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Biomedical subjects

J D Chen

Publications and source records attributed to J D Chen.

At least 163 records · Page 9Linked to original sources
PubMed1990

The effects of actinidia sinensis planch (kiwi) drink supplementation on athletes training in hot environments.

On the basis of studying the problems and experimental data of athletes training in hot environments, we designed an athletic drink choosing actinidia sinensis planch (ASP), also known as kiwi fruit, as the basic component, and assessed its effects in athletes both at site of training and in the laboratory. The main results were as follows: (1) In athletes riding on a Monark ergometer (maintaining HR at 150 beat/min), the work time to exhaustion was longer (149 +/- 3 min vs 120 +/- 1 min), and the work load was larger (947 +/- 36 KJ vs 833 +/- 28 KJ) when supplementing the ASP drik than when they drank the placebo, P less than 0.01) (2) Supplements with the ASP drink expanded the blood volume of athletes. Hematocrit increased significantly after exercise in athletes consuming placebo, but no significant changes were found in those consuming the ASP drink. (3) The ASP drink which contained 5% carbohydrate maintained the blood glucose concentration of athletes at a normal level even when training lasted more than 2.5 hours and without noticeable effect on plasma insulin levels. (4) Supplement of small amount of multi-minerals in the ASP drink helped to decrease the mineral level changes in serum and sweat after intensive training, but it did not cause kaliemia or affect urinary output. (5) Data on urinary vitamin C content indicated that the vitamin C status of athletes supplementing the ASP drink improved. The ASP drink is not only effective but also fragrant, tasty, refreshing and thirst quenching, and it appears to have no side effects.

Adolescent↗
PubMed1989

X-linked megalocornea: close linkage to DXS87 and DXS94.

In a family in which X-linked megalocornea is segregating, the disease locus was found to be closely linked to DXS87 (zeta max = 3.91, theta max = 0.00) and DXS94 (zeta max = 3.34, theta max = 0.00) in Xq21.3-q22.

Corneal Diseases↗
PubMed1989

Preliminary exclusion of an X-linked gene in Leber optic atrophy by linkage analysis.

The maternal inheritance in Leber optic atrophy suggests that it may be caused by a cytoplasmic or mitochondrial defect. However, the strong male bias and the strict tissue specificity can not be readily explained by a single mitochondrial gene defect alone. Wallace suggested a hypothesis that the disease could be the result of an interaction between an X-linked gene and a mitochondrial DNA defect. Linkage relationships between Leber optic atrophy and 15 X-chromosome markers were analyzed in three large Tasmanian families. The results of two-point linkage analysis showed no close linkage between Leber optic atrophy and any of the 15 markers. The results of multipoint linkage analysis suggested the exclusion of the assumed X-linked gene from almost the whole X chromosome in these families.

Female↗
PubMed1989

A genetic linkage map of five marker loci in and around the Duchenne muscular dystrophy locus.

Linkage analysis of five marker loci in and around the Duchenne muscular dystrophy (DMD) locus, DXS84, DXS206, DXS164, DXS270, and DXS28, was conducted with 499 families. Overall, the best multipoint distances were found to be DXS84-3.7 +/- 0.6 cM-DXS206-1.0 +/- 0.4 cM-DXS164-1.9 +/- 0.6 cM-DXS270-12.0 +/- 1.1 cM-DXS28. A comparison of this linkage map with the established physical map suggests the presence of hot spots for recombination in the DMD locus.

Chromosome Deletion↗
PubMed1989

Non-allelic mutations in X-linked retinitis pigmentosa.

Using RFLP studies, the disease locus in two X-linked retinitis pigmentosa families was found to be centromeric to DXS7 in one family and telomeric to DXS7 in another, suggesting non-allelic heterogeneity.

Blotting, Southern↗
PubMed1989

Lymphotropic papovavirus early region is specifically regulated transgenic mice and efficiently induces neoplasia.

Transgenic mice have been generated which carry the early region of lymphotropic papovavirus (LPV). Eight of eleven founder animals died before 3 months of age after developing one or both of two distinct proliferative disorders. Of the three surviving animals, two are known to have rearranged or partial copies of the LPV genes. The majority of the founder animals (six) developed debilitating choroid plexus tumors by 26 to 42 days. Although this is the same tumor type induced by the simian virus 40 T-antigen gene, those induced by LPV appeared at a much younger age. The LPV early region was expressed in the brain tumors of these mice, as well as in the thymus and spleen. Expression in the latter two tissues reflects the cell-type specificity of the LPV enhancer demonstrated in cultured cells (i.e., lymphoid cells). Two founder animals (LP41 and LP50) gave rise to lines of mice that routinely develop lymphoproliferative disorders. LP50 and its LPV-positive offspring developed aggressive lymphomas and choroid plexus tumors. The transgenic offspring of LP41 also developed lymphomas. High levels of LPV RNA were expressed in the lymphomas of these mice as well as in the spleens and thymuses. The origin of the lymphomas from B- and T-cell lineages suggests that the LPV early genes are expressed in and can transform both of these cell types in vivo.

Animals↗
PubMed1989

Characterization of a heat-resistant strain of Tilapia ovary cells.

Tilapia ovary cells (TO-2) cease to proliferate when moved from normal growth temperature of 31 degrees C to 37 degrees C, and arrest in G1 and G2 phases of the cell cycle. The ability of the arrested cells to re-enter the cell cycle when restored to 31 degrees C decreases inversely with time spent at 37 degrees C. A heat-resistant strain, TO-37c, cloned from the surviving fraction of TO-2 after heat treatment, has been found to re-enter the cell cycle with greater facility and to have a higher rate of survival. TO-37c cells have a smaller cell volume than TO-2 and show a distinct morphology at 37 degrees C. Most of the heat-shock proteins (hsps) induced on temperature change were similar, but in TO-37c the decline in the synthesis of a 27 X 10(3) Mr hsp was faster and a 37 degrees C-specific 60 X 10(3) Mr hsp was missing. Ultraviolet (u.v.) sensitivity was slightly affected if heat treatment was given after irradiation. However, when cells were preheated and then u.v. irradiated, the u.v. sensitivity increased sharply for TO-2 cells but not for TO-37c.

Animals↗
PubMed1989

The molecular basis for Duchenne versus Becker muscular dystrophy: correlation of severity with type of deletion.

About 60% of both Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) is due to deletions of the dystrophin gene. For cases with a deletion mutation, the "reading frame" hypothesis predicts that BMD patients produce a semifunctional, internally deleted dystrophin protein, whereas DMD patients produce a severely truncated protein that would be unstable. To test the validity of this theory, we analyzed 258 independent deletions at the DMD/BMD locus. The correlation between phenotype and type of deletion mutation is in agreement with the "reading frame" theory in 92% of cases and is of diagnostic and prognostic significance. The distribution and frequency of deletions spanning the entire locus suggests that many "in-frame" deletions of the dystrophin gene are not detected because the individuals bearing them are either asymptomatic or exhibit non-DMD/non-BMD clinical features.

Adolescent↗
PubMed1989

Experimental study on relative biological effectiveness of tritium and risk estimates of genetic damage.

The relative biological effectiveness (RBE) and the genetic effect of tritium internal exposure compared with those of Co-60 gamma rays external exposure are studied in mice. Two different irradiation models are used: 1) irradiation by single intake of tritium, or by Co-60 gamma rays external exposure with gradually decreasing doses simulating the exponential decreasing function of tritium in the mouse body; 2) irradiation by continual intake of tritium, or by Co-60 gamma rays external exposure at constant dose rates. The biological effective end points observed in this study are dominant lethal mutations, dominant skeleton mutations, survival rates of primary oocytes and spermatogonia and chromosome aberrations in spermatocytes. The experimental results show that the RBE values of tritium would be 2.24 to 2.99 in the dose range of 0.02-0.06 Gy/day. The risk estimates of genetic damage from dominant skeleton mutations are 10959/10(6). Gy for tritium beta rays and 3605/10(6). Gy for Co-60 gamma rays.

Animals↗
PubMed1989

Linkage heterogeneity between X-linked retinitis pigmentosa and a map of 10 RFLP loci.

In nine families in which X-linked retinitis pigmentosa (XLRP) is segregating, the lod scores of XLRP in a map of 10 RFLP loci were obtained by multipoint linkage analysis. The XLRP locus was located telomeric to DXS7 in seven of the families and centromeric to DXS7 in two of the families. Under the hypothesis of two XLRP loci, a heterogeneity (admixture) test was performed, providing significant evidence of heterogeneity in XLRP (P less than .01). No correlation was detected between the clinical manifestations of XLRP and the two different disease loci.

Chromosome Mapping↗
PubMed1988

Construction and properties of a new insertion vector, pJDC9, that is protected by transcriptional terminators and useful for cloning of DNA from Streptococcus pneumoniae.

A new Escherichia coli plasmid cloning vector, pJDC9, was constructed by replacing the TcR determinant of pMB9 with the erythromycin-resistance ermB determinant and the lacZ alpha gene of pUC19. Efficient transcriptional terminator signals were positioned at both ends of lacZ alpha. Evidence is presented that protection of the vector by terminator signals enabled cloning of many fragments of DNA from Streptococcus pneumoniae that were unstable in vectors lacking such protection, including pBR322. At the pneumococcal mal locus, three promoter sites required such protection, while overexpression of the malX protein appeared to be lethal despite such protection.

Cloning, Molecular↗
PubMed1988

Thermal adaptation and heat shock response of Tilapia ovary cells.

The growth of tissue culture TO-2 cells derived from the warm water fish Tilapia, the induction of thermotolerance, and protein synthesis profiles of these cells in response to temperature changes were examined. TO-2 cells can grow between 15 to 34 degrees, with an optimal growth temperature of 31 degrees. There is no apparent killing of the cells when the temperature is lowered to 4 degrees for up to 3 days. Survival of TO-2 cells at 43 degrees was studied after various preheat treatments: 1) acute heating at 40 degrees for 15 min followed by 31 degrees incubation, 2) chronic exposure at 37 degrees for several hr, or 3) long-term thermal adaptation at 34 degrees. The cells acquire thermotolerance from pre-exposure to 37 degrees for as short as 6 hr. Preheating at 40 degrees followed by incubation at 31 degrees also induces thermotolerance against a subsequent 43 degrees heat challenge. In addition, 34 degrees thermal adapted cells are resistant to 43 degrees heating. One- and two-dimensional gel electrophoresis of proteins after heat treatments show that three major heat shock proteins with molecular weights around 87, 70, and 27 kD are preferentially synthesized. The synthesis of two additional proteins with an isoelectric point of 6.9 and molecular weights of 60 and 44 kD are significantly enhanced in 34 degrees thermal-adapted and 37 degrees chronic heated cells, but not in cells subjected to an acute heat shock at either 40 degrees or 43 degrees. On the other hand, the 27 kD heat shock proteins are mainly present in the 43 degrees, 40 degrees, and 37 degrees heat-shocked cells, but not in the 34 degrees thermal-adapted cells.

Adaptation, Physiological↗
PubMed1988

Analysis of linkage relationships of X-linked retinitis pigmentosa with the following Xp loci: L1.28, OTC, 754, XJ-1.1, pERT87, and C7.

A number of variants of X-linked retinitis pigmentosa (XLRP) have been described. In one variant, listed in the McKusick (McK) catalogue (McKusick 1983) as entry no. 30320, the heterozygotes exhibit a golden metallic or tapetal reflex. Three large pedigrees segregating for XLRP with the characteristic tapetal reflex in the heterozygotes were examined, and the linkage between the XLRP locus and Xp loci, L1.28, OTC, 754, XJ-1.1, pERT87 and C7 was measured. The strongest linkage was found to be between the XLRP locus and OTC. In addition, recombinational evidence drawn from the three pedigrees suggests that the XLRP locus is distal to L1.28 and proximal to 754. This putative location of the XLRP gene between L1.28 and 754 taken together with the tight linkage to OTC, a locus already located between L1.28 and 754, leads us to propose a gene order of centromere-L1.28-OTC/XLRP-754-telomere.

DNA↗
PubMed1988

Two different genes for X-linked retinitis pigmentosa.

Linkage analysis was carried out in three large multigenerational kindreds with X-linked retinitis pigmentosa using DNA markers on Xp. About 10% recombination has been found between the retinitis pigmentosa locus (RP2) and the marker locus DXS7, assigned to band Xp11.3, which was reported earlier to be closely linked to RP2 in several independent families. In the kindreds described in this paper, however, RP2 shows close linkage and no recombination with the marker loci OTC and DXS148, both assigned to Xp21, indicating that, contrary to previous linkage studies, there is evidence of an RP locus distal to DXS7. This suggests that X-linked retinitis pigmentosa is genetically heterogeneous, i.e., caused by mutations at different loci.

Female↗
PubMed1988

Prenatal diagnosis and carrier detection by DNA studies in a Duchenne muscular dystrophy family with no living affected male.

Restriction fragment length polymorphism studies and gene dosage analysis using the intragenic probes pERT87 were used to detect deletions in potential carriers in a family with Duchenne muscular dystrophy in which the only affected male was deceased. Two females were found to have inherited the paternal pERT87 alleles but not the maternal alleles, suggesting that they have inherited the pERT87 deletion from their mothers. The hybridization signals of pERT87 from these two females upon gene dosage analysis also suggested that they had a single copy of pERT87. The chorionic villi of a male fetus from one of these two females was found to be deleted for pERT87, suggesting that it was affected. This result confirmed the carrier status of the mother.

Alleles↗
PubMed1988

Carrier detection in X-pigmentary retinal dystrophy (X-linked retinitis pigmentosa) by DNA restriction fragment length polymorphism studies.

As part of a patient care and DNA research programme commenced in 1985, a number of DNA markers on the short arm of the X chromosome have been used to demonstrate restriction fragment length polymorphisms (RFLPs) segregating with the X-pigmentary retinal dystrophy (X-linked retinitis pigmentosa) gene. The analysis of the segregation of the RFLPs in 3 kindreds enables carrier detection, to a high degree of probability, in females at risk who are not manifesting symptoms and signs.

Adult↗