COMPARATIVE EFFECTS OF THE OESTROGENS AND OTHER STEROID HORMONES ON SERUM LIPIDS AND PROTEINS IN XENOPUS LAEVIS DAUDIN

1969 ◽  
Vol 43 (1) ◽  
pp. 47-53 ◽  
Author(s):  
M. R. REDSHAW ◽  
B. K. FOLLETT ◽  
T. J. NICHOLLS
Keyword(s):  
Plasma Concentration ◽  
Xenopus Laevis ◽  
Steroid Hormones ◽  
South African ◽  
Calcium Binding ◽  
Serum Lipids ◽  
Response Curves ◽  
Yolk Formation ◽  
Log Linear ◽  
Relative Potencies

SUMMARY A comparison has been made between the effects of oestradiol-17β, oestrone, oestriol, progesterone, testosterone and cortisone on the plasma concentration of proteins and lipids in the South African clawed toad, Xenopus laevis Daudin. No major changes in the parameters studied were found with the non-oestrogenic steroids; only the three oestrogens induced the appearance in the plasma of a calcium-binding phospholipoprotein and esterified lipids associated with yolk formation. These results support the hypothesis that the oestrogens alone cause the vitellogenic response in oviparous vertebrates. Dose—response curves for oestradiol-17β, oestrone and oestriol were established for the effects on plasma protein, calcium, protein-bound phosphorus, phospholipid, lipid and cholesterol. The curves obtained were log.-linear over the range of doses employed (oestradiol-17β, 1–50 μg./day; oestrone, 4–100 μg./day; oestriol, 20–500 μg./day) with the exception of the cholesterol response to oestradiol. The relative potencies of the three oestrogens were compared for each of the plasma components measured. Oestradiol-17β was the most potent, being 3·9 times more active than oestrone and 13·7 times more active than oestriol.

Ethnicity and Voting Patterns in South Africa

1979 ◽  
Vol 27 (3) ◽  
pp. 458-468 ◽  
Author(s):  
Henry Lever
Keyword(s):  
South Africa ◽  
South African ◽  
Categorical Data ◽  
Economic Status ◽  
Party Choice ◽  
Political Choices ◽  
Electoral Behaviour ◽  
Log Linear ◽  
Published Research

There is some controversy concerning the role of ethnicity in South African electoral behaviour. Since the society is segmented on ethnic lines it is to be expected that ethnicity would play a crucial role in affecting political choices. Some writers have gone so far as to suggest that ethnicity is the only significant factor affecting voting preferences. The controversy arose at a time when Goodman's method of log-linear analysis for hierarchical models had not yet been developed. This method provides the most powerful tool available for the multivariate analysis of categorical data. A re-analysis of previously published research using Goodman's method shows that ethnicity is not the only significant factor having a bearing on voting preferences. The first four-way table of voting preferences in South Africa is presented. The order of importance of the variables affecting party choice is: (1) ethnicity (2) socio-economic status (3) age of the voter. The recursive model suggested by the analysis explains approximately 98 per cent of the data.

TISSUE DISTRIBUTION OF IMMUNOREACTIVE SOMATOSTATIN IN THE SOUTH AFRICAN CLAWED TOAD (XENOPUS LAEVIS)

1979 ◽  
Vol 80 (3) ◽  
pp. 407-408 ◽  
Author(s):  
B. SHAPIRO ◽  
M. SHEPPARD ◽  
S. KRONHEIM ◽  
B. L. PIMSTONE
Keyword(s):  
Xenopus Laevis ◽  
Tissue Distribution ◽  
South African ◽  
Rich Source ◽  
Gut Peptides ◽  
The South ◽  
The Brain

Immunoreactive somatostatin is present in the brain, gut and pancreas of the South African clawed toad, but is absent from the skin, a rich source of many other brain–gut peptides.

scholarly journals Developmental changes in oxygen consumption regulation in larvae of the South African clawed frog Xenopus laevis

1995 ◽  
Vol 198 (12) ◽  
pp. 2465-2475 ◽  
Author(s):  
D Hastings ◽  
W Burggren
Keyword(s):  
Oxygen Consumption ◽  
Lactic Acid ◽  
Xenopus Laevis ◽  
South African ◽  
Acute Hypoxia ◽  
Lactate Concentration ◽  
Aerobic Metabolism ◽  
Whole Body ◽  
Lactate Levels ◽  
Clawed Frog

Well-developed larval Xenopus laevis (NF stages 58­66) are oxygen regulators, at least during mild hypoxia. When and how they change from oxygen conformers (the presumed condition of the fertilized egg) to oxygen regulators is unknown. Also unknown is how anaerobic metabolic capabilities change during development, especially in response to acute hypoxia, and to what extent, if any, anaerobiosis is used to supplement aerobic metabolism. Consequently, we have investigated resting rates of oxygen consumption (M.O2) and concentrations of whole-body lactate (lactic acid) during development in normoxia and in response to acute hypoxia in Xenopus laevis. M.O2 increased in an episodic, non-linear fashion during development. Resting, normoxic M.O2 increased about tenfold (to approximately 0.20 µmol g-1 h-1) between NF stages 1­39 and 40­44, and then another tenfold between NF stages 45­48 and 49­51 (to approximately 2.0 µmol g-1 h-1), remaining at about 2 µmol g-1 h-1 for the remainder of larval development. M.O2 reached its highest level in newly metamorphosed frogs (nearly 4 µmol g-1 h-1), before decreasing to about 1.0 µmol g-1 h-1 in large adults. X. laevis embryos and larvae up to NF stage 54­57 were oxygen conformers when exposed to variable levels of acute hypoxia. The only exception was NF stage 45­48 (external gills present yet body mass still very small), which showed some capability of oxygen regulation. All larvae older than stage 54­57 and adults were oxygen regulators and had the lowest values of Pcrit (the oxygen partial pressure at which M.O2 begins to decline). Whole-body lactate concentration in normoxia was about 1 µmol g-1 for all larval groups, rising to about 12 µmol g-1 in adults. Concentrations of lactic acid in NF stages 1­51 were unaffected by even severe ambient hypoxia. However, whole-body lactate levels in NF stages 52­66 increased in response to severe hypoxia, indicating that some anaerobic metabolism was being used to supplement diminishing aerobic metabolism. The largest increases in concentration of lactate occurred in late larvae and adults.

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