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Biomedical subjects

S Koch

Publications and source records attributed to S Koch.

At least 55 records · Page 3Linked to original sources
PubMed2001

Validation of bone conversion in osteoconductive and osteoinductive bone substitutes.

Bone reconstruction can be performed with an autogeneic graft from various donor regions. Osteoconductive and osteoinductive bone substitutes originate from substances of diverse chemical and morphological types and can have a synthetic or a biological derivation. Alongside autogeneic bone transplants and allogenic and xenogeneic bone implants, alloplastic bone replacements of synthetic or semi-synthetic origin are being used for defect reconstruction. In an animal model in rabbits five bone substitutes and one autogeneic graft were surgically incorporated into identical bone defects (10times 10 mm in size) in six anatomically defined regions of the skull. With scintigraphic and histological methods, the metabolic dynamics of the bone is examined as it reacts to the transplantation of autogeneic bone or to implanted bone replacement material.The different autogeneic, xenogeneic and alloplastic bone replacement materials can be differentiated according to the functional quality of the new tissue and the dynamics of the bone conversion thus induced. In the comparison of mineralized, osteoconductive bone subsitutes (TCP, HA, calcium carbonate ceramics) with demineralized, osteoinductive implants (DBM new, DBM old) and autogeneic bone grafts, the bone inducing matrices show the largest quantity of new bone formation, making possible a volume-constant reconstruction.

Journal Article↗
PubMed2001

Incidence of endomycoses in autopsy material.

From 1970 to 1993, 93 endomycoses confirmed by postmortem examination were diagnosed in the autopsy material of the Berlin Charité, a large hospital with an average of 1,500 Hospital beds and maximum medical care. These comprised 51 candidoses (54.8%), 24 aspergilloses (36.5%), five cryptococcoses (5.4%), one zygomycosis, one trichosporosis and one coccidioidomycosis. This corresponded to 0.7% of the 13,275 deceased persons autopsied during this period. The frequency of autopsy was 85.3%. In 3,770 cases (2,418 adults and 1,352 children), brain dissection was performed. An adequate clinical putative diagnosis was made in only six out of 28 patients (18 adults, 10 children) with histologically confirmed cerebral mycosis: 11 candidoses (39.3%), 10 aspergilloses (35.7%) five cryptococcosis (17.8%), one trichosporosis and one coccidioidomycosis. About 80% of the mycoses of the CNS thus remained undetected while the patients were alive. The observations made in the present paper underscore the importance of clinical autopsy in endomycoses.

Adult↗
PubMed2001

Case study approach to removing physical restraint.

The pathway to discarding the use of restraints on older people with a dementing illness is cluttered with misinformation. While exploring the reasons restraints are used as an intervention on an older person with a dementing illness, we find duty of care is an important aspect. This paper presents the process that occurred when an aged care facility used an education and consultation approach in an attempt to remove the need for physical and chemical restraint. This case involved the family of an older person with a dementing illness and staff of the aged care facility.

Aged↗
PubMed2001

Anticoagulation and microembolus detection in a case of internal carotid artery dissection.

BACKGROUND: Microembolic signals (MES) have been demonstrated by transcranial Doppler (TCD) in cases of internal carotid artery dissection. The influence of treatment on MES in arterial dissection is uncertain. The authors here present a case of internal carotid artery dissection in which we detected a reduction of MES after the initiation of intravenous heparin. METHODS: A 37-year-old woman developed a right temporal headache 10 days prior to admission. This was followed by episodes of left arm numbness and weakness. Magnetic resonance imaging (MRI) showed a right frontal and deep subcortical ischemic infarct. Catheter angiography confirmed a right internal carotid artery dissection with intracranial extension. She was then monitored with TCD for MES before and after intravenous heparin was started. RESULTS: The first TCD, performed 12 days after symptom onset, showed 39 MES during 60 minutes of insonation of the right middle cerebral artery. Treatment with intravenous heparin resulted in a decline in MES by 50% after 96 hours. This decline continued and no further MES were detected after 11 days of anticoagulation. CONCLUSION: The authors were able to demonstrate a decline of MES with heparin anticoagulation in a case of internal carotid artery dissection.

Adult↗
PubMed2001

Mutations in mammalian cells induced by heavy charged particles: an indicator for risk assessment in space.

Induction of mutations at the HPRT locus in V79 Chinese hamster cells by heavy charged particles is reviewed. A unique dependence of mutation induction cross sections on LET or any other physical parameter of the particles cannot be found. There is, however, a general trend showing an increase up to about 100 keV/microm and an indication of a saturation with higher LET. An empirical expression is given approximating the data which may be useful for practical purposes. On the basis of this expression, it is suggested that the formula used by the ICRP for the quality factor overestimates the risk for very heavy particles. This may have implications for the assessment of the risk of exposure to iron ions in space.

Aerospace Medicine↗
PubMed2001

Characterization of four lipoprotein classes in human cerebrospinal fluid.

Lipoprotein metabolism in brain has not yet been fully elucidated, although there are a few reports concerning lipids in the brain and lipoproteins and apolipoproteins in the cerebrospinal fluid (CSF). To establish normal levels of lipoproteins in human CSF, total cholesterol, phospholipids, and fatty acids as well as apolipoprotein E (apoE) and apoA-I levels were determined in CSF samples from 216 individuals. For particle characterization, lipoproteins from human CSF were isolated by affinity chromatography and analyzed for size, lipid and apolipoprotein composition. Two consecutive immunoaffinity columns with antibodies, first against apoE and subsequently against apoA-I, were used to define four distinct lipoprotein classes. The major lipoprotein fraction consisted of particles of 13;-20 nm containing apoE and apoA-I as well as apoA-IV, apoD, apoH, and apoJ. In the second particle class (13;-18 nm) mainly apoA-I and apoA-II but no apoE was detected. Third, there was a small number of large particles (18;-22 nm) containing no apoA-I but apoE associated with apoA-IV, apoD, and apoJ. In the unbound fraction we detected small particles (10;-12 nm) with low lipid content containing apoA-IV, apoD, apoH, and apoJ. In summary, we established lipid and apolipoprotein levels in CSF in a large group of individuals and described four distinct lipoprotein classes in human CSF, differing in their apolipoprotein pattern, lipid composition, and size. On the basis of our own data and previous findings from other groups, we propose a classification of CSF lipoproteins.

Apolipoprotein A-I↗
PubMed2001

[Repetitive acute pancreatitis in a late-diagnosed cystic fibrosis: prevention of relapses by octreotide in the long term].

We report on the case of a 35 year-old woman who was initially admitted for acute pancreatitis in october 1995. The patient was suffering from asthma (since childhood) and diffuse abdominal pain (since adolescence). The diagnosis of cystic fibrosis was made fortuitously during a sterility evaluation. After extensive etiological screening the acute pancreatitis was considered to be a manifestation of the cystic fibrosis. Despite therapy with pancreatic enzymes, the patient continued to suffer from chronic abdominal pain. High intake of analgesics was required. Until December 1995, the patient was repeatedly admitted for episodes of acute pancreatitis. In January 1996, we initiated a preventive treatment with subcutaneous octreotide between 100 and 200 microgram, three time a day. Thereafter, there were fewer episodes of pancreatitis and the consumption of analgesics decreased. Side effects of octreotide were intermittent diarrhea and development of cholelithiasis that was complicated by biliary migration in November 1998. In June 1999, the prolonged-release form of the molecule was given without modification of the efficacy.

Acute Disease↗
PubMed2001

The impact on clinical practice of endoscopic ultrasonography used for the diagnosis and staging of pancreatic adenocarcinoma.

CONTEXT: Endoscopic ultrasonography is considered a highly accurate procedure for diagnosing small pancreatic tumors and assessing their locoregional extension. OBJECTIVE: To evaluate the impact of endoscopic ultrasonography on the management of pancreatic adenocarcinoma in clinical practice. PATIENTS: Sixty-four consecutive patients (mean age 70.5 plus/minus 11.9 years) hospitalized for staging or diagnosis of pancreatic adenocarcinoma were retrospectively (from January 1995 to November 1997) or prospectively studied (from December 1997 to August 1999). SETTING: Group 1 consisted of 52 patients with pancreatic adenocarcinoma which was discovered using computerized tomography scanning and/or ultrasound. Endoscopic ultrasonography was utilized for staging purposes only in patients who were considered to be operable and the tumor to be resectable based on computerized tomography scanning criteria. Group 2 consisted of 12 patients who were diagnosed as having a pancreatic adenocarcinoma using endoscopic ultrasonography whereas computerized tomography scanning and ultrasound was negative. MAIN OUTCOME MEASURES: The impact of endoscopic ultrasonography was analyzed on the basis of the number of patients requiring endoscopic ultrasonography as a staging procedure (Group 1) and by evaluating the performance of endoscopic ultrasonography in determining resectability (Groups 1 and 2) based on the surgical and anatomopathological results. RESULTS: Endoscopic ultrasonography was performed in 20 out of 64 patients (31.3%): 8/52 in Group 1 (15.4%) and all 12 patients of Group 2. Endoscopic ultrasonography correctly assessed an absolute contraindication to resection in 11 cases. Resection was confirmed in 8 of the 9 cases selected by endoscopic ultrasonography. The positive predictive value, negative predictive value and overall accuracy of endoscopic ultrasonography for determining resection were 89%, 100%, and 95%, respectively. CONCLUSIONS: The impact of endoscopic ultrasonography seems especially relevant for the detection of pancreatic tumors after negative computerized tomography scanning, and for the prevention of unnecessary laparotomies as complementary staging after ultrasonography and computerized tomography scanning.

Adenocarcinoma↗
PubMed2000

Splice variants reveal the region involved in oxygen sensing by recombinant human L-type Ca(2+) channels.

Regulation of vascular smooth muscle Ca(2+) channels by oxygen tension contributes importantly to hypoxic vasodilatation. We previously described the inhibitory effects of hypoxia on the recombinant human cardiac L-type Ca(2+) channel alpha(1C) subunit (hHT isoform) expressed in HEK 293 cells. We now demonstrate that hypoxia inhibits only one of the three naturally occurring splice variants of this channel that differ only in the C-terminal domain, permitting identification of a 71-amino acid insert in the C-terminal region of the channel that confers oxygen sensitivity. Selective restriction of the spliced insert allowed determination of a 39-amino acid region essential for oxygen sensing. This represents the first identification of the structural region of an ion channel required for sensing changes in oxygen tension.

Alternative Splicing↗
PubMed2000

Lithium increases N-acetyl-aspartate in the human brain: in vivo evidence in support of bcl-2's neurotrophic effects?

BACKGROUND: Recent preclinical studies have shown that lithium (Li) robustly increases the levels of the major neuroprotective protein, bcl-2, in rat brain and in cells of human neuronal origin. These effects are accompanied by striking neuroprotective effects in vitro and in the rodent central nervous system in vivo. We have undertaken the present study to determine if lithium exerts neurotrophic/ neuroprotective effects in the human brain in vivo. METHODS: Using quantitative proton magnetic resonance spectroscopy, N-acetyl-aspartate (NAA) levels (a putative marker of neuronal viability and function) were investigated longitudinally in 21 adult subjects (12 medication-free bipolar affective disorder patients and 9 healthy volunteers). Regional brain NAA levels were measured at baseline and following 4 weeks of lithium (administered in a blinded manner). RESULTS: A significant increase in total brain NAA concentration was documented (p < .0217). NAA concentration increased in all brain regions investigated, including the frontal, temporal, parietal, and occipital lobes. CONCLUSIONS: This study demonstrates for the first time that Li administration at therapeutic doses increases brain NAA concentration. These findings provide intriguing indirect support for the contention that chronic lithium increases neuronal viability/function in the human brain, and suggests that some of Li's long-term beneficial effects may be mediated by neurotrophic/neuroprotective events.

Adult↗
PubMed2000

Late endocytic compartments are major sites of annexin VI localization in NRK fibroblasts and polarized WIF-B hepatoma cells.

Annexin VI is an abundant calcium- and phospholipid-binding protein whose intracellular distribution and function are still controversial. Using a highly specific antibody, we have studied the distribution of annexin VI in NRK fibroblasts and the polarized hepatic cell line WIF-B by confocal microscopy. In NRK cells, annexin VI was almost exclusively found associated with endocytic compartments, which were defined by their ability to receive fluid-phase marker internalized from the cell surface. However, extensive colocalization of annexin VI and the endocytic marker was only observed after about 45 min, indicating that annexin VI was primarily in late endocytic compartments or (pre)lysosomes. Consistent with this, annexin VI was predominantly seen on structures that contained the lysosomal protein lgp120, although not on dense core lysosomes by electron microscopy. Two major populations of annexin VI-containing structures were present in polarized WIF-B hepatocytes. One correlated to lgp120-positive (pre)lysosomes and was still observed after treatment with brefeldin A (BFA), while the other appeared to be partially associated with Golgi membranes and was BFA-sensitive. The striking association with prelysosomal compartments in NRK and WIF-B cells suggests that annexin VI could play a role in fusion events in the late endocytic pathway, possibly by acting as a tether between membranes.

Animals↗
PubMed2000

Proliferation and number of Clara cell 10-kDa protein (CC10)-reactive epithelial cells and basal cells in normal, hyperplastic and metaplastic bronchial mucosa.

Clara cell 10-kDa protein (CC10) is an inhibitor of phospholipase A2 and binds to phosphatidylinositol. It may therefore interfere with intracellular signal transduction. Bronchial CC10-reactive cells have been described by several authors. In contrast to the bronchiolar CC10-containing Clara cell, which is a progenitor cell of terminally differentiated airway epithelium, the role of bronchial CC10-reactive cells remains to be elucidated. We assessed the number of bronchial CC10-reactive cells in relation to cytokeratin (CK) expression and proliferative activity in normal, hyperplastic and squamous metaplastic epithelium. Sixty-five human bronchial mucosal specimens were investigated immunohistochemically for CK expression (CK7, CK13 and CK5/6), proliferative activity (MIB-1) and number of CC10-reactive epithelia. The proliferation fraction of CC10-reactive cells was assessed with double staining for MIB-1 and CC10. The proliferation index of the epithelium differed significantly between normal, hyperplastic and metaplastic epithelium. The number of CC10-reactive cells was inversely related to the epithelial proliferation. Bronchial CC10-reactive cells showed no proliferative activity as assessed using immunohistochemical double staining for CC10 and MIB-1. In contrast to normal and hyperplastic epithelium, squamous metaplasia disclosed CK5/6 in all epithelial layers, a loss of CK7 and a gain of CK13. We conclude that CC10-reactive cells have no progenitor role in the bronchial mucosa. However, because the proliferative activity is inversely related to the number of CC10-reactive cells, the CC10 protein may play a role in the regulation of epithelial repair. Squamous metaplasia most likely originates from basal cells.

Adult↗
PubMed2000

Ultrasound enhancement of liposome-mediated cell transfection is caused by cavitation effects.

Cationic liposomes (CL) are widely used vectors for gene transfer. Recently, ultrasound (US) was reported to enhance liposome-mediated gene transfer to eucaryotic cells in culture. The present study was aimed at studying the effects of 2-MHz pulsed Doppler US on malignant brain tumor cells transfection by cationic liposome/plasmid-DNA complexes (lipoplexes). Cationic liposomes consisting of DOSPA/DOPE were complexed with a plasmid carrying the cDNA encoding green autofluorescent protein (EGFP). Rodent (9L) and canine (J3T) glioma cells were exposed to pulsed US in the presence of EGFP-lipoplexes. A diagnostic transcranial Doppler device (MultiDop L) was used for insonation for 30, 60, and 90 s at 2 MHz/0.5 W/cm(2). To eliminate US reflection and cavitation, a custom-made absorption chamber was designed, where US is applied through a water tank before interacting with the cells and is fully absorbed after passing through the cell layer. Expression of the marker gene EGFP was quantified by FACS analysis and intravital fluorescent microscopy. Cell viability was accessed by Trypan Blue staining. US treatment of tumor cells on microplates for 60 s yielded a significant increase in transfection rates without damaging the cells, but 90-s treatment killed most of the cells. In the absorption chamber, no significant effects of US on transfection were noted. Additional experiments employed US contrast agent (Levovist, Schering) which was able to significantly increase tumor cell transfection rate by enhancing cavitation effects, and also severely damaged most cells when applied at a concentration of 200 mg/mL. In conclusion, our results support the assumption that US effects on lipoplex transfection rates in brain tumor cells in culture are mediated by cavitation effects.

Animals↗
PubMed2000

Pulmonary aspergillosis in an unselected autopsy series.

The present study was performed to analyze the relationship between underlying diseases and the morphologic form of aspergillosis. This retrospective analysis of 3284 autopsies yielded 18 cases of aspergillosis. The specific diagnosis of aspergillosis was rendered by a monoclonal antibody versus Aspergillus spp. Patients with hematological disorders, such as acute leukemia and aplastic anemia, made up about 35% of all patients dying of invasive aspergillosis. Diseases of the airways and the pulmonary parenchyma constituted the second most pathogenetic factor for the development of aspergillosis. The morphologic form of aspergillosis was closely related to the underlying diseases. Non- and semi-invasive forms of aspergillosis--saprophytic infection and chronic necrotizing aspergillosis--were observed only in patients with an isolated underlying pulmonary disease devoid of any other precipitating factor. In contrast, seven patients, five of whom suffered from hematological diseases, had no underlying lung disease and developed aspergillus pneumonia. The remaining 5 patients with aspergillus pneumonia showed a combination of underlying extrapulmonary disease and pulmonary alterations that preceded aspergillosis. The local distribution of fungal infection showed a characteristic distribution pattern with a predominance of the upper lung lobes. Hematogeneous spread beyond the lungs occurred exclusively in cases with aspergillus pneumonia. We conclude that the different forms of aspergillosis are closely related to the nature of the underlying disease.

Adult↗
PubMed2000

Formaldehyde neurotoxicity in animal experiments.

The aim of this study was to determine whether the inhalation of formaldehyde has a neurotoxicological impact. Forty Wistar rats (Lew.1/K) were trained to find food in a maze within a particular time. When all animals were at an equal level, 13 rats inhaled 2.6 ppm and 13 others inhaled 4.6 ppm formaldehyde 10 min/d, 7 d/week for 90 d. The control group comprised 14 animals inhaling water steam according to the same exposure pattern. During the exposure period and the post-trial observation stage (30 d), the time required to find the food and the number of mistakes made on the way were recorded. Between the animals exposed to formaldehyde and the control group a statistically significant difference for both parameters was observed (p < 0.05). The animals exposed to formaldehyde needed more time and made more mistakes than the animals of the control group while going through the maze. The results underline the necessity for a systematic observance of precautions in case of occupational or dwelling-related formaldehyde exposure, and allow us to classify formaldehyde as "probably neurotoxic". Further investigations are required to assess the neurotoxicologic impact of subchronic formaldehyde exposure.

Administration, Inhalation↗
PubMed2000

Optical flow-cell multichannel immunosensor for the detection of biological warfare agents.

An automated optical flow cell multichannel immunosensor for the detection and identification of toxins, viruses and bacterial particles is presented. A solid phase ELISA, based on a peroxidase label for signal generation and on fused silica capillaries as a support for immobilized antibodies, has been employed for analyte detection and identification. The sensing and signal transducing component of the sensor consists of a light-emitting diode and a photodetector. The device is fitted with three channels allowing the simultaneous detection of three agents. An integrated flow injection analysis system ensures automation of the assay cycles. Data on the detection of the bacterial toxin staphylococcal enterotoxin B (SEB), the bacteriophage M13 as a viral agent, and Escherichia coli as a bacterial agent are presented.

Bacteriophage M13↗
PubMed2000

Characterization of a canine glioma cell line as related to established experimental brain tumor models.

A large animal tumor model for anaplastic glioma has been recently developed using immunotolerant allogeneic Beagle dogs and an established canine glioma cell line, J3T. This model offers advantages in terms of tumor morphology and similarity to human anaplastic glioma. The present study was aimed at evaluating the biological characteristics of the J3T canine glioma cell line as related to experimental gene therapy studies. Furthermore, development and morphology of canine brain tumors in a xenogeneic immunodeficient SCID mouse model was investigated. It was demonstrated that cultured J3T cells can be efficiently infected by adenovirus (AV), herpes-simplex type I (HSV), or retrovirus (RV) vectors, as well as by non-virus vectors such as cationic liposome/DNA complexes. Thus, in terms of infectability and transfectability, J3T cells seem to be closer to human glioma than the 9L rodent gliosarcoma. Cytotoxicity of selection antibiotics such as G418, puromycin, and hygromycin on J3T cells essentially resemble cytotoxicity seen with other established glioma lines, for example, 9L, U87, or U343. RV-mediated HSV-TK/GCV gene therapy demonstrated comparable LD50 for TK-expressing and control (non-expressing) J3T and 9L cells treated with Ganciclovir. Further, it was proven that J3T cells are tumorigenic and may grow heterotopically and orthotopically in a xenogeneic immunodeficient host, the SCID mouse, although morphology and growth pattern of these xenogeneic tumors differ from the demonstrated invasive phenotype in the Beagle dog.

3T3 Cells↗