To what extent is hindlimb suspension a model of disuse?

The extent to which the remaining active or passive components of muscle mechanical stress not associated with weightbearing are involved in preserving muscle morphological and functional characteristics in the rodent hindlimb suspension model is not known. Such information would be relevant to the construction of appropriate countermeasures for the disuse atrophy associated with muscle unloading. This question was addressed by superimposing 2 weeks of hindlimb suspension and neuromuscular quiescence, achieved by the chronic neural application of the sodium channel blocker tetrodotoxin.

A comparison of the isoenzymes of Trypanosoma (Duttonella) vivax isolates from East and West Africa.

The genetic diversity in 13 stocks and clones of Trypanosoma vivax from East and West Africa was compared by isoenzyme analysis. The Ugandan and West African stocks and clones showed a very high degree of genetic similarity to each other but they differed from the Kenyan stocks and clones. Two haemorrhagic stocks, IL 2337 (Galana, Kenya) and IL 3067 (Bamburi, Kenya), showed a high degree of similarity in enzyme banding patterns in electrophoresed preparations.

The "fastness" of rat motoneurones: time-course of afterhyperpolarization in relation to axonal conduction velocity and muscle unit contractile speed.

In normal adult rats, intracellular recordings were obtained from motoneurones of the medial gastrocnemius (MG) and other tibial-nerve muscle branches. Among the whole population of tibial motoneurones, there was a significant negative correlation between the duration of afterhyperpolarization (AHP) and axonal conduction velocity (CV). However, this AHP vs CV relationship differed from that previously demonstrated in cats, in that for a given axonal CV, the AHPs were briefer in the rat than in the cat.

Parasite-specific antibody responses of ruminants infected with Trypanosoma vivax.

Sera from goats and cattle that were infected with two Trypanosoma vivax clones (ILDat 1.2 and ILDat 2.1) derived from different stocks were analysed for antibody activity against the variable surface glycoproteins (VSGs) of the infecting clones by enzyme-linked immune assays (ELISA) and immune lysis.

Antigenic relatedness of stocks and clones of Trypanosoma vivax from east and west Africa.

The antigenic relationships of 7 stocks and 7 clones of Trypanosoma vivax from East and West Africa were compared by immune lysis. Sera from goats infected with different stocks and clones of T. vivax, collected on days 40 and 80 after infection, were used in the immune lysis test with homologous and heterologous stocks and clones of trypanosomes.

Classification of prostanoid receptors.

Although still at a preliminary stage the original working hypothesis that five distinct prostanoid receptor types exist (3) has been strengthened by studies testing a number of selective agonists and/or antagonists. Such compounds can be systematically used to probe the involvement/presence of prostanoid receptor types in tissues/disease processes to identify the desired profile of new drugs. Although this classification will probably be modified in the light of new pharmacological tools, it seems apparent that the use of such an approach is likely to lead to new therapeutic products in the prostanoid field.

Influence of weight bearing on the adaptations of rat plantaris to ablation of its synergists.

The present study was designed to determine the contribution of weight bearing to the adaptations of the plantaris (PL) to synergist removal. PL from female rats were exposed to 28 days of a simultaneous condition of synergist ablation and hindlimb suspension. At 28 days, contractile responses and morphological measures were obtained and compared with muscles that either had synergists intact or were weight bearing or a combination of both.

Haemorrhagic lesions resulting from Trypanosoma vivax infection in Ayrshire cattle.

Infection of Ayrshire cattle with a stock of Trypanosoma vivax from the Galana Ranch, Kenya, resulted in an acute disease characterised by profound anaemia and haemorrhage, which reached maximum severity between 3 and 5 weeks after infection. Bleeding from the ears, nose and rectum occurred. At necropsy, petechial and ecchymotic haemorrhages were widespread, but were particularly severe in the gastrointestinal tract.

Detection of antibodies to platelets and erythrocytes during infection with haemorrhage-causing Trypanosoma vivax in Ayrshire cattle.

Ayrshire cattle, which were infected with a stock of Trypanosoma vivax from Galana, Kenya, which produced haemorrhagic disease, were examined for the presence of antibodies to erythrocytes and platelets. Antibodies to normal erythrocytes and platelets were detected in the plasma of infected animals using the enzyme-linked immunosorbent assay (ELISA). The antibodies were detectable following the first peak of parasitaemia (10-15 days after infection) and antibody activity was maximal 30-35 days after infection.

Spironolactone metabolism: steady-state serum levels of the sulfur-containing metabolites.

Metabolism of spironolactone in man is extensive and complex. For many years the dethioacetylated metabolite, canrenone, was assumed to be the major metabolite. However, recent studies using specific high performance liquid chromatography (HPLC) have demonstrated the presence of spironolactone and the sulfur-containing metabolites 7 alpha-thiomethylspirolactone (IV) and 6 beta-hydroxy-7 alpha-thiomethylspirolactone (V), in addition to canrenone, in the serum after a single oral dose of spironolactone.

Influence of overload on recovery of rat plantaris from partial denervation.

A functional index of neural adaptability is the capacity of motoneurons to extend and establish supernumerary connections with neighboring denervated muscle fibers. The purpose of this study was to guage this response in rat plantaris muscles subjected to increased levels of activity resulting from the surgical removal of the synergistic gastrocnemius and soleus muscles. Thirty-seven days of overload increased plantaris absolute (69%) and relative (82%) weight, whole muscle (35%) and individual fiber (37%) mean cross-sectional area, half-relaxation time (1/2RT; 25%), and maximum tetanic tension (P0; 21%).

Recent studies of the biology of Trypanosoma vivax.

Recent biological investigations of the African trypanosomes have been moving away from their previous preoccupation with the phenomenon of antigenic variation. The feeling has arisen that antigenic variation, as demonstrated by the Trypanozoon and Nannomonas subgenera of trypanosomes, is too extensive, the number of serodemes too large and the coexistence of different species in many areas too complicated, to allow any immunoprophylaxis based on antibodies to variable antigens. This is, of course, not to rule out possible biochemical intervention in the biosynthesis or export of VSG molecules by trypanosomes.

Attempts to protect goats against challenge with Trypanosoma vivax by initiation of primary infections with large numbers of metacyclic trypanosomes.

Attempts were made to immunize goats by infection with large numbers of metacyclic trypanosomes of a clone of Trypanosoma vivax, followed by chemotherapy. Five groups of 6 goats each were infected intradermally with 5 different doses of cultured metacyclics of T. vivax, ranging from 10(2) to 10(6) trypanosomes/goat.

Physiological responses of rat plantaris motor units to overload induced by surgical removal of its synergists.

1. Rat plantaris muscles were subjected to chronic overload by the surgical removal of the soleus and most of the gastrocnemius muscles. Twelve to 16 wk later whole muscle and motor unit (ventral root dissection technique) contractile properties as well as histochemistry were determined.

Fast axonal transport of labeled proteins in motoneurons of exercise-trained rats.

In this study, the fast orthograde axonal transport of radiolabeled proteins was measured to determine the effects of endurance-running training on transport velocity and amounts of transported proteins in rat sciatic motoneurons. Female rats were subjected to a progressive running-training program for 10-12 wk. Twenty-four hours after the last training session, rats underwent right L4-L5 dorsal root ganglionectomy.

Recovery of muscle from tetrodotoxin-induced disuse and the influence of daily exercise. 2. Muscle enzymes and fatigue characteristics.

The fatigue characteristics and the activities of oxidative and glycolytic enzymes were determined in tetrodotoxin (TTX)-induced disuse muscles and in muscles of animals recovering from TTX-induced disuse (TTX-rec). In addition, the effects of additional daily exercise (grid-climbing and swimming) on the fatigue and metabolic profiles of muscles from TTX-rec and control animals were investigated. The activities of citrate synthase (CS), phosphofructokinase (PFK), and alpha-glycerophosphate dehydrogenase (alpha-GPD) were depressed following 28 days of inactivity produced by the chronic neural application of TTX.

Characterisation of receptors mediating the contractile effects of prostanoids in guinea-pig and human airways.

Receptors mediating the contractile effects of prostanoids in the airways of guinea-pig and man have been compared using a range of selective agonists and antagonists. In guinea-pig and human lung parenchymal strips, contractile responses to all prostanoid agonists were blocked by EP092 and AH23848 (antagonists of thromboxane-sensitive receptors) but were unaffected by the EP1 receptor antagonist, AH6809. In guinea-pig tracheal rings responses to the thromboxane mimetic U46619 were antagonised by EP092 and AH23848.

Extravascular foci of Trypanosoma vivax in goats: the central nervous system and aqueous humor of the eye as potential sources of relapse infections after chemotherapy.

Relapse of parasitaemia after drug treatment of trypanosome infection is normally attributed to drug-resistance on the part of the parasite, under-dosage of the drug or reinfection of the host. In addition, inaccessibility of parasites to drug through sequestration in privileged extravascular sites has been shown in the past to occur with Trypanosoma brucei, and we have obtained evidence that extravascular foci of T. vivax can also serve as a source of relapsing infections.

Absence of staircase following disuse in rat gastrocnemius muscle.

Repetitive stimulation of mammalian fast-twitch skeletal muscles will normally result in a positive staircase response. This phenomenon was investigated in the rat gastrocnemius muscle following a 2-week period of tetrodotoxin-induced disuse. Muscle inactivity was imposed by superfusing tetrodotoxin in saline over the left sciatic nerve via an implanted osmotic pump.