The study and correction of human gait by electrical stimulation

To gain a better understanding of the functions that the calf and vastus muscles perform in the human walking gait the author systematically increased the contractions of these muscles separately and in combination by applying Functional Electrical Stimulation (FES) to them, during walking tests performed by a subject with nonpathological gait, and a patient with a hemiplegic gait. A four-channel stimulator was used with foot switch activated control systems, which accurately sequenced the FES pulses and timed them in relation to the footswitch contacts. In normal gait FES applied to the calf muscles in the first third of the stance phase induced knee extension, but when applied later in the stance phase it increased the amount of plantar flexion and knee flexion at the push off. Strengthened vastus muscle contraction increased the amount and duration of stance phase knee extension, and interacted with the calf FES to increase the amount of heel rise at the push off. In the hemiplegic gait calf FES resulted in some increased knee flexion and ankle plantar flexion after the opposite heel strike, but a persistent lower limb extensor synergy prevented knee flexion from occurring simultaneously with plantar flexion and a heel rise, while the hemiplegic limb was still weight bearing.     

Prospective analysis of outcomes after microsurgical intussusception vasoepididymostomy

OBJECTIVE: To prospectively analyse the outcomes of microsurgical vasoepididymostomy using the intussusception technique, as vasoepididymostomy is considered the most challenging reconstructive microsurgery in urology. PATIENTS AND METHODS: From 1998 to 2003, of 324 men with obstructive azoospermia who had undergone microsurgical reconstruction of the reproductive tracts, 68 (21%) had intussusception vasoepididymostomy bilaterally or unilaterally in a functionally solitary testis. The outcomes of these patients were analysed prospectively. RESULTS: The mean age was 39.8 years for the men and 31.8 years for their partners. The causes of obstruction were after vasectomy in 31%, infection in 22%, iatrogenic in 19%, trauma in 1.5%, and idiopathic in 27%. The median duration of obstruction was 18.8 years; 37% of patients had had previous failed attempts at reconstruction. The mean (range) follow-up was 15.2 (1-36) months. The overall patency (>10 000 sperm/mL) rate was 84% (53/63). Patency was achieved in 60% (38/63) of men at 1 month after surgery. The mean best sperm count was 12.8 (0.01-80) x 10(6)/mL, with a 21 (0-30)% motility. Among patients with a follow-up of > 1 year, the natural paternity rate was 40%. The median time to achieve a natural pregnancy was 14.3 (3-30) months. Pregnancy was achieved with in vitro fertilization or intracytoplasmic sperm injection in 31% of cases, all using fresh ejaculated sperm. CONCLUSIONS: A favourable patency and pregnancy rate can be achieved using microsurgical intussusception vasoepididymostomy. Even when assisted-reproductive technology is needed, fresh ejaculated sperm can be used without requiring a subsequent sperm retrieval procedure. Thus, microsurgical reconstruction of the reproductive tract should be primary therapeutic method in cases of azoospermia from epididymal obstruction.     

Vasectomy reversal

Although vasectomy remains a popular method of contraception, the number of men requesting reversal has risen dramatically. The microsurgical Techniques described in this article have yielded excellent results.     

A metapopulation model of social group dynamics and disease applied to Yellowstone wolves

The population structure of social species has important consequences for both their demography and transmission of their pathogens. We develop a metapopulation model that tracks two key components of a species’ social system: average group size and number of groups within a population. While the model is general, we parameterize it to mimic the dynamics of the Yellowstone wolf population and two associated pathogens: sarcoptic mange and canine distemper. In the initial absence of disease, we show that group size is mainly determined by the birth and death rates and the rates at which groups fission to form new groups. The total number of groups is determined by rates of fission and fusion, as well as environmental resources and rates of intergroup aggression. Incorporating pathogens into the models reduces the size of the host population, predominantly by reducing the number of social groups. Average group size responds in more subtle ways: infected groups decrease in size, but uninfected groups may increase when disease reduces the number of groups and thereby reduces intraspecific aggression. Our modeling approach allows for easy calculation of prevalence at multiple scales (within group, across groups, and population level), illustrating that aggregate population-level prevalence can be misleading for group-living species. The model structure is general, can be applied to other social species, and allows for a dynamic assessment of how pathogens can affect social structure and vice versa.

Many vertebrate species live in social groups that shape behavioral interactions and demographic processes, particularly exposure to pathogens and their transmission. The social structure of groups varies considerably between species: at one end of this spectrum are diffuse, seasonal aggregations, as seen in migrating birds and many species of tropical fish; at the other end are social carnivores such as wolves (Canis lupus), wild dogs (Lycaon pictus), and lions (Panthera leo), in which groups hold territories for long time periods and both actively avoid and attack each other. The population dynamics of social species operate at the within-group and between-group scales, and the product of these interactions generates population-level dynamics. This modular population structure presents challenges to pathogen fitness in that behavior of group members minimizes contact and transmission rates between groups of hosts; thus, a pathogen must persist within each social group until an intergroup transmission event occurs (1–8).There are several important analogies between this type of dynamic and those of metapopulations (9, 10)—in order for a pathogen to persist in the population, it must balance tradeoffs between virulence, infectious period, and transmission within and between groups (2, 6, 8, 11–13). The persistence of host groups depends on individual birth and death rates, group fission and fusion dynamics, and how often competing groups attack each other. These rates may be different in the presence of pathogens, and the pathogen could potentially modify within-group social dynamics. To quantify the effects of pathogens, we must first understand the drivers of host social system dynamics in the absence of pathogens—we develop a flexible and analytically tractable model framework for this. We then add different types of pathogens to the model and compare metapopulation dynamics in the presence of pathogens and between different pathogens.Our central aim is to address the following question: “How do social and infectious disease dynamics interact in group-living mammals?” We answer this question by developing a hybrid form of metapopulation models that explicitly consider within-group dynamics of a hypothetical “average group” as well as the dynamics of the population of groups. We seek an understanding of the direct connections between a population’s vital rates, pathogen characteristics, group sizes, and number of groups in the population. Previously, socially structured disease models have assumed a static group structure and subsequently examined how networks of groups impact disease dynamics (6, 8, 14). This type of framework does not capture the impact of the pathogens on group structure and abundance (i.e., dynamics of the nodes themselves). For instance, mortality of some members within a social group can cause group dissolution and failed reproduction (e.g., ref. 15). Additionally, group size may influence contact among susceptible and infected individuals through dispersal and fission–fusion. The model framework we have developed allows us to explore this and compare the dynamics of the host population with and without pathogens.While the initial temptation might be to develop a detailed simulation model that tracks the abundance of every individual in each group, such a model would quickly become specific to the system under study, and the effects and interactions between parameters would be harder to distinguish. We prefer to adopt an approach that simplifies model structure in a way that provides general insights that can be used to reconsider patterns in empirical data or to focus data collection on ways that might falsify these patterns. We explore these issues and use demographic data from two decades of Yellowstone wolf research to structure and parameterize a general model framework within which different host–pathogen systems could be examined (Table 1).Table 1.Host–pathogen systems that could be examined using our model framework

Changes in the myoelectric signal (MES) power spectra during dynamic contractions

Power spectra of surface myoelectric signals (MES) have been estimated during dynamic contractions of the biceps brachii. The effect of applied torque, velocity of contraction and muscle length have been studied with respect to median frequency and total spectral power. The results of the investigation carried out thus far can be summarised as follows: (1) The median frequency is observed to vary with the applied torque and the muscle length but not with the velocity of contraction. (2) The expected dependence of the MES power with the applied torque, velocity and muscle length was confirmed. These results suggest that the power spectrum could be used to reveal changes in the electrophysiological characteristics of a muscle during dynamic contractions as is the case with static contractions.     

Diabetes Professionals Must Seize the Opportunity in Mobile Health

The number of diabetes management mobile applications (apps) available on the market has grown exponentially since 2009; however, most patients lack the skills necessary for finding relevant health care information. Thus, clinical best practices emphasize the need for ongoing patient education. Despite the importance of education in clinical guidelines, very few of these apps include education in their top functionalities. Most diabetes management mobile apps are not medical devices by definition, according to the U.S. Food and Drug Administration, and therefore do not require clearance or approval for market, and very few have been subject to clinical evaluation. There has been little research on the use of diabetes management mobile apps, marginalizing the role of diabetes professionals and educators in a burgeoning market, hungry for information and an improved quality of life. Still, mobile technology holds great promise as a platform for self-management. Health care providers must not only educate patients about these resources, but take steps to ensure that mobile apps follow accepted best practices and guidelines.     

Demineralized dentin, hydroxylapatite and dentin chips as apical plugs

Abstract Demineralized dentin, hydroxylapatite, or dentin chips were condensed into the apical 2 mm of canals with perforated apexes in 36 anterior teeth of 8 adult cynomolgus monkeys. The coronal sections of the canals were then obturated with gutta percha and Grossman's sealer. Twelve additional canals with perforated apexes were obturated 2 mm short of their radiographic apexes and served as controls. The amount of hard tissue formation and the degree of inflammation were evaluated after 3 and after 6 months. No differences were noted between the various materials after 3 months. However, after 6 months the samples with apical plugs of hydroxylapatite had more hard tissue formation and less inflammation than the others.