Altitude Group Research Articles

Phenotypic diversity of tetraploid wheat landraces from northern and north-central regions of Ethiopia

Twenty–seven tetraploid (2n = 4x = 28) wheat (Triticum turgidum L.) landrace populations consisting of 2876 entries collected from the north and north-central administrative regions of Ethiopia were studied for variation of eleven phenotypic characters that have two or more classes. Using the frequencies of each phenotypic class within a character, the Shannon-Weaver index (H') was employed to estimate and analyse the diversity on the basis of four regions and five altitudinal gradients. Most traits were polymorphic. However, monomorphism was common in many of the populations for dense spike, long beak, and glabrous glume. On character basis, seed colour, seed shape, and glume pubescence contributed the highest mean diversity indices (H' = 0.99, 0.96, and 0.88, respectively). Spike density contributed the lowest index (H' =0.24). However, it was the only trait that displayed significant differences (p < 0.01) among regions, lax-spike types being frequent only in Gojam region. Significant differences (p <0.05) among altitude groups were detected only for glume colour and beak length. Much of the variance was among populations within region and within altitude group. For the overall characters, significant differences (p<0.01) were revealed only among populations within region and altitude group, but not among regions or altitude groups. However, the highest mean diversity indices were obtained in Tigray region (H' = 0.70). and in the altitude range between 2401 and 2600 m.a.s.1. (H' = 0.68). No clear association was detected between overall phenotypic diversity and altitude. The overall index (H' = 0.70) for the north and north-central regions of this country is of the same magnitude as that of previously reported regions. Therefore, before any collection mission is undertaken, we suggest further studies to gain information on the interrelationships among morphological diversity, variation for biochemical markers, and ecogeographical variables.

Analysis of genetic diversity and structure in Ethiopian populations of Phytolacca dodecandra using RAPD.

The genetic diversity and structure in 17 wild populations (249 individuals) of Phytolacca dodecandra (endod) sampled along altitudinal gradients of 1600-3000 meters above sea level (m.a.s.l.) in Ethiopia was studied using random amplified polymorphic DNA (RAPD). A total of 70 polymorphic loci (P) scored from 12 RAPD primers were used to calculate different diversity indices within and between populations, habitats, geographical regions, climatic zones and altitude groups. The number of polymorphic loci and overall Shannon information measure (H) in the populations varied from 30 to 55 and from 0.228 to 0.418, respectively. In general, differences in population variability were found significantly correlated to effective population size. Both P and H were significantly higher in an undisturbed than in a disturbed habitat, and in the lowland and central-highland than in the highland altitude group. However, for both parameters the differences were not statistically significant between regions and climatic zones. Genetic distance between populations varied from 0.301 to 0.628. Cluster analysis performed using the genetic distance matrix revealed a clear separation of the highland populations (2501-3000 m.a.s.l.) from those of the lowland/central-highlands (1600-2500 m.a.s.l.) irrespective of their geographical regions and climatic zones. Analysis of molecular variance (AMOVA) indicated that differences in habitat, geographical regions and climatic zones explained 4.6%, 2.5% and 4.6%, respectively. But none of these differences were significant. Altitude explained 17.2% of the total variance and was highly significant. The data, therefore, clearly indicated the association of genetic structure in endod with altitude. The proportion of RAPD variation found among populations (21.2-35.0%) was somewhat intermediate between values reported for selfing and outcrossing species. The fixation index (FST) values (0.350 to 0.384) indicated very high genetic differentiation among populations.

Variation and association of morphological and biochemical characters in grass pea (Lathyrus sativus L.)

Fifty grass pea land race populations of Ethiopia that were selected based on administrative regions and different altitude classes were used in this study to determine variability in morphological characters, Oxalyl Diamino Propanoic acid(ODAP) – a causative agent of lathyrism, and protein contents and their associations. Highly significant differences were observed among the populations for most of the morphological characters. Populations collected from Gondar region and the higher altitude group (>2550 m) showed the highest mean and coefficient of variation indicating the presence of high genetic diversity in this region and altitude group. ODAP analysis from single plants showed significant variation both within a population and between populations. Four individual plants with low ODAP contents ranging from 0.149% to 0.182% (range within safe level) were identified in populations collected from different regions, indicating the diversity and variation of this trait with in one population and between regions. These low ODAP lines are considered important for further breeding. The association of ODAP with grain yield, biomass, plant height and seed size was negative, suggesting that the selection of tall and late maturing varieties with large seed size and high grain yield potential will enable the development of varieties with low ODAP content.

Variation and association analysis in grass pea (&lt;i&gt;Lathyrus sativus&lt;/i&gt; L.)

The study was conducted on 50 landrace populations of grass pea at Adet Research Center, Ethiopia, using randomised complete Block design in three replications to determine morphological variability and character associations. Evaluations were made on plant and yield characters from eight plants tagged randomly from each plot. The data were subjected to Analysis of Variance (anova), heritability, correlation and cluster analyses. Higher mean and cv values were recorded for most of the agronomic traits for populations collected from Gondar region and the higher altitude group (>2500 m) indicating the presence of high genetic diversity in this region and altitude group. Phenotypic coefficient of variation (pcv) was slightly higher than genotypic coefficient of variation (gcv) for all the characters studied signifying that genotypic factors exerted reasonable effect in estimating the variation. The wide difference between pcv (22.4%) and gcv (13.0%) for seed yield per plant indicated the complexity of this trait and the important role of other factors such as environment in influencing yield potential in addition to the genetic factors. The strong positive association of pods per plant, 100 seed weight and primary branches per plant with seed yield indicated the possibility of selecting lines for yield improvement based on these characters at the very early stage of the grass pea breeding program. Key words/phrases: Correlation grass pea, heritability, Lathyrus sativus, variation SINET: Ethiopian Journal of Science Vol.25(2) 2002: 191-204

Placental Villus Morphology in Relation to Maternal Hypoxia at High Altitude

Pregnancy at high altitude is associated with maternal hypoxaemic hypoxia with resultant intervillus blood hypoxia. Maternal haemoglobin concentration and blood gases were measured in pregnant women in two cities in Peru; Lima at sea level (n=18) and Cerro de Pasco at 4300 metres above sea level (n=12). Following delivery, placental sections from both groups were examined histomorphometrically using an image analysis system. Villus diameter, villus cross-sectional area, capillary diameter, capillary cross-sectional area and the percentage of villus cross-sectional area occupied by villus capillaries were calculated and parameters were compared between the two altitude groups. Maternal haemoglobin concentration and maternal blood pH were significantly higher, and maternal pO2, pCO2and O2saturation were significantly lower in the high altitude group compared to those at sea level. The villus vessel area as a percentage of villus cross-sectional area and capillary diameter were significantly greater in the cases from the high altitude group and villus vessel area as a percentage of the villus cross-sectional area was significantly related to maternal pO2(r=−0.7, P=0.01), and maternal pCO2(r=0.7,P =0.02), but multiple regression analysis demonstrated that only pO2remained significantly independently associated with these villus histological findings (P=0.03). Placental terminal villi from term pregnancies at high altitude show different morphological features from pregnancies at sea level, and these changes are primarily related to maternal pO2. The predominant morphological alteration is an increase in villus capillary diameter and therefore of the proportion of villus cross-sectional area occupied by capillary lumens.

Cardiovascular response to hypoxia after endurance training at altitude and sea level and after detraining.

The purpose of this study was to elucidate 1) the effects of endurance exercise training during hypoxia or normoxia and of detraining on ventilatory and cardiovascular responses to progressive isocapnic hypoxia and 2) whether the change in the cardiovascular response to hypoxia is correlated to changes in the hypoxic ventilatory response (HVR) after training and detraining. Seven men (altitude group) performed endurance training using a cycle ergometer in a hypobaric chamber of simulated 4,500 m, whereas the other seven men (sea-level group) trained at sea level (K. Katayama, Y. Sato, Y. Morotome, N. Shima, K. Ishida, S. Mori, and M. Miyamura. J. Appl. Physiol. 86: 1805-1811, 1999). The HVR, systolic and diastolic blood pressure responses (DeltaSBP/DeltaSa(O(2)), DeltaDBP/DeltaSa(O(2))), and heart rate response (DeltaHR/DeltaSa(O(2)); Sa(O(2)) is arterial oxygen saturation) to progressive isocapnic hypoxia were measured before and after training and during detraining. DeltaSBP/DeltaSa(O(2)) increased significantly in the altitude group and decreased significantly in the sea-level group after training. The changed DeltaSBP/DeltaSa(O(2)) in both groups was restored during 2 wk of detraining, as were the changes in HVR, whereas there were no changes in the DeltaDBP/DeltaSa(O(2)) and DeltaHR/DeltaSa(O(2)) throughout the experimental period. The changes in DeltaSBP/DeltaSa(O(2)) after training and detraining were significantly correlated with those in HVR. These results suggest that DeltaSBP/DeltaSa(O(2)) to progressive isocapnic hypoxia is variable after endurance training during hypoxia and normoxia and after detraining, as is HVR, but DeltaDBP/DeltaSa(O(2)) and DeltaHR/DeltaSa(O(2)) are not. It also suggests that there is an interaction between the changes in DeltaSBP/DeltaSa(O(2)) and HVR after endurance training or detraining.

EFFECT OF ALTITUDE TRAINING ON RUNNER'S SKELETAL MUSCLE

811 "Altitude training" has been linked to increases in muscle buffering capacity, oxidative enzymes and capillary density, although most studies have used either animal models, very few subjects, or high altitude. However, athletes rarely exceed elevations of 3000m during "altitude training". Therefore, we investigated the effect of 4 weeks training in low (1000-2000m) or moderate (2000-3000m) altitude on histologic and biochemical factors in the m. vastus lateralis of trained runners. Methods: Training was monitored. Base and interval pace running were characterized by velocity and VO2. VO2max, 5,000m time and O2 deficit were recorded. Three muscle biopsies were taken on each runner (12 women, 27 men, age 18-31, VO2 max 64±2 ml·kg−1·min−1, anaerobic capacity 56±4 ml·kg−1): 1) before 4 weeks sea level control training (0-200m, n=39); 2) before; and 3) after 4 weeks training at sea level (0-200m, n=13), low altitude (1250-1600m, n=13), or moderate altitude (2200-3000m, n=13, altitude groups lived at 2500m). Biopsies were analysed for fiber type and area, capillary density, activities of citrate synthase (CS), phosphofrucktokinase (PFK), 3,4 hydroxyacyl-CoA dehydrogenase (HAD), and buffer capacity. Results were analysed by ANOVA (p≤0.10). Results: There were no initial differences between groups. Training volume and relative intensity were not different between periods. Interval VO2 and velocity were lower at moderate altitude. VO2max improved in both altitude groups. 5,000m time improved only in the low altitude group. Although both fiber type areas were less during sea level training, and higher during experimental periods (in all groups), percent fiber type and capillary density did not change. There were no changes in the enzymes studied except for increased PFK activity in the sea level group during the experimental period. Tissue buffer capacity decreased in the group training at moderate altitude. Conclusions: Low altitude training is similar to sea level training. In contrast to previous work, moderate altitude training is associated with reduced tissue buffering capacity, no improvement in enzyme activities or capillary density, and may impair sea level performance.

Patterns of morphological diversity in tetraploid wheat (Triticum turgidum L.) landraces from Ethiopia

Thirty‐four tetraploid (2n = 4x = 28) wheat (Triticum turgidum L.) landrace populations collected from four regions in Ethiopia, and consisting of 4099 entries were characterized for glume colour, glume pubescence, beak awn, seed colour and spike density. The main objective was to analyse the diversity and distribution of these traits on the basis of administrative regions and altitudinal gradients. The Shannon‐Weaver Diversity Index (H') was used to estimate the magnitude of diversity. With the exception of spike density, all characters were polymorphic in all regions and most altitude groups. However, clinal patterns were observed in only a few cases. At the population level, the mean H’ varied from completely monomorphic (H’ = 0.00) to highly polymorphic (H’ = 0.80 ± 0.07). The highest diversity was found in regions with relatively better climatic conditions and in optimal altitude ranges. On country basis, seed colour (H’ = 0.98) and spike density (H’ = 0.43) displayed the highest and the lowest diversity indices, respectively. Spike density was the only character that exhibited significant differences (P<0.01) both “between regions”; and “between altitude groups”;. Across characters, most of the variance was due to the lowest hierarchy, the “within‐population”; component. The “between region”; and “between altitude group”; variances were significant, but spike density alone was responsible for the differences. The overall mean H’ for Ethiopia was 0.77 + 0.09 and did not seem to have reduced appreciably within the past 25 years or so, when compared to previous estimates.

Does hypercapillarization influence the branching pattern of terminal villi in the human placenta at high altitude?

This study tests the hypothesis that exposure of the placenta to hypobaric hypoxia at altitude results in an altered branchingpattern of the villous tree. Histological material from 20 term placentae delivered at altitudes over 3000 m was compared with matched controls from 500 m. Estimates of the mean star volume of intermediate and terminal villous domains were 1.40 × 10 6 μm 3 (s.d. 0.63) in the high altitude group and 1.90 × 10 6 μm 3 (s.d. 0.34) in the controls (F=9.07, P<0.005 The volume fraction of the villous tree occupied by trophoblastic bridges and syncytial knots was 8.1 per cent (s.d. 3.5) in the high altitude group and 3.2 per cent (s.d. 1.6) in the controls (F=29.45, P<0.0001). Previous studies have shown that the majority (80 per cent) of bridges are artefacts caused by the plane of section passing tangentially through the trophoblast layer at points of villous bending or branching. The results are, therefore, consistent with the hypothesis that peripheral villi are shorter, knob-like protrusions at high altitude, clustered more closely together. This modified branching pattern was confirmed by scanning electron microscopy. The change in architecture may be due to enhanced angiogenesis stimulated by the lower partial pressure of oxygen prevailing at high altitude.

Compliance of the Respiratory System in Infants Born at High Altitude

Populations living at high altitude are known to have a number of distinctive physiologic traits, including an increase in lung volume and compliance. We asked whether the factors that result in the increased compliance of high altitude natives were sufficiently expressed in utero that an increase in respiratory system compliance (Crs) could be detected at birth. Measurements were performed at about 1 day after birth on 34 infants born in La Paz, Bolivia (3,600 m, Pb about 495 mm Hg) and 36 born in Santa Cruz (400 m, Pb about 735 mm Hg). All infants were full-term and healthy, with body weights of at least 2,700 g. We measured Crs from expirations within the tidal volume range by the multiple occlusion method. Breathing pattern was measured from the spirometric record, and an index of chest wall distortion was obtained from the ratio of volume and abdominal displacement during spontaneous breathing and relaxations against closed airways. Rib cage and abdomen dimensions did not differ between the two groups. Crs values in Santa Cruz were similar to those previously obtained in Montreal and in other Caucasian infant populations at low altitudes. Crs was 33% and Crs/kg 37% greater (p less than 0.001) in the high altitude group, which included equal numbers of Amerindians and Mestizos of European ancestry. Dynamic elevation of the end-expiratory level was similar in both groups. Ventilation/kg and the distortion ratio were slightly yet significantly higher in the high altitude infants, suggesting an increased ventilatory drive.(ABSTRACT TRUNCATED AT 250 WORDS)

Vibration syndrome--with special reference to the effects of temperature on vibration-induced white finger.

AbstractIn order to clarify the effects of temperature on vibration‐induced white finger, two groups of chain saw operators in the forestry industry served as the subjects of this study. One group worked at a cold high altitude; the other group worked at a warm low altitude. Except for the difference in temperature, these two groups had similar work environments. The high altitude group had a high prevalence of white finger (75%), but none of the low altitude group suffered from this circulatory disturbance. After measuring the skin temperature and analyzing the results of the cold provocation test, we demonstrated that low temperature is an important factor in causing vibration‐induced white finger.

Grass production studies in the uplands of north‐east Scotland 2. The effects of fertilizer treatment

AbstractThe effects of fertilizer treatment were studied over two seasons on a 2 × 2 factorial arrangement of altitude and major soil group. The soil groups were brown earths and podzols and the altitudinal zones were 260–320 m and 380–440 m. Major responses were found to N only and these were generally linear in terms of overall dry matter yield up to the highest treatment level of 176 kg ha‐1. Productivity on brown earths was significantly higher than on podzols and differences between soil groups were not removed by increasing fertilizer input. In most instances 88–132 kg ha‐1 N would have to be added to podzols to achieve the same yields as on brown earths with no N input. Apparent fertilizer recoveries and responses per unit of fertilizer input did not, however, differ markedly between soil groups. Overall yields were comparable with those from lowland situations at similar levels of N input, but the growing season was short and 60–80% of production was obtained by early July.

Grass production studies in the uplands of north‐east Scotland 1. The effects of soil parent material, altitude and soil major group

AbstractSites were established on good quality grass swards in areas representative of three of the most extensive soil parent materials in north‐east Scotland and covering an altitudinal range of 260–460 m. Overall yields of herbage dry matter in 1975 were high, ranging from 6280 kg ha‐1 with no fertilizer to 9190 kg ha‐1 with an application of 100, 26 and 50 kg ha‐1 N, P and K respectively. Differences in production between parent material and altitude groupings were found to be associated with differences in major soils group and past land use, with long‐enclosed brown earths outyielding podzols recently reclaimed from heather moorland by about 30% overall. Increasing inputs of fertilizer appeared to reduce the effects of soil and climatic conditions. Brown earths showed higher apparent recoveries of N fertilizer than did podzols.

Effect of hypoxia (6,060 m) and cold (-5 degrees C) on sexual organs of male rabbits.

Studies have been carried out on 18 adult male rabbits divided into three groups. One group (hypoxic) was exposed to a simulated altitude (6,060 m for 6 h daily for 21 days), the second group was exposed to the same altitude plus cold (−5°C) for the same duration, and the third acted as control. The results showed no difference in the body weight of the three groups, but the weights of the sex organs in the exposed groups were significantly reduced. In both these groups the number, motility and survival time of spermatozoa decreased significantly; the sex organs showed atrophy on histological examination; and there was an increase in the alkaline and acid phosphatase activity and cholesterol concentration, and a fall in GPC level. These changes were more marked in the cold plus altitude group than in the group exposed to altitude alone. It has been concluded that hypoxia affects not only the testis but also the epididymis and the vas deferens. The spermatozoal quality of rabbits deteriorates. When cold and hypoxia are combined, their effects are additive.

A Dose-Response Relationship between Chromosome Aberrations and Hypoxic Insults in Overripened Hamster Ova

An attempt was made to analyze the quantitative occurrence of chromosome anomalies by the exposure of slightly overripened ova (delayed fertilization) to hypoxic insults in golden hamsters. Three groups were established: (1) a control group (PO2 = 152 mmHg); (2) a 4,500 m altitude group (PO2 = 87 m5 hr post-ovulatory aging revealed no striking effect on reproductive performance, as well as on the production of chromosome aberrations. Nervertheless, even in a slightly overripened condition ovum increased in susceptibility to the production of chromosome anomalies after hypoxic exposure equivalent to 4,500 m altitude. The dose-response relationship between hypoxia and the occurrence of triploidies was particularly distinguished. On the other hand, a similar relationship was not so evident in the production of aneuploidies, especially of trisomies. It can, therefore, be surmised that the change in the cytogenetic milieu at the time of the second polar body extrusion has some quantitative relation to the severity of environmental stressors.

Effect of high-altitude exposure for 10 days on stroke volume and cardiac output.

Resting stroke volume and cardiac output of 50 normal healthy sea-level residents (group A) were estimated by the noninvasive technique of electrical impedance plethysmography. They were then airlifted to an altitude of 3,658 m and serial estimations carried out at 0-4 h and 5-8 h and on the 2nd, 3rd, 4th, 5th, and 10th days. The subjects were brought back to sea level and studied for up to 5 days. Thirty permanent residents of high altitude (group B) and sixteen lowlanders temporarily resident at high altitude (group C) were also subjected to similar studies. It was found that resting stroke volume and cardiac output of group A started falling immediately on arrival at high altitude, reached the minimum on the 3rd day and tended to improved on the 4th and 5th day, but showed a secondary fall on the 10th day. The reduction in stroke volume in this group was not fully compensated by tachycardia. On return to sea level the cardiac output normalized immediately, the stroke volume on the 2nd day. At sea level goup A had values similar to group B and at high altitude to group C.

The carotid bodies in animals at high altitude.

The carotid bodies of a group of animals from high altitude were compared with those of a group from sea level. The carotid bodies from the high altitude group were larger and showed hyperplasia of the type I cells with cytoplasmic vacuolation. Electron microscopy revealed that this vacuolation was associated with changes in the membrane bound cytoplasmic bodies. It is suggested that the ultrastructural changes are related to the disturbance in chemoreceptor response found in subjects living at high altitude.

The effect of chronic hypoxia on in vitro lipolysis in the rat.

The responsiveness of the lipolytic system in chronically hypoxic rats (14 500 ft) was assessed by the in vitro release of free fatty acids (FFA) and glycerol, measured aerobically and anaerobically, in epididymal fat pads from fed, fasted, and fasted–refed animals. Basal aerobic release of FFA for fed rats was significantly higher in the altitude (ALT) group. In fasted rats both basal and norepinephrine (NE)-stimulated release of FFA and glycerol was higher when compared with heavier sea level (SL) controls. However, weight-matched (younger) controls showed no difference in release rates. Anaerobic NE-stimulated release of FFA, glycerol, and lactate was higher in ALT rats than in weight-matched SL controls only in those animals fasted and refed a high carbohydrate diet. Fat pad glycogen content in such animals was 0.207 mg/100 mg tissue for SL and 0.384 for ALT. Anaerobic in vitro FFA mobilization in adipose tissue from fasted–refed ALT rats is more sensitive to NE, and this physiological advantage may be a reflection of a greater potential for glycogen storage in the fat tissue of these acclimated animals. Additionally, weight matching is necessary in evaluating altitude-stressed animals, and use of dietary restrictions to obtain controls of equal age and weight may yield misleading metabolic data.

Effect of angiotensin on the kidney of the high altitude native.

Renal hemodynamics, sodium and water excretion were studied in six sea level residents and eight high altitude (4,500 m) natives before, during and after the infusion of small amounts of angiotensin (0.32 <i>µ</i>g/min). In basal conditions the high altitude group showed a mild reduction in the glomerular filtration rate, with a higher reduction in the renal plasma flow and a normal or slightly increased renal blood flow. During angiotensin infusion, both sea level and high altitude groups responded with a marked reduction in urine flow and sodium excretion. The glomerular filtration rate and renal plasma flow diminished with a greater fall in the latter. This changes were slighter in the high altitude group, except in the sodium to inulin clearance ratio, which was similar in both groups. Despite a high filtration fraction, the kidney of the high altitude native responds to angiotensin like the sea level kidney. These results are discussed in relation to the paradoxical renal response to angiotensin observed in the hypertensive patient.

Effects of decaborane on liver glycogen content of rats at ground level and at altitude. SAM-TR-69-48.

Abstract : The effect of decaborane (15 mg./kg.) on the hepatic glycogen of male rats maintained at altitude (18,000 ft.) under normoxic conditions was compared with the effect on similarly injected, ground level controls. Results showed that decaborane decreased the glycogen level of fed rats at ground level, but did not affect glycogen levels in the fed, altitude group. The hepatic glycogen level of fasted rats at altitude was the equivalent of that of fasted rats at ground level. These results indicate that the mechanism whereby decaborane produces a depletion of liver glycogen is altered under conditions of reduced pressure.