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Biomedical subjects

W A Clyde

Publications and source records attributed to W A Clyde.

At least 55 records · Page 3Linked to original sources
PubMed1975

Occurrence of Diplococcus pneumoniae in the upper respiratory tract of children.

The patterns of colonization of D. pneumoniae were studied over a 46-month period in a group of young children in a day-care center. Forty-four percent of nasal cultures yielded D. pneumoniae. The most frequently isolated serotypes--6, 19, and 23--accounted for 49% of the isolates; the nine most common serotypes included 80% of the isolates. Individual serotypes frequently were carried for several months. Reacquisition of a serotype previously carried occurred frequently. There was limited spread of serotypes among the children despite prolonged contact.

Age Factors↗
PubMed1975

Opsonin-reversible resistance of Mycoplasma pneumoniae to in vitro phagocytosis by alveolar macrophages.

Several species of mycoplasmas are responsible for respiratory disease in animals and man. As yet, little is known about the interaction of these pathogens with alveolar macrophages, one of the primary components of pulmonary resistance to infections. The present study was undertaken to develop an in vitro model to examine this organism-cell interaction, using a human pathogen, mycoplasma pneumoniae, and normal guinea pig alveolar macrophages. During a 24-h incubation of M. pneumoniae with a monolayer of macrophages, mycoplasmas were found to attach directly to the surface of the cells without inducing significant phagocytosis. Ultrastructurally, the organisms appeared bound to the cell membrane by their characteristic attachment organelles. Only after the addition of specific anti-mycoplasma serum were cells able to engulf attached and surrounding organisms. These data suggest that the interaction of M. pneumoniae and alveolar macrophages is a potentially important aspect of disease pathogenesis, and immune factors which might alter this interaction merit further examination.

Animals↗
PubMed1975

Respiratory infections due to Mycoplasma pneumoniae in infants and children.

Systematic monitoring of infants and children in a day-care center revealed infection with Mycoplasma pneumoniae to be more common than expected. Most of these infections were asymptomatic (74%) or associated with mild, nonspecific coryza and cough. Infected children ranged in age from 2 months to 8 years. Complement-fixing and growth-inhibiting antibodies in serum tended to wane rapidly and reinfection was detected in five children after one and one-half to 3 years. In vitro lymphocyte studies revealed antigen-reactive cells were detectable in few of the children under age 4, but thereafter lymphocyte reactivity was found in 53%. These findings suggest that recurrent, unsuspected M. pneumoniae infections occur during infancy and early childhood and that pneumonic disease, common above age 10 years, is an expression of increasing host immune response to the organism.

Acute Disease↗
PubMed1973

Tropism of Mycoplasma gallisepticum for arterial walls.

The fatal encephalopathy associated with M. gallisepticum strain S6 in turkey poults was completely curable by treatment with tylosin or pleuromutilin. The lesions of cerebral polyarteritis disappeared after therapy. Polyarthritis developed in some birds after recovery from encephalitis. Immunofluorescent studies revealed that intravenously injected organisms became localized as microcolonies within the walls of cerebral and periarticular arteries, and in the glomeruli. Turkey IgG deposition was demonstrated on the glomerular basement membranes, but not in the arterial lesions. The results suggest that the pathologic changes caused by this microorganism are due to selective localization and growth in arteries.

Animals↗
PubMed1971

Relationships Between Mycoplasma pneumoniae and Human Respiratory Epithelium.

The interaction was studied between Mycoplasma pneumoniae and its natural host cell, the human respiratory epithelium. Organized, ciliated cells provided by fetal trachea in organ culture enabled examination of the host-parasite relationship by light, immunofluorescence, and electron microscopy. Impairment of cellular function was reflected by disorganization and loss of ciliary motion; this was associated with a sequence of cytopathological changes denoting progressive cell injury. The organisms were found concentrated on the luminal surface of ciliated epithelium and cells lining the submucosal glands. A differentiated portion of the Mycoplasma, consisting of an extension of the unit membrane containing an electron-dense core surrounded by a lucent space, served as the means of attachment to host cells. The findings suggest that the pathogenicity of M. pneumoniae depends upon intimate extracellular infection with production of functional and structural changes initiated by host cell membrane injury.

Journal Article↗
PubMed1971

Immunopathology of experimental Mycoplasma pneumoniae disease.

Experimental Mycoplasma pneumoniae pneumonia in the Syrian hamster resembles natural disease of man and is characterized by peribronchial round cells as well as exudates in the air passages. The nature of these intralumenal exudates was analyzed to assess host-parasite interaction at the respiratory epithelial surface, where infection with the mycoplasma is concentrated. Cells recovered by tracheobronchial lavage revealed changing patterns during the course of experimental disease; free macrophages decreased, polymorphonuclear leukocytes increased, and rosettes of epithelial cells surrounded by leukocytes appeared. Studies on formation of the rosettes in vitro with M. pneumoniae, sera, and cells suggested that complement-dependent immune phenomena were involved. The cellular events were maximal by 2 weeks after inoculation of normal hamsters. When previously infected animals were challenged, the course of infection was shortened, peribronchial infiltrates appeared rapidly, and development of exudates was both exaggerated and accelerated. These findings suggest that leukocytes entering the pulmonary parenchyma and lumen participate in the immune response to M. pneumoniae and contribute to host protection.

Animals↗
PubMed1970

Protective Effect of Vaccines in Experimental Mycoplasma pneumoniae Disease.

The mechanisms of immunity to Mycoplasma pneumoniae were investigated by evaluating different vaccination procedures in an experimental animal model. Hamsters were immunized by intranasal inoculation of broth cultures or by parenteral injections of saline-suspended organisms. All vaccinees received a standardized intranasal challenge which produced pneumonia in 94% of controls. Intranasal immunization with virulent organisms produced a 71% reduction in pneumonia. Subcutaneous and intraperitoneal inoculation of the same organisms yielded 56 and 61% reductions, respectively. Animals similarly immunized with an attenuated strain developed resistance to pneumonia only after intranasal infection. Serum antibody levels did not correlate with protection. Growth-inhibiting activity was demonstrated in bronchial washings of challenged animals, suggesting the development of local antibody in response to infection with M. pneumoniae. Crosschallenge studies were performed in animals vaccinated intranasally with virulent and avirulent variants of the same strain. The avirulent vaccine prevented pneumonia in animals challenged with homologous virulent organisms but not in those receiving an unrelated strain; the virulent vaccine provided protection to both homologous and heterologous challenge. These studies indicate that organism strain variation as well as vaccination technique are important determinants of the immune response to M. pneumoniae.

Journal Article↗