Intracellular acetylation of desacetyl αMSH in the xenopus laevis neurointermediate lobe

High performance liquid chromatography (HPLC) followed by radioimmunoassay (RIA) of the chromatographic fractions were used to separate and quantify, respectively, the αMSH-like peptides stored in the neurointermediate lobe (NIL) of the Xenopus laevis (X. laevis) pituitary gland and released from the X. laevis NIL, in vitro. Immunoreactive (IR) material eluting with a similar HPLC retention time as desacetyl αMSH was the major IR peptide in the NIL. Material with a retention time similar to αMSH and immunological properties equivalent to αMSH was also present in the NIL. However, the retention times of the X. laevis and mammalian αMSH-like peptides were not identical, suggesting species difference in these peptides. Following incubation of NILs in the presence of [³H]-acetyl CoA, the X. laevis variant of αMSH was the major [³H]-labeled, immunoprecipitable material present. Following an incubation of NILs in the presence of [³H]-amino acids for 21 hours, immunoprecipitable [³H]-αMSH was detected in the NILs and the ratio of [³H]-desacetyl αMSH to [³H]-αMSH was similar to the ratio of IR-desacetyl αMSH to IR-αMSH. The X. laevis variant of αMSH was the major αMSH-like peptide released from the NILs into the incubation medium. Dopamine (50 μM) significantly inhibited the release of IR-αMSH but not IR-desacetyl αMSH. No net increase in total αMSH (sum of release and NIL content) was observed in the actively secreting (control) NIL group versus the dopaminetreated group. These results indicate that acetylation of desacetyl αMSH occurs intracellularly.     

Pro-opiomelanocortin and pro-vasopressin converting enzyme in pituitary secretory vesicles

Peptide hormones are synthesized from larger precursors by cleavages at paired basic residues. We have isolated a pro-hormone converting enzyme from bovine neural and intermediate lobe secretory vesicles that cleaves pro-vasopressin and pro-opiomelanocortin at Lys-Arg residues to yield vasopressin, and adrenocorticotropin/endorphin-related peptides, respectively. The enzyme from both lobes is an aspartyl protease of approximately 70,000 Da, is a glycoprotein and has an optimum pH range of 4.0-5.0. Present within the same secretory vesicles is an aminopeptidase B-like enzyme which is a metalloprotease that is inhibited by Co2+ and Zn2+. This enzyme may play a role in trimming off the N-terminal extended basic residues from peptides liberated by the pro-hormone converting enzyme.     

Evidence for intragranular processing of pro-opiocortin in the mouse pituitary intermediate lobe

Mouse pituitary neurointermediate lobes were pulse-incubated in [3H] arginine or [3H] lysine for 10 min and then chase-incubated for periods 0 to 4h. The labeled peptides from the lobes were analysed by immunoprecipitation with specific antisera, and thereafter, by acid-urea polyacrylamide gel electrophoresis. Using this paradigm, the synthesis of a prohormone common to adrenocorticotropin (ACTH) and endorphin was detected in 10 min pulse labeled lobes. Following a chase period, processing of the prohormone to several forms of ACTH (mol. wt. 25000, 23000, and 13000), beta-lipotropin and beta-endorphin was observed. To determine the intracellular site of processing of the prohormone, subcellular fractionation studies of labeled lobes were carried out. Analysis of the fractions from the pulse-labeled lobes revealed that the newly synthesized labeled prohormone was primarily localized in a granule-enriched fraction. In lobes that were pulsed and then chase-incubated for 1 h, there was a decrease in the amount of prohormone and an appearance of processed products in the granule-enriched fraction. In another paradigm, where the secretory granule-fraction was isolated from pulse-labeled lobes and then incubated in vitro for 6 h at pH 5.5, processing of the endogenous labeled prohormone within the isolated granule fraction was observed. These data suggest, that in the mouse neurointermediate lobe, the ACTH/endorphin prohormone (pro-opiocortin) is rapidly packaged into secretory granules after synthesis and processed intragranularly.     

A latent state space model for estimating brain dynamics from electroencephalogram (EEG) data

Modern neuroimaging technologies have substantially advanced the measurement of brain activity. Electroencephalogram (EEG) as a noninvasive neuroimaging technique measures changes in electrical voltage on the scalp induced by brain cortical activity. With its high temporal resolution, EEG has emerged as an increasingly useful tool to study brain connectivity. Challenges with modeling EEG signals of complex brain activity include interactions among unknown sources, low signal-to-noise ratio, and substantial between-subject heterogeneity. In this work, we propose a state space model that jointly analyzes multichannel EEG signals and learns dynamics of different sources corresponding to brain cortical activity. Our model borrows strength from spatially correlated measurements and uses low-dimensional latent states to explain all observed channels. The model can account for patient heterogeneity and quantify the effect of a subject's covariates on the latent space. The EM algorithm, Kalman filtering, and bootstrap resampling are used to fit the state space model and provide comparisons between patient diagnostic groups. We apply the developed approach to a case-control study of alcoholism and reveal significant attenuation of brain activity in response to visual stimuli in alcoholic subjects compared to healthy controls.     

Immunoreactive alpha-melanotropin and beta-endorphin in the toad pars intermedia: dissociation in storage, secretion and subcellular localization

Storage, secretion and subcellular localization of immunoreactive α -melanotropin (α -MSH_i) and β -endorphin (β -END_i) were examined in the pars intermedia of toads adapted to a black or white background. During white adaptation, there was a selective increase in storage of α -MSH_i but not β -END_i. Subcellular fractionation and release studies suggest the presence of two pools of peptides in the toad pars intermedia, each containing different molar ratios of α -MSH_i and β -END_i and regulated differently in their release.     

H3-cerebroside sulfate re-distribution induced by cation,opiate or phosphatidyl serine

Transfer of H³-cerebroside sulfate (CS) from aqueous phase to nonaqueous phases (heptane interface) was studied in the absence and presence of opiates, cations and phosphatidylserine. The degree of H³-CS re-distribution was dependent on the concentration of these substances used. The concentration of an opiate agonist (GPA-1657) required to increase H³-CS by 50% in the nonaqueous phase was much lower than that of its corresponding antagonist (GPA-2163) and the value for calcium was 100 times less than sodium. Opiate antagonist (GPA-2163) and phosphatidylserine inhibited the agonist induced re-distribution of H³-CS. Thus, the data seem to indicate that the distribution of H³-CS between these two phases was determined by hydrophobic-hydropholic balance of H³-CS and this balance was dependent on the counter ion pairing with CS. This finding is consistent with our previous observation that opiate agonist-CS complex was more hydrophobic than free CS of the CS-complex formed with opiate antagonist.     

The eggshell structure in apteryx; form,function, and adaptation

Apteryx is a genus of flightless birds endemic to New Zealand known to lay very large eggs in proportion to body weight. The eggshell of Apteryx is unusually thin and less porous than allometrically expected possibly as a compensation for a very long incubation period. Past studies have been carried out on Apteryx australis, a species which once comprised all kiwi with brown plumage, now separated into three distinct species. These species use different habitats and live at different latitudes and altitudes, therefore generating a need to revise our knowledge of the attributes of their eggshells. In this study, we measured the physical characteristics and water conductance on eggshell fragments of these three species and Great‐spotted Kiwi and relate them to the environmental conditions of their respective environments; we also measured the water vapor conductance of Brown Kiwi eggs of late stages of incubation. We found that several trade‐offs exist between incubation behavior, environmental conditions, and eggshell structure. We found differences between species in eggshell water vapor conductance seemingly related to altitude; Brown Kiwi and Rowi generally inhabiting lower altitudes had the highest conductance and Tokoeka, generally living in montane environments, the lowest. This is achieved by an increased eggshell thickness rather than a pore area reduction. Finally, the water vapor conductance late in incubation was 58% higher than infertile unincubated eggs, suggesting a drastic increase in conductance throughout the long incubation period. Using the values previously reported, we calculated the embryonic eggshell thinning to be 32.5% at the equatorial region of the eggshell. We describe several new features, such as triangular mineral particles in the cuticle, reported for the extinct Trigonoolithus amoei, and confirmed the existence of plugged pores. We suggest that these structures provide microbial protection needed by a burrow nesting species with a long incubation period.