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.     

Unravelling the nocturnal appearance of bogue Boops boops shoals in the anthropogenically modified shallow littoral

In the present study the role of the nocturnal migration of bogue Boops boops shoals to anthropogenically modified shallow littoral locations was examined, evaluating four alternative hypotheses: (1) feeding, (2) reproduction, (3) attraction of B. boops to artificial light and (4) concealment in the darkness related to predation avoidance. All hypotheses apart from predation avoidance were rejected, as B. boops tended to concentrate in shaded locations of wider illuminated areas, a finding not only important concerning fish behaviour, but also with significant management implications.     

Comparative responses of ovipositing Anopheles gambiae and Culex quinquefasciatus females to the presence of Culex egg rafts and larvae

Field observations have demonstrated that gravid Anopheles gambiae Giles s.s. (Diptera: Culicidae) are selective in their choice of oviposition sites. For example, immature stages of An. gambiae s.s. are rarely found in water that contains Culex quinquefasciatus Say immatures. The possibility that this may, in part at least, reflect a response by ovipositing An. gambiae s.s. females to volatile signals associated with Culex juveniles was evaluated by testing the response of An. gambiae s.s. females to varying densities of Cx. quinquefasciatus egg rafts and/or larvae in oviposition choice assays. For comparison, the oviposition choices of Cx. quinquefasciatus to conspecific egg rafts and/or larvae were similarly assayed. At a low density of Cx. quinquefasciatus egg rafts (1-15 egg rafts/100 mL water), An. gambiae s.s. females laid more eggs in the treatment water than in the control, with a maximum of twice as many in the treatment water at 5 egg rafts/100 mL water. At higher egg raft densities and in all treatments that included Cx. quinquefasciatus larvae, oviposition decreased significantly in the treatment dishes in a density-dependent manner. As previous studies have indicated, ovipositing Cx. quinquefasciatus females were attracted to and laid egg rafts in dishes containing conspecific egg rafts and, interestingly, also in dishes containing larvae.     

Effects of large Saduria entomon (Isopoda) on spatial distribution of their small S. entomon and Monoporeia affinis (Amphipoda) prey

We performed laboratory experiments to investigate the effects of predator avoidance and numerical effects of predation on spatial distribution of small Saduria entomon (Isopoda) and Monoporeia affinis (Amphipoda), with large S. entomon as predators. The horizontal distribution and mortality of the prey species, separately and together, were studied in aquaria with a spatial horizontal refuge. We also estimated effects of refuge on mortality of small S. entomon and M. affinis by experiments without the refuge net. In addition, we investigated whether predation risk from large S. entomon influenced the swimming activity of M. affinis, to clarify the mechanisms behind the spatial distribution. Both small S. entomon and M. affinis avoided large S. entomon. The avoidance behaviour of M. fffinis contributed about 10 times more to the high proportion in the refuge than numerical effects of predation. Due to the low mortality of small S. entomon the avoidance behaviour of this species was even more important for the spatial distribution. The combined effect of avoidance behaviour and predation in both species was aggregation, producting a positive correlation between the species in density. M. affinis showed two types of avoidance behaviour. In the activity experiments they reduced activity by 36% and buried themselves in the sediment. In the refuge experiments we also observed avoidance behaviour with the emigration rate from the predator compartment being twice the immigration rate. The refuge did not lower predation mortality in M. affinis, probably due to the small scale of the experimental units in relation to the mobility of the species. Predation mortality in small S. entomon was higher in absence of a refuge and especially high in absence of M. affinis.     

Early season root production and zoospore infection of cultivars of flue-cured tobacco that differ in level of partial resistance to Phytophthora parasitica var. nicotianae

Root production of four cultivars of flue-cured tobacco was quantified in the field, greenhouse and phytotron. The cultivars ranged in level of partial resistance to the black shank pathogen, Phytophthora parasitica var. nicotianae, from susceptible to highly resistant. In the field, root-observation plates were installed approximately 10 cm from plants, and in greenhouse and phytotron studies, plants were grown in 4-liter containers with one sloping transparent side for root observation. Root growth was determined weekly for four weeks after transplanting in the field and daily up to 14 days after transplanting in the greenhouse and phytotron. Root tracings were made on acetate sheets placed against the sloping transparent side of the containers or against the transparent observation plates in the field following removal of soil from the outside of the observation plate. Root growth was quantified by retracing the root pattern on the acetate sheets over a digitizing tablet attached to a personal computer. Numbers of roots, root length, and mean and maximum rate of root growth were determined. Cultivars Hicks (susceptible) and K-326 (low level of resistance) had significantly larger root systems than moderately resistant G-28 or highly resistant NC 82. Differences in total root length were due to increased branching that resulted in development of significantly greater numbers of roots in Hicks and K-326. For example, between day 21 and 28, Hicks produced more than three times the number of new roots as NC 82 in the field. The mean rate of root extension observed (2.17 mm hr^–1) was similar in all four cultivars. Infection efficiency on the different cultivars was determined in the field by inoculating roots with zoospores of P. p. nicotianae. Lesions were visible as water soaked areas within 24 hr of inoculation. At 48 hr after inoculation, percentages of inoculations that resulted in lesion formation were 57, 46, 23, and 16% for Hicks, K-326, G-28 and NC 82, respectively. The possible role of rooting intensity as a mechanism of avoidance to P. p. nicotianae in tobacco cultivars is discussed.     

Opportunities for female choice in the bed bug Cimex lectularius

Bed bugs are cited as exemplars of sexual conflict because mating can only occur via traumatic insemination. However, past antagonistic coevolution between the sexes does not necessarily preclude current female choice. Here, we investigate opportunities for precopulatory female choice in bed bugs. We examined whether females seek out mating opportunities when they gain the most benefit: when females are virgin and/or have recently fed. But, we found that female mating and feeding status had little effect on female attraction to males and male odor. To determine whether females approach male harborages (home crevices) to seek matings in nature, we investigated where matings occurred among unfamiliar pairs of bed bugs. We found that, despite female attraction to male odor, matings were most likely to take place in the female's harborage rather than the male's harborage. We also examined the effect of feeding on male and female ability to mate. Whereas previous research reported that engorgement impaired female ability to refuse matings, we found that male feeding status had a larger effect on the success of mating encounters than female feeding status. Fed males had poor mating success, suggesting that males may be faced with a trade‐off between mating and feeding.     

When not to avoid inbreeding

Avoidance of incestuous matings is widely reported across many animal taxa, and the adaptive value of such behavior is explained through inbreeding depression. However, an old and somewhat neglected theoretical result predicts that inbred matings offer another, positive effect on the inclusive fitness of parents: an individual who mates with a relative will help that relative to spread genes identical by descent. This benefit can be substantial, if the additional mating achieved by the relative does not harm his mating success otherwise, and in the context of selfing in plants the phenomenon is well known. Here, we develop a model that derives expected values of inbreeding tolerance, that is, the magnitude of inbreeding depression that is required to make individuals avoid inbreeding, for different animal life histories and parental investment patterns. We also distinguish between simultaneous and sequential mate choice, and show that inbreeding tolerance should often be remarkably high in the latter scenario in particular, although egalitarian parental care will lead to lower tolerance. There is a mismatch between theory and data: the almost complete lack of cases where individuals prefer to mate incestuously is at odds with a large overlap between the predicted range of inbreeding tolerance and estimates of inbreeding depression found in nature. We discuss four different solutions to this enigma, and suggest that inbreeding tolerance, where it is found, should not always be attributed to a simple constraint that has prevented finding any other mate.     

The cytoplasmic domain of MT1-MMP is dispensable for migration augmentation but necessary to mediate viability of MCF-7 breast cancer cells

Membrane-type-1 Matrix Metalloproteinase (MT1-MMP) is a multifunctional protease that regulates ECM degradation, proMMP-2 activation, and varied cellular processes including migration and viability. MT1-MMP is believed to be a central mediator of tumourigenesis whose role is dictated by its functionally distinct protein domains. Both the localization and signal transduction capabilities of MT1-MMP are dependent on its cytoplasmic domain, exemplifying diverse regulatory functions. To further our understanding of the multifunctional contributions of MT1-MMP to cellular processes, we overexpressed cytoplasmic domain altered constructs in MCF-7 breast cancer cells and analyzed migration and viability in 2D culture conditions, morphology in 3D Matrigel culture, and tumorigenic ability in vivo. We found that the cytoplasmic domain was not needed for MT1-MMP mediated migration promotion, but was necessary to maintain viability during serum depravation in 2D culture. Similarly, during 3D Matrigel culture the cytoplasmic domain of MT1-MMP was not needed to initiate a protrusive phenotype, but was necessary to prevent colony blebbing when cells were serum deprived. We also tested in vivo tumorigenic potential to show that cells expressing cytoplasmic domain altered constructs demonstrated a reduced ability to vascularize tumours. These results suggest that the cytoplasmic domain regulates MT1-MMP function in a manner required for cell survival, but is dispensable for cell migration.     

Molecular and phenotypic specificity of an antisense PHYB gene in Arabidopsis

The family of phytochrome photoreceptors plays an essential role in regulating plant growth and development in response to the light environment. An antisense PHYB transgene has been introduced into wild-type Arabidopsis and shown to inhibit expression of the PHYB sense mRNA and the phyB phytochrome protein 4- to 5-fold. This inhibition is specific to phyB in that the levels of the four other phytochromes, notably the closely related phyD and phyE phytochromes, are unaffected in the antisense lines. Antisense-induced reduction in phyB causes alterations of red light effects on seedling hypocotyl elongation, rosette leaf morphology, and chlorophyll content, similar to the phenotypic changes caused by phyB null mutations. However, unlike the phyB mutants, the antisense lines do not flower early compared to the wild type. Furthermore, unlike the phyB mutants, the antisense lines do not show a reduction in phyC level compared to the wild type, making it possible to unequivocally associate several of the photomorphogenic effects seen in phyB mutants with phytochrome B alone. These results indicate that an antisense transgene approach can be used to specifically inhibit the expression and activity of a single member of the phytochrome family and to alter aspects of shade avoidance responses in a targeted manner.     

An analysis of avoidance generalization and food preference transitivity in goldfish,Carassius auratus

To examine the effect of novelty in food selection by fishes, goldfish were trained by feeding them on red or green food pellets. Individual fish and fish in shoals of two, three, and five were then given a choice between equal numbers of familiar pellets and novel (yellow) pellets. In experimental groups, the yellow pellets were soaked in 15% quinine hydrochloride to make them unpalatable. Fish were next presented with equal numbers of familiar and a second novel pellet. It was expected that fish would generalize from their experience with the unpalatable pellets and demonstrate avoidance to sampling a second novel food item. However, as groups, neither controls nor experimentals were reluctant to sample the second novel pellets. Also, fish did not eat significantly more familiar than novel pellets when both were palatable. A third set of experiments examined food preference transitivity in which each pellet type was presented alone and in three pair-wise combinations to individual fish. Although red and yellow pellets were preferred over green, they were preferred equally, indicating an absence of transitivity in pellet choice and, perhaps, a “preference” for a mixture of red and yellow pellets.