The bioavailability time of commonly used thymidine analogues after intraperitoneal delivery in mice: labeling kinetics in vivo and clearance from blood serum

Detection of synthetic thymidine analogues after their incorporation into replicating DNA during the S-phase of the cell cycle is a widely exploited methodology for evaluating proliferative activity, tracing dividing and post-mitotic cells, and determining cell-cycle parameters both in vitro and in vivo. To produce valid quantitative readouts for in vivo experiments with single intraperitoneal delivery of a particular nucleotide, it is necessary to determine the time interval during which a synthetic thymidine analogue can be incorporated into newly synthesized DNA, and the time by which the nucleotide is cleared from the blood serum. To date, using a variety of methods, only the bioavailability time of tritiated thymidine and 5-bromo-2'-deoxyuridine (BrdU) have been evaluated. Recent advances in double- and triple-S-phase labeling using 5-iodo-2'-deoxyuridine (IdU), 5-chloro-2'-deoxyuridine (CldU), and 5-ethynyl-2'-deoxyuridine (EdU) have raised the question of the bioavailability time of these modified nucleotides. Here, we examined their labeling kinetics in vivo and evaluated label clearance from blood serum after single intraperitoneal delivery to mice at doses equimolar to the saturation dose of BrdU (150 mg/kg). We found that under these conditions, all the examined thymidine analogues exhibit similar labeling kinetics and clearance rates from the blood serum. Our results indicate that all thymidine analogues delivered at the indicated doses have similar bioavailability times (approximately 1 h). Our findings are significant for the practical use of multiple S-phase labeling with any combinations of BrdU, IdU, CldU, and EdU and for obtaining valid labeling readouts.

In vivo Characterization of the Radiosensitizing Effect of a Very Low Dose of BrdU in Murine Cells Exposed to Low-Dose Radiation

The aim of the present study was to characterize the in vivo radiosensitizing effect of a very low dose of bromodeoxyuridine (BrdU) in mice exposed to low-dose radiation by establishing the following: (1) the radiosensitizing effect during DNA synthesis using single-cell gel electrophoresis (SCGE) in murine bone marrow cells, and (2) the number and timing of the mechanisms of genotoxicity and cytotoxicity, as well as the correlation of both end points, using flow cytometry analysis of the kinetics of micronucleus induction in reticulocytes. Groups of mice received intraperitoneal injections of 0.125 mg/g of BrdU 24 h prior to irradiation with 0.5 Gy of ⁶⁰ Co gamma rays. DNA breaks measured using SCGE were determined at 30 min after exposure to radiation. The kinetics of micronucleated reticulocyte (MN-RET) induction was determined every 8 h after irradiation up to 72 h. The results from both experimental models indicated that low-level BrdU incorporation into DNA increased the sensitivity to 0.5 Gy of radiation, particularly in the S phase. The formation of micronuclei by gamma rays was produced at three different times using two main mechanisms. In the BrdU-substituted cells, the second mechanism was associated with a high cytotoxic effect that was absent in the irradiated BrdU-unsubstituted cells. The third mechanism, in which micronucleus formation was increased in irradiated substituted cells compared with the irradiated nonsubstituted control cells, was also related to an increase in cytotoxicity. Environ. Mol. Mutagen. 60:534-545, 2019. © 2019 Wiley Periodicals, Inc.

Enhanced radiosensitization by the cationic liposome-encapsulated thymidine analogue BrdU through the increased intracellular BrdU-uptake on human melanoma as compared to anionic or nonionic liposomal or free BrdU

The synthetic thymidine analogue, 5-bromo-2'-deoxy-uridine (BrdU) was encapsulated in cationic liposome composed of dipalmitoylphosphatidylcholine, cholesterol and stearylamine (molar ratio = 1/1/0.2; diameter = 120 nm), and the radiosensitization of cationic liposomal BrdU was assessed on human melanoma cells HMV-II, with comparing to anionic or nonionic liposomal BrdU and free-BrdU. HMV-II cells were pretreated by cationic liposomal BrdU or free-BrdU and then exposed to X-ray, followed by WST-8 assay to examine cell proliferation. The radiation-induced change of nuclei was defined with Hoechst33342 staining. The rates of thymidine replacement by BrdU and DNA double-strand breaks on HMV-II cells were determined with an anti-BrdU antibody and anti-53BP1 antibody, respectively. On 7th day after X-ray irradiation at 3 Gy, cell proliferation was suppressed more markedly in the administration of cationic liposomal BrdU than free-BrdU at equivalent BrdU doses. Giant polykaryocytes were observed in cationic liposomal BrdU-treated HMV-II cells. Radiosensitization was enhanced dose-dependently along with BrdU doses of 0.1-0.8 μM in the order: cationic liposomal BrdU > anionic liposomal BrdU > nonionic liposomal BrdU (see symbol) free-BrdU. Similarly, the cationic liposomal BrdU augmented the rate of thymidine-moiety replacement by BrdU and DNA double-strand breaks more appreciably than free-BrdU. Therefore, the cationic liposome-encapsulation of BrdU would be one of favorable drug deliveries for facilitating the X-ray therapy against cancer.

Repeated exposure to 5-bromo-2'-deoxyuridine causes decreased proliferation and low-grade inflammation in the lungs of mice

Incorporation of 5-bromo-2'-deoxyuridine (BrdU) into proliferating cells has been used to label dividing cells in many tissues. Although BrdU has been shown to be genotoxic, teratogenic and mutagenic, such adverse effects have largely been ignored by researchers. We determined whether long-term BrdU exposure causes any histopathological changes in the lungs of mice. Eight-week-old male C57/BL6J mice were administered BrdU by intraperitoneal injection on 3 consecutive days of each week for 14 weeks. While no obvious structural changes such as tissue damage, fibrosis, emphysema, airway remodeling, vascular thickening or tumorigenesis were noted, a moderate degree of macrophage infiltration was observed in the airways and lung parenchyma in the lungs of the mice exposed repeatedly to BrdU (BrdU-exposed mice). The proliferative activities of the airway and alveolar epithelial and mesenchymal cells were reduced in the BrdU-exposed mice, although the numbers of these cells in the lungs were maintained. Double immunofluorescence study of the lungs of the BrdU-exposed mice showed overexpression of IL-6 in the airway epithelial and alveolar wall cells, some of which were also double-positive for BrdU. These results indicate that long-term exposure to BrdU inhibits cell proliferation and induces low-grade inflammation in the lungs of mice. Our findings underscore the need for caution in the interpretation of studies that involve long-term exposure to BrdU.

Nogo receptor inhibition enhances functional recovery following lysolecithin-induced demyelination in mouse optic chiasm

BACKGROUND

Inhibitory factors have been implicated in the failure of remyelination in demyelinating diseases. Myelin associated inhibitors act through a common receptor called Nogo receptor (NgR) that plays critical inhibitory roles in CNS plasticity. Here we investigated the effects of abrogating NgR inhibition in a non-immune model of focal demyelination in adult mouse optic chiasm.

METHODOLOGY/PRINCIPAL FINDINGS

A focal area of demyelination was induced in adult mouse optic chiasm by microinjection of lysolecithin. To knock down NgR levels, siRNAs against NgR were intracerebroventricularly administered via a permanent cannula over 14 days, Functional changes were monitored by electrophysiological recording of latency of visual evoked potentials (VEPs). Histological analysis was carried out 3, 7 and 14 days post demyelination lesion. To assess the effect of NgR inhibition on precursor cell repopulation, BrdU was administered to the animals prior to the demyelination induction. Inhibition of NgR significantly restored VEPs responses following optic chiasm demyelination. These findings were confirmed histologically by myelin specific staining. siNgR application resulted in a smaller lesion size compared to control. NgR inhibition significantly increased the numbers of BrdU+/Olig2+ progenitor cells in the lesioned area and in the neurogenic zone of the third ventricle. These progenitor cells (Olig2+ or GFAP+) migrated away from this area as a function of time.

CONCLUSIONS/SIGNIFICANCE

Our results show that inhibition of NgR facilitate myelin repair in the demyelinated chiasm, with enhanced recruitment of proliferating cells to the lesion site. Thus, antagonizing NgR function could have therapeutic potential for demyelinating disorders such as Multiple Sclerosis.

Hippocampal neurogenesis protects against cocaine-primed relapse

Accumulating evidence demonstrates a functional role for the hippocampus in mediating relapse to cocaine-seeking behavior and extinction-induced inhibition of cocaine seeking, and dentate gyrus neurogenesis in the hippocampus may have a role. Here, we tested the hypothesis that disruption of normal hippocampal activity during extinction alters relapse to cocaine-seeking behavior as a function of dentate gyrus neurogenesis. Adult rats were trained to self-administer cocaine on a fixed-ratio schedule, followed by extinction and cocaine-primed reinstatement testing. Some rats received low-frequency stimulation (LFS; 2 Hz for 25 minutes) after each extinction session in the dorsal or ventral hippocampal formation. All rats received an injection of the mitotic marker 5-bromo-2'-deoxyuridine (BrdU) to label developing dentate gyrus neurons during self-administration, as well as before or after extinction and LFS. We found that LFS during extinction did not alter extinction behavior but enhanced cocaine-primed reinstatement. Cocaine self-administration reduced levels of 24-day-old BrdU cells and dentate gyrus neurogenesis, which was normalized by extinction. LFS during extinction prevented extinction-induced normalization of dentate gyrus neurogenesis and potentiated cocaine-induced reinstatement of drug seeking. LFS inhibition of extinction-induced neurogenesis was not due to enhanced cell death, revealed by quantification of activated caspase3-labeled cells. These data suggest that LFS during extinction disrupts hippocampal networking by disrupting neurogenesis and also strengthens relapse-like behaviors. Thus, newly born dentate gyrus neurons during withdrawal and extinction learning facilitate hippocampal networking that mediates extinction-induced inhibition of cocaine seeking and may play a key role in preventing relapse.

Distribution of BrdU label-retaining cells in eccrine sweat glands and comparison of the percentage of BrdU-positive cells in eccrine sweat glands and in epidermis in rats

Bromodeoxyuridine (BrdU) has commonly been used for detecting of label-retaining cells (LRCs). To determine if there are LRCs and the distributions of LRCs in eccrine sweat glands, 20 newborn SD rats within 24 h after birth were injected intraperitoneally with 50 mg/kg/time BrdU four consecutive times at 2-h intervals, or twice daily at 2-h intervals for four consecutive days. Six weeks after the last BrdU injection, rats were sacrificed, and the hind footpads were harvested, fixed and embedded in paraffin. Five-micrometer thickness tissue sections were cut and the expression of BrdU was detected immunohistochemically. The results showed that BrdU(+) cells were scatteredly distributed in coiled secretory part and coiled duct, as well as the straight duct, but not the intraepidermal duct of eccrine sweat glands. In secretory part, besides secretory cells, myoepithelial cells showed label retaining. The percentage of BrdU(+) cells in eccrine sweat gland of rat footpads had no significant difference between the two injection methods of BrdU (50 mg/kg/time BrdU four consecutive times at 2-h intervals vs. 50 mg/kg/time BrdU twice daily at 2-h intervals for four consecutive days) (P > 0.05). The percentage of BrdU(+) cells in eccrine sweat glands (4.2 ± 1.3 %) was significantly higher than that in stratum basale of epidermis (0.5 ± 0.1 ‰) (P < 0.05). In conclusion, there were LRCs in eccrine sweat glands of rat footpads, and these LRCs might play important roles in the homeostasis of skin and its appendages.

Distribution of BrdU label-retaining cells in eccrine sweat glands and comparison of the percentage of BrdU-positive cells in eccrine sweat glands and in epidermis in rats

Bromodeoxyuridine (BrdU) has commonly been used for detecting of label-retaining cells (LRCs). To determine if there are LRCs and the distributions of LRCs in eccrine sweat glands, 20 newborn SD rats within 24 h after birth were injected intraperitoneally with 50 mg/kg/time BrdU four consecutive times at 2-h intervals, or twice daily at 2-h intervals for four consecutive days. Six weeks after the last BrdU injection, rats were sacrificed, and the hind footpads were harvested, fixed and embedded in paraffin. Five-micrometer thickness tissue sections were cut and the expression of BrdU was detected immunohistochemically. The results showed that BrdU(+) cells were scatteredly distributed in coiled secretory part and coiled duct, as well as the straight duct, but not the intraepidermal duct of eccrine sweat glands. In secretory part, besides secretory cells, myoepithelial cells showed label retaining. The percentage of BrdU(+) cells in eccrine sweat gland of rat footpads had no significant difference between the two injection methods of BrdU (50 mg/kg/time BrdU four consecutive times at 2-h intervals vs. 50 mg/kg/time BrdU twice daily at 2-h intervals for four consecutive days) (P > 0.05). The percentage of BrdU(+) cells in eccrine sweat glands (4.2 ± 1.3 %) was significantly higher than that in stratum basale of epidermis (0.5 ± 0.1 ‰) (P < 0.05). In conclusion, there were LRCs in eccrine sweat glands of rat footpads, and these LRCs might play important roles in the homeostasis of skin and its appendages.

Effects of ethanol on hippocampal neurogenesis depend on the conditioned appetitive response

Neurogenesis in the subgranular layer of the dentate gyrus (DG) has been suggested to underlie some forms of associative learning. The present study was undertaken to determine whether there was also a role of neurogenesis in the ethanol (EtOH)-induced conditioned place preference (CPP). Outbreed Swiss mice were conditioned with EtOH (2.0 g/kg) in one compartment of a non-biased place preference chamber and saline in the other compartment. This procedure produced three groups of mice: some developed a conditioned preference (EtOH_Cpp), others developed a conditioned avoidance (EtOH_Cpa) and still others demonstrated indifference to the context previously paired with ethanol (EtOH_Ind). BrdU (40 mg/kg, i.p.) was administered 4 hours after each session comprising the conditioning phase. When measured 24 hours following the CPP test, there was no effect of EtOH on doublecortin (DCX) expression or Fluoro Jade B staining. However, there were decreases in the number of BrdU+ and Ki-67+ cells in the EtOH_Cpa and EtOH_Ind groups, but not in the EtOH_Cpp group. Most of BrdU+ cells were co-labeled with DCX. Similarly, in another experiment, in that the perfusion was done 28 days after CPP test, most BrdU+ cells were co-localized with NeuN. These results suggest that conditioned appetitive response is able to maintain normal levels of neurogenesis in DG and might counteract ethanol-produced decreased cell proliferation/survival rate.

Unusual morphological damage of Purkinje cells following postnatal BrdU administration in the cerebellar cortex of mouse

Postnatal development of the cerebellum lasts for weeks in rodents and can be disturbed by systemic 5-bromo-2'-deoxyuridine (BrdU) administration. This thymidine analogue incorporates into the DNA of proliferating cells, and result in more or less serious damage or death granule cells, the most actively dividing neuronal population in the developing cerebellar cortex. Further consequences of postnatal BrdU administration are the interrupted postnatal migration and integrations as well as partial loss of cerebellar Purkinje cells. In the present study, C57B16 mice were administered with 50 μg/g body weight BrdU, one sc. injection daily, between P0 and P11 postnatal days, respectively.Large "cavities" appeared in the cytoplasm of a subpopulation of Purkinje cells by P7 in about one-third of administered animals, their number are size of the cavities (and PCs exhibiting unusual morphology) decreased. EM studies revealed that the unusual Purkinje cells received numerous axonal inputs of unknown origin, first of all on their somatic and dendritic spines. The transitory appearance of a subpopulation of Purkinje cells possessing unusual morphology refers to the influence of other (neuronal, glial, or both) cells on their regular differentiation.

Dermatan sulfotransferase Chst14/D4st1, but not chondroitin sulfotransferase Chst11/C4st1, regulates proliferation and neurogenesis of neural progenitor cells

Chondroitin sulfates (CSs) and dermatan sulfates (DSs) are enriched in the microenvironment of neural stem cells (NSCs) during development and in the adult neurogenic niche, and have been implicated in mechanisms governing neural precursor migration, proliferation and differentiation. In contrast to previous studies, in which a chondroitinaseABC-dependent unselective deglycosylation of both CSs and DSs was performed, we used chondroitin 4-O-sulfotransferase-1 (Chst11/C4st1)- and dermatan 4-O-sulfotransferase-1 (Chst14/D4st1)-deficient NSCs specific for CSs and DSs, respectively, to investigate the involvement of specific sulfation profiles of CS and DS chains, and thus the potentially distinct roles of CSs and DSs in NSC biology. In comparison to wild-type controls, deficiency for Chst14 resulted in decreased neurogenesis and diminished proliferation of NSCs accompanied by increased expression of GLAST and decreased expression of Mash-1, and an upregulation of the expression of the receptors for fibroblast growth factor-2 (FGF-2) and epidermal growth factor (EGF). By contrast, deficiency in Chst11 did not influence NSC proliferation, migration or differentiation. These observations indicate for the first time that CSs and DSs play distinct roles in the self-renewal and differentiation of NSCs.

Effects of recession versus tenotomy surgery without recession in adult rabbit extraocular muscle

PURPOSE

Surgical recession of an extraocular muscle (EOM) posterior to its original insertion is a common form of strabismus surgery, weakening the rotational force exerted by the muscle on the globe and improving eye alignment. The purpose of this study was to assess myosin heavy chain (MyHC) isoform expression and satellite cell activity as defined by Pax7 expression in recessed EOMs of adult rabbits compared with that in muscles tenotomized but not recessed and with that in normal control muscles.

METHODS

The scleral insertion of the superior rectus muscle was detached and sutured either 7 mm posterior to its original insertion site (recession surgery) or at the same site (tenotomy). One day before euthanization, the rabbits received bromodeoxyuridine (BrdU) injections. After 7 and 14 days, selected EOMs from both orbits were examined for changes in fast, slow, neonatal, and developmental MyHC isoform expression, Pax7 expression, and BrdU incorporation.

RESULTS

Recession and tenotomy surgery resulted in similar changes in the surgical EOMs. These included a decreased proportion of fast MyHC myofibers, an increased proportion of slow MyHC myofibers, and increased BrdU-positive satellite cells. Similar changes were seen in the non-operated contralateral superior rectus muscles. The ipsilateral inferior rectus showed reciprocal changes to the surgical superior rectus muscles.

CONCLUSIONS

The EOMs are extremely adaptive to changes induced by recession and tenotomy surgery, responding with modulations in fiber remodeling and myosin expression. These adaptive responses could be manipulated to improve surgical success rates.

Epidermal cell proliferation in the equine hoof wall

REASONS FOR PERFORMING STUDY

Current theories explaining how the hoof wall 'grows' and moves past the stationary distal phalanx are speculative and based on incomplete evidence. Movement in the lamellar region could occur by cell proliferation or an enzyme-based remodelling process. Since laminitis pathogenesis appears to involve increased transcription and activation of enzymes normally involved in tissue remodelling, it is important to know precisely which process dominates the lamellar region of the hoof..

OBJECTIVES

To investigate epidermal cell proliferation in the equine hoof wall and calculate a proliferative index (PI) for the coronet, lamellae and toe.

METHODS

An analogue of thymidine, 5-bromo-2'-deoxyuridine (BRdU), was infused i.v. into 5 ponies. After tissue harvesting, BRdU (and therefore basal cell proliferation) was detected immunohistochemically using mouse anti-BRdU. PIs were calculated for the coronet and 10 levels of the dorsal hoof wall lamellae.

RESULTS

The highest PIs (mean +/- s.e.) were in the coronet; 12.04% +/- 1.59 and proximal lamellae (7.13% +/- 1.92) and are therefore growth zones of the proximal hoof wall. PIs of more distal lamellae were 0.11% +/- 0.04 to 0.97% +/- 0.29; significantly lower (P = 0.05) than the lamellar growth zone.

CONCLUSIONS

A 20-fold PI decrease between proximal and more distal lamellae suggests that the majority of the normal lamellae are nonproliferative and their main function is to suspend the distal phalanx within the hoof capsule. Remodelling within the hoof wall epidermal lamellae, which must occur as the hoof wall moves past the stationary distal phalanx, is a process not requiring epidermal cell proliferation.

POTENTIAL RELEVANCE

A hoof lamellar epidermis that remodels using the same MMPs involved in laminitis pathogenesis implies that laminitis is a normal process out of control. Understanding MMP control and how the normal lamellar epidermis achieves this will help in the development of better laminitis preventative and treatment strategies.

Identification of tumor stem-like cells in a mouse myeloma cell line

We used colony formation assay in the soft agar media or the serum-free media, the methods of identifying BrdU-label-retaining cells and the SP cells as well as the tumorigenicity test in BALB/c mice, respectively, to analyze tumor stem like cells in the SP2/0 cell line. The results showed that a few SP2/0 cells were capable of forming colonies in the soft agar media, contained BrdU-label-immortal strand in the SP2/0 cell line. The SP2/0 cells in the serum-free media gained higher tumorigenicity in the BALB/c mice than the SP2/0 cells cultivated in the complete media did. Overall, only a few of the SP2/0 cells were found to possess the characteristics of tumor stem-like cells, such as high proliferative potency, more self-renewal and stronger tumorigenesis, or greater similarity to the tumor stem cells (TSCs) traits. The biology of tumor stem-like cells contributes to the identification of molecular targets important for future tumor therapy.

[Preweaning exposure to enriched environment induces hippocampal neurogenesis: experiment with rats]

OBJECTIVE

To explore the effects of preweaning exposure to enriched environment on hippocampal neurogenesis and the underlying mechanisms.

METHODS

Thirty-six 10-day-old SD rats were randomly divided into the 2 equal groups: control group and enriched environment group (EE group. From the age of 10 days to 24 days the rats received intraperitoneal injection of bromodeoxyuridine (BrdU) 50 mg/kg every other day to label the newly proliferated cells in vivo, and the rats in EE group were daily exposed to enriched environment for 20 minutes. Six rats of each group were sacrificed whren they were 24 days of age. Nuclear protein of the hippocampus was extracted to undergo Western blotting to detect the levels of calmodulin and phosphorylated CREB (cAMP response element binding). Other rats were sacrificed at the age of 63 days. Coronal cryostat sections of brain were cut. Sections at the level 3.6 mm posterior to the bregma were obtained and stained with methyl aniline blue and the number of cells in the hippocampal dentate gurus (DG) of the right hemisphere were counted using x 400 microscope. BrdU immunohistochemistry and double immunofluorescence labeling with BrdU/NeuN or BrdU/GFAP were done, and the numbers of BrdU-labeled cells and ratios of neurons and astrocytes differentiated from BrdU-labeled cells were calculated.

RESULTS

The levels of calmodulin and phosphorylated CREB in the hippocampal nuclear extract of the EE group were 0.065 +/- 0.035 and 0.485 +/- 0.007 respectively, both significantly higher than those of the control group (0.245 +/- 0.035 and 0.220 +/- 0.014 respectively, P = 0.01 and P = 0.002). The number of cells in the DG area of right hippocampus 3.6 mm posterior to bregma of the EE group was 1580 +/- 72, significantly higher than that of the control rats (1375 +/- 62, t = -7.461, P < 0.01). The number of BrdU labeled cells of the EE group was 5363 +/- 487, significantly higher than that of the control group (2984 +/- 318, t = -14.177, P < 0.01). The ratio of neurons of the EE group was 85.0% +/- 2.8%, significantly higher than that of the control group (80.2% +/- 2.8%, t = -4.166, P < 0.01). The differentiation rate of astrocytes of the EE group was 4.0% +/- 0.5%, significantly higher than that of the control group (2.6% +/- 0.6%, t = -6.493, P < 0.01).

CONCLUSION

Preweaning exposure to enriched environment can induce neurogenesis. The underlying mechanism may be that enriched environment induces the activation of calmodulin and CREB in hippocampus.

A novel method for oral delivery of drug compounds to the neonatal SMNDelta7 mouse model of spinal muscular atrophy

Spinal muscular atrophy (SMA) is a devastating motor neuron disease that is one of the leading genetic causes of infant mortality. Currently, there is no cure for SMA. Mouse models that genetically and phenotypically resemble SMA have been generated and have the potential to be used for the discovery of novel therapeutics. Oral administration is a commonly used mode of drug delivery in humans as well as in rodents. Unfortunately, there is no method of drug delivery that can accurately and reliably deliver drug compounds orally to neonatal mice. In this report, we describe a novel method to orally administer compounds to neonatal SMA mice. Oral delivery to neonatal mice, usually starting at postnatal day 4 (PND04), is both rapid and safe to the pup. Oral delivery of two different commonly used vehicle formulations, distilled water and 2-hydroxypropyl-beta-cyclodextrin, does not affect the survival of SMA mice. After oral delivery for 3 days, 5-bromo-2'-deoxyuridine could be detected in the kidneys, brains and spinal cords of treated non-SMA as well as SMA neonatal pups. In conclusion, we have developed a method by which drugs can be safely and reliably administered orally to neural targets of neonatal mice. This approach offers a simple and rapid means by which potential therapeutics for SMA can be identified.

A rapid method for the quantification of mouse hippocampal neurogenesis in vivo by flow cytometry

Neural stem cells reside in the subventricular zone and the dentate gyrus of the hippocampus in adult mammalian brain. In the hippocampus, a number of factors are reported to modulate the rate of neural progenitor proliferation in the hippocampus, such as exercise, corticosteroids, and many pharmacological agents including several classes of antidepressants. It is currently unclear whether this increased proliferation is physiologically relevant, but it provides a potentially useful biomarker to assess novel antidepressant compounds. Changes in neurogenesis are typically quantified by administration of bromodeoxyuridine (BrdU) in vivo, and subsequent quantification of labelled nuclei. A robust and rapid means of quantifying BrdU labelling in adult hippocampus in vivo would allow higher throughput screening of potential antidepressant compounds. In this study we describe a FACS-based method for quantification of BrdU labelled cells in fixed cell suspensions from BrdU-treated adult mouse hippocampus. A variety of experimental conditions known to modulate proliferation were tested, including administration of corticosterone and the antidepressants imipramine and fluoxetine. The robust changes compared to control groups observed in these models were similar to previously reported studies, thus offering a more rapid and streamlined means to quantify effects of compounds on hippocampal proliferation.

Individually dosed oral drug administration to socially-living transponder-tagged mice by a water dispenser under RFID control

The sensitivity of behavioral and physiological parameters to even mildly stressful experiences such as drug injections creates a need for alternative methods. We have established a method of stress-free administration of drugs via drinking water that allows multiple, individually specific and exact dosages, even for socially-housed animals. The drug solution is supplied by a dispenser with automated volume control. Animals are PIT microchip-tagged with RFID transponders and identified in realtime at the water port. Computer control permits preprogramming of individual reward quantities so that drug administration is terminated after an individual has collected its daily dose. For our experiments, the substance 5-bromo-2'-deoxyuridine (BrdU) was given as a marker of proliferating cells that we quantified in the hippocampus of adult mice. Experimental groups received BrdU either via intraperitoneal injections or orally via the water dispensers. Immunohistochemical staining of BrdU-positive cells was of the same quality after oral administration as after injection. BrdU-positive cells did not differ statistically in cell numbers. Thus, water dispensers under transponder control allow the individual and stress-free application of drugs even to group-living animals without disturbing their behavior. This is useful where a complex temporal protocol of application is required, and for phenotyping experiments combining behavioral tests with neural, cellular or molecular analyses.

Chronic mild stress decreases survival, but not proliferation, of new-born cells in adult rat hippocampus

New-born cells continue to proliferate and survive to become mature granule cells in adult rat hippocampus. Although this process, known as neurogenesis, is inhibited by acute stress, it is not clear whether chronic stress affects neurogenesis. To determine whether chronic mild stress (CMS) influences neurogenesis in the adult rat hippocampus, male Sprague-Dawley rats were exposed to CMS and administered bromodeoxyuridine (BrdU) before or after CMS to observe the survival/differentiation or proliferation of new-born cells, respectively. In addition, we measured brain-derived neurotrophic factor (BDNF) mRNA in the granule cell layer (GCL) of the hippocampus, because BDNF is known to play an important role in the survival of new-born cells. CMS significantly decreased the survival of new-born cells in the GCL, but did not influence the proliferation or differentiation of new-born cells. CMS did not affect the proliferation and survival of new-born cells in the hilus. In addition, CMS did not change BDNF mRNA levels in the GCL. These results demonstrate that CMS reduces the survival of new-born cells but not of their proliferation, suggesting that repeated mild stress could influence a part of neurogenesis, but not the whole part of neurogenesis. These results raise the possibility that the survival of new-born cells may be suppressed in the presence of normal BDNF mRNA levels in GCL.

Running has differential effects on NPY, opiates, and cell proliferation in an animal model of depression and controls

Physical activity has documented beneficial effect in treatment of depression. Recently, we found an antidepressant-like effect of running in an animal model of depression, the Flinders Sensitive Line (FSL) and demonstrated that it was associated with increased hippocampal cell proliferation. In this study, we analyzed levels of mRNAs encoding the neuropeptide Y (NPY) and the opioid peptides dynorphin and enkephalin in hippocampus and correlated these to cell proliferation in the FSL and in the 'nondepressed' Flinders Resistant Line (FRL) strain, with/without access to running wheels. Running increased NPY mRNA in dentate gyrus and the CA4 region in FSL, but not in FRL rats. NPY mRNA increase was correlated to increased cell proliferation in the subgranular zone of dentate gyrus. Baseline dynorphin and enkephalin mRNA levels in the dentate gyrus were lower in the FSL compared to the FRL strain. Running had no effect on dynorphin and enkephalin mRNAs in the FSL strain but it decreased dynorphin mRNA, and there was a trend to increased enkephalin mRNA in the FRL rats. Thus, it would appear that the CNS effects of running are different in 'depressed' and control animals; modification of NPY, a peptide associated with depression and anxiety, in depressed animals, vs effects on opioids, associated with the reward systems, in healthy controls. Our data support the hypothesis that NPY neurotransmission in hippocampus is malfunctioning in depression and that antidepressive treatment, in this case wheel running, will normalize it. In addition, we also show that the increased NPY after running is correlated to increased cell proliferation, which is associated with an antidepressive-like effect.

Natural variation and genetic covariance in adult hippocampal neurogenesis

Adult hippocampal neurogenesis is highly variable and heritable among laboratory strains of mice. Adult neurogenesis is also remarkably plastic and can be modulated by environment and activity. Here, we provide a systematic quantitative analysis of adult hippocampal neurogenesis in two large genetic reference panels of recombinant inbred strains (BXD and AXB/BXA, n = 52 strains). We combined data on variation in neurogenesis with a new transcriptome database to extract a set of 190 genes with expression patterns that are also highly variable and that covary with rates of (i) cell proliferation, (ii) cell survival, or the numbers of surviving (iii) new neurons, and (iv) astrocytes. Expression of a subset of these neurogenesis-associated transcripts was controlled in cis across the BXD set. These self-modulating genes are particularly interesting candidates to control neurogenesis. Among these were musashi (Msi1h) and prominin1/CD133 (Prom1), both of which are linked to stem-cell maintenance and division. Twelve neurogenesis-associated transcripts had significant cis-acting quantitative trait loci, and, of these, six had plausible biological association with adult neurogenesis (Prom1, Ssbp2, Kcnq2, Ndufs2, Camk4, and Kcnj9). Only one cis-acting candidate was linked to both neurogenesis and gliogenesis, Rapgef6, a downstream target of ras signaling. The use of genetic reference panels coupled with phenotyping and global transcriptome profiling thus allowed insight into the complexity of the genetic control of adult neurogenesis.

Exposure to 5-Bromo-2′-deoxyuridine induces oxidative stress and activator protein-1 DNA binding activity in the embryo

BACKGROUND

During organogenesis the embryo is highly sensitive to oxidative stress. We hypothesize that oxidative stress and activation of a redox-sensitive transcription factor, activator protein-1 (AP-1), are early indicators of embryonic stress in response to a teratogenic insult. 5-Bromo-2'-deoxyuridine (BrdU) was chosen as a model teratogen to test this hypothesis; BrdU is a thymidine analog that is incorporated into replicating DNA.

METHODS

Timed pregnant CD1 mice were given vehicle or BrdU (400, 600, 800, or 1000 mg of BrdU/kg of body weight) on gestation day 9 (GD 9). Oxidative stress, assessed as the ratio of glutathione disulfide (GSSG) to reduced glutathione (GSH), and AP-1 DNA binding activity (c-Fos- and c-Jun-dependent DNA binding) were measured in the maternal livers and embryos 0.5, 3, and 6 hr after treatment. External and skeletal malformations were assessed on GD 18. N-acetylcysteine, a glutathione precursor, was coadministered with BrdU to further explore the relationship between teratogenicity and redox homeostasis.

RESULTS

BrdU exposure produced a dose-dependent increase in skeletal malformations, which included polydactyly, and delayed ossification of the sternebrae and vertebrae. Exposure to teratogenic doses of BrdU depleted GSH concentrations and increased oxidative stress, as assessed by the GSSG:GSH ratio, in both maternal livers and embryos. While c-Jun DNA binding activity in embryos was not affected, c-Fos DNA binding activity was elevated significantly 3 hr after BrdU exposure. Coadministration of N-acetylcysteine decreased the skeletal malformations and AP-1 DNA binding activity induced by BrdU.

CONCLUSIONS

BrdU exposure induced an embryonic stress response manifested as an increase in oxidative stress and AP-1 DNA binding activity; these data support the hypothesis that disturbances in redox homeostasis mediate the response of the conceptus to a teratogenic insult.

Botulinum toxin treatment of extraocular muscles in rabbits results in increased myofiber remodeling

PURPOSE

Botulinum toxin A (Botox) is commonly used for strabismus treatment. Although other muscles atrophy after intramuscular injection with Botox, extraocular muscles (EOMs) do not. A continuous process of myonuclear addition in normal uninjured adult myofibers in rabbit EOMs was studied. In this study, the effect of Botox-induced muscle paralysis on myofiber remodeling in adult EOMs was examined.

METHODS

The superior rectus muscles of adult rabbits were each injected with 5 units of Botox. The contralateral muscle received injections of saline only. Bromodeoxyuridine (BrdU) was administered for various periods after Botox treatment, followed by various BrdU-free periods. Myonuclear addition, the number of BrdU-positive satellite cells, and the number of MyoD-positive satellite cells were quantified, as were alterations in expression of immature myosins.

RESULTS

Intramuscular injection of Botox resulted in a significant increase in both the number of BrdU-positive myonuclei and satellite cells. MyoD expression in both satellite cells and myonuclei was significantly increased after Botox injection in EOMs. In Botox-treated EOMs, an increased number of myofibers positive for the neonatal myosin heavy chain (MyHC) isoform was detected in the orbital layer.

CONCLUSIONS

Botox-induced EOM paralysis resulted in a significant short-term increase in satellite cell activation and myonuclear addition in single myofibers in adult rabbit EOMs compared with control muscles. The appearance of MyoD-positive myonuclei suggests that protein synthesis becomes upregulated after Botox injection, and this, in turn, may help explain the minimal effects on myofiber size in EOMs after Botox injection. Understanding the effect of Botox on satellite cell activation and myonuclear addition in existing myofibers may suggest new ways to maximize the clinical effectiveness of Botox in patients with strabismus.

CCL23/myeloid progenitor inhibitory factor-1 inhibits production and release of polymorphonuclear leukocytes and monocytes from the bone marrow

OBJECTIVE

CCL23/Myeloid progenitor inhibitory factor-1 is a human CC chemokine with potent in vitro suppressor effects on both human and murine myeloid progenitor cells. This study concerns in vivo inhibitory effect of CCL23 on production of polymorphonuclear leukocytes (PMNs) and monocytes in the bone marrow and their release into the circulation.

METHODS

5'-Bromo-2'-deoxyuridine (BrdU; 100 mg/kg) was used to label dividing PMNs and monocytes in the bone marrow, and BrdU-labeled cells were followed for 10 days in the circulation and identified using immunocytochemistry. Rabbits were given CCL23 (100 mug/kg, n = 5) or saline (control: n = 5) intravenously daily for 3 days before labeling with BrdU. Turnover of PMNs and monocytes in the bone marrow and their transit times through the bone marrow were calculated.

RESULTS

CCL23 treatment tended to prolong transit time of PMN (98.4 +/- 4.3 hours vs 111.2 +/- 3.8 hours, control vs CCL23, p = 0.06) through the bone marrow and decreased the size of the bone marrow mitotic pool of PMN (p < 0.01). CCL23 treatment also prolonged the transit time of monocyte (43.4 +/- 3.1 hours vs 54.2 +/- 1.3 hours, control vs CCL23, p < 0.05) through the bone marrow and decreased turnover and pool size of monocytes in the bone marrow (p < 0.05).

CONCLUSION

We conclude that CCL23 suppresses PMN and monocyte progenitors, decreases the pool size and slows their turnover in the bone marrow.

Proliferation markers in the adult rodent brain: bromodeoxyuridine and proliferating cell nuclear antigen

The rostral migratory stream is one of the few regions of the adult mammalian central nervous system in which cellular migration and proliferation have been described. Most rostral migratory stream cells divide rapidly and hence different proliferation markers have been employed to identify them. Nitrogen base substitutes, such as tritiated thymidine or 5-bromo-2'-deoxyuridine (BrdU), together with endogenous molecules, such as Proliferating Cell Nuclear Antigen (PCNA), are the cell cycle markers most widely employed. Protocols for BrdU and PCNA localization are both plentiful and diverse, but to date no optimized protocol for obtaining trustworthy double staining of both markers has been described. In this work, we propose optimized protocols for achieving both single staining and the joint detection of BrdU and PCNA in the rodent brain using double-immunofluorescence procedures. The double labeling described allows the discrimination of different cell cycle stages in migratory cells from the mouse brain.

Neurogenesis in the hypothalamus of adult mice: potential role in energy balance

Ciliary neurotrophic factor (CNTF) induces weight loss in obese rodents and humans, and for reasons that are not understood, its effects persist after the cessation of treatment. Here we demonstrate that centrally administered CNTF induces cell proliferation in feeding centers of the murine hypothalamus. Many of the newborn cells express neuronal markers and show functional phenotypes relevant for energy-balance control, including a capacity for leptin-induced phosphorylation of signal transducer and activator of transcription 3 (STAT3). Coadministration of the mitotic blocker cytosine-beta-d-arabinofuranoside (Ara-C) eliminates the proliferation of neural cells and abrogates the long-term, but not the short-term, effect of CNTF on body weight. These findings link the sustained effect of CNTF on energy balance to hypothalamic neurogenesis and suggest that regulated hypothalamic neurogenesis in adult mice may play a previously unappreciated role in physiology and disease.

Discrimination of Cell Nuclei in Early S-phase, Mid-to-late S-phase, and G2/M-phase by Sequential Administration of 5-Bromo-2'-Deoxyuridine and 5-Chloro-2'-Deoxyuridine

5-Bromo-2'-deoxyuridine (BrdU) and 5-chloro-2'-deoxyuridine (CldU) were sequentially administered intraperitoneally into mice at 1-hr intervals. After one additional hr, the small intestines were resected, fixed, and embedded in paraffin. In histological sections stained with monoclonal antibody Br-3 reactive to both BrdU and CldU, and CldU antibody reactive only to CldU, three types of staining could be identified in the proliferating zone. Cells with nuclei stained only with Br-3 antibody were estimated to have completed DNA replication during the first 1 hr and were fixed in G2/M-phase. Those nuclei were frequently found in apical areas of the simple columnar epithelium of the intestine, whereas other nuclei were located basally in the cells. This observation suggested intracellular movement of cell nuclei in G2/M-phase. Identification of cells in early S-phase became possible using these antibodies in combination with DAB and fluorescence stainings. Replication sites in early S-phase nuclei were found to be numerous, whereas in late S-phase they were larger in size and much smaller in number.

Chronic developmental lead exposure reduces neurogenesis in adult rat hippocampus but does not impair spatial learning

The dentate granule cell (DG) layer of the hippocampal formation has the distinctive property of ongoing neurogenesis that continues throughout adult life. Although the function of these newly generated neurons and the mechanisms that control their birth are unknown, age, activity, diet and psychosocial stress have all been demonstrated to regulate this type of neurogenesis. Little information on the impact of environmental insults on this process has appeared to date. Developmental lead (Pb) exposure has been well documented to impair cognitive function in children and animals and reduce activity-dependent synaptic plasticity in the hippocampus of rodents. Therefore, we examined the effects of this classic environmental neurotoxicant on hippocampal-dependent learning and adult neurogenesis in the hippocampus. Pregnant rats were exposed to a low level of Pb-acetate (0.2%) via the drinking water from late gestation (GD 16) until weaning on postnatal day 21 (PN 21). At weaning, half of the Pb-exposed animals were weaned to control drinking water and the remainder were maintained on Pb water until termination of the study. Animals were paired- housed and on PN 75 were administered a series of injections of a thymidine analog bromodeoxyuridine (BrdU), a marker of DNA synthesis that labels proliferating cells and their progeny. At 12-h intervals for 12 days, rats received an ip injection of BrdU (50 mg/kg). Subjects were sacrificed and perfused 24 h and 28 days after the last injection. Spatial learning was assessed in an independent group of animals beginning on PN 110 using a Morris water maze. No Pb-induced impairments were evident in water maze learning. Immunohistochemistry for the detection of BrdU-labeled cells was performed on 40-microm coronal sections throughout the hippocampus. Continuous exposure to Pb (Life) reduced the total number of BrdU-positive cells at 28 days without affecting the total number of labeled cells evident 24 h after the last injection. No differences in the number of progenitor cells labeled or surviving were seen between control and treated animals whose Pb exposure was terminated at weaning. Double labeling with BrdU and the glial specific marker, glial acidic fibrillary protein (GFAP) indicated that the bulk of the surviving cells were of a neuronal rather than a glial phenotype. These data reveal that chronic low-level Pb exposure reduces the capacity for neurogenesis in the adult hippocampus. Despite deficits in synaptic plasticity previously reported from our laboratory, and now structural plasticity, no significant impact on spatial learning was detected.

Stress-induced decrease of granule cell proliferation in adult rat hippocampus: assessment of granule cell proliferation using high doses of bromodeoxyuridine before and after restraint stress

Stress is known to inhibit granule cell proliferation in the hippocampus. However, recent studies suggest that the commonly used dose of bromodeoxyuridine (BrdU) is insufficient to label all fractions of granule cells. Furthermore, stress-induced changes in BrdU availability may influence the labeling of newly born cells. To investigate whether changes in BrdU availability affect measurements of stress-induced granule cell proliferation, granule cell proliferation was assessed using injection of high doses of BrdU before and after restraint stress lasting 1 h. In addition, to determine whether stress-induced changes in plasma corticosterone levels were influenced by the BrdU, time-dependent changes in plasma corticosterone levels over 2 h after BrdU injection were compared with total accumulated plasma corticosterone levels [as determined by areas under the curve (AUC)]. Restraint stress significantly reduced the numbers of BrdU-labeled cells and clusters in the granule cell layer (GCL) of rats that received BrdU after stress, and decreases of similar magnitude were observed when the rats were given BrdU before stress. BrdU injection enhanced the stress-induced plasma corticosterone response, but there was no difference between the mean AUCs of plasma corticosterone levels of animals injected with BrdU before or after stress. These observations suggest that restraint stress decreases granule cell proliferation, and that this may be influenced by the extent and duration of plasma corticosterone increases rather than by changes in the availability of BrdU.

Low doses of bromo- and iododeoxyuridine produce near-saturation labeling of adult proliferative populations in the dentate gyrus

Cell proliferation can be detected by the incorporation of tritiated thymidine (3H-dT) or halopyrimidines during DNA synthesis in progenitor cells. Administration of two thymidine analogues at different times can further determine the cell-cycle kinetics of proliferating cells. Traditionally, this was done by combining bromodeoxyuridine (BrdU) immunocytochemistry and 3H-dT autoradiography, or by BrdU and iododeoxyuridine (IdU) double-labeling using two mouse antibodies. However, these methods either require lengthy exposure time or involve complicated histological procedures for differentiating between two antibodies of the same species. Here we report a simple and reliable method of distinguishing BrdU- and IdU-labeled cells by immunofluorescence. This method uses a mouse monoclonal antibody that recognizes both BrdU and IdU and a rat anti-BrdU antibody that has no cross-reactivity with IdU. When combined with species-specific secondary antibodies that are conjugated to different fluorophores, this method identifies BrdU- and IdU-incorporation as doubly and singly labeled cells, respectively. This method has broad applications. First, we demonstrate that this method can distinguish mouse cortical neurons generated on different embryonic days. Second, by administering IdU and BrdU at varying intervals, we used this method to calculate that the length of S-phase of neural progenitor cells in the adult mouse dentate gyrus is approximately 6 h. Finally, we show that a six-fold higher concentration of IdU detects only 10% more cells than the standard dose of BrdU (50 mg/kg) using the double-labeling method. These results suggest that the standard dose of BrdU is sufficient to label the majority of proliferative populations in the S-phase in pulse labeling experiments.

Serotonin modulates the suppressive effects of corticosterone on proliferating progenitor cells in the dentate gyrus of the hippocampus in the adult rat

This series of experiments explores the interaction between corticosterone and serotonin (5-HT) in the regulation of cell proliferation in the dentate gyrus of the adult rat. Intracerebroventricular 5,7-DHT (5,7-dihydroxytryptamine) (either 200 or 300 microg) resulted in highly significant depletion of 5-HT as measured by high performance liquid chromatography in the frontal cortex but had no effect on the number of proliferating cells in the dentate gyrus by measuring 5-bromo-2'-deoxyuridine (BrdU) and Ki-67 cytochemistry. Treatment with PCPA (p-chlorophenylalanine: a tryptophan hydroxylase inhibitor: 300 mg/kg initially followed by 100 mg/kg/day) resulted in reduced proliferation as measured by Ki-67 after 3 days treatment, but not by BrdU uptake, and not after 14 days treatment by either method. In addition, injection of corticosterone (10-40 mg/kg/day) for 8 days significantly reduced proliferation in the dentate gyrus, as expected, measured by both BrdU uptake and Ki-67 immunostaining. Adrenalectomized (ADX) rats with a replacement subcutaneous pellet of corticosterone showed reduced proliferation when given additional corticosterone (10 mg/kg/day for 8 days), but this was prevented by 5-HT depletion (i.c.v. 5,7-DHT). Finally, a dose-response study showed that progressive doses of corticosterone (0-40 mg/kg/day) in ADX rats resulted in diminished suppression of proliferation in 5-HT-depleted compared with 5-HT-intact rats. These results strongly suggest that 5-HT regulates the sensitivity of proliferating cells in the dentate gyrus to corticosterone.

Evidence for neurogenesis within the white matter beneath the temporal neocortex of the adult rat brain

Persistent neuron production in the adult CNS (adult neurogenesis) has been implicated in various brain functions such as learning/memory and mood control. Despite the widespread occurrence of neural stem/progenitor cells, active adult neurogenesis has been established only in two restricted regions. We explored in this study a previously overlooked neurogenic region in the adult rat brain and detected the evidence of neuron production within the subcortical white matter. Dividing Pax6- and Olig2-positive neural progenitor cells continually gave rise to doublecortin-positive new neurons in this region. However, the vast majority of newborn neurons were lost within a week of their birth. Accumulated apoptotic cells indicated the ongoing cell death in this area. In addition to providing the evidence of newborn cell migration to the hippocampus, these results suggest that cell genesis, death, and migration persist in a restricted subregion of the adult white matter.

Exogenous TGF-β1 Promotes Stromal Development in the Heifer Mammary Gland

The objectives of this study were to determine the local effects of transforming growth factor-beta1 (TGF-beta1) on mammary epithelial and stromal cell proliferation and expression of the TGF-beta1 responsive genes c-myc and fibronectin. A single slow-release plastic pellet containing 5 microg of TGF-beta1 and 20 mg of BSA was implanted in the parenchyma of the right rear quarter of the mammary gland of 9-mo-old prepubertal heifers. A control pellet containing 20 mg of BSA was implanted in the left rear quarter of each heifer. All heifers were treated with bromodeoxyuridine (BrdU) at 4, 12.5, and 22 h after the pellets were implanted to label proliferating cells. Two hours after the last BrdU injection, the animals were euthanatized, and their mammary glands were recovered. Proliferation of mammary stromal cells was significantly higher in TGF-beta1-treated quarters than in BSA-treated, control quarters (3.5 vs. 1.8% BrdU-positive cells). This result coincided with a lack of significant effect of TGF-beta1 on proliferation of mammary epithelial cells and apoptosis. By quantitative reverse transcriptase-polymerase chain reaction, we found that c-myc gene expression was unchanged after TGF-beta1 treatment, but fibronectin gene expression was increased 3-fold in TGF-beta1-treated quarters compared with BSA-treated, control quarters. Thus, we concluded that TGF-beta1 selectively acts on the stromal compartment of the bovine mammary gland by increasing cell proliferation and gene expression of the extracellular matrix protein fibronectin.

Treatment of intracranial rat glioma model with implant of radiosensitizer and biomodulator drug combined with external beam radiotherapy

PURPOSE

To evaluate an intracranial polymer implant containing bromodeoxyuridine (BrdUrd) and N-(phosphonacetyl)-L-aspartic acid (PALA) in combination with external beam radiotherapy (EBRT) in the treatment of a rat glioma.

METHODS AND MATERIALS

Combinations of the biomodulators 5-fluorouracil, methotrexate, or PALA with BrdUrd were evaluated as radiosensitizers in vitro by clonogenic assay. In in vivo experiments, BrdUrd and PALA were incorporated into a polyanhydride-based polymer, bis(p-carboxyphenoxy)propane sebacic acid, and implanted in the C6 rat glioma growing intracranially. The effectiveness of treatment was evaluated on the basis of survival. EBRT was given as 10-MV X-rays.

RESULTS

In tissue culture experiments, C6 cells were refractory to radiosensitization by BrdUrd even when the thymidine analog was combined with a biomodulator intended to reduce de novo thymidine synthesis. The most effective compound in vitro was PALA. When PALA and BrdUrd in a polymer formulation were implanted intracranially and combined with 10-Gy EBRT, the treatment was highly effective, with 83% of treated rats surviving 180 days.

CONCLUSION

Although the in vitro results were not encouraging, the combination of intratumoral BrdUrd and PAL with 10-Gy EBRT was highly effective in treating a rat glioma. These results indicate the clinical potential of combined and mixed modality treatments involving intratumoral sustained-release drug delivery.

The dynamics of precursor cells in the olfactory epithelium of juvenile and adult guinea pigs

The dynamics of precursor cells in the olfactory epithelium of juvenile and adult guinea pigs were examined by immunohistochemical double staining using bromodeoxyuridine (BrdU), the neural cell adhesion molecule (N-CAM) and the protein gene product 9.5 (PGP9.5). Expression of apoptotic cells in the olfactory epithelium with the use of the TdT-mediated dUTP biotin nick end labeling (TUNEL) method was also observed. BrdU was given to healthy guinea pigs at the ages of 2 weeks and 6 months old. Tissue specimens were serially collected 1 h to 28 days after administration. BrdU-labeled cells were seen above the basal cell layer after 1 h and migrated to the middle layer of the olfactory epithelium, after 1 day in juveniles and 5 days in adults with expression of N-CAM. PGP9.5 was observed in BrdU-labeled cells after 5 days in juvenile guinea pigs and 7 days in adult. At 14 days after administration, BrdU-labeled cells in the epithelium appeared to decrease. However, a few of these cells were recognized above the basal cell layer after 28 days. The number and location of TUNEL-positive cells did not significantly differ between the juvenile and adult olfactory epithelium. Therefore, we conclude that the division speed from stem cells in juveniles is faster than that in adults, and apoptosis is unaffected by aging in the normal olfactory epithelium.

Analysis of B-cell life-span and homeostasis

In the past, the life-span of B cells in rodents has been determined by a variety of methods, leading to conflicting results. Among the various techniques employed, labeling of dividing cells with the thymidine analog 5-bromo-2'-deoxyuridine (BrdU) has turned out to be a versatile and reliable procedure. Labeling of the cells can be easily performed in vivo by feeding BrdU in the drinking water for extended periods of time or by an ip injection of BrdU for short-term labeling experiments. Using the protocol described, it is possible to combine flow cytometric detection of incorporated BrdU simultaneously with fluorescence staining of various cell surface markers.

Brivudin (Bromovinyl Deoxyuridine)

Brivudin is an oral thymidine analogue indicated for the early treatment of acute herpes zoster in immunocompetent adults. It has high, selective activity against varicella zoster virus (VZV), inhibiting VZV replication, possibly through competitive inhibition of viral DNA polymerase, or by acting as an alternative substrate to deoxythymidine triphosphate, causing viral DNA strand breakage. In a large, 7-day, phase III trial in immunocompetent patients with herpes zoster, once-daily brivudin 125mg was significantly more effective than oral acyclovir 800mg five times daily in reducing the mean time from start of treatment to last vesicular eruption, and was as effective as acyclovir at healing lesions and alleviating acute zoster-related pain. The likelihood of developing post-herpetic neuralgia (PHN) in immunocompetent patients aged > or =50 years was significantly lower with brivudin than with acyclovir. Brivudin was as effective as oral famciclovir 250mg three times daily in terms of the prevalence of PHN, the time to last vesicular eruption and lesion healing in another large, 7-day, phase III study in immunocompetent patients with herpes zoster. Oral brivudin is generally well tolerated, with a similar tolerability profile to those of oral acyclovir or famciclovir. Nausea was the most commonly reported adverse event.

Comparison of in vivo lymphocyte proliferation between allogeneic and xenogeneic heart transplantation in mice

There are controversial in vitro data comparing the strength of the cellular immune response between allogeneic and xenogeneic stimulator/responder combinations. The present study therefore compares in vivo lymphocyte proliferation using heart transplantation (HTx) models in mice. Heterotopic HTx into BALB/c mice was performed using donor organs from mice (BALB/c and C57BL/6) or Lewis rats. Intraperitoneally given bromodeoxyuridine (BrdU) was incorporated into the DNA and was subsequently analyzed by flow cytometry. On postoperative days 3 and 5, proliferation of splenocytes, CD4(+) T-lymphocytes, and CD19(+) B-lymphocytes was significantly higher after xenogeneic than after allogeneic and isogeneic HTx. No significant difference was observed when proliferation of CD8(+) lymphocytes was determined. The increased in vivo proliferation after xenotransplantation may reflect an earlier and probably stronger cellular immune response compared to allogeneic transplantation. The higher CD4(+) lymphocyte proliferation underscores the importance of this cell population in xenograft rejection.

Brivudin als alternative systemische Therapie zu Aciclovir und Ganciclovir bei akutem retinalen Nekrosesyndrom durch Varizella-Zoster-Virus

BACKGROUND

Two cases of acute retinal necrosis (ARN-) syndrome caused by an infection with varicella zoster virus (VZV) are demonstrated. VZV-DNA was detected in vitreous biopsies by polymerase-chain-reaction (PCR). The course of retinal necrosis was decisively improved by changing antiviral therapy from aciclovir and/or ganciclovir to brivudine.

MATERIAL AND METHODS

Patient 1: 51 years, male, initial visual acuity 20/40; patient 2: 17 years, female, initial visual acuity 20/30. Both patients were immunocompetent and presented with an unilateral acute retinal necrosis syndrome with peripheral chorioretinitis, retinal vasculitis, vitreous inflammation and optic disc swelling, which resulted in progressive visual loss in a few days.

RESULTS

In both patients VZV-DNA was detected in vitreous biopsies with PCR. A regression of intraocular inflammation and necrotic retinal foci was only observed after changing the initial systemic therapy from aciclovir (Zovirax) intravenously 1500 mg/day) and/or ganciclovir (Cymeven) intravenously 250 mg/day) to brivudine (Zostex) per os 500 mg/day). Vitreoretinal surgery was necessary in both patients because of rhegmatogenous retinal detachment. Visual acuity stabilised in patient 1 to 20/200 and in patient 2 to 20/25 during a follow-up of 16 or 32 months, respectively.

CONCLUSION

Brivudine represents an alternative therapy, if standard treatment with aciclovir and/or ganciclovir failed in cases of ARN-syndrome due to presumed drug-resistant varicella zoster virus-subtypes. Complete remission and preservation of a satisfactory function can be achieved.

Inhibition of induced chemoresistance by cotreatment with (E)-5-(2-bromovinyl)-2'-deoxyuridine (RP101)

Induced chemoresistance leads to the reduction of apoptotic responses. Although several drugs are in development that circumvent or decrease existing chemoresistance, none has the potential to prevent or reduce its induction. Here, we present data from a drug that could perhaps fill this gap. Cotreatment of chemotherapy with (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU, RP101) prevented the decrease of apoptotic effects during the course of chemotherapy and reduced nonspecific toxicity. Amplification of chemoresistance genes (Mdr1 and Dhfr) and overexpression of gene products involved in proliferation (DDX1) or DNA repair (UBE2N and APEX) were inhibited, whereas activity of NAD(P)H: quinone oxidoreductase 1 (NQO1) was enhanced. During recovery, when treatment was with BVDU only, microfilamental proteins were up-regulated, and proteins involved in ATP generation or cell survival (STAT3 and JUN-D) were down-regulated. That way, in three different rat tumor models, the antitumor efficiency of chemotherapy was optimized, and toxic side effects were reduced. Because of these beneficial properties of BVDU, a clinical pilot Phase I/II study with five human tumor entities has been started at the University of Dresden (Dresden, Germany). So far, no unwanted side effects have been observed.

Prenatal development of the rodent rostral migratory stream

The aim of this study was to elucidate the embryological origins of the unique neuronal progenitor cells that form the rostral migratory stream (RMS), the path traversed by cells from the anterior part of the forebrain subventricular zone (SVZa) en route to the olfactory bulb. To determine when and where cells constituting the RMS initially exhibit their characteristic neuronal phenotype and high mitotic capacity, we analyzed the cells of the rat forebrain between embryonic day 14 (E14) and postnatal day 2 (P2). At E14, cells with a neuronal phenotype were observed within the ventricular zone in close proximity to the mantle layer of the future olfactory bulb. By E15, cells expressing neuronal markers are also PSA-NCAM immunoreactive and become aligned in chains of similarly oriented cells, a hallmark of the postnatal RMS. The cells that form chains organize into a patch that enlarges in the anterior-posterior and medial-lateral dimensions from E16 to E22 (birth). In comparing the forebrain cytoarchitecture to the pattern of cell type-specific staining, the patch constitutes only the central part of the proximal RMS. Early during development, the region of the RMS surrounding the patch expresses low levels of PSA-NCAM and neuron-specific markers. The proliferative activity of cells forming the patch vs. nonpatch regions of the RMS was analyzed following a short bromodeoxyuridine (BrdU) exposure. Between E15 and E22, the patch can be recognized by the mitotic activity of its cells; the cells of the patch incorporate less BrdU than the nonpatch portion of the RMS. The time course of appearance of cells forming the RMS indicates that the RMS arises in advance and independently of the cortical SVZ. Although the patch and the nonpatch regions of the embryonic RMS appear to merge postnatally, the two regions may originate separately under the influence of distinct intrinsic and extrinsic factors.

Primary central nervous system lymphoma: Phase I evaluation of infusional bromodeoxyuridine with whole brain accelerated fractionation radiation therapy after chemotherapy

BACKGROUND

The current study was performed to determine the maximum tolerated dose (MTD), toxicity, and outcome of infusional 5 bromo-2'-deoxyuridine (bromodeoxyuridine; BUdR) given with accelerated fractionation whole brain radiation therapy (WBRT) after chemotherapy for the treatment of primary central nervous system lymphoma (PCNSL).

METHODS

Twelve patients with untreated and histologically confirmed PCNSL were entered on the study between 1994 and 1996. Chemotherapy was comprised of one course of IDHAP plus high-dose methotrexate (HD-MTX). IDHAP is comprised of idarubicin at a dose of 1.5 mg/m(2)/day x 4 days intravenously by continuous infusion (i.v. CI), dexamethasone at a dose of 40 mg i.v. on Days 1-5, cytosine arabinoside at a dose of 2000 mg/ m(2) i.v. on Day 5 after cisplatin, and cisplatin at a dose of 25 mg/m(2)/day x 4 days i.v. CI. HD-MTX was given at a dose of 3.5 g/m(2) i.v. between Day 10 and Day 14 after IDHAP. BUdR was given as an i.v. CI over 48 hours, 2-3 days prior to WBRT and then weekly during WBRT. Dose escalation started at 1.5 g/m(2)/day for Cohort 1 with subsequent increments of 0.3 g/m(2)/day. The WBRT dose was 45 grays (Gy) at a dose of 1.5 Gy twice a day, 5 days per week. Neurocognitive testing was performed before, during, and after treatment.

RESULTS

Nine of 12 patients entered on the study received BUdR. One of 3 patients in Cohort 1 developed leukoencephalopathy (LEP), a dose-limiting toxicity (DLT), within 2 months of the completion of therapy. Therefore, the next cohort received the same dose level. Because no toxicity was observed in Cohort 2, the third cohort received a BUdR dose of 1.8 g /m(2)/day. Shortly after completing enrollment in Cohort 3, 3 more patients developed LEP, including 2 from Cohort 1 who had received a dose of 1.5 g/m(2)/day. Thus, DLT occurred at a dose of 1.5 g/m(2)/day, the starting level in the current study. As a result, the trial was stopped. Eight of 12 patients achieved a complete response, 3 achieved a partial response, and 1 patient died before response assessment.

CONCLUSIONS

Hyperfractionated WBRT with concurrent BUdR after chemotherapy was found to result in modest disease control but has unacceptable neurotoxicity.

Hippocampal cell proliferation and epileptogenesis after audiogenic kindling are not accompanied by mossy fiber sprouting or Fluoro-Jade staining

Repetitive sound-induced seizures, known as audiogenic kindling (AK), gradually induce the transference of epileptic activity from brainstem to forebrain structures along with behavioral changes. The aim of our work was to correlate the behavioral changes observed during the AK with possible alterations in neuronal proliferation, cell death, hippocampal mossy fiber sprouting and in the EEG pattern of Wistar audiogenic rats, a genetically susceptible strain from our laboratory. Susceptible and non-susceptible animals were submitted to repeated sound stimulations for 14-16 days and hippocampal mitotic activity was studied through the incorporation of bromodeoxyuridine (BrdU). Cell death and mossy fiber sprouting were assessed, respectively, by using Fluoro-Jade and Timm staining, 2 and 32 days after the last kindling stimulation. In addition, we used immunofluorescent double labeling for a glial and a mitotic marker to evaluate newly born cell identity. Some animals had hippocampus and amygdala electrodes for EEG recordings. Our results show that kindled animals with 6-11 generalized limbic seizures (class IV-V) had increased cell proliferation in the dentate gyrus when compared with animals with zero or one to three seizures. BrdU-positive cells labeled on day 2 and on day 32 were both GFAP negative. In the later group, rounded and well-defined BrdU-positive/GFAP-negative nuclei were seen in different portions of the granule cell layer. We did not observe any Fluoro-Jade or differential Timm staining in kindled animals at both killing times. However, EEG recordings showed intense epileptic activity in the hippocampus and amygdala of all animals with limbic seizures.Therefore, our data indicate that AK-induced limbic epileptogenicity is able to increase the hippocampal mitotic rate, even though it does not seem to promote neuronal death or mossy fiber sprouting in the supragranular layer of the dentate gyrus.

Brivudine: a herpes virostatic with rapid antiviral activity and once-daily dosing

Brivudine is an analog of thymidine, and is incorporated into the viral DNA. It blocks the action of DNA polymerases, thus inhibiting viral replication. It has a stronger antiviral effect against the varicella-zoster virus compared with reference compounds such as aciclovir or penciclovir. The efficacy of brivudine has been documented in a number of clinical trials in patients with herpesvirus-related infections, particularly in patients with herpes-zoster. At a dose of 125 mg once daily, brivudine has proved to be superior to aciclovir with respect to reducing the period of new blister production in patients with herpes-zoster, and has shortened the duration of post-herpetic neuralgia. Tolerability was equivalent to that of aciclovir or placebo, with occasional gastrointestinal disorders leading to treatment withdrawal in a minority of patients.

Proliferative activity and nestin expression in periventricular cells of the adult rat brain

Mitotic activity in the forebrain subventricular zone is well documented but only in vitro reports suggest the presence of multi-potent stem cells all along the adult mammalian neuraxis. We demonstrate, following cerebroventricular infusion of labeled nucleotides in rat brain, a mitotic activity in the choroid plexus, the ependymal and subependymal layers of the mid- and hindbrain. This proliferation, which probably enables renewal of these structures, was unaffected by the destruction of their serotonergic innervations. Nestin, a marker of immature neural cells, was observed in some proliferative subependymal cells, some classical ependymocytes and in the specialized ependymocytes of the subcommissural organ, the collicular recess and the tanycytes. These observations indicate the presence of immature proliferative cells in the third and fourth periventricular structures, which may generate neural cells.

The chronic inhibition of nitric oxide synthase enhances cell proliferation in the adult rat hippocampus

We investigated the effect of chronic blocking nitric oxide synthase (NOS), an enzyme producing NO from L-arginine, on granule cell proliferation in the dentate gyrus of adult rats under normal conditions. We treated 7-nitroindazole (7-NI) for 5, 15, and 25 days or N-nitro-L-arginine-methyl ester (L-NAME) for 25 days to block NOS activity and subsequently injected 5-bromo-2-deoxyuridine (BrdU) to detect proliferating cells. The BrdU-immunoreactive (IR) cell number was significantly increased in the 7-NI 15 and 25 day treated group, but not in the control or in the 7-NI 5 day treated group. L-NAME treatment for 25 days significantly increased BrdU-IR cells versus the control and 7-NI 25 day treated group. In addition, nissl staining showed no cell death occurred in the dentate gyrus after 7-NI or L-NAME 25 day treatments. Our results demonstrate that chronic inhibition of NOS increases cell proliferation and has no effect on cell death in the dentate gyrus of the rat hippocampus, which suggests that NO may regulate cell proliferation in the dentate gyrus.

In vivo cell kinetic measurements in a randomized trial of continuous hyperfractionated accelerated radiotherapy with or without mitomycin C in head-and-neck cancer

PURPOSE

Tumor cell repopulation is still considered to be a major cause of failure in radiotherapy. In this study, we investigated the influence of cell kinetic parameters on the outcome of patients treated in a randomized trial of accelerated fractionation, with or without mitomycin C, vs. conventional fractionation.

METHODS AND MATERIALS

Sixty-two patients were studied using administration of bromodeoxyuridine (BrdUrd), and cell kinetic parameters were measured using flow cytometry. The patients were treated with either 70 Gy for 7 weeks or 55.3 Gy for 17 continuous days (V-CHART) with or without 20 mg/m(2) mitomycin C on day 5.

RESULTS

The potential doubling time (Tpot) and labeling index (LI) failed to provide any prognostic information with regard to local control or survival. However, the duration of the S phase (Ts) revealed patients whose tumors had a long Ts had significantly worse local control (p = 0.028) and survival (p = 0.034) irrespective of treatment. A similar trend was evident within the different treatment arms particularly associated with overall survival.

CONCLUSIONS

The Ts values of head-and-neck squamous cell cancers provided prognostic information that predicted clinical outcome irrespective of treatment schedule in this study. This neglected parameter of the Tpot method might provide information related to redistribution of cells during fractionated radiotherapy.

A method for pulse and chase BrdU-labeling of early chick embryos

Pulse and chase BrdU labeling of early chick embryos represents a serious technical problem due to the hindrance of removing unincorporated BrdU after the pulse. We have developed a simple method that allows BrdU washout and control of pulse/chase duration. In this method, BrdU pulses are carried out in ovo. Afterwards, embryos are removed from the yolk, BrdU is washed out, and the embryos are maintained in a wholemount culture. Under these conditions, HH8-12 embryos continue with their normal development for at least 30 h. Morphological development of the nervous system and cell cycle kinetics of precursor cells seem to be normally maintained in cultured embryos. To prove the feasibility of the method, it has been applied to determine the onset of TUJ1 expression. TUJ1 is frequently considered an early neuronal marker, yet some reports have shown its expression in dividing progenitor cells and differentiating neurons. The application of this new method demonstrates that TUJ1 is expressed in newborn neurons as early as 1 h after cell cycle exit.