The Corpus Allatum and Oogenesis in Rhodnius Prolixus (Stål.)

1972 ◽  
Vol 56 (1) ◽  
pp. 201-214 ◽  
Author(s):  
G. E. PRATT ◽  
K. G. DAVEY
Keyword(s):  
Size Distribution ◽  
Size Range ◽  
Rhodnius Prolixus ◽  
Corpus Allatum ◽  
Primary Site ◽  
Yolk Protein ◽  
Follicle Cells ◽  
Free Access ◽  
Site Of Action ◽  
Terminal Oocyte

1. In the ovarioles of both normal and allatectomized females the spaces open between the cells of the follicle layer and vitellogenesis begins as the terminal oocyte grows through the 350-400 /µm size range. 2. In both normal and allatectomized ovarioles the growth of the larger oocytes is markedly co-ordinated so that, for example, each ovariole contains only one oocyte in active vitellogenesis. 3. A consideration of the size distribution of the terminal oocytes in normal and allatectomized ovarioles demonstrates that vitellogenesis begins later and proceeds more slowly in allatectomized animals. 4. Allatectomy markedly depresses the number of mitoses in the trophic primordium, but this is held to be a feedback phenomenon resulting from a decreased demand for the products of mature trophocytes. 5. There is a decreased level of yolk protein in the haemolymph of allatectomized animals. 6. This evidence favours the hypothesis that the primary site of action in Rhodnius of the gonadotropin from the corpus allatum is situated at the level of activation, whereby spaces open between the follicle cells and proteins from the haemolymph are allowed free access to the oocyte surface.

The Corpus Allatum and Oogenesis in Rhodnius Prolixus (Stål.)

1972 ◽  
Vol 56 (1) ◽  
pp. 215-221
Author(s):  
G. E. PRATT ◽  
K. G. DAVEY
Keyword(s):  
Normal Level ◽  
Size Range ◽  
Critical Size ◽  
Rhodnius Prolixus ◽  
Corpus Allatum ◽  
The Third ◽  
Ovarian Growth ◽  
Ponceau S

1. In females which have been re-fed after various periods of fasting there is a delay in the resumption of ovarian growth which becomes greater with longer periods of starvation. 2. In females kept without food for 28 days before re-feeding, vitellogenesis is not resumed until 4 or 5 days after the meal, whereas the concentration of yolk antigen in the haemolymph returns to its normal level by the third day after the meal. 3. A period of starvation induces an accumulation of oocytes in the size range below that of activation until the fourth or fifth day after re-feeding, when the terminal oocytes pass rapidly through the critical size range and enter vitellogenesis. 4. The tropharia of starved females exhibit a remarkably reduced affinity for the protein stain Ponceau S, and enlarged trophocytes with their characteristic inclusions are absent during the first 6 days after re-feeding.

THE EFFECT OF ULTRAVIOLET RADIATION UPON ENZYMATIC ACTIVITY AND VIABILITY OF THE YEAST CELL

1952 ◽  
Vol 30 (6) ◽  
pp. 561-570
Author(s):  
J. G. Aldous ◽  
D. K. R. Stewart
Keyword(s):  
Alcohol Dehydrogenase ◽  
Ultraviolet Radiation ◽  
Lactic Dehydrogenase ◽  
Population Viability ◽  
Primary Site ◽  
Hexokinase Activity ◽  
Viable Cells ◽  
Site Of Action ◽  
Survival Level ◽  
Nuclear Damage

Suspensions of the cells of baker’s yeast were irradiated with ultraviolet light for sufficient times to produce populations of 75, 50, 30, and 5% viable cells. After washing and drying, various enzyme solutions were prepared from these cells. Enzymatic activities, on a nitrogen basis, were compared to those of solutions prepared from a nonirradiated population. At the 50% survival level, hexokinase, carboxylase, and zymase were inhibited to a degree roughly proportional to the viability. Carboxylase, and to a certain extent, hexokinase activity varied directly as the population viability. Catalase, alcohol dehydrogenase, and lactic dehydrogenase showed no diminution in activity even at the 5% survival level. These results suggest that although ultraviolet radiation may produce nuclear damage, the primary site of action may be certain enzymes of the cytoplasm.

Two actions of juvenile hormone on the follicle cells of Rhodnius prolixus Stål

1975 ◽  
Vol 53 (8) ◽  
pp. 1187-1188 ◽  
Author(s):  
Randa Abu-Hakima ◽  
K. G. Davey
Keyword(s):  
Juvenile Hormone ◽  
Developmental Stages ◽  
Normal Animal ◽  
Rhodnius Prolixus ◽  
Follicle Cells ◽  
Follicular Epithelium ◽  
Intercellular Spaces

The follicular epithelium of vitellogenic oocytes from allatectomized females of Rhodnius fails to develop large intercellular spaces when exposed to juvenile hormone (JH) in vitro. This suggests that in the normal animal, the follicle cells require JH at two developmental stages. Differentiation of the cells in the presence of JH represents one requirement, and only those cells which have undergone this initial priming are fully competent to exhibit the second response, the development of intercellular spaces.

scholarly journals Particle size distribution and particle mass measurements at urban, near-city and rural level in the Copenhagen area and Southern Sweden

2003 ◽  
Vol 3 (6) ◽  
pp. 5513-5546 ◽  
Author(s):  
M. Ketzel ◽  
P. Wåhlin ◽  
A. Kristensson ◽  
E. Swietlicki ◽  
R. Berkowicz ◽  
...  
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Particle Number ◽  
Size Range ◽  
Urban Background ◽  
Total Particle ◽  
Urban Level ◽  
20 Nm ◽  
Traffic Source

Abstract. Particle size distribution (size-range 3–900 nm) and PM10 was measured simultaneously at an urban background station in Copenhagen, a near-city background and a rural location during a period in September-November 2002. The study investigates the contribution from urban versus regional sources of particle number and mass concentration. The total particle number (ToN) and NOx are well correlated at the urban and near-city level and show a distinct diurnal variation, indicating the common traffic source. The average ToN at the three stations differs by a factor of 3. The observed concentrations are 2500 # cm−3, 4500 # cm−3 and 7700 # cm−3 at rural, near-city and urban level, respectively. PM10 and total particle volume (ToV) are well correlated between the three different stations and show similar concentration levels, in average within 30% relative difference, indicating a common source from long-range transport that dominates the concentrations at all locations. Measures to reduce the local urban emissions of NOx and ToN are likely to affect both the street level and urban background concentrations, while for PM10 and ToV only measurable effects at the street level are probable. Taking into account the supposed stronger health effects of ultrafine particles reduction measures should address particle number emissions. The traffic source contributes strongest in the 10–200 nm particle size range. The maximum of the size distribution shifts from about 20–30 nm at kerbside to 50–60 nm at rural level. We also observe particle formation events in the 3–20 nm size range at rural location in the afternoon hours, mainly under conditions with low concentrations of pre-existing aerosol particles. The maximum in the size distribution of the "traffic contribution" seems to be shifted to about 28 nm in the urban location compared to 22 nm at kerbside. Assuming NOx as an inert tracer on urban scale let us estimate that ToN at urban level is reduced by 15–30% compared to kerbside. Particle removal processes, e.g. deposition and coagulation, which are most efficient for smallest particle sizes (<20 nm) and condensational growth are likely mechanisms for the loss of particle number and the shift in particle size.

Synthesis of vitellogenin by the follicle cells of Rhodnius prolixus

2000 ◽  
Vol 30 (7) ◽  
pp. 549-557 ◽  
Author(s):  
Ana Claudia A Melo ◽  
Denise Valle ◽  
Ednildo A Machado ◽  
Ana Paula Salerno ◽  
Gabriela O Paiva-Silva ◽  
...  
Keyword(s):  
Rhodnius Prolixus ◽  
Follicle Cells

scholarly journals Effects of an azasterol inhibitor of sterol 24-transmethylation on sterol biosynthesis and growth of Leishmania donovani promastigotes

1995 ◽  
Vol 308 (1) ◽  
pp. 31-38 ◽  
Author(s):  
P A Haughan ◽  
M L Chance ◽  
L J Goad
Keyword(s):  
Cell Proliferation ◽  
Leishmania Donovani ◽  
Primary Site ◽  
Sterol Biosynthesis ◽  
Proliferation Inhibition ◽  
Complete Replacement ◽  
Inhibition Of Growth ◽  
Absolute Requirement ◽  
Cell Proliferation Inhibition ◽  
Site Of Action

Leishmania donovani promastigotes were cultured in the presence of an azasterol (20-piperidin-2-yl-5 alpha-pregnane-3 beta,20-diol) to determine the effects on sterol biosynthesis and cell proliferation. Inhibition of growth increased gradually with azasterol concentrations up to 5 micrograms/ml; concentrations of azasterol exceeding 5 micrograms/ml were lethal. Sterol biosynthesis was affected by the azasterol when administered at concentrations as low as 100 pg/ml. The primary site of action was the alkylation at C-24 of a delta 24-sterol precursor. The 24-alkylated sterols [ergosta-5,7,24(24(1))-trien-3 beta-ol and ergosta-5,7,22-trien-3 beta-ol] of the protozoan were replaced by delta 24-cholesta-type sterols which then accumulated in the cells. Administration of the azasterol together with a bis-triazole inhibitor of the 14 alpha-methylsterol 14-demethylase reaction, which operates in sterol biosynthesis, resulted in depletion of 24-alkylsterols and their replacement with predominantly 14 alpha-methylsterols lacking a 24-alkyl group. Continuous subculture of promastigotes in the presence of the azasterol resulted in gradual depletion of 24-alkylsterols and their complete replacement by delta 24-cholesta-type sterols. Transfer of the azasterol-treated cells to medium lacking azasterol resulted in a gradual restoration, after several subcultures, of the normal 24-alkylsterol pattern. The results indicate that, although 24-alkylsterols are normally produced by the protozoan, it can nevertheless survive with sterols possessing only the cholestane skeleton. Thus there is no absolute requirement for 24-alkylsterols to fulfil some essential ‘sparking’ role associated with cell growth in promastigotes.

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