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Biomedical subjects

M Chung

Publications and source records attributed to M Chung.

At least 91 records · Page 5Linked to original sources
PubMed1997

Inhibition of prostate ductal morphogenesis by retinoic acid.

PURPOSE: To examine the effect of retinoic acid on prostate ductal morphogenesis. MATERIALS AND METHODS: Newborn male Balb/C mice were injected with 25 mg./kg. all-trans retinoic acid or vehicle alone. Animals were sacrificed at 60 days of age and prostate ductal morphology was quantitatively assessed by microdissection. Total prostate DNA was quantitated by DPA assay. RESULTS: The greatest effect was seen in the ventral prostate. Retinoic acid treated animals showed a 20% decrease in mean number of branch-points (p = 0.0006) with a corresponding 13% decrease in duct tips (p = 0.026). The combined ventral and dorsal prostate showed an effect with a 12% decrease in ductal branchpoints (p = 0.048). There was no effect on animal or organ weight and no effect on DNA content within the prostate. There was no difference in the prostate histology of treated and control animals. CONCLUSION: Retinoic acid administration in the newborn period inhibits mouse prostate ductal morphogenesis. This effect appears independent of an inhibition of overall growth.

Animals↗
PubMed1997

Multiplex sequencing of 1.5 Mb of the Mycobacterium leprae genome.

The nucleotide sequence of 1.5 Mb of genomic DNA from Mycobacterium leprae was determined using computer-assisted multiplex sequencing technology. This brings the 2.8-Mb M. leprae genome sequence to approximately 66% completion. The sequences, derived from 43 recombinant cosmids, contain 1046 putative protein-coding genes, 44 repetitive regions, 3 tRNAs, and 15 tRNAs. The gene density of one per 1.4 kb is slightly lower than that of Mycoplasma (1.2 kb). Of the protein coding genes, 44% have significant matches to genes with well-defined functions. Comparison of 1157 M. leprae and 1564 Mycobacterium tuberculosis proteins shows a complex mosaic of homologous genomic blocks with up to 22 adjacent proteins in conserved map order. Matches to known enzymatic, antigenic, membrane, cell wall, cell division, multidrug resistance, and virulence proteins suggest therapeutic and vaccine targets. Unusual features of the M. leprae genome include large polyketide synthase (pks) operons, inteins, and highly fragmented pseudogenes.

Amino Acid Sequence↗
PubMed1997

Novel receptor interaction and repression domains in the orphan receptor SHP.

SHP (short heterodimer partner) is a novel orphan receptor that lacks a conventional DNA binding domain and interacts with other members of the nuclear hormone receptor superfamily. We have characterized the SHP sequences required for interaction with other superfamily members, and have defined an SHP repressor domain. In the mammalian two-hybrid system, a fusion of full-length SHP to the GAL4 DNA binding domain shows 9-cis-retinoic acid-dependent interaction with a VP16-retinoid X receptor alpha (RXR alpha) fusion. By deletion analysis, sequences required for this RXR interaction map to the central portion of SHP (amino acids 92 to 148). The same region is required for interaction with RXR in vitro and in the yeast two-hybrid system, and results from the yeast system suggest that the same SHP sequences are required for interaction with other members of the nuclear hormone receptor superfamily such as thyroid hormone receptor and retinoic acid receptor. In mammalian cells, a GAL4-SHP fusion protein shows about 10-fold-decreased transcriptional activation relative to GAL4 alone, and fusion of SHP to the C terminus of a GAL4-VP16 fusion to generate a triple chimera also results in a strong decrease in transactivation activity. Sequences required for this repressor function were mapped to the C terminus of SHP. This region is distinct from that required for corepressor interaction by other members of the nuclear hormone receptor superfamily, and SHP did not interact with N-CoR in either the yeast or mammalian two-hybrid system. Together, these results identify novel receptor interaction and repressor domains in SHP and suggest two distinct mechanisms for inhibition of receptor signaling pathways by SHP.

Amino Acid Sequence↗
PubMed1997

Biology of sarcomas.

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Genes, Tumor Suppressor↗
PubMed1996

Younger women with breast carcinoma have a poorer prognosis than older women.

BACKGROUND: It is controversial whether breast cancer in young women is more aggressive than in older women. This study was initiated to determine age-associated outcome of women with breast carcinoma. METHODS: Patients with breast carcinoma, who were identified in a statewide tumor registry, were divided into age groups based on 10-year intervals (ages 40 and younger, 41 to 50, 51 to 60, 61 to 70, 71 to 80, and older than 80 years). Age at diagnosis, American Joint Committee on Cancer classification, 5-year disease free (5DFS) and cancer specific (5CSS) survival estimates using Kaplan-Meier analysis were determined. RESULTS: Between 1985 and 1992, 3722 women were diagnosed with invasive breast carcinoma. Approximately 5.6% (210) of the women were 40 years old or younger. The youngest age group had the worst 5CSS of 69.7%, followed by the oldest age group (> 80, 5CSS = 71.45%). The age groups 41 to 50, 51 to 60, 61 to 70, and 71 to 80 years had 5CSS of 80.30%, 78.45%, 82.06%, and 84.27%, respectively. The oldest age group (> 80) had the worst 5DFS (39.88%) followed by the youngest age group (< or = 40, 5DFS = 60.79%). The age groups 41 to 50, 51 to 60, 61 to 70, and 71 to 80 years had 5DFSs of 73.22%, 66.87%, 71.53%, and 63.11%, respectively. Analyzed by stage, young (< or = 40 years) women had a worse 5CSS when compared with the other age groups, except for those with Stage I disease. CONCLUSIONS: Our results indicate that women 40 years of age and younger have a worse 5CSS than their older counterparts. This difference in survival is not solely a reflection of more advanced disease but may reflect differences in tumor biology.

Adult↗
PubMed1996

Effect of time of administration on the pharmacokinetics and tolerance of doxazosin in healthy male volunteers.

A randomized, open-label, two-way crossover study of 24 normotensive, healthy male volunteers with nocturia was conducted to compare morning and evening administration of doxazosin in terms of pharmacokinetics and tolerance. In both the morning and evening phases, participants received doxazosin 1 mg once daily for 10 days, followed by 2 mg once daily for 5 days. Pharmacokinetic data were evaluated from blood samples serially collected for 72 hours after drug administration on the last day of each phase. Vital signs and adverse events were recorded throughout the study. Mean peak plasma concentrations (C(max)) were 16.98 and 15.76 ng/mL after morning and evening administration, respectively. Corresponding mean values of area under the plasma concentration-time curve (AUC0-24) were 227.90 and 253.66 ng.hr/mL, respectively. Statistical analysis of the log-transformed values for C(max) and AUC0-24 indicated that morning and evening administration of doxazosin were bioequivalent. There were no statistically or clinically significant differences between phases for mean apparent half-life (t1/2) or total body clearance. There were no clinically relevant differences in blood pressure or in pulse rate between phases, and no occurrences of orthostatic hypotension. The incidence of adverse experiences during morning and evening administration was similar. Morning and evening administration of doxazosin are equivalent and have similar tolerance profiles.

Adrenergic alpha-Antagonists↗
PubMed1996

Cloning and developmental expression analysis of the murine homolog of the spinocerebellar ataxia type 1 gene (Sca1).

Spinocerebellar ataxia type 1 (SCA1) is an autosomal dominant neurodegenerative disorder caused by the expansion of a CAG trinucleotide repeat which encodes glutamine in the novel protein ataxin-1. In order to characterize the developmental expression pattern of SCA1 and to identify putative functional domains in ataxin-1, the murine homolog (Sca1) was isolated. Cloning and characterization of the murine Sca1 gene revealed that the gene organization is similar to that of the human gene. The murine and human ataxin-1 are highly homologous but the CAG repeat is virtually absent in the mouse sequence suggesting that the polyglutamine stretch is not essential for the normal function of ataxin-1 in mice. Cellular and developmental expression of the murine homolog was examined using RNA in situ hybridization. During cerebellar development, there is a transient burst of Sca1 expression at postnatal day 14 when the murine cerebellar cortex becomes physiologically functional. There is also marked expression of Sca1 in mesenchymal cells of the intervertebral discs during development of the spinal column. These results suggest that the normal Sca1 gene, has a role at specific stages of both cerebellar and vertebral column development.

Amino Acid Sequence↗
PubMed1996

A clinical study of the natural remodeling of burst fractures of the lumbar spine.

Surgical decompression and fixation are considered by many to be the preferred treatment for burst fractures of the lumbar spine, regardless of neurologic deficit. For 6 patients with burst fracture of the lumbar spine but without neurologic deficit, computed tomography scans revealed >50% encroachment of the spinal canal. All 6 patients were treated conservatively, and during the followup period (range, 6-49 months), the narrowing of the spinal canal decreased progressively because of resorption of the fragments and natural remodeling. The presence of a neurologic deficit should be the primary indication for surgery in patients with a burst fracture of the lumbar spine.

Adult↗
PubMed1996

Vancomycin-resistant Enterococcus faecium on a pediatric oncology ward: duration of stool shedding and incidence of clinical infection.

OBJECTIVE: To determine the duration of stool shedding and incidence of clinical infection among pediatric oncology patients colonized with vancomycin-resistant Enterococcus faecium (VRE) in our institution. METHODS: Stool cultures were obtained from all patients admitted from May 15 to August 2, 1994. Patients were followed for evidence of clinical VRE infection and surveillance stool results through August 15, 1995. Genetic relatedness of stool-clinical isolate pairs and serial stool samples was evaluated using pulsed field gel electrophoresis. RESULTS: Twenty-three (32%) of 73 screened patients were colonized with VRE. Eight (35%) of the colonized patients cleared VRE from stool; 10 (43%) were persistent carriers, excreting organisms for 19 to 331 days (median, 112 days); and 5 patients had an insufficient number of stools to determine length of carriage. Persistent carriers had a median of 6 hospital readmissions; 8 of 10 were positive at first or second readmission Clinical VRE infection developed in 6 of 73 patients (annual incidence, 8.2%). Clinical cases had more days of neutropenia between colonization and infection than colonized patients during a comparable follow-up (49 vs. 16 days, P = 0.04). Five of 6 stool-clinical isolate pairs were identical by pulsed field gel electrophoresis. Serial stools from 6 of 7 patients (collected 20 to 343 days apart) were identical by pulsed field gel electrophoresis. CONCLUSION: Persistent gastrointestinal colonization with VRE is common among pediatric oncology patients. Carriage of the same VRE clone for up to 1 year was demonstrated. In the majority of cases invasive and colonizing isolates were identical by DNA fingerprinting techniques, suggesting that the colonizing VRE was the source of infection. Intermittent excretion of organisms in stool makes vigilant tracking and immediate isolation of such patients crucial to control efforts. Prolonged neutropenia may increase the risk of developing clinical infection among VRE-colonized patients.

Anti-Bacterial Agents↗