A comparison of the effects of cationic, anionic, and neutral amphipathic agents on the contractile behaviour of frog skeletal muscle. I. Twitches and potential threshold for contraction

Cationic, anionic, and neutral amphipathic agents displayed striking differences as well as similarities in their effects on the contractile function of frog skeletal muscle. Slowed repolarization during the action potential appeared to account for twitch potentiation by low concentrations of alkyl trimethylammonium and by small n-alkanols (propanol, butanol). Small n-alkanols also caused a decrease in the potential threshold for K contractures and slower relaxation of submaximum K contractures as well as enhancement of chloride withdrawal and caffeine contractures, but these effects were not observed with larger alkanols. For the ionic amphipathic agents, the direction of the changes in the relation between Ko and K-contracture tension could be accounted for on the basis of the expected changes in surface charge, but the effects of these two types of agents on the rate of relaxation of submaximum K contractures were disproportionate and with the cationic series were opposite in direction to those produced by inorganic divalent cations. The reductions in the amplitude of chloride-withdrawal contractures by cationic as well as anionic amphipaths indicated that both types of agents can impair excitation-contraction coupling. Similar depressant effects on caffeine contractures demonstrate that these responses also can be influenced by events restricted to the external lamina of the sarcolemma. It is concluded that opposite effects can be produced by similar perturbations in different regions of the sarcolemma and that electrostatic as well as hydrophobic interactions can make an important contribution to the effects of amphipathic agents on twitches and contractures in skeletal muscle.     

Effect of dietary fish oil on mouse testosterone level and the distribution of eicosapentaenoic acid-containing phosphatidylcholine in testicular interstitium

Low levels of serum testosterone are characteristically associated with diabetes, coronary atherosclerosis, obstructive sleep apnea, rheumatoid arthritis, and chronic obstructive pulmonary disease. Testosterone replacement therapy is effective against many of these disorders, indicating the importance of maintaining a healthy testosterone level. In this study, we investigated the effects of fish oil on murine testosterone metabolism and analyzed the dynamics of relevant lipids in testes by matrix-assisted laser desorption ionization mass spectrometry imaging. Testosterone was upregulated in mice that received fish oil. In the testicular interstitium, eicosapentaenoic acid-containing phosphatidylcholine was distributed characteristically. These data suggest that eicosapentaenoic acid is involved in testosterone metabolism.     

Electrical pacing in the gastroduodenal junction area of conscious dogs (author's transl)]

To determine whether the electric activities of the stomach and duodenum are related, the gastroduodenal junction area of the stomach of dogs was paced through implanted bipolar silver electrodes. It was found that the pacing rate of the basic electrical rhythm (BER) in the antrum of the stomach could be increased to a maximum of 8.9 cycles/min, without affecting the BER frequency in the duodenum. Conversely when the pacing rate of the BER in the duodenum was increased to a maximum of 24 cycles/min, the BER frequency in the antrum remained unaffected. These results show that the BER in the stomach and duodenum are independent, and imply that the BER cycles in the stomach and duodenum are due to the presence of two independent pace-maker areas.     

Pathogenesis of Hand-Foot Syndrome induced by PEG-modified liposomal Doxorubicin

PEGL-DOX is an excellent treatment for recurrent ovarian cancer that rarely causes side-effects like cardiotoxicity or hair loss, but frequently results in Hand-Foot Syndrome (HFS). In severe cases, it can become necessary to reduce the PEGL-DOX concentration or the duration of the drug therapy, sometimes making it difficult to continue treatment. In this study, we prepared an animal model to compare the effects of DOX versus PEGL-DOX, and we noticed that only treatment with PEGL-DOX resulted in HFS, which led us to conclude that extravasation due to long-term circulation was one of the causes of HFS. In addition, we were able to show that the primary factor leading to the skin-specific outbreaks in the extremities was the appearance of reactive oxygen species (ROS) due to interactions between DOX and the metallic Cu(II) ions abundant in skin tissue. ROS directly disturb the surrounding tissue and simultaneously induce keratinocyte-specific apoptosis. Keratinocytes express the thermoreceptor TRPM2, which is thought to be able to detect ROS and stimulate the release of chemokines (IL-8, GRO, Fractalkine), which induce directed chemotaxis in neutrophils and other blood cells. Those cells and the keratinocytes then undergo apoptosis and simultaneously release IL-1β, IL-1α, and IL-6, which brings about an inflammatory state. In the future, we plan to develop preventative as well as therapeutic treatments by trapping the ROS.     

Contributions of large wood to the initial establishment and diversity of riparian vegetation in a bar-braided temperate river

The purpose of this study was to examine the effects of large wood (LW) on the physical environment and the initial establishment of vascular plant species in the Rekifune River, a large bar-braided monsoonal river in Japan. The physical environment and the diversity and composition of plant species were compared in relation to the orientation of LW pieces. We found that shading effects were more prevalent in the immediate vicinity of LW pieces than in quadrats distant from LW. The effect was especially strong at the center of LW jams (the “jam center”). Fine sand and silt were concentrated in the quadrats downstream from the LW pieces. In contrast, cobbles dominated the upstream quadrats. The highest diversity was found in the jam center, while intermediate values were observed in the quadrats surrounding LW. Indicator species analysis detected 21 indicator species only in the jam center. The LW jams favored the deposition of plant fragments and sediment and created shaded areas within and around the structures. Buried seeds may be transported with LW during a flood, and seeds dispersed by wind and stream flows may be trapped by the complex structure of LW jams. The specific environmental conditions and the trapping of seeds and plant fragments result in the early establishment of mid-successional tree species at LW jams. In conclusion, the LW pieces deposited on gravel bars altered the light and substrate conditions and thereby provided specific safe sites for various riparian plant species.     

Mammal assemblages recorded by camera traps inside and outside the evacuation zone of the Fukushima Daiichi Nuclear Power Plant accident

In 2011, the Fukushima Daiichi Power Plant accident resulted in the evacuation of about 81,000 people from the evacuation zone, which suffered from high levels of radioactive contamination. Large-scale and long-term land abandonment can cause changes in species assemblages. Despite the extensive global attention this incident received, open and spatially-explicit datasets of mammal fauna from Fukushima remain quite limited. We established a continuous monitoring protocol using camera traps for mammals both inside and outside the evacuation zone; this paper presents our first dataset. These data represent the monitoring results from 45 camera traps from May 2014 to October 2014, including the location and actuation time of each camera, and the list of video records. After the publication of this initial data paper, we intend to continue monitoring until 2023 and the dataset will be hereafter updated with new observations.     

Retarded recovery of excitability and twitches of frog toe muscles after K-induced depolarization (slow inactivation) in the presence of alkyl amphipaths

Alkyl amphipaths resemble conventional local anesthetics in their ability to retard the recovery of excitability and twitch tension after depolarization at high Ko, an effect that is attributed to slow inactivation of potential-dependent sodium channels. The similar effect of low temperature offers an explanation for its ability to enhance the frequency-dependent effects of these agents.