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PubMed2005

Photochemistry of pyrrole: time-dependent quantum wave-packet description of the dynamics at the 1pi sigma*-S0 conical intersections.

The photoinduced hydrogen-elimination reaction in pyrrole via the conical intersections of the two (1)pi sigma(*) excited states with the electronic ground states [(1)B(1)(pi sigma(*))-S(0) and (1)A(2)(pi sigma(*))-S(0)] have been investigated by time-dependent quantum wave-packet calculations. Model potential-energy surfaces of reduced dimensionality have been constructed on the basis of accurate multireference ab initio electronic-structure calculations. For the (1)B(1)-S(0) conical intersection, the model includes the NH stretching coordinate as the tuning mode and the hydrogen out-of-plane bending coordinate as the coupling mode. For the (1)A(2)-S(0) conical intersection, the NH stretching coordinate and the screwing coordinate of the ring hydrogens are taken into account. The latter is the dominant coupling mode of this conical intersection. The electronic population-transfer processes at the conical intersections, the branching ratio between the dissociation channels, and their dependence on the initial preparation of the system have been investigated for pyrrole and deuterated pyrrole. It is shown that the excitation of the NH stretching mode strongly enhances the reaction rate, while the excitation of the coupling mode influences the branching ratio of different dissociation channels. The results suggest that laser control of the photodissociation of pyrrole via mode-specific vibrational excitation should be possible. The calculations provide insight into the microscopic details of ultrafast internal-conversion processes in pyrrole via hydrogen-detachment processes, which are aborted at the (1)pi sigma(*)-S(0) conical intersections. These mechanisms are of relevance for the photostability of the building blocks of life (e.g., the DNA bases).

Journal Article↗
PubMed1984

The early development of mystacial vibrissae in the mouse.

The initial generation of the pattern of mystacial vibrissae (whiskers) in the mouse is described. The maxillary process is present in 10-day embryos but has a relatively flat surface. Beginning at approximately 11.5 days, the first sign of vibrissal development is the formation of ridges and grooves on the maxillary and lateral nasal processes. The first vibrissal rudiment to form subsequently appears posterior to the most ventral groove on the maxillary process. It is the most ventral whisker of the posterior, vertical row. The next few rudiments appear: dorsal to the first, also in the vertical row; and anterior to the first, on the ventral-most ridge and in the groove beneath it. Formation of vibrissal rudiments continues in a dorsal and anterior progression usually by an apparent partitioning of the ridges into vibrissal units. The hypothesis that this patterning of mystacial vibrissae might be determined by the pattern of innervation in the early mouse snout was investigated. Nerve trunks and branches are present in the maxillary process well before any sign of vibrissal formation. Because innervation is so widespread there appears to be no immediate temporal correlation between the outgrowth of a nerve branch to a site and the generation of a vibrissa there. Furthermore, at the time just prior to the formation of the first follicle rudiment, there is little or no nerve branching to the presumptive site of that first follicle while branches are found more dorsally where vibrissae will not form until later. Thus, a one-to-one spatial correlation between nerve and follicle sites also appears to be lacking. The developmental changes in ultrastructure within the neurites of the trunks and branches as well as the apparent rearrangements of the nerve trunks suggest that early innervation of the snout is a labile phenomenon and that the vibrissal pattern begins to be established before the neural pattern is completely developed. The results indicate that vibrissal pattern formation is likely to be a complex process relying on the interplay of the cells and tissues involved, rather than on unidirectional instructions from neurons to other cell types.

Animals↗
PubMed1999

Origin and incidence of xiphoid branch of the internal thoracic artery.

The study presents the incidence of a variant terminal branch of the internal thoracic artery (ITA). The ITA's were cannulated in situ, injected with coloured latex and dissected together with its branches in 62 cadavers. Unlike the usual termination of the ITA bifurcating into the musculophrenic and superior epigastric arteries, this third branch arose from the medial border of the ITA at the level of the 6th costal cartilage. As it descends it inclines medially towards the angle between the xiphoid process and the 7th costal cartilage, giving off 2 or 3 fine branches to the lower sternum. It then passes deep to this angle and can be observed on the anterior surface of the xiphoid process, terminating in fine branches distributed to the inferior aspect of the xiphoid cartilage. It is proposed that this branch at the "trifurcation" of the ITA be termed the xiphoid branch. This branch was noted in 61.3%. An incidence of 30.7% was seen on the right and 21% on the left with bilateral presence in 9.7%. The xiphoid branch contributes to the supply to the lower sternal region and may be of special importance when the collateral supply to the region is compromised in the event of the internal thoracic or superior epigastric artery damage or when used as a conduit in coronary artery by-pass grafts.

Adult↗
PubMed2005

Mass spectral fragmentation of the intravenous anesthetic propofol and structurally related phenols.

Propofol (2,6-diisopropyl phenol) is a widely used intravenous anesthetic. To define its pharmacokinetics and pharmacodynamics, methods for its quantitation in biological matrixes have been developed, but its pattern of mass spectral fragmentation is unknown. We found that fragmentation of the [M - H](-) ion (m/z 177) of propofol in both APCI MS/MS and ESI MS/MS involves the stepwise loss of a methyl radical and a hydrogen radical from one isopropyl side chain to give the most intense product ion, [M -H - CH(4)](-), at m/z 161. This two-step process is also the preferred mode of fragmentation for similar branched alkyl substituted phenols. This mode of fragmentation of the [M - H](-) ion is supported by three independent lines of evidence: (1) the presence of the intermediary [M - H - CH(3)](-) radical ion under conditions of reduced collision energy, (2) the determination of the mass of the predominant [M - H - CH(4)](-) product ion by high resolution mass spectrometry, and (3) the pattern of product ions resulting from further fragmentation of the [M - H - CH(4)](-) product ion. Phenols with a single straight chain alkyl substituent, in contrast, undergo beta elimination of the alkyl radical irrespective of the length of the alkyl chain, yielding the most intense product ion at m/z 106. This product ion represents a special case of a stable intermediary radical for the two-step process described for branched side chains, because further elimination of a hydrogen radical from the beta carbon is not possible.

Anesthetics, Intravenous↗
PubMed1993

[Two cases of congenital defects within the transverse processes of the lumbar spine].

Two cases of congenital defects of transverse processes of lumbar spine causing lumbalgia are described. The first one was produced by direct contact of the elongated processes with subsequent pseudoarthrosis. Hypertrophied processes caused stenosis around intervertebral foramen and irritated posterior neural branch in the second case. Surgical resection of the hypertrophied transverse processes has brought the cure.

Adolescent↗
PubMed2001

Biosynthesis and function of beta 1,6 branched mucin-type glycans.

The contribution of carbohydrate structure to biomolecular, cellular, and organismal function is well-established, but has not yet received the attention it deserves, perhaps due to the complexity of the structures involved and to a lack of simple experimental methods for relating structure and function. In particular, beta1,6 GlcNAc branching plays a key functional role in processes ranging from inflammation and immune system function to tumor cell metastasis. For instance, synthesis of the core 2 beta1,6 branched structure in the mucin glycan chain by C2GnT enables the expression of functional structures at the termini of polylactosamine chains, such as blood group antigens and sialyl Lewis x. Also, IGnT can create multiple branches on the polylactosamine chain, which may serve as a mechanism for amplifying the functional potency of cell surface glycoproteins and glycolipids. The family of enzymes which creates beta1,6 branched structure in mucin glycans is proving to be quite complex, since multiple isoforms appear to exist for these enzymes, and some of the enzymes are adept at forming more than one type of beta1,6 branched structure, as in the case of C2GnT-M. Furthermore, the enzymes do not appear to be restricted to acting on mucin-type acceptor structures, but are able to act on glycolipid structures as well. Much remains to be learned regarding the specific biological niche filled by each of these enzymes and how their activities complement one another, as well as the manner in which the activities of these enzymes are regulated in the cell.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1992

Zinc iodide-osmium tetroxide impregnation of the "tubulo-vesicular system" in Tomes' process of the rat incisor ameloblast.

Zinc iodide-osmium tetroxide (ZIO) is a nonspecific but selective impregnation method that visualizes a tubulo-vesicular system in cells. The detailed structure and three-dimensional distribution of this ZIO-impregnated system was studied in the Tomes' process of secretory ameloblasts in the rat incisor. The ZIO-impregnated system consisted of an extensive array of smooth membrane-bound thick and thin tubules and vesicles. The interconnected thick and thin tubules formed a complex "core network" in the central cytoplasm of Tomes' process that enmeshed and often surrounded individual secretory granules. From the core network, radial branches extended toward the smooth cell membrane of the interdigitating portion of Tomes' process. Although the core network and branches frequently appeared connected to the secretory granules and the cell membrane, stereo-pair electron microscopy failed to show conclusive evidence of such continuity. However, many coated vesiclelike structures were attached to the core network and its branches. No special relationship was found between interrod and rod secretory sites and the tubulo-vesicular network. In thick sections, the ZIO-impregnated tubulo-vesicular network occupied a considerable volume of cytoplasm. The vinblastine-labile nature of this network as demonstrated previously (Nanci et al., 1987) indicated that the system undergoes rapid and extensive turnover. Considering the dynamic nature and sheer volume of the tubulo-vesicular system, we propose that it be regarded as a major cell organelle.

Ameloblasts↗
PubMed2007

Tailoring porous silica films through supercritical carbon dioxide processing of fluorinated surfactant templates.

The tailoring of porous silica thin films synthesized using perfluoroalkylpyridinium chloride surfactants as templating agents is achieved as a function of carbon dioxide processing conditions and surfactant tail length and branching. Well-ordered films with 2D hexagonal close-packed pore structure are obtained from sol-gel synthesis using the following cationic fluorinated surfactants as templates: 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoro-octyl)pyridinium chloride (HFOPC), 1-(3,3,4,4,5,5,6,6,7,8,8,8-dodecafluoro-7-trifluoromethyl -octyl)pyridinium chloride (HFDoMePC), and 1-(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluoro-decyl)pyridinium chloride (HFDePC). Processing the sol-gel film with CO2 (69-172 bar, 25 and 45 degrees C) immediately after coating results in significant increases in pore diameter relative to the unprocessed thin films (increasing from 20% to 80% depending on surfactant template and processing conditions). Pore expansion increases with CO2 processing pressure, surfactant tail length, and surfactant branching. The varying degree of CO2 induced expansion is attributed to the solvation of the "CO2-philic" fluorinated tail and is interpreted from interfacial behavior of HFOPC, HFDoMePC, and HFDePC at the CO2-water interface.

Carbon Dioxide↗
PubMed2006

[alpha-Oxidation of 3-methyl-branched fatty acids: unraveling of a pathway].

Peroxisomes have an important role in lipid metabolism e.g. beta-oxidation of long and very long chain fatty acids, 2-methyl-branched fatty acids, dicarboxylic fatty acids, prostanoids and bile acid intermediates, and synthesis of ether lipids. Also the process of alpha-oxidation of 3-methyl-branched fatty acids, with phytanic acid (3,7,11,15-tetramethylhexadecanoic acid) as the best known example, occurs in peroxisomes. alpha-Oxidation is a process in which fatty acids are shortened by one carbon atom. The alpha-oxidation sequence of 3-methyl-branched fatty acids starts with an activation to the corresponding CoA-ester. Subsequently this acyl-CoA-ester undergoes a 2-hydroxylation by the peroxisomal phytanoyl-CoA hydroxylase (PAHX). In a third step the peroxisomal 2-hydroxyphytanoyl-CoA lyase (2-HPCL) splits the carbon carbon bond of the 2-hydroxy-intermediate into a 2-methyl(n-1)aldehyde and formyl-CoA, which is subsequently converted to formate and CO2. Finally the aldehyde is dehydrogenated by an aldehyde dehydrogenase to the corresponding acid, which, after its conversion to the acyl-CoA ester, can be a substrate for beta-oxidation. 2-HPCL is the first thiamine pyrophosphate dependent peroxisomal enzyme in mammals. Apart from 2-hydroxy-3-methylacyl-CoAs also 2-hydroxyacyl-CoAs are substrates for this enzyme. This indicates that the 2-hydroxy function but not the 3-methyl function of acyl-CoA esters is needed for 2-HPCL-activity. Long and very long chain 2-hydroxy fatty acids are constituents of brain cerebrosides and sulfatides, which mainly occur in myelin.

Acyl Coenzyme A↗
PubMed1988

Branches of the hepatic artery in red fox.

In 30 red foxes (Vulpes vulpes) the origin, course and division of the branches of the hepatic artery were studied. The hepatic artery gave off 3 following branches: right lateral branch, right medial branch and left one. Most often (60% of cases) they arose as a common trunk. In 60% cases the right lateral branch supplied the right lateral hepatic lobe and caudate process of the liver while in 40% cases it supplied the right lateral hepatic lobe, only. Most often (66.7% of cases), the right medial branch supplied the right medial hepatic lobe and gall bladder. In 30% of cases the branch supplied furthermore the quadrate lobe of the liver and in few cases (3.3%) the both, right medial hepatic lobe and quadrate lobe. Rami of the left branch penetrate the left hepatic lobes, papillary process and quadrate lobe (73.3% of cases) and rarely, the left hepatic lobes and papillary process (26.7% of cases).

Animals↗
PubMed2003

A Neurexin-related protein, BAM-2, terminates axonal branches in C. elegans.

Neuronal axons connect to multiple target cells through the formation of collateral branches, but the mechanisms that regulate this process are largely unknown. We show that BAM-2, a neurexin-related transmembrane protein, is required for development of VC motoneuron branches in the worm Caenorhabditis elegans. Expression analysis and ectopic expression experiments suggest that BAM-2 functions as a branch termination cue and reveal a mechanism for selective control of branches that sprout off a primary axon.

Amino Acid Sequence↗
PubMedDate not supplied

Superior mesenteric artery branch aneurysm with absence of the celiac trunk.

Superior mesenteric artery and pancreaticoduodenal artery aneurysms are rare. Agenesis of the celiac axis has only been reported four times. The reported etiologies of superior mesenteric artery and branch artery aneurysms include infection, atherosclerosis, inflammatory processes such as pancreatitis, dissection, collagen vascular disorders, polyarteritis nodosa, and trauma. We report an aneurysm of the superior mesenteric artery (SMA) branch, the inferior pancreaticoduodenal artery, arising in a patient with congenital absence of the celiac trunk. The patient presented with intermittent left upper quadrant pain without weight loss or change in bowel habits. The aneurysm was identified on abdominal computed tomography scan with angiographic confirmation of the aberrant anatomy. The patient was treated by aneurysmectomy and pancreaticoduodenal artery reconstruction with an interposition vein graft from the SMA. The patient recovered without complications and is asymptomatic with a patent vein graft 2 years after operation.

Aneurysm↗
PubMed1985

Cryptic branch point activation allows accurate in vitro splicing of human beta-globin intron mutants.

The excised introns of pre-mRNAs and intron-containing splicing intermediates are in a lariat configuration in which the 5' end of the intron is linked by a 2'-5' phosphodiester bond (RNA branch) to a single adenosine residue near the 3' end of the intron. To determine the role of the specific sequence surrounding the RNA branch, we have mutated the branch point sequence of the human beta-globin IVS1. Pre-mRNAs lacking the authentic branch point sequence are accurately spliced in vitro; processing of the mutant pre-mRNAs generates RNA lariats due to the activation of cryptic branch points within IVS1. The cryptic branch points always occur at adenosine residues, but the sequences surrounding the branched nucleotide vary. Regardless of the type of mutation or the sequences remaining within IVS1, the cryptic branch points are 22 to 37 nucleotides upstream of the 3' splice site. These results suggest that RNA branch point selection is primarily based on a mechanism that measures the distance from the 3' splice site.

Adenosine↗
PubMed2004

RuvAB-directed branch migration of individual Holliday junctions is impeded by sequence heterology.

The Holliday junction, the key intermediate of recombination, is generated by strand exchange resulting in a covalent connection between two recombining DNA molecules. Translocation of a Holliday junction along DNA, or branch migration, progressively exchanges one DNA strand for another and determines the amount of information that is transferred between two recombining partners. In Escherichia coli, the RuvAB protein complex promotes rapid and unidirectional branch migration of Holliday junctions. We have studied translocation of Holliday junctions using a quantitative biochemical system together with a 'single-molecule' branch migration assay. We demonstrate that RuvAB translocates the junctions through identical DNA sequences in a processive manner with a broad distribution of individual branch migration rates. However, when the complex encounters short heterologous sequences, translocation of the Holliday junctions is impeded. We conclude that translocation of the junctions through a sequence heterology occurs with a probability of bypass being determined both by the length of the heterologous region and the lifetime of the stalled RuvAB complex.

Bacterial Proteins↗
PubMed1983

The catalytic mechanism of tryptophan synthase from Escherichia coli. Kinetics of the reaction of indole with the enzyme--L-serine complexes.

The mechanism by which indole condenses with L-serine in the active site of tryptophan synthase was studied by the stopped-flow technique. The single turnover occurs by rapid binding of indole to the pre-formed enzyme--L-serine complex, followed by C--C bond formation, reprotonation of the alpha carbon carbanion of L-tryptophan, and its final release. The effects of isotopic substitution at C-3 of indole, of pH, and of the presence of indolepropanol phosphate on these processes were also studied. The mechanism of binding of indole complements the known mechanisms of binding of L-serine and L-tryptophan to give a detailed picture of the mechanism of catalysis. It invokes two competent species of enzyme--L-serine complexes, leading to a branched pathway for the central condensation process. The rates of dehydration of L-serine and reprotonation of the carbanion of L-tryptophan are probably limited by rearrangements at the active site. Analysis of absorption, fluorescence and circular dichroic spectra, as well as of published data on the stereoisomers obtained by reduction with borohydride, suggests that the rearrangement includes a reorientation of the pyridoxal phosphate C-4' atom. The mechanism provides a detailed framework for explaining all available information, including the activating effect of the alpha subunit on the reaction catalyzed by the beta 2 subunit.

Catalysis↗
PubMed1984

Biosynthesis of blood group I antigens. Identification of a UDP-GlcNAc:GlcNAc beta 1-3Gal(-R) beta 1-6(GlcNAc to Gal) N-acetylglucosaminyltransferase in hog gastric mucosa.

A beta 1-6N-acetylglucosaminyltransferase has been identified in microsomal preparations from hog gastric mucosa which is able to synthesize branch points in branched lactosaminoglycans (blood group I antigenic structures). The enzyme can be assayed specifically using the synthetic trisaccharide GlcNAc beta 1-3Gal beta 1-4Glc beta-OMe as acceptor. The product of the transferase reaction was isolated and identified by methylation analysis as, (Formula: see text) Into this tetrasaccharide two galactose residues were incorporated by the specific beta-N-acetylglucosaminide beta 1-4-galactosyltransferase from bovine milk. Thus a hexasaccharide was formed which was shown to inhibit strongly a murine monoclonal and a human anti-I antibody. Using a variety of oligosaccharides and glycolipids, which correspond to structures found in linear lactosaminoglycan chains, the acceptor substrate specificity of the branching enzyme was determined. From these results it is concluded that branching occurs only during the elongation process at the nonreducing end and follows a well-defined order. N-Acetylglucosamine is first transferred to position 3 of a terminal galactose followed immediately by the addition of a second N-acetylglucosamine to position 6; only then the 1-3 and the 1-6 branches are further elongated by galactose residues.

Animals↗
PubMed1997

Striatal target-induced axonal branching of dopaminergic mesencephalic neurons in culture via diffusible factors.

The effects of striatal target cells on the morphological development of dopaminergic neurons were studied in dissociated cultures of embryonic rat mesencephalon. Mesencephalic neurons were cultured for four days in presence of target striatal cells or non target cerebellar ones. The outgrowth of dopaminergic neurons, visualized after tyrosine hydroxylase immunohistochemistry, was examined by quantitative morphometry. In cocultures, the increased complexity of dopaminergic neurites (branching) was the most striking pattern. It was dependent on the presence of target striatal cells as compared to non target ones. Cultures raised in presence or absence of serum lead to suggest the implication of striatal neurons rather than glia. Using MAP2 and phosphorylated neurofilaments immunohistochemistry in combination with tyrosine hydroxylase immunolabelling, it could be shown that the target-induced branching effect concerned only axonal and not dendritic processes. To further define whether diffusible factors from the striatal target would participate in the axonal branching effect, mesencephalic cells were cultured in conditioned medium from striatal neurons. Striatal conditioned medium enhanced dopamine uptake and dopamine neuron branching to the same extent as that observed in striatal cocultures. These findings demonstrate that soluble factors secreted by striatal neurons themselves selectively influence the branching of dopaminergic axons in vitro.

Animals↗