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At least 937 records · Page 52Linked to original sources
PubMed2004

Identification of a 98-kb DNA segment containing the rice Eui gene controlling uppermost internode elongation, and construction of a TAC transgene sublibrary.

The recessive 'tall rice' phenotype associated with the mutation eui (elongated upper-most internode) is an important agronomic trait that has been introduced into hybrid rice to eliminate panicle enclosure in all types of male-sterile lines and produce good-quality seeds in high yield and at low cost. Based on our previous Eui mapping data, we conducted fine-structure mapping and positional cloning of the gene using an F2 population comprising more than 5000 individuals derived from a cross of the near-isogenic lines 307T (eui/eui) with the recurrent parent Zhenshan 97 (Eui/Eui). In total 45 CAPS (cleaved amplified polymorphic sequences) markers located within an interval of 14.5 cM were analyzed in the subpopulation of 1298 homozygous recessive plants. The resulting high-resolution map defined a 98-kb interval containing the Eui locus flanked by the markers M0387 and M01, and three markers were found to co-segregate with Eui. In order to facilitate the identification of the Eui gene, we used a transformation-competent artificial chromosome (TAC) vector to construct a set of contiguous TAC clones from the Nipponbare BACs (obtained from the Clemson University Genome Institute; CUGI) spanning this region. These clones can be used to streamline complementation testing. The markers tightly linked to the Eui locus can also be used in breeding male-sterile lines with the elongated uppermost internode.

Base Sequence↗
PubMed1998

De novo expression of MHC class II molecules by microglial cells during acute rat renal allograft rejection.

The expression of MHC class I and class II molecules in the cerebral cortex of rats was investigated at daily intervals from day 3 to day 6 after fully allogeneic (DA-->LEW) and isogeneic (LEW-->LEW) kidney transplantation. MHC class II molecules were temporarily induced on the previously negative microglial cells and on the endothelia of arterioles and venules during acute rejection. On the endothelia of all brain vessels MHC class I expression was enhanced. MHC class I+ cells with microglial cell morphology were discernible within the diffusely MHC class I+ brain parenchyma. In contrast, the brain parenchyma of isograft recipients and untreated control animals did not express detectable levels of MHC molecules. In conclusion, we demonstrate that a strong immune reaction in the periphery is able to activate microglial cells in the central nervous system.

Acute Disease↗
PubMed1994

Growth plate abnormalities in a new dwarf mouse model: tich.

Growth plate cartilage calcification has been examined in a recently described mouse mutant, tich, which is co-isogenic with the A.TL strain. Long bones were studied from 1-day-old and 1-month-old mice which carried a homozygous recessive gene mutation making them short limbed and dumpy. Specimens were studied by routine histology, scanning electron microscopy and radiography. In 1-day-old tich mice the front of calcified cartilage was recessed behind the advancing periosteum and bone. No similar recess was seen in control mice. At 1 month of age, a number of the long bone growth plates were irregularly thickened, particularly in the central area. This produced a central tongue of non-calcified cartilage (particularly prominent in the proximal tibia) which gave rise to a corresponding pit in the calcified cartilage layer, in macerated specimens. This was accompanied by poor resorption of calcified cartilage. At both ages the presence of the respective defects was radiographically confirmed. At present it is not known whether this is primarily a defect of calcification or resorption but its presence, apparently from a single mutation in a genetically defined mouse strain, makes it a potentially valuable model.

Animals↗
PubMed2001

Expression of IL-18 by Mycobacterium avium-infected human monocytes; association with M. avium virulence.

Disseminated Mycobacterium avium infection is the most frequent bacterial infection in patients with advanced AIDS and also associated with interferon-gamma (IFN-gamma) or IL-12 receptor deficiency. IFN-gamma is a key cytokine in host defence against M. avium infection. Expression of IL-18, a potent IFN-gamma inducer, and IFN-gamma by human monocytes after infection with M. avium was examined. Monocytes were co-cultured with isogenic smooth-transparent (SmT: virulent) or smooth-domed (SmD: avirulent) M. avium strains (10 organisms per monocyte). Infection with the SmD strain induced significantly higher concentration of IL-18 and IFN-gamma in culture supernatants than did the SmT strain. IFN-gamma production in response to M. avium was partially inhibited by anti-human IL-18 MoAb. Both recombinant human IL-12 (77 +/- 42 pg/ml, control versus 1492 +/- 141 pg/ml, cultures with IL-12 1 ng/ml) and IL-18 (126 +/- 37 pg/ml, control versus 2683 +/- 864 pg/ml, cultures with IL-18 10 ng/ml) augmented M. avium-induced IFN-gamma production. Freshly isolated uninfected monocytes expressed constitutive levels of IL-18. Following infection with M. avium, enhancement of IL-18 mRNA expression peaked at 3-6 h. IL-18 protein was detected in monocyte lysates as early as 1 h after infection with both SmT and SmD M. avium strains by Western blotting. Higher IL-18 expression by monocytes infected with the avirulent strain may result in more IFN-gamma production, thus modulating its pathogenicity. Local induction of IL-18 may be important both for M. avium pathogenicity and host defence and become a potential candidate for immunotherapy.

Cells, Cultured↗
PubMed2006

Real-time studies of the progression of bacterial infections and immediate tissue responses in live animals.

By combining intravital multiphoton microscopy and bacterial genetics we have developed a technique enabling real-time imaging of bacterial proliferation and tissue responses in a live animal. Spatial and temporal control of the infection process was achieved by microinjecting GFP(+)-expressing uropathogenic Escherichia coli (UPEC) into tubules of exteriorized kidneys in live rats. GFP(+) was introduced in the clinical UPEC strain CFT073 as a single-copy chromosomal gene fusion. Within hours, bacterial colonization was accompanied by marked ischaemic effects, perivascular leakage, loss of tubular integrity and localized recruitment of immune cells. The pathophysiology was altered in response to an isogenic bacterial strain lacking the exotoxin haemolysin, revealing the subtle and temporal roles of bacterial virulence factors in vivo. Microdissection and RNA extraction of the injected nephron allowed molecular analysis of prokaryotic and eukaryotic gene expression. The techniques described here can be applied to study the integrated cell communication evoked by a variety of bacterial pathogens, assisting in the design of strategies to combat bacterial infections.

Animals↗
PubMed1996

Producer-cell modification of human immunodeficiency virus type 1: Nef is a virion protein.

Type 1 human immunodeficiency viruses encoding mutated nef reading frames are 10- to 30-fold less infectious than are isogenic viruses in which the nef gene is intact. This defect in infectivity causes nef-negative viruses to grow at an attenuated rate in vitro. To investigate the mechanism of Nef-mediated enhancement of viral growth rate and infectivity, a complementation analysis of nef mutant viruses was performed. To provide Nef in trans upon viral infection, a CEM derivative cell line (designated CLN) that expresses Nef under the control of the viral long terminal repeat was constructed. When nef-negative virus was grown in CLN cells, its growth rate was restored to wild-type levels. However, the output of nef-negative virus during the first 72 h after infection of CLN cells was not restored, suggesting that provision of Nef within the newly infected cell does not enhance the productivity of a nef-negative provirus. The genetically nef-negative virions produced by the CLN cells, however, were restored to wild-type levels of infectivity as measured in a syncytium formation assay in which CD4-expressing HeLa cells were targets. These trans-complemented, genetically nef-negative virions yielded wild-type levels of viral output following a single cycle of replication in primary CD4 T cells as well as in parental CEM cells. To define the determinants for producer cell modification of virions by Nef, the role of myristoylation was investigated. Virus that encodes a myristoylation-negative nef was as impaired in infectivity as was virus encoding a deleted nef gene. Because myristoylation is required for both membrane association of Nef and optimal viral infectivity, the possibility that Nef protein is included in the virion was investigated. Wild-type virions were purified by filtration and exclusion chromatography. A Western blot (immunoblot) of the eluate fractions revealed a correlation between peak Nef signal and peak levels of p24 antigen. Although virion-associated Nef was detected in part as the 27-kDa full-length protein, the majority of immunoreactive protein was detected as a 20-kDa isoform. nef-negative virus lacked both 27- and 20-kDa immunoreactive species. Production of wild-type virions in the presence of a specific inhibitor of the human immunodeficiency virus type 1 protease resulted in virions which contained only 27-kDa full-length Nef protein. These data indicate that Nef is a virion protein which is processed by the viral protease into a 20-kDa isoform within the virion particle.

CD4-Positive T-Lymphocytes↗
PubMed1988

A simplified alloperfused rat heart model for studying myocardial protection.

Isolated hearts are widely used to study myocardial protection because they allow for rigorous control of parameters that is not readily achievable by the in-vivo heart models. The classic Langendorff system and its modifications using asanguinous perfusates have an obvious limitation in that asanguinous reperfusion is clinically irrelevant. The available blood-perfused heart systems are complicated by the use of pumping circuits. In this study, an isolated rat heart, harvested under cold cardioplegia, is alloperfused with the blood coming from an isogenic support rat. The coronary effluent returns to the support rat by gravity. The model was validated by testing its response to normothermic ischemia and reperfusion, and the expected protective effects of hypothermic-cardioplegia are demonstrated. A marked difference in response to ischemia is shown between this model and the buffer-perfused heart. We conclude that alloperfused isolated rat heart model is an inexpensive and more clinically relevant method of screening various new modes of myocardial protection.

Animals↗
PubMed2000

Proliferation, zonal maturation, and steroid production of fetal adrenal transplants in adrenalectomized rats.

The present study investigated the histologic maturation, proliferative capacity, and steroid production of fetal adrenal transplants (Tx) in adrenalectomized rats. A pair of fetal adrenal glands (18-20 days of gestation) was transplanted into the omentum of syngeneic Lewis rats (n = 45). Four weeks later, in 5 animals the grafts were excised for morphologic evaluation. Proliferation was investigated by immunohistochemical staining for KI-67 protein and quantified by the proliferation index (PI = positive cells/100 counts). All other hosts (Tx; n = 40) underwent bilateral adrenalectomy (AE) to induce Addisonian crisis. Postoperatively, survival and concentrations of potassium, sodium, aldosterone, and corticosterone were recorded for 6 months. These data were compared to controls (C=only AE; n = 30) and a sham group (S; n = 10). At the end of the study period all surviving hosts were killed for histologic examination of grafts. At 4 weeks post-Tx the adrenal grafts demonstrated a distinct zona glomerulosa and frequent proliferation with a PI of 0.084, comparable to normal control (0.092). Following AE survival was significantly prolonged in Tx (86% vs 12% of C, P < 0.05). Control animals developed severe hyponatremia and hyperkalemia, whereas in Tx only transient signs of Addisonian crisis were recorded. Levels of aldosterone dropped within 7 days in the Tx and C groups, but returned to normal for Tx within 8 weeks. Corticosterone levels of Tx animals fell to 25% within week, but steadily increased to 70% by the end of the study. At 6 months, grafts revealed a mature adrenocortical structure with little proliferative activity, which was comparable to controls. In a syngeneic rat model fetal adrenal transplants thus mature and proliferate to provide sufficient steroid production for adrenalectomized hosts.

Adrenal Glands↗
PubMedDate not supplied

Beneficial effect of hepatic stimulatory substances on the survival of intrasplenically transplanted hepatocytes.

Intrasplenic hepatocyte transplantation has been demonstrated to have a tentative role in treating experimental liver disease, but methods for promoting the rapid proliferation of intrasplenic hepatocytes are still quite limited. In this study, hepatic stimulatory substances (HSS) obtained from regenerating porcine livers were injected directly into the subcutaneously translocated spleens of recipient rats that had received intrasplenic hepatocyte transplantation. The clusters of intrasplenic hepatocytes contained more than 100 cells, and formed cord structures at 2 wk after transplantation, and the hepatocytes still survived at 6 wk in the HSS-treated rats. In contrast, the clusters contained less than 10 hepatocytes at 2 wk after transplantation, and no surviving hepatocytes was observed at 4 and 6 wk in control rats. Additionally, marked proliferation of bile ductular-like structures appeared around the clusters of surviving hepatocytes in the splenic red pulp of the HSS-treated rats, but were not found in control rats at 4 and 6 wk after transplantation.

Animals↗
PubMed1984

Involvement of protease in L-glutamine control of nucleic acid and polyphosphate metabolism in cells transformed by 9,10-dimethyl-1,2-benzanthracene, SV40 and H-ras oncogene.

Mammalian cells transformed with either 9,10-dimethyl-1,2-benzanthracene, SV40 or H-ras oncogene dramatically changed their ability to synthesize DNA and RNA and metabolize polyphosphate when L-glutamine was withdrawn from the growth medium or when heat shocked (growth at 42 degrees C). Untransformed, DNA and RNA synthesis decreased by 50-80% when glutamine was withdrawn, but polyphosphate accumulated whether or not glutamine was supplied. Heat shock did not alter this response. Transformed isogenic cells responded differently; at 37 degrees C, they decreased their synthesis of DNA and RNA if starved for glutamine, whereas at 42 degrees C, synthesis was optimal without glutamine. Transformed cells accumulated polyphosphate at 37 degrees C when starved for glutamine, but at 42 degrees C, no polyphosphate accumulated. This apparent non-dependence on glutamine by transformed cells when heat shocked was found to be due to the production of glutamine from serum proteins through induction of a protease(s).

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1990

Characterization of TPI gene expression in isogeneic wild-type and gcr1-deletion mutant strains of Saccharomyces cerevisiae.

In Saccharomyces cerevisiae the enzymes of glycolysis constitute 30-60 percent of the soluble protein. GCR1 gene function is required for high level glycolytic gene expression. We have undertaken a biochemical and genetic characterization of TPI, a gene affected by gcr1 lesions. Northern analysis showed that steady-state levels of TPI transcripts are severely reduced in gcr1 mutant strains. However, primer extension experiments revealed that TPI transcripts isolated from wild-type and gcr1 mutant strains have identical 5' ends. To map the 5' boundary of TPI controlling region, we employed a TPI::lacZ gene fusion carrying 3.5 kb 5' to the translational start of the TPI structural gene. Nuclease Bal31 deletion analysis demonstrated that sequences sufficient for high level expression of TPI reside within 392 nucleotides preceding the start of the structural gene. We have identified GRF1/RAPI/TUF-binding site positioned 339 to 349 bp 5' to the translation start of TPI. DNA band shift assays were carried out with wild-type and gcr1 deletion mutant strains, and similar patterns of band shifting were observed.

Base Sequence↗
PubMedDate not supplied

Noradrenergic and cholinergic reinnervation of islet grafts in diabetic rats.

Grafted islets become denervated due to the islet transplantation procedure. The aim of the present study was 1) to examine whether islet grafts in the liver, the spleen, and under the kidney capsule in rats become reinnervated following the transplantation and experimental procedures used in our laboratory, 2) whether there is any difference in reinnervation at these different sites, and 3) how these results relate to previous physiological experiments. Isogeneic isolated islets were transplanted into diabetic Albino Oxford rats, resulting in normoglycaemia. After at least 5 wk, graft-receiving organs were removed and several antibodies were employed to detect insulin, neuron-specific proteins, and cholinergic and noradrenergic nerve fibers. Islets in all three receiving organs contained viable insulin-positive B-cells. Neuron-specific enolase (NSE) as well as the growth-associated protein B-50 was observed at all sites. The cholinergic marker choline acetyltransferase (ChAT) was localized in islets grafts at all sites, but with the lowest density in the spleen. Staining for the noradrenergic markers tyrosine hydroxylase (TH) and dopamine-beta-hydroxylase (DBH) was observed in islet grafts at all sites with the lowest density in grafts under the kidney capsule. All these neurochemical substances were most frequently observed in fibers associated with blood vessels, which may be the route along which nerves grow into the graft. It can be concluded that 1) islet grafts in the liver, in the spleen and under the kidney capsule become reinnervated; 2) the innervation pattern of the islet grafts differs only slightly from that in the control pancreatic islets; and 3) in combination with our previously physiological data, we can conclude that these nerve fibers are, at least partly, functionally active.

Animals↗
PubMed1991

Remyelination of demyelinated rat axons by transplanted mouse oligodendrocytes.

The injection of the gliotoxic agent ethidium bromide (EB) into spinal white matter produces a CNS lesion in which it is possible to investigate the ability of transplanted glial cells to reconstruct a glial environment around demyelinated axons. This study demonstrates that transplanted mouse glial cells can repopulate EB lesions in rats provided tissue rejection is controlled. In X-irradiated EB lesions in cyclosporin-A-treated rats, mouse oligodendrocytes remyelinated rat axons and, together with mouse astrocytes, re-established a CNS environment. When transplanted into nonirradiated EB lesions in nude rats, mouse glial cells modulated the normal host repair by Schwann cells to remyelination by oligodendrocytes. In both X-irradiated and non-irradiated EB lesions, transplanted mouse glial cells behaved similarly to isogenic rat glial cell transplants (Blakemore and Crang Dev Neurosci, 1988;10:1-10; J Neurocytol, 1989;18:519-528). These findings indicate that the cell-cell interactions involved in reconstruction of a glial environment are common to both mouse and rat.

Animals↗
PubMed1991

Molecular basis of Mycoplasma surface antigenic variation: a novel set of divergent genes undergo spontaneous mutation of periodic coding regions and 5' regulatory sequences.

Antigenic diversity is generated in the wall-less pathogen Mycoplasma hyorhinis by combinatorial expression and phase variation of multiple, size-variant membrane surface lipoproteins (Vlps). The unusual structural basis for Vlp variation was revealed in a cluster of related but divergent vlp genes, vlpA, vlpB and vlpC, which occur as single chromosomal copies. These encode conserved N-terminal domains for membrane insertion and lipoprotein processing, but divergent external domains undergoing size variation by loss or gain of repetitive intragenic coding sequences while retaining a motif with distinctive charge distribution. Genetic analysis of phenotypically switched isogenic lineages representing ON or OFF expression states of Vlp products ruled out chromosomal rearrangement or frameshift mutations as mechanisms for Vlp phase variation. However, highly conserved vlp promoter regions contain a tract of contiguous A residues immediately upstream of the -10 box which is subject to frequent mutations altering its length in exact correspondence with the ON and OFF phase states of specific genes. This suggests a mechanism of transcriptional control regulating high frequency phase variation and random combinatorial expression of Vlps. The multiple levels of diversity embodied in the vlp gene cluster represents a novel adaptive capability particularly suited for this class of wall-less microbe.

Amino Acid Sequence↗
PubMed1993

The rex genes of lambda prophage modify ultraviolet light and N-methyl-N-nitrosourea-induced responses to DNA damage in Escherichia coli.

Inactivation and mutagenesis of Escherichia coli by ultraviolet light and N-methyl-N-nitrosourea (MNU) were examined in isogenic strains that were (i) free of lambda phage, (ii) lysogenic for lambda or (iii) contained the lambda rexAB operon on a plasmid (prex20). Inactivation was enhanced when rex genes were present and this enhancement was greater for MNU than for UV. Mutagenesis was not greatly affected by the presence of the rex genes with one exception; UV-induced glnU degrees suppressor mutations were reduced in the strain harboring prex20. Control experiments using a strain containing only plasmid pACYC184 showed no effect on inactivation. A small depression in UV-induced mutagenesis was observed, however. These data suggest that the lambda RexAB proteins interfere with processes necessary for recovery from DNA damage and for fixation of one example of UV-induced mutation. This and other recent observations of effects by rex genes are discussed.

Bacteriophage lambda↗
PubMed1965

ABNORMAL IMMUNE MECHANISM IN ALLOGENEIC RADIATION CHIMERAS.

Mice were subjected to x-rays (950 roentgens) and injected with isogeneic (isologous) or allogeneic (homnologous) bone marrow. Six to 8 months later these chimeras were injected with Salmonella typhi flagellar antigen, and the formation of antibodies resistant and sensitive to destruction by treatment in vitro with 2-mercaptoethanol was determined. The allogeneic chimeras showed almost normal amounts of serumn antibody after a third injection of antigen but a relative defect in their ability to synthesize antibody resistant to 2-mercaptoethanol. Apparently control of antibody formation becomes abnormal in the presence of the immunologic tolerance existing between the host and the foreign hematopoietic graft.

Animals↗
PubMed1992

Murine model of cutaneous infection with gram-positive cocci.

Staphylococcus aureus has remained an important cause of nosocomial wound infections, but standardized or reproducible systems for analyzing cutaneous infections caused by S. aureus do not exist. A variety of foreign materials, variable inocula, and skin traumas have been used to promote infection. To minimize these variables and ensure reproducibility, we chose a model using subcutaneous injections of a fixed quantity of dextran microbeads (Cytodex) as the foreign material added to standardized broth suspensions of S. aureus. Suspensions (0.2 ml) injected into an outbred strain of immunocompetent hairless mice generated reproducible, measurable lesions. With S. aureus Smith Diffuse, fluctuant, erythematous lesions with a peak diameter of 15 mm were observed; these lesions yielded purulent material containing gram-positive cocci and neutrophils and yielded growth of S. aureus on culture. Lesion size was proportional to the bacterial inoculum size. Histologic examination of excised lesions revealed typical abscesses. A second strain of S. aureus (SLC3) produced dermonecrosis instead of abscesses at an inoculum size of 10(7) CFU. Control injections with a sterile Cytodex suspension regularly produced nondraining, nonerythematous nodules with maximum diameters of less than or equal to 5 mm. Streptococcus pyogenes produced late-onset necrotic lesions and abscesses. Using a foreign substance, this model generates easily observed and reproducible cutaneous infection with S. aureus and streptococci that can potentially discriminate between inter- and intrastrain differences. Such a model could be used to test the pathogenicity of isogeneic strains of these bacterial species and to evaluate the efficacy of antimicrobial agents.

Analysis of Variance↗