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Biomedical subjects

M Berg

Publications and source records attributed to M Berg.

At least 73 records · Page 4Linked to original sources
PubMed1999

Five-year follow-up of a bipolar steroid-eluting ventricular pacing lead.

Steroid-eluting pacing leads are known to attenuate the threshold peaking early after implantation. Long-term performance, however, is not yet settled. The lead design tested in this prospective study combines a 5.8-mm2 tip of microporous platinum-iridium with elution of 1.0 mg of dexamethasone sodium phosphate and tines for passive fixation (model 5024, Medtronic Inc.). In 50 patients (mean age 69 +/- 10 years), the electrode was implanted in the right ventricular apex. Follow-up was performed on days 0, 2, 5, 10, 28, 90, 180 and every 6 months thereafter for 5-years postimplant. At each visit, pacing thresholds were determined as pulse duration (ms) at 1.0 V and as the minimum charge (microC) delivered for capture. Lead impedance (omega) was telemetered at 2.5 V-0.50 ms, and sensing thresholds (mV) were measured in triplicate using the automatic sensing threshold algorithm of the pacemaker implanted (model 294-03, Intermedics Inc.). On the day of implantation, mean values were 0.10 +/- 0.03 ms, 0.12 +/- 0.03 microC, 758 +/- 131 omega, and 13.1 +/- 1.8 mV, respectively. Beyond 1-year postimplant, pacing thresholds did not vary significantly. Sensing thresholds and lead impedance values were stable during long-term follow-up. Five years after implantation, mean values were 0.23 +/- 0.11 ms, 0.24 +/- 0.07 microC, 670 +/- 139 omega, and 11.6 +/- 3.1 mV for pulse width and charge threshold, lead impedance, and sensing threshold, respectively, and all leads captured at 1.0 V with the longest pulse duration available (1.50 ms). It is concluded that the bipolar steroid-eluting tined ventricular lead showed stable stimulation thresholds, lead impedance values, and sensing thresholds for 5 years after implantation.

Adult↗
PubMed1999

Mild carotid artery atherosclerosis: assessment by 3-dimensional time-of-flight magnetic resonance angiography, with reference to intravascular ultrasound imaging and contrast angiography.

BACKGROUND AND PURPOSE: Our aim was to evaluate the usefulness of 3-dimensional time-of-flight magnetic resonance angiography (3-D TOF MRA) in detection and quantification of mild atherosclerotic changes of carotid arteries with reference to intravascular ultrasound (IVUS) and contrast angiography. METHODS: TOF MRA at 1.5 T, IVUS, and selective digital subtraction angiography were performed on 31 extracranial carotid arteries of 27 patients (mean age, 52 years; age range, 17 to 75 years) undergoing neuroendovascular interventions. The atherosclerotic lesions were registered, and quantitative measurements of plaque thickness, luminal diameters, and diameter stenosis were independently performed for the imaging modalities. RESULTS: Among 170 arterial segments analyzed, IVUS revealed a total of 48 atherosclerotic lesions (mean diameter stenosis, 17%; range, 4% to 40%), only 25 of which were depicted on digital subtraction angiography. Analysis of the axial source images of TOF MRA resulted in sensitivity of 77% to 83% and specificity of 71% to 80% in lesion depiction for the 2 readers with reference to IVUS. The values of diameter stenosis measured from MRA and IVUS were closely interrelated (r=0.53 to 0.61, P<0.001). CONCLUSIONS: Three-dimensional TOF MRA is feasible and moderately accurate for evaluation of mild atherosclerotic changes of carotid arteries.

Adolescent↗
PubMed1999

Heterologous expression and kinetic characterization of human cytochromes P-450: validation of a pharmaceutical tool for drug metabolism research.

Drug metabolism studies in the early phases of drug discovery and development will improve the selection of new chemical entities that will be successful in clinical trials. To meet the expanding demands for these studies on the numerous chemicals generated through combinatorial chemistry, we have heterologously expressed nine human drug-metabolizing cytochromes P-450 (CYPs) in Saccharomyces cerevisiae. The enzymes were characterized using known marker substrates CYP1A1/1A2 (ethoxyresorufin), 2C8 (paclitaxel), 2C9 (diclofenac), 2C19 (S-mephenytoin), 2D6 (bufuralol), 2E1 (chlorzoxazone), and 3A4/3A5 (testosterone). All of the CYPs showed the expected substrate specificity except for chlorzoxazone hydroxylation, which, in addition to CYP2E1 and 1A2, was also catalyzed by CYP1A1 with a high turnover. The apparent Michaelis-Menten parameters obtained for each CYP were within the ranges of those reported in the literature using human liver microsomes and/or recombinant CYPs. The K(m) for CYP2E1-catalyzed chlorzoxazone hydroxylation was, however, much higher (177 microM) than that obtained using liver microsomes (40 microM). CYP-selective inhibitors, alpha-naphthoflavone (CYP1A1/1A2), quercetin (2C8), sulfaphenazole (2C9), quinidine (2D6), and ketoconazole (3A4/3A5) showed significant isoform-selective inhibitory effects. We have shown that ticlopidine is a potent inhibitor of CYP2C19 (IC(50) = 4. 5 microM) and CYP2D6 (IC(50) = 3.5 microM) activities. We have therefore successfully set-up and validated an "in-house" heterologous system for the production of human recombinant CYPs for use in metabolism research.

Cytochrome P-450 Enzyme Inhibitors↗
PubMed1999

Patient education for adults with chronic eczema.

Seven patients with severe eczema participated in an individual education project. The aim of the education program was to maintain and improve health by providing knowledge in self-care treatment. Patients were provided with new knowledge of their disease and received sufficient information to enable them to apply self-care of their eczema.

Adult↗
PubMed1998

137Cesium-induced chromosome aberrations analyzed by fluorescence in situ hybridization: eight years follow up of the Goiânia radiation accident victims.

The radiation accident in focus here occurred in a section of Goiânia (Brazil) where more than a hundred individuals were contaminated with 137Cesium on September 1987. In order to estimate the absorbed radiation doses, initial frequencies of dicentrics and rings were determined in 129 victims [A.T. Ramalho, PhD Thesis, Subsidios a tecnica de dosimetria citogenetica gerados a partir da analise de resultados obtidos com o acidente radiologico de Goiânia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil, 1992]. We have followed some of these victims cytogenetically over the years seeking for parameters that could be used as basis for retrospective radiation dosimetry. Our data on translocation frequencies obtained by fluorescence in situ hybridization (FISH) could be directly compared to the baseline frequencies of dicentrics available for those same victims. Our results provided valuable information on how precise these estimates are. The frequencies of translocations observed years after the radiation exposure were two to three times lower than the initial dicentrics frequencies, the differences being larger at higher doses (>1 Gy). The accuracy of such dose estimates might be increased by scoring sufficient amount of cells. However, factors such as the persistence of translocation carrying lymphocytes, translocation levels not proportional to chromosome size, and inter-individual variation reduce the precision of these estimates.

Brazil↗
PubMed1998

Transient stimulation of the c-Jun-NH2-terminal kinase/activator protein 1 pathway and inhibition of extracellular signal-regulated kinase are early effects in paclitaxel-mediated apoptosis in human B lymphoblasts.

We demonstrate here that paclitaxel exposure to RPMI-1788 B lymphoblasts caused a dose- and time-dependent increase in nuclear factor activator protein 1 (AP-1) DNA binding activity. The basal DNA binding activities of nuclear factors NF-kappaB and Ets were not affected by paclitaxel. Consistent with these biochemical events, paclitaxel stimulated AP-1-dependent chloramphenicol acetyltransferase (CAT) reporter gene transcription in vivo, as directed from a tetradecanoyl phorbol acetate-inducible promoter. AP-1 binding activity of nuclear extracts isolated from paclitaxel treated cells was reduced following immunodepletion with antibodies directed against individual Jun family proteins, whereas anti-cFos, anti-Fra1, and anti-FosB antibodies were not inhibitory. Paclitaxel caused a rapid and transient increase in c-Jun NH2-terminal kinase (JNK) activity, a proposed mediator of stress activation pathways. By contrast, exposure to paclitaxel produced a transient reduction in the extracellular signal-regulated mitogen-activated protein kinase 2 (ERK2) activity, a proposed mediator of growth factor-stimulated proliferation pathways. Transient activation of the c-Jun-NH2-terminal kinase/AP-1 pathway, together with down-regulation of ERK2 activity, may be a key event in the early response of RPMI-1788 B lymphoblasts to paclitaxel exposure.

Antineoplastic Agents, Phytogenic↗
PubMed1998

The biotin protein MadF of the malonate decarboxylase from Malonomonas rubra.

The gene for the biotin protein MadF of the Na+-pumping malonate decarboxylase from Malonomonas rubra was expressed in Escherichia coli together with the gene for the biotin ligase birA. MadF was partially purified from cell lysates by ammonium sulfate precipitation. Almost pure biotin protein was obtained by subsequent gel chromatography. With recombinant MadF, malonate decarboxylase activity of M. rubra cell extracts previously inactivated by avidin was recovered. Thus, the biological activity of recombinant MadF was proven. Despite the coexpression of birA, MadF was poorly biotinylated. This effect was not caused by an insufficient cofactor supply due to elevated protein levels at constant biotin uptake rates. Attempts to improve the cofactor incorporation were made by site-directed mutagenesis, by coexpression of madK, and by N-terminal elongation of MadF. These measures improved the fraction of MadF containing biotin to maximally 5%. These results might indicate the existence of a biotin ligase in M. rubra with an altered substrate specificity different from that of BirA.

Amino Acid Sequence↗
PubMed1998

Multiple factors including subgenomic RNAs and reduced viral protein expression are associated with a persistent infection by porcine rubulavirus (LPMV).

The synthesis of virus specific RNA and the expression of viral proteins in PK-15 cells persistently infected with the porcine rubulavirus LPMV have been studied at two different cell-passages following establishment of persistency (passages 25 and 65). Protein analysis of persistently infected cells and the virus particles released from these failed to demonstrate the presence of the polymerase (L) protein. A decrease in the amount of the phospho- (P) protein was also noted. The genome and mRNAs, both mono- and bicistronic, could readily be identified in the persistently infected cells with the exception of the L mRNA. By analysis of transcription gradients generated using the NIH Image analysis software, as well as analysis of the editing frequency, it was concluded that the changes in viral protein levels in persistently infected cells could be associated with a reduction in the amount of L mRNA and a shift in editing of the P gene. In addition, several large subgenomic RNAs of both the internally deleted and copy-back type were found in the persistently infected cells. The relevance of these findings to the persistent state is discussed.

Animals↗
PubMed1998

A variant form of feline Borna disease.

Borna disease virus (BDV) is a neurotropic agent with capacity to infect and cause encephalomyelitis in a wide range of animals, including horses, sheep, cattle and cats. Recent interest in BDV as a potential human pathogen has been stimulated by reports of BDV-specific antibodies and nucleic acid in patients with neuropsychiatric diseases. The pathogenesis of Borna disease (BD) in naturally infected animals is believed to be immune-mediated, mainly through the action of cytotoxic T cells. In this paper, a case of feline BD with atypical clinical and histopathological features is reported. Clinically, the cat showed muscle fasciculation and proprioceptive defects. Despite absence of encephalitis, numerous neurons were infected with BDV as shown by in-situ hybridization. This indicates that BDV infection may lead to various disease patterns, depending on differences in viral pathogenicity, or on as yet unidentified host-specific factors.

Amino Acid Sequence↗
PubMed1998

A phase I study of paclitaxel in combination with etoposide in patients with stage IIIB/IV non-small cell lung cancer (NSCLC).

Paclitaxel is a new antineoplastic agent with activity in lung cancer. This phase I clinical trial was designed to determine the maximum tolerated dose (MTD) of paclitaxel in combination with etoposide in previously untreated patients with non-small cell lung cancer (NSCLC). Doses of paclitaxel were in the range of 150-225 mg/m2 (d1) and of etoposide in the range of 100-120 mg/m2 (d2-4). The drugs were administered by i.v. infusion over 3 h (paclitaxel) and 2 h (etoposide). The patients received four courses at 21-day intervals. Twenty-four patients (six female, 18 male) entered the trial. The characteristics of the patients were as follows: median age 64 (55-73) years; Karnofsky index 80% (70-90%); stage IIIB n = 7, IV n = 17; histology, 14 adenocarcinoma, 10 squamous carcinoma. Hypersensitivity reactions after paclitaxel were not observed. The most relevant toxic effect observed was neutropenia (WHO grade 3-4). Three episodes of febrile neutropenia, two episodes of absolute neutropenia (< 100/microliter for > 3 days), and one case of mucositis (WHO grade > or = 3 for > 7 days) occurred. It can be concluded that the MTD of paclitaxel in combination with etoposide was reached at doses of 200 mg/m2 paclitaxel (d1) and 100 mg/m2 etoposide (d2-4).

Aged↗
PubMed1998

A phenomenological study of women's experiences of complicated childbirth.

OBJECTIVE: To describe women's experiences of a complicated childbirth. DESIGN: A qualitative study using a phenomenological approach. Data were collected by tape-recorded interviews. SETTING: Sahlgrenska University Hospital, Göteborg, Sweden in 1995. PARTICIPANTS: 10 women, eight primiparous and two multiparous, who were interviewed two to five days post delivery. KEY FINDINGS: The essential meaning of women's experiences of complicated childbirth is the desire to be recognised and affirmed as a genuine subject. If this happens they feel accepted as childbearing women and as mothers-to-be, even if obstetric interventions are necessary and high technology is used. IMPLICATIONS FOR PRACTICE: By understanding and respecting every women as an individual the caregivers support women giving birth and make them feel accepted, thus paving the way for them to gain control over the situation. Through a true dialogue resulting in a trustful relationship, the women can manage even emergency situations. Separation of the mother and her baby should be avoided if possible.

Adolescent↗
PubMed1998

An introduction to anesthesia-related medications.

Many articles written about anesthesia and anesthetic agents can be rather in-depth and somewhat dry (i.e., boring). This article is an attempt to avoid some of those pitfalls. This article is based almost entirely on the opinions of a CRNA with 14 years experience. It is intended as a brief overview. It is not my intention to write a comprehensive, technical description of anesthesia, because this has been done multiple times much better than I could. Hopefully, this will give a description of the types of drugs commonly used in anesthesia. At the conclusion of this article is a brief example of the "context" in which these drugs are used.

Adjuvants, Anesthesia↗
PubMed1998

Patients with visual display unit-related facial symptoms are stingers.

Thirty patients without obvious skin disease but with subjective skin symptoms related to work with visual display units (VDUs) and 32 healthy persons were single-blind-tested with a solution of 5% lactic acid and pure water on their cheeks. Thirteen of the patients and 6 control persons reacted positively as "stingers" (p < 0.05) in this objective test of sensitive skin. The reason why some patients react with subjective symptoms like itching, burning, stinging, prickling or tingling is unclear. The result of this study, that patients with VDU-related skin symptoms have sensitive skin, does not tell anything about the aetiology of the symptoms. Former studies speak against the role of electric and magnetic fields and indicate that "techno-stress", cognitive factors or flickering from the VDUs or fluorescent tubes could be of importance, as could the Swedish mass media debate.

Adult↗
PubMed1998

Characteristics of users and nonusers of alternative medicine in dermatologic patients attending a university hospital clinic: a short report.

OBJECTIVES: To study the characteristics of users of alternative medicine in dermatologic outpatients attending a university clinic. DESIGN: A cross-sectional study analyzed by using a case-control methodology. SETTING, SUBJECTS, AND STUDY MEASURES: 118 dermatologic patients attending an outpatient university clinic responded to a structured questionnaire concerning demographic data, medical history, experience with alternative medicine, health beliefs, lifestyle, and locus of control. RESULTS: Thirty-five percent of the patients reported having used some form of alternative medicine. Use was related to disease duration, but not to patients' beliefs regarding whether or not they could influence their own health, nor to dissatisfaction with orthodox medicine. The most common reason for trying alternative medicine was that they "wanted to try everything" in an attempt to cure the skin disease. Users stated to a greater extent than nonusers, that they exercised sufficiently, possibly indicating that they are more health conscious. CONCLUSIONS: The study suggests that dermatologic patients using alternative medicine in general do not differ with regard to personal characteristics from nonusers. Rather, it appears that patients with long-standing skin disease turn to alternative medicine as a complement to orthodox treatment.

Case-Control Studies↗
PubMed1998

Two domains of the Borna disease virus p40 protein are required for interaction with the p23 protein.

Borna disease virus (BDV) has five major open reading frames, which encode the proteins p40, p23, gp18, p57 and p190. By analogy with other negative-strand RNA viruses, p40 is a putative nucleoprotein and p23 is a putative phosphoprotein. These proteins are known to form complexes with each other and with the polymerase protein in other viruses. In this paper, it is shown that BDV p40 and p23 can form complexes with each other in infected cells. Furthermore, the amino acids of p40 that are necessary for formation of this complex have been mapped.

Amino Acid Sequence↗
PubMed1998

Atrial lead implantation during atrial flutter or fibrillation?

In patients with sinoatrial disease, unexpected atrial flutter (Af) or fibrillation (AF) is a common problem during implantation of atrial-based pacing systems. As an alternative approach to blind atrial lead placement, lead positioning could be optimized by atrial electrogram mapping. It was the object of this study to evaluate if atrial lead implantation according to this approach and during ongoing arrhythmia is reasonable or if it should be postponed until restoration of sinus rhythm (SR). Twenty-nine consecutive patients (group I) with sick sinus syndrome received a dual-chamber pacemaker during an episode of Af (n = 11) or AF (n = 18). All but two atrial leads were of the screw-in type and had bipolar sensing. Atrial lead position was optimized by mapping the electrogram under fluoroscopy to find locations with high potential amplitudes. The patients were followed for 15.1 +/- 9.8 months, and atrial sensing threshold (AST), atrial pulse width threshold (PWT) at 2.0 V, the pacing mode programmed, and the clinical outcome (OUT) were recorded. The control group consisted of 30 patients (group II) who equally had a history of AF or Af, but were in SR during implantation. The atrial peak-to-peak potential (APEAK) after final lead placement was lower for AF (median value 2.5 mV, lower-upper quartile: 1.7-3.1 mV) as compared to Af (3.8 mV, 2.7-4.9 mV, P < 0.05) and SR (4.1 mV, 3.3-6.2 mV, P < 0.001). There was a correlation (P < 0.01) between APEAK during Af/AF and the postoperative AST immediately after restoration of SR. No lead in any group had to be corrected due to improper sensing in the postoperative course. Median chronic AST was 2.8 mV (2.0-4.0 mV) in group I and 4.0 mV (2.8-4.0 mV) in group II. Median chronic PWT at 2.0 V was 0.15 ms (0.12-0.26 ms) in group I and 0.15 ms (0.09-0.20 ms) in group II. There was no significant difference in chronic AST and PWT between both groups. All but two patients in group I preserved SR as the basic rhythm. A stable SR was observed in 10 of 29 patients, intermittent Af/AF was documented in 17 of 29 patients, seven of whom were asymptomatic. There was no significant difference in OUT between group I and II. Hence, sinus rhythm is not a prerequisite of atrial lead implantation. Mapping the Af or AF waves appears to be useful to guide lead placement and to achieve sufficient sensing and pacing conditions after conversion to sinus rhythm.

Aged↗
PubMed1998

Telemetry guided pacemaker programming: impact of output amplitude and the use of low threshold leads on projected pacemaker longevity.

In a prospective study, a low threshold screw-in electrode (Medtronic 5078, group I, n = 9) was compared to a conventional active fixation lead (Biotronik Y60BP, group II, n = 9) to investigate whether lower pacing thresholds really translate into longer projected service life of the pacemaker. The leads were implanted in the atrium and were connected to a dual chamber pacing system which included the same ventricular lead (Medtronic 5024) and the same pulse generator model (Intermedics 294-03) in both groups. Eighteen months after implantation, atrial and ventricular pacing thresholds were measured as the charge delivered per pulse [microC] at 0.5, 1.0, 1.5, 2.0, and 3.5 V, respectively. For chronic output programming in both channels, patients capturing at 0.5 V were set to 1.0 V, those capturing at 1.5 V were permanently programmed to 2.0 V with the double of the charge threshold as the safety margin for pacing ("safety charge"). A combination of atrial and ventricular output settings was optimal, if it resulted in minimum battery current drain (microA] as measured by pacemaker telemetry. In both groups, current consumption [microA] decreased significantly as output amplitude was decreased, exhibiting its lowest value at 1.0 V in either channel. All ventricular leads could be programmed to the optimum output amplitude of 1.0 V in groups 1 and 2. As the 2:1 "safety charge" values were almost identical, the ventricular channel essential contributes the same amount to the battery drain of the pacing system in both groups. In the atrium, all patients of group 1 could be programmed to the optimum output amplitude of 1.0 V with an average pulse duration of 0.42 +/- 0.15 ms. In group 2, however, all patients had to be programmed to 2.0 V with a mean pulse width of 0.52 +/- 0.15 ms. With the atrial and ventricular output being optimized, the average battery drain of the whole pacing system was 12.19 +/- 0.63 microA in group 1 versus 14.42 +/- 0.32 microA in group 2 (P < 0.001). As patients were chronically programmed to these output settings, this difference translates into a clinically relevant gain in projected pacemaker longevity of 17 months or 18.3% (121 +/- 4 vs. 104 +/- 2 months; P < 0.001). Thus, programming a 2:1 safety margin in terms of charge and optimizing the output parameters by real-time telemetry of the battery current is a useful approach to reduce battery current drain. Making the most of modern lead technology with a different performance in only one channel of an otherwise identical DDD pacing system translates into a significant prolongation of projected pacemaker service life which is of great importance with the increasing awareness of health care expenditures. The gain in projected longevity is mainly due to the option of reducing the output amplitude which is still significantly beneficial well below the nominal voltage of the power source.

Aged↗