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Biomedical subjects

A M Pierce

Publications and source records attributed to A M Pierce.

18 recordsLinked to original sources
PubMed1992

Vulvovaginitis: causes and management.

Over a period of 33 months in a paediatric accident and emergency department, the clinical pattern and possible causes of vulvovaginitis were studied prospectively in 200 girls presenting with genital discharge, irritation, pain, or redness. The major causes were poor hygiene and threadworms. The suspicion of sexual abuse arose in a few girls but no organisms of sexually transmitted disease were found. Urinary symptoms were common but only 20 patients had a significant bacteriuria and 40 had sterile pyuria. Specific skin problems occurred in 28 cases. Simple measures to improve hygiene and treatment of threadworms gave effective relief. Genital irritation caused urinary symptoms with no clinical evidence of infection, and it is advised that antibiotic treatment should await urine culture. Specific skin problems require help from a dermatologist. The possibility of sexual abuse must be considered especially if the vulvovaginitis is persistent or recurrent after adequate treatment.

Adolescent↗
PubMed1992

Hb Rancho Mirage [beta 143(H21)His----Asp]; a variant in the 2,3-DPG binding site showing normal oxygen affinity at physiological pH.

Hb Rancho Mirage was detected in a 17-year-old male in association with a mild anemia. Hemoglobin electrophoresis revealed the variant had a mobility between Hbs A and J on cellulose acetate (pH 8.6) and a mobility like Hb F on citrate agar (pH 6.4). A substitution of His----Asp was found at position 143 in the beta chain, a residue that contributes to the anionic 2,3-DPG binding site in Hb. This variant exhibited normal oxygen affinity at physiologic pH and reduced affinity at alkaline pH. This suggested a subtle shift in the allosteric equilibrium due most likely to the introduction of a negative charge that stabilized the 2,3-DPG pocket. Both homotrophic (heme-heme) and heterotropic (2,3-DPG and protons) effects were reduced; this might be a consequence of an alteration in the carboxyl terminal region of the beta-subunits. Although a His----Asp substitution would be considered to cause reasonable disruption of the 2,3-DPG and C-terminal conformation of the beta- subunits, the properties of Hb Rancho Mirage suggest that, in fact, there appear to be no major perturbation of the critical C-terminal residues.

2,3-Diphosphoglycerate↗
PubMed1991

Osteoclasts: structure and function.

Osteoclasts are multinucleated giant cells showing specialized membrane structures, clear zones and ruffled borders, which are responsible for the process of bone resorption. These cells arrive at the resorption site via the bloodstream as mononuclear cells, derived from haemopoietic precursors in the spleen or bone marrow, which fuse prior to resorption. The osteoclast may share an early progenitor cell, the granulocyte macrophage colony-forming unit (GM-CFU) with monocytes, macrophages and granulocytes, implying that osteoclasts share the pluripotent haemopoietic stem cell with all other haemopoietic cells. In the past, elucidation of the structure of these cells relied upon traditional ultrastructural techniques. Transmission electron microscopic studies revealed details of the unique ultrastructure of these cells and, in combination with stereological techniques, showed the response of cells to various hormonal stimuli. Scanning electron microscopy not only demonstrated the surface appearance of osteoclasts, and their predilection for spreading on various substratum components, but has also been used as an adjunct in resorption assays in which areas of resorption lacunae are measured as indicators of cell activity. Recent advances in fields such as immunocytochemistry and freeze fracture techniques have contributed towards a more detailed delineation of antigenic profile, cytoskeletal structure and localization of enzymatic pathways. The osteoclast is subject to extensive regulatory mechanisms and it has been established that the osteoblast plays a major rôle in mediating the effects of osteotropic hormones and local mediators on these cells. Hence, research aimed at elucidating the coupling mechanisms between these two cells may result in new therapies for bone disease.

Animals↗
PubMed1989

Experimental basis for the management of dental resorption.

Current evidence indicates that the mechanisms by which the mineralized tissues, bone and dentin, are resorbed are similar. Osteoclasts and dentinoclasts are possibly indistinguishable cell types that both resorb mineralized substrata. The principles of treatment of both dental and osseous resorptions should therefore have much in common. This article discusses the basis of hard tissue resorption and explores the rationale for experimental approaches towards the management of dental resorption.

Bone Resorption↗
PubMed1989

Attachment to and phagocytosis of mineral by alveolar bone osteoclasts.

The mechanisms by which the osteoclast attaches to and resorbs bone are not fully understood. Morphologic techniques have primarily been used to examine these mechanisms, but many studies have been based on decalcified material. In this study, the attachment of the osteoclast to alveolar bone and its relationship to the mineral component during the active resorption associated with tooth eruption in the rat was examined using transmission electron microscopy and techniques designed to minimize demineralization effects during processing. Large conglomerates of bone mineral were found within both the ruffled border and the vacuoles adjacent to this area. These deposits were clearly more extensive than the isolated mineral fragments described in other sites by previous investigators. Examination of demineralized sections showed that collagen was largely absent within the ruffled border, and not present within vacuoles. These observations suggest that phagocytosis of bone mineral may supplement its extracellular dissolution in situations associated with rapid bone turnover, such as tooth eruption. Two types of clear zone attachment to mineral were also observed, permitting further speculation on the mechanism by which osteoclasts attach to and move along the bone surface.

Animals↗
PubMed1989

Early responses by osteoclasts in vivo and dentinoclasts in vitro to corticosteroids.

The results of previous investigations examining the association between corticosteroids and bone resorption in vitro have been conflicting. Recent studies have shown that application of a triamcinolone-containing medicament to the dental pulp cavity inhibits dentinoclast-mediated tooth resorption in vivo and in vitro. The aims of this study were to quantitate early ultrastructural changes in osteoclasts in vivo in response to a single steroid dose, and to examine the attachment of dentinoclasts grown in steroid-supplemented cultures in vitro. Resorbing bone around erupting rat molars was examined using TEM and morphometrically quantitated for changes in ruffled border and clear zone areas 1 and 4 h after injections of NaCl, calcitonin, hydrocortisone and prednisolone. Dentinoclasts were harvested from resorption areas in mature rat molars, grown in cultures with calcitonin, hydrocortisone or prednisolone, and fixed and viewed with SEM after 30 min and 2 h. Results of TEM studies showed a significant reduction in areas of resorbing structures in osteoclasts treated with calcitonin at 1 and 4 h, and prednisolone at 4 h. At 1 and 4 h, hydrocortisone showed an increase in resorbing structure areas. SEM results indicated all experimental substances reduced dentinoclast spreading and attachment. It was concluded that the direct effect of steroids on clastic cells may be one of inhibition (the degree of which depends on the nature and dose of the steroid) whereas, in vivo, systemic administration may cause more secondary effects (such as PTH stimulation) to compete with this inhibition. The efficacy of steroid-containing medicaments in inhibiting dentinoclastic resorption may be due to their relatively localized area of application.

Adrenal Cortex Hormones↗
PubMed1987

Does fetal gut obstruction cause hydramnios and growth retardation?

In order to study the effects of impaired fetal intestinal absorption of amniotic fluid, two series of neonates (551 from Liverpool and 172 from Rome) with different types of congenital gut obstruction were divided into two groups and compared. Group A consisted of patients with complete obstruction at or above the proximal jejunum (within 15 cm of the ligament of Treitz). Patients of group B had either incomplete obstruction at group A level or either incomplete or complete obstruction at a lower level. Maternal hydramnios and fetal growth retardation rates were found to be significantly higher in group A than in group B. Maternal hydramnios was associated with an increased prematurity rate (P less than .001). Fetal growth retardation was not related to the presence of additional anomalies. In group A growth retardation was more frequent in babies born after 37 weeks of gestation (P less than .05). No differences were found between the Liverpool and Rome series of patients. These findings suggest that fetal gut function not only contributes to the control of amniotic fluid volume but also, in the final stages of pregnancy, to normal fetal growth. Maternal hydramnios may be the cause of premature delivery of fetuses with upper gut obstructions.

Birth Weight↗
PubMed1986

Evidence for capping of Fc gamma receptors on osteoclasts.

Fc receptors, cell surface structures which bind the Fc portion of immunoglobulins, facilitate endocytosis and mediate triggered enzyme release in the phagocytic cells of the mononuclear phagocyte system (MPS). The osteoclast and the macrophage share many similarities, and it has been suggested that they are both derived from a common MPS precursor cell. Nevertheless, Fc gamma receptors, found on both primitive and well-differentiated cells of the mononuclear phagocyte system, have yet to be demonstrated on the osteoclast cell membrane. The aim of the present study was first, to study the distribution of rat endogenous IgG around resorbing bone using immunohistochemistry and the avidin-biotin-peroxidase (ABC) technique; and second, to determine if rat osteoclasts express Fc gamma receptors, using a recently described technique based on the ABC method. Observations that endogenous IgG accumulated at osteoclast/bone interfaces, and that Fc gamma receptors, expressed by osteoclasts, "capped" in the same area, have important implications regarding the origin of this cell and its mechanisms of bone attachment and resorption.

Animals↗
PubMed1985

Inherited craniofacial fibrous dysplasia.

Craniofacial fibrous dysplasia occurring in a mother and two of her three daughters is reported. In all three patients, the condition was characterized by extensive bilateral and bimaxillary involvement. All patients exhibited radiographic evidence of abnormal maxillary and mandibular bone and tooth displacement. Morphologic examination of deciduous teeth from the daughters showed replacement of normal pulp tissue by fibro-osseous lesion. Because of the familial occurrence of the cases, it is proposed that they comprise an example of inherited craniofacial fibrous dysplasia.

Adult↗
PubMed1979

Identification of ergosta-8,24(28)-dien-3 beta,6 alpha-diol in A delta 8 goes to delta 7 sterol isomerase-blocked yeast mutant.

In addition to the monohydroxysterols found in the delta 8 goes to delta 7 isomerase-blocked Saccharomyces cerevisiae mutant erg 2, a noval dihydroxysterol, ergosta-8,24(38)-dien-3 beta,6 alpha-diol, was isolated. This sterol accumulated to the extent of 2.1% of the total sterol fraction when this mutant was treated with 23-azacholesterol, a known inhibitor of the 24-methylene-sterol-24(28)-reductase.

Chromatography, Gas↗
PubMed1979

The biosynthesis of the free sterols and sterol esters of Neurospora crassa.

The composition of the free and esterified sterols in Neurospora crassa was examined as a function of incubation time in starvation medium containing [2-14C]mevalonic acid. The 14C incorporation was monitored in nuclear methylated and 4,14-desmethyl sterol fractions. After 7 h incubation, sterol esterification had increased from an initial 5% in the log phase culture to 48% of the total sterol pool, with a concomitant decrease in free sterols. The relationship of the free and esterified sterol components in ergosterol biosynthesis is discussed.

Esters↗
PubMed1978

Azasterol inhibitors in yeast. Inhibition of the 24-methylene sterol delta24(28)-reductase and delta24-sterol methyltransferase of Saccharomyces cerevisiae by 23-azacholesterol.

The effects of 23-azacholesterol on sterol biosynthesis and growth of Saccharomyces cervisiae were examined. In the presence of 0.2, 0.5, and 1 micron 23-azacholesterol, aerobically-growing yeast produced a nearly constant amount of ergosta-5,7,22,24(28)-tetraenol (approx. 36% of total sterol) and slowly accumulated zymosterol with a concommitant decline in ergosterol synthesis. Growth and total sterol content of yeast cultures treated with 0.2-1 micron 23-azacholesterol were similar to that of the control culture. Yeast cultures treated with 5 and 10 micron 23-azacholesterol produced mostly zymosterol (58-61% of total sterol), while ergosta-5,7,22,24(28)-tetraenol production declined to less than 10% of total sterol. The observed changes in the distribution of sterols in treated cultures are consistent with inhibition of 24-methylene sterol 24(28)-sterol reductase (total inhibition at 1 micron 23-azacholesterol) and of 24-sterol methyltransferase (71% inhibition at 10 micron 23-azacholesterol). Yeast cultures treated with 10 micron 23-azacholesterol were found to contain 4,4-dimethylcholesta-8,14,24-trienol and 4alpha-methylcholesta-8,14,24-trienol, which were isolated and characterized for the first time.

Cholesterol↗
PubMed1978

Metabolism of delta24-sterols by yeast mutants blocked in removal of the C-14 methyl group.

We have investigated the metabolism of exogenously provided delta24-sterols by whole cell cultures of a polyene-resistant mutant (D10) of Candida albicans blocked at removal of the C-14 methyl group. Comparison of the relative efficiencies of transmethylation at C-24 of selected sterol substrates revealed the following substrate preferences of the Candida delta24-sterol methyltransferase (EC 2.1.1.41): zymosterol greater than 4alpha-methylzymosterol greater than 14alpha-methylzymosterol. Exogenous 4,4-dimethylzymosterol was not transmethylated by mutant D10. Incorporation of the 14C-labelled methyl group of S-adenosyl-L-[methyl-14C]methionine into the sterols of a D10 culture preloaded with zymosterol indicated that zymosterol was a better (40 X) substrate than endogenous lanosterolmfeeding zymosterol to D10 and a polyene-resistant strain of Saccharomyces cerevisiae (Nys-P100) that was also blocked at removal of the C-14 methyl group gave 24-methyl sterols possessing delta22 and ring B unsaturation. Mutant D10 was able to produce ergosterol from zymosterol whereas Nys-P100 produced ergosta-7,22-dienol. When grown in the presence of 3 micrometer 25-aza-24,25-dihydrozymosterol, a known inhibitor of the delta24-sterol methyltransferase, Nys-P100 accumulated 14alpha-methylzymosterol, a minor metabolite in this mutant under normal growth conditions and hitherto unidentified as a yeast sterol.

Candida albicans↗