Hormonal induction of riboflavin carrier protein in the chicken oviduct and liver: a comparison of kinetics and modulation

Estrogen (E) induction of riboflavin carrier protein (RCP) in the chicken oviduct and liver was investigated to compare and contrast the kinetics, hormonal specificity and modulation of its elaboration in the 2 steroid-responsive tissues. During primary stimulation, continued daily E administration to immature female chicks elicited, after an initial lag, rapid growth and RCP content of the oviduct; neither progesterone (P) nor testosterone (T) could substitute for E in this respect. Furthermore, P given along with E curtailed tissue growth and its RCP content, whereas E + T had a synergistic effect on tissue growth only. During secondary stimulation, E administration steeply enhanced both tissue weight and RCP content without any lag. Interestingly, P (but not T) could substitute for E in augmenting magnum RCP concentration to a comparable extent while a concomitant effect on tissue growth was less marked. In contrast, hepatic induction of RCP was absolutely E-specific during both primary and secondary stimulations. Secondary stimulation with either E or P of E-primed birds enhanced the rates of RCP synthesis in the oviduct relative to that of total protein, whereas in the liver only E was effective in this regard. The absolute rate of E-induced RCP synthesis in both the steroid-stimulated tissues was significantly higher than that of general protein elaboration.

Induction of carnitine acetyltransferase by clofibrate in rat liver

Administration of the anti-hypercholesterolaemic drug clofibrate to the rat increases the activity of carnitine acetyltransferase (acetyl-CoA-carnitine -acetyltransferase, EC 2.3.1.7) in liver and kidney. The drug-mediated increase in enzyme activity in hepatic mitochondria shows a time lag during which the activity increases in the microsomal and peroxisomal fractions. The enzyme induced in the particulate fractions is identical with one normally present in mitochondria. The increase in enzyme activity is prevented by inhibitors of RNA and general protein synthesis. Mitochondrial protein-synthetic machinery does not appear to be involved in the process. Immunoprecipitation shows increased concentration of the enzyme protein in hepatic mitochondria isolated from drug-treated animals. In these animals, the rate of synthesis of the enzyme is increased 7-fold.

Modified current source inverter fed induction motor drive with reduced torque pulsations

A new technique for reducing the torque pulsations in a conventional current source inverter fed induction motor drive is presented. This does not attempt to improve the current waveforms, but modifies the airgap MMF directly. This is based on the use of a motor with two sets of balanced phase windings, with a 30 electrical degree phase difference between them, and each set being fed from a conventional current source inverter. The two inverters are further connected in series so that they can operate from the same current source. As a consequence of this arrangement, the voltage rating of the components of each inverter is reduced, along with reduced torque ripple. This scheme has been experimentally verified and compared with the performance of a conventional scheme.

Microprocessor-Based Field-Oriented Control of A CSI-Fed Induction Motor Drive

This paper describes the method of field orientation of the stator current vector with respect to the stator, mutual, and rotor flux vectors, for the control of an induction motor fed from a current source inverter (CSI). A control scheme using this principle is described for orienting the stator current with respect to the rotor flux, as this gives natural decoupling between the current coordinates. A dedicated microcomputer system developed for implementing this scheme has been described. The experimental results are also presented.

Induction of riboflavin-carrier protein in the immature male rat by estrogen: kinetic and hormonal specificity

The kinetics of estrogen-induced accumulation of riboflavin-carrier protein in the plasma was investigated in immature male rats using a specific and sensitive homologous radio-immunoassay procedure developed for this purpose. Following a single injection of the steroid hormone, plasma riboflavin-carrier protein levels increased markedly after an initial lag period of approximately 24 h, reaching peak levels around 96 h and declining thereafter. A 1.5 fold amplification of the inductive response was evident on secondary stimulation with the hormone. The magnitude of the response was dependent on hormonal dose, whereas the initial lag phase and the time of peak riboflavin-carrier protein induction were unaltered within the range of the steroid doses (0.1–10 mg/ kg body wt.) tested. Simultaneous administration of progesterone did not affect either the kinetics or the maximum level of the protein induced. The hormonal specificity of this induction was further adduced by the effect of administration of antiestrogens viz., En and Zu chlomiphene citrates, which effectively curtailed hormonal induction of the protein. That the induction involvedde novo-protein synthesis was evident from the complete inhibition obtained upon administration of cycloheximide. Passive immunoneutralization of endogenous riboflavin-carrier protein with antiserum to the homologous protein terminated pregnancy in rats confirming the earlier results with antiserum to chicken riboflavin-carrier protein.

Lactic acid bacteria and their antimicrobial peptides : Induction,detection,partial characterization, and potential applications

Bacteriocin-producing lactic acid bacteria and their isolated peptide bacteriocins are of value to control pathogens and spoiling microorganisms in foods and feed. Nisin is the only bacteriocin that is commonly accepted as a food preservative and has a broad spectrum of activity against Gram-positive organisms including spore forming bacteria. In this study nisin induction was studied from two perspectives, induction from inside of the cell and selection of nisin inducible strains with increased nisin induction sensitivity. The results showed that a mutation in the nisin precursor transporter NisT rendered L. lactis incapable of nisin secretion and lead to nisin accumulation inside the cells. Intracellular proteolytic activity could cleave the N-terminal leader peptide of nisin precursor, resulting in active nisin in the cells. Using a nisin sensitive GFP bioassay it could be shown, that the active intracellular nisin could function as an inducer without any detectable release from the cells. The results suggested that nisin can be inserted into the cytoplasmic membrane from inside the cell and activate NisK. This model of two-component regulation may be a general mechanism of how amphiphilic signals activate the histidine kinase sensor and would represent a novel way for a signal transduction pathway to recognize its signal. In addition, nisin induction was studied through the isolation of natural mutants of the GFPuv nisin bioassay strain L. lactis LAC275 using fl uorescence-activated cell sorting (FACS). The isolated mutant strains represent second generation of GFPuv bioassay strains which can allow the detection of nisin at lower levels. The applied aspect of this thesis was focused on the potential of bacteriocins in chicken farming. One aim was to study nisin as a potential growth promoter in chicken feed. Therefore, the lactic acid bacteria of chicken crop and the nisin sensitivity of the isolated strains were tested. It was found that in the crop Lactobacillus reuteri, L. salivarius and L. crispatus were the dominating bacteria and variation in nisin resistance level of these strains was found. This suggested that nisin may be used as growth promoter without wiping out the dominating bacterial species in the crop. As the isolated lactobacilli may serve as bacteria promoting chicken health or reducing zoonoosis and bacteriocin production is one property associated with probiotics, the isolated strains were screened for bacteriocin activity against the pathogen Campylobacter jejuni. The results showed that many of the isolated L. salivarius strains could inhibit the growth of C. jejuni. The bacteriocin of the L. salivarius LAB47 strain, with the strongest activity, was further characterized. Salivaricin 47 is heat-stable and active in pH range 3 to 8, and the molecular mass was estimated to be approximately 3.2 kDa based on tricine SDS-PAGE analysis.

Inhibition of cortisol-mediated induction of hepatic tryptophan-2,3-dioxygenase by norepinephrine

Norepinephrine inhibits cortisol-mediated induction of hepatic tryptophan pyrrolase in rats. During cold exposure the stabilization of this enzyme appears to occur by an interaction of corticoids and norepinephrine on the induction process.

Induction of partial immunity in both males and females is sufficient to protect females against sexual transmission of Chlamydia

Sexually transmitted Chlamydia trachomatis causes infertility, and because almost 90% of infections are asymptomatic, a vaccine is required for its eradication. Mathematical modeling studies have indicated that a vaccine eliciting partial protection (non-sterilizing) may prevent Chlamydia infection transmission, if administered to both sexes before an infection. However, reducing chlamydial inoculum transmitted by males and increasing infection resistance in females through vaccination to elicit sterilizing immunity has yet to be investigated experimentally. Here we show that a partially protective vaccine (chlamydial major outer membrane protein (MOMP) and ISCOMATRIX (IMX) provided sterilizing immunity against sexual transmission between immunized mice. Immunizing male or female mice before an infection reduced chlamydial burden and disease development, but did not prevent infection. However, infection and inflammatory disease responsible for infertility were absent in 100% of immunized female mice challenged intravaginally with ejaculate collected from infected immunized males. In contrast to the sterilizing immunity generated following recovery from a previous chlamydial infection, protective immunity conferred by MOMP/IMX occurred independent of resident memory T cells. Our results demonstrate that vaccination of males or females can further protect the opposing sex, whereas vaccination of both sexes can synergize to elicit sterilizing immunity against Chlamydia sexual transmission.

Molecular basis of nitrate reductase induction in Candida utilis

Temporal separaton of transcription and translation during nitrate reductase induction oin Candida utilis was achieved by the use of actinomycin D and cycloheximide. The yeast failed to synthesize nitrate reductase when nitrate was not provided during transcription. Nitrate thus appeared to induce during transcription the capacity to synthesize nitrate reductase. Presence of nitrate, on the other hand, was not obligatory during translation except for its essential role in maintaining the stability of nitrate reductase after its formation as well as its mRNA.

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.