Electrophysiological evidence for rod and cone-based vision in the nocturnal flying squirrel

Summary The flying squirrel (Glaucomys volans) is a strongly nocturnal rodent. Previous anatomical observations suggested that the retina of this animal contains some cone-like receptors in addition to large numbers of rods. Evidence for duplicity of function in this visual system was obtained from an examination of three indices of visual activity: the electroretinogram (ERG), the isolated PIII retinal response, and the visually evoked cortical potential (VECP). The spectral sensitivity of the dark-adapted flying squirrel is similar to that of other mammals — it has a 500 nm peak (Figs. 3, 8). Responses of the ERG and isolated PIII to flickering light indicate the operation of two processes (Figs. 4, 7), one of which is unable to follow flickering light at repetition rates above 10–15 Hz. Spectral sensitivity measurements reveal that these two processes have different spectral sensitivities. The photopic mechanism in the flying squirrel visual system has peak sensitivity at about 520 nm (Figs. 5, 7, 9). The effects of steady light adaptation are much more obvious in the cortical potentials than they are in the retinal potentials.We thank David Birch for his advice and assistance. This research was supported by a Grant from the National Eye Institute (EY-00105).     

High-level expression of the tick-borne encephalitis virus NS1 protein by using an adenovirus-based vector: protection elicited in a murine model.

Tick-borne encephalitis virus (TBEV) encodes an abundant, highly immunogenic nonstructural glycoprotein, NS1. The function of this protein has yet to be determined. We have cloned the NS1 gene from the Neudorfl strain of TBEV under the control of the powerful constitutive cytomegalovirus major immediate-early promoter into an adenovirus E1 deletion mutant. The novel combination of the cytomegalovirus immediate-early promoter and the adenovirus vector produced extremely high levels of NS1 expression in cells which do not support replication of the adenovirus deletion mutant. The recombinant protein was shown to be indistinguishable from authentic TBEV NS1 in its (i) apparent molecular weight by polyacrylamide gel electrophoresis, (ii) glycosylation pattern, (iii) ability to form high-molecular-weight complexes, and (iv) ability to be secreted from cells. Appropriate processing of NS1 expressed by the adenovirus recombinant occurred independently of any additional TBEV-encoded gene function. When directly inoculated into mice, the recombinant adenovirus RAd51 was shown to elicit an antibody response to the TBEV NS1 protein. Immunization with RAd51 conferred protection against challenge with TBEV.     

A biostratigraphic zonation of the middle and upper siwaliks of the potwar plateau of Northern Pakistan

Two biostratigraphic reference sections are designated for the middle and upper Siwalik formations of northern Pakistan. The stratigraphic ranges of 41 mammalian taxa are established in the reference sections and the two sections are correlated to each other and to the standard Magnetic Polarity Time Scale by the magnetic-polarity stratigraphy. The resulting stratigraphic and magnetostratigraphic framework is used to define four contiguous biostratigraphic interval-zones. The proposed interval-zones are bounded by five important faunal events which are identified in the reference sections. The four proposed interval-zones and the approximate ages in the reference sections of their lower and upper boundaries are: (1) the “Hipparion s.l.” Interval-Zone 7.4–9.5 m.y. B.P.; (2) the Selenoportax lydekkeri Interval-Zone 5.3–7.4 m.y. B.P.; (3) the Hexaprotodon sivalensis Interval-Zone 5.3-2.9 m.y. B.P.; and (4) the Elephas planifrons Interval-Zone 2.9-1.5 m.y. B.P.The paleomagnetic and biostratigraphic evidence indicates that the Tatrot Beds, from which Pilgrim developed his “Tatrot Faunal Zone”, are between 2.5 and 3.4 m.y. B.P., with a preferred maximum age of 2.9 m.y. B.P. The biostratigraphic evidence indicates the Sethi Nagri locality (Y311)—the primary source of Pilgrim's “Nagri Faunal Zone”— is in the “Hipparion s.l.” Interval-Zone. The paleomagnetic evidence suggests an approximate age of 9 m.y. B.P. A major faunal event at 9.5 m.y. B.P. introduced equids, suids, and large giraffes from Eurasia into the Indain subcontinent. A second, more diffuse faunal event between 5.3 and 2.9 m.y. B.P. introduced several African taxa as well as Equus and cervids from Eurasia.     

Effect of Flavobacterium columnare inoculation, antibiotic treatments and resident bacteria on rainbow trout Oncorhynchus mykiss eyed egg survival and external membrane structure

This study was conducted to evaluate the potential pathogenicity of the bacterium Flavobacterium columnare on rainbow trout Oncorhynchus mykiss eyed eggs. Survival to hatching was unaffected by the inclusion in the incubation water of either 300 colony-forming units (CFU) ml⁻¹ or 3000 CFU ml⁻¹ of F. columnare at either 10 or 12° C in either McConaughy or Shasta strain eyed eggs. Bacterial numbers, obtained via scanning electron microscopy or culture, and external membrane morphology were also not significantly different among eggs receiving different concentrations of F. columnare . Initial F. columnare burdens were significantly and positively correlated to the presence of biofilm on the egg external membrane, and biofilm was in turn significantly correlated with increased membrane degradation. The use of either streptomycin or tetracyclin antibiotics significantly reduced bacterial numbers on McConaughy strain eggs, and more eggs survived to hatch in those dishes treated with antibiotics.