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Biomedical subjects

G Hahn

Publications and source records attributed to G Hahn.

At least 55 records · Page 3Linked to original sources
PubMed1996

Gravity-dependent phenomena in lung ventilation determined by functional EIT.

Gravity exerts an effect on the distribution of intrapulmonary ventilation. A study on the detection of gravity-dependent inhomogeneity of ventilation by a functional EIT technique is presented. The study was performed on five human subjects, whose ventilation distribution was modified by changes in body position. The subjects were studied during spontaneous tidal breathing. The qualitative and quantitative analysis of the functional EIT images revealed that the ventilation is higher in the dependent lung regions when compared with the non-dependent ones. These EIT findings correspond to current knowledge of the physiological behaviour of the lungs as derived from the radioactive-gas methods and raise the possibility of applying the less complicated functional EIT in future studies on ventilation distribution in the lungs. This may be of major interest in the monitoring of intensive care patients with severe pulmonary disorders.

Adult↗
PubMed1996

Local mechanics of the lung tissue determined by functional EIT.

A new functional EIT (f-EIT) evaluation technique providing information on the local dynamic behaviour of the lung is presented. Out of a series of single EIT thoracic images local time courses of the impedance change are extracted. To detect regional differences in the dynamic behaviour of the lung tissue the local time courses at different locations are related to the average time course of the impedance change over the whole thoracic cross section. The time shifts between this reference signal and the signals from separate positions are calculated from the phase information of the complex cross spectra and evaluated in terms of the local phase angle. The computed phaseshifts are imaged over the cross section creating an 'f-EIT phase image' characterizing the local dynamic properties. To relate the observed differences to the proper lung location the resulting images are presented as a combination of the f-EIT ventilation images, which represent the local amplitude of ventilation and the f-EIT phase images. The new imaging technique was tested in spontaneously breathing humans. Alterations to pulmonary dynamics were induced by changing the body posture of the subjects. The f-EIT phase imaging procedure was shown to identify lung regions with different dynamics and it is expected that this technique will also distinguish pathologically determined alterations.

Biomechanical Phenomena↗
PubMed1996

Follow-up after therapy for prostate cancer. Treating the problems and caring for the man.

With prostate cancer being diagnosed and treated in more than 300,000 men each year, the pool of long-term survivors is dramatically increasing. Because these patients are usually elderly, they are often receiving follow-up care for unrelated problems in a primary care setting. This offers the physician an excellent opportunity to assist in management of any long-term complications of therapy and in monitoring for cancer recurrence. In addition to performing follow-up evaluations, the physician can provide counseling about a number of testing and treatment issues, including the variability of prostate-specific antigen levels, the appropriateness of a watchful waiting approach to some cancers, and the management of treatment-induced incontinence and impotence, which often have a deleterious effect on quality of life but may be amenable to therapy and psychosocial support.

Aftercare↗
PubMed1995

Changes in the thoracic impedance distribution under different ventilatory conditions.

The present study was performed with the aim of checking the suitability of EIT in imaging regional thoracic impedance variations during lung ventilation under predefined conditions and to compare EIT with established reference techniques. A new technique of functional EIT imaging designed to visualize physiologically relevant information from the sequentially registered series of thoracic distributions was introduced. Experiments were performed on five spontaneously breathing healthy subjects and on 12 anaesthetized supine pigs. 16 electrodes were placed around the thorax and consecutive transthoracic impedance distributions were measured at a rate of 1 Hz (Sheffield APT system mark I, IBEES, Sheffield, UK). Several voluntary breathing manoeuvres were performed in human subjects and the tracings of local impedance were compared with standard spirometry. In animal experiments EIT was applied during artificial ventilation at different ventilation rates and during stepwise passive emptying and filling of either one or both lungs while the respiratory muscles were relaxes. Further, selective blockade of lung regions resulting in regionally reduced ventilation was performed and the capability of EIT to follow and differentiate local ventilatory disturbances was checked by reference techniques (x-ray and staining methods). The experiments revealed an overall agreement between the spirometric and impedance data in all breathing patterns performed. A linear relationship between changes of the air content of the lungs and the regional thoracic impedance was shown (intraindividual correlation coefficient range, 0.986-0.999; n = 12 animals). The functional images of the impedance distribution across the thorax reproduced adequately the typical anatomical characteristics of the pig and the human thorax. The spatial resolution of EIT functional images was sufficient to differentiate lung areas corresponding to approximately 20 ml tissue volume. EIT with the additional evaluation procedure of functional imaging was shown to be a suitable and reliable method of imaging different ventilatory conditions with the potential to become a useful tool for monitoring respiratory function.

Adult↗
PubMed1995

Using quality for daily work in ambulatory care settings.

How do we improve the delivery of quality health care? How do we continue to motivate and recognize employees who see layoffs, downsizing, reengineering, and cutbacks? Do we continue to work with obsolete systems in the same top-down management staffs used for the last 100 years? The answer is no. The answer is total quality management, continuous quality improvement, and process improvement, but with a new twist--activity-based resourcing.

Ambulatory Care Facilities↗
PubMed1994

Preoperative external beam radiotherapy followed by cytoreductive surgery and intraoperative radiotherapy for locally advanced primary or recurrent renal malignancies.

Patients with local persistence or local regional recurrence of cancer after nephrectomy for renal cell cancer are unlikely to respond well to systemic therapy or external irradiation alone. In this analysis, patients with locally recurrent (9) or persistent (2) cancer following nephrectomy (renal cell cancer in 8, transitional cell or squamous cell cancer in 3) usually received 4,500 to 5,040 cGy. preoperative external beam irradiation followed by maximal surgical debulking and intraoperative electron irradiation (1,000 to 2,500 cGy.). Of 8 renal cell cancer patients 6 were alive and 4 were without disease progression at 15 to 50 months (3 of 4 at 29 months or longer). One patient died free of disease at 10.5 months and 3 had metastases (regional in 1 and distant in 3). Of the 3 transitional or squamous cell carcinoma patients 1 died free of disease 28.5 months after initiation of treatment for recurrence and 2 died of disease progression (liver in 1 and local in 1). It appears that select patients with solitary local recurrence or persistence following radical nephrectomy for renal cell cancer may benefit from an aggressive local treatment approach using irradiation (preoperatively and intraoperatively) plus maximal surgical debulking. In patients with locally advanced high grade transitional cell cancer the locally aggressive approach should probably be combined with multi-drug chemotherapy because of increased systemic risks. For both groups (renal cell carcinoma and transitional/squamous cell carcinoma) the most ideal patient for such treatment is one who has not received prior chemotherapy or external irradiation to the site of relapse, since 3 of 5 patients with disease progression after our aggressive approach had received chemotherapy (2) or external beam irradiation (2) elsewhere before referral.

Aged↗
PubMed1994

Biochemical differences among human and animal streptococci of Lancefield group C or group G.

Pyogenic streptococci of Lancefield group C or group G from human or animal sources were examined with a view to increasing the number of diagnostic tests useful for their differentiation. Human strains of group G produced L-prolyl-L-arginine aminopeptidase but isolates of Streptococcus equisimilis (group C) did not. Tests for alpha-L-glutamate aminopeptidase together with fermentation of glycogen or sorbitol distinguished S. dysgalactiae from strains of S. equisimilis isolated from animals. It was confirmed that fermentation tests were helpful in the study of S. equi and S. zooepidemicus and that enzyme reactions helped distinguish between S. canis and the human strains of group G.

Aminopeptidases↗
PubMed1994

[Dynamic blood volume determination using the body transport function].

This paper describes a dynamic blood volume determination which is faster and more accurate than the classic method. The new method determines blood volume by means of the product of the mean transit time of the circulation and the cardiac output. The mean transit time is calculated from the body transport function. To examine the precision of the dynamic method the blood volume of 24 patients was determined in both the dynamic and the classical way, using radioactively labelled erythrocytes. The comparison of the two methods resulted in a correlation coefficient of r = 0.77. The dynamic method of blood volume determination will be helpful especially in risk patients to accurately determine the quantities of fluids to be administered.

Biological Transport↗
PubMed1993

Persistence of Borrelia burgdorferi in ligamentous tissue from a patient with chronic Lyme borreliosis.

OBJECTIVE: To document the persistence of Borrelia burgdorferi in ligamentous tissue samples obtained from a woman with chronic Lyme borreliosis. METHODS: Spirochetes were isolated from samples of ligamentous tissue, and the spirochetes were characterized antigenetically and by molecular biology techniques. The ligamentous tissue was examined by electron microscopy. Humoral and cellular immune responses were analyzed. RESULTS: Choroiditis was the first recognized manifestation of Lyme disease in this patient. Despite antibiotic therapy, there was progression to a chronic stage, with multisystem manifestations. The initially significant immune system activation was followed by a loss of the specific humoral immune response and a decrease in the cellular immune response to B burgdorferi over the course of the disease. "Trigger finger" developed, and a portion of the flexor retinaculum obtained at surgery was cultured. Viable spirochetes were identified. Ultramorphologically, the spirochetes were situated between collagen fibers and along fibroblasts, some of which were deeply invaginated by these organisms. The cultured bacteria were identified as B burgdorferi by reactions with specific immune sera and monoclonal antibodies, and by polymerase chain reaction amplification and Southern blot hybridization techniques. CONCLUSION: To our knowledge, this is the first report of the isolation of B burgdorferi from ligamentous tissue. This suggests that tendon tissues serve as a specific site of spirochete residence in human hosts.

Base Sequence↗
PubMed1993

Ultrasonic absorption frequency dependence of two widely used anti-cancer drugs: doxorubicin and daunorubicin.

Low intensity ultrasound (approximately 10(-6) W cm-2) in the frequency range 0.5-6.0 MHz was employed to investigate the ultrasound absorption properties of doxorubicin (DOX) at several temperatures. At physiological temperatures, we found enhanced ultrasound absorption from DOX, and its closely related analogue daunorubicin (DNR), in the upper kilohertz frequency range. The findings do not conform to classical theory of ultrasound absorption, thus suggesting an ultrasound coupling with the drug molecules via structural and/or chemical relaxation processes. The absorption spectra are analysed from the point of view of the non-classical theory of sound absorption due to physical and/or chemical relaxations. Only one spectral difference between the two anti-cancer agents is observed, around 2 MHz, and may be attributed to the sole difference in the chemical make-up of the side chain of the two antibiotics.

Absorption↗
PubMed1993

The pharmacokinetics of tranylcypromine enantiomers in healthy subjects after oral administration of racemic drug and the single enantiomers.

The pharmacokinetics of the two enantiomers of tranylcypromine were evaluated in six healthy subjects after oral dosage of the racemate (20 mg of the sulphate) and the single enantiomers (10 mg of the sulphate) using an enantiospecific assay. Significant differences in AUC, Cmax, lambda(z), and CLR of the two enantiomers were observed both on administration of the racemate and of the individual enantiomers. The plasma concentrations and urinary excretion rates of (-)-tranylcypromine exceeded those of (+)-tranylcypromine. AUCs of the (-)-enantiomer [arithmetical means 197 ng ml(-1) h after the racemate, 130 ng ml(-1) h after the enantiomer] were greater than those of the (+)-enantiomer [26 ng ml(-1) h after the racemate, 28 ng ml(-1) h after the enantiomer] (P = 0.0001). No in vivo racemisation was detected. The power of the study was insufficient to establish any enantiomer-enantiomer interaction except for a possible interaction at the level of renal clearance (P = 0.013 for both enantiomers).

Administration, Oral↗
PubMed1993

Modulation of monocyte activation in patients with rheumatoid arthritis by leukapheresis therapy.

One of the hallmarks in rheumatoid arthritis (RA) is the intense activation of the monocyte-macrophage system. In the present investigation, the modulation of blood monocyte activation was studied with regard to the secretion of cytokines and inflammatory mediators, and to the expression of cytokine receptors. Patients with severe active RA underwent repeated leukapheresis procedures that removed all circulating monocytes. Highly enriched monocyte preparations from the first and third leukapheresis were studied. There were striking differences between the two monocyte populations. Cells obtained from the first leukapheresis constitutively released large amounts of prostaglandin E2 (PGE2), neopterin, interleukin 1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha). In particular, IL-1 beta and neopterin production were further enhanced by stimulation with either interferon-gamma (IFN-gamma) or TNF-alpha without a synergistic effect. In contrast, cells derived from the third leukapheresis procedure showed a close to normal activation status with only low levels of cytokine and mediator production as well as a reduced response to cytokine stimulation. The number of the receptors for IFN-gamma and TNF-alpha was not changed between first and third leukapheresis. However, TNF-binding capacity was only detectable upon acid treatment of freshly isolated monocytes. A further upregulation was noted upon 24 h in vitro culture, suggesting occupation of membrane receptors and receptor down-regulation by endogenously produced TNF-alpha. Northern blot analysis of cytokine gene expression was in good correlation with the amount of mediators determined on the protein level. These data indicate that cells of the monocyte-macrophage system are already highly activated in the peripheral blood in RA patients with active disease. These cells can be efficiently removed by repeated leukapheresis and are replenished by monocytes that have, with respect to cytokine and mediator production, a considerably lower activation status.

Antigens, CD↗
PubMed1993

Genetic transmission of fibrodysplasia ossificans progressiva. Report of a family.

Fibrodysplasia ossificans progressiva is a rare connective-tissue disorder characterized by congenital malformation of the great toes and by progressive heterotopic ossification of the tendons, ligaments, fasciae, and skeletal muscles. We document the genetic transmission of fibrodysplasia ossificans progressiva from a sporadically affected father to each of his three children: two daughters and a son. Previous consideration of a genetic etiology was based on the fact that the disease has been reported in several sets of monozygotic twins, that an increased paternal age has been associated with sporadic occurrences of the disorder, and that there have been several reports of genetic transmission in the remote past. Although an autosomal-dominant genetic transmission has long been suspected, the findings in the family reported on here provide confirmation for such inheritance and a basis for the diagnosis and counseling of patients who have this disease.

Adult↗
PubMed1993

Naturalistic observation of adolescent tobacco use.

A naturalistic observation study of adolescent tobacco use was conducted to corroborate previous studies which used self-report questionnaire or structured interview methods to study this problem behavior. Several findings converged with previous accounts of adolescent tobacco use. For example, most use occurred in small groups. However, other findings diverged somewhat from previous research in that an unexpectedly low number of offers of tobacco was observed, nonusers were present in smoking groups, and solitary smoking was common. These data suggest that direct, normative social pressure to use tobacco may not be as frequent as more subtle informational social influence, at least in high school adolescent tobacco use groups.

Adolescent↗
PubMed1992

Enantiospecific high-performance liquid chromatographic assay with fluorescence detection for the monoamine oxidase inhibitor tranylcypromine and its applicability in pharmacokinetic studies.

In order to be able to measure low concentrations of tranylcypromine enantiomers in biological material, chiral fluorescent derivatization and high-performance liquid chromatography (HPLC) were employed. The internal standard S-(+)-amphetamine and borate-sodium hydroxide buffer pH 11 were added to plasma or urine sample aliquots. o-Phthaldialdehyde was used for precolumn derivatization in combination with the chiral mercaptan N-acetylcysteine. HPLC resolution of the diastereoisomeric derivatives was possible on an octadecylsilane column. The mobile phase consisted of sodium phosphate buffer solution pH 6.5, methanol and tetrahydrofuran. The fluorescence of the eluate was monitored at 344/442 nm. The intra-day coefficients of variation were below 10%, the limit of determination was 0.5 ng/ml. The assay was found to be applicable for routine analyses in a preliminary pharmacokinetic study, in which an oral dose of 20 mg racemic tranylcypromine sulfate was administered to three healthy volunteers. The plasma concentrations were generally low, and those of S-(-)-tranylcypromine significantly exceeded those of the R-(+)-enantiomer. Average maximum concentrations were 57.5 and 6.3 ng/ml for S- and R-tranylcypromine, respectively. While S-tranylcypromine was well detectable within the whole study period (8 h), R-tranylcypromine concentrations fell below the detection limit after 4 h in two out of the three studied volunteers.

Chromatography, High Pressure Liquid↗
PubMed1991

Rapid assay for the quantification of piretanide in biological fluids.

Piretanide was determined from plasma and urine using reversed-phase high-performance liquid chromatography. Plasma was extracted with diethylether at pH 4 using bumetanide as internal standard. The chromatographic separation was performed on an octadecylsilane column (ODS) with acetonitrile/pH 7 phosphate buffer (3:7, v/v). In order to determine piretanide in urine, bumetanide was added to a urine aliquot. Then the sample was centrifuged and the supernatant directly injected without extraction followed by chromatography on an ODS column with a mixture of methanol and pH 7 phosphate buffer (12:13, v/v). The compounds were detected by their intrinsic fluorescence, monitoring the eluate at 287/450 nm. Total chromatography times were 8 min for plasma and 13 min for urine samples. The method was applied for the assay of piretanide in plasma of healthy volunteers after i.v. or p.o. dosage of 6 mg piretanide.

Administration, Oral↗
PubMed1991

Antigenic and genetic homogeneity of Streptococcus uberis strains from the bovine udder.

DNA- fingerprints (Hind III) of Streptococcus uberis field isolates from New York State and Europe showed substantial homogeneity, but were different to those of the type strain of the newly proposed psychrophilic species S. parauberis. S. uberis strains had major SDS-heat extracted antigens of molecular masses (Mr) less than 14, 40-41, 42-43, 59-61, 80-86 and 118-122 kDa following immunoblotting with rabbit hyperimmune sera. Bovine sera and milk reacted with the 40-41 and 118-122 kDa antigens. Variations in the Mr of particular bands were too unevenly distributed to permit formation of subgroups. Although cross reactive, the sizes of the antigens of S. parauberis strain NCDO 2020 were substantially different to those of S. uberis, the most prominent antigen having a Mr of 50 kDa. The antigenic and genetic data therefore strongly support the introduction of S. parauberis as a distinct species. S. uberis strains reacted with antiserum to Lancefield groups B, E, G and P, their grouping reactions showing no correlation with DNA and immunoblot fingerprints. Lancefield grouping of S. uberis therefore appears to have little value in identification.

Animals↗