Molecular Characterization of the Mouse Tyrosinase Gene:Pigment Cell-Specific Expression in Transgenic Mice

Tyrosinase is the key enzyme in melanin synthesis, and is expressed in the pigment epithelium of the retina, a cell layer derived from the optic cup; and in neural crest-derived melanocytes of skin, hair follicle, choroid, and iris. The tyrosinase gene has been cloned and shown to map to the well-characterized c-locus (albino locus) of the mouse. Subsequent studies demonstrated that a functional tyrosinase minigene was able to rescue the albino phenotype in transgenic mice. The transgene was expressed in a cell type-specific manner in skin and eye. During development of the mouse, the tyrosinase gene is expressed in the pigment epithelium of the retina as early as day 10.5 of gestation. In the hair follicle, tyrosinase gene expression is detected from day 16.5 onwards. This cell-type–specific expression is largely reproduced in transgenic mice. Our results suggest that sequences in the immediate vicinity of the mouse tyrosinase gene are sufficient to provide cell type-specificity and developmental regulation in melanocytes and the pigment epithelium.     

Sampling subterranean termite species diversity and activity in tropical savannas: an assessment of different bait choices

Abstract.  1. Cellulose baits are commonly used for semi-quantitative sampling of subterranean wood-feeding termites, with a single food choice sampling programme implemented most often. In most situations, however, the composition and feeding preferences of the subterranean termite assemblage remain unknown.
2. The diversity, frequency, foraging activity, and intensity of attack of termites were assessed regularly at 144 baits representing 12 different bait choices over 8.5 months, in two northern Australian tropical savanna sites that differed in vegetation structure (closed vs open). Baits differed in type (paper rolls, cardboard, wooden stakes), position (surface, buried), and moisture status at installation (wet, dry).
3. Sixteen species were recorded, including 11 wood-feeders. Average species diversity, foraging activity, and bait consumption were greater at buried baits than at surface baits. Wooden baits were most attractive early in the experiment, and paper baits more attractive later. Mean species diversity was greatest at wooden stakes in the closed site. Species frequency of occurrence varied across bait choices.
4. A composite bait sampling protocol of stakes and paper rolls installed above and below ground gave an accurate assessment of the activity, diversity, and structure of the termite guild sampled across all baits over 8.5 months.
5. The choice of bait, its presentation, and time of examination are critical to the success of a termite baiting programme. If the aim is to characterise the structure and foraging activity of the subterranean termite assemblages that are attracted to baits, composite baiting protocols should be implemented.     

Two‐step vegetation response to enhanced precipitation in Northeast Brazil during Heinrich event 1

High resolution palynological and geochemical data of sediment core GeoB 3910‐2 (located offshore Northeast Brazil) spanning the period between 19 600 and 14 500 calibrated year bp (19.6–14.5 ka) show a land‐cover change in the catchment area of local rivers in two steps related to changes in precipitation associated with Heinrich Event 1 (H1 stadial). At the end of the last glacial maximum, the landscape in semi‐arid Northeast Brazil was dominated by a very dry type of caatinga vegetation, mainly composed of grasslands with some herbs and shrubs. After 18 ka, considerably more humid conditions are suggested by changes in the vegetation and by C_org and C/N data indicative of fluvial erosion. The caatinga became wetter and along lakes and rivers, sedges and gallery forest expanded. The most humid period was recorded between 16.5 and 15 ka, when humid gallery (and floodplain) forest and even small patches of mountainous Atlantic rain forest occurred together with dry forest, the latter being considered as a rather lush type of caatinga vegetation. During this humid phase erosion decreased as less lithogenic material and more organic terrestrial material were deposited on the continental slope of northern Brazil. After 15 ka arid conditions returned. During the humid second phase of the H1 stadial, a rich variety of landscapes existed in Northeast Brazil and during the drier periods small pockets of forest could probably survive in favorable spots, which would have increased the resilience of the forest to climate change.     

Studies on Chloroplast Degradation in vivo: III. THE EFFECT OF MAGNESIUM ON ELECTRON TRANSPORT AND PHOSPHORYLATIQN IN PLASTIDS ISOLATED FROM YOUNG AND AGEING COTYLEDONS

The magnesium dependence of NADP-reduction, oxygen evolutionand concomitant ATP-formation was studied as a function of theage of the Cucurbita cotyledons from which the chloroplastswere isolated. Whereas NADP-reduction under alkaline assay conditionsalways exhibits a stimulation upon addition of Mg⁺⁺, measurementsin an acidic medium show an age-dependent reversal to inhibition.The data for oxygen evolution are more complex in nature, dueto participation of consecutive reactions. The Mg⁺⁺ concentrationfor optimal ATP formation decreases with the age of the cotyledonarymaterial. The results are discussed from the viewpoint of apossible control of essential photosynthetic functions in vivoby magnesium.     

The role of ultrasonic bat detectors in improving inventory and monitoring surveys in Vietnamese karst bat assemblages

Bats account for 30% of mammal diversity in SE Asia and are potential bioindicators of wider biodiversity impacts resulting from habitat loss and climate change.As existing sampling techniques in the region typically fail to record bats that habitually fly in open areas and at higher altitudes,current inventory efforts are less than comprehensive.Acoustic sampling with bat detectors may help to overcome these limitations for insectivorous bats,but has yet to be tested in mainland SE Asia.To do so,we sampled...     

Investigation of PAR-1-type thrombin receptors in rat glioma C6 cells with a novel monoclonal anti-PAR-1 antibody (Mab COR7-6H9)

Rat glioma C6 cells have been demonstrated to be a suitable model in the investigation of PAR-1-type thrombin receptors in brain. However, anti-PAR-1 antibodies, which should be very helpful tools in studying PAR-1 in rat cells, have not been available up until now. Therefore, we prepared a monoclonal anti-thrombin receptor antibody (Mab COR7-6H9) directed against the peptide sequence GRAVYLNKSRFPPMPPPPFISEDASG in the N-terminus below the thrombin cleavage site of the rat PAR-1-type thrombin receptor. Using this antibody, we demonstrated the presence of PAR-1 binding sites on the plasma membrane of rat glioma C6 cells both with confocal laser fluorescence and with scanning electron microscopy. In addition, Mab COR7-6H9 was shown to block PAR-1-mediated transmembranal signaling as demonstrated by measurement of free intracellular calcium and cyclic AMP. This novel anti-PAR-1 antibody is therefore likely to be a very helpful tool in studying PAR-1-type thrombin receptors in rat brain.     

Differential effects of ecotoxicological substances on lipid peroxidation of plant cell protoplasts

Abstract The determination of ethane formation in the light and dark in the presence and absence of SHAM provides a memthod for the elucidation of the mechanism of membrane destruction in plant cell protoplasts, induced by chemical treatment. Accordingly, PCP is postulated to act via radical and enzymic-mediated lipid peroxidation. In contrast, HgCl₂ appears to inhibit the enzymic pathway, and causes damage to the membranes via a radical mediated mechanism alone.     

Greater energy stores enable flightless moulting geese to increase resting behaviour

Many species of waterfowl undergo a post‐breeding simultaneous flight feather moult (wing moult) which renders them flightless and vulnerable to predation for up to 4 weeks. Here we present an analysis of the correlations between individual time‐budgets and body mass states in 13 captive Barnacle Geese Branta leucopsis throughout an entire wing moult. The daily percentage of time spent resting was positively correlated with initial body mass at the start of wing moult. Behaviour of individual birds during wing moult is dependent on initial physiological state, which may in turn be dependent on foraging ability; the storage of energy before the start of wing moult will help birds to reduce exposure to the dangers of predation.