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Biomedical subjects

M C Cheng

Publications and source records attributed to M C Cheng.

At least 37 records · Page 2Linked to original sources
PubMed1995

High dose rate (HDR) brachytherapy technique: for carcinoma of uterine cervix using Nucletron applicators.

This study describes our existing treatment method for high dose rate (HDR) brachytherapy of carcinoma of uterine cervix using Nucletron applicators. Based on our clinical experience with low dose rate (LDR) brachytherapy since 1986, we deliver 40-45Gy by external and 30Gy by internal radiation therapy. The change in regimen using HDR brachytherapy is that internal radiation dose is given in 5 fractions at weekly intervals following external radiotherapy. We have analyzed the dosimetry of 20 patients; total of 100 treatments done at our center using ring-tandem (R-T) and ovoid-tandem (O-T) applicator combinations. Since O-T applicator has more flexibility of using desired tandem length and reduced rectum and bladder dose due to internal shielding inside the ovoids, we have made the transition from R-T to O-T combination of applicator. The dose volume histogram of the isodose curve indicates that there is an increase in isodose volume with the O-T applicator by as much as 1.5 times as compared to R-T applicator. In majority of the treatments, rectum and bladder doses are less than 70% of target dose, however in very few treatments, the bladder dose has increased to more than the target dose, in which case, the applicators were reseated and added more packing or reduced the dose per fraction, for better tolerance of late responding normal tissues. All our dose calculations are checked with an independent calculation method and agreement was obtained with in 5-7% discrepancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Brachytherapy↗
PubMed1995

Seroepidemiological survey of feline retrovirus infections in cats in Taiwan in 1993 and 1994.

In order to investigate the prevalence of infections with three feline retroviruses feline immunodeficiency virus (FIV), feline leukemia virus (FeLV) and feline syncytial virus (FSV) in Taiwan, we collected a total of 75 blood samples from cats from veterinary hospitals, a breeding cattery and a homeless shelter in 1993 and 1994. We examined the presences of anti-FIV and FSV antibodies and FeLV-p27 antigen in these samples by the indirect immunofluorescence and/or enzyme-linked immunosorbent assays. All of the serum samples positive for FIV were obtained from homeless cats and the overall FIV positive rate was 4%. The overall positive rates of FSV and FeLV were 28% and 1.3%, respectively. From these results, together with previous seroepidemiological surveys by others, it was revealed that the prevalence of FIV and FeLV infections appeared to be lower in Taiwan than in the United States or Japan. In contrast, the prevalence of FSV infection in Taiwan was as high as that in Japan.

Animals↗
PubMed1993

Confounded carcinogenicity study of sodium fluoride in CD-1 mice.

To determine its carcinogenic potential, sodium fluoride (NaF) was fed to CD-1 mice for up to 97 weeks. Mice given NaF at a dose of 4, 10, or 25 mg/kg of body weight per day added to a low-fluoride diet were compared to controls given either an unsupplemented low-fluoride diet or laboratory chow. Nonneoplastic changes consistent with those previously recognized from fluoride toxicity were observed in teeth, bones, and joints. Unexpectedly, osteomas occurred in all groups. The incidence of osteomas was similar in groups given the low-fluoride control diet, laboratory chow, or NaF doses of 4 or 10 mg/kg per day. The incidence of osteomas in these groups was increased over that historically experienced at the laboratory and reported in the literature for CD-1 mice. The incidence of osteomas in the mice given 25 mg NaF/kg per day added to a low-fluoride diet was increased over that in the other groups. Osteomas were first observed at Week 55. No malignant bone tumors were observed during the course of the study. The locations, multiplicity, and morphologic features of the osteomas in all groups were similar to those associated with virus-induced bone tumors. Electron microscopic examination revealed abundant retrovirus particles in all osteomas examined from control and test mice. It was concluded that the study was confounded by a retrovirus which contributed to the induction of the osteomas. Because the study was confounded, it cannot be considered a valid bioassay to be used for risk assessment.

Animals↗
PubMed1993

Characterization of the promoter of rice plastid psaA-psaB-rps14 operon and the DNA-specific binding proteins.

Transcriptional analysis of the promoter of rice psaA-psaB-rps14 operon was performed with Bal 31 deleted mutants in spinach chloroplast extracts. Two functional promoters in this operon (denoted as "-175" and "-129" promoters) were revealed to be utilized by the spinach transcription machinery; however only the "-175" promoter is utilized in vivo. The existence of psaA promoter-specific binding factors in the chloroplast extracts was indicated by competitive gel retardation assay and exonuclease III protection analysis. After ammonium sulfate fractionation of the extracts followed by heparin-agarose column chromatography, the sequence-specific binding factors were characterized to be 66-kDa and 31-kDa polypeptides. Southwestern analysis demonstrated that the two protein factors interact independently with the psaA promoter-containing DNA fragment.

Base Sequence↗
PubMed1992

[Dento-facial structural characteristics in Angle Class II malocclusion associated with abnormal facial divergency].

Lateral cephalometric radiographs of 60 adult patients with Angle class 11 malocclusion associated with abnormal facial divergency were collected from the Orthodontic Department of the National Taiwan University Hospital. They were divided into a hyperdivergent group (35 cases) and a hypodivergent group (25 case), according to mandibular plane angle (SN-MP). The 19 landmarks on each cephalometric tracing were digitized into a computer, then computer-aided cephalometric analysis was performed to calculate the 17 skeletal measurements and 13 dentoalveolar measurements. The dento-facial structural characteristics of the hyperdivergent and hypodivergent groups were compared. It was found that the subjects of the hyperdivergent group revealed a greater tendency of divergency in the anterior cranial base plane, Frank-fort horizontal plane, palatal plane, occlusal plane, and mandibular plane. Hyperdivergent facial type, supposedly indicating an open bite or a tendency toward an open bite, has a longer lower anterior facial height, shorter posterior facial height, longer upper anterior and posterior dental height. While, the majority of dentofacial characteristics of the hypodivergent facial type observed in is study were directly opposite to those of the hyperdivergent facial type. The relationships of incisor overbite depth and other skeletal and dentoalveolar parameters were illustrated by Pearson's correlation coefficient and stepwise multiple regression analysis by means of the SPSS/PC statistic program. With the incisor overbite depth as the dependent variable, the independent variables included on the regression analysis were the 10 items of skeletal and dentoalveolar parameters. The compared parameters showed a statistically significant correlation with the incisor overbite depth (P < 0.001). By the stepwise method, the variables included on the regression equation were (1) N-Go-Gn, (2) A-Gn-Ar, (3) N-Ans/ans-Me, and (4) U1L1. The value of R square (R2) in the regression analysis was 0.543. It demonstrated that only a 54.3% variation in incisor overbite depth can be explained by variations in those skeletal and dentoalveolar variables.

Adult↗
PubMed1990

Two-year carcinogenicity study of sodium fluoride in rats.

To determine the carcinogenic potential of sodium fluoride (NaF), we fed Sprague-Dawley rats a diet containing NaF for up to 99 weeks. Rats receiving NaF at a dose of 4, 10, or 25 mg/kg per day added to a low-fluoride diet were compared with controls receiving either a low-fluoride diet or laboratory chow. Each treatment group consisted of 70 rats of each sex. A 30% decrement in weight gain occurred at an NaF dose of 25 mg/kg per day. Evidence of fluoride toxicity was seen in the teeth, bones, and stomach, and the incidence and severity of these changes were related to the dose of NaF and the duration of exposure. Despite clear evidence of toxicity, NaF did not alter the incidence of preneoplastic and neoplastic lesions at any site in rats of either sex. Results from this study indicate that NaF is not carcinogenic in Sprague-Dawley rats.

Animals↗
PubMed1990

Role of surgery in the treatment of cancer of the cervix.

Of the four treatment modalities of invasive cancer of the cervix, surgery and radiotherapy remain the most effective. Surgery is preferred for microinvasive cancers. For stages 1B to 2B, surgery appears to have an edge over radiotherapy, whereas radiotherapy is more widely used for the more advanced cases.

Female↗
PubMed1989

Wertheim's operation--a study of 130 cases.

The Hsu's method of radical hysterectomy and lymphadenectomy procedure is a modification of the Okabayashi's radical hysterectomy. It involves the creation of the pararectal and paravesical spaces completely down to the pelvic floor and the excision en block of the uterus with its appendages, the parametria and the entire cardinal ligaments and the upper 1/3 to 1/2 of the vagina with its paracolpia. The vagina is lengthened by the Hsu's technique of suturing the vagina with a Boston suture incorporating the cut margin of the rectal serosa to the posterior rim of the vagina and stitching the visceral peritoneum 2 cm above the cut margin of the rectal serosa. The ovaries are preserved in young patients. Lymphadenectomy involves the dissection of the anterior and posterior chains of the common iliac nodes, the external iliac, obturator, internal iliac and presacral nodes. The author having been trained in the Hsu's method of radical hysterectomy by Professor Hsu himself, conducted a prospective study of the morbidity, sequelae and survival rates of this operation in Singapore. Between January 1982 and July 1987, 130 cases of cancer of the cervix were operated on by the author. Patients who had lymph node metastasis or parametrial infiltration were given adjuvant post operative irradiation. Every patient was followed up personally by the author. Only six patients were lost to follow-up at varying times after operation. Four cases were excluded from analysis. Of the remaining 126 cases, 67 were stage 1B, 20 stage 2A, 36 stage 2B, 2 were central recurrences following radiotherapy and one corpus cancer stage 2. Eleven patients (8.7%) had operative or post-operative morbidity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[The vector analysis of the anteroposterior relationship among the apical bases and the incisors].

Using the lateral cephalometric radiographs, the points A, B, maxillary incisor tip (U) and mandibular incisor tip (L) were projected onto the Frankfort horizontal plane and the projected points were defined as a, b, u and 1, respectively. According to the principle of the vector analysis, the vector formula ab - ul = au - bl can always stand irrespective of how the locations of the points a, b, u and 1 vary. The vectors ab, ul, au and bl represent the anteroposterior linear relationship between the upper jaw and the lower jaw, the upper incisor and the lower incisor (overjet), the upper jaw and the upper incisor, and the lower jaw and the lower incisor, respectively with reference to the FH plane. The lateral cephalometric radiographs taken from a total of 863 class I subjects, including 422 males and 441 females, were submitted for the study. The four vector values were obtained from the tracing of each radiograph and the mean values were computed according to sex and age. If a positive value was given to the vector ab, it denoted that point "a" was anterior to point "b", while a negative value denoted that "a" was posterior to "b". Both sexes of the subjects were divided according to their ages into junior primary (JP, 6-8 years), senior primary (SP, 9-11 years), junior high (JH, 12-14 years), and senior high (SH, 15-18 years) groups. No substantial or significant mean difference of each vector between the males and the females in each age group was noted. The mean values of the vector ab were 7.4, 6.8, 6.1 and 4.7 mm in JP, SP, JH and SH groups, respectively with the male and the female data pooled together. This indicates that there was a gradual catching up tendency of mandibular versus maxillary growth. The mean values of the vector ul were 1.4, 2.8, 2.9 and 2.8 mm in each successive age group, respectively showing that the overjet was rather constant with age except in the youngest group. The corresponding mean values were -0.4, -3.9, -5.2 and -6.1 mm for the vector au and -6.3, -8.0, -8.4 and -8.0 mm for the vector bl in JP, SP, JH and SH groups, respectively. The data indicate that both upper and lower incisors were relatively more upright in the youngest group when compared with the other age groups. In the remaining groups the upper incisors exhibited a tendency of gradual labial tipping with age, whereas the lower incisors kept stable in the procumbency.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1988

Developmental effects of impaired breathing in the face of the growing child.

Craniofacial morphology and occlusal pattern are evaluated in 71 subjects having impaired breathing as diagnosed by an otolaryngologist, and in an equal number of controls. The impaired group demonstrate characteristic combinations of craniofacial deformities and malocclusions, with the younger individuals demonstrating a lesser expression of malocclusion progression and morphologic deformities. This suggests that early recognition of such facial patterns may be utilized to identify those breathing compromised individuals who have a likely tendency to develop certain types of malocclusion.

Adolescent↗
PubMed1987

The combined use of size-exclusion and reversed-phase high-performance liquid chromatography for characterization of beta-endorphin processing pathways.

A method is described for the separation and analysis of multiple molecular forms of immunoreactive beta-endorphin and its alpha-N-acetylated congeners by a combination of reversed-phase and size-exclusion high-performance liquid chromatography coupled with two specific radioimmunoassays. Both chromatographic procedures are fast (less than 50 min per analysis) providing good resolution and high recovery (greater than 90%). The solvents used in both systems are ultraviolet transparent (less than 214 nm), non-corrosive, low salt (less than 0.05 M) and after evaporation fully compatible with subsequent radioimmunoassay. We have evaluated these techniques using both synthetic and purified peptide standards and have applied these procedures to characterize immunoreactive beta-endorphin and alpha-N-acetylendorphin in rat and sheep pituitary extracts, and the low levels found in sheep hypothalamus and rat ovary. These chromatographic procedures are not only applicable to the study of pro-opiomelanocortin-derived peptides, but also could be employed to examine the processing pathways of other biologically active polypeptides, in both central and peripheral tissue extracts.

Animals↗
PubMed1986

alpha-N-acetylated beta-endorphin is differentially processed in the normal and hypothalamo-pituitary-disconnected (HPD) ewe.

We have used specific radioimmunoassay and high-performance liquid chromatography (HPLC) to determine content and molecular forms of pituitary alpha-N-acetylated endorphin (NacEP) in the intact and hypothalamo-pituitary-disconnected (HPD) sheep. No significant differences were seen in anterior pituitary (AP) immunoreactive (ir-) NacEP levels (control = 4.34 +/- 0.45 ng/mg; HPD = 4.38 +/- 0.83 ng/mg; n = 4) or in HPLC profiles following pituitary disconnection. In contrast, levels of ir-NacEP in the HPD intermediate lobe (IL) (263 +/- 16.5 ng/mg; n = 4) were double those in the control (110 +/- 14 ng/mg; n = 4), accompanied by a marked change in the molecular profile. In the control IL, the major species were Nac alpha EP (30%), Nac gamma EP (30%) and Nac beta EP1-27 (35%); in HPD IL, Nac beta EP1-27 (65%) is the dominant molecular form, with Nac alpha EP (11%) and Nac gamma EP (9%) relatively minor components.

Animals↗
PubMed1986

A prospective randomized comparative trial of the Gravigard, Latex Leaf, Dalkon Shield and Multiload Cu 250 IUDs.

This prospective randomized trial in 843 patients compared the effectiveness and complications of 4 intrauterine devices. At 24 months the gross accidental pregnancy rate for the Dalkon Shield was higher than for the 7Cu200 (p less than 0.05) and the ML Cu250 (p less than 0.05). The 7Cu200 had a higher expulsion rate than the Dalkon Shield (p less than 0.01), Latex Leaf (p less than 0.001) and ML Cu250 (p less than 0.001). Use-related terminations were higher for the 7Cu200 than for the ML Cu250 (p less than 0.01). Removal for pelvic inflammatory disease was necessary in 8 women (2 for the Latex Leaf and 3 each for the 7Cu200 and Dalkon Shield). There was no significant difference in termination rates between the ML Cu250 and Latex Leaf but subsequently the Leaf has given problems with removal particularly in women who have defaulted follow-up for several years.

Adult↗