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Biomedical subjects

I H Chen

Publications and source records attributed to I H Chen.

At least 55 records · Page 3Linked to original sources
PubMed1995

Cytochrome P4502E1 genetic polymorphisms and risk of nasopharyngeal carcinoma: results from a case-control study conducted in Taiwan.

CYP2E1 is responsible for the metabolic activation of nitrosamines believed to be involved in the pathogenesis of various tumors. Nasopharyngeal carcinoma (NPC) is a tumor thought to be linked to nitrosamine exposure. To investigate the possible role of CYP2E1 genetic polymorphisms in the etiology of this tumor, we investigated 50 histologically confirmed NPC cases from Taiwan and 50 controls matched to cases on age, sex, and residence. Samples were examined for RFLPs in the CYP2E1 gene by PCR amplification followed by digestion with DraI and RsaI. Among healthy controls, the allelic frequency of wild-type and variant forms of CYP2E1 were 79 and 21%, respectively, using DraI enzyme digestion and 82 and 18%, respectively, using RsaI enzyme digestion. As compared with individuals who were homozygous for the wild-type CYP2E1 gene, those found to be homozygous for the variant form of the gene by DraI digestion were at a 5-fold excess risk of disease (95% confidence interval = 0.95-16). Similarly, subjects homozygous for the variant form of the CYP2E1 gene by RsaI digestion were at 7.7-fold excess risk of developing NPC (95% confidence interval = 0.87-68). Individuals found to be heterozygous for the gene were at similar risk of disease compared to those homozygous for the wild-type gene. A strong association was observed between the RFLPs detected by DraI and RsaI digestion of CYP2E1; a correlation coefficient of 0.86 for controls and 0.91 for cases was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Trunk muscle activation. The effects of torso flexion, moment direction, and moment magnitude.

OBJECTIVES: This study was performed to quantify the electromyographic trunk muscle activities in response to variations in moment magnitude and direction while in forward-flexed postures. METHODS: Recordings were made over eight trunk muscles in 19 subjects who maintained forward-flexed postures of 30 degrees and 60 degrees. In each of the two flexed postures, external moments of 20 Nm and 40 Nm were applied via a chest harness. The moment directions were varied in seven 30 degrees increments to a subject's right side, such that the direction of the applied load ranged from the upper body's anterior midsagittal plane (0 degree) to the posterior midsagittal plane (180 degrees). RESULTS: Statistical analyses yielded significant moment magnitude by moment-direction interaction effects for the EMG output from six of the eight muscles. Trunk flexion by moment-direction interactions were observed in the responses from three muscles. CONCLUSIONS: In general, the primary muscle supporting the torso and the applied load was the contralateral (left) erector spinae. The level of electromyographic activity in the anterior muscles was quite low, even with the posterior moment directions.

Adult↗
PubMed1994

Kinematics of the cervical spine canal: changes with sagittal plane loads.

Spondylotic myelopathy is a result of decreased spinal canal space due to degeneration. The space also may change with physiological movements. The knowledge of the normal physiological changes is necessary for a better understanding of the clinical symptoms. Using a novel technique, we measured the changes in disk bulge, ligamentum flavum bulge, and anteroposterior canal diameter in response to tension-compression forces (up to 40 N each) and combined loading: 2 Nm of flexion or extension moment combined with 20 N compression force in five human cadaveric lower cervical spine specimens (C4-C7). From tension to compression, the average disk bulge changed 1.13 mm or 10.1% of the original canal diameter. The ligamentum flavum bulge changed 0.73 mm or 6.5% of the canal diameter. From flexion to extension the average disk bulb changed 1.16 mm or 10.8% of the canal diameter, whereas the ligamentum flavum bulge changed 2.68 mm or 24.3% of the canal diameter. Most of the changes in the bulges occurred with a small load application around the neutral position of the spine. The results of this study demonstrate that ligamentum flavum bulge can contribute significantly to canal encroachment in extension and that a flexed posture increases the sagittal diameter of the spinal canal.

Aged↗
PubMed1994

Effectiveness of shunting in patients with normal pressure hydrocephalus predicted by temporary, controlled-resistance, continuous lumbar drainage: a pilot study.

From 1984 to 1992 15 consecutive cases of normal pressure hydrocephalus were included in this pilot study. A series of tests included CT of the brain, grading of the cognitive mental state with the mini-mental state examination; urodynamic studies, and gait evaluation. These tests were carried out on admission, and repeated on day 1, day 3, and day 5 after controlled-resistance, continuous lumbar drainage (CRCLD). During this period, eight patients showed significant improvements of cognitive mental state, urodynamic studies, or gait and were regarded as CRCLD responders; the remaining seven patients were regarded as CRCLD non-responders. The CRCLD was routinely removed on day 6 after the drainage procedure and a ventriculoperitoneal (VP) or a lumboperitoneal (LP) shunt was randomly selected for each patient. The tests were repeated one week after shunting and a year later. All the CRCLD responders continued to benefit from shunting at one week and one year after the procedure irrespective of the type of shunting they received. By comparison, none of the CRCLD non-responders showed any improvement a year after the shunting. In conclusion, CRCLD proved to be a safe and effective way to predict the effectiveness of shunting in patients with normal pressure hydrocephalus.

Aged↗
PubMed1994

Measurement of cervical canal sagittal diameter in Chinese males with cervical spondylotic myelopathy.

BACKGROUND: Cervical canal encroachment can be properly assessed from lateral cervical radiographs either by defining its magnification rate or by a ratio-method. Data of the latter obtained from Chinese males with cervical myelopathy were compared with the data of general population in different age groups. METHODS: A total of 200 Chinese males were included in this study. Half of them had undergone decompressive procedures for cervical myelopathy, while the remaining 100 cases were volunteers. Sagittal diameters of cervical canal and vertebra were measured from C3 to C6 on lateral cervical radiographs, while ratios (Torg-Pavlov's ratios) of the two reflected the extent of sagittal canal encroachment. Cut-off values and discriminant rates of these parameters in different age groups were obtained by discriminant analysis. The tube-to-film distance was set as 40 inches. RESULTS: In myelopathic group (age < 55 y/o), Torg-Pavlov's ratios, as expressed by mean +/- standard deviation, were 0.77 +/- 0.12 for C3, 0.75 +/- 0.14 for C4, 0.80 +/- 0.14 for C5, and 0.81 +/- 0.15 for C6. In control group (age < 55 y/o) the ratios were 0.94 +/- 0.12, 0.95 +/- 0.13, 0.97 +/- 0.13, and 0.97 +/- 0.13 respectively. In myelopathic group (age > or = 55 y/o), the ratios were 0.76 +/- 0.09, 0.71 +/- 0.10, 0.73 +/- 0.11, and 0.76 +/- 0.11; while in control group (age > or = 55 y/o), the ratios were 0.93 +/- 0.10, 0.89 +/- 0.09, 0.88 +/- 0.11, and 0.91 +/- 0.12 respectively. The cutoff values and their discriminant rates are also presented. CONCLUSIONS: The differences of canal sagittal diameter as well as Torg-Pavlov ratio between myelopathic and control group of Chinese males in individual age group were statistically significant. It is concluded that congenitally narrow cervical canal is a major predisposing factor to cervical spondylotic myelopathy.

Adult↗
PubMed1994

Measurement of Chinese lumbar pedicles: with special reference to transpedicular screw fixation.

BACKGROUND: Thorough understanding of the morphometric parameters of the lumbar pedicles is essential for transpedicular screw fixation. The purpose of this study is to establish a database for proper spinal instrumentations in Chinese patients. METHODS: A total of 764 pedicles (L2-S1) were measured from spinal computed tomography (CT) of 100 Chinese volunteers. Parameters related to transpedicular fixation include pedicle width (PW), pedicle transverse angle (PTA), pedicle angle measured from the entry point of Roy-Camille through the midpoint of the pedicle (PPA), screw insertion depths to the anterior cortex from the entry point of Roy-Camille along the line parallel to the midsagittal line (PPLP) and from the entry point of Magerl along the pedicle axis (PPLS). RESULTS: The mean age of the volunteers was 46.2 years. The average PWs from L2 to S1 were: 0.85 +/- 0.15 cm for L2, 0.92 +/- 0.22 cm for L3, 1.19 +/- 0.24 cm for L4, 1.70 +/- 0.28 cm for L5 and 2.31 +/- 0.35 cm for S1. The average PTAs from L2 to S1 were: 13.9 degrees +/- 4.9 degrees for L2, 13.4 degrees +/- 5.1 degrees for L3, 16.2 degrees +/- 5.9 degrees for L4, 27.8 degrees +/- 7.2 degrees for L5 and 44.0 degrees +/- 8.4 degrees for S1. The average PPAs from L2 to S1 were: 5.3 degrees +/- 2.4 degrees for L2, 6.3 degrees +/- 2.2 degrees for L3, 7.2 degrees +/- 2.5 degrees for L4, 10.1 degrees +/- 3.6 degrees for L5 and 17.0 degrees +/- 4.8 degrees for S1. The average PPLPs from L2 to S1 were: 5.64 +/- 0.82 cm for L2, 5.05 +/- 0.62 cm for L3, 4.99 +/- 0.89 cm for L4, 4.42 +/- 0.77 cm for L5 and 4.23 +/- 0.72 cm for S1. The average PPLSs from L2 to S1 were: 5.75 +/- 0.72 cm for L2, 5.24 +/- 0.75 cm for L3, 5.27 +/- 0.84 cm for L4, 4.88 +/- 0.72 cm for L5 and 4.99 +/- 0.72 cm for S1. CONCLUSIONS: Transpedicular screw fixation should be tailored on individual basis. Though variation exists, no sufficient evidence can be found to suggest major morphometric differences of the Chinese lumbar pedicles from the studies in the English literature.

Adult↗
PubMed1994

Traumatic atlantoaxial distractive instability: case report.

We present an uncommon case of traumatic atlantoaxial distractive instability which manifested itself clinically in a respirator-dependent quadriplegic. The initial radiographic finding was anterior atlantoaxial dislocation. The patient was managed initially by halo traction and, 8 weeks later, demonstrated occipitocervical fusion with gratifying results.

Adult↗
PubMed1993

Reappraisal of skeletal tuberculosis: role of radiological imaging.

Skeletal tuberculosis (TB) can present with a broad spectrum of variable clinical manifestations which may cause diagnostic difficulties. To further elucidate these possible diagnostic pitfalls, 14 cases of bacteriologically or histologically proven skeletal TB, which were initially diagnosed otherwise, are reviewed. In five cases with lumbar or midthoracic spinal involvement, concomitant traumatic history and degenerative radiological changes were the main reasons for not suspecting the possibility of skeletal TB. A differential diagnosis between TB and metastatic lesions can be difficult in the very early stage when X-ray images usually have a low contrast and are not sharp. In nine cases with bone and joint involvement, a long-lasting discharging sinus led the clinician to an initial impression of septic arthritis; sometimes concomitant gouty arthritis can mask the clinical manifestations of skeletal TB. In five cases, minor erosive lesions over the peripheral margin of the involved bone were the earliest findings on the plain X-ray films and were overlooked. To facilitate the early diagnosis of skeletal TB and to avoid the possibility of complications in the management of patients, medical practitioners should be familiar with the usual forms of the condition and the wide variety of clinical manifestations.

Adult↗
PubMed1993

Diverse applications of continuous lumbar drainage of cerebrospinal fluid in neurosurgical patients.

From 1984 to 1991, continuous lumbar drainage (CLD) of cerebrospinal fluid (CSF) had been applied in 48 neurosurgical patients. Eleven of them had CSF accumulation and/or leakage at the operative sites and 37 of them suffered from CSF rhinorrhea. Successful treatment was achieved in 98% (47/48) of patients. There was neither death nor infection noted in this series. Complication was found in only one patient who developed acute subdural haematoma with pneumocephalus six days after CLD. After emergency craniotomy and evacuation of haematoma, the patient recovered without neurological deficit. The results suggest that CLD is a simple, safe and effective method in the treatment of CSF accumulation and/or leakage at the operative sites, as well as CSF rhinorrhea of various aetiologies.

Catheters, Indwelling↗
PubMed1992

An infrequent point mutation of the p53 gene in human nasopharyngeal carcinoma.

Point mutations in the p53 gene have been detected in a variety of human cancers; the mutations are clustered in four "hot-spots" located in the coding region of exons 5, 7, and 8, which coincide with the four most highly conserved regions of the gene. We report the finding of a heterozygous G----C mutation at codon 280 (exon 8), position 2, of the p53 gene in a nasopharyngeal carcinoma (NPC) cell line, originating from Guangdong, a province in the People's Republic of China that leads the world in NPC incidence. A survey of nasopharyngeal tissues and NPC biopsies revealed that 1 out of 12 NPC samples from Hunan, another province in the People's Republic of China with high NPC incidence, had the same heterozygous mutation at codon 280 of p53, and none of 10 biopsies from Taiwan showed a mutation within exons 5-8 of the p53 gene. No other alteration of gene structure, including gross rearrangement or loss of heterozygosity or abnormality of gene expression was detected in NPC cell lines or NPC biopsies. We conclude from this study that mutational or other alterations of the p53 gene are not common in nasopharyngeal carcinogenesis and that a codon-280 mutation of p53 may be involved in less than 10% of NPC cases. This result contrasts with the relatively high frequency of p53 mutations associated with several other human carcinomas and suggests the importance of other genes in NPC genesis.

Base Sequence↗
PubMed1992

Microvascular decompression for hemifacial spasm: analyses of operative findings and results in 310 patients.

The operative findings and results of microvascular decompression (MVD) on 310 Chinese patients with hemifacial spasm are analyzed in this report. The operations were performed at the Neurological Institute of the Veterans General Hospital-Taipei between January 1983 and June 1990. The length of follow-up ranged from 6 months to 8 years (mean, 4.3 years); 273 patients (88%) had complete relief of spasm within 3 days after one MVD, and the remaining 37 patients (12%) showed no immediate postoperative improvement. Sixteen (5.2%) of these 37 initially unresponsive patients subsequently experienced complete relief, which occurred from 4 days to 22 months (median, 21 days) after one MVD; 13 others (4.2%) had complete relief immediately after the second MVD; another 3 (1%) had delayed complete relief 6, 9, and 11 months after the second MVD, respectively; and the remaining 5 (1.6%) only had delayed partial relief, which occurred 2 to 9 weeks after one MVD. Late recurrence occurred in three patients (1%). These immediate and long-term results lend support to the conclusion that the timing of reoperation can be postponed for a period of 3 to 4 weeks in the event of an initial failure to get improvement, and that a second MVD may be of value.

Adult↗
PubMed1991

[Effects of nasal continuous positive airway pressure on patients with obstructive sleep apnea syndrome].

To evaluate the efficacy of nasal continuous positive airway pressure (CPAP) on patients with obstructive sleep apnea syndrome, 20 patients with moderate to severe obstructive sleep apnea syndrome (respiratory disturbance index greater than or equal to 20) were studied. The patients were evaluated using the Grass polysomnograph model 78 during an overnight sleep one to two weeks apart with and without a nasal CPAP produced by 10 to 15 cm of water. The results showed that nasal CPAP significantly reduced the respiratory disturbance index (RDI) (p less than 0.001) and the desaturation index (p less than 0.001), and significantly raised the lowest oxygen saturation level. Nasal CPAP not only reduced RDI, but also improved the respiratory patterns during obstructive apnea events by shifting the obstructive apnea events to hypopnea events. Nasal CPAP also significantly decreased the relative time spent in stage 1 NREM sleep (p less than 0.001), and increased the relative time spent in stages 3+4 NREM and REM sleep (p less than 0.05). Most of the patients also felt better the morning after using nasal CPAP. Nasal CPAP significantly reduced the frequency and duration of apnea and the degree of nocturnal oxygen desaturation, and improved the respiratory patterns during obstructive apnea events, as well as the sleep architecture in obstructive sleep apnea patients. We conclude that nasal CPAP is effective in moderate to severe obstructive sleep apnea syndrome patients.

Adult↗
PubMed1991

Plate fixation for anterior cervical interbody fusion.

From April 1989 to April 1990, 13 patients with cervical spinal fracture/dislocation, spondylosis or metastasis were treated at the respective hospitals. There were 4 women and 9 men whose ages ranged from 25 to 70 years (mean 45 years). All of them were treated with neural decompression, bone grafting and anterior spinal interbody fusion. All iliac crest or fibular bone grafts were anchored to the vertebral bodies with plates and screws. The clinical outcomes were evaluated retrospectively. The results showed that all had improvement of neurological symptoms and signs. The radiographic evaluation revealed satisfactory alignment and sound union of the cervical spine in all 13 patients. No serious complications were found except screw loosening in two instances without impairment of clinical results. We concluded that anterior cervical plates provide effective stabilization which is essential for good results. Furthermore, from this study and a review of the literature, we advocated that it was not necessary for the tip of the screws to reach or even penetrate the posterior cortex of the vertebral body.

Adult↗