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Biomedical subjects

C Gonzalez

Publications and source records attributed to C Gonzalez.

At least 253 records · Page 14Linked to original sources
PubMed1989

Quantitative light-microscopic study of the nucleus medialis dorsalis of the thalamus in the intact cat, and after prefrontal cortical ablations.

The volume of the prefrontal cortex and of the thalamic nucleus medialis dorsalis, and the number of neurons in this nucleus were obtained, for adult cats of both sexes, using paraffin embedding and standard quantitative histological procedures. Changes in the nucleus medialis dorsalis after prefrontal cortical ablations were also quantified. All data were corrected for shrinkage. In the intact cat, the average volume of the prefrontal cortex was 235 mm3, the average volume of the nucleus medialis dorsalis was 24.5 mm3, and the number of neurons in this nucleus was 232,000. After cortical ablations which eliminated between 64% and 93% of the prefrontal cortex, the number of surviving neurons in the nucleus medialis dorsalis remained at 70%-55% of controls. When additional cortex (which surrounds the prefrontal cortex and is connectionally related to it) was damaged, the decrease in volume and neuron counts in the nucleus medialis dorsalis was proportional to the amount of cortex ablated. Even after large cortical ablations of this kind, over 45% of the neurons in the nucleus medialis dorsalis still survived. Some of the surviving neurons appeared in the core of maximal gliosis in the nucleus. No unquestionable side or sex differences were found.

Animals↗
PubMed1989

Cricoarytenoid subluxation: complication of blind intubation with a lighted stylet.

Transillumination of the cervical airway with the light wand for blind intubation is a valuable adjunct to anesthesiologists and emergency room physicians, particularly for management of the complicated airway in which direct visualization of the larynx is not possible. However, as an alternative to traditional methods, this technique should be practiced in simple cases before it is attempted in more difficult airway cases. The technique is easy to learn but requires practice to master. The incidence of complications remains low but complications may be serious when they occur. We present a case of cricoarytenoid subluxation after blind intubation with a lighted stylet.

Adult↗
PubMed1988

Activation of the release of dopamine in the carotid body by veratridine. Evidence for the presence of voltage-dependent Na+ channels in type I cells.

Veratridine (50 microM), an agent known to activate voltage-dependent Na+ channels, induced a strong release of [3H]dopamine from the rabbit carotid body in vitro. The effect of veratridine was dependent on the presence of both Na+ and Ca2+ in the extracellular medium and was abolished by 1 microM tetrodotoxin. These results suggest that chemoreceptor type I cells have voltage-dependent Na+ channels, which could be involved in the depolarization of the cell membrane and activation of voltage-dependent Ca2+ channels.

Animals↗
PubMed1988

Strabismus surgery on the nonamblyopic eye.

To date most surgeons operate only on the nonamblyopic eye in patients with strabismus and amblyopia with unpredictable, initial, surgical results. We present a series of 13 patients with amblyopia and strabismus plus anomalous head positions who underwent surgery on their nonamblyopic eye. The good, initial, surgical results in 77% of these patients suggest that operating on the good eye is important to dictate the final surgical results in correcting the deviation and normalizing the head position.

Adolescent↗
PubMed1987

Mechanisms for termination of the action of dopamine in carotid body chemoreceptors.

The possible presence of a high affinity uptake mechanism for dopamine and the metabolism of this amine was investigated in the rabbit carotid body. The type I cells of this sensory organ contain high levels of dopamine and share with sympathetic nerve endings (which possess a high affinity uptake mechanism for catecholamines) the properties of being presynaptic catecholaminergic elements, but also have in common with chromaffin cells from intact adrenal medulla (which lack a high affinity catecholamine uptake) a similar embryological origin and ultrastructural appearance. Our experiments revealed only a low affinity uptake process (Km = 6.76 X 10(-4) M [3H]dopamine; Vmax = 1.84 X 10(-9) mol [3H]dopamine/mg protein/min) in the rabbit carotid body. In agreement with our kinetic findings, the uptake of [3H]dopamine was found to be independent of the Na+ concentration in the incubation media. The efflux from the tissue of incorporated [3H]dopamine was very fast (88% wash-out with a half-time of 4 min). DOPAC was the principal catabolite of dopamine in the carotid body, and the organ exhibited a very low capacity for norepinephrine synthesis. Neither chronic carotid sinus nerve section nor chronic sympathectomy modified the uptake of [3H]dopamine, suggesting that the lack of expression of a high affinity uptake was not a consequence of trophic suppression by the neural innervation of the organ. We conclude that overflow, or wash-out, of released dopamine may be quantitatively the most important mechanism for the inactivation of this putative neurotransmitter in the rabbit carotid body.

Animals↗
PubMed1986

Synthesis and release of catecholamines by the cat carotid body in vitro: effects of hypoxic stimulation.

The role of catecholamines (CAs) in cat carotid body chemoreception has been controversial. On the basis of pharmacological experiments, it would appear that endogenous dopamine (DA) may act either as an inhibitory or excitatory transmitter. Neurochemical studies on the effects of natural stimulation on the release of carotid body CAs in the cat have also been inconclusive. In the present study, we have characterized the synthesis and release of CAs in the in vitro cat carotid body preparation in response to different levels of hypoxic stimulation and have correlated these measures with the chemosensory activity of the carotid sinus nerve. The synthesis of [3H]DA and [3H]norepinephrine was linear for at least 4 h in carotid bodies incubated with their natural precursor [3H]tyrosine. Synthesis of both [3H]CAs plateaued when the [3H]tyrosine concentration in the media reached 40 microM, which is a concentration similar to that found in cat plasma. Exposure of the animals to an atmosphere of 10% O2 in N2 for 3 h prior to removal and incubation of the carotid bodies with [3H]tyrosine resulted in an approximately 100% increase in the rate of [3H]DA synthesis but no change in [3H]norepinephrine synthesis. This selective increase in [3H]DA synthesis was not detected when [3H]dihydroxyphenylalanine was used as precursor. Carotid bodies first incubated with [3H]tyrosine and later superfused with solutions equilibrated with different gas mixtures (0-100% O2 in N2) exhibited an increase in [3H]DA release and carotid sinus nerve discharge which were inversely related to the oxygen concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Effects of 2-deoxy-D-glucose on in vitro cat carotid body.

The process of chemosensory transduction in the arterial chemoreceptors is not well understood. According to the metabolic hypothesis of chemoreception, a decrease in arterial pO2 will produce a decrease in the adenosine triphosphate (ATP) content in the chemosensory type I cells, leading to release of a neurotransmitter and increased sensory neural activity. There is a paucity of direct experimental support for this hypothesis, and in the present work, we have tested the postulates of the metabolic hypothesis in an in vitro preparation of cat carotid body using 2-deoxy-D-glucose as an ATP-depleting agent. This preparation, when superfused with Tyrode containing 5 mM Na+-pyruvate instead of glucose, responds normally to hypoxia, low pH and acetylcholine, and maintains normal ATP levels. Under these conditions, 2-deoxy-D-glucose is a chemostimulant, i.e. electrical activity in the carotid sinus nerve is increased, with a threshold concentration of 0.25 mM and a maximum response at about 2-4 mM. These concentrations of 2-deoxyglucose evoke a dose-dependent release of [3H]dopamine (synthesized from [3H]tyrosine) from the carotid bodies which parallels the electrical activity. The 2-deoxy-D-glucose-evoked release and electrical activity is dependent on the presence of extracellular Ca2+. These same concentrations of 2-deoxy-D-glucose significantly reduce the ATP content of the carotid bodies. The events postulated by the metabolic hypothesis, i.e. decrease in ATP content, release of a putative neurotransmitter and activation of the sensory nerve endings are found to occur simultaneously. A possible cause-effect relationship between these three events is discussed.

Action Potentials↗
PubMed1986

An improved cytological silver staining method for the demonstration of neuronal nuclear bodies.

A simple cytological method for the selective impregnation of neuronal "nuclear bodies" is described. This procedure involves glutaraldehyde fixation, pretreatment with methanol-acetic acid, impregnation in a 1.5% colloidal solution of silver nitrate containing gelatin, and pyrogallic reduction of whole tissue blocks. After block staining the material was either dehydrated and embedded in araldite for light and electron microscopy studies, or processed for the elaboration of neuronal smear preparations, which were used for the quantitative analysis of nuclear bodies. By light microscopy, nuclear bodies appear as conspicuous, intensely impregnated inclusions, 0.3-0.9 micron in diameter. Both the nucleoli and cytoplasmic Nissl bodies can be counterstained with Toluidine blue. Overimpregnation produces an additional staining of the nucleolar fibrillar component.

Animals↗
PubMed1986

Complication of acute epiglottitis.

Acute airway obstruction secondary to supraglottic inflammation is a regional manifestation of epiglottitis in children. Pneumonia, meningitis, cervical adenitis and septic shock are systemic manifestations which can complicate the course of acute epiglottitis. Prompt airway control and institution of appropriate high dose i.v. antibiotics are both important to continue to decrease the morbidity and mortality associated with the regional and systemic manifestations of acute epiglottitis in children.

Acute Disease↗
PubMed1986

Effects of high potassium on the release of [3H]dopamine from the cat carotid body in vitro.

Using an in vitro preparation of the cat carotid body, we have characterized the release of [3H]dopamine (DA) induced by high extracellular K+. Pulse superfusion (3 min) with high K+ Tyrode solution (20-80 mM) evoked a concentration-dependent release of [3H]DA from type I cells with a threshold at about 20 mM-extracellular K+ and a plateau at about 60 mM-extracellular K+. Equivalent low extracellular Na+ concentration ([Na+]o) solutions osmotically balanced with sucrose did not induce release. The high extracellular K+ concentration ([K+]o)-evoked release of [3H]DA by type I cells was dependent on the presence of Ca2+ in the superfusion media. On prolonged (10-14 min) superfusion with high K+ Tyrode solution, the [3H]DA release evoked by 60 mM-extracellular K+ was transient, while that evoked by 30 mM-extracellular K+ was sustained. In preparations superfused for 6 min with 60 mM-extracellular K+ and zero extracellular Ca2+ concentration ([Ca2+]o) Tyrode solution, reintroduction of Ca2+ did not elicit a secretory response. Ba2+ was a potent secretagogue of [3H]DA in preparations superfused with normal and zero [Ca2+]o Tyrode solution. Additionally, Ba2+ was capable of eliciting a secretory response from type I cells in preparations previously exposed (6 min) to 60 mM-extracellular K+, whether or not [Ca2+]o was present. With regards to stimulus-secretion coupling, our results indicate that high [K+]o probably depolarizes type I cells. This effect would, in turn, activate voltage-dependent Ca2+ channels, allowing the entrance of this ion to activate the neurosecretory response.

Action Potentials↗
PubMed1986

Duration of intubation in children with acute epiglottitis.

Nasotracheal intubation has been demonstrated to be effective in supporting the airways of children with acute epiglottitis. Length of intubation and criteria used for extubation are still controversial. A 6-year retrospective review at Children's Hospital of Pittsburgh identified 100 cases of acute epiglottitis, which were initially managed with nasotracheal intubation. Extubation was based on direct laryngeal inspection performed in the operating room (1979-1981) and, more recently, in the intensive care unit (1982-1984). Length of intubation decreased from 63.8 hours in 1979 to 42.1 hours in 1984. The percent of children intubated longer than 48 hours decreased from 69% to 22% in the same time period. These data indicate that a shorter period of intubation is aided by daily laryngeal inspection in the ICU. We propose a staging system for acute epiglottitis to aid in the decision to safely extubate these children.

Acute Disease↗
PubMed1986

Prevention of recurrent acute otitis media: chemoprophylaxis versus tympanostomy tubes.

Otitis media has long been recognized as one of the most common diseases of childhood. Several therapeutic modalities have been advocated for the prevention of recurrent episodes of acute otitis media (AOM). A blinded, prospective, randomized study was designed to determine the efficacy of tympanostomy tubes, antibiotic prophylaxis, and placebo. Children with recurrent AOM were entered in the study and followed for at least 6 months. A total of 65 children completed the protocol. Sixty-three of those were under the age of 4 years. Treatment failure was defined as two or more episodes of AOM or otorrhea in less than 3 months. Five of 22 children in the tympanostomy tube group failed, compared to 12 of 20 in the placebo group (p = .02). There were 8 or 21 treatment failures in the sulfisoxazole group. Children with otitis media with effusion (OME) at the time of their initial visit had significantly less middle ear disease when treated with tympanostomy tubes. Tympanostomy tube insertion for prophylaxis of recurrent acute otitis is supported by these findings. Improvement of recurrent AOM was observed in the sulfisoxazole group, but was not statistically significant.

Child, Preschool↗
PubMed1985

Correlation between adenosine triphosphate levels, dopamine release and electrical activity in the carotid body: support for the metabolic hypothesis of chemoreception.

An unsolved issue for the arterial chemoreceptors is the mechanism by which hypoxia and other natural stimuli lead to an increase of activity in the carotid sinus nerve. According to the 'metabolic hypothesis', the hypoxic activation of the carotid body (CB) is mediated by a decrease of the ATP levels in the type I cells, which then release a neurotransmitter capable of exciting the sensory nerve endings. Using an in vitro preparation of cat CB, we report that ATP levels in the CB do in fact decrease when the organs are exposed to moderate, short lasting hypoxia (5 min 20% O2). Additionally, we found that decreases in ATP levels induced by 2-deoxyglucose (2 mM) or sodium cyanide (0.1 mM) are closely correlated with dopamine release from type I cells and electrical activity in the carotid sinus nerve elicited by these agents. The possible cause-effect relationship of these events is discussed.

Adenosine Triphosphate↗
PubMed1985

Localization and function of cat carotid body nicotinic receptors.

Acetylcholine and nicotinic agents excite cat carotid body chemoreceptors and modify their response to natural stimuli. The present experiments utilized [125I]alpha-bungarotoxin [( 125I]alpha-BGT) to localize within the chemosensory tissue the possible sites of action of exogenous and endogenous nicotinic cholinergic substances. In vitro equilibrium binding studies of intact carotid bodies determined a Kd of 5.57 nM and a Bmax of 9.21 pmol/g of tissue. Chronic section (12-15 days) of the carotid sinus nerve (CSN) did not change the amount of displaceable toxin binding. In contrast, the specific binding was reduced by 46% following removal of the superior cervical ganglion. Light microscope autoradiography of normal, CSN-denervated and sympathectomized carotid bodies revealed displaceable binding sites concentrated in lobules of type I and type II cells. Treatment of carotid bodies with 50 nM alpha-BGT in vitro reduced by 50% the release of [3H]dopamine (synthesized from [3H]tyrosine) caused by hypoxia or nicotine, and also significantly reduced the stimulus-evoked discharges recorded from the CSN. The data suggest an absence of alpha-BGT binding sites on the afferent terminals of the CSN and that nicotinic receptors located with parenchymal cell lobules may modulate the release of catecholamines from these cells.

Animals↗
PubMed1985

Carbonic anhydrase in the carotid body and the carotid sinus nerve.

It is well known that carbonic anhydrase plays an important role in the physiological responses of carotid-body chemoreceptors to hypercapnia. Nevertheless the precise location of the enzyme within the carotid body has been a matter of controversy for many years. Using the Hansson method we found histochemical evidence that this enzyme is localized in type I cells. Type II cells and nerve terminals did not show enzymatic activity. These results allow us to define the carotid body as a secondary receptor in the context of the "acidic hypothesis" of transduction in the carotid body.

Animals↗