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Biomedical subjects

T M Schroeder

Publications and source records attributed to T M Schroeder.

At least 19 recordsLinked to original sources
PubMed1996

Kinetics of aluminum-induced inhibition of delta-aminolevulinic acid dehydratase in vitro.

Anemia, one consequence of aluminum toxicity, may be due to inhibition of enzymes in the heme biosynthetic pathway. In this study, the in vitro effect of aluminum on rat liver and erythrocyte delta-aminolevulinic acid dehydratase (delta-ALA dehydratase), an enzyme that is sensitive to a number of metal ions, was investigated. The presence of 1-10 microM AlCl3 caused a concentration-dependent inhibition of liver delta-ALA dehydratase activity. The Ki for AlCl3-induced inhibition of delta-ALA dehydratase was 4.1 microM, and 10 microM AlCl3 virtually abolished delta-ALA dehydratase activity (99% inhibition). Erythrocyte delta-ALA dehydratase was also inhibited by similar concentrations of AlCl3 and displayed a Ki of 1.1 microM. AlCl3 (5 microM) decreased the Vmax by 50% but did not change the Km, suggestive of reversible, noncompetitive inhibition. Sodium citrate (50 microM) when added with AlCl3 completely restored delta-ALA dehydratase activity to basal levels. Thus, disruption of delta-ALA dehydratase occurred at low micromolar levels of AlCl3 in vitro, which may help to explain abnormalities in the heme pathway in cases of aluminum poisoning.

Aluminum↗
PubMed1985

Spontaneous 6-thioguanine-resistant lymphocytes in Fanconi anemia patients and their heterozygous parents.

The incidence of spontaneous 6-thioguanine-resistant (TGr) lymphocytes was studied in the peripheral blood collected from seven Fanconi anemia (FA) patients and five of their heterozygous parents using an autoradiographic or a lymphocyte cloning method. Five of the seven patients showed a significantly elevated incidence of TGr lymphocytes as compared to age- and sex-matched healthy controls. There was, however, no difference between FA heterozygotes and controls. These results suggest some variability among the patients similar to those reported in clinical and cytogenetic investigations. The basis for the increase in TGr cells in the patients is not known, but the inherent genomic instability reflected as increased frequencies of chromosomal aberrations is one possible explanation.

Adolescent↗
PubMed1982

Genetics, pathoanatomy and prenatal diagnosis of Potter I syndrome and other urogenital tract diseases.

We report on 12 early prenatal diagnoses of "Potter syndrome" and other severe fetal kidney diseases by ultrasonic observations of persistent oligohydramnios and absence of kidney function; seven pregnancies were terminated. These cases are discussed together with others observed in a total of 23 families. Special attention is given to the difficulty of classifying the various kidney diseases pathoanatomically, and also of determining the recurrence risk in the affected families. For genetic counselling, the possibility of early prenatal diagnosis is a practical solution to this problem. Routine ultrasound supervision of pregnancies can already detect a first, sporadic case of the various kidney diseases.

Abnormalities, Multiple↗
PubMed1982

Genetically determined chromosome instability syndromes.

Spontaneously increased chromosomal instability is well documented in the three autosomal recessive diseases, Fanconi's anemia (FA), Bloom's syndrome (BS), and ataxia telangiectasia (AT). Other conditions have been reported to be associated with chromosomal breakage. Some are still single observations: in Werner's syndrome only fibroblasts are affected, and systemic sclerosis may not be an inherited disease. Various aspects of FA, BS, and AT are discussed which have emerged since recent reviews have been published. The differential diagnosis in FA has become more important than it was in the past. Proven heterogeneity in FA demands definition of what to name FA and FA variants. The analysis of cancer frequencies and types in FA and AT lacks important clues. This should stimulate all of us to mutual exchange of data and creation of registries not only of patients and follow-ups, but also of characterized cell strains. A synopsis of results from cell and cytogenetic studies demonstrates similarities and differences in detail of the general phenomenon of chromosomal instability which FA, BS, and AT share. Results from biochemical studies at the DNA level together with cytogenetic findings indicate different but still undefined failures in DNA metabolism or DNA repair mechanisms due to the different genes. A new approach to analyzing the impairment of DNA repair in FA is briefly described. DNA related enzymes are produced in the cytoplasm and have to be transported to the nucleus. The subcellular distribution of topoisomerase activity was found to be unusual in three placentas of FA patients. Other DNA enzymes were distributed normally. Thus, a specific mechanism for movement of the enzyme through the nuclear membrane seems to be defective.

Anemia, Aplastic↗
PubMed1981

Quantitative and qualitative assay of amniotic-fluid acetylcholinesterase in the prenatal diagnosis of neural tube defects.

In 110 amniotic fluids the specific acetylcholinesterase was determined quantitatively and qualitatively. In the quantitative assay there were a considerable number of false positives and false negatives, although the mean value of the normal controls differed significantly from that of neural tube defect pregnancies. By the electrophoretic separation of acetylcholinesterase, however, all fluid samples with borderline alpha-fetoprotein levels or fetal blood contamination could be correctly classified. With the exception of one skin-covered spina bifida all neural tube defects in the second trimester could be identified by this method. The second fast-moving band characteristic of the specific acetylcholinesterase was also present in abdominal wall defects and intrauterine death.

Acetylcholinesterase↗
PubMed1980

[Genetic amniocentesis: technique and results in 1,000 first trimester amniocenteses (author's transl)].

The results of 1,000 transabdominal amniocenteses between 15 and 20 weeks gestation are reported. The method is described. The bio-chemical and cytogenetic results are reported. - Amniocentesis in the first trimester is not a routine investigation since fetal and maternal risks are associated with this procedure. The risk of abortion following amniocentesis was lowered from 6/1000 to 2/500 by improvement of the technique under ultra-sound control. The worst maternal complication observed was a septic abortion one day after amniocentesis. 96% of all cyto-genetic examinations showed normal karotypes. The largest group at risk were mothers over 35 years of age. In this group chromosome anomalies were found in 17 cases. All neural tube defects were found by determination of the alpha-fetoprotein in the amniotic fluid. 26 terminations of pregnancy for fetal indications were carried out. Two patients refused therapeutic abortions despite trisomy 21 for ethical reasons. One patient continues her pregnancy with a 47 XYZ pregnancy.

Abortion, Induced↗
PubMed1979

Mutagenic effects of isonicotinic acid hydracide in Fanconi's anemia.

Isonicotinic acid hydracide (INH) increases substantially the chromosomal instability in Fanconi's anemia (FA) cells. The same concentrations of INH do not significantly break chromosomes in heterozygous or normal cells. INH does not induce alkylation or cross-links in the DNA, like other mutagens known to increase breakage in FA cells. Possible mechanisms of the effect of INH are discussed. One consequence of this experiment is the possibility of an exact and doubtless prenatal diagnosis of a homozygous FA fetus.

Adolescent↗
PubMed1979

Fanconi's anemia: terminal leukemia and "Forme fruste" in one family.

Two adult sisters are described. One with a full clinical, hematological and cytogenetic picture of Fanconi's anemia died of monocytic leukemia. The other woman has several malformations and clinical signs which are found in Fanconi's anemia, but does not show any hematological disorder or sign of bone marrow insufficiency. Cytogenetic findings in this case are comparable to those typical cases with Fanconi's anemia. This case is therefore considered to represent a "forme fruste" of Fanconi's anemia.

Abnormalities, Multiple↗
PubMed1979

[Fanconi's anemia (author's transl)].

A 6.6 years old girl is described who shows the typical symptom complex of Fanconi's anemia. Pathogenesis, clinical findings, cytogenetic results, therapy and prognosis of Fanconi's anemia are discussed.

Adrenal Cortex Hormones↗
PubMed1978

The problem of partial endoreduplication.

Partial endoreduplication (PE) as defined by Lejeune et al. (1966) has only been found in a few instances. Similar configurations, also called PEs, seem to originate from a different process. A series of 12 PEs is presented in this paper, discovered in metaphases from healthy individuals, and in patients with or without chromosome-breakage syndrome and after treatment with chromosome-breaking agents. Interpretations of the microscopic appearance of each configuration led to the conclusion that there are three different modes of origin for such rare events, one being true partial endoreduplication, the second a partial pseudoendoreduplication, and the third a homologous triradial chromatid translocation.

Chromosome Aberrations↗
PubMed1978

Rapidly adhering cells in two cases of anencephaly.

We report the successful use of a new method described by Gosden and Brock (1977) in two cases of anencephaly; according to this method 'rapidly adhering cells' are identified as neural cells of a specific morphology. Although the original method described adherence of cells during the first 20 h, we were able to identify a considerable number of such cells after a delay of three days due to mailing of the amniotic fluid.

Adult↗
PubMed1978

Entrapment of sized emboli by the KMA-Greenfield intracaval filter.

Clinical studies demonstrating the effectiveness of the Kim-Ray Greenfield vena caval filter in the management of pulmonary emboli have stimulated efforts to accurately define this filter's capability to entrap sized emboli and maintain caval patency. Twenty-three dogs had filters inserted and positioned distal to the renal veins. Radiopaque emboli measuring 2 to 5 mm were introduced via the femoral vein. Cineradiography allowed direct observation of emboli capture and filter flow dynamics. Probability of entrapment was found to be related to (1) emboli size, (2) depth of filling of the conical-shaped filter by prior entrapment of emboli, and (3) absence of distal venous hypertension. The geometric design of the filter, which allows progressive vertical filling while maintaining circumferential blood flow, is thought to be responsible for entrapment of emboli and avoidance of venous thrombosis and hypertension.

Animals↗
PubMed1977

Clinical and cytogenetic observations during a six-year period in an adult with Fanconi's anaemia.

A male adult patient suffering from Fanconi's anemia is described who was diagnosed 5 years before the onset of clinical symptoms by cytogenetic findings of chromosomeinstability in a lymphocyte culture. Repeated clinical, haematological and biochemical investigations of the untreated patient have been made during the observation period of six years. In the same period of time cytogenetic studies have been carried out which show no correlation in results compared with the clinical or physical findings. Four well defined lymphocyte clones have been discovered. The patient is still under observation of the clinic and the cytogenetic department.

Adult↗
PubMed1977

Clinical experience with the Kim-Ray Greenfield vena caval filter.

Over a four year period in two institutions, 85 Kim-Ray Greenfield vena caval filters were inserted in 76 patients who have been followed for a minimum of 6 to 53 months. The most frequent indication for placement was pulmonary embolism during anticoagulant therapy. Both femoral and jugular routes were used for transvenous insertion, and fewer complications were associated with the jugular approach. Surgical mortality within two weeks of operation occurred in three patients (4%), none from recurrent embolism. Late complications included recurrent thrombophlebitis in 7% and persistent extremity edema in 12% of patients. Two patients developed recurrent embolism (2.6%) which also was seen in 2 patients after clips were placed on the vena cava above the filter after misplacement. Venacavagrams in 31 patients an average of 11 months postoperative showed patency in 30 (97%) and lysis of trapped thrombi in four patients. No episodes of migration have occurred and the filter offers the advantages of sustained patency and effective filtration without vena caval occlusion.

Adolescent↗
PubMed1977

Glucose utilization and role of blood in endotoxin shock.

The present study was conducted to explore influences modifying glucose uptake in canine blood administered LD100 E. coli endotoxin. Particular emphasis was given to assay the role of the white blood cell (WBC) in glucose utilization. Significant increases in glucose uptake and lactic acid production, attributed to increased activity of the WBC, were observed 1-3 h after endotoxin was added to blood in vitro. Although a net increase in glucose utilization was noted, endotoxin simultaneously exerted adverse effects by depressing glucose uptake below predicted values (Q10 = 2.12 with LD100 endotoxin vs. 2.78 in saline controls) and increasing WBC mortality rate. Blood from dogs pretreated with sublethal doses of endotoxin in vivo utilized glucose at an accelerated rate when subjected to endotoxin in vitro. Excess glucose was consumed because of elevated numbers of white blood cells although additional glucose requirements after endotoxin were independent of temperature between the ranges of 34-41 degrees C. All animals pretreated with daily sublethal injections of endotoxin for 3 days survived superlethal doses of endotoxin.

Animals↗