An automated differential thermal and potentiometric titration apparatus for binding studies

A differential pH-thermal titration apparatus is described which can detect pH differences with a sensitivity of +/- 0.0001 pH units and a thermal sensitivity of +/- 0.00002 degree C at a time constant of 0.1 s. With a reaction which yields 1 kcal mol-1, the current system can detect concentrations as low as 4 X 10(-6) M or, in a 2 ml volume, a total amount of 40 nmol. With a time constant of 0.1 s, the sensitivity is 20 +/- 4 micro degrees C. The experimental protocol is specified by a microprocessor and three modes of operation are possible: titration at constant rate of reagent addition, titration at variable rates of addition so that the contents of both cells are at either constant pH or at a constant temperature and variable rate when a rate of change is specified. Experimental data are collected in files, corrected for heat loss, initial baseline drift, and changes in volume. The final corrected data from the standardized run of 0.01338 M HCl in 0.2 M KCl at 25 degrees C calibrate the pH scale and yield the calorimetric conversion constants and pKw which are calculated and stored for subsequent corrections for the titration of an unknown acid or the measurement of binding constants and heats.

Megakaryocytopoiesis in bone marrow-derived stromal-hemopoietic cells co-cultures: action of Tamm-Horsfall glycoprotein

Murine bone marrow cells are cultured in agar in the presence of marrow-derived fibroblasts and pokeweed-stimulated spleen conditioned medium. Granulo-monocytic colonies and a few megakaryocytic and mixed colonies are induced. The addition of Tamm-Horsfall glycoprotein - a human glycoprotein produced in the kidneys - increases the number of colonies and stimulates megakaryocytopoiesis. The glycoprotein does not have colony-stimulating activity nor does it induce megakaryocytopoiesis in monolayer cultures. Its major glycopeptide retains the ability to increase the number of colonies, but not to induce megakaryocytopoiesis. Cell-cell interactions occurring in the hemopoietic microenvironment and the effect of glucides are discussed.

Tumor-specific tRNA modifications in mouse plasmacytomas and other tumors

RPC-5 chromatography has been used to analyze the aa-tRNA populations found in normal organs and in various tumors in experimental animals. The most extensively studied animal systems have been mineral-oil-induced mouse plasmacytomas and carcinogen-induced rat hepatomas. Certain aa-tRNA species appear to be tumor-specific, e.g., rat hepatoma phenylalanyl-tRNA1 and plasmacytoma asparaginyl-tRNAs2-4. In addition, one of the tumor-specific peaks of asparaginyl-tRNA can be found in normal livers of animals bearing plasmacytomas at a distant site. Many other significant quantitative and qualitative differences among histologically similar plasmacytomas and between normal tissues and plasmacytomas were observed in the chromatographic patterns of isoaccepting aa-tRNAs for 11 of 20 amino acids. Some of the qualitative differences in chromatographic patterns could be correlated with the tumorous nature of the tissue using computer analysis. The program utilized cluster analysis to compare the RPC-5 patterns of aa-tRNAs from 11 plasmacytomas and two normal tissues for each of the 20 amino acids. The variations in these chromatographic profiles are though to be caused by varying degrees of incomplete synthesis of some of the normally modified nucleosides in tRNAs.

TdT-positive and TdT-negative human leukemic cells: specific density and morphology

Peripheral blood cells from 9 E- and 6 D+ SIg- ALL patients and from 11 CML patients in TdT+ blastic crisis were subjected to discontinuous albumin gradient separation according to Dicke's method, and TdT assayed in the six fractions recovered therefrom. The major results were: (i) in E- ALL and in CML-BC, TdT+ cells could be recovered either within a narrow range of specific densities or were spread over most of the gradient, which might suggest differences in cell maturation among the patients; (ii) in some instances, most leukemic blasts were found in TdT-negative or faintly positive fractions; (iii) in most, but not all, E- All and BC, the majority of TdT+ cells was found in low density fractions; (iv) all E+ ALL had high density TdT+ cells. Cell Fractions of most patients were also examined at the electron microscope, and correlations between morphology and marker characterization were tentatively drawn.

[Incidence of HBeAg in hemodialysis patients: preliminary data (author's transl)]

The incidence of HBeAg in HBsAg positive hemodialysis patients in reported. 21.2% of hemodialysis patients have been resulted positive for serum HBsAg. 63.6% of HBsAg positive patients resulted to have HBeAg in their serum. Anti-HBe antibody was never found. The Authors emphasize the importance of HBeAg in hemodialysis patients to evaluate their infectivity.

Biochemical changes induced by tumors at distant sites: altered transfer RNA profiles in livers of mice bearing plasmacytomas

Tumor growth is known to have systemic effects upon the host's metabolism. We report here for the first time that histologically normal livers of mice bearing subcutaneous plasmacytomas contain chromatographic peaks of asparaginyl-, aspartyl-, histidinyl-, and tyrosinyl-transfer RNAs not found in significant amounts in normal livers. Lysyl-, prolyl-, seryl-, threonyl-, tryptophanyl-, and valyl-transfer RNAs, from normal tissues, but these tRNAs are not altered in livers of tumor bearing mice. This suggests that distant tumor growth causes a derangement in one of the liver enzymes that normally modify transfer RNA after transcription.

Transfer ribonucleic acids from eleven immunoglobulin-secreting mouse plasmacytomas. Constant and variable chromatographic profiles compared with the myeloma protein sequences

In order to test the concepts that aminoacyl-tRNAs in plasmacytomas may on the one hand modulate the protein synthesized or on the other hand reflect the structure of the synthesized protein, the RPC-5 chromatographic profiles of aminoacyl-tRNAs for all 20 amino acids were studied in tRNA prepared from normal mouse liver and 11 plasmacytomas. The patterns of isoaccepting tRNA were compared with the structure of the myeloma protein being synthesized. The elution profiles of aminoacyl-tRNAs for nine of the amino acids were constant, i.e. they were the same for liver and all plasmacytomas. Significant variability was observed in the profiles of the other 11 families of aminoacyl-tRNAs: asparagine, serine and tryptophan, had peaks of isoaccepting tRNAs found in tumors and not in liver; glutamic acid, histidine and lysine, had different patterns of aminoacyl-tRNAs in plasmacytomas which could be distinguished from the elution profile of liver; and isoleucine, proline, threonine and tyrosine, showed pattern variability in only a few of the tumors. Valyl-tRNA uniquely had one isoacceptor present in liver but absent in the tumors. This variability is thought to be associated with different posttranscriptional modification of the tRNAs rather than regulation of individual tRNA genes in response to particular amino acid sequences in secreted myeloma proteins. Similarily, the lack of correlation of isoacceptors with sequence differences makes the modulation of protein fine structure by tRNA availability unlikely.

Tumor-associated phenylalanyl transfer RNA found in a wide spectrum of rat and mouse tumors but absent in normal adult, fetal, and regenerating tissues

RPC-5 chromatography was used to examine the phenylalanyl transfer RNA (Phe-tRNA) of 25 normal rat and mouse tissues including adult, fetal, and regenerating liver; whole embryos; and other adult organs. Only a single major isoaccepting Phe-tRNA was found in every case. Phe-tRNA's from 25 transplantable rat tumors and 33 transplantable mouse tumors were similarly examined. Seventeen rat tumors and 10 mouse tumors, of a wide spectrum of histological types, were found to have an additional, tumor-associated Phe-tRNA isoacceptor. This tumor-associated Phe-tRNA was not found in the livers of animals bearing tumors that contained this isoacceptor. Differences in chromatographic behavior between the rat and mouse tumor-associated Phe-tRNA's strongly suggest that they have different structures. Our data suggest that these differences result from different degrees of incompleteness of posttranscriptional modification, most likely at the normally very hypermodified Wye (formerly called Y) base.

Multiple chromatographic peaks of phenylalanyl-tRNA associated with spontaneous hydrolysis of Y base during isolation

In contrast to the single phenylalanyl-tRNA found in normal cells, some tumours are known to have more than one phenylalanine isoacceptor. However, during certain steps in tRNA isolation from normal or tumour tissue, additional chromatographic peaks can be artificially produced which may be confused with the tumour-specific Phe-tRNA. Such procedures as extraction with unbuffered phenol and unbuffered gel filtration chromatography appear to produce adventitious isoacceptors by hydrolysis of Y base.