Assay of β-galactosidase activity by Flow Injection Analysis (FIA)

Summary A novel method to analyze -galactosidase by Flow Injection Analysis is presented with a linear working range extended to at least 2150 U/mL, being the detection limit 25 U/mL with 55 samples per hour frecuency and a BSD of 0.954% versus 2.4% obtained by manual assay. The method was tested with optimal results with samples from Escherichia coli cultures producing -galactosidase.     

Evolutionary variants of simian virus 40 which are impaired in early lytic functions but transform nonpermissive cells

From an undiluted passaged virus stock, two size classes of defective simian virus 40 (SV40) DNA were isolated from which two evolutionary variants were cloned. By means of restriction enzyme and heteroduplex analysis, physical maps of the mutants have been constructed. Both mutants contained the region of SV40 DNA coding for the early proteins plus some adjacent sequences (the region from 0.120 to 0.685 map unit, clockwise, on the standard SV40 DNA map). Furthermore, each mutant contained, in the form of two inverted repeats, four times the sequences from the region 0.625 to 0.685 map unit, clockwise. Some biological properties of the mutant DNA were examined, and we found that the mutant DNA (i) has, as compared with SV40 DNA, an impaired ability to induce T antigen in permissive and nonpermissive cells; (ii) does not complement a thermosensitive A mutant of SV40; (iii) replicates very inefficiently without a helper; and (iv), as an apparent contradiction, transforms nonpermissive baby rat kidney cells as well as SV40 DNA. A hypothetical mechanism for the expression of the mutant DNA that might explain the observed biological properties is presented.     

Effect of Oxotremorine on Ornithine Decarboxylase Activity of the Adrenal Gland in Rat

Abstract: In this work we have studied the mechanism for the increase of adrenal ODC (ornithine decarboxylase, EC 4.1.1.17) activity provoked by oxotremorine, a muscarinic agonist. 1. Oxotremorine increased medullary ODC activity maximally at 2 h. Cortical enzyme responded much more slowly. 2. Blockade of peripheral muscarinic receptors with methylatropine partially reduced the response to oxotremorine in the medulla, but not cortex. 3. Hy-pophysectomy abolished the cortical, but not the medullary, responses to oxotremorine. Methylatropine reduced the effect of oxotremorine on medullary ODC in hypophysectomized rats. 4. In unilaterally splanchnicotomized rats oxotremorine caused an increase of ODC activity of the denervated adrenal gland relative to control value; activities in both medulla and cortex were significantly lower than those observed in the innervated gland. Evidence was obtained for a compensatory increase of ODC activity of the adrenal cortex (but not medulla) on the intact side of unilaterally operated rats. 5. Surgical intervention, in the form of a sham operation for transection of the spinal cord, leads to an increase of ODC activity in both parts of the adrenal gland. Transection of the cord attenuates these increases. 6. The additional increase of medullary ODC activity owing to the administration of oxotremorine to sham-operated rats is partially reduced in the adrenal medulla by muscarinic blockade, and completely in the cortex. This effect of methylatropine in regard to cortical ODC activity was not apparent in the other experiments with intact or unilaterally splanchnicotomized (unoperated side) rats. The results with unilaterally splanchnicotomized rats and those with transected spinal cord suggest that oxotremorine-induced modifications of adrenal ODC activity are centrally mediated, above the level of origin of the splanchnic nerves in the spinal cord (T_8–10). Experiments with hypophysectomized rats show that the response of the adrenal cortex to oxotremorine is entirely mediated by the hypophysis.     

Hydroreactivity of stomata in kale leaves of different insertion level as determined by analysis of transpiration curves

Values of the water saturation deficit (WSD) for hydroactive stomatal movements of kale leaves were estimated using the method of transpiration curve analysis. Stomata of young leaves started closing at WSD values of 5 to 6 per cent and were completely closed at 18 to 20 per cent WSD. During maturation and ageing of leaves these WSD values increased to 12.5 and 18 to 23 per cent respectively. Thus the stomatal reaction is more sensitive to changes in WSD in adult leaves than in young ones. After maturation is attained both values decrease. In apparently withering leaves the individual phases of transpiration curves can barely be distinguished, probably for the reason that even under optimal conditions their stomata remain half-closed and at high WSD values an incomplete closing of the aperture occurs. The injured cuticle of withering leaves affects the shape of the transpiration curve as well.     

Interplay between the RNA binding‐protein Musashi and developmental signaling pathways

Musashi comprises an evolutionarily conserved family of RNA‐binding proteins (RBP) that regulate cell fate decisions during embryonic development and play key roles in the maintenance of self‐renewal and differentiation of stem cells and adult tissues. More recently, several studies have shown that any dysregulation of MSI1 and MSI2 can lead to cellular dysfunctions promoting tissue instability and tumorigenesis. Moreover, several reports have characterized many molecular interactions between members of the Musashi family with ligands and receptors of the signaling pathways responsible for controlling normal embryonic development: Notch, Transforming Growth Factor Beta (TGF‐β), Wingless (Wnt) and Hedgehog Signaling (Hh); all of which, when altered, are strongly associated with cancer onset and progression, especially in pediatric tumors. In this context, the present review aims to compile possible cross‐talks between Musashi proteins and members of the above cited molecular pathways for which dysregulation plays important roles during carcinogenesis and may be modulated by these RBP.     

Regulation of ovule initiation by gibberellins and brassinosteroids in tomato and Arabidopsis: two plant species,two molecular mechanisms

Ovule primordia formation is a complex developmental process with a strong impact on the production of seeds. In Arabidopsis this process is controlled by a gene network, including components of the signalling pathways of auxin, brassinosteroids (BRs) and cytokinins. Recently, we have shown that gibberellins (GAs) also play an important role in ovule primordia initiation, inhibiting ovule formation in both Arabidopsis and tomato. Here we reveal that BRs also participate in the control of ovule initiation in tomato, by promoting an increase on ovule primordia formation. Moreover, molecular and genetic analyses of the co‐regulation by GAs and BRs of the control of ovule initiation indicate that two different mechanisms occur in tomato and Arabidopsis. In tomato, GAs act downstream of BRs. BRs regulate ovule number through the downregulation of GA biosynthesis, which provokes stabilization of DELLA proteins that will finally promote ovule primordia initiation. In contrast, in Arabidopsis both GAs and BRs regulate ovule number independently of the activity levels of the other hormone. Taken together, our data strongly suggest that different molecular mechanisms could operate in different plant species to regulate identical developmental processes even, as for ovule primordia initiation, if the same set of hormones trigger similar responses, adding a new level of complexity.