Changes in chromosome morphology during the mitotic prophase in the ascus of the apomictic ascomycete,Podospora arizonensis

Summary The cytology of Podospora arizonensis, an apomictic pyrenomycete, has been studied from crozier formation to the first mitotic division in the ascus, using phase contrast light microscopy. Increase in ascus size is accompanied by morphological changes in the chromosomes which are reminiscent of the changes associated with meiosis in normal ascomycetes. The nucleolus is seen to increase in size during the phase of maximal ascus growth, and to decrease thereafter. The significance of these events is discussed.     

Complexes prepared from protein A and human serum,IgG, or Fcγ fragments: characterization by immunochemical analysis of ultracentrifugation fractions and studies on their interconversion

Summary Protein A of Staphylococcus aureus is an Fc receptor for IgG that has been used as a therapeutic reagent to treat cancer in humans and experimental animals. We used ultracentrifugation combined with analysis of isolated fractions by radioimmunoprecipitation and competitive radioimmunoassay with chicken antibodies that bind free protein A or protein A in complexes but do bind free immunoglobulin reagents to localize and characterize the types of complexes formed with different molar ratios of ¹²⁵I-protein A and human ¹³¹I-IgG alone or in serum, and ¹³¹1-Fc fragments. This approach offers a distinct advantage over direct counting of radioactivity in the fractions because resolution of complexes and free reagents is much improved. With excess ¹³¹I-IgG or ¹³¹1-Fc, all the ¹²⁵I-protein A is present only in complexes that contained 4 molecules of immunoglobulin reagent and 2 molecules of protein A (4:2 complexes), whereas with excess ¹²⁵I-protein A the stoichiometry of the complexes was 1:1. We have also shown the preformed 4:2 and 1:1 complexes will interconvert in the presence of added excess protein A or IgG, respectively, and that fresh IgG will exchange with IgG or Fc in preformed complexes. Because protein A has been found to elute from an immobilized reagent used in serotherapy of human cancer and is present in a large excess of IgG, the 4:2 complexes may play an active role in the tumoricidal or toxic reactions observed.Abbreviations SpA protein A of Staphyloccus aureus - VBS EDTA gel, 0.0055 M veronal buffered saline containing 0.01 M EDTA and 0.1% gelatin, pH 7.4 - PBS 0.01 M phosphate buffered saline, pH 7.4     

Cytophotometric evidence of variation in genome size of desmognathine salamanders

The amount of DNA per haploid genome, the C-value, is often directly correlated with nuclear and cell volume, but inversely correlated with cell replication rate. Also, rates of cellular growth sometimes appear to be correlated with organismal developmental rates and life history patterns. Among vertebrates, salamanders exhibit the greatest variation in genome size. In the present study we have examined interspecific and intraspecific variation in blood cell DNA levels in the genus Desmognathus, which shows greater variation in life history traits than any other salamander genus. Specimens of Desmognathus quadramaculatus, D. monticola, D. ochrophaeus and D. wrighti were collected from nature at two localities in the southern Appalachian Mountains. Estimates of genome size in pg of DNA were obtained from blood smears by DNA-Feulgen cytophotometry, using erythrocyte nuclei of Xenopus laevis as an internal reference standard of 6.35 pg DNA per cell. C-values of Desmognathus are the smallest in the order Caudata. Although significant variation in DNA levels was found among the four species, the differences were small, and do not support previously proposed relationships between C-value and life-history variation.     

Changes in the ribonucleic acid metabolism of aging mouse tissues with particular reference to the prostate gland

1. Mouse mast-cell tumours P815 Y and HC were shown to contain glycoprotein material composed of glucosamine, galactosamine, sialic acid, galactose and mannose. 2. The major amino acids released after acid hydrolysis of Pronase-treated digests of the glycoprotein are aspartic acid, glutamic acid, serine, threonine, proline, glycine and alanine. The Pronase-digested material is not degraded in alkaline solution. 3. On incubation of mast cells with [(35)S]sulphate, heparin is the major radioactive product. However, [1-(14)C]glucosamine and d-[(14)C]glucose are incorporated largely into the glycoprotein. 4. The fate of [(35)S]sulphate-labelled and [1-(14)C]glucosamine-labelled material was studied. In each case high-molecular-weight radioactive material is released from the cells into the culture medium. The t((1/2)) of [(35)S]sulphate-labelled material in cells is 70hr. and that of [1-(14)C]-glucosamine-labelled material in cells is 40hr. 5. About 60% of the [(35)S]sulphate-labelled material is present in the mitochondrial and granular fraction. [1-(14)C]-Glucosamine-labelled material is present in both microsomal and mitochondrial and granular fractions, [(14)C]sialic acid being concentrated in the microsomal fraction.     

The effect of castration on the ribonucleic acid metabolism of an experimental prostatic tumour

1. The incorporation of [(14)C]phenylalanine into the protein of microsomes obtained from an androgen-dependent transplantable prostatic tumour has been investigated. 2. The incorporation of [(14)C]ATP into the RNA of the nuclei from the same tumour has also been examined. 3. The castration of the host animal depresses the incorporation of both labelled compounds on subsequent incubation in vitro. 4. The uptake of phenylalanine can be markedly stimulated by polyuridylic acid only in tumours obtained from castrated host animals. 5. The tumour RNA-polymerase activity appears to be dependent on the concentrations of androgens in the host animal.     

The use of digital image segmentation to quantify an aminoanthraquinone dye biotransformation by white-rot fungi

Summary Three methods are presented for the objective, digital evaluation of Remazol Brilliant Blue R dye biotransformation by the white rot fungi, Pycnoporus cinnabarinus and Phanerochaete chrysosporium. This screening technique uses computerized image analysis and a binary logical and function to provide a rapid (2 min per analysis), quantitative, digital densitometry interpretation of enzyme induced chromophore conversion by fungi. A kinetic measure of metabolic activity (enzyme activity coefficient, ) may also be determined. It is shown that chromophore conversion is more rapid and extensive by P. cinnabarinus.     

Differential response of cycling and noncycling cells to inducers of DNA synthesis and mitosis

The objective of this study was to determine whether cells in G(0) phase are functionally distinct from those in G(1) with regard to their ability to respond to the inducers of DNA synthesis and to retard the cell cycle traverse of the G(2) component after fusion. Synchronized populations of HeLa cells in G(1) and human diploid fibroblasts in G(1) and G(0) phases were separately fused using UV-inactivated Sendai virus with HeLa cells prelabeled with [(3)H]ThdR and synchronized in S or G(2) phases. The kinetics of initiation of DNA synthesis in the nuclei of G(0) and G(1) cells residing in G(0)/S and G(1)/S dikaryons, respectively, were studied as a function of time after fusion. In the G(0)/G(2) and G(1)/G(2) fusions, the rate of entry into mitosis of the heterophasic binucleate cells was monitored in the presence of Colcemid. The effects of protein synthesis inhibition in the G(1) cells, and the UV irradiation of G(0) cells before fusion, on the rate of entry of the G(2) component into mitosis were also studied. The results of this study indicate that DNA synthesis can be induced in G(0)nuclei after fusion between G(0)- and S-phase cells, but G(0) nuclei are much slower than G(1) nuclei in responding to the inducers of DNA synthesis because the chromatin of G(0) cells is more condensed than it is in G(1) cells. A more interesting observation resulting from this study is that G(0) cells is more condensed than it is in G(1) cells. A more interesting observation resulting from this study is that G(0) cells differ from G(1) cells with regard to their effects on the cell cycle progression of the G(2) nucleus into mitosis. This difference between G(0) and G(1) cells appears to depend on certain factors, probably nonhistone proteins, present in G(1) cells but absent in G(0) cells. These factors can be induced in G(0) cells by UV irradiation and inhibited in G(1) cells by cycloheximide treatment.     

The regulation of haemoglobin synthesis in cultured chick blastoderms by steroids related to 5beta-androstane.

1. After 24h of incubation, the blastoderm may be dissected from the early developing chick embryo and successfully maintained under conditions of organ culture in vitro. 2. Low concentrations of steroids related to 5beta-androstane stimulate the synthesis of foetal haemoglobins, types E and P, in a highly steroid- and tissue-specific manner.     

Nuclear components responsible for the retention of steroid--receptor complexes, especially from the standpoint of the specifcity of hormonal responses.

1. By covalently linking nuclear components from hormone-sensitive cells to Sepharose 2B, it is possible to investigate the interaction between nuclear components and cytoplasmic receptor-steroid complexes by affinity chromatography. 2. Many factors are implicated in the specifity of nuclear-cytoplasmic interactions, including the nature of the nuclear components, the presence of the cytoplasmic receptor protein and the provision of the appropriate steroid ligand. 3. Two distinct sets of binding sites are present in nuclear extracts immobilized to Sepharose 2B, namely a small number of specific high-affinity sites and a larger number of non-specific low affinity-sites. 4. Considerable evidence supports the importance of the high-affinity binding sites in the manifestation of hormonal specificity in different tissues. Although the study has centred largely on androgenresponsive systems, the findings are germane to cytoplasmic-nuclear interactions in general. 5. The high-affinity or acceptor sites in nuclear extracts reside in the basic but non-histone protein fraction. 6. Hormonal specificity is seemingly maintained by both the cytoplasmic and nuclear components, and the results are discussed in the context of the mechanism of action of steroid hormones.