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Biomedical subjects

A Garcia

Publications and source records attributed to A Garcia.

At least 289 records · Page 16Linked to original sources
PubMed1989

Partial deduced sequence of the 110-kD-calmodulin complex of the avian intestinal microvillus shows that this mechanoenzyme is a member of the myosin I family.

The actin bundle within each microvillus of the intestinal brush border is laterally tethered to the membrane by bridges composed of the protein complex, 110-kD-calmodulin. Previous studies have shown that avian 110-kD-calmodulin shares many properties with myosins including mechanochemical activity. In the present study, a cDNA molecule encoding 1,000 amino acids of the 110-kD protein has been sequenced, providing direct evidence that this protein is a vertebrate homologue of the tail-less, single-headed myosin I first described in amoeboid cells. The primary structure of the 110-kD protein (or brush border myosin I heavy chain) consists of two domains, an amino-terminal "head" domain and a 35-kD carboxy-terminal "tail" domain. The head domain is homologous to the S1 domain of other known myosins, with highest homology observed between that of Acanthamoeba myosin IB and the S1 domain of the protein encoded by bovine myosin I heavy chain gene (MIHC; Hoshimaru, M., and S. Nakanishi. 1987. J. Biol. Chem. 262:14625-14632). The carboxy-terminal domain shows no significant homology with any other known myosins except that of the bovine MIHC. This demonstrates that the bovine MIHC gene most probably encodes the heavy chain of bovine brush border myosin I (BBMI). A bacterially expressed fusion protein encoded by the brush border 110-kD cDNA binds calmodulin. Proteolytic removal of the carboxy-terminal domain of the fusion protein results in loss of calmodulin binding activity, a result consistent with previous studies on the domain structure of the 110-kD protein. No hydrophobic sequence is present in the molecule indicating that chicken BBMI heavy chain is probably not an integral membrane protein. Northern blot analysis of various chicken tissue indicates that BBMI heavy chain is preferentially expressed in the intestine.

Amino Acid Sequence↗
PubMed1989

Indium-111-labeled platelets in monitoring human pancreatic transplants.

We have performed 59 111In-labeled platelet scintigraphies in 12 patients with pancreas transplant, and we have compared retrospectively the 111In platelet uptake with the graft immunological situation. A diffuse uptake in the graft was seen in five of six patients with pancreatic rejection. The scans became positive before changes in biochemical tests were detected. No 111In platelet uptake was seen in five of seven normally functioning grafts. Two cases of venous thrombosis and two perigraft hematomas appeared like a focal 111In platelet accumulation. Indium-111-labeled platelet scintigraphy can be a useful method for monitoring pancreas transplants. It may be helpful in the early detection of pancreatic allograft rejection and in the differential diagnosis between this and other complications such as thrombosis or hematomas.

Adult↗
PubMed1988

Evidence for the presence of carbonic anhydrase in the plasma membrane of rat hepatocytes.

The cellular distribution of carbonic anhydrase is a key characteristic for the role of the enzyme in cell function. In several epithelia involved in bicarbonate transport this enzyme is located in the plasma membrane. Because bicarbonate secretion is an important mechanism in bile formation by the liver, we investigated the presence of carbonic anhydrase activity in isolated plasma membranes from rat hepatocytes. Carbonic anhydrase activity was enriched 1.79-fold in plasma membrane preparations. This activity was inhibited by acetazolamide and activated by Triton X-100, but was insensitive to Cl- or CNO-. It is highly unlikely that the low contamination of cytoplasm and intracellular membranes could account for the presence of carbonic anhydrase activity in plasma membrane preparations. Moreover, the results from resuspension/washing of plasma membrane fractions in ionic media suggest an absence of soluble carbonic anhydrase adsorption upon plasma membrane. Accordingly, the present findings provide strong evidence for the presence of carbonic anhydrase in the plasma membrane of rat hepatocytes.

Animals↗
PubMed1988

Characterization of muscarinic receptor subtypes in human tissues.

The affinities of selective, pirenzepine and AF-DX 116, and classical, N-methylscopolamine and atropine, muscarinic cholinergic receptor antagonists were investigated in displacement binding experiments with [3H]Pirenzepine and [3H]N-methylscopolamine in membranes from human autoptic tissues (forebrain, cerebellum, atria, ventricle and submaxillary salivary glands). Affinity estimates of N-methylscopolamine and atropine indicated a non-selective profile. Pirenzepine showed differentiation between the M1 neuronal receptor of the forebrain and the receptors in other tissues while AF-DX 116 clearly discriminated between muscarinic receptors of heart and glands. The results in human tissues confirm the previously described selectivity profiles of pirenzepine and AF-DX 116 in rat tissues. These findings thus reveal the presence also in man of three distinct muscarinic receptor subtypes: the neuronal M1, the cardiac M2 and the glandular M3.

Brain↗
PubMed1988

Bacteriological studies with ampicillin/sulbactam on selected strains of gram-negative bacteria.

Antibacterial activity of sulbactam or ampicillin alone and in combination on ampicillin-resistant, beta-lactamase-producing Gram-negative bacteria (Citrobacter freundii and Escherichia coli) was studied. Inhibition of beta-lactamase activity by sulbactam was investigated using intact and disrupted cells. Minimal inhibitory concentrations of ampicillin were high but decreased significantly in the presence of sulbactam. Similar enzyme inhibition was observed with intact and disrupted bacterial cells, thus indicating efficient penetration by sulbactam into the periplasmic space. Bacterial killing was achieved in approximately 4 hrs with ampicillin/sulbactam at concentrations that neither killed nor inhibited the same strains when the drugs were used alone. Sulbactam was more effective against plasmid-cured strain of E. coli than the same plasmid-containing organism.

Ampicillin↗
PubMed1988

Sequence of human villin: a large duplicated domain homologous with other actin-severing proteins and a unique small carboxy-terminal domain related to villin specificity.

Villin is a calcium-regulated actin-binding protein that caps, severs, and bundles actin filaments in vitro. This 92,500-D protein is a major constituent of the actin bundles within the microvilli of the brush border surface of intestinal and kidney proximal tubule cells. Villin is a very early marker of cells involved in absorption and its expression is highly increased during intestinal cell differentiation. The amino acid sequence deduced from the cDNA sequence revealed that human villin is composed of three domains. The first two domains appear as the result of a duplication: their structural organization is similar. We can then define a basic unit in which a slightly hydrophilic motif is followed by three hydrophobic motifs, similar between themselves and regularly spaced. The duplicated domain is highly homologous to three other actin-severing proteins and this basic structure represents the whole molecule in severin and fragmin, while two basic units compose gelsolin. The third domain which is carboxy terminal is villin specific: it is unique among actin modulating proteins so far known. It could account for its actin-binding properties (dual regulation by calcium of severing and bundling activities). We propose that it may also be related to the subcellular localization of villin in different epithelial cell types.

Actins↗
PubMed1988

DNA-binding activity associated with the v-myb oncogene product is not sufficient for transformation.

The product of the v-myb oncogene of avian myeloblastosis virus is a nuclear protein with an associated DNA-binding activity. We demonstrated that the highly conserved amino-terminal domain of p48v-myb is required for its associated DNA-binding activity. This activity is not required for the nuclear localization of p48v-myb. Furthermore, the associated DNA-binding activity and nuclear localization of p48v-myb together are not sufficient for transformation.

Autoradiography↗
PubMed1988

Influence of glucocorticoids on the secretion of pancreatic juice in the rat.

The influence of adrenalectomy and hydrocortisone treatment on the exocrine pancreatic secretion has been studied in anaesthetized rats. In the adrenalectomized animals Na+ administered in the saline solution provided for drinking was able to maintain standard sodium levels in serum. In these animals an increase of Na+ secretion in pancreatic juice was observed. Furthermore, the osmotic effect created by the increase in Na+ would account for the increase in pancreatic flow. In these adrenalectomized rats, an increase in K+ output is observed, which can be explained by the high K+ concentrations in serum. Likewise adrenalectomy decreased pancreatic enzyme secretion and produced a loss in weight of the organ that is accounted for by a lack of glucocorticoids. Hydrocortisone administration did not affect neither the secretion nor the weight of the pancreas of the control rats but the hormone proved to be effective in adrenalectomized rats producing a pancreatic secretion close to normal, balancing the secretory rate of water, Na+ and K+, completely restoring total protein secretion and the weight of the pancreas but amylase secretion in part only. It is therefore concluded that the weight of the pancreas and its exocrine secretion are clearly influenced by adrenalectomy and by substitution therapy with hydrocortisone. The administration of this hormone (25 mg.kg-1.day-1 along 6 days) did not affect intact animals.

Adrenal Glands↗
PubMed1988

[Social and health care factors and perinatal mortality in Spain--ecological study].

The results of the multiple regression and correlation analysis between perinatal mortality and social and health care variables in Spanish provinces between 1975 and 1979 are presented. Although the perinatal mortality rates of Spanish provinces correlate significantly with a series of socioeconomic variables (family income available per capita, percentage of active population in primary sector, educational level of women at childbearing age) and health care variables (active obstetricians per 1000 live births and active pediatricians per 1000 live births), the multiple correlation and regression analysis has shown that the most important variable is the family income available per capita: 44% of the variability of perinatal mortality in Spanish provinces can be accounted for by this factor. By regression analysis, it is also possible to predict a decrease of 0.065 points in perinatal mortality for every additional 1000 pesetas in the family income available per capita.

Child Health Services↗
PubMed1987

False-positive early indium-111 leukocyte scan.

An In-111 leukocyte scan was performed in a cirrhotic patient with ascitic fluid infection to rule out an abdominal abscess. Scintigraphy showed localized uptake in the area between the liver and right lung 30 minutes after reinjection of the labeled cells. The 24-hour study was negative. No purulent collection was demonstrated in any location.

False Positive Reactions↗