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PubMed2005

Case Study Part 1: How to calculate appropriate deterministic long-term toxicity to exposure ratios (TERs) for birds and mammals.

In the European Union, first-tier assessment of the long-term risk to birds and mammals from pesticides is based on calculation of a deterministic long-term toxicity/exposure ratio (TER(lt)). The ratio is developed from generic herbivores and insectivores and applied to all species. This paper describes two case studies that implement proposed improvements to the way long-term risk is assessed. These refined methods require calculation of a TER for each of five identified phases of reproduction (phase-specific TERs) and use of adjusted No Observed Effect Levels (NOELs) to incorporate variation in species sensitivity to pesticides. They also involve progressive refinement of the exposure estimate so that it applies to particular species, rather than generic indicators, and relates spraying date to onset of reproduction. The effect of using these new methods on the assessment of risk is described. Each refinement did not necessarily alter the calculated TER value in a way that was either predictable or consistent across both case studies. However, use of adjusted NOELs always reduced TERs, and relating spraying date to onset of reproduction increased most phase-specific TERs. The case studies suggested that the current first-tier TER(lt )assessment may underestimate risk in some circumstances and that phase-specific assessments can help identify appropriate risk-reduction measures. The way in which deterministic phase-specific assessments can currently be implemented to enhance first-tier assessment is outlined.

Animals↗
PubMed2006

Identifying environmental determinants of diurnal distribution in marine birds and mammals.

Marine birds and mammals move between various habitats during the day as they engage in behaviors related to resting, sleeping, preening, feeding, and breeding. The per capita rates of movement between these habitats, and hence the habitat occupancy dynamics, often are functions of environmental variables such as tide height, solar elevation, wind speed, and temperature. If the system recovers rapidly after disturbance, differential equation models of occupancy dynamics can be reduced to algebraic equations on two time scales. Identification of environmental factors that influence movement between habitats requires time series census data collected in both the absence and presence of disturbance.

Algorithms↗
PubMed2001

Correlation of fatty acid unsaturation of the major liver mitochondrial phospholipid classes in mammals to their maximum life span potential.

Free radical damage is considered a determinant factor in the rate of aging. Unsaturated fatty acids are the tissue macromolecules that are most sensitive to oxidative damage. Therefore, the presence of low proportions of fatty acid unsaturation is expected in the tissues of long-lived animals. Accordingly, the fatty acid compositions of the major liver mitochondrial phospholipid classes from eight mammals, ranging in maximum life span potential (MLSP) from 3.5 to 46 yr, show that the total number of double bonds is inversely correlated with MLSP in both phosphatidylcholine (PtdCho) and phosphatidylethanolamine (PtdEtn) (r = 0.757, P < 0.03, and r = 0.862, P < 0.006, respectively), but not in cardiolipin (P = 0.323). This is due not to a low content of unsaturated fatty acids in long-lived animals, but mainly to a redistribution between kinds of fatty acids on PtdCho and PtdEtn, shifting from arachidonic (r = 0.911, P < 0.002, and r = 0.681, P = 0.05, respectively), docosahexaenoic (r = 0.931 and r = 0.965, P < 0.0001, respectively) and palmitic (r = 0.944 and r = 0.974, P < 0.0001, respectively) acids to linoleic acid (r = 0.942, P < 0.0001, for PtdCho; and r = 0.957, P < 0.0001, for PtdEtn). For cardiolipin, only arachidonic acid showed a significantly inverse correlation with MLSP (r = 0.904, P < 0.002). This pattern strongly suggests the presence of a species-specific desaturation pathway and deacylation-reacylation cycle in determining the mitochondrial membrane composition, maintaining a low degree of fatty acid unsaturation in long-lived animals.

Animals↗
PubMed2002

What is the role of alpha-linolenic acid for mammals?

This review examines the data pertaining to an important and often underrated EFA, alpha-linolenic acid (ALA). It examines its sources, metabolism, and biological effects in various population studies, in vitro, animal, and human intervention studies. The main role of ALA was assumed to be as a precursor to the longer-chain n-3 PUFA, EPA and DHA, and particularly for supplying DHA for neural tissue. This paper reveals that the major metabolic route of ALA metabolism is beta-oxidation. Furthermore, ALA accumulates in specific sites in the body of mammals (carcass, adipose, and skin), and only a small proportion of the fed ALA is converted to DHA. There is some evidence that ALA may be involved with skin and fur function. There is continuing debate regarding whether ALA has actions of its own in relation to the cardiovascular system and neural function. Cardiovascular disease and cancer are two of the major burdens of disease in the 21st century, and emerging evidence suggests that diets containing ALA are associated with reductions in total deaths and sudden cardiac death. There may be aspects of the action and, more importantly, the metabolism of ALA that need to be elucidated, and these will help us understand the biological effects of this compound better. Additionally, we must not forget that ALA is part of the whole diet and should be seen in this context, not in isolation.

Animals↗
PubMed2001

Cecropins, antibacterial peptides from insects and mammals, are potently fungicidal against Candida albicans.

Natural products are the major source of lead compounds for drugs against human pathogens. Among the first natural peptides from animals for which a potent antibacterial activity has been recognized were the cecropins. The 30- to 40-residue alpha-helical peptides display their activity by permeabilizing the membranes of bacteria. Although originally isolated from insect hemolymph, a structural and functional correlate was also found in a mammal. Here, we report on the finding that cecropin A and B from the silk moth Cecropia as well as the porcine cecropin P1 are capable of inhibiting the growth of and to kill yeast-phase Candida albicans. The peptides were tested in radial diffusion and microbroth dilution assays. They displayed potent activity against a clinical isolate as well as against defined culture strains of the pathogenic yeast but are of exceedingly low cytotoxicity towards the human cell line Jurkat. The candidacidal properties of the intensely studied molecules known to be highly active against Gram-positive and Gram-negative bacteria may renew the interest in these natural broad-spectrum peptide antibiotics and their limited cytotoxicity to human cells may be exploited for the development of topical therapeutics against pathogens resistant to classical antibiotics.

Animals↗
PubMed1989

Quantitative distribution of GABA-immunoreactive neurons in cetacean visual cortex is similar to that in land mammals.

Sections of the anterior portion of the visual cortex in the lateral gyrus of the Black Sea porpoise were studied to determine the neuronal architecture and numerical density, and the distribution of neurons immunoreactive to gamma-aminobutyric acid (GABA). Cytoarchitecture and neuronal density are similar to those described in another cetacean, the bottlenose dolphin. GABA-positive neurons are distributed through all layers of the visual cortex but are especially dense in layers II and III, and comprise some 20% of the total neuronal population in this part of the cortex. The distribution of GABA-positive neurons is similar to that found in land mammals.

Animals↗
PubMedDate not supplied

Working within the law: guidelines for veterinary surgeons and wildlife rehabilitators on the rehabilitation of wild mammals.

In recent years there has been a considerable increase in the numbers of both veterinary surgeons and wildlife rehabilitators involved in the care and rescue of wildlife. Several publications are available offering practical advice on what to do, but many of the people working in this field are unclear as to which laws apply to wildlife rehabilitation. This paper provides a summary of the legal position as it relates to the rehabilitation of wild mammals in Britain.

Animal Welfare↗
PubMed1994

Transberingian dispersal of cestodes in mammals.

During Pleistocene glaciations, eustatic lowering of sea-level exposed the continental shelf between northeastern Eurasia and northwestern North America. That land in combination with unglaciated areas on the adjacent continents formed a vast region open to the west but bounded on the east by continental ice. Organisms from Eurasia spread into the unglaciated Beringian refugium, which was biotically an eastward extension of the Palaearctic. With rising sea-levels following glacial periods, the Bering Strait was formed and organisms of Eurasian origin were left within the nearctic sector of Beringia. As the continental ice disappeared, plants and animals spread eastward and southward from Beringia, while organisms from beyond the southern margins of the ice extended their ranges northward. The significance of Beringia is discussed with reference to the dispersal of host-specific cestodes in mammals that attained holarctic status during the late Pleistocene.

Animals↗
PubMed1984

Scaling of standard energy metabolism in mammals: I. Neglect of circadian rhythms.

The original data employed to derive the three-quarters power rule relating standard or basal energy metabolism in mammals to adult body weight are examined. It is shown that the data may contain a systematic bias due to an (apparent) neglect of circadian rhythms. Correction for this bias would tend to decrease the slope of the regression line, bringing it into better conformity with the value of about two-thirds obtained in a recent study of a larger sample by Bartels (1982).

Animals↗
PubMed1982

The lymphocytes of small mammals. A model for research in cytogenetics?

The influence of nuclear characteristics such as chromosome number, chromosome arm number or amount of R-band material on the yield of radiation-induced chromosome aberrations has been re-evaluated on the basis of some recent experiments with the harlequin-staining method to distinguish the first from subsequent divisions. The results obtained up to now show that differences in cell kinetics of stimulated peripheral blood lymphocytes, causing a different distribution of first and following mitoses at the time of observation, can result in an underestimate of the incidence of unstable chromosome aberrations such as dicentric chromosomes when the observations are performed at a standardized fixation time without taking into account the cell generation. If, however, only first-division mitoses are considered, the radiosensitivity of the cells appears to be independent on nuclear characteristics. Furthermore, observations on whole-body irradiated animals show that, owing to the very short survival time of lymphocytes carrying chromosome aberrations, mammals generally available for such experiments represent inappropriate models when cytogenetic effects in somatic cells are to be followed for long periods of time after an acute exposure to ionizing radiation or after a chronic exposure.

Animals↗
PubMed1992

Local sequence dependence of rate of base replacement in mammals.

I have analysed the local sequence context of base replacement changes in 78 processed pseudogenes. Transversions occur more often than transitions in a ratio of 3.37 to 1, and G:C is replaced 1.4 times more frequently than A:T. In addition, the bases to the 5' and 3' of the mutating base also influence the rate at which bases change, purine:pyrimidine and pyrimidine:purine pairs changing 1.2 times as fast as purine:purine and pyrimidine:pyrimidine pairs. I discuss implications of this for the mechanism of DNA polymerization in mammals.

Animals↗
PubMed1982

Capillary supply of heart and skeletal muscle of small bats and non-flying mammals.

Capillary density (CD), fiber cross-section area, capillary-to-fiber ratio and intercapillary distance of papillary and a calf muscle were evaluated in four species of bats (body weight 23-150 g) and six non-flying mammalian species (2.5-170 g). In bats the pectoralis muscle was studied additionally. In both groups CD increased in papillary as well as in calf muscle with decreasing body weight. The papillary muscles showed the highest CD in the 2.5 g shrew Suncus etruscus (7287 cap./mm2) and the 23 g bat Myotis myotis (6748 cap./mm2). The flight muscle of the 38 g bat Molossus ater showed the highest CD (4992 cap./mm2) of all skeletal muscles investigated. The slopes of regressions of CD versus body weight for papillary (calf) muscles were -0.42 (-0.70) for bats and -0.15 (-0.26) for non-flying mammals, indicating that bats have a higher increase of weight-specific metabolic rate with decreasing body weight. This holds for species with a body weight below 30 g.

Animals↗
PubMed1978

Parasitological and ecological aspects of Schistosomiasis mansoni in the valley of the Paraíba do Sul River (São Paulo State, Brazil) I. Natural infection of small mammals with Schistosoma mansoni.

Small mammals naturally infected with Schistosoma mansoni were studied in the valley of the Paraíba do Sul river (São Paulo State, Brazil). 192 animals of 12 species were examined post mortem. Cavia aperea, Holochilus brasiliensis leucogaster, Nectomys squamipes squamipes, Oryzomys nigripes eliurus and Zygodontomys brachyurus were found infected. Most schistosome eggs found in the faeces were mature but no eggs were found in the faeces of C. aperea although adults were recovered. In the other infected animals the number of eggs per gram of faeces showed a marked daily variation. Perfusion of the portal system demonstrated that in H. b. leucogaster worms usually remained in the mesenteric veins. In C. aperea 75.7% of worms were found in the portal and intra-hepatic veins. H. b. leucogaster seems to be the rodent most likely to play a role in the epidemiology of schistosomiasis mansoni in the valley of the Paraíba do Sul river.

Animals↗
PubMed1990

Organic mercury in Greenland birds and mammals.

Muscle, liver and kidney samples of 20 species of birds, seals, whales and polar bear were analyzed for total and organic mercury. Organic mercury concentrations varied considerably between individuals. A general tendency towards age accumulation was found, together with log-linear correlations between organic mercury concentrations in the three tissues. The major part of the muscle mercury was organic (maximum concentration found was 1235 micrograms kg-1 wet wt). This also applied to liver of birds, while in mammal liver organic mercury concentrations approached a level of 2000 micrograms kg-1 wet wt, which was not exceeded even when the total mercury concentration was greater than 100,000 micrograms kg-1 wet wt. The percentage of organic mercury in relation to total mercury in kidney of seals and whales was 10-20% (maximum 982 micrograms organic mercury kg-1 wet wt), while in polar bear it was less than 6% (maximum 217 micrograms kg-1 wet wt). For the monitoring of local food in the Arctic, the simpler and less expensive analysis of total mercury suffices when testing muscle, whereas liver and kidney should be tested for organic mercury as well.

Animals↗
PubMed1986

Evolution of low molecular weight immunoglobulins. V. Degree of antigenic relationship between the 7S immunoglobulins of mammals, birds, and lower vertebrates to the turkey IgY.

There are close antigenic relations between the turkey IgY--the dominant 7S Ig of serum--and the corresponding IgY-like Igs of chicken, duck, goose, tortoise, and frog as well as serum or colostral IgA of man and swine. The RIA-systems used for the determination of immunological cross-reactivity among the Ig types consisted of 125-I-labelled turkey IgY and class-specific rabbit anti-turkey IgY antibodies. The results stand in a good agreement with our findings demonstrating strong antigenic relationships between various serum or colostral Igs of IgY and IgA types, respectively, to the chicken IgY. Therefore, the IgY-like Igs seem to be the precursors for the IgA class of mammals.

Animals↗
PubMed1990

Regulatory sites in the melatonin system of mammals.

The hormone melatonin was first identified about 30 years ago as a secretory product of the pineal gland. In mammals, the daily rhythm of pineal melatonin synthesis is controlled by neural inputs. The CNS is thought to be a primary target organ involved in mediating the influence of melatonin on a variety of physiological and behavioral processes, including biological rhythms, neuroendocrine function, activity levels and sleep. It now appears that melatonin is also produced in the retina and affects various aspects of retinal physiology. The purpose of this article is to provide a brief overview of potential regulatory sites involved in the production and action of melatonin. In particular, this review focuses on the rapid advances being made in the characterization and localization of melatonin receptors in the CNS, retina and pituitary and on recent findings pertaining to the regulation of melatonin synthesis in the mammalian pineal gland and retina.

Animals↗
PubMed1983

Tissue-specific differences in DNA methylation in various mammals.

The only naturally occurring modified base in vertebrate DNA is 5-methylcytosine. Using a precise high-performance liquid chromatographic analysis of DNA enzymatically digested to deoxynucleosides, we have shown that rats, mice and four types of monkey display tissue-specific as well as species-specific differences in the extent of methylation of their cytosine residues. Several similarities in the patterns of tissue-specific DNA methylation in these mammals and in the previously studied human samples were observed. Compared to most other types of DNA examined, brain and thymus DNAs were hypermethylated which suggests that this hypermethylation is a determinant or a necessary byproduct of mammalian differentiation. In all of the studied rodents and primates, the highly repeated DNA sequence fraction was more methylated than the moderately repetitive or single copy fractions. The tissue-specific differences in overall DNA methylation showed no correlation with what is known about average cell turnover rates nor with the percentage of the genome that is transcribed. Liver regeneration in the rat following partial hepatectomy did not detectably alter 5-methylcytosine levels in liver DNA. A considerable increase in the extent of methylation of total liver DNA was observed during normal development of the rat. The latter phenomenon may be due to a major change in the cellular composition of the liver.

5-Methylcytosine↗
PubMed1993

Epigenetic inheritance in mammals.

The epigenetic phenomena of genome imprinting and X-chromosome inactivation, found in mammals, both entail homologous genes or chromosomes behaving differently within the same cell. Although both have consequences for genic balance in the whole genome, in imprinting the control seems mainly at the single gene level, whereas in X-chromosome inactivation there is coordinated regulation of the whole chromosome, and single gene effects are relatively minor.

Animals↗