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Query: UMLS:C0344329 (collapse)
 28,634 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Comparative in vivo absorption of cyanocobalamin from two dosage forms, gelatin capsule and liquid, was studied. Forty-two subjects received simultaneous doses of cyanocobalamin in capsule and liquid form, labeled with cobalt-57 and cobalt-60, respectively. Excretion, a measure of absorption, was between 2 percent and 66 percent greater with the liquid form. In vitro dissolution studies showed that the capsules had a tendency to collapse into a stringy mass and to dissolve slowly.
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PMID:Comparison of the bioavailability of cyanocobalamin from capsule and liquid dosage forms. 119 Feb 17

When the growth cone of a chick dorsal root ganglion (DRG) neurite contacts the neurite of a chick retinal ganglion cell in vitro, the growth cone typically responds by withdrawing its lamellipodia and filopodia and collapsing. We have used the fluorescent calcium indicator dye fura-2 and digital imaging microscopy to measure calcium levels within DRG growth cones and to determine whether changes in calcium levels are responsible for the collapse of growth cone morphology when a DRG growth cone contacts a retinal ganglion cell neurite. Calcium levels within DRG growth cones were stable during neurite outgrowth. Calcium was typically distributed homogeneously throughout the growth cone, though occasionally gradients of free calcium were present. When calcium gradients were observed, calcium levels appeared higher in the active veil regions than in the central core region. Calcium levels in DRG growth cones appeared to remain stable during the period of contact-mediated growth cone collapse. Low concentrations of the calcium ionophore ionomycin increased calcium levels two- to threefold without having any observable morphological effects on DRG growth cones. Likewise, depolarization with 15 mM KCl caused a transient two- to threefold increase in calcium levels without having any observable morphological effect. These results suggest that changes in calcium levels are not responsible for contact-mediated collapse of growth cone structure. A growth cone collapsing activity has been solubilized from embryonic chick brain (Raper and Kapfhammer, 1990). Application of this material to cultures of DRG neurons caused growth cones to collapse but had no effect on calcium levels within the growth cones. The crude growth cone collapsing activity was not blocked by the presence of cobalt, nickel, lanthanum, nifedipine, or reduced-calcium medium, suggesting that transmembrane calcium fluxes were not required for growth cone collapse. These results suggest that the morphological changes associated with the collapse of growth cone structure can be independent of changes in growth cone calcium levels, and that second messengers other than calcium are likely to be involved in the regulation of many growth cone behaviors.
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PMID:Intracellular calcium levels do not change during contact-mediated collapse of chick DRG growth cone structure. 204 78

Compression isotherms of astaxanthin (AX; 3,3'-dihydroxy-4,4'-dioxo-beta-carotene) monolayers, recorded at the air/water interface show, on the one hand, the collapse pressure to depend on the subphase pH, indicating the ionisation of AX at high pH values, and on the other hand, the subphase Co2+ ions to have a condensing effect upon the monolayer and to entail the increase of its collapse pressure. The latter effects are assigned to surface complex formation. The interfacial tension at the benzene/water interface (the benzene phase containing AX, the water phase Co2+ ions) exhibit a maximum at a molar ratio AX: Co of about 3.6, pleading for the formation of relatively stable Co(AX)4 type interfacial complex. Geometric model and ligand field considerations show besides the dative type sigma-bond formation, the possibility of both dative and retrodative type pi-bond formation between Co2+ and the AX ligands. Under the working conditions used, the formation of a neutral non-electrolyte type complex of the composition [Co(LH)2L2] is postulated, where LH stands for the neutral AX molecule, L- for its anion.
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PMID:Surface complexes of xanthophyll films with transition metal ions. 251 60

Authors report one case of intravertebral vacuum phenomenon associated with a multiple myeloma. Initially, there occurred a collapse and a lysis of the L4 vertebral body. Two months later, after chemotherapy and cobalt-therapy, X-ray examination showed a vacuum cleft phenomenon within the body of L4 and a backward displacement of the L4 posterior wall. At the same time the patient complained of a cruralgia. Recovery occurred after decompression surgery. Histologic sampling of the L4 vertebral body revealed bone necrosis without any abnormal plasmocytosis. Authors draw attention to the neurological complications occurring in the course of the vertebral necrosis and to the fact that, even in case of multiple myeloma, the occurrence of a transverse vacuum cleft may result from osteonecrosis.
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PMID:Intravertebral vacuum phenomenon in multiple myeloma. 344 11

DNA molecules collapse into compact structures in the presence of multivalent cations. To probe the possible importance of supercoiling and conformational effects, pUC18 plasmids (2686 bp) were modified by inserting 12-bp and 20-bp alternating d(CG)n sequences, which are capable of converting to a left-handed Z-conformation under appropriate conditions, into the polycloning region. Condensation was induced by rapid addition of hexaammine cobalt(III) [Co(NH3)6(3+)] and monitored by laser light scattering and electron microscopy. Light scattering shows that plasmids with longer d(CG)n inserts condense more extensively at natural superhelical densities. Electron microscopy indicates that the morphological distribution of condensed d(CG)n-containing plasmids changes as a function of Co(NH3)6(3+) concentration. At lower Co(NH3)6(3+) concentration, the proportion of rods is higher, and at higher Co-(NH3)6(3+) concentration, most of the condensates have the form of toroids. In addition, the inner radii of the toroids are much smaller relative to condensed pUC18 under the same conditions. Enzymatic analysis and chemical probing show that the d(CG)n inserts in naturally supercoiled plasmids have extensively converted from B-form to Z-form in the presence of Co(NH3)6(3+) at the upper range of concentrations under which condensation occurs. To determine whether the enhanced condensation of d(CG)n-containing plasmids results from the change of superhelical density due to the B-Z transition, we treated wild-type pUC18 molecules with topoisomerase I and varying amounts of ethidium bromide to generate a range of supercoil densities. Light scattering indicates that supercoiling did not affect the condensation process.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Condensation of plasmids enhanced by Z-DNA conformation of d(CG)n inserts. 789 47

The interaction of calf-thymus DNA with cobalt-hexammine and cobalt-pentammine cations was investigated, in aqueous solution at pH 6-7 with cation/DNA(phosphate) molar ratios r = 1/80, 1/40, 1/20, 1/10, 1/4, 1/2 and 1, using Fourier Transform infrared (FTIR) difference spectroscopy. Correlations between spectral changes, DNA condensation and helical stabilization due to the cation interaction as well as conformational features are established. At a very low cation concentration (r = 1/80), the binding of cobalt-hexammine cation with DNA is through the H-bond formation between cation NH3 groups and the PO2 groups of the backbone, resulting in duplex stability. As the cation concentration increases, hydrogen bonding expands towards guanine N-7 and O-6 atoms. At r > 1/20, DNA condensation occurs with major reduction in the intensity of several DNA in-plane vibrations and that of the phosphate group. The cobalt-pentammine cation binding is via the PO2 groups (directly) at very low metal cation concentration (r = 1/80) and the guanine N-7 and the O-6 groups (indirectly) at higher ratios. At r > 1/10, DNA condensation begins with some degree of direct cation-base binding. No major conformational changes from the B-family structure were observed before and after DNA collapse, in the presence of cobalt-ammine cations.
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PMID:The effects of cobalt-hexammine and cobalt-pentammine cations on the solution structure of calf-thymus DNA. DNA condensation and structural features studied by FTIR difference spectroscopy. 821 50

The response of neonatal rat locus coeruleus neurons to contact with myelin extracts prepared from the CNS and PNS was examined. The growth cones of these neurons collapsed following contact with central myelin, but continued to elongate on contact with peripheral myelin. Central myelin elicited an increase in the intracellular free calcium concentration in these growth cones, while peripheral myelin did not. This increase appeared to require transmembrane calcium flux, since it was blocked by extracellular EGTA, and also by extracellular cobalt. These neurons express N- and L-type calcium channels. Exposure to 5 microM omega-conotoxin GVIA, a specific blocker of N-type channels, prevented both the myelin-evoked increase in growth cone calcium concentration and the collapse of growth cones.
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PMID:Omega-conotoxin prevents myelin-evoked growth cone collapse in neonatal rat locus coeruleus neurons in vitro. 822 95

Cyanide poisoning presents in many forms. Industrial intoxications occur due to extensive use of cyanide compounds as reaction products. Smoke inhalation, a polyintoxication, is most often responsible for domestic cyanide poisonings. Suicidal poisonings are rare. Cyanogenic compounds may produce acute or subacute toxicity. Signs of cyanide poisoning include headache, vertigo, agitation, confusion, coma, convulsions and death. Definitive laboratory confirmation is generally delayed. Elevated plasma lactate, associated with cardiovascular collapse, should suggest cyanide intoxication. Immediate treatment includes 100% oxygen, assisted ventilation, decontamination, correction of acidosis and blood pressure support. Antidotes include oxygen, hydroxocobalamin, di-cobalt EDTA and methaemoglobin-inducers. Hydroxocobalamin is an attractive antidote due to its rapid cyanide binding and its lack of serious side-effects, even in the absence of cyanide intoxication. Sodium thiosulphate acts more slowly than other antidotes and is indicated in subacute cyanogen poisoning and as an adjunct to acute cyanide poisoning. Initial evaluation of antidotal efficacy is based on correction of hypotension and lactic acidosis; the final analysis rests on the degree of permanent central nervous system injury.
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PMID:Acute cyanide poisoning: clinical spectrum, diagnosis, and treatment. 898 94

The elastic response of single plasmid and lambda phage DNA molecules was probed using optical tweezers at concentrations of trivalent cations that provoked DNA condensation in bulk. For uncondensed plasmids, the persistence length, P, decreased with increasing spermidine concentration before reaching a limiting value 40 nm. When condensed plasmids were stretched, two types of behavior were observed: a stick-release pattern and a plateau at approximately 20 pN. These behaviors are attributed to unpacking from a condensed structure, such as coiled DNA. Similarly, condensing concentrations of hexaammine cobalt(III) (CoHex) and spermidine induced extensive changes in the low and high force elasticity of lambda DNA. The high force (5-15 pN) entropic elasticity showed worm-like chain (WLC) behavior, with P two- to fivefold lower than in low monovalent salt. At lower forces, a 14-pN plateau abruptly appeared. This corresponds to an intramolecular attraction of 0.083-0.33 kT/bp, consistent with osmotic stress measurements in bulk condensed DNA. The intramolecular attractive force with CoHex is larger than with spermidine, consistent with the greater efficiency with which CoHex condenses DNA in bulk. The transition from WLC behavior to condensation occurs at an extension about 85% of the contour length, permitting looping and nucleation of condensation. Approximately half as many base pairs are required to nucleate collapse in a stretched chain when CoHex is the condensing agent.
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PMID:Stretching of single collapsed DNA molecules. 1073 75

Understanding the energetic consequences of molecular structure in aqueous solution is a prerequisite to the rational design of synthetic motifs with predictable properties. Such properties include ligand binding and the collapse of polymer chains into discrete three-dimensional structures. Despite advances in macromolecular structure determination, correlations of structure with high-resolution thermodynamic data remain limited. Here we compare thermodynamic parameters for the binding of Zn(II), Cu(II), and Co(II) to human carbonic anhydrase II. These calorimetrically determined values are interpreted in terms of high-resolution X-ray crystallographic data. While both zinc and cobalt are bound with a 1:1 stoichiometry, CAII binds two copper ions. Considering only the high-affinity site, there is a diminution in the enthalpy of binding through the series Co(II) --> Zn(II) --> Cu(II) that mirrors the enthalpy of hydration; this observation reinforces the notion that the thermodynamics of solute association with water is at least as important as the thermodynamics of solute-solute interaction and that these effects must be considered when interpreting association in aqueous solution. Additionally, DeltaC(p) data suggest that zinc binding to CAII proceeds with a greater contribution from desolvation than does binding of either copper or cobalt, suggesting Nature optimizes binding by optimizing desolvation.
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PMID:Thermodynamics of metal ion binding. 1. Metal ion binding by wild-type carbonic anhydrase. 1133 Sep 96


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