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1.
Y Iwasa S Minamiguchi I Konishi H Onodera J Zhou H Yamabe 《Canadian Metallurgical Quarterly》1996,46(7):510-514
A unique case of bilateral luteinized thecomas of the ovary associated with sclerosing peritonitis is reported and the clinical and pathological features of this and previously reported cases are reviewed. The patient, 52 years of age, presented with abdominal distension and diarrhea. Pelvic imaging studies revealed bilateral ovarian tumors with ascites. Total abdominal hysterectomy and bilateral salpingo-oophorectomy with adhesiotomy of the small bowel were performed. Histologically, the ovarian tumor was composed of closely packed spindle to round-shaped cells, and within the spindle cell population, lutein-like cells were scattered singly or in clusters. Mitotic counts of spindle cells revealed 12 mitotic figures (MF) per 10 high-power fields (HPF) in one part of the left ovarian tumor, but other areas of the tumor showed less than 3 MF/10 HPF on average. The lesion from the resected small bowel showed prominent fibrosis, confined to the serosa with no evidence of metastasis from the ovarian tumor. The patient has undergone adhesiotomy with partial resection of the small bowel seven times since the first laparotomy because of the recurrent small bowel obstruction. The patient has survived with complications due to short bowel syndrome for 7 years after the initial surgery and so far no recurrence or metastasis of the ovarian tumor has been identified. The case reported here also supports the idea that luteinized thecoma of the ovary associated with sclerosing peritonitis may be a distinct clinicopathologic entity, in terms of the unique association and of the unique features of thecoma; that is, bilateral, hormonally inactive and apparently benign in spite of its highly mitotic activity. Additional attention should be paid to the patient's quality of life, which is often degraded by peritoneal fibrosis and small bowel obstruction. 相似文献
2.
Eight ewes each with an autotransplanted ovary received infusions of tritium-labelled pregnenolone (41 muCi/hr) for 8 hr into the artery supplying the ovary, together with prostaglandin (PG) F-2alpha (30 mug/hr) for 3 hr beginning 2 hr after the start of the pregnenolone infusion. All animals exhibited oestrus 2-3 days after the start of the experiment. During the PGF-2alpha infusion blood flow through the ovaries was increased by 13%, but subsequently returned to pre-infusion levels. Secretion rates of endogenous progesterone and 20alpha-hydroxypregn-4-en-3-one dropped rapidly 5 hr after the PGF-2alpha infusion had started from values of 250 mug/hr and 25 mug/hr to values below 60 mug/hr and 8 mug/hr, respectively. At this time the conversion of radioactive pregnenolone to progesterone was reduced by 50% of its initial value, but the secretion of endogenous pregnenolone and the formation of radioactive metabolites other than progesterone were not diminished. In 4 control animals, which received pregnenolone only, no changes in ovarian blood flow, steroid secretion rates, or in the conversion of labelled pregnenolone were observed. These results suggest a possible involvement of PGF-2alpha in the regulation of progesterone biosynthesis by an action on the 3beta-hydroxysteroid oxidoreductase-delta5(-4) isomerase enzyme system. 相似文献
3.
ET Mambetisaeva VA Kosykh AIu Misharin EI Kosenkov EA Podrez VS Repin 《Canadian Metallurgical Quarterly》1993,58(7):1126-1132
The effects of three novel synthetic derivatives of cholesterol with ethoxy (I), aminoethoxy (II), azidoethoxy (III) and toluenesulfonyloxyethoxy (IV) groups in the 3 beta-hydroxy position of cholesterol on cholesterol synthesis as well as on apolipoprotein B and bile acid secretion in cultured rabbit hepatocytes have been studied. 3 beta-(2-hydroxyethoxy)-cholest-5-en (I) was used as a standard. It was found that the inhibiting effect of these compounds on cholesterol synthesis depends on their structure. Compound II (1 microgram/ml), which inhibited acetate incorporation into cholesterol by 30-50%, appeared to be the most effective among the other compounds tested. This derivative had no effect on the production of bile acids. Compound III was less effective, while compound IV had no effect on cholesterol synthesis. All the compounds under study reduced by 20-36% the secretion of the total apolipoprotein B as measured by the enzyme-linked immunosorbent assay (ELISA). None of the synthetic cholesterol derivatives influenced the leucine incorporation into the total protein fraction. The results obtained indicate that 3 beta-(2-aminoethoxy)cholest-5-en, the most effective compound among other cholesterol derivatives tested in the study, can serve as a basis for synthesizing novel cholesterol derivatives able to inhibit cholesterol biosynthesis in liver cells and to decrease the secretion of very low density lipoproteins in cultured rabbit hepatocytes. 相似文献
4.
PURPOSE: To characterize cidofovir (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl) cytosine) transport in the pigmented rabbit conjunctiva and to evaluate the formulation influence on its transport. METHODS: The excised pigmented rabbit conjunctiva was mounted in the modified Ussing chamber. Cidofovir transport was initiated by applying 3H-cidofovir to the donor compartment and assayed by measuring the radioactivity accumulated in the receiver fluid over 180 min. RESULTS: Cidofovir flux in the mucosal-to-serosal direction increased proportionally with drug concentration over the 0.01 to 1 mM range. Cidofovir transport (0.01 mM) at 37 degrees C in the mucosal-to-serosal direction was not significantly different from that in the opposite direction or from that at 4 degrees C. Hypotonicity (80 mOsm/kg), 0.5% EDTA, and 0.0125% benzalkonium chloride increased the apparent permeability coefficient of cidofovir 3, 21, and 49 times, respectively. This was accompanied by a corresponding 43%, 86%, and 96% reduction in the transconjunctival electrical resistance over 180 min. The reduction in transepithelial electrical resistance elicited by hypotonicity was reversible. There was a good correlation between apparent permeability coefficient and the transconjunctival conductance, suggesting that cidofovir may undergo paracellular passive diffusion in the conjunctiva. CONCLUSION: Cidofovir transport in the rabbit conjunctiva may be via paracellular passive diffusion. Formulation changes may improve cidofovir absorption from the conjunctival route. 相似文献
5.
Hormone-sensitive lipase (HSL) is an intracellular enzyme that functions as both a neutral triglyceride and cholesteryl ester hydrolase. In order to explore the effects of HSL on cholesterol homeostasis, Chinese hamster ovary (CHO) cells were transfected with rat HSL and several different stable cell lines that overexpress HSL mRNA, HSL protein, and HSL activity approximately 600-fold were isolated. Cells transfected with HSL contained less cholesteryl esters and unesterified cholesterol than control cells. HSL transfectants expressed 20-60% fewer LDL receptors than control cells when grown in lipid-depleted media or in the presence of mevinolin, as assessed by binding and degradation of LDL and immunoblotting of LDL receptors. In contrast, the rate of cholesterol synthesis and the activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase were increased 3- to 14-fold in HSL transfectants grown in sterol replete media. The rate of cholesterol synthesis and the activity of HMG-CoA reductase increased when cells were grown in lipid-depleted media, and remained markedly elevated compared to control cells. These results show that the regulation of LDL receptor expression and cholesterol synthesis can be dissociated through the actions of HSL and suggest multiple control mechanisms for sterol-responsive genes. 相似文献
6.
We compared the severity of clinical symptoms and laboratory test results of tsutsugamushi disease patients in Oita Prefecture according to the serotype of infected R. tsutsugamushi. Of the 45 patients, except one with the Karp-type, who were suffering in Oita Prefecture between 1992 and 1994, 20 were the Irie-type and 24 were the Hirano-type. There was no apparent difference with regard to clinical symptoms between the two groups of patients. Laboratory tests showed that CRP increased almost equally in the two groups. The ESR level was slightly higher in the Irie-type patients than in the Hirano-type, but did not differ significantly between the two groups. Both leukocyte count in the acute stage and platelet count decreased in the Hirano-type, as compared with those of normal ranges in the Irie-type. GPT values elevated in proportion to the day of illness in the acute stage. This trend continued after the initiation of specific chemotherapy in the Hirano-type. The median GOT, GPT and LDH values were 71, 65 and 709 IU/l for the patients in the Hirano-type, as compared with 37, 36.5 and 546.5 for the patients in the Irie-type, respectively. Above results show that the Hirano-type rickettsiae produces a more severe illness than the Irie-type ricketsia. Platelet count had a significant correlation with ESR, suggesting the pathophysiologic changes leading to disseminated intravascular coagulation, a symptom of severe tsutsugamushi disease. There may be common causes in leukopenia and thrombopenia, as being suggested by the significant correlation between leukocyte count and platelet count. 相似文献
7.
Rabbit pancreatic cholesterol esterase (CEase, carboxyl ester lipase, EC 3.1.1.3) has been cloned from a lambda gt11 library of adult rabbit pancreatic cDNA. The open reading frame consists of 1788 nucleotides which encodes 576 amino acids of the functional protein and a 20 amino acid leader peptide. When compared to other species, the greatest homology is observed between residues 82-248 with little or no homology at the C-terminal end where proline-glutamate-serine-threonine (PEST) segments are a characteristic feature of the human CEase. Rabbit CEase (RCEase) retains the active-site serine (gxsxg), the active-site histidine and the tentative heparin binding site (KKRCLQ) at similar positions in comparison to pancreatic CEases of other species. When rabbit CEase cDNA is expressed in monkey kidney (COS-7) cells, enzymatic hydrolytic activity is detected in the growth medium as is a 67 kDa protein by Western blotting with polyclonal anti-CEase antibody. Northern blot analysis shows two mRNA (2.2 and 3.2 kb) species. 相似文献
8.
SL Nyberg HJ Mann MY Hu WD Payne WS Hu FB Cerra RP Remmel 《Canadian Metallurgical Quarterly》1996,24(6):643-648
OBJECTIVE: The initially well-fixed implants of total hip replacement (THR) are in the long-term subject to aseptic loosening. Many cytokines can contribute to osteolysis due to osteoclast recruitment and/or activation. However, in this respect tumor necrosis factor-alpha (TNF-alpha) plays a pivotal role, because it upregulates interleukin-1 and 6 and granulocyte-macrophage colony stimulating factor. The aim of this study was to assess the eventual presence, cellular localization and extent of expression of TNF-alpha in the synovial-like membrane at the implant or at the cement to bone interface compared to control synovial membrane. METHODS: Twenty samples from the synovial-like membrane of the periprosthetic tissues were compared to control samples. TNF-alpha containing cells were visualized using an avidin-biotin-peroxidase complex (ABC) method and analyzed by light microscopy, double labelling and image analysis. RESULTS: TNF-alpha was found in the periprosthetic tissues in fibroblasts and vascular endothelial cells, but mainly in the macrophages was it found to coincide with areas containing implant-derived debris. TNF-alpha containing cells were more numerous in the synovial-like membrane in the interface tissue from the proximal stem area (2816 +/- 318 cells) than in the control synovial membrane (565 +/- 93 cells, p < 0.01). Interestingly, similarly high TNF-alpha expression (3452 +/- 582 cells) was also seen in the synovial-like membrane of the pseudocapsule. CONCLUSION: These findings suggest that the foreign body-type host reaction caused by THR is characterized by the high expression of TNF-alpha. Because such expression occurred in the interface tissue between the implant and surrounding bone, TNF-alpha, due to its pivotal direct and indirect role in the activation and recruitment of osteoclasts, may contribute to periprosthetic osteolysis and to the loosening of THR. 相似文献
9.
Serum concentrations and metabolism of cholesterol were studied in vegetarians basally and during a dietary cholesterol load. Cholesterol absorption efficiency was normal and synthesis was slightly enhanced, even though serum cholesterol precursors were not increased. The serum concentrations of total and low-density-lipoprotein cholesterol were decreased proportionally to the reduced intake and absolute absorption of cholesterol. Fecal plant sterols were negatively correlated with the absorption efficiency of cholesterol and positively with fecal sterols and cholesterol synthesis, suggesting interference of high plant sterol intakes with cholesterol absorption. Cholesterol saturation and bile acid composition of the bile were not changed. The increased serum plant sterol-cholesterol ratios were positively related to the intake and negatively to the biliary secretion of plant sterols. Cholesterol feeding increased absolute cholesterol absorption and serum concentrations of total and low-density-lipoprotein cholesterol, did not change absorption efficiency or synthesis of cholesterol, but increased fecal cholestanol excretion. 相似文献
10.
The hormone serotonin (5-hydroxytryptamine) has been implicated as the cause of the diarrhea seen in many patients with the carcinoid syndrome. To determine whether serotonin is an intestinal secretagogue, the effect of serotonin on intestinal water and electrolyte transport was evaluated in the rabbit. Two weeks of daily subcutaneous injection of serotonin suspended in oil resulted in a blood serotonin level elevated to twice that of controls. Intestinal transport was studied in vivo by a perfusion technique. Serotonin treatment resulted in ileal secretion and decreased mid-jejunal absorption of water and electrolytes but did not effect water absorption in the proximal jejunum or colon. Intestinal absorption of D-glucose and the amino acid L-tryptophan and glucose-dependent water and electrolyte absorption were normal in serotonin-treated animals. Serotonin-induced ileal secretion was reversed by methysergide, a peripheral antagonist of serotonin action. No alterations in intestinal histology or permeability occurred in serotonin-treated animals. Serotonin-induced intestinal secretion was not associated with alterations in the activities of intestinal mucosal adenylate cyclase, cyclic nucleotide phosphodiesterase, or Na-K-ATPase. 相似文献
11.
PURPOSE: To determine whether an Na+-dependent monocarboxylate transport process exists on the mucosal side of the pigmented rabbit conjunctiva and to evaluate how it may contribute to the absorption of ophthalmic monocarboxylate drugs. METHODS: L-lactate was used as a model substrate. The excised pigmented rabbit conjunctiva was mounted in a modified Ussing chamber for the measurement of short-circuit current (Isc) and 14C-L.-lactate transport. RESULTS: When added to the mucosal side at 37 degrees C and at pH 7.4, applications of as much as 40 mM L- and D-lactate increased Isc in a saturable manner. By contrast, no change in Isc was observed at 4 degrees C or under the mucosal Na+-free condition. 14C-L-lactate transport in the mucosal-to-serosal (m-s) direction at 0.01 mM revealed directionality, temperature dependency, Na+ dependency, and ouabain sensitivity, but not pH dependency. L-lactate transport in the m-s direction consisted of a saturable Na+-dependent process by the transcellular pathway and a nonsaturable process by the paracellular pathway. For the saturable process, the apparent Michaelis-Menten constant was 1.9 mM, the maximum flux was 8.9 nanomoles/cm2 per hour, and the apparent Na+ :L-lactate coupling ratio was 2:1. 14C-L-lactate transport in the m-s direction was significantly inhibited (46% to 83%) by the mucosal presence of various monocarboxylate compounds, but not by dicarboxylate compounds, zwitterionic compound, D-glucose, amino acids, and peptidomimetic antibiotics. Monocarboxylate nonsteroidal anti-inflammatory drugs and the antibacterial fluoroquinolones inhibited 14C-L-lactate transport by 40% to 85%, whereas prostaglandins and cromolyn had no effect. CONCLUSIONS: An Na+-dependent monocarboxylate transport process that may be used by non-steroidal anti-inflammatory and fluoroquinolone antibacterial drugs for transport appears to be present on the mucosal side of the pigmented rabbit conjunctiva. A possible physiologic role for the Na+-dependent monocarboxylate transport process may be to salvage tear lactate. 相似文献
12.
M Marchut 《Canadian Metallurgical Quarterly》1976,32(9):1211-1213
4-14C-Progesterone and 4-14C-pregnenolone are metabolized in vitro by rabbit placenta, at day 15 and 28 of gestation, exclusively to compounds reduced in ring A (5beta) and at carbon 3 and 20. 相似文献
13.
The objective of this study was to characterize Na(+)-coupled L-arginine (L-Arg) transport in the pigmented rabbit conjunctiva. The excised pigmented rabbit conjunctiva was mounted in the modified Ussing chamber for measurement of short-circuit current (Isc), 3H-L-arginine (3H-L-Arg) flux, and 22Na flux. L-Arg when added to the mucosal side led to 0.32-2.65 microA cm-2 increases in the Isc at 37 degrees C, but not at 4 degrees C or in a Na(+)-free solution. L-Arg at 1 mM stimulated net Na+ absorption by 0.12 microEq cm-2 h-1. The evidence for carrier-mediated transport of L-Arg includes: (1) temperature dependence and saturability over 0.01-10 mM, (2) Na+ dependence and ouabain sensitivity, (3) 84 +/- 2% reduction in the apparent permeability coefficient (Papp) of 3H-L-Arg in the presence of excess unlabeled L-Arg (1 mM), and (4) 16-fold difference in L-Arg transport (at 0.1 mM) between the mucosal-to-serosal and the serosal-to-mucosal direction. Moreover, L-Arg transport was inhibited by basic amino acids, large neutral amino acids, and nitric oxide synthase inhibitors, but not by acidic and small neutral amino acids. Kinetic analysis revealed the possible existence of both high and low affinity processes for L-Arg transport. A half maximal concentration (Km) and maximal L-Arg flux (Jmax) values of the low and high affinity processes were 5.90 and 0.07 mM, and 1,248 and 111 pmol cm-2 min-1, respectively. Hill analysis of L-Arg transport at 0.1 mM in the presence of varying Na+ concentrations in the mucosal bathing fluid yielded a Hill coefficient of 0.93, suggesting a 1:1 coupling between Na+ and L-Arg. In conclusion, Na(+)-coupled transport process(es) for L-Arg in accordance with a 1:1 stoichiometry appear to be present on the mucosal side of the pigmented rabbit conjunctiva. The pattern of inhibition by basic and large neutral amino acids and Na+ dependency are suggestive of system B0,(+)-mediated L-Arg transport. 相似文献
14.
Caveolin is a 22-kDa membrane protein found associated with a coat material decorating the inner membrane surface of caveolae. A remarkable feature of this protein is its ability to migrate from caveolae directly to the endoplasmic reticulum (ER) when membrane cholesterol is oxidized. We now present evidence caveolin is involved in transporting newly synthesized cholesterol from the ER directly to caveolae. MA104 cells and normal human fibroblasts transported new cholesterol to caveolae with a half-time of approximately 10 min. The cholesterol then rapidly flowed from caveolae to non-caveolae membrane. Cholesterol moved out of caveolae even when the supply of fresh cholesterol from the ER was interrupted. Treatment of cells with 10 microg/ml progesterone blocked cholesterol movement from ER to caveolae. Simultaneously, caveolin accumulated in the lumen of the ER, suggesting cholesterol transport is linked to caveolin movement. Caveolae fractions from cells expressing caveolin were enriched in cholesterol 3-4-fold, while the same fractions from cells lacking caveolin were not enriched. Cholesterol transport to the cell surface was nearly 4 times more rapid in cells expressing caveolin than in matched cells lacking caveolin. 相似文献
15.
MK Hellerstein 《Canadian Metallurgical Quarterly》1995,6(3):172-181
The measurement of dynamic fluxes of lipids (biosynthesis, oxidation, and intermediary metabolism) poses difficult challenges. Two fundamental advances have been made recently for measuring the biosynthesis of lipids, namely mass isotopomer distribution analysis and labeled water incorporation. These techniques have resolved the central methodologic problem in biosynthesis by establishing the true precursor isotope enrichment. Mass isotopomer distribution analysis also permits uncontaminated pulse-chase decay curves and intracellular precursor fluxes to be measured. In contrast, the isotopic measurement of lipid oxidation rates remains unreliable because of the wide variability in the recovery of labeled carbon dioxide. 相似文献
16.
In view of the reported excess prevalence of atherosclerosis and cholelithiasis in diabetes, we investigated several aspects of cholesterol metabolism under metabolic ward conditions in six Pima Indians with maturity-onset diabetes mellitus. Cholesterol balance (13.5 versus 11.0 mg per kilogram per day, P less than 0.05), fecal bile acid excretion (415 versus 261 mg per day, P less than 0.05), bile acid pool size (3150 versus 1950 mg, P less than 0.05), fasting plasma cholesterol (193 versus 160 mg per deciliter, P less than 0.05) and plasma triglycerides (251 versus 150 mg per deciliter, P less than 0.05) were higher during uncontrolled hyperglycemia than during relative euglycemia on insulin. The increased plasma lipid levels and total cholesterol synthesis during hyperglycemia may contribute to the acceleration of atherosclerosis in diabetes mellitus. Gallbladder bile was significantly more saturated with cholesterol (181 per cent versus 114 per cent, P less than 0.05) during insulin treatment than during uncontrolled hyperglycemia. Bile lipid composition was thus more favorable to cholesterol precipitation and gallstone formation during insulin treatment than in the untreated diabetic state. 相似文献
17.
The neurosteroid pregnenolone sulphate (PS) interacts allosterically with ionotropic glutamate receptors and thereby could be an important modulator of activity within the hypothalamic magnocellular nuclei. The present in-vitro study therefore examined the effect of perifusion of PS (100 microM) on activity of supraoptic oxytocin (OT) and vasopressin (VP) neurones, in which firing was stimulated by local application of glutamate, NMDA or AMPA. In the presence of locally applied glutamate, PS significantly potentiated firing in putative VP neurones, but had little effect on putative OT neurones. In both cell types, PS increased firing in the presence of NMDA and depressed firing in the presence of AMPA. The action of PS on glutamate- and NMDA-stimulated firing was unaffected by addition of the GABA(A) receptor antagonist, picrotoxin (50 microM). The suppressive action of PS on AMPA-stimulated firing was, however, reversed by picrotoxin and therefore probably requires intact GABAergic transmission for its expression. When putative VP neurones were stimulated by local application of K+, in the presence of picrotoxin, PS evoked a small increase in the ongoing activity, although this did not reach significance. When the glutamate receptor antagonists, NBQX (20 microM) and AP5 (40 microM), were included in the medium, no change in K+ -stimulated firing was observed. Hence PS has no effect on activity of putative VP neurones in the absence of exogenous and endogenous glutamate excitation. In conclusion, PS selectively potentiates glutamate-stimulated activity in putative VP neurones, probably via NMDA receptors, thus providing a mechanism whereby this neurosteroid might exert rapid non-genomic effects on VP secretion. The lack of effect of PS in putative OT neurones probably relates to the relatively small involvement of NMDA receptors in mediating glutamate excitation in this cell type. 相似文献
18.
In rats with third-degree burns, the blood glucose level increased remarkably, with a concomitant suppression of insulin secretion from the pancreas after an oral glucose load. The energy charge (ATP + 1/2 ADP/ATP + ADP + AMP) levels of the kidney decreased to 0.659 as compared with 0.858 of controls at 8 hr after the burn (p less than 0.001). The phosphorylative activity of the kidney mitochondria fell to one third of controls at 8 hr after the burn (p less than 0.001), and that of heart mitochondria decreased to approximately 70% (p less than 0.005); the fall in liver and brain was less remarkable. The decrease in mitochondrial phosphorylative activity was accompanied by a reduction in the respiratory control ratio, P/O ratio, and state 3 respiration. The concentrations of cytochrome a(+a3) in the kidney mitochondria decreased to 69.9% of controls at 8 hr after the burn (p less than 0.001), those of cytochrome b to 82.6%, and those of cytochrome c + c1 to 75.3% (p less than 0.001). The decreased energy charge and oxidative phosphorylation of the kidney in burned rats were remarkably restored by subcutaneous administration of insulin. It is suggested that a reduction in insulin secretion from the pancreas may play an important role in initiating an impairment of adenine nucleotide and mitochondrial metabolism of the kidney. 相似文献
19.
This paper reviews the model of the control of mitochondrial substrate oxidation by Ca2+ ions. The mechanism is the activation by Ca2+ of four mitochondrial dehydrogenases, viz. glycerol 3-phosphate dehydrogenase, the pyruvate dehydrogenase multienzyme complex (PDH), NAD-linked isocitrate dehydrogenase (NAD-IDH) and 2-oxoglutarate dehydrogenase (OGDH). This results in the increase, or near-maintenance, of mitochondrial NADH/NAD ratios in the activated state, depending upon the tissue and the degree of 'downstream' activation by Ca2+, likely at the level of the F1Fo ATPase. Higher values of the redox span of the respiratory chain allow for greatly increased fluxes through oxidative phosphorylation with a minimal drop in protonmotive force and phosphorylation potential. As PDH, NAD-IDH and OGDH are all located within the inner mitochondrial membrane, it is changes in matrix free Ca2+ [Ca2+]m which act as a signal to these activities. In this article, we review recent work in which [Ca2+]m is measured in cells and tissues, using different techniques, with special emphasis on the question of the degree of damping of [Ca2+]m relative to changes in cytosol free Ca2+ in cells with rapid transients in cytosol Ca2+, e.g. cardiac myocytes. Further, we put forward the point of view that the failure of mitochondrial energy transduction to keep pace with cellular energy needs in some forms of heart failure may involve a failure of [Ca2+]m to be raised adequately to allow the activation of the dehydrogenases. We present new data to show that this is so in cardiac myocytes isolated from animals suffering from chronic, streptozocin-induced diabetes. This raises the possibility of therapy based upon partial inhibition of mitochondrial Ca2+ efflux pathways, thereby raising [Ca2+]m at a given, time-average value of cytosol free Ca+2. 相似文献
20.
WJ Powers JL Rosenbaum CS Dence J Markham TO Videen 《Canadian Metallurgical Quarterly》1998,18(6):632-638
Few data regarding early developmental changes in cerebral (blood-to-brain) glucose transport (CTXglc) and CMRglc are available for humans. We measured CBF, CTXglc, and CMRglc with positron emission tomography at 4 to 7 days of life in six preterm human infants whose estimated gestational age was 25 to 34 weeks. The Michaelis-Menten constants Kt and Tmax were estimated from CTXglc and the calculated cerebral capillary plasma glucose concentration. Mean CMRglc was 8.8 mumol 100 g-1 min-1. The CMRglc did not correlate with plasma glucose concentration (r = .315, P = .543), whereas CTXglc showed a significant correlation with plasma glucose concentration (r = .836, P = .038). Estimation of the Michaelis-Menten constants from the best fit to the measured data produced values of Kt = 6.0 mumol mL-1 and Tmax = 32.6 mumol 100 g-1 min-1. These values for Kt in the developing human brain are similar to those that have been reported for the mature brain of adolescent and adult humans and adult nonhuman primates, indicating the affinity of the glucose transport protein for D-glucose is similar. However, Tmax is approximately one third to one half of the comparable values for mature brain, indicating a reduced number of available luminal transporters. 相似文献