Biomedical subjects
N Ambrose
Publications and source records attributed to N Ambrose.
Immune responses to Dermatophilus congolensis infections.
Complex mechanisms underly the establishment of dermatophilosis, an exudative and proliferative skin disease of ruminants. This multicomponent system involves the bacterium Dermatophilus congolensis, transmission by various routes including flies, host genetic factors and immunosuppression by Amblyomma variegatum ticks. Here, Nick Ambrose and colleagues summarize recent evidence for an association between A. variegatum and severe chronic dermatophilosis in cattle. Breed-based differences in resistance to dermatophilosis are probably related to immunity to ticks or resistance to the immunosuppressive effects of ticks. Immunity to dermatophilosis might involve non-classic responses mediated by CD1 antigen presentation and gammadelta T cells. Progress towards vaccination is further complicated by strain-specific acquired immunity to D. congolensis.
Characterization and discrimination of three Theileria parva stabilates involved in East Coast fever vaccination.
Three vaccine stabilates of Theileria parva, of which sporozoites are being used against East Coast fever, were characterized by immunological and molecular biology techniques before being used for a national vaccination campaign in Kenya. T. parva Marikebuni stabilates 316 and 3014, and T. parva Lanet were used in this study and were discriminated from other Kenyan field Theileria isolates. IFAT results showed that all the animals were producing antibodies regardless of the stock used. Primers designed on the TPR1 gene sequence were used for PCR and Decamers were used for RAPD. Specific DNA band patterns (1,877 bp; 1,059 bp, and 443 bp) for the three vaccine stocks were observed. These molecular markers could be used to trace vaccinated animals in Kenya and to identify which isolates are responsible for reactions in animals.
Children recovered from stuttering without formal treatment: perceptual assessment of speech normalcy.
Current evidence suggests that young children who recover from stuttering are essentially stutter-free. However, there is no evidence to indicate if their speech is perceptually indistinguishable from normally fluent peers or whether they retain perceptually unusual speech. One important example of recovery from stuttering is children who have recovered without receiving formal treatment. An investigation was conducted to determine if the speech of these children is perceptually different from the speech of children who have never stuttered. Speakers consisted of 10 preschool and early school-age children documented as recovered from stuttering without benefit of formal treatment. In a series of studies they were compared with 10 children who had never stuttered. Three groups of judges-sophisticated, unsophisticated, and experienced-were separately asked, using videotaped speech samples of the children, to decide which samples were from children who used to stutter. Results revealed that the children who recovered from stuttering were perceptually indistinguishable from the normal controls. The same result was obtained regardless of whether the samples were presented in paired-stimulus or single-stimulus mode. Two of the groups of judges were also instructed to rate the speech naturalness of the speech samples. The speakers were not distinguished on this measure either. Methodological issues and the implications of the findings are discussed.
Genetics of stuttering: a critical review.
The fact that stuttering runs in families has been documented over a long period and has led to speculations and research about the role of a genetic component to this disorder. Although the genetic factor cannot be proved by familial aggregation and twin studies alone, such research has continued to provide support for a relationship between stuttering and genetics. The purposes of this article are to review and critique the research in this area. The article first assesses research methodologies that have been employed in familial studies of stuttering. It proceeds to review and critique incidence, twin, and aggregation studies. In addition, it includes sections on subgroups, genetic models of stuttering, and implications for future research as well as for clinical work. With a focus on improved methodology and recent findings, a current perspective on our knowledge of the genetic component to stuttering is provided. Among other conclusions, the article emphasizes that failure to consider epidemiologic factors has probably biased previous results regarding the genetics of stuttering. New preliminary data also appear to provide evidence that spontaneous recovery and chronicity are influenced by genetic factors. Generally, however, the review of incidence and twin studies, as well as of evidence for the various inheritance models, confirms previous conclusions about the interaction between genetic and environmental factors in stuttering.
Culture filtrate proteins of Dermatophilus congolensis.
In previous studies on the antigens of Dermatophilus congolensis very little attention has been given to the hyphae and to excreted-secreted products (ESP) of actively growing bacteria. In this study we have grown four isolates of D. congolensis in a serum free synthetic liquid culture medium based on RPMI 1640. Diafiltration and ultrafiltration were used to prepare ESP from infected culture fluid. These methods produced sufficient quantities of ESP that the polypeptide profiles of the four isolates could be examined by SDS-PAGE and Western immunoblotting. The four isolates produced a large number of polypeptides in culture, most of which were produced by all four isolates. However each isolate produced polypeptides that were unique to it. Western immunoblotting studies using pooled sera from chronically affected animals from Ghana showed that a number of polypeptides in ESP of a Ghanaian isolate were antigenic. When the same sera was tested against ESP from a Scottish isolate a number of polypeptides of the same molecular weight as those in the Ghanaian isolate and some at different molecular weights were recognized. This indicates that isolates of D. congolensis from different geographical areas produce ESP with shared antigenic determinants.
Cellular responses in experimental chronic and acute dermatophilosis infections of sheep.
The cellular infiltrate into the dermis in dermatophilosis lesions is composed of a range of cell types. The aim of this study was to establish if the composition of the cellular infiltrate in chronic lesions was different from that in healing lesions. Experimental Dermatophilus congolensis infections of sheep were used to study the sequential changes in cell types during the course of chronic and acute infections. Infestations of adult Amblyomma variegatum ticks were used to produce chronic lesions on infected sheep, infections of tick-free sheep provided acute lesions. Histopathology and immunohistochemistry were used to stain and label cell types in the dermis of infection sites. Neutrophils dominated the early response and were present in larger numbers in chronic lesions. Plasma cells were present in both types of lesion, however they persisted in chronic lesions but disappeared from the skin at acute lesion sites after the lesions had resolved. There were 2-3 times as many mononuclear cells in chronic than acute lesions from as early as 4 days post infection and these cells persisted in the chronic lesions. In the chronic lesions the mononuclear cell population was composed of T-helper and T-cytotoxic/suppressor lymphocytes in equal proportions whereas in acute lesions at 14 days post infection, when lesion resolution is underway, there were greater numbers of T-helper cells than T-cytotoxic/suppressor cells.
A longitudinal study of stuttering in children: a preliminary report.
The objectives of this pilot study were to establish methods for longitudinal research of stuttering in children and to provide preliminary data on the variations that occur in disfluencies during the developmental course of stuttering. Twenty-seven preschool-aged children were followed for a minimum of 2 years shortly after they began stuttering. Tape-recorded speech samples were obtained from the children at several intervals during this period. The number of various types of disfluencies was counted in the speech samples obtained in each testing period. Twenty-one children continued to be followed for varying periods of up to 12 years. Eighteen of the 27 subjects received a few speech treatment sessions during the initial period of the study, whereas 9 children did not receive direct treatment. Results indicated that for the two subgroups there was a marked deceleration over time in the mean frequency of stuttering-like disfluencies. Individual subjects' data showed considerable variability in the longitudinal development of disfluency but most subjects followed the patterns of the group means. Much of the reduction took place during the early stage of the disorder, especially near the end of the first year post-onset. There were indications that group differences between chronic and recovering stutterers become distinct by approximately 20 months post-onset.
Onset of stuttering in preschool children: selected factors.
This investigation provides updated information on the onset of stuttering, explores variations in the onset, and studies possible relationship of stuttering onset to the factors of age, gender, familial history, severity, and stress. Data were obtained for 87 preschool children through parent interviews, using a standardized questionnaire. Interviews were conducted within 12 months after the disorder was first diagnosed. Results for selected items indicated that onset tended to occur at an earlier age than was previously thought and was sudden and/or severe in a substantial number of cases. Physical or emotional stress and familial histories of stuttering were reported for many of the participating children. A significant gender factor was found. About twice as many boys as girls stuttered and girls began stuttering at a significantly earlier age. There was a positive relationship between severe stuttering and sudden onset. Several other tendencies for relationship between factors were either weak or not significant for the present sample size. The findings are discussed with special reference to the possible relationship between stuttering onset and maturational processes and the possible contribution of data on onset to the differentiation of stutterers.