Active Cl− absorption by the Chinese crab (Eriocheir sinensis) gill epithelium measured by transepithelial potential difference

Summary Isolated posterior gills from Chinese crabs (Eriocheir sinensis) acclimated to tap-water were perfused and bathed with full, physiological saline (containing Na⁺ and Cl^–). Under these conditions they developed an outside positive transepithelial potential difference (PD_te). Substitution of Na⁺ by choline on both sides of the epithelium resulted in a substantial hyperpolarization of the PD_te, while substitution of Cl^– by gluconate reverses PD_te to outside negative values.The magnitudes of the potential differences were strongly related to the adaptation media (artificial seawater or tap-water).The KCN-sensitive, outside positive PD_te was shown to be strongly dependent on Cl^–. Application of thiocyanate and 4-acetamido-4-isothiocyanato-stilbene-2,2 disulfonic acid (SITS) to the bath solution resulted in a reduction of the PD_te, while the Cl^–-channel blocker, diphenylamine-2-carboxylic acid (DPC), showed no effect. The PD_te was markedly reduced by acetazolamide, an inhibitor of carbonic anhydrase (CA), and these results are discussed with reference to the presence of a Cl^–/HCO ₃ ^– -exchanger in the apical membrane.Chloride was shown to pass the basolateral membrane via Cl^–-channels: Diphenylamine-2-carboxylic acid (DPC) reduced the PD_te with an IC₅₀ of 3.7×10^–5 mol/l when added to the perfusion saline. A basolateral K⁺-channel and its linkage to Cl^– uptake could be demonstrated by using the K⁺-channel blocker, Ba²⁺, or increased K⁺ concentrations in the perfusion saline (PD_te decrease). Ouabain did not reduce the PD_te under nominally Na⁺-free conditions, indicating that the Cl^– transport is independent of the Na⁺/K⁺-ATPase. In this paper we shall discuss the possible energy sources and linkages between pH regulation and active Cl^– absorption under these experimental conditions.Abbreviations A9C anthracene-9-carboxylic acid - CA carbonic anhydrase - DMSO dimethylsulfoxide - DPC diphenylamino-2-carboxylic acid - PD _te transepithelial potential difference - SITS 4-acetamido-4-isothiocyanato-stilbene-2,2-disulfonic acid - TEA tetraethyl-ammoniumchloride     

Wistar Rats and Premature Infants

The molar proportions of essential amino acids in the fasting plasma of Wistar rats were shown to have utility in: (i) Determining the limiting essential amino acid for peanut butter and whole egg protein; (ii) Ranking in proper order peanut butter protein supplemented with two levels of lysine and whole egg protein according to their Biologic value and net protein utilization.

The molar proportions of the essential amino acids in the fasting plasma of adult humans were shown to have utility in ranking five rations according to their Biol.ogic value and net protein utilization by premature infants.     

The Anopheles gambiae cE5 salivary protein: a sensitive biomarker to evaluate the efficacy of insecticide-treated nets in malaria vector control

Evaluation of vector control is crucial for improving malaria containment and, according to World Health Organization, new complementary indicators would be very valuable. In this study the IgG response to the Anopheles-specific cE5 salivary protein was tested as a tool to evaluate the efficacy of insecticide-treated nets in reducing human exposure to malaria vectors. Sera collected during a longitudinal study carried out in Angola, and including entomological and parasitological data, were used to assess the IgG response to the Anopheles gambiae cE5 in both children and adults, before and after the application of insecticide-treated nets. Seasonal fluctuation of specific IgG antibody levels according to exposure was only found in children (up to ≈14 years old) whose anti-cE5 IgG response dropped after bed nets installation. These results were fully consistent with previous findings obtained with the same set of sera and indicating a substantial reduction of human-vector contact shortly after nets implementation. Overall, children IgG response to the cE5 protein appeared a very sensitive biomarker, which allowed for the detection of even weak exposure to Anopheles bites, indicating it may represent a reliable additional tool to evaluate the efficacy of vector control interventions.     

The role of the United States military in the development of vector control products,including insect repellents,insecticides, and bed nets

Arthropod‐borne diseases such as malaria, dengue, scrub typhus, and leishmaniasis continue to pose a significant threat to U.S. military forces deployed in support of operational and humanitarian missions. These diseases are transmitted by a variety of arthropods, including mosquitoes, ticks, chiggers, sand flies, and biting midges. In addition to disease threats, biting arthropods can cause dermatitis, allergic reactions, and sleep loss; therefore, monitoring of vector impact and integrated use of personal protective measures (PPM) and methods to reduce the vector populations are needed to protect service members. The U.S. military has played a vital role in vector identification tools and the development and testing of many of the most effective PPM and vector control products available today, including the topical repellent DEET and the repellent/insecticide permethrin, which is applied to clothing and bed nets. Efforts to develop superior products are ongoing. Although the U.S. military often needs vector control products with rather specific properties (e.g., undetectable, long‐lasting in multiple climates) in order to protect its service members, many Department of Defense vector control products have had global impacts on endemic disease control.     

Mitogen-activated protein kinases are in vivo transducers of osmosensory signals in fish gill cells

The abundance and activity of three subgroups of mitogen-activated protein (MAP) kinases, the extracellular signal regulated kinase 1 (ERK1), stress-activated protein kinase 1/ Jun N-terminal kinase (SAPK1), and stress-activated protein kinase 2/ p38 (SAPK2), were measured in gill epithelium of the euryhaline teleost Fundulus heteroclitus exposed for 1 h to 4 weeks to hyper- and hyposmotic stress. The abundance of ERK1, SAPK1 and SAPK2 was analyzed by standard Western immunodetection. MAP kinase activity is a function of phosphorylation and was measured using phospho-specific and MAP kinase subgroup-specific antibodies. The abundance of the 63 kDa fish isoform of SAPK2 increases significantly during hyper- but not hyposmotic stress while ERK1 and SAPK1 protein levels remain unchanged during both types of osmotic stress. In contrast to this small effect of osmotic stress on MAP kinase abundance, the activity of all MAP kinases decreases significantly in response to hyperosmotic stress and increases significantly during hyposmotic stress. These results demonstrate for the first time that the activity of all major MAP kinases is osmoregulated in gill epithelium of euryhaline fish. Based on these results we conclude that MAP kinases are important components of salinity adaptation and participate in osmosensory signaling pathways in gill epithelium of euryhaline fishes.     

Cyprinid herpes virus-3 (CyHV-3) bears genes of genetically distant large DNA viruses

A large DNA virus, designated koi herpes virus (KHV), carp interstitial nephritis gill necrosis virus (CNGV) and Cyprinid herpes virus-3 (CyHV-3), causes massive mortality of carp. Morphologically, the virus resembles herpes viruses, but it contains a genome of ca 295 kbp, larger than that of any Herpesviridae member. Interestingly, three CyHV-3 genes, thymidylate monophosphate kinase (TmpK), ribonucleotide reductase and thymidine kinase, which are involved in deoxynucleotide tri-phosphate synthesis, resemble those of pox viruses. In addition to the TmpK gene, which is nonexistent in the genome of herpes viruses, CyHV-3 contains a B22R-like gene, exclusively expressed by pox viruses. These results raise questions on the phylogenic origin of CyHV-3.     

Early development of the digestive tract (pharynx and gut) in the embryos and pre-larvae of the European sea bass Dicentrarchus labrax

The European sea bass Dicentrarchus labrax is a marine teleost important in Mediterranean aquaculture. The development of the entire digestive tract of D. labrax , including the pharynx, was investigated from early embryonic development to day 5 post hatching (dph), when the mouth opens. The digestive tract is initialized at stage 12 somites independently from two distinct infoldings of the endodermal sheet. In the pharyngeal region, the anterior infolding forms the pharynx and the first gill slits at stage 25 somites. The other three gill arches and slits are formed between 1 and 5 dph. Posteriorly, in the gut tube region, a posterior infolding forms the foregut, midgut and hindgut. The anus opens before hatching, at stage 28 somites. Associated organs (liver, pancreas and gall bladder) are all discernable from 3 dph. Some aspects of the development of the two independent initial infoldings seem original compared with data in the literature. These results are discussed and compared with embryonic and post-embryonic development patterns in other teleosts.     

Small subunit ribosomal RNA sequence of Henneguya exilis (class Myxosporea) identifies the actinosporean stage from an oligochaete host

Several transmission studies, as well as recent molecular data, have indicated that the two classes Myxosporea and Actinosporea represent different life cycle stages of Myxozoa. To evaluate the life cycles of myxozoa in catfish aquaculture systems, the small subunit (18S) ribosomal RNA gene sequences of Henneguya exilis, a myxosporean from channel catfish Ictalurus punctatus, and an actinosporean (previously designated as Aurantiactinomyxon janiszewskai) from the aquatic oligochaete Dero digitata were determined. The sequences were identical, indicating that H. exilis and the actinosporean are alternate life stages of a single species. This is the first report identifying the actinosporean stage of the genus Henneguya.     

Freshwater adaptation during larval, juvenile and immature periods of starry flounder Platichthys stellatus, stone flounder Kareius bicoloratus and their reciprocal hybrids

The freshwater tolerance of starry flounder Platichthys stellatus , stone flounder Kareius bicoloratus and their reciprocal hybrids, produced by artificial insemination, were examined in the larval, juvenile and immature phases. Survival rate on being transferred to fresh water in the pre-settlement phase was 0% in stone flounder and hybrids and 16·7% in starry flounder. This rate in the post-settlement phase was elevated to >50% in starry flounder and hybrids but was still 0% in stone flounder and similarly in the immature period starry flounder and hybrids survived in fresh water, although stone flounder did not. The lamella chloride cells of the gill epithelium increased in starry flounder and hybrids in fresh water in all periods. Densities of lamella chloride cells increased from 1·6 ± 0·4 (mean ± s . e . number of cells per 1 mm filament) before the transferral (day 0) to 60·3 ± 6·2 on 14 days after the transfer to fresh water (day 14) in starry flounder in the immature period. These densities in hybrids were 0·6 ± 0·3 and 1·0 ± 0·3 on day 0, and, 35·3 ± 2·8 and 23·2 ± 4·6 on day 14, respectively. Stone flounder did not show a substantial change in chloride cell densities throughout the experimental period. These results suggest that low salinity tolerance was well developed in the settlement period in starry flounder and hybrids, and hybrids were also adapted to fresh water sufficiently regardless of the cross type.     

Morphological changes to the gills of killifish associated with severe parasite infection

Highly significant changes were found in digenean metacercariae infected gills of killifish Fundulus heteroclitus with respect to gill abnormalities. Gills infected with >1000 metacercariae exhibited up to 42 additional gill branches per fish when compared to less parasitized conspecifics. A strong positive correlation was found between abnormal gill morphology (number of branches) and the number of endoparasites present.