Poleward increase in feeding efficiency of leafminer Stigmella lapponica (Lepidoptera: Nepticulidae) in a latitudinal gradient crossing a boreal forest zone

Damage to plant communities imposed by insect herbivores generally decreases from low to high latitudes. This decrease is routinely attributed to declines in herbivore abundance and/or diversity, whereas latitudinal changes in per capita food consumption remain virtually unknown. Here, we tested the hypothesis that the lifetime food consumption by a herbivore individual decreases from low to high latitudes due to a temperature-driven decrease in metabolic expenses. From 2016 to 2019, we explored latitudinal changes in multiple characteristics of linear (gallery) mines made by larvae of the pygmy moth, Stigmella lapponica, in leaves of downy birch, Betula pubescens. The mined leaves were larger than intact leaves at the southern end of our latitudinal gradient (at 60°N) but smaller than intact leaves at its northern end (at 69°N), suggesting that female oviposition preference changes with latitude. No latitudinal changes were observed in larval size, mine length or area, and in per capita food consumption, but the larval feeding efficiency (quantified as the ratio between larval size and mine size) increased with latitude. Consequently, S. lapponica larvae consumed less foliar biomass at higher latitudes than at lower latitudes to reach the same size. Based on space-for-time substitution, we suggest that climate warming will increase metabolic expenses of insect herbivores with uncertain consequences for plant–herbivore interactions.     

Fossil Homo femur from Berg Aukas,northern Namibia

The proximal half of a hominid femur was recovered from deep within a paleokarst feature at the Berg Aukas mine, northern Namibia. The femur is fully mineralized, but it is not possible to place it in geochrono logical context. It has a very large head, an exceptionally thick diaphyseal cortex, and a very low collodiaphyseal angle, which serve to differentiate it from Holocene homologues. The femur is not attributable to Australopithecus, Paranthropus, or early Homo (i.e., H. habilis sensu lato). Homo erectus femora have a relatively longer and AP flatter neck, and a shaft that exhibits less pilaster than the Berg Aukas specimen. Berg Aukas also differs from early modern femora in several features, including diaphyseal cortical thickness and the degree of subtrochanteric AP flattening. The massive diaphyseal cortex of Berg Aukas finds its closest similarity within archaic H. sapiens (e.g., Castel di Guido) and H. erectus (e.g., KNM-ER 736) samples. It has more cortical bone at midshaft than any other specimen, although relative cortical thickness and the asymmetry of its cross-sectional disposition at this level are comparable with those of other Pleistocene fem ora. The closest morphological comparisons with Berg Aukas are in archaic (i.e., Middle Pleistocene) H. sapiens and Neandertal samples. © 1995 Wiley-Liss, Inc.     

Regulation of the host response to bacterial lipopolysaccharides

Bacterial endotoxins or lipopolysaccharides (LPS) are unique glycolipids present in the outer cell membrane of all gram-negative bacteria. It is now generally recognized that LPS is of primary importance in initiating the pathophysiological changes that often accompany gram-negative bacillary infections in humans including hypotensive shock, disseminated intravascular coagulation, and metabolic abnormalities. Although the biochemical mechanisms of these changes are not well understood, increasing emphasis has been placed on defining the biochemical response of the macrophage (M phi) to LPS. In this paper we describe two M phi-derived factors induced by LPS that may be important in the expression of endotoxic activity in the host. These are a procoagulant activity, which is present on the cell membrane of LPS-treated rabbit liver M phi and acts by directly activating coagulation factor X, and a factor released into the supernatant by LPS-treated peritoneal exudate M phi, which suppresses steroidogenesis in explanted adrenocortical cells. The potential role of the M phi in regulating the binding of LPS to high-density lipoproteins through the induction of acute phase proteins is also considered.     

Estradiol 17β-dehydrogenase and 20α-hydroxysteroid dehydrogenase from human placental cytosol: one enzyme with two activities?

The soluble enzyme estradiol 17β-dehydrogenase (17β-ED) from human term placental cytosol is reported to be a stereospecific oxidoreductase for estrogen substrates. A published purification scheme (heat treatment and affinity chromatography) yielded a homogeneous protein which had the reported characteristics of pure 17β-ED and also had 20α-hydroxysteroid dehydrogenase (20α-HSD) activity. Spectrophotometric assay when the buffer contained albumin, 8 mg/ml, masked the 20α-HSD activity observed in albumin-free conditions and may explain why this bifunctional activity has gone unrecognized. In human placenta, one enzyme may catalyze stereospecific oxidation/reduction of both estrogen and progesterone.     

Restriction analysis of the Streptomyces glaucescens genome by agarose gel electrophoresis

A method for the analysis of total DNA of Streptomyces glaucescens is described. The relevant steps are (a) extraction and purification of DNA, (b) restriction of DNA samples with type II restriction enzymes, (c) one dimensional separation of restriction fragments by agarose gel electrophoresis. A typical banding pattern was obtained for each wild type strain, independant of growth conditions or age of the culture. Mutant strains exhibited in most cases the same banding pattern as the parent wild type strain. Only in one specific mutant class a fragment of about 9 megadalton was missing.     

The natural history of the helicoidal occlusal plane and its evolution in early Homo

In modern man the pitch of the occlusal plane may vary along the tooth-row. When anterior cheek-teeth show a plane sloping upward palatally, whilst that on posterior cheek-teeth slopes upward buccally, there results a twisted or helicoidal occlusal plane (Ackermann). Several hypotheses have been proposed for the structural basis of the helicoidal occlusal plane. Campbell's proposal ('25) has gained widest acceptance, namely that the helicoid results from anteroposterior differences in upper and lower alveolar arch width. In the early 1960s, while studying the Olduvai hominids assigned to Homo habilis, the author noted changing occlusal slopes along the tooth-row and a slight helicoid, although these featues had not been noted in other early hominids. Subsequently, Wallace showed a total absence of the helicoid from South African australopithecines, and its presence in Swartkrans Homo, SK 45 and SK 80. Recent studies confirm the presence of the helicoid in all available specimens of H. habilis, including Stw 53 found at Sterkfontein in 1976. Hence, this trait may distinguish between Australopithecus and early Homo. Measurements of the maxillary arch widths have shown that, whereas in Australopithecus arch widths increase to a maximum at M3, in early Homo maxillary arch widths are greatest at M2. The decline in posterior maxillary arch width is part of a general reduction of that region. Thus despite striking elongation of premolars and M1 in early Homo, M2 and M3 are mesiodistally abbreviated. It is hypothesized that the onset of posterior arch reduction, with the appearance of a helicoid, was a structural and functional concomitant of the transition from the presumed australopithecine ancestor to H. habilis.     

Cloning and functional analysis of the ubiquitin-specific protease gene UBP1 of Saccharomyces cerevisiae

In eukaryotes, both natural and engineered fusions of ubiquitin to itself or other proteins are cleaved by processing proteases after the last (Gly76) residue of ubiquitin. Using the method of sib selection, and taking advantage of the fact that bacteria such as Escherichia coli lack ubiquitin-specific enzymes, we have cloned a gene, named UBP1, of the yeast Saccharomyces cerevisiae that encodes a ubiquitin-specific processing protease. With the exception of polyubiquitin, the UBP1 protease cleaves at the carboxyl terminus of the ubiquitin moiety in natural and engineered fusions irrespective of their size or the presence of an amino-terminal ubiquitin extension. These properties of UBP1 distinguish it from the previously cloned yeast protease YUH1, which deubiquitinates relatively short ubiquitin fusions but is virtually inactive with longer fusions such as ubiquitin-beta-galactosidase. The amino acid sequence of the 809-residue UBP1 lacks significant similarities to other known proteins, including the 236-residue YUH1 protease. Null ubp1 mutants are viable, and retain the ability to deubiquitinate ubiquitin-beta-galactosidase, indicating that the family of ubiquitin-specific proteases in yeast is not limited to UBP1 and YUH1.     

Stability of a model beta-sheet in water.

We have used molecular dynamics simulations to determine the stability in water of a model beta-sheet formed by two alanine dipeptide molecules with two intermolecular hydrogen bonds in the closely spaced antiparallel arrangement. In this paper we describe our computations of the binding free energy of the model sheet and a portion of the free energy surface as a function of a reaction co-ordinate for sheet formation. We used the free energy surface to identify stable conformations along the reaction co-ordinate. To determine whether or not the model sheet with two hydrogen bonds is more stable than a single amide hydrogen bond in water, we compared the results of the present calculations to results from our earlier study of linear hydrogen bond formation between two formamide molecules (the formamide "dimer"). The free energy surfaces for the sheet and formamide dimer each have two minima corresponding to locally stable hydrogen-bonded and solvent-separated configurations. The binding free energies of the model sheet and the formamide dimer are -5.5 and -0.34 kcal/mol, respectively. Thus, the model sheet with two hydrogen bonds is quite stable while the simple amide hydrogen bond is only marginally stable. To understand the relative stabilities of the model sheet and formamide dimer in terms of solute-solute and solute-water interactions, we decomposed the free energy differences between hydrogen-bonded and solvent-separated conformations into energetic and entropic contributions. The changes in the peptide-peptide energy and the entropy are roughly twice as large for the sheet as they are for the formamide dimer. The magnitude of the peptide-water energy difference for the sheet is less than twice (by about 3.5 kcal/mol) that for the formamide dimer, and this accounts for the stability of the sheet. The presence of the side-chains and/or blocking groups apparently prevents the amide groups in the sheet from being solvated as favorably in the separated arrangement as in the formamide dimer, where the amide groups are completely exposed to the solvent.