Translocation of amino acids in the xylem of apple (Malus domestica Borkh.) trees in spring as a consequence of both N remobilization and root uptake

Nitrogen is remobilized from storage for the growth of Malus domestica leaves each spring. Seasonal patterns of N translocation in the xylem sap as a consequence of remobilization were determined in 2-year-old 'Golden delicious' trees grafted on M9 rootstocks. The trees were grown in sand culture and (15)NH(4)(15)NO(3) at 10.4 atom% abundance supplied during August-September. The following year no further N was supplied and destructive harvests were taken during bud burst and leaf growth to determine the patterns of N remobilization together with the isolation of xylem sap for an analysis of their amino acid profiles and (15)N enrichments by GC-MS. The concentration of amino acids in the xylem sap rose following bud burst, peaked at full bloom and then fell again during petal fall and fruit set. The peak in amino acid concentration corresponded with the period when the rate of N remobilization was the fastest. The majority of labelled N was recovered in Asn, Gln + Glu and Asp demonstrating that they were being translocated as a consequence of remobilization. In a second experiment, 8-year-old trees growing in an orchard were fertilized with N either in the autumn or spring. Xylem sap samples were collected in the spring and early summer and, by comparison with the amino acid profiles recovered in trees from both treatments, Asn was identified as the main compound translocated as a consequence of both remobilization and root uptake of N, although there was evidence that root uptake of N occurred later. The data are discussed in relation to quantifying the internal cycling of N in trees.

Eosinophilic cholecystitis as a possible late manifestation of the eosinophilia-myalgia syndrome

We describe a case of acute acalculous cholecystitis occurring in a 43-year-old woman with a history of the eosinophilia-myalgia syndrome, associated with the ingestion of 1-tryptophan. The patient underwent a laparoscopic cholecystectomy and subsequent histological examination of the gallbladder revealed an infiltrate predominantly of eosinophils, suggesting a possible relationship to the underlying condition. This may represent a late complication of the eosinophilia-myalgia syndrome--such an association has not previously been reported in the literature. The gastrointestinal and hepatic complications of this syndrome are discussed.

Power lines: Derrida, discursive psychology and the management of accusations of teacher bullying

This study connects broad issues of classroom control and the disciplining of pupils by teachers with a detailed examination of the way teachers deal with an implied accusation that they have been bullying. The analysis of interviews develops with reference to discursive psychology and Derrida's development of deconstruction. Billig's (1992) insights into ways that participants' accounts can neutralize threats to established social arrangements are employed in relating detailed analytic points to the broader power relations between teacher and pupil. Interviews were conducted with Scottish secondary school teachers, and subjected to close textual analysis. This resulted in the development of three themes: (1) Subjectivity Construction, in which the functional role of the construction of mental entities is examined; (2) Normalizing Techniques, identifying strategies whereby intimidation can be constructed as normal; and (3) Figuration, examining the utility of figurative language--metaphors, maxims, and so on. These themes display the subtlety and complexity of teachers' strategies for distancing themselves from being held accountable for reported intimidation. To conclude, three broader features of the study are discussed: the contribution to discursive psychology that Derrida's deconstructive philosophy can make; the respecification of psychology and subjectivity as participants' resources for action; and the contribution that this type of detailed study can make to issues of power and social critique.

Clinical experience with an inactivated hepatitis A vaccine

Clinical trials of an inactivated hepatitis A vaccine have encompassed 104 studies completed by December 1993 in 27 countries. Studies involved 50,677 subjects and administration of > 120,000 vaccine doses. Results show that the vaccine is safe, clinically well-tolerated, and highly immunogenic in all age groups. A seroconversion rate of 100% is achieved 1 month after primary vaccination. Vaccine-induced antibody titers persist after a primary vaccination course for > or = 1 year with a single dose of 1440 ELISA units (EL.U.) in adults and after two doses of 360 EL.U. in children. A booster dose 6-12 months after the first vaccine dose induces very high antibody titers, which according to a mathematical model, are expected to protect against hepatitis A for > 20 years. The vaccine is equally immunogenic when administered simultaneously with other traveler vaccines, therefore enabling flexible and convenient vaccination against hepatitis A.

A simple procedure for the expression of genes in transgenic soybean callus tissue

Cotyledons from germinating seeds of the soybean cultivar Peking were inoculated with virulent Agrobacterium tumefaciens strain A281:pZA-7 which carries a wild type Ti plasmid pTiBo542 and a disarmed Ti plasmid (a binary vector)pZA-7 which contains the βglucuronidase (uidA) and neomycin phosphotransferase (nptII) genes. Tumors were produced on all inoculated explants and 82% of these tumor lines were cotransformed by the nptII gene from the binary vector pZA-7 as shown by PCR analysis (18 of 22 lines tested). Eleven of these 18 lines were also resistant to kanamycin. Eleven lines expressed β-glucuronidase activity (GUS), six of which were also kanamycin resistant. Since there is a high rate of coexpression of genes carried by the binary vector, this system provides a simple and rapid method for the expression of genes of interest in transformed soybean tissue which has been used successfully to test constructs designed for soybean transformation.

The role of inositol lipids in the activation of monocytes by interleukin-1 and bacterial endotoxin

The effect of interleukin-1 (IL-1) and bacterial endotoxin (lipopolysaccharide, LPS) on the activation of phosphoinositidase C (PIC) and on prostaglandin E2 release was studied in monocytes (M phi). Both IL-1 alpha and IL-1 beta increased the release of PGE2 in a concentration-dependent manner, with EC50s of 0.48 nM and 0.12 nM, respectively. Intact M phi were prelabelled with [3H]inositol and the formation of inositol phosphates (IPs) was estimated by ion exchange chromatography. PIC activity was estimated directly by measuring the conversion of [3H]phosphatidylinositol-4,5-bisphosphate to aqueous soluble radioactivity by M phi homogenates. IL-1 alpha (5.8 nM) increased the accumulation of IPs within 1-4 minutes and increases in IP3 and IP4 occurred before the increase in IP1+2 whereas LPS only increased the IPs level after at least 30 min. IL-1 alpha increased PIC activity in M phi homogenates within 15 min with an EC50 of 0.58 nM and IL-1 beta (0.1 nM) also increased activity. Neither IL-1 alpha nor IL-1 beta affected the PIC activity of membrane or cytosolic fractions. LPS decreased activity in all fractions. These data indicate that IL-1, but not LPS, can directly lead to an increased activity of PIC which may be involved in eicosanoid formation in M phi.

Factors affecting transient gene expression in electroporated Glycine max protoplasts

Electroporation was used to evaluate parameters affecting transient gene expression in Glycine max protoplasts. Protoplast viability and reporter enzyme activity for chloramphenicol acetyl transferase (CAT) and ß-glucuronidase (GUS) depended on the field strength employed. Maximum CAT and GUS activity was obtained when a field strength of 500 V/cm at 1000 μF and a protoplast concentration of 1-3 × 10(6)/ml was used. Transformation efficiencies up to approximately 1.6% GUS positive protoplasts were obtained. Transient gene expression increased with increasing plasmid DNA concentration and with the time after electroporation, reaching a maximum after 48 hr. Addition of polyethylene glycol at 5.6% and heat shock (5 rain at 45 °C) given to the protoplasts before adding DNA further enhanced the transformation efficiency. Under the optimized experimental conditions, CAT and GUS activity increased simultaneously, thereby indicating that the increased expression is caused by DNA uptake by more cells rather than greater DNA uptake by the same cells. Our results demonstrate that both GUS and CAT can be used as efficient screenable markers for transformation studies in soybean.

Diadenosine 5',5'''-P1,P4-tetraphosphate (AP4A) levels under various proliferative and cytotoxic conditions in several mammalian cell types

Diadenosine 5',5'''-P1,P4-tetraphosphate (Ap4A) has been proposed as an intracellular signal for growth. In order to test this hypothesis Ap4A levels were followed in several cell types under various conditions. Quiescent dog thyroid cells in a primary culture were induced to proliferate by addition of a mixture of epidermal growth factor, thyrotropin and foetal calf serum; V79 cells were synchronized by serum depletion then stimulated to proliferate by addition of foetal calf serum. Protein and DNA synthesis increased in both cases, although no significant changes in Ap4A levels per cell could be demonstrated. HeLa D98/AH2 and L929 cells were treated with human recombinant tumour necrosis factor alpha which caused marked cell death. This was measured by a decrease in DNA content and a release into extracellular medium of incorporated radioactive precursor. No concomitant variations in Ap4A concentrations could be observed under these conditions. The data from these various systems do not support the hypothesis that changes in Ap4A levels regulate cellular proliferation.

Tumor necrosis factor-alpha induces the phosphorylation of 28kDa stress proteins in endothelial cells: possible role in protection against cytotoxicity?

Tumor necrosis factor-alpha has been shown to rapidly increase the phosphorylation of three 28 kDa proteins in bovine aortic endothelial cells but not in L929 cells. Tumor necrosis factor-alpha induces the necrosis of the latter cells but not of the former. Arsenite enhanced the phosphorylation of the same 28kDa proteins as tumor necrosis factor-alpha in the endothelial cells. As stress proteins often play a protective role, we suggest that the phosphorylation of these proteins in endothelial cells may be responsible for the resistance of these cells to tumor necrosis factor-alpha.

Endocytic pathway of recombinant murine tumor necrosis factor in L-929 cells

The fate of TNF after binding to the surface of L-929 cells was followed by using murine rTNF coupled to colloidal gold as a probe. A time-course study using electron microscopy was performed. Our results confirm previous indications obtained from biochemical studies suggesting that TNF is internalized by this cell type. They further directly show that internalization proceeds through the classical receptor-mediated endocytosis pathway, i.e., via clathrin-coated structures and endosomes before accumulation in secondary lysosomes.

Endocytic pathway of recombinant murine tumor necrosis factor in L-929 cells

The fate of TNF after binding to the surface of L-929 cells was followed by using murine rTNF coupled to colloidal gold as a probe. A time-course study using electron microscopy was performed. Our results confirm previous indications obtained from biochemical studies suggesting that TNF is internalized by this cell type. They further directly show that internalization proceeds through the classical receptor-mediated endocytosis pathway, i.e., via clathrin-coated structures and endosomes before accumulation in secondary lysosomes.

Effect of adenosine 3',5' monophosphate on the mutation frequency induced by N-methyl-N'-nitro-N-nitrosoguanidine

The effect of increased cellular concentrations of adenosine 3',5' monophosphate (cAMP) upon mutation frequency induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was studied in V79 Chinese hamster lung cells. Incubation with either forskolin, which increased the accumulation of cAMP, or 8BrcAMP, an analogue of cAMP, resulted in an increase in the mutation frequency which was concentration-dependent, regardless of whether these agents were added before or after mutagen treatment. Increased cAMP concentrations were shown in these cells to inhibit growth; however, this does not seem to be the mechanism responsible for the increase in mutation frequency as low serum concentrations which also retard growth reduced the mutation frequency observed with MNNG.

Rapid phosphorylation of a 27 kDa protein induced by tumor necrosis factor

Tumor necrosis factor (TNF) has been shown to induce the phosphorylation of a 27 kDa protein in a time- and concentration-dependent manner in HeLa D98/AH2, ME 180 and bovine aortic endothelial cells. This phosphorylation could be reproduced by the calcium ionophore, A23187. However, this phosphorylation was not observed in L929 cells, for which TNF is highly cytotoxic, suggesting that it might play a role in actions of TNF other than the induction of cell death.

Modulation of tumor necrosis factor-alpha cytotoxicity in L929 cells by bacterial toxins, hydrocortisone and inhibitors of arachidonic acid metabolism

L929 cells were incubated with tumor necrosis factor-alpha (TNF-alpha) in the presence or absence of various inhibitors of arachidonic acid metabolism. The addition of either hydrocortisone or nordihydroguaiaretic acid (NDGA) decreased the cytotoxic effect of TNF-alpha but exogenously added arachidonate or linoleate, indomethacin and eicosatetraynoic acid (ETYA) were without effect. While it was found that TNF-alpha stimulated arachidonic acid release, no metabolites of this fatty acid could be evidenced. Cytotoxicity of TNF-alpha could also be decreased by the addition of either cholera or pertussis toxin. These results suggest that a GTP-binding protein is involved in the cytotoxic action of TNF-alpha. Arachidonic acid, released possibly by a phospholipase A2, might also play a role, but probably not via its conversion to known metabolites.

Action of TSH on nuclear ADP-ribosylation in dog thyroid slices

Treatment of dog thyroid slices with thyrotropin (TSH) results in an increase in ADP-ribosylation in nuclei isolated thereafter. This increase is time-dependent and is observed with concentrations of TSH eliciting physiological responses. The technique described here does not involve permeabilization of cell membranes, thereby avoiding artefacts which could arise from hypotonic shock. Cyclic AMP mimicked the stimulatory action of TSH.

Verbal and nonverbal aspects of mothers' directives

Maternal directives to children aged 10 and 18 months were analysed with respect to both verbal and concomitant nonverbal aspects. The findings emphasize the multimodal nature of mothers' communicative messages and draw attention to the way in which language occurs in an action context and not as an isolated output. No indication was found for this age range that verbal devices come to replace nonverbal ones. At both ages most utterances were accompanied by some form of nonverbal behaviour; the precise nature of the association, however, gives little support to the idea of parallel coding. The child's own behaviour is also shown to form part of the context in which maternal speech takes place.

Evidence for the existence of actomyosin ATPase in the rat pancreas. Isolation and biochemical characterization

In a crude extract of rat pancreas, myosin was associated with a protein having the same electrophoretic mobility as actin. This myosin was purified after dissociation of the actomyosin complex with KI-ATP. On sodium dodecylsulfate/acrylamide gel electrophoresis, the isolated pancreatic myosin showed a major component of approximately 200 kDa, and two smaller components with apparent molecular weight of 22 and 15 kDa, respectively. This purified myosin exhibited high ATPase activity in the presence of K+ + EDTA or Ca2+ and very little activity in the presence of Mg2+. (K+ + EDTA)-ATPase activity showed one pH optimum at 8.0, while Ca2+-ATPase activity showed two pH optima at 6.0 and 9.0, respectively. (K+ + EDTA)-stimulated enzyme activity was specific for ATP whereas Ca2+-stimulated activity showed low specificity for nucleoside triphosphates.