Shell variation in sympatric freshwater Lymnaea peregra and L. ovata (Gastropoda: Lymnaeidae)

Snails of the genus Lymnaea are morphologically variable and their taxonomy is unclear. In particular, the forms peregra and ovata , distinguished by shell shape, are often considered variants of the same species, L. peregra. We studied a rare situation in a Swiss mountain lake where both forms are sympatric. First, we found that the forms shows complete separation for a number of allozymes. Second, we examined the response of the two snail forms to infection by the trematode Diplostomum phoxini . For the ovata form, there was a transitory, 10% increase in the growth of infected snails compared to uninfected controls. The peregra form showed no gigantism and had higher parasite-induced mortality. Third, we assessed differences between the forms in reproduction under different environmental conditions. Density negatively influenced egg production to the same degree in both forms. However, decreasing water levels, characteristic of part of the lake studied, led to a 30% decrease in egg production for the ovata form, but only a 10% decrease for the peregra form. These differences are discussed in relation to the microdistributions of the snails in the lake and we conclude that the two forms are almost certainly separate species.     

Molecular evidence that diploid Stylosanthes humilis and diploid Stylosanthes hamata are progenitors of allotetraploid Stylosanthes hamata cv. Verano.

Restriction fragment length polymorphism analysis, using peroxidase, O-methyltransferase, phenylalanine ammonia-lyase, and coniferyl alcohol dehydrogenase cDNAs isolated from Stylosanthes humilis, as probes, provided molecular evidence for the genetic origin of the naturally occuring allotetraploid genotype Stylosanthes hamata cv. Verano (2n = 4x = 40). Hybridization patterns strongly suggest that the likely progenitors of S. hamata cv. Verano were a diploid S. humilis (2n = 2x = 20) and a diploid S. hamata (2n = 2x = 20) species.     

Randomised double blind controlled clinical trial of intranasal budesonide in treatment of hay fever.

The effectiveness of budesonide, a new non-halogenated glucocorticoid administered by nasal inhaler, was evaluated in a double blind comparison with placebo in patients presenting with hay fever. Patients were supplied with antihistamine tablets and eye drops for use when they considered that their symptoms were inadequately controlled by their inhaler. Patients recorded the severity of their symptoms in a daily diary card and visited their general practitioner for assessment weekly for four weeks. All nasal symptoms of hay fever were appreciably reduced in the group taking budesonide and, although their eye symptoms were more severe than in the group taking placebo, they did not use appreciably more eye drops than the latter. The placebo group used appreciably more antihistamine tablets than those in the budesonide group. No patients were withdrawn from the budesonide group because of treatment failure or unacceptable side effects. The results suggest that budesonide is an acceptable and effective treatment for the nasal symptoms of hay fever.     

The lupus syndrome induced by hydralazine: a common complication with low dose treatment.

The true incidence of the lupus syndrome induced by hydralazine was determined in a longitudinal study of 281 patients consecutively starting hydralazine for hypertension over a 51 month period. Data on the duration of treatment and the maximum dose achieved were examined using life table analysis. After three years'' treatment with hydralazine the incidence of the lupus syndrome was 6.7% (95% confidence limits 3.2-10.2%). The incidence was dose dependent, with no cases recorded in patients taking 50 mg daily and incidences of 5.4% with 100 mg daily and of 10.4% with 200 mg daily. The incidence was higher in women (11.6%) than in men (2.8%). In women taking 200 mg daily the three year incidence was 19.4%. Hydralazine is an effective antihypertensive drug that has come to be used in restricted dosage (not more than 200 mg daily) because of its risk of inducing the lupus syndrome. This study shows that the true incidence of the syndrome is still unacceptably high even when the drug is prescribed according to current recommendations.     

Evidence for polarizing zone in the limb buds of Xenopus laevis

To test for the presence of polarizing mesoderm in an amphibian, Xenopus laevis hindlimb bud tips were rotated 180° on the proximodistal axis and returned to the stump. Supernumerary outgrowths were induced in the preaxial stump and preaxial tip tissues, and the most postaxial digit always formed next to the grafted postaxial tissue. The occurrence of polarized supernumerary outgrowths indicated that the posterior limb border contained a polarizing zone. When the limb tip was cut at varying known lengths from the body wall, rotated, and grafted to the limb stump, the incidence of twinning along the proximodistal axis permitted insight into the distribution of the polarizing zone along the posterior border. The location of polarizing tissues was found to be similar to that in the chick wing bud at comparable stages. To confirm the posterior border stump influence on the rotated preaxial limb tip tissues, 180° tip rotations were made at the proximodistal level with the highest incidence of twinning. In these cases, the adjacent stump posterior border tissues (polarizing zone) were removed, leaving a substantial amount of the deeper postaxial stump tissue, however. The frequency of twinning from tip tissues was greatly reduced in these larvae compared to those with rotated limb tips on intact stumps. Cytological examination of supernumerary outgrowths resulting from grafts of two-nucleolate tips onto one-nucleolate stumps confirmed the preaxial source of the supernumerary outgrowths.     

Liquid chromatographic demonstration of catecholamine release in fish heart.

High-pressure liquid chromatography (HPLC) was used to assay for catecholamines released into the heart of the goldfish (Carassius auratus L.) upon stimulation of vagal nerve fibers. Stimulation induced the release of norepinephrine, epinephrine and dopamine into the lumen of the perfused, isolated heart. The results suggest that heart activity in teleosts is directly modulated by functional adrenergic, cardioacceleratory nerve fibers.     

Ammonia excretion in the seawater blue crab (Callinectes sapidus) occurs by diffusion, and not Na+/NH4+ exchange

Summary A series of experiments was conducted to investigate whether ammonia is excreted across the seawater-acclimated blue crab's gills as ionized NH ₄ ⁺ or as the free base, NH₃. The net excretion rate of ammonia was not changed by transfer of the crabs to reduced (150 mM) Na⁺ solutions, by transfer to Na⁺- and K⁺-free artificial sea water, or by the sodium transport inhibitor amiloride. Ammonia excretion, therefore, does not appear to be linked to Na⁺ uptake in these animals, and appears to take place by passive diffusion. Since ammonia could diffuse either as NH ₄ ⁺ or NH₃, we examined two other kinds of evidence. The trans-epithelial potential was measured in sea water and the various artificial media. In spite of a 10 mV more negative potential in Na⁺-, K⁺-free medium, the ammonia excretion was not reduced. Also, in alkalinized seawater in which the partial pressure gradient of NH₃ was reduced, but the concentration gradient of NH ₄ ⁺ increased, ammonia excretion was reduced by about 70%. These results are consistent with the conclusion that ammonia excretion takes place by diffusion of the free base, NH₃.Abbreviations SW sea water - ASW artificial sea water - t.e.p. transepithelial potential The University of Texas Marine Science Institute Contribution No. 461Supported by NSF Grant PCM77-24358     

The metabolism of benzyl isothiocyanate and its cysteine conjugate.

1. The corresponding cysteine conjugate was formed when the GSH (reduced glutathione) or cysteinylglycine conjugates of benzyl isothiocyanate were incubated with rat liver or kidney homogenates. When the cysteine conjugate of benzyl isothiocyanate was similarly incubated in the presence of acetyl-CoA, the corresponding N-acetylcysteine conjugate (mercapturic acid) was formed. 2. The non-enzymic reaction of GSH with benzyl isothiocyanate was rapid and was catalysed by rat liver cytosol. 3. The mercapturic acid was excreted in the urine of rats dosed with benzyl isothiocyanate or its GSH, cysteinyl-glycine or cysteine conjugate, and was isolated as the dicyclohexylamine salt. 4. An oral dose of the cysteine conjugate of [14C]benzyl isothiocyanate was rapidly absorbed and excreted by rats and dogs. After 3 days, rats had excreted a mean of 92.4 and 5.6% of the dose in the urine and faeces respectively, and dogs had excreted a mean of 86.3 and 13.2% respectively. 5. After an oral dose of the cystein conjugate of [C]benzyl isothiocyanate, the major 14C-labelled metabolite in rat urine was the corresponding mercapturic acid (62% of the dose), whereas in dog urine it was hippuric acid (40% of the dose). 5. Mercapturic acid biosynthesis may be an important route of metabolism of certain isothiocyanates in some mammalian species.