196,123 research outputs found
Two selective rat adrenomedullin (AM)-receptor antagonists: AM20-50 and AM24-50
No full textAdrenomedullin (AM) is a hypotensive peptide, which is produced in several organs and tissues, the functions of which it regulates in a autocrine-paracrine manner. Rat (r) and human (h) AM are 50- and 52-amino acid peptides, which differ for 2-amino acid deletions and six substitutions and contain a disulfide bridge-formed six-membered ring between adjacent cysteine residues in the 14 and 19 and 16 and 21 positions, respectively. The amidated C-terminal sequence is needed for AM to bind its receptors, and the ring structure (but not t he N-terminal sequence) seems to be required for AM to activate its receptors. Hence, we examined the effectiveness of some N-terminus and ring-lackingAM fragments as AM-receptor antagonists in the rat zona glomerulosa (ZG), whose cells are provided with abundant AM binding sites and display an AM-induced inhibition of K+-stimulated aldosterone secretion. Quantitative autoradiographic studies showed that cold rAMI-50, rAM20-50 and rAM24-50 displaced [125I]AM1-50 binding from rat ZG with the same potency and efficacy, which were significantly higher than those of hAM1-52, hAM22-52 and hAM26-52. Accordingly, rAM20-50 and rAM24-50 reversed the inhibitory effect of 10(-8) M rAMI-50 on aldosterone response of dispersed rat ZG cells to 10(-2) M K+ with significantly higher potency and efficacy than hAM22-52 and hAM26-52. Taken together, our findings confirm that CONH2-terminal AM fragments, lacking the six-membered ring structure, act as antagonists of AM receptors in the rat ZG. Moreover, they provide the first evidence that rAMI-50 and its fragments should be used in the investigations carried out in the rat
Subacute sensory ataxia and optic neuropathy with thiamine deficiency
No full textBackground. A 71 year-old man with a history of partial gastrectomy presented to the emergency department with subacute gait instability associated with painful dysesthesias and clumsiness in both hands. 10 years before presentation he had received a diagnosis of megaloblastic anemia, with no neurological involvement, as a result of vitamin B 12 and folate deficiency, for which he was receiving regular supplements.Investigations. Neurological examination; routine laboratory testing; MRI of the spine and brain; lumbar puncture; electromyography; sensory, motor and visual evoked potentials, optic nerve optical coherence tomography; immunoelectrophoresis; cryoglobulins; immunological and infection tests; screening for onconeural antibodies; measurement of serum metabolic values, including vitamins B 12 and E, folates, homocysteine, copper, zinc and pyruvic acid; transketolase activity; gastrointestinal endoscopies; and the glucose breath test.Diagnosis. Subacute sensory ataxia with bilateral optic neuropathy related to thiamine deficiency resulting from remote partial gastrectomy.Management. Parenteral thiamine supplementation followed by chronic oral thiamine and short-term, low-dose multivitamins. © 2010 Macmillan Publishers Limited. All rights reserved
Comparative assessment of respiratory chain and antioxidant enzymatic methods in skeletal muscle biopsies
No full textMitochondrial disorders of the nuclear genome
No full textBACKGROUND: Mitochondrial myopathies are regulated by two genomes: the nuclear DNA, and the mitochondrial DNA. While, so far, most studies have dealt with mitochondrial myopathies due to deletions or point mutations in the mitochondrial DNA, a new field of investigation is that of syndromes due to mutations in the nuclear DNA. These latter disorders have mendelian inheritance.
RESULTS: Three representative cases have been selected: one with COX deficiency and a Leigh syndrome due to a SURF1 gene mutation, one due to a defect of Coenzyme Q synthesis and one with dominant optic atrophy due to a mutation in the OPA1 gene.
CONCLUSIONS: Future developments will show that many neurodegenerative disorders are due to mutations of nuclear genes controlling mitochondrial function, fusion and fission
Impaired Copper and Iron Metabolism in Blood Cells and Muscles of Patients Affected by Copper Deficiency Myeloneuropathy.
No full textAbstract
AIMS:
Severe copper deficiency leads to a treatable multisystem disease characterized by anaemia and degeneration of spinal cord and nerves, but its mechanisms have not been investigated in humans. We tested whether copper deficit leads to alterations in fundamental copper dependent proteins and in iron metabolism in blood cells and muscles of patients affected by copper deficiency myeloneuropathy, and if these metabolic abnormalities are associated with compensatory mechanisms for copper maintenance.
METHODS:
We evaluated the expression of critical copper-enzymes, of iron-related proteins, and copper chaperones and transporters in blood and muscles from five copper deficient patients presenting with subacute sensory ataxia, muscle paralysis, steatosis, and variable anaemia. Severe copper deficiency was caused by chronic zinc intoxication in all of the patients, with an additional history of gastrectomy in two cases.
RESULTS:
The antioxidant enzyme SOD1 and subunit 2 of cytochrome c oxidase were significantly decreased in blood cells and in muscles of copper-deficient patients compared to controls. In muscle, the iron storage protein ferritin was dramatically reduced despite normal serum ferritin, and the expression of the heme-proteins cytochrome c and myoglobin was impaired. Muscle expression of the copper transporter CTR1 and of the copper chaperone CCS, were strikingly increased, while antioxidant protein 1 was diminished.
CONCLUSIONS:
Critical copper-dependent enzymes involved in antioxidant defenses, in mitochondrial energy production, and in iron metabolism are affected in blood cells and muscles of patients with profound copper deficiency leading to myeloneuropathy. Homeostatic mechanisms are strongly activated to increase intracellular copper retention
Effects of leptin and leptin fragments on corticosterone secretion and growth of cultured rat adrenocortical cells
No full textCompelling evidence indicates that leptin, acting via specific receptors (Ob-Ra and Ob-Rb) modulates adrenocortical-cell secretion. However, the results are controversial, inasmuch as either secretagogue or antisecretagogue effects have been reported. Hence, we decided to study the effects of a 96-h incubation with leptin and leptin fragments 116-130, 150-167, 138-167, 93-105, 22-56 and 26-39 (10(-8) and 10(-6) M) on the secretion and growth of cultured rat adrenocortical cells. Reverse transcription-polymerase chain reaction showed that control cultures expressed both Ob-Ra and Ob-Rb isoforms. As expected, ACTH (10(-8) M) raised corticosterone secretion and lowered proliferation rate of cultured cells. Native leptin elicited ACTH-like effects, while fragment 116-130 was ineffective. Leptin fragments 150-167 and 26-39 stimulated corticosterone production, and fragments 138-167 and 22-56 inhibited it. Fragment 93-105 exerted a dose-dependent biphasic effect on corticosterone secretion (i.e. stimulation and inhibition at the concentration of 10(-8) and 10(-6) M, respectively). Leptin fragment 26-39 enhanced proliferation of cultured cells, while fragments 138-167 and 22-56 were ineffective. Fragments 150-167 and 93-105 displayed proliferogenic and antiproliferogenic effects at the concentration of 10(-8) and 10(-6) M, respectively. Taken together, these findings allows us to conclude that native leptin and its fragments interact differently with Ob-Rs or interact with different Ob-R isoforms, thereby variously modulating secretion and growth of cultured rat adrenocortical cells
Assessment of mitochondrial respiratory chain enzymatic activities on tissues and cultured cells.
No full textThe assessment of mitochondrial respiratory chain (RC) enzymatic activities is essential for investigating mitochondrial function in several situations, including mitochondrial disorders, diabetes, cancer, aging and neurodegeneration, as well as for many toxicological assays. Muscle is the most commonly analyzed tissue because of its high metabolic rates and accessibility, although other tissues and cultured cell lines can be used. We describe a step-by-step protocol for a simple and reliable assessment of the RC enzymatic function (complexes I-IV) for minute quantities of muscle, cultured cells and isolated mitochondria from a variety of species and tissues, by using a single-wavelength spectrophotometer. An efficient tissue disruption and the choice for each assay of specific buffers, substrates, adjuvants and detergents in a narrow concentration range allow maximal sensitivity, specificity and linearity of the kinetics. This protocol can be completed in 3 h
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