Modified structure and kinetics of cytochrome-c oxidase in fibroblasts from patients with Leigh syndrome

In this study we compared the properties of cytochrome-c oxidase (COX) in cultured fibroblasts from two patients with Leigh Syndrome with COX from control fibroblasts. The fibroblasts from patients showed decreased growth reates and elevated lactate production. COX activity of patients fibroblasts was about 25% of control. Kinetic studies with isolated mitochondria showed a higher K_m for cytochrome c and a markedly reduced molecular turnover of COX from patients, indicating a different structure of the enzyme. A biphasic change of COX activity was obtained by titration of dodecylmaltoside solubilized mitochondria from control fibroblasts with increasing concentrations of anions. With patient mitochondria we found only the inhibiting phase of COX activity and, in contrast to control mitochondria, irreversible inhibition of COX activity by guanidinium chloride. ELISA titrations with monoclonal antibodies to subunit II, IV, Vab, VIac and VIIab indicated a normal amount of mitochondrial coded subunit II, but a reduced amound of nuclear coded subunits. The data indicate incompletely assembled nuclear coded subunits of COX from patient fibroblasts.     

血清胃泌素变化与急性胃粘膜病变关系的研究

对大白鼠血清中胃泌素水平的变化与急性胃粘膜病变的关系进行了初步的研究,结果表明以消炎痛为诱因引起的急性胃粘膜病变大白鼠血清胃泌素水平明显增高。而维酶素可以抑制因消炎痛引起的急性胃粘膜病变时血清胃泌素的释放,对胃粘膜具有保护作用。     

休眠与萌发过程中苹果种子的呼吸代谢

“秦冠”苹果种子的总呼吸强度和EMP途径的呼吸强度在2℃条件下层积之后逐渐增加,解除休眠临界期大体在层积后第30天发生,此后增长速度较快。HMP途径和TCAC在临界期之前变化极慢,而后急剧增加。种子萌发后子叶和胚轴的总呼吸强度、EMP和TCAC初期呈急剧上升趋势,大约当胚轴长度达2cm时迅速下降,HMP在萌发过程中始终呈上升趋势。细胞透性层积之后逐渐降低,解除休眠至萌发阶段呈上升趋势。用不同浓度呼吸抑制剂处理解除休眠种子的试验结果表明,除1mM碘乙酸能明显刺激萌发和生长外,NaCN、SHAM和丙酮酸都表现为抑制作用。     

六种选矿药剂对藻类的毒性比较

本文评价了六种选矿药剂对藻类的毒性效应,它们对斜生栅藻的毒性大小排列顺序是:二号油>Fu>0145>Yx>MPA>S-808,96h-EC_(50)值分别为41.2,50.1,82.0,177.8,198.2和900ppm。六种选矿药剂对藻类毒性最大的是二号油,毒性最小的是S-808。对藻类细胞形态的观察结果表明,0145对藻类的细胞形态有轻度的致畸效应,在其它五种药剂的培养物中,均未发现畸变细胞。在室温下存放10d后MPA,0145和二号油,毒性明显下降,其下降速率的顺序是:MPA>0145>二号油。藻类对S-808具有净化脱色作用,100ppm浓度的S-808溶液经藻类作用32d后,其色度可减少48％,作用62d和93d,色度分别降低54％和58％。0145抑制藻类的光合放氧,经50,100和200ppm浓度的0145处理4h后,与对照相比,藻类的光合放氧速率分别下降15、34和36％。     

Contractile proteins in podocytes: immunocytochemical localization of actin and alpha-actinin in normal and nephrotic rat kidneys

Actin and alpha-actinin immunoreactive sites have been localized at the electron microscope level by the protein A-gold immunocytochemical technique in podocytes of normal and nephrotic rat renal tissues. In normal renal glomeruli, fibrillar networks located in the core of foot processes or bundles of micro filaments interconnecting them were found to be labelled for these two cytoskeletal proteins. On the other hand, in nephrotic renal glomeruli, concomitant with the loss of podocytic foot processes a reorganization of the podocytic cytoskeleton and a concentration of some of its elements into thick uniform bands was observed. Actin and alpha-actinin were revealed in these bands. Control experiments confirmed the specificity of the labelling obtained. Our results suggest that normal podocytes contain an actin-based contractile system that might contribute to the maintenance of the particular cell shape of these cells and that the rearrangement of the podocytic cyto-skeleton occurring in the nephrotic syndrome might account for the changes in the foot processes and contribute to the alteration in glomerular function. This work was supported by grants from the Medical Research Council of Canada     

Effect of ferric nitrilotriacetate on rostral mesencephalic cells

After murine fetal cells from the rostral mesencephalic tegmentum were isolated, prepared, and cultured; neuronal and glial cells in primary mixed cell cultures were exposed to ferric nitrilotriacetate (Fe-NTA) at varying concentrations. Studies were performed at 23 days in culture after 14 day exposure to Fe-NTA. In addition to morphologic studies, biochemical assays including specific [³H]flunitrazepam (FLU) binding, clonazepam (CLO)-displaceable [³H]-FLU binding, Ro5-4864-displaceable [³H]-FLU binding, [³H]dopamine (DA) uptake, [³H]haloperidol (HAL) binding, [³H]spiperone (SP) binding, glutamine synthetase activity (GS), and protein determinations were performed. The data demonstrate that chelated ferric iron has an adverse effect on these cells. The data also demonstrate that increasing concentrations of Fe-NTA resulted in massive neuronal dropout leaving the culture population virtually all glial; however, the specific binding of [³H]HAL and [³H]SP increased. There was a concomitant decrease in both glutamine synthetase activity and overall protein content. The mechanism of enhancement in the presence of Fe-NTA of [³H]HAL and [³H]SP binding is unknown and may be unique, but may be related to the known increase in D₂ receptor ligand affinity in the presence of other multivalent cations (Ca²⁺ and Mg²⁺).     

High-affinity [3H]inositol uptake by dissociated brain cells and cultured fibroblasts from fetal mice

The accumulation of [³H]inositol by mechanically dissociated brain cells and cultured skin fibroblasts from fetal mice was examined. Uptake by both tissues was strongly dependent on temperature and the presence of sodium ions. Brain and fibroblast uptake also responded similarly to inhibition by inositol isomers and phloridzin. At lower concentrations of inositol, both tissues exhibited high-affinity uptake kinetics with apparent K_m values near 30 M, similar to values observed previously in human fibroblasts and other cultured cells. The activity of brain high-affinity uptake was nearly an order of magnitude lower than that of fibroblasts, however, and was in part confounded by the presence of a low-affinity or simple diffusion system operating at inositol concentrations above 100M. Brain preparation from adult mice also showed evidence of high-affinity, Na⁺ dependent uptake, but its activity was significantly diminished relative to that of fetal brain preparations. Our results demonstrate that a high-affinity inositol transport system closely resembling that found in cultured cells is expressed in the developing mouse brain.     

Dopamine Metabolism in Hypoxanthine-Guanine Phosphoribosyltransferase-Deficient Variants of PC12 Cells

Lesch-Nyhan syndrome results from a deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT). It is manifest by behavioral abnormalities, including self-mutilation, and evidence of abnormal 3,4-dihydroxyphenylethylamine (dopamine) metabolism. To assess whether an HPRT deficiency in a dopaminergic cell can adversely affect dopamine metabolism in that cell, dopamine metabolism was examined in HPRT-deficient variants of PC12 pheochromocytoma cells and in cells that had regained HPRT activity by virtue of transformation with a recombinant retrovirus containing the human gene for HPRT. There was no correlation between HPRT activity and endogenous dopamine levels, dopamine uptake, dopamine release, or monoamine oxidase activity. Transformation with the HPRT retrovirus did not adversely affect dopamine metabolism.     

Regional Amino Acid Concentration in the Brains of Rats Exposed to High Pressures

Regional amino acid concentrations were measured in rat brain fixed by microwave irradiation at three levels of elevated atmospheric pressure corresponding to different phases of the high-pressure neurological syndrome [20 atmospheres absolute (ATA), no clinical signs; 60 ATA, tremor; 85 ATA, severe tremor and myoclonic jerks]. No changes in amino acid content occurred at 20 or 60 ATA. At 85 ATA glutamine content increased in hippocampus, striatum, cerebellum, and substantia nigra, and gamma-aminobutyric acid content increased in hippocampus. It is suggested that enhanced glutamate release in various subcortical structures contributes to the myoclonic activity observed at 85 ATA.