Adrenaline causes potassium influx in skeletal muscle and potassium efflux in cardiac muscle in rats: the role of Na/K ATPase

Previous in vitro evidence suggests that adrenaline causes K influx in skeletal muscle by stimulating a ouabain sensitive Na/K ATPase membrane pump. However in rabbits, adrenaline induced hypokalaemia was not significantly altered by pretreatment with digoxin (50 micrograms/kg). Rats were infused with adrenaline or saline after being given a tracer dose of 42KCl. Adrenaline caused a highly significant uptake of 42K in skeletal muscle and a decrease in 42K uptake in ventricle. Rats were also studied after receiving a high dose of digoxin (1.4 mg/kg) which by itself produced a significant increase in plasma K, a decrease in plasma Na and a decreased uptake of 42K in ventricle and lung. These results suggest that adequate widespread Na/K ATPase inhibition had been achieved by this dose of digoxin but despite this, adrenaline still caused hypokalaemia and also still caused significant 42K tissue uptake by skeletal muscle. These results suggest that adrenaline causes K influx by skeletal muscle and K efflux by cardiac tissue. Furthermore, the former mechanism was not inhibited by pretreatment with digoxin.     

Targeting the proteome/epitome,implementation of subtractive immunization

Monoclonal antibody technology has generated invaluable tools for both the analytical and clinical sciences. However, standard immunization approaches frequently fail to provide monoclonal antibodies with the desired specificity. Subtractive immunization provides a powerful alternative to standard immunization and allows for the production of truly unique antibodies. With the intent of targeting specific epitopes within the proteome, subtractive immunization has been broadly and successfully implemented for the production of monoclonal antibodies otherwise unobtainable by standard immunization. Subtractive immunization utilizes a distinct immune tolerization approach that can substantially enhance the generation of monoclonal antibodies to desired antigens. The approach is based on tolerizing the host animal to immunodominant or otherwise undesired antigen(s) (tolerogen) that may be structurally or functionally related to the antigen of interest. Tolerization of the host animal can be achieved through one of three methods: High Zone, Neonatal, or Drug-induced tolerization. The tolerized animal is then inoculated with the desired antigen (immunogen) and antibodies generated by the subsequent immune response are screened for the desired antigenic reactivity. Over the past 15 years a large number of investigators have used the subtractive approach with cleverly chosen tolerogen-immunogen combinations and successfully generated uniquely reactive antibodies which are often neutralizing or function-blocking. This review will focus on the implementation of subtractive immunization for the production of antibodies otherwise unobtainable by standard immunization.     

Phylogeography and genetic ancestry of tigers (Panthera tigris)

Eight traditional subspecies of tiger (Panthera tigris),of which three recently became extinct, are commonly recognized on the basis of geographic isolation and morphological characteristics. To investigate the species' evolutionary history and to establish objective methods for subspecies recognition, voucher specimens of blood, skin, hair, and/or skin biopsies from 134 tigers with verified geographic origins or heritage across the whole distribution range were examined for three molecular markers: (1) 4.0 kb of mitochondrial DNA (mtDNA) sequence; (2) allele variation in the nuclear major histocompatibility complex class II DRB gene; and (3) composite nuclear microsatellite genotypes based on 30 loci. Relatively low genetic variation with mtDNA,DRB,and microsatellite loci was found, but significant population subdivision was nonetheless apparent among five living subspecies. In addition, a distinct partition of the Indochinese subspecies P. t. corbetti in to northern Indochinese and Malayan Peninsula populations was discovered. Population genetic structure would suggest recognition of six taxonomic units or subspecies: (1) Amur tiger P. t. altaica; (2) northern Indochinese tiger P. t. corbetti; (3) South China tiger P. t. amoyensis; (4) Malayan tiger P. t. jacksoni, named for the tiger conservationist Peter Jackson; (5) Sumatran tiger P. t. sumatrae; and (6) Bengal tiger P. t. tigris. The proposed South China tiger lineage is tentative due to limited sampling. The age of the most recent common ancestor for tiger mtDNA was estimated to be 72,000-108,000 y, relatively younger than some other Panthera species. A combination of population expansions, reduced gene flow, and genetic drift following the last genetic diminution, and the recent anthropogenic range contraction, have led to the distinct genetic partitions. These results provide an explicit basis for subspecies recognition and will lead to the improved management and conservation of these recently isolated but distinct geographic populations of tigers.     

Angiopoeitin-2 modulates Survivin expression in OxLDL-induced endothelial cell apoptosis

Angiopoeitin-2 (Ang-2) antagonizes Angiopeitin-1 (Ang-1)-mediated Tie-2 signaling. Ang-1 is reported to up-regulate anti-apoptotic Survivin expression. Here, we investigated the interplay between Ang-2 and Survivin in response to oxidized low density lipoprotein (OxLDL)-induced apoptosis. We demonstrate that treatment of human aortic endothelial cells (HAEC) with 100 μg/ml of OxLDL down-regulated Ang-2 expression as early as 4h after treatment and persisted up to 24h (p<0.05, n=3), but did not down-regulate Survivin until the 24h point. Further, treatment of HAEC with recombinant Ang-2 up-regulated Survivin expression (at Ang-2 ≥200 ng/ml, p<0.05, n=3) and attenuated the OxLDL-mediated down-regulation of Survivin (p<0.05, n=3). Knockdown of Ang-2 further down-regulated Survivin expression, whereas over-expression of Survivin attenuated OxLDL-induced HAEC apoptosis (p<0.05, n=3). Hence, Ang-2 mediated Survivin expression in response to OxLDL-induced endothelial apoptosis.     

Effects of rapid experimental temperature increases on acute physiological stress and behaviour of stream dwelling juvenile chinook salmon

We experimentally heated small streams in summer and investigated the short-term behavioural changes and physiological stress responses of juvenile chinook salmon (Oncorhynchus tshawytscha). We rapidly raised temperatures ∼1–4 °C for 1.5 h above ambient levels of ∼7–15 °C in groundwater fed tributary streams and ∼19–23 °C in side-channel streams. Juvenile chinook rearing in groundwater fed tributaries were generally unaffected behaviourally; however, we found that temperature increase caused fish in the tributary trials to be physiologically stressed (elevations in mean cortisol concentrations ranged from 116% to 253%). Side-channel trials caused some mortality of juvenile chinook and a stronger display of behaviours indicative of stress and avoidance such as erratic swimming, abnormal posture, and aggregative behaviour. Foraging rates increased over 56 times in response to heating in side-channel trials. Cortisol levels did not increase in side-channel trials, but rather showed a trend to levels below control values suggesting an impaired stress response possibly due to chronic stress. Our results may reflect conservative responses in terms of what we may find with other salmonid species since juvenile chinook have been described as the most tolerant of the Pacific salmon species to elevated temperatures.     

The discovery of highly potent CGRP receptor antagonists

Rational modification of a previously identified spirohydantoin lead structure has identified a series of potent spiroazaoxindole CGRP receptor antagonists. The azaoxindole was found to be a general replacement for the hydantoin that consistently improved in vitro potency. The combination of the indanylspiroazaoxindole and optimized benzimidazolinones led to highly potent antagonists (e.g., 25, CGRP K_i = 40 pM). The closely related compound 27 demonstrated good oral bioavailability in dog and rhesus.     

Conservation genetics of the Far Eastern leopard (Panthera pardus orientalis)

The Far Eastern or Amur leopard (Panthera pardus orientalis) survives today as a tiny relict population of 25-40 individuals in the Russian Far East. The population descends from a 19th-century northeastern Asian subspecies whose range extended over southeastern Russia, the Korean peninsula, and northeastern China. A molecular genetic survey of nuclear microsatellite and mitochondrial DNA (mtDNA) sequence variation validates subspecies distinctiveness but also reveals a markedly reduced level of genetic variation. The amount of genetic diversity measured is the lowest among leopard subspecies and is comparable to the genetically depleted Florida panther and Asiatic lion populations. When considered in the context of nonphysiological perils that threaten small populations (e.g., chance mortality, poaching, climatic extremes, and infectious disease), the genetic and demographic data indicate a critically diminished wild population under severe threat of extinction. An established captive population of P. p. orientalis displays much higher diversity than the wild population sample, but nearly all captive individuals are derived from a history of genetic admixture with the adjacent Chinese subspecies, P. p. japonensis. The conservation management implications of potential restoration/augmentation of the wild population with immigrants from the captive population are discussed.     

Endogenous opiate involvement in acute and chronic stress-induced changes in plasma LH concentrations in the male rat

The present study was carried out to examine the possible role of the endogenous opioid peptides ( EOP 's) on the pituitary luteinizing hormone (LH) response to both acute and chronic stress and to food deprivation. Thirty minutes after acute (2 min.) exposure to ether, plasma LH levels were elevated compared to controls; morphine (MOR) treatment prior to stress prevented this response. More prolonged etherization (15 minutes) significantly depressed circulating LH, whereas naltrexone ( NALT ), a specific opiate antagonist, reversed this decline. Immobilization for 8 hours resulted in a significant initial increase in LH release, followed by a decline toward baseline levels. Naltrexone treatment increased the magnitude of the acute LH rise, and attenuated the subsequent decrease in plasma LH. The effect of chronic stress on circulating LH was also examined. Plasma LH levels were depressed for 3 consecutive days following subcutaneous gauze pad implantation, whereas 3 daily NALT injections returned LH to control levels. Complete food deprivation for 5 days also resulted in a significant decline in circulating LH. Injection of NALT 3 times daily reversed this decline on days 2, 3 and 4 of treatment. These results support the hypothesis of a mediatory role for the EOP 's in the effect of both chronic stress and food deprivation on LH release in the rat.