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Biomedical subjects

H Y Lau

Publications and source records attributed to H Y Lau.

At least 37 records · Page 2Linked to original sources
PubMed1996

Seven fractions of twice daily high dose-rate brachytherapy for node-negative carcinoma of the mobile tongue results in loss of therapeutic ratio.

From June 1989 to December 1993, a Phase I/II protocol using high dose-rate (HDR) interstitial brachytherapy for early stage node-negative squamous cell carcinoma of the mobile tongue was undertaken to assess the toxicity and efficacy of this modality. A total of 27 patients were treated: T1-10 patients, T2-15 patients, and T3-two patients. Seven fractions x 6.5 Gy of HDR brachytherapy were given on a twice daily schedule, with a minimum interval time of 6 h, over a period of 3.5 days. The actuarial tumor control probability after HDR brachytherapy was 53% at 5 years. Local control rates for the T1 and T2 tumors were lower than comparable historical controls treated at our institution using low dose-rate (LDR) radium or cesium needle implants and iridium wire implants. This is despite the fact that the HDR schedule was calculated by the linear quadratic formula to have equal tumor killing effects as 60 Gy in 6 days of LDR radiation. In addition, there was a trend towards higher incidence of severe complications for the HDR patients compared to historical controls treated with LDR. We would caution against the use of this schedule of HDR brachytherapy until further studies are done.

Actuarial Analysis↗
PubMed1996

Short communication: CT-MRI image fusion for 3D conformal prostate radiotherapy: use in patients with altered pelvic anatomy.

We describe the application of CT-MRI fusion software for 3D conformal radiotherapy in two patients with localized prostate cancer who had significantly altered pelvic anatomy due to prior surgery. Patient A had a hemipelvectomy for fibrosarcoma and Patient B had an abdominoperineal resection (APR) for rectal carcinoma. Using the Picker AcQSIM 3D treatment planning software equipped with CT-MRI fusion capabilities, we were able to construct 3D conformal treatment plans for the two patients. The CT-MRI fusion was invaluable in the 3D conformal treatment planning of these cases with distorted pelvic anatomy. It allowed for accurate identification of the clinical target volume (CTV) and was also able to better visualize normal structures so that the radiation beams could be placed to minimize toxicity to the normal tissues.

Adenocarcinoma↗
PubMed1994

Effects of beta 2-adrenergic agonists on isolated guinea pig lung mast cells.

The mast cell protective effects of the newly developed long-acting beta 2-agonists salmeterol and formoterol were compared with those of conventionally used beta 2-agonists, non-specific beta-agonists, disodium cromoglycate (DSCG) and theophylline. With the exception of DSCG, all the test agents inhibited ovalbumin-induced histamine release from enzymically dispersed guinea pig lung mast cells in a dose-dependent fashion. At the maximum concentration tested, theophylline produced the highest level of protection, inhibiting up to 90% of ovalbumin-induced histamine release whereas DSCG produced only 10% inhibition. The maximum inhibition produced by all the beta 2-agonists tested was around 45%. While salmeterol was equipotent with salbutamol, formoterol was at least a 100-fold more potent. Hence the present study confirmed the previously reported mast cell stabilizing actions of conventional beta 2-agonists and extended the observation to the newly developed long-acting analogues.

Adrenergic beta-2 Receptor Agonists↗
PubMed1994

Effects of long-acting beta 2-adrenoceptor agonists on mast cells of rat, guinea pig, and human.

The effects of two recently developed long-acting beta 2-adrenoceptor agonists, formoterol and salmeterol, on mast cells from different sources were compared with those of the prototype short-acting analogue, salbutamol. With the exception of high concentrations of salmeterol (> 10(-5) M), none of the tested beta 2-adrenoceptor agonists inhibited the anti-IgE-induced histamine release from rat peritoneal mast cells. In contrast, all three compounds dose dependently inhibited the immunologically induced histamine release from isolated lung mast cells of guinea pig and human at concentrations < or = 10(-5) M.

Adrenergic beta-Agonists↗
PubMed1992

Blunt traumatic disruption of the thoracic aorta: a rare injury in children.

Rupture of the thoracic aorta secondary to blunt chest trauma is an exceedingly uncommon injury in pediatric patients. We present a case of blunt traumatic aortic disruption in a 10-year-old child who was successfully managed by primary aortic repair using partial cardiopulmonary bypass. The epidemiology and pathophysiology of this injury, with particular reference to children, is reviewed. The ongoing controversies regarding the diagnosis and operative management of this injury are summarized.

Aorta, Thoracic↗
PubMed1991

Mast cells from human gastric mucosa: a comparative study with lung and colonic mast cells.

Mast cells isolated from human gastric mucosa released histamine on challenge with IgE-directed ligands and calcium ionophores but were essentially unresponsive to a variety of non-immunological stimuli. Moreover, immunologically induced histamine secretion from these cells was inhibited by a number of anti-allergic agents including anti-asthmatic chromones, beta-adrenoceptor agonists and phosphodiesterase inhibitors. In total, these data indicate that mast cells from the human gastric mucosa are in many respects functionally similar to their lung and colonic counterparts.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1991

The human skin mast cell: a comparison with the human lung cell and a novel mast cell type, the uterine mast cell.

The functional and histochemical properties of isolated mast cells from human skin, uterine myometrium and lung parenchyma were compared. The skin cell showed a marked difference in responsiveness to both secretagogues and anti-allergic compounds when compared to mast cells from the uterus and lung. The latter cell types responded more strongly to immunologically-directed ligands and calcium ionophores than the skin cell. However, the skin cell released histamine in response to a wide variety of polycationic compounds whilst the lung and uterine cells were essentially refractory to these agents. The antiallergic drugs, disodium cromoglycate (DSCG) and nedocromil sodium, were weakly inhibitory against the skin cell but were in contrast more effective against the lung and uterine cells.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1991

Topical sucralfate: effective therapy for the management of resistant peristomal and perineal excoriation.

Peristomal and perineal excoriation commonly occurs despite preventive measures. Drainage from around gastrostomy tubes or ongoing perineal soilage after a pull-through procedure can lead to chemical irritation, cutaneous denudation, and chronic discomfort. A multitude of topical agents have been tried with variable results. We present our experience using topical sucralfate. Fifteen patients with stomal or perineal skin ulceration were treated with topical sucralfate only after other agents had failed. Clinical photographs were obtained first. Sucralfate, prepared as either a powder or an emollient, was liberally applied to the affected area during diaper changes or when the stomal appliance was emptied. For tube gastrostomy sites, sucralfate was applied every 4 to 6 hours as required to maintain a visible layer. In 13 patients, complete healing occurred. Recovery time was dependent on the severity and extent of skin denudation. Partial healing occurred in one patient. In another patient, the skin excoriation healed but a residual candidal rash required addition of an antifungal agent. General observations included: (1) a lag time of 2 to 3 days before visible healing was evident; (2) healing occurred from the perimeter; (3) sucralfate was soothing and reduced discomfort; (4) it was ineffective for fungal dermatitis; and (5) sucralfate did not appear to have toxic or systemic effects. Topically applied sucralfate is soothing, safe, and effective.

Abdomen↗
PubMed1991

The absence of clinically significant tracheomalacia in patients having esophageal atresia without tracheoesophageal fistula.

The association of tracheomalacia (TM) with esophageal atresia (EA) has been well described. This study attempted to find a correlation between the severity of TM and the presence or absence of an associated tracheoesophageal fistula (TEF) in patients with EA. A review of all patients presenting at this institution with EA through the years 1970 to 1990 was carried out. Six patients with EA without fistula (type A) and 61 patients having EA with fistula (types B, C, D, and E) were analyzed. Five of the six type A patients required esophageal dilatations and antireflux procedures; none had clinically significant TM. Thirty-five of the 61 patients with fistula required esophageal dilatation, and 8 had an antireflux procedure; 11 (18%) required either long-tube tracheostomy or aortopexy for TM. This small study supports a recent hypothesis of different embryological events resulting in different types of esophageal and tracheal anomalies. When EA occurs without fistula, it appears that no significant alteration in tracheal development occurs.

Abnormalities, Multiple↗
PubMed1991

Emergency separation of conjoined twins.

Female omphalopagus conjoined twins were successfully delivered vaginally and required emergency surgical separation shortly after birth for gastroschisis. Shared tissue included conjoined bowel; one twin also had a complex cloacal abnormality and patent urachus. A 2-year follow-up is presented. A review of the relevant literature confirms that this is the first example of gastroschisis conjoining omphalopagus twins.

Abdominal Muscles↗
PubMed1990

Effects of antihistamines on isolated rat peritoneal mast cells and on model membrane systems.

We have examined the effect of a range of histamine H1- and H2-receptor agonists and antagonists on rat peritoneal mast cells. Most of the compounds had a dual action: at low concentrations they inhibited the histamine release produced by immunologic activation of the cell whereas at higher concentrations they themselves induced a cytotoxic release of the amine. The test agents did not affect intracellular levels of cyclic AMP. In model systems, the majority of the drugs had no effect on the integrity of artificial liposomes but did protect rat erythrocytes against osmotic shock. We then propose that these agents produce their effects on mast cells by a direct action on the cell membrane, with low concentrations becoming incorporated into the bilayer in such a way as to stabilize the structure and high concentrations disrupting the membrane and leading to cell lysis.

Animals↗
PubMed1990

Mast cells from human colonic mucosa and submucosa/muscle: a comparison with human lung mast cells.

The functional properties of enzymically dispersed mast cells from human lung parenchyma, colonic mucosa and colonic submucosa/muscle were compared. In general, the cells responded in a similar fashion to the histamine releasing action of a variety of immunological and non-immunological stimuli. However, some differences were observed in their responses to anti-allergic compounds. In total, these data indicate that there are subtle variations between human colonic and pulmonary mast cells but that these differences are much less sharply defined than in the rodent.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1990

Balloon catheter dilatation for hypertrophic pyloric stenosis.

Balloon dilating catheters (BDC) have provided a non-operative means of managing obstructive lesions within the gastrointestinal tract. Its potential utility in infants with hypertrophic pyloric stenosis (HPS) was studied. Six patients with HPS underwent balloon catheter dilatation of the pylorus under the direct observation of the surgeon. The pylorus was exposed using a standard right upper quadrant incision. The BDC was passed transorally into the stomach and manipulated into the pyloric canal by the surgeon. The balloon was inflated with saline to a maximum pressure of 50 psi for 2 minutes. Four patients were dilated with a 10-mm diameter balloon catheter, and in two patients, a 15-mm balloon was used. Success was defined as the complete and longitudinal disruption of the seromuscular ring without violation of mucosal integrity. Using this criterion, none had successful pyloric dilatation. No disruption occurred in three patients, partial disruption in two. These patients subsequently underwent a Ramstedt pyloromyotomy. Complete disruption was observed in one; however, a breach of the mucosa was evident. This was repaired without incident. All seromuscular breaks occurred at the point of vascular entry along the lesser curve, presumably the weakest point of the ring. Pyloric dilatation using BDC does not reliably disrupt the muscular ring. This preliminary report recognizes that major refinements must occur before this method will supplant the time-honored surgical pyloromyotomy for HPS.

Catheterization↗
PubMed1989

Effects of antihistamines on isolated human lung mast cells, basophil leucocytes and erythrocytes.

Low concentrations of H1- and H2-receptor directed compounds inhibited the immunologic secretion of histamine from human lung mast cells and basophil leucocytes and protected human erythrocytes from hypotonic lysis. Higher concentrations induced a release of the amine from the histaminocytes. These results are discussed in terms of the possible membrane effects of the test compounds.

Basophils↗
PubMed1988

Effects of sodium cromoglycate and nedocromil sodium on histamine secretion from human lung mast cells.

Sodium cromoglycate and nedocromil sodium produced a dose dependent inhibition of histamine secretion from human pulmonary mast cells obtained by bronchoalveolar lavage and by enzymatic dissociation of lung parenchyma. Both compounds were significantly more active against the lavage cells than against the dispersed lung cells, and nedocromil sodium was an order of magnitude more effective than sodium cromoglycate against both cell types. Tachyphylaxis was observed with the parenchymal cells but not with the lavage cells. Nedocromil sodium and sodium cromoglycate also inhibited histamine release from the lavage cells of patients with sarcoidosis and extrinsic asthma.

Asthma↗