Lipid droplets in skeletal muscle during grass snake (Natrix natrix L.) development

Lipid droplets (LDs) are common organelles observed in Eucaryota. They are multifunctional organelles (involved in lipid storage, metabolism, and trafficking) that originate from endoplasmic reticulum (ER). LDs consist of a neutral lipid core, made up of diacyl- and triacylglycerols (DAGs and TAGs) and cholesterol esters (CEs), surrounded by a phospholipid monolayer and proteins, which are necessary for their structure and dynamics.Here, we report the protein and lipid composition as well as characterization and dynamics of grass snake (Natrix natrix) skeletal muscle LDs at different developmental stages. In the present study, we used detailed morphometric, LC-MS, quantitative lipidomic analyses of LDs isolated from the skeletal muscles of the snake embryos, immunofluorescence, and TEM.Our study also provides a valuable insight concerning the LDs' multifunctionality and ability to interact with a variety of organelles. These LD features are reflected in their proteome composition, which contains scaffold proteins, metabolic enzymes signalling polypeptides, proteins necessary for the formation of docking sites, and many others. We also provide insights into the biogenesis and growth of muscle LDs goes beyond the conventional mechanism based on the synthesis and incorporation of TAGs and LD fusion. We assume that the formation and functioning of grass snake muscle LDs are based on additional mechanisms that have not yet been identified, which could be related to the unique features of reptiles that are manifested in the after-hatching period of life, such as a reptile-specific strategy for energy saving during hibernation.     

Retinal projections in a snake, Thamnophis sirtalis

The retinofugal projections of the snake Thamnophis sirtalis were studied by the method of experimentally induced Wallerian degeneration stained by the Fink-Heimer method. The retinal ganglion cells project to all parts of the contralateral lateral geniculate complex, nucleus lentiformis mesencephali, nucleus geniculatus pretectalis, nucleus posterodorsalis, basal optic nucleus and superficial layers of the optic tectum. In addition, the retinofugal projections were observed terminating in portions of the ipsilateral lateral geniculate complex and nucleus posterodorsalis. Examination of the morphology of the retinal terminal areas stained for Nissl substance with cresyl violet led to the conclusion that these regions are well differentiated and should not be considered poorly developed when compared with other reptilian forms such as turtles.     

lntracortical Connections in the Snakes Natrix sipedon and Thamnophis sirtalis

The association and commissural connections between the four cortical areas in water (Natrix sipedon) and garter (Thamnophis sirtalis) snakes were studied by placing lesions on the cortical surface and studying the resulting degeneration in Fink-Heimer preparations. Lateral cortex projects to the outer one third of layer 1 of ipsilateral medial cortex. Dorsal cortex projects to the middle third of layer 1 of ipsilateral medial cortex. Dorsomedial cortex projects bilaterally to the inner third of layer 1 and to layer 3 of me dial cortex. It also projects to layer 1 of contralateral dorsomedial cortex. Medial cortex projects ipsilaterally to each of the other cortical areas. With the apparent exception of the projection of medial cortex to lateral cortex, each projection is organized such that each rostrocaudal segment of a cortical area projects to all segments of the target area lying at the same or more caudal levels.     

Novel microsatellite loci in the grass snake (Natrix natrix) and cross-amplification in the dice snake (Natrix tessellata)

Six novel polymorphic microsatellite loci are presented for the grass snake (Natrix natrix), a species with declining populations in many regions. The number of alleles per locus ranged from two to seven. Four dice snake (Natrix tessellata) microsatellites were polymorphic in the grass snake with three to four alleles. At two loci, the expected heterozygosity differed significantly from observed heterozygosity. Cross-amplification of the grass snake markers in the dice snake showed two polymorphic microsatellites with two and four alleles.     

Haematology of the grass snake Natrix natrix natrix L.

1. Haematological parameters and cytomorphological picture of circulating blood of the grass snake Natrix natrix natrix L. were studied. Mean annual values of the haemoglobin concentration, haematocrit level, red cell counts, erythrocytes indices, erythrocyte sedimentation rate, thrombocyte and leucocyte counts, per cent composition of white blood cells and size of morphotic elements were determined for a population sample (N = 154) of the species, considering the sex of snakes. 2. Parameters of red blood cell system (RCC, Hb, Hct) were statistically significantly higher in males, remaining indices showed no statistically significant differences. 3. A strict positive correlation was found between RCC, Hb and Hct in the studied sample. 4. Cytomorphology of blood is presented in microphotographs. 5. In the discussion haematological data for the grass snake and other snakes are compared.     

Quantitative handling of characters useful in snake systematics with particular reference to intraspecific variation in the Ringed Snake Natrix natrix (L.)

This paper is based on the numerous characters used in a biometric study of the intraspecific variation of Natrix natrix (L.). These characters are drawn from the internal morphology, scalation, colour pattern, body proportions, dentition and dermal sense organs. The criteria involved in selecting these characters for taxonomic work are considered.
The alternative methods for quantifying the above features are discussed and so are the theoretical problems involved in coding the continuous characters.
The value of the characters in studying the geographic variation, ontogenetic variation and sexual dimorphism in N. natrix is indicated.
The use of a wider range of characters than just the scalation and colour pattern is urged when diagnosing the lower taxonomic levels of ophidians. The neglected internal morphology may well be able to supply characters to this end.     

Variation in seasonal ultrastructure of sexual granules in the renal sexual segment of the Northern Water Snake, Nerodia sipedon sipedon

The renal sexual segment of the kidney (RSS) can be found in many male squamate reptiles, encompassing the distal region of the nephron and, in some cases, collecting ducts. This sexually dimorphic structure exhibits varying degrees of hypertrophy and regression throughout the year. Although researchers have been aware of and have investigated this unique structure for over a century, its ultimate function remains under discussion. In many studies hypertrophy and regression of the RSS have been correlated with testicular activity and androgen secretion. As in most of the snakes studied to date, the male Northern Water Snake (Nerodia s. sipedon) does not exhibit a dramatic cycle of hypertrophy and regression, as reported in lizards. Following the initial hypertrophy at maturity, the male Northern Water Snake maintains a level of RSS hypertrophy throughout the year. Variations in the appearance and makeup of the sexual granules provide an identifiable and quantifiable seasonal pattern that can be correlated with the concentration of plasma androgens. In the Northern Water Snake, plasma androgens are elevated upon emergence and the RSS epithelial cells are filled with solid granules. As androgen levels decline during spring, sexual granule content appears to be breaking down (utilized?), becoming diffuse in appearance. By mid‐ to late summer androgen synthesis is at a maximum, increasing circulating androgens and stimulating the development and return of the solid granules. This study utilized electron microscopy and steroid radioimmunoassay to examine seasonal cycles of sex granules, in terms of development, maintenance, and regression, correlated with plasma androgen concentration. In addition, this investigation provides evidence of a possible secondary source of androgen secretion. J. Morphol. 261:70–80, 2004. © 2004 Wiley‐Liss, Inc.     

Motor reactivity of isolated heart of the grass-snake (Natrix natrix L.)

Stimulation of the vagus nerve with a volley of electric impulses changed the action of grass-snake heart producing a negative chronotropic and inotropic effect. The effect of vagal stimulation was not different from the effect of acetylcholine administration and it was absent in the presence of atropine and hexamethonium. It was not possible to demonstrate sympathetic nervous fibres in the stimulated segment of the vagus nerve and trials of finding a separate nerve increasing the heart rate were unsuccessful. Parasympathicotonic agents caused bradycardia and a fall in the amplitude of cardiac contractions, and in sufficiently high doses they arrested the heart in diastole. The action of muscarine-like agents was stronger than that of nicotine, and the anticholinergic action of tubocurarine was weaker than that of atropine. Catecholamines exerted a positive inotropic and chronotropic effect which was completely blocked by propranolol in some tests only.     

Seasonal changes of circulating blood parameters in the grass snake Natrix natrix natrix L.

• 1.1. Seasonal changes of circulating blood parameters of Natrix n. natrix were evident and involved both sexes to the same extent.
• 2.2. A significant decrease in red cell count, haematocrit and haemaglobin concentration in the mating period, and an increase in those parameters and mean cell volume in autumn were observed, and haemodilution during winter torpor.
• 3.3. The changes during the breeding season had probably a hormonal background; in winter, they resulted first of all from a decreased erythropoietic activity and, to a lesser extent, from an increased red blood cell breakdown rate. However, the possibility that some erythrocytes were withdrawn from the circulation cannot be excluded.
• 4.4. Winter lymphocytopenia, eosinocytopenia and neutrophilic granulocytosis in females during egg laying were expressions of changes of leucocyte formula.
• 5.5. Seasonal cyclicity was found only with respect to the white cell count in males and the eosinophile fraction in males and females.
• 6.6. Probable reasons for, and mechanisms of the changes in blood composition are discussed.

     

Microgeographic population genetic structure in the northern water snake, Nerodia sipedon sipedon detected using microsatellite DNA loci

We describe the isolation and genetic characterization of eight microsatellite DNA loci from the northern water snake, Nerodia sipedon sipedon and use these loci to analyse levels of genetic differentiation between local (< 2 km apart) populations of these snakes in Ontario. These loci are variable, with expected heterozygosities ranging from 0.28 to 0.91, and can correctly exclude nonsires in parentage analyses with a high probability (0.998). Population analyses reveal significant deviation from expected heterozygosity levels for one population, probably a result of a null allele(s) at a single locus and small but significant levels of genetic differentiation among all three populations. This demonstrates that microgeographic genetic structure exists in this species, possibly due to limited dispersal.     

Immune response in the water snake,Natrix erythrogaster transversa

One month after an intramuscular injection of bovine albumin, the plasma of a water snake (Natrix erythrogaster transversa) contained a macroglobulin which bound radiolabeled bovine serum albumin.