Determining concentric and eccentric force-velocity profiles during squatting.

PURPOSE: The force-velocity relationship of muscular contraction has been extensively studied. However, previous research has focussed either on isolated muscle or single-joint movements, whereas human movement consists of multi-joint movements (e.g. squatting). Therefore, the purpose of this study was to investigate the force-velocity relationship of isovelocity squatting. METHODS: Fifteen male participants (24 ± 2 years, 79.8 ± 9.1 kg, 177.5 ± 6 cm) performed isovelocity squats on a novel motorised isovelocity device (Kineo Training System) at three concentric (0.25, 0.5, and 0.75 m s-1) and three eccentric velocities (- 0.25, - 0.5, and - 0.75 m s-1). Peak vertical ground reaction forces, that occurred during the isovelocity phase, were collected using dual force plates (2000 Hz) (Kistler, Switzerland). RESULTS: The group mean squat force-velocity profile conformed to the typical in vivo profile, with peak vertical ground reaction forces during eccentric squatting being 9.5 ± 19% greater than isometric (P = 0.037), and occurring between - 0.5 and - 0.75 m s-1. However, large inter-participant variability was identified (0.84-1.62 × isometric force), with some participants being unable to produce eccentric forces greater than isometric. Sub-group analyses could not identify differences between individuals who could/could not produce eccentric forces above isometric, although those who could not tended to be taller. CONCLUSIONS: These finding suggest that variability exists between participants in the ability to generate maximum eccentric forces during squatting, and the magnitude of eccentric increase above isometric cannot be predicted solely based on a concentric assessment. Therefore, an assessment of eccentric capabilities may be required prior to prescribing eccentric-specific resistance training.

Systemic Amyloid A Amyloidosis in Island Foxes (Urocyon littoralis): Severity and Risk Factors.

Systemic amyloid A (AA) amyloidosis is highly prevalent (34%) in endangered island foxes (Urocyon littoralis) and poses a risk to species recovery. Although elevated serum AA (SAA) from prolonged or recurrent inflammation predisposes to AA amyloidosis, additional risk factors are poorly understood. Here we define the severity of glomerular and medullary renal amyloid and identify risk factors for AA amyloidosis in 321 island foxes necropsied from 1987 through 2010. In affected kidneys, amyloid more commonly accumulated in the medullary interstitium than in the glomeruli (98% [n= 78 of 80] vs 56% [n= 45], respectively;P< .0001), and medullary deposition was more commonly severe (19% [n= 20 of 105]) as compared with glomeruli (7% [n= 7];P= .01). Univariate odds ratios (ORs) of severe renal AA amyloidosis were greater for short- and long-term captive foxes as compared with free-ranging foxes (ORs = 3.2, 3.7, respectively; overall P= .05) and for females as compared with males (OR = 2.9;P= .05). Multivariable logistic regression revealed that independent risk factors for amyloid development were increasing age class (OR = 3.8;P< .0001), San Clemente Island subspecies versus San Nicolas Island subspecies (OR = 5.3;P= .0003), captivity (OR = 5.1;P= .0001), and nephritis (OR = 2.3;P= .01). The increased risk associated with the San Clemente subspecies or captivity suggests roles for genetic as well as exogenous risk factors in the development of AA amyloidosis.

Development of Autoimmune-Mediated ß Cell Failure After Total Pancreatectomy With Autologous Islet Transplantation.

Total pancreatectomy with islet autotransplantation (TPIAT) is performed for definitive treatment of chronic pancreatitis; patients are not diabetic before surgery, or have C-peptide positive pancreatogenous diabetes. Thus, TPIAT recipients are not traditionally considered at risk for autoimmune loss of the islet graft. We describe a 43-year-old female who underwent TPIAT with high mass islet graft of 6031 IEQ/kg, with no evidence of presurgical ß cell autoimmunity who developed type 1 diabetes within the first year after TPIAT, resulting in complete loss of beta cell function. The patient had positive GAD and insulin autoantibodies at 1 year and 18 months after TPIAT, not present prior, and undetectable C-peptide after mixed meal and intravenous glucose tolerance testing at 18 months. Glucagon secretion was preserved, suggesting the transplanted alpha cell mass was intact. HLA typing revealed a DR3/DR4 class II haplotype. This case highlights the need to consider de novo type 1 diabetes in patients with unexpected islet graft failure after TPIAT.

Molecular profiling reveals prognostically significant subtypes of canine lymphoma.

We performed genomewide gene expression analysis of 35 samples representing 6 common histologic subtypes of canine lymphoma and bioinformatics analyses to define their molecular characteristics. Three major groups were defined on the basis of gene expression profiles: (1) low-grade T-cell lymphoma, composed entirely by T-zone lymphoma; (2) high-grade T-cell lymphoma, consisting of lymphoblastic T-cell lymphoma and peripheral T-cell lymphoma not otherwise specified; and (3) B-cell lymphoma, consisting of marginal B-cell lymphoma, diffuse large B-cell lymphoma, and Burkitt lymphoma. Interspecies comparative analyses of gene expression profiles also showed that marginal B-cell lymphoma and diffuse large B-cell lymphoma in dogs and humans might represent a continuum of disease with similar drivers. The classification of these diverse tumors into 3 subgroups was prognostically significant, as the groups were directly correlated with event-free survival. Finally, we developed a benchtop diagnostic test based on expression of 4 genes that can robustly classify canine lymphomas into one of these 3 subgroups, enabling a direct clinical application for our results.

Intramuscular, intravenous and oral levetiracetam in dogs: safety and pharmacokinetics.

Intravenous (IV) levetiracetam (LEV) is available for humans for bridge therapy when the oral route is unavailable. We investigated the safety and pharmacokinetics of LEV administered intramuscularly (IM), IV, and orally to dogs. Six Hound dogs received 19.5-22.6 mg/kg of LEV IM, IV and orally with a wash-out period in between. All dogs received 500 mg LEV orally and 5 mL of 100 mg/mL LEV IM. Three dogs received 500 mg of LEV IV and three dogs received 250 mg LEV IV with 250 mg given perivascularly to approximate extravasation. Safety was assessed using a pain scale at time of IM administration and histopathological examination 24 h to 5 days after injection. Intravenous LEV half-life was 180 +/- 18 min. Bioavailability of IM LEV was 100%. Mean time to T(max) after IM was 40 +/- 16 min. The mean C(max) IM was 30.3 +/- 3 mug/mL compared to the C(0) of 37 +/- 5 mug/mL for IV. Mean inflammation score (0-4 scale) for IM LEV was 0.28 and for saline 0.62. Extravasation did not cause tissue damage. Parenteral LEV is well tolerated and appears safe following IM and IV injections in dogs. Parenteral LEV should be evaluated for use in dogs with epilepsy.

Modulation of fatty acid metabolism and immune suppression are features of in vitro tumour sphere formation in ontogenetically distinct dog cancers.

Non-adherent, 3-dimensional sphere formation is used as an in vitro surrogate to evaluate cellular potential for tumour initiation and self-renewal. To determine if a shared molecular program underlies the capacity for sphere formation by cells originating from diverse tumour types, we characterized molecular and functional properties of 10 independent cell lines derived from 3 ontogenetically distinct dog cancers: hemangiosarcoma, osteosarcoma and glial brain tumours. Genome-wide gene expression profiling identified tumour-of-origin-dependent patterns of adjustment to sphere formation in a uniform culture condition. However, expression of the stem/progenitor markers CD34 and CD117, resistance to cytotoxic drugs and dye efflux (side population assays) showed no association with these gene expression profiles. Instead, primary sphere-forming capacity was inversely correlated with the ability to reform secondary spheres, regardless of tumour ontogeny. Primary sphere formation seemed to be proportional to the number of pre-existing cells with sphere-forming capacity in the cell lines. Cell lines where secondary sphere formation was more proficient than primary sphere formation showed enrichment of genes involved in fatty acid synthesis and immunosuppressive cytokines. In contrast, cell lines where secondary sphere formation was approximately equivalent to or less proficient than primary sphere formation showed upregulation of CD40 and enrichment of genes involved in fatty acid oxidation. Our data suggest that in vitro sphere formation is associated with upregulation of gene clusters involved in metabolic and immunosuppressive functions, which might be necessary for self-renewal and for tumour initiation and/or tumour propagation in vivo.

Methylome of human skeletal muscle after acute & chronic resistance exercise training, detraining & retraining.

DNA methylation is an important epigenetic modification that can regulate gene expression following environmental encounters without changes to the genetic code. Using Infinium MethylationEPIC BeadChip Arrays (850,000 CpG sites) we analysed for the first time, DNA isolated from untrained human skeletal muscle biopsies (vastus lateralis) at baseline (rest) and immediately following an acute (single) bout of resistance exercise. In the same participants, we also analysed the methylome following a period of muscle growth (hypertrophy) evoked via chronic (repeated bouts-3 sessions/wk) resistance exercise (RE) (training) over 7-weeks, followed by complete exercise cessation for 7-weeks returning muscle back to baseline levels (detraining), and finally followed by a subsequent 7-week period of RE-induced hypertrophy (retraining). These valuable methylome data sets described in the present manuscript and deposited in an open-access repository can now be shared and re-used to enable the identification of epigenetically regulated genes/networks that are modified after acute anabolic stimuli and hypertrophy, and further investigate the phenomenon of epigenetic memory in skeletal muscle.

An in vitro model of early islet amyloid polypeptide (IAPP) fibrillogenesis using human IAPP-transgenic mouse islets.

The mechanisms underlying insufficient insulin secretion and loss of beta-cell mass in feline and human type 2 diabetes mellitus are incompletely understood. However, islet amyloid polypeptide (IAPP)-derived islet amyloidosis (IA) has been linked to increased rates of beta-cell apoptosis and, therefore, our goal was to develop an in vitro model of IAPP fibrillogenesis using isolated pancreatic islets from mice transgenic for human IAPP (hIAPP Tg mice). Islets from hIAPP Tg mice, from mice transgenic for non-amyloidogenic murine IAPP (mIAPP Tg mice), and from the FVB background strain were exposed to normal (5.5 mM) or high (28 mM) glucose conditions in cell culture for 8 days. On days 0 and 8, islets were collected for electron microscopy (EM). EM showed no abnormalities in the mIAPP Tg or FVB islets at either time point. On day 8, hIAPP Tg islets cultured at high glucose concentration formed extracellular IAPP-derived flocculent deposits. No significant differences in rates of apoptosis were found between groups. Our findings, therefore, show that in vitro culture of hIAPP Tg mouse islets under high glucose conditions produces a readily available and rapidly inducible model of IAPP-derived fibrillogenesis and enables the study of early phases of the molecular pathogenesis of IA.

Effects of plasma treatment with purified protein A and Staphylococcus aureus Cowan I on spontaneous animal neoplasms.

Eleven dogs with spontaneous neoplasms were intensively treated with an immunoadsorption system consisting of a continuous flow centrifuge, Protein A-Sepharose columns, and a semi-automatic elution system. Despite consistent and substantial lowering of immunoglobulin G levels, tumor regression was noted in only one of 11 dogs. In contrast, infusion of small volumes of plasma after incubation with heat and formalin-treated Staphylococcus aureus Cowan I resulted in a tumoricidal response in five of six animals. These results suggest that tumor necrosis is probably not induced by Protein A-mediated removal of humoral "blocking" factors.

Newly identified pancreatic protein islet amyloid polypeptide. What is its relationship to diabetes?

Islet amyloid polypeptide (IAPP) or amylin is a newly identified 37-amino acid COOH-terminal-amidated polypeptide that is the major protein constituent of amyloid deposits in insulinomas and amyloid deposits in pancreatic islets of non-insulin-dependent (type II) diabetic humans and adult diabetic cats. IAPP is stored with insulin in beta-cell secretory vesicles and is cosecreted with insulin in response to glucose and several secretagogues. IAPP has been demonstrated in normal pancreatic islets of many species, but IAPP-derived amyloid develops commonly in the islets of only a few species (e.g., humans and cats), especially in association with age-related diabetes. IAPP from the human and cat inherently contains a short amyloidogenic sequence that is not present in species that do not form islet amyloid. Studies in animals indicate that an aberration in the synthesis or processing of IAPP, leading to a local increase in concentration of IAPP in the islet, is also required to facilitate the conversion of IAPP to amyloid. The formation of islet amyloid may contribute to the development of type II diabetes by causing disruption of islet cells and by replacement of islets. It has also been proposed that an abnormality of IAPP homeostasis underlies the pathogenesis of type II diabetes. A significant causal relationship between IAPP and type II diabetes is based on reports that IAPP inhibits glucose-stimulated insulin release by beta-cells and that IAPP inhibits insulin-stimulated rates of glycogen synthesis and glucose uptake by skeletal muscle cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Islet amyloid polypeptide and insulin secretion from isolated perfused pancreas of fed, fasted, glucose-treated, and dexamethasone-treated rats.

Rats from four experimental treatment groups, including fed controls, 24- to 30-h fasted, dexamethasone-treated, and intraperitoneal glucose-treated, were used to assess the effects of these treatments on the immunohistochemically detectable islet amyloid polypeptide (IAPP) content in the pancreatic islets. Isolated perfused pancreases from additional animals in these groups were used to assess insulin and IAPP secretion and relative amounts of these hormones secreted into the perfusate under low-glucose (2.75 mM) and high-glucose (16.7 mM) conditions. Insulin and IAPP concentrations in the perfusate were measured by radioimmunoassays. Titration of immunohistochemical staining revealed the highest levels of IAPP in the dexamethasone- and glucose-treated groups, followed by the fed controls; the least amount was observed in the fasted group. In the perfusion experiments, the dexamethasone-treated group had significantly higher IAPP secretion than did all of the other groups under stimulation with 16.7 mM glucose. In addition, both dexamethasone treatment and glucose treatment increased the relative amount of IAPP to insulin secretion during 16.7 mM glucose stimulation in comparison with fed controls and fasted groups. Fasting tended to have the opposite effect and significantly decreased the relative amount of IAPP to insulin secreted under stimulation with 16.7 mM glucose. In all groups, IAPP and insulin secretion were generally parallel, which is consistent with their colocalization in the beta-cell secretory vesicle and co-release after glucose stimulation. However, significant differences in the insulin-IAPP ratios between experimental groups is consistent with the hypothesis that production of IAPP and insulin are regulated differently in the beta-cell.(ABSTRACT TRUNCATED AT 250 WORDS)

Islet amyloid polypeptide in human insulinomas. Evidence for intracellular amyloidogenesis.

Amyloid deposits that characteristically form in the pancreatic islets of patients with non-insulin-dependent diabetes mellitus (NIDDM) and in insulinomas are both derived from islet amyloid polypeptide (IAPP). Evidence from previous studies has suggested that deposition of IAPP-derived amyloid is related to inherent amyloidogenic sequences present within normal human IAPP, together with an increased production and local concentration of IAPP. However, whether the aggregation of IAPP to form amyloid fibrils is primarily an intra- or extracellular event is not clear. To address this question, we studied 20 human insulinomas by light and electron microscopy. By light microscopy, amyloid deposits were demonstrated in 13 of 20 (65%) human insulinomas. Furthermore, evaluation of Congo red-stained tumor sections showed small, globular or irregular, congophilic amyloid deposits within the cytoplasm of many tumor cells in 10 of 13 (77%) amyloid-containing insulinomas. Dense, punctate areas of IAPP immunoreactivity within tumor cells corresponded with the congophilic intracellular deposits. Ubiquitin immunoreactivity also was observed as punctate intracellular labeling and within large extracellular amyloid deposits. Among the 10 insulinomas available for electron microscopic evaluation, pathological IAPP-immunoreactive (immunogold) deposits were found in 3 of 5 insulinomas in which amyloid was demonstrated by light microscopy and in none of 5 tumors found negative for amyloid by light microscopy. Morphology of IAPP-immunoreactive deposits varied from those with the classical distinct 7- to 10-nm diameter nonbranching fibrils to those with distinct but faint fibrillarity to those without discernable fibrils.(ABSTRACT TRUNCATED AT 250 WORDS)

Treatment with growth hormone and dexamethasone in mice transgenic for human islet amyloid polypeptide causes islet amyloidosis and beta-cell dysfunction.

Islet amyloid derived from islet amyloid polypeptide (IAPP) is a well-recognized feature of type II diabetes. However, the mechanism of islet amyloidogenesis is unknown. In vitro studies suggest that amino acid residues 20-29 in human, but not mouse, IAPP confer amyloidogenicity consistent with the absence of spontaneous islet amyloidosis in mice. Several clinical and in vitro studies suggest that increased synthetic rates of IAPP predispose to IAPP-amyloidosis. In the present study, we sought to test the hypothesis that pharmacological induction of insulin resistance in a mouse transgenic (TG) for human IAPP would induce islet amyloid and beta-cell dysfunction. TG and non-transgenic (N-TG) control mice were treated with both rat growth hormone (12 micrograms/day) and dexamethasone (0.24 mg/day) (dex/GH) or received no treatment for 4 weeks, after which animals were killed to examine islet morphology. Treatment with dex/GH caused hyperglycemia (7.3 +/- 0.4 vs. 5.2 +/- 0.1 mmol/l, TG vs. N-TG, P < 0.001) associated with a decreased plasma insulin concentration (595 +/- 51 vs. 996 +/- 100 pmol/l, TG vs. N-TG, P < 0.05) in TG versus control mice. Islet amyloid was induced in treated TG mice but not in control mice. Islet amyloid was identified in both intra- and extracellular deposits, the former being associated with evidence of beta-cell degeneration. We conclude that dex/GH treatment in mice TG for human IAPP induces IAPP-derived islet amyloid, hyperglycemia, and islet dysfunction. The present model recapitulates the islet morphology and phenotype of type II diabetes.

Structure of cat islet amyloid polypeptide and identification of amino acid residues of potential significance for islet amyloid formation.

Cats and humans, unlike most rodent species, develop amyloid in the islets of Langerhans in conjunction with non-insulin-dependent diabetes mellitus. The amyloid consists of a 37-amino acid polypeptide referred to as islet amyloid polypeptide (IAPP). The primary structures of IAPP from human and three rodent species have previously been determined. Sequence divergence was seen in the region corresponding to amino acid residues 20-29, which in human IAPP has been suggested to confer the amyloidogenic properties to the molecule. Using polymerase chain-reaction methodology, we determined the primary sequence of cat IAPP. Amino acid region 20-29 shows specific similarities and differences compared with human and rodent IAPP, respectively. A synthetic cat IAPP20-29 decapeptide formed amyloid fibrils spontaneously in vitro. Comparison between the structure and amyloid fibril-forming activity of various synthetic peptides suggests that the amino acid residues at positions 25-26 in mature IAPP are important for the amyloidogenic properties of the molecule.

Islet amyloidosis in a patient with chronic massive insulin resistance due to antiinsulin receptor antibodies.

We report islet hyperplasia, nesidioblastosis, and abundant islet amyloidosis (derived from islet amyloid polypeptide) in a case of severe insulin resistance due to a circulating antiinsulin receptor antibody. Massive chronic beta-cell stimulation (as well as noninsulin-dependent diabetes mellitus and insulinoma) appears to be associated with islet amyloid.

Diabetes mellitus in cystic fibrosis is characterized by islet amyloidosis.

A high proportion of patients with cystic fibrosis (CF) develop diabetes mellitus. In common with type II diabetes mellitus, diabetes mellitus in CF is characterized by a progressive decline in beta-cell function and an approximately 50% decline in beta-cell mass. It is not known whether islet amyloidosis (characteristic of type II diabetes mellitus) is present in diabetes mellitus complicating CF. To address this, pancreatic samples were obtained at autopsy from 9 control cases (without CF) and 41 cases of CF that were, in turn, subdivided into 13 nondiabetic, 12 borderline diabetic, and 16 diabetic cases based on clinical criteria. Islet amyloid was detected by light microscopy in 69% cases of CF with diabetes mellitus, 17% of cases with borderline diabetes mellitus, and none of the nondiabetic cases. Islet amyloid was not present in any of the control cases. Islet amyloidosis derived from islet amyloid polypeptide is a characteristic feature of diabetes mellitus in CF as well as type II diabetes mellitus.

A beta-associated cerebral angiopathy and senile plaques with neurofibrillary tangles and cerebral hemorrhage in an aged wolverine (Gulo gulo).

In this study of an aged wolverine (Gulo gulo), we document neuropathologic lesions (cerebral amyloid angiopathy (CAA), neuritic plaques (NPs), neurofibrillary tangles (NFTs), and granulovacuolar degeneration strikingly similar to those present in aging and Alzheimer's disease (AD), with the additional finding of concurrent cerebral hemorrhage. A beta immunoreactive cerebral amyloid angiopathy and senile plaques (neuritic and diffuse) were present throughout the cerebral cortex and hippocampus. Ubiquitin immunoreactivity was noted in peripheral portions of some of the plaques. Argyrophilic intracellular neurofibrillary tangles containing abnormally phosphorylated (Ser 202) tau protein were present within cortical and hippocampal neurons. The wolverine should be added to the list of nonhuman species (dogs, nonhuman primates, polar bears) with amyloid deposits similar to those in aged humans and in humans with AD. The aged wolverine appears to be distinct from other nonhuman species in possessing plaques and NFTs, as well as other histologic cerebral lesions frequently associated with AD.

Pathogenesis of feline diabetes mellitus.

The common form of spontaneous diabetes mellitus that occurs in domestic cats bears close resemblance clinically and pathologically to human type 2 diabetes mellitus (T2DM). For example, the typical diabetic cat is obese and middle-aged, and has low but detectable circulating insulin levels. However, the most striking similarity is the occurrence of islet amyloidosis (IA) in nearly all diabetic cats and in over 90% of humans with T2DM. IA in both humans and cats is derived from islet amyloid polypeptide (IAPP, or amylin) which is a hormone produced and secreted along with insulin by the pancreatic beta cells. Since all cats and humans normally produce IAPP, additional factors must be invoked in order to explain the development of IA. Several lines of evidence support the concept that IA is caused by chronically increased stimulus for beta cells to secrete IAPP (and insulin). For example, peripheral insulin resistance such as in chronic obesity results in increased IAPP and insulin secretion. A recent study, in which diabetes mellitus was induced in cats, demonstrated that IAPP hypersecretion was induced by treatment with a sulfonylurea drug and resulted in 4/4 cats in this group developing IA. In contrast, cats treated with insulin had low IAPP secretion and minimal IA developed in 1/4 cats. Several human-IAPP transgenic mouse models, in which there is IAPP overexpression, also support the notion that prolonged high expression of IAPP leads to IA. In vitro models of IAPP overexpression also support this mechanism for IA formation and by demonstrating an association between IA formation and beta cell toxicity, suggest a linkage between IA formation and loss of beta cells in T2DM. A recent study has indicated that intermediate-sized IAPP-derived amyloid fibrils can disrupt cell membranes and therefore, may be involved in the destruction of beta cells. Striking parallels between the pathogenesis of IA and beta-amyloid plaque formation in Alzheimer's disease suggest possible parallel pathogenetic mechanisms of cell death and provide potential avenues for future studies into the pathogenesis of IA.

Gray-scale sonographic characterization of aminoglycoside-induced nephrotoxicosis in a canine model.

RATIONALE AND OBJECTIVES: The diagnostic usefulness of gray-scale sonography was evaluated in a canine model of aminoglycoside-induced nephrotoxicosis. METHODS: Sonography was performed before and during the onset and progression of nephrotoxicosis induced by administration of a toxic dosage of gentamicin. Subjective visualization of increased renal cortex echogenicity (IRCE) was objectified with digital image analysis methods. Results of both subjective and objective evaluation were correlated with clinicopathologic tests and renal cortex biopsy obtained concurrently. RESULTS: Subjective visualization of IRCE was associated with significant nephrotoxicosis and was superior to serum creatinine elevation in nephrotoxicity detection. Objective detection of IRCE improved nephrotoxicity detection sensitivity to that of increased urine enzymuria. CONCLUSIONS: Based on the above results, subjective visualization of IRCE in patients with aminoglycoside-induced nephrotoxicity may occur before azotemia and is suggestive of significant renal dysfunction; application of digital image analysis methods may lead to earlier sonographic recognition of nephrotoxicity.