The usual model of intermittent hypoxia (sleep apnoea) corresponds to repeated episodes of hypoxia from a few seconds to a few hours interspersed with episodes of normoxia. The aim of this study was to evaluate in rats the effect of two periods of intermittent exposure for 2 months to hypoxia (IHX1,24 h in hypoxia (428 Torr), 24 h in normoxia; IHX2,48 h in hypoxia (428 Torr), 24 h in normoxia) as a new model of hypoxia simulating intermittent exposure to high altitude experienced by Andean miners. We assessed the haematological parameters, time course of resting heart rate and systolic blood pressure. We also evaluated the expression of adrenergic and muscarinic receptors. IHXl and IHX2 produced an increase in haematocrit, haemoglobin concentration and mean corpuscular volume as previously seen in most hypoxic models. IHXl and IHX2 induced a simiiar sustained elevation of systolic blood pressure (132 k 2 and 135 f 3 mmHg, respectively, vs. the control level of 121 & 16 mmHg) after I0 days of exposure without change in heart rate. Right ventricular (RV) hypertrophy (225 f 13 and 268 k 15 mg g-I, vs. 178 k 7 mg g-') and downregulation of a,-adrenoceptor (RV 127 k 21 and 94 k 16 fmol mg-' vs. 157 f 8 fmol mg-'; left ventricle (LV): 141 f 5 and 126 f 9 fmol mg-' vs. 152 f 5 fmol mg-') have been found in both groups, with right ventricular hypertrophy being greater and a,-adrenoceptor density being lower in IHX2 than in HX1 groups. These data indicate that both parameters are related to the time of exposure to hypoxia. IHXl and IHXZ produced the same magnitude of upregulation of muscarinic receptors (LV, 60%; RV, 40%), and no change in /3-adrenoceptors. In conclusion, exposure to intermittent hypoxia led to polycythaemia and RV hypertrophy as observed in other types of hypoxia. A specific cardiovascular response was seen, that is an increase in blood pressure without change in heart rate, which was different from the one observed in episodic and chronic hypoxia. Furthermore, this model involved specific modifications of a,-adrenergic and muscarinic expression. Expen 'mental Physiologv (2002) 87.4,453-460.

Abstract. Chronic hypobaric hypoxia (CHH) induces a decrease in sperm output and spermatogenesis in male rats. The mechanisms that underlie these changes in testicular function are unknown and could involve changes in the hypophysis-gonad axis. We have tested the hypothesis that changes take place in the endocrine status (FSH, follicle stimulating hormone; LH, luteinizing hormone; testosterone) of rats subjected to CHH. Male Wistar rats were maintained under normobaric or hypobaric conditions (428 torr, 4,600 m). On days 0, 5, 15 and 30 post-exposure, 12 rats were anesthetized, their body weights were measured and blood samples were collected. The testicles were fixed in 4% formaldehyde and processed for histological analysis. In this time course, the FSH levels rose by day 5 post-exposure. On subsequent days, the FSH levels decreased in rats subjected to CHH with a tendency to remain higher than the normoxic group. The LH plasma levels decreased in rats exposed to CHH. Consistent with the decrease in LH levels, the plasma testosterone level decreased significantly after 30 days of CHH exposure. Integrated analysis of hormonal changes in rats subjected to CHH and the body dehydration that occurs in HH allows us to conclude that the effects of CHH on spermatogenesis may be partially related to changes in the hypophysis-gonad hormonal axis. Key words: Fertility, High altitude, Hypobaric hypoxia, Testicular function, Testis (J. Reprod. Dev. 54: [18][19][20][21] 2008) hronic hypobaric hypoxia (CHH) is experienced by an increasing number of sea level natives exposed to high altitude because of tourism, border patrol, mining or rural health and education activities [1]. It has been suggested that hypobaric hypoxia reduces fertility in humans. Nonetheless, epidemiological studies of high and low altitude populations have not been able to verify this proposal [2]. Based on the hormonal changes observed in men and rats at high altitude, some authors have proposed that CHH affects the hypothalamic/gonad axis (e.g. [3][4][5]). However, the results in the literature have been controversial. Nelson et al. reported that the plasma levels of GH, LH, FSH and TSH of hypoxic rats did not differ from the control values [3]. These results are in agreement with the reported absence of changes in the testosterone levels of rats exposed to hypoxia compared with sea level controls published by Gonzales et al. [5]. Instead, Sawhaney et al. [4] reported a decrease in the LH and testosterone levels in men exposed to CHH. Exposure of male rats to chronic hypobaric hypoxia and intermittent hypobaric hypoxia induced evident changes in testicular morphology [6][7][8][9], strong metabolic stress and loss of spermatogenic cells [8]. Local changes observed in testicles exposed to hypoxia include neovascularization and an increase in temperature. Thus, local changes that could lead to the observed effects on spermatogenesis do occur. However, it is highly likely that these local changes are also accompanied by changes in the hypophysis-gon...

Farias, Jorge G., Jorge Osorio, Gustavo Soto, Julio Brito, Patricia Siques, and Juan G. Reyes. Sustained acclimatization in Chilean mine workers subjected to chronic intermittent hypoxia. High Alt. Med. Biol. 7:302-306, 2006--We wanted to know if sea-level mine workers exposed previously to chronic intermittent hypoxia reached a steady acclimatization at 36 months under hypobaric hypoxia. An intermittently exposed group of mine workers (IE, n = 25) were subjected to submaximal exercise (100 W) at 4500 m. Their systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and hemoglobin oxygen saturation (HbSatO(2)) were monitored. Two comparison groups of unacclimatized sea-level workers (n = 17) were studied. A nonexposed group (NE) performed 5 min of submaximal exercise at sea level. Some kind of exercise was performed both by an acutely exposed group (AE) and IE group at 4500 m. No statistical differences were found for HR, SBP, and DBP (p > 0.05) during exercise between IE and AE groups. Resting HbSatO(2) of IE (87 +/- 6%) was lower than NE (97 +/- 3%) (p < 0.05), but was higher than AE (82 +/- 4%) (p < 0.05). In the exercise condition, HbSatO(2) of IE (85 +/- 5%) was lower than NE (95 +/- 3%) (p < 0.05), but was higher than AE (76 +/- 2%) (p < 0.05). These responses were maintained through the 6 months of the study period. Thus, mine workers subjected to intermittent hypobaric condition for 3 years showed a good degree of acclimatization that was maintained through time.

The presence of micrometastases in patients with Stages I and II colorectal cancer seems not to have any impact on cancer-specific survival.

No abstract