Effect Of Species Differences Research Articles

Molecular Determinants of Species Specificity of α-Conotoxin TxIB towards Rat and Human α6/α3β4 Nicotinic Acetylcholine Receptors.

Conotoxins are widely distributed and important for studying ligand-gated ion channels. TxIB, a conotoxin consisting of 16 amino acids derived from Conus textile, is a unique selective ligand that blocks rat α6/α3β2β3 nAChR (IC50 = 28 nM) without affecting other rat subtypes. However, when the activity of TxIB against human nAChRs was examined, it was unexpectedly found that TxIB had a significant blocking effect on not only human α6/α3β2β3 nAChR but also human α6/α3β4 nAChR, with an IC50 of 537 nM. To investigate the molecular mechanism of this species specificity and to establish a theoretical basis for drug development studies of TxIB and its analogs, different amino acid residues between human and rat α6/α3 and β4 nAChR subunits were identified. Each residue of the human species was then substituted with the corresponding residue of the rat species via PCR-directed mutagenesis. The potencies of TxIB towards the native α6/α3β4 nAChRs and their mutants were evaluated through electrophysiological experiments. The results showed that the IC50 of TxIB against h[α6V32L, K61R/α3]β4L107V, V115I was 22.5 μM, a 42-fold decrease in potency compared to the native hα6/α3β4 nAChR. Val-32 and Lys-61 in the human α6/α3 subunit and Leu-107 and Val-115 in the human β4 subunit, together, were found to determine the species differences in the α6/α3β4 nAChR. These results also demonstrate that the effects of species differences between humans and rats should be fully considered when evaluating the efficacy of drug candidates targeting nAChRs in rodent models.

The effect of species differences in bacteria of the genera Bacillus and Pseudomonas, suspended in saline, on the rate of recovery iodonitrotetrazolium chloride

The effect of species differences in bacteria of the genera Bacillus and Pseudomonas, suspended in saline, on the rate of recovery iodonitrotetrazolium chloride

Comparative hepatotoxicity of a herbicide, epyrifenacil, in humans and rodents by comparing the dynamics and kinetics of its causal metabolite.

A new herbicide, epyrifenacil (S-3100), inhibits protoporphyrinogen oxidase (PPO) in plants. Repeated administration of epyrifenacil in laboratory animals led to some toxicological changes related to PPO inhibition, e.g., hepatotoxicity caused by porphyrin accumulation and anemia caused by the inhibition of heme biosynthesis. In vitro studies revealed that an ester-cleaved metabolite, S-3100-CA, is predominant in mammals, exhibits PPO-inhibitory activity, and thus is the cause of epyrifenacil-induced toxicity. To assess the human risk, the effects of species differences on the dynamics (PPO inhibition) and kinetics (liver uptake) of epyrifenacil were evaluated separately. The results of in vitro assays revealed an approximately tenfold weaker inhibition of PPO by S-3100-CA in humans than in rodents and six- to thirteen-fold less hepatic uptake of S-3100-CA in humans than in mice. Finally, it was suggested that humans are less sensitive to the toxicity of epyrifenacil than are rodents, although further mechanistic research is highly anticipated.

Effects of species differences on oocyte regulation of granulosa cell function

Effects of species differences on oocyte regulation of granulosa cell function

Effects of species differences on oocyte regulation of granulosa cell function

The aims were to investigate whether oocyte-secreted growth factors from a high (i.e. rat) and low (i.e. sheep) ovulation rate species could stimulate (3)H-thymidine incorporation in granulosa cells (GC) from antral follicles from the same or across species. Denuded oocytes (DO) were co-incubated with GC with or without specific antibodies to growth differentiating factor 9 (GDF9) or bone morphogenetic protein 15 (BMP15). Co-incubations of DO-GC from the same or across species significantly increased thymidine incorporation in GC with increasing numbers of DO. GDF9 immuno-neutralisation reduced thymidine incorporation in rat GC co-incubated with either rat or ovine DO and in ovine GC co-incubated with ovine or rat DO. BMP15 immuno-neutralisation only reduced thymidine incorporation when ovine DO were co-incubated with either ovine or rat GC. Western blotting of oocytes co-incubated with GC identified GDF9 and BMP15 proteins for sheep and GDF9 protein for rats in oocyte lysates and incubation media. With respect to rat BMP15, a promature protein was identified in the oocyte lysate but not in media. Expression levels of GDF9 relative to BMP15 mRNA in DO co-incubated with GC were highly correlated (R (2)=0.99) within both species. However, the expression ratios were markedly different for the rat and sheep (4.3 vs 1.0 respectively). We conclude that during follicular development, rat oocytes secrete little, if any, BMP15 and that GDF9 without BMP15 can stimulate proliferation of rat and ovine GC. In contrast, ovine oocytes secrete both BMP15 and GDF9, and both were found to stimulate proliferation in ovine and rat GC.

Effects of root architecture, physical tree characteristics, and soil shear strength on maximum resistive bending moment for overturning Salix babylonica and Juglans ailanthifolia

Effects of root architecture, physical tree characteristics, and soil shear strength on overturning moment due to flooding were investigated using Salix babylonica and Juglans ailanthifolia, exotic and invasive plants in Japanese rivers. Tree-pulling experiments that simulated flood action were conducted, and the resulting damage was examined to assess the effects of physical tree characteristics and root architecture on the maximum resistive bending moment (M max) for overturning. In situ soil shear strength tests were conducted to measure soil strength parameters. The effects of species differences on the M max were examined by analyzing root architecture. S. babylonica has a heart-root system that produces a greater overturning moment due to the strong root anchorage and the large amount of substrate that must be mobilized during overturning. J. ailanthifolia has a plate-root system that produces a smaller overturning moment. However, trees with the plate-root system may withstand overturning better due to an increased root:shoot ratio. The results of the study show that the M max of a tree for overturning had significant (P < 0.05) correlations with a tree’s physical characteristics, including height (H), trunk diameter at breast height (D bh), D bh 2 , height multiplied by the second power of D bh (trunk volume index H × D bh 2 ), and root–soil plate depth (R d), and root–soil plate radius (R r). Considering the strategy of J. ailanthifolia to increase the root:shoot ratio for anchoring in the substrate, the trunk volume index (H × D bh 2 ) is a better parameter than D bh 2 because it indirectly involves the difference in below-ground volume and surface area. Different soil cohesion values were found at different experimental sites, and the average M max for overturning each species decreased linearly with increasing soil cohesion.

Tropical tree species composition affects the oxidation of dissolved organic matter from litter

Plant species effects on soil nutrient availability are relatively well documented, but the effects of species differences in litter chemistry on soil carbon cycling are less well understood, especially in the species-rich tropics. In many wet tropical forest ecosystems, leaching of dissolved organic matter (DOM) from the litter layer accounts for a significant proportion of litter mass loss during decomposition. Here we investigated how tree species differences in soluble dissolved organic C (DOC) and nutrients affected soil CO2 fluxes in laboratory incubations. We leached DOM from freshly fallen litter of six canopy tree species collected from a tropical rain forest in Costa Rica and measured C-mineralization. We found significant differences in litter solubility and nutrient availability. Following DOM additions to soil, rates of heterotrophic respiration varied by as much as an order of magnitude between species, and overall differences in total soil CO2 efflux varied by more than four-fold. Variation in the carbon: phosphorus ratio accounted for 51% of the variation in total CO2 flux between species. These results suggest that tropical tree species composition may influence soil C storage and mineralization via inter-specific variation in plant litter chemistry.

Effects of N‐supply on the rates of photosynthesis and shoot and root respiration of inherently fast‐ and slow‐growing monocotyledonous species

Are there intrinsic differences in the rates of photosynthesis, shoot‐ and root‐respiration between inherently fast‐ and slow‐growing monocotyledons at high and low nitrogen supply? To analyze this question we grew 5 monocotyledons, widely differing in their inherent relative growth rate at high and low nitrogen supply in a growth room. Nitrate was exponentially added to the plants, enabling us to compare inherent differences in plant characteristics, without any effect of species differences in the ability to take up nutrients.At high nitrogen supply, the fast‐growing species from productive habitats had a higher photosynthetic nitrogen use efficiency and rate of root respiration than the slow‐growing ones from unproductive habitats. Only minor differences were observed in their rates of photosynthesis and shoot respiration per unit leaf area. At low nitrogen supply, the rates of photosynthesis and shoot‐ and root respiration decreased for all species, even though there were no longer any differences in these processes between inherently fast‐ and slow‐growing species. The photosynthetic nitrogen use efficiency increased for all species, and no differences were found among species.Differences in the photosynthetic nitrogen use efficiency among species and nitrogen treatments are discussed in terms of the utilization of the photosynthetic apparatus, whereas differences in respiration rate are discussed in terms of the energy demand for growth, maintenance and ion uptake and their related specific respiratory energy costs. It is concluded that the relatively high abundance of slow‐growing species compared to fast‐growing ones in unproductive habitats is unlikely to be explained by differences in rates of photosynthesis and respiration or in photosynthetic nitrogen use efficiency.

Effect of species differences and dietary vitamin C on the concentration of ascorbate- and acid-soluble thiol in fish eye

Data presented confirm the essentiality of modification of the dinitrophenylhydrazine (DNPH) method to analyze the total ascorbic acid and dehydroascorbic acid in ocular tissues and stress the need of corrections for the interfering substances. Variations in ascorbate and thiol concentrations in the lens, retina and aqueous humour of freshwater fish belonging to the Cyprinidae family were examined. The interspecific variability of ascorbate concentration was highest in the aqueous humour and lowest in the retina. The high ascorbate concentration in the retina seems to reflect the importance of the sense of vision in fish life-style as compared to chemo- and acoustico lateralis senses. The regional distribution of the total ascorbate is in the order of decreasing concentrations: retina, lens and aqueous humour. However, the retinal ascorbate is almost exclusively in the oxidized form, and the lenticular ascorbate is almost exclusively in the reduced form. Thiol concentration in the lens is five- to tenfold that in the retina and aqueous humour. This explains the oxidation status of ascorbate in different eye compartments of the eye. After 30 days on diets containing various levels of ascorbic acid or ascorbic acid sulphate, the ascorbate concentration in the eye compartments of common carp ( Cyprinus carpio L.) was determined. Ocular tissue can be used to monitor the development of the ascorbate status in fish, and the retina is the most responsive tissue to the enhanced or depleted ascorbate levels.

EFFECT OF SPECIES DIFFERENCES OF MICE ON THE BIO-ASSAY OF THYROTROPIN.

The McKenzie bio-assay for TSH was modified to permit the handling of large numbers of mice and the consequent analysis of many samples during a single assay run. An attempt was made to find a strain of mice significantly more sensitive to TSH than the Swiss-Webster albino (SWA) animals normally used. Twenty-two strains of inbred mice and 2 strains of deer mice (Peromyscus maniculalus) were tested. The results of the assays of the various strains of animals were computed with the aid of a digital computer. The relation between the logarithm of the responses to TSH and the doses of TSH was found to be the most useful index. The deer mice were insensitive to the doses of TSH used. Although some of the strains of inbred mice were found to be significantly more sensitive to TSH than the SWA controls, in no case was the increased sensitivity of the inbred mice sufficient to increase the usefulness of the assay. (Endocrinology 76: 890, 1965)