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Biomedical subjects

M H Cheng

Publications and source records attributed to M H Cheng.

At least 19 recordsLinked to original sources
PubMed2001

Stereocontrolled synthesis of acyclic 1,3-diols via condensation of tungsten-syn-pi-pentadienyl complexes with aldehydes. A new Prins reaction via s-trans-diene cationic intermediates.

In the presence of BF(3).Et(2)O, condensation of CpW(CO)(2)(syn-pi-2-methoxycarbonylpentadienyl) with aldehydes generated tungsten-eta(4)-trans-diene cation in cold toluene, and hydrolysis of this salt afforded tungsten-pi-allyl-anti-1,3-diols in good yields. This new synthesis of anti-1,3-diols represents an atypical Prins reaction that is applicable to normal aldehydes. The anti/syn ratios of 1,3-diols increased with an increase in the size of the aldehydes. These anti-1,3-diols were transformed into various complex oxygen heterocycles based on two demetalations: (1) conversion to an allyl cation followed by nucleophilic attack and (2) condensation with aldehydes via its CpW(NO)Cl derivative, to give functionalized alpha-methylene butyrolactones. A semi-emperical calculation was performed to deduce the transition-state structure to rationalize the anti-stereoselectivity.

Journal Article↗
PubMed2001

One-stage posterior decompression and fusion using a Luque rod for occipito-cervical instability and neural compression.

STUDY DESIGN: Original article. OBJECTIVE: The authors present seven cases who underwent one-stage suboccipital, C1 and/or C2 posterior decompression and fusion by Luque rod, wiring and autogenic bone graft for occipito-cervical instability and neural compression. SETTING: Chang Gung University and Medical Center at Kaohsiung, Taiwan. METHOD: Since January 1996, 20 cases of craniovertebral and upper cervical spinal instability were encountered. Seven of these cases had no neurological improvment under Cone-Barton Skeletal traction. Imaging studies revealed poor reduction with persistent neural compression. One patient underwent unsuccessful anterior trans-oral vertebrectomy for decompression. All patients underwent posterior suboccipital craniectomy, C1 and/or C2 laminectomy for decompression. Contoured Luque rod with wiring and autogeneic bone graft was used for craniocervical fusion. After surgical treatment, halo-vest or sterno-occipito-mandibular immobilizer (SOMI) was used for 3-6 months. RESULTS: Suboccipital craniectomy and C1 laminectomy could afford a 30-50% increment of anteroposterior diameter in the neural canal and effective decompression of the low medulla and cord. All patients made neurological improvement. The ASIA-MIS scores improved from pre-operative 49 (mean) to 78. Four patients can walk without any support. There were no major complications except for one case requiring readjustment of the halo-vest brace. CONCLUSION: The authors recommend this procedure as one choice for relieving craniocervical instability with neurological compromise. A programmed rehabilitation will afford better neurological improvement.

Adult↗
PubMed2001

The outcome of failed free flaps in head and neck and extremity reconstruction: what is next in the reconstructive ladder?

The indications for free flaps have been more or less clarified; however, the course of reconstruction after the failure of a free flap remains undetermined. Is it better to insist on one's initial choice, or should surgeons downgrade their reconstructive goals? To establish a preliminary guideline, this study was designed to retrospectively analyze the outcome of failed free-tissue transfers performed in the authors hospital. Over the past 8 years (1990 through 1997), 3361 head and neck and extremity reconstructions were performed by free-tissue transfers, excluding toe transplantations. Among these reconstructions, 1235 flaps (36.7 percent) were transferred to the head and neck region, and 2126 flaps (63.3 percent) to the extremities. A total of 101 failures (3.0 percent total plus the partial failure rate) were encountered. Forty-two failures occurred in the head and neck region, and 59 in the extremities. Evaluation of the cases revealed that one of three following approaches to handling the failure was taken: (1) a second free-tissue transfer; (2) a regional flap transfer; or (3) conservative management with debridement, wound care, and subsequent closure by secondary intention, whether by local flaps or skin grafting. In the head and neck region, 17 second free flaps (40 percent) and 15 regional flaps (36 percent) were transferred to salvage the reconstruction, whereas conservative management was undertaken in the remaining 10 cases (24 percent). In the extremities, 37 failures were treated conservatively (63 percent) in addition to 17 second free flaps (29 percent) and three regional flaps (5 percent) used to salvage the failed reconstruction. Two cases underwent amputation (3 percent). The average time elapsed between the failure and second free-tissue transfer was 12 days (range, 2 to 60 days) in the head and neck region and 18 days (range, 2 to 56 days) in the extremities. In a total of 34 second free-tissue transfers at both localizations, there were only three failures (9 percent). However, in the head and neck region, seven of the regional flaps transferred (47 percent) and four cases that were conservatively treated (40 percent) either failed or developed complications that lengthened the reconstruction period because of additional procedures. Six other free-tissue transfers had to be performed to manage these complicated cases. Conservative management was quite successful in the extremities; most patients' wounds healed, although more than one skin-graft procedure was required in 10 patients (27 percent). In conclusion, a second free-tissue transfer is, in general, a relatively more reliable and more effective procedure for the treatment of flap failure in the head and neck region, as well as failed vascularized bone flaps in the reconstruction of the extremities. Conservative treatment may be a simple and valid alternative to second (free) flaps for soft-tissue coverage in extremities with partial and even total losses.

Extremities↗
PubMed2001

Effects of stimulus intensity on latency and conduction time of short-latency somatosensory evoked potentials.

We studied the effect of stimulus intensity on latencies of short-latency somatosensory evoked potentials (SSEP) by measuring both onset and peak latencies individually. The latencies of N9, N13, N20 and N9-N13 peripheral conduction time (PCT) of median nerve (MN) SSEP, and N8, N23, P37 and N8-N23 PCT of tibial nerve (TN) and sural nerve (SN) SSEP significantly shortened with increasing stimulus intensity by onset latency measurement. However, those latencies by peak latency measurement were less significantly shortened or had only a trend of latency shortening without statistical significance. In contrast to PCT, N13-N20 central conduction time (CCT) of MN-SSEP and N23-P37 CCT of TN- or SN-SSEP showed no latency changes with the increased stimulus intensity by both onset and peak latencies measurement. As peak latencies had greater interindividual variability than onset latencies shown by larger standard deviation, shortening of onset latencies were more consistent than that of peak latencies. We think shortening of onset latencies indicates the recruitment of faster conduction fiber along with increased stimulus intensity. As the degree of latency shortening was less if stimulus intensity was above 2.5 times sensory threshold, the stimulus intensity greater than 2.5 times the sensory threshold should be used for clinical application.

Adult↗
PubMed2001

[The cloning of apple ferritin gene (Apfl) from Malus xiaojinensis Cheng et Jiang and its structure analysis].

The special primers were designed based on the sequence information of plant ferritin genes reported in the literature and used for polymerase chain reaction (PCR) with the genomic DNA of Malus xiaojinensis Cheng et Jiang in an attempt to clone apple ferritin gene. A single fragment of 771 bp was successfully obtained from the PCRs and cloned in this study. The sequence and homology analysis results of the fragment showed that the deduced amino acids of the fragment had a ninety-nine percent homology to that of the soybean ferritin gene reported by Lescure et al. (1991). A comparison in details of the nucleotide sequence of the clone and that of the soybean ferritin gene showed that they consisted of the same open reading frame (ORF, 753 bp) and that the cloned fragment had complete initial and stop codes. Within the ORF no introns were found and there were no nucleotide difference in the transit peptide region (TP) of the gene, but five nucleotide mutations were found in the mature peptide region (MP), among which four were synonymous mutations.

Amino Acid Sequence↗
PubMed2000

Clinical application of NMP22 and urinary cytology in patients with hematuria or a history of urothelial carcinoma.

For evaluation of the clinical application of immunoassay for nuclear matrix protein 22 (NMP22 immunoassay) and urinary cytology for early diagnosis and detection of bladder cancer in patients with hematuria and/or a previous history of bladder cancer, 209 urine samples obtained from 137 patients presenting episodes of hematuria or a history of bladder cancer were assayed for NMP22 levels and/or prepared for cytology examination. Biopsy was performed when any visible tumor was identified during cystoscopy examination. The median NMP22 concentrations measured in samples taken from patients with active bladder cancer, from patients with a history of bladder cancer but no active disease, from patients with hematuria, and from healthy volunteers were 18.95, 5.45, 6.39, and 3.75 U/ml, respectively. The urinary NMP22 level recorded for patients with urothelial carcinoma was significantly higher than that noted for individuals without active disease. The sensitivity of the NMP22 assay and of urinary cytology in diagnosing bladder cancer was 69% and 67%, respectively. In contrast, the specificity of these two diagnostic modalities reached 72% and 93%, respectively. The NMP22 assay is slightly more sensitive but less specific than urinary cytology in detecting bladder cancer. This study indicates that determination of urinary NMP22 levels is a useful and noninvasive tool for the detection of bladder cancer because of its high sensitivity. The urinary NMP22 assay may be used as a first-line routine screening method; however, it cannot replace the use of urinary cytology because of its lower specificity.

Carcinoma, Transitional Cell↗
PubMed2000

Devices for ischemic preconditioning of the pedicled groin flap.

BACKGROUND: Early division of the pedicled groin flap can be achieved by using ischemic preconditioning. The goal of this study was to investigate the devices available for ischemic preconditioning and determine which device is the most effective and results in lowest patient discomfort. METHODS: Rubber bands, custom-made Orthoplast sheets, long-nose locking pliers, intestinal clamps, and a pneumatic tourniquet device were used for ischemic preconditioning on 13 patients who sustained severe hand injuries with reconstruction of pedicled groin flaps. The devices were compared by using laser Doppler flowmetry and the patient's local pain levels. RESULTS: Twelve of 13 flaps were successfully divided at a mean period of 8.3 days by using a custom-made Orthoplast sheet or a pneumatic tourniquet device. All devices except the rubber bands could result in a biologic zero flow level. CONCLUSION: The pneumatic tourniquet device is the most desirable ischemic preconditioning device, having the advantages of excellent ischemic effect, easy application, and minimal discomfort.

Adult↗
PubMed2000

Atlantal stenosis: a rare cause of quadriparesis in a child. Case report.

The authors report the case of a 3-year-old boy who suffered from quadriparesis and respiratory distress after failing to execute a somersault properly. Neuroimaging revealed spinal cord contusion with marked spinal canal stenosis at the level of the atlas. No subtle instability, occult fracture, or other congenital abnormalities were confirmed. Spinal cord contusion with marked canal stenosis is rare, and only several adult cases have been reported. Severe stenosis at the level of the atlas may predispose individuals to severe spinal cord contusion, as occurred in our patient after sustaining trivial trauma.

Adult↗
PubMed2000

Current seroprevalence of hepatitis A virus infection among kindergarten children and teachers in Taiwan.

Taiwan was a hyperendemic area for hepatitis A virus (HAV) infection before the late 1980s. The seroprevalence of HAV infection was higher than 90% with most HAV infection occurring during childhood. This study was to estimate the seroprevalence of HAV infection among preschool children in central Taiwan. A community-based survey was carried out in 54 kindergartens in 10 urban areas, 10 rural areas and 2 aboriginal areas randomly selected through stratified sampling. Serum samples of 2,549 healthy preschool children and 104 teachers in study kindergartens were screened for the HAV antibodies (anti-HAV) by means of a commercially available microparticle enzyme immunoassay (AxSYM HAVAB). Among aboriginal kindergarten children, more than 96% of them were anti-HAV seropositive due to a mass HAV vaccination program. In urban and rural areas, kindergarten children had a very low prevalence of anti-HAV (0.4%) in contrast to a high seroprevalence in their teachers (78%). There was no gender difference in seroprevalence of anti-HAV, while the anti-HAV seroprevalence was significantly higher in urban areas than in rural areas. Crowdedness of living in urban areas might facilitate the person-to-person transmission of infectious agents.

Adult↗
PubMed1999

Microvascular vastus lateralis muscle flap for chronic empyema associated with a large cavity.

Thoracic empyema can be disabling and may need microvascular free flaps in some intractable cases. After repeated failure of conventional thoracic surgical procedures, 2 patients with empyema were treated with microvascular free vastus lateralis muscle flaps for obliteration of the large empyema cavity. The reconstruction was successful in wound closure and eradication of infection. The donor site morbidity was minimal, and the patients resumed normal daily activities. Microvascular vastus lateralis muscle flap is the best option if free flaps are required for reconstruction of empyema.

Aged↗
PubMed1999

Role of fibronectin deposition in cystogenesis of Madin-Darby canine kidney cells.

BACKGROUND: Madin-Darby canine kidney (MDCK) cells cultured within collagen I gel exhibit clonal growth and form spherical multicellular cysts. The cyst-lining epithelial cells are polarized with the basolateral surface in contact with the collagen gel and the apical surface facing the lumen. To understand whether MDCK cysts construct the basal lamina, we characterized the composition of the extracellular matrix deposited by MDCK cysts. The cyst-lining cells produced an apparently incomplete basal lamina containing a discontinuous laminin substratum. In addition, the basal cell surface of the cyst was surrounded by a thick layer of fibronectin. This study was conducted to delineate the role of fibronectin deposition in cystogenesis. METHODS: MDCK cells cultured in collagen gel were employed. We first used Arg-Gly-Asp (RGD) peptides containing disintegrin rhodostomin to disturb the interaction between fibronectin and the cell surface integrin. We then established several stable transfectants expressing the fibronectin antisense RNA and with which to directly examine the role of fibronectin in cystogenesis. RESULTS: Rhodostomin markedly decreased the growth rates of the MDCK cyst, suggesting the importance of a normal interaction between fibronectin and integrins. The stable transfectants overexpressing the fibronectin antisense RNA exhibited relatively lower levels of fibronectin and markedly lower cyst growth rates than the control clone. The lower growth rate was correlated with an increase in collagen gel-induced apoptosis. CONCLUSIONS: The results indicate that the deposition of fibronectin underlying the cyst-lining epithelium serves to prevent apoptosis induced by three-dimensional collagen gel cultures, and hence facilitates cyst growth of MDCK cells.

Animals↗
PubMed1999

Combined ischemic preconditioning and laser Doppler measurement for early division of pedicled groin flap.

OBJECTIVES: The main disadvantage of the pedicled groin flap for hand reconstruction is the long period of immobilization required. Early division of the pedicled groin flap is desirable for both patients and surgeons. The aims of this study were to investigate whether ischemic preconditioning can effectively accelerate the neovascularization of the junction between the donor and recipient sites in the pedicled flap, and the most objective method of judging the timing of early division of the pedicled groin flap. This report is the first prospective study to use ischemic preconditioning for early division of pedicled cutaneous flap combined with laser Doppler measurement. METHODS: The severe hand injuries of 12 patients were reconstructed by using the pedicled groin flap method. The ischemic preconditioning program was prospectively performed as scheduled for 5 to 7 days postoperatively. The pedicled groin flap was monitored with laser Doppler when the flap was elevated, inset, with clamping and nonclamping postoperatively. RESULTS: Eleven of the 12 pedicled groin flaps were divided safely and survived completely. Only one pedicled groin flap with a simultaneous harvest of iliac bone graft had partial flap loss, giving a success rate of 90.1%. CONCLUSION: With ischemic preconditioning, the pedicled groin flap can be safely divided postoperatively at a mean period of 8.4 days according to the laser Doppler measurement, especially when the perfusion unit ratio of clamping over nonclamping reaches more than 36.6%.

Adult↗
PubMed1999

Microsurgical combined scapular/parascapular flap for reconstruction of severe neck contracture: case report and literature review.

OBJECTIVE: The reconstruction for severe neck contracture is difficult, because it may include not only the necessity the use of a large flap but also the ability for three-dimensional movement of the neck. METHODS: A 41-year-old woman sustained a severe neck contracture with retraction of the lower lip and limited range of neck motion after a chemical burn. We used the combined scapular/parascapular flap to reconstruct the soft-tissue defect in the neck after excision of hypertrophic scar and release of contracture. The scapular portion was transferred to cover the defect vertically, and the parascapular portion was transferred to cover the transverse portion of the neck. This kind of design would allow the patient to move her neck more easily. RESULTS: Postoperatively, the range of motion of the neck was full in the vertical and horizontal directions after 6 months of rehabilitation. Also, the patient was satisfied with the final aesthetic results. CONCLUSION: The microsurgical combined scapular/parascapular flap, providing a large area of tissue for coverage in three dimensions with a reliable blood supply by only one pedicle anastomosis during surgery, is a good option for reconstruction of the severe neck contracture. We classify the inset of the combined scapular/parascapular flap into three types with six subtypes, according to the location of defects and the relation of the parascapular flap to the scapular flap.

Adult↗
PubMed1999

Free fibula osteoseptocutaneous-pedicled pectoralis major myocutaneous flap combination in reconstruction of extensive composite mandibular defects.

Lateral composite mandibular defects resulting from excision of advanced oral carcinoma often require mandible, intra-oral lining, external face, and soft-tissue bulk reconstruction. Ignorance of importance soft-tissue deficit in those patients may cause significant morbidity and functional loss. Such defects, therefore, can be reconstructed best with a double free flap technique. However, this procedure may not be feasible for every patient or surgeon. An alternative procedure is a free fibula osteoseptocutaneous flap combined with a pedicled pectoralis major myocutaneous flap. This combination was used in reconstruction of extensive composite mandibular defects in 14 patients with T3/T4 oral squamous cell carcinoma. All patients were men, and the average age was 54.3 years. The septocutaneous paddle of the fibula flap was used for the mucosal lining of the defects while the bony part established the rigid mandibular continuity. The pectoralis major flap then covered the external skin defect in the face and cheek, and the dead spaces left by the extirpated masticator muscles, buccal fat, and parotid gland. One free fibula flap failed totally, and one pectoralis major flap developed marginal necrosis. At the time of final evaluation, nine patients (64.3 percent) were alive, surviving an average of 25.7 months. All patients eventually regained their oral continence and an acceptable cosmetic appearance. In conclusion, the fibula osteoseptocutaneous flap plus regional myocutaneous flap choice is a successful and technically less demanding alternative to the double free flap procedures in reconstruction of extensive lateral mandibular defects.

Adult↗
PubMed1998

Biphasic subcellular localization of the DAZL-related protein boule in Drosophila spermatogenesis.

The Drosophila boule gene is expressed exclusively in the male germline and encodes an RNA binding protein closely related to the mammalian fertility factors encoded by the DAZ (Deleted in Azoospermia) and DAZL (DAZ-like) genes. Mutation of boule blocks both meiotic divisions. Differentiation nonetheless continues, resulting in tetraploid spermatids that fail to mature into sperm. We have found that Boule localizes premeiotically to a perinucleolar region and then translocates to the cytoplasm at the onset of meiosis. We show that deletion of the Y chromosome ks-1 fertility locus eliminates Boule nuclear localization, although it does not perturb entry into meiosis. Based on these observations we propose that Boule acts in the cytoplasm to regulate the stability or translation of messenger RNA encoding an essential meiotic factor.

Animals↗