Venous pressure dynamics of the healthy human leg. Role of muscle activity, joint mobility and anthropometric factors

The delicate interplay between the muscle-joint unit and intact venous valves is mandatory for normal venous blood return from the human leg. We have investigated the potential role of (1) muscle activity and joint mobility, and (2) anthropometric factors for peripheral venous pressure physiology. 20 healthy young subjects (10 males, 10 females; mean age: 25.6 +/- 3.1 years) underwent direct venous blood pressure measurements during walking on a treadmill in 12 experimental conditions (duration, 1 min each): these resulted from a combination of two different walking velocities, two different degrees of ascent, and three different walking conditions. Anthropometric parameters (e.g., body height, weight and calf circumference) were also measured in all subjects. Outcome measures were the pressures (mm Hg) during quiet standing (resting pressure, P(0)), the maximal activity-induced pressure reduction (Delta P(max)), i.e., the difference between the resting pressure (P(0)) and minimal pressure during exercise (P(min)), the times (s) to minimal pressure during exercise (T(Pmin)) and to half-maximal recovery of P(0) after exercise (T(max1/2)). We found that the maximal venous pressure reduction (Delta P(max)) during walking increased at the higher walking speed and decreased with restricted joint mobility (p = 0.0001). Taller and heavier subjects, or subjects with a greater calf circumference had higher P(0) (p = 0.0001), showed greater Delta P(max) (p < 0.010), and took longer to achieve minimal pressure during exercise (T(Pmin); p < 0.010) than their corresponding counterparts. Females had lower levels of P(0) (p = 0.0001), but not of Delta P(max), and shorter T(Pmin) (p = 0.0076) than males. These gender effects largely result from differences in body height, weight, and calf circumference (p = 0.0001 for the appropriate ANOVA interaction terms). We conclude that during walking, a higher degree of muscle activity and a greater muscle mass enhance venous emptying of the healthy human leg. Conversely, impairments of joint mobility reduce the efficacy of the muscle-vein pump. Moreover, body height and weight significantly influence venous pressure physiology under both resting and activity-related conditions. These anthropometric factors also largely explain sex differences in peripheral venous hemodynamics.     

Macular pigment and visual performance under glare conditions

PURPOSE: Many parameters of visual performance (e.g., contrast sensitivity) are compromised under glaring light conditions. Recent data indicate that macular pigment (MP) is strongly related to improvements in glare disability and photostress recovery based on a filtering mechanism. In this study, we assessed the causality of this relation by supplementing lutein and zeaxanthin for 6 months while measuring MP, glare disability, and photostress recovery. METHODS: Forty healthy subjects (mean age = 23.9) participated in the study. Subjects were followed for 6 months and assessed at baseline, 1, 2, 4, and 6 months. Spatial density profiles of MP were measured using heterochromatic flicker photometry. Disability glare was measured using a 1 degree-diameter circular grating surrounded by a broadband glare source (a xenon-white annulus). The intensity of the annulus (11 degree inner and 12 degree outer diameters) was adjusted by the subject until the grating target was no longer seen. For the photostress recovery experiment, the time required to detect a 1 degree-diameter grating stimulus after a 5-s exposure to a 2.5 muW/cm2, 5 degree-diameter disk was recorded. Subjects were tested under central viewing and eccentric viewing (10 degree temporal retina) conditions. RESULTS: At the baseline time point, MP optical density (OD) at 30' eccentricity ranged from 0.08 to 1.04, and was strongly correlated with improved visual performance in the two glare tasks. After 6 months of lutein (L) and zeaxanthin (Z) supplementation, average MPOD (at 30' eccentricity) had increased from 0.41 to 0.57, and was shown to significantly reduce the deleterious effects of glare for both the visual performance tasks assessed. CONCLUSIONS: MP is strongly related to improvements in glare disability and photostress recovery in a manner strongly consistent with its spectral absorption and spatial profile. Four to 6 months of 12 mg daily L + Z supplementation significantly increases MPOD and improves visual performance in glare for most subjects.     

Major gene effect and additive familial pattern of inheritance of asthma exist among families of probands with sickle cell anemia and asthma.

In the United States, sickle cell anemia (SCA) affects approximately 1 in 400 African-American newborns. Acute episodes of pain and acute chest syndrome (ACS) are the two leading causes of hospitalization. A relationship between the diagnosis of asthma and the incidence of pain and ACS has been established. We tested the hypothesis that a familial pattern of inheritance of asthma exists among first degree relatives of probands with SCA and asthma. Segregation analysis was performed in 104 families ascertained through affected probands. Of these, 19.7% (41/208) of the parents and 31.8% (28/88) of siblings of affected probands reported having been told by a doctor he or she had asthma at any age. Modes of inheritance were tested, using the Pedigree Analysis Package parameterized for the discrete trait of asthma affection status. A major effect was present and significant. Further tests were performed to determine whether transmission probabilities of the major effect followed Mendelian expectations. The additive mode of inheritance was the most parsimonious, while the residual heritability was found negligible. Our results support the hypothesis that a familial pattern of inheritance of asthma exists among first degree relatives of probands with SCA and asthma, suggesting that asthma is a co-morbid condition with SCA rather than a lung disease phenotype mimicking asthma.     

Effects of denture teeth on the dimensional accuracy of acrylic resin denture bases

The Michigan Computer-Graphics Coordinate Measurement System was used to determine the effects of artificial denture teeth on the accuracy of acrylic resin denture bases. Two poly(methyl methacrylate) acrylic resins and two processing techniques were tested. Groups processed with denture teeth reproduced more accurate points than groups processed without denture teeth. Groups processed with a conventional heat-polymerized acrylic resin reproduced more accurate points than groups polymerized with an injection pressing type of acrylic resin.     

Resident work hours and working environment in otolaryngology. Analysis of daily activity and resident perception

OBJECTIVE.--To analyze the working environment and work hours of a cohort of otolaryngology--head and neck surgery residents. DESIGN.--Environmental analysis questionnaire and a log of daily activities. SETTING.--Residents were on a clinical rotation system. PARTICIPANTS.--Fifty-nine residents from six programs, including three public and three private institutions, from geographically diverse regions of the country were involved in the study. Residents were equally distributed from their second year through their fifth year of postgraduate work. All eligible residents participated in and completed the study. INTERVENTION.--The environmental analysis survey was designed to elicit resident perception of different aspects of their working environment. The daily activity log required the resident to report on activities for each half-hour period for 7 consecutive days. RESULTS.--Residents were on call an average of 52.8 hours (2.2 days) and worked 79.4 hours per week. Seventy-five percent believed that the level of faculty supervision and the degree of resident responsibility was about right. Two major inefficiencies were the time involved in completion of paperwork and the lack of nonmedical support services. Thirty-one percent of the residents responded that fatigue resulted in substandard patient care 10% of the time. Forty-seven percent responded that their educational experience was substandard 25% of the time secondary to fatigue. Two thirds responded that the demands of residency training had a negative impact on their family and personal life. CONCLUSIONS.--Seventy percent of the otolaryngology--head and neck surgery residents surveyed at six institutions believe that an 80-hour workweek, including being on call every third night with no more than 24 hours of continuous work without sleep, approximates a reasonable, maximum work schedule. Residents working the longest hours expressed concern about rendering substandard care and developing negative attitudes toward patients. Noneducational inefficiencies were identified and solutions were proposed. Demands of residency training, even within guidelines established as reasonable, can have detrimental effects on residents' educational activities and personal life.     

Atypical paraneoplastic myasthenic syndrome: Lambert-Eaton syndrome or myasthenia?]

We report a case of paraneoplastic myasthenic syndrome with clinical features suggesting Lambert Eaton syndrome but without the electromyographic elements required for diagnosis. Anti-calcium channel antibodies were also lacking. The electromyogram evidenced a block and the Tensilon test was positive. The efficacy of anticholinesterases argued in favor of myasthenia but anti-acetylcholine receptor antibodies were negative. The block was more of a mixed nature, involving both presynaptic transmission as in Lambert Eaton syndrome and post-synaptic transmission as in paraneoplastic myasthenia. The primary tumor was identified as a small-cell neuroendocrine lung carcinoma on mediastinal biopsies obtained directly on CT-scan guided puncture of a mediastinal node. Thoracotomy was thus avoided. The Lambert Eaton syndrome is a paraneoplastic manifestation of small-cell lung cancer in 50% of the cases unlike generalized myasthenia which apparently is never associated with small-cell lung cancer. A mixed paraneoplastic neuro-muscle junction disorder with aspects of each can be exceptionally observed.     

The effectiveness of citric acid as an adjunct to surgical re-attachment procedures in humans

The purpose of this study was to clinically evaluate the effect of citric acid on re-attachment and re-adaptation in conjunction with periodontal surgery. A split-mouth design was used in 10 patients involving 30 quadrants of surgery. A total of 120 teeth were treated. Each quadrant consisted of at least 2 teeth from cuspid to second molar. One quadrant was treated with a modified Widman flap alone while the root surfaces of the contralateral side were also treated with a 3 min application of citric acid. Immediately following hygienic phase and at 3 and 6 months postsurgically, the following measurements were taken in this sequence: gingival index, gingival crevicular fluid flow, plaque index, furcation involvement, level of attachment and probing depth. All the data were statistically analyzed using the paired t-test, chi 2 and Fisher exact probability test. The biometric results showed that both surgical techniques resulted in a loss of attachment in shallow pockets and a gain in deeper pockets. Both techniques resulted in similar amounts of recession and probing depth reduction at 6 months. Gingival index, plaque index and furcation values decreased at 3 and 6 months postsurgically. The gingival crevicular fluid values remained essentially the same up to 6 months postsurgically.