AT(1) receptor inhibition does not reduce arterial wall hypertrophy or PDGF-A expression in renal hypertension

To separate the role of ANG II from pressure in hypertrophy of the vascular wall in one-kidney, one-clip (1K1C) hypertension, experimental and sham-operated rats were given the AT(1)-receptor antagonist losartan (20 mg x kg(-1) x day(-1)) or tap water for 14 days. Mean arterial pressure was elevated in both experimental groups compared with controls. Rats were anesthetized with pentobarbital sodium, and the thoracic aorta and carotid, small mesenteric, and external spermatic arteries were harvested and embedded in paraffin. Tissue sections were used for morphological analysis, immunohistochemistry for 5-bromo-2'-deoxyuridine (BrdU) and platelet-derived growth factor (PDGF)-AA, stereological measurements, and in situ hybridization with a (35)S-labeled riboprobe for PDGF-A mRNA. Elevated cross-sectional areas of thoracic, carotid, and small mesenteric artery in 1K1C rats were not reduced by losartan. The internal diameter of the external spermatic artery and microvascular density of the cremaster muscle were reduced in 1K1C rats. The number of BrdU-positive nuclei per cross section did not differ between 1K1C and control arteries. PDGF-A mRNA was elevated in the arterial walls of 1K1C rats compared with controls and was hardly changed by losartan. PDGF-A protein stained strongly in the media of 1K1C arteries and was not inhibited by losartan; it appeared in the adventitia of all aortas and carotid arteries. These observations demonstrate that effects of ANG II mediated through the AT(1) receptor are not necessary for hypertrophy of the vascular wall during 1K1C hypertension or expression of PDGF-A.     

Mixing gilts in early pregnancy does not affect embryo survival

There is general acceptance that mixing sows during the first 3 weeks of gestation is detrimental to embryo development and survival. However, there is a paucity of data describing the influence of group housing and remixing during the first 14 days of gestation on pregnancy outcomes. Using 96 purebred maternal (Large White)/terminal (Duroc) line gilts, the current study determined the effects of regrouping, and the timing of regrouping, during the pre-implantation period on embryo mortality. The study was conducted in 2 blocks, with 12 gilts allocated to each of 4 treatments in each block. At 175 days of age, the combination of PG600 and 20 min of daily physical boar contact was used to stimulate puberty, with boar contact resuming 12 days after first detection of oestrus and gilts receiving two artificial inseminations (AIs), 24 h apart, at their second oestrus. After their first AI gilts were allocated to one of four treatment groups (n=12 gilts/treatment). Gilts in one treatment group were housed individually in stalls (STALL). The remaining gilts continued to be housed in their pre-AI groups and were either not remixed (NOMIX), or remixed to form new groups on day 3/4 (RMIXD3/4) or day 8/9 (RMIXD8/9) of gestation (day 0=day of first detection of second oestrus and first insemination). Group-housed gilts were housed in groups of 6, with a space allowance of 2.4 m2/gilt. All gilts were fed once a day (2.2 kg/gilt). Reproductive tracts were collected on day 26.6+/-0.13 of gestation, and the number of corpora lutea (CL) and viable embryos counted. Pregnancy rate was similar across all treatments, averaging 94.5% across the four treatment groups. The number of embryos present on day 26 of gestation was unaffected by housing treatments (P>0.05); gilts in the STALL, NOMIX, RMIXD3/4 and RMIXD8/9 groups possessed 13.2+/-0.67, 12.9+/-0.66, 14.1+/-0.46 and 13.8+/-0.57 embryos, respectively. Similarly, embryo survival rates were 0.91+/-0.04, 0.85+/-0.04, 0.91+/-0.02 and 0.87+/-0.05 for the STALL, NOMIX, RMIXD3.4 and RMIXD8/9 groups, respectively (P>0.05). In conclusion, the current data indicate that individually housing gilts immediately after their first AI does not improve embryo survival. There also appear to be no adverse effects on embryo development or survival when group-housed, mated gilts are remixed during the first 10 days of gestation.     

Neospora caninum infection does not affect early pregnancy in dairy cattle

This study was designed to evaluate the relationship between Neospora caninum infection prior to pregnancy, as determined through maternal serology, and the subsequent occurrence of abortion in dairy cattle. Special emphasis was placed on pregnancy losses in the first trimester of pregnancy. Neospora caninum antibodies were analyzed by commercial ELISA in 2773 pregnant animals (2022 parous cows and 751 heifers) from six herds. The mean seroprevalence of antibodies to N. caninum in the herds was 15.1% (n = 419). From gestation Day 34 to the 90th day of pregnancy, there were 183 abortions (6.6% of all pregnancies) (23 in Neospora positive animals). After 90 days of pregnancy, the number of abortions was 146 (5.3%); 126 occurring during the second and 20 during the third trimester of pregnancy (105 in Neospora positive animals). Multiple logistic regression analyses were performed on data from each animal using abortion before or after 90 days of pregnancy as the dependent variable, and Neospora positivity, herd, pregnancy season, and parity (parous or nonparous) as independent factors. No significant effects of Neospora positivity and herd were found on the abortion rate before 90 days of pregnancy. Based on the odds ratio, the abortion rate was 4 times higher (P < 0.0001) in animals that became pregnant in the warm than in the cool period, and 3.7 times higher (P < 0.0001) in parous than in nonparous animals. Neospora positivity was the only variable included in the logistic regression model for abortions occurring after 90 days of pregnancy. Seropositivity in an animal increased the probability of abortion by an odds ratio of 18.9 (P < 0.0001; 95% confidence interval 12.9-27.8). Season, parity, and herd showed no effect. The results of the present study suggest that chronic N. caninum infection prior to pregnancy appears not to affect the early fetal period, but does have a significant abortive effect after 90 days of gestation.     

H1-receptor antagonist, tripelennamine, does not affect arterial hypoxemia in exercising Thoroughbreds.

It has been suggested that pulmonary injury and inflammation-induced histamine release from airway mast cells may contribute to exercise-induced arterial hypoxemia (EIAH). Because stress failure of pulmonary capillaries and EIAH are routinely observed in exercising horses, we examined whether preexercise administration of an H1-receptor antagonist may mitigate EIAH. Two sets of experiments, placebo (saline) and antihistaminic (tripelennamine HCl at 1.10 mg/kg iv, 15 min preexercise) studies, were carried out on seven healthy, exercise-trained Thoroughbred horses in random order 7 days apart. Arterial and mixed venous blood-gas and pH measurements were made at rest before and after saline or drug administration and during incremental exercise leading to maximal exertion at 14 m/s on 3.5% uphill grade for 120 s. Galloping at this workload elicited maximal heart rate and induced exercise-induced pulmonary hemorrhage in all horses in both treatments, thereby indicating that capillary stress failure-related pulmonary injury had occurred. In both treatments, EIAH, desaturation of hemoglobin, hypercapnia, and acidosis of a similar magnitude developed during maximal exertion, and statistically significant differences between the placebo and antihistaminic studies could not be demonstrated. The failure of the H1-receptor antagonist to modify EIAH significantly suggests that pulmonary injury-induced histamine release may not play a major role in bringing about EIAH in Thoroughbred horses.     

Sexual stimulation does not affect plasma LH nor testosterone levels in New-Zealand male rabbits

Young sexually naive (3-4 months) and sexually experienced (2-3 years) male rabbits were subjected to various sexual stimulation procedures. Blood samples were taken just before and 30 min after mounting (unreceptive females) or coitus (receptive females). Testosterone and luteinizing hormone were assayed using specific radioimmunoassays. Sexual stimulation did not affect postcoital testosterone and LH levels in naive and experienced males while in females LH levels were significantly increased. We may conclude that the postcoital neuroendocrine reflex which causes a massive release of pituitary LH in female rabbit does not exist in males.     

Preexercise hypervolemia does not affect arterial hypoxemia in Thoroughbreds performing short-term high-intensity exercise.

It is reported that preexercise hyperhydration caused arterial O(2) tension of horses performing submaximal exercise to decrease further by 15 Torr (Sosa-Leon L, Hodgson DR, Evans DL, Ray SP, Carlson GP, and Rose RJ. Equine Vet J Suppl 34: 425-429, 2002). Because hydration status is important to optimal athletic performance and thermoregulation during exercise, the present study examined whether preexercise induction of hypervolemia would similarly accentuate the arterial hypoxemia in Thoroughbreds performing short-term high-intensity exercise. Two sets of experiments (namely, control and hypervolemia studies) were carried out on seven healthy, exercise-trained Thoroughbred horses in random order, 7 days apart. In resting horses, an 18.0 +/- 1.8% increase in plasma volume was induced with NaCl (0.30-0.45 g/kg dissolved in 1,500 ml H(2)O) administered via a nasogastric tube, 285-290 min preexercise. Blood-gas and pH measurements as well as concentrations of plasma protein, hemoglobin, and blood lactate were determined at rest and during incremental exercise leading to maximal exertion (14 m/s on a 3.5% uphill grade) that induced pulmonary hemorrhage in all horses in both treatments. In both treatments, significant arterial hypoxemia, desaturation of hemoglobin, hypercapnia, acidosis, and hyperthermia developed during maximal exercise, but statistically significant differences between treatments were not found. Thus preexercise 18% expansion of plasma volume failed to significantly affect the development and/or severity of arterial hypoxemia in Thoroughbreds performing maximal exercise. Although blood lactate concentration and arterial pH were unaffected, hemodilution caused in this manner resulted in a significant (P < 0.01) attenuation of the exercise-induced expansion of the arterial-to-mixed venous blood O(2) content gradient.     

Anti-inflammatory agent, dexamethasone, does not affect exercise-induced arterial hypoxemia in Thoroughbreds.

In view of the suggestion that pulmonary injury-induced release of histamine and/or other chemical mediators from airway inflammatory and mast cells contribute to the exercise-induced arterial hypoxemia (EIAH) in human athletes, we examined the effects of pretreatment with a potent anti-inflammatory agent, dexamethasone, on EIAH and desaturation of hemoglobin in horses. Seven healthy, sound, exercise-trained Thoroughbreds were studied in the control (no medications) experiments, followed in 7 days by intravenous dexamethasone (0.11 mg.kg(-1).day(-1) for 3 consecutive days) studies. Blood-gas measurements were made at rest and during incremental exercise leading to maximal exertion at 14 m/s on a 3.5% uphill grade. Galloping at this workload induced pulmonary hemorrhage in all horses in both treatments, thereby indicating that stress failure of pulmonary capillaries had occurred. In both treatments, significant EIAH, desaturation of hemoglobin, hypercapnia, acidosis, and hyperthermia developed during maximal exercise, but significant differences between the control and dexamethasone treatments were not discerned. The failure of pretreatment with dexamethasone to significantly affect EIAH suggests that pulmonary injury-evoked airway inflammatory response may not play a major role in EIAH in racehorses. However, our observations in both treatments that EIAH developed quickly (being evident at 30 s of exertion) and that its severity remained unaffected by increasing exercise duration (to 120 s) suggest that EIAH has a functional basis, probably related to significant shortening of the transit time for blood in the pulmonary capillaries as cardiac output increases dramatically.     

Indomethacin does not potentiate renovascular constriction during hypercapnia in unanesthetized rabbits

The role of prostanoids in regulation of the renal circulation during hypercapnia was examined in unanesthetized rabbits. Renal blood flow (RBF) was determined with 15 μm radioactive microspheres during normocapnia (PaCO₂ 30 mmHg) and hypercapnia (PaCO₂ 60 mmHg), before and after intravenous administration of indomethacin (10 mg/kg) or vehicle (n=6 for each group). Arterial blood pressure was not different among the 4 conditions in each group. RBF was 438±61 and 326 ± 69 (P<0.05) ml/min per 100 g during normocapnia and hypercapnia, respectively, before indomethacin, and following administration of indomethacin, RBF was 426 ± 59 ml/min per 100 g during normocapnia and 295 ± 60 ml/min per 100 g during hypercapnia (P<0.05). In the vehicle group, RBF was 409±74 and 226±45(P<0.05) ml/min per 100 g during normocapnia and hypercapnia, respectively, before vehicle; and following administration of vehicle, RBF was 371±46 ml/min per 100 g during normocapnia and 219 ± 50 (P<0.05) per 100 g during hypercapnia. RBF during normocapnia was not affected by administration of indomethacin or vehicle. The successive responses to hypercapnia were not different within the indomethacin and vehicle groups, and the second responses to hypercapnia were not different between the two groups. These findings suggest that prostanoids do not contribute significantly to regulation of the renal circulation during normocapnia and hypercapnia in unanesthetized rabbits.     

Indomethacin does not potentiate renovascular constriction during hypercapnia in unanesthetized rabbits

The role of prostanoids in regulation of the renal circulation during hypercapnia was examined in unanesthetized rabbits. Renal blood flow (RBF) was determined with 15 micron radioactive microspheres during normocapnia (PaCO2 congruent to 30 mmHg) and hypercapnia (PaCO2 congruent to 60 mmHg), before and after intravenous administration of indomethacin (10 mg/kg) or vehicle (n = 6 for each group). Arterial blood pressure was not different among the 4 conditions in each group. RBF was 438 +/- 61 and 326 +/- 69 (P less than 0.05) ml/min per 100 g during normocapnia and hypercapnia, respectively, before indomethacin, and following administration of indomethacin, RBF was 426 +/- 59 ml/min per 100 g during normocapnia and 295 +/- 60 ml/min per 100 g during hypercapnia (P less than 0.05). In the vehicle group, RBF was 409 +/- 74 and 226 +/- 45 (P less than 0.05) ml/min per 100 g during normocapnia and hypercapnia, respectively, before vehicle; and following administration of vehicle, RBF was 371 +/- 46 ml/min per 100 g during normocapnia and 219 +/- 50 (P less than 0.05) ml/min per 100 g during hypercapnia. RBF during normocapnia was not affected by administration of indomethacin or vehicle. The successive responses to hypercapnia were not different within the indomethacin and vehicle groups, and the second responses to hypercapnia were not different between the two groups. These findings suggest that prostanoids do not contribute significantly to regulation of the renal circulation during normocapnia and hypercapnia in unanesthetized rabbits.     

Human-like receptor specificity does not affect the neuraminidase-inhibitor susceptibility of H5N1 influenza viruses

If highly pathogenic H5N1 influenza viruses acquire affinity for human rather than avian respiratory epithelium, will their susceptibility to neuraminidase (NA) inhibitors (the likely first line of defense against an influenza pandemic) change as well? Adequate pandemic preparedness requires that this question be answered. We generated and tested 31 recombinants of A/Vietnam/1203/04 (H5N1) influenza virus carrying single, double, or triple mutations located within or near the receptor binding site in the hemagglutinin (HA) glycoprotein that alter H5 HA binding affinity or specificity. To gain insight into how combinations of HA and NA mutations can affect the sensitivity of H5N1 virus to NA inhibitors, we also rescued viruses carrying the HA changes together with the H274Y NA substitution, which was reported to confer resistance to the NA inhibitor oseltamivir. Twenty viruses were genetically stable. The triple N158S/Q226L/N248D HA mutation (which eliminates a glycosylation site at position 158) caused a switch from avian to human receptor specificity. In cultures of differentiated human airway epithelial (NHBE) cells, which provide an ex vivo model that recapitulates the receptors in the human respiratory tract, none of the HA-mutant recombinants showed reduced susceptibility to antiviral drugs (oseltamivir or zanamivir). This finding was consistent with the results of NA enzyme inhibition assay, which appears to predict influenza virus susceptibility in vivo. Therefore, acquisition of human-like receptor specificity does not affect susceptibility to NA inhibitors. Sequence analysis of the NA gene alone, rather than analysis of both the NA and HA genes, and phenotypic assays in NHBE cells are likely to adequately identify drug-resistant H5N1 variants isolated from humans during an outbreak.     

血管紧张素II2型受体基因缺失不影响肾素—血管紧张素系统

基于目前对血管紧张素Ⅱ２型受体（ＡＴ２）功能的认识,认为血管紧张素Ⅱ１型受体（ＡＴ１）和ＡＴ２受体有相互拮抗作用。依据上述论点,本研究利用ＡＴ２受体基因敲出小鼠,观察了ＡＴ２受体缺失后是否造成肾素－血管紧张素系统其它成分代偿性紊乱。结果发现,ＡＴ２受体基因缺失小鼠血浆和肾组织中血管紧张素Ⅱ的浓度以及肾组织中肾素、ＡＴ１Ａ受体的基因表达均未发生明显改变,表明ＡＴ２受体缺失未对肾素－血管紧张素系统产生     

Ketamine does not affect intestinal microcirculation in pentobarbital-anaesthetized rats during experimental endotoxaemia

The objective of the study was to evaluate the effects of ketamine on intestinal microcirculation in pentobarbital-anaesthetized rats during experimental endotoxaemia. A prospective, randomized, controlled study was carried out using 32 male Lewis rats. The animals were divided into four groups (n = 8 each). All animals were initially anaesthetized with 60 mg/kg pentobarbital (i.p.). Group 1 served as a control (18.5 mg/kg/h pentobarbital i.v.). Groups 2 and 4 received an endotoxin intravenous infusion of 15 mg/kg lipopolysaccharide (LPS) from Escherichia coli. Groups 3 and 4 also received 10 mg/kg/h ketamine (i.v.). After 2 h of observation, the animals were examined for intestinal functional capillary density (FCD) and leukocyte adherence to the venular endothelium by means of intravital fluorescence microscopy (IVM). Subsequent to this examination, blood samples were collected to determine release of the cytokines tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6 and IL-10. Endotoxaemia tended to decrease intestinal FCD (mucosa: -10.1%, muscularis longitudinalis: -2%, muscularis circularis: -9.8%) and significantly increase leukocyte adherence within submucosal venules (collecting venules: +133%, postcapillary venules: +207%; P<0.05). TNF-alpha, IL-1beta, IL-6 and IL-10 levels were significantly elevated following endotoxin challenge. The addition of ketamine to pentobarbital anaesthesia did not significantly affect FCD, leukocyte behaviour or cytokine levels. In conclusion, intravenous pentobarbital anaesthesia with the additional administration of ketamine did not cause alterations within the microcirculation or changes in cytokine release during endotoxaemia. In rats, the combination of pentobarbital and ketamine is suitable for use during the study of intestinal microcirculation in experimental endotoxaemia.     

Nitric oxide synthase inhibition does not affect the exercise-induced arterial hypoxemia in Thoroughbred horses.

Because sensitivity of equine pulmonary vasculature to endogenous as well as exogenous nitric oxide (NO) has been demonstrated, we examined whether endogenous NO production plays a role in exercise-induced arterial hypoxemia. We hypothesized that inhibition of NO synthase may alter the distribution of ventilation-perfusion mismatching, which may affect the exercise-induced arterial hypoxemia. Arterial blood-gas variables were examined in seven healthy, sound Thoroughbred horses at rest and during incremental exercise protocol leading to galloping at maximal heart rate without (control; placebo = saline) and with N(omega)-nitro-L-arginine methyl ester (L-NAME) administration (20 mg/kg iv). The experiments were carried out in random order, 7 days apart. At rest, L-NAME administration caused systemic hypertension, pulmonary hypertension, and bradycardia. During 120 s of galloping at maximal heart rate, significant arterial hypoxemia, desaturation of hemoglobin, hypercapnia, hyperthermia, and acidosis occurred in the control as well as in NO synthase inhibition experiments. However, statistically significant differences between the treatments were not found. In both treatments, exercise caused a significant rise in hemoglobin concentration, but the increment was significantly attenuated in the NO synthase inhibition experiments, and, therefore, arterial O(2) content (Ca(O(2))) increased to significantly lower values. These data suggest that, whereas L-NAME administration does not affect pulmonary gas exchange in exercising horses, it may affect splenic contraction, which via an attenuation of the rise in hemoglobin concentration and Ca(O(2)) may limit performance at higher workloads.     

Apoptosis does not affect the vasculature of the corpus luteum of pregnancy in the rat

There has been much research into the mechanics of angiogenesis and many studies have demonstrated that newly formed vessels regress during angiogenesis. This vascular involution has been shown to involve basement membrane dissolution and endothelial cell apoptosis. The corpus luteum provides an ideal in vivo model to study physiologic angiogenesis and studies have shown that involution of newly formed vessels occurs during corpus luteum regression. However, few studies to date have investigated the role of apoptosis on the vasculature which develops during pregnancy. By the use of the TUNEL technique to detect apoptotic cells and immunohistochemistry to distinguish between endothelial cells and pericytes, this present study demonstrated that the vasculature of the corpus luteum of pregnancy in the rat does not undergo apoptosis.     

Lack of the nociceptin receptor does not affect acute or chronic nociception in mice

The peptide nociceptin/orphanin FQ (N/OFQ) and its receptor ORL-1, also designated opioid receptor 4 (OP(4)) are involved in the modulation of nociception. Using OP(4)-knockout mice, we have studied their response following opioid receptor stimulation and under neuropathic conditions.In vas deferens from wild-type and OP(4)-knockout mice, DAMGO (mu/OP(3) agonist), deltorphine II (delta/OP(1) agonist) and (-)-U-50488 (kappa/OP(2) agonist) induced similar concentration-dependent inhibition of electrically-evoked contractions. Naloxone and naltrindole (delta/OP(1) antagonists) shifted the curves of DAMGO (pA(2)=8.6) and deltorphine II (pA(2)=10.2) to the right, in each group. In the hot-plate assay, N/OFQ (10 nmol per mouse, i.t.) increased baseline latencies two-fold in wild-type mice while morphine (10mg/kg, s.c.), deltorphine II (10 nmol per mouse, i.c.v.) and dynorphin A (20 nmol per mouse, i.c.v.) increased hot-plate latencies by about four- to five-fold with no difference observed between wild-type and knockout mice. Furthermore, no change was evident in the development of the neuropathic condition due to chronic constriction injury (CCI) of the sciatic nerve, after both thermal and mechanical stimulation.Altogether these results suggest that the presence of OP(4) receptor is not crucial for (1) the development of either acute or neuropathic nociceptive responses, and for (2) the regulation of full receptor-mediated responses to opioid agonists, even though compensatory mechanisms could not be excluded.     

Prostacyclin does not affect insulin secretion in humans

The effects of Prostacyclin (PGI₂) infusion on insulin secretion and glucose tolerance were investigated in 7 healthy subjects. PGI₂ infusion caused no statistically significant changes of either glucose or insulin concentration, over the range 2.5–20 ng/Kg/min. A constant PGI₂ infusion (10 ng/Kg/min) did not inhibit acute insulin responses to a glucose (20 g i.v.) pulse (response before PGI₂ = 612±307%; during PGI₂ = 515±468%, mean ± SD, mean change 3–5 min insulin, % basal; P=NS). Glucose disappearance rates were similar after the first and second glucose pulse.Thus, in contrast to PGE₂, PGI₂ does not affect insulin secretion nor glucose disposal at doses producing platelet and vascular changes. It is hypothesized that an altered PGI₂/PGE₂ balance in diabetes may represent a link between vascular, platelet and metabolic changes.