Action of exogenous potassium and calcium ions on in vitro metacyclogenesis in Trypanosoma cruzi

The cations Ca2+ and K+ and the anions Cl-, HCO3-, and PO4- were studied for their contribution to metacyclic trypomastigote formation of Trypanosoma cruzi in starvation media consisting of phosphate-buffered saline (PBS) + 10 mM proline + 10 mM sodium acetate as well as one of the following salts: 0.035% NaHCO3 (PBSNPA), 0.035% K2CO3 (PBSKPA) or 0.035% K2HPO4 (PBSPPA). Isolates CL and DM28c were activated to transform with 5% CO2 and the percent metacyclogenesis determined after incubation for 96 h in PBS starvation media. Maximal metacyclogenesis was found with CaCl2 and KCl. In the presence of K+, the percent transformation was highest with the phosphate salt, followed by the carbonate and the chloride salts. Cells incubated in PBSNPA and the cationic ionophores A23187 (5 x 10(-6) M), lasalocid (5 x 10(-6) M), and valinomycin (10(-8) M) do not survive; addition of 2 mM CaCl2 or 17 mM KCl to DM28c cells, reversed the lethal action of the ionophores permitting differentiation into metacyclic forms. The addition of CaCl2 to CL cells incubated in ionophores abrogated the lethal effect of the ionophores but transformation was significantly different than in control preparations. Adding KCl to ionophore incubated cells resulted in normal levels of transformation except in the case of valinomycin. DM28c and CL cells incubated in PBSKPA show significantly greater metacyclogenesis in the presence of 5 mM EGTA. These results indicate that exogenous concentrations of several cations and anions significantly influence T. cruzi metacyclogenesis and that the degree of response by the parasite to free ion levels may be strain dependent.

Plasma apolipoprotein E, high density lipoprotein1 (HDL1) and urinary mevalonate excretion in pancreatectomized diabetic dogs: effects of insulin and lovastatin

Hypercholesterolemia and increased concentrations of an apolipoprotein E (apoE)-containing HDL subclass, high density lipoprotein1 (HDL1) have been observed in streptozocin-alloxan diabetic dogs consuming normal amounts of dietary cholesterol. The aim of this study was to characterize the response of HDL1 and its targeting ligand, apoE, to insulin and HMG-CoA reductase inhibitor treatment in pancreatectomized diabetic dogs. Following induction of diabetes, plasma total cholesterol, HDL1, and apoE concentrations were all increased. Urinary mevalonate excretion, an index of cholesterol synthesis in humans, was 6-fold that of nondiabetic controls. Lipoprotein fractionation by Pevikon block electrophoresis and gel filtration chromatography showed that the increased cholesterol and apoE were associated with alpha 2-migrating particles corresponding to HDL1. Insulin treatment, resulting in near normal fasting blood glucose concentrations in the group as a whole (average 5.1 mM, 92 mg/dl), led to variable reductions in apoE, total plasma cholesterol, and HDL1. Uncorrected dyslipidemia during intensified insulin treatment appeared to be related to failure to achieve euglycemia. Despite unremitting hyperglycemia, treatment with lovastatin resulted in pronounced decreases in plasma cholesterol, HDL1 and apoE to concentrations below those observed in nondiabetic animals. Mevalonate excretion also fell, but remained twice normal. Thus neither modality corrected all of the abnormalities in canine diabetic dyslipidemia. Since apoE-containing HDL1 may mediate cholesterol traffic between the periphery and the liver (reverse cholesterol transport), the present observations suggest that increased cholesterol synthesis is accompanied by parallel abnormalities in cholesterol flux through the reverse transport pathway in the canine model.

Energy consumption in paraplegic ambulation using the reciprocating gait orthosis and electric stimulation of the thigh muscles

The energy consumption of six thoracic paraplegic persons ambulating in the reciprocating gait orthosis (RGO) with and without functional electric stimulation (FES) of their thigh muscles was determined as a function of walking speed. Plots of Kcal/kg-min and Kcal/kg-m vs walking speed in the RGO and RGO & FES were experimentally determined in this study and compared with the energy cost of walking in the long leg brace (LLB), the hip guidance orthosis (HGO), and an FES walking aid from data available in the literature. The RGO powered with electric stimulation of the thigh muscles required the lowest energy expenditure in Kcal/kg-m across the full range of walking speeds. The RGO, HGO, LLB, and FES walking orthoses ranked second, third, fourth, and fifth respectively. The lowest energy costs in Kcal/kg-min were associated with the RGO & FES, followed by the RGO, HGO, LLB, and FES for walking speeds below .28m/sec. At walking speeds higher than .28m/sec the HGO demonstrates lower energy cost followed by the RGO & FES, RGO, FES, and LLB. At the end of a 30-m walk, patients using the RGO & FES had a mean heart rate (HR) which was 12 beats/min less than the mean HR when using the RGO without FES, 31 beats/min less than the HR when using the LLB, and 42 beats/min less than the HR when using FES only. It was concluded that the FES-powered RGO combines the advantages of a passive mechanical orthosis with those of FES to provide substantial improvements in energy cost which may provide paraplegic persons with a mode of independent ambulation superior to the wheelchair.

Further studies on substrates inducing metacyclogenesis in Trypanosoma cruzi

Epimastigotes of Trypanosoma cruzi, Peru strain, incubated in Contreras' artificial triatomine urine transformed into metacyclic trypomastigotes when 10 mM L-glutamine, L-asparagine or D-fructose was added to the medium. Metacyclogenesis with these substrates was comparable to the percent metacyclic morphotype formation induced by L-proline and significantly greater than that stimulated by 10 mM D-glucose. Sodium acetate (10 mM) increased transformation induced by L-proline, and L-hydroxyproline (10 mM) increased transformation induced by D-fructose. Phosphoenolpyruvate (10 mM) inhibited L-proline-induced metacyclic trypomastigote stage formation. Three antimetabolites, azetidine 2-carboxylate (5 mM), malonic acid (1 mM), and desthiobiotin (5 mM), completely inhibited D-fructose-induced but not L-proline-induced transformation. The Costa Rica, Y, and CL strains of T. cruzi showed different patterns of percent metacyclogenesis with substrates that induce transformation in the Peru strain.

The paradox of alpha 2 adrenergic regulation of prolactin (PRL) secretion. II. PRL-releasing action of the alpha 2 receptor antagonists

It has been suggested that the stimulation of the secretion of PRL by the alpha 2 adrenergic receptor antagonists (yohimbine, piperoxane) results from blockade of an inhibitory influence imposed on PRL release by the central alpha 2 receptors (7, 15). Our present results do not support these conclusions for the following reasons: 1) The effectiveness of the alpha 2 receptor antagonists yohimbine (YOH), rauwolscine (RAU), Wy 26392 and idazoxan (IDAZ) respectively to activate secretion of PRL was not related to their alpha 2 antagonist potencies. RAU was more effective in activation of PRL secretion than either YOH or Wy 26392 although it had a similar alpha 2 antagonist activity, while IDAZ, the most potent alpha 2 blocker among the four compounds, did not stimulate PRL secretion. 2) The PRL-releasing effect of YOH or Wy 26392 was reversed by the alpha 2 agonist clonidine but the same effect of RAU was not, speaking against a common alpha 2-mediated mechanism of action of the three antagonists. 3) The PRL-stimulating effect of YOH, RAU or Wy 26392 persisted following inhibition of NE synthesis and presumably release with FLA 63, DDC or combination of reserpine and DDC. 4) Conversely, we found no indication for an inhibiting influence of activation of the alpha 2 receptors on the secretion of PRL. We conclude that the stimulation of PRL secretion by the alpha 2 receptor antagonists is not derived from blockade of the central alpha 2 receptors but from other, not yet defined properties of the drugs.

The paradox of alpha 2 adrenergic regulation of prolactin (PRL) secretion. I. The PRL-releasing action of the alpha 2 receptor agonists

Systemic (IV) administration of the alpha 2 receptor agonist clonidine is known to stimulate secretion of PRL and growth hormone (GH) suggesting a stimulatory role of the central alpha 2 receptors in the regulation of the two hormones. The present work confirms this notion for GH but indicates that the alpha 2 agonists stimulate PRL release by a peripheral action not involving central alpha 2 receptors. This conclusion is based on the following findings: 1) The minimum effective IV dose of clonidine or UK 14304 was four times larger for activation of PRL than GH secretion and had already manifest extracentral effects (elevation of arterial BP). 2) Subcutaneous injection of UK 14304 (220 micrograms/kg) elevated plasma GH but not PRL levels indicating that an effective activation of the central alpha 2 receptors does not stimulate PRL release. 3) Peripherally acting alpha 2 agonists (p-aminoclonidine, oxymetazoline) had no effect on GH secretion but stimulated PRL release in a manner identical with the effect of clonidine or UK 14304. 4) The peripherally acting alpha 2 antagonist DG-5128 blocked only the PRL secretory response to UK 14304 whereas the peripherally and centrally active yohimbine blocked the PRL and GH responses.

Prolactin (PRL) release-inhibiting properties of the alpha 2 adrenergic receptor antagonist idazoxan: comparison with yohimbine

The effects of the alpha 2 adrenergic receptor antagonists yohimbine (YOH) and Idazoxan (ID) on secretion of PRL were compared in nonanesthetized male rats bearing permanent intraatrial cannulae for i.v. drug delivery and serial blood sampling. YOH induced a dose-related elevation of basal plasma PRL levels. ID had either no effect or a tendency to lower them and effectively inhibited stimulation of PRL secretion with morphine, 5-hydroxytryptophan (5HTP), quipazine or restraint stress. YOH at low doses did not alter the PRL secretory responses to these stimuli or enhanced them at the highest dose used (1.56 mg/kg). ID inhibited the PRL-stimulating, effect of 5HTP or morphine following inhibition of NE synthesis with FLA63 or pretreatment with clonidine. It also blocked the effect of quipazine in rats pretreated with prazosin. It is concluded that ID, in a complete contrast to YOH effectively inhibits PRL secretion. The inhibitory mechanism appears to be unrelated to its interaction with the alpha adrenergic receptors.

Comparison of the clearances of serum chylomicron triglycerides enriched with eicosapentaenoic acid or oleic acid

Rat mesenteric lymph chylomicrons containing triglycerides enriched with either [14C]oleic acid (OA) or [14C]-eicosapentaenoic acid (EPA) were prepared by ultracentrifugation of lymph samples collected for 6 hr after a single duodenal infusion of an emulsion containing either fatty acid. These chylomicrons were injected into the jugular vein of recipient rats and, at various time intervals, blood was drawn and serum was assayed for radioactivity. In separate animals, serum lipoprotein fractions were separated by ultracentrifugation, and the redistribution of labeled fatty acid among circulating lipoproteins was determined by liquid scintillation spectrometry. When the early disappearance rates (10 min) of either total serum radioactivity or specifically the chylomicron fraction were compared, there were no differences between the groups receiving OA- or EPA-enriched chylomicrons. However, disappearance rates of EPA-enriched chylomicrons were slower than those of OA-enriched chylomicrons from 25 to 90 min. The small but significant differences in the disappearance rates for the longer time periods cannot be ascertained without further studies. At 5 min after injection of either type of chylomicron, the d less than 1.006 g/ml lipoprotein fraction of serum chylomicrons and very low density lipoproteins contained almost 90% of the original radioactivity. By 240 min, when less than 2% of the radioactivity remained, this radioactivity in the d less than 1.006 g/ml fraction was 43-46%, with concomitant increases in the low and high density lipoprotein fractions and in the lipoprotein-free serum.

Stimulation of intestinal cytokinetics and mucin turnover in rats fed wheat bran or cellulose

Rats were fed defined diets containing no fiber, 10% wheat bran or 10% cellulose, and intestinal morphology and cytokinetics were assessed by light microscopy and autoradiography, respectively. In bran-fed animals, there were no differences in morphological appearance of the jejunum, in the number of cells/villus column or in numbers of goblet cells compared to controls. Autoradiographic analysis, at one and 24 h after [3H]thymidine, however, suggested an increased turnover and villus transit of intestinal cells. There was also a 2.5 fold increase in incorporation of labeled sulfate, and a 2-fold increase in [3H]glucose incorporation into total intestinal glycoproteins and mucins. Similar, albeit less dramatic results were obtained in rats fed diets containing cellulose. These studies provide evidence that diets containing certain fiber derivatives can alter aspects of intestinal cell turnover, and support the earlier morphological observations suggesting increased goblet cell secretory activity in response to feeding these fiber derivatives.

Neoplastic proliferation in a case of epidermotropic high-grade malignant lymphoma associated with hypercalcemia

We report a case of epidermotropic high-grade malignant lymphoma associated with hypercalcemia occurring in a European woman aged 30 years. The clinical, histological, and biological presentation of the patient could enter the spectrum of HOTS (hypercalcemia, osteolysis, T cell lymphoma syndrome). The proliferation of neoplastic lymphocytes was very high in patch, plaques, and nodules of the skin.

A comparative study between interdermal tests with phytohemagglutinin and delayed hypersensitivity reactions elicited by tuberculin

Intradermal (i.d.) tests with phytohemagglutinin (PHA) and tuberculin are used in clinical practice to evaluate the cell-mediated immunity. The biologic significance of the skin response to PHA, clinically evaluated by the extent of erythema and induration, was studied histologically after incorporation of tritiated thymidine. It was compared to tuberculin tests. The rate of recruitment and the respective amount of inflammatory cells varied between patients and in time. In PHA tests the inflammatory reaction occurred in two phases, the first one consisting in the predominance of polymorphonuclears, the second one being characterized by chemotactism of lymphoblasts many of which synthesized DNA. The "in vivo" reaction to PHA is therefore complex; the same clinical evaluation corresponds to markedly different stages and events in the biological reaction. The histological grading of the PHA test is therefore desirable in the evaluation of the cell-mediated immunity because only the blastic proliferation is of importance in its rating and not the edema and the accumulation of polymorphonuclears.

Granulomatous vasculitis of Wegener

We report a case of granulomatous vasculitis of Wegener. Systemic involvement occurred in spite of chemotherapy and concomitantly with the development of immunological disturbances. The differential diagnosis with other angiocentric granulomatoses and the estimation of the risk of extension to internal organs are primordial because of their prognostic importance.