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Biomedical subjects

M Löhr

Publications and source records attributed to M Löhr.

At least 55 records · Page 3Linked to original sources
PubMed1999

Development of cellulose sulfate-based polyelectrolyte complex microcapsules for medical applications.

Microencapsulation, as a tool for immunoisolation for allogenic or xenogenic implants, is a rapidly growing field. However most of the approaches are based on alginate/polylysine capsules, despite this system's obvious disadvantages such as its pyrogenicity. Here we report a different encapsulation system based on sodium cellulose sulfate and polydiallyldimethyl ammonium chloride for the encapsulation of mammalian cells. We have characterized this system regarding capsule formation, strength and size of the capsules as well as viability of the cells after encapsulation. In addition, we demonstrate the efficacy of these capsules as a "microfactory" in vitro and in vivo. Using encapsulated hybridoma cells we were able to demonstrate long-term release of antibodies up to four months in vivo. In another application we could show the therapeutic relevance of encapsulated genetically modified cells as an in vivo activation center for cytostatic drugs during tumor therapy.

Alginates↗
PubMed1999

[Intestinal lymphoma. A long diagnostic path].

CASE REPORT: We describe the case of a 43-year-old patient with a Burkitt lymphoma in the small intestine, who initially presented with abdominal discomfort, weight loss, constipation and neurological symptoms. DIAGNOSIS: In terms of differential diagnosis other inflammatory and tumorous diseases had to be considered. Non-Hodgkin lymphomas are common malignant afflictions of the GI-tract. The total body tumor burden is the principal determinant of prognosis. Serum lactate dehydrogenase (LDH) level is one parameter that reflects the tumor burden. On the other hand abdominal mass, bone marrow and central nervous system involvement are negative prognostic factors. Lymphomas can invade in the CNS at any time during the course of disease. This is generally associated with a poor prognosis if not treated immediately. TREATMENT: High doses of cyclophosphamid and MTX have been shown successful in the treatment of Burkitt lymphoma. Almost all relapses occur on therapy or shortly after termination of treatment. Therefore, criteria are needed to select patients of higher and lesser risk to protect the latter from the further intensification of therapy.

Adult↗
PubMed1999

A double-blind, randomized, multicentre, crossover study to prove equivalence of pancreatin minimicrospheres versus microspheres in exocrine pancreatic insufficiency.

BACKGROUND: Modern pancreatin preparations consist of enteric-coated microspheres to protect the enzymes from gastric acid. There are, however, no clinical trials comparing different sizes of pancreatin microspheres with regard to fat excretion and fat intake. AIM: To prove both equivalent efficacy and safety of conventional pancreatin microspheres and smaller pancreatin minimicrospheres in patients with exocrine insufficiency due to chronic pancreatitis. METHODS: In this prospective, randomized, double-blind, multicentre, crossover trial, patients with a stool fat excretion of > 7.5 g/day during a placebo period were randomly assigned either to the minimicrosphere/microsphere treatment sequence or vice versa. The primary end-point was the coefficient of fat absorption, which was calculated from fat excretion and fat intake during the course of a standardized diet. Stool weight, clinical symptoms and the safety of the preparations were also evaluated. RESULTS: Thirty-seven patients entered the study, of whom 23 fulfilled the criteria for the crossover period. In the per protocol analysis (n=18), the 90% confidence intervals for the coefficient of fat absorption of both crossover periods lay entirely within the equivalence range (P=0.02). The intention-to-treat analysis revealed similar results, but the equivalence range was slightly missed (P=0.07). Similar results were obtained for the secondary parameters and the reported adverse events. CONCLUSIONS: Pancreatin minimicrospheres have been shown to be equally effective as microspheres in improving the coefficient of fat absorption in patients with exocrine insufficiency due to chronic pancreatitis.

Adult↗
PubMed1999

Molecular adsorbent recycling system (MARS): clinical results of a new membrane-based blood purification system for bioartificial liver support.

The use of xenogenic or genetically engineered cell types in bioartificial liver support systems requires separation methods between the patients' blood and the liver support bioreactors that guarantee the sufficient transfer of pathophysiologically relevant substances but prevent complications. The present paper describes a new membrane separation system that is nearly impermeable to proteins but enables the exchange of water soluble and protein bound toxins by a special membrane and a recycled protein containing dialysate. Because the full range of toxins in hepatic failure has still not been identified, the value of this membrane separation method was evaluated clinically. Thirteen patients suffering from life threatening hepatic failure who had not responded to state of the art therapy were treated with this device, the molecular adsorbent recycling system (MARS). The overall survival rate was 69%. All patients showed positive response to the therapy, indicating that the presented membrane separator combines therapeutic effectivity with the highest safety criteria for the patient by cutting the exchange of substances below the level of proteins.

Adsorption↗
PubMed1999

Simple method for DNA extraction from pancreatic juice for PCR amplification assays.

CONCLUSION: Preparation of DNA from pancreatic juice for subsequent polymerase chain reaction (PCR) is difficult, but manageable. The protocol presented offers a simple and fast solution. This method might be applicable to other complicated samples, such as saliva, would secretions, or stool washings. BACKGROUND: Of all the biological samples used for PCR amplification, pancreatic juice is the most problematic because of the presence of potential inhibitory substances and the amount of nucleases. This demands a DNA preparation procedure that is suitable for routine diagnostic PCR, and is therefore efficient and safe. This is particularly true for pancreatic juice obtained during routine endoscopy. METHODS: We describe here a simple method utilizing modified phenol/chloroform extraction and precipitation directly from native pancreatic juice suitable for diagnostic PCR applications, such as oncogenes. RESULTS: DNA could be prepared in quantitative amounts from routine endoscopic specimens. DNA could also be prepared from samples kept several days at room temperature.

DNA↗
PubMed1998

Effects of extracellular cadmium on renal basolateral organic anion transport.

Heavy metal ions are well-known nephrotoxic agents. Usually, they induce a damage of various renal transport systems. Cd2+, however, has been shown to enhance renal basolateral organic cation transport. Therefore, the effects of Cd2+ on the basolateral p-aminohippuric acid (PAH) uptake of microdissected nonperfused rabbit kidney S2 proximal tubule segments were investigated. Incubation with Cd2+ induced a bell-shaped concentration response curve with a 2-fold increase of the PAH transport at a Cd2+ concentration of 10(-6) M. Since Cd2+ has been described to activate protein kinase C (PKC), the effects of the PKC inhibitor staurosporine were also tested. Staurosporine (10(-8) M) could, however, not reduce the effects of Cd2+. Cd2+ may exert its effects by an as yet unknown mechanism that is different from the PKC-activating mechanism of phorbol esters. A stimulation of the tricarboxylic acid cycle in kidney cells by Cd2+ may, however, increase the delivery of alpha-ketoglutarate. Indeed, incubation of proximal tubules with alpha-ketoglutarate increased PAH transport across the basolateral membrane significantly. Thus, the observed effects of Cd2+ may be due to an enhanced transport of p-aminohippuric acid by stimulation of exchange of PAH with alpha-ketoglutarate. The modulation of renal organic anion transport may be another aspect of Cd2+ nephrotoxicity.

Animals↗
PubMed1998

Intratumoral injection of encapsulated cells producing an oxazaphosphorine activating cytochrome P450 for targeted chemotherapy.

The prognosis of pancreatic adenocarcinoma is poor and current treatment is for the most part ineffective. We describe here a novel treatment strategy using a mouse model system for pancreatic cancer. Human embryonic epithelial cells have been genetically modified to express the cytochrome P450 2B1 enzyme under the control of a CMV immediate-early promoter. This CYP2B1 gene converts oxazaphosphorines (ifosfamide or cyclophosphamide) to their active cytotoxic compounds, phosphoramide mustard, which alkylates DNA, and acrolein, which alkylates proteins. A number of assays were performed to demonstrate the CYP2B1 gene function as well as toxic effects on neighbouring cells (bystander effect). The cells were then encapsulated in a cellulose sulphate formulation shown to be well tolerated in the pancreas of immunocompetent mice, and injected 1 cm away from pre-established tumours derived from a human pancreatic tumour cell line (PaCa-44). Intraperitoneal administration of low-dose ifosfamide to tumour bearing mice that received the encapsulated cells results in partial or even complete tumour ablation. Such an in situ chemotherapy strategy utilizing genetically modified cells in an immunoprotected environment may prove useful for solid tumour therapy in man.

Adenocarcinoma↗
PubMed1998

Targeted chemotherapy by intratumour injection of encapsulated cells engineered to produce CYP2B1, an ifosfamide activating cytochrome P450.

The prognosis of pancreatic adenocarcinoma is poor and current treatment ineffective. A novel treatment strategy is described here using a mouse model system for pancreatic cancer. Cells that have been genetically modified to express the cytochrome P450 2B1 enzyme are encapsulated in cellulose sulphate and implanted into pre-established tumours derived from human pancreatic cells. Cytochrome P450 2B1 converts the chemotherapeutic agent ifosfamide to toxic metabolites. Administration of ifosfamide to tumour-bearing mice that were recipients of implanted encapsulated cells results in partial or even complete tumour ablation. These results suggest that in situ chemotherapy with genetically modified cells in an immunoprotected environment may prove useful for application in man.

Adenocarcinoma↗
PubMed1998

Increasing the transfection efficacy and subsequent long-term culture of resting human pancreatic duct epithelial cells.

Preparation of pancreatic duct epithelial cells from adult organs is possible by limited digestion and outgrowth of cells. These primary cells are mitotically active for only a short period. Therefore transfection with SV40 large-T antigen is one method to obtain an immortalized cell clone. Because the transfection efficacy of primary cells with conventional vectors is comparatively low, our aim was to develop conditions with improved transfection rates. Best transfection rates (approximately 6% of the resting cells) were obtained by using the BES buffered saline (BBS) calcium phosphate (Ca-P) coprecipitation technique at low pH. By using these optimized transfection parameters, primary cultures of human pancreatic duct epithelial cells were successfully transfected with the plasmid pSV3neo, bearing the large- and small-T antigen of SV40. A G 418 resistant clone (E4) was maintained in culture for 14 months before reaching terminal crisis.

Animals↗
PubMed1998

Secretory immunoglobulin A in pancreatic juice and pancreatic tissue of patients with chronic pancreatitis.

BACKGROUND: The predominance of secretory IgA (S-IgA) in intestinal secretions compared with blood is well established, but concentrations of this protein in pancreatic juice and its origin, especially in chronic pancreatitis, are unknown. AIMS: To investigate the role of S-IgA in chronic pancreatitis. PATIENTS: Twenty one patients with chronic pancreatitis (group I), three patients with proven malignancies (group II), and 12 patients without pancreatic disease (group III). METHODS: Pure human pancreatic juice was collected endoscopically in four fractions after consecutive stimulation with secretin and cholecystokinin (CCK). Samples were analysed for S-IgA, protein, trypsinogen, and proteolytic activity. RESULTS: The S-IgA level was significant increased in fraction 1 of pancreatic juice of group I (1210 (1411) ng/ml) compared with controls (33 (70) ng/ml). Protein concentrations and trypsinogen content were lower in group I than in the other groups. Proteolytic activity could be observed in 53% of all 133 pancreatic juice samples, but in 87% of fraction 1. In pancreatic tissue of three patients with chronic pancreatitis both IgA and secretory component were detected by immunohistology. Expression of the secretory component by human pancreatic epithelial cells was increased in patients with chronic pancreatitis compared with normal controls. The concentration of S-IgA in pancreatic juice did not correlate with the serum S-IgA level. In contrast, serum levels of S-IgA were decreased in patients with chronic pancreatitis. CONCLUSION: There are high levels of S-IgA in human pancreatic juice following chronic inflammation and a protective role is suggested for this immunoglobulin.

Adult↗
PubMed1998

Faecal elastase 1: not helpful in diagnosing chronic pancreatitis associated with mild to moderate exocrine pancreatic insufficiency.

BACKGROUND/AIM: The suggestion that estimation of faecal elastase 1 is a valuable new tubeless pancreatic function test was evaluated by comparing it with faecal chymotrypsin estimation in patients categorised according to grades of exocrine pancreatic insufficiency (EPI) based on the gold standard tests, the secretin-pancreozymin test (SPT) and faecal fat analysis. METHODS: In 64 patients in whom EPI was suspected, the following tests were performed: SPT, faecal fat analysis, faecal chymotrypsin estimation, faecal elastase 1 estimation. EPI was graded according to the results of the SPT and faecal fat analysis as absent, mild, moderate, or severe. The upper limit of normal for faecal elastase 1 was taken as 200 micrograms/g, and for faecal chymotrypsin 3 U/g stool. Levels between 3 and 6 U/g stool for faecal chymotrypsin are usually considered to be suspicious for EPI. In this study, both 3 and 6 U/g stool were evaluated as the upper limit of normal. RESULTS: Exocrine pancreatic function was normal in 34 patients, of whom 94, 91, and 79% had normal faecal elastase 1 and faecal chymotrypsin levels (< 3 U/g and < 6 U/g) respectively. Thirty patients had EPI, of whom 53, 37, and 57% had abnormal faecal enzyme levels (differences not significant). When EPI was graded as mild, moderate, or severe, 63% of patients had mild to moderate EPI, and 37% had severe EPI. In the latter group, between 73 and 91% of patients had abnormal faecal enzymes. In the group with mild to moderate EPI, abnormal test results were obtained for both faecal enzymes in less than 50% of the patients (differences not significant). Some 40% of the patients had pancreatic calcifications. There were no significant differences for either faecal enzyme between the two groups with and without pancreatic calcifications. In 62% of the patients who underwent an endoscopic retrograde cholangiopancreatography (ERCP), abnormal duct changes were found. Again, there were no significant differences for either faecal enzyme between the two groups with abnormal and normal ERCP. CONCLUSION: Estimation of faecal elastase 1 is not distinctly superior to the traditional faecal chymotrypsin estimation. The former is particularly helpful only in detecting severe EPI, but not the mild to moderate form, which poses the more frequent and difficult clinical problem and does not correlate significantly with the severe morphological changes seen in chronic pancreatitis.

Cholangiopancreatography, Endoscopic Retrograde↗
PubMed1998

Immunohistochemical characterization of the pancreatic cellular infiltrate in normal pancreas, chronic pancreatitis and pancreatic carcinoma.

BACKGROUND/AIMS: Chronic pancreatitis is histologically characterized by an extended fibrosis and infiltration of leukocytes. We intended to differentiate the infiltration to evaluate the inflammatory process. METHODS: Samples of tissues of normal pancreas (NP, n = 12), of chronic pancreatitis (CP, n = 7), and pancreatic tissues surrounding pancreatic carcinoma (CA, n = 7) were investigated by immunohistochemical staining using the APAAP technique. RESULTS: In normal pancreas, mononuclear cells (47.1 +/- 26.0 cells/mm2) were observed with a predominance of macrophages (56.3%) and T lymphocytes (31.3%) which were differentiated in CD8+ lymphocytes (9.3 +/- 7.2 cells/ mm2) and CD4+ lymphocytes (6.7 +/- 3.2 cells/mm2). Rarely, plasma cells (5.3%) and B lymphocytes (7.1%) could be detected. In pancreatic tissue of patients with CP and in CA there was a significant increase of mononuclear cells to 264.4 +/- 120.3 cells/mm2 and 284.3 +/- 67.8 cells/mm2, respectively. In both diseases percentages of T lymphocytes (CP: 50.5%; CA: 48.1%) were higher than in normal controls. CD4+/CD8+ ratio of 0.77 in CP and 0.82 in CA demonstrated a predominance of CD8+ cells compared to the peripheral blood. In NP and CA, nearly all T lymphocytes expressed CD45R0 identifying memory cells, while only 58% of T lymphocytes were CD45R0 positive in CP. CONCLUSION: Our data suggest that the investigated cases of CP were of a common inflammatory type rather than due to an autoimmunological reaction. CD8+ T lymphocytes were the predominant T cell subset in the inflammatory infiltrates in both CP and CA.

Adenocarcinoma↗
PubMed1997

Pancreatic fibrosis in experimental pancreatitis induced by dibutyltin dichloride.

BACKGROUND & AIMS: Regulatory mechanisms in chronic pancreatitis finally resulting in pancreatic fibrosis cannot be studied sufficiently in human pancreas. Results of a new pancreatitis model in rats suitable for investigation of the processes leading to pancreatic fibrosis are presented. METHODS: Experimental pancreatitis was induced by intravenous application of 8 mg/kg body wt dibutyltin dichloride. Pancreatitis was characterized by histology, serum parameters, and immunohistochemistry, detecting inflammatory cells. Gene expression of collagen type I and transforming growth factor beta1 was shown by Northern blot analysis. RESULTS: Dibutyltin dichloride induced an acute edematous pancreatitis within 24 hours. Extensive infiltration with mononuclear cells could be observed after day 7 followed by the development of fibrosis. Parallel to the cell infiltration, an upregulation of messenger RNA-encoding collagen type I and transforming growth factor beta1 could be shown. An active inflammatory process could be shown until the end of the observation period, i.e., 2 months. CONCLUSIONS: The findings suggest that dibutyltin dichloride-induced pancreatitis in rats is suitable to study cellular interactions and mediators involved in the development of pancreatic fibrosis.

Animals↗