Quantitative Measurement of Ovalbumin Messenger Ribonucleic Acid Activity

Nuclear receptors and female reproduction: a tale of 3 scientists, Jensen, Gustafsson, and O'Malley

Work on the estrogen receptor and glucocorticoid receptor laid the foundation for the discovery of a family of receptors known as the nuclear receptors. Discovery of these receptors has expanded our understanding of many hormonal and nonhormonal substances, which act through the nuclear receptors. These receptors are actually ligand-binding intracellular transcription factors, which induce nuclear expression of specific mRNAs, leading to synthesis of specific proteins with biological activity. This review for the benefit of gynecologists and reproductive physiologists focuses on the work of 3 scientists who were pioneers in the work on the estrogen, glucocorticoid, and progesterone receptors, which has had a major impact on our understanding of reproductive physiology and on the field of nuclear receptors.

A Life-Long Search for the Molecular Pathways of Steroid Hormone Action

The O'Malley laboratory first showed that estrogen and progesterone act in the nucleus to stimulate synthesis of specific mRNAs (ovalbumin and avidin), coding for their respective inducible proteins. The overall molecular pathway of steroid-receptor-DNA-mRNA-protein-function was then established and provided a coherent foundation for future studies of the impact of estrogen and progesterone receptors on endocrine tissue development, adult function, and in pathologies such as cancer. The lab group went on to: biochemically demonstrate ligand-induced conformational activation of progesterone and estrogen receptors, discover the concept of ligand-independent activation of steroid receptors, discover key steroid receptor coactivator intermediary coactivators for receptor function, and define the role of coactivators/corepressors in selective receptor modulator drug action and in cell homeostasis. This body of work advanced our molecular understanding of the critical role of steroid hormones in normal and abnormal physiology and also generated a base of scientific knowledge that served to further modern hormonal therapy and disease management.

Estrogen induction of alcohol dehydrogenase in the uropygial gland of mallard ducks

Treatment of mallard ducks with estradiol, or a combination of estradiol and thyroxine, has been shown to result in the proliferation of peroxisomes and production of diesters of 3-hydroxy fatty acids, the female pheromones, in the uropygial gland of male and female mallard ducks. Such a treatment results in the induction of a unique set of proteins. A cDNA library enriched in hormone-induced transcripts was subjected to differential screening. The nucleotide sequence of one of the two unique cDNA clones, DGH1, had high similarity to the Human class I alcohol dehydrogenase (ADH) gamma subunit and represented the carboxy-terminus of the protein from amino acid 190-374. SDS/PAGE and Western blot analysis of the proteins indicated that the level of a 38-kDa protein that cross-reacted with antibodies prepared against the chicken ADH was increased 5-7-fold by hormone treatment. Assays for ADH activity in the uropygial gland extracts of male mallards showed a 5-7-fold induction of the enzyme by hormone treatment. The 1.9-kb ADH mRNA levels were increased 12-14-fold under these conditions. Of all the tissues tested, the uropygial gland had the highest levels of ADH mRNA. Induction of ADH by estradiol treatment occurred only in this tissue. Elevated levels of ADH were also observed in the glands of male mallards in eclipse, the post-nuptial condition when the hormonal balance is shifted to higher estrogen levels, suggesting that this enzyme is regulated by estrogens in this period. Estradiol treatment caused an 80% decrease in the NAD+/NADH ratio in the uropygial gland and a twofold increase in the fatty alcohol oxidation rate catalyzed by the gland extract. These observations could help explain how increased levels of ADH could contribute to the production of the diesters.

Isolation of RNA for dot hybridization by heparin-DNase I treatment of whole cell lysate

We have developed a new procedure for the rapid preparation of undegraded total RNA from cultured cells for specific quantitation by dot blotting analysis. Pelleted cells are resuspended in hypotonic solution containing a ribonuclease inhibitor and heparin and disrupted by freeze-thaw. Heparin is employed as an agent for nuclear lysis, dissociation of chromosomal protein, and release of mRNA from rough endoplasmic reticulum. We eliminate chromosomal DNA by digestion with DNase I and denature the RNA in the lysate with formaldehyde. After centrifugation to remove debris, the supernatant is used directly for dot blotting. All manipulations are performed in the same microfuge tube and recovery of RNA is quantitative. The procedure is especially useful for processing large numbers of samples. We illustrate its versatility by analysis of specific RNAs in Drosophila, rat, and human cell lines. In reconstruction experiments, less than 80 molecules per cell of a small RNA (beta-globin) can be detected under highly stringent hybridization conditions, using only moderately labeled double-stranded plasmid DNA probes and short film exposures.

Iron deficiency in the elderly

Iron deficiency in the elderly almost always results from blood loss. The loss of iron can be viewed as occurring in four stages, which are reflected in the different tests used to diagnose iron deficiency. Tests used to diagnose iron deficiency have certain limitations regarding their ability to detect iron deficiency before the overt anaemia occurs. The tests which diagnose iron deficiency most accurately are low serum ferritin and reduced iron staining of a bone marrow aspirate. Because iron is present in many metabolic processes besides the production of haemoglobin, iron deficiency results in a variety of defects which are manifested at biochemical, tissue, and functional levels. Iron is a component of several enzymes in the respiratory electron transport chain. Adequate haem and iron levels are necessary to control cytoplasmic and mitochondrial protein synthesis. Iron deficiency results in tissue defects, including those affecting the gastrointestinal tract, and defects of mitochondria and lymphocytes. Normal iron levels seem to be necessary for normal work capacity. A deficiency of iron, independent of the anaemia, results in reduced exercise capacity that can be measured in both physiological and economic terms. Elderly patients complaining of increased fatigue should therefore be screened for iron deficiency. There is evidence to suggest that iron deficiency may predispose individuals to certain infections. Other information points to the promotion of certain bacterial and parasitic infections after rapid correction of iron deficiency. Thus elderly patients having iron replacement therapy should be followed closely. A deficiency of iron has been shown to result in certain behavioural and learning abnormalities. Iron deficiency has been shown to result in impaired control of body temperature, resulting in an increase in catecholamine levels. The impairment in heat-generating ability was shown to result from reduced conversion of T4 to T3 in the peripheral tissues.

Comparison of the effects of exogenous native phytochrome and in-vivo irradiation on in-vitro transcription in isolated nuclei from barley (Hordeum vulgare)

In barley seedlings the transcription of genes coding for the light-harvesting chlorophyll a/b protein (LHCP) is stimulated and the transcription of genes coding for the NADPH-protochlorophyllide oxidoreductase (reductase) is repressed by light working via the phytochrome system. This phytochrome-mediated control of gene expression has been studied by monitoring in-vitro transcription in isolated nuclei. Two different experimental approaches have been used to elucidate the function of phytochrome (Pfr) during the transduction of the light signal. Concentrations of phytochrome were varied experimentally either by illuminating intact plants or macerated plant material prior to the isolation of nuclei or by adding purified phytochrome (Pfr) in its native 124-kDa form to the isolated nuclei. Our results indicate that there are at least two different steps involved in the phytochrome control of specific gene expression. (i) There is a rapid and transient change in the transcription rate which is saturated by very low levels of Pfr. (ii) There is a change in the duration and the maximum range of the transient change; this step requires relatively high Pfr concentrations and thus reacts very sensitively and rapidly to changes in Pfr levels as induced by secondary irradiations. This second step, but not the first one, could be triggered by the addition of purified oat phytochrome to a reconstituted nuclear system. This effect of purified phytochrome could only be shown if nuclei isolated from red-light (R)-irradiated seedlings were used. It was thus possible to simulate the effect of an in-vivo-applied second R pulse by the addition of Pfr to nuclei isolated from R-preirradiated plants.

Properties of cells transformed by the middle T-antigen-coding region of polyomavirus

A series of 10 Fischer rat transformed clonal cell lines were independently obtained in infections with a defective polyomavirus containing a scrambled genome except for an intact middle and small T-antigen-coding region. These cells synthesize middle and small T antigens; no fragment of large T antigen can be detected in any of them. The transformed phenotype of this set of cell lines (designated LT-) has been studied with respect to serum dependence, saturation density, and anchorage independence and compared with the phenotype of a set of six transformants (designated LT+) which synthesize detectable to high levels of shortened or normal-sized large T antigen. Both the LT+ and the LT- groups of polyomavirus transformants display a range of transformed phenotypes. These ranges overlap, and the variations within each group are larger than the variations between the two groups. Thus, the results suggest that, for established Fischer rat fibroblasts, the maintenance of any of the three phenotypes tested and, in particular, of serum independence is not necessarily correlated with the levels of large T antigen or fragments thereof.

In vitro translation of human pheochromocytoma messenger RNAs: characterization of tyrosine-hydroxylase and dopamine-beta-hydroxylase

mRNAs extracted from human pheochromocytoma were translated in vitro in a lysate of a rabbit reticulocytes. Two enzymes of the biosynthetic pathway of the catecholamines, tyrosine-hydroxylase (TH) and dopamine-beta-hydroxylase (DBH), were characterized as translation products after immunoprecipitation by specific antisera and electrophoretic analysis. The precursor of TH is a polypeptide having a molecular mass of 62,000 identical to that found for the mature protein. The molecular mass of the precursor of DBH 73,000 while that of the mature form is 79,000. TH and DBH have been translated from mRNAs having sedimentation coefficients of 22S and 25S, respectively.

Afrikander cattle congenital goiter: size heterogeneity in thyroglobulin mRNA

The mRNA coding for thyroglobulin in cattle homozygous for an autosomal recessive defect of thyroglobulin synthesis was investigated using a recombinant plasmid containing bovine mRNA coding sequence. Total RNA preparations from goiter contained one third of the thyroglobulin mRNA sequences found in normal thyroid tissue. This mRNA was not translated into thyroglobulin by Xenopus oocytes. Northern transfer analysis revealed both a normal sized and a smaller thyroglobulin mRNA in the goiter.

Human keratinocytes that have not terminally differentiated synthesize laminin and fibronectin but deposit only fibronectin in the pericellular matrix

Fibronectin and laminin production by human keratinocytes cultured in serum-free, low-calcium medium without a fibroblast feeder layer were examined by several techniques. By indirect immunofluorescence, fibronectin but not laminin appeared as short radial fibrils between the cells and the substratum, and in the pericellular matrix. Synthesis of fibronectin and laminin by 7-day keratinocyte cultures was determined by 18 hr 35S-methionine metabolic labeling followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography. Fibronectin accounted for 2.9% of total synthesized protein, 26.5% of fluid phase protein secretion, and 4.3% of deposited ECM protein. In contrast, only 0.1% of the total synthesized protein was laminin, little (6.3%) of this product was secreted, and none of this product was deposited in the ECM. Our results indicate that human keratinocytes under culture conditions that prevent terminal differentiation in vitro can synthesize, secrete, and deposit fibronectin in the extracellular matrix. Although these cells synthesize laminin, they secrete very little and deposit no detectable laminin in the matrix under these culture conditions. From these data we believe that fibronectin may play an important role in the interaction of epidermal cells with connective tissue matrix during wound healing or morphogenesis in in vivo situations in which the epidermis is not terminally differentiated.

Optimisation of protein synthesis rates in reticulocyte lysates and reconstituted systems

Means of increasing the very low activity of a reconstituted protein synthesising system from rabbit reticulocytes were investigated. Increasing the concentration of labelled amino acid, addition of polyamines, use of Sepharose-filtered as opposed to centrifuged ribosomes, use of untreated as opposed to gel-filtered cytosol and an increase in ratio of cytosol to ribosomes all contributed to the increase in activity of the system to the point where activity was clearly consistent with initiation taking place. Similar activities could not be attained with rat liver cytosol though rat liver ribosomes incorporated well in reticulocyte cytosol. Incorporation by lysates was also found to be dependent on the concentration of the labelled amino acid added.

The chick oviduct in tissue culture. II. Estrogen affects ovalbumin synthesis differently than oviduct cell proliferation

The addition of estradiol alone to oviduct cell cultures was sufficient to induce ovalbumin synthesis, detectable both by immunofluorescence and immunoprecipitation of newly synthesized protein. Most cells stained positively for ovalbumin indicating that the culture conditions promoted the growth of the ovalbumin synthesizing tubular gland cells relative to other cell types. The rate of ovalbumin synthesis was lower than that expected in vivo but as high as or higher than that found in organ culture. In tissue culture ovalbumin gene expression was under the direct influence of estrogen. Previous work showed that estrogen did not stimulate rapid proliferation of oviduct cell cultures (S. S. Seaver, J. van der Bosch & G. Sato, Exp cell res 155 (1984) 241) [5]. Therefore further experiments were done in vivo to correlate the effects of different hormonal regimes on oviduct growth and ovalbumin synthesis. In several instances the hormones affected oviduct growth differently than they affected ovalbumin synthesis. However, there was a strong correlation between the ability of a hormonal regime to stimulate oviduct growth in vivo and the ability of the serum from those chicks to stimulate oviduct cellular proliferation in culture. In vivo estrogen also stimulates oviduct growth by very different mechanisms than it stimulates the expression of the egg white protein genes.

Human keratinocytes synthesize, secrete, and deposit fibronectin in the pericellular matrix

Fibronectin production by human keratinocytes cultured in serum-free, low-calcium medium without a fibroblast feeder layer was examined using several techniques. Immunohistochemical examination confirmed that the cultures were not contaminated with fibroblasts or Langerhans cells. By indirect immunofluorescence, fibronectin appeared as intracellular granules within all cells and as short radial fibrils between the cells and the substratum, and in the pericellular matrix. Conditioned media taken from 4-, 6-, 8-, 10-, and 12-day cultures contained fibronectin as measured by enzyme-linked immunosorbent assay in proportion to the cell number in cultures. Synthesis of fibronectin by 7-day keratinocyte cultures was determined by 18-h [35S]methionine metabolic labeling followed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography. Fibronectin accounted for 12% of the secreted protein under these culture conditions. Our results indicate that human keratinocytes under conditions that prevent terminal differentiation in vitro can synthesize, secrete, and deposit fibronectin in the extracellular matrix.

Heparin-mediated inactivation and transformation of mammary cytoplasmic glucocorticoid receptor

Glucocorticoid receptor of lactating mouse mammary gland cytosol was exposed to heparin when the receptor was either steroid-free or steroid-bound. Heparin caused a dose-dependent and time-dependent loss of steroid binding activity (inactivation) of the steroid-free receptor; this heparin-induced inactivation was inhibited by molybdate. In contrast, steroid-bound receptor maintained its steroid binding capacity in the presence of heparin but the heparin caused transformation of receptor as detected by increased binding to DNA-cellulose and ATP-Sepharose. Heparin also converted steroid-bound receptor from the 7-8S form to the 4S form. Molybdate inhibited both the heparin-induced transformation and associated conversion to the 4S form.

A structural concept for nucleoli of Dictyostelium discoideum deduced from dissociation studies

We aimed to establish whether there is a matrix structure in the nucleolus to which the ribosomal DNA (rDNA) is strongly attached. To detect artifacts that might occur during the harsh histone extraction procedures frequently used for matrix preparation, we dissociated nucleoli of Dictyostelium discoideum with a range of NaCl or heparin concentrations. With heparin treatment significant amounts of rDNA were solubilized into the dissociating solution. When the residual nucleoli were digested with Eco RI, none of the Eco RI fragments of the rDNA remained preferentially bound to the residual nucleoli, indicating that there is no matrix attached to a specific site on the rDNA. When residual nucleoli were examined by electron microscopy, a correlation was found between the extent of solubilization of rDNA, the loss of nucleosomes, and, in heparin-treated nucleoli, the loss of ribonucleoprotein-bound components. These results suggest that the rDNA is released from the nucleoli as soon as nucleosomes have been dissociated and transcription complexes disrupted. Electron microscopy also showed that the NaCl concentration required for dissociation of nucleosomes was higher when divalent cations (Ca2+, Mg2+, Cu2+) were used during the isolation or the treatment of the nucleoli prior to dissociation in high salt. Furthermore, the residual, high-salt-resistant structures were much larger when nucleoli were pretreated with divalent cations or when they were purified in the presence of Ca2+ than when they were purified in its absence. Hence divalent cations, which induce chromatin condensation, prevented nucleolar dissociation whereas treatment with chelating agents, which loosen chromatin compaction, led to much smaller residual matrixlike structures. Nucleoli could be dissociated with heparin to a larger extent than with NaCl so that in Ca2+-free preparations no residual nucleolar matrixlike structures could be detected. Our results suggest that the nucleolar "matrix" seen in the electron microscope is due to incomplete dissociation of the nucleolar material. We propose that in nucleoli of Dictyostelium the rDNA is not attached to a tightly binding matrix structure, but that nucleoli are stabilized by side-to-side contacts between chromatin fibers and transcription complexes.

The cloning, isolation and characterization of a biologically active human enzyme, urokinase, in E. coli

We have cloned double-stranded cDNA copies of plasminogen activator messenger RNA isolated from human fetal kidney cells. Some of the clones express protein of discrete sizes ranging from 32,000 to 150,000 daltons. These products possess antigenic determinants related to human plasminogen activator from kidney cells, bind to an affinity column specific for serine protease and activate human plasminogen to dissolve fibrin clots.

In vitro synthesis of polypeptides of moderately large size by poly(A)-containing messenger RNA from postmortem human brain and mouse brain

Studies were undertaken to optimize the conditions for isolation and in vitro translation of poly(A)-containing mRNA from human postmortem brain. The comparison of several methods for preparation of mRNA from frozen mouse brain indicated that although the yield of mRNA was increased using polysomes prepared in the presence of ribonucleoside vanadyl complexes and subsequently extracted with guanidinium thiocyanate, the translation products were indistinguishable from those synthesized by total cellular RNA directly extracted from tissue with guanidinium thiocyanate. The oligo d(T)-cellulose-purified poly(A)-containing mRNA preparations were translated in vitro in a rabbit reticulocyte lysate in the presence of L-[35S]methionine. Messenger RNA from frozen mouse brain stimulated protein synthesis from 9- to 20-fold over endogenous mRNA. Over 450 polypeptides were reproducibly synthesized and separated by two-dimensional polyacrylamide gel electrophoresis (PAGE); size classes up to 130,000 daltons were present. Direct extraction of RNA from frozen human cerebral cortex and cerebellum with guanidinium thiocyanate followed by oligo d(T)-cellulose chromatography yielded 1.8 micrograms/g and 2.0 micrograms/g, respectively, of poly(A)-containing mRNA; this represents a two- to fourfold increase over our earlier results. In the rabbit reticulocyte translation system human brain mRNA stimulated protein synthesis nearly threefold over endogenous mRNA. Compared with earlier studies, the number of newly synthesized polypeptides was increased by 30%. Over 300 species were separated by two-dimensional PAGE, and size classes up to 130,000 daltons were present, as compared to 70,000 in an earlier report. The polypeptides synthesized by human cerebral cortex and cerebellum were indistinguishable. However, several appeared to be uniquely human when compared with the products synthesized by mouse brain mRNA. The method described for the preparation of postmortem human brain mRNA eliminates the need to prepare polysomes, which are recovered in variable and low yield from the postmortem human brain. The procedure appears applicable to studies on the synthesis of moderately large human brain polypeptides and for investigations of brain protein polymorphism when relatively large numbers of products are required for analysis.

Developmental regulation of glycerol-3-phosphate dehydrogenase synthesis in Drosophila

Methods have been developed to measure the synthesis of glycerol-3-phosphate dehydrogenase (GPDH) during the development of Drosophila melanogaster. In emerged adult flies, GPDH is a principal component of protein synthesis, comprising between 1 and 2% of the protein synthetic effort. This high relative rate of protein synthesis continues throughout adult life during a period of stable enzyme concentration. Therefore, it is evident that GPDH undergoes continual turnover. Analysis of GPDH synthesis in the adult segments reveals that this enzyme is synthesized in head, thorax, and abdomen. In 5-day-old flies, the relative rates of GPDH synthesis in the thorax and abdomen are similar. However, the concentration of GPDH in the thorax greatly exceeds that found in the abdomen. Therefore, it appears that the turnover rate of GPDH in the abdomen must be greater than the turnover rate of GPDH in the GPDH-containing cells (flight muscle) of the thorax. GPDH represents between 0.5 and 0.9% of the protein synthetic effort of larvae. The principle GPDH-containing tissue of larvae is fat body. The turnover of GPDH in larvae is similar to that in adult abdomen. This may be related to the concurrent presence of GPDH isozyme-3 in both tissues. Our studies indicate that the cell type-specific control of GPDH occurs at several levels.

Distribution, quantification and biological activity of messenger RNA coding for human chorionic somatomammotropin during normal pregnancy

Synthesis of hCS by RNA fractions from human placentas obtained at different stages of pregnancy was estimated either by immunological or electrophoretical methods in wheat-germ and reticulocyte cell-free systems. hCS synthesis is preferentially associated with polyribosomes bound to the membrane of the endoplasmic reticulum, as is assumed for a secreted protein. In both translational systems we determined only one precursor form of this hormone of a molecular weight near 24 000. Full-term placentas synthesize hCS as the major protein. This conveniently allowed us to isolate the messenger RNA coding for the hormone and to synthesize a specific hCS complementary DNA which we used as a probe for quantifying sequences of RNA coding for hCS during pregnancy. In placentas from first-trimester pregnancy, the concentration of hCS mRNA was 4 times less than in the full-term organs, and the hCS synthesis per microgram of RNA added into the translational medium was diminished in the same order of magnitude. In placentas from second-trimester pregnancy, the concentration of hCS mRNA was similar to that obtained at term, and in vitro the hCS synthesis per microgram of translated RNA was also similar to that observed at the end of pregnancy. However, the hCS mRNA content per placenta from mid-term pregnancy was much lower than from full-term gestation. We established a good parallelism, as pregnancy progressed, between the hCS mRNA content, its capacity of hCS synthesis in vitro and the maternal plasma hCS level, indicating that hCS production is controlled essentially by the biological active mass of the placenta.

Immunoglobulin gene expression in a coupled transcription/translation system from mouse plasmacytoma cell-free extracts

Mouse plasmacytoma cytoplasmic extracts and sonicated nuclei have been incubated under conditions which resulted in translation and transcription, respectively. When the cell-free systems were combined, incorporation of radioactive precursors into RNA and protein was enhanced and extended. Coupling of transcription and translation was indicted by the inhibition of protein synthesis, and specifically immunoglobulin synthesis, by actinomycin D and alpha-amanitin. When immunoglobulin synthesis was investigated in MOPC-104E cells Which contain both lambda and K mRNAs but secrete only lambda light chains, the extracts synthesized both K and Lambda light chains. These results indicated that the unexpressed MOPC-104E K mRNA could be translated on homologous ribosomes under the appropriate conditions and suggested that postranscriptional controls may play a role in k-chain gene expression in MOPC-104E cells.

The ovalbumin gene family: hormonal control of X and Y gene transcription and mRNA accumulation

The ovalbumin gene family is composed of three genes, X, Y and ovalbumin, which are expressed in laying hen oviduct. We have analyzed the in vivo transcription products of X and Y genes and the effect of steroid hormones on their synthesis and accumulation. As in the case of ovalbumin, the complete gene transcripts and processing intermediates are present in the poly(A)+ RNA fraction. The mature RNAs are found in polysomes and are translated into proteins. The expression of X and Y genes is controlled by steroid hormones: X and Y RNAs are not detectable in oviducts from chicks withdrawn from estrogen stimulation, whereas in chicks stimulated with estrogen for 7 days, X RNA represents 0.3% and Y RNA 0.8% of ovalbumin mRNA. In laying hen, however, the levels of X and Y RNAs are about 2% of ovalbumin mRNA. After stimulation with other steroid hormones, alone or in combination, the level of X and Y RNA does not achieve that detected in laying hen. Progesterone has a much weaker effect on X RNA accumulation than on that of Y and ovalbumin mRNAs. Studies with isolated nuclei show that X and Y gene expression is regulated by hormones at the level of transcription. However, the differences observed between the transcription rates and the accumulation of X and Y mRNAs suggest that the expression of X and Y genes could also be controlled at the levels of RNA processing and/or mRNA stability.

Induction of plasma proangiotensin by steroid hormones in nephrectomized rats

The response of plasma proangiotensin to various steroids was studied in bilaterally nephrectomized rats. In male animals, estradiol and testosterone increased the proangiotensin level up to 250% and 180% respectively. In female animals, both hormones lead to an increase of proangiotensin up to 220% of the controls, when given at optimal dose. The dose dependence on estradiol and testosterone was about the same in male rats, whereas in female animals the formation of proangiotensin was stimulated by much lower doses of estradiol as compared to testosterone. Adrenalectomy plus nephrectomy reduced the proangiotensin level to 20-30% of the value measured in animals nephrectomized only. Cortisol caused a rapid increase of plasma proangiotensin up to 1000% in adrenalectomized animals. Independent from the adrenal state, the amounts of cortisol necessary to induce proangiotensin were very low as compared to the dose response of other proteins, biosynthesis of which is regulated by cortisol. 21-Dehydrocortisol and aldosterone induced proangiotensin with the same efficiency as cortisol, whereas several other chemically related steroids were less active or inactive. Comparing the biological activity of the various steroids tested, it has to be concluded that the delta 4-ene-3-one structure of ring A, the 11 beta-OH group of ring C and the carbonyl group at C-20 of the ketol side-chain of cortisol are very important with respect to proangiotensin induction. The response of proangiotensin to cortisol, 21-dehydrocortisol and aldosterone could be inhibited by actinomocin D and cycloheximide, whereas the effects of estradiol and testosterone could be reversed by cycloheximide only.

Expression of a chicken chromosomal ovalbumin gene injected into frog oocyte nuclei

Ovalbumin is synthesized by Xenopus oocytes injected with a plasmid containing either the chicken chromosomal ovalbumin gene or a plasmid from which the 5' region of the chromosomal gene has been deleted. However, oocytes injected with a plasmid containing full-length ovalbumin cDNA do not synthesize ovalbumin, despite the fact that at least as much stable, ovalbumin-specific RNA is transcribed from the cDNA as from the chromosomal gene.

Membrane-associated ribosomes in producing and nonproducing mouse myeloma cells

Mouse myeloma cell lines synthesize large amounts of immunoglobulin on their membrane-associated polyribosomes. Variants which no longer synthesize immunoglobulins have been studied and shown to have the same number of tightly bound membrane-associated polyribosomes as the parental cell lines. These polyribosomes are still active in the synthesis of nonimmunoglobulin proteins.

Effect of cycloheximide on the in vivo and in vitro synthesis of ribosomal RNA in rat liver

The action of low (5 mg/kg body wt;) and high (20 mg/kg body wt.) doses of cycloheximide, both causing a rapid and almost complete inhibition of protein synthesis in rat liver is investigated. Short-term (15 min) [14C]orotate incorporation into nucleolar rRNA in vivo is inhibited only by the high dose acting for periods longer than 1 h. The effect may be correlated with a strongly reduced labelling of the cellular pool of free uridine nucleotides. These results indicate that in vivo transcription of rRNA genes may not be under stringent control. The activity of template-bound RNA polymerase A in nuclei isolated from animals treated with both doses of cycloheximide is reduced within 1 h to about 50% of controls reaching nearly plateau levels at longer times of action of the drug. The differential effect of cycloheximide inhibition of protein synthesis on in vivo and in vitro rRNA synthesis suggests the existence of elongation control protein(s) characterized by a rapid turnover and a loose association with the nucleus.

Purification of messenger ribonucleic acids for fast and slow myosin heavy chains by indirect immunoprecipitation of polysomes from embryonic chick skeletal muscle

Fast and slow myosin heavy chain mRNAs were isolated by indirect immunoprecipitation of polysomes from 14-day-old embryonic chick leg muscle. The antibodies were prepared against myosin heavy chains purified by NaDod-SO4-polyacrylamide gel electrophoresis and were shown to be specific for fast and slow myosin heavy chains. The RNA fractions directed the synthesis of myosin heavy chains in a cell-free translation system from wheat germ. Several smaller peptides were also synthesized in lower concentrations. These probably are partial products of myosin heavy chains, since they are immunoprecipitated with antibodies to myosin heavy chains. Immunoprecipitation of the translation products with the antibodies to fast and slow myosin heavy chains showed the RNA preparations to be approximately 94% enriched for fast myosin heavy chain mRNA and approximately 84% enriched for slow myosin heavy chain mRNA with respect to myosin HC type. Peptides having slightly different mobilities on NaDodSO4-polyacrylamide gels were immunoprecipitated by antibodies to fast and slow myosin heavy chains.

[Atypical bile acids (author's transl)]

The metabolism of bile acids in man is disturbed under the conditions of cholestasis. Besides of the main bile acids atypical bile acids can be found, which are mainly eliminated by renal excretion as sulphate esters and glucuronides. The pattern of urinary bile acids up to now renders no conclusions with respect to the underlying disease, although intrahepatic cholestasis seems to be in some way connected with disturbances in the metabolism of 3 beta-hydroxy-5-cholenoic acid, a bile acid, which exerts cholestatic effects by itself. The metabolites to be found seem to reflect a derepression of a genotypical synthesis program, which is not phenotypically apparent in healthy adults, but which may have been active during prenatal developmental stages of the liver.

Improvements in immunoprecipitation of specific messenger RNA. Isolation of highly purified conalbumin mRNA in high yield

We have described previously procedures for the isolation of specific mRNA employing immunoprecipitation of polysomes. In spite of our success with ovalbumin mRNA in the chicken oviduct, we have had considerable difficulties in applying these same published techniques to the immunopurification of conalbumin mRNA, despite the fact that the chicken oviduct synthesizes up to 10% of protein as conalbumin. Here we describe a number of modifications and refinements which have proved essential in obtaining intact conalbumin mRNA in high purity and high yields. These refinements include: (a) improved purification of conalbumin in order to remove contaminating proteins that result in impure antibodies; (b) improved isolation of specific conalbumin antibody in high yields; (c) improved methods for reducing contamination by non-specific polysomes; (d) improved techniques for isolation of RNA from immunoprecipitates resulting in less degradation and higher recovery of conalbumin mRNA; (E) improved techniques for efficient translation of conalbumin mRNA involving treatment of the RNA with methylmercury prior to translation. We conclude that problems involved in the immunoprecipitation of different mRNAs may differ, and that various refinements in techniques may be required for obtaining highly purified preparations of intact mRNA in high yields.