The Effect of Prednisolone on Canine Neutrophil Function: In Vivo and in Vitro Studies

The in vivo effect of a therapeutic dose of prednisolone on canine neutrophil adherence, random migration, Chemotaxis, phagocytosis of IgG and C3b opsonized yeast cells, chemiluminescence, Fc- and CR3-receptor expression was investigated. Prednisolone was also added in vitro to neutrophils as isolated cells and in whole blood. In the in vivo study, prednisolone increased the IgG mediated ingestion of yeast cells and the number of activated neutrophils in the phagocytosis assay, while flow cytometric investigation of the IgG-receptor FcγRIII with a monoclonal antibody showed similar expression before, during and after treatment. Prednisolone also increased the ingestion of C3b-opsonized yeast cells, while the expression of CR3-receptors (CD11b CD18) measured by flow cytometry was unchanged. Chemiluminescence and the chemotactic response towards zymosan activated serum were increased, while adherence to nylon wool was decreased. The in vitro studies revealed that prednisolone had no or a dampening effect on neutrophils in cell suspensions. Adherence as well as IgG mediated ingestion was decreased at the highest prednisolone concentration (800 ng/ml) in whole blood. The present study suggests that the part of the antiinflammatory effect of corticosteroids mediated through their influence on neutrophils, besides reduced adherence, may be exerted by increased clearance of microorganisms and IgG-complexes through an elevated functional capacity.     

Effects of Calf Removal at Parturition on Postpartum Ovarian Activity in Zebu (Bos indicus) Cows in the Humid Tropics

To assess endocrine and morphological responses of ovaries to total weaning at parturition, 6 Zebu (Bos indicus) cows 5 years or older were investigated. Following parturition, blood samples were collected daily during the first month and twice weekly thereafter until day 60 to determine concentrations of progesterone (P4) and prostaglandin F2α metabolite. It took between 25 to 32 days to complete uterine involution.The prostaglandin metabolite remained elevated for a mean period of 14.2 days (range, 4-21) postpartum. Five of the animals resumed cyclicity with a short estrous cycle starting between days 7 to 34 and lasting between 7 and 14 days. No estrous behavior was recorded prior to the short estrous cycles, but subsequent normal-length estrous cycles were all preceded by signs of estrus. In the 1 animal that resumed cyclicity with an estrous cycle of normal length on day 37 (length 20 days), the cycle was preceded by estrous behavior. Progesterone concentrations reached a mean maximum of 4.8 nmol liter−1 during the short estrous cycles, and prostaglandin metabolite concentrations peaked while P4 concentrations were decreasing. P4 concentrations reached a mean maximum of 12.2 nmol liter−1 during the estrous cycles of normal length. The interval from parturition to the first estrous cycle of normal length varied between 16 and 48 days, and the length of the cycle was 18 to 22 days. Starting 2 days postpartum, ovaries from 5 of the cows were scanned by ultrasonography every second day until day 30 postpartum. Medium-sized follicles were detected between days 4 to 7 postpartum in 4 of the scanned cows that later had short estrous cycles. The time between parturition and the appearance of the first dominant follicle was 7.6 days (range 6-10 days). The interval between parturition and the appearance of the first ovulatory-sized follicle was 10.2 days (range 8-13 days). In 3 of the scanned cows this ovulatory-sized follicle ovulated. We conclude that cyclic ovarian activity in Zebu cows can start early in the postpartum period in the absence of offspring, and that short luteal phases, not preceded by estrous behavior, may play an important role in establishing normal postpartum ovarian activity.     

Pleiotrophic effects of point mutations in yeast tRNA(Asp) on the base modification pattern.

The base-modification pattern has been studied in several synthetic variants of yeast tRNA(Asp) injected into Xenopus laevis oocytes. Certain point mutations in the D-stem and the variable loop of the tRNA led to considerably decreased levels of m1G37, psi 40 and Q34/manQ34 in the anticodon stem or loop and an increased rate of synthesis for m5C49 in the T-stem. The formation of m2G6 in the aminoacyl-stem was not affected in any of the tRNA-variants. Thus, mutations in one part of the tRNA-molecule can have long-range effects on the interactions between another part of the tRNA and the tRNA modifying enzymes.     

Patterns of Plasma Oestradiol-17ß in Relation to the Interval from Weaning to Oestrus in Sows

Sows generally are anoestrus during lactation. Weaning the litter normally results in a rapid increase in follicular growth that terminates in oestrus and ovulation. Follicular development after weaning is characterized by an elevation in the blood concentrations of oestradiol-17ß (E2). Although the post-weaning patterns of E2 in blood circulation have been reported previously (Cox & Britt 1982, Edwards & Foxcroft 1983, Rojanasthien 1988), the plasma patterns of E2 in relation to the interval from weaning to oestrus (WOI), to our knowledge, have not been assessed. The purpose of this study was therefore to relate the blood patterns of E2 to the WOI in sows exhibiting their first oestrus within 10 days after weaning.     

Blood levels of 15-keto-13, 14-dihydroprostaglandin F(2alpha) during the postpartum period in primiparous cows

Plasma levels of the PGF(2alpha) metabolite 15-keto-13, 14-dihydroprostaglandin F(2alpha) were determined postpartum in 51 primiparous Black and White Lowland cows. The highest geometric mean was 1702 pmol/l on day 3 and lowest 190 pmol/l on day 21. It should be noted that variation between animals in the concentration of the metabolite is high. For instance, on days 4, 10, 16 and 22, concentration of metabolite ranged from 775-2500, 209-2450, 45-851 and 30-398 pmol/l, respectively. The duration of the massive postpartum release of PGF(2alpha) could be determined in only 29 cows. Significant correlations were found between the duration of elevated PGF(2alpha) metabolite levels and the time required for completion of uterine involution (r = -0.41, P < 0.05) and between the duration of increased PGF(2alpha) metabolite levels and the interval from parturition to occurrence of the first ovulation followed by a normal luteal phase length (r = -0.37, P < 0.05). The occurrence of the first ovulation followed by a normal luteal phase length in the 29 cows was positively correlated with the time needed for completion of uterine involution (r = 0.54, P < 0.01).     

Oophorectomy During Different Stages of Pregnancy in the Cow

Thirteen cows of the Swedish Red and White Breed (SRB) were subjected to bilateral oophorectomy in the period 105–251 days of pregnancy. Eleven of the animals delivered their fetuses before the expected day of parturition, while 2 which were oophorectomized on days 205 and 212 calved at the expected time. Eleven of the cows had retained fetal membranes following abortion/ parturition. Following surgery the peripheral plasma levels of progesterone dropped to levels about 10 % of the pretreatment levels. Animals oophorectomized between days 105 and 157 of pregnancy had a lower postsurgical progesterone concentration than cows operated on at days 205–251 of pregnancy. No increase of the peripheral plasma levels of estrone in connection with abortion was seen in cows operated on in early stages of pregnancy (&lt; 200 days) while those operated on in later stages and maintaining the pregnancy for at least 17 days post oophorectomy showed an increase of estrone before parturition. The 2 cows that calved at the expected time had an increase of prepartum estrone similar to that seen at spontaneous calving.     

Hormonal Interrelationships in Postpartum Suckled Dairy Cows

Three cross-bred cows calved in March and April and were followed until day 62 after parturition. Each animal was suckled by 2 calves ad libitum. All calves were removed from the cows on day 55 after parturition. Blood was collected 3 times per day from the jugular vein by venipuncture. On 4 occasions after parturition - i.e. days 7–8, 21–22, 35–36 and 49–50, the cows were bled through a jugular venous catheter every 30 min during the 24 h. The plasma samples were analyzed for the content of 15-keto-13,14-dihydro-PGF2α (main PGF2α metabolite), LH, prolactin, Cortisol and progesterone by radioimmunoassay methods. The concentration of PGF2α increased from 280 to 730 pmol/1 within the last 4 days before parturition. The highest geometric mean was 3106 pmol/1 on the day of parturition. Thereafter a steady decrease of PGF2α metabolite concentration was seen until day 21 when it reached plateau at 148 pmo/1. In all cows plasma LH concentrations increased significantly (P<0.05) from about 1.6 µg/l on days 7–8 to 2.4 µg/1 on days 21–22 post partum. The frequency of LH pulses showed no tendency to increase as the postpartum period progressed and averaged 6.5 pulses/24 h. Mean plasma LH concentrations increased from 2.1 µg/l 2 days before weaning to 3.2 µg/l 2 days after weaning (P<0.05). LH peaks occurred less frequently in association with prolactin and Cortisol peaks than in their absence. A partial positive correlation between PGF2α metabolite and Cortisol (r = 0.30) was found on days 7–8 post partum. Correlation between prolactin and Cortisol on days 7–8 and 21–22 post partum was also positive (r = 0.20 and r = 0.27, respectively). There was a negative correlation between LH and Cortisol on days 7–8 (r = −0.27) and days 49–50 (r = −0.21) post partum. The first and short progesterone increase observed after weaning was terminated in conjuction with PGF2α metabolite peaks.     

Enzyme and immunohistochemical assessment of myocardial damage after ischaemia and reperfusion in a closed-chest pig model

The usefulness of different enzyme and immunohistochemical stains to distinguish reversible and irreversible myocardial cell injury after experimental coronary artery occlusion of varying duration and reperfusion with or without superoxide dismutase as adjunct was investigated. Biopsies or parts of the infarcted and non-infarcted area were rapidly frozen and sectioned in series for enzyme and immunohistochemical evaluation. Sections were stained for the demonstration of phosphorylase, myofibrillar ATPase and mitochondrial oxidative enzymes and also with periodic acid-Schiff, alizarin red S and routine histological stains. Other sections in series were stained with antibodies against fibronectin and the intermediate filament proteins desmin and vimentin. In 49 biopsies a blind quantitative estimation of the area stained for fibronectin, phosphorylase and alizarin red S was performed and evaluated statistically. Phosphorylase, periodic acid-Schiff, fibronectin and alizarin red S allowed delineation of affected myocardium after 30 min of ischaemia followed by reperfusion whereas with the other stains, affected myocardium was readily detectable only after 60 or 90 min of ischaemia followed by reperfusion as well as after 24 h of ischaemia without reperfusion. The immunostaining for fibronectin was very distinct and inversely related to the phosphorylase activity. We show that fibronectin is an excellent marker for damaged cells and that these positively stained myocytes are necrotic as confirmed ultrastructurally. Using alizarin red S as a marker of calcium accumulation in myocytes, a marked discrepancy was observed between the area of fibronectin-containing myocytes and that of myocytes stained by alizarin red S. Calcium accumulation in mitochondria is thus not a prerequisite for myocyte necrosis but does occur only in some of the irreversibly damaged cells. Of special interest is the finding that there was a significant reduction of intracellular calcium in pigs where superoxide dismutase had been used as an adjunct at reperfusion, thus supporting the theory that free radicals do play a role during reperfusion of ischaemic myocardium.     

Effect of induced suprabasal progesterone levels around estrus on plasma concentrations of progesterone, estradiol-17beta and LH in heifers

A controlled study was carried out to investigate the effects of suprabasal plasma progesterone concentrations on blood plasma patterns of progesterone, LH and estradiol-17beta around estrus. Heifers were assigned to receive subcutaneous silicone implants containing 2.5 g (n=4), 5 g (n=4), 6 g (n=3), 7.5 g (n=3) or 10 g (n=4) of progesterone, or implants without hormone (controls, n=5). The implants were inserted on Day 8 of the cycle (Day 0=ovulation) and left in place for 17 d. The time of ovulation was determined by ultrasound scanning. Blood was collected daily from Days 0 to 14 and at 2 to 4-h intervals from Days 15 to 27. Control heifers had the lowest progesterone concentrations on Days 20.5 to 21 (0.5 +/- 0.1 nmol L(-1)); a similar pattern was observed in heifers treated with 2.5 and 5 g of progesterone. In the same period, mean progesterone concentrations in the heifers treated with 6, 7.5 and 10 g were larger (P < 0.05) than in the controls, remaining between 1 and 2.4 nmol L(-1) until implant removal. A preovulatory estradiol increase started on Days 16.4 to 18.4 in all the animals. In the controls and in heifers treated with 2.5 and 5 g of progesterone, estradiol peaked and was followed by the onset of an LH surge. In the remaining treatments, estradiol release was prolonged and increased (P < 0.05), while the LH peak was delayed (P < 0.05) until the end of the increase in estradiol concentration. The estrous cycle was consequently extended (P < 0.05). In all heifers, onset of the LH surge occurred when progesterone reached 0.4 to 1.2 nmol L(-1). The induction of suprabasal levels of progesterone after spontaneous luteolysis caused endocrine asynchronies similar to those observed in cases of repeat breeding. It is suggested that suprabasal concentrations of progesterone around estrus may be a cause of disturbances oestrus/ovulation.