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Biomedical subjects

B Wells

Publications and source records attributed to B Wells.

At least 55 records · Page 3Linked to original sources
PubMed1986

Nodulation inhibition by Rhizobium leguminosarum multicopy nodABC genes and analysis of early stages of plant infection.

During analysis of early events in the infection and nodulation of Vicia hirsuta roots inoculated with normal and mutant strains of Rhizobium leguminosarum and strains containing cloned nodulation (nod) genes, a number of novel observations were made. (i) Alternating zones of curled and straight root hairs were seen on roots of V. hirsuta inoculated with the wild-type strain of R. leguminosarum. This phasing of root hair curling was not seen if plants were grown under continuous light or continuous dark conditions. (ii) Reduced nodulation and delayed nodule initiation was observed with a strain carrying a Tn5 mutation in the nodE gene. In addition the phased root hair curling was absent, and root hair curling was observed along the length of the root. (iii) The nodABC genes cloned on a multicopy plasmid in a wild-type strain inhibited nodulation but induced a continuous root hair curling response. Those few nodules that eventually formed were found to contain bacteria which had lost the plasmid carrying the nodABC genes. (iv) With a strain of Rhizobium cured of its indigenous symbiotic plasmid, but containing the cloned nodABCDEF genes, continuous root hair curling on V. hirsuta was observed. However, no infection threads were observed, and surprisingly, it did appear that initial stages of nodule development occurred. Observations of thin sections of these early developing nodules indicated that early nodule meristematic divisions may have occurred but that no bacteria were found within the nodules and no infection threads were observed either within the nodule bumps or within any of the root hairs. It was concluded that for normal infections to occur, precise regulation of the nod genes is required and that overexpression of the root hair curling genes inhibits the normal infection process.

Bacterial Proteins↗
PubMed1985

Monoclonal antibodies to antigens in the peribacteroid membrane from Rhizobium-induced root nodules of pea cross-react with plasma membranes and Golgi bodies.

Three rat hybridoma lines that produced monoclonal antibodies reacting with the peribacteroid membrane from Pisum sativum were isolated, and these all appeared to recognize the same antigenic structure. Using one of these monoclonal antibodies, AFRC MAC 64, electron microscopy of immunogold-stained thin sections of nodule tissue revealed that the antigen, present in the peribacteroid membrane, was also found in the plant plasma membranes and in the Golgi bodies, but not in the endoplasmic reticulum. When peribacteroid membrane proteins were separated by SDS-polyacrylamide gel electrophoresis and transferred to nitrocellulose by electro-blotting, it was found that MAC 64 bound to a series of protease-sensitive bands that migrated in the mol. wt. range 50-85 K. The epitope was sensitive to periodate oxidation and its structure may therefore involve the carbohydrate component of a membrane glycoprotein. We suggest that this structure originates in the Golgi apparatus and is subsequently transferred to the peribacteroid membranes and plasma membranes. The monoclonal antibody also reacted with peribacteroid membranes from nodules of Vicia and lupin, and with plasma membranes and Golgi membranes from uninfected plant cells, including root tip cells from onion (Allium cepa), indicating that the antigen is highly conserved in the plasma membranes of plant cells.

Antibodies, Monoclonal↗
PubMed1985

The legume-Rhizobium symbiosis: a cell surface interaction.

This review will examine the early stages of infection of legume roots by strains of Rhizobium that induce nitrogen-fixing nodules. The object is to show that, at least in terms of ultrastructure, the interactions between the plant and the rhizobia occur at the cell surface interface between these organisms. This situation exists at all stages, from the time the bacteria attach to the surface of the root hairs to the time they occur as the nitrogen-fixing form in the cytoplasm of the nodule cells, enclosed by peribacteroid membranes.

Cell Adhesion↗
PubMed1985

Rhizobium leguminosarum genes involved in early stages of nodulation.

Nodulation genes from Rhizobium leguminosarum have been subcloned and transferred to a strain of R. phaseoli with its symbiotic plasmid deleted (and therefore its nodulation and nitrogen fixation genes). Normal infection and nodule development occurred when these strains were added to the roots of Pisum sativum (peas) and Vicia hirsuta. The pea nodules were examined by electron microscopy; bacteroid forms were seen surrounded by peribacteroid membranes and using immuno-gold labelling it was shown that the nodule cells contained leghaemoglobin within the cytoplasm. By subcloning and analysing the nodulation region it was found that a small (3.2 X 10(3) bases) fragment of DNA contained three genes involved in root hair curling, the first observed step in the interaction between R. leguminosarum and the root hair cells of these legumes.

Cell Membrane↗
PubMed1985

The cytoskeleton underlying side walls and cross walls in plants: molecules and macromolecular assemblies.

Plant cells organize their growth by reinforcing side walls during interphase (causing them to elongate) and by positioning and orienting the cross wall at cytokinesis. In the first part of this presentation we review progress made in identifying different cytoskeletal components that underlie side walls and that are involved in the deposition of the cross wall. During interphase, the cortical microtubule arrays co-distribute with an antigen recognized by a 'universal' monoclonal antibody to intermediate filaments. Using rhodaminyl-lysine-phalloidin no F-actin could be detected at the cortex but endoplasmic, axial cables were found. The cytokinetic apparatus--the phragmoplast--contains microtubules and we find that F-actin and the intermediate filament antigen also co-distribute with this array. We describe the three-dimensional arrangement of microtubules forming the interphase array in cells enlarging by both tip-growth and intercalary growth. In root hairs of higher plants and in apical cells of the filamentous stage of moss Physcomitrella patens, microtubules (MT) are detected at the apices and it is suggested from this that fragmentation of microtubules and absence of MTs from the tip are preparation artefacts. Using human serum from a scleroderma patient, possible microtubule nucleating sites are detected in meristematic cells; these segregate with the broad spindle poles and they surround the nucleus during early interphase--implying a peri-nuclear origin for the cortical MT array. The interphase microtubule array is described in terms of a dynamic helical model, which proposes: that the MT array is an integral complex; that microtubules form helices; that helices can change their pitch--the array converting to the various conformations.

Actins↗
PubMed1985

Microtubules are at the tips of root hairs and form helical patterns corresponding to inner wall fibrils.

Root hairs have sometimes provided contradictory evidence for microtubule/microfibril parallelism. This tissue was re-examined using optimized conditions for the fixation, before immunofluorescence, of root hairs. In phosphate buffer, microtubules did not enter the apical tip of radish root hairs and were clearly fragmented. However, in an osmotically adjusted microtubule-stabilizing buffer, microtubules were observed within the apical dome and appeared unfragmented. Microtubules are not, therefore, absent from the region where new cell wall is presumed to be generated during tip growth. A spiralling of microtubules was seen at the apices of onion root hairs. Using shadow-cast preparations of macerated radish root hairs, it was confirmed that steeply helical microtubules matched the texture of the inner wall. In onion, the 45 degrees microtubular helices are accompanied by similarly wound inner wall fibrils. Results do not support the view that microtubules are not involved in the oriented deposition of fibrils in root hairs. Instead, they are interpreted in terms of a flexible helical cytoskeleton, which is capable of changing its pitch but is sensitive to fixation conditions.

Cell Membrane↗
PubMed1983

Differential dose-response effects of dexamphetamine sulphate on hunger, arousal and mood in human volunteers.

The effect of dexamphetamine (d-Amp) and placebo on visual analogue scale (VAS) ratings of hunger, arousal and mood in nine male volunteers was observed. d-Amp (10 mg) significantly depressed hunger ratings but did not significantly affect arousal and mood ratings. d-Amp (20 mg) had a significant effect on all three ratings. There was a difference in the pattern of dose-response effects. Whereas 20 mg d-Amp produced greater changes than 10 mg in ratings of mood and arousal, there was no significant difference on ratings of hunger. These differences in dose-response relationships may reflect differences in the underlying neurochemical mechanisms mediating the stimulant and anorectic effects of d-Amp.

Adult↗
PubMed1982

Combination chemotherapy-radiotherapy with and without the methanol-extraction residue of Bacillus Calmette-Guerin (MER) in small cell carcinoma of the lung: a prospective randomized trial of the Piedmont Oncology Association.

The effect of addition of the nonspecific immunostimulant, MER, to combined treatment with chemotherapy and radiotherapy in small cell carcinoma of the lung was evaluated in a prospective randomized trial involving 102 evaluable patients. Chemotherapy consisted of cyclophosphamide, Adriamycin, vincristine, methotrexate, and CCNU; and radiotherapy was administered to the primary lesion, mediastinum, supraclavicular areas, and whole brain. Of 47 patients administered MER 400 mcg intradermally every six weeks, 12 (26%) attained complete remission with a median survival of 22.9 months. Complete remission was observed in 17 (31%) of 55 patients who received no MER with a median survival of 20.0 months (P greater than 0.05). Survival greater than or equal to 2 years has been observed in five patients who received MER and two patients who did not receive MER. The response rate and duration, survival, and toxicity of the two treatment arms were similar with the exception of cutaneous and occasional systemic reaction to MER. MER as used in this study has not influenced the overall results of a combined modality treatment program for patients with small cell carcinoma of the lung.

Adult↗
PubMed1981

Physiological significance of benzo(alpha)pyrene adsorbed to carbon blacks: elution studies, AHH determinations.

Desorption of benzo(alpha)pyrene from commercial carbon blacks by tissue fluids in vitro is compared to arylhydrocarbon hydroxylase induction in mice at three levels of carbon black exposure. Less than 0.005% of the adsorbed benzo(alpha)pyrene content determined by soxhlet extraction in toluene is eluted by human plasma, swine serum, swine lung homogenate and swine lung washings. Statistically significant differences in elution efficiency are observed by the various tissue fluids and carbon blacks. There is no detectable increase in AHH level in mouse lung or liver tissues even at the highest carbon black exposure and consumption rate of 1g/g bdywt/year.

Adsorption↗
PubMed1981

Double-blind comparative clinical trial of pimozide and chlorpromazine in mania. A test of the dopamine hypothesis.

Pimozide (PMZ), a relatively specific dopamine (DA) receptor blocking drug, was compared to chlorpromazine (CPZ) in a double-blind, between-patient clinical trial in mania. The trial lasted 14 days. Twenty-three patients who fulfilled Feighner's criteria for mania entered the trial (one patient entering on two separate occasions). Both drugs led to clinical improvement, with a significant effect being noted within 24 hours. According to one of the two rating scales used, initial improvement was greater with chlorpromazine, probably due to its greater sedative effect. By 7 days both drugs were equally effective. Sedative side effects were more frequent in patients on CPZ; extrapyramidal side effects were more frequent with PMZ. The finding that the relatively specific DA receptor blocking drug PMZ was as effective as CPZ in the treatment of mania is consistent with the view that hyperactivity of central DA pathways is involved in the pathogenesis of this condition.

Adult↗
PubMed1981

A Vibrio cholerae infection in a transient teamster.

An illness indistinguishable clinically from classical cholera but caused by a non-cholera vibrio occurred in an over-the-road truck driver. The infecting organism was not finally identified as Vibrio cholera, Smith serotype 113 toxin positive, until 4 weeks after his hospital discharge. Hospital laboratories in most parts of the United States are unlikely to identify Vibrio cholerae in stool cultures unless specifically requested to do so. If one recognizes the chronic cholera carriers have been documented, that small epidemics do occur in unlikely places, and the lack of evidence that toxigenic V. cholerae 01 differs from toxigenic V. cholerae non-01 in these two respects, then the potential for epidemics in the United States is real.

Cholera↗
PubMed1979

A fluorescent derivative of ribosomal protein S18 which permits direct observation of messenger RNA binding.

70 S Escherichia coli ribosomes were reacted with the fluorescent dye N-(iodoacetylaminoethyl)-5-naphthylamine-1-sulfonic acid for 10 min under mild conditions. The resulting ribosomes were fully active. 30 S subunits isolated from these particles were also fully active. They contain approximately 0.7 eq of fluorescent dye. Nearly all of it is attached to protein S18. Competitive reaction with N-ethylmaleimide implies that the fluorescent dye is located at cysteine 10 of the protein. The labeled 30 S particles will recombine with 50 S subunits to form stable 70 S particles. Thus the procedures we have developed allow the large scale preparation of an active fluorescent conjugate of the 70 S ribosome. The fluorescence of the 70 S particles is sensitive to the binding of mRNA, showing both quenching and a shift in emission spectra. Thus it affords a simple way to quantitate mRNA binding directly. In pilot studies without tRNA, the binding constant of the initiation triplet codon adenylyl-(3' leads to 5')-uridylyl-(3' leads to 5')-guanosine to 70 S ribosome was found to be an order of magnitude larger than that of polyuridylic acid.

Escherichia coli↗