Timing and Modulation of Activity in the Lower Limb Muscles During Indoor Rowing: What Are the Key Muscles to Target in FES-Rowing Protocols?

The transcutaneous stimulation of lower limb muscles during indoor rowing (FES Rowing) has led to a new sport and recreation and significantly increased health benefits in paraplegia. Stimulation is often delivered to quadriceps and hamstrings; this muscle selection seems based on intuition and not biomechanics and is likely suboptimal. Here, we sample surface EMGs from 20 elite rowers to assess which, when, and how muscles are activated during indoor rowing. From EMG amplitude we specifically quantified the onset of activation and silencing, the duration of activity and how similarly soleus, gastrocnemius medialis, tibialis anterior, rectus femoris, vastus lateralis and medialis, semitendinosus, and biceps femoris muscles were activated between limbs. Current results revealed that the eight muscles tested were recruited during rowing, at different instants and for different durations. Rectus and biceps femoris were respectively active for the longest and briefest periods. Tibialis anterior was the only muscle recruited within the recovery phase. No side differences in the timing of muscle activity were observed. Regression analysis further revealed similar, bilateral modulation of activity. The relevance of these results in determining which muscles to target during FES Rowing is discussed. Here, we suggest a new strategy based on the stimulation of vasti and soleus during drive and of tibialis anterior during recovery.

TIME Impact - a new user-friendly tuberculosis (TB) model to inform TB policy decisions

Tuberculosis (TB) is the leading cause of death from infectious disease worldwide, predominantly affecting low- and middle-income countries (LMICs), where resources are limited. As such, countries need to be able to choose the most efficient interventions for their respective setting. Mathematical models can be valuable tools to inform rational policy decisions and improve resource allocation, but are often unavailable or inaccessible for LMICs, particularly in TB. We developed TIME Impact, a user-friendly TB model that enables local capacity building and strengthens country-specific policy discussions to inform support funding applications at the (sub-)national level (e.g. Ministry of Finance) or to international donors (e.g. the Global Fund to Fight AIDS, Tuberculosis and Malaria).TIME Impact is an epidemiological transmission model nested in TIME, a set of TB modelling tools available for free download within the widely-used Spectrum software. The TIME Impact model reflects key aspects of the natural history of TB, with additional structure for HIV/ART, drug resistance, treatment history and age. TIME Impact enables national TB programmes (NTPs) and other TB policymakers to better understand their own TB epidemic, plan their response, apply for funding and evaluate the implementation of the response.The explicit aim of TIME Impact's user-friendly interface is to enable training of local and international TB experts towards independent use. During application of TIME Impact, close involvement of the NTPs and other local partners also builds critical understanding of the modelling methods, assumptions and limitations inherent to modelling. This is essential to generate broad country-level ownership of the modelling data inputs and results. In turn, it stimulates discussions and a review of the current evidence and assumptions, strengthening the decision-making process in general.TIME Impact has been effectively applied in a variety of settings. In South Africa, it informed the first South African HIV and TB Investment Cases and successfully leveraged additional resources from the National Treasury at a time of austerity. In Ghana, a long-term TIME model-centred interaction with the NTP provided new insights into the local epidemiology and guided resource allocation decisions to improve impact.

Increased thrombogenic potential of human monocyte-derived macrophages spontaneously transformed into foam cells

This study investigated whether spontaneous lipid enrichment of human macrophages affects their thrombogenic potential as measured by increased production of tissue factor (TF) and plasminogen activation inhibitor types 1 and 2 (PAI-1 and PAI-2). Macrophages were obtained following a 7-day culture period of monocytes, isolated from the same donor, in autologous serum (HS) or in fetal bovine serum (FBS). Those cultured in HS underwent marked lipid accumulation relative to those cultured in FBS that was accompanied by increased production of TF and PAI-1, but not of PAI-2, and decreased production of interleukin-1beta. They also contained more arachidonic and linoleic acid and lower amounts of n-3 polyunsaturated fatty acids, particularly docosahexaenoic acid (22: 6). These data indicate that the transformation of macrophages into foam cells results in an increase in their thrombogenic and antifibrinolytic potential and provide a possible explanation of the thrombotic sequelae frequently consequent on plaque fissuring and disruption.

Vastatins inhibit tissue factor in cultured human macrophages. A novel mechanism of protection against atherothrombosis

We examined the effect of fluvastatin, the first entirely synthetic 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor that is structurally different from other vastatins, on tissue factor (TF) expression in human macrophages spontaneously differentiated in culture from blood monocytes. Fluvastatin decreased TF activity in a dose-dependent manner (1 to 5 mumol/L) in both unstimulated and lipopolysaccharide-stimulated macrophages, and this reduction paralleled the decrease in immunologically recognized TF protein. The same results were obtained with another lipophilic vastatin, simvastatin, but not with hydrophilic pravastatin. The reduction in TF expression was also observed in macrophages enriched in cholesterol after exposure to 50 micrograms/mL acetylated low density lipoprotein. The inhibitory effect of fluvastatin on TF activity and antigen was fully reversible by coincubation with 100 mumol/L mevalonate or 10 mumol/L all-trans-geranylgeraniol but not with dolichol, farnesol, or geraniol. Suppression of TF antigen and activity was accompanied by a diminution in TF mRNA levels, which was completely prevented by mevalonate. Furthermore, fluvastatin impaired bacterial lipopolysaccharide-induced binding of c-Rel/p65 heterodimers to a kappa B site in the TF promoter, indicating that this drug influences induction of the TF gene. We conclude that lipophilic vastatins inhibit TF expression in macrophages, and because this effect is prevented by mevalonate and geranylgeraniol, a geranylgeranylated protein plays a crucial role in the regulation of TF biosynthesis. The suppression of TF in macrophages by vastatins indicates a potential mechanism by which these drugs interfere with the formation and progression of atherosclerotic plaque as well as thrombotic events in hyperlipidemic patients.

Platelet-neutrophil interaction and superoxide anion generation: involvement of purine nucleotides

Stimulated platelets secrete a variety of physiologically active substances that affect many neutrophil functions. We have examined the capacity of platelets to modulate superoxide anion generation by neutrophils. The amounts of superoxide anion produced by neutrophils in the presence of platelets were markedly enhanced when platelet-neutrophil coincubations were stimulated with agents that simultaneously activate both cell types, as the calcium ionophore A23187 and sodium arachidonate. This effect was dependent upon the number of platelets added to the incubation media and was not affected by inhibitors of arachidonic acid pathway or by preincubation of platelets with an antibody anti-P-selectin. The hypothesis of an involvement of purine nucleotides released by platelets during aggregation on the observed effect of enhancement of superoxide anion generation by neutrophils was then tested. Experimental evidence indicates that platelets release, during A23187-induced aggregation, amounts of ATP that are of the same order (5-10 microM) of those demonstrated to enhance superoxide anion generation by neutrophils. In addition, platelet lysates mimicked the effect of intact platelets in enhancing superoxide anion generation by A23187 stimulated neutrophils. Interestingly, at variance with the results obtained with intact platelets and platelet lysates, supernatants of thrombin-stimulated platelets did not increase O2.- by neutrophils. The enhancing effect of these supernatants was, however, restored when platelets were preincubated with an antibody anti P-selectin. These data indicate that platelets, through the release of purine nucleotides, enhance superoxide generation by neutrophils, thus increasing the cytotoxic potential of these cells.

Binding and internalization in vivo of [125I]hCG in Leydig cells of the rat

The present study was performed to demonstrate the binding, mode of uptake, pathway and fate of iodinated human chorionic gonadotropin ([125I]hCG) by Leydig cells in vivo using electron microscope radioautography. Following a single injection of [125I]hCG into the interstitial space of the testis, the animals were fixed by perfusion with glutaraldehyde at 20 minutes, 1, 3, 6 and 24 hours. The electron microscope radioautographs demonstrated a prominent and qualitatively similar binding of the labeled hCG on the microvillar processes of the Leydig cells at 20 minutes, 1, 3, and 6 hours. The specificity of the [125I]hCG binding was determined by injecting a 100-fold excess of unlabeled hormone concurrently with the labeled hormone. Under these conditions, the surface, including the microvillar processes of Leydig cells, was virtually unlabeled, indicating that the binding was specific and receptor-mediated. In animals injected with labeled hCG and sacrificed 20 minutes later, silver grains were also seen overlying the limiting membrane of large, uncoated surface invaginations and large subsurface vacuoles with an electron-lucent content referred to as endosomes. A radioautographic reaction was also seen within multivesicular bodies with a pale stained matrix. At 1 hour, silver grains appeared over dense multivesicular bodies and occasionally over secondary lysosomes, in addition to the structures mentioned above, while at 3 and 6 hours, an increasing number of secondary lysosomes became labeled. At 24 hours, binding of [125I]hCG to the microvillar processes of Leydig cells persisted but was diminished, although a few endosomes, multivesicular bodies and secondary lysosomes still showed a radioautographic reaction. No membranous tubules that were seen in close proximity to, or in continuity with, endosomes and multivesicular bodies were observed to be labeled at any time interval. Likewise, an attempt to correlate silver grains with small coated or uncoated pits, the stacks of saccules of the Golgi apparatus and other Golgi-related elements including GERL, proved unsuccessful, since these structures were mostly unlabeled. These in vivo experiments thus demonstrate the specific binding of [125I]hCG to the plasma membrane of Leydig cells predominantly on their microvillar processes, and the subsequent internalization of the labeled hCG to secondary lysosomes. In addition, binding and internalization of hCG persisted for long periods of time.

Evolution of the endoplasmic reticulum during spermiogenesis of the rooster: an electron microscopic study

The endoplasmic reticulum (ER) of rooster's spermatids was analyzed during spermiogenesis, which was subdivided into eight distinct steps on the basis of changes observed with the electron microscope in the nucleus, acrosome-perforatorium system, manchette, and flagellum. In steps 1 and 2, spermatids' ER cisternae presented the following specializations: A loose network of tubular cisternae was distributed throughout the cytoplasm. Six to eight tight networks of anastomosed tubular cisternae parallel to each other were closely stacked to form a discoid body (1.5-2.5 microns in diameter and 0.5-0.8-micron thick) in which spheroidal vesicles (0.4 micron in diameter) were inserted. Close to and connected with this body, called the alveolar body, there was a stack of annulate lamellae. Large, flattened ER cisternae were seen singly or in piles of two or three running parallel to the nuclear surface. A collection of tubular ER cisternae faced plaques of thickened plasma membranes. These elements of the ER system appear continuous with each other. During steps 3-5 of spermiogenesis, no modification of the alveolar body-annulate lamellae complex was noted; the large flattened ER cisternae disappeared, however, and the broad network of tubular cisternae developed markedly. During steps 6 and 7, the latter network of tubular cisternae fragmented into vesicles that swelled to give a vacuolated appearance to the cytoplasm. The alveolar body-annulate lamellae complex remained visible until late step 7, when it disintegrated just before spermiation. Thus the system of ER cisternae underwent marked structural modifications during spermiogenesis.

Intracellular pathways of endocytosed tracers in Leydig cells of the rat

The endocytic activity of Leydig cells was examined by electron microscopy following the injection, into the interstitial space, of tracers used to examine fluid-phase endocytosis, ie, native ferritin and horseradish peroxidase-colloidal gold (horseradish peroxidase-gold), and adsorptive endocytosis, ie, cationic ferritin. At 5 minutes after injection, native ferritin or horseradish peroxidase-gold was present in the interstitial space and free in the lumen of large endocytic vesicles forming at the cell surface. At 15 minutes, these tracers appeared in the matrix of pale multivesicular bodies, while at 30 minutes and 1 hour, the matrix of dense multivesicular bodies became labeled. Beginning at 1 hour, dense membrane-delimited bodies identified cytochemically as lysosomes were labeled. In the case of cationic ferritin, two distinct pathways were taken. In one pathway, cationic ferritin was observed 5 minutes after injection bound to the plasma membrane of Leydig cells and to the membrane of small and large endocytic vesicles. At subsequent time intervals, cationic ferritin appeared consecutively in pale, dense multivesicular bodies and lysosomes. In a second pathway, cationic ferritin was observed at 5, 15, and 30 minutes bound to the membrane of vesicles of intermediate size seen near the cell surface. At 1, 1 1/2 and 2 hours, cationic ferritin-containing intermediate vesicles appeared in increasing number in the Golgi region. However, cationic ferritin was never observed in the Golgi saccules themselves. At later time intervals (3-6 hours), intermediate vesicles labeled with cationic ferritin progressively disappeared from the Golgi region and the cell. Thus in Leydig cells, while fluid-phase tracers reached lysosomes exclusively, cationic ferritin, a tracer of adsorptive endocytosis, not only reached the lysosomes, but was also carried by the intermediate vesicles to the Golgi region of the cell.

Ultrastructural localization of nicotinamide adenine dinucleotide phosphatase (NADPase), thiamine pyrophosphatase (TPPase), and cytidine monophosphatase (CMPase) in the Golgi apparatus of early spermatids of the rat

At the early steps 3-7 of spermiogenesis the hemispherical Golgi apparatus elaborates and is closely associated to the acrosomic system which grows at the surface of the spermatid's nucleus. It shows two distinct zones, a cortex made up of flattened saccules and related membranous tubules, and a medulla containing various types of vesicular profiles. The various components of the cortex of the Golgi apparatus were tested for their reactivity to three phosphatases. Nicotinamide adenine dinucleotide phosphatase activity (NADPase, Smith, 1980) was observed in the middle two to six saccules in the stack with a midsaccule being more reactive than the saccules above and below. A weak and spotty reaction was also noted in the remaining saccules on the trans-face of the stack and in the thick elements making up the GERL on the trans aspect of the stacks of saccules. Thiamine pyrophosphatase activity (TPPase, Novikoff and Goldfisher, 1961) was found in one or two saccules on the trans-face of the stacks but was absent from the other Golgi components. Cytidine monophosphatase activity (CMPase, Novikoff, 1967) was observed in the GERL, in vesicles of the medulla and in the developing acrosomic system. In the intersaccular regions of the cortex the branching membranous tubules showed the same reactivity for the phosphatases to that of the saccules to which they are connected. ER cisternae associated with the Golgi apparatus, anastomotic membranous tubules seen in the peripheral Golgi region, small vesicles, as well as the first saccule on the cis-face of the stacks were all negative for the three enzymes studied. These data indicated that in the cortex of the Golgi apparatus there were several distinct compartments that could be distinguished on the basis of structural and cytochemical features.

Structural changes of the head components of the rat spermatid during late spermiogenesis

The transformation of the nucleus, acrosomic system, and peri-nuclear theca (perforatorium and post-acrosomal dense lamina) was analyzed during the maturation phase, i.e., steps 14 to 19 of spermiogenesis. Following partial condensation of chromatin from steps 11-14, the nucleus continues to condense during the following steps until the end of spermiogenesis. The redundant nuclear envelope which forms along the apical and ventral aspects of the nucleus and around the implantation fossa regresses during steps 17-19. The acrosomic system splits into two portions early in step 15 to give rise to: a) the main portion with its crest-like acrosome running along the dorsal aspect of the nucleus and head cap extending over the lateral surfaces of the nucleus: and b) a smaller head-cap segment which is seen in steps 15 and 16 along one side of the nucleus at its apical extremity. This separated head-cap segment reaches the apical-ventral aspect of the head during step 17 and condenses in synchrony with the rest of the acrosomic system in step 19 of spermiogenesis. The large crescentic acrosome, which in step 15 forms a large fin at the caudal extremity of the acrosomic apparatus, moves anteriorly during steps 16 and 17, while the whole acrosomic system extends farther apically beyond the tip of the nucleus. The perforatorium and post-acrosomal dense lamina form a rigid capsule (perinuclear theca) that covers tightly the sickle-shaped nucleus and binds the inner acrosomal membrane and the post-acrosomal membranes. The post-acrosomal dense lamina, which includes the ventral spur, appears early in step 15 as a dense cytoplasmic layer applied to the nuclear envelope at the caudal extremity of the nucleus except over the perifossal zone. The perforatorium forms during step 19 of spermiogenesis as a result of the condensation of a wispy cytoplasmic material which has accumulated in the subacrosomal space during steps 14-18. Thus the spermatid's head is deeply modified during the maturation phase and takes its definitive shape only at the last step of spermiogenesis.

Arrangement of connective tissue components in the walls of seminiferous tubules of man and monkey

In primates the membrane separating the seminiferous epithelium from the interstitial space is composed of one to three (monkey) or two to six layers (man) of myoid cells associated with one to two layers of fibrocyte-like adventitial cells. All these cells are separated from each other by irregular spaces filled with various connective tissue intercellular components. Subjacent to the elements of the seminiferous epithelium is a continuous, often redundant, basement membrane. A similar basement membrane-like material forms a layer next to and over small areas of the plasma membrane of myoid cells. Collagen fibrils grouped in bundles of various sizes are seen in all connective tissue layers but are particularly abundant in the space between the seminiferous epithelium and the innermost layer of myoid cells. Elastic fibrils demonstrated by the Verhoeff iron hematoxylin technique are also present. Composed of a homogeneous material, the elastic fibrils are short, irregular, branching entities with a diameter comparable to or smaller than that of collagen fibrils. In addition, an abundance of microfibrils with a diameter of 12-15 nm is present in the various connective tissue layers. These microfibrils have a densely stained cortex and a lightly stained core. When seen close to the myoid cells, bundles of micro fibrils appear to insert on well defined areas next to the plasma membrane. These areas commonly face the patches of electron-dense material observed on the inner aspect of the plasma membrane of the myoid cells and in which the actin filaments are inserted. Bundles of microfibrils often span the gap between myoid cells of the same layer as well as those of adjacent layers. Microfibrils are also closely related to the surface of elastic fibrils and are seen intertwining with collagen fibrils. Thus microfibrils appear to bridge and bind together adjacent myoid cells and anchor the surface of these cells to the bundles of elastic and collagen fibrils present in the intercellular spaces of the limiting membrane.