Search PubMed⌕ Search

Biomedical subjects

D J Ferguson

Publications and source records attributed to D J Ferguson.

At least 109 records · Page 6Linked to original sources
PubMed1994

Cheveux incoiffables--diagnostic, clinical and hair microscopic findings, and pathogenic studies.

Three possible mechanisms of the hair shaft abnormality in cheveux incoiffables have been investigated in nine patients. Cheveux incoiffables hairs were found to exhibit a normal distribution of cystine-rich protein within both the cuticle and the cortex, as determined by silver methenamine ultrastructural cytochemistry. Resistance to stretching, at 65% relative humidity and constant temperature, was similar to normal controls. Resistance to bending forces was also assessed, and was equivalent in both groups. On scanning electron microscopy, all patients with cheveux incoiffables demonstrated longitudinal grooving of the hair shaft, and the hairs were triangular or heart-shaped in cross-section. In addition, there appeared to be minimal cuticular weathering. Even hairs of 20-30 cm length showed only minimal cuticular and cortical weathering, compared with normal hair shafts of similar length and diameter. It is possible that the reduced progressive weathering renders the hair shaft more rigid, and could serve to explain the 'stand on end' appearance of the hair which is typical of this condition. However, the characteristic cross-sectional shape of the hair shaft in cheveux incoiffables may render it more rigid and resistant to bending forces. This latter theory has yet to be fully investigated.

Child↗
PubMed1994

Specific tolerance to an acetylcholine receptor epitope induced in vitro in myasthenia gravis CD4+ lymphocytes by soluble major histocompatibility complex class II-peptide complexes.

In autoimmune disorders, inactivation of pathogenic antigen-specific T cells, rather than global immunosuppression, would be highly desirable. One way to achieve this would be to deliver the first antigen-specific signal to the T cell in the absence of the second costimulatory signal. Myasthenia gravis (MG) is a well-characterized autoimmune disease in which T cell-dependent autoantibodies are directed against the acetylcholine receptor (A ChR) at the neuromuscular junction. AChR-specific T cells have been cloned from MG patients, and in this study, we have induced long-lasting tolerance in vitro in one particular clone (PM-A1) with a known peptide epitope (alpha 144-163) and MHC class II restriction (DR4 Dw14.2 or 4.2) by using soluble MHC-class II peptide complexes. Preincubation of PM-A1 T cells with such complexes induced death by apoptosis in < or = 40-50% of the AChR-specific cells. Surviving cells remained refractory to stimulation with AChR-derived synthetic peptides or recombinant polypeptides for < or = 38 d after complex treatment. These effects were highly specific, dose-dependent and required > 2 h preincubation. The T cells could be protected from the tolerizing effects of complex by coincubation with DR-matched or -mismatched antigen-presenting cells. This work shows that antigen-specific T cells can be selectively killed or anergized using soluble MHC class II: peptide complexes. Such an antigen-specific therapy offers a rational approach to the immunotherapy of autoimmune or allergic disease in vivo.

Adolescent↗
PubMed1994

An ultrastructural study of the effect of treatment with atovaquone in brains of mice chronically infected with the ME49 strain of Toxoplasma gondii.

The morphological effects of drug treatment with atovaquone in the brains of mice chronically infected with Toxoplasma gondii was examined by light and electron microscopy. As early as 1 and 2 weeks of treatment there appeared to be fewer tissue cysts compared to untreated controls and this reduction was more significant after 4 weeks treatment. There also appeared to be a decrease in the number of inflammatory nodules and the severity of the meningitis. Ultrastructurally, the cysts of both treated and control animals were located within host cells. There was a marked increase in both the number of cysts with lysed bradyzoites and the number of degenerate bradyzoites after 4 weeks treatment. It is probable that the drug is more active against the metabolically active immature bradyzoites than the mature organisms. Drug treatment does not appear to result in rupture of tissue cysts or release of Toxoplasma antigens since there is a reduction rather than an increase in the inflammatory response. This drug may be useful in treating chronic toxoplasmosis since it appears to be active against the bradyzoites reducing the parasite burden (cyst number) without initiating a destructive inflammatory response.

Animals↗
PubMed1993

Ultrastructural features of fetal erythroid precursors infected with parvovirus B19 in vitro: evidence of cell death by apoptosis.

Human parvovirus B19 cannot be cultured in standard cell lines and relatively little is known about the intracellular life-cycle of the virus. In this study, ultrastructural features of B19 infection were examined using haemopoietic cell suspension cultures derived from human fetal liver. Erythroblasts from infected cultures frequently contained crystalline arrays of both full and empty virus-like particles. The number and size of these arrays increased with the duration of culture, and their location changed from exclusively nuclear at 24 h post-infection to both nuclear and cytoplasmic at 3 days post-infection. Arrays were occasionally found in cytoplasmic protuberances which appeared to be pinching off from the cell. The location of the arrays corresponded to the distribution of viral capsid protein determined by immunolabelling at the light microscope level. Cells containing viral crystalline arrays also exhibited nucleolar degeneration, extreme margination of the nuclear heterochromatin, and cytoplasmic vacuolation. These features are typical of cells undergoing individual programmed cell death or 'apoptosis'. The triggering of apoptosis in erythroid precursors by parvovirus B19 may help to explain the apparent lack of a strong inflammatory response to fetal B19 infection and may have implications for understanding the mechanisms of viral spread throughout the host.

Apoptosis↗
PubMed1993

Intracellular localization of parvovirus B19 nucleic acid at the ultrastructural level by in situ hybridization with digoxigenin-labelled probes.

Conditions suitable for immunogold detection of digoxigenin-labelled DNA probes hybridized to parvovirus B19-infected erythroid cells embedded in Lowicryl K4M and LR White acrylic resins were established at the electron microscope level. The protocol was initially optimized using a positive control probe for whole human DNA which produced signal over the heterochromatin of all nucleated cells. In cultures harvested 2 days postinfection, B19 nucleic acid was detected mainly within the centrinuclear region of erythroid cells exhibiting characteristic margination of the chromatin. The B19 hybridization signal was largely unaffected by denaturation and was resistant to RNase digestion but sensitive to DNase digestion, indicating that it was mainly single-stranded B19 DNA. Relatively few gold particles were found over crystalline arrays of viral capsids, consistent with the observation that they are composed of mainly 'empty' capsids. B19 nucleic acid was detected in apparent transit from nucleus to cytoplasm through pores in the nuclear membrane. While the sensitivity of this system is limited by the fact that hybridization occurs only at the surface of the section, it is a rapid and specific means of localizing viral nucleic acids with a high degree of resolution.

Cells, Cultured↗
PubMed1993

Identification of the renal erythropoietin-producing cells using transgenic mice.

Regulation of erythropoietin production by the kidneys is central to the control of erythropoiesis. Uncertainty about the identity of the renal cells involved has been a major obstacle to understanding this mechanism. We have used sequence from the mouse erythropoietin locus to direct expression of a marker gene, SV40 T antigen, to these cells in transgenic mice. The transgenic constructs contained an oligonucleotide marker (Epo-M) or SV40 sequence (Epo-TAg) in the 5' untranslated region of the mouse erythropoietin gene, flanked on each side by 9 and 7.5 kb of DNA from the mouse erythropoietin locus. Anemia-inducible expression of Epo-M and Epo-TAg was observed in the kidney. In one of thirteen lines, homologous integration of Epo-TAg into the mouse erythropoietin locus occurred. In transgenic mice bearing Epo-TAg at homologous and heterologous insertion sites, renal expression was restricted to a population of cells in the interstitium of the cortex and outer medulla. Immunohistochemical characterization by light and electron microscopy shows that these are the fibroblast-like type I interstitial cells.

Animals↗
PubMed1993

A comparison of four solutions for cold storage of pancreatic islets.

Clinical pancreatic islet transplantation requires cold storage of islets for some hours. The best solution for cold storage will be that which maintains islet viability for the longest time. We have examined the viability of rat and human islet after storage at 4 degrees C for up to 6 days in Hanks' balanced salt solution, University of Wisconsin solution (UW), and 2 modified versions of this last solution, Sumimoto D (SD) and histidine-lactobionate (HL). The integrity of cold-stored rat and human islets of Langerhans has been examined using supravital stains and electron microscopy. In addition, the viability of cold-stored rat islets was tested by intraportal transplantation into syngeneic streptozotocin-induced diabetic recipients. The in vitro studies showed good preservation of islets stored in UW, SD, and HL for up to 72 hr. In comparison, storage for periods as short as 24 hr in HBSS markedly reduced islet integrity. The transplantation studies showed that rat islets cold stored in HBSS solution for 24 hr were not able to reverse experimental diabetes, whereas those stored in the other 3 solutions for 24 hr successfully reversed diabetes within 1 week of transplantation. After 48-hr cold storage, only islets preserved in HL solution were uniformly capable of producing functioning islet grafts. None of the tested solutions was able to maintain islet viability sufficiently to allow successful transplantation after more than 48 hr of cold storage. These experiments demonstrate that good islet viability is maintained for up to 24 hr of storage in UW, SD, and HL, and even after 48-hr cold storage in HL solution, whereas preservation in HBSS solution was deleterious to islet viability within 24 hr.

Adenosine↗
PubMed1993

Monilethrix: a clinicopathological illustration of a cortical defect.

We describe two sisters aged 2 and 7 years, with monilethrix. The older sister was clinically less severely affected but, microscopically, the features of weathering and alternating nodes and internodes were more obvious. The younger girl had more severe alopecia, with shorter hair, but the microscopic features were less marked. Scanning-electron microscopy demonstrated only slight cuticular weathering in both cases, and evidence of breakage in the cuticle at points of no obvious cuticular pathology. Transmission-electron microscopy showed normal cuticle cells in cross-section, but an abnormal cortex. The abnormalities included areas of homogeneous non-fibrillar material, and a deviated axis of some microfibrils. We consider that these findings support the possibility that a cortical defect contributes significantly to the fragility of hair in monilethrix. This might explain why hair with marked beading can be stronger than hair from an affected sibling with less apparent abnormality.

Child↗
PubMed1993

Meningococcal Opa and Opc proteins: their role in colonization and invasion of human epithelial and endothelial cells.

Neisseria meningitidis (Nm) isolates from disease or during carriage express, on their outer membranes, one or more of a family of closely related proteins designated Opa proteins. In this study, we have examined the potential roles of Nm Opa proteins in bacterial attachment and invasion of endothelial as well as epithelial cells and compared the influence of Opa proteins with that of Opc protein, which has been previously shown to increase bacterial interactions with eukaryotic cells. Several variants expressing different Opa proteins (A, B, D) or Opc were selected from a culture of capsule-deficient non-piliated bacteria of strain C751. Although the Opa proteins increased bacterial attachment and invasion of endothelial cells, Opc was the most effective protein in increasing bacterial interactions with these cells. In contrast, attachment to several human epithelial cells was facilitated at least as much by OpaB as Opc protein. OpaA was largely without effect whereas OpaD conferred intermediate attachment. OpaB also increased invasion of epithelial cells; more bacteria were internalized by Chang conjunctival cells compared with Hep-2 larynx carcinoma or A549 lung carcinoma cells. Monoclonal antibody reacting with OpaB inhibited bacterial interactions with the host cells. Opa-mediated interactions were also eliminated or significantly reduced in variants expressing capsule or those with sialylated lipopolysaccharide. These data are consistent with the notion that environmental factors controlling capsule and lipopolysaccharide phenotype may modulate bacterial interactions mediated by these OM proteins. In permissive microenvironments, some Opa proteins may be important in bacterial colonization and translocation in addition to Opc. The data also support the notion that Nm Opa may confer tissue tropism.

Animals↗
PubMed1993

Pilus-facilitated adherence of Neisseria meningitidis to human epithelial and endothelial cells: modulation of adherence phenotype occurs concurrently with changes in primary amino acid sequence and the glycosylation status of pilin.

Adherence of capsulate Neisseria meningitidis to endothelial and epithelial cells is facilitated in variants that express pili. Whereas piliated variants of N. meningitidis strain C311 adhered to endothelial cells in large numbers (> 150 bacteria/cell), derivatives containing specific mutations that disrupt pilE encoding the pilin subunit were both non-piliated and failed to adhere to endothelial cells (< 1 bacterium/cell). In addition, meningococcal pili recognized human endothelial and epithelial cells but not cells originating from other animals. Variants of strain C311 were obtained that expressed pilins of reduced apparent M(r) and exhibited a marked increase in adherence to epithelial cells. Structural analysis of pilins from two hyper-adherent variants and the parent strain were carried out by DNA sequencing of their pilE genes. Deduced molecular weights of pilins were considerably lower compared with their apparent M(r) values on SDS-PAGE. Hyper-adherent pilins shared unique changes in sequence including substitution of Asn-113 for Asp-113 and changes from Asn-Asp-Thr-Asp to Thr-Asp-Ala-Lys at residues 127-130 in mature pilin. Asn residues 113 and 127 of 'parental' pilin both form part of the typical eukaryotic N-glycosylation motif Asn-X-Ser/Thr and could potentially be glycosylated post-translationally. The presence of carbohydrate on pilin was demonstrated and when pilins were deglycosylated, their migration on SDS-PAGE increased, supporting the notion that variable glycosylation accounts for discrepancies in apparent and deduced molecular weights. Functionally distinct pilins produced by two fully piliated variants of a second strain (MC58) differed only in that the putative glycosylation motif Asn-60-Asn-61-Thr-62 in an adherent variant was replaced with Asp-60-Asn-61-Ser-62 in a non-adherent variant. Fully adherent backswitchers obtained from the non-adherent variant always regained Asn-60 but retained Ser-62. We propose, therefore, that functional variations in N. meningitidis pili may be modulated in large part by primary amino acid sequence changes that ablate or create N-linked glycosylation sites on the pilin subunit.

Amino Acid Sequence↗
PubMed1992

Comprehensive correction of the craniofacial deformity in achondroplastic dwarfism.

The treatment of this patient serves to demonstrate a craniofacial team approach to a unique and moderately severe problem. By the modification and careful combination of standard techniques, i.e., frontofacial advancement, and Le Fort I and vertical mandibular osteotomy, a good correction has been obtained. Analysis of the problem clearly indicated the need for moving multiple components of the facial skeleton into new positions to provide correction. The upper and lower midface required simultaneous movements in exactly opposite directions to normalize the skeletal deformity. To address the excess forehead height and projection, a modification of the usual frontofacial advancement was necessary. Rotation of the frontofacial segment forward inferiorly allowed correction of the orbital deficiency while also allowing shortening of the vertical forehead dimension. This is a deviation from the straight linear advancement usually dissected. Simultaneous retroposition and rotation of the maxilla allowed correction of the plane of occlusion while lengthening the midface. The unique combination and application of standard techniques of craniofacial surgery in this patient allowed a very good result.

Achondroplasia↗
PubMed1992

Variations in the expression of pili: the effect on adherence of Neisseria meningitidis to human epithelial and endothelial cells.

The effect of variations in Neisseria meningitidis pili on bacterial interactions with three epithelial cell lines as well as human umbilical vein endothelial cells was studied using a panel of seven strains expressing Class I or Class II pili. Comparison of adherence of piliated and pilus-deficient variants of each strain to epithelial cells suggested that Class I pili may mediate bacterial adherence with all three epithelial cell lines. In contrast, Class II pili of the strains used did not increase bacterial adherence to Hep-2 larynx carcinoma cells, although an increase in adherence to Chang conjunctival and A549 lung carcinoma epithelial cells was observed in the Class II pili-expressing strains. In addition to these interclass functional variations, differences in adherence to epithelial cells were also observed among Class I and Class II strains. Functionally different pilin variants of one Class I strain, MC58, were obtained by single colony isolation. One piliated variant was identified which had concurrently lost the ability to adhere to both Chang and Hep-2 cells ('non-adherent' phenotype; adherence of less than 2 bacteria per cell). In addition, several adherent pilin variants were isolated from non-adherent Pil- and Pil+ bacteria by selection on Chang cells (adherence of 10-25 bacteria per cell). In contrast to epithelial cells, all variant pili, whether of Class I or Class II, adhered to endothelial cells in substantially larger numbers (greater than 50 bacteria per cell) and therefore implied the existence of distinct mechanisms in pilus-facilitated interactions of N. meningitidis with endothelial and epithelial cells.

Bacterial Adhesion↗