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Biomedical subjects

J L Frazier

Publications and source records attributed to J L Frazier.

14 recordsLinked to original sources
PubMed2000

TNF-alpha blockade by a dimeric TNF type I receptor molecule selectively inhibits adaptive immune responses.

Tumor necrosis factor-alpha (TNF-alpha) is a mediator of severe inflammatory processes, including rheumatoid arthritis. Suppression of TNF with a soluble type I or type II receptor molecule (TNF-RI or TNF-RII) has the potential to decrease cytokine levels and modulate inflammatory diseases in humans. However, it has recently been reported that treatment of mice with a TNF-RI:Fc immunoadhesin protein augmented Gram positive infections and subsequent mortality. To determine if TNF-alpha blockade with soluble TNF-alpha receptors might alter immune system function, assays were assessed in rodents treated with a dimeric form of the p55 TNF-RI, Tumor Necrosis Factor-binding protein (TNFbp). Administration of TNFbp resulted in suppression of primary and secondary IgG antibody responses and cell-mediated immune function. No treatment-related differences were detected in immune-enhancing assays or non-specific immune function parameters. Bacterial host resistance assays with Listeria monocytogenes, Staphylococcus aureus or Escherichia coli showed an increase in tissue colony counts only with L. monocytogenes challenged animals following TNFbp administration. These results suggest that TNFbp has the capacity to inhibit adaptive immune function in experimental animal models. Studies suggest that while reducing TNF-alpha is important in controlling cytokine-dependent disease states, maintenance of a threshold level may be critical for normal immune function.

Animals↗
PubMed2000

Phase I/II trial of recombinant methionyl human tumor necrosis factor binding protein PEGylated dimer in patients with active refractory rheumatoid arthritis.

OBJECTIVE: To evaluate the safety, immunogenicity, pharmacokinetics, and efficacy of intravenous administration of tumor necrosis factor binding protein (TNFbp) dimer in patients with rheumatoid arthritis (RA). METHODS: This phase I/II study was a multicenter, randomized, double blind, placebo controlled, ascending dose study evaluating TNFbp dimer administered by i.v. infusion. Thirty-three patients with RA divided into 3 cohorts received TNFbp dimer (30, 100, 300 microg/kg) or placebo during a 5 min infusion at baseline and at 3 and 6 weeks; patients were followed at routine intervals after each infusion through 77 days postinfusion. Pharmacokinetics were analyzed using a log-linear regimen and comparisons were made between half-life after first, 2nd, and 3rd doses. Plasma TNFbp dimer concentrations and serum antibody levels were used in the measurement of pharmacokinetics. RESULTS: Administration of 30 microg/kg of TNFbp dimer was generally well tolerated; the maximum tolerated dose was 100 microg/kg. No serious adverse events were reported. A significant antibody response affected the half-life and clearance of TNFbp dimer at each dose group. Anti-TNFbp antibodies were noncytotoxic and nonagonistic. Clinical evaluations provided evidence of in vivo activity of TNFbp dimer in these patients. CONCLUSION: TNFbp dimer administered to patients with long standing RA resulted in significant antibody production to the study drug. This effect reduced the half-life and clearance of the TNFbp. This TNFbp will not be a viable option for treating patients with RA secondary to immunogenicity.

Adult↗
PubMed1998

Action potential classifiers: a functional comparison of template matching, principal components analysis and an artificial neural network.

Multiunit neural activity occurs often in electrophysiological studies when utilizing extracellular electrodes. In order to estimate the activity of the individual neurons each action potential in the recording must be classified to its neuron of origin. This paper compares the accuracy of two traditional methods of action potential classification--template matching and principal components--against the performance of an artificial neural network (ANN). Both traditional methods use averages of action potential shapes to form their corresponding classifiers while the artificial neural network 'learns' a nonlinear relationship between a set of prototype action potentials and assigned classes. The set of prototypic action potentials and the assigned classes is termed the training set. The training set contained action potentials from each class which exhibited the full range of amplitude variability. The ANN provided better classification results and was more robust in analysis of across-animal data sets than either of the traditional action potential classification methods.

Action Potentials↗
PubMed1995

Vitamin E and the risk of coronary artery disease.

Before the widespread use of vitamin E in any dosage regimen can be recommended for the prevention of CAD, more information on its efficacy and adverse effects must be obtained. Unfortunately, the results of ongoing studies will not be available for several years. Until then, pharmacists can play a major role in monitoring vitamin E supplementation and educating both patients and other healthcare professionals about its potential role in decreasing the risk of coronary artery disease.

Animals↗
PubMed1986

Isolation and characterization of a Chinese hamster ovary cell line requiring ethanolamine or phosphatidylserine for growth and exhibiting defective phosphatidylserine synthase activity.

A mutant cell line (designated M.9.1.1) requiring ethanolamine for growth was derived from Chinese hamster ovary (CHO-K1) cells using 5-bromodeoxyuridine enrichment. The ethanolamine requirement was readily replaced by 20 microM phosphatidylserine and 10 microM lysophosphatidylethanolamine. When M.9.1.1 cells were supplemented with phosphatidyl[3H]serine it was rapidly taken up, and subsequently decarboxylated to form phosphatidyl[3H]ethanolamine. The incorporation of [3H]serine into phosphatidylserine in the mutant cells was 57% of that in the parental cells. Phosphatidylethanolamine synthesis from [3H]serine in the mutant cells was 35% of that in parental cells. When M.9.1.1 cells were deprived of ethanolamine for 48 h the level of phosphatidylserine decreased 34% and the level of phosphatidylethanolamine decreased 26% compared to parental cells. At the same time the rate of turnover of phosphatidylserine was reduced to half that found in parental cells. Examination of the enzymes of phosphatidylserine metabolism indicated defective phosphatidylserine synthase activity in the mutant. When exogenous phosphatidylcholine was used as the phospholipid substrate for the reaction the apparent kinetic constants were Vmax (mutant) = 5.7 pmol/min/mg protein and Vmax (parental) = 17.5 pmol/min/mg protein. Measurement of the back reaction (ATP-independent incorporation of choline into phospholipid) gave no detectable activity in the mutant cells. The data indicate that the phosphatidylcholine-dependent synthesis of phosphatidylserine is the primary lesion in M.9.1.1.

Animals↗
PubMed1983

Measurements of iron absorption from prenatal multivitamin--mineral supplements.

Although prenatal multivitamin--mineral supplements containing 60 to 65 mg of iron, taken once daily, are used widely to assure that pregnant women absorb the approximately 3.5 mg of supplemental iron per day that they require, there have been no studies concerning the absorption of iron from these preparations. Using cross-over studies in groups of normal nonpregnant women of childbearing age, such iron absorption was assessed using a technique in which absorption is calculated from the measured increase in serum iron after the oral ingestion of iron in various forms. With each of 4 different brands of prenatal supplements, mean iron absorption was less than the required 3.5 mg and ranged from 1.8 to 3.0 mg. These values were significantly less (P less than .01) than the 8.1 mg that was absorbed from 65 mg of iron alone. Decreased iron absorption in the prenatal supplements was shown to be due to inhibition by calcium carbonate and magnesium oxide and, in some cases, to poor iron release. When one of the 4 brands was reformulated to contain less calcium carbonate and less magnesium oxide, mean iron absorption increased to 4.5 mg. It is concluded that the amount of iron absorbed from many prenatal multivitamin--mineral supplements is significantly less than with standard forms of iron in nonpregnant women and that bioavailability studies should be performed on pregnant patients to determine whether these commercial preparations provide adequate amounts of iron during pregnancy.

Absorption↗
PubMed1982

Studies of the transferrin receptor on both human reticulocytes and nucleated human cells in culture: comparison of factors regulating receptor density.

The transferrin receptor, present on reticulocytes and nucleated cells in tissue culture, has been measured with both immunoassay techniques and transferrin binding studies. The total cellular immunoreactive receptor is rapidly lost from erythrocytes during the process of reticulocyte maturation (from as many as 400,000 molecules to <20,000 molecules/reticulocyte). This event parallels the loss of cell surface transferrin binding sites and RNA content, and correlates with previous studies that have measured the decline in hemoglobin synthesis.Nonhemoglobin-producing normal human fibroblasts, which appear to have a much lower iron requirement than reticulocytes, contain similar numbers of immunoreactive receptors per cell (400,000 receptor molecules), when in an active state of proliferation. Although receptor density on fibroblasts is directly related to cell proliferation, our studies demonstrate that nonproliferating fibroblasts still retain significant numbers of immunoreactive receptors (150,000 molecules/cell) and transferrin binding sites. Since additional studies indicate that proliferating cells have increased iron uptake, a simple hypothesis would predict that the parallel increase in transferrin binding sites and total cellular immunoreactive receptor associated with proliferation is related to an increased cellular iron requirement. However, the number of immunoreactive receptor molecules and transferrin binding sites is not changed when cells are grown in iron-deficient media, or in media with added transferrin-iron. This result and the lack of marked differences in receptor number on both hemoglobin-producing and nonhemoglobin-producing cells indicate that other factors besides receptor density play major roles in the regulation of cellular iron uptake, retention, and loss.

Anemia, Sickle Cell↗
PubMed1979

Splenic influence on the development of a local pulmonary immune response.

The role of the spleen in the development of specific antibody-forming cells (sAFC) in the pulmonary draining lymph nodes (pdLNC) of hamsters after local inoculation of sheep erythrocytes (SRBC) was evaluated. The role of the spleen was viewed from two vantage points. Panels of animals were either splenectomized with appropriate sham-operated controls before intratracheal inoculation of SRBC, or panels were immunized intravenously simultaneously with the local inoculation of antigen. The presence of an intact spleen was not necessary for the induction of a sAFC response to occur in the pdLNC. Similar numbers of immunoglobulin M (IgM) sAFC were recorded in the pdLNC on day 4 of both sham-operated and splenectomized animals. However, an enhancement of this local response occurred on day 7 if the animals were systemically immunized and therefore demonstrated active participation of the spleen in the specific immune response. The results support the hypothesis that although a local response may occur in the pdLFC in the absence of a spleen or a splenic response, the presence of a systemic or splenic response appears to be important for the enhancement of local IgM sAFC response. These observations suggest that the immune defenses involved in the lower respiratory tract may differ from those in upper respiratory tract and other mucosally lined organs in that the response of the spleen to the antigen affects the local response to that antigen.

Animals↗
PubMedDate not supplied

Wallerian degeneration and inflammation in rat peripheral nerve detected by in vivo MR imaging.

To investigate the role of MR imaging in wallerian degeneration, a series of animal models of increasingly complex peripheral nerve injury were studied by in vivo MR. Proximal tibial nerves in brown Norway rats were either crushed, transected (neurotomy), or transected and grafted with Lewis rat (allograft) or brown Norway (isograft) donor nerves. The nerves distal to the site of injury were imaged at intervals of 0-54 days after surgery. Subsequent histologic analysis was obtained and correlated with MR findings. Crush injury, neurotomy, and nerve grafting all resulted in high signal intensity along the course of the nerve observed on long TR/TE sequences, corresponding to edema and myelin breakdown from wallerian degeneration. The abnormal signal intensity resolved by 30 days after crush injury and by 45-54 days after neurotomy, when the active changes of wallerian degeneration had subsided. These changes were not seen in sham-operated rats. Our findings suggest that MR is capable of identifying traumatic neuropathy in a peripheral nerve undergoing active wallerian degeneration. The severity of injury may be reflected by the corresponding duration of signal abnormality. With the present methods, MR did not distinguish inflammatory from simple posttraumatic neuropathy.

Animals↗
PubMedDate not supplied

Current concepts in the pathogenesis and treatment of reflux esophagitis.

The etiology, pathogenesis, diagnosis, and treatment of reflux esophagitis are reviewed. Reflux esophagitis is the subjective or objective response to gastroesophageal reflux (GER), which is defined as the entrance of gastroduodenal contents into the esophagus not associated with vomiting or belching. The pathogenesis of reflux esophagitis may involve a number of mechanisms, including changes in lower esophageal sphincter pressure, gastric volume, composition of the refluxate, esophageal acid clearance, and esophageal tissue resistance. The most common symptom of reflux esophagitis is heartburn. Regurgitation of fluid into the mouth, usually after bending or during the night, is an unequivocal symptom of GER. Treatment can be divided into three phases. Phase 1 involves the avoidance of certain foods and habits, elevation of the bed head, antacid, and alginic acid-antacid therapy. Phase 2 involves drug therapy with agents not yet approved by the FDA for this indication: bethanechol chloride, cimetidine, and metoclopramide hydrochloride. Bethanechol chloride 25 mg is generally given four times daily. Cimetidine is given in doses of 300-400 mg after meals and at bedtime. Metoclopramide hydrochloride is administered in doses of 10 mg before meals and at bedtime. Phase 3 is antireflux surgery. Clinical experience has shown that phase 1 therapy is successful for about 75% of all patients. Of the 25% that do not respond to phase 1 therapy, about 90% will respond to phase 2 therapy, leaving only 5-10% of all patients with this disorder who will require phase 3 treatment. Current data favor cimetidine and bethanechol over metoclopramide. The least proof of efficacy and the most frequent adverse side effects are seen with metoclopramide. Cimetidine and bethanechol appear to have similar efficacy and relatively infrequent side effects. Evidence confirming the superiority of cimetidine over bethanechol is lacking. Further research is needed to determine the optimal pharmacologic combinations and treatment regimens.

Animals↗