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K-C Chang

Publications and source records attributed to K-C Chang.

7 recordsLinked to original sources
PubMed2006

Adaptation of multiple logistic regression to a multiple inverse sampling design: application to the Isfahan healthy heart program.

In observational and experimental studies in the health sciences involving human populations, it is sometimes considered desirable to recruit subjects according to designs that specify a predetermined number of subjects in each of several mutually exclusive classes (generally but not necessarily demographic in nature). This type of adaptive sampling design, now generally referred to as multiple inverse sampling (MIS), has received recent attention, and estimation methods are now available for several sequential MIS sampling designs. In this class of designs, subjects are sampled randomly and sequentially, usually one at a time, until all classes have the pre-specified number of subjects. In this paper, we extend MIS for finite population sampling to estimation of the parameters in multiple logistic regression under MIS. Using estimated logistic regression parameters and cost components obtained from the Isfahan Healthy Heart Program (IHHP), we report findings from a simulation experiment in which it appears that, at fixed cost, MIS at the last stage of sampling compares favourably to simple random sampling. The IHHP is a large community intervention study for prevention of cardiovascular disease being conducted in Isfahan, Iran and two other cities in Iran. The IHHP identified subjects through a multistage sample survey in which MIS was used at the final stage of sampling. MIS is one of several methods of adaptive sampling that are generating considerable interest and show promise of being useful in a wide variety of applications.

Age Factors↗
PubMed2006

Activation of STAT3 in thymic epithelial tumours correlates with tumour type and clinical behaviour.

The STAT3 (signal transducers and activators of transcription 3) signalling pathway plays a pivotal role in oncogenesis and appears essential for postnatal maintenance of thymic architecture and thymocyte survival. The association of STAT3 activation with thymic epithelial tumours (TETs) and myasthenia gravis (MG) has not been elucidated. In this study, 118 cases of TET and 25 non-neoplastic thymic tissue samples were evaluated for STAT3 and phospho-STAT3 (pSTAT3) expression immunohistochemically. In addition, 44 normal thymuses of different ages were included for comparison. It was found that STAT3 activation in thymic epithelial cells (TECs), as evidenced by pSTAT3 expression and/or nuclear STAT3, was present in the majority of non-neoplastic thymuses (88%, 22/25), including those from young children, but not in fetal thymus. In thymoma (n = 73), activated STAT3 was noted at a significantly higher frequency in the cases of lymphocyte-rich thymoma (ie types AB, B1, and B2, 46%, 23/50) in comparison with lymphocyte-depleted thymoma (types A and B3, 1/23) (p = 0.009). Thymoma with activated STAT3 tended to present at an earlier stage, show complete resectability and less aggressive behaviour, and have a higher correlation with MG than the STAT3-negative/inactive group (p < 0.05). In contrast, thymic carcinoma with activated STAT3 (14/45, 31%) had significantly higher rates of unresectability, vascular invasion, and regional lymph node metastasis (p < 0.05). These data provide the first evidence that constitutive STAT3 activation is seen in both benign and neoplastic thymic tissue and is associated with the persistence of thymic tissue and the presence of MG. It is likely to be induced by different factors in thymoma and thymic carcinoma.

Adolescent↗
PubMed2006

Arterial stiffening and cardiac hypertrophy in a new rat model of type 2 diabetes.

BACKGROUND: We determined the effects of NIDDM on haemodynamic parameters describing arterial wall elasticity and cardiac hypertrophy in rats administered streptozotocin (STZ) and nicotinamide (NA), using the aortic impedance analysis. METHODS: Male Wistar rats at 2 months were administered intraperitoneally 180 mg kg(-1) of NA, 30 min before an intravenous injection of 50 mg kg(-1) STZ, to induce type 2 diabetes. The STZ-NA rats were divided into two groups, 4 weeks and 8 weeks after induction of diabetes, and compared with untreated age-matched controls. Pulsatile aortic pressure and flow signals were measured by a high-fidelity pressure sensor and electromagnetic flow probe, respectively, and were then subjected to Fourier transformation for the analysis of aortic input impedance. RESULTS: In each diabetic group, the experimental syndrome was characterized by a moderate and stable hyperglycaemia and a relative deficiency of insulin secretion. However, the 8-week but not the 4-week STZ-NA diabetic rats showed a decrease in cardiac output in the absence of any significant changes in mean aortic pressure, having increased total peripheral resistance. The diabetic syndrome at 8 weeks also contributed to an increase in aortic characteristic impedance, from 1.49 +/- 0.33 (mean +/- SD) to 1.95 +/- 0.28 mmHg s mL(-1) (P < 0.05), suggesting a detriment to the aortic distensibility in NIDDM. Meanwhile, the STZ-NA diabetic animals after 8 weeks had an increased wave reflection factor (0.46 +/- 0.09 vs. 0.61 +/- 0.13, P < 0.05) and decreased wave transit time (25.8 +/- 3.8 vs. 20.6 +/- 2.8 ms, P < 0.05). Ratio of the left ventricular weight to body weight was also enhanced in the 8-week STZ-NA diabetic rats. CONCLUSION: The heavy intensity with early return of the pulse wave reflection may augment systolic load of the left ventricle coupled to the arterial system, leading to cardiac hypertrophy in the rats at 8 weeks after following STZ and NA administration.

Animals↗
PubMed2006

Aminoguanidine prevents arterial stiffening in a new rat model of type 2 diabetes.

BACKGROUND: Formation of advanced glycation end-products (AGEs) on collagen within the arterial wall may be responsible for the development of diabetic vascular injury. This study focused on investigating the role of aminoguanidine (AG), an inhibitor of AGE formation, in the prevention of noninsulin-dependent diabetes mellitus (NIDDM)-derived arterial stiffening and cardiac hypertrophy in rats. MATERIALS AND METHODS: The NIDDM was induced in male Wistar rats, which were administered intraperitoneally with 180 mg kg(-1) nicotinamide (NA) 30 min before an intravenous injection of 50 mg kg(-1) streptozotocin (STZ). After induction of diabetes mellitus type 2, animals receiving daily peritoneal injections with 50 mg kg(-1) AG for 8 weeks were compared with the age-matched, untreated, diabetic controls. RESULTS: After exposure to AG, the STZ-NA diabetic rats had improved aortic distensibility, as evidenced by 18.8% reduction of aortic characteristic impedance (P < 0.05). Treatment of the experimental syndrome with AG also resulted in a significant increase in wave transit time (+23.7%, P < 0.05) and a decrease in wave reflection factor (-26.6%, P < 0.05), suggesting that AG may prevent the NIDDM-induced augmentation in systolic load of the left ventricle. Also, the glycation-derived modification on aortic collagen was found to be retarded by AG. The diminished ratio of left ventricular weight to body weight suggested that prevention of the diabetes-related cardiac hypertrophy by AG may correspond to the drug-induced decline in aortic stiffening. CONCLUSIONS: Long-term administration of AG to the STZ-NA diabetic rats imparts significant protection against the NIDDM-derived impairment in vascular dynamics, at least partly through inhibition of the AGE accumulation on collagen in the arterial wall.

Animals↗
PubMedDate not supplied

Signet-ring stromal tumor of the ovary: a case report.

Signet-ring stromal tumor of the ovary is a rare disease and only four cases had been reported in the literature. The primary significance is to differentiate this benign disease from the malignant signet-ring adenocarcinoma. We report a case of signet-ring stromal tumor of the ovary in a 76-year-old woman who had suffered from low abdominal pain for one month. She underwent left oophorectomy, and the diagnosis was made based on immunohistochemical and electron microscopic characteristics. She has been well and free from recurrence for one year.

Aged↗