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PubMed2001

Development of a method for mRNA differential display in filamentous fungi: comparison of mRNA differential display reverse transcription polymerase chain reaction and cDNA amplified fragment length polymorphism in Leptosphaeria maculans.

We modified a technique, cDNA-AFLP, for identifying differentially expressed genes in plants to work in the filamentous fungus Leptosphaeria maculans (Desmaz.) Ces. & De Not. The cDNA fragments generated by our method ranged in size from approximately 100 to 400 bps. On average, twice as many cDNA fragments were amplified per primer set with cDNA amplified fragment length polymorphism in comparison with mRNA differential display reverse transcription polymerase chain reaction. The DNA fragments of interest were excised from gels and analyzed by single-stranded conformation polymorphism to eliminate nondifferentially expressed cDNA contamination. The method was used to examine gene expression differences between cultures grown in the presence or absence of an analog of the Brassica phytoalexin brassinin. Eleven of the fourteen fragments examined were determined by reverse Northern blot to be differentially expressed. In examining gene expression differences between young cultures not producing sirodesmins and older cultures that were producing these phytotoxins, we found 17 of 25 fragments were differentially expressed. Northern blots with these fragments confirmed the results.

Ascomycota↗
PubMed1984

Vertebral burst fractures: CT analysis of the retropulsed fragment.

Ten cases of retropulsed thoracolumbar vertebral body fragments that had been documented by CT were reviewed to define and characterize the nature, appearance, and position of the retropulsed fragment. All of the retropulsed fragments arose from the superior aspect of the vertebral body. Five of ten patients had a vertical fracture within the retropulsed fragment. Three of ten fragments had anteriorly rotated 90 degrees +/- 60 degrees, so that the cartilaginous end plate faced anteriorly; also, they had migrated 3-8 mm in a craniad or caudad direction. Six of ten patients had an associated vertical or Y-shaped fracture originating from the region of the basivertebral foramen and passing into the inferior one-half of the vertebral body. The presence of a retropulsed fragment is nearly pathognomonic of an axial compression injury. Characteristics of this lesion that may hinder surgical reduction are the intra-fragment fracture, rotation, and craniocaudad movement.

Humans↗
PubMed1990

Intact stones or fragments? Potential pitfalls in the imaging of patients after biliary extracorporeal shock wave lithotripsy.

Ultrasound is used after extracorporeal shock wave lithotripsy of gallbladder stones to assess fragmentation. In many patients with apparently successful fragmentation, the posttreatment studies show an intraluminal, echogenic focus within the gallbladder, with posterior acoustic shadowing characteristic of an intact stone. Cholesterol gallstones were fragmented in vitro by means of lithotripsy, and the sonographic appearance of the fragmented stones was followed up over time to study factors that might affect the process. After lithotripsy, fragments settled and produced an echogenic focus with posterior shadowing indistinguishable from the appearance of an intact stone. These experimental observations led to the development of a clinical maneuver to overcome the diagnostic pitfalls posed by the reaggregation of stone fragments in situ. This rollover maneuver helps distinguish between intact stones and fragments, and prevents both diagnostic errors in follow-up and unnecessary retreatment.

Cholelithiasis↗
PubMed2005

Fibrinogen and fragment D-induced vascular constriction.

Elevated fibrinogen (Fg) concentration in blood is a high risk factor for many cardiovascular diseases. We hypothesize that Fg and its early degradation product, fragment D, may result in arterial constriction by binding endothelial intercellular adhesion molecule-1 (ICAM-1). The vasoconstriction induced by Fg and fragment D was studied in third- and second-order arterioles (3As and 2As, respectively) of Sprague-Dawley rat cremaster muscle in vivo, in aortic and femoral artery rings, and in the segments of first-order arterioles (1As) isolated from rat cremaster muscle. Intravascular infusion of Fg induced significant constriction of 3As and 2As (by 33.4 +/- 3.4 and 23.7 +/- 4.3%, respectively) in vivo and was abolished in the presence of the specific endothelin type A receptor blocker BQ-610. Fg and fragment D produced significant constriction of both aortic and femoral artery rings. Isolated 1As constricted in response to Fg (0.3 microM) and fragment D (3 microM) by 31 +/- 1.4 and 12 +/- 1.5%, respectively. Fluorescently labeled Fg and fragment D bound to the vascular wall, whereas albumin bound to a significantly lesser degree. The binding of Fg and fragment D to the arteriolar wall and constriction of aortic and femoral artery rings as well as isolated 1As were abolished in the presence of anti-Fg and anti-ICAM-1 antibodies. These results indicate that binding of Fg and fragment D to the vascular wall through ICAM-1 may contribute to the increased vascular tone and resistance that compromise circulation.

Animals↗
PubMed1994

Effects of sleep deprivation and sleep fragmentation on upper airway collapsibility in normal subjects.

Sleep deprivation can induce or worsen nocturnal respiratory disturbances. In patients with sleep apnea hypopnea, sleep abnormalities consist of repetitive episodes of arousals and awakenings that lead to sleep fragmentation. Because the propensity for upper airway collapse is increased in these patients, we wondered if sleep fragmentation could increase upper airway collapsibility and contribute to the pathogenesis of this disease. In eight normal subjects, upper airway collapsibility was assessed during sleep by progressively decreasing the pressure in a nasal mask while recording airflow, mask, and esophageal pressures. The critical pressure was determined by the relationship between breath-by-breath values of maximal inspiratory airflow of each flow-limited inspiratory cycle and the corresponding mask pressure. Critical pressure was measured twice in each subject: after one night of total sleep deprivation and after one night of sleep fragmentation using auditory stimuli. The two measures were done in random order 1 wk apart. A polysomnographic recording was obtained the night after each measurement of critical pressure. Sleep architecture was identical after sleep deprivation and fragmentation. Sleep-related breathing abnormalities were more frequent after sleep fragmentation than after sleep deprivation. Critical pressure was -17.1 +/- 6.8 cm H2O (mean +/- SEM) after sleep deprivation, and -12.3 +/- 6.3 cm H2O after sleep fragmentation (p < 0.05), corresponding to an earlier closing of the upper airway. We conclude that sleep fragmentation leads to a higher upper airway collapsibility than does sleep deprivation.

Adult↗
PubMed1980

Effect of sleep fragmentation on ventilatory and arousal responses of sleeping dogs to respiratory stimuli.

We studied the effects of sleep fragmentation on arousal and ventilatory responses to hyperoxic hypercapnia, isocapnic hypoxia, and chemical stimulation of the larynx during sleep in 5 dogs. Sleep fragmentation was induced by repeatedly arousing the dogs with acoustic stimuli throughout 2 to 3 consecutive nights. Responses to respiratory stimuli were then studied during a subsequent daytime sleep. Arterial O2 saturation was measured with an ear oximeter, and sleep stage was determined by electroencephalographic and behavioral criteria. Hypercapnic and hypoxic ventilatory responses were unimpaired by sleep fragmentation. In contrast, alveolar PCO2 levels at arousal increased after sleep fragmentation, from a mean +/- SEM of 52.2 +/- 1.4 mm Hg to 55.6 +/- 1.5 mm Hg (p < 0.05) during slow-wave sleep, and from 57.9 +/- 1.5 mm Hg to 61.3 +/- 2.2 mm Hg (p < 0.05) during rapid-eye movement sleep. Similarly, arterial O2 saturation at arousal decreased after sleep fragmentation from 80.1 +/- 1.0% to 70.2 +/- 2.7% (p < 0.05) during slow-wave sleep, and from 66.3 +/- 3.6% to < 55% (p < 0.05) during rapid-eye-movement sleep. Arousal responses to laryngeal stimulation were also impaired after sleep fragmentation. We conclude that arousal responses to respiratory stimuli are decreased by sleep fragmentation.

Animals↗
PubMed1980

Electron microsocpy of plasmic fragments of human fibrinogen as related to trinodular structure of the intact molecule.

We have examined rotary shadowed, purified plasmic fragments of human fibrinogen with the electron microscope and have determined the relation of these fragments to the intact fibrinogen molecule. Both intact fibrinogen and its earliest cleavage product, fragment X, are trinodular. The next largest product, fragment Y, consists of two linked nodules. The two terminal products, fragments D and E, are single nodules. From measurements of simultaneously shadowed specimens of these different species, we conclude that the outer nodules of the trinodular fibrinogen molecule are the fragment D-containing regions and the central nodule is the fragment E-containing region.

Electrophoresis, Polyacrylamide Gel↗
PubMed1983

Specific uptake of radioiodinated fragment E1 by venous thrombi in pigs.

Fragment E1, a product of plasmic digestion of cross-linked fibrin, binds specifically in vitro to polymerized fibrin but not to fibrinogen. Purified human Fragment E1 was radiolabeled with 125I or 131I by the Iodogen technique. The uptake of radioiodinated Fragment E1 in vitro into forming or preformed clots was demonstrated. Animal biodistribution studies of radioiodinated Fragment E1 showed its rapid removal from the circulation; radioactive catabolites did not reside long in any organ and were excreted in the urine. The uptake in vivo was evaluated in pigs with preexisting venous thrombi of various ages from 1 h up to 5 d at the time of intravenous systemic injection of the tracer. Radioiodinated fibrinogen was also injected into the same animals to compare the uptake of the two tracers. Thrombus-to-blood ratios for Fragment E1 averaged 43:1 (range 10-108) and 29:1 (range 8-107) in thrombi 1-6 h and 1-5 d old, respectively. In contrast, mean thrombus-to-blood ratios for fibrinogen were, in the same time intervals, 26:1 (range 17-41) and 2:1 (range 0.5-3.9), respectively. It is concluded that radioiodinated Fragment E1 is a specific marker of thrombi in vivo: its uptake by fresh thrombi is better than that of labeled fibrinogen and, in contrast to radioiodinated fibrinogen, this fragment is incorporated into old thrombi as well.

Animals↗
PubMed1984

The self-priming effect of gonadotropin-releasing hormone on luteinizing hormone release: observations using rat anterior pituitary fragments and dispersed cells continuously perifused in parallel.

To study in vitro the self-priming effect of GnRH on LH release, rat anterior pituitaries were prepared either as fragments or dispersed cells and continuously perifused in parallel chambers. The experimental groups consisted of rats killed at 0800 h on diestrus day 1, diestrus day 2, proestrus or estrus, or at 1400 h on proestrus. To insure truly independent observations, each experimental preparation was tested on three occasions. After basal LH release had stabilized, the tissue preparations were exposed to 10 nM GnRH as two 30-min challenges separated by 1 h. LH secretory rates (nanograms per min/pituitary for fragments; nanograms per min/10(7) cells for dispersed cells) were calculated 1) for basal release (during the 20-min period immediately preceding each GnRH challenge), 2) in response to GnRH, and 3) as the sum of basal and GnRH-stimulated release. Comparison of the two preparations revealed that basal and GnRH-stimulated LH release by pituitary fragments was more variable than LH release by dispersed cells. In addition, while dispersed cells responded promptly to the addition/withdrawal of stimuli, fragments did so more gradually. With respect to GnRH self-priming, the second mean secretory rate for basal LH release by fragments (range, 28.8-46.5) was significantly (0.1 greater than P greater than 0.01) higher than the first rate (range, 14.4-22.0) on diestrus day 1, diestrus day 2, proestrus at 0800 h, and estrus. With dispersed cells, the first and second basal rates were similar to each other on diestrus day 1 and estrus, but on diestrus day 2 and on proestrus at 0800 and 1400 h, the second basal rate (range, 36.8-93) was significantly (P less than 0.001) higher than the first range (range, 17.7-31.7). When fragments received GnRH, the second mean secretory rate (range, 35.2-64.2) was significantly (0.1 greater than P greater than 0.03) higher than the first rate (range, 13.4-34.1) on diestrus day 2 and proestrus at 0800 h. With dispersed cells, the mean secretory rate in response to the second GnRH challenge was higher only on diestrus day 2 (37.0 +/- 4.1 vs. 60.3 +/- 3.8; P less than 0.05). When considered as the total of basal plus GnRH-stimulated LH release, the second secretory rate by fragments (range, 54.5 - 110.8) was significantly (0.1 greater than P greater than 0.02) higher than the first rate (range, 27.9 - 51.4) on diestrus day 1, diestrus day 2, and proestrus at 0800 h.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1980

Evidence for a peptide similar to 16K fragment in man. Its relationship to ACTH.

A radioimmunoassay directed toward the NH2-terminal region of mouse pro-ACTH/endorphin (called 16K fragment) was used to examine human samples. Culture media from two corticotropic adenomas and plasmas from 11 patients with various ACTH hypersecretory syndromes gave parallel displacement curves; displacement curves for human samples were not parallel to purified mouse 16K fragment. Following sodium dodecyl sulfate polyacrylamide gel electrophoresis of culture medium from one adenoma, a major peak of 16K fragment immunoreactivity with an apparent molecular weight of ca. 16,000 was detected. A significant correlation (r = 0.963 ; p less than 0.001) was found between immunoreactive 16K fragment and ACTH in the patients' plasmas. These data indicate that a peptide similar to 16K fragment exists in man ; that human and mouse 16K fragment are immunologically distinguishable and that human 16K fragment appears to be secreted concomitantly with ACTH.

Addison Disease↗
PubMed1999

Cleavage of recombinant human corticotropin-releasing factor (CRF)-binding protein produces a 27-kilodalton fragment capable of binding CRF.

CRF is both a peripheral and a central mediator of inflammation, the activity of which is modified by the presence of a 37-kDa binding protein (CRF-BP). The objective of this study was to measure and characterize this protein in the synovial fluid of rheumatoid arthritis patients and to observe the effects of this inflammatory condition on its structure and properties. Measured by immunoradiometric assays, the mean CRF-BP concentration in synovial fluid from 27 arthritic patients was 0.51 nmol/L (SD = 0.24 nmol/L); that for CRF was 6.31 pmol/L. The mean plasma concentration of CRF-BP in 24 control subjects was 1.38 nmol/L (SD = 0.35 nmol/L) and that for 10 arthritic patients was 2.89 nmol/L (SD = 0.84 nmol/L). Synovial fluids were found by immunoblotting to contain intact CRF-BP and a 10-kDa C-terminal CRF-BP fragment; synovial fluid from healthy controls was not examined. We previously reported that after purification of recombinant CRF-BP, spontaneous cleavage frequently occurs, resulting in a 27-kDa N-terminal and a 10-kDa C-terminal fragment. Because concentrations of native CRF-BP in synovial fluid were insufficient to study the effects of cleavage on ligand binding, they were determined using recombinant human CRF-BP. Tryptophan excitation fluorescence spectra of intact and cleaved recombinant CRF-BP revealed that cleavage was accompanied by conformational change in the N-terminal fragment, leading to exposure of the sole tryptophan residue to polar molecules (emission peak shift from 310 to 250 nm). Using gel filtration chromatography to separate the N- and C-terminal fragments, it was found that the N-terminal fragment of the recombinant protein bound human CRF, although dimerization was somewhat impaired. The C-terminal fragment did not bind CRF. Scatchard analysis confirmed that the affinity of both intact and cleaved CRF-BP for CRF was 1 x 10(10) L/mol. We conclude that synovial fluid contains intact CRF-BP in molar excess to CRF and fragmented CRF-BP. The significance of cleavage and the role of cleavage products have yet to be determined, although they may represent the generation of a novel bioactivity.

Animals↗
PubMed2004

Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. A comparison of fragmentation patterns of linear dextran obtained by in-source decay, post-source decay and collision-induced dissociation and the stability of linear and cyclic glucans studied by in-source decay.

In the first part of this study fragmentation patterns from a range of dextran oligomers (containing 4-20 anhydroglucose units) were compared in three different methods of analysis coupled with matrix-assisted laser desorption/ionisation (MALDI) mass spectrometry. Collision-induced-dissociation (CID), prompt in-source decay (ISD) and post-source decay (PSD) all caused cleavage of the glycosidic bonds. Both CID and to a lesser extent ISD caused further cleavage of pyranose rings of the individual sugar residues. There was very little cleavage of pyranose rings detected in the PSD spectrum. Derivatisation of the reducing end-groups of the oligodextrans with 1-phenyl-3-methyl-5-pyrazolone (PMP) restricted cleavage in the MALDI mass spectrometer to the non-reducing end, and further it enabled the saccharides to be separated by HPLC so that a single chain length could be examined as a standard. Maltoheptaose was also used as a standard. In the second part of the study prompt ISD-MALDI mass spectrometry was used to compare the fragmentation of three oligoglucans, dextran, maltodextrin and gamma cyclodextrin, that have different linkages and different secondary structure. The results showed that the degree of fragmentation correlated with the degree of freedom in the saccharide chains in solution determined by NMR. Dextran the most random conformation was fragmented most whereas there was little evidence of any fragments, not even glycosidic bond breakage from cyclodextrin, even when the laser power was increased considerably. The fragmentation pattern of maltodextrin was intermediate. The patterns of fragmentation produced by MALDI mass spectrometry, particularly where standards are available to calibrate the spectrum and the energy of the laser is controlled, can be used to predict the type of linkage present.

Dextrans↗
PubMed2006

Isomerization and fragmentation reactions of gaseous dimethyl phenylarsane radical cations and methyl phenylarsenium cations. A study by tandem mass spectrometry and density functional theory calculations.

The unimolecular reactions of the radical cation of dimethyl phenylarsane, C6H5As(CH3)2, 1*+ and of the methyl phenylarsenium cation, C6H5As+CH3, 2+, in the gas phase were investigated using deuterium labeling and methods of tandem mass spectrometry. Additionally, the rearrangement and fragmentation processes were analyzed by density functional theory (DFT) calculations at the level UBHLYP/6- 311+G(2d,p)//UBHLYP/5-31+G(d). The molecular ion 1*+ decomposes by loss of a .CH3 radical from the As atom without any rearrangement, in contrast to the behavior of the phenylarsane radical cation. In particular, no positional exchange of the H atoms of the CH3 group and at the phenyl ring is observed. The results of DFT calculations show that a rearrangement of 1*+ by reductive elimination of As and shift of the CH3 group is indeed obstructed by a large activation barrier. The MIKE spectrum of 2+ shows that this arsenium cation fragments by losses of H2 and AsH. The fragmentation of the trideuteromethyl derivative 2-d3+ proves that all H atoms of the neutral fragments originate specifically from the methyl ligand. Identical fragmentation behavior is observed for metastable m-tolyl arsenium cation, m-CH3C6H4As+H, 2tol+. The loss of AsH generates ions C7H7+ which requires rearrangement in 2+ and bond formation between the phenyl and methyl ligands prior to fragmentation. The DFT calculations confirm that the precursor of this fragmentation is the benzyl methylarsenium cation 2bzl+, and that 2bzl+ is also the precursor ion fo the elimination of H2. The analysis of the pathways for rearrangements of 2+ to the key intermediate 2bzl+ by DFT calculations show that the preferred route corresponds to a 1,2-H shift of a H atom from the CH3 ligand to the As atom and a shift of the phenyl group in the reverse direction. The expected rearrangement by a reductive elimination of the As atom, which is observed for the phenylarsenium cation and for halogeno phenyl arsenium cations, requires much more activation enthalpy.

Arsenic↗
PubMed1998

Fragmentation of massive pulmonary embolism using a pigtail rotation catheter.

STUDY OBJECTIVES: The purpose of this study was the evaluation of the efficacy and safety of mechanical fragmentation of acute massive pulmonary emboli with a rotatable pigtail catheter. MATERIAL AND METHODS: Ten patients (4 female, 6 male, age 53.8+/-9.5 years) with acute massive pulmonary embolism with hemodynamic impairment were included in the study. The fragmentation catheter device (William Cook Europe A/S; Bjaerverskov, Denmark) consisted of a 5F catheter embedded in a flexible 5.5F sheath. Pulmonary emboli were fragmented by mechanical action of the recoiled rotating pigtail, while the guide wire was exiting an oval side hole proximal to the pigtail tip. In eight cases, an additional thrombolysis was performed. RESULTS: Fragmentation was successful in 7 of 10 patients. Average percentage of recanalization by fragmentation was 29.2+/-14.0%, and 36.0+/-10.0% exclusively of the seven successful cases. Average shock index decreased significantly prefragmentation to postfragmentation from 1.52 to 1.22 (p = 0.03) and to 0.81 48 h later (p < 0.001). Decrease of the average mean arterial pulmonary pressure prefragmentation to postfragmentation was insignificant (from 33 to 31 mm Hg, p = 0.14); further decrease within the 48 h follow-up was highly significant (from 31 to 21 mm Hg, p < 0.001) due to a synergy of fragmentation and thrombolysis (average dose 63+/-25 mg plasminogen activator). There were no procedure-related complications. Overall mortality rate was 20%. CONCLUSION: Fragmentation of massive pulmonary emboli with the pigtail rotation catheter achieved rapid partial recanalization in most cases, with ease of instrumentation, and without complications. Hemodynamic stabilization was completed in synergy with thrombolysis.

Acute Disease↗
PubMed2000

Iodine-125 decay in a synthetic oligodeoxynucleotide. I. Fragment size distribution and evaluation of breakage probability.

Lobachevsky, P. N. and Martin, R. F. Iodine-125 Decay in a Synthetic Oligodeoxynucleotide. I. Fragment Size Distribution and Evaluation of Breakage Probability. Incorporation of (125)I-dC into a defined location of a double-stranded oligodeoxynucleotide was used to investigate DNA breaks arising from decay of the Auger electron-emitting isotope. Samples of the oligodeoxynucleotide were also labeled with (32)P at either the 5' or 3' end of either the (125)I-dC-containing (so-called top) or opposite (bottom) strand and incubated in 20 mM phosphate buffer or the same buffer plus 2 M dimethylsulfoxide at 4 degrees C during 18-20 days. The (32)P-end-labeled fragments produced by (125)I decays were separated on denaturing polyacrylamide gels, and the (32)P activity in each fragment was determined by scintillation counting after elution of fragments from the gel. The relative fragment size distributions were then normalized on a per decay basis and converted to a distribution of single-strand break probabilities as a function of distance from the (125)I-dC. The results of three to five experiments for each of eight possible combinations of labels and incubation conditions are presented as a table showing the relative numbers of (32)P counts in different fragments as well as graphs of normalized fragment size distributions and probabilities of breakage. The average numbers of single-strand breaks per (125)I decay are 3. 3 and 3.7 in the top strand and 1.3 and 1.5 in the bottom strand with and without dimethylsulfoxide, respectively. Every (125)I decay event produces a break in the top strand, and breakage of the bottom strand occurs in 75-80% of the events. Thus a double-strand break is produced by (125)I decay with a probability of approximately 0.8.

Base Sequence↗
PubMed2006

Demographic feedback between clonal growth and fragmentation in an invasive seaweed.

Many abundant plants, invertebrates, and seaweed are clonal, and this allows the formation of high-density aggregations, foraging, and the placement of modules into new space, and rapid rates of expansion. For these species, population density and rates of expansion are functions of recruitment of asexual modules and post-recruitment vegetative growth and survivorship. In this study, we provide the first experimental test of the relative importance of these two processes in determining the abundance of a clonal seaweed using Caulerpa taxifolia, an invasive green alga that spreads rapidly and reaches very high abundance. We asked two main questions: What is the relative importance to abundance (biomass) of vegetative stolon growth and fragment recruitment during expansion of established patches? Does greater fragment recruitment result in greater abundance in established patches? Vegetative growth of stolons underpinned patch expansion. Plots with stolons growing into them always had a greater abundance than plots where stolons were removed, even when fragment recruitment was increased. Greater recruitment only resulted in greater abundance when stolons were absent, a situation analogous to the establishment of new populations. Although post-recruitment processes were more important in determining abundance during patch expansion, there was greater ambient fragment recruitment when stolons were present compared to when they were absent, and as the abundance of C. taxifolia increased, demonstrating an important feedback between stolon growth, abundance, and fragment recruitment. In established patches, greater fragment recruitment over six months (six levels ranging from 0 to 480 recruits x m(-2) x mo(-1)) had no effect on biomass. Our experiments demonstrate that the rapid expansion and high abundance of invasive C. taxifolia are underpinned by post-recruitment vegetative growth and, during expansion, by a feedback between vegetative growth and asexual fragmentation.

Ecosystem↗
PubMed2006

Independent effects of fragmentation on forest songbirds: an organism-based approach.

The degree to which spatial patterns influence the dynamics and distribution of populations is a central question in ecology. This question is even more pressing in the context of rapid habitat loss and fragmentation, which threaten global biodiversity. However, the relative influence of habitat loss and landscape fragmentation, the spatial patterning of remaining habitat, remains unclear. If landscape pattern affects population size, managers may be able to design landscapes that mitigate habitat loss. We present the results of a mensurative experiment designed to test four habitat loss vs. fragmentation hypotheses. Unlike previous studies, we measured landscape structure using quantitative, spatially explicit habitat distribution models previously developed for two species: Blackburnian Warbler (Dendroica fusca) and Ovenbird (Seiurus aurocapilla). We used a stratified sampling design that reduced the confounding of habitat amount and fragmentation variables. Occurrence and reoccurrence of both species were strongly influenced by characteristics at scales greater than the individual territory, indicating little support for the random-sample hypothesis. However, the type and spatial extent of landscape influence differed. Both occurrence and reoccurrence of Blackburnian Warblers were influenced by the amount of poor-quality matrix at 300- and 2000-m spatial extents. The occurrence and reoccurrence of Ovenbirds depended on a landscape pattern variable, patch size, but only in cases when patches were isolated. These results support the hypothesis that landscape pattern is important for some species only when the amount of suitable habitat is low. Although theoretical models have predicted such an interaction between landscape fragmentation and composition, to our knowledge this is the first study to report empirical evidence of such nonlinear fragmentation effects. Defining landscapes quantitatively from an organism-based perspective may increase power to detect fragmentation effects, particularly in forest mosaics where boundaries between patches and matrix are ambiguous. Our results indicate that manipulating landscape pattern may reduce negative impacts of habitat loss for Ovenbird, but not Blackburnian Warbler. We emphasize that most variance in the occurrence of both species was explained by local scale or landscape composition variables rather than variables reflecting landscape pattern.

Animals↗
PubMed2004

Loss of fixation of the volar lunate facet fragment in fractures of the distal part of the radius.

BACKGROUND: The purpose of the present study is to report on a cohort of patients with a volar shearing fracture of the distal end of the radius in whom the unique anatomy of the distal cortical rim of the radius led to failure of support of a volar ulnar lunate facet fracture fragment. METHODS: Seven patients with a volar shearing fracture of the distal part of the radius who lost fixation of a volar lunate facet fragment with subsequent carpal displacement after open reduction and internal fixation were evaluated at an average of twenty-four months after surgery. One fracture was classified as B3.2 and six were classified as B3.3 according to the AO comprehensive classification system. All seven fractures initially were deemed to have an adequate reduction and internal fixation. Four patients required repeat open reduction and internal fixation, and one underwent a radiocarpal arthrodesis. At the time of the final follow-up, all patients were assessed with regard to their self-reported level of functioning and with use of Sarmiento's modification of the system of Gartland and Werley. RESULTS: At a mean of two years after the injury, six patients had returned to their previous level of function. The result was considered to be excellent for one patient, good for four, and fair for two. The average wrist extension was 48 degrees, or 75% of that of the uninjured extremity. The average wrist flexion was 37 degrees, or 64% of that of the uninjured extremity. The one patient who underwent radiocarpal arthrodesis had achievement of a solid union. The four patients who underwent repeat internal fixation had maintenance of reduction of the lunate facet fragment. The two patients who declined additional operative intervention had persistent dislocation of the carpus with the volar lunate facet fragment. CONCLUSIONS: The stability of comminuted fractures of the distal part of the radius with volar fragmentation is determined not only by the reduction of the major fragments but also by the reduction of the small volar lunate fragment. The unique anatomy of this region may prevent standard fixation devices for distal radial fractures from supporting the entire volar surface effectively. It is preferable to recognize the complexity of the injury prior to the initial surgical intervention and to plan accordingly.

Adult↗