Coupling of a Jahn-Teller pseudorotation with a hindered internal rotation in an isolated molecule: 9-hydroxytriptycene

The irregular vibronic structure in the S-1<--S-0 resonant two-photon ionization (R2PI) spectrum of supersonically cooled triptycene is a result of a classic Exe Jahn-Teller effect [A. Furlan et al., J. Chem. Phys. 96, 7306 (1992)]. This is well characterized and can be used as an effective probe of intramolecular perturbations. Here we examine the S-1<--S-0 R2PI spectrum of 9-hydroxytriptycene and the fluorescence from various excited state vibronic levels. In this system the pseudorotation of the Jahn-Teller vibration is strongly coupled to the torsional motion of the bridgehead hydroxy group. This torsional motion results in a tunneling splitting in both the ground and excited states. The population of the upper level in the ground electronic state results in additional vibronic transitions becoming symmetry allowed in the R2PI spectrum that are forbidden in the bare triptycene molecule. The assignment of the R2PI and fluorescence spectra allows the potential energy surfaces of these vibrational modes to be accurately quantified. The full C-3v vibronic point group must be used to interpret the spectra. The time scale of the internal rotation of the-OH group and the butterfly flapping of the Jahn-Teller pseudorotation are of similar magnitude. The tunneling between the nine minima on the three dimensional potential energy surface is such that the Jahn-Teller pseudorotation occurs in concert with the-OH internal rotation. The Berry phase that is acquired during this motion is discussed. The simple physical picture emerges of the angle between two of the three benzene moieties opening in three equivalent ways in the S-1 electronic state. This geometry follows the position of the hydroxy group, which preferentially orients itself to point between these two rings. (C) 1998 American Institute of Physics. [S0021-9606(98)02348-4].

mRNA differential display of 2-amino-1-methyl-6-phenylinlidazo[4,5-b]pyridine-induced rat mammary gland tumors

The mRNA differential display technique was used to compare mRNAs between normal mammary gland and turner-derived epithelial cells from female Sprague-Dawley rat mammary gland tumors induced by the heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and promoted by a high-fat diet (23.5% corn oil). Two genes, beta-casein and transferrin, were identified as differentially expressed. The expression of these genes was examined across a bank of rat mammary gland tumors derived from animals on a low-fat diet (5% corn oil) or the high-fat diet. Carcinomas had over a 10- and 50-fold lower expression of beta-casein and transferrin, respectively than normal mammary gland. In addition, carcinomas from animals on the high-fat diet showed on average a 5-fold higher expression of beta-casein, and transferrin than carcinomas from animals on the low-fat diet. The results indicate the process of mammary gland tumorigenesis alters the expression of certain genes in the mammary gland, and that the level of dietary fat further modulates the expression of these genes.

Fibroblast growth factor receptor expression in outer hair cells of rat cochlea

FIBROBLAST growth factors (FGFs) are critical for normal development of the organ of Corti, and may also protect hair cells from ototoxic damage. Four different fibroblast growth factors are known, three of which have different splice variants in the extracellular immunoglobin-like (Ig) III FGF-binding domain, giving different patterns of sensitivity to the different FGFs. Analysis of a cDNA library of rat outer hair cells by the polymerase chain reaction, using isoform specific primers, showed expression only of FGF receptor 3, splice variant IIIc. This allows us to predict the pattern of sensitivity to applied FGFs, may be useful in targeting outer hair cells selectively during an FGF-based strategy for cochlear therapy. (C) 1998 Lippincott Williams & Wilkins.

Histologic and immunohistochemical responses after aortic valve allografts in the rat

Background. Human aortic valve allografts elicit a cellular and humoral immune response. It is not clear whether this is important in promoting valve damage. We investigated the changes in morphology, cell populations, and major histocompatibility complex antigen distribution in the rat aortic valve allograft. Methods. Fresh heart valves from Lewis rats were transplanted into the abdominal aorta of DA rats. Valves from allografted, isografted, and presensitized recipient rats were examined serially with standard morphologic and immunohistochemical techniques. Results. In comparison with isografts, the allografts were infiltrated and thickened by increased numbers of CD4(+) and CD8(+) lymphocytes, macrophages, and fibroblasts. Thickening of the valve wall and leaflet and the density of the cellular infiltrate was particularly evident after presensitization. Endothelial cells were frequently absent in presensitized allografts whereas isografts had intact endothelium. Cellular major histocompatibility complex class I and II antigens in the allograft were substantially increased. A long-term allograft showed dense fibrosis and disruption of the media with scattered persisting donor cells. Conclusions. The changes in these aortic valve allograft experiments are consistent with an allograft immune response and confirm that the response can damage aortic valve allograft tissue. (C) 1998 by The Society of Thoracic Surgeons.

Chronic ethanol exposure and withdrawal influence NMDA receptor subunit and splice variant mRNA expression in the rat cerebral cortex

Chronic ethanol exposure and subsequent withdrawal are known to change NMDA receptor activity. This study examined the effects of chronic ethanol administration and withdrawal on the expression of several NMDA receptor subunit and splice variant mRNAs in the rat cerebral cortex. Ethanol dependence was induced by ethanol vapour exposure. To delineate between seizure-induced changes in expression during withdrawal and those due to withdrawal per se, another group of naive rats was treated with pentylenetetrazol (PTZ) injection (30 mg/kg, i.p.). RNA samples from the cortices of chronically treated and withdrawing animals were compared to those from pairfed controls. Changes in NMDA receptor mRNA expression were determined using ribonuclease protection assays targetting the NR2A, -2B, -2C and NR1-pan subunits as well as the three alternatively spliced NR1 inserts (NR1-pan describes all the known NR1 splice variants generated from the 5' insert and the two 3' inserts). The ratio of NR1 mRNA incorporating the 5' insert vs, that lacking it was decreased during ethanol exposure and up to 48 h after withdrawal. NR2B mRNA expression was elevated during exposure, but returned to control levels 18 h after withdrawal. Levels of NR2A, NR2C, NR1-pan and both 3' NR1 insert mRNAs from the ethanol-treated groups did not alter compared with the pair-fed control group. No changes in the level of any NMDA receptor subunit mRNA was detected in the PTZ-treated animals. These data support the hypothesis that changes in NMDA receptor subunit composition may underlie a neuronal adaptation to the chronic ethanol-inhibition and may therefore be important in the precipitation of withdrawal hyperactivity. (C) 1999 Elsevier Science B.V. All rights reserved.

Relative dispersions of intra-albumin transit times across rat and elasmobranch perfused livers, and implications for intra- and inter-species scaling of hepatic clearance using microsomal data

It is recognized that vascular dispersion in the liver is a determinant of high first-pass extraction of solutes by that organ. Such dispersion is also required for translation of in-vitro microsomal activity into in-vivo predictions of hepatic extraction for any solute. We therefore investigated the relative dispersion of albumin transit times (CV2) in the livers of adult and weanling rats and in elasmobranch livers. The mean and normalized variance of the hepatic transit time distribution of albumin was estimated using parametric non-linear regression (with a correction for catheter influence) after an impulse (bolus) input of labelled albumin into a single-pass liver perfusion. The mean +/- s.e. of CV2 for albumin determined in each of the liver groups were 0.85 +/- 0.20 (n = 12), 1.48 +/- 0.33 (n = 7) and 0.90 +/- 0.18 (n = 4) for the livers of adult and weanling rats and elasmobranch livers, respectively. These CV2 are comparable with that reported previously for the dog and suggest that the CV2 Of the liver is of a similar order of magnitude irrespective of the age and morphological development of the species. It might, therefore, be justified, in the absence of other information, to predict the hepatic clearances and availabilities of highly extracted solutes by scaling within and between species livers using hepatic elimination models such as the dispersion model with a CV2 of approximately unity.

Effects of beta-escin and saponin on the transverse-tubular system and sarcoplasmic reticulum membranes of rat and toad skeletal muscle

Mechanically skinned skeletal muscle fibres from rat and toad were exposed to the permeabilizing agents beta-escin and saponin. The effects of these agents on the sealed transverse tubular system (t-system) and sarcoplasmic reticulum (SR) were examined by looking at changes in the magnitude of the force responses to t-system depolarization, the time course of the fluorescence of fura-2 trapped in the sealed t-system, and changes in the magnitude of caffeine-induced contractures following SR loading with Ca2+ under defined conditions. In the presence of 2 mu g ml(-1) beta-escin and saponin, the response to t-system depolarization was not completely abolished, decreasing to a plateau, and a large proportion of fura-2 remained in the sealed t-system. At 10 mu g ml(-1), both agents abolished the ability of both rat and toad preparations to respond to t-system depolarization after 3 min of exposure, but a significant amount of fura-2 remained in sealed t-tubules even after exposure to 100 mu g ml(-1) beta-escin and saponin for 10 min. beta-Escin took longer than saponin to reduce the t-system depolarizations and fura-2 content of the sealed t-system to a similar level. The ability of the SR to load Ca2+ was reduced to a lower level after treatment with beta-escin than saponin. This direct effect on the SR occurred at much lower concentrations for rat (2 mu g ml(-1) beta-escin and 10 mu g ml(-1) saponin) than toad (10 mu g ml(-1) beta-escin and 150 mu g ml(-1) saponin). The reverse order in sensitivities to beta-escin and saponin of t-system and SR membranes indicates that the mechanisms of action of beta-escin and saponin are different in the two types of membrane. In conclusion, this study shows that: (1) beta-escin has a milder action on the surface membrane than saponin; (2) beta-escin is a more potent modifier of SR function; (3) simple permeabilization of membranes is not sufficient to explain the effects of beta-escin and saponin on muscle membranes; and (4) the t-system network within muscle fibres is not a homogeneous compartment.

Errors in lamina growth of primary olfactory axons in the rat and mouse olfactory bulb

In the adult olfactory nerve pathway of rodents, each primary olfactory axon forms a terminal arbor in a single glomerulus in the olfactory bulb. During development, axons are believed to project directly to and terminate precisely within a glomerulus without any exuberant growth or mistargeting. To gain insight into mechanisms underlying this process, the trajectories of primary olfactory axons during glomerular formation were studied in the neonatal period. Histochemical staining of mouse olfactory bulb sections with the lectin Dolichos biflorus-agglutinin revealed that many olfactory axons overshoot the glomerular layer and course into the deeper laminae of the bulb in the early postnatal period. Single primary olfactory axons were anterogradely labelled either with the lipophilic carbocyanine dye, 1,1'-dioctodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI), or with horseradish peroxidase (HRP) by localized microinjections into the nerve fiber layer of the rat olfactory bulb. Five distinct trajectories of primary olfactory axons were observed in DLI-labelled preparations at postnatal day 1.5 (P1.5). Axons either coursed directly to and terminated specifically within a glomerulus, branched before terminating in a glomerulus, bypassed glomeruli and entered the underlying external plexiform layer, passed through the glomerular layer with side branches into glomeruli, or branched into more than one glomerulus. HRP-labelled axon arbors from eight postnatal ages were reconstructed by camera lucida and were used to determine arbor length, arbor area, and arbor branch number. Whereas primary olfactory axons display errors in laminar targeting in the mammalian olfactory bulb, axon arbors typically achieve their adult morphology without exuberant growth. Many olfactory axons appear not to recognize appropriate cues to terminate within the glomerular layer during the early postnatal period. However, primary olfactory axons exhibit precise targeting in the glomerular layer after P5.5, indicating temporal differences in either the presence of guidance cues or the ability of axons to respond to these cues. (C) 1999 Wiley-Liss, Inc.

Solution structure of a defensin-like peptide from platypus venom

Three defensin-like peptides (DLPs) were isolated from platypus venom and sequenced. One of these peptides, DLP-1, was synthesized chemically and its three-dimensional structure was determined using NMR spectroscopy. The main structural elements of this 42-residue peptide were an anti-parallel beta-sheet comprising residues 15-18 and 37-40 and a small 3(10) helix spanning residues 10-12. The overall three-dimensional fold is similar to that of beta-defensin-12, and similar to the sodium-channel neurotoxin ShI (Stichodactyla helianthus neurotoxin I). However, the side chains known to be functionally important in beta-defensin-12 and ShI are not conserved in DLP-1, suggesting that it has a different biological function. Consistent with this contention, we showed that DLP-1 possesses no anti-microbial properties and has no observable activity on rat dorsal-root-ganglion sodium-channel currents.

Description of Gluconacetobacter sacchari sp. nov., a new species of acetic acid bacterium isolated from the leaf sheath of sugar cane and from the pink sugar-cane mealy bug

A new species of the genus Gluconacetobacter, for which the name Gluconacetobacter sacchari sp. nov. is proposed, was isolated from the leaf sheath of sugar cane and from the pink sugar-cane mealy bug, Saccharicoccus sacchari, found on sugar cane growing in Queensland and northern New South Wales, Australia, The nearest phylogenetic relatives in the alpha-subclass of the Proteobacteria are Gluconacetobacter liquefaciens and Gluconacetobacter diazotrophicus, which have 98.8-99.3% and 97.9-98.5% 16S rDNA sequence similarity, respectively, to members of Gluconacetobacter sacchari. On the basis of the phylogenetic positioning of the strains, DNA reassociation studies, phenotypic tests and the presence of the Q10 ubiquinone, this new species was assigned to the genus Gluconacetobacter. No single phenotypic characteristic is unique to the species, but the species can be differentiated phenotypically from closely related members of the acetic acid bacteria by growth in the presence of 0.01% malachite green, growth on 30% glucose, an inability to fix nitrogen and an inability to grow with the L-amino acids asparagine, glycine, glutamine, threonine and tryptophan when D-mannitol was supplied as the sole carbon and energy source. The type strain of this species is strain SRI 1794(T) (= DSM 12717(T)).

Ameloblast apoptosis and IGF-1 receptor expression in the continuously erupting rat incisor model

Enamel-producing cells (ameloblasts) pass through several phenotypic and functional stages during enamel formation. In the transition between secretory and maturation stages, about one quarter of the ameloblasts suddenly undergo apoptosis. We have studied this phenomenon using the continuously erupting rat incisor model. A special feature of this model is that all stages of ameloblast differentiation are presented within a single longitudinal section of the developing tooth. This permits investigation of the temporal sequence of gene and growth factor receptor expression during ameloblast differentiation and apoptosis. We describe the light and electron microscopic morphology of ameloblast apoptosis and the pattern of insulin-like growth factor-1 receptor expression by ameloblasts in the continuously erupting rat incisor model. In the developing rat incisor, ameloblast apoptosis is associated with downregulated expression of the insulin-like growth factor-1 receptor. These data are consistent with the hypothesis that ameloblasts are hard wired for apoptosis and that insulin-like growth factor-1 receptor expression is required to block the default apoptotic pathway. Possible mechanisms of insulin-like growth factor-1 inhibition of ameloblast apoptosis are presented. The rat incisor model may be useful in studies of physiological apoptosis as it presents apoptosis in a predictable pattern in adult tissues.

Expression of galectin-1 in the olfactory nerve pathway of rat

The olfactory neuroepithelium is characterised by the mosaic distribution of primary olfactory neurons that express different odorant receptors and cell surface glycoconjugates. Carbohydrates are believed to form a glycocode that mediates sorting out and fasciculation of primary olfactory axons through interactions with carbohydrate-binding proteins such as galectin-1. In the present study, we describe in detail the expression pattern of galectin-1 in the developing and adult rat olfactory system. We demonstrate that galectin-1 is expressed by olfactory ensheathing cells both in olfactory nerve and within the nerve fibre layer of the olfactory bulb of the embryonic and adult rat. In the adult rat, galectin-1 was preferentially expressed by olfactory ensheathing cells in the nerve fibre layer of the ventromedial and lateral surfaces of the olfactory bulb. Galectin-1 was also expressed by subsets of periglomerular cells and granule cells, particularly in the ventromedial region of the olfactory bulb. In adult rat, the galectin-1 ligand, N-acetyl-lactosamine, was expressed by primary olfactory axons that terminated in glomeruli present in the ventromedial and lateral olfactory bulb. These results suggest that expression of galectin-1 may provide a mechanism for the sorting of subpopulations of axons in the nerve fibre layer of the olfactory bulb during development as well as play a role in the postnatal maintenance of specific glomerular connections. (C) 1999 Elsevier Science B.V. All rights reserved.