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Biomedical subjects

J E Thompson

Publications and source records attributed to J E Thompson.

At least 235 records · Page 13Linked to original sources
PubMed1983

Disorder in human myelin induced by superoxide radical: an in vitro investigation.

Potassium superoxide (KO.2), applied as a source of superoxide radical directly in vitro to white matter from young adult human brain, caused the lipid phase of the myelin to change from a crystalline (ordered) state to a liquid crystalline (disordered) state. The myelin transition temperature decreased from 65 degrees C to 37 degrees C. This alteration was accompanied by a dramatic increase in the levels of lipid peroxidation products--malondialdehyde, a conjugated diene, and ethane. These changes in human myelin, induced by direct application of O2-. radical, simulated myelin deterioration that occurs in the course of natural aging, thus, providing further substantiation for the notion that O2-. might be a major toxic agent associated with the aging process.

Brain↗
PubMed1983

X-ray computed tomography of brain tumors in cats.

X-ray computed tomography (CT) was used to depict intracranial space-occupying lesions in 5 cats. Computed tomographic findings were confirmed by surgical biopsy in 2 cases and at necropsy in 3 cases. The detailed anatomic information provided by CT scans facilitated surgical removal of a brain tumor in 2 cats, and allowed accurate tumor localization and dose optimization for radiation therapy in 1 cat. It was concluded that CT provides information required for accurate diagnosis and treatment of feline brain tumors.

Animals↗
PubMed1983

Changes in lipid phase behaviour in human myelin during maturation and aging. Involvement of lipid peroxidation.

The biophysical properties of human myelin isolated from white matter of patients aged two months to 74 years were investigated using wide-angle X-ray diffraction. The myelin transition temperature increased from 13 degrees C to 65 degrees C as age increased from two months to 17 years, demonstrating an increase in the myelin lipid stability. Following this maturation period, the myelin transition temperature remained constant at 65 degrees C until age 50. Beyond age 50, the transition temperature of myelin decreased by 13 degrees C indicating that myelin stability decreased with aging. During this aging period, the levels of malondialdehyde and conjugated diene increased, indicating an increasing amount of lipid peroxidation. Although evidence is indirect, the results of this investigation strongly suggest that free radicals could be a primary factor in the acceleration of the aging processes in the human brain.

Adolescent↗
PubMed1983

Development of DNA-mediated transformation systems for plants.

The genetic engineering of plants by DNA-mediated gene transfer requires that efficient transformation systems be developed. Considerable progress has been made in manipulating the Ti plasmid of Agrobacterium tumefaciens as a vehicle for delivery of foreign genes into protoplasts of dicotyle-donous plants. Part of the Ti plasmid, the T-DNA, can be incorporated into the genome of the host cell; the T-DNA can carry a foreign DNA sequence which co-integrates with it; under normal conditions, the tumorigenic-causing portion of the T-DNA can be inactivated so that transformed protoplasts can be regenerated and T-DNA with an inserted foreign gene can be stably maintained during regeneration, meiosis and gamete formation. A foreign gene has yet to be expressed in regenerated plants although a T-DNA gene for opine synthesis can function in regenerates. Developing a more ubiquitous transformation system for monocotyledons is further from fruition. Based on transformation systems for simple eukaryotic organisms, it is reasonable to expect that a DNA vector which is capable of amplifying a novel plant gene and which contains both a drug resistance marker to facilitate the selection of transformed plant protoplasts and a species-specific autonomously replicating sequence to ensure the stable maintenance of the input gene in the recipient cell can be constructed.

Journal Article↗
PubMed1983

Bicarbonate/CO(2)-Facilitated Conversion of 1-Amino-cyclopropane-1-carboxylic Acid to Ethylene in Model Systems and Intact Tissues.

Bicarbonate markedly enhances ethylene production from 1-aminocyclopropane-1-carboxylic acid (ACC) in model chemical systems where the conversion is free radical-mediated, in thylakoid membrane suspensions of Phaseolus vulgaris L. cv Kinghorn where the reaction is light-dependent, and in microsomal membrane suspensions and intact tissues where the reaction is enzymically mediated. In two model systems generating free radicals-the Fenton reaction and a reaction mixture containing xanthine/xanthine oxidase, NaHCO(3) (200 millimolar) increased the formation of ethylene from ACC by 84-fold and 54-fold, respectively. Isolated thylakoid membranes also proved capable of ACC-dependent ethylene production, but only upon illumination, and this too was enhanced by added NaHCO(3). As well, light-induced inhibition of ACC-dependent ethylene production by leaf discs was relieved by adding 200 millimolar NaHCO(3). Finally, NaHCO(3) (200 millimolar) augmented ACC-dependent ethylene production from young carnation flowers by about 4-fold, and the conversions of ACC to ethylene by microsomes isolated from carnation flowers and etiolated pea epicotyls were higher by 1900 and 62%, respectively, in the presence of 200 millimolar NaHCO(3).This increased production of ethylene appears not to be due to bicarbonate or CO(2)-induced release of the gas from putative receptor sites, since the addition of NaHCO(3) to sealed reaction mixtures after the ACC to ethylene conversion had been terminated had no effect. Spin-trapping studies have confirmed that bicarbonate does not facilitate the formation of free radicals thought to be involved in the conversion of ACC to ethylene. Nor did bicarbonate alter the physical properties of the membrane bilayer, which might indirectly modulate the activity of the membrane-associated enzyme capable of converting ACC to ethylene. Rather, bicarbonate appears to directly facilitate the conversion of ACC to ethylene, and the data are consistent with the view that CO(2) derived from bicarbonate is the active molecular species.

Journal Article↗
PubMed1983

A study of the interaction between progesterone and membrane lipids.

The ability of progesterone to associate with phospholipid was examined in a model membrane system. Molecular interaction was assessed by measuring the enthalpy of the phase transition of dipalmitoylphosphatidylcholine liposomes by differential scanning calorimetry. The response was compared to cholesterol, a constituent of cellular membranes. Unlike cholesterol, progesterone caused minimal disruption of the phospholipid bilayer phase properties at concentrations ranging from 5-33 mol %. However, it interacted with the phospholipid to a greater degree when cholesterol was included in the liposomes. These results indicate that progesterone can intercalate into phospholipid bilayers containing cholesterol, and raise the prospect that there may be some diffusion of the hormone across the plasma membrane.

Calorimetry, Differential Scanning↗
PubMed1982

Factors in management of acute cholangitis.

Ninety episodes of acute cholangitis in 66 patients have been analyzed. In 71% of the episodes, an operation was performed. Eight deaths occurred, for a patient mortality rate of 12%. Sixty-seven per cent of the operations were performed after at least 72 hours of antibiotic therapy, whereas only 17% had to be done as life-threatening emergencies within 24 hours of admission to the hospital. Although 86% of the operative deaths occurred in the group operated on more than 72 hours after admission, this was not statistically significant. However, death did correlate with failure to respond to antibiotic therapy (p less than 0.001) irrespective of time of operation. Biliary cancer and congenital lesions were etiologic for 31% of the operative cases in this series, but were responsible for 71% of the postoperative deaths (p less than 0.05). We conclude that acute cholangitis has a wide spectrum of severity and that most cases will respond to antibiotic therapy, affording the surgeon the luxury of operating in an elective fashion. Moreover, acute cholangitis complicated by failure to respond to antibiotic therapy is more likely to occur in biliary cancer and congenital lesions, and subsequently will have a poorer prognosis.

Acute Disease↗
PubMed1982

Mesenteric vascular problems. A 26-year experience.

Mesenteric vascular problems are infrequent, but may be catastrophic. During a 26-year period, 55 private patients were treated for the following disorders: (1) 12 patients with visceral artery aneurysms, (2) 8 with celiac compression syndrome, (3) 13 with chronic mesenteric ischemia, (4) 12 with acute mesenteric ischemia, and (5) 10 with mesenteric ischemia associated with aortic reconstructions. Splenic artery aneurysms were managed by excision and splenectomy, while celiac and hepatic had excision with graft replacement. Patients with celiac compression syndrome underwent lysis of the celiac artery. Two patients had compression of both celiac and superior mesenteric artery (SMA). One patient required vascular reconstruction of both arteries for residual stenoses. Patients having chronic mesenteric ischemia were treated with bypass grafts, with one death (7.7% mortality) and good long-term results. Those with acute mesenteric ischemia were treated by SMA embolectomy, bowel resection, or both, with a mortality of 67%. When associated with aortic reconstructions, mesenteric ischemia carried a mortality of 100% if bowel infarction occurred after operation, but when prophylactic mesenteric revascularization was performed at the time of aortic surgery, prognosis was greatly improved, with only one death among six patients. An aggressive approach including prompt arteriography with early diagnosis and surgical therapy is advocated for these catastrophic acute mesenteric problems.

Adult↗
PubMed1982

Acceleration of membrane senescence in cut carnation flowers by treatment with ethylene.

The lipid microviscosity of microsomal membranes from senescing cut carnation (Dianthus caryophyllus L. cv. White Sim) flowers rises with advancing senescence. The increase in membrane microviscosity is initiated within 3 to 4 days of cutting the flowers and coincides temporally with petal-inrolling denoting the climacteric-like rise in ethylene production. Treatment of young cut flowers with aminoethoxyvinylglycine prevented the appearance of petal-inrolling and delayed the rise in membrane microviscosity until day 9 after cutting. When freshly cut flowers or aminoethoxyvinylglycine-treated flowers were exposed to exogenous ethylene (1 microliter per liter), the microviscosity of microsomal membranes rose sharply within 24 hours, and inrolling of petals was clearly evident. Thus, treatment with ethylene accelerates membrane rigidification. Silver thiosulphate, a potent anti-ethylene agent, delayed the rise in microsomal membrane microviscosity even when the flowers were exposed to exogenous ethylene. Membrane rigidification in both naturally senescing and ethylene-treated flowers was accompanied by an increased sterol:phospholipid ratio reflecting the selective loss of membrane phospholipid that accompanies senescence. The results collectively indicate that the climacteric-like surge in ethylene production during senescence of carnation flowers facilitates physical changes in membrane lipids that presumably lead to loss of membrane function.

Journal Article↗
PubMed1982

Amebic abscess of the liver: surgical aspects.

During the past five years, ten documented cases of hepatic amebic abscess have required surgical intervention at Olive View Hospital, Van Nuys, California. Three of the patients underwent laparotomy when an hepatic abscess ruptured into the peritoneal cavity, and two required surgical intervention when an abscess invaded adjacent organs. Another abscess continued to enlarge despite metronidazole therapy and still another became superinfected with bacteria. In the remaining three patients, surgical procedure would have been avoided if the correct diagnosis had been made. In fact, the preoperative diagnosis in five cases was acute appendicitis. All patients survived. The incidence of Entamoeba histolytica infestation is increasing in our community. Although most patients rapidly improve with metronidazole therapy, surgical complications do arise and diagnoses are missed. This series of cases emphasizes the need for surgeons working in Southern California to familiarize themselves with the clinical features, complications and appropriate surgical treatment of amebiasis.

Abdomen, Acute↗
PubMed1981

Perturbation of lipid membranes by organic pollutants.

The ability of a range of organic pollutants--hexachlorobenzene, mirex(1,1a,2,2,3,3a,4,5,5,5a,5b,6-dodecachlorooctahydro-1,3,4-metheno-1H cyclobuta(cd) pentalene), 1,3,5-trichlorobenzene, 2,4,6-trichlorophenol, p-nitrophenol, p-chlorophenol, DDT, and pentachlorophenol--to perturb liposomes of dipalmitoyl phosphatidylcholine (DPPC) has been measured by differential scanning calorimetry. The degree of perturbation was measured by the increase in breadth of the main DPPC phase transition in both heating and cooling scans. DDT and the phenol derivatives were effective perturbers of phospholipid, broadening the transition by as much as 12-fold. Hexachlorobenzene and mirex did not perturb at all when mixed with DPPC at concentrations as high as 20 mol%, although 1,3,5-trichlorobenzene caused slight broadening of the main transition at this concentration. Perturbation is facilitated by the presence of a hydroxyl group on the benzene ring and hindered by increasing degrees of chloride substitution. An apparent correlation exists between the extent of phospholipid perturbation measured by differential scanning calorimetry and LD50 values for these compounds taken from the literature. This suggests the possibility of formulating an "index of perturbation" which could be used to screen certain classes of organic compounds for potential biological toxicity on a routine basis.

Animals↗