Population dynamics in changing environments: the case of an eruptive forest pest species

In recent decades we have seen rapid and co‐occurring changes in landscape structure, species distributions and even climate as consequences of human activity. Such changes affect the dynamics of the interaction between major forest pest species, such as bark beetles (Coleoptera: Curculionidae, Scolytinae), and their host trees. Normally breeding mostly in broken or severely stressed spruce; at high population densities some bark beetle species can colonise and kill healthy trees on scales ranging from single trees in a stand to multi‐annual landscape‐wide outbreaks. In Eurasia, the largest outbreaks are caused by the spruce bark beetle, Ips typographus (Linnaeus), which is common and shares a wide distribution with its main host, Norway spruce (Picea abies Karst.). A large literature is now available, from which this review aims to synthesize research relevant for the population dynamics of I. typographus and co‐occurring species under changing conditions. We find that spruce bark beetle population dynamics tend to be metastable, but that mixed‐species and age‐heterogeneous forests with good site‐matching tend to be less susceptible to large‐scale outbreaks. While large accumulations of logs should be removed and/or debarked before the next swarming period, intensive removal of all coarse dead wood may be counterproductive, as it reduces the diversity of predators that in some areas may play a role in keeping I. typographus populations below the outbreak threshold, and sanitary logging frequently causes edge effects and root damage, reducing the resistance of remaining trees. It is very hard to predict the outcome of interspecific interactions due to invading beetle species or I. typographus establishing outside its current range, as they can be of varying sign and strength and may fluctuate depending on environmental factors and population phase. Most research indicates that beetle outbreaks will increase in frequency and magnitude as temperature, wind speed and precipitation variability increases, and that mitigating forestry practices should be adopted as soon as possible considering the time lags involved.     

Murine H-2Dd-reactive monoclonal antibodies recognize shared antigenic determinant(s) on human HLA-B7 or HLA-B27 molecules or both

We have evaluated the serological relationships between the murine H-2Dd and human HLA molecules using four H-2Dd-reactive monoclonal antibodies (mAbs) produced in the A.BY (KbIbDb) anti-A.TL (KsIkDd) combination. In the mouse, these reagents exhibited three distinct reactivity patterns: Dd, Ks, and H-2u (mAb 81.L); Dd, H-2p, and H-2u (mAb 81.R); and Dd, Kd, H-2p, H-2u, and H-2v (mAbs 97.G and 97.H). Sequential immunoprecipitation and cross-competitive mAb binding experiments revealed that these mAbs recognized determinants in two spatially distinct polymorphic domains on the H-2Dd molecule of B10.A(5R) cells (defined by mAbs 81.L and 81.R, 97.H, and 97.G, respectively). MAbs 81.R, 97.G, and 97.H, but not 81.L, also defined an HLA-linked polymorphism in the human, the main characteristics of which can be summarized as follows: (i) on B lymphoblastoid cell lines, mAbs 81.R and 97.H bound to cells expressing the HLA-B7, HL-B27 or Bw40 cross-reacting specificities, (ii) on peripheral blood lymphocyte (PBL) panel mAb 81.R exerted C dependent cytotoxicity to 118 of 400 cells tested, including almost all HLA-B7 or HLA-B27 cells or both (r: 0.952), (iii) the expression of the 81.R cross-reacting determinant segregated in an informative family with the parental haplotype carrying the HLA-B7 allele, and (iv) mAbs 81.R, 97.G, and 97.H recognized topologically related determinants on the same class I molecule(s) of the human B lymphoblastoid cells JY (HLA-A2,2, -B7,7). These data support the view that some, but not all H-2Dd allotopes have been conserved throughout evolution and are associated in the human with the HLA-B7, -B27 cross-reacting specificities.     

A quantitative autoradiographic method for the measurement of local rates of brain protein synthesis

We have developed a new method for measuring local rates of brain protein synthesis in vivo. It combines the intraperitoneal injection of a large dose of low specific activity amino acid with quantitative autoradiography. This method has several advantages: 1) It is ideally suited for young or small animals or where immobilizing an animal is undesirable. 2) The amino acid injection floods amino acid pools so that errors in estimating precursor specific activity, which is especially important in pathological conditions, are minimized. 3) The method provides for the use of a radioautographic internal standard in which valine incorporation is measured directly. Internal standards from experimental animals correct for tissue protein content and self-absorption of radiation in tissue sections which could vary under experimental conditions.A preliminary report of this work was presented at the 11th annual meeting of the Society for Neuroscience, Los Angeles, California, October 18–23, 1981.     

Hypothesis: Iron chelation plays a vital role in neutrophilic inflammation

Neutrophil influx into tissues occurs in many diverse diseases and can be associated with both beneficial and injurious effects. We hypothesize that the stimulus for certain neutrophilic inflammatory responses can be reduced to a series of competing reactions for iron, with either a labile or reactive coordination site available, between host chelators and chelators not indigenous to that specific living system. The iron focuses the transport of host phagocytic cells through a metal catalyzed generation of oxidant sensitive mediators including cytokines and eicosanoids. Many of these products are chemotactic for neutrophils. We also postulate that the iron increases the activity of the phagocyte associated NADPH oxidoreductase in the neutrophil. The function of this enzyme is likely to be the generation of superoxide in the hostÕs attempt to chemically reduce and dislodge the iron from its chelate complex. After the reoxidation of Fe in an aerobic environment, Fe will be coordinated by host lactoferrin released by the neutrophil. When complexed by this glycoprotein, the metal does not readily undergo oxidation/reduction and is safely transported to the macrophages of the reticuloendothelial system where it is stored in ferritin. Finally, we propose that the neutrophil will attempt to destroy the chelator not indigenous to the host by releasing granular contents other than lactoferrin. Inability to eliminate the chelator allows this sequence to repeat itself, which can lead to tissue injury. Such persistence of a metal chelate in the host may be associated with biomineralization, fibrosis, and cancer.     

Alcaloides du Strychnos tchibangensis

The structure of a new bisindole alkaloid has been elucidated by chemical correlation and analysis of ¹³C NMR spectra.     

Alternative splicing regulates targeting of malate dehydrogenase in Yarrowia lipolytica

Alternative pre-mRNA splicing is a major mechanism contributing to the proteome complexity of most eukaryotes, especially mammals. In less complex organisms, such as yeasts, the numbers of genes that contain introns are low and cases of alternative splicing (AS) with functional implications are rare. We report the first case of AS with functional consequences in the yeast Yarrowia lipolytica. The splicing pattern was found to govern the cellular localization of malate dehydrogenase, an enzyme of the central carbon metabolism. This ubiquitous enzyme is involved in the tricarboxylic acid cycle in mitochondria and in the glyoxylate cycle, which takes place in peroxisomes and the cytosol. In Saccharomyces cerevisiae, three genes encode three compartment-specific enzymes. In contrast, only two genes exist in Y. lipolytica. One gene (YlMDH1, YALI0D16753g) encodes a predicted mitochondrial protein, whereas the second gene (YlMDH2, YALI0E14190g) generates the cytosolic and peroxisomal forms through the alternative use of two 3'-splice sites in the second intron. Both splicing variants were detected in cDNA libraries obtained from cells grown under different conditions. Mutants expressing the individual YlMdh2p isoforms tagged with fluorescent proteins confirmed that they localized to either the cytosolic or the peroxisomal compartment.     

Sperm production and mating potential of males after a cold shock on pupae of the parasitoid wasp Dinarmus basalis (Hymenoptera: Pteromalidae)

For ectothermic species, temperature is a key environmental factor influencing several aspects of their physiology and ecology, acting particularly on reproduction. To measure the consequences of a severe thermal stress during development on male reproduction, a cold shock (1h at -18 degrees C) was tested on Dinarmus basalis pupae. D. basalis (Hymenoptera: Pteromalidae) is a parasitoid wasp in which sperm management in both male and female is of prime importance. After a cold shock, developmental success was reduced, with a quarter of cold-shocked males not emerging correctly. The stress effects were estimated at the level of sperm stock in seminal vesicles of males at different ages and on the ability of 2-day-old males to access females in single and multiple mating and in male-male competition. Cold-shocked males had a reduced sperm stock compared to control males and this difference persisted with age. The rate of sperm production was similar in both groups. The consequences of a cold shock on male reproductive ability were perceptible in multiple mating and male-male competition but not in single mating. Cold-shocked males were at a disadvantage, inseminating fewer females and copulating less frequently. Finally, male pupae of D. basalis were able to withstand severe temperature stresses and their reproductive functions were partially preserved.