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Biomedical subjects

A Zaritsky

Publications and source records attributed to A Zaritsky.

At least 73 records · Page 4Linked to original sources
PubMed1994

Nucleoid partitioning and the division plane in Escherichia coli.

Escherichia coli nucleoids were visualized after the DNA of OsO4-fixed but hydrated cells was stained with the fluorochrome DAPI (4',6-diamidino-2-phenylindole dihydrochloride hydrate). In slowly growing cells, the nucleoids are rod shaped and seem to move along the major cell axis, whereas in rapidly growing, wider cells they consist of two- to four-lobed structures that often appear to advance along axes lying perpendicular or oblique to the major axis of the cell. To test the idea that the increase in cell diameter following nutritional shift-up is caused by the increased amount of DNA in the nucleoid, the cells were subjected to DNA synthesis inhibition. In the absence of DNA replication, the nucleoids continued to move in the growing filaments and were pulled apart into small domains along the length of the cell. When these cells were then transferred to a richer medium, their diameters increased, especially in the region enclosing the nucleoid. It thus appears that the nucleoid motive force does not depend on DNA synthesis and that cell diameter is determined not by the amount of DNA per chromosome but rather by the synthetic activity surrounding the nucleoid. Under the non-steady-state but balanced growth conditions induced by thymine limitation, nucleoids become separated into small lobules, often lying in asymmetric configurations along the cell periphery, and oblique and asymmetric division planes occur in more than half of the constricting cells. We suggest that such irregular DNA movement affects both the angle of the division plane and its position.

Cell Division↗
PubMed1993

Pediatric resuscitation pharmacology. Members of the Medications in Pediatric Resuscitation Panel.

The goal of resuscitation pharmacology is to restart the heart as quickly as possible while preserving vital organ function during chest compression. Unfortunately, the application of advanced life support to pediatric cardiac arrest patients is often unsuccessful. The goal of this paper is to review the scientific rationale and educational considerations used to derive the guidelines for medication use in the pediatric patient during CPR. The first step in drug delivery during CPR is to achieve vascular access. The endotracheal route and intraosseous route may be used, although the former is not reliable. To maximize endotracheal drug effect, a larger dose should be instilled into the airway as deeply as possible. Any vascular access, including intraosseous, is preferable to endotracheal drug administration. Although other alpha-adrenergic agents are theoretically superior, epinephrine remains the drug of choice in pediatric resuscitation. The previously recommended dose, however, may be inadequate; a dose 10 to 20 times larger (100-200 micrograms/kg) should be considered, particularly if the standard dose is ineffective. Lacking convincing data, the indications and dose for calcium are unchanged. Similarly, there are no data advocating a change in the indications or dose for lidocaine, bretylium, or atropine. The treatment of arrest-induced acidosis remains controversial. The mainstay of therapy consists of efforts to maximize oxygenation and tissue perfusion. Bicarbonate is not a first-line drug; its use should be considered when the patient fails to respond to advanced life support efforts, including the administration of high-dose epinephrine. Bicarbonate may be helpful in the postresuscitation setting, but its use should not supplant efforts to maximize tissue perfusion. Adenosine is an effective and generally safe medication for the treatment of supraventricular tachycardia in infants and children. Therefore, its indications, dose, and toxicities should be included in the new guidelines. Finally, a summary of research initiatives are included, including a call for the development of a multi-institutional pediatric clinical resuscitation research group. Large numbers of patients must be enrolled in a standardized manner to better evaluate the benefits and adverse effects of various therapies. This includes the use of high-dose epinephrine, calcium, bicarbonate, and other buffer agents such as Carbicarb and THAM. Animal models simulating the etiology and pathophysiology of pediatric arrest also are needed. In both clinical and animal studies, neurologic outcome and long-term survival should be assessed rather than simply the rate of restoration of spontaneous circulation.

Acidosis↗
PubMed1993

Dimensional rearrangement of Escherichia coli B/r cells during a nutritional shift-down.

In a search for the mechanism underlying dimensional changes in bacteria, the glucose analogue methyl alpha-D-glucoside was used to effect a rapid reduction in the mass growth rate of Escherichia coli by competitively inhibiting glucose uptake, a so-called nutritional shift-down. The new steady-state cell mass and volume were reached after 1 h, during which the rate of cell division was maintained; rearrangement of the linear dimensions (cell length, diameter), however, required an additional 2 h and caused an undershoot in cell length, consistent with the view that E. coli is slow to modify its diameter. The results are compared with the overshoot in cell length that occurs following nutritional shift-up.

Cell Division↗
PubMed1992

Sensitivity to plating of Escherichia coli cells expressing the cryA gene from Bacillus thuringiensis var. israelensis.

The gene (cytA) coding for the 27 kDa polypeptide of the Bacillus thuringiensis var. israelensis mosquito larvicidal delta-endotoxin, was cloned into a plasmid containing the T7 bacteriophage promoter. The plasmid was used to transform an Escherichia coli strain containing the T7 RNA polymerase gene 1, under the control of lacP. Loss of colony-forming ability without substantial lysis, associated with immediate inhibition of DNA synthesis, was observed after induction of transformed cells. The cytA gene product may kill E. coli cells by disrupting their chromosome replicating apparatus.

Bacillus thuringiensis↗
PubMed1992

Digestion of Bacillus thuringiensis var. israelensis spores by larvae of Aedes aegypti.

The larvicidal activity of Bacillus thuringiensis var. israelensis against mosquitoes and the blackfly is included in parasporal crystalline bodies which are produced during sporulation. Following ingestion, the crystals are solubilized in the larval midgut and induce death within a short time; the spores germinate in the dead larvae and complete a growth cycle. The fate of the spores in surviving live larvae was elucidated by using a nonlarvicidal B. thuringiensis var. israelensis mutant. When introduced as the only food source, spores of this mutant support development to the adult stage of newly hatched Aedes aegypti larvae at a rate directly related to spore concentration. The conclusion that spores of B. thuringiensis var. israelensis are digested in the larval gut was substantiated by following the incorporation of [35S]methionine-labeled spores into larval tissues.

Aedes↗
PubMed1992

Neural computing in discovering RNA interactions.

High-order RNA structures are involved in regulating many biological processes; various algorithms have been designed to predict them. Experimental methods to probe such structures and to decipher the results are tedious. Artificial intelligence and the neural network approach can support the process of discovering RNA structures. Secondary structures of RNA molecules are probed by autoradiographing gels, separating end-labeled fragments generated by base-specific RNases. This process is performed in both conditions, denaturing (for sequencing purposes) and native. The resultant autoradiograms are scanned using line-detection techniques to identify the fragments by comparing the lines with those obtained by 'alkaline ladders'. The identified paired bases are treated by either one of two methods to find the foldings which are consistent with the RNases' 'cutting' rules. One exploits the maximum independent set algorithm; the other, the planarization algorithm. They require, respectively, n and n2 processing elements, where n is the number of base pairs. The state of the system usually converges to the near-optimum solution within about 500 iteration steps, where each processing element implements the McCulloch-Pitts binary neuron. Our simulator, based on the proposed algorithm, discovered a new structure in a sequence of 38 bases, which is more stable than that formerly proposed.

Algorithms↗
PubMed1992

Length-based endotracheal tube and emergency equipment in pediatrics.

HYPOTHESIS: Pediatric endotracheal (ET) tubes can be accurately selected based on body length using a specialized emergency tape. POPULATION: Derivation set: Two hundred five children undergoing elective surgery. Validation set: Two hundred thirteen children undergoing elective surgery. Each child served as his or her own control. METHODS: Derivation phase: Two hundred twenty-one children undergoing ET intubation for elective surgery had their body length and leak pressures measured. The 205 children who had leak pressures between 10 and 40 cm H2O constituted the derivation set. The body length for a given ET tube size was derived from the interquartile range of patient lengths in this derivation set. Sizes for other resuscitative equipment items were chosen by a panel of experts using a modified Delphi technique. This information was placed by length on a color-coded tape. Validation phase: The tape was validated by using it to select ET tube size in another group of 203 children undergoing elective surgery. Criteria for acceptable fit in this group included leak pressure as above and the anesthesiologists' decision to accept the tube size or to retintubate. In the validation phase, length-based ET tube selections were compared with age-based rules: (age + 16)/4, and (age + 18)/4. RESULTS: The tape selected the appropriate ET tube size by leak pressure criterion in 77% of the cases and was within +/- 0.5 mm of the "correct" size 99% of the time. This was significantly better (P less than .005) than two widely used age-based rules, which gave the correct initial size in only 47% and 9% of these cases, and were within +/- 0.5 mm for 86% and 59%. The anesthesiologists chose to continue with the tape-sized tube rather than to reintubate in 89% of cases. CONCLUSION: A system for length-based selection of emergency equipment represents a significant adjunct to emergency physicians and paramedics who must deal with critically ill children. Length-based ET tube selection is clearly superior to age-based rules, which are difficult to remember and require accurate estimation of a patient's age.

Body Height↗
PubMed1992

Nonphysician transport of intubated pediatric patients: a system evaluation.

OBJECTIVE: To evaluate the occurrence of complications and patient deteriorations during the air and ground transportation of intubated pediatric patients, performed by a nonphysician-based team under the direction of an intensive care attending physician or fellow. DESIGN: Retrospective chart review. SETTING: A 600-bed university hospital with a 16-bed neonatal ICU and a 12-bed pediatric ICU. PATIENTS: All intubated pediatric patients (422 of 614 patients transported during the study period) transported by the dedicated neonatal/pediatric transport team from April 1988 to April 1990. MEASUREMENTS AND MAIN RESULTS: The transport records of intubated pediatric patients were abstracted. Recorded data included age, weight, gestational age, vital signs, diagnosis, interventions received, and use of paralytic agents and sedatives/analgesics. Patients were analyzed in three groups: group 1 (n = 295) included neonates; group 2 (n = 66) included patients greater than 1 month and less than 1 yr of age; and group 3 patients (n = 61) were ages greater than 1 yr. Group 1 had nine (3.1%) complications or patient deteriorations; four (1.4%) were related to the endotracheal tube. Group 2 had one (1.5%) airway complication and one deterioration. Group 3 had no complications or deteriorations. All but one of the airway complications were effectively handled by the transport team. At the referring hospital, the transport nurse or respiratory therapist intubated 62 (19.8%) patients in group 1, five (7.5%) in group 2, and three (4.9%) patients in group 3. Sixty-seven (23%), 21 (32%), and 30 (49%) patients of groups 1, 2, and 3, respectively, were paralyzed for transport. No complications were secondary to the use of paralytic agents or sedatives. CONCLUSIONS: Under proper medical guidance, well-trained nonphysician personnel can provide low-risk transport of intubated pediatric patients. Use of sedatives and paralytic drugs did not increase the risk of complications or patient deterioration.

Child↗
PubMed1992

Rate maintenance of cell division in Escherichia coli B/r: analysis of a simple nutritional shift-down.

A competitive (nonmetabolizable) inhibitor of glucose uptake, alpha-methylglucoside, was used to limit the growth of Escherichia coli. Cell division during such a nutritional shift-down was studied in batch cultures and with the "baby-machine" technique. Following a brief delay, the rate of division was maintained for 60 to 70 min in batch cultures and for an extended period in the baby machine. Decreases in cell size were due, in part, to a possible reduction in the mass per chromosome origin at the time of replication initiation and a shorter time interval between initiation and the subsequent division. These unusual findings suggest that this method for abrupt change in growth rate without modifying repression patterns is useful for studying the control of various aspects of the bacterial cell.

Cell Division↗
PubMed1991

Role of early fluid resuscitation in pediatric septic shock.

OBJECTIVE: To examine the association of the volume of fluid administered at 1 and 6 hours after presentation, with survival and the occurrence of the adult respiratory distress syndrome, cardiogenic pulmonary edema, and persistent hypovolemia during the resuscitation of children with septic shock. SETTING AND PATIENTS: All pediatric patients with septic shock presenting to the emergency department over a 6-year period and having a pulmonary artery catheter inserted by 6 hours after presentation were identified. METHODS: Patients were analyzed together and in three groups based on fluid volume in the first hour: group 1, less than 20 mL/kg; group 2, 20 to 40 mL/kg; and group 3, more than 40 mL/kg. Adult respiratory distress syndrome was diagnosed by the presence of alveolar infiltrates, hypoxemia, and a pulmonary capillary wedge pressure of 15 mm Hg or less. Cardiogenic pulmonary edema was diagnosed similarly, except the pulmonary capillary wedge pressure was greater than 15 mm Hg. Hypovolemia was diagnosed by the presence of oliguria, hypotension, and a pulmonary capillary wedge pressure of 8 mm Hg or less 6 hours after presentation. RESULTS: We identified 34 patients (median age, 13.5 months). At 1 and 6 hours, respectively, group 1 (n = 14) received 11 +/- 6 and 71 +/- 29 mL/kg (mean +/- SD) of fluid; group 2 received 32 +/- 5 and 108 +/- 54 mL/kg of fluid; and group 3 received 69 +/- 19 and 117 +/- 29 mL/kg of fluid. Survival in group 3 (eight of nine patients) was significantly better than in group 1 (six of 14 patients) or group 2 (four of 11 patients). Adult respiratory distress syndrome developed in 11 patients (32%) and cardiogenic pulmonary edema developed in five patients (15%). Having adult respiratory distress syndrome was associated with increased mortality, but adult respiratory distress syndrome was not increased in any group. Similarly, cardiogenic pulmonary edema was not associated with the fluid volume received or with decreased survival. Hypovolemia occurred in six patients in group 1 and two patients in group 2; all eight subsequently died. CONCLUSION: Rapid fluid resuscitation in excess of 40 mL/kg in the first hour following emergency department presentation was associated with improved survival, decreased occurrence of persistent hypovolemia, and no increase in the risk of cardiogenic pulmonary edema or adult respiratory distress syndrome in this group of pediatric patients with septic shock.

Adolescent↗
PubMed1991

A simulation program to display specific digestion products of predicted RNA foldings.

A parameterizable program in Pascal was developed for VAX/VMS computers to simulate the autoradiograms of gel-separated RNA fragments generated by partial cleavage of a folded RNA molecule using five specific RNases. Each screen displays the results of cleavage by either one enzyme or all five, with the RNA molecule labeled at either of its ends (5' or 3'); each run is performed with three different lengths and against a ladder containing alkaline hydrolysis products of the same RNA molecule as size markers. The program should be useful for comparing actual results with predicted functional foldings of RNA molecules.

Algorithms↗