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J A Gordon

Publications and source records attributed to J A Gordon.

At least 37 records · Page 2Linked to original sources
PubMed1997

Conversion of arachidonic acid to tetradecadienoic acid by peroxisomal oxidation.

Human skin fibroblasts convert [5,6,8,9,11,12,14,15-3H]arachidonic acid to two radiolabeled polar metabolites that accumulate in the culture medium. Previous studies identified the most abundant of these products as 4,7,10-hexadecatrienoic acid (16:3). We have now identified the second metabolite as 5,8-tetradecadienoic acid (14:2). Fibroblasts deficient in mitochondrial long-chain acyl coenzyme A dehydrogenase produce increased amounts of 14:2 from arachidonic acid. By contrast, Zellweger fibroblasts which are deficient in peroxisomal beta-oxidation do not convert arachidonic acid to either 14:2 or 16:3. These results demonstrate that 14:2 can be synthesized from arachidonic acid, that this oxidative process occurs in the peroxisomes, and that the pathway does not function in Zellweger's syndrome and similar diseases where there is a genetic deficiency in peroxisomal beta-oxidation.

Acyl-CoA Dehydrogenase, Long-Chain↗
PubMed1996

Experience-dependent plasticity of binocular responses in the primary visual cortex of the mouse.

An activity-dependent form of synaptic plasticity underlies the fine tuning of connections in the developing primary visual cortex of mammals such as the cat and monkey. Studies of the effects of manipulations of visual experience during a critical period have demonstrated that a correlation-based competitive process governs this plasticity. The cellular mechanisms underlying this competition, however, are poorly understood. Transgenic and gene-targeting technologies have led to the development of a new category of reagents that have the potential to help answer questions of cellular mechanism, provided that the questions can be studied in a mouse model. The current study attempts to characterize a developmental plasticity in the mouse primary visual cortex and to demonstrate its relevance to that found in higher mammals. We found that 4 d of monocular lid suture at postnatal day 28 (P28) induced a maximal loss of responsiveness of cortical neurons to the deprived eye. These ocular dominance shifts occurred during a well-defined critical period, between P19 and P32. Furthermore, binocular deprivation during this critical period did not decrease visual cortical responses, and alternating monocular deprivation resulted in a decrease in the number of binocularly responsive neurons. Finally, a laminar analysis demonstrated plasticity of both geniculocortical and intracortical connections. These results demonstrate that an activity-dependent, competitive form of synaptic plasticity that obeys correlation-based rules operates in the developing primary visual cortex of the mouse.

Animals↗
PubMed1996

Deficient plasticity in the primary visual cortex of alpha-calcium/calmodulin-dependent protein kinase II mutant mice.

The recent characterization of plasticity in the mouse visual cortex permits the use of mutant mice to investigate the cellular mechanisms underlying activity-dependent development. As calcium-dependent signaling pathways have been implicated in neuronal plasticity, we examined visual cortical plasticity in mice lacking the alpha-isoform of calcium/calmodulin-dependent protein kinase II (alpha CaMKII). In wild-type mice, brief occlusion of vision in one eye during a critical period reduces responses in the visual cortex. In half of the alpha CaMKII-deficient mice, visual cortical responses developed normally, but visual cortical plasticity was greatly diminished. After intensive training, spatial learning in the Morris water maze was severely impaired in a similar fraction of mutant animals. These data indicate that loss of alpha CaMKII results in a severe but variable defect in neuronal plasticity.

Animals↗
PubMed1995

The impact of immunosuppressive regimens on the cost of liver transplantation--results from the U.S. FK506 multicenter trial.

In an effort to determine the total one-year cost of liver transplantation, the underlying drivers of that cost, and any cost differences between alternative immunosuppressive regimens, an analysis was performed comparing the average one-year posttransplant charges of 322 patients participating in the "U.S. Multi-center Prospective Randomized Trial Comparing FK-506 to Cyclosporine in Liver Transplantation." Total one-year inpatient charges including all readmissions were examined. Professional fees and outpatient charges were excluded. Costs for tacrolimus drug and blood assays were assumed to be equal to those in the CsA group. For patients completing the study, the tacrolimus group had an average length of stay and average one-year cost seven days (P = .06) and $19,290 (P = .05) lower than the CsA group. The difference in rejection profiles between the two arms seems to largely account for the lower costs. The tacrolimus arm consistently had fewer patients in the more severe rejection groups. Increased incidence and severity of rejection were directly related to higher average lengths of stay and costs of transplantation (P < .001). Tacrolimus immunosuppression during the first year after liver transplantation is more cost-effective than CsA in achieving similar patient and graft survival rates. Differing incidence and severity of rejection can dramatically affect the first-year cost of liver transplantation.

Cost-Benefit Analysis↗
PubMed1995

Regulation of differentiation of peritoneal B-1a (CD5+) B cells. Activated peritoneal macrophages release prostaglandin E2, which inhibits IgM secretion by peritoneal B-1a cells.

The B-1a (CD5+) subset of B cells comprises the majority of B cells in the peritoneal cavity and is implicated in the pathogenesis of certain autoimmune diseases and lymphoproliferative disorders. When we stimulated purified B-1a cells with LPS, they produced more than four times as much IgM as similarly stimulated whole peritoneal cells (containing the same number of B-1a cells). Reconstitution experiments using FACS-purified peritoneal cell populations revealed that resident peritoneal macrophages (Mac1+, B220-) profoundly inhibited the LPS response of peritoneal B-1a cells. Culture of B-1a cells with peritoneal macrophages at a ratio of 3:1 (reflecting the in vivo ratio) resulted in a fivefold or greater reduction in the IgM response to LPS. LPS activation of macrophages resulted in production of a soluble factor that inhibited LPS-induced B cell differentiation by 86% when used at a concentration of 5%. When [3H]arachidonic acid-pulsed macrophages were stimulated with LPS, the major arachidonic acid metabolite secreted was PGE2 (a potent inhibitor of B cell differentiation). The inhibitory capacity of the macrophage-derived supernatant was reversed by the addition of anti-PGE2. These findings indicate that macrophage-derived PGE2 functions as an important regulator of polyclonal response of B-1a cells to LPS.

Animals↗
PubMed1994

Understanding and treating Bartter syndrome.

Most of its clinical manifestations are the result of hypokalemia. The diagnosis is one of exclusion, mainly of surreptitious vomiting and diuretic abuse. The primary cause remains unknown but the most likely candidate is reduced sodium chloride reabsorption in the thick ascending limb of Henle's loop. Current therapy focuses on multiple agents to reduce massive potassium loss.

Bartter Syndrome↗
PubMed1994

Formation and release of a peroxisome-dependent arachidonic acid metabolite by human skin fibroblasts.

Human skin fibroblasts labeled with [5,6,8,9,11,12,-14,15-3H]arachidonic acid produce a radioactive metabolite that has a shorter retention time on reverse-phase high-performance liquid chromatography than arachidonic acid. This product is not retained in the cells; it is released entirely into the extracellular fluid in a time-dependent manner. The metabolite does not cochromatograph with any of the eicosanoid standards, and its formation is not prevented by the addition of cyclooxygenase, lipoxygenase, or cytochrome P-450 inhibitors. The compound is not produced by fibroblasts labeled with [1-14C]arachidonic acid, suggesting that it is formed through an oxidative process. Chemical analyses indicated that the metabolite is 4,7,10-hexadecatrienoic acid (16:3). Peroxisome-deficient human skin fibroblasts did not produce 16:3, indicating that it probably is formed through peroxisomal beta-oxidation. Human umbilical vein endothelial cells and porcine pulmonary artery smooth muscle cells also release radioactive 16:3 following labeling with [3H]arachidonic acid. Therefore, the production of this metabolite is not limited only to fibroblasts. The fact that 16:3 is released into the extra-cellular fluid suggests that it may be a new type of lipid mediator derived from arachidonic acid, formed through a peroxisome-dependent oxidative process.

Animals↗
PubMed1994

15-HETE: selective incorporation into inositol phospholipids of MDCK cells.

The interaction of 15-hydroxyeicosatetraenoic acid (15-HETE) and cultured MDCK renal tubular epithelial cells was investigated to determine whether incorporation of this lipoxygenase product will affect polyphosphoinositide formation. MDCK cells were incubated with 1 microM [3H]-15-HETE for 15 to 120 minutes. Maximum uptake occurred between 15 and 30 minutes, and after 60 minutes, 70% of the incorporated 15-HETE was present in the phosphatidylinositol (PI) fraction. Some 15-HETE was also incorporated into phosphatidylinositol-4-monophosphate (PIP) and phosphatidylinositol-4,5-bisphosphate (PIP2). However, even though more 15-HETE than arachidonic acid was incorporated into PI, the fractional amount of 15-HETE present in the polyphosphoinositides was smaller than arachidonic acid. Therefore, although 15-HETE is selectively channeled into PI, conversion of PI species containing 15-HETE to PIP and PIP2 is relatively impaired. This suggests that either PI containing 15-HETE is a less effective substrate for phosphorylation, or PI containing arachidonic acid is a preferred substrate. MDCK cells converted 15-HETE to polar metabolites that were released into the extracellular fluid. This process may constitute a renal tubular mechanism for the clearance of 15-HETE and related lipoxygenase products.

Animals↗
PubMed1994

Mitochondrial metabolism of 12- and 15-hydroxyeicosatetraenoic acids.

We have previously demonstrated that peroxisomal-deficient human skin fibroblasts and mutant Chinese hamster ovary cells do not convert 12- and 15-hydroxyeicosatetraenoic acids (HETEs) to chain-shortened, polar metabolites, suggesting that peroxisomes are the intracellular location for beta-oxidation of these compounds. This implies that mitochondria do not beta-oxidize HETEs. To test this hypothesis we incubated highly purified rat liver mitochondria with [3H]12-(S)- and [3H]15-(S)-HETE in the presence of carnitine and an acylcoenzyme A-generating system. Extracts obtained from these incubations were analyzed for radiolabeled polar metabolites. Both HETEs were converted to apparent products of beta-oxidation, although the 12-HETE compound was a markedly better substrate. The presence of 50 microM 2-tetradecyloxirane carboxylate, a potent inhibitor of carnitine palmitoyl transferase, completely blocked 12- and 15-HETE conversion to these metabolites as did omission of carnitine from the medium. These data demonstrate carnitine-dependent beta-oxidation of HETEs in isolated mitochondria and suggest that mitochondria are competent to carry out this metabolic process in eukaryotic cells. Prevailing metabolic conditions in subcellular compartments may have precluded observation of mitochondrial activity in our earlier work with cultured cells. Alternatively, transport mechanisms may exist in the cell types studied that distribute 12-(S)- and 15-(S)-HETEs specifically to peroxisomes.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1994

The new simplified Sim-Gordon orthodontic analysis.

The new Sim-Gordon Computerized Analysis is simple to use, basic in the orthodontic diagnostic values that need to be measured and entered, and serves as an extremely useful guide for the treatment planning of orthodontic patients. It will run on any IBM compatible computer, and uses less than 740 Kb of space on a disk. So far as is known, all insurance companies will accept it. It is a pleasure to announce the availability of this reasonable and cost-effective, simplified, IAO-accepted, professional orthodontic diagnostic system to our fellow practitioners. The authors would like to thank Dr. Duane Keller, Dr. Yosh Jefferson, Dr. Thomas Hughes, Dr. Rudy Postema, Dr. Michel Champagne, Dr. John Byland, Dr. Kenneth Lyle, and Dr. Janet Doerr for their helpful suggestions and aid in the selection of values to be measured.

Adolescent↗
PubMed1993

Attenuated prostaglandin formation in peroxisomal-deficient human skin fibroblasts.

Peroxisomal-deficient skin fibroblasts from patients with Zellweger's syndrome or infantile Refsum's disease produced fewer prostaglandins than normal skin fibroblasts. Radioimmunoassay indicated a 45-55% decrease in prostaglandin E2 (PGE2) production when Zellweger's fibroblasts were incubated with arachidonic acid. This deficiency was not overcome by pretreatment of the Zellweger's fibroblasts with media containing arachidonic acid, and it was not due to channeling of arachidonic acid into other eicosanoid products. Modifications in the peroxide tone of the Zellweger's fibroblasts by addition of H2O2 or catalase failed to increase PGE2 production. Using Northern analysis, we were unable to detect an mRNA transcript for PGH synthase in unstimulated Zellweger fibroblasts but identified a 4.2-kb mRNA transcript after treatment with phorbol myristate acetate (PMA). Treatment for 6 h with 10 nM PMA raised PGE2 production in normal and Zellweger fibroblasts to equivalent levels. These increases were prevented by addition of H-7, staurosporine, cycloheximide, or actinomycin D. Our findings suggest that the reduced PGE2 production in peroxisomal deficient fibroblasts is due to a decrease in PGH synthase mRNA. The reduction in PGH synthase can be overcome by treatment of the cells with agents which enhance gene expression.

Arachidonic Acid↗
PubMed1992

Thrombotic microangiopathy: a case report and review of the literature.

Thrombotic microangiopathy most likely represents a spectrum of diseases consisting of multiple etiologies that has a final common pathway of multiorgan microvascular thrombosis. The variable responses to several different modes of therapy would suggest that more than one pathogenetic mechanism is involved. Untreated, it has been associated with very high morbidity and mortality rates. A poor understanding of the basic disease process has prevented specific treatment modalities, although early diagnosis and availability of dialysis and blood product transfusion services remain crucial. Several modes of therapy have been used to date, with plasma exchange being the most effective method studied and shown to improve survival. On the basis of current knowledge, this form of treatment should be instituted promptly in severe cases. Anecdotal reports of recovery with vincristine or IgG alone or with the use of IgG after the apparent failure of plasma therapy appear promising and deserve further investigation as initial therapeutic measures used in thrombotic microangiopathy. Although the majority of patients recover with normal renal function, those with severe thrombotic microangiopathy may heal through sclerosis with residual hypertension and chronic renal impairment requiring continual medical therapy.

Adult↗
PubMed1991

Hydroxyeicosatetraenoic acid oxidation in Chinese hamster ovary cells: a peroxisomal metabolic pathway.

To evaluate the peroxisomal requirement for beta-oxidation of hydroxyeicosatetraenoic acids (HETES), we tested 5-, 12- and 15-HETE oxidation in wild-type and mutant Chinese hamster ovary (CHO) cells. Mutant CHO cells contain peroxisomal ghosts, have random cytosolic localization of catalase and lack two of the enzymes necessary for peroxisomal beta-oxidation. Reverse-phase HPLC indicated that 33% of 12-HETE radioactivity was converted by wild-type CHO cells during a 2 h incubation to one major and several minor polar metabolites. Wild-type CHO cells also converted 15-HETE to one major and several minor polar metabolites. Neither 12- nor 15-HETE were converted to any metabolites by the mutant CHO cell lines, despite appreciable cellular uptake of these hydroxyeicosanoids. 5-HETE was not converted to any metabolic products by either the wild-type or the mutant CHO cells. Docosahexaenoic acid beta-oxidation was substantially reduced in the mutants as compared to the wild-type cells, palmitic acid beta-oxidation was reduced to an intermediate extent in the mutants, but octanoate beta-oxidation and citrate synthase activity were not impaired. Protein immunoblotting for mitochondrial manganese superoxide dismutase indicated a single band of identity at 20 kDa in both wild-type and mutant CHO cells. Since mutant CHO cells fail to convert 12- and 15-HETE to oxidative metabolites but contain normal mitochondrial enzymatic activities, intact peroxisomes appear to be the organelle responsible for HETE oxidation.

Animals↗