Species Differences In Effects Research Articles

Structure, expression and activation of fish ras genes

Ras genes encode proteins that play a central role in cell growth signaling cascades. The fish ras genes characterized to date, have a high degree of nucleotide sequence and deduced amino acid similarity with the mammalian ras gene counterparts. A large proportion and wide variety of mammalian tumors possess mutant forms of ras. In such cases, the localization of ras mutations has been restricted to exons I and II, and to codons 12, 13 and 61. Experimental exposure of fish to a range of genotoxic compounds has similarly led to the production of a ras mutational profile for selected species. The inducing compound, tissue investigated and the fish species studied affect the ras mutational spectrum and incidence observed, despite the apparent conserved sequence homology. Furthermore, the fish ras mutational profile differs from that observed in rodent models, including a novel codon (16) mutation. The role of ras genes in tumor formation in feral fish has been investigated using several species collected from areas of high hydrocarbon contamination. Tomcod ( Microgadus tomcod), winter flounder ( Pseudopleuronectes americanus) and dragonet ( Callionymus lyra) liver samples display evidence of ras gene mutations, though for the latter species the codon affected is not characteristic of ras gene mutational profiles. English sole ( Pleuronectes vetulus) and European flounder ( Platichthys flesus) liver tumor samples so far examined, on the other hand, do not display ras gene mutations. Thus, the pattern and incidence of ras gene mutations in environmentally-induced tumors also appear to be species specific. In determining the basis of both the species susceptibility observed in the field and species differences in effects of laboratory controlled exposures, the interaction of fish ras genes with other components of the cell growth signaling cascade (such as protein kinase C, additional oncogenes and tumor suppressor genes) are discussed. The effect of promoting agents following contaminant-induced initiation could similarly provide answers in unraveling the question of species susceptibility.

Competition among Secondary-Successional Pine Communities: A Field Study of Effects and Responses

Three common associates on secondary-successional pine sites (Andropogon virginicus, Liquidambar styraciflua, and Pinus taeda) were established in a field study in which a wide array of plant densities and species proportions were established using an additive series design. To mimic a specific competitive scenario (i.e., a managed early-successional Pinus stand), Andropogon and Liquidambar were established a year prior to the establishment of Pinus. Competitive effect (the attenuation of resources) and competitive response (the growth of each species as a function of resource availability) were determined. Effect on soil water varied among species, depth of soil, and time. In the surface soil, soil water was largely influenced through non-uptake effects, while uptake effects were predominant in deeper portions of the solum. When competitor abundance was expressed on an aboveground biomass basis, rather than a density basis, species differences in effects on soil water were eliminated. Differences among the species in effects on soil water per unit leaf area or leaf biomass appear to be largely explained by differences in stomatal conductance. Predawn leaf-water potential was integrated over the season using a water-stress integral. Analysis of the water-stress integral suggested that Liquidambar and Andropogon both affected water available to Pinus; however, only Liquidambar affected Andropogon, and only Andropogon affected seasonal water available to Liquidambar. Light was most strongly influenced by Liquidambar density; however, as Andropogon density increased, the effects of Liquidambar were reduced. Andropogon response was correlated with light but not with water stress or leaf nitrogen. This reflects high light requirements and high water use efficiency of C4 plants. Liquidambar response was related to water stress and leaf nitrogen, perhaps reflecting the greater nitrogen requirements of hardwoods. Pinus response was significantly related to all three resources individually, i.e., water stress, light, and leaf nitrogen. Pinus response was better explained by a regression model that included light and water stress than by water stress or light alone. Pinus growth as a function of water stress and light indicated that communities dominated by Liquidambar largely reduced Pinus growth through reduction in light, while communities dominated by Andropogon reduced Pinus growth primarily by increasing water stress. In mixed communities of Liquidambar and Andropogon, pine growth was constrained more equally by light and water stress.

COMPETITION AMONG SECONDARY-SUCCESSIONAL PINE COMMUNITIES: A FIELD STUDY OF EFFECTS AND RESPONSES

Three common associates on secondary-successional pine sites (Andropogon virginicus, Liquidambar styracifiua, and Pinus taeda) were established in a field study in which a wide array of plant densities and species proportions were established using an additive series design. To mimic a specific competitive scenario (i.e., a managed early- successional Pinus stand), Andropogon and Liquidambar were established a year prior to the establishment of Pinus. Competitive effect (the attenuation of resources) and competitive response (the growth of each species as a function of resource availability) were determined. Effect on soil water varied among species, depth of soil, and time. In the surface soil, soil water was largely influenced through non-uptake effects, while uptake effects were predominant in deeper portions of the solum. When competitor abundance was expressed on an aboveground biomass basis, rather than a density basis, species differences in effects on soil water were eliminated. Differences among the species in effects on soil water per unit leaf area or leaf biomass appear to be largely explained by differences in stomatal conductance. Predawn leaf-water potential was integrated over the season using a water- stress integral. Analysis of the water-stress integral suggested that Liquidambar and An- dropogon both affected water available to Pinus; however, only Liquidambar affected Andropogon, and only Andropogon affected seasonal water available to Liquidambar. Light was most strongly influenced by Liquidambar density; however, as Andropogon density increased, the effects of Liquidambar were reduced. Andropogon response was correlated with light but not with water stress or leaf nitrogen. This reflects high light requirements and high water use efficiency of C4 plants. Liquidambar response was related to water stress and leaf nitrogen, perhaps reflecting the greater nitrogen requirements of hardwoods. Pinus response was significantly related to all three resources individually, i.e., water stress, light, and leaf nitrogen. Pinus response was better explained by a regression model that included light and water stress than by water stress or light alone. Pinus growth as a function of water stress and light indicated that communities dominated by Liquidambar largely reduced Pinus growth through reduction in light, while communities dominated by Andropogon reduced Pinus growth primarily by increasing water stress. In mixed communities of Liquidambar and Andropogon, pine growth was constrained more equally by light and water stress.

An Overview of Species Differences in the Effects of a Water Extract of Cotton Bract on Isolated Airway Smooth Muscle, and Effects of E. coli Lipopolysaccharide

Our laboratory has been comparing the activity of a water extract of cotton bract (CBE) with the isolated trachealis smooth muscle of the dog, guinea pig, and cat. CBE induced contractions that were not mediated by 5-hydroxytryptamine (5-HT), histamine, or muscarinic receptors. The active agent(s) in CBE was dialyzable (less than 14,000 molecular weight), and substantial activity was retained after low-temperature ashing. CBE potentiated contractions of dog trachealis to histamine and 5-HT and relaxation responses to isoproterenol, whereas it had no effect on responses to methacholine and KCl. In the guinea pig trachealis, CBE reduced responsiveness to KCl, potentiated relaxations to adenosine and ATP, and did not alter the responses to the remaining agents. Responses of cat trachealis to KCl and isoproterenol were potentiated by CBE, while those to 5-HT were unaffected. Neurogenic cholinergic contractile responses were potentiated by CBE in the trachealis of the dog, but not of the guinea pig, while neurogenic relaxations were potentiated by CBE in guinea pig trachealis but not in the dog trachealis. There are thus marked species differences in the acute effects of CBE on airway smooth muscle. Due to recent interest in the possible involvement of bacterial endotoxins in the etiology of byssinosis, we examined the effects of E. coli lipopolysaccharide (LPS) in guinea pig trachealis. An initial examination revealed that LPS potentiated responses to histamine, but not those to methacholine and isoproterenol. This effect vanished upon a second appraisal with a different batch of LPS. The effect of LPS in airway smooth muscle is thus, at present, equivocal.

Effect of halothane anesthesia on end-tidal PCO and pattern of respiration in the rat.

End-tidal Pco2 (petco2) and ventilation of the rat anesthetized with halothane were measured. The Petco2 measured by an infrared analyzer agreed well with the simultaneously measured Paco2 in the range from 20-60mm Hg (2.7-8.0 kPa). When the level of anesthesia was deepened by increasing the halothane concentration from 0.9-3.0%, minute ventilation was decreased progressively accompanied by a rise in Petco2 and the CO2 output was reduced. Halothane induced a progressive decrease in frequency of respiration (f) with almost constant or even slight increase in tidal volume (VT)). Decrease in f was caused largely by the prolongation of expiratory duration (TE). Changes in inspiratory duration (T1) were small and the mean VT/T1 ratio remained unaltered at different levels of anesthesia. These changes in respiratory pattern induced by halothane anesthesia contrasted with the simultaneous decrease in VT, f and VT/T1 ratio and apparent changes of both T1 an TE reported in other species. Species differences in effects of anesthesia on ventilation were discussed. Restraining the rat on a stereotaxic apparatus with head holders, especially with ear bars, elicited an initial transient stimulation of ventilation which was followed by a strong depression.

Species and sex differences in the reductive dechlorination of DDT by supplemented liver preparations

p, p′-DDT was converted to DDD, 1,1-dichloro-2,2-bis( p-chlorophenyl)ethane, by unheated 12,000 g supernate supplemented with NADPH, made from liver of rat, mouse, hamster, quail, chicken and pigeon. The additional presence of exogenous riboflavin did not augment reduction. If, however, riboflavin was added to unheated microsomes supplemented with NADPH or NADH the rate of reduction was more than doubled. Heated 12,000 g supernate, unsupplemented or containing only exogenous riboflavin, did not reduce DDT. When NAD(P)H was present, big species differences in activity occurred, the pigeon and cockerel scarcely reducing any DDT in 2 hr, the Wistar rat supernate being most active. Addition to heated 12,000 g supernate of 30 μg riboflavin as well as NAD(P)H resulted in increased reductive activity for all six species. The species difference in effect of exogenous riboflavin between the pigeon and rat was also observed using four DDT analogs as substrates. A sex-related difference in activity of preheated, supplemented 12,000 g supernate from livers of the chicken and Norwegian hooded rat was not found when unheated preparations were used. In contrast to the activity possessed by preheated 12,000 g supernate of rat liver supplemented with NAD(P)H, similarly supplemented preheated microsomes did not reduce DDT. On adding riboflavin as well as NAD(P)H, however, preheated hepatic microsomes of both pigeon and rat produced DDD, and this activity was further increased by addition of unheated microsomal (105,000 g) supernate. The biocatalytic system functioning in preheated preparations appears to need at least one component of heated microsomes, NAD(P)H and one or more water-soluble components.

Species Differences in Effect of Electroreceptor Input on Electric Organ Pacemakers and Other Aspects of Behavior in Electric Fish; pp. 102–118

Species Differences in Effect of Electroreceptor Input on Electric Organ Pacemakers and Other Aspects of Behavior in Electric Fish; pp. 102–118

Species Differences in Effect of Electroreceptor Input on Electric Organ Pacemakers and Other Aspects of Behavior in Electric Fish; pp. 85–101

Species Differences in Effect of Electroreceptor Input on Electric Organ Pacemakers and Other Aspects of Behavior in Electric Fish; pp. 85–101

Species differences in effects of apomorphine as an adrenergic agent

Species differences in effects of apomorphine as an adrenergic agent

Species differences in effect of gram-negative endotoxin on circulation.

Studies were made in 5 monkeys, 7 rabbits, and 33 cats of the effect of gram-negative endotoxin on aortic, pulmonary artery (PAP), and portal venous (PVP) pressures; and on changes in weight of a short segment of intestine. Studies of blood pooling were also made in 12 cats. The responses in these species were compared with those previously observed in the dog. Although variable degrees of hypotension developed at one time or another in all animals following injection of endotoxin, the early precipitous hypotension that characteristically occurs in the dog was observed only in the cat. However, in this species the dramatic fall in pressure could be ascribed to pulmonary vascular constriction and acute right ventricular hypertension and failure, and not to splanchnic pooling. PAP also became elevated in the monkey and the rabbit, but usually was of lesser magnitude and did not appear to explain the development of the relatively late hypotension that occurred in these species. The absence of significant increases in gut weight and the minor increments in PVP in all animals indicate that in none of these species is hepatic vein constriction and splanchnic pooling a significant mechanism in producing early shock as it is in the dog. Pathologic gross and microscopic studies in the monkey and gross examinations in the other species supported this conclusion.