Requirement for cell proliferation for the effects of 5-bromo-2'-deoxyuridine on cultures of chick chondrocytes

Ontogeny of the glucocorticoid receptor and its relationship to tyrosine aminotransferase induction in cultured foetal hepatocytes

The glucocorticoid receptor activity that can be detected in the liver from 15-day foetal rats would appear to be associated with the haemopoietic cells. In hepatocytes, purified by culture for 1-2 days from 15-day foetal rats, the glucocorticoid receptor activity is low and dexamethasone does not induce the enzyme tyrosine aminotransferase. If culture is continued both receptor activity and steroid responsiveness are acquired. Cultured hepatocytes from 19-day foetal liver contain receptor from the first day of culture and, furthermore, the subsequent level of response to glucocorticoids is directly correlated with the actual receptor concentration. It would appear that the glucocorticoid receptor is not acquired by hepatocytes until after 18 days of gestation. Nevertheless, the fact that bromodeoxyuridine has no effect on the rate of accumulation of receptor in hepatocytes suggests that the differentiative event leading to the subsequent appearance of the receptor has already occurred before day 15 of gestation. However, the acquisition of the receptor would appear to be dependent on mitosis as cytosine arabinoside can inhibit the process.

The effect of cytosine arabinoside and bromodeoxyuridine on the appearance of tyrosine aminotransferase in cultured foetal hepatocytes of the rat

1. The acquisition of dexamethasone-inducibility of tyrosine aminotransferase activity by hepatocytes cultured from 15-day-foetal rat liver is blocked in the presence of cytosine arabinoside. 2. Similar results are obtained in the presence of bormodeoxyuridine. 3. No effects on steroid-inducibility of tyrosine aminotransferase are obtained with either of the above compounds in hepatocytes cultured from 19-day-foetal liver. 4. the inhibitory effects of the agents are substantially reversed after their removal from the culture medium. 5. The effects of bromodeoxyuridine suggest that cell differentiation, with respect to tyrosine aminotransferase-inducibility, occurs in cultures of 15-day-doetal hepatocytes. 6. The effects of cytosine arabinoside suggest that such an event is dependent on mitosis.

Effect of 5-bromo-2'-deoxyuridine on growth and differentiation of cultured embryonic retinal pigment cells

Chicken embryo retinal pigment cells cultured for 2 weeks in 1 or 10 microns BrdU accumulate only 25% of the amount of melanin found in controls. Growth is inhibited by 10 microns BrdU but not by 1 micron BrdU. Cells cultured with BrdU had decreased tyrosinase activity and lost the typical epithelial appearance of controls. Equimolar concentrations of deoxythymidine did not prevent the inhibition of melanogenesis due to BrdU but did prevent the growth inhibition of the higher concentration of BrdU (10 microns). Tenfold higher concentrations of deoxythymidine prevented inhibition of epithelial differentiation and melanogenesis. Ultrastructurally, BrdU produced an absence of melanosomes and disruption of the lamellar array of rough endoplasmic reticulum. The perinuclear arrangement of microfilaments became irregular. The cell surface was radically affected as membranes were no longer ruffled and cell junctions disappeared. Melanogenesis is a complex form of differentiated function, involving synthesis of tyrosinase and control of its activity, macromolecular synthesis of the melanosome, and the subsequent synthesis of melanin within the melanosome. BrdU appears to inhibit melanogenesis through a coordinated and simultaneous interference with these processes, suggesting that there may be a "program" of gene activity for melanogenesis that is regulated as a unit.

Establishment of a new human chondrosarcomatous cell line

A new cultured cell line (HuOS) was established from tumor cells obtained from the pulmonary metastatic foci of a patient diagnosed as chondroblastic osteosarcoma. The tumor cell line was maintained for over 19 months, and morphological and biological characteristics were studied. These cells retained their malignant properties and produced nodules when transferred intramuscularly to nude mice. Morphologically, these nodules revealed a chondromatous pattern.

The effect of 5-bromodeoxyuridine on the postnatal development of the rat cerebellum: a biochemical study

The effect of a thymidine analog, 5-bromodeoxyuridine (BrdU), on the postnatal development of the cerebellum was studied. Rats were injected with 15 mg per 100 gram body weight of BrdU twice a day for 3 consecutive days from the second day after birth, and were killed at 5, 7, 15, 22 and 35 days of age. One hour prior to killing, the rats were given tritiated thymidine. The cerebellar DNA, RNA, protein and cerebroside, and the incorporation of thymidine were measured. BrdU administration caused a markedly retarded growth of the body and the cerebellum. At 35 days of age, the weights of the body and the cerebellum were 42 and 69% of the controls. Quantitative measurements of cerebellar nucleic acids and isotope uptake correlated well with previous morphological observation, and indicated that the analog caused a transient inhibition of cell formation and possibly destruction of stem cell population of the external granular layer. This inhibitory effect was compensated later by a more rapid DNA deposition and a prolongation of the period of cell proliferation. However, the restitution was incomplete and resulted in a permanent deficit in the final cell number, as reflected by the reduction in the size of the cerebellum of the BrdU-treated rats.

Distribution of 5-bromodeoxyuridine and thymidine in the DNA of developing chick cartilage

In order to study the mechanism of the irreversible effects of BrdUrd on the differentiation of limb bud mesenchyme to cartilage, the reannealing behavior of DNA obtained from such cells was examined. Cells incubated with [3H]thymidine ([3H]dThd) during days 1 and 2 of culture incorporated label into repetitive, moderately repetitive, and unique classes of DNA. In contrast, when 5-bromo-2'-[3H]deoxyuridine ([3H]Brd Urd) was added during the first 48 hr (in the presence of 32 muM BrdUrd), the label was preferentially incorporated into a late moderately repetitive region. Simultaneous incubation of unlabeled BrdUrd and [3H]dThd revealed a selective inhibition of [3H]dThd incorporation into moderately repetitive regions. Cultures incubated during days 3 and 4 with [3H]dThd incorporated label into all three classes of DNA; however, when [3H]dThd was present during days 3 and 4 in cultures previously incubated with BrdUrd during days 1 and 2, the [3H]dThd was incorporated preferentially in the late moderately repetitive region. The melting behavior of this reannealed DNA was identical with that of the reannealed 1-2 day [3H]BrdUrd-labeled, late moderately repetitive DNA. Turnover experiments revealed that whereas there was no loss of [3H]deoxycytidine or [3H]dThd, 37% of [3H]BrdUrd activity was lost from the DNA in 2 days after removal of the isotopes.

Effect of 5-bromo-2'-deoxyuridine or cytosine-B-D-arabinofuranoside hydrochloride on myelination in newborn rat cerebellum cultures following removal of myelination inhibiting antiserum to whole cord or cerebroside

Myelination was inhibited in cultures of newborn rat cerebellum by exposure to antisera prepared by injecting rabbits with whole guinea pig spinal cord or cerebrosixde mixed with bovine serum albumin. At 15 days in vitro (DIV), when 90-100% of our control cultures were myelinated, antiserum inhibited cultures were washed and refed routine culture medium or medium containing 5-bromo-2'-deoxyuridine (BUdR) or cytosine-B-D-arabinofuranoside hydrochloride (ara-C) in concentrations previously shown to inhibit myelination in our system. The disinhibited cultures myelinated within 2-5 days of removal of antiserum regardless of the presence of BUdR or ara-C. The evidence suggests that the myelin-forming oligodendrocytes do not undergo cell division before myelination during disinhibition from antiserum. In addition, cultures exposed to BUdR on 5-7 DIV in the presence of antiserum and disinhibited at 10 DIV did not have myelinated axons as observed by light microscopy at 15 DIV. Thus, the BUdR sensitive oligodendrocyte division remained intact in antiserum inhibited cultures. We conclude that the antisera inhibit myelin formation without interrupting the pattern of cell division or the covert differentiation of oligodendrocytes.

Analysis of changes in collagen biosynthesis that occur when chick chondrocytes are grown in 5-bromo-2'-deoxyuridine

Chick embryo chondrocytes, in primary culture, initially synthesize only Type ii collagen (chain composition, [alpha1(II)13), as judged by two criteria: (i) carbosymethyl-cellulose chromatography of the denatured collagen, and (ii) carbosymethyl-cellulose chromatography of the cyanogen bromide peptides derived from the isolated chains. After a period of growth in 5-bromo-2'-deoxyuridine, however, synthesis of two different types of collagen could be detected after differential salt precipitation of the newly synthesized native collagens from neutral salt solutions at 2.2 M NaCl and subsequently at 0.01 M Na2hPO4. By criteria indicated above, the collagen precipitating at 2.2 M NaCl was identified as Type I collagen (chain composition, [alpha(I)]2alpha2), whereas the collagen subsequently precipitated at 0.01 M Na2HPO4 was found to be comprised entirely of alpha1(I) chains, indicating a chain composition, [alpha](I)]3. We propose to designate the latter type of molecule as the Type I trimer.

The effect of 5-bromodeoxyuridine on DNA replication and cell division in Tetrahymena pyriformis

Populations of Tetrahymena pyriformis were grown in a chemically defined medium containing the thymidine analogue 5-bromodeoxyuridine (BUdR). About 65% of the thymidine sites in DNA were substituted by BUdR. During the first generation in the presence of BUdR, all DNA became hybrid. After the following cell division, in about 80% of the cells the second DNA replication round was initiated but no further cell division took place. The cells could be rescued by removing BUdR and adding thymidine. New replication took place before the first cell division. However, although the cells contained double heavy as well as hybrid DNA, only the hybrid DNA was replicated. After a full replication of the hybrid DNA, normal growth was restored. Melting profiles of normal, hybrid, and double heavy DNA indicated a structural change of the double heavy DNA.