Search PubMed⌕ Search

Biomedical subjects

R Carroll

Publications and source records attributed to R Carroll.

At least 73 records · Page 4Linked to original sources
PubMed1994

A human immunodeficiency virus type 1 (HIV-1)-based retroviral vector system utilizing stable HIV-1 packaging cell lines.

We have constructed stable human immunodeficiency virus (HIV) packaging cell lines that when transfected with an HIV-based retroviral vector produce packaged vectors capable of transducing susceptible CD4+ cells. This HIV-1-based retroviral vector system has the potential for providing targeted delivery and regulated expression of immunogens or antiviral agents in CD4+ cells.

Animals↗
PubMed1994

Platelet-derived growth factor expression and stimulation in human meningiomas.

The platelet-derived growth factor (PDGF) family consists of subunits A and B and receptors alpha and beta. This paper evaluates the potential role of the homodimer PDGF-BB as a growth factor in meningiomas. It analyzes the expression of messenger RNA in members of the PDGF family in these tumors, measures the growth response of meningiomas to exogenous PDGF-BB in culture, and examines the induction of the c-fos proto-oncogene by PDGF-BB. Northern blot analysis was carried out on tissue from 20 meningiomas to measure the expression of PDGF-A, PDGF-B, PDGF-alpha receptor (PDGF-alpha-R) and PDGF-beta receptor (PDGF-beta-R). All tumors expressed PDGF-A and PDGF-B subunits. Nineteen of the 20 tumors expressed PDGF-beta-R and none expressed PDGF-alpha-R as measured by this technique. Because the beta receptor is selectively sensitive to stimulation by the PDGF-B subunit, these data suggest that meningiomas might be susceptible to stimulation by PDGF-BB. To test this hypothesis, the effect of exogenous PDGF-BB on meningioma growth was evaluated by incubating cells from 10 human meningiomas. Tritiated thymidine incorporation was used to evaluate stimulation of growth over a 48-hour period using PDGF-BB concentrations of 1, 3, or 6 ng/ml. Linear regression analysis and multiple-factor analysis of variance were used to measure PDGF-BB effects. Three of the 10 tumor specimens responded significantly to PDGF-BB, with a three- to sixfold increase in thymidine incorporation over 72 hours of exposure, and there was a significant overall growth-stimulating effect of PDGF-BB in the 10 tumor specimens tested. In the last set of experiments, the functionality of the PDGF-beta-R was determined by examining the induction of the proto-oncogene c-fos by PDGF-BB in meningioma cell cultures. A significant increase in c-fos protein was observed 3 hours after PDGF-BB addition. These findings demonstrate that PDGF-A, PDGF-B, and PDGF-beta-R are expressed in meningiomas and suggest that the beta receptor is functional: when it is activated, c-fos levels are increased, and an increase in meningioma cell division is observed after the addition of PDGF-BB. These studies support the hypothesis that PDGF acts as a growth factor in meningiomas.

Adult↗
PubMed1993

Alpha-helical distorting substitution disrupt coupling between m3 muscarinic receptor and G proteins.

Acetylcholine stimulation of the m3 or m2 muscarinic receptor expressed in Xenopus laevis oocytes induces either a fast transient or slowly oscillating calcium-sensitive chloride current. The speed of these currents reflects the efficiency of receptor coupling to guanine nucleotide-binding proteins and phosphatidylinositol (PI) turnover. Point mutations of the m3 receptor were made in a region of the third cytoplasmic loop to test whether receptor function relied on an alpha-helical structure of the G protein-coupling domain. Proline substitution for glutamate at position 257 disrupted the m3 response. Also, single alanine insertions between residues 259 and 260 disrupted the m3 receptor-stimulated response while double alanine insertions at this site had no effect. Based on these results, we suggest that a region of the third cytoplasmic loop of the m3 receptor possesses an amphipathic alpha-helical conformation.

Acetylcholine↗
PubMed1993

Preparation of a cell-free translation system with minimal loss of initiation factor eIF-2/eIF-2B activity.

Cell-free translation systems prepared from suspension-cultured HeLa S3 cells or mouse L cells by hypotonic shock followed by Dounce homogenization poorly initiated the translation of exogenous mRNA. In contrast, cell extracts prepared from cells exposed to the detergent lysolecithin translated exogenous mRNA readily. The block in initiation in the former lysates was localized to the ribosome fraction. During in vitro translation polysomes from homogenized cells disaggregated but the run-off ribosomes were unable to reinitiate translation. The block resulted from a decrease in eukaryotic initiation factor 2 (eIF-2) or the guanine nucleotide exchange factor (eIF-2B) activity, since the addition of eIF-2 or eIF-2B to these latter extracts substantially improved the capacity of the extract to initiate translation of exogenous mRNA. Extracts from homogenized cells, but not from detergent-treated cells, showed enhanced ability to phosphorylate the alpha subunit of exogenous eIF-2. We show that the method of cell extract preparation greatly influences the state of eIF-2/eIF-2B activity in the resulting extract and that extracts in which this activity is maintained can readily initiate translation on exogenous mRNA and reinitiate on endogenous mRNA.

Animals↗
PubMed1993

Association among serum lipid and lipoprotein concentrations and physical activity, physical fitness, and body composition in young children.

OBJECTIVE: To examine the relationships among indicators of physical activity, physical fitness, and body composition with serum lipid and lipoprotein levels in young children. DESIGN: Cross-sectional and 1-year prospective cohort. SETTING: Studies of Child Activity and Nutrition (SCAN) program, Galveston, Tex. SUBJECTS: One hundred twenty-three 4- or 5-year-old black, Hispanic (of Mexican origin), and white children. MEASUREMENTS: Body composition, resting heart rate, and cardiovascular fitness variables and serum lipid and lipoprotein levels were measured at age 3 or 4 years (study year 1) and at age 4 or 5 years (study year 2), and day-long heart rate was measured and the Children's Activity Rating Scale was administered between study years 1 and 2. RESULTS: Year-1 waist/hip ratios were inversely correlated with total serum cholesterol (TSC) and low-density lipoprotein (LDL) levels. Mean activity level was inversely correlated with waist/hip ratios. On the basis of multiple regression analysis, the sum of seven skin-fold measurements, height, and gender explained 15.4% of the variation in triglyceride levels. The sum of seven skin-fold measurements was inversely correlated with the high-density lipoprotein (HDL) level. Resting heart rate, waist/hip ratio, and the slope of the exercise heart rate during fitness testing explained 19.5% of the variation in the concentration of an HDL subclass, HDL2. These children's levels of physical activity were associated with higher fitness levels. Year-1 waist/hip ratios and year-2 sum of seven skin-fold measurements were positively correlated with the LDL/HDL and TSC/HDL ratios. CONCLUSION: Higher levels of cardiovascular fitness and lower levels of fatness were associated with more favorable serum lipid and lipoprotein levels in these young children. Physical activity appeared to have an indirect association with serum lipid and lipoprotein values through its relationship with higher fitness levels and lower levels of fatness.

Activities of Daily Living↗
PubMed1993

Translation of equine infectious anemia virus bicistronic tat-rev mRNA requires leaky ribosome scanning of the tat CTG initiation codon.

We have examined the translational regulation of the equine infectious anemia virus (EIAV) bicistronic tat-rev mRNA. Site-directed mutagenesis of the tat leader region followed by expression of the tat-rev cDNA both in vitro and in transiently transfected cells established that tat translation is initiated exclusively at a CTG codon. Increasing the efficiency of tat translation by altering the CTG initiator to ATG resulted in a dramatic decrease in translation of the downstream (rev) cistron, indicating that leaky scanning of the tat CTG initiation codon permitted translation of the downstream rev cistron. Since the tat leader sequences precede the major EIAV splice donor and are therefore present at the 5' termini of both spliced and unspliced viral mRNAs, the expression of all EIAV structural and regulatory proteins is dependent on leaky scanning of the tat initiator.

Amino Acid Sequence↗
PubMed1993

Mourning: a concern for medical-surgical nurses.

Medical-surgical nurses working in a variety of settings with dying patients and their families play an important role in facilitating grieving. They can do much to help dying patients have a more peaceful death by listening to them. They can facilitate healing among families prior to death. They can help surviving family members begin a more healthy pattern of mourning. The tasks of mourning offer a useful guide for responding to the needs of the bereaved from a variety of cultural perspectives. Nurses can gain a greater sense of satisfaction in working with dying patients and grieving survivors by incorporating this framework into their practice.

Attitude to Death↗
PubMed1992

Proinsulin processing by the subtilisin-related proprotein convertases furin, PC2, and PC3.

Experiments using recombinant vaccinia viruses expressing rat proinsulin I coinfected into COS-7 cells with recombinant vaccinia virus expressing human furin, human PC2, mouse PC3 (subtilisin-related proprotein convertases 1-3, respectively), or yeast Kex2 indicate that in this system both Kex2 and furin produce mature insulin, whereas PC2 selectively cleaves proinsulin at the C-peptide-A-chain junction. This is a property consistent with its probable identity with the rat insulinoma granule type II proinsulin processing activity as described by Davidson et al. [Davidson, H. W., Rhodes, C. J. & Hutton, J. C. (1988) Nature (London) 333, 93-96]. PC3 generates mature insulin but cleaves preferentially at the proinsulin B-chain-C-peptide junction. This pattern of cleavage by PC3 is similar, but not identical, to that of the highly B-chain-C-peptide junction-selective type I activity as described by Davidson et al., perhaps due to the presence of a P4 arginine residue near the C-peptide-A-chain junction unique to the rat proinsulins. These results along with data presented on the expression of both PC2 and PC3 in islet beta cells strongly support the conclusion that these proteases are involved in the conversion of proinsulin to insulin in vivo.

Amino Acid Sequence↗
PubMed1992

Activation of lipoprotein lipase in cardiac myocytes by glycosylation requires trimming of glucose residues in the endoplasmic reticulum.

Incubation of cycloheximide-treated cardiac myocytes results in a time-dependent increase in cellular and heparin-releasable lipoprotein lipase (LPL) activities. N-Methyldeoxynojirimycin (1 mM) and castanospermine (100 micrograms/ml), inhibitors of glucosidases in the endoplasmic reticulum (ER), prevented the increase in cellular LPL activity. The glucosidase inhibitors did not influence the synthesis or turnover of LPL protein. Therefore activation of LPL by glycosylation in cardiac myocytes requires the trimming of glucose residues in oligosaccharide chains by glucosidases of the ER.

1-Deoxynojirimycin↗
PubMed1992

Inhibition of myocardial lipoprotein lipase by U-57,908 (RHC 80267).

U-57,908 (RHC 80267) was shown to inhibit lipoprotein lipase (LPL) activity in cardiac myocytes from rat hearts; the concentrations required for inhibition to 50% of control activity were 1.1 microM and 2.5 microM for myocyte homogenates and a post-heparin medium preparation, respectively. The inhibition of LPL activity by U-57,908 was not changed when the concentration of the triolein substrate and apolipoprotein CII activator in the assay was reduced. The availability of U-57,908 as a potent and selective LPL inhibitor may provide a useful experimental approach in studies on lipoprotein metabolism.

Animals↗
PubMed1992

Inhibition of human immunodeficiency virus type 1 Tat activity by coexpression of heterologous trans activators.

We examined the mechanism of Tat-mediated trans activation through competition experiments employing Tat proteins of human immunodeficiency virus type 1 (HIV-1) and equine infectious anemia virus (EIAV). EIAV Tat, as well as chimeric EIAV/HIV-1 Tat proteins, inhibited HIV-1 Tat-mediated trans activation in a cell-type-dependent fashion. Furthermore, these proteins inhibited trans activation by Tat-bacteriophage R17 coat protein chimeras. Inhibition resulted from competition between activation domains of effectors and competitors for a limiting cellular cofactor. The context in which competitor activation domains were expressed contributed to the extent of inhibition. In transfected cells, EIAV Tat and all chimeric competitors were located primarily in the cytoplasm, whereas HIV-1 Tat was primarily located in the nucleus. These data are consistent with a model for trans activation in which the activation domain of Tat associates with and conveys a cellular factor to the transcription complex via the trans-acting-responsive element (TAR).

Amino Acid Sequence↗
PubMed1991

A minimal lentivirus Tat.

Transcriptional regulatory mechanisms found in lentiviruses employ RNA enhancer elements called trans-activation responsive (TAR) elements. These nascent RNA stem-loops are cis-acting targets of virally encoded Tat effectors. Interactions between Tat and TAR increase the processivity of transcription complexes and lead to efficient copying of viral genomes. To study essential elements of this trans activation, peptide motifs from Tats of two distantly related lentiviruses, equine infectious anemia virus (EIAV) and human immunodeficiency virus type 1 (HIV-1), were fused to the coat protein of bacteriophage R17 and tested on the long terminal repeat of EIAV, where TAR was replaced by the R17 operator, the target of the coat protein. This independent RNA-tethering mechanism mapped activation domains of Tats from HIV-1 and EIAV to 47 and 15 amino acids and RNA-binding domains to 10 and 26 amino acids, respectively. Thus, a minimal lentivirus Tat consists of 25 amino acids, of which 15 modify viral transcription and 10 bind to the target RNA stem-loop.

Amino Acid Sequence↗