Biomedical subjects

D A Freeman

Publications and source records attributed to D A Freeman.

At least 37 records · Page 2Linked to original sources

PubMed1999

Behavior of stabled horses provided continuous or intermittent access to drinking water.

OBJECTIVE: To compare quantitative measures and clinical assessments of behavior as an indication of psychologic well-being of stabled horses provided drinking water continuously or via 1 of 3 intermittent delivery systems. ANIMALS: 22 Quarter Horse (QH) or QH-crossbred mares and 17 Belgian or Belgian-crossbred mares (study 1) and 24 QH or QH-crossbred mares and 18 Belgian or Belgian-crossbred mares (study 2). PROCEDURE: Stabled horses were provided water continuously or via 1 of 3 intermittent water delivery systems in 2 study periods during a 2-year period. Continuous 24-hour videotaped samples were used to compare quantitative measures and clinical assessments of behavior among groups provided water by the various water delivery systems. RESULTS: All horses had clinically normal behavior. Significant differences in well being were not detected among groups provided water by the various delivery systems. CONCLUSIONS AND CLINICAL RELEVANCE: Various continuous and intermittent water delivery systems can provide adequately for the psychologic well-being of stabled horses.

Aggression↗

PubMed1998

Oocyte transfer in mares.

Oocytes were collected from dominant preovulatory follicles of donor mares 24 hours after administration of human chorionic gonadotropin. Oocytes were incubated in vitro for 12 or 18 hours before transfer to recipient mares, representing maturation times after human chorionic gonadotropin administration of 36 and 42 hours, respectively. Pregnancy rates after transfer were 4 of 5 in the 36-hour group and 2 of 3 in the 42-hour group. The overall pregnancy rate achieved (6/8 mares) indicated that oocyte transfer may be useful clinically.

Animals↗

PubMed1997

Internalized plasma membrane cholesterol passes through an endosome compartment that is distinct from the acid vesicle-lysosome compartment.

Cholesterol from the plasma membrane of MA-10 Leydig tumor cells is internalized into the cell and either esterified or used as substrate for steroid hormone synthesis. In the present studies we show that chloroquine and sphinganine cause LDL cholesterol and cholesteryl esters to accumulate in the cells. A lysosome fraction contained the excess cholesterol and cholesteryl esters. Both inhibitors blocked the conversion of plasma membrane cholesterol into intracellular cholesteryl esters and caused dose-dependent inhibition of dibutyryl-cAMP-stimulated progesterone synthesis. Radiolabeled cholesterol applied to the plasma membrane of MA-10 cells accumulated in the lysosome fraction of chloroquine and sphinganine-treated cells. Evidence that these inhibitors did not require the Golgi was provided by experiments using brefeldin A. Experiments utilizing a fluorescent cholesterol analogue and a lysosomal marker indicated that cholesterol entered the cells in structures that were different than the acidic vesicle-lysosome compartment. Consistent with this observation was the observation that the peak fluorescence fractions of cells subjected to density gradient centrifugation was of lower density than the lysosome fraction.

4-Chloro-7-nitrobenzofurazan↗

PubMed1997

Hormone synthesis and responsiveness of spontaneous granulosa cell tumors in (SWR x SWXJ-9) F1 mice.

Granulosa cell tumors spontaneously occur in approximately 10-25% of female (SWR x SWXJ-9) F1 mice. The present studies were designed to test whether tumor-bearing mice produce a distinct hormonal profile by which they could be identified and determine whether cultured tumor cells are responsive to hormones and growth factors that regulate normal granulosa cells. Samples of female mouse blood taken from age 3 to 10 weeks allowed estimation of serum FSH, 17beta-estradiol, and inhibin levels for normal mice and for mice destined to develop tumors. These studies indicated that FSH and 17beta-estradiol values differed between normal and tumor-bearing animals, but overlapped sufficiently that such values could not accurately predict the tumor-bearing state. Inhibin concentrations did differentiate normal from tumor-bearing animals in all cases. Increased levels of inhibin were observed coincident in time with visibly detectable tumors within the ovaries. Compared to inhibin synthesis in vivo, hormonal responsiveness in vitro was much more variable. Steroidogenesis was stimulated in all tumors by dibutyryl-cAMP and low-density lipoprotein (LDL). Some, but not all, tumors responded to IGF1, EGF, FSH, and hCG. In about one-half of the tumors tested, FSH could induce hCG or dibutyryl-cAMP responsiveness. IGF1 pretreatment consistently increased the responsiveness of tumor cells stimulated by dibutyryl-cAMP and LDL. Production of inhibin by isolated tumor cells was detectable and decreased by EGF or dibutyryl-cAMP treatments. We conclude that granulosa tumor cell secretion of inhibin may be under different control than secretion from normal granulosa cells and acts as an excellent marker for these tumors.

Animals↗

PubMed1997

Evidence that the circadian system mediates photoperiodic nonresponsiveness in Siberian hamsters: the effect of running wheel access on photoperiodic responsiveness.

Juvenile male Siberian hamsters from a line of hamsters selected for nonresponsiveness to short photoperiod (PNRj) and animals from the general colony (UNS) were separated at weaning into two groups. Group 1 males were moved into short days (10 h light:14 h dark [10L:14D]) with free access to running wheels (RW). Group 2 animals were the male siblings of Group 1 hamsters; they were moved at the same time into the same room, but were housed in cages without access to RW. Group 2 hamsters only had access to RW for the final week of short-day exposure (Week 8). Animals were blood sampled at the time of sacrifice for analysis of serum prolactin (PRL) and follicle-stimulating hormone (FSH) concentrations. At sacrifice, paired testis weights were obtained and pelage color was scored. Animals from the UNS line showed the expected declines in testis weight, body weight, and serum concentrations of both PRL and FSH, regardless of the presence or absence of RW. These animals also exhibited a high proportion of individuals molting to winter-type pelage. By contrast, a marked difference was noted between siblings from the PNRj line depending on whether RW access was provided at the time of weaning. Animals with access to RW exhibited identical responses to those of the UNS responder animals, whereas PNRj animals without access to RW showed no adjustments to short days (i.e., testis regression, pelage molt, expansion of alpha). In a second experiment, PNRj and UNS males were placed in constant darkness (DD), with or without RW access. The results of this experiment indicated that PNRj animals respond to DD regardless of the presence or absence of RW. In DD, PNRj hamsters also exhibited significantly longer free-running period lengths (taus) than did UNS hamsters; all the PNRj hamsters had taus > 24 h, whereas none of the UNS hamsters had a tau > 24 h. These results indicate that PNRj hamsters retain the proper neural pathways for responding to short day lengths and establish a role for locomotor activity feedback in modulating the circadian system and, subsequently, photoperiodic responsiveness in PNRj hamsters.

Activity Cycles↗

PubMed1997

Photoperiod nonresponsive Siberian hamsters: effect of age on the probability of nonresponsiveness.

Groups from three different breeding lines of Siberian hamsters (UNS = general colony animals, PNRa = selected for photoperiod nonresponsiveness as adults, PNRj = selected for photoperiod nonresponsiveness as juveniles) were exposed to short days at weaning and again as adults (Experiment 1) or only as adults (Experiment 2). The proportion of photoperiod nonresponsive individuals in each line was determined by measuring testis length after 6 weeks of exposure to short days (juveniles) or by paired testis weights after 12 weeks in short photoperiod (adults). Adults were blood sampled on the day of sacrifice (Experiment 1) or on Weeks 3, 4, 5, 6, 8, 10, and 12 (Experiment 2) for determination of serum prolactin (PRL) and follicle-stimulating hormone (FSH) concentrations. Nonresponsive individuals were present in all three lines of hamsters. Furthermore, all three lines of hamsters showed an increase in the proportion of nonresponders with age; some individuals are responsive to short days as juveniles, but become nonresponsive in adulthood. The two PNR lines exhibited a greater proportion of nonresponders at both ages compared to the UNS line, with the PNRj line exhibiting the greatest proportion of nonresponders at each age. During exposure to short days, nonresponders exhibited significantly higher serum PRL and FSH concentrations that did the UNS line; nonresponders also exhibited larger testis size, and fewer animals molted to winter-type pelage. The results indicate that (a) in all three lines, a significantly higher proportion of animals are nonresponsive to short photoperiod as adults than as juveniles; (b) selection for nonresponsiveness as juveniles can produce a line of hamsters that, as adults, are nearly all nonresponsive to short days; and (c) some individuals from each line are responsive to short photoperiod early in life, but become nonresponsive as adults.

Aging↗

PubMed1997

Photoperiodism in hamsters: abrupt versus gradual changes in day length differentially entrain morning and evening circadian oscillators.

In studies of photoperiodism, animals typically are transferred abruptly from a long (e.g., 16 h light per day [16L]) to a short (8L) photoperiod, and circadian oscillators that regulate pineal melatonin secretion are presumed to reentrain rapidly to the new photocycle. Among rats and Siberian hamsters, however, reentrainment rates vary depending on whether additional darkness is added to morning or evening, and a subset of hamsters (nonresponders) fails ever to reentrain normally to short photoperiods. The authors assessed whether several short-day responses occurred at different rates when darkness was extended into morning versus evening hours and the effectiveness of abrupt versus gradual shortening in day lengths (DLs). Entrainment patterns of photoresponsive hamsters also were compared to those of photononresponsive hamsters. Responsive hamsters transferred on a single day from 16L to 8L underwent more rapid gonadal regression, weight loss, decreases in follicle-stimulating hormone titers, and expansion of nocturnal locomotor activity when darkness was added to morning versus evening. When the dark phase was extended gradually by 8 h over 16 weeks, short-day responses occurred at the same rate whether darkness was appended to morning or evening or was added symmetrically. Darkness added to evening promoted more rapid short-day responses when it was added gradually rather than abruptly, despite the fact that average DLs were significantly shorter for the latter group. Among nonresponders, morning extensions of darkness transiently increased activity duration, whereas evening extensions did not. Gradual and abrupt decreases in DL differentially affect entrainment of evening and morning circadian oscillators. The authors argue for the incorporation of simulated natural photoperiods in studies of photoperiodism.

Animals↗

PubMed1997

The use of alternate-day lovastatin in hypercholesterolemic men.

OBJECTIVE: To quantitate the therapeutic effects of alternate-day lovastatin on serum lipoprotein values in a small group of men with primary hypercholesterolemia. DESIGN: Retrospective review of medical, pharmacy, and laboratory records. A paired Student's t-test was performed on absolute changes in lipoprotein values with an a priori p value less than or equal to 0.05 being statistically significant. SETTING: A lipid clinic within a tertiary care Department of Veterans Affairs Medical Center. PATIENTS: Twenty men (mean age 62.5 +/- 8.3 y) with mean +/- SD baseline low-density lipoprotein cholesterol (LDL-C) concentration of 161.3 +/- 21.9 mg/dL and triglyceride concentrations below 400 mg/dL. INTERVENTION: All patients had been prescribed lovastatin 20 mg every other day. MAIN OUTCOME MEASURES: The mean absolute and percent changes in lipoprotein values from baseline for patients receiving lovastatin 20 mg every other day and the percentage of patients attaining a target mean LDL-C concentration as defined by the National Cholesterol Education Panel Adult Treatment Panel II guidelines. RESULTS: Mean +/- SD total cholesterol and LDL-C were significantly reduced by 32.4 +/- 17.8 (14.0% +/- 7.8%) and 34.1 +/- 14.6 mg/dL (21.5% +/- 9.7%), respectively. No significant changes were seen in high- density lipoprotein cholesterol or triglycerides. Four of 20 patients (20%) attained a goal LDL-C concentration. CONCLUSIONS: Lovastatin 20 mg every other day may effectively lower LDL-C in some elderly men, and target LDL-C concentrations may be obtained in some patients.

Aged↗

PubMed1997

Adrenal carcinoma.

Explore the source record for details and available documents.

Adrenal Gland Neoplasms↗

PubMed1996

Alpha-tocopherol, selenium and polyunsaturated fatty acid concentrations in the serum and feed of spring-calving dairy heifers.

The objectives of this study were to provide baseline data for alpha-tocopherol, selenium and polyunsaturated fatty acid concentrations in the serum and feed of New Zealand dairy cattle, and to assess the likelihood that abnormal peroxide metabolism has a role in the impaired lactational and reproductive performance noted in selenium-deficient cattle. Twenty-four Friesian heifers were randomly allocated one of four winter diets consisting of hay with or without selenium supplementation, or pasture and silage with or without selenium supplementation. A winter diet consisting exclusively of hay (alpha-tocopherol concentration 19 mg/kg of dry matter) resulted in a pre-calving serum alpha-tocopherol concentration of 1.2 mg/l compared to 4.5 mg/l for pastured heifers (p<0.01). The pre-calving alpha-tocopherol concentration for the heifers fed hay fell into the range considered deficient (<2.0 mg/l), whereas heifers fed pasture and silage remained in the range considered adequate throughout the study period. Serum fatty acid concentration, and the proportion of fatty acids that were polyunsaturated, were lowest in the hay-fed heifers before calving (1.0 mg/ml, 37.1% respectively), and remained unchanged following re-introduction to pasture after calving in late July and August. Serum fatty acid concentration did not increase following the re-introduction of the heifers to pasture because of the unexpectedly low fatty acid concentration (4.8 g/kg of dry matter) of the mature winter pasture. In October, however, the proportion of fatty acids in serum that were polyunsaturated increased (50%) as did serum cy-tocopherol concentrations (greater than 13 mg/l). Mean serum selenium concentrations in the unsupplemented heifers ranged from 139 to 204 nmol/l, being lowest in October (p<0.01). Supplementation with intraruminal selenium pellets (two pellets delivering about 3 mg of selenium/day) increased serum selenium concentration and glutathione peroxidase activity (p<0.01) whereas the type of winter diet had no effect (p>0.05). These results suggest that dairy cattle wintered on hay can become Vitamin E-depleted, whereas the feeding of pasture and silage should provide adequate Vitamin E. The pasture offered following calving during July and August provided a low dietary polyunsaturated fatty acid challenge, suggesting that abnormal peroxide metabolism is unlikely to be an important mechanism in the impaired performance of selenium-deficient adult cattle which calve at this the of year.

Journal Article↗

PubMed1996

Constitutive steroidogenesis does not require the actions of cAMP on cholesteryl ester hydrolysis or internalization of plasma membrane cholesterol.

The R2C Leydig tumor cells demonstrate constitutive steroidogenesis as well as the constitutive production of the steroidogenic acute regulatory peptide (StAR). Since the introduction of StAR into cells does not by itself reproduce the steroidogenic response of cAMP, the present studies were designed to determine whether processes normally stimulated by cAMP in responsive cells were maximally, constitutively expressed in the R2C cells. Measurements of cholesteryl ester hydrolytic rate and plasma membrane cholesterol internalization revealed that both processes are stimulated by dibutyryl-cAMP in R2C cells. The effect of cAMP on these processes was of the same magnitude as that detected in hormonally responsive cells. Thus, in R2C cells the unstimulated basal rate of either process was sufficient to maintain maximal stimulation of steroidogenesis.

Bucladesine↗

PubMed1996

The pharmacokinetics of salicylate in dairy cattle are not altered by simultaneous intravenous ceftiofur sodium and DL-lysine-acetyl salicylate (aspirin).

This study evaluated potential alterations to the pharmacokinetics of salicylate by concurrently administered ceftiofur sodium. The trial design was a cross-over using 10 non-lactating, non-pregnant dairy cows. In the first period each cow received intravenously (i.v.) 26 mg/kg of DL-lysine acetyl salicylate (aspirin) followed immediately by 2 mg/kg ceftiofur sodium. In the second period each cow received 26 mg/kg of aspirin i.v. Plasma samples were harvested for determination of salicylate concentration by HPLC. The data best fitted a single compartment open model, using weighted non-linear regression. No alterations to the pharmacokinetic parameters of salicylate in cattle by concurrently administered ceftiofur sodium were detected (P < 0.05). Using 90% confidence intervals, and testing for changes of > 20%, control values, elimination half-life (t1/2), apparent volume of distribution (Vd), area under the plasma concentration versus time curve (AUC) and mean residence time (MRT) were not altered. For control animals the elimination rate constant (k(el)) and total body clearance (Cl) were 1.35 +/- 0.43 h-1 and 20.2 +/- 6.1 ml/h.kg respectively (mean +/- SD). Since ceftiofur sodium did not affect the pharmacokinetics of salicylate, dose regimens for aspirin in cattle need not be altered when ceftiofur sodium is administered concurrently.

Animals↗

PubMed1996

Effect of alkaloids in cigarette smoke on human granulosa cell progesterone synthesis and cell viability.

Inhibition of corpus lutea progesterone synthesis by alkaloids in cigarette smoke might, in part, explain the generally poorer outcome of pregnancy in women who smoke. The present experiments evaluated the effects of alkaloids in cigarette smoke on progesterone biosynthesis and cell viability. Studies were initiated using primary cultures of human granulosa cells. Incubation of the granulosa cells with nicotine, cotinine, anabasine, the combination of nicotine, cotinine and anabasine, or an aqueous extract of cigarette smoke resulted in inhibition of progesterone synthesis. The alkaloids and smoke extract decreased the DNA content of the culture dish. These findings suggested a cytotoxic effect of the alkaloids. Growth curves conducted using the gonadotropin-responsive, progesterone-synthesizing MA-10 cell line confirmed growth inhibition by the alkaloids and smoke extract. Together, these data suggest that cigarette alkaloids inhibit cellular progesterone synthesis both by inhibiting progesterone synthesis and by causing less-specific toxic effects to the cell.

Alkaloids↗

PubMed1996

Effect of selenium and lodine supplementation on growth rate and on thyroid and somatotropic function in dairy calves at pasture.

The effects of Se and I supplementation on growth rate and on thyroid and somatotropic function were examined for heifer calves from two herds fed pasture. Supplementation of calves with intraruminal Se pellets increased the basal plasma concentration of 3,5,3'-triiodothyronine and reduced the basal plasma concentration of thyroxine for both herds. For one herd, supplementation with Se increased the triiodothyronine response to challenge with thyrotropin-releasing hormone, increased BW gain, and tended to increase the plasma concentration of IGF-I. The plasma concentration of growth hormone was unaffected by Se supplementation. Supplementation with I increased the response of thyroid hormones to thyrotropin-releasing hormone but did not increase BW gain. Interaction between Se and I treatment within the herds was not apparent for any outcome variable. These data suggest that the effects of Se deficiency in grazing calves may be mediated by alterations in thyroid hormone metabolism but apparently are not mediated through modulation of the peripheral concentration of growth hormone.

Animals↗

PubMed1995

Diethylumbelliferyl phosphate inhibits steroidogenesis by interfering with a long-lived factor acting between protein kinase A activation and induction of the steroidogenic acute regulatory protein (StAR).

Diethylumbelliferyl phosphate (DEUP) is an organophosphate cholesteryl ester hydrolase inhibitor that blocks steroidogenesis mainly by preventing cholesterol transport into the mitochondria of steroidogenic cells. In the present study, we show that DEUP blocks the cAMP-stimulated mitochondrial accumulation of the 30-kDa mitochondrial proteins (recently named steroidogenic acute regulatory StAR proteins) that are believed to be the cycloheximide-sensitive factors induced by trophic hormones and cAMP. Inhibition of mitochondrial StAR accumulation by DEUP is dose dependent and closely parallels inhibition of progesterone synthesis. Stimulated lactate production, another cAMP-dependent process in MA-10 cells, is also inhibited by DEUP. Inhibition of protein kinase A (PKA) action would explain the inhibition of these two unrelated processes. However, the cytosolic PKA activity of DEUP-treated MA-10 10 cells was normal. Moreover, the activity of purified PKA was unaffected by DEUP. The inhibition of StAR synthesis was not caused by a direct effect of DEUP on the labile proteins since DEUP-treated cells required more than 24 h to recover steroidogenic capacity after DEUP treatment. Further evidence that the synthesis of StAR was not directly affected was obtained using the constitutively active R2C cells. Progesterone synthesis by these cells also involves StAR, but neither StAR synthesis or steroid synthesis is sensitive to DEUP. Lactate formation in dibutyryl-cAMP-stimulated R2C cells is, however, sensitive to inhibition by DEUP. These data can be best explained by DEUP acting on a long-lived factor involved in the cAMP/PKA response pathway, but not involved in constitutive steroidogenesis.

Animals↗

PubMed1995

Immunohistochemical localization of pregnancy-related placental protein 4 in human placenta, umbilical cord and adult human female genital tissues.

Placental protein 4 (PP4) is a soluble placental tissue protein which was isolated from human placenta. The aim of the present study was to demonstrate the localization of cells containing PP4 in human placenta and in various female genital tissues under normal conditions. PP4 immunoreactive structures were demonstrated by using the peroxidase-antiperoxidase immunohistochemical technique. The samples were obtained from normal human placenta, umbilical cord, uterine cervix, endometrium, ovary and vulva. The most differentiated trophoblastic cells, the syncytiotrophoblasts, as well as the intermediate trophoblast cells contained PP4. PP4 immunoreactivity was present in umbilical cord as well. Occasionally PP4 was detected in normal ovarian, endometrial or vulvar tissue samples. Cervix and myometrium were free of PP4 immunoreactive material. PP4 staining was cytoplasmic. Our findings indicate that PP4 cannot be considered specific for the placenta since it is present in some human adult tissues as well.

Annexin A5↗

PubMed1995

The effects on the pharmacokinetics of intravenous ceftiofur sodium in dairy cattle of simultaneous intravenous acetyl salicylate (aspirin) or probenecid.

Ceftiofur sodium is a third-generation cephalosporin antibiotic. It is possible that non-steroidal anti-inflammatory drugs such as acetyl salicylate (aspirin) may be used concomitantly with ceftiofur sodium in dairy cattle. Therefore this study evaluated potential pharmacokinetic interactions between ceftiofur sodium and aspirin. In addition, this study evaluated the potential for interaction between ceftiofur and its active metabolites and the organic anion transporter. The organic anion transporter substrate used in this evaluation was probenecid. Ten healthy, non-pregnant, non-lactating dairy cows were used in a randomized complete three-way crossover design. In repeated experiments all cows were administered: (1) 2 mg of ceftiofur sodium per kg body weight by intravenous bolus or (2) 10 mg of probenecid per kg body weight by intravenous bolus, followed immediately by 2 mg of ceftiofur sodium per kg body weight by intravenous bolus or (3) 26 mg of aspirin per kg body weight by intravenous bolus, followed immediately by 2 mg of ceftiofur sodium per kg body weight by intravenous bolus. For treatment with ceftiofur sodium alone, the mean volume of distribution at steady-state Vd(ss) was 0.2 +/- 0.06 L/kg, the mean volume of distribution by the area method Vd(area) was 0.38 +/- 0.22 L/kg, mean residence time (MRT) was 6.5 +/- 1.8 h, mean residence time in peripheral tissues (MRTp) was 2.6 +/- 1.0 h, total body clearance (Cl) was 0.032 +/- 0.013 L/kg/h and elimination rate constant (beta) was 0.097 +/- 0.044 h-1 (mean +/- standard deviation). No statistically significant changes were detected as a result of preceding treatment with aspirin.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1994

Factors underlying the variability of lipid droplet fluorescence in MA-10 Leydig tumor cells.

Neutral lipids accumulate in cellular lipid droplets. These droplets vary remarkably in number and amount between cells. In the present studies, the variability in lipid content was quantified by comparing the coefficient of variation of fluorescence histograms of nile red lipid-stained cells to the variability of cell size or cell protein distributions. This measure of lipid droplet variability persisted through a wide range of cell lipid content and averaged 4.4-fold more variability than cell size and 2.6-fold more variability than cell protein content. While looking for possible explanations for this variability, it was determined that cell to cell variability could not be explained by multiple clonal populations of cells or the confluence of the cell monolayer. Analysis of lipid variability using a more droplet-specific fluorescent dye, bodipy, reduced variability by about 44%. Cell cycle analysis revealed that G2 + M cells contained more lipid than S-phase cells, which in turn contained more lipid than G0 + G1 cells, but that variability was equally large throughout the cell cycle. The cholesteryl ester hydrolase inhibitor, diethylumbelliferyl phosphate, inhibited hydrolysis of both cholesteryl esters and triglycerides. Lipid content of diethylumbelliferyl phosphate-treated cells increased while the variability in lipid staining decreased by an average of 72%. Thus, the excess lipid fluorescence variability compared to cell size or protein fluorescence could in part be explained by variability in cellular hydrolysis of triglyceride and cholesteryl ester. Excess lipid fluorescent variability could be reduced by an average of 44% when a more lipid droplet-specific stain was used instead of nile red.

Animals↗