Response of foundation macrophytes to near‐natural simulated marine heatwaves

Marine heatwaves have been observed worldwide and are expected to increase in both frequency and intensity due to climate change. Such events may cause ecosystem reconfigurations arising from species range contraction or redistribution, with ecological, economic and social implications. Macrophytes such as the brown seaweed Fucus vesiculosus and the seagrass Zostera marina are foundation species in many coastal ecosystems of the temperate northern hemisphere. Hence, their response to extreme events can potentially determine the fate of associated ecosystems. Macrophyte functioning is intimately linked to the maintenance of photosynthesis, growth and reproduction, and resistance against pathogens, epibionts and grazers. We investigated morphological, physiological, pathological and chemical defence responses of western Baltic Sea F. vesiculosus and Z. marina populations to simulated near‐natural marine heatwaves. Along with (a) the control, which constituted no heatwave but natural stochastic temperature variability (0HW), two treatments were applied: (b) two late‐spring heatwaves (June, July) followed by a summer heatwave (August; 3HW) and (c) a summer heatwave only (1HW). The 3HW treatment was applied to test whether preconditioning events can modulate the potential sensitivity to the summer heatwave. Despite the variety of responses measured in both species, only Z. marina growth was impaired by the accumulative heat stress imposed by the 3HW treatment. Photosynthetic rate, however, remained high after the last heatwave indicating potential for recovery. Only epibacterial abundance was significantly affected in F. vesiculosus. Hence both macrophytes, and in particular F. vesiculosus, seem to be fairly tolerant to short‐term marine heatwaves at least at the intensities applied in this experiment (up to 5°C above mean temperature over a period of 9 days). This may partly be due to the fact that F. vesiculosus grows in a highly variable environment, and may have a high phenotypic plasticity.     

Movement of Kinetin and Gibberellic Acid in Leaf Petioles during Water Stress-induced Abscission in Cotton

Movement of [¹⁴C]kinetin and [¹⁴C]gibberellic acid was examined in cotton (Gossypium hirsutum L.) cotyledonary petiole sections independent of label uptake or exit from the tissue. Sections 20 millimeters in length were taken from well watered, stressed, and poststressed plants. Transport capacity was determined using a pulse-chase technique. Movement of both kinetin and gibberellic acid was found to be nonpolar with a velocity of 1 millimeter per hour or less, suggesting passive diffusion. Neither water stress nor anaerobic conditions during transport of labeled material affected the transport capacity of the petioles.     

Isolation and characterization of a membrane-attack-complex-inhibiting protein present in human serum and other biological fluids.

Cytosolic, detergent-solubilized and membrane-bound growth hormone (GH) receptors from rabbit adipose tissue and liver were tested for reactivity with a panel of monoclonal antibodies (MAbs). The cytosolic and detergent-solubilized forms of adipose tissue and liver GH receptors were identically reactive with four precipitating and two hormone-binding-site-directed MAbs. However, the membrane-bound form of the adipose receptor was 1000-fold less reactive with one binding-site-directed MAb (MAb 7) than the membrane-bound liver GH receptor. Reactivity with another inhibitory MAb (MAb 263) was identical for adipose tissue and liver membrane GH receptors. The relative potency of 22,000-Mr and 20,000-Mr forms of human GH was identical in assays with liver and adipose tissue membrane receptors. Thus, contrary to earlier suggestions, the discrepancy between the growth-promoting and insulin-like activities of 20,000-Mr human GH cannot be rationalized by a difference in the affinity of this hormone for 'somatogenic' and 'metabolic' receptors when the comparison is made in the same species. Cross-linking studies showed that the major GH-binding subunit of liver and adipose tissue GH receptors had the same Mr (54,000 +/- 5000, reduced). The ligand-binding subunits of liver and adipose tissue receptors are identical by several criteria, but one epitope on the adipose tissue receptor appears to be masked upon membrane insertion, possibly by close association with a tissue-specific component. Tissue specificity may be determined by association of a ubiquitous GH-binding subunit with tissue-specific membrane components, rather than by differences in amino acid sequence.     

Male tree weta are attracted to cuticular scent cues but do not discriminate according to sex or among two closely related species

Recognition of conspecifics is an essential precursor of successful mating. Where related species coexist, species discrimination might be important, but because related species are similar, species signal recognition may actually be low. Chemical cues such as cuticular hydrocarbons (CHCs) are frequently used by insects to identify suitable sexual partners. We predicted that New Zealand tree weta (Hemideina spp.), a genus of nocturnal ensiferan Orthoptera that live both allopatrically and sympatrically, use chemical signals from either frass or CHCs to find mates. In a series of six laboratory trials using both H. thoracica and H. crassidens, we found that male tree weta, but not female tree weta, occupied cavities primed with female cuticular cues more often than cavities without. However, males did not discriminate between chemical cues of male and female conspecifics, or between conspecifics and heterospecifics. In field trials, tree weta did not occupy artificial cavities primed with either female frass or female cuticular cues more often than unscented cavities. However, in both trials weta preferentially returned to cavities that had already been occupied earlier in the trials. A final field trial confirmed the presence of mixed species harems during the mating season in one region of sympatry. Our results suggest that selection on sex and species specific chemical cues that could be used to find conspecific mates is weak. Mixed species aggregations suggest that identification of conspecific mating cues has not evolved to be species specific. We infer that for male tree weta, the cost of mating with heterospecifics is likely less than not mating at all.     

Eps15 homology domain-NPF motif interactions regulate clathrin coat assembly during synaptic vesicle recycling

Although genetic and biochemical studies suggest a role for Eps15 homology domain containing proteins in clathrin-mediated endocytosis, the specific functions of these proteins have been elusive. Eps15 is found at the growing edges of clathrin-coated pits, leading to the hypothesis that it participates in the formation of coated vesicles. We have evaluated this hypothesis by examining the effect of Eps15 on clathrin assembly. We found that although Eps15 has no intrinsic ability to assemble clathrin, it potently stimulates the ability of the clathrin adaptor protein, AP180, to assemble clathrin at physiological pH. We have also defined the binding sites for Eps15 on squid AP180. These sites contain an NPF motif, and peptides derived from these binding sites inhibit the ability of Eps15 to stimulate clathrin assembly in vitro. Furthermore, when injected into squid giant presynaptic nerve terminals, these peptides inhibit the formation of clathrin-coated pits and coated vesicles during synaptic vesicle endocytosis. This is consistent with the hypothesis that Eps15 regulates clathrin coat assembly in vivo, and indicates that interactions between Eps15 homology domains and NPF motifs are involved in clathrin-coated vesicle formation during synaptic vesicle recycling.     

Disease associated balanced chromosome rearrangements (DBCR): report of two new cases

Disease associated balanced chromosome rearrangements (DBCR) causing truncation, deletion, inactivation or over-expression of specific genes are instrumental in identifying and cloning several disease genes and are estimated to be much more common than anticipated. In one survey, the minimal frequency of combined balanced de novo reciprocal translocations and inversions causing abnormal phenotype is estimated to be 0.17%, a sixfold increase compared to the general population suggesting a causative linkage between the abnormality and the observed phenotypic traits. Here, we report two new cases of apparently balanced de novo translocations resulting in developmental delay and dysmorphic features.     

New evidence for hominid presence in the Lower Pleistocene of the Southern Levant

The site of 'Ubeidiya is located in the Jordan Valley, Israel and has been biochronologically dated to 1.5 m.y.a. It exhibits large lithic and faunal assemblages. Previous published hominid material includes a molar (UB 1701) and I(2) (UB 1700). A recent review of the faunal material from previous excavations has revealed a highly worn hominid right lateral lower incisor (UB 335). The tooth was found in situ in the Lower Pleistocene deposits of stratum I-26a, which is comprised of sand and conglomerates of flint, limestone and basalt indicative of a pebbled lakeshore environment. Taphonomic analysis of the macromammal assemblage indicates high-energy fluvial transport. Paleoecological reconstruction suggests a large woodland fauna with a small percent of open steppe species.UB 335 did not differ significantly from the Lower Pleistocene hominid and modern populations but did differ significantly from all other fossil populations. Two-tailed Student t -test and single classification Model II ANOVA of the buccolingual diameter did not distinguish between Lower Pleistocene species: Homo habilis, H. ergaster and H. cf. erectus. Thus, UB 335 can be identified as a Lower Pleistocene hominid although it cannot be securely assigned to any particular species within that time frame. The current date of the 'Ubeidiya deposits and the location of the site within the Levantine corridor suggests a tenative identification as H. ergaster.     

Formation of a copper specific binding site in non-native states of beta-2-microglobulin

A debilitating complication of long-term hemodialysis is the deposition of beta-2-microglobulin (beta2m) as amyloid plaques in the joint space. We have recently shown that Cu(2+) can be a contributing, if not causal, factor at concentrations encountered during dialysis therapy. The basis for this effect is destabilization and incorporation of beta2m into amyloid fibers upon binding of Cu(2+). In this work, we demonstrate that while beta2m binds Cu(2+) specifically in the native state, it is binding of Cu(2+) by non-native states of beta2m which is responsible for destabilization. Mutagenesis of potential coordinating groups for Cu(2+) shows that native state binding of Cu(2+) is mediated by residues and structures that are different than those which bind in non-native states. An increased affinity for copper by non-native states compared to that of the native state gives rise to overall destabilization. Using mass spectrometry, NMR, and fluorescence techniques, we show that native state binding is localized to H31 and W60 and is highly specific for Cu(2+) over Zn(2+) and Ni(2+). Binding of Cu(2+) in non-native states of beta2m is mediated by residues H13, H51, and H84, but not H31. Although denatured beta2m has characteristics of a globally unfolded state, it nevertheless demonstrates the following strong specificity of binding: Cu(2+) > Zn(2+) > Ni(2+). This requires the existence of a well-defined structure in the unfolded state of this protein. As Cu(2+) effects are reported in many other amyloidoses, e.g., PrP, alpha-synuclein, and Abeta, our results may be extended to the emerging field of divalent ion-associated amyloidosis.     

Integrated effects of multiple modulators on human liver glycogen phosphorylase a

Hepatic glucose production is increased in people with type 2 diabetes. Glucose released from storage in liver glycogen by phosphorylase accounts for approximately 50% of the glucose produced after an overnight fast. Therefore, understanding how glycogenolysis in the liver is regulated is of great importance. Toward this goal, we have determined the kinetic characteristics of recombinant human liver glycogen phosphorylase a (HLGPa) (active form) and compared them with those of the purified rat enzyme (RLGPa). The Michaelis-Menten constant (K(m)) of HLGPa for P(i), 5 mM, was about fivefold greater than the K(m) of RLGPa. Two P(i) (substrate) concentrations were used (1 and 5 mM) to cover the physiological range for P(i). Other effectors were added at estimated intracellular concentrations. When added individually, AMP stimulated, whereas ADP, ATP and glucose inhibited, activity. These results were similar to those of the RLGPa. However, glucose inhibition was about twofold more potent with the human enzyme. UDP-glucose, glucose 6-phosphate, and fructose 1-phosphate were only minor inhibitors of both enzymes. We reported previously that when all known effectors were present in combination at physiological concentrations, the net effect was no change in RLGPa activity. However, the same combination reduced HLGPa activity, and the inhibition was glucose dependent. We conclude that a combination of the known effectors of phosphorylase a activity, when present at estimated intracellular concentrations, is inhibitory. Of these effectors, only glucose changes greatly in vivo. Thus it may be the major regulator of HLGPa activity.