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Biomedical subjects

C Gonzalez

Publications and source records attributed to C Gonzalez.

At least 235 records · Page 13Linked to original sources
PubMed1990

Comparison of the erbium-yttrium aluminum garnet and carbon dioxide lasers for in vitro bone and cartilage ablation.

The in vitro bone- and cartilage-ablation characteristics of the solid-state erbium:yttrium aluminum garnet laser were compared to those of the carbon dioxide laser. Ablations of fresh, frozen cadaver septal cartilage and maxillary sinus bone were performed using total energies between 1 and 6 J. Specimens were studied using hematoxylin and eosin stain and digitized, computer-assisted measurements of 35-mm photographs. Erbium-yttrium aluminum garnet-ablated bone averaged 5 microns of adjacent tissue thermal injury, compared with 67 microns with carbon dioxide-ablated bone. Erbium-yttrium aluminum garnet-ablated cartilage averaged 2 microns of adjacent tissue thermal injury, compared with 21 microns with the carbon dioxide-ablated cartilage. The tissue-ablation characteristics of the erbium-yttrium aluminum garnet laser are promising for future otolaryngologic applications.

Aluminum↗
PubMed1990

The supraoptic nucleus: a morphological and quantitative study in control and hypophysectomised rats.

Several quantitative and morphometric parameters were analysed in the pars principalis of the supraoptic nucleus (SON) of the hypothalamus in control and hypophysectomised rats at several postnatal ages. The cell number in the control group remained approximately constant from Day 1, when it was 5034 +/- 348 (mean +/- S.D.M.), until Day 90 when the number of cells was 5234 +/- 110. In the group that was hypophysectomised on Day 60, the number of neurons on Day 90 was 1366 +/- 131, which represents a loss of 74% of the neurons. Morphometric parameters on Day 90 indicated a significant difference in nuclear size, 52.1 +/- 6.7 microns 2 in controls and 57.3 +/- 6.8 microns 2 in the hypophysectomised group. Based on these results, it is concluded that there is no postnatal loss of neurons in the pars principalis of the SON in normal rats. As a consequence of the stress induced by hypophysectomy, the remaining cell population undergoes adaptive changes in the nuclear RNA synthesis machinery of neurohypophyseal hormone precursors in order to compensate for the reduction in the number of neurosecretory neurons.

Age Factors↗
PubMed1989

Sequential 1H-NMR assignment and solution structure of bovine pancreatic ribonuclease A.

Assignments for 1H-NMR resonances of most of the residues of bovine pancreatic ribonuclease (RNase A) have been obtained by sequence-specific methods. Identification and classification of spin systems have been carried out by two-dimensional phase-sensitive correlated spectroscopy (360 MHz) and single relayed coherence transfer spectroscopy. Sequence-specific assignments have been achieved by phase-sensitive two-dimensional nuclear Overhauser effect spectroscopy. To overcome the problem of spectral overlap use has been made of (a) an exhaustive analysis of partly exchanged RNase A (spectra in D2O), (b) a comparison with the subtilisin-modified enzyme (RNase S) and (c) small spectral perturbations caused by changes in pH and temperature. The secondary structure elements have been identified from the observed sequential, medium and long-range nuclear Overhauser effects together with data from amide-exchange rates. All information collected leads to the conclusion that the crystal and the solution structures are closely similar.

Amino Acid Sequence↗
PubMed1989

Effects of cyanide and uncouplers on chemoreceptor activity and ATP content of the cat carotid body.

In cat carotid bodies (c.b.'s) incubated in vitro with [3H]tyrosine to label the stores of catecholamines, it was found that CN promotes dose- and Ca2+-dependent release of [3H]dopamine (DA) from c.b. tissues in parallel to the increased electrical activity recorded from the carotid sinus nerve (c.s.n.). Two different uncouplers, dinitrophenol (DNP) and carbonyl-cyanide-m-chlorophenyl-hydrazone (CCCP), both activate also in a dose-dependent fashion, release of DA and electrical activity in the c.s.n. However, while cyanide (CN) (10(-4) M) applied during 5 min reduced the adenosine triphosphate (ATP) content of the c.b. by 45%, DNP (2.5 x 10(-4) M) and CCCP (10(-6) M) applied for the same period of time did not modify the ATP levels of the organ. At the above concentrations, the 3 agents increased about 8-fold the electrical activity recorded from the c.s.n. Thus, contrary to the postulates of the metabolic hypotheses, our findings indicate that the decrease in the ATP content in the c.b. is not a prerequisite for the activation of the chemoreceptors. We propose alternative mechanisms to explain the chemostimulant action of the metabolic poisons.

Action Potentials↗
PubMed1989

Microbiology of obstructive tonsillar hypertrophy and recurrent tonsillitis.

A qualitative and quantitative analysis of the tonsillar surface and core of children with recurrent streptococcal tonsillitis and children with obstructive tonsillar hypertrophy was performed. No qualitative difference was found within the two population groups. Haemophilus influenzae and Bacteroides melaninogenicus were the most prevalent beta-lactamase-producing isolates in both groups. Staphylococcus aureus had the highest rate of beta-lactamase production on the tonsillar surface of children with recurrent tonsillitis, while Streptococcus pyogenes was more prevalent in the tonsillar surface cultures of children with obstructive tonsillar hypertrophy. The bacterial density was high but not significantly different in both groups of children. The similar microbial composition and density of both groups and the higher rate of S pyogenes recovery may signify a subclinical disease or normal flora in children with obstructive tonsillar hypertrophy.

Adolescent↗
PubMed1989

Laryngotracheal involvement in epidermolysis bullosa.

Epidermolysis bullosa (EB) is a rare hereditary skin disease of infancy that can involve the mucous membranes of the oral cavity. Laryngotracheal involvement is rare. The disease is characterized by bullae formation in response to minor trauma. There are at least 18 described types of EB, however, there are 3 basic categories. These are simplex (with disruption above the basement membrane), dystrophic (in which disruption is below the basement membrane), and junctional (in which the split is within the lamina lucida). The prognosis of the different types ranges from early death usually secondary to overwhelming sepsis, to long term survivals with lack of growth retardation or significant dystrophic scarring. Presently, survival appears to be the only reliable criteria for distinguishing the benign and lethal forms of EB. Airway obstruction secondary to laryngotracheal involvement should be considered in any child with epidermolysis bullosa presented with symptoms of respiratory distress. Because there are few predictive prognostic indicators in the neonatal period, tracheotomy should be considered early in an effort to prevent further laryngeal injury from intubation, in those patients that will survive.

Epidermolysis Bullosa↗
PubMed1989

The relationship between nasal obstruction and craniofacial growth.

The relationship between nasal obstruction and craniofacial growth is unclear. The literature indicates that upper-airway compromise produces chronic mouth breathing, especially in the dolichocephalic (narrow-faced) child. It has been shown that a greater tendency exists toward the skeletal pattern associated with long face syndrome in dolichocephalic head types. Therefore, it becomes difficult to assess whether the long face syndrome is a cause or an effect of increased nasal airway resistance. Nevertheless, animal studies have demonstrated the development of typical craniofacial anomalies in experimentally induced nasal obstruction. Some of these changes are also noted to be reversed by removing the nasal obstruction. Although much of the concern for nasal obstruction and abnormal dentofacial growth has centered around adenotonsillar hypertrophy, other causes for nasal obstruction should be sought. Allergic rhinitis and choanal atresia also should be considered. Longitudinal data are lacking to support conclusively abnormal dentofacial growth as an indication for surgical intervention. Available literature would suggest, however, that relief of nasal obstruction should be attempted in an effort to establish a patent airway and decrease the possibility of abnormal craniofacial development. The more information we gain about nasal obstruction and abnormal dentofacial development, the greater our diagnostic ability becomes. We can now incorporate information from a thorough nasal-oral examination with rhinomanometry and cephalometrics to provide a rational treatment plan for these children. Future directions should investigate genetic influences on craniofacial morphology and growth.

Cephalometry↗
PubMed1989

Immune response to the iron-deprivation-induced proteins of Salmonella typhi in typhoid fever.

Iron starvation conditions limited the growth of Salmonella typhi, as evidenced by an increase in the lag phase of a culture and a decrease in the number of bacteria reached in the stationary phase. The analysis of the outer membrane of bacteria grown under these conditions identified new protein components with apparent molecular weights of 83,000, 78,000, and 69,000. The extent of induction of these proteins was regulated by increased iron deprivation. Immunoblot analysis showed that the serum of patients with typhoid fever exhibited an immunoglobulin G response to these iron-deprivation-induced proteins. The results of bioassays and DNA-DNA hybridization experiments indicated that pathogenic strains of S. typhi produced enterochelin but not aerobactin. Immunodetection with an anti-FepA antiserum confirmed that one of the induced proteins is the S. typhi analog of the Escherichia coli fepA gene product. These studies suggest a role for iron uptake in the pathogenesis of typhoid fever and confirm the immunogenicity of some of the outer membrane proteins of this pathogen.

Antibodies, Bacterial↗
PubMed1989

Metabolic activation of carotid body glomus cells by hypoxia.

The effects of low O2 on glucose consumption in the rabbit carotid body were studied using the in vitro 2-deoxyglucose technique. Metabolically active structures within the tissue were localized autoradiographically after freeze-drying and vacuum fixation/embedding of selected incubated tissue samples. In 100% O2-equilibrated media, the mean basal glucose consumption calculated from the rate of 2-[1,2-3H]deoxy-D-glucose phosphorylation and its specific activity in the incubation media was 61 nmol.g tissue-1.min-1 in the carotid body and 42 nmol.g tissue-1.min-1 in parallel experiments with nodose ganglia. Low PO2 (20% O2-equilibrated media in vitro) increased glucose consumption in the carotid body by 44% but did not alter glucose metabolism of nodose ganglia. Autoradiographic data showed that preneural type I parenchymal cells are the principal site of glucose consumption in carotid chemosensory tissue. The mechanisms responsible for the hypoxia-induced increase in glucose consumption by the type I cells are discussed in relation to sensory transduction by the carotid body chemoreceptors.

Animals↗
PubMed1989

Effects of histamine and serotonin on the contractility of isolated pregnant and nonpregnant human myometrium.

The effects of histamine and serotonin and their antagonists on contractile activity of pregnant and nonpregnant human uterine strips were studied. Both histamine and serotonin (5-HT) increased contractions, pregnant preparations were more responsive than nonpregnant ones. The effects of histamine and 5-HT were blocked by pyrilamine and methysergide, respectively. Pyrilamine (10(-7)-10(-6) M) acted as a competitive antagonist of the effect of histamine, whereas methysergide (10(-7)-10(-6) M) inhibited the response to 5-HT in a noncompetitive manner. Cimetidine and ketanserine were completely ineffective at the doses tested. It is suggested that the increase of contractile activity observed at the end of pregnancy could be partly mediated by the effect of histamine and 5-HT on smooth muscle of the human myometrium.

Cimetidine↗
PubMed1989

Mitosis in Drosophila development.

Many aspects of the mitotic cycle can take place independently in syncytial Drosophila embryos. Embryos from females homozygous for the mutation gnu undergo rounds of DNA synthesis without nuclear division to produce giant nuclei, and at the same time show many cycles of centrosome replication (Freeman et al. 1986). S phase can be inhibited in wild-type Drosophila embryos by injecting aphidicolin, in which case not only do centrosomes replicate, but chromosomes continue to condense and decondense, the nuclear envelope undergoes cycles of breakdown and reformation, and cycles of budding activity continue at the cortex of the embryo (Raff and Glover, 1988). If aphidicolin is injected when nuclei are in the interior of the embryo, centrosomes dissociate from the nuclei and can migrate to the cortex. Pole cells without nuclei then form around those centrosomes that reach the posterior pole (Raff and Glover, 1989); the centrosomes presumably must interact with polar granules, the maternally-provided determinants for pole cell formation. The pole cells form the germ-line of the developing organism, and as such may have specific requirements for mitotic cell division. This is suggested by our finding that a specific class of cyclin mRNAs, the products of the cyclin B gene, accumulate in pole cells during embryogenesis (Whitfield et al. 1989). Other genes that are essential for mitosis in early embryogenesis and in later development are discussed.

Animals↗