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Biomedical subjects

R Colombo

Publications and source records attributed to R Colombo.

At least 181 records · Page 10Linked to original sources
PubMed1983

Immunocytochemical localization of acrosin in boar spermatozoa.

Acrosin was localized on the acrosomal membranes of boar sperm by immunofluorescence and immunoelectron microscopy. Indirect labeling of sperm head sections was performed with an Imposil (iron-dextran) antibody conjugate. The results of electron microscopy indicated a preferential deposition of the antiacrosin antibodies on the outer acrosomal membrane, although a lesser deposition was also found on the inner acrosomal membrane. No labeling was detected in the acrosomal content when such material was still present.

Acrosin↗
PubMed1983

Actin behaviour in doxorubicin treatment.

The inhibition of neural tube closure in early chick embryos explanted in vitro by New's technique was used as a model to study the possible involvement of actin polymerization during doxorubicin treatment. The investigation was performed with indirect immunofluorescence staining, fluorescence staining with NBD-Ph, and DNase I inhibition activity. 8 x 10(-6) M doxorubicin induces alteration in the distribution of actin fluorescence on neural tube and in CEF cell cytoskeleton, and an appreciable increase in the critical concentration of monomeric actin as measured in cell extracts.

Actins↗
PubMed1983

4-Chloromethylphenoxyacetyl polystyrene and polyamide supports for solid-phase peptide synthesis.

Two functionalised supports for the solid-phase synthesis of peptides under mild reaction conditions were prepared: 4-chloromethylphenoxyacetamidomethyl-copoly (styrene-1%-divinylbenzene) and 4-chloromethylphenoxyacetyl-norleucyl-poly (dimethylacrylamide). They were devised in order to avoid the danger of racemization which exists during base-catalyzed esterification of the first protected amino acid to the 4-alkoxybenzyl alcohol resins formerly employed in combination with N alpha-9-fluorenylmethoxycarbonyl and tert.-butyl side-chain protecting groups. Esterification of N alpha-protected amino acids to the new resins can be achieved easily and without significant levels of racemization by means of their caesium salts, while cleavage from the supports is possible by treatment with trifluoroacetic acid. The 4-chloromethylphenoxyacetyl polystyrene resin was tested by the synthesis of Leu-enkephalin which was cleaved, at the end of the synthesis, from the solid support in 91% yield by 60% trifluoroacetic acid in methylene chloride, and was shown to be more than 99% pure by ion-exchange chromatography and reverse phase high pressure liquid chromatography.

Glycolates↗
PubMed1983

Neurilemmoma of the ciliary body: report of a case.

A case of ciliary body neurilemmoma is described. This neoplasm is extremely rare in the uveal tract and has been reported only once in the ciliary body. After extensive clinical studies of the rapidly growing tumour enucleation was performed. Subsequent histological examination showed typical features of highly vascular benign neurilemmoma. The main clinical and pathological features are reported and diagnostic problems are discussed.

Adult↗
PubMed1983

Determination of isoxsuprine in human plasma by gas chromatography with electron capture detection.

A rapid and sensitive gas chromatographic method for the determination of the beta-adrenergic agent isoxsuprine in human plasma has been developed. The procedure involves the extraction of the drug with ether and an internal standard (propranolol) from plasma at alkaline pH, solvent evaporation, and the formation of a tri-trifluoroacetyl derivative by reaction with trifluoroacetic anhydride in ethyl acetate. Analyses were carried out by gas-liquid chromatography on a 3% OV-17 column using an electron capture detector. The minimum detectable amount of isoxsuprine was 0.5 ng/ml of plasma and the electron capture detector response was tested to be linear (r2 greater than 0.999) between 0.5 and 20 ng/ml. No interferences from endogenous substances were found. Precision of the method was found to be 9.9, and 6.1% coefficient of variation at 1 ng/ml and 10 ng/ml of plasma, respectively. Determination of isoxsuprine at the nanogram level in cord plasma samples from newborns at the time of the delivery was possible using the described procedure.

Chromatography, Gas↗
PubMed1983

Actin in Xenopus yolk platelets: a peculiar and debated presence.

Our previous work showed that Xenopus yolk platelets exhibited, when reacted with actin antibodies or fluorescent DNase 1, a shiny halo of fluorescence, which revealed an external actin cover around the platelets themselves. This structure was named the 'actin-shell'. Now we have demonstrated the actin-containing coat of Xenopus yolk platelets by agglutination tests, using anti-Xenopus-muscle-actin rabbit serum, and by indirect immunofluorescence microscopy, when the platelets reacted with antibodies directed against DNase 1. We chose these procedures to minimize the difficulties of the techniques used previously and to confirm the data obtained.

Actins↗
PubMed1982

Is there really actin around Xenopus laevis yolk platelets?

Our previous immunofluorescence experiments (1) on actin localization in Xenopus development showed a fluorescent halo around Xenopus yolk platelets. This fact suggests the presence of a sort of actin covering of the yolk platelet; we have called this structure the 'actin-shell'. In this work, by the use of a DNase I-fluorochrome complex, we were able clearly to demonstrate the presence of the actin-shell around Xenopus yolk platelets. A proposal about the function of the actin-shell is made; its presence could mark the difference between autosynthetic and heterosynthetic eggs.

Actins↗
PubMed1982

Solid-phase synthesis of chicken vasoactive intestinal peptide by a mild procedure using N alpha-9-fluorenylmethyloxycarbonyl amino acids.

The octacosapeptide amide corresponding to the entire amino acid sequence of chicken vasoactive peptide (VIP) was assembled on a p-benzyloxybenzylamine resin support using the base-labile 9-fluorenylmethyloxycarbonyl as N alpha-protecting group, cleaved by mild acid treatment, and purified by gel-filtration and ion-exchange chromatography. The symmetrical anhydride coupling was employed and monitored by two independent methods, and acetic anhydride termination was incorporated to minimize formation of deletion peptides. The homogeneity of the final product, obtained in 18% yield, was assessed by t.l.c., disc electrophoresis, amino-terminal amino acid analysis, and amino acid analyses of acid and enzyme hydrolysates. The purified chicken VIP was shown to be active on gastric acid secretion and on pancreatic blood flow. Previously reported ring closure of the Asp-Asn unit seemed to be at a minimum, owing to the mild basic and acid treatments.

Amino Acids↗
PubMed1982

Effect of in vivo increase of free fatty acids on human plasma protein binding of furosemide.

The in vivo effects of increased free fatty acid (FFA) plasma levels on the protein binding of furosemide were investigated in 30 adult-onset diabetics and 22 patients suffering from bacterial infections (gram- negative bacilli and gram-positive cocci). In diabetics, FFA were 2.43 +/- 1.63 mEq/l, and in subjects with bacterial infections 1.82 +/- 0.92 mEq/l. Furthermore, the percent of oleic acid and, to a very lesser extent, palmitoleic acid increased linearly with the increase of the FFA plasma level. The free furosemide fraction was about 1% or less in subjects with a molar ratio of FFA to albumin below 4, but a displacement of the drug from the plasma proteins occurred consistently when this ratio was above 4. At a molar ratio of FFA to albumin as high as 9.34, the free furosemide was 6.7% of the total concentration (8.9 microgram/ml). These results do not quantitatively agree with previous in vitro studies employing single fatty acids and human serum albumin, suggesting that in vivo plasma composition is not adequately reproduced during in vitro experiments on protein-binding displacement of drugs by FFA.

Adult↗
PubMed1981

Degradation of propildazine in water.

Propildazine degradation in water at pH 7.4 was studied under aerobic conditions. Three main products were isolated by column chromatography and identified on the basis of IR, UV, and NMR spectroscopy and mass spectrometry and by comparison with synthetic samples. Drug disappearance in water was monitored by UV spectroscopy and was concentration, pH, temperature, and oxygen dependent. Propildazine degradation also was followed in methanol at various pH values.

Antihypertensive Agents↗
PubMed1981

Determination of the dissociation constant of carbonic anhydrase inhibitors: a computerized kinetic method based on esterase activity assay.

We evaluate a reliable procedure for in vitro determination of the dissociation constant, Ki, of carbonic anhydrase inhibitors. This pharmacologically important parameter is estimated, using a mathematical model derived from the Ackermann-Potter equation, by a computer-assisted nonlinear regression analysis of kinetic data from the enzyme-catalyzed hydrolysis of p-nitrophenyl acetate. The proposed method has the additional advantage, over the ones that require the use of only paper and pencil, of giving standard errors for the estimated parameters. Based on our findings, a comparison of the reported values for the inhibition of carbonic anhydrase by twelve sulfamoyl drugs is presented, and the difficulties associated with the determination of dissociation constants for carbonic anhydrase inhibitors are discussed.

Carbonic Anhydrase Inhibitors↗