A theoretical study of the origin of rotational barriers in push-pull ethylenes

Using the B3LYP/6-31G* ab initio method, we have studied the rotation about the C=C bonds in 15 push-pull ethylenes of the general formula (X,Y)C=C(CHO)(2) [X, Y = NH2, NHCH3, N(CH3)(2), OCH3, SCH3] in the gas phase. Two stationary points (minimum and transition state) were located for all compounds. The geometry, dipole moments, natural bond orbital atomic charges, as well as the rotational barriers were examined. The torsion angle 0 depends essentially on the presence or absence of intramolecular hydrogen bonds, and the barrier is a function of the torsion angle. (C) 2002 Elsevier Science B.V. All rights reserved.

Axonal regeneration of retinal ganglion cells after optic nerve pre-lesions and attachment of normal or pre-degenerated peripheral nerve grafts

Axonal regeneration of retinal ganglion cells (RGCs) into a normal or pre-degenerated peripheral nerve graft after an optic nerve pre-lesion was investigated. A pre-lesion performed 1-2 weeks before a second lesion has been shown to enhance axonal regeneration in peripheral nerves (PN) but not in optic nerves (ON) in mammals. The lack of such a beneficial pre-lesion effect may be due to the long delay (1-6 weeks) between the two lesions since RGCs and their axons degenerate rapidly 1-2 weeks following axotomy in adult rodents. The present study examined the effects of the proximal and distal ON pre-lesions with a shortened delay (0-8 days) on axonal regeneration of RGCs through a normal or pre-degenerated PN graft. The ON of adult hamsters was transected intraorbitallv at 2 mm. (proximal lesion) or intracranially at 7 mm (distal lesion) from the optic disc. The pre-lesioned ON was re-transected at 0.5 mm from the disc after 0, 1, 2, 4, or 8 days and a normal or a pre-degenerated PN graft was attached onto the ocular stump. The number of RGCs regenerating their injured axons into the PN graft was estimated by retrograde labeling with FluoroGold 4 weeks after grafting. The number of regenerating RGCs decreased significantly when the delay-time increased in animals with both the ON pre-lesions (proximal or distal) compared to control animals without an ON pre-lesion. The proximal ON pre-lesion significantly reduced the number of regenerating RGCs after a delay of 8 days in comparison with the distal lesion. However, this adverse effect can be overcome, to some degree, by a pre-degenerated PN graft applied 2, 4, or 8 days after the distal ON pre-lesion enhanced more RGCs to regenerate than the normal PN graft. Thus, in order to obtain the highest number of regenerating RGCs, a pre-degenerated PN should be grafted immediately after an ON lesion.

Intraorbital anatomy of the koala (Phascolarctos cinereus)

This is the first documented study of the anatomical details of the contents of the normal koala orbit, excluding the bulbus oculi. Baseline data were established which are necessary for understanding and treating ocular disease in the koala (Phascolarctos cinereus). The anatomy of the orbital contents of the koala were examined and described from animals that presented dead or were euthanized for humane reasons. Dissections of the orbital cavity were performed under magnification. Polymethyl methacrylate (PMMA) casts of the nasolacrimal system and the vascular supply of the orbit were also made in order to study these systems. The superficial lymphatic drainage of the conjunctival tissues was studied by subcutaneous injection of Evan's Blue into the palpebral conjunctiva of a freshly deceased animal, and by Microfil casts of the efferent lymphatics. In general, the orbital contents of the koala are consistent with those of other carnivorous polyprotodont and herbivorous diprotodont marsupials.

Bony orbital anatomy of the koala (Phascolarctos cinereus)

This is the first documented study of the anatomical details of the normal koala orbit. Baseline data are established which are necessary for understanding and treating ocular disease in the koala (Phascolarctos cinereus). The bony anatomy of the orbit of the koala was examined and described from animals that presented dead or had been euthanized for humane reasons. Dissections of the orbital cavity were performed under magnification, and descriptions of the orbital bones were from macerated skulls that had been boiled and cleaned, In general, the orbital bones of the koala, and their respective foramina, are consistent with those of other carnivorous polyprotodont and herbivorous diprotodont marsupials.

Vision in the peafowl (Aves : Pavo cristatus)

The visual sense of the Indian blue-shouldered peafowl Pavo cristatus was investigated with respect to the spectral absorption characteristics of the retinal photoreceptors, the spectral transmittance of the ocular media and the topographic distribution of cells in the retinal ganglion cell layer. Microspectrophotometry revealed a single class of rod, four spectrally distinct types of single cone and a single class of double cone. In the case of the single cone types, which contained visual pigments with wavelengths of maximum absorbance (lambda(max)) at 424, 458, 505 and 567 nm, spectral filtering by the ocular media and the different cone oil droplets with which each visual pigment is associated gives predicted peak spectral sensitivities of 432, 477, 537 and 605 nm, respectively. Topographic analysis of retinal ganglion cell distribution revealed a large central area of increased cell density (at peak, 35,609 cells mm(-2)) with a poorly defined visual streak extending nasally. The peafowl has a calculated maximum spatial resolution (visual acuity) in the lateral visual field of 20.6 cycles degrees(-1). These properties of the peafowl eye are discussed with respect to its visual ecology and are compared with those of other closely related species.

Solution Structures of the cis- and trans-Pro30 Isomers of a Novel 38-Residue Toxin from the Venom of Hadronyche Infensa sp. that Contains a Cystine-Knot Motif within Its Four Disulfide Bonds

The primary sequence and three-dimensional structure of a novel peptide toxin isolated from the Australian funnel-web spider Hadronyche infensa sp. is reported. ACTX-HI:OB4219 contains 38 amino acids, including eight-cysteine residues that form four disulfide bonds. The connectivities of these disulfide bonds were previously unknown but have been unambiguously determined in this study. Three of these disulfide bonds are arranged in an inhibitor cystine-knot (ICK) motif, which is observed in a range of other disulfide-rich peptide toxins. The motif incorporates an embedded ring in the structure formed by two of the disulfides and their connecting backbone segments penetrated by a third disulfide bond. Using NMR spectroscopy, we determined that despite the isolation of a single native homologous product by RP-HPLC, ACTX-HI:OB4219 possesses two equally populated conformers in solution. These two conformers were determined to arise from cis/trans isomerization of the bond preceding Pro30. Full assignment of the NMR spectra for both conformers allowed for the calculation of their structures, revealing, the presence of a triple-stranded antiparallel sheet consistent with the inhibitor cystine-knot (ICK) motif.

Expression of anterior Hox genes during larval development of the gastropod Haliotis asinina

We report the spatial expression patterns of five anterior Hox genes during larval development of the gastropod mollusc Haliotis asinina, an unsegmented spiralian lophotrochozoan. Molecular alignments and phylogenetic analysis indicate that these genes are homologues of Drosophila HOM-C genes labial, proboscipedia, zen, Deformed, and Sex combs reduced, the abalone genes are named Has-Hox1, -Hox2, -Hox3, -Hox4, and -Hox5. Has-Hox transcripts are first detected in the free-swimming trochophore larval stage- and restricted to the posttrochal ectoderm. Has-Hox2, -Hox3, and -Hox4 are expressed in bilaterally symmetrical and overlapping patterns in presumptive neuroectodermal cells on the ventral side of the trochophore. Has-Hox1 expression is restricted to a ring of cells on the dorsoposterior surface, corresponding to the outer mantle edge where new larval shell is being synthesized. There appears to be little change in the expression domains of these Has-Hox genes in pre- and posttorsional veliger larvae, with expression maintained in ectodermal and neuroectodermal tissues. Has-Hox2, -Hox3, -Hox4, and-Hox5 appear to be expressed in a colinear manner in the ganglia and connectives in the twisted nervous system. This pattern is not evident in older larvae. Has-Hox1 and-Hox4 are expressed in the margin of the mantle in the posttorsional veliger, suggesting that Hox genes play a role in gastropod shell formation.

Occlusable corneas in toadfishes: light transmission, movement and ultrastruture of pigment during light- and dark-adaptation

The toadfishes Tetractenos hamiltoni and Torquigener pleurogramma (Tetraodontidae) possess occlusable yellow corneas. We examine the light transmission and location of the yellow/orange pigment throughout the cornea, the temporal properties of pigment migration and the ultrastructure of the pigmented processes during light- and dark-adaptation. Each species was dark-adapted during the day and light-adapted during the night and then exposed to either sun illumination or darkness for different lengths of time (0-70 min). Movement of corneal pigment could be induced in both species regardless of time of day or night. The pigment was able to migrate in a dorsal or ventral direction and changed from minimal to maximal pigmentation within 60 min. Three types of transmission curves were found with varying degrees of transmission in the 400-500 nm waveband, indicating that the pigment distribution is not uniform across the cornea; some areas of the cornea transmit near UV light, while others absorb blue light. The gradual change of the transmission characteristics in different areas of the cornea indicates the presence of different concentrations of a single type of pigment. Ultrastructural examination of the corneas showed that the layer containing the pigment is situated within the scleral cornea either surrounding (T. pleurogramma) or abutting (T. hamiltoni) an iridescent layer. Long sheet-like processes or chromatophores extending centrally from dorsal and ventral reservoirs are filled with pigment during the light-adapted state but empty in the dark-adapted state.

Trichostome ciliates from Australian marsupials. I. Bandia gen nov (Litostomatea : Amylovoracidae)

A new genus of amylovoracid ciliates, Bandia gen.nov., is described. They are endosymbiotic/endocommensal in the stomachs of macropodid marsupials. Six new species, B. beveridgei, B. equimontanensis, B. tammar, B. deveneyi, B. cribbi and B. smalesae, are described from Setonix brachyurus, Petrogale assimilis, Macropus eugenii, M. robustus, M. parryi and M. agilis respectively. The gross morphology of Bandia is similar to that of Bitricha, with holotrichous somatic ciliation in two fields, longitudinal dorsal and oblique ventral. The somatic kineties are arranged in groups between non-ciliated. major interkinetal ridges; the groups of kineties thus give the cell a banded appearance. Several species are bimorphic, one form holotrichous and the other with a glabrous right body groove which appears to be derived from an ingrowth of one of the major interkinetal ridges. The groove may function in attachment either in sequestration or conjugation. The ultrastructure of the somatic kineties and the oral structures is similar to that of Amylovorax. Bandia also has unique ultrastructural features associated with the major interkinetal ridges, right body groove and a karyophore. Morphological evolution within the Amylovoracidae may have proceeded from simple forms such as Amylovorax via a process of cellular torsion and/or oral migration to forms similar to Bitricha and by further torsion and cellular elaboration to Bandia.

Visual Biology of Hawaiian Coral Reef Fishes. III. Environmental Light and an Integrated Approach to the Ecology of Reef Fish Vision

In the previous two papers in this three-part series, we have examined visual pigments, ocular media transmission, and colors of the coral reef fish of Hawaii. This paper first details aspects of the light field and background colors at the microhabitat level on Hawaiian reefs and does so from the perspective and scale of fish living on the reef. Second, information from all three papers is combined in an attempt to examine trends in the visual ecology of reef inhabitants. Our goal is to begin to see fish the way they appear to other fish. Observations resulting from the combination of results in all three papers include the following. Yellow and blue colors on their own are strikingly well matched to backgrounds on the reef such as coral and bodies of horizontally viewed water. These colors, therefore, depending on context, may be important in camouflage as well as conspicuousness. The spectral characteristics of fish colors are correlated to the known spectral sensitivities in reef fish single cones and are tuned for maximum signal reliability when viewed against known backgrounds. The optimal positions of spectral sensitivity in a modeled dichromatic visual system are generally close to the sensitivities known for reef fish. Models also predict that both UV-sensitive and red-sensitive cone types are advantageous for a variety of tasks. UV-sensitive cones are known in some reef fish, red-sensitive cones have yet to be found. Labroid colors, which appear green or blue to us, may he matched to the far-red component of chlorophyll reflectance for camouflage. Red cave/hole dwelling reef fish are relatively poorly matched to the background they are often viewed against but this may be visually irrelevant. The model predicts that the task of distinguishing green algae from coral is optimized with a relatively long wavelength visual pigment pair. Herbivorous grazers whose visual pigments are known possess the longest sensitivities so far found. Labroid complex colors are highly contrasting complementary colors close up but combine, because of the spatial addition, which results from low visual resolution, at distance, to match background water colors remarkably well. Therefore, they are effective for simultaneous communication and camouflage.