Biomedical subjects

F J Lin

Publications and source records attributed to F J Lin.

At least 37 records · Page 2Linked to original sources

PubMed1996

A deficiency in prothoracicotropic hormone transduction pathway during the early last larval instar of Bombyx mori.

The prothoracicotropic hormone (PTTH) is an insect cerebral peptide that stimulates the prothoracic glands to produce ecdysteroids that initiate moulting and metamorphosis. During the last larval instar of holometabolous insects, a reduction in the hemolymph juvenile hormone (JH) levels is a necessary step in initiating larval-pupal transformation. Recently we have demonstrated that very low ecdysteroid levels in the early last larval instar of Bombyx mori initiate the complete inactivation of corpora allata (CA). Results presented here further indicate that PTTH signal transduction pathways undergo specific developmental changes, with a deficiency in transduction in prothoracic gland cells occurring during the early last instar. Glands from the early last instar showed no increase in either cAMP levels or steroidogenesis to the stimulation of PTTH, indicating the absence of the PTTH receptors in gland cells. We propose that this absence of PTTH receptors plays a critical role in directing larval-pupal transformation.

Animals↗

PubMed1996

Longitudinal decline in lung function in patients with occupational asthma due to western red cedar.

BACKGROUND: There are few reports about longitudinal changes in lung function in asthmatic patients. Patients with asthma had a greater loss of lung function than normal healthy adults. To date, there have been no studies about the longitudinal changes in lung function in patients with occupational asthma. METHODS: 280 male patients with red cedar asthma (RCA) who were followed up for at least one year were the study group. The exposed controls consisted of 399 male sawmill workers. Forced expiratory volume in one second (FEV1) was measured with a Collins water spirometer. Changes in FEV1 over time (FEV1 slope) were calculated by a two point method for each subject. Atopy was considered to be present if the subjects showed at least one positive response to three allergens by skin prick test. RESULTS: Multiple regression analysis was carried out to examine factors that might affect longitudinal decline in FEV1. Patients with RCA who were still exposed had a greater decline in FEV1 slope (-26 ml/y) than sawmill workers. Smokers also showed a greater rate of decline in FEV1 (-43 ml/y) than non-smokers. CONCLUSIONS: Patients with RCA who continued to be exposed had a greater rate of decline in FEV1 than sawmill workers. Early diagnosis of occupational asthma and removal of these patients from a specific sensitiser is important in the prevention of further deterioration of lung function and respiratory symptoms.

Adult↗

PubMed1995

Prevalence and predictors of asthma in working groups in British Columbia.

We evaluated the prevalence of asthma and its predictors in studies of several male working groups: 619 cedar sawmill, 724 grain elevator, 399 pulpmill, 798 aluminum smelter, and 1,127 unexposed workers. These workers had taken part in health studies for assessment of chronic respiratory effects of various workplace exposures between 1979 and 1982. The American Thoracic Society Adult Questionnaire (ATS-DLD-78) was used for these studies. Allergy skin tests were also performed. The participation rates were > 80%. The overall prevalance of physician-diagnosed asthma was 4.6%, and current asthma 3%. The prevalence of asthma after employment in the current industry, as a surrogate for work-related asthma, was 3.9 times higher in cedar sawmill workers, 2.2 times higher in pulpmill and aluminum smelter workers, and 1.7 times higher in grain elevator workers compared with unexposed workers. Atopy and a positive parental history of asthma, but not smoking, were important risk factors for asthma before the onset of first employment. Also, for asthma after employment in the current industry, atopy and a positive parental history of asthma were important risk factors. Smoking was associated with a significant reduction in the risk for asthma after employment in the current industry. Within specific work groups, the prevalence of atopy was significantly higher among pulpmill workers with asthma after employment in current industry than those without asthma. Conversely, cedar sawmill workers who had asthma after employment in the current industry were nonatopic and nonsmokers.

Adult↗

PubMed1995

New method for an occupational dust challenge test.

OBJECTIVES: Specific challenge tests with a suspected allergen in the workplace are standard to confirm the diagnosis of asthma. Facilities for sophisticated exposure tests are available only in a few institutions. A pilot study was carried out that used a novel approach for an occupational dust challenge test with a rotahaler. METHODS: Nine consecutive patients were enrolled in this study. Six of these proved to have asthma to red cedar by challenge tests with plicatic acid. They were challenged with a maximum dosage of 80 mg of red cedar dust and spruce dust (control) with a rotahaler on separate days in a single blinded manner. A positive reaction was defined as a fall in the forced expiratory volume in one second (FEV1) or the peak expiratory flow (PEF) after a challenge test of > or = 20% below the baseline value. RESULTS: Three of the six patients who reacted to plicatic acid also had a positive response to red cedar dust delivered through a rotahaler. All three patients with a negative response to challenge with plicatic acid also showed a negative response to red cedar dust. CONCLUSIONS: This pilot study showed that a positive challenge test with a rotahaler to deliver red cedar dust was specific in the diagnosis of red cedar asthma but a negative response could not rule out the diagnosis. The rotahaler has merits of being easy to operate, safe, inexpensive, and readily available. The usefulness of this method and its reproducibility have to be examined in a series of patients.

Adult↗

PubMed1995

The role of flow cytometry in non-resected cervical carcinoma.

Flow cytometry (FCM) has a prognostic value for many malignant neoplasms in terms of treatment response rate and survival. However, its role in non-resected cervical carcinoma remains uncertain. We have collected 96 paraffin-embedded specimens taken from non-resected cervical cancer patients treated by radiotherapy (RT) alone between 1984 and 1986. Our data revealed that FCM has little correlation with patients' age, pathological grade and clinical stage. Ploidy pattern and clinical stage correlate significantly with complete remission (CR) rate (p = 0.001 and 0.03). Most diploid or low-stage tumours (IB to IIA) obtained CR after RT alone. The application of an intravaginal extension electron cone (IVEC) (p = 0.019) and CR status (p = 0.0001) yield significant better overall survival (OS) rates than their alternative groups. The Cox regression model has confirmed these two variables as having an independent influence on OS. We thus conclude that both ploidy pattern and S-phase fraction (SPF) predict neither pre-treatment biological behaviour of the tumours nor overall survival. However, ploidy pattern has an independent influence on CR rate.

Adult↗

PubMed1995

Immediate skin reactivity in adult asthmatic patients.

BACKGROUND: A high prevalence of positive skin reaction is commonly seen in children with asthma. Very little information is available on the prevalence of immediate skin test reactivity in adult patients with asthma. METHODS: We performed allergen skin tests on 260 patients with asthma and 168 patients with red cedar asthma using a battery of 24 allergens. Immediate skin test reactivity was considered to be present if the subject reacted to at least one allergen. RESULTS: Forty-eight percent of adult asthmatic patients had immediate skin test reactivity. Age, sex, and race were predictors of prevalence of immediate skin test reactivity. The number of allergens used for skin testing also determined the prevalence. More than half the patients who had immediate skin test reactivity reacted to house dust mite allergen. CONCLUSIONS: There was a high proportion of immediate skin test reactivity in adult patients with asthma and half of them had positive skin reactions to house dust mite. As avoidance of house dust mites has been shown to be effective in patients with asthma, allergy evaluation should be included in the management of adult patients with asthma.

Adult↗

PubMed1994

Effect of grain exposure and smoking on the longitudinal changes in immediate skin reactivity.

The study was carried out to investigate the effect of occupational exposure and smoking on the longitudinal changes of immediate skin reactivity over 3 years in working populations. A total of 480 grain elevator workers and 707 transit and ferry (control) workers were included because they had allergy skin tests on both surveys. Skin-prick texts using three common allergens and a negative and histamine controls were administered during both surveys. The reaction was considered positive if the mean weal size was 3 mm or greater than that of the negative control. Conversion was defined as a change from the non-atopic state in the initial survey to the atopic state in the follow-up survey. Reversion was defined as a change from the atopic state in the initial survey to the non-atopic state in the follow-up survey. The findings showed that grain workers had two times risk of conversion than control workers. Recent smokers, who changed their habit from non-smoker/ex-smoker to smoker in the follow-up survey, were at a three times risk of conversion than non-smokers. The reversion of skin-test reactivity was not associated with age, smoking habits, or working exposure. When investigating studies of longitudinal changes in immediate skin reactivity, the effects of age, changes in smoking habit and occupational exposure should be considered.

Adult↗

PubMed1993

A multivariate analysis of prognostic factors in management of pineal tumor.

PURPOSE: A multivariate analysis of prognostic factors of treatment outcome of pineal tumor. METHODS AND MATERIALS: From February 1979 to June 1987, 25 patients with primary pineal tumors were treated in our department. Patients were treated with either AECL Co-60 unit or 10 MV linear accelerator to the primary tumor with an adequate margin or to the whole brain (median dose of 36 Gy) with or without a cone-down boost of 10 to 20 Gy. Craniospinal irradiation was performed in two patients with positive CSF cytology. Minimum follow-up was 40 months. Patients were further stratified according to tumor type. Group I consisted of seven patients with pineal germinoma. Group II included nine patients with nongerminoma, and Group III represented nine patients treated without a histological verification but clinical diagnosis. RESULTS: The relapse-free survival (RFS) of Group I patients was 100% and 86% at 2 and 5 years, respectively. Relapse-free survival was 55% and 21% at 2 and 5 years, respectively, for Group II patients. Six of 9 patients in Group II died of disease due to either local recurrence or tumor seeding. Eight of 9 patients in Group III remain no evidence of disease, and RFS was 89% at 2 and 5 years. Multivariate analysis revealed that tumor histology is the only significant prognosticator. Age, gender, type of surgical procedure, RT field, and tumor dose were not. Cox's regression model also failed to demonstrate a significant correlation of tumor seeding with the type of surgery. CONCLUSION: The type of tumors in the pineal region dictates the treatment outcome. Definitive radiation therapy is effective in controlling germinoma, whereas a more aggressive approach is needed to improve local control for nongerminoma. For a localized pineal lesion, we advocate that treatment can be tailored to the primary tumor with adequate margins. However, for locally advanced tumors whole brain or craniospinal irradiation should be considered. No definitive correlation between type of surgery and the probability of tumor seeding was identified.

Actuarial Analysis↗

PubMed1993

Implementation of stereotactic focal radiotherapy for intracranial arteriovenous malformations using a linear accelerator.

A system of stereotactic focal radiotherapy using a linear accelerator has been developed in cooperation with a neurosurgeon. The treatment is delivered using a carefully calibrated 10 MV machine and the Cosman-Roberts-Wells (CRW) system. The precision of the method as well as its quality assurance is described. Eight patients with intracranial arteriovenous malformations (AVM) received irradiation from August 1990 to November 1991. The prescribed dose at the periphery of the AVM was 8 Gy per session, with six patients receiving two sessions and two patients receiving one session. The field size, encompassing the 90% isodose, ranged from 20 mm to 35 mm. In four patients, follow-up angiography was performed one year after the full course of therapy; total obliteration of the AVM was noted in three (75%) with a partial response in the other. In the other four patients, follow-up angiography was not performed; one patient, who had only one session of irradiation, experienced rebleeding six months later and died, and the other three patients had no further episodes of bleeding during their follow-up of 28, 18 and 14 months, respectively. Linear accelerator-based stereotactic focal radiotherapy can attain a precisely defined and reproducible dose distribution. The effects of this treatment may take one to two years to develop. Our preliminary study suggests that it is an effective alternative treatment for surgically inaccessible lesions. Patients with a small cavernous sinus dural AVM appear to have a better and more rapid response.

Adult↗

PubMed1993

Impact of prophylactic cranial irradiation in adenocarcinoma of the lung.

Out of 148 patients who had metastatic adenocarcinoma of the lung and were referred to Chang Gung Memorial Hospital for treatment from 1979 to 1987, 20% had symptomatic brain metastases. We have attempted to determine the subset of high-risk patients who might benefit from prophylactic cranial irradiation. In 25 patients with a complete remission, 36% (n = 9) eventually developed brain metastases after a minimum follow-up of 24 months. Patients with initial mediastinal node metastases showed a higher incidence of brain metastases (75%) than those harboring only hilar node metastases (25%, p = 0.03). Age, sex, tumor location and clinical staging had no significant correlation in the prognosis of brain metastases. Since the median recurrence-free survival rate of six months for patients with brain metastases was significantly shorter than for those without (14 months), we recommend that prophylactic cranial irradiation be conducted in complete responders with mediastinal nodal lesions to see if such treatment will prolong patients' recurrence-free survival via a reduction in brain metastases, thus improving their quality of life.

Adenocarcinoma↗

PubMed1993

Concurrent radiotherapy and continuous 5-fluorouracil infusion in the management of locally advanced esophageal cancer.

From 1987 to 1989, a total of 22 patients with locally advanced non-metastatic esophageal cancer were treated by a combination of radiation therapy (RT) and chemotherapy (CT). RT, consisting of 250 cGy tumor dose per fraction with four fractions per week up to a total dose of 6000 cGy, was given concurrently with CT: 96 hours of continuous 5-fluorouracil (5-FU) infusion at a dose level of 250 g/kg/day. RT+CT was repeated every other week for a total of six cycles in 11 weeks. Toxicity data revealed that only mild to moderate mucositis, nausea/vomiting and myelosuppression occurred, and no patients developed unacceptable levels of toxicity necessitating discontinuation of the 5-FU infusion. Complete response (CR) was noted in nine out of 22 (41%) patients. The median progression-free survival period (MPFS) was 10 months, and the median absolute survival (MAS) was 13 months. Corresponding figures for our 61 previously RT treated patients (matched for sex, age, histopathology, tumor extent and location with current study group) were: CR rate, 8%; MPFS, three months; and MAS, six months. Kaplan and Meiers' survival curves and Log Rank test revealed a statistically significant difference in favor of the combined modality group (PFS, p = 0.0001; AS, p = 0.0001). The relatively good response rate and survival data appear to warrant further dose escalation in 5-FU since no major dose limiting toxicities were observed at 25 mg/kg/day.

Combined Modality Therapy↗

PubMed1992

Prognostic assessment of tumor regression after external irradiation for cervical cancer.

From February 1980 to December 1986, 428 cases of cervical cancer in Stage I through IVA were given curative radiation therapy at Chang Gung Memorial Hospital, Taipei. All of them received external irradiation and intracavitary brachytherapy. The degree of tumor regression was assessed immediately before the first intracavitary brachytherapy treatment. Patients were classified at this time as having (a) no gross residual tumor, or (b) gross residual tumor. Factors found to be associated with tumor regression by logistic regression analysis were stage, age and hemoglobin level. Patients with advanced cancer (Stage III, IVA), young age (less than 40 years), and low hemoglobin level (less than 10 g/dl) had a low incidence of no gross residual tumor. Five-year survival rate was 77% in patients with no gross residual tumor and 31% in patients with gross residual tumor (p less than 0.001). This significant difference held true even when one compared these two groups stage for stage; the difference was 77% versus 41% (p less than 0.001) in Stage II and 72% versus 28% (p less than 0.001) in Stage III. The local relapse rate was 59% in the gross residual tumor groups, significantly greater (p less than 0.001) than the 12% found in the no gross residual tumor group. It was concluded that patients whose tumors did not regress after external pelvic irradiation tended to recur after intracavitary brachytherapy, most often locally. This would justify a more aggressive treatment to improve local tumor control in this subset of high risk patients.

Adenocarcinoma↗

PubMed1992

[Implementation of stereotactic focal radiotherapy using 10 MV x-ray].

Stereotactic focal irradiation is also called stereotactic radiosurgery by some neurosurgeons. This irradiation is used for the treatment of brain AVM (arterio-venous malformation) and small tumor. Application of stereotactic focal irradiation was developed with CRW (Cosman-Roberts-Wells) stereotactic device and two dimensional (2D) computer treatment planning system using 10 MV x-ray from a linear accelerator. This process of irradiation includes: (a) Identification and localization of a target volume in CRW stereotactic frame by CT scan or angiography. (b) To verify the alignment, a linear accelerator was used as a simulator to take portal films in anterior and lateral views. This was done to ascertain the angles between arc therapy, to encompass the target volume, and to exclude the critical organs such as lens at 0 degrees, 45 degrees, 90 degrees and 315 degrees couch angles. (c) A 2D computer treatment planning system was used to generate an isodose curve distribution for each couch angle. Then this was used to calculate the monitor unit per degree for rotation treatment. (d) 10 MV x-ray was used to implement the stereotactic focal radiotherapy.

Humans↗

PubMed1992

Occurrence of nasopharyngeal carcinoma in aboriginals of Taiwan: report of 14 cases.

The authors describe the rare occurrence of nasopharyngeal carcinoma (NPC) in 14 aboriginals of Taiwan (ABT), a minor ethnic group now accounting for less than 2% of the total population in Taiwan. The observation is epidemiologically unusual, representing a low-risk ethnic group in an NPC prevalent area. With regard to patient characteristics, symptomatology and pathology, we have not found any appreciable differences in reports from other geographic areas. Serological profiles of antiEBV-VCA (Epstein-Barr virus, viral capsid antigen) antibody in 7/9 patients available for review of IgA and 5/7 patients available for review of IgG were found significantly elevated, ranging respectively from 1:40-640/1:160-1280. Interestingly, 12 of the 14 patients were found to be exclusively from the Paiwan tribe residing in Pintung, a district in southern Taiwan. Since the exact prevalence of NPC in this minority remains unknown, it is not clear whether the apparent preponderance is real or merely causal due in part to geographic bias. To a lesser extent, however, our observations indicate that NPC is not an uncommon malignancy in Paiwan aboriginals of southern Taiwan.

Adult↗

PubMed1992

[Measurements of dose distribution in small fields of 10 MV X-rays].

Dose distribution measurement in small fields include: 1. Field size factor, 2. Percentage depth dose, 3. Isodose curves charts, 4. Tissue-phantom ratio, and 5. Penumbra width. Field size factor was measured by using different detectors and it was found that the dimension of detector must be less than half of the field size to avoid under-estimation. If a 0.6 cc cylindrical ion chamber was used for small fields measurement, it would under-estimate the field size factor by 19.7% for a 2x2 cm2 field. The percentage depth dose and the tissue-phantom ratio increased with increasing the field size. The penumbra width increased with increasing the field size which was larger for a square field than the corresponding circular field by less than 1 mm.

Humans↗

PubMed1991

High-dose-rate afterloading technique in the radiation treatment of uterine cervical cancer: 399 cases and 9 years experience in Taiwan.

Carcinoma of the uterine cervix has been the leading malignant neoplasm treated in our department. A comparative study was carried out using conventional low dose rate (LDR) with 137Cs sources (less than or equal to 100 cGy/hr) versus high dose rate (HDR) with 60Co sources (greater than 100 cGy/min) in the intracavitary (IC) application following external pelvic irradiation. A total of 399 patients were treated with external RT plus HDR radiation treatment alone from February 1980 through December 1985. Stage IIb and IIIb comprised 79.4% of cases (317 cases). The rate of initial complete response of the tumor, local control, and survival rate seemingly were better in the HDR group, but there was no significant difference statistically. The actuarial survival rates in all cases/definitive RT cases are 85%/85% for Stage 0-IIa, 53%/70% for IIb, 43%/49% for IIIa, 43%/53% for IIIb, 42%/47% for IVa, respectively. Complications were similar and the rectal complications were slightly higher in HDR group. The combination of pelvic irradiation with HDR intracavitary irradiation was more convenient for patients and also for personnel. The HDR technique may be a good substitution for IC treatment.

Adult↗

PubMed1990

[Evaluation of compensator used in radiation therapy].

A radiation beam incident on an irregular or sloping surface produces skewing of isodose curves and may give rise to unacceptable nonuniformity of the dose distribution within the target volume or cause excessive irradiation of sensitive tissues. The concept of using a compensator, first introduced by Ellis, to circumvent the skewness of isodose curves was elegant. Other workers followed suit elaborating further and extending the procedures. The treatment of chest wall tumors is of special interest and compensators were frequently used in their management. The compensators of aluminum and copper were systematically examined for 6 and 10 MV X-rays. Compensating thickness ratios was determined from equivalent dose measurement at compensating depth by placing compensator at the regular blocking tray for maintaining the skin sparing feature of high energy photon beams. The compensator must compensate not only for the reduction of the primary beam attenuation due to tissue deficit, but also for the loss of scattering by the missing tissues. It was found that the compensating thickness ratios (CTR) was not a constant value and was dependent on the tissue deficit, field size, compensating depth and the material of compensator, but was independent of the energy. As the tissue deficit is increased, the CTR decreases, since the loss of scattering for the deficit volume can be compensated by the lowered attenuation of the compensator. As the field size is increased, the CTR decreases. From the study of central axis depth dose for various deficit thickness, normalized at the median plane of no tissue deficit, it was found that compensator can compensate the dose accurately to one depth only and the compensation to other depth is approximate, and that the compensating error is increased with greater tissue deficit and further depth. The effectiveness of the compensating system with a stair-step polystyrene phantom representative of varying tissue deficits over a small treatment field (20 cm x 20 cm) was also studied with film dosimetry and the error was within 3%. The compensator thickness ratios must be measured in different radiation beams from different treatment machines and in different irradiation conditions because there are major difference between the CTR data obtained directly from experiments and the data besed on calculation from attenuation coefficient mu, physical density rho or electronic density, rho e. The specific CTR reported for aluminum and copper in the literature should only be used as a guideline.

Humans↗

PubMed1990

[Evaluation of dose distribution in the region of small air space in human body by Co-60 and 10 MV X-ray beams].

In many parts of human body, air-filled spaces are components of normal anatomical structures, such as nasopharynx and paranasal sinuses, and the inclusion of these spaces in radiation treatment fields may create inhomogeneous dose distribution, due to the loss of scattering electron equilibrium, the lack of backscatter and the alteration in primary beam attenuation. Accurate determination or measurement of dose in the region of irregular air spaces has been experimentally difficult. However, tumors growing on the surface of the air cavities do cause serious concern by conscientious radiation therapists and physicist about the possibility of underdose. Using the models of simulated air cavities, combined air cavity and air channel, and taking measurement with a small window parallel plate ionization chamber in solid phantoms, it is found that the air spaces in the human body will cause underdose or overdose at the exit air space surface for 10MV X-ray and Co-60 r-ray. Surface dose were evaluated by a gain/loss factors (G/L) which was defined as the ratio of exit air space surface dose and the dose measured in a same but homogeneous phantom. The G/L factors are greater than 1.0 (overdose) where the air spaces are much smaller than radiation field sizes and are less than 1.0 (underdose) in extreme situations where the air spaces are larger than radiation field sizes and where the scattered volume of cavity wall in the treatment fields in also small. In addition, these effects of overdose and underdose are enhanced by increasing air space thickness and higher photon energy. We suggest that the radiation therapists and clinical physicists be cautious in applying these useful guidelines for treatment planning.

Cobalt Radioisotopes↗