White Cane Update, Fall 2004

The White Cane Update newsletter includes information about the latest happenings at the Iowa Department for the Blind.

White Cane Update, Winter 2004

The White Cane Update newsletter includes information about the latest happenings at the Iowa Department for the Blind.

White Cane Update, Summer 2006

The White Cane Update newsletter includes information about the latest happenings at the Iowa Department for the Blind.

White Cane Update, Spring 2004

The White Cane Update newsletter includes information about the latest happenings at the Iowa Department for the Blind.

White Cane Update, Winter 2005

The White Cane Update newsletter includes information about the latest happenings at the Iowa Department for the Blind.

White Cane Update, Spring 2005

The White Cane Update newsletter includes information about the latest happenings at the Iowa Department for the Blind.

White Cane Update, Spring 2005

The White Cane Update newsletter includes information about the latest happenings at the Iowa Department for the Blind.

White Cane Update, Fall 2005

The White Cane Update newsletter includes information about the latest happenings at the Iowa Department for the Blind.

White Cane Update, Winter 2006

The White Cane Update newsletter includes information about the latest happenings at the Iowa Department for the Blind.

Effects of thyromimetic drugs on aldosterone-dependent sodium transport in the toad bladder.

Aldosterone increases transepithelial Na+ transport in the urinary bladder of Bufo marinus. The response is characterized by 3 distinct phases: 1) a lag period of about 60 min, ii) an initial phase (early response) of about 2 hr during which Na+ transport increases rapidly and transepithelial electrical resistance falls, and iii) a late phase (late response) of about 4 to 6 hr during which Na+ transport still increases significantly but with very little change in resistance. Triiodothyronine (T3, 6 nM) added either 2 or 18 hr before aldosterone selectively antagonizes the late response. T3 per se (up to 6 nM) has no effect on base-line Na+ transport. The antagonist activity of T3 is only apparent after a latent period of about 6 to 8 hr. It is not rapidly reversible after a 4-hr washout of the hormone. The effects appear to be selective for thyromimetic drugs since reverse T3 (rT3) is inactive and isopropyldiiodothyronine (isoT2) is more active than T3. The relative activity of these analogs corresponds to their relative affinity for T3 nuclear binding sites which we have previously described. Our data suggest that T3 might control the expression of aldosterone by regulating gene expression, e.g. by the induction of specific proteins, which in turn will inhibit the late mineralocorticoid response, without interaction with the early response.

Testosterone: a specific competitive antagonist of aldosterone in the toad bladder.

Testosterone (100 nM to 40 microM) antagonized the effect of aldosterone (10 nM) on Na+ transport in the toad bladder measured in vitro as short-circuit current (SCC). Half-maximal inhibition occurred at an antagonist-agonist molar ratio of 150:1. The antagonist action of testosterone was reversed by addition of more aldosterone. The antagonism was specific in the sense that testosterone (20 microM) did not inhibit the response of the SCC to oxytocin (50 mU/ml). By itself, testosterone (up to 20 microM) had no agonist activity on base-line SCC. Finally, testosterone (500 nM to 20 microM) specifically displaced [3H]aldosterone (5 nm) from its cytoplasmic and nuclear binding sites in bladders incubated in vitro at 25 or 0 degrees C and labeled at steady state. There was a significant linear correlation between the effect of testosterone on the aldosterone-dependent SCC and its effect on [3H]aldosterone binding sites in the cytoplasm and in the nucleus. We conclude that 1) testosterone is a specific competitive antagonist of aldosterone, and 2) [3H]aldosterone nuclear and cytoplasmic binding sites could be mineralocorticoid receptors, mediating the action of aldosterone on Na+ transport.

Thirteen polymorphic microsatellite markers for the European green toad Bufo viridis viridis, a declining amphibian species.

We report 13 new polymorphic microsatellite markers for the European green toad Bufo viridis viridis (B. viridis subgroup), a declining amphibian from Central, Southeastern and Eastern Europe. Diversity at these loci estimated for 19 individuals ranged from two to ten alleles. Most of these primers also cross-amplify in related West-Mediterranean green toad species (Bufo balearicus, B. siculus and B. boulengeri). These microsatellites will be useful for conservation genetics of threatened Bufo viridis viridis populations and evolutionary studies of green toad taxa in secondary contact to examine hybridization.

White Cane Update, Summer 2006

The White Cane Update newsletter includes information about the latest happenings at the Iowa Department for the Blind.

White Cane Update, Winter 2007

The White Cane Update newsletter includes information about the latest happenings at the Iowa Department for the Blind.