Can the size principle be detected in conventional emg recordings?

According to Henneman's size principle, small motor units are recruited before large ones. It is commonly believed that this can be detected in routine conventional EMG recordings even among the earliest recruited motor units. That is, the MUP amplitude, area, and thickness should increase with recruitment order. We studied the first four motor unit potentials (MUPs) recruited within the pickup area of the electrodes. Data were obtained from 179 different sites in monopolar recordings and in 153 concentric recordings from 5 health subjects. In the pooled material, amplitude, area, and thickness increased slightly between consecutively recruited MUPs. However, at individual recording sites the size of consecutively recruited MUPs varied considerably. At some recording sites the first recruited MUP had the largest amplitude and the later MUPs has successively smaller amplitudes. We conclude that, at individual recording sites, the size principle cannot be detected in low threshold motor units with monopolar or concentric EMG electrodes. The reason for this is the small uptake area of these electrodes in relation to the motor unit territory. © 1995 John Wiley & Sons, Inc.     

The bleeding gastric ulcer--will it bleed again, and if so, why? A case for repeat endoscopy in evaluating stigmata

Nine patients qualified for surgery for a bleeding gastric ulcer--all had a 'visible vessel'. Three of these vessels were thrombosed including 2 in patients who had been in shock. The smallest patent vessel was 0,35 mm in diameter, and 6 of the bleeding vessels were subserosal. The features thought to predispose to further bleeding were vessel size, a lateral hole in the main trunk of the vessel and, possibly, previous recanalization or ingestion of a drug which affected haemostasis. Five of 6 patent arteries had a cap of thrombus over the breach forming a false aneurysm. It is suggested that clinically these should pulsate, enlarge, leak--with persistent fresh thrombus in the ulcer crater on repeat endoscopy--and finally rupture. Where the underlying vessel is thrombosed the stigmata of a non-pulsatile 'visible vessel' or thrombus in the ulcer should disappear on repeat endoscopy. The sizes of the arteries in the normal antrum are tabulated.     

Occupational Stress in Special Education: A Challenge for School Health Professionals

Results of this study support the hypothesis that the majority of special educators, their support personnel, and general education administrators do not experience more job dissatisfaction than comparable occupational groups. However, they do report lower levels of subjective well-being when compared with normal populations. Furthermore, 18% of the educators in the study perceived themselves as failing to cope with their job, experienced more frequent symptoms of poor physical health, and reported significantly poorer subjective well-being. Health promotion programs for public school personnel should initiate prevention-oriented health education programs for all employees. For those identified as more vulnerable to stress-related mental and physical health problems, therapeutic approaches may be necessary. However, self-help and mutual support groups may offer both groups a social support system to help meet human needs in addition to offering the potential for reducing perceived occupational stress. School health personnel may be in the best position to influence policies, procedures, and practices in schools that would support the work-related needs of all employees.     

Extraction of Dopa from the Integument of Pigmented Animals

The occurrence of high amounts of dopa has been demonstrated chemically in the piliary system of pigmented animals (guinea-pig, rabbit, and dog). Histochemically, a formaldehyde-induced fluorescence was recorded only in melanocytes of hair-bulbs. The spectral characterictics of these cells did not agree with those of the authentic dopa fluorophore. The discrepancy between the chemical and histochemical findings is discussed. Little or no dopa was found in non-pigmented skin of albino and multi-coloured guinea-pigs. This indicates that the integumentary dopa is related to the pigment formation.     

Experimental and/or genetically controlled alterations of the renal microsomal cytochrome P450 epoxygenase induce hypertension in rats fed a high salt diet.

Excess dietary salt induces a cytochrome P450 arachidonic acid epoxygenase isoform in rat kidneys (Capdevila, J. H., S. Wei, J. Yang, A. Karara, H. R. Jacobson, J. R. Falck, F. P. Guengerich, and R. N. Dubois. 1992. J. Biol. Chem. 267:21720-21726). Treatment of rats on a high salt diet with the epoxygenase inhibitor, clotrimazole, produces significant increases in mean arterial blood pressure (122 +/- 2 and 145 +/- 4 mmHg for salt and salt- and clotrimazole-treated rats, respectively). The salt- and clotrimazole-dependent hypertension is accompanied by reductions in the urinary excretion of epoxygenase metabolites and by a selective inhibition of the renal microsomal epoxygenase reaction. The prohypertensive effects of clotrimazole are readily reversed when either the salt or clotrimazole treatment is discontinued. The indication that a salt-inducible renal epoxygenase protects against hypertension, are supported by studies with the Dahl rat model of genetic salt-sensitive hypertension. Dahl resistant animals responded to excess dietary salt by inducing the activity of their kidney microsomal epoxygenase(s) (0.102 +/- 0.01 and 0.240 +/- 0.04 nmol of products formed/min per mg of microsomal protein for control and salt-treated rats, respectively). Despite severe hypertension during excess dietary salt intake (200 +/- 20 mmHg), Dahl salt-sensitive rats demonstrated no increase in renal epoxygenase activity. These studies indicate that acquired or inherited abnormalities in renal epoxygenase activities and/or regulation can be related to salt-sensitive hypertension in rodents. Studies on the human renal epoxygenase and its relationship to salt hypertension may prove useful.     

Topical nitroglycerin ointment in Raynaud's phenomenon

The purpose of the study was to evaluate the hemodynamics of nitroglycerin ointment in Raynaud's phenomenon. 22 patients (15 women and 7 men aged 25-75 years) suffering from Raynaud's phenomenon were investigated in a double-blind paradigm. Blood flow measurements were performed by venous occlusion plethysmography. Cardiac output was registered by means of impedance cardiography. 800 mg nitroglycerin ointment 2% was applied on one hand only. In the placebo group, finger blood flow, blood pressure, heart rate, and cardiac output did not change significantly. In the group receiving nitroglycerin, finger blood flow increased significantly from 21.6 +/- 6.0 to 31.7 +/- 7.0 ml/100 ml/min. Systolic blood pressure decreased from 126 +/- 4 to 118 +/- 3 mmHg. Cardiac output significantly decreased from 7.3 +/- 0.8 to 6.3 +/- 0.5 l/min. It is concluded that nitroglycerin ointment in Raynaud's phenomenon has a local and a systemic effect as well, because, on the one hand, cardiac output and blood pressure decreased whereas, on the other hand, the increase in finger blood flow was more marked in the treated hand than in the contralateral control fingers.     

Cardiovascular and renal actions of cytochrome P-450 metabolites of arachidonic acid

Cytochrome P-450 is the terminal oxidase of the electron transport chain the endoplasmic reticulum. Arachidonic acid (AA) can be oxidatively metabolized by cytochrome P-450 hemoproteins to an array of compounds identified as constituents of tissues and biological fluids. Their synthesis can be manipulated by pharmacologic probes and altered in pathophysiologic conditions. These novel eicosanoids stimulate release of peptide and steroid hormones, inhibit platelet and leukocyte aggregation, influence Na+-K+-atpase and alter vasomotor tone. They also participate in fluid and electrolyte homeostasis, stimulus-secretion coupling, and regulation of tissue blood flow. Since these novel AA metabolites may participate in receptor-mediated signal transduction, and have been implicated in the generation of second messengers and changes in intracellular calcium,these studies have important implications for understanding basic biological mechanisms.     

The aluminum-formaldehyde (ALFA) histofluorescence method for improved visualization of catecholamines and indoleamines. 2. Model experiments

The fluorescence-promoting effects of sodium, magnesium and aluminum ions in the histochemical formaldehyde (FA) reaction with catecholamines and indoleamines have been studied in protein models. The positive effects of aluminum and magnesium salts on the monoamine fluorescence yields, seen in tissue, could partly be reproduced in a simple protein matrix. The fluorescence-promoting potency was greatest for aluminum, moderate for magnesium and small for sodium. The aluminum effect was markedly concentration-dependent, with an optimum at a concentration of 5-10 mM in the model solution. Optimum pH was around 3.8. Experiments with synthetic fluorophores indicate that the principal action of the metal ions is on the fluorescence properties of the monoamine fluorophores rather than on the yield of fluorophores in the reaction of the monoamines with FA. The presence of aluminum ions in the models thus causes both increases in the fluorescence efficiency of the fluorophores as well as changes in their spectral properties. The direct effects on the monoamine fluorophores cannot, however, account for all effects of the metal salts seen in tissue. It is suggested that aluminum and magnesium ions, in addition, can act as acid catalysts in the FA-monoamine reactions, and that the metal salts have a direct effect on the tissue environment, leading to a 'locking-in' of the intracellular monoamines.     

l-Tryptophan and neuroendocrine regulation in neurologic patients: gonadotrophin secretion, sexual motivation and responsiveness during l-tryptophan treatment in patients with multiple sclerosis (MS)

(1) Patients suffering from multiple sclerosis (MS) were treated with l-tryptophan for one month in a dosage of 500 mg together with 50 mg of peripheral decarboxylase inhibitor three times daily. Placebo was given for a month, as well. The dosage of l-tryptophan was earlier seen to accelerate serotonin metabolism in the central nervous system of these patients. (2) Plasma immunoreactive gonadotrophin and somatotrophin levels were assayed during l-tryptophan and placebo periods. (3) Sexual motivation and sexual responsiveness of patients were tested by using sexual stimulation and interviews. (4) l-Tryptophan treatment slightly lowered plasma lutrophin levels in men. (5) l-Tryptophan treatment did not alter the patient's responses to the sexual stimulation tests and to interviews.