Targeted disruption of the Pak5 and Pak6 genes in mice leads to deficits in learning and locomotion

PAK6 is a member of the group B family of PAK serine/threonine kinases, and is highly expressed in the brain. The group B PAKs, including PAK4, PAK5, and PAK6, were first identified as effector proteins for the Rho GTPase Cdc42. They have important roles in filopodia formation, the extension of neurons, and cell survival. Pak4 knockout mice die in utero, and the embryos have several abnormalities, including a defect in the development of motor neurons. In contrast, Pak5 knockout mice do not have any noticeable abnormalities. So far nothing is known about the biological function of Pak6. To address this, we have deleted the Pak6 gene in mice. Since Pak6 and Pak5 are both expressed in the brain, we also generated Pak5/Pak6 double knockout mice. These mice were viable and fertile, but had several locomotor and behavioral deficits. Our results indicate that Pak5 and Pak6 together are not required for viability, but are required for a normal level of locomotion and activity as well as for learning and memory. This is consistent with a role for the group B PAKs in the nervous system.     

Synergistic effects of α-pinene and exo-brevicomin on pine bark beetles and associated insects in Arizona

The southern pine beetle (Dendroctonus frontalis) and western pine beetle (Dendroctonus brevicomis) cause significant mortality to pines in the southern and western United States. The effectiveness of commercial lures at capturing these bark beetles in Arizona has not been tested and may vary from other regions of their distribution. We conducted experiments using baited Lindgren funnel traps to investigate (i) if D. frontalis is more attracted to the standard commercial lure for D. brevicomis (frontalin + exo‐brevicomin + myrcene) than the D. frontalis lure (frontalin + terpene blend), (ii) whether replacement of myrcene with α‐pinene changes trap catches of Dendroctonus and associated insects, and (iii) whether the attraction to these lures varies across the geographical range of ponderosa pine forests throughout Arizona. In 2005, we tested various combinations of frontalin, exo‐brevicomin, myrcene and α‐pinene to D. frontalis, D. brevicomis and associated species. Dendroctonus frontalis, D. brevicomis and the predator Temnochila chlorodia were most attracted to lures with exo‐brevicomin. The replacement of the myrcene component with α‐pinene in the D. brevicomis lure resulted in the capture of twice as many bark beetles and Elacatis beetles. However, T. chlorodia did not differentiate between monoterpenes. In 2006, traps were set up in 11 locations around Arizona to test the relative attraction of lure combinations. In 9 out 11 locations, the D. brevicomis lure with α‐pinene was more attractive than the lure with myrcene or a terpene blend. These results suggest that the D. brevicomis lure with α‐pinene rather than myrcene is more effective lure to capture D. brevicomis and D. frontalis in Arizona. However, geographical variation in attractiveness to lures is evident even within this region of the beetles’ distributions. Differential attraction of Dendroctonus and their predators to these lures suggests potential use in field trapping and control programmes.     

Chemistry in Eriocaulaceae

Eriocaulaceae is a pantropical family that comprises about 1100 species distributed in 11 genera. The infrafamilial relationships are still unsatisfactorily resolved, because of the tiny flowers and generalized morphology, which makes the taxonomy very difficult. Flavonoid and naphthopyranone profiles have proved to be important in order to contribute to the alignment of genera into the family. We here present a survey of the chemical data of Eriocaulaceae with a discussion about their contribution to the taxonomy of Eriocaulaceae.     

A MIP-based impedimetric sensor for the detection of low-MW molecules

Mimicking the selectivity and sensitivity of biological systems for sensor devices is of increasing interest in biomedical, environmental and chemical analysis. Synthetic materials with imprinted nanocavities, acting as highly selective artificial receptors, are a tailor-made solution in obtaining such a sensor. Incorporation of such molecularly imprinted polymers (MIPs) in a platform suitable for electrochemical measurements, can offer high sensitivity together with device miniaturization and an electronic read-out. As a proof of principle, a MIP-based sensor for L-nicotine has been developed. To this end, the molecular structure of L-nicotine was imprinted in a polymer matrix of polymethacrylic acid (PMAA). Subsequently, microparticles of the imprinted polymer were immobilized on thin films of the conjugated polymer OC(1)C(10)-PPV. These films were incorporated in an impedimetric sensing device. Using electrochemical impedance spectroscopy, the real part of the impedance was monitored for various concentrations. This setup allows for the detection of l-nicotine from 1 to 10 nM and is insensitive for the resembling molecule L-cotinine.     

High-performance liquid chromatographic separation and identification of polyphenolic compounds from the infusion of Davilla elliptica St. Hill

The isolation of polyphenolic compounds from an infusion of the Brazilian plant Davilla elliptica (Dilleniaceae), used as tea by virtue of its digestive properties, is described. An improved preparative HPLC method was used in order to isolate pure polyphenols from the complex mixture. Liquid-liquid extraction and solid-phase extraction were employed to minimise the interference of polymeric compounds and to provide an enriched fraction of the compounds of interest. The identification of the isolated compounds was performed using analytical HPLC as well as direct injection electrospray ionisation ion trap tandem mass spectrometry (ESI-IT-MS/MS). The high flavonoid content suggests that D. elliptica may be a promising source of compounds to produce natural phytomedicines.     

Regulation of thermogenesis in flowering Araceae: the role of the alternative oxidase

The inflorescences of several members of the Arum lily family warm up during flowering and are able to maintain their temperature at a constant level, relatively independent of the ambient temperature. The heat is generated via a mitochondrial respiratory pathway that is distinct from the cytochrome chain and involves a cyanide-resistant alternative oxidase (AOX). In this paper we have used flux control analysis to investigate the influence of temperature on the rate of respiration through both cytochrome and alternative oxidases in mitochondria isolated from the appendices of intact thermogenic Arum maculatum inflorescences. Results are presented which indicate that at low temperatures, the dehydrogenases are almost in full control of respiration but as the temperature increases flux control shifts to the AOX. On the basis of these results a simple model of thermoregulation is presented that is applicable to all species of thermogenic plants. The model takes into account the temperature characteristics of the separate components of the plant mitochondrial respiratory chain and the control of each process. We propose that 1) in all aroid flowers AOX assumes almost complete control over respiration, 2) the temperature profile of AOX explains the reversed relationship between ambient temperature and respiration in thermoregulating Arum flowers, 3) the thermoregulation process is the same in all species and 4) variations in inflorescence temperatures can easily be explained by variations in AOX protein concentrations.     

The biogeographical assignment of a west Kenyan rain forest remnant: further evidence from analysis of its reptile fauna

Aim The Kakamega Forest, western Kenya, has been biogeographically assigned to both lowland and montane forest biomes, or has even been considered to be unique. Most frequently it has been linked with the Guineo‐Congolian rain forest block. The present paper aims to test six alternative hypotheses of the zoogeographical relationships between this forest remnant and other African forests using reptiles as a model group. Reptiles are relatively slow dispersers, compared with flying organisms (Aves and Odonata) on which former hypotheses have been based, and may thus result in a more conservative biogeographical analysis. Location Kakamega Forest, Kenya, Sub‐Saharan Africa. Methods The reptile diversity of Kakamega Forest was evaluated by field surveys and data from literature resources. Faunal comparisons of Kakamega Forest with 16 other African forests were conducted by the use of the ‘coefficient of biogeographic resemblance’ using the reptile communities as zoogeographic indicators. Parsimony Analysis of Endemism and Neighbour Joining Analysis of Endemism were used to generate relationship trees based on an occurrence matrix with paup *. Results The analysis clearly supports the hypothesis that the Kakamega Forest is the easternmost fragment of the Guineo‐Congolian rain forest belt, and thus more closely related to the forests of that Central–West African complex than to any forest further east, such as the Kenyan coastal forests. Many Kenyan reptile species occur exclusively in the Kakamega Forest and its associated forest fragments. Main conclusions The Kakamega Forest is the only remnant of the Guineo‐Congolian rain forest in the general area. We assume that the low degree of resemblance identified for the Guineo‐Congolian forest and the East African coastal forest reflect the long history of isolation of the two forest types from each other. Kenyan coastal forests may have been historically connected through forest ‘bridges’ of the southern highlands with the Congo forest belt, allowing reptile species to migrate between them. The probability of a second ‘bridge’ located in the region of southern Tanzanian inselbergs is discussed. Although not particularly rich in reptile species, the area should be considered of high national priority for conservation measures.     

Pendrin in the mouse kidney is primarily regulated by Cl- excretion but also by systemic metabolic acidosis

The Cl(-)/anion exchanger pendrin (SLC26A4) is expressed on the apical side of renal non-type A intercalated cells. The abundance of pendrin is reduced during metabolic acidosis induced by oral NH(4)Cl loading. More recently, it has been shown that pendrin expression is increased during conditions associated with decreased urinary Cl(-) excretion and decreased upon Cl(-) loading. Hence, it is unclear if pendrin regulation during NH(4)Cl-induced acidosis is primarily due the Cl(-) load or acidosis. Therefore, we treated mice to increase urinary acidification, induce metabolic acidosis, or provide an oral Cl(-) load and examined the systemic acid-base status, urinary acidification, urinary Cl(-) excretion, and pendrin abundance in the kidney. NaCl or NH(4)Cl increased urinary Cl(-) excretion, whereas (NH(4))(2)SO(4), Na(2)SO(4), and acetazolamide treatments decreased urinary Cl(-) excretion. NH(4)Cl, (NH(4))(2)SO(4), and acetazolamide caused metabolic acidosis and stimulated urinary net acid excretion. Pendrin expression was reduced under NaCl, NH(4)Cl, and (NH(4))(2)SO(4) loading and increased with the other treatments. (NH(4))(2)SO(4) and acetazolamide treatments reduced the relative number of pendrin-expressing cells in the collecting duct. In a second series, animals were kept for 1 and 2 wk on a low-protein (20%) diet or a high-protein (50%) diet. The high-protein diet slightly increased urinary Cl(-) excretion and strongly stimulated net acid excretion but did not alter pendrin expression. Thus, pendrin expression is primarily correlated with urinary Cl(-) excretion but not blood Cl(-). However, metabolic acidosis caused by acetazolamide or (NH(4))(2)SO(4) loading prevented the increase or even reduced pendrin expression despite low urinary Cl(-) excretion, suggesting an independent regulation by acid-base status.