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Biomedical subjects

C Ng

Publications and source records attributed to C Ng.

83 records · Page 5Linked to original sources
PubMed1983

Differential cytotoxicity of cis-platinum and blenoxane against human carcinoma KBE cells in multicellular spheroids of different ages: response at different temperatures.

Human KBE epidermoid carcinoma cells were reproducibly grown in suspension as multicellular spheroids (MCS). Initial aggregation at 48 hours is followed by a rapid diameter increase until day 10. The size increase then continues with daily refeedings, under the growth conditions used, but at a slower rate. When cells are treated in MCS with either blenoxane (bleomycin) or cis-diamminedichloroplatinum (II) (cis-platinum), the survival of cells (by cloning efficiency (CE) essay) varied from that of surface attached (SA) cells. The survival was dependent on the age of the MCS as well as their size; the age response was significantly different for cis-platinum and blenoxane. Hyperthermic incubation of KBE cells in MCS at different ages for 1 hour (40-43 degrees C) resulted in cell killing similar to that observed after hyperthermic incubation of surface attached cells. In combined hyperthermia/chemotherapy experiments, simultaneous treatment with blenoxane resulted in little or no increase in MCS cell toxicity at 40 degrees C; at 42.5 degrees C, there was increased toxicity. The increase in toxicity was similar for MCS of different ages. Upon simultaneous cis-platinum treatment, an increase in toxicity was observed at 40 degrees C, but only in older MCS. At 42.5 degrees C, an increased toxicity (relative to treatment at 37 degrees C) was observed in MCS of all ages. These results are, in general, similar to those described for other in vitro and in vivo systems, but emphasize the differences in the survival response which can result for treatment of human cancer cells in MCS of different ages over even a small size range (up to 1 mm diameter). This is much smaller than clinically detectable tumors. This reproducible human cancer cell multicellular spheroid model has great potential for representing the variability likely to be present in micrometastases of different sizes, and in small regions of solid tumors, and therefore for assisting in preliminary evaluation of combined modality protocols.

Bleomycin↗
PubMedDate not supplied

Elemental and molecular imaging of human hair using secondary ion mass spectrometry.

Secondary ion mass spectrometry (SIMS) is used to image the spatial distribution of elemental and molecular species on the surface and in cross sections of doped human hair using a magnetic sector SIMS instrument operated as an ion microprobe. Analysis of electrically insulating, non-planar hair samples requires one of two different methods of charge compensation to be used depending on the polarity of the sputtered secondary ions. For detection of positive secondary ions, the hair is imaged using a approximately 0.5 micron diameter, 19.5 keV impact energy, O- microbeam with no auxiliary electron bombardment. For detection of negative secondary ions, a approximately 0.2 micron diameter, 14.5 keV impact energy Cs+ microbeam is used in conjunction with normal incidence, low-energy electron bombardment. Both of these methods allow submicrometer spatial resolution elemental and molecular secondary ion images to be obtained from hair samples without metallic coating of the sample surface prior to analysis. Several examples are presented that reflect potential application areas for these analytical methods.

Barium↗
PubMedDate not supplied

Suppression of defective-sporulation phenotypes by mutations in transcription factor genes of Bacillus subtilis.

Mutations in the Bacillus subtilis major RNA polymerase sigma factor gene (rpoD/crsA47) and a sensory receiver gene (spoOA/rvtA11) are potent intergenic suppressors of several stage 0 sporulation mutations (spoOB, OE, OF & OK). We show here that these suppressors also rescue temperature-sensitive sporulation phenotypes (Spots) caused by mutations in RNA polymerase, ribosomal protein, and protein synthesis elongation factor EF-G genes. The effects of the crsA and rvtA suppressors on RNA polymerase and ribosomal protein spots mutations are similar to those previously described for mutations in another intergenic suppressor gene rev. We have examined the effects of rvtA and crsA mutations on the expression of sporulation-associated membrane proteins, including flagellin and penicillin binding protein 5* (PBP 5*). Both suppressors restored sporulation and synthesis of PBP 5* in several spoO mutants. However, only rvtA restored flagellin synthesis in spoO suppressed backgrounds. The membrane protein phenotypes resulting from the presence of crsA or rvtA suppressors in spoO strains suggests that these suppressors function via distinct molecular mechanisms. The rvtA and crsA mutations are also able to block the ability of ethanol to induce spoO phenocopies at concentrations of ethanol which prevent sporulation in wild type cells. The effects of ethanol on sporulation-associated membrane protein synthesis in wild type and suppressor containing strains have been examined.

Bacillus subtilis↗
PubMedDate not supplied

Abdominal manifestations of sarcoidosis. CT appearances.

Sarcoidosis frequently involves the abdomen, although imaging studies often fail to demonstrate disease. The most common computed tomography (CT) findings in abdominal sarcoidosis are hepatosplenomegaly and retroperitoneal adenopathy, followed by focal low-attenuation lesions of the liver and spleen. Other abdominal viscera are involved infrequently. We present four cases of abdominal sarcoidosis demonstrating a range of CT findings.

Adult↗
PubMedDate not supplied

A Delphi survey of clinical nursing research priorities in Western Australia.

In 1989-1990 an investigation was undertaken to ascertain which problems WA nurses considered required researching. A modified Delphi technique was employed to obtain data from nurses in hospitals and health care agencies throughout the metropolitan and rural regions in the state. Participants worked in areas of acute care, mental health, paediatrics, gerontology, community health and domiciliary services and addictions. Problems identified were categorised into three streams; clinical, management and staff development. Respondents were required to assign a value to items according to their importance to nurses and to patients. They were also asked to indicate whether they considered there was an adequate research base relevant to each item. Results reported here are based on the 10 priority items identified in the clinical stream.

Clinical Nursing Research↗
PubMedDate not supplied

A Western Australian Delphi survey of staff development research priorities.

A modified Delphi survey conducted during 1989-1990 identifies problems that Western Australian nurses consider research priorities. Participants were employed in hospital and health-care agencies throughout metropolitan and rural regions of the state. The large number of topics generated were analyzed and categorized into three areas of nursing: staff development, clinical practice, and management. Participants rated each topic on its importance to nurses and patients. The results are based on the 10 priority items identified in the staff development field.

Delphi Technique↗
PubMedDate not supplied

Effects of microtubule inhibitors-taxol, vinblastine and estramustine on the growth and p53 gene expression in the hormone independent human prostatic JCA-1 cells.

Treatment of the JCA-1 prostate cells with different concentrations of microtubule inhibitors-taxol (paclitaxel) vinblastine, and estramustine-was accompanied by reduced cell growth and, correspondingly, characteristic morphological changes. The reduction of cellular proliferation was unlikely to be attributable to an inhibitory effect of the antimicrotubule agents on cell cycling, but was correlated with the decreased expression of the p53 gene. These results suggest that antimicrotubule agents may be considered as potentially complementary treatment modalities for patients with hormonally independent prostate cancer.

Antineoplastic Agents↗
PubMedDate not supplied

Transforming growth factor-beta1 (TGF-beta1) in penile and prostate growth in the rat during sexual maturation.

The goal of this study was to determine whether transforming growth factor-beta1 (TGF-beta1) may contribute to the arrest of penile growth and the down-regulation of androgen receptors (AR) that occur during sexual maturation in the rat penis. For this purpose, body, penis, and prostate weights were obtained from male rats of increasing ages, and penis and prostate TGF-beta1 concentrations were determined by a sandwich enzyme-linked immunosorbent assay. The cytosol fraction was obtained from the shafts and glandes of immature (19-day-old) and adult (90-day-old) rat penises, and ARs were measured by a western blot assay. The effect of exogenous TGF-beta1 on penile growth was examined in vivo in two groups of immature rats (21 and 27 days old) implanted with miniosmotic pumps delivering either human TGF-beta1 or vehicle only directly into the corpora cavernosa for 6 days. The penises, prostates, and testes were weighed, and the AR content was estimated by western blot. The growth rate of the penis declined after 8 weeks of age, whereas the ventral prostate growth rate increased until 14 weeks of age and then slowed down. The content of penile AR protein decreased seven-fold in the adult rats compared to the immature animals. Penile TGF-beta1 concentration increased nearly three-fold from the 19-day-old rats to a peak at 60 days of age and then decreased over the next 4 months to the initial levels. In contrast, TGF-beta1 concentration in the prostate was not significantly affected by age and remained below the lowest penile values in all age groups. Transforming growth factor-beta1 given locally to the penis reduced penile shaft weight by 38 and 22% in two groups of immature rats, while the weights of the penile glans, testis, and ventral prostate remained unaffected. Androgen receptor content was higher in the glans than in the shaft and was not changed by TGF-beta1 treatment. These results suggest that the increase of TGF-beta1 levels in the penis may reinforce growth arrest caused by the down-regulation of penile ARs, whereas the maintenance of a high content of ARs and a low TGF-beta1 concentration may allow prostate growth to continue.

Aging↗