A unique family of endothelial cell polypeptide mitogens: the antigenic and receptor cross-reactivity of bovine endothelial cell growth factor, brain-derived acidic fibroblast growth factor, and eye-derived growth factor-II

Bovine brain, hypothalamus, pituitary, and retina contain potent anionic polypeptide mitogens for endothelial cells. Immunological assays using murine monoclonal antibodies against bovine endothelial cell growth factor (ECGF) and radioreceptor assays using [125I]ECGF were performed to determine the cross-reactivity of ECGF with bovine acidic pI brain-derived fibroblast growth factor (acidic FGF) and bovine eye-derived growth factor-II [EDGF-II). We observed that acidic FGF and EDGF-II are recognized by anti-ECGF monoclonal antibodies and compete with [125I] ECGF for receptor occupancy. Furthermore, the biological activity of ECGF, acidic FGF, and EDGF-II is potentiated by the glycosaminoglycan, heparin. These results argue that ECGF, acidic FGF, and EDGF-II belong to a common family of polypeptide growth factors.     

Further evidence for the presence of specific binding sites for prolactin in the rabbit brain. Preferential distribution in the hypothalamus and substantia nigra

In the present research we have extended our work on the presence of binding sites for prolactin in the rabbit brain focusing our attention on the brain areas with high dopamine cell bodies density. Among these areas the hypothalamus showed the highest specific binding of labeled ovine prolactin (oPRL). Clearly detectible specific binding was observed also in substantia nigra, whereas in other brain regions the specific binding was very small, except for the striatum where a low but not negligible binding was found in female rabbits. The binding of 125I-oPRL showed a hormonal specificity and Scatchard analysis of the binding showed no clear difference in dissociation constant (Kd) between hypothalamus, nigra and striatum.     

Structural differences in the cell binding region of human fibronectin molecules isolated from cultured normal and tumor-derived human cells

Fibronectins isolated from human plasma (pFN) and from the conditioned media of normal (N-cFN) and tumor (T-cFN) human cells were compared by cathepsin D digestion followed by immunostaining of released fragments with the monoclonal antibody 3E3, specific for the cell binding site. Two different staining patterns were obtained, one specific for pFN and N-cFN, the second common to fibronectins from the 3 different kinds of tumors studied. This indicates structural differences between N-cFN and T-cFN in the cell binding region of the fibronectin molecule.     

Isoelectric focusing of brain cortex GSH S-transferase activity in mammals: evidence that polymorphism is absent in man

Specific activities of GSH S-transferase toward different model substrates were determined in the cytosol prepared from rat, guinea pig, rabbit, mouse, sheep, beef, pig and human brain cortex. The GSH S-transferase composition of the eight mammalian brain cortices was studied by using density gradient isoelectric focusing technique. Human brain cortex GSH S-transferase was resolved into a single peak of activity centered at pH 4.6, whereas the supernatants of all other mammals consisted of more than one enzymatic form. The kinetic properties of all forms isolated were compared.     

Analysis of fluorescence quenching of ribosome-bound virginiamycin S

The two virginiamycin components VM and VS interact synergistically with bacterial ribosomes in vitro and in vivo. Ribosome affinity for virginiamycin S increases about 10-fold upon incubation with virginiamycin M. This effect has been previously traced by spectrofluorimetric measurement based on the enhancement of virginiamycin S fluorescence upon its binding to the 50 S ribosomal subunit. In the present work the action of two virginiamycin S fluorescence quenchers, acrylamide and iodide, has been explored to gather information about the accessibility of ribosome-bound virginiamycin S and the variation of the accessibility level in the presence of virginiamycin M. Both acrylamide (non-ionized quencher) and iodide (ionized quencher) proved powerful quenchers of free virginiamycin S solutions. Since a comparable effect was obtained on 3- hydroxypicolinamide , the latter was indicated as the part of the molecule involved in the fluorescence effect. Fluorescence quenching by either agent was of the dynamic, i.e. collisional, type. Such an inference was based on the fact that these quenchers merely modified the emission spectrum (not the absorption spectrum), the bimolecular rate constant for the quenching process decreased linearly with the viscosity of the medium (static-type quenching is viscosity-independent), and that linear Stern-Volmer plots were obtained. The quenching ability of both agents underwent a sharp decrease in the presence of ribosomes; however, the Stern-Volmer equation was followed only in the case of acrylamide, whereas Lehrer 's relationship had to be applied in the case of iodide. When ribosomes were incubated with virginiamycin M, the fluorescence quenching ability of acrylamide and iodide was significantly reduced. Conclusions are as follows: a) the 3- hydroxypicolinyl residue of virginiamycin S is buried within an open well on the ribosome surface and is likely to be involved in the interaction with the binding site; b) the accessibility to the well is partly controlled by electrostatic forces; c) interaction of ribosomes with virginiamycin M entails a conformational change whereby the access to the well is reduced. These findings provide a molecular explanation for the previously observed increase of the association constant of virginiamycin S to ribosomes incubated with virginiamycin M which was found to be due to the decrease of the dissociation rate constant (the association rate constant remains practically the same).     

Genetic relationship between o6 and pro-1 mutants in maize

Summary This paper reports that the opaque-6 (o6) mutation of maize, which causes seedling lethality and interferes in the endosperm with the synthesis of zeins and b-32 protein, is a proline requiring mutant functionally allelic to proline-1 (pro-1). Furthermore, immunological studies on the b-32 content of ten independently originated o6 and pro-1 alleles demonstrated that four alleles contain an apparently normal b-32 protein while the others are either devoid of it or contain trace amounts of cross-reacting proteins of lower molecular weight.     

Glutathione redox cycle enzyme activities in erythrocytes of multiple sclerosis patients

The erythrocytes of multiple sclerosis patients with elevated superoxide dismutase levels were tested for the activities of glutathione redox cycle enzymes. No differences were observed between multiple sclerosis and normal control erythrocytes when the activities were referred to either hemoglobin concentration or lactate dehydrogenase content. Our results indicate that no adaptative changes occur in the activities of glutathione redox cycle enzymes in erythrocytes of multiple sclerosis subjects as a consequence of an elevated superoxide dismutase level.     

Spontaneously active and ATPMg-dependent protein phosphatase activity in vascular smooth muscle

A spontaneously active (Mr greater than 350,000) and an ATPMg-dependent phosphatase (Mr congruent to 140,000) were identified in bovine aortic smooth muscle. The spontaneously active phosphatase was effective in dephosphorylating both phosphorylase a (240nmol32P/min/mg) and phosphorylated myosin light chains (1000nmol32P/min/mg). In contrast, the ATPMg-dependent phosphatase was only effective in dephosphorylating phosphorylase a (400nmol32P/min/mg). Phosphorylase phosphatase activity of the ATPMg-dependent enzyme was suppressed by the well-characterized modulator protein (inhibitor-2), whereas the activity of the spontaneously active enzyme was unaffected. The aortic spontaneously active phosphatase did not convert to an ATPMg-dependent form when it was stored at 4 degrees or incubated at 30 degrees C in either the presence or absence of modulator protein. These findings suggest that spontaneous and ATPMg-dependent phosphatase activities described in these studies are probably ascribable to different enzymes. Since both phosphorylase and myosin light chains are phosphorylated when smooth muscle contracts these phosphatases may participate in coordinating arterial contractility and metabolism.