Circadian and seasonal variations in pineal gland intercellular canaliculi in the white rat.

Seventy Wistar rats are used to study the changes in pineal intercellular canaliculi over a 21-hour period and for two different photoperiods (pre-autumn, first week of September, and winter, first week of February). The study considers these changes at pineal body, cortical and medullar level separately, and compares the values obtained. The results show variations in canalicular surface at different point times (10:00, 14:00, 18:00) and for both photoperiods. The variations are found to favour the cortical layer, and are also observed between nocturnal and diurnal hours. Canalicular surface to greater during the diurnal hours of both photoperiods. Interesting histological findings are described that suggest an important function of the intercellular canaliculi in pineal gland metabolic exchange.     

Kinetics of cellular proliferation and hormonal receptors in EVSA-T breast cancer cell line.

The hormone-independent human breast cancer cell line EVSA-T, originally described as negative estrogen and progesterone receptors is shown to become positive hormone receptors when the cellular proliferation rate is slowed down. The experimental procedure included the following steps: 1) EVSA-T cells were seeded in minimum essential medium supplemented with 10% fetal bovine serum and kept undisturbed for 2 days; 2) culture medium was replaced with Dulbecco's solution and Ham's F-12 and cells were incubated in serum-free media for another 24 h; 3) then, cells were "rescued" with 10% FBS supplemented medium and estrogen (ER) and progesterone receptors (PgR) were measured immediately, time 0, and 6, 12, 18, 24 and 30 h after the media were changed. Cell yield was quantified at the same times. Experimental data indicate that changing the proliferation kinetics makes it possible to detect estradiol and progesterone receptors on EVSA-T cells. Estrogen receptor appeared at 18 h after rescue, 6 hours before progesterone receptor could be detected. Immunohistochemical analysis of ER content confirmed this observation, showing maximal positive stain at 18 h. Furthermore, ER disappeared when cells recovered their normal proliferation rate.     

Birefringence of macromolecules. Wiener''s theory revisited, with applications to DNA and tobacco mosaic virus.

We summarize Wiener's theory of the dielectric constant of heterogeneous systems and extend its application to suspensions of particles with corrugated surfaces and interstitial solvent. We retain a simple geometrical shape for the particles and account specifically for the solvent associated with the particles. We calculate the birefringence of the rodshaped Tobacco Mosaic Virus (TMV) particle and of DNA and find excellent agreement between our numerical results and experimental values from the literature.     

Effect of alpha factor pheromone on the activity of enzymes which catalyze the synthesis and hydrolysis of cell wall structural polymers from Saccharomyces cerevisiae

Cells of Saccharomyces cerevisiae of the a mating type treated with alpha factor contain an increased amount of structural polymers (beta-glucans and chitin) in their cell walls and, consequently, exhibit higher glucan synthetase and chitin synthetase activities than untreated cells. However, alpha factor has no detectable effect on the activities of these enzymes when they are assayed, "in vitro", in the presence of the pheromone. On the other hand, the activity of beta-glucanases remains constant during the time that growth of a cells is kept arrested by alpha factor at the G1 phase of the cell division cycle and starts to increase when budding of the cells is reinitiated.     

R1881 regulation of steroidogenesis in cultured testicular cells

The influence of a synthetic androgen R1881 upon hCG stimulated steroidogenesis in cultured rat testicular cells was investigated. Testicular cells were cultured for 8 days in medium alone and thereafter reincubated for 48 h with appropriate treatments before the collection of media for steroid RIA. Addition of R1881 (10(-6) M) resulted in an overall decrease of hCG (0.3-10 ng/ml) stimulated pregnenolone and progesterone production by cultured cells. The conversion of exogenous steroids of the delta 4 pathway (progesterone,17 alpha-OH-P and delta 4-A) was also studied in cultures supplemented with cyanoketone (10(-5) M) and/or spironolactone (10(-5) M) to prevent endogenous testosterone production. R1881 inhibited progesterone and 17 alpha-OH-P conversion to testosterone (T) and was ineffective when delta 4-A served as precursor for T biosynthesis. The inhibitory effect of R1881 upon Testosterone production was prevented by concomitant treatment with CPA. These observations suggest that R1881 decreases the hCG stimulated testosterone production via inhibition of CSCCE,3 beta-HSD,C17-20 Lyase and likely 17 alpha-Hydroxylase, whereas no effect on 17 beta-HSD could be observed.     

Role ofβ-oxidation in inhibitingLactobacillus leichmanii by fatty acids

The effect of saturated fatty acids from 6∶0 to 16∶0 and oleic acid onLactobacillus leichmanii ATCC 4797 growing in non-skim-milk media was determined. The inhibition by lauric acid was higher than that obtained with any other fatty acid. A mutant (MC12) resistant to the fatty acid inhibition with high β-oxidation activity was also studied. A positive correlation between the ability ofL. leichmanii ATCC 4797 and its derivative MC12 to degrade fatty acids and their resistance to the fatty acid inhibition is shown in this report.     

Isolation of mutants ofLactobacillus bacterias,grown in skim milk,that resist fatty acid inhibition

The effect of saturated fatty acids from 60 to 160 and oleic acid was determined onLactobacillus leichmannii growing in skim milk. The growth of this strain was markedly inhibited by fatty acids from 80 to 120 but not by straight chain fatty acids greater than 130 or less than 70 and oleate. Laurate was the fatty acid with the highest bactericidal effect. Similar results, with little changes depending on strains, were obtained withL. casei, L. plantarum, L. bulgaricus, L. lactis, L. helveticus. Mutants from theseLactobacillus organisms, resistant to fatty acid inhibition, were isolated by a recycling selection procedure. These mutants exhibited high levels of oxidation for laurate. The presence of 2 mM of this compound in the skim milk culture increased the fatty acid oxidation activity four to ten times higher than was exhibited by the parent strains. The practical implications of these observations are discussed.     

Chromosome number evolution in stem derived calluses ofHordeum vulgare L. culturedin vitro

Summary A study of the chromosome numbers of calluses obtained fromin vitro cultured stem nodes of barley over a period of time was carried out. The cells in division in the calluses were found only in growth centres (g.c.) which were independent of one another and easily isolated. At the beginning of the observations, the cell dividing population showed the diploid chromosome number. Tetraploid dividing cells appeared in the 5-month-old calluses and their frequency increased gradually. After 36 months of culture, the frequency of diploid and tetraploid cells was fixed at approximately 50%. The histological observation showed that in the 2-month-old cultures, the calluses were being formed from the epidermis as well as from the stem cortical parenchyma. The medullar parenchyma of the stem was not involved in the callus formation until 5 months of culture. Thus, it was possible to correlate the increase of the tetraploid dividing cell population with the formation of the calluses from the medullar parenchyma.     

Genetic interactions in the control of mitochondrial function in Paramecium

Summary In an attempt to understand the genetic interactions between nuclear and mitochondrial genomes leading to mitochondrial biogenesis, different combinations of known nuclear and mitochondrial mutations have been constructed by microinjection. Eleven different tetrazolium resistant mutant strains, many clearly affecting mitochondrial function, were mjected with mitochondria from four different erythromycin resistant mitochondrial mutants. Cases were found in which mutant mitochondria were unable to replicate in tetrazolium resistant mutants. The successful mitochondrial transfers were characterized for growth rate, temperature and cold sensitivity. Several selected combinations were characterised also for cytochrome spectra and cyanide resistance. Many different phenotypes were produced by the interaction of the different nuclear and mitochondrial mutations. These ranged from a positive interaction in which mutant mitochondria were selected by a nuclear mutant in preference to wild-type, through apparent absence of interaction, to negative interaction in which the mitochondrial-nuclear combination was temperature sensitive even though both parents were thermoresistant. The possible molecular basis of these interactions is discussed.     

Genetic interactions in the control of mitochondrial functions in Paramecium

Summary The genetic and physiological properties of two nuclear mutants of Parameccium tetraurelia affecting mitochondrial properties, and first screened as resistant to tetrazolium (TTC) are described. The mutant TTC _64-1 ^R is strongly deficient in cytochrome c and the mutant TTC _66p ^R is partially deficient in cytochrome aa₃; both mutants display cyanide insensitive respiration in exponential growth phase. In the double mutant TTC _64-1 ^R -TTC _66p ^R /TTC _64-1 ^R -TTC _66p ^R the deficiency in cytochrome aa₃ due to the TTC _64-1 ^R mutation is suppressed. The mutation TTC _64-1 ^R does not suppress cytochrome aa₃ deficiencies due to mitochondrial mutations, but does interact with another nuclear mutation, cl ₁, (compatible only with mitochondria deficient in cytochrome oxidase) in such a way that the double mutant TTC _64-1 ^R -cl ₁/TTC _64-1 ^R -cl ₁ displays a normal amount of cytochrome aa₃. The possible mechanisms and physiological significance of these suppressive effects are discussed.Abbreviations TTC^R/TTC^S resistant/sensitive to tetrazolium - KCN^R/KCN^S cyanide insensitive/sensitive respiration - aa ₃ ^- /aa ₃ ⁺ deficient/normal amount of cytochrome aa₃ - c^-/c⁺ deficient/normal amount of cytochrome c