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Biomedical subjects

L C Wright

Publications and source records attributed to L C Wright.

49 records · Page 3Linked to original sources
PubMed1986

Cellular resistance to vinblastine is associated with altered respiratory function.

Human leukaemic T lymphoblasts made resistant to low levels (20-40 ng/ml) of vinblastine have altered respiratory capacity. Cellular oxygen uptake was greater in resistant cells compared with sensitive cells, and vinblastine (40 ng/ml) caused immediate inhibition of oxygen uptake in sensitive cells, but not in resistant cells. Isolated mitochondria reflected the changes observed in the intact cells. Rates of oxidation of cytochrome c, succinate and glutamine were higher in mitochondria from resistant cells and were little affected by challenge with vinblastine, whereas vinblastine at 40 ng/ml was completely inhibitory for sensitive cell mitochondria. Azide inhibited vinblastine efflux from sensitive and resistant cells in both the presence and absence of glucose. Levels of protein, total lipid, free cholesterol and cardiolipin were elevated in vinblastine-resistant lymphoblasts.

Cell Line↗
PubMed1985

Phospholipid and ether linked phospholipid content alter with cellular resistance to vinblastine.

The phospholipid and ether linked phospholipid content of leukaemic lymphocytes alters when the cells become resistant to low levels of the anti-cancer drug, vinblastine. Sphingomyelin and cardiolipin increase, and phosphatidyl ethanolamine and serine decrease in resistant cells. In addition, increases in 1-alkyl-2-acyl phosphatidyl choline and 1-alkenyl-2-acyl-phosphatidyl ethanolamine are concomitant with decreased 1,2-diacyl phosphatidyl choline and ethanolamine. Changes to the ultrastructure of the inner half of the plasma membrane bilayer, as a consequence of drug resistance, are illustrated by freeze-fracture electron microscopy.

Binding Sites↗
PubMed1985

Lipid domain in cancer cell plasma membrane shown by 1H NMR to be similar to a lipoprotein.

Human blood lipoproteins have been characterised by 1H NMR methods and chemical analysis, and comparisons made with the properties of the triglyceride-rich plasma membrane domain found in cancer cells. By means of selective and non-selective T1 experiments, the lipids in HDL and LDL are shown to be in diffusive exchange. In contrast, the lipids of chylomicra and VLDL do not exhibit lipid diffusion, and therefore resemble the neutral lipids of cancer cell plasma membranes. 2D scalar correlated NMR (COSY) spectra of cancer cells or solid tumours are similar to those obtained from VLDL and LDL. The long T2 relaxation value observed for neutral lipid methylenes in metastatic cancer cells (greater than 300 ms) was not observed for any of the 4 lipoproteins studied. None of the lipoprotein classes gave a T2 longer than 250 ms.

Adenocarcinoma↗
PubMed1984

High-resolution proton nuclear magnetic resonance analysis of metastatic cancer cells.

High-resolution proton nuclear magnetic resonance (NMR) studies of intact cancer cells revealed differences between cells with the capacity to metastasize and those that produce locally invasive tumors. The NMR resonances that characterize the metastatic cells were associated with an increased ratio of cholesterol to phospholipid and an increased amount of plasma membrane-bound cholesterol ester. High-resolution NMR spectroscopy could therefore be used to assess the metastatic potential of primary tumors.

Animals↗
PubMed1982

Thermal behavior and lipid composition of cauliflower plasma membranes in relation to ATPase activity and chilling sensitivity.

A plasma-membrane fraction rich in ion-stimulated ATPase activity was isolated from cauliflower (Brassica oleracea L.) buds. The activity of the ATPase was dependent on Mg(2+) and stimulated 4-fold by K(+). The lipids of the membrane fraction contained 57% by weight of phospholipid, 16% glycolipid including sterol glycosides, and 27% neutral lipids. Sterols and sterol esters comprised 9% by weight of the total lipid fraction, and the m ratio of total sterol to phospholipid was 0.5. Fatty acid unsaturation of the membrane lipids was 75%. Arrhenius plots of the Mg(2+) and Mg(2+) + K(+) stimulated ATPase activity were biphasic with an increase in activation energy occurring below about 12 degrees C, a response typical of some membrane-associated enzymes of chilling-sensitive plants. No thermal transitions were detected in the membranes or membrane lipids between 0 and 30 degrees C using differential scanning calorimetry and electron spin resonance spectroscopy. This type of thermal behavior is typical of membranes of chilling-resistant plants. It was concluded that the low temperature increase in activation energy of the ion-stimulated, membrane-associated ATPase is an intrinsic property of the enzyme system and not the result of a transition in the bulk membrane lipid.

Journal Article↗
PubMed1981

Correlation between Changes in Mitochondrial Membranes of Artichoke Tubers and Their Hardening and Dormancy.

Spin labeling studies using mitochondrial membranes of Jerusalem artichoke (Helianthus tuberosus L.) showed that the decrease during winter in the temperatures of the upper and lower lipid transitions correlated with the development of freezing hardiness of the tubers. The killing temperature for tuber tissue reached a minimum of -12 C, about 5 C degrees lower than the lower transition. Freeze-hardiness decreased when the lower transition increased at the time of sprouting.Low temperature storage was not required to induce freeze-hardiness or to lower the transitions. These changes occurred in tubers under field conditions and at a constant growth temperature of 25 +/- 1 C. In both conditions, tuber dormancy preceded the mitochondrial membrane changes.In young nondormant tubers, cessation of growth by storage at 0 or 4 C and the induction of dormancy with abscisic acid led to decreased temperatures of the upper and lower transitions.Changes in Arrhenius activation energy of succinate oxidase were correlated with the seasonal changes in the upper and lower transitions confirming that these were indeed a reflection of altered thermal responses of mitochondrial membranes, which might be part of a general mechanism in this plant of insuring membrane integrity during the freeze-thaw process. In contrast with chilling injury, there is no precise correlation between the temperature of the lower transition and the temperature below which freezing injury occurs.

Journal Article↗
PubMed1979

Seasonal Changes in the Structure and Function of Mitochondrial Membranes of Artichoke Tubers: A Requisite for Surviving Low Temperatures during Dormancy.

The temperature limits of the order-disorder transition, and the Arrhenius activation energy of succinate oxidase activity for mitochondria of Jerusalem artichoke (Helianthus tuberosus L.) tubers were determined from the initiation to the termination of dormancy. The temperature limits for the transition at the initiation of dormancy were 25 and 3 C. These changed to 9 and -5 C at mid-dormancy and returned to 25 and 2 C at the termination of dormancy. The Arrhenius activation energy measured in the temperature range above the transition was 35 kilojoules per mole at middormancy and decreased to 17 kilojoules per mole at the termination of dormancy when sprouting was evident. The coincidence of the changes in membrane structure and function with dormancy suggests that artichokes possess a mechanism for regulating membrane lipid structure so that cellular integrity of tuber tissue is maintained even when the tubers are exposed to low temperatures.

Journal Article↗
PubMed1976

Circulating IgG antibodies against factors IX and VIII in multiple sclerosis.

A 64-year-old man with multiple sclerosis developed a circulating anticoagulant. Three immunoglobulin fractions (I = IgG; II =IgG+IgA; III = IgM) were separated from patient serum by 33-percent ammonium sulfate precipitation and DEAE-52 cellulose column chromatography. Fractions I (IgG) and II (IgG+IgA) had factor VIII inhibitory activity on incubation. Fraction I (IgG) possessed, in addition, immediate anti-IX activity which did not require incubation. Absorption studies characterized the VIII inhibitors as IgG-gamma in fraction I and IgG-gamma+IgG-lambda in fraction II. Immediately reactive IgG anti-IX antibodies associated with kinetically distinct IgG anti-VIII antibodies have not been described previously.

Blood Coagulation↗
PubMedDate not supplied

Cytological and cytoarchitectural changes in the feline cerebral cortex during experimental infantile hydrocephalus.

While many reports have documented the effects of hydrocephalus on the ependyma and periventricular white matter, primarily in adult animal models, little is known about alterations specific to neurons. The present study has evaluated qualitatively the effects of hydrocephalus on the neurons and vasculature of the cerebral cortex in a neonatal animal model. The cisterna magna of 4 to 11-day-old kittens was injected with a solution of 25% kaolin to induce hydrocephalus. Ultrasonographic evidence of hydrocephalus was noted within 3-5 days of injection. Hydrocephalus progressed until day 18-25 postinjection when the animals were sacrificed. The cytologic and cytoarchitectural changes within the cortical mantle of affected animals were compared with control age-matched counterparts who had undergone intracisternal saline injections. Areas 4 (primary motor), 22 (association) and 17 (primary visual sensory) were examined light microscopically. Neurons from hydrocephalic brains exhibited 3 types of pathological response. Pyknotic somata were shrunken, disoriented and so hyperchromatic that neither nuclei or nucleoli could be delineated. Reactive somata were also shrunken and hyperchromatic, but nuclei and nucleoli could still be observed. Many neurons contained an abundance of vacuoles, giving their somata a flocculent appearance; these cells were termed 'spongy' neurons. Both normal and pathological neurons were smaller and disoriented, with a considerable decrease in neurons noted in areas 22 and 17 from severely hydrocephalic animals. The deeper cortical layers were more affected than the more superficial laminae in that more reactive and pyknotic neurons were present in layers V and VI. As the ventriculomegaly became more severe, changes could be observed in neurons within layers II and III. Furthermore, the cerebral vasculature exhibited a decrease in the number of vessels and a preponderance of profiles oriented parallel to the meningeal surface. The severity of these effects followed a rostral to caudal gradient, such that the occipital cortex demonstrated the most damage. These results suggest that both the motor deficits and the subtle cognitive deficiencies seen with hydrocephalus may be attributed to perturbation of neuronal and vascular elements in the cerebral cortex.

Animals↗