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.     

Synaptic mechanisms of excitatory amino acids and NMDA receptor mediated brain excitability

L-Glutamate and related excitatory amino acids (EAA) are firmly established as major excitatory synaptic transmitter substances in the vertebrate central nervous system. Questions which have been addressed include: How many receptors are there for the EAAs?; What ion channels and/or 'second-messenger' systems are regulated by these receptors?; What are the roles of EAAs in higher neural functions?; Are they involved in neurological disorders? EAA receptors appear not only to mediate normal synaptic transmission along excitatory pathways but also to participate in the modification of synaptic connections during development. However, overaction of receptors can also mediate neuronal degeneration and even cell death. NMDA receptor antagonists markedly attenuate neuronal necrosis. Therefore, it appears that ischemia- and hypoglycemia-associated brain damage results not from a lack of energy substrates but rather via the mediation of NMDA receptors and 'excitotoxic' mechanisms. The action of ketamine anesthesia is closely associated with a block of the NMDA receptor. Ketamine binds to a site within the lumen of the NMDA-activated channel and can become trapped there when the channel closes. Current evidence indicated that NMDA receptor antagonists will be of value for the treatment of delayed neuronal death. NMDA receptor will lead to understanding the mechanisms underlying learning and memory, the control of neuronal excitability and neuronal death.     

Value and limits of bypassing the distal ileum in the treatment of hypercholesterolemia

Partial ileal bypass (PIB) was performed in 8 young adults (5 males and 3 females, mean age 37 +/- 5 years) with a history of vascular surgery (aorto-coronary bypass, ACB, n = 6; stroke, n = 2), presenting with hyperlipidemia (II B: n = 7; IIA: n = 1). None of the patients had diabetes, 2 had mild hypertension, and all were cigarette smokers. Hypolipidemic drugs were discontinued prior to PIB. Following bypass surgery, patients received vitamin B12 injections twice monthly. Total plasma cholesterol (TPC) and total plasma triglycerides (TPT) were assayed at 3 months and 1 year after surgery. The mean follow-up period was 84 months. Mean TPC level was significantly lower (3.96 +/- 0.57 preoperatively vs 2.19 +/- 0.79 (p less than 0.001) and 2.54 +/- 0.76 (p less than 0.01) 3 months and 1 year postsurgery, respectively. Mean TPT level was significantly lower 3 months after the intervention (4.85 +/- 2.37 vs 2.33 +/- 0.62, p. less than 0.02), but not after one year. Similar trends were observed throughout the follow-up period. One of the ACB patients died of drowing, while three others had recurring angina pectoris symptoms. Coronary angiography showed that, despite low TPC levels, coronary artery disease had extended either to other vessels not included in the former bypass, or beyond the anastomoses. Patients with a history of stroke were asymptomatic. PIB is effective in normalizing TPC. Nonetheless, this isolated procedure is insufficient to prevent the evolution of multifactorial atherosclerosis.     

Effects of cimetropium bromide on gallbladder contraction in response to oral and intraduodenal olive oil

Summary To evaluate the influence of the stomach and the cholinergic system on gallbladder contraction induced by physiological stimuli, the reduction in gallbladder volume in 7 healthy volunteers has been studied by real-time ultrasonography after the oral and intraduodenal administration of olive oil, preceded by pretreatment with cimetropium bromide or placebo. After an overnight fast, each subject swallowed 50 ml olive oil or it was administered through a naso-duodenal tube in the proximal duodenum. Cimetropium bromide 5 mg or placebo was given intravenously under double-blind control.After the placebo pretreatment, gallbladder contraction was greater and faster after intraduodenal oil than after oral oil. Cimetropium bromide decreased the extent, velocity and duration of gallbladder contraction induced by intraduodenal olive oil but it only reduced the velocity of the contraction induced by oil given orally.It is concluded that in normal human subjects the stomach modulates the extent and velocity of postprandial gallbladder contraction and that anticholinergic agents antagonize the gastric and duodenal phases of the response of the gallbladder to a meal.     

The effect of nortriptyline-specific active immunization on amitriptyline toxicity and disposition in the rabbit

Rabbits were actively immunized by a conjugate of nortriptyline (NT) to study the effect of specific anti-NT antibodies on toxicity and disposition of amitriptyline (AT). Control and immunized rabbits received 115 mg/kg AT intraperitoneally (i.p.). The lethality dose (LD) profile exhibited a gentle slope; LD100 and LD0 were separated by 100 mg/kg. Mortality was significantly reduced from LD67 to LD43 (P less than 0.05). Total plasma concentrations of the toxin were increased in the immunized group compared to the control group. AUC0.5-24 h value was 5-fold higher in the immunized group than in the control group. Moreover, a smaller fraction of unbound toxin in plasma was observed in the immunized group than in the control group. These observations indicate that AT was actively sequestered by antibodies. The intensity of this phenomenon was a function of both the antibody affinity constant (10(9) M-1) and the neutralizing capacity (varying from 0.005 to 0.2 mg/kg) of the circulating antibodies in each immunized rabbit. Results clearly show that anti-NT antibodies are able to effectively sequestrate AT.     

Locked intramedullary nailing of fractures of femur and tibia

The results of 194 consecutive interlocking nailings for 95 fractures in the tibia and 99 fractures in the femur with a median observation time of 22 months are presented. Three fractures were not consolidated radiologically at follow-up; three deep infections were recorded, all of which healed. Shortening > 1cm was recorded in 17 fractures, rotatory malalignment > 5 ° in 21, and angular malalignment > 5 ° occurred in 17. The end result was excellent in 121 fractures, good in 41, fair in 28, and poor in 4.