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The morphology of the mature spermatozoa of the closely-related freshwater pulmonates, Bulinus afncanus and Bulinus globosus, was examined using scanning and transmission electron microscopy. A comparison showed no useful differences that could be used to distinguish the species though they did differ in one respect from Bulinus tropicus, the only other bulinid for which sperm morphology is known.

Reduction in endothelium-derived hyperpolarizing factor (EDHF)-mediated dilatory function in large, elastic arteries during hypertension is reversed after blood pressure normalization. We investigated whether similar mechanisms occurred in smaller mesenteric resistance arteries from aged Wistar-Kyoto (WKY) rats, spontaneously hypertensive rats (SHRs), and SHRs treated with the angiotensin-converting enzyme inhibitor, enalapril, using immunohistochemistry, serial-section electron microscopy, electrophysiology and wire myography. Unlike the superior mesenteric artery, EDHF relaxations in muscular mesenteric arteries were not reduced in SHRs, although morphological differences were found in the endothelium and smooth muscle. In WKY rats, SHRs and enalapril-treated SHRs, relaxations were mediated by small-, large-, and intermediate-conductance calcium-activated potassium channels, which were distributed in the endothelium, smooth muscle, and both layers, respectively. However, only WKY hyperpolarizations and relaxations were sensitive to gap junction blockers, and these arteries expressed more endothelial and myoendothelial gap junctions than arteries from SHRs. Responses in WKY rats, but not SHRs, were also reduced by inhibitors of epoxyeicosatrienoic acids (EETs), 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE) and miconazole, although sensitivity to EET regioisomers was endothelium-independent in all rats. Enalapril treatment of SHRs reduced blood pressure and restored sensitivity to 14,15-EEZE, but not to gap junction blockers, and failed to reverse the morphological changes. In conclusion, the mechanisms underlying EDHF in muscular mesenteric arteries differ between WKY rats and SHRs, with gap junctions and EETs involved only in WKY rats. However, reduction of blood pressure in SHRs with enalapril restored a role for EETs, but not gap junctions, without reversing morphological changes, suggesting a differential control of chemical and structural alterations.

Control of cerebral vasculature differs from that of systemic vessels outside the blood-brain barrier. The hypothesis that the endothelium modulates vasomotion via direct myoendothelial coupling was investigated in a small vessel of the cerebral circulation. In the primary branch of the rat basilar artery, membrane potential, diameter, and calcium dynamics associated with vasomotion were examined using selective inhibitors of endothelial function in intact and endothelium-denuded arteries. Vessel anatomy, protein, and mRNA expression were studied using conventional electron microscopy high-resolution ultrastructural and confocal immunohistochemistry and quantitative PCR. Membrane potential oscillations were present in both endothelial cells and smooth muscle cells (SMCs), and these preceded rhythmical contractions during which adjacent SMC intracellular calcium concentration ([Ca2+]i) waves were synchronized. Endothelium removal abolished vasomotion and desynchronized adjacent smooth muscle cell [Ca2+]iwaves. NG-nitro-l-arginine methyl ester (10 μM) did not mimic this effect, and dibutyryl cGMP (300 μM) failed to resynchronize [Ca2+]iwaves in endothelium-denuded arteries. Combined charybdotoxin and apamin abolished vasomotion and depolarized and constricted vessels, even in absence of endothelium. Separately,37,43Gap27 and40Gap27 abolished vasomotion. Extensive myoendothelial gap junctions (3 per endothelial cell) composed of connexins 37 and 40 connected the endothelial cell and SMC layers. Synchronized vasomotion in rat basilar artery is endothelium dependent, with [Ca2+]iwaves generated within SMCs being coordinated by electrical coupling via myoendothelial gap junctions.

Dried leaf material of a Mexican plant, Agave attenuata, was found to be highly toxic to the target snail, Bulinus africanus, intermediate host of Schistosoma haematobium in South Africa. The molluscicidal potency of the plant underwent seasonal variation, but remained stable over a range of pH values, after exposure to sunlight and organic matter, and during dry storage. It was unstable in aqueous suspension. The toxicity of the molluscicide to crop plants, invertebrates, fish and mammals was lacking or low. Given these properties, A. attenuata may provide a substitute for niclosamide and be used safely for snail control by rural communities.

Apodytes dimidiata has recently come to the fore as a potential plant molluscicide for schistosomiasis control in rural communities in South Africa. Prior to field applications of its leaves and extract to waterbodies, selected acute and sub-acute mammal toxicity tests were conducted in accordance with the Organisation of Economic Cooperation and Development (OECD) Guidelines to identify any potential hazards that might arise form the plant's use. Acute and sub-acute mammal toxicity test results classified A. dimidiata as non-toxic and non-irritating. Based on this toxicity evaluation, the dried leaf material and aqueous extracts of this plant are considered safe for use in preliminary field trials.

The crude aqueous leaf extract of a South African tree, Apodytes dimidiata , has been identified as a potential molluscicide for snail control in anti-schistosomiasis programmes in rural communities. Before preliminary field trials could be implemented its acute toxic effects on two non-target organisms were examined in accordance with the OECD guidelines to identify any potential hazards that might arise from the plant's use. Laboratory results showed that working molluscicidal concentrations of the plant extract were non-toxic to earthworms suggesting that it is non-hazardous to soil-dwelling fauna. The plant extract proved toxic to fish and was assigned the risk phrase `harmful to the aquatic environment' according to the EEC classification scheme. Based on these toxicity evaluations, aqueous extracts of A. dimidiata are considered safe for use in preliminary field trials.

Background Hypertension is a complex disease with many contributory genetic and environmental factors. We aimed to identify common targets for therapy by gene expression profiling of a resistance artery taken from animals representing two different models of hypertension. We studied gene expression and morphology of a saphenous artery branch in normotensive WKY rats, spontaneously hypertensive rats (SHR) and adrenocorticotropic hormone (ACTH)-induced hypertensive rats. Results Differential remodeling of arteries occurred in SHR and ACTH-treated rats, involving changes in both smooth muscle and endothelium. Increased expression of smooth muscle cell growth promoters and decreased expression of growth suppressors confirmed smooth muscle cell proliferation in SHR but not in ACTH. Differential gene expression between arteries from the two hypertensive models extended to the renin-angiotensin system, MAP kinase pathways, mitochondrial activity, lipid metabolism, extracellular matrix and calcium handling. In contrast, arteries from both hypertensive models exhibited significant increases in caveolin-1 expression and decreases in the regulators of G-protein signalling, Rgs2 and Rgs5. Increased protein expression of caveolin-1 and increased incidence of caveolae was found in both smooth muscle and endothelial cells of arteries from both hypertensive models. Conclusion We conclude that the majority of differences in gene expression found in the saphenous artery taken from rats with two different forms of hypertension reflect distinctive morphological and physiological alterations. However, changes in common to caveolin-1 expression and G protein signalling, through attenuation of Rgs2 and Rgs5, may contribute to hypertension through augmentation of vasoconstrictor pathways and provide potential targets for common drug development.

The bark of Apodytes dimidiata (Icacinaceae) yielded two major compounds, the iridoid genipin (1) and its 10-monoacetate derivative 2. Using Bulinus africanus as host snail, we show here that LD 50 values for both compounds were in the range 22 -26 ppm.

An exotic fresh-water gastropod recently discovered in South Africa is identified as Aplexa (Stenophysa) marmorata (Physidae) and is considered conspecific with a population known from West Africa since at least 1911 and a single record from Mozambique dating from 1886. It is speculated that these introductions could have occurred via the Portuguese slave trade during the 16th and 17th centuries. A key to A. marmorata, another introduced physid Physa acuta and the indigenous, sinistral genus Bulinus is presented.