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Biomedical subjects

C Monge

Publications and source records attributed to C Monge.

At least 19 recordsLinked to original sources
PubMed1996

Hemoglobin affinity and structure in high-altitude and sea-level carnivores from Peru.

We compared hemoglobin affinity (P50) and structure of high altitude (HA) carnivores with populations of the same species or genus living at sea level (SL). P50 was measured in cats, pumas and foxes. It differed in animals occupying both niches. SL: cat 29.3 torr, puma 36.3 torr, fox 26.2 torr; HA: cat 22.5 torr, puma 31.1 torr, fox 18.5 torr. Heme and globins were fractionated by HPLC. Puma and fox hemoglobins also showed structural differences. P50 is lower in genotypically HA-adapted species studied and can differentiate SL and HA populations of the same species.

Altitude↗
PubMed1994

Similarity of PO2 and PCO2 values in the air cell of eggs of birds and in the alveolar gas of humans at sea level and at high altitude.

At the end of incubation, the partial pressures of oxygen and carbon dioxide in the air cell of sea-level avian eggs are similar to those in the expiratory air of adult birds. At high altitude, changes in the permeability of the shell and probably in the embryo metabolism partially compensates the increase in the gas diffusion constant resulting from the low barometric pressure. The aim of this study was to test whether--despite of the adaptive responses of the high altitude avian embryo--the air cell values would be similar to those of the alveolar air of high altitude human natives. Air cell O2 (48.3 +/- 1.6 torr) and CO2 (20.9 +/- 0.85 torr) pressure values were obtained by studying naturally incubated eggs of the Andean gull (Larus serranus) at 4650 m. Sea-level chicken (Gallus gallus) air cell pressure values of O2 (102.3 +/- 2.7 torr) and of CO2 (43.3 +/- 1.3 torr) were obtained from the literature for comparison. Both these values were similar to those found in the alveolar air of humans at sea level (O2: 104.4 +/- 0.4 torr, CO2: 40.1 +/- 0.25 torr) and at high altitude (4540 m) (O2: 50.5 +/- 0.53 torr, CO2: 29.1 +/- 0.37 torr). Despite very large evolutionary changes in morphology and physiology of the respiratory organs, the head pressure of O2 that oxygenates the blood keeps a constant value in the pre-pipping avian embryo and in the alveolar air of adult mammals. This constancy holds valid at high altitude.

Altitude↗
PubMed1994

Inhibitory effect of an alpha 1-adrenergic antagonist on erythropoiesis in normoxic or hypoxic mice.

The present study was undertaken to assess the effect of prazosin, a selective postsynaptic alpha 1-adrenergic receptor blocking agent, on normoxic and hypoxic mice, in order to evaluate experimentally its use in the treatment of the excessive erythrocytosis that characterizes chronic mountain sickness. The drug, injected intraperitoneally to adult mice at a dose of 400 micrograms/kg per day, induced a significant depression of the rate or erythropoiesis, as measured by red blood cell 59iron uptake, with a decrease in the hematocrit from the 3rd day. The drug also inhibited the oxygen-dependent secretion of erythropoietin (estimated by the plasma immunoreactive hormone concentration) in hypoxemic mice when injected between 0 and 2 h after initiation of the hypoxic stimulation. When injected daily into mice exposed to intermittent hypobaric hypoxia, prazosin limited the degree of polycythemia or induced a sustained decrease in the hematocrit when polycythemia was already present due to previous exposure. It is postulated that the drug, by reducing the peripheral vascular resistance seen during hypoxia, could increase renal blood flow, thus improving the renal oxygen supply and partially restoring the imbalance between gas supply and demand, which drives erythropoietin formation.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed1994

Bone marrow oxygen consumption and erythropoiesis in chronically hypoxic rats.

Bone marrow oxygen consumption (VO2) was determined weekly in 16 Holtzman rats exposed to continuous hypobaric hypoxia (CHH) during 30 days. The results were compared with those obtained in 10 sea level control animals (SL). The VO2 expressed as ng.at.O2/min, decreased progressively with time of exposure to hypoxia. VO2 (mean +/- SD) was 0.0936 +/- 0.135 in SL rats. In CHH animals, it was 0.1001 +/- 0.0292 after 8 days of hypoxia, 0.1030 +/- 0.0206 after 16 days, 0.0594 +/- 0.0148 (p = 0.002) after 24 days and 0.0136 +/- 0.404 (p = 0.000) after 30 days. Protein concentration in bone marrow was progressively higher in hypoxics when compared to control, with significant differences since the first week of exposure. Blood hemoglobin increased in parallel to protein concentration in the bone marrow. These findings suggest an increase in the cells of the erythroid series whose oxygen consumption is less than cells in the early stages of differentiation. The increased protein concentration is in agreement with the fact that globin mRNA appears in cells with a progressively increasing anaerobic metabolism at relatively late stages of erythropoiesis.

Animals↗
PubMed1994

Ventilatory response to severe acute hypoxia in guinea-pigs and rats with high hemoglobin-oxygen affinity induced by cyanate.

Baseline ventilation, hemoglobin concentration (Hb) and P50 were significantly lower in guinea-pigs than in rats. Chronic sodium cyanate (NaOCN) administration did not significantly increase hemoglobin concentration in either guinea-pigs or rats. It decreased the P50 significantly less in guinea-pigs than in rats. The high Hb-O2 affinity experimentally induced did not modify the hypoxic ventilatory response (HVR) of guinea-pigs and rats. At the same level of acute hypoxia, HVR was significantly lower in NaOCN guinea-pigs than in NaOCN rats. Guinea-pigs, genotypically adapted animals to high altitude, displayed relatively minor ventilatory and Hb-O2 affinity changes to NaOCN, and a relatively minor HVR to acute hypoxia. They probably use tissue and biochemical adaptive mechanisms, in addition to their limited extracellular responses to successfully tolerate ambient hypoxia.

Acute Disease↗
PubMed1993

High altitude tissue adaptation in Andean coots: capillarity, fibre area, fibre type and enzymatic activities of skeletal muscle.

Capillarity, fibre types, fibre area and enzyme activities of different skeletal muscles (pectoralis, extensor digitorum longus), tibialis anterior, plantaris and the myocardium) were compared in Andean coot (Fulica americana peruviana) native to high altitude (Junín, Perú, 4200 m) and the same species nesting at sea level. Numbers of capillaries per square millimeter were higher in all high-altitude muscles when compared with sea-level muscles (P < 0.0001). Moreover, values for capillaries per fibre and capillaries in contact with each fibre were higher in digitorum and tibialis high-altitude muscles. Muscle fibres were classified as Type I, Type IIA or Type IIB on the basis of their myofibrillar ATPase pH lability. Pectoralis muscle of high-altitude and sea-level coots presented only fibres of Type IIA. In contrast, all the leg muscles studied showed a mosaic pattern of the three fibre types. Fibre areas were determined using a Leitz Texture Analysis System. Significant differences in fibre area were observed (P < 0.01) between high-altitude and sea-level muscles. Mean muscle fibre diameters were also lower in the high-altitude group than in the sea-level group. The enzyme activities studied were hexokinase, lactate dehydrogenase, citrate synthase and 3-hydroxyacyl-CoA-dehydrogenase. The oxidative capacity, as reflected by citrate synthetase and hydroxyacyl-CoA-dehydrogenase activities, was greater for myocardial and pectoralis than for leg muscles. However, analysis of maximal enzyme activities showed that there were no significant differences between the glycolytic and oxidative enzyme activities of high-altitude and sea-level coots.(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed1993

Blood gases, pH and hematology of montane and lowland coot embryos.

Blood gases, air cell-blood gas differences, blood pH, and hematology were compared in embryonic coots (Fulica americana peruviana) at 4150 m and sea level in Peru. Neither arterialized nor venous O2 tensions differed significantly between montane and lowland groups but blood CO2 tensions of the two groups differed significantly. The air cell PO2-arterialized blood PO2 difference of montane eggs was less than half the value in lowland eggs. Both arterialized and venous CO2 tensions differed substantially between montane and lowland groups. Despite these differences, plasma pH at both altitudes was statistically indistinguishable, due in part to variation in plasma [HCO3-]. Hematocrits of montane embryos were significantly higher than that of their lowland counterparts.

Altitude↗
PubMed1992

Effects of cocaine on oxygen consumption and mitochondrial respiration in normoxic and hypoxic mice.

The administration of cocaine hydrochloride intraperitoneally (25 mg/kg) produces a drop in VO2 in both normoxic and hypoxic mice. The critical PO2 is also decreased and so is the body temperature. The mitochondrial respiration shows a large fall in ST3 and RCR. The addition of cocaine in-vitro to the incubating medium induces changes in the mitochondrial respiration similar to those found after in-vivo administration. This report shows that in addition to its in-vivo actions cocaine alters the respiratory function of the isolated liver mitochondria.

Animals↗
PubMed1992

Enzyme mechanisms for pyruvate-to-lactate flux attenuation: a study of Sherpas, Quechuas, and hummingbirds.

During incremental exercise to fatigue under hypobaric hypoxia, Andean Quechua natives form and accumulate less plasma lactate than do lowlanders under similar conditions. This phenomenon of low lactate accumulation despite hypobaric hypoxia, first discovered some half century ago, is known in Quechuas to be largely unaffected by acute exposure to hypoxia or by acclimatization to sea level conditions. Earlier Nuclear Magnetic Resonance (NMR) spectroscopy and metabolic biochemistry studies suggest that closer coupling of energy demand and energy supply in Quechuas allows given changes in work rate with relatively modest changes in muscle adenylate and phosphagen concentrations, thus tempering the activation of glycolytic flux to pyruvate--a coarse control mechanism operating at the level of overall pathway flux. Later studies of enzyme activities in skeletal muscles of Quechuas and of Sherpas have identified a finely-tuned control mechanism which by adaptive modifications of a few key enzymes apparently serves to specifically attenuate pyruvate flux to lactate.

Adaptation, Physiological↗
PubMed1991

Metabolic effects of cyanate on mice at sea level and in chronic hypobaric hypoxia.

In order to evaluate the toxic effects of Sodium Cyanate (NaOCN), it was orally administered to growing mice at sea level (SL-CN) and to mice chronically exposed to intermittent hypobaric hypoxia (IHH-CN). The effects on body weight, in-vivo O2 consumption (VO2) and the respiratory function of liver mitochondria were evaluated. At sea level, the animals on cyanate lost weight in contrast with the controls that gained weight. When exposed to IHH, the controls lost weight and the animals on cyanate regained weight. After 2 months observation the weights of the IHH-CN and IHH-C were similar. The VO2 after one month of treatment was similar in the SL-C and in the SL-CN but it was lower in the IHH-CN when compared with IHH-C. The substrate-stimulated respiration of isolated liver mitochondria (ST4) was not affected by NaOCN, but the ADP-stimulated respiration (ST3) was reduced. The ratio ST3/ST4 (RCR) was also lower. These changes were present in both SL and in IHH and were much larger after three months of treatment. The toxic effects of chronic administration of NaOCN are discussed.

Administration, Oral↗
PubMed1991

A genetic response to high altitude hypoxia: high hemoglobin-oxygen affinity in chicken (Gallus gallus) from the Peruvian Andes.

A population of chicken (Gallus gallus) from the Peruvian Andes (4,000 m) carrying a high hemoglobin-oxygen affinity has been identified. This property remained stable after over 1 year residence at sea level and was transmitted to the descendants born at sea level. Chicken were introduced in South America during the Spanish conquest and therefore their adaptation time to high altitude is less than 500 years. This finding shows that a genotypic change in hemoglobin function can occur in an extremely short evolutionary time and leads to some reflections on the high altitude adaptation of the mammals that migrated to South America during the great Plio-Pleistocene interchange.

Altitude↗
PubMed1987

Shell conductance, daily water loss, and water content of Andean gull and Puna ibis eggs.

Characteristics of Andean gull (Larus serranus) and Puna ibis (Plegadis ridgwayi) eggs laid at 4,400 m in the Peruvian Andes were studied to determine how the conflicting requirements of maximizing O2 availability to the embryo while minimizing excessive losses of water vapor and CO2 have been met by avian populations breeding at high altitudes. Egg masses, linear dimensions, and surface areas of these montane eggs were similar to those of Heermann's gull (Larus heermanni) and glossy ibises (Plegadis falcinellus), but conductance to water vapor (GH2O, standardized to 760 torr) of Andean gull and Puna ibis eggs averaged 74.5% and 68.4%, respectively, of lowland values. The difference in GH2O of Andean gull eggs was caused primarily by a reduction in the number of pores per egg; both an increased shell thickness and a smaller number of pores reduced GH2O of Puna ibis eggs. Since the reduction of GH2O of montane eggs did not fully compensate for the change in barometric pressure (59% of sea level) and the increase in gaseous diffusion coefficients at 4,400 m, the "effective" conductance of the eggs at that altitude was greater than at sea level. Therefore, the eggs lost substantially more water during incubation than did lowland eggs. The modifications in eggshell characteristics of montane eggs may have resulted from selection to increase O2 availability to the embryo.

Altitude↗
PubMed1986

Maternal hypoxic ventilatory response, ventilation, and infant birth weight at 4,300 m.

To test the hypothesis that increased hypoxic ventilatory responsiveness (HVR) raised maternal ventilation and arterial oxygenation during high-altitude pregnancy and related to the birth weight of the offspring, we studied 21 residents of Cerro de Pasco, Peru (4,300 m), while eight of them were 36 +/- 0 wk pregnant and 15 of them 13 +/- 0 wk postpartum. HVR was low in the nonpregnant women (mean +/- SE shape parameter A = 23 +/- 8) but increased nearly fourfold with pregnancy (A = 87 +/- 17). The increase in HVR appeared to account for the 25% rise in resting ventilation with pregnancy (delta VE observed = 2.4 +/- 0.7 l/min BTPS vs. delta VE predicted from delta HVR = 2.6 +/- 1.7 l/min BTPS, P = NS). Hyperoxia decreased ventilation in the pregnant women (P less than 0.01) to levels similar to those measured when nonpregnant. The increased ventilation of pregnancy raised arterial O2 saturation (SaO2) from 83 +/- 1 to 87 +/- 0%, and SaO2 was correlated positively with HVR in the pregnant women. The rise in SaO2 compensated for a 0.9 g/100 ml decrease in hemoglobin concentration to preserve arterial O2 content at levels present when nonpregnant. Cardiac output in the 36th wk of pregnancy did not differ significantly from values measured postpartum. The increase in HVR correlated positively with infant birth weight. An increase in HVR may be an important contributor to increased maternal ventilation with pregnancy and infant birth weight at high altitude.

Adult↗