Reproductive biology of Pseudococcus maritimus (Hemiptera: Pseudococcidae)

This study characterized several parameters associated with reproductive behaviors of a Californian population of the grape mealybug, Pseudococcus maritimus (Ehrhorn). Experiments with caged adults confirmed that females from this population could not reproduce parthenogenetically. Both sexes were capable of mating multiple times on the same day and on sequential days. Median times between copulations were short (< 10 min) on the first day that males were presented with females, but tended to increase with sequential copulation events. Unmated females lived for up to 19 wk, whereas mating and oviposition resulted in reduced longevity. We hypothesized that constant exposure to pheromone might stimulate males to leave their cocoons sooner and increase their activity levels compared with males that were not exposed to pheromone, resulting in shortened life-spans. However, whereas exposure to pheromone did stimulate males to emerge slightly sooner than control males, pheromone exposure had no effect on the longevity of males. The implications of the results of these experiments for pheromone-based methods of detection and control of mealybugs are discussed.     

Insights into protein structure and function from disorder-complexity space

Intrinsically disordered proteins have a wide variety of important functional roles. However, the relationship between sequence and function in these proteins is significantly different than that for well-folded proteins. In a previous work, we showed that the propensity to be disordered can be recognized based on sequence composition alone. Here that analysis is furthered by examining the relationship of disorder propensity to sequence complexity, where the metrics for these two properties depend only on composition. The distributions of 40 amino acid peptides from both ordered and disordered proteins are graphed in this disorder-complexity space. An analysis of Swiss-Prot shows that most peptides have high complexity and relatively low disorder. However, there are also an appreciable number of low complexity-high disorder peptides in the database. In contrast, there are no low complexity-low disorder peptides. A similar analysis for peptides in the PDB reveals a much narrower distribution, with few peptides of low complexity and high disorder. In this case, the bounds of the disorder-complexity distribution are well defined and might be used to evaluate the likelihood that a peptide can be crystallized with current methods. The disorder-complexity distributions of individual proteins and sets of proteins grouped by function are also examined. Among individual proteins, there is an enormous variety of distributions that in some cases can be rationalized with regard to function. Groups of functionally related proteins are found to have distributions that are similar within each group but show notable differences between groups. Finally, a pattern matching algorithm is used to search for proteins with particular disorder-complexity distributions. The results suggest that this approach might be used to identify relationships between otherwise dissimilar proteins.     

Two genetic pathways for age-related macular degeneration

The discovery of strong associations of the His402 variant of complement factor H (CFH) and the change in the promoter region of HtrA serine peptidase 1 (HTRA1) with age-related macular degeneration (AMD) have altered our conception of the pathophysiology of this disease. The complement system has been placed at the center of a flurry of research interest, and a similar growth in attention to the serine proteases is not far behind. The specific role of these variants in causing AMD is unknown, but they will undoubtedly lead to a deeper understanding of the biological mechanisms and will point to new avenues for pharmacologic management. Furthermore, these variants will enable clinicians and investigators to identify people at high risk for this condition, thereby establishing the preconditions for preventing the disease.     

Neural-Specific Deletion of Htra2 Causes Cerebellar Neurodegeneration and Defective Processing of Mitochondrial OPA1

HTRA2, a serine protease in the intermembrane space, has important functions in mitochondrial stress signaling while its abnormal activity may contribute to the development of Parkinson’s disease. Mice with a missense or null mutation of Htra2 fail to thrive, suffer striatal neuronal loss, and a parkinsonian phenotype that leads to death at 30–40 days of age. While informative, these mouse models cannot separate neural contributions from systemic effects due to the complex phenotypes of HTRA2 deficiency. Hence, we developed mice carrying a Htra2-floxed allele to query the consequences of tissue-specific HTRA2 deficiency. We found that mice with neural-specific deletion of Htra2 exhibited atrophy of the thymus and spleen, cessation to gain weight past postnatal (P) day 18, neurological symptoms including ataxia and complete penetrance of premature death by P40. Histologically, increased apoptosis was detected in the cerebellum, and to a lesser degree in the striatum and the entorhinal cortex, from P25. Even earlier at P20, mitochondria in the cerebella already exhibited abnormal morphology, including swelling, vesiculation, and fragmentation of the cristae. Furthermore, the onset of these structural anomalies was accompanied by defective processing of OPA1, a key molecule for mitochondrial fusion and cristae remodeling, leading to depletion of the L-isoform. Together, these findings suggest that HTRA2 is essential for maintenance of the mitochondrial integrity in neurons. Without functional HTRA2, a lifespan as short as 40 days accumulates a large quantity of dysfunctional mitochondria that contributes to the demise of mutant mice.     

Effects of hypothyroidism on myosin heavy chain composition and fibre types of fast skeletal muscles in a small marsupial, Antechinus flavipes

Effects of drug-induced hypothyroidism on myosin heavy chain (MyHC) content and fibre types of fast skeletal muscles were studied in a small marsupial, Antechinus flavipes. SDS-PAGE of MyHCs from the tibialis anterior and gastrocnemius revealed four isoforms, 2B, 2X, 2A and slow, in that order of decreasing abundance. After 5 weeks treatment with methimazole, the functionally fastest 2B MyHC significantly decreased, while 2X, 2A and slow MyHCs increased. Immunohistochemistry using monospecific antibodies to each of the four MyHCs revealed decreased 2b and 2x fibres, and increased 2a and hybrid fibres co-expressing two or three MyHCs. In the normally homogeneously fast superficial regions of these muscles, evenly distributed slow-staining fibres appeared, resembling the distribution of slow primary myotubes in fast muscles during development. Hybrid fibres containing 2A and slow MyHCs were virtually absent. These results are more detailed but broadly similar to the earlier studies on eutherians. We hypothesize that hypothyroidism essentially reverses the effects of thyroid hormone on MyHC gene expression of muscle fibres during myogenesis, which differ according to the developmental origin of the fibre: it induces slow MyHC expression in 2b fibres derived from fast primary myotubes, and shifts fast MyHC expression in fibres of secondary origin towards 2A, but not slow, MyHC.     

Structure of the extracellular surface of the gap junction by atomic force microscopy.

The extracellular surface of the gap junction cell-to-cell channels was imaged in phosphate-buffered saline with an atomic force microscope. The fully hydrated isolated gap junction membranes adsorbed to mica were irregular sheets approximately 1-2 microns across and 13.2 (+/- 1.3) nm thick. The top bilayer of the gap junction was dissected by increasing the force applied to the tip or sometimes by increasing the scan rate at moderate forces. The exposed extracellular surface revealed a hexagonal array with a center-to-center spacing of 9.4 (+/- 0.9) nm between individual channels (connexons). Images of individual connexons with a lateral resolution of < 3.5 nm, and in the best case approximately 2.5 nm, were reliably and reproducibly obtained with high-quality tips. These membrane channels protruded 1.4 (+/- 0.4) nm from the extracellular surface of the lipid membrane, and the atomic force microscope tip reached up to 0.7 nm into the pore, which opened up to a diameter of 3.8 (+/- 0.6) nm on the extracellular side.     

Probable Site of Sex Pheromone Emission in Female Vine and Obscure Mealybugs (Hemiptera: Pseudococcidae)

In laboratory bioassays, male Pseudococcus viburni (Signoret) and Planococcus ficus Signoret were attracted to body sections of females that included the metathoracic legs. Extracts of the metathoracic legs of female P. ficus were much more attractive to males than extracts of the other legs, and males exhibited copulatory behavior towards these extracts. Scanning electron microscopy showed the presence of translucent pores on the coxae of mature but not immature females. Collectively, the data suggest that the female-produced sex pheromones of these species are released from the metathoracic legs, probably from the translucent pores.     

Mycobacterium massiliense is differentiated from Mycobacterium abscessus and Mycobacterium bolletii by erythromycin ribosome methyltransferase gene (erm) and clarithromycin susceptibility patterns

Erythromycin ribosome methyltransferase gene (erm) sequences of Mycobacterium massiliense and Mycobacterium bolletii isolates were newly investigated. Forty nine strains of M. massiliense that were analyzed in the present study had a deleted erm(41). Due to a frame‐shift mutation, large deletion, and truncated C‐terminal region, the Erm(41) of M. massiliense had only 81 amino acids encoded by 246 nucleotides. Corresponding to these findings, most of the M. massiliense isolates (89.8%) were markedly clarithromycin susceptible, but resistant strains invariably had a point mutation at the adenine (A₂₀₅₈ or A₂₀₅₉) in the peptidyltransferase region of the 23S rRNA gene, which is quite different from Mycobacterium abscessus and M. bolletii. In addition, erm(41) sequences of M. massiliense were more conserved than those of M. abscessus and M. bolletii. The results of species identification using erm(41) showed concordant results with those of multi‐locus sequence analysis (rpoB, hsp65, sodA and 16S‐23S ITS) where there were originally inconsistent results between rpoB and hsp65 sequence analysis in previous research. Therefore, erm(41) PCR that was used in the present study can be efficiently used to simply differentiate M. massiliense from M. abscessus and M. bolletii.     

Localization of human cardiac beta-myosin heavy chain gene (MYH7) to chromosome 14q12 by in situ hybridization

The genes coding for each human cardiac myosin heavy chain (alpha-MHC and beta-MHC, MYH6 and MYH7, respectively) are tightly linked and the alpha-MHC gene has been assigned to chromosome 14. In order to provide a more precise regional localization, in situ hybridization experiments were carried out using a 3H-labeled probe derived from a beta-MHC genomic clone. The results demonstrated that the human cardiac MHC genes are located within the q12 band of chromosome 14.