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Biomedical subjects

M M Thompson

Publications and source records attributed to M M Thompson.

At least 19 recordsLinked to original sources
PubMed1992

Elements of the smooth muscle alpha-actin promoter required in cis for transcriptional activation in smooth muscle. Evidence for cell type-specific regulation.

To assess the role of cis-acting elements within the smooth muscle alpha-actin gene in smooth muscle cells (SMC), we transfected chicken smooth muscle alpha-actin promoter-chloramphenicol acetyltransferase gene fusion plasmids into SMC derived from rat and chicken aortas. In marked contrast to effects in chicken skeletal myoblasts and fibroblasts, p122CAT (positions -122 to +19), containing two conserved CArG elements, elicited a modest increase in chloramphenicol acetyltransferase reporter activity in chicken SMC. Addition of upstream sequences between -122 and -151 (p151CAT) increased activity in adult chicken SMC. Addition of sequence between positions -151 and -257 (p257CAT) resulted in a 7-fold increase in chloramphenicol acetyltransferase activity over that of p151CAT in rat SMC, but not in chicken SMC. A genomic clone encoding the rat smooth muscle alpha-actin gene was isolated, and the 5'-flanking region was partially characterized. Comparison of primary sequence between rat and chicken promoters showed a conserved E box motif at position -214 in the chicken gene and at position -213 in the rat gene. Results of these studies demonstrate that regions upstream of the conserved CArG elements exert potent regulatory effects on transcription and that SMC require different cis-acting elements than other cell types to transcriptionally regulate this gene.

Actins↗
PubMed1992

Audit of general practitioner referrals to an acute surgical unit.

One hundred and ninety referrals from general practitioners (GPs) to an acute surgical unit were audited prospectively over a 6-month period. A total of 78 admissions were considered inappropriate of whom 23 patients were thought to have needed neither surgical admission nor opinion. The estimated expenditure resulting from admissions deemed inappropriate was 25,000 pounds. The daytime commitments of more senior staff on routine emergency duty days meant they were not easily available to deal with calls concerning acute GP referrals. These admissions reduce the efficiency of the service; this may be improved by a senior member of the team accepting and screening GP calls.

Acute Disease↗
PubMed1992

Peripheral tuberculous lymphadenopathy: a review of 67 cases.

Peripheral tuberculous lymphadenopathy is the commonest form of extrapulmonary tuberculosis. Sixty-seven patients with peripheral tuberculous lymphadenopathy who presented to general surgeons and underwent lymph node biopsy between 1979 and 1989 are reviewed. Fifty-four patients (81 per cent) were of Indian subcontinent ethnic origin and 13 (19 per cent) were of white ethnic origin. The sites most commonly affected were the cervical lymph nodes. Biopsy specimens obtained by open operation were sent for microbiological examination in all but 13 cases, of whom seven were patients of white ethnic origin. Tuberculous lymphadenopathy remains an important differential diagnosis of cervical lymphadenopathy and it is essential that peripheral lymph node biopsies are examined both histologically and microbiologically.

Adult↗
PubMed1992

Role of sequential leucocyte counts and C-reactive protein measurements in acute appendicitis.

The accurate clinical diagnosis of acute appendicitis is difficult, and many techniques have been suggested to improve diagnostic accuracy such as laparoscopy, ultrasonography and barium enema examination. In this study serial total leucocyte counts and serial C-reactive protein (CRP) concentrations in acute appendicitis were measured. The sensitivity and specificity of serial leucocyte counts in acute appendicitis were 92 and 100 per cent, and for CRP concentrations 69 and 75 per cent, respectively. The sensitivity and specificity of serial total leucocyte counts fulfilled the criteria for a diagnostic test. It is suggested that in patients with equivocal clinical findings, clinical observation combined with serial leucocyte counts may improve decision making.

Acute Disease↗
PubMed1992

Presentation of abdominal tuberculosis to general surgeons.

Abdominal tuberculosis (TB) continues to give rise to diagnostic and therapeutic challenges. A total of 24 patients with abdominal TB who presented to general surgeons over a 9-year period have been reviewed. Most (92 per cent) of these patients were Asian; only one had a past history of pulmonary TB. The most common presenting complaint was abdominal pain in 21 patients (88 per cent) with the associated symptoms of weight loss in 18 (75 per cent), anorexia in 15 (62 per cent) and night sweats in 13 (54 per cent). A tissue diagnosis was obtained in 18 patients (75 per cent) and 17 patients (71 per cent) underwent laparotomy. These results show that the diagnosis of abdominal TB is still difficult to establish, and that many patients undergo laparotomy despite the existence of less invasive diagnostic procedures.

Abdominal Pain↗
PubMed1992

Screening urine of 3-week-old newborns: transient methylmalonic and hydroxyphenyllactic aciduria.

Urinary methylmalonic acid (MMA) and 4-hydroxyphenyllactic acid (HPL) have been determined in 3345 and 2498 3-week-old newborns, respectively. Urine was collected onto filter paper and assayed by a rapid gas chromatography-mass spectrometry method. Forty-six infants (1.7%) had elevated MMA levels (greater than 58.5 micrograms/mg creatinine, means + 5 SD) and 31 infants (1.2%) had elevated levels of HPL (greater than 87.7 micrograms/mg creatinine, means + 5 SD). Fifteen infants with elevated values of MMA were retested from one to several months after the first test. In 12 infants the MMA levels normalized, while in the remaining three, elevated methylmalonic acid persisted. Nine infants with elevated values of HPL were retested, and in all except one, HPL levels normalized. No access to clinical evaluation of the infants was available. Transient methylmalonic aciduria and transient tyrosyluria affect a substantial number of infants and the clinical significance of this phenomenon has yet to be determined.

Humans↗
PubMed1992

Endothelial cell seeding of damaged native vascular surfaces: prostacyclin production.

Endothelial cell seeding has been successful in reducing the thrombogenicity of prosthetic vascular grafts in animal and clinical studies. The reduction in thrombogenicity may be attributed to the intrinsic properties of endothelial cells themselves, and their ability to produce anti-thrombogenic mediators such as prostacyclin, and endothelium-derived relaxing factor. Endothelial seeding of damaged vascular surfaces produced during percutaneous transluminal angioplasty and endarterectomy is an attractive possibility due to the excellent attachment characteristics of the sub-endothelial tissue exposed during these procedures. The ability of endothelial seeded damaged vascular surfaces to produce prostacyclin was measured in an in vitro model of vascular injury. Endothelial-seeded damaged surfaces produced significantly higher prostacyclin release than did vessels damaged by balloon dilatation (265.5 pg cm-2 min-1 and 87.5 pg cm-2 min-1 respectively). This study provides evidence that endothelial seeding of damaged native vascular surfaces is technically feasible and that seeding may reduce the thrombogenicity of vascular surfaces following balloon dilatation.

Angioplasty, Balloon↗
PubMed1992

Platelet-derived growth factor-BB-induced suppression of smooth muscle cell differentiation.

Previously, we demonstrated that treatment of postconfluent quiescent rat aortic smooth muscle cells (SMCs) with platelet-derived growth factor (PDGF)-BB dramatically reduced smooth muscle (SM) alpha-actin synthesis. In the present studies, we focused on the expression of two other SM-specific proteins, SM myosin heavy chain (SM-MHC) and SM alpha-tropomyosin (SM-alpha TM), to determine whether the actions of PDGF-BB were specific to SM alpha-actin or represented a global ability of PDGF-BB to inhibit expression of cell-specific proteins characteristic of differentiated SMCs. SM-MHC and SM-alpha TM expression were assessed by one- or two-dimensional gel electrophoretic analysis of proteins from cells labeled with [35S]methionine, as well as by Northern analysis of mRNA levels. Synthesis of both SM-specific proteins was decreased by 50-70% in PDGF-BB--treated cells as compared with cells treated with PDGF vehicle. Treatment of cells with 10% fetal bovine serum, which produced a mitogenic effect equivalent to that of PDGF-BB, decreased SM-MHC synthesis by 40% but increased SM-alpha TM synthesis. SM-MHC and SM-alpha TM mRNA expression was decreased by 80% at 24 hours in PDGF-BB--treated postconfluent SMCs, whereas treatment with 10% fetal bovine serum did not decrease the expression of SM-alpha TM mRNA but did inhibit SM-MHC mRNA expression by 36%. Consistent with the absence of detectable PDGF alpha-receptors on these cells, PDGF-AA had no effect on either mitogenesis or expression of SM-MHC or SM-alpha TM.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Therapeutic options in subclavian artery disease.

Chronic ischaemia of the upper limb secondary to subclavian artery disease is uncommon. These patients may present with a variety of symptoms caused by cerebrovascular or upper limb hypoperfusion. If these symptoms are severe, revascularization may be required. This may be accomplished by percutaneous transluminal angioplasty or surgery. The experience of the management of these patients has been reviewed to document their presentation, treatment and outcome.

Adult↗
PubMed1991

A case of dextrocardia with normal situs.

We report here a case of dextrocardia with normal situs in an 81-year-old man who died from non-pulmonary causes. Removal of the chest wall revealed a large, but otherwise anatomically normal, left lung occupying the entire left hemithorax and extending across the midline to overlap the left border of the heart which was positioned in the right hemithorax. The gross anatomy of the heart was normal save its position and the presence of only 2 pulmonary veins. Dissection of the heart showed all chambers in their classically described position, and there were no valvular defects. The anatomy of the great vessels was also normal. The right lung was hypoplastic and lay posterior to the heart. This lung lacked any lobular structure, but the presence of carbon particles throughout it suggested that it was capable of normal inflation.

Aged↗
PubMed1991

Mechanisms of angiotensin II- and arginine vasopressin-induced increases in protein synthesis and content in cultured rat aortic smooth muscle cells. Evidence for selective increases in smooth muscle isoactin expression.

Previous studies from this laboratory have demonstrated that angiotensin II (Ang II) and arginine vasopressin (AVP) are potent hypertrophic agents in cultured rat aortic smooth muscle cells. The present study identified major proteins that accumulate in Ang II-induced and AVP-induced hypertrophic cells and initiated studies of the mechanisms that contribute to their accumulation. Smooth muscle cell hypertrophy induced by Ang II and/or AVP (1 microM each) was associated with widespread increases in the content of many cellular proteins that were resolved by one- and two-dimensional gel electrophoresis. However, increases were also selective in nature, with increases in certain individual proteins, including actin (twofold to threefold), vimentin (2.5-fold to sevenfold), tropomyosin (threefold to sixfold), and myosin heavy chain, far exceeding overall increases in cellular protein content (20-40%). Increases in actin content were due largely to increased expression of smooth muscle alpha-actin (3.6- to 7.5-fold), as opposed to nonmuscle beta-actin (1.7- to 2.5-fold). Increases in smooth muscle alpha-actin were accompanied by a fivefold to eightfold increases in smooth muscle alpha-actin mRNA, indicating that these changes were not due exclusively to translational controls. Results demonstrate that contractile agonist-induced hypertrophy in cultured smooth muscle cells is due, in part, to increased expression of smooth muscle contractile proteins. Furthermore, the fact that Ang II and AVP induced selective increases in smooth muscle alpha-actin suggests that these agonists may not only regulate growth of vascular smooth muscle but may also promote expression of smooth muscle-specific contractile proteins during differentiation of vascular smooth muscle.

Actins↗
PubMed1989

Differential effect of platelet-derived growth factor- versus serum-induced growth on smooth muscle alpha-actin and nonmuscle beta-actin mRNA expression in cultured rat aortic smooth muscle cells.

Previous studies have demonstrated that rat aortic smooth muscle cells (SMC) show marked changes in smooth muscle (SM) alpha-actin content and fractional synthesis as a function of cell density and growth (Owens, G. K., Loeb, A., Gordon, D., and Thompson, M. M. (1986) J. Cell Biol. 102, 343-352; Blank, R., Thompson, M. M., and Owens, G. K. (1988) J. Cell Biol. 107, 299-306). Results of this study show that, although there is a 6-fold increase in SM alpha-actin content in postconfluent density arrested cultures as compared to proliferating subconfluent cultures, SM alpha-actin mRNA levels are not different between these cells. This suggests that the SM alpha-actin gene is constitutively active under both of these conditions and that accumulation of SM alpha-actin in postconfluent cells is due to translational and/or post-translational controls. The relationship between growth and cytodifferentiation was further explored by examining the effects of platelet-derived growth factor (PDGF)- or serum-induced growth on actin expression in postconfluent, quiescent cultures maintained in a defined serum-free media. Although both factors have been shown to stimulate proliferation and decrease fractional SM alpha-actin synthesis (Blank et al., 1988), their effects on actin mRNA levels were quite different. PDGF was found to induce a dramatic drop in SM alpha-actin steady state mRNA level but had no effect on nonmuscle beta-actin mRNA level. In contrast, serum stimulation was shown to increase nonmuscle beta-actin mRNA level, whereas SM alpha-actin mRNA level remained constant. Taken together these results indicate that PDGF is a specific and potent repressor of SM alpha-actin expression in vascular SMC and implicate a possible developmental role for PDGF in control of SMC differentiation. In addition, the observation that the level of SM alpha-actin mRNA is unaltered in serum-stimulated cells indicates that an absolute decrease in SM alpha-actin mRNA is not obligatory for cell cycle entrance.

Actins↗
PubMed1989

Heme inhibits cartilage metabolism and growth in vitro.

The present study was designed to investigate the potential role of heme as a direct inhibitor of cartilage metabolism and growth. We used the embryonic chick pelvic rudiment bioassays and the hypophysectomized rat cartilage sulfation bioassay, both sensitive to growth factors and growth inhibitors. In the chick bioassay pelvic rudiment growth was inhibited when heme was added to the culture medium at 0.1 mmol/L (after five days in culture, cartilage weight 224% +/- 11% of initial with normal serum, but 141% +/- 3% of initial with serum plus heme 0.25 mmol/L); the heme-induced growth inhibition was promptly reversible when cartilages were placed in heme-free medium. This was due, at least in part, to heme-induced inhibition of (1) [35S] sulfate incorporation into proteoglycans by as little as 0.05 mmol/L heme (66% +/- 5% of assay buffer); (2) [14C] leucine incorporation into proteins by greater than or equal to 0.05 mmol/L heme (85% +/- 6% of assay buffer); and (3) [3H] uridine incorporation by greater than or equal to 0.10 mmol/L heme (50% +/- 4% of assay buffer). In the rat cartilage sulfation bioassay (the literature "standard" bioassay for skeletal growth studies) a dose-dependent inhibition of [35S] sulfate incorporation occurred with greater than or equal to 0.01 mmol/L added heme (82% +/- 3% of assay buffer). Heme caused a dose-dependent and reversible inhibition of cartilage metabolism and growth, and it may have a novel role in the pathophysiology of growth retardation associated with some chronic disease.

Animals↗