Search PubMed⌕ Search

Biomedical subjects

S Metcalfe

Publications and source records attributed to S Metcalfe.

At least 55 records · Page 3Linked to original sources
PubMed1992

Inhibition of the serine/threonine protein phosphatases PP1 and PP2A in lymphocytes: effect on mRNA levels for interleukin-2, IL-2R alpha, krox-24, p53, hsc70 and cyclophilin.

Lymphocyte activation requires signal transduction mediated by reversible phosphorylation. Changing profiles of phosphorylated intermediates relate to the progressive series of transduction pathways in cells moving from G0 to G1, and thereafter through the cell cycle. We have previously shown that transient inhibition of the serine/threonine protein phosphatases PP1 and PP2A by okadaic acid enhances early mitogenic stimulation. Thus target proteins of PP1/PP2A may be involved in regulation of early mitogenic signalling, with the phosphorylated form(s) being associated with signal enhancement. Later, pathways require dephosphorylation of these proteins, since continuous treatment with okadaic acid blocks lymphocyte progression through the cell cycle. Delayed addition of okadaic acid showed that this blockade occurs between 8 and 24 hr. Here we have furthered these observations to the level of gene induction by measuring messenger RNA (mRNA) levels for the following proteins: interleukin-2 (IL-2) and IL-2R alpha; p53, a tumour suppressor protein; the transcription factor krox-24; and two mediators of protein folding, namely cyclophilin and the heat-shock protein hsc70. An external standard was used to quantitate the mRNA levels per cell. We found that 24 hr exposure to okadaic acid has a general suppressive effect on concanavalin A (Con A)-stimulated gene induction. However, at 4 hr okadaic acid enhanced IL-2 mRNA levels induced by Con A. Moreover, in unstimulated lymphocytes, okadaic acid caused the induction of krox-24, indicating a role for PP1 and PP2A in the regulation of this gene in resting cells.

Amino Acid Isomerases↗
PubMed1991

Serum levels of Mullerian inhibiting substance in boys with cryptorchidism.

Serum levels of Mullerian inhibiting substance (MIS) were measured in boys with cryptorchidism (n = 104) and paired, age-matched controls (n = 104) using an enzyme immunoassay. Control MIS levels were high during the first year of life with a peak level at 4 to 12 months, subsequently diminishing with age. MIS levels in patients with undescended testes also declined with age, although a surge was not found in the first year. Mean MIS concentration of cryptorchid boys was significantly lower than controls (P less than .001). There was a significant reduction of the mean MIS level in children with bilateral cryptorchidism compared with those with unilateral undescended testis (P less than .05). These differences might support the hypothesis that MIS initiates transabdominal testicular descent. However, because most undescended testes are probably the result of anatomical or functional abnormalities during transinguinal testicular descent, differences in MIS levels more likely result from secondary testicular degeneration. In the future, MIS immunoassay should play an important role in the investigation of gonadal function in boys with various genital disorders, including cryptorchidism.

Adolescent↗
PubMed1990

Phosphatases PP1 and PP2A act after the G0/G1 interface in lymphocyte activation.

An understanding of the progressive events required for lymphocyte activation is a prerequisite to understanding the molecular mechanism of immunosuppressive reagents, and is of central relevance to autoimmunity and immune tolerance. Although reversible phosphorylation is a major control mechanism in T cell activation, few facts are known about phosphatases in T cells. It has recently become possible to block selectively the serine/threonine specific protein phosphatases PP1 and PP2A by okadaic acid, a C38 polyether fatty acid produced by dinoflagellates. Here we have used this new and powerful biochemical probe to identify and quantify the activities of PP1 and PP2A at various times during lymphocyte activation. The selected model was mouse T cell activation by concanavalin A because this gave a reproducible experimental system that allowed large scale experiments in defined, serum-free conditions. Our results show the following: (1) levels of PP1 and PP2A in lymphocytes appear to be unusually low, effects being measured at 10 nM okadaic acid compared to 1 microM reported for other cell types; (2) the okadaic acid effect was readily reversible; (3) okadaic acid stimulated mitogenesis when present in early G1 but inhibited mitogenesis in late G1; (4) levels of PP1 and PP2A remained relatively constant over the first 7 h following stimulation; (5) lymphocytes activated in the presence of okadaic acid became resistant to subsequent treatment with FK506; and (6) combined or consecutive treatment with okadaic acid and FK506 resulted in additive drug effects. We conclude that PP1 and PP2A are not involved in the G0-G1 transition as defined by the FK506-sensitive step.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The nasopharynx and under-aeration of the middle-ear.

This study compared nasopharyngeal sepsis with under-aeration ear disease. Nasopharyngeal sepsis was assessed by culture taken directly from the surface of removed adenoid tissue. 156 cases were studied; 100 showed varying degrees of middle-ear under-aeration and 56 had no active ear disease or history of it. In addition, an assessment of post-nasal obstruction was made and this too was compared with middle-ear status. The conclusions suggested that, whilst normal ears can exist in the presence of accepted nasal pathogens, diseased ears are rarely seen in the absence of nasal sepsis. The degree of post-nasal obstruction seemed irrelevant. The commonest nasopharyngeal pathogen was Haemophilus influenzae and when found alone this had a particularly detrimental affect on middle-ear aeration, causing a significant incidence of mucoid middle-ear effusion in this group.

Adolescent↗
PubMed1987

Simple method of monitoring colonising microbial load in chronic bronchial sepsis: pilot comparison of reduction in colonising microbial load with antibiotics given intermittently and continuously.

Aerobic and anaerobic culture of sputum on selective bacteriological media, combined with a new method of plating and plate reading, permitted rapid identification and quantitation of three genera of bacteria commonly associated with chronic bronchial sepsis (Haemophilus spp, Pseudomonas aeruginosa, and Staphylococcus aureus) and avoided time consuming serial dilution of sputum and subculture of organisms. The accuracy of this new technique was assessed in patients with chronic bronchial sepsis and was used to detect changes in the colonising microbial load of Haemophilus spp and Ps aeruginosa in patients with bronchiectasis receiving one of three different antibiotic regimens: intermittent seven day courses of amoxycillin for exacerbations; or a six month course of continuous oral or nebulised amoxycillin. The colonising microbial load of Haemophilus spp was reduced only temporarily (+++ to ++) after each intermittent course of antibiotic, but a sustained and greater reduction in the colonising microbial load of both Haemophilus spp (+++ to +) and antibiotic resistant P aeruginosa (+++ to +) was seen during both continuous treatments. Sputum purulence decreased in parallel with colonising microbial load, reflecting a reduction in host inflammatory response to the colonising microbial load.

Amoxicillin↗
PubMed1987

Testicular cancer: B5, a new tumour marker.

Tumour markers which occur in blood or urine are of value in the management of cancer patients because they allow disease status to be monitored by non-invasive techniques at low cost. An antigen, 'B5', on erythrocytes has been shown to become enhanced when cancer develops, regardless of tumour type, and thus the B5 antigen may be utilised as a 'universal' tumour marker. A simple haemagglutination test gives reliable quantitative assessment of the B5 marker status. Here, serial measurements of B5 status in 63 patients presenting with testicular cancer confirms a preliminary finding that both teratoma and seminoma are marked by B5. Of 28 patients with seminoma, 2 had a raised BHCG, whilst 20 (71%) were B5-positive, including 13 of 20 patients with stage-1 disease. After successful treatment, the large majority of patients showed a significant downward shift in their B5 status. Control subjects differed in that their B5 status remained constant and was often also very weak.

Adult↗
PubMed1984

Identification of synergistic combinations of spirogermanium with 5-fluorouracil or cisplatin using a range of human tumour cell lines in vitro.

A series of continuous human tumour cell lines, derived from various tumour types, were used to establish whether the combination of spirogermanium (SP) with other 'standard' antitumour drugs proved superior to these as single agents in reducing cell survival in vitro. A non-cytotoxic concentration of SP was selected and when combined with a range of concentrations of cisplatin or 5-fluorouracil (5-FU), definite synergistic cell kill was noted in all lines tested. In contrast, the combination of SP with various other antitumor drugs, including adriamycin, methotrexate and the vinca alkaloids and with X-irradiation did not enhance cytotoxicity. These pre-clinical in vitro studies suggest that benefit may accrue from combining SP with either 5-FU or cisplatin and provide a basis for their clinical evaluation in colo-rectal tumours or transitional cell cancer of the bladder, respectively.

Antineoplastic Agents↗
PubMed1984

A new indicator of human malignant tumour.

In haemagglutination tests we have found that the monoclonal antibody B5 discriminates between erythrocytes from patients with malignant cancer (total 386; greater than 80% B5 positive) and individuals with no known tumour (total 247; less than 20% B5 positive). The B5 antigen detected on intact erythrocytes is a tightly bound surface component which does not appear to be derived from the plasma. The B5 antigen is not T, Tn, Ca1, CEA or the Forsmann antigen; nor is it related to any of the major blood group antigens. Abnormal levels of surface B5 are found on erythrocytes from patients with a great diversity of tumours and this fact presents B5 as an indirect marker of malignancy. Successful eradication of tumour is associated with a switch from positive to negative B5 haemagglutination. We believe that B5 is a valuable addition to the few useful tumour markers already employed for monitoring tumour status.

Antibodies, Monoclonal↗