The effect of age and sex on peak oxygen uptake during upper and lower body exercise: A systematic review

BACKGROUND

Large scale population norms for peak oxygen uptake (VO2peak) during cycle ergometry (CE) have been published for men and women across a wide range of ages. Although upper body functional capacity has an important role in activities of daily living far less is known regarding the effect of age and sex on upper body functional capacity (i.e. arm crank ergometry; ACE). The aim of this review was to determine the effect of age and sex on VO2peak obtained during ACE and CE in the same participants.

METHOD

The review was pre-registered with PROSEPERO (Ref: CRD42022349566). A database search using Academic Search Complete including CINAHL complete, CINHAL Ultimate, Medline, PubMed, SPORTDiscus was undertaken.

RESULTS

The initial search yielded 460 articles which was reduced to 243 articles following removal of duplicates. Twenty-five articles were subsequently excluded based on title resulting in 218 articles considered for retrieval. Following review of the abstracts, 78 further articles were excluded leaving 140 to be assessed for eligibility. Eighty-five articles were subsequently excluded, resulting in 55 articles being included. The decrease in VO2peak with age during CE was consistent with previous studies. Decreases in VO2peak during ACE with age, although paralleling those of CE, appeared to be of greater functional importance. When changes in VO2peak were considered below the age of 50 years little change was observed for absolute VO2peak during ACE and CE. In contrast, relative VO2peak demonstrated decreases in VO2peak for both ACE and CE likely reflecting increases in body mass and body fat percentage with age. After 50 years of age absolute and relative VO2peak demonstrated more similar and subtle responses. Heterogeneity across studies for both absolute and relative VO2peak between ACE and CE was large. Although strict inclusion criteria were applied, the inter-individual variation in sample populations was likely the main source of heterogeneity. There was a considerable lack data sets available for ages above 40 years of age.

CONCLUSIONS

These responses suggest that upper body VO2peak decreases in line with that of the lower body but, due to the lower peak values achieved during ACE, decreases in VO2peak may have more profound functional impact compared to that for the lower body. Using absolute and relative measures of VO2peak results in different age-related profiles when considered below 50 years of age. To further our understanding of whole body ageing more data is required for participants in mid and later life. The association between VO2peak and underlying physiological factors with age needs to be studied further, particularly in conjunction with activities of daily living and independent living.

Malformed trilobites from the Cambrian, Ordovician, and Silurian of Australia

Biomineralised remains of trilobites provide important insight into the evolutionary history of a diverse, extinct group of arthropods. Their exoskeletons are also ideal for recording malformations, including evidence of post-injury repair. Re-examination of historic collections and the study of new specimens is important for enhancing knowledge on trilobite malformations across this diverse clade. To expand the records of these abnormalities and present explanations for their formation, we document eight malformed trilobite specimens, as well as one carcass, housed within the Commonwealth Palaeontological Collection at Geoscience Australia in Canberra. We present examples of Asthenopsis, Burminresia, Centropleura, Coronocephalus, Dolicholeptus, Galahetes, Papyriaspis, and Xystridura from Cambrian, Ordovician, and Silurian deposits of Australia. Most of the malformed specimens show W-, U-, or L-shaped indentations that reflect injuries from either failed predation or complications during moulting, and a mangled carcass is ascribed to either successful predation or post-mortem scavenging. We also uncover examples of teratologies, such as bifurcated pygidial ribs and pygidial asymmetry, in addition to evidence of abnormal recovery (i.e., fusion of thoracic segments) from a traumatic incident.

Five new malformed trilobites from Cambrian and Ordovician deposits from the Natural History Museum

Injured trilobites present insight into how a completely extinct group of arthropods responded to traumatic experiences, such as failed predation and moulting complications. These specimens are therefore important for more thoroughly understanding the Paleozoic predator-prey systems that involved trilobites. To expand the record of injured trilobites, we present new examples of injured Ogygopsis klotzi and Olenoides serratus from the Campsite Cliff Shale Member of the Burgess Shale Formation (Cambrian, Miaolingian, Wuliuan), Paradoxides (Paradoxides) paradoxissimus gracilis from the Jince Formation (Cambrian, Miaolingian, Drumian), Ogygiocarella angustissima from the Llanfawr Mudstones Formation (Middle-Late Ordovician, Darriwilian-Sandbian), and Ogygiocarella debuchii from the Meadowtown Formation, (Middle-Late Ordovician, Darriwilian-Sandbian). We consider the possible origins of these malformations and conclude that most injuries reflect failed predation. Within this framework, possible predators are presented, and we uncover a marked shift in the diversity of animals that targeted trilobites in the Ordovician. We also collate other records of injured Ogygo. klotzi and Ol. serratus, and Ogygi. debuchii, highlighting that these species are targets for further understanding patterns and records of trilobite injuries.

Examining abnormal Silurian trilobites from the Llandovery of Australia

Abnormal trilobites present insight into how arthropods with fully biomineralised exoskeletons recovered from injuries, genetic malfunctions, and pathologies. Records of abnormal Silurian trilobites in particular show an abundance of specimens with teratologies and a limited record of injuries. Here we expand the record of abnormal Silurian trilobites by presenting seven new abnormal specimens of Odontopleura (Sinespinaspis) markhami from the early Silurian (Llandovery, Telychian) Cotton Formation, New South Wales. We use these specimens to illustrate novel evidence for asymmetric distribution of pleural thoracic spine bases. These abnormal bases likely reflect genetic complications, resulting in morphologies that would unlikely have aided the fitness of abnormal individuals. In considering records of malformed Silurian trilobites more broadly, we propose that the largest trilobites may have been prey at this time. This indicates a possible change in the trophic position of trilobites when compared to Cambrian and Ordovician palaeoecosystems.

A-43 Effects of Subthreshold Exercise on Post-concussive Symptom Endorsement and Cognition: A Pilot Randomized Clinical Trial

Purpose: The current study examined the effects of subthreshold exercise on symptom endorsement and neurocognitive functioning in adolescents with persisting concussion symptoms (>1 month). Methods: Sixteen participants (age M = 16.2, SD = 1.4) with persisting concussion symptoms were randomly assigned to control or subthreshold exercise intervention groups (Leddy et al., 2019). Participants engaged in concussion education before assignment to 6 weeks (3x weekly) of intervention: control (stretching) or subthreshold exercise. Both groups completed evaluations at baseline, midpoint, and follow-up, including a hybrid battery of assessments (yielding composites of processing speed and memory), a concussion symptom scale (PCS-R), and psychological inventories. Results: Both the intervention group and control group reported significant reduction in concussive symptom severity during the study period (PCS-R Change M = -21.29, SD = 13.54). Baseline endorsement of anxiety significantly differed across groups (p < 0.05); when controlling for anxiety, the intervention group demonstrated greater reduction in symptom endorsement compared to controls (F(1,13) = 7.30, p < 0.05, partial eta2 = 0.40). In contrast, after controlling for performance validity and the baseline anxiety difference, there was no significant difference (p > 0.05) in processing speed performance (partial eta2 = 0.14) or memory performance (partial eta2 = 0.11) by intervention group. Both groups remained generally intact normatively from the baseline to the follow-up evaluation across measures. Conclusions: Current results support the use of subthreshold exercise to reduce persisting symptoms of concussion post-acutely; additionally, results suggest that anxiety significantly impacted response to intervention. Lastly, there was no effect on cognitive indices by the intervention, suggesting that subthreshold exercise may have less impact on cognition than symptom endorsement in the post-acute phase of recovery.

An earliest Triassic age for Tasmaniolimulus and comments on synchrotron tomography of Gondwanan horseshoe crabs

Constraining the timing of morphological innovations within xiphosurid evolution is central for understanding when and how such a long-lived group exploited vacant ecological niches over the majority of the Phanerozoic. To expand the knowledge on the evolution of select xiphosurid forms, we reconsider the four Australian taxa: Austrolimulus fletcheri, Dubbolimulus peetae, Tasmaniolimulus patersoni, and Victalimulus mcqueeni. In revisiting these taxa, we determine that, contrary to previous suggestion, T. patersoni arose after the Permian and the origin of over-developed genal spine structures within Austrolimulidae is exclusive to the Triassic. To increase the availability of morphological data pertaining to these unique forms, we also examined the holotypes of the four xiphosurids using synchrotron radiation X-ray tomography (SRXT). Such non-destructive, in situ imaging of palaeontological specimens can aid in the identification of novel morphological data by obviating the need for potentially extensive preparation of fossils from the surrounding rock matrix. This is particularly important for rare and/or delicate holotypes. Here, SRXT was used to emphasize A. fletcheri and T. patersoni cardiac lobe morphologies and illustrate aspects of the V. mcqueeni thoracetronic doublure, appendage impressions, and moveable spine notches. Unfortunately, the strongly compacted D. peetae precluded the identification of any internal structures, but appendage impressions were observed. The application of computational fluid dynamics to high-resolution 3D reconstructions are proposed to understand the hydrodynamic properties of divergent genal spine morphologies of austrolimulid xiphosurids.

A Lagerstätte from Australia provides insight into the nature of Miocene mesic ecosystems

Reduced precipitation in the Miocene triggered the geographic contraction of rainforest ecosystems around the world. In Australia, this change was particularly pronounced; mesic rainforest ecosystems that once dominated the landscape transformed into the shrublands, grasslands, and deserts of today. A lack of well-preserved fossils has made it difficult to understand the nature of Australian ecosystems before the aridification. Here, we report on an exceptionally well-preserved rainforest biota from New South Wales, Australia. This Konservat-Lagerstätte hosts a rich diversity of microfossils, plants, insects, spiders, and vertebrate remains preserved in goethite. We document evidence for several species interactions including predation, parasitism, and pollination. The fossils are indicative of an oxbow lake in a mesic rainforest and suggest that rainforest distributions have shifted since the Miocene. The variety of fossils preserved, together with high fidelity of preservation, allows for unprecedented insights into the mesic ecosystems that dominated Australia during the Miocene.

Teratological trilobites from the Silurian (Wenlock and Ludlow) of Australia

Documentation of malformed trilobites has presented invaluable insight into the palaeobiology of a wholly extinct euarthropod group. Although the northern hemisphere record is relatively well documented, examples of abnormal trilobites from Australia are limited. Furthermore, most recorded specimens are from Cambrian-aged rocks. To extend this limited record, we document five new examples of malformed Australian trilobites from the Middle and Late Silurian (Wenlock and Ludlow) deposits of the Yarralumla Formation of the Australian Capital Territory and Yarwood Siltstone Member, Black Bog Shale in New South Wales. We record the first examples of abnormal pygidial and thoracic nodes and present new evidence for bifurcating pygidial ribs. These abnormal features are considered teratological morphologies. The aberrant nodes likely arose through developmental malfunctions, while the bifurcating ribs represent either similar defects, or an injury that developed into a teratological feature. Explanations for the limited record of malformed Australian trilobites and for the decrease in injured trilobites after the end-Ordovician are presented. Further documentation of malformed Australian trilobites from the middle-to-late Paleozoic will undoubtedly paint a more complete picture of how Gondwanan taxa recovered from injuries or unfortunate developmental complications.

Exploring the genetics underpinning dynamic laryngeal collapse associated with poll flexion in Norwegian-Swedish Coldblooded Trotter racehorses

BACKGROUND

Dynamic laryngeal collapse (DLC) associated with poll flexion is the most common disorder of the upper respiratory tract (URT) in the Norwegian-Swedish Coldblooded Trotter (NSCT). The disorder, which has also been diagnosed in other breeds of trotters and gaited horses, appears to be related to anatomic phenotypes and only occurs during poll flexion when the horse is exercised 'on the bit'.

OBJECTIVES

Identify genomic regions associated with DLC in the NSCT by combining a rigorous phenotyping protocol with genomic data from a high-density equine genotyping array.

STUDY DESIGN

Prospective case/control study.

METHODS

High-speed treadmill endoscopy was used to phenotype horses (n = 61) for DLC, distinguishing between cases and controls. Genome-wide association (GWA) analysis of DLC status was then performed using a principal component approach (PCA) with haplotype analyses subsequently performed for regions containing single-nucleotide polymorphisms (SNPs) above the suggestive genome-wide significance (GWS) threshold (P<1.0 × 10^-5 ).

RESULTS

One region containing 10 SNPs (Equus caballus chromosome [ECA] 7: 89,601,935-94,647,192) was above the suggestive GWS threshold. Two inferred haplotypes in this region demonstrated significant differences (P<0.001) between cases and controls, with the most frequent haplotype resulting in a significantly increased risk of DLC.

MAIN LIMITATIONS

Small sample size as a result of stringent phenotyping protocols.

CONCLUSIONS

The current study highlights a candidate genomic region on ECA7 as potentially important with regard to the manifestation of DLC. Further exploration of this region and the genes included within it will bring veterinarians and researchers closer to fully understanding the biological mechanisms underlying DLC in horses.

Trilobites and agnostids from the Goyder Formation (Cambrian Series 3, Guzhangian; Mindyallan), Amadeus Basin, central Australia

A new assemblage containing twenty-two species of trilobites and agnostids is described from the Goyder Formation (Cambrian Series 3) in the Ross River Syncline and Gardiner Ranges of the Amadeus Basin, Northern Territory, central Australia. New trilobite taxa described include the genus, Trephina gen. nov., and four new species Adelogonus prichardi sp. nov., Hebeia stewarti sp. nov., Liostracina joyceae sp. nov., and Trephina ranfordi sp. nov. Two agnostid taxa previously known only from Antarctica, Ammagnostus antarcticus Bentley, Jago Cooper, 2009 and Hadragnostus helixensis Jago Cooper, 2005, are also documented. Of the two agnostid species, the latter is the most age diagnostic, previously reported from the Cambrian Series 3 (Guzhangian; late Mindyallan; Glyptagnostus stolidotus Zone) Spurs Formation in Northern Victoria Land. This age for the Goyder Formation assemblage is supported by the co-occurrence of the trilobites Biaverta reineri Öpik, 1967, Blackwelderia repanda Öpik, 1967, Henadoparia integra Öpik, 1967, Monkaspis cf. travesi (Öpik, 1967), Nomadinis pristinus Öpik, 1967, Paraacidaspis? priscilla (Öpik, 1967), and Polycyrtaspis cf. flexuosa Öpik, 1967, also known from the late Mindyallan (G. stolidotus Zone) successions of the neighbouring Georgina Basin (Northern Territory and Queensland). The generic assemblage of the Goyder Formation is also similar to those from the Guzhangian (Mindyallan) of other parts of Australia (New South Wales, South Australia, and Western Australia), in addition to East Antarctica and North and South China.

Fibre Endoscopic Insertion of Palliative Oesophageal Tubes with the Nottingham Introducer1

Using the Nottingham introducer and diazepam sedation, 93 of 100 patients with oesophagogastric malignancy have been successfully intubated, 67 with Celestin tubes and 26 with Atkinson tubes. Their mean age was 72 years (range 36–91). Six of the failures were in patients with fundal adenocarcinoma. Sixty-nine patients were discharged from hospital after initial intubation (74%). Nine patients developed a perforation, 6 died and there were 5 deaths from aspiration. Nine patients are alive up to 11 months later. The mean survival after discharge was four months with a maximum of 18 months. Later 11 tubes obstructed and 12 Celestin tubes displaced upward.

Endoscopic insertion of oesophageal prosthetic tubes provides satisfactory palliation for inoperable oesophagogastric malignancy. The development of the Atkinson tube with a distal flange has eliminated tube displacement upwards.

Examining age differences in duration of wage replacement by injury characteristics

BACKGROUND

One explanation for why older age is associated with greater duration of wage replacement following a work-related injury may be that older workers sustain more severe injuries and different types of injury compared with their younger counterparts.

AIMS

To examine the role of injury-related characteristics in explaining the impact of age on wage replacement duration, and whether the relationship between age and wage replacement duration is consistent across injury types and levels of severity.

METHODS

A secondary analysis of workers' compensation claims in the Australian state of Victoria. In Victoria, only injuries which have accumulated >10 days of wage replacement, or have health care expenditures above a financial threshold, are eligible for compensation. Nested regression models were used to examine the relative contribution of injury-related characteristics to age differences in wage replacement duration.

RESULTS

Older age was associated with greater days of wage replacement among men and women, even after adjusting for injury characteristics. Adjustment for differences in injury types and compensation reporting practices resulted in moderate attenuation of the age-duration relationship among men and small attenuation among women. The age-duration relationship was consistent across injury types/severity.

CONCLUSIONS

The relationship between older age and greater duration of wage replacement is ubiquitous across injuries of different types and severity. Future research is required to understand better why older age is consistently associated with worse compensation outcomes following work-related injury.

Minor genomic differences between related B6 and B10 mice affect severity of schistosome infection by governing the mode of dendritic cell activation

Infection with the helminth Schistosoma mansoni results in hepatointestinal granulomatous inflammation mediated by CD4 T cells directed against parasite eggs. The severity of disease varies greatly in humans and mice; however, the genetic basis of such a heterogenous immune response remains poorly understood. Here we show that, despite their close genetic relationship, C57BL/10SnJ (B10) mice developed significantly more pronounced immunopathology and higher T helper 17 cell responses than C57BL/6J (B6) mice. Similarly, live egg-stimulated B10-derived dendritic cells (DCs) produced significantly more IL-1β and IL-23, resulting in higher IL-17 production by CD4 T cells. Gene expression analysis disclosed a heightened proinflammatory cytokine profile together with a strikingly lower expression of Ym1 in B10 versus B6 mice, consistent with failure of B10 DCs to attain alternative activation. To genetically dissect the differential response, we developed and analyzed congenic mouse strains that capture major regions of allelic variation, and found that the level of inflammation was controlled by a relatively small number of genes in a locus mapping to chromosome 4 117-143 MB. Our study has thus identified novel genomic regions that regulate the severity of the schistosome infection by way of controlling the mode of DC activation and consequent CD4 T-cell subset development.

Hypothalamic-anterior pituitary hormone deficiencies following traumatic brain injury in dogs

Traumatic brain injury is an important cause of hypopituitarism in human beings, but limited information exists in the veterinary literature regarding this condition. The primary study objective was to investigate whether hypothalamic-anterior pituitary axis dysfunction exists following traumatic brain injury in 17 client owned dogs. In this retrospective, observational, open, cohort study, information about dogs presented to four separate referral centres between April 2008 and October 2013 was reviewed. Cases were included if they had suffered from non-fatal traumatic brain injury, resulting in neurological dysfunction, and follow-up evaluation included measurement of the serum concentration of insulin-like growth factor 1 (IGF-1), endogenous adrenocorticotrophic hormone (ACTH), basal cortisol, thyroid-stimulating hormone, total thyroxine (TT4) and, if appropriate, free thyroxine. Decreased IGF-1 concentration was the most common abnormality detected (7/17, 41 per cent; median 132 ng/ml, range <15-536), followed by a decreased TT4 concentration (4/17, 23 per cent; median 19, range 4-49). Basal cortisol concentration was less than 20 nmol/l in two cases (2/17, 12 per cent; median 65, range <20-1735), with concurrently undetectable ACTH (<5 pg/ml). This study demonstrates that dogs with a history of traumatic brain injury can develop endocrine abnormalities indicative of hypothalamic-anterior pituitary dysfunction.

Corpus callosal abnormalities in dogs

BACKGROUND

Corpus callosal abnormalities (CCA) in dogs have been only sporadically reported and are poorly characterized.

HYPOTHESIS/OBJECTIVES

To describe the clinical presentation and magnetic resonance imaging (MRI) characteristics of dogs with CCA.

ANIMALS

Fifteen client-owned dogs.

METHODS

Retrospective study. Records of the contributing institutions were reviewed to identify dogs diagnosed with malformations affecting the corpus callosum (CC); cases in which the CCA was thought to be secondary were excluded.

RESULTS

The most represented breeds were Staffordshire Bull Terriers (5/15) and Miniature Schnauzers (3/15; n = 3, 20%) and the mean age at time of presentation of 19 months (range 3-81 months). The clinical signs most commonly reported were adipsia/hypodipsia with associated hypernatremia (12/15), tremors (6/15), and seizures (6/15). Review of the MR images revealed that 10 dogs had absence of the rostral CC and hypoplasia of the caudal portion, 4 dogs had a diffusely hypoplastic and dysplastic CC, and 1 dog had a diffusely hypoplastic CC. In 14 cases, there was abnormal cortical development with fusion of the ventral frontal lobes and part of the diencephalon, indicating lobar holoprosencephaly.

CONCLUSIONS AND CLINICAL IMPORTANCE

Previous literature has mainly associated CCA with adipsia and only 12 of 15 dogs in the current series demonstrated this abnormality. There are different degrees of the malformation but in 10 dogs the rostral portion of the CC is most severely affected. Fourteen dogs have simultaneous fusion of the midline structures rostral to the CC; this region has several structures involved in thirst regulation and might explain this derangement.

The microbial metabolites, short-chain fatty acids, regulate colonic Treg cell homeostasis

Regulatory T cells (Tregs) that express the transcription factor Foxp3 are critical for regulating intestinal inflammation. Candidate microbe approaches have identified bacterial species and strain-specific molecules that can affect intestinal immune responses, including species that modulate Treg responses. Because neither all humans nor mice harbor the same bacterial strains, we posited that more prevalent factors exist that regulate the number and function of colonic Tregs. We determined that short-chain fatty acids, gut microbiota-derived bacterial fermentation products, regulate the size and function of the colonic Treg pool and protect against colitis in a Ffar2-dependent manner in mice. Our study reveals that a class of abundant microbial metabolites underlies adaptive immune microbiota coadaptation and promotes colonic homeostasis and health.

The psychosocial work environment and incident diabetes in Ontario, Canada

BACKGROUND

Relatively few longitudinal studies have explored the relationship between psychosocial work conditions and diabetes incidence. Given the increasing global burden of diabetes this is an important area for public health research.

AIMS

To examine the relationships between dimensions of the psychosocial work environment on the subsequent incidence of diabetes among men and women in Ontario, Canada over a 9 year period.

METHODS

We used data from Ontario respondents (35 to 60 years of age) to the 2000-01 Canadian Community Health Survey linked to the Ontario Health Insurance Plan database for physician services and the Canadian Institute for Health Information Discharge Abstract Database for hospital admissions. Our sample of actively employed labour market participants with no previous diagnoses for diabetes was followed for a 9 year period to ascertain incident diabetes.

RESULTS

There were 7443 participants. Low levels of job control were associated with an increased risk of diabetes among women, but not among men. Counter to our hypotheses high levels of social support were also associated with increased diabetes risk among women, but not among men. No relationship was found between any psychosocial work measure and risk of diabetes among men.

CONCLUSIONS

Given the increasing prevalence of diabetes worldwide, job control could potentially be an import ant modifiable risk factor to reduce the incidence of diabetes among female, but not among male, workers. More research is needed to understand the pathways through which low social support may protect against the development of diabetes.

Induction and regulation of pathogenic Th17 cell responses in schistosomiasis

Schistosomiasis is a major tropical disease caused by trematode helminths in which the host mounts a pathogenic immune response against tissue-trapped parasite eggs. The immunopathology consists of egg antigen-specific CD4 T cell-mediated granulomatous inflammation that varies greatly in magnitude in humans and among mouse strains in an experimental model. New evidence, covered in this review, intimately ties the development of severe pathology to IL-17-producing CD4 T helper (Th17) cells, a finding that adds a new dimension to the traditional CD4 Th1 vs. Th2 cell paradigm. Most examined mouse strains, in fact, develop severe immunopathology with substantial Th17 as well as Th1 and Th2 cell responses; a solely Th2-polarized response is an exception that is only observed in low-pathology strains such as the C57BL/6. The ability to mount pathogenic Th17 cell responses is genetically determined and depends on the production of IL-23 and IL-1β by antigen presenting cells following recognition of egg antigens; analyses of several F2 progenies of (high × low)-pathology strain crosses demonstrated that quantitative trait loci governing IL-17 levels and disease severity vary substantially from cross to cross. Low pathology is dominant, which may explain the low incidence of severe disease in humans; however, coinfection with intestinal nematodes can also dampen pathogenic Th17 cell responses by promoting regulatory mechanisms such as those afforded by alternatively activated macrophages and T regulatory cells. A better understanding of the pathways conducive to severe forms of schistosomiasis and their regulation should lead to interventions similar to those presently used to manage other immune-mediated diseases.

Cardiovascular actions of leptin in the subfornical organ are abolished by diet-induced obesity

The subfornical organ (SFO), a sensory circumventricular organ lacking the normal blood-brain barrier with well documented roles in cardiovascular regulation, has recently been identified as a potential site at which the adipokine, leptin, may act to influence central autonomic pathways. Systemic and central leptin administration has been shown to increase blood pressure and it has been suggested that selective leptin resistance contributes to obesity-related hypertension. Given the relationship between obesity and hypertension, the present study aimed to investigate the cardiovascular consequences of the direct administration of leptin into the SFO of young lean rats and in the diet-induced obesity (DIO) rat model, which has been shown to be leptin-resistant. Leptin administration (500 fmol) directly into the SFO of young rats resulted in rapid decreases in blood pressure (BP) [mean area under the curve (AUC) = -677.8 ± 167.1 mmHg*s; n = 9], without an effect on heart rate (mean AUC = -21.2 ± 13.4 beats; n = 9), and these effects were found to be dose-related as microinjection of 5 pmol of leptin into the SFO had a larger effect on BP (mean AUC = -972.3 ± 280.1 mmHg*s; n = 4). These BP effects were also shown to be site-specific as microinjection of leptin into non-SFO regions or into the ventricle was without effect on BP (non-SFO: mean AUC = -22.4 ± 55.3 mmHg*s; n = 4; ventricle: mean AUC = 194.0 ± 173.0 mmHg*s; n = 6). By contrast, microinjection of leptin into leptin-resistant DIO rats was without effect on BP (mean AUC = 205.2 ± 75.1 mmHg*s; n = 4). These observations suggest that the SFO may be an important relay centre through which leptin, in normal weight, leptin responsive rats, acts to maintain BP within normal physiological limits through descending autonomic pathways involved in cardiovascular control and that, in obese, leptin-resistant, rats leptin no longer influences SFO neurones, resulting in an elevated BP, thus contributing to obesity-related hypertension.

The pathogenic Th17 cell response to major schistosome egg antigen is sequentially dependent on IL-23 and IL-1β

CBA/J mice infected with the helminth Schistosoma mansoni develop severe CD4 T cell-mediated hepatic granulomatous inflammation against parasite eggs associated with a robust Th17 cell response. We investigated the requisites for Th17 cell development using novel CD4 T cells expressing a transgenic TCR specific for the major Sm-p40 egg Ag, which produce IL-17 when stimulated with live schistosome eggs. Neutralization of IL-23 or blockade of the IL-1 receptor, but not IL-6 neutralization, abrogated egg-induced IL-17 secretion by transgenic T cells, whereas exogenous IL-23 or IL-1β reconstituted their ability to produce IL-17 when stimulated by syngeneic IL-12p40-deficient dendritic cells. Kinetic analysis demonstrated that IL-17 production was initiated by IL-23 and amplified by IL-1β. Significantly, schistosome-infected IL-12p40-deficient or IL-1R antagonist-treated CBA/J mice developed markedly reduced hepatic immunopathology with a dampened egg Ag-specific IL-17 response. These results demonstrate that the IL-23-IL-1-IL-17 axis has a central role in the development of severe schistosome egg-induced immunopathology.

The gut microbiota and mucosal T cells

It is intuitive that immune cells in the gut may require microbiota-derived cues for their differentiation. The proximity between host and microbe in the intestine would seemingly necessitate co-adaptation. However, it has been challenging to determine the members and features of the gut microbiota that influence immune system development and function. The recent identification of immunomodulatory members of the commensal microbiota is providing insight into the dependence of select, intestinal immune cell subsets on specific microbial species. In this review, we focus on the gut microbiota's influence on the development and function of mucosal T cells subsets, specifically intraepithelial lymphocytes and lamina propria CD4 T cells.

Solute Trapping in Metals

Many of the advances in rapid solidification processing of metallic alloys exploit the trapping of solute which occurs at high solidification velocities. The difficulty of performing experiments which measure such high solidification velocities in metals has until now prevented accurate measurements of solute trapping in these systems. We have observed the transition from near-equilibrium solute partitioning to solute trapping during solidification at m/s velocities in aluminum alloys, and have compared the predictions of various solute trapping models. Aluminum thin films deposited on insulators were ion-implanted with Sn, Cu, Ge, and In, and were pulsed-laser melted; plane-front solidification was achieved, and regrowth velocities of 0.6 m/s to 5 m/s were measured with the transient conductance technique. Of the existing solute trapping models, the Continuous Growth Model of Aziz was found to fit the observed dependence of the partition coefficient on solidification velocity more closely than any other single-parameter model. The diffusive speed, which locates the transition from solute partitioning to solute trapping, was found to vary from 6 m/s to 38 m/s for various solutes in aluminum. We have examined correlations between the diffusive speed in the Continuous Growth Model and known alloy properties in order to allow better estimates of the diffusive speed to be made for alloy systems in which it has not been measured; the relation between the diffusive speed and the equilibrium partition coefficient will be discussed.

Time-Resolved Measurements of Solidification and Undercooling in Metals and Alloys

We have performed nanosecond-resolution measurements of the lateral electrical resistivity of thin metal films on insulating substrates. Comparison of transient resistivity measurements with optical reflectivity measurements and heat-flow calculations permits the determination of the position and velocity of a planar crystal/melt interface, and an estimate of undercooling during pulsed laser melting of metals. We report detailed results for rapid solidification of Ni, including the observation of hypercooling of .liquid Ni.

Differential risk of employment in more physically demanding jobs among a recent cohort of immigrants to Canada

OBJECTIVE

To examine the proportion of a recent cohort of immigrants to Canada who were working in jobs that were more physically demanding than those in which they worked before migration to Canada.

DESIGN

Longitudinal cohort of immigrants to Canada with occupational position measured before and 2 and 4 years after arrival in Canada.

SUBJECTS

Respondents to Statistics Canada's Longitudinal Survey of Immigrants to Canada (LSIC). The LSIC surveyed a representative sample of immigrants, aged 15 and older, who arrived in Canada between November 2000 and December 2001. For the purpose of this study, the sample was restricted to respondents who had worked before immigrating and were working when re-interviewed 2 (n = 4331) or 4 (n = 4238) years after arrival in Canada.

MAIN OUTCOME

Employment in an occupation with higher physical demands than that employed in before arrival in Canada.

RESULTS

Respondents with less proficiency at speaking English and family class or refugee applicants were the most likely to be employed in occupations with higher physical demands both 2 and 4 years after arrival in Canada.

CONCLUSIONS

Employment in a more physically demanding occupation may pose particular risks of workplace injury. In this sample of immigrants to Canada, respondents with poorer English skills and refugees (factors that may increase this risk) were more likely to be employed in more physically demanding occupations. Greater attention to the prevention of workplace injuries among particular groups of new immigrants to Canada is required.

T-bet protects against exacerbation of schistosome egg-induced immunopathology by regulating Th17-mediated inflammation

C57BL/6 mice infected with Schistosoma mansoni naturally develop mild CD4(+) T-cell-mediated immunopathology characterized by small hepatic granulomas around parasite eggs. However, immunization with soluble egg Ag in CFA markedly exacerbates the lesions by inducing a potent proinflammatory environment with high levels of IFN-gamma and IL-17, which are signature cytokines of distinct Th1- versus Th17-cell lineages. To determine the relative role of these subsets in disease exacerbation, we examined mice deficient in T-bet (T-bet(-/-)), which is required for Th1 differentiation and IFN-gamma production. We now report that immunization with soluble egg Ag in CFA caused a significantly greater enhancement of egg-induced hepatic immunopathology in T-bet(-/-) mice compared with WT controls, and analysis of their granulomas disclosed a higher proportion of activated DC and CD4(+) T cells, as well as a marked influx of neutrophils. The absence of IFN-gamma in the T-bet(-/-) mice correlated with a marked increase in IL-23p19, IL-17 and TNF-alpha in granulomas and MLN. In contrast, T-bet(-/-) mice had lower levels of IL-4, IL-5 and IL-10 and a reduction in FIZZ1 and FoxP3 expression, suggesting diminished regulatory activity, respectively, by alternatively activated macrophages and Treg. These findings demonstrate that T-bet-dependent signaling negatively regulates Th17-mediated immunopathology in severe schistosomiasis.

Genetic control of severe egg-induced immunopathology and IL-17 production in murine schistosomiasis

Infection with the trematode parasite Schistosoma mansoni results in a distinct heterogeneity of disease severity, both in humans and in an experimental mouse model. Severe disease is characterized by pronounced hepatic egg-induced granulomatous inflammation in a proinflammatory cytokine environment, whereas mild disease corresponds with reduced hepatic inflammation in a Th2 skewed cytokine environment. This marked heterogeneity indicates that genetic differences play a significant role in disease development, yet little is known about the genetic basis of dissimilar immunopathology. To investigate the role of genetic susceptibility in murine schistosomiasis, quantitative trait loci analysis was performed on F(2) progeny derived from SJL/J and C57BL/6 mice, which develop severe and mild pathology, respectively. In this study, we show that severe liver pathology in F(2) mice 7 wk after infection significantly correlated with an increase in the production of the proinflammatory cytokines IL-17, IFN-gamma, and TNF-alpha by schistosome egg Ag-stimulated mesenteric lymph node cells. Quantitative trait loci analysis identified several genetic intervals controlling immunopathology as well as IL-17 and IFN-gamma production. Egg granuloma size exhibited significant linkage to two loci, D4Mit203 and D17Mit82, both of which were inherited in a BL/6 dominant manner. Furthermore, a significant reduction of hepatic granulomatous inflammation and IL-17 production in interval-specific congenic mice demonstrated that the two identified genetic loci have a decisive effect on the development of immunopathology in murine schistosomiasis.

Dendritic cell IL-23 and IL-1 production in response to schistosome eggs induces Th17 cells in a mouse strain prone to severe immunopathology

Infection with schistosomes results in a CD4 T cell-mediated inflammatory reaction against parasite eggs that varies greatly in magnitude both in humans as well as in mice. In the murine disease, the severe form of immunopathology correlates with high levels of IL-17. We now report that live schistosome eggs stimulate dendritic cells from high pathology-prone CBA mice to produce IL-12p40, IL-6, and TGF-beta, whereas those from low pathology-prone BL/6 mice only make TGF-beta. Moreover, egg-stimulated dendritic cells plus naive CD4 T cells from CBA mice resulted in increased levels of IL-6, IL-23, IL-1beta, as well as IL-17 and the chemokines CXCL1, CXCL2, and CCL2, whereas similarly treated BL/6 cell cocultures instead expressed higher IL-4, IL-5, IL-10, and the transcription factor Foxp3. Neutralization of IL-23 and IL-1, but not of IL-6 or IL-21, profoundly inhibited egg-induced IL-17 production in the CBA cocultures. Conversely, stimulation with schistosome eggs in the presence of exogenous IL-23 and IL-1beta induced BL/6 cells to make IL-17. These findings identify IL-23 and IL-1 as critical host factors that drive IL-17 production, and suggest that parasite recognition followed by a genetically determined innate proinflammatory response induces the development of Th17 cells and thus controls the outcome of immunopathology in schistosomiasis.

Thoracic stenosis causing lateral compression of the spinal cord in two immature Dogues de Bordeaux

This case report describes a novel developmental vertebral malformation in two young Dogues de Bordeaux, which was diagnosed by magnetic resonance imaging. Both dogs were treated surgically with reasonable success.

The subfornical organ: a central nervous system site for actions of circulating leptin

Adipose tissue plays a critical role in energy homeostasis, secreting adipokines that control feeding, thermogenesis, and neuroendocrine function. Leptin is the prototypic adipokine that acts centrally to signal long-term energy balance. While hypothalamic and brain stem nuclei are well-established sites of action of leptin, we tested the hypothesis that leptin signaling occurs in the subfornical organ (SFO). The SFO is a circumventricular organ (CVO) that lacks the normal blood-brain barrier, is an important site in central autonomic regulation, and has been suggested to have a role in modulating peripheral signals indicating energy status. We report here the presence of mRNA for the signaling form of the leptin receptor in SFO and leptin receptor localization by immunohistochemistry within this CVO. Central administration of leptin resulted in phosphorylation of STAT3 in neurons of SFO. Whole cell current-clamp recordings from dissociated SFO neurons demonstrated that leptin (10 nM) influenced the excitability of 64% (46/72) of SFO neurons. Leptin was found to depolarize the majority of responsive neurons with a mean change in membrane potential of 7.3 +/- 0.6 mV (39% of all SFO neurons), while the remaining cells that responded to leptin hyperpolarized (-6.9 +/- 0.7 mV, 25% of all SFO neurons). Similar depolarizing and hyperpolarizing effects of leptin were observed in recordings from acutely prepared SFO slice preparations. Leptin was found to influence the same population of SFO neurons influenced by amylin as three of four cells tested for the effects of bath application of both amylin and leptin depolarized to both peptides. These observations identify the SFO as a possible central nervous system location, with direct access to the peripheral circulation, at which leptin may act to influence hypothalamic control of energy homeostasis.

Examining the relationships between job control and health status: a path analysis approach

OBJECTIVE

To examine the pathways through which job control affects health status; to examine if the effects of job control on health status are attenuated by including other measures associated with lower socioeconomic status, and to examine if the relationship between job control and health status is consistent across socioeconomic status groups.

DESIGN

A prospective observational cohort study over eight years (1994-2002).

PARTICIPANTS

4886 Respondents aged 25-60 years, who were non-self-employed labour force participants, working more than 20 hours per week, without physical or mental limitations restricting the type or amount of work they could do at baseline. After longitudinal attrition, the remaining study sample was 3411 (87% of the original study sample who did not die or become pregnant during the survey period).

MAIN RESULTS

Low job control in 1994 was associated with worse than expected self-rated health in 2002, both directly and indirectly via a lower physical activity level in 1996. Adjustment for other factors associated with low socioeconomic status did not attenuate these relationships to a large extent. No differences were found in the effects of job control on physical activity or health status between socioeconomic groups (high and low education and high and low household income).

CONCLUSIONS

The inclusion of other factors associated with lower socioeconomic status did not attenuate the direct and indirect effects of job control on health status. The finding that low job control is associated with lower physical activity levels deserves further investigation, given the increasing concern about rising levels of obesity in the developed world.

Comparing the risk of work-related injuries between immigrants to Canada and Canadian-born labour market participants

OBJECTIVES

To examine the burden of work-related injuries among immigrants to Canada compared to Canadian-born labour force participants.

METHODS

Using data from the 2003 and 2005 Canadian Community Health Surveys (n = 99,115), two nationally representative population samples, we examined the risk of self-reported, activity limiting work-related injuries among immigrants with varying time periods since arrival in Canada. Models were adjusted for hours of work in the last 12 months as well as various demographic and work-related variables.

RESULTS

Immigrant men in their first 5 years in Canada reported lower rates of activity limiting injuries compared to Canadian-born respondents. Surprisingly, the percentage of injuries that required medical attention was much higher among recent immigrants compared to Canadian-born respondents, resulting in an increased risk of activity limiting injuries requiring medical attention among immigrant men compared to Canadian-born labour force participants. No excess risk was found among female immigrants compared to Canadian-born female labour market participants.

CONCLUSIONS

Immigrant men in their first 5 years in Canada are at increased risk of work-related injuries that require medical attention. A similar risk is not present among immigrant women. Further, given differences in the number of activity limiting injuries requiring medical attention across immigrant groups, we believe this excess risk among immigrant men may be underestimated in the current data source. Future research should attempt to fully capture the barriers faced by immigrants in obtaining safe employment, the number of injuries that are sustained by immigrants while working, and the consequences of these injuries.

Transcriptome analysis reveals human cytomegalovirus reprograms monocyte differentiation toward an M1 macrophage

Monocytes are primary targets for human CMV (HCMV) infection and are proposed to be responsible for hematogenous dissemination of the virus. Monocytes acquire different functional traits during polarization to the classical proinflammatory M1 macrophage or the alternative antiinflammatory M2 macrophage. We hypothesized that HCMV induced a proinflammatory M1 macrophage following infection to promote viral dissemination because, biologically, a proinflammatory state provides the tools to drive infected monocytes from the blood into the tissue. To test this hypothesis of monocyte conversion from a normal quiescent phenotype to an inflammatory phenotype, we used Affymetrix Microarray to acquire a transcriptional profile of infected monocytes at a time point our data emphasized is a key temporal regulatory point following infection. We found that HCMV significantly up-regulated 583 (5.2%) of the total genes and down-regulated 621 (5.5%) of the total genes>or=1.5-fold at 4 h postinfection. Further ontology analysis revealed that genes implicated in classical M1 macrophage activation were stimulated by HCMV infection. We found that 65% of genes strictly associated with M1 polarization were up-regulated, while only 4% of genes solely associated with M2 polarization were up-regulated. Analysis of the monocyte chemokinome at the transcriptional level showed that 44% of M1 and 33% of M2 macrophage chemokines were up-regulated. Proteomic analysis using chemokine Ab arrays confirmed the secretion of these chemotactic proteins from HCMV-infected monocytes. Overall, the results identify that the HCMV-infected monocyte transcriptome displayed a unique M1/M2 polarization signature that was skewed toward the classical M1 activation phenotype.

Findings on low-field cranial MR images in epileptic dogs that lack interictal neurological deficits

Recurrent seizuring is a common neurological problem in dogs and can present diagnostic difficulties for the attending clinician. Associated interictal neurological deficits strongly suggest brain disease but the frequency of structural abnormalities in patients without such deficits is unknown. In this study the prevalence of clinically significant magnetic resonance imaging (MRI) abnormalities was determined in two groups of interictally normal dogs, those younger than 6 years and those older than 6 years of age. In the former group, only 1/46 dogs (2.2%) had significant MRI abnormalities, whereas in the latter group, 8/30 (26.7%) were abnormal. None of the dogs had an identifiable metabolic cause for the seizures. These findings suggest that the diagnostic yield of advanced neuroimaging techniques in young seizuring dogs without interictal neurological deficits is low, but reaffirms their value in similar older individuals.

Antiperspirant compositions based on titanium salts

Antiperspirant compositions have traditionally relied upon aluminium-based active compounds to reduce sweating. Titanium is a physiologically inert metal, and titanium metal chelates appear to induce superficial physical pore blockage to provide effective antiperspirancy in a variety of product types. Titanium metal chelates can be formed from titanium alkoxides and organic acids. Conflicting opinions as to the salt structure exist and, in the case of part-neutralized ammonium titanium lactate (ATL) salt, evidence has been seen for a range of ligands bound to different strengths at different stages of hydrolysis. Aluminium is thought to work by ductal diffusion to give antiperspirancy via neutralization to a polymeric, relatively superficial gel obstruction. ATL mimics conventional alumiunium salts in that it is mainly a topical antiperspirant active, with ATL-treated skin restored to normal patterns of sweating activity after a few tape-strips. Under acidic and near-neutral pH conditions, the ATL active is relatively stable to hydrolysis and can be formulated into topical compositions as either an aqueous solution of the active or as a free-flowing powder in anhydrous systems. When judged by an in vitro efficacy technique which is thought to predict in vivo performance, ATL functions as an effective antiperspirant.

In vitro and in vivo characterization of equine herpesvirus type 1 (EHV-1) mutants devoid of the viral chemokine-binding glycoprotein G (gG)

Glycoprotein G (gG) of equine herpesvirus type 1 (EHV-1), a structural component of virions and secreted from virus-infected cells, was shown to bind to a variety of different chemokines and as such might be involved in immune modulation. Little is known, however, about its role in the replication cycle and infection of EHV-1 in vivo. Here we report on the function of gG in context of virus infection in vitro and in vivo. A gG deletion mutant of pathogenic EHV-1 strain RacL11 (vL11DeltagG) was constructed and analyzed. Deletion of gG had virtually no effect on the growth properties of vL11DeltagG in cell culture when compared to parental virus or a rescuant virus vL11DeltagGR, respectively, and virus titers and plaque formation were unaffected in the absence of the glycoprotein. Similarly, in the murine model of EHV-1 infection, no significant differences in virulence between the gG deletion mutant and RacL11 or vL11DeltagGR were found at high doses of infection. However, infection of mice at lower doses revealed that the gG deletion mutant was able to replicate to higher titers in lungs of infected mice. Additionally, these mice lost significantly more weight than those infected with RacL11 and a more pronounced inflammatory response in lungs was observed. Therefore we concluded that deletion of gG in EHV-1 seems to lead to an exacerbation of respiratory disease in the mouse.

Brain abscess in a dog immunosuppressed using cyclosporin

This report describes a dog that developed brain abscesses following prolonged immunosuppression with cyclosporin. Bacteria within the abscess were most likely Nocardia, an organism well recognised in immunosuppressed humans, and probably reached the brain through haematogenous spread from a more long-standing abscess in the mediastinum. Bacterial brain abscesses developing in this manner are very rare in dogs and this case highlights the wider range of possible diagnoses that need to be considered in immunosuppressed patients and the care with which potent drugs such as cyclosporin should be used.

Cardiovascular actions of orexin-A in the rat subfornical organ

Orexin-A is a neuropeptide, primarily produced in the lateral hypothalamic/perifornical hypothalamus. Orexin receptors and immunoreactive neuronal fibres are widely distributed throughout the brain, suggesting integrative neurotransmitter roles in a variety of physiological systems. Intracerebroventricular injections of orexin-A increase blood pressure and stimulate drinking, and the subfornical organ (SFO), a circumventricular structure implicated in autonomic control, is a potential site at which orexin may act to exert these effects. We have therefore used microinjection techniques to examine the effects of orexin-A administered directly into the SFO on blood pressure and heart rate in urethane anaesthetised male Sprague-Dawley rats. Orexin-A microinjection (50 fmol) into the SFO caused site-specific decreases in blood pressure (SFO: mean area under curve (AUC) = -681.7 +/- 46.8 mmHg*s, n = 22 versus non-SFO: 63.68 +/- 54.69 mmHg*s, n = 15, P < 0.001), and heart rate (SFO: mean AUC = -26.7 +/- 2.8 beats, n = 22, versus non-SFO: mean AUC = 1.62 +/- 2.1 beats, n = 15, P < 0.001). Vagotomy did not alter the hypotensive or bradycardic responses elicited by orexin-A microinjection. Prior alpha-adrenoceptor blockade with phenoxybenzamine (1 mg/kg, i.v.) masked the orexin-A induced blood pressure (mean AUC = -122.6 +/- 17.6 mmHg*s, n = 4, P < 0.01 paired t-test) and heart rate (mean AUC = -6.7 +/- 1.7 beats, n = 4, P < 0.05, paired test) response. The orexin-A induced heart rate response was attenuated when beta-adrenoceptors were blocked with propranolol (1 mg/kg, i.v.; mean AUC = 0.6 +/- 2.8 beats, n = 5, P < 0.01 paired t-test). These studies demonstrate that microinjection of orexin-A into the SFO causes site specific decreases in blood pressure and heart rate which is mediated by a reduction in sympathetic tone.

The influence of ramp rate on VO2peak and "excess" VO2 during arm crank ergometry

The principal aim of this study was to examine how different ramp rates influenced the attainment of peak physiological responses during incremental arm crank ergometry (ACE). Additionally, the study examined whether there was any evidence for the development of an "excess" VO (2) during ACE due to upward curvi-linearity in the VO (2)-work rate relationship, and whether this was influenced by the ramp rate. Sixteen physically active, though non-specifically trained, men (mean +/- S age 30 +/- 8 years; height 1.79 +/- 0.07 m; body mass 84.7 +/- 13.2 kg) volunteered to participate. Having completed a familiarisation test, all subjects returned to the laboratory to complete two ramp tests on an electrically-braked ergometer in a counter-balanced order. Both ramp tests started at 60 W with work rate subsequently incremented by either 6 or 12 W . min (-1). Pulmonary gas exchange was measured breath-by-breath throughout the tests. Subjects achieved a greater final work rate during the 12 W . min (-1) test compared to the 6 W . min (-1) test (168 +/- 28 vs. 149 +/- 26 W; p < 0.001). The VO (2peak) (3.06 +/- 0.65 vs. 2.96 +/- 0.48 L . min (-1); p = 0.27), HR (peak) (179 +/- 15 vs. 177 +/- 16 b . min (-1); p = 0.17) and V.E (peak) (112 +/- 22 vs. 105 +/- 16 L . min (-1); p = 0.09) were not different between the tests, but VCO (2peak) (3.54 +/- 0.64 vs. 3.27 +/- 0.46 L . min (-1); p = 0.01) RER (peak) (1.17 +/- 0.07 vs. 1.11 +/- 0.06; p < 0.001), and end-exercise blood (lactate) (11.9 +/- 2.1 vs. 10.8 +/- 2.6 mmol . L (-1); p = 0.005) were all higher in the 12 W . min (-1) test. An "excess" VO (2) was observed in 13 out of 16 tests at 12 W . min (-1) and in 15 out of 16 tests at 6 W . min (-1). Neither the magnitude of the "excess" VO (2) (0.42 +/- 0.41 vs. 0.37 +/- 0.18 L . min (-1); p = 0.66) nor the VO (2) at which the V.O (2)-work rate relationship departed from linearity (2.17 +/- 0.34 vs. 2.18 +/- 0.32 L . min (-1); p = 0.94) were significantly different between the two ramp tests. These data indicate that differences in ramp rate within the range of 6 - 12 W . min (-1) influence the peak values of work rate, VCO (2) and RER, but do not influence peak values of VO (2) or HR during ACE. The development of an "excess" VO (2) appears to be a common feature of ramp exercise in ACE, although the mechanistic basis for this effect is presently unclear.

The effect of crank rate on physiological responses and exercise efficiency using a range of submaximal workloads during arm crank ergometry

This study examined the effects of variations in crank rate on physiological responses during submaximal arm ergometry. Fifteen non-specifically trained male subjects volunteered to participate in this study. Each subject undertook a discontinuous arm crank ergometry test (30, 50, 70, 90 W) on three separate occasions using crank rates of 50, 70, and 90 rev.min(-1). Respiratory parameters and heart rate were continuously monitored. An 80-microL capillary blood sample was obtained immediately following each exercise bout for the determination of whole blood lactate. Measures of efficiency were calculated using specific caloric equivalents of oxygen consumption (V(O2)). Heart rate was lowest (p < 0.05) at 30, 50, and 70 W using 50 rev.min(-1). Values of gross and net efficiency tended to be higher (p < 0.05) using 50 rev.min (-1) at the lower absolute workloads, but no differences (p > 0.05) were observed between the three crank rates at 90 W. No differences (p > 0.05) were observed between crank rates for delta efficiency. This study confirms that variations in crank rate can influence gross and net values of V(O2) and exercise efficiency at low absolute workloads, but crank rate ceases to be an influential factor at moderate workloads. Further research is required to identify the specific mechanisms underpinning the observations reported in the present study relating to the interaction between crank rate, workload, and exercise efficiency during arm crank ergometry.