An assessment of the cis-influence in coenzyme B12 Models. The structure of the mixed schiff-base/oxime complex: Aquo(3,9-dimethyl-2,10-diethyl-1,4,8,1 1-tetra-azaundeca-1,3,8,10-tetraen-11-ol-1-olato)(methyl)cobalt(III)hexafluorophosphate

The title compound is the first accurately determined structure in the general class of ‘Costa’ B₁₂ models. The data permit comparisons of structural results to other relevant B₁₂ models and the construction of a cis effect series.Crystal Data: C₁₄H₂₀CoF₆N₄O₃P, M = 504.4, monoclinic, space group P2₁/c, a = 14.316(3), b = 6.819(1), c = 22.741(5) Å and β = 99.91(2)°, V = 2186.9 ų, D_m = 1.52, Z = 4, D_c = 1.53 g cm^?3, μ(MoKα) = 9.2 cm^?1, λ(MoKα) = 0.7107 Å. Unit cell parameters were refined and intensity data collected on a CAD4 computer-controlled diffractometer, using graphite-monochromated MoKα radiation. A total of 5803 reflections were collected and corrected for Lorentz-polarization factor, 2802 independent reflections with I > 3σ(I) being used in the subsequent calculations.The CoO bond length to the axial water is 2.102- (3) Å. This value places the Costa model structural cis influence as being comparatively close to corrin based systems, somewhat greater than cobaloximes and definitely lower than Schiff-base complexes.     

Observations on the morphology,submicroscopic structure and biological properties of satellite cells (S.C.) in sensory ganglia of mammals

Zusammenfassung Die Untersuchung der perisomatischen und periaxonalen Satelliten in sensiblen Ganglien verschiedener Säuger hat folgende Ergebnisse:Es wird nachgewiesen, daß die Satelliten um das Neuron eine ununterbrochene Hülle bilden, die es von den Bindegewebsstrukturen des Ganglions vollständig trennt. Jeder Satellit ist von seiner eigenen Zellmembran scharf begrenzt; die Membranen der anliegenden Zellen sind durch Zwischenräume von etwa 200 Å getrennt. Die Form der Satelliten ist im wesentlichen laminär: die Abbildungen von Zellen mit feinen verzweigten Fortsätzen, die hauptsächlich durch Silberimprägnation gewonnen wurden, geben meistens Artefakte wieder.Die Satelliten haben innige Beziehungen zum Neuron, von dem sie durch einen dünnen Zwischenraum (etwa 200 Å), von den entsprechenden Zellmembranen abgegrenzt, getrennt sind: die Satelliten passen sich jeder Unregelmäßigkeit der Neuronenoberfläche an, die durch kleine Paraphyten hervorgerufen wird.Wo der Neurit erscheint, stellen sich die perisomatischen Satelliten ein. Sie werden von den periaxonalen Satelliten ersetzt und diese ihrerseits von den Schwannschen Zellen.Die Satelliten enthalten manchmal ergastoplasmische Bildungen. Im großen und ganzen ist die Struktur dieser Zellen derjenigen der Schwannschen Zellen und vieler protoplasmatischen Gliocyten des Zentralnervensystems ähnlich.Während des körperlichen Wachstums erfahren die Satelliten eine bedeutend geringere Volumen-Zunahme als die Neurone, aber sie vermehren sich häufig durch mitotische Teilung. Beim Erwachsenen sind die Mitosen dagegen sehr selten. Das endgültige Volumen der Satelliten ist eher gleichmäßig, es entspricht dem Drieschschen-Gesetz. Auf Grund der gewonnenen Daten kann man diese Zellen als stabile Elemente im Sinne Bizzozero's betrachten.Über den funktionellen Wert der Satelliten äußert sich der Verfasser auf Grund der morphologisch und biologisch gesammelten Daten. Da diese Zellen immer zwischen den Blutgefäßen und den Neuronen liegen, muß ihre Tätigkeit trophischer Art sein. Die morphologischen Untersuchungen können allerdings nicht feststellen, ob diese trophische Funktion nur in einer Filtrierung der von den Blutgefäßen herkommenden Substanzen oder auch in ihrer Verarbeitung besteht.Schließlich behauptet der Verfasser, daß die perisomatischen und periaxonalen Satelliten einerseits eine große Ähnlichkeit mit den perineuronalen protoplasmatischen Gliocyten des Zentralnervensystems aufweisen, andererseits mit den Schwannschen Zellen. Es ist vielleicht möglich, in einer Kategorie viele Zellen zusammenzufassen, die in enger Beziehung zu den Neuronen stehen und ähnliche funktionelle Eigenschaften besitzen, Zellen, die sowohl dem zentralen als auch dem peripheren Nervensystem angehören.

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Research supported by a C.N.R. Grant.     

Two μ1,5-dicyanamide bridged 2D and 3D metal complexes formed by covalent bonding and weak interactions

One 2D and one 3D dicyanamide bridged complexes, [Cu(dca)₂(et₂-en)]_n (1) and [Mn(dca)₂(im)₂]_n (2) [dca=dicyanamide, et₂-en=N,N-diethyl-ethylenediamine, im=imidazole], have been synthesized. Both the complexes are 1D by covalent bonding but interchain H-bonding promotes dimensionality. Moreover, π-π interaction among the imidazole ligands also plays an important role to have an interlocked 3D structure for 2. Magnetic study of both the complexes shows weak antiferromagnetic interaction between the metal centers. The magnetic data have been fitted with appropriate equations yielding best fit parameters for 1: J=−0.58±0.02 cm⁻¹, g=2.11±0.01 with R=3.2×10⁻⁶ and for 2, J=−0.21 cm⁻¹, g=2.00 and R=5.6×10⁻⁴.     

An Aging Interventions Testing Program: study design and interim report

The National Institute on Aging's Interventions Testing Program (ITP) has developed a plan to evaluate agents that are considered plausible candidates for delaying rates of aging. Key features include: (i) use of genetically heterogeneous mice (a standardized four-way cross), (ii) replication at three test sites (the Jackson Laboratory, TJL; University of Michigan, UM; and University of Texas, UT), (iii) sufficient statistical power to detect 10% changes in lifespan, (iv) tests for age-dependent changes in T cell subsets and physical activity, and (v) an annual solicitation for collaborators who wish to suggest new interventions for evaluation. Mice in the first cohort were exposed to one of four agents: aspirin, nitroflurbiprofen (NFP), 4-OH-alpha-phenyl-N-tert-butyl nitrone (4-OH-PBN), or nordihydroguiaretic acid (NDGA). An interim analysis was conducted using survival data available on the date at which at least 50% of the male control mice had died at each test site. Survival of control males was significantly higher, at the interim time-point, at UM than at UT or TJL; all three sites had similar survival of control females. Males in the NDGA group had significantly improved survival (P = 0.0004), with significant effects noted at TJL (P < 0.01) and UT (P < 0.04). None of the other agents altered survival, although there was a suggestion (P = 0.07) of a beneficial effect of aspirin in males. More data will be needed to determine if any of these compounds can extend maximal lifespan, but the current data show that NDGA reduces early life mortality risks in genetically heterogeneous mice at multiple test sites.     

Helicobacter pylori releases a factor(s) inhibiting cell cycle progression of human gastric cell lines by affecting cyclin E/cdk2 kinase activity and Rb protein phosphorylation through enhanced p27(KIP1) protein expression

Helicobacter pylori, the main cause of chronic gastritis, plays a central role in the etiology of peptic ulcer disease and gastric cancer. In vitro studies have shown that H. pylori increases gastric epithelial cell turnover, thus increasing the risk for the development of neoplastic clones. The mechanisms by which H. pylori promotes perturbation of cell proliferation are not yet elucidated. To investigate whether products released by H. pylori in culture media interfere with cell cycle progression of human gastric epithelial cells, four cell lines (MKN 28, MKN 7, MKN 74, and AGS) were incubated in the presence of H. pylori broth culture filtrate. Cell cycle analysis showed that a H. pylori-released factor(s) significantly inhibited the G1- to S-phase progression of MKN 28 and MKN 7 cell lines, with a reversible, nonlethal mechanism, independent of the expression of VacA, CagA, and/or urease. The cell cycle inhibition occurred concomitantly with an increase in p27(KIP1) protein levels, a reduction in Rb protein phosphorylation on serine residues 807-811, and a significant decrease in cyclin E-associated cdk2 activity. In contrast, the cell cycle progression of MKN 74 and AGS cell lines was not affected by the H. pylori-released factor(s). In normal human fibroblasts, G1-phase cell accumulation was concomitant with the reduction in Rb protein phosphorylation; that, however, appeared to be dependent on p21(WAF1/CIP1) rather than on p27(KIP1) protein. A preliminary characterization showed that the molecular mass of the partially purified cell cycle inhibitory factor(s) was approximately 40 kDa. These results suggest that H. pylori releases a soluble factor(s) that may affect cell cycle progression of gastric epithelial cells through elevated levels of cdk inhibitor p27(KIP1). This factor(s) might act in vivo on noncolonized distant cells, the most proliferating cells of human gastric mucosa.     

Guest driven self-assembly of a rectangular box from methylaquacobaloxime and 4,4′-biphenyldiboronic acid

We described the guest-induced synthesis of a rectangular host derived from methylaquacobaloxime CH₃Co(dmgH)₂H₂O and 4,4′-biphenyldiboronic acid containing 4,4′-bipyridine (bipy) molecule as guest. The assembly, monitored by a time dependent ¹H NMR experiment, showed that the guest thermodynamically drives the organization of the host. The structural characterization of the complex evidenced a centrosymmetric rectangular box having two biphenyldiboronate units and a central 4,4′-bipyridine spacer connecting the cobaloxime units (1). The spacers have coplanar rings, being negligible the tilt angle around the central C-C bond. The molecular structure of 1 and of the dinuclear complex [CH₃Co(dmgH)₂]₂(bipy) indicates close comparable intermetallic distance for the rigid bipy bridge and a coplanar arrangement of the cobaloxime moieties that facilitates the formation of the molecular box. The other tested ditopic ligands L (α,α′-diamino-p-xylene and 1,6-diaminohexane) used in this study allowed only a partial assembly. These derivatives and the related dinuclear complexes [CH₃Co(dmgH)₂]₂(L), which were synthesized with the aim to obtain further insights about the formation of the molecular boxes, were also characterized by X-ray structural analysis. The structures of [CH₃Co(dmgH)₂]₂(L), beside the expected flexibility of L, indicate not facing cobaloxime moieties. CV measurements suggest the formation of dinuclear non organometallic Co(II) and Co(I) species after the first reduction for all the dinuclear compounds that are stable in solution. For 1 no electronic coupling is shown, in spite of coplanar conformation of the 4,4′-bipyridine rings.     

Region-specific effects on brain metabolites of hypoxia and hyperoxia overlaid on cerebral ischemia in young and old rats: a quantitative proton magnetic resonance spectroscopy study

Background  

Both hypoxia and hyperoxia, deregulating the oxidative balance, may play a role in the pathology of neurodegenerative disorders underlain by cerebral ischemia. In the present study, quantitative proton magnetic resonance spectroscopy was used to evaluate regional metabolic alterations, following a 24-hour hypoxic or hyperoxic exposure on the background of ischemic brain insult, in two contrasting age-groups of rats: young - 3 months old and aged - 24 months old.     

Identification and characterisation of a novel acylpeptide hydrolase from Sulfolobus solfataricus: structural and functional insights

A novel acylpeptide hydrolase, named APEH-3(Ss), was isolated from the hypertermophilic archaeon Sulfolobus solfataricus. APEH is a member of the prolyl oligopeptidase family which catalyzes the removal of acetylated amino acid residues from the N terminus of oligopeptides. The purified enzyme shows a homotrimeric structure, unique among the associate partners of the APEH cluster and, in contrast to the archaeal APEHs which show both exo/endo peptidase activities, it appears to be a "true" aminopeptidase as exemplified by its mammalian counterparts, with which it shares a similar substrate specificity. Furthermore, a comparative study on the regulation of apeh gene expression, revealed a significant but divergent alteration in the expression pattern of apeh-3(Ss) and apeh(Ss) (the gene encoding the previously identified APEH(Ss) from S. solfataricus), which is induced in response to various stressful growth conditions. Hence, both APEH enzymes can be defined as stress-regulated proteins which play a complementary role in enabling the survival of S. solfataricus cells under different conditions. These results provide new structural and functional insights into S. solfataricus APEH, offering a possible explanation for the multiplicity of this enzyme in Archaea.     

Oxygen-Derived Free Radicals Mediate Liver Damage in Rats Subjected to Tourniquet Shock

The placement of rubber band tourniquets upon rat hind-limbs for 5 h followed by reperfusion of the extremities results in a severe form of circulatory shock characterized by hypotension and death within 24 h of tourniquet release. Oxidative damage to muscle tissue is an early consequence of hind-limb reperfusion on tourniquet release, yet this local damage does not explain the lethal hypotensive shock state which evolves within the next 24 h. Multiple system organ failure (MSOF), of as of yet unknown causes, is usually described in relation to several shock states. It has been suggested that injured or necrotic tissue may activate neutrophils, platelets, and the coagulation system leading to embolization in remote tissues. Effective decreases in hepatic blood flow have been observed in several forms of sepsis which precedes the biochemical evidence consistent with an ischemic insult of the liver. In support of our original hypothesis, that organ failure has its genesis in a primary perfusion abnormality with secondary ischemic organ injury, herein we have assessed the possibility that oxygen-derived free radicals are generated in the liver of rats after reperfusion of their hind-limbs on release of the tourniquets. We report on the protective effects of allopurinol (ALLO) and a mixture of superoxide dismutase (SOD) catalase (CAT) and dimethylfulfoxide (DMSO) on liver free sulfhydryl content (SH), thiobarbituric acid-reactive substances (TBARS), and on the release of aspartic acid (AsT) and alanine aminotransferase (AIT) activities, and of alkaline phosphatase during a 5 h tourniquet period and after 2 h of reperfusion of the hind-limbs. During the hind-limb ischemic period hepatis tissue SH levels remained essentially constant during the first hour (6.02 ± 0.36 to 5.65 ± 0.20 μmoles/g wet tissue), and decreased significantly, over and above the normal circadian decrease of liver glutathione levels, to 4.02 ± 0.69 μmoles/g wet tissue after the third hour and remained lowered until tourniquet release. A further significant decrease (3.11 ± 0.49 μmoles/g wet tissue) was observed after 2h of reperfusion. TBARS production remained constant during the 5 h hind-limb ischemic period (168.4 ± 37.3 μmoles/g wet tissue) and rose by 55+ to 261.7 ± 55.8 μmoles/g wet tissue after 2 h of tourniquet release. ALLO, but not the SOD-CAT-DMSO combination, protected hepatic SH loss during the hind-limb ischemic insult, yet both offered protection after 2 h of tournoquet release. With regard to TBARS production, ALLO and the SOD-CAT-DMSO mixture had no effect on basal levels during the ischemic period, but both significantly reduced liver TBARS production after the two hour reperfusion period of hind limb reperfusion. Plasma AsT levels rose 8-fold from 99.4 ± 7.2 to 193 ± 17.0 U/L after the 5-hour tourniquet period, and to 844.8 ± 75.1 U/L two hours after hind-limb reperfusion. The plasma levels of AsT were significantly lower in both the ALLO and SOD-CAT-DMSO pre-treated animals. This was not the case with plasma AIT levels which increased 3-fold during the reperfusion period, but which could not be protected with these same pre-treatment protocols. Alkaline phosphatase plasma levels increased 2-fold during the same period. It is concluded that oxidative stress to the liver, as a result of himd-limb ischemia followed by reperfusion, is partly responsible for the MSOF which leads to circulatory derangements and death of rats subjected to this tourniquet shock model.