Milk Protein Polymorphism in Kangayam Cattle

This paper reports the milk protein polymorphism, the allele frequencies of variants and the possible linkages among various combinations of milk protein phenotypes in the Kangayam cattle of south India. Milk samples from 156 Kangayam cows were typed by starch gel and polyacrylamide gel electrophoresis for caseins and whey proteins, respectively. All the four milk protein components studied, _s1-casein, -casein, -lactoglobulin and -lactalbumin, exhibited polymorphism with high allele frequencies of 0.9231±0.0151 for _s1-casein C, 0.9263±0.0148 for -casein A, 0.9135±0.0159 for -lactoglobulin B and a relatively high frequency of 0.6218±0.0275 for -lactalbumin A. The mean heterozygosity estimated over all the four milk protein loci was 0.2420. Genetic equilibrium was observed among all the loci studied, except -lactalbumin. Linkage analysis confirmed the non-independence between _s1- and -caseins and between caseins and -lactalbumin phenotypes.     

Acute and Subacute Metabolic and Endocrine Effects of Clenbuterol in Female Pigs

The aim of the study was to assess the relationship between acute and subacute metabolic and endocrine effects after intravenous administration of the ₂-adrenergic agonist clenbuterol in a growth-promoting dose to female pigs. Acute metabolic and endocrine effects were assessed by measuring the blood glucose, serum insulin and nonesterified fatty acid (NEFA) concentrations during 300 min after a single administration of clenbuterol. Significantly higher serum insulin and NEFA concentrations (19.90±2.50 U/ml, p<0.01, and 0.69±0.04 mmol/L, p<0.001, respectively) were measured 30 min after the preprandial administration of clenbuterol in female pigs. Over the same period, the levels of blood glucose (4.42±0.30 mmol/L) showed no difference from those of control pigs. The postprandial serum NEFA concentration decreased moderately during 210 min after feeding. Postprandial blood glucose and insulin concentrations increased and reached maximal levels 120 min after clenbuterol administration (10.91±0.60 mmol/L and 85.22±7.24 U/ml, respectively), and returned to basal levels at 300 min (4.20±0.21 mmol/L and 7.75±1.60 U/ml, respectively) after the administration of clenbuterol. Subacute metabolic and endocrine effects were assessed by measuring the blood glucose, serum insulin and NEFA concentrations for 21 days after the repeated doses of clenbuterol. In addition, the influence of clenbuterol administration on the endocrine regulation of the onset of the next expected oestrus in female pigs was assessed by measuring their serum 17-oestradiol and progesterone concentrations. Blood glucose, serum insulin and NEFA concentrations after the last administration of clenbuterol did not differ significantly from those in control animals. The onset of the next expected oestrus occurred regularly without any significant difference in serum 17-oestradiol or progesterone concentrations between the treated (9.83±2.60 pg/ml and 0.15±0.03 ng/ml) and control pigs (8.52±2.70 pg/ml and 0.25±0.06 ng/ml). The study results suggest the duration of intravenous administration of clenbuterol in a growth-promoting dose necessary to influence the metabolic and endocrine activities in female pigs.     

Feed intake and rumen motility in dwarf goats. Effects of some α-adrenergic agonists,prostaglandins and posterior pituitary hormones

The purpose of the present investigation was to test the hypothesis that drug-induced changes in rumen contractions influence feed intake in dwarf goats. Intravenous (i.v.) administration of clonidine (1 g kg^-1 min^-1 for 10 min), xylazine (1 g kg^-1 min^-1 for 10 min), and PGF-2 (10 g kg^-1 min^-1 for 15 min) caused bradycardia and inhibition of rumen contractions. However, no appetite-stimulating effect of these drugs was observed. Other clinical changes induced by the ₂-adrenergic agonists included slight sedation and a decrease in body temperature; all clinical effects of clonidine and xylazine were partly antagonized by tolazoline pretreatment (10 g kg^-1 min^-1 for 30 min). These results suggest that the CNS control of feeding differs in ruminants and monogastric species.In dwarf goats fasted for 2 h, i.v. administration of oxytocin (0.01 IU kg^-1 min^-1 for 15 min), vasopressin (0.01 IU kg^-1 min^-1 for 15 min), octapressin (0.003 IU kg^-1 min^-1 for 15 min) or PGE (0.8 g kg^-1 min^-1 for 15 min) did not change feeding behaviour during the two observation periods (0–30 min and 180–210 min after drug infusion, respectively). In previous studies, similar doses of these drugs induced changes in heart rate and inhibition of rumen contraction in goats. These findings demonstrate that drug-induced changes in forestomach contractions do not simply cause changes in feeding behaviour. The i.v. infusion of the PGF₂ analogues etiproston (10 g kg^-1 min^-1 for 15 min), luprostiol (30 g kg^-1 min^-1 for 15 min), cloprostenol (1 g kg^-1 min^-1 for 15 min) and tiaprost (1 g kg^-1 min^-1 for 15 min) induced hypophagic effects and stimulated intestinal propulsion.     

Detection of β2-agonists in milk replacer

₂-Agonist drugs may be illegally used as growth promoters for feedlot calves, when mixed into milk replacer immediately before feeding. To check for the presence of clenbuterol, salbutamol and terbutaline in such food, an analytical system was established using a screening method based on two commercial qualitative competitive ELISA tests, with antibodies raised against the arylamino group and thet-butyl group. The extraction procedure was based on precipitation of the milk samples with acetonitrile followed by filtration. The absence of any significant interference by other substances in the filtrate allowed detection of ₂-agonist drugs in spiked samples at the lowest concentration having a repartitioning effect (50 ppb for clenbuterol, mabuterol and terbutaline, 500 ppb for salbutamol). In view of a false positive response with tetracycline in milk samples and a cross-reaction between clenbuterol and mabuterol, an HPLC-MS technique was developed which, after extraction and purification of the samples with SPE C18 Polar Plus, was able to confirm the presence of these drugs. The good recovery after extraction (ranging from 84% to 90.2%) and the low detection limit with this method (250 ng/ml for clenbuterol, mabuterol and terbutaline, and 2.5 µg/ml for salbutamol) allowed easy confirmation and simultaneous detection of the four ₂-agonists at the lowest concentrations at which they are used in adulterated milk for calves.Abbreviations B optical density of the sample - B maximal optical density in total absence of competition - %B/B ₀ percentage of inhibition - ELISA enzyme-linked immunosorbent assay - EIA enzyme immunoassay - HPLC-MS high-performance liquid chromatography-mass spectrometry - m/z mass to charge ratio - ppb parts per billion - ppm parts per million - SPE solid-phase extraction     

Muscarinic receptor subtypes, β-adrenoceptors and cAMP in the tracheal smooth muscle of conventional and double-muscled calves

The total muscarinic (M₁ + M₂ + M₃) and -adrenergic receptors in the tracheal smooth muscle of conventional and double-muscled calves were identified and characterized with the non-specific antagonists [³H]quinuclidinyl benzilate ([³H]QNB) and [³H]dihydroalprenolol ([³H]DHA) respectively.Although the quantity of -adrenoceptors in double-muscled calves was 25% lower (p<0.05) than in conventional calves (B _max=327±89 fmol/mg protein), adenylate cyclase assays indicated that the basal adenylate cyclase activity and the (–)-isopropylnoradrenaline (ISO)- and sodium fluoride (NaF)-stimulated values were not significantly different between these calves. However, the density of muscarinic receptors in double-muscled calves was 40% higher (p<0.01) than in conventional calves (B _max=2955±625 fmol/mg protein). Subtypes of muscarinic receptors were studied with [³H]telenzepine (M₁-receptors), [³H]AF-DX 384 (M₂-receptors) and [³H]4DAMP (M₁ and M₃-receptors). It was found that in both double-muscled and conventional calves about 40% of the receptors were of the M₃-subtype, the remaining 60% being M₂-receptors.From these results, it is suggested that inflammation of the respiratory tract in double-muscled calves may be complicated by an imbalance between the cholinergic bronchoconstrictor and the -adrenergic bronchodilator components of the autonomic nervous system.     

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 (PGF₂) 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 in response to OT challenge or in the parameters describing the pulse of ovarian OT secretion after PGF₂ injection (n=7 for each) between days 12 and 14. Ovulatory follicular development was assessed by ultrasound monitoring and plasma 17-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.Abbreviations F XI factor XI - OT oxytocin - PGF₂ prostaglandin F₂ - PGFM 13,14-dihydro-15-keto-prostaglandin F₂ - i.m. intramuscularly     

Identification of Functional α-Adrenoceptor Subtypes in the Bovine Female Genital Tract During Different Phases of the Oestrous Cycle

The concentration and functionality of the -adrenoceptor (-AR) subtypes in the genital tract of cyclic heifers were investigated. In each tissue sample, a single class of ₁-ARs was observed, whereas two distinct classes of ₂-ARs were discriminated: low-affinity (LA) and high-affinity (HA) ₂-ARs. Statistical analysis showed the presence of significantly (p < 0.05) higher concentrations of all -AR subtypes in the follicle than in the corpus luteum. No significant differences were found in the ovary or myometrium between the luteal and follicular phases. In the ovary, the density of ₁-ARs was significantly (p < 0.05) higher than that of ₂-ARs. By contrast, there were significantly (p < 0.05) more ₂-ARs than ₁-ARs in the myometrium. As far as ₂-ARs are concerned, LA ₂-ARs were significantly (p < 0.05) higher than HA ₂-ARs in all tested tissues. Competition studies suggested that the rank order of potency of antagonists for ₁-ARs was prazosin > phentolamine > yohimbine, whereas for ₂-ARs the order of potency was yohimbine phentolamine > prazosin. Functional assays performed on myometrium showed that noradrenaline, phenylephrine and clonidine elicited concentration-dependent contractions only in dioestrus and pro-oestrus preparations and that clonidine was more effective than phenylephrine as a contractile agent. It appeared that there were no significant modifications in -AR affinity or concentration during the different stages of bovine oestrous cycle, whereas the uterine spontaneous activity and the responsiveness to -adrenergic stimulation was strongly influenced by hormonal levels. The modifications of uterine contractility observed during the oestrous cycle may be related to modifications induced in the transductional mechanisms of -ARs.     

Bovine Immunodeficiency Virus Expression in Vitro is Reduced in the Presence of β-Chemokines,MIP-1α, MIP-1β and RANTES

The inhibition of HIV expression in vitro by a cocktail of the -chemokines MIP-1, MIP-1 and RANTES provided the initial evidence that HIV utilizes chemokine receptors as co-receptors for infection of cells. Bovine immunodeficiency virus (BIV), a lentivirus, infects a wide variety of leukocyte populations, but the cellular receptor(s) utilized by this virus for infection of cells is not known. The purpose of this study was to determine whether MIP-1, MIP-1 and RANTES affect BIV expression in vitro, as a prelude to identifying the cellular receptors utilized by this virus. Fetal bovine lung (FBL) cells were pretreated with serial dilutions of a cocktail of the chemokines, and then the cells were infected with BIV. Virus expression in these cells was determined by counting the syncytia that had developed in the cultures by five days after infection. A significant decrease in syncytium formation, corresponding to increasing concentrations of the chemokines, was the result. Reacting the chemokines with chemokine-specific neutralizing antibodies prior to treatment of the cells neutralized the effect of the chemokines on virus replication in a dose-dependent manner, restoring viral expression to a level similar to that of untreated cells. The presence of a CCR5 homologue on the surface of FBL cells was confirmed using an anti-CCR5 monoclonal antibody and FACS analysis. Collectively, these data provide preliminary evidence that BIV may utilize the CCR5 receptor for infection of cells in vitro, but additional studies are necessary to confirm this.     

Haemophilus influenzae and the β-adrenergic system: A review

Haemophilus influenzae is a bacterium that often can be isolated from the deeper respiratory airways of patients with chronic asthmatic bronchitis. In the present study the effects ofH. influenzae vaccination on guinea pig pulmonary -adrenoceptor number and function (in vitro and in vivo) have been evaluated. Functioning of -adrenoceptors is determined by measuring the -mimetic effect of isoprenaline on the inhibition of anaphylactic mediator release and isolated tracheal strip relaxation. The number of -adrenoceptor binding sites was measured by means of a³H-dihydroalprenolol binding assay.Also the mechanism of action underlying the changes in -adrenoceptor functioning was evaluated. Furthermore, it was established that the effect on the -adrenoceptor system was not specific forH. influenzae and that other respiratory pathogens were also biologically active in this respect.     

The influence of clenbuterol on prostaglandin F2α-induced dyspnoea in calves

Pulmonary function tests were performed in six healthy calves. Prostaglandin F₂ causes severe narrowing of both upper and lower airways (total lung resistance increased, dynamic compliance decreased). Clenbuterol administered intravenously fifteen minutes prior to prostaglandin F₂ aerosol, and in increasing doses (0, 0.4, 0.8, 1.2 g/kg), on days 1, 2, 4 and 6 of the experiment, effectively but not entirely suppressed these responses.These data indicate that -adrenergic receptors are present in the bovine airways and that the use of clenbuterol (0.8 g/kg) may be effective in treating clinical respiratory disease such as bronchopneumonia in calves.     

Leukocyte and Cytokine Accumulation in the Ovine Teat and Udder during Endotoxin-Induced Inflammation

Persson Waller, K., Colditz, I.G., Flapper, P. and Seow, H.-F., 1997. Leukocyte and cytokine accumulation in the ovine teat and udder during endotoxin-induced inflammation. Veterinary Research Communications, 21 (2), 101-115The accumulation of leukocytes, ovine serum albumin and the cytokines interleukin-1 (IL-1), tumour necrosis factor- (TNF-), interleukin-8 (IL-8), granulocyte-macrophage colony-stimulating factor (GM-CSF) and interferon- (IFN-) was studied during endotoxin-induced inflammation in lactating and dry ovine udders, and in the teat cisterns of dry ewes after surgical closure of the passage between the teat and udder cisterns. Samples were taken before infusion and hourly up to 10 h after infusion of 0.1, 1 or 10 µg of endotoxin, or infusion of pyrogen-free saline (PFS) as a control. Rectal temperatures were measured.A significant dose- and time-dependent accumulation of leukocytes, mainly neutrophils, was observed in the lactating udders and in the teat cisterns. In the dry udders, the leukocyte accumulation was significant for time but not for dose. Peak numbers of cells were reached at 3-4 h in the dry udders and in the teat cisterns, but not until 10 h after infusion in the lactating udders. The changes in the ovine serum albumin concentrations mostly paralleled changes in leukocyte numbers.A role was indicated for TNF-, IL-8 and GM-CSF, but not for IL-1 and IFN-, during endotoxin-induced inflammation in the ovine udder. Release of TNF-, IL-8 and GM-CSF was most prominent in lactating udders, peaking at 2 or 3 h after infusion, but was also detected in dry udders and teat cisterns. Detectable levels of IL-1 and IFN- were occasionally found in all three groups.     

Plasma,Urinary and Biliary Residues in Cattle Following Intramuscular Injection of Nortestosterone Laurate

The synthetic androgen 19-nortestosterone (-NT) has been used illegally as a growth promoter in cattle production in the European Union. Elimination of -NT and its metabolites in plasma, urine and bile was studied in three cattle with cannulated gallbladders following intramuscular injection at a single site of 500 mg of the laurate ester (NTL) containing 300.5 mg -NT. Using enzyme immunoassay quantification, plasma Cmax of free -NT was 0.5±0.15 g/L (mean±SEM). Concentrations of free -NT in plasma were consistently greater than the assay limit of quantification (0.12 g/L) for 32.7±13.42 days. Mean residence time for free -NT in plasma was 68.5±20.75 days. Following sample preparation by immunoaffinity chromatography, high-resolution GC-MS was used to quantify -NT and -NT in urine and bile. -NT was detected irregularly in urine from two of the three animals post injection. The principal metabolite present in the urine, -NT, was detected for 160.3±22.67 days post injection. Cmax for -NT in urine was 13.7±5.14 g/L. Mean urinary AUC0–183 days for -NT was 845.7±400.90 (g h)/L.In bile, -NT was the only metabolite detected for 174.3±8.67 days post treatment. Cmax for -NT in bile was 40.8±12.70 g/L and mean biliary AUC0–183 days for -NT was 1982.6±373.81 (g h)/L. Concentrations of -NT in bile samples were greater than those in urine samples taken at the same time. The mean ratio of biliary:urinary AUC0–183 days was 3.0±0.72. It is concluded that bile is a superior fluid for detection of -NT following injection of NTL, owing to the longer period during which residues may be detected after administration.     

Effect of antisecretory drugs on experimentally induced weanling diarrhoea in piglets

In 45 newly-weaned 3 to 4-week-old piglets, diarrhoea was induced by a combined infection with transmissible gastroenteritis (TGE) virus and enterotoxigenic E. coli (ETEC) strains. In untreated control animals this dual inoculation resulted in profuse diarrhoea, vomiting, hypovolaemic shock and death of 77% of the animals within five days of TGE virus inoculation. Antisecretory drugs were administered intramuscularly for three consecutive days after experimental infection. The neurolepticum chlorpromazine, at 2 mg/kg/24 h, resulted in a significant inhibition of diarrhoea and vomiting, and in an increase in weight gain and survival. Sedation and hypothermia, however, were serious side-effects. The ₂ agonist clonidine, at 80 g/kg/12 h, induced a significant antidiarrhoeal effect and a reduction in mortality. The drug, however, provoked decreased activity of ₂-adrenergic excitation and incoordination. The -adrenergic antagonist propranolol, at 0.33 mg/kg/8 h, and the calcium channel blocker verapamil, at 2 mg/kg/8 h, had no beneficial effect on the experimentally induced diarrhoea.     

Nephrotoxicity and hepatotoxicity in calves apparently caused by experimental feeding withNarthecium ossifragum

Seven calves were fed a mixture of bog plants containing 15 g (wet matter)Narthecium ossifragum per kg live weight for two consecutive days. Their serum creatinine, urea and magnesium concentrations increased, whereas the serum calcium concentration decreased. Histopathological examination of the kidneys of the 5 calves that were killed revealed tubular epithelial cell degeneration and necrosis. There were signs of liver dysfunction in all the calves including increased aspartate aminotransferase (ASAT), glutamate dehydrogenase (GLDH) and -glutamyltransferase activities.All the calves refused to ingestN. ossifragum after 2 days feeding, and their appetite for hay and concentrate was also reduced. It can be concluded thatN. ossifragum is nephrotoxic and hepatotoxic to calves.Abbreviations ALP alkaline phosphatase - ASAT aspartate aminotransferase - -HBA -hydroxybutyric acid - CK creatine kinase - d.m. dry matter - -GT -glutamyltransferase - GFR glomerular filtration rate - GLDH glutamate dehydrogenase - MCV mean cell volume - RBC red blood cells - SEM standard error of the mean - WBC white blood cells - w.m. wet matter     

β-Adrenoceptors in Equine Trachea and Heart

The density and subtype pattern of -adrenoceptors in equine tracheal epithelium, tracheal smooth muscle and heart from 6–9 horses were investigated by radioligand binding studies using the non-selective -adrenoceptor antagonist 125I-cyanopindolol (ICYP). The specific binding of ICYP was 341±162 fmol/mg protein (mean±SD) for epithelium, 42±13 fmol/mg for smooth muscle and 124±39 and 101±19 fmol/mg for the cardiac atrium and ventricle, respectively. The Kd value of ICYP was 6.7–10.2 pmol/L.In competition studies, different concentrations of either the 2-selective drug ICI 118551 or the 1-selective CGP 20712A competed with 25 pmol/L ICYP for the binding sites. The competition curves for tracheal smooth muscle and epithelium were monophasic with an approximate Kd value for ICI 118551 of 1 nmol/L and for CGP 20712A of 10 000 nmol/L. This corresponds to known Kd values for these substances binding to 2-adrenoceptors. 2-Adrenoceptors were also found in the heart, most pronounced in the atrium, where the density was 29%±6% (mean±SD) of the total receptor density. CGP 20712A and ICI 118551 bound to the dominating binding site of 1-adrenoceptors in the heart with Kd values of approximately 1 nmol/L and 100 nmol/L, respectively.     

Antibody Responses in Sheep Vaccinated against Staphylococcus aureus Mastitis: A Comparison of Two Experimental Vaccines Containing Different Adjuvants

A double-blind, placebo-controlled study was conducted to compare two vaccines using different adjuvants with regard to their ability to stimulate antibody production against the - and -toxins and the exopolysaccharide of Staphylococcus aureus. The vaccines contained identical antigens, consisting of inactivated whole bacteria of two strains of S. aureus in addition to - and -toxoid. One vaccine contained mineral oil, while the other used a water-soluble acrylic acid polymer resin (Carbopol) as adjuvant. Saline served as the placebo. One hundred and forty ewes were vaccinated twice before lambing, by subcutaneous injection with vaccine or placebo in the region of the supramammary lymph node, and were observed and sampled over a period of 6 months. The vaccine containing mineral oil as adjuvant induced significantly greater immune responses to the - and -toxins than did the vaccine containing Carbopol. The latter vaccine induced higher levels of antibodies to exopolysaccharide. The degree of local adverse reactions did not differ between the two groups. The results indicate differences between the oil-adjuvanted and Carbopol-adjuvanted vaccines with regard to their ability to stimulate antibody production against S. aureus protein antigens in sheep.     

The pharmacokinetics of a slow-release theophylline preparation in horses after intravenous and oral administration

The pharmacokinetics of a slow-release theophylline formulation was investigated following intravenous and oral administration at 10 mg/kg in horses. A tricompartmental model was selected to describe the intravenous plasma profile. The elimination half-life (t1/2) was 16.91 ± 0.93 h, the apparent volume of distribution (V _d) was 1.35 ± 0.18 L/kg and the body clearance (Cl_B) was 0.061 ± 0.009 L kg^–1 h. After oral administration the half-life of absorption was 1.24 ± 0.30 h, and the calculated bioavailability was above 100%. Thet1/2 after oral administration was 18.51 ± 1.75 h, only a little longer than that after intravenous administration. The slow release formulation did not exhibit any advantage in prolonging thet1/2 of theophylline in the horse.     

Measurement of Cortisol Metabolites in Faeces of Ruminants

Twenty-one metabolites were detected in faecal samples collected after infusion of (¹⁴C)cortisol into the jugular vein of sheep, using high-performance liquid chromatography/radiometric analysis plus mass spectrometry. One group of metabolites had molecular weights of between 302 and 308, and another group of 350, which indicates that the substances have a C₁₉O₃ or a C₂₁O₄ structure. Therefore, an enzyme immunoassay against 5-androstane-3-o1-11,17-dione-17-CMO:BSA was established. Faecal samples were collected from 10 cows immediately after transport and then during a course in which non-invasive diagnostic procedures were being taught (course 1). For comparison, faeces were sampled from another 5 cows that were being used for teaching invasive procedures (course 2). Six cows from a university farm served as controls. In the animals used in course 1, the highest concentrations of cortisol metabolites were measured immediately after transport to the university (median value: 2.2 mol/kg faeces). During the first 5 days at the university, the concentrations decreased to 0.52 mol/kg (median) and remained at this level during the rest of the course. The median concentration in the samples that were taken during course 2 (collected about 2 months after transport) was 0.48 mol/kg. There was no significant difference in the excretion of cortisol metabolites between these cows and the controls. We conclude from these data that, using the enzyme immunoassay against 5-androstane-3-o1-11,17-dione-17-CMO, we were able to detect transport/novel environment stress but not the potential disturbance that cows experience during diagnostic procedures.     

Pharmacokinetics and distribution of sulphadimidine in plasma,milk and uterine fluid of female buffaloes

The pharmacokinetics of sulphadimidine after a single dose (200 mg/kg i.v.) was studied in five healthy lactating buffaloes. The study revealed that the drug attained its peak concentration of 314.0±13.0, 242.4±3.0 and 100.2±2.5 g/ml at 15 min, 30 min and 12 h in plasma, milk and uterine fluid, respectively. The pharmacokinetic parameters calculated by a 2-compartment open model gave values for t₁, t₁ and vd_area of 2.10±0.36 h, 12.36±0.57 h and 1.23±0.07 L/Kg, respectively. A high vd_area as well as a value of 0.74±0.08 for K₁₂:K₂₁- (tissue Plasma) indicates better penetration of the drug into the different body fluids and tissues, which is further supported by a high concentration obtained in milk and uterine fluid. The therapeutic concentration (50 g/ml) was maintained for around 24 h in plasma and milk and 12 h in uterine fluid. The results suggest that, apart from its use in systemic infections, the drug can be effectively used by the i.v. route in uterine and mammary gland infections. The dosages for maintaining concentration of 50 g/ml, 100 g/ml and 150 g/ml at convenient dosage intervals of 12 and 24 h were also determined.     

Dynamics of Protein 27 of Avian Leukosis Virus and Transforming Growth Factor β2 in Lymphoid Leukosis Susceptible and Resistant Broiler Chicken Breeding Stock

The dynamics of the serum concentration of protein 27 (P27) of avian leukosis virus and transforming growth factor ₂ (TGF-₂) were compared during the period between 29 and 59 weeks of age in two flocks of broiler chicken breeding stock undergoing outbreaks of severe lymphoid leukosis (LL) associated with persistent high mortality (susceptible) and in another two flocks of breeding stock with the presence of avian leukosis virus in association with low mortality due to LL (resistant). The average mean concentration of serum P27 in the LL-susceptible flocks was significantly higher (<0.05) than that in the LL-resistant flocks in six out of seven samplings performed at 5-week intervals, between 29 and 59 weeks of age. The peak in the average rise of serum P27 in the LL-resistant flocks (309 pg/ml) was associated with the highest level of TGF-₂ (1282 pg/ml) among all flocks and at all sampling times. The significance of TGF-₂ in inhibition of lymphoid tumour development is discussed.