Postnatal changes in regional blood flow during cold-induced shivering in sow-reared piglets.

To determine whether newborn pigs are able to display adequate cardiovascular adjustments favouring shivering thermogenesis in skeletal muscles soon after birth, regional blood flow and fractional distribution of cardiac output were determined in 1-day-old (n = 6) and 5-day-old (n = 6) conscious piglets at thermal neutrality and during cold exposure, using coloured microspheres. Five-day-old piglets stayed with the sow before the experiment. The cold challenge was designed to induce a similar increase (approximately +90%) in heat production at both ages. Skeletal muscle blood flow increased with both age (p < 0.05) and cold exposure (p < 0.001), with the effect of cold being more pronounced in 5-day-old piglets than in 1-day-old piglets (+60%, p < 0.05). The difference between individual muscles increased with age, with fractional blood flow being 41% higher in rhomboideus than in longissimus thoracis muscle during cold exposure in 5-day-old piglets (p < 0.05). Cardiac output was similar at both ages and increased by 23% in the cold (p < 0.001). At 1 day of age, there was no redistribution of cardiac output among the internal organs during the cold challenge, while at 5 days of age, the increase in muscle fractional blood flow was associated with a reduction (p < 0.05) in the fraction of cardiac output reaching the skin (-24%), the small intestine (-21%), and the liver (-20%). In conclusion, these results suggest that there is a rapid postnatal improvement of cardiovascular adjustments favouring blood perfusion and probably heat production during cold-induced shivering in the most oxidative muscles studied. This cardiovascular response may play a role in the postnatal enhancement of thermoregulation in piglets.     

Effect of conjugated linoleic acid on dietary lipids utilization, liver morphology and selected immune parameters in sea bass juveniles (Dicentrarchus labrax)

Increased energy content in fish feeds has led to an enhanced fat deposition, particularly in European sea bass, concerning fish farmers. Inclusion of conjugated linoleic acid (CLA) could reduce fat deposition as in other vertebrates. To determine if dietary CLA affects fat deposition, lipid metabolism, lipid composition and morphology of different tissues, growth and selected immune parameters, European sea bass juveniles were fed 4 graded levels of CLA (0, 0.5, 1 and 2%). Growth and feed conversion were not affected by CLA, whereas feed intake was reduced (P < 0.05) by feeding 2% CLA. In these fish perivisceral fat was also reduced (P < 0.05), particularly reducing (P < 0.05) monounsaturated fatty acids. CLA has not affected tissue proximal composition, but reduced (P < 0.05) saturated and monounsaturated fatty acids and increased (P < 0.05) the n−3 and n−3 highly unsaturated fatty acids in muscle and increase (P < 0.05) CLA content in muscle, liver and perivisceral fat. A progressive reduction in lipid vacuolization of hepatocytes cytoplasm and regular-shaped morphology was found in fish fed increased CLA levels, together with a progressive increase in malic enzyme activity (only significant in fish fed 1% CLA). Finally, inclusion of CLA up to 1% increased (P < 0.05) plasma lysozyme activity and was positively correlated with alternative complement pathway.     

Effect of different selenium source (sodium selenite and selenium yeast) on broiler chickens

A feeding experiment was carried out to compare the effects of supplementing a poultry meal-based diet with selenium as sodium selenite or selenium yeast on broiler chickens. Three groups with three replicates of broiler chickens (mean weight 710 ± 5.3 g) were given a basal diet either unsupplemented (control) or supplemented with 0.2 mg Se kg⁻¹ as sodium selenite (trial 1) or selenium yeast (trial 2) respectively, for 21 days. There was significant difference (P<0.05) in Feed Conversion Ratio (FCR) of trials 1 and 2 compared with the control. However, there were no significant differences (P>0.05) in FCR between trials 1 and 2. Final weight, survival rate and Daily Gain (DG) were not affected by the dietary Se source. Chickens fed the basal diet showed lower (P<0.05) selenium content in muscle, kidney, liver and pancreas compared to that fed selenium supplements (trials 1 and 2). Furthermore, trial 2 showed the highest value (P<0.05) among these treatments. However, there was no significant difference (P>0.05) in muscle selenium content of chickens between trials 1 and 2. Glutathione peroxidase (GSH-Px) activities in broiler chickens plasma and liver of all selenium treatment groups (trials 1 and 2) were significantly different (P<0.05) from that of the control. The GSH-Px activity in plasma was higher (P<0.05) in trial 2 compared with trial 1 and the control. However, there was no difference (P>0.05) in hepatic glutathione peroxidase between trials 1 and 2 although the average value of GSH-Px activity in trial 2 presented the trend of increase.     

RELEASE OF SOLUBLE TUMOUR NECROSIS FACTOR ALPHA RECEPTORS DURING AND AFTER PAEDIATRIC CARDIOPULMONARY BYPASS. CORRELATION WITH HAEMODYNAMIC AND CLINICAL VARIABLES

The release of cytokines during cardiopulmonary bypass (CPB) may contribute to haemodynamic alternations encountered after open heart surgery. Regulatory mechanisms exist and include soluble cytokine receptors. We have measured blood levels of tumour necrosis factor (TNF) and its soluble receptor (TNFsr) during and after open heart surgery in children. Correlation analysis to haemodynamic and clinical variables was performed.Using immunoassays the authors registered a significant increase in plasma levels of TNFsr with peak levels 2 h post?operatively at a level of 1702 ± 170 pg/ml. The concentration of TNFsr remained significantly elevated until 48 h postoperatively but TNF was not significantly elevated.An inverse correlation existed between peak TNFsr and mean arterial pressure (rho = −0.827,P< 0.05), between TNFsr and cardiac index (rho = −0.8,P< 0.05), between TNFsr and left ventricular stroke work index (rho = −0.983,P< 0.01), between TNFsr and weight (rho = −0.85,P< 0.05) and between TNFsr and body surface area (rho = −0.867,P< 0.05).The authors demonstrate that the smallest children experienced the highest TNFsr concentration post-operatively. Furthermore cardiac performance, expressed as cardiac index and left ventricular stroke work index, correlated inversely to peak TNFsr level post-operatively.     

Differences in cold and drought tolerance of high arctic and sub-arctic populations of Megaphorura arctica Tullberg 1876 (Onychiuridae: Collembola)

The springtail Megaphorura arctica (Onychiuridae: Collembola) inhabits the arctic and sub-arctic parts of the northern hemisphere where it on a seasonal basis will be exposed to severe cold and desiccating conditions. In the present study we compared how traits of stress resistance differed between two populations of M. arctica that were collected at a high arctic site (Spitsbergen) and a sub-arctic site (Akureyri, Iceland) with contrasting thermal environments. In addition we investigated how cold and desiccation affected the phospholipid fatty acid composition of M. arctica from Spitsbergen. The springtails from Spitsbergen were the most cold tolerant and this was linked to an almost three times higher level of trehalose accumulation during cryoprotective dehydration (15% and 5% of tissue dry weight in the Spitsbergen and Iceland populations, respectively). Although cryoprotective dehydration is intimately related to desiccation stress it was shown that M. arctica had a higher mortality when dehydrated over ice (−10 or −20 °C) than when dehydrated at temperatures above 1 °C. Thus, survival was lower after exposure to −10 °C than after exposure to a relative humidity of 91.2% RH at +1 °C although both treatments led to the same level of dehydration. Exposure to both cold (−10 and −20 °C) and desiccation at +1 °C caused significant changes in the phospholipid fatty acid composition with some similarities. These changes included a decrease in average chain length of the fatty acids due primarily to an increase in the phospholipid fatty acids 16:0 and a decrease in 18:3 and 20:4ω6.     

Interaction of the autonomic nervous system with intrinsic cardiac rate regulation in the guinea-pig, Cavia porcellus

In the denervated mammalian heart a change in right atrial pressure will still alter heart rate (intrinsic rate response, IRR). We have examined the IRR in isolated right atria of the guinea-pig maintained in oxygenated Krebs–Henseleit solution at 37°C, to compare with and extend studies in other species, and to determine whether the guinea-pig is a suitable model for electrophysiological studies of the IRR. Baseline diastolic transmural pressure was set at 2 mmHg. A 6-mmHg increase in right atrial pressure (RAP) caused an increase in atrial rate that reached a steady value of 15 min⁻¹ after 1–2 min. This response was enhanced by carbamylcholine and attenuated by isoprenaline. The influence of RAP on the rate response to vagal stimulation was examined. With RAP set at 8 mmHg, the reduction in atrial rate following vagal stimulation was 72±5% of that at 2 mmHg (n=6, mean±S.E., P<0.005). Continuous vagal stimulation produced a sustained bradycardia, and the effect of this bradycardia on the IRR was examined. When atrial rate was reduced 6% by vagal stimulation, the IRR was augmented to 202±21% of the control (n=6, P<0.005). This augmentation was larger (P<0.05) than that seen when atrial rate was reduced 8% by carbamylcholine (130±8% of control; n=7, P<0.05). Overall, the IRR in the guinea-pig is similar to that in the rabbit, and shows similar interactions with the autonomic nervous system.     

Elevated endogenous testosterone concentrations potentiate muscle androgen receptor responses to resistance exercise

The purpose of this study was to determine the influence of endogenous circulating testosterone (T) on muscle androgen receptor (AR) responses to acute resistance exercise (RE). Six healthy men (26 ± 4 years; 176 ± 5 cm; 75.8 ± 11.4 kg) performed a knee extension exercise protocol on two occasions separated by 1–3 weeks. Rest preceded one trial (i.e., control [CON] trial) and a high-volume upper-body RE protocol designed to increase circulating T preceded the other trial (i.e., high T [HT] trial). Serial blood samples were obtained throughout each trial to determine circulating T concentrations. Biopsies of the vastus lateralis were obtained pre-RE (REST), 10-min post-RE (+10), and 180-min post-RE (+180) to determine muscle AR content. Circulating T concentrations remained stable during CON. Alternately, HT significantly (p ≤ 0.05) increased T concentrations above resting values (+16%). Testosterone area-under-the-time curve during HT exceeded CON by 14%. AR content remained stable from REST to +10 in both trials. Compared to the corresponding +10 value, muscle AR content at +180 tended to decrease during CON (−33%; p = 0.10) but remained stable during HT (+40%; p = 0.17). Muscle AR content at +180 during the HT trial exceeded the corresponding CON value. In conclusion, acute elevations in circulating T potentiated muscle AR content following RE.     

Influence of level of zilpaterol chlorhydrate supplementation on growth performance and carcass characteristics of feedlot lambs

Forty-eight Pelibuey × Katahdin (38.8 ± 0.67 kg) crossbred male lambs were used in a 32-day feeding trial (four pens per treatment in a randomized complete block design), to evaluate the influence of zilpaterol (β₂-agonist) supplementation level on growth performance and carcass characteristics. Lambs were fed a dry-rolled corn-based finishing diet (3.04 Mcal/kg of ME) supplemented with 0, 0.15, 0.20, or 0.25 mg/kg of live weight d⁻¹ zilpaterol (as zilpaterol chlorhydrate, Zilmax^®, Intervet México, México City). DM intake averaged 1.099 ± 0.042 kg/d and was not affected (P = 0.40) by treatments. Compared with control lambs, zilpaterol supplementation increased gain efficiency (15.8%, P < 0.03), apparent energy retention per unit DMI (10.9%, P = 0.03), and tended to increased daily gain (16%, P < 0.07) and total gain (17.7%, P < 0.08). Zilpaterol supplementation did not affect (P = 0.20) carcass weight, longissimus muscle area (LM), or fat thickness, but increased (2.3%, P = 0.04) carcass dressing percentage and reduced (36%, P < 0.01) kidney-pelvic fat. Increasing level of zilpaterol supplementation increased total weight gain (linear component, P < 0.05), gain:feed (linear component, P < 0.01), and dressing percentage (linear component, P < 0.02), and decreased (linear component, P < 0.01) kidney-pelvic fat. We conclude that zilpaterol supplementation enhances growth performance and dressing percentage in lambs in a manner comparable to that of cattle (greater muscle accretion, reduced body fat). Responses to zilpaterol was optimal when supplemented at 0.20 mg of zilpaterol/kg of live weight d⁻¹.     

Does cold acclimation induce nonshivering thermogenesis in juvenile birds? Experiments with Pekin ducklings and Japanese quail chicks

The capability to produce heat in cold by nonshivering thermogenesis (NST) was studied in Pekin ducklings and Japanese quail chicks acclimated to cold for 3 weeks using indirect calorimetry (oxygen consumption) and electromyography from breast (M. pectoralis) and leg muscles (quails: M. gastrocnemius; ducklings: M. gastrocnemius, M. iliofibularis). Respiration of muscles in vitro was studied by measuring cytochrome c oxidase activity. In both species, cold acclimation induced clear morphometric and physiological changes, but no clear evidence of nonshivering thermogenesis. This was evident because increased shivering at least in one muscle coincided with increased oxygen consumption. In ducklings, however, amplitudes of shivering EMGs were low (<30 μV) in all muscles studied in both the control and cold-acclimated groups. Ducklings reacted to cold mainly by means of increasing body weight (1796 g in control, 2095 g in cold-acclimated) and circulatory changes. Acclimation did not change oxygen consumption either in vivo or in vitro. In quails, in addition to increased body weight (78.1 g control, 89.9 g cold-acclimated), improved insulation and metabolic adaptation to cold (increased respiration in vivo and in M. pectoralis in vitro) was also utilized. In Japanese quail chicks, 3 weeks of cold acclimation does not seem to induce NST, while in Pekin ducklings the existence of NST could not be totally excluded because of weak overall shivering activity. Accepted: 13 July 2000     

Variation in δC values for the seagrass Thalassia testudinum and its relations to mangrove carbon

Carbon isotope ratios (¹³C/¹²C) were measured for the leaves of the seagrass Thalassia testudinum Banks ex König and carbonates of shells collected at the seagrass beds from seven sites along the coast of southern Florida, U.S.A. The δ¹³C values of seagrass leaves ranged from −7.3 to −16.3‰ among different study sites, with a significantly lower mean value for seagrass leaves from those sites near mangrove forests (−12.8 ± 1.1‰) than those far from mangrove forests (−8.3 ± 0.9‰; P < 0.05). Furthermore, seagrass leaves from a shallow water area had significantly lower δ¹³C values than those found in a deep water area (P < 0.01). There was no significant variation in δ¹³C values between young and mature leaves (P = 0.59) or between the tip and base of a leaf blade (P = 0.46). Carbonates of shells also showed a significantly lower mean δ¹³C value in the mangrove areas (−2.3 ± 0.6‰) than in the non-mangrove areas (0.6 ± 0.3‰; P <0.025). In addition, the δ¹³C values of seagrass leaves were significantly correlated with those of shell carbonates (δ¹³C seagrass leaf = −9.1 + 1.3δ¹³C shell carbonate (R² = 0.83, P < 0.01)). These results indicated that the input of carbon dioxide from the mineralization of mangrove detritus caused the variation in carbon isotope ratios of seagrass leaves among different sites in this study.     

Oxidative stress in toadfish (Halobactrachus didactylus) cardiac muscle: Acute exposure to vanadate oligomers

Vanadate solutions as ‘metavanadate’ (containing ortho and metavanadate species) and ‘decavanadate’ (containing manly decameric species) (5 mM; 1 mg/kg) were injected intraperitoneously in Halobatrachus didactylus (toadfish), in order to evaluate the contribution of decameric vanadate species to vanadium (V) intoxication on the cardiac tissue. Following short-term exposure (1 and 7 days), different changes on antioxidant enzyme activities—superoxide dismutase (SOD), catalase (CAT), selenium-glutathione peroxidase (Se-GPx), total glutathione peroxidase (GPx), lipid peroxidation and subcellular vanadium distribution were observed in mitochondrial and cytosolic fractions of heart ventricle toadfish. After 1 day of vanadium intoxication, SOD, CAT and Se-GPx activities were decreased up to 25%, by both vanadate solutions, except mitochondrial CAT activity that increased (+23%) upon decavanadate administration. After 7 days of exposure, decavanadate versus metavanadate solutions promoted different effects mainly on cytosolic CAT activity (−56% versus −5%), mitochondrial CAT activity (−10% versus +10%) and total GPx activity (+1% versus −35%), whereas lipid peroxidation products were significantly increased (+82%) upon 500 μM decavanadate intoxication. Accumulation of vanadium in total (0.137±0.011 μg/g) and mitochondrial (0.022±0.001 μg/g) fractions was observed upon 7 days of metavanadate exposure, whereas for decavanadate, the concentration of vanadium increased in cytosolic (0.020±0.005 μg/g) and mitochondrial (0.021±0.009 μg/g) fractions. It is concluded that decameric vanadate species are responsible for a strong increase on lipid peroxidation and a decrease in cytosolic catalase activity thus contributing to oxidative stress responses upon vanadate intoxication, in the toadfish heart.     

Both substrate availability and utilisation contribute to the defence of core temperature in response to acute cold

Acute cooling significantly increases energy demand in non-hibernators for the defence of core temperature but the contribution of the liver to thermogenesis is poorly understood. A two-tracer method to estimate lipid metabolism in cold-naïve control (CON) and cold-acclimated (CA) rats was employed to quantify hepatic rates of fat metabolism. Both fenofibrate, to increase liver mass and fat oxidation and dichloroacetate (DCA) to inhibit fat oxidation were used to alter lipid metabolism in CON animals. Following acute cooling, CA led to a doubling of the time to reach a core temperature 25 °C (P < 0.001), whereas DCA treatment decreased time of cooling (P < 0.01). DCA-treatment increased the gradient of Arrhenius-transformed rate–pressure product (P < 0.01). CA increased both palmitate uptake (P < 0.001) and β-oxidation (P < 0.01) whilst DCA treatment decreased uptake (P < 0.01) and β-oxidation (P < 0.05). Tissue-specific estimates of metabolism revealed that CA led to a 12-fold increase in β-oxidation for brown adipose tissue (P < 0.001) whilst fenofibrate halved β-oxidation in the liver (P < 0.01) despite doubling the liver mass (P < 0.001) and DCA decreased hepatic β-oxidation to 15% of control levels. Taken together, these results suggest that the liver has minimal contribution to thermogenesis in the rat, with brown adipose tissue significantly increasing both fat uptake and oxidation in response to CA.     

Identification of polymorphism and association analysis with reproductive traits in the porcine RNF4 gene

The ring finger protein 4 gene (RNF4), which might play a role in fetal germ cell development as well as in oocyte and granulosa cell maturation, was one of the potential candidate genes for reproductive traits. In the present work, we isolated the complete coding sequence of porcine RNF4 gene, identified a single nucleotide polymorphism (SNP: T/C) in intron5, and developed a PCR-SacII-RFLP genotyping assay. Association of this SNP with reproductive traits was assessed in three populations with diverse genetic backgrounds. One was Chinese Qingping sows. Another was consisted of crossbred sows derived from Landrace, Large White, Chinese Tongcheng and/or Chinese Meishan (Line DIV). The third is Large White × Meishan (LW × M) F₂ slaughtered population. Statistical analysis demonstrated that, in the first parity, the difference between RNF4 genotypes and reproductive traits of both Qingping and Line DIV sows was not significant. In the second and subsequent litters, CC animals in Qingping population had more piglets born (+1.74 piglets) and piglets born alive (+2.02 piglets) than sows with the TT genotype (P < 0.05). Line DIV sows inheriting the CC genotype had additional 0.69 piglets born compared to the TC animals (P < 0.05) in second and subsequent litters. No significant difference was observed between genotypes and reproductive tracts components in F₂ animals. In addition, we found RNF4 gene has a significant additive effect on both piglet born and piglet born alive in Qingping animals (P < 0.05). Results here suggested that the RNF4 SNP was significantly associated with litter size in two populations and could be useful in selection for increasing litter size in pigs. Further studies were needed to confirm these preliminary researches.     

Metabolic rate, maximum metabolism, and advantages of torpor in the fat mouse Steatomys pratensis natalensis Roberts, 1921 (Dendeomurinae)

1. The fat mouse Steatomys pratensis natalensis (mean body mass 37.4±0.43 (se)) has a low euthermic body temperature T_b=30.1–33.8 °C and a low basal metabolic rate (BMR)=0.50 ml O₂ g⁻¹ h⁻¹.

2. Below an ambient temperature (T_a)=15 °C, the mice were hypothermic.

3. The lowest survivable T_a=10 °C.

4. Torpor is efficient in conserving energy between T_a=15–30 °C, below T_a=15 °C, the mice arouse.

5. Euthermic and torpid mice were hyperthermic at T_a=35 °C.

6. Thermal conductance was 0.159 ml O₂ g⁻¹ h⁻¹ °C⁻¹, 98.8% of the expected value.

7. Non-shivering thermogenesis (NST) was 2.196 ml O² g⁻¹ h⁻¹ (3.69×BMR).

8. Maximal oxygen consumption, however, was 3.83 ml O₂ g⁻¹ h⁻¹ (6.44×BMR), indicating that other methods of heat production are additive.

9. Because fat mice conserve energy by torpor only between T_a=15–30 °C, we suggest that torpor may be a more important mechanism for surviving food shortages than for surviving cold weather.

Season of the year influences semen output and concentrations of testosterone in circulation of yaks (Poephagus grunniens L.)

Seasonal changes in plasma testosterone concentration and semen quality were evaluated in yak bulls throughout a 1-year period. Blood samples were collected every week from adult yak bulls (n = 15). These blood samples were analyzed for testosterone using a highly sensitive enzyme-linked immunoassay. Ejaculates were collected from five representative bulls each week. Ejaculate volume, progressive motility, live sperm count and sperm concentrations were determined. Mean testosterone in plasma was 1.03 ± 0.25 ng/ml. Concentrations of testosterone changed throughout the year (P < 0.05) and were found to be highest during the winter. It was also higher during the autumn than in summer and spring (P < 0.05). Mean ejaculate volume, progressive motility, live sperm count and spermatozoa concentration were 2.7 ± 0.3 ml, 72.8 ± 1.4%, 82.3 ± 0.9% and 968 ± 233 × 10⁶ ml⁻¹, respectively. Ejaculate volume and sperm concentration were higher (P < 0.05) in autumn than in other seasons. To conclude, a highly sensitive EIA for testosterone was developed and validated for yak plasma. Seasonal changes in semen quality were associated with changes in the concentration of testosterone in plasma from yak bulls.     

Influence of low plasma progesterone concentrations on the release of prostaglandin F2α during luteolysis and oestrus in heifers

A study was conducted to determine the effect of suprabasal plasma concentrations of progesterone on the release of prostaglandin F_2α (PGF_2α) at luteolysis and oestrus. Heifers received silicone implants containing 2.5 (n = 4), 5 (n = 4), 6 (n = 3), 7.5 (n = 3), 10 (n = 4), or 15 (n = 3) g of progesterone, or an empty implant (controls, n = 4) between Days 8 and 25 post ovulation. Blood was collected frequently between Days 14 and 28 and assayed for progesterone and 15-ketodihydroprostaglandin F_2α. Basal progesterone concentrations in control heifers did not differ from those in heifers with 2.5- or 5-g implants and remained around 0.4−0.5 nmol l⁻¹ until ovulation in all three groups. In the heifers treated with 6–15 g of progesterone, basal concentrations were maintained at higher (P < 0.05) levels compared with those in the controls, ranging from 0.8 to 1.6 nmol 1⁻¹. The effect of these elevated progesterone levels was to delay ovulation by prolonging the growth of the ovulatory follicle, which continued growing until the implant was removed. In all experimental groups, the first significant increase of the PGF_2α metabolite occurred between Days 15.3 and 16.3 (P > 0.05) and was associated with the onset of a decrease in progesterone concentrations, which had reached levels below 3 nmol 1⁻¹ by Days 17.4−19.1. PGF_2α metabolite peaks associated with luteolysis were frequent until Day 20. In the period from Day 20 until implant removal, sporadic peaks were observed, ranging in number from 1.0 ± 1.2 (mean ± SEM) in the control group to 3.0 ± 1.4 peaks in the heifers treated with 7.5 g of progesterone (P > 0.05). The number of PGF_2α metabolite peaks during that period was higher (P < 0.05) in heifers treated with 10 and 15 g than in controls. A positive correlation was found between the basal concentration of progesterone and the number of PGF_2α peaks after luteolysis (r = 0.54; P < 0.01). Plasma progesterone concentrations above approximately 1.4 nmol l⁻¹ were able to maintain the release of PGF_2α until the progesterone implants were removed and plasma levels decreased to basal values. These heifers had a preovulatory PGF_2α release pattern resembling that found in repeat breeder heifers.     

In vitro studies of the effect of Environmental Conditions on the anthacnose pathogen of bananas, Colletotrichum musae

In vitro studies were undertaken to determine the effect of pH, temperature, water availability and carbon dioxide (CO₂) concentration on germination and growth of Colletotrichum musae, the causal pathogen of anthracnose of bananas. The optimum pH for germination and growth varied between 4·0 and 5·0 depending on temperature. At low pH (< 3·0) and 15°C, both germination and growth were significantly reduced, with a marked increase in the lag time, in days, prior to growth. C. musae germinated and grew over a wide range of water activities (a_w; 0·995−0·94 and 0·995−0·92, respectively) at 20, 25 and 30°C. In all cases where germination occurred appresoria were subsequently produced. Optimum growth occurred at 30°C and 0·995 a_w, although this changed to 0·98 a_w at 35°C. Increasing CO₂ concentration to 15% or reducing oxygen concentration to 1% resulted in a significant (P < 0·05) reduction in growth, but did not inhibit growth completely.     

High-salt intake primes the rat kidney to respond to a subthreshold uroguanylin dose during ex vivo renal perfusion

In a variety of animal models, uroguanylin causes diuresis, natriuresis and kaliuresis and is found in larger concentrations in the urine compared to controls after oral salt intake or in conditions of excess salt and fluid retention. It has been proposed that uroguanylin functions as an intestinal natriuretic hormone following intake of meals high in salt content. In the present work, we examined if 10 days of salt ingestion resulted in an enhanced response to uroguanylin in the isolated perfused rat kidney. Rats were given normal water, 1% NaCl (HS1%), or 2% NaCl (HS2%) for 10 days, at which time the right kidneys were surgically removed and perfused with a modified Krebs-Henseleit solution for 30 min. After a 30-min control period, the kidneys were perfused with a modified Krebs-Henseleit solution containing 0.06 μM uroguanylin for an additional 90 min. Compared to vehicle-matched time controls, 0.06 μM uroguanylin perfusion of kidneys from rats maintained on HS2% resulted in a significantly increased urine flow (UF; from 0.17 ± 0.01 to 0.23 ± 0.01, after 60 min, n = 6, P < 0.05), fractional Na⁺ excretion (%E_Na+; from 16.6 ± 0.7 to 30 ± 2, after 60 min, n = 6, P < 0.05), fractional K⁺ excretion (%E_K+; from 20.5 ± 0.58 to 37.4 ± 2.1, after 60 min, n = 6, P < 0.05), and fractional Cl⁻ excretion increased from 18.16 ± 0.52 to 35.2 ± 2.0 at 60 min, n = 6, P < 0.05. With the exception of a significant increase in the %E_K+, no other effect was observed in the kidneys from the rats maintained on HS1%, and no significant effects were seen in those that were maintained on normal water. The effect of a higher dose (0.6 µM) of uroguanylin on urinary flow, sodium or potassium excretion was also significantly increased by 2% NaCl (HS2%) treatment (P < 0.05). We also observed an expressive upregulation of the GC-C and a slight downregulation of the GC-A receptor in high-salt treated rats. These data demonstrate that prolonged salt ingestion primes the kidney to enhanced renal responses to uroguanylin.     

Nitric oxide regulates steroid synthesis by bovine antral granulosa cells in a chemically defined medium

Nitric oxide (NO) in bovine ovary has been characterized as one of the controllers of granulosa cells’ (GC) steroidogenesis and apoptosis. One of the pathways used by NO to have these effects is cGMP. The objectives of the present study were to verify the effect of sodium nitroprusside (SNP), a NO donor, on steroidogenesis, cell viability (mitochondrial activity) and GC cell cycle distribution and if this effect occurs by the NO-cGMP signaling pathway with the addition of SNP with or without 1H-[1,2,3] oxadiaziolo[4,3a]quinoxaline-1-one (ODQ), a selective soluble guanylate cyclase inhibitor. The antral GC from 3 to 5 mm diameter cattle follicles was cultured without treatment (control), with ODQ (10⁻⁴ M) and 10⁻⁵, 10⁻³ and 10⁻¹ M SNP with or without ODQ for 24 h. Nitrate/nitrite (NO₃⁻/N0₂⁻) concentrations were evaluated by Griess method, progesterone (P₄) and 17β-estradiol (E₂) concentrations by chemiluminescence, viability and cell cycle stage by MTT method (3-[4,5-dimethylthiazol-2yl]-2,3 dipheniltetrazolium bromide) and flow cytometry, respectively. Nitrate/nitrite concentration in culture medium increased (P < 0.05) in a dose-dependent manner according to SNP concentration added to the culture medium. The GC cultured without treatment, with ODQ and with 10⁻⁵ M SNP in the presence or absence of ODQ developed into cell aggregates and did not vary in cell viability (P > 0.05), while GC cultured with 10⁻³ and 10⁻¹ M SNP with or without ODQ presented disorganized GC aggregates or did not develop into cell aggregates and also had substantially decreased cell viability (mitochondrial activity inhibition) and steroids synthesis (P < 0.05), and effects were not reversed with us of ODQ. Most GC cultured without treatment (control) or with ODQ, 10⁻⁵ and 10⁻³ M SNP with or without ODQ were in the G0/G1 (80–75%) stage and in a lesser proportion (20–25%) in the S + G2/M stage of the cell cycle, while the 10⁻¹ M SNP treatment resulted in GC in G1 phase arrest. The treatment with 10⁻⁵ M SNP increased (P < 0.05) E₂ synthesis and inhibited (P < 0.05) progesterone synthesis. The addition of ODQ reversed (P < 0.05) the stimulatory effect of 10⁻⁵ M SNP treatment on E₂, but not on P₄ synthesis (P > 0.05). These results demonstrated that E₂ synthesis by antral GC from small follicles is modulated by lesser NO concentrations via the cGMP pathway, but not P₄ while steroids inhibition cGMP pathway independent, mitochondrial damage and the interference on cell cycle progression caused by greater NO concentration can lead to cell death.