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At least 235 records · Page 13Linked to original sources
PubMed2005

SUR, ABC proteins targeted by KATP channel openers.

The sulfonylurea receptor SUR is an ATP binding cassette (ABC) protein of the ABCC/MRP family. Unlike other ABC proteins, it has no intrinsic transport function, neither active nor passive, but associates with the potassium channel proteins Kir6.1 or Kir6.2 to form the ATP-sensitive potassium (K(ATP)) channel. Within the channel complex SUR serves as a regulatory subunit which fine-tunes the gating of Kir6.x in response to alterations in cellular metabolism. It constitutes a major pharmaceutical target as it binds numerous drugs, K(ATP) channel openers and blockers, capable of up- or down-regulating channel activity. We here review current knowledge on the molecular basis of the interaction of classical K(ATP) channel openers (cromakalim, pinacidil, diazoxide) with SUR.

ATP-Binding Cassette Transporters↗
PubMed2003

Protein PknE, a novel transmembrane eukaryotic-like serine/threonine kinase from Mycobacterium tuberculosis.

Protein PknE from Mycobacterium tuberculosis has been overproduced and purified, and its biochemical properties have been analyzed. This protein is shown to be a eukaryotic-like (Hanks'-type) protein kinase with a structural organization similar to that of membrane-bound eukaryotic sensor serine/threonine kinases. It consists of a N-terminal catalytic domain located in the cytoplasm, linked via a single transmembrane-spanning region to an extracellular C-terminal domain. The full-length enzyme, as well as the cytosolic domain alone, can autophosphorylate on serine and threonine residues. Such autokinase activity requires the presence of a lysine residue at position 45 in subdomain II, which is known to be essential also for eukaryotic kinase activity. Involvement of PknE in the transduction of external signals into the cytosol of bacteria is proposed.

Amino Acid Motifs↗
PubMed2003

Inhibition of ATP-sensitive K+ channels by substituted benzo[c]quinolizinium CFTR activators.

The substituted benzo[c]quinolizinium compounds MPB-07 and MPB-91 are novel activators of the cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel. High homologies between CFTR and the sulfonylurea receptor (SUR), which associates with the potassium channel Kir6.2 to form the ATP-sensitive K(+) (K(ATP)) channel, prompted us to examine possible effects of these compounds on K(ATP) channels using electrophysiological recordings and binding assays. Activity of recombinant K(ATP) channels expressed in Xenopus oocytes was recorded in the inside-out configuration of the patch-clamp technique. Channels were practically unaffected by MPB-07 but were fully blocked by MPB-91 with half-inhibition achieved at approximately 20 microM MPB-91. These effects were similar on channels formed by Kir6.2, and either the SUR1 or SUR2A isoforms were independent of the presence of nucleotides. They were not influenced by SUR mutations known to interfere with its nucleotide-binding capacity. MPB-91, but not MPB-07, was able to displace binding of glibenclamide to HEK cells expressing recombinant SUR1/Kir6.2 channels. Glibenclamide binding to native channels from pancreatic MIN6 cells was also displaced by MPB-91. A Kir6.2 mutant able to form channels without SUR was also blocked by MPB-91, but not by MPB-07. These observations demonstrate that neither MPB-07 nor MPB-91 interact with SUR, in spite of its high homology with CFTR, and that MPB-91 blocks K(ATP) channels by binding to the Kir6.2 subunit. Thus, caution should be exercised when planning to use MPB compounds in cystic fibrosis therapy, specially MPB-91 which could nonetheless find interesting applications as the precursor of a new class of K channel blockers.

Animals↗
PubMed2000

An elastic analysis of Listeria monocytogenes propulsion.

The bacterium Listeria monocytogenes uses the energy of the actin polymerization to propel itself through infected tissues. In steady state, it continuously adds new polymerized filaments to its surface, pushing on its tail, which is made from previously cross-linked actin filaments. In this paper we introduce an elastic model to describe how the addition of actin filaments to the tail results in the propulsive force on the bacterium. Filament growth on the bacterial surface produces stresses that are relieved at the back of the bacterium as it moves forward. The model leads to a natural competition between growth from the sides and growth from the back of the bacterium, with different velocities and strengths for each. This competition can lead to the periodic motion observed in a Listeria mutant.

Actins↗
PubMed2000

Growing an actin gel on spherical surfaces.

Inspired by the motility of the bacteria Listeria monocytogenes, we have experimentally studied the growth of an actin gel around spherical beads grafted with ActA, a protein known to be the promoter of bacteria movement. On ActA-grafted beads F-actin is formed in a spherical manner, whereas on the bacteria a "comet-like" tail of F-actin is produced. We show experimentally that the stationary thickness of the gel depends on the radius of the beads. Moreover, the actin gel is not formed if the ActA surface density is too low. To interpret our results, we propose a theoretical model to explain how the mechanical stress (due to spherical geometry) limits the growth of the actin gel. Our model also takes into account treadmilling of actin. We deduce from our work that the force exerted by the actin gel on the bacteria is of the order of 10 pN. Finally, we estimate from our theoretical model possible conditions for developing actin comet tails.

Actins↗
PubMed2001

A convenient preparation of aldonohydroxamic acids in water and crystal structure of L-erythronohydroxamic acid.

Hydroxamic acids derived from aldonic acids, namely aldonohydroxamic acids, have become an increasingly important class of inhibitors of enzymes involved in the metabolism of carbohydrates. We now report the straightforward preparation of various types of aldonohydroxamic acids by a new methodology involving the use of commercial 50% aqueous hydroxylamine as the source of the free base hydroxylamine that reacts directly with the corresponding aldonolactone dissolved in water. The reaction proceeds almost instantaneously in water at room temperature, yielding generally pure products in quantitative yield. To date, this methodology is probably the most facile and efficient way to synthesize aldonohydroxamic acids. We also determined by X-ray diffraction analysis the first crystal structure of a free aldonohydroxamic acid reported to date. Crystals of L-erythronohydroxamic acid belonged to the monoclinic system, space group P2(1), a=5.511(3), b=7.556(1), c=8.071(3) A, beta=109.10 degrees, and Z=2.

Crystallization↗
PubMed1998

p53-independent DNA repair and cell cycle arrest in embryonic stem cells.

The role of p53 in DNA repair and cell cycle checkpoint after ultraviolet irradiation was investigated in an embryonic stem cell line homozygous for a targeted deletion of p53. Results indicate that loss of p53 does not alter the capacity of ES cells to respond to DNA damage. Wild-type and p53-deficient cells showed similar cessation of DNA synthesis after UV damage and similar ultimate capacity to repair a transiently transfected reporter plasmid. Interestingly, in the absence of DNA damaging treatment, the transit of p53-deficient cells through S phase was slower than wild-type cells. We suggest that this may result from the absence of a p53-dependent response to endogenous DNA damage: without p53 sensing endogenous damage leading to immediate repair, such damage may persist and thus delay DNA synthesis.

Animals↗
PubMed1999

Alternative exon 3 splicing of the human major protein zero gene in white blood cells and peripheral nerve tissue.

The major protein zero (MPZ) is involved in peripheral myelin folding. Using nested reverse transcription-PCR, we amplified several fragments of MPZ mRNAs in white blood cells and in peripheral nerve tissue. Cloning of PCR products revealed the existence of three alternative splicing patterns: one resulted in the complete loss of exon 3 and two others induced partial skipping of the exon 3 sequence. All three alternative splicing mechanisms produced a frame-shift and created an identical premature stop codon in exon 4. We conclude that the existence of these MPZ RNA transcript variants may be the result of deliberate splicing decisions and may have functional implications in the cell.

Actins↗
PubMed2003

Plasma lipoprotein lipase, hepatic lipase activities, VLDL, LDL compositions at different times of hemodialysis.

The effects of hemodialysis duration (HD) on lipoprotein lipase (LPL) and hepatic lipase (HL) activities and very low density lipoprotein (VLDL), low density lipoproteins (LDL) amounts and compositions were investigated in 58 patients, divided according to HD: GI: under 1 year, GII: 1-5 years, GIII: 5-13 years. HL and LPL activities were reduced in GIII versus GI (P<0.01) and 47% of GIII patients had negligible HL activity. LPL and HL activities were correlated with HD (r=-0.80, P<0.001). Apo C-III concentrations were correlated with HD (r=0.58, P<0.05). Compared with controls, triacylglycerols (TG) were increased in GI, GII (P<0.01) and GIII (P<0.001), and were correlated with HD (r=0.75, P<0.05). VLDL amounts and VLDL-cholesteryl esters (CE) were enhanced in GIII versus GI and GII (P<0.05). VLDL-TG and VLDL-phospholipids (PL) were correlated with HD (r=0.60, P<0.05). LDL-apolipoproteins and unesterified cholesterol (UC) were increased in GII versus GI (P<0.05) and in GIII versus GII and GI (P<0.01). LDL-PLs were decreased in GIII versus GI (P<0.05). Compared with controls, LDL-TGs were higher in GI and GII (P<0.01) and in GIII (P<0.05). Long-term treatment with acetate hemodialysis using cuprophane membrane does not improve lipolytic activity decrease and lipoprotein alterations generated by chronic renal failure (CRF).

Adult↗
PubMed2000

Characterization of odorant compounds of mussels (Mytilus edulis) according to their origin using gas chromatography-olfactometry and gas chromatography-mass spectrometry.

Gas chromatography-olfactometry consists of sniffing the effluent of a gas chromatograph and leads to the direct determination of potent odorants in food. GC-olfactometry and GC-MS were applied in order to identify volatile compounds, and to characterize potent odorants of cooked wild mussels and bouchot mussels. Eighty-five volatiles were identified by GC-MS, among those the majority were identified for the first time in mussels. Using GC-olfactometry, the main contributors of cooked mussels aroma were characterized. Of the 85 volatiles identified in the flavor, only 33 were odor-active and contribute to the overall aroma of mussels. Dimethyl disulfide (sulfury odor) was the odorant the most differently perceived between the two extracts and seems to be characteristic of wild mussels. Combined GC-MS and GC-olfactometry made it possible to point out odorants which actually contribute to the aroma of cooked mussels and those which showed typical dependence on the origin of mussels.

Animals↗
PubMed1975

Separation and characterization of the reduced metabolites of the 18-hydroxydeoxycorticosterone hormone by gas-liquid chromatography-mass spectrometry. Occurrence of stereoisomeric forms in rat adrenals and liver.

In order to study the metabolism of 18-OH-11-deoxycorticosterone, the mineralocorticoid hormone responsible for hypertension in rats and humans, we have synthesized the following dihydrogenated and tetrahydrogenated reference derivatives: 18,21-dihydroxy-5alpha-pregnane-3,20-dione, 18,21-dihydroxy-5beta-pregnane-3,20-dione, 3alpha,18,21-trihydroxy-5alpha-pregnan-20-one (I), 3beta,18,21-trihydroxy-5alpha-pregnan-20-one (II), 3alpha,18,21-trihydroxy-5beta-pregnan-20-one (III) and 3beta,18,21-trihydroxy-5beta-pregnan-20-one (IV). A complete separation of these compounds from each other and from tetrahydrocorticosterone isomers has been realized only by the association of thin-layer chromatography and gas-liquid chromatography on high-efficiency glass capillary columns. Characterization by gas-liquid chromatography-mas spectrometry is described. The stereoisomer distribution in rats is: adrenals of adult males and females (compounds I and II in the ratio 4:1); adrenals of 23-day-old males and females (compounds I, II and III, 11:11:3); liver of females (compound I and traces of III); and the liver of adult male (compounds II, III and IV, 4.5:4.5:1).

18-Hydroxydesoxycorticosterone↗
PubMed1994

Partial albinism with immunodeficiency (Griscelli syndrome).

Partial albinism with immunodeficiency is a rare and fatal immunologic disorder characterized by pigmentary dilution and variable cellular immunodeficiency. To define the phenotype, therapy, and outcome, we retrospectively analyzed seven consecutive patients. Primary abnormalities included a silvery-grayish sheen to the hair, large pigment agglomerations in hair shafts, and an abundance of mature melanosomes in melanocytes, with reduced pigmentation of adjacent keratinocytes. Clinical onset occurred between the ages of 4 months and 4 years and was characterized by accelerated phases (lymphohistiocytic infiltration of multiple organs, including the brain and the meninges), triggered by viral and bacterial infections. Characteristic laboratory features included pancytopenia, hypofibrinogenemia, hypertriglyceridemia, and hypoproteinemia. Consistent immunologic abnormalities were characterized by absent delayed-type cutaneous hypersensitivity and impaired natural killer cell function. Some patients had secondary hypogammaglobulinemia, impaired major histocompatibility complex-mediated cytotoxic effects, a decreased capacity of lymphocytes to trigger a mixed lymphocyte reaction, or various functional granulocytic abnormalities. The disease seems to be invariably lethal without bone marrow transplantation; the mean age at the time of death was 5 years. Bone marrow transplantation has been performed in three cases; two patients died in the immediate posttransplantation period of infectious complications, but one patient is cured after a follow-up of 5 years. We conclude that partial albinism with immunodeficiency (Griscelli syndrome) can be differentiated from Chédiak-Higashi syndrome by pathognomonic histologic features. One of the underlying immunologic defects may be a defective function of natural killer cells, predisposing the patient to virus-associated hemophagocytic syndrome or accelerated phases. The prognosis is very poor unless early bone marrow transplantation is carried out.

Adrenal Cortex Hormones↗
PubMed1997

Staphylococcal necrotizing fasciitis in the mammary region in childhood: a report of five cases.

OBJECTIVE: Necrotizing fasciitis is a highly lethal soft tissue infection rarely reported in childhood. The initiating site is usually a local trauma or a surgical wound. We observed five cases of necrotizing fasciitis the initiating site for which was the mammary region and discuss their management. STUDY DESIGN: We describe these five patients and review the clinical characteristics of their presentation. RESULTS: Staphylococcal necrotizing fasciitis was observed in the mammary region in all five cases. Four children were newborn infants with a mammitis preceding the onset of necrotizing fasciitis. Surgical débridement was done only after the fourth day from onset of illness. All children were discharged in good condition after 1 month. Two have been followed until puberty, with destruction of the mammary gland in one case and good development in the other one. CONCLUSION: Mammitis may be the initiating event for necrotizing fasciitis in neonates. Necrotizing fasciitis is a life-threatening disease; patients require early intensive care, parenteral antibiotic therapy, and surgical débridement. In a few instances surgery can be carefully delayed until the necrotic area is more delineated if the condition is diagnosed early during disease evolution and appropriate treatment is instituted in intensive care units.

Anti-Bacterial Agents↗
PubMed2001

Endoscopic treatment of urinary incontinence: long-term evaluation of the results.

PURPOSE: We report on the use of polydimethylsiloxane for endoscopic treatment of urinary incontinence in children with neurogenic bladder and discuss our results to determine optimal criteria for patient selection. MATERIALS AND METHODS: A total of 44 children (19 males) have been treated endoscopically for urinary incontinence since 1995. Etiology was spina bifida in 35 cases. Previous surgery had been performed on 24 patients, including bladder neck reconstruction with (17) or without bladder augmentation. Mean patient age at injection was 13 years (range 7 to 17). A single transurethral injection was given in 23 cases, 2 in 17 and 3 or more in 4. Mean volume at each injection was 3.5 cc and for each patient the total volume injected was 5.7 cc. Mean delay between 2 injections was 6 months (range 3 to 15). RESULTS: Followup ranged from 6 to 53 months (median 28). Of the patients 15 (34%) are dry (continent greater than 4 hours, no urinary pad during the day), 11 (25%) are improved (continent 2 to 3 hours, occasional pad) and 18 had poor results. In the entire series only gender and preoperative hyperactivity influenced the results, as the best results were achieved in females with a stable bladder (44% of girls versus 21% of boys were cured). Good results persisted at 12-month followup in patients treated with only 1 injection (until 36 months for older patients) and after the last of 2 injections. Of the patients treated with 3 or more injections 1 was dry at 12-month followup and treatment failed in 3. CONCLUSIONS: Injection of polydimethylsiloxane at the bladder neck achieved continence in 34% of neurogenic bladder cases. Results were better in girls with a stable bladder. Results deteriorated in the first 12 months of followup. No more than 3 injections are advised if a satisfactory result is not achieved.

Adolescent↗
PubMed1975

Adrenal and liver metabolites of 18-hydroxy-11-deoxycorticosterone in the rat. Identification of reduced compounds (18-OH-TH-DOC).

The presence of reduced metabolites of 18-hydroxy-11-deoxycorticosterone has been investigated in the adrenals of 23 day-old and adult rats and in the liver of adult rats. By thin-layer chromatography a fraction of the adrenal steroid extract migrating like tetrahydrocorticosterone has been isolated. By gas chromatography-mass spectrometry several isomers of 3,18,21-trihydroxy-pregnan-20-one (18-OH-TH-DOC) have been separated in this fraction and identified by comparison with authentic samples which have been chemically and enzymatically synthesized. The major tetrahydrogenated metabolite in the adult and prepuberal rat adrenals is 3beta,18,21-trihydroxy-5alpha-pregnan-20-one (18-OH-TH-DOC II). The 3alpha,18,21-trihydroxy-5beta-pregnan-20-one has been found only in the prepuberal rat adrenal. A third tetrahydrogenated isomer has been tentatively indentified as 3alpha,18,21-trihydroxy-5alpha-pregnan-20-one. Quantitative measurements by mass fragmentography show that adrenal reductase activity on 18-hydroxy-11-deoxycorticosterone is higher than on corticosterone. The 18-OH-TH-DOC II has been identified in the liver of adult male rat.

Adrenal Glands↗
PubMed2002

Abiotic behavior of entrapped petroleum products in the subsurface during leaching.

Petroleum products are generally volatile hydrocarbon mixtures. These mixtures may contaminate land surfaces, the unsaturated zone and ground waters at numerous sites and thus represent a long-term source of environmental subsurface pollution. Based on laboratory and field evidence obtained by our research groups and others we emphasize in the present review paper the effect of leaching on the abiotic processes controlling the fate of volatile petroleum hydrocarbon mixtures (VPHMs) in the soil environment. The modification of petroleum hydrocarbon mixtures due to changes in the soil water content is considered the result of a "leaching phenomenon". The experimental evidence of VPHM behavior in the porous media is linked to four major processes: retention, redistribution and attenuation in the subsurface, and dissolution in the soil water. Once VPHMs reach the soil surface, their residual concentration and composition is influenced by the amount and quality of the leaching water. The transport and natural attenuation of the VPHMs in the unsaturated zone is affected by the amount and rate of leaching. Since VPHM are a mixture of volatile and non-volatile hydrocarbons whose components differ by several orders of magnitude in their vapor pressure and water solubility, their fates in the soil environment under leaching will be diverse too. This will influence the temporal concentrations of the VPHM components and their distributions with depth, as vapors, solutes, or water-immiscible solutions. Wetting the soil before or after the VPHMs reach it, differentially affects the abiotic processes governing petroleum products behavior into the porous media.

Environmental Monitoring↗