Analysis of ligand binding curves in terms of species fractions

The ligand binding curve for a macromolecular system presents the average number or ligand molecules bound per macromolecule as a function of the chemical potential or the logarithm of the ligand concentration. We show that various observable properties of this curve, for example its asymptotes and derivatives, are expressible in terms of linear combinations of the mole fractions α_i of macromolecules binding i molecules of ligand. Whenever enough such properties of the binding curve are known, the linear equations in α_i can be solved to give the mole fractions of each of the various macromolecular species. An application of these results is that a Hill plot for hemoglobin-ligand equilibrium where the asymptotes approach unit slope can be made to yield the four Adair constants by a simple algebraic method. A second use is that a knowledge of the first and second derivatives of the binding curve at points along the curve can yield the species fractions as functions of the degree of saturation without direct knowledge of the ligand binding constants. These methods are illustrated by some numerical examples.     

Modelling growth of brown trout, Salmo trutta, in terms of weight and energy units

1. The chief objectives were: (i) to compare two growth models, one based on weight and the other on energy, using the same data set for the analyses; (ii) to discover if weight and energy units can be simply interchanged for growth assessment. The data set was for 183 brown trout, Salmo trutta (live weight 1–300 g), fed to satiation on shrimps, Gammarus pulex, and grown individually over 42 days at constant temperatures (range 3.8–20.4 °C). 2. Rates of change in weight or energy content, and final weight or energy content at the end of 42 days growth, were estimated from the models and were excellent fits to the experimental data (P < 0.001). The shape of the temperature relationship for rates of change or final values was triangular for the weight model and curvilinear for the energetics model. Optimum temperatures for growth according to the weight and energetics models were 13.1 and 13.9 °C, respectively, for rates of change and 13.1 and 13.5 °C, respectively, for final values. When the growth period was extended to 100 and then 300 days, the triangular relationship and optimum temperature remained the same for the weight model, but the curvilinear relationship became more triangular for the energetics model and the optimum temperature identical to that in the weight model. The relationship between gross efficiency and temperature also differed in shape between the two models but maximum efficiencies occurred at a similar value of 9 ± 0.1 °C (18 and 32% for weight and energetics models). As fish weight increased, gross efficiency remained constant in terms of energy units, but decreased markedly in terms of weight. 3. These comparisons showed that different conclusions can be drawn from the two models, even if the same data set was analysed. There was a close relationship between initial wet weight and energy content for stock trout used in the experiments, but the relationship was not so close at the end of the experiments, and interchangeability of units could no longer be assumed. A variable error, often as high as 10–12%, would occur if the relationship for initial values was used to predict one unit from the other. Therefore, weight and energy units cannot be simply interchanged for growth assessment, especially in comparisons for trout of different sizes.     

Chylomicron metabolism. Chylomicron uptake by bone marrow in different animal species

Previously it was shown in rabbits that 20-40% of the injected dose of chylomicrons was cleared from the plasma by perisinusoidal bone marrow macrophages. The present study was undertaken to determine whether the bone marrow of other species also cleared significant amounts of chylomicrons. Canine chylomicrons, labeled in vivo with [14C]cholesterol and [3H] retinol, were injected into marmosets (a small, New World primate), rats, guinea pigs, and dogs. Plasma clearance and tissue uptake of chylomicrons in these species were contrasted with results obtained in rabbits in parallel studies. The chylomicrons were cleared rapidly from the plasma in all animals; the plasma clearance of chylomicrons was faster in rats, guinea pigs, and dogs compared with their clearance from the plasma of rabbits and marmosets. The liver was a major site responsible for the uptake of these lipoproteins in all species. However, as in rabbits, the bone marrow of marmosets accounted for significant levels of chylomicron uptake. The uptake by the marmoset bone marrow ranged from one-fifth to one-half the levels seen in the liver. The marmoset bone marrow also took up chylomicron remnants. Perisinusoidal macrophages protruding through the endothelial cells into the marrow sinuses were responsible for the accumulation of the chylomicrons in the marmoset bone marrow, as determined by electron microscopy. In contrast to marmosets, chylomicron clearance by the bone marrow of rats, guinea pigs, and dogs was much less, and the spleen in rats and guinea pigs took up a large fraction of chylomicrons. The uptake of chylomicrons by the non-human primate (the marmoset), in association with the observation that triglyceride-rich lipoproteins accumulate in bone marrow macrophages in patients with type I, III, or V hyperlipoproteinemia, suggests that in humans the bone marrow may clear chylomicrons from the circulation. It is reasonable to speculate that chylomicrons have a role in the delivery of lipids to the bone marrow as a source of energy and for membrane biosynthesis or in the delivery of fat-soluble vitamins.     

Same habitat,different species: otolith microchemistry relationships between migratory and resident species support interspecific natal source classification

We tested the hypothesis that otolith trace elemental signatures (microchemistries) of mottled sculpin Cottus bairdi, slimy sculpin C. cognatus, and juvenile coho salmon Oncorhynchus kisutch were predictive of those of juvenile steelhead O. mykiss across many sites within the Lake Michigan basin. Laser ablation inductively coupled plasma mass spectrometry was used to generate otolith microchemistry signatures for each individual fish. For each species pair, statistical correlations of mean otolith concentrations of Mg, Mn, Cu, Zn, Sr, Ba, and Pb for each site were estimated. Linear equations describing these relationships were used to transform juvenile steelhead otolith microchemistry data to those of each of the other species. Transformed otolith microchemistry data were subjected to random forest classifications developed for mottled sculpin, slimy sculpin, and juvenile coho salmon to assess interspecific natal source assignment accuracies. Steelhead otolith concentrations of Sr were significantly correlated with those of each of the other species, whereas otolith concentrations of Ba and Mn were significantly correlated among some species pairs, but not others. Natal source assignment accuracies of juvenile steelhead to site and watershed generally decreased when otolith microchemistry data were transformed to those of mottled sculpin, slimy sculpin, and coho salmon. Miss-assigned fish often classified into nearby watersheds within larger hydrologic units, leading to higher assignment accuracies at coarser geographical resolutions (75–97% correct assignment to hydrologic unit for each species). These findings suggest that applications of otolith microchemistry data may extend beyond the species from which they are collected.     

Molecular basis of COVID-19 relationships in different species: a one health perspective

Outside the Hubei province, China, the mild form of infection and the progressive recover of the COVID-19 patients suggest the intervention of “unconventional” biological mechanisms worthy of attention. Based on the high-homology between the Spike protein epitopes of taxonomically-related coronaviruses, we hypothesized that past contact with infected dogs shield humans against the circulating SARS-CoV-2. Elseways, the recurrent virus exposure over a short time-lapse might result in the Antibody Dependent Enhancement, triggering the violent immune reaction responsible for the severe clinical outcomes observed in the Hubei province. Nevertheless, further experimental studies are desired for a confidential evaluation of the postulated hypotheses.     

Length and weight relationships of five different fish species from northern areas of Pakistan

In present study five different species were studied from three different rivers from northern Pakistan. Specimens were collected in the period of January to December 2017 using cast nets (10–12 mm mesh size) for Barilius, Glyptothorax and Schistura species while cast nets (mesh size 1.25 × 1.25 cm) used for Schizothorax species. Total length (TL) and fork length (FL) to the nearest 0.1 cm and body weight (BW) to the nearest 0.1 g were recorded for each individual.     

Invading species in the Eel River, California: successes, failures, and relationships with resident species

We examined invasions of non-native fishes into the Eel River, California. At least 16 species of fish have been introduced into the drainage which originally supported 12–14 fish species. Our study was prompted by the unauthorized introduction in 1979 of Sacramento squawfish, Ptychocheilus grandis, a large predatory cyprinid. From 1986 to 1990, we conducted growth and diet studies of squawfish, conducted intensive surveys of the distribution and habitat associations of both native and introduced species, and examined the nature of species-habitat and interspecies relationships. We found no evidence for increased growth or expanded feeding habits, compared to native populations, of Sacramento squawfish as they invaded the Eel River drainage. Ten of the introduced species were well established, with four species limited to a reservoir and six species established in streams. The success or failure of introductions of stream species appeared to be a function of the ability of a species to survive the fluctuating, highly seasonal, flow regime. The present mixture of native and exotic species has not formed stable fish assemblages but it seems likely that four habitat-associated assemblages will develop. The overall effect of the successful species introductions has been to assemble a group of species, with some exceptions, that are native to and occur together in many California streams. The assemblages now forming are similar to those found in other California streams. The assemblage characterized by squawfish and suckers is likely to be resistant to invasion, in the absence of human caused habitat modifications.     

Analysis of genome-specific sequences inPhleum species: Identification and use for study of genomic relationships

Sau3AI shot gun cloning and colony hybridization with total genomic probes were used to isolate genome-specific sequences inPhleum species. The total DNA isolated from diploid speciesP. alpinum andP. bertolonii was partially digested withSau3AI and cloned using pUC19 as a vector to anE. coli strain DH5mcr. A partial genomic DNA library consisting of 3030 colonies for the genome ofP. alpinum and one consisting of 3240 colonies for the genome ofP. bertolonii were constructed. Twelve hundred and thirty colonies from the DNA library ofP. alpinum and 1320 from that ofP. bertolonii were respectively blotted to membrane filters and hybridized to the total genomic probes from these two species. Eight clones specific toP. alpinum and 13 specific toP. bertolonii were isolated through colony hybridization and further dot-blot hybridization. Most of these clones may carry highly or moderately repetitive sequences. Three sequences specific toP. alpinum and 3 specific toP. bertolonii were used as probes to hybridize theEcoRI-digested DNA samples from four species,P. alpinum,P. bertolonii,P. pratense andP. montanum, on Southern blot. The results from these hybridization experiments showed that all 3P. bertolonii-specific probes and 2 of the 3P. alpinum-specific probes hybridized to the DNA ofP. pratense, thus confirming the conclusion of the close relationships between the cultivated timothy and its two wild relatives that was drawn in our previous study using the C-banding technique.