Biomedical subjects

D B Archer

Publications and source records attributed to D B Archer.

At least 127 records · Page 7Linked to original sources

PubMed1991

Heterologous protein production by filamentous fungi.

There are clearly many facets to successful production of heterologous proteins from filamentous fungi. The objectives are to exploit the natural ability of some species to secrete high levels of protein. The heterologous target proteins produced in a fungal host must be acceptable to the public and be economic to produce, i.e. the targets must be authentic (in structure and activity) and be produced in high yield to necessary levels of purity. The appearance of heterologous products from fungi on the market is testament to some success but, equally, there are considerable limitations in our ability to produce desired yields of many target proteins. We endorse the view of van den Hondel, Punt and van Gorcom (1991) that for the commercial production of heterologous proteins from filamentous fungi more information is required on transcriptional control, introns, mRNA stability and processing, translational efficiency, protein secretion, glycosylation and proteolysis. In addition, there is scope for yield improvement based on a better understanding of the physiology of growth/product secretion coupled to appropriate bioreactor operation. The authenticity of product is an aspect which will assume increasing importance, particularly for therapeutic proteins. The level at which the structures and functional activity of heterologous proteins are assessed will ultimately be determined by legislation. The analytical methods currently available are not always sufficient, for example, to reveal folded structures, and most proteins are not amenable to analysis by two-dimensional NMR. The authenticity of target heterologous proteins will also need to be assessed in relation to the glycosylation level and pattern. This is not easily done and explains the paucity of detailed information published to date on glycosylation of fungal proteins. Novel engineered proteins are already being produced from filamentous fungi where expression is an aid to investigation of structure-function relationships. Commercial production of such engineered proteins will require approval subject to a range of stringently applied tests and analyses. This imposes an even greater need to be able to specify and control, in a rational manner, the structures of recombinant proteins. The research needs for realization of improved yields are equally important in assuring authenticity of product. It is encouraging that progress is being made on all fronts, primarily with Aspergillus spp. and T. reesei, but also with other species, such as N. crassa.

Animals↗

PubMed1990

Orbital infiltration by eyelid skin carcinoma.

This paper presents 5 patients seen in the Eye Clinic, Royal Victoria Hospital, Belfast with orbital infiltration of malignant eyelid tumours. The physical features and natural progression of the disease are described. The value of CT scans in determining the extent of the disease and patient management are described.

Aged↗

PubMed1990

Cephalic radiation and retinal vasculopathy.

The retinal vascular complications in patients receiving cephalic radiation for various lesions over a ten year period were reviewed. The incidence of retinopathy was 17% overall, but increased with proximity of the treatment site to the eye, being highest in irradiation of the eye/orbit (85.7%), paranasal sinuses (45.4%) and nasopharynx (36.4%). The risk of retinopathy increased significantly when the total dose of radiation exceeded 3000 cGy. The occlusive vasculopathy and capillary incompetence which were the most clinically important features of radiation retinopathy may be exacerbated by pre-existing diabetes. Radiation retinopathy has a long latency and may not be clinically detectable for eight years or more. Long follow-up times with sequential fundoscopy should increase early detection and optimise treatment with laser photocoagulation.

Adolescent↗

PubMed1990

DNA analysis and recombination in X-linked retinitis pigmentosa.

X-linked retinitis pigmentosa is a hereditary retinal degenerative disorder which has been localised to the proximal short arm of the X chromosome. Recent evidence suggests that the disorder is heterogeneous with two possible loci for the disease mutation. DNA analysis on the family presented in this paper showed that the mutation mapped to the more telomeric locus (RP3), thus enabling two flanking polymorphic DNA probes (XJ1.1 and M27 beta) to be used for the detection of female carriers in the family. In none of the carriers was a tapetal reflex (metallic sheen) observed.

Adult↗

PubMed1990

Autonomic function in Holmes Adie syndrome.

Autonomic function was studied in a group of 11 patients with Holmes Adie Syndrome. Autonomic function was assessed by the measurement of cardiovascular reflexes. Heart rate responses to respiration, valsalva manoeuvre and standing were studied. The change in systolic blood pressure on moving from the lying to the standing position was measured. Abnormalities of parasympathetic function were found in three patients, compared with matched controls. Autonomic dysfunction in Holmes Adie Syndrome may be more widespread than previously suspected.

Adie Syndrome↗

PubMed1990

Fluorescein angiographic features, natural course and treatment of radiation retinopathy.

Fifteen patients who developed retinopathy following radiotherapy for cephalic tumours were studied by fluorescein angiography. Nine patients with unilateral or bilateral retinopathy had serial angiograms at six monthly or yearly intervals. Angiography revealed a wide range of retinal microvascular changes which were graded 1-4 according to the extent and degree of capillary malformation, incompetence and closure. All patients showed slow progression of retinopathy with remodelling of the affected microvasculature and increased capillary fallout and leakage to dye. The earliest retinopathic changes were capillary dilatation and closure and microaneurysm formation. Telangiectatic-like vessels were a feature of the established retinopathy and probably represented collateral channels which bordered sites of capillary occlusion. Two patients with progressive macular oedema and declining vision responded favourably to focal laser photocoagulation which returned a measure of competence to some residual dilated capillaries.

Capillaries↗

PubMed1990

Hen egg white lysozyme expressed in, and secreted from, Aspergillus niger is correctly processed and folded.

We transformed Aspergillus niger with the full length cDNA gene encoding hen egg-white lysozyme (HEWL) and its secretion signal sequence. Lysozyme levels up to 12 mg/l were secreted when expression was controlled by the A. awamori glucoamylase (GAM) promoter and 1 mg/l when controlled by the A. nidulans glyceraldehyde-3-phosphate dehydrogenase (GPD) promoter. N-terminal sequence analysis of the recombinant protein indicated that the signal peptide was correctly processed by the A. niger secretory apparatus. The specific catalytic activity of the recombinant protein was identical to that of authentic hen lysozyme. The recombinant HEWL was examined by 2D 1H-NMR spectroscopy and shown to have a spectrum identical to that of authentic HEWL indicating that the protein was correctly folded.

Amino Acid Sequence↗

PubMed1989

Long-term glycaemic control and diabetic retinopathy.

216 patients with insulin-dependent diabetes mellitus were studied by retinal photography, and the absence or presence of retinopathy was related to the mean of serial glycosylated haemoglobin measurements (mean HbA1) carried out every 3 months during the previous 6 years. 122 patients had no diabetic retinopathy, 86 had background retinopathy, and 8 proliferative retinopathy. Mean HbA1 levels showed a strong correlation with increasingly severe grades of retinopathy, even when differences in duration of diabetes were taken into account. Proliferative retinopathy was seen only in patients with mean HbA1 above 10%. These results support the view that the development of diabetic retinopathy is related to long-term glycaemic control and emphasise the desirability, and possible benefit, of achieving control as close to normal as is possible for each individual patient.

Adolescent↗

PubMed1989

Early ultrastructural changes after low-dose X-irradiation in the retina of the rat.

In this study Lister rats were given doses of X-rays ranging from 200-2,000 Rads to the retina of one eye, sacrificed at various time intervals between one hour and one month later and the irradiated eye processed for electron microscopy. The rod photoreceptor cells were by far the most radiosensitive cells in the retina, their outer segments showing distinctive membrane damage at one hour after 200 Rads of X-rays. Photoreceptor cell death was not seen at doses less than 1,000 Rads in the time period of the experiment. The retinal pigment epithelial (RPE) cells showed damage in the form of mitochondrial swelling but only in doses over 500 Rads. Retinal pigment epithelial cell loss did not occur under 2,000 Rads. The inner retinal neurones, glial elements and the retinal vasculature did not show any ill effects in the time period of this study.

Animals↗

PubMed1989

Methanogenesis from ethanol by defined mixed continuous cultures.

Methanogenesis from ethanol by defined mixed continuous cultures was studied. Under sulfate-free conditions, a Desulfovibrio strain was used as the ethanol-degrading species producing acetic acid and hydrogen. In a two-membered mutualistic coculture, the hydrogen was converted to methane by a Methanobacterium sp. and pH was maintained at neutrality by the addition of alkali. Introduction of a third species, the acetate-utilizing Methanosarcina mazei, obviated the need for external pH control. Methanogenesis by the co-and triculture was studied at various dilution rates in the steady state. The mutualistic coculture performed like a composite single species, as predicted from the theory of mutualistic interactions. Coupling between the mutualistic coculture and the acetate-utilizing methanogen was less tight. Increasing the dilution rate destabilized the triculture; at low dilution rates, instability was soon recovered, but at higher dilution rates imbalance between the rates of production and removal of acetic acid led to a drop in pH. Flocs formed in the triculture. An annulus of the Methanobacterium sp. and Desulfovibrio sp. was retained around the Methanosarcina sp. by strands of material probably derived from the Methanosarcina sp.

Journal Article↗

PubMed1989

A light microscopic and autoradiographic study of non-irradiated and irradiated ocular wounds.

Focal gamma irradiation was used to limit the intraocular extension of scar tissue which typically occurs after posterior perforating injury to the eye. Standard posterior perforating injuries were created in the right eye of forty-eight rabbits, half of which had the site of perforation focally irradiated using a Cobalt 60 ophthalmic plaque. Non-irradiated wounds healed with profuse formation of highly cellular and vascularised granulation tissue which invaded the vitreous to form contractile vitreo-retinal membranes. In irradiated eyes vitreo-retinal membrane formation was infrequent; the wounds showing only sparse granulation tissue with little or no extension into the vitreous cavity. Autoradiographic studies carried out in a second group of 40 animals showed that the episclera was the main source of the proliferating fibroblasts, and cell counts confirmed that the inflammatory and repair responses in irradiated wounds were both delayed and attenuated.

Animals↗

PubMed1989

Focal irradiation of perforating eye injuries.

Plaques constructed with 125I were used to irradiate the sites of perforating ocular injuries in rabbits. An approximate dose of 16Gy given over a period of 6 days was shown to significantly reduce intraocular cellular proliferation when irradiation was commenced within 24 hours after injury. If irradiation was delayed until day 5, this reduction in cellular proliferation and intraocular membrane formation did not occur. Smaller radiation doses of approximately 6Gy given within 24 hours post-injury and administered over 6 days also reduced the extent of cellular proliferation but was not as effective as the 16Gy dose.

Animals↗

PubMed1988

Retinal ultrastructural findings in cone degeneration.

We studied an eye from a 73-year-old man with a sporadic type of retinal cone degeneration and choroidal melanoma. Histologic and ultrastructural studies of the nasal retina unaffected by the choroidal melanoma showed alterations at the outer retina predominantly involving the photoreceptors and retinal pigment epithelium. A wide spectrum of pathologic changes were observed, ranging from near normal retina showing only photoreceptor outer segment disease (distortion and kinking) to grossly pathologic regions where photoreceptor cell bodies were sparse and their outer segments absent. The retinal pigment epithelium in minimally affected regions of the retina showed an increased proportion of the melanin complement of the cell within complex granules. In severe disease, many cells showed only giant complex granules with no free melanin. Retinal pigment epithelial cell migration and relocation around blood vessels was also noted in severe disease.

Aged↗

PubMed1988

Traumatic retinal angiopathy--associated with wearing of car seat belts.

Three patients who were involved in road traffic accidents and sustained seat belt related injuries developed a retinal angiopathy characterised by retinal haemorrhage, oedema and focal ischaemia. Significant unilateral visual loss (2/60 - 6/18) was reported 1-48 hours following injury and central or paracentral annular scotomata were present. Although there was good recovery of visual acuity all patients had permanent scotomata, colour vision defects and loss of contrast sensitivity. Residual retinal microvascular and haemodynamic changes were noted on fluorescein angiography and the visually evoked responses were uniformly depressed. The structural and functional alterations in the retina of patients who have sustained seat belt injuries have important medico-legal implications.

Accidents, Traffic↗

PubMed1988

Intra-ocular pressure changes during induction of anaesthesia and tracheal intubation. A comparison of thiopentone and propofol followed by vecuronium.

Intra-ocular pressure was measured during induction of anaesthesia with propofol (n = 40) or thiopentone (n = 40) followed by vecuronium to facilitate tracheal intubation which was carried out 3 minutes after the administration of relaxant. The average induction doses were 2.15 and 4.83 mg/kg for propofol and thiopentone, respectively. Half the patients in each group received a supplementary dose of the same induction agent (propofol 1.0 mg/kg or thiopentone 2.0 mg/kg) (corrected) prior to intubation. Both propofol and thiopentone produced a significant reduction in intra-ocular pressure which decreased further after administration of vecuronium as well as the second smaller dose of the induction agents. Intra-ocular pressure prior to intubation was lower in the two propofol groups in comparison to the corresponding thiopentone groups. Intubation was associated with an increase in intra-ocular pressure but it still remained significantly below the baseline values except in the group given one dose of thiopentone. Supplementary doses of induction agents before intubation attenuated the increase in intra-ocular pressure. Propofol was significantly more effective in this respect and this group showed the lowest intra-ocular pressure throughout the study period. However, administration of propofol resulted in a 30% incidence of pain on injection and a decrease in systolic arterial pressure of more than 30% in about half the patients.

Adolescent↗

PubMed1988

Response of populations of human faecal bacteria to viscosity in vitro.

The effects of viscosity on cultures of human faecal bacteria in vitro were studied. The composition of the microbial populations which developed during in vitro incubation were affected by viscosity. The proportion of Bacteroides species was decreased at high viscosities and it is concluded that the 'viscotolerance' of a bacterial population contributes towards its composition. Viscosity alters the enzyme activity of cultures. Cell-associated total, and specific, beta-galactosidase activities of cultures of human faecal bacteria were decreased at high viscosity.

Bacteria↗

PubMed1988

Isolation and characterization of methanogenic bacteria from landfills.

Methanogenic bacteria were isolated from landfill sites in the United Kingdom. Strains of Methanobacterium formicicum, Methanosarcina barkeri, several different immunotypes of Methanobacterium bryantii, and a coccoid methanogen distinct from the reference immunotypes were identified.

Antibodies, Archaeal↗

PubMed1988

Enzyme-Linked Immunosorbent Assays for the Specific and Sensitive Quantification of Methanosarcina mazei and Methanobacterium bryantii.

Three microtitration plate enzyme-linked immunosorbent assays (ELISAs) have been developed: a competitive ELISA and a two-site (or indirect sandwich) ELISA for Methanosarcina mazei S6 and a two-site ELISA for Methanobacterium bryantii FR-2. The assays were sensitive, with limits of cell protein detection of 3 ng ml, 5 ng ml, and 50 ng ml, respectively, and showed good precision. The M. mazei assays used monoclonal antibodies and were entirely species specific, showing no cross-reaction with methanogens of other genera or with other species of the same genus. The Methanobacterium bryantii assay, which used two polyclonal antisera, showed only a slight cross-reaction with one other Methanobacterium species but no cross-reaction with methanogens of other genera. The use of the ELISAs for quantitative analysis of mixed cultures and of sewage sludge samples was investigated. Sludge diluted at 1:10 or more caused no significant interference in any of the three ELISAs. Various cultures of bacteria, methanogens, and nonmethanogens at a protein concentration of 50 mug ml showed no significant interference in the M. mazei competitive assay and the Methanobacterium bryantii two-site assay, although they did cause falsely low results in the M. mazei two-site assay.

Journal Article↗