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Biomedical subjects

G R Campbell

Publications and source records attributed to G R Campbell.

At least 19 recordsLinked to original sources
PubMed1992

Heparan sulfate-degrading enzymes induce modulation of smooth muscle phenotype.

Macrophages cocultured with rabbit aortic smooth muscle cells at a ratio of 1:3 degraded all the 35S-labeled heparan sulfate proteoglycan from the smooth muscle surface into free sulfate (Kav of 0.84 on Sepharose 6B). Concomitantly, the same macrophages induced a decrease in the volume fraction of myofilaments (Vvmyo) of the smooth muscle cells and a decrease in alpha-actin mRNA as a percentage of total actin mRNA. Both macrophage lysosomal lysate at neutral pH and heparinase degraded cell-free 35S-labeled matrix deposited by smooth muscle cells into fragments which eluted at a Kav of 0.63 and which were identified as heparan sulfate chains by their complete degradation in the presence of low pH nitrous acid. At acid pH the macrophage lysosomal lysate completely degraded the heparan sulfate to free sulfate (Kav 0.84). Both macrophage lysosomal lysate and commercial heparinase at neutral pH induced smooth muscle phenotypic change while other enzymes such as trypsin and chondroitin ABC lyase had no effect. It was therefore suggested that the active factor present in the macrophages is a lysosomal heparan sulfate-degrading endoglycosidase (heparinase). Only a small amount of heparan sulfate-degrading activity was released into the incubation medium by living macrophages, and there was no heparinase activity on their isolated plasma membranes, although proteolytic enzymes were evident in both instances. In pulse-chase studies, high Vvmyo smooth muscle cells were seen to constantly internalize and degrade 35S-labeled heparan sulfate proteoglycan from their own pericellular compartment, suggesting that this may be the mechanism by which smooth muscle phenotype is maintained under normal circumstances and that removal of heparan sulfate from the surface of smooth muscle cells and its degradation by macrophages temporarily interrupts this process, inducing smooth muscle phenotypic change.

Animals↗
PubMed1992

Effect of perindopril on the development of atherosclerosis in the cholesterol-fed rabbit.

1. The aim of the study was to examine the effect of the angiotensin-converting enzyme inhibitor perindopril on the development of atheroma in the cholesterol-fed rabbit. 2. The normal human carotid artery, like most large human arteries, has a preformed diffuse intimal thickening. To model this thickening, the right carotid artery of the 12-week-old rabbit had an expanded balloon catheter passed down it to remove the endothelium and partially damage the media. 3. Fourteen weeks after this operation, a myointimal thickening similar in almost all respects to the human intimal thickening had developed. The rabbits were then divided into six groups of six rabbits fed on: (i) a 1% cholesterol diet; (ii) a 1% cholesterol diet plus a hypotensive dose of perindopril (0.3 mg/kg per day); (iii) a 1% cholesterol diet plus a non-hypotensive dose of perindopril (0.01 mg/kg per day); (iv) a normal diet; (v) a normal diet plus a hypotensive dose of perindopril (0.3 mg/kg per day); and (vi) a normal diet plus a non-hypotensive dose of perindopril (0.01 mg/kg per day). 4. After 6 weeks of treatment the animals were sacrificed. There were ameliorating effects of both hypotensive and non-hypotensive doses of perindopril on the development of plaques, as determined by the area of intima covered by Oil Red-O-staining plaque and light microscopy. 5. Cell culture studies indicated that perindopril has no effect on smooth muscle proliferation, but increases collagen and non-collagen synthesis by smooth muscle cells and decreases their binding of the atherogenic lipoprotein beta-very low density lipoprotein (beta-VLDL).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1992

Siderotic cerebral macrophages in the acquired immunodeficiency syndrome.

Excessive hemosiderin-laden perivascular macrophages have been described in the brains of patients with the acquired immunodeficiency syndrome (AIDS) who underwent autopsy; its meaning remains unclear. In the brains of 53 patients with AIDS who consecutively underwent autopsy, we quantified the abnormality, elucidated its relationship to the pathologic features of AIDS, and asked if there was some relationship to endogenous iron storage and transport proteins in brain macrophages and microglia. The number of perivascular siderotic macrophages was significantly increased in patients with AIDS compared with age-matched control subjects. Macrophage siderosis was strongly correlated with the presence of disseminated mycobacterial infection and vacuolar myelopathy at autopsy; a generalized wasting (cachexia) also was related significantly. Many other pathologic abnormalities were not related, including putative human immunodeficiency virus-specific neuropathologic changes such as multinucleated cells and myelin pallor. Activated macrophages and microglial cells in the central nervous system had dense intracytoplasmic accumulation of ferritin (iron storage protein) in AIDS and non-AIDS patients. These results suggest that siderosis of cerebral macrophages is related to an ill-defined nonspecific systemic imbalance associated with the breakdown of abundant stores of endogenous intracellular ferritin. Understanding chronic "secondary" effects of human immunodeficiency virus type 1 infection will become increasingly important as improved survival in patients with AIDS is realized.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Glutamine-enhanced enteral diet improves nitrogen balance without increasing portal ammonia.

Following surgical stress the jejunum actively metabolizes endogenous glutamine, a non-essential amino acid, to produce alanine and ammonia, which augments substrate flow to the liver at a time when oral intake of nutrients is decreased. Oral glutamine supplementation theoretically may modify the response to injury. This study was designed to demonstrate the role of the jejunum in postinjury glutamine metabolism and to evaluate the influence of enteral glutamine supplements on nitrogen and ammonia metabolism after laparotomy and bowel resection in dogs. Oral glutamine in the presence of an intact small bowel significantly improved nitrogen balance (461 mg kg body-weight-1 day-1) compared with a control diet (-370 mg kg-1 day-1) (P less than 0.05, analysis of variance). Removal of the proximal small bowel prevented this beneficial effect of glutamine (-507 mg kg-1 day-1). Glutamine-supplemented and control diets were associated with similar portal ammonia concentrations throughout the study.

Ammonia↗
PubMed1991

Density-related expression of caldesmon and vinculin in cultured rabbit aortic smooth muscle cells.

Quantitative immunoblotting techniques were used to study the effects of seeding density on the expression of caldesmon and vinculin variants, which are sensitive markers of vascular smooth muscle cell (SMC) phenotypic modulation in culture. Rabbit aortic SMC were seeded at different densities: 13 x 10(4) cells/cm2 (high density), 3 x 10(4) cells/cm2 (medium density), and 0.2 x 10(4) cells/cm2 (low density) and cultured in the presence of 5% fetal calf serum. Irrespective of cell density and growth phase, caldesmon150 was gradually and irreversibly substituted by caldesmon77, but at high seeding density this substitution proceeded at a slower rate. The fraction of meta-vinculin (smooth muscle variant of vinculin) was reduced after seeding SMC in culture, but was reestablished when the cells reached confluency. Thus, high SMC seeding density is essential but not sufficient to keep vascular SMC cultured in the presence of serum in the contractile phenotype.

Animals↗
PubMed1991

The macrophage as an initiator of atherosclerosis.

1. Heparan sulfate proteoglycan in the basal lamina of smooth muscle cells is important in the maintenance of the 'contractile', high volume fraction of myofilaments (Vvmyo) phenotype. The mechanism by which this occurs may involve the continuous internalization of heparan sulfate by the smooth muscle cells themselves. 2. One macrophage can degrade all the heparan sulfate from three smooth muscle cells by the action of heparan sulfate-degrading enzymes in their lysosomes, thus leaving none available for internalization by the smooth muscle cell until it has synthesized more, and leading to the induction of smooth muscle phenotypic change from a high Vvmyo to a low Vvmyo. 3. In this altered phenotype the smooth muscle cells proliferate in response to mitogens, synthesize large amounts of extracellular matrix and accumulate lipid, all characteristics of the smooth muscle cell in developing atheroma.

Actin Cytoskeleton↗
PubMed1991

Molecular biology of vascular hypertrophy.

In chronic models of hypertension such as the spontaneously hypertensive rat (SHR), thickening of the media of large arteries occurs mainly through smooth muscle cell (SMC) hypertrophy accompanied by DNA replication resulting in large polyploid cells. In resistance vessels of SHR, medial hypertrophy occurs through a hyperplastic response. It has been suggested that this hyperplasia is due to mitogens such as platelet-derived growth factor (PDGF), while the hypertrophied polyploid cells occur from stimulation by angiotensin II from within the vessel wall. Angiotensin II activates many of the same cellular pathways as PDGF, including stimulation of phospholipase C, mobilization of intracellular calcium and activation of Na+/H+ exchange. Both induce transient increases in the proto-oncogenes c-fos and c-myc. However, a possible explanation for the difference in SMC response may be involvement of an intracellular pathway stimulated by PDGF (but not by angiotensin II), such as stimulation of JE (a cytokine-like molecule), which may activate transcriptional events necessary for mitogenesis. In atherosclerosis vascular hypertrophy occurs in the form of focal intimal thickening and results from hyperplasia of diploid SMC and their greatly increased production of extracellular matrix, (particularly collagen) and the accumulation of intra- and extracellular lipid. The SMC involved in atherogenesis are phenotypically modified compared with the SMC of undiseased regions, and amongst other features have a lower volume fraction of myofilaments (Vvmyo). Associated with modulation to a low Vvmyo are increases in SMC expression of mRNA for collagens type I (alpha 1 and alpha 2) and type III (alpha 1), elastin, fibronectin, as well as massive increases in collagen protein (26- to 45-fold), glycosaminoglycans (5-fold), and lipid accumulation (7-fold).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Collagen synthesis by cultured rabbit aortic smooth-muscle cells. Alteration with phenotype.

Enzymically isolated rabbit aortic smooth-muscle cells (SMC) in the first few days of primary culture express a 'contractile phenotype', but with time these cells modulate to a 'synthetic phenotype'. Synthetic-state SMC are able to proliferate, and, provided that they undergo fewer than 5 cumulative population doublings, return to the contractile phenotype after reaching confluency [Campbell, Kocher, Skalli, Gabbiani & Campbell (1989) Arteriosclerosis 9, 633-643]. The present study has determined the synthesis of collagen, at the protein and mRNA levels, by cultured SMC as they undergo a change in phenotypic state. The results show that, upon modulating to the synthetic phenotype, SMC synthesized 25-30 times more collagen than did contractile cells. At the same time, non-collagen-protein synthesis increased only 5-6-fold, indicating a specific stimulation of collagen synthesis. Steady-state mRNA levels are also elevated, with alpha 2(I) and alpha 1(III) mRNA levels 30 times and 20 times higher respectively, probably reflecting increased transcriptional activity. Phenotypic modulation was also associated with an alteration in the relative proportions of type I and III collagens synthesized, contractile SMC synthesizing 78.1 +/- 3.6% (mean +/- S.D.) type I collagen and 17.5 +/- 4.7% type III collagen, and synthetic cells synthesizing 90.3 +/- 2.0% type I collagen and 5.8% +/- 1.8% type III collagen. Enrichment of type I collagen was similarly noted at the mRNA level. On return to the contractile state, at confluency, collagen production and the percentage of type I collagen decreased. This further illustrates the close association between the phenotypic state of SMC and their collagen-biosynthetic phenotype.

Animals↗
PubMed1979

Different nucleosome structures on transcribing and nontranscribing ribosomal gene sequences.

Monomeric DNA lengths from Physarum nuclear chromatin occur in two subunit forms which differ from each other and from higher oligomers of nucleosomes in content of transcribed ribosomal DNA sequences. Labeled DNA restriction fragments from ribosomal RNA coding regions reanneal most rapidly with DNA from a monomeric subunit fraction. A particles, isolated from growing plasmodia and containing 144 base pairs of DNA in an extended conformation. Higher oligomers of nucleosomes are depleted in sequences from transcribing gene regions but are enriched in sequences from the nontranscribed central spacer of the ribosomal DNA palindrome. Nucleosome configuration on two 26S gene intervening sequences resembles that on adjacent coding regions.

Cell Nucleolus↗
PubMed1979

Unique sequence arrangement of ribosomal genes in the palindromic rDNA molecule of Physarum polycephalum.

R-loop and restriction mapping procedures reveal the organization of coding regions at each end of the giant rDNA palindrome of Physarum polycephalum. A 19S coding region of 2.10 +/- 0.21 kb is located at each end of a very long central spacer (35.64 +/- 2.08 kb). An internal spacer of 1.66 +/- 0.12 kb lies distal to the 19S gene. The 5.8S rRNA coding region is located in this spacer. The 26S gene lies distal to the internal spacer. The 26S gene is unusual among those of eukaryotes in that it consists of 3 coding regions (alpha, beta and gamma) interrupted by 2 intervening sequences. The 26S alpha (most central) coding segment of 2.41 +/- 0.33 kb is separated from the 26S beta segment by an intervening sequence of 0.68 +/- 0.13 kb. The 26S beta segment (0.70 +/- 0.11 kb) is separated from the most distal 26S gamma segment (0.59 +/- 0.14 kb) by an intervening sequence of 1.21 +/- 0.14 kb. The 2 intervening sequences are present in at least 88% of ribsomal genes from active plasmodia, indicating that genes containing these sequences are transcribed. The rDNA termini contain a heterogeneous region which varies in length by +/- 300 base pairs.

Base Sequence↗
PubMed1979

Antibody staining of 10-nm (100-A) filaments in cultured smooth, cardiac and skeletal muscle cells.

Antibodies were prepared against the SDS-denatured 10-nm filament protein 'skeletin' extracted from chicken gizzard. The specificity of the antibody to the 10-nm filament protein was shown by immunodiffusion before and after purification of the protein on SDS gels by the enzyme-linked immunoabsorbent assay (ELISA) and by its specific absorption with purified skeletin. In immunofluorescence (where preimmune sera and antigen-absorbed antisera gave negative results), cultured cardiac, skeletal and smooth muscle cells and endothelial cells stained intensely. No staining was observed in fibroblasts present in these cultures, nor was there staining in glial cells or nerve cell bodies and fibres from sympathetic ganglion and Auerbach's plexus cultures. Smooth muscle cells (regardless of their source and phenotypic state) and endothelial cells stained intensely in the perinuclear region and in a fine filamentous network that existed throughout the cytoplasm. In both chick and rat skeletal and cardiac muscle (cultures and frozen sections) filamentous network staining was observed, while in rat muscle the antibody was additionally localized in a regular pattern in the region of the Z-disk, and in the case of cardiac muscle associated with the intercalated disk. The addition of 10(-6) M colchicine to the culture medium of smooth and striated muscle and endothelial cells resulted in an aggregation of the filaments in the nuclear region. Cultured smooth and striated muscle and endothelial cells and freshly isolated smooth muscle cells extracted of actomyosin and tubulin by high and low ionic strength solutions gave a staining pattern similar to non-extracted cells and in the electron microscope, exhibited filaments of predominantly 10 nm diameter.

Animals↗
PubMed1978

Lack of effect of receptor blockers on the formation of long-lasting associations between sympathetic nerves and cardiac muscle cells in vitro.

Sympathetic nerves in vitro form long-lasting, intimate, functional relationships with cardiac muscle cells, but not with fibroblasts. In the presence of an adrenergic beta-blocker and a cholinergic muscarinic blocker, long-lasting relationships still take place. It was concluded that neurotransmitter "receptors" are not involved in the mechanism of "recognition" of cardiac muscle cells by sympathetic nerves.

Animals↗
PubMed1978

Evidence for the presence of non-muscle actin in LW13K2 rat neoplastic cells.

It was demonstrated that I-bands in cultured cardiac muscle cells and non-interrupted fibrils in smooth muscle cells, irrespective of phenotypic state and number of subculture, stained with an antibody directed against native actin from chicken gizzard smooth muscle, but that non-muscle cells in the same cultures did not stain. Neoplastic rat LW13K2 cells, whether confluent or subconfluent, did not stain with the same muscle-actin antibody. This is by no means evidence of a non-muscle origin of LW13K2 cells. However, it does show that these cells express in culture an actin which is not the same as that in muscle cells, and consequently that it can be used as a source of non-muscle actin.

Actins↗