Diversity of bacteria associated with natural aphid populations

The bacterial communities of aphids were investigated by terminal restriction fragment length polymorphism and denaturing gradient gel electrophoresis analysis of 16S rRNA gene fragments generated by PCR with general eubacterial primers. By both methods, the gamma-proteobacterium Buchnera was detected in laboratory cultures of six parthenogenetic lines of the pea aphid Acyrthosiphon pisum and one line of the black bean aphid Aphis fabae, and one or more of four previously described bacterial taxa were also detected in all aphid lines except one of A. pisum. These latter bacteria, collectively known as secondary symbionts or accessory bacteria, comprised three taxa of gamma-proteobacteria (R-type [PASS], T-type [PABS], and U-type [PAUS]) and a rickettsia (S-type [PAR]). Complementary analysis of aphids from natural populations of four aphid species (A. pisum [n = 74], Amphorophora rubi [n = 109], Aphis sarothamni [n = 42], and Microlophium carnosum [n = 101]) from a single geographical location revealed Buchnera and up to three taxa of accessory bacteria, but no other bacterial taxa, in each aphid. The prevalence of accessory bacterial taxa varied significantly among aphid species but not with the sampling month (between June and August 2000). These results indicate that the accessory bacterial taxa are distributed across multiple aphid species, although with variable prevalence, and that laboratory culture does not generally result in a shift in the bacterial community in aphids. Both the transmission patterns of the accessory bacteria between individual aphids and their impact on aphid fitness are suggested to influence the prevalence of accessory bacterial taxa in natural aphid populations.     

A Comparison of Internal Eliminated Sequences in the Genes that Encode Two K+-Channel Isoforms in Paramecium tetraurelia

We examined both the somatic (macro-) and the germinal (micronuclear) DNAs that encode two K⁺-channel isoforms. PAK1 and PAK11 , in Paramecium tetraurelia. The coding regions of these two isoforms are 88% identical in nucleotides and 95% identical in amino acids. Their introns are also highly conserved. Even some of the internal eliminated sequences in PAK1 and PAK11 are clearly related. PAK1 has five IESs; PAK11 has four. The first (5'-most) IESs of the two genes are located at the same site in the coding sequence but differ in size. The 2nd IES in PAK1 (206-bp), the largest among the nine IESs, has no PAK11 counterpart. The 3rd, 4th and 5th IESs in PAK1 have a counterpart in PAK11 that is similar in size and in sequence, and identical in its position in the coding sequence. In addition, the first IES of PAK11 bears some resemblance to the 4th one of PAK1. The similarities and differences between the two sets of IESs are discussed with respect to the origin and divergence of the two K⁺-channel isoforms.     

Evaluation of LH-RH stimulation of testosterone as an index of reproductive status in rams and its application in wild antelope

In rams a positive correlation (P less than 0.001) existed between average testosterone levels from 30-min blood sampling for 18 h and average testosterone levels of samples taken 0, 1 and 2 h after injection of LH-RH administered 90 min after anaesthesia. Attempts were therefore made to assess testosterone status by LH-RH challenge and limited blood sampling in animals immobilized in their natural habitat. In impala (Aepyceros melampus) territorial males had higher plasma testosterone values than did bachelors after LH-RH challenge (8.1 compared with 2.6 ng/ml, P less than 0.05). In blesbok (Damaliscus dorcas), the relationship was less clear, but testicular volume was correlated with plasma testosterone concentration and with testicular responsiveness measured by testosterone produced per unit of LH (P less than 0.001 and P less than 0.05, respectively). The LH-RH challenge technique therefore has value as a measure of testicular function and permits study of ungulates in their natural environment.     

Evidence for the Neurotrophic Regulation of Collagen-Tailed Acetylcholinesterase in Immature Skeletal Muscle by β-Endorphin

Abstract: Acetylcholinesterase (AChE) was extracted in a high-saline medium from gastrocnemius muscles of rat embryos and young rats aged 14 days'gestation to 40 days post partum. The molecular forms of the enzyme were separated by low-salt precipitation, followed by velocity sedimentation. During gestation, all molecular forms increased in activity, particularly the 16 S (A₁₂) form. During the first 2 weeks of life, there was a large increase in the activity of soluble AChE (G forms), whilst the activity of insoluble AChE (A forms) was reduced. Denervation of the muscle reversed the change in the relative proportions of the molecular forms. The embryonic pattern of activities of AChE forms persisted in cultures of myotubes obtained at 20 days'gestation and maintained in the absence of spinal cord. When myotubes were maintained in medium previously conditioned by developing spinal cord explants, 16 S AChE declined while the soluble (4 and 6 S) forms increased in activity in a manner resembling that seen in early postnatal muscles in vivo . β-Endorphin (β-EP) immunoreactivity was detected in the spinal cord-conditioned medium and was identified by HPLC and ion-exchange chromatography as β-EP-(l–31) plus its shortened and N -acetylated forms. Cultivation of myotubes in the presence of synthetic camel β-EP resulted in a reversible change in the pattern of AChE forms which was similar to that seen with spinal cord-conditioned medium. These studies provide evidence for the neuroregulation of AChE A and G forms in immature skeletal muscle. A major candidate for this role is β-EP, produced and released by developing spinal cord.     

Age-related augmentation of phosphorylase b kinase in hepatic tissue from the glycogen-storage-disease (gsd/gsd) rat.

The effects of food deprivation on body weight, liver weight, hepatic glycogen content, glycogenolytic enzymes and blood metabolites were compared in young and old phosphorylase b kinase-deficient (gsd/gsd) rats. Although the concentration of glycogen in liver from 9-week-old female gsd/gsd rats (730 mumol of glucose equivalents/g wet wt.) was increased by 7-8% during starvation, total hepatic glycogen was decreased by 12% after 24 h without food. In 12-month-old male gsd/gsd rats the concentration of liver glycogen (585 mumol of glucose equiv./g wet wt.) was decreased by 16% and total hepatic glycogen by nearly 40% after food deprivation for 24 h. Phosphorylase b kinase and phosphorylase a were present at approx. 10% of the control activities in 9-week-old gsd/gsd rats, but both enzyme activities were increased more than 3-fold in 12-month-old affected rodents. It is concluded that the age-related ability to mobilize hepatic glycogen appears to result from the augmentation of phosphorylase b kinase during maturation of the gsd/gsd rat.     

Species-Specific Viromes in the Ancestral Holobiont Hydra

Recent evidence showing host specificity of colonizing bacteria supports the view that multicellular organisms are holobionts comprised of the macroscopic host in synergistic interdependence with a heterogeneous and host-specific microbial community. Whereas host-bacteria interactions have been extensively investigated, comparatively little is known about host-virus interactions and viral contribution to the holobiont. We sought to determine the viral communities associating with different Hydra species, whether these viral communities were altered with environmental stress, and whether these viruses affect the Hydra-associated holobiont. Here we show that each species of Hydra harbors a diverse host-associated virome. Primary viral families associated with Hydra are Myoviridae, Siphoviridae, Inoviridae, and Herpesviridae. Most Hydra-associated viruses are bacteriophages, a reflection of their involvement in the holobiont. Changes in environmental conditions alter the associated virome, increase viral diversity, and affect the metabolism of the holobiont. The specificity and dynamics of the virome point to potential viral involvement in regulating microbial associations in the Hydra holobiont. While viruses are generally regarded as pathogenic agents, our study suggests an evolutionary conserved ability of viruses to function as holobiont regulators and, therefore, constitutes an emerging paradigm shift in host-microbe interactions.     

β-Catenin Inactivation Is a Pre-Requisite for Chick Retina Regeneration

In the present study we explored the role of β-catenin in mediating chick retina regeneration. The chick can regenerate its retina by activating stem/progenitor cells present in the ciliary margin (CM) of the eye or via transdifferentiation of the retinal pigmented epithelium (RPE). Both modes require fibroblast growth factor 2 (FGF2). We observed, by immunohistochemistry, dynamic changes of nuclear β-catenin in the CM and RPE after injury (retinectomy). β-catenin nuclear accumulation was transiently lost in cells of the CM in response to injury alone, while the loss of nuclear β-catenin was maintained as long as FGF2 was present. However, nuclear β-catenin positive cells remained in the RPE in response to injury and were BrdU-/p27+, suggesting that nuclear β-catenin prevents those cells from entering the cell cycle. If FGF2 is present, the RPE undergoes dedifferentiation and proliferation concomitant with loss of nuclear β-catenin. Moreover, retinectomy followed by disruption of active β-catenin by using a signaling inhibitor (XAV939) or over-expressing a dominant negative form of Lef-1 induces regeneration from both the CM and RPE in the absence of FGF2. Our results imply that β-catenin protects cells of the CM and RPE from entering the cell cycle in the developing eye, and specifically for the RPE during injury. Thus inactivation of β-catenin is a pre-requisite for chick retina regeneration.