Effect of thyroid hormone on the abundance of Na,K-adenosine triphosphatase alpha-subunit messenger ribonucleic acid

The effects of thyroid hormone on Na,K-ATPase alpha-subunit mRNA (mRNA alpha) content and Na,K-ATPase activity were measured in renal cortex, heart, and cerebrum of hypothyroid rats 24 and 72 h after injection of diluent or T3. Use of a cDNA probe complementary to rat brain mRNA alpha in Northern blot analysis revealed a single 26-27 S band in RNA isolated from these three tissues regardless of thyroid status. Tissue mRNA alpha content was estimated by dot blot analysis of whole cell extracts and isolated total RNA. Injection of T3 augmented mRNA alpha content by 2.1- to 2.5-fold in kidney cortex and myocardium at 24 h. After three daily injections of T3, the increases in mRNA alpha were evident despite a global increase in RNA content associated with hypertrophy of these target tissues. Furthermore, the increases in abundance of mRNA alpha after 72 h of T3 treatment correlated with enhancement of Na,K-ATPase activity. In contrast, both mRNA alpha and enzyme activity were invariant in the cerebrum. These data suggest that T3-induced augmentation of Na,K-ATPase activity is mediated, at least in part, by increased mRNA alpha content in target tissues.     

Antibody-induced antigenic modulation is antigen dependent: characterization of 22 proteins on a malignant human B cell line

Expression of several of the surface antigens on normal and malignant hematopoietic cells is reduced or is modulated by incubation with specific antibodies. Although antigenic modulation provides a means by which cells can escape antibody-mediated immune destruction, the physiologic significance and frequency of this phenomenon are both poorly understood. To begin to address these issues, we identified and characterized surface antigens on the malignant B cell line Laz 221 established from a patient with acute lymphoblastic leukemia (ALL). Indirect immunofluorescence analysis with the use of 26 hematopoietic cell populations and immune precipitation studies with the use of iodinated ALL cells indicate that 163 monoclonal antibodies (MoAb) identify 22 different proteins on this cell line, including at least six previously described surface molecules. Seven of these antigens are expressed by all nucleated cells examined, whereas only the mu chain of immunoglobulin is B cell specific. Incubation of specific MoAb with cultures of Laz 221 cells at 37 degrees C reduces or modulates surface expression of five of these 22 antigens (p45, immunoglobulin mu chain, transferrin receptor, common ALL antigen (CD10), and p105). Studies that made use of multiple MoAb specific for the same antigen suggest that the capacity for antigenic modulation is an intrinsic property of individual antigens. These studies also suggest that the murine immune response to shared human antigens varies from one immunizing cell population to another. For example, three of the antigens present on Laz 221 cells were only identified by MoAb raised to the Burkitt's cell line Ramos and vice-versa. Only one of these six shared antigens is present in greater amounts on the immunogenic cell population. Immunogenicity of individual human antigens in the mouse may be a function of their cell surface environment.     

Solubility of proteins

A theory is presented on the solubility of proteins, in the hydrated as well as in the dry state, and in water as well as in organic solvents. To this effect, colloidal stability is assimilated with the solubility of the proteins, considered as hydrated entities. By means of a surface thermodynamic approach it can be shown that an increase in size of a hydrated protein must lead to insolubility, even in the absence of any change in a protein's surface properties. This can be substantiated experimentally by comparing the surface properties of immune complexes with those of their constituent immunoglobulins, as well as by comparing some of the properties of intact tobacco mosaic virus with those of its monomeric capsid subunits. Insolubilization of proteins by means of charge interactions as well as by dehydration is studied; an explanation is given of why precipitation caused by charge interactions is more likely to lead to partial irreversible denaturation than precipitation caused by protein-protein interactions brought about by partial dehydration (e.g., by “salting-out”). A link is established between the smallness (or even the negative value) of the interfacial tension between given proteins and various solvents and their solubility in these solvents. The energy of hydration of proteins can also be measured, and the differences between the free energies of interaction of dried and hydrated proteins with water point toward the additional processes underlying the solubilization, i.e., toward the conformational change of a protein in the process of becoming hydrated. The parameter of conformational change of a protein, while becoming hydrated, appears to be more closely linked to its degree of hydration than to its hydration energy.     

Binding studies of substance P anterior pituitary binding sites: changes in substance P binding sites during the rat estrous cycle

Previous studies have shown that substance P (SP), an undecapeptide widely distributed in the gastrointestinal tract and in the peripheral and central nervous system, is a putative regulatory peptide involved in the control of reproductive function. Specifically, SP inhibited, at the anterior pituitary (AP) level, the stimulatory action of a physiological concentration (10(-8) M) of Gonadotropin Releasing Hormone (GnRH) on the release of the luteinizing hormone (LH). In the present work, we have demonstrated the presence of specific SP binding sites in the AP and related changes in the number of these sites to GnRH receptor number, hypothalamic SP and GnRH content and LH secretion during the rat estrous cycle. High affinity saturable SP binding sites (Kd, 1.5 approximately equal to 10 nM) were demonstrated in AP membranes using [3H]-SP or a novel analog, [125I]-(D-Tyr0, NorLeu11)SP. The binding affinity of SP fragments decreased with progressive removal of amino acid residues from N or C termini of the molecule. Other neuropeptides had low affinity for the SP binding sites. During the rat estrous cycle, SP and GnRH binding capacity of the anterior pituitary were inversely related. At the time of the proestrous LH surge, the AP binding capacity was low for GnRH but high for SP. The highest content of SP in the hypothalamus were recorded during the afternoon of proestrus when hypothalamic GnRH levels were lowest and the preovulatory surge occurred. These studies have established the presence of high affinity specific binding sites for SP in the AP which alter during the estrous cycle in a manner appropriate for mediating the direct inhibitory effects of SP on LH release in vitro.     

Relative regeneration proficiency ofArabidopsis thaliana ecotypes

We have compared regeneration proficiency for cultured explants from different tissues of different ecotypes ofArabidopsis thaliana. Proficiency varies widely with both tissue and ecotype, and is highest when the flux of light during regeneration is low. Analysis of F1 hybrids suggests that high proficiency is dominant to low proficiency.     

Plant growth in relation to a rain incident in Wadi Agag,South Egypt

Plant growth in the extremely arid southern part of the Eastern Desert of Egypt is supported by the torrential moisture stored in the subsurface layers of wadi-fill deposits. The space-time stratification of the soil moisture and corresponding adaptive stratification of root systems lead to the niche separation of the species. The survivorship of all studied plants except Zilla spinosa, has a low mortality at early and middle life, but a rapid change to high mortality at a later stage. Zilla spinosa shows the high juvenile and low adult mortality which related significantly to the population density.     

Changes in UsnRNA biosynthesis during rat liver regeneration

Partial hepatectomy (P.H.) induces a partially synchronized growth response of liver under normal regulation of growth. In this phase changes in cellular morphology, radial distribution pattern of cells and other biological as well as major biochemical changes are well documented [24]. Here, we have shown that the cellular content of UsnRNAs altered during this proliferative phase as well. The level of spliceosomal UsnRNAs (U1, U2, U4–U6) gradually decreased by 30–50% upto 48 hrs of P.H. followed by gradual increase to reach the normal level within one month of P.H. The U3 snRNA level on the other hand, was nearly equal to that in normal liver at 48 hrs of P.H. but in 24 and 72 hrs of P.H. its level was high (4 fold) in contrast to that in other UsnRNAs. Thus, it is clear from our data that the level of all the six UsnRNAs decreased during 48 hrs of P.H. compared to that after first 24 hrs. This has been correlated in the kinetics of UsnRNAs' synthesis (in terms of labelling) in isolated hepatocytes, where the rate of labelling of all the six UsnRNAs increased 20–30% in 24 hrs regenerating hepatocytes (R.H.) followed by sharp decrease by 30–50% within next 24 hrs, compared to that in the normal hepatocytes. But from 72 hrs onwards in R.H. the rate of labelling of all the six UsnRNAs again increased by 30–50% (compared to that in normal hepatocytes) followed by decrease of their labelling-rate to reach the normal level in R.H. within one month of P.H. Thus, it may be concluded that the changes in UsnRNAs' level during the proliferative phase of liver regeneration may be either due to the alteration in the rate of synthesis (in terms of labelling) or along with it differential turn over rate; this phenomenon may have some consequences with the regenerative process of liver.This paper was published in Molecular and Cellular Biochemistry131:67–73, 1994. Kluwer Academic Publishers regret the publication of the only partly corrected version.     

Genetic control of male fertility in Arabidopsis thaliana: structural analysis of premeiotic developmental mutants

We have taken a mutational approach to identify genes important for male fertility in Arabidopsis thaliana and have isolated a number of nuclear male/ sterile mutants in which vegetative growth and female fertility are not altered. Here we describe detailed developmental analyses of four mutants, each of which defines a complementation group and has a distinct developmental end point. All four mutants represent premeiotic developmental lesions. In ms3, tapetum and middle layer hypertrophy result in the degeneration of microsporocytes. In ms4, microspore dyads persist for most of anther development as a result of impaired meiotic division. In ms5, degeneration occurs in all anther cells at an early stage of development. In ms15, both the tapetum and microsporocytes degenerate early in anther development. Each of these mutants had shorter filaments and a greater number of inflorescences than congenic male-fertile plants. The differences in the developmental phenotypes of these mutants, together with the non-allelic nature of the mutations indicate that four different genes important for pollen development, have been identified.