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Biomedical subjects

L P Kok

Publications and source records attributed to L P Kok.

At least 19 recordsLinked to original sources
PubMed1996

4D confocal microscopy for visualisation of bone remodelling.

Until recently it was very time consuming and difficult to make three-dimensional (3D) images of newly formed bone. With the advent of confocal technologies and increased computer power, 3D imaging is greatly facilitated. In this paper we demonstrate that enhanced confocal visualisation of newly formed bone is possible when bone is labelled in vivo sequentially with two osteotropic markers (xylenol orange and tetracycline). Computer-assisted reconstruction of the confocal optical sections was achieved through the use of the CONVEX Application Visualisation System (AVS). The computerised image data provides the researcher with ample flexibility in displaying the results. It was found that CSLM combined with AVS is excellent for visualising the remodelling process in three and four dimensions, in which the fourth dimension is time. With this approach visualised bone remodelling has become possible in a manner not easily achieved by other techniques.

Animals↗
PubMed1996

Insomnia in the community.

This study is the first to document the prevalence of insomnia in Malays and Chinese in a Singapore community. The overall rate of insomnia was low at 15.3% with females and Malays at higher risk. Patients with insomnia had significantly higher sleep latency, awakenings at night, as well as a report of not feeling fresh throughout the day. There was an association between insomnia patients with increased stress levels, especially at home, and a higher rate of co-morbid minor psychiatric disorder. However, most patients do not seek medical help, and even less resort to sleeping pills.

Adolescent↗
PubMed1995

Confocal microscopy of false-negative breast aspirates.

Even when using a novel optimized FNA-21 for breast fine-needle aspiration biopsy, our series of 163 breast lesions with consecutive histology, including 110 carcinomas, contained eight cancer cases with a negative cytologic diagnosis. Two consisted exclusively of thick, undiagnosable epithelial fragments and were devoid of detached malignant cells on which the proper diagnosis could have been made. Optical sectioning of the original smears by the confocal microscope allowed us to reclaim from these epithelial fragments the diagnostic abnormal chromatin patterns, even in the air-dried smears. In the thin optical sections the cancerous tubular or cribriform growing pattern was visualized. The high spatial resolution of the confocal microscope can be further exploited with the application visualization system (AVS). The AVS three-dimensional reconstructions allow us to see the surface of these malignant cells in a detail approaching that of scanning electron microscopy. Furthermore, the internal aspects of the malignant nuclei can be visualized with these techniques.

Biopsy, Needle↗
PubMed1995

Semiautomatic PAPNET analysis of proliferating (MiB-1-positive) cells in cervical cytology and histology.

With the event of microwave-antigen retrieval it has become possible to detect proliferating cells (staining positive for MiB-1) in cervical smears containing epithelial fragments and in paraffin sections containing cancerous cervical epithelium. The PAPNET system, using neural network computing, is able to collect from the slides epithelial fragments with positive-staining nuclei. The nuclei in epithelial fragments are semiautomatically quantitated using the PAPNET-digitized images. The parameter PPN (proportion-positive nuclei), in which the nuclear area of the positive nuclei is taken into account, prove to be superior to the proliferation index for distinguishing moderate dysplasia from carcinoma in situ. In repair cells, all four quantitative parameters are close to those of moderate dysplasias, indicating that this method is unfit for distinguishing these two entities. However, we show that MiB-1 staining is valuable for the analysis of "false-negative" and "false-positive" smears, and for quantifying proliferation in sections of carcinoma in situ.

Antigens, Nuclear↗
PubMed1995

N-[18F]-fluoroalkylation of noraporphines: microwave versus thermal treatment.

A comparable study of microwave versus thermal heating is described for the N-[18F]-fluoroalkylation of noraporphines. As compared to thermal treatment, different products were obtained during microwave treatment. Thermal treatment resulted in the loss of the protection of the catechol functionality of the noraporphines (O-deacylation), whereas during microwave treatment N-[18F]-fluoroalkylation was observed. The results described in this report might suggest that the influence of microwaves on chemical transformations is not exclusively thermal.

Alkylation↗
PubMed1995

A controlled double-blind trial of moclobemide and imipramine in the treatment of depression.

The aim of this study is to compare the antidepressant efficacy and side effects of moclobemide with imipramine (a standard antidepressant). Moclobemide is a reversible inhibitor of monoamine-oxidase-A (RIMA) with selectivity for the MAO type A isoenzyme. Thirty-two patients who met DSM-3R criteria for major depressive episode or dysthymia were randomly assigned to receive either moclobemide or imipramine in a double-blind prospective study. The results indicated no difference in antidepressive efficacy between the two drugs, but imipramine had more anticholinergic side-effects. Neither drug had significant effects on pulse rate, blood pressure, weight changes or blood chemistry. These results were confirmed by previous studies.

Adult↗
PubMed1995

Ultrarapid vacuum-microwave histoprocessing.

A novel histoprocessing method for paraffin sections is presented in which the combination of vacuum and microwave exposure is the key element. By exploiting the decrease in boiling temperature under vacuum, the liquid molecules in the tissues have been successfully extracted and exchanged at relatively low temperatures during each of the steps from dehydration, clearing, and impregnation. In this vacuum-microwave method, an extremely short time suffices for the preparation of optimal-quality paraffin blocks. No xylene (but isopropanol instead) was used as the intermediate solvent. Thirty biopsies (thickness 2-4 mm) can be processed in 40 min. In addition, this approach can be used to produce large sections of giant blocks (4 x 6 x 1 cm3) which can be easily cut on a routine microtome due to the optimal paraffin impregnation. These giant blocks do not shrink during this vacuum-microwave histoprocessing.

Biopsy↗
PubMed1995

Follow-up study of female transsexuals.

The aim of this study was to examine the social and sexual adjustments of Singapore female transsexuals following sex reassignment surgery. All female transsexuals who were operated on since 1989 were interviewed. There were a total of 17 transsexuals with a mean age of 29 years (range, 20 to 41 years) at the time of inception. Before surgery, all were single. After surgery, 6 out of 11 subjects had married abroad. Before surgery, some had problems with identity cards, passports, travelling and work which were resolved with surgery. They were better accepted and had better sexual adjustment after surgery. All were satisfied with the change in sex, but only 65% were satisfied with the surgery. Only 59% said they were willing to undergo the operation again. After a test case in court, they were unable to marry in Singapore. Their primary motive to undergo sex reassignment surgery was to become a member of the opposite sex, so that they could be recognised socially and legally.

Adult↗
PubMed1995

How sexually permissive are Singaporeans?

This paper presents data on two surveys done in 1989 and 1992 that indicated the attitudes of Singaporeans to sexuality. Both surveys revealed that Singaporeans have sexually conservative attitudes and those who have a lower education, are single, above the age of 40, are Malays/Muslims hold more conservative views.

Adolescent↗
PubMed1995

Incest and other intrafamilial sexual abuse.

This study describes eight female adolescents who were sexually abused in childhood. Four were victims of incest. The mean age of onset of sexual abuse was 9.8 years and except for one, all had multiple incidents. All were from the lower socioeconomic class. The majority had disorganised families. The reactions of the majority of the victims were fear, intense anger and self mutilation. All were separated from their families on disclosure of the abuse. A significant clinical sequela was that of suicidal tendency in all of them, six of whom attempted suicide repeatedly. Promiscuous behaviour at adolescence occurred in one victim of father-child incest. Lesbianism resulted in one other. None suffered from any formal psychiatric disorder.

Adolescent↗
PubMed1995

The two-step vacuum-microwave method for histoprocessing.

When microwaving and vacuum is combined, decrease of boiling temperature can be exploited in the histoprocessing procedures allowing a completely novel approach for impregnating tissue with paraffin. We found that, if the pressure is sufficiently low in the paraffin step, no ethyl-alcohol step is necessary for the dehydration. In that case, the fixed tissue blocks can be directly placed into the isopropanol and, after that, in the hot paraffin, in which the final dehydration of the tissue takes place. The full histoprocessing procedure can thus be shortened into two steps only, with a processing time (for 72 biopsies) of a mere 40 min. Working completely without ethyl alcohol might be of interest for countries in which ethyl alcohol is difficult or expensive to obtain. We conclude that vacuum-microwave histoprocessing allows us to omit ethyl-alcohol dehydration and to replace xylene, resulting in a two-step 'green' (ecological) method.

Histological Techniques↗
PubMed1995

Fluoxetine in the treatment of depression in Asian (Chinese and Indian) patients in Singapore.

The aim of this paper is to study the efficacy and side-effects of fluoxetine. Fluoxetine is a specific serotonin reuptake inhibitor. Nineteen Asian (Chinese and Indian) patients who satisfied the DSM-3R criteria for major depressive episode were treated with fluoxetine 20 mg daily for 12 weeks. They were monitored two weekly. The results showed that during the period of treatment there was significant improvement in depressive symptoms and no serious side-effects. There were no significant changes in weight, temperature, blood pressure and pulse rate throughout the 12 weeks. This study showed that fluoxetine was well-tolerated and relieved the symptoms of depression effectively. Most of the results are supported by other studies.

Adult↗
PubMed1994

Confocal optical sectioning and three-dimensional reconstruction of carcinoma fragments in Pap smears using sophisticated image data processing.

Carcinoma fragments found in Pap smears contain important diagnostic information not available to the light microscopist because of their thickness and consequent blurring. Optical sectioning by the confocal microscope allows us to reclaim the mitotic figures, glandular architecture, and abnormal chromatin patterns in the restained original smears. The high spatial resolution of the confocal microscope can be further exploited by processing the digital images with the sophisticated Application Visualization System (AVS) on a CONVEX computer. Serial sections in which the fluorescent signals are color coded by this software package and three-dimensional reconstructions of the nuclei and mitotic figures expand our knowledge of these malignant epithelial fragments.

Adenocarcinoma↗
PubMed1994

Programming the microwave oven.

Microwaves can be used to stimulate chemical bonding, diffusion of reagents into and out of the specimen, and coagulation processes in preparatory techniques. Temperature plays an important role in these processes. There are several ways of controlling the temperature of microwave-exposed tissue, fluids and solids that are used in these preparatory techniques. In this paper we describe our accumulated experience with monitoring and controlling microwave-oven parameters with the help of a personal computer (PC). A specially designed microwave oven was used with an advanced temperature probe. The oven was connected to an IBM-compatible PC. This enabled us to analyze the quality of temperature control, and the relationship between displayed and actual temperature. We show that for microwave-transparent materials the addition of a microwave-absorbent plate to the material results in better temperature control.

Ethanol↗
PubMed1994

Microwaves for immunohistochemistry.

Microwaves are now widely used in immunohistochemistry for fixing and stabilizing tissue prior to embedding and cutting, for antigen retrieval and for immunoincubations. These techniques can be used for frozen sections and for material embedded in paraffin and plastic. Material prepared in this way shows high contrast in light microscopy. In principle, these microwave methods can also be used for electron microscopy. To be successful in the application of these techniques, insight into the physics of exposure to microwaves and the effects of microwaves on the material is a must. Microwave immunohistochemistry depends on optimal temperature control. To guarantee this, special measures should be taken and dedicated laboratory ovens should be used. The recently developed Coverplate units facilitate immunoincubations in the microwave oven. We show that the total microwave approach, combining microwave fixation, embedding and immunoincubations, is very useful for confocal microscopy.

Antigens↗
PubMed1994

Susceptibility of Singapore Chinese schoolgirls to anorexia nervosa--Part I (Psychological factors).

Of 656 GCE "O" level Chinese Singapore schoolgirls, it was found that 56% perceived themselves as being too fat, and 38% had been teased about being overweight. On the Eating Disorders Inventory (EDI), 15 (2%) had a score at the anorectic range. Compared to a group of American undergraduates, Singaporean subjects had no significant difference on the drive for thinness scores, but had significantly higher scores on bulimia, ineffectiveness, body dissatisfaction, interpersonal distress and greater maturity fears. In a population which appears to be susceptible to anorexia nervosa, possible reasons for the low incidence of this disorder is discussed.

Adolescent↗
PubMed1994

De Clerambault syndrome and medical practitioners: medico legal implications.

De Clerambault's syndrome or erotomania is a condition in which a patient, usually a woman, develops a delusional belief that a man, usually older and of higher social status, is in love with her. This paper describes such cases where medical practitioners were involved. In a case where a doctor was brought to court, the judge stressed that because of the nature of the allegation, it was vital that there be corroborative evidence. When faced with such patients, a prudent doctor would ensure that a nurse be in attendance at all times, that notes be carefully kept and phone calls recorded. Other measures might be necessary, depending on the situation.

Delusions↗