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Biomedical subjects

R Lozano

Publications and source records attributed to R Lozano.

At least 91 records · Page 5Linked to original sources
PubMed1988

Role of beta-adrenoreceptors in the inhibition of gastric acid secretion after duodenal acidification in dogs.

The role of the adrenergic system in the duodenal mechanisms that inhibit gastric acid secretion (GAS) after duodenal acidification (DA) was studied. In 12 mongrel dogs, with gastric and duodenal fistulas, six experiments were carried out evaluating pentagastrin-stimulated GAS and serum secretin levels: DA (HCl 2 ml/min) for 1 h (group A); DA (HCl 2 ml/min) for 1 h plus propranolol (group B); DA (HCl 2 ml/min) for 1 h plus phentolamine (group C); duodenal instillation of saline (2 ml/min) for 1 h (group D); (duodenal instillation of saline (2 ml/min) for 1 h plus propranolol (group E), and duodenal instillation of saline (2 ml/min) for 1 h plus phentolamine (group F). Significantly (p less than 0.05) high percentages of inhibition of GAS (49-70.5%) paralleled with increases of serum secretin levels (48.4-84%) were noted in group A and C experiments. However, DA did not inhibit GAS nor did it increase the levels of secretin in group B and D-F experiments. It is concluded that the inhibition of GAS after DA is controlled, at least in part, by the action of the beta-adrenoreceptors.

Adrenergic alpha-Antagonists↗
PubMed1988

Variation in T helper cell/T cytotoxic-suppressor cell index during cardiac operations.

After surgical procedures, humoral and cell-mediated immunity responses decrease. Both anesthesia and surgical trauma play an important role in this effect. Cardiac operations induce a greater decrease in immunologic response than other surgical operations. On the other hand, identification of functional lymphocyte subclasses by means of appropriate monoclonal antibodies appears to provide an accurate measurement of cellular immune competence. Employing these methods, we found a significant decrease of T helper cell/T cytotoxic-suppressor cell ratio in the periperal blood of 20 patients undergoing cardiac operations. This decrease during the period of anesthesia (before surgical incision) is due as much to a decrease of T helper cell percentage as to an increase of T cytotoxic cell percentage. However, during the surgical trauma period (surgical incision to the end of the operation) it is due to a greater increase of T cytotoxic-suppressor cell percentage without significant changes in the percentage of T helper cells.

Adult↗
PubMed1987

Metabolism of sterols of varying ring unsaturation and methylation by Caenorhabditis elegans.

The metabolism of three dietary 4,4-desmethylsterols and two 4 alpha-methylsterols was investigated in the free-living nematode Caenorhabditis elegans. Dietary cholestanol was converted mostly to lathosterol. Dietary lathosterol, 7-dehydrocholesterol, 4 alpha-methylcholest-7-enol and 4 alpha-methylcholest-8(14)-enol each remained largely unchanged. An absolute requirement for a substantial quantity of 7-dehydrocholesterol in C. elegans did not exist. C. elegans was unable to remove a 4 alpha-methyl group or introduce a double bond at C-5 and also demonstrated the lack of a delta 7-reductase. Its nutritional sterol requirement was satisfied by cholestanol, lathosterol or 7-dehydrocholesterol; growth was comparable to that obtained previously in media containing delta 5-sterols. However, the two 4 alpha-methylsterols appeared to be unsatisfactory sterol nutrients. The possible physiological importance of 4 alpha-methylsterols is discussed briefly.

Animals↗
PubMed1986

Purification of a liver DNA-synthesis promoter from plasma of partially hepatectomized rats.

A protein was isolated from plasma of partially (70%) hepatectomized rats that, injected in mice, increases the uptake of [3H]thymidine by liver DNA by 200-300% over that by injected control saline. The purification procedure consists essentially of three chromatography steps, employing Sephadex G-75, DEAE-cellulose and hydroxyapatite. The hepatic promoter (HP) preparation shows a single band in SDS/polyacrylamide (15%)-gel electrophoresis (silver stained), with an Mr of 64 000; its activity is suppressed by trypsin or pepsin and is unaffected by deoxyribonuclease or ribonuclease. On injection into mice (150 ng/mouse), it increases the mitotic index of the liver. It shows organ-specificity, acting on liver but not on spleen, kidney, lung or brain. In primary liver cultures, it produces an increase in uptake of [3H]thymidine into DNA in the range 1-10 ng/ml. In this system in vitro, it increases the uptake of 22Na+ immediately after addition.

Animals↗
PubMed1986

Prophylaxis of postoperative infections after open-heart surgery by administration of human pepsinated immunoglobulin.

The present controlled study examines the effect of intravenously administered human pepsinated immunoglobulin G (HPIG, Gamma-Venin) on the postoperative incidence of infections in patients undergoing heart surgery supported by extracorporeal circulation. This particular form of surgery normally produces markedly diminished serum IgG levels, but the results of the study showed that these recovered more rapidly after treatment with HPIG. A statistically significant difference in the number of infections between the group treated with HPIG and the control group (p less than 0.05) was found. It may be concluded that, with regard to postoperative infection, patients undergoing open-heart surgery may benefit from the administration of HPIG.

Adolescent↗
PubMed1985

Inhibition of sterol biosynthesis by ergosterol and cholesterol in Saccharomyces cerevisiae.

When accumulation of squalene was used as a measure of the flow of carbon into the sterol pathway in whole cells of semi-anaerobic Saccharomyces cerevisiae, both ergosterol and cholesterol were found to be inhibitory. However, at equivalent concentrations in the medium ergosterol was substantially the more potent inhibitor. Marked differences found in the absorption and esterification of the two sterols failed to account for the observed difference in their capacities to act as feedback agents. Cholesterol was much more effectively absorbed as well as esterified, but, when the abilities of the two sterols to lower the squalene level were calculated on the basis of free sterol in the cells, ergosterol remained more effective by a factor of four.

Cholesterol↗
PubMed1985

Inhibition of C28 and C29 phytosterol metabolism by N,N-dimethyldodecanamine in the nematode Caenorhabditis elegans.

Effects on the metabolism of campesterol and stigmasterol in Caenorhabditis elegans were investigated using N,N-dimethyldodecanamine, a known inhibitor of growth, reproduction and the delta 24-sterol reductase of this nematode. 7-Dehydrocholesterol was the predominant sterol (51%) of C. elegans grown in stigmasterol-supplemented media, whereas addition of 25 ppm amine resulted in a large decrease in the relative percentage of 7-dehydrocholesterol (23%) and the accumulation of a substantial proportion (33%) of delta 24-sterols (e.g., cholesta-5,7,24-trienol) and delta 22,24-sterols (e.g., cholesta-5,7,22, 24-tetraenol) but yielded no delta 22-sterols. Dealkylation of stigmasterol by C. elegans proceeded in the presence of the delta 22-bond; reduction of the delta 22-bond occurred prior to delta 24-reduction. Addition of 25 ppm amine to campesterol-supplemented media altered the sterol composition of C. elegans by increasing the percentage of unmetabolized dietary campesterol from 39 to 60%, decreasing the percentage of 7-dehydrocholesterol from 26 to 12%, and causing the accumulation of several delta 24-sterols (6%). C. elegans also was shown to be capable of dealkylating a delta 24 (28)-sterol as it converted 24-methylenecholesterol to mostly 7-dehydrocholesterol. The proposed role of 24-methylenecholesterol as an intermediate between campesterol and 7-dehydrocholesterol was supported by the results.

Amines↗
PubMed1984

Comparative effects of growth inhibitors on sterol metabolism in the nematode Caenorhabditis elegans.

An analogous series of dimethylalkyl compounds, consisting of four amines, an amide, and a phosphonate ester, inhibited motility and reproduction of the nematode Caenorhabditis elegans. Dimethylamines with straight-chain lengths of 12, 14, or 16 carbon atoms were equally active nematicides, causing greater than 80% population growth inhibition at a concentration of 25 ppm. The C12 straight-chain amine and its corresponding amide produced similar inhibition and were much more potent than either the corresponding C12 phosphonate or a C12 branched-chain amine. Inhibition of the delta 24-sterol reductase system was exhibited by all four amines, but not by the amide or phosphonate, in the following order of activity: C12 branched-chain amine greater than C12 straight-chain amine greater than C14 amine greater than C16 amine. The C12 branched amine also blocked the C-24(28)-dehydrogenase system in the conversion of sitosterol to fucosterol, the initial step in sitosterol dealkylation.

Amides↗
PubMed1984

[Immunologic responses following surgical resection of gastrointestinal carcinomas].

The amount of IgG, IgM, IgA, C3, C4 and C5 in serum, and the response to delayed hypersensitivity tests with PPD, varidase, candidin and mumps antigens were estimated in patients submitted to radical surgery for gastric and colorectal cancer (group I), before and at intervals after the operation was performed, and compared with cancer patients undergoing palliative abdominal surgery (group II), and with patients submitted to major abdominal surgery for diseases other than cancer (group III). Group I showed a decrease of all the immunoglobulins (Igs) and complement fractions (F) during the first week after operation, and a significant increase after one month. Similar changes were observed in group III, the augmentation of Igs and F after one month being somewhat smaller. Group II showed a larger number of positiveness than either group I or II in both the preoperative and early postoperative periods (p = 0.001). After 2 and 3 months, the number of positive cases was larger in group I than in group II (p = 0.05). According to these results, the immune response is recovered one month after the excision of gastric and colorectal malignant tumors, being this the best moment to receive a complementary cytoreductive therapy.

Complement C3↗
PubMed1983

Stereochemically distinct roles for sterol in Saccharomyces cerevisiae.

Cholesterol, (E)- but not (Z)-17(20)-dehydrocholesterol, 5 alpha-cholestan-3 beta-ol, sitosterol, and certain other sterols lacking a 24 beta-methyl group will replace (spare) most but not all of the 24 beta-methylsterol which has recently been found to be absolutely necessary for growth of oxygen-deprived wild type Saccharomyces cerevisiae in the presence of 2,3-iminosqualene. The results imply the existence of two stereochemically distinct roles for sterol in this organism. One of them (perhaps regulatory) requires, whereas the other (probably playing the so-called "bulk" membranous role) does not require the presence of the 24 beta-methyl group. The latter function, for which most of the sterol is needed, can be performed by various 24-alkyl- and 24-desalkylsterols.

Cholesterol↗
PubMed1983

Novel nuclear methylation of sterols by the nematode Caenorhabditis elegans.

Caenorhabditis elegans possesses a unique sterol methylation pathway not reported to occur in any other organism and also removes the C-24 ethyl group of sitosterol (a plant sterol). This nematode produced substantial quantities of 4 alpha-methyl-5 alpha-cholest-8(14)-en-3 beta-ol and smaller amounts of lophenol from dietary cholesterol, desmosterol or sitosterol. When C. elegans was propagated in media containing sitosterol plus 25-azacoprostane hydrochloride (25-aza-5 beta-cholestane hydrochloride), an inhibitor of delta 24-sterol reductase in insects, its 4 alpha-methylsterol fraction largely consisted of equal amounts of 4 alpha-methyl-5 alpha-cholesta-7,24-dien-3 beta-ol and 4 alpha-methyl-5 alpha-cholesta-8(14),24-dien-3 beta-ol. Thus 25-azacoprostane hydrochloride inhibited both a delta 24-sterol reductase and a delta 7-sterol isomerase in C. elegans.

Animals↗
PubMed1980

[Late postgastrectomy sequellae: primary cancers of the gastric stump].

The authors describe 8 cases of carcinoma of the gastric stump, 6 after Billroth II and 2 after Billroth I resection. They were observed after a free interval of 18.5 years and formed 3 per 100 of the treated gastric and duodenal malignant tumors. The authors indicate the surgical technique they recommend to prevent the malignant degeneration following operations for benign gastric or duodenal ulcers.

Aged↗