bluuebunny/crossref_metadata_2025 huggingface dataset:
Development and functional anatomy of pods of Colophospermum mopane (Caesalpinioideae: Dietarieae)
Authors: Jordaan A. , Krüger H.
Published: February 2005

Pod development of Colophospermum mopane was studied from its initiation until it was fully developed and completely filled by the seed. After fertilisation, meristematic activity in various regions of the pericarp causes fruit enlargement. The carpel symmetry and vascularisation displayed by the pods is of the follicular type. One dorsal and two unfused ventral bundles supply the pod. The funicle originates from one of the ventral bundles. The vascular supply of both the dorsal and ventral bundles is elaborate as secondary growth of a cambium increases the diameters of the bundles significantly. During early stages of fruit development the 3–5 innermost parenchyma layers of the mesophyll that borders the inner epidermis differentiate into small thin-walled parenchyma cells that differ considerably in size from the larger outer parenchymatous mesophyll cells. The inner zone of small parenchyma cells eventually differentiates into several collenchyma layers. At a later stage, the innermost parenchyma cells next to the collenchyma layers differentiate into sclerenchyma. As the fruit expands laterally, new vascular bundles continue to differentiate towards the centre of the fruit from the ground parenchyma of the dorsal fruit margin. The area of the fruit margin that is occupied by vascular bundles eventually becomes extensive. The xylem and phloem in the dorsal fruit margin are separated by a cambium. When the pod is mature the cell walls of the parenchymatous mesocarp become thickened and lignified, whereas the collenchymatous stratum becomes partly sclerenchymatous. The zone where the follicle eventually opens is characterised by thick-walled unlignified parenchyma cells between the two ventral bundles at the ventral suture. This unlignified zone is closely connected to the sclerenchymatous flanges of the ventral vascular bundles. The outer epidermis of mature brown pods consists of cells with thick lignified and cutinised walls. The mesophyll of fully developed pods consists of an outer stratum of mesophyll cells with lignified walls and an inner stratum of three or four layers of cells with unlignified walls. The unlignified zone is bordered by a sclerenchymatous stratum that originated from the inner mesophyll layers bordered by another sclerenchymatous stratum that originated from the outer layers of the collenchymatous stratum. The walls of the inner layers of the collenchymatous stratum remain unlignified. Between the sclerenchymatous and non-sclerenchymatous zone of the original collenchyma layers is a transition zone where secondary walls are present but they are unlignified or in various stages of lignification. The inner sclerenchymatous layers of the pericarp probably have a protective function. The inner collenchymatous layers may contribute to fruit opening under dry conditions. The usual method of fruit opening is, however, when the seed forces the fruit valves apart during imbibition.
A novel in vitro rooting method employing an aerobic medium
Authors: Newell Chris , Growns Digby J. , McComb Jen A.
Published: February 2005

The beneficial influence of an aerobic propagation medium for in vitro cultures during the rooting phase was found for 28 Australian species and genotypes from the families Liliaceae, Haemodoraceae, Myrtaceae, Thymelaeaceae, Proteaceae, Goodeniaceae and Rutaceae. Microcuttings from established shoot cultures were pulsed for 7 days in the dark on a high-auxin (40 µM indole-3-butyric acid, IBA), agar-solidified medium. The microcuttings were then transferred either to an agar-solidified medium without plant-growth regulators (M1) or a sterile propagation mix. The protocol utilising propagation mix used is referred to as IVS (in vitro soil-less medium). The pulsed cuttings in agar or IVS were placed in the culture room under standard light and temperature regimes and allowed to root. When compared over two harvest times, the use of IVS as a rooting medium gave consistent improvements over the use of M1 medium for percentage rooting, average total root length and root number per microcutting. In total, 27 of the 28 species tested rooted in IVS medium at equal or better rates than in M1. In three cases, Actinodium cunninghamii, one of the genotypes of Pimelea physodes and one of the genotypes of Eriostemon australasis shoots did not root in M1 but showed good root development in IVS medium. With few exceptions, average root length and root number in microcuttings rooted in IVS were superior to the lengths and numbers recorded in agar medium. The materials handing advantages and the application of IVS are discussed.
Effects of leaf age and psyllid damage on the spectral reflectance properties of Eucalyptus saligna foliage
Authors: Stone Christine , Chisholm Laurie , McDonald Simon
Published: February 2005

Leaf chlorophyll content is influenced directly by many environmental stress factors. Because leaf pigment absorption is wavelength dependent, numerous narrow-band reflectance-based indices have been proposed as a means of assessing foliar health and condition. Chlorophyll content, however, also varies with leaf developmental stage. In this study, a range of morphological and physiological traits including insect damage, relative chlorophyll content (SPAD values), chlorophyll fluorescence (Fv/Fm) and reflectance spectra was measured of leaves sampled from mature Eucalyptus saligna. Relative differences among three leaf-age cohorts were compared with differences obtained from mature leaves that were either healthy or infested with the psyllid Glycaspis baileyi. Differences in relative chlorophyll content were greater between immature and mature foliage than between damaged and healthy mature leaves. These differences were confirmed in the comparisons of reflectance spectra and indices. As many eucalypt species have opportunistic crown phenology and long-lived leaves, leaf-age composition of crowns needs to be taken into account when applying reflectance-based indices to assess foliar condition of eucalypts.
Probing site-specific conformational distributions in protein folding with solid-state NMR
Authors: Havlin Robert H. , Tycko Robert
Published: February 2005

We demonstrate an experimental approach to structural studies of unfolded and partially folded proteins in which conformational distributions are probed at a site-specific level by 2D solid-state
13
C NMR spectroscopy of glassy frozen solutions. Experiments on chemical denaturation of the 35-residue villin headpiece subdomain, a model three-helix-bundle protein with a known folded structure, reveal that
13
C-labeled residues in the three helical segments of the folded state have markedly different conformational distributions in the unfolded state. Moreover, the 2D solid-state NMR line shapes near the unfolding midpoint do not fit a simple two-state model, in which the conformational distributions of the unfolded component are assumed to be independent of denaturant concentration. Comparison with solid-state NMR spectra of peptides containing the individual helical segments suggests an alternative two-step description of conformational distributions in partially folded states of the helical villin headpiece subdomain, in which chemical denaturation is viewed as a disruption of tertiary contacts followed by equilibration of local secondary structure according to the intrinsic helical propensities of individual segments.
Preparation of new organotin polymers via exchange reactions
Authors: Azab M.M. , El‐Dougdoug W.I.A.
Published: February 2005

Purpose

Preparation of new organotin polymers via a new synthetic route based on the exchange reactions of pentachlorophenyl acrylate or methacrylate with amino‐tri‐phenyltin benzoates or hydroxyl‐tri‐phenyltin benzoates.

Design/methodology/approach

The pentachlorophenyl acrylate or methacrylate was prepared by polymerisation in solution with azobisisobutyrontrile as a free radical initiator. The polymers obtained were allowed to undergo exchange reactions with amino‐tri‐phenyltin benzoates or hydroxyl‐tri‐phenyltin benzoates. The structure of the polymers prepared was confirmed by IR spectroscopy. Films were prepared from purified organotin polymers solution on glass, PVC and tin plates. The release of tin compound from the films, when immersed in aqueous media, was assessed. The concentration of the released tin (ppm) was measured by atomic adsorption spectrophotometer.

Findings

The new synthetic route was effective, the organotin polymers prepared had good film properties and the release of tin compounds increased with the content of tin in the organotin polymers.

Research limitations/implications

The alkaline resistance of the polymeric films prepared needs improvement.

Practical implications

The polymers prepared provide a family of effective polymeric fungicide useful for a number of applications including water sterilisation.

Originality/value

The polymers prepared contained pendent triphenyltin moieties which slowly hydrolysed to give fungicidal and antifouling effects.
Structural and mechanistic studies of chloride induced activation of human pancreatic α‐amylase
Authors: Maurus Robert , Begum Anjuman , Kuo Hsin‐Hen , Racaza Andrew , Numao Shin , Andersen Carsten , Tams Jeppe W. , Vind Jesper , Overall Christopher M. , Withers Stephen G. , Brayer Gary D.
Published: February 2005

The mechanism of allosteric activation of α‐amylase by chloride has been studied through structural and kinetic experiments focusing on the chloride‐dependent N298S variant of human pancreatic α‐amylase (HPA) and a chloride‐independent TAKA‐amylase. Kinetic analysis of the HPA variant clearly demonstrates the pronounced activating effect of chloride ion binding on reaction rates and its effect on the pH‐dependence of catalysis. Structural alterations observed in the N298S variant upon chloride ion binding suggest that the chloride ion plays a variety of roles that serve to promote catalysis. One of these is having a strong influence on the positioning of the acid/base catalyst residue E233. Absence of chloride ion results in multiple conformations for this residue and unexpected enzymatic products. Chloride ion and N298 also appear to stabilize a helical region of polypeptide chain from which projects the flexible substrate binding loop unique to chloride‐dependent α‐amylases. This structural feature also serves to properly orient the catalytically essential residue D300. Comparative analyses show that the chloride‐independent α‐amylases compensate for the absence of bound chloride by substituting a hydrophobic core, altering the manner in which substrate interactions are made and shifting the placement of N298. These evolutionary differences presumably arise in response to alternative operating environments or the advantage gained in a particular product profile. Attempts to engineer chloride‐dependence into the chloride‐independent TAKA‐amylase point out the complexity of this system, and the fact that a multitude of factors play a role in binding chloride ion in the chloride‐dependent α‐amylases.
Impact of remote mutations on metallo‐β‐lactamase substrate specificity: Implications for the evolution of antibiotic resistance
Authors: Oelschlaeger Peter , Mayo Stephen L. , Pleiss Juergen
Published: February 2005

Metallo‐β‐lactamases have raised concerns due to their ability to hydrolyze a broad spectrum of β‐lactam antibiotics. The G262S point mutation distinguishing the metallo‐β‐lactamase IMP‐1 from IMP‐6 has no effect on the hydrolysis of the drugs cephalothin and cefotaxime, but significantly improves catalytic efficiency toward cephaloridine, ceftazidime, benzylpenicillin, ampicillin, and imipenem. This change in specificity occurs even though residue 262 is remote from the active site. We investigated the substrate specificities of five other point mutants resulting from single‐nucleotide substitutions at positions near residue 262: G262A, G262V, S121G, F218Y, and F218I. The results suggest two types of substrates: type I (nitrocefin, cephalothin, and cefotaxime), which are converted equally well by IMP‐6, IMP‐1, and G262A, but even more efficiently by the other mutants, and type II (ceftazidime, benzylpenicillin, ampicillin, and imipenem), which are hydrolyzed much less efficiently by all the mutants. G262V, S121G, F218Y, and F218I improve conversion of type I substrates, whereas G262A and IMP‐1 improve conversion of type II substrates, indicating two distinct evolutionary adaptations from IMP‐6. Substrate structure may explain the catalytic efficiencies observed. Type I substrates have R2 electron donors, which may stabilize the substrate intermediate in the binding pocket. In contrast, the absence of these stabilizing interactions with type II substrates may result in poor conversion. This observation may assist future drug design. As the G262A and F218Y mutants confer effective resistance to Escherichia coli BL21(DE3) cells (high minimal inhibitory concentrations), they are likely to evolve naturally.
Contributions of hydrophobic domain interface interactions to the folding and stability of human γD‐crystallin
Authors: Flaugh Shannon L. , Kosinski‐Collins Melissa S. , King Jonathan
Published: February 2005

Human γD‐crystallin (HγD‐Crys) is a monomeric eye lens protein composed of two highly homologous β‐sheet domains. The domains interact through interdomain side chain contacts forming two structurally distinct regions, a central hydrophobic cluster and peripheral residues. The hydrophobic cluster contains Met43, Phe56, and Ile81 from the N‐terminal domain (N‐td) and Val132, Leu145, and Val170 from the C‐terminal domain (C‐td). Equilibrium unfolding/refolding of wild‐type HγD‐Crys in guanidine hydrochloride (GuHCl) was best fit to a three‐state model with transition midpoints of 2.2 and 2.8 M GuHCl. The two transitions likely corresponded to sequential unfolding/refolding of the N‐td and the C‐td. Previous kinetic experiments revealed that the C‐td refolds more rapidly than the N‐td. We constructed alanine substitutions of the hydrophobic interface residues to analyze their roles in folding and stability. After purification from E. coli, all mutant proteins adopted a native‐like structure similar to wild type. The mutants F56A, I81A, V132A, and L145A had a destabilized N‐td, causing greater population of the single folded domain intermediate. Compared to wild type, these mutants also had reduced rates for productive refolding of the N‐td but not the C‐td. These data suggest a refolding pathway where the domain interface residues of the refolded C‐td act as a nucleating center for refolding of the N‐td. Specificity of domain interface interactions is likely important for preventing incorrect associations in the high protein concentrations of the lens nucleus.
Dynamics of the gp130 cytokine complex: A model for assembly on the cellular membrane
Authors: Schroers Andreas , Hecht Oliver , Kallen Karl‐Josef , Pachta Michael , Rose‐John Stefan , Grötzinger Joachim
Published: February 2005

Cytokines of the interleukin‐6 (IL‐6)‐type family all bind to the glycoprotein gp130 on the cell surface and require interaction with two gp130 or one gp130 and another related signal transducing receptor subunit. In addition, some cytokines of this family, such as IL‐6, interleukin‐11, ciliary neurotrophic factor, neuropoietin, cardiotrophin‐1, and cardiotrophin‐1‐like‐cytokine, interact with specific ligand binding receptor proteins. High‐ and low‐affinity binding sites have been determined for these cytokines. So far, however, the stoichiometry of the signaling receptor complexes has remained unclear, because the formation of the cytokine/cytokine‐receptor complexes has been analyzed with soluble receptor components in solution, which do not necessarily reflect the situation on the cellular membrane. Consequently, the binding affinities measured in solution have been orders of magnitude below the values obtained with whole cells. We have expressed two gp130 extracellular domains in the context of a Fc‐fusion protein, which fixes the receptors within one dimension and thereby restricts the flexibility of the proteins in a fashion similar to that within the plasma membrane. We measured binding of IL‐6 and interleukin‐b receptor (IL‐6R) by means of fluorescence‐correlation spectroscopy. For the first time we have succeeded in recapitulating in a cell‐free condition the binding affinities and dynamics of IL‐6 and IL‐6R to the gp130 receptor proteins, which have been determined on whole cells. Our results demonstrate that a dimer of gp130 first binds one IL‐6/IL‐6R complex and only at higher ligand concentrations does it bind a second IL‐6/IL‐6R complex. This view contrasts with the current perception of IL‐6 receptor activation and reveals an alternative receptor activation mechanism.
Test of the Binding Threshold Hypothesis for olfactory receptors: Explanation of the differential binding of ketones to the mouse and human orthologs of olfactory receptor 912‐93
Authors: Hummel Patrick , Vaidehi Nagarajan , Floriano Wely B. , Hall Spencer E. , Goddard William A.
Published: February 2005

We tested the Binding Threshold Hypothesis (BTH) for activation of olfactory receptors (ORs): To activate an OR, the odorant must bind to the OR with binding energy above some threshold value. The olfactory receptor (OR) 912‐93 is known experimentally to be activated by ketones in mouse, but is inactive to ketones in human, despite an amino acid sequence identity of ∼66%. To investigate the origins of this difference, we used the MembStruk first‐principles method to predict the tertiary structure of the mouse OR 912‐93 (mOR912‐93), and the HierDock first‐principles method to predict the binding site for ketones to this receptor. We found that the strong binding of ketones to mOR912‐93 is dominated by a hydrogen bond of the ketone carbonyl group to Ser105. All ketones predicted to have a binding energy stronger than EBindThresh = 26 kcal/mol were observed experimentally to activate this OR, while the two ketones predicted to bind more weakly do not. In addition, we predict that 2‐undecanone and 2‐dodecanone both bind sufficiently strongly to activate mOR912‐93. A similar binding site for ketones was predicted in hOR912‐93, but the binding is much weaker because the human ortholog has a Gly at the position of Ser105. We predict that mutating this Gly to Ser in human should lead to activation of hOR912‐93 by these ketones. Experimental substantiations of the above predictions would provide further tests of the validity of the BTH, our predicted 3D structures, and our predicted binding sites for these ORs.
Structure and mechanism of ADP‐ribose‐1″‐monophosphatase (Appr‐1″‐pase), a ubiquitous cellular processing enzyme
Authors: Kumaran Desigan , Eswaramoorthy Subramaniam , Studier F. William , Swaminathan Subramanyam
Published: February 2005

Appr‐1″‐pase, an important and ubiquitous cellular processing enzyme involved in the tRNA splicing pathway, catalyzes the conversion of ADP‐ribose‐1″monophosphate (Appr‐1″‐p) to ADP‐ribose. The structures of the native enzyme from the yeast and its complex with ADP‐ribose were determined to 1.9 Å and 2.05 Å, respectively. Analysis of the three‐dimensional structure of this protein, selected as a target in a structural genomics project, reveals its putative function and provides clues to the catalytic mechanism. The structure of the 284‐amino acid protein shows a two‐domain architecture consisting of a three‐layer αβα sandwich N‐terminal domain connected to a small C‐terminal helical domain. The structure of Appr‐1″‐pase in complex with the product, ADP‐ribose, reveals an active‐site water molecule poised for nucleophilic attack on the terminal phosphate group. Loop‐region residues Asn 80, Asp 90, and His 145 may form a catalytic triad.
Microsecond timescale backbone conformational dynamics in ubiquitin studied with NMR R1ρ relaxation experiments
Authors: Massi Francesca , Grey Michael J. , Palmer Arthur G.
Published: February 2005

NMR spin relaxation experiments are used to characterize the dynamics of the backbone of ubiquitin. Chemical exchange processes affecting residues Ile 23, Asn 25, Thr 55, and Val 70 are characterized using on‐ and off‐resonance rotating‐frame 15N R1ρ relaxation experiments to have a kinetic exchange rate constant of 25,000 sec−1 at 280 K. The exchange process affecting residues 23, 25, and 55 appears to result from disruption of N‐cap hydrogen bonds of the α‐helix and possibly from repacking of the side chain of Ile 23. Chemical exchange processes affecting other residues on the surface of ubiquitin are identified using 1H‐15N multiple quantum relaxation experiments. These residues are located near or at the regions known to interact with various enzymes of the ubiquitin‐dependent protein degradation pathway.
Binding of the anti‐tubercular drug isoniazid to the arylamine N‐acetyltransferase protein from Mycobacterium smegmatis
Authors: Sandy James , Holton Simon , Fullam Elizabeth , Sim Edith , Noble Martin
Published: February 2005

Isoniazid is a frontline drug used in the treatment of tuberculosis (TB). Isoniazid is a prodrug, requiring activation in the mycobacterial cell by the catalase/peroxidase activity of the katG gene product. TB kills two million people every year and the situation is getting worse due to the increase in prevalence of HIV/AIDS and emergence of multidrug‐resistant strains of TB. Arylamine N‐acetyltransferase (NAT) is a drug‐metabolizing enzyme (E.C. 2.1.3.5). NAT can acetylate isoniazid, transferring an acetyl group from acetyl coenzyme A onto the terminal nitrogen of the drug, which in its N‐acetylated form is therapeutically inactive. The bacterium responsible for TB, Mycobacterium tuberculosis, contains and expresses the gene encoding the NAT protein. Isoniazid binds to the NAT protein from Salmonella typhimurium and we report here the mode of binding of isoniazid in the NAT enzyme from Mycobacterium smegmatis, closely related to the M. tuberculosis and S. typhimurium NAT enzymes. The mode of binding of isoniazid to M. smegmatis NAT has been determined using data collected from two distinct crystal forms. We can say with confidence that the observed mode of binding of isoniazid is not an artifact of the crystallization conditions used. The NAT enzyme is active in mycobacterial cells and we propose that isoniazid binds to the NAT enzyme in these cells. NAT activity in M. tuberculosis is likely therefore to modulate the degree of activation of isoniazid by other enzymes within the mycobacterial cell. The structure of NAT with isoniazid bound will facilitate rational drug design for anti‐tubercular therapy.
Damages Caps, Insurability, and the Performance of Medical Malpractice Insurance
Authors: Viscusi W. Kip , Born Patricia H.
Published: February 2005

Abstract

This article uses the complete property‐casualty insurance files of the National Association of Insurance Commissioners from 1984 to 1991 to assess the effect of medical malpractice reforms pertaining to damages levels and the degree to which these damages are insurable. Limits on noneconomic damages were most influential in affecting insurance market outcomes. Several punitive damages variables specifically affected the medical malpractice insurance market, including limits on punitive damage levels, prohibitions of the insurability of punitive damages, and prohibition of punitive damages awards. Estimates for insurance losses, premiums, and loss ratios indicate effects of reform in the expected directions, where the greatest constraining effects were for losses. The quantile regression analysis of losses indicates that punitive damages reforms and limits were most consequential for firms at the high end of the loss spectrum. Tort reforms also enhanced insurer profitability during this time period.
Trust as a foundation for the therapeutic intervention for patients with borderline personality disorder
Authors: LANGLEY G. C. , KLOPPER H.
Published: February 2005

A qualitative, exploratory, descriptive and contextual study using an ‘interpretive descriptive approach’ was undertaken in order to develop a practice‐level model for the facilitation of mental health of patients diagnosed as having Borderline Personality Disorder by the community psychiatric nurse. The context of the study was the in the Psychiatric Community Services in the greater Johannesburg region, South Africa. Individual and focus group interviews were conducted with patients and mental health clinicians representing the multidisciplinary team with experience in managing the condition, either in a personal capacity or as professional mental health practitioners. Themes extrapolated from the transcribed interviews were further explored and a practice‐based theory was constructed. This article reports on the first theme ‘Trust’, the concept identified by both patients and clinicians as crucial for the establishment and maintenance of the therapeutic relationship that forms the vehicle for care of patients with this disorder in psychiatric mental health care.
A system of patient classification in long‐term sychiatric inpatients: Resource Utilization Groups T‐18 (RUG T‐18)
Authors: IGLESIAS C. , ALONSO VILLA M. J.
Published: February 2005

This paper shows the application of a ‘case mix’ system (Resources Utilization Groups T18 or RUG‐T18) to a Spanish long‐term inpatient psychiatric sample. Objective: To examine the capacity of RUG‐T18 to predict patient resource use (spent time of care) in a long‐term psychiatric sample. Subjects and research design: Data included an assessment of 163 patients’ characteristics, corresponding to groups of the RUG‐T18, and detailed measurement of nursing staff care over a 24‐h period. Results: ‘Severe behavioural problems’ was the most frequent RUG‐T18 category. There were significant differences in the spent time of care in the different groups and high variability in the distribution of time of care within groups and in the total sample. Conclusions: The RUG T‐18 system should be improved to become a useful case mix system in long‐term psychiatric inpatients. The high variance intragroups could be minimized improving the psychopathological aspects of the system.
Population pharmacokinetics of isoniazid in the treatment of Mycobacterium tuberculosis among Asian and African elephants (Elephas maximus and Loxodonta africana)
Authors: MASLOW J. N. , MIKOTA S. K. , ZHU M. , ISAZA R. , PEDDIE L. R. , DUNKER F. , PEDDIE J. , RIDDLE H. , PELOQUIN C. A.
Published: February 2005

We recently described the clinical presentation and treatment of 18 elephants from six herds infected with TB. Treatment protocols and methods varied between herds to include both oral and rectal dosing using multiple drug doses and formulations. In this paper we present information regarding the pharmacokinetics (PK) of isoniazid (INH) in elephants and provide suggestions regarding initial treatment regimens. Forty‐one elephants received INH daily by either oral or rectal administration with different formulations. Population PK analysis was performed using Non‐linear Mixed Effect Modeling (NONMEM). Results of oral administration indicated that compared with premixed INH solution, the drug exposure was highest with a suspension prepared freshly with INH powder. When INH was concomitantly given as an admixture over food, Tmax was delayed and variability in drug absorption was significantly increased. Compared with oral administration, similar drug exposures were found when INH was dosed rectally. The data generated suggest that a starting dose of 7.5 mg/kg of INH is appropriate for initial TB treatment in elephants when premixed solution is administered directly into the oropharynx or rectal vault and 4 mg/kg are when INH is administered following immediate suspension from powdered form.
Pharmacokinetics of azithromycin after intravenous and intramuscular administration to goats
Authors: CÁRCELES C. M. , FONT A. , ESPUNY A. , FERNÁNDEZ‐VARÓN E. , SERRANO J. M. , ESCUDERO E.
Published: February 2005

Azithromycin is the first of a class of antimicrobial agents designated azalides. The aim of the present study was to investigate the disposition pharmacokinetics of azithromycin in goats and determine its bioavailability. A cross‐over study was carried out in two phases separated by 30 days. Azithromycin was administered at a single dose of 20 mg/kg body weight by i.v. and i.m. routes. Plasma concentrations of azithromycin were determined by a modified agar diffusion bioassay. After a single i.v. dose plasma concentrations were best fitted to a three‐compartment open model. A two‐compartment open model with first‐order absorption fitted best after i.m. administration. The values of the pharmacokinetic parameters after i.v. administration were: half‐life 32.5 h, apparent volume of distribution at the steady‐state 34.5 L/kg, clearance 0.85 L/kg. and mean residence time (MRT) 40.1 h. After i.m. administration half‐life of 45.2 h, a MRT of 60.3 h, maximum plasma concentration 0.64 mg/L and a bioavalability 92.2% were obtained. The pharmacokinetic parameters of azithromycin after i.m. administration, principally its long half‐life and high bioavailability, could provide an alternative to the oral route of administration in goats, although more studies are needed to establish a suitable pharmaceutical formulation, propose optimun dosage regimens, investigate clinical efficacy and study the tolerability of repeated doses.
Distribution of emamectin benzoate in Atlantic salmon (Salmo salar L.)
Authors: SEVATDAL S. , MAGNUSSON Å. , INGEBRIGTSEN K. , HALDORSEN R. , HORSBERG T. E.
Published: February 2005

The aims of this study were to investigate the content of emamectin in blood, mucus and muscle following field administration of the recommended dose, and correlation with sea lice infection on the same fish (elimination study). The tissue distribution of tritiated emamectin benzoate after a single oral dose in Atlantic salmon was also investigated by means of whole‐body autoradiography and scintillation counting (distribution study). In the elimination study, concentrations of emamectin benzoate reached maximum levels of 128, 105 and 68 ng/g (p.p.b.) for blood, mucus and muscle respectively, on day 7, the last day of administration. From day 7, the concentration in the blood declined until concentration was less than the limit of detection on day 77. The concentration was higher in mucus compared with plasma (P < 0.05) except on days 7 and 21. The concentration of emamectin benzoate decreased gradually from the end of treatment (day 7) to day 70 with half‐lives of 9.2, 10.0 and 11.3 days in muscle, plasma and mucus respectively. The distribution study demonstrated a high quantity of radioactivity in mucous membranes (gastrointestinal tract, gills) throughout the observation period (56 days). Activity was high in the epiphysis, hypophysis and olfactory rosette throughout the study. The highest activity was observed in the bile, indicating this to be an important route for excretion. The distribution study confirmed the results from the elimination study with respect to concentrations in blood, skin mucous and muscle.
Pharmacokinetics of dexamethasone with pharmacokinetic/pharmacodynamic model of the effect of dexamethasone on endogenous hydrocortisone and cortisone in the horse
Authors: SOMA L. R. , UBOH C. E. , LUO Y. , GUAN F. , MOATE P. J. , BOSTON R. C.
Published: February 2005

A compartmental model was used to describe the pharmacokinetics of dexamethasone (DXM) and changes in the plasma concentration of endo‐genous cortisone (COR) and hydrocortisone (HYD) following intravenous (i.v.) administration of DXM (0.05 mg/kg) in horses. Quantification of DXM, COR and HYD in equine plasma was achieved using liquid chromatography interfaced with triple spray quadrupole quantum tandem mass spectrometry (LC/TSQ‐MS/MS). The median alpha (t1/2α), beta (t1/2β), and gamma (t1/2γ) half‐lives were 0.33, 2.2, and 10.7 h respectively. The area under the DXM plasma concentration curve (AUC) was 113.5 ng·h/mL. At 72 h post‐DXM administration, the plasma concentration of DXM in all horses was below the level of quantification (100 pg/mL). The baseline plasma concentration of COR was 3.5 ± 0.69 ng/mL and declined significantly (P < 0.02) to 2.9 ± 0.86 ng/mL at 1 h. The nadir in COR plasma concentration was 0.65 ± 0.12 ng/mL at 28.8 ± 9.0 h, and the DXM plasma concentration was 0.19 ± 0.13 ng/mL. COR concentration returned to baseline at 96 h. Baseline plasma concentration of HYD was 58.8 ± 11.7 ng/mL and declined significantly (P < 0.001) to 41.1 ± 14.9 ng/mL at 1 h following DXM administration but recovered to baseline at 96 h. The sensitivity of LC/TSQ‐MS/MS allowed complete description of the pharmacokinetics of DXM and its effect on plasma concentrations of both COR and HYD.
Differential usage of photoreceptors for chalcone synthase gene expression during plant development
Authors: Frohnmeyer Hanns , Ehmann Bruno , Kretsch Thomas , Rocholl Martin , Harter Klaus , Nagatani Akira , Furuya Masaki , Batschauer Alfred , Hahlbrock Klaus , Schäfer Eberhard
Published: February 2005

Photoregulation of chalcone synthase (CHS) mRNA accumulation was analysed in parsley (Petroselinum crispum) and mustard (Sinapis alba) plants at different developmental stages. In both species, CHS mRNA accumulation in young etiolated seedlings was primarily under phytochrome control. In leaves of adult re‐etiolated plants, a UV‐B photoreceptor was predominantly involved in photocontrol. The reduced red light control in mature leaves was not due to the absence of immunoreactive phytochrome. The apparent dependence of photoreceptor usage on the developmental state of the cell or organism was in accordance with observations on the photoregulation of fusion constructs between CHS promoters from parsley or mustard and the β‐glucuronidase reporter gene (GUS). When tested in the parsley protoplast transient expression system, both constructs yielded the same type of photoregulation as observed for the endogenous CHS gene.
Differential gene expression during somatic embryogenesis in Digitalis Ianata analyzed by in vivo and in vitro protein synthesis
Authors: Reinbothe Christiane , Tewes Annegret , Luckner Martin , Reinbothe Steffen
Published: February 2005

During somatic embryogenesis in Digitalis Ianata, proembryogenic masses (PEMs) develop into globular‐, heart‐ and torpedo‐shaped embryos. The morphogenesis is correlated with drastic alterations in the composition of cellular and extracellular polypeptides. By comparing the spectra of in vivo translated polypeptides after two‐dimensional gel electrophoresis, three main classes of polypeptides were distinguished: (i) decreasing proteins; (ii) increasing proteins; (iii) constitutive polypeptides. Distinct subclasses of PEM‐ and embryo‐specific proteins could be discerned. The embryo‐specific polypeptides reached the highest relative prevalence in either the globular‐, heart‐ or torpedo‐shaped embryos and were not expressed in a non‐embryogenic cell line of D. Ianata, strain 119, indicating their temporally defined and embryogenesis‐related pattern of expression.

The alterations of protein synthesis did not correlate with corresponding changes in the spectrum of abundant in vitro ‐translatable mRNAs. Relatively few PEM‐and embryo‐specific mRNAs could be discerned from constitutive messengers suggesting a posttranscriptional mode of control for the majority of protein genes during embryogenesis. However, for those in vitro synthesized (homologous) polypeptides which had a counterpart of identical isoelectric point and relative molecular mass among the in vivo translated polypeptides, a transcriptional type of gene expression was implied, since the mRNA content and the in vivo rate of protein synthesis changed similarly.
A multi‐recombination model for the mtDNA rearrangements seen in maize cmsT regenerated plants
Authors: Fauron Christiane M.‐R. , Casper Mark , Gesteland Raymond , Albertsen Marc
Published: February 2005

Regeneration of plants from maize cytoplasmic male sterile type T (cmsT) callus tissue culture promotes, in some instances, genetic variability in their mitochondrial genomes. These mutations have been analyzed in various cmsT regenerated plants that have or have not regained the male fertile phenotype.

A unique multi‐recombination model explains the various mitochondrial genome rearrangements. First, recombination involving two different sets of direct repeats gives rise to subgenomic recombinant circles. Second, intermolecular recombination between some selected subgenomes gives rise to a new rearranged master chromosome.

The consequence of these events is the formation of a new master chromosome containing sequence deletions and duplications when compared to the progenitor. This new mitochondrial genome seems stable, although it does not contain the entire genetic complexity of the progenitor.
Preparedness for rural community leadership and its impact on practice location of family medicine graduates
Authors: Woloschuk Wayne , Crutcher Rodney , Szafran Olga
Published: February 2005

Objective:  To identify non‐clinical dimensions of preparedness for rural practice and to determine whether preparedness for rural practice is predictive of rural practice location.

Design:  Cross‐sectional postal survey mailed in 2001.

Setting:  Communities across Canada where graduates were practising.

Subjects:   Graduates (n = 369) of the family medicine residency program at the universities of Alberta (U of A) and Calgary (U of C) between 1996 and 2000, inclusive.

Interventions:  Using a 4‐point scale, graduates rated the extent to which the residency program prepared them for eight dimensions of rural practice: clinical demands of rural practice, understanding rural culture, small community living, balancing work and personal life, establishing personal/professional boundaries, becoming a community leader, handling a ‘fish bowl’ lifestyle, and choosing a suitable community.

Main outcome measure:  Identification of non‐clinical dimensions of preparedness for rural practice and whether scores on preparedness scales are predictive of rural practice location.

Results:  The overall response rate was 76.4%. Factor analysis of the eight preparedness items produced two factors, ‘rural culture’ and ‘rural community leader’ which explained 72% of the variance. The alpha coefficient for each factor was 0.87. Odds ratios revealed that family medicine graduates prepared for rural community leadership roles were 1.92 (CI = 1.03–3.61) times more likely to be in rural practice. Rural physicians were also 2.14 (CI = 1.13–4.03) times as likely to have a rural background.

Conclusions:  Preparedness to be a rural community leader and having a rural background were predictive of rural practice. Educators should consider this in both family medicine residency admissions policy and practice and when designing and implementing family medicine residency curricula.
Caring for depressed patients in rural communities: general practitioners’ attitudes, needs and relationships with mental health services
Authors: Wright Megan J. , Harmon Karen D. , Bowman Jennifer A. , Lewin Terry J. , Carr Vaughan J.
Published: February 2005

Objective:  To examine the needs and practices of rural GPs and their relationships with local acute mental health services, particularly in the provision of care to depressed patients.

Design:  Postal survey.

Setting:  Rural general practices.

Subjects:  Ninety‐nine GPs (63 males, 36 females) from the Hunter Valley region of NSW, Australia.

Main outcome measures:  GPs’ self‐reported contact rates, confidence, needs and beliefs.

Results:  Depression was the most commonly seen mental disorder, with an average of 1.44 patients per GP per month referred to local acute mental health services, most commonly for suicidality. The preferred form of feedback after the referral of a depressed patient was a follow‐up letter, while the most requested type of patient management support was cognitive behavioural therapy (CBT) groups. GPs were most confident in recognising depression, compared to other mental disorders except anxiety, and they were most confident in treating depression, compared to all other mental disorders. The most common barrier to providing care for depressed patients was reported to be ‘time constraints’ on GPs.

Conclusions:  The challenge for mental health services is to develop ways to collaborate more effectively with GPs in the provision of psychological services for depressed patients in rural communities.
What factors influence survival in patients with unresected synchronous liver metastases after resection of colorectal cancer?
Authors: Chafai N. , Chan C. L. H. , Bokey E. L. , Dent O. F. , Sinclair G. , Chapuis P. H.
Published: February 2005

Objective  The aim of this study was to determine whether the survival of patients with untreated synchronous liver metastases after resection of a colorectal cancer was associated with any features of the primary tumour.

Methods  Information for 398 consecutive patients with unresected liver metastases in the period 1971–2001 was examined by multivariate survival analysis.

Results  Of 19 clinical and pathological variables considered, survival was independently associated only with residual tumour in a line of resection (hazard ratio (HR) 1.95), venous invasion (HR 1.87), right colonic tumour (HR 1.68), lymph node metastasis (HR 1.54), and extra‐hepatic metastasis (HR 1.16); 8.3% of patients had none of these adverse features. Their 2‐year overall survival rate was 39.2%, compared with only 16.5% (P < 0.001) in those with one or more adverse features.

Conclusions  These findings may assist in selecting patients most likely to benefit from treatment of hepatic metastases and in counselling patients and their relatives.
Ano‐cutaneous flap repair for complex and recurrent supra – sphincteric anal fistula
Authors: Hossack T. , Solomon M. J. , Young J. M.
Published: February 2005

Background  Suprasphincteric fistulae remain the most difficult to cure.

Objectives  The purpose of this study was to evaluate the healing rate of suprasphincteric anal fistula treated by ano‐cutaneous advancement flap repair, and the impact of this procedure on continence and quality of life.

Method  Sixteen patients with complex, recurrent or chronic suprasphincteric fistulae associated with significant tissue damage (necrotizing fasciitis, keyhole deformity and anal stenosis) or who had failed previous surgical procedures were treated by ano‐cutaneous flap closure. They were assessed pre and postoperatively by the treating surgeon for wound healing and fistula recurrence and later followed up by phone interview using the St Mark's Hospital incontinence score and the Perianal Disease Activity Index (PDAI) as indicators of treatment outcome.

Results  Fifteen patients had successful healing of their fistula with the cutaneous flap, with recurrence in only one. The most common short‐term complications were minor graft site wound separation, which healed in all cases without intervention, and wound pain, which settled over time and was not associated with recurrence. Continence improved for almost 70% of the patients, with a significant reduction in St Mark's incontinence scores (t = 2.62, 15 d.f., P = 0.02). PDAI also decreased significantly (t = 7.55, 15 d.f., P < 0.001), demonstrating improvement in quality of life for most patients.

Conclusion  Ano‐cutaneous flap can achieve healing of complex and recurrent suprasphincteric anal fistula in patients who had previously failed at other forms of treatment thus improving their quality of life and continence.
Rifaximin‐ciprofloxacin combination therapy is effective in chronic active refractory pouchitis
Authors: Abdelrazeq A. S. , Kelly S. M. , Lund J. N. , Leveson S. H.
Published: February 2005

Objective  Treatment of chronic refractory pouchitis is often difficult and disappointing and some of the affected pouches subsequently fail. This study was conducted to evaluate the efficacy and tolerability of treatment with rifaximin, a nonabsorbable oral antibiotic with immunomdulatory functions, in combination with ciprofloxacin for chronic active refractory pouchitis.

Patients and methods  Eight patients with chronic active refractory pouchitis were treated orally with a combination of rifaximin 1 g b.d and ciprofloxacin 500 mg b.d. for two weeks. Clinical assessment, endoscopic and histological evaluations were performed before and after therapy using the Pouchitis Disease Activity Index (PDAI) score. Improvement was defined as a decrease of at least three points in the PDAI score and remission as a PDAI score of 0. The Wilcoxon signed rank test was used to compare pre‐ and post‐treatment PDAI scores. The long‐term outcome of the treated patients was prospectively monitored.

Results  Seven of the eight patients either went into remission (n = 5) or improved (n = 2). The median (range) PDAI scores before and after therapy were 12 (9–18) and 0 (0–15), respectively, (P = 0.018). All patients were compliant and no side effects were reported. Pouchitis recurred in two of the seven responding patients but returned into remission after further courses of the same combination. After a median follow‐up of 30 months, the seven responding patients still had satisfactory pouch function.

Conclusion  Rifaximin‐ciprofloxacin combination therapy is safe and objectively effective in chronic active refractory pouchitis and may salvage a significant percentage of ‘at risk pouches’.
Topographic mediation of growth in high elevation foxtail pine (Pinus balfouriana Grev. et Balf.) forests in the Sierra Nevada, USA
Authors: Bunn Andrew G. , Waggoner Lindsey A. , Graumlich Lisa J.
Published: February 2005

Aim  Climate variability is an important mediating agent of ecosystem dynamics in cold, semi‐arid regions such as the mountains of western North America. Climatically sensitive tree‐ring chronologies offer a means of assessing the impact of climate variability on tree growth across temporal scales of years to centuries and spatial scales of metres to subcontinents. Our goal was to bring practices from landscape ecology that highlight the impact of landscape heterogeneity on ecological pattern and processes into a dendroclimatic study that shows that the biophysical setting of target trees affects ring‐width patterns.

Location  This study was conducted at two sites near alpine treeline in the Sequoia National Park, USA (36°30′ 00′ N, 118°30′ 00′ W).

Methods  We collected stand information and increment cores from foxtail pines (Pinus balfouriana Grev. et Balf.) for eight tree‐ring chronologies in four extreme biophysical settings at two sites using proxies for soil moisture and radiation derived from a digital elevation model.

Results  Biophysical setting affected forest age–class structure, with wet and bright plots showing high recruitment after 1900 ad, but had no obvious effect on immature stem density (e.g. seedlings). Biophysical setting strongly affected ring‐width patterns, with wet plots having higher correlation with instrumental temperature records while dry plots correlated better with instrumental precipitation records. Ring‐width chronologies from the wet plots showed strong low‐frequency variability (i.e. hundreds of years) while ring‐width chronologies from the dry plots showed strong variability on multidecadal scales.

Main conclusions  There was a strong association between biophysical setting and age‐class structure, and with ring‐width patterns in foxtail pine. The mediation of ring widths by biophysical setting has the potential to further the understanding of the expression of synoptic‐scale climate across rugged terrain. When combined with remotely sensed imagery, a priori GIS modelling of tree growth offers a viable means to devise first‐order predictions of climatic impacts in subalpine forest dynamics and to develop flexible and powerful monitoring schemes.