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Biomedical subjects

C Gonzalez

Publications and source records attributed to C Gonzalez.

At least 217 records · Page 12Linked to original sources
PubMed1991

Ionic mechanisms for the transduction of acidic stimuli in rabbit carotid body glomus cells.

1. The release of [3H]dopamine (DA) in response to inhibition of the Na+ pump or to intracellular acid load was studied in rabbit carotid bodies (CB) previously incubated with the precursor [3H]tyrosine. The ionic requirements of the release response and the involvement of specific ion transport systems were investigated. 2. Inhibition of the Na+ pump, by incubating the CB with ouabain or in K(+)-free medium, evokes a DA release response which requires the presence of Na+ and Ca2+ in the medium and is insensitive to nisoldipine. This suggests that the response is triggered by entry of external Ca2+ through Na(+)-Ca2+ exchange, a consequence of the increase in intracellular Na+ resulting from inhibition of the pump. 3. Incubation of the CB in medium equilibrated with 20% CO2 at pH 6.6, or in medium containing the protonophore dinitrophenol (DNP) or the weak acid propionate, elicits a DA release response which requires also the presence of Na+ and Ca2+ in the medium and is insensitive to dihydropyridines. 4. Ethylisopropylamiloride (EIPA), an inhibitor of the Na(+)-H+ exchanger, markedly decreases the release response elicited by DNP or propionate in bicarbonate-free medium, but has not any effect in bicarbonate-buffered medium. In the latter condition, the EIPA-insensitive release of DA is inhibited by reducing the HCO3- concentration in the medium to 2 mM or by removal of Cl-, suggesting that in bicarbonate-buffered medium a Na(+)-dependent HCO3(-)-Cl- exchanger is involved in the release response. 5. It is concluded that the release of DA by the chemoreceptor cells in response to acidic stimulation is triggered by entry of external Ca2+ through Na(+)-Ca2+ exchange. This exchange is promoted by the increase of intracellular Na+ that results from the operation of Na(+)-coupled H(+)-extruding mechanisms activated by the acid load.

Acids↗
PubMed1991

Dosage dependence of maternal contribution to somatic cell division in Drosophila melanogaster.

Most mitotic mutants in Drosophila do not lead to lethality in early development despite the highly abnormal chromosome behaviour that they elicit. This has been explained as being the effect of maternally provided wild-type products. We have tested this hypothesis by studying cuticular clones derived from cells in which there has been loss of a marked Y chromosome due to chromosome nondisjunction in individuals homozygous for the mutation abnormal spindle who are progeny of heterozygous mothers. We have found that the size and frequency of these clones are higher than in control flies. Furthermore, by analysing flies whose female parents have different doses of the asp+ gene, we have found that there is a correlation between the amount of maternally contributed asp+ product and the frequency and size of cuticular clones. We have also estimated the time in development when the first mitotic mistakes take place, i.e. the time when maternal products are no longer sufficient to carry out normal cell division.

Alleles↗
PubMed1991

Corneal ulcers associated with contact lenses including experience with disposable lenses.

We conducted a retrospective study of corneal ulcers that had been managed on the Cornea Service at Wills Eye Hospital in 1988 and 1989. Forty-four percent (51 of 116) of the ulcers were associated with contact lens use. Pseudomonas was the most often isolated organism (25 of 116, 22%) and was most frequently associated with cosmetic soft contact lenses (16 of 25, 64%). Ulcers associated with disposable contact lenses (five cases) were similar to those associated with conventional extended wear myopic lenses (15 cases). Pseudomonas was the predominant organism with both disposable (four of five, 80%) and conventional extended wear lenses (nine of 15, 60%). Staphylococcus aureus (19 cases) and Staphylococcus epidermidis (19 cases) were the next most frequently isolated organisms and usually occurred in ulcers not associated with contact lenses (29 of 38, 76%). Ulcers were treated 3.3 times more often in people using extended wear than in those using daily wear myopic lenses. Disposable contact lenses have not eliminated the problem of corneal ulcers associated with extended wear contact lenses.

Bacteria↗
PubMed1991

Juvenile aggressive fibromatosis: report of three cases and review of the literature.

AF is a non-encapsulated, non-metastasizing fibrous tumor that has a tendency for local recurrence in up to 70% of cases. We suspect possible genetic disposition. Microscopically, AF is a poorly circumscribed fibrous tumor that infiltrates surrounding tissues. It presents as a painless, rapidly growing mass with a predilection for bone destruction. Treatment consists of a carefully planned en bloc resection after biopsy and accurate radiologic evaluation of the extent of the tumor. Radiation therapy and chemotherapy can be used as adjuvant therapy in selected patients. Three patients with AF of the head and neck are described, of which two were found to have congenital disorders of mesodermal development.

Adolescent↗
PubMed1990

Differential stimulus coupling to dopamine and norepinephrine stores in rabbit carotid body type I cells.

Recent studies suggest that preneural type I (glomus) cells in the arterial chemoreceptor tissue of the carotid body act as primary transducer elements which respond to natural stimuli (low O2, pH or increased CO2) by releasing chemical transmitter agents capable of exciting the closely apposed afferent nerve terminals. These type I cells contain multiple putative transmitters, but the identity of the natural excitatory agents remains an unresolved problem in carotid body physiology. Characterization of putative transmitter involvement in the response to natural and pharmacological stimuli has therefore become fundamental to further understanding of chemotransmission in this organ. The present study demonstrates that a natural stimulus (hypoxia) evokes the release of dopamine (DA) and norepinephrine (NE) in approximate proportion to their unequal stores in rabbit carotid body (DA release/NE release = 8.2). In contrast, nicotine (100 microM), a cholinomimetic agent thought to act on the nicotinic receptors present on the type I cells, evokes the preferential release of NE (DA release/NE release = 0.17). These findings suggest that distinct mechanisms are involved in a differential mobilization of these two catecholamines from the rabbit carotid body.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1990

Superior oblique muscle dysfunction following anterior ethmoidal artery ligation for epistaxis.

Superior oblique muscle palsy is a frequently encountered acquired muscle deficit accounting for vertical and torsional diplopia. There were two cases of residual isolated superior oblique palsy following anterior ethmoidal artery ligation for epistaxis, a finding not previously reported. The mechanism is suggested to be due either to direct trochlear damage by separation from the periosteum or to localized hematoma formation beneath the periosteum with resultant fibrosis and displacement of the trochlea from its normal apposition to the frontal bone.

Arteries↗
PubMed1990

The A- and B-type cyclins of Drosophila are accumulated and destroyed in temporally distinct events that define separable phases of the G2-M transition.

We show that the sequence of Drosophila cyclin B has greater identity with B-type cyclins from other animal phyla than with Drosophila cyclin A, suggesting that the two cyclins have distinct roles that have been maintained in evolution. Cyclin A is not detectable in unfertilized eggs and is present at low levels prior to cellularization of the syncytial embryo. In contrast, the levels of cyclin B remain uniformly high throughout these developmental stages. In cells within cellularized embryos and the larval brain, cyclin A accumulates to peak levels in prophase and is degraded throughout the period in which chromosomes are becoming aligned on the metaphase plate. The degradation of cyclin B, on the other hand, does not occur until the metaphase-anaphase transition. In cells arrested at c-metaphase by treating with microtubule destabilizing drugs to prevent spindle formation, cyclin A has been degraded in the arrested cells, whereas cyclin B is maintained at high levels. These observations suggest that cyclin A has a role in the G2-M transition that is independent of spindle formation, and that entry into anaphase is a key requirement for the degradation of cyclin B.

Amino Acid Sequence↗
PubMed1990

Caffeine, an inhibitor of endocytosis in Dictyostelium discoideum amoebae.

The effect of the trimethylxanthine, caffeine, was examined on the growth and endocytosis pathways of the vegetative amoebae of the cellular slime mold Dictyostelium discoideum. Caffeine at concentrations of 1.5-3 mM was found to inhibit axenic growth, fluid-phase pinocytosis, and secretion of lysosomal enzymes. Cell viability was unaffected by incubation for 16 hours with 5 mM caffeine but decreased markedly thereafter. Phagocytosis of the bacterium Escherichia coli by Dictyostelium amoebae was also inhibited by caffeine, although at concentrations twofold to threefold higher. Caffeine rapidly entered into amoebae to reach an equilibrium between extracellular and intracellular concentrations, and it was not appreciably metabolized by Dictyostelium. Inhibition of growth and endocytosis was reversible upon removal of the drug and was partially counteracted by 10 mM adenosine. As caffeine discharged intracellular calcium stores in Dictyostelium (Abe et al., 1988), its inhibitory effect on endocytosis could result from the perturbation of calcium homeostasis. In agreement with this hypothesis, the cation La3+ (10 microM), a Ca2(+)-transport inhibitor, also strongly reduced fluid-phase pinocytosis.

Acid Phosphatase↗
PubMed1990

A case of facial diplegia associated with acute bilateral otitis media.

A 32-month-old toddler developed facial diplegia in association with a bout of acute bilateral otitis media. After 28 days of antibiotic therapy and placement of tympanostomy tubes, the patient demonstrated 100% symmetrical recovery. A brief discussion of the pathophysiology is included.

Acute Disease↗
PubMed1990

Endobronchial tuberculosis in children. A case report and review.

Unilateral obstructive emphysema seen on chest X-ray in a pediatric patient is usually associated with a foreign body in a bronchus. We present a 31-month-old female who presented with a 2-week history of increasing expiratory stridor. Endoscopic examination revealed a polypoid mass in the right main bronchus. Biopsies and cultures were consistent with endobronchial tuberculosis. We review the presentation and treatment of tuberculosis in children. Endobronchial tuberculosis is a rare complication of pulmonary tuberculosis which may result in stenosis of the bronchus.

Bronchi↗
PubMed1990

Effects of serotonin on vascular tone of isolated human placental chorionic veins.

Vasomotor effects of serotonin (5-hydroxytryptamine; 5-HT) were studied in isolated human placental chorionic veins in vitro. 5-HT produced marked contraction with a maximum of 89 +/- 5.05% of the K(+)-induced contractions. This response was specifically and competitively antagonized by ketanserin at doses of 10(-9) and 10(-8) M (pA2 = 9.65). Ketanserin, at concentrations up to 10(-7) M, induced noncompetitive inhibition of the contractions. These findings show a marked vasoconstrictor effect of 5-HT on the capacitance vessels of the human placenta, which suggests that this amine could play an important role as a mediator of fetal circulation. The possible therapeutic effect of ketanserin as a vasodilator to improve blood flow in the uteroplacental unit, is also discussed, based on the ability of this drug to block competitively 5-HT effects on chorionic veins.

Chorion↗
PubMed1990

Endotracheal tube safety with the erbium:yttrium aluminum garnet laser.

The erbium:yttrium aluminum garnet (Er:YAG) laser operates in the infrared spectrum at a wavelength of 2.94 microns. The absorption coefficient for water at this wavelength is approximately 10 times that of the carbon dioxide laser. It is anticipated that this laser will produce more precise surgical ablation with decreased surrounding tissue destruction. The results of impacting endotracheal tubes with the Er:YAG laser are presented. The CO2 laser was used as a reference. Metallic tape that was not perforated by the CO2 laser after 240 seconds of continuous exposure at 20 W was perforated by the Er:YAG laser with use of 15 pulses of 1 J per pulse. Silver foil tape with a Meroplicable to otolaryngology, modification of current safety standards will be necessary.

Aluminum↗
PubMed1990

Abnormal meiotic spindles cause a cascade of defects during spermatogenesis in asp males of Drosophila.

Since spermatogenesis in Drosophila is a series of interconnected and interdependent steps and most of the spermatogenic events take place in the absence of transcription, failures in a given stage can give rise to a cascade of defects later on. The asp locus of Drosophila melanogaster codes for a non-tubulin component implicated in proper spindle structure and/or function (Ripoll et al. 1985). Homozygous asp males exhibit abnormal meiotic spindles giving rise to altered segregation of chromosomes and mitochondria and failures in cytokinesis. Postmeiotic spermatogenic stages of asp males show a series of alterations that we interpret as due to the previously occurring defective meiosis because meiotic spindles are the only microtubular structure altered in mutant testes. The most conspicuous alterations are: (i) variable size of nuclei and nebenkerns of early spermatids, which are also multinucleate instead of having single and uniformly sized nuclei; (ii) elongating spermatids in which abnormal-sized mitochondrial derivatives elongate alongside more than one axoneme; (iii) failures in the individualization process, where abnormal spermatids remain syncytial, and seem to be eliminated during the coiling stage.

Animals↗
PubMed1990

Mutations at the asp locus of Drosophila lead to multiple free centrosomes in syncytial embryos, but restrict centrosome duplication in larval neuroblasts.

Mutations at abnormal spindle result in abnormally long and wavy microtubules in the meiotic spindles of males. Some of these spindles have a single pole and take the form of unopposed hemi-spindles. Unfertilised eggs produced by homozygous asp females may have either no nuclei, or a small number of large nuclei, consistent with there also being an effect upon female meiosis. Such eggs also display free centrosomes and independent arrays of microtubules. Embryos that have this phenotype are also present among the progeny of fertilised homozygous asp females, together with embryos that undergo varying degrees of aberrant morphogenesis, developing a variety of abnormal cuticle patterns. This latter category shows asynchronous mitoses prior to cellularisation, and has abnormal arrays of spindle microtubules. Such embryos can develop large areas that are either devoid of or have a reduced number of nuclei, in which there are centrosomes that have dissociated from the mitotic spindles. Neuroblasts in the brains of homozygous asp larvae display a high mitotic index, and have condensed chromosomes aligned as if blocked at metaphase. Immunostaining reveals that many cells contain a single centrosome connected to the metaphase chromosomes by microtubules in a hemi-spindle-like structure.

Alleles↗