Long-term responses of zooplankton to invasion by a planktivorous fish in a subarctic watercourse

1. Introduced or invading predators may have strong impacts on prey populations of the recipient community mediated by direct and indirect interactions. The long-term progression of predation effects, covering the invasion and establishment phase of alien predators, however, has rarely been documented.
2. This paper documents the impact of an invasive, specialized planktivorous fish on its prey in a subarctic watercourse. Potential predation effects on the crustacean plankton, at the community, population and individual levels, were explored in a long-term study following the invasion by vendace ( Coregonus albula ).
3. Over the 12-year period, the density and species richness of zooplankton decreased, smaller species became more abundant and Daphnia longispina , one of the largest cladocerans, was eliminated from the zooplankton community.
4. Within the dominant cladocerans, including Daphnia spp., Bosmina longispina and Bosmina longirostris , the body size of ovigerous females and the size at first reproduction decreased after the arrival of the new predator. The clutch sizes of Daphnia spp. and B. longirostris also increased.
5. Increased predation pressure following the vendace invasion induced many effects on the crustacean zooplankton, and we document comprehensive and strong direct and indirect long-term impacts of an introduced non-native predator on the native prey community.     

Modulation of late sodium current by Ca2+, calmodulin, and CaMKII in normal and failing dog cardiomyocytes: similarities and differences

Augmented and slowed late Na(+) current (I(NaL)) is implicated in action potential duration variability, early afterdepolarizations, and abnormal Ca(2+) handling in human and canine failing myocardium. Our objective was to study I(NaL) modulation by cytosolic Ca(2+) concentration ([Ca(2+)](i)) in normal and failing ventricular myocytes. Chronic heart failure was produced in 10 dogs by multiple sequential coronary artery microembolizations; 6 normal dogs served as a control. I(NaL) fine structure was measured by whole cell patch clamp in ventricular myocytes and approximated by a sum of fast and slow exponentials produced by burst and late scattered modes of Na(+) channel gating, respectively. I(NaL) greatly enhanced as [Ca(2+)](i) increased from "Ca(2+) free" to 1 microM: its maximum density increased, decay of both exponentials slowed, and the steady-state inactivation (SSI) curve shifted toward more positive potentials. Testing the inhibition of CaMKII and CaM revealed similarities and differences of I(NaL) modulation in failing vs. normal myocytes. Similarities include the following: 1) CaMKII slows I(NaL) decay and decreases the amplitude of fast exponentials, and 2) Ca(2+) shifts SSI rightward. Differences include the following: 1) slowing of I(NaL) by CaMKII is greater, 2) CaM shifts SSI leftward, and 3) Ca(2+) increases the amplitude of slow exponentials. We conclude that Ca(2+)/CaM/CaMKII signaling increases I(NaL) and Na(+) influx in both normal and failing myocytes by slowing inactivation kinetics and shifting SSI. This Na(+) influx provides a novel Ca(2+) positive feedback mechanism (via Na(+)/Ca(2+) exchanger), enhancing contractions at higher beating rates but worsening cardiomyocyte contractile and electrical performance in conditions of poor Ca(2+) handling in heart failure.     

Ranolazine combined with enalapril or metoprolol prevents progressive LV dysfunction and remodeling in dogs with moderate heart failure

Acute intravenous infusion of ranolazine (Ran), an anti-ischemic/antiangina drug, was previously shown to improve left ventricular (LV) ejection fraction (EF) without a concomitant increase in myocardial oxygen consumption in dogs with chronic heart failure (HF). This study examined the effects of treatment with Ran alone and in combination with metoprolol (Met) or enalapril (Ena) on LV function and remodeling in dogs with HF. Dogs (n = 28) with microembolization-induced HF were randomized to 3 mo oral treatment with Ran alone [375 mg twice daily (bid); n = 7], Ran (375 mg bid) in combination with Met tartrate (25 mg bid; n = 7), Ran (375 mg bid) in combination with Ena (10 mg bid; n = 7), or placebo (PL; Ran vehicle bid; n = 7). Ventriculographic measurements of LV end-diastolic volume (EDV) and end-systolic volume (ESV) and LV EF were obtained before treatment and after 3 mo of treatment. In PL-treated dogs, EDV and ESV increased significantly. Ran alone prevented the increase in EDV and ESV seen in the PL group and significantly increased EF, albeit modestly, from 35 +/- 1% to 37 +/- 2%. When combined with either Ena or Met, Ran prevented the increase in EDV, significantly decreased ESV, and markedly increased EF compared with those of PL. EF increased from 35 +/- 1% to 40 +/- 1% with Ran + Ena and from 34 +/- 1% to 41 +/- 1% with Ran + Met. Ran alone or in combination with Ena or Met was also associated with beneficial effects at the cellular level on histomorphometric parameters such as hypertrophy, fibrosis, and capillary density as well as the expression for pathological hypertrophy and Ca2+ cycling genes. In conclusion, Ran prevented progressive LV dysfunction and global and cellular myocardial remodeling, and Ran in combination with Ena or Met improved LV function beyond that observed with Ran alone.     

Reversed-phase liquid chromatography of lisinopril conformers

The effect of flow rate, temperature, pH, organic solvent and counter ion on peak shape and separation of the cis and trans conformers of lisinopril are investigated by HPLC. It was demonstrated that complete separation of the two isomers can be achieved at low temperature at either neutral or low pH together with appropriate type and concentration of organic solvent, whereas the elution of lisinopril as a single peak is favored by a decrease of flow rate, elevated temperature, choice of organic solvent (type and amount) and the use of an appropriate counter ion concentration.     

Caspase inhibitors affect the kinetics and dimensions of tracheary elements in xylogenic Zinnia (<Emphasis Type="Italic">Zinnia elegans</Emphasis>) cell cultures

Background  

The xylem vascular system is composed of fused dead, hollow cells called tracheary elements (TEs) that originate through trans-differentiation of root and shoot cambium cells. TEs undergo autolysis as they differentiate and mature. The final stage of the formation of TEs in plants is the death of the involved cells, a process showing some similarities to programmed cell death (PCD) in animal systems. Plant proteases with functional similarity to proteases involved in mammalian apoptotic cell death (caspases) are suggested as an integral part of the core mechanism of most PCD responses in plants, but participation of plant caspase-like proteases in TE PCD has not yet been documented.     

Fatty streak development in the vicinity of aortic coarctations in hypercholesterolemic rabbits

The influence of altered local hemodynamics on fatty streak development in rabbits fed high cholesterol diets was investigated. An aortic coarctation was created in the abdominal aorta of nine rabbits by placing a partially constricting gold or silver band (1.7 mm x 10 mm) around the aorta between the renal arteries and aortic bifurcation. Controls were 20 rabbits; seven sham operated and 13 unoperated rabbits. The abdominal aorta 1-2 cm proximal to the coarctation showed lipid deposition involving 45 +/- 8% (mean +/- SEM) of the luminal surface which was more than occurred within or distal to the obstruction (p less than 0.05) and also more than in controls (p less than 0.05). Within the coarctation, 4 +/- 2% of the luminal surface showed lipid deposition which was less than either proximally or distally (p less than 0.01) and also less than in comparable regions in controls (p less than 0.05). The aorta 1-2 cm distal to the coarctation showed lipid deposition involving 18 +/- 4% of the surface which was similar to control rabbits. Lipid deposition in corresponding regions of the control rabbits was involved in 17 +/- 4%, 19 +/- 5% and 19 +/- 4% of the luminal surface, respectively. Fatty streak development, therefore, appeared to be inhibited within the coarctation and enhanced proximal to it. The results suggest that some early step in the process of lipid accumulation may be affected by local fluid dynamics or modification of the wall of the vessel.