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Biomedical subjects

K M Chen

Publications and source records attributed to K M Chen.

At least 37 records · Page 2Linked to original sources
PubMed2000

Microwave life-detection systems for searching human subjects under earthquake rubble or behind barrier.

A new sensitive microwave life-detection system which can be used to locate human subjects buried under earthquake rubble or hidden behind various barriers has been constructed. This system operating at 1150 MHz or 450 MHz can detect the breathing and heartbeat signals of human subjects through an earthquake rubble or a construction barrier of about 10-ft thickness. The basic physical principle for the operation of a microwave life-detection system is rather simple. When a microwave beam of appropriate frequency (L or S band) is aimed at a pile of earthquake rubble covering a human subject or illuminated through a barrier obstructing a human subject, the microwave beam can penetrate the rubble or the barrier to reach the human subject. When the human subject is illuminated by a microwave beam, the reflected wave from the human subject will be modulated by the subject's body movements, which include the breathing and the heartbeat. If the clutter consisting of the reflected wave from stationary background can be completely eliminated and the reflected wave from the human subject's body is properly modulated, the breathing and heartbeat signals of the subject can be extracted. Thus, a human subject buried under earthquake rubble or hidden behind barriers can be located. This system has been tested extensively in a simulated earthquake rubble in the laboratory and also in a field test using realistic earthquake rubble conducted by a Federal Emergency Management Agency (FEMA) Task Force.

Diagnosis, Computer-Assisted↗
PubMed2000

The natural resistance-associated macrophage protein gene in African Americans with sarcoidosis.

The histologic and clinical similarities between tuberculosis and sarcoidosis suggest a shared underlying pathophysiology. Human natural resistance-associated macrophage protein (NRAMP1), which is closely related to the mouse gene, has been associated with susceptibility to tuberculosis in some human populations. Given the importance of the Nramp1 gene in animal models of granulomatous disorders, the association with human tuberculosis, and the possible role of NRAMP1 in macrophage activation and function, we hypothesized that human NRAMP1 plays a role in susceptibility to sarcoidosis. We analyzed several NRAMP1 gene polymorphisms in a case-control study of 157 African American patients with sarcoidosis and 111 African American control subjects. Our results, in contrast to those in tuberculosis patients, showed that the less common genotypes were found more often in control subjects than in case patients (odds ratio, 0.48; 95% confidence interval, 0.28-0.81). In particular, one polymorphism, a (CA)(n) repeat in the immediate 5' region of the gene, was found to have a protective effect (P = 0. 014). Whereas NRAMP1 polymorphisms have been associated with increased susceptibility to tuberculosis, our results suggest that at least one NRAMP1 polymorphism may decrease susceptibility in sarcoidosis.

Adult↗
PubMed2000

Effect of electromagnetic field exposure on chemically induced differentiation of friend erythroleukemia cells.

Whether exposure of humans to extremely low frequency electromagnetic fields (ELF-EMF) can cause cancer is controversial and therefore needs further research. We used a Friend erythroleukemia cell line that can be chemically induced to differentiate to determine whether ELF-EMF could alter proliferation and differentiation in these cells in a manner similar to that of a chemical tumor promoter. Exposure of this cell line to 60 Hz ELF-EMF resulted in a dose dependent inhibition of differentiation, with maximal inhibition peaking at 40% and 40 mG (4 microT). ELF-EMF at 10 mG (1.0 microT) and 25 mG (2.5 microT) inhibited differentiation at 0 and 20%, respectively. ELF-EMF at 1.0 (100) and 10.0 G (1,000 microT) stimulated cell proliferation 50% above the sham-treated cells. The activity of telomerase, a marker of undifferentiated cells, decreased 100[times] when the cells were induced to differentiate under sham conditions, but when the cells were exposed to 0.5 G (50 microT) there was only a 10[times] decrease. In summary, ELF-EMF can partially block the differentiation of Friend erythroleukemia cells, and this results in a larger population of cells remaining in the undifferentiated, proliferative state, which is similar to the published results of Friend erythroleukemia cells treated with chemical-tumor promoters.

Cell Differentiation↗
PubMed1999

Guamanian neurodegenerative disease: electrophysiologic findings.

Amyotrophic lateral sclerosis (ALS), parkinsonism and/or dementia are highly prevalent among the Chamorro population of Guam. The incidence of Guamanian ALS has markedly declined in recent years, but these incidence figures may reflect underascertainment of subclinical disease. Guamanian Chamorro patients have not been systematically studied using modern clinical neurophysiological techniques. Electromyography (EMG: needle exam and nerve conduction studies) was used to study 29 patients with the major subtypes of Guamanian neurodegenerative disease, as well as 11 neurologically normal Guamanian Chamorro subjects. Central conduction was assessed by somatosensory evoked potentials (SEP's) in 16 patients. EMG evidence of peripheral neuropathy, (often subclinical) was found in 45% of Guamanian patients but no Chamorro control subjects. Diabetes mellitus, which is highly prevalent in this population, was present in some, but not all of these cases. Clinically unsuspected motor neuron disease was identified by EMG in only one of the 23 Guamanian patients with parkinsonism and/or dementia and in none of the 11 Chamorro control subjects. Two of seven patients with the clinical phenotype of Guamanian ALS had a more benign EMG pattern on the needle electrode exam with absence of fibrillation and fasciculation potentials. Three of 16 patients (all with parkinsonism and dementia) had mildly abnormal tibial SEP's. No patient had EMG evidence of myopathy or a defect of neuromuscular transmission. We conclude: (1) peripheral neuropathy may be a manifestation of Guamanian neurodegenerative disease; (2) the declining prevalence of ALS on Guam is not associated with the development of a subclinical form of motor neuron disease; (3) the substantial overlap of Guamanian ALS with parkinsonism-dementia reported in prior decades is no longer apparent; (4) abnormal central conduction, as assessed by tibial SEP's, is present in some patients with Guamanian parkinsonism-dementia.

Adult↗
PubMed1999

Oral urografin in postoperative small bowel obstruction.

The aim of our study was to determine whether Urografin has the potential to offer surgeons a way of differentiating complete from partial small bowel obstruction and whether partial small bowel obstruction can be treated nonoperatively. Altogether 116 patients who had postoperative small bowel obstructions without any toxic signs underwent Urografin studies. Urografin (40 ml) mixed with 40 ml of distilled water was administrated either orally or via nasogastric tube to each patient. Serial plain abdominal radiographs were taken 2, 4, and 8 hours later. A total of 74 patients (63.8%) whose contrast medium reached the colon within the first 8 hours were considered to have partial obstruction and were successfully treated with intravenous hydration and nasogastric decompression. The remaining 42 patients (36.2%) in whom the contrast medium failed to reach the colon within the first 8 hours were regarded as having complete obstruction, and 34 of those patients (81.0%) underwent surgery; 8 (19.0%) received conservative treatment. Adhesion bands with complete bowel obstruction were observed in all 34 patients (100.0%) during laparotomy. Regardless of the presence of an air-fluid level on a plain abdominal radiograph or abdominal pain, a liquid diet followed by a soft diet could be given to those patients whose Urografin emptied into the colon. All the patients with partial bowel obstruction were treated successfully with nonoperative methods. The presence of Urografin in the colon within 8 hours of ingestion as an indicator for nonoperative treatment had a sensitivity of 90.2%, a specificity of 100%, and an accuracy of 93. 1%. Urografin, a safe and reliable water-soluble contrast medium, can be used to differentiate partial intestinal obstruction from complete intestinal obstruction. Early oral intake was found to be a major advantage of Urografin use in this study, and the potential of Urografin use to shorten the period of conservative treatment for postoperative small bowel obstruction needs further investigation.

Administration, Oral↗
PubMed1999

A research-based use of Tai Chi/movement therapy as a nursing intervention.

Tai Chi has been widely practiced in China for centuries as an art form, religious ritual, relaxation technique, exercise, and a method of self-defense for people of all ages. It has been used to improve balance; promote postural stability; decrease falls; enhance cardiovascular and ventilatory functions; rehabilitate persons with acute myocardial infarction and rheumatoid arthritis; and reduce pain, stress, and nightmares. The purpose of this article is to summarize, synthesize, and critically evaluate the research-based use of Tai Chi presented in the current literature and give implications and directions for future research. Additional studies about the effects of Tai Chi from a nursing perspective are needed to make clear when it is beneficial as a nursing intervention.

Arthritis, Rheumatoid↗
PubMed1999

The Blau syndrome gene is not a major risk factor for sarcoidosis.

BACKGROUND: A genetic predisposition to sarcoidosis has long been postulated, although no specific susceptibility genes are known. Candidate genes for the two granulomatous inflammatory disorders with clinical similarities to sarcoidosis, Blau syndrome and Crohn's disease, have been localized to a 40 centimorgan region spanning the chromosome 16 centromere. PATIENTS AND METHODS: Using a sample of 35 African-American sibling pairs, who both had clinically confirmed sarcoidosis, we tested for genetic linkage between the 16p12-q21 interval (the likely location of the Blau syndrome gene) and sarcoidosis. RESULTS: We found no evidence for linkage to any of the eight markers we tested in the 16p12-q21 interval. Ninety percent of the 16p12-q21 region had a LOD score < -2 for a dominant gene conferring a relative risk of 3 or greater for sarcoidosis. One hundred percent of the region had a LOD score < -2 for a dominant gene with a relative risk of 3.5 or greater or recessive gene with relative risk of 2.5 or greater. Based on simulation results we could not exclude a dominant gene with relative risk < 5 at the 0.05 significance level, nor a recessive gene with relative risk < 3, over the entire 16p12-q21 interval. CONCLUSIONS: While the clinical similarities between Blau Syndrome and sarcoidosis suggest genetic homogeneity between the disorders, we found no evidence for linkage of sarcoidosis to the Blau syndrome locus. Our exclusion results suggest that the Blau Syndrome gene does not have a major effect on sarcoidosis susceptibility.

Adult↗
PubMed1998

Abdominal sonography screening of clinically diagnosed or suspected appendicitis before surgery.

We conducted a prospective study to evaluate the value of abdominal sonography in the diagnosis of acute appendicitis and determine the need for abdominal sonography before operation. Altogether 191 patients with clinically diagnosed or suspected appendicitis underwent an abdominal sonography examination performed by a staff surgeon before operation. The sonographic findings are classified into three categories: appendicitis, other diseases, or normal screening. A total of 158 patients (82.7%) with positive findings of appendicitis proceeded to surgery; 18 patients (9.4%) were found to have other diseases, and they were treated for their conditions; and 15 patients (7.9%) with normal screening were discharged from the hospital and were reevaluated 2 weeks later. Only one patient had a false-negative finding. Of the 158 patients undergoing operation, 143 (90.5%) were proved to have appendicitis by the pathologic reports. A total of 32 negative appendectomies (16.8%) were prevented after sonographic examination. Abdominal sonography for detecting acute appendicitis had a sensitivity of 99.3%, a specificity of 68.1%, an accuracy of 91.6%, a positive predictive value of 90.5%, and a negative predictive value of 97.0%. The value of meticulous history-taking, physical examination, and laboratory tests cannot be overemphasized. Our experience suggests that patients with clinically diagnosed or suspected acute appendicitis should routinely undergo abdominal sonography examination, performed by an experienced surgeon, to further decrease the negative appendectomy rates.

Acute Disease↗
PubMed1998

Overexpression of p53 predicts shorter survival in diffuse type gastric cancer.

BACKGROUND: It has been suggested that p53 plays an important part in gastric carcinogenesis but the data remain inconclusive. METHODS: Alteration of the tumour suppressor gene p53 was prospectively investigated by immunohistochemistry in 168 primary gastric cancers. RESULTS: Positive staining, indicative of gene mutations, was detected in 34 tumours (20.2 per cent). No correlation was observed between expression of p53 and various clinicopathological factors, including age, sex, tumour site, gross type, tumour size, depth of invasion, lymph node metastases, distant metastases, and tumour node metastasis stage. However, p53 overexpression was different between intestinal and diffuse type gastric cancer. Survival analysis revealed a significant survival disadvantage of p53 expression in diffuse type gastric cancer (P=0.039) but not in the intestinal type. Multivariate analysis of all 168 patients revealed that independent predictors of recurrent disease included age, invasion depth and nodal involvement but not p53 expression. CONCLUSION: The presence of p53 overexpression may identify a subset of more aggressive tumours with a poor prognosis in diffuse type gastric cancer.

Adenocarcinoma↗
PubMed1998

Analysis of HLA-DPB1 polymorphisms in African-Americans with sarcoidosis.

Several studies have found weak associations between certain human leukocyte antigen (HLA) alleles and sarcoidosis, but none have been conclusive. Glutamic acid at position 69 in HLA-DPB1 has been reported to be strongly associated with chronic beryllium disease. The immunopathologic and clinical similarities between chronic beryllium disease (CBD) and sarcoidosis suggest that similar immune-response genes may be involved in susceptibility in both diseases. We analyzed the DNA sequence of HLA-DPB1 exon 2, which contains the hypervariable regions involved in binding antigens, in blood samples from African-American sarcoidosis patients and healthy controls. Results indicate that Val36 (odds ratio [OR] = 2.30) and Asp55 (OR = 2.03) are associated with increased risk for sarcoidosis, but no association with Glu69 was found. These results suggest that although HLA-DPB1 Glu69 is not associated with sarcoidosis, other alleles may make some contribution to susceptibility to sarcoidosis in African-Americans.

Adult↗
PubMed1998

Fifteen years' experience with gastric partitioning for obesity treatment.

Most reports derived from experiences in Western countries indicate that surgery offers the best hope for morbidly obese patients. We report our experience with gastric partitioning in 63 Chinese patients (17 men and 46 women) aged 14 to 42 years, whose preoperative excess weights ranged from 62.3% to 166.7% above their ideal body weight. Transverse stapling was performed in 30 patients treated before April 1983, while vertical stapling gastric partitioning with a window and a Marlex band to encircle the outlet tract was done in 33 patients after that. No patient died, but one had leakage at the anastomosis. Success was defined as a return to within 50% of the ideal body weight. Vertical-windowed gastric partitioning with a Marlex-banded outlet resulted in a significantly higher success rate than transverse stapling--70% vs 37%. Our experience suggests that vertical-windowed gastric partitioning with a Marlex-banded outlet is a safe and effective surgical treatment for morbidly obese Chinese people.

Adolescent↗
PubMed1997

Distinct pathological features of the gallyas- and tau-positive glia in the Parkinsonism-dementia complex and amyotrophic lateral sclerosis of Guam.

We examined 50 patients with parkinsonism-dementia complex of Guam (Guam PDC), 10 Guamanian patients with amyotrophic lateral sclerosis (ALS), 5 patients with combined PDC and ALS (PDC-ALS), and 20 non-PDC non-ALS Guamanians, who had been autopsied between 1979 and 1982, paying special attention to glial inclusions. Gallyas-positive and tau-immunopositive intracytoplasmic inclusions were observed in many of the glial cells, in addition to extensive neurofibrillary tangles (NFTs) in the brains of Guam PDC and PDC-ALS patients. Granular hazy inclusions were seen in the astrocytes, and some crescent/coiled inclusions were observed in the oligodendroglia. Many granular hazy inclusions were observed in the amygdaloid nucleus, inferior olivary nucleus, and lateral funiculus of the spinal cord. The crescent/coiled inclusions were observed predominantly in the anterior nucleus of the thalamus, motor cortex, midbrain tegmentum, pyramids of the medulla oblongata, and lateral funiculus of the spinal cord. The granular hazy inclusions have never been reported previously, and the topographic distribution of the crescent/coiled inclusions in Guam PDC and PDC-ALS differs from those reported previously in other NFT-forming diseases. These findings indicate that Guam PDC and PDC-ALS involve not only neurons but also glia, and that their morphological and topographic differences from other NFT-forming diseases may provide further insights into their distinct etiopathogenesis, and thus prove useful for diagnosis.

Adult↗
PubMed1996

Breast cancer vascularity: color Doppler sonography and histopathology study.

In this prospective study, the authors examined 50 patients with breast tumors (malignant, n = 32; benign, n = 18) to investigate the correlation between color Doppler flow mapping and histopathological findings and to evaluate the clinical significance of color Doppler mapping. Among the 32 patients with breast cancer, color Doppler signals were detected in 24 patients (75%). The maximum flow velocities varied from 5 to 34 cm/sec, with 16 (67%) of them above 15 cm/sec. Among the 18 patients with benign tumors, color Doppler signals could be detected in 7 (39%). The maximum flow velocity varied from 3 to 30 cm/sec but was over 15 cm/sec in only two patients (28%). Histological studies revealed that color Doppler signals detected by Doppler sonography correlated with disordered neovascularization penetrating the lesion from its periphery, consisting of thin-walled blood vessels and large arteriovenous shunts. Although large tumors tend to have high Doppler flow, there is no significant correlation between the maximum flow velocity and tumor size. There is also no significant correlation between the detection of high flow color Doppler signals and the age, receptor status, tumor size, lymph node metastases, or clinical stage of patients with breast cancer. However, there is a positive association (p < 0.05) between nodal metastases and higher tumor flow velocity in T1 (< or = 2 cm) breast tumors, but not in larger tumors. It is concluded that color Doppler is useful in the assessment of tumor vascularity but is of limited value in the differentiation of benign from malignant lesions. However, the presence of color Doppler signals in T1 breast cancer suggesting early dissemination of the cancer might be of important clinical significance in detecting those small, apparently early, but aggressive tumors with poor prognosis.

Adult↗
PubMed1996

Occult breast carcinoma--use of color Doppler in localization.

Occult breast carcinoma presenting with axillary metastases is a difficult clinical problem. Mammography is recommended as the diagnostic tool for detecting breast masses, but is very insensitive. In two consecutive patients with nonpalpable carcinoma of the breast, the detection of breast lesions was made by color Doppler sonography. The sensitivity of the technique makes it a useful diagnostic aid in patients with negative mammograms.

Adult↗
PubMed1996

Changes in T-lymphocyte subpopulations and serum lymphokine concentrations after partial hepatectomy in rats.

The relationship between liver regeneration and immunological response does exist. Extrathymic T cells and serum lymphokines are believed to be changed after partial hepatectomy, but there is still much controversy. This study evaluates the changes of peripheral blood T-lymphocyte subpopulations, natural killer (NK) cells, serum lymphokines, and NK cells in the remnant liver after partial hepatectomy. Male Wistar rats weighing around 200 g were used as subjects. Partial hepatectomies (67%) were done. Counting T-lymphocyte subpopulations (includes T3, T4, T8, T-IL2R, and NK cells) by using fluorescin isothiocyanate or phycoerythrin was performed preoperatively and on 1,2,3,5,7, and 10 d postoperatively. Serum gamma-interferon (gamma-IFN), interleukin-2 and interleukin-2 receptor concentrations were measured. Absolute number of NK cells in the remnant liver was also counted. Rats with right-side nephrectomy, sham operation, and no operation were used as control groups. Comparing the difference between all groups, we found that all T-lymphocyte subpopulations in peripheral blood, serum gamma-IFN, peripheral blood NK cells, and the absolute number of NK cells in the remnant liver of hepatectomized rats increased markedly, and were significantly higher than control groups rats, on the fifth and seventh post-hepatectomy day. It is suggested that gamma-IFN and NK cells were activated markedly and might play important roles in the regulation of liver regeneration after partial hepatectomy.

Animals↗
PubMed1996

P53 tumour-suppressor gene mutations are mainly localised on exon 7 in human primary and metastatic prostate cancer.

Mutations in the p53 tumour-suppressor gene are among the most common genetic alterations in human cancers. In the present study we analysed the mutations in the p53 tumor-suppressor gene in 25 primary and 20 metastatic human prostate cancer specimens. DNA extracted from the paraffin-embedded sections was amplified by hot-start polymerase chain reaction, and p53 gene mutations in the conserved mid-region (exons 4-9) were examined using single-strand conformation polymorphism (SSCP) analysis and immunohistochemistry. In the present study, we used a novel hot-start PCR-SSCP technique using DNA Taq polymerase antibody, which eliminates primer-dimers and non-specific products. Because of this new technique, the results of PCR-SSCP showed very high resolution. Polymerase chain reaction products were sequenced directly for point mutations for the p53 gene. Mutations were found in 2 out of 25 primary prostate cancers (8%) and 4 out of 20 metastatic cancers (20%). Mutations were observed exclusively in exon 7 and not in exons 4, 5, 6, 8 or 9. Nuclear accumulation of p53 protein, determined by immunohistochemistry, correlated with the degree of metastasis in prostatic cancer.

Adenocarcinoma↗
PubMed1996

Clinicopathologic characteristics and prognosis of gastric stump cancer.

To evaluate the prognosis of patients with gastric stump cancer after previous distal gastrectomy for benign gastroduodenal disease, we compared 25 patients with resected gastric remnant cancer with 143 patients with primary cancer in the upper third of the stomach. The histopathological differences between gastric remnant cancer and primary cancer were not significant, except for esophageal invasion. The percentage of esophageal invasion in gastric remnant cancer is 16%, significantly lower than 56.6% in primary cancer. The overall 5-year survival rates were 46% and 25% for patients with resected remnant cancer (n = 25) and resected primary cancer (n = 143), respectively, and there was no statistical difference between the two groups. The 5-year survival rates for gastric remnant cancer with stage I or II and primary cancer with the same stages were 89% (n = 11) and 39% (n = 50), a statistically significant (p < 0.02) difference. On contrast, the 5-year survival rate for gastric remnant cancer with stage III or IV was 0%, which was significantly worse than 17% for primary cancer with the same stages (p < 0.05). The prognosis of gastric remnant cancer is better than that of primary cancer in the upper third of the stomach at its early stages, but it is worse at its late stages. An aggressive resection is recommended for gastric stump cancer.

Adolescent↗