Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new Azidothymidine derivative, di-(thymidine-3'- azido-2',3'-dideoxy-D-riboside)-5'-5'-p1-p2-pyrophosphate (AZTp2AZT), was encapsulated in human erythrocytes according to a conservative procedure of hypotonic shock-isotonic resealing and reannealing. Like in erythrocyte lysates supplemented with 1 mM ATP, intact red cells too were found to convert AZTp2AZT to 3'-Azido-3'-deoxythymidine which was then released linearly in plasma. The major metabolic pathway involved in this conversion was the symmetrical hydrolysis of AZTp2AZT to yield two 3'-Azido-3'- deoxythymidine-5'-phosphate molecules which were then dephosphorylated to 3'-Azido-3'-deoxythymidine. At late times of incubation, also a limited asymmetrical hydrolysis of AZTp2AZT became apparent in the intact erythrocytes, yielding 3'-Azido-3'-deoxythymidine-5'-diphosphate that was then converted to the triphosphorylated derivative. Therefore, erythrocytes loaded with AZTp2AZT act "in vitro" as bioreactors ensuring sustained and potentially useful release of 3'-Azido-3'-deoxythymidine.
 ...
PMID:Azidothymidine homodinucleotide-loaded erythrocytes and bioreactors for slow delivery of the antiretroviral drug azidothymidine. 860 44

The rat nucleus accumbens contains medium-sized, spiny projection neurons and intrinsic, local circuit neurons, or interneurons. Sub-classes of interneurons, revealed by calretinin (CR) or parvalbumin (PV) immunoreactivity or reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry, were compared in the nucleus accumbens core, shell and rostral pole. CR, PV and NADPH-diaphorase-containing neurons are shown to form three non-co-localising populations in these three areas. No significant differences in neuronal population densities were found between the subterritories. NADPH-diaphorase-containing neurons could be further separated morphologically into three sub-groups, but CR- and PV-immunoreactive neurons form homogeneous populations. Ultrastructurally, NADPH-diaphorase-, CR- and PV-containing neurons in the nucleus accumbens all possess nuclear indentations. These are deeper and fewer in neurons immunoreactive for PV than in CR- and NADPH-diaphorase-containing neurons. CR-immunoreactive boutons form asymmetrical and symmetrical synaptic specialisations on spines, dendrites and somata, while PV-immunoreactive boutons make only symmetrical synaptic specialisations. Both CR- and PV-immunoreactive boutons form symmetrical synaptic specialisations with medium-sized spiny neurons and contact other CR- and PV-immunoreactive somata, respectively. A novel non-carcinogenic substrate for the peroxidase reaction (Vector Slate Grey, SG) was found to be characteristically electron-dense and may be distinguishable from the diaminobenzidine reaction product. We conclude that the three markers used in this study are localised in distinct populations of nucleus accumbens interneurons. Our studies of their synaptic connections contribute to an increased understanding of the intrinsic circuitry of this area.
 ...
PMID:A light and electron microscopic study of NADPH-diaphorase-, calretinin- and parvalbumin-containing neurons in the rat nucleus accumbens. 870 62

The reason for a post and core preparation is to provide an anchoring system for a final restoration to the tooth root. This experiment was divided into two groups with the following systems; ExactaCast and Parapost. Casts for these systems were fabricated in photoelastic plastic and cemented with zinc phosphate cement. These photoelastic blocks were placed in a special jig on a universal testing machine. The experiment compared the photoelastic stresses generated for these two systems in two different stress modes; vertically at 30 pounds and obliquely (at a 26 degree angle) at 20 and 30 pounds. Specimens were then photographed after cementation in the unloaded and loaded states. Minimal stresses were observed for the ExactaCast in the unloaded state, while symmetric, even patterns of stresses concentrated coronally were present in the loaded vertical and oblique states. Minimal stresses were observed for the Parapost in the unloaded state, while asymmetric, uneven patterns of stresses concentrated apically were present in the loaded vertical and oblique states. The presence of the multiple tiered system for the Exacta-Cast clearly directs stresses in a symmetric pattern, while the single tiered Parapost system directs stresses in asymmetrical pattern. The symmetric even stresses for the ExactaCast are more favorable than the asymmetric, uneven stresses for the Parapost.
 ...
PMID:Comparison of the photoelastic stress properties for two combination prefabricated cast post systems. 877 35

Dinucleoside 5',5"'-P1,P4-tetraphosphate hydrolase (EC 3.6.1.17) has been purified to homogeneity from tomato (Lycopersicon esculentum) cells grown in suspension. The purification procedure comprised ammonium sulphate fractionation following five standard chromatography steps and a final chromatography on Ap4A-Sepharose. The homogeneous hydrolase has a molecular mass of 20 kDa and an isoelectric point of 4.5. The enzyme hydrolyses diadenosine tetraphosphate (Ap4A) asymmetrically to AMP and ATP. Among other naturally occurring dinucleoside oligophosphates, Ap5A and Ap6A are substrates whereas Ap3A is not. Of various phosphonate analogues tested, the Ap5A analogue, AppCH2pCH2ppA, was not cleaved and the Ap3A analogue, ApCH2CH2ppA, was a very poor substrate. Enzyme activity is stimulated by 5 mM Mg2+ and inhibited by fluoride anion; I50 = 6.25 microM. The K(m) value for Ap4A is 0.8 microM. The enzyme exhibits a broad pH optimum from pH 6.5 to 9.0. In order to analyze the protein at the molecular level an internal peptide sequence from the homogeneous enzyme was identified. Within the sequence of 17 amino acids a kinase II motif as a general part of a conserved sequence of nucleotide binding sites was found. Against the internal peptide sequence a polyclonal antiserum was raised. By investigating the intracellular level of Ap4A hydrolase under different kinds of environmental stress, no changes occurred in response to heat shock. But, heavy metal stress and phosphate deprivation lead to a decrease in Ap4A hydrolase.
 ...
PMID:Diadenosine 5',5"'-P1,P4-tetraphosphate (Ap4A) hydrolase from tomato (Lycopersicon esculentum cv. Lukullus)--purification, biochemical properties and behaviour during stress. 881 90

PI-SceI, a double-stranded DNA endonuclease from Saccharomyces cerevisiae, is generated by protein splicing of an intein, which is an internal polypeptide within a larger precursor protein. The enzyme initiates the mobility of the intein by cleaving at inteinless alleles of the VMA1 gene. Genetic and biochemical studies reveal that the enzyme makes numerous base-specific and phosphate backbone contacts with its 31 bp asymmetrical recognition site. This site can be divided into two regions, both of which contain nucleotides that are essential for cleavage by PI-SceI. Region I contains the PI-SceI cleavage site while Region II includes an adjacent sequence that covers two helical turns. Mutational, interference and DNA mobility shift analyses demonstrate that Region II is sufficient for high-affinity PI-SceI binding. Within this region, PI-SceI uses primarily phosphate backbone and some major groove interactions to contact the DNA, while within Region I, protein binding involves predominantly major groove interactions that overlap and lie proximal to the cleavage site. Interestingly, DNA binding by PI-SceI induces DNA conformational changes within Region II that are entirely exclusive of Region I sequences. Furthermore, additional distortion occurs when PI-SceI binds to Region I in conjunction with Region II. The importance of this latter distortion in the cleavage pathway is underscored by substrate mutations at or near the cleavage site that reduce or eliminate both Region I DNA bending and substrate cleavage. Based on these findings, we propose a model in which sequence-specific contacts made by PI-SceI contribute to its localization to the cleavage site and to its stabilization of a DNA conformation that is required for catalysis. Finally, we discuss how the recognition characteristics of PI-SceI may have allowed the evolution of other endonucleases with altered, but similar, specificities.
 ...
PMID:Substrate recognition and induced DNA distortion by the PI-SceI endonuclease, an enzyme generated by protein splicing. 891 99

The aim of this study was to evaluate the friction during double-sided tablet compression. Dicalcium phosphate dihydrate and lactose were tabletted with a compaction simulator with symmetrical and asymmetrical double-sided sawtooth punch displacement profiles. The estimation of force transmission in a powder column was based on an exponential equation, including the material parameter consisting of both the friction coefficient and Poisson's ratio. This parameter was predetermined from a single-sided compression. A novel equation was derived from a previously presented equation for friction work in single-sided tablet compression. The basic assumption was drawn from the linearly decreasing movement of infinitely thin particle layers, which are produced as the compressing punch surface approaches the other punch. This calculation was also based on the assumption that the equilibrium point, where the particles do not move, is halfway between the punches in the symmetrical profile and at a distance proportional to the amplitudes of the asymmetrical upper and lower sawtooth profiles. The tensile strength of tablets compressed with single-double-sided profiles was identical, and thus the behavior of the materials studied under compression was independent of the compression profiles. The friction work values that were calculated with the proposed expression for double-sided profiles were close to the theoretical values, as estimated by calculations based on compressions with single-sided profiles. In conclusion, the novel mathematical expression opens new possibilities for the evaluation of friction in double-sided compression; for example, in rotary press tabletting.
 ...
PMID:Frictional work in double-sided tablet compression. 910 53

The present study investigated the ultrastructure of neurons in the caudal spinal trigeminal nucleus. These neurons which are believed to function as interneurons in the transmission of orofacial nonreflexive nociceptive information, measured 20 microns x 11 microns, and were nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) positive. The reaction product, formazan, was localized in the nuclear envelope, mitochondria, rough endoplasmic reticulum, and multivesicular bodies of these neurons. It was also localized in the membrane of the smooth endoplasmic reticulum at the axon terminal. The neurons were contacted by both axosomatic and axodendritic synapses formed by both NADPH-d positive and NADPH-d negative axon terminals. Two types of NADPH-d positive axon terminals could be recognized. The first was a large terminal containing many stained mitochondria and unstained small round agranular vesicles mixed with some slightly flattened ones. It formed asymmetrical axodendritic synapse. The second type of axon terminals contained pleomorphic synaptic vesicles and formed asymmetrical synapses upon both dendrites and soma. The sources of NADPH-d positive axon terminals were discussed. Most of the unstained axon terminals forming axosomatic and axodendritic synapses with stained cell bodies and dendrites contained flattened vesicles. In addition to the above, complicated synaptic configurations showing NADPH-d positive axoaxonic synapses in relation to NADPH-d negative dendritic spines were also seen in which a NADPH-d negative dendritic spine was completely contacted by a NADPH-d positive bouton which was in turn contacted by another NADPH-d positive bouton.
 ...
PMID:Ultrastructural study of NADPH-d positive neurons in laminae I and II of the rat caudal spinal trigeminal nucleus. 939 13

Neurons in the rat subiculum that are capable of producing nitric oxide were studied by using an antibody to the neuronal isoform of nitric oxide synthase (nNOS). In the light microscope, the staining pattern with the nNOS antibody closely resembled that seen following histochemical processing with nicotinamide adenine dinucleotide phosphate diaphorase. Immunostained neurons were found in all layers, and, in addition, large dendrites in the apical dendrite layer were also immunopositive. Although a few immunolabelled cells had the typical morphology of interneurons, most were found to have the characteristics of pyramidal neurons. In the subiculum, these immunoreactive pyramidal neurons were concentrated mainly in the most superficial cell layers and closest to the CA1 region, but pyramidal neurons in the CA1 layer of the hippocampus were consistently immunonegative. Immunopositive profiles in the subiculum were studied in the electron microscope and compared with unlabelled structures. Ultrastructural criteria suggest that both pyramidal and nonpyramidal subicular neurons are immunopositive for nNOS. Large, spiny dendrites and smaller, varicose dendrites were found to be immunoreactive for nNOS. Vesicle-containing profiles were probably presynaptic axons, and immunopositive boutons were seen to make symmetrical and asymmetrical synaptic contacts.
 ...
PMID:Light and electron microscopic study of neuronal nitric oxide synthase-immunoreactive neurons in the rat subiculum. 960 72

In the adult frog, structural asymmetry of the left dorsal habenula in respect to the right counterpart has been repeatedly documented in previous studies. In the present investigation, histochemical expression of beta-nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity was examined in the habenulae of the developing and adult Rana esculenta. In tadpoles and during metamorphosis, selective neuropil staining was consistently found within a lateral compartment of the medial subnucleus of the left dorsal habenula. The staining was still present in the same location, but much less intense, in the mature frog, indicating that the neurochemical pattern observed during development was at least in part transient. Thus, the present data point out a peculiar neurochemical pattern of the habenular asymmetry in the frog, suggesting that nitric oxide may be involved in the developmental shaping which leads to an asymmetrical configuration of the habenulae. In addition, NADPH-diaphorase-positive cells were detected in the frontal organ (the extracranial component of the pineal complex in strict relationship with the habenulae in the frog), and labeled fibers were found in the frontal nerve, which arises from the frontal organ. This latter finding supports the postulated relationship of the habenular asymmetry with the occurrence of the frontal organ. The finding of NADPH-diaphorase histochemical reactivity confined to a distinct portion of the medial subnucleus of the left dorsal habenula prompted a reexamination of the cytoarchitecture of the developing and mature habenular complex in the frog. The bicompartmentalization detected with histochemistry in the medial subnucleus of the left dorsal habenula of the developing and adult frog was fully supported by the study of Nissl-stained epithalamic sections. These data point out that the left-right structural differences of the frog habenular complex are more complex than previously believed, and may be subserved by chemically regulated developmental processes.
 ...
PMID:Nitric oxide synthase activity reveals an asymmetrical organization of the frog habenulae during development: A histochemical and cytoarchitectonic study from tadpoles to the mature Rana esculenta, with notes on the pineal complex. 1041 78

The secretion of milk depends on the activity of a large number of membrane transport systems located on the apical and basolateral membranes of mammary secretory cells. It follows that a thorough knowledge of individual mammary tissue membrane transport systems is required if we are to fully understand the process of milk secretion. The distribution of the transporters between the apical and basolateral poles of the mammary epithelium must be asymmetrical given that the mammary gland is capable of vectorial transport. This is particularly evident in the case of glucose and amino acid transport systems: the transport mechanisms for these compounds are predominantly situated in the blood-facing aspect of the secretory cells. In addition. it is apparent that there is a polarized distribution of transport systems (carriers and channels) which accept sodium, potassium, chloride, phosphate, and calcium as substrates.
 ...
PMID:Mammary gland membrane transport systems. 1081 12


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>