Extinct Beringian wolf morphotype found in the continental U.S. has implications for wolf migration and evolution

Pleistocene diversity was much higher than today, for example there were three distinct wolf morphotypes (dire, gray, Beringian) in North America versus one today (gray). Previous fossil evidence suggested that these three groups overlapped ecologically, but split the landscape geographically. The Natural Trap Cave (NTC) fossil site in Wyoming, USA is an ideally placed late Pleistocene site to study the geographical movement of species from northern to middle North America before, during, and after the last glacial maximum. Until now, it has been unclear what type of wolf was present at NTC. We analyzed morphometrics of three wolf groups (dire, extant North American gray, Alaskan Beringian) to determine which wolves were present at NTC and what this indicates about wolf diversity and migration in Pleistocene North America. Results show NTC wolves group with Alaskan Beringian wolves. This provides the first morphological evidence for Beringian wolves in mid‐continental North America. Their location at NTC and their radiocarbon ages suggest that they followed a temporary channel through the glaciers. Results suggest high levels of competition and diversity in Pleistocene North American wolves. The presence of mid‐continental Beringian morphotypes adds important data for untangling the history of immigration and evolution of Canis in North America.     

Hoechst 33342 staining of mouse bone marrow: effects on colony-forming cells

We have systematically studied the effect on hemopoietic colony-forming cells of staining cellular DNA with the bisbenzimidazole dye, Hoechst 33342. Mouse bone marrow cells could be adequately stained in a 30-60 min incubation with a 5 microM concentration of stain. Flow-cytometric analysis of stained cells provided cell distributions with coefficients of variation for the G1 peaks of 6% or less under these conditions. We found considerable heterogeneity among hemopoietic colony-forming cells with respect to the toxicity of the dye. Toxicity in the proliferatively quiescent stem cell population was not changed when the population became proliferatively active. In the sequence of most sensitive to least sensitive, the five progenitors studied could be arranged as follows: CFU-M, a megakaryocyte colony-forming cell; CFU-E, a relatively differentiated erythroid precursor; BFU-E, a primitive erythroid precursor; CFU-GM, a granulocyte-macrophage precursor; and CFU-S, the spleen colony-forming cell or hemopoietic stem cell. A staining procedure involving a 30-min exposure to 5 microM Hoechst 33342 provided optimal staining and no loss in four of the five progenitor populations; the CFU-M population was diminished by about 50%. We conclude that Hoechst can be regarded as a vital DNA stain for most bone marrow precursor populations, including the hemopoietic stem cell.     

The effects of cyanide on intracellular ionic exchange in ferret and rat ventricular myocardium

The effects of cyanide on Ca2+ exchange in isolated ventricular myocytes and on the intracellular concentrations of Ca2+, Na+ and H+ have been investigated to assess the contribution that mitochondria might play in cellular Ca2+ metabolism. Ionic levels were measured with ion-selective electrodes. KCN (2.5 mM) inhibited a component of Ca2+ exchange in myocytes that could be attributed to mitochondrial exchange, but was without effect on non-mitochondrial Ca2+ exchange. NaCN (2.5 mM) caused a transient reduction of [H+]i, [Na+]i and [Ca2+]i when applied to the superfusate bathing ventricular trabeculae or papillary muscles. The transient changes of [Na+]i were accentuated when the preparation was exposed to a solution which would be expected to increase the cellular calcium content. The reduction of [Na+]i which accompanies a reduction of the extracellular sodium concentration, [Na]o, was attenuated in the presence of NaCN, but the intracellular acidosis resulting from a reduction of [Na]o was unaffected by NaCN. A small, but significant, rise of [Ca2+]i accompanied a reduction of [Na]o but only when NaCN was present in the superfusate. It is concluded that cyanide ions have a reasonably specific action on cardiac cellular ionic metabolism. Its primary action is to prevent mitochondrial Ca2+ sequestration. It is postulated that a Na+/H+ exchange, possibly at the sarcolemma, could account for some of the changes to sarcoplasmic ionic levels observed. In a solution of low [Na]o, it is concluded that mitochondria could sequester at least 30% of the calcium accumulated by the cell even though the sarcoplasmic [Ca2+] does not exceed 0.3 microM.     

A mathematical model for the growth of bacterial microcolonies on marine sediment

Counts of bacterial microcolonies attached to deep-sea sediment particles showed 4-, 8-, 16-, and 32-celled microcolonies to be very rare. This was investigated with a mathematical model in which microcolonies grew from single cells at a constant growth rate (), detached from particles at constant rate (), and reattached as single cells. Terms for attachment of foreign bacteria (a) and death of single cells (d) were also included. The best method of fitting the model to the microcolony counts was a weighted least-squares approach by which(0.83 hour^–1) was estimated to be about 20 times greater than(0.038 hour^–1). This showed that the bacteria were very mobile between sediment particles and this mobility was explained in terms of attachment by reversible sorption. The implications of the results for the frequency of dividing cell method for estimating growth rates of sediment bacteria are discussed. The ratio of and was found to be very robust both in terms of the errors associated with the microcolony counts and the range of microcolony sizes used to obtain the solution.     

Determination of intracellular potassium ion concentration in isolated rat ventricular myocytes

The sarcoplasmic potassium concentration of a suspension of rat ventricular myocytes, prepared by collagenase-induced disruption of the myocardial mass, was determined by a null-point technique. Addition of digitonin resulted in a release of potassium from the cells which was interpreted as a flux from the sarcoplasm. The intracellular potassium concentration was estimated to be 113 +/- 6mM.     

The use of agarose wedge-gel electrophoresis for resolving both small and large naturally occurring plasmids

A wedge-shaped, horizontal agarose gel gave better electrophoretic resolution of both large and small plasmids than conventional linear gels. The wedge-gel increased mobility and separation of the larger plasmids whilst retarding the mobility of the smaller plasmids and tightening the bands. The linearity of the relationship between log₁₀ molecular size and log₁₀ relative mobility, for a range of plasmids from 2.1 to 221 kb, was increased. Therefore, estimations of plasmid sizes are more accurate using a wedge-gel than with conventional gels.     

Sulfate-dependent iron oxidation by Thiobacillus ferrooxidans: characterization of a new EPR detectable electron transport component on the reducing side of rusticyanin

Iron(II) oxidation by pH 2.5 HCl-washed cells of Thiobacillus ferrooxidans is known to be sulfate dependent. Sulfate dependence of the autooxidation of a novel component in the electron transport pathway is demonstrated. This component exhibits an electron paramagnetic resonance (EPR) signal in the oxidized state at g = 2.005 distinguishable from the g = 2.08 signal attributed to rusticyanin. The novel component is proposed to be a three-iron-sulfur cluster based upon the g value, lineshape, and temperature dependence. Oxyanion specificity for the EPR signal has the same dependence on sulfate as does iron(II) oxidation. By using azide to inhibit electron transfer to oxygen, sulfate was shown to be involved in electron transfer from the g = 2.005 component to the copper of rusticyanin.     

The role of respiration during adaptation of the freshwater cyanobacterium Synechococcus 6311 to salinity

Growth of the freshwater cyanobacterium Synechococcus 6311 under saline conditions stimulated respiration tenfold during the first 24 h, while growth and photosynthesis were inhibited. The elevated respiration rate was seen under both light and dark conditions, was uncoupler and cyanide sensitive, and did not decrease upon salt removal. Membrane preparations from salt-grown cells exhibited a tenfold increase in cytochrome oxidase activity, while electron transfer rates from NADPH to cytochrome c only increased threefold. Cytochrome oxidase activities were correlated with levels of EPR detectable Cu2+ in the salt and control membranes. Sodium-driven proton (antiproter) gradients in salt-grown cells were sensitive to cyanide but not dicyclohexylcarbodiimide, indicating the direct role of respiratory electron transport in maintaining low intracellular sodium levels.     

Proposal of a ‘hot lock’ as a barrier to fish invasion: an afterthought

Environmental Biology of Fishes -