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Biomedical subjects

D J Ferguson

Publications and source records attributed to D J Ferguson.

At least 19 recordsLinked to original sources
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↗
PubMed1992

Expression of the Opc protein correlates with invasion of epithelial and endothelial cells by Neisseria meningitidis.

Whereas capsulate strains of Neisseria meningitidis are dependent on pili for adhesion to human endothelial and epithelial cells, strains which lacked assembled pili and were partially capsule-deficient adhered to and invaded human endothelial and epithelial cells if they expressed the Opc protein. Bacteria expressing low or undetectable levels of Opc protein failed to adhere to or invade eukaryotic cells. In addition, the presence of OpaAC751 protein on the surface of bacteria did not increase bacterial interactions with host cells. Association of Opc-expressing bacteria was inhibited by antibodies against Opc. Invasion was dependent on the host-cell cytoskeletal activity and was inhibited by cytochalasin D. In some cells, infected at the apical surface, bacteria emerging from basal surface were detected by electron microscopy. Opc is found in diverse meningococci and may represent a common virulence factor which facilitates adherence and invasion by these bacteria.

Animals↗
PubMed1992

Recombinant Salmonella typhimurium strains that invade nonphagocytic cells are resistant to recognition by antigen-specific cytotoxic T lymphocytes.

To address the question of whether Salmonella-infected nonphagocytic cells could serve as target cells for recognition by antigen-specific, major histocompatibility complex class I-restricted cytotoxic T lymphocytes (CTL), four recombinant Salmonella typhimurium constructs that expressed full-length, or fragments of, influenza A virus nucleoprotein (NP) were made. The bacteria were shown to infect Chinese hamster ovary (CHO) cells. Appropriate major histocompatibility complex restriction molecules, HLA-B27 and H-2 Db, were transfected into CHO cells, which were then infected with recombinant S. typhimurium and used as targets for NP-specific CTL. The cells in which NP was expressed by intracellularly replicating bacteria were not lysed by NP-specific CTL, although they were killed when appropriate influenza A virus or peptides were used. Thus, S.typhimurium bacteria within nonphagocytic cells were resistant to CTL recognition. In contrast to these results, mice infected with recombinant S.typhimurium that expressed fragments of NP in the periplasm were primed for NP-specific CTL responses. The results indicate that CTL responses specific to Salmonella antigens can be generated, but the bacteria may be safe from the CTL attack once they have entered the nonphagocytic cells.

Animals↗
PubMed1991

Identification of human erythrocyte blood group antigens on the C3b/C4b receptor.

The Knops/McCoy (Kn/McC) human erythrocyte blood group system belongs to the category of blood group Ag that generate so-called "high titer low avidity" antibodies in immunized transfusion recipients. Screening of red cells lacking certain high titer low avidity Ag demonstrated markedly diminished CR1 expression on McC(d-) and Kn/McC "null" (Kn(a-)McC(a-b-c-d-e-f-] erythrocytes. Additional testing by other methods confirmed these data, and biochemical assays demonstrated no detectable immunoreactive CR1 protein in membranes from Kn/McC null red cells. Human antisera to various Kn/McC Ag were then used to demonstrate that many of these antisera could be used to isolate a protein of identical m.w. to that isolated from the same cells using murine mAb CR1 antisera. Finally, protein isolated by using murine mAb anti-CR1 reacted specifically with anti-Kn/McC antibodies, demonstrating the identity of the Kn/McC and CR1 proteins. Thus, CR1 protein bears the human erythrocyte Kn/McC blood group Ag.

Antibodies, Monoclonal↗
PubMed1991

Interactions of Haemophilus influenzae with cultured human endothelial cells.

The interactions of capsulate (b+) and capsule-deficient (b-) Haemophilus influenzae type b with endothelial cells were studied in vitro using human umbilical vein endothelial cells (Huvecs). Association was determined by estimation of colony forming units (cfu) as well as the binding of 3H-thymidine-labelled bacteria. Bacteria associated with Huvecs rapidly and in a dose-dependent manner. The presence of capsule on bacteria resulted in a decrease in the rate of cell-association. Internationalisation of bacteria by Huvecs was quantitated after elimination of extracellular bacteria with gentamicin. It was found that larger numbers of b- bacteria were internalised compared to b+ bacteria. Incubation in the presence of metabolic inhibitors had little effect on the association of bacteria to Huvecs whereas internalisation was dependent on the integrity of host cellular functions. Electron microscopic studies confirmed phagocytic ingestion of both b+ and b- variants and suggested that the majority of the internalised bacteria remained viable within endothelial cell vacuoles. Haemophilus influenzae were translocated within vacuoles both from the apical to basal and the basal to apical direction.

Bacterial Adhesion↗
PubMed1991

Shear, torsional, and tensile bond strengths of ceramic brackets using three adhesive filler concentrations.

The effect of changes in adhesive filler concentration on the shear, torsional, and tensile bond strength of a chemical, a mechanical, and a chemical/mechanical retained ceramic bracket was evaluated. Two hundred ten bovine teeth were bonded with one of three ceramic brackets using a 30%, 55%, or 80% filled adhesive. The brackets were debonded with a shear, torsional, or tensile force to test the bond strength and the site of bond failure. No significant difference was found in the shear, torsional, or tensile bond strength of each ceramic bracket type in relation to changes in the adhesive filler concentration. However, there was a trend toward increased bond strength with increasing filler concentration. Combining the data according to adhesive type revealed that the 80% filled adhesive displayed a significantly greater shear bond strength than the 30% or 55% filled adhesive and a greater torsional bond strength than the 30% filled adhesive. This supports the hypothesis of increased bond strength with increased adhesive filler concentration. The mechanically retained ceramic bracket showed greater shear bond strength and maximum shear bond strength in torsion than the chemical or chemical/mechanical retained ceramic bracket. The tensile bond strength of the mechanically retained ceramic bracket was similar to that of metal brackets reported in other studies, and the failure site was at the bracket-adhesive interface.

Adhesives↗
PubMed1991

An evaluation of temporomandibular joints and jaw muscles after orthodontic treatment involving premolar extractions.

Experimental subjects (n = 29) were patients who had undergone orthodontic treatment in combination with extraction of maxillary or mandibular premolar teeth, or both. Control subjects (n = 29) were healthy dental students with no orthodontic or extraction experience. Sagittal (corrected axis) tomograms of the TMJs were used to determine the narrowest linear distances between the anterior and posterior outlines of the TMJ condyle and the TMJ fossa, expressed as the joint space ratio. There were no significant (p greater than 0.05) differences between the control and experimental ratios. Bipolar surface electromyograms of the masseter and anterior temporalis muscles were used to determine the isometric contraction velocities of these muscles until 50% and 100% voluntary isometric contraction effort (teeth clenching) was achieved. There were no significant (p greater than 0.05) differences between the control and experimental subjects. Electromyograms were also used to determine the relative contribution of the masseter and anterior temporalis muscles to the bite force developed during brief maximum voluntary tooth clenching, expressed as the activity index. There were no significant (p greater than 0.05) differences between the control and experimental subjects.

Adolescent↗
PubMed1991

Bone resorption by macrophage polykaryons of giant cell tumour of tendon sheath.

The antigenic phenotype, ultrastructure and bone resorbing ability of mononuclear and multinucleated giant cells of four giant cell tumour of tendon sheath (GCTTS) lesions was assessed. Both the giant cells and the mononuclear cells exhibited the antigenic phenotype of cells of the monocyte/macrophage lineage. The giant cells, unlike osteoclasts, did not respond morphologically to calcitonin and showed ultrastructural and immunophenotypic features of macrophage polykaryons. However, like osteoclasts, the giant cells showed direct evidence of resorption pit formation on bone slices. This indicates that the GCTTS is composed of cells of histiocytic differentiation with the giant and mononuclear cell components expressing a similar antigenic phenotype. Bone resorption by macrophage polykaryons shows that this is not a unique defining characteristic of osteoclasts. Qualitative differences in the degree and pattern of bone resorption by macrophage polykaryons distinguish it from that of osteoclasts and may underlie the clinical behaviour of osteolytic lesions.

Adult↗
PubMed1991

Capsulation gene loss and 'rescue' mutations during the Cap+ to Cap- transition in Haemophilus influenzae type b.

Genes for Haemophilus influenzae type b capsule expression are duplicated to form a potentially unstable structure, cap, of directly-repeated chromosomal regions of approximately 17 kb. Capsule-deficient mutants arise in a two-stage process, initiated by rec-dependent reduction of this region from two copies to one. This recombinational event is usually lethal, only about 1/200 surviving to form slow-growing colonies of organisms that continue to synthesize polysaccharide but are defective in its export. A variety of secondary 'rescue' mutations within cap can occur to reduce polysaccharide synthesis and restore normal organism appearance and colony morphology.

Bacterial Capsules↗
PubMed1991

The role of pili in the interactions of pathogenic Neisseria with cultured human endothelial cells.

The influence of the two surface structures of Neisseria meningitidis, capsule and pili, in bacterial interactions with human endothelial cells was investigated. Increased association correlated with the presence of pili on bacteria while capsule type had no apparent effect. Strains expressing both Class I and Class II pili associated with endothelial cells in significantly larger numbers compared with the non-piliated variants of the same strains (greater than 10x). Variants of Neisseria gonorrhoeae strain P9 expressing antigenically distinct pili also associated with endothelial cells in larger numbers (greater than 30x) compared with the non-piliated variant. Electron microscopic studies confirmed these data and showed that gonococci were internalized more frequently compared with meningococci. One consequence of increased association was an increase in the cytopathic effect of bacteria on the target cells.

Bacterial Capsules↗
PubMed1991

Pathological changes in the brains of mice infected with Toxoplasma gondii: a histological, immunocytochemical and ultrastructural study.

The pathological changes in the brains of mice infected with T. gondii were studied at various intervals between 7 days and 22 months post-infection using histology, immunocytochemistry and electron microscopy. Initially, a few single parasites were observed (day 7) but necrotic lesions and microglial and inflammatory nodules rapidly appeared (9-I4 days). The majority of the lesions between days 9 and I4 contained proliferating toxoplasma and early cyst formation but from 2I days onwards the vast majority of nodules contained neither parasites nor Toxoplasma antigen. Intact intracellular cysts persisted throughout the period of study eliciting no host response. A generalized meningoencephalitis developed by day II and persisted with varying degrees of severity throughout the 22 months studied. At first, the inflammatory cells consisted of lymphocytes and monocyte/macrophages but during the chronic phase plasma cells predominated. In chronic infections, the number of microglial/inflammatory nodules was relatively constant with only a few containing toxoplasmic material resulting from recent cyst rupture. A few brains contained small nodules of dystrophic calcification. This study shows that in these asymptomatic animals, the major feature is perivascular cuffing by mononuclear cells and localized microglial/inflammatory nodules. After the development of the chronic state, there is no obvious increase or decrease in the severity of the pathological changes with time.

Animals↗
PubMed1990

Evaluation of reticulocyte counts by flow cytometry in a routine laboratory.

Reticulocyte counting using flow cytometry and a membrane-permeable fluorescent dye, thiazole orange, was evaluated as an alternative to the conventional manual method. The flow cytometric method was more precise (mean c.v. of 4.3%) than the imprecise manual technique (mean c.v. of 22.4%). Linearity was highly acceptable (r = 0.99) over the reticulocyte count range of 1.8-30.1%. Flow cytometry allows processing of large numbers of samples with reduction in technologist time, and the improved precision and tenfold increase in the number of cells counted should considerably improve the clinical utility of the reticulocyte count.

Adult↗
PubMed1990

Matting of scalp hair during shampooing--a new look.

We present a new case of irreversible hair matting, a rare, but important and alarming, acquired hair disorder. This case was investigated to test the causal hypothesis proposed in 1984. At the same time four other specimens of matted hair from patients and tangles from normal individuals were also examined. Light and electron microscopy showed dramatic permanent twisting and bending of the hairs through 180 degrees. There was marked variation in the fibre width of hairs from matted samples, with some longitudinally split along a considerable length. This bending and entanglement of hairs of varying widths (felting) seemed to be the main reason for the hairs becoming so dramatically knotted together in four of the cases. In only one case was there any evidence of a viscous fluid binding the hair together. This finding suggests that there may be two different mechanisms involved in hair matting.

Adult↗