Obesity affects short-term folate pharmacokinetics in women of childbearing age.

Maternal folate status and body mass index (BMI) are independent risk factors for neural tube defects (NTD). Population-based studies have identified an inverse association between serum folate and BMI, after adjusting for intake. The objective of this intervention study was to compare the relationship between BMI and the short-term pharmacokinetic response to an oral dose of folic acid. Healthy obese (BMI 30.0 kg m(-2); n=16) and normal-weight (BMI 18.5-24.9 kg m(-2); n=16) women of childbearing age (18-35 years) were administered a single oral dose of folic acid (400 µg). Blood samples were collected over a 10-h period to evaluate the serum folate response. Fasting baseline serum folate was lower in the obese group (P=0.005); in contrast, red blood cell folate was higher (P=0.05). Area-under-the-curve for the absorption phase (0-3 h) and peak serum folate concentrations were lower in obese versus normal-weight women (P<0.005). Overall serum folate response (0-10 h) was lower in obese versus normal-weight women (repeated-measures ANOVA, P=0.001). Data suggest body distribution of folate is significantly affected by obesity, and, should pregnancy occur, may reduce the amount of folate available to the developing embryo. These findings provide additional support for a BMI-adjusted folic acid intake recommendation for NTD risk reduction.

Evidence of low-temperature superparamagnetism in Mn3O4 nanoparticle ensembles.

Using ac-susceptibility, dc-magnetization, and transmission electron microscopy, we have investigated the magnetic behavior of Mn(3)O(4) nanoparticle ensembles at temperatures below the paramagnetic-to-ferrimagnetic transition of the title material (T(N) approximately equal 41 K). Our data show no evidence of the complex magnetic ordering exhibited by bulk Mn(3)O(4), or of a magnetic behavior around T(N) that has a dynamic (relaxation) origin. Instead, we find a low-temperature (at approximately 11 K) magnetic anomaly that manifests itself as a peak in the out-of-phase component of the ac-susceptibility. Analysis of the frequency and average-particle-size dependence of the peak temperature demonstrates that this behavior is due to the onset of superparamagnetic relaxation, and not to a previously hinted at spin-glass-like transition. Indeed, the relative peak temperature variation per frequency decade DeltaT/TDeltalog(f) is 0.11, an order of magnitude larger than the value expected for collective spin freezing, but within the range of values observed for superparamagnetic blocking. Furthermore, attempts to fit the frequency f/observation time tau = 1/2pif dependence of the peak temperature by a power law led to parameter values unexpected for a spin-glass transition. On the other hand, a Vogel-Fulcher law tau = tau(0)exp[E(B)/k(B)(T - T(0))]-where E(B) is the energy barrier to magnetization reversal, k(B) is the Boltzmann constant, tau(0) and T(0) are constants related to the attempt frequency and the interparticle interaction strength-correctly describes the peak shift and yields values consistent with the superparamagnetic behavior of a slightly interacting system of nanoparticles. In addition, the peak temperature T is sensitive to minute changes in the average particle size (D), and scales as (T - T(0) is proportional to(D)3, another signature of superparamagnetic relaxation.

Cerebroventricular propranolol elevates cerebrospinal fluid norepinephrine and lowers blood pressure.

Ventriculocisternal administration of dl- and d-propranolol produced dose-dependent increases in cerebrospinal fluid norepinephrine and reductions in blood pressure. A highly significant correlation was found between the increase in norepinephrine and the hypotensive effect. The propranolol-induced hypotension was prevented by intracisternal phentolamine. These data indicate that the hypotensive effect of centrally administered propranolol results from a drug-induced release of norepinephrine, which stimulates central alpha receptors to lower arterial pressure.

Effects of alpha-difluoromethylornithine and recombinant interferon-alpha 2 on the growth of a human renal cell adenocarcinoma xenograft in nude mice.

The effects of human recombinant interferon-alpha 2 (IFN-alpha 2) and alpha-difluoromethylornithine (DFMO) as single agents and in combination were studied for efficacy against the renal cell adenocarcinoma (JDF-1) in an in vitro clonogenic assay and in vivo as xenografts in nude mice. In vitro studies showed dose-dependent inhibition of JDF-1 colony formation by IFN-alpha 2. DFMO alone did not significantly inhibit colony formation even though ornithine decarboxylase activity was significantly inhibited. The combination of IFN-alpha 2 and DFMO synergistically inhibited JDF-1 colony formation. The synergism was more readily observed at low IFN-alpha 2 concentrations. In vivo studies showed a similar tumor growth inhibition pattern. JDF-1 tumors were implanted s.c. in nude mice, and drugs were administered continuously by Alza minipumps (IFN-alpha 2) and in drinking water (DFMO) for 28 days. IFN-alpha 2 alone significantly inhibited JDF-1 growth, while DFMO alone had no significant inhibitory effect. The combination of IFN-alpha 2 and DFMO inhibited tumor growth in an apparent additive manner at the doses used. This was reflected in the mean tumor weights obtained at the termination of the experiment: control, 1484 +/- 187 (S.E.) mg; DFMO only, 1106 +/- 129 mg; IFN-alpha 2 only, 941 +/- 186 mg; and DFMO plus IFN-alpha 2, 620 +/- 109 mg. Assessment of mouse natural killer cell activity at the time of sacrifice showed that DFMO inhibited natural killer cell activity, while IFN-alpha 2 had no effect. DFMO was observed to inhibit ornithine decarboxylase activity in JDF-1 tumors by 78%, IFN-alpha 2 by 18%, and the combination by 78%. In addition, the drugs individually and in combination had similar inhibitory effects on JDF-1 spermidine content. One of the unexpected findings was the alteration in the spermine:spermidine ratio in the tumors treated with the combination of DFMO and IFN-alpha 2. The ratio in this group decreased to 0.44, while ratios for control, IFN-alpha 2 only, and DFMO only were 0.99, 0.66, and 0.88, respectively. These results clearly show that combined therapy with DFMO and IFN-alpha 2 is more effective than is single-drug therapy. The mechanism by which these drugs coordinately inhibit tumor growth is unclear but appears to be associated with direct inhibition of tumor cell proliferation, possibly by modulation of polyamine metabolism.

Nonsuperoxide lucigenin-enhanced chemiluminescence from phospholipids and human saphenous veins.

The use of lucigenin-enhanced chemiluminescence (CL) for the detection of superoxide (O2.-) has grown in popularity due to an increased demand for a simple and specific system capable of measuring superoxide. In this study we report a lucigenin-CL signal emanating from human saphenous veins (SV) that was not inhibited by superoxide dismutase (SOD) and lasted for more than 24 h. A larger CL-signal with similar properties was produced by saphenous veins that had been dehydrated. A similar, non-SOD-inhibitable lucigenin-CL was also produced with a variety of phospholipids and phosphatidic acid. The chemical moiety responsible for the phospholipid CL is oxygen dependent but remains unidentified because a variety of lipids and phosphate containing species failed to produce such a signal. These results suggest that the use of lucigenin as a specific CL enhancer for O2.- must be clearly discriminated with a specific O2.- inhibitor when used in biological systems.

The use of methylene blue as an extravascular surgical marker impairs vascular responses of human saphenous veins.

Methylene blue is occasionally applied to the adventitia of blood vessels during coronary artery bypass and other vascular procedures to assist in the orientation of the vessel. Inherent in this method is the assumption that extravascular application of methylene blue is innocuous with regard to vascular function. In the first part of this study, the in vitro vascular reactivity of methylene blue-labeled saphenous veins was compared with that of veins that were not marked with methylene blue. The vasoactive agents tested were designed to examine multiple pathways. They included potassium chloride, prostaglandin F2 alpha, phenylephrine, serotonin, angiotensin II, BHT-933 (alpha 2-adrenergic agonist), sodium nitroprusside, acetylcholine, isoproterenol, and verapamil. Compared with unmarked veins, those marked with methylene blue demonstrated a significant impairment of both vasoconstrictor and vasodilator function. These observations were made on a relatively small number of patients and could therefore be attributed to inherent differences between patients or surgical procedures. In the second part of this study, these variables were eliminated by dividing a single vein from one patient into three segments for a 45-minute exposure to external only methylene blue, internal and external methylene blue, or no methylene blue. The segments were then evaluated for vasoreactivity in vitro. Externally applied methylene blue reduced vasoconstriction regardless of the agonist. Further, both endothelium-dependent and -independent vasodilation was diminished by external methylene blue exposure. In veins exposed to methylene blue both internally and externally the results were similar but the magnitude of impairment greater. It is concluded that surgical marking of blood vessels with methylene blue has the potential to adversely affect vascular reactivity and therefore the use of alternative dyes should be considered.

Relationship of plasma clonidine to growth hormone concentrations in children and adolescents.

The relationships of plasma clonidine to increases in growth hormone, blood pressure response and degree of sedation were studied in nine children with short stature after a 0.15 mg/m2 oral clonidine tolerance test. A direct correlation was found between the peak plasma clonidine concentration and the increase in plasma growth hormone (P = 0.055). The patients experienced varying degrees of blood pressure reduction and sedation that were unrelated to age. No correlation was found between the plasma clonidine concentration and degree of blood pressure reduction or degree of sedation. The half-life of oral clonidine ranged from 1.75 to 2.38 hours, which is significantly less than that for adults.

Increases in CSF norepinephrine associated with the onset of digoxin-induced arrhythmias.

The present study utilized a time course of CSF catecholamine concentrations during peripheral digoxin administration in vivo to provide a clarification of central catecholaminergic mechanisms involved in digitalis cardiotoxicity. A continuous peripheral digoxin infusion produced significant increases in CSF norepinephrine just prior to arrhythmogenesis in anesthetized dogs. Phentolamine pretreatment significantly increased the arrhythmogenic and lethal doses of digoxin. These results suggest that activation of central noradrenergic neurons may be the initiating factor in digoxin-induced arrhythmogenesis.

Catecholaminergic and opioidergic mechanisms involved in the hypotensive response of pindolol.

The present study evaluated the involvement of opioidergic and catecholaminergic mechanisms in the hypotensive action of pindolol. Pindolol (1 mg/kg i.a.) was administered to unanesthetized spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats instrumented for direct arterial pressure monitoring. Peripheral administration of pindolol produced a significant decrease in blood pressure in both SHR and WKY rats with SHR animals having a greater response. Heart rate was reduced in SHR; however, a tachycardia was observed in WKY rats. Pretreatment with naloxone (100 micrograms/kg i.a.) 10 min prior to pindolol administration prevented the hypotensive response. Similar pretreatment with yohimbine, an alpha 2-receptor antagonist, also prevented the pindolol-induced hypotensive response in both SHR and WKY rats. Neither naloxone nor yohimbine alone significantly affected blood pressure or heart rate. These results suggest that opioidergic and catecholaminergic mechanisms are involved in the hypotensive action of pindolol.

A simplified technique for chronic cerebrospinal fluid collection in the awake dog.

A modified design for a guide tube to facilitate collection of cerebrospinal fluid from the lateral ventricle of awake dogs was developed. The modifications allowed for rapid, inexpensive and secure implantation. The tested guide tubes remained in place and patent for 20 weeks.

Interaction of propranolol with central serotonergic neurons.

Central monoaminergic mechanisms are believed to be involved in cardiovascular regulation. The present study was designed to evaluate the involvement of central serotonergic pathways in the antihypertensive action of propranolol in pentobarbital anesthetized mongrel dogs. Ventriculocisternal perfusion of propranolol (25 ug/kg/min for 30 min) decreased serotonin turnover as indicated by a significant decrease in cerebrospinal fluid levels of 5-hydroxyindoleacetic acid (5-HIAA). This effect was accompanied by a significant reduction in mean arterial pressure and heart rate. These results indicate that propranolol decreases central serotonergic activity and suggests a possible role for central serotonergic pathways in the antihypertensive action of propranolol. Several studies have indicated that central serotonergic pathways participate in the regulation of blood pressure. Brainstem regions including the nucleus tractus solitarius, the raphe nucleus and the anterior hypothalamic preoptic region are involved in cardiovascular control and contain a dense population of serotonergic neurons. A centrally-mediated hypotensive effect of propranolol has been demonstrated. Centrally administered propranolol increases cerebrospinal fluid (CSF) levels of norepinephrine and reduces blood pressure possibly due to decreased peripheral sympathetic nerve activity. Central serotonergic pathways may also be involved in the antihypertensive action of some beta-adrenoceptor antagonists. Destruction of central serotonergic neurons with 5,7-dihydroxytryptamine and desipramine abolished the antihypertensive effect of intracisternal propranolol in sinoaortic denervated dogs. Acute administrations of (-)-propranolol and (-)-pindolol decreased the synthesis rate of serotonin, while acute administration of salbutamol, a beta 2-adrenoceptor agonist, increased 5-HIAA levels in rat brain structures. The present study was designed to evaluate the involvement of central serotonergic pathways in the antihypertensive action of propranolol.

Central mechanisms of action involved in cocaine-induced tachycardia.

The present study was designed to determine the central effects of cocaine on heart rate and blood pressure in Wistar Kyoto rats (WKY) and to evaluate mechanisms involved in the response. Cocaine (0.025-4 mg/kg) was administered to unanesthetized, unrestrained rats via a cannula placed into the lateral ventricle. Procaine (0.1 and 4 mg/kg) was also administered centrally. Cocaine did not significantly alter blood pressure at doses of 0.025, 0.1, or 0.5 mg/kg, icv. Only the highest dose, 4 mg/kg, icv produced a significant pressor response. Cocaine produced significant dose-dependent tachycardia, with the maximum increase in heart rate occurring within 5 min. Procaine (4 mg/kg, icv) produced tachycardia, but the effect was significantly less than that produced by cocaine (4 mg/kg, icv). Cocaine also produced tachycardia at a dose of 0.1 mg/kg, but procaine did not significantly alter heart rate at the same dose. Central phentolamine pretreatment (0.1 mg/kg, icv) significantly attenuated the increase in heart rate produced by cocaine. These results indicate that the centrally mediated tachycardia produced by cocaine is partly due to its local anesthetic activity and to indirect stimulation of alpha receptors.

Naloxone inhibits the centrally-mediated hypotensive actions of BHT-933 (azepexole).

Central administration of BHT 933, a highly selective alpha 2 agonist, to pentobarbital-anesthetized, normotensive dogs resulted in a rapid, significant decrease in blood pressure. The maximal response occurred at 30 min and remained significantly decreased for 60 min. Concomitant with the hypotensive response was a decrease in heart rate. Pretreatment with naloxone 15 min prior to the administration of BHT 933 completely abolished the hypotensive response and significantly inhibited the bradycardia. These results suggest a role for central opioidergic systems in the control of blood pressure which may serve as important sites of antihypertensive drug action. The central regulation of sympathetic tone by catecholaminergic systems plays an important role in the control of cardiovascular function in both normal and pathological states. A high density of catecholaminergic nerve terminals is found in regions of the brainstem involved in cardiovascular control. Stimulation of the alpha receptors in these areas decreases peripheral sympathetic tone and subsequently lowers blood pressure. Recent histochemical evidence has demonstrated the presence of opioid peptides in the nucleus tractus solitarii, nucleus ambiguous and hypothalamus as well as other discrete brain areas associated with cardiovascular control. Activation of the opiate receptors in these brain areas decreases sympathetic tone and blood pressure. Additionally, both catecholaminergic and opioidergic systems have been implicated in the reaction to certain stimuli (i.e., pain, stress) which entail important hemodynamic adaptations. The similarity between the central opiate and catecholaminergic systems suggests a relationship between the two systems in blood pressure control and a potential site of antihypertensive drug action. The purpose of the present study was to determine if an opioidergic component is involved in the hypotensive action of BHT 933 (azepexole). BHT 933 is a relatively new hypotensive agent which is a much more specific alpha 2 agonist than clonidine.

Hemodynamic effects of centrally administered, norcocaine in the rat.

Norcocaine is the N-demethylated metabolite of cocaine. It is present in the CNS and is reported to be pharmacologically active. The present study was designed to evaluate the cardiovascular actions of norcocaine following central administration. Wistar Kyoto (WKY) rats were anesthetized with pentobarbital and instrumented for measurement of blood pressure and renal and hindlimb blood flow (via Doppler flowprobes). A cerebroventricular cannula was placed in the lateral ventricle for drug administration. Cocaine or norcocaine was administered centrally in a dose range of 0.025 to 4.0 mg/kg. Under the above experimental conditions, 4.0 mg/kg of norcocaine decreased blood pressure without a significant change in either hind limb or renal blood flow. Central administration of cocaine also produced a similar depressor response. In conscious, unrestrained rats, cocaine produced a pressor response while norcocaine did not significantly alter blood pressure. The depressor response to both cocaine and norcocaine in the anesthetized animal is speculated to be due to the local anesthetic properties of the drugs.

Enhanced hemodynamic response to [D-ALA2,D-MET5]-methionine enkephalin (DAME) in streptozotocin-induced diabetic rats is reversed by insulin replacement.

The present study examined the alterations of hemodynamic responses to [D-ala2,D-Met5]-methionine enkephalin (DAME) in diabetic animals. Male Sprague-Dawley rats (12 weeks old) were used for this study. Diabetes was induced by a single injection of streptozotocin (65 mg/kg, i.v.). After 7 days, blood glucose levels were determined to confirm the diabetic state. Animals were anesthetized and instrumented to monitor mean arterial pressure, hindlimb bloodflow and hindlimb vascular resistance. Administration of DAME produced a significantly greater reduction in blood pressure, increase in hindlimb bloodflow and decrease in hindlimb vascular resistance in diabetic vs. control rats. These effects were blocked by naloxone. All hemodynamic changes were attenuated after pretreatment with the ganglionic blocker, hexamethonium, indicating that the responses were mediated either within the central nervous system or at the ganglia. Insulin reversed the exaggerated depressor effect of DAME on streptozotocin-treated rats. Collectively, these results suggest that diabetic rats have altered opioidergic hemodynamic responses to DAME due to mu receptor alterations in the CNS or in autonomic ganglia. These effects were reversed by replacement of insulin.

Effect of St. John's wort on free radical production.

St. John's wort (Hypericum perforatum) is an herbal compound used in the treatment of burns, bruises, swelling, anxiety, and most recently, mild to moderate depression. The present study was designed to evaluate the antioxidant properties of St. John's wort in both cell-free and human vascular tissue. The experiment was performed initially in a cell-free system using Krebs buffer and a combination of xanthine/xanthine oxidase to initiate the production of the superoxide radical. Additionally, human placental vein was incubated in Krebs buffer without xanthine or xanthine oxidase to study the effects of St. John's wort on human tissue in vitro. Commercially available formulations of St. John's wort, standardized to either hypericin or hyperforin, were dissolved in an alkaline solution, and the following dilutions were made: 1:1, 1:2.5, 1:5, 1:7.5, 1:10, and 1:20. Lucigenin chemiluminescence was used to measure free radical production in both systems. A pro-oxidant effect was seen at the highest concentration, 1:1. Lower concentrations revealed antioxidant properties of the compound. All dilutions below 1:1 in both systems showed a dose-related inverse relationship of superoxide inhibition. The largest suppression was seen at the most dilute concentration, 1:20. The addition of 10(-3) M tiron inhibited the chemiluminescence signal, thereby confirming the production of superoxide. The results of this study suggest that St. John's wort inhibits free radical production in both cell-free and human vascular tissue.

The effect of copper deficiency on adriamycin toxicity.

The effect of copper (Cu) deficiency on antioxidant status of liver and heart and its effect on adriamycin toxicity was assessed. Weanling rats were fed Cu-adequate (+Cu) and Cu-deficient (-Cu) diets for 3 weeks and then injected intraperitoneally once with saline or adriamycin (8 mg/kg). All -Cu rats had increased heart/body weight ratios compared to +Cu rats. Regardless of Cu status, adriamycin decreased body weight and increased heart cytochrome c oxidase, but had no effect on Cu,Zn-superoxide dismutase, glutathione peroxidase, the thiobarbituric acid (TBA) index or liver cytochrome c oxidase activity. -Cu, adriamycin rats had significantly decreased heart weights (0.54 + 0.02 g/kg body wt.) compared to -Cu, saline rats (0.69 +/- 0.05 g/kg body wt.). Four of 6 -Cu rats given adriamycin had abnormal EKGs, with 3 showing extrasystoles and 1 having a severe bradycardia. All +Cu rats given adriamycin had normal EKGs. Pathological changes detected with electron microscopy were most severe in -Cu rats given adriamycin.

Zidovudine serum, cerebrospinal fluid, and brain concentrations following chronic administration of a new zidovudine formulation via an implantable pump in dogs [corrected].

Zidovudine (AZT), prepared as an alkaline solution, was administered iv and intraarterially (ia) by continuous infusion via an implantable pump in dogs. The AZT serum and cerebrospinal fluid (CSF) concentrations were measured over a 28-day treatment period by HPLC. Terminal brain AZT concentrations were also measured. Control (vehicle only) animals were also studied. All animals were evaluated for pathological changes associated with the AZT and vehicle infusions in catheterized vessels and other organs. In the iv AZT treatment group, serum AZT concentrations were relatively constant, with individual coefficients of variations (%CV) of 20% or less. Mean CSF:serum and brain:serum AZT concentration ratios were 0.149 and 0.212, respectively. In the ia AZT treatment group, serum AZT concentrations were more variable than in the iv group, with %CV ranging from 22 to 79%. The fluctuations in serum concentrations were attributed to temporary blockages of the outflow catheter. Mean CSF:serum and brain:serum AZT concentration ratios were 0.126 and 0.249, respectively. Pathological changes, similar in both control and treatment groups, included endothelial denudation and myointimal proliferation at the infusion sites. The conclusions of the study are (1) steady-state greater than 1 microM AZT serum concentrations can be maintained chronically by use of an implantable pump containing a basic pH AZT solution; (2) ia delivery of AZT did not increase central nervous system uptake compared with iv administration; and (3) morbidity associated with the infused solutions does not seem to be a limitation for this mode of therapy.

Differential routes of cocaine administration indicate a peripheral cardiotoxic action.

The present study utilized different routes of administration in unanesthetized Wistar Kyoto (WKY) rats to determine whether cocaine-induced death was mediated through a peripheral or central site of action. Administration of cocaine via a route that resulted in high concentrations of cocaine reaching the heart produced arrhythmias, convulsions, a decrease in heart rate and mean arterial pressure, and death. However, administration of the same dose via a route that resulted in passage of cocaine through the liver before reaching the heart produced only a pressor response. Additionally, administration of the same dose via a route that resulted in high levels of cocaine reaching the brain did produce a pressor response that was followed by a decrease in blood pressure and heart rate, arrhythmias, convulsions and death. However, these effects were delayed in comparison to the response when high concentrations of cocaine reached the heart immediately. These results support a peripheral site of action for cocaine-induced death.

Opioidergic receptors in the arcuate nucleus are not involved in the cardiovascular effects of clonidine.

The arcuate nucleus is the bed nucleus for the pro-opiomelancortin system of the brain with important connections with other nuclei involved in cardiovascular function. Clonidine has been reported to produce its cardiovascular effects through an interaction with opioid and alpha 2-adrenergic receptors. The present study examined the arcuate nucleus as a site of action of clonidine. Male spontaneously hypertensive rats were anesthetized with pentobarbital and were instrumented for the measurement of blood pressure and heart rate. Cannulae were placed either through the cisterna magna (IC) or in the arcuate nucleus. Administration of clonidine (0.03-3.75 micrograms, IC) produced a dose-dependent hypotension and bradycardia. Pretreatment with naloxone (30 micrograms, IC) prior to clonidine administration resulted in a significant attenuation of both the clonidine-induced hypotension and bradycardia. In contrast, administration of naloxone (100 ng) into the arcuate nucleus prior to the central administration of clonidine did not alter the cardiovascular effects of clonidine. These results support the role of central opioidergic receptors in the cardiovascular effects of clonidine but do not support the arcuate nucleus as the site of action.