Water and ion transport across the eversible vesicles in the collophore of a springtail Orchesella cincta

ABSTRACTSpringtails (Collembola) are ancient close relatives of the insects. The eversible vesicles are their unique paired transporting organs, which consist of an epithelium located inside a tube-like structure on the first abdominal segment called the collophore. The vesicles can be protruded out of the collophore and several lines of evidence indicate that they have a vital function in water uptake and ion balance. However, the amount of water absorbed by the vesicles and which other ions apart from sodium are transported remain unknown. Using Orchesella cincta as a model, we developed protocols for two assays that enabled us to study water and ion movement across the eversible vesicles in whole living springtails. Using an inverse Ramsay assay we demonstrate that the eversible vesicles absorb water from a droplet applied onto their surface. Using the scanning ion-selective electrode technique (SIET) we show that the vesicles absorb Na+ and Cl− from the bathing medium, secrete NH4+, and both absorb and secrete K+, H+ is secreted at a low level in the anterior part and absorbed at the posterior. We did not detect transport of Ca2+ at significant levels. The highest flux was the absorption of Cl−, and the magnitude of ion fluxes were significantly lower in fully hydrated springtails. Our data demonstrate that the eversible vesicles are a transporting epithelium functioning in osmo- and ionoregulation, nitrogenous waste excretion and likely acid-base balance.

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Higher Dietary Acidity is Associated with Lower Bone Mineral Density in Postmenopausal Iranian Women, Independent of Dietary Calcium Intake

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000207 ◽

2014 ◽

Vol 84 (3-4) ◽

pp. 0206-0217 ◽

Cited By ~ 8

Author(s):

Seyedeh-Elaheh Shariati-Bafghi ◽

Elaheh Nosrat-Mirshekarlou ◽

Mohsen Karamati ◽

Bahram Rashidkhani

Keyword(s):

Calcium Intake ◽

Dietary Calcium ◽

Dietary Calcium Intake ◽

Dietary Intakes ◽

Iranian Women ◽

Acid Base Balance ◽

Mineral Density ◽

Acid Base ◽

Base Balance ◽

Dietary Acid

Findings of studies on the link between dietary acid-base balance and bone mass are relatively mixed. We examined the association between dietary acid-base balance and bone mineral density (BMD) in a sample of Iranian women, hypothesizing that a higher dietary acidity would be inversely associated with BMD, even when dietary calcium intake is adequate. In this cross-sectional study, lumbar spine and femoral neck BMDs of 151 postmenopausal women aged 50 - 85 years were measured using dual-energy x-ray absorptiometry. Dietary intakes were assessed using a validated food frequency questionnaire. Renal net acid excretion (RNAE), an estimate of acid-base balance, was then calculated indirectly from the diet using the formulae of Remer (based on dietary intakes of protein, phosphorus, potassium, and magnesium; RNAERemer) and Frassetto (based on dietary intakes of protein and potassium; RNAEFrassetto), and was energy adjusted by the residual method. After adjusting for potential confounders, multivariable adjusted means of the lumbar spine BMD of women in the highest tertiles of RNAERemer and RNAEFrassetto were significantly lower than those in the lowest tertiles (for RNAERemer: mean difference -0.084 g/cm2; P=0.007 and for RNAEFrassetto: mean difference - 0.088 g/cm2; P=0.004). Similar results were observed in a subgroup analysis of subjects with dietary calcium intake of >800 mg/day. In conclusion, a higher RNAE (i. e. more dietary acidity), which is associated with greater intake of acid-generating foods and lower intake of alkali-generating foods, may be involved in deteriorating the bone health of postmenopausal Iranian women, even in the context of adequate dietary calcium intake.

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