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31.
Chromaffin cells of the adrenal medulla and their tumor counterparts, the pheochromocytoma (PC12) cells, are well-established
model systems in neurobiology. The development of sympathoadrenal progenitor cells to chromaffin cells can be studied with
regard to developmental signals which trigger the differentiation. With regard to potential treatments of neurological disorders
like Parkinson’s disease chromaffin cell grafting can be used as one therapeutical approach. The beneficial effect of chromaffin
cell grafts is possibly not only related to the release of dopamine but may also be linked to the release of growth factors.
One of the growth factors that is synthesized by chromaffin and PC12 cells is basic fibroblast growth factor (FGF-2). The
experimental data available so far, are in agreement with different functional roles of FGF-2. This article summarizes the
putative physiological functions of FGF-2 in the adrenal medulla. Three differential functional roles of FGF-2 are discussed:
(1) as a differentiation factor for sympathoadrenal progenitor cells; (2) as a target-derived neurotrophic factor for preganglionic
sympathetic neurons which innervate adrenal medullary cells; (3) as an auto-/paracrine factor in the adrenal medulla.
Accepted: 21 August 1996 相似文献
32.
Binding of a specific dopamine D1 receptor antagonist,125I-SCH 23982, was measured in rat brain sections by quantitative autoradiography at various time intervals, following a knife cut through the striatonigral pathway. Twenty-four hours after lesioning, accumulations of D1 receptor binding sites were found in sagittal sections both rostral and caudal to the lesion site. No other regions studied (caudate-putamen, nucleus accumbens, olfactory tubercle, and substantia nigra pars reticulata) showed any change in D1 receptor binding 24h after the lesion. In brain sections obtained 10 days after lesioning, only the substantia nigra pars reticulata had a significant decrease in D1 receptors ipsilateral to the lesion. These findings suggest the possibility of a presence of bidirectional axonal transport of D1 receptors in rat striatonigral pathway. 相似文献
33.
无毒棉籽液抗腹泻作用研究 总被引:2,自引:1,他引:1
通过对正常小鼠、生大黄致泻小鼠及脾虚小鼠的作用研究表明,无毒棉籽液有较好的抑制排便频度、治疗腹泻的作用.无毒棉籽液6g/kg可极其显著地抑制正常小鼠的排便频度,无毒棉籽液6g/kg和3g/kg可极其显著地抑制生大黄致泻小鼠及脾虚小鼠的排便频度.6g/kg无毒棉籽液且可极其显著地抑制正常小鼠及脾虚小鼠的小肠推进运动. 相似文献
34.
35.
Twenty-four-hour records of arterial pressure (AP), heart rate(HR), oral temperature (OT) and physical and mental performancewere obtained in air traffic controllers during morning (n=16),afternoon (n=17) and night (n=19) shifts. Data were analyzedby the cosinor method. The results obtained during the morningshift were as follows (mesor/amplitude/;acrophase): systolicAP (mm Hg)113.6/10.0/16:03 h; diastolic AP71.1/8.215:19h; mean AP85.6/8.8/15:41 h; HR (beats/min)77.5/8.9/16:00h; OT (dg C)36.71/0.21/15:49 h; right-hand grip strength(kg)49.8/2.0/17:43 h; left-hand grip strength46.1/2.0/16.08h; mental performance (calculations/min)14.9/1.1/16:39h. During the night shift either no change of the circadianacrophases (HR, right-hand grip strength) or acrophase delaysranging from about 2 h (systolic AP, OT, mental performance)up to 3 h (diastolic and mean AP, left-hand grip strength) wereobserved. Our data suggest that the shift system studied doesnot significantly alter the circadian rhythms, and does notinduce a desynchronization, particularly as concerns arterialpressure and oral temperature. 相似文献
36.
Brett Claire M. Washington Carla B. Ott Ronda J. Gutierrez Marcelo M. Giacomini Kathleen M. 《Pharmaceutical research》1993,10(3):423-426
The therapeutic efficacy of nucleosides and nucleoside analogues as antitumor, antiviral, antiparasitic, and antiarrhythmic agents has been well documented. Pharmacokinetic studies suggest that many of these compounds are actively transported in the kidney. The goal of this study was to determine if therapeutically relevant nucleosides or analogues interact with the recently characterized Na+-driven nucleoside transport system of the brush border membrane of the human kidney. Brush border membrane vesicles (BBMV) were prepared from human kidney by divalent cation precipitation and differential centrifugation. The initial Na+-driven 3H-uridine uptake into vesicles was determined by rapid filtration. The effect of several naturally occurring nucleosides (cytidine, thymidine, adenosine), a pyrimidine base (uracil), a nucleotide (UMP), and several synthetic nucleoside analogues [zidovudine (AZT), cytarabine (Ara-C), and dideoxycytidine (ddC)] on Na+–uridine transport was determined. At a concentration of 100 µM the naturally occurring nucleosides, uracil, and UMP significantly inhibited Na+-uridine transport, whereas the three synthetic nucleoside analogues did not. Adenosine competitively inhibited Na+-uridine uptake with a K
i of 26.4 µM (determined by constructing a Dixon plot). These data suggest that naturally occurring nucleosides are substrates of the Na+–nucleoside transport system in the renal brush border membrane, whereas synthetic nucleoside analogues with modifications on the ribose ring are not. The K
i of adenosine is higher than clinically observed concentrations and suggests that the system may play a physiologic role in the disposition of this nucleoside. 相似文献
37.
P.H. Andersen H. Vestergaard S. Lund P. Vedel S. Junker B.B. Kahn O. Pedersen 《Diabetic medicine》1993,10(8):699-706
Studies in normal man and rodents have demonstrated that the expression of the dominant glucose transporter in skeletal muscle, GLUT4, is regulated by insulin at supraphysiological circulating levels. The present study was designed to determine whether intensified insulin replacement therapy for 24 h given to patients with Type 1 diabetes in poor metabolic control was associated with an adaptive regulation of GLUT4 mRNA and protein levels in vastus lateralis muscle. Nine Type 1 diabetic patients with a mean HbA1c of 10.3% were included in the protocol. After intensified treatment with soluble insulin for 24 h the fasting plasma glucose concentration decreased from 20.8 ± 2.3 (SD) to 8.7 ± 2.3 mmol 1?1 whereas the fasting serum insulin level increased from 0.06 ± 0.02 to 0.17 ± 0.09 nmol 1?1 However, despite a 2.8-fold increase in serum insulin levels and more than a halving of the plasma glucose concentration for at least 15 h no significant alterations occurred in the amount of GLUT4 protein (0.138 ± 0.056, poor control vs 0.113 ± 0.026 arb. units, improved control, p = 0.16) or GLUT4 mRNA (96432 ± 44985, poor control vs 81395 ± 25461 arb. units, improved control, p = 0.54). These results suggest, that in spite of evidence that high insulin levels affect GLUT4 expression in muscle, changes in serum insulin within the physiological range do not play a major role in the short-term regulation of GLUT4 expression in Type 1 diabetic patients. 相似文献
38.
Patrick Goethals Manuella Coene Guido Slegers Philippe Agon Joris Deman Karel Schelstraete 《European journal of nuclear medicine and molecular imaging》1988,14(3):152-154
A method for producing carrier free 66Ga (T1/2:9.4h; +) by 4He bombardment of natural copper targets is presented. 66Ga is formed by means of the 63Cu (4He, n) 66Ga reaction. Production yields are given in the 17.5 to 8 MeV 4He energy range. Chemical purification of 66Ga from the copper target is described. The only radionuclidic impurity found in the final product was 67Ga. Albumin colloids from commercially available kits designed for use with 99mTc could easily be labeled with 66Ga and employed for studies of the lymphatic system by positron emission tomography. 相似文献
39.
Smith Philip Mirabelli Christopher Fondacaro Joseph Ryan Frederick Dent John 《Pharmaceutical research》1988,5(9):598-603
We have employed an in vitro system to study transport and metabolism of organic molecules by gastrointestinal tissues. Such a system would aid in the evaluation of the potential for oral delivery of organic molecules. Transport and metabolism of 5-fluorouracil (5-FU) were studied using rabbit intestinal preparations. Unidirectional fluxes and metabolism were measured in vitro in Ussing chambers under short-circuit conditions. Results from these studies reveal that in ileum, proximal, and distal colon, steady-state fluxes of 5-FU (10 µM added to both bathing solutions) are established after 30 min and remain constant for at least 110 min. Transport of 5-FU under sink conditions with 10 µM 5-FU present in the mucosal or serosal bathing solution alone demonstrated similar rates of transport as under nonsink conditions. The concentration dependence of 5-FU fluxes indicates that the mucosal (m)-to-serosal (s) flux is composed of both a saturable and a linear component over the range of 1–100 µM in the ileum, whereas the s-to-m flux in the ileum and both fluxes in the colon are linear functions of concentration. Over the concentration range employed and the time course of these studies, 5-FU had no effect on the electrical properties of the ileum or colon. In the ileum, the m-to-s but not the s-to-m flux of 5-FU was reduced by (1) serosal ouabain (0.1 mM); (2) reduction of the bathing solution Na concentration; and (3) addition of uracil, thy mine, thymidine, uridine, 2-deoxyuridine, or uridine-5-monophosphate. These results indicate that 5-FU absorption in the ileum occurs by a Na-dependent mechanism that is inhibited by uracil and structurally related compounds. In distal colon, no evidence for an active transport mechanism was obtained. High-performance liquid chromatography (HPLC) analysis reveals that both ileum and distal colon metabolize 5-FU to more polar compounds. Metabolism in ileum is quantitatively greater than in distal colon. Metabolites are found predominantly on the side to which transport has occurred, suggesting that metabolism occurs concomitantly with transport. Since the intestinal cells metabolize 5-FU to more polar compounds and active absorption is inhibited in a competitive manner by related compounds, these results may provide an explanation for the variable oral activity reported for 5-FU. 相似文献
40.
Previous work in our laboratory has shown that neural trauma results in a disparity between oxidative and glycolytic rates. In non-neural tissue, glycolysis and oxidative phosphorylation have been shown to work independently of one another, a phenomenon known as "energy compartmentalization". We believe that functional compartmentalization of energy production may also occur in the brain with glycolysis providing energy for membrane bound ionic pumps. Spreading depression, induced in rodent brain by topical KCl application, results in K+ shifts. The restoration of K+ gradients is accomplished by energy dependent Na(+)-K+ pumps. If these pumps depend upon glycolysis, blocking glycolysis should prevent reconstitution of normal [K+]e levels. The present series of experiments were designed to suggest that energy compartmentalization may also exist in brain, and that glycolytic energy production is preferentially used by Na(+)-K+ pumps to maintain normal ionic homeostasis by observing the dynamics of spreading depression induced K+ shifts before and after glycolytic blockade. Spreading depression was associated with increased K+ (48.6 +/- 16.6 mM over control) that normalized within 2.9 +/- 0.3 minutes. Following superfusion with a glycolytic blocking agent, spreading depression produced similar increases in [K+]e (40.6 +/- 12.0 mM over control) but time for reconstitution of the normal [K+]e was 400% longer than controls (2.9 +/- 0.3 to 14.9 +/- 2.1 minutes, P less than 0.001). Time required for recovery of EEG was identical pre- and post-blockade. We believe these data suggest that energy compartmentalization may exist in neural tissue and that glycolytic pathways of energy production are functionally tied to membrane Na(+)-K+ pumps.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献