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Biomedical subjects

J C Lin

Publications and source records attributed to J C Lin.

At least 109 records · Page 6Linked to original sources
PubMed1997

Application of chromosome 4q35-qter marker (pFR-1) for DNA rearrangement of facioscapulohumeral muscular dystrophy patients in Taiwan.

Facioscapulohumeral muscular dystrophy (FSHD) has been found to be linked to chromosome 4qter. A chromosome 4q35-ter marker, pFR-1 (subclone of the cosmid c51), has been recently isolated and used as a probe for mapping near, or within, the FSHD gene. To examine FSHD-associated DNA rearrangements in the Taiwan population, we used the pFR-1 probe to perform Southern blot analysis on 142 individuals, including 32 FSHD patients within 9 autosomal dominant families, five sporadic FSHD patients from 4 families (include one pair of twins), three sporadic scapuloperoneal syndrome (SPS) patients and two sporadic polymyositis patients with their unaffected parents, and 29 healthy controls. In 29 healthy individuals, 3 SPS and 2 polymyositis patients with their families, probe pFR-1 analysis revealed that all had polymorphic restriction fragments that were larger than 28 kb in length. All but 1 FSHD-affected individual had specific smaller EcoRI fragments (ranging in size from 10.5 to 27 kb). Two point linkage analysis between pFR-1 and the FSHD locus provided significant evidence for FSHD linkage (Z(max)=6.84). A similar smaller fragment was also present in 5 sporadic patients, while this smaller fragment could not be found in one of their parents. Identical EcoRI restriction fragment length polymorphism (RFLP) patterns linked to FSHD were shown in the monozygotic twins, even though they showed extreme variability in the expression of FSHD. We conclude that the pFR-1 probe is a tightly linked marker of FSHD and can be used to detect most DNA rearrangements associated with this disease in the Taiwan population. However, the same RFLP patterns may represent extreme variability in the expression of the FSHD gene.

Adolescent↗
PubMed1997

Treatment of Nocardia asteroides keratitis with polyhexamethylene biguanide.

PURPOSE: Polyhexamethylene biguanide (PHMB) is a polymeric biguanide disinfectant that has been used previously in the treatment of Acanthamoeba keratitis. The authors report the first case of Nocardia asteroides keratitis treated successfully with PHMB. Further studies documenting the efficacy of PHMB against N. asteroides in vitro also are presented. METHODS: A soft contact lens wearer presented with an infectious keratitis. Cultures from the cornea grew N. asteroides. The infection resolved with the treatment with PHMB 0.02%. Serial dilutions of PHMB were performed against N. asteroides in culture. RESULTS: In vitro dilution studies determined that the minimal inhibitory concentration for PHMB against the tested isolate of N. asteroides was 0.01%. This is a concentration that has been shown to be well tolerated by the cornea in vivo. CONCLUSIONS: Polyhexamethylene biguanide is effective against both Acanthamoeba and Nocardia and may have a wider range of usefulness than that currently recognized. Further testing, both in vitro and in vivo, is required.

Adolescent↗
PubMed1997

Texture analysis of direct magnification radiographs of vertebral specimens: correlation with bone mineral density and biomechanical properties.

RATIONALE AND OBJECTIVES: The authors used direct magnification radiographs, combines with texture analysis, to investigate the trabecular structure of human vertebral specimens and compared these techniques with measurement of bone mineral density (BMD) by using quantitative computed tomography to predict bone strength. METHODS: Direct magnification radiographs and BMD measurements were obtained from 38 motion segments from the thoracolumbar spines of 11 female human cadavers. Maximum compressive strength (MCS) was determined with a materials testing machine. Morphologic parameters, digital skeletons, and fractal dimension were obtained from the radiographs in three different regions of interest. RESULTS: Correlations between BMD and MCS were statistically significant (r = .81, P < .01). With morphologic parameters, correlation coefficients of up to .64 (P < .01) were obtained. Use of multivariate regression analysis with one morphologic parameter (the width of the black pixels, or thicknessB) in addition to BMD improved correlations versus MCS (P < .01). CONCLUSION: In an experimental setting, BMD showed statistically significant correlation with bone strength, whereas the structural parameters demonstrated only modest correlations. BMD together with one of these measures (thicknessB), however, showed the highest correlation.

Adult↗
PubMed1997

Effect of exercise and exogenous glucocorticoid on serum level of intact parathyroid hormone.

Most previous studies suggest that physical exercise, or physiological response to exercise such as cortisol and adrenaline secretion regulate parathyroid hormone (PTH) secretion in humans. To investigate the effects and possible interaction of exercise and excessive glucocorticoid on PTH secretion, we examined the serum of levels of intact-PTH, cortisol, adrenocorticotrophic hormone (ACTH), calcium, magnesium and phosphorus before and during one-hour of bicycle-ergometric exercise at 60% of maximal oxygen uptake. These exercise tests were performed on eight Chinese male volunteers aged between 20 and 25 years, once with and once without pretreatment with 0.5 mg of dexamethasone taken orally 9.5 hours in advance. The results showed that dexamethasone pretreatment significantly lowered basal levels of cortisol and ACTH, but intact PTH did not change. After 60 minutes of bicycling, intact PTH level increases by 50% of baseline both with and without dexamethasone pretreatment. Serum levels of calcium, corrected for changes in serum albumin concentration, phosphorus and magnesium also increased in both cases. This study demonstrated an increase of intact-PTH with exercise which was not associated with hypocalcemia or hypomagnesemia, and was not altered in the presence of mild exogenous glucocorticoid excess and suppressed endogenous cortisol secretion.

Adrenocorticotropic Hormone↗
PubMed1997

Pilot study of concurrent chemotherapy and radiotherapy for stage IV nasopharyngeal cancer.

Nasopharyngeal carcinoma (NPC) is a more radio- and chemosensitive tumor than all other head and neck cancers. Between September 1991 and December 1992, a total of 19 patients (13 men and six women; median age, 44 years) with AJCC stage IV NPC were entered into a pilot study of concurrent chemoradiotherapy. Pathology showed either poorly differentiated epidermoid carcinoma or undifferentiated carcinoma. Radiotherapy was delivered using a telecobalt unit and 10-MV x-rays and by conventional fractionation (1.8-2.0 Gy/fraction, 5 fractions/week). The total doses delivered were 70-75 Gy to the primary tumor and neck positive region, and 50-55 Gy to the neck negative area. Chemotherapy with cisplatin (10 mg/m2/day, days 1-5) and 5-fluorouracil (500 mg/m2/day, continuously infused for 5 days) was administered concurrently during weeks 1 and 5 of radiotherapy. The major toxicities were mucositis (42% had grade III and 58% grade II) and leukopenia (nadir white blood cells <3,000/mm3 in eight of 19). Although four patients required a delay in their second cycle of concurrent chemotherapy or had their radiotherapy interrupted for 1 week, all 19 patients completed the planned treatment and achieved a 100% complete response rate. After a median follow-up period of 42 months, one patient suffered from neck recurrence plus distant metastasis, and three patients developed distant metastases alone. The 3-year overall and disease-free survival rates are 89.5% and 83.3%, respectively. Our data indicated that concurrent chemoradiotherapy for advanced NPC is both feasible and effective, with acceptable toxicities. A phase III randomized trial to compare the efficacy of concurrent chemoradiotherapy and radiotherapy alone deserves to be studied further.

Adolescent↗
PubMed1997

Theoretical study of magnetic field of current monopoles in special volume conductor using symmetry analysis.

We derive a formula for the magnetic field outside volume conductors having axial symmetry with radial and axial symmetrically distributed source currents. The magnetic field is shown to have components only along the cylindrical polar angle direction and its magnitude to depend only on the topological structure of the volume conductor and the location of the source current. With this formula, the magnetic field generated by the volume current of a current monopole within and on the symmetrical axis of several volume conductors (such as semi-infinite volume, infinite slab, sphere, infinite cylinder, semi-infinite cylinder, finite cylinder, prolate spheroid, and oblate spheroid) is shown to be equivalent to the magnetic field generated by a line current calculated using the Biot-Savart's law. In the first three volume conductors, the monopole solution of the magnetic field allows the calculation of magnetic fields generated by arbitrarily distributed (and balanced for finite volume conductors) current monopoles.

Biophysical Phenomena↗
PubMed1997

Correlation of trabecular bone structure with age, bone mineral density, and osteoporotic status: in vivo studies in the distal radius using high resolution magnetic resonance imaging.

High resolution magnetic resonance (MR) images of the distal radius were obtained at 1.5 Tesla in premenopausal normal, postmenopausal normal, and postmenopausal osteoporotic women. The image resolution was 156 microm in plane and 700 microm in the slice direction; the total imaging time was approximately 16 minutes. An intensity-based thresholding technique was used to segment the images into trabecular bone and marrow, respectively. Extensions of standard stereological techniques were used to derive measures of trabecular bone structure from these segmented images. The parameters calculated included apparent measures of trabecular bone volume fraction, trabecular thickness, trabecular spacing, and trabecular number. Fractal-based texture parameters, such as the box-counting dimension, were also derived. Trabecular bone mineral density (BMD) and cortical bone mineral content (BMC) were measured in the distal radius using peripheral quantitative computed tomography (pQCT). In a subset of patients, spinal trabecular BMD was measured using quantitative computed tomography (QCT). Correlations between the indices of trabecular bone structure measured from these high-resolution MR images, age, BMD, and osteoporotic fracture status were examined. Cortical BMC and trabecular BMD at the distal radius, spinal BMD, trabecular bone volume fraction, trabecular thickness, trabecular number, and fractal dimension all decreased with age. Trabecular spacing showed the greatest percentage change and increased with age. In addition, significant differences were evident in spinal BMD, radial trabecular BMD, trabecular bone volume fraction, trabecular spacing, and trabecular number between the postmenopausal nonfracture and the postmenopausal osteoporotic subjects. Trabecular spacing and trabecular number showed moderate correlation with radial trabecular BMD but correlated poorly with radial cortical BMC. High resolution MR imaging, a potentially useful tool for quantifying trabecular structure in vivo, may have applications for understanding and evaluating skeletal changes related to age and osteoporosis.

Adult↗
PubMed1997

Clonidine antagonizes pressor effect of N-methyl-D-aspartate in the rostral ventrolateral medulla of rats.

The purpose of the present study was to investigate the modulatory actions of adrenoreceptor agonists on N-methyl-D-aspartate (NMDA)-induced pressor effect in rostral ventrolateral medulla (RVLM). These drugs were locally applied into RVLM of urethane-anesthetized Sprague-Dawley rats through multibarrel pipettes. Microinjection of NMDA increased the arterial pressure, an effect which was abolished by pretreatment with clonidine, whereas neither the beta-adrenergic agonist isoproterenol nor the alpha 1-adrenergic agonist phenylephrine did alter this pressor response. Previous experiments demonstrated that clonidine binds to noradrenergic alpha 2 and imidazoline receptors in the RVLM. Norepinephrine, which has high affinity for the alpha 2 receptor and low affinity to the imidazoline receptor, partially antagonized NMDA-induced hypertension. On the other hand, administration of selective imidazoline receptor antagonist idazoxan partially reversed clonidine-mediated antagonism of NMDA. Taken together, these results suggest that clonidine may modulate the excitatory amino acid-induced pressor response through noradrenergic alpha 2 and imidazoline receptors in the RVLM.

Adrenergic alpha-Agonists↗
PubMed1996

Partially hyperfractionated accelerated radiotherapy and concurrent chemotherapy for advanced nasopharyngeal carcinoma.

PURPOSE: A newly designed concomitant chemoradiotherapy was undertaken to assess the feasibility and efficacy for advanced nasopharyngeal carcinoma (NPC). METHODS AND MATERIALS: Sixty-three patients with biopsy-proven NPC were entered in this Phase II trial from March 1992 to November 1993. Most patients present with Stage IV disease (93.4%) and poorly differentiated epidermoid carcinoma or undifferentiated carcinoma were the major pathologic type. Radiotherapy was delivered using a telecobalt unit and 10 MV x-rays and by altered fractionation (72-74 Gy/45 fractions/6 weeks). Chemotherapy with cisplatin 75 mg/m2, 2 h infusion at day 1, followed by 5-FU 400 mg/m2/day, continously infused for 4 days was given concurrently during the first and fifth weeks of radiotherapy. RESULTS: The major toxicity was mucositis (61% belong to Grade 3, 31% to Grade 2). Weight loss, leucopenia, and skin reaction were frequently encountered. Three patients withdrew from treatment at 15, 25, and 55.5 Gy, three patients interrupted the radiotherapy for 1-4.5 weeks, and two patients refused the second cycle of concomitant chemotherapy due to toxicities. The initial tumor response showed 100% overall response rate, with 90.5% complete response. After a median follow-up time of 38 months, five patients failed at the primary and/or neck (four recurrent and one persistent), and 14 patients developed distant metastases alone. The 3-year primary disease-free, regional disease-free, distant disease-free, and overall survival rates are 89.1, 92.8, 74.3, and 73.6%, respectively. The late complication rate is acceptable so far. CONCLUSIONS: Our data indicates that concurrent chemoradiotherapy for advanced NPC is both feasible and effective, with acceptable toxicities. Distant metastases are the major site of treatment failure. Postradiation adjuvant chemotherapy to eradicate subclinical distant metastasis should be further studied.

Adult↗
PubMed1996

Detailed deletion mapping with a refined physical map of 7q31 localizes a putative tumor suppressor gene for breast cancer in the region of MET.

In breast cancer, loss of heterozygosity (LOH) has been described on the long arm of chromosome 7 at band q31, suggesting the presence of a tumor suppressor gene in this region. To define the deleted region, we analysed 73 cases of breast cancer and matched normal DNAs with 17 polymorphic markers. A minimal area of LOH was identified as the chromosomal interval flanked by markers D7S687 and metH, spanning a segment of 2 Mb on chromosome 7q31. Of the 73 breast cancer patients studied, all were informative for at least one marker in this region and nine patients showed LOH at one or more loci (12.3%). To define the physical size of the deletion and to ensure the correct interpretation of the LOH deletion studies, we redefined the physical map of markers within this region of 7q31. We present a new physical order for markers at 7q31. More significantly, we have mapped the minimum deletion of 7q31 in the breast cancers studied to date to a physical distance of 1000 kb, contained on a single YAC clone, which includes the MET receptor tyrosine kinase but no other known genes.

Breast Neoplasms↗
PubMed1996

Bilateral enophthalmos associated with hydrocephalus and ventriculoperitoneal shunting.

BACKGROUND: Progressive bilateral enophthalmos in the absence of previous trauma is rare. METHODS: Three patients with progressive bilateral severe enophthalmos whose only significant medical history was that of congenital hydrocephalus were treated by ventriculoperitoneal shunt placement. RESULTS: The patients demonstrated severe bilateral enophthalmos with poor eyelid apposition to the globes resulting in superficial keratopathy. Orbital computed tomographic scans confirmed the severe enophthalmos, with apparent reduced orbital fat volume. Orbital bony anatomy appeared normal. CONCLUSIONS: Bilateral progressive enophthalmos may be associated with hydrocephalus and ventriculoperitoneal shunting. The causal mechanism remains speculative.

Adult↗
PubMed1996

Expression of p53 protein in colorectal carcinoids.

OBJECTIVE: To determine the frequency and prognostic significance of p53 protein expression in colorectal carcinoid tumors. DESIGN: Thirty-one paraffin-embedded specimens of colorectal carcinoid tumor were studied by immunohistochemical staining to detect p53 protein expression. The association of p53 expression with tumor site, tumor size, invasion level, tumor stage, DNA pattern, and patient survival were analyzed. RESULTS: p53 protein was detected in five (16%) of 31 colorectal carcinoid tumors. There was a correlation between p53 overexpression and tumor site, tumor size, tumor stage, and DNA ploidy (P < .05) but not for the depth of tumor invasion (P = .06). In addition to tumor size, invasion, stage, and DNA aneuploidy, p53 protein overexpression was also indicative of a poor prognosis (P < .001). CONCLUSIONS: The overexpression of p53 protein is uncommon in colorectal carcinoid tumors. However, the expression of p53 protein has a correlation with clinicopathologic-predicting criteria in colorectal carcinoid tumors and may be used as an associated prognostic parameter to assess patient survival.

Carcinoid Tumor↗
PubMed1996

Radio frequency electromagnetic exposure: tutorial review on experimental dosimetry.

Radio frequency (RF) dosimetry is the quantification of the magnitude and distribution of absorbed electromagnetic energy within biological objects that are exposed to RF fields. At RF, the dosimetric quantity, which is called the specific absorption rate (SAR), is defined as the rate at which energy is absorbed per unit mass. The SAR is determined not only by the incident electromagnetic waves but also by the electrical and geometric characteristics of the irradiated subject and nearby objects. It is related to the internal electric field strength (E) as well as to the electric conductivity and the density of tissues; therefore, it is a suitable dosimetric parameter, even when a mechanism is determined to be "athermal." SAR distributions are usually determined from measurements in human models, in animal tissues, or from calculations. This tutorial describes experimental techniques that are used commonly to determine SAR distributions along with the SAR limitations and unresolved problems. The methods discussed to obtain point, planar, or whole-body averaged SARs include the use of small E-field probes or measurement of initial rate of temperature rise in an irradiated object.

Animals↗
PubMed1996

High complete response rate of concomitant chemoradiotherapy for locally advanced squamous cell carcinoma of the uterine cervix.

A prospective study with a newly designed schedule of concomitant chemoradiotherapy was initiated for 42 patients with previously untreated squamous cell carcinoma of the uterine cervix. Their ages ranged from 34 to 77 years, median 57 years. There were 13 FIGO stage IIB, 1 IIIA, 27 IIIB, and 1 IVA. Radiotherapy was administered using 1.8 Gy/day, 5 days a week, to the whole pelvis (50.4 Gy/28 fractions) with local boost if indicated. Intracavitary brachytherapy of 5 Gy for five times was delivered after 1-2 weeks of rest. The first 21 patients received concomitant chemotherapy of biweekly PEB regimen (100 mg/m2 etoposide + 50 mg/m2 cisplatin + 50 mg/m2 bleomycin) for two to three cycles during external irradiation. The chemotherapy for the latter 21 patients was modified to weekly PEBF (50 mg/m2 etoposide + 20 mg/m2 cisplatin + 10 mg/m2 bleomycin + 800 mg/m2 5-FU, mixed in normal saline, 24-hr continuous iv infusion) for five to six cycles. All except 1 patient achieved complete response (97.6%) and sustain so after a median follow-up time of 30 months. There were three relapses--one with persistent pelvic disease and two with distant metastasis. Two-year overall survival and disease-free survival rates were 97.6 and 92.9%, respectively. Myelosuppression was moderate but fully recovered. Other acute toxicities were tolerated except for 1 patient who encountered grade IV radiation colitis with cecum perforation and required surgery. As to late morbidity, the incidence of radiation proctitis was high (21.4%) but of a mild degree, with 1 patient needing repeated transfusion. One patient developed chronic cystitis with an acontractile bladder. Our preliminary results show that concomitant chemoradiotherapy for advanced cervical carcinoma is both feasible and effective with acceptable toxicities. Further follow-up is mandatory to ensure whether this high complete response protocol will translate into long-term local control and survival.

Adult↗
PubMed1996

Vascular dementia of Binswanger's type: clinical, neuroradiological and 99mTc-HMPAO SPET study.

In 24 patients with vascular dementia of Binswanger's type (VDBT) and 14 age-matched neurologically normal volunteers, we investigated the relationship between clinical features, white matter lesions (leuco-araiosis) and cerebral atrophy on computed tomographic (CT) scan, and regional cerebral blood flow. All subjects underwent the Mini-Mental State Examination of Taiwan, version 1 (MMSE-T1), for assessing the severity of cognitive impairment. The patients were subdivided into two groups, one with mild to moderate (group I, MMSE-T1 scores: 11-24, n=11), and the other with severe dementia (group II, MMSE-T1 scores: below 10, n=13). White matter degeneration was evaluated with densitometric methods. Loss of brain parenchyma was estimated with seven linear measurements (Evan's ratio, third ventricle ratio, width of temporal horn tip, anterior-posterior length of temporal horn, anterior-posterior length of Sylvian fissure and width of frontal interhemispheric fissure) by CT scans. Regional cerebral blood flow was determined with technetium-99m hexamethylpropylene amine oxime (HMPAO) single-photon emission tomography (SPET). In neuroimaging studies, subcortical leuco-araiosis was localized at the frontal region in group I patients and scattered diffusely in group II patients. 99mTc-HMPAO SPET analysis revealed reduction of regional cerebral blood flow in the frontal lobe in group I patients and widespread reduction of regional cerebral blood flow in group II patients. A correlation between frontal leuco-araiosis and perfusion defect of the frontal pole was demonstrated in group I patients, showing findings typical of subcortical dementia. There was no difference in frontal atrophic measurements between group I patients and controls. Ratios of volumes of lost brain parenchyma and leuco-araiosis were significantly higher in group II patients than in the age-matched controls, corresponding to a diffuse cerebral perfusion defect. These results suggest that patients with VDBT have early frontal lobe involvement with posterior progression. Patients with mild VDBT are more likely to show reduction of frontal cerebral blood flow and leuco-araiosis, while those with severe VDBT are more likely to have diffuse leuco-araiosis, cerebral hypoperfusion and brain atrophy.

Aged↗