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Normal vertebrate development requires appropriate amounts of Vitamin A and retinoic acid (RA), yet exogenously supplied Vitamin A metabolites cause teratogenic effects. All-trans retinoic acid (all-trans RA) and 9-cis retinoic acid (9-cis RA) are potent metabolites of Vitamin A and operate by binding to retinoic acid receptors that are transcription factors. These isomers directly affect gene expression by the binding of all-trans RA or 9-cis RA to retinoic acid receptors (RARs) and the binding of 9-cis RA to retinoid X receptors (RXRs). In zebrafish, exogenous application of the retinoid isomers is known to have deleterious effects of varying magnitudes on development; however, little is known about the comparative effects of 9-cis and all-trans RA on the development of Japanese killifish (Oryzias latipes) embryos. In this study, we report the effects of exposing neurula embryos to concentrations of retinoids ranging from one micromolar to one nanomolar for 72 hours. The data indicate a dose-dependent inhibition of hatching irrespective of the retinoid isomer used. In addition, heart formation and cranial structure development are inhibited in a dose-dependent manner with both all-trans and 9-cis RA. Concentrations of 9-cis and all-trans RA below .01μM result in hatching of apparently normal fry.
Changes in pattern of activity may help shrews survive harsh winter conditions. In particular, shrews may become less active and less nocturnal during winter. To better understand the mechanisms underlying the shrew response to winter conditions we measured several kinds of activity and an index of nocturnality (night-day ratio) for six northern short-tailed shrews (Blarina brevicauda) in laboratory activity chambers. Experimental conditions were light:dark (L:D) cycles of 16:8 or 8:16 crossed with temperatures of 5°C or 19°C. Shrews were given unlimited food and prevented from hoarding. Feeding activity was greater (P < 0.001) and time spent out of the den was less concentrated during night (P = 0.021) at 5°C than 19°C. Overall activity did not vary with photoperiod or temperature, but shrews were more consistently active through the day at lower temperatures. Shrews may become less strictly nocturnal during winter because of the need to forage more frequently during the day. Food limitation and hoarding, which were not considered in this study, may be important factors affecting the reduced levels of activity during winter observed in other studies of shrews.
Volatile organic compounds (VOCs) are naturally and industrially produced organic chemicals that can exist in the air as gases. Most VOCs can easily be deposited in natural water through precipitation and point and non-point sources. Previous research has shown that the natural waters of Columbia County, Arkansas contain the following VOCs: vinyl chloride; bromoform; 1,3-dichlorobenzene; 1,2-dichlorobenzene; chloromethane; bromomethane; chlorobenzene; and dichloromethane. The purpose of this study was to determine if Beech Creek, a major tributary of Lake Columbia, contains these or other VOCs. Water samples were collected from seven bridges that cross Beech Creek. The samples were analyzed using a gas chromatograph (GC) equipped with a flame ionization detector (FID). Vinyl chloride was found to be the predominant VOC with concentrations from 3.92 to 7.16 mg/L. Trans-1,2-dichloroethylene, chlorobenzene, and bromoform were also found at concentrations of 4.69, 6.16, and 23.29 mg/L respectively. The Environmental Protection Agency (EPA) has designated VOCs as being either regulated or unregulated. Regulated VOCs are monitored with proposed Maximum Contaminant Levels (MCLs). Unregulated VOCs are monitored only to determine their presence in drinking water and have not been assigned MCLs. Vinyl chloride, trans-1,2-dichloroethylene, and chlorobenzene are regulated VOCs with MCLs of 2, 100, and 100 μg/l respectively. Bromoform is an unregulated VOC and does not have a MCL. The results show that Beech Creek has VOCs in its waters and that there is a slight possibility of VOCs contaminating local drinking water at levels higher than EPA standards.
Adaptations of proteins towards an increased thermostability can be observed in nature in environments such as the marine hydrothermal vents. The principles behind an increased thermostability can then be used in the biotech industry in order to design proteins with high stability. The demand for an increased stability has to be balanced by the dynamic required for maintaining catalytic activity of the enzyme. The (hyper-)thermophilic proteins are composed of the common 20 natural amino acids. Optimization of interactions between the amino acids in the peptide chain is hence a key feature for an increased stability. By comparing structures of (hyper-)thermophilic proteins with the mesophilic counterparts it is demonstrated that an increased stability is achieved through a combination of a variety of stabilizing interactions. The thermostabilizing interactions include improved packing of the protein structure and optimization of hydrophobic and electrostatic interactions. Furthermore the structure could be stabilized by a covalent crosslink in terms of a disulfide bond. In this paper the different interactions are presented and examples are given on how the interactions can be optimized to increase the thermostability of specific proteins. Finally, lactate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase serve as two illustrative examples of how the different interactions can be used in combination in order to improve the thermostability.