A general basis for quarter-power scaling in animals

It has been known for decades that the metabolic rate of animals scales with body mass with an exponent that is almost always <1, >2/3, and often very close to 3/4. The 3/4 exponent emerges naturally from two models of resource distribution networks, radial explosion and hierarchically branched, which incorporate a minimum of specific details. Both models show that the exponent is 2/3 if velocity of flow remains constant, but can attain a maximum value of 3/4 if velocity scales with its maximum exponent, 1/12. Quarterpower scaling can arise even when there is no underlying fractality. The canonical “fourth dimension” in biological scaling relations can result from matching the velocity of flow through the network to the linear dimension of the terminal “service volume” where resources are consumed. These models have broad applicability for the optimal design of biological and engineered systems where energy, materials, or information are distributed from a single source.

Molecular typing of Salmonella serotypes prevalent in animals in England: assessment of methodology

Salmonella enterica serotypes Derby, Mbandaka, Montevideo, Livingstone, and Senftenberg were among the 10 most prevalent serotypes isolated from farm animals in England and Wales in 1999. These serotypes are of potential zoonotic relevance; however, there is currently no "gold standard" fingerprinting method for them. A collection of isolates representing the former serotypes and serotype Gold Coast were analyzed using plasmid profiling, pulsed-field gel electrophoresis (PFGE), and ribotyping. The success of the molecular methods in identifying DNA polymorphisms was different for each serotype. Plasmid profiling was particularly useful for serotype Derby isolates, and it also provided a good level of discrimination for serotype Senftenberg. For most serotypes, we observed a number of nontypeable plasmid-free strains, which represents a limitation of this technique. Fingerprinting of genomic DNA by ribotyping and PFGE produced a significant variation in results, depending on the serotype of the strain. Both PstI/SphI ribotyping and XbaI-PFGE provided a similar degree of strain differentiation for serotype Derby and serotype Senftenberg, only marginally lower than that achieved by plasmid profiling. Ribotyping was less sensitive than PFGE when applied to serotype Mbandaka or serotype Montevideo. Serotype Gold Coast isolates were found to be nontypeable by XbaI-PFGE, and a significant proportion of them were found to be plasmid free. A similar situation applies to a number of serotype Livingstone isolates which were nontypeable by plasmid profiling and/or PFGE. In summary, the serotype of the isolates has a considerable influence in deciding the best typing strategy; a single method cannot be relied upon for discriminating between strains, and a combination of typing methods allows further discrimination.

Attaching-effacing bacteria in animals

Enteric bacteria with a demonstrable or potential ability to form attaching-effacing lesions, so-called attaching-effacing (AE) bacteria, have been found in the intestinal tracts of a wide variety of warm-blooded animal species, including man. In some host species, for example cattle, pigs, rabbits and human beings, attaching-effacing Escherichia coli (AEEC) have an established role as enteropathogens. In other host species, AE bacteria are of less certain significance. With continuing advances in the detection and typing of AE strains, the importance of these bacteria for many hosts is likely to become clearer. The pathogenic effects of AE bacteria result from adhesion to the intestinal mucosa by a variety of mechanisms, culminating in the formation of the characteristic intimate adhesion of the AE lesion. The ability to induce AE lesions is mediated by the co-ordinated expression of some 40 bacterial genes organized within a so-called pathogenicity island, known as the "Locus for Enterocyte Effacement". It is also believed that the production of bacterial toxins, principally Vero toxins, is a significant virulence factor for some A-EEC strains. Recent areas of research into AE bacteria include: the use of Citrobacter rodentium to model human AEEC disease; quorum-sensing mechanisms used by AEEC to modulate virulence gene expression; and the potential role of adhesion in the persistent colonization of the intestine by AE bacteria. This review of AE bacteria covers their molecular biology, their occurrence in various animal species, and the diagnosis, pathology and clinical aspects of animal diseases with which they are associated. Reference is made to human pathogens where appropriate. The focus is mainly on natural colonization and disease, but complementary experimental data are also included. (C) 2004 Elsevier Ltd. All rights reserved.

Spermatogenesis in the blue swimming crab, Portunus pelagicus, and evidence for histones in mature sperm nuclei

Spermatogenesis in the blue swimming crab, Portunus pelagicus, is described by light and electron microscopy. The testis is composed of anterior (AT) and posterior (PT) lobes, that are partitioned into lobules by connective tissue trabecula, and further divided into zones (germinal, transformation and evacuation), each with various stages of cellular differentiation. The vas deferens is classified into three distinct regions: anterior (AVD), median (MVD), and posterior (PVD), on the presence of spermatophores and two secretions, termed substance I and II. Based on the degree and patterns of heterochromatin, spermatogenesis is classified into 13 stages: two spermatogonia (SgA and SgB), six primary spermatocytes (leptotene, zygotene, pachytene, diplotene, diakinesis, and metaphase), a secondary spermatocyte (SSc), three spermatids (St 1–3), and a mature spermatozoon. Spermatid stages are differentiated by chromatin decondensation and the formation of an acrosomal complex, which is unique to brachyurans. Mature spermatozoa are aflagellated, and have a nuclear projection and a spherical acrosome. AUT-PAGE and Western blots show that, during chromatin decondensation, there is a reduction of most histones, with only small amounts of H2B and H3 remaining in mature spermatozoa.

Molting and reproduction in portunus pelagicus

This investigation describes ovarian maturation stages in the female reproductive system, evidence for histones in sperm nuclei and novel morphological changes that occur during spermiogenesis in the male blue swimming crab, portunus pelagicus. It also identifies dual functionality of the molt inhibiting hromone on molting and vitellogenesis through RNA inteference.

Life history and the ecology of stress: how do glucocorticoid hormones influence life-history variation in animals?

Glucocorticoids hormones (GCs) are intuitively important for mediation of age-dependent vertebrate life-history transitions through their effects on ontogeny alongside underpinning variation in life-history traits and trade-offs in vertebrates. These concepts largely derive from the ability of GCs to alter energy allocation, physiology and behaviour that influences key life-history traits involving age-specific life-history transitions, reproduction and survival. Studies across vertebrates have shown that the neuroendocrine stress axis plays a role in the developmental processes that lead up to age-specific early life-history transitions. While environmental sensitivity of the stress axis allows for it to modulate the timing of these transitions within species, little is known as to how variation in stress axis function has been adapted to produce interspecific variation in the timing of life-history transitions. Our assessment of the literature confirms that of previous reviews that there is only equivocal evidence for correlative or direct functional relationships between GCs and variation in reproduction and survival. We conclude that the relationships between GCs and life-history traits are complex and general patterns cannot be easily discerned with current research approaches and experimental designs. We identify several future research directions including: (i) integration of proximate and ultimate measures, including longitudinal studies that measure effects of GCs on more than one life-history trait or in multiple environmental contexts, to test explicit hypotheses about how GCs and life-history variation are related and (ii) the measurement of additional factors that modulate the effects of GCs on life-history traits (e.g. GC receptors and binding protein levels) to better infer neurendocrine stress axis actions. Conceptual models of HPA/I axis actions, such as allostatic load and reactive scope, to some extent explicitly predict the role of GCs in a life-history context, but are descriptive in nature. We propose that GC effects on life-history transitions, survival probabilities and fecundity can be modelled in existing quantitative demographic frameworks to improve our understanding of how GC variation influences life-history evolution and GC-mediated effects on population dynamics Lay Summary Functional Ecology

Duration of spermatogenesis in the bullfrog (Lithobates catesbeianus)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Ultrastructural Aspects of Spermatogenesis in Phalloceros caudimaculatus (Teleostei, Poeciliidae)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Epidemiological and Serological Aspects in Canine Toxoplasmosis in Animals with Nervous Symptoms

The presence of anti-Toxoplasma gondii IgM and IgG antibodies was studied in samples of blood serum taken from eighty dogs with nervous symptoms at the Serviço de Enfermidades Infecciosas dos Animais, Faculdade de Medicina Veterinária e Zootecnia, Unesp, Botucatu, São Paulo, Brazil. The frequency of IgG titers were 16 (13.7%), 64 (13.7%), and 256 (5%), and for IgM titers were 16 (7.5%), 64 (15%), and 256 (8.7%). Positive reactions were more frequent in the older animals, males, from a rural environment, in constant contact with small animals, principally birds and rodents. There was a higher frequency of a positive reaction in dogs fed with kitchen food, especially in those fed with raw ingredients. The most common neurological pictures were alterations in consciousness, in movement, and in the hand-cart test. The percentage of reagents with specific IgM antibodies was high, indicating active infections, but the possibility of co-infection with the distemper virus can not be discarded, and this may be a predisposing factor for toxoplasmosis infection, once the distemper virus has a potent immunosupressive action.

Morphological study of the spermatogenesis in the teleost Piaractus mesopotamicus

The spermatogenesis of Piaractus mesopotamicus was investigated under light and transmission electron microscopy. The specimens were captured from their natural environment (Rio Miranda and Rio Aquidauana, Pantanal Matogrossense, Brazil) during April and September. The results were compared with the spermatogenic data of specimens under captivity condition. In both conditions, P mesopotamicus presented the typical spermatogenesis pattern of the teleost fishes, showing no significative differences. The spermatozoon was classified as type 1, which has a globular head without acrosome, a short middle piece and a long tail constituted only by the flagellum. This type of spermatozoon is considered the basic type in fishes.

Karyotype and spermatogenesis in Triatoma lenti (Hemiptera: Triatominae), a potential Chagas vector

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)