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S Quiroga

Publications and source records attributed to S Quiroga.

At least 37 records · Page 2Linked to original sources
PubMed1995

Insulin-like growth factor I receptors of fetal brain are enriched in nerve growth cones and contain a beta-subunit variant.

Nerve growth cones isolated from fetal rat brain are highly enriched in a 97-kDa glycoprotein, termed beta gc, that comigrates with the beta subunit of the IGF-I receptor upon two-dimensional PAGE and is disulfide-linked to this receptor's alpha subunit. Antibodies prepared to a conserved domain shared by the insulin and IGF-I receptor beta subunits (AbP2) or to beta gc were used to study receptor distribution further. Subcellular fractionation of the fetal brain segregated most AbP2 immunoreactivity away from growth cones, whereas most beta gc immunoreactivity copurified with growth cones. Experiments involving ligand-activated receptor autophosphorylation confirmed the concentration of IGF-I but not of insulin receptors in growth cone fractions. These results indicate the enrichment of IGF-I receptors in (presumably axonal) growth cones of the differentiating neuron. Furthermore, the segregation of beta gc from AbP2 immunoreactivity suggests that such neurons express an immunochemically distinct variant of the IGF-I receptor beta subunit at the growth cone.

Animals↗
PubMed1995

A direct non-competitive idiometric enzyme immunoassay for serum oestradiol.

We report a novel non-competitive enzyme immunoassay for oestradiol based on the use of two types of anti-idiotypic antibody that recognize different epitopes within the hypervariable region of the primary anti-oestradiol idiotypic antibody (Ab1). The first anti-idiotype, the betatype, competes with the analyte for an epitope of the primary antibody at the binding site. On the other hand, the second anti-idiotype, the alphatype, binds to the Ab1 in the presence of analyte but does not bind to the betatype/Ab1 complex because of steric hindrance. In the present format the biotinylated alphatype was captured onto anti-biotin IgG which was adsorbed on the surface of microtitre wells. Reaction mixtures containing the Ab1 complexed sequentially with an enzyme labelled second antibody reagent, with oestradiol standards or serum samples and with the betatype anti-idiotypic antibody were then allowed to react with the immobilized alphatype anti-idiotypic antibody. The enzyme activity of the bound fraction measured at 405 nm increased with increasing oestradiol concentrations over the range 0.06-2.5 ng/ml. The detection limit of the assay was 28 pg/ml. The intra-assay variation ranged from 3.5 to 12.4%, and inter-assay variation from 6 to 13.4%. The results obtained by the colorimetric idiometric immunoassay correlated well with those obtained by a direct radioimmunoassay (n = 85, r = 0.97). This non-competitive immunoassay, termed idiometric assay, for haptens permits the development of sensitive immunoassays with a wide working range, and a variety of end-point determinations depending on the label used (e.g., enzyme, chemiluminescent or fluorogenic compound).

Animals↗
PubMed1995

High-density lipoprotein inhibits UDP-N-acetylgalactosamine:GM3, N-acetylgalactosaminyltransferase and differentiation of cultured cerebral cells: comparison with a formerly described inhibitor of this enzyme.

We have previously described a thermostable inhibitor of the UDP-N-acetylgalactosamine:GM3,N-acetylgalactosaminyltransferase (GM2 synthase) purified from chicken blood serum. Some properties of the GM2 synthase inhibitory preparation (IP) resemble those of high-density lipoprotein (HDL), i.e., both have a MW of 200,000 in native conditions and are resistant to denaturation by heat. These and other facts prompted us to test the possibility that lipoproteins regulate ganglioside biosynthesis in the CNS. For this purpose, serum lipoprotein fractions were isolated from chicken serum by flotation and were assayed as inhibitors of GM2 synthase activity and of neuron differentiation in culture. HDL (in contrast to fractions containing very low-density or low-density lipoprotein) inhibited GM2 synthase with the same specific activity as IP and inhibited neuron cell differentiation in culture in a similar way. Furthermore, these two preparations also share several other characteristics; i.e., both have the same cholesterol content, the same floating behavior on KBr gradients, and the same polypeptide pattern as detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and staining with Coomassie Blue, or after western blot and revealing with an antibody prepared against IP, which is able to diminish the inhibitory effect of this preparation. The results described indicate identity between HDL and IP and suggest that HDL (particularly apolipoprotein A) could play an important role on ganglioside biosynthesis modulation during CNS development. The antineuritogenic effect of HDL described in this study could be of physiological relevance during CNS development and response to injury.

Animals↗
PubMed1994

Characterization of gp93, a novel, highly heterogeneous glycoprotein present in growth cone membranes.

gp93 was first described in growth cones from fetal rat brain as a 90-97-kDa glycoprotein family that binds wheat-germ agglutinin and consists of at least 12 different isoelectric variants (pl range approximately 4.9-6.4). Of particular interest is that different sets of gp93 variants are expressed in growth cones isolated from different brain regions. The preparation of a polyclonal antibody to gp93 allowed further characterization of this glycoprotein. The carbohydrate groups of gp93 were partially characterized by digestion with different glycosidases. The results indicate that most or all oligosaccharide units are N-linked (asparagine-linked) and contain sialic acid. Two-dimensional polyacrylamide gel electrophoresis and western blot with anti-gp93 show that deglycosylated gp93 is an only slightly heterogeneous polypeptide of 66 kDa, indicating that gp93 heterogeneity is due, primarily or exclusively, to differential glycosylation. Analysis of the tissue distribution in fetal rat showed gp93 to be highly enriched in the brain. Immunoblots and immunostaining of cross sections of developing cerebellum revealed that gp93 is developmentally regulated in this tissue, associated primarily with growing parallel fibers and Purkinje dendrites. Immunostaining of neurons in culture shows significant amounts of gp93 in elongating neurites and growth cones. Our results indicate that gp93 is a developmentally regulated glycoprotein of the brain that is most prominent in growth cones and growing neurites and that appears to be glycosylated differentially by different neurons.

Animals↗
PubMed1994

Juvenile rheumatoid arthritis of the knee: evaluation with US.

PURPOSE: To evaluate the value of ultrasound (US) in assessing joint inflammation in patients with juvenile rheumatoid arthritis (JRA) of the knee. MATERIALS AND METHODS: US scans obtained in 36 children (mean age, 8 years) with JRA of the knee were compared with those obtained in 30 healthy children. RESULTS: Changes in synovial membrane (synovial thickness), presence of fluid in the suprapatellar bursa, and alterations in the contour (blurring) of the articular cartilage showed statistically significant differences between JRA patients and control subjects. US was more sensitive than physical examination for detecting a minimal amount of intra-articular fluid in 21% of JRA-affected knees with no clinical evidence of active disease. CONCLUSION: US is a simple, rapid, inexpensive, and accurate method for assessing joint inflammation in patients with JRA of the knee.

Adolescent↗
PubMed1993

Spontaneous duodenal fistula due to hepatic hydatid cyst.

Communication of a hepatic hydatid cyst to the duodenum appears to be extremely rare. This is the first case described in the imaging literature of hepatic echinococcosis fistulized to the duodenum studied by computed tomography.

Duodenal Diseases↗
PubMed1992

Variable membrane glycoproteins in different growth cone populations.

The question of whether growth cones generated by different neurons contain distinctive membrane glycoproteins was examined. Growth cone particles (GCPs) were isolated from specific regions of fetal or early postnatal brain, and their membrane proteins were analyzed by 2D gel electrophoresis and Western blotting, using WGA as a probe. These blots were compared to those generated by synaptosomes from adult brain. The patterns reveal a number of WGA-binding glycoproteins that are uniformly present in these subcellular fractions and others that are found in GCPs from selected brain regions only. The results indicate, therefore, substantial pattern diversity for the different, restricted growth cone populations. Some of the WGA-binding glycoproteins seen in GCPs disappear with increasing age and are absent from synaptosomes, while others seem to become more prominent. One of the glycoprotein complexes present in all GCP and synaptosome fractions analyzed is gp93. It has an apparent molecular weight of 90-97 kDa and exhibits unusually high heterogeneity in GCPs from whole fetal brain. The gp93 complex covers a pI range from about 4.9 to about 6.4 and consists of at least 12 different species, probably isoelectric variants. In GCPs from different brain regions, the sets of gp93 species observed are different and characteristic. Neuraminidase digestion shifts the gp93 pattern to a more neutral pI but simplifies it only partially, indicating that variable sialic acid content explains the molecular diversity to some extent. Thus, gp93 is a glycoprotein complex whose members are expressed and/or posttranslationally processed differentially in different growth cone populations. Such a glycoprotein family may be involved in selective cell-cell recognition.

Aging↗
PubMed1991

Internalization of the inhibitor of the N-acetylgalactosaminyltransferase by chicken embryonic retina cells: reversibility of the inhibitor effects.

Retina cells from 6-day-old chicken embryos were cultured in the presence of an 125I-labeled protein inhibitor of the UDP-N-acetylgalactosamine:GM3,N-acetylgalactosaminyltransferase. The cells were labeled and did not lose the incorporated radioactivity when treated with 0.125% trypsin or 1 M NaCl at 37 degrees C for 1 hr, indicating that the iodinated inhibitor was inside the cells. Immunostaining procedures using an anti-inhibitor antibody were applied to the cells cultured in the presence of the inhibitor after permeabilization of the cells. The inhibitor was found inside the round cells virtually devoid of neurites, but not in flat glial-like cells or in process-bearing neural cells. Also found was an apparent self-recovery effect of the cells for both the anti-neuritogenic effect and the modification of the pattern of labeled gangliosides produced by the inhibitor when the agent was withdrawn from the culture medium after the initial period of 20 hr. This recovery was clearly observed 72 hr after the removal of the inhibitor.

Animals↗
PubMed1991

Growth-regulated proteins and neuronal plasticity. A commentary.

Growth-regulated proteins (GRPs) of the neuron are synthesized during outgrowth and regeneration at an increased rate and enriched in nerve growth cones. Therefore, they can be used to some degree as markers of neurite growth. However, these proteins are not unique to the growing neuron, and their properties are not known sufficiently to assign them a functional and/or causal role in the mechanisms of outgrowth. During synaptogenesis, GRPs decrease in abundance, and growth cone functions of motility and organelle assembly are being replaced by junctional contact and transmitter release. However, there is a stage during which growth cone and synaptic properties overlap to some degree. We propose that it is this overlap and its continuation that allow for synaptic plasticity in developing and adult nervous systems. We also propose a hypothesis involving (a) trophic factor(s) that might explain the regulation of synaptic sizes and collateral sprouting. Some GRPs, especially GAP43/B50/pp46/F1, are more prominent in adult brain regions of high plasticity, and they undergo change, such as phosphorylation, during long-term potentiation (LTP). Without precise functional knowledge of GRPs, it is impossible to use changes in such proteins to explain the plasticity mechanism. However, changes in these "growth markers" are likely to be an indication of sprouting activity, which would explain well the various phenomena associated with plasticity and learning in the adult. Thus, plasticity and memory may be viewed as a continuation of the developmental process into adulthood.

Animals↗
PubMed1990

An endogenous inhibitor of N-acetylgalactosaminyltransferase inhibits retina neuron differentiation in culture.

An inhibitor of N-acetylgalactosamine:GM3, N-acetylgalactosaminyltransferase (EC 2.4.1.92) from chicken blood serum, was tested for its activity on embryonic chicken neural retina in culture. The inhibitor did not change the cellular protein content of the cultures but produced a significant reduction of the labeling of gangliosides. The ratio of labeling of GD3 to GD1a increased from about 0.1 to about 0.8 in the cells cultured without or with the inhibitor, respectively. A striking effect of the inhibitor was seen on the morphology of the neurons, those cultured in its presence being practically devoid of neurites. Glial flat cells were apparently not affected.

Animals↗
PubMed1989

Interovarian relationship in the secretion of progesterone during the luteal phase of the capuchin monkey (Cebus apella).

In basal conditions, progesterone concentrations were similar in the ovarian veins of the ovary +CL (3211 +/- 526 ng/ml) and the ovary -CL (3165 +/- 554 ng/ml), but after blocking the blood flow between the ovary +CL and the uterus, the progesterone values in the vein draining the ovary -CL decreased to 1218 +/- 394 ng/ml (P less than 0.01). When [3H]progesterone was injected in the ovary +CL, the radioactivity appeared earlier and more concentrated in the vein draining the ovary -CL (30 sec, 0.53% of injected dose) than in the femoral vein (150 sec, 0.08% of injected dose). Removal of the ovary +CL was followed by a brief maintenance of peripheral progesterone within luteal-phase levels. The in-vitro progesterone production by a suspension of cells isolated from the corpus luteum was 47.5 +/- 12.8 ng/ml/2 h, whereas luteal-like cells isolated from the ovary -CL secreted 14.3 +/- 6.0 ng/ml/2 h (P less than 0.01) into the medium. We therefore suggest that the symmetrical and high secretion rate of progesterone by the ovaries of the capuchin monkey indicates a between-ovary communication system, and that the luteal-like tissue of the ovary -CL can produce relatively large amounts of progesterone.

Animals↗
PubMed1988

An inhibitor of the UDP-N-acetylgalactosamine:GM3, N-acetylgalactosaminyltransferase: purification and properties, and preparation of an antibody to this inhibitor.

An inhibitor of the UDP-N-acetylgalactosamine:GM3, N-acetylgalactosaminyltransferase (EC 2.4.1.92) has been purified close to 100-fold from chicken blood serum. The method of purification includes heating, dialysis, passage through a column of DEAE-Sephadex, filtration through Amicon XM 100, and passage through Sepharose 6B. The molecular weight determined by Sepharose 6B was 200,000, but on sodium dodecyl sulfate-polyacrylamide gel electrophoresis it appears as if the compound dissociated into components of 68,000. The inhibitor was not active on other glycosyl transferases and lost its inhibitory activity following treatment with pronase and trypsin. alpha-Chymotrypsin did not affect the inhibitor. An antibody to this inhibitor was prepared which decreased its inhibitory capability and precipitated with it in a radial double immunodiffusion experiment.

Animals↗
PubMed1984

Inhibition of the chicken retinal UDP-GaINAc:GM3, N-acetylgalactosaminyl-transferase by blood serum and by pineal gland extracts.

The effects of the pineal gland extract and blood serum on the activity of the UDP-GalNAc:GM3, N-acetylgalactosaminyltransferase (GM3:GalNAc-T) from chicken retina were studied. Both preparations have inhibitory capability on the enzyme activity. Two types of inhibitory capabilities were found: one is heat labile and decomposes UDP-GalNAc and another is heat stable. When the pineal gland extracts were prepared from light-exposed chickens, the inhibitory capability increased with respect to the extracts from dark-maintained animals; vice versa, blood serum from dark-maintained animals had higher heat-labile and heat-stable capabilities than that from light-exposed chickens. In in vitro experiments, no difference was found in the inhibitory capability of blood serum extracts from pinealectomized animals compared to control animals. In vivo labeling experiments with pinealectomized animals in either light or dark showed similar differences in the labeling of the optic tectum gangliosides as the normal animals.

Animals↗
PubMed1984

Hormonal monitoring of early pregnancy by a direct radioimmunoassay of steroid glucuronides in first morning urine.

The usefulness of the direct 4-hour radioimmunoassay of estriol-16-glucuronide (E3G) and pregnanediol-3-glucuronide (P2G) in first morning urine (FMU) for establishing a prognosis of the early pregnancy outcome was evaluated in 106 patients that became pregnant. Microaliquots of FMU were serially assayed from day 3 of the conception cycle until day 80 of pregnancy. The E3G and P2G profiles of 19 pregnancies which terminated in spontaneous abortion with either a diagnosis of the blighted ovum syndrome (n = 11) or presumption of a corpus luteum/trophoblast failure (n = 8) have been compared with those of clinically normal pregnancies (n = 87). Normal pregnancies displayed typical patterns of E3G and P2G development, while variations were observed in abortive events that reflected changes of the fetoplacental unit.

Abortion, Spontaneous↗
PubMed1984

Direct assay of urinary steroid glucuronides for monitoring the approach of ovulation.

The concentrations of estrone-3-glucuronide (E(1)3G) and pregnanediol-3-glucuronide (P(2)3G) in daily samples of early morning urine (EMU) were correlated with the levels of estradiol (E2), progesterone (P) and LH in respective plasma samples. Forty-six menstrual cycles were studied, in order to determine the practical usefulness of the urine assays for detecting: a) an individualized estrogen concentration threshold value, announcing the approach of ovulation. b) an individualized signal provided by P(2)3G in urine from which it can be assumed that ovulation has already occurred. The results showed that the concentration of E2 in plasma, in any day of the cycle, can be precisely inferred from the respective concentration of E(1)3G in EMU. The estimation of the plasmatic P values from those of P(2)3G in EMU had to be based on different factors according to the phase of the cycle, fact that suggests the presence of a phase-related variation in the glucuronization of P metabolites. Considering three consecutive E(1)3G urinary assay results, it was possible to identify a threshold value termed Estrogen-Peak Initiating Rise (E-PIR), which anticipated in 3.02 +/- 0.18 days the occurrence of an LH peak. The attempts to detect the occurrence of ovulation by an individualized urinary P(2)3G signal proved disappointing. The signal was detected, either before, simultaneously or after the LH peak.

Adult↗