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Biomedical subjects

J Lim

Publications and source records attributed to J Lim.

At least 181 records · Page 10Linked to original sources
PubMed1993

Color mixing in dental porcelain.

For esthetic reasons, pigments and opacifiers are added to porcelains used in restorative dentistry. The purpose of this study was to use Kubelka-Munk theory (Kubelka and Munk, 1931) to predict and analyse the colors of porcelains modified by the addition of two pigments and an opacifying agent. The base porcelain was composed of 88% potassium feldspar, 6% quartz and 6% kaolin. The porcelain was modified by the addition of a yellow (Pr-Zr-Si) or a brown (Fe-Cr-Zn) stain and an opacifier (10% SnO in base porcelain). After firing at 1200 degrees C for 30 min, reflectance spectra of the various combinations were obtained with a spectrophotometer. Reflectance spectra, except at low wavelengths, were influenced by increased scattering due to the addition of the opacifier. Calculated values from Kubelka-Munk theory for absorption coefficients and scattering coefficients with appropriate correction factors were compared with the values from the reflectance spectra of the combinations. In general, good agreement was obtained if the scattering coefficient of the opacifier is set equal to 1.0. Using the L*a*b* transform of the CIE color space, it was found that this transform provided uniform color intervals for equal changes in pigment concentration.

Analysis of Variance↗
PubMed1993

Variation in antibody reactivity to the hepatitis C virus by comparative immunoscreening and enzyme immunoassay.

The detection of antibody to the hepatitis C virus C100-3 antigen from the nonstructural region (NS3/NS4) of the viral genome was the first useful marker developed to detect past or potentially active infection with the hepatitis C virus. A systematic epitope survey of the nonstructural region has uncovered other immunogenic antigens. In order to assess the possible diagnostic utility of these antigens, their reactivity against a limited panel of sera from patients with chronic liver disease due to hepatitis C virus and other etiologies was tested. Antibody assays were performed using an immunoblot plaque assay and an enzyme-linked immunosorbent assay (ELISA). In a study of 16 C100-3-reactive individuals, all 16 patients were reactive using the plaque assay for the NS3 3' (409-1-1) and NS3 5' (C33u). In this same group of patients, antibodies by ELISA were reactive to NS3 3' in 12 of 16 patients (75%), NS3 5' in 15 of 16 patients (93%), and a capsid antigen (NC450) in 14 of 16 patients. In a group of five patients who were diagnosed with cryptogenic liver disease (C100-3 negative), 4 of 5 patients were reactive for antibody to all of the above epitopes. In a survey of 23 patients with other forms of chronic liver disease (nonviral liver disease, hepatitis B, alcoholic liver disease, cholestatic liver disease, and autoimmune hepatitis), only 1 of 23 patients was reactive for antibody to the C100-3 and 4 of 23 patients were reactive for antibodies to structural and nonstructural regions of the virus.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1993

Patterns of survival in patients with Hodgkin's disease: long follow up in a single centre.

BACKGROUND: Prolonged remission can now be induced in the majority of patients with Hodgkin's disease with chemotherapy and/or irradiation. However, there is a significant proportion of patients in whom this approach fails, either at presentation or subsequently. Survival is the definitive endpoint to assess treatment efficacy. In this study, the survival patterns of a large group of consecutive patients treated in a single institution are presented. RESULTS: The overall median survival was 18.3 years. Clinical remission (complete remission plus good partial remission) was induced in 443 (85%); the median survival of patients in remission has not been reached. Fifty-eight patients achieved responses less than clinical remission with initial therapy (partial response) or had progressive disease, the median survival of this group being 1.4 years. With further therapy, remission was subsequently induced in 10; 5 are still alive, 5 have died between 1.9 years and 14.3 years. Twenty patients died before completion of therapy. Recurrence has been documented in 147 of the patients in remission (following initial therapy) over a median follow up period of 13 years (minimum 5 years). One hundred forty-three of these patients were retreated following recurrence (105 chemotherapy, 28 radiotherapy, 6 combined modality treatment and 4 surgery). Second remission was induced in 109/143 (76%). There was a trend towards better second remission induction in patients whose first remission was longer than 1 year (p = 0.06). The median duration of second remission was inferior to first remission duration (p < 0.001). There was no correlation between duration of first remission and survival following recurrence (p = 0.8) or with duration of second remission (p = 0.54). There was no significant difference in duration of second remission between patients who were initially treated with radiotherapy or chemotherapy (p = 0.3). The median survival following second remission was 12.0 years, being the same for patients with initially localized disease (stages I and II) treated with radiation alone and for patients with advanced Hodgkin's disease (stages III and IV) treated with chemotherapy. Survival after recurrence is significantly better for patients under 50 years at the time of recurrence (p < 0.001). Second recurrence was documented in 46 patients, third remission being reinduced in 22, the median survival of the latter being 5.1 years. CONCLUSION: These results illustrate the importance of prolonged follow up in defining the clinical course of patients with HD and are vital for planning experimental chemotherapy at the time of treatment failure or recurrence.

Adolescent↗
PubMed1993

The management of recurrent acute myelogenous leukaemia at a single centre over a fifteen-year period.

One hundred and sixty-two patients initially treated at St Bartholomew's Hospital between 1974 and 1988 developed recurrent acute myelogenous leukaemia (AML). In the majority, the intention was to administer intensive chemotherapy again; 22/162 were re-treated palliatively. A second complete remission (CR) was achieved in 50/126 (40%) evaluable patients. Several different regimens were employed over this time period; the treatment used was the only factor that correlated with achievement of second CR (P = 0.04). Ten of the 50 patients received myeloablative therapy with either allogeneic or autologous bone marrow transplantation in second CR. The median duration of second CR for those patients who did not proceed to intensive consolidation with bone marrow transplantation was 7 months. There was no correlation between second remission duration and age, or with the administration of either intensive or conventional consolidation therapy. The median survival from first recurrence for all patients was 4 months, increasing to only 5 1/2 months for those re-treated with chemotherapy and to 12 months for those patients in whom a second CR was achieved, confirming the very poor prognosis of these patients.

Adolescent↗
PubMed1993

Fludarabine in low-grade lymphoma.

During the last 4 years, 88 patients with low-grade non-Hodgkin's lymphoma have received fludarabine, 25 mg/m2 daily for 5 days, repeated every 3 to 4 weeks. Fifty-one patients received fludarabine at recurrence or when the disease was deemed resistant to conventional treatment, 21 patients received the drug in the context of "minimal residual disease" in the hope of complete remission being achieved with a view to proceeding to myeloablative therapy (cyclophosphamide and total body irradiation) with autologous bone marrow transplantation, and 16 newly diagnosed patients received fludarabine as first-line therapy. Myelosuppression was the predominant toxicity, with 55% and 31% of previously treated and newly diagnosed patents, respectively, becoming neutropenic (neutrophils < or = 1.0 X 10(9)/L). The response rate (complete and partial response) was 44% for both patients with recurrent/resistant disease (20 of 45 evaluable patients) and for those with "minimal residual disease" (nine of 20 evaluable patients). In newly diagnosed patients, the response rate was 69% (11 of 16 patients). Five patients died of infection while neutropenic. These results confirm the activity of fludarabine in low-grade non-Hodgkin's lymphoma. Its precise role remains to be determined.

Adult↗
PubMed1993

Mitoxantrone and cytosine arabinoside as treatment for acute myelogenous leukemia (AML) at first recurrence.

A total of 107 patients with newly diagnosed acute myeloblastic leukemia (AML) were referred to the ICRF Department of Medical Oncology at St Bartholomew's Hospital between August 1986 and July 1989. Of those referred, 92 (87%) were treated with remission induction chemotherapy comprising: Adriamycin, cytosine arabinoside (ara-C) and 6-thioguanine if aged < 60 years (57 patients) or mitoxantrone (MTN) and ara-C if aged > 60 years (35 patients). Of those treated, 54 (58%) entered complete remission (CR). Recurrent AML developed in 38 out of these 54 patients (70%) of whom 25 aged 19-73 years (median 50 years) subsequently received MTN and ara-C as reinduction therapy. The 19 younger patients (under 60 years old) received MTN at 12 mg/m2, intravenously, daily for 5 days and ara-C at 100 mg/m2, intravenously, twice daily for 7 days. The six older patients received the same ara-C schedule but the dose of MTN was reduced to 10 mg/m2 for 5 days. Second CR was achieved in 16 out of 25 patients (64%) [12/19 (63%) and 4/6 (67%) for patients aged under or over 60 years, respectively]. Eight of the patients in whom second CR was achieved were aged under 50 years and were thus eligible for additional consolidation comprising myeloablative therapy with autologous bone marrow transplantation (ABMT). Four patients actually received the latter treatment: two remain in second CR at 21 and 46 months. Three of the remaining eight patients aged > 50 years in whom second CR was achieved remain in second CR 8 to 43 months later. Censored for myeloablative therapy + ABMT, the overall median duration of second CR was 5 months. Although remissions tended to be short, in younger patients the possibility of proceeding to myeloablative therapy with autologous bone marrow support makes the regimen worthwhile and, even in older patients, it was sometimes possible to achieve prolonged second remissions.

Adolescent↗
PubMed1992

Audit of compliance with antenatal protocols.

OBJECTIVE: To assess the implementation of action protocols dictated by antenatal risk factors noted at the initial (booking) antenatal visit. DESIGN: Retrospective study of 2000 women delivered between 1 March 1990 and 29 March 1991. SETTING: Maternity department of a district general hospital supporting a multiethnic population in inner London. MAIN OUTCOME MEASURES: Comparison of clinical actions performed against those dictated by the department's protocols. Analysis according to clinical importance, gestation at booking, maternal age, parity, birth order, ethnic origin, and certainty of gestational age. RESULTS: Interobserver agreement between the two auditors was good (kappa statistic for risk factors detected, 0.78; for actions generated, 0.80). Of the 15,658 actions dictated by department protocols, 3673 (23.5%) were actually performed by the clinicians. The 63 combinations of risk factors and actions believed by consultants to be of particular clinical importance had an action rate of 28.3% compared with 18.6% for those considered less important (p < 0.001). Mothers who first visited the hospital antenatal clinic at or before 24 weeks' gestation had 25.2% of relevant protocols fulfilled (p < 0.001). Compliance was significantly improved in women aged 36 or over (32.4%), black women (24.9%), and cases of uncertain gestation (24.5%). Parity and birth order were not associated with an altered action rate. Ethnic origin deemed as "other" (than white, black, Asian, or oriental) or "unknown" was associated with poor compliance (19.3%). CONCLUSIONS: Compliance to a set of agreed protocols was poor even though a computer system was available and a protocol manual had been distributed. Protocols were more likely to be implemented in women who booked early and in some groups of women deemed at high risk including older mothers, black women, and those denoted as having uncertain gestational age.

Clinical Protocols↗
PubMed1992

Determination of a cephalosporin antibiotic, ceftibuten, in human plasma with column-switching high-performance liquid chromatography with ultraviolet detection.

A column-switching high-performance liquid chromatographic assay combined with a heart-cutting technique and UV detection (LC/LC/UV) was developed to determine ceftibuten, a new oral cephalosporin, in human plasma. Plasma samples were directly injected into the first chromatographic column for sample cleanup and extraction. Thereafter, a switching valve, located at the junction of the first cleanup column and the second analytical column, opened during a 4-6-min interval after injection to transfer the segment containing ceftibuten into the analytical column for quantitation. The method was used routinely in pharmacokinetic studies and has the advantages of simplicity, improved sensitivity, and selectivity. Concentrations of ceftibuten in plasma over a range of 0.1-20 micrograms/mL can be determined with high precision and reproducibility. A single, oral, 200-mg dose of ceftibuten in humans resulted in a maximum concentration of 9.79 micrograms/mL, an area under the plot of concentration of drug in plasma versus time (0-12 h) of 47.77 micrograms.h/mL, and a half-life of 3.2 h. These results document the utility of the LC/LC/UV method in clinical pharmacokinetic studies.

Administration, Oral↗
PubMed1992

Patterns of survival in patients with advanced Hodgkin's disease (HD) treated in a single centre over 20 years.

A total of 164 consecutive adults with newly confirmed stage IIIB, IVA or IVB Hodgkin's disease (HD) commenced cyclical combination chemotherapy comprising mustine, vinblastine, prednisolone and procarbazine (MVPP) every 6 weeks (145 patients) or minor variants (19) at St Bartholomew's Hospital between 1968 and 1984. The median follow-up period is 14 years. Complete remission (CR) was achieved in 97/164 (59%) and partial remission (PR) in 23/164 (14%) with lesser responses or death being documented in 44. Achievement of CR correlated with stage, serum albumin and serum beta2 microglobulin level at presentation on univariate and multivariate analysis; 55/97 (58%) remain in continuous CR, the median duration of remission not having been reached. Twelve patients died in first remission; there have been 30 recurrences, one occurring after 13 years. Second remission was achieved in 17/30; 6/17 remain in continuous second remission and two have died in second remission. There have been nine second recurrences, third remission being achieved in 6/9. Two continue in third remission, two patients have died in third remission: 82/164 patients are alive with a minimum follow-up of 6 years. Eighty-two patients have died; 66 with evidence of HD, six with second malignancy, one each of haemorrhage and infection, eight of unrelated causes, the cause of death was unknown in one. The overall median survival from presentation is 14 years, being the same for patients in CR and PR with minimal residual abnormality (good partial remission, GPR), and being better for those for whom remission was achieved than those for whom it was not. The median survival following first recurrence is 4 years, being significantly longer for younger patients (less than 50 years). These results emphasise the importance of long-term follow-up to determine the clinical course of HD and are vital for planning experimental chemotherapy at the time of early treatment failure or recurrence.

Adolescent↗
PubMed1992

Short term therapy (STT) for acute myelogenous leukaemia (AML).

Between 1978 and 1988 (median follow up 5 1/2 years), 396 newly diagnosed adults with AML (age range 14-59 years, median 44) received STT comprising daily Adriamycin: 25mg/m2 for 3 days, Cytosine arabinoside (ara-C): 100mg/m2 bd and 6-thioguanine: 100mg/m2 bd, each for 7 days. A maximum of 6 cycles was administered with as short an intercycle time as possible. No further treatment was given. Complete remission (CR) was achieved in 243/396 patients (62%), 71 patients (18%) having resistant leukaemia and 82 (21%) dying within 6 weeks. Antecedent myelodysplasia and advanced age correlated unfavourably with achievement of CR (p = less than 0.001 and 0.005 respectively). Sixty nine patients continue in first remission between 2 1/2 and 12 years; the median duration of remission was 1 year. M3 morphology (p = 0.005) and absence of hepatosplenomegaly (p = 0.001) correlated favourably with duration of remission. Ninety one patients remain alive with an actuarial survival of 22% at 5 years. More recently, additional consolidation comprising high-dose ara-C and total body irradiation (TBI) with autologous bone marrow transplantation (ABMT) has been evaluated in an open study. CR has been achieved in 41/66 patients under the age of 50 but only 19/41 have proceeded to ara-C + TBI + ABMT. Twenty two have not (early recurrence 10, allogeneic BMT 4, debility 6, refusal 2). 11/19 who proceeded to ablative therapy continue in remission (4 treatment related deaths, 4 recurrences) as compared to 9/22 who did not. Currently the overall median duration of remission for the 41 patients intended to proceed is identical to that of age-matched historical controls illustrating the difficulties inherent in demonstrating benefit for the use of myeloablative therapy and ABMT in patients with AML in first remission.

Adolescent↗
PubMed1991

Preimplantation genetics: chromosomes of fragmented human embryos.

STUDY OBJECTIVE: To examine the chromosome makeup of fragmented human embryos. DESIGN: Prospective. SETTING: Assisted reproductive technology (ART) program. PATIENTS: One hundred twenty-one poor-quality embryos from 58 patients 31 to 40 years of age admitted for an ART program were examined for chromosome makeup. RESULTS: Chromosome anomalies were observed in 31.9% (29/91) of poor-quality embryos, 19.8% (18/91) displayed mosaicism (diploid/haploid, diploid/triploid, diploid/aneuploid), 5.5% (5/91) showed polyploidy, 2.2% (2/91) had pulverized chromosomes, 2.2% (2/91) revealed aneuploidy, 1.1% (1/91) had prematurely condensed chromosomes, and 1.1% (1/91) had structural rearrangements involving chromosome number 2. The mean age of patients showing anomalies (36.5 years) was not significantly higher than the mean for the entire group (35.5 years). CONCLUSIONS: The incidence of chromosome anomalies in fragmented human embryos is high. These anomalies originate either in the gametes or through mitotic nondisjunction within the embryos. It is not advisable to replace such embryos into patients going through in vitro fertilization.

Adult↗
PubMed1991

Pharmacokinetics of ceftibuten-cis and its trans metabolite in healthy volunteers and in patients with chronic renal insufficiency.

The impact of renal insufficiency on the dispositions of 300 mg of orally administered ceftibuten-cis, a new broad-spectrum oral cephalosporin, and its primary metabolite ceftibuten-trans was characterized in 30 adult subjects. Subjects were divided into five groups of six subjects each on the basis of their 24-h ambulatory creatinine clearances (CLCR). The apparent total body clearance (CLP/F; where F is absolute bioavailability) and renal clearance of ceftibuten-cis were significantly lower in subjects with end-stage renal disease (on maintenance hemodialysis; group V) and in those with severe (CLCR, 5 to 29 ml/min; group IV) and moderate (CLCR, 30 to 49 ml/min; group III) renal insufficiency than in those with mild renal insufficiency (CLCR, 50 to 80 ml/min; group II) or normal renal function (CLCR, greater than 80 ml/min; group I). A significant correlation was observed between CLCR and ceftibuten-cis CLP/F. The mean apparent steady-state volume of distribution (V beta/F) of ceftibuten-cis ranged from 0.21 to 0.24 liter/kg in subjects in group I, II, III, and IV. V beta/F was significantly greater in the group V subjects with end-stage renal disease (V beta/F, 0.39 +/- 0.27 liters/kg). These changes in V beta/F cannot be separated from possible changes in bioavailability. The maximum concentration of ceftibuten-trans in plasma was significantly higher and occurred significantly later in group IV subjects than it did in subjects in the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗