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Biomedical subjects

M Brito

Publications and source records attributed to M Brito.

At least 37 records · Page 2Linked to original sources
PubMed1990

Purification of adhesive proteins from mussels.

The adhesive polyphenolic proteins from the mussels Mytilus chilensis and Choromytilus chorus have been purified based on their solubility in dilute perchloric acid and on differential precipitation with acetone containing about 0.3 N HCl. The specific activity of the proteins obtained was 0.16 mg of 3,4-dihydroxyphenylalanine per milligram of protein, or higher. The proteins have an apparent molecular weight of about 100,000 and they contain a high proportion of 3,4-dihydroxyphenylalanine, lysine, and proline.

Acetone↗
PubMed1990

Better predictors of successful His-bundle ablation analysis of first shocks.

We have reported here that a longer HV interval in association with a larger His amplitude yields a high rate of success when used to position the ablating catheter for His-bundle ablation. Additionally, we have shown that double discharge shocks are more effective than single discharge shocks, and that negative polarity is more effective than positive polarity. The use of bipolar or tripolar, and not quadripolar catheters, was also associated with a higher success rate. In our institution, using a bipolar catheter, we attempt to record an HV interval greater than 55 msec and a His amplitude greater than 0.35 mV. When both of these criteria are fulfilled, we use 3 to 4 joules per kg, and a single discharge shock. When one or the other of these criteria are not fulfilled, we use the double discharge shock method. Using these techniques, we have achieved successful His-bundle ablation with only one shock in all but one of the most recent 21 consecutive patients.

Bundle of His↗
PubMed1990

Bioadhesives: a biotechnological opportunity.

Marine mussels secrete the byssus in order to attach to solid surfaces and to survive under the turbulent effects of waves. The adhesive responsible for this attachment is the polyphenolic protein secreted by the phenol gland in the foot of the animal. To purify this adhesive protein from the chilean mussel Mylilus chilensis, a modification of previous procedures has been developed. Accordingly, the protein is differentially precipitated with acetone in the presence of 0.25 N HCl. The purified protein is rich in the amino acids lysine, 3,4-dihydroxyphenylalanine, serine, threonine, proline and hydroxyproline. The protein exhibited strong adhesion to glass and other solid supports. Moreover, it has been found that the adhesive protein can mediate the immobilization of beta-galactosidase to glass. About 75% of the enzyme activity was immobilized under the experimental conditions described. This is the first study reporting the use of the polyphenolic protein to immobilize enzymes.

Amino Acids↗
PubMed1989

Presence of RNA in the sperm nucleus.

The RNase-colloidal gold procedure for the ultrastructural localization of RNA was used for rat testis. Along with other structures, it was found that the testicular sperm nucleus was well stained. Similar labelling was observed in the nucleus of rat epididymal sperm and human sperm. The RNA was extracted from sperm and analyzed by electrophoresis on 10% polyacrylamide gel and 7 M urea. The electrophoretic profile revealed a complex set of bands ranging in size from tRNA to high molecular weight components. On the average, a content of about 0.1 pg of RNA per rat or human sperm was found.

Animals↗
PubMed1989

The major component of the rat sperm fibrous sheath is a phosphoprotein.

The fibrous sheath from rat epididymal sperm was isolated by sequential extraction, first with Triton X-100 and dithiothreitol, and then with 6 M urea and dithiothreitol. The latter extraction procedure solubilized most of the sperm components, leaving the head and the fibrous sheath as the only intact structures. This material was purified by sucrose gradient centrifugation. Electron microscopy confirmed the purity of the isolated material and revealed the characteristic structural features of the fibrous sheath. Polyacrylamide gel electrophoresis (in the presence of sodium dodecyl sulfate) of the fibrillar material, showed a complex polypeptide composition. The polypeptides with molecular weights of 80,000, 24,000, and 11,500 accounted for about 65% of the total protein of the fibrous sheath. Peptide map analyses indicated that the components of molecular weights of 80,000 and 24,000 are unrelated to the polypeptides of similar size of the outer dense fibers. On the other hand, it appears that the fibrous sheath and the outer dense fibers share the polypeptide of 11,500 daltons. The component of 80,000 daltons contains on the average about 3 mol of phosphoserine per mol of polypeptide, indicating that the most abundant polypeptide of the fibrous sheath is a phosphoprotein.

Amino Acids↗
PubMed1987

Concentration of copper and zinc in liver of fetuses and infants.

Hepatic concentrations of copper (Cu) and zinc (Zn) were studied in 38 fetuses and infants, who died of various causes, from 26 weeks of gestation up to 16 weeks post-natally. The six fetuses of 28-32 weeks gestation had median and mean hepatic Cu concentrations micrograms/g fresh tissue) comparable to those found in the 21 born at term, but the range of values was much narrower: all of the Cu values for those born prematurely were at or below 40 micrograms/g. Values at 10 micrograms/g and below were found in five infants at term and five who died at 1-4 months of age. There was a comparable range of Zn values for both pre-term and term babies (10 to 300 micrograms/g fresh tissue). The value of 10 micrograms/g was found only in one 4-month-old infant. The accumulation of both Cu and Zn occurs independently in the fetuses. The socioeconomic status did not influence significantly the concentration of liver Cu or Zn in babies born at term. However, size of babies as measured by liver weight showed that larger babies had significantly higher mean Cu concentration (37 +/- 24 micrograms/g) than smaller babies (21 +/- 14 micrograms/g. The same trend, but without significant difference, was observed for hepatic Zn between larger (104 +/- 78 micrograms/g) and smaller (74 +/- 59 micrograms/g babies.

Copper↗
PubMed1987

Biosynthesis of rat sperm outer dense fibers during spermiogenesis. In vivo incorporation of [3H]leucine into the fibrillar complex.

The temporal incorporation profile of [3H]leucine into the outer dense fiber polypeptides was determined after the intratesticular injection of the radioisotope. Groups of four rats were killed on alternate days after injection, and the outer dense fibers were isolated from the caput epididymal sperm. The radioactivity incorporated into the whole sperm and into the isolated fibers showed a sharp peak at 10 days after injection. Therefore, considering the known kinetics of spermatogenesis in the rat, the maximal incorporation of radioactivity into the fibers occurred during the second half of spermiogenesis. The radioactivity incorporated into the six major polypeptides of the fibers separated by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate accounted for 95 percent of the total radioactivity associated with the isolated fibrillar complex. Furthermore, analysis of the time-course incorporation of [3H]leucine into the polypeptides of the fibers indicated that the maximal incorporation into each of the six major components took place within the same period of time. Using two different procedures, the specific activity of each major polypeptide was determined at the time of maximal incorporation. It was found that the specific activity of the most abundant components (molecular weights of 30,400 plus 26,000) was approximately twice that of the other polypeptides.

Animals↗
PubMed1985

Natriuretic effect and changes in renal haemodynamics induced by enalapril in essential hypertension.

The purpose of this study was to evaluate the natriuretic effect and renal haemodynamic changes induced by enalapril in patients with essential hypertension. In a group of 11 patients with mild to moderate hypertension with normal renal function, and on a controlled sodium intake (80 mmol/day), a decrease in systolic and diastolic blood pressure was observed (p less than 0.001) after 16 weeks of enalapril treatment (20 mg/day), without a change in heart rate. An increase in plasma renin activity (p less than 0.05) without changes in serum aldosterone, and a decrease in exchangeable sodium (p less than 0.001) were present at the end of the treatment period. In 10 hypertensive patients also taking a dietary sodium of 80 mmol/day, the renal haemodynamics, humoral changes, and urinary sodium excretion were measured during 4 days of enalapril treatment (20 mg/day). There was an increase in urinary sodium excretion on the 3rd and 4th days of treatment (p less than 0.01). The effective renal plasma flow and fractional sodium excretion increased 72 hours after the beginning of treatment (p less than 0.01); the glomerular filtration rate did not change, and filtration fraction decreased at 72 hours. Mean blood pressure fell 2 hours after the first dose (p less than 0.01), and the maximum drop in intrarenal vascular resistance occurred after 72 hours of treatment (p less than 0.01). Plasma renin activity increased (p less than 0.05) and serum aldosterone decreased (p less than 0.01) 2 hours after the first dose. Thereafter, serum aldosterone increased progressively until it reached values similar to those with placebo at 48 and 72 hours of treatment. Urinary kallikrein fell during the 2nd and 3rd day of treatment (p less than 0.01). It was concluded that the decrease in exchangeable sodium was due to a natriuretic effect of enalapril. This effect presumably results from renal haemodynamic changes due to the reduction of angiotensin II. Other mechanisms, such as the reduction of aldosterone and accumulation of kinins, could be contributory factors.

Adolescent↗
PubMed1984

Polypeptide composition of rat sperm outer dense fibers. A simple procedure to isolate the fibrillar complex.

Treatment of caput or cauda epididymal rat sperm with a low concentration (0.05%) of the cationic detergent cetyltrimethylammonium bromide and 30 mM 2-mercaptoethanol solubilized most of the sperm structures except for the sperm head and the outer dense fiber-connecting piece complex. The latter were purified, and about 10% of these complexes are formed by nine fibers attached to the connecting piece. Of these fibers, two are shorter than the other seven and presumably correspond to fibers 3 and 8 (Fawcett, D.W. (1975) Dev. Biol. 44, 394-436). Electron microscopy confirmed the purity of the isolated outer dense fibers and revealed their characteristic irregular cross-sectional shape. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate showed six major polypeptides (Mr = 87,000, 30,400, 26,000, 18,400, 13,000, and 11,500) with a high content of serine, aspartic and glutamic acids, proline, cysteine, leucine, and tyrosine. Furthermore, several lines of evidence indicate a close structural relationship between the components of 30,400 and 26,000 Da. The six major components of the fibers are phosphorylated at serine residues. These results indicate that the major components of rat sperm outer dense fibers are a unique family of phosphoproteins.

Amino Acids↗
PubMed1981

Effects of brief and intermediate exposures to sulfate submicron aerosols and sulfate injections and cardiopulmonary function of dogs and tracheal mucous velocity of sheep.

Pulmonary mechanics of anesthetized dogs were not changed or were minimally altered by breathing the following compounds as submicron aerosols in concentrations up to 17.3 mg/m3 for 7.5 min: (1) sodium chloride (as a control), (2) sodium sulfate, (3) ammonium sulfate, (4) zinc sulfate, (5) zinc ammonium sulfate, (6) ammonium bisulfate, (7) aluminum sulfate, (8) manganese sulfate, (9) nickel sulfate, (10) copper sulfate, (11) ferrous sulfate, and (12) ferric sulfate. Submicron aerosols of these compounds in concentrations of 4.1-8.8 mg/m3, administered for 4 h to anesthetized dogs, did not affect mechanics of breathing, hemodynamics, and arterial blood gases. In conscious sheep, tracheal mucous velocity was not altered by exposure to the submicron aerosols of the sulfate compounds. None of these compounds, injected iv in a dose of 1 mg, had adverse effects on mechanics of breathing, pulmonary and systemic hemodynamics, or arterial blood gases. In 100-mg injections, zinc sulfate and zinc ammonium sulfate produced a fall in cardiac output, systemic hypotension, hypoxemia, and metabolic acidosis. Copper sulfate at this dose produced pulmonary hypertension, a fall in cardiac output, hypoxemia, respiratory acidosis, and a decrease of specific total respiratory conductance. It is concluded that submicron aerosols of sulfate salts do not have adverse cardiopulmonary effects when administered in high concentrations for up to 4 h. However, prolonged exposure to high concentrations of zinc sulfate, zinc ammonium sulfate, and copper sulfate aerosols should be carefully monitored because of the possibility that lower levels of these compounds in the bloodstream for long time period might have adverse cardiopulmonary effects.

Aerosols↗
PubMed1977

Assessment of five quantitative methods for determination of total proteins in urine.

1. We assessed five quantitative methods for the determination of urinary total proteins, three of them with precipitation followed by spectrophotomollowed by spectrophotometry (Tsuchyga/Benedict, Tsuchyga/Biuret and TCA/Biuret); one with gel-filtration (Sephadex G50/Biuret) and a Turbidimetric procedure (SSA). 2. Day-to-day precision was between 3.58 %CV (Tsuchyga/Benedict) and 11.46 %CV (Sephadex/Biuret). The Tsuchyga/Benedict method showed the closest values to controls quantitated by the Kjeldahl method and the lowest detection limit )17.3 mg of total proteins per liter). Recovery studies showed that a level of 100-200 mg/l the Tsuchyga/Benedict recovered over the 96% of the protein added. 3. Comparison studies of 66 24-hour urine samples showed that the best correlation was obtained between the Tsuchyga/Benedict and the Tsuchyga/Biuret methods (r = 0.996). 4. We conclude that the Tsuchyga/Benedict is a sensitive, precise and accurate procedure for the routine quantitation of urinary total proteins.

Biuret Reaction↗