Lactate and epinephrine during exercise in altitude natives

Kayser, Bengt, Roland Favier, Guido Ferretti, DominiqueDesplanches, Hilde Spielvogel, Harry Koubi, Brigitte Sempore, and HansHoppeler. Lactate and epinephrine during exercise in altitudenatives. J. Appl. Physiol. 81(6):2488-2494, 1996.We tested the hypothesis that the reported lowblood lactate accumulation ([La]) during exercise inaltitude-native humans is refractory to hypoxia-normoxia transitions byinvestigating whether acute changes in inspiredO₂ fraction(FI_O2) affect the[La] vs. power output ()relationship or, alternatively, as reported for lowlanders, whetherchanges in [La] vs. on changes inFI_O2 are related tochanges in blood epinephrine concentration ([Epi]). Altitude natives [n = 8, age 24 ± 1 (SE) yr, body mass 62 ± 3 kg, height 167 ± 2 cm]in La Paz, Bolivia (3,600 m) performed incremental exercise with twolegs and one leg in chronic hypoxia and acute normoxia (AN). Submaximalone- and two-leg O₂ uptake (O₂) vs. relationships were not altered byFI_O2. AN increased two-legpeak O₂ by 10% and peak by 7%. AN paradoxically decreasedone-leg peak O₂ by 7%,whereas peak remained the same. The[La] vs. relationships were similar tothose reported in unacclimatized lowlanders. There was a shift to theright on AN, and maximum [La] was reduced by 7 and 8% forone- and two-leg exercises, respectively. [Epi] and[La] were tightly related (mean r = 0.81) independently ofFI_O2. Thus normoxiaattenuated the increment in both [La] and [Epi]as a function of , whereas the correlation between[La] and [Epi] was unaffected. These data suggest loose linkage of glycolysis to oxidative phosphorylation under influence from [Epi]. In conclusion, high-altitudenatives appear to be not fundamentally different from lowlanders with regard to the effect of acute changes inFI_O2 on [La] during exercise.

     

Influence of Androgenicity on Adipocytes and Precursor Cells in Female Rats

We examined the effects of overexposure of testosterone (T) on fat cell morphology and adipocyte precursor pools in inguinal and retroperitoneal fat depots of ovariectomized rats. In both tissues peripubertal T decreased weights without affecting adipocyte mean cell size or the size distribution profiles, but adipocyte number was decreased by 65% in the inguinal and by 38% in the retroperitoneal depots. Immunofluorescent flow cytometry utilizing a specific antibody to rat adipose tissue lipoprotein lipase was used to quantify regional precursor cell populations. T sharply reduced the percentages of differentiated and undifferentiated preadipocytes in the inguinal depot, from 43.2 ± 5.3 to 23.5 ± 2.1% and from 57.7 ± 4.0 to 43.6 ± 5.3%, respectively, with a concomitant increase in fibroblasts from 1.6 to 32.9%. On the other hand, T had no effect on retroperitoneal preadipocyte pools. Perinatal andro-genization exacerbated the decline in the inguinal weight (1.4 ± 0.1 vs. 2.2 ± 0.1g) but otherwise did not influence the actions of peripubertal T. Androgens may thus act in a tissue-specific manner to regulate fat cell growth potential in the femoral region in the female.     

Socioeconomic determinants of rates of consultation in general practice based on fourth national morbidity survey of general practices.

OBJECTIVE--To identify the socioeconomic determinants of consultation rates in general practice. DESIGN--Analysis of data from the fourth national morbidity survey of general practices (MSGP4) including sociodemographic details of individual patients and small area statistics from the 1991 census. Multilevel modelling techniques were used to take account of both individual patient data and small area statistics to relate socioeconomic and health status factors directly to a measure of general practitioner workload. RESULTS--Higher rates of consultations were found in patients who were classified as permanently sick, unemployed (especially those who became unemployed during the study year), living in rented accommodation, from the Indian subcontinent, living with a spouse or partner (women only), children living with two parents (girls only), and living in urban areas, especially those living relatively near the practice. When characteristics of individual patients are known and controlled for the role of "indices of deprivation" is considerably reduced. The effect of individual sociodemographic characteristics were shown to vary between different areas. CONCLUSIONS--Demographic and socioeconomic factors can act as powerful predictors of consultation patterns. Though it will always be necessary to retain some local planning discretion, the sets of coefficients estimated for individual level factors, area level characteristics, and for practice groupings may be sufficient to provide an indicative level of demand for general medical services. Although the problems in using socioeconomic data from individual patients would be substantial, these results are relevant to the development of a resource allocation formula for general practice.     

Protection of hepatocytes from Fas-mediated apoptosis by a non-transforming SV40 T-antigen mutant

Apoptosis is crucial for the normal development of multicellular organisms and is also important for clearing injured cells, such as virus-infected cells or cancer cells. Defective regulation of apoptosis may contribute to viral pathogenesis and aetiology of cancer. Apoptosis of injured cells is principally triggered by the immune system through cytokines such as Fas-ligand and TNF-alpha. Thus, one of the functions of a viral oncogene, such as SV40T-antigen, may be to inhibit cytokine-mediated apoptosis. We previously demonstrated that Fas-mediated apoptosis of hepatocytes is blocked by the wild-type SV40T-antigen during hepatocarcinogenesis. We determined whether this inhibition was directly related to the T-antigen or whether it is a secondary event of cell transformation, by generating transgenic mice expressing a non-transforming T-antigen mutant able to bind endogenous p53 in the liver. This T-antigen mutant cannot induce hepatocarcinoma, unlike the wild-type T-antigen. However, like the wild-type T-antigen, the mutant was a potent inhibitor of apoptosis induced by the Fas-receptor, but not by the TNF-receptor. Therefore, SV40T-antigen has a new property; the inhibition of Fas-mediated apoptosis, which could facilitate the emergence of transformed hepatocytes, but is not sufficient to induce it.     

Rates of net nitrogen mineralization in disturbed and undisturbed soils

Quantification of net nitrogen mineralization (NNM) in soils is indispensable in order to optimize N fertilization of crops. Two long-term laboratory incubation methods were applied to determine rates of net nitrogen mineralization (r_NNM) of soils from two sites of arable land (sandy loam soil, silty loam soil) at four temperature levels (2°C, 8°C, 14°C, 21°C). Since variability within replicates was small, the modified 12-week incubation method of Stanford and Smith (1972) using disturbed soils allowed to establish reliable Arrhenius functions with reasonable expenditure. The fit of the functions derived from the 5-month incubation of 23 undisturbed soil columns (4420 cm³) was worse. This was caused by greater variability and less differentiation between temperature levels. Results of both experiments could be described best by zero-order kinetics. Mean mineralization rates of disturbed samples were approximately twice as high than those of undisturbed samples. The suitability of both methods for the prediction of NNM at site conditions is discussed. Actual respiration (AR) at incubation temperatures and substrate induced respiration (SIR) were measured at the end of the incubation of undisturbed soil columns. The results presented reveal that soil microbial communities develop in a different manner during long-term incubation at different temperatures. This behavior offends the underlying assumption that soil microbes remain in steady-state during incubation and that rising rates are physiological reactions to temperature enhancement. Therefore soil microbial biomass (SMB) dynamics during the experiment has to be accounted for when rates of NNM and Arrhenius functions are established. R Merck Section editor     

Fatty acids of the scleractinian coral Galaxea fascicularis: effect of light and feeding

In order to investigate nutritional interactions in the symbiotic scleractinian coral-zooxanthella association, fatty acids of the coral Galaxea fascicularis were analysed in two groups of cultured microcolonies. The first group was fed with Artemia sp., while the second group was starved. After an initial 1-month period during which both groups were subjected to the same normal light conditions (constant irradiance of 125 E·cm^-2·s^-1 and 14:10 h light:dark), a light cap was used to cover the aquarium and keep all the microcolonies in permanent darkness for 20 days. During the light phase of the experiment it was shown that the nutritional status lead to large variations in the percentage of saturated, mono-unsaturated and polyunsaturated fatty acids. Palmitic acid (C16:0) was the most abundant fatty acid in both groups. Important differences between fed and starved microcolonies occurred during the dark phase of the experiment. In the fed group the dark phase was characterized by a significant increase in polyunsaturated fatty acids. Particularly arachidonic acid (C20:4 n-6) became the most important fatty acid followed by docosatrienoic acid (C22:3 n-3). A slight increase in these two fatty acids was also found in the starved group but the bulk of polyunsaturated fatty acids was significantly decreased. In this group, palmitic acid remained the most important fatty acid while an increased concentration of cis-vaccenic acid (C18:1 n-7) was found at the end of the experiment. The increased concentration of cis-vaccenic acid might indicate that bacteria serve as a source of energy. While the number of zooxanthellae per milligram of protein and the chlorophyll a to protein ratio strongly decreased in the starved microcolonies immediately after the beginning of the dark period, the decrease in fed microcolonies was delayed for about 10 days. Furthermore, after 20 days of dark incubation the chlorophyll a to protein ratio was the same as measured at the beginning of the dark period. This suggests that in the dark the metabolic requirements of the zooxanthellae are in part met from the animal host through a heterotrophic mode of nutrition.Abbreviations CZ cultured zooxanthellae - FAME fatty acid methylester(s) - FDM fed dark microcolonies - FLM fed light microcolonies - MUFA monounsaturated fatty acid(s) - PUFA polyunsaturated fatty acid(s) - SDM starved dark microcolonies - SFA saturated fatty acids - SLM starved-light microcolonies - SW sea water - TFA total fatty acids     

Comparative chromosome painting between two marsupials: origins of an XX/XY1Y2 sex chromosome system

Cross-species chromosome painting was used to investigate genome rearrangements between tammar wallaby Macropus eugenii (2n = 16) and the swamp wallaby Wallabia bicolor (2n = 10♀/11♂), which diverged about 6 million years ago. The swamp wallaby has an XX female:XY₁Y₂ male sex chromosome system thought to have resulted from a fusion between an autosome and the small original X, not involving the Y. Thus, the small Y₁ should represent the original Y and the large Y₂ the original autosome. DNA paints were prepared from flow-sorted and microdissected chromosomes from the tammar wallaby. Painting swamp wallaby spreads with each tammar chromosome-specific probe gave extremely strong and clear signals in single-, two-, and three-color FISH. These showed that two tammar wallaby autosomes are represented unchanged in the swamp wallaby, two are represented by different centric fusions, and one by a tandem fusion to make the very long arms of swamp wallaby Chromosome (Chr) 1. The large swamp wallaby X comprises the tammar X as its short arm, and a tandemly fused 7 and 2 as the long arm. The acrocentric swamp wallaby Y₂ is a 2/7 fusion, homologous with the long arm of the X. The small swamp wallaby Y₁ is confirmed as the original Y by its painting with the tammar Y. However, the presence of sequences shared between the microdissected tammar Xp and Y on the swamp wallaby Y₂ implies that the formation of the compound sex chromosomes involved addition of autosome(s) to both the original X and Y. We propose that this involved fusion with an ancient pseudoautosomal region followed by fission proximal to this shared region. Received: 16 October 1996/Accepted: 30 January 1997