Photoaffinity labelling of the TSH receptor on FRTL5 cells

An investigation of the properties of TSH receptors on FRTL5 cells using affinity labelling with a 125I-labelled photoactive derivative of TSH is described. Our studies suggest that FRTL5 cells contain 2 principal types of cell surface TSH receptors. One form, probably a precursor, consists of a single polypeptide chain (Mr 120,000) with an intrachain loop of amino acids formed by a disulphide bridge. The other type of receptor consists of a water-soluble A chain (Mr 55,000) linked to an amphiphilic B chain (Mr 35,000) by a disulphide bridge. The 2 chain structure is probably derived from the single chain 120,000 protein by enzymatic cleavage of peptide sequences within the loop of amino acids formed by the intrachain disulphide bridge.     

Effects of bicarbonate on fluid and electrolyte transport by the guinea pig gallbladder: A bicarbonate-chloride exchange

Summary Fluid transport and net fluxes of Na, K, Cl and HCO₃ by guinea pig gallbladder were investigatedin vitro. A perfused gallbladder preparation was devised to simultaneously study unidirectional fluxes of²²Na and³⁶Cl. The net Cl flux exceeded the net Na flux during fluid absorption in the presence of HCO₃. This Cl excess was counter-balanced by a net HCO₃ secretion: a HCO₃–Cl exchange. PGE₁ reversed the direction of fluid transport and abolished the net Cl flux. The magnitude of the HCO₃ secretion remained unchanged, but shifted from a HCO₃–Cl exchange to a net secretion of NaHCO₃ and KHCO₃. Furosemide inhibited both the HCO₃–Cl exchange and HCO₃ secretion after PGE₁ without influencing fluid absorption. Ouabain inhibited the HCO₃–Cl exchange as well as fluid absorption; only the effect on the HCO₃ secretion was entirely reversible. Secreted HCO₃ appeared not to be derived from metabolic sources since HCO₃ secretion was abolished in a HCO₃-free bathing medium. HCO₃ secretion was also dependent on the Na concentration of the bathing fluid. Three lines of evidence are presented in favor of an active HCO₃ secretion in guinea pig gallbladder. HCO₃ is secreted against: (i) a chemical gradient, (ii) an electrical gradient and (iii) the direction of fluid movement under control conditions.     

Defining dysbiosis and its influence on host immunity and disease

Mammalian immune system development depends on instruction from resident commensal microorganisms. Diseases associated with abnormal immune responses towards environmental and self antigens have been rapidly increasing over the last 50 years. These diseases include inflammatory bowel disease (IBD), multiple sclerosis (MS), type I diabetes (T1D), allergies and asthma. The observation that people with immune mediated diseases house a different microbial community when compared to healthy individuals suggests that pathogenesis arises from improper training of the immune system by the microbiota. However, with hundreds of different microorganisms on our bodies it is hard to know which of these contribute to health and more importantly how? Microbiologists studying pathogenic organisms have long adhered to Koch's postulates to directly relate a certain disease to a specific microbe, raising the question of whether this might be true of commensal–host relationships as well. Emerging evidence supports that rather than one or two dominant organisms inducing host health, the composition of the entire community of microbial residents influences a balanced immune response. Thus, perturbations to the structure of complex commensal communities (referred to as dysbiosis) can lead to deficient education of the host immune system and subsequent development of immune mediated diseases. Here we will overview the literature that describes the causes of dysbiosis and the mechanisms evolved by the host to prevent these changes to community structure. Building off these studies, we will categorize the different types of dysbiosis and define how collections of microorganisms can influence the host response. This research has broad implications for future therapies that go beyond the introduction of a single organism to induce health. We propose that identifying mechanisms to re‐establish a healthy complex microbiota after dysbiosis has occurred, a process we will refer to as rebiosis, will be fundamental to treating complex immune diseases.     

Signaling unmasked: Autophagy and catalase promote programmed cell death

Autophagy contributes to the removal of harmful cellular refuse, whereas catalase plays an important protective role by detoxifying reactive oxygen species. We recently found that autophagy and catalase are also required for promoting programmed cell death induced during plant immune responses. Here we discuss the difficulties in identifying cell death effectors, which are also required to maintain cellular homeostasis, and how their prodeath roles were unmasked using an unbiased forward genetics approach.     

Chromium distribution in subcellular components between fresh and starved subsurface bacterial consortium

Summary The distribution of chromium in subcellular components was examined with a fresh and starved denitrifying consortium by performing Cr⁺⁶ equilibration and cell fractionation tests. The cell wall fraction of 50 day starved cells adsorbed approximately 100% more chromium than did the cell wall fraction in fresh cells. The soluble fraction of 50 day old cells showed less affinity for chromium than fresh cells.     

Engineering mammalian mucin-type O-glycosylation in plants

Mucin-type O-glycosylation is an important post-translational modification that confers a variety of biological properties and functions to proteins. This post-translational modification has a particularly complex and differentially regulated biosynthesis rendering prediction and control of where O-glycans are attached to proteins, and which structures are formed, difficult. Because plants are devoid of GalNAc-type O-glycosylation, we have assessed requirements for establishing human GalNAc O-glycosylation de novo in plants with the aim of developing cell systems with custom-designed O-glycosylation capacity. Transient expression of a Pseudomonas aeruginosa Glc(NAc) C4-epimerase and a human polypeptide GalNAc-transferase in leaves of Nicotiana benthamiana resulted in GalNAc O-glycosylation of co-expressed human O-glycoprotein substrates. A chimeric YFP construct containing a 3.5 tandem repeat sequence of MUC1 was glycosylated with up to three and five GalNAc residues when co-expressed with GalNAc-T2 and a combination of GalNAc-T2 and GalNAc-T4, respectively, as determined by mass spectrometry. O-Glycosylation was furthermore demonstrated on a tandem repeat of MUC16 and interferon α2b. In plants, prolines in certain classes of proteins are hydroxylated and further substituted with plant-specific O-glycosylation; unsubstituted hydroxyprolines were identified in our MUC1 construct. In summary, this study demonstrates that mammalian type O-glycosylation can be established in plants and that plants may serve as a host cell for production of recombinant O-glycoproteins with custom-designed O-glycosylation. The observed hydroxyproline modifications, however, call for additional future engineering efforts.     

Differentiating Biological Colours with Few and Many Sensors: Spectral Reconstruction with RGB and Hyperspectral Cameras

Background

The ability to discriminate between two similar or progressively dissimilar colours is important for many animals as it allows for accurately interpreting visual signals produced by key target stimuli or distractor information. Spectrophotometry objectively measures the spectral characteristics of these signals, but is often limited to point samples that could underestimate spectral variability within a single sample. Algorithms for RGB images and digital imaging devices with many more than three channels, hyperspectral cameras, have been recently developed to produce image spectrophotometers to recover reflectance spectra at individual pixel locations. We compare a linearised RGB and a hyperspectral camera in terms of their individual capacities to discriminate between colour targets of varying perceptual similarity for a human observer.

Main Findings

(1) The colour discrimination power of the RGB device is dependent on colour similarity between the samples whilst the hyperspectral device enables the reconstruction of a unique spectrum for each sampled pixel location independently from their chromatic appearance. (2) Uncertainty associated with spectral reconstruction from RGB responses results from the joint effect of metamerism and spectral variability within a single sample.

Conclusion

(1) RGB devices give a valuable insight into the limitations of colour discrimination with a low number of photoreceptors, as the principles involved in the interpretation of photoreceptor signals in trichromatic animals also apply to RGB camera responses. (2) The hyperspectral camera architecture provides means to explore other important aspects of colour vision like the perception of certain types of camouflage and colour constancy where multiple, narrow-band sensors increase resolution.