[Possible factors associated with epidemic neuropathy in Cuba]. / Posibles factores asociados con la neuropatía epidémica en Cuba.

Of the 115 patients who suffered from epidemic neuropathy and received attention from March 16 de April 30, 1993, at the Center for Medical and Surgical Research (CMSR), in Havana City, 114 controls were selected at random in the community. In the univariate analysis it was found a significant association mainly with the smoking habit (odds ratio = 3.45 [95% confidence interval 1.85 to 6.35)] and with the consumption of edible fat of uncertified procedence (odds ratio = 2.77 [95% confidence interval 1.34 to 5.8]). All were ratified in the multivariate logistical regression analysis. Association (odds ratio = 8.8 [95% confidence interval 2.58 to 30.55] with the presence of antibodies against the Coxsackie virus A-9 strain 47 was also found among the 182 individuals who had serological test. It seems that the toxic factor derived from the smoking habit, together with the deficiency of some nutrients due to the changes occurred in the diet, as well as the contact with the isolated virus in one of the patients facilitated the clinical expression of this disease and therefore in the origin of the epidemics.

Phylogeography of the West Indian manatee (Trichechus manatus): how many populations and how many taxa?

To resolve the population genetic structure and phylogeography of the West Indian manatee (Trichechus manatus), mitochondrial (mt) DNA control region sequences were compared among eight locations across the western Atlantic region. Fifteen haplotypes were identified among 86 individuals from Florida, Puerto Rico, the Dominican Republic, Mexico, Columbia, Venezuela, Guyana and Brazil. Despite the manatee's ability to move thousands of kilometers along continental margins, strong population separations between most locations were demonstrated with significant haplotype frequency shifts. These findings are consistent with tagging studies which indicate that stretches of open water and unsuitable coastal habitats constitute substantial barriers to gene flow and colonization. Low levels of genetic diversity within Florida and Brazilian samples might be explained by recent colonization into high latitudes or bottleneck effects. Three distinctive mtDNA lineages were observed in an intraspecific phylogeny of T. manatus, corresponding approximately to: (i) Florida and the West Indies; (ii) the Gulf of Mexico to the Caribbean rivers of South America; and (iii) the northeast Atlantic coast of South America. These lineages, which are not concordant with previous subspecies designations, are separated by sequence divergence estimates of d = 0.04-0.07, approximately the same level of divergence observed between T. manatus and the Amazonian manatee (T. inunguis, n = 16). Three individuals from Guyana, identified as T. manatus, had mtDNA haplotypes which are affiliated with the endemic Amazon form T. inunguis. The three primary T. manatus lineages and the T. inunguis lineage may represent relatively deep phylogeographic partitions which have been bridged recently due to changes in habitat availability (after the Wisconsin glacial period, 10 000 B P), natural colonization, and human-mediated transplantation.

Specific blockage of squid axon resting potassium permeability by Haliclona viridis (Porifera: Haliclonidae) toxin (HvTX).

The action of partially purified HvTX, toxin of the marine sponge H. viridis, was explored on the giant axon of the tropical squids Doryteuthis plei and Sepioteuthis sepioidea. HvTX depolarizes the nerves dose dependently. The effect occurs after blocking sodium channels with tetrodoxin (1 microM), removing external Na+, blocking electrically excitable K+ channels with 3,4-diaminopyridine (10 mM) or internal and external application of tetraethylammonium (40 mM). Ouabain (up to 10 mM) does not modify HvTX effect. The action of HvTX occurs only when it is applied to the outer phase of the nerve membrane; microinjection of the toxin into the axons lacks depolarizing effects. HvTX reduces the dependence of membrane potential on external potassium concentration. The apparent 86Rb+ permeability (pi') was measured in axons of S. sepioidea. The value of pi' in normal artificial sea water was 80 (61,96) nm/sec (median and its 95% confidence interval, n = 8) and raised to 1030 (588, 2113) nm/sec (n = 7) when the axons were depolarized to 0 mV raising external K+ to 300 mM. In axons depolarized with HvTX (10 mM external K+) to 0 mV, pi' was 88 (55, 97) nm/sec (n = 8). HvTX could not prevent (P >> 0.05) the increase in pi' induced by 300 mM K+ when the ion concentration was raised before toxin application [pi' = 660 (354, 1876) nm/sec, n = 7]. Most of the 86Rb+ permeability increase in high K+ was prevented if HvTX was added before external K+ was raised [pi' = 298 (264, 337) nm/sec, n = 8]. All the measures of pi' were carried out in solutions containing 1 microM tetrodotoxin, 1 mM 3,4-diaminopyridine and 2 mM ouabain.