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Biomedical subjects

C Larraín

Publications and source records attributed to C Larraín.

At least 19 recordsLinked to original sources
PubMed2006

Carotid body chemosensory activity and ventilatory chemoreflexes in cats persist after combined cholinergic-purinergic block.

Acetylcholine (ACh) and ATP have been proposed as excitatory co-transmitters operating at synapses between glomus cells and sensory nerve endings of the carotid body (CB). To test such hypothesis, we performed experiments on cats under pentobarbitone anesthesia and breathing spontaneously. Cholinergic and purinergic agonists and antagonists were given into one common carotid artery. Chemoreflex ventilatory changes initiated from the ipsilateral CB or chemosensory activity from the ipsilateral carotid nerve were recorded. Agonists ACh, nicotine, epibatidine, ATP, betagamma-methylene-ATP and gammaS-ATP induced transient chemoreflex enhancements of ventilation or increased chemosensory activity. When given in combination, mecamylamine and suramin suppressed both nicotine- and ATP-induced ventilatory chemoreflexes or chemosensory responses. However, neither chemoreflex hyperventilation induced by brief hypoxic exposures or steady-state hypoxic levels, nor chemosensory excitation elicited by these maneuvers were eliminated. Asphyxia-induced chemosensory excitation was not reduced by combined blockade of ACh and ATP receptors. Furthermore, ventilatory or chemosensory depression evoked by 100% O2 tests was unmodified, thus evidencing that basal chemosensory drive in normoxia was not suppressed by combined cholinergic-purinergic blockade. Therefore, although ACh and ATP may participate in chemoexcitation of the CB, their involvement fails to explain the origin of chemosensory discharges from synaptic transmission between glomus cells and chemosensory nerve endings of the CB.

Acetylcholine↗
PubMed2006

Effects of combined cholinergic-purinergic block upon cat carotid body chemoreceptors in vitro.

Since acetylcholine (ACh) and ATP have been proposed as excitatory co-transmitters at synapses between glomus cells and sensory nerve endings of the carotid body (CB), we tested such hypothesis by studying the effects of combined cholinergic-purinergic block on the chemosensory activity recorded from cat's carotid bodies perfused and/or superfused in vitro. The preparations were bathed with Tyrode's solution, either normoxic (PO2=98.5+/-13.5 Torr) or hypoxic (PO2=31.8+/-5.2 Torr), and the frequency of chemosensory impulses (fchi) was recorded from the carotid (sinus) nerve. Dose-response curves for fchi increases evoked by intra-stream boluses of acetylcholine, nicotine and ATP were studied. A combination of mecamylamine 2 microM and suramin 50 microM, applied through the perfusate or superfusate, suppressed nicotine- and ATP-induced increases in fchi, but the basal chemosensory activity in normoxia and the chemosensory excitation elicited by hypoxic superfusion were preserved, although variably reduced in most preparations. Thus, in spite of the excitatory effects provoked by applying ACh and ATP to the perfused/superfused CB in vitro, a co-release of these substances cannot account entirely for the chemosensory excitation induced by hypoxic stimulation of the CB.

Acetylcholine↗
PubMed1999

[A tribute to Professor Mario Plaza de los Reyes, MD].

Revista Médica de Chile renders a tribute to Professor Mario T Plaza de los Reyes, one of the founders of Nephrology as a specialty in Chile, a brilliant teacher and scholar. As Member of the Sociedad Médica de Santiago (Chilean Society of Internal Medicine) and former President (1964-1965) he had an active role as contributor, reviewer and reader of our journal.

Chile↗
PubMed1998

[Contribution of Professor Armando Roa to humanities and medical ethics at the University of Chile's School of Medicine].

Dr. Roa was the first professor of the Faculty of Medicine of the University of Chile to give an ethics course to medical students, even when the importance of formal teaching of medical ethics was not yet recognized internationally. His efforts contributed to the creation of the Center for Bioethical and Humanistic Studies in 1988 and to the creation of official ethics courses for first and sixth year medical students in 1993. During 20 years, be chaired the Ethics Committee of the Faculty of Medicine of the University of Chile. He also promoted a diffusion program about medical ethics through meetings, conferences and symposia. He was responsible for the Ministry of Health's decision to create ethics committees in public hospitals in 1988 and for the Presidental decision about organ transplantation in 1995. He carried out anthropology courses and gave numerous lectures on humanistic aspects of medicine. His ethical principles are resumed in what he called the "ethics of generosity", in which the dignity of human beings is respected above all, in his opinion, the way civilizations see goodwill has been preponderant in the course of history. The recent proposal to teach humanistic fundamentals to medical students is a tribute to the memory of Professor Roa.

Chile↗
PubMed1995

[Adult cyclic neutropenia: acute ileitis as an initial clinical manifestation].

Cyclic neutropenia is a rare disease in which blood neutrophils periodically decrease and almost disappear, ensuing acute infections of variable severity. We report a 37 years old female presenting with severe abdominal pain, fever and neutropenia. During a surgical abdominal exploration, an acute ileitis was found. During a follow-up of 6.5 months, transient episodes of neutropenia (mean count of 0.33 x 10(9)/l), every 22-28 days, were detected. Coinciding with these episodes, band and segmented neutrophils disappeared from the bone marrow and its response to functional stimulation with prednisone was insufficient. No cyclical changes in lymphocytes, monocytes and packed red cell volume were observed. The episodes of severe transient neutropenia and infections persist after three years of follow up.

Acute Disease↗
PubMed1994

Effects of dopaminergic blockade upon carotid chemosensory activity and its hypoxia-induced excitation.

The effects of domperidone, antagonist of D2 receptors, on arterial chemoreceptor activity were studied in spontaneously breathing and pentobarbitone anesthetized cats, in which recordings of chemosensory impulse activity were obtained simultaneously from both cut carotid (sinus) nerves. Intravenous injections of domperidone 50 micrograms/kg produced a maintained increase in the basal frequency of chemosensory discharges, after which hyperoxic tests (breathing 100% O2 for 30 s) evoked larger falls in the rate of chemosensory impulses. Chemosensory responses evoked by hypoxic hypoxia (100% N2 tests) and by cytotoxic hypoxia (i.v. injections of NaCN) reached higher impulse rates after domperidone treatment. The effects of domperidone reveal that a resting release of dopamine from glomus cells maintains a low level of basal chemosensory activity under normoxic conditions. Domperidone turns off such restraining dopaminergic control and enhances the transient chemosensory responses to hypoxic stimuli. Present data support a modulatory role for dopamine within the chemoreceptor process, but not its participation as excitatory transmitter between glomus cells and sensory nerve endings.

Animals↗
PubMed1994

[Congenital blood coagulation factor X deficiency. Successful result of the use prothrombin concentrated complex in the control of ++cesarean section hemorrhage in 2 pregnancies].

There is little experience in the prevention of the severe hemorrhagic diathesis of factor X coagulation factor deficiency, before surgical procedures. A female with congenital deficiency of factor X that received prothrombin complex concentrates that contained 1.000 IU of factor X (16.7 U/l Kg BW) immediately prior to a cesarean section in two occasions, is reported. Factor X concentration rose from 1 to 25% in the first occasion and from 10 to 63% in the second. In both episodes, factor X decreased in the first 24 h of the postoperative period and required new infusions of prothrombin complex concentrates. No episodes of abnormal bleeding were observed. It is concluded that the infusion of prothrombin complex concentrates prevents the hemorrhagic diathesis of factor X deficiency, despite its modest increase in plasma. A initial infusion of 1.000 UI of factor X (16-20 IU/Kg BW), followed by 500 IU (8-10 IU/Kg) every 24 hours is suggested for an adequate management of this condition.

Adult↗
PubMed1992

Severe hemorrhagic syndrome secondary to active circulating inhibitors of the intrinsic phase of blood coagulation in 3 patients.

The study of three adults with severe bleeding due to the presence of acquired anticoagulants that inhibit procoagulant action of Factor VIII and to a lesser degree of factors IX and XI, is described. In one case, this phenomenon occurred during the course of a rheumatoid arthritis, in one case coincided with a megaloblastic anemia (pernicious anemia) and the last case did not have any coexisting disease. Corticosteroids were useless, intravenous cyclophosphamide improved one patient and given orally failed in other patient. The circulating inhibitor disappeared in the patient successfully treated with cyclophosphamide and persisted and was the cause of death in the other two patients. In one patient, column fractioning demonstrated that the anticoagulant was an G immunoglobulin, with higher activity at pH 6.5.

Aged↗
PubMed1991

[Present status of cancer treatment].

Cancer is the second cause of mortality in Chile: 12,000 deaths and 27,000 admissions were registered during 1982. Gastric and pulmonary cancer account for the highest mortality rates (23.2 and 9.7/100,000). Cancer prognosis has improved in thyroid, uterus and testes cancers, melanoma, Hodgkin's Disease etc, with 67 to 92% 5-year survival rates, while results are not as good in lung, gastric, colorectal, kidney, pancreas, etc, with only 3 to 52% 5-year survival rates. Treatment failure is attributed to cellular mutations and early metastases. At present, surgery is less aggressive and is associated to radiotherapy and chemotherapy; megavoltage radiation equipment and the use of radiosensitizers allow double radiation dose; chemotherapy complications are avoided with hematopoietic growth factors. It is possible to improve the prognosis of lung cancer avoiding the use of tobacco and of colorectal cancer reducing fats in the diet of these pts. Early detection and better chemotherapy have improved the prognosis of breast and uterus cancer. With these measures a 20 to 50% reduction in cancer rates is expected in the USA for the year 2000. Their application is urgent in our country.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1990

[Platelet labelling with In-111-oxine: platelet survival and the images].

We studied 10 male and 2 female normal non-smoker volunteers (mean age 25) by labeling of autologous platelets with 111-In oxine. Daily samples for platelet survival were obtained in all, gamma-camera images in 10 and blood pool digital subtraction with 99m-Tc labeled erythrocytes in 6. Mean platelet count was 594 +/- 235 10(3)/mm3; collagen platelet aggregation pre and post labeling was 74 +/- 4.8 and 70 +/- 10%, respectively. Mean labeling efficacy was 65 +/- 15.4%, mean labeling dose was 201 +/- 79.5 microCi. A linearized initial survival of 7.9 +/- 1 day was obtained. Scintigraphic images showed circulating activity, greater in the spleen, persisting after digital subtraction. The method described can be used for clinical evaluation of platelet disorders and thrombosis.

Adult↗
PubMed1989

[Cytogenetic study of acute and chronic leukemias].

From 1983 to 1987 we studied 30 patients with leukemia searching for chromosomal alterations. Cytogenetic studies of bone marrow showed an abnormal karyotype in 19 (67%). Seven out of 14 cases of acute leukemia presented different chromosomic alterations. The Philadelphia chromosome was found in 11 patients with chronic myeloid leukemia and 3 patients with chronic lymphatic leukemia; a Pseudo-Philadelphia chromosome was present in one patient, this being the first such finding in Chile. Thus, the karyotype is a valuable complementary study not only in chronic myeloid leukemia but also in chronic lymphatic leukemia and the acute lymphoblastic and non-lymphoblastic varieties.

Adolescent↗
PubMed1989

Correlative contribution of carotid and aortic afferences to the ventilatory chemosensory drive in steady-state normoxia and to the ventilatory chemoreflexes induced by transient hypoxia.

The contributions of the peripheral arterial chemoreceptors to the tonic and phasic reflex ventilatory regulation were studied in spontaneously breathing pentobarbitone anesthetized adult cats. The chemosensory drive during eucapnic normoxia was inferred from the transient ventilatory effects induced by anesthetic blockade of the buffer nerves. Aortic nerves block did not modify ventilation. Carotid nerves block provoked transient ventilatory depression, decreasing VT by 46% and fR by 26%, followed by recovery to steady-state values in VT, fR and PETCO2. Changes in PETCO2 were correlated with those in VT, but not with those in fR. The ventilatory effects of blocking a given carotid nerve were more intense when the contralateral carotid nerve was already blocked. This effect may be an expression of hypoadditive interactions between carotid nerves inputs with respect to chemosensory drive of ventilation. Analysis of the dose-response curves for the ventilatory reflexes evoked by NaCN i.v., before and after blockade of the buffer nerves, revealed major contributions of the carotid nerves, with small contributions of the aortic nerves to the those responses to high doses of NaCN. The contributions of each carotid nerve to the tonic chemosensory drive and to the phasic ventilatory chemoreflexes were highly correlated (rs = 0.90; p less than 0.01). We propose that a family of modulatory functions may describe the effects exerted by the peripheral arterial chemoreceptors upon the tonic ventilatory drive in normoxia and the phasic reflex responses evoked by hypoxia. While the carotid nerves mediated modulation is evident in normoxia, that provided by both aortic nerves is only expressed during pronounced hypoxia.

Afferent Pathways↗
PubMed1989

[Hematologic changes in anorexia nervosa].

We studied the hematologic values of 25 patients with anorexia nervosa. Age ranged from 12 to 38 years and 22 were females. Mean hematocrit was decreased to 36% and total leukocyte count to 4.400/microliters. Anemia was diagnosed in 13 patients. It was normocytic in 7 hypochromic microcytic in 7 and megaloblastic in 2. Seven of these anemic patients corrected their anemia with the treatment of anorexia nervosa, 3 required iron supplement and 2 folic acid. Bone marrow studies in 23 patients demonstrated hypoplasia in 17. Four patients had global bone marrow hypoplasia with decreased numbers of erythroblasts and megakaryocytes. A mucopolysaccharide substance substituted for a decreased fat content of bone marrow. A decreased bone marrow reserve of neutrophils and their margination in blood vessels contributed to leukopenia, which was not associated to an increased number of infections. Blood coagulation tests and platelet aggregation were normal.

Adolescent↗