In Vivo Evaluation of Blood Based and Reference Tissue Based PET Quantifications of [11C]DASB in the Canine Brain

This first-in-dog study evaluates the use of the PET-radioligand [¹¹C]DASB to image the density and availability of the serotonin transporter (SERT) in the canine brain. Imaging the serotonergic system could improve diagnosis and therapy of multiple canine behavioural disorders. Furthermore, as many similarities are reported between several human neuropsychiatric conditions and naturally occurring canine behavioural disorders, making this tracer available for use in dogs also provide researchers an interesting non-primate animal model to investigate human disorders. Five adult beagles underwent a 90 minutes dynamic PET scan and arterial whole blood was sampled throughout the scan. For each ROI, the distribution volume (V_T), obtained via the one- and two- tissue compartment model (1-TC, 2-TC) and the Logan Plot, was calculated and the goodness-of-fit was evaluated by the Akaike Information Criterion (AIC). For the preferred compartmental model BP_ND values were estimated and compared with those derived by four reference tissue models: 4-parameter RTM, SRTM2, MRTM2 and the Logan reference tissue model. The 2-TC model indicated in 61% of the ROIs a better fit compared to the 1-TC model. The Logan plot produced almost identical V_T values and can be used as an alternative. Compared with the 2-TC model, all investigated reference tissue models showed high correlations but small underestimations of the BP_ND-parameter. The highest correlation was achieved with the Logan reference tissue model (Y = 0.9266 x + 0.0257; R² = 0.9722). Therefore, this model can be put forward as a non-invasive standard model for future PET-experiments with [¹¹C]DASB in dogs.     

生物转化生产D-塔格糖的食品级菌种选育及L-阿拉伯糖异构酶的克隆表达

L-阿拉伯糖异构酶(L-arabinose isomerase,L-AI)是一种可以催化D-半乳糖为D-塔格糖的胞内异构化酶。随着塔格糖在食品工业中越来越广泛的应用,能够将半乳糖转化为塔格糖的食品级微生物以及食品级来源的L-AI受到更大的关注。文中从各种酸奶制品、泡菜及其他一些食品中采集不同的样品,筛选出1株具有L-AI酶活的食品级菌株,经过生理生化鉴定以及16S rDNA序列测定,确定该菌株为戊糖片球菌,命名为Pediococcus pentosaceus PC-5。以该菌基因组为模板,克隆L-AI基因,并在大肠杆菌BL21成功地异源表达。表达产物经粗提取后,在40℃下加入Mn2+,使D-半乳糖转化为D-塔格糖的转化率为33%。     

Modes of control by the circadian oscillator and the hourglass mechanism of the activities of cytoplasmic and chloroplast glyceraldehyde 3-phosphate dehydrogenases in Lemna gibba G3

Two types of clocks, i.e., the circadian oscillator and thehourglass mechanism, which under continuous light and darknessrespectively control the mutually inverse temporal changes inthe activities of Cyt-NAD-GPD and Chl-NADP-GPD of Lemna gibbaG3, were studied. Both clocks controlled the apparent Km values,not the Vmax values, of the GPD reactions for their substrateand coenzymes. A red light pulse inserted 3 hr after the onsetof the dark period eliminated the sigmoidal changes in darkness,but evoked rhythmical changes which otherwise did not occurin continuous darkness. Thus, the photosynthetic rhythm, ifpresent, would not sustain the GPD rhythms. This effect of ared light pulse was not nullified by a subsequent far red lightpulse. A far red light pulse given at the 3rd hour of an extendeddark period made conspicuous the sigmoidal changes in activityof GPDs in the dark period, and its effect was nullified bya subsequent red light pulse, suggesting that phytochrome isinvolved in the hourglass mechanism. (Received September 26, 1978; )     

Influence of surface anesthesia on the pressure pain threshold measured with different-sized probes

Transcutaneous pressure with pressure probes of arbitrary diameters have been commonly used for measuring the threshold and magnitude of muscle pain, yet this procedure lacks scientific validation. To examine the valid probe dimensions, we conducted physiological experiments using 34 human subjects. Pin-prick pain, pressure pain threshold (PPT) to pressure probes of various diameters, heat pain threshold, and electrical pain threshold of deep tissues were measured before and after application of surface lidocaine anesthesia to the skin surface over the brachioradial muscle in a double-blinded manner. The anesthesia neither affected PPT with larger probes (diameters: 1.6 and 15?mm) nor increased electric pain threshold of deep structures, whereas it diminished pain count in pin-prick test and PPT with a 1.0?mm diameter probe, suggesting that mechanical pain thresholds measured with 1.6 and 15?mm probes reflect the pain threshold of deep tissues, possibly muscle. Pain thresholds to heat did not change after application of the anesthesia. These results suggest that larger pressure probes can give a better estimation of muscular pain threshold.     

Chloroplast Development in the Chloroplast Ribosome Deficient Mutant (y-1 ac-20) of Chlamydomonas reinhardtii

To study the participation of chloroplast protein synthesisduring the three phases [Matsuda (1974) Biochim. Biophys. Acta366:45] of the greening process in Chlamydomonas reinhardtiiy-1, the greening characteristics in the low-chloroplast ribosomemutant y-1 ac-20 were compared with those in the y-1. In thedouble mutant cells Chl synthesis proceeded with an extendedlag and without a second transition point. The development ofpotential for rapid Chl synthesis (P-factor formation) was alsodelayed. Furthermore, PS I activity increased significantly,whereas PS II activity developed very little during greeningof the double mutant cells. The results indicate that greeningin double mutant cells occurs with no apparent late phase. (Received November 26, 1984; Accepted February 25, 1985)     

Identification of cancer hallmark‐associated gene and lncRNA cooperative regulation pairs and dictate lncRNA roles in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most common malignant tumour in the oral and maxillofacial region. Numerous cancers share ten common traits (“hallmarks”) that govern the transformation of normal cells into cancer cells. Long non‐coding RNAs (lncRNAs) are important factors that contribute to tumorigenesis. However, very little is known about the cooperative relationships between lncRNAs and cancer hallmark‐associated genes in OSCC. Through integrative analysis of cancer hallmarks, somatic mutations, copy number variants (CNVs) and expression, some OSCC‐specific cancer hallmark‐associated genes and lncRNAs are identified. A computational framework to identify gene and lncRNA cooperative regulation pairs (GLCRPs) associated with different cancer hallmarks is developed based on the co‐expression and co‐occurrence of mutations. The distinct and common features of ten cancer hallmarks based on GLCRPs are characterized in OSCC. Cancer hallmark insensitivity to antigrowth signals and self‐sufficiency in growth signals are shared by most GLCRPs in OSCC. Some key GLCRPs participate in many cancer hallmarks in OSCC. Cancer hallmark‐associated GLCRP networks have complex patterns and specific functions in OSCC. Specially, some key GLCRPs are associated with the prognosis of OSCC patients. In summary, we generate a comprehensive landscape of cancer hallmark‐associated GLCRPs that can act as a starting point for future functional explorations, the identification of biomarkers and lncRNA‐based targeted therapy in OSCC.     

Arthropod community composition along snowmelt gradients in snowbeds in the Snowy Mountains of south‐eastern Australia

Environmental gradients drive variation in community composition across a range of spatial scales. In alpine regions, areas of long‐lasting snow (‘snow patches’) create snowmelt gradients that drive considerable change in vegetation structure and composition over small spatial scales. This study examined whether there is parallel variation in arthropod communities using snowmelt gradients in the Australian Alps. Mites (Acarina) were the most common arthropods in snow patches, followed by springtails while, among the insects, the orders Hymenoptera (primarily Formicidae), Diptera, Coleoptera (primarily Carabidae) and Hemiptera (primarily Cicadellidae) dominated. Along the snowmelt gradient, arthropod assemblages changed from having equal proportions of predators and herbivores in early‐melting zones to being predator‐dominated in late‐melting zones, particularly early in the growing season. This followed a transition in vegetation cover and composition and was driven by higher numbers of predacious carabid beetles in later‐melting zones. Overall, however, our results suggest that snowbed arthropod communities in the Australian alpine zone are more sensitive to short‐term effects, such as time since snowmelt, than to differences in vegetation structure and composition or long‐term patterns of snowmelt. Continued advancement of snowmelt timing due to warmer spring temperatures is therefore likely to have more impact on the seasonality of snowbed arthropod communities than on the overall community composition.     

Anaerobic microbial communities and their potential for bioenergy production in heavily biodegraded petroleum reservoirs

Most of the oil in low temperature, non-uplifted reservoirs is biodegraded due to millions of years of microbial activity, including via methanogenesis from crude oil. To evaluate stimulating additional methanogenesis in already heavily biodegraded oil reservoirs, oil sands samples were amended with nutrients and electron acceptors, but oil sands bitumen was the only organic substrate. Methane production was monitored for over 3000 days. Methanogenesis was observed in duplicate microcosms that were unamended, amended with sulfate or that were initially oxic, however methanogenesis was not observed in nitrate-amended controls. The highest rate of methane production was 0.15 μmol CH₄ g⁻¹ oil d⁻¹, orders of magnitude lower than other reports of methanogenesis from lighter crude oils. Methanogenic Archaea and several potential syntrophic bacterial partners were detected following the incubations. GC–MS and FTICR–MS revealed no significant bitumen alteration for any specific compound or compound class, suggesting that the very slow methanogenesis observed was coupled to bitumen biodegradation in an unspecific manner. After 3000 days, methanogenic communities were amended with benzoate resulting in methanogenesis rates that were 110-fold greater. This suggests that oil-to-methane conversion is limited by the recalcitrant nature of oil sands bitumen, not the microbial communities resident in heavy oil reservoirs.     

Impacts of predator-mediated interactions along a climatic gradient on the population dynamics of an alpine bird

According to classic theory, species'' population dynamics and distributions are less influenced by species interactions under harsh climatic conditions compared to under more benign climatic conditions. In alpine and boreal ecosystems in Fennoscandia, the cyclic dynamics of rodents strongly affect many other species, including ground-nesting birds such as ptarmigan. According to the ‘alternative prey hypothesis’ (APH), the densities of ground-nesting birds and rodents are positively associated due to predator–prey dynamics and prey-switching. However, it remains unclear how the strength of these predator-mediated interactions change along a climatic harshness gradient in comparison with the effects of climatic variation. We built a hierarchical Bayesian model to estimate the sensitivity of ptarmigan populations to interannual variation in climate and rodent occurrence across Norway during 2007–2017. Ptarmigan abundance was positively linked with rodent occurrence, consistent with the APH. Moreover, we found that the link between ptarmigan abundance and rodent dynamics was strongest in colder regions. Our study highlights how species interactions play an important role in population dynamics of species at high latitudes and suggests that they can become even more important in the most climatically harsh regions.