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K Roberts

Publications and source records attributed to K Roberts.

At least 127 records · Page 7Linked to original sources
PubMed1992

Identification of a transitional cell state in the developmental pathway to carrot somatic embryogenesis.

We have located a novel carbohydrate epitope in the cell walls of certain single cells in embryogenic, but not in non-embryogenic, suspension cultures of carrot. Expression of this epitope, recognized by the mAb JIM8, is regulated during initiation, proliferation, and prolonged growth of suspension cultures such that changes in the abundance of JIM8-reactive cells always precede equivalent changes in embryogenic potential. Therefore, a direct correlation exists between the presence of the JIM8-reactive cell wall epitope and somatic embryo formation. The JIM8-reactive cell wall epitope is expressed in the cell walls of three types of single cells and one type of cell cluster. One of the single cell types seems able to follow one of two phytohormone-controlled developmental pathways, either a cell elongation pathway that eventually leads to cell death, or a cell division pathway that gives rise to proembryogenic masses. We demonstrate that all JIM8-reactive cell types in embryogenic carrot suspension cultures are developmentally related, and that the switch by one of them to somatic embryogenesis is accompanied by the immediate dissipation of the JIM8-reactive cell wall epitope. The cell wall carbohydrate epitope recognized by JIM8 therefore represents a cell wall marker for a very early transitional cell state in the developmental pathway to carrot somatic embryogenesis.

Antibodies, Monoclonal↗
PubMed1992

Fourier transform infrared microspectroscopy is a new way to look at plant cell walls.

Highly reproducible Fourier transform infrared (FTIR) spectra from both single onion (Allium cepa) cell walls and their constituent polymers were obtained under a variety of sampling conditions. The specificity of the chemical extraction sequence used in the preparation of the material was confirmed: pectins only are extracted by cyclohexanediaminetetraacetic acid and sodium carbonate, whereas xyloglucans are extracted by increasing concentrations of potassium hydroxide. There was very little contamination of the first potassium hydroxide extract with residual pectin. The low abundance of both phenolics and protein was also confirmed. The first sodium carbonate extraction almost completely removes esters remaining in the cell wall. We have demonstrated that FTIR spectroscopy can detect large conformational changes in pectic polymers on removal from the cell wall and on drying. FTIR spectroscopy provides a powerful and rapid assay for wall components and putative cross-links by identifying polymers and functional groups nondestructively in muro. The availability of micro-sampling and data acquisition techniques that permit subtraction of the blanket absorption of water make FTIR spectroscopy particularly suitable for studies of cell wall architecture. The use of polarizers with the microscope accessory permits determination of the orientation of particular functional groups with respect to the direction of cell elongation in carrot suspension cells.

Journal Article↗
PubMed1991

Immunoregulatory role of gamma delta T cells.

While the major population of T lymphocytes express T cell receptor (TCR) alpha beta-chains and recognize peptide antigens in association with either Major Histocompatibility Complex class I or class II molecules, a consensus view does not exist concerning either the nature of the antigen recognized or the nature of the restriction element utilized by the minor population of T cells which express TCR gamma delta-chains. We have identified a unique subpopulation of gamma delta T cells which uniformly express the C gamma 4, V delta 6 TCR and which produce a number of cytokines in the absence of exogenous stimulation. Adaption of these cell lines to serum-free culture conditions resulted in a cessation of cytokine production which could then be induced by the addition of extracellular matrix (ECM)-proteins to the culture. The response to the ECM-proteins could be completely inhibited by an antibody to the murine vitronectin receptor (VNR). However, engagement of the VNR by its ligand was not sufficient for the induction of cytokine production as anti-TCR antibodies inhibited the response to ECM-proteins and gamma delta TCR loss mutants failed to respond. Collectively, these data demonstrate that not only is coexpression of the VNR and the gamma delta TCR required for the induction of cytokine production by this subpopulation of T cells, but that the TCR must also be engaged by its ligand, most likely a cell surface autoantigen expressed by the T cells themselves.

Animals↗
PubMed1991

The mouse vitronectin receptor is a T cell activation antigen.

In this report, we demonstrate that the T cell activation antigen, recognized by monoclonal antibody H9.2B8, is the murine homologue of the vitronectin receptor (VNR) and, thereby, we provide initial evidence that VNR is expressed on lymphoid cells. VNR is expressed on a variety of T cell lines, tumors, and Con A-activated splenocytes, but not resting T cells, and is capable of binding to the extracellular matrix proteins fibronectin, fibrinogen, and vitronectin, via the tripeptide sequence RGD. There was no evidence of novel beta chains pairing with the VNR alpha chain, as has been demonstrated in some human cells. In view of recent studies demonstrating that this molecule functions as an accessory molecule in T cell activation, the VNR may play an important role in mouse T cell functions.

Amino Acid Sequence↗
PubMed1991

The vitronectin receptor serves as an accessory molecule for the activation of a subset of gamma/delta T cells.

Constitutive production of cytokines was observed in 3 of 12 gamma/delta T cell lines derived from murine epidermis and correlated with the expression of the C gamma 4, V delta 6 T cell receptor (TCR). After adaptation of one of the lines (T195/BW) to serum-free culture conditions, cessation of the "spontaneous" production of interleukin 4 (IL-4) was observed and IL-4 production could then by induced by the addition of RGD-containing extracellular matrix (ECM) proteins to the culture. The response to the ECM proteins could be completely inhibited by a mAb to the murine vitronectin receptor (VNR). However, the induction of IL-4 production could also be inhibited by anti-CD3 and by an anti-clonotypic mAb to the TCR-gamma/delta of T195/BW. As TCR-gamma/delta loss mutants of T195/BW also failed to respond to ECM proteins, these data demonstrate that engagement of the VNR by its ligand is necessary, but not sufficient, for the induction of IL-4 production. Furthermore, the VNR is expressed by many other T cell clones (both gamma/delta and alpha/beta), none of which produce lymphokines constitutively. Taken together, these observations strongly favor the view that not only is coexpression of the VNR and TCR required for the induction of IL-4 production, but that the TCR must also be engaged by its ligand, most likely a cell surface antigen expressed by the hybridoma itself.

Animals↗
PubMed1991

A comparison of selected health-related data from surveys of a general population and a sporting population.

This paper presents a comparison of health-related data from two surveys of British adults. Respondents from one survey formed a representative sample of the British population, whilst respondents from the other were characterised by their participation in sport. Statistical analysis revealed that sports participants had significantly lower body mass index values, lower blood pressures and lower resting pulse rates (P less than 0.05). In addition, sports participants possessed better self-perceived health and perceived themselves overall to be more active than members of the general population. When controls were introduced for gender and age, many of these differences remained, particularly among females. It is concluded that despite the cross-sectional nature of these data, evidence is provided that supports the health-promoting case for sport.

Adolescent↗
PubMed1991

The tobacco mosaic virus 30K movement protein in transgenic tobacco plants is localized to plasmodesmata.

Transgenic tobacco plants expressing a gene encoding the tobacco mosaic virus (TMV) movement protein (30K) were studied using immunocytochemical techniques. The movement protein was shown to be localized within or on most of the plasmodesmata observed in the transformed plant. These results are consistent with the idea that the movement protein interacts with the plasmodesmata to facilitate the cell-to-cell spread of TMV.

Capsid Proteins↗
PubMed1991

Expression of the tobacco mosaic virus movement protein using a baculovirus expression vector.

A cDNA clone of the tobacco mosaic virus 30K movement protein (MP) gene was constructed and introduced into an Autographa californica nuclear polyhedrosis baculovirus expression vector. Infection of Spodoptera frugiperda cells with the vector resulted in the synthesis of low levels of MP, which was detected by anti-MP serum as two closely related species of Mr approximately 34K and a third species of 32K. The authenticity of the recombinant MP was confirmed by comparison of the protein, on the basis of migration during SDS-PAGE, with authentic MP from several sources. It appeared that the recombinant MP was not modified by N-linked glycosylation, but was phosphorylated. The recombinant MP was produced in both a phosphorylated and an unphosphorylated state and the former species was shown to comigrate with plant-expressed MP during SDS-PAGE.

Animals↗
PubMed1991

Metabolism of Inositol(1,4,5)trisphosphate by a Soluble Enzyme Fraction from Pea (Pisum sativum) Roots.

Metabolism of the putative messenger molecule d-myo-inositol(1,4,5)trisphosphate [Ins(1,4,5)P(3)] in plant cells has been studied using a soluble fraction from pea (Pisum sativum) roots as enzyme source and [5-(32)P]Ins(1,4,5)P(3) and [2-(3)H]Ins(1,4,5)P(3) as tracers. Ins(1,4,5)P(3) was rapidly converted into both lower and higher inositol phosphates. The major dephosphorylation product was inositol(4,5)bisphosphate [Ins(4,5)P(2)] whereas inositol(1,4)bisphosphate [Ins(1,4)P(2)] was only present in very small quantities throughout a 15 minute incubation period. In addition to these compounds, small amounts of nine other metabolites were produced including inositol and inositol(1,4,5,X)P(4). Dephosphorylation of Ins(1,4,5)P(3) to Ins(4,5)P(2) was dependent on Ins(1,4,5)P(3) concentration and was partially inhibited by the phosphohydrolase inhibitors 2,3-diphosphoglycerate, glucose 6-phosphate, and p-nitrophenylphosphate. Conversion of Ins(1,4,5)P(3) to Ins(4,5)P(2) and Ins(1,4,5,X)P(4) was inhibited by 55 micromolar Ca(2+). This study demonstrates that enzymes are present in plant tissues which are capable of rapidly converting Ins(1,4,5)P(3) and that pathways of inositol phosphate metabolism exist which may prove to be unique to the plant kingdom.

Journal Article↗
PubMed1991

Expression patterns of myb genes from Antirrhinum flowers.

Six genes that contain sequence encoding the DNA binding domain of the Myb oncoproteins have been isolated from a cDNA library prepared from Antirrhinum majus (snapdragon) flowers using oligonucleotide probes directed against part of this domain. The derived amino acid sequences of these genes reveal acidic domains in their carboxy termini, suggesting that they might act as transcriptional activators. Analysis of their expression patterns with respect to organ specificity, floral differentiation, and response to light suggests that these genes are not involved in controlling anthocyanin biosynthesis, unlike the characterized myb-related genes C1 and Pl from maize. One of the genes is expressed mainly in the nectary and the transmitting tract of the style, two major secretory tissues of the flower, suggesting that the function of this gene is related to active carbohydrate secretion. We conclude that plants contain a number of myb-related transcriptional activators involved in a diversity of gene regulation.

Amino Acid Sequence↗
PubMed1990

Changing perceptions of the requirements of cavity preparations.

Perceptions of the requirements of cavity preparations have changed over the years. These have had a significant effect on undergraduate teaching at the University of Bristol Dental School, an explanation of which may help general dental practitioners in their quest for information on this important aspect of dental practice. A method is described for teaching undergraduate dental students cavity preparation in caries-free teeth, based upon the position, shape and extent of imaginary carious lesions. Scale diagrams of teeth are used, on which imaginary caries at the amelodentinal junction has been marked. The students are instructed to apply the principles of cavity preparation to equivalent, but caries-free, teeth in the laboratory. 'Outline forms' and other predetermined cavity shapes are not taught. Dental practitioners may find it appropriate to apply similar thinking to cavities they prepare in everyday practice, in an endeavour to avoid the unnecessary removal of tooth tissue that would be better retained.

Audiovisual Aids↗
PubMed1990

Blood cholesterol screening in several environments using a portable, dry-chemistry analyzer and fingerstick blood samples. Lipid Research Clinics Cholesterol Screening Study Group.

A multicenter study of blood cholesterol screening was performed in several typical environments, such as community sites (shopping malls and a supermarket), health care sites, work sites, a blood bank and a school. Cholesterol was measured with a portable, dry-chemistry analyzer using capillary blood obtained by fingerstick. Data are reported from a total of 13,824 participants, spanning the entire age spectrum. Overall, 25% of screened subjects had blood cholesterol levels above the age-specific cutpoints used in the current study. Although in the aggregate this screening experience very closely approximates the expected level of referrals, the proportion of referred screened subjects differed significantly among the 5 types of screening environments and by gender. Follow-up telephone interviews indicated that 53% of referrals had initiated a physician contact. More than 75% of those who had seen a physician reported that the diagnosis of hypercholesterolemia had been confirmed, and almost 72% had been prescribed a diet. A large proportion of referred screened subjects reported having modified their diet, particularly when recommended to do so by a physician. This study has yielded encouraging evidence that physicians gave referred screened subjects appropriate initial advice for managing hypercholesterolemia. The new technology for blood cholesterol measurement evaluated in the current study has proven to be a feasible and reliable means for measuring blood cholesterol in typical screening settings.

Adult↗
PubMed1990

Immunoscintigraphy of colorectal cancer with an antibody to epithelial membrane antigen (EMA).

Immunoperoxidase staining of LICR-LON M8, a mouse monoclonal antibody reactive with epithelial membrane antigen, showed a strong reaction with colorectal cancer. This finding prompted an immunoscintigraphic study of colorectal cancer patients using this antibody. Sixteen patients had external gamma scintigraphy after intravenous injection of indium 111-labeled M8. Positive scans were obtained in 11 of the 13 patients with primary colorectal cancers, and 2 of the 3 patients with recurrent tumors. The high indium 111 background in the liver prevented the detection of hepatic metastases in 5 patients. Twelve patients had samples taken of tumor, normal colon, and venous blood at the time of surgery. The ratio of labeled antibody uptake in tumor to that of blood was 5.1 (+/- 3.6 S.D.), which was significantly different (P = 0.001) to that of the similar ratio for normal colon (2.0 +/- 1.6 S.D.). The tumor to normal colon uptake ratio was 2.6 (+/- 1.3 S.D.). These results suggest a specific uptake of indium 111-labeled M8 by colorectal cancer.

Aged↗
PubMed1990

Low-dose sufentanil in major surgery.

The purpose of this study was to assess the efficacy of sufentanil 1 micrograms.kg-1 during N2O-O2 and intermittent isoflurane anaesthesia in major non-cardiac surgery. Thirty-one patients (18 females, 13 males; mean age 47 yr), undergoing cholecystectomy received a 1 microgram.kg-1 bolus of sufentanil before the induction of anaesthesia with thiopentone. On average, three sufentanil increments were administered, to a total (bolus + maintenance) dose of 1.5 micrograms.kg-1. Cardiovascular stability was not achieved in eleven patients who then were given isoflurane. The arterial pressure decreased after sufentanil (P less than 0.05), reaching a nadir (mean 108/65 mmHg, heart rate 63 bpm) at one minute post-incision. Clinically important hypertension or hypotension did not occur in any patient. One patient, receiving beta-blocker therapy, required atropine to control bradycardia. Postoperative respiratory depression did not occur in patients who received less than one micrograms.kg-1.hr-1 with the last increment being given more than 20 minutes before the end of anaesthesia. Slight respiratory depression in the recovery room was reported in one patient, who had received a total of 1.3 micrograms.kg-1.hr-1 of sufentanil, and the last sufentanil increment 24 min before the end of surgery. The most frequently reported side-effects were nausea (35 per cent) and vomiting (23 per cent). Induction, maintenance and recovery from anaesthesia were rated as "good" in 87, 87, and 74 per cent of the cases, respectively, and "satisfactory" in the remainder. We conclude that this technique is valuable to assure good protection of the cardiovascular system without undue respiratory depression during recovery.

Adolescent↗
PubMed1990

Self-perceived health among sports participants and non-sports participants.

This paper examines and compares the self-perceived health (SPH) of a sample of sports participants (n = 1385) and a matched sample of non-participants (n = 292). Ratings of health were generally found to be favourable among both samples, but a non-parametric analysis of their distributions revealed that the SPH of sports participants was significantly (P less than 0.0001) better than that of the non-participants. SPH improved with age among both samples, but above the age of 34, the non-participants' perceived health ceased to be inferior to that of participants. Controlling for age and gender revealed no difference in SPH above 24 years among males and 34 years among females. SPH was related to a variety of additional health-related factors. Multiple regression analysis was used to identify the predictors of SPH for both samples, and highlighted marked differences between them in the type and number of contributory factors. It is suggested that participation in active sports may enhance health awareness, especially among the young, and that future studies of this kind among sports populations should take account of the levels of commitment (frequency, duration and intensity) to sport.

Activities of Daily Living↗
PubMed1990

X linked neonatal centronuclear/myotubular myopathy: evidence for linkage to Xq28 DNA marker loci.

We have studied the inheritance of several polymorphic Xq27/28 DNA marker loci in two three generation families with the X linked neonatal lethal form of centronuclear/myotubular myopathy (XL MTM). We found complete linkage of XLMTM to all four informative Xq28 markers analysed, with GCP/RCP (Z = 3.876, theta = 0.00), with DXS15 (Z = 3.737, theta = 0.00), with DXS52 (Z = 2.709, theta = 0.00), and with F8C (Z = 1.020, theta = 0.00). In the absence of any observable recombination, we are unable to sublocalise the XLMTM locus further within the Xq28 region. This evidence for an Xq28 localisation may allow us to carry out useful genetic counselling within such families.

Cell Nucleus↗