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Biomedical subjects

R Castillo

Publications and source records attributed to R Castillo.

At least 199 records · Page 11Linked to original sources
PubMed1977

Substrate selectivity of squalene synthetase.

Six 1-3H-labeled analogues of farnesyl pyrophosphate have been studied as potential substrates for yeast and rat liver squalene synthetases: 2-methylfarnesyl pyrophosphate (4), 3-demethylfarnesyl pyrophosphate (5), 7,11-dimethyl-3-ethyl-2,6,10-dodecatrienyl pyrophosphate (6), 6,7,10,11-tetrahydrofarnesyl pyrophosphate (7), 4-methylthiofarnesyl pyrophosphate (8), and 4-fluorofarnesyl pyrophosphate (9). Analogues 4 and 5 are enzymatically incorporated into 11-methylsqualene (10) and 10-demethylsqualene (11), respectively, even if no farnesyl pyrophosphate is added to the incubations. None of the other analogues gives nonpolar products with either the yeast or liver enzymes. No tritium is enzymatically released to the medium from any of the analogues, indicating that they are not accepted at the first (proton exchanging) site. The data rule out formation of dead-end presqualene pyrophosphate products with analogues as first, but not as second, substrates. Implications of these results for the enzyme active-site topology and mechanism are discussed.

Animals↗
PubMed1977

Inhibition of squalene synthetase by farnesyl pyrophosphate analogues.

The pyrophosphates of the following farnesol analogues have been synthesized: 2-methylfarnesol; 7,11-dimethyl-3-ethyl-2,6,10-dodecatrien-1-ol; 3-demethylfarnesol; 4-methylthiofarnesol; 7,11-dimethyl-3-iodo-2,6,10-dodecatrien-1-ol; 7,11-dimethyl02-iodo-2,6,10-dodecatrien-1-ol; 7,11-dimethyldodeca-6,10-dien-2-yn-1-ol; phytol; 3,7,11-trimethyl-2-dodecen-1-ol; 3,7,11-trimethyldodecan-1-ol; and geraniol. The double bonds in all the above compounds were in the E configuration, except phytol, which was a 7:3 mixture of 2E and 2Z isomers. Each of the pyrophosphates inhibits the incorporation of labeled farnesyl pyrophosphate into squalene by a yeast enzyme preparation. Free alcohols and monophosphates are inactive. The analogues, listed in order of decreasing inhibitory strength, are, by kinetic analysis, competitive or mixed inhibitors. Irreversible inhibition is not observed. The results suggest that binding to the enzyme is primarily mediated by the pyrophosphate moiety assisted by relatively nonspecific lipophilic interactions. Decreasing the chain length and saturating double bonds severely reduces binding, while substitution at the 2,3, and 4 positions, and lengthening of the chain, is well tolerated.

Diphosphates↗
PubMed1977

HLA antigens in Forestier's disease, ankylosing spondylitis, and polyarthrosis of the hands.

HLA antigens were studied in three different groups of 50 patients each. These included (a) Forestier's disease, (b) ankylosing spondylitis, and (c) polyarthrosis of the hands. HLA typing included 12 specificities from locus A and 15 from locus B, the frequencies being compared to those in 700 normal controls. No significant differences were found in the frequency of distribution between the polyarthrosis patients and the normal population. In patients with Forestier's disease, B5 was increased, but this was not a significant difference. The antigen B27 was present in 94 per cent of patients with ankylosing spondylitis, confirming previous studies.

Adolescent↗
PubMed1977

Os odontoideum removed by a transoral approach.

A case of atlanto-axial dislocation secondary to the presence of an "Os Odontoideum" is reported in which there was no history or evidence of trauma before the onset of symptoms. The treatment of this unusual clinical condition is discussed.

Axis, Cervical Vertebra↗
PubMed1976

Inhibition of human platelet aggregation by the proteolytic effect of streptokinase. Role of the human factor-VIII-related protein.

Defective ADP-induced aggregation was observed in in vitro streptokinases(SK)-treated normal platelet-rich plasma. Classic haemophilia and normal platelet poor plasma (PPP) treated with SK inhibit the aggregation of washed platelets; plasmin-treated normal human serum also shows an inhibitory effect on platelet aggregation. However, SK-treated von Willebrand plasmas do not inhibit the aggregation of washed platelets. This confirms the fact that the anti-aggregating effect is mainly linked to the digested factor VIII) but not to the digested fibrinogen. Defective ristocetin-induced platelet aggregation has also been observed in SK-treated plasmas. The presence of normal PPP does not modify the inhibition of the ADP-induced aggregation of washed platelets in SK-treated PPP. However, it does correct the ristocetin-induced aggregation. These results suggest that the inhibition of the ADP-induced aggregation is caused by the factor VIII degradation products, while the inhibition of the ristocetin-induced aggregation appears because of a defective von Willebrand activity of the factor VIII molecule.

Adenosine Diphosphate↗
PubMed1974

Fusion of normal rabbit alveolar macrophages induced by supernatant fluids from BCG-sensitized lymph node cells after elicitation by antigen.

Cell-free supernatant fluids obtained from BCG-sensitized lymph node cells (6 x 10(6) cell/ml) incubated in tissue culture flasks containing heat-killed BCG (5 mug/ml) induced extensive development of multinucleated giant cells when incubated with normal alveolar macrophages. In contrast, supernatant fluids obtained after incubation of similar samples of the same lymph node cell population in flasks with (i) no mycobacteria, (ii) heat-killed Escherichia coli, or (iii) heat-killed Bacillus subtilis failed to produce giant cells when added to normal alveolar macrophages. Giant-cell formation was observed in experiments using Nocardia brasiliensis as the eliciting antigen, indicating cross-reactivity between the antigens of this organism and BCG. These experiments indicate that BCG-sensitized lymphoid cells produce a soluble macrophage fusion factor after specific antigen stimulation. The fusion factor is a nondialyzable substance which is resistant to heating at 80 C for 30 min.

Animals↗