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Biomedical subjects

T Lam

Publications and source records attributed to T Lam.

At least 37 records · Page 2Linked to original sources
PubMed1996

Serum progesterone and human chorionic gonadotrophin measurements in the evaluation of ectopic pregnancy.

We evaluated the clinical usefulness of measuring the serum concentrations of human chorionic gonadotrophin (HCG) and progesterone to distinguish between early viable and nonviable pregnancies. We investigated 110 women with clinical symptoms of abnormal pregnancy. A single HCG measurement did not clearly distinguish between ectopic and failing intrauterine pregnancies; an HCG value below 3,000 IU/L, together with a serum progesterone below 40 nmol/L, predicted abnormal pregnancy outcome in 97% of women (positive predictive value: 91%; negative predictive value: 95%). Serum HCG value above 3,000 IU/L or progesterones above 40 nmol/L, discriminated between an ongoing pregnancy and an abnormal pregnancy in 87% women (positive predictive value: 95%; negative predictive value: 91%) and provided reassurance of an ongoing pregnancy. Our results suggest that a combination of serum progesterone and HCG measurements provide clinically useful biochemical information which enhances the prediction of pregnancy outcome.

Chorionic Gonadotropin↗
PubMed1995

A 55-kilodalton antigen encoded by a gene on a Borrelia burgdorferi 49-kilobase plasmid is recognized by antibodies in sera from patients with Lyme disease.

We have identified a 55-kDa antigen encoded by a gene on a 49-kb plasmid of Borrelia burgdorferi. The screening of a B. burgdorferi DNA expression library (N40 strain) with rabbit anti-B. burgdorferi serum and then with serum from a patient with Lyme disease arthritis revealed a clone that synthesized an antigen that was reactive with both sera. DNA sequence analysis identified an operon with two genes, s1 and s2 (1,254 and 780 nucleotides), that expressed antigens with the predicted molecular masses of 55 and 29 kDa, respectively. Pulsed-field gel electrophoresis showed that the s1-s2 operon was located on the 49-kb plasmid. Recombinant S1 was synthesized as a glutathione S-transferase fusion protein in Escherichia coli. Antibodies to recombinant S1 bound to a 55-kDa protein in lysates of B. burgdorferi, indicating that cultured spirochetes synthesized S1. Thirty-one of 100 Lyme disease patients had immunoglobulin G (IgG) and/or IgM antibodies to S1. IgG antibodies to S1 were detected by enzyme-linked immunosorbent assay and immunoblots in the sera of 21 (21%) of 100 patients with Lyme disease; 11 (27.5%) of the S1-positive samples were from patients (40) with early-stage Lyme disease, and 10 (16.7%) were from patients (60) with late-stage Lyme disease. Fifteen (38.5%) of 40 serum samples from patients with early-stage Lyme disease had IgM antibodies to S1. These data suggest that the S1 antigen encoded by a gene on the 49-kb plasmid is recognized serologically by a subset of patients with early- or late-stage Lyme disease.

Amino Acid Sequence↗
PubMed1994

Major and minor Kb-restricted epitopes encoded by the endogenous ecotropic murine leukemia virus AKR623 that are recognized by anti-AKR/Gross MuLV CTL.

C57BL/6 mice can generate a type-specific and class IH-2Kb-restricted CTL response against histocompatible AKR/Gross murine leukemia virus (MuLV) cell surface antigen positive (GCSA+) tumor cells. These anti-AKR/Gross MuLV CTL are also known to lyse SC.Kb/623 target cells expressing the molecular MuLV clone AKR623 (derived from the endogenous ecotropic MuLV provirus emv-11). To help identify AKR623 viral epitopes recognized by these CTL, four chimeric proviruses were constructed from two parental plasmids, pAKR623 and pAK7. It has been shown that SC.Kb/7 fibroblast targets expressing the emv-14-derived molecular clone AK7 are only poorly lysed by anti-AKR/Gross MuLV CTL. Data from experiments employing SC.Kb cells infected with the chimeras as targets against anti-AKR/Gross MuLV CTL supported the location of a previously identified immunodominant epitope located within the viral p15E transmembrane envelope protein, peptide TM134-141 (KSP-WFTTL). Furthermore, the use of Kb-motif-defined AKR623 encoded peptides together with data obtained using the chimeric viruses allowed the identification of three additional anti-AKR/Gross MuLV CTL epitopes. Peptides representing these epitopes, MA125-132 (RSALY-PAL), RT142-149 (SHRWYTVL), and RT456-463 (RMTHYQAM), are characterized herein with respect to their ability to confer lysis upon EMV- target cells and to stimulate tumor primed splenocytes in vitro. The identification and characterization of these additional epitopes allow for a better understanding of both the CTL response against GCSA+ tumor cells and the dysfunctional CTL response against EMV-14 and AK7.

AKR murine leukemia virus↗
PubMed1994

TGF-beta 1 and 25-hydroxycholesterol stimulate osteoblast-like vascular cells to calcify.

Previous studies in our laboratory demonstrated messenger RNA for bone morphogenetic protein-2a in human calcified plaque, suggesting that arterial calcification is a regulated process, similar to osteogenesis. To further test this hypothesis, we have isolated and cloned a subpopulation of cells from bovine aortic media that show osteoblastic potential. These novel cells are primarily distinguished from smooth muscle cells by expression of a surface marker preliminarily identified as a modified form of the ganglioside sialyl-lactosylceramide (GM3). Osteoblastic potential was indicated by high levels of alkaline phosphatase and collagen I, expression of osteopontin and osteonectin (SPARC), and production of bone-specific osteocalcin and hydroxyapatite. Cultures of these cells were stimulated to form increased numbers of calcium-mineral-producing nodules by the oxysterol 25-hydroxycholesterol as well as by transforming growth factor-beta 1, both known to be present in atherosclerotic lesions. The stimulation of calcifying vascular cells in the artery wall by these two factors suggests a possible mechanism for the colocalization of calcification with atherosclerosis in vivo.

Alkaline Phosphatase↗
PubMed1994

Maternal serum screening in the Sioux Lookout Zone. Complicated test for an unspecified need.

We investigated whether the incidence of fetal abnormalities among patients in Sioux Lookout Zone differs from incidence elsewhere in Canada, whether First Nations people would agree to screening, how information could be disseminated, and what practical considerations would affect implementation. Incidence appears to be similar to elsewhere, but First Nations people's cultural and spiritual beliefs and the difficulty of taking action once results are confirmed make current screening programs inappropriate.

Chorionic Gonadotropin↗
PubMed1993

Fish oil modifies effect of high cholesterol diet on intestinal absorption in diabetic rats.

Omega-3 fatty acids ('fish oil') reduce the intestinal absorption of glucose and lipids in normal and in diabetic rats, but their effect is altered by the presence of saturated or poly-unsaturated omega-6 fatty acids in the diet. This study was undertaken to test the hypothesis that the influence of fish oil on the intestinal uptake of nutrients in diabetic rats is also influenced by the cholesterol content of the diet. Streptozotocin diabetic rats were raised for 2 wk on semisynthetic diets in which the lipid composition was derived mainly from beef tallow (BT), beef tallow plus cholesterol (BTC), fish oil (FO), or fish oil plus cholesterol (FOC). Food intake and weight gain was similar in the 4 diet groups, although the fasting blood glucose was lowest in diabetic rats fed BT. Cholesterol supplementation increased intestinal wall and mucosal weights when fed with BT, but the opposite effect was seen with FO, with lower wall and mucosal mass with FOC than with FO. Ileal uptake of D-glucose was lower in FO than in BT or FOC. Cholesterol feeding was associated with enhanced jejunal uptake of cholesterol when fed with BT, but the converse was observed with FO. Thus, 1) the reduction of glucose absorption associated with feeding fish oil is blunted in the presence of a supplemented intake of cholesterol; and 2) a fish oil diet reduces cholesterol uptake even in the presence of a high level of dietary cholesterol. It remains to be established what is the optimal ratio of dietary saturated, polyunsaturated omega-3 and omega-6 fatty acids, and cholesterol required to normalize intestinal transport function in diabetic rats.

Animals↗
PubMed1991

The extracellular domain of p185/neu is released from the surface of human breast carcinoma cells, SK-BR-3.

The human breast carcinoma cell line SK-BR-3, expresses the neu oncogene product, p185, which is a receptor tyrosine kinase. Using a double monoclonal antibody capture enzyme-linked immunosorbent assay for p185, activity was detected in conditioned media from cultures of SK-BR-3 cells. Two monoclonal antibodies specific for the extracellular domain of p185/neu immunoprecipitated a protein with a molecular mass of approximately 105 kDa. p105 was further shown to compete with p185 for binding to monoclonal antibodies and pulse-chase experiments indicate that it was generated by post-translational processing. Peptide maps showed that p105 and p185 are related polypeptides. Since p105 is close to the predicted size for the extracellular domain of p185/neu, we propose that SK-BR-3 cells specifically process and release this portion of the receptor into the medium. The release of the extracellular domain may have implications in oncogenesis and its detection could prove useful as a cancer diagnostic.

Adenocarcinoma↗
PubMed1991

A case of early carcinoma of the oesophagus in association with annular pancreas.

A Chinese patient presented with a 3-week history of vomiting. Pre-operative barium swallow and upper endoscopy and biopsy revealed a squamous cell carcinoma of the lower oesophagus. Operative findings included a relatively early carcinoma of the oesophagus and an annular pancreas with dilated proximal duodenum. Oesophagectomy was performed and the whole stomach used for reconstruction. A pylorojejunostomy provided drainage for the stomach as well as decompression of the proximal duodenum. This patient's congenital anomaly, with its attendant symptoms, led to the early diagnosis and treatment of an oesophageal malignancy with an expected improved prognosis.

Aged↗
PubMed1991

Restricticin, a novel glycine-containing antifungal agent.

Restricticin (1) is a naturally-occurring antifungal agent which contains triene, pyran and glycine ester functionalities and is unrelated to any previously known family of natural products. This unstable compound, as well as its corresponding N,N-dimethyl derivative (2), have been produced and isolated from both solid and liquid fermentations of Penicillium restrictum. The desglycyl hydrolysis product, restrictinol (3), was produced via the hydrolysis of pure restricticin and as an artifact of the isolation of restricticin.

Antifungal Agents↗
PubMed1990

Transplantation of the rabbit medial collateral ligament. I. Biomechanical evaluation of fresh autografts.

This investigation was designed to study the biomechanical recovery of a free bone-ligament-bone graft that was returned to its normal extra-articular position, with as little disturbance to its mechanical and biological environments as possible. Twenty-five adult New Zealand white rabbits had their right bone-medial collateral ligament (MCL)-bone complex removed completely and replaced immediately using internal fixation. Animals were allowed unrestricted cage activity before sacrifice in groups of five at intervals of 3, 6, 12, 24, and 48 weeks posttransplantation. Contralateral legs served as internal controls and a separate series of normal animals served as external controls. All MCLs were tested biomechanically using a detailed testing protocol. Results showed early deterioration of 20-35% in autograft complex structural behavior, with weakening of both ligament substance and insertions. Viscoelastic behavior of these ligaments was also affected, showing increases in the amount of both cyclic load-relaxation and static load-relaxation at early healing intervals. These properties were statistically indistinguishable, however, from controls at 48 weeks. Failure behavior of autografts was even better preserved, reaching a low of 65% of control values at 24 weeks and recovering to within 10% of controls at 48 weeks. These results, plus the major changes in failure modes that occurred over that duration, suggest that autograft incorporation is a slow but dynamic process. These results further suggest that at least some connective tissue autografts, when placed under, as yet undefined, "proper biological and mechanical conditions," can retain and recover a number of biomechanical properties over a period of 1 year. The longer-term fate of these autografts and the exact nature of their similarities or differences from other graft alternatives (e.g., tendon for ligament), however, is unknown.

Animals↗
PubMed1990

Transplantation of the rabbit medial collateral ligament. II. Biomechanical evaluation of frozen/thawed allografts.

This study was designed to test the mechanical behavior of a frozen/thawed bone-medial collateral ligament (MCL)-bone allograft in a rabbit model and to compare allograft behavior with contralateral unoperated ligaments as well as a group of normal bone-ligament-bone preparations prior to freezing. Twenty-five mature rabbits received similarly frozen bone-MCL-bone allografts and were subsequently allowed to heal without immobilization in groups of five for 3, 6, 12, 24, or 48 weeks after transplantation. A series of biomechanical tests was performed on each allograft, contralateral, and external normal control ligament. Results demonstrated that allografts were significantly tighter than controls at 3 weeks and they remained tight over time. All allografts, however, had inferior structural and material behaviors as compared with controls. Allograft insertional bone and substance deteriorated to about 60% of contralateral strength at 12 and 48 weeks. Bony insertions became the most common site of graft weakness. Both stress at failure and the elastic modulus of allograft substance similarly reached a plateau at those intervals, but at about 30% of contralateral controls. Cyclic and load relaxation properties of allografts, on the other hand, did not deteriorate and were, in fact, indistinguishable from contralateral and normal values at 48 weeks. Comparison with a series of fresh autografts suggests that, with the exception of this viscoelastic recovery, allografts were mechanically inferior to autografts in their healing at the intervals tested. Collectively, these results suggest that allograft MCL healing in this composite model is dynamic but slow, featuring changes in bone and soft tissue over the first year after transplantation. Although "viable" and vascular, allografts have not normalized mechanically and, in fact, appear to have reached a new equilibrium whereby properties are neither improving nor deteriorating. Despite this apparent equilibrium, the trend for some viscoelastic recovery provides hope that allografts may have further potential for improvement. Longer-term studies of MCL allograft mechanical behaviors are clearly required.

Animals↗
PubMed1990

Radiation and the small intestine. Future perspectives for preventive therapy.

Radiotherapy continues to enjoy a prominent role in the treatment of certain human tumors. Unfortunately, the undesired effect of radiation upon normal intestinal tissue often limits its therapeutic potential. While there is abundant information on the effects of radiation on the morphology of the intestine and on the proliferative process which occurs in the intestinal crypts, there is a paucity of information on the early and late effects of sublethal doses of radiation upon the absorptive functions of the intestine. The intestinal epithelium has a rapid turnover rate and is highly radiosensitive. Radiotherapy for malignant human neoplasms is a relatively safe and effective form of treatment, but it may become limited by its undesired side effects upon the gastrointestinal tract. A variety of clinical tests have been suggested as potential indicators of impending intestinal damage, but there is little information on the time course of radiation damage and the associated impairment of intestinal function. Such basic information is essential to assess early functional changes and to thereby allow for the development of suitable clinical tests to allow for the prediction of impending intestinal damage. Provision of this information to the radiotherapist would permit alterations to the timing or dose schedules of radiotherapy and would allow continued treatment, while avoiding or reducing unwanted side effects. In recent years, there has been extensive research on radiation injury to small intestine. This article will review some of the progress in this field, and will focus on potential future therapy to prevent or treat radiation damage to the intestine. These agents include WR-2721, enprostil, vasopressin, defined-formula diets and alterations in the ratio of dietary polyunsaturated-saturated fatty acids.

Forecasting↗
PubMed1989

The effect of cryopreservation on the biomechanical behavior of bovine articular cartilage.

The short-term effect of cryopreservation on specific mechanical behaviors of bovine articular cartilage has been investigated. A flat-ended nonporous indentor was used in a nondestructive, repetitive, axisymmetric unconstrained testing system. Cyclical indentation from a fixed position to a fixed load was applied until a steady-state load-deformation relationship (limit cycle) was achieved. Indentation behaviors measured from the limit cycles of each articular cartilage specimen before and after treatment were compared. Testing was done in vitro using fresh, mature bovine radiocarpal joints. Twenty pairs of cartilage-subchondral bone cores from anatomically similar sites on contralateral joints were separated into three groups; thickness controls, dimethylsulfoxide (DMSO) controls, and cryopreserved experimental samples. Thickness controls and DMSO controls were used to examine the isolated effects of the thickness measurement and DMSO incubation techniques on articular cartilage indentation characteristics. Experimental samples were cryopreserved using DMSO, their thicknesses similarly measured and indentation behaviors examined. Following testing, histological and histochemical assessment of the specimens confirmed the nondestructive nature of the tests. Intra- and intergroup comparisons of controls and experimentals revealed no statistical differences in the mechanical behaviors measured from the limit cycle or in cartilage thickness. These results indicate that the cryopreservation protocol used did not have an effect that we could measure on these specific mechanical behaviors of articular cartilage.

Animals↗
PubMed1989

Lack of protective effect of oral enprostil, a synthetic prostaglandin E2, on intestinal transport and morphology following abdominal irradiation in the rat.

Previous studies have demonstrated that abdominal irradiation alters intestinal uptake of nutrients. The purpose of this study was to determine the effect of an orally administered synthetic prostaglandin E2, enprostil, given on three occasions shortly prior to a single exposure to 600 cGy external abdominal irradiation, on intestinal active and passive transport processes and villus morphology measured 7 days later. Animals were sham-irradiated (CONT) or were exposed to a single dose of 600 cGy external abdominal irradiation (RAD); two and one mornings before the day of irradiation or sham irradiation, and 1 h before irradiation or sham irradiation enprostil was administered. One half of CONT and RAD groups were dosed orally with enprostil, 5 micrograms/kg body weight, and the other half of the CONT and RAD groups were dosed with placebo. Seven days later the in vitro uptake of glucose, galactose, long-chain fatty acids, and cholesterol was determined in the four groups (CONT with and without enprostil, and RAD with and without enprostil). In CONT, enprostil was associated with increased jejunal uptake of glucose and ileal uptake of galactose. In RAD given enprostil, there was increased jejunal uptake of galactose but reduced ileal uptake of glucose and galactose. The expected radiation-associated decline in jejunal galactose uptake was prevented with enprostil. In CONT given enprostil, there was increased jejunal uptake of fatty acid (FA) 14:0 and 16:0 but reduced uptake of FA 18:0, 18:1, and 18:2; enprostil had no effect on lipid uptake in the ileum in CONT.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Saturated fatty acid diet prevents radiation-associated decline in intestinal uptake.

Adult female Sprague-Dawley rats were fed isocaloric semipurified diets containing a high content of either polyunsaturated (P) or saturated (S) fatty acids; these diets were nutritionally adequate, providing for all known essential nutrient requirements. On day 3 after beginning S or P, one group of animals was exposed to a single 6-Gy dose of abdominal radiation, and the other half was sham irradiated. S or P diets were continued for a further 14 days. Brush-border membrane purification and sucrase-specific activities were unaffected by diet or by abdominal irradiation. In rats fed P, irradiation was associated with an increase in jejunal brush-border membrane total phospholipid and the ratio of phospholipid to cholesterol; these changes were not observed in animals fed S. In irradiated rats, ileal brush-border membrane phospholipid per cholesterol was high in animals fed S compared with P. In irradiated animals fed P, there was reduced jejunal and ileal uptake of several medium- and long-chain saturated and unsaturated fatty acids and cholesterol, and the ileal uptake of higher concentrations of glucose was reduced in irradiated animals fed P. In contrast, lipid uptake was similar in control and irradiated animals fed S except for cholesterol uptake, which was reduced. Ileal uptake of higher concentrations of glucose was increased in irradiated animals fed S. Quantitative autoradiography failed to demonstrate any change in the distribution of leucine or lysine transport sites along the villus 1 or 2 wk after abdominal irradiation or in response to feeding S or P. Also, these differences in transport achieved by feeding S to radiated animals were not explained by variations in the animals' food consumption or intestinal mucosal surface area. Thus the use of short-term feeding with a saturated fatty acid diet in the prevention of acute irradiation damage to the intestine warrants further investigation in humans.

Amino Acids↗
PubMed1989

Generation and characterization of monoclonal antibodies specific for the human neu oncogene product, p185.

A series of monoclonal antibodies specific for the extracellular domain of the human neu gene product (p185) have been produced. The generation of these monoclonal antibodies, and their biochemical and immunological characterization is described. The immunization protocol utilized a series of injections of NIH3T3 cells, cyclophosphamide, and a neu transfected NIH3T3 cell line (designated 18-3-7) which expressed the full length human neu-encoded protein. This immunization regimen induced an immune response to the extracellular portion of p185 on the 18-3-7 cells. A panel of ten hybridomas were identified which secreted monoclonal antibodies with a variety of epitope specificities, and reacted with p185 in a number of different experimental formats. As the neu gene product has been associated with human breast cancers, a series of monoclonal antibodies such as these could prove useful in the diagnosis, prognosis and/or treatment of these human malignancies.

Animals↗
PubMed1987

The photodecomposition of aminopterin.

Aminopterin is used in cell fusion experiments to select for hybrid cells by killing unfused cells which are deficient in enzymes for nucleotide salvage pathways. Aqueous aminopterin solutions exposed to fluorescent room light (wavelength greater than 300 nm) were found to lose cytotoxicity. Inactivation was accompanied by changes in the ultraviolet absorption spectra of the solutions. The ultraviolet spectrum of an irradiated aminopterin solution is used to provide a quantitative measure of its cytotoxicity. Aminopterin appears to be photolytically cleaved at the C9-N10 methylene-anilino bond in a reaction analogous to that known for the photolysis of folic acid irradiated at 365 nm (Lowry et al., 1949).

Aminopterin↗