Regulatory response to washout of amniotic fluid in sheep

To test the hypothesis that a substance present in the amniotic fluid could serve as a regulator of amniotic fluid volume, we drained and discarded amniotic fluid while replacing it with lactated Ringer solution that was isotonic to amniotic fluid. Seven ewes with singleton fetuses at 119 +/- 1 days of gestation (mean +/- SE) were instrumented with multiple indwelling catheters in the pedal artery, pedal vein, and amniotic cavity. During the exchange periods, an average of 3,019 +/- 171 ml/day of lactated Ringer solution was infused into the amniotic cavity while an equal amount of amniotic fluid was pumped out and discarded. During the control period, amniotic fluid composition and volume were not altered. Exchange and control periods started with the same amniotic fluid volume, lasted 3 or 4 days, and were randomized with regard to order. Amniotic fluid volume measured by vacuum drainage was 556 +/- 98 ml at the end of the control period and 986 +/- 209 ml (P = 0.03) at the end of the exchange period. Fetal arterial blood gases, hemodynamic parameters and the osmolality gradient between fetal plasma and amniotic fluid were not altered by the exchange process. A linear relationship between the control amniotic fluid volume and the volume at the end of the exchange period (P = 0.003) suggests that the animals with larger control volumes responded to isovolumic dilution with a larger volume increase. We conclude that amniotic fluid may contain a substance that regulates amniotic volume.     

In vivo brown fat response to hypothermia and norepinephrine in the ovine fetus

The goal of this study was to assess the response of fetal brown fat in vivo to hypothermia and norepinephrine infusion. In 10 unanaesthetized, chronically-prepared fetal sheep (133 +/- 2 days of gestation) cold water was passed through tubing encircling the fetus in utero and plasma glycerol concentration was measured as an indicator of brown fat activity. Following cooling for 60 min, amniotic fluid temperature fell 7.79 degrees C to 31.66 +/- 1.73 degrees C (n = 8, P less than 0.001) and maternal temperature fell 0.63 degree C to 38.63 +/- 0.08 degrees C (n = 9, P less than 0.001). Eight of the fetuses were subjected to a second experiment in which norepinephrine was infused intravenously for 15 min. During infusion fetal arterial temperature fell 0.38 degrees C to 39.05 +/- 0.25 degrees C (n = 7, P less than 0.05). Amniotic fluid temperature (n = 7, NS) and maternal arterial temperature (n = 7, NS) remained constant. Glycerol concentration during the infusion increased from 0.73 to 1.27 mg/dl, a 74% increase over control (n = 8, P less than 0.001). Although clearly detectable, these glycerol responses to hypothermia and norepinephrine stimulation are one-third or less of those achieved after birth, indicating that thermogenesis remains quiescent in the near-term fetal sheep, despite powerful stimuli for activation.     

Absorption of amniotic fluid by amniochorion in sheep

Swallowing of amniotic fluid and lung fluid inflow were eliminated in 10 chronically instrumented fetuses. The urachus was ligated, and fetal was urine drained to the outside. At the beginning and the end of 21 experiments of 66 +/- 5 (SE) h duration, all amniotic fluid was temporarily drained to the outside for volume measurement and sampling. Amniotic fluid osmolalities and oncotic pressures were experimentally controlled. Amniochorionic absorption of amniotic fluid depended strongly on the osmolality difference between amniotic fluid and fetal plasma (P < 0.001), but at zero osmolality difference there still was a mean absorption rate of 23.8 +/- 4.7 (SE) ml/h (P < 0.001). Absorption was unaffected by the protein concentration difference between amniotic fluid and fetal plasma, but infused bovine albumin in the amniotic fluid was absorbed at a rate of 1.8 8 +/- 0.4 g/h (P < 0.001), corresponding to a volume flow of fluid of 33.8 8 +/- 6.1 ml/h (P < 0.001). Fluid absorption in the amniochorion is driven in part by crystalloid osmotic pressure, but about 25 ml/h is absorbed by a path that is permeable to protein. That path has the physiological characteristics of lymphatic drainage, although no anatomic basis is known to exist for a lymphatic system in the amniochorion.     

Maternal dietary fat alters amniotic fluid and fetal intestinal membrane essential n-6 and n-3 fatty acids in the rat

We investigated whether maternal fat intake alters amniotic fluid and fetal intestine phospholipid n-6 and n-3 fatty acids. Female rats were fed a 20% by weight diet from fat with 20% linoleic acid (LA; 18:2n-6) and 8% alpha-linolenic acid (ALA; 18:3n-3) (control diet, n = 8) or 72% LA and 0.2% ALA (n-3 deficient diet, n = 7) from 2 wk before and then throughout gestation. Amniotic fluid and fetal intestine phospholipid fatty acids were analyzed at day 19 gestation using HPLC and gas-liquid chromotography. Amniotic fluid had significantly lower docosahexaenoic acid (DHA; 22:6n-3) and higher docosapentaenoic acid (DPA; 22:5n-6) levels in the n-3-deficient group than in the control group (DHA: 1.29 +/- 0.10 and 6.29 +/- 0.33 g/100 g fatty acid; DPA: 4.01 +/- 0.35 and 0.73 +/- 0.15 g/100 g fatty acid, respectively); these differences in DHA and DPA were present in amniotic fluid cholesterol esters and phosphatidylcholine (PC). Fetal intestines in the n-3-deficient group had significantly higher LA, arachidonic acid (20:4n-6), and DPA levels; lower eicosapentaenoic acid (EPA; 20:5n-3) and DHA levels in PC; and significantly higher DPA and lower EPA and DHA levels in phosphatidylethanolamine (PE) than in the control group; the n-6-to-n-3 fatty acid ratio was 4.9 +/- 0.2 and 32.2 +/- 2.1 in PC and 2.4 +/- 0.03 and 17.1 +/- 0.21 in PE in n-3-deficient and control group intestines, respectively. We demonstrate that maternal dietary fat influences amniotic fluid and fetal intestinal membrane structural lipid essential fatty acids. Maternal dietary fat can influence tissue composition by manipulation of amniotic fluid that is swallowed by the fetus or by transport across the placenta.     

Chemical dilution and clearance studies to estimate amniotic fluid volume and amniotic fluid ingestion in normal baboon pregnancies

Amniotic fluid volume (AFV) and amniotic fluid ingestion rate (or fetal swallowing rate, FSR) were estimated by inulin and para-aminohippurate (PAH) dilution in 14 normal baboon pregnancies. Mean (± SE) AFV was significantly lower at 137–140 days of pregnancy (preterm) than at 173–178 days (term) (inulin: 326 ± 22.9 ml vs 483 ± 55.9 ml, P = 0.014; PHA:269 ± 39.4 ml vs 471 ± 39.4 ml, P = 0.002). In proportion to fetal weight, however, mean AFV was similar throughout the third trimester of pregnancy (inulin: 582 ± 40.9 ml/kg; PAH: 541 ± 39.8 ml/kg). Mean FSR was lower in preterm than in term animals when estimated by inulin dilution (587 ± 55.5 ml/day vs 784 ± 55.0 ml/day, P = 0.030) but not when estimated by PAH dilution (753 ± 65.7 ml/day vs 625 ± 50.6 ml/day). In proportion to their weights, however, preterm fetuses swallowed amniotic fluid more rapidly than term fetuses (inulin: 1,216 ± 117.6 ml/kg/day vs 840 ± 67.5 ml/kg/day, P = 0.025; PAH: 1,561 ± 142.9 ml/kg/day vs 682 ± 62.7 ml/kg/day, P < 0.001). Furthermore, our data suggest that the commonly accepted technique for estimating AFV may be based on inaccurate premises, that insulin may be a better marker than PAH to estimate AFV and FSR, and that needle aspiration of amniotic fluid does not appear to be an adequate technique to validate chemical dilution methods. Our data, however, provide estimates which indicate that the baboon is an appropriate animal model in which to seek refinements and validation of our techniques.     

Effect of physical training on the capacity to secrete epinephrine

Epinephrine responses to hypoglycemia and to identical relative work loads have been shown to be higher in endurance-trained athletes than in untrained subjects. To test the hypothesis that training increases the adrenal medullary secretory capacity, we studied the effects of glucagon (1 mg/70 kg iv), acute hypercapnia (inspired O2 fraction = 7%), and acute hypobaric hypoxia (inspired Po2 = 87 Torr), respectively, on the epinephrine concentration in arterialized hand vein blood in eight endurance-trained athletes [T, O2 uptake = 66 (62-70) ml.min-1.kg-1] and seven sedentary males [C, O2 uptake = 46 (41-50)]. In response to identical increments in glucagon concentrations, plasma epinephrine increased more in T than in C subjects [0.87 +/- 0.11 vs. 0.38 +/- 0.14 (SE) nmol/l, P less than 0.05]. In response to hypercapnia [arterial PCO2 = 56 +/- 0.7 Torr (T) and 55 +/- 0.4 (C), P greater than 0.05], the increment in epinephrine was significant in T (0.38 +/- 0.11 nmol/l) but not (P less than 0.1) in C subjects (0.22 +/- 0.11). Hypoxia [arterial PO2 = 42 +/- 2 Torr (T) and 41 +/- 2 (C), P greater than 0.05] increased epinephrine in T (0.22 +/- 0.10 nmol/l, P less than 0.05) but not in C subjects (0.01 +/- 0.07). The plasma norepinephrine concentration never changed, whereas heart rate always increased, the increase being higher (P less than 0.05) in T than in C subjects only during hypercapnia. The results indicate that training increases the capacity to secrete epinephrine.     

Ventilatory behavior during sleep among A/J and C57BL/6J mouse strains.

The pattern of breathing during sleep could be a heritable trait. Our intent was to test this genetic hypothesis in inbred mouse strains known to vary in breathing patterns during wakefulness (Han F, Subramanian S, Dick TE, Dreshaj IA, and Strohl KP. J Appl Physiol 91: 1962-1970, 2001; Han F, Subramanian S, Price ER, Nadeau J, and Strohl KP, J Appl Physiol 92: 1133-1140, 2002) to determine whether such differences persisted into non-rapid eye movement (NREM) and rapid eye movement (REM) sleep. Measures assessed in C57BL/6J (B6; Jackson Laboratory) and two A/J strains (A/J Jackson and A/J Harlan) included ventilatory behavior [respiratory frequency, tidal volume, minute ventilation, mean inspiratory flow, and duty cycle (inspiratory time/total breath time)], and metabolism, as performed by the plethsmography method with animals instrumented to record EEG, electromyogram, and heart rate. In all strains, there were reductions in minute ventilation and CO2 production in NREM compared with wakefulness (P < 0.001) and a further reduction in REM compared with NREM (P < 0.001), but no state-by-stain interactions. Frequency showed strain (P < 0.0001) and state-by-strain interactions (P < 0.0001). The A/J Jackson did not change frequency in REM vs. NREM [141 +/- 15 (SD) vs. 139 +/- 14 breaths/min; P = 0.92], whereas, in the A/J Harlan, it was lower in REM vs. NREM (168 +/- 14 vs. 179 +/- 12 breaths/min; P = 0.0005), and, in the B6, it was higher in REM vs. NREM (209 +/- 12 vs. 188 +/- 13 breaths/min; P < 0.0001). Heart rate exhibited strain (P = 0.003), state (P < 0.0001), and state-by-strain interaction (P = 0.017) and was lower in NREM sleep in the A/J Harlan (P = 0.035) and B6 (P < 0.0001). We conclude that genetic background affects features of breathing during NREM and REM sleep, despite broad changes in state, metabolism, and heart rate.     

High frequency of vitamin B12 deficiency in asymptomatic individuals homozygous to MTHFR C677T mutation is associated with endothelial dysfunction and homocysteinemia

The aim of this study was to examine the association of homozygosity for the methylenetetrahydrofolate reductase (MTHFR) C677T mutation and vitamin B12 deficiency in 360 asymptomatic individuals and to investigate forearm endothelial function in C677T homozygotes. MTHFR C677T mutation and levels of vitamin B12, folic acid, and homocysteine were measured in study participants. Frequency of homozygosity for the C677T mutation was 67/360 (18.6%). Homocysteine levels were elevated in homozygous compared with heterozygous subjects or those without the mutation (20.6 +/- 18.8 vs. 9.4 +/- 3.2 mumol/l; P < 0.0001). The number of subjects with vitamin B12 deficiency (<150 pmol/l) was significantly higher among the homozygote than the heterozygote subjects or subjects without mutation [20/67 (29.8%) vs. 27/293 (9.2%); P < 0.0001]. Homozygote subjects had 4.2 times higher probability of having B12 deficiency (95% confidence interval = 2.1-8.3). Forearm endothelial function was assessed in 33 homozygote and 12 control subjects. Abnormal endothelial function was observed in homozygous subjects and was worse in homozygote subjects with vitamin B12 deficiency. Endothelial function was normalized after B12 and folic acid treatment. We found that homozygosity for the C677T mutation is strongly associated with B12 deficiency. Coexistence of homozygosity for the C677T mutation and B12 deficiency is associated with endothelial dysfunction and can be corrected with vitamin B12 and folic acid treatment.     

Maternal dehydration: impact on ovine amniotic fluid volume and composition

Maternal dehydration consistent with mild water deprivation or moderate exercise results in maternal and fetal plasma hyperosmolality and increased plasma arginine vasopressin (AVP). Previous studies have demonstrated a reduction in fetal urine and lung fluid production in response to maternal dehydration or exogenous fetal AVP. As fetal urine and perhaps lung liquid combine to produce amniotic fluid, maternal dehydration may affect the amniotic fluid volume and/or composition. In the present study, six chronically-prepared pregnant ewes with singleton fetuses (128 +/- 1 day) were water deprived for 54 h to determine the effect on amniotic fluid. Maternal plasma osmolality (306.5 +/- 0.9 to 315.6 +/- 1.9 mOsm/kg) and AVP (1.9 +/- 0.2 to 22.2 +/- 3.2 pg/ml) significantly increased during dehydration. Similarly, fetal plasma osmolality (300.0 +/- 0.9 to 312.7 +/- 1.7 mOsm/kg) and AVP (1.4 +/- 0.1 to 10.4 +/- 2.4 pg/ml) increased in parallel to maternal values. Amniotic fluid osmolality (276.8 +/- 5.7 to 311.6 +/- 6.5 mOsm/kg) and sodium (139.8 +/- 4.8 to 154.0 +/- 5.4 mEq/l) and potassium (9.1 +/- 1.3 to 13.9 +/- 2.4 mEq/l) concentrations increased while a significant (35%) reduction in amniotic fluid volume occurred (871 +/- 106 to 520 +/- 107 ml). These results indicate that maternal dehydration may have marked effects on maternal-fetal-amniotic fluid dynamics, possibly contributing to the development of oligohydramnios.     

Elevated interstitial fluid volume in rat soleus muscles by hindlimb unweighting.

Hindlimb unweighting is a commonly used model to study skeletal muscle atrophy associated with disuse and exposure to microgravity. However, a discrepancy in findings between single fibers and whole muscle has been observed. In unweighted solei, specific tension deficits are greater in whole muscle than in single fibers. Also, metabolic enzyme activity when normalized per gram of mass is depressed in whole muscle but not in single fibers. These observations suggest that soleus muscle interstitial fluid volume may be elevated with atrophy caused by unweighting in rats. The purpose of this study was to determine if soleus muscle atrophy induced by unweighting is accompanied by alterations in muscle interstitial fluid volume and to calculate the effect of any such alterations on the muscle specific tension (N/cm2 muscle cross-sectional area). Nine female Wistar rats (200 g) were hindlimb unweighted (HU) by tail suspension. Soleus muscles were studied after 28 days and compared with those from five age-matched control (C) rats. Interstitial fluid volume ([3H]inulin space) and maximum tetanic tension (Po) were measured in vitro at 25 degrees C. Soleus muscles atrophied 58% because of unweighting (C = 147.8 +/- 2.3 mg; HU = 62.3 +/- 3.6 mg, P less than 0.001). Relative muscle interstitial fluid volume increased 107% in HU rats (35.5 +/- 2.8 microliters/100 mg wet mass) compared with the control value of 17.2 +/- 0.5 microliters/100 mg (P less than 0.001); however, absolute interstitial fluid volume (microliters) was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)     

Threonine dehydrogenase is a minor degradative pathway of threonine catabolism in adult humans

The threonine dehydrogenase (TDG) pathway is a significant route of threonine degradation, yielding glycine in experimental animals, but has not been accurately quantitated in humans. Therefore, the effect of a large excess of dietary threonine, given either as free amino acid (+Thr) or as a constituent of protein (+P-Thr), on threonine catabolism to CO(2) and to glycine was studied in six healthy adult males using a 4-h constant infusion of L-[1-(13)C]threonine and [(15)N]glycine. Gas chromatography-combustion isotope ratio mass spectrometry was used to determine [(13)C]glycine produced from labeled threonine. Threonine intakes were higher on +Thr and +P-Thr diets compared with control (126, 126, and 50 micromol x kg(-1) x h(-1), SD 8, P < 0.0001). Threonine oxidation to CO(2) increased threefold in subjects on +Thr and +P-Thr vs. control (49, 45, and 15 micromol x kg(-1) x h(-1), SD 6, P < 0.0001). Threonine conversion to glycine tended to be higher on +Thr and +P-Thr vs. control (3.5, 3.4, and 1.6 micromol x kg(-1) x h(-1), SD 1.3, P = 0.06). The TDG pathway accounted for only 7-11% of total threonine catabolism and therefore is a minor pathway in the human adult.     

Differences in amniotic fluid and maternal serum cytokine levels in early midtrimester women without evidence of infection

The amniotic fluid cytokine profile has been shown to be indicative of various disease states, and changes may be associated with preterm labor or infection. Anti-inflammatory cytokine profiles may be essential for successful normal pregnancy. However, there are currently few normative data on the concentration of cytokines in amniotic fluids during pregnancy. The aim of this study was to provide new amniotic fluid cytokine data for future comparative studies in disease states, notably in utero viral infections, and to compare these with maternal serum levels. Amniotic fluid was obtained from 100 pregnant women undergoing elective amniocentesis at the Royal Hospital for Women, Randwick. Concentrations of 27 cytokines were simultaneously measured in amniotic fluid and a subset of matching maternal sera (n=33) using a multiplex bead-based immunoassay system (Bio-Plex, Bio-Rad). To exclude infection, nested multiplex PCR targeting 17 known congenital infectious agents were performed on all amniotic fluid and maternal serum samples, and serological testing was also performed against some of these agents. Maternal serum concentration was positively correlated with amniotic fluid levels for MIP-1beta (r=0.39, P=0.027). IL-1ra was positively correlated to maternal age (r=0.210, P=0.036), and mean IL-5 levels were significantly higher in amniotic fluids from pregnancies with male fetuses than those with female fetuses (P=0.036). Normal amniotic fluid concentrations for five cytokines (IL-6, IL-8, IP-10, MCP-1, IL-1ra) were found to be significantly elevated over maternal serum concentrations in matched pairs (P<0.05). Concentrations of 12 cytokines (eotaxin, IFN-gamma, IL-9, IL-12, IL-15, IL-17, MIP-1alpha, MIP-1beta, RANTES, TNF-alpha, VEGF, PDGF bb) were significantly elevated in maternal serum compared to paired amniotic fluid at midtrimester (P<0.05). Amniotic fluid may be more representative of the fetal cytokine profile than cytokine analysis on antenatal sera as it represents predominantly fetal urinary and respiratory secretions. This study provides new normative data for multiple cytokine levels in amniotic fluid and maternal sera at 14-16 weeks gestation, and is a valuable tool for future diagnostic and comparative studies.     

Thermal adjustments to nonexertional heat stress in mature and senescent Fischer 344 rats

The purpose of this study was to test the hypothesis that the rise in colonic temperature (Tc) during nonexertional heat stress is exaggerated in senescent (SEN, 24 mo, n = 12) vs. mature (MAT, 12 mo, n = 15) conscious unrestrained Fischer 344 rats. On 2 separate days (48 h apart) each SEN and MAT animal was exposed to an ambient temperature (Ta) of 42 degrees C (relative humidity 20%) until a Tc of 41 degrees C was attained and then cooled at a Ta of 26 degrees C until Tc returned to the initial control level. Control Tc was similar in the two groups for both trials. The rate of Tc change during heating was 63% greater (0.070 +/- 0.005 vs. 0.043 +/- 0.004 degrees C/min, P less than 0.05) and the time to 41 degrees C reduced by 36% (54 +/- 6 vs. 85 +/- 10 min, P less than 0.05) in MAT vs. SEN animals during the first exposure, although the cooling rate was slower in the MAT (0.048 +/- 0.004 degrees C/min) vs. SEN (0.062 +/- 0.006 degrees C/min) animals (P less than 0.05). The heating rate was unchanged in MAT animals between trials 1 and 2. However, SEN animals had a 95% increase in heating rate in trial 2 compared with trial 1 (P less than 0.05), and the corresponding time to 41 degrees C was decreased by 44% (P less than 0.05). As a result, rate of heating and time to 41 degrees C were similar in the two groups during trial 2. The cooling rate was similar between trials within each group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mild streptozotocin diabetes in the Göttingen minipig. A novel model of moderate insulin deficiency and diabetes

Nonrodent models of diabetes are needed for practical and physiological reasons. Induction of mild insulin-deficient diabetes was investigated in male G?ttingen minipigs by use of streptozotocin (STZ) alone (75, 100, and 125 mg/kg) or 125 mg/kg combined with pretreatment with nicotinamide (NIA; 0, 20, 67, 100, 150, and 230 mg/kg). Use of NIA resulted in a less steep slope of the regression line between fasting plasma glucose and changing doses compared with STZ [-7.0 +/- 1.4 vs. 29.7 +/- 7.0 mM. mg(-1). kg(-1), P < 0.0001]. Intermediate NIA doses induced moderate changes of glucose tolerance [glucose area under the curve increased from 940 +/- 175 to 1,598 +/- 462 mM. min, P < 0.001 (100 mg/kg) and from 890 +/- 109 to 1,669 +/- 691 mM. min, P = 0.003 (67 mg/kg)] with reduced insulin secretion [1,248 +/- 602 pM. min after 16 days and 1,566 +/- 190 pM. min after 60 days vs. 3,251 +/- 804 pM. min in normal animals (P < 0.001)] and beta-cell mass [5.5 +/- 1.4 mg/kg after 27 days and 7.9 +/- 4.1 mg/kg after 60 days vs. 17.7 +/- 4.7 mg/kg in normal animals (P = 0.009)]. The combination of NIA and STZ provided a model characterized by fasting and especially postprandial hyperglycemia and reduced, but maintained, insulin secretion and beta-cell mass. This model holds promise as an important tool for studying the pathophysiology of diabetes and development of new pharmacological agents for treatment of the disease.     

The effect of prolonged exposure of pregnant rats to high ambient temperature on several constituents of the genital tract's fluids

1. Various constituents of the genital tract's (GT) fluids were measured in heat-exposed rats (kept for at least 30 days at 35 +/- 1 degree C) and control rats (maintained at 22 +/- 2 degrees C). 2. There were no differences between the groups in the GT fluid volume, protein, free amino acids and glucose contents. 3. Arterial and venous blood glucose levels, pO2 and pH values were similar in both groups. 4. GT fluid protein hydrolysate from heat-exposed rats showed significantly reduced contents of glycine and alanine and elevated contents of valine and lysine as compared with controls. 5. The GT fluid's free amino acid components showed reduced glycine and elevated valine and isoleucine in the heat-exposed group as compared with controls. 6. Progesterone levels in GT fluid of heat-exposed rats was 60% higher than that of controls. 7. It is suggested that the higher progesterone concentration and the altered relative contents of several free amino acids with a possible change in the proteins of the GT fluid may affect the development of the embryo in heat-exposed rats.     

Chronic hypoxia induces nonreversible right ventricle dysfunction and dysplasia in rats

The purpose of this study was to evaluate the reversibility of right ventricular (RV) remodelling after pulmonary artery hypertension (PAHT) secondary to 3 wk of hypobaric hypoxia. A group of 10 adult male Wistar rats were studied and were the following: control normoxic (C), after 3 wk of chronic hypoxia (CH), and after 3 wk of exposure to hypoxia followed by 3 wk of normoxia recovery (N-RE). Mean pulmonary artery pressure was 11 +/- 2 mmHg in the C group, 35 +/- 2 mmHg in the CH group, and 14 +/- 3 mmHg in the N-RE group. RV function was assessed by echocardiography. In the CH group, the pulmonary flow measured in Doppler mode depicted a midsystolic notch and a decrease of the pulmonary acceleration time compared with control [17 +/- 1 vs. 34 +/- 1 ms (n = 10), respectively; P < 0.05]. RV thickening measured in M-mode was apparent in the CH group compared with the control group [2.84 +/- 0.40 vs. 1.73 +/- 0.26 mm (n = 10), P < 0.05]. In the N-RE group, the RV wall was significantly thinner compared with the CH group [1.56 +/- 0.08 vs. 1.73 +/- 0.26 mm (n = 10), P < 0.05]. The calculated RV diameter shortness fraction was not different between the CH group and C group (34 +/- 4.2% vs. 36 +/- 2.8%) but decreased in the N-RE group [20 +/- 2.4% (n = 10), P < 0.01]. The E-to-A wave ratio on the tricuspid Doppler inflow was significantly lower in the CH group and N-RE group compared with the C group [0.70 +/- 0.8 and 0.72 +/- 0.1 vs. 0.88 +/- 0.2 (n = 10), respectively; P < 0.05]. In the isolated perfused heart using the Langendorff method, RV compliance was increased in the CH group and decreased in the N-RE group. In the N-RE group, fibrous bands with metaplasia were observed on histological sections of the RV free wall. We conclude that PAHT induces nonreversible RV dysfunction with dysplasia.     

Role of skin blood flow and sweating rate in exercise thermoregulation after bed rest.

Two potential mechanisms, reduced skin blood flow (SBF) and sweating rate (SR), may be responsible for elevated intestinal temperature (T(in)) during exercise after bed rest and spaceflight. Seven men underwent 13 days of 6 degrees head-down bed rest. Pre- and post-bed rest, subjects completed supine submaximal cycle ergometry (20 min at 40% and 20 min at 65% of pre-bed rest supine peak exercise capacity) in a thermoneutral room. After bed rest, T(in) was elevated at rest (+0.31 +/- 0.12 degrees C) and at the end of exercise (+0.33 +/- 0.07 degrees C). Percent increase in SBF during exercise was less after bed rest (211 +/- 53 vs. 96 +/- 31%; P < or = 0.05), SBF/T(in) threshold was greater (37.09 +/- 0.16 vs. 37.33 +/- 0.13 degrees C; P < or = 0.05), and slope of SBF/T(in) tended to be reduced (536 +/- 184 vs. 201 +/- 46%/ degrees C; P = 0.08). SR/T(in) threshold was delayed (37.06 +/- 0.11 vs. 37.34 +/- 0.06 degrees C; P < or = 0.05), but the slope of SR/T(in) (3.45 +/- 1.22 vs. 2.58 +/- 0.71 mg x min-1 x cm-2 x degrees C-1) and total sweat loss (0.42 +/- 0.06 vs. 0.44 +/- 0.08 kg) were not changed. The higher resting and exercise T(in) and delayed onset of SBF and SR suggest a centrally mediated elevation in the thermoregulatory set point during bed rest exposure.     

Circadian uterine activity in the pregnant rhesus macaque: do prostaglandins play a role?

Eight rhesus macaques between 127 and 132 days of gestation had catheters implanted into maternal femoral vessels and the amniotic fluid cavity and were placed in a vest-and-tether system for chronic catheter maintenance. Uterine activity was continuously recorded, and paired maternal arterial blood and amniotic fluid samples were collected at 0900 h (AM) and 2100 h (PM) until delivery and analyzed for prostaglandin metabolites (PGFM and PGEM-II). A circadian pattern in uterine contractility was observed, with peak activity occurring between 1900 and 0100 h (p less than 0.001). No significant AM-PM differences were observed in maternal plasma PGFM (240 +/- 24 AM vs. 273 +/- 35 PM) or PGEM-II (537 +/- 41 AM vs. 484 +/- 34 PM) or amniotic fluid PGFM (360 +/- 72 AM vs. 287 +/- 70 PM) or PGEM-II (1626 +/- 383 AM vs. 1771 +/- 431 PM). All values represent mean +/- SEM, pg/ml. Additional samples were collected at 3-h intervals for 24 h at selected times during the study. This more intensive sampling protocol also failed to reveal any significant time trends in maternal plasma or amniotic fluid prostaglandins. Despite the lack of AM-PM differences, amniotic fluid PGFM and PGEM-II increased significantly as delivery approached (p less than 0.01). It appears that circadian uterine activity is not related to changes in maternal plasma or amniotic fluid prostaglandins. Although prostaglandins are responsible for the progression of labor, other factors may be involved in the generation of uterine activity rhythms prior to the initiation of labor.     

Effects of dietary phytoestrogens on cardiac remodeling secondary to chronic volume overload in female rats.

Previously, we demonstrated that intact female rats fed a standard rodent diet containing soybean products exhibit essentially no adverse left ventricular (LV) remodeling in response to aortocaval fistula-induced chronic volume overload. We hypothesized that phytoestrogenic compounds in the diet contributed to the female cardioprotection. To test this hypothesis, four groups of female rats were studied: sham-operated (Sham) and fistula (Fist) rats fed a diet with [P(+)] or without [P(-)] phytoestrogens. Eight weeks postfistula, systolic and diastolic cardiac function was assessed by using a blood-perfused, isolated heart preparation. High-phytoestrogen diet had no effect on body, heart, and lung weights, or cardiac function in Sham rats. Fistula groups developed LV hypertrophy, which was not reduced by dietary phytoestrogens [1,184 +/- 229 mg Fist-P(-) and 1,079 +/- 199 mg Fist-P(+) vs. 620 +/- 47 mg for combined Sham groups, P < 0.05]. Unstressed LV volume increased in Fist-P(-) rats (428 +/- 16 vs. 300 +/- 14 microl Sham, P < 0.0001), but it was not different from Sham for Fist-P(+) animals (286 +/- 17 microl). Fist-P(-) rats developed increased ventricular compliance (5.3 +/- 0.8 vs. 2.3 +/- 0.3 microl/mmHg Sham, P < 0.01), whereas Fist-P(+) rats had no change in compliance (2.8 +/- 0.4 mul/mmHg). Intrinsic ventricular contractility was maintained in the Fist-P(+) rats, but it was reduced (P < 0.001) in the Fist-P(-) rats [systolic pressure-volume slope: 1.04 +/- 0.03, 0.60 +/- 0.06, and 0.99 +/- 0.08 mmHg/microl, for Fist-P(+), Fist-P(-), and Sham, respectively]. These data indicate that dietary phytoestrogens contribute significantly to female cardioprotection against volume overload-induced adverse ventricular remodeling and that studies evaluating gender differences in cardiovascular remodeling must consider the influence of dietary phytoestrogens.     

Bovine amniotic and allantoic fluids for the culture of murine embryos

This study evaluated bovine amniotic and allantoic fluids as culture media for two-cell murine embryos to the hatched blastocyst stage. Amniotic and allantoic fluids were collected from four 70-d periods of pregnancy and pooled from at least five different animals. In Experiment 1 (n = 470) the fluids were frozen twice. Treatments consisted of twice frozen amniotic or allantoic fluid from each pregnancy period, Whitten's medium and fetal calf serum. The later two media were controls. Twice-frozen amniotic fluid <70 d pregnancy period, fetal calf serum and Whitten's medium supported the development of embryos to the hatched blastocyst stage. Whitten's medium was superior to twice-frozen amniotic fluid <70 d pregnancy period or fetal calf serum (P<0.01). Biochemical analysis showed lower glucose in amniotic and allantoic fluids than in Whitten's medium. Experiment 2 (n = 425) was performed to evaluate the effect of glucose supplementation to amniotic fluid. No benefit of glucose supplementation of the amniotic fluid was observed. In Experiment 3 (n = 432), the fluids were transported nonfrozen on ice. Treatments consisted of nonfrozen amniotic fluid <70 d pregnancy period; nonfrozen amniotic fluid <70 d pregnancy period + glucose), nonfrozen allantoic fluid <70 d pregnancy period; and Whitten's medium. The percentages of embryos developing to hatched blastocyst stage were 66.6, 56.5, 57.4 and 63.9% respectively, for each of the four treatments. No differences were found between any two treatments (P<0.05). In Experiment 4 (n = 231) the fluids were stored at -20 degrees C for 15 d. Whitten's medium was superior to amniotic or allantoic fluid <70 d pregnancy period in sustaining embryo development (P<0.05). In conclusion, these data indicate that nonfrozen bovine amniotic or allantoic fluid <70 d pregnancy period can support the development of murine embryos to the hatched blastocyst stage comparable to culture in Whitten's medium. Glucose supplementation of the amniotic fluid offered no advantage, and freezing of fluids had an adverse effect on in vitro embryo development.