Mechanisms of adaptation in a predator-prey arms race: TTX-resistant sodium channels

Populations of the garter snake Thamnophis sirtalis have evolved geographically variable resistance to tetrodotoxin (TTX) in a coevolutionary arms race with their toxic prey, newts of the genus Taricha. Here, we identify a physiological mechanism, the expression of TTX-resistant sodium channels in skeletal muscle, responsible for adaptive diversification in whole-animal resistance. Both individual and population differences in the ability of skeletal muscle fibers to function in the presence of TTX correlate closely with whole-animal measures of TTX resistance. Demonstration of individual variation in an essential physiological function responsible for the adaptive differences among populations is a step toward linking the selective consequences of coevolutionary interactions to geographic and phylogenetic patterns of diversity.     

Galaxy disruption in a halo of dark matter

The relics of disrupted satellite galaxies have been found around the Milky Way and Andromeda, but direct evidence of a satellite galaxy in the early stages of disruption has remained elusive. We have discovered a dwarf satellite galaxy in the process of being torn apart by gravitational tidal forces as it merges with a larger galaxy's dark matter halo. Our results illustrate the morphological transformation of dwarf galaxies by tidal interaction and the continued buildup of galaxy halos.     

Eva:A midseason golden nematode- and virus-resistant variety for use as tablestock or chipstock

Eva is a new potato variety being released by the New York and Pennsylvania Experiment Stations. Eva is notable for its bright clear skin and attractive round to oval shape. It produces a chip color comparable to Monona from 9 C storage and has specific gravity 014 less than that of Atlantic. It has exceptionally long tuber dormancy and has extreme resistance to PVX, PVY, and race RO1 of the golden nematode. Scab resistance is like that of Monona. It is expected that Eva will find primary acceptance as a tablestock variety.     

The effects of moisture on the thermosensitivity ofglobodera rostochiensis (nematoda)

The sensitivity ofGlobodera rostochiensis second-stage juveniles in eggs inside cysts (encysted J2) to heat was evaluated over a range of temperature and moisture levels. Encysted J2 in air dried cysts incubated in dry sand were less sensitive to thermal stress than those maintained under moist conditions. Heating of moist cysts to 50°C for 20 minutes in wet sand resulted in death of the encysted J2. Presoaking air dried cysts for 48 hours in water prior to heating in dry sand did not increase the sensitivity of encysted J2 to heat. Thermal sensitivity of encysted J2 presoaked for 48 hours in water or glycerine and then heated to 51°C or 56°C indicated that both water and glycerine conducted heat to the J2. Hydrated (water soaked) encysted J2 were killed at lower temperatures and at shorter exposures than were anhydrobiotic (glycerine soaked) encysted J2. Presoaking cysts in potato root diffusate to initate hatching did not increase the thermal sensitivity of encysted J2.     

Inheritance of the resistance toMeloidogyne incognita,M. javanica,andM. arenaria in potatoes

The objectives of this research were: 1) to try to determine the inheritance of the resistance toMeloidogyne incognita, M. javanica, andM. arenaria and 2) to study genetic relationships among the three species of root-knot nematodes in potatoes. The source of resistance used wasSolanum sparsipilum. The progenies analyzed in this study may be grouped into a few discrete segregation patterns, three forM. incognita andM. javanica and two forM. arenaria. More than one dominant locus, but not many loci are needed to explain the segregation obtained in the three species. Susceptible clones ofS. sparsipilum possess recessive or epistatic genes which affect the pattern of segregation for resistance, when these clones are crossed to resistant clones. Maternal effects were expressed in reciprocal crosses between susceptible and resistant clones when they were tested for resistance toM. arenaria. Clones in this study which are resistant toM. arenaria are also resistant toM. incognita andM. javanica     

The loss of expression of theH 1 gene inBt transgenic potatoes

During evaluation of potato clones and cultivars from the Cornell seed production program to confirm their resistance toGlobodera rostochiensis (Wollenweber) Behrens (golden nematode) pathotype Ro1, several cysts developed on the transgenic cultivar Atlantic NewLeaf. This transformed cultivar resulted from the insertion of aBt endotoxin gene into the golden-nematode-resistant cultivar Atlantic. In subsequent bioassay tests, golden nematode cysts developed freely on the transgenic cultivar that originated from Atlantic NewLeaf clone 6, but not on Atlantic NewLeaf clones 31 and 36. Clones 31 and 36 were from differentBt transformation events of the cultivar Atlantic that were never commercialized. RFLP analysis of Atlantic used in the transformations and the Atlantic NewLeaf clones 6, 31, and 36 showed that they possessed the marker for theH ₁ gene that confers resistance to golden nematode pathotype Rol. These data indicate that theBt transformation process adversely affected the expression of theH ₁ gene in the transgenic cultivar Atlantic NewLeaf. This finding highlights the importance of pre-release evaluation of transgenic plants for any previously known major traits such as pest and disease resistance before they are commercialized.     

Vascular smooth muscle reactivity in normotensive and hypertensive rats

Aortic strips from spontaneously hypertensive rats were less responsive than normal animals to the contractile effects of norepinephrine, serotonin, and potassium chloride but more reactive to the relaxant effects of the stimulant of beta receptors, isoproterenol. Thus, hypertension is not the result of an absence of beta receptor or a hypersensitivity of the vascular smooth muscle.     

Aneurysmal bone cyst in a Holstein bull.

A 3-year-old Holstein bull was examined because of a mass involving the cranial portion of the right hemimandible and the oral cavity. The mass had been observed 2 weeks earlier. The bull had lost weight throughout the 45 days before admission, and was anorectic at the time of admission. An aneurysmal bone cyst of the mandible was diagnosed.     

Correlation of blood and brain levels of the neurotoxic pyrethroid deltamethrin with the onset of symptoms in rats

Rats were injected intraperitoneally with ¹⁴C-labelled deltamethrin at the threshold doses required to produce the motor symptoms of toxicity of tremor and choreoathetosis. Blood and brain samples were analysed for their total radiolabel content, and were also extracted with ethyl acetate to determine the levels of extractable parent deltamethrin and 3-phenoxybenzyl-derived acid (the final radiolabelled metabolite after oxidative cleavage) and the residual radiolabel after this extraction. There was a clear correlation between symptom onset and blood and brain levels of deltamethrin. It was found that certain threshold levels of parent deltamethrin in the blood and brain were required for symptom development, and that the symptom persisted for as long as this threshold was maintained. The distribution of the radiolabel in various tissues was also followed over the time course of the blood and brain studies.