Effect of precocious locomotor activity on the development of motoneurones and motor units of slow and fast muscles in rat.

We have investigated the effect of precociously increasing locomotor activity during early postnatal development by daily treatment with the monoaminergic precursor L-DOPA on the survival of motoneurones supplying the slow soleus (SOL) muscle and the fast, tibialis anterior (TA) and extensor digitorum longus (EDL) muscles as well as the contractile and histochemical properties of these muscles. L-DOPA treatment resulted in a significant loss of motoneurones to the slow SOL muscle, but not to the fast TA and EDL muscles. Moreover, motoneurones to fast muscles also die as when exposed to increased activity in early life, if their axons are repeatedly injured. The loss of normal soleus motoneurones was accompanied by an increase in force of the remaining motor units and sprouting of the surviving axons suggesting a remodelling of motor unit organisation. The time to peak contraction of both SOL and EDL muscles from L-DOPA treated rats was prolonged at 8 weeks of age. At 4 weeks the soleus muscles of the L-DOPA treated animal developed more tension than the saline treated one. This difference between the two groups did not persist and by 8 weeks of age the muscle weight and tetanic tension from either group were not significantly different from control animals. The present study shows that early transient, precocious locomotor activity induced by L-DOPA is damaging to normal soleus but not to normal EDL/TA motoneurones.

Motoneurones that innervate the rat soleus muscle mature later than those to the tibialis anterior and extensor digitorum longus muscles.

The response of motoneurones that innervate either the soleus or tibialis anterior (TA) and extensor digitorum longus (EDL) muscles to increased locomotor activity or to nerve injury at different stages after birth was examined. Increased locomotor activity of rat pups was induced by daily treatment with L-dopa during the first 12 days after birth, and the number of surviving motoneurones to the soleus or TA/EDL muscles was established by retrograde labelling. Treatment with L-dopa resulted in the loss of a significant number of motoneurones within the soleus motor pool but had no effect on the survival of those motoneurones innervating the TA/EDL. Furthermore, following nerve injury during the first few days postnatally, more motoneurones within the soleus motor pool die than in the TA/EDL pool. These results indicate that motoneurones to the soleus muscle mature later than those to the TA/EDL muscles.

Influence of fungi associated with bananas on nutritional content during storage.

Botryodiplodia theobromae, Rhizopus oryzae, Aspergillus niger, A. flavus and Fusarium equiseti were found to be associated with the ripening of bananas and also caused rot during storage. Bananas stored in baskets with ash fire wood ripened 2-3 days earlier than bananas stored in fibre sacks and under constant light. The infected bananas showed a decrease in the quantity of total soluble sugars, protein, lipid, crude fibre, ash, ascorbic acid and mineral elements when compared with the control fruit. Paper chromatographic studies showed the presence of glucose, sucrose, fructose, maltose and raffinose in healthy control fruit, while only sucrose appeared during storage in bananas infected with B. theobromae. The total soluble sugar and crude protein contents increased during ripening.

Transient muscle paralysis in neonatal rats renders motoneurons susceptible to N-methyl-D-aspartate-induced neurotoxicity.

Paralysis of the soleus muscle in newborn rats causes a large proportion of motoneurons to die by 10 weeks of age. However, all of these neurons are still present at three to four weeks of age. We have previously shown that although nerve injury at five days does not result in any motoneuron death, it does render these neurons susceptible to the toxic effects of the glutamate agonist N-methyl-D-aspartate. Using retrograde labelling of soleus motoneurons, in this study we show that an increased susceptibility to glutamate also plays a role in the eventual death of those motoneurons which survive for three weeks after interruption of neuromuscular transmission at birth but die by 10 weeks. Treatment with dizocilpine maleate an antagonist of the N-methyl-D-aspartate receptor increased the survival of motoneurons to alpha-bungarotoxin-treated soleus muscles. By 10 weeks of age the size of motoneurons to alpha-bungarotoxin-treated soleus muscles is smaller than that of controls, but after treatment with dizocilpine maleate the sizes of motoneurons to control and treated muscles are similar. Moreover, only 55 +/- 2.7% of motoneurons to the soleus muscle paralysed at birth with alpha-bungarotoxin survive for three weeks after a single injection of N-methyl-D-aspartate at 12 days of age. This motoneuron death is due to the application of N-methyl-D-aspartate since treatment with alpha-bungarotoxin alone causes no loss of neurons at this age.(ABSTRACT TRUNCATED AT 250 WORDS)

Monoclonal antibody-mediated, immunodiagnostic competitive enzyme-linked immunosorbent assay for equine monocytic ehrlichiosis.

Competitive enzyme-linked immunosorbent assay (CELISA), mediated by a monoclonal antibody designated HybI, was developed for the diagnosis of equine monocytic ehrlichiosis. Inhibition of binding of HybI by the horse antibodies to Ehrlichia risticii was optimum at dilutions of 1:20 for serum and 1:10,000 for HybI. Mean optical densities (ODs) of positive and negative sera were 0.158 and 0.855, respectively. A comparison of ODs obtained by CELISA and indirect enzyme-linked immunosorbent assay (ELISA) indicated a marked tendency of positive and negative samples to cluster separately with respect to CELISA ODs, whereas the ELISA results displayed a continuum of ODs from negative to positive. Analysis of diagnosis by indirect fluorescent-antibody test (IFA), ELISA, and CELISA for 66 field-collected serum samples indicated that CELISA was superior to IFA and ELISA. Among 11 acute-phase serum samples negative by IFA which were obtained from horses that subsequently seroconverted, CELISA clearly demonstrated antibodies in 8 of these acute-phase sera, whereas 5 were borderline positive by ELISA. The presence of agent-specific humoral antibodies could be demonstrated conclusively by 14 days after infection. The results suggest that CELISA is more sensitive than IFA and ELISA and, owing to the marked differences between positive and negative samples, can be easily adapted for use in the field for detection of horse antibodies to E. risticii.