Caloric restriction does not alter effects of aging in cardiac side population cells

The aged heart displays a loss of cardiomyocyte number and function, possibly due to the senescence and decreased regenerative potential that has been observed in some cardiac progenitor cells. An important cardiac progenitor that has not been studied in the context of aging is the cardiac side population (CSP) cell. To address this, flow cytometry-assisted cell sorting was used to isolate CSP cells from adult (6–10 months old) and aged (24–32 months old) C57Bl/6 mice that were fed either a control diet or an anti-aging diet (caloric restriction, CR). Aging caused a 2.3-fold increase in the total number of CSP cells and a 3.2-fold increase in the cardiomyogenic sca1⁺/CD31⁻ subpopulation. Aging did not affect markers of proliferation or senescence, including telomerase activity and expression of cell cycle genes, in sca1⁺/CD31⁻ CSP cells. In contrast, the aged cells had reduced expression of genes associated with differentiation, including smooth muscle actin and cardiac muscle actin (5.1- and 3.2-fold, respectively). None of these age effects were altered by CR diet. Therefore, it appears that the manner in which CSP cells age is distinct from the aging of post-mitotic tissue (and perhaps other progenitor cells) that can often be attenuated by CR.     

Cocaine does not alter cardiac glycogen content at rest or during exercise

Cocaine is a potent sympathomimetic drug, and has been implicated as a causative factor in cardiac seizures. However, little is known about the effect of the drug on myocardial substrate utilization. In the present study, rats were injected intravenously with saline solution or one of three doses of cocaine-HCl (1.25, 5.0, 10.0 mg/kg) and subsequently rested or exercised (22 m/min at 15% grade) for 20 minutes. Hearts were removed and frozen within 30 seconds after the injection of anesthetic and within 10 seconds after opening the thoracic cavity. The mean values for resting glycogen content ranged from 24.9 to 27.0 mumol/g, and for glucose-6-phosphate, from 0.27 to 0.30 mumol/g across groups. These values were unaffected by cocaine or exercise. We conclude, based on the conditions of this study, that cocaine has no direct or indirect effect on glycogen storage of the myocardium at rest or during exercise.     

Naloxone does not alter haemodynamics in cirrhosis. Studies in humans and rats

In order to test the hypothesis that endogenous opioids may mediate some of the circulatory derangements in cirrhosis, we studied the haemodynamic effects of naloxone, an opioid antagonist, in patients and in a rat model of biliary cirrhosis. In 9 patients with alcoholic cirrhosis and 5 control patients without significant liver disease, cardiac output, systemic vascular resistance, mean arterial pressure, heart rate, hepatic venous pressures and O2 content, hepatic and azygos blood flows and serum catecholamines were measured before and 30 min after naloxone 3.2 mg i.v. bolus. No significant changes were observed in either group of patients. Similarly in 16 conscious rats, 8 sham-operated and 8 with cirrhosis due to bile duct ligation, cardiac output, systemic vascular resistance, mean arterial pressure, heart rate, and splanchnic organ blood flows were measured by radioactive microspheres, before and 20 min after naloxone 1 mg/kg i.v. bolus. No significant changes were observed in either group. We failed to detect any evidence that endorphins are involved in tonic haemodynamic control in cirrhosis.     

Reduction of hypothalamic norepinephrine does not alter the osmoregulation of vasopressin in rats

The supraoptic nuclei of the hypothalamus are known to be heavily innervated by noradrenergic neurons. However, the role of these neurons in regulating secretion of the antidiuretic hormone, arginine vasopressin, remains unsettled. In an effort to clarify this question, we studied the effect of multiple small doses of D,L alpha-methyl-p-tyrosine (alpha-MpT) on hypothalamic norepinephrine and the osmoregulation of vasopressin in rats. We found that, at the doses employed (80 mg/kg every 6 h for 24 h), alpha-Mpt reduced mean (+/- SD) hypothalamic norepinephrine by about 50% but did not affect plasma osmolality, sodium, glucose, urea, or vasopressin either under basal conditions or during osmotic stimulation by ip injection of hypertonic saline. During the latter, plasma vasopressin correlated directly with plasma osmolality and the regression lines that described the relationships in the control and drug-treated rats were identical. Hematocrit and mean arterial pressure were also unaffected by alpha-MpT. These findings do not support the concept based on previous studies that central noradrenergic pathways mediate the vasopressin response to osmotic stimuli.     

Gonadectomy and androgen replacement alter cardiac performance in conscious adult male rats

Gender disparities in cardiac function have been described. Yet the extent to which gender related differences in cardiac performance are due to the presence of sex-specific biological factors are unclear. We used a longitudinal study aimed at examining whether castration and androgen replacement affects cardiac performance in conscious adult male rats. Adult male rats were implanted with Piezoelectric transit-time gauges and radio telemetry devices to measure regional myocardial segment length and hemodynamic variables before and after castration and after androgen replacement. Androgen withdrawal accelerated average heart rates by 7% (p=0.010). Heart rate was lowered to intact values when androgens were restored to normal physiological levels (p=0.004). Mean arterial pressure was not affected by androgen deprivation and androgen replacement. However, androgen withdrawal produced a 40% decrease in the velocity of circumferential shortening and a 46% reduction in the rate of myocardial relaxation. Androgen supplementation completely restored contractile function. These results provide the first evidence that androgen withdrawal and androgen replacement produces dramatic alterations on cardiac performance in conscious animals and demonstrates the significance of androgens as a cardio-regulatory hormone in males. Sex steroids are likely contributors to gender-related differences in cardiac function.     

Somatostatin does not alter insulin-mediated glucose disposal

We examined the effect of somatostatin (SRIH) infusion on insulin-mediated glucose disposal (Rd) in normal young subjects (n = 8) to determine the influence of SRIH on insulin action. Paired 3-h euglycemic insulin clamp studies were performed in random order employing insulin alone (25 mU/m2 X min) or insulin with SRIH (250 micrograms/h) and replacement of basal glucagon (0.4 ng/kg X min). Basal plasma glucose, insulin, glucagon (IRG), and GH concentrations, hepatic glucose production, and Rd were similar on each occasion. Steady state (10-180 min) plasma insulin insulin alone, 283 +/- 10 (+/- SEM); insulin, IRG, and SRIH, 284 +/- 10 pmol/L) and glucagon levels (insulin alone, 84 +/- 7; insulin, IRG, and SRIH, 82 +/- 7 ng/L) were similar. Hepatic glucose production (insulin alone, 0.66 +/- 0.12; insulin, IRG, and SRIH, 0.78 +/- 0.48 mg/kg X min) and Rd (insulin alone, 8.16 +/- 0.62; insulin, IRG, and SRIH, 8.17 +/- 0.61 mg/kg X min) were not different at steady state. We conclude that SRIH infusion with glucagon replacement does not augment insulin-mediated glucose disposal in normal young subjects at physiological insulin levels.     

The PPARgamma-activator rosiglitazone does not alter remodeling but increases mortality in rats post-myocardial infarction

OBJECTIVE: Peroxisome proliferator-activated receptor gamma (PPARgamma) activators may be beneficial in heart failure due to their metabolic and antihypertrophic effects, but these agents can cause oedema. We hypothesized that, on balance, the PPARgamma activator rosiglitazone would be beneficial in heart failure post-myocardial infarction. METHODS AND RESULTS: Rosiglitazone (3 mg/kg/day p.o.) given to male Wistar rats for 14 days, caused a 31% increase in left ventricular (LV) dP/dt(max) (P<0.05 vs. placebo). A separate group of rats was subjected to sham (SH) or coronary artery ligation and randomised to: untreated (UT); rosiglitazone 3 mg/kg/day (R); captopril, 2 g/l in drinking water (C); captopril+rosiglitazone (C+R). Mean LV infarct sizes were similar for all groups at 40+/-2%. After 8 weeks, echocardiographic ejection fractions were 82+/-3, 40+/-3, 50+/-2*, 49+/-2, 50+/-3% for SH, UT, R, C and C+R groups, respectively (*P<0.05 vs. UT). Captopril prevented LV dilatation, but rosiglitazone did not. In vivo hemodynamics showed that only UT had significantly elevated LV end-diastolic pressures and reduced +dP/dt(max), with R partially, and C and C+R almost completely preventing the increase in LVEDP. Captopril, but not rosiglitazone, significantly reduced LV hypertrophy [LV/bw; 1.97+/-0.09 (SH), 2.15+/-0.04 (UT), 2.10+/-0.05 (R), 1.81+/-0.04* (C), 1.88+/-0.07 (C+R); *(P<0.05 vs. UT)]. Rosiglitazone increased 8-week mortality, which was 26% for R and 19% for C+R compared with 0% for UT and C (P=0.03 vs. UT). CONCLUSIONS: Rosiglitazone did not modulate LV remodeling, but was associated with increased mortality post-myocardial infarction (MI) in rats. The mechanisms require further study, but these results caution against use of PPARgamma activators in post-MI heart failure in non-diabetics.     

Leptin administration to normal rats does not alter catecholamine responsiveness to insulin-induced hypoglycemia

We previously showed, through direct neural recording in conscious rats, that hypoglycemia increases adrenal sympathetic nerve activity (SNA) both acutely and 24 hours following the second of 2 daily antecedent hypoglycemic episodes. Nonetheless, antecedent hypoglycemia impaired catecholamine responsiveness to subsequent acute hypoglycemia. Here we hypothesized that antecedent, nonhypoglycemic adrenal sympathetic stimulation by leptin would impair acute adrenal catecholamine responsiveness to subsequent hypoglycemia. We also hypothesized that acute leptin administration (after 2 days of antecedent hypoglycemia) would enhance adrenal SNA and thereby enhance catecholamine responsiveness to concurrent hypoglycemia. Leptin or saline was administered to normal rats in repeated subcutaneous injections for 2 days prior to acute insulin-induced hypoglycemia. In contrast to our hypothesis, antecedent leptin did not change catecholamine responsiveness or glycemic change in response to subsequent acute insulin administration. In additional studies, intravenous leptin or saline was acutely administered beginning 1 hour before insulin-induced hypoglycemia. All rats had been exposed to antecedent hypoglycemia. In these experiments, acute leptin did not alter catecholamine responses to insulin or glycemic change during or after termination of insulin. We conclude that antecedent nonhypoglycemic sympathetic stimulation by leptin does not alter subsequent catecholamine or glycemic responses to insulin. Moreover, concurrent leptin does not enhance catecholamine responses to insulin in rats exposed to antecedent hypoglycemia.     

Caloric restriction does not alter thyrotropin secretion in hypothyroidism

The effect of caloric restriction, as a model of nonthyroid illness, on serum thyroid hormone and TSH concentrations in hypothyroid patients was studied to determine if pituitary-thyroid function is altered in such patients, as it is in euthyroid subjects. Serum T4, T3, and TSH concentrations and serum TSH responses to TRH were measured in 5 untreated hypothyroid patients and 10 hypothyroid patients receiving T4 replacement therapy before and after restriction of caloric intake to 500 cal daily for 7 days. In 5 untreated hypothyroid patients, the mean serum T3 concentration declined 17%, from 75 +/- 14 (+/- SE) to 62 +/- 11 ng/dl. The mean basal serum TSH concentrations were 154 +/- 67 (+/- SE) microU/ml before and 161 +/- 75 microU/ml at the end of the period of caloric restriction, and the serum TSH responses to TRH were similar on both occasions. In 10 T4-treated hypothyroid patients, the mean serum T3 concentration declined 35%, from 110 +/- 8 to 71 +/- 8 ng/dl. In this group, mean basal serum TSH concentrations were 17 +/- 5.1 microU/ml before and 18.2 +/- 7.0 microU/ml at the end of the period of caloric restriction, and as in the untreated hypothyroid patients, the serum TSH responses to TRH were similar on both occasions. Mean serum T4 concentrations and serum free T4 index values did not change in either group. These results indicate that caloric restriction in both untreated and T4-treated hypothyroid patients is accompanied by 1) reduced serum T3 concentrations, as it is euthyroid subjects, and 2) no alterations in basal or TRH-stimulated TSH secretion.     

Inhibition of neuronal nitric oxide synthase activity does not alter vasopressin secretion in septic rats

Background/Purpose

During the early phase of sepsis, hypotension is accompanied by increase of plasma vasopressin hormone (AVP) levels, which decline during the late phase. This hypotension is due in part to increase of nitric oxide (NO) synthesis by nitric oxide synthase (NOS) enzyme. Neuronal isoform of this enzyme (nNOS) is present in vasopressinergics neurons of hypothalamus, but its role in vasopressin secretion during sepsis is unknown.

Methods

We evaluated the role of nNOS in NO production and vasopressin secretion during sepsis. Wistar rats received 7-nitroindazole (50 mg/kg, i.p.), an inhibitor of nNOS activity, or vehicle and were submitted to septic stimulus by cecal ligation and puncture (CLP). At the time points 0, 4, 6, 18 and 24 h after sepsis induction the animals were decapitated and neurohypophysis and hypothalamus were removed for analysis of vasopressin content and NOS activity, respectively. Hematocrit, serum sodium, osmolality, proteins and plasmatic AVP were quantified.

Results

Mortality was not affected by 7-nitroindazole (7-NI). Sodium and plasma proteins levels decreased after CLP and the treatment anticipated the protein loss, and delayed serum sodium decrease. Septic animals treated with 7-NI showed decrease of osmolality 4 h after CLP. Nitric oxide synthase activity in hypothalamus increased at 4 and 24 h after CLP and was reduced with 7-NI. Neurohypophysis content of AVP diminished after CLP and 7-NI did not alter this parameter. Plasma AVP levels increased at 6 h and decreased 18 and 24 h after CLP. Treatment with 7-NI did not alter plasma vasopressin levels.

Conclusion

We concluded that nNOS does not have a substantial role in vasopressin secretion during experimental sepsis.

     

Clofibrate does not alter cyclic nucleotide metabolism in muscle

Clofibrate is a hypolipidemic agent that causes muscle protein breakdown in rats, and an acute muscular syndrome in man. It also inhibits adenylate cyclase in fat tissue. Muscle protein metabolism has been shown to be regulated by cyclic nucleotides. In the present experiments were measured several parameters of cyclic nucleotide metabolism to determine the role that cyclic nucleotides play in clofibrate-induced muscle protein degradation. It was found that clofibrate treatment did not alter cyclic nucleotide levels, nor did it change the activities of basal or hormone-stimulated adenylate cyclase, or cyclic nucleotide phosphodiesterase in muscle. Our results suggest that muscle protein breakdown in clofibrate-treated rats is not regulated by cyclic nucleotides.     

Flexible fiberoptic bronchoscopy does not alter airway responsiveness

Flexible fiberoptic bronchoscopy (FFB) can induce respiratory mucosal damage. Epithelial damage has been proposed to be of importance in the induction of bronchial hyperresponsiveness. We have examined the influence of FFB on airway responsiveness. Histamine chloride challenge tests were performed in 21 healthy non-smoking volunteers before and after FFB. Since bronchoscopy was performed after pretreatment with atropine and under topical anesthesia with lignocaine, histamine chloride tests were also performed in 6 asthmatics before and after atropine, and in 6 asthmatics before and after local anesthesia with lignocaine. Airway responsiveness was not altered by FFB. Atropine and lignocaine did not have any major influence on airway responsiveness. We suggest that epithelial damage in the central airways induced by FFB is not sufficient to induce bronchial hyperresponsiveness.     

Chronic cyclooxygenase-2 inhibition does not alter blood pressure and kidney function in renovascular hypertensive rats

BACKGROUND: It has been shown that the macula densa participates in the regulation of increased renin expression in two-kidney one-clip (2K1C) renovascular hypertension. Prostaglandins might be one of the mediators of macula densa function, because the cyclooxygenase-2 (COX-2), one of the rate-limiting enzymes of the prostaglandin pathway, is upregulated in 2K1C renovascular hypertensive rats. We tested the effect of chronic COX-2 inhibition on blood pressure, urinary aldosterone excretion and kidney morphology, as well as kidney function. METHODS: Four groups were established: two groups of 2K1C renovascular hypertensive rats treated with the specific COX-2 inhibitor Celecoxib (cele) (15 mg/kg per day) or placebo immediately after operation, and two sham-operated control groups fed with Celecoxib or placebo. RESULTS: Long-term COX-2 inhibition in 2K1C renovascular hypertensive rats did not alter blood pressure at any point of time. Urinary aldosterone excretion was elevated by clipping the renal artery (2K1C, 8.1 +/- 1.9, versus controls, 3.6 +/- 0.5 ng/24 h; P = 0.05) but was not influenced by treatment with Celecoxib. Also, Celecoxib treatment did not alter glomerular filtration rate (GFR), serum sodium, serum creatinine, serum urea or proteinuria in 2K1C renovascular hypertensive rats. Interstitial fibrosis of the left clipped kidney was markedly reduced (2K1C, 6.19 +/- 0.83% versus 2K1C + cele 3.00 +/- 0.68% of total area; P = 0.012), whereas the interstitial fibrosis of the non-clipped kidney or the glomerulosclerosis of both kidneys were not affected by Celecoxib treatment. CONCLUSIONS: Celecoxib reduces the interstitial fibrosis of the clipped kidney. Blood pressure, urinary aldosterone excretion or whole kidney function were not affected in renal hypertensive rats.     

Bronchoalveolar lavage does not alter airway responsiveness in asthmatic subjects

Bronchoalveolar lavage (BAL) during fiberoptic bronchoscopy is being used increasingly for the investigation of asthma. Airway responsiveness to methacholine is a sensitive indicator of the presence and severity of asthma. Therefore, we studied the effect of BAL on methacholine airway responsiveness in stable asthmatics. Geometric mean methacholine PC20 was 1.34 mg/ml before and 1.80 mg/ml after BAL (p = 0.26) in asthmatics. Immediate symptoms of airway narrowing after BAL occurred only in the 3 asthmatics with moderate to severe hyperresponsiveness. These symptoms were rapidly relieved by inhaled bronchodilator. There was no relationship between the occurrence of symptoms and the amount of topical lidocaine used for local anaesthesia or the volume of lavage fluid returned. The absence of an effect of BAL on airway responsiveness supports the safety of this procedure in the controlled asthmatic patient with near normal FEV1, irrespective of the level of baseline airway responsiveness.     

Gonadal suppression by a GnRH analogue does not alter somatic growth in rats with complete GH deficiency

Sexual dimorphism of somatic growth in rats appears to reflect differing actions of sex steroids. However, mechanisms of gonadal steroid effects on the somatotropic axis are incompletely understood. To evaluate whether GH is involved in the effects of long-term gonadal suppression on somatic growth in rats, a GnRH agonistic analogue (GnRHa) was administered to normal Sprague-Dawley rats (controls) and to a strain of rats with complete growth hormone deficiency (GHD; n=4-6 in each group). Subcutaneous injection of GnRHa (2 mg/kg) or saline were given within 48 h after birth and repeated every 3 weeks. GnRHa treatment significantly reduced serum gonadal steroid levels in rats of both sexes with small testes in males and impaired development of internal genitalia in females. GnRHa-treated control females became significantly heavier (P<0.01 ANOVA for repeated measures) than saline-treated rats beginning at 8 weeks. However, female GHD rats with GnRHa treatment did not differ in body weight from rats receiving saline. In male rats, GnRHa treatment did not change body weight in either control or GHD rats. Serum IGF-I concentrations did not differ between treatment groups in GHD and control rats of either sex. Hepatic GH binding was reduced significantly by GnRHa treatment in female control rats (P<0.01), but not in female GHD rats. These data suggest that sexual dimorphism in body size and its modulation by estrogens are independent of circulating IGF-I levels suggesting non-endocrine IGF-I-mediated mechanisms, and that GH-induced somatic growth is modulated by estrogens, but not androgens, in rats.     

Between-meal risedronate does not alter bone turnover in nursing home residents

OBJECTIVES: To assess the effect of between-meal weekly risedronate and daily calcium 630 mg and vitamin D 400 IU on bone turnover markers. DESIGN: Randomized,double-blind,placebo-controlled trial. SETTING: Skilled nursing home (NH). PARTICIPANTS: Sixty skilled-NH residents (46 men, 14 women), mean age+/-standard deviation of 76+/-6, were randomized to receive risedronate 30 mg (n=31) or matching placebo (n=29) once weekly for 12 weeks. All received 315 mg calcium with 200 IU vitamin D twice daily. MEASUREMENTS: Bone-specific alkaline phosphatase (BSAP), N-telopeptide of type 1 collagen (NTx), 25-hydroxyvitamin D (25OHD), and parathyroid hormone were measured at baseline and 6 and 12 weeks. RESULTS: Risedronate reduced BSAP significantly more than placebo (P<.05) at 6 weeks but not at 12 weeks; no treatment effect on serum NTx was observed. Defining hypovitaminosis D as a serum 25OHD concentration below 32 ng/mL, 50 of 53 (94%) study participants were low at baseline (mean 25OHD 19 ng/mL). Vitamin D levels remained insufficient in 74% of participants after 12 weeks. CONCLUSION: In this NH population, weekly risedronate administered using a between-meal dosing schedule reduced serum BSAP at 6 weeks of treatment; this effect was not observed at 12 weeks. The overall lack of change in bone turnover markers suggests that this risedronate dose and schedule would not be expected to increase bone density or reduce fracture risk in this population. Hypovitaminosis D was common and not reliably corrected by 400 IU of vitamin D daily. Despite an extremely high osteoporotic fracture risk in NH residents, additional study is required to determine under which conditions pharmacological treatment is efficacious in this population and define approaches that assure vitamin D repletion.     

Tenoxicam does not alter renal function during anaesthesia in normal individuals

Background : Anaesthesia and surgery alter renal function. Inhibition of prostaglandin synthesis by non-steroidal anti-inflammatory drugs (NSAIDs) administered with anaesthesia may further compromise renal function.
Aim : To study the effects of tenoxicam (NSAID) administered immediately prior to anaesthesia on renal function in normal individuals undergoing routine surgery.
Methods : A randomised single blind placebo controlled study comparing tenoxicam (40 mg intravenously) with placebo was carried out in 20 healthy (ASA I) patients undergoing lower spinal surgery. Glomerular filtration rate (GFR) was determined by creatinine clearance and renal tubular function measured as osmolar and free water clearance.
Results : GFR fell by 60% at the end of surgery but returned to pre-operative values by six hours post-operatively. There was no difference between placebo or tenoxicam with regard to changes in GFR. Tubular function was not altered by tenoxicam.
Conclusions : Current clinical practice of using NSAIDs for post-operative analgesia in low risk individuals appears to have no adverse effects on renal function.