781 research outputs found
The hormonal and humoral regulators of myocardial protein metabolism : the in vivo measurement of the physiologic role of insulin and amino acids in cardiac protein kinetics
Does the Community Reinvestment Act influence lending? an analysis of changes in bank low-income mortgage activity
Anecdotal evidence that the Community Reinvestment Act (CRA) influences the lending behavior of financial institutions has not been uniformly supported by empirical research. We revisit this issue by evaluating changes in low-income mortgage lending at commercial banks over the 1992-96 period. Our empirical results fail to support a hypothesis that banks respond to public and regulatory pressure exerted as a result of a downgrade in CRA rating by increasing low-income mortgage lending. The findings are consistent with the contention that during this period regulators stressed adjustments in the lending process of banks (e.g., documentation of lending program and efforts directed at targeted markets) more than lending performance. The findings underscore the importance of regulatory efforts made later in the decade to more closely link enforcement of the CRA to lending outcomes.Community Reinvestment Act of 1977 ; Mortgages ; Bank loans ; Financial institutions
Membrane fusion of secretory vesicles and liposomes Two different types of fusion
Secretory vesicles isolated from adrenal medulla were found to fuse in vitro in response to incubation with Ca2+. Intervesicular fusion was detected by electron microscopy and was indicated by the appearance of twinned vesicles in freeze-fractured suspensions of vesicles and in thin-sectioned pellet. Two types of fusion could be distinguished: Type I, occurring between 10−7 M and 10−4 M Ca2+, was specific for Ca2+, was inhibited by other divalent cations and was abolished by pretreatment of vesicles with glutaraldehyde, neuraminidase or trypsin. Fusion type I was linear with temperature. A second type of intervesicular fusion was elicited by Ca2+ in concentrations higher than 2.5 mM and was morphologically characterized by multiple fusions of secretory vesicles. This type of fusion was found to be similar to fusion of liposomes prepared from the membrane lipids of adrenal medullary secretory vesicles: Ca2+ could be replaced by other divalent cations, the effect of different divalent cations was additive and pretreatments attacking membrane proteins were ineffective. Fusion type II of intact secretory vesicles as well as liposome fusion was discontinuous with temperature. Liposome fusion could be detected within 35 ms and persisted for 180 min. Using liposomes containing defined Ca2+ concentrations we have not found a major influence of Ca2+ asymmetry on fusion. Incorporation of the ganglioside GM3, which is present in the membranes of intact adrenal medullary secretory vesicles did not change the properties of liposomes fusion. Using a Ca2+-selective electrode we have identified in secretory vesicle membranes both high affinity binding sites for Ca2+ (Kd = 1.6 · 10−6M) and low affinity sites (Kd = 1.2 · 10−4M)
Fusion of secretory vesicles isolated from rat liver
Secretory vesicles isolated from rat liver were found to fuse after exposure to Ca2+. Vescle fusion is characterized by the occurrence of twinned vesicles with a continuous cleavage plane between two vesicles in freeze-fracture electron microscopy. The number of fused vesicles increases with increasing Ca2+-concentrations and is half maximal around 10–6 m. Other divalent cations (Ba2+, Sr2+, and Mg2+) were ineffective. Mg2+ inhibits Ca2+-induced fusion. Therefore, the fusion of secretory vesiclesin vitro is Ca2+ specific and exhibits properties similar to the exocytotic process of various secretory cells.
Various substances affecting secretionin vivo (microtubular inhibitors, local anethetics, ionophores) were tested for their effect on membrane fusion in our system.
The fusion of isolated secretory vesicles from liver was found to differ from that of pure phospholipid membranes in its temperature dependence, in its much lower requirement for Ca2+, and in its Ca2+-specificity. Chemical and enzymatic modifications of the vesicle membrane indicate that glycoproteins may account for these differences
Fusion of isolated myoblast plasma membranes
Fusion of plasma membranes isolated from myoblasts grown in culture has been investigated.
1. 1. Membrane fusion was specifically dependent on Ca2+ at physiological concentrations. However, at higher concentrations of cations, fusion could be triggered not only by Ca2+, but by Mg2+ and Sr2+ as well.
2. 2. The amount of fusion was directly proportional to temperature.
3. 3. Fusion was found to depend on the state of maturation of the myoblast membranes.
4. 4. Experiments with chemically and enzymatically modified membranes and with membranes derived from myoblasts grown in the presence of inhibitors of protein biosynthesis suggest the participation of proteinaceous membrane components in the fusion mechanism
Sexual Differentiation of the Surge Mode of Gonadotropin Secretion: Prenatal Androgens Abolish the Gonadotropin‐Releasing Hormone Surge in the Sheep
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106142/1/j.1365-2826.1996.tb00698.x.pd
Quantitative analysis of transient and sustained transforming growth factor-β signaling dynamics
Mathematical modeling and experimental analyses reveal that TGF-β ligand depletion has an important role in converting short-term graded signaling responses to long-term switch-like responses
Thermodynamics of doubly charged CGHS model and D1-D5-KK black holes of IIB supergravity
We study the doubly charged Callan-Giddings-Harvey-Strominger (CGHS) model,
which has black hole solutions that were found to be U-dual to the D1-D5-KK
black holes of the IIB supergravity. We derive the action of the model via a
spontaneous compactification on S^3 of the IIB supergravity on S^1*T^4 and
obtain the general static solutions including black holes corresponding to
certain non-asymptotically flat black holes in the IIB supergravity.
Thermodynamics of them is established by computing the entropy, temperature,
chemical potentials, and mass in the two-dimensional setup, and the first law
of thermodynamics is explicitly verified. The entropy is in precise agreement
with that of the D1-D5-KK black holes, and the mass turns out to be consistent
with the infinite Lorentz boost along the M theory circle that is a part of the
aforementioned U-dual chain.Comment: 21 pages, Revte
3',5'-Cyclic Adenosine Monophosphate- and Ca2+-Calmodulin-Dependent Endogenous Protein Phosphorylation Activity in Membranes of the Bovine Chromaffin Secretory Vesicles: Identification of Two Phosphorylated Components as Tyrosine Hydroxylase and Protein Kinase Regulatory Subunit Type II
Abstract: Membranes of the secretory vesicles from bovine adrenal medulla were investigated for the presence of the endogenous protein phosphorylation activity. Seven phosphoprotein bands in the molecular weight range of 250,000 to 30,000 were observed by means of the sodium dodecyl sulphate electrophoresis and autoradiography. On the basis of the criteria of molecular weight, selective stimulation of the phosphorylation by cyclic AMP (as compared with cyclic GMP) and immunoprecipitation by specific antibodies, band 5 (molecular weight 60,300) was found to represent the phosphorylated form of the secretory vesicle-bound tyrosine hydroxylase. The electrophoretic mobility, the stimulatory and inhibitory effects of cyclic AMP in presence of Mg2+ and Zn,2+ respectively, and immunoreactivity toward antibodies showed band 6 to contain two forms of the regulatory subunits of the type II cyclic AMP-dependent protein kinase, distinguishable by their molecular weights (56,000 and 52,000, respectively). Phosphorylation of band 7 (molecular weight 29,800) was stimulated about 2 to 3 times by Ca2+ and calmodulin in the concentration range of both agents believed to occur in the secretory tissues under physiological conditions
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