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Biomedical subjects

S Ma

Publications and source records attributed to S Ma.

At least 37 records · Page 2Linked to original sources
PubMed2004

Induction of FOS expression by acute immobilization stress is reduced in locus coeruleus and medial amygdala of Wistar-Kyoto rats compared to Sprague-Dawley rats.

Activation of the brain noradrenergic system during acute stress is thought to play an important integrative function in coping and stress adaptation by facilitating transmission in many brain regions involved in regulating behavioral and physiologic components of the stress response. Compared with outbred control Sprague-Dawley (SD) rats, inbred Wistar-Kyoto (WKY) rats exhibit an exaggerated hypothalamic-pituitary-adrenal (HPA) response as well as increased susceptibility to certain forms of stress-related pathology. However, we have also shown previously that WKY rats exhibit reduced anxiety-like behavioral reactivity to acute stress, associated with reduced activation of the brain noradrenergic system. Thus, to understand better the possible neurobiological mechanisms underlying dysregulation of the stress response in WKY rats, we investigated potential strain differences in stress-induced neuronal activation in brain regions that are both involved in regulating behavioral and neuroendocrine stress responses, and are related to the noradrenergic system, either as targets of noradrenergic modulation or as sources of afferent innervation of noradrenergic neurons. This was accomplished by visualizing stress-induced expression of Fos immunoreactivity in the paraventricular nucleus of the hypothalamus, lateral bed nucleus of the stria terminalis, central nucleus of the amygdala, and medial nucleus of the amygdala (MeA), as well as the noradrenergic nucleus locus coeruleus (LC). Stress-induced Fos expression was found to be decreased in the LC and MeA of WKY rats compared with similarly stressed SD rats, whereas no strain differences were observed in any of the other brain regions. This suggests that strain-related differences in activation of the MeA may be involved in the abnormal neuroendocrine and behavioral stress responses exhibited by WKY rats. Moreover, as the MeA is both an afferent as well as an efferent target of the brainstem noradrenergic system, reduced MeA activation may either be a source of reduced noradrenergic reactivity seen in WKY rats, or possibly a consequence. Nonetheless, understanding the mechanisms underlying altered stress reactivity in models such as the WKY rat may contribute to a better understanding of stress-related psychopathologies such as depression, post-traumatic stress disorder or other anxiety disorders.

Amygdala↗
PubMed2004

An association between sex chromosomal aneuploidy in sperm and an abortus with 45,X of paternal origin: possible transmission of chromosomal abnormalities through ICSI.

BACKGROUND: Although it has been speculated that the increased de-novo chromosomal abnormalities in ICSI pregnancies may be associated with an increase of aneuploidy in sperm from infertile men, little direct evidence exists to support this claim. We studied sperm from an infertile man with an abortus from ICSI to determine if increased sex chromosomal aneuploidy in the sperm could have contributed to the karyotype of the abortus. METHODS: The couple underwent ICSI due to severe oligozoospermia. Spontaneous aborted material was subjected to cytogenetic and molecular tests to ascertain the existence, type and origin of a chromosomal abnormality. Sperm from the man were analysed by multi-coloured fluorescent in-situ hybridization (FISH) with probes specific for chromosomes X, Y and 18. RESULTS: At 8+ weeks after embryo replacement, the patient spontaneously miscarried. Both cytogenetic and comparative genomic hybridization analysis of aborted material showed a 45,X karyotype. Origin of the abnormality was established as a loss of the paternal X chromosome. FISH analysis of sperm revealed 19.6% (1990/10,164) nullisomy for a sex chromosome and 18.6% (1886/10,164) with XY disomy, which is significantly increased when compared to controls with 0.3% (58/20,429) and 0.1% (20/20,429) respectively (P<0.0001). CONCLUSIONS: This study indicates that the paternal origin of the 45,X abortus was likely the result of a high level of nullisomy in the sperm and provides evidence for the transmission of chromosomal abnormality from sperm to the conceptus through ICSI.

Abortion, Spontaneous↗
PubMed2004

Effects of single nucleotide polymorphisms in the RANTES promoter region in healthy and HIV-infected indigenous Chinese.

We determined the occurrence of the single nucleotide polymorphisms (SNPs) -403A/G and -28C/G in the promoter region of RANTES in 1082 Chinese blood donors from northern and southern China and 249 HIV patients from southern China. Compared to healthy adults, Chinese AIDS patients had a significantly higher frequency of the -403G allele and haplotype I, -403G/-28C (P < 0.05), and a lower frequency of the -403A/A genotype (P < 0.01). Symptomatic patients had a higher frequency of the -28G allele and a lower frequency of the -28C/C genotype (P < or = 0.01). The plasma RANTES level was significantly lower in blood donors homozygous for haplotype I than in those who were homozygous for haplotypes II and III (P < 0.05). The frequency of the -403G allele was found to be higher in Chinese than in indigenous Africans, but lower than in Caucasians, Hispanics, and African Americans. The frequency of the -28G allele was comparable in Chinese and Japanese; this allele is rare in other ethnic groups. Results suggest that -403G may be associated with increased susceptibility to HIV infection, while -28G may be associated with advanced disease progression. The impact of SNPs on HIV infection appears to be unique in Chinese.

Chemokine CCL5↗
PubMed2004

Birthweight and psychological distress in adult twins: a longitudinal study.

AIM: To assess the relation between birthweight and psychological distress as measured by the Malaise Inventory in adult twins. METHODS: Data were drawn from the 1958 British birth cohort study, which included twins followed from birth to age 42 y. We examined the relation between birthweight and psychological distress at ages 23, 33 and 42 y measured by the psychological scale of the Malaise Inventory. Analyses were performed both between subjects (n = 282) and within twin pairs (n = 112). The generalized estimating equations approach was used to handle the repeated measurements. RESULTS: Between the 282 twins, the difference in psychological distress score was -0.45 (95% confidence interval -0.74 to -0.15) per Z-score increase in birthweight-for-gestational age. Within twin pairs, the heavier co-twins tended to have a psychological distress score lower than that of their lighter co-twins, the mean difference being -0.35 (-0.78 to 0.09). CONCLUSION: Results from the between-subject analysis agreed with previous findings from adult singletons that psychological health is related to birthweight. The within-pair analysis suggested a similar relation but did not attain statistical significance.

Adult↗
PubMed2004

The prevalence of asthma and allergies in Singapore; data from two ISAAC surveys seven years apart.

BACKGROUND AND AIMS: Over the past few decades, the prevalence of asthma has been increasing in the industrialised world. Despite the suggestion of a similar increase in Singapore, the 12 month prevalence of wheeze among schoolchildren in 1994 was 2.5-fold less than that reported in western populations. It was hypothesised that with increasing affluence in Singapore, the asthma prevalence would further increase and approach Western figures. A second ISAAC survey was carried out seven years later to evaluate this hypothesis. METHODS: The cross-sectional data from two ISAAC questionnaire based surveys conducted in 1994 (n = 6238) and in 2001 (n = 9363) on two groups of schoolchildren aged 6-7 and 12-15 years were compared. The instruments used were identical and the procedures standardised in both surveys. RESULTS: Comparing data from both studies, the change in the prevalence of current wheeze occurred in opposing directions in both age groups--decreasing in the 6-7 year age group (16.6% to 10.2%) but increasing to a small extent in the 12-15 year age group (9.9% to 11.9%). The 12 month prevalence of rhinitis did not change; there was an increase in the current eczema symptoms in both age groups. CONCLUSION: The prevalence of current wheeze, a surrogate measure of asthma prevalence, has decreased significantly in the 6-7 year age group. Eczema was the only allergic disease that showed a modest increase in prevalence in both age groups.

Adolescent↗
PubMed2004

Mandatory temperature monitoring in schools during SARS.

During the SARS outbreak, temperature monitoring was mandatory for all Singapore schoolchildren. None of the Singapore children with SARS were detected through school temperature screening. However, temperature monitoring procedures have a powerful psychological effect of reassuring parents and the public that schools are safe during a SARS outbreak.

Adolescent↗
PubMed2003

O6-methylguanine-DNA-methyltransferase expression and gene polymorphisms in relation to chemotherapeutic response in metastatic melanoma.

In a retrospective study, O(6)-methylguanine-DNA-methyltransferase (MGMT) expression was analysed by immunohistochemistry using monoclonal human anti-MGMT antibody in melanoma metastases in patients receiving dacarbazine (DTIC) as single-drug therapy or as part of combination chemotherapy with DTIC-vindesine or DTIC-vindesine-cisplatin. The correlation of MGMT expression levels with clinical response to chemotherapy was investigated in 79 patients with metastatic melanoma. There was an inverse relationship between MGMT expression and clinical response to DTIC-based chemotherapy (P=0.05). Polymorphisms in the coding region of the MGMT gene were also investigated in tumours from 52 melanoma patients by PCR/SSCP and nucleotide sequence analyses. Single-nucleotide polymorphisms (SNPs) in exon 3 (L53L and L84F) and in exon 5 (I143V/K178R) were identified. There were no differences in the frequencies of these polymorphisms between these melanoma patients and patients with familial melanoma or healthy Swedish individuals. Functional analysis of variants MGMT-I143V and -I143V/K178R was performed by in vitro mutagenesis in Escherichia coli. There was no evidence that these variants decreased the MGMT DNA repair activity compared to the wild-type protein. All melanoma patients with the MGMT 53/84 polymorphism except one had tumours with high MGMT expression. There was no significant correlation between any of the MGMT polymorphisms and clinical response to chemotherapy, although an indication of a lower response rate in patients with SNPs in exon 5 was obtained. Thus, MGMT expression appears to be more related to response to chemotherapy than MGMT polymorphisms in patients with metastatic melanoma.

Adult↗
PubMed2003

X-chromosome inactivation (XCI) patterns in placental tissues of a paternally derived bal t(X;20) case.

Non-random X-chromosome inactivation (XCI) is often seen in female carriers of balanced X-autosome translocations and is generally attributed to a selective growth of cells that inactivate the normal X chromosome. However, little is known concerning when in development the selection acts, and thus whether skewed XCI would also be seen in placental tissues. Furthermore, as males with X-autosome translocations are normally infertile, all translocations studied to date for XCI-skewing have been either maternal or de novo in origin. We now present an analysis of XCI status in cord blood, umbilical cord and four different extraembryonic tissues from a female carrier of a paternally derived balanced (X;20) translocation. Using methylation based assays to determine XCI status, we found preferential inactivation of the non-translocated X in cord blood, umbilical cord and amnion samples of the propositus. Remarkably, random XCI was evident in several placental tissues analyzed (chorion, and chorionic villi trophoblast and mesenchyme). While these findings support the hypothesis of strong selection against cells with an inactive translocated X-chromosome in most embryonic/fetal tissues, they also suggest weaker selective forces taking place during placental development. Additionally, the finding of normal placental development in the present case, rules out the possibility of a parental bias to XCI in human extraembryonic tissues as a requisite for normal development. The finding of hypomethylation in extraembryonic tissues for two out of three markers used in the study is consistent with previous findings demonstrating low levels of methylation in these tissues.

Chromosomes, Human, Pair 20↗
PubMed2003

Cytogenetic and molecular study of a premature male infant with 46,XX derived from ICSI: case report.

We investigated the aetiology of the male phenotype in a premature infant derived from ICSI with a 46,XX karyotype. A karyotypically normal couple underwent ICSI because of obstructive azoospermia in the male partner. Sperm were retrieved by testicular sperm extraction (TESE), cryopreserved, and later used for ICSI. The pregnancy after ICSI ended at 20 weeks. A normal-appearing male was delivered but he did not survive. Umbilical cord blood and placenta were sampled and used for molecular and cytogenetic investigation. The 46,XX karyotype from G-banding in this male infant correlated to a balanced female comparative genomic hybridization (CGH) profile in placental tissue. No PCR amplification of SRY on the p arm of the Y chromosome was observed while fluorescence in-situ hybridization (FISH) with the SRY probe also could not detect the gene in cord blood or placental tissues. CGH and FISH, with X and Y centromeric probes, failed to detect mosaicism in the trophoblast, stroma and amnion. Skewed X-chromosome inactivation (81%) was found in the chorionic villi. The molecular and cytogenetic studies indicated a 46,XX male infant without the SRY gene or 46,XX/XY mosaicism. The possible mechanism in this SRY-negative XX male by ICSI is discussed.

Adult↗
PubMed2002

Novel O6-methylguanine-DNA methyltransferase SNPs: a frequency comparison of patients with familial melanoma and healthy individuals in Sweden.

The DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) is involved in the cellular defense against alkylating agents. Genetic alterations in the MGMT gene may impair the protein's ability to remove alkyl groups from the O6-position of guanine, thereby raising the mutation rate and increasing the risk of cancer. We assessed polymorphisms in the promoter region and the 5 exons of the MGMT gene by PCR/SSCP and nucleotide sequence analysis of DNA extracted from blood samples. The population studied consisted of 89 melanoma patients, each belonging to a different family with a hereditary predisposition for melanoma, and 76 healthy individuals (blood donors). A total of 11 single nucleotide polymorphisms (SNPs) were detected, five in the promoter region, one in exon 1, two in exon 3 and three in exon 5. Six of the alterations were novel polymorphisms, of which five were located in the promoter region and one in exon 5. When the distribution of specific SNPs in cases and controls with only one variant was calculated; C575A was present only in melanoma patients (p=0.072). Moreover, while 20% of the healthy individuals had no SNPs this was the case in only 12.4% of the melanoma patients. However, no statistically significant differences were seen between cases and controls for any of the 11 SNPs.

Base Sequence↗
PubMed2002

Analysis of O(6)-methylguanine-DNA methyltransferase in melanoma tumours in patients treated with dacarbazine-based chemotherapy.

In a retrospective study we analysed the levels of the DNA repair protein O(6)-methylguanine-DNA methyltransferase (MGMT) in melanoma metastases in patients receiving dacarbazine (DTIC) either as a single drug or as part of combination chemotherapy regimens, and related the expression levels to the clinical response to treatment. Biopsies of subcutaneous and lymph node metastases obtained before chemotherapy in 65 patients with disseminated malignant melanoma were examined for MGMT protein levels by immunohistochemistry using a monoclonal anti-human MGMT antibody. All patients received chemotherapy with DTIC, given either as a single drug or in combination with vindesine and in some cases cisplatin. DTIC as single agent was given to 44 patients, while 21 received combination chemotherapy. Objective responses to chemotherapy were seen in 12 patients, while 53 patients failed to respond to treatment. The expression of MGMT was determined according to the proportion of antibody-stained tumour cells, using a cut-off level of 50%. In 12 of the patients more than one metastasis was analysed, and in seven of these cases the MGMT expression differed between tumours in the same individual. Among the responders a larger proportion (six out of 12, 50%) had tumours containing less than 50% MGMT-positive tumour cells than among the non-responders (12 out of 53, 23%). These data are consistent with the hypothesis that MGMT contributes to resistance to DTIC-based treatment, although the difference between responders and non-responders with respect to the proportion of MGMT-positive tumour cells was not statistically significant (P = 0.077).

Adult↗
PubMed2002

Decreasing STD incidence and increasing condom use among Chinese sex workers following a short term intervention: a prospective cohort study.

OBJECTIVE: To describe the impact of a repeating behavioural intervention focused on preventive education and provision of STD testing and treatment services to female sex workers. METHODS: A prospective cohort study of 966 sex workers (first of its kind in China) was conducted in Guangzhou from March 1998 to October 1999. At each visit information was collected on sexual behaviour, condom use and knowledge about HIV transmission and condom use, education was given, STD were diagnosed, and treatment was provided free of charge. We evaluated trends in condom use, knowledge about HIV transmission and condom use, and STD incidences. Generalised estimating equations were applied to control for repeated measurements. RESULTS: The proportion of consistent condom use increased from the intake through the third follow up visit (from 30% to 81%), as well as the proportion of having good knowledge on HIV transmission (4.3% to 98.6%) and condom use (23.6% to 79.3%). The incidence of gonorrhoea, trichomoniasis, and chlamydia decreased over each follow up visit; from 17.5/100 person years (PY), 22.4/100PY, 65.9/100PY at the first follow up visit to 5.1/100PY, 3.0/100PY, 16.1/100PY at the third follow up visit, for each STD respectively. CONCLUSIONS: STD care and prevention programmes targeting sex workers are feasible in China and, more importantly, intervention consisting of prevention education and STD care is likely to reduce unprotected sexual behaviour and STD incidence in this group at high risk for HIV and other STD infection.

Adult↗
PubMed2001

Strain-based sequence variations and structure analysis of murine prostate specific spermine binding protein using mass spectrometry.

Mouse spermine binding protein (SBP) has been characterized using mass spectrometry, including its localization within the prostate, sequence verification, and its posttranslational modifications. MALDI (matrix-assisted laser desorption/ionization) mass spectrometry was employed for localization of proteins expressed by different lobes of the mouse prostate obtained after tissue blotting on a polyethylene membrane. The mass spectra showed complex protein profiles that were different for each lobe of the prostate. The prostate-specific spermine binding protein (SBP), primarily identified by its in-source decay fragment ion signals, was found predominantly expressed by the ventral lobe of the prostate. The MALDI in-source decay measurements combined with nanoESI (nanoelectrospay ionization) MS/MS measurements obtained after specific proteolysis of SBP, allowed the exact positioning of a single N-linked carbohydrate group, and the identification of a pyroglutamate residue at the sequence N-terminus. The N-linked carbohydrate component was further investigated and the general pattern of the N-linked carbohydrate identified. The presence of a disulfide bridge between cysteine78 and cysteine124 was also established. The full sequence characterization of SBP showed several strain-based sequence differences when compared to the published gene sequence.

Amino Acid Sequence↗
PubMed2001

A physical and transcript map of the MCOLN1 gene region on human chromosome 19p13.3-p13.2.

Mutations in MCOLN1 have been found to cause mucolipidosis type IV (MLIV; MIM 252650), a rare autosomal recessive lysosomal storage disorder found primarily in the Ashkenazi Jewish population. As a part of the successful cloning of MCOLN1, we constructed a 1.4-Mb physical map containing 14 BACs and 4 cosmids that encompasses the region surrounding MCOLN1 on human chromosome 19p13.3-p13.2-a region to which linkage or association has been reported for multiple diseases. Here we detail the precise physical mapping of 28 expressed sequence tags that represent unique UniGene clusters, of which 15 are known genes. We present a detailed transcript map of the MCOLN1 gene region that includes the genes KIAA0521, neuropathy target esterase (NTE), a novel zinc finger gene, and two novel transcripts in addition to MCOLN1. We also report the identification of eight new polymorphic markers between D19S406 and D19S912, which allowed us to pinpoint the location of MCOLN1 by haplotype analysis and which will facilitate future fine-mapping in this region. Additionally, we briefly describe the correlation between the observed haplotypes and the mutations found in MCOLN1. The complete 14-marker haplotypes of non-Jewish disease chromosomes, which are crucial for the genetic diagnosis of MLIV in the non-Jewish population, are presented here for the first time.

Chromosome Mapping↗
PubMed2001

[Pregnancy and its outcome in women with malformed uterus].

OBJECTIVE: To analyze the clinical characteristics of fertility and pregnancy in women with congenital uterine malformations and explore optimal treatments to improve the prognosis. METHODS: A retrospective study was conducted on the fertility and obstetric outcome in 153 in patients with uterine malformations treated in our hospital from January 1984 to December 1998. Twenty-seven cases with other kinds of genital and/or urinary anomalies but with normal uterus was used as the control group. RESULTS: The infertility rate was 22.2% (34/153). The miscarriage rate was 44.3% (86/194), preterm labor rate was 9.3% (18/194). Abnormal fetal presentation rate was as high as 28.4% (29/102), the cesarean section rate was 61.8% (63/102), perinatal mortality rate was 11.8% (12/102). CONCLUSION: Women with congenital uterine malformation usually have higher incidence of infertility and complications during pregnancy and delivery. Bicornuate and septate uterus could be associated with poorer obstetric outcome.

Abortion, Spontaneous↗
PubMed2001

Molecular motors and membrane traffic in Dictyostelium.

Phagocytosis and membrane traffic in general are largely dependent on the cytoskeleton and their associated molecular motors. The myosin family of motors, especially the unconventional myosins, interact with the actin cortex to facilitate the internalization of external materials during the early steps of phagocytosis. Members of the kinesin and dynein motor families, which mediate transport along microtubules (MTs), facilitate the intracellular processing of the internalized materials and the movement of membrane. Recent studies indicate that some unconventional myosins are also involved in membrane transport, and that the MT- and actin-dependent transport systems might interact with each other. Studies in Dictyostelium have led to the discovery of many motors involved in critical steps of phagocytosis and membrane transport. With the ease of genetic and biochemical approaches, the established functional analysis to test phagocytosis and vesicle transport, and the effort of the Dictyostelium cDNA and Genome Projects, Dictyostelium will continue to be a superb model system to study phagocytosis in particular and cytoskeleton and motors in general.

Actins↗