Regional adrenal blood flow responses to adrenocorticotropic hormone after chronic embolization of the fetal placental circulation in sheep

To ascertain whether repeated hypoxic stress would alter the response of the adrenal cortex to adrenocorticotropic hormone (ACTH), by premature activation of the hypothalamic-pituitary-adrenal axis, we studied fetal sheep subjected to daily reduction of arterial oxygen content by embolization of the fetal placental circulation with 15 microns microspheres for 8 days from about day 124 of gestation (term approximately 147 days) and sham-embolized controls. Starting before the final embolization (or sham-embolization) on day 8, and continuing for 24 h, the fetus was given an intravenous infusion of ACTH1-24 (0.5 microgram/h) or vehicle. Fetal and maternal blood samples were taken for determination of immunoreactive cortisol, and regional adrenal and fetal placental blood flows were measured by the microsphere technique at three time points: 1 h before infusion, 3 h after the start of the infusion (1 h after embolization), and after 24 h of infusion. Prior to infusion of ACTH or vehicle, fetal placental blood flow was lower in microsphere-embolized fetuses than in sham-embolized controls (199 +/ 15 vs 292 +/- 25 ml/min per 100 g tissue; mean +/- S.E.; P<0.01). However, plasma cortisol and adrenal cortical blood flow did not differ between embolized fetuses and controls. Adrenal vascular responses to the 24-h infusion of ACTH were similar in embolized and sham-embolized fetuses. Adrenal cortical blood flow increased 3-fold (P<0.05) due to decreased vascular resistance (P<0.01), with no change in adrenal medullary blood flow. Thus, while daily embolization of the fetal placental circulation caused a sustained decrease in cotyledonary blood flow, no evidence of altered responsiveness of the adrenal cortex to ACTH was found in these experiments.

Catecholamine and serotonin concentrations in fetal guinea-pig brain: relation to regional cerebral blood flow and oxygen delivery in the growth-restricted fetus

To test the hypothesis that intrauterine growth restriction (IUGR) would lead to altered neurotransmitter metabolism in the brain because of poorer oxygenation, blood flows and tissue concentrations of noradrenaline, dopamine, serotonin and their metabolites were measured in 14 parts of the brain of guinea-pig fetuses at 61-64 days' gestation. Eight fetuses with IUGR induced by uterine artery ligation were compared with 8 controls. Regional brain blood flows were determined by the microsphere method and tissue concentrations of monoamines by HPLC with electrochemical detection. The oxygen content of preductal arterial blood was significantly lower in IUGR fetuses than in controls (2.3 +/- 0.6 v. 3.5 +/- 0.5 mM; P < 0.001). Although this was compensated by increases in blood flow to many areas of the brain, significant decreases occurred in oxygen delivery to the temporal and occipital cortex, hippocampus and cerebellum of IUGR fetuses. In contrast, oxygen delivery to brainstem areas was maintained. Noradrenaline concentrations were closely similar in brains from the two groups, except for an increase in the caudate nucleus of IUGR fetuses. Dopamine concentrations were significantly elevated in brainstem areas. Concentrations of 3,4-dihydroxyphenylglycol (DOPEG), a noradrenaline metabolite, and 3,4-dihydroxyphenylacetic acid (DOPAC), a dopamine metabolite, showed a similar pattern of increase in brains of IUGR fetuses, possibly resulting from increased synthesis of noradrenaline and dopamine rather than from decreased degradation. Concentrations of serotonin were significantly higher in frontal and temporal cortex of IUGR fetuses, and the serotonin metabolite 5-HIAA increased significantly in cortical areas. Changes in neurotransmitter metabolism could not be related to oxygen supply, since serotonin concentrations increased in the forebrain, despite reduced oxygen delivery and the known dependence of tryptophan-5-hydroxylase on tissue PO2, and dopamine levels were elevated in the brainstem, where the oxygen supply was maintained.

Effect of arginine vasopressin on regional adrenal blood flow and plasma cortisol concentration in fetal sheep

OBJECTIVE

To determine whether arginine vasopressin (AVP) at plasma concentrations measured during moderate hypoxemia affects adrenal blood flow.

STUDY DESIGN

Regional blood flows were measured in 5 unanesthetized normoxemic fetuses (124-128 days' gestation) during a 24-h intravenous infusion of AVP in isotonic saline solution. Another 5 fetuses received an infusion of vehicle. Blood flows were determined before the infusion and at 2 h and 24 h from its onset using radionuclide-labeled microspheres.

RESULTS

At 2 h and 24 h of AVP infusion, fetal plasma concentrations of IR-AVP had risen from 4.7 +/- 0.9 pg/ml to 9.8 +/- 1.1 pg/l and 9.4 +/- 0.7 pg/ml, respectively. Thus we achieved plasma concentrations of IR-AVP comparable to those previously reported during moderate hypoxemia. There was no significant effect of treatment on fetal plasma concentrations of immunoreactive adrenocorticotropic hormone (ACTH) or cortisol. AVP infusion significantly decreased fetal heart rate and raised cotyledonary blood flow from 198 +/- 18 ml/min per 100 g to 235 +/- 17 ml/min and 218 +/- 10 ml/min per 100 g at 2 h and 24 h, respectively, from the start of the AVP infusion. Basal values for adrenal medullary and cortical blood flows were similar in the AVP and saline groups, and did not change significantly during the infusions.

CONCLUSION

These findings suggest that the rise in adrenal blood flow seen after hypoxemia is not due to a direct action of systemic AVP, but is attributable to other influences, likely including changes in circulating ACTH.

Inhibition of ACTH secretion blocks hypoxia-induced increase of adrenal cortical blood flow in fetal sheep

To examine the role of endogenous adrenocorticotropic hormone (ACTH) in adrenal blood flow responses to hypoxia, we studied unanesthetized ovine fetuses during an intravenous infusion of cortisol or vehicle. Fetal hypoxia was induced after 5 h of cortisol or vehicle infusion. Control fetuses were not made hypoxic. Blood flows were determined before and at three time points during the infusions. At 2 and 6 h of hypoxia, in vehicle-infused fetuses, fetal plasma concentrations of immunoreactive ACTH (irACTH) had risen from 9 +/- 3 (SE) pg/ml to 68 +/- 25 and 127 +/- 37 pg/ml, respectively. No significant change in fetal plasma irACTH occurred in the other groups. Adrenal cortical blood flow rose three- to fourfold during hypoxia in vehicle-infused fetuses but did not change from prehypoxia levels in cortisol-infused fetuses (P < 0.005). Medullary flow rose with hypoxemia, and this was not affected by concurrent cortisol infusion. Adrenal blood flows did not change in the control groups. Thus prior infusion of cortisol suppressed the rise in fetal plasma ACTH during hypoxia and selectively blocked the increase in adrenal cortical blood flow.

Local transfer of hormones between blood vessels within the adrenal gland may explain the functional interaction between the adrenal cortex and medulla

The adrenal cortex has a local stimulatory action on synthesis and secretion of adrenaline by the adrenal medulla. This interaction may be based on nervous transmission and/or on glucocorticoids secreted trom the cortex either exerting paracrine effects or reaching the medulla through the local vascular system. The existence of a dual capillary network, a portal system, now seems unlikely. However, a new concept is postulated: the high demand for glucocorticoids in the medulla may be met by local transfer to blood vessels within the adrenal gland, particularly the medullary arteries.

CHAMPUS psychiatric inpatient savings: military management versus contractor, the Fort Polk experience

Inpatient psychiatric costs were a significant part of the CHAMPUS bill at Bayne Jones Army Community Hospital. With implementation of Gateway to Care, a case management program was developed for intervention. In May 1993, Foundation Health Federal Services Inc. began a modified CHAMPUS Reform Initiative program providing an opportunity to retrospectively analyze two methods of managed care. Civilian hospital inpatient admissions for both programs during fiscal year (FY) 1993 were compared to corresponding periods in FY 1992. Under the case management program, admissions were reduced by 67%, occupied bed days by 74%, and costs by 76%. Under the Foundation Health Program, admissions were reduced by 13%, occupied bed days by 15%, and total costs by 42%. Both methods achieved savings over standard CHAMPUS. In spite of constraints that Foundation Health did not have, the case management program appeared to be more effective, demonstrating that a managed health care program directed by the hospital commander can significantly reduce costs.

Polymorphisms of the plasminogen activator inhibitor-1 gene in type 1 and type 2 diabetes, and in patients with diabetic retinopathy

To identify whether genotype contributes to the difference in PAI-1 levels in type 1 and type 2 diabetic subjects and whether genotype relates to the development of retinopathy, a Hind III restriction fragment length polymorphism and two dinucleotide repeat polymorphisms were studied. In 519 Caucasian diabetic subjects (192 type 1, 327 type 2) and 123 Caucasian control subjects there were no differences in the frequency of the Hind III restriction alleles (type 1 vs type 2 vs control: allele 1 0.397 vs 0.420 vs 0.448; allele 2 0.603 vs 0.580 vs 0.552) nor in the allelic frequency at either dinucleotide repeat sequence. In 86 subjects with no retinopathy at 15 years or more from diagnosis of diabetes and 190 subjects with diabetic retinopathy there was no difference in the frequency of Hind III restriction alleles (retinopathy present vs retinopathy absent: allele 1 0.400 vs 0.467; allele 2 0.600 vs 0.533) nor in the allelic frequencies at either dinucleotide repeat sequence. The results indicate that there is no or minimal influence of the PAI-1 gene on either PAI-1 levels or the development of diabetic retinopathy in patients with diabetes mellitus.

Regulation of insulin-like growth factor-II gene expression in the ovine fetal adrenal gland by adrenocorticotropic hormone and cortisol

Maturation and activation of the fetal adrenal gland is crucial to fetal organ maturation and the onset of parturition in sheep. Insulin-like growth factors (IGFs) have been demonstrated to promote fetal adrenal mitogenesis and steroidogenesis in some species. Our previous studies showed that IGF-II mRNA is expressed in the steroidogenic cells of the fetal sheep adrenal, suggesting that IGF-II may be an important regulator of fetal adrenal function. However, the regulation of IGF-II gene expression is poorly understood. In the present study we measured the changes in IGF-II mRNA level in fetal sheep adrenals during late gestation in response to ACTH and cortisol. Either saline (0.5 ml/h) or cortisol (1 mg/24 h) was infused for 100 h to fetal sheep beginning on day 95 or 96 of pregnancy, or saline (0.5 ml/h), ACTH (0.5 micrograms/h) or cortisol (1 mg/h) was infused for 84 h to fetal sheep beginning on days 120-125 of pregnancy (term = 145 days). Adrenal RNA was subjected to Northern blot analysis with an ovine IGF-II cDNA probe. The relative abundance of total IGF-II mRNA decreased significantly in the ACTH- and cortisol-treated fetuses. IGF-II mRNA was localized by in situ hybridization using a 35S-labeled antisense ovine IGF-II cRNA probe, and IGF-II peptide was localized by immunohistochemistry. There were no differences in the cellular distribution patterns of IGF-II mRNA and IGF-II peptide after treatments, but the intensity of the hybridization signal for IGF-II mRNA and of immunostaining for IGF-II peptide decreased in adrenals from fetuses treated with ACTH or cortisol. These results suggest that ACTH and cortisol decrease IGF-II gene expression in the ovine fetal adrenal. We speculate that the cortisol surge observed in the late gestation ovine fetus may be responsible for down-regulation of IGF-II gene expression in the fetal adrenal at or just before birth.

Hepatic histology in intrauterine growth retardation following uterine artery ligation in the guinea pig

Hepatic histology was examined in guinea pig fetuses in which intrauterine growth retardation (IUGR) was induced by unilateral uterine artery ligation and compared with that of control (well-grown) fetuses from uterine horns with intact circulations. From all animals, sections taken from the six lobes of the liver were prepared using hematoxylin and eosin stains. Periodic acid-Schiff and Prussian blue stains (both on fixed samples) and Oil Red O stains on frozen tissues were performed on a subset of samples. Comparisons revealed greater fat content in hepatocytes (P < .05) and decreased total hepatic hematopoiesis (P < .01) in IUGR animals than in controls. No differences in hepatocyte histology among lobes were observed in control animals. IUGR animals had increased fat content and decreased extramedullary hematopoiesis in the lobes receiving the portal circulation (P < .05). These data indicate significant abnormalities of hepatic lipid metabolism in IUGR animals following uterine artery ligation. An unexpected and counterintuitive finding was the decrease in hepatic hematopoiesis in the right side of the liver.

Regional adrenal blood flow responses to adrenocorticotropic hormone in fetal sheep

To determine whether adrenocorticotropic hormone (ACTH) at plasma concentrations measured during mild hypoxemia and at term affects adrenal blood flow, we measured regional blood flows in five unanesthetized normoxemic fetuses (125-130 days gestation) during a 24-h intravenous infusion of ACTH-(1-24) in isotonic saline solution. Another five fetuses received an infusion of vehicle. Blood flows were determined before the infusion, at 2 and 24 h from its onset, and 24 h afterward using radionuclide-labeled microspheres. Blood flow to the adrenal medulla was fivefold greater than that to the adrenal cortex. Adrenal blood flow rose 99% at 24 h of the ACTH infusion. There was a large increase in adrenal cortical blood flow of 272% at this time but medullary blood flow did not change significantly during ACTH infusion. The rise in cortical blood flow was attributable to decreased vascular resistance. No significant alterations occurred in fetal arterial blood pressure and heart rate, or in blood flow to other lower body organs of the fetus or to the placental cotyledons. These findings are consistent with the hypothesis that the increase in adrenal blood flow observed during fetal hypoxia is associated with changes in plasma ACTH concentration. They are also indicative of selective regulation of cortical and medullary blood flows in the sheep fetus at this stage of gestation.

The rate of blood flow through the inverted yolk sac placenta of the anesthetized guinea-pig

The rate of blood flow through the yolk sac placenta of late gestation guinea-pig fetuses was estimated by an indirect approach: radionuclide-labelled microspheres were injected in a saphenous vein and the ratio of radioactivity in the yolk sac to that in one of several reference organs was calculated. The ratio was then multiplied by a constant derived from separate experiments in which blood flows to the fetal abdominal organs and chorioallantoic placenta were determined. Stomach blood flow was positively correlated to arterial oxygen content (r = 0.74, P < 0.05), as was the weight-specific splenic blood flow (r = 0.66, P < 0.05). Perfusion of the small and large bowel, kidneys and chorioallantoic placenta was not related to arterial pH or oxygen content and these organs were used as references for the estimation of vitelline blood flow. A positive correlation was found between yolk sac blood flow and arterial oxygen content (r = 0.91, P < 0.01). In normoxaemic guinea-pig fetuses, yolk sac blood flow is 100-300 microliters per min.

Gastrin releasing peptide immunoreactivity is present in ovine amniotic fluid and fetal and maternal circulations. MRC Group in Fetal and Neonatal Health and Development

Using antisera directed towards the C-terminal region of gastrin releasing peptide (GRP), significant quantities of GRP-like immunoreactivity (GRPLI) were detected in ovine amniotic fluid and in the fetal and maternal circulations. The highest GRPLI levels were found in amniotic fluid (2135 +/- 829 fmol/ml, n = 12; mean +/- SEM), followed by those in ovine fetal (604 +/- 267 fmol/ml, n = 13) and maternal plasma (229 +/- 89 fmol/ml, n = 13). On gel filtration chromatography, the predominant GRPLI form in each fluid eluted in an identical position consistent with the entity being of apparently larger molecular size than porcine GRP1-27. Certain fetal plasma samples contained a second GRPLI peak eluting at the void volume. Hence, during ovine pregnancy a GRPLI entity circulates in fetal and maternal plasma; the entity is of apparently larger molecular size than GRP1-27 but contains a structure immunologically indistinguishable from the bioactive c-terminal region of GRP1-27. Given the recognized bioactivities of GRP, this entity may be an important hormone during ovine fetal life.

The metabolism of free fatty acids and triacylglycerols by the fetal liver in a guinea pig model of intrauterine growth retardation

The aim of this study was to determine whether intrauterine growth retardation (IUGR) is associated with an alteration in hepatic lipid metabolism. IUGR was induced in 25 guinea pigs by uterine artery ligation on gestational d 30. On d 62, after anesthesia, an infusion of [1-14C]-palmitic acid was given. Fetuses were exposed at 15, 30, and 45 min, and simultaneous maternal and umbilical venous blood samples were taken. Livers were divided into right lobe, right and left sublobes of the quadrate lobe, and left lobe. In control fetuses, plasma radiolipids rose in parallel with, but were about half the value of, maternal levels. In IUGR fetuses, plasma radiolipids were lower than in controls at 15 and 30 min but were comparable at 45 min. Most of the radiolipid in the maternal plasma was FFA, with only 6% incorporated into triglycerides at 45 min. In control and IUGR fetal plasmas, 36-37% of the radiolipid was triglycerides by 45 min. Radiolabel incorporation into the right lobe was less than into the left lobe and left half of the quadrate lobe in control and IUGR fetuses. Compared with controls, radiolabel incorporation in IUGR fetuses was less in some or all liver lobes at each time point. The proportion of label associated with FFA and triglycerides did not vary with time, between lobes, or between control and IUGR fetuses. The difference in uptake between lobes reflects their blood supply, implying that most FFA is extracted during the first passage of the umbilical venous blood. Growth retardation was not associated with compromised hepatic FFA metabolism.

Contribution of the umbilical and portal veins to the hepatic blood supply of guinea pig fetuses--an angiographic study

The interlobular distribution of the umbilical and portal venous blood flow within the liver was examined in 35 guinea pig fetuses between 59 and 65 days of gestation. Contrast medium was injected into the umbilical or vitelline vein, and its passage through the liver was monitored by serial angiography. In four experiments, injections were made into both the umbilical and vitelline veins of the same fetus. To ease interpretation of the angiograms obtained in vivo, we also made a postmortem examination of livers in which the venous system had been filled with an aqueous suspension of barium sulphate in gelatin. These combined experiments demonstrated no passage of contrast medium from the placenta to the inferior vena cava, which is in accordance with independent evidence that the term guinea pig fetus lacks a functional ductus venosus. The area supplied by the umbilical and portal veins was clearly and consistently delineated. The umbilical vein supplied the left lobe and the left sublobe of the quadrate lobe. The portal vein supplied the right lobe, the smaller caudate lobe, and all or most of the right sublobe of the quadrate lobe. This pattern of distribution appears to be determined by flow and pressure gradients within the hepatic circulation.

Regional brain blood flow and oxygen supply in guinea pig fetuses near term

To examine brain blood flow and oxygen supply to 14 brain regions in fetal guinea pigs near term, 6 fetuses were catheterized under general anaesthesia of the dam between days 61 and 63 of pregnancy. Fetal arterial blood pressure was measured and a blood sample was taken from the right axillary artery to determine fetal blood gases and acid-base balance. Isotope-labelled microspheres were then injected in a lateral saphenous vein and a reference blood sample was taken from the right axillary artery according to Carter and Gu. Preductal arterial haemoglobin oxygen saturation ranged from 16-33% (26.7 +/- 6.3 mean +/- SD) and pH from 7.08-7.30 (7.20 +/- 0.09); oxygen content varied between 3.0-6.7 ml/dl. Blood flow to the whole brain was 105-258 ml/min per 100 g (167 +/- 58), oxygen supply to the brain was 6.6-10.7 ml O2/min per 100 g (8.0 +/- 1.6). Both regional brain blood flow and oxygen supply were significantly different in the various brain parts. They were highest in the spinal medulla and in other parts of the brain stem and lowest in the cerebrum. Brain blood flow increased significantly with increasing pCO2 and systolic blood pressure and with decreasing haemoglobin oxygen saturation, pH, base excess, and arterial oxygen content. On the other hand, except for the mid portion of the spinal medulla, there were no correlations between blood gas and acid-base balance variables and the oxygen supply to the whole brain or to various regions of the brain.(ABSTRACT TRUNCATED AT 250 WORDS)

The blood supply to the heart and brain in the growth retarded guinea pig fetus

Blood flow to the heart and brain of 31 control and 15 growth retarded (IUGR) guinea pig fetuses was measured between 60-64 days of pregnancy by the microsphere technique. The animals were anaesthetized with diazepam and pentobarbitone. Brain weight was reduced by 11% in IUGR fetuses from 2.61 +/- 0.03 to 2.33 +/- 0.05 g and heart weight by 39% from 0.42 +/- 0.01 to 0.25 +/- 0.01 g, compared to a decrease in body weight of 42% from 83.6 +/- 2.3 to 48.2 +/- 2.2 g. The myocardial blood flow of control animals was negatively correlated to arterial O2 content (r = 0.78, P less than 0.001) and arterial pH (r = 0.68, P less than 0.001). Brain blood flow was inversely correlated to arterial O2 content in control fetuses (r = 0.79, P less than 0.001). Eight regions of the brain were examined: cerebral hemispheres, caudate nucleus, hippocampus, thalamus + hypothalamus, cerebellum, pons, and medulla. Regional blood flows were significantly correlated to fetal oxygenation in the controls. Growth retarded fetuses were characterized by poor oxygenation (arterial O2 content less than or equal to 2.5 mM) and were frequently acidaemic (pH less than 7.20). No relation could be demonstrated between the myocardial or cerebral blood flows of IUGR fetuses and arterial O2 content or pH. It is concluded that growth retarded fetuses are unable to maintain O2 delivery to the brain and myocardium by increases in blood flow. Although O2 extraction could be increased to meet the O2 requirements of the heart, IUGR fetuses had a lower rate pressure product, suggesting a decline in myocardial O2 consumption.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood flow to the placenta and lower body in the growth-retarded guinea pig fetus

Blood flow to the placenta and lower body of control and growth retarded (IUGR) guinea pig fetuses was measured between 60-64 days of pregnancy by the microsphere technique. Further information about the hepatic blood supply and its interlobular distribution was obtained by injecting microspheres into the umbilical vein and a branch of the portal vein. Liver weight was reduced by 60% in IUGR fetuses from 5.0 +/- 0.2 to 2.0 +/- 0.1 g, compared to a decrease in body weight of 50% from 91.6 +/- 3.0 to 45.4 +/- 2.6 g. In addition, there was a proportionately greater reduction in the size of the right liver lobe. Umbilical blood flow was 10.8 +/- 1.0 ml min-1 in control fetuses and 4.9 +/- 1.2 ml.min-1 in IUGR fetuses, whilst blood flow in the portal vein was reduced from 1.4 +/- 0.1 to 0.8 +/- 0.3 ml min-1 and that in the hepatic artery from 0.6 +/- 0.1 to 0.3 +/- 0.1 ml.min-1. Since ductus venosus flow was absent or negligible, the umbilical venous return accounted for greater than 80% of the hepatic blood supply in both control and IUGR fetuses. Blood flows were, however, unequally distributed between the liver lobes. The right lobe was supplied mainly by the portal vein in IUGR fetuses as well as the controls, and received less than 6% of the umbilical venous return. No significant change occurred in total liver perfusion, which was 2.8 +/- 0.2 ml min-1 per g in control fetuses and 2.6 +/- 0.4 ml min-1 per g in IUGR fetuses. It is therefore suggested that a high rate of liver metabolism is maintained in IUGR, but by a smaller tissue mass, and that the rate of umbilical blood flow may be one factor determining the size of the liver. The relatively greater reduction in size of the right lobe in IUGR is probably the result of poor oxygenation of the portal venous blood.

Factors affecting gas transfer across the placenta and the oxygen supply to the fetus

The factors that affect placental gas exchange are reviewed, with particular reference to recent measurements of the effect of changes in one or more of these factors on O2 delivery to the fetus and on fetal O2 uptake. Fetal or maternal placental blood flows and blood O2 capacities can be altered by 50% without any major change occurring in fetal O2 uptake: umbilical venous O2 content and fetal O2 delivery fall, but the O2 consumption of the fetus is maintained by increasing the fractional extraction of O2 from the blood. There is evidence that the fetus can also cope with a reduction in blood O2 affinity resulting from replacement of fetal with maternal blood. The critical level of O2 delivery is about 0.6 mmol.min-1.kg-1 in the fetal sheep. When O2 delivery is reduced below this level, by decreasing maternal placental blood flow, raising or lowering fetal haematocrit, decreasing maternal O2 capacity, or decreasing fetal O2 affinity, fetal O2 uptake tends to fall. The resultant tissue hypoxia and inability to maintain oxidative metabolism is reflected in a lowering of arterial blood pH and base excess. Whilst the results of short-term experiments suggest that there exists a large reserve for placental O2 transfer and fetal O2 supply, there is evidence that fetal O2 uptake is more tightly linked to O2 delivery when the latter is reduced for a period of days or weeks. In the long term, restriction of the supply of O2 and nutrients leads to a reduced rate of fetal growth and a reprogramming of tissue development.

Blood gas tensions, acid-base status and cardiovascular function in miniature swine anaesthetized with halothane and methoxyflurane or intravenous metomidate hydrochloride

Göttingen mini-pigs were given atropine and anaesthetized with one of the following drug combinations: 1) azaperone + metomidate, 2) acepromazine + thiopentone for endotracheal intubation, followed by halothane + methoxyflurane in oxygen. Respiration rate, arterial O2 and CO2 tensions, arterial pH, mean arterial blood pressure and heart rate were recorded at 15 min. intervals from 30 to 120 min. after the induction of anaesthesia. The azaperone-metomidate combination, which requires continuous intravenous access, caused a mild respiratory acidosis, but acid-base status was stable, whereas blood pressure and heart rate rose steadily throughout the observation period. The second combination depressed respiratory and cardiovascular function, but the condition of the animals did not deteriorate further during 2 hrs of surgical anaesthesia. Endotracheal intubation for inhalation anaesthesia should, however, be performed after a single injection of metomidate, as thiopentone tended to cause respiratory arrest.

Cerebral blood flow in the fetal guinea-pig

To measure brain blood flow in the fetal guinea-pig, radioactive microspheres were injected in the lateral saphenous vein whilst a reference sample of blood was withdrawn from the right axillary artery. Measurements were made near term of pregnancy, on the 60th-66th day, during anaesthesia with pentobarbitone and diazepam. Fetal blood pressure was 4.25 +/- 0.12 kPa and fetal heart rate was 250 +/- 7 beats per min. The arterial oxygen content varied between 1.9-5.1 mmol 1(-1). Blood flow to the whole brain (mean 1.13 +/- 0.14 ml min-1 g-1) was significantly correlated to the reciprocal of arterial oxygen content (r = 0.84). Four regions of the brain were examined: the cerebral hemispheres, the cerebellum, the thalamus and midbrain, and the pons and medulla. In each region blood flow was inversely related to arterial oxygen content (r = 0.80-0.83) but the rate of perfusion of the brain stem was greater than that of the cerebral hemispheres or cerebellum.

Migratory birds of central Washington as reservoirs of Campylobacter jejuni

Migratory ducks, Canada geese, and sandhill crane from the Pacific North American Flyway have been screened for Campylobacter spp. Samples (298) from these birds were examined and the incidence of Campylobacter spp. in the samples were as follows: sandhill crane (Grus canadensis tabida), 81%; ducks (Aythya collaris, Anas carolinensis, Aythya americana, and Anas platyrhynchos), 73%; and Canada geese (Branta canadensis), 5%. All isolates were identified as Campylobacter jejuni. To our knowledge this is the first report of the isolation of C. jejuni from sandhill crane. The high frequency of isolation in both the sandhill crane and migratory ducks indicated that these bird populations may play a significant role in the dissemination of the bacterium. Because of their migratory habits, these birds may be particularly important in spreading C. jejuni to remote areas.

Small rodents and other mammals associated with mountain meadows as reservoirs of Giardia spp. and Campylobacter spp

Sixty-five percent (469 of 722) of the fecal samples collected from small rodents in the central Washington Cascade mountains were positive for Giardia spp. Trapping studies showed that microtines of the genus Microtus were heavily infected with the parasite. Morphologically the cysts and trophozoites were of the Giardia duodenalis type. Small-rodent populations appear to maintain their infection throughout the year. Our data suggest that there is no difference in the percentage of positive animals in areas receiving a lot of human use as opposed to animals in those areas receiving very little or no human use. Giardia spp. were also found in elk and beaver fecal samples. Campylobacter spp. were recovered infrequently from the small rodents inhabiting alpine meadows. Of 551 specimens cultured, less than 1% were positive for the bacterium, and the isolates were identified as Campylobacter coli. Water voles were susceptible to a human isolate of Campylobacter jejuni and shed the bacterium for several weeks. C. jejuni was also isolated from a bear fecal sample collected from a protected watershed. Our studies indicate that microtines and possibly other small rodents inhabiting mountain meadows have a potential to act as a reservoir for both Giardia spp. and Campylobacter spp. Because these animals may carry human pathogens, they should be included in animal surveys designed to assess the health risks associated with mountain watersheds.

Seasonal occurrence of Campylobacter spp. in surface waters and their correlation with standard indicator bacteria

Campylobacter jejuni, Campylobacter coli, and a Campylobacter-like organism were isolated from a number of natural water sources in central Washington, including ponds, lakes, and small mountain streams at elevations ranging from 1,460 to 5,400 feet (ca. 445 to 1,646 m) above sea level. At the two sites where extensive sampling was done, the bacteria were recovered throughout the year. Generally, the recovery rates were highest in the fall and winter months and lowest during the spring and summer months. Campylobacter density did not show significant correlation with microbiological (plate counts of fecal and total coliforms, fecal streptococci, and heterotrophic bacteria) or physical (water temperature, pH, and conductivity) parameters.

An improved algorithm and a computer program for the analysis of capillary gas exchange

In most models of capillary gas exchange, the binding curves for O2 and CO2 are represented by simple analytical expressions, and the interactions among the haemoglobin ligands are either neglected or are assigned fixed values independent of PO2, PCO2, pH and red cell DPG. We here present algorithms and a computer program in which the binding curves are described in a near-rigorous manner. This enables solution of a set of typical equations for a unit of blood which undergoes gaseous and proton exchange. We have applied the algorithms to the problem of calculating pulmonary blood flow from the gaseous exchange in the lung by the single-breath method of Kim et al. (1966), where the CO2 binding curves of arterial and mixed venous blood are approximated by straight lines. The application of the algorithms shows that this approximation introduces significant errors in the calculated pulmonary blood flow.

Placental gas exchange in the guinea-pig: fetal blood gas tensions following the reduction of maternal oxygen capacity with carbon monoxide

The effect of CO hypoxia on the placental exchange of respiratory gases was studied in anaesthetized pregnant guinea-pigs near term. Fetal PO2 and PCO2 were measured by mass spectrometry from a blood gas catheter in the right atrium. Administration of 5 ml CO over 65 s reduced maternal oxygen capacity by 26%. There was a rapid fall in fetal arterial PO2 and a more gradual rise in fetal PCO2. It was shown in separate experiments that the carboxyhaemoglobin content of fetal blood did not alter greatly in the first few min. after CO administration, which is the interval within which fetal PO2 was seen to fall. The alteration in fetal gas tensions can therefore be ascribed to the increased oxygen affinity and reduced oxygen capacity occasioned by the presence of carboxyhaemoglobin in the maternal blood. The alteration in placental oxygen transfer was calculated from the experimental findings, using a mathematical model of placental gas exchange in the guinea-pig. The total reduction in the oxygen transfer was 32% of the initial value. It was calculated that the reduction in maternal oxygen capacity was responsible for about two-thirds of this decrease, the remainder being due to the increased oxygen affinity of maternal blood.

Excitatory response of guinea-pig myometrium to intravenous noradrenaline declines towards term

Guinea-pigs were anaesthetized at three stages of pregnancy. Intrauterine pressure was recorded for a 1-h control period and during 10-min intravenous infusions of noradrenaline at rates of 1.0 and 10 micrograms/(min X kg). The mean and maximum amplitude of contractions occurring during the infusions was compared with that of contraction cycles registered in the control period. At 18-21 and 35-43 days post coitum, noradrenaline invariably evoked a rapid and sustained rise in intrauterine pressure, the amplitude of the contractions being greater than during spontaneous contraction cycles recorded in the control period. In late pregnancy, 59-68 days p.c., infusion of 1.0 micrograms noradrenaline/(min X kg) failed to elicit a clear response; contractions occurring during infusion of 10 micrograms noradrenaline/(min X kg) had amplitudes similar to those of the control period and were without a sustained contracture. The absence of denervation hypersensitivity, despite the occurrence of sympathetic denervation in the course of pregnancy, may be due to a generalized effect on excitation-contraction coupling, possibly caused by relaxin.

Influence of injectable anaesthetic combinations on blood gas tensions and acid-base status in laboratory rats

Outbred Mol:SPRD rats were maintained in surgical anaesthesia for two hours by using five different drug combinations: 1) pentobarbitone, 2) ketamine + diazepam, 3) ketamine + pentobarbitone, 4) atropine + diazepam + fentanyl + fluanisone, 5) atropine + etorphine + acepromazine. Respiratory rate, arterial O2 and CO2 tensions, arterial pH, base excess, mean arterial blood pressure and heart rate were recorded at set intervals from 30 to 120 min. from the initiation of anaesthesia. Atropine + diazepam + fentanyl + fluanisone caused no disturbance of acid-base balance, whereas the other drug combinations induced moderate to severe acidosis. Arterial blood pressure was reduced by all methods. Pentobarbitone and regimens including ketamine reduced heart rate, whereas combinations with etorphine and fentanyl caused a rise in heart rate.

Contribution of the Bohr effect to the fall in fetal PO2 caused by maternal alkalosis

A decrease in the PO2 of fetal arterial blood is observed in maternal alkalosis caused by hyperventilation in labour or exercise. The contribution of altered blood oxygen affinity to this effect was studied experimentally and by computer simulation of placental gas exchange. Thirteen guinea pigs near term of pregnancy were anesthetized and the right atrium of the fetus was catheterized to enable continuous and simultaneous measurement of PO2 and PCO2 by mass spectrometry. An infusion of base was given through a catheter in the descending aorta of the dam and the effect on fetal respiratory gas tensions observed. The mean change in maternal arterial pH measured in blood taken from a femoral artery was 0.07 +/- 0.04 (mean +/- S. D.). There was an immediate decrease in PO2 in the right atrium of the fetus, but no consistent alteration in PCO2. Two minutes after the start of the infusion, PO2 had fallen by 3.2 +/- 1.6 Torr (p less than 0.001) and PCO2 had risen by 1.7 +/- 1.8 Torr (not significant). The experiments were simulated using a mathematical model of placental gas exchange in the guinea pig. The model was able to predict the change in fetal arterial PO2, given numerical values for the pH, PO2 and PCO2 of fetal and maternal arterial blood prior to infusion of base and for maternal blood during the infusion of base. These values were obtained from the experimental data. Other input variables of the model were maternal and fetal hematocrit and DPG concentration, and the rates of blood flow on the two sides of the placenta.(ABSTRACT TRUNCATED AT 250 WORDS)

The blood supply to the abdominal organs of the fetal guinea-pig

Guinea-pigs near term of pregnancy were anaesthetized with diazepam and sodium pentobarbitone. A fetus was exposed and the vitelline artery catheterized to measure blood pressure and heart rate or to render a reference sample of blood for the determination of organ blood flow by the microsphere technique. The radioactive microspheres were injected through a catheter in the right atrium. Mean arterial blood pressure was 4.0 kPa and heart rate was 261 beats min-1. The liver, spleen, pancreas and gut receive most of their blood supply from the same trunk as the vitelline artery. The sample from this vessel was also used to calculate blood flow to the adrenal glands, kidneys, urogenital tract, and placenta, assuming even mixing of microspheres and blood in the abdominal aorta. Umbilical blood flow, corrected to a fetal weight of 100 g, averaged 7.5 ml min-1. The adrenal glands, which are known to increase their cortisol secretion near term, had a very high rate of perfusion. If the microspheres were injected in the umbilical vein, almost all were trapped in the liver, confirming the absence of a ductus venosus in the guinea-pig fetus. Most of these microspheres were found in the quadrate lobe of the liver. Hepatic arterial blood flow was also unequally distributed, with more than two-thirds going to the right lobe of the liver. Although the distribution of portal venous blood flow is not known, it is evident that different areas of the liver are presented with blood of greatly varying oxygen saturation.

Crystal structure of Bis(8-hydroxyquinolinium) chloride tetrachloroferrate(III), a hydrogen chloride vapour pressure reference source?

The crystal structure of the title compound, [C9H8NO]2[FeCl4]C1, has been determined by single-crystal X-ray diffraction methods at 295 K and refined by least squares to a residual of 0.043 for 2415 independent 'observed' reflections. Crystals are triclinic, P1, a 14.243(5), b 10.177(3), c 7.583(3) �, α 84.71(3), β 86.96(3), γ 86.50(3�, Z 2. The organic moiety is protonated at the nitrogen atom, with the discrete chloride ions hydrogen-bonded in lattice tunnels; this offers a rationale for the finite but small hydrogen chloride partial pressure at room temperature.

Acid-base status of pregnant guinea pigs during neuroleptanalgesia with diazepam and fentanyl-fluanisone

Neuroleptanalgesia was induced in late pregnancy in guinea pigs with diazepam and fentanyl-fluanisone. Hypotension occurred, but the arterial acid-base status after 45-60 min was near normal. When repeated injections of fentanyl-fluanisone were given to maintain neuroleptanalgesia, the blood pressure fell further and severe metabolic acidosis developed. Placental blood flow determined with radioactive microspheres was much lower during maintained neuroleptanalgesia than in guinea pigs anaesthetized with diazepam and pentobarbitone.

Effect of noradrenaline on circulation in the genital tract of early and late pregnant guinea-pigs

Noradrenaline infusions were given to anaesthetized guinea-pigs in early (19--23 days) and near-term (61--66 days) pregnancy. Radioactive microspheres (15 micrometers) were used to determine blood flow in various regions of the genital tract. In late gestation, a 10-min intravenous infusion of 1 micrograms noradrenaline/min/kg elicited moderate increases in vascular resistance that were counteracted by the pressor response. Uterine and placental blood flow remained unchanged, although there was a 27% decrease in perfusion of the uterine cervix and a fall of 19% in vaginal blood flow. In early pregnant guinea-pigs, blood pressure rose but vascular resistance was unaffected, resulting in an augmentation of placental blood flow. During infusion of 10 micrograms noradrenaline/min/kg, the vasonconstrictor response in late pregnancy was accentuated, and a strong decrease in tissue perfusion was noted in the placenta (-36%), uterine horns (-39%), cervix (-70%) and vagina (-56%). At the higher rate of noradrenaline infusion, vascular resistance also increased in the genital tract of early pregnant animals, although to a lesser extent than in late pregnancy. The results indicate an enhancement of the vasoconstrictor response to circulating catecholamines in near-term pregnancy.

Blood gas tensions and acid-base status in the fetal guinea-pig

To establish reference values for blood gas tensions in the fetal guinea-pig, blood was obtained by cardiac puncture or by puncture of the umbilical vein and analysed for pH, PCO2, PO2, haemoglobin concentration (Hb), oxyhaemoglobin saturation (SO2), and packed red cell volume. The measurements were made near term of pregnancy, on the 61st-66th day, and the dams were anaesthetized with diazepam and sodium pentobarbitone. In the umbilical venous blood, mean values for pH, PCO2, PO2, Hb and SO2, respectively, were 7.324, 45.1 mmHg, 29.5 mmHg, 8.8 mmol 1(-1), and 0.57 mol O2 per mol of haemoglobin monomer. The corresponding values for arterial blood from the heart were 7.265, 53.4 mmHg, 18.6 mmHg, 9.2 mmol 1(-1) and 0.25. Thus, blood gas tensions in the fetal guinea-pig are much closer to those of fetal primates and ungulates than has been recognized previously.

Increased myometrial blood flow evoked by vasoactive intestinal polypeptide in the non-pregnant goat

1. The effect of vasoactive intestinal polypeptide (VIP) on myometrial blood flow was evaluated in anaesthetized goats. A solution of VIP, or vehicle alone, was infused into the right internal iliac artery for a period of 10 min. The myometrial blood flow in both uterine horns was measured from the third to the seventh min of the infusion by the gas clearance technique after local injection of (133)xenon in 10 mul. saline solution. Blood samples were collected from both utero-ovarian veins 5 min from the onset of the infusion and the plasma concentration of VIP determined by radio-immunoassay.2. During infusion of vehicle before VIP, myometrial blood flow was of the same magnitude in both uterine horns, i.e. 0.06-0.12 ml./min per g. The blood flow of the right horn increased to 0.20-0.39 ml./min per g during infusion of VIP (300 p-mole/min) in the ipsilateral artery, whilst that of the left horn rose to 0.13-0.26 ml./min per g. The effect was sometimes observed to last for more than 40 min.3. Increased myometrial blood flow was observed with infusion rates down to 3 p-mole/min. Once a response to VIP had been provoked, however, the vasculature sometimes became refractory to further stimulation.4. The plasma concentration of VIP increased in both utero-ovarian veins during unilateral infusion of the peptide.5. Methylene blue given through the infusion catheter stained tissue in both uterine horns, further evidencing that their blood supply is not entirely separate.6. Uterine motility was observed to diminish during the VIP infusions.7. During infusion of VIP (300 p-mole/min) heart rate rose from 146 +/- 6 to 158 +/- 7 beats/min. No significant change occurred in arterial blood pressure.8. It is concluded that the increase in blood flow is due to a local response and that, since VIP has been demonstrated in uterine nerve endings, it may act as a neuro-transmitter mediating vasodilatation in the uterus.

Effects of VIP in the female genital tract

Vasoactive Intestinal Polypeptide (VIP) has been demonstrated in the female genitourinary tract, localized in neurons which seem to innervate vessels and non-vascular smooth muscle. The present work has demonstrated that the concentration of immunoreactive VIP varies between different mammalian species and within the genital tract of the same species. Using various in vivo and in vitro preparations the peptide was found to have a dose-dependent inhibitory effect on the myoelectrical activity and contractility of the uterine muscle, and to increase myometrial blood flow. The findings support the hypothesis that VIP may play a physiological role in the local control of uterine motility and blood flow.

Adrenergic and cholinergic responses in the uteroplacental vascular bed of the guinea pig

The effects on uterine and maternal placental circulation of adrenergic and cholinergic drugs, injected selectively in the ovarian and uterine arteries of guinea pigs, were analysed by serial angiography. Noradrenaline, 0.5 nmol/kg, was found to cause a reduction in both ovarian and uterine blood flow, associated with arterial vasoconstriction and impairment of the placental circulation. This response could be prevented by alpha-adrenergic blockade with 25 nmol/kg phenoxybenzamine. At injection into the ovarian artery, phenoxybenzamine alone increased ovarian blood flow and elicited arterial vasodilatation. At injection into the uterine artery the response was more variable, but vasodilatation was observed in four animals of six. Acetylcholine, 0.5 to 5.0 nmol/kg, evoked an increase in both ovarian and uterine blood flow and arterial vasodilatation. When the dose was increased to 50 nmol/kg, dilatation of the extrinsic uterine arteries was maintained, but the placental circulation was reduced due to concomitant contraction of the myometrium. All the effects of acetylcholine could be blocked by prior administration of 10 nmol/kg atropine. This dose of atropine did not affect uterine or placental circulation when given alone.

Regional blood flow measurements with 15 micron and 50 micron microspheres in pregnant guinea-pigs

Two sizes of microsphere were used to determine regional blood flow in pregnant guinea-pigs. Tissue perfusion measured with 50 micron microspheres was significantly greater than that measured with 15 micron microspheres in the small intestine, uterus, vagina, and placenta. A significantly larger proportion of the smaller microspheres passed through the systemic vasculature and could be detected in the lungs.

Myoendothelial and placental blood flow responses to ritodrine infusion in the guinea pig

The effect of ritodrine hydrochloride on uterine blood flow was investigated in near-term guinea pigs. The infusion of ritodrine in doses sufficient to inhibit uterine activity provoked tachycardia, and the cardiac output tended to rise. The percentage of cardiac output reaching the gravid uterus did not alter during the infusion of 12 micrograms per minute of ritodrine but decreased from 12% to 10% when the infusion rate was 120 micrograms per minute. There was an increase in the myoendothelial fraction of cardiac output in both instances, whereas the placental fraction decreased at the higher rate of infusion. Perfusion of the myoendothelial tissue improved during the infusion of 12 or 120 micrograms per minute of ritodrine, increasing by 25% and 18% respectively. No significant alteration occurred in the perfusion of the placental tissue.

Effect of terbutaline sulphate on ovarian, uterine and maternal placental blood flow in the anesthetized guinea pig

The effect of terbutaline sulphage, a beta-adrenergic agonist, on uteroplacental blood flow was studied in the guinea pig during late pregnancy. Organ blood flows and cardiac output were assessed by the radioactive microsphere technique. Infusion of terbutaline at a rate of 2nmol min-1 kg-1 body weight caused a significant increase in cardiac output and in the perfusion of the uterus and ovaries, but there was no significant alteration in maternal placental blood flow. When the infusion rate was increased tenfold, there was also a significant rise in the blood supply to the bronchi, urinary bladder, kidneys, and adrenal glands. Maternal placental blood flow was not adversely affected even by this large dose of the drug, although there was a significant reduction in the placental share of the cardiac output.

Actions of a new vasopressin analogue (1-deamino-6-carba-[8-arginine]-vasopressin) on regional blood flow in pregnant guinea pigs

Regional blood flow responses to 1-deamino-6-carba-(8-arginine)-vasopressin (dCAVP) were investigated in pregnant guinea pigs by the radioactive microsphere technique. Intravenous injection of 0.1 microgram/kg body weight caused a moderate rise in mean arterial blood pressure from 6.8 to 7.9 kPa, a significant reduction in tissue perfusion of the stomach, mammary gland, urinary bladder and vagina, and a significant increase in renal and cerebral blood flow. In a small number of animals given 1.0 microgram/kg of dCAVP, which evoked a strong pressor response, it was also possible to demonstrate a reduction in cutaneous and pancreatic blood flow and an augmentation of adrenal blood flow. Uterine and maternal placental blood flow did not alter significantly following administration of this vasopressin analogue.

Effect of 1-deamino-6-carba- (8-arginine)- vasopressin on organ blood flow in the female guinea pig

An analogue of (8-arginine)-vasopressin, characterized by removal of the Nalpha-amino group and replacement of the disulphide bridge with a thioether bridge (dCAVP), was found to increase blood flow to the brain, kidneys and adrenal glands of female guinea pigs whilst decreasing perfusion of the skin and skeletal muscle. An increase was noted in the proportion of 15 micrometer microspheres trapped in the spleen, probably contingent upon reduced arteriole-venous shunting. These responses were obtained both at estrus and during the luteal phase of the estrous cycle. In contrast, uterine and vaginal blood flows showed a significant reduction only during the luteal phase.

Blood flow to the genital tract of oestrous and dioestrous guinea-pigs

Ovarian, uterine and vaginal blood flow were determined in 22 virgin guinea-pigs by the tracer microsphere technique. Measurements were made during oestrus, when cornified cells appeared in the vaginal smear (Day 1), or during the luteal phase of the cycle (Day 11). The total rate of blood flow to the genital tract was 0-58 ml.min-1 on Day 11 and 2-92 ml.min-1 on Day 1. This difference was largely due to an 8-fold increase in uterine blood flow from 0-26 to 2-01 ml.min-1. Although uterine weight increased over the same period, there was a significant increase in uterine tissue perfusion from 0-32 to 1-18 ml.min-1.g-1. The vagina exhibited a similar pattern, including a significant increase in tissue perfusion. Ovarian blood flow decreased from a value of 0-19 ml.min-1 during the luteal phase to 0-10 ml.min-1 at oestrus. Perfusion of the ovarian tissue was considerably greater on Day 11 than on Day 1 (2-86 versus 1-39 ml.min-1.g-1).

Effect of a vasopressin analogue (Nalpha-glycyl-glycyl-glycyl-[8-lysine]-vasopressin) on organ blood flow in the pregnant guinea pig

Nalpha-triglycyl-(8-lysine)-vasopressin (TGLVP) was administered intravenously to pregnant guinea pigs and the effect on regional blood flow examined by the radioactive microsphere technique. A dose of 10 mug/kg TGLVP caused an elevation of the mean arterial blood pressure, from 6.4 to 11.1 kPa, a significant reduction in blood flow to the gut, skin and skeletal muscle and a significant increase in blood flow to the spleen. The number of 15 +/- 5 mum microspheres reaching the lungs diminished significantly after 10 mug/kg TGLVP, indicating that this dose constricted arterio-venous short circuits in the systemic circulation. There was also a decrease in blood flow to the urogenital tract, including the placentae. When 3 mug/kg TGLVP was injected, the mean arterial blood pressure rose from 6.5 to 8.7 kPa and there was no longer any consistent effect on maternal placental blood flow. It is suggested that pregnancy constitutes a contraindication for TGLVP, since a reduction in uterine and maternal placental blood flow might occur with clinically relevant doses.