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Biomedical subjects

K Kramer

Publications and source records attributed to K Kramer.

At least 109 records · Page 6Linked to original sources
PubMed1993

Epithelioid osteosarcoma of bone. Immunocytochemical evidence suggesting divergent epithelial and mesenchymal differentiation in a primary osseous neoplasm.

BACKGROUND: The combination of a primary osteosarcoma of bone with a second carcinomatous cell type has been recognized, although immunohistochemical studies currently have not been performed in an attempt to understand the histogenesis of such a tumor. METHODS: In this report, the authors performed immunohistochemical studies on a primary osseous carcinosarcoma. Using a biotin-streptavidin peroxidase conjugate technique, the expression of keratin, epithelial membrane antigen, and vimentin was analyzed. RESULTS: The epithelial cells expressed cytokeratin and epithelial membrane antigen but did not express vimentin. The mesenchymal cells strongly expressed vimentin, and only rare cells expressed cytokeratin. CONCLUSIONS: The clinical, morphologic, and immunophenotypic data in this instance strongly suggest divergent differentiation of a primitive multipotential uncommitted stem cell in a primary osseous tumor.

Adolescent↗
PubMed1993

Optimization of a monoclonal antibody-based enzyme immunoassay for the detection of terbuthylazine.

The application of immunoassays in pesticide residue analysis is of increasing interest due to the sensitivity, simple handling and fast throughput of samples. For a wide application of these assays, a sufficient supply of standardized antibodies over a long period of time is necessary. The monoclonal antibody technology is solving this problem with an increasing number of cell lines which produce antibodies against different pesticides. Hybridomas were produced by cell fusion of spleen cells from mice immunized with dichloroatrazine conjugated to bovine serum albumin and mouse myeloma cells (PAI-B3 Ag8I). After screening with a competitive enzyme immunoassay, a monoclonal antibody that was specific for terbuthylazine and was produced by a permanent hybridoma cell line was selected for immunoassay development and optimization. For this purpose, an antigen- and antibody-immobilized ELISA technique was improved by varying the test parameters. Comparing both methods, the latter turned out to be superior (50% binding = 0.8 microgram/l, detection limit = 0.14 microgram/l).

Antibodies, Monoclonal↗
PubMed1993

Control of physical exercise of rats in a swimming basin.

To study the mutual interaction between physical exercise and antioxidant systems in rats, we selected swimming as a model for exercise performance. Swimming belongs to the natural behavior of a rat, which under proper experimental conditions, primarily involves physical exercise with little emotional arousal. Therefore, we developed a swimming basin in which the intensity of exercise was manipulated by swimming speed and swimming duration. A laser beam interruption system enables recording of swimming patterns. For comparison we also used the basin to induce emotional arousal. Hereto the basin was transformed into a maze, in which unexpected blockade of a learned swimming route induced a panic-like emotional reaction. The antioxidant enzyme superoxide dismutase decreased in rat plasma after emotional arousal, not after physical exercise. Depletion of the antioxidant glutathione in the liver by diethyl maleate led to decrease of swimming performance. Noradrenaline but not adrenaline plasma levels increased in response to physical exercise. After emotional arousal the ratio noradrenaline/adrenaline did not change. In contrast, lactate only increased in response to emotional arousal. Plasma levels of glucose increased after both stress situations. Beta-adrenoceptor function, determined in the heart and in erythrocytes, only changed after physical exercise. The sensitivity to the beta-agonist (-)isoprenaline in the right atrium decreased and a downregulation of the beta-adrenoceptor density was observed in the erythrocyte.

Animals↗
PubMed1993

Use of telemetry to record electrocardiogram and heart rate in freely moving mice.

This paper describes for the first time the possibility to record the electrocardiogram (ECG) and heart rate (HR) with a commercially available telemetry and data acquisition system in freely moving mice. The system comprises a telemetry transmitter implanted in the peritoneal cavity and a receiver, placed underneath the home cage, an A/D converter (MacLab) and a Macintosh LC II 4/80 computer with software (MacLab, Chart/Scope). The raw analog ECG data are digitized within the MacLab and can be converted to HR data additionally. The effects of surgery for implanting the transmitter, handling and anesthesia by either Nembutal or a mixture of Hypnorm, Dormicum, and water, on the changes in ECG and HR were examined. The telemetry system for recording the ECG and HR provides an accurate and reliable method for monitoring the direct effects of handling on HR. By using this telemetry system, we maintain that measurements in freely moving animals are more efficient, reliable, and less labor-intensive than the measurement techniques described in the literature thus far.

Animals↗
PubMed1993

Human endogenous retroviral element K10 (HERV-K10) encodes a full-length gag homologous 73-kDa protein and a functional protease.

The gag-homologous region of the human endogenous retrovirus K10 (HERV-K10) was amplified by PCR from human genomic DNA and was analyzed by DNA cloning, sequencing, and expression of open reading frames in the prokaryotic pATH expression system. The analysis of genomic DNA of three donors provided evidence that HERV-K10 genes contain an open reading frame of 1966 bp spanning the entire gag-homologous region. In the prokaryotic system the entire reading frame of the HERV-K10 gag gene could be expressed as a fusion protein exhibiting a molecular weight of about 110,000. In addition, when the gag-homologous region and the adjacent HERV-K10 protease gene were prokaryotically expressed, we observed a Gag-protease fusion protein that exhibited specific autoproteolytic activities and processing of HERV-K10 Gag protein. By introducing deletions on the right end of the putative protease gene an autocatalytic site could be localized within 300 bp of the putative HERV-K10 protease gene. For the first time, these results provide evidence that the HERV-K10 encodes a full-length Gag protein and a functional protease.

Base Sequence↗
PubMed1992

Small cell carcinoma of the lung. Treatment in the community.

The results of nonprotocol treatment of 232 patients with small cell lung cancer seen by a group of community-based medical oncologists over a 13-year period were evaluated. Factors associated with improved survival also were assessed. The following patient characteristics significantly improved survival: limited stage of disease at diagnosis, treatment of extensive (but not limited) disease with regimens including etoposide and cisplatin, tumor resection, age younger than 70 years, radiation therapy to the chest, and female sex (extensive disease only). Comparison of the data from this study with published results of protocol studies showed similar outcomes.

Aged↗
PubMed1992

Glutathione mobilization during cerebral ischemia and reperfusion in the rat.

1. Cerebral ischemia applied for 15 min and followed by a 30 min reperfusion did not change the glutathione (GSH) levels and beta-adrenoceptor density (Bmax) in brain cortex. 2. A significant increase in erythrocyte-lysate GSH concentration (vs control) and a significant decrease of Bmax values in erythrocyte membranes (vs control) was found at the same time. 3. Pretreatment with the alpha-adrenoceptor antagonist phentolamine (5 mg/kg i.p.) prevented the erythrocyte GSH increase but not the decrease of Bmax value. Pretreatment with the beta-antagonist propranolol (2 mg/kg i.p.) did not influence the increase in erythrocyte GSH but circumvented the decrease of Bmax.

Animals↗
PubMed1991

Do microscopic abnormalities at resection margins correlate with increased anastomotic recurrence in Crohn's disease? Retrospective analysis of 100 cases.

The relationship between histologic changes at resection margins and anastomotic recurrence was evaluated in patients with Crohn's disease. Pathology and medical records from 1960 to 1977 identified 100 patients who met the following criteria: 1) no prior surgery for Crohn's disease, 2) small bowel or small bowel and colonic resection with anastomosis done for Crohn's disease at the Cleveland Clinic, and 3) resection margins available for microscopic analysis. The following histologic features of the margins were evaluated: edema, inflammation, lymphoid aggregates, pyloric metaplasia, fibrosis, cryptitis and crypt abscesses, ulcers, granulomas, villous shortening, mucin depletion, neuronal hyperplasia, and transmural inflammation. Additionally, margins were categorized as histologically normal, showing nonspecific changes, showing changes suggestive of Crohn's disease, and showing changes diagnostic for Crohn's disease. Anastomotic recurrence occurred in 50 patients after an average follow-up period of 11.5 years. Cumulative recurrence-free rates for the four margin categories were not significantly different. Anastomotic recurrence was not associated with any clinical or histologic feature or combination of features.

Adolescent↗
PubMed1991

Substituent effect on the stereochemistry of H2-receptor antagonists of the phenylformamidine series. A conformation-dependent mode of interaction with the H2 receptor.

The influence of alkyl substitution on the stereoisomerism of the formamidine cation (E,E vs E,Z) of several N-substituted (imidazolylphenyl)formamidines (1-10) was investigated. As (imidazolylphenyl)formamidines having alkyl substituents of more than three carbon atoms bind to H2-receptor preparations in a pseudoirreversible mode causing unsurmountable antagonism, the four isomeric butylformamidines (5-7 and 9) having comparable lipophilic character but different E,E/E,Z composition were investigated in H2-receptor assays to determine quantitatively any difference in their pseudoirreversible inhibitory pattern. It was found that the geometry of the formamidine cation is affected by the steric bulk of the substituent on the formamidine nitrogen. A relationship between the percentage of the E,E conformation of the formamidine cation and degree of pseudoirreversible antagonism was also found. The present studies support the hypothesis that bidentate hydrogen bonding plays an important role in the interaction of (imidazolylphenyl)formamidines with the H2 receptor.

Amidines↗
PubMed1990

Irreversible H2-antagonism of the four isomeric butyl analogues of mifentidine.

It has been hypothesized that bidentate hydrogen bonding plays an important role in the interaction of imidazolylphenylformamidines with the H2-receptor. The present study, in which the degree of pseudo-irreversible H2-antagonism of the four isomeric butyl substituted mifentidine analogues was determined on the spontaneously beating right atrium of the male guinea-pig, lends further support to this hypothesis. In solution the EE/EZ ratio is different for the four isomeric butylated mifentidine analogues. The rank order of the percentage of E,E conformation, which favors a bidentate interaction, of the formamidine moiety parallels the rank order of pseudo-irreversible H2-antagonism.

Animals↗
PubMed1990

Evidence for cell type dependent mechanisms in agonist-induced down-regulation of beta-adrenoceptors.

Processing of the beta-adrenoceptors by mammalian tumor cells, Chang liver cells and HeLa cells both containing beta-2-adrenoceptors, was studied using 125I-labeled iodocyanopindolol and 3H-labeled CGP12177. No difference could be detected between the results obtained with these two ligands. During desensitization of these cells by the beta-adrenergic agonist isoproterenol a time dependent decrease of intracellular cyclic-AMP was accompanied by loss of beta-adrenoceptors. The loss of receptors could not be prevented by the cytoskeleton disrupting agents colchicine and cytochalasin B. The effect of the lysosomotropic agent chloroquine is dependent upon the cell type. It showed no effect on the agonist-induced down-regulation of beta-adrenoceptors on Chang liver cells in contrast to a prominent inhibiting effect on HeLa cells. These results highly suggest that lysosomal enzymes are involved in the process of down-regulation of beta-adrenoceptors on certain cell types only. Colchicine and cytochalasin B, as well as Gpp(NH)p were able to uncouple the guanine nucleotide binding protein and the beta-adrenoceptor. This uncoupling however, did not inhibit the loss of receptors measured by radioligand binding techniques during challenge with agonists. From experiments performed to separate membrane fractions on non-linear sucrose gradients it cannot be concluded that receptors are redistributed intracellular or in the plane of the membrane. Withdrawal of the agonist during receptor down-regulation resulted in the reappearance of measurable receptors within 20 hr for receptors on HeLa cells and within 60 hr for Chang liver cells. The reappearance of receptors could be totally blocked by cycloheximide, indicating that these receptors were newly synthesized and not internalized receptors. From the results of our experiments it is concluded that beta-adrenoceptors, present on Chang liver cells and HeLa cells are down-regulated during desensitization by isoproterenol without uptake in intracellular structures of the cells. The fate of these down-regulated receptors remains unclear. It is also concluded that no universal mechanism can be proposed for beta-adrenoceptor down-regulation on mammalian cells.

Adrenergic beta-Agonists↗
PubMed1990

Effect of PO2 and metabolic inhibitors on ionic fluxes across the isolated rabbit corneal endothelium.

Bicarbonate and sodium fluxes were measured across the isolated rabbit corneal endothelium under the influence of several inhibitors. Depression of PO2 in the bathing medium decreased net sodium movement but increased bicarbonate movement. Furosemide did not alter bicarbonate fluxes at either 10(-4) or 10(-5) M, but increased passive sodium flux leading to a decrease in net flux. Thiocyanate, at 5 x 10(-3) or 5 x 10(-2) M, decreased active bicarbonate flux and hence net flux, but had no effect on sodium fluxes. Dinitrophenol increased only the passive bicarbonate flux while decreasing both active and passive sodium fluxes, albeit unequally, leading to a decreased net flux. Ethacrynic acid affected only passive bicarbonate flux, while decreasing net sodium flux. The stilbene derivatives, SITS and DIDS caused opposite effects on both sodium and bicarbonate fluxes. SITS decreased net bicarbonate flux by decreasing active and increasing passive flux, yet increased net sodium flux. DIDS, however, increased net bicarbonate flux but decreased net sodium flux. The results may be explained by current models for endothelial ion transport that include a Na+/H+ antiport and a HCO3-/Na+ symport system in parallel with an independent pathway for HCO3- exit from the endothelial cells. When compared with prior corneal swelling data using these same inhibitors, the maintenance of corneal thickness appears to be dependent on the variation of ion fluxes from normal values, and the dissociation of the two active ion fluxes. In addition, there appears to be a significant ability of ion transport systems to compensate for disturbances to other ion exchange or transport mechanisms.

Animals↗
PubMed1988

Vitamin E and selenium regulate balance between beta-adrenergic and muscarinic responses in rat lungs.

The effects of hydrogen peroxide on the beta-adrenergic and muscarinic responses of the rat trachea muscle were studied in vitro, after feeding rats, for 6 weeks, either a diet deficient in vitamin E and selenium or a control diet. In the control situation after incubation with 1 mM hydrogen peroxide for 30 min, a reduction of the maximal response to methacholine of 39% occurred whereas no pD2 shift could be demonstrated. Moreover, no response to isoprenaline after precontraction with 3 x 10(-7) M methacholine was left. In the deficient situation, we found a reduction to 64% of the response to methacholine after incubation with 1 mM hydrogen peroxide. Again isoprenaline became inactive, i.e. no relaxation with isoprenaline was observed after precontraction with 3 x 10(-7) M methacholine. We therefore conclude that vitamin E and selenium protect against oxidative stress in lung tissue and thus regulate the (patho-) physiological balance between adrenergic and muscarinic responses.

Animals↗
PubMed1988

Irreversible binding of the fluorescent beta-adrenoceptor probes alprenolol-NBD and pindolol-NBD to specific and non-specific binding sites.

The fluorescent 4-nitrobenzo-2-oxa-1,3-diazolyl (NBD) derivatives of alprenolol and pindolol bind irreversible to beta-adrenoceptors and non-receptor binding sites. This was established in functional experiments on the guinea pig right atrium and trachea smooth muscle, and by radioligand binding assay of beta-adrenoceptors on Chang liver cells in culture. The pD2'-values of alprenolol-NBD and pindolol-NBD for the beta-adrenoceptors on the right atrium were: 8.3 +/- 0.1 and 8.5 +/- 0.1; on the tracheal smooth muscle strip: 8.2 +/- 0.1 and 8.8 +/- 0.1; and its pKd on Chang liver cells: 8.5 +/- 0.1 and 8.9 +/- 0.1 respectively. The results indicated that no selectivity for the beta-adrenoceptor subtypes was introduced by the addition of NBD. The irreversible binding characteristic to beta-adrenoceptors and non-receptor binding sites of the fluorescent NBD derivatives of alprenolol and pindolol makes these drugs unsuitable to label beta-adrenoceptors specifically. As the irreversible binding is introduced by the coupling of the drug with NBD, it is concluded that NBD derivatives of beta-adrenoceptor antagonists are not suitable to visualize the two-dimensional motion of beta-adrenoceptors during challenge with agonists.

4-Chloro-7-nitrobenzofurazan↗
PubMed1987

The effect of ischemia and recirculation, hypoxia and recovery on anti-oxidant factors and beta-adrenoceptor density. Is the damage in the erythrocytes a reflection of brain damage caused by complete cerebral ischemia and by hypoxia?

This investigation was focussed on the gravity of tissue injury caused by complete ischemia (for five min) and hypoxia (for three weeks) in the cerebral cortex (homogenate) and the erythrocyte lysate or the erythrocyte membrane of the rat in order to investigate if the changes that occur in brain tissue are reflected in the erythrocyte. To this end, glutathione (GSH), superoxide dismutase (SOD) and catalase were measured, also alterations in beta-adrenoceptor density under these two conditions were examined. It was found that in ischemia partial parallelism in changes that occur in the central nervous system (cerebral cortex) and the erythrocyte exists. The SOD activity became higher and the beta-adrenoceptor density (measured as specific (-)-[125I] iodocyanopindolol binding) was decreased in both tissues. However after the hypoxic condition we established a decrease in the number of beta-adrenoceptors in the cerebral cortex but an increase in beta-adrenoceptor density in the erythrocyte.

Animals↗
PubMed1987

Functional reconstitution of N-methyl-D-aspartate receptors in artificial lipid bilayers.

Functional reconstitution of the N-methyl-D-aspartate (NMDA) receptors was achieved by adding synaptic membranes from rat brain to large planar bimolecular lipid membranes (BLMs). The reconstituted receptors exhibited several properties of the NDMA receptors described using a variety of biochemical and electrophysiological techniques. Addition of NMDA at concentrations between 5 and 50 microM produced large, voltage-dependent increases in membrane conductivity. The selective antagonist of NMDA receptors, amino-2-phosphonopentanoate (AP-7), totally blocked the response of the bilayers to NMDA as did micromolar concentrations of magnesium; this latter effect was also voltage-dependent. These results indicate that BLMs can be used to study the ion channels and regulatory processes associated with NMDA receptors from adult brain in ways that could not be accomplished with conventional neurophysiological techniques.

Aspartic Acid↗
PubMed1987

A disbalance between beta-adrenergic and muscarinic responses caused by hydrogen peroxide in rat airways in vitro.

The effect of hydrogen peroxide on adrenergic and muscarinic responses of rat airway smooth muscle was studied. The trachea muscle and the lung parenchymal strip were contracted with methacholine and relaxed with (-)-isoprenaline. Recording of three (-)-isoprenaline curves on the trachea muscle and the lung parenchymal strip was followed by treatment for 30 min with hydrogen peroxide (H2O2) (1mM) after which a new dose response curve for (-)-isoprenaline was constructed. Using the trachea muscle this treatment with H2O2 resulted in a decrease of 61% of the maximum contraction by methacholine compared with the control and a complete inhibition of the relaxation by (-)-isoprenaline. In the lung parenchymal strip preparation we found, after the same treatment no reduction of the contraction by methacholine and 61% reduction of the relaxation by (-)-isoprenaline, compared with the control. The results demonstrate that the adrenergic response in rat airways is more susceptible to hydrogen peroxide than the muscarinic response.

Animals↗