Inhibitory action of norepinephrine on the induction of tryptophan-2,3-dioxygenase by cortisol: Mediation by the I-receptor

Induction of hepatic tryptophan-2,3-dioxygenase in rats by cortisol or corticosterone was inhibited on treatment with norepinephrine. The I-adrenergic blockers showed a small potentiating effect of the norepinephrine-mediated inhibition. The I-adrenergic blockers significantly reversed this inhibition, suggesting that norepinephrine acts Image the I-receptor in inhibition of the cortisol-mediated induction of this enzyme.

Purification, properties and induction of a specific benzoate-4-hydroxylase from Aspergillus niger (UBC 814)

An inducible benzoate-4-hydroxylase has been partially purified from crude extracts of the mycelial felts of Aspergillus niger. This enzyme catalyzes the transformation of benzoate to p-hydroxybenzoate with equimolar consumption of NADPH and O2. It requires tetrahydropteridine as a prosthetic group. The optimum activity was found at pH 6.2 with a Km value at 30°C of 1.6 · 10−4 M for NADPH and 1.3 · 10−4 M for benzoate. Fe2+ (iron) is required for the enzyme activity. The enzyme is stabilized by the inclusion of benzoate, EDTA and glutathione in the extracting buffer. The enzyme is specific for benzoate as substrate. Sulfhydryl group(s) are essential for enzyme activity as indicated by p-chloromercuri-benzoate and N-ethylmaleimide inactivation. Benzoate-4-hydroxylase activity is decreased in the mycelial felts of Aspergillus niger grown in the presence of higher concentrations of benzoate. Maximum activity of the enzyme was observed at 36 h after inoculation.

Oestrogen induction of riboflavin-binding protein in immature chicks. Nature of the secretory protein.

The riboflavin-binding protein isolated from sera of oestrogen-treated male chicks as well as that synthesized and secreted in vitro by the chicken liver have the same molecular size as that of the egg-yolk protein. Functionally the serum and yolk proteins are similar. This is in contrast with the hormone-induced synthesis, secretion and deposition of phosvitin and lipovitellin in the ovary.

Nature of induction of tryptophan pyrrolase in cold exposure

The activity of hepatic tryptophan pyrrolase in rats exposed to cold increased rapidly and reached a maximum of three-fold at 8 h. On continued exposure up to 48 h stress, the activity partly decreased but remained at a level higher than the initial. Withdrawal from the cold stress reversed the change. Adrenalectomy or treatment with inhibitors of protein synthesis abolished the increase in the enzyme activity during cold stress indicating a possible involvement of corticosteroids and de novo protein synthesis. Treatment with drugs known to block autonomic nervous system failed to inhibit the cold-mediated increase in enzyme activity. The results suggest that the increase in enzyme activity obtained on cold exposure is mediated by corticosteroids and not by either indoleaklylamines or autonomic nervous system. The changes in the enzyme obtained under cold stress with respect to the overshoot phenomenon, relationship to the degree of stress and reversibility on withdrawal from the stress indicate the "adaptate" nature of the response.

Time-Domain Measurement of Voltage Induction by Transient EM Fields

An efficient measurement technique for studying the effect of transient electromagnetic fields under controlled conditions has been described. Broad-band TEM fields with a rise-time of a few nanoseconds were generated using a stripline method. Theoretical results are obtained and experimental measurements which confirm these results are described. The work will form the basis for a study of the susceptibility of digital integrated circuits and their interconnections to transient electromagnetic fields.

Site of action of iron in the induction of δ-aminolevulinate dehydratase in Neurospora crassa

δ-Aminolevulinate (ALA) dehydratase, the second and rate limiting enzyme of the heme biosynthetic pathway in the mold Neurospora crassa is induced maximally in 30 min by the addition of iron to iron-deficient cultures. The induction of the enzyme is blocked by cycloheximide, protoporphyrin, 8-azaguanine and cordycepin. Iron also brings about an increase in poly(A)-containing RNA synthesis under conditions of induction. The iron dependent increase in poly(A)-containing RNA synthesis is blocked by protoporphyrin. It is suggested that at the time intervals examined, bulk of the messenger RNA synthesized in response to iron addition represents the messenger for ALA dehydratase.

Professional learning places and spaces: The staffroom as a site of beginning teacher induction and transition

This paper argues that the staffroom is an important professional learning space where beginning teachers interact to understand who they are and the nature of their professional work. The authors highlight the theoretical importance of space and place in the construction and negotiation of beginning teacher subjectivities. To illustrate the staffroom as a particular place where important professional learning could occur the authors use two narratives based on the lived experiences of two beginning teachers, one in a primary context, the other secondary. The authors conclude by calling for greater research attention to the significance of the staffroom and its interaction with teacher subjectivities. At the level of practice we also call for the teaching profession to recognise staffrooms as important sites of professional learning and places that should support induction and mentoring of beginning teachers. Such recognition could enhance the retention, satisfaction, and effectiveness of new and experienced teachers alike.

Negative sequence compensation within fundamental positive sequence reference frame for a stiff micro-grid generation in a wind power system using slip ring induction machine

An isolated wind power generation scheme using slip ring induction machine (SRIM) is proposed. The proposed scheme maintains constant load voltage and frequency irrespective of the wind speed or load variation. The power circuit consists of two back-to-back connected inverters with a common dc link, where one inverter is directly connected to the rotor side of SRIM and the other inverter is connected to the stator side of the SRIM through LC filter. Developing a negative sequence compensation method to ensure that, even under the presence of unbalanced load, the generator experiences almost balanced three-phase current and most of the unbalanced current is directed through the stator side converter is the focus here. The SRIM controller varies the speed of the generator with variation in the wind speed to extract maximum power. The difference of the generated power and the load power is either stored in or extracted from a battery bank, which is interfaced to the common dc link through a multiphase bidirectional fly-back dc-dc converter. The SRIM control scheme, maximum power point extraction algorithm and the fly-back converter topology are incorporated from available literature. The proposed scheme is both simulated and experimentally verified.

Bond graph model of doubly fed three phase induction motor using the Axis Rotator element for frame transformation

Induction motor is a typical member of a multi-domain, non-linear, high order dynamic system. For speed control a three phase induction motor is modelled as a d–q model where linearity is assumed and non-idealities are ignored. Approximation of the physical characteristic gives a simulated behaviour away from the natural behaviour. This paper proposes a bond graph model of an induction motor that can incorporate the non-linearities and non-idealities thereby resembling the physical system more closely. The model is validated by applying the linearity and idealities constraints which shows that the conventional ‘abc’ model is a special case of the proposed generalised model.

Growth factor induction in intervertebral disc tissue: Observations in basic mechanisms of disc degeneration and rearrangement

The intervertebral disc is composed of concentrically arranged components: annulus fibrosus, the transition zone, and central nucleus pulposus. The major disc cell type differs in various parts of the intervertebral disc. In annulus fibrosus a spindle shaped fibroblast-like cell mainly dominates, whereas in central nucleus pulposus the more rounded chondrocyte-like disc cell is the major cell type. At birth the intervertebral disc is well vascularized, but during childhood and adolescence blood vessels become smaller and less numerous. The adult intervertebral disc is avascular and is nourished via the cartilage endplates. On the other hand, degenerated and prolapsed intervertebral discs are again vascularized, and show many changes compared to normal discs, including: nerve ingrowth, change in collagen turnover, and change in water content. Furthermore, the prolapsed intervertebral disc tissue has a tendency to decrease in size over time. Growth factors are polypeptides which regulate cell growth, extracellular matrix protease activity, and vascularization. Oncoproteins c-Fos and c-Jun heterodimerize, forming the AP-1 transcription factor which is expressed in activated cells. In this thesis the differences of growth factor expression in normal intervertebral disc, the degenerated intervertebral disc and herniated intervertebral disc were analyzed. Growth factors of particular interest were basic fibroblast growth factor (bFGF or FGF-2), platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF), and transforming growth factor beta (TGFβ). Cell activation was visualized by the expression of the AP-1 transcription promoters c-Fos and c-Jun. The expression was shown with either mono- or polyclonal antibodies by indirect avidin-biotin-peroxidase immunohistochemical staining method. The normal control material was collected from a tissue bank of five organ donors. The degenerated disc material was from twelve patients operated on for painful degenerative disc disease, and herniated disc tissue material was obtained from 115 patients operated on for sciatica. Normal control discs showed only TGFβ immunopositivity. All other factors studied were immunonegative in the control material. Prolapsed disc material was immunopositive for all factors studied, and this positivity was located either in the disc cells or in blood vessels. Furthermore, neovascularization was noted. Disc cell immunoreaction was shown in chondrocyte-like disc cells or in fibroblast-like disc cells, the former being expressed especially in conglomerates (clusters of disc cells). TGFβ receptor induction was prominent in prolapsed intervertebral disc tissue. In degenerated disc material, the expression of growth factors was analyzed in greater detail in various parts of the disc: nucleus pulposus, anterior annulus fibrosus and posterior annulus fibrosus. PDGF did not show any immunoreactivity, whereas all other studied growth factors were localized either in chondrocyte-like disc cells, often forming clusters, in fibroblast-like disc cells, or in small capillaries. Many of the studied degenerated discs showed tears in the posterior region of annulus fibrosus, but expression of immunopositive growth factors was detected throughout the entire disc. Furthermore, there was a difference in immunopositive cell types for different growth factors. The main conclusion of the thesis, supported by all substudies, is the occurrence of growth factors in disc cells. They may be actively participating in a network regulating disc cell growth, proliferation, extracellular matrix turnover, and neovascularization. Chondrocyte-like disc cells, in particular, expressed growth factors and oncoproteins, highlighting the importance of this cell type in the basic pathophysiologic events involved in disc degeneration and disc rearrangement. The thesis proposes a hypothesis for cellular remodelling in intervertebral disc tissue. In summary, the model presents an activation pattern of different growth factors at different intervertebral disc stages, mechanisms leading to neovascularization of the intervertebral disc in pathological conditions, and alteration of disc cell shape, especially in annulus fibrosus. Chondrocyte-like disc cells become more numerous, and these cells are capable of forming clusters, which appear to be regionally active within the disc. The alteration of the phenotype of disc cells expressing growth factors from fibroblast-like disc cells to chondrocyte-like cells in annulus fibrosus, and the numerous expression of growth factor expressing disc cells in nucleus pulposus, may be a key element both during pathological degeneration of the intervertebral disc, and during the healing process after trauma.