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Biomedical subjects

J Kirchner

Publications and source records attributed to J Kirchner.

At least 91 records · Page 5Linked to original sources
PubMed1995

A comparison of anesthetic techniques for awake intubation in neurosurgical patients.

Two different methods of achieving upper airway anesthesia for awake fiberoptic intubation were prospectively compared in patients undergoing surgery for cervical spine instability. Forty patients were randomized to either topical anesthesia or nerve block groups. Topical anesthesia patients were administered nebulized 4% lidocaine (approximately 20 ml) via the oropharynx plus a transtracheal injection of 4% lidocaine (3 ml). Nerve block patients underwent bilateral glossopharyngeal and superior laryngeal nerve blocks with 2% lidocaine (0.5-2 ml per injection site) plus a transtracheal injection of 4% lidocaine (3 ml). The quality of anesthesia for intubation was graded by observers blinded to group assignment. Mean arterial pressure, heart rate, Pao2, Paco2, pHa, SpO2, and plasma lidocaine concentrations were measured during the intubation sequence. Patient recall of intubation and discomfort were assessed during the postoperative period with visual analog scales. Time required for successful intubation and quality of intubation were not different between groups. Physiologic values for the two groups were similar. The mean total dose of lidocaine in the topical anesthesia group was approximately 2 times greater than that in the nerve block group (815 versus 349 mg; p < 0.0001). In contrast, mean plasma lidocaine concentration at initiation of intubation in the topical anesthesia group was half that of nerve block group (2.16 versus 4.23 micrograms/ml; p < 0.0001). Ten minutes later there was no difference for plasma lidocaine concentration between groups. No patients had evidence of seizures or neurologic change during the procedure. There was no difference in patient perception of discomfort during the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Rat mitochondrial aldehyde dehydrogenase polymorphism and major histocompatibility complex RT1.A phenotypes are not associated with alcohol drinking in P and NP rats.

Previous studies revealed polymorphisms in mitochondrial aldehyde dehydrogenase (ALDH2) and the major histocompatibility complex RT1.A that appeared in association with alcohol drinking preference in the alcohol-preferring (P) and alcohol-nonpreferring (NP) rat lines. To determine the strength of these associations, the P and NP lines were crossed, and cosegregation studies were performed in the F2 progeny. The ALDH2Q allele and the ALDH2R allele, found in the P and NP lines, respectively, were found not to be associated with the high and low drinking animals in the F2 progeny. Kinetic studies with ALDH2Q and ALDH2R isozymes purified from the mitochondria of P and NP rat livers, respectively, showed that the polymorphism would not be expected to be associated with altered aldehyde metabolism. The association between RT1.A and alcohol preference (RT1.Auu with high and RT1.AII with low alcohol intake) also could not be confirmed in the segregating F2 progeny of the P x NP intercross.

Alcohol Drinking↗
PubMed1993

Proteolytic processing of Ty3 proteins is required for transposition.

Ty3 is a retroviruslike element found in Saccharomyces cerevisiae. It encodes GAG3 and GAG3-POL3 polyproteins which are processed into mature proteins found in the Ty3 viruslike particle. In this study, the region encoding a protease that is homologous to retroviral aspartyl proteases was identified and shown to be required for production of mature Ty3 proteins and transposition. The Ty3 protease has the Asp-Ser-Gly consensus sequence found in copia, Ty1, and Rous sarcoma virus proteases, rather than the Asp-Thr-Gly found in most retroviral proteases. The Asp-Ser-Gly consensus is flanked by residues similar to those which flank the active sites of cellular aspartyl proteases. Mutations were made in the Ty3 active-site sequence to examine the role of the protease in Ty3 particle maturation and to test the functional significance of the Ser active-site variant in the consensus sequence. Mutation of the active-site Asp blocked processing of Gag3 and Gag3-Pol3 and allowed identification of a GAG3-POL3 polyprotein. This protein was turned over rapidly in cells expressing the mutant Ty3. Changing the active-site Ser to Thr caused only a modest reduction in the levels of certain Ty3 proteins. Five putative cleavage sites of this protease in Ty3 GAG3 and GAG3-POL3 polyproteins were defined by amino-terminal sequence analysis. The existence of an additional protein(s) of unknown function, encoded downstream of the protease-coding region, was deduced from the positions of these amino termini and the sizes of known Ty3 proteins. Although Ty3 protease cleavage sites do not correspond exactly to known retroviral protease cleavage sites, there are similarities. Residues P3 through P2' in the regions encompassing each of the five sites are uncharged, and no P1 position is occupied by an amino acid with a branched beta carbon.

Amino Acid Sequence↗
PubMed1993

A comparison of five different methods for describing sagittal jaw relationship.

Analysis of sagittal jaw relationship is important in orthodontic diagnosis and treatment planning, and can be investigated by angular or linear parameters. In the present study an analysis was performed using profile cephalograms of 40 children with skeletal Class II malocclusion. A correlation analysis is presented, involving five different methods of expressing sagittal jaw relationships. Whilst some degree of agreement could be noted, it was not possible to suggest a pair of measurements, which in combination, could give a more accurate picture of sagittal jaw relationships.

Cephalometry↗
PubMed1992

RexAB proteins of bacteriophage lambda enhance the effect of photolyase-dimer complexes on lacZ gene expression in Escherichia coli.

Expression of the lacZ gene in Escherichia coli is inactivated by exposure to ultraviolet light (UV). Inactivation is exceptionally effective when cells contain amplified levels of DNA photolyase (which forms complexes with pyrimidine dimers in the absence of light for actual photoreversal) and a lambda prophage. Without amplified photolyase, the lambda prophage or both, inactivation rates are similar and much lower. UV-inactivation of lacZ gene expression in the presence of both amplified photolyase and lambda is even more effective if lambda cI857 is used in place of the wildtype prophage but is wholly unexceptional if the prophage carries defects in the lambda genes rexA or rexB. When Rex AB proteins are provided by expression from a plasmid and the cell also contains amplified photolyase, exceptional inactivation rates again obtain; in fact inactivation is most effective under these conditions. The data are considered to reveal a role for Rex AB proteins, which mediate superinfection exclusion, in the exceptional inactivation of gene expression by photolyase bound to pyrimidine dimers in DNA. Photolyase-dimer complexes may mimic the structure of certain complexes that arise during phage development and thus influence Rex A and/or B proteins, thereby shutting down cell metabolism.

Bacteriophage lambda↗
PubMed1992

An SOS-inducible defective retronphage (phi R86) in Escherichia coli strain B.

In Escherichia coli, RecA protein regulates the DNA damage-inducible survival-enhancing SOS response. Mutant allele recA730, which causes constitutive SOS expression, is lethal at high temperatures in B/r, a derivative of wild-type B, but not in K-12 or in certain B/r--K-12 hybrids. We present evidence that killing is due to SOS induction of a defective retronphage, phi R86, which is integrated into the B/r chromosome at 19 min, but is absent in K-12. phi R86 contains retron EC-86 which encodes reverse transcriptase and a small multicopy DNA-RNA complex, msDNA-RNA. Induction of phi R86 in recA730 B/r strains results in inhibition of host DNA replication before cell death. A retronphage 'killer' gene, ORF336, when overexpressed from a plasmid, causes similar effects without SOS induction. phi R86 is not detectably u.v.-inducible in recA+ strains.

Coliphages↗
PubMed1992

Transposition of a Ty3 GAG3-POL3 fusion mutant is limited by availability of capsid protein.

Ty3 encodes structural proteins in its upstream open reading frame (GAG3) and catalytic proteins in an overlapping open reading frame (POL3). As is the case for retroviruses, high levels of structural protein versus catalytic proteins are synthesized and we show here that catalytic proteins are derived from a GAG3-POL3 fusion polyprotein. To evaluate the relative contributions of structural and catalytic components of the Ty3 particle, we perturbed the balance of these proteins by fusing the GAG3 and POL3 frames. This fusion Ty3 was capable of complementing low levels of transposition of a donor Ty3 which contained only cis-acting sequences required for transposition. Examination of extracts of cells expressing the GAG3-POL3 fusion mutant showed that particle formation differed qualitatively and quantitatively from viruslike particle formation by wild-type Ty3. Suprisingly, expression of 238 codons of GAG3, encoding only capsid protein, complemented transposition and particle formation defects of the fusion mutant, showing that the limiting deficiency was in capsid, and not in nucleocapsid, function. In addition, protein containing the capsid domain expressed alone accumulated in the same particulate fraction as viruslike particles, showing that it was sufficient for particle formation. The activity of the Ty3 fusion mutant contrasts with the inviability of mutant retroviruses in which gag and pol frames were fused and argues that retrotransposons tolerate considerable variation in the nucleoprotein complexes that permit replication and integration.

Amino Acid Sequence↗
PubMed1991

["Routine" versus "on demand" ultrasonography in the surgical intensive care patient. A prospective randomized study].

Between May 1988 und March 1989 all patients who underwent elective or emergency surgery followed by intensive care were randomly assigned to group A (n = 149): routine sonography at the postoperative day 1, 3, 7 and 9, group B (n = 151): sonography on demand. In these two groups, the following parameters were compared: number of relaparotomies, lethality of relaparotomies, total lethality, moment of relaparotomy, period of hospitalisation, time spent with sonography. In the analyzed parameters, our examination showed no difference between the two groups. For this we state that the routine sonographical control of the surgical patient with intensive care being opposed to the sonography on demand shows no significant advantage. The demand for a routine sonography as a postoperative control can not be generally supported.

Adult↗
PubMed1989

Neuromuscular and cardiovascular effects of mivacurium chloride in surgical patients receiving nitrous oxide-narcotic or nitrous oxide-isoflurane anaesthesia.

The neuromuscular and cardiovascular effects of mivacurium chloride were studied during nitrous oxide-oxygen narcotic (fentanyl) (n = 90) and nitrous oxide-oxygen isoflurane (ISO) anaesthesia (n = 45). In addition, a separate group (n = 9) received succinylcholine during fentanyl anaesthesia to compare its neuromuscular effects with mivacurium. Mivacurium was initially administered as a single bolus in doses from 0.03 mg.kg-1 to 0.25 mg.kg-1 to study the dose-response relationships, as well as the cardiovascular effects of mivacurium. Neuromuscular block (NMB) was measured by recording the twitch response of the adductor pollicis muscle following ulnar nerve stimulation (0.15 Hz, 0.2 ms supramaximal voltage). The ED95 values for mivacurium were estimated to be 0.073 mg.kg-1 and 0.053 mg.kg-1 in the fentanyl and ISO groups respectively. The duration of block (time from injection to 95 per cent recovery) for a dose of 0.05 mg.kg-1 mivacurium was 15.3 +/- 1.0 min and 21.5 +/- 1.3 min for fentanyl and ISO anaesthesia, respectively. The recovery index (25-75 per cent) between initial bolus dose (6.1 +/- 0.5 min), repeat bolus doses (7.6 +/- 0.6 min), mivacurium infusion (6.7 +/- 0.7 min) and succinylcholine infusion (6.8 +/- 1.8 min) were not significantly different. There was minimal change in mean arterial pressure (MAP) or heart rate (HR) following bolus doses of mivacurium up to 0.15 mg.kg-1. Bolus administration of 0.20 mg.kg-1 or 0.25 mg.kg-1 of mivacurium decreased MAP from 78.2 +/- 2.5 to 64.0 +/- 3.2 mmHg (range 12-59 per cent of control) (P less than 0.05). The same doses when administered slowly over 30 sec produced minimal change in MAP or HR.

Adult↗
PubMed1980

Characteristics and surgical management of respiratory complications accompanying pathologic lesions of the brain stem.

Three life-threatening respiratory complications are regularly encountered in patients who survive the initial insult from a diffuse brain stem lesion--central alveolar hypoventilation, upper airway obstruction, and aspiration pneumonitis. From treating 13 patients who did survive, a surgical plan for managing the respiratory sequelae of such injuries has evolved and consists of: 1)Diaphragm pacing to correct hypoventilation; 2) tracheostomy for bypass of the upper airway obstruction; 3) gastrostomy for bypass of the impaired structures of swallowing; 4) surgical closure of the larynx to prevent aspiration. All 13 patients manifested central apnea, which was controlled in five by bilateral phrenic nerve stimulation and in eight by unilateral stimulation. All patients required tracheostomy to provide an airway for artificial ventilation and for secretion removal. In ten patients aspiration necessitated gastrostomy. The spontaneous recovery of the ability to swallow allowed closure of the gastrostoma in three but in others aspiration remained a serious complication. One patient died of massive aspiration after discharge from the hospital. Three patients had surgical closure of the larynx to prevent aspiration. Seven patients are alive; six of them are leading productive lives, though several have severe disability due to paresis or ataxia. Six died after discharge from the hospital. Three deaths were not related to the basic problem but the three others may have been.

Adolescent↗