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Biomedical subjects

C Koch

Publications and source records attributed to C Koch.

At least 181 records · Page 10Linked to original sources
PubMed1997

[CT-angiography for diagnostic assessment of intracranial vascular aneurysms].

Intracranial aneurysms bear a high risk of morbidity and mortality especially when they have become symptomatic due to rupture or represent a space occupying lesion. Therefore operative treatment is aimed at the obliteration of the aneurysm to eliminate the risk of hemorrhage. Planning of treatment requires a diagnostic resolution capable of showing aneurysms and their anatomic relationship to the adjacent structures. Due to technical advances computed tomography has reached a diagnostic accuracy sufficient to plan aneurysm treatment. This report describes the present state of three-dimensional spiral-CT angiography (3D-spiral-CTA) and our protocol to examine the arteries of the Circle of Willis for the presence and microanatomy of aneurysms. The experience of 46 patients with 64 aneurysms is reported and the diagnostic value of the method in comparison to conventional angiography is evaluated.

Aneurysm, Ruptured↗
PubMed1997

[Cranial dural arteriovenous fistulas--current status of therapy].

Spontaneous dural arteriovenous fistulas (DAVF) are abnormal arteriovenous shunts with a nidus within the dura mater. The exact etiology of the spontaneous DAVFs remains uncertain. Arterial inflow is from the meningeal branches in the region, which can be from an extracranial or an intracranial source. The venous drainage is through the dural sinuses, although cortical or deep venous drainage may be recruited. The critical symptoms are highly dependent on the venous drainage. Computed tomography and/or magnetic resonance imaging demonstrates the epiphenomena rather than the DAVF itself. Angiography is the most important modality in evaluating a DAVF. Based on the patterns of the venous drainage, a classification of the DAVF is possible. This classification enables decision-making about the appropriate therapy. Also the risk of each DAVF may be determined.

Arteriovenous Fistula↗
PubMed1997

[Differential therapy of cerebral angiomas].

Patients with cerebral arteriovenous malformations (cAVMs) are usually young at the time of diagnosis with a mean age of 32 years. These patients are in a crucial phase of their lives, starting a family and establishing a professional position. Facing a relative annual risk of 2 to 3% for a severe hemorrhage which cumulates to a 50% risk of hemorrhage over the next four decades of their lives, these patients have to make the decision about possible treatment of their cAVM. Advice can only be given to the patients on an individual basis because there are almost no two identical lesions. Nevertheless, based on a grading system and within established treatment regimens, risk estimations are possible and particularly with close neuroradiological/neurosurgical cooperation these risks can be defined and minimized. In this context we report a series of 184 patients with cAVMs which were taken care of at the Departments of Neurosurgery and Neuroradiology at the University of Hamburg between February 1988 and July 1996 and who were treated according to a standardized joint protocol with interventional and microsurgical options.

Adult↗
PubMed1997

[The pharmacologic basis of postoperative pain therapy. Epidural opioid administration].

The administration of epidural opioids is alternatively used in the management of postoperative analgesia. However, the administration is associated with side effects, including respiratory depression, somnolence and pruritus. A rational opioid selection between the hydrophilic and lipophilic opioids morphine, hydromorphone, alfentanil, fentanyl and sufentanil is discussed in this mini-review. Thus, the administration of the lipophilic opioid sufentanil might has some advantages. Notwithstanding, epidural opioid administration alone offers no marked clinical advantages compared to the intravenous route. In future, reduced doses of lipophilic opioids and local anaesthetics like bupivacaine 0.05-0.1% may provide benefits over the use of either drug alone and may offer marked clinical advantages over the intravenous route of opioids alone. The same holds true for alpha 2-adrenoceptor agonists as adjuvants. However, multicenter dose-ranging studies are necessary to determine both the ideal concentrations of the drug combinations and the general outcome. Moreover, we must also determine cost effectiveness for our postoperative analgesic techniques.

Analgesia, Epidural↗
PubMed1997

Double-monoclonal immunofluorometric assays for pregnancy-associated plasma protein A/proeosinophil major basic protein (PAPP-A/proMBP) complex in first-trimester maternal serum screening for Down syndrome.

Four double-monoclonal time-resolved immunofluorometric assays (TrIFMAs) have been developed for the specific determination of pregnancy-associated plasma protein A/proeosinophil major basic protein (PAPP-A/ proMBP) complex in first-trimester maternal serum samples. The assays have a functional sensitivity of < 4 mIU/L and a working range from 4 to 1000 mIU/L. These 4 assays, together with a polyclonal sandwich TrIFMA, were compared for their ability to discriminate between normal pregnancies (n = 149) and pregnancies carrying a Down syndrome fetus (n = 36) in maternal serum screening samples from gestational weeks 4-13. In 26 Down syndrome pregnancies from gestational weeks 7-12, the median PAPP-A multiples of the median concentration in controls (MoMs) determined by monoclonal antibody combinations 234-3/234-2*, 234-4/234-2*, 234-4/234-5*, and 234-5/234-6* were 0.35, 0.37, 0.42, and 0.44, respectively, whereas the median MoM determined by the polyclonal assay was 0.56. ROC curve analysis also showed that better overall diagnostic accuracy and detection rates were achieved by the monoclonal TrIFMAs than by the polyclonal TrIFMA. This report is the first to describe assays that specifically measure PAPP-A/proMBP complex without possible interference from other proMBP-containing complexes.

Antibodies, Monoclonal↗
PubMed1997

Immunopurified extracellular Bartonella henselae antigen for detecting specific antibodies by enzyme immunoassay.

Protein antigens of Bartonella henselae bacterial sonicate supernatant and concentrated cell-free culture filtrate were examined by SDS-PAGE. The sonicate supernatant gave 38 bands and the culture filtrate at least 21, of which 18 were of bacterial origin. Immunoblotting against 13 monoclonal antibodies obtained from mice infected with live B. henselae showed that 10 of these antibodies reacted with a narrow 225 kDa band and varying smears of bands ranging from 36 to 240 kDa in the sonicate, but only with a single 200 kDa band in the culture filtrate. Testing of pre- and post-infection rabbit sera in immunoblotting against culture filtrate demonstrated that the 200 kDa component gave the most prominent specific reaction with post-infection sera. The 200 kDa antigen was isolated by immunoaffinity chromatography of concentrated culture filtrate, and its molecular size determined by size-exclusion chromatography as > 1000 kDa. The immunopurified antigen was compared with bacterial sonicate as coating antigen in EIA for determining humoral immune responses in rabbits inoculated with live B. henselae. The two antigens gave almost identical results for IgM and IgG responses. The specificity of the immunopurified antigen was tested in EIA against hyperimmune rabbit sera and sera of rabbits inoculated with live B. henselae, B. quintana and Afipia felis. Only the hyperimmune serum against B. henselae and the sera of the rabbits inoculated with live B. henselae reacted with the immunopurified antigen, whereas the B. henselae sonicate cross-reacted with hyperimmune and post-infection sera of rabbits inoculated with B. quintana and A. felis.

Animals↗
PubMed1996

From stimulus encoding to feature extraction in weakly electric fish.

Animals acquire information about sensory stimuli around them and encode it using an analogue or a pulse-based code. Behaviourally relevant features need to be extracted from this representation for further processing. In the electrosensory system of weakly electric fish, single P-type electroreceptor afferents accurately encode the time course of random modulations in electric-field amplitude. We applied a stimulus estimation method and a signal-detection method to both P-receptor afferents and their targets, the pyramidal cells in the electrosensory lateral-line lobe. We found that although pyramidal cells do not accurately convey detailed information about the time course of the stimulus, they reliably encode up- and downstrokes of random modulations in electric-field amplitude. The presence of such temporal features is best signalled by short bursts of spikes, probably caused by dendritic processing, rather than by isolated spikes. Furthermore, pyramidal cells outperform P-receptor afferents in signalling the presence of temporal features in the stimulus waveform. We conclude that the sensory neurons are specialized to acquire information accurately with little processing, whereas the following stage extracts behaviourally relevant features, thus performing a nonlinear pattern-recognition task.

Action Potentials↗
PubMed1996

Characterization of two ELISAs for NGAL, a newly described lipocalin in human neutrophils.

NGAL is a newly described member of the lipocalin protein family, secreted from specific granules of human neutrophils upon activation of the cells. Its ability to bind the bacterial chemotactic formylpeptide FMLP indicates, that NGAL may have modulatory effects on the immune response. We here describe monoclonal and polyclonal antibodies against NGAL, which can be used for Western blotting and immunohistochemistry, and furthermore describe two ELISAs using either exclusively the polyclonal anti-NGAL antibodies or the polyclonal and monoclonal antibodies in combination. The assays are equally specific, reproducible, accurate, and sensitive, with a detection limit of 32 ng/l. The antibodies and assays will be valuable tools in the future investigation of NGAL expression in inflammatory and malignant disorders and in the elucidation of the function of NGAL as a modulator of the inflammatory response.

Acute-Phase Proteins↗
PubMed1996

[Glucose tolerance in patients with cystic fibrosis].

In order to define prevalence and incidence of diabetes mellitus in cystic fibrosis, we followed 191 unselected patients above two years of age (median 13.6) in a five-year prospective study with annual oral glucose tolerance tests. The prevalence of diabetes increased from 11 to 24% during the study period with an annual age-dependent incidence rate of 4-9%. Diabetes was diagnosed at a median age of 21 years (range 3-40). At diagnosis of diabetes, hyperglycaemia, fasting hyperglycaemia (> or = 7.8 mmol/l), and increased haemoglobin Alc levels (> 6.4) were present in 33%, 16% and 16% of the diabetic patients, respectively. Impaired glucose tolerance implied a higher risk than normal glucose tolerance for the development of diabetes (odds ratio 5.6). In 58% of cases with impaired glucose tolerance, however, glucose tolerance was normalised at the next annual test. Normal glucose tolerance was found in only 37% of the patients at all five tests. Within this group of patients, median fasting and two-hour post-load plasma glucose concentrations and haemoglobin Alc levels increased by 6-8% during five years. Thus, the prevalence and incidence of diabetes in patients with cystic fibrosis is very high and increases with age. Since symptoms of hyperglycaemia and increased fasting plasma glucose and haemoglobin Alc levels are inconstant findings in newly diagnosed diabetic cystic fibrosis patients, we recommend annual oral glucose tolerance tests in all cystic fibrosis patients above the age of 10 years.

Adolescent↗
PubMed1996

[Reduced concentration of insulin-like growth factor I in patients with cystic fibrosis].

Cystic fibrosis is frequently accompanied by a catabolic condition with low body mass index caused by a number of disease complications. Insulin-like growth factor I (IGF-I) is an anabolic hormone and an important marker of nutritional status, liver function and linear growth. Using radioimmunoassay we measured IGF-I once in 235 of our 240 patients (114 males, 121 females, median age 16.2 years, range 0.1-44.0 years). IGF-I was significantly reduced compared with a healthy Scandinavian control population: Mean (-2SD to +2SD) IGF-I-SD score -0.97 (-3.7 to 1.7) in males and -0.67 (-3.2 to 1.9) in females, both values were significantly different from zero (p < 0.001). Height SD score was -0.95 (-3.3 to 1.4) in males and -0.81 (-3.2 to 1.6) in females (p < 0.001). The low IGF-I concentrations may reflect the catabolic state of many patients with cystic fibrosis and play a part in their abnormal growth pattern.

Adolescent↗
PubMed1996

Temporal precision of spike trains in extrastriate cortex of the behaving macaque monkey.

How reliably do action potentials in cortical neurons encode information about a visual stimulus? Most physiological studies do not weigh the occurrences of particular action potentials as significant but treat them only as reflections of average neuronal excitation. We report that single neurons recorded in a previous study by Newsome et al. (1989; see also Britten et al. 1992) from cortical area MT in the behaving monkey respond to dynamic and unpredictable motion stimuli with a markedly reproducible temporal modulation that is precise to a few milliseconds. This temporal modulation is stimulus dependent, being present for highly dynamic random motion but absent when the stimulus translates rigidly.

Action Potentials↗
PubMed1996

Interaction of CD31 with a heterophilic counterreceptor involved in downregulation of human T cell responses.

CD31 is a 130-kD glycoprotein of the immunoglobulin (Ig) superfamily expressed on the surface of endothelial cells, platelets, and several leukocyte subsets. Previous reports indicated that CD31 can mediate intercellular adhesion via both homophilic and heterophilic interaction mechanisms. Using a soluble recombinant CD31-Ig fusion protein (CD31 receptor globulin [Rg]), we demonstrate here that human CD31- T lymphocytes and CD4+CD31- T cell clones express a heterophilic CD31 ligand that is upregulated 18 h after activation. Interaction of CD31Rg with CD31- T helper cell (Th) clones was divalent cation independent but could be blocked by heparin, thus indicating that the CD31 counterreceptor on T cells can be distinguished from the ligands identified on other cell types. Moreover, a single chain protein of 120 kD was precipitated by CD31Rg from the lysates of CD31- Th clones. CD31Rg completely downregulated the proliferative response and cytokine production (interleukin-4, interferon-gamma, and tumor necrosis factor-alpha) of CD31- Th clones when the cells were maximally stimulated via immobilized CD3 monoclonal antibody. These results suggest that interaction of CD31 with a heterophilic counterreceptor on T lymphocytes can interfere with a positive regulatory pathway of T cell activation, or directly signal T cells to downregulate immune function.

Antigens, Differentiation, Myelomonocytic↗
PubMed1996

[Extrinsic and intrinsic asthma from childhood to early adult age. A 10-year follow-up].

The purpose of this study was to describe factors of potential importance for the outcome in children with intrinsic and extrinsic asthma. Of 85 consecutive children, five to 15 years of age, with asthma, 70 (82%) participated in a ten year follow up examination. At the time of referral all children underwent certain tests for asthma (case history, total IgE, skin prick tests, radioallergosorbent tests (RAST) and specific bronchial provocations). On the basis of these tests 24 children had intrinsic asthma and 46 extrinsic asthma. At the follow up examination 60 of the 70 adults (86%; 20 with intrinsic asthma) had current symptoms; 54 of the 60 (90%; 18 with intrinsic asthma) were receiving maintenance therapy. Both FEV1 %pred (from 73% +/- 19% to 92% +/- 17%) and FEV1/FVC (from 75% +/- 13% to 80% +/- 12%) increased significantly from childhood to early adulthood (p < 0.0002 and p < 0.001, respectively); a corresponding amelioration of symptoms was also observed (p < 0.0001). In children with intrinsic asthma the outcome seems to be predicted by a combination of the initial frequency of symptoms (p = 0.04), initial FEV1 (p = 0.001), active smoking (p = 0.001) and age at onset of respiratory symptoms (p = 0.001), whereas the initial FEV1 (p < 0.001) seems to be a strong predictor for the outcome in children with extrinsic asthma. These findings suggest that the pathogenetic mechanisms underlying intrinsic and extrinsic asthma in children may differ.

Adolescent↗
PubMed1996

Catalase and superoxide dismutase activities as biomarkers of oxidative stress in workers exposed to mercury vapors.

For this article we investigated the role of three blood antioxidant enzyme activities and total antioxidant status (TAS) as biological markers of oxidative stress in workers exposed to mercury (Hg(o)) vapors. Twenty-two female workers took part in the study. The examination included a questionnaire on age, educational level, occupational history, actual health status, previous accidents and diseases, smoking and dietary habits, and alcohol consumption. Blood and urine sampling for biological analyses completed this examination. The workers were classified into three subgroups according to their creatinine-corrected Hg concentration in urine. Blood antioxidant enzyme activities and TAS were compared between groups with nonparametric distribution-free methods. A significant difference existed in catalase activity and a slight, but not significant, difference existed in Cu2+/Zn2+ superoxide dismutase (Cu2+/Zn2+ SOD) activity between the three groups. No differences were observed in either the glutathione peroxidase activity or the TAS between these groups. Catalase and Cu2+/Zn2+ SOD activities were increased in the groups of workers with higher creatinine-corrected urinary Hg concentrations when compared with the group of lower creatinine-corrected urinary Hg concentrations. Catalase activity was positively correlated with the creatinine-corrected concentration of Hg in urine, and Cu2+/Zn2+ SOD activity was slightly correlated with the creatinine-corrected concentration of Hg in urine. The role of erythrocyte catalase and Cu2+/Zn2+ SOD activities we have measured is in agreement with the hypothesis of the involvement of reactive oxygen species production as an important event in chronic exposure to Hg(o) vapors in humans. In spite of the small size of the sample, these results indicate that erythrocyte catalase and Cu2+/Zn2+ SOD activities could be considered as markers of biological effect in workers exposed to Hg(o) vapors.

Adult↗
PubMed1996

The HTLV-1 Rex protein induces nuclear accumulation of unspliced viral RNA by avoiding intron excision and degradation.

The human T-cell leukemia virus (HTLV-1) Rex protein is essential for the cytoplasmic accumulation of incompletely spliced transcripts that code for the viral structural proteins. In this study effects of Rex on the amounts of total, spliced and unspliced RNA from HTLV-1 were determined. In transfected fibroblasts Rex production resulted in reduced amounts of spliced RNA and increased quantities of unspliced RNA in the nucleus. However, the total amount of viral RNA was not affected and the stability of spliced transcripts was not changed, thus indicating that only the rate of splicing was reduced. Rex action also reduced splicing in immortalized human cord blood T-cells. However, the total amount of viral transcripts and the stability of unspliced RNA in these cells were also increased in the presence of Rex. This indicates that Rex also prevents the degradation of unspliced transcripts in T-cells. The changes in the relative amounts of spliced and unspliced RNA induced by Rex were observed not only in the cytoplasm but also in the nucleus. Thus Rex affects the nucleocytoplasmic transport, splicing and stability of HTLV-1 RNA in the nucleus. These observations may suggest that Rex directs the unspliced viral RNA to the cytoplasm via a nuclear compartment that is not accessible to splicing and degradation factors.

Animals↗