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Biomedical subjects

S K Yap

Publications and source records attributed to S K Yap.

11 recordsLinked to original sources
PubMed2000

Effects of irradiance and spectral quality on leaf structure and function in seedlings of two Southeast Asian Hopea (Dipterocarpaceae) species.

We studied the development of leaf characters in two Southeast Asian dipterocarp forest trees under different photosynthetic photon flux densities (PFD) and spectral qualities (red to far-red, R:FR). The two species, Hopea helferi and H. odorata, are taxonomically closely related but differ in their ecological requirements; H. helferi is more drought tolerant and H. odorata more shade tolerant. Seedlings were grown in replicated shadehouse treatments of differing PFD and R:FR. We measured or calculated (1) leaf and tissue thicknesses; (2) mesophyll parenchyma, air space, and lignified tissue volumes; (3) mesophyll air volumes (V(mes)/A(surf)) and surfaces (A(mes)/A(surf)); (4) palisade cell length and width; (5) chlorophyll/cm and a/b; (6) leaf absorption; and (7) attenuance/absorbance at 652 and 550 nm. These characters varied in response to light conditions in both taxa. Characters were predominantly affected by PFD, and R:FR slightly influenced many characters. Leaf characters of H. odorata were more plastic in response to treatment conditions. Characters were correlated with each other in a complex fashion. Variation in leaf anatomy is most likely a consequence of increasing leaf thickness in both taxa, which may increase mechanical strength and defense against herbivory in more exposed environments. Variation in leaf optical properties was most likely affected by pigment photo-bleaching in treatments of more intense PFD and was not correlated with A(max). The greater plasticity of leaf responses in H. odorata helps explain the acclimation over the range of light conditions encountered by this shade-tolerant taxon. The dense layer of scales on the leaf undersurface and other anatomical characters in H. helferi reduced gas exchange and growth in this drought-tolerant tree.

Journal Article↗
PubMed1998

Frontal sinus mucoceles causing proptosis--two case reports.

Paranasal sinus mucoceles can present with a multitude of different symptoms including ophthalmic disturbances. We describe two patients with frontal sinus mucoceles presenting with non-axial proptosis, and give details of their presentation, investigations and treatment. Possible ocular manifestations of mucoceles and the diagnostic imaging techniques used are discussed. The treatment of mucoceles is reviewed. It is stressed that a team approach involving the ophthalmologist, otolaryngologist and radiologist is essential for accurate diagnosis and management.

Adult↗
PubMed1997

Quality of life survey among day release patients at View Road Hospital.

OBJECTIVES: The aim of this study was to identify factors that contributed to the chronic patient's quality of life from both the patients' and staff's point of view. We were also interested in any lack of congruence between staff and patient perception as these could have significant implications for planning long-term care. METHOD: Fifty of the patients under the Day Release Scheme at View Road Hospital and their staff were given a modified questionnaire concerning the patients' quality of life. RESULTS: Generally the patients reported satisfaction with life domain items covering their living conditions. The majority felt safe in the current setting, enjoyed their work, their regular outings and parole to the nearby shopping centers. Significant differences were observed between the staff and patients' perception in life domain items relating to general well-being, knowledge and education, relationships, in-patient care, leisure and vocational rehabilitation. The staff group perceived having good food, money, good treatment and in employment as being important to their patients' well-being. Patients emphasised having money, family support or a partner, being employed, having time for recreational activities and eating good food. Having good health, medication and feeling at peace were also considered important by many of our patient. CONCLUSIONS: The findings of the study are discussed with regard to implications in planning rehabilitation services and improving the quality of care given to patients.

Female↗
PubMed1996

Diurnal changes in leaf gas exchange characteristics in the uppermost canopy of a rain forest tree, Dryobalanops aromatica Gaertn. f.

Dryobalanops aromatica Gaertn. f. is a major tropical canopy species in lowland tropical rain forests in Peninsular Malaysia. Diurnal changes in net photosynthetic rate (A) and stomatal conductance to water vapor (g(s)) were measured in fully expanded young and old leaves in the uppermost canopy (35 m above ground). Maximum A was 12 and 10 micro mol m(-2) s(-1) in young and old leaves, respectively; however, because of large variation in A among leaves, mean maximum A in young and old leaves was only 6.6 and 5.5 micro mol m(-2) s(-1), respectively. Both g(s) and A declined in young leaves when T(leaf) exceeded 34 degrees C and leaf-to-air vapor pressure deficit (DeltaW) exceeded 0.025, whereas in old leaves, g(s) and A did not start to decline until T(leaf) and DeltaW exceeded 36 degrees C and 0.035, respectively. Under saturating light conditions, A was linearly related to g(s). The coefficient of variation (CV) for the difference between the CO(2) concentrations of ambient air and the leaf intercellular air space (C(a) - C(i)) was smaller than the CV for A or g(s), suggesting that maximum g(s) was mainly controlled by mesophyll assimilation (A/C(i)). Minimum C(i)/C(a) ratios were relatively high (0.72-0.73), indicating a small drought-induced stomatal limitation to A and non-conservative water use in the uppermost canopy leaves.

Journal Article↗
PubMed1996

Spasmus nutans.

Spasmus nutans is classically described as a triad of nystagmus, head nodding and torticollis. It occurs in children, beginning in infancy and usually disappears in childhood. It is uncommon but its prompt recognition by ophthalmologists, paediatricians and neurologists can provide reassurance to the family of its benign nature. It is important to distinguish it from more serious conditions like gliomas which may present with signs mimicking spasmus nutans. We describe a case of a 3-year-old boy with acquired horizontal pendular nystagmus associated with head nodding and torticollis. The diagnosis of spasmus nutans, its implications and its management are discussed.

Child, Preschool↗
PubMed1992

Post-menopausal smear patterns--a review of vaginal smears in 480 women.

Cytohormonal evaluation was done on the vaginal smears of 480 normal, asymptomatic, post-menopausal women whose ages ranged from 36 to 74 years. About 50% showed atrophic smears consistent with total oestrogen lack. 41% had mild to moderately proliferative smears compatible with sub-optimal oestrogen stimulus. 9% showed a highly proliferative pattern typical of unopposed oestrogen effect and in this group two women had atypical endometrial cells in their smears, which subsequently were found to come from an atypical endometrial hyperplasia and an endometrial adenocarcinoma-in-situ. The clinical relevance of cytohormonal studies in post-menopausal women is briefly discussed.

Adult↗
PubMed1976

Development of a stable sublingual nitroglycerin tablet II: formulation and evaluation of tablets containing povidone.

Stable and pharmaceutically elegant sublingual nitroglycerin tablets were formulated using povidone to retard volatilization of the drug. Formulation and processing variables were investigated to produce an acceptable product. A blend of two grades of povidone, of different degrees of cross-linkage and water solubility, provided stable tablets which exhibited rapid disintegration. Directly compressed sublingual tablets made in this study retained over 80% of the initial nitroglycerin when exposed to the atmosphere at room temperature for 2 months. The direct compression tablets are of good appearance and low friability, and the formulation is readily compressed without problems. An interesting relationship among the hardness, disintegration time, and compaction pressure is described.

Drug Compounding↗
PubMed1975

Factors affecting the kinetic assay of nitroglycerin in dosage forms.

Parameters affecting the spectrophotometric kinetic assay for nitroglycerin are described. It is shown that the assay is highly specific; results are not significantly affected by many of the tablet diluents found in commercially-available nitroglycerin tablets. Further, the assay is insensitive to glycerol, nitrate, nitrite and glyceryl dinitrates. This simple, precise and specific nitroglycerin assay is well suited for routine analysis of the drug in commercial tablets and parenteral solutions in hospital pharmacies.

Chemistry, Pharmaceutical↗