TRANSECTION OF THE PANCREAS BY BLUNT TRAUMA

If a diagnosis of traumatic pancreatitis is made and the patient does not improve clinically during the first 24 hours, transection of the pancreas should be suspected. If this is found to be the case at operation, the distal pancreas should be resected and the proximal end of the pancreas closed carefully with interrupted mattress suture of non-absorbable suture material. Particularly, the pancreatic duct should be ligated to prevent the formation of an external fistula. Any attempt at reapproximation of the transected pancreas will invariably result in an external pancreatic fistula if the patient survives the immediate postoperative period.     

Social Context–Induced Song Variation Affects Female Behavior and Gene Expression

Social cues modulate the performance of communicative behaviors in a range of species, including humans, and such changes can make the communication signal more salient. In songbirds, males use song to attract females, and song organization can differ depending on the audience to which a male sings. For example, male zebra finches (Taeniopygia guttata) change their songs in subtle ways when singing to a female (directed song) compared with when they sing in isolation (undirected song), and some of these changes depend on altered neural activity from a specialized forebrain-basal ganglia circuit, the anterior forebrain pathway (AFP). In particular, variable activity in the AFP during undirected song is thought to actively enable syllable variability, whereas the lower and less-variable AFP firing during directed singing is associated with more stereotyped song. Consequently, directed song has been suggested to reflect a “performance” state, and undirected song a form of vocal motor “exploration.” However, this hypothesis predicts that directed–undirected song differences, despite their subtlety, should matter to female zebra finches, which is a question that has not been investigated. We tested female preferences for this natural variation in song in a behavioral approach assay, and we found that both mated and socially naive females could discriminate between directed and undirected song—and strongly preferred directed song. These preferences, which appeared to reflect attention especially to aspects of song variability controlled by the AFP, were enhanced by experience, as they were strongest for mated females responding to their mate's directed songs. We then measured neural activity using expression of the immediate early gene product ZENK, and found that social context and song familiarity differentially modulated the number of ZENK-expressing cells in telencephalic auditory areas. Specifically, the number of ZENK-expressing cells in the caudomedial mesopallium (CMM) was most affected by whether a song was directed or undirected, whereas the caudomedial nidopallium (NCM) was most affected by whether a song was familiar or unfamiliar. Together these data demonstrate that females detect and prefer the features of directed song and suggest that high-level auditory areas including the CMM are involved in this social perception.     

Structural and functional imaging with carbon nanotube AFM probes

Atomic force microscopy (AFM) has great potential as a tool for structural biology, a field in which there is increasing demand to characterize larger and more complex biomolecular systems. However, the poorly characterized silicon and silicon nitride probe tips currently employed in AFM limit its biological applications. Carbon nanotubes represent ideal AFM tip materials due to their small diameter, high aspect ratio, large Young's modulus, mechanical robustness, well-defined structure, and unique chemical properties. Nanotube probes were first fabricated by manual assembly, but more recent methods based on chemical vapor deposition provide higher resolution probes and are geared towards mass production, including recent developments that enable quantitative preparation of individual single-walled carbon nanotube tips [J. Phys. Chem. B 105 (2001) 743]. The high-resolution imaging capabilities of these nanotube AFM probes have been demonstrated on gold nanoparticles and well-characterized biomolecules such as IgG and GroES. Using the nanotube probes, new biological structures have been investigated in the areas of amyloid-beta protein aggregation and chromatin remodeling, and new biotechnologies have been developed such as AFM-based haplotyping. In addition to measuring topography, chemically functionalized AFM probes can measure the spatial arrangement of chemical functional groups in a sample. However, standard silicon and silicon nitride tips, once functionalized, do not yield sufficient resolution to allow combined structural and functional imaging of biomolecules. The unique end-group chemistry of carbon nanotubes, which can be arbitrarily modified by established chemical methods, has been exploited for chemical force microscopy, allowing single-molecule measurements with well-defined functionalized tips.     

Newly discovered linkages between the cortical (pellicular) ridges of Opalina

Samples of Opalina ranarum have been prepared for electron microscopy by ultra-rapid cryofixation followed by substitution fixation in a solvent containing tannic acid. This technique has made it possible to see that very thin linkages exist between the pleated ridges that form the surface of the cell. Between any two adjacent cortical ridges, the linkages, which are approximately 0.1 μm long, occur as a single row, 0.1 μm below the free edge, with an impressively regular spacing of 0.1 μm. The cortical ridges of the Opalinids are spaced with remarkable uniformity, even when thrown into undulating patterns. The linkages described here will inevitably stabilize the complex architecture of the cortex. Other possible functions are discussed.     

Direct haplotyping of kilobase-size DNA using carbon nanotube probes

We have implemented a method for multiplexed detection of polymorphic sites and direct determination of haplotypes in 10-kilobase-size DNA fragments using single-walled carbon nanotube (SWNT) atomic force microscopy (AFM) probes. Labeled oligonucleotides are hybridized specifically to complementary target sequences in template DNA, and the positions of the tagged sequences are detected by direct SWNT tip imaging. We demonstrated this concept by detecting streptavidin and IRD800 labels at two different sequences in M13mp18. Our approach also permits haplotype determination from simple visual inspection of AFM images of individual DNA molecules, which we have done on UGT1A7, a gene under study as a cancer risk factor. The haplotypes of individuals heterozygous at two critical loci, which together influence cancer risk, can be easily and directly distinguished from AFM images. The application of this technique to haplotyping in population-based genetic disease studies and other genomic screening problems is discussed.     

Spectral specific responses in the visual behavior of the greenhouse whitefly,Trialeurodes vaporariorum (Homoptera: Aleyrodidae)

Attraction of the greenhouse whiteflyTrialeurodes vaporariorum Westw. to reflected and to transmitted light of various wavelength compositions was measured by trapping and counting adults on greased, colored surfaces. The wavelength composition of the reflecting or transmitting surfaces was spectrophotometrically determined.The whiteflies showed a strongly positive response to surfaces with maximum reflectance or transmittance in the yellow-green region (520–610 nm), and a moderately positive response to ultra-violet (<400 nm). Light in the blue-violet region seemed to inhibit the response, and red (610 to ca. 700 nm) might also be moderately inhibitory.The response to the most excitatory hues sharply decreases with darker shades or with less saturated tints of the same hues.The implications of these responses in the mechanisms of host selection by the greenhouse whitefly are discussed.

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Zusammenfassung Die Attraktion der Weißen Fliege zu remittiertem und transmittiertem Licht verschiedener Wellenlängen-Kombinationen (spektrometrisch bestimmt) wurde gemessen durch Fang und Auszählen von angeflogenen Adulten an geleimten, farbigen Oberflächen. Die Weißen Fliegen zeigten eine starke positive Reaktion zu Oberflächen mit maximaler Remission oder Transmission im Gelg-Grün-Bereich (520–610 nm) und eine mäßige positive Reaktion zu UV (<400 nm). Licht im Blau-Violett-Bereich scheint die Reaktion zu hemmen und Rot (610 bis etwa 700 nm) scheint ebenfalls hemmend zu sein.Die Reaktion zu den Farbtönen mit höchster Wirksamkeit nimmt stark ab bei geringerer Intensität (Schwarzverhüllung) oder geringerer Sättigung (Weissverhüllung) der Farbtöne.Die Bedeutung dieser Reaktionen für den Mechanismus der Wirtswahl der Weißen Fliege wird diskutiert.

     

Studies on metatherian sex chromosomes. XII. Sex-linked inheritance and probable paternal X-inactivation of alpha-galactosidase A in Australian marsupials

An investigation of genetic variation in the electrophoretic mobility of the enzyme alpha-galactosidase A (EC 3.2.1.22) has been carried out for 33 species of Australian metatherian (marsupial) mammals. The results are compatible with the enzyme being sex-linked in macropodids (kangaroos and wallabies) and probably in dasyurids (marsupial 'mice', etc.), as it is in eutherian (placental) mammals. The results also suggest that the mode of dosage compensation for this locus is the same as for other sex-linked loci in kangaroos, i.e. paternal X inactivation, rather than the random X inactivation system of eutherian mammals. The bearing of the enzyme mobility data on phylogenetic relationships among macropodid species is discussed.     

Decoding at the ribosomal A site: antibiotics, misreading and energy of aminoacyl-tRNA binding

The binding of Phe-tRNAPhe at the programmed ribosomal A site has been investigated using antibiotics that influence this binding in different ways. The adhesion of Phe-tRNAPhe, the consumption of GTP and the extent of the peptidyl transfer reaction were monitored. All of the five known misreading-inducing antibiotics that were tested stabilised the binding of Phe-tRNAPhe after its affixture to the A site by EF-Tu with GTP hydrolysis. The stabilisation was sufficient to overcome a single mismatch in the codon-anticodon interaction. Combinations of stabilising and destabilising influences were found to be additive, thus supporting the concepts: (1) that there is a 'correct' binding energy for aminoacyl tRNA in the A site, whose reduction hampers polypeptide synthesis and whose increase makes it inaccurate by by-passing proofreading; and (2) that the different antibiotics affect the bound aminoacyl tRNA at different points.     

Copper uptake and translocation in chicory ( Cichorium intybus L. cv. Grasslands Puna) and tomato (Lycopersicon esculentum Mill. cv. Rondy) plants grown in NFT system. I. Copper uptake and distribution in plants

The uptake and distribution of copper was examined in chicory (Cichorium intybus L. cv. Grasslands Puna) and tomato (Lycopersicon esculentumMill. cv. Rondy) plants grown in a Nutrient Film Technique System (NFT) with addition of 0.05, 5, 10 and 20 mg Cu L^-1. Biomass production of shoots and roots of both chicory and tomato was strongly depressed by Cu concentrations higher than 5 mg Cu L^-1 in the rooting media. Although Cu concentrations in both shoots and roots of both species increased with increasing Cu concentrations in the rooting media, the increase in roots was very much greater than that in shoots, in which the range of concentrations was small. A large proportion of total Cu uptake was retained by roots except when plants were grown in solution Cu concentrations of 0.05 mg Cu L^-1. Copper retention by roots limited Cu translocation to xylem and shoots. Copper adsorption by the root appears to buffer against increases of Cu in the rooting media. A cupric-sensitive electrode used in conjunction with total Cu analysis by graphite furnace atomic absorption spectrophotometry (GFAAS) indicated that more than 99.6% of total Cu in xylem sap was in a complexed form. Large differences between measured and predicted Cu accumulation by shoots of tomato (0.134–0.243 mg Cu plant^-1, 0.660–4.274 mg Cu plant^-1, respectively) and chicory (0.095–0.203 mg Cu plant^-1, 0.626–1.620 mg Cu plant^-1, respectively) suggest that some xylem transported Cu is recirculated to roots via the phloem. This revised version was published online in June 2006 with corrections to the Cover Date.