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Biomedical subjects

P Penfold

Publications and source records attributed to P Penfold.

At least 19 recordsLinked to original sources
PubMed2001

Glyt-1 expression in cultured human Müller cells and intact retinae.

In this study, we demonstrate that Müller cells cultured from human retinas are capable of strongly expressing the glycine transporter Glyt-1 as assessed by immunocytochemistry. By contrast, intact normal and pathological human retinas exhibit Glyt-1 immunoreactivity only in neurons. These data suggest that Glyt-1 expression in cultured Müller cells is an epiphenomenon associated with culturing in vitro, rather than a normal physiological or even pathophysiological phenomenon in vivo.

Aged↗
PubMed2000

Pre-admission clerking of urology patients by nurses.

Pre-admission clerking by nurse specialists is as effective as that by medical staff in preventing cancellation of elective surgery. Patients assessed at a pre-admission clinic by nurses developed fewer postoperative complications.

Aged↗
PubMed1994

Crystallization and preliminary X-ray diffraction studies of the soluble 14 kDa beta-galactoside-binding lectin from bovine heart.

The soluble 14 kDa beta-galactoside-binding lectin from bovine heart, a member of the S-type lectin family, has been crystallized in a form suitable for X-ray diffraction analysis. The crystals, in the absence of a saccharide ligand, diffract beyond 2.5 A resolution. They are obtained from polyethylene glycol 6000 at pH 6.0. Crystals grow as monoclinic plates, space group P2(1), with cell dimensions: a = 35.47 A, b = 64.33 A, c = 58.78 A and beta = 91.7 degrees. The asymmetric unit contains two molecules related by a 2-fold non-crystallographic axis. Two lectin monomers in the asymmetric unit give a Vm of 2.4 A3/Da, i.e. a solvent content of approximately 50%. The complex of lectin with the saccharide ligand, N-acetyllactosamine, crystallizes in the space group P2(1)2(1)2 with cell dimensions: a = 63.55 A, b = 82.13 A and c = 62.39 A. Crystals of this complex diffract beyond 2.0 A resolution. Two complexes in the asymmetric unit lead to a Vm value of 2.8 A3/Da (57% solvent).

Amino Sugars↗
PubMed1994

Immunohistochemistry study of the glaucomatous and normal human trabecular meshwork.

Although class II-expressing cells have been reported previously in the human trabecular meshwork (HTM), the exact identity of these cells and their possible role in the normal and the pathological state remains unclear. Preliminary results suggest increased human leucocyte antigen (HLA)-DR expression in the glaucomatous TM. To investigate this possibility, 20 trabeculectomy specimens obtained from patients with primary open-angle glaucoma (POAG) were examined immunohistochemically for HLA-DR, leucocyte common antigen (LCA; CD45) and a macrophage marker (CD68). The patients varied in age from 42 to 86 years (average, 69 years). The degree of antibody staining in the TM was compared with that of 20 human control eyes obtained from an eye bank less than 24 h after death. The donors varied in age from 47 to 91 years (average, 69 years); there was no known history of eye disease amongst the control group. Evaluation of specimen was performed by two observers using a grading system ranging from negative (0) to strongly positive (3) and by computer-aided optic densitometry. HLA-DR-positive cells were present in both the normal and the glaucomatous TM. Occasional cells stained for LCA and CD68 in the TM of both groups. Subpopulations of the HLA-DR-staining cells were apparent on serial sectioning. An age effect on antigen staining was not observed; postmortem delay of greater than 48 h resulted in decreased specimen antigenicity. Both evaluation techniques failed to reveal a significant difference in HLA-DR, LCA or CD68 staining between the glaucomatous and the normal TM.

Adult↗
PubMed1991

Studies of the binding specificity of the soluble 14,000-dalton bovine heart muscle lectin using immobilised glycolipids and neoglycolipids.

The aim of the present study has been to investigate the binding specificity of the soluble 14,000-dalton lectin of bovine heart muscle towards immobilised oligosaccharides in clustered form. To this end, chromatogram overlay assays and quantitative plastic-microwell-binding assays have been performed using several natural glycolipids and neoglycolipids containing one or more of the disaccharide units, beta-D-Galp-(1----4 or 3)-D-GlcNAc or beta-D-Galp-(1----4)-D-Glc and related structures. The microwell assay gave the most consistent results. It was observed that for binding by the soluble lectin the optimal sequence, which is beta-D-Galp-(1----4 or 3)-D-GlcNAc, must occur at the nonreducing end of longer oligosaccharides when linked to lipid. These oligosaccharides may be of poly(N-acetyllactosamine) type or they may be mono- or multi-antennary, complex-type chains in which the disaccharide is joined directly to a trimannosyl core. The lectin bound to such immobilised lipid-linked oligosaccharides on which the terminal D-galactosyl groups are substituted with alpha-L-Fucp-(1----2), alpha-D-Galp-(1----3), or alpha-NeuAc-(2----3) groups. However, no binding was detected if the terminal D-galactosyl groups were substituted with an alpha-NeuAc-(2----6) group or the subterminal N-acetylglucosamine units with an alpha-L-Fucp-(1----3 or -4) group. Internally located N-acetyllactosamine units where the D-galactose units are disubstituted by beta-D-GlcNacp-(1----3) and -(1----6) units, as in branched poly(N-acetyllactosamine) backbones were not bound by the bovine lectin. These results are in accord with previous observations on the bovine lectin and the corresponding human and rat lectins, using structurally defined oligosaccharides as inhibitors of binding. The results of comparative binding experiments using paragloboside and ceramide hexasaccharide which contain one and two N-acetyllactosamine units, respectively, joined in linear sequence to the lactosylceramide core, were equivocal with respect to the availability of the internal N-acetyllactosamine units for binding by the bovine lectin.

Animals↗
PubMed1987

Effect of diazoxide or glucagon on hepatic glucose production rate during extreme neonatal hypoglycaemia.

The relation between hepatic glucose production rate (HGPR) and plasma concentrations of insulin and glucagon was investigated in four term neonates who had severe hypoglycaemia. The hepatic glucose production rate was less than 20% of normal for fasting term neonates in all four babies and yet insulin concentrations were never greater than 12 microU/ml; two babies had very low glucagon concentrations (less than 60 ng/l). Two further neonates with similar histories also had plasma glucagon concentrations that were also extremely low (less than 20 ng/l). A single intravenous bolus of glucagon caused a rapid rise in hepatic glucose production rate towards the normal range, which was sustained for many hours after the bolus had been given. Diazoxide given to one baby suppressed previously 'normal' insulin concentrations still further (4.2 to less than 1.6 microU/ml) and thereby restored the hepatic glucose production rate to normal. In view of the normal plasma insulin concentrations at a time when the hepatic glucose production rate was reduced, we feel that the absolute concentration of insulin may be less important than the insulin/glucagon molar ratio in the control of glucose homeostasis in this group of infants. The changing of this ratio by means of boluses of glucagon may be useful in preventing rebound hypoglycaemia, which so often occurs when dextrose infusions are reduced either accidentally or in an attempt to restart oral feeds.

Blood Glucose↗
PubMed1985

Retinal changes in myotonic dystrophy: a clinicomorphological study.

This report appears to be the first ultrastructural study of the maculopathy and peripheral pigmentary retinopathy in myotonic dystrophy. Nine eyes from five patients observed during life are described. The findings were similar in all eyes, the retinal pigment epithelium in the macular region containing an accumulation of lipofuscin in large hyperpigmented cells. Pigment-laden profiles found in the subpigment epithelial space or subretinal space were interpreted as an attempt to discharge the pigment. Stress fibres of actin microfilaments were thrown into prominence by the irregularity of the pigment epithelium. In the periphery migration of retinal pigment cells into the retina occasionally resulted in the formation of bone corpuscles around occluded vessels, as occurs in retinitis pigmentosa; but more often the clumps were coarser and surrounded basement membrane material. Central and peripheral epiretinal membranes were also observed.

Cataract↗
PubMed1984

Permeability of the human placenta to bicarbonate: in-vitro perfusion studies.

The effect of maternal acidosis on fetal acid-base balance was studied in a dual circuit perfusion of a single cotyledon in normal, term, human placentas. Both the fetal and maternal (intervillous) circulations were perfused with a Krebs-Ringer solution adjusted to pH values between 7.35 and 7.45. After a control period, the perfusate in the maternal circulation was replaced by an acidified medium (mean pH 7.06) for 30 min. This was followed by a second control period of 30 min during which the acidified maternal perfusate was replaced with the original medium. During the 30 min of maternal acidosis, fetal vein pH was not significantly altered despite the large decrease in maternal artery pH, but there was an efflux of total CO2 (tCO2) from the placenta into the maternal circulation which was not matched by an influx of tCO2 from the fetal circulation. The tCO2 transferred was in the form of bicarbonate rather than dissolved CO2, but the maximal rate of tCO2 transfer of in the form of bicarbonate was lower than the rate of placental transfer of tCO2 necessary in vivo. It is probable therefore that bicarbonate does not play a major role in placental CO2 transfer but the placental tissue bicarbonate pool may play an important part in buffering the fetus against changes in maternal pH or blood gas status.

Acidosis↗
PubMed1984

An ultrastructural study of the role of leucocytes and fibroblasts in the breakdown of Bruch's membrane.

Ultrastructural examination was performed on 30 eyes selected on the basis of a light microscopic classification as representing all stages of macular degeneration. The eyes belonged to 29 patients aged 40 to 91 years at death and all patients with the exception of the 40-year-old had been examined during life. The results indicate that monocytes, lymphocytes, fibroblasts and mast cells may play a role in the formation of breaks in Bruch's membrane at early and late stages of macular degeneration. The implications of these observations are discussed in the context of their possible role in choroidal neovascularization.

Adult↗
PubMed1979

Case note descriptions of the placenta: are they worthwhile?

In 429 placentae, measurements were made of weight, diameter, shape, eccentricity of the cord and weight and length of the cord, and the results were compared with Apgar score of the infant at birth and its standardized birth weight. There was no evidence that cord eccentricity, placental shape or "thickness", or the dimensions of the cord had any significant relation to the growth of the fetus or its condition at birth. The value of routine recording of crude measurements and qualitative assessments of the placenta in case notes is questioned.

Apgar Score↗
PubMed1979

Evidence for antibody-dependent cell-mediated cytotoxicity by T cells bearing receptors for IgG.

Human lymphocyte populations comprising T cells, T depleted lymphocytes, and T cells enriched for, or depleted of, IgG Fc receptor-bearing (TG) cells, were separated using rosette techniques. All lymphocytes were assessed for the ability to lyse antibody-coated chicken erythrocytes and SL2 mouse lymphoma cells. Their activity was compared with that of monocytes and neutrophil-enriched preparations. IgG Fc receptor positive cells within the T population were highly active in both cytotoxicity assays; the activity could not be ascribed to contamination by monocytes or neutrophils. The TG cells forming junctions with the target cells possessed a characteristic ultrastructure.

Antibody-Dependent Cell Cytotoxicity↗
PubMedDate not supplied

Studies of a single placental cotyledon in vitro: III. The dimensions of the villous capillaries.

The capillary beds of ten isolated perfused placental cotyledons were examined by injecting microspheres ranging from 2 microgram to more than 20 microgram diameter into the villous circulation. As many as 25 per cent of capillaries may be less than 4 microgram in diameter; there are virtually none whose diameter exceeds 11 microgram and there is no evidence of large diameter vascular shunts.

Capillaries↗