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971.
972.
Cerebral vasomotor reactivity at high altitude in humans 总被引:3,自引:0,他引:3
The purpose of this study was twofold:1) to determine whether at highaltitude cerebral blood flow (CBF) as assessed during CO2 inhalation and duringhyperventilation in subjects with acute mountain sickness (AMS) wasdifferent from that in subjects without AMS and2) to compare the CBF as assessedunder similar conditions in Sherpas at high altitude and in subjects atsea level. Resting control values of blood flow velocity in themiddle cerebral artery (VMCA), pulseoxygen saturation (SaO2), andtranscutaneous PCO2 were measured at4,243 m in 43 subjects without AMS, 17 subjects with AMS, 20 Sherpas,and 13 subjects at sea level. Responses ofCO2 inhalation andhyperventilation onVMCA,SaO2, and transcutaneous PCO2 were measured, and the cerebralvasomotor reactivity (VMR = VMCA/PCO2)was calculated as the fractional change ofVMCA per Torrchange of PCO2, yielding ahypercapnic VMR and a hypocapnic VMR. AMS subjects showeda significantly higher resting controlVMCA than didno-AMS subjects (74 ± 22 and 56 ± 14 cm/s, respectively;P < 0.001), andSaO2 was significantly lower (80 ± 8 and 88 ± 3%, respectively; P < 0.001). Resting control VMCA values inthe sea-level group (60 ± 15 cm/s), in the no-AMS group, and inSherpas (59 ± 13 cm/s) were not different. Hypercapnic VMR valuesin AMS subjects were 4.0 ± 4.4, in no-AMS subjects were 5.5 ± 4.3, in Sherpas were 5.6 ± 4.1, and in sea-level subjects were 5.6 ± 2.5 (not significant). Hypocapnic VMR values were significantly higher in AMS subjects (5.9 ± 1.5) compared with no-AMS subjects (4.8 ± 1.4; P < 0.005) but werenot significantly different between Sherpas (3.8 ± 1.1) and thesea-level group (2.8 ± 0.7). We conclude that AMS subjects havegreater cerebral hemodynamic responses to hyperventilation, higherVMCAresting control values, and lower SaO2 compared with no-AMSsubjects. Sherpas showed a cerebral hemodynamic patternsimilar to that of normal subjects at sea level. 相似文献
973.
Rehman A Nourooz-Zadeh J Möller W Tritschler H Pereira P Halliwell B 《FEBS letters》1999,448(1):120-122
Gas chromatography-mass spectrometry was used to measure the oxidative DNA damage in diabetic subjects and controls. Levels of multiple DNA base oxidation products, but not DNA base de-amination or chlorination products, were found to be elevated in white blood cell DNA from patients with type II diabetes as compared with age-matched controls. The chemical pattern of base damage is characteristic of that caused by an attack on DNA by hydroxyl radical. An increased formation of the highly reactive hydroxyl radical could account for many of the reports of oxidative stress in diabetic subjects. There was no evidence of an increased DNA damage by reactive nitrogen or chlorine species. 相似文献
974.
Split flexor carpi radialis muscle 总被引:7,自引:0,他引:7
Hua J Kumar VP Pereira BP Lim AY Pho RW Liu J 《Plastic and reconstructive surgery》1999,103(3):930-934
A detailed anatomic and intramuscular neural staining study in 22 human and 5 monkey upper limbs revealed that the flexor carpi radialis can be raised on its proximal neurovascular pedicle and that the muscle can be split along its tendon into two independently functioning neuromuscular compartments, each with its own nerve and blood supply. A study of the muscle architecture in the human specimens found the radial compartment to have significantly longer fiber length and a larger physiologic cross-sectional area than the ulnar compartment. Independence of function of each compartment was demonstrated in electrical stimulation studies in six monkeys (Macaca fascicularis), but no significant difference was noted in the peak isometric load between the two compartments (p = 0.68) in the monkey. The extra functioning muscle units become important in local transfers for restoring function in multiple nerve palsies as in Hansen's disease, severe traumatic loss of muscle in crush injuries and compartment syndromes, and after wide resection in infective and neoplastic conditions in the forearm and hand. 相似文献
975.
976.
Almendra MJ Brondino CD Gavel O Pereira AS Tavares P Bursakov S Duarte R Caldeira J Moura JJ Moura I 《Biochemistry》1999,38(49):16366-16372
An air-stable formate dehydrogenase (FDH), an enzyme that catalyzes the oxidation of formate to carbon dioxide, was purified from the sulfate reducing organism Desulfovibrio gigas (D. gigas) NCIB 9332. D. gigas FDH is a heterodimeric protein [alpha (92 kDa) and beta (29 kDa) subunits] and contains 7 +/- 1 Fe/protein and 0.9 +/- 0.1 W/protein. Selenium was not detected. The UV/visible absorption spectrum of D. gigas FDH is typical of an iron-sulfur protein. Analysis of pterin nucleotides yielded a content of 1.3 +/- 0.1 guanine monophosphate/mol of enzyme, which suggests a tungsten coordination with two molybdopterin guanine dinucleotide cofactors. Both M?ssbauer spectroscopy performed on D. gigas FDH grown in a medium enriched with (57)Fe and EPR studies performed in the native and fully reduced state of the protein confirmed the presence of two [4Fe-4S] clusters. Variable-temperature EPR studies showed the presence of two signals compatible with an atom in a d(1) configuration albeit with an unusual relaxation behavior as compared to the one generally observed for W(V) ions. 相似文献
977.
We explore the behavior of richly connected inhibitory neural networks under parameter changes that correspond to weakening
of synaptic efficacies between network units, and show that transitions from irregular to periodic dynamics are common in
such systems. The weakening of these connections leads to a reduction in the number of units that effectively drive the dynamics
and thus to simpler behavior. We hypothesize that the multiple interconnecting loops of the brain’s motor circuitry, which
involve many inhibitory connections, exhibit such transitions. Normal physiological tremor is irregular while other forms
of tremor show more regular oscillations. Tremor in Parkinson’s disease, for example, stems from weakened synaptic efficacies
of dopaminergic neurons in the nigro-striatal pathway, as in our general model. The multiplicity of structures involved in
the production of symptoms in Parkinson’s disease and the reversibility of symptoms by pharmacological and surgical manipulation
of connection parameters suggest that such a neural network model is appropriate. Furthermore, fixed points that can occur
in the network models are suggestive of akinesia in Parkinson’s disease. This model is consistent with the view that normal
physiological systems can be regulated by robust and richly connected feedback networks with complex dynamics, and that loss
of complexity in the feedback structure due to disease leads to more orderly behavior. 相似文献
978.
Meirelles MN Pereira MC Singer RH Soeiro MN Garzoni LR Silva DT Barbosa HS Araujo-Jorge TC Masuda MO Capella MA Lopes AG Vermelho AB 《Memórias do Instituto Oswaldo Cruz》1999,94(Z1):149-152
The present paper summarizes new approaches regarding the progress done to the understanding of the interaction of Trypanosoma cruzi-cardiomyocytes. Mannose receptors localized at the surface of heart muscle cell are involved in binding and uptake of the parasite. One of the most striking events in the parasite-heart muscle cells interaction is the disruption of the actin cytoskeleton. We have investigated the regulation of the actin mRNA during the cytopathology induced in myocardial cells by the parasite. T. cruzi invasion increases calcium resting levels in cardiomyocytes. We have previously shown that Ca2+ ATPase of the sarcoplasmic reticulum (SERCA) is involved in the invasion of T. cruzi in cardiomyocytes. Treating the cells with thapsigargin, a drug that binds to all SERCA ATPases and causes depletion of intracellular calcium stores, we found a 75% inhibition in the T. cruzi-cardiomyocytes invasion. 相似文献
979.
980.
The effect of dexamethasone (a synthetic glucocorticoid) on the activity of antioxidant enzymes (superoxide dismutase (SOD), catalase and glutathione peroxidase) of the lymphoid organs (mesenteric lymph nodes (MLN), spleen and thymus) was investigated. For comparison with non-immune tissues, skeletal muscles (soleus and gastrocnemius (GC) were also studied. As an indication of the occurrence of lipid peroxidation, the content of thiobarbituric acid reactant substances (TBARs) was also determined. Dexamethasone treatment decreased the TBARs content of the lymphoid organs and raised it in the GC and soleus muscles. The activity of Cu/Zn-SOD was reduced in all tissues. However, the activity of Mn-SOD was decreased in the MLN and soleus muscle only. The activity of catalase was reduced in the MLN and thymus and raised in the spleen and GC and soleus muscles. The imposed treatment raised the activity of GPX in the MLN, thymus and spleen and reduced it in GC and soleus muscles. These data led us to postulate that the mechanism for the therapeutic effect of glucocorticoids as antiinflammatory and immunosuppressive agents might include modification of antioxidant enzyme activities. 相似文献