Effects of amiloride on calcium uptake by myocytes isolated from adult rat hearts

Amiloride at high concentrations inhibits the uptake of Ca by rat heart myocytes containing elevated levels of intracellular Na and retards the development of Ca-dependent hypercontracture in these cells. In contrast, amiloride enhances the net uptake of Ca in Ca-tolerant myocytes containing normal levels of Na. The results suggest that amiloride may inhibit Na-Ca exchange across the sarcolemma of cardiac myocytes.     

Acdidophilic thermophilic archaebacteria: Potential application for metals recovery

Abstract The acidophilic thermophilic archaebacteria Sulfolobus and Acidianus have the potential for applid use in the recovery of metal values from ores through the process of baterial leaching. These microbes readily adapt to the conditions of low pH and high concentrations of metals required for bacterial leaching. In addition, these archaebacteria can exist at high temperatures which can occur during the oxidation of metal sulfides in bioleaching reactors. The acidophilic of copper and molybdenum from chalcopyrite and molybdenite minerals, respectively. The microbes can also enhance the recovery of gold by oxidation of pyrite which occludes gold preventing recovery by standard metallurgical procedures. The ability of this group of microbes to facilitate metals recovery is yet to be developed on a commercial scale.     

Magnesium transport by mitochondria

The pathways for the uptake and extrusion of Mg²⁺ by mitochondria are not well defined. the present evidence suggests that uptake occurs by nonspecific diffusive pathways in response to elevated membrane potential. There is disagreement as to some of the properties of Mg²⁺ efflux from mitochondria, but the reaction resembles K⁺ efflux in many ways and may occur in exchange for H⁺. Matrix free magnesium ion concentration, [Mg²⁺], can be measured using fluorescent probes and is set very close to cytosol [Mg²⁺] by a balance between influx and efflux and by the availability of ligands, such as P_i. There are indications that matrix [Mg²⁺] may be under hormonal control and that it contributes to the regulation of mitochondrial metabolism and transport reactions.     

The evolving role of preprints in the dissemination of COVID-19 research and their impact on the science communication landscape

The world continues to face a life-threatening viral pandemic. The virus underlying the Coronavirus Disease 2019 (COVID-19), Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has caused over 98 million confirmed cases and 2.2 million deaths since January 2020. Although the most recent respiratory viral pandemic swept the globe only a decade ago, the way science operates and responds to current events has experienced a cultural shift in the interim. The scientific community has responded rapidly to the COVID-19 pandemic, releasing over 125,000 COVID-19–related scientific articles within 10 months of the first confirmed case, of which more than 30,000 were hosted by preprint servers. We focused our analysis on bioRxiv and medRxiv, 2 growing preprint servers for biomedical research, investigating the attributes of COVID-19 preprints, their access and usage rates, as well as characteristics of their propagation on online platforms. Our data provide evidence for increased scientific and public engagement with preprints related to COVID-19 (COVID-19 preprints are accessed more, cited more, and shared more on various online platforms than non-COVID-19 preprints), as well as changes in the use of preprints by journalists and policymakers. We also find evidence for changes in preprinting and publishing behaviour: COVID-19 preprints are shorter and reviewed faster. Our results highlight the unprecedented role of preprints and preprint servers in the dissemination of COVID-19 science and the impact of the pandemic on the scientific communication landscape.

An analysis of bioRxiv and medRxiv during the first 10 months of the COVID-19 pandemic reveals that the pandemic has resulted in a cultural shift in the use of preprints for disseminating pandemic-related science.     

Depth-dependent swimbladder compression in herring Clupea harengus observed using magnetic resonance imaging

Changes in swimbladder morphology in an Atlantic herring Clupea harengus with pressure were examined by magnetic resonance imaging of a dead fish in a purpose-built pressure chamber. Swimbladder volume changed with pressure according to Boyle's Law, but compression in the lateral aspect was greater than in the dorsal aspect. This uneven compression has a reduced effect on acoustic backscattering than symmetrical compression and would elicit less pronounced effects of depth on acoustic biomass estimates of C. harengus .     

Differentiation of muscle fiber types in aneurogenic brachial muscles of the chick embryo

Cross-reinnervation studies performed ex ovo with newly hatched chicks demonstrate that peripheral motor neurons control the phenotypic characteristics of avian muscles. The present experiments were designed to determine whether or not nerves play a similar role during the initial expression of muscle fiber types. Previous experiments indicated that differentiation of specific fiber types occurs during the first week of embryogenesis, temporally coincident with the penetration of nerves within muscle masses. These observations suggested that peripheral nerves may be associated with the initial differentiation of fiber types. To test this hypothesis directly, anterior limb buds of the chick embryo were rendered aneurogenic by deletion of the brachial segment of the neural tube. To ensure a completely aneurogenic environment for developing brachial muscles, surgery was performed at day 2 in ovo before the exit of ventral root fibers. Experimental and control embryos from Stage (St) 25 (4.5 d) through St 45 (19d) were analyzed histochemically by a silver-cholinesterase reaction to detect nerves and by the myosin ATPase reaction, following alkali and acid preincubation, to determine the fiber type composition of the muscles. In addition, the total volume of aneurogenic and control muscles was compared. Results demonstrate that the characteristic myosin ATPase profiles of individual aneurogenic and innervated (control) muscles were identical throughout the entire period analyzed. Therefore, we conclude that these enzymic profiles are endogenously expressed and are not under neuronal control during early embryogenesis. Furthermore, the entire sequence of events from the migration of myogenic cells to the anterior limb bud through the division of the primary muscle masses to form individual brachial muscles proceeded on schedule in the absence of nerves. Since the growth of aneurogenic muscles was impaired, we conclude that during embryogenesis peripheral motor nerves are necessary initially for the proper growth of muscles and ultimately, for their survival. They are not involved, however, with either the initial formation or initial differentiation of individual brachial muscles.     

Ruthenium red-induced loss of matrix K+ from uncoupled heart mitochondria

Ruthenium red induces the loss of endogenous K⁺ from isolated beef heart mitochondria treated with an uncoupler. This induction of K⁺ loss occurs at the same ruthenium red titer as the inhibition of the Ca²⁺-uniporter. This raises the possibility that ruthenium red may alter the Ca²⁺-uniporter in such a way as to produce a K⁺-conducting channel.