Monoclonal antibodies to cell-specific cell surface carbohydrates in plant cell biology and development.
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Animals↗
Biomedical subjects
K Roberts
Publications and source records attributed to K Roberts.
Management of internal jugular vein phlebectasia.
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Aged↗
Ethylene is a positive regulator of root hair development in Arabidopsis thaliana.
Evidence is provided that ethylene is a positive regulator of hair cell development in the root epidermis of Arabidopsis thaliana. Treatment of seedlings with increasing concentrations of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC) results in progressively more root hair cells developing in positions normally occupied by non-hair cells. Consistent with these findings are observations that treatments that block either ethylene synthesis or its perception reduce the number of root hairs. A model is proposed in which either ethylene or ACC is a signal involved in specifying the pattern of cell differentiation in the Arabidopsis root epidermis.
Arabidopsis↗
The plant extracellular matrix: in a new expansive mood.
Plant cell expansion requires the integration of local wall loosening and the controlled deposition of new wall materials. Although we still know little of the latter process, two new classes of proteins have been discovered that may function in the former. Evidence is increasing that the plant extracellular matrix can exert a regulatory effect over cell behaviour. New approaches, in particular a molecular genetic analysis of cell wall mutants, are likely to speed up our understanding of wall biosynthesis, structure and function.
Cell Division↗
The 3a protein from cucumber mosaic virus increases the gating capacity of plasmodesmata in transgenic tobacco plants.
The 3a protein, encoded by RNA 3 of cucumber mosaic virus (CMV), is the putative movement protein of viral progeny in infected plants. An analysis of transgenic tobacco plants constitutively expressing the CMV 3a protein showed that the protein is accumulated in leaves at every stage of development. In fully expanded leaves the protein is immunodetectable mostly in a cell-wall-enriched fraction. Dye-coupling experiments using fluorescent-dextran probes were performed on fully expanded leaves to study the modifying effect of CMV 3a protein on the gating capacity of plasmodesmata. Movement of fluorescein-isothiocyanate-labelled dextran with a mean molecular mass of 10,000 Da, and an approximate Stokes' radius of 2.3 nm, was detected between cells of the 3a protein transgenic plants, but not in the control plants. These results are consistent with the idea that the CMV 3a protein is involved in the modification of plasmodesmata and, therefore, in the cell-to-cell spread of the virus.
Blotting, Western↗
Plasmodesmata of maize root tips: structure and composition.
A procedure is described for obtaining clean maize cell wall preparations that contain embedded plasmodesmata. Negative staining and rotary shadowing have been used with transmission electron microscopy to visualise the plasmodesmata in these isolated walls, and to assess the effects of simple biochemical treatments on plasmodesmal components. Light protease treatment removes material from the exposed ends of plasmodesmata but does not extract the plasmodesmal core, which lies within the cell wall. However, heavy proteolysis occasionally removes the complete plasmodesma, including its enclosing collar structure, from the wall. Extraction with urea has a similar effect. The collar itself appears not to be proteinaceous in composition, although protein may bind it into the wall. Callose is localised in the wall around plasmodesmata, but does not appear to be a constituent of the collar. The membrane components of the plasmodesma (plasma membrane and desmotubule) can be extracted with membrane-solubilising detergents. This treatment releases from the wall a small number of proteins that are regarded as being potentially of plasmodesmal origin. These results show that plasmodesmata from maize can be dissected biochemically and suggest a strategy for the characterisation of individual molecular components.
Cell Fractionation↗
The mucosal T cell integrin alpha M290 beta 7 recognizes a ligand on mucosal epithelial cell lines.
The integrin alpha M290 beta 7 is expressed at high levels on mucosal T cells, particularly on those within the epithelium of the gut. We now report that a mouse T cell hybridoma, MTC-1, with similar surface expression of this molecule, adhered strongly to cells of the mouse rectal carcinoma line CMT93 and that adhesion was blocked completely by the monoclonal antibody (mAb) M290. Other mAb to the alpha M290 or beta 7 subunits had little or no inhibitory effect. M290 also inhibited adhesion of the hybridoma to cells of the mouse lung carcinomas CTM64/61 and KLN205 but had little or no effect on adhesion to seven other mouse epithelial cell lines or to the human colon carcinoma line, HT29. Intraepithelial lymphocytes (IEL) isolated from the small intestine of BALB/c mice displayed potent T cell receptor-dependent cytotoxic effector function against CMT93 in the presence of low concentrations of Phytolacca americana lectin. This cytotoxic activity also was inhibited by the M290 mAb. Treatment of CMT93 cells with tumor necrosis factor-alpha and interferon-gamma induced expression de novo of ICAM-1 and reduced the inhibitory effect of M290 in tests both for adhesion and cytotoxicity. In further experiments cytotoxic activity of IEL against the mastocytoma P815 was investigated. This target cell was considered not to possess a ligand for the integrin. In this case cytotoxic effector function was triggered by anti-CD3 mAb and, in contrast to results with CMT93, target cell lysis was increased in the presence of M290 and other antibodies to the integrin, suggesting a co-stimulatory effect. These results show that alpha M290 beta 7 recognizes a ligand on the surface of certain epithelial cell lines. Further, they provide the first clear indication that this integrin may play an important role in functional interactions between T cells and the mucosal epithelium.
Animals↗
Aseptic meningitis in infants < 2 years of age: diagnosis and etiology.
Standard virologic methods were used to characterize the relative contribution of each of the enterovirus classes to the etiology of aseptic meningitis during a prospective study of this disease among children < 24 months old. Viruses were isolated in cell culture from 164 (60%) of 274 cases identified over 5 years and in newborn mice from only 2 of 104 remaining cell culture-negative cases. Serologic tests identified the viral pathogen in 3 additional cases. The group B coxsackieviruses and the echoviruses were implicated in 156 (92%) of the 169 laboratory-diagnosed cases. Forty-eight percent of all diagnosed cases were due to group B coxsackievirus serotypes 2, 4, and 5; 78% of all cases were attributable to only 8 of the 67 known enterovirus serotypes. Polioviruses were the only viruses isolated from 7 children, including a cerebrospinal fluid isolate from 1 child and a urine isolate from another. Disease was attributable to the group A coxsackie-viruses for only 3 cases.
Adenoviruses, Human↗
Effect of the alfalfa mosaic virus movement protein expressed in transgenic plants on the permeability of plasmodesmata.
Symplastic transport of different sized fluorescent probes has been assessed in leaf epidermal cells of transgenic Nicotiana plants expressing the movement protein (MP) of alfalfa mosaic virus (AMV). In both N. tabacum and N. benthamiana, the size exclusion limit (SEL) of plasmodesmata increased from M(r) 1000, which represents the commonly accepted limit, to over 4.4K. However, in control plants, movement of a 3K probe was seen in 11 to 22% of the injections, indicating that plasmodesmata may on occasion allow the passage of molecules larger than was previously thought. The increase of SEL due to the presence of the AMV MP, although significant, remains insufficient to permit the passage of viral particles and the possibility of other mechanisms involved in viral cell-to-cell spread is discussed.
Alfalfa mosaic virus↗
Cellular organisation of the Arabidopsis thaliana root.
The anatomy of the developing root of Arabidopsis is described using conventional histological techniques, scanning and transmission electron microscopy. The root meristem is derived from cells of the hypophysis and adjacent cells of the embryo proper. The postembryonic organization of the root is apparent in the mature embryo and is maintained in the growing primary root after germination. Cell number and location is relatively invariant in the primary root, with 8 cortical and endodermal cell files but more variable numbers of pericycle and epidermal cells. The organisation of cells in lateral roots is similar to that of the primary root but with more variability in the numbers of cell files in each layer. [3H]thymidine labeling of actively growing roots indicates that a quiescent centre of four central cells (derived from the hypophysis) is located between the root cap columella and the stele. This plate of four cells is surrounded by three groups of cells in, proximal, distal and lateral positions. The labeling patterns of these cells suggest that they are the initials for the files of cells that comprise the root. They give rise to four sets of cell files: the stele, the cortex and endodermis, the epidermis and lateral root-cap and the columella. A model of meristem activity is proposed based on these data. This description of Arabidopsis root structure underpins future work on the developmental genetics of root morphogenesis.
Arabidopsis↗
Root development in Arabidopsis: four mutants with dramatically altered root morphogenesis.
A genetic analysis of root development in Arabidopsis thaliana has identified mutants that have abnormal morphogenesis. Four of these root morphogenesis mutants show dramatic alterations in post-embryonic root development. The short-root mutation results in a change from indeterminate to determinate root growth and the loss of internal root cell layers. The cobra and lion's tail mutations cause abnormal root cell expansion which is conditional upon the rate of root growth. Expansion is greatest in the epidermal cells in cobra and in the stele cells in lion's tail. The sabre mutation causes abnormal cell expansion that is greatest in the root cortex cell layer and is independent of the root growth rate. The tissue-specific effects of these mutations were characterized with monoclonal antibodies and a transgenic marker line. Genetic combinations of the four mutants have provided insight into the regulation of growth and cell shape during Arabidopsis root development.
Arabidopsis↗
Orientation of macromolecules in the walls of elongating carrot cells.
When round cells from a carrot cell suspension culture are diluted into fresh medium without auxin, the cells elongate to almost 50 times their original diameter within three days. This process of elongation is accompanied by changes in both the composition and the orientation of cell wall polymers. We have obtained information on the orientation of wall polymers in elongating cells by two complementary techniques, one using microscopy and one spectroscopy. Images obtained by the fast-freeze, deep-etch, rotary-shadowed replica technique show that walls of round carrot cells have no net orientation of cellulose microfibrils, and that many thin fibres can be seen cross-linking microfibrils. Walls of elongated carrot cells, in contrast, show a marked net orientation of microfibrils at right angles to the axis of elongation. Fourier Transform Infrared (FTIR) spectra obtained from defined areas of single cell walls show that walls of round carrot cells contain more protein, esters and phenolics in a given area (10 microns x 10 microns) than walls of elongated carrot cells, that contain proportionally more carbohydrate. The orientation of particular functional groups, with respect to the direction of elongation of the cell, can be determined by inserting a polariser into the path of the infrared beam, before it passes through a cell wall sample mounted on the stage of the microscope accessory. In the walls of elongated cells, ester bands, amide bands characteristic of proteins, and stretching frequencies in the carbohydrate region of the spectrum all show a net orientation transverse to the long axis of the cells. In the walls of round carrot cells, however, there is no such net orientation of polymers. Spectra obtained from 25 microns-thick fresh sections of the etiolated stem of a carrot seedling show that different wall components are polarised in different tissue types. These techniques have therefore enabled us to define differences in both the composition and the architecture of walls of elongating cells at the level of a single cell, and to suggest that polymers not previously thought to be ordered, such as pectin and protein, are strictly oriented in some wall types.
Antibodies, Monoclonal↗
Deaf students' self-appraisals, achievement outcomes, and teachers' inferences about social-emotional adjustment in academic settings.
35 deaf students completed the Self-description Questionnaire I and their teachers completed the Meadow/Kendall social-emotional inventory for deaf students. Significant positive but small correlations were found among reading scores, reading appraisals, and social-emotional adjustment inferences. Achievement, particularly reading, appears associated with concepts of self.
Adaptation, Psychological↗
Aseptic meningitis in infants younger than 2 years of age: acute illness and neurologic complications.
OBJECTIVE: We report the clinical features and cerebrospinal fluid (CSF) laboratory values for 277 children younger than 24 months of age with aseptic meningitis who were prospectively evaluated at three Baltimore hospitals between July 1986 and December 1990. A major objective was to define the incidence, etiology, and outcome of neurologic complications occurring during the acute illness. METHODS: Cases were identified by surveillance in the ambulatory care departments of each of the three hospitals, pertinent historical and clinical data were obtained by interview of the parents and by review of the medical records, initial CSF laboratory values were recorded, and appropriate specimens were submitted to determine the viral etiology. A subset of 216 children who participated in a long-term natural history study were followed periodically with neurologic examinations and formal neurodevelopmental testing. RESULTS: Most cases occurred in very young infants; 63.5% of patients were 8 weeks of age or younger, and 84.1% were younger than 16 weeks of age. In this very young cohort, the dominant symptoms were fever and irritability; only 8.7% had evidence of meningeal irritation at the initial examination. The acute illness was complicated by either complex seizures, physical evidence of increased intracranial pressure, or coma in 25 (9.0%) cases. Within the age group under study, these complications were each significantly more likely to occur in patients older than 12 weeks of age than in younger infants. The risk of neurologic complications was similar among infants infected with group B coxsackieviruses and echoviruses, the two major enterovirus classes observed to cause disease. Acute central nervous system (CNS) complications could not be correlated with extremely abnormal CSF laboratory indices. Importantly, there was no risk of long-term neurologic sequelae attributable to acute CNS complications. CONCLUSIONS: While approximately 9% of infants and children younger than 2 years of age with aseptic meningitis experience acute CNS complications in the form of complex seizures, increased intracranial pressure, or coma, the prognosis for long-term cognitive development appears to be as favorable as the prognosis for children with aseptic meningitis who do not experience these complications.
Acute Disease↗
Childhood injury prevention counseling in primary care settings: a critical review of the literature.
OBJECTIVES: The American Academy of Pediatrics (AAP) believes that health education, through office-based counseling, can contribute to childhood injury prevention. This report presents the results of a critical review of the scientific literature on the effectiveness of primary care-based counseling to prevent childhood unintentional injury. METHODS: A panel selected from the AAP Committee and the AAP Section on Injury and Poison Prevention searched the English-language scientific literature for all articles about childhood unintentional injury prevention counseling. A standardized format was developed to record data on each study. Two members of the panel independently reviewed each article. Articles that were original reports and in which unintentional injury prevention counseling took place in a primary care setting were included. Articles were encoded and analyzed by computer and then grouped by quality of evidence using the US Preventive Services Task Force (USPSTF) method of categorizing results of medical care evaluation. Articles were rated by strength of study design in order to compare studies within each USPSTF group. RESULTS: Twenty articles met the criteria for inclusion. Of these, 18 showed positive effects of injury prevention counseling including five randomized/controlled, 10 non-randomized/controlled, two multiple time series, and one descriptive study. In 15 of the positive studies, physicians performed the counseling. Positive outcomes as measured by increased knowledge, improved behavior, or decreased injury occurrence were reported for both motor vehicle and non-motor vehicle injuries. CONCLUSIONS: The literature review supports the recommendation of the AAP to include injury prevention counseling as part of routine health supervision. This recommendation has implications for health care reimbursement and care content.
Accident Prevention↗
Gene transfer demonstrates that the V gamma 1.1C gamma 4V delta 6C delta T cell receptor is essential for autoreactivity.
Murine T cell lines and hybridomas derived from the epidermis that express the V gamma 1.1C gamma 4V delta 6C delta TCR and may, therefore, recognize an autoantigen, secrete cytokines spontaneously in culture. In addition, activation of these cells requires engagement of the vitronectin receptor (VNR) by extracellular matrix proteins. To further evaluate the role of the TCR, the VNR, and the putative autoantigen in the activation of this T cell subset, we cloned complete cDNA encoding the V gamma 1.1C gamma 4 and V delta 6C delta TCR and transfected the cDNA constructs into a TCR- murine hybridoma and into a TCR- variant of the human Jurkat line. The murine transfectant spontaneously produced IL-2 in culture and IL-2 production could be inhibited by anti-CD3, anticlonotypic mAb to the transfected TCR, and anti-VNR mAb, as well as by RGDS. These results demonstrate that transfection of the gamma delta TCR confers to recipient T cells the phenotype of constitutive activation, as well as dependence on engagement of the VNR as an accessory molecule. In contrast, the Jurkat gamma delta transfectant failed to produce cytokines spontaneously, although the transfected TCR was capable of signal transduction after stimulation by anti-TCR mAb. Surprisingly, neither the murine transfectant nor the human transfectant could be induced to respond to autoantigen bearing cells in coculture assays. One interpretation of these results is that coexpression on the surface of the same cell of the V gamma 1.1 V delta 6 TCR, the VNR, and a putative autoantigen are necessary for T cell activation in this system.
Animals↗
The pattern of plant annexin gene expression.
Peptide sequence data derived from a plant annexin, P34 [Smallwood, Keen & Bowles (1990) Biochem. J. 270, 157-161] was used to design amplimers for PCR. A unique fragment of 95 bp, amplified from tomato (Lycopersicon esculertum) genomic DNA, was used in Northern analyses and demonstrated a differential pattern of expression in vegetative tissues of tomato, potato (Solanum tuberosum) and barley (Hordeum vulgare). The tissue-specific abundance of the annexin transcript was found to correlate closely with abundance of annexin protein as revealed by their partial purification and analysis with antisera specific for annexins isolated from tomato suspension-culture cells.
Amino Acid Sequence↗
Mouse autoreactive gamma/delta T cells. I. Functional properties of autoreactive T cell hybridomas.
A minor population of dendritic epidermal T cells (DETC) express the V gamma 1.1C gamma 4V delta 6 T cell receptor and T cell clones and hybridomas derived from this subset constitutively secrete cytokines in culture secondary to recognition of an autoantigen. Activation of these autoreactive cells requires the use of the vitronection receptor (VNR) as an accessory molecule which interacts with the Arg-Gly-Asp-Ser (RGDS) sequence of extracellular matrix (ECM) proteins. We have compared the functional properties of C gamma 4+ hybridomas derived from newborn thymocytes and from adult spleen with the DETC hybridomas/lines in terms of their ability to secrete cytokines spontaneously and for the use of the VNR as an accessory molecule. Almost all the C gamma 4+ thymocyte hybridomas secreted cytokines spontaneously and in the majority of lines the most prominent cytokine secreted was granulocyte-monocyte colony-stimulating factor. In contrast, none of the four splenic C gamma 4+ hybridomas secreted cytokines spontaneously although all were capable of cytokine production following activation via the T cell receptor. Although the thymocyte hybridomas did not grow as adherent cell lines in culture, constitutive cytokine production required engagement of the VNR by its ligand in ECM proteins. In all cases, cytokine production could be inhibited by an anti-VNR monoclonal antibody as well as by soluble RGDS. The strong correlation of functional and molecular properties between thymocyte C gamma 4+ hybridomas and C gamma 4+ DETC suggests that the C gamma 4+ DETC may be of thymic origin and that cells with potential for autoreactivity residing in the thymus at birth may populate other peripheral locations in the mouse. The data also support the concept that the VNR, and possibly other integrins, play a role as accessory elements for autoreactive cells and may be essential for the regulation of such activity.
Animals↗