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Biomedical subjects

K Kramer

Publications and source records attributed to K Kramer.

At least 127 records · Page 7Linked to original sources
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↗
PubMed1979

Immunization of experimental monkeys against Plasmodium falciparum: use of synthetic adjuvants.

The replacement of Freund's adjuvant by a possible safe adjuvant for effective immunization of owl monkeys (Aotus trivirgatus griseimembra) against a human malaria parasite, Plasmodium falciparum, has been investigated. Experiments involved the use of two synthetic adjuvants: MDP (N-acetylmuramyl-L-alanyl-D-isoglutamine) and stearoyl-MDP (6-O-stearoyl-N-acetylmuramyl-L-alanyl-D-isoglutamine). In both cases, P. falciparum merozoites obtained through short-term in vitro cultivation were used as antigen. MPD was used as adjuvant in 5 owl monkeys; 2 control monkeys died and of the 3 experimental monkeys only 1 survived. In contrast, in another experiment where stearoyl-MDP was used as adjuvant, there was 100% protection of 4 immunized monkeys against a challenge with the homologous strain of P. falciparum. The results of the second experiment are encouraging for the development of an effective and safe vaccine for human malaria.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1979

In vitro production and partial purification of Plasmodium falciparum antigen.

A simple technique for achieving high yields of Plasmodium falciparum parasites on a continuous basis is described. The technique is applicable in any laboratory. The culture apparatus is also simple and inexpensive and allows multiple cultures to be run simultaneously. A total of approximately 1-2 x 10(9) parasites can be harvested per culture flask per week requiring the use of only 40.0 ml of culture medium (RPMI 1640), 5.0 ml of human sera, and 2.0 ml of outdated human whole blood. P. falciparum parasites (segmenters containing individual merozoites) are cultured in vitro and concentrated 10-15 fold through the use of discontinuous bovine serum albumin gradient centrifugation.Commercial saponin is purified on a Sephadex G-25 column. The haemolytic effect of purified saponin related to human red blood cell concentration is studied. Preliminary observations on the action of some synthetic detergents and enzymes on human erythrocytes are also reported. Purified saponin is used to lyse red blood cells infected with in vitro cultured P. falciparum for the preparation of merozoite antigen. Further purification of parasite material is carried out by sucrose density gradient centrifugation.

Animals↗
PubMed1978

Vaccination of experimental monkeys against Plasmodium falciparum: a possible safe adjuvant.

Owl monkeys (Aotus trivirgatus griseimembra) were effectively immunized against a human malaria parasite, Plasmodium falciparum. Two injections of antigen, primarily mature segmenters with fully developed merozoites, mixed with adjuvant (6-O-stearoyl-N-acetylmuramyl-L-alanyl-D-isoglutamine and liposomes) were administered intramuscularly at a 4-week interval. Approximately 2 weeks after the second vaccination, the monkeys were challenged with the homologous strain of P. falciparum. All immunized monkeys survived the challenge. The substitution of Freund's complete adjuvant is an encouraging step toward the development of an effective and safe vaccine for human malaria.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1978

Partial protection of Plasmodium falciparum-vaccinated Aotus trivirgatus against a challenge of a heterologous strain.

Two Aotus trivirgatus griseimenbra monkeys which had been immunized with the merozoite-enriched FUP strain of Plasmodium falciparum were protected against a primary challenge with the homologous strain. The results described here show that these two monkeys were protected against a subsequent challenge with a heterologous strain (FVO) of P. falciparum. The unimmunized control monkey died of FVO infection by day 18.

Animals↗
PubMed1977

Studies on the suitability of a cyanine dye (Viher-Test) for indicator dilution technique and its application to the measurement of pulmonary artery and aortic flow.

The spectrum of a cyanine compound [Viher-Test (VT)] was recorded in distilled water, 5% glucose, 0.9% NaCl. The absorption maximum of these solutions was at 760 nm; after adding to plasma or blood the maximum was shifted to 785 nm. The time required for this spectral stabilization was less than 1 s at 37 degrees C for VT in H2O or glucose, it was slowed to 7 s at room temperature, and for VT in NaCl it was more than 30 s at 37 degrees C. VT binds to plasma proteins to at least 95%. The absorbance of VT in H2O (1000 mg/l) decreased by 1.0% per hour. Toxicity (LD50) of VT in H2O given i.v. in mice was 115 mg/kg body weight. Dye dilution determination of the flow in an artificial circulation with VT was within +/- 5% of direct measurements. Data indicate that VT is as suitable as Cardiogreen for indicator dilution technique using cuvette densitometer or reflection photometry. Simultaneous determinations of pulmonary artery and aortic flow from one dye bolus showed no significant difference on the average, but pulmonary artery flow diverged by up to +/- 25% from aortic flow due to incomplete mixing of dye and blood, respiratory changes of cardiac output or transient differences in right and left heart output.

Animals↗
PubMed1975

The quantitative distribution of gold in skin during chrysotherapy.

Gold concentrations in epidermis, dermis, and whole skin were measured by neutron activation analysis after formation of suction bullae in 8 patients who had received protracted cyrysotherapy. Epidermis contained 3% (median) of the gold content of whole skin. A direct correlation between cumulative gold dose and skin gold level was noted. These findings suggest that apparent gold concentrations in skin are influenced by the depth of the biopsy, that keratinous tissues have little affinity for gold, and that the gold storage capability of skin is not saturated by large cumulative doses of gold. The beneficial effect of gold in pemphigus may not be mediated at the site of blister formation.

Adult↗
PubMed1975

[Sodium and water balance in the dog under halothane and methoxyflurane anesthesia (author's transl)].

In our model of volume expanded dogs with an equilibrium between input and renal output of sodium and water halothane anesthesia (1,5 Vol.-% insp.) was performed. In deepening halothane anesthesia we found a progressive decrease of mean aortic pressure, GFR and renal sodium and water excretion. There was a strong correlation between GFR and sodium excretion. With a high GFR significantly more sodium was excreted under halothane, whilst reduction of GFR led to an overproportional decrease of sodium excretion. Urine osmolality, too, depended on GFR under halothane. The results of methoxyflurane anesthesia were quite similansion. Concentrations of inorganic fluoride in serum and urine, which we measured in these experiments, did not result in visible changes of sodium or water balance, compared with the conscious state.

Animals↗
PubMed1975

[Sodium and water balance and renal function in volume expanded dogs under neuroleptanalgesia (author's transl)].

In 8 volume expanded dogs with an equilibrium between input and renal output of sodium and water neuroleptanalgesia of 6 hours duration with a total of 9 mg/kg of droperidol and 0.35 mg/kg of fentanyl was performed. Under anaesthesia GFR was increased by about 10% (p less than 0,02) compared with the conscious state, whilst renal sodium and water excretion was reduced by about 50%. From this we conclude that active tubular transport of sodium is augmented under neuroleptanalgesia. Due to decreased excretion, retention of sodium and water increased during anaesthesia changes of functional ECFV tending into the same direction. Plasma volume and intravascular protein did not change under neuroleptanalgesia compared with the conscious state. Urine osmolality and negative free water clearance (TcH2O) increased by about 60% under droperidol and fentanyl. In volume expanded dogs under neuroleptanalgesia intravenous application of 0.5-1.0 mg of atropine resulted in a temporary water diuresis.

Animals↗
PubMed1975

[Sodium- and water balance in the dog in the conscious state and under nitrous-oxide and barbiturate anesthesia (author's transl)].

By a suitable pattern of saline infusion we established an equilibrium between input and renal output of sodium and water in the conscious animal, which was maintained for six hours. During this period of equilibrium we found an increase in GFR, plasma volume and functional ECFV of about 30% each, the amount of intravascular protein and albumin being unchanged. Under nitrous-oxide and thiopentone anaesthesia renal sodium and water excretion was unchanged compared with values of conscious animals. However there was a striking decrease in plasma volume as well as in circulating protein and albumin by approximately 20%. Similarly functional ECFV (sulphate space) was found to be reduced under thiopentone anaesthesia. Retention of sodium about 12 hours after the end of anesthesia amounted to 7% of the quantities infused (about 50 mval per animal), whilst the applied water load had been completely excreted.

Anesthesia↗