Hyperventilation Facilitates Induction of Supraventricular Tachycardia: A Novel Method and the Possible Mechanism

INTRODUCTION: Hyperventilation has been demonstrated to alter autonomic function. Sympathomimetic drugs (isoproterenol) and parasympatholytic drugs (atropine) may be needed to facilitate induction of supraventricular tachycardia (SVT). The aim of this study was to test the clinical utility and mechanisms of hyperventilation to facilitate SVT initiation. METHODS AND RESULTS: Fourteen patients with clinically documented SVT (9 AV nodal reentrant tachycardia and 5 AV reciprocating tachycardia) but noninducible during baseline electrophysiologic study were included. Immediately after hyperventilation test (at least 30 respirations/min) for 2 minutes, systolic blood pressure, sinus cycle length, anterograde and retrograde 1:1 conduction, and induced SVT were measured. Arterial blood gas, pH, and heart rate variability before and after hyperventilation were measured. Seven of nine patients with AV nodal reentrant tachycardia and 3 of 5 patients with AV reciprocating tachycardia could be induced immediately after the hyperventilation test. After hyperventilation, anterograde AV and retrograde VA 1:1 conduction were improved, sinus cycle length was decreased, and heart rate variability were decreased in both groups. CONCLUSION: Hyperventilation can facilitate induction of SVT. Improvement of conduction properties and changes of autonomic function are the possible mechanisms.     

Evaluation of Lactobacillus Preparation on Enterotoxigenic E. Coli-induced Rabbit Ileal Loop Reactions

A commercially available lactobacillus-containing preparation has been used extensively in the treatment of diarrhea but few laboratory tests have been performed to determine the efficacy of this product. The rabbit ileal loop reaction was used here to determine the effect of the lactobacillus preparation and its ingredients on E. coli enterotoxin-induced loop fluid response. Enterotoxigenic E. coli cells grown overnight in shake cultures were washed and resuspended in saline to the original volume. They were then diluted in TSB suspensions of the lactobacillus preparation or its ingredients and injected into ileal loops. E. coli diluted in TSB served as positive controls. Fluid response was measured after 18 hours and the loop fluid ratio (LFR) (ml./cm.) of the lactobacillus preparations was compared to the positive controls. The positive controls always showed a high loop fluid ratio (> 1.1 ml./cm.) and negative saline controls showed no fluid response. The lactobacillus granules and tablets had low LFR's (0.08 and 0.05, respectively). Ingredients (whey, talc, sugar, evaporated milk, mineral oil) had variable LFR's (0.65, 0.78, 1.39, 1.46 and 1.54, respectively). Individual ingredients used to make this preparation show little antifluid response when used separately but the final product exhibits a significant antienterotoxin response.     

An interview study of participants in the Tacoma, Washington, syringe exchange

Although European and Australian studies of syringe exchange programs have reported safer injection among participants and no increase in drug use, the generalizability of these findings to the US is uncertain. We report on the operations and potential effectiveness of the longest-operating syringe exchange in the US and compare our results to studies of exchange programs outside the US. The sample of 204 study subjects reported no change in the frequency of injection, from 155 to 152 injections per month, and a decline in the frequency of unsafe injections, from 56 to 30 times per month, while participating in the program. In all studies, participants report reduction in unsafe injections, and no increase in illicit drug use. However, the comparison also suggests that a high proportion of Tacoma exchangers have higher initial rates of drug injection, unsafe injection and homelessness, all of which were associated with unsafe injection while using the exchange. These indicate a need for additional services but that the Tacoma program is no less effective than European and Australian programs.     

THE CHEMISTRY AND CONFORMATIONAL AND BIOLOGICAL ANALYSIS OF VITAMIN D3, ITS METABOLITES AND ANALOGUES

The chemical properties, sterochemical relationships and solution confromation, as assessed in part by proton NMR spectroscopy, for vitamin D₃, its major metabolites [including 1α, 25-(OH)₂ D₃, its hormonally active form] and a number of A-ring and side chain analogues are evaluated and discussed in relation ot their biological activity. In particular the relative ability of many of these seco-steroids to compet both with 25-OHD₃ for its chick serum binding protein and 1α, 25-(OH)₂-D₃ for its chick intenstinal cytosol-chromation receptor systme was quantitated, in vitro , Further, the relative effectiveness of all these metabolites and analogues to mediate in vivo intestinal calcium absorption and bone calcium mobilization was determined. Collectiveily these chemical and bilogical studies constitute a 'systems analysis'of the various steroid structural parameters both required and tolerated by the multi-stepped endocrine system associated with the bilogical actions of vitamin D.