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Biomedical subjects

G Baer

Publications and source records attributed to G Baer.

At least 37 records · Page 2Linked to original sources
PubMed1998

Recovery after halothane anaesthesia induced with thiopental, propofol-alfentanil or halothane for day-case adenoidectomy in small children.

We studied recovery from halothane anaesthesia in 93 children, aged 1-3 yr, undergoing day-case adenoidectomy. Children were allocated randomly to receive thiopental 5 mg kg-1 (group TH), alfentanil 10 micrograms kg-1 and propofol 3 mg kg-1 (group PAH) or 5% halothane (group HH) for induction of anaesthesia. In group TH, tracheal intubation was facilitated with succinylcholine (suxamethonium) 1.5 mg kg-1. In groups PAH and HH, tracheal intubation was performed without neuromuscular block, and succinylcholine was used only if required. Anaesthesia was maintained with 1-3% halothane during spontaneous respiration. Times to achieving predetermined recovery end-points were recorded. Quality of recovery was assessed using a score of 1-9 (best to worst) for sedation, crying, restlessness and agitation. A postoperative questionnaire was used to determine the well-being of the child at home, 24 h after operation. Emergence from anaesthesia (response to non-painful stimuli) occurred earlier in group HH (mean 9 (SD 6) min) than in groups PAH (13 (6) min, P < 0.01) and TH (18 (14) min, P < 0.01). Sitting up, walking and home readiness were achieved earlier in groups PAH and HH than in group TH (P < 0.05 for each variable). Children in group TH were more sedated during the first 30 min after anaesthesia than those in the two other groups (P < 0.05) while emergence-related delirium was more common in group HH than in group TH (P < 0.01). Well-being at home was similar in all groups. We conclude that induction of halothane anaesthesia with propofol-alfentanil or halothane provided more rapid recovery and earlier discharge than that with thiopental.

Adenoidectomy↗
PubMed1997

The inhibitory role of nitric oxide in the control of porcine and human sphincter of Oddi activity.

BACKGROUND: The possible role of nitric oxide in the regulation of the sphincter of Oddi is not known in species with a resistor-like sphincter of Oddi such as humans and pigs. METHODS: Sphincter of Oddi perfusion manometry and simultaneous electromyography (EMG) were recorded transduodenally in eight anaesthetised pigs. Acetylcholine (4 micrograms/kg) was given intra-arterially, with or without sodium nitroprusside (10-100 micrograms/kg), an exogenous nitric oxide donor. For in vitro studies the sphincter was removed from the eight pigs and from six patients undergoing pancreaticoduodenectomy, cut into rings, and the amplitude of contraction was measured in an ex vivo bath. Each ring was stimulated with acetylcholine (100 microM) and KCl (125 mM). The stimulation was repeated after incubation with L-NAME (a stereospecific competitive inhibitor of nitric oxide synthase), with L-NAME plus L-arginine (a substrate for nitric oxide synthase), and with sodium nitroprusside. The sphincter rings were then submersed in liquid nitrogen and stored. Immunohistochemical analysis was used to localise nitric oxide synthase in the pig and human sphincter specimens. RESULTS: In vivo EMG revealed 2-3 phasic bursts per minute with the basal pressure variation 6-40 mm Hg. Acetylcholine induced a large electrical burst and the pressure increased by (mean (SE)) 20 (10) mm Hg (p < 0.01) for 17 (4) seconds. After sodium nitroprusside (10 micrograms/kg) acetylcholine did not induce pressure changes and electrical activity was almost abolished. In vitro, L-NAME increased the KCl induced sphincter contraction in both pig and human specimens (p < 0.01). In human, but not in pig, specimens L-NAME increased the amplitude of acetylcholine induced contraction (p < 0.01). L-Arginine partly reversed the effect of L-NAME in both pig and human specimens. Sodium nitroprusside decreased the acetylcholine and KCl induced contractions in both pig and human specimens. Immunohistochemical studies localised nitric oxide synthase to rich plexi of nerve fibres in the mucosa and the muscle in both pig and human sphincter of Oddi. CONCLUSIONS: The sphincter of Oddi in both pigs and humans has endogenous nitric oxide synthase activity and immunoreactivity. Inhibition of endogenous nitric oxide production enhances contractility while exogenous nitric oxide decreases sphincter contractility and electrical activity.

Acetylcholine↗
PubMed1995

MEG burst suppression in an anaesthetized dog.

Recording of the magnetic fields of the brain, magnetoencephalography (MEG), has proved to be a valuable method in neurophysiological research. In order to study the feasibility of MEG recording during anaesthesia we recorded magnetoecephalographic burst suppression in a dog during enflurane and propofol anaesthesia. The observed signal distribution implies a complex current distribution underlying the burst activity. This experiment also proves that an essentially artefact-free MEG recording can be obtained during respirator-assisted anaesthesia.

Anesthesia, Inhalation↗
PubMed1991

Spatial arrangement of sigma-factor and core enzyme of Escherichia coli RNA polymerase. A neutron solution scattering study.

By means of neutron solution scattering we determined the position and orientation of core enzyme and sigma-factor within the Escherichia coli RNA polymerase holoenzyme with the aim of improving existing models. The individual components, core enzyme (E) and sigma-factor (sigma), were highlighted by deuterium labeling and their center-to-center distances determined in the monomeric and the dimeric holoenzyme. The following distance parameters were obtained: dE1-sigma 1 = 8.6(+/- 1) nm, dE1-E2 = 11.5(+/- 1) nm, d sigma 1-sigma 2 = 12.0(+/- 0.7) nm, dE1-sigma 2 = 9(+/- 3) nm. Using a triangulation procedure the position of the sigma-factors, sigma 1 and sigma 2, were determined with respect to the mass center of the core enzyme molecules, E1 and E2, assuming a symmetrical arrangement of the holoenzyme molecules in the dimer (C2 symmetry). In addition, the orientation of the sigma-factor with respect to core enzyme was estimated by means of model calculations. The obtained model of holoenzyme depicts the sigma-factor as buried in a groove of core enzyme, probably between the large subunits beta' and beta.

DNA-Directed RNA Polymerases↗
PubMed1989

The quaternary structure of Tet repressors bound to the Tn10-encoded tet gene control region determined by neutron solution scattering.

The spatial arrangement of Tet repressor dimer, both free and in complex with an 80 bp DNA fragment spanning the wild-type Tn10-encoded tet transcriptional control sequence containing a tandem repeat of two operators, has been determined by neutron small-angle scattering. The active, free Tet repressor dimer is an elongated and flat molecule with a maximum dimension of 11 +/- 1.5 mm which can be approximated by an ellipsoid with the half-axes 6 nm, 2.5 nm and 1 nm. The overall conformation undergoes no detectable change when the repressor dimer is bound to a DNA fragment containing a single tet operator. The normal distance between the centre of gravity of the protein and the DNA axis is 3.0 +/- 0.1 nm, indicating that the repressor dimer is mainly located on one side of the DNA. When bound to the wild type tet control DNA, the two repressor dimers have a centre-to-centre distance of 11.0 +/- 0.5 nm. Their minimal distance is 5 +/- 2 nm. Protein-protein contacts via loop formation of the DNA by repressor binding is excluded. The repressors are well separated and have no direct contact. A model is proposed where the two repressor dimers are located on opposite sides of the DNA and the DNA is not strongly bent in the complex.

Base Sequence↗
PubMed1989

Optic nerve enlargement and central retinal-artery occlusion secondary to retrobulbar anesthesia.

Optic nerve injury after retrobulbar injection of anesthetic agents may damage the optic nerve and vascular supply to the eye. We describe a case of documented orbital optic nerve injury with central artery occlusion after retrobulbar injection before cataract surgery. Early computed tomography documentation of optic nerve injury associated with retrobulbar injection is suggested to allow early consideration of optic nerve sheath decompression.

Aged↗
PubMed1988

Spatial arrangement of DNA-dependent RNA polymerase of Escherichia coli and DNA in the specific complex. A neutron small angle scattering study.

In this paper we demonstrate that neutron small angle scattering is a suitable method to study the spatial arrangement of large specific protein-DNA complexes. We studied the complex of DNA-dependent RNA polymerase of Escherichia coli and a 130 base-pair DNA fragment containing the strong promoter A1 of bacteriophage T7. Contrast variation of the complex with deuterium allowed us to "visualize" either RNA polymerase, or DNA, or both components in situ. From the corresponding scattering curves information was derived about: (1) Conformational changes of RNA polymerase and DNA by complex formation: comparison of the scattering profiles of the isolated and complexed components showed that by specific complex formation the cross-section of RNA polymerase decreases, while the DNA fragment does not undergo a gross conformational change. (2) The spatial arrangement of RNA polymerase and DNA in the specific complex from the cross-sectional radii of gyration of the complex the normal distance dn between the centre of gravity of the RNA polymerase and the axis of the DNA fragment was derived as 5.0 (+/- 0.3) nm. On the basis of these and footprinting data a low resolution model of the RNA polymerase-promoter complex is proposed. The main feature of this model is the positioning of RNA polymerase to only one side of the DNA.

DNA, Bacterial↗
PubMed1987

Large-scale preparation of a DNA fragment containing the strong promoter A1 of the phage T7.

A procedure has been developed to isolate DNA fragments on a large scale. A DNA fragment of 130 base-pairs containing the strong promoter A1 of the phage T7 was purified to homogeneity in amounts of 10 mg. The procedure includes the rapid purification of gram amounts of plasmid DNA, a new, simple method to separate small DNA fragments from the vector by a phenol/water partitioning system, and a liquid-liquid PEG-dextran partition chromatography for the final purification of the fragment. The fragment was cloned in two vector systems: The vector pDS1, to1+ (1), containing an efficient terminator downstream from the promoter integration site, gives high yields, 3-4 mg plasmid DNA per liter medium. In the plasmid pWH802 (2), which is not specially designed for the amplification of a strong promoter, the integration of the promoter was possible but the yield decreased by a factor of about 50. The stability of the inserts was tested in both systems. Monomeric inserts were stable in both plasmids, multimeric inserts up to a tetramer were only stable in pWH802. Only one orientation of the fragment was found.

Biotechnology↗
PubMed1987

Vaccinia virus recombinants expressing rabiesvirus glycoprotein protect against rabies.

Six recombinants of New York Board of Health (NYBH) vaccinia virus containing cDNA for Challenge Virus Standard (CVS) rabiesvirus glycoprotein (G) were produced by directing gene insertion into the vaccinia thymidine kinase (TK) locus. To regulate expression of G the promoter P7.5 (functions at early and late times postinfection) from the gene for the vaccinia 7.5 kilodalton (kD) protein was used in two of the recombinants; late promoter P11 of the vaccinia 11 kD protein was used in four recombinants. The six differed in nucleotide sequences flanking the translation start codon; in two constructs the encoded signal peptide of G was fused to several additional amino acids. Cells infected with each recombinant made G that reacted with G-specific antibodies, comigrated with authentic G, and was transported to the plasma membrane. The highest amounts of G were made with fusion or standard versions of G with P11 provided that the mRNA leader sequences were identical to the natural gene. Each recombinant in mice and one in dogs induced rabiesvirus neutralizing antibodies and protection against lethal rabiesvirus challenge.

Amino Acid Sequence↗
PubMed1986

Solution structure of a short DNA fragment studied by neutron scattering.

The solution structure of a DNA fragment of 130 base pairs and known sequence has been investigated by neutron small-angle scattering. In 0.1 M NaCl, the overall structure of the DNA fragment which contains the strong promoter A1 of the Escherichia coli phage T7 agrees with that expected for B-DNA. The neutron scattering curve is well fitted by that of a rigid rod with a length of 44 nm and a diameter of 2 nm. The results were confirmed by quasi-elastic light scattering and analytical centrifugation. The neutron measurements in H2O and D2O buffer reveal a cross-sectional inhomogeneity not detected by X-ray small-angle scattering. This inhomogeneity is caused by the hydration layer around the DNA core and not by the helical structure. The primary solvent shell has a density increased by at least 4-9% compared to bulk water.

Base Composition↗
PubMed1984

The use of skills training procedures in the treatment of a child-abusive parent.

Recent behavioral formulations suggest that child abuse can often be conceptualized in terms of skill deficits of the parent. In the present case study, training was used to improve an abusive parent's anger-assertion, child management, and personal problem-solving skills; deficits in all three areas were functionally related to prior episodes of violence. Treatment across these skill areas was introduced in multiple baseline fashion. The effectiveness of treatment was demonstrated by assessments of assertion, child management, and problem-solving knowledge following each training session; parent monitoring data on the frequency of child-related and anger problems at home throughout the intervention; performance on skill generalization measures; and objectively-rated parent-child interactions during pre- and post-training home observation probes.

Adult↗
PubMed1983

[Recovery after ketamine-diazepam and thiopental-fentanyl-infusion anesthesia with jet-ventilation for laryngomicroscopy].

Using two infusion anaesthesiamethods for laryngomicroscopy in 187 non-selected patients we studied the recovery phase with the aid of a special questionnaire filled in by the recovery room nurse. Premedication was with Thalamonal and atropine. Muscle relaxation was achieved by a succinylcholine drip. Induction doses: fentanyl 0.05-0.1 mg and thiopental 3-5 mg/kg bodyweight (Th-group) or diazepam 10-20 mg and ketamine 1 mg/kg bodyweight (K-group). Infusion doses: Thiopental 11.7 mg/min. (Th-group) or diazepam 0.2 mg/min. and ketamine 2 mg/min (K-group). Anaesthesia lasted for 20-30 min. We observed and noted during recovery: Breathing, cough-frequency and -quality, alertness, reaction to speech and stimulation, orientation, motor behaviour and well-being. Anaesthesia was sufficient in both groups. The patients of the K-group woke up earlier and their laryngeal reflexes seemed to stabilize quicker than in the Th-group. Because of the elevation of blood pressure caused by the stimulation of the laryngoscopy both methods are not recommended for patients at risk from high blood pressure.

Adult↗
PubMed1982

Massive hemothorax in a child after removal of subclavian vein catheter.

A case is described where a near-fatal hemothorax developed in a child (age 13 months) right after the removal of the subclavian vein catheter. The catheter was introduced a week earlier and it had functioned without disorder. The possible mechanism of the complication is discussed. Even though this kind of complication is very rare, we recommend that the patients, especially children, must be carefully watched also after removal of the subclavian vein catheter to find a possibly life-threatening complication immediately.

Catheterization↗
PubMed1981

[Ketamine-induced psychopathological changes in normal volunteers during conditions used for experimental psychoses (author's transl)].

The psychotomimetic properties of ketamine were studied in 9 physically and psychically normal medical students and nurses during 20 single-blind experiments. During the experiments any disturbance to the subject was avoided. A dose of 0.25 mg/kg produced psychical changes in every case, and 1 mg/kg caused an experimental psychosis every time. The latter starts in an "ideal" case with an expressive disturbance of consciousness down to the level of surgical anesthesia. 5-7 minutes after the start of the experiments the scalar change of consciousness lessens enabling the qualitative changes to become obvious. Strong short-time memory disturbance however prevents the subjects from describing coherently the large number of hallucinations and illusions which are frequently experienced. For several moments at the end of the experiment a strong disturbance of body-feeling combined with ataxia may still be present when consciousness is almost normal. - According to the observed psychopathological changes ketamine may be classified as a not LSD-typical hallucinogen. - It should be possible to lower the frequency of adverse reactions to ketaminemonanesthesia by preparing the patients for the strange experiences possible during emergence.

Adult↗
PubMed1981

[Our experiences during cannulation of the subclavian vein in children (author's transl)].

With 260 children under 12 years of age we tried to cannulate the subclavian vein during 3 years 455 times, and were successful 391 times (85.9%). 43.8% of the patients were younger than 1 year. The success rate correlated to the childrens' bodyweight and was less with lower weight of the patients. - In 68.8% of the cases we found the tip of the cannula in the upper caval vein, 19.9% were in the internal jugular vein, and 6.1% were in the opposite subclavian vein. - In this study participated 7 members of the staff and 8 specializing doctors; catheterizations per participant, mean = 30,2, SD 21,49, minimum 6, maximum 65. - Cannulas functioned for 5 +/- 2, max. 19 days. - The most serious complications were 2 pneumo- and one pneumo-hydrothorax, 2 times suspicion of thrombosis and 1 hemorrhage due to a not known hemophilia. None of the complications caused therapeutical problems.

Body Weight↗
PubMed1981

[Documentation of central venous catheterization using a computer laboratory system (author's transl)].

Full documentation of every case of central venous catheterization is a prerequisite for reducing the incidence of failures and complications. A laboratory computer program already in use was modified for this purpose: the start of the operation is put in in "real time", abandoned or failed procedures or incomplete data are detected, and can be queried on the day of patient is discharged from hospital. Adverse effects are shown up at an early stage by the quarterly print-out. The program involves less work than a conventional system without computer. The experiences gained with this modified system in the course of one year (including the run-in period) are reviewed.

Catheterization↗