‘ An investigation of the nervous control of defecation ’ by Denny-Brown and Robertson: a classic paper revisited

In 1935 two young neurologists, Derek Denny-Brown and E. Graeme Robertson, published an article explaining the mechanisms underlying human defaecation based on a manometric study in patients with sacral root and spinal cord lesions, and normal subjects. This article is still routinely cited in studies of rectal and sphincter ani function. Unfortunately, however, the article itself is not written well, being composed of long convoluted sentences and containing 79 often indecipherable figures. Difficult-to-understand articles were common to the publications of Denny-Brown, who became one of the most prominent neurologists of the twentieth century. In accord with our prior work explaining Denny-Brown and Robertson's earlier paper on micturition, we provide here what we hope is a clear explanation of the methods and results in their study on defaecation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73905/1/j.1463-1318.2004.00636.x.pd

Virtual Patients and Sensitivity Analysis of the Guyton Model of Blood Pressure Regulation: Towards Individualized Models of Whole-Body Physiology

Mathematical models that integrate multi-scale physiological data can offer insight into physiological and pathophysiological function, and may eventually assist in individualized predictive medicine. We present a methodology for performing systematic analyses of multi-parameter interactions in such complex, multi-scale models. Human physiology models are often based on or inspired by Arthur Guyton's whole-body circulatory regulation model. Despite the significance of this model, it has not been the subject of a systematic and comprehensive sensitivity study. Therefore, we use this model as a case study for our methodology. Our analysis of the Guyton model reveals how the multitude of model parameters combine to affect the model dynamics, and how interesting combinations of parameters may be identified. It also includes a “virtual population” from which “virtual individuals” can be chosen, on the basis of exhibiting conditions similar to those of a real-world patient. This lays the groundwork for using the Guyton model for in silico exploration of pathophysiological states and treatment strategies. The results presented here illustrate several potential uses for the entire dataset of sensitivity results and the “virtual individuals” that we have generated, which are included in the supplementary material. More generally, the presented methodology is applicable to modern, more complex multi-scale physiological models

Polymorphism in NEDD4L Is Associated with Increased Salt Sensitivity, Reduced Levels of P-renin and Increased Levels of Nt-proANP

OBJECTIVE: Neuronal precursor cell expressed developmentally down-regulated 4-like (NEDD4L) is a regulator of the amiloride-sensitive epithelial sodium channel (ENaC), thus a candidate gene for salt sensitivity. Carriers of an intact NEDD4L C2-domain, encoded by the NEDD4L rs4149601 (G/A) GG genotype, together with the C-allele of the NEDD4L rs2288774 (C/T) polymorphism have previously been shown to have increased blood pressure. Our aim was to test if genetic variation in NEDD4L is associated with increased salt sensitivity. METHODS: 39 normotensive subjects were studied. The difference in 24-hour systolic blood pressure after four weeks on 150 mmol/day NaCl intake and four weeks on 50 mmol/day NaCl was defined as salt sensitivity. The rs4149601 and rs2288774 polymorphisms were genotyped using PCR-based techniques. RESULTS: Carriers of the rs4149601 GG-genotype together with the rs2288774 CC-genotype had significantly higher salt sensitivity (median, IQR) (18.0, 7.5–20.0 mmHg vs 6.0, 0.0–10.0 mmHg, P = 0.007) and lower plasma renin concentration (P-renin) (6.0, 2.0–9.5 mU/L vs 15.0, 9.0–24.0 mU/L, P = 0.005) as compared to non-carriers of these genotypes. In carriers of the rs4149601 GG-genotype together with the rs2288774 CC- or CT-genotype, as compared to non-carriers, salt sensitivity was (8.0, 6.0–18.0 mmHg vs 5.0, 0.0–10.0 mmHg, P = 0.07) and P-renin (9.0, 6.0–16.0 mU/L vs 15.0, 9.0–28.0 mU/L, P = 0.03). CONCLUSION: Genetic NEDD4L variation seems to affect salt sensitivity and P-renin in normotensive subjects, suggesting that genotyping of NEDD4L may be clinically useful in order to identify subjects who benefit from dietary salt restriction in the prevention of hypertension

Safety assessment of near infrared light emitting diodes for diffuse optical measurements

BACKGROUND: Near infrared (NIR) light has been used widely to monitor important hemodynamic parameters in tissue non-invasively. Pulse oximetry, near infrared spectroscopy, and diffuse optical tomography are examples of such NIR light-based applications. These and other similar applications employ either lasers or light emitting diodes (LED) as the source of the NIR light. Although the hazards of laser sources have been addressed in regulations, the risk of LED sources in such applications is still unknown. METHODS: Temperature increase of the human skin caused by near infrared LED has been measured by means of in-vivo and in-vitro experiments. Effects of the conducted and radiated heat in the temperature increase have been analyzed separately. RESULTS: Elevations in skin temperature up to 10°C have been observed. The effect of radiated heat due to NIR absorption is low – less than 0.5°C – since emitted light power is comparable to the NIR part of sunlight. The conducted heat due to semiconductor junction of the LED can cause temperature increases up to 9°C. It has been shown that adjusting operational parameters by amplitude modulating or time multiplexing the LED decreases the temperature increase of the skin significantly. CONCLUSION: In this study, we demonstrate that the major risk source of the LED in direct contact with skin is the conducted heat of the LED semiconductor junction, which may cause serious skin burns. Adjusting operational parameters by amplitude modulating or time multiplexing the LED can keep the LED within safe temperature ranges

Regulation of sensory nerve conduction velocity (SCV) of human bodies responding to annual temperature variations in natural environments

The extensive research interests in environmental temperature can be linked to human productivity/performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature-sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S-shaped trend of SCV with operative temperatures from 5 °C to 40 °C. The SCV increased linearly with operative temperatures from 14.28 °C to 20.5 °C and responded sensitively for 10.19 °C - 24.59 °C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature-invoked risks to human health and well-being

Stochasticity of flow through microcirculation as a regulator of oxygen delivery

<p>Abstract</p> <p>Objective</p> <p>Observations of microcirculation reveal that the blood flow is subject to interruptions and resumptions. Accepting that blood randomly stops and resumes, one can show that the randomness could be a powerful means to match oxygen delivery with oxygen demand.</p> <p>Method</p> <p>The ability of the randomness to regulate oxygen delivery is based on two suppositions: (a) the probability for flow to stop does not depend on the time of uninterrupted flow, thus the number of interruptions of flow follows a Poisson distribution; (b) the probability to resume the flow does not depend on the time for flow being interrupted; meaning that time spent by erythrocytes at rest follows an exponential distribution. Thus the distribution of the time to pass an organ is a compound Poisson distribution. The Laplace transform of the given distribution gives the fraction of oxygen that passes the organ.</p> <p>Result</p> <p>Oxygen delivery to the tissues directly depends on characteristics of the irregularity of the flow through microcirculation.</p> <p>Conclusion</p> <p>By variation of vasomotion activity it is possible to change delivery of oxygen to a tissue by up to 8 times.</p

Network Physiology reveals relations between network topology and physiological function

The human organism is an integrated network where complex physiologic systems, each with its own regulatory mechanisms, continuously interact, and where failure of one system can trigger a breakdown of the entire network. Identifying and quantifying dynamical networks of diverse systems with different types of interactions is a challenge. Here, we develop a framework to probe interactions among diverse systems, and we identify a physiologic network. We find that each physiologic state is characterized by a specific network structure, demonstrating a robust interplay between network topology and function. Across physiologic states the network undergoes topological transitions associated with fast reorganization of physiologic interactions on time scales of a few minutes, indicating high network flexibility in response to perturbations. The proposed system-wide integrative approach may facilitate the development of a new field, Network Physiology.Comment: 12 pages, 9 figure

The renin‐angiotensin‐aldosterone system and its suppression

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/148403/1/jvim15454-sup-0001-supinfo.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148403/2/jvim15454-sup-0002-figures.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148403/3/jvim15454-sup-0005-TableS3.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148403/4/jvim15454-sup-0004-TableS2.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148403/5/jvim15454-sup-0007-TableS5.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148403/6/jvim15454_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148403/7/jvim15454.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148403/8/jvim15454-sup-0006-TableS4.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148403/9/jvim15454-sup-0003-TableS1.pd

Assessment of occupational health problems and physiological stress among the brick field workers of West Bengal, India

Objectives: The brick field industry is one of the oldest industries in India, which employs a large number of workers of poor socioeconomic status. The main aim of the present investigation is i) to determine the prevalence of musculoskeletal disorders among brick field workers, ii) to determine the prevalence of respiratory disorders and physiological stress among brick field workers compared to control workers. Material and Methods: For this study, a total of 220 brick field workers and 130 control subjects were selected randomly. The control subjects were mainly involved in hand-intensive jobs. The Modified Nordic Questionnaire was applied to assess the discomfort felt among both groups of workers. Thermal stress was also assessed by measuring the WBGT index. The pulmonary functions were checked using the spirometry. Physiological assessment of the workload was carried out by recording the heart rate and blood pressure of the workers prior to work and just after work in the field. Results: Brick field workers suffered from pain especially in the lower back (98%), hands (93%), knees (86%), wrists (85%), shoulders (76%) and neck (65%). Among the brick-making activities, brick field workers felt discomfort during spading for mud collection (98%), carrying bricks (95%) and molding (87%). The results showed a significantly lower p value < 0.001 in FVC, FEV1, FEV1/FVC ratio and PEFR in brick field workers compared to the control group. The post-activity heart rate of the brick field workers was 148.6 beats/min, whereas the systolic and diastolic blood pressure results were 152.8 and 78.5 mm/Hg, respectively. Conclusions: This study concludes that health of the brick field workers was highly affected due to working in unhealthy working conditions for a long period of time