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Biomedical subjects

K Y Chan

Publications and source records attributed to K Y Chan.

At least 109 records · Page 6Linked to original sources
PubMed1989

[MRI in the diagnosis of recurrent cholesteatoma of the petrous bone].

Nine cases of recurrent petrous cholesteatomas have been studied by a 1,5 T MR unit. Gadolinium was injected in 1 case. In all cases, comparison between MR, CT and clinical findings were made. MR allows for accurate topographic study and assessment of cholesteatomas extension, in particular in the posterior fossa and skull base. Relationships with the internal carotid artery and the jugular vein are clearly depicted.

Adult↗
PubMed1988

In vitro growth of Chlamydia trachomatis in conjunctival and corneal epithelium.

This study used primary cultures of conjunctival and corneal epithelial cells from rabbit, monkey and humans to investigate the infection process and host interactions of chlamydia. The epithelial cells were isolated from bulbar and palpebral conjunctivae and the cornea following incubation with EDTA or dispase and microdissection. The cells were trypsinized and grown in microtest wells or Rose Chambers (gelatin-coated glass substratum). The cell origin of the cultured epithelial cells was verified by immunofluorescence staining with anticytokeratins. The cells were nonreactive when stained with antivimentin, a fibroblast marker. The growth kinetics of the cultured epithelial cells were determined by morphological criteria. Cells reached confluency by 5-7 days, and remained as such for 18 days. The cells were maintained as long as 32 days in primary culture. After the cells had attained confluency (5-7 days), they were infected with ocular strains B/TW-5/OT or C/TW-3/OT C. trachomatis. Chlamydial inclusions were identified by light and electron microscopy. Direct FITC C. trachomatis staining (species-specific monoclonal antibody) of the inclusions was used to determine the infectivity of the various types of epithelial cells. The dynamics of the infection process was documented by time lapse photomicroscopy. Small inclusions were identified by 18 hr postinoculation (pi). By 48 hr pi, the inclusions had dramatically increased in size, occupying much of the host perikarya. The reticulate bodies were very active at this time. By 70 to 100 hr pi, the inclusions contained the highly infectious elementary bodies. At this time, rupture of the inclusion and lysis of the infected cells usually occurred.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Biotransformation and pharmacokinetic overview of enoximone and its sulfoxide metabolite.

Enoximone possesses both positive inotropic and vasodilatory activities and may be useful in the treatment of patients with congestive heart failure (CHF). In all animal species investigated (rat, dog, monkey and man), the major urinary metabolite is the sulfide oxidation product (sulfoxide); very little unchanged drug appears in urine. Both in vitro and in vivo animal studies indicate reversibility of the sulfoxidation reaction; therefore, it is presumed that sulfoxidation is reversible in man. In normal healthy subjects, no difference in extent of absorption due to dietary state is observed. In patients with New York Heart Association class III to IV CHF, median terminal disposition half-lives for enoximone and its sulfoxide metabolite are 6.2 to 7.6 hours, respectively. Enoximone and sulfoxide plasma concentrations from high dose intravenous infusion studies in patients with class III to IV CHF were also investigated. The collective data suggest nonlinearity in one or more pharmacokinetic processes, of which one may be saturation of sulfoxidation. No direct relation between enoximone and/or the sulfoxide metabolite plasma concentration and pharmacologic effect has been established.

Absorption↗
PubMed1987

Studies on cellulase production by a Bacillus subtilis.

Bacillus subtilis AU-1 was found to produce carboxymethylcellulase (CMCase) and Avicelase activities in the culture supernatant when grown on a variety of carbohydrates as major carbon source. Maximum CMCase production was obtained in a liquid medium containing 0.2% D (+) raffinose as inducer, 0.5% each of yeast extract, casamino acids and proteose peptone at 50 degrees C and at an initial pH of 6.0. CMCase activity was detected at early log phase of growth, and reached the maximum level at early stationary phase of growth which occurred at the 10th hour of cultivation. The optimal temperature for CMCase activity was 65 degrees C, and the enzyme was highly stable up to 60 degrees C. CMCase synthesis was subjected to catabolite repression by glucose and cellobiose.

Bacillus subtilis↗
PubMed1987

Release of neuronotrophic factor from rabbit corneal epithelium during wound healing and nerve regeneration.

Epithelial neuronotropic factor (ENF) is secreted by cultured epithelial cells of rabbit cornea and conjunctiva, and is active in promoting survival and inducing neurite outgrowth of cultured trigeminal neurons. This study evaluated the relation of ENF to corneal nerve regeneration utilizing a model of heptanol-induced epithelial wounding. The organ culture technique was used to collect ENF from the intact corneal epithelium, and a neuronal bioassay was utilized to quantify ENF. The results revealed no change in ENF secretion either during initial wound closure or after 1 week, when the epithelium had regenerated. However, ENF secretion was elevated 2.4 times in 2 weeks after wounding. Morphometric analysis of corneal nerves stained by gold chloride impregnation showed that the first sign of regeneration of intraepithelial nerves was observed after 2 weeks, and the normal pattern of epithelial neural density was re-established after 3 weeks. However, the neural density was still subnormal (35-47% less than the control) in the wounded epithelium up to 4 weeks after wounding. Thus it appears that a surge in ENF secretion occurred after epithelial regeneration but before nerve regeneration. The results suggest that ENF may mediate corneal nerve regeneration.

Animals↗
PubMed1987

The role of prostaglandins in the nociceptive response induced by intraperitoneal injection of zymosan in mice.

Intraperitoneal injection of zymosan (1 mg in 0.5 ml saline) in mice induces a transient writhing response accompanied by the synthesis of small amounts of prostaglandin E2(PGE2, less than 2 ng) and larger amounts of PGI2 (200 ng per mouse), measured as its non-enzymatic breakdown product, 6-keto-PGF1 alpha. Although both centrally-acting analgesics (morphine, clonidine) and prostaglandin biosynthesis inhibitors (aspirin, indomethacin, ibuprofen) blocked the writhing response to intraperitoneal injection of zymosan, only the latter reduced prostaglandin levels in the peritoneal cavity. The writhing response correlated equally well with PGE2 levels and 6-keto-PGF1 alpha levels when data from mice treated with centrally-acting analgesics were excluded. However, intraperitoneal injection of PGI2, but not PGE2, reversed the analgesia induced by indomethacin in zymosan-injected mice. Centrally-acting agents, but not ibuprofen, blocked the ability of PGI2 to reverse the analgesic activity of indomethacin. PGI2 (2 micrograms per mouse), injected intraperitoneally in otherwise untreated mice, induced writhing. These data indicate that PGI2 is the prostaglandin involved in mediation of the writhing response to zymosan and that prostaglandin biosynthesis inhibitors, but not centrally-acting analgesics, exert their analgesic activity by reducing the peritoneal level of PGI2. It is possible that PGI2 may have the ability to stimulate pain receptors directly in the mouse peritoneal cavity, in addition to its previously recognized ability to sensitize pain receptors to other pain-producing stimuli.

Animals↗
PubMed1987

Efficacy of verapamil in the conversion of supraventricular tachycardia in Singapore children.

The efficacy of verapamil in the conversion of 47 episodes of supraventricular tachycardia in 22 children was evaluated. The age of the patients ranged from 15 days to 10 years. Tachycardia was the main mode of presentation. Ten out of 22 children had viral infections. Two patients developed mild cardiac failure. Six patients had underlying cardiac abnormalities. Forty-four out of 47 episodes of supraventricular tachycardia were converted to sinus rhythm by a single dose of verapamil (0.11 +/- 0.08 mg/kg). No significant side-effects were observed. Intravenous verapamil is an effective and safe drug for the conversion of supraventricular tachycardia in children.

Child↗