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C A Schmidt

Publications and source records attributed to C A Schmidt.

At least 73 records · Page 4Linked to original sources
PubMed1994

Heterogeneity of V delta 2 TCR delta gene rearrangements in acute myeloid leukemia.

In a previous study, we described the occurrence of T-cell receptor (TCR)delta gene rearrangements in 9/100 acute myeloid leukemia (AML) cases. In this study, we further characterized these rearrangements by Southern Blot hybridization using a V delta 2 specific probe and polymerase chain reaction (PCR). Southern Blot analysis revealed that rearrangements involved the V delta 2 gene segment in four patients. Interestingly the restriction fragments detected by the V delta 2 probe differed markedly in size. PCR analysis revealed a complete V delta 2(Dn)J delta 1 gene rearrangement, an incomplete V delta 2D delta 3 rearrangement and a large amplification product, which cannot be explained with normal VDJ recombinatorial processes, in one case each. Furthermore although V delta 2 and J delta were rearranged, no comigration of rearranged fragments was observed and no PCR product was obtained in one case. Obtained results in AML differ from findings in acute lymphoblastic leukemia (ALL) of B-cell lineage, where a more homogeneous pattern of rearrangements has been described. This heterogeneity might be related to the illegitimate occurrence of TCR delta gene rearrangements in AML.

Adult↗
PubMed1994

Demonstration of cytomegalovirus after bone marrow transplantation by polymerase chain reaction, virus culture and antigen detection in buffy coat leukocytes.

We prospectively monitored buffy coat leukocytes of 47 patients after 50 marrow transplantations (autologous n = 18, allogeneic n = 32) by polymerase chain reaction (PCR) for the presence of cytomegalovirus (CMV). None of the 18 autologous graft recipients (9 seropositive, 9 seronegative) had positive PCR results or CMV disease throughout the post-transplantation course. Six of 32 allograft recipients (19 seropositive, 13 seronegative) became PCR positive, four of whom developed CMV disease. PCR positive patients were found more often (5 of 10) in the group with acute GVHD grade II-IV compared with 1 of 22 in the group without or with grade I acute GVHD (p = 0.002). Comparison of PCR with antigen assay and virus culture showed an agreement in 90 of 96 (94%) samples. Discordant results were due to a higher sensitivity of the PCR compared with antigen assay (n = 4) and virus culture (n = 6). In conclusion, PCR helps to identify those patients who will not develop CMV disease and narrows down the number of patients who eventually will suffer symptomatic CMV infection. Furthermore, PCR is a useful tool for following the post-transplantation course with respect to CMV and for judging the effect of antiviral treatment.

Adolescent↗
PubMed1994

Ras point mutations occur in acute myeloid leukemia with illegitimate T-cell receptor delta gene rearrangement.

Mutations in the ras proto-oncogenes are the most frequently observed molecular alteration in acute myeloid leukemia (AML). Whether ras mutations occur as late or relatively early events in the multistep process of myeloid transformation, remains an open question. We previously described illegitimate T-cell receptor (TCR)-delta gene rearrangements in a subset of AML. These recombinations were detected in 9 out of 100 de novo AML cases. Southern blot analysis suggested the presence of these recombinations in the vast majority of AML cells and thus could be used as clonal markers. In order to more accurately define the role of ras proto-oncogene mutations in the multistep process of malignant transformation in myeloid leukemias, we performed single strand conformation polymorphism (SSCP) assays, slot blot and direct sequencing analysis on these nine cases with illegitimate TCR delta gene rearrangements. Ras proto-oncogene mutations were found in three of nine cases. Interestingly, SSCP, slot blot and sequencing suggested the presence of the respective mutations in most of the leukemic cells. Thus, ras mutations presumably occurred early in the process of transformation in these three cases.

Adult↗
PubMed1993

Opioid receptor density changes in Alzheimer amygdala and putamen.

Since opioids can influence the release of acetylcholine, substance P and a number of other neurotransmitters that have been implicated in the pathogenesis of Alzheimer's disease (AD), it is of interest to assess opioid receptor levels in AD. We have examined mu, delta and kappa opioid receptor binding parameters, binding sensitivity to a GTP analog and distribution in amygdala, frontal cortex and putamen of AD brain. Control brains were matched according to age, sex, post-mortem interval and storage time. Kd values and GTP analog binding sensitivity did not differ in AD and control brains. Bmax values for mu ([3H]DAMGE) sites also appeared unaffected by in vitro binding assays. In contrast, kappa ([3H]U69593) and delta ([3H]DSLET) opioid receptor levels, were significantly changed. In AD amygdala kappa Bmax values increased from control levels of 123 +/- 12 to 168 +/- 13 fmol/mg protein, whereas densities of kappa and delta sites were decreased from 94 +/- 8 to 48 +/- 8 and 102 +/- 3.6 to 69 +/- 8.5 fmol/mg protein, respectively, in putamen. Autoradiography revealed corresponding differences in the distribution of kappa opioid receptors. The findings indicate that the kappa binding site, which is quantitatively the major opioid receptor class in human brain, undergoes marked changes in AD amygdala and putamen.

Aged↗
PubMed1993

Decreased resistance to N,N-dimethylated anthracyclines in multidrug-resistant Friend erythroleukemia cells.

Doxorubicin-resistant Friend erythroleukemia cells, line F4-6 ADM2R, were selected by exposure of wild-type F4-6 cells to doxorubicin concentrations of up to 1 microgram/ml. In these cells, increased expression of multidrug resistance (MDR) genes was demonstrated by Northern blot analysis. The growth-inhibitory effect of doxorubicin, daunorubicin, N,N-dimethyldoxorubicin, N,N-dimethyldaunorubicin, morpholinodoxorubicin, and pyrromycin was comparatively investigated in resistant and wild-type cells. The doxorubicin-resistant F4-6 cells showed approx. 200-fold resistance to doxorubicin and about 100-fold resistance to daunorubicin with respect to the drug-sensitive counterpart. A dramatic decrease in resistance was observed for the N,N-dimethylated derivatives of doxorubicin and daunorubicin as well as for the N,N-dimethylated natural anthracycline pyrromycin and for morpholinodoxorubicin. Uptake studies using [14C]-daunorubicin and [14C]-N,N-dimethyldaunorubicin in resistant F4-6 cells showed a decreased accumulation of daunorubicin but no significant reduction in N,N-dimethyldaunorubicin accumulation as compared with the wild-type cells. Treatment with verapamil led to increased intracellular levels of daunorubicin in resistant cells, whereas an excess of N,N-dimethyldaunorubicin did not have this effect. Thus, the decreased resistance of the doxorubicin-resistant F4-6 cells to the N-alkylated anthracyclines may at least in part be due to a reduced affinity of these compounds for the efflux pump. The results indicate that the dimethylation of the amino group of the anthracycline sugar moiety and its incorporation within a morpholinyl ring may overcome MDR by similar mechanisms.

Antibiotics, Antineoplastic↗
PubMed1993

Altered DNA topoisomerase II in multidrug resistance.

The characteristic feature of multidrug resistance (MDR) associated with drugs that interact with DNA topoisomerase II (topo II) is alterations in topo II activity or amount (at-MDR). We have characterized the at-MDR phenotype in human leukemic CEM cells selected for resistance to the topo II inhibitor, VM-26. Compared to drug-sensitive cells, the key findings are that at-MDR cells exhibit (i) decreased topo II activity; (ii) decreased drug sensitivity, activity and amount of nuclear matrix topo II; (iii) increased ATP requirement of topo II; (iv) a single base mutation in topo II resulting in a change of Arg to Gln at position 449, at the start of the motif B/nucleotide binding site; and (v) decreased topo II phosphorylation, suggesting decreased kinase or increased phosphatase activities. Recent results using single-stranded conformational polymorphism analysis reveals the presence of a mutation in the motif B/nucleotide binding site of the topo II alpha gene in CEM at-MDR cells and in another leukemic cell line selected for resistance to m-AMSA. Finally, we have observed marked changes in the nuclear distribution of topo II in cells treated with anti-topo II drugs and have also found these changes to be attenuated in drug-resistant cells. We postulate that traditional inhibitors of topo II alter the equilibrium of the strand-passing reaction such that the number of enzyme-DNA covalent complexes increases. We further suggest that when the enzyme is bound to DNA it is protected from proteolysis, thus allowing more topo II molecules to be detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Detection of p53 mutations using nonradioactive SSCP analysis: p53 is not frequently mutated in myelodysplastic syndromes (MDS).

p53 is one of the most frequently mutated genes in human cancers. Since p53 has been implicated in lymphatic and some myeloid leukemias, such as the blastic phase of chronic myelogenous leukemia, we sought to address the role of p53 gene mutations within exons 4-9 in myelodysplastic syndromes (MDS), a myeloid preleukemic condition. In order to avoid the potential hazard of using radioactive single-strand conformation analysis (SSCP), we used a nonradioactive SSCP method based on the silver stain of small minigels. In cell lines with known point mutations of the p53 gene, aberrant migrating bands were found. Serial dilutions indicated a sensitivity comparable to radioactive methods. Furthermore, a common polymorphism within the 4th exon of the p53 gene was easily detected. However, of 17 primary samples from patients with MDS, none harbored a p53 gene mutation. We conclude that this nonradioactive method can easily be used to screen for p53-gene mutations, and that p53-gene mutations do not play a major role in the pathogenesis of MDS.

Alleles↗
PubMed1993

Molecular alterations in a patient with Turcot's syndrome.

Cells of a patient with Turcot's syndrome and of her parents were evaluated for the presence of molecular alterations in the p53 and the Ki-ras gene. Deletions on chromosome 17p, overexpression and point mutations of the p53 gene as well as mutations of the Ki-ras gene were detected in primary and metastatic tumour but not in the germline of the patient nor in her parents.

Adenocarcinoma↗
PubMed1993

Demonstration of cytomegalovirus by polymerase chain reaction after liver transplantation.

The polymerase chain reaction (PCR) is a highly sensitive and specific technique for detection of cytomegalovirus DNA. With this method we prospectively analyzed buffy coat leukocytes at weekly intervals over 3 months in 60 patients after liver transplantation (LTX). The PCR results were correlated with the pretransplant donor/recipient CMV antibody status and with the occurrence of CMV-induced disease. Thirty-three of 60 (55%) patients became PCR-positive during their posttransplant course. None of the 27 patients with permanent negative PCRs developed CMV disease. Of 33 patients with positive PCRs, 13 (39%) became ill. CMV disease developed in 9 of 22 (41%) antibody-negative recipients but only in 4 of 38 (10%) seropositive graft recipients. The incidence of CMV disease was 75% (9 of 12 patients) in seronegative recipients who converted to positive PCR results and 19% (4 of 21 patients) in seropositive patients with positive PCR findings. The predictive value of a positive PCR was 75% in seronegative patients but it was low (19%) in seropositive recipients. The predictive value of a negative PCR is 100%. Thus, PCR determinations are useful in identifying patients who will not develop CMV disease and in narrowing down the number of individuals who will become sick. Further, PCR is a helpful tool in the follow-up of patients under antiviral treatment.

Adult↗
PubMed1993

Demonstration of chimerism after allogeneic bone marrow transplantation by polymerase chain reaction of Y-chromosome-specific nucleotide sequences--characterization of a new technical approach.

Various techniques are applied to assess chimerism after allogeneic bone marrow transplantation. The polymerase chain reaction (PCR) of donor- and/or host-specific gene sequences provides a rapid and highly sensitive technique. We describe the characterization and application of PCR for the amplification of Y-chromosome-specific DNA in blood cells recovered from stored slides. Four different primer pair combinations were used. PCR can be rapidly performed on stained or unstained slide material with varying sensitivity--depending on the primer combination. The lowest limit of detection is one male cell in 500-1000 female cells. The technique was applied to follow the early post-transplant course of 15 male patients who received grafts from female donors and found a high incidence of mixed chimerism during the first three months after BMT and a striking fluctuation between positive and negative results in the follow-up of individual patients. We conclude that PCR for the detection of male-specific DNA sequences can be successfully performed with high sensitivity on material recovered from stored blood slides.

Adolescent↗
PubMed1993

Genetic alterations in the p53 gene in the blast crisis of chronic myelogenous leukemia: analysis by polymerase chain reaction based techniques.

Rearrangements of the c-abl protooncogene and the bcr-gene are found in > 90% of patients in chronic phase of chronic myelogenous leukemia (CML). The molecular events leading to blast crisis, however, have not been well characterized. Gross alterations of the p53 gene have been detected in 30% of patients with blast crisis. Since point mutations in the p53 gene appear to be important in the process of transformation in many epithelial tumors, we looked for these mutations in the critical regions of the p53 gene (exons 4, 5, 6, 7, and 8). We used the polymerase chain reaction (PCR), direct sequencing, differential PCR, and single strand conformation polymorphism (SSCP) analysis to detect mutations of the p53 gene in samples from 21 patients with CML blast crisis. Two of 21 patients exhibited an intragenic deletion or rearrangement in p53. In addition, these patients were homozygous for the mutant p53 allele. No mutations were found in the p53 gene of the remaining 19 patients. However, sequencing of the CML blast crisis cell line, K562, revealed an insertion of a C at base position 956 within the fifth exon, causing a frame shift mutation and an early translational stop at codon 148. We conclude that, in contrast to solid tumors, mutations in exons 4-8 of p53 are not frequently seen in primary samples from CML blast crisis. However, deletions and/or rearrangements within the p53 gene do occur and may contribute to the progression from chronic phase to blast crisis in a limited number of patients with CML.

Base Sequence↗
PubMed1992

Pericardioplasty.

When so desired, a simple technique can be performed to close the pericardium after a cardiac operation. The only requirement is to think about it during the opening of the pericardium and make the appropriate cuts.

Cardiac Surgical Procedures↗
PubMed1992

Primary repair of traumatic aortic rupture: a preferred approach.

Eighty patients with traumatic rupture of the thoracic aorta were treated. Seven patients died during the initial resuscitation. Forty-three patients underwent surgical repair using the clamp-and-sew technique; 14 patients had a heparin-bonded shunt placed, and 16 patients were repaired using cardiopulmonary bypass. An interposition Dacron graft was used in only 19 patients (26%). The last 32 consecutive patients underwent primary repair of the ruptured aorta. Overall mortality was 19.2% (14 of 80); 9 of 14 patients (64%) had laparotomies along with the aortic repair, and 13 of 14 patients (92%) had three or more associated major injuries. Paraplegia occurred in four cases (5.6%). Traumatic aortic rupture remains a difficult surgical problem. Primary repair, without graft interposition, is the preferred technique and can be accomplished even when the two aortic ends have retracted several centimeters.

Adolescent↗