Pathways of apoptosis and importance in development

The elimination of cells by programmed cell death is a fundamental event in development where multicellular organisms regulate cell numbers or eliminate cells that are functionally redundant or potentially detrimental to the organism. The evolutionary conservation of the biochemical and genetic regulation of programmed cell death across species has allowed the genetic pathways of programmed cell death determined in lower species, such as the nematode Caenorhabditis elegans and the fruitfly Drosophila melanogaster to act as models to delineate the genetics and regulation of cell death in mammalian cells. These studies have identified cell autonomous and non-autonomous mechanisms that regulate of cell death and reveal that developmental cell death can either be a pre-determined cell fate or the consequence of insufficient cell interactions that normally promote cell survival.     

Melatonin,immune function and aging

Aging is associated with a decline in immune function (immunosenescence), a situation known to correlate with increased incidence of cancer, infectious and degenerative diseases. Innate, cellular and humoral immunity all exhibit increased deterioration with age. A decrease in functional competence of individual natural killer (NK) cells is found with advancing age. Macrophages and granulocytes show functional decline in aging as evidenced by their diminished phagocytic activity and impairment of superoxide generation. There is also marked shift in cytokine profile as age advances, e.g., CD3+ and CD4+ cells decline in number whereas CD8+ cells increase in elderly individuals. A decline in organ specific antibodies occurs causing reduced humoral responsiveness. Circulating melatonin decreases with age and in recent years much interest has been focused on its immunomodulatory effect. Melatonin stimulates the production of progenitor cells for granulocytes-macrophages. It also stimulates the production of NK cells and CD4+ cells and inhibits CD8+ cells. The production and release of various cytokines from NK cells and T-helper lymphocytes also are enhanced by melatonin. Melatonin presumably regulates immune function by acting on the immune-opioid network, by affecting G protein-cAMP signal pathway and by regulating intracellular glutathione levels. Melatonin has the potential therapeutic value to enhance immune function in aged individuals and in patients in an immunocompromised state.     

Evolution of the WANCY region in amniote mitochondrial DNA

In most vertebrate mitochondrial genomes, the site for initiation of light-strand replication, OL, is found within a cluster of five transfer RNA (tRNA) genes (tRNA(Trp), tRNA(Ala), tRNA(Asn), tRNA(Cys), and tRNA(Tyr)). This region and part of the adjacent cytochrome c oxydase subunit I (COI) gene were sequenced for two crocodilian, two turtle, and one snake species and for Sphenodon punctatus; part of the adjacent nicotinamide adenine dinucleotide dehydrogenase subunit 2 (ND2) gene was also sequenced for the crocodilian and turtle species. All had the typical vertebrate gene order. The turtles and the snake have a lengthy noncoding sequence between the tRNA(Asn) and tRNA(Cys) genes that we assumed to be homologous to the mammalian OL. The crocodilians and Sphenodon lack such a sequence, a condition they share with birds. Most proposed phylogenies for the amniotes require that OL at this position was lost at least twice during their diversification or was evolved independently more than once. Within the five tRNA genes, frequencies of substitutions are much higher in loops than in stems. Many loops vary dramatically in size among the species; in the most extreme case, the D-arm of the Sphenodon tRNA(Cys) is a "D-arm replacement" loop of seven nucleotides. Frequency of transitions in stems is relatively uniform across tRNAs, but frequency of transversions varies greatly. Mismatches in stems are infrequent, and their relative frequency in a specific tRNA is unrelated to the frequency of substitution in the corresponding gene. Several features of mammalian mitochondrial tRNAs are conserved in WANCY tRNAs throughout amniotes. The inferred initiation codon for COI is GTG in crocodilians, turtles, and the snake, a condition they share with fishes, certain amphibians, and birds. TTG appears to be the initiation codon for COI in Sphenodon; if correct, this would be a novel initiation codon for vertebrate mitochondrial DNA. Phylogenetic analyses of the inferred amino acid sequences of ND2 and COI support the sister-group relationship of birds and crocodilians and suggest that mammals are an early derived lineage within the amniotes.      

Mesozooplankton community structure changes in the Mfolozi–Msunduzi estuarine system,South Africa,during contrasting river flow conditions

The Mfolozi–Msunduzi estuarine system is subject to periodic dry and wet cycles, with subsequent changes in the abiotic and biotic characteristics of the system. The aim of the current study was to compare its mesozooplankton composition during relatively dry and wet periods. Mesozooplankton samples were collected between 2007 and 2010 in both the Mfolozi and the Msunduzi, covering a dry period between 2007 and 2008 and a period of relatively high freshwater inputs during 2009 and 2010. High flows during the wet period reduced the densities of most of the dominant estuarine mesozooplankton taxa in the Mfolozi Estuary, such as estuarine calanoids Pseudodiaptomus stuhlmanni (Poppe & Mrázek, 1895) and Acartiella natalensis (Connell & Grindley, 1974). The Msunduzi Estuary functioned as a reservoir from which recolonisation by estuarine taxa would quickly take place after the Mfolozi was scoured by floodwaters. Densities of dominant meroplankton taxa, such as zoeae of the crab Paratylodiplax blephariskios and Macrobrachium spp., were not noticeably different in the Mfolozi–Msunduzi system between the low- and high-flow periods.     

Idiosyncratic species effects confound size-based predictions of responses to climate change

Understanding and predicting the consequences of warming for complex ecosystems and indeed individual species remains a major ecological challenge. Here, we investigated the effect of increased seawater temperatures on the metabolic and consumption rates of five distinct marine species. The experimental species reflected different trophic positions within a typical benthic East Atlantic food web, and included a herbivorous gastropod, a scavenging decapod, a predatory echinoderm, a decapod and a benthic-feeding fish. We examined the metabolism–body mass and consumption–body mass scaling for each species, and assessed changes in their consumption efficiencies. Our results indicate that body mass and temperature effects on metabolism were inconsistent across species and that some species were unable to meet metabolic demand at higher temperatures, thus highlighting the vulnerability of individual species to warming. While body size explains a large proportion of the variation in species'' physiological responses to warming, it is clear that idiosyncratic species responses, irrespective of body size, complicate predictions of population and ecosystem level response to future scenarios of climate change.     

Factors affecting hematology and plasma biochemistry in the southwest carpet python (Morelia spilota imbricata)

Despite increased worldwide popularity of keeping reptiles as pets, we know little about hematologic and biochemical parameters of most reptile species, or how these measures may be influenced by intrinsic and extrinsic factors. Blood samples from 43 wild-caught pythons (Morelia spilota imbricata) were collected at various stages of a 3-yr ecological study in Western Australia. Reference intervals are reported for 35 individuals sampled at the commencement of the study. As pythons were radiotracked for varying lengths of time (radiotransmitters were surgically implanted), repeated sampling was undertaken from some individuals. However, because of our ad hoc sampling design we cannot be definitive about temporal factors that were most important or that exclusively influenced blood parameters. There was no significant effect of sex or the presence of a hemogregarine parasite on blood parameters. Erythrocyte measures were highest for pythons captured in the jarrah forest and at the stage of radiotransmitter implantation, which was also linked with shorter time in captivity. Basophil count, the only leukocyte influenced by the factors tested, was highest when the python was anesthetized, as was globulin concentration. Albumin and the albumin:globulin ratio were more concentrated in summer (as was phosphorous) and at the initial stage of radiotransmitter placement (as was calcium). No intrinsic or extrinsic factors influenced creatinine kinase, aspartate aminotransferase, uric acid, or total protein. This study demonstrates that factors including season, location, surgical radiotransmitter placement, and anesthetic state can influence blood parameters of M. s. imbricata. For accurate diagnosis, veterinarians should be aware that the current reference intervals used to identify the health status of individuals for this species are outdated and the interpretation and an understanding of the influence of intrinsic and extrinsic factors are limited.