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Biomedical subjects

K C Carter

Publications and source records attributed to K C Carter.

At least 73 records · Page 4Linked to original sources
PubMed1993

Genetic control of drug-induced recovery from murine visceral leishmaniasis.

The influence of host genetic background on the response of Leishmania donovani-infected mice to chemotherapy was studied using the H-2d and H-2b haplotypes on a BALB or a B10 genetic background. Animals were treated with free or liposomal sodium stibogluconate and parasite burdens in the liver, spleen and bone marrow were assessed. In all the mouse strains and their congenic derivatives examined, the liver responded best to therapy regardless of drug formulation, whilst the spleen and the bone marrow respectively were increasingly less responsive to chemotherapy. Treatment with free drug was more effective in congenic mice carrying the H-2b haplotype than in those carrying the H-2d haplotype and in mice carrying the same H-2 haplotype, animals from a BALB background were better responders than those from a B10 genetic background. Liposomal drug was more effective than free drug treatment in all four mouse strains and produced a similar significant suppression (> 99%, P < 0.001) in liver parasite burdens to that obtained using a six times greater free drug dose. This liposomal drug dose was more effective than free drug in reducing bone marrow parasite burdens in all four mouse strains and equally (BALB/c mice) or more effective (P < 0.01, BALB/B, B10 and B10.D2 strains) in reducing spleen parasite numbers. Liposomal dependent influences apparent using free sodium stibogluconate. These results are discussed in relation to the genetic factors which are known to control the course of L. donovani infection in mice.

Animals↗
PubMed1993

The distribution of free and non-ionic vesicular sodium stibogluconate in the dog.

The pharmacokinetics and tissue distribution of antimony after the administration of sodium stibogluconate in a free form or entrapped in vesicles prepared from non-ionic surfactant were studied in the dog. Animals were given either one or two intravenous bolus injection(s) equivalent to 45 mg Sb kg-1 as free drug or 0.625 or 0.685 mg Sb kg-1 as vesicular drug. Blood samples were taken at various times after dosing and antimony levels in various tissues were determined at 3 h, 48 h and 6 days after dosing. After free stibogluconate antimony clearance from the blood occurred in a rapid elimination phase with a blood half-life of 0.58 +/- 0.08 h. This rapid elimination phase did not occur after vesicular drug. Both drug preparations gave similar antimony levels in the spleen, liver and femur and humerus bone marrow at all time points assessed even though the vesicular dose was one-seventieth of the free drug dose. After the free drug there was marked urinary excretion of antimony and, as a result, increased kidney loading at the expense of other tissue. Vesicle-mediated drug delivery suppressed renal excretion and a much greater proportion of the antimony dose was recovered from tissue than was obtained after free drug. A hypothesis is presented to account for the differences in tissue antimony concentrations produced by the two formulations.

Animals↗
PubMed1992

The use of 35S-labelled Toxocara canis to determine larval numbers in tissues.

The potential of using 35S-labelled larvae to determine the number of second-stage Toxocara canis larvae present in the tissues of infected animals was assessed. Infective larvae were labelled by in vitro culture with medium containing 35S-methionine. The amount of radiolabel attached to larvae decayed exponentially with time and had an in vitro mean half life of 3.54 +/- 0.65 days. The 'lost' radiolabel was incorporated into proteins which formed part of the worm's excretory/secretory products. The levels of radioactivity present in different organs of BALB/c mice, infected with 35S-labelled T. canis larvae, varied over the course of infection. Initially most of the radioactivity was present in liver, but over the course of infection 35S liver levels gradually decreased and brain levels increased. By day 14 post-infection the majority of the isotope was present in the brain (p < 0.01). Assessment of antibody levels on day 14 post-infection showed that infection with 35S labelled T. canis larvae induced the production of parasite-specific IgM, IgG and IgG1 antibodies.

Animals↗
PubMed1992

Visceral leishmaniasis in the BALB/c mouse: antimony tissue disposition and parasite suppression after the administration of free stibogluconate.

BALB/c mice with an acute or chronic Leishmania donovani infection were treated with intravenous sodium stibogluconate solution and the parasite suppressions determined in the spleen, liver and femur bone marrow. Antimony concentrations in these and other tissues were determined by hydride generation-atomic absorption spectrophotometry. There was little correlation between tissue antimony levels one hour after treatment and drug efficacy. It would appear that the peak tissue antimony concentration achieved soon after dosing, rather than the lower concentrations which are readily sustained in most tissues, is the most important factor in the antileishmanial activity of stibogluconate. A high peak antimony concentration occurred in the liver, where parasites were significantly suppressed, and was not observed in the two other sites of infection, where the parasites were apparently less susceptible to stibogluconate therapy.

Acute Disease↗
PubMed1991

Differential expression of the mouse alpha 1-acid glycoprotein genes (AGP-1 and AGP-2) during inflammation and aging.

In this study we investigated the expression of the Balb/c mouse alpha 1-acid glycoprotein genes. Mice, like humans, have two distinct alpha 1-acid glycoprotein mRNAs. As in humans and rats, mouse alpha 1-acid glycoprotein is a strong acute-phase reactant and its expression can be induced by acute-phase stimulatory agents such as bacterial lipopolysaccharides. Southern analysis and partial sequencing of different alpha 1-acid glycoprotein genomic clones indicated the existence of three distinct alpha 1-acid glycoprotein genes in the Balb/c genome. Using oligonucleotide hybridization, we showed that two of the three genes were expressed while the third gene was either not expressed or expressed at extremely low levels. The mRNA levels for the two expressed genes, alpha 1-acid glycoprotein-1 and alpha 1-acid glycoprotein-2, were both induced during the acute-phase response. However, alpha 1-acid glycoprotein-2 mRNA was present in at least 10-fold higher levels in both induced and uninduced mice. There were also differences in the developmental patterns of the two mRNAs in that the constitutive alpha 1-acid glycoprotein-1 mRNA levels increased 20-fold between 2 and 7 months, while alpha 1-acid glycoprotein-2 mRNA pools remained constant. During the acute-phase response in aged animals, there was an increase in the time required for both mRNAs to respond, and the maximum induced level of both mRNAs decreased. These studies set the stage for future experiments to determine the mechanisms by which the different alpha 1-acid glycoprotein genes are regulated during the acute-phase response and how aging affects these regulatory processes.

Aging↗
PubMed1991

Induction of several acute-phase protein genes by heavy metals: a new class of metal-responsive genes.

Acute-phase reactants, metallothioneins, and heat-shock proteins are the products of three families of genes that respond to glucocorticoids and cytokines. Metallothioneins and heat-shock proteins, however, are also stimulated by heavy metals, whereas very little is known about the effect of heavy metals on acute-phase-reactant genes. We have studied the effect of heavy metals (Hg, Cd, Pb, Cu, Ni, and Zn) and Mg on the acute-phase reactants alpha 1-acid glycoprotein, C-reactive protein, alpha 1-antitrypsin and alpha 1-antichymotrypsin. alpha 1-Acid glycoprotein and C-reactive protein mRNA levels were increased severalfold in livers of heavy-metal-treated Balb/c mice. The strongest induction was mediated by Hg, followed in order of response by Cd greater than Pb greater than Cu greater than Ni greater than Zn greater than Mg. None of the metals affected the mRNA levels of albumin, alpha 1-antitrypsin, and alpha 1-antichymotrypsin. Furthermore, failure to repress albumin, a negative acute-phase reactant, indicated that the induction of these genes was not due to a metal-mediated inflammatory response. The metals also induced alpha 1-acid glycoprotein and C-reactive protein in adrenalectomized animals, indicating that induction by the heavy metals is not mediated by the glucocorticoid induction pathway. Sequence analysis has revealed a region of homology to metal-responsive elements in the alpha 1-acid glycoprotein and C-reactive protein promoters. Additionally, an alpha 1-acid glycoprotein expression vector, pAGP(-595)CAT, responded to Hg and Cd when transfected into human HepG2 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute-Phase Proteins↗
PubMed1991

DNA and RNA within the nucleus: how much sequence-specific spatial organization?

Spatial organization of various nuclear components is often proposed as a means by which nuclei more efficiently carry out their various tasks. Such functional compartmentalization may involve a sequence-specific packaging and placement of DNA and RNA. Here we review recent insights, allowed primarily by advances in fluorescent in situ hybridization methodology, into the organization of nucleic acids within individual nuclei.

Cell Cycle↗
PubMed1991

Localizing DNA and RNA within nuclei and chromosomes by fluorescence in situ hybridization.

The enormous potential of in situ hybridization derives from the unique ability of this approach to directly couple cytological and molecular information. In recent years, there has been a surge of success in powerful new applications, resulting from methodologic advances that bring the practical capabilities of this technology closer to its theoretical potential. A major advance has been improvements that enable, with a high degree of reproducibility and efficiency, precise visualization of single sequences within individual metaphase and interphase cells. This has implications for gene mapping, the analysis of nuclear organization, clinical cytogenetics, virology, and studies of gene expression. This article discusses the current state of the art of fluorescence in situ hybridization, with emphasis on applications to human genetics, but including brief discussions on studies of nuclear DNA and RNA organization, and on applications to clinical genetics and virology. Although a review of all of the literature in this field is not possible here, many of the major contributions are summarized along with recent work from our laboratory.

Animals↗
PubMed1991

Discrete nuclear domains of poly(A) RNA and their relationship to the functional organization of the nucleus.

The functional organization of the nucleus was studied using a fluorescence microscopy approach which allowed integration of positional information for RNA, DNA, and proteins. In cells from sea urchin to human, nuclear poly(A) RNA was found concentrated primarily within several discrete "transcript domains" which often surrounded nucleoli. Concentrations of poly(A) RNA were coincident with snRNP antigen clusters, providing evidence for the localization of pre-mRNA splicing at these sites. The spatial relationship of transcript domains with respect to various classes of DNA was established, in that the poly(A) RNA-rich regions coincided with discrete regions of low DNA density and were non-randomly distributed with respect to specific DNA sequences. Centromeric DNA and late-replicating DNA did not overlap transcript domains, whereas a subset of early-replicating DNA may. Results indicate that transcript domains do not result directly from a simple clustering of chromatin corresponding to metaphase chromosomes bands. Finally, observations on the reassembly of these domains after mitosis suggest that the clustering of snRNP antigens may be dependent on the reappearance of pol II transcription. Implications of these findings for overall nuclear structure and function are considered, including a discussion of whether transcript domains may be sites of polymerase II transcription reflecting a clustering of active genes.

Antigens↗
PubMed1991

The effect of aging on constitutive mRNA levels and lipopolysaccharide inducibility of acute phase genes.

Eukaryotic organisms possess natural defense processes associated with their response to injury, inflammation and pollutants. One of these, the acute phase (AP) host response, is characterized by a series of hepatic physiological reactions triggered by factors released as a result of bacterial infection, inflammation or tissue injury and is believed to be the mechanism by which cells and tissues are protected against further damage and injury. The capacity to respond to these physiological insults is known to be affected by aging. We propose that the AP response represents a series of intrinsic processes and interactions that may be affected by aging. Furthermore, we propose that this may be due to the progressive failure of the acute phase response. In this study we examine the relationship between aging and the expression of both positive and negative acute phase reactants, i.e., acute phase serum proteins whose levels are increased or decreased in response to systemic injury and infection. The mRNA levels of the positive acute phase reactants, alpha 1-acid glycoprotein (AGP), alpha 1-antitrypsin (AT), and the negative acute phase reactant, albumin were measured in both normal and inflammation-induced mice of ages 2, 7, 12, and 24 months. A significant decrease in the constitutive levels of AT and albumin mRNAs occurred as a function of increased age. Furthermore, aging decreased the ability of the AGP and albumin genes to respond to inflammation. Our studies indicate that aging may affect the transcription of these genes, processing of their mRNA or stability of the mRNA levels.

Acute-Phase Proteins↗
PubMed1989

Deadenylation of alpha 1-acid glycoprotein mRNA in cultured hepatic cells during stimulation by dexamethasone.

During acute phase induction in rats, alpha 1-acid glycoprotein (AGP) mRNA is modified by a reduction in poly(A) tail size (Shiels, B.R., Northemann, W., Gehring, M.R., and Fey, G.H. (1987) J. Biol. Chem. 262, 12826-12831). In the studies presented here, we analyzed AGP mRNA induction and poly(A) tail modification in both primary rat hepatocytes and in the rat hepatoma cell line HTC. Poly(A) tail shortening occurred during stimulation by both glucocorticoids and hepatocyte stimulating factor. Induction of AGP by the glucocorticoid dexamethasone resulted in an approximately 50-fold increase in transcription by 4 h, which was followed by an equally rapid decrease. The large mRNA pool that resulted from this early burst of transcription was very stable, having a half-life of well over 24 h, and the individual molecules in this pool had an average poly(A) tail length of 200-250 bases. This stable pool of AGP mRNAs was then deadenylated to form a pool with an average tail length of 20-50 bases; the time course of this shortening followed that seen in the liver. Ongoing RNA synthesis, but not ongoing protein synthesis, was required for shortening of the tail. In contrast to the conclusion of Shiels et al. (1987), our data indicate that deadenylation occurs in the cytoplasm rather than the nucleus. Our data also suggest that shortening of AGP mRNA represents a specific example of the general deadenylation seen in earlier studies of total cellular RNA.

Animals↗
PubMed1989

Microtubule depolymerization inhibits the regulation of alpha 1-acid glycoprotein mRNA by hepatocyte stimulating factor.

Hepatocyte stimulating factor (HSF, a polypeptide cytokine) is a major regulatory hormone responsible for hepatic acute-phase reactant (APR) induction following acute systemic injury. The mechanisms by which HSF regulates APR synthesis in the liver are unknown. Microtubules are involved in a number of polypeptide hormone-mediated events which can be modified, either positively or negatively, by microtubule depolymerizing agents. In this study we have used colchicine (a microtubule depolymerizing drug) to assess whether or not HSF-mediated changes in rat hepatic alpha 1-acid glycoprotein (AGP) or albumin mRNA levels require an intact microtubule cytoskeletal system. Cultured rat hepatocytes were pretreated for 30 min with either colchicine (10(-6) M), or the inactive isomer lumicolchicine (10(-6) M), or fresh medium. Following pretreatment, purified murine macrophage HSF (10 units/ml) was added and the cells were incubated for an additional 12 h. Colchicine, but not lumicolchicine, significantly inhibited the HSF-dependent regulation of mRNA for the positive APR, AGP, but had no effect on the mRNA levels of albumin, a negative APR. Furthermore, removal of colchicine from previously inhibited cultures allowed HSF to restimulate AGP mRNA expression. These data suggest that microtubules may play a regulatory role in controlling the expression of the genes for positive acute-phase proteins and may explain the temporal differences found in vivo between positive and negative APR expression.

Animals↗
PubMed1989

The induction of protective immunity to Leishmania major in the BALB/c mouse by interleukin 4 treatment.

The ability of interleukin 4 (IL4), administered subcutaneously around the cutaneous lesion in the form of hydrophilic gels, to affect the development of established Leishmania major infections in the BALB/c mouse was studied. IL4 had a therapeutic effect on L. major lesion growth compared with control mice, causing not only resolution of the parasite lesions over a period of 10 weeks but also rendering animals resistant to reinfection. Adoptive transfer of splenic T cells, obtained from IL4-treated animals, conferred significant resistance to L. major infection in naive BALB/c mice compared with controls. These results demonstrate that IL4 is capable of not only reversing the usual (i.e. non-curing) course of L. major infection in the BALB/c mouse, but also of promoting the generation of protective immunity. The nature of the gel used to deliver the cytokine was found to be important since the therapeutic activity of IL4 in poloxamer gel was not observed when a hydroxypropylmethyl cellulose (hypromellose) gel was used as the IL4 vehicle.

Animals↗