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Biomedical subjects

M A Lopes

Publications and source records attributed to M A Lopes.

At least 19 recordsLinked to original sources
PubMed1995

A defective signal peptide in the maize high-lysine mutant floury 2.

The maize floury 2 (fl2) mutation enhances the lysine content of the grain, but the soft texture of the endosperm makes it unsuitable for commercial production. The mutant phenotype is linked with the appearance of a 24-kDa alpha-zein protein and increased synthesis of binding protein, both of which are associated with irregularly shaped protein bodies. We have cloned the gene encoding the 24-kDa protein and show that it is expressed as a 22-kDa alpha-zein with an uncleaved signal peptide. Comparison of the deduced N-terminal amino acid sequence of the 24-kDa alpha-zein protein with other alpha-zeins revealed an alanine to valine substitution at the C-terminal position of the signal peptide, a histidine insertion within the seventh alpha-helical repeat, and an alanine to threonine substitution with the same alpha-helical repeat of the protein. Structural defects associated with this alpha-zein explain many of the phenotypic effects of the fl2 mutation.

Amino Acid Sequence↗
PubMed1995

Identification of two opaque2 modifier loci in quality protein maize.

Genetic modifiers of opaque2 convert the soft, starchy endosperm of opaque2 maize mutants to a hard, vitreous phenotype, while maintaining the enhanced lysine content of the grain. Genetic analysis of F2 segregating seeds from crosses of opaque2 by modified opaque2 genotypes indicated that the modifiers are complex traits that act codominantly. We developed two different segregating F2 populations and mapped the modifier loci by restriction fragment length polymorphism (RFLP) analysis. A relationship was found between formation of vitreous endosperm and the locus encoding the gamma-zein storage protein, which maps near the centromere of chromosome 7. Endosperm modification was consistently associated with the presence of two rather than one gamma-zein gene at this locus. A second modifier locus was mapped near the telomere of chromosome 7L.

Alleles↗
PubMed1995

Effects of captopril on the human foetal placental circulation: an interaction with bradykinin and angiotensin I.

1. The mechanism underlying the foetal toxicity induced by captopril is not well understood. Since bradykinin and angiotensin II appear to be important in the regulation of the placental circulation, experiments were performed to assess the effects of captopril on the vascular actions of these peptides on the human foetal placental circulation. 2. Full-term human placentas, obtained from normal pregnancy, were perfused with a modified Tyrode solution bubbled with O2 using a pulsatile pump. The placental perfusion pressure was measured with a Statham pressure transducer and recorded continuously on a Hewlett-Packard polygraph. 3. Bradykinin (0.1, 0.3 and 1.0 nmol) injected into the placental arterial circulation produced an increase in placental perfusion pressure in all experiments. This effect of bradykinin was significantly inhibited by indomethacin (3 x 10(-7) M). 4. Captopril (10(-7) M) significantly potentiated the pressor effect of bradykinin on the human placental circulation (n = 6). This effect of captopril was reversed by indomethacin (3 x 10(-7) M). 5. Angiotensin I (n = 6) and angiotensin II (n = 6), injected into the placental arterial circulation, both produced dose-dependent increases in placental perfusion pressure. The dose-response curves to angiotensin I (n = 6) were significantly displaced to the right by captopril in a concentration-dependent manner. 6. We suggest that the toxic effects of captopril on the foetus, rather than reflecting an inhibition of angiotensin II formation, may instead be related to a potentiation of the vasoconstrictor effect of bradykinin on the foetal placental circulation, thereby reducing blood flow and causing foetal damage. The reasons for this are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin I↗
PubMed1995

Laminin and collagen IV distribution and ultrastructure of the basement membrane of the gingiva of the rat incisor.

The continuous growth of the rat incisor is associated with renovation of the junctional epithelium and resorption of the periodontal ligament. The circumdental papilla separates the connective tissue suffering resorption from the rest of the gingiva. Laminin and collagen IV were detected by the immunoperoxidase technique on the basement membrane of all regions of the gingival epithelium of the rat incisor, except the internal basal lamina and the internal surface of the circumdental papilla. The internal basal lamina is formed by a granular electron-dense material, without the organization of a typical basal lamina. Areas of the internal surface of the circumdental papilla, negative for laminin and collagen IV, lack the basal lamina. These data suggest that these molecules are not components of the dento-epithelial junction of the distal surface of the rat incisor. In addition, the basal lamina is absent or fragmented on the internal surface of the circumdental papilla, adjacent to the areas of the connective tissue undergoing resorption.

Animals↗
PubMed1994

Synthesis of an unusual alpha-zein protein is correlated with the phenotypic effects of the floury2 mutation in maize.

The soft, starchy endosperm of the maize (Zea mays L.) floury 2 mutant is associated with a reduction in zein mRNA and protein synthesis, unique protein body morphology, and enhanced levels of a 70 kDa protein, that has been shown to be the maize homolog of a chaperonin found in the endoplasmic reticulum. We found an unusual alpha-zein protein of 24 kDa to be consistently associated with the zein fraction from floury 2 mutants. Three additional alpha-zein proteins with molecular weights ranging from ca. 25 to 27 kDa are detected in the storage protein fraction of a high percentage of floury 2 kernels and a low percentage of normal kernels in a genetically segregating population. The four proteins in a genetically segregating population. The four proteins can be distinguished from one another by immunostaining on Western blots. Synthesis of the 24 kDa protein is regulated by Opaque2, since the 24 kDa protein is lacking in the storage protein fraction of opaque2/floury2 double mutants. The synthesis of an abnormal alpha-zein protein in floury2 could explain many features of the mutant, such as the abnormal protein body morphology, induction of the 70 kDa chaperonin, and hypostasis to opaque2 (o2). Although we cannot prove that the accumulation of this protein is responsible for the floury2 phenotype, we were able to detect a restriction fragment length polymorphism (RFLP) linked to the floury2 locus with a 22 kDa alpha-zein probe. We hypothesize that the unique characteristics of the floury2 mutant could be a response to the accumulation of a defective alpha-zein protein which impairs secretory protein synthesis.

Gene Expression Regulation, Plant↗
PubMed1994

Larva migrans that affect the mouth.

As air travel expands, tropical diseases are increasingly likely to be encountered. We report a case of a nematode infection from dogs and cats that appeared in the mouth as larva migrans, and we review the literature.

Adult↗
PubMed1994

Oral lichen planus and chronic active hepatitis B: a salutary tale.

Oral lichen planus is occasionally associated with chronic active hepatitis or primary biliary cirrhosis. This paper describes a patient who presented with oral lichen planus and proved to have chronic active hepatitis, evidently related to hepatitis B virus infection. Oral lichen planus appears occasionally to be associated with systemic infection with hepatitis B or hepatitis C viruses, particularly in patients from southern Europe.

Hepatitis B↗
PubMed1993

Brief communication: gut morphology of Callithrix nigriceps and Saguinus labiatus from western Brazilian Amazonia.

Quantitative data on the gut proportions of the recently-described black-headed marmoset (Callithrix nigriceps) from western Brazilian Amazonian are presented. Like other marmosets, C. nigriceps exhibits a relatively large caecum and colon associated with adaptations for gummivory. The degree of gut specialisation recorded is greater than that for any other platyrrhine for which quantitative data are available. Gum was found in the stomach contents of all four individuals examined, although the fruit/seeds of as many as seven different plant taxa were also encountered, in addition to insects of six different orders. Gut proportions of two Saguinus labiatus from the same region were typical of the more frugivorous tamarins, and stomach contents included only fruit and insects. Relative gut proportions of both species were closely similar to those of congeners from the same region.

Animals↗
PubMed1993

The interexaminer reliability of a galvanic skin response instrument.

OBJECTIVE: To determine the interexaminer reliability of a protocol of use of a galvanic skin resistance device for detection of low resistance areas along the spinal column, in relatively pain-free subjects. DESIGN: A blinded investigation of concordance of skin resistance examination findings over the spinal column using two clinicians experienced in the use of the instrument. SETTING: A private practice chiropractic outpatient clinic. PATIENTS: Sixty-four male and female chiropractic college students (mean age: 35 yr). The Visual Analog Pain Scale indicated a mean response of 7.6 mm on a 100-mm range. INTERVENTIONS: None. MAIN OUTCOME MEASURES: Concordance of examiners evaluated with the kappa statistic. RESULTS: The results indicated modest levels of concordance for the first study sample (n = 46). The average kappa was 0.37. The second group assessed (n = 18) also demonstrated only modest levels of interexaminer concordance. The average kappa value for this sample was 0.36. CONCLUSION: The use of the Electrical Conductor Scanner instrument for evaluating putative spinal pathology through manifestations in skin resistance in relatively asymptomatic subjects is not supported by the results of this experiment. The unevenness of data generated from this experiment in certain spinal regions necessitates further investigation prior to making any strong conclusions regarding the usefulness of this instrument in the clinical setting.

Adult↗
PubMed1993

[Echocardiographic relation criteria. A new selection method for mitral valvotomy with balloon catheter].

PURPOSE: To find out new subjects that could be useful to select patients between 9 and 12 points, according to Block's Criteria, to mitral balloon valvotomy. METHODS: One hundred and forty patients underwent mitral balloon valvotomy. Among them, 29 (21%) had between 9 and 12 points. These patients were divided into two groups: group A-patients with mitral valve area > or = 1.5cm2, immediately after balloon valvotomy and in the follow-up period; group B-patients with mitral valve area < 1.5cm2 immediately after or during the follow-up period, patients with severe mitral regurgitation after the procedure and patients who died in the follow-up period. All patients were analyzed by echocardiographic relation criteria (ERC): calcification + subvalvar disease/thickness + mobility. Each one was quantified from 1 to 4 points according to the degree of valvular disease. RESULTS: Group A was composed of 17 (51%) and group B 12 (41%) patients. The variables age, sex, previous mitral commissurotomy and atrial fibrillation did not show difference between groups. In group A mitral valve area (cm2) increased from 1.15 +/- 0.25 to 1.97 +/- 0.26 (p < 0.00001) keeping stable during the follow-up period. In group B percutaneous mitral balloon valvotomy resulted in an increase from 1.26 +/- 0.19 to 1.77 +/- 0.16 (p < 0.00001), however, there was an important decrease in the follow-up period to 1.34 +/- 0.15 (p < 0.00001). The ERC showed that all group A patients had a relation < 1. However, in group B, 10 patients (83%), the relation was > or = 1, and in only 2 patients (17%) was < 1 (p < 0.00001). CONCLUSION: The group of patients between 9 and 12 points in the Block's criteria is heterogenic, therefore, each case might be evaluated individually and the echocardiographic relation criteria should be used in order to select these patients to the procedure.

Adult↗
PubMed1991

opaque-2 modifiers increase gamma-zein synthesis and alter its spatial distribution in maize endosperm.

Through the action of opaque-2 modifier genes, the soft, floury endosperm of opaque-2 mutants is converted to a vitreous phenotype. This change in endosperm texture is associated with a twofold to threefold increase in gamma-zein content. To investigate the effect of opaque-2 modifiers on the expression of gamma-zein genes, we analyzed the synthesis and distribution of gamma-zein protein and the level of gamma-zein mRNAs in developing endosperms of the inbreds W64A and W64Ao2, a modified opaque-2 mutant Pool 34 QPM, and their reciprocal F1 hybrids. We also characterized the number and organization of gamma-zein genes in these and related maize genotypes. Our studies show that opaque-2 modifiers are semidominant genes, resulting in a twofold to threefold increase in gamma-zein gene expression in both opaque-2 and normal genetic backgrounds. The increase in gene expression appears to be a consequence of enhanced mRNA transcription or stability rather than gene amplification because gamma-zein genes occur in one or two copies in modified as well as nonmodified genetic backgrounds. Ultrastructural studies showed that gamma-zein occurs in high concentrations in the first few subaleurone cells of nonmodified endosperms, but high concentrations of gamma-zein occur in the subaleurone and central endosperm cells of modified opaque-2 mutants. The increased concentration and distribution of gamma-zein in modified endosperms are highly correlated with the activity of opaque-2 modifier genes.

Microscopy, Immunoelectron↗
PubMedDate not supplied

Seroprevalence of HIV, HTLV-I/II and other perinatally-transmitted pathogens in Salvador, Bahia.

Generation of epidemiological data on perinatally-transmitted infections is a fundamental tool for the formulation of health policies. In Brazil, this information is scarce, particularly in Northeast, the poorest region of the country. In order to gain some insights of the problem we studied the seroprevalence of some perinatally-transmitted infections in 1,024 low income pregnant women in Salvador, Bahia. The prevalences were as follow: HIV-1 (0.10%), HTLV-I/II (0.88%), T.cruzi (2.34%). T.pallidum (3.91%), rubella virus (77.44%). T.gondii IgM (2.87%) and IgG (69.34%), HBs Ag (0.6%) and anti-HBs (7.62%). Rubella virus and T.gondii IgG antibodies were present in more than two thirds of pregnant women but antibodies against other pathogens were present at much lower rates. We found that the prevalence of HTLV-I/II was nine times higher than that found for HIV-1. In some cases such as T.cruzi and hepatitis B infection there was a decrease in the prevalence over the years. On the other hand, there was an increase in the seroprevalence of T.gondii infection. Our data strongly recommend mandatory screening tests for HTLV-I/II, T.gondii (IgM), T.pallidum and rubella virus in prenatal routine for pregnant women in Salvador. Screening test for T.cruzi, hepatitis and HIV-1 is recommended whenever risk factors associated with these infections are suspected. However in areas with high prevalence for these infections, the mandatory screening test in prenatal care should be considered.

Adult↗