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Biomedical subjects

G Hoffmann

Publications and source records attributed to G Hoffmann.

At least 19 recordsLinked to original sources
PubMed2002

Electromagnetic coupling on an atomic scale.

Light emission from a scanning tunneling microscope is used to investigate the electromagnetic coupling (EMC) of a metal tip and a metal sample. Subatomic scale modifications of the tip-sample region cause spectral shifts of the fluorescence as demonstrated for a monatomic step and by variation of the tip-sample distance. For sharp tips the EMC is confined to a lateral range of a few nm. The results are consistent with model calculations of the electromagnetic response of an appropriate tip-sample geometry.

Journal Article↗
PubMed2002

Pulse-mode scanning ion conductance microscopy--a method to investigate cultured hippocampal cells.

Scanning ion conductance microscopy (SICM) takes advantage of the increase in the resistance which occurs if a glass microelectrode is closely approached to a poorly conducting membrane (Science 243 (1989) 641) and has been shown to be a promising technique to study membranes of living cells (Biophys J 73 (1997a) 653; J Microsc 188 (1997b) 17). Based on a newly designed set-up on top of an inverted light microscope in combination with a speed optimized low noise intracellular amplifier, a novel mode for control of the distance between the probe and surface has been developed. By application of current pulses, the change in the resistance is monitored independently from electrode drift and parasitic DC currents. We demonstrate the applicability by showing first high-resolution images of neural cells produced with the pulse-mode operated SICM.

Animals↗
PubMed2002

Lambda spectra in 11.6A GeV/c Au-Au collisions.

E896 has measured Lambda production in 11.6A GeV/c Au-Au collisions over virtually the whole rapidity phase space. The midrapidity p(t) distributions have been measured for the first time at this energy and appear to indicate that the Lambda hyperons have different freeze-out conditions than protons. A comparison with the relativistic quantum molecular dynamics model shows that while there is good shape agreement at high rapidity the model predicts significantly different slopes of the m(t) spectra at midrapidity. The data, where overlap occurs, are consistent with previously reported measurements.

Journal Article↗
PubMed2002

[Reduction of severe cardiac complications during implantation of cemented total hip endoprostheses in femoral neck fractures].

Intraoperative circulatory and pulmonary problems occuring during the repair of femoral neck fractures with cemented hip arthroplasty are a common problem, that cannot be ultimately explained. As a possible reason for this problem is air embolism during the polymerisation of the methylmethacrylat discussed. We started a prospective randomised clinical examination with 72 patients to prove the efficiency of palacos mixed in vacuum, with respect to the reduction of severe cardiovascular complication during endoprosthetic repair of femoral neck fractures. In the control group with 36 patients, surgical repair was performed with palacos mixed conventionally. In the second group (vacuum group), also consisting of 36 patients, surgical repair was performed with palacos mixed in vacuum. Invasive hemodynamic monitoring and transesophageal echocardiography was performed in all cases. In the control group pulmonary embolism occurred echocardiographically in 86% of the cases vs. 14% in the vacuum group. 53% of the control patients--vs. 11% of the vacuum patients--showed clinical complications in form of significant decrease of arterial oxygenation and circulatory insufficiency with the need of catecholamines. Clinical complications occurred in the control group in 80% of the patients--vs. 13.7% in the vacuum group--whose pulmonal arterial pressure was higher than 30 mmHg preoperatively and only in 18.8% of the cases--vs. 7.1% in the vacuum group--with a normal pulmonal arterial pressure. Mortality in the control group amounted to 13.8% in the vacuum group to 2.8%. Through the use of methylmethacrylate mixed in vacuum for surgical repair of femoral neck fractures with cemented hip arthroplasty, the incidence of severe cardiac complications could be reduced significantly. Patients with increased pulmonal arterial pressure have the highest risk for cardiac complications.

Aged↗
PubMed2002

Neopterin as a marker of immunostimulation: an investigation in anaesthetic workplaces.

Personnel working in operating theatres and recovery rooms are exposed to a variety of noxious substances. The results of studies of the effects of occupational exposure on immune parameters are conflicting. Neopterin is an acknowledged marker of immunostimulation. Urinary neopterin levels of 58 anaesthetists and anaesthetic nurses were measured over a 3-week period. Neopterin analyses were performed using high performance liquid chromatography. Neopterin levels were within the normal range for all subjects. Younger subjects (aged < or = 35 years) had significantly higher urinary neopterin concentrations than older subjects (aged > 35 years). The present study is the first to investigate the influence of anaesthetic exposure on neopterin levels. No evidence of immunostimulation was found.

Adult↗
PubMed2002

Analysis of 8-oxo-7,8-dihydro-2'-deoxyguanosine and DNA strand breaks in white blood cells of occupationally exposed workers: comparison with ambient monitoring, urinary metabolites and enzyme polymorphisms.

The relationship between biomarkers of effect (8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo, HPLC system) and tail extent moment (comet assay)), markers of external and internal exposure, and biomarkers of susceptibility was evaluated for coke-oven and graphite-electrode-producing plant workers exposed to polycyclic aromatic hydrocarbons (PAHs). Mean 8-oxodGuo levels in white blood cells (WBC) of exposed workers were between 1.38 times (coke-oven, n = 20; P < 0.01) and 2.15 times (graphite-electrode-producing plant, n = 30; P < 0.01) higher than levels found in control samples (mean +/- SD 0.52 +/- 0.16 8-oxodGuo/10(5) dGuo, n = 47). The mean tail extent moment in lymphocytes was 1.38 times higher for coke-oven workers (n = 19; P = 0.09) and 3.13 times higher for graphite-electrode-producing plant workers (n = 29; P < 0.01) when compared with controls (mean plus minus SD 2.54 +/- 0.68, n = 32). Elevated tail extent moments (>3.73) were found in the majority (84%) of PAH-exposed workers showing increased DNA adduct levels (>0.78 8-oxodGuo/10(5) dGuo). However, no association (P > 0.05) was found between DNA damage (8-oxodGuo/10(5) dGuo or tail extent moment) in WBC of all PAH-exposed workers and either benzo[a]pyrene levels or the sum of 16 PAH levels in the air at work place. Furthermore, no relation (P > 0.05) could be established between DNA damage in WBC and biomarkers of internal exposure (1-hydroxypyrene (1-OHP) and sum of five hydroxyphenanthrenes (OHPHs)). Higher exposure to airborne pyrene and phenanthrene led to increasing concentrations of the metabolites 1-OHP (P < 0.01) and the sum of five OHPHs (P < 0.01) in the urine of PAH-exposed workers. The polymorphisms of genes CYP1A1, GSTM1, GSTT1 and GSTP1 (biomarkers of susceptibility) showed no association with biomarkers of effect. In conclusion, both biomarkers of effect may be appropriate for further surveillance studies of workers under PAH exposure.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2002

Correlations using the NREM-REM sleep cycle frequency support distinct regulation mechanisms for REM and NREM sleep.

Polysomnograms of most homeothermic species distinguish two states, rapid eye movement (REM) and non-REM (NREM) sleep. These alternate several times during the night for reasons and following rules that remain poorly understood. It is unknown whether each state has its own function and regulation or whether they represent two facets of the same process. The present study compared the mean REM/NREM sleep ratio and the mean number of NREM-REM sleep cycles across 3 consecutive nights. The rationale was that, if REM and NREM sleep are tightly associated, their ratio should be comparable whatever the cycle frequency in the night. Twenty-six healthy subjects of both sexes were recorded at their home for 4 consecutive nights. The correlation between the REM/NREM sleep ratio and the number of cycles was highly significant. Of the two sleep components, REM sleep was associated to the number of cycles, whereas NREM sleep was not. This suggests that the relationship between REM sleep and NREM sleep is rather weak within cycles, does not support the concept of NREM-REM sleep cycles as miniature units of the sleep process, and favors the concept of distinct mechanisms of regulation for the two components.

Adolescent↗
PubMed2001

Shorter REM latency associated with more sleep cycles of a shorter duration in healthy humans.

A significant association between rapid eye movement (REM) sleep latency and the number of non-REM/REM sleep cycles was found 15 years ago in a large retrospective study. The present prospective study further explored this intra-sleep relationship and analyzed the links between these two variables and the mean cycle duration. It was based on a carefully selected group of healthy control subjects whose sleep was polysomnographically recorded at home for 4 sequential nights. The latency of REM sleep was inversely correlated with the number of cycles and positively correlated with the mean cycle duration, both in individual nights and on means of 4 nights. The present study demonstrated that variations in the number of cycles or the mean cycle duration between the nights are far less important than the substantial differences observed between subjects. Present outcomes support the study of sleep cycle periods and frequencies in those psychiatric disorders where REM sleep latencies have been found to be shorter, and they suggest that these variables be included in sleep studies in which cycles are compared with each other.

Adolescent↗
PubMed2001

Luminescence from metallic quantum wells in a scanning tunneling microscope.

The tunneling current of a scanning tunneling microscope is reported to cause light emission from the metallic quantum well system Na on Cu(111). Optical spectra along with tunneling spectroscopy show that one component of the emission is due to interband transitions between quantum well states of the Na layer. The other component is similar to plasmon-mediated emission observed previously from noble metals. The emission is a unique local probe of the electronic structure of this quantum well system.

Journal Article↗
PubMed2001

Detection and direct genomic sequencing of multiple rare unknown flanking DNA in highly complex samples.

By identifying the sequence of retro- and lentiviral integration sites in peripheral blood leukocytes, the clonal composition and fate of genetically modified hematopoietic progenitor and stem cells could be mapped in vitro and in vivo. Previously available methods have been limited to the analysis of mono- or oligoclonal integration sites present in high copy numbers. Here, we perform characterization of multiple rare retroviral and lentiviral integration sites in highly complex DNA samples. The reliability of this method results from nontarget DNA removal via magnetic extension primer tag selection (EPTS) preceding solid-phase ligation-mediated PCR. EPTS/LM-PCR allowed the simultaneous direct genomic sequencing of multiple proviral LTR-flanking sequences of retro- and lentiviral vectors even if only 1 per 100 to 1000 cells contained the provirus. A primer walking "around" the integration locus demonstrated the adaptability of EPTS/LM-PCR to study unknown flanking DNA regions unrelated to proviruses. The technique is fast, inexpensive, and sensitive in minimal samples. It enables studies of retro- and lentiviral integration, viral vector tracking in gene therapy, insertional mutagenesis, transgene integration, and direct genomic sequencing that until now have been difficult or impossible to perform.

Animals↗
PubMed2001

Antithrombin III enhances inducible nitric oxide synthase gene expression in vascular smooth muscle cells.

Evidence suggests that antithrombin III (ATIII) exerts anti-inflammatory properties in addition to its anti-coagulative mechanisms. In animal models of sepsis, ATIII affected cytokine plasma concentrations with a decrease of pro-inflammatory cytokines. In addition to cytokines, excessive production of nitric oxide (NO) derived from inducible nitric oxide synthase (iNOS) might represent another important mediator of the cytotoxic events during sepsis. Regarding ATIII as a potential anti-inflammatory modulator, one may speculate that ATIII inhibits the synthesis of iNOS-derived NO. However, our data demonstrate that ATIII further stimulates iNOS gene expression when applied together with either interleukin-1 beta or the combination of lipopolysaccharide plus interferon-gamma. The most prominent synergistic effects on NO synthesis were found when ATIII was given at higher concentrations (1, 5, and 10 U/ml). Although the mechanisms of ATIII signal transduction remain to be established, intensification of interleukin-1 beta or interferon-gamma/lipopolysaccharide-induced NO synthesis by ATIII does not attribute to the anti-inflammatory properties of ATIII.

Animals↗
PubMed2001

Recombinant granulocyte colony-stimulating factor (G-CSF) in infectious diseases: still a debate.

Granulocyte colony-stimulating factor (G-CSF), a central mediator of the endogenous response to infection and inflammation, is approved for use in the prevention of infection-related complications in patients with nonmyeloid malignancies during antineoplastic therapy associated with high risk of severe neutropenia. Administration of granulocyte colony-stimulating factor results in improvement of host defence paired with anti-inflammatory effects. There is evidence from animal and clinical studies that administration of granulocyte colony-stimulating factor may also be beneficial in non-neutropenic infections. This review focuses mainly on the results of different animal and clinical studies of granulocyte colony stimulating factor used in the treatment of severe infections and sepsis.

Animals↗
PubMed2001

Nitric oxide-dependent apoptosis in ovarian carcinoma cell lines.

OBJECTIVE: In a recent study, we found different profiles of inducible nitric oxide synthase (iNOS) gene expression in the ovarian carcinoma cell lines OVCAR-3, HOC-7, and 2774 following stimulation by proinflammatory cytokines. The present study was performed to determine whether nitric oxide (NO) synthesis correlates with programmed cell death in these cells. METHODS: NO-Dependent apoptosis was detected by DNA fragmentation analysis and fluorescence-activated cell sorter analysis. RESULTS: NO formation in response to interferon gamma (IFN-gamma), interleukin-1beta (IL-1beta), and tumor necrosis factor alpha (TNF-alpha) was correlated with programmed cell death in the investigated cells. DNA fragmentation was most prominent in OVCAR-3 (34.17 +/- 1.81%), less pronounced in HOC-7 (12.86 +/- 0.45%), and undetectable in 2774 (4.54 +/- 0.40%) cells. The rate of apoptosis correlated with the amount of NO formation in cytokine-treated cells. Moreover, coincubation of OVCAR-3 and HOC-7 with the specific iNOS inhibitor aminoguanidine suppressed apoptosis induced by IFN-gamma, IL-1beta, and TNF-alpha. CONCLUSION: Our data indicate that in OVCAR-3 and HOC-7 cells, NO synthesis induced by IFN-gamma, IL-1beta, and TNF-alpha is correlated with the degree of apoptotic cell death. In clinical situations, this might in part explain the benefit of cytokine application in ovarian carcinoma patients (e.g., documented for IFN-gamma).

Apoptosis↗
PubMed2001

[MR mammography of response-control in primary chemo-brachytherapy in BCT-inoperable breast cancer].

PURPOSE: To evaluate (1) if neoadjuvant chemo-brachytherapy interferes with MR imaging, (2) if MR can predict the size of the remaining tumor after therapy and (3) if MR can give prognostic information after the onset of therapy. MATERIALS/METHODS: 14 patients enrolled in a preoperative tumor-reduction protocol (4 cycles of chemotherapy combined with interstitial radiotherapy) were examined by dynamic contrast enhanced MR mammography (1 T, temporal resolution 93 s, spatial resolution 1.9 min, 0.1 mmol/kg GdDTPA), before therapy, after the first two cycles of chemotherapy, after radiotherapy and the third cycle, and after completion of therapy. MR findings were evaluated for (1) artificial enhancement after radiotherapy, (2) correlation of enhancement after therapy with histology and (3) changes in enhancement dynamics after the first 2 cycles. RESULTS: (1) 54% of patients had diffuse enhancement that occurred after radiotherapy but vanished before the end of therapy. (2) 4 patients had complete histological remissions after therapy, 3 had dispersed single tumor cells, 7 had remaining nodular tumor. While MR could not differentiate between complete remission and single tumor cells, it accurately predicted the diameter of remaining nodular tumor, except for one case that showed false-positive enhancement. (3) MR dynamics after the first cycles of chemotherapy could not predict overall response. CONCLUSIONS: MR is an accurate tool in assessing tumor response after neoadjuvant chemobrachytherapy. Negative effects from radiotherapy are only transient.

Adult↗
PubMed2001

[Vault fixation by fascial sling (Williams-Richardson technique) or sacrospinous/sacrotubed fixation (Amreich-Richter technique) - Is there a difference in indications?].

There are many techniques in the treatment of female genital descent. We analysed sacrospinous/sacrotuberal fixation in comparison to abdominal fixation using fascial slings. One of the aims of the study presented was to determine whether there is a differentiation in indications in the use of either technique. There was no difference in recurrence rates, stress incontinence did not occur in a significant number of cases postoperatively. Recovery was different in both techniques. Apparently the fascial sling technique is effective in cases where intraabdominal surgery has to be performed at the same time and descent is limited to the upper third of the vagina. The use of sacrospinous/sacrotuberal fixation is only limited by simultaneous appearance of excessive lateral detachment defect. It seems to be most effective in cases where larger recto-enteroceles have to be treated at the same time. A lateral defect has to be approached differently in all cases.

Adult↗
PubMed2001

GB virus C/hepatitis G virus infection in patients investigated for chronic liver disease and in the general population in southern Sweden.

Serum samples from patients referred for liver biopsy for investigation of suspected chronic liver disease (n = 286) and from healthy middle-aged volunteers (n = 445) were analyzed for markers of exposure to GB virus C/hepatitis G virus (GBV-C/HGV), hepatitis B virus and hepatitis C virus. GBV-C/HGV analyses included GBV-C/HGV PCR for detection of viremia and GBV-C/HGV enzyme-linked immunosorbent assay for anti-GBV-C/HGV E2 antibodies. Liver biopsies were re-evaluated by a hepatopathologist. GBV-C/HGV markers were detected in 97/286 (34%) patients (GBV-C/HGV RNA = 26; anti-GBV-C/HGV E2 antibodies = 74) compared to 86/445 (19%; p < 0.0001) controls (GBV-C/HGV RNA = 7, anti-GBB-C/HGV E2 antibodies = 79). A significantly higher proportion of GBV-C/HGV-exposed subjects in the patient group were viremic compared to controls (27% vs. 8.1%; p = 0.0015). GBV-C/HGV markers were more commonly found in patients with chronic hepatitis B and C. In patients with GBV-C/HGV viremia, a higher occurrence of bile duct degeneration was detected than in non-viremic patients. Markers of GBV-C/HGV infection were over-represented among patients investigated for chronic liver disease, and ongoing GBV-C/HGV viremia was more common in this group than in controls. Apart from a higher prevalence of bile duct degeneration in viremic patients, infection with GBV-C/HGV did not confer any specific histological characteristics.

Biomarkers↗