Role of areoles on prey abundance and diversity in the hooded pitcher plant (<Emphasis Type="Italic">Sarracenia minor</Emphasis>, <Emphasis Type="Italic">Sarraceniaceae</Emphasis>)

The hooded pitcher plant, Sarracenia minor, is a carnivorous facultative wetland species native to the southeastern USA and is listed as threatened by the state of Florida. Pitchers of S. minor possess white, semitranslucent spots (areoles), which have been hypothesized to aid in the capture of prey (= visual lures) by increasing the amount of light entering the back of the hood, which persuades insects to enter and fall into the base of the pitcher. In this study, the role of the areoles in prey capture abundance and diversity were experimentally investigated under variable lighting conditions in situ. Plants in two populations experiencing different light intensities, which varied in the amount of canopy cover and incident light reaching the plants, were experimentally manipulated by coloring varying percentages of areoles, ranging from 0 to 100 % (in increments of 25 %), with indelible ink. After 2 months, pitchers were collected and dissected to determine the number and identity of prey captured (approximately 18,000 prey were sampled). Although total prey abundance was approximately five times higher at McGirt’s Creek (sunny site) compared to UNF (shaded site), the effect of areoles on prey capture rates and biodiversity was site dependent. Reducing the number of visual lures of plants at the sunny site produced a significant decrease in the number of prey captured, but prey biodiversity (community composition) was unaffected. However, total prey capture was unaffected at the shaded site, while prey biodiversity was negatively correlated with the percent of areoles colored. Results from the current study suggest that areoles conditionally act as visual lures, but their overall importance is dependent on local environmental variables—especially canopy cover and the amount of incident sunlight reaching the plants.     

Ischemic preconditioning exaggerates cardiac damage in PKC-delta null mice

Ischemic preconditioning confers cardiac protection during subsequent ischemia-reperfusion, in which protein kinase C (PKC) is believed to play an essential role, but controversial data exist concerning the PKC-delta isoform. In an accompanying study (26), we described metabolic changes in PKC-delta knockout mice. We now wanted to explore their effect on early preconditioning. Both PKC-delta(-/-) and PKC-delta(+/+) mice underwent three cycles of 5-min left descending artery occlusion/5-min reperfusion, followed by 30-min occlusion and 2-h reperfusion. Unexpectedly, preconditioning exaggerated ischemia-reperfusion injury in PKC-delta(-/-) mice. Whereas ischemic preconditioning increased superoxide anion production in PKC-delta(+/+) hearts, no increase in reactive oxygen species was observed in PKC-delta(-/-) hearts. Proteomic analysis of preconditioned PKC-delta(+/+) hearts revealed profound changes in enzymes related to energy metabolism, e.g., NADH dehydrogenase and ATP synthase, with partial fragmentation of these mitochondrial enzymes and of the E(2) component of the pyruvate dehydrogenase complex. Interestingly, fragmentation of mitochondrial enzymes was not observed in PKC-delta(-/-) hearts. High-resolution NMR analysis of cardiac metabolites demonstrated a similar rise of phosphocreatine in PKC-delta(+/+) and PKC-delta(-/-) hearts, but the preconditioning-induced increase in phosphocholine, alanine, carnitine, and glycine was restricted to PKC-delta(+/+) hearts, whereas lactate concentrations were higher in PKC-delta(-/-) hearts. Taken together, our results suggest that reactive oxygen species generated during ischemic preconditioning might alter mitochondrial metabolism by oxidizing key mitochondrial enzymes and that metabolic adaptation to preconditioning is impaired in PKC-delta(-/-) hearts.     

Sequence-dependent conformational changes in DNA induced by polynuclear platinum complexes

In this work, the B-->Z transition of poly(dG-dC).poly(dG-dC) and the B-->A transition of poly(dG).poly(dC) and of calf thymus (CT) DNA fragments modified by antitumor bifunctional polynuclear platinum complexes were investigated by circular dichroism (CD). The transition from the B- to Z-form of DNA was inducible with all three compounds studied, as indicated by an inversion of the B-form spectra. The B-->A transition in poly(dG).poly(dC) was induced easily by platinum complex binding alone, while the B-->A transition in CT DNA was induced by ethanol but inhibited by coordination of all polynuclear platinum compounds used here. It was shown that the compound [?cis-PtCl(NH3)2?2 mu-?H2N(CH2)6NH2?] (NO3)2 (1,1/c,c) was most effective at inhibiting the B-->A transition in CT DNA, and [?trans-PtCl(NH3)2?2 mu-?trans-Pt(NH3)2(H2N(CH2)6NH2)2?] (NO3)4 (1,0,1/t,t,t) was least effective, while the effectiveness of [?trans-PtCl(NH3)2?2 mu-?H2N(CH2)6NH2?] (NO3)2 (1,1/t,t) fell between the two. This corresponded to the relative amounts of interstrand crosslinks in double-stranded DNA caused by each compound.     

Mapping,quantitative distribution and origin of substance P- and VIP-containing nerves in the Uvea of guinea pig eye

Summary VIP- and substance P-like immunoreactivities were found in considerable concentrations (VIP: 17.3±4.8 pmol/g, mean ± SEM; substance P:11.1±1.8 pmol/g) in the uveal portion of the guinea pig eye.d Immunocytochemistry localised these two regulatory peptides to nerve fibres found principally in a plexus in the iris (substance P) and in an extensive network surrounding the blood vessels of the choroid (VIP). A remarkable anatomical demarcation of the two types of peptide-containing nerves was established by the staining of substance P-containing nerves, which stops at the level of the ciliary body. This uveal area is known to be involved in the ocular responses to nociceptive stimuli. At the ultrastructural level, immunoreactivity for both peptides was localised to distinct subpopulations of p-type nerves, distinguishable by the size of their large dense-cored vesicles. Those immunoreactive for VIP were significantly larger (p<0.0005) than those immunoreactive for substance P (95±7 nm and 82±9 nm respectively; mean ± SD). Interruption of the trigeminal pathway produced a remarkable decrease of substance P immunoreactivity in the anterior portion of the uvea (9.1±1.5 pmol/g, mean ± SEM, control; 5.3±1.3 pmol/g, denervated), but not of VIP immunoreactivity in the choroid. Following colchicine treatment, VIP-immunoreactive neuronal cell bodies were localised in the choroid. The separate anatomical localisations and distributions of the two uveal peptides appear to be related to their different origins and functional roles in the response of the eye to noxious stimuli.To whom offprint requests should be sent     

Identification of ARAP3, a novel PI3K effector regulating both Arf and Rho GTPases, by selective capture on phosphoinositide affinity matrices.

We show that matrices carrying the tethered homologs of natural phosphoinositides can be used to capture and display multiple phosphoinositide binding proteins in cell and tissue extracts. We present the mass spectrometric identification of over 20 proteins isolated by this method, mostly from leukocyte extracts: they include known and novel proteins with established phosphoinositide binding domains and also known proteins with surprising and unusual phosphoinositide binding properties. One of the novel PtdIns(3,4,5)P3 binding proteins, ARAP3, has an unusual domain structure, including five predicted PH domains. We show that it is a specific PtdIns(3,4,5)P3/PtdIns(3,4)P2-stimulated Arf6 GAP both in vitro and in vivo, and both its Arf GAP and Rho GAP domains cooperate in mediating PI3K-dependent rearrangements in the cell cytoskeleton and cell shape.     

Tryptic digestion of human GPIIIa. Isolation and biochemical characterization of the 23 kDa N-terminal glycopeptide carrying the antigenic determinant for a monoclonal antibody (P37) which inhibits platelet aggregation.

Early digestion of pure human platelet glycoprotein IIIa (GPIIIa) leads to a single cleavage of the molecule at 23 kDa far from one of the terminal amino acids. Automated Edman degradation demonstrates that GPIIIa and the smaller (23 kDa) tryptic fragment share the same N-terminal amino acid sequence. A further cleavage occurs in the larger fragment (80 kDa), reducing its apparent molecular mass by 10 kDa. The 23 kDa fragment remains attached to the larger ones in unreduced samples. Stepwise reduction of early digested GPIIIa with dithioerythritol selectively reduces the single disulphide bond joining the smaller (23 kDa) to the larger (80/70 kDa) fragments. Two fractions were obtained by size-exclusion chromatography of early digested GPIIIa after partial or full reduction and alkylation. The larger-size fraction contains the 80/70 kDa fragments, while the 23 kDa fragment is isolated in the smaller. The amino acid compositions of these fractions do not differ very significantly from the composition of GPIIIa; however the 23 kDa fragment contains only 10.2% by weight of sugars and is richer in neuraminic acid. Disulphide bonds are distributed four in the 23 kDa glycopeptide and 20-21 in the 80/70 kDa glycopeptide. The epitope for P37, a monoclonal antibody which inhibits platelet aggregation [Melero & González-Rodríguez (1984) Eur. J. Biochem. 141, 421-427] is situated within the first 17 kDa of the N-terminal region of GPIIIa, which gives a special functional interest to this extracellular region of GPIIIa. On the other hand, the epitopes for GPIIIa-specific monoclonal antibodies, P6, P35, P40 and P97, which do not interfere with platelet aggregation, are located within the larger tryptic fragment (80/70 kDa). Thus, the antigenic areas available in the extracellular surface of GPIIIa for these five monoclonal antibodies are now more precisely delineated.