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Biomedical subjects

G Colacicco

Publications and source records attributed to G Colacicco.

36 records · Page 2Linked to original sources
PubMed1972

Surface properties of membrane systems: apoprotein of the Folch-Lees proteolipid from beef-brain myelin.

Structural proteins in biological membranes are bimodal and ideally possess a unique surface activity that should be amenable to study by monolayer techniques. Proteins so studied, however, display, of necessity, a surface activity that reflects the laboratory history of the protein. The Folch-Lees proteolipid apoprotein was isolated from calf-brain myelin in both an organic solvent (CHCl(3)-CH(3)OH-CH(3)COOH; 50:50:1) and water. The apoprotein did not spread as a film from water, but did spread readily from the organic solvent into films that had high saturation pressures. The partitioning of the apoprotein from organic solvent to water was found to be reversible, as was the gain and loss of surface activity. Infrared spectroscopy demonstrated that the preponderant structure in films of the apoprotein was not that of extended polypeptide chains. The results suggested that the preferred structures at the interface are bimodal coils of alpha helix. This structure can sustain the high film pressures observed, whereas beta keratin structures would build films with high surface viscosity and very low surface pressure.

Animals↗
PubMed1968

Lipid monolayers: interactions with the apoprotein of high density plasma lipoprotein.

Monolayer techniques were used to study the interactions of various lipids (cholesterol, lysophosphatidyl choline, phosphatidal ethanolamine, phosphatidyl choline, sphingomyelin, stearic acid, and lipids extracted from plasma high density lipoproteins and very low density lipoprotein) with the lipid-free protein subunit of rat plasma high density lipoprotein and with rat plasma albumin. The proteins were injected under the lipid monolayer at fixed area, and the increase in surface pressure (decrease in surface tension) was measured as a function of time. With all lipids, both the rate and magnitude of this increase were greater with the apolipoprotein than with albumin. The degree of film penetration of pure lipid films (at an initial film pressure of 15 dynes/cm) by the two proteins followed the same order: cholesterol > phosphatidal ethanolamine > phosphatidyl choline > stearic acid > sphingomyelin > lysophosphatidyl choline. Other variables studied were protein concentration, initial film pressure, and pH. Two distinctive properties of the apolipoprotein were the penetration of lipid films at pressures above the collapse pressure of the protein, and the formation of a film even at low salt concentration. High surface activity and strong interaction of HDL-protein with lipid monolayers may be associated with the flexibility of the protein molecule due to absence of disulfide bridges. The unusual surface activity of HDL-protein may be intimately related to the mechanism of formation of the lipoprotein.

Animals↗
PubMed1966

Lipid monolayers: action of phospholipase A of Crotalus atrox and Naja naja venoms on phosphatidyl choline and phosphatidal choline.

The activity of phospholipase A on phosphatidyl choline and phosphatidal choline spread as monolayers on phosphate buffers containing snake venom (Crotalus atrox or Naja naja) was studied by measuring the fall of surface potential as a function of time, pH, film pressure, temperature, and concentrations of phosphate and venom. At 25 degrees C, pH 7.0, and 0.2 micrograms of venom per ml, optimal activity was observed with both venoms on both substrates at 12 dynes/cm film pressure on 0.04 m phosphate. Under these conditions, the pH optimum for C. atrox was broad (6.6-7.4) and that for N. naja was sharp (8.0) for the action on phosphatidyl choline, whereas both venoms had a sharp optimum at pH 8.0 in their action on phosphatidal choline. The optimal temperature with phosphatidyl choline was 27.5 degrees C for N. naja and 40 degrees C for C. atrox. In line with studies of phospholipase A activity in bulk phase in ether, phosphatidal choline was attacked much more slowly than phosphatidyl choline by C. atrox. Under conditions where both venoms had equal activity on phosphatidyl choline, C. atrox was only half as active as N. naja on phosphatidal choline. The studies suggest that the linkage of the hydrophobic chains in glycerophosphatides may affect their interaction with proteins.

Animals↗
PubMedDate not supplied

Cultured lung cells: interplay effects of beta-mimetics, prostaglandins and corticosteroids in the biosynthesis of dipalmitoyl lecithin.

Cell lines derived from type II lung cells were used to study interplays of substances affecting incorporation of labeled precursors [1(-14)C]palmitate and [methyl-3H]choline into phosphatidyl choline. Ethanol stimulated markedly biosynthesis of dipalmitoyl phosphatidyl choline in cloned rabbit lung cells; the stimulating action of ethanol was reduced very much by cortisol and less by ritodrine. In the presence of 0.1 microM isoproterenol, two prostaglandins, E2 and F2alpha, caused marked depressions in the incorporation of both precursors by cell line A 549 derived from human lung adenocarcinoma. One concluded that among the agents studied, ethanol and cortisol are potent antagonists, and so were also the prostaglandins and isoproterenol.

Animals↗
PubMedDate not supplied

Electromagnetic modulation of biological processes: bicarbonate effect and mechanistic considerations in the Ca-uptake by embryonal chick tibia in vitro.

Electromagnetically induced currents pulsating at very low frequency stimulated calcium uptake by chick embryo tibia rudiments only when bicarbonate was present in the culture medium. A bicarbonate-dependent Ca2+-ATPase might be implicated in coupling of the electromagnetic signal with processes that promote Ca-transport and storage in bone tissue.

Animals↗
PubMedDate not supplied

Electromagnetic modulation of biological processes: ATPase function and DNA production by Raji cancer cells in vitro.

Addition of either ATP or ouabain to the culture medium markedly depressed thymidine incorporation into DNA in Raji cells. The electromagnetic field, pulsating at very low frequency, did not affect DNA synthesis in normal culture media nor did it alter its ouabain-inhibition, but it partially reversed the ATP-inhibition. In spite of the presence of ATP, ouabain prevented stimulation of ATPase and DNA synthesis by the field. Although no mechanism is known for the action of either ATP or the field, the results may be interpreted in light of existing speculations. In the absence of the field, external ATP may go into an ATP pool that either blocks ATPase or feeds adenyl cyclase, which hinders DNA synthesis. In contrast, the electromagnetic field may either turn off adenyl cyclase or simply stimulate the ATP-depressed ATPase.

Adenosine Triphosphatases↗