Possible serotonin-agonist action of veratramine

Veratramine produces a characteristic excitatory action on the central nervous system, producing both tremor and a characteristic “struggling” behavior. This behavioral excitation is accompanied by changes in serotonin content in hypothalamus. The central serotonin agonist methysergide in doses of 5–15 mg per kg produces a dose-dependent inhibition of veratramine's action, while parachlorophenylalanine has no effect. These results are consistent with a serotonin agonist mechanism to explain veratramine's action.     

Severe head trauma: pathophysiology and management

Acute traumatic brain injury is a leading cause of morbidity and mortality. Intensive management is aimed at early evacuation of intracranial mass lesions, control of intracranial hypertension, and prevention of medical complications.     

A randomized, blinded, placebo-controlled evaluation of calcium chloride and epinephrine for inotropic support after emergence from cardiopulmonary bypass.

Forty hemodynamically stable patients were randomized to receive an intravenous bolus of either calcium chloride (5 mg/kg) (n = 20) or placebo (n = 20) (phase I). Six minutes later, they received either an epinephrine (30 ng.kg-1.min-1) (n = 20) or placebo (n = 20) infusion (phase II). Hemodynamic and ionized calcium measurements were obtained in phase I at baseline and at 3 and 6 min after the bolus, and in phase II, at 3 and 6 min (study times 9 and 12 min) after initiation of the infusion. Compared with placebo, calcium did not significantly increase cardiac index but significantly increased mean arterial pressure. Calcium improved cardiac index from 2.46 +/- 0.12 (mean +/- SEM) to 2.74 +/- 0.12 L.min-1.m-2; likewise, placebo improved cardiac index from 2.51 +/- 0.15 to 2.74 +/- 0.15 L.min-1.m-2. Mean arterial blood pressure increased with calcium from 74 +/- 2 to 82 +/- 3 mm Hg compared with a placebo change of 74 +/- 2 to 76 +/- 2 mm Hg. Patients who received the epinephrine infusion (n = 20) demonstrated a significant increase in cardiac index at time 12 min compared with patients receiving only placebo (n = 20). Cardiac index of the epinephrine group increased from 2.56 +/- 0.15 to 2.92 +/- 0.22 L.min-1.m-2, whereas in the placebo group it decreased from 2.86 +/- 0.13 to 2.78 +/- 0.12 L.min-1.m-2. Prior administration of calcium did not alter the subsequent response to epinephrine (n = 10) compared with patients receiving epinephrine alone (n = 10). We conclude that cardiac index improves with time without drug therapy after bypass. Calcium chloride increases mean arterial blood pressure but not cardiac index immediately after cardiopulmonary bypass, whereas low-dose epinephrine significantly increases both cardiac index and mean arterial blood pressure without causing tachycardia in these patients. Calcium chloride (5 mg/kg) did not augment or inhibit the hemodynamic response to an epinephrine infusion.     

Nutritional status of children with schistosomiasis mansoni in two different areas of Machakos District, Kenya.

A possible association between nutritional status and Schistosoma mansoni infection or morbidity was investigated by comparing anthropometric indices among 362 children from 3 primary schools in Machakos District, Kenya. Matithini was a prosperous school in an area (Kangundo) of moderate intensity of schistosome infection but low associated morbidity. A second area (Kambu) showed more severe schistosome-associated morbidity: in this area, Kitengei school was prosperous and with high intensities of schistosome infection, while Misuuni school was less prosperous and with low intensities of infection. Nutritional status was assessed by measurement and appropriate standardization of height, weight and skinfold thickness and by questionnaires concerning diet. Children in Kangundo were better nourished than those in Kambu. Within Kambu, children from Misuuni showed low mean skinfold thickness and low mean weight-for-height ('wasting'): this was associated with a lack of dietary variety and of intake of animal products. In contrast, those from Kitengei showed low mean height-for-age ('stunting'). The relationship between intensity of schistosome infection and nutritional indices, although significant, was complex and not readily interpretable. However, intensity of infection was also correlated with hepatomegaly, which was more clearly related to nutritional status. Depending on the school, children with hepatomegaly were significantly more stunted and/or wasted than those without, and had less variety in their diet. Possible reasons for the observed associations are discussed and, of various possibilities, the hypothesis is suggested that schistosome-associated morbidity leads to a subsequent nutritional defect. This hypothesis can now be tested by appropriate intervention studies.     

Chemically induced cell proliferation in carcinogenesis.

Carcinogenesis can proceed by a variety of pathways involving the sequential mutation of normal cellular growth control genes and the clonal expansion of the resulting precancerous or cancerous cells. Chemical carcinogens may act by inducing mutations and/or altering cellular growth control. One class of chemical carcinogens are the genotoxicants. These compounds or their metabolites are DNA reactive and directly induce mutations or clastogenic changes. The observation that most mutagens are also carcinogenic is the basis for many current predictive assays and risk assessment models; however, there are different classes of nongenotoxic carcinogens that do not interact with DNA. Mitogens directly induce cell proliferation in the target tissue; cytotoxicants produce cell death followed by regenerative cell proliferation. Differential toxicity and/or growth stimulation induced by mitogens and cytotoxicants may provide a preferential growth advantage to spontaneous or chemically induced precancerous or cancerous cells. Mutagens are much more effective carcinogens at doses that also induce cell proliferation, and mutational activity may occur as an event secondary to cell proliferation. Thus, chemically induced cell proliferation is an important mechanistic consideration for both genotoxic and nongenotoxic carcinogens. The complex quantitative relationships between chemically induced cell proliferation and carcinogenic activity are under study in many laboratories. Such information should be considered in setting doses for cancer bioassays, for classifying chemical carcinogens and in providing more realistic approaches to risk assessment. Of particular concern in extrapolating cancer risk from rodent models to humans are those nongenotoxic agents that exhibit carcinogenic activity only at doses that also produce cytolethality and regenerative cell proliferation in the target organ.