Social situation,sperm competition and sex allocation in a simultaneous hermaphrodite parasite,the cestode Schistocephalus solidus

Evolutionary theory predicts an influence of mating group size on sex allocation in simultaneous hermaphrodites. We experimentally manipulated the social situation during reproduction in a simultaneous hermaphrodite parasite, the tapeworm Schistocephalus solidus, by placing worms as singles, pairs or triplets into an in vitro system that replaces the final host. We then determined the reproductive allocation patterns after 24 h (i.e. before the start of egg release) and after 72 h (i.e. around the peak of egg release rate) using stereology. After 24 h, sex allocation strongly depended on worm volume (which is determined in the second intermediate host), but was not significantly affected by the social situation experienced during reproduction. After 72 h, worms in groups had less vesicular sperm (i.e. sperm to be used in future inseminations) than singles. They also stored significantly more received sperm in their seminal receptacles than singles, suggesting that more sperm had been transferred in groups. Moreover, worms in triplets stored significantly more received sperm than worms in pairs, suggesting that they either mated more often and/or transferred more sperm per mating. This suggests a behavioural response to the increased risk of sperm competition in triplets. We further discuss the relative importance of sex allocation decisions at different life‐history stages.     

Limbic frontal cortex in hominoids: A comparative study of area 13

The limbic frontal cortex forms part of the neural substrate responsible for emotional reactions to social stimuli. Area 13 is one of the cortical areas long known to be part of the posterior orbitofrontal cortex in several monkey species, such as the macaque. Its presence nevertheless in the human brain has been unclear, and the cortex of the frontal lobe of the great and lesser apes remains largely unknown. In this study area 13 was identified in human, chimpanzee, bonobo, gorilla, orangutan, and gibbon brains, and cortical maps were generated on the basis of its cytoarchitecture. Imaging techniques were used to characterize and quantify the microstructural organization of the area, and stereological tools were applied for estimates of the volume of area 13 in all species. Area 13 is conservative in its structure, and features such as size of cortical layers, density of neurons, and space available for connections are similar across hominoids with only subtle differences present. In contrast to the homogeneity found in its organization, variation is present in the relative size of this cortical area (as a percentage of total brain volume). The human and the bonobo include a complex orbitofrontal cortex and a relatively smaller area 13. On the contrary the orangutan stands out by having a shorter orbitofrontal region and a more expanded area 13. Differences in the organization and size of individual cortical areas involved in emotional reactions and social behavior can be related to behavioral specializations of each hominoid and to the evolution of emotions in hominids. Am J Phys Anthropol 106:129–155, 1998. © 1998 Wiley-Liss, Inc.     

Measurement of soil macropore geometry by image analysis of sections through impregnated soil

The geometry of the soil pore space affects root growth directly by providing pathways for root extension and indirectly through its effects on soil aeration and on water infiltration, redistribution and drainage. Image analysis of sections through impregnated blocks of undisturbed soil allows quantitative assessment of the pore space. Samples are dehydrated and impregnated with resin containing a fluorescent dye. Once the resin has hardened, the blocks can be cut to reveal a section through the structure. An image of the pore space, which is now filled with resin, can be obtained using ultra-violet light either photographically or digitally. Digital images are segmented into pore space and solid. Image analysis techniques can be used to classify the pore space into channels, fissures and packing pores. This allows appropriate measurements to be made on each class so that stereology can be used to estimate 3-D parameters from the measurements made on the image. Various indices can also be derived to quantify the pore structure.     

Quantitative studies on the distribution of myofilaments in intrafusal muscle fibres

Summary Muscle spindles contain two types of intrafusal muscle fibre, nuclear bag fibres and nuclear chain fibres. The intrafusal fibres of rabbit and guinea pig spindles have been studied using quantitative stereological techniques at the ultrastructural level. The crosssectional areas occupied by myofilaments have been measured in the polar and equatorial regions of both types of intrafusal fibre. There are considerably fewer myofilaments in the equatorial regions of both types of fibre compared with their polar regions.This work was carried out with the aid of grants from the Medical Research Council and the Science Research Council of Great Britain.     

Effect of fixation protocols on muscle preservation and in situ diffusion distances

In order to examine the effects of various methods for tissue preparation on ultrastructural analyses, and hence standardize reported values, six commonly used fixatives were examined for their quantitative effect on muscle fibre size and capillary dimensions. Both the composition and osmolarity of fixatives affected structural indices significantly, producing a range of values of similar magnitude to that presented in reports of structural adaptations. When comparing data from different studies, therefore, it is essential to establish that dissimilar values reflect different tissue composition, rather than methodologies. The method of choice for quantitative analysis of intracellular diffusion pathways uses a combined aldehyde fixative with a metabolic poison, and an isotonic buffer as vehicle.     

Analysis of different methods to estimate fecundity in bivalve molluscs

Abstract

We analyzed the advantages and disadvantages of three methods to estimate potential fecundity in the bivalve molluscs Pinctada mazatlanica and Atrina maura, both species having commercial value in northwestern Mexico. Data of gonad samples collected during the breeding season in March 1999 (P. mazatlanica) and March 2003 (A. maura) were processed with histological techniques combined with Cavalieri’s Principle; stereological analysis of the gonad with the caliper method; and estimation of the theoretical radius of oocytes. These estimates were compared to a reference value obtained from direct counts of the number of oocytes stripped from the gonad. Compared to other methods, potential fecundity determined with the caliper method was more accurate in both species: A. maura (9.8–15 × 10⁶ cells ind^?1 and P. mazatlanica (10.8–17 × 10⁶ cells ind^?1). The potential of the caliper method, combined with image analysis software may offer accurate estimates of aspects of reproduction in different bivalve species, which has direct applications in hatcheries and conservation programs.     

Normothermic Cardiac Arrest and Cardiopulmonary Resuscitation: A Mouse Model of Ischemia-Reperfusion Injury

Acute Kidney Injury (AKI) is a common, highly lethal, complication of critical illness which has a high mortality^1-4 and which is most frequently caused by whole-body hypoperfusion.^5,6 Successful reproduction of whole-body hypoperfusion in rodent models has been fraught with difficulty.^7-9,9,10 Models which employ focal ischemia have repeatedly demonstrated results which do not translate to the clinical setting, and larger animal models which allow for whole body hypoperfusion lack access to the full toolset of genetic manipulation possible in the mouse.^11,12 However, in recent years a mouse model of cardiac arrest and cardiopulmonary resuscitation has emerged which can be adapted to model AKI.¹³ This model reliably reproduces physiologic, functional, anatomic, and histologic outcomes seen in clinical AKI, is rapidly repeatable, and offers all of the significant advantages of a murine surgical model, including access to genetic manipulative techniques, low cost relative to large animals, and ease of use. Our group has developed extensive experience with use of this model to assess a number of organ-specific outcomes in AKI.^14,15     

Effects of high fat diet induced obesity on peripheral nerve regeneration and levels of GAP 43 and TGF-β in rats

The increasing frequency of obesity is important because of its accompanying related health problems. The effects of obesity on peripheral nerves have not been elucidated. We investigated the effects of obesity on sciatic nerve regeneration using electrophysiology, stereology, immunohistochemistry, histopathology and functional tests. We used control, obese, control injured and obese injured groups of rats. Electrophysiological results showed that nerve conduction velocity and EMG were same in the experimental groups, but the amplitude of the compound action potential of the control group was significantly higher than that of the obese group. Examination of the nerves showed that the control and obese groups had both larger axon diameters and thicker myelin sheaths. The number of myelinated axons was decreased in both of the injured groups. Axon diameters and myelin sheath thicknesses of the control injured group were significantly greater those of the obese injured group. There were no significant differences in functional tests among the groups. Although growth associated protein 43 immunostaining in the control injured group was significantly greater than that of the obese injured group, no significant difference was observed between the control and obese groups. There was no significant difference in immunohistochemical staining for transforming growth factor beta 3 between the control injured and obese injured groups. Our results suggest that obesity may affect peripheral nerve regeneration negatively after crush injury.     

A stereological and histopathological study of the effects of exposure of male rat testes to mercury vapor

Mercury is ubiquitous in the environment; it is an occupational pollutant and a potential toxicant. We investigated the effects of exposure of rat testes to mercury vapor (Hg⁰). Twelve male rats were divided into two groups of six: the rats of the Hg⁰ group were exposed to mercury (1 mg/m³/day) in a chamber for six weeks; the control group rats were housed under the same conditions without exposure to Hg⁰. After the experimental period, the testes were removed, sections of testis were evaluated histopathologically after hematoxylin and eosin staining, and stereologically using the Cavalieri principle and optical fractionator methods. We found significant decreases in the total volume of testis, diameters of seminiferous tubules and total volume of seminiferous tubules. Significant decreases were detected in the numbers of Sertoli cells, spermatogonia, spermatocytes and spermatids of the Hg⁰ group compared to the control group. In the Hg⁰ exposed group, spermatogenic cells were degenerated and seminiferous tubules were atrophied.     

Effects of Nigella sativa oil on ovarian volume,oxidant systems,XIAP and NF-kB expression in an experimental model of diabetes

ABSTRACT

We investigated the effects of Nigella sativa oil on ovary volume, nuclear factor-kappaB (NF-κB), X-linked inhibitor of apoptosis protein (XIAP) expression, and serum malondialdehyde (MDA), superoxide dismutase (SOD), total antioxidant status (TAS) and total oxidant status (TOS) levels in diabetic rats. We divided 21 adult female rats into three groups: controls, diabetics and diabetics + N. sativa oil. The diabetics + N. sativa oil group was given 0.2 mg/kg/day N. sativa oil 6 days/week for 4 weeks. NF-κB and XIAP expression was assessed in ovarian sections using immunohistochemistry. The right and left ovary volumes were calculated using stereology. We also measured serum MDA, SOD, TAS and TOS levels. We found that N. sativa oil reduced hyperglycemia, but not to control levels. N. sativa oil also exhibited antioxidant properties as demonstrated by reduced serum TOS and MDA levels, and increased SOD and TAS levels compared to controls. We found no significant difference in total ovarian volume, XIAP or NF-κB expression among the groups, which may be due to the short study period. Our findings suggest that N. sativa oil may be useful for reducing blood glucose levels and elevated oxidant activity in diabetic patients.