Biomedical subjects

M T Koh

Publications and source records attributed to M T Koh.

At least 19 recordsLinked to original sources

PubMed2001

Naloxone attenuates the conditioned place preference induced by wheel running in rats.

Pairings, during which an episode of wheel running is followed by confinement in a distinctive place, produce conditioned place preference (CPP) in rats. This finding indicates that wheel running has a rewarding effect that outlasts the activity itself. In two similar experiments, we tested the hypothesis that this rewarding effect of wheel running is mediated by endogenous opioids. During a paired trial, the rats in the naloxone group were first allowed to wheel run for 2 h, then injected with naloxone (0.5 or 0.1 mg/kg in Experiments 1 and 2, respectively), and 10 min later placed in a distinctive chamber. During an unpaired trial, these rats were confined in an adjoining chamber without wheel running. Naloxone was injected before placement in both chambers, so that if naloxone-induced conditioned place aversion occurred, it would have counteracting effects on performance during the preference test. The rats in the saline group were similarly treated, except that saline was injected instead of naloxone. CPP occurred in the saline group, but not in the naloxone group. Thus, naloxone attenuated the CPP induced by wheel running. This finding supports the hypothesis that the rewarding effect of wheel running is mediated by endogenous opioids.

Animals↗

PubMed2001

Preadaptation to the feeding schedule does not eliminate activity-based anorexia in rats.

To test whether activity-based anorexia (ABA) still occurs after preadaptation to the feeding schedule, 20 rats were first exposed to a feeding schedule of one 90-min meal per day until adaptation occurred (measured by maintenance of stable body weight). Then, during ABA training, half the rats (wheel group) were confined in running wheels except during the daily meal, and half (cage group) were not. Wheel running suppressed feeding--that is, food intake in the wheel group was less than that in the cage group. Also, the rats in the wheel group lost weight, whereas those in the cage group did not. Wheel running increased over days. Thus, the defining characteristics of ABA were evident in rats that were not subjected to ABA training until after they had become well adapted to the feeding schedule. These findings support the view that the suppression of feeding produced by wheel running triggers the vicious circle of ABA. They also cast doubt on the hypothesis that activity-induced interference with adaptation to the feeding schedule plays a key role in causing ABA.

Adaptation, Psychological↗

PubMed2001

NaCl detection thresholds: comparison of Fischer 344 and Wistar rats.

Adult Fischer 344 (F344) rats fail to display any preference for NaCl solutions at concentrations typically preferred by other rat strains. To determine whether this behavior is due to a strain difference in NaCl detection threshold, a conditioned taste aversion (CTA) was first established to a suprathreshold concentration of NaCl (0.1 M). Then, a series of dilute NaCl solutions, ranging from 0.0 to 0.011 M NaCl, were presented to F344 (n = 16) and Wistar (n = 16) rats. The lowest concentration at which there was a reliable difference in the preference scores of conditioned and control rats was defined as the detection threshold. Results indicate that the detection threshold for NaCl lies between 0.001 and 0.002 M NaCl for both F344 and Wistar rats. The addition of the sodium channel blocker amiloride to the NaCl solutions raised the detection threshold 10-fold to 0.03-0.04 M NaCl for both strains of rats. These results suggest that the NaCl detection thresholds of F344 and Wistar rats are similar and that these strains do not differ in the degree to which amiloride raises this threshold.

Amiloride↗

PubMed2001

Factor V inhibitor in neonatal intracranial hemorrhage secondary to severe congenital factor V deficiency.

We report a newborn infant girl, born to consanguineous parents, with recurrent intracranial hemorrhage secondary to congenital factor V deficiency with factor V inhibitor. Repeated transfusions of fresh-frozen plasma (FFP) and platelet concentrates, administrations of immunosuppressive therapy (prednisolone and cyclophosphamide), and intravenous immunoglobulin failed to normalize the coagulation profiles. Exchange transfusion followed-up by administrations of activated prothrombin complex and transfusions of FFP and platelet concentrates caused a temporary normalization of coagulation profile, enabling an insertion of ventriculoperitoneal (VP) shunt for progressive hydrocephalus. The treatment was complicated by thrombosis of left brachial artery and ischemia of left middle finger. The child finally died from another episode of intracranial hemorrhage 10 days after insertion of the VP shunt.

Brachial Artery↗

PubMed2001

Acquired immunodeficiency syndrome presenting as childhood non-Hodgkin's lymphoma.

Two children with non-Hodgkin's lymphoma (NHL) as the presenting illness of acquired immunodeficiency syndrome (AIDS) are described. There was a delay in diagnosing the underlying AIDS in both cases. In the first case, an 18-month-old boy with stage IV, high-grade,T-cell NHL, the diagnosis of underlying AIDS was suspected only when he developed recurrent and profound opportunistic infection during chemotherapy. The second case, an eight-month-old female infant presented initially with hepatosplenomegaly and thrombocytopenia of undetermined cause. She had progressive abdominal distension and swelling of her right eye one year later due to high grade B-cell NHL. She was later found to be sero-positive for HIV during pre-chemotherapy screening. As the prevalence of HIV infection continues to increase, HIV infection should be considered in the differential diagnoses of childhood hepatosplenomegaly and thrombocytopenia, and as a possible underlying cause of childhood cancer, especially NHL.

Fatal Outcome↗

PubMed2000

Pairings of a distinctive chamber with the aftereffect of wheel running produce conditioned place preference.

Wheel running reinforces behavior that precedes it. Also, wheel running can produce activity anorexia, a marked suppression of feeding in food-restricted rats. Some authors propose that the activity anorexia effect is produced by activation of the same reward system that mediates the reinforcing effect. One hypothesis is that such activation persists after wheel running stops and results in a rewarding aftereffect that suppresses feeding. Alternatively, such activation may give rise to an opponent process, an aversive aftereffect that suppresses feeding. The method of place conditioning was used to test whether the aftereffect of wheel running is rewarding or aversive. Food-deprived rats received pairings of a distinctive chamber with the aftereffect of wheel running. In Experiment 1, 2 h in a running wheel followed by 30 min in a distinctive chamber produced conditioned place preference. In Experiment 2, 22-22.5 h in a running wheel was followed by 30 min in the chamber and then a 60-min feeding test. Wheel running suppressed feeding and produced conditioned place preference. The conditioned place preference indicates that the aftereffect of wheel running is reinforcing rather than aversive. This finding supports the idea that the activation of the reward system persists after wheel running stops, thereby suppressing food intake.

Animals↗

PubMed2000

Activity in the circular alley does not produce the activity anorexia syndrome in rats.

The activity anorexia syndrome is characterized by reduced food intake and body weight compared to control levels and increasing levels of physical activity. To induce it, food-restricted rats are confined in running wheels except during the daily meal. We tested whether activity in a flat circular alley also produces the activity anorexia syndrome. In Experiment 1, food-restricted rats were maintained in alleys, wheels, or home cages (control condition). In Experiment 2, they were maintained in alleys, wheels, novel cages, or home cages. The novel cage was added to control for the possibility that the alley might produce an anorectic effect simply because it was a new living space. The alley did not produce the activity anorexia syndrome whereas the wheel did. Although weight loss was greater in the alley than home-cage condition, the alley produced weak, inconsistent suppression of feeding. Moreover, the suppression produced by the alley may have stemmed simply from living in a novel environment. Finally, in contrast to wheel running, alley activity decreased over days. Alley activity, unlike wheel running, may not be reinforcing. Likely, a physical activity must be reinforcing to produce the activity anorexia syndrome. Implications for anorexia nervosa were discussed.

Animals↗

PubMed2000

The predictive value of uvulo-palatoglossal junctional ulcers as an early clinical sign of exanthem subitum due to human herpesvirus 6.

BACKGROUND: The clinical sign of uvulo-palatoglossal junctional (UPJ) ulcers was first noted in 1983 in a 5.5-month-old baby with exanthem subitum (ES). An earlier prospective clinical study showed that there was a strong association of UPJ ulcers and occurrence of ES with a positive predictive value of 95.3% and negative predictive value of 100%. OBJECTIVE: To determine the value of uvulo-palatoglossal junctional (UPJ) ulcers as an early clinical sign of exanthem subitum (ES) due to human herpesvirus 6 (HHV 6) infection. STUDY DESIGN: A case-control study of 20 febrile children with UPJ ulcers versus 26 febrile children without UPJ ulcers. These children were followed up for any development of ES and investigated for human herpesvirus 6 (HHV 6) as the causative agents of the febrile episodes. RESULTS: In this study, 20 out of 46 febrile children aged 3 months to 3 years with UPJ ulcers were virologically and/or serologically confirmed to be due to primary HHV 6 infection. The rest of the 26 children without ulcers did not have HHV 6 infection. Of the 20 children with UPJ ulcers, only 17 of the 19 children with adequate follow-up till subsidence of fever developed ES. None of the 26 children without UPJ ulcers developed ES. CONCLUSION: Statistically, there was a significant association of UPJ ulcers as an early sign of ES with a positive predictive value of 89.5% and negative predictive value of 100%. This finding also suggests that the presence of UPJ ulcers is a useful pathognomic clinical sign of symptomatic primary HHV 6 infection.

Antibodies, Viral↗

PubMed1998

Chlordiazepoxide attenuates activity-induced anorexia and weight loss in rats.

In Experiment 1, the effect of repeated injections of 2.5, 5.0, or 10.0 mg/kg of chlordiazepoxide (CDP) on food intake and body weight was studied in rats on an activity anorexia (AA) regimen. For several days before CDP testing began, rats lived in activity wheels and had one 60-min meal per day. During CDP testing, this regimen continued except that each rat was injected with an appropriate dose of CDP or saline 30 min before each meal. CDP enhanced food intake; 5.0 mg/kg seemed most effective. However, the CDP-induced increase in eating did not noticeably stem weight loss. In Experiment 2, after several days of AA training, CDP (5.0 mg/kg) was tested under less severe conditions; food remained restricted, but access to the wheels was discontinued. Rats given CDP ate more and gained more weight than controls. These findings suggest that benzodiazepines such as CDP may help in treating anorexia nervosa and other anorectic conditions in humans.

Animals↗

PubMed1998

Epidemiology and in vitro activity of antimycotics against candidal vaginal/skin/nail infections in Singapore.

BACKGROUND: Candidal infections of the skin/nails and vagina are very common worldwide. Various in vitro test systems are available to help to determine the antifungal activity of drugs. The minimum inhibitory concentration (MIC) is a standard measure of the in vitro potency of drugs against yeasts. METHODS: Vaginal smears and skin/nail scrapings of 50 consecutive patients with candidal vaginitis and 46 consecutive patients (28 women, 18 men) with cutaneous/nail candidosis were used in the study. Direct microscopy and culture from vaginal smears and skin scrapings were performed on all patients. The MICs were determined using the broth dilution method. RESULTS: For vaginal candidosis, the mean age of the patients was 28.2 years (range, 9-49 years). Candida albicans accounted for 58% of the isolates, C. glabrata for 32%, C. tropicalis for 6%, and C. parasilosis for 4%. At the MIC of < or = 4 mg/L, 65-95% of C. albicans, 66-94% of C. glabrata, 33-100% of C. tropicalis, and 0-50% of C. parasilosis were susceptible to the drugs tested (ketoconazole, itraconazole, nystatin, amorolfine, clotrimazole, and miconazole). For cutaneous/nail candidosis, the mean age of the patients was 45 years (range, 19-82 years). C. albicans made up 59% of the isolates, C. parasilosis 20%, C. krusei 13%, C. glabrata 4%, and C. tropicalis 4%. At the MIC of < or = 4 mg/L, 59-96% of C. albicans, 100% of C. glabrata, 83-100% of C. krusei, 89-100% of C. parasilosis, and 100% of C. tropicalis were susceptible to the drugs tested (ketoconazole, itraconazole, nystatin, amorolfine, clotrimazole, and miconazole). CONCLUSIONS: C. albicans is the most common Candida species causing cutaneous/nail and vaginal candidosis in Singapore. The in vitro antifungal activities of ketoconazole, itraconazole, nystatin, amorolfine, clotrimazole, and miconazole are similar against the various Candida species. C. parasilosis in vaginal candidosis appears to be less susceptible. Here, itraconazole and amorolfine may be more effective.

Adolescent↗

PubMed1997

Chlordiazepoxide counteracts activity-induced suppression of eating in rats.

Because benzodiazepines such as chlordiazepoxide increase food intake, the present experiments tested the effect of chlordiazepoxide on food intake in an animal model of anorexia nervosa, called activity anorexia (AA). To induce AA, rats (Rattus norvegicus) were maintained in activity wheels and restricted to a single 60-min feeding period each day. As previously found, this procedure suppressed food intake. After several days of this training, food intake was measured 30 min after the rats were injected with chlordiazepoxide (5 mg/kg) or saline. In 2 experiments, chlordiazepoxide counteracted the suppression of food intake produced by AA. Because benzodiazepines have been found to increase food intake in many mammalian species including primates, the present results suggest that benzodiazepines could be useful in the treatment of anorexia nervosa.

Animals↗

PubMed1997

The incidence of human herpesvirus 6 infection in children with febrile convulsion admitted to the University Hospital, Kuala Lumpur.

From October 1996 to March 1997, 31 children with febrile convulsions were admitted to the University Hospital, Kuala Lumpur. Human Herpesvirus 6 (HHV 6) was virologically and/or serologically confirmed to be the cause of the febrile episode in 5 of these children (16.1%). Age, sex and other associated clinical features (diarrhoea, cough, running nose and type of seizure) were not useful in differentiating cases of febrile convulsion due to HHV 6 from those of other aetiology. However, uvulo-palatoglossal junctional ulcers were noted in children in whom the cause of the seizure could be attributed to HHV 6 but not in the remaining cases in the study group. HHV 6 DNA was detected in peripheral blood mononuclear cells from all patients with febrile convulsions attributed to HHV6, and in patients shown serologically to have already been exposed to the virus by nested polymerase chain reaction amplification. Only genotype HHV 6B was detected from patients with seizure due to HHV 6 but both genotype 6A and 6B were detected in the remaining cases studied.

Child, Preschool↗

PubMed1996

Hyperplasia of thymic gland.

Hyperplasia of the thymus is the most common anterior mediastinal mass in infants. It is however exceedingly difficult to evaluate by the weight of the gland as it continues to grow after birth until puberty and thereafter undergoes progressive atrophy. It normally maintains most of the radiographic characteristics of the normal thymus. Massive thymic hyperplasia, a rare variant of true thymic hyperplasia is extremely rare during the first two decades of life and clinically can cause mediastinal compression or acute and recurrent pulmonary infection. Two such cases are reported and the clinico-pathology is briefly described and discussed.

Diagnosis, Differential↗

PubMed1995

Early congenital syphilis--a continuing problem in Malaysia.

Between February 1990 and May 1993, 13 cases of early congenital syphilis (ECS) were managed in the Paediatrics Unit, University Hospital, Kuala Lumpur. Twelve mothers were unbooked with 10 inborn babies. Only one mother had antenatal booking at this hospital but she defaulted antenatal follow-up. Several risk factors associated with ECS were identified: inadequate or no prenatal care (5/13), failure to repeat a serological test for syphilis in the third trimester when it was tested negative at first booking (5/13), sexual promiscuity, substance abuse and a past history of contracting sexually transmitted disease. All 10 mothers who had their serological test repeated at delivery were found to have a positive VDRL and TPHA. Adequate antenatal care early referral of infected, expectant mothers for treatment, and a repeat serological test for syphilis could have prevented these cases of ECS.

Adult↗

PubMed1994

In vitro evaluation of griseofulvin, ketoconazole, and itraconazole against various dermatophytes in Singapore.

BACKGROUND: Superficial cutaneous fungal infection, principally dermatophytosis, is an extremely common skin disease. Various in vitro test systems have been developed in recent years to determine the antifungal activity of various drugs. The minimum inhibitory concentration (MIC) obtained may give an indication of the in vivo potency of the drugs. METHODS: One hundred patients (69 men and 31 women) with a clinical diagnosis of dermatophytosis were entered into the study. Direct microscopy and culture were done on all patients. The MICS were determined using the broth dilution method. RESULTS: The age range was 1-76 years. The most common diagnosis was tinea corporis (36%), followed by tinea cruris (22%), and tinea pedis (19%). The most common fungus isolated was T. rubrum (58%), followed by E. floccosum (14%), and T. mentagrophytes (10%). The majority of the isolates was sensitive to the three drugs tested (griseofulvin, ketoconazole, and itraconazole). Of the isolates, 82% were sensitive to griseofulvin, 78% to ketoconazole, and 81% to itraconazole, all at a concentration of < 0.25 micrograms/mL. For T. rubrum, there were four isolates that had an MIC of > or = 64 micrograms/mL to griseofulvin, seven isolates and nine isolates with an MIC > or = 64 micrograms/mL to ketoconazole and itraconazole, respectively. T. interdigitale was relatively resistant to the three drugs in vitro with four of seven isolates having an MIC > or = 4 micrograms/mL with griseofulvin, one of seven isolate with an MIC > or = 64 micrograms/mL with ketoconazole, and three of seven isolates with an MIC > or = 32 micrograms/mL with itraconazole. CONCLUSIONS: The in vitro antifungal activity of griseofulvin, ketoconazole, and itraconazole are similar against dermatophytes in Singapore. Griseofulvin may be given as the first-line drug for treating such infections in Singapore.

Adolescent↗

PubMed1994

Disseminated Geotrichum infection.

Intensive chemotherapy has prolonged survival in cancer patients. Unfortunately it has also predisposed them to unusual infections because of their immunocompromised state. We report a case of fungal septicaemia caused by Geotrichum candidum, an imperfect yeast of low virulence in a young girl with acute lymphoblastic leukaemia. It was successfully treated with amphotericin B. The morphological characteristics of this fungus leading to its identification are described.

Amphotericin B↗

PubMed1992

Cerebro-costo-mandibular syndrome.

Cerebro-costo-mandibular syndrome (CCM) is a very rare entity with oro-facial features closely resembling Pierre-Robin anomaly (1,2). We describe a patient with typical features: severe micrognathia, glossoptosis, central cleft soft palate and multiple posterior rib-gap defects seen on chest radiograph. Respiratory distress which was evident soon after birth was relieved by an oro-pharyngeal airway. He suffered from a cardiorespiratory arrest and succumbed, presumably secondary to aspiration of milk feeds, before a tracheostomy could be performed.

Humans↗

PubMed1991

Depressed skull fracture in a newborn successfully managed conservatively: a case report.

A preterm baby was born to a multiparous mother by emergency caesarean section at 36 weeks of gestation. Apart from a depression on the right temporo-parietal region measuring 3 cm x 3 cm x 0.5 cm, no other abnormality was noted. A CT scan of the brain excluded the presence of intracranial haematoma and pressure effect on the brain. Spontaneous reduction of the fracture without any adverse neurological sequelae suggests that these fractures can be managed conservatively in some instances.

Cesarean Section↗