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Biomedical subjects

G Gonzalez

Publications and source records attributed to G Gonzalez.

At least 109 records · Page 6Linked to original sources
PubMed1989

Adrenergic interactions in uterus and vascular smooth muscle in rats in vivo.

Simultaneous blood pressure and uterine responses to norepinephrine infusions were recorded in urethane-anesthetized, pentolinium-indomethacin treated rats in natural estrus under conditions in which no blockers or blockers of alpha 1-, alpha 2-, and beta-adrenergic receptors or of "reuptake" of norepinephrine were present. The contributions of alpha 1- and alpha 2-adrenergic receptors to the blood pressure response were similar during the initial portion of the response. At later times, however, alpha 1-adrenergic receptors were responsible for the major portion of the response. The tachyphylaxis of the pressor response that occurs during norepinephrine infusion could be prevented by preventing norepinephrine "reuptake" with imipramine. In the uterus, the initial small alpha-adrenergic contractile response (seen only at the lowest infusion rate) was quickly overwhelmed by a beta-adrenergic relaxing component. Administration of the beta-adrenergic receptor blocker, propranolol, during norepinephrine infusion caused similar increases in blood pressure in control, yohimbine-, and prazosin-treated rats. Uterine contractions, in contrast, were only significantly elevated during beta-adrenergic receptor blockade when yohimbine or imipramine had also been administered.

Adrenergic alpha-Agonists↗
PubMed1989

Calibration of respiratory inductive plethysmograph during natural breathing.

We describe a single-posture method for deriving the proportionality constant (K) between rib cage (RC) and abdominal (AB) amplifiers of the respiratory inductive plethysmograph (RIP). Qualitative diagnostic calibration (QDC) is based on equations of the isovolume maneuver calibration (ISOCAL) and is carried out during a 5-min period of natural breathing without using mouthpiece or mask. In this situation, K approximates the ratio of standard deviations (SD) of the uncalibrated changes of AB-to-RC volume deflections. Validity of calibration was evaluated by 1) analyzing RIP waveforms during an isovolume maneuver and 2) comparing changes of tidal volume (VT) amplitude and functional residual capacity (FRC) level measured by spirometry (SP) with RIP values. Comparisons of VT(RIP) to VT(SP) were also obtained in a variety of postures during natural (uninstructed) preferential RC and AB breathing and with voluntary changes of VT amplitude and FRC level. VT(RIP)-to-VT(SP) comparisons were equal to or closer than published reports for single posture, ISOCAL, multiple- and linear-regression procedures. QDC of RIP in supine posture with comparisons to SP in that posture and others showed better accuracy in horizontal than upright postures.

Calibration↗
PubMed1989

Sonography of the painful hip in children: 500 consecutive cases.

Five hundred children with a painful hip or a limp were evaluated prospectively by plain films and sonography. The clinical, radiographic, and sonographic findings were correlated with the final diagnoses. Sonography disclosed hip effusion in 235 patients, and plain films were abnormal in 58 of these 235 patients and in four others. Both sonography and plain films were normal in 261 patients. No sonographic signs served to differentiate sterile, purulent, or hemorrhagic effusion. Follow-up sonograms were performed in 202 patients. Sonography showed that 73% of patients with presumed transient synovitis had no effusion 2 weeks after diagnosis. Patients with hip disorders other than transient synovitis had persistent effusion for more than 2 weeks; however, that was also observed in 27% of patients with presumed transient synovitis. Sonography was more sensitive than plain films for detecting hip effusion. However, sonographic detection of effusion changed the therapeutic approach in only six patients.

Adolescent↗
PubMed1989

Occupational injuries suffered by flight attendants while on board.

Inflight occupational injuries suffered by flight attendants are an important cause of medical disabilities. Mexicana Airlines has made an evaluation of this problem from 1983 to 1987. The injuries most frequently observed were contusions, skin cuts, sprains, fractures, spine disorders, and severe barotitis. The anatomic regions commonly affected were the hands, feet, and spine. These injuries are responsible for 15,573 work days lost for the average of 1,631 flight attendants. This study identified some unsafe actions and conditions in the flight attendants' working environment. The company has initiated an extensive training program to avoid unsafe actions and to eliminate certain unsafe conditions where possible.

Absenteeism↗
PubMed1988

Treatment of retinoblastoma. Results obtained from a prospective study of 51 patients.

During 4 years, 51 patients with retinoblastoma were studied (unilateral 32, and bilateral 19). Treatment consisted of enucleation of those eyes which showed massive involvement followed by radiotherapy when there was optic nerve and/or orbit involvement. Systemic chemotherapy was administered to all patients who underwent nonsurgical treatment and when the histologic examination showed choroidal optic nerve head and/or optic nerve involvement or residual tumor after enucleation. When there was compromise of the central nervous system intrathecal chemotherapy was administered. Nonsurgical treatment consisted of radiotherapy and/or light coagulation. Survival was 90.6% for unilateral cases and 84.2% for the bilateral. The median follow-up was 31 months and 29 months, respectively. Of 19 conservated eyeballs, 16 preserve useful vision (63%).

Antineoplastic Agents↗
PubMed1988

Verapamil blockade of pressor and uterine responses to AVP-OT analogue, oxypressin.

The effects of the calcium channel blocker verapamil on simultaneously recorded uterine and pressor responses to the equipotent (in eliciting these responses) oxytocin-vasopressin analogue, oxypressin, were studied in urethan-anesthetized and pentolinium- and indomethacin-treated rats during injections and infusions of this analogue. Doses of verapamil that almost completely blocked the pressor response to infused oxypressin had no effect on a pressor response to injected oxypressin of equal magnitude. Larger doses of verapamil blocked the pressor response to injected oxypressin somewhat. Uterine responses were only marginally affected by these doses of verapamil, and there was no significant difference between infusion and injection or between estrus and diestrus.

Animals↗
PubMed1987

In vivo simultaneous comparison of pressor and uterine responses to a single agonist (oxypressin) in estrous rats.

To try to compare receptor compartment kinetics, receptor binding, and binding-response coupling for two smooth muscle types in vivo, pressor and uterine responses to oxypressin, an equipotent analog of oxytocin and vasopressin, were studied simultaneously in urethane-anesthetized, pentolinium-indomethacin treated rats. Access of peptide to the pressor and uterine receptor compartments and peptide-receptor dissociation rate had a negligible effect on the two responses. During both injections and infusions, the blood pressure response seemed to be determined largely by plasma levels of oxypressin. The uterine response to oxypressin, however, was paradoxical. The heights of individual uterine contractions seemed to be determined throughout by plasma oxypressin concentrations. The interval between contractions also seemed to be determined by plasma peptide concentrations during injections. However, as plasma peptide increased and reached steady state during infusion, contraction interval behaved as if plasma peptide concentrations were decreasing. This effect was more marked at the beginning of infusion. The implication of these results is that binding determines the pressor response to oxypressin and binding-response coupling does not change. In contrast, although binding determines the uterine response to oxypressin during injection and binding-response coupling appears constant, some factor in addition to binding affects the contraction interval portion of the uterine response and modifies the apparent binding-response coupling of this parameter during infusion.

Animals↗
PubMed1987

Human T-cell lymphotropic virus-III (HTLV-III) seropositivity and related disease among 71 consecutive patients in whom tuberculosis was diagnosed. A prospective study.

The incidence of tuberculosis has recently risen in Southeast Florida. In order to determine the number and proportion of tuberculosis cases and the characteristics of tuberculosis that might be related to human T-cell lymphotrophic virus-III (HTLV-III) infection, all patients seen by the Dade County Florida Public Health Department-Tuberculosis Clinic during a 6-month period were medically evaluated and screened for HTLV-III antibody by an enzyme-linked immunosorbent assay. Of 71 consecutive patients confirmed to have tuberculosis (70 by culture) during the study period, 22 (31%) were seropositive and 49 (69%) were seronegative for HTLV-III antibody. The seropositive group had a significantly higher proportion of patients who were black, Haitian, and within the age group of 25 to 44 yr. The seropositive group also had a significantly higher rate of mild-to-moderate serum aspartate transaminase elevations (less than or equal to 5 times normal), tuberculin skin test false negativity, extrapulmonary tuberculosis (especially lymphatic), and pulmonary tuberculosis with an atypical radiographic picture. The seropositive group had a significantly lower proportion of patients with sputum cultures positive for M. tuberculosis. There was no significant difference between the groups with respect to the proportion of patients with positive sputum smears when sputum cultures were positive, serious antituberculosis drug reactions (requiring discontinuation of therapy), or percent of home contacts who were tuberculin skin tested and found to be positive. At the time of the diagnosis of tuberculosis, only 6 (27%) of the seropositive patients with tuberculosis had clinical evidence of AIDS or AIDS-related complex (unexplained thrush).(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1986

Intranuclear crystalloids in arcuate nucleus neurons after clomiphene citrate administration.

The action of high doses of clomiphene citrate on the nuclei of hypothalamic arcuate neurons of male cats has been studied. Clomiphene produces an accumulation of typical crystalloid material in the nuclei. After administration of a protein-synthesis inhibitor, no such material was observed in clomiphene-treated animals. These ultrastructural features could possibly be due to a more intense protein synthesis in the hypothalamic arcuate neurons.

Animals↗
PubMed1986

Off-center spherical model for dosimetry calculations in chick brain tissue.

This paper presents calculations for the electric field and absorbed power density distribution in chick brain tissue inside a test tube, using an off-center spherical model. It is shown that the off-center spherical model overcomes many of the limitations of the concentric spherical model, and permits a more realistic modeling of the brain tissue as it sits in the bottom of the test tube surrounded by buffer solution. The effect of the unequal amount of buffer solution above the upper and below the lower surfaces of the brain is analyzed. The field distribution is obtained in terms of a rapidly converging series of zonal harmonics. A method that permits the expansion of spherical harmonics about an off-center origin in terms of spherical harmonics at the origin is developed to calculate in closed form the electric field distribution. Numerical results are presented for the absorbed power density distribution at a carrier frequency of 147 MHz. It is shown that the absorbed power density increases toward the bottom of the brain surface. Scaling relations are developed by keeping the electric field intensity in the brain tissue the same at two different frequencies. Scaling relations inside, as well as outside, the brain surface are given. The scaling relation distribution is calculated as a function of position, and compared to the scaling relations obtained in the concentric spherical model. It is shown that the off-center spherical model yields scaling ratios in the brain tissue that lie between the extreme values predicted by the concentric and isolated spherical models.

Animals↗