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Biomedical subjects

N Tang

Publications and source records attributed to N Tang.

53 records · Page 3Linked to original sources
PubMed1994

Chloracne. Some recent issues.

Chloracne is an acneiform skin eruption that is still the most sensitive indicator of systemic poisoning caused by chemicals belonging to the group of chlorinated polycyclic aromatic hydrocarbons. Generally these chemicals are known as dioxins, dibenzofuranes, and PCBs. The cause of chloracne is probably interference of these chemicals with vitamin A metabolism in the skin, resulting in disturbances of the epithelial tissues of the pilosebaceous duct. A study of workers in a factory where chloracne is endemic is described. The product manufactured, pentachlorophenol, a wood preservative, was found to be contaminated with dioxins (congeners of TCDD) and dibenzofuranes. Blood levels of these chemicals in affected workers are given, along with supporting evidence of disturbances in vitamin A (retinoid) metabolism as demonstrated in skin biopsies.

Acne Vulgaris↗
PubMed1993

Cd(2+)-induced c-myc mRNA accumulation in NRK-49F cells is blocked by the protein kinase inhibitor H7 but not by HA1004, indicating that protein kinase C is a mediator of the response.

Cd2+ is a toxic cation that, at sublethal and marginally lethal levels, modifies cell growth and metabolism. Cd2+ exposure of NRK-49F cells results in inhibition of early EGF-induced DNA synthesis, but induction of delayed DNA synthesis; in stimulation of anchorage independent growth; in accumulation of specific oncogene mRNAs; and in an hypertrophic response. Determining whether specific signal transduction pathways (STPs) are involved in specific gene deregulation by cadmium in NRK-49F cells is important to defining possible mechanisms by which Cd2+ elicits these physiological responses. In this study it is shown that Cd2+ induces delayed myc (8-10 h) and jun (12 h) mRNA accumulation, as well as both early (0.5-1 h) and late (12 h) fos but not TGF beta mRNA accumulation. The times of appearance of Cd(2+)-induced c-fos, c-myc and c-jun expression are dose dependent. The Cd2+ induced accumulation of these specific mRNAs is insensitive to cycloheximide and therefore not due to preinduction of TGF beta or other gene-activating growth factors, but rather to direct induction of oncogene expression and/or mRNA stabilization. Accumulation of c-myc mRNA is shown further to be inhibited by the protein kinase inhibitor H7 but not HA1004, indicating a role for one or more protein kinases C in the STPs by which Cd2+ induces oncogene expression. Thapsigargin, a compound which stimulates increased cytosolic [Ca2+], induces c-myc expression also by an H7 sensitive, HA1004 insensitive pathway. These results suggest that Cd2+ acts through one or more defined signal transduction pathways involving specific protein kinases C to induce the accumulation of c-fos, c-myc and c-jun messenger RNAs.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1992

Cadmium's action on NRK-49F cells to produce responses induced also by TGF beta is not due to cadmium induced TGF beta production or activation.

Transforming growth factor beta (TGF beta) is a multifunctional regulator of cell growth that has either a stimulatory or inhibitory effect on cell proliferation, depending on TGF beta concentration and on cell type, history and culture conditions. Cadmium mimics some of the effects of TGF beta in cultured cells. In this study the effects of Cd2+ and TGF beta on EGF-induced DNA synthesis in a clonal subpopulation (N1) of NRK-49F cells were compared. It was found that TGF beta 1 and cadmium both inhibit EGF-induced DNA synthesis and cell proliferation in a dose-dependent fashion, but that neither inhibits EGF-induced myc oncogene accumulation. TGF beta 1 and cadmium added at the same time as EGF or several hours after EGF addition showed similar inhibitory effects on EGF-induced [3H]Tdr incorporation, indicating that the inhibitory effect of TGF beta 1 and cadmium on EGF-induced DNA synthesis does not involve early G1 events. Rather, they occur in late G1, at the G1/S boundary or during S phase. Because of the similarities in nature and timing of the Cd2+ and TGF beta responses, the possibility that Cd2+ acts through stimulation of TGF beta production and/or activation was explored. It is shown in this paper however that TGF beta neutralizing antibody blocks the effects of TGF beta 1, but not the cadmium effects, on EGF-induced DNA synthesis, suggesting that cadmium is not functioning through activation or preinduction of TGF beta.

Cadmium↗
PubMed1991

Cd++ inhibits EGF induced DNA synthesis but not EGF induced myc mRNA accumulation in serum starved NRK-49F cells.

Cd++ inhibits EGF-induced 3H-thymidine incorporation in serum deprived NRK-49F cells in a dose dependent pattern. The underlying mechanisms for this inhibition are largely unknown. EGF-induced myc mRNA accumulation in NRK-49F cells and the effects of Cd++ on this response were examined under conditions that result in partial or complete inhibition of EGF-induced DNA synthesis. It was found that doses of Cd++ that inhibit EGF-induced DNA synthesis do not inhibit EGF-induced protein synthesis and myc mRNA accumulation. Cd++ doses of 0.5 microM and 1 microM were found actually to increase EGF-induced myc mRNA accumulation and amino acid incorporation. These results show that the effect of Cd++ on EGF-induced DNA synthesis is not due to inhibition of entrance into G1, but rather that Cd++ acts on events subsequent to myc accumulation; that is, events associated with either G1 progression, entry into S or DNA synthesis.

Amino Acids↗
PubMed1991

Cadmium induces hypertrophy accompanied by increased myc mRNA accumulation in NRK-49F cells.

Previous studies showed that Cd++ inhibits EGF-induced DNA synthesis but not EGF-induced myc mRNA accumulation or amino acid incorporation into protein in serum-starved NRK-49F cells. In this study, flow cytometry was used to analyze the DNA and protein content of individual cells stimulated with Cd++ and/or epidermal growth factor (EGF). myc oncogene expression in these cells was also measured. It was found that, in both parental NRK-49F cells and in a clonal subpopulation, N1, Cd++ induces an hypertrophic response. In parental NRK-49F cells, however, lower doses of Cd++ (0.5 microM) induced more pronounced hypertrophic responses than did higher doses (4 microM); whereas in N1 cells, the Cd+(+)-induced hypertrophic response shows a pattern of increasing response with doses of Cd++ from 0.5 to 4 microM. myc mRNA accumulation measured 2 hours after stimulation correlated with the hypertrophic responses in both NRK-49F cells and in N1 cells. The results show that Cd+(+)-induced hypertrophy in NRK-49F cells is associated with increased myc oncogene mRNA accumulation, indicating that cell proliferation and cell hypertrophy may in part share common activation pathways.

Animals↗
PubMed1991

TGF beta elicits opposite responses in clonal subpopulations of NRK-49F cells.

Clonal subpopulations of NRK-49F cells were isolated and characterized for their responses to transforming growth factor beta (TGF beta). Two fibroblastic clones, N1 and N4, were found to have opposite TGF beta responses. TGF beta inhibits EGF-induced proliferation in growth-arrested, subconfluent monolayer cultures of N1 but not N4 cells. In contrast, TGF beta stimulates DNA synthesis and an increase in cell number in N4 but not N1 cells. The inhibitory effect of TGF beta on DNA synthesis in N1 cells is due not to modulation of the EGF receptor or other early G1 events. EGF-induced myc mRNA accumulation is not inhibited, and the action point for TGF beta inhibition of the entry into S of N1 cells is at the G1-S boundary.

Animals↗
PubMed1990

Zinc levels in urine of female farmers in nonpolluted regions of Japan.

In the winter of 1987-88, 1472 urine samples were collected from female farmers in eight regions of Japan. The wet digests of the samples, previously analyzed for manganese, were used for the determination of zinc (i.e., Zn-U) by inductively coupled plasma emission spectrometry. The logarithms of the values after adjustment to a specific gravity of 1.016 were normally distributed; the geometric mean (geometric standard deviation) was 0.23 mg1-1 (2.00). Effects of aging and smoking on Zn-U were not evident. Inter-regional differences appeared to exist. As no sex differences are apparent from the literature, it appears most likely that the value may possibly represent the "background" level for both men and women, either smokers or nonsmokers, among the general Japanese population. When the Zn-U levels by region and age decade were compared with the concentrations of cadmium, a significant (p less than 0.01) positive correlation was detected, which suggests metabolic parallelism between the two elements.

Adult↗
PubMed1990

Blood lead levels of Beijing (China) citizens.

Lead levels were determined in 856 blood samples obtained from Beijing citizens who were either factory workers or clerks with no known occupational exposure to heavy metals including lead. Additional analyses were conducted on 74 samples from factory workers in the small city of Jinxi, China. The geometric mean blood lead level (Pb-B) among the general Beijing population 99.2 and 76.1 micrograms 1-1 for non-drinking and non-smoking men and women, respectively, with a statistically significant difference between the two sexes. The effect of drinking was not detectable, whereas that of smoking was suggested, but not conclusive. The Pb-B levels among Jinxi workers did not differ from the levels among Beijing citizens. The Pb-B for inhabitants of Beijing was similar to the levels of inhabitants of a medium-sized city, Hefei, and lower than the values for residents of two heavily industrialized large cities, Shanghai and Shenyang. The values for Chinese citizens appear to be higher than those for Japanese and Korean farmers, but the possibility of urban-rural differences remains to be examined.

Adolescent↗
PubMed1989

[Appraisal of the protective effect of vitamin E against CCl4 liver poisoning].

VE (at dosage of 200mg/kg) significantly depressed the liver microsomal lipid peroxidation induced by 50 mg/kg CCl4; on the other hand, VE potentiated the SGPT, or liver triglyceride, or liver microsomal cytochrome P450 during CCl4 poisoning. The interaction between VE and CCl4 should be carefully taken in to consideration, especially when using VE in preventing and curing CCl4 poisoning.

Animals↗
PubMed1978

A new surgical approach to traumatic rectourethral fistulas.

To solve the dual problem of recurring stenosis of the posterior urethra and difficult closure of the fistulous tract in traumatic rectourethral fistulas the Johanson urethroplasty has been used in 4 cases of lower fistulas and the direct urethra-bladder neck anastomosis has been used in 4 cases of upper fistulas. The good results obtained seem to confirm the value of these methods. Direct urethra-bladder neck anastomosis also has been used successfully to treat posterior urethral strictures.

Adolescent↗
PubMedDate not supplied

Vitamin B12 deficiency--need for a new guideline.

OBJECTIVES: Many patients with vitamin B12 deficiency do not have anemia or macrocytosis, but the prevalence of B12 deficiency in patients without macrocytosis is not known. METHODS: We investigated the prevalence of B12 deficiency among patients with normocytosis and microcytosis and recommended a screening strategy. All patients (n = 3714) with serum B12 measured at the Prince of Wales Hospital in 1996 were reviewed. The prevalence of serum B12 less than 140 pmol/L was determined for the following patient subgroups: younger than 70 y, older than 70 y, anemic, non-anemic, macrocytic, normocytic, microcytic, documented iron deficiency, and documented thalassemia. RESULTS: The prevalence of B12 deficiency (<140 pmol/L) ranged from 4.8% to 9.8% among the different subgroups. CONCLUSIONS: Whatever screening criteria were used, a significant number of B12-deficient patients will be missed. Therefore, there may be a case for universal vitamin B12 screening.

Age Factors↗
PubMedDate not supplied

Decompression and stable internal fixation of femoral neck fractures in children can affect the outcome.

Pediatric femoral neck fracture is rare and known to be associated with a high complication rate. The effect of early decompression and operative fixation is not frequently reported in the literature. This is a retrospective study of 14 patients younger than 16 years with traumatic fractures of the femoral neck and intertrochanteric region over a 10-year period with a follow-up of 2-11 years (mean, 4.6 years). Road traffic accidents and falls from a height were the main causative factors, and the fractures were subclassified into transcervical, 58%; intertrochanteric, 29%; transepiphyseal, 7%; and cervicotrochanteric, 7%. Of all the fractures, 10 (71%) were displaced. Decompression of the hip by aspiration and closed reduction and internal fixation was performed for all the displaced fractures within 24 h after admission. Three cases required open reduction. Complete fracture healing and functional recovery was achieved in 13 patients with only one delayed union. No patient had radiographic evidence of avascular necrosis. When compared with earlier studies, the current aggressive management protocol for displaced fracture significantly minimized the complications of avascular necrosis, non-union, delayed union, and premature physeal closure.

Adolescent↗
PubMedDate not supplied

Reduction of myocardial ischemia-reperfusion injury by isovolumic hemodilution.

In order to study the effects of isovolumic hemodilution and its combination with Danshen solution on acute ischemic reperfused canine myocardium, 24 adult hybrid dogs were used and divided into four groups. Group I was the control group, groups II-IV were treated with Dextron 40, Danshen solution and a combination of the two, respectively. The results showed that either Dextron 40 or Danshen solution alone had a significant increase of +/- dp/dt-max when compared with group I (p < 0.05). Although no significant difference existed between group II and III, the former showed more rapid action. The combination of the two therapies improved +/- dp/dt-max and LVSP, and significantly reduced the necrotic sizes and the MDA contents in the ischemic myocardia compared with not only group I, but also group II or group III (all p < 0.05). The results suggest that isovolumic hemodilution or Danshen may protect the ischemic reperfused myocardium and the former may come into action more rapidly, and that the combination of the two may show a better synergism than each one of the two by itself.

Animals↗