On the mechanism by which dopamine inhibits prolactin release in the anterior pituitary

An $\text{in}$$\text{vitro}$ perfusion system was used to assess the effects of chloride channel blockers, dopamine (DA) receptor agonists and antagonists, and GABA receptor agonists and antagonists on prolactin release from the mouse anterior pituitary. Dopamine and muscimol inhibited prolactin release ($\text{IC}{}_{50}{}^1\text{= 6 × 10}{}^{\mathrm{?8}}\text{M and}\text{10}{}^{\mathrm{?5}}\text{M}$ respectively). The GABA receptor antagonist bicuculline blocked the inhibition of prolactin release by muscimol but not dopamine. The dopamine receptor antagonist chlorpromazine blocked the dopamine- but not muscimol-induced inhibition of prolactin release. Haloperidol, however, reversed both the muscimol and dopamine induced inhibition of prolactin release. Furthermore, the chloride channel blocker picrotoxinin blocked the inhibition of prolactin release elicited by both dopamine and muscimol. These later results suggest that the anterior pituitary dopamine receptor which mediates the inhibition of prolactin release may be coupled to a picrotoxinin sensitive chloride ionophore and that haloperidol may affect the function of both DA and GABA receptors in the anterior pituitary.     

Environmental Particulate (PM2.5) Augments Stiffness-Induced Alveolar Epithelial Cell Mechanoactivation of Transforming Growth Factor Beta

Dysfunctional pulmonary homeostasis and repair, including diseases such as pulmonary fibrosis (PF), chronic obstructive pulmonary disease (COPD), and tumorigenesis have been increasing over the past decade, a fact that heavily implicates environmental influences. Several investigations have suggested that in response to increased transforming growth factor - beta (TGFβ) signaling, the alveolar type II (ATII) epithelial cell undergoes phenotypic changes that may contribute to the complex pathobiology of PF. We have previously demonstrated that increased tissue stiffness associated with PF is a potent extracellular matrix (ECM) signal for epithelial cell activation of TGFβ. The work reported here explores the relationship between tissue stiffness and exposure to environmental stimuli in the activation of TGFβ. We hypothesized that exposure of ATII cells to fine particulate matter (PM2.5) will result in enhanced cell contractility, TGFβ activation, and subsequent changes to ATII cell phenotype. ATII cells were cultured on increasingly stiff substrates with or without addition of PM2.5. Exposure to PM2.5 resulted in increased activation of TGFβ, increased cell contractility, and elongation of ATII cells. Most notably, on 8 kPa substrates, a stiffness greater than normal but less than established fibrotic lung, addition of PM2.5 resulted in increased cortical cell stiffness, enhanced actin staining and cell elongation; a result not seen in the absence of PM2.5. Our work suggests that PM2.5 exposure additionally enhances the existing interaction between ECM stiffness and TGFβ that has been previously reported. Furthermore, we show that this additional enhancement is likely a consequence of intracellular reactive oxygen species (ROS) leading to increased TGFβ signaling events. These results highlight the importance of both the micromechanical and biochemical environment in lung disease initiation and suggest that individuals in early stages of lung remodeling during fibrosis may be more susceptible than healthy individuals when exposed to environmental injury adjuvants.     

The congenital cataract-causing mutations P20R and A171T are associated with important changes in the amyloidogenic feature,structure and chaperone-like activity of human αB-crystallin

Cataract is the major reason for human blindness worldwide. α-Crystallin, as a key chaperone of eye lenses, keeps the lenticular tissues in its transparent state over time. In this study, cataract-causing familial mutations, P20R and A171T, were introduced in CRYАB gene. After successful expression in Escherichia coli and subsequent purification, the recombinant proteins were subjected to extensive structural and functional analyses using various spectroscopic techniques, gel electrophoresis, and electron microscopy. The results of fluorescence and Raman assessments suggest important but discreet conformational changes in human αB-Cry upon these cataractogenic mutations. Furthermore, the mutant proteins exhibited significant secondary structural alteration as revealed by FTIR and Raman spectroscopy. An increase in conformational stability was seen in the human αB-Cry bearing these congenital cataractogenic mutations. The oligomeric size distribution and chaperone-like activity of human αB-Cry were significantly altered by these mutations. The P20R mutant protein was observed to loose most of the chaperone-like activity. Finally, these cataractogenic mutant proteins exhibited an increased propensity to form the amyloid fibrils when incubated under environmental stress. Overall, the structural and functional changes in mutated human αB-Cry proteins can shed light on the pathogenic development of congenital cataracts.     

Synaptonemal complex spreading in Allium cepa and A. fistulosum

The general features and fine structure of homologous chromosome alignment and pairing have been investigated in two species of Allium (A. fistulosum and A. cepa), which have similar karyotypes but very different patterns of chiasma distribution. Although there is no support for the occurrence of a general pre-meiotic alignment of homologous chromosomes, both species show some alignment of homologues as an immediate prelude to synaptonemal complex (SC) formation. In both species pairing usually commences at sub-terminal sites and is succeeded by numerous separate intercalary initiations of pairing in interstitial and distal regions and then in proximal regions. The last parts to pair, in both species, are pericentromeric and telomeric regions. There is, therefore, no evident relationship between the sequence of pairing and chiasma distribution in these species. Regularly alternating convergences and divergences of aligned axial cores (ACs), termed multiple association sites, are frequently observed. It is proposed that these represent potential pairing initiation sites and from observations on their spatial distribution it is argued that they may be evenly distributed through most of the genome. Small spherical or ellipsoid nodules are found at association sites and between closely aligned ACs which persist in the SC segments present during zygotene, but most of them disappear abruptly at the end of zygotene. These are termed zygotene nodules (ZN) and it is proposed that they are involved in matching corresponding sites on homologous chromosomes as well as possibly having a recombinational role. Their composition, structure, mode of action and relationship to pachytene recombination nodules are at present unknown.     

Time-resolved x-ray diffraction and calorimetric studies at low scan rates: I. Fully hydrated dipalmitoylphosphatidylcholine (DPPC) and DPPC/water/ethanol phases

The phase transitions in fully hydrated dipalmitoylphosphatidylcholine (DPPC) and DPPC/water/ethanol phases have been studied by lowangle time-resolved x-ray diffraction under conditions similar to those employed in calorimetry (scan rates 0.05-0.5°C/min and uniform temperature throughout the samples). This approach provides more adequate characterization of the equilibrium transition pathways and allows for close correlations between structural and thermodynamic data. No coexistence of the rippled gel (P_β') and liquid-crystalline (L_α) phases was found in the main transition of DPPC; rather, a loss of correlation in the lamellar structure, observed as broadening of the lamellar reflections, takes place in a narrow temperature range of ~100 mK at the transition midpoint. Formation of a long-living metastable phase, denoted by P_β'(mst), differing from the initial P_β' was observed in cooling direction by both x-ray diffraction and calorimetry. No direct conversion of P_β'(mst) into P_β' occurs for over 24 h but only by way of the phase sequence P_β'(mst) → L_β' → P_β'. According to differential scanning calorimetry (DSC), the enthalpy of the P_β'(mst)-L_α transition is by ~5% lower than that of the P_β'-L_α transition. The effects of ethanol (Rowe, E. S. 1983. Biochemistry. 22:3299-3305; Simon, S. A., and T. J. McIntosh. 1984. Biochim. Biophys. Acta 773:169-172) on the mechanism and reversibility of the DPPC main transition were clearly visualized. At ethanol concentrations inducing formation of interdigitated gel phase, the main transition proceeds through a coexistence of the initial and final phases over a finite temperature range. During the subtransition in DPPC recorded at scan rate 0.3°C/min, a smooth monotonic increase of the lamellar spacing from its subgel (L_c) to its gel (L_β') phase value takes place. The width of the lamellar reflections remains unchanged during this transformation. This provides grounds to propose a “sequential” relaxation mechanism for the subgel-gel transition which is not accompanied by growth of domains of the final phase within the initial one.     

Phylogenetic analysis and identification of different serovars of Mycobacterium intracellulare at the molecular level

Comparative 16S rRNA sequencing was used to infer the phylogenetic relationship among different serovars of the Mycobacterium avium-M. intracellulare complex as well as to define signature nucleotides characteristic for different serovars. In general, the groups defined by rRNA sequencing reflect the classification obtained with sensitin tests and pathogenicity examinations in chickens. Unique 16S rRNA sequence patterns could be defined for (1) M. avium, (2) M. intracellulare serovars 4, 5, 6, 8, 9, 10 and 11, (3) M. intracellulare serovars 12, 13, 14, 15, 17, 19 and 20, (4) M. intracellulare serovar 7 and (5) M. intracellulare serovar 18. Phylogenetically, groups 1 and 2 on one hand and groups 3, 4 and 5 on the other hand each share a common ancestor. M. paratuberculosis was indistinguishable from M. intracellulare serovars 4, 5, 6, 8, 9, 10 and 11 by this kind of analysis.     

Materno-embryonally transferred antibodies precipitate autoimmune thyroiditis in obese strain (OS) chickens

In Obese strain (OS) chickens the role of maternal antibodies, passively transferred through the egg to the developing chick, was evaluated as a causative factor in the early development of spontaneous autoimmune thyroiditis (SAT). In the egg, passive antibody titers were highest in the yolk and lower in the allantoic fluid and sera of developing embryos. This passage of antibodies was documented by use of radiolabeled antibodies. In dams with high antibody titers, antibodies could be found in the sera of chicks at the time of hatch. Thyroglobulin was absent in the yolk of OS eggs during embryonal life, as compared with its detection in normal eggs. Immune complexes (thyroglobulin-autoantibody) detected in the thyroids of OS, but not CS, chicks at the time of hatch, or earlier, appear to reflect the presence of the maternally transferred antibodies. A pair of crosses between OS chickens, with thyroiditis, and the C strain (CS), without thyroiditis, was made to evaluate the role of transferred antibodies in the pathogenesis of autoimmune disease. When an OS chicken was the dam, maternal antibodies could be passively transferred; when a CS chicken was the dam, no maternal antibodies were present to be transferred. Nevertheless, both hybrids developed full-blown thyroiditis, demonstrating that binding of transferred maternal antibody to thyroglobulin is not a prerequisite for the induction of SAT. However, presence of maternal antibodies precipitated the onset of disease. Immune complexes formed in the embryonic thyroid are likely to participate in early autoimmune disease, although the development of full-blown thyroiditis may await the competency of the chick's immune system to provide the characteristic cellular infiltrate.