Membrane electrical parameters in turtle bladder measured using impedance-analysis techniques

Summary Equivalent-circuit impedance analysis experiments were performed on the urinary bladders of freshwater turtles in order to quantify membrane ionic conductances and areas, and to investigate how changes in these parameters are associated with changes in the rate of proton secretion in this tissue. In all experiments, sodium reabsorption was inhibited thereby unmasking the electrogenic proton secretion process. We report the following: (1) transepithelial impedance is represented exceptionally well by a simple equivalent-circuit model, which results in estimates of the apical and basolateral membrane ionic conductances and capacitances; (2) when sodium transport is inhibited with mucosal amiloride and serosal ouabain, the apical and basolateral membrane conductances and capacitances exhibit a continual decline with time; (3) this decline in the membrane parameters is most likely caused by subtle time-dependent changes in cell volume, resulting in changes in the areas of the apical and basolateral membranes; (4) stable membrane parameters are obtained if the tissue is not treated with ouabain, and if the oncotic pressure of the serosal solution is increased by the addition of 2% albumin; (5) inhibition of proton secretion using acetazolamide in CO₂ and HCO ₃ ^– -free bathing solutions results in a decrease in the area of the apical membrane, with no significant change in its specific conductance; (6) stimulation of proton transport with CO₂ and HCO ₃ ^– -containing serosal solution results in an increase in the apical membrane area and specific conductance. These results show that our methods can be used to measure changes in the membrane electrophysiological parameters that are related to changes in the rate of proton transport. Notably, they can be used to quantify in the live tissue, changes in membrane area resulting from changes in the net rates of endocytosis and exocytosis which are postulated to be intimately involved in the regulation of proton transport.     

Sampling Atriplex bladders: a comparison of methods

Abstract. A major objection to the convenient sampling of Chenopodiacean bladders by brushing in aqueous solutions is the suspected leakage of ions from the leaf blade. To overcome this problem, a new method of sampling bladder hair is described, which also achieves rapid and quantitative separation and, at the same time, yields bladder samples of undoubtedly high purity. Leakage is stopped by the aid of liquid nitrogen. Comparison of this method to removal of bladders by brushing in aquenous solutions effectively confirm the validity of the customary method beyond dispute.     

Intra‐ and Intersexual swim bladder dimorphisms in the plainfin midshipman fish (Porichthys notatus): Implications of swim bladder proximity to the inner ear for sound pressure detection

The plainfin midshipman fish, Porichthys notatus , is a nocturnal marine teleost that uses social acoustic signals for communication during the breeding season. Nesting type I males produce multiharmonic advertisement calls by contracting their swim bladder sonic muscles to attract females for courtship and spawning while subsequently attracting cuckholding type II males. Here, we report intra‐ and intersexual dimorphisms of the swim bladder in a vocal teleost fish and detail the swim bladder dimorphisms in the three sexual phenotypes (females, type I and II males) of plainfin midshipman fish. Micro‐computerized tomography revealed that females and type II males have prominent, horn‐like rostral swim bladder extensions that project toward the inner ear end organs (saccule, lagena, and utricle). The rostral swim bladder extensions were longer, and the distance between these swim bladder extensions and each inner‐ear end organ type was significantly shorter in both females and type II males compared to that in type I males. Our results revealed that the normalized swim bladder length of females and type II males was longer than that in type I males while there was no difference in normalized swim bladder width among the three sexual phenotypes. We predict that these intrasexual and intersexual differences in swim bladder morphology among midshipman sexual phenotypes will afford greater sound pressure sensitivity and higher frequency detection in females and type II males and facilitate the detection and localization of conspecifics in shallow water environments, like those in which midshipman breed and nest.     

Distribution of neurons in the major pelvic ganglion of the rat which supply the bladder,colon or penis

Summary In male rats a large number of the postganglionic neurons which innervate the pelvic organs are located in the major pelvic ganglion. In the present study we have identified the location within this ganglion of neurons which project to either of three pelvic organs, the penis, colon or urinary bladder. Two fluorescent retrogradely-transported dyes, Fast Blue and Fluoro-Gold, were used. For most animals one dye was injected into the cavernous space of the penis, the wall of the distal colon or the wall of the urinary bladder. In a small number of animals two organs were injected, each with a different dye. One to six weeks after injection the major pelvic ganglia were fixed in buffered formaldehyde. The distribution of fluorescent dye-labelled cells was observed in whole mounts of complete ganglia and, in most cases, also in small accessory ganglia located between the ureter and the prostate. The studies showed a unique pattern of distribution for each organ-specific group of neurons. Most of the colon neurons are located in the major pelvic ganglion near the entrance of the pelvic nerve, whereas almost all of the penis neurons are near or within the penile nerve. Bladder neurons are relatively evenly distributed throughout the ganglion. These results demonstrate a distinct topographical organization of organ-specific neurons of the major pelvic ganglion of the male rat, a phenomenon which has also been observed in other peripheral ganglia.     

Creatine kinase activity of urinary bladder and skeletal muscle from control and streptozotocin-diabetic rats

The urinary bladder depends on intracellular ATP for the support of a number of essential intracellular processes including contraction. The concentration of ATP is maintained constant primarily via the rapid transfer of a phosphate from creatine phosphate (CP) to ADP catalyzed by the enzyme creatine kinase (CK). Since muscular pathologies associated with diabetes are in part related to intracellular alterations in metabolism, we have characterized the CK activity in both skeletal muscle and urinary bladder from control and streptozotocin-diabetic rats.The following is a summary of the results: 1) Bladder tissue from control rats showed linear kinetics with a V_max = 390 nmoles/mg protein/min, and a K_m = 275 µM. 2) Urinary bladder tissue isolated from diabetic rats displayed biphasic kinetics with V_max = 65 and 324 nmoles/mg protein/min, and K_m's = 10 µM and 190 µM respectively. 3) Skeletal muscle isolated from control rats showed linear kinetics with an approximate V_max of 800 nmoles/mg protein/min and a K_m of 280 µM CP. 4) Homogenates of skeletal muscle from diabetic rats showed complex kinetics not separable into distict component forms. 5) The K_m for ADP for both skeletal muscle and bladder was approximately 10 µM.These studies demonstrate that whereas bladders isolated from both control and diabetic rats possess a low-affinity isomer(s) of CK with similar maximum enzymatic activity, there is a high affinity isomer present within the urinary bladder muscle of diabetic rats that is not present in bladder tissue isolated from control rats. Skeletal muscle isolated from both diabetic and control rats exhibited a maximal activity 2 to 3 times higher than that of the bladder.     

Are galling insects better protected against parasitoids than exposed feeders?: a test using tenthredinid sawflies

ABSTRACT.

• 1 Data mostly from the published literature were used to assess the effect of galling on the number of parasitoid species per host species in the phylogeny of nematine sawflies from free external feeders (colonial and solitary) to leaf gallers and shoot gallers.
• 2 The strongest effects of galling were the total elimination of the species-rich cocoon-attacking guild of parasitoids, and eonymphal parasitoids, from the parasitoid community on shoot gallers, all of which are in the genus Euura.
• 3 All tachinid larval parasitoids were also eliminated by the galling habit.
• 4 The cumulative effects of these exclusions resulted in a decline in mean number of parasitoid species per host species from almost sixteen species on external colonial feeders to 4.0 species on shoot gallers.
• 5 General patterns in per cent parasitism by non-tachinid and tachinid larval parasitoids, eonymphal and cocoon parasitoids, on exposed feeders to shoot gallers, showed declines in non-tachinid attack and elimination of tachinid, eonymphal and cocoon parasitoids. But leaf gallers tended to be attacked more than exposed feeders by non-tachinid larval parasitoids.
• 6 The galling habit had a long-term impact by reducing the number of parasitoid species attacking nematine sawfly gallers and per cent mortality inflicted, so that natural enemies may have been important as a selective factor in the evolution of galling nematine sawflies.

     

Very low osmotic water permeability and membrane fluidity in isolated toad bladder granules

Summary Osmotic water permeability of the apical membrane of toad urinary epithelium is increased greatly by vasopressin (VP) and is associated with exocytic addition of granules and aggrephores at the apical surface. To determine the physiological role of granule exocytosis, we measured the osmotic water permeability and membrane fluidity of isolated granules, surface membranes and microsomes prepared from toad bladder in the presence and absence of VP.P _f was measured by stopped-flow light scattering and membrane fluidity was examined by diphenylhexatriene (DPH) fluorescence anisotropy. In response to a 75mm inward sucrose gradient, granule size decreased with a single exponential time constant of 2.3±0.1 sec (sem, seven preparations, 23°C), corresponding to aP _f of 5×10^–4 cm/sec; the activation energy (E _a ) forP _f was 17.6±0.8 kcal/mole. Under the same conditions, the volume of surface membrane vesicles decreased biexponentially with time constants of 0.13 and 1.9 sec; the fast component comprised 70% of the signal. Granule, surface membrane and microsome time constants were unaffected by VP. However, in surface membranes, there was a small decrease (6±2%) in the fraction of surface membranes with fast time constant. DPH anisotropies were 0.253 (granules), 0.224 (surface membrane fluidity is remarkably lower than that of surface and microsomal membranes, and (4) rapid water transport occurs in surface membrane vesicles. The unique physical properties of the granule suggests that apical exocytic addition of granule membrane may be responsible for the low water permeability of the unstimulated apical membrane.     

Constitutive and transport-related endocytotic pathways in turtle bladder epithelium

Summary Proton secretion in the urinary bladder of the fresh-water turtle is mediated by a proton pump located in the apical membrane of a population of cells characteristically rich in carbonic anhydrase. Earlier studies have demonstrated that these cells exhibit apical-membrane endocytotic and exocytotic processes which are thought to be involved in the regulation of the rate of proton transport via alterations in the number of pumps within the apical membrane. In this study, we sought to characterize these processes using two different methods. Analysis of transepithelial impedance yielded estimates of membrane capacitance which could be related to membrane area, thereby allowing one to monitor net changes in apical-membrane area resulting from changes in the net rates of endo-and exocytosis. Uptake of the fluid-phase marker FITC-dextran provided a measure of net extracellular volume uptake which was related to net rates of endocytosis. Our major conclusions are summarized as follows. The bladder cells exhibit a high baseline rate of endocytosis which appears to be a constitutive process similar to pinocytosis. This process is completely inhibited when ambient temperature is reduced to 15°C. In addition, serosal application of 0.5mm acetazolamide causes a transient increase in the rate of endocytosis, concomitant with a decrease in the rate of transport. Reduction of ambient temperature to 15°C reduces the rate of acetazolamide-induced endocytosis, but does not abolish it. Addition of 1mm serosal azide not only prevents the acetazolamide-induced increase in endocytosis, but also prevents the decrease in transport caused by acetazolamide. Azide has no effect on the baseline rate of endocytosis, nor does it prevent inhibition of carbonic anhydrase by acetazolamide. The specificity of azide, coupled with the different temperature sensitivities, demonstrate that the constitutive and transport-dependent endocytotic pathways are distinct processes. The observation that azide prevents both the acetazolamide-induced increase in endocytosis and the decrease in transport strongly supports the notion that endocytosis of proton-pump-containing membrane is requisite for the inhibition of transport by acetazolamide. Finally, the results also demonstrate that acetazolamide does not inhibit proton secretion simply by inhibiting carbonic anhydrase.