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This paper examines the synergism among diet, disease, and ecology at two related coastal Maya sites in Belize (Marco Gonzalez and San Pedro) for the Postclassic and Historic periods (1350-1650 AD), which immediately follow the Classic period collapse. Stable carbon- and nitrogen-isotope ratios in collagen and stable carbon-isotope ratios in structural carbonate were analysed for bones from 65 humans and a wide variety of faunal species. There are no apparent differences in whole diets or degree of carnivory between individuals with lesions indicative of anemia and those without, but those with lesions appear to have consumed significantly more C4 foods and protein from lower trophic levels. Non-specific infection (periostitis) and vitamin C deficiency (scurvy) are also present in high frequencies and appear to co-occur with lesions indicative of anemia, particularly in childhood. Individuals with scurvy also appear to have consumed significantly more C4 foods than normal individuals. Spondyloarthropathy is common in adults. These findings are discussed in light of: (1) the debate on how anemia versus scurvy are manifest and diagnosed, (2) Spanish ethnohistoric descriptions of the poor state of Maya health at the time of contact, and (3) the Osteological Paradox. We suggest that although this coastal environment exacerbated morbidity because of possible parasitic infection, the inhabitants were probably able to survive physiological stresses better than either their inland contemporaries or their modern counterparts.
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PMID:Pathoecology and paleodiet in postclassic: historic Maya from northern coastal Belize. 1730 7

A luminescence pulse is observed from laser-created bubbles in pressurized liquid nitrogen and argon, occurring at the first collapse point of the bubble motion. The duration of the light pulse depends linearly on the bubble size, ranging from 200 ns to 1 micros for bubbles with maximum diameters between 0.2 and 1 mm. The spectrum of the light consists entirely of atomic lines, which surprisingly turns out to contain strong emission lines from excited states of the neutral chromium atom. It is likely that this results from small microflakes of stainless steel knocked off the walls of the sample cell by the shock waves generated from the laser pulse. The small metallic flakes are preferentially ionized by the laser, resulting in bubbles containing chromium and other metal atoms in their interior. An analysis of the relative intensities of the triplet chromium lines shows that the compression in the bubble collapse is heating the chromium to temperatures of order 4500 K.
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PMID:Luminescence from laser-created bubbles in cryogenic liquids. 1767 55

The microstructure of temperature-quenched solutions of reverse micelles formed by sodium, cobalt, ytterbium, and cobalt/ytterbium bis(2-ethylhexyl)sulfosuccinate in n-heptane has been investigated by SAXS and EXAFS. Some changes in the X-ray absorption spectra with respect to the same systems at room temperature have been observed. The analysis of the SAXS spectra leads to the hypothesis that at 77 K the closed spherical structure of reverse micelles is retained and that during the temperature quench they undergo a clustering process involving the transition from a quite random dispersion to the formation of more or less large clusters of strongly packed reverse micelles. This behavior is attributed to competitive effects caused by the temperature decrease. The prevalence of intermicellar attractive interactions with respect to Brownian motions leading to a collapse to more compact structure is in competition with the rapid decrease of reverse micelle diffusion rate involving a freezing of the local structures. In the case of cobalt, ytterbium, and cobalt/ytterbium bis(2-ethylhexyl)sulfosuccinate reverse micelles, further information from EXAFS measurements indicates that within the reverse micelle core exists a quite ordered nanosized domain composed of water, surfactant counterions, and oxygen atoms of the SO3- head groups. The conservation of local order and inverse structure during the clustering phenomenon that results from the fast freezing with liquid nitrogen of solutions of reverse micelles could have biological implications, i.e., the preservation of tissue samples at cryogenic temperatures.
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PMID:Structural characterization of frozen n-heptane solutions of metal-containing reverse micelles. 1791 98

Numerical simulations of nonequilibrium chemical reactions in a pulsating air bubble have been performed for various ultrasonic frequencies (20 kHz, 100 kHz, 300 kHz, and 1 MHz) and pressure amplitudes (up to 10 bars). The results of the numerical simulations have indicated that the main oxidant is OH radical inside a nearly vaporous or vaporous bubble which is defined as a bubble with higher molar fraction of water vapor than 0.5 at the end of the bubble collapse. Inside a gaseous bubble which is defined as a bubble with much lower vapor fraction than 0.5, the main oxidant is H2O2 when the bubble temperature at the end of the bubble collapse is in the range of 4000-6500 K and O atom when it is above 6500 K. From the interior of a gaseous bubble, an appreciable amount of OH radical also dissolves into the liquid. When the bubble temperature at the end of the bubble collapse is higher than 7000 K, oxidants are strongly consumed inside a bubble by oxidizing nitrogen and the main chemical products inside a bubble are HNO2, NO, and HNO3.
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PMID:Relationship between the bubble temperature and main oxidant created inside an air bubble under ultrasound. 1794 68

Reactive oxygen species (ROS) have been implicated in the pathogenesis of renal injury after ischemia/reperfusion (I/R). Recently, green tea polyphenols (GTP) have been found to protect the myocardium and liver against II/R injury. Less attention, however, has been paid to the protective effects of GTP with respect to the kidneys. This study was designed to determine whether GTP could protect renal cells from ischemic injury. The rabbits were divided into three groups of equal size: control (sham-operated), I/R + vehicle (normal saline) and I/R + GTP groups. Each group consisted of six rabbits. Animals underwent 30, 60, 90 and 120 min of ischemia, followed by 24 h of reperfusion, respectively. GTP (200 microg/kg) or the vehicle was administered 45 min prior to commencement of I/R. The results demonstrated that GTP administration resulted in a significant (P < 0.05) reduction of renal damage after 90 min of ischemia, as indicated by the decreased levels of creatinine and urea nitrogen in serum. These results were confirmed by histological examinations, which showed that GTP pretreatment inhibited necrosis and sloughing of the proximal tubules induced by I/R. Examinations also showed decreased necrotic areas in the medulla and decreased glomerular collapse in the I/R-injured rabbits. Moreover, the infiltration of CD8+ T cells was considerably decreased in GTP-treated kidneys. The results of this study suggest that GTP can reduce renal injury by preventing the oxidative stress dependent on I/R and may be used in renal transplantation as an antioxidant.
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PMID:Protection of rabbit kidney from ischemia/reperfusion injury by green tea polyphenol pretreatment. 1808 14

Parkinson's disease (PD) is characterized by selective depletion of nigral dopamine (DA) neurons containing neuromelanin (NM), suggesting the involvement of NM in the pathogenesis. This study reports induction of apoptosis by NM in SH-SY5Y cells, whereas protease-K-treated NM, synthesized DA- and cysteinyl dopamine melanin showed much less cytotoxicity. Cell death was mediated by mitochondria-mediated apoptotic pathway, namely collapse of mitochondrial membrane potential, release of cytochrome c, and activation of caspase 3, but Bcl-2 over-expression did not suppress apoptosis. NM increased sulfhydryl content in mitochondria, and a major part of it was identified as GSH, whereas dopamine melanin significantly reduced sulfhydryl levels. Western blot analysis for protein-bound GSH demonstrated that only NM reduced S-glutathionylated proteins in mitochondria and dissociated macromolecular structure of complex I. Reactive oxygen and nitrogen species were required for the deglutathionylation by NM, which antioxidants reduced significantly with prevention of apoptosis. These results suggest that NM may be related to cell death of DA neurons in PD and aging through regulation of mitochondrial redox state and S-glutathionylation, for which NM-associated protein is absolutely required. The novel function of NM is discussed in relation to the pathogenesis of PD.
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PMID:Neuromelanin selectively induces apoptosis in dopaminergic SH-SY5Y cells by deglutathionylation in mitochondria: involvement of the protein and melanin component. 1839 61

To study the effect of titanium alloy cage on the treatment of the ischemic necrosis of femoral head in dog, the model of the ischemic necrosis of femoral head was made with the liquid nitrogen in 15 hybrid adult dogs. The titanium alloy cage made of a hollow cylinder was driven into the subchondral bone of necrotic femoral head via central channel. The dogs were divided into 3 groups, each group was sacrificed 3, 6, 12 weeks after the operation respectively. No collapse of femoral head was observed after the operation. The position of the cages was good on radiograph. Microscopically, the cancellous bone of necrotic femoral head rebuilt gradually and grew into cage. After 12 weeks of creeping substitution, the cancellous bone filled up the hollow cavity and holes of the cages. It is concluded that the titanium alloy cage can provide structural support for the subchondral bone and prevent collapse and can be used for the treatment of the ischemic necrosis of femoral head.
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PMID:Titanium alloy cage implantation for the treatment of ischemic necrosis of femoral head in dogs. 1848 Sep 88

Bubbles are levitated in a resonator driven by an ultrasound wave. Their highly nonlinear oscillations feature a strong collapse, where fluidlike densities and temperatures of several thousand degrees Kelvin are reached, resulting in the emission of ultrashort light pulses. Previous experiments and theories explained the observed stable bubble dynamic and emission on long time scales with the requirement of a noble gas. Recent experiments reveal stable sonoluminescent emission of nitrogen bubbles in chilled water without the presence of a noble gas. Numerical calculations show that a diffusive and dissociative equilibrium can be reached when the temperature within a nitrogen bubble is limited due to the presence of water vapor. Calculated stability lines agree with published experimental results. The results show that noble-gas-free stable single bubble sonoluminescence of nitrogen bubbles is possible.
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PMID:Stability of a sonoluminescing nitrogen bubble in chilled water. 1851 29

Penicillin-binding protein 5 (PBP 5) of Escherichia coli hydrolyzes the terminal D-Ala-D-Ala peptide bond of the stem peptides of the cell wall peptidoglycan. The mechanism of PBP 5 catalysis of amide bond hydrolysis is initial acylation of an active site serine by the peptide substrate, followed by hydrolytic deacylation of this acyl-enzyme intermediate to complete the turnover. The microscopic events of both the acylation and deacylation half-reactions have not been studied. This absence is addressed here by the use of explicit-solvent molecular dynamics simulations and ONIOM quantum mechanics/molecular mechanics (QM/MM) calculations. The potential-energy surface for the acylation reaction, based on MP2/6-31+G(d) calculations, reveals that Lys47 acts as the general base for proton abstraction from Ser44 in the serine acylation step. A discrete potential-energy minimum for the tetrahedral species is not found. The absence of such a minimum implies a conformational change in the transition state, concomitant with serine addition to the amide carbonyl, so as to enable the nitrogen atom of the scissile bond to accept the proton that is necessary for progression to the acyl-enzyme intermediate. Molecular dynamics simulations indicate that transiently protonated Lys47 is the proton donor in tetrahedral intermediate collapse to the acyl-enzyme species. Two pathways for this proton transfer are observed. One is the direct migration of a proton from Lys47. The second pathway is proton transfer via an intermediary water molecule. Although the energy barriers for the two pathways are similar, more conformers sample the latter pathway. The same water molecule that mediates the Lys47 proton transfer to the nitrogen of the departing D-Ala is well positioned, with respect to the Lys47 amine, to act as the hydrolytic water in the deacylation step. Deacylation occurs with the formation of a tetrahedral intermediate over a 24 kcal x mol(-1) barrier. This barrier is approximately 2 kcal x mol(-1) greater than the barrier (22 kcal x mol(-1)) for the formation of the tetrahedral species in acylation. The potential-energy surface for the collapse of the deacylation tetrahedral species gives a 24 kcal x mol(-1) higher energy species for the product, signifying that the complex would readily reorganize and pave the way for the expulsion of the product of the reaction from the active site and the regeneration of the catalyst. These computational data dovetail with the knowledge on the reaction from experimental approaches.
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PMID:Investigation of the mechanism of the cell wall DD-carboxypeptidase reaction of penicillin-binding protein 5 of Escherichia coli by quantum mechanics/molecular mechanics calculations. 1857 37

The sessile lifestyle of plants constrains their ability to acquire mobile nutrients such as nitrate. Whereas proliferation of roots might help in the longer term, nitrate-rich patches can shift rapidly with mass flow of water in the soil. A mechanism that allows roots to follow and capture this source of mobile nitrogen would be highly desirable. Here, we report that variation in nitrate concentration around roots induces an immediate alteration of root hydraulic properties such that water is preferentially absorbed from the nitrate-rich patch. Further, we show that this coupling between nitrate availability and water acquisition results from changes in cell membrane hydraulic properties and is directly related to intracellular nitrate concentrations. Split-root experiments in which nitrate was applied to a portion of the root system showed that the response is both localized and reversible, resulting in rapid changes in water uptake to the portions of the roots exposed to the nitrate-rich patch. At the same time, water uptake by roots not supplied with nitrate was reduced. We believe that the increase in root hydraulic conductance in one part causes a decline of water uptake in the other part due to a collapse in the water potential gradient driving uptake. The translation of local information, in this case nitrate concentration, into a hydraulic signal that can be transmitted rapidly throughout the plant and thus coordinate responses at the whole plant level, represents an unexpected, higher level physiological interaction that precedes the level of gene expression.
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PMID:Nitrate control of root hydraulic properties in plants: translating local information to whole plant response. 1875 87


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