Ligand-induced conformational changes in the Na,K-ATPase alpha subunit.
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Adenosine Triphosphate↗
Biomedical subjects
S Daoud
Publications and source records attributed to S Daoud.
Identification of two conformationally sensitive cysteine residues at the extracellular surface of the Na,K-ATPase alpha-subunit.
Na,K-ATPase in right-side-out oriented vesicles was stabilized in different conformations, and the location of intramembrane Cys residues of the alpha-subunit was assessed with membrane-permeable and membrane-impermeable Cys-directed reagents. In the presence of Mg2+ and Pi, Cys964 was the most accessible for both membrane-impermeable 4-acetamido-4'-maleimidylstilbene-2, 2'disulfonic acid (or stilbene disulfonate maleimide, SDSM) and membrane-permeable 7-diethylamino-3-(4'-maleimidyl)-4-methylcoumarin (CPM). In the presence of K+, Cys964 was modified only by hydrophobic CPM, indicating that the environment around Cys964 was different in these two conformations. Cys964 seems to mark the extracellular border of transmembrane segment M9. Cys911 in transmembrane segment M8 showed similar behavior; however, it was not so readily modified. Complete modification of Cys964 and Cys911 causes only partial (about 50%) inactivation of both ATPase activity and Rb+ (or K+) occlusion, indicating that the effect on cation occlusion is indirect and not within the occlusion cavity. The ATP binding capacity remains unaltered by the modifications. Treatment of the K+-stabilized post-tryptic preparation of purified Na, K-ATPase revealed labeling of several cysteines by CPM, none of which were labeled with SDSM. Removal of K+ ions from the preparation, which we have previously shown is accompanied by release of the M5M6 hairpin to the supernatant (), causes changes in the organization of the C-terminal 21-kDa fragment. In particular Cys983 in M10 became labeled by both CPM and SDSM, pointing to a tight association between the C terminus and the M5M6 hairpin of the alpha-subunit.
Amino Acid Sequence↗
Modulation of vascular ATP diphosphohydrolase by fatty acids.
Endothelial cells (EC) possess several protective thromboregulatory mechanisms that may be perturbed by cell activation or injury. Vascular ATP-diphosphohydrolase (ATPDase) has been demonstrated on both aortic EC and smooth muscle cells and may play a key regulatory role in hemostasis and platelet reactivity by converting extracellular ATP and ADP to AMP. We have examined the role of exogenous saturated or unsaturated fatty acids in the modulation of EC associated ATPDase activity in vitro. EC growth was not dramatically influenced by supplementation with fatty acids whereas viability was enhanced by oleic, butyrate and eicosapentaenoic acid. EC cultures supplemented with saturated or a monounsaturated (oleic acid) fatty acid(s) had markedly increased ATPDase activity, whereas those exposed to polyunsaturated fatty acids showed substantive decreases. Exogenous oleic acid could also protect against the significant loss of ATPDase activity, following exposure to reactive oxygen intermediates in vitro. We conclude that endothelial ATPDase activity may be regulated by exogenous fatty acids and that underlying mechanisms include alterations in the nature of the phospholipid composition of EC membranes that influence responses to oxidative stress reactions.
Animals↗
Purification, characterization, and localization of two ATP diphosphohydrolase isoforms in bovine heart.
Two ATP diphosphohydrolase (ATPDase) isoforms have been purified from the bovine heart ventricle. The purification procedure includes the following steps: differential centrifugation, sucrose cushion centrifugation, solubilization with Triton X-100, DEAE agarose ion exchange, and Affi-Gel blue-Sepharose and concanavalin A (con A)-Sepharose chromatographies. The purified enzyme has an optimum pH of catalysis of 7.5 and requires Ca2+ or Mg2+. The apparent Michaelis constant of the enzyme, with ADP as the substrate, is 29 microM, and the apparent maximal velocity is 1.6 mumol.min-1.mg protein-1. Substrate specificity, heat-inactivation curves, and copurification of adenosinetriphosphatase (ATPase) and adenosinediphosphatase (ADPase) activities confirmed the identity of the purified enzyme as an ATPDase. In addition, polyacrylamide gel electrophoresis, under nondenaturing conditions, showed identical migration patterns for the protein involved in ATPase and ADPase activities. Western blot analysis, with an antibody that specifically recognizes the NH2-terminal sequence of pig pancreas ATPDase and specifically reacts with bovine and human ATPDases, showed cross-reactivity with the purified ATPDase isoforms from the bovine heart. Immunocytochemical localization in the ventricle produced strong reactions with the plasma membrane of Purkinje fiber cells and the majority of myocardial cells. Immunoreactivity was variable, producing a mosaic-like aspect. As expected, smooth muscle cells and endothelial cells of coronary vessels were highly reactive. This ectoenzyme could play a protective role against the potentially deleterious effects of extracellular ATP. In tandem with 5'-nucleotidase, it produces adenosine, a powerful vasodilator, especially in hypoxic or ischemic conditions that favor the release of ATP.
Animals↗
[Vitamin-resistant rickets cured by removal of a bone tumor. Review of the literature].
PURPOSE OF THE STUDY: Rickets secondary to bone or soft tissue tumors are rare in children. Majority of the reported cases occurred in adults older than thirty. This entity can be cured after tumor removal. The authors present a case in a ten year boy and literature review. MATERIAL: A ten year boy complained of diffuse bone and muscle weakness for two years. A diagnosis of arthritis was made but the patient continued to complain. Serum calcium level was normal (2.33 mmol/l), phosphorus was very low (0.43 mmol/l), serum alkaline phosphatase was high, parathyroid hormone and vitamin D level were normal. Urinalysis showed abnormal phosphate excretion. METHODS: The absence of malabsorption, no family history of rickets or hypophosphatermy presence of a marked excess of urinary phosphate, very low serum phosphate and normal serum calcium, vitamin D and parathyroid hormone levels led us to consider a diagnosis of tumor induced osteomalacia. Radiographs showed a large round radiolucent lesion in the left superior pubic ramus and generalized demineralisation. RESULTS: We performed a complete tumor resection and the space was filled with bone graft. On histopathologic examination it was a benign mesenchymal tumor. Rapid reversal of biochemical anomalies, radiographs anomalies and clinical manifestation were observed after complete tumor resection. DISCUSSION: The authors have described the tumor, the osteomalacia and the pathogenesis of tumor rickets. Histologically the most common causative tumors were vascular tumors, mesenchymal tumors and non ossifying tumors. The tumor were of bone or soft tissue origin. Clinical symptoms were muscular weakness, bone and muscle pain. Biochemically there is a very low phosphate level, a normal serum calcium level as well as a normal vitamin D and PTH level. There is a significant high level of urinal phosphate. The mechanism proposed to explain oncogenic osteomalacia includes tumor secretion of phosphaturic substance other than PTH and calcitonin. Another hypothesis is a substance interfering with normal vitamin D metabolism. The pathogenesis is not clearly defined. CONCLUSION: Regardless to the mechanism of osteomalacia, complete removal of the tumor will cure the patient. A diligent search for tumors should be done in patients with vitamin D resistant rickets.
Bone Neoplasms↗
Characterization of the human cDNA and genomic DNA encoding CART: a cocaine- and amphetamine-regulated transcript.
PCR differential display screening has recently identified a rat mRNA termed CART (cocaine- and amphetamine-regulated transcript) which is transcriptionally regulated in the striatum following acute administration of psychomotor stimulants. The endogenous CART transcript is expressed in diverse rat brain structures, as well as endocrine tissues. The deduced CART protein contains a hydrophobic signal sequence, suggesting that it may be targeted for secretion. Thus, the CART protein may represent a novel neuroendocrine signaling molecule. The study described here represents a complete analysis of the human CART cDNA and gene. The complete nucleotide (nt) sequence of the approx. 900-nt human CART transcript is contained within three distinct exons, with the entire human CART gene localized to a segment of genomic DNA approx. 2 kb in length. The human CART cDNA sequence is 80% identical to the corresponding rat cDNA, with 92% homology observed within the deduced protein-coding region. Third-nt changes account for most of the latter differences, with CART exhibiting 95% identity between these two species at the amino-acid sequence level. PCR/Southern blot analysis of DNA isolated from human/rodent somatic cell hybrid panels localizes the CART gene to human chromosome 5. Lastly, Northern blot analysis reveals that the gross pattern of distribution of CART mRNA in human brain is similar to that previously observed in rat. These overall similarities suggest that CART plays a conserved role within the mammalian neuroendocrine system.
Amino Acid Sequence↗
Reproducibility of the cardiovascular reactivity to a computerized version of the Stroop stress test in normotensive and hypertensive subjects.
The 1-month reproducibility of haemodynamic and sympathoadrenal responses to a standardized mental stress test was studied in ten normotensive and ten hypertensive individuals. The stress test was a computerized adaptation of the Stroop test and sympathetic activity was evaluated by measuring urinary catecholamine excretion. Three-way analysis of variance (stress, session, blood pressure) revealed significant increases in systolic and diastolic blood pressures and in heart rate during the stress test. Test-retest correlation coefficients for basal stress levels, and stress-induced variations were significant (r from 0.59 to 0.88). The stress test induced a significant increase in urinary noradrenaline excretion with large intra- and interindividual variability. The significant test-retest correlations and the lack of period effect for haemodynamic parameters indicated good temporal stability. However, a slight decrease in stress-induced reactivity was observed. This standardized mental stress test may be useful in epidemiological and therapeutic trials to measure blood pressure and heart rate responses, but measurement of urinary catecholamine excretion does not provide any additional information.
Adult↗
Chronic hepatitis C, cryoglobulinemia, and cutaneous necrotizing vasculitis. Clinical, pathologic, and immunopathologic study of twelve patients.
BACKGROUND: Several patients with chronic hepatitis C infection and cutaneous vasculitis have been described. OBJECTIVE: The objective of this study was to define better the features of necrotizing vasculitis and mixed cryoglobulinemia in patients with hepatitis C infection. METHODS: A retrospective review of 611 patients with hepatitis C antibodies was conducted. Patients with clinical and histopathologic findings of cutaneous necrotizing vasculitis were identified. Clinical, histologic, and laboratory data were recorded. RESULTS: Twelve patients with necrotizing vasculitis and chronic hepatitis C infection were identified. Palpable purpura was the most common clinical presentation. Onset of skin lesions was usually more than 10 years after infection. The lower extremities were affected in all patients. Cryoglobulinemia of the mixed type II was present in 10 of 11 patients. Liver function tests were evaluated at the time of vasculitis in most of the patients. Rheumatoid factor was elevated in all nine patients tested. Total complement was decreased in seven of nine patients, and C4 was decreased in six of seven patients. CONCLUSION: Cutaneous vasculitis associated with cryoglobulinemia and hypocomplementemia is not uncommon in the course of chronic active hepatitis C infection. The triad of necrotizing vasculitis, chronic hepatitis C infection, and cryoglobulinemia occurs late after initial infection with hepatitis C. Antibodies to hepatitis C virus should be determined in a patient with necrotizing vasculitis, especially if liver function tests are elevated.
Adult↗
Interest of umbilical fold incision for pyloromyotomy.
We report the results of a study concerning 80 infants undergoing a pyloromyotomy over a 3-and-a-half-year period. 40 infants had a right upper quadrant transverse rectus incision and 40 infants had an umbilical fold incision. Morbidity and cosmetic aspect of the two techniques were compared. We insist on the umbilical fold incision which presents the same advantages as the classic one and a better cosmetic result.
Humans↗
Aleukemic monocytic leukemia cutis.
Aleukemic leukemia cutis is a rare condition in which leukemic cells invade the skin before they appear in peripheral blood or bone marrow specimens. Herein we describe a 67-year-old man who underwent assessment because of papules and nodules on his back and lower extremities. A biopsy of these lesions confirmed a dense, predominantly monocytic infiltrate of the dermis and subcutaneous tissue. Immunohistochemical stains were positive for CD43 (Leu-22) as well as monocytic markers. Bone marrow and peripheral blood examinations failed to reveal leukemia. Treatment was based on the results of the skin biopsy, and the patient is doing well 1 year after therapy.
Aged↗
Absence of microchimerism in long-term tolerant living-donor kidney graft recipients.
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Chimera↗
Evaluation of a hydrocolloid dressing.
A hydrocolloid dressing was compared to adhesive skin tapes on children's postoperative wounds. A total of 170 children of varying ages were randomised in two parallel groups, in nine centres of plastic, thoracic, gastrointestinal, urogenital and orthopaedic surgery. Skin closure was satisfactory in both groups, with 76 (89.4%) healthy closures without dehiscence in the hydrocolloid group and 81 (95.3%) in the control group; a relationship was found between partial closures/dehiscence and the type of surgical procedure. No product-related maceration, infection or adverse event was reported during the study and both groups showed very satisfactory cosmetic results.
Adhesives↗
[Type AA renal amyloidosis in sarcoidosis].
Sarcoidosis is an uncommon cause of secondary amyloidosis. We describe in this paper the case of a 39 years old patient, with a pulmonary and hepatosplenic sarcoidosis. A nephrotic syndrome led to a renal biopsy which showed AA type amyloidosis. As no other cause of amyloidosis has been found we admitted that it was a result of sarcoidosis which was associated with the unusual inflammatory syndrome.
Adult↗
Nonoperative management of biliary tract fistulas after blunt abdominal trauma in a child.
Nonoperative treatment was carried out in a 12-year-old girl who presented with biliary fistulas after blunt abdominal trauma with hepatic injury. A computed tomography-guided percutaneous puncture showed biliary peritonitis and permitted the positioning of an efficient intraperitoneal drainage. Endoscopic retrograde cholangiography was very helpful for visualization and accurate localization of biliary injuries. This permitted positioning a nasobiliary drain to reduce intrabiliary pressure and to bypass a lesion of the common hepatic duct. This nonoperative management allowed healing of fistulas within 20 days, without bile duct stricture (noted on the follow-up intravenous cholangiogram 18 months later).
Abdominal Injuries↗
Chronic hepatitis C and skin diseases: a review.
OBJECTIVE: To emphasize the ongoing role of chronic hepatitis C virus (HCV) infection in the cause or exacerbation of severe dermatologic disorders. DESIGN: We present two case reports to outline the pertinent findings in hepatitis C-related cryoglobulinemia, leukocytoclastic vasculitis, and lichen planus and discuss the main disorders associated with chronic HCV infection. RESULTS: Chronic HCV infection has recently been recognized in association with various skin disorders. The most commonly reported association is the triad of leukocytoclastic vasculitis, cryoglobulinemia, and chronic HCV infection. Other cutaneous disorders associated with HCV infection include porphyria cutanea tarda, lichen planus, erythema nodosum, urticaria, erythema multiforme, and polyarteritis nodosa. CONCLUSION: Patients with onset or exacerbation of these disorders should undergo assessment for HCV infection.
Adult↗
Hepatitis C virus infection in renal transplantation.
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Azathioprine↗
[Treatment of hip dislocations and subluxations by Petit's splints].
PURPOSE OF THE STUDY: The management of DDH in infants less than one year old is not yet definite. Many ambulant therapeutic methods are described and Pavlik's harness is widely employed. The use of Petit's splints is less well known and we report our experience with 169 cases. MATERIAL AND METHOD: Between 1973 and 1991, Petit's splints were used in 112 cases, following abduction cushions in 55 cases and after Pavlik's harness in 2 cases. 103 hips were dislocated but reducible. This permitted progressive abduction of the hips in order to obtain the reduction of the dislocation and to ensure stabilization by retraction of the slack articular capsule. RESULTS: Only 8 dislocations (4,7 per cent) couldn't be reduced by this procedure and necessitated another treatment. Hips were normal after 5 years of follow up in 118 cases and there were 43 residual dysplasias. 6 post reductional avascular necrosis (3,7 per cent) were recorded as a complication of this method among which only one was a serlous from. DISCUSSION: This ambulatory method for treatment of congenital hip dislocation seems to be forsaken by many authors. Nevertheless its effectiveness has been demonstrated with a complication rate lower than with Pavlik's harness procedure.
Female↗
Effects of lisinopril on stress-induced peak blood pressure and sodium excretion: a double-blind controlled study.
A stress test was performed before (S1) and after a 1-month treatment period (S2) in patients with essential hypertension, randomly allocated to receive either an angiotensin-converting enzyme inhibitor (ACEI), lisinopril (n = 10), or placebo (n = 10). The two groups were similar with regard to systolic and diastolic blood pressure (SBP, DBP), body weight, renal function, and 24-h sodium excretion. At S1, stress induced a significant increase in SBP of 18 +/- 9 mm Hg and in DBP of 10 +/- 6 mm Hg and a significant reduction in sodium excretion from 258 +/- 105 to 204 +/- 72 mumol/min. Stress-induced sympathetic stimulation was assessed by a significant increase in urinary norepinephrine (NE) excretion from 21 +/- 10 to 26 +/- 10 micrograms/g creatinine. One-month treatment by placebo did not change stress-induced BP reactivity, sodium retention, or urinary NE excretion. In the lisinopril group, rest and stress BP were significantly reduced by the treatment. Stress-induced sodium retention was higher after 1-month placebo treatment (72 +/- 78 vs 48 +/- 67 mumol/min), whereas this retention was significantly reduced by lisinopril (13 +/- 27 vs 69 +/- 60 mumol/min).
Blood Pressure↗