Infrared monitoring of dinitrotoluenes in sunflower and maize roots.

Infrared microspectroscopy (IMS) is emerging as an important analytical tool for the structural analysis of biological tissue. This report describes the use of IMS coupled to a synchrotron source combined with principal components analysis (PCA) to monitor the fate and effect of dinitrotoluenes in the roots of maize and sunflower plants. Infrared imaging revealed that maize roots metabolized 2,4-dinitrotoluene (DNT) and 2,6-DNT. The DNTs and their derivative aromatic amines were predominantly associated with epidermis and xylem. Both isomers of DNT altered the structure and production of pectin and pectic polysaccharides in maize and sunflower plant roots. Infrared peaks diagnostic for aromatic amines were seen at the 5 mg L concentrations for both DNTs in maize and sunflower treated tissue. However, only infrared peaks for nitro groups, not aromatic amines, were present in the maize treated at 10 mg L For sunflower, the 10 mg L level was toxic and also produced very dark root systems making spectra difficult to obtain. Maize and sunflower seem unable to metabolize effectively at concentrations higher than about 5 mg L DNT in hydroponic solution. Based on the results of this study, IMS combined with PCA can be an effective means of determining the fate and metabolism of organic contaminants in plant tissue when isotopically labeled compounds are not available.

Meningococcal disease in a backpackers hostel in Scotland: a risk assessment for prophylaxis.

This paper outlines the risk assessment and communication strategy carried out by the Lothian Health Protection Team after notification of a probable case of meningococcal disease (later confirmed as Neisseria meningitidis) in a resident of a city centre backpackers hostel. Six close contacts were identified from the hostel and given rifampicin prophylaxis. Two days after commencing rifampicin one of these contacts was admitted to hospital with a purpuric/petechial rash and thrombocytopenia. The final diagnosis for this contact was thrombocytopenia, either idiopathic or secondary to rifampicin. This example and the potential side effects of administering rifampicin prophylaxis highlight the importance of a thorough risk assessment of contacts of a case to avoid prescribing prophylaxis to anyone other than those at highest risk of becoming a subsequent case.

Nitrogenase IX. Effect of the MgATP generator on the catalytic and EPR properties of the enzyme in vitro.

Nitrogenase(nitrogen:(acceptor) oxidoreduction, EC 1.7.99.2) of Clostridium pasteuranium is very sensitive to the ratio of MgADP/MgATP in dithionite oxidation assays. Variation of concentration of creatine kinase, an ATP-regenerating enzyme, can be used to control the ratio of ADP/ATP and thereby the dithionite oxidation activity of nitrogenase. The in vitro properties of nitrogenase support the suggestion of Haaker (Haaker, H., deKok, A. and Veeger, C. (1974) Biochim. Biophys. Acta 357, 344-357) that in vivo the nucleotide ratio and not the electron supply normally regulates nitrogenase activity. In EPR experiments it has been shown that the "steady state" varies as a function of the concentration of creatine kinase. The spectral differences are interpreted as being a function of the ratio of MgADP/MgATP obtained in the pseudo steady-state condition, which occurs as a result of variation in relative rates of ATP-utilizing and ATP-generating reactions, that is, the relative nitrogenase and creatine kinase activities. Implications of these finding for interpretation of previously reported kinetic and EPR studies are discussed.

Nitrogenase. VII. Effect of component ratio, ATP and H2 on the distribution of electrons to alternative substrates.

Some kinetic properties of purified component I (Mo-Fe protein) and component II (Fe protein) of nitrogenase (EC 1.7.99.2) from Azotobacter vinelandii have been examined. The apparent Km values for reducible substrates (0.1 atm for N2, 0.01 atm for acetylene) and dithionite (0.5 mM) are similar for osmotically shocked cell lysates and purified components. However, the ATP dependence of acetylene and N2 reduction varies sigmoidally with ATP concentration and as a function of the relative and absolute concentration of components I and II in the assay. Acetylene is reduced in preference to N2 in competitive assays when component I is in relative excess. Acetylene reduction is not as dependent upon ATP concentration as is N2 reduction, so that acetylene is also a preferred substrate at lower ATP levels. Hydrogen specifically inhibits N2 reduction, diverting electrons to acetylene when both substrates are present in the assay. We propose a model of the enzyme activity, in which the substrates for reduction are bound to component I with electrons being activated by component II. ATP may be involved in activating electrons and in maintaining the appropriate conformation or reduction state of components to allow effective reduction of substrates. The relative rate of reduction of alternative substrates is dependent on the concentration of the particular state(s) capable of reacting with each substrate. The concentration of a particular state of component I is a function of components I, II and ATPL

Nitrogenase. VI. Acetylene reduction assay: Dependence of nitrogen fixation estimates on component ratio and acetylene concentration.

Acetylene reduction, an assay for nitrogenase activity (nitrogen:(acceptor) oxidoreductase, EC 1.7.99.2), Is dependent on the ratio of the two protein components of nitrogenase as well as on C2H2 concentration. As the component I : component II ratio (based on activity) is increased, the C2H2 reduction : N2 fixation ratio decreases to a minimum of 3.4 and then increases. The minimum is found at a ratio near 1 : 1. At a component I : component II ratio of 20 : 1, the C2H2 reduction : N2 fixation ratio is 5.3. Acetylene exhibits substrate inhibition in assays for nitrogenase activity. Both the apparent Km and Ki for acetylene vary as a function of the relative concentrations of components I and II present in the assay. When the more labile component II is limiting in the assay and "saturating" levels of C2H2 (above 0.1 atm) are used, N2-fixation capacity may be greatly under-estimated.

Nitrogenase. VIII. Mössbauer and EPR spectroscopy. The MoFe protein component from Azotobacter vinelandii OP.

We have studied the molybdenum-iron protein (MoFe protein, also known as component I) from Azobacter vinelandi using Mössbauer spectroscopy and electron paramagnetic resonance on samples enriched with 57Fe. These spectra can be interpreted in terms of two EPR active centers, each of which is reducible by one electron. A total of four different chemical environments of Fe can be discerned. One of them is a cluster of Fe atoms with a net electronic spin of 3/2, one of them is high-spin ferrous iron and the remaining two are iron in a reduced state (probably in clusters). The results are as follows: Chemical analysis yields 11.5 Fe atoms and 12.5 labile sulfur atoms per molybdenum atom; the molecule contains two Mo atoms per 300 000 daltons. The EPR spectrum of the MoFe protein exhibits g values at 4.32, 3.65 and 2.01, associated with the ground state doublet of a S = 3/2 spin system. The spin Hamiltonian H = D(S2/z minus 5/4 + lambda(S2/x minus S2/y)) + gbeta/o S-H fits the experimental data for go = 2.00 and lambda = 0.055. Quantitative analysis of the temperature dependence of the EPR spectrum yields D/k = 7.5 degrees K and 0.91 spins/molybdenum atom, which suggests that the MoFe protein has two EPR active centers. Quantitative evaluation of Mössbauer spectra shows that approximately 8 iron atoms give rise to one quadrupole doublet; at lower temperatures magnetic spectra, associated with the groud electronic doublet, are observed; at least two magnetically inequivalent sites can be distinguished. Taken together the data suggest that each EPR center contains 4 iron atoms. The EPR and Mössbauer data can only be reconciled if these iron atoms reside in a spin-coupled (S = 3/2) cluster. Under nitrogen fixing conditions the magnetic Mössbauer spectra disappeared concurrently with the EPR signal and quadrupole doublets are obserced at all temperatures. The data suggest that each EPR active center is reduced by one electron. The Mössbauer investigation reveals three other spectral components characteristic of iron nuclei in an environment of integer or zero electronic spin, i.e. they reside in complexes which are "EPR-silent". One of the components (3-4 iron atoms) has Mössbauer parameters characteristic of the high-spin ferrous iron as in reduced ruberdoxin. However, measurements in strong fields indicate a diamagnetic environment. Another component, representing 9-11 iron atoms, seems to be diamagnetic also. It is suggested that these atoms are incorporated in spin-coupled clusters.

Interaction with magnesium and ADP stabilizes both components of nitrogenase from Klebsiella pneumoniae against urea denaturation.

The nitrogenase enzyme of Klebsiella pneumoniae consists of two separable proteins, each with multiple subunits and one or more oxygen sensitive metallocenters. The wild-type nitrogenase proteins are stable to electrophoresis in high concentrations of urea under anaerobic conditions. Addition of Mg+2 and ADP greatly increases the stability of the smaller Fe protein (from <4 to >6 M for full unfolding), an effect directly analogous to stabilization in p21ras induced by Mg+2 and GDP. Stabilization by Mg+2 is slight for the holo MoFe protein (from approximately 1.5 to approximately 2.4 M) but more dramatic for the apo protein form of the MoFe protein accumulated by certain Fe protein (nifH gene) mutants. The potent product inhibitor of nitrogenase function, MgADP, increases stability of the MoFe protein more than Mg+2 alone, to approximately 3.6 M, showing that nucleotides interact with the MoFe protein. Mutations of the nifM gene result in slower accumulation of less stable Fe protein, indicating that NifM is involved in correct folding of the Fe protein. Mutationally altered proteins are often difficult to purify for study because of their inherent instability, low expression level, or oxygen lability. Crude extracts of 11 different mutants of Fe protein (nifH gene) were examined by transverse urea gradient gels to rapidly screen for stabilizing interactions in the presence or absence of substrate or inhibitor analogs. Amino acid alterations D44N and R188C, at the interface of the dimer, in the vicinity of the nucleotide binding site(s), have significantly lower stability than the wild-type enzyme in the absence of Mg+2 but comparable stability in its presence, showing the importance of Mg+2 in the subunit interactions. Mutations N163S and E266K, in which residues normally involved in hydrogen bonding far from the active site were altered, are more labile than the wild-type even with Mg+2 added. Seven other mutants, though nonfunctional, did not appear altered in stability compared to the wild-type.

Broad-zone active-enzyme chromatography. Keto-acid dehydrogenases as associating systems.

We have extended the method of active-enzyme chromatography to include the use of broad zones of enzyme. This allows examination of interacting systems in a way formally analogous to sedimentation velocity so that simulation of the observed activity profiles is possible. The method has been applied using pyridine nucleotide-linked active enzyme assays. At the concentrations presently accessible by this technique, hexokinase and glucose-6-phosphate dehydrogenase, both associating systems, show single symmetrical boundaries, as does isolated diaphorase, while pyruvate and alpha-ketoglutarate dehydrogenases show more complex patterns, with the position of the reaction boundary for diaphorase activity being dependent on enzyme concentration.

Sideport incision paracentesis versus antiglaucoma medication to control postoperative pressure rises after intraocular lens surgery.

Twenty-eight patients who had an intraocular pressure greater than 30 mm Hg within 24 hours after cataract surgery were randomly assigned to be treated with medication or by paracentesis through a sideport incision. Paracentesis provided an immediate reduction in intraocular pressure, but within one hour pressures rebounded. Within two to three hours after treatment, the medication group had significantly greater mean reductions in intraocular pressure than the paracentesis group.

Comments, with reply, on ;Tomographic reconstruction from experimentally obtained cone-beam projections' by S. Webb, et al.

The above paper (ibid., vol.MI-6, p.67-73, 1987) purports to propose an algorithm and implementation formulas for cone-beam reconstruction. The commenters point out that the exposition of the paper is little more than a paraphrase of their own earlier work (J. Opt. Soc. Amer. A, vol.1, no.6, p.612-19, 1984). All the benefits claimed are intrinsic to the algorithm proposed and were pointed out in the commenters paper. Webb et al. also suggest the use of a modified convolution scheme previously proposed for fan-beam reconstruction. Use of this scheme does not alter the basic premise of the commenters' work and does not entitle Webb et al. to claim to have developed a new algorithm. The authors reply that their paper presents experimental results that are based on the commenters' theoretical results, which were cited in the formers' paper.

Comment on "Analysis of optimal velocity model with explicit delay".

The effect of including an explicit delay time (due to driver reaction) on the optimal velocity model is studied. For a platoon of vehicles to avoid collisions, many-vehicle simulations demonstrate that delay times must be well below the critical delay time determined by a linear analysis for the response of a single vehicle. Safe platoons require rather small delay times, substantially smaller than typical reaction times of drivers. The present results do not support the conclusion of Bando et al. [M. Bando, K. Hasebe, K. Nakanishi, and A. Nakayama, Phys. Rev. E 58, 5429 (1998)] that explicit delay plays no essential role.

Multilane simulations of traffic phases.

The optimal velocity model, as modified by the author, is used in simulations of traffic on a dual-lane highway and a single-lane highway with an on-ramp. The equilibrium solutions of the modified model cover a two-dimensional region of flow-density space beneath the fundamental-diagram curve, rather than just lying on the curve as in the original model. Thus it satisfies a requirement of the three-phase model of Kerner [Phys. Rev. Lett. 81, 3797 (2002)]. Synchronization of velocity across dual lanes due to frequent lane changes is observed in free flow. True synchronized flow, as determined by the region of density-flow space it occupies, is obtained in on-ramp simulations with typical driver reaction times. A gradual change to the formation of a jam is observed for increasing delay times.

Effect of adaptive cruise control systems on traffic flow.

The flow of traffic composed of vehicles that are equipped with adaptive cruise control (ACC) is studied using simulations. The ACC vehicles are modeled by a linear dynamical equation that has string stability. In platoons of all ACC vehicles, perturbations due to changes in the lead vehicle's velocity do not cause jams. Simulations of merging flows near an onramp show that if the total incoming rate does not exceed the capacity of the single outgoing lane, free flow is maintained. With larger incoming flows, a state closely related to the synchronized flow phase found in manually driven vehicular traffic has been observed. This state, however, should not be considered congested because the flow is maximal for the density. Traffic composed of random sequences of ACC vehicles and manual vehicles has also been studied. At high speeds (approximately 30 m/s ) jamming occurs for concentrations of ACC vehicles of 10% or less. At 20% no jams are formed. The formation of jams is sensitive to the sequence of vehicles (ACC or manual). At lower speeds (approximately 15 m/s ), no critical concentration for complete jam suppression is found. Rather, the average velocity in the pseudojam region increases with increasing ACC concentration. Mixing 50% ACC vehicles randomly with manually driven vehicles on the primary lane in onramp simulations shows only modestly reduced travel times and larger flow rates.

Training Mexican American mental health personnel in behavior therapy.

Fourteen Mexican American mental health workers were trained in basic behavior therapy principles and behavior contracting in 10 weekly, 2 hr sessions. A significant increase was found in knowledge of principles, and attitudes toward behavior therapy became more positive. In addition, clinical skill in doing a behavior analysis and formulating a behavior therapy plan also improved. A 6 month follow-up suggested continued application of training. Results and match of behavior therapy training to differing cultures are discussed.

Bovine sire selection based on maintenance energy affects muscle fiber type and meat color of F1 progeny.

A total of 42 F(1) Red Angus progeny from sires divergent in maintenance energy (ME(M)) EPD were analyzed to determine whether selecting for sire ME(M) would alter end-product meat quality. Data from animals were grouped based on the divergence of the ME(M) EPD of their sire from the Red Angus Association-reported breed average and defined as either high or low, the assumption being that high-ME(M) cattle are less efficient because their maintenance requirements represent a larger proportion of their dietary intake. Steer progeny (n = 7) from the high group produced bottom round steaks with a greater a* (redness) color value (P = 0.02) after 5 d in a simulated retail display when compared with bottom round steaks from the low group (n = 18). Bottom round steaks from the high group had a greater b* (yellowness) color value at d 1 (P = 0.03) and d 5 (P = 0.01) of retail display. Samples from the biceps femoris were taken at 12 mo (from both steers and heifers) and 15 mo (from steers only) of age for fiber type proportion analysis. At 12 mo of age, steers from the low group had more type I fibers (P = 0.02), whereas steers from the high group had more type IIb fibers (P = 0.01). Furthermore, samples from steers in the low group at 15 mo had more type I fibers (P = 0.02), and steers from the high group maintained more type IIb fibers (P = 0.02). No changes in fiber type proportions were observed between the high- and low-ME(M) EPD heifers (n = 17). Relative mRNA abundance of genes involved in the synthesis, storage, and breakdown of glycogen were analyzed as a variable important for meat quality, but no statistical differences were observed. At 12 mo age, glycogenin (glyc) was negatively correlated with the proportion of type IIa fibers (r = -0.32 and P = 0.12) as well as with the proportion of type IIb fibers (r = -0.42 and P = 0.03) in the biceps femoris of the steers. In samples taken from the biceps femoris at 15 mo age, glyc was negatively correlated with the proportion of type IIa fibers (r = -0.42 and P = 0.03) in the steers. This indicates that relative mRNA expression of glyc may serve as a marker of muscle glycogen storage capacity in steers. Thus, selection for efficient Red Angus beef cattle based on sire ME(M) EPD does not adversely affect meat quality in F(1) progeny, based on the variables assessed in this study. Furthermore, selection for progeny from low-ME(M) EPD sires may improve fresh meat quality within Red Angus beef cattle.

Relationships among performance, residual feed intake, and product quality of progeny from Red Angus sires divergent for maintenance energy EPD.

Energy expenditure is a physiological process that may be closely associated with residual feed intake (RFI). The maintenance energy (ME(M)) EPD was developed by the Red Angus Association of America (RAAA) and is used as an indicator of energy expenditure. The objectives of this study were to evaluate and quantify the following relationships using progeny of Red Angus (RA) sires divergent for ME(M) EPD: 1) postweaning RFI and finishing phase feed efficiency (FE), 2) postweaning RFI and end-product quality, and 3) postweaning RFI and sire ME(M) EPD. A total of 12 RA sires divergent for ME(M) EPD were chosen using the RAAA-generated ME(M) EPD values and were partitioned into 2 groups: high ME(M) EPD (≥4 Mcal/mo) and low ME(M) EPD (<4 Mcal/mo), based on the breed average of 4 Mcal/mo. Commercial crossbred cows were inseminated to produce 3 cohorts of progeny, which were tested for postweaning RFI (cohorts 1, 2, and 3) and finishing phase FE (cohorts 1 and 3). Results indicate that postweaning RFI and finishing phase FE of steer progeny tended to be positively correlated (r = 0.38; P = 0.06) in cohort 1 and were positively correlated (r = 0.50; P = 0.001) in cohort 3. In addition, postweaning RFI was not phenotypically correlated (P > 0.05) with any carcass traits or end-product quality measurements. Sire ME(M) EPD was phenotypically correlated (P < 0.05) with carcass traits in cohort 1 (HCW, LM area, KPH, fat thickness, and yield grade) and cohort 2 (KPH and fat thickness). Since variation in measured LM area was not explained by the genetic potential of rib eye area EPD, and therefore, the observed correlation between sire ME(M) EPD and measured LM area may suggest an association between ME(M) EPD and LM area. A correlation (r = 0.24; P = 0.02) was observed between postweaning RFI and ultrasound intramuscular fat percentage in cohort 2 but was not detected in cohorts 1 or 3. In addition, no phenotypic relationship was observed (P > 0.05) between progeny postweaning RFI and sire ME(M) EPD. Therefore, results suggest 1) RFI measured during the postweaning growth phase is indicative of FE status in the finishing phase, 2) neither RFI nor sire ME(M) EPD negatively affected carcass or end-product quality, and 3) RFI and sire ME(M) EPD are not phenotypically associated.

NPY family of hormones: clinical relevance and potential use in gastrointestinal disease.

The neuropeptide Y (NPY), peptide YY (PYY) and pancreatic polypeptide (PP) family of hormones exhibit a wide variety of biological actions on the mammalian gastrointestinal tract through known G-protein coupled receptor pathways. At least four receptor subtypes, denoted as Y(1), Y(2), Y(4) an Y(5), each with specific affinities to NPY ligands, serve as regulators of mucosal function, gastrointestinal motility and secretion. Investigations to date, however, have implicated the NPY peptides as mediators in the pathogenesis of numerous gastrointestinal disorders, including malabsorption, short gut, inflammatory bowel diseases, and forms of pancreatitis. Our understanding of these diseases and the interactions of NPY peptides have been advanced by the development of receptor agonists and antagonists that can be used experimentally in animal models. Potent selective PYY agonists have been developed that exhibit clinical potential as proabsorptive agents. NPY receptor agonists and antagonists as well as mice harboring null mutations in the Y(1) and Y(4) receptors have provided novel approaches in preventing intestinal inflammation and diarrhea. The use of competitive antagonists and Y(2) receptor knockouts have also aided in understanding secretory tone and electrogenic ion transport in the colon. In the pancreas, PYY suppresses amylase and cytokine release, which would be desirable in the clinical therapy of pancreatitis. Protein/DNA array analysis has revealed that PYY reduces transcription factor binding activity and disrupts signal transduction pathways activated by TNF-alpha in acinar cells. The present review gives an overview of NPY research in gastrointestinal disease and discusses its clinical relevance and potential use as therapy.