Biomedical subjects

D F Chen

Publications and source records attributed to D F Chen.

At least 37 records · Page 2Linked to original sources

PubMed1997

Skeletal and CNS defects in Presenilin-1-deficient mice.

Presenilin-1 (PS1) is the major gene responsible for early-onset familial Alzheimer's disease (FAD). To understand the normal function of PS1, we have generated a targeted null mutation in the murine homolog of PS1. We report that PS1-/- mice die shortly after natural birth or Caesarean section. The skeleton of homozygous mutants is grossly deformed. Hemorrhages occur in the CNS of PS1 null mutants with varying location, severity, and time of onset. The ventricular zone of PS1-/- brains is markedly thinner by embryonic day 14.5, indicating an impairment in neurogenesis. Bilateral cerebral cavitation caused by massive neuronal loss in specific subregions of the mutant brain is prominent after embryonic day 16.5. These results show that PS1 is required for proper formation of the axial skeleton, normal neurogenesis, and neuronal survival.

Alzheimer Disease↗

PubMed1997

Bcl-2 promotes regeneration of severed axons in mammalian CNS.

Most neurons of the mammalian central nervous system (CNS) lose the ability to regenerate severed axons in vivo after a certain point in development. At least part of this loss in regenerative potential is intrinsic to neurons. Although embryonic retinal ganglion cells (RGCs) can grow axons into tectum of any age, most RGCs from older animals fail to extend axons into CNS tissue derived from donors of any age, including the embryonic tectum. Here we report that the proto-oncogene bcl-2 plays a key role in this developmental change by promoting the growth and regeneration of retinal axons. This effect does not seem to be an indirect consequence of its well-known anti-apoptotic activity. Another anti-apoptotic drug, ZVAD, supported neuronal survival but did not promote axon regeneration in culture. This finding could lead to new strategies for the treatment of injuries to the CNS.

Animals↗

PubMed1997

pBECKS. A flexible series of binary vectors for Agrobacterium-mediated plant transformation.

A series of binary T-DNA vectors (pBECKS) has been created for use in the Agrobacterium-mediated genetic transformation of plants. The pBECKS series has corrected the undesirable features of the popular pBIN19 vector; the deleterious mutation within the coding sequence of nptII has been amended and the cloning sites are now adjacent to the right border repeat in order to reduce the possibility of producing truncated sequences of novel genes within transformants. One set of vectors incorporates various combinations of the marker genes gusA, C1/Lc, nptII, hph, and bar, for pursuit of early and stable transformation events. A set of constructs which contain deleted T-DNA borders in various combinations and display predictably altered efficacies for gene transfer has also been created. A modular set of vectors has been designed to facilitate the insertion and transfer of novel gene sequences by providing a nptII-linked plant expression cassette or lacZ-multiple cloning site. A range of antibiotic resistance genes has been incorporated into the non-T-DNA part of the vectors in order to facilitate their selection across the range of Agrobacterium virulence strains.

Binding Sites↗

PubMed1997

Agrobacterium-mediated transformation of élite indica and japonica rice cultivars.

A rapid, efficient, routine system has been established for Agrobacterium tumefaciens-mediated production of hundreds of fertile transgenic plants from commercially important rice cultivars, including an indica cultivar, Pusa Basmati 1. Calli induced from embryos of mature rice seeds were cocultivated with A. tumefaciens strain LBA4404 carrying the plasmid pTOK233, then exposed to hygromycin selection followed by an efficient regeneration system. Based on the total number of calli co-cultivated, the transformation frequencies of independent transgenic rice plants including cultivars Pusa Basmati 1, E-yi 105, E-wan 5 and Zhong-shu-wan-geng, were 13.5, 13.0, 9.1, and 9.3%, respectively. T1 seeds were harvested within 7-8 mo of initiation of mature embryo cultures. Data from Southern hybridization analysis proved that foreign genes on T-DNA were stably integrated into the rice genome at low copy/site numbers. Mendelian inheritance of the transgenes was confirmed in T1 progeny.

Agrobacterium tumefaciens↗

PubMed1997

NMDA receptor-dependent refinement of somatotopic maps.

We have examined the role of NMDA receptor-mediated neural activity in the formation of periphery-related somatosensory patterns, using genetically engineered mice. We demonstrate that ectopic expression of a transgene of an NMDAR1 splice variant rescues neonatally fatal NMDAR1 knockout (KO) mice, although the average life span varies depending on the level of the transgene expression. In NMDAR1 KO mice with "high" levels of the transgene expression, sensory periphery-related patterns were normal along both the trigeminal and dorsal column pathways. In the KO mice with "low" levels of the transgene expression, the patterns were absent in the trigeminal pathway. Our results indicate that NMDA receptor-mediated neural activity plays a critical role in pattern formation along the ascending somatosensory pathways.

Alternative Splicing↗

PubMed1997

Anti-AIDS agents--XXVI. Structure-activity correlations of gomisin-G-related anti-HIV lignans from Kadsura interior and of related synthetic analogues.

Bioactivity-directed fractionation of an ethanolic extract of the stems of Kadsura interior led to the isolation and identification of 12 known lignans (1-12). Seven of these compounds (1, 6, 8-12) were active as anti-HIV agents. Gomisin-G (11) exhibited the most potent anti-HIV activity with EC50 and therapeutic index (TI) values of 0.006 microgram/mL and 300, respectively. Schisantherin-D (6), kadsuranin (8), and schisandrin-C (10) showed good activity with EC50 values of 0.5, 0.8, and 1.2 micrograms/mL, and TI values of 110, 56, and 33.3, respectively. Ten related synthetic biphenyl compounds, five variously substituted bismethylenedioxy, dimethoxy, and dimethoxycarbonyl isomers (18-22) and five brominated derivatives (23-27) also were evaluated for inhibitory activity against HIV-1 replication in acutely infected H9 cells. The total syntheses of two new isomers (21 and 22) are reported for the first time. The anti-HIV data indicated that the relative position and types of substituents on the phenolic hydroxy groups of either the natural lignans or the synthetic biphenyl compounds rather than the numbers of bromine(s) on the aromatic rings are of primary importance. In the cyclooctane ring of the natural lignans, the position and substitution of hydroxy groups are also important to enhanced anti-HIV activity.

Anti-HIV Agents↗

PubMed1997

A novel DRB10801 haplotype carrying DRB30202 found in a German pedigree.

DRB1*08 haplotypes have not been known to carry a DRB3 gene. We have found a patient suffering from liver disease who has a novel HLA haplotype of DRB1*0801 with DRB3*0202 as established by family segregation. These two genes were confirmed by sequencing. DR8 and DR52 antigen specificities were serologically detected, indicating expression of these genes.

Female↗

PubMed1997

Simultaneous genotyping of human platelet antigens by hot start sequence-specific polymerase chain reaction with DNA polymerase AmpliTaq Gold.

OBJECTIVES: Human platelet alloantigen (HPA) typing has potential clinical relevance in a variety of contexts. We can improve methods for HPA genotyping by complementing our knowledge of the DNA sequence polymorphisms of HPA genes and experience with various DNA-based HPA typing techniques. METHODS: A newly available DNA polymerase, AmpliTaq Gold (Perkin Elmer), provided in an inactive state and activated by heat, makes it possible to perform a hot start polymerase chain reaction (PCR) in order to prevent nonspecific amplification during the setup of PCR. To establish a practical procedure for HPA-1, 2, 3 and 5 genotyping, we applied the AmpliTaq Gold for a hot start PCR and employed 8 pairs of published sequence-specific primers (SSP). A simple simultaneous genotyping of these 4 HPA systems could be rapidly achieved with high specificity. RESULTS: The HPA gene frequencies observed in 126 randomly selected German blood donors were 0.82 and 0.18 for HPA-1a and 1b, 0.92 and 0.08 for HPA-2a and 2b, 0.63 and 0.37 for HPA-3a and 3b and 0.90 and 0.10 for HPA-5a and Sb, respectively. CONCLUSION: Using our hot start PCR-SSP procedure with AmpliTaq Gold a simple, rapid and reproducible genotyping for HPA-1, 2, 3 and S systems could be achieved.

Alleles↗

PubMed1996

Subregion- and cell type-restricted gene knockout in mouse brain.

Using the phage P1-derived Cre/loxP recombination system, we have developed a method to create mice in which the deletion (knockout) of virtually any gene of interest is restricted to a subregion or a specific cell type in the brain such as the pyramidal cells of the hippocampal CA1 region. The Cre/loxP recombination-based gene deletion appears to require a certain level of Cre protein expression. The brain subregional restricted gene knockout should allow a more precise analysis of the impact of a gene mutation on animal behaviors.

Animals↗

PubMed1996

Neural tube defects and abnormal brain development in F52-deficient mice.

F52 is a myristoylated, alanine-rich substrate for protein kinase C. We have generated F52-deficient mice by the gene targeting technique. These mutant mice manifest severe neural tube defects that are not associated with other complex malformations, a phenotype reminiscent of common human neural tube defects. The neural tube defects observed include both exencephaly and spina bifida, and the phenotype exhibits partial penetrance with about 60% of homozygous embryos developing neural tube defects. Exencephaly is the prominent type of defect and leads to high prenatal lethality. Neural tube defects are observed in a smaller percentage of heterozygous embryos (about 10%). Abnormal brain development and tail formation occur in homozygous mutants and are likely to be secondary to the neural tube defects. Disruption of F52 in mice therefore identifies a gene whose mutation results in isolated neural tube defects and may provide an animal model for common human neural tube defects.

Animals↗

PubMed1996

Simplified PCR-SSO procedure for DQA and DQB typing. Simultaneous hybridization of two probes to one membrane.

To simplify DQA and DQB oligotyping, we applied our improved PCR-SSO procedure for DR typing. We used 12 oligonucleotide probes for DQA typing and 18 for DQB typing. Oligonucleotide probes that require the same hybridization and stringent washing conditions were selected as pairs for simultaneous hybridization to a dot-blot membrane containing various DNA samples. One probe of each pair was labeled with digoxigenin and the other with biotin. After hybridization, the dot-blot membranes were incubated with a mixture of conjugates. Specific binding of the corresponding DNA probes was visualized on an X-ray film using a chemiluminescent substrate (CSPD) and by staining using a chromogenic substrate (TMB). This approach, previously employed for DR typing, is also suitable for DQA and DQB oligotyping and significantly reduces the labor inherent in PCR-SSO typing.

Genotype↗

PubMed1996

Two new lignans, interiotherins A and B, as anti-HIV principles from Kadsura interior.

Two new lignans, interiotherins A (1) and B (2), along with two known lignans, angeloylgomisin R (3) and schisantherin D (4), were isolated from Kadsura interior. Their structures and stereochemistries were determined from spectral data. Compounds 1 and 4 inhibit HIV replication with EC50 values of 3.1 and 0.5 micrograms/mL, respectively.

Anti-HIV Agents↗

PubMed1996

No significant influence of HLA determinants on susceptibility to hepatitis C virus infection in Caucasian patients with end-stage renal disease.

In hepatitis C, both susceptibility to infection and the course of disease may depend on differences in the immune response. As the major histocompatibility complex (MHC) plays a crucial role in antigen presentation, we investigated a possible relationship between susceptibility to hepatitis C virus (HCV) infection and human leucocyte antigen (HLA) alleles. Therefore, phenotype frequencies of HLA were compared in 186 anti-HCV positive patients with end-stage renal disease (ESRD) to 328 anti-HCV negative patients with ESRD. HLA class I alleles were determined serologically and HLA class II alleles (DRB1, DQA1, DQB1) by the polymerase chain reaction sequence-specific oligonucleotide (PCR-SSO) technique. Additionally, in anti-HCV positive patients we looked for a relationship between the activity of hepatitis C (indicated by elevation of transaminases or the presence of viremia) and HLA determinants. For the three criteria (antibody status, elevation of transaminases and viremia) a significant association to HLA alleles was not found in patients with ESRD. This suggests that neither susceptibility to HCV infection nor the biochemical activity of hepatitis and HCV-RNA positivity seem to be strongly related to HLA status in Caucasian patients with end-stage renal disease.

Adult↗

PubMed1996

Relationship between human leukocyte antigen determinants and courses of hepatitis B virus infection in Caucasian patients with end-stage renal disease.

BACKGROUND: Divergent results have been reported with regard to the relationship between the course of hepatitis B virus (HBV) infection and the human leukocyte antigen (HLA) determinants. The aim of the present study was to investigate the phenotype frequencies of HLA class-I and -II alleles in Caucasians with and without HBV infection. METHODS: Fifty-eight patients with persistent HBV infection (group 1), 119 patients with resolved HBV infection (group 2), and 106 patients neither infected by HBV nor vaccinated against HBV (group 3) were analyzed. All patients had end-stage renal disease. HLA class-I antigens were serologically determined. For HLA class-II typing we performed DRB1, DQA1, and DQB1 genotyping using a polymerase chain reaction-sequence-specific oligonucleotide procedure. RESULTS: Compared with group 2, group 1 showed increased frequencies of HLA-B8, DR3 (P < 0.05), A30, DQA1*0501 (P < 0.01), and a decreased frequency of HLA-B12 (P < 0.05). Decreased frequencies of HLA-B27, B40, DR13, and DQ1*0604 (P < 0.05) and an increased frequency of HLA-B35 (P < 0.05) were found in groups 1 and 2 compared with controls (group 3). None of the differences detected in the phenotype frequencies of HLA alleles were statistically significant after correction. CONCLUSIONS: We conclude that the susceptibility to HBV infection and the different courses of HBV infection are not strongly related to HLA status in Caucasians.

Adult↗

PubMed1996

Anti-lipid peroxidation of gomisin J on liver mitochondria and cultured myocardial cells.

AIM: To study the influences of gomisin J on lipid peroxidation and calcium paradox. METHODS: Using two in vitro models of rat liver mitochondria membrane lipid peroxidation (LPO) and cultured myocardial cells. RESULTS: Gomisin J inhibited Fe2+/ascorbic acid and ADP/NADPH-induced LPO with IC50 (95% confidence limits) 5.5 (4.5-6.7) and 4.7 (2.8-7.8) mumol.L-1, respectively, when cultured myocardial cells preincubated with Ca(2+)-free medium for 2 min were incubated with normal medium containing Ca2+, a marked increase of malondialdehyde (MDA) formation occurred and gomisin J 10 mumol.L-1 protected myocardial cells through decreasing MDA formation. CONCLUSION: Gomisin J inhibits LPO in rat liver mitochondria and protects cultured myocardial cells from being injured by calcium paradox.

Animals↗

PubMed1995

Tonegawa defended.

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Competitive Behavior↗

PubMed1995

Intrinsic changes in developing retinal neurons result in regenerative failure of their axons.

The failure of mature mammalian central nervous system axons to regenerate after transection is usually attributed to influences of the extraneuronal milieu. Using explant cocultures of retina and midbrain tectum from hamsters, we have found evidence that these influences account for failure of regrowth of only a small minority of retinal axons. For most of the axons, there is a programmed loss of ability to elongate in the central nervous system. We show that there is a precipitous decline in the ability of retinal axons to reinnervate tectal targets when the retina is derived from pups on or after postnatal day 2, even when the target is embryonic. By contrast, embryonic retinal axons can regrow into tectum of any age, overcoming growth-inhibiting influences of glial factors.

Age Factors↗

PubMed1995

Type IV hyperlipoproteinemia and moderate instability of CAG triplet expansion in the androgen-receptor gene. Lipid, sex hormone and molecular study in a Chinese family with Kennedy-Alter-Sung disease.

Kennedy-Alter-Sung (KAS) disease in a hereditary lower motor neuron disease. In this study, we investigate 2 KAS patients presenting with progressive muscle weakness and wasting, action tremor, perioral fasciculation and gynecomastia. Three carriers and 5 healthy members from this 3-generation KAS Chinese family and 60 normal Chinese controls were included in this study. Hormone studies revealed normal serum level in thyrotropin, prolactin, testosterone, leuteinizing hormone, follicle stimulating hormone, and estradiol. Lipid study disclosed type IV hyperlipoproteinemia in 2 KAS patients and 3 healthy members. Molecular studies revealed that the number of CAG triplet repeats in the first exon of androgen receptor gene of the normal allele is in the range of 15-19 and 12-25 in this family and normal controls, respectively. However, the number of CAG repeat of androgen receptor gene were unstable in the mutant alleles with a range of 41-45 and increased from generation to generation (genomic anticipation) in the 2 KAS patients and 3 female carriers. We conclude that the CAG triplet repeats in mutant allele were unstable in the family with the KAS disease. Furthermore, type IV hyperlipoproteinemia may be a co-transmitted syndrome in the family with KAS disease.

Alleles↗