Methods for exploring the morpho-functional relations of the aortic depressor nerve in experimental diabetes.

The present study investigated morpho-functional relations of the aortic depressor nerve (ADN) 5, 15 and 120 days after the onset of streptozotocin-induced diabetes in rats. Time control animals received vehicle. Under pentobarbital anesthesia, ADN activity was recorded simultaneously with arterial pressure. After the recordings, nerves were prepared for light microscopy study and morphometry. ADN function was accessed by means of pressure-nerve activity curve (fitted by sigmoidal regression) and cross-spectral analysis between mean arterial pressure (MAP) and ADN activity. The relation between morphological (myelinated fibers number and density, total myelin area, total fiber area and percentage of occupancy) and functional (gain, signal/noise relation, frequency) parameters were accessed by linear regression analysis and correlation coefficient calculations. Functional parameters obtained by means of the sigmoidal regression curve as well as by cross-spectral analysis were similar in diabetic and control rats. Morphometric parameters of the ADN were similar between groups 5 days after the onset of diabetes. Average myelin area and myelinated fiber area were significantly smaller on diabetic rats 15 and 120 days after the onset of diabetes, being the myelinated fiber and respective axons area and diameter also smaller on 120 days group. Nevertheless, G ratio (ratio between axon and fiber diameter) was nearly 0.6 and not different between groups or experimental times. No significant relationship between morphological and functional parameters was detected in all experimental groups. The present study suggests that ADN diabetic neuropathy was time-dependent, with damage to myelinated fibers to be the primary event, not evidenced by physiological methods.

Aestivation in the South American lungfish, Lepidosiren paradoxa: effects on cardiovascular function, blood gases, osmolality and leptin levels.

The African (Protopterus sp.) and South American lungfish (Lepidosiren paradoxa) inhabit shallow waters, that seasonally dry out, which induces aestivation and cocoon formation in Protopterus. Differently, L. paradoxa has no cocoon, and it aestivates in a simple burrow. In water PaCO(2) is 21.8+/-0.4mmHg (mean values+/-S.E.M.; n=5), whereas aestivation for 20 days increased PaCO(2) to as much as 37.6+/-2.1mmHg, which remained the same after 40 days (35.8+/-3.3mmHg). Concomitantly, the plasma [HCO(3)(-)]-values for animals in water were 22.5+/-0.5mM, which after 20 days increased to 40.2+/-2.3mM and after 40 days to 35.8+/-3.3mM. Initially in water, PaO(2) was 87.7+/-2.0mmHg, but 20 days in aestivation reduced the value to 80.5+/-2.2 and later (40 days) to 77.1+/-3.0mmHg. Meanwhile, aestivation had no effect on pHa and hematocrit. The blood pressures were equal for animals in the water or in the burrow (P(mean) approximately 30mmHg), and cardiac frequency (f(H)) fell from 31beats min(-1) to 22beats min(-1) during 40 days of aestivation. The osmolality (mOsmkgH(2)O(-1)) was elevated after 20 and 40 days of aestivation but declined upon return to water. The transition from activity to aestivation involves new set-points for the variables that determine the acid-base status and PaO(2) of the animals, along with a reduction of cardiac frequency.

Ultrastructural anatomy of the renal nerves in rats.

The innervation within mammalian kidneys (intrinsic innervation) has been extensively described in the literature, particularly for rats. In contrast, there is still a lack of detailed description of the morphology of the extrinsic renal nerves leading to the kidney. The aim of the present study was to describe, in detail, the morphology of the renal nerves in rats. Left renal nerves were evaluated in 6 normal adult Wistar rats. After nerve recordings, in order to ascertain that the nerves studied were the extrinsic renal nerves, rats were killed and the nerves prepared for transmission electron microscopy. Morphometry was carried out with the aid of computer software. The total numbers of myelinated and unmyelinated fibers were 22+/-6 and 1246+/-110, respectively, with a ratio of unmyelinated/myelinated fiber of 109+/-26. The diameters of myelinated fibers showed an unimodal distribution with a peak at 3.0 microm but more than 17% of the fibers showed diameters larger than 5 microm. Unmyelinated fiber distribution was unimodal, with peak between 0.5 and 0.7 microm. The present study adds new information on the morphology of renal nerves in rats and provides morphological basis for further studies involving the structural basis of altered renal responses in conditions such as hypertension, ageing, diabetes and peripheral neuropathies.