Measurements on the kidneys and vasa recta of various mammals in relation to urine concentrating capacity.

Maximum urine-concentrating capacity (UCC) differs widely among mammals of different species, being very high in some desert species (e.g. kangaroo rats) and very low in freshwater acquatic species (e.g. beaver). In this study, kidneys of 21 species of mammals from widely different habitats were studied in histological sections to determine whether differences in UCC can be attributed to differences in kidney structure. Parameters studied included the ratio of medullary to cortical thickness, the proportional subdivision of the medulla into inner and outer zones, and the dimensions of the vasa recta expressed in terms of the total area and the number of lumens within the vascular bundles. Determinations were made at a level where the size of individual vasa recta bundles has reached a constant maximum size, i.e. in the distal half of the outer zone. A positive correlation was found between the UCC and the ratio of medullary length to cortical thickness. No clear correlation existed between the proportion of the medullary length comprised of outer or inner zones and the UCC, although a trend to higher UCC in animals with relatively longer inner zones was apparent. Thus, it appears that the relative length of the entire medullary region is a major factor determining UCC, but the length of individual medullary zones is of lesser importance. A correlation was also found between the density of vasa recta per cubic millimeter of medullary tissue (the number of lumens regardless of identify in bundles, based on the number counted at the level sampled) and the UCC of the species. Data reported here support the view that UCC can be correlated with two parameters of kidney structure - the length of medulla relative to that of cortex and the density of vasa recta within the outer zone. It is proposed that the anatomical characteristics of the vascular supply to the medulla - that is, the vasa recta - are equally as important for the concentration of urine as is the primary mechanism determined by the characteristics of the loop of Henle and collecting ducts.     

Cytochrome b evolution in birds and mammals: an evaluation of the avian constraint hypothesis.

Patterns of molecular evolution in birds have long been considered anomalous. Compared with other vertebrates, birds have reduced levels of genetic divergence between groups of similar taxonomic ranks for a variety of nuclear and mitochondrial markers. This observation led to the avian constraint hypothesis, which identifies increased functional constraint on avian proteins as the cause for the reduction in genetic divergence. Subsequent investigations provided additional support for the avian constraint hypothesis when rates of molecular evolution were found to be slower in birds than in mammals in a variety of independent calibrations. It is possible to test the avian constraint hypothesis as an explanation for this avian slowdown by comparing DNA sequence data from protein-coding regions in birds and homologous regions in mammals. The increased selective constraints should lead to a reduction in the proportion of amino acid replacement substitutions. To test for such a decrease, we calculated the numbers of amino acid replacement substitutions per replacement site (dN) and silent substitutions per silent site (dS) for the complete mitochondrial cytochrome b gene using 38 avian and 43 mammalian comparisons that were phylogenetically independent. We find that dN/dS is significantly smaller in birds than in mammals. This difference cannot be explained by differences in codon bias affecting dS values. We suggest that the avian slowdown can be explained, at least in part, by a decreased tolerance for amino acid substitutions in avian species relative to mammalian species.     

Molecular and functional characterization of a vasotocin-sensitive aquaporin water channel in quail kidney

Both mammals and birds can concentrate urine hyperosmotic to plasma via a countercurrent multiplier mechanism, although evolutionary lines leading to mammals and birds diverged at an early stage of tetrapod evolution. We reported earlier (Nishimura H, Koseki C, and Patel TB. Am J Physiol Regul Integr Comp Physiol 271: R1535-R1543, 1996) that arginine vasotocin (AVT; avian antidiuretic hormone) increases diffusional water permeability in the isolated, perfused medullary collecting duct (CD) of the quail kidney. In the present study, we have identified an aquaporin (AQP) 2 homolog water channel in the medullary cones of Japanese quail, Coturnix coturnix (qAQP2), by RT-PCR-based cloning techniques. A full-length cDNA contains an 822-bp open reading frame that encodes a 274-amino acid sequence with 75.5% identity to rat AQP2. The qAQP2 has six transmembrane domains, two asparagine-proline-alanine (NPA) sequences, and putative N-glycosylation (asparagine-124) and phosphorylation sites (serine-257) for cAMP-dependent protein kinase. qAQP2 is expressed in the membrane of Xenopus laevis oocytes and significantly increased its osmotic water permeability (P(f)), inhibitable (P < 0.01) by mercury chloride. qAQP2 mRNA (RT-PCR) was detected in the kidney; medullary mRNA levels were higher than cortical levels. qAQP2 protein that binds to rabbit anti-rat AQP2 antibody is present in the apical/subapical regions of both cortical and medullary CDs from normally hydrated quail, and the intensity of staining increased only in the medullary CDs after water deprivation or AVT treatment. The relative density of the approximately 29-kDa protein band detected by immunoblot from the medullary cones was modestly higher in water-deprived/AVT-treated quail. The results suggest that 1) medullary CDs of quail kidneys express a mercury-sensitive functioning qAQP2 water channel, and 2) qAQP2 is at least partly regulated by an AVT-dependent mechanism. This is the first clear identification of AQP2 homolog in nonmammalian vertebrates.     

Body mass,phylogeny and diet composition affects kidney morphology in passerine birds

We studied the renal morphology of 16 species of passerines to assess whether the composition of the diet of birds have been paralleled by differences in the characteristics of the kidneys. We determined the number and length of the medullary cones and the percentage of renal medulla in birds with contrasting dietary habits and then correlated these features with the percentage of nitrogen and proportion of invertebrates in the diet. To examine the correlation between kidney and diet variables, we first used standard correlation and least square regression, and correlation and regression on phylogenetically independent data. We found that the mass of the medullary portion of the kidney, and the medullary cone length were negatively correlated with the percentage of invertebrates present in the diet. We hypothesized that the further development of the renal medulla observed in granivorous birds may be correlated with the small amount of water present in the seeds. Our results suggest that the availability of water in different foods is probably one of the main factors that have led to structural and probably functional changes of the kidney in the studied species. J. Morphol., 2012. © 2012 Wiley Periodicals, Inc.     

江豚的小肾结构指数和尿浓缩能力

对江豚的六项小肾结构指数的测定发现,黄海沿岸江豚的小肾结构指数明显高于长江江豚的。提示前者具有较高的尿浓缩能力。对尿的分析所获结论相同,反映出二者对所栖水域的不同渗透浓度的适应。     

Relationship between body size, Na+-K+-ATPase activity, and membrane lipid composition in mammal and bird kidney

We investigated the relationship between body size, Na(+)-K(+)-ATPase molecular activity, and membrane lipid composition in the kidney of five mammalian and eight avian species ranging from 30-g mice to 280-kg cattle and 13-g zebra finches to 35-kg emus, respectively. Na(+)-K(+)-ATPase activity was found to be higher in the smaller species of both groups. In small mammals, the higher Na(+)-K(+)-ATPase activity was primarily the result of an increase in the molecular activity (turnover rate) of individual enzymes, whereas in small birds the higher Na(+)-K(+)-ATPase activity was the result of an increased enzyme concentration. Phospholipids from both mammals and birds contained a relatively constant percentage of unsaturated fatty acids; however, phospholipids from the smaller species were generally more polyunsaturated, and a complementary significant allometric increase in monounsaturate content was observed in the larger species. In particular, the relative content of the highly polyunsaturated docosahexaenoic acid [22:6(n-3)] displayed the greatest variation with body mass, scaling with allometric exponents of -0.21 and -0.26 in the mammals and birds, respectively. This allometric variation in fatty acid composition was correlated with Na(+)-K(+)-ATPase molecular activity in mammals, whereas in birds molecular activity only correlated with membrane cholesterol content. These relationships are discussed with respect to the metabolic intensity of different-sized animals.     

The integration of digestion and osmoregulation in the avian gut

We review digestion and osmoregulation in the avian gut, with an emphasis on the ways these different functions might interact to support or constrain each other and the ways they support the functioning of the whole animal in its natural environment. Differences between birds and other vertebrates are highlighted because these differences may make birds excellent models for study and may suggest interesting directions for future research. At a given body size birds, compared with mammals, tend to eat more food but have less small intestine and retain food in their gastrointestinal tract (GIT) for shorter periods of time, despite generally higher mass‐specific energy demands. On most foods, however, they are not less efficient at digestion, which begs the question how they compensate. Intestinal tissue‐specific rates of enzymatic breakdown of substrates and rates of active transport do not appear higher in birds than in mammals, nor is there a demonstrated difference in the extent to which those rates can be modulated during acclimation to different feeding regimes (e.g. diet, relative intake level). One compensation appears to be more extensive reliance on passive nutrient absorption by the paracellular pathway, because the avian species studied so far exceed the mammalian species by a factor of at least two‐ to threefold in this regard. Undigested residues reach the hindgut, but there is little evidence that most wild birds recover microbial metabolites of nutritional significance (essential amino acids and vitamins) by re‐ingestion of faeces, in contrast to many hindgut fermenting mammals and possibly poultry. In birds, there is some evidence for hindgut capacity to breakdown either microbial protein or protein that escapes the small intestine intact, freeing up essential amino acids, and there is considerable evidence for an amino acid absorptive capacity in the hindgut of both avian and mammalian hindgut fermenters. Birds, unlike mammals, do not excrete hyperosmotic urine (i.e. more than five times plasma osmotic concentration). Urine is mixed with digesta rather than directly eliminated, and so the avian gut plays a relatively more important role in water and salt regulation than in mammals. Responses to dehydration and high‐ and low‐salt loads are reviewed. Intestinal absorption of ingested water is modulated to help achieve water balance in one species studied (a nectar‐feeding sunbird), the first demonstration of this in any terrestrial vertebrate. In many wild avian species the size and digestive capacity of the GIT is increased or decreased by as much as 50% in response to nutritional challenges such as hyperphagia, food restriction or fasting. The coincident impacts of these changes on osmoregulatory or immune function of the gut are poorly understood.     

The kidney of Leptonychotes weddelli (Pinnipedia: Phocidae) with some observations on the kidneys of two other southern phocid seals

The structure of the kidney of Leptonychotes weddelli was examined using corrosion casts, India ink injection, and histological methods. Some observations were made on the kidney of the crabeater seal (Lobodon carcinophagus) and the elephant seal (Mirounga leonina). The kidneys in all three species are reniculate, as in many other marine mammalian species. Features that have not been described previously in a phocid seal are a peripyramidal muscle, and venous drainage characterized by a large extrinsic system and a small intrinsic system. Examination of specialized fornices, relative medullary thickness, and the volumes of juxtamedullary relative to peripheral glomeruli (all of which relate to urine concentrating ability) revealed that each reniculus of Leptonychotes is similar to the unilobar kidney of a small mammal that produces only moderately concentrated urine. The high glomerular volume to cortical volume ratio may be related to high glomerular filtration rates after feeding observed in marine mammals. It is concluded that reniculation is more likely to be related to the large size of most marine mammals than to some factor related directly to the marine environment.     

Glucose transporter expression in English sparrows (Passer domesticus)

Patterns of glucose transporter expression have been well-characterized in mammals. However, data for birds is currently restricted to isolated cells, domestic chickens and chicks, and ducklings. Therefore, in the present study, protein and gene expression of various glucose transporters (GLUTs) in English sparrow extensor digitorum communis, gastrocnemius and pectoralis muscles as well as heart, kidney, and brain tissues were examined. The hypothesis is that the expression pattern of avian GLUTs differs from mammals to maintain the high plasma glucose levels of birds and insulin insensitivity. Our studies failed to identify a GLUT4-like insulin responsive transporter in sparrows. GLUT1 gene expression was identified in all tissues examined and shares 88% homology with chicken and 84% homology with human GLUT1. Compared to the rat control, GLUT1 immunostaining of sparrow extensor digitorum communis muscle was weak and appeared to be localized to blood vessels whereas immunostaining of gastrocnemius muscles was comparable to rat muscle controls. Gene expression of GLUT3 was identified in all tissues examined and shares 90% gene sequence homology with chicken embryonic fibroblast and 75% homology with human GLUT3. Protein expression of GLUT3 was not determined as an avian antibody is not available. Moreover, the C-terminus of the mammalian GLUT3 transporter, against which antibodies are typically designed, differs significantly among species. The predominant difference of chicken and sparrow GLUT expression patterns from that of mammals is the lack of an avian GLUT4. The absence of this insulin responsive GLUT in birds may be a contributing factor to the observed high blood glucose levels and insulin insensitivity.     

An allometric study of pulmonary morphometric parameters in birds, with mammalian comparisons

Comprehensive pulmonary morphometric data from 42 species of birds representing ten orders were compared with those of other vertebrates, especially mammals, relating the comparisons to the varying biological needs of these avian taxa. The total lung volume was strongly correlated with body mass. The volume density of the exchange tissue was lowest in the charadriiform and anseriform species and highest in the piciform, cuculiform and passeriform species. The surface area of the blood-gas (tissue) barrier, the volume of the pulmonary capillary blood and the total morphometric pulmonary diffusing capacity were all strongly correlated with body mass. The harmonic mean thickness of both the blood-gas (tissue) barrier and the plasma layer were weakly correlated with body mass. The mass-specific surface area of the blood-gas (tissue) barrier (surface area per gram body mass) and the surface density of the blood-gas (tissue) barrier (i.e. its surface area per unit volume of exchange tissue) were inversely correlated (though weakly) with body mass. The passeriform species exhibited outstanding pulmonary morphometric adaptations leading to a high specific total diffusing capacity per gram body mass, consistent with the comparatively small size and energetic mode of life which typify passeriform birds. The relatively inactive, ground-dwelling domestic fowl (Gallus gallus) had the lowest pulmonary diffusing capacity per gram body mass. The specific total lung volume is about 27% smaller in birds than in mammals but the specific surface area of the blood-gas (tissue) barrier is about 15% greater in birds. The ratio of the surface area of the tissue barrier to the volume of the exchange tissue was also much greater in the birds (170-305%). The harmonic mean thickness of the tissue barrier was 56-67% less in the birds, but that of the plasma layer was about 66% greater in the birds. The pulmonary capillary blood volume was also greater (22%) in the birds. Except for the thickness of the plasma layer, these morphometric parameters all favour the gas exchange capacity of birds. Consequently, the total specific mean morphometric pulmonary diffusing capacity for oxygen was estimated to be about 22% greater in birds than in mammals of similar body mass. This estimate was obtained by employing oxygen permeation constants for mammalian tissue, plasma and erythrocytes, as avian constants were not then available.(ABSTRACT TRUNCATED AT 400 WORDS)     

Cytoplasmic NADP-linked dehydrogenase activities in avian tissues

Cytoplasmic activities of NADP-linked malic enzyme (E.C. 1.1.1.40), glucose-6-phosphate dehydrogenase (E.C. 1.1.1.49) and NADP-linked isocitrate dehydrogenase (E.C. 1.1.1.42) were determined in tissues of selected avian species, and compared with those in mammals. Malic enzyme was generally more active in avian liver and kidney than in the corresponding mammalian tissues. Hepatic activities as high as 200 units/g wet wt and 100 units/g wet wt were recorded in the Nectariniidae and the Ploceidae respectively. Glucose-6-phosphate dehydrogenase was generally less active in avian tissues than malic enzyme. In passerine birds activities were very low indeed, and in most cases spectrophotometrically undetectable. Malic enzyme and glucose-6-phosphate dehydrogenase were highly active in the adipose tissue of mammals but were inactive in the adipose tissue of birds. Marked increases in hepatic malic enzyme and glucose-6-phosphate dehydrogenase activities were associated in birds with premigratory fattening. Activities of isocitrate dehydrogenase were comparable in the corresponding avian and mammalian tissues, including adipose tissue.     

Behavioral and physiological studies of hearing in birds.

Studies of hearing thresholds and frequency- and intensity-difference limens for birds are reviewed. Where possible these are related to limitations placed on auditory function by stimulus processing at peripheral levels of the avian auditory system. The high frequency limit of bird hearing is about 10 kHz; this limit is shown to be imposed in part by middle ear function and in part by cochlear mechanisms. For frequencies greater than 1.0 kHz, frequency-difference limens (DLs) show a similar dependence on frequency in birds as in mammals. Correspondingly, cochlear filtering is shown to be as good in birds as in mammals. At frequency below 1.0 kHz, frequency DLs in birds are poorer than in mammals. These low frequency differences may not be attributable to peripheral processing. Intensity-difference limens are worse in birds than mammals; there seem to be no differences in peripheral processing between birds and mammals which can account for this behavioral difference. Finally, complexities in processing at higher levels of the avian auditory system which have been related to detection of species-specific vocalizations are shown to appear in the first brainstem auditory nuclei.     

Relationships between renal morphology and diet in 26 species of new world bats (suborder microchiroptera)

The renal morphology of 24 species of mormoopid and phyllostomid bats feeding on six different diets was examined to test evolutionary changes in several structural traits presumably led by dietary shifts from ancestral insectivorous diets. The kidneys of a fish-eating vespertilionid and an insect-eating emballonurid were also examined but not included in the phylogenetic comparison. The length, width, and breadth of the kidneys were used to calculate relative medullary thickness (RMT). Tissues were processed for stereological analysis, and the volumes of the kidney, nephron components, and vasculature were determined. RMT did not correlate with body mass in either animal-eating or plant-eating phyllostomid and mormoopid bats. The shift from insectivory to frugivory and nectarivory was accompanied by a reduction in RMT, a reduction in the percent of renal medulla, and an increase in the percent of renal cortex. No changes in these traits were observed in bats that shifted to carnivorous, omnivorous or sanguinivorous habits. No changes were observed in renal vasculature, in the percentage of cortical and medullary nephron components or of capillaries surrounding the nephrons in any feeding group. Vespertilionid and emballonurid species had similar values in all traits examined as compared to insectivorous phyllostomids and mormoopids. Our data suggest that diet does not influence a single area of the nephron, but rather the entire nephron such that the relative amounts of renal cortex and medulla are affected.     

Global diversity and adaptations of avian eggshell thickness indices

The amniote eggshell is a fundamental aspect of the embryo life-support system, protecting it from UV light, microbes and mechanical damage, while regulating gas exchange and providing calcium for growth. The thickness of eggshells is highly diverse across modern birds and influences multiple eggshell functions, yet the selective pressures driving eggshell thickness have not been clearly identified. Here, we use a global dataset of avian eggshell thickness indices for 4260 (> 41%) avian species to assess trends in eggshell thickness across the phylogeny, as these indices are strongly correlated with direct measures of eggshell thickness and are non-destructive to the sample. We analysed the dataset within a phylogenetic framework to assess the relative importance of climatic and ecological explanations for variation in eggshell thickness indices. The distribution of avian eggshell thickness indices across species was found to be primarily driven by phylogenetic relatedness, in addition to evolutionary processes that do not match a Brownian model of evolution. Across modern birds, thicker eggshells were more prevalent in species (1) with precocial young, (2) which exhibit a scavenger-based diet, (3) which primarily feed on vertebrates or plants (excluding nectivores, seed and fruit specialists) and (4) which breed in open habitats. Thicker eggshells found in species with precocial young probably enable higher rates of calcium removal for the more advanced embryo development. Excessive light transmission through the shell damages developing embryos, while too little light transmission can impede development. Eggs in shaded habitats experience low light exposure, and thus thinner shells are more prevalent in these environments potentially to increase light transmission through the shell. Overall, variation in eggshell thickness indices appears to be driven largely by phylogeny, with certain life-history traits linked to embryo growth rate, calcium content of their food, and the need to mitigate excessive light transmission through the shell.     

Avian toll-like receptors

Analysis of the genomes of two distantly related bird species, chicken and zebra finch (divergence of about 100 million years), indicate that there are ten avian toll-like receptors and that five of these, TLR2a, 2b, 3, 4, 5 and 7, are clear orthologs to TLRs found in mammals. Duplication of genes has led to TLR1La and 1Lb, TLR2a and 2b, and two TLR7s in the zebra finch. Avian TLR21 may be orthologous to TLR21 found in fish and amphibians, and avian TLR15, which is phylogenetically related to the TLR2 family, appears to be unique to avian species. While TLR2 is conserved between mammalian and avian species, the other TLR2 family members evolved independently. Dimerization between either of the two avian TLR2 species and TLR1La or 1Lb permits recognition of the same broad range of molecules as recognized by mammalian TLR2 dimerized with either TLR1, 6 and 10. Similarly, while TLR9 has been lost from the avian genome, DNA high in unmethylated CpG motifs is immunostimulatory through avian TLR21 which is absent in mammals. Thus, while some TLR members were commonly retained in both mammals and birds, others were separately lost or gained, or diverged independently; but broadly speaking the TLRs of the two classes of vertebrates evolved to recognize very similar spectra of microbial products. Components of downstream TLR signaling are also mostly conserved but with some losses in avian species; notably, TRAM is absent in avian genomes and, hence, the TRIF/TRAM-dependent signaling pathway utilized by mammals in LPS activation appears to be absent in birds.     

Allometry of paracellular absorption in birds

Water-soluble nutrients can be absorbed across the intestinal epithelium by transcellular and paracellular processes. Recent studies suggest that small birds (<180 g) have more extensive paracellular absorption of glucose than nonflying mammals. This may be a feature that compensates for a reduced small intestine size because small birds have smaller mass-corrected intestinal length than do nonflying mammals, but the difference diminishes in larger birds. We hypothesized that if this explanation were correct, there would be a negative correlation between paracellular absorption and body mass in birds and that larger birds would have paracellular absorption comparable to that of nonflying mammals. We tested this hypothesis, using consistent methodology, by measuring the extent of absorption of a series of inert carbohydrate probes in heavier bird species (>300 g) selected from diverse taxa: American coots, mallards, pheasants, and pigeons. Absorption of carbohydrate probes was inversely related to body mass in birds, and absorption of these probes in large birds (>500 g) was comparable to absorption measurements in nonflying mammals. Higher paracellular uptake in the smaller avian species may offer a physiologically inexpensive means of nutrient absorption to compensate for a reduced small intestine size but may make those species more vulnerable to toxicant absorption.     

Urinary concentrating processes in vertebrates.

Avian and mammalian kidneys can produce a urine hyperosmotic to the blood by means of a renal countercurrent system. Birds are uricotelic; mammals are ureotelic. It is proposed that the inner medulla present in mammalian, but not in avian kidneys serves specifically to accumulate urea in the inner and outer medulla. Among mammalian kidneys the degree to which urea accumulates in the inner medulla is inversely related to the complexity of the vascular bundles (in the outer medulla) and the cortical urea recycling index. A model is proposed for urea recycling via the vascular bundles. The renal pelvis varies in size among mammals. Its relative size is unrelated to the type of vascular bundles, cortical recycling index; or urea accumulation in the inner medulla. Since urine refluxes into the renal pelvis during rising urine flow only, the function of the pelvis could be that of bringing the more dilute urine into contact with the outer medulla and underlying capillaries, thereby aiding in reducing the urea concentration in outer and inner medulla during rising urine flow. The size of the renal pelvis may be related to the volume of the inner medulla. Other factors may also be involved.     

Peroxisomes in permanent and provisional kidneys

Peroxisomes in three forms of vertebrate kidney (pronephros, mesonephros, and metanephros), as permanent or provisional kidney, are summarized concerning their ultrastructure and developmental changes. Because the peroxisome is known to be diverse in mammalian metanephros, and species difference is its distinctive feature among cell organelles, information should be obtained on each kidney of each species. The ultrastructural and biochemical features of peroxisomes have at least been partly delineated in the metanephros and mesonephros, but nothing is known about the pronephros. Ultrastructural studies of the metanephric peroxisomes are present in mammals, birds, and reptiles, but information on their development is restricted to mammals and birds. As for the mesonephric peroxisomes, both ultrastructural and developmental data have been accumulating on mammals and amphibians, and ultrastructural information is present on fishes, but not on birds and reptiles. At present, studies on peroxisomes of provisional kidney have been restricted to mammalian mesonephros. The common features of renal peroxisomes previously examined are that they are spherical cell organelles with a single limiting membrane in ultrastructure, and are positive for catalase. Information on the ultrastructure and enzymes is not sufficient at present for comparing the ontogenesis of renal peroxisomes with their phylogenesis. Part of this study appeared as an original paper (11), and was presented as a poster at the International Symposium/CREST Research Conference, Peroxisome: Biogenesis, Function and Disease.     

Different contributions of birds and mammals to seed dispersal of a fleshy-fruited tree

Birds and mammals are important seed dispersers of fleshy-fruited plants. Although their behaviors are different, they frequently consume the same species. Thus to understand the dispersal of fleshy-fruited plants, the contribution of birds and mammals to seed dispersal has to be evaluated. Besides, within birds or mammals, some species may functionally different from others. In this study, we examined seed dispersal of the fleshy-fruited tree Swida controversa focusing on the difference between two frugivore groups (birds and mammals), and differences between species within groups. Collected seeds and S. controversa trees were identified using simple sequence repeat (SSR) genotyping, thus enabling to determine the distance between mother tree and dispersed seeds. The avian species were identified by DNA barcoding of feces, whereas the mammalian species were identified by the shape and smell of feces. Most seeds that fell near or under the maternal trees were dispersed by birds, resulting in short seed dispersal distances (average, 13 m). DNA barcoding detected five taxa of avian dispersers. No differences were detected in seed dispersal distance by different avian taxa (i.e., the distance between dispersed seeds and their maternal trees within the research plot); however the rate of seed immigration from outside the research plot by some avian taxa varied significantly. The seed dispersal distance by mammals was significantly further (127 m; min > 50 m) than that by birds. Additionally, immigrated seeds accounted for approximately two-thirds of mammal-dispersed seeds, indicating that these seeds were from outside the research plot, and that mammals significantly contributed to the long-distance seed dispersal of S. controversa. No differences in seed dispersal distance were detected between different mammalian taxa. Overall, this study revealed that birds and mammals show clearly different seed dispersal patterns, and thus, they play different roles in the regeneration of S. controversa.     

A comparative study on tissue distribution and metabolic adaptation of IMP-GMP 5'-nucleotidase.

1. Activity of a cytoplasmic 5'-nucleotidase which preferentially hydrolyzes IMP and GMP (IMP-GMP 5'-nucleotidase) was determined by a specific immunochemical method in two species of birds and two species of mammals. 2. The activity was markedly high in avian liver, and it increased two-fold in response to a high protein diet in chicken liver. 3. In mammals, the activity was high in testis and spleen. In the rat, the activities in liver, kidney and heart extracts increased by about 30% in response to the high protein diet, while they increased three-fold in regenerating liver. 4. Low activities were detected in skeletal muscles and in erythrocytes of all the species studied.