Biomedical subjects
Publications and source records attributed to M Weiss.
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A convenient method for purifying RNA tumor viruses is described. Viruses banded in isopycnic gradients are contaminated with membranes that can be removed by velocity sedimentation in glycerol gradients. On sodium dodecyl sulfate (SDS) gel electrophoresis, the particles purified by these procedures from mouse mammary tumor tissue show protein profiles typical of those observed with virus purified from milk.
By employing the theory of biological similarity, equations concerning the dependence of the clearance on the body weight are being presented for different elimination processes. Changes in the biological half-life depending on the body weight are demonstrated by way of the one and two compartment model. The discussion of the results based on our own data as well as those derived from literature shows that it is very ofter possible to estimate the weight-depending differences between half-lives of various species by simple empirical formulas.
Heparin cofactor activity as measured by an amidolytic method has been investigated in 48 patients undergoing cardiac surgery with extra-corporeal circulation (E.C.C.). Heparin cofactor activity is reduced soon after the start of E.C.C., due to hemodilution but it returns towards initial levels at the completion of the procedure and 3 hours later. Thus heparin cofactor does not seem to play a role in the heparin rebound phenomenon. In our patients bubble oxygenators did not modify heparin cofactor activity more than did membrane oxygenators.
Our previous work demonstrated that electric vagal stimulation in conjunction with Congo red as a dye-indicator is the faster and more reliable method for delineating the corpus-antral boundary in rats. Based on this finding, our study was extended to a larger animal model, the dog; this study proved the electrical vagal stimulation along with Congo red is a reliable method for adequate demonstration of this corpus-antral boundary. No untoward effect on the cardiac function was observed during stimulation of subdiaphragmatic portion of vagal trunks.
A study of two-stage pulmonary autotransplantation was performed on 29 dogs; 12 dogs died after the first stage, which was always a right lung reimplantation, and 17 dogs underwent the second stage after varying intervals of time. In the group of six dogs operated upon with very short intervals between stages (2 to 8 days) there were no survivors. There were seven long-term survivors in the subgroup with an interval longer than 4 weeks, and they constitute the largest published series obtained with this particular procedure. The interval between operative stages was the only significant controlled variable, as only minor technical or operative differences were allowed to occur. Ischemia times of the lungs were usually quite short. The surviving animals were utilized for studies of the regeneration of the afferent pulmonary nerves (Hering-Breure reflex and effects of capsaicin) as permitted by a long follow-up period of up to 3 years.
A survey is given on the most important theoretical methods which are necessary for the analysis of pharmacokinetic data in clinic and experiment. According to their importance in practice the stress is on the description of the analysis of linear pharmacokinetic systems. Issuing from the general multicompartment theory the one- and two-compartment models important in clinic are dealt with more in detail. The problems of the model identification in models with three and more compartments are explained. With the help of the example of the one-compartment model the authors deal with the problems of the non-linear kinetics, which may appear in drugs with high plasma concentration. Summarizing are finally some hints given at the use of these theoretical methods in practice.
For the first time, it has been possible to solubilize a significant amount of heart valve collagen from 6 month old pigs by pepsin treatment. Chromatographic and electrophoretic analysis of this pepsin-soluble collagen gives evidence for the presence of two types of collagen molecules: type I collagen and another type which has properties similar to those of type III collagen. For example, this collagen, present as a gamma component, gives rise, when reduced by dithiothreitol, to two bands by SDS-acrylamide gel electrophoresis: a beta band and an alpha band. Furthermore, the collagenic web of this tissue is highly polymerized, which explains the inability to solubilize all of the collagen molecules and the presence of high-molecular-weight molecules in the pepsin-soluble fractions.
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Explore the source record for details and available documents.
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Explore the source record for details and available documents.
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The study of collagen fibers by X-ray diffraction, utilizing semiquantitative indices for appraisal of "structuration" and "orientation" was applied to 30 aortic valve grafts. These grafts, of pig origin, were studied in the fresh state, after tanning with aldehydes, and after having been implanted in patients for at least 18 months. It was shown that the collagen fibers are preferentially orientated parallel to the transverse axis of the valve cusps, and that this arrangement, enhanced by tanning, had a tendency to disappear in the post-implantation samples. The structuration index which concerns the fibril network was also augmented by tanning, and was found a little high or slightly diminished in post-implantation cusps. Evidence for a new compound, probably fibrin, was found in the diffraction patterns of implanted cusps, but crystallized calcium was noticeably absent.
In 10 patients with hepatic cirrhosis of various etiology both the insorption and the volume of distribution of tritiated water are determined. Indicator for the velocity of insorption is the time interval between the oral application of 200 mu-Ci THO distributed in 100 ml tap water and the appearance of a peak concentration of the isotope in the serum. In comparison with normal controls the insorption of THO is protracted in patients with hepatic cirrhosis from 37.0 plus or minus 4.4 min (S.E.) to a mean of 69.0 plus or minus 29.6 min. Individually the "insorption time" can be quite normal. The prolongation of the process of insorption is independent of the apparent volume of distribution of THO or of the etiology of hepatic cirrhosis. In the early phases of the insorption which are characterized by the main increase of the radioactivity in serum there is no difference between patients with hepatic cirrhosis and normal controls. Although an alteration of body fluid metabolism can not be excluded as a source of the prolonged equilibration, it is suggested that changes of the intestinal blood flow, of the tissue pressure and of the colloidosmotic pressure are due to a disturbance of the insorption of tritiated water in patients with hepatic cirrhosis.
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