of immunization procedures against somatostatin (SRIF) on growth and concentrations of somatotropin in plasma. In Trial 1, eight heifers 37 weeks of age were inoculated with cyclic-SRIF conjugated to human alpha-globulin. Final body weight, average daily gain, and measurements of body size were not significantly different between control and SRIF-immunized calves. Apparent total tract nutrient digestibilities and efficiency of feed utilization also were not significantly different between treatments. Plasma concentrations of somatotropin were increased and plasma concentrations of urea nitrogen were decreased in calves immunized against SRIF compared to controls, but these mean differences were not significant. In Trial 2, eleven bull calves seven weeks of age were inoculated with cyclic-SRIF conjugated to keyhole limpet hemocyanin. Calves immunized against SRIF had larger average daily gains (P less than .06) than did control calves. Body size, efficiency of feed utilization, and concentrations of somatotropin in plasma were not significantly different for SRIF immunized calves and control calves. Urea nitrogen in plasma was lower (P less than .04) for calves immunized against somatostatin than for control calves. Data indicate that Holstein calves can produce auto-antibodies against SRIF; however, additional research will be required before such immunization techniques can be effectively used to improve weight gains in cattle.

Animals↗
PubMed1988

Effects of abomasal or intravenous administration of arginine on milk production, milk composition, and concentrations of somatotropin and insulin in plasma of dairy cows.

Holstein cows just past peak lactation were used in a 3 x 3 Latin square design to determine the effects of arginine infusion on concentrations of somatotropin and insulin in plasma, milk production, and milk composition. Treatments were: 1) control; 2) arginine injection into jugular vein, and 3) arginine infusion into abomasum. Concentrations of arginine and ornithine in plasma were increased by injection of arginine into the jugular vein compared with the control. The concentration of ornithine in plasma was increased shortly after injection of arginine into the jugular vein, and both arginine and ornithine concentrations in plasma decreased rapidly. Abomasal infusion of arginine significantly increased concentrations of arginine, ornithine, and urea in plasma compared with concentrations in the control treatment. Injection of arginine into the jugular vein increased concentrations of somatotropin and insulin in plasma, but the increase did not persist for more than 30 min. A secondary peak in plasma somatotropin concentration occurred approximately 1 h after the initial peak. Arginine infusion into the abomasum did not alter plasma concentrations of either somatotropin or insulin. Dry matter intake, milk production, and milk composition were not affected by treatments. Lack of changes in milk production and milk composition suggest that acute increases in somatotropin with concomitant increases in insulin are not sufficient to stimulate synthesis of milk and milk components by cows during established lactation.

Abomasum↗
PubMed1988

Effects of feed intake and sodium bicarbonate on milk production and concentrations of hormones and metabolites in plasma of cows.

Eight Holstein cows were used to investigate the effects of DM intake and sodium bicarbonate on lactational performance and concentrations of hormones and metabolites in plasma. Cows were fed a diet with or without 1.0% sodium bicarbonate (dry matter basis) in a switchback design. Four cows were fed ad libitum and four cows were fed approximately 80% of their recommended nutrient requirements by restriction of DM intake throughout the three 21-d periods. Supplementing the diet with sodium bicarbonate increased DM intake of cows fed ad libitum. There was a feed intake by sodium bicarbonate interaction for production of 4% FCM. This interaction may be explained by the difference in DM intake of cows fed ad libitum or restricted amounts of feed and supplemented with sodium bicarbonate. Cows fed restricted amounts of feed had lower milk, milk fat, milk protein, milk SNF, and milk energy yields. Restriction of feed intake increased plasma concentrations of somatotropin and nonesterified fatty acids but decreased concentrations of insulin, triidothyronine, thyroxine, glucagon, and prolactin. In contrast, feeding supplemental sodium bicarbonate did not affect concentrations of hormones or metabolites in plasma at either feed intake.

Animals↗
PubMed1987

Serum beta-carotene, retinol, and alpha-tocopherol levels during mineral oil therapy for constipation.

Twenty-five children with chronic constipation underwent serial monitoring of serum beta-carotene, retinol (vitamin A1), and alpha-tocopherol (vitamin E) levels during mineral oil therapy. Mineral oil was administered between meals. Patients were monitored for up to four months of therapy. Mean serum beta-carotene levels fell from 1.0 +/- 0.5 mumol/L (55.7 +/- 26.0 micrograms/dL) to 0.7 +/- 0.4 mumol/L (35.9 +/- 22.1 micrograms/dL) after the first month of mineral oil therapy and remained depressed throughout the remainder of the study. Serum alpha-tocopherol levels remained unchanged throughout the observation period. There was a modest increase in serum retinol levels during the study, especially after three months (from 1.48 +/- 0.84 mumol/L [42.3 +/- 24.1 micrograms/dL] to 2.22 +/- 0.77 mumol/L [63.5 +/- 22.1 micrograms/dL]). We conclude that while a short course of mineral oil can induce a reduction in the serum level of beta-carotene, the treatment has no adverse effect on serum levels of retinol and alpha-tocopherol.

Adolescent↗
PubMed1987

Fluorescence properties of allophycocyanin and a crosslinked allophycocyanin trimer.

Data on the wavelength and temperature dependence of both time-resolved and steady state fluorescence emission are presented for allophycocyanin (AP) and for a crosslinked allophycocyanin trimer (XL-AP) (Ong LJ and Glazer AN: Physiol Veg 23:777-787, 1985). AP dissociates at high dilution and is not stable above 40 degrees C even at moderate protein concentration. In contrast, XL-AP does not dissociate even at very low protein concentrations and is completely stable up to 60 degrees C in the presence of 0.75 M NaK-phosphate, pH 7.0. The results show that XL-AP is superior to AP for use in conjugates that absorb and emit in the red region of the spectrum. The high stability of XL-AP at elevated temperatures at high phosphate concentrations suggests that this derivative may be useful in conjunction with nucleic acid probes.

Computers↗
PubMed1987

Triphenylethylene antiestrogen binding sites (TABS) specificity.

The relative binding affinities (RBA) of various compounds for the triphenylethylene antiestrogen binding sites (TABS) were examined. The ability of tamoxifen to inhibit the binding of [3H]tamoxifen to salt extracted (0.4 M KCl) TABS from rat liver nuclei was used as a standard by which other compounds were compared (tamoxifen RBA, 100; Kd approximately 1 nM). Nafoxidine was the most effective triphenylethylene compound used (RBA 333; Kd approximately 0.3 nM) whereas the RBA of zuclomiphene and enclomiphene was not different from tamoxifen. MER-29 was the weakest inhibitor of the triphenylethylene derivatives (RBA 10; Kd approximately 10 nM). Trifluoperazine, chlorpromazine and the anti-calmodulin drugs W-13 and W-12 had RBA's of 25, 1, 1 and 0.1 respectively. The binding affinities of cholesterol and 7-ketocholesterol were significant (Kd approximately 22 nM) while the steroid hormones, estradiol, testosterone, progesterone and corticosterone displayed not observable affinity. Various compounds obtained from Merrill Dow Pharmaceuticals and the Eli Lilly Company which contained alklaminoethoxy side chains linked to aromatic ring structures had RBA's ranging from 1-0.3. We conclude, as other investigators have also concluded, that the similar binding affinities of various triphenylethylene antiestrogens for TABS and their divergent activities as antiestrogens makes it unlikely that TABS are directly involved in estrogen antagonism. The moderate but significant affinity of TABS for trifluoperazine and other drugs thought to be involved in calmodulin regulation indicates that TABS may be a linked in some way to calmodulin function. The binding of cholesterol and 7-ketocholesterol is also significant and may indicate that TABS are involved in cholesterol metabolism.

Animals↗
PubMed1987

Cytosol type II sites in the rat uterus: interaction with an endogenous ligand.

Previous studies from our laboratory demonstrated that normal, but not malignant tissues, contain a ligand which competes for [3H]estradiol binding to nuclear type II sites in the rat uterus. Since elevated nuclear levels of type II sites are correlated with estrogen stimulation of uterine growth and DNA synthesis, we believe this ligand may regulate cell growth. The present studies show that the ligand for nuclear type II sites also interacts with type II sites in uterine cytosol. This was demonstrated by dilution experiments which show that greater quantities of type II sites are measured in dilute (10 mg/ml) than in concentrated (40 mg/ml) uterine cytosol. Furthermore, stripping of uterine cytosol with 1% dextrancoated charcoal, or pre-binding cytosol type II sites to hydroxylapetite (HAP) prior to binding analysis, removed the ligand from these preparations such that high levels of type II sites were measured. Following charcoal stripping, cytosol type II sites demonstrated good specificity for estrogenic hormones but not progesterone, corticosterone, or the triphenylethylene anti-estrogen, nafoxidine. Since the level of type II sites in the cytosol always preceded and exceeded the level of this site measured in uterine nuclei at all times following estrogen treatment (0-96 h), we believe cytosol type II sites may function as an type II-ligand binding protein (LBP) which regulates the availability of the ligand for interaction with nuclear type II sites. This is consistent with our observation that type II sites are not depleted from uterine cytosol by estrogen treatment and nuclear type II sites are very tightly associated with the nuclear matrix.

Animals↗
PubMed1987

Structure-function properties of the chicken progesterone receptor A synthesized from complementary deoxyribonucleic acid.

The chicken progesterone receptor (PR) cDNA has been cloned and sequenced in our laboratory. Functional receptor A was synthesized from cDNA in two independent systems, by transient transfection of receptor-negative COS M6 cells and by in vitro transcription and translation. These receptors exhibited DNA and hormone binding properties similar to the native PR from oviduct. The ability of receptor to induce target gene transcription was measured by cotransfection of receptor-negative CV-1 cells with expression vectors containing the receptor A cDNA and a progesterone-inducible promotor linked to the chloramphenicol acetyl transferase (CAT) gene. In these assays, receptor A produced hormone-dependent induction of CAT activity. In order to define the functional domains of receptor A, expression constructs coding for C-terminal deletion proteins were prepared. Deletion of the C-terminus resulted in loss of hormone binding activity as well as a loss of CAT induction. However, when 290 amino acids were removed from the C-terminus, this severely truncated receptor protein produced hormone-independent target gene activation. Mutant receptor proteins which retained the highly conserved cysteine-rich (C1) region were able to bind to DNA-cellulose, although removal of 290 amino acids from the C-terminus resulted in reduced affinity for DNA. Deletion of part or all of the C1 region resulted in loss of both DNA-binding and transcriptional activation capacities. These results confirm that C1 functions in DNA binding and transcriptional activation and that hormone binding activity can be localized to the C-terminal half of the protein.

Animals↗