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Biomedical subjects

J Koh

Publications and source records attributed to J Koh.

At least 73 records · Page 4Linked to original sources
PubMed1988

Duchenne muscular dystrophy: high frequency of deletions.

DNA probes are available for Duchenne muscular dystrophy (DMD) carrier detection and prenatal diagnosis. With probes for about 25% of the proximal portion of the gene, we found the proximal probes detected deletions in 23% of nonselected DMD boys, while a single distal probe detected 17% more as deletions. The combined percentage was 39% for all probes tested. Prenatal diagnosis and carrier detection are more accurate if deletions are mapped rather than by use of restriction fragment length polymorphism analysis. The effort involved in screening all affected boys for deletions is considerably less, and provides an accurate genetic marker for subsequent prenatal diagnosis in the family and prospective counseling for female relatives. It seems likely that, once the entire gene (cDNA) is available for screening, most DMD boys will show deletions.

Child↗
PubMed1988

Myotonic dystrophy: update on progress to define the gene.

Using standard likelihood linkage techniques, the gene for dystrophia myotonica has been localized to the proximal long arm of chromosome 19. Several large families provided the substrate for detecting linkage of restriction fragment length polymorphisms which were developed in the laboratory from flow-sorted chromosome 19 genomic libraries. In over 500 family members from five families only a single cross-over with ApoC2 was detected. Thus a useful probe for antenatal and preclinical diagnosis is now available. Details of the strategy employed within the framework of clinical diagnosis, genetic epidemiology and recombinant DNA techniques is described.

Child↗
PubMed1988

Update on the molecular genetics of Duchenne muscular dystrophy.

Three separate lines of evidence led to the assignment of the Duchenne muscular dystrophy (DMD) gene to the 21.2 band on the short arm of the X chromosome. A portion of the putative gene, thought to extend over 1-2 million base pairs has been recently cloned. DNA probes from the Xp21.2 region detect large deletions in 5-20% DMD boys and are presumed to lead to the DMD phenotype in those individuals. Deletions have also been noted in the DNA of patients with Becker muscular dystrophy. These exciting developments have a direct bearing on carrier detection and prenatal diagnosis. Prenatal diagnosis in deletion families approaches greater than 99% accuracy and can be utilized to save 50% of normal male fetuses carried by carrier mothers who would otherwise choose to abort all male fetuses.

Cloning, Molecular↗
PubMed1988

[Experimental chemo- and chemoendocrine therapy of human breast carcinomas serially transplanted into nude mice].

Four human breast carcinoma strains serially transplanted into nude mice were used for the experimental chemotherapy and combination chemoendocrine therapy. Whereas three of these strains (MCF-7, Br-10, TM-61) possessed cytosol estrogen receptor (ERc) and were dependent on estradiol for the tumor growth, the other strain (MX-1) without ERc was hormone independent. For the chemotherapy, mitomycin C (MMC), adriamycin (ADM), cyclophosphamide (CPM) and 5-fluorouracil (5-FU) were administered 3 times every 4 days. To know the stability of ERc after chemotherapy, binding sites of ERc were measured 4 days after MMC administration at doses of 1, 2 and 4.5 mg/kg. For the chemoendocrine therapy, 1 or 2 mg/kg of MMC was administered once followed by treatment by tamoxifen (TAM). The effect of treatment was evaluated by T/C ratio of the tumor weight. MMC showed the most excellent antitumor effect and CPM and ADM showed a moderate effect. As ERc was found to be stable by MMC treatment, TAM was used after MMC, and this combination of MMC and TAM revealed an additive effect against ERc positive strains and no combination effect was observed in MX-1 without ERc. The dose response curves of 4 strains to MMC alone against 4 strains were made and the effect of combination chemoendocrine therapy was converted to the effect of MMC alone, showing the dose of MMC could be significantly reduced. Binding sites of ERc which were measured 4 days after MMC administration (1, 2 and 4.5 mg/kg) was found to be stable, suggesting TAM treatment after MMC might be reasonable. From these results, chemoendocrine therapy of MMC followed by TAM was considered to be beneficial modality for clinical treatment of the cytotoxic agent and increasing the antitumor effect.

Animals↗
PubMed1988

Results of 21 Wagner limb lengthenings in 20 patients.

Roentgenograms and charts were reviewed on 20 patients (average age: 13.2 years) who had 21 Wagner limb lengthenings since 1975. Lengthenings included 15 femora (six acquired, eight congenital, and one fibrous dysplasia), four tibiae, and two humeri (one acquired and one congenital). Average femoral lengthening was 6.6 cm; tibial, 5.9 cm; and humeral, 9.7 cm. Lengthening of femora with congenital shortening (6.5 cm) was nearly the same as femora with acquired shortening (6.8 cm), and 85% of all lengthenings were greater than 5 cm. Humeri were lengthened more than 50%. Seventy-two percent of patients were in the 50th percentile or less of stature; 61% were in the 15th percentile or less of stature. Seventy-five percent had complications, with 65% having more than one major complication: pin tract and superficial infections in 40%; deep infections in 20%. All infections were in femoral lengthenings. Nonunion occurred in two patients (10%), and fracture after plate removal in two patients (10%). Five patients (25%) had nerve palsies, and four of these resolved without treatment. Malunion rate was 20%. Five patients developed joint contractures. Complications did not correlate with amount of lengthening but congenital deformities had a higher incidence of complication. Eleven patients required 19 additional procedures necessitated by the lengthening procedure. Wagner leg lengthening is generally recommended when amputation is only other surgical alternative and a full, complete informed consent is given to the parents and patient.

Adolescent↗
PubMed1988

[Hormone independent murine carcinoma BX-1 spontaneously arising from nude mouse bearing Br-10, a hormone dependent human breast carcinoma strain].

BX-1, an adenocarcinoma spontaneously arising from nude mouse bearing Br-10, a human breast carcinoma strain was characterized. And the purification of a hormone independent murine carcinoma strain, BX-1 was found in August 1986 in three institutes where a hormone dependent transplantable human breast carcinoma cell line Br-10 has been serially passaged. The histological features of BX-1 were different from any other strains which were maintained in these three institutes. Estrogen receptor of BX-1 was negative and no estrogen dependency was observed while Br-10 was the receptor positive and the growth of Br-10 was dependent on estrogen. Although the graft of BX-1 into the thymus intact littermates was rejected, the chromosomal analysis revealed only murine chromosomes for BX-1, while both of human and murine chromosomes were detected in Br-10 tumor. By incubating Br-10 tumor in untreated female nude mice for 2 months and stimulating the growth of the tumor by exogenous estradiol, the purification of Br-10 from BX-1 could be achieved. Whereas the stability of human tumor xenografts in nude mice is confirmed, the spontaneously arising murine tumor from nude mice bearing human tumor xenografts should be considered for the experiments.

Adenocarcinoma↗
PubMed1987

Zinc selectively blocks the action of N-methyl-D-aspartate on cortical neurons.

Large amounts of zinc are present in synaptic vesicles of mammalian central excitatory boutons and may be released during synaptic activity, but the functional significance of the metal for excitatory neurotransmission is currently unknown. Zinc (10 to 1000 micromolar) was found to have little intrinsic membrane effect on cortical neurons, but invariably produced a zinc concentration-dependent, rapid-onset, reversible, and selective attenuation of the membrane responses to N-methyl-D-aspartate, homocysteate, or quinolinate. In contrast, zinc generally potentiated the membrane responses to quisqualate or alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate and often did not affect the response to kainate. Zinc also attenuated N-methyl-D-aspartate receptor-mediated neurotoxicity but not quisqualate or kainate neurotoxicity. The ability of zinc to specifically modulate postsynaptic neuronal responses to excitatory amino acid transmitters, reducing N-methyl-to-aspartate receptor-mediated excitation while often increasing quisqualate receptor-mediated excitation, is proposed to underlie its normal function at central excitatory synapses and furthermore could be relevant to neuronal cell loss in certain disease states.

Animals↗
PubMed1987

Cutaneous necrotizing granulomatous vasculitis with evolution to T cell lymphoma.

The evolution of unusual cutaneous vasculitis to a systemic T cell lymphoma was observed over a 12-year period. Precise classification of the skin biopsy specimens during the course of this patient's illness was difficult. Different observers suggested malignant hemangioendothelioma, malignant lymphoma, regressing atypical histiocytosis, and granulomatous vasculitis. In retrospect, the biopsy specimens likely represented the spectrum of cutaneous lymphomatoid granulomatosis. This condition is yet another example of a reactive lymphoid proliferation proceeding to a malignant lymphoma.

Diagnosis, Differential↗
PubMed1987

Familial inheritance of a DXS164 deletion mutation from a heterozygous female.

Restriction-fragment-length-polymorphism analysis was used to examine a female who is segregating for Duchenne muscular dystrophy (DMD) and a deletion of the DXS164 region of the X chromosome. The segregating female has no prior family history of DMD, and she has two copies of the DXS164 region in her peripheral blood lymphocytes. The following two hypotheses are proposed to explain the coincidence of the DMD phenotype and deletion of the DXS164 region in her offspring: (1) she may be a gonadal mosaic for cells with two normal X chromosomes and cells with one normal X chromosome and an X chromosome with a deletion of the DXS164 region; and (2) she may carry a familial X;autosome translocation in which the DXS164 region is deleted from one X chromosome and translocated to an autosome. The segregation of DMD and the DXS164 deletion in this family illustrates the importance of extended pedigree analysis when DXS164 deletions are used to identify female carriers of the DMD gene.

Chromosome Deletion↗
PubMed1986

Brief exposure to zinc is toxic to cortical neurons.

Recent evidence suggests that large amounts of releasable zinc are present in central synaptic vesicles, and that substantial (several hundred microM) transient elevations in extracellular zinc may accompany intense neuronal excitation. Brief pulse exposure of cortical cell cultures to similar concentrations of zinc resulted in widespread dose-dependent neuronal injury; exposure to higher concentrations resulted in the addition of glial injury. The results suggest that zinc should be included on the growing list of endogenous central neurotoxins which may be involved in the pathogenesis of CNS cell loss in a variety of disease states.

Animals↗
PubMed1986

Amoxycillin-resistant streptococci in dental plaque.

This investigation was undertaken to study the prevalence of amoxycillin-resistant oral streptococci in normal healthy patients and patients with a cardiac condition, susceptible to infective endocarditis. Samples of supragingival dental plaque were collected from two test groups, children with congenital heart disease and adults with a history of rheumatic fever, and two control groups comprising normal healthy children and normal healthy adults. Bacteria from these samples were grown on a medium selective for oral streptococci, as well as on the same medium containing known concentrations of amoxycillin. The results indicate that a high percentage of rheumatic heart patients and children with congenital heart disease harboured amoxycillin-resistant oral streptococci. The level of amoxycillin resistance in the plaque of adults with rheumatic heart disease was significantly greater than in that of normal adults. In view of the high percentage of patients at risk harbouring amoxycillin-resistant streptococci, it is important that the individual clinical situation be monitored. Perhaps antibiotic sensitivity tests should be performed to select an appropriate antibiotic for prophylaxis of infective endocarditis.

Adolescent↗