Exploring the Change in Metabolic Cost of Walking before and after Familiarization with a Passive Load-Bearing Exoskeleton: A Case Series.

OCCUPATIONAL APPLICATIONSMilitary personnel are at greater risk of injuries due to frequent load carriage. Novel exoskeleton technology may have benefits for soldiers, such as reduced physical burden through load carriage support that may result in decreased metabolic cost, reduced fatigue, and lower risk of injuries during walking. However, as for most assistive devices, a familiarization period is likely necessary to obtain the full potential of the device. Our results show that the metabolic cost of walking (MWC) was initially increased significantly upon provision of the passive exoskeleton, though it returned to baseline values after a 9-day familiarization period. The exoskeleton remained effective after a three-month pause, with a MCW below baseline. These results suggest that to properly assess the assistance of an exoskeleton, a sufficient familiarization period should be mandatory.

Background: Military load carriage has been shown to alter gait patterns, resulting in an increased metabolic cost during walking (MCW). Soldiers' burden could be mitigated by wearing a passive exoskeleton, but the additional payload of the device can alter movement patterns during gait, rendering it detrimental. Integrating principles of motor learning during a familiarization period could allow users to develop adaptive motor strategies, thereby decreasing MCW.Purpose: The aim of this study was to explore the influence of a familiarization period on MCW when soldiers wear a passive, load-bearing, prototype exoskeleton (Exo).Methods: Three male soldiers walked on a treadmill with a 38 kg payload at eight speeds (1.8-6.0 km/h) under five conditions: 1) no exoskeleton (NoExo); 2) exoskeleton pre-familiarization (Exo_Pre); 3) exoskeleton post-familiarization (Exo_Post); 4) no exoskeleton follow-up (NoExo_FU); and 5) exoskeleton follow-up (Exo_FU). Each experimental trial consisted of 10 minutes of standing followed by 10 minutes of walking at a constant speed. Metabolic data were normalized to walking speed (J/kg·m) to obtain the MCW. The familiarization period consisted of 9 days of activities with the exoskeleton using a standardized protocol. Differences in MCW with and without the Exo were compared at the eight walking speeds using a nonparametric analysis of Longitudinal Data.Results: There was a statistically significant decrease in MCW after familiarization with the Exo, particularly during Exo_FU with a relative treatment effect of 0.11 − 0.19. There were also significant reductions in MCW during Exo_FU when compared to NoExo_FU [participant 01 = 0.37; participant 02 = 0.27; participant 03 = 0.35].Conclusions: A first exposure to the exoskeleton increased MCW. After familiarization, however, the MCW with the Exo returned to the NoExo level or below with a payload of 38 kg among three soldiers. A familiarization period of 3 hours per day over 2 weeks of familiarization may optimize the use of an exoskeleton.

A review of ultrastructural and ultracytochemical studies of infection processes in some plant wilt diseases: the opaque matter extensively involved, its links with pathogen elements, insights into its nature.

The present review is based on results of several years of investigation on the pathogenesis of plant wilt diseases using for one of the main aspects, several labeling techniques at the ultrastructural level: autoradiography with (3)H-thymidine; gold-tagged lectins, enzymes, polyclonal, and monoclonal antibodies. Thus, opaque matter (OM), labeling for DNA with the appropriate markers, can be abundant in and associated with host tissue reactions and pronounced alterations (particularly in newly differentiated xylem). The presence of structures (called P-elements) in OM, paralleled by a similar occurrence in nuclei of both the host and pathogen cells, is considered as being also indicative of a cytoplasmic nature for this OM and most likely originating from fungal elements.

Influence of Plant Age on Symptom Development in Ulmus minor Following Inoculation by Ophiostoma novo-ulmi.

In American and European breeding programs, numerous elm trees from many species (Ulmus spp.) and hybrids have been inoculated annually with the fungus Ophiostoma novo-ulmi (the Dutch elm disease pathogen) in screening tests for resistance. Because trees were inoculated at different ages, it appeared necessary to study the influence of host age on the symptoms shown. Four Ulmus minor trees and one U. minor × U. pumila tree were cloned annually from 1994 to 1999. The replicates obtained (usually n = 6) were inoculated on 17 May 2000 with an O. novoulmi strain. At the end of the season, 2-year-old U. minor trees showed average wilting of 8 ± 3% (ES), significantly less than that of 3-year-old trees (34 ± 5%) (P ≤ 0.01). Elms that were 4, 5, 6, and 7 years old showed wilting values of around 50%. A positive relationship between the symptoms shown and the diameter of the elm xylem vessels was observed, and the implications for elm resistance and breeding are discussed. Breeders and pathologists should use trees of the same age and physiological phase when determining the relative resistance among elm clones. It is concluded that under the growing conditions of this experiment, the optimal age for U. minor screening was 4-year-old plants.

Cytochemical labeling for fungal and host components in plant tissues inoculated with fungal wilt pathogens.

Antibodies to detect pectin in present investigations attached to distinct fibrils in vessel lumina. In carnation infected with an isolate of Fusarium oxysporum f.sp., labeling of pathogen cells also occurred; in a resistant cultivar (cv.), it was coincident with proximate pectin fibrils and linked to altered fungal walls, which was the opposite in the susceptible cv., indicating that hindrance of pathogen ability to degrade pectin may be related to resistance. Labeling of the fungus in culture was nil, except in media containing pectin, showing that pectin is not native to the pathogen. Labeling of fungal walls for cellulose in elm (inoculated with Ophiostoma novo-ulmi) and carnation also occurred, linked to adsorbed host wall components. The chitin probe often attached to dispersed matter, in vessel lumina, traceable to irregularly labeled fungal cells and host wall degradation products. With an anti-horseradish peroxidase probe, host and fungal walls were equally labeled, and with a glucosidase, differences of labeling between these walls were observed, depending on pH of the test solution. Fungal extracellular matter and filamentous structures, present in fungal walls, predominantly in another elm isolate (Phaeotheca dimorphospora), did not label with any of the probes used. However, in cultures of this fungus, extracellular material labeled, even at a distance from the colony margin, with an anti-fimbriae probe.

A genealogical study of Alzheimer disease in the Saguenay region of Quebec.

We performed an analysis of inbreeding and kinship among the ascending genealogies of 205 autopsy-confirmed Alzheimer disease (AD) subjects recruited in the Saguenay area of Québec. We hypothesized that if some traits pertaining to the disease were determined by inherited factors, and if the corresponding genes were not too frequent in the population, it might be possible to detect some clusters of patients related to common ancestors and presenting a level of kinship and/or inbreeding higher than is observed in the unaffected population of the same age. In view of the heterogeneity of the disease, we also verified if some of the factors investigated could be associated more specifically with subsets of cases based on age of onset and on apolipoprotein E (APOE) genotype. Results were compared with those obtained on 205 controls matched for gender, place and year of birth. We found that late-onset AD cases with an APOE-epsilon 4 were significantly more inbred than controls and that this increase was explained by the high level of inbreeding of a few cases whose parents were related at the first-cousin level. This could possibly indicate the implication of a recessive element in a small subset of AD cases in the Saguenay population. We also found that late-onset epsilon 4+ cases were significantly more closely related among themselves than with controls. This increase in kinship may be attributable to the presence of the epsilon 4 allele or to some other unidentified genetic factor possibly acting in conjunction with APOE-epsilon 4.

Immunocytochemical Evidence that Secretion of Pectin Occurs During Gel (Gum) and Tylosis Formation in Trees.

ABSTRACT During gel (gum) formation in angiosperm trees, fibrillar material accumulated in protective layers of xylem parenchyma cells before being secreted across half-bordered pit membranes into vessel elements. Immunogold labeling demonstrated that this fibrillar material was mainly composed of partially esterified pectic polysaccharides. The primary wall of expanding tyloses, an extension of the parenchyma protective layer, secreted similar pectic substances to completely block vessel elements. In most studies, these occluding structures were reported to be formed in response to causative factors such as aging processes, injuries, or infections. Current observations support the view that partial to complete embolism, which almost always accompanies these factors, might be the main cause triggering the formation of vessel occlusions. Whereas pectin seems to be the basic component of gels (gums) and of the external layer of tyloses, other substances, such as phenols, were also detected either as a part of these plugs or as accumulations beside them in vessels. Finally, it is proposed that the term 'gel' instead of 'gum' be used in future studies to describe the occluding material secreted by ray and paratracheal parenchyma cells.

Comparison of ribosomal DNA length and restriction site polymorphisms in Gremmeniella and Ascocalyx isolates.

The small subunit (SSU) and the internal transcribed spacer (ITS) of nuclear ribosomal DNA genes from 27 specimens of the fungal genera Gremmeniella and Ascocalyx were amplified by PCR. Length polymorphisms were observed in the SSU and allowed the differentiation of four groups among the isolates tested: (i) Ascocalyx abietis; (ii) Gremmeniella isolates from Picea spp.; (iii) Gremmeniella isolates from Abies balsamea; and (iv) Gremmeniella isolates from Abies sacchalinensis, Larix spp., and Pinus spp. The amplified ITS was the same length for all Gremmeniella specimens and was 60 bp longer in A. abietis. Phylogenetic analysis of length polymorphisms and of 24 restriction sites in the SSU and ITS showed that Gremmeniella isolates were more related to each other than to the Ascocalyx isolate. Furthermore, seven groups were evident within the genus Gremmeniella. Our results confirm that Gremmeniella and Ascocalyx should be kept as different taxa and suggest that the taxonomy of the former could be revised to consider isolates from Abies balsamea and from Picea spp. to be two different varieties while incorporating Gremmeniella laricina into G. abietina, as a new variety.

Intertrochanteric fractures of the femur in rheumatoid arthritis patients.

In a series of 33 intertrochanteric femoral fractures in patients suffering from classic rheumatoid arthritis (RA), the typical patient was about 70 years of age, osteopenic, and severely affected by longstanding polyarticular RA of joints other than the hip. Prefracture involvement of the hip joint (other than osteopenia) was apparent radiographically in only 9.1% of patients. There was a higher rate of avascular necrosis (9.7%) and nonunion (6.5%) than expected in the nonrheumatoid general population. There was also a high rate of secondary displacement. Of three patients with avascular necrosis, two had had corticosteroid treatment.

A Cytochemical Study of Extracellular Sheaths Associated with Rigidoporus lignosus during Wood Decay.

An ultrastructural and cytochemical investigation of the development of Rigidoporus lignosus, a white-rot fungus inoculated into wood blocks, was carried out to gain better insight into the structure and role of the extracellular sheaths produced by this fungus during wood degradation. Fungal sheaths had a dense or loose fibrillar appearance and were differentiated from the fungal cell wall early after wood inoculation. Close association between extracellular fibrils and wood cell walls was observed at both early and advanced stages of wood alteration. Fungal sheaths were often seen deep in host cell walls, sometimes enclosing residual wood fragments. Specific gold probes were used to investigate the chemical nature of R. lignosus sheaths. While labeling of chitin, pectin, beta-1,4- and beta-1,3-glucans, beta-glucosides, galactosamine, mannose, sialic acid, RNA, fucose, and fimbrial proteins over fungal sheaths did not succeed, galactose residues and laccase (a fungal phenoloxidase) were found to be present. The positive reaction of sheaths with the PATAg test indicates that polysaccharides such as beta-1,6-glucans are important components. Our data suggest that extracellular sheaths produced by R. lignosus during host cell colonization play an important role in wood degradation. Transportation of lignin-degrading enzymes by extracellular fibrils indicates that alteration of plant polymers may occur within fungal sheaths. It is also proposed that R. lignosus sheaths may be involved in recognition mechanisms in fungal cell-wood surface interactions.

Identification of Gremmeniella abietina Races with Random Amplified Polymorphic DNA Markers.

Seven random amplified polymorphic DNA (RAPD) markers amplified from four oligonucleotides (10-mers) by the polymerase chain reaction were used to distinguish between the North American and European races of Gremmeniella abietina, the causal agent of Scleroderris canker of conifers. Forty-three isolates of the pathogen from 11 different host species originating from 11 countries, states, and provinces were tested; race designation was consistent with results from immunogenic and soluble-protein assays. By using RAPD markers, it was possible to identify G. abietina races by DNA amplifications directly from fruiting bodies, thus eliminating the need to culture the fungus, as is necessary with immunogenic and soluble-protein assays. Two isolates which had been previously classified as intermediate were clearly identified as belonging to either one of the two races by using RAPD markers. No interracial hybrids were detected in our survey. Patterns of amplification products from the European race in North America were identical to patterns of European isolates, further substantiating that this is an introduced race to the North American continent.

Immunocytochemical localization of laccase L1 in wood decayed by Rigidoporus lignosus.

The cellular distribution of laccase L1 during degradation of wood chips by Rigidoporus lignosus, a tropical white rot fungus, was investigated by using anti-laccase L1 polyclonal antisera in conjunction with immunolabeling techniques. The enzyme was localized in the fungal cytoplasm and was associated with the plasmalemma and the fungal cell wall. An extracellular sheath, often observed around fungal cells, often contained laccase molecules. Diffusion of laccase within apparently unaltered wood was seldom observed. The enzyme penetrated all degraded cell walls, from the secondary wall toward the primary wall, including the middle lamella. Xylem cells showing advanced stages of decay were sometimes devoid of significant labeling. These data suggest that the initial attack on wood was not performed by laccase L1 of R. lignosus. Previous alteration of the lignocellulose complex may facilitate the movement of laccase within the wood cell walls. This immunogold study revealed that laccase localization during wood degradation seems limited not in space but in time.

Nonimaging light concentration using total internal reflection films.

We present a method of fabricating nonimaging light concentrators from total internal reflection film. A prototype has been made and tested and found to operate in agreement with predictions of ray-tracing codes. The performance of the prototype is comparable with that of concentrators made from specular reflecting materials.

Phenotype reversal in induced mutants of CHO cells: analysis of the reversed cell lines.

We have previously shown that descendants of CHO-derived hprt or aprt mutants induced by ethyl methanesulphonate usually undergo a rapid loss of the mutant phenotype during the 10 generations or so of culture in non-selective medium immediately following mutagenesis (Bradley, 1980; Bradley and Laviolette, 1989). We now present an analysis of several mutants and their descendants which have lost the mutant phenotype, or 'reversed'. The drug-resistance properties of reversed cells were generally intermediate between W.T. and mutant, and message level and enzyme-specific activity were also intermediate, correlating with the phenotype. Although this was consistent with a model of inactivation-reactivation of the target gene to explain the reversal phenomenon, the model was ruled out by Northern blot analysis of several induced mutants, which showed no correlation between level of message and tendency of the mutant to lose its phenotype. Karyotype analysis showed that three out of four reversed lines were near-tetraploid and the fourth had a substantial proportion of near-tetraploid cells. This suggests cell fusion between a mutant and a W.T. cell may explain the phenomenon. A prediction of this model, namely that mutagen treatment increases cell hybrid formation, was tested and found to be true.

Reversible hepatitis associated with diclofenac.

We describe the clinical features, liver histology, and ultrastructure in reversible diclofenac-induced hepatitis and review previous reports of this entity. Although rarely reported, diclofenac hepatitis may be severe, and even fatal. Symptoms, which develop from 1 week to 11 months after starting the drug, include jaundice, pruritus, fever, abdominal pain, nausea, vomiting, and rash. Bilirubin and alkaline phosphatase are mildly elevated, transaminases often markedly so. The nature of the idiosyncratic injury appears variable, some cases having features of a hypersensitivity reaction, most being more suggestive of a toxic metabolic effect. Light microscopy shows a nonspecific hepatitis with portal and lobular activity, and focal hepatocellular injury that may progress to zonal or massive necrosis. The ultrastructural features in our case are typical of drug or toxin injury. This may be of value in distinguishing this entity from other forms of hepatitis, which is important in view of the frequent reversibility of this potentially lethal form of injury.

Failure of internal fixation of displaced femoral neck fractures in rheumatoid patients.

We reviewed the records and radiographs from 10 hospitals to identify 50 patients with rheumatoid arthritis (RA) who had sustained 52 femoral neck fractures. Most patients were female (88%), elderly (mean age 66 years) and had had severe polyarticular disease for a mean duration of 16 years. Over half had taken systemic corticosteroids, nearly all were severely osteopenic but few had rheumatoid changes in the hip. Of the 20 fractures treated by internal fixation 12 had complications including nonunion (5), osteonecrosis (5), infection (1), and intertrochanteric fracture (1). Only one of the nine undisplaced fractures required reoperation, but seven of the 11 displaced fractures had revision surgery. Twenty fractures were treated by primary total hip arthroplasty with only one early complication. The other 12 fractures had been treated by hemiarthroplasty (9), hip excision (1) or non-operatively (2). Our results suggest that, in elderly rheumatoid patients, severely displaced femoral neck fractures should be treated by total hip replacement.

Recurrent hemorrhage from an invaginated Meckel's diverticulum in a 78-year-old man.

Complications arising from Meckel's diverticulum are uncommon in adults and are seldom, if ever, seen in the elderly. When they do occur in adults, intestinal obstruction or inflammation is the usual mode of presentation, hemorrhage being much less common. The patient described in this case report was 78 yr old, presented initially with iron deficiency anemia and, later, developed severe acute hemorrhage. The cause of the hemorrhage was ulceration at the tip of an invaginated Meckel's diverticulum. The ulceration was not peptic in origin, as is usually the case in similar presentations in children, no ectopic oxyntic mucosa being detected in the diverticulum of our patient. In previous reports, invaginated Meckel's diverticula have always been accompanied by intussusception, and abdominal pain has been an important part of the symptom complex in such patients. Our patient had no abdominal pain, and no intussusception was noted at surgery. This case emphasizes the need for considering a Meckel's diverticulum as the source of acute or chronic hemorrhage, irrespective of the patient's age. The utility of radionuclide blood pool imaging in arriving at a diagnosis in these cases is discussed.

Attachment and multiplication, morphology and protein production of human fetal primary liver cells cultured in hormonally defined media.

We established for human fetal liver cells (cultured for 2 wk) in a hormonally defined medium, optimal conditions for attachment, multiplication, and preservation of epithelial morphology as well as production and secretion of serum proteins characteristic of fetal (alpha l-fetoprotein, AFP) and adult (albumin and hemopexin) life. Conditions were considered optimal when cell number, albumin, and hemopexin levels were maintained throughout the 2-wk culture period. However, the decrease in AFP concentration, which occurred after a few days of culture, could not be reversed. The culture system developed is a suitable model for studying regulatory mechanisms governing structure and function during differentiation and may prove useful for testing the effect of toxic agents during fetal development of the human liver.

DNA methylation and genetic inactivation at thymidine kinase locus: two different mechanisms for silencing autosomal genes.

Patterns of methylation of CpG dinucleotides in the promoter region of the thymidine kinase (TK) gene in wild-type and TK-deficient Chinese hamster cell lines were studied. Whereas wild-type cells were unmethylated, three conventionally derived TK-deficient cell lines were all almost completely methylated in the promoter region. Demethylation at a number of different CpG sites was observed upon selection for reexpression of the TK gene. Of thirteen HhaI (GCGC) or HpaII (CCGG) sites studied, the highest correlation between absence of methylation and at least partial TK activity was obtained at one HhaI site within 20 bp of the putative cap site. Silencing in the three conventionally derived mutants is therefore accompanied by hypermethylation of the promoter-associated CpG-rich island. We contrast this situation with another type of silencing event, in which TK was coordinately inactivated at a high frequency with at least one other linked allele. Methylation of the promoter region of TK was not associated with this event, but two lines of evidence suggested a role for methylation at sites other than in the promoter region of TK.

Ultrastructural localization of glycoconjugates in the fungus Ascocalyx abietina, the Scleroderris canker agent of conifers, using lectin-gold complexes.

Different glycoconjugates were revealed in the fungus Ascocalyx abietina (Lagerberg.) Schlaepfer-Bernhard, by using various lectin-gold complexes. N-acetylglucosamine, N-acetylgalactosamine, and D-mannose were specifically localized in cell walls of fungal cells. N-acetylneuraminic acid (sialic acid) and L-fucose were detected in structures corresponding to lipid bodies, whereas they were totally absent in the cell wall. This is the first report on the occurrence of sialic acid in fungi and of fucose in Ascomycetes. The great advantage of using lectin-gold complexes for ultrastructural localization of sugars in phytopathogenic fungi, as well as in studies concerning host-pathogen interactions, is discussed.