Biomedical subjects

E C Chan

Publications and source records attributed to E C Chan.

At least 91 records · Page 5Linked to original sources

PubMed1993

Plasma corticotropin-releasing hormone, beta-endorphin and cortisol inter-relationships during human pregnancy.

To investigate the dynamic relationships among corticotropin-releasing hormone (CRH), beta-endorphin (beta EP), cortisol and obstetric events during pregnancy, blood samples were collected from 193 women at 28 weeks, 38 weeks, during labour and on the second postnatal day. Cord blood at delivery was also obtained. We found that: (1) Maternal plasma CRH, beta EP and cortisol rose from 28 to 38 weeks. (2) During the third trimester maternal plasma CRH and beta EP were correlated (r = 0.30, p < 0.001). (3) During labour, no correlations were found among maternal plasma CRH, beta EP and cortisol. (4) Maternal CRH at labour and the duration of labour were not correlated. (5) Maternal plasma CRH tended to be higher in women who delivered early (more than seven days prior to estimated date of confinement [EDC]) relative to those who were on time (within seven days' EDC) or late (greater than seven days after EDC). (6) CRH in maternal plasma at labour and cord blood were correlated (r = 0.29, p < 0.05) as were maternal and fetal beta EP (r = 0.43, p < 0.001). (7) Fetal obstetric difficulty was correlated with fetal beta EP (r = 0.54, p < 0.001). Our findings support the hypothesis that maternal plasma CRH regulates maternal beta EP during the third trimester, but other factors are involved during labour and in response to maternal obstetric stress.

Adult↗

PubMed1992

Beta-endrophin immunoreactivity during human pregnancy.

The human placenta has been implicated as a source of numerous peptide hormones during pregnancy. Since the immunoassay detection of the proopiomelanocortin derived peptide beta-endorphin (beta E) in placental extracts in 1978, it has remained uncertain whether placental beta E immunoreactivity (IR) is 1) secreted into the maternal circulation and 2) opiate receptor active during pregnancy. To elucidate the nature of beta E IR in the placenta, both beta E IR and N-alpha-acetylated beta E (Ac beta E) IR were simultaneously measured in extracts of human pituitaries, placentas, and plasma by two homologous RIAs. Pituitary extracts (n = 6) contained 38 +/- 7 nmol beta E IR per g wet wt tissue (mean +/- SEM), of which only 20 +/- 4 pmol/g were Ac beta E IR. Term placental extracts (n = 19) had 201 +/- 30 fmol/g wet wt total beta E IR and 30 +/- 3 fmol/g wet wt total Ac beta E IR, which comprised 15% of total beta E IR in placental extracts. Total plasma beta E IR rose from 28 weeks gestation (8.5 +/- 0.3 fmol/mL, n = 159) to peak at labor (50 +/- 4 fmol/mL, n = 98; P < 0.01) but total Ac beta E IR was found in only four 28-week (1.7 +/- 0.9 fmol/mL) and 42 labor plasma samples (0.9 +/- 0.1 fmol/mL). Gel filtration chromatography of placental and pituitary extracts showed that while less than 1% of the beta E31-size material was acetylated in the pituitary, up to 60% of the beta E31-size material in placental extracts was acetylated. In pooled third trimester plasma extracts, however, only 4% of the beta E31-size material was acetylated. Furthermore, the ratio of beta E31:beta-lipotropin in pituitary extracts (n = 3) was 0.5; pooled plasma-0.5, and placental extracts (n = 5)-1.2. These data indicate that 1) the placenta extensively N-alpha-acetylates beta E31 destroying its opiate bioactivity while the pituitary does not; 2) beta E IR in pregnant women's plasma is similar to pituitary beta E IR, being mostly nonacetylated and similar in size to beta-lipotropin. These findings are consistent with a pituitary source for the elevated plasma beta E IR found during late pregnancy which may, in turn, be a consequence of elevated plasma concentrations of placentally secreted plasma corticotropin-releasing factor IR present during the third trimester.

Acetylation↗

PubMed1991

Purification of phospholipase C by hydrophobic interaction affinity chromatography.

A simple procedure is described for the purification of phosphatidylcholine-hydrolyzing phospholipase C(PLC). Lecithin, the substrate for PLC, was ligated hydrophobically to octyl-Sepharose in 2 M (NH4)2SO4. The washed lecithin-conjugated resin was then used to purify PLC from crude preparations by affinity chromatography. PLC binds to the lecithin moiety in the presence of Zn2+ and is eluted with an acidic buffer containing EDTA. PLC activity was recovered in the eluate. Both sodium dodecyl sulphate polyacrylamide gel electrophoresis and pI electrofocusing showed that the eluate contained a single monomeric protein with an apparent molecular mass of 66 kDa and a pI of 5.5.

Chromatography, Affinity↗

PubMed1991

Perifused ovine placental tissue secretes beta-endorphin immunoreactivity.

In vitro release of one of the pro-opiomelanocortin (POMC)-derived peptides, the endogenous opioid beta-endorphin (beta EP) has been examined in the sheep placenta by means of a perifusion system. Two zones of the cotyledon, the chorionic villus (highly vascularized fetal and maternal tissues in close apposition) and the maternal basal plate (or capsule), were examined in placenta at two stages of gestation--120 days (119.0 +/- 4.7, N = 4) and 140 days (143 +/- 1.8, N = 5) just before term. The chorionic villous tissue released more beta EP-like immunoreactivity (beta EP-IR) than did the basal plate tissue at both gestational ages. At 120 days' gestation the basal concentration of beta EP-IR released from the chorionic villus was 52 +/- 0.5 fmol mL-1 (n = 4), almost double the maternal basal plate tissue at 28.4 +/- 0.4 fmol mL-1 (n = 8). beta EP-IR secretory capacity increased significantly (P less than 0.05) with advancing gestational age. By Day 140, release had increased 3-4-fold to 181.8 +/- 0.8 fmol mL-1 (n = 16) in the chorionic villous tissue, and to a lesser extent in the basal plate tissue to 50.7 +/- 0.6 fmol mL-1 (n = 14). No stimulation of beta EP-IR secretion was observed in any tissue as a result of 30 min exposure to corticotrophin-releasing hormone (100 nmol L-1), a vital physiological secretagogue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Clinical documentation and occurrence of putative periodontopathic bacteria in human immunodeficiency virus-associated periodontal disease.

Human immunodeficiency virus (HIV)-associated gingivitis (HIV-G) and HIV-associated periodontitis (HIV-P) are two intraoral lesions manifested by patients with HIV infection. Periodontal indices were measured for 87 subjects in 5 study groups: HIV-seropositive patients with healthy periodontium (HIV-H), with HIV-G, or with HIV-P; and non-HIV-infected subjects with healthy periodontium (H) or with adult chronic periodontitis (P). The quantitative clinical parameters were compared and statistically significant intergroup differences were noted. The mean scores on PI and PD do not discriminate between HIV-seropositive and non-HIV-infected seronegative cohorts, but a significant difference in the GI between HIV-H and H was noted. When categories of PD and AL are examined, some differences become apparent. Generally, the PD and AL of HIV-P are not as great as those of P. PI correlates well with GI (r = 0.86) in P, but does not (r = 0.33) in HIV-P. In addition, the occurrence of selected putative periodontopathic bacteria (Porphyromonas gingivalis, spirochetes, and motile eubacteria) in these lesions was determined by brightfield (after staining), darkfield and immunofluorescent microscopy. No difference in microbiological profile in the bacterial groups monitored was found between P and HIV-P. Spirochetes were found to be more abundant than P. gingivalis in the lesions of P and HIV-P. In marked contrast, P. gingivalis was found to be in highest numbers in samples from the gingival crevice of H as determined by indirect immunofluorescence.

Acquired Immunodeficiency Syndrome↗

PubMed1991

Comparison of two popular methods for removal and killing of bacteria from dentures.

A study was undertaken to compare the efficacy of a soaking solution (Efferdent Extra-Strength Denture Cleanser Tablets) to mechanical cleaning with a denture paste (Advanced Formula Dentu-Creme Denture Cleaning Paste) to remove and kill plaque bacteria from removable dentures. The study was conducted in a randomized, four-way crossover fashion with 18 subjects. At each clinic visit, subjects were randomized to one of four treatment regimens: 1) no treatment; 2) brushing with denture paste; 3) soaking in Efferdent; 4) brushing followed by soaking in Efferdent. Microbiological sampling for plaque bacteria was made before and after each treatment. Aliquot samples of 10-fold serial dilutions were plated on supplemented Schaedler Agar (for total anaerobes) and on CVE agar (for fusobacteria). Analysis of covariance was performed on the log10 transformed scores at posttreatment using the pre-treatment scores as covariates. Significant treatment effects were: F(3,41) = 81.60, p less than 0.001 for anaerobes and F(3,50) = 104.38, p less than 0.001 for fusobacteria. Pairwise comparisons using Tukey hsd post hoc tests showed that for total anaerobes, treatments 1 and 2 yielded higher scores than treatments 3 and 4. For fusobacteria, treatment 1 greater than 2 greater than 3 or 4; no difference between treatments 3 and 4. The results demonstrated the superior performance of Efferdent over Dentu-Creme.

Analysis of Variance↗

PubMed1990

Intracellular mechanisms governing the acute phase of beta-endorphin secretion from the corticotrope in vitro.

It is not certain which protein kinase (A, C or both) is involved in the acute phase of beta-endorphin (beta-EP) release stimulated in the corticotrope by vasopressin (VP) and corticotropin-releasing factor (CRF). We have employed an isolated ovine anterior pituitary cell superfusion system to determine the dynamic effects of forskolin, a protein kinase A (PKA) stimulator, and phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator. Both secretagogues stimulated beta-EP release within 5 min and therefore both PKA and PKC are potential mediators of the acute phase of hormonal stimulation of the corticotrope. Pretreatment with PMA specifically desensitized the pituitary cell columns to subsequent PMA exposure while not significantly altering sensitivity to forskolin or 50 mM KCl.

Animals↗

PubMed1990

Mood changes, obstetric experience and alterations in plasma cortisol, beta-endorphin and corticotrophin releasing hormone during pregnancy and the puerperium.

The relationships between mood change, obstetric experience and alterations in plasma cortisol, beta-endorphin (beta-EP) and corticotrophin-releasing hormone (CRH) were examined in a prospective study of 97 primiparous Australian women. Psychological measures were administered between the 28th week of pregnancy and the 3rd postnatal month, including the Profile of Mood States (POMS) and the Montgomery Asberg Depressive Rating Scale (MADRS). Blood samples were collected for cortisol, beta-EP and CRH assay on most of these occasions and during labour. Factor analysis was used to identify key subsets of psychological variables for use in the subsequent analyses. 'Mood disturbance' and 'tiredness' factors peaked at 38 weeks' gestation, while 'difficulty falling asleep' was greatest around the time of birth. Cortisol, beta-EP and CRH concentrations rose significantly as pregnancy advanced and peaked at birth; plasma CRH correlated with plasma cortisol (r = 0.54) and beta-EP (r = 0.32). Women with the highest 'mood disturbance' and MADRS depression scores at 28 weeks' gestation received significantly more pain relief during labour. Those women whose mood deteriorated from 38 weeks' gestation to postnatal day 2 had larger falls in plasma beta-EP after delivery (p less than 0.01) than those women whose mood improved or remained constant. Women in this mood-deteriorated subgroup also had significantly higher MADRS depression scores at 3 months (p less than 0.01). Mild antenatal depression (MADRS greater than 13) occurred in 5.2% of women and mild postnatal depression in 4.7%. Overall, these data suggest a role for circulating CRH in the regulation of maternal cortisol secretion and significant relationships between maternal postnatal mood states and beta-EP and between antenatal mood states and obstetric events.

Adult↗

PubMed1990

Urinary corticotropin-releasing hormone immunoreactivity is elevated during human pregnancy.

Plasma corticotropin-releasing hormone immunoreactivity (CRH IR) rises with gestational age in women. In order to investigate the physiological changes of the hormone in pregnant women's urine, CRH IR was measured by radioimmunoassay in urine collected over a 24-hour period, a blood sample and a subsequent single collection of urine after the 24-hour collection (spot urine). Plasma CRH IR in pregnant subjects, 8682.8 +/- 2063.0 pg CRH IR/ml plasma (mean +/- SEM, n = 25), was significantly higher than that in the non-pregnant controls (7.2 +/- 1.6 pg/ml, n = 5; separate t = 4.21, p = 0.0003, d.f. = 24). Similarly, pregnant women had higher spot urine CRH IR - 54.6 +/- 15.5 pg/mumol creatinine (Cr) versus 5.0 +/- 0.5 pg/mumol Cr (separate t = 3.20, p = 0.0038, d.f. = 24.0) - and 24-hour urine CRH IR - 13.7 +/- 1.2 pg/mumol Cr compared with 7.7 +/- 0.8 pg/mumol Cr (separate t = 4.28, p = 0.003, d.f. = 24.4) than the non-pregnant cohort. The difference between urinary excretion of CRH IR as estimated by 24-hour urine (13.7 +/- 1.2 pg/mumol Cr) and spot urine (54.6 +/- 15.5 pg/mumol Cr) indicated that CRH IR in 24-hour urine may be degraded during storage. The weak associations between plasma and 24-hour urine CRH IR of pregnant women (correlation coefficient r = 0.34, p greater than 0.1), and total 24-hour urine and spot urine CRH IR (r = 0.25, p less than 0.1) further indicate CRH degradation. Plasma and spot urinary CRH IR, however, were strongly correlated (r = 0.80, p = 0.001). The total CRH IR excreted as estimated from the spot urine value (0.5 +/- 0.1 micrograms/day) compared with the total filtered load of CRH IR in the pregnant group (1306.9 +/- 324.6 micrograms/day) showed that 99.97% of the filtered CRH IR was reabsorbed or metabolized by the kidneys. Acidic gel chromatography of spot and 24-hour urine samples showed a CRH IR peak at CRH41 standard elution position (Kd = 0.5), indicating that the molecular form in urine is similar to the 41-residue standard. Pregnancy-induced hypertension correlated positively with plasma CRH IR (r = 0.62, p less than 0.001) and spot urine CRH IR (r = 0.46, p less than 0.01), and negatively with parity (r = -0.60, p less than 0.001). Plasma CRH IR and parity also negatively correlated (r = -0.41, p less than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

Corticotropin-Releasing Hormone↗

PubMed1989

In vitro susceptibilities of oral bacterial isolates to spiramycin.

Four hundred strains of oral bacteria were tested for their susceptibility to spiramycin. Actinobacillus actinomycetemcomitans and most species of Lactobacillus were resistant to the antibiotic. All strains of cariogenic Streptococcus mutans and most strains of bacterial species implicated in adult chronic periodontitis (Bacteroides gingivalis, B. intermedius, and Treponema denticola) were susceptible to spiramycin.

Bacteria↗

PubMed1989

Synthesis and secretion of phospholipase C by oral spirochetes.

Four strains of oral treponemes and Treponema phagedenis Reiter synthesize and secrete phospholipase C (PLC), which was detected by the hydrolysis of p-nitrophenylphosphorylcholine. PLC was detected in gingival crevicular fluid from diseased but not from healthy sulci. The initiation and progression of periodontal lesions may begin with the hydrolysis of membrane phospholipids by PLC.

Choline↗

PubMed1989

Effects of adjunctive treatment of periodontitis with tetracycline and spiramycin.

The present study was undertaken to compare the efficacy of two antibiotics, spiramycin and tetracycline, with a placebo when used adjunctively with scaling and root planing in the treatment of advanced adult chronic periodontitis. This was a double-blind, parallel, randomized trial with one factor (drug) at three levels. Ninety-six patients (mean age 46 +/- 1) were randomly assigned into one of three groups. All groups were scaled and root planed with each respective group receiving either spiramycin, tetracycline, or a placebo for 2 weeks. Two sites with probing depth of at least 7 mm were evaluated and the following clinical parameters were measured at baseline, 2, 8, 12, and 24 weeks: plaque index, bleeding on probing, crevicular fluid, probing depth, and change in the attachment level. The changes in the subgingival bacteria were monitored also using a differential staining technique. Seventy-nine patients completed the study. At the end of 24 weeks, although all three groups had shown clinical improvement when compared to the baseline data, there were no significant intergroup differences in any of the clinical parameters measured. While the proportion of spirochetes were significantly decreased (P less than 0.05) at 2- and 8-week intervals in both tetracycline and spiramycin groups (26% to 0.04% and 28% to 0.04%, respectively), compared to the placebo group (30% to 7%), only in the spiramycin group was the proportion of spirochetes significantly lower than the placebo group at the 24-week interval (3% and 11%, respectively). At week 24, the proportion of spirochetes in the tetracycline group had rebounded to 7%, which was not significantly different from the placebo group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1989

Restriction of placental growth in sheep enhances placental metabolism of fetal beta-endorphin-like immunoreactivity.

The opioid polypeptide beta-endorphin is present in fetal blood but it is not clear whether its source is the fetus or the placenta. We therefore measured beta-endorphin in extracts of fetal femoral arterial and umbilical venous blood plasma in sheep by radioimmunoassay to determine whether the fetus or the placenta is the major source of beta-endorphin in the fetal circulation. Chromatographic analysis of extracts of fetal arterial plasma showed that beta-lipotropin and other precursors of beta-endorphin made only a minor contribution to the immunoreactivity detected. Concentrations of immunoreactive beta-endorphin were higher in the femoral artery than in the umbilical vein in fetal sheep between 113 and 128 days of pregnancy. Therefore the placenta removes beta-endorphin or a closely related polypeptide of fetal origin from the umbilical circulation in sheep at this stage of gestation. Acute hypoxaemia and hypoglycaemia increase the concentrations of immunoassayable beta-endorphin in blood plasma of adult and fetal sheep, but little is known about the effects of chronic hypoxaemia or hypoglycaemia on the circulating levels of beta-endorphin and related polypeptides in the fetus. Therefore we also measured immunoreactive beta-endorphin in blood plasma from fetal sheep in which growth retardation in association with restricted placental growth was produced by removal of endometrial caruncles before mating. Intra-uterine growth retardation was accompanied by chronic hypoglycaemia and chronic hypoxaemia in the fetuses. This was not associated with higher concentrations of beta-endorphin-like immunoreactivity in fetal arterial or umbilical venous plasma, but was accompanied by significantly increased placental extraction of fetal immunoreactive beta-endorphin from the umbilical circulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1988

Differential processing of corticotrophin-releasing hormone by the human placenta and hypothalamus.

The molecular forms of corticotrophin-releasing hormone (CRH) in human placentae and hypothalami were investigated by gel permeation chromatography of water extracts. Hypothalamic extracts produced one peak of immunoreactivity which coeluted with human CRH at Kd = 0.53. Placental extracts, however, had in addition to that peak, two other peaks eluting earlier at the void and at Kd = 0.35-0.38. Tryptic digestion of the middle peak produced immunoreactivity which coeluted with the standard. Larger forms were also found in plasma of women in the third trimester of pregnancy and during labour but not in eluates from superfused placental fragments which had only CRH41-sized material. These data indicate that tissue-specific post-translational processing occurs for CRH, and suggests that the link between synthesis and secretion is more immediate in the placenta than hypothalamus.

Chromatography, Gel↗

PubMed1988

The effect of repetitive haemorrhage on plasma cortisol, beta-endorphin and N-terminal pro-opiomelanocortin in conscious sheep.

We measured the effect of repeated haemorrhagic stress, performed on four consecutive days in conscious adult sheep, on the plasma concentrations of cortisol and ACTH-related peptides to determine whether the pituitary-adrenal response was altered by stress repetition. Peptides from the C-terminus of the ACTH pro-hormone was measured by beta-endorphin RIA. Glycopeptides derived from the N-terminus of the ACTH pro-hormone were measured by tau 3-MSH RIA. The immunoreactive tau 3-MSH in sheep plasma was found to have an apparent molecular weight of approximately 10,000 by gel chromatography through Sephadex G-75, which is similar to the size of the major circulating form of pro-tau-MSH found in human and rat plasma. Daily haemorrhage consistently elevated plasma concentrations of cortisol and pro-tau-MSH. There was no significant difference in the daily responses of either cortisol or pro-tau-MSH when considered individually. However, there was a significant change over the four days in the relationship between the cortisol and pro-tau-MSH responses, as judged by analysis of variance of the difference in daily z-scores of cortisol and pro-tau-MSH. This trend indicated a relative increase in the secretion of pro-tau-MSH from the pituitary compared to the cortisol response, and suggested that repeated exposure to stressful stimuli may alter the pituitary-adrenal-axis.

Animals↗

PubMed1988

Comparison of spiramycin and tetracycline used adjunctively in the treatment of advanced chronic periodontitis.

This study was designed to compare both clinical and microbiological changes during the treatment of advanced periodontal disease with mechanical debridement, with or without the adjunctive use of either spiramycin or tetracycline. The study, which included 96 patients with advanced periodontitis, was performed as a controlled double-blind parallel randomized trial. All patients received thorough scaling and root planing as well as adjunctive placebo or spiramycin or tetracycline. Probing depth measurements, attachment level changes, plaque level, gingival crevicular fluid, bleeding on probing and microbiological evaluation were carried out at baseline, 2-, 8-, 12- and 24-week visits. Seventy-nine patients (24 placebo, 27 tetracycline and 28 spiramycin) completed the study. At 24 weeks there were no intergroup differences in the improvement of any of the clinical parameters. Spiramycin was the only antibiotic which produced a significantly greater decrease in the proportion of spirochaetes than the placebo group at the 24-week visit. It was concluded that mechanical debridement alone was sufficient in decreasing the subgingival bacteria to a level which would result in the return to periodontal health. The study was not long enough to determine whether or not the difference in spirochaete level was an indication that the spiramycin group would have maintained the benefits of treatment for a longer time.

Adult↗

PubMed1988

Isolation of a chymotrypsinlike enzyme from Treponema denticola.

A chymotrypsinlike protease with an Mr of 95,000 was extracted from Treponema denticola ATCC 35405 and was partially purified by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The proteolytic activity was detected in an electrophoretogram containing polyacrylamide that was conjugated to bovine serum albumin. A single band of activity was detected when the T. denticola extract was solubilized and electrophoresed in the presence of sodium dodecyl sulfate. No activity was found in extracts of Treponema vincentii. The enzyme hydrolyzed transferrin, fibrinogen, alpha 1-antitrypsin, immunoglobulin A, immunoglobulin G, gelatin, bovine serum albumin, and a synthetic peptide containing phenylalanine. It did not degrade collagen or synthetic substrates containing arginine or proline. For the hydrolysis of azocoll, the pH optimum of the enzyme was 7.5. Heating at temperatures above 50 degrees C destroyed the activity. Reducing agents and the chelators EDTA and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid increased the enzyme activity, while phenylmethylsulfonyl fluoride, L-1-tosylamide-2-phenylethyl chloromethyl ketone, sulfhydryl reagents, and human serum reduced activity. The ability of the enzyme to hydrolyze a number of humoral proteins suggests that it may be involved in spirochete invasiveness and tissue destruction.

Chymotrypsin↗

PubMed1988

Locomotory characteristics of Treponema denticola.

Locomotion of pathogenic spirochetes has been suggested as a virulence factor in their pathogenesis. Little is known of the locomotory characteristics of oral anaerobic spirochetes. We have determined the optimal conditions for motility of seven strains of Treponema denticola in menstrua of different viscosities. The viscosity for optimum motility for all strains was found to be 9.57 centipoises at 25 degrees C. Under these conditions the average speeds for each strain was computed from the motility tracks as recorded by timed exposures under dark-field microscopy. Differences in speeds were found between the various strains. In addition, we have determined the "persistence" (direct distance/actual pathlength travelled) of cell movement of each strain. Interstrain differences were also noted. These locomotory characteristics contribute to the locomotory phenotypes of the various strains and therefore may aid in their characterization and provide an insight into locomotion as a virulence factor in periodontitis.

Cell Movement↗