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Biomedical subjects

S Y Chan

Publications and source records attributed to S Y Chan.

At least 145 records · Page 8Linked to original sources
PubMed1993

Assessment of human sperm acrosome reaction by flow cytometry: validation and evaluation of the method by fluorescence-activated cell sorting.

OBJECTIVE: To determine the applicability of flow cytometry to assess human sperm acrosome reaction. DESIGN: Prospective evaluation of semen samples incubated overnight for the development of spontaneous acrosome reaction or exposed to the calcium ionophore A23187 (5 microM) for 3 hours for induction of the acrosome reaction. SETTING: University-affiliated tertiary care center. PATIENTS: Normal healthy volunteers. INTERVENTIONS: The spermatozoa were stained with fluorescein isothiocyanate (FITC)-labeled pea agglutinin. The labeled samples were assessed visually and also subjected to analytic flow cytometry and fluorescence-activated cell sorting. MAIN OUTCOME MEASURES: Acrosome reaction assessed visually and by flow cytometry. RESULTS: Flow cytometric analysis showed a single peak of FITC fluorescence in the washed semen samples. A second peak of lower FITC fluorescence intensity was noted after overnight incubation or exposure to A23187, suggesting loss of fluorescence, which indicated the occurrence of the acrosome reaction. There was a statistically significant correlation between the assessment by the two methods (n = 41). However, although the mean difference between the methods was small (2.49%), the difference between the two methods for each individual sample can vary between -24% to +29%. When the sperm cells were subjected to cell sorting based on green fluorescence intensity, reanalysis and visual scoring verified that the low intensity peak contained a majority of acrosome-reacted spermatozoa (77.52% +/- 2.39%). CONCLUSION: These results validated the flow cytometric method for assessment of acrosome-reacted spermatozoa. Although flow cytometry is more objective and less time consuming when many samples are assessed at the same time, the visual method remains a useful and practical procedure in the clinical andrology laboratory.

Acrosome↗
PubMed1993

Continuous chemotherapy in responsive metastatic breast cancer: a role for tumour markers?

A biochemical response index comprising ESR, CEA and CA 15.3 was evaluated in 67 patients with systemic breast cancer treated by chemotherapy; 55 were assessable by UICC criteria and the response index (96% of all UICC assessable patients). Marker changes at 2 and 4 months showed a highly significant correlation with the UICC assessed response at 3 and 6 months (P < 0.001); sensitivity 100%, specificity 87%; positive predictive value 85%; negative predictive value 100%. This index was then used to select out truly responsive patients and to prospectively direct their chemotherapy. Twenty-six responding (biochemical/clinical) patients were randomised to discontinue cytotoxics after 6 months and move to maintenance hormones (n = 13) or continue chemotherapy whilst the biochemical markers kept falling or remained within the normal range. Biochemical progression prompted a change of chemotherapy. Continuous chemotherapy in biochemically defined responders was associated with a significant lengthening of remission duration and an improved quality of life and survival. We are now using the index to routinely direct chemotherapy and select out true responders for maintenance chemotherapy.

Adult↗
PubMed1993

Sequence variants of human papillomavirus type 16 from couples suggest sexual transmission with low infectivity and polyclonality in genital neoplasia.

Human papillomavirus type 16 (HPV-16) is causally involved in the pathogenesis of genital neoplasia, but important details of the natural history of infection and disease are not yet understood. Many individual HPV-16 DNA isolates differ by characteristic point mutations. In a study of the HPV-16 variants from genital lesions of 32 married couples, HPV-16 was detected in both the husband and the wife in 8 couples. Of these, 4 demonstrated identical HPV-16 variants between husband and wife, and 4 had mismatching HPV-16 variants. Five of 31 biopsies showed simultaneous presence of two different HPV-16 variants. The data suggest that sexual transmission of HPV-16 does occur, but with low infectivity, and that HPV-16-related premalignant lesions are frequently polyclonal.

Adult↗
PubMed1993

Human spermatozoal tail hypo-osmotic swelling test, motility characteristics in hypotonic saline, and survival of spermatozoa after cryopreservation.

Normozoospermic semen samples (n = 82) were examined to investigate whether the degree of sperm tail swelling in hypo-osmotic medium (fructose and sodium citrate; 150 mOsm/l), and motility characteristics after a 15-min exposure to hypotonic saline (sodium chloride; 150 mOsm/l) could predict the cryosurvival rate (% post-thaw motility/% pre-freeze motility x 100%) of spermatozoa after cryopreservation by the liquid nitrogen vapour freezing method using the TEST-glycerol-egg yolk buffer. The CellSoft automated semen analyser was used to analyse sperm motility in pre-freeze and post-thaw semen samples, and after exposure to hypotonic saline. Sperm tail hypo-osmotic swelling and sperm motility in pre-freeze semen showed no significant correlations (P > 0.05) with the cryosurvival rate. There were significant correlations (P < 0.05) between the cryosurvival rate and the following sperm motility parameters in hypotonic saline: % motility (r = 0.2846), motility index (% motility x curvilinear velocity; r = 0.2809) and % decrease in motility index from the baseline value in semen (r = 0.3378). The % decrease in motility index after hypotonic saline treatment was significantly less (P < 0.05) in the normal (> or = 50% cryosurvival rate; mean +/- SEM 5.9 +/- 3.2%; n = 33) compared with the subnormal (< 50% cryosurvival rate; 27.3 +/- 4.8%; n = 49) cryosurvival groups. This parameter was also determined, by multivariate discriminant analysis, to be capable of classifying each pre-freeze semen sample into either cryosurvival group with 69.5% accuracy.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Survival↗
PubMed1993

Association between human in vitro fertilization rate and pregnancy outcome: a possible involvement of spermatozoal quality in subsequent embryonic viability.

A conventional view of mammalian fertilization is that the active component of the process: the spermatozoon, by virtue of its progressive motility and acrosomal enzymes, penetrates an otherwise passive oocyte. This concept has placed bias on spermatozoal normality as largely determining the outcome of fertilization; once this has been achieved then the contribution of the spermatozoon is often forgotten, and attention switches to the maternally derived "blue-print" for early embryonic development. Paternal genomic contribution is known to start at the eight-cell stage in the human, but this is usually after the time when early cleavage stage (2 to 8-cell stage) embryos are replaced in human assisted reproductive technologies (ART) procedures such as in vitro fertilization and embryo transfer (IVF-ET). Hence, fundamental abnormal contributions to embryogenesis derived from the fertilizing spermatozoon have often been ignored. Human IVF-ET has permitted far greater powers of analysis of the fertilization event, and fertilization success appears to be determined in such a system by three main factors: spermatozoal quality, oocyte quality, and quality of in vitro culture conditions (the gamete environment). If the second two factors are more carefully controlled than the first, as is the usual emphasis in routine human IVF practice, then any large variation in fertilization rates that are also significantly related to embryonic viability and ultimately pregnancy outcome, may be thought to be more directly associated with original quality of the fertilizing spermatozoon. An analysis of results of 758 IVF cases provides preliminary evidence to show that there is a close association between human in vitro fertilization rate and subsequent embryo viability following replacement. In accepting this hypothesis as a possibility, we should drastically change our attitude from one of the spermatozoon as a robust, simple initiator of embryonic development, and embrace the idea of the vulnerability of such germ cells both during and after their production, and how detrimental influences on this might profoundly affect embryogenesis after successful fertilization.

Cell Survival↗
PubMed1993

The genetic drift of human papillomavirus type 16 is a means of reconstructing prehistoric viral spread and the movement of ancient human populations.

We have investigated the diversity of a hypervariable segment of the human papillomavirus type 16 (HPV-16) genome among 301 virus isolates that were collected from 25 different ethnic groups and geographic locations. Altogether, we distinguished 48 different variants that had diversified from one another along five phylogenetic branches. Variants from two of these branches were nearly completely confined to Africa. Variants from a third branch were the only variants identified in Europeans but occurred at lower frequency in all other ethnic groups. A fourth branch was specific for Japanese and Chinese isolates. A small fraction of all isolates from Asia and from indigenous as well as immigrant populations in the Americas formed a fifth branch. Important patterns of HPV-16 phylogeny suggested coevolution of the virus with people of the three major human races, namely, Africans, Caucasians, and East Asians. But several minor patterns are indicative of smaller bottlenecks of viral evolution and spread, which may correlate with the migration of ethnic groups in prehistoric times. The colonization of the Americas by Europeans and Africans is reflected in the composition of their HPV-16 variants. We discuss arguments that today's HPV-16 genomes represent a degree of diversity that evolved over a large time span, probably exceeding 200,000 years, from a precursor genome that may have originated in Africa. The identification of molecular variants is a powerful epidemiological and phylogenetic tool for revealing the ancient spread of papillomaviruses, whose trace through the world has not yet been completely lost.

Africa↗
PubMed1993

Evolution of human papillomavirus type 18: an ancient phylogenetic root in Africa and intratype diversity reflect coevolution with human ethnic groups.

Papillomaviruses are an ideal model system for the study of DNA virus evolution. On several levels, phylogenetic trees of papillomaviruses reflect the relationship of their hosts. Papillomaviruses isolated from remotely related vertebrates form major branches. One branch of human papillomaviruses (HPVs) includes an ape and two monkey papillomaviruses, possibly because the diversification of the viruses predated the separation of the infected-primate taxa. This hypothesis predicts that the root of the evolution of some if not all HPV types should point to Africa, since humans evolved from nonhuman primates in this continent. We tested this hypothesis and compared the genomic sequences of HPV type 18 (HPV-18) isolates from four continents. Diversity within HPV-18 correlates with patterns of the evolution and spread of Homo sapiens: HPV-18 variants, just like HPV-16 variants, are specific for the major human races, with maximal diversity in Africa. Outgroup rooting of the HPV-18 tree against HPV-45, which is closely related to HPV-18, identifies African HPV-18 variants at the root of the tree. The identification of an African HPV-45 isolate further reduces the evolutionary distance between HPV-18 and HPV-45. HPV-18 variants from Amazonian Indians are the closest relatives to those from Japanese and Chinese patients and suggest that a single point mutation in the phylogenetically evaluated genomic segment represents at least 12,000 years of evolution. We estimate that diversity within HPV-18 and probably within other HPV types evolved over a period of more than 200,000 years and that diversity between HPV types evolved over several million years.

Africa↗
PubMed1993

N-hexane neuropathy in offset printers.

In an offset printing factory with 56 workers, 20 (36%) developed symptomatic peripheral neuropathy due to exposure to n-hexane. Another 26 workers (46%) were found to have subclinical neuropathy. The initial change in the nerve conduction study was reduced amplitude of the sensory action potentials, followed by reduced amplitude of the motor action potentials, reduction in motor conduction velocities and increase in distal latencies. These changes indicate primary axonal degeneration with secondary demyelination. Sural nerve biopsy in a severe case showed giant axonal swellings due to accumulation of 10nm neurofilaments, myelin sheath attenuation and widening of nodal gaps. The development of neuropathy bore no direct relationship to the duration of exposure, hence factors such as individual susceptibility may be important. Optic neuropathy and CNS involvement were uncommon and autonomic neuropathy was not encountered.

Adolescent↗
PubMed1993

Quantitative evaluation of drug-induced erythema by using a tristimulus colour analyzer: experimental design and data analysis.

Pulsed-light reflectance using the Minolta Chroma Meter CR-200 was evaluated as a quantitative method for the noninvasive assessment of drug-induced erythema on the flexor surface of the forearm. Nicotinate esters were used as model vasodilators. Several parameters derived from the data were analysed using analysis of variance (ANOVA) and Tukey's multiple range tests appropriate for the study designs used. The effects of varying concentrations of methylnicotinate and of different nicotinate esters were found to be statistically significant. This non-invasive technique was found to be particularly useful in ranking the cutaneous responses elicited by the topical application of increasing concentrations of methylnicotinate in a single subject, as well as in a group of 6 volunteers.

Adult↗
PubMed1993

"Whoosh" test as a teaching aid in caudal block.

Fifty-three patients presenting for minor gynaecological procedures received caudal blocks performed by residents. These residents used the standard technique which relied on the "give" felt as a needle penetrates the sacrococcygeal membrane and the loss of resistance to air when the needle is correctly placed. The "whoosh" test was noted by the supervising anaesthetist who did not reveal his findings to the residents. A positive test consisted of a characteristic "whoosh" sound on auscultation of the thoracolumbar region when 2 to 3 ml of air was injected into the caudal extradural space. The predictive value of a positive test was found to be 78%, 80.7% and 97.7% (P < 0.01) for a positive "give", loss of resistance and "whoosh" test respectively. Negative tests had no predictive value for "give" and loss of resistance whilst the predictive value of an absent "whoosh" was 100% (P < 0.05). Thus we conclude that the "whoosh" test is an excellent aid in the teaching of caudal anaesthesia.

Adult↗
PubMed1993

The effects of Vero (green monkey kidney) cell coculture on the motility patterns of cryopreserved human spermatozoa.

OBJECTIVE: To determine the effects of Vero (a primate, urogenital epithelium-derived cell line) cell monolayer coculture on cryopreserved human sperm function in vitro. DESIGN: Prospective, controlled investigation in which cryopreserved semen specimens were thawed, processed, and then simultaneously exposed to control media (Dulbecco's modified Eagle's medium with either 10% heat-inactivated fetal bovine serum [FBS] or 10% heat-inactivated pooled human sera [PHS]) or the same media with the addition of confluent Vero cell monolayers. A second series of investigations was also performed to study the effect of Vero cell conditioned media (CM). SETTING: In vitro fertilization/andrology service of tertiary center. PATIENTS: Donors with normal semen parameters. INTERVENTIONS: Coculture of human spermatozoa with Vero cell monolayers or Vero cell CM. MAIN OUTCOME MEASURES: General and hyperactivated (HA) motility patterns, multifactor, repeated measures ANOVA. RESULTS: General sperm motility parameters, including percentage motility, mean velocity, and mean amplitude of lateral head displacement were significantly greater than controls in the Vero cell monolayer-FBS group at 6 hours and in both the Vero cell monolayer-FBS and Vero cell monolayer-PHS groups by 24 hours. Hyperactivated motility was increased after 3 hours in the Vero cell monolayer-FBS coculture group. A significant decrease in the total sperm concentration over the time course of the study in the Vero cell monolayer, but not the control or Vero CM groups, was also noted. Vero CM did not exert significant effects on any sperm motility parameter, in spite of a sample size sufficient to detect relevant increases with a power of 0.80. CONCLUSIONS: Vero cell monolayers have a positive influence on cryopreserved sperm function as assessed by general and HA motility patterns. Epithelial cell to spermatozoon contact seems to be important in this process.

Animals↗
PubMed1993

Human sperm hyperactivation and acrosome reaction and their relationships to human in vitro fertilization.

OBJECTIVE: To determine the relationships between human sperm hyperactivation (HA) and acrosome reaction with fertilization of human oocytes in vitro. DESIGN: Prospective analysis of infertile patients undergoing IVF. SETTING: Tertiary center for infertility and assisted reproductive technology. PATIENTS: Fifty-two couples who underwent IVF or GIFT were studied. The male partners had normal semen parameters on routine analyses. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Sperm HA in seminal fluid and after 1 and 6 hours incubation in capacitation media; sperm acrosome reaction after 0, 6, and 24 hours' incubation in capacitation media; and fertilization rate of human oocytes. RESULTS: The percent spermatozoa with transitional HA after 6 hours of incubation correlated significantly with the fertilization rate of human oocytes. Multivariate discriminant analyses selected six sperm HA and acrosome reaction variables of predictive value in classifying semen samples that achieved fertilization rates above and below 70% threshold. Combination of the selected sperm HA and acrosome reaction variables in seminal fluid and after different times of incubation in capacitation medium classified the samples achieving good or poor fertilization rate with > 80% accuracy. CONCLUSIONS: Assessment of sperm HA and acrosome reaction may be of prognostic value in prediction of human oocyte fertilization rates.

Acrosome↗
PubMed1992

Comparison of maximal myocardial blood flow during adenosine infusion with that of intravenous dipyridamole in normal men.

OBJECTIVE: This study compared quantitatively the efficacy of intravenous adenosine and dipyridamole for pharmacologic induction of myocardial hyperemia. BACKGROUND: Pharmacologic vasodilation is used increasingly for induction of myocardial hyperemia in conjunction with radionuclide imaging of myocardial blood flow. Although both intravenous dipyridamole and adenosine have been used, the magnitude of hyperemia induced by these agents and the hyperemia to baseline blood flow ratios have not been quantified and compared. METHODS: Twenty normal volunteers were studied with dynamic positron emission tomography (PET) and intravenous nitrogen-13 ammonia. Myocardial blood flow was quantified with a two-compartment tracer kinetic model. RESULTS: Myocardial blood flow at rest averaged 1.1 +/- 0.2 ml/min per g and increased significantly to 4.4 +/- 0.9 ml/min per g during adenosine and 4.3 +/- 1.3 ml/min per g after dipyridamole administration. Hyperemia to baseline flow ratios averaged 4.3 +/- 1.6 for adenosine and 4.0 +/- 1.3 for dipyridamole. The average flow ratios and the maximal flows achieved were similar for both agents, but there was considerable variation in the individual response to these agents, as indicated by the range of hyperemia to baseline flow ratios (from 2.0 to 8.4 for adenosine and from 1.5 to 5.8 for dipyridamole). In addition, the hyperemic responses to dipyridamole and to adenosine differed by greater than 1 ml/min per g in nine subjects. CONCLUSIONS: Despite these inter- and intraindividual differences, we conclude that both agents are equally effective in producing myocardial hyperemia.

Adenosine↗
PubMed1992

Differential sperm performance as judged by the zona-free hamster egg penetration test relative to differing sperm penetration techniques.

A prospective study on 61 unselected semen samples from infertile patients was conducted to evaluate the effects of sperm preparation techniques on the outcomes of the zona-free hamster egg penetration test (HEPT) to assess the in-vitro fertilizing capacity of spermatozoa. Each semen sample was divided into two equal portions before separation of the spermatozoa from seminal plasma either by the single-tube swim-up method, or using a two-layer discontinuous Percoll gradient. Spermatozoa were incubated overnight for initiation of capacitation after which HEPT was performed. The swim-up spermatozoa were further divided into two subgroups before HEPT as follows: with or without (control) treatment for 20 min with 50% (v/v) pooled, human follicular fluid (hFF) which had not been heat-inactivated. It was demonstrated (P less than 0.05) that the Percoll-separated spermatozoa exhibited higher penetration scores (percentage penetration rate and penetration index) than the control or the hFF-treated swim-up spermatozoa. A short exposure (20 min) to hFF significantly increased the penetration scores in HEPT for swim-up spermatozoa (P less than 0.05) but the average results were still significantly lower (P less than 0.05) than those of the Percoll separated spermatozoa, which had received no hFF treatment. Based on these findings, we conclude that the Percoll separation technique is better than the centrifugal pelleting and single-tube swim-up technique for reducing the false-negative results in HEPT. In addition, the use of hFF can significantly improve the performance of the swim-up sperm samples in HEPT.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Comparative study on the use of human follicular fluid or egg yolk medium to enhance the performance of human sperm in the zona-free hamster oocyte penetration assay.

A prospective study was conducted on 61 unselected semen samples from infertile patients to compare the efficacy of human follicular fluid (hFF) or TEST-egg yolk medium treatment in enhancing sperm performance in the zona-free hamster oocyte penetration (HOP) test. Both hFF and TEST-egg yolk enhanced penetration scores significantly in the HOP test in comparison with the control swim-up sperm preparation. The TEST-egg yolk medium treatment, however, exhibited the highest penetration scores, and there were higher percentages of preparations passing the 10 or 20% penetration rate cut-off point with sperm exposed to the TEST-egg yolk medium than those exposed to hFF. These results indicate that modification of the original HOP-test protocol by incorporation of TEST-egg yolk medium gives a greatly increased penetration rate when compared to the addition of hFF in such a system.

Animals↗
PubMed1992

Quantitative skin blanching assay of corticosteroid creams using tristimulus colour analysis.

The potencies of four proprietary corticosteroid creams were ranked using blanching measured by a tristimulus colour analyser as an index. Intra-subject variation was measured in a trial using a single subject while in a second study inter-subject variation was quantified using six volunteers. Discriminative parameters were derived from the extended multiple-point chromaticity coordinates L* and a* recorded after application of the steroid creams under occlusion. Analysis of variance of the data using the linear regression model was followed by Tukey's multiple comparison tests. Ranking of the creams using parameters of the pharmacodynamic response corresponded with the generally accepted rank order of the potencies of the corticosteroid creams. It is proposed that this multiple-point skin blanching assay of topical corticosteroids using an internationally accepted clear measurement standard and the subsequent data analysis be adopted as a standard protocol.

Administration, Topical↗
PubMed1992

Phylogenetic analysis of 48 papillomavirus types and 28 subtypes and variants: a showcase for the molecular evolution of DNA viruses.

Papillomaviruses are attractive models for studying the molecular evolution of DNA viruses because of the large number of isolates that exhibit genomic diversity and host species and tissue specificity. To examine their relationship, we selected two amino acid sequences, one of 52 residues within the early gene E1 and the other of 44 residues within the late gene L1, which allowed insertion- and deletion-free alignment of all accessible papillomavirus sequences. We constructed phylogenetic trees from the amino acid and corresponding nucleotide sequences from 28 published and 20 newly determined animal and human papillomavirus (HPV) genomic sequences by using distance matrix, maximum-likelihood, and parsimony methods. The trees agreed in all important topological aspects. One major branch with two clearly separated clusters contained 11 HPV types associated with epidermodysplasia verruciformis. A second major branch had all the papillomaviruses involved in genital neoplasia and, in distant relationship, the cutaneous papillomaviruses HPV type 2a (HPV-2a), HPV-3, and HPV-10 as well as the "butcher's" papillomavirus HPV-7 and two simian papillomaviruses. Four artiodactyl (even-toed hoofed mammal) papillomaviruses, the cottontail rabbit papillomavirus, and avian (chaffinch) papillomavirus type 1 formed a third major branch. Last, four papillomaviruses exhibited little affinity to any of these three branches; these were the cutaneous types HPV-1a, HPV-4, and HPV-41 and B-group bovine papillomavirus type 4. The phylogeny suggests that some branches of papillomavirus evolution are restricted to particular target tissues and that a general process of long-term papillomavirus-host coevolution has occurred. This latter hypothesis is still conjectural because of bias in the current data base for human types and the paucity of animal papillomavirus sequences. The comparison of evolutionary distances for the most closely related types with those of 28 subtypes and variants of HPV-2, HPV-5, HPV-6, HPV-16, and HPV-18 supports the type as a natural taxonomic unit, with subtypes and variants being expressions of minor intratype genomic diversity similar to that found in the natural populations of all biological species. An exception to this seems to be HPV-2c, which has an evolutionary distance from HPV-2a of the intertype magnitude and may eventually have to be regarded as a distinct type. We describe an experimental approach that estimates the taxonomic and phylogenetic positions of newly identified papillomaviruses without viral isolation and complete genomic sequencing.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗