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Biomedical subjects

F M Goñi

Publications and source records attributed to F M Goñi.

At least 145 records · Page 8Linked to original sources
PubMed1981

Influence of pH on the transition from yeast-like cells to chlamydospores in Aureobasidium pullulans.

When A. pullulans is grown on a glucose medium with a limiting nitrogen source and low buffer capacity, the yeast-like cells that are originally present undergo a transition to chlamydospores. The initial pH must be around 6 for the transition to take place under optimal conditions. On the above-mentioned medium pH decreases to values below 2 in the first two days; if this decrease is prevented, either by buffering the medium or by repeatedly adjusting the pH to its original value no chlamydospores form.

Hydrogen-Ion Concentration↗
PubMed1981

Influence of carbon and nitrogen sources on the transition from yeast-like cells to chlamydospores in Aureobasidium pullulans.

The transition from yeast-like cells to chlamydospores of Aureobasidium pullulans can be induced by growing the microorganism on a glucose medium with a limiting nitrogen source and a low buffer capacity. When glucose is used as the carbon source, a concentration higher than 3% (w/v) is required to induce the transition. On the other hand, growth limiting concentrations of the N source (ammonium sulphate) are not required, and higher concentrations actually stimulate the appearance of chlamydospores. Other N sources, such as glutamate or ammonium phosphate, do not induce the transition from yeast-like cells to chlamydospores.

Ammonia↗
PubMed1980

Triton X-100 solubilization of mitochondrial inner and outer membranes.

Rat liver mitochondrial inner and outer membranes were subjected to the solubilizing effect of the nonionic detergent Triton X-100 under various conditions. After centrifugation, the supernatants (containing the solubilized fraction) and pellets were characterized chemically and/or ultrastructurally. The detergent seems to act by inducing a phase transition from membrane lamellae to mixed protein-lipid-detergent micelles. Different electron-microscopy patterns are shown by the inner membranes after treatment with different amounts of surfactant, whereas the corresponding images from outer membranes vary but slightly. Selective solubilization of various components is observed, especially in the case of the inner membrane. Some membrane lipids (e.g., cardiolipin) are totally solubilized at detergent concentrations when others, such as sphyngomyelin, remain in the membrane. Other inner-membrane components (flavins, cytochromes, coenzyme Q) show different solubilization patterns. This allows the selection of conditions for optimal solubilization of a given membrane component with some degree of selectivity. The influence of Triton X-100 on various mitochondrial inner-membrane activities was studied. The detergent seems to act especially through disruption of the topology of the functional complexes, although the activity of the individual enzymes appears to be preserved. Relatively simple enzyme activities, such as ATPase, are more or less solubilized according to the detergent concentration, whereas the more complex succinate-cytochrome c reductase activity practically disappears even at low Triton X-100 concentrations.

Animals↗
PubMed1980

Lipid composition and the transition from yeast-like to chlamydospore cells of Pullularia pullulans.

The lipid composition of the fungus Pullularia pullulans has been investigated at different stages of the morphogenetic transition from yeast-like, through the so-called "large cells," to chlamydospores. The first 3 days of culture correspond to the period of exponential growth. There is a rapid consumption of glucose and ammonium, until the latter becomes exhausted, and a concomitant decrease of pH down to values of about 2. A decrease in fatty acid unsaturation takes place at this stage, together with an increase in the proportion of long-chain aldehydes. The period between days 3 and 6 is dominated by the large cells. They accumulate large amounts of triacylglycerols; phospholipids and free sterols are also synthesized in this period, suggesting de novo synthesis of membranes. Chlamydospores can be seen from the 6th day on. Simultaneously, a decrease in free sterols and phospholipids takes place, while saturated triacyglycerol production goes on. The lipid composition of chlamydospores suggests that these are resistance forms, induced by the hostile environmental conditions of the medium after the end of the exponential growth.

Cell Differentiation↗
PubMed1979

Protein-lipid interactions. A nuclear magnetic resonance study of sarcoplasmic reticulum Ca2,Mg2+-ATPase, lipophilin, and proteolipid apoprotein-lecithin systems and a comparison with the effects of cholesterol.

Deuterium Fourier transform nuclear magnetic resonance (NMR) spectra at 34 MHz (corresponding to a magnetic field strength of 5.2 T) have been obtained of a variety of protein-lipid systems containing specifically deuterated phospholipids. The following systems were investigated as a function of temperature: sarcoplasmic reticulum ATPase (ATP phosphohydrolase, EC 3.6.1.3) complexed with 1-myristoyl-2-(14,14,14-trideuteriomyristoyl)-sn-glycero-3-phosphocholine (DMPC-d3) or 1,2-bis(16,16,16-trideuteriopalmitoyl)-sn-glycero-3-phosphocholine (DPPC-k6); human brain lipophilin complexed with DPPC-d6 or 1,2-bis(6,6-dideuteriopalmitoyl)-sn-glycero-3-phosphocholine (DPPC-6,6-d4); beef brain myelin proteolipid apoprotein (PLA) reconstituted with DMPC labeled as CD2 (or CD3) at one or more of positions 3, 4, 6, 8, 10, 12, or 14 of the sn-2 chain. For purposes of comparison, spectra were also obtained for bilayers containing cholesterol (CHOL). The results show that proteins either disorder or have little effect on hydrocarbon chain order in membranes above the gel to liquid-crystal phase transition temperature (Tc) of the pure lipids. Cholesterol, however, causes a very large ordering of the hydrocarbon chains above Tc, but both cholesterol and protein prevent chain crystallization (by effectively disordering chain packing) immediately below Tc. No evidence for any ordered "boundary lipid" in association with protein was found above Tc, perhaps due to the rough nature of protein surfaces. Above Tc, exchange between free bilayer and protein associated lipid is fast on the time scale of the deuterium NMR experiment (greater than or similar to 10(3) s-1). We have also obtained proton-decoupled phosphorus-31 nuclear magnetic resonance spectra at 60.7 MHz (corresponding to a magnetic field strength of 3.5 T) of DMPC, DMPC-AT-Pase, and DMPC-CHOL complexes. The results indicate that ATPase and CHOL CAUSE SMALL DECREASES IN 31P chemical shielding anisotropies but that in addition ATPase causes a four- to fivefold increase in 31P spin-lattice and Carr-Purcell spin-spin relaxation rates, suggesting the possibility of polar group protein-lipid interaction leading to increased correlation times in the region of the lipid phosphate head group.

Animals↗
PubMed1979

Assay of mitochondrial membrane-bound enzyme activities in the presence of triton X-100.

Mitochondrial ATPase and cytochrome c oxidase activities are not severely affected by Triton X-100 concentrations between 0.1 and 2.0% (w/v). The former is solubilized by the effect of the detergent, while the latter is not. Succinate: cytochrome c reductase and rotenone-sensitive NADH: cytochrome c reductase activities are destroyed even a low detergent concentrations. Succinate:coenzyme Q oxidoreductase is affected by the surfactant in a more complex way, so that selective solubilization of some subunit(s) could be involved.

Adenosine Triphosphatases↗
PubMed1978

Complex phosphoglycerides from rat liver outer mitochondrial membranes.

The ethanolic extract from rat liver mitochondrial membranes contains a number of highly polar complex lipids, which are found in the aqueous layer when subjected to the usual chloroform-water partition procedures. Two of these lipids have been purified by thin-layer chromatography, and their structures partially elucidated. Apparently, both are derivatives of phosphatidylglycerol, with a bulky polar head containing sugars and aminoacids. They are specifically located in the outer membrane. Several structures are suggested, as well as a possible functional rôle for these compounds.

Animals↗
PubMed1978

Aminoacid composition and hydrophobicity index of mitochondrial polypeptides.

The aminoacid composition of protein stained bands in polyacrylamide gels, after electrophoresis of proteins from inner mitochondrial membranes, was investigated hydrolyzing directly the gel slices. The Hydrophobicity Index of 18 prominent polypeptide bands was calculated after their aminoacid analysis. The polypeptides less related to the membrane have low hydrophobicity as inferred from their Hydrophobicity Indexes.

Amino Acids↗
PubMed1978

Carotenoids from marigold (Tagetes erecta) petals and their esterified fatty acids.

The main carotenoid in Tagetes erecta petals is lutein, which is found either free or esterified to one or two fatty acids. Column and thin-layer chromatographic methods are described for the separation of the different lutein species, and compared to other, previously published, techniques. In addition, fatty acid distributions are given for whole marigold plants, crude carotenoid extracts and purified mono and diesterified luteins obtained from fresh petals as well as from commercial powdered petal preparations.

Carotenoids↗