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Biomedical subjects

M D Bick

Publications and source records attributed to M D Bick.

At least 19 recordsLinked to original sources
PubMed1980

Antithrombin III patterns in disseminated intravascular coagulation.

Antithrombin III-heparin cofactor has now been recognized as a major inhibitor of thrombin and other serine proteases in the blood coagulation system. Since the reaction between antithrombin III and serine proteases is irreversible, one would expect antithrombin III consumption in the face of pathologic intravascular coagulation and attendant generation of thrombin, IXa, Xa, XIa, XIIa, and plasmin. Using a new assay system for antithrombin III that is unaffected by heparin or fibrino (geno) lytic degradation products, antithrombin III was monitored before and during therapy in 38 patients who had acute or chronic disseminated intravascular coagulation. It was found that early and significant decreases in anththrombin III occur in disseminated intravascular coagulation and thus may serve as a useful diagnostic tool. It was further found that monitoring antithrombin III during therapy reflected a cessation of antithrombin III consumption and, thus, served as an indicator of the efficacy of therapy in stopping the clotting process. Since the assay system is unaffected by fibrino(geno)lytic degradation products and heparin, it proved useful in monitoring the efficacy of heparin therapy for disseminated intravascular coagulation. In addition for this group of patients, it appeared that mini-heparin therapy and large doses of heparin were equally efficacious in correcting other laboratory abnormalities of disseminated intravascular coagulation, and in controlling clinical hemorrhage in disseminated intravascular coagulation.

Anticoagulants↗
PubMed1979

Proteins of BrdU-dependent hamster cell lines as characterized by two-dimensional gel electrophoresis.

Cell lines which exhibit the BrdU-dependent phenotype (B4 and HAB) were studied with respect to BrdU-induced alterations in genetic expression by two-dimensional gel electrophoresis. A comparison of the proteins from the HAB cells, in which the DNA is 100% substituted by BrdU, to those of the unsubstituted parent line (3460) showed 55 protein alterations; the synthesis of 15 increased while that of the other 40 decreased. When 3460 cells were grown in BrdU such that their DNA was greater than 50% substituted, 27 protein changes could be detected; of these, the synthesis of 10 increased while that of 17 decreased. A comparison of all these changes in the various cell lines showed six which were common to the BrdU-substituted cell lines. The proteins from another Syrian hamster cell line, BHK-21 (C-13) and those of HAB cells grown in thymidine or BrdC were also examined on two-dimensional gels. Although BrdU has a dramatic effect on many cellular functions, relatively few changes in the pattern of protein synthesis could be detected in these cell lines, perhaps reflecting the specialized action of this analogue on particular cellular functions.

Animals↗
PubMed1978

Bromodeoxyuridine induction of deoxycytidine deaminase activity in a hamster cell line.

The Syrian hamster cell line, RPMI 3460, was found to express barely detectable levels of the enzyme deoxycytidine deaminase. In contrast, the cell lines B4 and HAB, which are derived from 3460 cells and have approx. 60 and 100% bromodeoxyuridine substitution in DNA, respectively, show an approx. 50-fold higher enzyme activity. Deoxycytidine deaminase activity can be "induced" in 3460 cells by growth in 10(-5) M bromodeoxyuridine, as well as by the other halogenated pyrimidines, iododeoxyuridine and chlorodeoxy-uridine. The time required for maximal enzyme activity to accrue (approx. 8 days) suggests that new genetic expression is required for enhanced deoxycytidine deaminase activity and inhibition of induction in the presence of Ara. C shows that bromodeoxyuridine must be incorporated into DNA. In addition, the extent of enhanced deoxycytidine deaminase activity is directly related to the level of bromodeoxyuridine substitution in DNA. Another hamster cell line, BHK21/C13, which shows no detectable deoxycytidine deaminase activity, cannot be induced by bromodeoxyuridine. These results are discussed with respect to a mechanism by which bromodeoxyuridine may alter gene expression due to an altered binding of both positive and negative regulatory proteins to DNA.

Bromodeoxyuridine↗
PubMed1978

Estrogen receptor has enhanced affinity for bromodeoxyuridine-substituted DNA.

The estrogen receptor (E2R) from rabbit uterus has an enhanced affinity for BrdUrd-substituted DNA compared to unsubstituted DNA. Increasing levels of BrdUrd substitution (from 0 to 100%) in a DNA sample are associated with increasingly tighter binding of E2R to that DNA as measured by equilibrium competition experiments and by rates of dissociation (or receptor transfer experiments). Although the rates of dissociation of E2R-DNA complexes vary greatly, depending on the BrdUrd-substitution level in the DNA, no differences were detected between the rates of association of E2R with unsubstituted and fully BrdUrd-substituted DNA. The E2R-DNA complex dissociates more rapidly in 150 mM KCl than in 50 mM KCl; but, at both ionic strengths, BrdUrd substitution in the DNA confers enhanced stability on the complex. The demonstration that a specific mammalian regulatory protein has an enhanced affinity for BrdUrd-substituted DNA further strengthens the possibility that BrdUrd modulates gene expression through an altered binding of regulatory proteins.

Animals↗
PubMed1977

Bromodeoxyuridine inhibition of Friend leukemia cell induction. Mechanism of reversal by deoxycytidine.

Deoxycytidine (dC) reverses bromodeoxyuridine (brdUrd) inhibition of induction in Friend leukemia cells only if added within the first 6 h after the addition of brdUrd. dC is shown to reduce the uptake of [3H]brdUrd into both soluble nucleotide pools and DNA, substantially expand the dTTP pool, and result in a lower level of brdUrd substitution in DNA. When the conversion of dC to thymidine nucleotides is prevented in BATH medium (containing brdUrd, aminopterin, thymidine, and hypoxanthine), dC no longer reverses brdUrd inhibition. These results show that dC exerts its primary effect via alterations in thymidine pools and probably through the resultant lower substitution of brdUrd in DNA.

Bromodeoxyuridine↗
PubMed1977

Interaction of chromosomal proteins with BrdU substituted DNA as determined by chromatin-DNA competition.

Chromatin-DNA competition has been utilized to examine the general nature of chromosomal proteins interacting more strongly with BrdU substituted DNA. When chromatin is incubated with an excess of purified DNA, a portion of the chromosomal proteins will exchange to the purified DNA. These two complexes can then be separated on Metrizamide gradients due to their differing protein/DNA ratios. Using this technique we observe that most nonhistone chromosomal proteins will exchange to a competitor DNA, the extent of exchange being directly dependent upon the competitor DNA being present in excess. While essentially the same proteins will migrate to either unsubstituted or BrdU substituted DNA, the substituted DNA is found to be a quantitatively better competitor and its effectiveness as a competitor is directly related to the level of BrdU substitution.

Bromodeoxyuridine↗
PubMed1976

Nucleotide analysis of DNA and RNA in cells with thymidine totally replaced by bromodeoxyuridine.

The nucleotide composition of nuclear DNA has been determined in a cell line (HAB) that has grown for 275 generations with complete substitution of bromodeoxyuridine (BrdU) for thymidine in nuclear DNA. Within 50 generations there is a approximately 3% decrease in the G content and an equivalent increase in the BrdU content of DNA, relative to the unsubstituted parent cell line. However, these alterations do not continue to accumulate when the cells are grown for up to 275 generations with fully substituted DNA, suggesting that they are not brought about by BrdU-induced base transitions due to mispairing. RNA transcription has been examined both in vivo and in vitro to determine whether or not BrdU substitution in DNA results in large-scale transcriptional errors. The nucleotide composition of 18S and 28S rRNA from cells 0, 60%, and 100% substituted with BrdU does not significantly differ. Further, when DNA from these cells is transcribed in vitro with E. coli RNA polymerase, there is no evidence for altered incorporation of nucleotides into RNA made from the substituted templates.

Bromodeoxyuridine↗
PubMed1976

Thermal denaturation of DNA from bromodeoxyuridine substituted cells.

The thermal denaturation of DNA from cell lines extensively substituted with bromodeoxyuridine has been examined spectrophotometrically over a wide range in ionic strength and by thermal elution from hydroxyapatite columns. BrdU substitution stabliizes DNA at all ionic strengths between 7.5 mM and 1350 mM potassium ion concentration, although a plot of log ionic strength vs Tm deviates from linearity above 150 mM. This nonlinearity is most pronounced with BrdU-substituted DNAs, resulting in a lowered delta Tm between unsubstituted and substituted DNA with increasing ionic strength. DMSO is shown to decrease the Tm of both unsubstituted and BrdU-substituted DNA equally, at a rate of .5 degrees C per 1% DMSO.

Bromodeoxyuridine↗
PubMed1975

A new method for mapping nucleic acid sequence homology by electron microscopy.

We describe here a new method for the electron microscopic mapping of sequence homology in nucleic acids. Specific segments of the T7 chromosome have been isolated following digestion with the restriction endonuclease from Hemophilus aegyptious (Haey). Denatured segments are annealed to the l-strand of T7 DNA; treatment of the hybrid with glyoxal allows only guanosine residues in the single-chain region to the reacted, producing an adduct which will no longer hydrogen bond with its complement on the r-strand. When the segment is displaced and the glyoxalated l-strand allowed to renature with the r-strand, "H" shaped structures are produced in which the duplex region corresponds to the position of sequence homology with the segment. The conditions employed for glyoxalation do not detectably disrupt duplex regions as small as 400 base pairs. This procedure should be generally useful for observing sequence homology in more complex DNA molecules containing duplex regions which can be specifically enriched for and their arrangement determined by electron microscopy.

Base Sequence↗
PubMed1975

Misincorporation of (TP during transcription of poly dAT-dAT and poly dABU-dABU.

The synthetic DNA alternating copolymers poly dAT-dAT and dABU-dABU have been transcribed with E. coli RNA polymerase to measure the level of BrdU-induced misincorporation of guanine during transcription. GTP is found to be misincorporated into both copolymers at a frequency of 1 per 1000-2000 nucleotides polymerized. Using alpha-32P-GTP, the nearest neighbors to GMP are found to be UMP (approximately 63%), GMP (approximately 25%) and AMP (approximately 17%), with no apparent difference between the two templates. These results suggest that BrdU-substitution in DNA does not necessarily increase the potential for base mispairing during transcription, and hence, promote the production of faulty RNA molecules.

Adenine Nucleotides↗
PubMed1974

Total substitution of bromodeoxyuridine for thymidine in the DNA of a bromodeoxyuridine-dependent cell line.

In an attempt to isolate cells that could survive with total replacement of thymidine by bromodeoxyuridine in nuclear DNA, cells of a bromodeoxyuridine-dependent Syrian hamster line were cultured in medium containing aminopterin and bromodeoxyuridine but no thymidine. A line of cells, called HAB, was isolated. The HAB cells have been maintained in continuous cultivation for over nine months and have undergone more than 125 population doublings. Direct base analysis showed that the level of substitution of bromodeoxyuridine for thymidine in nuclear DNA was at least 99.8%, and possibly 100%. The existence of such cells raises many questions. The expected high frequency of bromodeoxyuridine-induced base transitions, including errors in both replication and transcription, would seem to be incompatible with the apparently stable transmission and expression of the genetic information in these cells.

Aminopterin↗