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Biomedical subjects

M Kwan

Publications and source records attributed to M Kwan.

35 records · Page 2Linked to original sources
PubMed1988

Indistinguishable patterns of protooncogene expression in two distinct but closely related tumors: Ewing's sarcoma and neuroepithelioma.

Genetic characterization of human tumors promises new insights of biological importance and clinical relevance. We have found that two solid tumors, peripheral neuroepithelioma and Ewing's sarcoma of bone, which share a common cytogenetic rearrangement, are characterized by an indistinguishable and highly reproducible pattern of protooncogene expression. c-myc, N-myc, c-myb, and c-mil/raf-1 are all expressed at similar levels in these tumors. c-fes and c-sis expression was not detected in any specimens of either tumor. In contrast, the protooncogene c-ets-1, located near the breakpoint of the chromosomal translocation in these tumors, is variable in its expression. We also detected high levels of choline acetyltransferase in these tumors, which suggests a common neural origin. Since it is likely that the clinical behavior and therapeutic responsiveness of tumors relate closely to their biological and genetic features, the pattern of protooncogene expression of individual tumors may provide a novel basis for their characterization.

Bone Neoplasms↗
PubMed1988

Non-surgical sterilization using phenol-mucilage: acceptability versus efficacy.

Sterilization has become a popular means of birth control and many methods have been developed to meet the needs of different groups of women. In a pilot study, non-surgical sterilization using phenol-mucilage was found to be extremely acceptable to a group of Chinese women despite its failure rate. The method is simple, safe and inexpensive. It is suggested that this method would be suitable for women who are afraid of surgical sterilization.

Adhesives↗
PubMed1988

Therapeutic functional bracing in upper limb fracture-dislocations.

The authors utilized the principle of functional bracing in the management of 307 fractures and/or dislocations of the upper limb. There were 29 humeral fractures, 111 fracture-dislocations around the elbow, 32 fractures of the forearm, and 135 fractures of the distal radius. The average follow-up was 9 months. The results showed that more than 95% of the patients regained good range of motion and power. The details of the technique and the protocols are described. The conclusion drawn from an analysis of the results is that functional bracing is a safe and effective method in the management of upper limb fracture dislocations.

Adolescent↗
PubMed1985

The varied responses of different F1-ATPases to chlorpromazine.

The effects of chlorpromazine on various properties of the F1-ATPases from bovine heart mitochondria (MF1), the plasma membranes of Escherichia coli (EF1), and plasma membranes of the thermophilic bacterium PS3 (TF1) have been examined. While chlorpromazine inhibited MF1 with an I0.5 of about 50 microM and EF1 with an I0.5 of about 150 microM at 23 degrees C, the ATPase activity of TF1 was stimulated by chlorpromazine concentrations up to 0.6 mM at this temperature. Maximal activation of about 20% was observed at 0.2 mM chlorpromazine at 23 degrees C. Chlorpromazine concentrations greater than 0.6 mM inhibited TF1 at 23 degrees C. At 37 degrees C the ATPase activity of TF1 was doubled in the presence of 0.5 mM chlorpromazine, the concentration at which maximal stimulation was observed at this temperature. Chlorpromazine inhibited the rate of inactivation of EF1 by dicyclohexylcarbodiimide (DCCD) at 23 degrees C and pH 6.5. Concentrations of chlorpromazine which inhibited the ATPase activity of TF1 at pH 7.0 accelerated the rate of inactivation of the enzyme by DCCD at pH 6.5, while lower concentrations of the phenothiazine, which stimulated the ATPase, had no effect on DCCD inactivation. Chlorpromazine concentrations up to 1.0 mM had no effect on the rate of inactivation of TF1 by DCCD at 37 degrees C and pH 6.5. Chlorpromazine at 0.5 mM accelerated the rate of inactivation of MF1 by 5'-p-fluorosulfonylbenzoyladenosine (FSBA), while it slowed the rate of inactivation of EF1 by FSBA. The inactivation of TF1 by FSBA in the absence of chlorpromazine was complex and was not included in this comparison. Chlorpromazine protected MF1 and EF1 against cold inactivation. Whereas 100 microM chlorpromazine afforded about 90% stabilization of MF1 at 4 degrees C, only about 30% stabilization of EF1 was observed under the same conditions in the presence of 400 microM chlorpromazine. Each of the ATPases was inactivated by the structural analog of chlorpromazine, quinacrine mustard. Whereas 5 mM ATP and 5 mM ADP protected MF1 and TF1 against inactivation by 0.5 mM quinacrine mustard, the rate of inactivation of EF1 by quinacrine mustard was accelerated fourfold by 5 mM ATP and slightly accelerated by 5 mM ADP.

Adenosine↗
PubMed1985

Effects of estrogen treatment on sexual behavior in male-to-female transsexuals: experimental and clinical observations.

The effects of oral estrogen treatment on sexual physiology and behavior were examined in seven presurgical male-to-female transsexuals engaged in cross-living. Subjects were studied prior to hormone treatment, during long-term hormone treatment, and during an experimental double-blind period in which the effects of their usual hormone regimen were compared to those of placebo during successive 4-week periods. Subjects maintained daily logs of their spontaneous erections, sexual activity (masturbation), and feelings throughout the study. Nocturnal penile tumescence was measured, using home monitors, in order to estimate estrogen-induced changes in erectile capacity. Erectile response to sexually arousing stimuli (erotic films and self-generated fantasy) was also assessed in the laboratory. Blood samples were taken at intervals for testosterone and sex-hormone-binding globulin measurements and free testosterone levels were calculated. Estrogen treatment inhibited sexual activity, spontaneous erections, and nocturnal penile tumescence. No significant effects on psychophysiological response to film and fantasy or frequency of sexual feelings were found, but the psychophysiological data were very variable. Testosterone levels were suppressed by estrogen, but not to the extent that free testosterone levels were. It appears that declining free testosterone level is associated with inhibition of spontaneous erections (during both sleep and waking) and of sexual activity, though the latter relationship is less clear. No evidence of an effect on film or fantasy-induced erections was obtained.

Adult↗
PubMed1985

Cross-sectional study of semen parameters in a large group of normal Chinese men.

Testicular size, semen characteristics and serum reproductive hormone levels were studied in 1239 normal Chinese men. The mean testicular size of 17 ml in this group of subjects was similar to other reports in Orientals but was smaller than that reported in Caucasians. Semen volume, and the sperm count, motility and morphology were comparable to those described for Caucasian subjects. The cervical mucus penetration test (Kremer's test) and the zona-free hamster egg penetration test were also studied in some of the subjects. Age showed a positive correlation with the serum levels of FSH and LH, which were highly correlated with each other. Sperm concentration and the total sperm count were positively correlated with testicular volume, the length of abstinence, the % of sperm with an oval head, and the zona-free hamster egg penetration test, but were negatively correlated with serum FSH. Sperm motility was negatively correlated with the duration of abstinence but was positively correlated with the % normal sperm. The results constitute a normal data base from Chinese men for comparison with studies in male infertility and fertility regulation.

Adult↗
PubMed1985

Rapid urinary LH assay for prediction of ovulation.

The results of the cervical mucus score (CMS), basal body temperature (BBT) and a rapid urine luteinizing hormone (LH) assay by haemagglutination immunoassay were compared with plasma LH radioimmunoassay in 28 ovulatory cycles. There was good correlation of the CMS peak with the plasma LH peak while the urine LH peak usually occurred one day later. The first day when the CMS was greater than or equal to 8 occurred within +/- 1 day of the plasma LH peak in 89.3% of cycles. The first day when the urine LH was greater than or equal to 100 iu/l occurred within +/- 1 day of the plasma LH peak in all the cycles. BBT nadir could be identified in only 82% of cycles and it coincided with the plasma LH peak in only 28.6% of cases. These findings suggest that both the CMS and the rapid urine LH assay are acceptable methods for determining the time of ovulation while the BBT is not useful.

Body Temperature↗
PubMed1984

Vaginal scent marking: effects on ultrasonic calling and attraction of male golden hamsters.

Male hamsters were tested for their responses to areas that had been scent marked by intact or vaginectomized females to determine the effects of naturally deposited vaginal secretions on male behavior. In the first experiment males produced more ultrasonic courtship calls when investigating areas marked by intact females than areas scented by vaginectomized females, demonstrating that vaginal marks facilitate such calling. In a wind-tunnel preference test situation in which scent-marked alleys and clean alleys served as sources of odor, males approached the scented alley first if it had been freshly marked by intact females but not if it had been scented by vaginectomized females or other males. Thus, the odors of vaginal marks are sufficient to attract males over short distances. After males entered these alleys they showed a preference for odors of both intact and vaginectomized females over no odors, but still spent significantly more time investigating the odors of intact females than those of vaginectomized females. These experiments indicate that vaginal secretions are one of the primary cues that elicit male courtship calling, and the small quantities of vaginal secretions deposited by females in vaginal marks are sufficient to elicit ultrasonic calling and attract males over short distances. Thus it is likely that vaginal scent marking and ultrasonic calling by females interact to facilitate attraction and location of mates during courtship.

Animals↗
PubMed1983

Maintenance of sexual function in a castrated man treated with ovarian steroids.

Sexual function, mood states, and endocrine levels were studied in a 48-year-old man who had been castrated bilaterally because of severe post-vasectomy orchialgia and who habitually uses oral estrogen and progestin. He reported satisfactory sexual behavior with a usual coital frequency of at least twice per week while on treatment with Premarin and Provera. Though his nocturnal penile tumescence (recorded on a portable home monitor) was very low while on this treatment, psychophysiological tests showed that erectile responses to erotic film were well within the normal range for control subjects in this laboratory. A double-blind experiment was performed to assess his sexual functioning and mood states during treatment with placebo, testosterone enanthate, and estradiol valerate, with and without progesterone (one injection of each, with 4-week intervals between treatments). All treatments generated prolonged changes in circulating hormone levels; testosterone treatment was associated with elevated estradiol levels, and estradiol with massively increased plasma prolactin. Coital frequency was highest with the estrogen-progestin treatment and lowest with placebo. Testosterone precipitated a very high frequency of spontaneous erections and severe negative affect. The subject also reported low sexual drive and poor mood states while taking Provera alone. It was concluded that the preferred estrogen-progestin treatment of this patient, probably in conjunction with minimal androgen levels from his adrenal, are most likely responsible for maintaining his satisfactory sexual functioning. There is no evidence that other castrates would necessarily benefit from a similar hormonal regimen.

Castration↗
PubMed1983

The nature of androgen action on male sexuality: a combined laboratory-self-report study on hypogonadal men.

Sexual function and the effects thereon of testosterone enanthate were studied in six hypogonadal men with the objective of delineating the specific components of male sexuality affected by androgen. To obtain a detailed picture of these components, prospective self-report data (from daily logs) of sexual activity and feelings, recordings of all night penile tumescence, and laboratory psychophysiological data were assessed. Double blind placebo experiments with cross-over design were used to compare the effects of placebo and 200- and 400-mg doses of testosterone enanthate. Erectile responses to erotic film and fantasy were not lower in the hypogonadal patients than in normal men and, in fact, were higher on some parameters, especially prolongation of detumescence time after exposure to film or fantasy. Three subjects who kept consistent daily logs had increased frequencies of sexual acts and feelings, orgasms, and spontaneous erections after testosterone administration. Nocturnal penile tumescence and spontaneous daytime erections were reduced in untreated hypogonadal men and were significantly increased after testosterone treatment, but the laboratory-tested erectile responses to film and fantasy were not affected by testosterone. These data and previous findings lead to the conclusion that the major androgen action on male sexuality involves libido factors (i.e. sexual motivation/interest). Though stimulus-bound erections elicited in the laboratory were not reduced in hypogonadal men, spontaneous (sleep or waking) erections were clearly testosterone dependent.

Adult↗
PubMed1982

Hormonal replacement and sexuality in men.

Only in the last few years has the scientific study of hormonal replacement therapy for hyposexuality begun in earnest with the advent of appropriately controlled experiment studies. Dose-response relationships can be demonstrated between testosterone (T) and sexual measures, but these have not yet been investigated in detail. Some aspects of sexual function are maintained in the presence of androgen levels well below the normal range, but preliminary evidence suggests that within a normal population high levels of T are correlated with more vigorous responses to visual erotic stimuli. Though T (and to a greater extent free T) declines with aging in parallel with the decline of sexual function, these hormonal changes contribute only to a minor extent to the behavioural change. Some non-aromatizable androgens may be less effective in stimulating sexual behaviour than T, but initial data on effects of dihydrotestosterone suggests that the capacity of an androgen to be aromatized (converted to oestrogen) is not a requirement for its sexual action. While T apparently increases the incidence of all types of male sexual activity, recent data contradict the belief that it directly facilitates the erectile mechanism in men, even though erection frequency is greatly reduced in untreated hypogonadal men. At the present juncture, it appears that the initial action of T may be on libido factors which lead in turn to the stimulation of other aspects of sexuality. Specifically, we propose that androgen acts through stimulating genital sensations and/or other pleasurable awareness of sexual response rather than directly through cognitive processes such as sexual imagery.

Adult↗
PubMed1981

In vivo aqueous humor oxygen tension--as estimated from measurements on bare stroma.

Aqueous humor oxygen tension of the in vivo rabbit eye was estimated by a relatively atraumatic procedure. The anterior corneal surface of the eye was first scraped free of its epithelial layer. A polarographic oxygen electrode was then used to measure the oxygen tension at the bare stromal surface. Aqueous humor oxygen tension can be estimated from this measured steady-state stromal surface oxygen tension by correcting the measured oxygen tension for the tension drop across the stroma and endothelium. When animals breathed room air (155 mm Hg oxygen tension), the oxygen tension of the aqueous humor was 13 mm Hg; this rose to 150 mm Hg when the inspired oxygen tension was 713 mm Hg.

Animals↗
PubMed1980

The role of vaginal secretion in hamster sexual behavior: males' responses to normal and vaginectomized females and their odors.

The importance of hamster vaginal secretion relative to other femine odors for attraction of males and elicitation of copulatory behavior was examined by comparing the behavior of males toward normal females with that toward vaginectomized females. Males were more attracted to intact females than to vaginectomized females when odors were the only cues available and also when auditory, visual, and odor cues were available but contact was prevented. There were no differences in the attractiveness of estrous and diestrous females, whether intact or vaginectomized. When males and females were allowed to interact, there were no differences in any measures of male sexual behavior toward normal versus vaginectomized females, which indicates that the presence of vaginal secretion is not necessary for male sexual behavior. The significance of these findings for conceptions of pheromone action in mammals is discussed.

Animals↗
PubMedDate not supplied

Factors affecting the success of artificial insemination by frozen donor semen.

The records of 227 couples who received artificial insemination by frozen donor semen in 984 treatment cycles were analysed to find out the factors affecting the pregnancy rates. The cumulative pregnancy rate at 6 months was 46.8% and the pregnancy rate per cycle was 10%. The pregnancy rates were adversely affected by (1) increase in the recipient age above 30 years, (2) irregularity of menstrual cycles, (3) the use of clomiphene citrate for induction of ovulation, and (4) low cervical mucus scores. Among our donor semen samples selected with a set of criteria, the sperm counts and initial and post-thaw motility did not affect the pregnancy rates.

Adult↗