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K Kramer

Publications and source records attributed to K Kramer.

At least 127 records · Page 7Linked to original sources
PubMed1987

Relation between pharmacological response and receptor binding with histamine blocking drugs. Irreversible antagonism of three analogues of mifentidine on right atrium and cerebral cortex of the guinea-pig.

The effects of the H2-receptor antagonists cimetidine, ranitidine, mifentidine and three analogues of mifentidine, were studied on the spontaneously beating right atrium (H2-antagonism) and membranes of the cerebral cortex (displacement of 3H-tiotidine), both obtained from the male guinea-pig. The choice of these compounds was based on preliminary experiments in which some mifentidine analogues were shown to displace tiotidine from the H2-receptor in a deviant manner. In the present study we investigated the relation between pharmacological response and receptor binding, also testing the degree of irreversible antagonism of these compounds in the atrium (functional) and cerebral cortex (binding) model. Our data indicate that a relation between the two different approaches for measuring the effect on the H2-receptor can be found, although some differences emerged as well.

Animals↗
PubMed1987

Malignant epithelioid hemangioendothelioma of the colon. Report of a case.

Angiosarcoma of the colon with epithelioid and histiocytoid features, a malignant counterpart of epithelioid hemangioendothelioma, was observed in a 72-year-old man. The disease first manifested as a right cervical mass, with the histologic appearance of malignant, undifferentiated, large-cell epithelioid neoplasm. Light microscopy of the colonic tumor disclosed angiosarcoma, with active erythrophagocytosis and positive immunoperoxidase reactions to lysozyme, alpha-1-antitrypsin, and alpha-1-antichymotrypsin. Ultrastructural features of the tumor cells were those of intermediate between endothelial and histiocytic cells. The disease took a rapid fatal course with recurrence, peritoneal dissemination, and massive peritoneal hemorrhage. The cause remains unknown.

Aged↗
PubMed1987

Studies on the active molecular species of the H2 receptor antagonists cimetidine and mifentidine.

The N'-(4-1H-imidazol-4-ylphenyl)formamidines were recently introduced as a new class of active H2 antagonists; the authors of the compounds (Donetti et al. of de Angeli, Italy) have suggested that these compounds interact with the H2 receptor through their monocations. This is at variance with the model proposed for cimetidine by the SK&F (Smith Kline & French, UK) group who proposed the neutral molecule as the species active at the H2 receptor. In the present study we have investigated the issue whether the neutral or charged species is the active one by measuring the pA2 values of mifentidine and cimetidine at different pH values. Changing the pH will influence the species equilibria of both compounds and thereby affect their activity. The activity changes measured for both compounds are consistent with the proposition that cimetidine as well as mifentidine elicit their activity through their neutral species.

Animals↗
PubMed1987

Family affair.

Explore the source record for details and available documents.

Allied Health Personnel↗
PubMed1987

Vaginitis emphysematosa.

Vaginitis emphysematosa is rare, as only 173 cases, to our knowledge, have been reported in the English literature, the last in 1967. We report three new cases and bring the subject up to date. The ages of our patients ranged from 42 to 65 years; one patient complained of vaginal discharge, and the other two cases were found on routine examination, one at autopsy for breast carcinomatosis. The lesions were described as nodules in the vagina, on occasion producing a "popping sound" that relieved the pressure sensation. Microscopically, variably sized cysts were seen containing pink hyalinlike material and foreign body-type giant cells in the cyst's wall, accompanied by minimal chronic inflammatory cell infiltrate. Vaginitis emphysematosa is an uncommon self-healing disease of unknown cause that produces no sequelae deleterious to the patient.

Adult↗
PubMed1986

Influence of lipid peroxidation on beta-adrenoceptors.

The peroxidation of lipids in biological membranes is a destructive phenomenon that can be elicited in various ways. Surface receptor molecules that allow cells to respond to hormones are possibly inactivated during lipid peroxidation. Effects of lipid peroxidation on receptors have not been extensively examined thus far. This investigation shows that there is a decrease in beta-adrenoceptor density (measured as specific (-)-[125I]iodocyanopindolol binding) during lipid peroxidation, in both lungs and erythrocytes of the rat. To this end, lung membranes (containing both beta 1- and beta 2-adrenoceptors) and intact erythrocytes (containing a homogeneous beta 2-adrenoceptor population) were pretreated with cumene hydroperoxide (lung membranes with 0.1 mM and erythrocytes with 1 mM) and Fe2+ (1 X 10(-5) M) for 60 min which resulted in extensive lipid peroxidation measured as malondialdehyde formation. The ration beta 1-:beta 2-adrenoceptor density in lung membranes after treatment with cumene hydroperoxide did not change and remained at 30%:70%. A single injection (i.p.) with the herbicide paraquat (50 mg/kg, 24 h), which is known to cause lung damage via lipid peroxidation, resulted in similar alterations in receptor density to those caused by cumene hydroperoxide in the in vitro experiments.

Animals↗
PubMed1986

The effects of 4-hydroxy-2,3-trans-nonenal on beta-adrenoceptors of rat lung membranes.

Lung membranes are susceptible to oxygen radicals, formed during inflammation, redox cycling of toxic agents, exposition to ozon etc. Oxygen radicals may modify the beta-adrenergic response. However, at the same time beta-adrenoceptors of the lung are frequently addressed in therapy. We embarked upon this problem by studying the effects of the aldehyde 4-hydroxy-2,3-transnonenal (HNE), one of the major products of lipid peroxidation, on the density of beta-adrenoceptors of rat lung membranes. It is shown, that the physiological important sulfhydryl blocking agent HNE inactivates the beta-adrenoceptors in a time- and concentration dependent (0.5-2.5 mM) way, indicated by a decrease in (-)-[3H]dihydroalprenolol (DHA) binding to lung membranes. Moreover, it is shown that combined treatment of HNE with (-)-isoproterenol (0.5 microM) or 1-alprenolol (0.5-10 nM) does not influence the extent of inactivation of beta-adrenoceptors by HNE. This is in contrast with previous studies, conducted with other, synthetic, sulfhydryl blocking agents, such as N-ethylmaleimide (NEM), suggesting that an other mechanism of inactivation is involved upon HNE treatment.

Aldehydes↗
PubMed1985

High affinity non-beta-adrenoceptor binding of beta-adrenergic ligands.

Two types of saturable binding, besides the well-known non-specific binding, were found when hydrophobic ligands were used for investigating the vesiculization of beta-adrenoceptors on cultured HeLa and Chang liver cells. The first (compartment I) representing beta-adrenoceptors with high affinity ([3H]DHA 0.8 nM, 125I-CYP 27 pM) and low capacity (10-20 fmol/mg protein), the second (compartment II) had a rather high affinity ([3H]DHA 400 nM, 125I-CYP 30 nM) and a very high capacity (20 000-25 000 fmol/mg protein). The affinity of adrenergic agents for compartment II correlates very well (r = 0.9418) with the calculated hydrophobicity. It is concluded that these types of binding sites might interfere with the determination of adrenoceptor binding sites when hydrophobic ligands are used. When using hydrophobic ligands like these special care should be taken to avoid such interference.

Adrenergic beta-Agonists↗
PubMed1985

Non-specific binding of the fluorescent beta-adrenergic receptor probe alprenolol-NBD.

The fluorescent beta-adrenergic receptor probe alprenolol-NBD was found to exhibit a high affinity (Kd 3.2 nM) and a low capacity (10 fmol/mg protein) for the beta 2-adrenergic receptor on living Chang liver cells but also a high affinity (Kd 320 nM) for non-beta-adrenergic receptor binding sites with a very high capacity (28,000 fmol/mg protein). Calculations are presented which make clear that less than 3% of the binding of alprenolol-NBD during visualization experiments is beta-adrenergic receptor related. Furthermore, it is shown that besides the downregulation of beta-adrenergic receptors during incubation with isoproterenol, the high-affinity non-beta-receptor binding sites are also deminishing during incubation with isoproterenol. Based on our findings it is concluded that the results of Henis et al. who claimed the visualization of the beta-adrenergic receptor population on Chang liver cells by alprenolol-NBD must be interpreted as an almost completely non-specific fluorescence.

4-Chloro-7-nitrobenzofurazan↗
PubMed1984

Low concentrations of potassium inhibit the Na-dependent [3H]glutamate binding to rat hippocampal membranes.

Potassium at low concentrations was found to inhibit the Na-dependent [3H]L-glutamate binding to rat hippocampal synaptic membranes. This inhibition was probably due to a competition between potassium and sodium at the ionic locus of the recognition site for glutamate of the uptake process. In addition, potassium inhibited the high-affinity [3H]L-glutamate uptake in hippocampal synaptosomes. These results provide an additional mechanism for the spreading of depression which accompanies seizure activity in the hippocampus.

Animals↗
PubMed1984

The esophagogastric polyp-fold complex.

A polyp-fold complex at the gastroesophageal junction is a rare finding. We made this diagnosis in a 51-year-old man who presented with abdominal discomfort after an episode of protracted vomiting. The esophagogastric polyp-fold complex is not always associated with reflux esophagitis, as was originally proposed.

Diagnosis, Differential↗
PubMed1983

Irreversibility and time course of calcium stimulated [3H]glutamate binding to rat hippocampal membranes.

Previous studies have indicated that calcium ions induce an irreversible increase of [3H]glutamate binding to rat hippocampal membranes. The present study was intended to provide an estimate of the time-course for this effect. The calcium chelator EGTA and the proteinase inhibitor leupeptin were introduced at various times during the incubation of hippocampal membranes with calcium and the binding of [3H]glutamate subsequently assayed. Both compounds totally blocked the calcium-induced increase in binding when added at the beginning of the incubation period but produced progressively less inhibition when added after longer delays. This method indicates that calcium produces its maximal effect between 5 and 10 min of incubation, a time-course compatible with the hypothesis that calcium stimulates a membrane-bound proteinase which results in the unmasking of [3H]glutamate binding sites.

Animals↗
PubMed1983

Classification and properties of acidic amino acid receptors in hippocampus. III. Supersensitivity during the postnatal period and following denervation.

The effects of excitatory amino acids on 22Na efflux rate in rat hippocampal slices were determined at various postnatal days and following removal of a major afferent system. Two weeks after a unilateral hippocampal aspiration, the 22Na efflux induced by potassium ions, D-glutamate, N-methylaspartate, and kainate is significantly decreased in the contralateral intact hippocampus whereas the effect of L-glutamate is substantially increased. Analysis of concentration-response curves suggests that the increased responsiveness to L-glutamate is due to an increase in the maximal effect rather than to changes in the half-maximal concentration for the amino acid. Partial denervation does not detectably change efflux elicited by D,L-homocysteic acid nor does it modify the properties of [3H]glutamate binding to hippocampal membranes. The effects of potassium ions, N-methylaspartate, and kainate but not of D,L-homocysteate are significantly decreased in slices incubated in the absence of calcium. All of the amino acids tested are considerably more potent in slices prepared from 11-day-old rats than in those from adult rats; the differences in responsiveness reflect an increase in maximal effect without changes in the half-maximal concentration. The responses to L-glutamate and D,L-homocysteate decline steadily between postnatal days 11 and 30, at which time adult values are reached. Together, the results from the denervation and development studies suggest a different localization and different modes of regulation for various classes of excitatory amino acid receptors.

Aging↗
PubMed1983

Classification and properties of acidic amino acid receptors in hippocampus. II. Biochemical studies using a sodium efflux assay.

The properties of excitatory amino acid receptors in hippocampal slices were analyzed using agonist-induced stimulation of 22Na efflux rate. Several amino acids (L- and D-glutamate, N-methylaspartate) produce progressively smaller responses upon successive applications, whereas D,L-homocysteate does not. Several lines of evidence suggest that depletion of an intracellular pool of 22Na is not responsible for the apparent desensitization. Addition of the amino acids in the presence of an antagonist does not affect the response of the slices to subsequent applications, indicating that desensitization is dependent upon the interaction of the agonist with its receptor. The antagonist D-alpha-aminoadipate discriminates between various excitatory amino acids, completely blocking the responses to N-methylaspartate, D-glutamate, and D,L-homocysteate; partially antagonizing those of quisqualate and kainate; and being without effect on L-glutamate. The order of potency of several excitatory amino acids on the stimulation of 22Na efflux rate in hippocampal slices is highly correlated with their relative effects measured with electrophysiological techniques, but does not correlate with their relative potencies to inhibit [3H]glutamate binding to hippocampal membranes. The similarities in the properties of excitatory amino acid receptors evidenced with the 22Na efflux assay or with the electrophysiological approach in the in vitro hippocampal slice preparation indicate that the same receptors are sampled by the two techniques. The results are discussed in terms of a classification of these receptors into four different groups: a synaptic receptor, activated by D,L-homocysteate (tentatively defined as a G1 receptor), an extrasynaptic glutamate receptor (defined as a G2 receptor), an N-methylaspartate receptor, and a kainate receptor.

2-Aminoadipic Acid↗
PubMed1982

Lymphatic and transcapillary forces in patients with edema following operation for lower limb atherosclerosis.

Intralymphatic end pressure and Starling pressures (interstitial fluid pressure (Pif), plasma and interstitial fluid colloid osmotic pressures (COPpl and COPif)) were measured in leg subcutaneous tissue in 5 patients with local leg edema following femoropopliteal reconstruction for lower limb atherosclerosis. Superficial lymphatics were cannulated proximal to the ankle and the catheter was connected to either syringes for determination of lymph flow and colloid osmotic pressure (COPl), or to a pressure transducer for measurement of intralymphatic end pressure. Samples of interstitial fluid were collected by implantation of nylon wicks and Pif was measured by the "wick-in-needle" technique. In all patients normal end pressure waves with maximum values ranging between 30 and 40 mmHg were recorded, indicating that the ischemia prior to surgery had not significantly affected the intrinsic mechanism for lymph propulsion. COPif of the operated leg averaged 5.7 mmHg +/- 1.0 which was 0.9 mmHg +/- 0.7 higher than the corresponding COPl. This supports the theory of "preferential channels" between the capillaries and the lymphatics. There was a statistically significant correlation between lymph flow and estimated capillary pressure (reabsorption pressure), capillary filtration coefficient, calf blood flow and Pif. According to this study the capillary pressure should at least be 11 mmHg before production of lymph occurs.

Aged↗
PubMed1981

Hemodynamic properties of St. Jude medical and Björk-Shiley valvular prostheses in mitral position in the pulse duplicator.

A general lack of standardization of the pre-clinical testing of artificial valves leads to an actual comparison of different prosthetic models at the time of a first clinical trial, frequently with contradictory results. Therefore, a pulse duplicator was developed in order to compare different valves of comparable size under identical standardized conditions in aortic and mitral positions. Comparison of Björk-Shiley and St. Jude medical prostheses in the duplicator revealed a linear relationship between pump setting and stroke volume delivered (r less than or equal to 0.9) for both valves. Pressure loss across the mitral valves showed a linear relationship to stroke volume (less than or equal to 0.9) and frequency (less than or equal to 0.9). The gradient, expressed per milliliter stroke volume, for identical frequencies appeared as the simplest and most suitable parameter for comparison of the hydraulic function of different valves. Using this parameter, the valves showed individual differences over a wide physiological range of testing. The differences, however, are of a magnitude that can hardly be detected under clinical testing conditions.

Aortic Valve↗