Search PubMed⌕ Search

Biomedical subjects

M Schmidt

Publications and source records attributed to M Schmidt.

At least 685 records · Page 38Linked to original sources
PubMed1990

Increase of DNA content in tissue stages of Entamoeba histolytica strain SFL 3.

The DNA content of culture forms and tissue stages of pathogenic E. histolytica strain SFL 3 were measured photometrically after the nuclei had been stained with the fluorochrome BAO. As a control, the DNA guartity of E. histolytica strain HK 9 and E. invadens were determined by the same method and compared with reference values. Tissue stages were obtained from hamsters experimentally infected by intrahepatic injection of SFL 3 amoebae. Further studies concerning possible changes in the DNA content of tissue stages involved the following methods: (a) isolation of tissue stages from the liver, followed by distinct suspension periods. (b) Infected liver pieces were directly transferred into culture medium; amoebae emigrating therefrom were cultivated. The study demonstrated that tissue stages contained up to 4 times more DNA than did culture forms. After 3 h cultivation, the DNA content of tissue stages decreased to the level of culture forms. Possible reasons for this change are discussed.

Amebiasis↗
PubMed1990

Behaviour problems and developmental status of 3-month-old infants in relation to organic and psychosocial risks.

In a prospective longitudinal study starting at birth 384 infants and their families were investigated. The subjects were distributed across the nine cells of a two-factorial design (3 x 3), factor 1 representing the degree of organic, factor 2 the degree of psychosocial risk. At age 3 months there was a significant influence of organic risk factors on all developmental parameters. Psychosocial risks were only relevant for cognitive development and behaviour problems. Organic high-risk children who adapted quickly after birth showed an especially good development status.

Asphyxia Neonatorum↗
PubMed1990

Allergens in Hymenoptera venom. XXII. Comparison of venoms from two species of imported fire ants, Solenopsis invicta and richteri.

Venoms were collected by electrical stimulation from the two major species of imported fire ants found in the United States, Solenopsis invicta (Sol i) and S. richteri (Sol r). Antigens similar to three of the four known Sol i venom proteins (I, II, III, and IV) were isolated from Sol r. The N-terminal amino acid sequences for the antigens III were identical; but those for the antigens II demonstrated only nine of 20 residues to be identical. Two monoclonal antibodies raised against Sol i II did not react to Sol r. No protein IV could be detected in Sol r by molecular weight, charge, or immunologically with either polyclonal mouse antibodies or five monoclonal antibodies. Both venoms were compared with a panel of 60 sera from Sol i-allergic individuals; mean bindings were similar with an r = 0.94 for linear regression. RAST inhibition was performed with 17 individual sera representing a variety of Sol i allergen specificities. Four sera were tested from patients resident in the Sol r endemic area and five sera from patients who experienced reactions to S. xyloni stings. All sera reacted comparably to both imported fire ant venoms. The two venoms appear to be allergenically similar, although antigen IV is absent from Sol r and the antigens II have significant sequence variation. Sol i venom appears to be sufficient for diagnostic purposes.

Allergens↗
PubMed1990

New polymorphic DNA marker close to the fragile site FRAXA.

DNA from a human-hamster hybrid cell line, 908-K1B17, containing a small terminal portion of the long arm of the human X chromosome as well as the pericentric region of 19q was used as starting material for the isolation of an X-chromosome-specific DNA segment, RN1 (DXS369), which identifies a XmnI RFLP. Linkage analysis in fragile X families resulted in a maximum lod score of 15.3 at a recombination fraction of 0.05 between RN1 and fra(X). Analysis of recombinations around the fra(X) and distal to DXS105. Analysis of the marker content of hybrid cell line 908K1B17 suggests the localization of RN1 between DXS98 and fra(X). Heterozygosity of DXS369 is approximately 50%, which extends the diagnostic potential of RFLP analysis in fragile X families significantly.

Animals↗
PubMed1990

Asynchronous replication of homologous loci on human active and inactive X chromosomes.

The two X chromosomes in mammalian females replicate asynchronously, the inactive later than the active one. Using BrdUrd-sensitive restriction and UV irradiation to identify newly synthesized DNA directly on Southern blots, and restriction fragment length differences to discriminate alleles on active and inactive human X chromosomes, we examined the replication of hypoxanthine phosphoribosyltransferase (HPRT) and clotting factor IX (F9) loci in clonal populations of mouse-human hybrids. We find that HPRT replicates at different times during the period of DNA synthesis (S phase), depending on its activity: It replicates in early S phase, when expressed (on the active X chromosome), and in late S phase when silent (on the inactive X chromosome). Furthermore, when reactivated, the derepressed locus is earlier replicating, supporting a relationship between replication and transcription. Neither F9 allele is expressed in these cells, and both replicate in the second half of S phase, (slightly earlier on active than on inactive X chromosome).

Alleles↗
PubMed1990

Molecular action of the l(2)gl tumor suppressor gene of Drosophila melanogaster.

Tumor suppressor genes act as recessive determinants of cancer. These genes contribute to the normal phenotype and are required for regulating cell growth and differentiation during development. Inactivation of tumor suppressor genes leads to an unrestricted pattern of growth in specific cell types. In Drosophila, a series of genes have been identified that cause tissue-specific tumors after mutation. Of these, the lethal(2)giant larvae (l(2)gl) gene is the best studied. Homozygous l(2)gl mutations cause the development of malignant tumors in the brain and the imaginal discs. Genomic DNA from the l(2)gl locus has been cloned, introduced back into the genome of l(2)gl-deficient animals, and shown to reinstate normal development. The nucleotide sequence of the l(2)gl gene has been determined, as well as the sequences of two classes of transcripts. Analysis of the spatial distribution of both l(2)gl transcripts and proteins revealed that during early embryogenesis the l(2)gl gene is uniformly expressed in all cells and tissues. In late embryos, the l(2)gl expression becomes gradually restricted to tissues presenting no morphological or neoplastic alteration in the mutant animals. Further mosaic experiments revealed that l(2)gl gene loss can cause three distinct phenotypes: neoplastic transformation, abnormal differentiation, and normal development. These phenotypes depend upon the extent of gene activity in the stem cells prior to the formation of l(2)gl- clones. These analyses indicate that the critical period for the establishment of tumorigenesis occurs during early embryogenesis at a time when the l(2)gl expression is most intense in all cells.

Animals↗
PubMed1990

Microbial metabolism of quinoline and related compounds. V. Degradation of 1H-4-oxoquinoline by Pseudomonas putida 33/1.

A bacterial strain was isolated with the ability to use 1H-4-oxoquinoline as the sole source of carbon, nitrogen and energy. On the basis of its physiological properties, this isolate was classified as Pseudomonas putida. 1H-3-Hydroxy-4-oxoquinoline, N-formylanthranilic acid, anthranilic acid and catechol were identified as intermediates in the degradation pathway. The latter was further degraded by ortho-cleavage. The enzymatic conversion of 1H-4-oxoquinoline into 1H-3-hydroxy-4-oxoquinoline requires oxygen and NADH. Experiments with 18O2 showed that the oxygen consumed in this enzymatic reaction is derived from the atmosphere.

Aerobiosis↗
PubMed1990

[Inhibitor hemophilia A--diagnostic and therapeutic significance of controlled substitutions with factor VIII].

10 haemophiliacs with constant low inhibitor levels to factor VIII (0.5-2.5 Bethesda units (BU) per ml) and 4 patients without antibodies were examined by a controlled substitution with factor VIII. We investigated the factor VIII in-vivo-recovery, the half disappearance time and the biological half-life. 4 different reaction patterns could be observed: 6 patients with antibodies showed the same recovery as those haemophiliacs without inhibitors but the half life was shorter. 2 inhibitor patients did not achieve the expected increments of factor VIII, but had normal half life. One patient had reduced recovery and shortened half life. Only in one patient (inhibitor levels 0.8-1.0 BU/ml) all parameters were in the normal range.

Adolescent↗
PubMed1990

Influence of sorbitol and mannitol on the reactions of kidney excretory function evoked by arterial chemoreceptor stimulation with almitrine in anaesthetized and artificially ventilated cats.

The reactions of renal hemodynamics, as well as of excretory and concentrating function (clearance-technique) in response to arterial chemoreceptor stimulation by almitrine bismesylate were studied in 3 groups of chloralosed, relaxed, and constantly ventilated cats. In 2 groups of chemoreceptor-intact animals an osmotic diuresis was induced by intravenous infusion of an isoionic solution containing equivalent amounts of either sorbitol or mannitol. Under similar conditions the 3rd series of experiments was carried out in cats under mannitol diuresis but with deafferented arterial chemoreceptors. The changes of mean arterial and central venous pressures as well as of the parameters of the arterial acid-base balance were similar in all groups of cats studied. The chemoreceptor-intact animals undergoing sorbitol diuresis did not show any natriuresis in response to the drug but reacted with a remarkable increase in their U/Posm and TCH2O/Cosm ratios. In contrast, the chemoreceptor-intact animals infused with mannitol in saline reacted to almitrine with a transient natriuresis but with only a weak increase in their U/Posm and TCH2O/Cosm ratios. The data suggest that arterial chemoreceptor stimulation inhibits proximal tubular sodium reabsorption. In the sorbitol-experiments during chemoreceptor stimulation the enhanced delivery of sodium by the proximal fluid was reabsorbed in the thick ascending limb of Henle's loop thus increasing medullary osmolality and renal concentrating ability. Mannitol apparently limited this additional sodium reabsorption in the thick ascending limb of Henle's loop; therefore in the mannitol-experiments during chemoreceptor stimulation a natriuresis but only relatively weak changes of renal concentrating function occurred. The data also suggest that a pharmacological chemoreceptor stimulation might support the recovery of renal excretory function post-anaesthetically, although the optimal solution infused to induce an osmotic diuresis remains to be determined.

Almitrine↗
PubMed1990

[Kininase II (SACE) and renin in sarcoidosis patients and healthy probands in exercise testing].

Over a period of three years, we investigated the behaviour of renin and kininase II in 26 patients with active, histologically confirmed sarcoidosis in comparison with healthy test subjects, during ergometer exercise. Renin activity was determined radioimmunologically, and kininase II by means of spectral photometry (Cushman-Lieberman method). In both groups, a significant increase in renin and kininase II during the course of exercise on the ergometer was observed, which, however, was more marked in the sarcoidosis group of patients. Furthermore, the activities of both enzymes were highly significantly elevated as compared with the group of healthy subjects in each individual phase of exercise. In addition--if we consider the average values of the two enzymes in each of the individual subjects--it would seem possible in most cases to correctly ascribe the person involved to the group healthy subjects or patients, in particular when the average values of renin and kininase II obtained as described above, are multiplied together.

Exercise Test↗
PubMed1990

[Pelvimetry using computerized tomography. I. Theoretical and methodical fundamentals].

The first part of our article deals with the basic aspects of using computed tomography in obstetrical pelvimetry. A macerated osseous female pelvis was used to measure the true conjugate, the transverse plane of the pelvic inlet, the interspinous line and the distance between the ischial tuberosities. The same pelvis was then examined computed tomographically. A lateral and a posterior-anterior scan, and a single scan through the iliac spines were performed. The results of the direct measurement agreed highly with the values achieved computed tomographically if the phantom was positioned exactly on the mid-line of the examination-table, if not, the true conjugate was elongated. Measurements of the superficial and the intravaginal radiation dose in patients demonstrated a significantly lower risk in computed tomography than in conventional x-ray methods. We recommend computed tomography in obstetrics as a safe, accurate and reliable method.

Female↗
PubMed1990

Protease inhibitors reduce lysosomal acid phospholipase A1 activity in cultured rat hepatocytes.

When rat hepatocytes were cultured in the presence of various specific protease inhibitors, lysosomal acid phospholipase A1 activity decreased progressively. Exposure of the cultured cells to 0.1 micrograms/ml of pepstatin, E 64, leupeptin or chymostatin also reduced the catalytic activities of several lysosomal marker enzymes. Irrespective of the protease inhibitor type employed, acid phospholipase A1 activity reacted most sensitively, followed by acid phosphatase, acid beta-N-acetyl-D-hexosaminidase and acid beta-glucuronidase. Of the protease inhibitors studied, pepstatin appeared to be most potent in reducing lysosomal enzyme activities in cultured hepatocytes. These findings suggest that proteolytic processes at as yet unknown, possibly extralysosomal sites play an important role in the turnover rates of lysosomal enzymes.

Animals↗
PubMed1990

[Proteolytic activities in bronchoalveolar lavage fluid in pneumonia and chronic bronchitis].

In 63 patients with chronic bronchitis, 61 patients with acute bacterial pneumonia, and in 11 control subjects, broncho-alveolar lavage fluid was investigated for its protease content. In smokers, we found the usual pronounced protease burden. As was expected, the two pathological groups also differed markedly on other points. In pneumonia, not only free elastase activity (from granulocytes (PMN] was markedly elevated, but also cathepsin-B-like activity (from alveolar macrophages (AM] was greatly increased, which would point up the important role of AM in this form of inflammatory. In this case of chronic bronchitis, function-analytically determinable obstruction parameters were associated with an increase in the elastase-like enzyme (from PMN), so that chronic obstructive bronchitis probably represents a special form of inflammation.

Bacterial Infections↗
PubMed1990

[The nerve entry into the human femoral quadriceps muscle].

Taking into account differing results about the distribution velocity of excitation processes in muscles after nerve stimulation we intended to prepare those branches of N. femoralis that were in close topographical relation to the caputs of M. quadriceps femoris. For reasons of interindividual comparability and of the possibility of studies in living human beings we decided to express the estimated "real entry height" as part of the total distance between Spina iliaca anterior superior and the proximal margin of the patella. In case of entering several nerve branches the same muscle the distance between the almost proximal and the almost distal branch was defined as the area of nerve entry. Our results give reason to suppose that there are great individual differences in the spatial organisation of innervation zones (motoric endplates). To further strengthen this idea investigation about the intramuscular route of the nerves as well as selective staining of motoric endplates are indispensable necessary.

Femoral Nerve↗
PubMed1990

Physical mapping of new DNA probes near the fragile X mutation (FRAXA) by using a panel of cell lines.

The fragile X syndrome is a very common disorder, but there has been little progress toward isolating the fragile X mutation (FRAXA). We describe a panel of 14 somatic cell hybrid lines, lymphoblastoid cell lines, and peripheral lymphocytes with X-chromosome translocation or deletion breakpoints near FRAXA. The locations of the breakpoints were defined with 16 established probes between pX45d (DXS100) and St14-1 (DXS52). Seven of the cell lines had breakpoints between the probes RN1 (DXS369) and U6.2 (DXS304), which flank FRAXA at distances of 3-5 centimorgans. The panel of cell lines was used to localize 16 new DNA probes in this region. Six of the probes-VK16, VK18, VK23, VK24, VK37, and VK47--detected loci near FRAXA, and it was possible to order both the X-chromosome breakpoints and the probes in relation to FRAXA. The order of probes and loci near FRAXA is cen-RN1,VK24-VK47-VK23-VK16,FRAXA-++ +VK21A-VK18-IDS-VK37-U6.2-qter. The breakpoints near FRAXA are sufficiently close together that probes localized with this panel can be linked on a large-scale restriction map by pulsed-field gel electrophoresis. This panel of cell lines will be valuable in rapidly localizing other probes near FRAXA.

Animals↗
PubMed1990

Genetics and evolution of chloroplast isozymes of triosephosphate isomerase.

Triosephosphate isomerase is an ubiquitous and highly conservative dimeric enzyme, consisting of subunits of Mr 26,000-27,000. Plants usually contain one cytosolic and one plastid isozyme. While 2x wheats also contain one plastid isozyme, 4x wheats contain 3, and 6x cultural wheats contain five plastid isozymes. The multiplicity of the isozyme pattern in 6x wheats is explainable by the presence of three different genomes (AABBDD), each contributing a distinct triosephosphate isomerase gene (alpha',beta,delta), and by the formation of homodimeric and heterodimeric isozyme forms. While the beta beta-form was, as expected, also found in Aegilops speltoides which is regarded as donor of the B genome, the descent of the other genes for plastid triosephosphate isomerase did not occur in accordance with common contentions on the evolution of 6x cultural wheat and its presumptive ancestors. In the reciprocal intergeneric hybrids between wheat and rye, Secalotricum and Triticale, the patterns of both the cytosolic and the plastid-specific triosephosphate isomerases were biparentally inherited, indicating also that the plastid isozyme was nuclear-encoded. Data which are available about amino acid sequences and gene organization and immunological observations show that the cytosolic triosephosphate isomerase of plants is strongly related to other eukaryotic animal triosephosphate isomerase genes. Multiple evidence has been presented that the plastid- specific isozyme represents a distinct polypeptide and is specified by a distinct gene, relative to the cytosolic isozyme. Immunological comparisons indicate that the plastid isozyme shares homologies with the cytosolic isozyme but is not related to the enzyme from prokaryotic cyanobacteria or bacteria. To enable a more precise comparison, plastid triosephosphate isomerase has been cloned from a cDNA library from rye, and cDNA clones are being sequenced. The plastid enzyme of triosephosphate isomerase appears to have evolved from a duplication on an ancestral nuclear gene of the primordial plant cell. For other plastid-specific isozymes evidence exists that their genes were incorporated into the nucleus by gene transfer from a prokaryotic endosymbiont.

Biological Evolution↗