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S J Powis

Publications and source records attributed to S J Powis.

17 recordsLinked to original sources
PubMed1992

Proteasome subunits encoded by the major histocompatibility complex are not essential for antigen presentation.

Major histocompatibility complex (MHC) class I molecules bind and deliver peptides derived from endogenously synthesized proteins to the cell surface for survey by cytotoxic T lymphocytes. It is believed that endogenous antigens are generally degraded in the cytosol, the resulting peptides being translocated into the endoplasmic reticulum where they bind to MHC class I molecules. Transporters containing an ATP-binding cassette encoded by the MHC class II region seem to be responsible for this transport. Genes coding for two subunits of the '20S' proteasome (a multicatalytic proteinase) have been found in the vicinity of the two transporter genes in the MHC class II region, indicating that the proteasome could be the unknown proteolytic entity in the cytosol involved in the generation of MHC class I-binding peptides. By introducing rat genes encoding the MHC-linked transporters into a human cell line lacking both transporter and proteasome subunit genes, we show here that the MHC-encoded proteasome subunit are not essential for stable MHC class I surface expression, or for processing and presentation of antigenic peptides from influenza virus and an intracellular protein.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Effect of polymorphism of an MHC-linked transporter on the peptides assembled in a class I molecule.

Short antigenic peptides bound in the groove of class I major histocompatibility complex molecules enable T cells to detect intracellular pathogens. It has been assumed that structural features of the class I molecule alone select which peptides are bound. It is now demonstrated that a complex polymorphism in one of the major histocompatibility complex-encoded putative peptide-transporter genes is associated with an altered spectrum of bound peptides.

Alleles↗
PubMed1992

Subsets of null and gamma delta T-cell receptor+ T lymphocytes in the blood of young pigs identified by specific monoclonal antibodies.

Rat monoclonal antibodies (mAb) against isolated pig Null T cells were derived using a novel two-colour cytofluorometric assay. One (MAC320) identified all blood CD2-sIg- 'Null' cells (present at up to approximately 6 x 10(6)/ml). Another type (MAC319 and MAC318) identified a subset comprising approximately 60% or approximately 30% of the Null cell population. This percentage appears genetically determined. This subset partially overlapped with a gamma delta T-cell receptor+ (TcR+) population which consisted of approximately 40% of Null T cells. The antibodies did not react with other leucocyte or lymphocyte populations. In non-reducing conditions, MAC320 precipitated two molecules at approximately 270,000-280,000 MW in SDS-PAGE; the larger of which was also precipitated by MAC319 (and MAC318, which binds to the same epitope). Under reducing conditions, MAC320 immunoprecipitated two or three polypeptide chains at approximately 130,000-160,000 MW; MAC319 precipitated only the largest of these polypeptides. The large MAC319+ MAC320+ molecule on one subset is removed by bromelain treatment; the smaller MAC319- MAC320+ molecule on the remaining Null cells is not bromelain sensitive. Several properties of this new antigen complex specific to pig Null T cells show that it is distinct from the ruminant T19 complex.

Animals↗
PubMed1991

The major histocompatibility complex class II-linked cim locus controls the kinetics of intracellular transport of a classical class I molecule.

The dominant trans-acting major histocompatibility complex (MHC)-linked class I modifier (cim) locus, previously recognized through its ability to determine altered alloantigenicity of a rat class I molecule, RT1.A3, is shown here to influence class I intracellular transport. The MHC recombinant laboratory rat strains PVG.R1 and PVG.R8 display unusually long retention of RT1.Aa within the endoplasmic reticulum or cis-Golgi. In appropriate F1 hybrid cells heterozygous for RT1.Aa and another class I MHC allele, RT1.Ac, only the RT1.Aa protein is subject to slow transport. The cim gene product therefore shows class I allele specificity in its action, cim appears to be a polymorphic locus whose product is directly involved in the processes of class I MHC assembly and/or intracellular transport.

Animals↗
PubMed1991

Cim: an MHC class II-linked allelism affecting the antigenicity of a classical class I molecule for T lymphocytes.

Two alleles at the major histocompatibility complex (MHC)-linked locus cim determine "gain and loss" changes in the rat RT1.Aa class I molecule which affect its structure both as an alloantigen and as a restriction element. Alleles at the cim locus also influence the post-translational modification of RT1.Aa. These effects may reflect the participation of the cim gene product in the processes of peptide loading or assembly of RT1.Aa. In this study we have used the discriminating RT1.Aa-specific monoclonal antibody JY3/84, as well as cytotoxic T cells raised in appropriate combinations, to determine the cim alleles of eight haplotypes in 15 independent inbred strains of rat. We have also employed the same techniques to analyse a panel of F1 hybrid animals derived from various MHC recombinant strains. These experiments map the cim locus to the class II region of RT1, probably between the DP-related genes (RT1.H) and the DQ-related RT1.B alpha.

Alleles↗
PubMed1977

Prophylactic use of cephazolin against wound sepsis after cholecystectomy.

A trial of antibiotic prophylaxis with cephazolin against postoperative wound sepsis was carried out on 201 patients undergoing routine cholecystectomy. Wound sepsis occurred in 11 out of 65 controls (16.9%), who were not given the drug; two out of 63 patients (3.2%) given a single dose preoperatively; and four out of 73 patients (5.5%) given the single preoperative dose plus a five-day course postoperatively. The difference between the controls and patients given the single preoperative dose was significant.

Cefazolin↗
PubMed1977

The influence of biliary disease on the excretion of cefazolin in human bile.

Forty-five patients with varying biliary pathology were injected with one gram of intramuscular cefazolin sodium prior to surgery. Serum, gallbladder bile, and common duct bile levels were measured. The type of biliary disease did not influence serum levels (mean, 29 mug per milliliter) which reached a peak one hour after injection. Mean common duct bile levels were reduced from 52 mug per milliliter in nonjaundiced patients to 4 mug per milliliter in those with jaundice (p less than 0.001). Patients with radiologically functioning gallbladders had significantly higher mean gallbladder bile levels (21 mug per milliliter; p less than 0.005). Surprisingly, the mean gallbladder bile level in acute cholecystitis was 25 mug per milliliter. As the minimum inhibitory concentration of cefazolin for organisms commonly found in the bile is 0.5 to 6 mug per milliliter, we suggest that cefazolin sodium may be of value in the treatment of biliary disease, particularly acute cholecystitis.

Bile↗
PubMed1976

Preoperative skin preparation: clinical evaluation of depilatory cream.

Preoperative hair removal by a depilatory cream was compared with routine shaving. Although the incidence of wound infection was similar in both groups, cream depilation was found to be better. It was effective, atraumatic, non-toxic, and could be self-administered. Furthermore, it could be used safely on granulating wounds and did not support bacterial growth. Depilation was associated with a significant reduction in skin surface bacteria and proved to be cheaper than shaving.

Calcium Hydroxide↗
PubMed1975

Preparation of the bowel by whole-gut irrigation.

Experience with whole-gut irrigation as a method of bowel preparation in eightyone patients is described. The mean (+/-S.D.) weight-gain during irrigation was 1-9 +/- 0-8 kg; potassium losses in the effluent after one hour (4-0 +/- 2-5 g) were not significantly altered by adding potassium chloride to the irrigant. Eight irrigations were unsatisfactory, three being due to unrecognised obstructive neoplasms. The method provided excellent preparation for colonoscopy and large-bowel resection with anastomosis and was well tolerated by the patients.

Aged↗
PubMedDate not supplied

Restoration of antigen presentation to the mutant cell line RMA-S by an MHC-linked transporter.

In mammalian cells, short peptides derived from intracellular proteins are displayed on the cell membrane associated with class I molecules of the major histocompatibility complex (MHC). The surface presentation of class I-peptide complexes presumably alerts the immune system to intracellular viral protein synthesis. Peptides derived from the cytosol must reach the cisternae of the endoplasmic reticulum where they are required for the assembly of stable class I molecules, and it has been proposed that the products of the two MHC-encoded ATP-binding cassette (ABC) transporter genes function to deliver the peptides across the membrane of the endoplasmic reticulum. This idea is supported by experiments in which transfection of a human cell line defective in class I expression with a complementary DNA of one of these genes restored cell surface expression levels. Here we show that the complete phenotype of the mouse mutant cell line RMA-S, in which lack of surface expression of stable class I molecules correlates with an inability to present viral peptides originating in the cytosol, is repaired by the cDNA of the other transporter gene. These results are consistent with the possibility that the two transporter polypeptides form a heterodimer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMedDate not supplied

Renal function following aortic surgery.

Following aortic surgery nearly two thirds of patients (65%) have demonstrable renal tubular damage, which is related to the disease process (aneurysmal disease being more commonly associated with renal damage than occlusive disease), the duration of aortic cross clamping and the volume of blood transfused. No relationship appears to exist between age, pre-operative hypertension, or chronic renal failure, and post operative renal tubular function.

Acute Kidney Injury↗