PubMed Health⌕ Search

Biomedical subjects

C Chan

Publications and source records attributed to C Chan.

At least 37 records · Page 2Linked to original sources
PubMed1990

Worldwide status of poliomyelitis in 1986, 1987 and 1988, and plans for its global eradication by the year 2000.

In 1986, a total of 28,951 cases of poliomyelitis were reported to WHO by 175 countries/areas. For 1987, 35,685 cases were reported by 168 countries/areas. Reporting is incomplete for 1988, based on data available as of December 1989. Trends in regional incidence rates for poliomyelitis over a 15-year period from 1974 to 1988 suggest a decline in the incidence of the disease, especially since 1982. However, the reported data underreport actual disease incidence. During 1986, 1987 and 1988, the Expanded Programme on Immunization (EPI) estimates that 200,000-250,000 cases of paralytic poliomyelitis occurred each year. With the current level of polio immunization coverage, it is estimated that 360,000 cases of paralytic poliomyelitis were prevented in 1988. In 1974, when the EPI was started, it was estimated that less than 5% of children in the developing world were adequately immunized against six common childhood diseases, including poliomyelitis. In 1988 (based on data available as of December 1989) 67% of children worldwide received a full course of polio vaccine before 12 months of age. The progress of the EPI has provided optimism that poliomyelitis can be eradicated. In May 1988, the Forty-first World Health Assembly committed WHO to the global eradication of poliomyelitis by the year 2000. The eradication of poliomyelitis will represent, along with the eradication of smallpox, a fitting gift from the XXth to the XXIst century. To reach this goal, action will be required in several main areas. Immunization coverage will need to be raised and sustained in every district. Vaccine quality must be assured by using vaccines which meet WHO requirements and maintaining the cold chain. Surveillance must be strengthened so that prompt, regular reporting of suspected cases leads to disease-containment measures. Additional actions include improving laboratory diagnostic capabilities, developing special training materials, increasing public awareness, supporting rehabilitation services and conducting essential research.

Forecasting↗
PubMed1989

Absorbed radiation by various tissues during simulated endodontic radiography.

The amount of absorbed radiation by various organs was determined by placing lithium fluoride thermoluminescent chip dosimeters at selected anatomical sites in and on a human-like X-ray phantom and exposing them to radiation at 70- and 90-kV X-ray peaks during simulated endodontic radiography. The mean exposure dose was determined for each anatomical site. The results show that endodontic X-ray doses received by patients are low when compared with other radiographic procedures.

Dental Pulp Cavity↗
PubMed1989

Opportunistic research in general practice using a low cost microcomputer based medical record system as a tool.

A low cost microcomputer-based medical record system was used to facilitate opportunistic research projects in the teaching clinic of the Chinese University of Hong Kong. An example of an actual clinical trial comparing the effectiveness of three methods of teaching breast self-examination to clinic patients was used and the process of setting up the research protocol, the sampling of patients, and the analysis of early results after one and a half years were described. It was found that the sampling bias in opportunistic research was that subjects selected were more likely to be older with more problems, and have a higher attendance rate at the clinic. The bias could be corrected during the analysis of data by stratifying the selected sample into groups of different attendance rates. Another potential sampling bias was due to non-compliance of both the patients and the clinical staff. However, it was found to be possible to obtain useful results from opportunistic research. It was easy to implement this type of research with the help of a computerized medical record system.

Adult↗
PubMed1989

The prognostic value of a prior spermatozoa study for human in vitro fertilization.

Patients admitted for treatment of in vitro fertilization (IVF) were subjected to a semen investigation about 1-2 weeks prior to actual IVF and again during IVF. In addition to routine semen analyses, the recovery efficiency of motile spermatozoa by swim-up technique and Percoll gradient separation, the level of semen lactate dehydrogenase and the viability of the spermatozoa in the insemination medium were also studied. There is a significant correlation between the results of the pre-IVF analyses and that observed during IVF suggesting that a prior investigation of semen profile and sperm function is useful to screen potential IVF candidates. Among the various parameters, sperm motility in the semen and the swim-up preparation, percent normal spermatozoa and in vitro viability were significantly related to the outcome of IVF.

Fertilization in Vitro↗
PubMed1989

L-663,536 (MK-886) (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2 - dimethylpropanoic acid), a novel, orally active leukotriene biosynthesis inhibitor.

L-663,536 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2, 2-dimethylpropanoic acid) is a potent inhibitor of leukotriene (LT) biosynthesis in intact human polymorphonuclear leukocytes (PMN) (IC50, 2.5 nM). Similarly, L-663,536 inhibited A23187-induced LTB4 formation by rat peripheral blood and elicited PMN. At concentrations where inhibition of leukotriene biosynthesis occurred in human whole blood (1.1 microM), no effect was seen on cyclooxygenase or 12-lipoxygenase, an effect also observed in washed human platelets. The compound had no effect on rat or porcine 5-lipoxygenase indicating that L-663,536 is not a direct 5-lipoxygenase inhibitor. When administered in vivo L-663,536 was a potent inhibitor of antigen-induced dyspnea in inbred rats pretreated with methysergide (ED50, 0.036 mg/kg p.o.) and of Ascaris-induced bronchoconstriction in squirrel monkeys (1 mg/kg p.o.). The compound inhibited leukotriene biosynthesis in vivo in a rat pleurisy model (ED50, 0.2 mg/kg p.o.), an inflamed rat paw model (ED50, 0.8 mg/kg), a model of leukotriene excretion in rat bile following antigen provocation, and a model in the guinea-pig ear where leukotriene synthesis was induced by topical challenge with ionophore A23187 (ED50, 2.5 mg/kg p.o. and 0.6 micrograms topically). The results indicate that L-663,536 is a potent inhibitor of leukotriene biosynthesis both in vitro and in vivo indicating that the compound is suitable for studying the role of leukotrienes in a variety of pathological situations.

Animals↗
PubMed1988

Multilocus analysis of the fragile X syndrome.

A multilocus analysis of the fragile X (fra(X] syndrome was conducted with 147 families. Two proximal loci, DXS51 and F9, and two distal loci, DXS52 and DXS15, were studied. Overall, the best multipoint distances were found to be DXS51-F9, 6.9%, F9-fra(X), 22.4%; fra(X)-DXS52, 12.7%; DXS52-DXS15, 2.2%. These distances can be used for multipoint mapping of new probes, carrier testing and counseling of fra(X) families. Consistent with several previous studies, the families as a whole showed genetic heterogeneity for linkage between F9 and fra(X).

Chromosome Mapping↗
PubMed1988

Mitogenic activation of EL-4 cells does not require surface Thy-1 expression.

The ability of monoclonal anti-Thy-1 antibodies to stimulate IL-2 production and T-cell proliferation has raised the possibility that Thy-1 may play an important role in T-cell activation. To examine this postulated role we have produced Thy-1-negative variants of the murine T lymphoma EL-4 by mutagenesis with ethyl methanesulfonate (EMS) and subsequent negative selection with anti-Thy-1 monoclonal antibodies (mAbs) and complement. Although the parental EL-4 cell line produced interleukin-2 (IL-2) in response to concanavalin A (Con A), phytohemagglutinin, anti-Thy-1 mAbs, and an anti-T3 mAb, as well as after exposure to phorbol myristate acetate (PMA), only PMA was capable of inducing IL-2 production by several Thy-1-negative cell lines. The loss of responsiveness to cell surface stimulatory ligands appeared to be correlated with loss of Thy-1 expression because mutagenized cells selected for high levels of Thy-1 expression all responded normally to Con A. However, when Thy-1 expression was reconstituted in the "nonresponder" (Thy-1-negative) cell lines either by transfection of a Thy-1.2 gene or by 5-azadeoxycytidine treatment, the revertant cell lines were still unable to produce IL-2 when stimulated with Con A, anti-Thy-1, or anti-T3. Furthermore, several other independently derived Thy-1-negative EL-4 cell lines responded normally to mitogens and mitogenic mAbs. Taken together, these results suggest that Thy-1 expression is not required for the T-cell activation process and that the EMS mutagenesis procedure resulted in an additional mutation(s) responsible for the inability of certain Thy-1-negative cell lines to be triggered by mitogens and mitogenic mAbs. These cell lines may prove to be valuable tools for further biochemical and molecular studies of the sequence of events associated with T-cell activation.

Animals↗
PubMed1988

Expanded programme on immunization.

The Expanded Programme on Immunization (EPI) was established in 1974 to develop and expand immunization programmes throughout the world. In 1977, the goal was set to make immunization against diphtheria, pertussis, tetanus, poliomyelitis, measles and tuberculosis available to every child in the world by 1990. Problems encountered by the Programme have included: lack of public and governmental awareness of the scope and seriousness of the target diseases; ineffective programme management; inadequate equipment and skills for vaccine storage and handling; and insufficient means for monitoring programme impact as reflected by increasing immunization coverage levels and decreasing incidence of the target diseases. When the EPI was initiated in 1974, fewer than 5% of children in developing countries were receiving a third dose of DPT and poliomyelitis vaccines in their first year of life. These coverage levels have now surpassed 50% in developing countries, and millions of cases of the target disease have been prevented. Over 700,000 measles deaths were prevented by immunization in developing countries in 1987, and an increasing number of neonatal tetanus deaths is now being prevented by maternal immunization and improved childbirth conditions. Poliomyelitis immunization efforts have been so successful that the Pan American Health Organization is leading a drive to eradicate poliomyelitis from the Americas by 1990. The successes of the Programme represent a major public health achievement, but much remains to be done.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1988

Implementation of a microcomputer-based opportunistic health maintenance programme in a general practice teaching clinic.

The general practice teaching clinic at the Chinese University of Hong Kong uses a microcomputerbased medical record system. To implement a uniform and up-to-date health maintenance programme, a set of protocols has been written for a list of health maintenance items, and the computer has been programmed to identify the items which should be carried out at each patient encounter. Over a period of 16 months, after the start of this programme, 99% of the 1120 clinic patients had a minimum of two items performed. Of a selected sample of 203 patients 119 attended the clinic more than once in the same period and 47% of these patients had all of the health maintenance items recommended for their age and sex group completed. Abnormal screening results led to action by the general practice team. The process of implementing a health maintenance programme has helped the team to discuss current recommendations and to agree on standards. The programme has also helped with undergraduate teaching. The automated opportunistic health maintenance programme is a practical tool for improving patient care.

Adolescent↗
PubMed1987

What proportion of couples undergoing unrestricted in vitro fertilization treatments can expect to bear a child?

A 200-patient cohort has been established so that longitudinal analysis can determine the likelihood of an individual in vitro fertilization (IVF) entrant achieving a viable uterine pregnancy or a live baby. After a minimum of 39 months of access to repeated treatment cycles, 24% have achieved at least one viable pregnancy by undergoing an average of 2.48 treatment cycles per cohort member. Life-table analysis shows that most of these pregnancies have occurred in the first year after entering the program. Many members have undergone only one or two treatment cycles. In the future, greater emphasis will need to be placed on factors which encourage couples to undergo additional cycles of treatment. This, as much as technical advances, may increase outcome figures.

Actuarial Analysis↗
PubMed1987

Early and delayed indium 111 leukocyte imaging in Crohn's disease.

Twenty-seven patients with Crohn's disease were studied for the presence and location of activity by both early (4 h) and delayed (18-24 h) indium 111 leukocyte imaging. The results were compared with other parameters of disease activity including Crohn's disease activity index, barium studies, and endoscopy. There was a correlation between early images and Crohn's disease activity index (r = 0.78) and between delayed images and index (r = 0.82). Based upon the corresponding Crohn's disease activity index, the sensitivity of early and delayed imaging was 81.0% and 95.2%, respectively. Specificity of early and delayed imaging was 75.0% and 87.0%, respectively. Presence of activity on the early and delayed imaging agreed with activity on barium studies and colonoscopy in approximately 80% of cases. Correlation of location of disease by leukocyte imaging and x-ray was observed in 58.9% of early scans and 55.0% of delayed scans. Correlation of the location of disease by imaging and endoscopy was observed in 71.4% of early and 75.0% of delayed studies. Because of the possibility of occurrence of false-negative results in early images, delayed imaging should always be included in evaluation of disease activity in patients with Crohn's disease who are suspected of having mild activity. Delayed imaging is not required if the early imaging study clearly shows activity.

Adult↗
PubMed1987

Influence of group function and canine guidance on electromyographic activity of elevator muscles.

A comparative EMG study was done between two types of occlusal guidances: group function and canine guidance. The purpose was to determine which of the two occlusal schemes causes a greater reduction in muscle activity and thereby a decrease in muscle tension in eccentric mandibular positions. Full-coverage occlusal splints were made for six test subjects with normal function of the stomatognathic system. Left- and right-side integrated EMG recordings were made of the masseter and temporal muscles during static (clenching) and dynamic (lateral excursion and clenching) maximal contractions. The results showed an EMG activity reduction of the elevator muscles with group function relative to their activity in centric occlusion. A more marked reduction was observed on the mediotrusive side, mainly in the temporal muscle. With canine guidance, the reduction in elevator muscle activity is much greater, more significant, and mainly in the temporal muscle of the mediotrusive side. The clinical implications of this study suggest the use of canine guidance in laterotrusion for therapy with full-coverage occlusal splints.

Adolescent↗
PubMed1986

Role of Ly-6 in lymphocyte activation. II. Induction of T cell activation by monoclonal anti-Ly-6 antibodies.

The Ly-6 locus controls the expression and/or encodes for alloantigenic specificities found primarily on subpopulations of murine T and B lymphocytes. We have recently identified and characterized a new rat mAb, D7, that recognizes a nonpolymorphic Ly-6 specificity. After crosslinking by anti-Ig reagents or by Fc receptor-bearing accessory cells, mAb D7 could induce IL-2 production from T cell hybridomas, and in the presence of PMA could trigger a vigorous proliferative response in resting peripheral T cells. The addition of mAb D7 to cultures of antigen- and alloantigen-, but not mitogen-stimulated T cells resulted in a marked augmentation of the proliferative response. A number of other well-characterized mAbs to Ly-6 locus products could also stimulate a T cell proliferative response after crosslinking by anti-Ig and in the presence of PMA. These results strongly suggest that Ly-6 molecules may play a critical role in the T cell activation cascade, either as receptors for an unidentified soluble or cell-associated ligand or as transducing molecules that modulate signals initiated by antigen stimulation of the T3-Ti complex.

Animals↗