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Biomedical subjects

S K Lin

Publications and source records attributed to S K Lin.

At least 73 records · Page 4Linked to original sources
PubMed1995

Clinical features and carotid duplex sonography in patients with carotid transient ischemic attacks.

BACKGROUND: Transient ischemic attack (TIA) is recognized as a precursor of cerebral infarction. It is prompted by an embolism from extracranial carotid artery disease. However, extracranial carotid disease is less prevalent in Chinese patients. Non-invasive duplex sonography has been used for initial screening for extracranial carotid artery disease. METHODS: One hundred and twenty-seven consecutive patients with carotid TIA were divided into two groups according to sonographic results, Group I: < or = 50%, and Group II: > 50% stenosis of the carotid artery. The two groups were compared for the clinical manifestations, risk factors, brain computed tomography (CT) findings and subsequent stroke. An age and sex-matched group of patients with lacunar stroke was also collected from the same neurosonological data bank for further comparative analysis. RESULTS: The mean age at onset was 59 +/- 12 (mean SD) years. Hypertension was the most common risk factor. The most common symptom was transient focal motor deficit (73%) with or without other complaints. Eighty-two percent of the TIA episodes were less than one hour in duration. In Group I, there were 114 patients (90%) with stenosis < or = 50% ipsilateral to the symptomatic side. Group II included only 13 patients (10%) with the ipsilateral carotid artery stenosis > 50%. Mean age was older and cigarette smoking was more common in Group II (p < 0.05). Otherwise, no significant difference was noted between the two groups in initial characteristics of TIAs, risk factors, brain CT findings or subsequent stroke. Further, there was no statistical significant difference between the TIA and lacunar stroke groups in the degree of carotid stenosis. CONCLUSIONS: Hypertension was the most common risk factor for carotid TIAs. The prevalence of extracranial carotid artery disease was low in Chinese patients with carotid TIAs. The severity of the carotid artery was not predictive of recurrence of TIA or of subsequent stroke. There was no significant difference between patients with TIA and with lacunar stroke in sonographic findings of extracranial carotid arteries.

Adult↗
PubMed1994

Disposition of clozapine and desmethylclozapine in schizophrenic patients.

The disposition of the atypical clozapine and its desmethyl metabolite were evaluated in fourteen male chronic patients. A single 100 mg dose of clozapine was administered and blood sampling performed over the following 72 hours. The mean (SD) oral clearance and half-life of clozapine were 55.4 (29.7) L/hr and 13.7 (9.9) hours, respectively. The mean (SD) AUC for clozapine and desmethylclozapine was 2389.9 (1406) and 751.1 (622.9) ng.hr/mL, respectively. The elimination of the metabolite is rate limited by its formation from cloza-pine. A wide interpatient variability in clozapine and desmethylclozapine pharmacokinetics was observed.

Adult↗
PubMed1994

Intramedullary spinal tuberculomas during treatment of tuberculous meningitis.

A case of multiple intramedullary spinal tuberculomas developing paradoxically during effective treatment of tuberculous meningitis is described. Serial MR imagings with Gd-DTPA enhancement studies showed initial homogeneous enhanced lesion representing myelitis or the early tuberculoma stage, which evolved to show ring enhancement with hypointense center later. Their appearance was similar to those described in brain tuberculoma. Gd-DTPA enhancement MR imaging is more sensitive than MR imaging without enhancement in demonstrating the lesions of tuberculoma and arachnoiditis. Antituberculous medication was effective with marked clinical improvement.

Adult↗
PubMed1994

Oral post-radiation malignant fibrous histiocytoma: a clinicopathological study.

Five cases of oral malignant fibrous histiocytoma (MFH) in patients who had previously received radiotherapy in the head or neck region were included in this study. There were 3 men and 2 women. Four patients had been irradiated for nasopharyngeal carcinoma (NPC) and the other for a squamous cell carcinoma (SCC) involving the tongue and mouth floor. The MFH developed 2.5-11 years after the initial radiotherapy. Two cases of MFH occurred in the maxilla, two in the mandible, and the remaining one in the tongue, floor of mouth and mandible. Clinically, the oral post-radiation MFH presented as tender, reddish, elastic, lobulated masses with surface ulceration. Radiographic examination of the involved jaws revealed a poorly defined radiolucent lesion without any periosteal or endosteal reaction. The prognosis of these tumors was very poor. Although aggressive multimodality treatment had been applied, 3 of 5 patients eventually died of the disease, with a mean survival time of 17 months after establishing the diagnosis of MFH. In order to ensure the early diagnosis and treatment of this radiation-induced second malignancy, close oral follow-up is mandatory for patients who have received radiotherapy for head and neck malignancies.

Adult↗
PubMed1994

Carotid duplex and transcranial color-coded sonography in evaluation of carotid-cavernous sinus fistulas.

We performed carotid duplex and transcranial color-coded sonography in three patients with traumatic and one patient with spontaneous carotid-cavernous fistulas. High flow and low resistance were detected by carotid Doppler imaging in the extracranial internal carotid artery in three cases and in the external carotid artery in one case. The fistula could be demonstrated directly as heterogenous color flashes with turbulent flow by transcranial color-coded sonography through the orbital or temporal window. The transorbital approach showed that the ophthalmic venous flow was normal or to-and-fro bidirectional in patients without proptosis and was retrograde, away from the cavernous sinus with arteriolization in patients with proptosis. Combination of carotid duplex and transcranial color-coded sonography provides a noninvasive method for more accurate hemodynamic study of cerebral circulation and direct imaging of CCF.

Adult↗
PubMed1993

Determination of clozapine and desmethylclozapine in human plasma by high-performance liquid chromatography with ultraviolet detection.

A method using reversed-phase high-performance liquid chromatography for the simultaneous determination of clozapine and its desmethyl metabolite in human plasma has been established. Clozapine and N-desmethylclozapine were extracted with n-hexane-isoamyl alcohol (98.5:1.5, v/v). Protriptyline served as the internal standard. The limits of detection for clozapine and desmethylclozapine are 2 and 1 ng/ml, respectively. The sensitivity and precision of this method can be utilized for pharmacokinetic studies and therapeutic drug monitoring regimens.

Adult↗
PubMed1993

Prolonged haloperidol and reduced haloperidol plasma concentrations after decanoate withdrawal.

Haloperidol and reduced haloperidol plasma concentrations were measured in twelve schizophrenic patients upon cessation of haloperidol decanoate (HLD) treatment. Each patient received HLD 100 mg every 4 weeks for five injections. After the fifth injection, HLD was discontinued. Haloperidol and reduced haloperidol plasma concentrations were obtained prior to cessation and at weeks 1, 3, 4, 5, 7, 9, 11, and 13 post-injection. Haloperidol and reduced haloperidol plasma concentrations were assayed by HPLC. Both haloperidol and reduced haloperidol plasma concentrations were detectable 13 weeks post HLD discontinuation. Maximal haloperidol plasma concentrations were observed at one week post cessation and gradually declined. The mean elimination half-life for haloperidol was 27.4 +/- 8.6 days (range 19.0-47.0 days). Reduced haloperidol plasma concentrations declined very slowly. Our results show that both haloperidol and reduced haloperidol plasma concentrations can remain for extended time periods after HLD is discontinued.

Adult↗
PubMed1993

Plasma homovanillic acid and treatment response in a large group of schizophrenic patients.

Plasma levels of homovanillic acid (pHVA), a metabolite of dopamine, were measured in ninety-five Chinese schizophrenic patients free of neuroleptics for at least four weeks. These patients were treated with classical antipsychotics for six weeks. Pretreatment pHVA was positively correlated with the subsequent clinical response (r = 0.408, p < 0.0001). Good responders (BPRS improvement > or = 50%, n = 47) had higher pretreatment pHVA levels than poor responders (BPRS improvement < 50%, n = 48) (15.7 +/- 8.4 ng/ml versus 9.9 +/- 3.7 ng/ml, p < 0.0001). A higher than 15 ng/ml pretreatment pHVA level was associated with a more consistent clinical response to the subsequent treatment. Using a pHVA level of 12 ng/ml as a demarcation point, 72% of patients (34 of 47) who had pHVA > or = 12 responded whereas 65% (31 of 48) who had < 12 did not respond (chi-square = 13.02, p < 0.0001). These results suggest that higher pretreatment pHVA levels may predict a better clinical response to antipsychotics. Based upon the pHVA findings, two hypothetical subtypes of schizophrenia are proposed.

Adolescent↗
PubMed1993

Comparison of commercial diagnostic tests for Helicobacter pylori antibodies.

A number of serological tests measuring the presence of Helicobacter pylori-specific serum immunoglobulin G (IgG) are now commercially available. The aim of this study was to evaluate the clinical accuracy of five commercial H. pylori antibody tests: GAP-IgG (Biomerica), HELpTEST (AMRAD, Kew, Victoria, Australia), HELICO-G (Porton Cambridge), Pyloriset (Orion Diagnostica), and ROCHE (Roche Diagnostics). A total of 162 subjects presenting for routine upper endoscopy were studied. H. pylori was diagnosed if culture, histology, or both were positive. Ten milliliters of venous blood was collected at the time of endoscopy for serological assessment. The sensitivity and specificity of each test (GAP-IgG, HELpTEST, HELICO-G, Pyloriset, and ROCHE) were as follows: 83 and 79%, 92 and 77%, 86 and 65%, 89 and 56%, and 98 and 69%, respectively. Positive and negative predictive values were 97 and 83%, 90 and 91%, 76 and 83%, 68 and 84%, and 86 and 97%, respectively. The specificity of most tests increased by approximately 10% when sera from subjects less than 45 years old were examined. The number of sera falling into the grey zone for each test (an indeterminate result with respect to H. pylori status) varied between 2.5 and 19%. This study highlights the need for all serological kits to be independently evaluated on the population to be studied by testing against a microbiologically defined panel of H. pylori-positive and -negative sera.

Adolescent↗
PubMed1993

Comparison of haloperidol plasma concentrations between twice-a-day and once-a-day dosing in Chinese schizophrenic patients.

There is a trend in clinical psychiatric practice to make the dosing schedules of psychotropic medications as simple as possible. In this study, the authors measured the steady state haloperidol plasma levels in patients on different dosing schedules. Twenty-three schizophrenic in-patients were placed on haloperidol with a twice-a-day (10 mg bid) schedule for 14 days; the patients were then changed to a once-a-day (20 mg qd) schedule for another 14 days. Plasma haloperidol (HAL) and reduced haloperidol concentrations were measured at the end of each two-week period. The mean HAL plasma concentrations obtained from the bid and qd dosing schedules were 16.6 +/- 4.9 ng/mL and 12.7 +/- 5.3 ng/mL, respectively. These results are reasonable as the elimination half-life of HAL, as reported by most investigators, is about 24 hours. The present study suggests that a once-a-day dosing schedule in HAL treatment is adequate for most chronic patients.

Adult↗
PubMed1993

Hyaline ring granuloma: a case report with histochemical and polarized microscopic studies.

An unusual case of hyaline ring granuloma arising from the connective tissue wall of a residual apical periodontal cyst is reported. Hyaline rings with foreign-body type giant cell inclusions were a significant feature in the histopathologic diagnosis. Histochemical and polarized light microscopic studies suggested that the introduction of foreign material, possibly cellulose, through the postextraction socket into the cystic wall may have caused the granulomatous reaction and formation of the hyaline ring granuloma. The clinical features of this case and 66 previously reported cases, as well as the pathogenesis of the hyaline rings, are discussed.

Adult↗
PubMed1993

[Establishment of dental pulp hyperemia in an animal experiment model].

To establish an animal model of dental pulp hyperemia, 96 molars in 12 Wistar rats were studied. In each rat, the four right molars, including the right upper and lower first and second molars, were assigned as the experimental group. The four left corresponding molars in each rat were included in the control group. The animals were anesthetized and a 3% silver nitrate solution was applied to the exposed dentin at the cusp tip of the molars for one minute. After 2, 5, and 24 hours, four animals in each subgroup were sacrificed. The upper and lower jaws in conjunction with the dentition were removed and fixed in a 10% neutral formalin solution for 24 hours. The first and second molars and the surrounding alveolar bone in en bloc were trimmed off, fixed for another 24 hours, and processed according to routine histological procedures. The histopathologic changes in the dental pulp were examined by light microscopy. For convenience of interpretation, the intensity of the pulp tissue reaction was graded as follows: grade O: normal pulp tissue; grade I: vessel dilatation and congestion, as well as stromal edema; grade II: focal pulp hemorhage and plasma extravasation; grade III: pulp tissue destruction including pyknotic change in the odontoblastic nuclei; and grade IV: abscess formation in the pulp tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Reduced haloperidol/haloperidol ratios after oral haloperidol and decanoate administration in schizophrenics.

1. Haloperidol and reduced haloperidol plasma concentrations were measured in thirteen stable schizophrenic patients that received both oral haloperidol and haloperidol decanoate. 2. Significant correlations between reduced haloperidol/haloperidol ratios from oral haloperidol and haloperidol decanoate occurred at week two and week 16, respectively. 3. The formation of RH was consistent during haloperidol decanoate treatment.

Administration, Oral↗
PubMed1992

Collagen gene expression in human dental pulp cell cultures.

Pulp cells from human permanent molars were isolated and established in culture; 40% showed positive alkaline phosphatase staining. When incubated with 50 micrograms/ml of ascorbic acid and 10 mM of beta-glycerophosphate, the cells formed a mineralized extracellular matrix; they could thus have the potential to differentiate into odontoblast-like cells in vitro. Collagen synthesis was analysed by SDS interrupted gel electrophoresis, Northern blot and slot blot: the cells produced predominantly (approximately 99%) type I collagen and only trace amount of type III collagen. The ratio of alpha 1 (I) to alpha 2(I) procollagen chains was about 68:32, indicating that no significant amount of collagen type I trimer was synthesized in this system. The ratios of alpha 1(I), alpha 2(I) and alpha 1(III) procollagen mRNAs were about 61:25:1; these were compatible with the ratios of corresponding procollagen alpha chains. In addition, a novel 5.8 kb pro alpha 1(III) mRNA was detected. These observations indicate that collagen synthesis in these cultured pulp cells was regulated at the transcriptional level.

Adolescent↗
PubMed1992

Comparison of haloperidol and reduced haloperidol plasma levels in four different ethnic populations.

1. Plasma haloperidol and reduced haloperidol concentration were measured in four ethnic populations. 2. Plasma samples were obtained under steady-state conditions and obtained 10-12 hours post bedtime dose and prior to the morning dose. 3. Haloperidol and reduced haloperidol plasma levels were assayed by radioimmunoassay and liquid chromatography. 4. A wide interpatient variability between haloperidol dose and plasma concentration was observed for each ethnic group. 5. The Chinese group differed from the other ethnic populations. 6. A nonlinear relationship was observed between haloperidol and reduced haloperidol plasma levels in each ethnic group. Further, the relationship of haloperidol to reduced haloperidol plasma levels differed for each ethnic group. These results suggest that various ethnic groups could metabolize haloperidol and reduced haloperidol differently.

Black or African American↗
PubMed1991

Dose-dependent reduced haloperidol/haloperidol ratios in schizophrenic patients.

Plasma haloperidol (HAL) and reduced HAL (RHAL) concentrations were measured in 113 Chinese schizophrenic patients. Daily doses of HAL ranged from 8 to 65 mg. Samples were obtained under steady-state conditions and drawn 10-12 hours after the bedtime dose and before the morning dose. In all, 313 blood samples were collected. Multiple samples were obtained at the same doses in 63 patients and at two or three different doses in 31 patients. HAL and RHAL concentrations were assayed by high performance liquid chromatography. Interpatient variation in plasma HAL levels at a given dosage was up to sixfold. However, there was a high positive correlation between plasma levels and daily dosages with the equation of HAL plasma level (ng/ml) = 0.88 x dosage (mg/day) -0.56 or 46.0 x dosage (mg/day/kg) + 0.28. The expected values are about 15-55% higher than those obtained from non-Chinese patients as reported in the literature. The RHAL/HAL ratios were dose-dependent. The greater the dose used, the higher the ratio. An upper therapeutic limit of plasma HAL level is suggested to be 25 ng/ml, which can be achieved at dosages about 30 mg/day in most Chinese patients. Based upon the dose-dependent increase in RHAL/HAL ratios, the importance of RHAL in determining the therapeutic benefit of HAL treatment is discussed.

Adolescent↗