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Biomedical subjects

Z Wong

Publications and source records attributed to Z Wong.

11 recordsLinked to original sources
PubMed1998

Group psychoeducation of relatives of schizophrenic patients: two-year experiences.

In order to assess the feasibility and acceptability of group psychosocial education for the relatives of schizophrenics in the community, a 2-year project was carried out in two cities: Jinan and Shanghai, China. The completed sample included 682 cases in the experimental group and 366 cases in the control group. The experimental group received group psychotherapy including 14 lectures and five group discussions with conventional services, and the control group had conventional services only. The annual relapse rate in the experimental group was much lower than that in the control group (17.6 and 23.2%, P < 0.01) and the rate of regular work in the experimental group was higher than that in the control group (37.5 and 30.0%, P < 0.05). At the end of the second year, the relatives in the experimental group had less care burden, better mental and physical health status and more knowledge of caring for schizophrenics than those in the control group. This approach was well accepted by both mental health workers and relatives of schizophrenics and the rate of drop-out was 18.4% only during the 2-year period.

Adult↗
PubMed1997

[Dose distributions of linac-based radiosurgery for pineal region mass].

The doses of linac convergent-beam irradiations to pineal region were measured in an anthropomorphic phantom. The feasibility of a linac accelerator as a radiosurgery tool to treat small sized intracranial masses was evaluated. The influences of some irradiation parameters on the dose distributions were discussed. Linac-based radiosurgery can result in dose distributions similar to those achieved by gamma knife, so it is another safe and effective treatment technique of neurosurgery. The smaller the aperture is and the greater the irradiation arc travel is, the larger the dose gradient will be and the better the dose distribution will be. The maximum target doses are dependent greatly upon the collimater aperture. The appropriate irradiation arc travel and margin isodose were also discussed.

Brain Neoplasms↗
PubMed1990

A novel human DNA polymorphism resulting from transfer of DNA from chromosome 6 to chromosome 16.

A cloned minisatellite, termed lambda MS29, that is unusual because it detects two variable loci in human DNA has been isolated. One locus, DNF21S1, located in the terminal region of the short arm of human chromosome 6, is also present in great apes. The second minisatellite locus, DNF21S2, is located interstitially on chromosome 16p11 and is absent both from non-human primates and from some humans. Physical mapping and sequencing show that the second locus has arisen recently in evolution by duplication of a large (greater than 15 kb) segment of chromosome 6 DNA containing a minisatellite and transposition onto chromosome 16 into a member of a novel low-copy-number repetitive DNA family. This unusual duplication/transposition event appears to represent the first example of a human DNA polymorphism arising through DNA-mediated, rather than RNA-mediated, transfer between autosomes.

Alleles↗
PubMed1989

Sequences flanking the repeat arrays of human minisatellites: association with tandem and dispersed repeat elements.

We present DNA sequences flanking cloned hypervariable human minisatellites. In addition to providing confirmatory evidence that minisatellites cluster with other tandem repeats, these flanking sequences contain a high frequency of interspersed repetitive elements. These elements include a retroviral LTR-like sequence, from which one of the minisatellites appears to have expanded, and a recently described short interspersed repeat. We present our own findings concerning this element, in particular that those examples studied do not show significant evolutionary conservation, despite suggestions that the element may have a cis-acting function.

Base Sequence↗
PubMed1988

Spontaneous mutation rates to new length alleles at tandem-repetitive hypervariable loci in human DNA.

Tandem-repetitive minisatellite regions in vertebrate DNA frequently show substantial allelic variation in the number of repeat units. This variation is thought to arise through processes such as unequal crossover or replication slippage. We show here that the spontaneous mutation rate to new length alleles at extremely variable human minisatellites is sufficiently high to be directly measurable in human pedigrees. The mutation rate at different loci increases with variability in accord with the neutral mutation/random drift hypothesis, and rises to 5% per gamete for the most unstable human minisatellite isolated. Mutations are sporadic, occur with similar frequencies in sperm and oocytes, and can involve the gain or loss of substantial numbers of repeat units, consistent with length changes arising primarily by unequal exchange at meiosis. Germline instability must therefore be taken into account when using hypervariable loci as genetic markers, particularly in pedigree analysis and parenthood testing.

Alleles↗
PubMed1988

Clustering of hypervariable minisatellites in the proterminal regions of human autosomes.

Six of the human minisatellites detected by DNA fingerprint probes have been localized by in situ hybridization to human metaphase chromosomes. These hypervariable loci are not dispersed at random in the human genome, but show preferential, though not exclusive, localization to terminal G-bands of human autosomes. Two of the proterminal minisatellites are very closely linked to other variable loci. Sequence analysis of one of these additional minisatellites suggests that the two linked minisatellites arose by independent amplification of different repeat units. The proterminal regions of human autosomes may therefore be rich in minisatellites, analogous to the pseudoautosomal terminal pairing region of human sex chromosomes that is similarly abundant in hypervariable minisatellites.

Base Sequence↗
PubMed1987

Characterization of a panel of highly variable minisatellites cloned from human DNA.

Five of the most variable loci detected in human DNA by hybridization with DNA fingerprint probes have been cloned and characterized. Each locus consists of a tandem-repetitive minisatellite, with repeat units ranging in length from 9 to 45 base pairs depending on the locus. All of these cloned minisatellites act as locus-specific hybridization probes, and detect extremely variable Mendelian loci with heterozygosities ranging from 90 to 99%. These five hypervariable loci, together with a previously-isolated minisatellite designated p lambda g3, are dispersed over four autosomes (chromosomes 1, 5, 7 and 12). Syntenic pairs on chromosomes 1 and 7 show no detectable pair-wise linkage, and thus these hypervariable loci show no evidence of clustering within the genome and should provide valuable markers for mapping inherited disease. The locus-specific minisatellites act as very sensitive hybridization probes, and can be pooled to detect several hypervariable loci simultaneously. The applications of these probes in individual identification, paternity testing and analysis of cell chimaerism are discussed, and are illustrated by an analysis of forensic specimens from two victims who had been sexually assaulted and murdered.

Chromosomes↗
PubMed1987

Linkage analysis of British and Indian families with Von Recklinghausen neurofibromatosis.

Linkage analysis has been undertaken in two British and three South African Indian families with Von Recklinghausen neurofibromatosis. Eleven polymorphic DNA probes were studied, including both random DNA sequences and candidate oncogenes. Although no evidence for linkage of these probes to the disease was detected, substantial exclusion regions were established on six of the chromosomes studied.

Genetic Linkage↗
PubMed1986

Cloning a selected fragment from a human DNA 'fingerprint': isolation of an extremely polymorphic minisatellite.

A large hypervariable DNA fragment from a human DNA fingerprint was purified by preparative gel electrophoresis and molecular cloning. The cloned fragment contained a 6.3 kb long minisatellite consisting of multiple copies of a 37 bp repeat unit. Each repeat contained an 11 bp copy of the "core" sequences, a putative recombination signal in human DNA. The cloned minisatellite hybridized to a single locus in the human genome. This locus is extremely polymorphic, with at least 77 different alleles containing 14 to 525 repeat units per allele being resolved in a sample of 79 individuals. All alleles except the shortest are rare and the resulting heterozygosity is very high (approximately 97%). Cloned minisatellites should therefore provide a panel of extremely informative locus-specific probes ideal for linkage analysis in man.

Base Sequence↗
PubMedDate not supplied

Deletion of genes on chromosome 1 in endocrine neoplasia.

Recent studies have identified normal cellular DNA sequences which are lost in the development of embryonal and adult tumours. These tumours are thought to arise after a primary mutation in one allele of such a sequence is followed by loss of its normal homologue. In familial cases, the primary mutation is transmitted in the germ line. The secondary mutation may involve a substantial loss of chromosomal material and thus lead to identification of the site of the inherited mutation. We have examined constitutional and tumour genotypes of medullary thyroid carcinomas and phaeochromocytomas which develop in the dominantly inherited cancer syndrome multiple endocrine neoplasia type 2 (MEN2) to locate the predisposing gene in this syndrome. We observed deletion of a hypervariable region of DNA on the short arm of chromosome 1 in seven out of fourteen tumours. Analysis of the parental origin of the deleted allele in two families showed that it was derived from the affected parent in one case, which suggests that the deletion does not reflect the site of the inherited mutation in MEN2. The deleted region is distal to the breakpoint commonly detected in neuroblastomas, which share with the tumours of MEN2 embryological origin from neuroectoderm.

Carcinoma↗