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Biomedical subjects

L Gonzalez

Publications and source records attributed to L Gonzalez.

At least 73 records · Page 4Linked to original sources
PubMed1997

Urinary calcium excretion in healthy school children.

Two hundred and twenty Argentinian primary school children (122 boys, 98 girls, aged 6-13 years) were studied to establish reference values of 24-h urinary calcium excretion (UCa) and calcium/creatinine ratio (Ca/Cr) in 24-h urine collections and in first-morning urine samples. Mean UCa excretion was 2.05 +/- 1.40 mg/kg per day and the 95th percentile was 4.74 mg/kg per day. UCa excretion was higher in boys than girls (2.33 +/- 1.47 and 1.70 +/- 1.24 mg/kg per day respectively, P < 0.001). Statistically significant differences were found between the 6- to 9-year and the 10- to 13-year age groups (2.37 +/- 1.49 vs. 1.73 +/- 1.25 mg/kg per day, P < 0.001). Mean Ca/Cr ratios in 24-h collections and in first-morning urine samples were 0.129 +/- 0.086 and 0.105 +/- 0.079 for the group overall (P < 0.001). The Ca/Cr ratio in the first-morning urine sample correlated poorly with the 24-h calcium excretion, suggesting that the Ca/Cr ratio in first-morning urine samples cannot replace the 24-h measurement.

Adolescent↗
PubMed1997

Synthetic-peptide-based enzyme-linked immunosorbent assay for screening human serum or plasma for antibodies to human immunodeficiency virus type 1 and type 2.

A synthetic-peptide-based enzyme-linked immunosorbent assay (EIA) capable of screening for antibodies to both human immunodeficiency virus type 1 (HIV-1) and HIV-2 has been developed for use in blood banks and diagnostic laboratories. Microtiter wells are coated with two synthetic peptides, one corresponding to the highly conserved envelope region of HIV-1 and another corresponding to the conserved envelope region of HIV-2. Overall, sensitivity was 100% in 303 individuals diagnosed with AIDS and 96 individuals diagnosed with AIDS-related complex, 14.8% in a study of 500 high-risk group members, 99.9% in 600 EIA repeatedly reactive (RR)-HIV-1 Western blot (WB)-positive repository specimens, and 100% for 222 geographically diverse HIV-1 specimens and 216 confirmed HIV-2-positive specimens evaluated. The specificity was determined to be 99.72% for a total of 13,004 serum and plasma samples from random volunteer donors evaluated across five blood banks. Forty donors who were found to be EIA RR-WB indeterminate but nonreactive on the United Biomedical, Inc., test (UBI HIV 1/2 EIA) were prospectively followed as an additional measure of specificity. None of the 40 low-risk cases evolved into a positive WB pattern at follow-up. The sensitivity and specificity of this new assay are comparable to those of other Food and Drug Administration-licensed HIV-1 and HIV-1-HIV-2 assays that are currently available in the United States. The UBI HIV 1/2 EIA affords laboratories another choice in the detection of antibodies for HIV-1 and HIV-2 with a test based on an alternative antigen format.

AIDS Serodiagnosis↗
PubMed1997

Treatment of penicillin-resistant pneumococcus with penicillin: a case report.

Antibiotic resistance of Streptococcus pneumoniae is on the rise in many parts of the world, and varies widely across the United States. This is of growing concern as organisms become resistant to cephalosporins and macrolides as well as to beta-lactam antibiotics. Susceptibility testing has become a critical element in antibiotic selection. In vitro susceptibility, however, may not correlate with clinical susceptibility. For example, penicillin G in appropriate doses is often effective therapy for drug-resistant Streptococcus pneumoniae pneumonia. This report takes into account in vitro susceptibility as well as the patient's coexisting morbidities in the treatment of penicillin-resistant S pneumoniae with penicillin G.

Humans↗
PubMed1996

An engineered allosteric switch in leucine-zipper oligomerization.

Controversy remains about the role of core side-chain packing in specifying protein structure. To investigate the influence of core packing on the oligomeric structure of a coiled coil, we engineered a GCN4 leucine zipper mutant that switches from two to three strands upon binding the hydrophobic ligands cyclohexane and benzene. In solution these ligands increased the apparent thermal stability and the oligomerization order of the mutant leucine zipper. The crystal structure of the peptide-benzene complex shows a single benzene molecule bound at the engineered site in the core of the trimer. These results indicate that coiled coils are well-suited to function as molecular switches and emphasize that core packing is an important determinant of oligomerization specificity.

Allosteric Regulation↗
PubMed1996

Crystal structures of a single coiled-coil peptide in two oligomeric states reveal the basis for structural polymorphism.

Each protein sequence generally adopts a single native fold, but the sequence features that confer structural uniqueness are not well understood. To define the basis for structural heterogeneity, we determined the high resolution X-ray crystal structures of a single GCN4 leucine-zipper mutant (Asn 16 to aminobutyric acid) in both dimeric and trimeric coiled-coil conformations. The mutant sequence is accommodated in two distinct structures by forming similarly-shaped packing surfaces with different sets of atoms. The trimer structure, in comparison to a previously-characterized trimeric mutant with substitutions in eight core residues, shows that the twist of individual helices and the helix-helix crossing angles can vary significantly to produce the most favoured packing arrangement.

Amino Acid Sequence↗
PubMed1996

Buried polar residues and structural specificity in the GCN4 leucine zipper.

A conserved asparagine (Asn 16) buried in the interface of the GCN4 leucine zipper selectively favours the parallel, dimeric, coiled-coil structure. To test if other polar residues confer oligomerization specificity, the structural effects of Gln and Lys substitutions for Asn 16 were characterized. Like the wild-type peptide, the Asn 16Lys mutant formed exclusively dimers. In contrast, Gln 16, despite its chemical similarity to Asn, allowed the peptide to form both dimers and trimers. The Gln 16 side chain was accommodated by qualitatively different interactions in the dimer and trimer crystal structures. These findings demonstrate that the structural selectivity of polar residues results not only from the burial of polar atoms, but also depends on the complementarity of the side-chain stereochemistry with the surrounding structural environment.

Amino Acid Sequence↗
PubMed1995

Stigma: the hidden burden of infertility.

Infertility is experienced by 5 million U.S. couples, some of whom perceive it a stigmatizing condition. Recent technological innovations have created a multitude of medical interventions for those infertile individuals who can financially afford them. For some infertile women, those interventions also transform infertility from a private pain to a public, prolonged crisis. Our research focuses on 25 U.S. women who sought medical treatment for infertility and describes their perception of the stigma associated with infertility. We apply a critical, feminist perspective to our analysis of the women's lived experiences within the social and medical contexts in which they occur.

Adult↗
PubMed1994

Yeast heat shock transcription factor contains a flexible linker between the DNA-binding and trimerization domains. Implications for DNA binding by trimeric proteins.

All heat shock transcription factors (HSFs) share two regions of homology, identified as the DNA binding and trimerization regions. The DNA binding region consists of two parts, an 89-amino-acid minimal DNA-binding domain and an additional 21 amino acids which are not necessary for specific DNA binding of a monomeric DNA-binding domain. These 21 amino acids may act as a flexible linker between the DNA-binding and trimerization domains. Saccharomyces cerevisiae HSF has an additional 52 amino acids between the proposed flexible linker and the trimerization domain. Deletion of this unique region has no effect on the structural integrity or essential in vivo functions of HSF. To investigate the role of the 21-amino-acid proposed linker, a series of internal deletions was created in fragments containing the DNA-binding and trimerization domains. The deletions have no effect on the structural integrity of the protein as assayed by circular dichroism spectroscopy. However, alterations of the linker do affect affinity of trimeric HSF binding to its target DNA. In addition, deletion of part or all of the proposed linker from full-length yeast HSF, an essential protein, disrupts growth of yeast.

Amino Acid Sequence↗
PubMed1994

Testosterone modulates mesolimbic dopaminergic activity in male rats.

Male rats were castrated before puberty. When they were adult, the activity of their mesolimbic dopamine system was tested by ventral striatum microdialysis. Amphetamine injections increased dopamine more in castrated rats than in normal rats. This exaggerated response was attenuated by testosterone replacement therapy. The mechanism by which androgens modulate the activity of the mesolimbic dopamine system is discussed.

Amphetamine↗
PubMed1994

Patient position during cinedefecography. Influence on perineal descent and other measurements.

PURPOSE: This study was undertaken to assess the reproducibility of cinedefecography measurements and abnormal findings between the left lateral decubitus and seated positions. METHODS: Prospective patient evaluation included all patients who had lateral radiographs of the pelvis taken at rest, during squeezing, and pushing in both positions. Anorectal angle, perineal descent, and puborectalis length measurements were calculated for each set of radiographs. Pelvic floor dynamics during evacuation were measured as the changes between rest and pushing. Abnormal findings included both increased dynamic and fixed perineal descent, nonrelaxing puborectalis, and premature evacuation. RESULTS: One hundred five consecutive patients underwent cinedefecography. There were statistically significant differences between the positions with regard to anorectal angle (P < 0.0001), perineal descent (P = 0.0001), and puborectalis length (P = 0.0001). Dynamic changes of the anorectal angle, perineal descent, and puborectalis length were not significantly different (P > 0.05). However, 6 of 22 (27 percent) patients with fecal incontinence had premature evacuation severe enough to impede measurement only when seated (P = 0.05). CONCLUSION: Because of the statistically significant differences between the two positions, centers should always employ the same position for a given diagnostic group.

Adult↗
PubMed1994

Prolactinoma in a sheep.

This report describes the incidental finding of an acidophilic adenoma of the pituitary gland in an adult ewe with clinical signs of a nervous disorder. Immunohistochemical examination demonstrated prolactin in the tumour cells, justifying the use of the term "prolactinoma" for the first time in veterinary medicine. This tumour should be considered in the differential diagnosis of nervous diseases of sheep.

Animals↗
PubMed1994

Immunoreactivity to chromogranin and to vasoactive intestinal peptide in a canine phaeochromocytoma.

A canine phaeochromocytoma was diagnosed by (1) argyrophil methods, (2) immunoreactivity to chromogranin and to vasoactive intestinal peptide (VIP), and (3) the demonstration of typical electron-dense granules by transmission electron microscopy. This is the first report of immunoreactivity to general neuroendocrine markers such as chromogranin, and to VIP, in a phaeochromocytoma in domestic animals. The use of these markers for the differential diagnosis of phaeochromocytoma, and the role of VIP in the severe chronic diarrhoea shown by the dog in this study are discussed.

Adrenal Gland Neoplasms↗
PubMed1994

Faculty mentors for minority undergraduate students.

The author discusses the Faculty Mentoring Program, its' effects on minority student academic progression, retention and graduation rates at a large regional university campus in the west. Results of a comprehensive program evaluation are discussed.

Education, Nursing, Baccalaureate↗
PubMed1993

Developmental plasticity in cerebellar tactile maps: fractured maps retain a fractured organization.

Plasticity following deafferentation has been repeatedly demonstrated in topographic sensory maps in the mammalian brain. In this paper we investigated the developmental plasticity of the fractured somatotopic map found in the tactile regions of the rat cerebellum. At various stages of postnatal development between postnatal days 1 and 30, we cauterized the infraorbital branch of the trigeminal nerve, which innervates the upper lip, furry buccal pad, and vibrissae that are represented within cerebellar folium crus IIa. The organization of the crus IIa map was then examined 2 to 3 months after denervation. We found that tactile receptive fields had reorganized throughout the denervated area but maintained a fractured somatotopy. Comparison of the reorganization in different animals showed that the denervated upper lip region was consistently and predominantly replaced by representation of the upper incisors. Analysis of evoked field potentials revealed an alteration, in denervated animals, of the response of the granule cell layer to brief tactile stimulation. This response in normal animals consists of two components at different latencies. Animals lesioned later in development were less likely to have the short latency component. This result suggests a difference in the developmental sensitivity of different cerebellum-related pathways to nerve lesions.

Animals↗
PubMed1993

IgE antibodies against bovine serum albumin in a case of eosinophilic gastroenteritis.

Eosinophilic gastroenteritis is a disease characterized histologically by an eosinophilic infiltration of the gut. The cause of this disease remains unclear, although both food allergy and food intolerance have been implicated in its pathogenesis. We report the case of a 22-year-old man in whom gastrointestinal symptoms first appeared in childhood, with involvement of mucosa and muscularis layers of stomach and bowel. He presented high IgE blood levels, and his prick test was positive to bovine, pig, and lamb sera. Immunoblots from calf, pig, and lamb sera, incubated with the patient's serum and revealed by autoradiography, demonstrated the presence of a 65-kDa protein band that was recognized by IgE antibodies but not by IgG. This band corresponded to bovine serum albumin, while IgE did not show reactivity with human albumin. These data suggest a possible role for IgE-mediated hypersensitivity mechanisms in the pathogenesis of eosinophilic gastroenteritis.

Adult↗