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Biomedical subjects

C Schwartz

Publications and source records attributed to C Schwartz.

At least 19 recordsLinked to original sources
PubMed1992

Inactivation of a volume-sensitive basolateral potassium conductance in turtle colon: effect of metabolic inhibitors.

Previous work has shown that the basolateral membrane of turtle colon epithelium contains a quinidine-sensitive potassium conductance which can be activated by osmotic cell swelling. In this work and in the present study, potassium flow across the basolateral membrane was measured as a short-circuit current across intact pieces of epithelial tissue in which amphotericin B was used to permeabilize the apical membrane. Quinidine-sensitive currents were generated when the mucosal bath contained chloride, a permeant anion. Replacement of chloride by sulfate or addition of sucrose to the bathing solutions abolished 75-90% of the current and caused the quinidine-inhibitable fraction of the current to go from over 90% to around 6%--suggesting that decreases in cell volume had brought about inactivation of the quinidine-sensitive conductance. When metabolic inhibitors were present, inactivation of the conductance by these maneuvers was prevented. Activation of the conductance by replacement of mucosal SO4 by Cl, however, was not affected.

Amphotericin B↗
PubMed1992

Evidence of founder chromosomes in fragile X syndrome.

The mutation responsible for fragile X syndrome and myotonic dystrophy involves the amplification of a simple trinucleotide repeat sequence, which increases in successive generations of affected pedigrees accounting for increasing penetrance of both disorders. This common molecular basis suggests that the two diseases may share other genetic features, but whereas myotonic dystrophy exhibits a significant founder chromosome effect, fragile X syndrome apparently has a very high mutation frequency. By haplotype analysis of microsatellite markers which flank the fragile X unstable element, we have uncovered evidence of founder chromosomes of the fragile X 'mutation'. Disorders caused by heritable unstable elements may therefore exhibit common genetic properties including anticipation and founder chromosomes.

Base Sequence↗
PubMed1992

Difficult diagnosis of the fragile X syndrome made possible by direct detection of DNA mutations.

Genetic recombination near the fragile X locus (Xq27.3) has frequently been a problem in linkage studies of families in which the fragile X is segregating. This case report illustrates the resolution of a difficult situation in a fragile X family for whom cytogenetic studies were inconclusive and where recombination had twice confounded attempts at prenatal DNA diagnosis by RFLP analysis. Using a newly developed DNA probe, StB12.3, for direct detection of DNA instability in the fragile X locus, the presence of the fragile X was ascertained definitively in a prenatal DNA sample.

Blotting, Southern↗
PubMed1992

Chronic respiratory conditions and acupuncture therapy.

Acupuncture effectively enhances the treatment of chronic allergic bronchitis and asthma in the cat and dog. According to Traditional Chinese Medicine, chronic respiratory conditions can arise from lung, spleen/pancreas, liver or kidney deficiencies. Proper diagnosis is made from patient history, as well as examination of tongue and pulse. Acupuncture points are chosen according to involved energy pathways (meridians) and classical acupuncture combinations. In most cases, medication can be reduced as the acupuncture takes effect.

Acupuncture Points↗
PubMed1991

Molecular heterogeneity of the fragile X syndrome.

The fragile X syndrome is an X-linked disorder which has been shown to be associated with the length variation of a DNA fragment containing a CGG trinucleotide repeat element at or close to the fragile site. Phenotypically normal carriers of the disorder generally have a smaller length variation than affected individuals. We have cloned the region in cosmids and defined the area containing the amplified sequence. We have used probes from the region to analyse the mutation in families. We show that the mutation evolves in different ways in different individuals of the same family. In addition we show that not all fragile X positive individuals show this amplification of DNA sequence even though they show expression of the fragile site at levels greater than 25%. One patient has alterations in the region adjacent to the CGG repeat elements. Three patients in fragile X families have the normal fragment with amplification in a small population of their cells. These observations indicate that there is molecular heterogeneity in the fragile X syndrome and that the DNA fragment length variation is not the only sequence responsible for the expression of the fragile site or the disease phenotype.

Base Sequence↗
PubMed1991

Uniparental paternal disomy in a genetic cancer-predisposing syndrome.

The 11p15.5 region of human chromosome 11 seems to contain a locus or loci involved in congenital overgrowth anomalies as well as in the genesis of many tumours associated with the Beckwith-Wiedemann syndrome (BWS). Given the unusual differential parental allele involvement in the different aetiological forms of BWS and the loss of maternal alleles in associated tumours, we have now used 11p15.5 markers to determine the parental origin of chromosome 11 in eight sporadic cases of BWS. Probands in three informative families had uniparental paternal disomy for region 11p15.5. Further, an overall greatly increased frequency of homozygosity for several 11p15.5 markers in 21 sporadic BWS patients suggests that isodisomy probably accounts for an even higher proportion of BWS sporadic cases. This demonstrates that uniparental paternal disomy can be associated with a genetic cancer-predisposing syndrome.

Beckwith-Wiedemann Syndrome↗
PubMed1991

Genotype prediction in the fragile X syndrome.

Fragile X positive, mentally retarded males have been shown to have an insertion or amplification of DNA sequences at, or close to, the site of expression of the fragile site. We show here the application of the detection of such changes to the diagnosis of affected males and female carriers and the identification of normal transmitting males. One fragile X negative male with the clinical features of the Martin-Bell syndrome also possesses an inserted/amplified DNA sequence. The implications of these results for screening for the fragile X syndrome are discussed.

Blotting, Southern↗
PubMed1990

Quantification of the DNA content of structurally abnormal X chromosomes and X chromosome aneuploidy using high resolution bivariate flow karyotyping.

Quantification of the Hoechst and chromomycin A3 fluorescence intensities of mitotic human chromosomes isolated from karyotypically normal and abnormal cells was performed with a dual beam flow cytometer. The resultant flow karyotypes contain information about the relative DNA content and base composition of chromosomes and their relative frequencies in the mitotic cell sample. The relative copy number of X and Y chromosomes was determined for 38 normal males and females and 6 cell lines with X or Y chromosome aneuploidy. Flow karyotype diagnoses corresponded with conventional cytogenetic results in all cases. We show that chromosome DNA content can be derived from peak position in Hoechst vs. chromomycin flow karyotypes. These values are linearly related to propidium iodide staining intensity as measured with flow cytometry and to the binding of gallocyanin chrome alum to phosphate groups as measured with slide-based scanning photometry. Cell lines with deleted or dicentric X chromosomes ranging in length from 0.53 to 1.95 times normal were analyzed by using flow cytometry. The measured difference in DNA content between a normal X and each of the structurally abnormal chromosomes was linearly correlated to the difference predicted from cytogenetics and/or probe analyses. Deletions of 3-5 Mb, which were at and below the detection limits of conventional cytogenetics, could be quantified by flow karyotyping in individuals with X-linked diseases such as Duchenne muscular dystrophy, choroideremia, and ocular albinism/ichthyosis. The results show that the use of flow karyotyping to quantify the size of restricted regions of the genome can complement conventional cytogenetics and other physical mapping techniques in the study of genetic disorders.

Aneuploidy↗
PubMed1990

Transposition of the oncogene ets-1 in t(11;19) translocation in acute leukemia.

The specific chromosomal rearrangement t(11;19)(q23;p13) has been identified as a nonrandom chromosomal rearrangement in acute leukemia. The breakpoint, 11q23, coincides with the ets-1 oncogene locus. However, only very few studies have been done to verify the genomic alteration and transposition of ets-1 in the t(11;19) chromosomal rearrangement. In the present study, we identified the t(11;19)(q23;p13) translocation in two acute leukemic cases. One of the cases, biphenotypic leukemia, has been followed thoroughly. An abnormal karyotype was identified in the patient's blood and marrow samples at diagnosis and at relapse, while only normal karyotypes were identified at remission. In situ hybridization of chromosomal preparations with the ets-1 probe pHE5.4 resulted in silver grains nonrandomly localized to 19p13 in the metaphase spreads prepared from the blood sample taken at relapse, while no detectable grains were found on chromosome 19p13 in a sample taken at remission. To determine if genomic alterations of ets-1 are associated with this translocation, Southern blot hybridizations with the pHE5.4 probe were performed on deoxyribonucleic acid (DNA) isolated from blood or marrow samples of the patient at remission and relapse as well as on DNA from a disease-free normal control. Any DNA digested with AvaII, SstI, XbaI, and Bam HI, followed by hybridization with pHE5.4, demonstrated no genomic alterations or amplification of the ets-1 oncogene. Our study indicates that the ets-1 oncogene is transposed in the t(11;19) translocation without detectable alteration at the DNA level. The absence of ets-1 amplification in t(11;19) and its presence in the t(4,11) and t(9;11) translocations demonstrated by others suggests the possible existence of different molecular mechanisms involving the ets-1 oncogene in the pathogenesis of these leukemias.

Blotting, Southern↗
PubMed1990

Prevention of bacteremia attributed to luminal colonization of tunneled central venous catheters with vancomycin-susceptible organisms.

Forty-five children with oncologic or hematologic disorders requiring tunneled central venous catheters (TCVC) for the administration of immunosuppressive therapy were randomized to receive either 10 U/mL heparin (H) (24 patients) or a solution of 10 U/mL H and 25 micrograms/mL vancomycin (H-V) (21 patients) for all catheter flushes. Episodes of fever or suspected sepsis were evaluated to determine whether the addition of vancomycin to the flush solution would alter the incidence of symptomatic bacteremia attributed to luminal colonization of TCVC with vancomycin-susceptible bacteria. Patients were enrolled for 247 +/- 150 days, accounting for a total of 11,095 days of catheter use. Bacteremia attributed to luminal colonization with vancomycin-susceptible organisms occurred in five patients (six infections) receiving H alone compared with zero patients receiving H-V (P = .035). The time to the first episode of bacteremia with vancomycin-susceptible organisms, analyzed by Kaplan-Meier survival curves, was significantly longer in patients receiving H-V (P = .04). There were no differences in the incidence of other infections including bacteremia attributed to luminal colonization with vancomycin-resistant organisms, other bacteremias (including those arising from the catheter exit site), exit-site cellulitis, or fungal infections. No organisms resistant to vancomycin were identified. Vancomycin could not be detected in the peripheral blood of patients receiving vancomycin in the flush solution. No vancomycin-related toxicities were noted. We conclude that the use of an H-V flush solution in immunocompromised patients with TCVC can decrease the frequency of bacteremia attributed to luminal colonization with vancomycin-susceptible bacteria.

Adolescent↗
PubMed1990

Foscarnet therapy of cytomegalovirus retinitis in AIDS.

Cytomegalovirus (CMV) retinitis is the most common cause of blindness in AIDS. Twenty patients were treated with a 21-day course of foscarnet therapy by continuous infusion. Response to therapy was good in eight (47%) of 17 evaluable patients; partial arrest of progression was observed in eight (47%); and no response was obtained in one (6%). Foscarnet therapy did not lead to suppression of urinary excretion of CMV in four of 12 patients who nonetheless had improvement in retinal lesions. Toxic effects, especially reversible renal failure, were common, with blood creatinine increase in 50% and dialysis in two patients. Renal toxicity occurred primarily during the third week of therapy. Anemia (hemoglobin less than 80 g/L) occurred in 10 patients after a mean of 14.5 +/- 5.1 days of therapy and required transfusion. Review of this study and of data from a previous case series, however, was inconclusive regarding the additional benefit of a third week of therapy. Maintenance therapy was given to seven patients. Four had recurrence of CMV retinitis at a mean interval of 62 +/- 52 days. Only one patient has maintained prolonged remission on maintenance (greater than 24 weeks). Toxicity on the maintenance protocol included anemia (two of seven patients) and increased creatinine blood levels (one of seven patients). Zidovudine therapy in six patients did not contribute to increased toxicity of induction or maintenance therapy. Drug levels during continuous infusion were stable for individual patients but showed wide inter-patient variability. Peak levels of post-maintenance infusion varied both within and between patients.

Acquired Immunodeficiency Syndrome↗