Mast cell activation involves plasma membrane potential- and thapsigargin-sensitive intracellular calcium pools

Summary— The regulation and role of the intracellular Ca²⁺ pools were studied in rat peritoneal mast cells. Cytosolic free calcium concentration ([Ca²⁺]i) was monitored in fura-2 loaded mast cells. In the presence of Ca²⁺ and K+, compound 48/80 induced a biphasic increase in [Ca²⁺]i composed of a fast transient phase and an apparent sustained phase. The sustained phase was partially inhibited by the addition of Mn²⁺. DTPA, a cell-impermeant chelator of Mn²⁺, reversed this inhibition, suggesting that a quenching of fura-2 fluorescence occurs in the extracellular medium. In the absence of extracellular Ca²⁺, the transient phase, but not the sustained one, could be preserved, provided that mast cells were depolarized. The transient phase was completely abolished by thapsigargin, a microsomal Ca²⁺-ATPase inhibitor. Maximum histamine release induced by either compound 48/80 or antigen was obtained in the absence of added Ca²⁺ only when mast cells were depolarized. These histamine releases were inhibited by low doses (< 30 nM) of thapsigargin. Thapsigargin at higher doses induced histamine release which was unaffected by changing the plasma membrane potential, but was completely dependent on extracellular Ca²⁺, showing that a Ca²⁺ influx is required for thapsigargin-induced exocytosis. Together, these results suggest that the mobilization of Ca²⁺ from thapsigargin sensitive-intracellular pools induced by compound 48/80 or antigen is sufficient to trigger histamine release. The modulation of these pools by the plasma membrane potential suggest their localization is close to the plasma membrane.     

Improved sib-pair linkage test for disease susceptibility loci

An improved sib-pair test for linkage is introduced which is superior to the previously proposed tests. The test is derived from the standard chi-squared goodness of fit statistic by restricting the alternative hypothesis to the genetically possible. Critical values are given and exact power comparisons are made with the previously proposed tests. The new test is shown to be more powerful for finite samples as well as being asymptotically uniformly most powerful. © 1993 Wiley-Liss, Inc.     

Neuroprotection with felbamate: a 7- and 28-day study in transient forebrain ischemia in gerbils

The use of glutamate antagonists and GABA agonists may protect neurons from the effects of transient ischemia. Felbamate is a new antiepileptic drug with glutamate antagonist and GABA agonist properties, We tested the efficacy of felbamate in a gerbil model of transient forebrain ischemia. Damage assessment was done with silver staining at 7 and 28 days after 5 min of bilateral carotid occlusion, Cerebral cortex, hippocampus (CA1 and CA4), thalamus and striatum were evaluated on a 4-point scoring system, The animals sacrificed at 28 days were also tested in a water-maze task to assess recovery of function, The initial dose of felbamate (300 mg/kg) was given 30 min before the ischemic insult in one set of animals and 30 min after the insult in another set of animals. There were 8 animals tested per group (total: 48 animals). There was significant neuronal protection with the use of felbamate, both before and after ischemia in all regions of the brain. Protection was seen in animals sacrificed at 7 and 28 days, Protection was moderate when felbamate was used before ischemia. It was highly significant when felbamate was given 30 min after the insult. Behavioral studies however did not show any difference in the felbamate treated animals versus the saline treated controls. The structural protection with felbamate was very significant when used in the post-ischemic period. This window for protection merits further evaluation in relation to the clinical setting of stroke.     

Quality of life on treatment with Metoprolol in Dilated Cardiomyopathy: Results from the MDC trial

Summary Quality of life in heart failure patients is receiving increased attention as a reflection of a treatment's potential secondary benefit of general well-being and daily functioning. The Metoprolol in Dilated Cardiomyopathy (MDC) trial was conducted as a large, multicenter trial to establish the effects of metoprolol on mortality and need for heart transplantation in patients with symptomatic idiopathic cardiomyopathy. It was found that metoprolol was well tolerated, improved symptoms and cardiac function, and prevented clinical deterioration in patients with symptomatic idiopathic dilated cardiomyopathy. Quality of life was evaluated as a secondary endpoint in 345 out of 383 randomized patients using a disease-specific questionnaire, the Quality of Life in Heart Failure Questionnaire, depicting physical activity, somatic symptoms, emotions, and life satisfaction. In a comparison of patients treated with metoprolol or placebo, patients treated with metoprolol noted a significantly more favorable response than those treated with placebo in terms of the overall treatment evaluation (p<0.05). Additionally, an analysis of the changes from baseline to 18 months, using 95% confidence intervals, revealed that patients treated with metoprolol showed a significant improvement from baseline to 18 months in life satisfaction, physical activity, and the total score, while patients treated with placebo did not change at all. The improvement in quality of life was supported by the correlations with improvement in traditional clinical parameters.     

Functional role and histological demonstration of nitric-oxide-mediated inhibitory nerves in dog sphincter of Oddi

Abstract Nitric oxide (NO) plays an important physiological role in regulating gastrointestinal motility. Involvement of endogenous NO was evaluated in the response to non-adrenergic, non-cholinergic (NANC) nerve stimulation of the dog sphincter muscle of Oddi. Transmural electrical stimulation (TES), nicotine (10^?5M) and K⁺ (10 mM) produced only a relaxation in the sphincter muscle strips contracted with substance P, which was not potentiated by atropine. The TES-induced relaxation was abolished by tetrodotoxin (3 times 10^?7 M) and oxyhaemoglobin (1.6 times 10^?5 M), but not affected by atropine (10^?7 M), propranolol (10^?7 M), phentolamine (10^?7 M), indomethacin (10^?6 M), chole-cystokinin (CCK, 10^?8 M) and vasoactive intestinal polypeptide (VIP, 10^?8 M). The relaxation was also abolished by treatment with N^G-nitro-L-arginine (L-NA, 10^?5 M), an NO synthase inhibitor. Nicotine produced a transient relaxation, which was abolished by tetrodotoxin, hexamethonium (10^?5 M) and L-NA, but not affected by atropine and N^G-nitro-D-arginine (D-NA, 10^?5 M). The addition of K⁺ elicited a transient relaxation, which was abolished by tetrodotoxin and L-NA. The inhibitory effects of L-NA were antagonized by L-arginine (10^?3 M). The presence of neurons containing nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase was histochemically demonstrated in the sphincter of Oddi. These findings may indicate that TES, nicotine and K⁺ liberate NO from NANC inhibitory nerve which is involved in the relaxation of the dog sphincter of Oddi. The muscular tone does not seem to be regulated by cholinergic nerves under the experimental conditions used.     

Population kinetics of gentamicin in neonates

A population kinetic analysis was carried out on sparse plasma gentamicin (GE) concentration data from 469 neonates obtained as part of a routine therapeutic drug monitoring (TDM) programme in the hospital neonatology unit.The best predictors of the kinetic parameters of the monoexponential model, volume of distribution (Vd) and clearance (CL), were the weight (WT) and gestational age (GA). Vd of the neonates was only related to WT, whereas the half-life was only related to the GA.     

Prenatal lead exposure in relation to gestational age and birth weight: A review of epidemiologic studies

Although the adverse effect on pregnancy outcomes at high levels of lead exposure in the workplace has been recognized for years, there is uncertainty regarding the impact of exposure at the lower community exposure levels commonly encountered today. This review summarizes the epidemiologic literature and discusses pertinent methodologic issues and possible sources of interstudy variation. The authors conclude that prenatal lead exposure is unlikely to increase the risk of premature membrane rupture but does appear to increase the risk of preterm delivery. Whether prenatal lead exposure decreases gestational age in terms of infants is unclear. Prenatal lead exposure also appears to be associated with reduced birth weight, but results vary in relation to study design and degree of control for confounding. Adjustment for gestational age, a possible confounder of the birth weight-lead exposure association, did not yield clearer results.     

How adverse drug reactions can play a role in innovative drug research

We describe how adverse drug reactions (ADRs) can play an important role in pharmaceutical research and drug development. Not only do ADRs represent the risks and drawbacks associated with drugs but they can also be related to other knowledge available in pharmaceutical and medical research. We offer a model that can be used to systematically map the pathways through which ADRs can lead to innovative research. These pathways include chemical, therapeutic or pathophysiological steps that can be taken to arrive at new knowledge based on ADRs. We used the development of angiotensin-converting enzyme inhibitors, especially captopril, as a case study. The similarity between the ADR profiles of captopril and penicillamine was a starting point for further innovation. Historical analysis shows that in several instances research in the field of angiotensin-converting enzyme inhibitors has been triggered by ADRs. The model presented here might be applicable to other areas of innovative drug research.     

Demonstration of synergistic effects of hyperthermia and photodynamic therapy using the chick chorioallantoic membrane model.

The chick chorioallantoic membrane (CAM) model was used to study vascular effects of photodynamic therapy (PDT) and hyperthermia (HPT) and the synergism of these modalities. The CAM is a convenient medium for monitoring the modifications of the vasculature. It is possible to view the CAM and to examine structural changes of individual blood vessels in real time. Moreover, the CAM is a closed system which lends itself to mathematical modeling of the temporal and spatial temperature profile and in which HPT can be performed quantitatively and to a selected depth, using different lasers. A porphyrin-type photosensitizer solution was applied to areas of the CAM, defined by teflon O-rings placed on the surface. Uptake dynamics of the sensitizer into the CAM was determined by analyzing its fluorescence in vivo. The CAM area was irradiated with a dual-wavelength laser system composed of a dye laser at 644 nm (to induce PDT) and a CO2 laser at 10.6 microns (to bring about HPT). Damage to the CAM vasculature, due to combined PDT+HPT, was compared to the outcome of the separate modalities, and a synergistic effect of about 40% was observed.