Cytochemical investigation into the Ca-dependence of positive and negative hormonal imprinting in Tetrahymena

Insulin gives rise to positive imprinting in Tetrahymena pyriformis, but to negative imprinting in T. thermophila, as revealed by the respective increases and decreases in the insulin-binding capacity of these organisms observed during later interactions with this hormone. We found that changes in insulin-binding capacity exhibited parallelism with fluctuations of the levels of free, intracellular Ca2+ detectable by Quin-2 labeling. An exception was the second interaction of T. thermophila with insulin, which although showing a positive trend, produced a relatively small increase in the level of intracellular Ca2+. These observations suggest an interrelationship between hormone-binding capacity and the fluctuation of intracellular Ca2+ levels. Either hormone binding depends on the availability of Ca2+, or, alternatively, the latter depends on the binding capacity. Further studies are required to elucidate the true nature of this interdependence.     

Substrate specificity of DNA polymerases. I. Enzyme-catalysed incorporation of 5-''1-alkenyl)-2''-deoxyuridines into DNA.

A series of (E)-5-(1-alkenyl)-dUTPs as well as 5-vinyl-and (Z)-5-(1-propenyl)-dUTP have been synthesized to study steric requirements in DNA polymerase reactions. Experiments were carried out in E. coli DNA polymerase I Klenow fragment enzyme system. Substrates were characterized by KM and Vmax-values, initial incorporation rates as well as by total extent of incorporation of the analogues into poly(dA-dT) as a template-primer. Incorporation of the analogues could be best correlated with Vmax-values as well as the very similar initial incorporation rate values. Reactivity (Vmax/KM) showed no correlation with the extent of incorporation. 5-Vinyl-dUTP proved to be as good a substrate of the enzyme as dTTP, whereas (E)-5-(1-heptenyl)-and (E)-5-(1-octenyl)-dUTPs were very poor substrates, their incorporation was strongly limited and they also proved to be very efficient inhibitors of DNA replication, as shown by Ki-values. Substrate specificity of the Klenow enzyme can be explained by the steric hindrance of C-5 substituent, by the "orientational steric substituent effect" concept.     

Discrepancy in hormone binding and information transfer between sister cells of Tetrahymena clones

Tetrahymena cells treated with insulin in mass cultures were separated to single-cell clones or one of the "sister-cells" of dividing Tetrahymena (in single-cell culture) was treated with insulin. In both cases the FITC-insulin binding of sister-cells were compared. The insulin imprinting significantly increased the insulin binding of cells. There was also a significant difference between the imprinted and not imprinted sisters as well as between the not imprinted sisters. This demonstrates the existence of a difference (in hormone binding) between sister-cells and justifies that the information of the first hormone treatment (imprinting) is not equally divided between the sister-cells.     

Induction of hormone receptor formation in the unicellular tetrahymena

Studies based on treatment with antibodies to thyrotropic hormone, luteotropic hormone, growth hormone or adrenocorticotropic hormone have shown that although the unicellular Tetrahymena does not possesssui generis receptors to all polypeptide hormones, such binding structures may arise, or become established in the membrane of the unicellular Tetrahymena in the presence of exogenous hormone. The Tetrahymena subjected to hormonal imprinting still contained an increased amount of hormone after six generation changes, which suggested that either hormone production had been induced by treatment, or the internalized hormone had not been degraded intracellularly. Thus the role of hormonal imprinting in receptor formation has also been substantiated by the immunocytochemical approach used in the present study.     

No effect of isolation on blood pressure and daily electrolyte excretion in rats

The effects of isolation stress on mean blood pressure (BP) and on body weight, water and food intake as well as on urine flow, urinary sodium and potassium excretion were studied in CFY and Long Evans rats. During a 7 day isolation period, food and water intake as well as urine flow, urinary sodium and potassium excretion, as expressed for 100 g body weight, were not changed in either group. Body weight increased similarly in isolated (38 +/- 2 g) and aggregated (41 +/- 5 g) CFY rats. Compared to group housed rats, BP in male CFY animals was not increased after a 7 day isolation (111 +/- 3 vs 111 +/- 3 mmHg, NS). In additional experiments high sodium intake by physiological saline drinking slightly elevated blood pressure but failed to induce arterial hypertension in isolated rats (118 +/- 2 vs 121 +/- 3 mmHg, NS). We conclude that, contrary to some reports from other laboratories, isolation stress has no detectable effect on BP and/or water and electrolyte balance.     

Cytological aspects of in vitro androgenesis in wheat (Triticum aestivum L.) using fluorescent microscopy

Summary Two winter wheat genotypes (Diószegi 200 and Mv 15) were compared for their in vitro androgenic capacity. On average, the induction frequency of embryogenic structures was 71.7% in Diószegi 200 and only 4.3% in Mv 15. The haploid induction ability of the two genotypes differed considerably, with Diószegi 200 being much higher. The difference in the in vitro inductability of the microspores may result from genetic differences which are manifested in the survival rate of the microspores during the culture period and their adaptability to in vitro conditions. Special DNA fluorochrornes were suitable for studying the different pathways of in vitro androgenesis. Our data indicate that the repeated equal divisions of the microspore nucleus might lead to pollen embryo formation, and subsequent divisions of the vegetative portion of the pollen grain after the first asymmetric microspore mitosis can result in pollen callus formation.     

Steady-state sodium absorption and chloride secretion of colon and coprodeum,and plasma levels of osmoregulatory hormones in hens in relation to sodium intake

Summary The plasma levels of four osmoregulatory hormones and their target ion-transport systems in the lower intestines of the domestic fowl were determined in order to elucidate their interrelationship and their setpoints in relation to NaCl intake. White Plymouth Rock hens were adapted to six intake levels of NaCl (0.20±0.02–24.7±1.9 mmoles Na⁺·kg bw^–1·day^–1) for 6 weeks. The Na⁺ absorption and the Cl^– secretion of colon and coprodeum were characterized in vitro by the effects of hexoses, amino acids, amiloride, and theophylline on the short-circuit current (SCC) and electrical potential difference (PD). The NaCl-conserving system of the adult chicken is set at low intake levels of NaCl as the 80% range (quantitized by non-linear, logistic regression analyses) of the change in the plasma [ALDO], the amiloride-inhibitable Na⁺ absorption of coprodeum and colon ( SCC), occurred from 0.18 to 2.3, from 0.9 to 4.3, and from 1.2 to 7.3 mmoles Na⁺·kg bw^–1·day^–1, respectively. These results demonstrate that the amiloride-inhibitable Na⁺ absorption of coprodcum is more closely linked to plasma [ALDO] than that of colon. The aminoacid-Na⁺ coabsorption of colon increased over exactly the same range of Na⁺ intake as the colonic amiloride-inhibitable Na⁺ absorption decreased, whereas the hexose-Na⁺ coabsorption increased at higher levels of Na⁺ intake, from 2 to 11 mmoles Na⁺·kg bw^–1·day^–1. Both these Na⁺ absorption types had reached their maximums at 24.7 mmoles Na⁺·kg bw^–1·day^–1, whereas the plasma [AVT] and plasma [PRL], although significantly increased, apparently had not; their 80% range of change occurred from 9.9 to 99 mmoles Na⁺·kg bw^–1·day^–1, and the main changes in plasma osmolity were predicted to occur from 5.4 to 107 mmoles Na⁺·kg bw^–1·day^–1. These results suggest that these colonic and hormonal variables conserve osmotically-free water and operate at high NaCl intake. The theophylline-induced colonic Cl^– secretion did not change with NaCl intake, whereas the stimulation of SCC in coprodeum decreased with increasing NaCl intake: The main change occurred between 0 and 3.2 mmoles Na⁺·kg bw^–1·day^–1. Thus, all ion-transport capacity disappears in coprodeum with increased dietary NaCl intake, whereas colon maintains its ion-transport capacity (although the nature of the Na⁺ transport changes). It is suggested that hormones defending the extracellular volume and composition are regulated close to zero input and output of both NaCl and water, regardless of whether they are NaCl conserving or free-water conserving. Therefore, changes in their stable plasma concentrations occur at the extremes of tolerable range of NaCl intake.Abbreviation AA aminoacids - ALDO aldosterone - AMI amiloride - AVT arginine vasotocin - bw body weight - CS corticosterone - HEX hexoses - INDO indomethacin - PD potential difference - PRL prolactin - R resistance - SCC short-circuit current - SD standard deviation - SEM standard error of mean - THEO theophylline     

Comparison of the effect of hypoxia on the secretion of the atrial natriuretic factor in spontaneously hypertensive and normotensive rats.

The effect of short lasting hypoxia on blood pressure, plasma atrial natriuretic peptide level and number of specific atrial granules were studied in 26 male spontaneously hypertensive and 24 normotensive Wistar rats. A great difference occurred in ANP secretion between hypertensive and normotensive rats. In the hypertensive animals elevated plasma ANP concentration (130 +/- 27 pg/ml) and decreased granularity in the right atria (73 +/- 2) were found on the first day of hypoxia with a slight elevation in urinary sodium content versus normotensive controls. The blood pressure also decreased although not significantly (190 +/- 14 mm Hg). In Wistar rats increased plasma ANP (130 +/- 34 pg/ml) and decreased atrial granularity versus normotensive controls (72 +/- 10 in the left and 113 +/- 16 in the right atrium) were observed only on the third day of hypoxia without changes in blood pressure and natriuresis. In SHR the rapid but short timed ANP release might be of right atrial origin and probably the consequence of a continuous and perhaps increased secretion of the peptide in normoxic conditions too. In Wistar rats the plasma ANP elevation could be secondary due to the increased plasma level of different vasoactive hormones to hypoxia. In the altered effect of ANP in hypertensive and normotensive hypoxic animals, structural and functional changes in the vascular bed may play a role.