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Biomedical subjects

A Zaritsky

Publications and source records attributed to A Zaritsky.

At least 109 records · Page 6Linked to original sources
PubMed1986

Biological control of mosquitoes by the larvicidal activity of Bacillus thuringiensis var. israelensis delta endotoxin.

Bacillus thuringiensis var. israelensis (B.t.i.) is a promising, safe toxic agent for control of mosquitoes, but the rapid disappearance of its toxicity makes its use in practice economically unattractive. The lack of evidence for B.t.i. multiplication in water also makes the natural ecology of B.t.i. puzzling. The observation that mosquito larvae readily cannibalize carcasses of B.t.i.-killed larvae, and that the carcasses become toxic to scavenging larvae provides a possible solution to this puzzle. Several experimental techniques have been developed to study these phenomena (e.g., quantitative determination of spore numbers despite aggregation, protocols for following toxicity development, etc.). Results suggest a cycle involving larval poisoning and death due to delta-endotoxin of ca. 1,000 spores, germination, vegetative growth and sporulation (with toxin production) of B.t.i. after multiplication to several million in the carcass. Implications of these results for the ecology of B.t.i., and for practical applications in mosquito control, are discussed.

Animals↗
PubMed1986

Advanced pediatric life support: state of the art.

Cardiopulmonary resuscitation in children is not well studied; many of the current recommendations for advanced pediatric life support (APLS) are based on anecdotal experience rather than scientific study. The following are unique issues in APLS requiring a consensus decision: What are the best methods of vascular access and of drug delivery and dosages? What constitutes minimal paramedic training and equipment? There are also many shared controversies between APLS and ACLS, including the use of calcium, epinephrine vs isoproterenol, methoxamine, and bicarbonate. This article presents the scientific basis for these controversial issues and highlights areas where information is lacking. A discussion of these questions generated a consensus on some issues and hopefully will stimulate further study to answer the questions that were raised.

Bicarbonates↗
PubMed1985

Homeoviscous adaptation, growth rate, and morphogenesis in bacteria.

Fluorescence polarization, P, of 1,6-diphenyl-1,3,5-hexatriene was studied in Escherichia coli B/r. Modification of nutritional conditions was not compensated by homeoviscous adaptation, demonstrated to exist for temperature variations. Cell diameter, which is known also to vary with nutrition but not with temperature, was found to be positively correlated with 1/P, and may therefore be regulated by membrane lipid order and fluidity.

Culture Media↗
PubMed1984

Helical macrofiber formation in Bacillus subtilis: inhibition by penicillin G.

The folding process required for helical macrofiber formation after the outgrowth of Bacillus subtilis spores was found to be blocked by very low concentrations of penicillin G (1 to 3 ng/ml). Under such conditions, growth and septation without cell separation resulted in characteristic disorganized multicellular structures. Higher concentrations (4 and 10 ng/ml) were needed to inhibit spore outgrowth and vegetative growth, respectively.

Bacillus subtilis↗
PubMed1984

Epinephrine absorption after intratracheal administration.

Tracheal intubation during cardiopulmonary resuscitation often precedes establishment of an intravenous route for the administration of drugs. To determine the efficacy of intratracheal administration of drugs during cardiopulmonary resuscitation we measured plasma catecholamine levels and hemodynamic responses to intratracheal epinephrine (EPI) administration using a double-blind, randomized crossover design in 7 male baboons (Papio anubis), each studied twice, who received 5 ml of 1:10000 EPI on one day and 5 ml of 0.9% NaCl on another day. Arterial blood samples for measurement of plasma EPI and norepinephrine (NE) concentrations were collected, and heart rate (HR) and mean arterial blood pressure (MAP) were measured before and 1, 2, 4, 8, 16, and 30 min after intratracheal drug administration. Intratracheal EPI significantly (P less than 0.05) elevated HR to 120 +/- 6 from 105 +/- 6 beats/min, MAP to 120 +/- 4 from 112 +/- 5 mm Hg, and plasma EPI to 8882 +/- 2143 from 928 +/- 209 pg/ml within 1 min of administration, and these effects persisted for 30 min. Plasma NE levels did not change after intratracheal EPI administration. None of the four variables changed after intratracheal saline was given. We conclude that in subhuman primates, intratracheal EPI is rapidly absorbed and is an effective pressor agent when given by this route; and that these data lend support to the clinical practice of intratracheal EPI administration during cardiac arrest or in the treatment of shock.

Absorption↗
PubMed1984

Hypomagnesemia is a common complication of aminoglycoside therapy.

Normal therapeutic dosages of aminoglycosides can cause hypomagnesemia in more than one-third of patients. Hypomagnesemia occurs early in therapy, results in renal Mg++ wasting and may produce hypocalcemia and hypokalemia. Patients who are NPO, eating poorly or not receiving supplemental Mg++ are at high risk for hypomagnesemia. Hypomagnesemia, hypocalcemia and hypokalemia respond to Mg++ replacement therapy. We recommend serial monitoring of serum Mg++ levels in patients receiving aminoglycoside therapy.

Aminoglycosides↗
PubMed1983

Sympathetic nervous system "switch off" with severe hypothermia.

Hypothermia occurs frequently in the critically ill patient, yet little is known about the endogenous catecholamine response to this stress. To study this problem, we measured heart rate (HR), mean arterial blood pressure (MAP), and plasma levels of norepinephrine (NE) and epinephrine (Epi) in subhuman primates (baboons) during progressive hypothermia from 37 degrees to 29 degrees C and then during rewarming to 37 degrees C. As the core temperature decreased from 37 degrees to 33 degrees C, HR and MAP increased significantly (p less than 0.05), but as core temperature further decreased from 33 degrees to 29 degrees C, the HR and MAP fell to prehypothermic levels. Plasma concentrations of NE and Epi increased significantly (p less than 0.01) as core temperature fell from 37 degrees to 31 degrees C, but as core temperature dropped from 31 degrees to 29 degrees C, plasma NE and Epi levels decreased towards prehypothermic concentrations. These findings indicate that the sympathetic nervous system (SNS) responds quickly to hypothermia but may be "switched off" at a threshold temperature of about 29 degrees C. We speculate that hypotensive patients with temperatures less than or equal to 29 degrees C may benefit from infusions of exogenous catecholamines, especially if there have been only minimal benefits achieved with conventional therapy such as fluids, and an increase in ambient temperature.

Animals↗
PubMed1982

Primary structure of the immunoglobulin J chain from the mouse.

The primary structure of the murine J chain was investigated by sequence analysis of the J chain cDNA inserts from two independently cloned chimeric plasmids. The sequence data showed that (i) the two cDNA inserts accounted for all but approximately 100 5' nucleotides of the J chain mRNA and (ii) the J chain mRNA encodes a prepeptide of at least 23 amino acids, a mature protein of 137 residues, and an untranslated 3' region of 707 nucleotides exclusive of the 3' poly(A) tract. The amino acid sequence deduced for the mature mouse J chain was found to be 74% identical with that previously determined for the human J chain. By analyzing the conserved features of the sequence, a two-domain structure was generated for the J chain which correlates well with its functions in the polymerization of IgM and IgA. Moreover, by comparing the homologies of the J and heavy chains in mouse and man, evidence was obtained that the structures involved in polymerization are the most conserved elements of immunoglobulin molecules.

Amino Acid Sequence↗
PubMed1981

DNA synthesis in Escherichia coli during a nutritional shift-up.

DNA synthesis in a thymine-requiring Escherichia coli K12 strain was studied by exploiting deoxyguanosine, so simulating the behaviour of Thy+ strains. DNA synthesis is inhibited during the first 24 min after a nutritional shift-up. The new DNA/mass is lower than that predicted by current models for initiation control.

Cell Division↗
PubMed1981

Sensitivity of exponentially growing populations of Escherichia coli to photo-induced psoralen-DNA interstrand crosslinks.

Experimental survival curves for Escherichia coli K 12 (CR 34) were determined after exposure to 4,5',8-trimethylpsoralen and near ultraviolet light. The lethal action was shown to arise exclusively from interstrand crosslinks, cell vulnerability increasing markedly with the doubling time of the culture. To account for these results, two quite different models are considered. The first assumes that a cell survives as long as at least one copy of its genome remains undamaged; a variant of this permits repair by DNA strand exchange. The second model allows for a limited period of time during which DNA repair can take place. A crosslink in a stretch of DNA due to be replicated within this interval constitutes a fatal lesion. Theoretical survival curves are computed for bacterial populations with defined age distributions and chromosome configurations. While the first model completely fails to provide a satisfactory description of the experimental results, the second model does predict the presence of a shoulder in the survival curves and, in one of its forms, it seems to agree rather well with the measured data over a wide range of crosslink concentrations and doubling times.

DNA Repair↗
PubMed1981

Effects of lipophilic cations on motility and other physiological properties of Bacillus subtilis.

Lipophilic cations (tetraphenylarsonium, tetraphenylphosphonium, and triphenylmethylphosphonium) caused a number of major changes in the physiology of Bacillus subtilis. Macromolecular synthesis was inhibited, adenosine 5'-triphosphate concentration increased, swimming speed was reduced, tumbling was suppressed, and the capacity to take up the cations was greatly enhanced; respiration was not significantly altered. The effects occurred at lipophilic cation concentrations in the range commonly employed for measurement of membrane potential. Neither the enhancement of cation uptake nor the motility inhibition was a consequence of alteration of membrane potential, since both effects were still seen in the presence of valinomycin, with the extent of 86Rb+ uptake indicating a constant potential. Because suppression of tumbling accompanied speed reduction, as has also been found when protonmotive force is reduced, it is likely that lipophilic cations are perturbing the process of conversion of proton energy into work, rather than simply causing structural damage.

Adenosine Triphosphate↗