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S J Powis

Publications and source records attributed to S J Powis.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1990

Concerted evolution of class I genes in the major histocompatibility complex of murine rodents.

Full-length cDNA sequences of two class I major histocompatibility complex molecules from the DA strain of Rattus norvegicus are reported. One codes for the classical class I restriction element RT1.Aa, which maps to the locus in the rat major histocompatibility complex homologous to H-2K in the mouse. The other probably codes for a soluble nonclassical class I molecule present in DA rat serum; a short deletion in the fifth exon implies that the translated product will terminate in the membrane-spanning region. These sequences have been compared with mouse classical class I sequences as well as with three published rat class I cDNA partial sequences. The results show, first, that "locus-specific" substitutions from the H-2K, H-2D, and H-2L data set are scrambled in the RT1.Aa molecule; a majority of these substitutions have H-2D/L-specific features. Second, the data show that the four rat sequences are strikingly similar to one another regardless of locus or haplotype of origin; they share a number of apparently species-specific features that distinguish them all from mouse classical class I sequences, which likewise share distinctive features of their own. The results suggest that segmental sequence exchange plays a major role in determining the evolution of sequence in class I major histocompatibility complex molecules.

Amino Acid Sequence↗
PubMed1989

A trans-acting major histocompatibility complex-linked gene whose alleles determine gain and loss changes in the antigenic structure of a classical class I molecule.

The RT1.A locus of the rat MHC encodes the H chain of the single classical class I molecule of this species. One of the alleles of this polymorphic locus, RT1.Aa, is present in several laboratory inbred, congenic, and MHC recombinant rat strains. Studies of the RT1.Aa class I molecule from a number of these strains as a target for CTL show that its antigenicity, both as an alloantigen and a restricting element, is subject to gain and loss alterations by the action of a gene mapping in the MHC to the right of RT1.A. This locus is apparently present in two allelic forms (one possibly a null allele) corresponding to the presence or absence of a dominant transacting modifier, and has been named class I modification, or cim. The antigenic change brought about by cim is scarcely detectable serologically but highly immunogenic for CTL. Biochemical investigations show that cim affects the post-translational modification of RT1.Aa.

Alleles↗
PubMed1989

Anticoagulation in abdominal aortic aneurysm surgery: the approach of vascular surgeons in Great Britain and Ireland.

A questionnaire was sent to 283 vascular surgeons in Great Britain and Ireland regarding their use of heparin in elective abdominal aortic aneurysm surgery. The answers form the basis of this study and show that there is great variation. The majority of surgeons routinely anticoagulate their patients peroperatively. Heparin is usually given intravenously--most giving the drug 2 to 3 min prior to cross clamping the aorta. Approximately half of the respondents use the same dose in all patients, whilst the remainder vary the dose, usually on the basis of weight or "size". Most surgeons use 5000 units but the range of dose varies from 400 to 20,000 units. Just under a quarter of surgeons continue to anticoagulate their patients postoperatively, almost all of these using subcutaneous heparin for prophylaxis against deep vein thrombosis. Only approximately 10% of surgeons routinely reverse the heparin with protamine.

Aorta, Abdominal↗
PubMed1988

A case of metachronous aneurysm of the infrarenal abdominal aorta.

The case history of an 84 year old woman presenting with a metachronous aneurysm of the infrarenal abdominal aorta is presented. At operation this second aneurysm was replaced by a further straight tube Dacron inlay graft. This report raises the important question as to whether the whole of the infrarenal aorta should be replaced when resecting an infrarenal abdominal aortic aneurysm, rather than the more conventional approach of suturing the graft to the neck of the aneurysm above and the aortic bifurcation below.

Aged↗
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↗