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Biomedical subjects

T Mandel

Publications and source records attributed to T Mandel.

At least 19 recordsLinked to original sources
PubMed2001

Expression and distribution of a vaculoar aquaporin in young and mature leaf tissues of Brassica napus in relation to water fluxes.

Recently, it has been shown that water fluxes across biological membranes occur not only through the lipid bilayer but also through specialized water-conducting proteins, the so called aquaporins. In the present study, we investigated in young and mature leaves of Brassica napus L. the expression and localization of a vacuolar aquaporin homologous to radish gamma-tonoplast intrinsic protein/vacuolar-membrane integral protein of 23 kDa (TIP/VM 23). In-situ hybridization showed that these tonoplast aquaporins are highly expressed not only in developing but also in mature leaves, which export photosynthates. No substantial differences could be observed between different tissues of young and mature leaves. However, independent of the developmental stage, an immunohistochemical approach revealed that the vacuolar membrane of bundle-sheath cells contained more protein cross-reacting with antibodies raised against radish gamma-TIP/VM 23 than the mesophyll cells. The lowest labeling was detected in phloem cells. We compared these results with the distribution of plasma-membrane aquaporins cross-reacting with antibodies detecting a domain conserved among members of the plasma-membrane intrinsic protein 1 (PIP1) subfamily. We observed the same picture as for the vacuolar aquaporins. Furthermore, a high density of gold particles labeling proteins of the PIP1 group could be observed in plasmalemmasomes of the vascular parenchyma. Our results indicate that gamma-TIP/VM 23 and PIP1 homologous proteins show a similar expression pattern. Based on these results it is tempting to speculate that bundle-sheath cells play an important role in facilitating water fluxes between the apoplastic and symplastic compartments in close proximity to the vascular tissue.

Aquaporins↗
PubMed2001

Assimilatory sulfate reduction in C(3), C(3)-C(4), and C(4) species of Flaveria.

The activity of the enzymes catalyzing the first two steps of sulfate assimilation, ATP sulfurylase and adenosine 5'-phosphosulfate reductase (APR), are confined to bundle sheath cells in several C(4) monocot species. With the aim to analyze the molecular basis of this distribution and to determine whether it was a prerequisite or a consequence of the C(4) photosynthetic mechanism, we compared the intercellular distribution of the activity and the mRNA of APR in C(3), C(3)-C(4), C(4)-like, and C(4) species of the dicot genus Flaveria. Measurements of APR activity, mRNA level, and protein accumulation in six Flaveria species revealed that APR activity, cysteine, and glutathione levels were significantly higher in C(4)-like and C(4) species than in C(3) and C(3)-C(4) species. ATP sulfurylase and APR mRNA were present at comparable levels in both mesophyll and bundle sheath cells of C(4) species Flaveria trinervia. Immunogold electron microscopy demonstrated the presence of APR protein in chloroplasts of both cell types. These findings, taken together with results from the literature, show that the localization of assimilatory sulfate reduction in the bundle sheath cells is not ubiquitous among C(4) plants and therefore is neither a prerequisite nor a consequence of C(4) photosynthesis.

Asteraceae↗
PubMed2000

Limited correlation between expansin gene expression and elongation growth rate.

The aim of this work was to study the role of the cell wall protein expansin in elongation growth. Expansins increase cell wall extensibility in vitro and are thought to be involved in cell elongation. Here, we studied the regulation of two tomato (Lycopersicon esculentum cv Moneymaker) expansin genes, LeExp2 and LeExp18, in rapidly expanding tissues. LeExp2 was strongly expressed in the elongation zone of hypocotyls and in the faster growing stem part during gravitropic stimulation. LeExp18 expression did not correlate with elongation growth. Exogenous application of hormones showed a substantial auxin-stimulation of LeExp2 mRNA in etiolated hypocotyls and a weaker auxin-stimulation of LeExp18 mRNA in stem tissue. Analysis of transcript accumulation revealed higher levels of LeExp2 and LeExp18 in light-treated, slow-growing tissue than in dark-treated, rapidly elongating tissue. Expansin protein levels and cell wall extension activities were similar in light- and dark-grown hypocotyl extracts. The results show a strong correlation between expansin gene expression and growth rate, but this correlation is not absolute. We conclude that elongation growth is likely to be controlled by expansin acting in concert with other factors that may limit growth under some physiological conditions.

Blotting, Northern↗
PubMed2000

Auxin regulates the initiation and radial position of plant lateral organs.

Leaves originate from the shoot apical meristem, a small mound of undifferentiated tissue at the tip of the stem. Leaf formation begins with the selection of a group of founder cells in the so-called peripheral zone at the flank of the meristem, followed by the initiation of local growth and finally morphogenesis of the resulting bulge into a differentiated leaf. Whereas the mechanisms controlling the switch between meristem propagation and leaf initiation are being identified by genetic and molecular analyses, the radial positioning of leaves, known as phyllotaxis, remains poorly understood. Hormones, especially auxin and gibberellin, are known to influence phyllotaxis, but their specific role in the determination of organ position is not clear. We show that inhibition of polar auxin transport blocks leaf formation at the vegetative tomato meristem, resulting in pinlike naked stems with an intact meristem at the tip. Microapplication of the natural auxin indole-3-acetic acid (IAA) to the apex of such pins restores leaf formation. Similarly, exogenous IAA induces flower formation on Arabidopsis pin-formed1-1 inflorescence apices, which are blocked in flower formation because of a mutation in a putative auxin transport protein. Our results show that auxin is required for and sufficient to induce organogenesis both in the vegetative tomato meristem and in the Arabidopsis inflorescence meristem. In this study, organogenesis always strictly coincided with the site of IAA application in the radial dimension, whereas in the apical-basal dimension, organ formation always occurred at a fixed distance from the summit of the meristem. We propose that auxin determines the radial position and the size of lateral organs but not the apical-basal position or the identity of the induced structures.

Adenine↗
PubMed1998

Localized upregulation of a new expansin gene predicts the site of leaf formation in the tomato meristem.

Expansins are extracellular proteins that increase plant cell wall extensibility in vitro and are thought to be involved in cell expansion. We showed in a previous study that administration of an exogenous expansin protein can trigger the initiation of leaflike structures on the shoot apical meristem of tomato. Here, we studied the expression patterns of two tomato expansin genes, LeExp2 and LeExp18. LeExp2 is preferentially expressed in expanding tissues, whereas LeExp18 is expressed preferentially in tissues with meristematic activity. In situ hybridization experiments showed that LeExp18 expression is elevated in a group of cells, called I1, which is the site of incipient leaf primordium initiation. Thus, LeExp18 expression is a molecular marker for leaf initiation, predicting the site of primordium formation at a time before histological changes can be detected. We propose a model for the regulation of phyllotaxis that postulates a crucial role for expansin in leaf primordium initiation.

Amino Acid Sequence↗
PubMed1997

Prevention of splenic granuloma formation in adjuvant arthritis by 2-acetyl-4-tetrahydroxybutylimidazole (THI).

Adjuvant-induced arthritis (AA) in Lewis rats is a widely used model of chronic inflammatory arthritis. Non-articular features such as weight loss and necrotizing granulomas of the spleen and lymph nodes also occur in this model. The compound 2-acetyl-4-tetrahydroxybutylimidazole (THI) marginally delayed the development of AA. However, this agent had no effect on the incidence or severity of disease. In contrast, THI totally prevented granuloma formation in the spleen and associated splenomegaly. We conclude that THI may be a useful adjunctive agent for some inflammatory diseases.

Animals↗
PubMed1996

Cis and trans requirements for stable episomal maintenance of the BPV-1 replicator.

Papillomavirus genomes are maintained as multicopy nuclear plasmids in transformed cells. To address the mechanisms by which the viral DNA is stably propagated in the transformed cells, we have constructed a cell line CH04.15 expressing constitutively the viral proteins E1 and E2, that are required for initiation of viral DNA replication. We show that these viral proteins are necessary and sufficient for stable extrachromosomal replication. Using the cell line CH04.15, we have shown that the bovine papillomavirus-1 (BPV-1) minimal origin of replication (MO) is absolutely necessary, but is not sufficient for stable extrachromosomal replication of viral plasmids. By deletion and insertion analysis, we identified an additional element (minichromosome maintenance element, MME) in the upstream regulatory region of BPV-1 which assures stable replication of the MO-containing plasmids. This element is composed of multiple binding sites for the transcription activator E2. MME appears to function in the absence of replication but requires E1 and E2 proteins for activity. In contrast to, for example, Epstein-Barr virus oriP, stably maintained BPV-1 plasmids are not subject to once-per-cell cycle replication as determined by density labelling experiments. These results indicate that papillomavirus episomal replicators replicate independently of the chromosomal DNA of their hosts.

Animals↗
PubMed1996

Lack of autoimmune serological reactions in rodent models of insulin dependent diabetes mellitus.

Spontaneous insulitis with insulin-dependent diabetes mellitus (IDDM) in rodent models, the BB rat and NOD mouse, has clarified the pathogenesis of and guided decisions on interventional therapy for human IDDM. However, the occurrence in such models of a standard marker of human IDDM, autoantibodies to beta islet cell constituents, has been controversial. Hence we assessed diabetes-prone rodents for the frequencies of raised levels of auto-antibodies to glutamic acid decarboxylase GAD (anti-GAD), insulin and heat shock protein 65 (HSP-65) in relation to levels in non-diabetes-prone animals and levels in human diabetic sera. Assays were performed sequentially at various ages of life. The immunoassays used for anti-GAD and anti-insulin were those validated for sensitivity and specificity for detection of the corresponding autoantibodies in human IDDM sera at international workshops. Positive controls included human IDDM sera with reactivity with GAD or insulin and, for mouse anti-GAD, the highly reactive monoclonal antibody, GAD-6. The results were that levels of autoantibodies in diabetes-prone BB rats or NOD mice to the "IDDM-relevant' autoantigens in our panel did not exceed levels in control rats or mice, and were much lower than levels in humans with IDDM. We conclude that the BB rat and NOD mouse represent a model, but not a facsimile, of human IDDM and that therapeutic successes in such models should be interpreted with caution in relation to interventional therapy for human IDDM.

Animals↗
PubMed1996

Office Microlaparoscopy Under Local Anesthesia

We assessed the utility, tolerance, and costs associated with office microlaparoscopy under local anesthesia using fiberoptic microlaparoscopes (<2 mm) and accessory instrumentation (<2 mm) for 100 of the following procedures: diagnostic laparoscopy to evaluate infertility including chromopertubation; diagnostic laparoscopy for chronic pelvic pain (CPP), including biopsy of endometriosis and conscious pain mapping; and early second-look laparoscopy including lysis of adhesions. A prospective nonselected cohort study was conducted on all women with CPP or infertility who consented to office microlaparoscopy under local anesthesia. A questionnaire was developed to follow all aspects of patient acceptance and tolerance of the procedures, and women were screened preoperatively, and 30 minutes and 1 week postoperatively. Pain was evaluated with modification of the McGill pain inventory relative intensity scale. A subset of questions evaluated the recovery period, and time and length of all aspects of the procedure and recovery were recorded. Second-look procedures were significantly more painful than diagnostic ones, and women with CPP experienced significantly greater pain than those with infertility. Virtually all expressed high satisfaction with the procedure. There were no complications, and no procedures required general anesthesia. Compared with traditional laparoscopy, there was a reduction in costs greater than 70%.

Journal Article↗
PubMed1996

TOL plasmid transcription factor XylS binds specifically to the Pm operator sequence.

XylS, an AraC family transcription factor, positively regulates transcription of Pseudomonas putida TOL plasmid meta operon from the Pm promoter. A tandem of 15 bp homologous direct repeats, separated by 6 bp and overlapping with the -35 hexamer of the promoter, is required for the activation of Pm by XylS in vivo. In this study we have characterized specific binding of XylS to the Pm operator Om. XylS was overexpressed with an epitope tag in its N-terminus. Tagged XylS (N-XylS) was immunopurified and was shown to specifically bind to Om. We have used matrix-bound N-XylS in DNA footprinting and methylation interference experiments. Binding of N-XylS protects 44 bp in the Om region on both strands from DNase I digestion and generates hypersensitive sites (within the protected area) which lie on the same face of the DNA helix. Results of hydroxyl radical footprinting and methylation interference assays indicate that XylS binds along one side of the DNA and covers four helical turns. The protein has base-specific contacts in four adjacent major groove regions on the same helical face. Our data are in accord with the prediction of the presence of two separate DNA-binding units in an XylS molecule which are involved in base-specific contacts in two adjacent major-groove regions of a half-site. The direct repeat arrangement of the binding site and the mode of DNA binding of XylS are similar to the arrangement of recognition sites and the DNA contact pattern of AraC protein from Escherichia coli.

Bacterial Proteins↗
PubMed1996

Tissue-specific expression and promoter analysis of the tobacco Itp1 gene.

The Nicotiana tabacum Itp1 gene (Ntltp1) encodes a small basic protein that belongs to a class of putative lipid transfer proteins. These proteins transfer lipids between membranes in vitro, but their in vivo function remains hotly debated. This gene also serves as an important early marker for epidermis differentiation. We report here the analysis of the spatial and developmental activity of the Ntltp1 promoter, and we define a sequence element required for epidermis-specific expression. Transgenic plants were created containing 1346 bp of the Ntltp1 promoter fused upstream of the beta-glucuronidase (GUS) gene. In the mature aerial tissues, GUS activity was detected predominantly in the epidermis, whereas in younger aerial tissues, such as the shoot apical meristem and floral meristem, GUS expression was not restricted to the tunica layer. Unexpectedly, GUS activity was also detected in young roots particularly in the root epidermis. Furthermore, the Ntltp1 promoter displayed a tissue and developmental specific pattern of activity during germination. These results suggest that the Ntltp1 gene is highly expressed in regions of the plant that are vulnerable to pathogen attack and are thus consistent with the proposed function of lipid transfer proteins in plant defense. Deletions of the promoter from its 5' end revealed that the 148 bp preceding the translational start site are sufficient for epidermis-specific expression. Sequence comparison identified an eight-nucleotide palindromic sequence CTAGCTAG in the leader of Ntltp1, which is conserved in a number of other Itp genes. By gel retardation analysis, the presence of specific DNA-protein complexes in this region was demonstrated. The characterization of these factors may lead to the identification of factors that control early events in epidermis differentiation.

Base Sequence↗
PubMed1995

Highly conserved genes coding for eukaryotic translation initiation factor eIF-4A of tobacco have specific alterations in functional motifs.

Eukaryotic translation initiation factor eIF-4A is an ATP-dependent RNA helicase that is required for the binding of mRNA to ribosomes. Plant eIF-4A-like proteins are highly homologous to eIF-4As from yeast, mouse and Drosophila melanogaster. The pattern of intron-exon boundaries in eIF-4A-like genes are conserved within tobacco, but are not conserved with other organisms. Fixed spacings between the functionally important sequence motifs, GKT-PTRELA (72 bp), DEAD-SAT (81 bp) and SAT-HRIGR (426 bp), are conserved between plants, mouse, Drosophila and yeast.

Amino Acid Sequence↗
PubMed1995

Definition of constitutive gene expression in plants: the translation initiation factor 4A gene as a model.

The NeIF-4A10 gene belongs to a family of at least ten genes, all of which encode closely related isoforms of translation initiation factor 4A. The promoter region of NeIF-4A10 was sequenced, and four mRNA 5' ends were determined. Deletions containing 2750, 689 and 188 bp of untranscribed upstream DNA were fused to the GUS reporter gene and introduced into transgenic tobacco. The three constructs mediated GUS expression in all cells of the leaf, stem and shoot apical meristem. Control experiments using in situ hybridization and tissue printing indicated that the observed GUS expression matches the expression patterns of NeIF-4A mRNA and protein. This detailed analysis at the level of mRNA, protein and reporter gene expression shows that NeIF-4A10 is an ideal constitutively expressed control gene. We argue that inclusion of such a control gene in experiments dealing with specifically expressed genes is in many cases essential for the correct interpretation of observed expression patterns.

Base Sequence↗
PubMed1995

Aerobic fermentation in tobacco pollen.

We characterized the genes coding for the two dedicated enzymes of ethanolic fermentation, alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC), and show that they are functional in pollen. Two PDC-encoding genes were isolated, which displayed reciprocal regulation: PDC1 was anaerobically induced in leaves, whereas PDC2 mRNA was absent in leaves, but constitutively present in pollen. A flux through the ethanolic fermentation pathway could be measured in pollen under all tested environmental and developmental conditions. Surprisingly, the major factor influencing the rate of ethanol production was not oxygen availability, but the composition of the incubation medium. Under optimal conditions for pollen tube growth, approximately two-thirds of the carbon consumed was fermented, and ethanol accumulated into the surrounding medium to a concentration exceeding 100 mM.

Alcohol Dehydrogenase↗
PubMed1995

The effect of 2-acetyl-4-tetrahydroxybutylimidazole on lymphocyte subsets during a contact hypersensitivity response in the NOD mouse.

The compound 2-acetyl-4-tetrahydroxybutylimidazole (THI) is known to suppress a contact hypersensitivity (CH) response. The effect of THI on lymphocyte subsets during treatment and in a CH response has not been shown in mice. To further define the immunosuppressive potential of THI, a time-course study during the CH response to oxazolone (OX) was performed. While THI can prevent the induction of CH, if treatment is started before sensitization, it has a low therapeutic capability since it could not significantly inhibit the response when continuous oral treatment was commenced during the course of CH. We report that during this response continuous oral treatment of non-obese diabetic (NOD) mice with THI reduced the number of CD4+ and CD8+ T cells in the peripheral blood. In the draining lymph nodes THI treatment had no effect on lymphocyte subsets prior to contact sensitization, but subsequent sensitization and elicitation with OX could not stimulate a significant increase in the number of CD4+ T cells in the treated mice, whereas untreated control mice showed elevated numbers of these lymphocytes. These findings suggest that THI can inhibit an CH response by preventing the recruitment of CD4+ T cells in the draining lymph nodes through an unknown mechanism.

Animals↗