Relation between energy expenditure and body composition in man: specific energy expenditure in vivo of fat and fat-free tissue

The relationship between energy expenditure and body composition, in terms of fat and fat-free masses, has previously been described by a variety of predictive regression equations with parameters devoid of physiological content. We present here results obtained by calculating the specific energy expenditure, ie, the energy expenditure per unit of mass, of fat and fat-free tissue on the basis of measurements of the total energy expenditure (EE), the masses of fat (FM), and fat-free (FFM) tissue using the following simple model: EE = k1.FM + k2.FFM where k1 and k2 are the specific energy expenditures of fat and fat-free tissue, respectively. The results of observations on 104 women at rest yielded values for k1 and k2 of 0.31 and 1.35 watts/kg of fat and fat-free mass, respectively, with standard errors of estimate of 0.074 and 0.052 watts/kg, respectively. Analysis of several series of measurements, from other sources and on smaller samples of subjects, yielded similar values at rest but with larger standard errors of estimate. Data from subjects performing varying amounts of work in 24-h measurements showed, as expected, larger values for both tissues. The results explain to a very large extent the well-established relation between resting metabolic rate and body weight, ie, a linear relation with a non-zero intercept. The results also offer a clear-cut explanation for the well known difference in energy expenditure between men and women with the same body weight.     

Myelinated fiber regeneration after crush injury is retarded in sciatic nerves of aging mice

To compare nerve regeneration in young adult and aging mice, the right sciatic nerves of 6- and 24-month-old mice were crushed at the sciatic notch. Two weeks later, both groups of mice were perfused with an aldehyde solution, and, after additional fixation, the sciatic nerves were processed so that the transverse sections of each nerve subsequently studied by light and electron microscopy included the entire posterior tibial fascicle 5 mm distal to the crush site. The same level was sectioned in unoperated contralateral nerves; these nerves served as controls. Electron micrographs and the Bioquant Image Analysis System IV were used to measure areas of posterior tibial fascicles and count the number of myelinated axons, the number of unmyelinated axons, and their frequency in Schwann cell units. In aging mice, the total number of regenerating myelinated axons was significantly reduced, but totals of regenerating unmyelinated axons in aging and young adults did not differ significantly. In aging mice, the frequency of Schwann cells that contained a single unmyelinated axon was greater, suggesting that before myelination began, Schwann cell ensheathment of axons also was slowed. After axotomy by a crush injury, the area of the posterior tibial fascicle was less than that in young adults and the distal disintegration of myelin sheath remnants also appeared to be retarded. The results indicate that responses of neurons, axons, and Schwann cells could be important in slowing the regeneration of myelinated fibers found in sciatic nerves from aging mice.     

High-quality controlled trials on preventing episodes of back problems: systematic literature review in working-age adults

Background contextBack problems (BPs), with their cost and disability, are a substantial burden for individuals, employers, and society.PurposeThis systematic review of controlled trials evaluates the effectiveness of interventions to prevent BP episodes in working age adults.Data sourcesWe searched MEDLINE/EMBASE through May 2007, and COCHRANE/Trials Registry through August 22, 2008 using search terms of back pain, back injuries or sciatica, linked to prevention, control, workplace interventions, or ergonomics and searched article bibliographies.Study selectionFor systematic review inclusion, articles had to describe prospective controlled trials of interventions to prevent BPs in working-age adults, with intervention assignment either to individual participants or preexisting groups. Of 185 articles identified as potentially relevant, 20 trials (11%) met inclusion criteria.Data extractionResearchers extracted relevant information from controlled trials and graded methodological quality. Because of heterogeneity of trials, meta-analysis was not performed.ResultsOnly exercise was found effective for preventing self-reported BPs in seven of eight trials (effect size 0.39 to >0.69). Other interventions were not found to reduce either incidence or severity of BP episodes compared with controls. Negative trials included five trials of education, four of lumbar supports, two of shoe inserts, and four of reduced lifting programs.ConclusionsTwenty high-quality controlled trials found strong, consistent evidence to guide prevention of BP episodes in working-age adults. Trials found exercise interventions effective and other interventions not effective, including stress management, shoe inserts, back supports, ergonomic/back education, and reduced lifting programs. The varied successful exercise approaches suggest possible benefits beyond their intended physiologic goals.Level of evidenceSystematic review Level I evidence.     

Accessory phallic urethra in adult female

Duplication of the urethra with an accessory phallic urethra in females is a rare anomaly usually discovered early in life because of associated genitourinary anomalies. We report on a thirty-three-year-old female with this anomaly who presented with double urinary stream and recurrent urinary tract infections. The nature of this anomaly, its diagnosis, and management are reviewed.     

Experimental rabies in skunks and foxes. Pathogenesis of the spongiform lesions

The pathogenesis of rabies spongiform lesions in striped skunks (Mephitis mephitis) and red foxes (Vulpes vulpes) was studied by light and electron microscopy and peroxidase-antiperoxidase immunocytochemistry. Studies in skunks included use of several street virus variants (different antigenic profiles as tested by monoclonal antibodies) different routes of inoculation (intranasal, intracerebral and intramuscular), immunosuppression of infected skunks, different preparations of virus (brain and salivary gland suspensions and infective tissue culture fluids), and sequential development of the lesions. Foxes (Vulpes vulpes) were infected intramuscularly with a street virus isolate. Except for the group of immunosuppressed skunks, all animals that developed clinical signs of rabies had encephalitis characterized by varying degrees of mononuclear perivascular cuffing, focal gliosis, and Negri bodies. Spongiform change occurred in the neuropil of the grey matter (especially thalamus and cerebral cortex) in rabid animals from all groups, but not in controls or exposed animals that did not develop rabies. Rabies antigen (detected by peroxidase-antiperoxidase immunocytochemistry) occurred only in small amounts in many thalami; some vacuolated areas were devoid of antigen. Ultrastructurally, there was a gradation in lesions from small to large membrane-bound vacuoles in cellular processes (mainly dendrites, less frequently axons) and to large tissue spaces containing granular and/or membranous material. These studies indicate that rabies spongiform change occurs in skunks given street virus of several different antigenic profiles and challenge virus standard rabies virus and that the distribution of the lesions has remarkable similarities to those of the traditional spongiform encephalopathies. The occurrence of the lesion is not affected by the immune response, the route of inoculation of virus, the preparation (suspension of salivary gland or brain, or tissue culture fluid), or the incubation period. The paucity of antigen in many thalami suggests that incorporation of viral components into vacuolar membranes is not necessary for development of the spongiform change. The development of the lesions includes formation of small membrane-bound vacuoles in cellular processes, rapid enlargement (less than 3 days) with compression of adjacent neural tissue, and rupture resulting in the large tissue spaces readily visible by light microscopy.     

The agent of Human Granulocytic Ehrlichiosis resides in an endosomal compartment.

The composition of cytoplasmic vacuoles containing the agent of Human Granulocytic Ehrlichiosis (HGE) was studied to investigate how this pathogen exists within infected host cells. Electron microscopy demonstrated that the HGE organism resides in a membrane-bound compartment within HL-60 cells: early forms of the HGE agent have a round reticular appearance while later structures are small and dense. Vacuoles containing HGE bacteria incorporated endocytosed colloidal gold particles, suggesting that they are part of the endocytic pathway. Antibodies directed to the mannose-6-phosphate receptor labeled vacuole membranes. Antibodies to the transferrin receptor and to the lysosomal membrane glycoprotein LAMP 1 did not. Moreover, 3-(2,4-dinitroanilino)-3'-amino-N-methyldipropylamine, which normally accumulates in compartments with low pH, was not present inside these vacuoles. These results suggest that vacuoles containing the agent of HGE fail to mature into phagolysosomes. We conclude that the agent of HGE appears to enter and modify part of the endocytic pathway.