Giovanni Casotti

Renal anatomy in sparrows from different environments

The renal anatomy of three species of sparrows, two from mesic areas, the House Sparrow (Passer domesticus) and Song Sparrow (Melospiza melodia), and one salt marsh species, the Savannah Sparrow (Passerculus sandwichensis) was examined. Electron microscopy was used to describe the ultrastructure of the nephron. In addition, stereology was used to quantify the volumes of cortex, medulla, and major vasculature of the kidneys, and the volumes and surface areas occupied by individual nephron components. There appeared to be no differences in the ultrastructural anatomy of the nephrons among the sparrows. Proximal tubules contained both narrow and wide intercellular spaces filled with interdigitations of the basolateral membrane. The thin limbs of Henle contained very wide intercellular spaces which were absent in the thick limbs of Henle. The distal tubule cells contained short, apical microvilli and infoldings of the basolateral membrane. In cross section, the medullary cones of all birds display an outer ring of thick limbs of Henle which surround an inner ring of collecting ducts, which in turn surround a central core of thin limbs of Henle. The Savannah Sparrow has a significantly higher volume of medulla compared to the two more mesic species. Within the cortex, the Savannah Sparrow also has a significantly higher volume of proximal tubules but a significantly lower volume of distal tubules than the other species. Within the medulla, the Savannah Sparrow has a significantly higher volume and surface area of capillaries, and a significantly higher surface area of thick limbs of Henle and collecting ducts than the mesic species. These data suggest that the salt marsh Savannah Sparrow has the renal morphology necessary to produce a more highly concentrated urine than the mesic zone species. J. Morphol. 243:283–291, 2000

IONIC COMPOSITION OF URATE-CONTAINING SPHERES IN THE URINE OF DOMESTIC FOWL

Abstract Birds excrete urate in their urine in the form of small spherical concretions. In addition to urate, these concretions contain protein and inorganic ions. Energy dispersive x-ray microanalysis was used to determine the inorganic ion composition of the urate-containing spheres to gain a better understanding of how the spheres are formed. Ureteral urine was collected from six female white leghorn domestic fowl, Gallus gallus . The urine was filtered to separate the spheres into size categories to determine if the ionic composition varied with the size of the spheres. The spheres were placed on scanning electron microscope stubs, dried and coated with carbon. All samples were examined at an accelerated voltage (kV) of 20. The results showed that in all birds, the spheres contained the ions calcium and potassium (approximately 70% and 30%, respectively, of the total inorganic ions present). However, in one bird, the percent of calcium and potassium was reversed (i.e., calcium 30% and potassium 70%). In all birds, chloride and magnesium were also detected, but in comparatively small amounts (less than 1%). There were no significant differences in the ion content of spheres of different sizes. These data suggest that calcium and potassium may play an important role in the formation of the spheres and are not random inclusions as the spheres are formed. We suggest that the spheres form to facilitate the excretion of urate without blocking or damaging the renal tubules.

Leaf nitrogen and its effects on the rate of herbivory on selected eucalypts in the jarrah forest

This study measured the relationship between the rate of leaf consumption by insect herbivores and the level of leaf nitrogen in selected species of eucalypts. Sampling was carried out on a monthly basis from Eucalyptus accedens, Eucalyptus resinifera and Eucalyptus marginata in areas rehabilitated following bauxite mining and from E. marginata in a forest regenerated after clearfelling. The rate of herbivory was examined on leaves aged 1–3 years. The mean monthly rate of herbivory of all species varied from 0.9 to 1.9% of the total leaf area and was positively correlated (P < 0.05) with the level of leaf nitrogen in E. marginata. The previous months level of nitrogen was also positively correlated to the rate of herbivory in the current month in all species. The level of leaf nitrogen was negatively correlated to the current and previous months level of herbivore abundance and the current months rate of herbivory in E. resinifera. These correlations suggest two possibilities. Firstly, that in some eucalyptus the level of leaf nitrogen may be lowered when the level of predation on leaves is high. Secondly, the herbivorous insects may preferentially feed on eucalypt leaves having a high amount of nitrogen.

Inosine ameliorates the effects of hemin-induced oxidative stress in broilers

The objective of these studies was to determine whether inosine, a precursor of the antioxidant uric acid, can ameliorate hemin-induced oxidative stress. Dietary inclusion of inosine was begun either before or after hemin-induced oxidative stress. Broilers (4 weeks) were divided into four treatment groups (Control, Hemin, Inosine, Hemin/Inosine). Throughout the study control birds (n=10) were injected daily with a buffer solution, while hemin birds (n=10) were injected daily (i.p.) with a 20 mg/kg body weight hemin buffer solution. Leukocyte oxidative activity (LOA) and concentrations of plasma uric acid (PUA) were measured. Results from the first study showed that hemin birds had increased levels of LOA (P=0.0333) and lower PUA (P=0.1174). On day 10, control and hemin birds were subdivided into inosine birds (n=5) and hemin/inosine birds (n=5). These birds were given 0.6 M/kg of feed/day of dry inosine. Plasma concentrations of uric acid and LOA were then measured on day 15. Results showed that inosine raised concentrations of PUA (P=0.0001) and lowered LOA (P=0.0044) as induced by hemin. In the second study pretreatment of broilers with hemin prevented the increase in LOA induced by hemin (P=0.0001). These results show that modulating the concentrations of uric acid can markedly affect oxidative stress.

FUNCTIONAL MORPHOLOGY OF THE GLOMERULAR FILTRATION BARRIER OF GALLUS GALLUS

The anionic charge barrier and the endothelial and epithelial pore sizes on the glomerular filtration barrier (GFB) were examined in white leghorn chickens (Gallus gallus). Ruthenium red was used to stain anionic charge sites on the GFB. The tissue was treated by normal dehydration and freeze substitution dehydration for transmission electron microscopy (TEM). In addition, the basal lamina was isolated for study. The results of our study indicate that G. gallus possess a thick, negatively charged glycocalyx surrounding the podocytes and slit diaphragm and on the endothelium. However, in all cases, little anionic charge is present in the basal lamina. The pores on the endothelium are elliptical and have mean dimensions of 148 × 110 nm. This is in contrast to mammals, which have smaller, round pores. The epithelial pores in G. gallus measure approximately 35 nm in length, approximately 4 times larger than those found in mammals. These results indicate that the avian glomerulus may allow the filtration of larger molecules from the plasma than occurs in mammals and that the charge on the molecule may not be as restrictive a filtration characteristic as in mammals.

Teaching physiology online: successful use of case studies in a graduate course.

To address the need for greater flexibility in access to higher education, an online graduate course in physiology using case studies was developed and offered in summer 2012. Topics in both animal and human physiology were organized as modules that contained a case study with questions, a prerecorded online lecture, and three research journal articles. We followed best practices for teaching and learning in distance education, including the preparation of materials before the course starting date, a discussion board for responding to pre- and postcase discussion questions, and prompt reply to student queries. For exams, students generated their own questions based on new cases and developed their own case study for the final project. Although only 20% of students had previously taken an online course, all students stated that they would recommend this course to others. Postcase assessment indicated that students found the cases interesting, informative, and presented at the appropriate level. Most students said that the online course took them more time but that they learned more content and used the primary literature more than in a traditional class. Our results indicate that a well-organized physiology course using a case study format is a very effective model for online learning.

Luminal morphology of the avian lower intestine: evidence supporting the importance of retrograde peristalsis for water conservation.

Tissue from the lower intestine of two species of sparrow, the house sparrow Passer domesticus and savannah sparrow Passerculus sandwichensis was sectioned in an unbiased manner and examined quantitatively using stereology. The tissue was processed for light microscopy, and scanning and transmission electron microscopy to examine the extent to which microvilli enhanced the epithelial surface area of the cecae, rectum, and coprodeum. Parameters measured included individual microvillus surface area, microvilli packing density, and absolute surface area. In both species, the average surface area, packing density, and absolute surface area of microvilli decreased distally along the rectum and coprodeum. All three measured variables were not statistically significant (P > 0.05) between species. Surface area amplification on the cecae due to microvilli was low, and approximated values equivalent to distal regions of the rectum and coprodeum. In the cecae, microvilli within the savannah sparrow had a significantly higher (P < 0.05) individual surface area, packing density, and absolute surface area than in the house sparrow. The functional implications of a change in microvilli population are discussed in relation to retrograde peristalsis within the lower intestine of birds. Anat Rec 263:289–296, 2001.