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PubMed2006

The mechanism of enhanced biological phosphorus removal washout and temperature relationships.

In this study, the combined effects of temperature and solids retention time (SRT) on enhanced biological phosphorus removal (EBPR) performance and the mechanism of EBPR washout were investigated. Two pilot-scale University of Cape Town (South Africa) systems fed with synthetic wastewater were operated at 5 and 10 degrees C. The results showed that the phosphorus removal performance was optimum at total SRT ranges of 16 to 24 days and 12 to 17 days for 5 and 10 degrees C, respectively, and steady-state phosphorus removal was greater at the lower temperature. Higher SRT values of up to 32 days at 5 degrees C and 25 days at 10 degrees C slightly reduced EBPR performance as a result of increased extent of endogenous respiration, which consumed internally stored glycogen, leaving less reducing power for poly-hydroxy alkanoate (PHA) formation in anaerobic stages. The phosphorus-accumulating organism (PAO) washout SRTs of the systems were determined as 3.5 days at 5 degrees C and 1.8 days at 10 degrees C, considerably less than the washout SRTs of nitrifiers. Polyphosphorus, the main energy reserve of the EBPR bacterial consortium, was not completely depleted, even at washout points. The inability of EBPR biomass to use glycogen to generate reducing power for PHA formation was the major reason for washout. The results not only suggest that glycogen mechanism is the most rate-limiting step in EBPR systems, but also that it is an integral part of EBPR biochemistry, as proposed originally by Mino et al. (1987), and later others (Pereira et al., 1996, Erdal et al., 2002; Erdal, Z. K., 2002). The aerobic washout SRT values (2.1 and 1.2 days for 5 and 10 degrees C, respectively) of this study did not fit the linear line for PAO washout developed by Mamais and Jenkins (1992). Perhaps this was because the feeds used during this study were chemical-oxygen-demand-limited (acetate-based synthetic feed), whereas the feeds used for their study were phosphorus-limited (external acetate added to domestic wastewater), resulting in different ratios of PAOs and nonPAOs in the biomass.

Acetates↗
PubMed1994

Anatomy and forebrain projections of the olfactory and vomeronasal organs in axolotls (Ambystoma mexicanum).

We examined the anatomy of the nasal cavity and forebrain in the axolotl (Ambystoma mexicanum) to determine whether the olfactory and vomeronasal systems are present in this neotenic aquatic salamander. The current study was motivated by two considerations: (a) little is known of the anatomy of the vomeronasal system in aquatic vertebrates, and (b) the presence of both olfactory and vomeronasal systems in larval amphibians has broad implications for the evaluation of these systems in vertebrates. From cresyl-violet-stained sections of snouts we determined that the nasal cavity of axolotls is much like that of terrestrial salamanders. The main chamber of the nasal cavity contains an olfactory epithelium, which is confined to grooves between longitudinal ridges of connective tissue covered in a nonsensory epithelium which lacks goblet cells. Using transmission electron microscopy, we found morphologically distinct olfactory receptor cells: many receptor cells terminate in microvillar dendrites, and fewer terminate in motile cilia with the 9 + 2 microtubule array typical of vertebrate olfactory receptor cells. The ciliated and microvillar cells occur in clusters with little intermingling. Horseradish peroxidase labeling revealed that axons of the olfactory receptor cells terminate in large glomeruli in the main olfactory bulb at the rostral end of the telencephalon. Lateral to the main chamber of the nasal cavity is a diverticulum that is entirely lined with a vomeronasal epithelium containing basal cells, microvillar receptor cells, sustentacular cells that lack specialized processes on the apical surface, and large ciliated cells that may function to move fluid across the vomeronasal epithelium. Unlike the olfactory epithelium, the vomeronasal epithelium lacks Bowman's glands. Using horseradish peroxidase, we determined that the axons of the vomeronasal receptor cells project to the accessory olfactory bulb, a distinct structure dorsal and caudal to the main olfactory bulb. The presence of both olfactory and vomeronasal systems in axolotls and other neotenic salamanders implies that both systems are pleiomorphic in larval amphibians; we therefore suggest that the vomeronasal system may not have originated as an adaptation to terrestrial life.

Ambystoma mexicanum↗
PubMed1994

Limited expression of C/EBP family proteins during B lymphocyte development. Negative regulator Ig/EBP predominates early and activator NF-IL-6 is induced later.

The importance of C/EBP proteins in B cell biology is suggested by the occurrence of functionally important C/EBP binding sites in Ig gene enhancers and promoters, and the knowledge that family member NF-IL-6 is induced in other systems in response to regulators of B cell differentiation. We have studied the expression pattern and activity of C/EBP family transcriptional regulators in B cells at different developmental stages by using B cell lines and normal splenic B cells. Two family members, Ig/EBP and NF-IL-6, seem to be the major regulators of C/EBP site-dependent transcriptional activity in B cells. Negative regulator Ig/EBP is predominantly present in early B cells; activator NF-IL-6 increases in more mature B cells and is induced by LPS activation of splenic B cells. LIP, an N-terminally truncated form of NF-IL-6, was found in most B cell lines tested; LIP can act as a weak transcriptional activator in B cell lines. Partly as a result of the differential amounts of C/EBP family proteins, C/EBP sites do not function as activator sites in early B cells but are activator sites in terminally differentiated B cells.

Animals↗
PubMed1990

Differentiation patterns in two- and three-dimensional culture systems of human squamous carcinoma cell lines.

Relative quantification of the pattern of differentiation of two squamous carcinoma cell lines of the female genital tract, A431 and CaSki, was studied in various experimental tissue culture states that are frequently used to evaluate drug and radiation effects on human tumors. Two- and three-dimensional in vitro cultures, ie, monolayers and multicellular tumor spheroids (MCTS), and nude mice-xenograft tumors as in vivo tumor models were compared. In addition, epidermal growth factor (EGF) was used comparatively in the in vitro studies. Morphologic signs of epithelial differentiation could be recognized in both cell lines gradually increasing from monolayers to MCTS to xenograft tumors. Cytokeratin (CK) expression is described as stable in A431 cells. Using immunohistochemistry, however, partial masking of CK antigens was found when applying the antibody 8.12 on monolayer cells and could be quantified by flow cytometric measurements. Fundamental cellular changes were found in a CaSki xenograft tumor, which showed newly established features of a keratinizing carcinoma after late onset of tumor growth. Epidermal growth factor caused reduction of both intercellular contacts and later onset of necrosis in MCTS, leading to an increased viability of the spheroids. Significant differences in differentiation of the tumor model systems indicates that the characterization of differentiation with immunohistochemistry and flow cytometry is necessary to assist interpretation of data obtained with these different tumor models.

Antibodies, Monoclonal↗
PubMedDate not supplied

Reveal for Salmonella test system.

The Reveal for Salmonella (RSS) test system is a presumptive qualitative test that detects the presence of Salmonella organisms in foods within 21 h total testing time, allowing the user to release negative products 24 h earlier than when using other rapid test kits. Foods are enriched with a proprietary resuscitation medium called Revive and then selectively enriched with either Selenite Cystine or Rappaport-Vassiliadis selective media. The enriched culture is used to inoculate the RSS detection device, which initiates a lateral flow through a reagent zone containing anti-Salmonella antibodies conjugated to colloidal gold particles that capture antigens present in the culture. The antigen-antibody complex migrates farther and is captured by an additional anti-Salmonella antibody, causing the colloidal gold to precipitate and form a visual line, indicating a positive result. A procedural control line also will form regardless of the presence of Salmonella organisms to indicate the test is working properly. Existing AOAC Official Methods for Salmonella organisms require a 48 h enrichment before testing. Hence, a food product has to be held before release, adding extra cost to the company and the consumer. The RSS test system was evaluated by quantitative spiking studies. Although AOAC encourages inclusion of naturally contaminated foods, almost all microbiological AOAC validation studies have been performed with artificially contaminated foods for absolute control over the study. The RSS test system is designed to test many food types for Salmonella organisms and has a limit of detection of 5-10 colony-forming units (cfu)/25 g with a false-negative rate of < 1% and a false-positive rate of < 5.0%. It showed an 81% overall agreement with the traditional procedure of the U.S. Department of Agriculture's Food Safety Inspection Service.

Animals↗
PubMed1991

Resolution and information limitations from transducer arrays.

The factors limiting the resolution achievable with array-based imaging methods are considered. The limitations on beamwidth and field of view for beam scanning systems are first examined using plane wave diffraction theory, treating focusing and any array curvature as separable to the plane wave analysis. It is found that in all cases the number of half-beamwidths (maximum to null) across the field of view cannot exceed the number of electrically addressable elements in the array. The minimum beamwidth achievable by strong focusing is shown to be limited to twice the inter-element pitch. Digital reconstruction is then considered as an alternative to beam scanning. Here the number of image points recoverable across the field of view is equal to the number of elements in the array. The mathematical equivalence of the two methods is demonstrated, and the inference is made that the half-beamwidth represents a fundamental measure of lateral resolution. Alternative array configurations, suitable for CT methods, are then compared to probe arrays and it is found that the total number of resolution cells within a two-dimensional image is dependent on the pulse length and number of elements, rather than on the array configuration and imaging method. This again reveals the fundamental similarity of the various methods, essentially in combining position line information from the separate elements, albeit in different orders. Finally an expression for the information capacity of a scanning system is presented which relates the limitations on spatial and contrast resolution to the bandwidth and dynamic range of the system and the number of elements in the array.

Medical Laboratory Science↗
PubMed1999

Voluntary ethanol drinking during the first three postnatal weeks in lines of rats selectively bred for divergent ethanol preference.

BACKGROUND: Using a procedure first developed by Hall (1979), we examined ethanol self-administration in preweanling pups from Wistar rats and in lines of rats selectively bred for divergent ethanol preference (alcohol-preferring P, alcohol-nonpreferring NP, high-alcohol-drinking HAD-1 and -2, and low-alcohol-drinking LAD-2) to determine if factors contributing to high and low alcohol intakes are present early in development. METHODS: From postnatal days 5 to 20, nondeprived male and female rat pups received 30 min daily access to either water or a 15% (v/v) ethanol solution. In each daily session, pups were placed in a heated chamber containing Kimwipes soaked with a water or ethanol solution. Pups were weighed before and after each session, and intake levels were calculated as a percentage of body weight change. RESULTS: Similar to previous reports, Wistar pups exhibited over a 2-fold higher level of ethanol ingestion than water on postnatal days 9 through 14, with ethanol intakes approaching 3 g/kg body weight. When the drinking patterns of the selected lines were examined, only the HAD replicate lines showed a comparable preference for ethanol versus water during the preweanling period. The ethanol consumption of P, NP, and LAD lines was not consistently distinguishable from water intake levels. To reveal whether early ethanol exposure would influence later ethanol drinking behavior, a subset of HAD and LAD rat pups received free-choice ethanol access upon weaning. Although the divergent ethanol preference between high- and low-alcohol-drinking lines was evident within the first 4 days of access (>4 g/kg/day for HAD; <2 g/kg/day for LAD), preweanling ethanol exposure did not alter the acquisition or maintenance of ethanol drinking in either line. CONCLUSIONS: Overall, these results suggest that (a) the enhanced ethanol ingestion observed during the middle portion of the preweanling period is a robust phenomenon and generalizes across nonselected strains of rats, (b) selective breeding for divergent alcohol preference has arrested this age-specific effect in all but the HAD lines of rats, and (c) early ethanol exposure does not alter genetic dispositions for later high or low alcohol preference.

Alcohol Drinking↗
PubMed1993

Interactive use of on-line portal imaging in pelvic radiation.

We have evaluated a fluoroscopic on-line portal imaging system in routine clinical radiotherapy, involving the treatment of 566 pelvic fields on 13 patients. The image was typically generated by delivering a radiation dose of 6-8 cGy. Comparison between portal image and simulator film was done by eye and all visible errors were corrected before continuing irradiation. If possible, these corrections were performed from outside the treatment room by moving the patient couch by remote control or by changing collimator parameters. Adjustments were performed on 289/530 (54.5%) evaluable fields or 229/278 (82.4%) evaluable patient set-ups. The lateral couch position was most frequently adjusted (n = 254). The absolute values of the adjustments were 6.8 mm mean (SD 6.6 mm) with a maximum of 40 mm. All absolute values of adjustments exceeding 25 mm were recorded in one patient and those exceeding 15 mm were observed in two patients. Both patients were obese females. Adjustments exceeding 5 mm were observed in all 13 patients. Related to the use of on-line portal imaging, treatment time was increased by a median of 36.5% (mean 45.8%; SD 42.1%). The range was 7.7 to 442%. The fraction of the total treatment time to perform corrections was 22.7% median (mean: 26.0; SD: 11.8%). Statistically significant systematic in-plane errors were found in 7/13 patients. A systematic error was detected on the lateral position of the field in five patients. In one patient a systematic error of the longitudinal field position and in one patient a rotational error was detected. For adjustments in the lateral direction the present method does not allow to detect lateral shifts of less than 2 mm. For adjustments in the longitudinal direction the sensitivity could not be estimated but the available data suggest that 80% of errors < or = 5 mm were not adjusted. In obese patients, random errors may be surprisingly large.

Evaluation Studies as Topic↗
PubMed1998

Interleukin-1beta and its type 1 receptor are expressed in developing neural circuits in the frog, Xenopus laevis.

The cytokine interleukin-1 beta (IL-1beta) is an evolutionarily conserved molecule that was originally identified in the immune system. In addition to regulating peripheral immune responses, IL-1beta plays an important role in mediating neural-immune interactions and regulating glial activities during healing and repair in the damaged nervous system. Active IL-1beta is produced by interleukin-converting enzyme (ICE), a caspase thought to be involved in the induction of apoptosis. We report that, in the developing frog, Xenopus laevis, IL-1beta and the IL-1 type 1 receptor proteins are coexpressed in specific neurons that comprise early sensory-motor circuits. IL-1beta and IL-1 type 1 receptor proteins are colocalized in specific midbrain and hindbrain reticular cells, including Mauthner's neuron; specific cells in the trigeminal (fifth), lateral line (seventh), and vestibular (eighth) cranial ganglia; oculomotor neurons; and the primordial Purkinje cells of the lateral cerebellar auricle. In the spinal cord, Rohon-Beard sensory neurons, dorsal root ganglion cells, and primary motoneurons are immunopositive. Anteriorly, the olfactory pits, olfactory nerves, and olfactory bulbs are labeled, as are retinal cells, especially photoreceptor inner segments. With regard to the function of IL-1beta during neural development, IL-1beta and its type 1 receptor are present throughout the course of neural development in identifiable, long-lived neurons, such as Mauthner's neuron. These and other data suggest that IL-1beta and its type 1 receptor may be involved in the maintenance of cell survival rather than induction of neuronal death.

Animals↗
PubMed2003

Transient in vivo reporter gene assay for ecdysteroid action in the Bombyx mori silk gland.

To analyze the molecular mechanisms underlying hormone-regulated gene expression during molt and metamorphosis, we developed a transient reporter gene assay system using the silkworm anterior silk gland. Reporter plasmids were delivered into dissected anterior silk glands by particle bombardment and bombarded glands transplanted into other larvae, to which hormones were then administered. When the green fluorescent protein gene, coupled with the constitutive cytoplasmic actin gene A3 promoter, was introduced into the anterior silk gland, strong green fluorescence was observed a few days later. Bombarded silk glands transplanted into other larvae showed the same morphological changes as intrinsic glands after 20-hydroxyecdysone (20E) alone or 20E plus juvenile hormone (JH) treatment, indicating that the transplanted gland received hormonal signals properly. When a 20E-responsive reporter construct containing four tandemly repeated pal-1 ecdysone response elements upstream from the luciferase gene was delivered into the gland, an approximately 50-fold increase in luciferase activity was detected 30 h after 20E injection. This induction was comparable to that in an ecdysteroid-responsive Bombyx cell line. This in vivo reporter assay system is thus a rapid, effective tool for analyzing gene expression regulated by 20E and probably by JH.

Animals↗
PubMed1999

Preventing drowsiness accidents by an alertness maintenance device.

The reported experiment investigated in an advanced driving simulator whether drivers' alertness can be maintained in drowsiness-inducing conditions by a special game-like system, a 'gamebox'. Drowsiness was assessed by self-rating and eye-closures. Mental effort was assessed by a subjective workload rating scale and by a physiological measure (the 0.1 Hz component of heart rate). Driving quality and safety were assessed by steering movements, time-to-line crossings, and by the occurrence of safety-related driving errors--solid line crossings, driving off-road incidents and accidents. When driving with the gamebox, drivers reported a lower degree of drowsiness and fewer instances of sleep episodes as compared to a control condition. Driving with the device resulted in fewer incidents and accidents, and these occurred later in the session. The quality of vehicle control deteriorated progressively over the course of the session, but less so in the gamebox condition. Hence, the results corroborate the notion that mental activity counteracts drowsiness in prolonged driving.

Accidents, Traffic↗
PubMed2002

Mapping QTLs for root morphology of a rice population adapted to rainfed lowland conditions.

In the rainfed lowlands, rice ( Oryza sativa L.) develops roots under anaerobic soil conditions with ponded water, prior to exposure to water stress and aerobic soil conditions that arise later in the season. Constitutive root system development in anaerobic soil conditions has been reported to have a positive effect on subsequent expression of adaptive root traits and water extraction during progressive water stress in aerobic soil conditions. We examined quantitative trait loci (QTLs) for constitutive root morphology traits using a mapping population derived from a cross between two rice lines which were well-adapted to rainfed lowland conditions. The effects of phenotyping environment and genetic background on QTLs identification were examined by comparing the experimental data with published results from four other populations. One hundred and eighty-four recombinant inbred lines (RILs) from a lowland indica cross (IR58821/IR52561) were grown under anaerobic conditions in two experiments. Seven traits, categorized into three groups (shoot biomass, deep root morphology, root thickness) were measured during the tillering stage. Though parental lines showed consistent differences in shoot biomass and root morphology traits across the two seasons, genotype-by-environment interaction (GxE) and QTL-by-environment interaction were significant among the progeny. Two, twelve, and eight QTLs for shoot biomass, deep root morphology, and root thickness, respectively, were identified, with LOD scores ranging from 2.0 to 12.8. Phenotypic variation explained by a single QTL ranged from 6% to 30%. Only two QTLs for deep root morphology, in RG256-RG151 in chromosome 2 and in PC75M3-PC11M4 in chromosome 4, were identified in both experiments. Comparison of positions of QTLs across five mapping populations (the current population plus populations from four other studies) revealed that these two QTLs for deep root morphology were only identified in populations that were phenotyped under anaerobic conditions. Fourteen and nine chromosome regions overlapped across different populations as putative QTLs for deep root morphology and root thickness, respectively. PC41M2-PC173M5 in chromosome 2 was identified as an interval that had QTLs for deep root morphology in four mapping populations. The PC75M3-PC11M4 interval in chromosome 4 was identified as a QTL for root thickness in three mapping populations with phenotypic variation explained by a single QTL consistently as large as 20-30%. Three QTLs for deep root morphology were found only in japonica/indica populations but not in IR58821/IR52561. The results identifying chromosome regions that had putative QTLs for deep root morphology and root thickness over different mapping populations indicate potential for marker-assisted selection for these traits.

Journal Article↗
PubMed2026

First isolation and characterisation of human Rotavirus alphagastroenteritidis from cerebrospinal fluid in Malaysia.

Rotavirus infection is a major cause of paediatric gastroenteritis and has increasingly been associated with neurological complications, although direct evidence of central nervous system involvement remains limited. In this study, Rotavirus A was detected in both cerebrospinal fluid and stool samples from a child presenting with encephalopathy and seizures, and infectious virus was successfully propagated in mammalian cell lines. Genomic analysis revealed a Wa-like genotype constellation, G1-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1. Although lateral flow immunoassay yielded negative results, molecular diagnostic approaches proved valuable for identifying atypical RVA infections.

Cerebrospinal fluid↗
PubMed1984

Effects of hypothermia on the cat brain-stem auditory evoked response.

Effects of systemic hypothermia on the brain-stem auditory evoked responses (BAERs) in 4 pentobarbital anesthetized adult cats placed on total cardiopulmonary bypass were investigated. Hypothermia was achieved by slowly cooling the bypass blood through a heat exchanger. Serial BAERs were recorded at 2 min intervals as brain temperature was lowered from 37 to 22 degrees C and then rewarmed over a 1-2 h period. Temperatures were recorded from the brain, esophagus and rectum. Three effects were produced by controlled systemic hypothermia. First, latencies of each component wave (I-V) of the BAER increased exponentially as brain temperature was lowered to 19 degrees C. Latencies of earlier waves (I-III) increased less than those of the later waves (IV-V). Arrhenius plots of inverse latency (rate) versus reciprocal of the absolute temperature generated a family of straight lines of similar slope for each of the 5 component waves of the BAER. The activation energy for each of the 5 BAER waves was derived from the slope of the Arrhenius plot. The mean and standard deviation of the activation energy of all 5 waves was 9.7 +/- 0.5 kcal/mole degree C. The fact that the activation energy was similar for each BAER component wave (I-V) indicated that the increase in latencies for all 5 waves was governed by the same rate-limiting, temperature-dependent process(es). Second, the rise time and duration of each of the component waves of the BAER increased with decreasing temperature. Third, wave amplitudes increased from 37 to 32 degrees C in a quasiparabolic relation and then, decreased at approximately a linear rate. The BAER wave form completely disappeared below 20.3 degrees C. Slow rewarming of the brain to its initial temperature restored the BAER component waves to their original latencies and amplitudes.

Animals↗
PubMed1997

Multiple visuospatial working memory buffers: evidence from spatiotemporal patterns of brain activity.

Numerous studies have shown that the visual system involves different cortical pathways in the perception of object (ventral visual pathway) and spatial (dorsal visual pathway) information. The present study was concerned with whether human visuospatial working memory divides along similar lines. We used event-related brain potentials (ERPs) recorded from scalp of normal humans to show the existence of different buffering systems for the retention of object and spatial visual information. Subjects were presented with object or spatial stimuli to be retained for a 3.6-sec interval. The ERPs isolated brain activity associated with retention from earlier storage and later retrieval processes. The ERP scalp topographies indicated that the underlying patterns of brain activation were different during retention of object and spatial information.

Adult↗
PubMed1996

Cell-to-cell scanning in capillary electrophoresis.

A widespread limitation in using cell-based biosensors for repetitive chemical analysis is loss of agonist-induced response caused by receptor desensitization. We overcome this problem by scanning an array of immobilized cells underneath a capillary electrophoresis column outlet. In this way, electrophoretically fractionated components that exit the separation capillary are always directed onto cells previously unexposed to receptor agonists. To demonstrate this concept of response recovery using a scanning format, we have chosen the bradykinin B2 receptor system in the NG108-15 cell line, which is known to undergo desensitization. Whereas four subsequent injections of 250 microM bradykinin separated by 120 s are found to reduce the NG108-15 cell response markedly, scanning to new cells can fully restore the response during the separation. Furthermore, by pretesting individual NG108-15 cells for an agonist response and then later scanning back to the same cell, we achieved a 100% success rate in detecting bradykinin in subsequent electrophoretic separations.

Animals↗
PubMedDate not supplied

Experience with preexposure rabies vaccination.

Preexposure rabies vaccination, presently limited to high-risk target populations, is facilitated by cell culture vaccines. Officially recommended programs comprise either two doses administered on days 0 and 28 or three doses given on days 0, 7, and 21 or 28. A first booster 1 year later ensures a good duration of immunity; follow-up studies now cover 5-8 years. These results were obtained by the intramuscular and subcutaneous injection routes; intradermal programs have been explored with the aim of reducing costs. Preexposure immunization is well tolerated, despite some systemic allergic reactions. Efficacy has been observed universally, but certain factors may affect results. Several lines of evidence favor an extension of preexposure vaccination. In Scandinavian countries, the majority of vaccine doses are used preexposure, while about 40%, 15%, and 10% are so used in the United Kingdom, the United States, and France, respectively. However, preventive immunization is rare in developing countries, where the risk of infection is maximal and permanent. The more economical new vaccines, such as purified Vero rabies vaccine, permit a reevaluation of preventive vaccination. Vaccine combinations including rabies may prove economical.

Humans↗
PubMed2003

Activation of cell proliferation by brassinolide application in tobacco BY-2 cells: effects of brassinolide on cell multiplication, cell-cycle-related gene expression, and organellar DNA contents.

Brassinosteroids (BRs) are steroidal phytohormones that are essential for many processes in plant growth and development, such as cell expansion, vascular differentiation, and responses to stress. The effects of BRs on cell division are unclear, as attested by contradictory published results. To determine the effect of BRs on cell division, the tobacco (Nicotiana tabacum) BY-2 cell line, which is a widely-used model system in plant cell biology, was used. It was found that brassinolide (BL) promoted cell division only during the early phase of culture and in the absence of auxin (2,4-D). This promotion of cell division was confirmed by RNA gel blot analyses using cell-cycle-related gene probes. At later stages in the culturing periods of BL-supplied and 2,4-D-supplied BY-2 cells, differences in cell multiplication and cell-cycle-related gene expression were observed. Moreover, the BL-treated BY-2 cells had morphological differences from the 2,4-D-treated cells. To determine whether suppressed organellar DNA replication limited this promotion of cell division during the early culture phase, this replication was examined and it was found that BL treatment had no effect on activating organellar (plastid- and mitochondrial-) DNA synthesis. As preferential organellar DNA synthesis, which is activated by 2,4-D, is necessary during successive cell divisions in BY-2 cells, these data suggest that the mechanism of the promotion of cell division by BL treatment is distinct from that regulated by the balance of auxin and cytokinin.

Brassinosteroids↗