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Biomedical subjects

P A Gentry

Publications and source records attributed to P A Gentry.

At least 37 records · Page 2Linked to original sources
PubMed1996

Fibronectin concentrations correlate with ovarian follicular size and estradiol values in equine follicular fluid.

The amounts of total protein, albumin, fibronectin, alpha 2-macroglobulin (alpha 2-M), immunoglobulin G, ceruloplasmin and antithrombin were determined in fluids collected from 53 preovulatory equine follicles and compared with the contents of estradiol-17 beta, progesterone and androstenedione, with follicle size and the amounts of the equivalent proteins in normal equine plasma. The concentration of fibronectin and the fibronectin/albumin ratios increased significantly with follicle size and with follicular estradiol levels. The alpha 2-M levels and alpha 2-M/albumin ratios correlated with follicle size but not with hormone content. Both fibronectin and alpha 2-M were present in lower amounts in follicular fluid compared with plasma while the other proteins were present in similar amounts. Among the proteins evaluated, there was a positive correlation between the amount of the protein in the follicular fluid and the molecular weight of the protein.

Albumins↗
PubMed1996

Modulation of bovine platelet function by C-reactive protein.

The addition of C-reactive protein (CRP) to bovine platelets suspended in homologous plasma consistently produced a reversible aggregation response following stimulation with either platelet activating factor or adenosine diphosphate while untreated control samples exhibited irreversible aggregation. This deaggregation response was independent of the amount of CRP incorporated into the platelet aggregates but did appear to be mediated through a component either present in bovine plasma or loosely bound to the exterior platelet membrane. The aggregation response of bovine platelets, separated from plasma by gel-filtration, was not affected by the addition of CRP to the platelet suspensions. It is proposed that one of the physiological actions of bovine CRP is to modulate platelet function.

Animals↗
PubMed1996

Plasminogen activator activity in the bovine oocyte-cumulus complex and early embryo.

In this study fibrinolytic assay systems were used to assess the plasminogen activator (PA) potential and plasmin generating ability of oocyte-cumulus complexes isolated from preovulatory bovine follicles (2-8 mm diameter) and of fertilized oocytes from the day of fertilization up to, and including, the hatched blastocyst stage (day 12). During embryo development, the culture medium was changed every 24 hr and samples examined for PA activity. Irrespective of the stage of maturity, no plasminogen or PA could be detected in unfertilized oocytes from which the cumulus layer had been removed. Both plasminogen and PA were found in the cumulus layer indicating that this, rather than the oocyte, was the source of these proteins in the oocyte-cumulus complex. Following oocyte fertilization, no PA activity was detected in either the developing embryo or in the culture medium before day 7. When the embryos had developed to the expanded blastocyst stage, days 7-8, PA production began with activity being detected in both the embryos and their culture medium. Between days 8 and 12, when embryos had reached the hatched blastocyst stage, the PA activity had increased significantly (p<0.05). Analysis of the culture media confirmed this increase in production of PA activity and, based on zymography, it was estimated that the molecular weight of the PA was 78 k daltons.

Animals↗
PubMed1995

The hemostatic profile of equine ovarian follicular fluid.

The coagulation factors VII and X and fibrinogen were detected in equine ovarian follicular fluid. The amounts of fibrinogen and factor X were approximately 40 percent of that found in normal equine plasma while the level of factor VII was lower, at approximately 14 percent. The addition of human recombinant tissue factor caused fibrin formation in the follicular fluid. The thrombin generating activity appears to be confined to the tissue factor pathway since no activity associated with factors VIII:C, IX or IX was detected. Fibrinolytic activity, at higher levels than that found in plasma, was detected in all follicular fluid samples. It is proposed that the hemostatic mechanism may be modulated in follicular fluid in a manner analogous to that in plasma since inhibitory proteins including AT-III and antiplasmin were present in the follicular fluid samples at relatively constant levels that approached those found in normal equine plasma.

Animals↗
PubMed1995

Preliminary findings of altered follicular activity in Holstein cows with coagulation factor XI deficiency.

Factor XI (F XI) deficiency is an autosomal recessive coagulopathy found in Holstein cattle. Affected animals have a 50% greater prevalence of repeat breeding. Therefore, several parameters describing ovarian function were studied. Daily blood sampling revealed that progesterone concentrations were slower to decline from a peak at day 16 (p < 0.01) to values less than 3 nmol/L in F XI-deficient cows (5.14 +/- 0.69 days (mean +/- SD) versus 4.05 +/- 0.63 days in control animals), resulting in an oestrous cycle length of 24.7 +/- 2.1 days compared to 22.9 +/- 3.0 days, respectively. This was not due to an alteration in the availability of prostaglandin F2 alpha (PGF2 alpha) or oxytocin (OT) involved in luteolysis. No significant differences (p > 0.05) were seen between normal (n = 7) and F XI-deficient (n = 7) cows in the peak values or the area under the curve for the pulse in 13,14-dihydro-15-keto PGF2 alpha in response to OT challenge or in the parameters describing the pulse of ovarian OT secretion after PGF2 alpha injection (n = 7 for each) between days 12 and 14. Ovulatory follicular development was assessed by ultrasound monitoring and plasma 17 beta-oestradiol values at 8-h intervals after a luteolytic injection of cloprostenol (n = 6 for each). Follicular diameter was smaller (p < 0.05) and accompanied by lower peak oestradiol values near the time of ovulation in F XI-deficient cows. The results suggest that the oestrous cycle in F XI-deficient cows is characterized by a slower process of luteolysis that may be associated with smaller follicular development.

Animals↗
PubMed1995

Hemostatic profile of bovine ovarian follicular fluid.

The hemostatic profile of bovine ovarian follicular fluid was evaluated and the levels of procoagulant, fibrinolytic, and inhibitory activity compared with plasma. The results of the prothrombin time assay and the presence of fibrinogen along with factor VII and factor X activity indicate that bovine follicular fluid possesses components of the "extrinsic" or "tissue factor" coagulation system. The absence of factor VIII:C activity, along with the extremely low levels of factors IX and XI, indicates that there is not a functional "intrinsic" coagulation pathway. The fluid derived from large follicles exhibited increased levels of factors VII and X activity and a shorter prothrombin time compared with fluid obtained from the less mature small follicles. Similar alterations in the levels of the inhibitory proteins antithrombin III and alpha 2-macroglobulin were observed. Overall the amount of antithrombin III was similar to that in plasma, the levels of fibrinogen and factor X were approximately 2-fold lower, and the levels of factor VII and factor X were approximately 10-fold lower than in plasma. The fibrinolytic activity in follicular fluid was greater than the procoagulant or inhibitory activity. Plasminogen activator activity was 5-fold higher, while both plasminogen and antiplasmin values were similar to plasma levels.

Animals↗
PubMed1994

Competency of blood coagulation in the newborn calf.

This study evaluated the haemostatic profiles of a group of 11 female and seven male calves from the day of birth until they were 60 days of age. Similar results were found for both sexes. At birth the plasma activity of the procoagulant proteins, Factors VII, VIII:C, IX, X and XI and fibrinogen were all close to the adult values. Factors VII, VIII:C and fibriogen increased transiently during the first seven days of life but the increases were not sufficient to influence routine coagulation screening assays such as the activated partial thromboplastin time and the prothrombin time. At birth, the plasma concentration of the protease inhibitor, alpha 2-macroglobulin, was approximately 50 per cent of adult values and increased slowly during the first seven days of life; the plasma concentration of antithrombin III was higher than that of alpha 2-macroglobulin. The changes in the plasma concentration of fibronectin paralleled the changes in fibrinogen and Factor VIII:C from birth to 60 days of age; the concentrations of total plasma protein and plasma albumin remained stable and within the adult ranges throughout the 60 days. The plasma concentration of glucose increased transiently during the first 48 hours after birth.

Aging↗
PubMed1994

Coagulation factor XI deficiency in Holstein cattle: expression and distribution of factor XI activity.

Factor XI (F XI) is a plasma protein that participates in the blood coagulation process. A study of the expression of F XI activity in Holstein cattle has confirmed that the inheritance of F XI deficiency is autosomal with severe deficiency in homozygotes (mean F XI level 2%, SD 1%), and partial deficiency in heterozygotes (mean F XI level 38%, SD 10%; normal mean F XI level 94%, SD 21%). In a total of 1469 males evaluated for F XI levels, 47 or 3.1% were identified as heterozygous and only one as homozygous for the disorder. In part because of the lack of a discrete distinction in the expression of F XI between heterozygous and normal animals, not all of the animals tested could be uniquely classified on the basis of the plasma F XI values. A mean F XI value of 53% (SD 7%) was found in a group of animals that were categorized as low normal/high heterozygous. If this group of cattle had been classified on the basis of the criterion used to classify human beings then these animals would have been categorized as heterozygous since the mean F XI value for proven bovine heterozygotes is approximately 20% lower than the values found in the human counterpart. Like the human form of the disease, however, there appears to be a low frequency of hemorrhagic episodes associated with F XI deficiency in cattle.

Animals↗
PubMed1992

Adrenocorticotrophic hormone fails to alter plasma fibrinogen and fibronectin values in calves but does so in rabbits.

The intramuscular administration of adrenocorticotrophic hormone (ACTH) to calves, in either a short-acting form (cosyntrophin) or a longer-acting form (ACTHAR Gel), failed to induce any alteration in circulating fibrinogen or fibronectin values, despite marked elevations in plasma cortisol concentrations. With the longer-acting ACTH, plasma cortisol was elevated for at least 12 h following treatment and induced the expected physiological response of an elevation in blood glucose. In contrast, both forms of ACTH induced marked increases (p < 0.01) in plasma fibrinogen and fibronectin when administered to rabbits. The elevation in the circulating levels of these proteins was first observed 24 h after ACTH administration, by which time plasma corticosteroid values had returned to pre-treatment values. With both ACTH preparations the increases in the circulating levels of these proteins were sustained for at least 96 h. The results suggest that, in cattle, the well-recognized increases in plasma fibrinogen values following stress are not associated with the concomitant increase in plasma cortisol. Further, the results clearly illustrate the marked species differences in the response of acute-phase reactant proteins to elevated glucocorticoids.

Adrenocorticotropic Hormone↗
PubMed1992

Trichothecene mycotoxins inhibit phosphoinositide hydrolysis in bovine platelets stimulated with platelet activating factor.

The effects of the trichothecene mycotoxins, acetyl T-2 toxin, T-2 toxin, HT-2 toxin, diacetoxyscirpenol (DAS), deoxynivalenol (DON) and T-2 tetraol on phospholipid turnover were determined in bovine platelets prelabelled with [1-14C]arachidonic acid (AA). In resting, non-stimulated platelets exposed to acetyl T-2 toxin, a marked decrease in [1-14C]phosphatidylinositol (PI) along with a marked increase in [1-14C]phosphatidic acid (PA) were observed, whereas T-2 toxin, and HT-2 toxin only induced a significant increase in [1-14C]PA. In contrast, in platelet activating factor (PAF)-stimulated platelets, the mycotoxins were found to suppress both the agonist-induced loss of [1-14C]PI and the appearance of [1-14C]PA with acetyl T-2 toxin being the most effective and T-2 toxin, HT-2 toxin, and DAS essentially equally effective. T-2 tetraol and DON did not affect phospholipid metabolism either in unstimulated or PAF stimulated platelets. The alterations in [1-14C]PI and [1-14C]PA suggest that the inhibitory toxins may activate a specific phospholipase C (PLC) in the unstimulated platelets and then impede further PLC activation in PAF-stimulated platelets.

Animals↗
PubMed1992

An evaluation of the effect of reagent modification on routine laboratory coagulation tests.

The purpose of this study was to evaluate the effect of modifying commercial reagents for the laboratory evaluation of several haemostatic parameters in normal, non-pregnant mares. The routine coagulation screening assays, namely, the activated partial thromboplastin time (APTT) and the one-stage prothrombin time (PT), and the specific coagulation assays for the determination of the biological activity of Factors VII, VIII:C and IX, are discussed.

Animals↗
PubMed1992

Evaluation of the haemostatic profile in the pre- and post parturient mare, with particular focus on the perinatal period.

Various haemostatic analytes were systematically evaluated for four months pre-partum and five months post partum in 14 healthy mares. The plasma fibrinogen concentration and both Factor VIII:C and von Willebrand factor activity showed gradual increases from mid-gestation and reached maximal, or near maximal activity at parturition. These increases were paralleled by an increase in plasma fibronectin concentration, the appearance of fibrinogen degradation products, and a modest rise in antithrombin III concentration. In contrast, the activity of Factor VII and Factor IX, and the one-stage prothrombin (PT) time and the activated partial thromboplastin (APTT) time remained relatively constant throughout the pre- and post parturient period.

Animals↗
PubMed1992

Bovine platelets retain functional activity in the presence of penicillin G.

It has been reported that antibiotics of the penicillin family impair the functional response of human, canine and lapine platelets to a broad range of agonists. In contrast, we have shown that the bovine platelet retained full functional responses to stimulation by adenosine diphosphate (ADP) or platelet activating factor (PAF) following administration of penicillin G to clinically normal cattle at 20,000 IU/kg for three days. The aggregation response to collagen was transiently reduced to approximately 50% of pretreatment values, but only while the drug was detectable in the circulation. When penicillin was added to platelet rich plasma suspensions, ADP-induced aggregation was similar to that of the control untreated platelets, while the PAF-induced aggregation response was reduced by not more than 25%. Only collagen-induced aggregation exhibited a modest dose-dependent inhibitory response in the presence of penicillin. It is postulated that the relative insensitivity of the bovine platelet to penicillin may be related to differences in postreceptor biochemical events compared to the human platelet.

Animals↗
PubMed1992

The effects of administering methylmercury in combination with ethanol in the rat.

Methylmercury (MeHg) is a potent neurotoxicant and nephrotoxicant in several animal species including humans. Although the in vivo toxicity of MeHg per se is well known, the interaction between MeHg and other pollutants and with nutritional factors is not well understood. Since ethanol (EtOH) is a widely consumed toxicant which has been shown to enhance the histopathologic effects of MeHg on renal tissues, a study was undertaken to examine the effects of the combined administration to rats of MeHg and EtOH on renal function and on mercury distribution in body tissues. Forty-eight rats were divided into 6 treatment groups of 8 rats each. Rats in groups 1, 2 and 3 were given feed ad libitum, a restricted liquid diet of 70 mL/d or distilled water orally, respectively. Rats in groups 4, 5 and 6 were given 1.5 mg MeHg/kg bw, 2.0 g EtOH/kg bw, or 1.5 mg MeHg + 2.0 g EtOH/kg bw, respectively, by oral gavage daily for 45 d. All rats except those in group 1 (ad libitum) were fed 70 mL of liquid diet/d for the entire study period. The ingestion of MeHg + EtOH in combination induced a greater increase in renal weight compared to treatment with either MeHg + EtOH alone. Only those rats given MeHg in combination with EtOH exhibited oliguria and elevated blood urea nitrogen levels. Despite this antidiuresis, urinary concentrating ability was impaired in those rats given both MeHg and EtOH. In contrast, the ingestion of MeHg by itself caused the most rapid loss of glucose in urine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Longitudinal study of haematological and biochemical constituents in blood of the Asian elephant (Elephas maximus).

1. Haematological parameters and biochemical analytes were determined in four elephants over a period of one year. 2. The haematological profile remained constant over time and was similar between animals. 3. Values for biochemical analytes were stable except for alkaline phosphatase, gamma glutamyl transferase and creatinine which rose during musth in male elephants. 4. The association of elevated enzyme levels with increased testosterone concentrations is discussed.

Alkaline Phosphatase↗
PubMed1989

Structure-function relationship of the action of T-2 toxin on bovine platelets.

The effect of the trichothecene mycotoxin, T-2 toxin, on the ultrastructure of bovine platelets was investigated. In both toxin-treated and untreated platelets, the ultrastructure of the resting bovine platelet was characterized by the absence of an extensive open canalicular system and the appearance of granules and vacuoles which frequently impinged on the outer platelet membrane. No major ultrastructural changes were produced by T-2 toxin under conditions in which the platelet aggregation response was significantly inhibited. In bovine platelets exposed to the toxin, as in untreated platelets, there is evidence of pseudopod formation, indicating that T-2 toxin does not impair the initial response of platelets to stimulation. This observation is consistent with the companion function study which showed that, while T-2 toxin can impair both the rate and extent of aggregate formation, the most dramatic change is the relative instability of the platelet aggregates that form in the presence of the toxin.

Adenosine Diphosphate↗
PubMed1989

Platelet aggregation in the Asian elephant is not dependent on thromboxane B2 production.

1. The platelet aggregation response to several known platelet agonists was evaluated in four Asian elephants. The platelets were highly responsive to stimulation with platelet-activating factor (PAF) and collagen, less responsive to adenosine diphosphate (ADP) and non-responsive to arachidonic acid, serotonin and epinephrine. 2. Arachidonic acid (1 x 10(-4) M), while inducing no aggregation, caused the release of 1248 +/- 1147 pg/ul (mean +/- SD) of thromboxane B2 (TXB2), the stable metabolite of thromboxane A2 from stimulated platelet. The addition of 1 x 10(-4) M ADP to platelets caused suboptimal aggregation and the release of only 25 +/- 10 pg TXB2/microliters. 3. The calcium channel blocker, verapamil, produced a dose-dependent inhibition of PAF-induced but not collagen-induced aggregation. The cyclooxygenase inhibitor, acetylsalicylic acid, produced no inhibition of either collagen- or PAF-induced aggregation.

Adenosine Diphosphate↗