Use-dependent corticospinal excitability is associated with resilience and physical performance during simulated military operational stress.

Simulated military operational stress (SMOS) provides a useful model to better understand resilience in humans as the stress associated with caloric restriction, sleep deficits, and fatiguing exertion degrades physical and cognitive performance. Habitual physical activity may confer resilience against these stressors by promoting favorable use-dependent neuroplasticity, but it is unclear how physical activity, resilience, and corticospinal excitability (CSE) relate during SMOS. To examine associations between corticospinal excitability, physical activity, and physical performance during SMOS. Fifty-three service members (age: 26 ± 5 yr, 13 women) completed a 5-day and -night intervention composed of familiarization, baseline, SMOS (2 nights/days), and recovery days. During SMOS, participants performed rigorous physical and cognitive activities while receiving half of normal sleep (two 2-h blocks) and caloric requirements. Lower and upper limb CSE were determined with transcranial magnetic stimulation (TMS) stimulus-response curves. Self-reported resilience, physical activity, military-specific physical performance (TMT), and endocrine factors were compared in individuals with high (HIGH) and low CSE based on a median split of lower limb CSE at baseline. HIGH had greater physical activity and better TMT performance throughout SMOS. Both groups maintained physical performance despite substantial psychophysiological stress. Physical activity, resilience, and TMT performance were directly associated with lower limb CSE. Individual differences in physical activity coincide with lower (but not upper) limb CSE. Such use-dependent corticospinal excitability directly relates to resilience and physical performance during SMOS. Future studies may use noninvasive neuromodulation to clarify the interplay among CSE, physical activity, and resilience and improve physical and cognitive performance.NEW & NOTEWORTHY We demonstrate that individual differences in physical activity levels coincide with lower limb corticospinal excitability. Such use-dependent corticospinal excitability directly relates to resilience and physical performance during a 5-day simulation of military operational stress with caloric restriction, sleep restriction and disruption, and heavy physical and cognitive exertion.

Reliability of corticospinal excitability estimates for the vastus lateralis: Practical considerations for lower limb TMS task selection.

Transcranial magnetic stimulation (TMS) is increasingly used to examine lower extremity corticospinal excitability (CSE) in clinical and sports research. Because CSE is task-specific, there is growing emphasis on the use of ecological tasks. Nevertheless, the comparative reliability of CSE measurements during established (e.g. knee extensions; KE) and more recent ecological (e.g. squats; SQT) lower extremity tasks has received less attention. The aim of this study was to compare the test-retest reliability of CSE, force, and muscle activity (EMG) during isometric SQT and KE. 19 right-footed men (age: 25 ± 5 yrs) with similar fitness and body composition performed SQT (N = 7) or KE (N = 12) on two consecutive days. Force and EMG were recorded during maximum voluntary isometric contractions (MVC). Corticospinal excitability was determined in the dominant leg during light (15% MVC) contractions based on motor evoked potential (MEP) stimulus-response-curves (SRC). Test-retest reliability, absolute agreement, and consistency were determined for force, EMG, and SRC MEP maximum (MEPMAX) and rising phase midpoint (V50). As a secondary analysis, all outcomes were compared between groups with mixed-methods ANCOVAs (Task × Time, covariate: body-fat-percentage). Compared with SQT, KE displayed better test-retest reliability and agreement for MEPMAX whereas V50, force, and EMG were similarly reliable. Force (p = 0.01) and MEPMAX (p = 0.02) were also greater during KE despite a similar V50 (p = 0.11). Differences in test-retest reliability, absolute agreement, and between-group comparisons highlight the need to carefully select lower limb TMS assessment tasks and encourage future efforts to balance ecological validity with statistical sensitivity.

Characterizing off-target corticospinal responses to double-cone transcranial magnetic stimulation.

INTRODUCTION: The double-cone coil (D-CONE) is frequently used in transcranial magnetic stimulation (TMS) experiments that target the motor cortex (M1) lower-limb representation. Anecdotal evidence and modeling studies have shed light on the off-target effects of D-CONE TMS but the physiological extent remains undetermined. PURPOSE: To characterize the off-target effects of D-CONE TMS based on bilateral corticospinal responses in the legs and hands. METHODS: Thirty (N = 30) participants (9 women, age: 26 ± 5yrs) completed a stimulus-response curve procedure with D-CONE TMS applied to the dominant vastus lateralis (cVL) and motor-evoked potentials (MEPs) recorded in each active VL and resting first dorsal interosseous (FDI). As a positive control (CON), the dominant FDI was directly targeted with a figure-of-eight coil and MEPs were similarly recorded in each active FDI and resting VL. MEPMAX, V50 and MEP latencies were compared with repeated-measures ANOVAs or mixed-effects analysis and Bonferroni-corrected pairwise comparisons. RESULTS: Off-target responses were evident in all muscles, with similar MEPMAX in the target (cVL) and off-target (iVL) leg (p = 0.99) and cFDI compared with CON (p = 0.99). cFDI and CON MEPMAX were greater than iFDI (p < 0.01). A main effect of target (p < 0.001) indicated that latencies were shorter with CON but similar in all muscles with D-CONE. DISCUSSION: Concurrent MEP recordings in bilateral upper- and lower-extremity muscles confirm that lower-limb D-CONE TMS produces substantial distance-dependent off-target effects. In addition to monitoring corticospinal responses in off-target muscles to improve targeting accuracy in real-time, future studies may incorporate off-target information into statistical models post-hoc.

Nanospace engineering of KOH activated carbon.

This paper demonstrates that nanospace engineering of KOH activated carbon is possible by controlling the degree of carbon consumption and metallic potassium intercalation into the carbon lattice during the activation process. High specific surface areas, porosities, sub-nanometer (<1 nm) and supra-nanometer (1-5 nm) pore volumes are quantitatively controlled by a combination of KOH concentration and activation temperature. The process typically leads to a bimodal pore size distribution, with a large, approximately constant number of sub-nanometer pores and a variable number of supra-nanometer pores. We show how to control the number of supra-nanometer pores in a manner not achieved previously by chemical activation. The chemical mechanism underlying this control is studied by following the evolution of elemental composition, specific surface area, porosity, and pore size distribution during KOH activation and preceding H(3)PO(4) activation. The oxygen, nitrogen, and hydrogen contents decrease during successive activation steps, creating a nanoporous carbon network with a porosity and surface area controllable for various applications, including gas storage. The formation of tunable sub-nanometer and supra-nanometer pores is validated by sub-critical nitrogen adsorption. Surface functional groups of KOH activated carbon are studied by microscopic infrared spectroscopy.

Microbial contamination of fuel ethanol fermentations.

Microbial contamination is a pervasive problem in any ethanol fermentation system. These infections can at minimum affect the efficiency of the fermentation and at their worse lead to stuck fermentations causing plants to shut down for cleaning before beginning anew. These delays can result in costly loss of time as well as lead to an increased cost of the final product. Lactic acid bacteria (LAB) are the most common bacterial contaminants found in ethanol production facilities and have been linked to decreased ethanol production during fermentation. Lactobacillus sp. generally predominant as these bacteria are well adapted for survival under high ethanol, low pH and low oxygen conditions found during fermentation. It has been generally accepted that lactobacilli cause inhibition of Saccharomyces sp. and limit ethanol production through two basic methods; either production of lactic and acetic acids or through competition for nutrients. However, a number of researchers have demonstrated that these mechanisms may not completely account for the amount of loss observed and have suggested other means by which bacteria can inhibit yeast growth and ethanol production. While LAB are the primary contaminates of concern in industrial ethanol fermentations, wild yeast may also affect the productivity of these fermentations. Though many yeast species have the ability to thrive in a fermentation environment, Dekkera bruxellensis has been repeatedly targeted and cited as one of the main contaminant yeasts in ethanol production. Though widely studied for its detrimental effects on wine, the specific species-species interactions between D. bruxellensis and S. cerevisiae are still poorly understood.

A biomechanical study of Jefferson fractures.

STUDY DESIGN: Fifteen specimens of the first cervical vertebra were tested by the application of pure tensile forces to failure. Seven specimens had intact transverse ligaments, and eight had transection of the transverse ligament before testing. Specimens were tested to failure by the rapid application of laterally directed tensile force to the ring; this force then was exerted through the lateral masses to simulate the mechanism of injury for this fracture as proposed by Jefferson. OBJECTIVES: To measure the biomechanical characteristics of the C1 ring, including the fracture patterns created with tensile loading, and to describe the influence of the transverse ligament on the behavior of the ring as it failed under tension. SUMMARY OF BACKGROUND DATA: Jefferson fractures have been reproduced in the laboratory by subjecting head and neck preparations to axial load. However, no previous detailed biomechanical studies of the fracture characteristics of the isolated C1 vertebra have been reported. METHODS: Specimens were tested to failure by rapid application of laterally directed tensile forces to the ring. RESULTS: Eleven two-part and three three-part fractures occurred. The mean tensile strength of the atlas was found to be 2,280 N. The average deformation required to fracture the C1 ring was 1.57 mm. The total energy absorbed by the ring averaged 1.99 N-m. There was no statistically difference between those specimens with the transverse ligament intact and those without a transverse ligament. CONCLUSIONS: The results of this study show that fractures of the C1 ring of greater than two parts can occur with pure tensile loading. The ring will fracture with as little as 1 mm of deformation.

The aggregated form of an AAMP derived peptide behaves as a heparin sensitive cell binding agent.

A peptide termed P189, derived from the sequence of a newly discovered protein, AAMP (angio-associated migratory cell protein), contains a motif that is predicted to a bind heparin. It occurs near the amino terminal end of AAMP. Previous studies have shown that in its solubilized form P189 (RRLRRMESESES) binds heparin and melanoma cells. The peptide is bipolar in that it contains positive charges at its amino end and negative charges at its carboxyl end. It forms strongly aggregated particles that require exposure to 50% DMSO and 100 degrees C for solubilization to occur. Now heparin and cell binding (heparin sensitive) are also demonstrated for the peptide in its particular form. Cell binding/clustering to the peptide particles is strong and resists exposure to various reagents (sugars and inhibitors of glycolysis and protein synthesis) except heparin. Tumor cell migration is partially inhibited by the presence of the peptide. On electron photomicrographs the peptide is seen in close apposition to cell membranes. Heparin sensitivity of the cell binding indicates that cell surface glycosaminoglycans are involved. The aggregated peptide binds heparin in a saturable manner with a dissociation constant, K(d), of 306 pmol. Cell binding/clustering studies using peptide variants of P189, which have substitutions in either the charged and/or nonpolar residues, show that the specific sequence of P189 optimizes heparin-sensitive cell aggregation. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 54: 365-372, 1997.

AAMP, a conserved protein with immunoglobulin and WD40 domains, regulates endothelial tube formation in vitro.

Angio-associated migratory cell protein (AAMP) is a newly discovered protein that is widely distributed with strong expression in endothelial cells and others with migratory potential (cytotrophoblasts, carcinoma cells, etc). AAMP is 52 kd with an isoelectric point of 5.2. Its sequence contains immunoglobulin type domains, WD40 repeats, a large acidic region with an acid box, a potential transmembrane region, potential serine/threonine phosphorylation sites, and a positively charged amino-terminal region with strong heparin binding potential (Kd = 14 pmol). Human umbilical vein endothelial cells cultured on Matrigel, a basement membrane material, form endothelial tubes (capillary-like structures). Anti-recombinant AAMP (anti-rAAMP) (1 to 10 microg/ml) inhibits this process under conditions that favor cross-linking of its ligand (AAMP). Immunofluorescent staining has shown that AAMP is distributed both intracellularly and extracellularly in cultures of endothelial cells and tubes. Molecular analysis of AAMP's protein sequence shows a striking evolutionary relationship with the YCR072c protein in Saccharomyces cerevisiae. Both the human and yeast proteins show an unusual and almost identical arrangement of immunoglobulin type domains, WD40 repeats, a protein kinase C phosphorylation consensus site in the carboxyl region, and a positively charged amino-terminal region that in AAMP has heparin binding potential. Detection of YCR072c's immunoglobulin type domains is new. Thus, AAMP is a protein that has been highly conserved in evolution and may function in the regulation of endothelial tube formation.

AAMP, a newly identified protein, shares a common epitope with alpha-actinin and a fast skeletal muscle fiber protein.

AAMP (angio-associated migratory cell protein) shares a common epitope with alpha-actinin and a fast-twitch skeletal muscle fiber protein. An antigenic peptide, P189, derived from the sequence of AAMP was synthesized. Polyclonal antibodies generated to P189 readily react with AAMP (52 kDa) in brain and activated T lymphocyte lysates, alpha-actinin (100 kDa) in all tissues tested, and a 23-kDa protein in skeletal muscle lysates. The antibody's reactivity for alpha-actinin can be competed with the purified protein. Activation of T lymphocytes does not alter the degree of alpha-actinin reactivity with anti-P189 as it does for AAMP's reactivity in these lysates. Competition studies with peptide variants show that six amino acid residues, ESESES, constitute a common epitope in all three proteins in human tissues. The antigenic determinant is continuous in AAMP but discontinuous (or assembled) in alpha-actinin. alpha-Actinin does not contain this epitope in its linear sequence so reactivity is attributed to an epitope formed by its secondary structure. Limited digestion of the reactive proteins with thermolysin destroys anti-P189's reactivity for alpha-actinin while reactivity for recombinant AAMP is retained. Specificity of anti-P189 for human skeletal muscle fast fibers seen on immunoperoxidase staining may be explained by anti-P189's reactivity with a 23-kDa protein found only in skeletal muscle lysates. Its pattern of reactivity is the same as that obtained using monoclonal anti-skeletal muscle myosin heavy chain in type II (fast-twitch) fibers.

Identification of a new immunoglobulin superfamily protein expressed in blood vessels with a heparin-binding consensus sequence.

A novel immunoglobulin-type protein expressed in blood vessels has been identified. The cDNA for AAMP (angio-associated, migratory cell protein) was first isolated from a human melanoma cell line during a search for motility-associated cell surface proteins. Upon analysis of the tissue distribution of AAMP, it was found to be expressed strongly in endothelial cells, cytotrophoblasts, and poorly differentiated colon adenocarcinoma cells found in lymphatics. The sequence of AAMP predicts a protein (M(r) 49,000) with distant identity (25%) to known proteins. It contains immunoglobulin-like domains [one with multiple homologies to deleted in colon carcinoma (DCC) protein], the WD40 repeat motif, and a heparin-binding consensus sequence. A 1.6-kilobase mRNA transcript of AAMP is detected in tissue culture cell lines and tissues. Affinity-purified polyclonal antibodies, anti-recombinant AAMP, and anti-peptide 189 (AAMP derived) recognize a M(r) 52,000 protein in human tissue and cellular extracts. The protein size is in keeping with the mRNA and predicted sequence. The AAMP-derived peptide, P189, contains a heparin-binding domain (dissociation constant, 14 pmol) and mediates heparin-sensitive cell adhesion. The shared expression of AAMP in endothelial cells, trophoblasts, and tumor cells implies a common function in migrating cells.

Oxyphilic papillary thyroid carcinomas.

Oxyphilic papillary carcinomas of the thyroid have not been extensively studied because they are rare. The morphology and behavior of 34 cases were described. The average age was 44.1 years, the female-to-male ratio was 3.9:1, and the average diameter of the tumors was 2.3 cm. All had papillary structures present. In 31 cases, there was capsular or parenchymal invasion. Six cancers had local lymph node metastases. The average follow-up for 29 patients was 8.1 years. Tumors reappeared in four patients; one patient died from recurrent disease, one patient with disease died due to an unrelated carcinoma, and two patients were treated successfully. Twenty-seven patients at the end of follow-up were alive with no detectable thyroid cancer. The majority of patients remained free of tumor, especially those younger than 50 years.

Tumor cell motility.

Tumor cell motility is required for invasion and metastasis. The locomotory machinery of the cell includes cell projections called pseudopodia which are regulated by a complicated linkage between cell surface receptors or sensors and the internal cytoskeleton. Recently a new class of motility stimulating cytokines have been identified. These cytokines can function as autocrine motility factors and require a pertussis toxin sensitive G protein pathway to transduce a random motile response.

Cell motility, a principal requirement for metastasis.

In studying the role of motility in the metastasis of tumor cells, we have described an autocrine motility factor. This agent, which stimulates random motility, probably contributes to the initial dissociation of the cells from the primary tumor mass. Extracellular matrix components, via several different mechanisms, may facilitate the crossing of biological barriers by the cells prior to the entry into the circulation. In locating at new sites, the tumor cells may be induced to exit from the circulation in response to attractants such as IGFs that could emanate from the target organ. These same growth factors could then stimulate cellular proliferation for another metastatic cycle. It is quite probable that detection of AMF may provide a new tool in cancer diagnosis. The complete characterization of AMF may also yield valuable therapeutic approaches: design of low molecular size antagonists of the attractants and antibodies that might be effective therapeutically as well as diagnostically. It seems clear, in any event, that immobilizing the tumor cell may be a crucial step in inhibiting metastasis.

Glycolysis as primary energy source in tumor cell chemotaxis.

The energy requirements via glycolytic pathways were directly measured in migrating tumor cells. Motility in the metastatic human melanoma cell line A2058, stimulated by insulinlike growth factor I (IGF-I), depends on glycolysis in the presence of glucose as its principal source of energy. Motility in glucose-free medium was 75% reduced and utilized mitochondrial respiration (inhibited by oligomycin). With increasing (physiologic) glucose concentrations, there was a dramatic shift to anaerobic glycolysis as the energy source and 93% elimination of the oligomycin inhibition of motility. Oxamate, an inhibitor of glycolysis, inhibited motility at all glucose concentrations. CO2 production from glycolysis and from the hexose monophosphate shunt was measured in migrating tumor cells. The time course and glucose-dose dependence of glycolytic CO2 production correlated directly with motility. In contrast, mitochondrial CO2 production was inversely related to glucose concentration. A monoclonal antibody for the IGF-I receptor inhibited both motility and glycolytic CO2 production, indicating that both processes are receptor mediated.

Solid and cystic ultimobranchial body remnants in the thyroid.

In this study we determined the incidence rate (89%) and characterized the morphology of ultimobranchial body (UBB) remnants found in 18 serially sectioned neonatal thyroid glands. Although UBB remnants are often referred to as solid cell nests, we found cystic features in 55%. Ciliated columnar cells were seen in 23%. One contained a large pseudo-papilla. The UBB cells had nuclei with features reminiscent of papillary carcinoma nuclei in that they were enlarged, oval, and contained finely dispersed chromatin when compared with follicular cell nuclei. Both papillary carcinomas and UBB remnants are common, occur as tiny, solid, or cystic thyroid entities in patients of all ages, may contain papillary structures, and share some common nuclear features. Therefore, it is important to include UBB remnants in the differential diagnosis of minute thyroid entities and to recognize their morphologic features.

Mitochondrial adenosine triphosphatase in the oxyphil cells of a renal oncocytoma.

Oxyphil cells are characterized by cytoplasm packed with large numbers of mitochondria. Study of these unusual cells may provide information about the regulation of mitochondrial biogenesis. Although it has been suggested that this is a compensatory proliferation due to a mitochondrial dysfunction, no such dysfunction has been well documented. In this study we considered the possibility of dysfunction in the mitochondrial enzyme F1/Fo-adenosine triphosphatase(ATPase) as a stimulating factor involved in the mitochondrial proliferation of oxyphil cells. Mitochondria isolated from frozen tissue of a renal oncocytoma showing structural integrity and purity by electron microscopy were studied. Submitochondrial particles formed by sonic disruption showed the presence of the F1 component of mitochondrial ATPase with electron microscopy which was functionally active. The oligomycinsensitive ATPase activity from the renal oncocytoma was 0.133 mumol/min.mg submitochondrial particle protein which was higher than the readings obtained from normal kidney tissue (0.091 mumol/min.mg SMP protein) obtained from hamsters. Normal human renal tissue obtained at autopsy contained only nonfunctional mitochondria and therefore could not be used as control tissue. Mitochondrial ATPase dysfunction does not appear to be the inciting factor in the proliferation of mitochondria seen in oxyphil cell metaplasia and future studies should consider other possibilities. Preliminary functional studies of this nature can be performed with properly prepared frozen surgical tissue.

Dehydroepiandrosterone reduces cancellous bone osteopenia in ovariectomized rats.

The effects of dehydroepiandrosterone (DHA) on cortical bone at the tibial diaphysis and cancellous bone at the tibial metaphysis were determined in intact and ovariectomized rats. Total plasma DHA was reduced at 10 and 16 wk after ovariectomy. Intact and ovariectomized rats were implanted monthly with controlled-release subcutaneous pellets containing 2.5 mg of DHA or placebo. Plasma DHA was elevated in DHA-treated intact rats and was near normal in hormone-treated ovariectomized rats. Ovariectomy resulted in severe cancellous bone osteopenia, which was reduced in DHA-treated animals. Cross-sectional and cortical areas were increased at the diaphysis in ovariectomized rats, and this was not altered by DHA treatment. Bone formation at the endosteal and periosteal surfaces of the tibial diaphysis was decreased 16 wk after ovariectomy, and DHA treatment appeared to antagonize these changes. We interpret these results as evidence that decreased peripheral DHA levels contribute to the skeletal changes in ovariectomized rats.

Cytologic diagnosis and ultrastructure of fine-needle aspirates of ganglion cysts.

This report describes 28 ganglion cysts in 21 patients. The presence of a colorless to pale-yellow gelatinous material in the aspirate is pathognomonic of ganglion cyst. The smears are fairly monotonous, and show abundant mucoid material, single cells resembling histiocytes, a few tight clusters of cells, some collagen fibers, and some red blood cells with altered shapes. Ultrastructural studies performed on five specimens reveal the fibroblastic and/or histiocytic nature of the cells in the aspirates.