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Biomedical subjects

S T Tan

Publications and source records attributed to S T Tan.

At least 19 recordsLinked to original sources
PubMed1997

Hypertelorism: nosologic analysis of 90 patients.

The word hypertelorism is used to describe increased interorbital distance, a condition that is causally and pathogenically heterogeneous. Because not all wide-set eyes are the same, accurate terminology and nosology are critical to understanding and management. Orbital hypertelorism signifies an increased distance between both medial sides and lateral sides of the orbits. Interorbital hypertelorism denotes increased distance only between the inner orbital walls. In this retrospective analysis of 90 patients with hypertelorism, the most common cause was frontonasal malformation (n = 30), a heterogeneous category of nonfamilial disorders including a newly described subgroup, rugose frontonasal malformation. The second most common cause was craniofrontonasal dysplasia (n = 18), a genetic syndrome comprising coronal synostosis, frontonasal anomalies, "frizzy" hair, narrow/sloping shoulder girdle deformity, and longitudinal ridging of nails in association with various truncal and extremity anomalies. Paramedian craniofacial cleft(s) (n = 10) and (sincipital) encephalocele (n = 6) were infrequent causes of hypertelorism. The fifth, miscellaneous category comprised well-defined, mostly chromosomal and syndromic disorders (n = 26). Patients in the various diagnostic categories were designated as having either orbital or interorbital hypertelorism. Hypertelorism also was graded as either first, second, or third degree based on deviation from age- and gender-matched normative data. The etiology and type of hypertelorism influence the selection of operative procedure, whereas the grade of severity indicates the need for surgical correction.

Adolescent↗
PubMed1996

Isolation and characterization of a novel Deinococcus radiodurans mutant abnormally susceptible to mutation induction by UV, gamma-ray, and mitomycin C.

We isolated and characterized a novel, radiation 'hypermutable' mutant of Deinococcus radiodurans. Compared with the wild-type strain D. radiodurans IR, this mutator strain, designated S101, exhibited sensitivity to UV light, gamma-ray, mitomycin C, and N-methyl-N'-nitro-N-nitrosoguanidine. Spontaneous revertants of S101 that restored wild-type phenotype (non-mutability and resistance to these DNA-damaging agents) were also isolated. Furthermore, the increased susceptibility to DNA-damaging agents and mutability observed in S101 could be mimicked by treating D. radiodurans IR with Mn(II) ions. Our results suggest a putative new pathway of DNA repair in the extremely radioresistant bacterium D. radiodurans.

Antibiotics, Antineoplastic↗
PubMed1996

Vertical orbital dystopia.

Many pathologic processes may lead to vertical orbital dystopia. We reviewed 47 consecutive cases seen over a 13-year period. Twenty-nine patients underwent eye leveling procedures to improve cosmesis, 2 of these by camouflage procedures and 27 by orbital translocation. Ten patients had 16 secondary operations. There was one death, serious complications occurred in 3 patients, and nuisance complications occurred in 20 others. Seven patients developed diplopia postoperatively, and in 6 patients it was troublesome. In these, it resolved fully in 2 patients, improved to be of no consequence in 2, and in the remaining 2 troublesome symptoms persisted requiring inferior oblique muscle recession in 1. Binocular vision was never restored when not present preoperatively, and in 3 patients temporary loss occurred. There was an overall modest but significant improvement in appearance after surgery. It is concluded that vertical orbital translocation is rewarding and worthwhile.

Abnormalities, Multiple↗
PubMed1995

Hemifacial hypoplasia and hypomelanosis of Ito.

We present three cases of hemifacial hypoplasia associated with hypomelanosis of Ito. The facial deformity is often severe with marked soft tissue shortage and underlying skeletal hypoplasia posing difficulty in reconstruction. The external ear is relatively uninvolved, although a degree of hypoplasia is usually present. The hallmark of hypomelanosis of Ito is linear depigmentation of skin often associated with asymmetric abnormalities. It is a heterogenous disorder due to chromosomal mosaicism, but cytogenetic confirmation of the diagnosis may be difficult. The relationship between mosaicism and anatomical asymmetry is discussed.

Abnormalities, Multiple↗
PubMed1994

When do ears become prominent?

Non-hypoplastic congenital ear deformities are amenable to non-surgical treatment with splinting in the neonatal period. It is therefore important to determine when the deformity occurs. 100 postal questionnaires were sent to parents to study, retrospectively, the evolution of the prominent ear deformity in their children. 79 questionnaires were returned. As remembered by parents, the deformity was first noted at birth in 48 (61%) children, in 68 (86%) by 6 months and in all cases by 5 years. Therefore a large number of patients with prominent ears could be treated effectively, non surgically, early in life, without anaesthetic and with minimal cost.

Adolescent↗
PubMed1994

A splint for correction of congenital ear deformities.

Fourteen non-hypoplastic congenitally deformed ears were treated with a simple splint with satisfactory results in all but one. These deformities can be treated non-surgically in the early neonatal period, effectively, without anaesthetic, and with minimal cost. We confirm other reports that better results are obtained and a shorter duration of splintage is needed if treatment is started early in the neonatal period. Our neonatal paediatric colleagues and midwives should be encouraged to manage these deformities in this way, and the need for surgical correction may be largely avoided in the future.

Age Factors↗
PubMed1993

Comparing DuoDERM E with scarlet red in the treatment of split skin graft donor sites.

A prospective, randomised, controlled study compared DuoDERM E (DE) with scarlet red (SR) in the treatment of split skin graft donor areas in 60 patients. Healing and donor site comfort were significantly better in the DE group. There was no clinical infection in either group. The wound leakage rate was higher in the DE group, requiring an average of 0.8 replacement dressings per donor site as compared with an average of 0.04 for the SR group. An estimate of the cost per donor site for the first ten days of dressing is given.

Adolescent↗
PubMed1993

A comparison of Zenoderm with DuoDERM E in the treatment of split skin graft donor sites.

A prospective, randomised, controlled study compared Zenoderm (ZM) with DuoDERM E (DE) in the treatment of split skin graft donor areas in 64 patients. The donor site comfort was similar in the two groups. DE usage resulted in significantly faster healing but also a higher leakage rate than ZM. Two patients in the ZM group developed infection in their donor sites. The cost is significantly less with ZM than DE.

Acrylic Resins↗
PubMed1992

Development of a method for the determination of zopiclone in whole blood.

Mass spectrometry in both electron-impact and positive chemical ionisation modes has been used to elucidate the structures of the decomposition products of zopiclone after gas chromatography. A high-performance liquid chromatographic method has been developed for the determination of zopiclone in whole blood. After selective extraction (butyl chloride) the extracts are chromatographed on Spherisorb ODS-5 (5 microns) using dibasic ammonium phosphate-acetonitrile (40:60). The zopiclone is measured by ultraviolet detection with a limit of quantitation of 4 ng/ml. This method has been successfully applied to the determination of zopiclone in post-mortem blood. Zopiclone levels found in five post-mortem cases are presented.

Azabicyclo Compounds↗
PubMed1992

Lignocaine vs bupivacaine in prominent ear correction: a controlled trial.

Thirty patients were assigned to two equal groups to compare the effects of ear infiltration with bupivacaine versus lignocaine prior to correction of prominent ears. There was a statistically significant decrease in narcotic requirement in the first 4 h postoperatively in the bupivacaine group, associated with a decrease in the antiemetic requirement. The choice of local anaesthetic did not significantly affect the incidence of vomiting.

Acetaminophen↗
PubMed1991

Salt-mediated multicell formation in Deinococcus radiodurans.

The highly radiation-resistant tetracoccal bacterium Deinococcus radiodurans exhibited a reversible multi-cell-form transition which depended on the NaCl concentration in the medium. In response to 0.8% NaCl addition into the medium, the pair/tetrad (designated 2/4) cells in a young culture grew and divided but did not separate and became 8-, 16-, and 32-cell units successively. In exponential growth phase, the cells divided in a 16/32 pattern. Potassium ions were equally effective as Na+ in mediating this multicell-formation effect; Mg2+, Li+, and Ca2+ also worked but produced less multiplicity. This effect appears to be species specific. This-section micrographs revealed that in a 16/32-cell unit, eight 2/4 cells were encased in an orderly manner within a large peripheral wall, showing five cycles of septation. Our results suggest the presence of a salt-sensitive mechanism for controlling cell separation in D. radiodurans.

Cell Division↗
PubMed1990

Nucleotide sequence and expression of the isoamylase gene from an isoamylase-hyperproducing mutant, Pseudomonas amyloderamosa JD210.

The isoamylase gene (ISO) of Pseudomonas amyloderamosa JD210, an isoamylase-hyperproducing mutant, was cloned in an isoamylase-deficient and transformable mutant strain K31. By deletion analysis, the ISO gene was found to be located within a 3.3 kilobases BamHI fragment. Its nucleotide sequence contained an open reading frame of 2328 nucleotides (776 amino acids) encoding a secreted isoamylase precursor. The ISO gene fragment was inserted into plasmids pKT230 and pBR 322 in opposite orientations. The expression of the ISO gene in the constructed plasmids was compared in P. amyloderamosa K31, Pseudomonas aeruginosa PAO1-161, Pseudomonas putida mt-2 and Escherichia coli HB101. In all transformed cells, the majority of the isoamylase produced was secreted and higher isoamylase activities were obtained in transformats with the transcriptional direction of the ISO gene similar to the nearby drug-determinant gene of the vector.

Amino Acid Sequence↗
PubMed1990

Manganese(II) induces cell division and increases in superoxide dismutase and catalase activities in an aging deinococcal culture.

Addition of Mn(II) at 2.5 microM or higher to stationary-phase cultures of Deinococcus radiodurans IR was found to trigger at least three rounds of cell division. This Mn(II)-induced cell division (Mn-CD) did not occur when the culture was in the exponential or death phase. The Mn-CD effect produced daughter cells proportionally reduced in size, pigmentation, and radioresistance but proportionally increased in activity and amount of the oxygen toxicity defense enzymes superoxide dismutase and catalase. In addition, the concentration of an Mn-CD-induced protein was found to remain high throughout the entire Mn-CD phase. It was also found that an untreated culture exhibited a growth curve characterized by a very rapid exponential-stationary transition and that cells which had just reached the early stationary phase were synchronous. Our results suggest the presence of an Mn(II)-sensitive mechanism for controlling cell division. The Mn-CD effect appears to be specific to the cation Mn(II) and the radioresistant bacteria, deinococci.

Catalase↗
PubMed1987

Mechanism of neurotensin depolarization of rabbit colonic smooth muscle.

The aims of this study were (1) to measure the effect of neurotensin on the membrane potential of circular muscle of the distal colon of the rabbit and (2) to determine the mechanism by which neurotensin affects the membrane potential of this tissue. The membrane potential was measured with microelectrodes placed intracellularly and the double sucrose gap. Neurotensin (10(-11) M to 10(-7) M) dose-dependently decreased the membrane potential. The maximum decrease in membrane potential occurred with 10(-9) M neurotensin. The ED50 of neurotensin depolarization of the membrane potential was 0.87 +/- 0.33 X 10(-10) M. The frequency of the slow waves was unchanged after neurotensin. The voltage response to a constant current pulse decreased as the concentration of neurotensin increased. The amplitude of the voltage response after a 0.6 microA current pulse decreased by 6 +/- 0.5 mV after neurotensin (10(-7) M) compared to the Krebs control (P less than 0.05). Decreasing the [Na+]o to 0-23 mM did not affect the decrease in membrane potential after neurotensin. However, perfusion with a test solution containing no added Ca2+ or verapamil (10(-5) M) inhibited neurotensin depolarization of the tissue. Evidence was found that neurotensin depolarizes colonic circular smooth muscle, and the decrease in membrane potential is associated with an increase in conductance which is dependent on influx of Ca2+.

Animals↗
PubMed1987

Effects of bethanechol and the octapeptide of cholecystokinin on colonic smooth muscle in the cat.

The aim of this study is to compare the action of the cholinergic agonist, bethanechol, with the action of the octapeptide of cholecystokinin (CCK-OP) on feline circular colonic smooth muscle membrane potential and isometric tension, using the double sucrose gap. Depolarization of the membrane greater than 10 mV by K+ or bethanechol increased tension and spontaneous spike activity. CCK-OP (10(-9) M) depolarized the membrane (6.1 +/- 1.3 mV) without an increase in tension or spike activity. Depolarization of the membrane by increasing [K+]o was associated with a decrease in the membrane resistance. The slow-wave duration (2.3 +/- 0.2 s) was unchanged by administration of K+ or bethanechol but was prolonged after increasing concentrations of CCK-OP. The maximum effect occurred at a 10(-10) M concentration of CCK-OP (4.5 +/- 0.4 s, P less than 0.01). At higher concentrations of CCK-OP (greater than 10(-10) M), the slow-wave pattern became disorganized. Addition of increasing concentrations of [K+]o or bethanechol, but not CCK-OP, stimulated a concentration-dependent increase in the maximum rate of rise (dV/dtmax) of an evoked spike potential. These studies suggest 1) bethanechol decreased the membrane potential without altering the slow-wave activity, whereas CCK-OP has a minimal effect on the membrane potential but distorted the slow-wave shape; 2) an increased amplitude of the spike and dV/dtmax of the spike were associated with an increase in phasic contractions after bethanechol or increased [K+]o; 3) the lack of an increase in the spike amplitude and the dV/dtmax to CCK-OP was associated with no increase in phasic contraction.

Animals↗
PubMed1987

Effect of tetraethylammonium on an evoked spike potential in feline colonic muscle.

The purpose of these studies is to examine the contribution of calcium influx and potassium efflux to the amplitude and maximum rate of rise of an evoked spike potential in colonic circular smooth muscle. The double sucrose gap was used to record changes in the membrane potential after passing a constant depolarizing current. Tetraethylammonium (TEA) (5 mM) increased the amplitude of the evoked potential to 58 +/- 5 mV (P less than 0.001) from 32 +/- 4 mV in regular Krebs solution. The duration of the potential increased from 121 +/- 3 to 216 +/- 5 ms when a solution of 5 mM [TEA+]o bathed the tissue. The addition of [TEA+]o did not alter the dV/dtmax of the evoked spike. Other K+ channel blockers, cesium and 4-aminopyridine, did not alter the spike potential. Verapamil (10(-6) M) decreased the dV/dtmax of the evoked potential recorded from tissue bathed in 4.5 and 40 mM [K+]o. Verapamil also decreased the amplitude of the spike potential in tissue pretreated with 5 mM TEA. These studies suggest that the amplitude of an electrically evoked spike potential is dependent on Ca2+ influx in circular colonic muscle and an increase in K+ efflux, which occurs early after the current pulse, limits the amplitude of the evoked potential.

Animals↗
PubMed1986

Simple method to demonstrate radiation-inducible radiation resistance in microbial cells.

A simple method for detection of radiation-inducible radiation resistance was developed by irradiating aliquots (0.01 ml) of cell suspension on agar plates. Part of each experimental plate was subjected to an induction treatment, and subsequent radiation resistance was compared with that of untreated cells on the same plate. The UV radiation resistance of a Micrococcus sp. was increased approximately 1.6 times by an induction treatment. This simple procedure of irradiating cells in a "fixed" position on agar avoided washing, centrifugation, and cell enumeration required in traditional methods.

Agar↗