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Biomedical subjects

J Tan

Publications and source records attributed to J Tan.

302 records · Page 17Linked to original sources
PubMed1975

Oral contraceptive continuation rates in the Singapore National Program. 1966-1972.

A study of a random sample of 3,564 oral contraceptive acceptors in the Singapore national program clinics with a maximum of 60 months of experience produced findings as follows: The typical pill acceptor was aged 26.9 years with 2.5 children, married for 4.2 years, had at least primary education, was not working, and started on the pill 2.3 months after her last pregnancy. Thirty-three percent of the oral contraceptive acceptors were still continuing with the pill by the cutoff date for the study, 30 June 1972, and the median period of pill use among those still using was 33.6 cycles. The median number of cycles of pill use among discontinued users was only 5.2. The main reasons for discontinuation were side effects of the pill and planned pregnancy. For the discontinued users, 43 percent had used alternative methods of protection, mainly condoms. Cumulative continuation rates per thousand women were 792 after the first cycle, 680 after the third, and 475, 346, 247, and 225 after cycles 12, 24, 48, and 59, respectively.

Adult↗
PubMedDate not supplied

Projections from the red nucleus and surrounding areas to the brainstem and spinal cord in the cat. An HRP and autoradiographical tracing study.

HRP injections at the C2, T1 and S1 spinal levels and in the medullary lateral tegmental field revealed that the contralaterally projecting rubro-bulbospinal neurons are located not only in the caudal but also to a certain extent in the rostral red nucleus (RN). These RN projections are somatotopically organized. Neurons projecting to the sacral cord are located in the ventrolateral RN, those projecting to the upper part of the spinal cord lie in the dorsomedial RN and those projecting to the medullary lateral tegmentum were found in the dorsal portions of the RN. These last neurons are smaller than many of the other RN neurons. The HRP results also revealed that the RN does not project to the caudal raphe nuclei. The autoradiographical results confirmed the HRP findings. They further indicated that the contralateral RN projections to the caudal brainstem precerebellar nuclei (nucleus corporis pontobulbaris, lateral reticular nucleus, lateral cuneate nucleus) and the dorsal column nuclei are also somatotopically organized. This was also true for the RN projections to the dorsomedial and intermediate facial subnuclei and the caudal pontine and medullary lateral tegmental field. These areas receive afferents from mainly the dorsal portions of the RN. Regarding the RN projections to the spinal cord, the autoradiographical tracing results revealed somatotopically organized contralateral RN projections to laminae V, VI and VII. Moreover, a small but distinct RN projection to a dorsolaterally located group of motoneurons at the C8-T1 level was demonstrated. Ipsilaterally a minor projection to the cervical and upper thoracic lateral intermediate zone was observed. Finally, strong ipsilateral projections from the rostral mesencephalon to the inferior olive were seen. These projections were derived from various rostral mesencephalic areas, including the nucleus of Darkschewitsch, the nucleus accessorius medialis of Bechterew, the interstitial nucleus of Cajal and the area of the rostral interstitial nucleus of the medial longitudinal fasciculus. In the cat it was difficult to define which of the mesencephalic areas projecting to the inferior olive represented the parvocellular RN. A new subdivision of the RN is proposed based on its projections and not on the size of its cells. In this concept the first group is formed by the RN neurons projecting contralaterally to the caudal brainstem and spinal cord. The second group consists of RN neurons projecting to the inferior olive.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

CD40 signaling and Alzheimer's disease pathogenesis.

The interaction between CD40 and its cognate ligand, CD40 ligand, is a primary regulator of the peripheral immune response, including modulation of T lymphocyte activation, B lymphocyte differentiation and antibody secretion, and innate immune cell activation, maturation, and survival. Recently, we and others have identified CD40 expression on a variety of CNS cells, including endothelial cells, smooth muscle cells, astroglia and microglia, and have found that, on many of these cells, CD40 expression is enhanced by pro-inflammatory stimuli. Importantly, the CD40-CD40 ligand interaction on microglia triggers a series of intracellular signaling events that are discussed, beginning with Src-family kinase activation and culminating in microglial activation as evidenced by tumor necrosis factor-alpha secretion. Based on the involvement of microglial activation and brain inflammation in Alzheimer's disease pathogenesis, we have investigated co-stimulation of microglia, smooth muscle, and endothelial cells with CD40 ligand in the presence of low doses of freshly solubilized amyloid-beta peptides. Data reviewed herein show that CD40 ligand and amyloid-beta act synergistically to promote pro-inflammatory responses by these cells, including secretion of interleukin-1 beta by endothelial cells and tumor necrosis factor-alpha by microglia. As these cytokines have been implicated in neuronal injury, a comprehensive model of pro-inflammatory CD40 ligand and amyloid-beta initiated Alzheimer's disease pathogenesis (mediated by multiple CNS cells) is proposed.

Alzheimer Disease↗
PubMedDate not supplied

Interleukin-12 cDNA skin transfection potentiates human papillomavirus E6 DNA vaccine-induced antitumor immune response.

Human papillomaviruses are associated with >90% of all cases of uterine cervical tumors. The E6 and E7 oncoproteins of human papillomavirus are potentially ideal targets of immune therapy for cervical cancer, because their expression is necessary for cellular transformation. Although both E6 and E7 proteins contain numerous predicted cytotoxic T lymphocyte (CTL) epitopes that are capable of binding to human leukocyte antigens, the majority of earlier in vivo tumor rejection studies have focused on E7. We show here that gene gun-mediated skin transfection of plasmid vector encoding the nontransforming, amino-terminal half of E6 resulted in the induction of E6-specific CTL activity and tumor rejection in a murine model. The use of recombinant murine interleukin-12 (rmIL-12) as a vaccine adjuvant has been shown to result in both an enhancement and suppression of immune responses, depending upon the doses of rmIL-12 and the experimental systems used. We demonstrate here that local expression of transgenic mIL-12 at the E6 DNA vaccination site potentiated E6-specific CTL responses and increased vaccine-induced antitumor therapeutic efficacy. Our results indicate that transfection of the mIL-12 gene at the vaccination site may represent an attractive adjuvant for cancer gene immunotherapy.

Animals↗
PubMedDate not supplied

Heightened expression of cyclooxygenase-2 and peroxisome proliferator-activated receptor-delta in human endometrial adenocarcinoma.

Epidemiological studies indicate that nonsteroidal anti-inflammatory drugs (NSAIDs) significantly reduce the risk and mortality from colorectal cancer, in part by inhibiting prostaglandin (PG) synthesis. Cyclooxygenase (COX), the rate-limiting enzyme in PG biosynthesis, exists in two isoforms, COX-1 and COX-2. Genetic and pharmacological evidence suggest that COX-2 is involved in the development of colorectal cancer. We have previously shown that COX-2-derived prostacyclin participates in blastocyst implantation through activation of peroxisome proliferator activated receptor delta (PPARdelta), a member of the nuclear hormone receptor family. Furthermore, our recent studies suggest that a similar pathway is operative during colorectal carcinogenesis. These observations prompted us to examine whether the COX-2-PPARdelta signaling pathway is also involved during development of uterine adenocarcinoma. Here we describe for the first time the heightened expression of COX-2 and PPARdelta, but not COX-1, in uterine endometrial adenocarcinoma.

Adenocarcinoma↗
PubMedDate not supplied

Relationship between bone mineral density of the proximal femur and strength of hip muscles in postmenopausal women.

The relationship between muscle strength and bone density is well known, but only a limited number of studies relating muscle strength to bone mineral density of a site-specific limb have been performed. The main purposes of this study were as follows: (1) to assess the relationship between the strength of hip muscles and bone mineral density of the proximal femur in 100 postmenopausal women; (2) to compare strength values of three subgroups, which were formed on the basis of the femoral neck Z-scores. By using an isokinetic dynamometer (Cybex 350), muscle strength tests were performed for hip muscles and bone mineral density measurements were obtained by dual energy x-ray absorptiometry. Statistical analysis demonstrated a moderately positive correlation between bone mineral density of the femoral neck and hip muscle strength (with abductors: r = 0.267, P = 0.008; with adductors: r = 0.276, P = 0.007). A moderate correlation was also found between bone mineral density of Ward's triangle and hip adductors (r = 0.327; P = 0.001). When muscle strength mean values of subgroups were compared with each other, there was no statistically significant differences. These data may suggest that the isokinetic strength of hip muscles may not contribute to the bone mineral density of the proximal femur.

Adult↗
PubMedDate not supplied

Quantitative proton-decoupled 31P MRS of the schizophrenic brain in vivo.

Quantitative proton MR spectroscopy (MRS) and proton-decoupled phosphorus MRS were applied in the parietal cortex of 13 schizophrenic subjects (11 drug-treated and 2 neuroleptic-naive) and 15 normal control subjects. Significantly increased concentrations of glycerophosphorylcholine (1.18 +/- 0.16 vs. 0.93 +/- 0.14 mmol/kg brain; p < 0.001), glycerophosphoethanolomine (0.70 +/- 0.19 vs. 0.59 +/- 0.07 mmol/kg; p < 0.04), and phosphocreatine (3.73 +/- 0.39 vs. 3.41 +/- 0.13 mmol/kg; p < 0.007), but no differences in N-acetylaspartate, total creatine, or myo-inositol, were determined in treated schizophrenic subjects. Identical abnormalities were found in two neuroleptic-naive patients. These results provide new evidence of disordered cerebral membrane and high energy phosphate metabolism in schizophrenia.

Adult↗
PubMedDate not supplied

Lung adenocarcinomas metastatic to the brain with and without ultrastructural evidence of rootlets: an electron microscopic and immunohistochemical study using cytokeratins 7 and 20 and villin.

Adenocarcinomas metastatic to brain from lung or colon may pose differentiation difficulties. Ultrastructurally, both may have brush borders with rootlets. This study examines the ultrastructural morphology and immunohistochemical expression of villin (associated with rootlets), cytokeratin 7 (present in lung adenocarcinomas), and cytokeratin 20 (present in colon adenocarcinomas) in 19 formalin-fixed sequential surgical biopsies of lung adenocarcinomas metastatic to brain as compared to 13 colonic adenocarcinoma metastases. Of lung tumor metastases, mucinous differentiation with rootlets was most common [6/19(32%)]. All colon tumor metastases were cytokeratin 7(-), 20(+), and profusely villin(+). Well-formed rootlets were seen. All lung metastases were cytokeratin 7(+) and 20(-). 5/6(83%) lung metastases with rootlets were focally villin(+). 12/13(95%) without rootlets were villin(-). Rootlets are extremely common in lung adenocarcinoma metastatic to brain. Villin immunoreactivity closely correlates with rootlets. Its distribution is a useful adjunct to cytokeratin 7 and 20 in differentiation of lung versus colon adenocarcinomas metastatic to the brain.

Adenocarcinoma↗
PubMedDate not supplied

Isokinetic and isometric strength in osteoarthrosis of the knee. A comparative study with healthy women.

Dynamic stability of the knee joint depends on the appropriate strength ratio of quadriceps and hamstring muscles. The purpose of this investigation was to determine the maximum peak torque (MPT) and MPT ratios of hamstrings to quadriceps (H/Q) muscles in patients with knee osteoarthritis (OA). Two groups of patients were included in the study. The first group consisted of 30 patients (Group A) with the clinical and radiologic findings of knee OA. The second group consisted of 30 patients (Group B) exhibiting knee joint pain without roentgenologic findings of knee OA. The findings of two patient groups were compared with each other and also with 30 healthy subjects (Group C). Isokinetic (at 60 degrees/s and at 180 degrees/s) and isometric (at 30 degrees and at 60 degrees of knee flexion) tests were performed by the rate-limiting isokinetic dynamometer system. Isokinetic and isometric MPT loss of knee flexors and extensors was found in both patient groups with respect to controls, but MPT ratios of H/Q muscles did not show a statistically significant difference compared with the control group. This may be related to the equal strength loss of knee flexors and knee extensors in patients with knee OA. It is concluded that strengthening exercises of hamstring muscles is as important as quadriceps strengthening in rehabilitation of knee OA.

Adult↗