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At least 109 records · Page 6Linked to original sources
PubMed1997

Reciprocating gait orthoses: a multicenter study of their use by spinal cord injured patients.

OBJECTIVE: Use of reciprocating orthosis (RGO, ARGO, HGO) by 74 patients with complete traumatic spinal cord injury was studied. Lesion levels ranged from T1 to T12. STUDY DESIGN: Patients were enrolled in seven Italian rehabilitation centers an average of 37 weeks after acute trauma. The training period averaged 39 days. Discontinued use of the device was recorded at follow-up. Before discharge, functional walking, gait velocity, donning and doffing time, and the ability to climb stairs were recorded. The same items were evaluated at 6-month follow-up. RESULTS: At follow-up, 24 patients had abandoned the orthosis, 19 used the device for therapeutic exercise, 31 used it for functional gait, and 9 also used it outside the home. Functional walking was correlated with age, level of lesion, ability to climb stairs, duration of training, and lapse of use of the orthosis. The results showed a correlation between use of the orthosis and the ability to climb stairs, as well as a high Garrett score. CONCLUSION: This orthosis is not considered as an alternative to the wheelchair, despite its greater speed, simplicity of use, and greater autonomy provided to the user.

Adolescent↗
PubMed1998

Speed dependence of crutch force and oxygen uptake: implications for design of comparative trials on orthoses for people with paraplegia.

OBJECTIVE: To determine speed dependence of crutch force and oxygen uptake, and to discuss the implications of differences in self-selected walking speed between orthoses in a comparative trial. DESIGN: Cross-sectional comparison. SETTING: Treadmill experiments and gait laboratory experiments were performed at five and three different imposed walking speeds, respectively. PATIENTS: Five paraplegic subjects with lesions between T9 and T12 were included. All subjects had experience with ambulation using the advanced reciprocating gait orthosis (ARGO) as well as walking on a treadmill. MAIN OUTCOME MEASURES: Crutch force time integral (CFTI), crutch peak force on stance and swing side (CPFstance and CPFswing), oxygen uptake (VO2), oxygen cost (EO2). RESULTS: VO2, EO2, and CFTI were strongly dependent on walking speed. CPFstance and CPFswing were less dependent. However, depending on the clinically relevant difference that should be detected in a comparative trial, the peak forces can still be confounded by walking speed. CONCLUSION: CFTI, CPFswing, VO2, and EO2 should be adjusted for walking speed if differences in walking speed between orthoses are found, but this correction is relevant only if there is no effect modification. Such modification (different slopes between orthoses) cannot be excluded for the studied outcome measures. In addition, because determination of effect modification is difficult in small studies, standardization of walking speed, by means of a three-point design, is recommended.

Adult↗
PubMed1999

Validity and reproducibility of crutch force and heart rate measurements to assess energy expenditure of paraplegic gait.

OBJECTIVE: To determine the validity and reproducibility of heart rate (HR) and crutch force measurements to estimate energy expenditure during paraplegic walking. Usefulness of these outcome measures in comparative trials was assessed in terms of responsiveness. DESIGN: Cross-sectional validity was determined using one single (first) measurement. Longitudinal validity as well as reproducibility were calculated using repeated measurements. SETTING: Oxygen uptake and HR during steady state as well as axial crutch load were measured at subjects' self-selected walking speeds. PATIENTS: Ten subjects with thoracic-level spinal cord injury were included in the study. All subjects had considerable experience with ambulation in the advanced reciprocating gait orthosis (ARGO). MAIN OUTCOME MEASURES: Oxygen uptake (VO2, mL/min) and oxygen cost (EO2, mL/m) were used as criterion standards. Crutch peak force (CPF), crutch force time integral (CFTI), HR, and physiological cost index (PCI) were used to estimate energy expenditure. RESULTS: The PCI was found to be sensitive to detect differences between sessions in criterion standard (r = .86). Smallest detectable difference (ie, point where difference exceeds measurement error) ranged from approximately 15% for CPF to 33.7% and 41.8% for EO2 and PCI, respectively. CONCLUSIONS: Although PCI is expected to be a valid measure for within-patient differences in VO2, responsiveness was lower compared to EO2 and CPF. The limited number of patients who can be included in studies on paraplegic locomotion requires reproducible outcome measures. Therefore, CPF and EO2 are advocated in favor of PCI.

Adult↗
PubMed1998

An autoregulatory cascade of EGF receptor signaling patterns the Drosophila egg.

Intercellular signaling through the EGF receptor (EGFR) patterns the Drosophila egg. The TGF alpha-like ligand Gurken signals from the oocyte to the receptor in the overlying somatic follicle cells. We show that in the dorsal follicle cells this initial paracrine signaling event triggers an autocrine amplification by two other EGFR ligands, Spitz and Vein. Spitz only becomes an effective ligand in the presence of the multitransmembrane domain protein Rhomboid. Consequent high-level EGFR activation leads to localized expression of the diffusible inhibitor Argos, which alters the profile of signaling. This sequential activation, amplification, and local inhibition of the EGFR forms an autoregulatory cascade that leads to the splitting of an initial single peak of signaling into two, thereby patterning the egg.

Animals↗
PubMed1996

A comparison of structural relationships among alpha-crystallin, human Hsp27, gamma-crystallins and beta B2-crystallin.

The 3D structures of alpha-crystallin, a major eye lens protein, and related small heat shock proteins are unresolved. It has been assumed that alpha-crystallin is primarily a beta-sheet globular protein similar to alpha-crystallin (Siezen and Argos, Biochim. Biophys. Acta, 1983, 748, 56-67) containing sequence repeats in its two domains (Wistow, FEBS Lett. 1985, 181, 1-6). Positional flexibility of amino acid residues and far UV-circular dichroism spectroscopy were used to investigate structural relationships among these proteins. The utility of flexibility plots for predicting protein structure is demonstrated by the excellent correlation of these plots with the known 3D X-ray structures of beta/gamma-crystallins. Similar analyses of alpha-crystallin subunits, alpha A and alpha B, and human heat shock protein 27 show that the C-terminal domains and connecting segments of these proteins are very similar while the N-terminal domains have significant structural differences. Unlike beta/gamma-crystallins, both Hsp27 and alpha-crystallin subunits are asymmetrical with highly flexible C-terminal domains. Flexibility is considered essential for protein functional activity. Therefore, the C-terminal region may play an active role in alpha-crystallin and small heat shock protein function. Differences in flexibility profiles and estimated secondary structure distribution in alpha-crystallin by three recent/updated algorithms from far UV-CD spectra support our predicted 3D structure and the concept that alpha-crystallin and members of beta/gamma superfamily are structurally dissimilar.

Algorithms↗
PubMed2003

Species-specific activation of EGF receptor signaling underlies evolutionary diversity in the dorsal appendage number of the genus Drosophila eggshells.

In Drosophila melanogaster, the patterning of dorsal appendages on the eggshell is strictly controlled by EGFR signaling. However, the number of dorsal appendages is remarkably diverse among Drosophila species. For example, D. melanogaster and D. virilis have two and four dorsal appendages, respectively. Here we show that during oogenesis the expression patterns of rhomboid (rho) and argos (aos), positive and negative regulators of EGFR signaling, respectively, were substantially different between D. melanogaster and D. virilis. Importantly, the number and position of both the rho expression and MAPK activation were consistent with those of the dorsal appendages in each species. Despite the differences in the spatial expression, these results suggest that the function of EGFR signaling in dorsal appendage formation is largely conserved between these two species. Thus, our results link the species-specific activation of EGFR signaling and the evolution of eggshell morphology in Drosophila.

Acute-Phase Proteins↗
PubMed1997

Differential requirement for EGF-like ligands in Drosophila wing development.

Signaling through the Drosophila EGF receptor (DER) is important for the growth and differentiation of the wing. These processes may be mediated by different DER ligands including Spitz (Spi) and Vein (Vn). Here I investigate the roles of these ligands and other DER pathway components in wing disc development using in vivo culture to produce mutant discs from genotypes which are normally embryonic lethal. I find no role for spi in wing disc growth, whereas vn is essential. spi mutant wing discs are morphologically normal as judged by expression of the vein marker rhomboid (rho) and analysis of the differentiated wing tissue. rho, Star (S) and argos (aos) which are known to be involved in Spi/DER signaling are likewise not required for wing growth, whereas pointed (pnt), which acts at the end of the intracellular pathway, is required. The results suggest different ligands and molecular mechanisms control DER signaling in wing growth and differentiation.

Animals↗
PubMed1997

Control of midline glia development in the embryonic Drosophila CNS.

The midline glial cells are required for correct formation of the axonal pattern in the embryonic ventral nerve cord of Drosophila. Initially, six midline cells form an equivalence group with the capacity to develop as glial cells. By the end of embryonic development three to four cells are singled out as midline glial cells. Midline glia development occurs in two steps, both of which depend on the activation of the Drosophila EGF-receptor homolog and subsequent ras1/raf-mediated signal transduction. Nuclear targets of this signalling cascade are the ETS domain transcription factors pointedP2 and yan. In the midline glia pointedP2 in turn activates the transcription of argos, which encodes a diffusible negative regulator of EGF-receptor signalling.

Animals↗
PubMed1997

Control of midline glia development in the embryonic Drosophila CNS.

The midline glial cells are required for correct formation of the axonal pattern in the embryonic ventral nerve cord of Drosophila. Initially, six midline cells form an equivalence group with the capacity to develop as glial cells. By the end of embryonic development three to four cells are singled out as midline glial cells. Midline glia development occurs in two steps, both of which depend on the activation of the Drosophila EGF-receptor homolog and subsequent ras1/raf-mediated signal transduction. Nuclear targets of this signalling cascade are the ETS domain transcription factors pointedP2 and yan. In the midline glia pointedP2 in turn activates the transcription of argos, which encodes a diffusible negative regulator of EGF-receptor signalling.

Animals↗
PubMed1998

An interplay between two EGF-receptor ligands, Vein and Spitz, is required for the formation of a subset of muscle precursors in Drosophila.

Activation of the Drosophila EGF-receptor (DER) is spatially and temporally controlled by the release of its various ligands. DER and its ligand Spitz mediate the formation of specific somatic muscle precursors. We show that a second DER ligand, Vein, complements the activity of Spitz in the development of various somatic muscle precursors. In vn mutant embryos, the DER-dependent muscle precursors do not form in some of the segments. This phenotype is significantly enhanced in embryos carrying only one copy of wild type spitz. Our analysis suggests that Vein activation of DER differs qualitatively from that of Spitz in that it does not lead to the expression of the inhibitory protein Argos, possibly leading to a continuous activation of the DER signaling pathway.

Animals↗
PubMed2001

A primary role for the epidermal growth factor receptor in ommatidial spacing in the Drosophila eye.

BACKGROUND: The differentiation of regularly spaced structures within an epithelium is a common feature of developmental pattern formation. The regular spacing of ommatidia in the Drosophila eye imaginal disc provides a good model for this phenomenon. The correct spacing of ommatidia is a central event in establishing the precise hexagonal pattern of ommatidia in the Drosophila compound eye. The R8 photoreceptors are the founder cells of each of the ommatidia that comprise the adult eye and are specified by a bHLH transcription factor, Atonal. RESULTS: We find that the epidermal growth factor receptor (Egfr) has a primary function in regulating R8 spacing. The receptor's activation within nascent ommatidia induces the expression of a secreted inhibitor that blocks atonal expression, and therefore ommatidial initiation, in nearby cells. The identity of the secreted inhibitor remains elusive but, contrary to previous suggestions, we show that it is not Argos. This Egfr-dependent inhibition acts in parallel to the inhibition of atonal by the secreted protein Scabrous. The activation of the Egfr pathway is dependent on Atonal function via the expression of Rhomboid-1. Our results also allow us to conclude that Egfr's role in promoting cell survival is largely independent of its role in photoreceptor recruitment; even when cell death is blocked, most photoreceptors fail to form. CONCLUSIONS: Based on our data and those of others, we propose a model for R8 spacing that comprises a self-organizing network of signaling molecules. This model describes how successive rows of ommatidia form out of phase with each other, leading to the hexagonal array of facets in the compound eye.

Animals↗
PubMed1997

Requirement for EGF receptor signalling in neural recruitment during formation of Drosophila chordotonal sense organ clusters.

BACKGROUND: Drosophila proneural genes act in the process of selecting neural precursors from undifferentiated ectoderm. The proneural gene atonal is required for the development of precursors of both chordotonal organs (stretch receptors) and photoreceptors. Although these types of sensory element are dissimilar in structure and function, they both occur as organized arrays of neurons. Previous studies have shown that clustering of photoreceptors involves local recruitment, and that signalling by the Drosophila epidermal growth factor receptor (DER) pathway is involved in the recruitment process. We present evidence that a similar mechanism is required for the clustering of embryonic chordotonal organs. RESULTS: We have examined the expression patterns of atonal and genes of the DER pathway in wild-type and mutant backgrounds. Expression of atonal was restricted to a subset of the atonal-requiring chordotonal precursors, which we call founder precursors. The remaining precursors required DER signalling for their selection. Signalling by the founder precursors was initiated by atonal activating, directly or indirectly, rhomboid expression in these cells. Signalling by these founder precursors then provoked a response in the surrounding ectodermal cells, as shown by the activation of expression of the DER target genes pointed and argos. The signal and response then led to recruitment of some of the ectodermal cells to the chordotonal precursor cell fate. DER hyperactivation by misexpression of rhomboid resulted in excessive chordotonal precursor recruitment. CONCLUSIONS: Increased numbers of chordotonal precursors are recruited by homeogenetic induction involving signalling via DER from founder precursors to surrounding ectodermal cells. We suggest that the reason chordotonal organs and photoreceptors share a requirement for the proneural gene atonal is that this gene activates a common pathway leading to neural aggregation.

Animals↗
PubMed1991

Solution conformation of a peptide fragment representing a proposed RNA-binding site of a viral coat protein studied by two-dimensional NMR.

The first 25 amino acids of the coat protein of cowpea chlorotic mottle virus are essential for binding the encapsidated RNA. Although an alpha-helical conformation has been predicted for this highly positively charged N-terminal region [Argos, P. (1981) Virology 110, 55-62; Vriend, G., Verduin, B. J. M., & Hemminga, M. A. (1986) J. Mol. Biol. 191, 453-460], no experimental evidence for this conformation has been presented so far. In this study, two-dimensional proton NMR experiments were performed on a chemically synthesized pentacosapeptide containing the first 25 amino acids of this coat protein [Ten Kortenaar, P. B. W., Krüse, J., Hemminga, M. A., & Tesser, G. I. (1986) Int. J. Pept. Protein Res. 27, 401-413]. All resonances could be assigned by a combined use of two-dimensional correlated spectroscopy and nuclear Overhauser enhancement spectroscopy carried out at four different temperatures. Various NMR parameters indicate the presence of a conformational ensemble consisting of helical structures rapidly converting into more extended states. Differences in chemical shifts and nuclear Overhauser effects indicate that lowering the temperature induces a shift of the dynamic equilibrium toward more helical structures. At 10 degrees C, a perceptible fraction of the conformational ensemble consists of structures with an alpha-helical conformation between residues 9 and 17, likely starting with a turnlike structure around Thr9 and Arg10. Both the conformation and the position of this helical region agree well with the secondary structure predictions mentioned above.

Amino Acid Sequence↗
PubMed1996

Design challenges for hemoproteins: the solution structure of apocytochrome b5.

In order to characterize the structural and dynamic factors that determine the assembly in b hemoproteins, the solution structure of the 98-residue protein apocytochrome b5 was determined by NMR methods. Over 800 experimental restraints derived from a series of two- and three-dimensional experiments were used. Holocytochrome b5, the protein with iron protoporphyrin-IX liganded to His-39 and His-63, contains in sequence the following elements of secondary structure: beta 1-alpha 1-beta 4-beta 3-alpha 2-alpha 3-beta 5-alpha 4-alpha 5-beta 2-alpha 6 [Mathews, F.S., Czerwinski, E. W., & Argos, P. (1979) The Porphyrins, Vol. 7, pp. 107-147, Academic Press, New York]. The folded holoprotein possesses two hydrophobic cores: an extensive, functional core around the heme (core 1), and a smaller, structural core remote from the heme (core 2). The apoprotein was found to contain a stable four-stranded beta-sheet encompassing beta 1, beta 2, beta 3, and beta 4 and three alpha-helices, corresponding to alpha 1, alpha 2, and alpha 6. Two short alpha-helices (alpha 3 and alpha 5) appear to form partially, and alpha 4 is not detected. These three helices and beta 5 border the heme binding pocket and are disordered in the apoprotein NMR structure. According to backbone 1H-15N NOE results, the most flexible region of the apoprotein, except for the termini, extends from Ala-50 (in beta 5) to Glu-69 (in alpha 5). The polypeptide segment bearing His-63 (located immediately prior to alpha 5) exhibits faster internal motions than that bearing His-39 (at the C-terminal end of alpha 2). The latter imidazole samples a restricted region of space, whereas the former can adopt many orientations with respect to the stable core. It was concluded that heme removal affects the structure and dynamics of most of core 1 whereas it leaves core 2 largely intact. The results provide guidelines for the rational design of b hemoproteins: a modular structure including a packed, stable core and a partially folded binding site is anticipated to present strong kinetic and thermodynamic advantages compared to approaches relying on the complete formation of secondary structure prior to heme binding.

Amino Acid Sequence↗
PubMed2002

Synthesis and evaluation of poly(oxyethylene glycol) polymer (POP) supports.

Mono- and alpha,omega-bis-styryl-oligo(oxyethylene glycol) ethers have been constructed in an efficient two-step synthesis. From these precursors, poly(oxyethylene glycol) polymer (POP) supports of varying monomer and cross-linker composition have been produced. The swelling properties and mass-solvent uptake of these novel materials have been evaluated in a variety of solvents, demonstrating that POP supports exhibit enhanced solvent compatibilities over the commercial resins TENTA-GEL, ARGO-GEL, and Merrifield's resin. The utility of POP supports in solid-phase organic chemistry has also been demonstrated successfully. It is anticipated that these high-loading polymeric supports will have generic application in the solid-phase synthesis of combinatorial libraries and the in situ screening of these libraries in the aqueous environment of a bioassay.

Journal Article↗
PubMed2000

naked cuticle encodes an inducible antagonist of Wnt signalling.

During animal development, cells have to respond appropriately to localized secreted signals. Proper responses to Hedgehog, transforming growth factor-beta, epidermal growth factor and fibroblast growth factor/Ras signals require cognate inducible antagonists such as Patched, Dad, Argos and Sprouty. Wnt signals are crucial in development and neoplasia. Here we show that naked cuticle (nkd), a Drosophila segment-polarity gene, encodes an inducible antagonist for the Wnt signal Wingless (Wg). In fly embryos and imaginal discs nkd transcription is induced by Wg. In embryos, decreased nkd function has an effect similar to excess Wg; at later stages such a decrease appears to have no effect. Conversely, overproduction of Nkd in Drosophila and misexpression of Nkd in the vertebrate Xenopus laevis result in phenotypes resembling those of loss of Wg/Wnt function. nkd encodes a protein with a single EF hand (a calcium-binding motif) that is most similar to the recoverin family of myristoyl switch proteins. Nkd may therefore link ion fluxes to the regulation of the potency, duration or distribution of Wnt signals. Signal-inducible feedback antagonists such as nkd may limit the effects of Wnt proteins in development and disease.

Amino Acid Sequence↗
PubMed1997

Rehabilitation of walking for paraplegic patients by means of a treadmill.

The present study was aimed at investigating the use of a treadmill for ambulation training of paraplegic subjects. To investigate the likely effectiveness of this modality of rehabilitation, six paraplegic patients (three male and three female) were studied, using new generation reciprocating gait orthoses (RGO and ARGO), in a treadmill training program. Oxygen consumption, heart rate, and pulmonary ventilation were measured when the subjects were walking at their most comfortable speed on the treadmill and on the open field. These measurements were carried out at the beginning of the study and after two and six months of treadmill training. The following findings were significant: the treadmill walking required 30% less energy than open field ambulation prior to training (P < 0.001) and 50% after training (P < 0.05). The most comfortable walking speed was faster on the treadmill than on the open field by 18% prior to training (P < 0.05) and 42% afterwards (P < 0.05). The energy cost was 50% less after 2 months training on the treadmill (P < 0.05) showing that treadmill training can improve the efficiency of over ground ambulation. It can be concluded that the treadmill training improves the RGO/ARGO walking capability, probably both the walking efficiency (short term adaptation) and physical fitness (long term adaptation).

Adult↗
PubMed1996

An evaluation of the CELL-DYN 1700 haematology analyser: automated cell counting and three-part leucocyte differentiation.

The performance of the CELL-DYN 1700 (Abbott Diagnostics, Abbott Park, IL, USA) was evaluated in a tertiary care hospital laboratory using the guidelines proposed by the German Society of Clinical Chemistry. Precision, accuracy, linearity, background counts, and carry-over were satisfactory for all measured standard parameters including haemoglobin concentration, haematocrit, red blood cell count, mean corpuscular volume (MCV), red cell distribution width (RDW), white blood cell count and platelet count. With 259 selected normal and abnormal blood samples the results of the CELL-DYN 1700 (CD1700) compared very well (r > 0.96 for all parameters with exception of RDW) with those obtained with the Bayer Diagnostic H-1 and the Hoffmann-La Roche Cobas Argos systems. This study considered in particular the performance of the CD1700 three-part leucocyte differential. For those samples without instrument-generated suspect flags, the neutrophil and lymphocyte percentages were highly correlated with the results of the H-1 blood cell counter (r = 0.97 and 0.98, respectively) and with manual 400-cell differentials (r = 0.91 and 0.88, respectively). In contrast, the CD1700 mid-fraction which comprised the composite total of monocytes, eosinophils, basophils and precursor white cells (when present) could not be directly compared to the differentials from the H-1 system or from manual microscopy. For those samples with CD1700 instrument suspect flags, the neutrophil and lymphocyte differential results also compared well with both the H-1 (r = 0.93 and 0.93, respectively) and manual estimates (r = 0.89 and 0.87, respectively). In conclusion, the CD1700 is an accurate haematology analyser for cellular blood counts and three-part leucocyte differentiation.

Adult↗