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Biomedical subjects

J Seifert

Publications and source records attributed to J Seifert.

At least 73 records · Page 4Linked to original sources
PubMed1991

The effect of lentinan on proliferative processes in parenchymal organs of rats--I. The effect on pyrimidine and nucleic acid syntheses.

The present study investigated the effect of Lentinan on the biochemical events associated with the pyrimidine and nucleic acid syntheses in the liver, kidney, thymus and spleen of rats. Lentinan was used at a dose of 4 mg/kg/day (twice) and in a single dose of 20 mg/kg. The following changes were observed. (1) The utilization of (14C)orotic acid for the synthesis of uridine components of liver acid-soluble extract and RNA uracil was activated after the administration of both doses of the drug. The specific activity of cytidine components of the acid-soluble extract and RNA were, on the other hand, not affected. The same holds true for the kidney. The ratio of the specific activity of cytidine:uridine components of the acid soluble extract as well as RNA decreased after the administration of both doses of the drug. The specific activity of DNA cytosine and thymine are slightly suppressed in the liver after the administration of a high dose of Lentinan; no effect was observed in the kidney. (2) The uptake of (14C)cytidine by the liver was not affected; the specific activity of DNA cytosine and thymine were increased after the administration of a high dose of Lentinan. (3) The uptake of (14C)thymidine by the liver was not affected; the specific activity of liver DNA thymine was increased after the administration of both doses of the drug. In the thymus an increase of specific activity of DNA thymine has also been observed. (4) Repeated doses of the drug (4 mg/kg for 6 consecutive days) increased the weight of the spleen. The specific activity of DNA thymine of the liver and spleen were significantly increased.

Animals↗
PubMed1991

The mechanisms of stone disintegration by shock waves.

Through interpretation of high-speed films at 10,000 frames per second of shock wave action on kidney stones and gallstones, the mechanism of stone destruction was analyzed in detail. This shows that the interaction of the shock wave with the targets firstly produces fissures in the stone material. Liquid then enters these small cracks. The actual disintegration is caused later by the enormous violence of imploding cavitation bubbles within these small split lines. That cavitation acts inside the stone and causes fragmentation even within the human gallbladder could furthermore be demonstrated by using scanning electron microscopy. These results should lead to a different process in gallstone lithotripsy leaving intervals between the shock wave treatments. This will allow the viscous bile fluids to occupy the fissures of the stones more completely and, therefore, should increase the cavitational activity on the subsequent treatment with shock pulses.

Cholelithiasis↗
PubMed1991

tert-Butylbicycloortho[3H]benzoate (3H-TBOB) toxicokinetics and disposition in rats.

1. Toxicokinetics of tert-butylbicycloortho[3H]benzoate (3H-TBOB) administered into the right atrium of rat heart can be described by the biexponential equation: ct = Ae-1.6t + Be-0.013t. 2. The fast initial phase of 3H-TBOB decline in blood (t1/2 = 0.5 min) is due to its absorption by lungs. 3H-TBOB is then transferred into liver, the primary organ of its metabolic detoxication. The high apparent distribution volumes for 3H-TBOB (1.3 and 7.1 l/kg for the initial and the terminal phase, respectively) are probably due to its lipophilicity and partitioning into lipoid tissue membranes. 3. Acid-labile TBOB is not completely hydrolysed in gastric fluid. A portion of 3H-TBOB administered into the stomach is absorbed within 3 min into the circulatory system. 4. Intra-arterially administered 3H-TBOB distributes in the brain in a lateral and regional pattern. 5. Two types of 3H-TBOB metabolites are excreted in urine and faeces. Both are more polar than the parent compound. The major components of the fraction were tentatively identified as hippuric and benzoic acid.

Animals↗
PubMed1990

Effect of 3,7-bis-(4-trifluoromethylphenyl)-1,5,3,7-dioxadiazocane on pyrimidine and DNA synthesis in rat organs.

The administration of the lipophilic 3,7-bis-(4-trifluoromethylphenyl)- 1,5,3,7-dioxadiazocane (TFMPD) to rats induced the following effects on the biosynthesis of DNA in the liver, kidney, thymus and spleen: (a) The utilization of [3H]thymidine for the synthesis of liver DNA thymine was decreased after the administration of a single dose of the drug. The depression of the specific activities of DNA pyrimidines of liver DNA in experimental groups was observed also after an injection of [14C]orotic acid. (b) A decreased incorporation of labeled thymidine had occurred also in the spleen during the prereplicative period. Thereafter the specific activity of DNA thymine was higher than in the control group. (c) The observed mitogenic response in the spleen showed a protracted effect; after the administration of a single dose of the drug the specific activity of DNA thymine as well as the thymidine kinase activity of spleen cytosol have been rising up to the ninth day. The same holds true for DNA thymine of the thymus; the activity of thymidine kinase was not affected. (d) Both the single and repeated doses of TFMPD had no marked effect on the levels of microsomal cytochromes P-450 and b5 in the liver and kidney.

Administration, Oral↗
PubMed1990

[Distribution of radioactively labeled digitalis in the eye].

Twenty-four hours after instillation of radioactively labeled digoxin into the conjunctival sac the radioactivity is concentrated in the various ocular tissues. A fourfold enrichment was observed in highly vascularized tissues such as the iris, ciliary body, and retina, as opposed to tissues with minimal vascularization such as the sclera. No concentration of digoxin was observed in the untreated control eye. Only in the sclerae was there a slight enrichment, corresponding to that found in the blood. Values in the untreated control tissues (skeletal muscle and skin) were minimal. These experiments show that the retina, ciliary body, and iris have a selective affinity for locally administered digoxin.

Animals↗
PubMed1990

[Cooperation between experimental and clinical surgery--from the experimental viewpoint].

Experimental surgery in german various forms of organisation and different aims as regards cooperation between experimental and clinical surgery. The best and most effective form is that of an institute with good personnel, adequate finances and sufficient space. An essential prerequisite for good cooperation between experimental and clinical surgeons is that the scientific aims be initiated by both. Success is possible only, if continuity can be guaranteed over a longer period. This is possible only in well established institutes of experimental surgery.

Germany↗
PubMed1990

Expression of the E. coli nadB gene and characterization of the gene product L-aspartate oxidase.

Quinolinic acid is synthesized in E. coli by the enzymes L-aspartate oxidase and quinolinate synthase A, the genes of which are named nadB and nadA. In our previous work we cloned and characterized the two genes (Flachmann, R., Kunz, N., Seifert, J., Gütlich, M., Wientjes, F.J., Läufer, A. & Gassen, H.G. (1988) Eur. J. Biochem. 175, 221-228). Here we report on the expression of the nadB gene under control of the inducible left promoter of the bacteriophage lambda. The yield of the active gene product L-aspartate oxidase was enhanced up to 20% of the soluble cell protein. The enzyme was purified to homogeneity in a three-step procedure and the reading frame of the L-aspartate oxidase gene was confirmed by Edman degradation of five cyanogen bromide peptides. L-Aspartate oxidase shows no classical Michaelis-Menten behaviour but is subject to a substrate inactivation. The apparent Km values were different for substrate concentrations below and above 1mM and were determined to 0.5 mM and 4.1mM, respectively. The active form of the enzyme is a monomer of 60,284 Da and contains one molecule of FAD and nine cysteine residues, four of which built up two disulfide bonds. The isoelectric point of the protein was determined to be at pH 5.6. Chemical modifications of the enzyme showed that at least one tyrosine and one histidine residue are essential for enzyme activity. The coenzyme-binding domain is located in the amino-terminal part of the polypeptide chain as revealed by a sequence comparison to other dinucleotide binding enzymes. Furthermore, there is evidence for a relationship to fumarate reductase and succinate dehydrogenase of E. coli.

Amino Acid Oxidoreductases↗
PubMed1990

[Experimental animal studies of the stability of colon anastomoses after supplementary fibrin glue sealing].

Sutures of the colon can be insufficient or leaking. This leads in some cases to a peritonitis or sepsis sometimes with lethal outcome. Therefore experiments in animals were performed to investigate the effect of additional applied biogenic glue. Especially in the beginning of the wound healing, at the 4th postoperative day, the firmness could be improved by fibrin glue. The bursting pressure of fibrin glue sealed colon sutures was 94 mmHg, whereas only 66 mmHg was observed in the control group. This additional firmness remains over the whole observation time of 3 weeks. An intensified proliferation of the connective tissue is responsible for this observation which could be substantiated by histological investigations and by measuring the thickness of the scar. If biogenic glue is used in animals it can have the consequence that the recipient reacts with the production of antibodies, since the components of the glue are proteins from different species. Investigations of the serum of animals which had been treated with fibrin glue revealed in a part of them precipitating antibodies against fibrinogen. With regard to this observation a second application of biogenic glue must be done with the necessary precaution.

Anastomosis, Surgical↗
PubMed1990

[Is brain death actually death?].

The paper rejects "brain death" as a new criterion, or definition, of actual death. The main theses are two: 1. Brain death as such--in any of its meanings--is not man's death and this can be proven by means of many cogent and some plausible arguments. 2. Even if the theoretical arguments against the identification of man's actual death with brain death did not demonstrate their non-identity, the opposite position would still be uncertain, at least. In view of this undeniable fact, a minimal ethical responsibility demands that we must not act, by organ retrievals, on the assumption of the identity of "brain death"--in any of its meanings--with man's actual death. We must avoid those actions which, like killing, presuppose a high degree of moral certainty concerning death, given that we cannot attain such certainty, as in the case of brain death. Thus organ and heart-explantations are found to be unethical. A newly thought out notion of biological death of the human organism as a whole ("clinical death" as irreversible cessation of all vital bodily functions, in particular of cardiopulmonary and cerebral functions) is proposed as theoretically best founded and ethically safest medical criterion of death.

Brain Death↗
PubMed1990

Rapid insorption of small particles in the gut.

Little is known about the uptake of small particles by the epithelium of the gastrointestinal tract. In our study, we investigated the absorption and transport of synthetic and natural particles by means of scanning electron microscopy (SEM). In Wistar rats, closed loops of jejunum with intact mesenteric blood supply were established in ether anesthesia so that we might study the absorption of latex particles of different sizes. After variable absorption times, loops were removed and prepared for examination by microscopic techniques. The average surface of M-cells was 35 +/- 2 microns2, whereas the total number was dependent on follicle size. The proportion of M-cells to absorptive-like enterocytes on follicle epithelium was 1:12. Latex particles were found easily on the surface of M-cells, and for the most part they were surrounded by microfolds. In only 10 min from the time of application, latex beads were concentrated or even included within macrophages of the dome of lymph follicles. The results indicate that primary insorption of small particles occurs in M-cells of Peyer's patches, and time of insorption is dependent on particle size.

Animals↗
PubMed1990

The effect of cyclosporine A on renal and hepatic microsomal mixed function oxidase systems in rats.

The effect of cyclosporine A (CsA), the immunosuppressant used in transplantation and also in the treatment of some autoimmune diseases, on the microsomal mixed function oxidase (MFO) systems in rat kidney and liver was studied. Since CsA given intragastrically (50 mg/kg/day) for three consecutive days decreased body, liver and kidney weights, in rats, the results were compared not only with the control untreated animals but also with the group of fully starved rats. In the liver the cytochrome P-450 level and aniline-hydroxylase activity were slightly higher than in the control rats but not as high as in the fully starved animals. This suggests that in the liver the effect might be the result of the antagonism between the CsA action and partial starvation of the CsA-treated animals. On the other hand, in the kidney the cytochrome P-450 level was as high as in the fully starved animals and the aniline-hydroxylase activity was significantly increased as compared to both the control and fully starved animals. Thus, in the kidney the microsomal MFO system seems to be induced after short-term CsA treatment. The activities of aminopyrine-N-demethylase and the levels of cytochrome bs did not change significantly after CsA treatment in both organs.

Animals↗
PubMed1989

[New aspects of the diagnosis of pancreatic cancer by determination of granulocyte elastase].

Elastase determination via elastase-alpha 1-antitrypsin-complex is recommended for the prognosis of septic infections. Since it is described that elastase values are increased in the serum of tumor patients it was the aim of the investigations to test elastase in the serum of different surgical tumor patients postoperatively. For comparison patients with septic complications as well as patients without any postoperative complication were also tested. It could be shown that in septic patients elastase values are markedly increased. They were measured at 390 ng/ml in mean, whereas patients without complications after operation had only values of 229 ng/ml. Elastase values in tumor patients were only slightly increased (290 ng/ml). It was, however, generally noticed that patients with pancreas head carcinoma showed regularly markedly increased elastase values (375 ng/ml). From this it was concluded that the determination of elastase values in tumor patients gives no reliable information except in patients with pancreas head carcinoma. In these patients the determination of the elastase could be helpful especially because the normal enzyme diagnosis is often misleading.

Female↗
PubMed1989

Alterations of pyrimidine and nucleic acid synthesis during adaptive growth of liver induced by nafenopin, a peroxisome proliferator. An in vivo study.

The de novo synthesis of pyrimidine nucleotides in the rat liver after administration of nafenopin (NFP) was studied with the aid of [14C]orotic acid; the utilization of preformed nucleosides (salvage pathways) was followed using the [14C]cytidine and [14C]thymidine. A single dose (400 mg/kg) as well as repeated doses (100 mg/kg/day) of NFP increased the concentration of the cytidine and uridine components of the acid-soluble extract (ASE) of rat liver. Increase in the concentration of the cytidine components preceded the increase in the uridine components. The uptake of [14C]cytidine by the liver of rats that had been given a single dose of NFP was observed 24 h after the administration of the drug and a decrease followed after this period. The specific activity of RNA and DNA cytosine paralleled the changes of the specific activity of ASE. A single dose of NFP had no marked effect on the uptake of [14C]orotic acid. The specific activity of the uridine components of ASE remained unaltered for 2 days. After this period it decreased because of an increase in the amount of the soluble uridine components. A mild drop of the specific activity of cytidine components of ASE occurred on the second day, the total radioactivity of cytidine components increased 24 h after the administration of NFP. The specific activity of DNA pyrimidines was markedly increased 24 h after administration of the drug. On the fourth day the specific activity of DNA cytosine in the experimental group was the same as in the control group, whereas the activity of DNA thymine was lower. Following repeated administration of NFP (100 mg/kg/day) a decreased uptake of [14C]orotic acid was observed; its utilization for the synthesis of the uridine components of ASE, expressed as total radioactivity of soluble uridine components, was continuously suppressed. No changes in the specific activity of cytidine components were observed. The specific activity of DNA cytosine and thymine was distributed unevenly. During later periods of the drug action the specific activity of cytosine increased whereas the activity of thymine was lower. This phenomenon may be accounted for by the formation of a thymidylate precursor, dUMP, directly from uridine phosphates.

Animals↗
PubMed1989

[Types of equipment, technical developments and peculiarities of extracorporeal lithotripsy--problems in locating the calculus].

Three methods are used for the extracorporeal distintegration of gallstones and kidney stones. Shock waves can be generated by an underwater spark, the discharge of piezoelectric crystals, or electromagnetic waves. The shock waves must then be focussed to disintegrate the stones. Depending on how they are generated the focus of the shock waves is like a dot or an ellipsoid. In most cases the stones can be localized by ultrasound. X-ray localization should also be possible.

Cholelithiasis↗
PubMed1988

Molecular biology of pyridine nucleotide biosynthesis in Escherichia coli. Cloning and characterization of quinolinate synthesis genes nadA and nadB.

The two genes, nadA and nadB, responsible for quinolinate biosynthesis from aspartate and dihydroxyacetone phosphate in Escherichia coli were cloned and characterized. Quinolinate (pyridine-2,3-dicarboxylate) is the biosynthetic precursor of the pyridine ring of NAD. Gene nadA was identified by complementation in three different nadA mutant strains. Sequence analysis provided an 840-bp open reading frame coding for a 31,555-Da protein. Gene nadB was identified by complementation in a nadB mutant strain and by the L-aspartate oxidase activity of its gene product. Sequence analysis showed a 1620-bp open reading frame coding for a 60,306-Da protein. For both genes, promoter regions and ribosomal binding sites were assigned by comparison to consensus sequences. The nadB gene product, L-aspartate oxidase, was purified to homogeneity and the N-terminal sequence of 19 amino acids was determined. The enzyme was shown to be specific for L-aspartate. High-copy-number vectors, carrying either gene nadA, nadB or nadA + nadB, increased quinolinate production 1.5-fold, 2.0-fold and 15-fold respectively. Both gene products seem to be equally rate-limiting in quinolinate synthesis.

Amino Acid Oxidoreductases↗