Biomedical subjects
Publications and source records attributed to R Hugo.
The synthesis and identification of a novel series of inhibitors of integrin VLA-4 are described. Their in vitro activity and selectivity against closely related integrins are also presented.
We have developed a homogeneous high-capacity assay format for measuring integrin- and selectin-dependent cell binding to immobilized ligand using V-well microtiter plates. 2',7'-Bis(2-carboxyethyl)-5-(and-6)-carboxylfluorescence, acetoxymethylester-labeled cells are added to ligand-coated V-shaped microtiter wells. Bound cells are separated from free cells using centrifugal force to produce shear stress. Nonadherent cells accumulate in the nadir of the well and are measured using a fluorescence plate reader. Antibody or low-molecular-weight inhibitors of either the ligand or the cell surface receptor result in less cell binding, more cells in the pellet, and increased signal. The optimization and validation of the very late antigen-4/vascular cell adhesion molecule-1 assay is described in detail. We demonstrate that this assay can be rapidly adapted to measure other integrin- and selectin-mediated interactions. This assay format has several advantages over conventional assays. The centrifugal process is biologically relevant and eliminates the washing steps to remove nonadherent cells that can cause well-to-well and plate-to-plate variation. Because the assay is robust with a high signal-to-noise ratio and low variability, it is ideally suited for studying multiple parameters of cell adhesion and for high capacity screening.
The in vitro cell killing potency of an immunotoxin reflects the aggregate of several independent biochemical properties. These include antigen binding affinity; internalization rate, intracellular processing and intrinsic toxin domain potency. This study examines the influence of antigen binding affinity on potency in various immunotoxin fusion proteins where target antigen binding is mediated by single chain antibody variable region fragments (scFv). Firstly, the relationship between affinity and potency was examined in a panel of four scFv immunotoxins generated from different anti-CD3 monoclonal antibodies fused to the 38 kDa fragment of Pseudomonas aeruginosa exotoxin A (PE38). Of these four scFv-PE38 immunotoxins, the one derived from the anti-CD3 monoclonal antibody UCHT1 has highest cell killing potency. Analysis of these four scFv-PE38 immunotoxins indicated a correlation between antigen binding affinity and immunotoxin potency in the cell killing assay with the exception of the scFvPE38 immunotoxin derived from the antibody BC3. However this scFv appeared to suffer a greater drop in affinity ( approximately 100x), relative to the parent Mab than did the other three scFvs used in this study (2-10x). Secondly, the scFv(UCHT1)-PE38 immunotoxin was then compared with a further panel of scFv(UCHT1)-derived immunotoxins including a divalent PE38 version and both monovalent and divalent Corynebacterium diphtheriae toxin (DT389) fusion proteins. When the scFv-UCHT1 domain was amino-terminally positioned relative to the toxin, as in the scFv(UCHT1)-PE38, an approximately 10-fold higher antigen-binding affinity was observed than with the C-terminal fusion, used in the DT389-scFv(UCHT1) molecule. Despite this lower antigen-binding activity, the DT389-scFv immunotoxin had a 60-fold higher potency in the T-cell-killing assay. Thirdly, a divalent form of the DT389-scFv construct, containing tandem scFv domains, had a 10-fold higher binding activity, which was exactly reflected in a 10-fold increase in potency. Therefore, when comparing immunotoxins in which scFvs from different antibodies are fused to the same toxin domain (DT or PE) a broad correlation appears to exist between binding affinity and immunotoxin potency. However, no correlation between affinity and potency appears to exist when different toxin domains are combined with the same scFv antibody domain.
We describe a high-capacity in vivo assay to measure drug-mediated transplant immunosuppression using a mouse model of Sa1 tumor rejection. Sa1 grew poorly and was rejected by 14 days in immunocompetent allogeneic recipient mice. In nude (nu/nu) mice, Sa1 grew more rapidly and was not rejected, confirming the T cell dependence of this response. In immunocompetent animals, administration of immunosuppressive agents resulted in increased tumor growth relative to vehicle-treated animals. Treatment with immunosuppressive drugs such as cyclosporin A (CsA), 40-O-(2-hydroxyethyl)-rapamycin (SDZ RAD), or 2-amino-2-[2-(4-octylphenyl)ethyl]-1,2-propanediol hydrochloride (FTY720) produced dose-dependent inhibition of tumor rejection. By contrast, the drugs did not affect Sa1 tumor growth in nu/nu mice, which is consistent with their predicted indirect effect on tumor size by suppressing immunity, rather than by directly stimulating Sa1 growth. Drug potency, which is usually not described for immunosuppressive agents, was calculated from the linear relationship between drug dose and tumor volume. The potency of CsA was inversely related to the stringency of the histocompatibility barrier. Another advantage of this assay is that the endpoint is an objective size measurement over a short time period, compared with transplant models where the endpoint may not be reached for many weeks and may be more subjective. In addition, this model can measure the potency of combination drug treatments and compare new immunosuppressive drug regimens. For example, the administration of SDZ RAD or FTY720 with CsA resulted in a more than additive increase in potency, compared with the sum of the drugs as single agents.
The aim of this study was to determine the value of educational audiology in the in-service training of teachers of children with hearing loss, in the South African context. Two questionnaires were developed which teachers and headmasters of schools for the deaf/hard of hearing in the Gauteng and Northwest provinces completed. The aim of the first questionnaire was to obtain background information regarding the 10 schools included in this study. The purpose of the second questionnaire was to determine the knowledge of 211 teachers regarding the child with a hearing loss. The background information obtained from the first questionnaire made it possible for the researchers to compare the knowledge of two different groups of teachers on the basis of in-service training. The results indicated definite limitations in the knowledge of the teachers, which must be viewed in light of the specific audiological needs of the child with a hearing loss, who may thus not fulfill his/her potential in the school setting. In spite of in-service training there was no significant difference between the two groups of teachers, which questions the value of existing training.
A combinatorial approach towards identifying inhibitors of VALA-4 was investigated. A library of piperazine-peptoid-bisarylureas was assembled in solid phase and screening in the novel v-well assay enabled the identification of active compounds.
Traditional models of service delivery prevent speech-language therapists and audiologists from identifying and implementing early communication intervention (ECI) in South Africa. This study utilized the framework of the transdisciplinary team approach to develop a collaborative partnership between community nurses and speech-language therapists and audiologists. An interdisciplinary in-service training programme was implemented with 24 community nurses employed at family health clinics in Kwa-Zulu Natal; with the aim of enhancing their knowledge and attitudes toward the early identification and referral of at-risk children to speech-language therapists and audiologists. Three questionnaires were used to evaluate the nurses' knowledge and attitudes. Results indicated that the training programme significantly improved the nurses' knowledge regarding ECI but not their attitudes. Implications of these findings are discussed in terms of service delivery for ECI, and the education and training of early interventionists in the South African context.
Universities in Southern Africa are currently deeply involved in transformation processes in order to ensure world class tertiary education. More specifically in the case of vocationally oriented tertiary programmes, it has become necessary to provide answers to questions like: are the academic outcomes of higher education relevant to and accountable in the context of the workplace? For the Department of Communication Pathology at the University of Pretoria the answer is unequivocal--a programme that aims to provide learning opportunities for professionals who must eventually render a service to a specific population (the individual with a speech, voice, language or hearing disorder), should ensure that the characteristics of this population serve as the basis for strategic planning. This population is an African population. Educational programmes, research projects and community service must therefore be africanised.
The aim of the study was to examine the failure rate of Black and Indian subjects within the excessive cerumen category of the Middle Ear Screening Protocol (MESP). The subjects included four to five year old Black and Indian children attending pre-schools in the Durban Central Region. Thus, a sample of 728 subjects (average age = 4.6 years), 312 Black (135 male and 180 female) and 413 Indian (223 male and 190 female) was screened using referral criteria based on a Middle Ear Screening Protocol (MESP). The results of the study indicated that a significant percentage of Black (38.4%) and Indian (49.9%) subjects failed, due to excessive cerumen. These results are discussed with reference to the literature. A cerumen management program has been outlined and recommended to be implemented in preschools in South Africa.
This study investigated the early communication functioning and hearing abilities of 44 infants with cleft lip and palate, ages 3 to 31 months old. The results revealed that 64% of the subjects had a history of recurrent otitis media with effusion and 33% displayed associated anomalies. 26% of the subjects had mild hearing losses and middle ear pathology at the time of data collection. The subjects as a group displayed average developmental levels for perceptual-cognitive, socio-personal and receptive language skills, but a limited phonetic repertoire and a statistically significant expressive language delay. The results indicated that the subjects experienced a motor developmental delay, but this was not statistically significant. The implications for early communication intervention are to conduct regular hearing measurements and to conduct regular parent-centered therapy with individualized home programmes. Efforts should be directed towards expanding early communication intervention services to include all infants with cleft lip and palate in South Africa.
The speech production changes of a postlingually deaf child and adult with a multichannel cochlear implant were spectrographically analyzed over a period of time. The segmental analysis in both case studies included the measurement of vowel, fricative, and plosive burst duration; first and second vowel formant frequency relationship; and centroid frequencies of fricatives and plosive bursts. The suprasegmental analysis in the second case study (adult) investigated sentence duration, pitch variation, and word stress. Results of both case studies indicated an overall improvement in the accuracy of consonant and vowel productions following the multichannel cochlear implant, in terms of duration, centroid frequencies, and vowel formant frequency relationships. The suprasegmental analysis indicated an overall improvement with the use of the cochlear implant over time. These positive changes in speech production may be indicative of the improved auditory feedback information provided by the cochlear implant.
The aim of the study was to determine the prevalence of middle ear disorders in 4-5 year old Black and Indian children attending preschools in the Durban Central region. Thus, a sample of 728 subjects (mean age = 4, 6 years), 315 Black (135 male and 180 female) and 413 Indian (223 male and 190 female) subjects was screened using referral criteria based on a Middle Ear Screening Protocol (MESP). The results of this study indicated that there was a significant relationship (chi2 = 13,237, p < 0.0001) between race and the likelihood of subjects passing and failing the MESP. A prevalence of 13.0% failures on the middle ear screening tests (visual inspection of the eardrum and tympanometry) was found in the Black subjects and 14.3% failure in the Indian subjects. No statistically significant differences were found between sex (Black male, Black female and Indian male, Indian female) and the likelihood of subjects passing and failing on the middle ear screening tests. Due to excessive cerumen, a significant percentage of Black (38.4%) and Indian (49.9%) subjects failed on outer ear tests. These results are discussed with reference to the literature. The limitations, research and practical implications of the research are also discussed.
Early communication intervention has advanced to include neonatal assessment and management. Currently, however, there are limited diagnostic tools developed from a speech-language pathology and audiology perspective. The purpose of the study was to design a comprehensive neonatal communication assessment protocol and use it to describe the communication skills of 50 biologically at-risk neonates (852 g-3060 g birthweight). The results indicated that the subjects' general development was within normal limits, but their communication abilities displayed a serious delay. A high risk register consisting of 13 factors predicting the subjects' communication abilities was compiled. The length of time before the subjects could successfully take bottle feeds was found to be the strongest predictor of their communication development. The study is of particular relevance to the present South African context which has an increased incidence of low birth weight, thus rendering an enlarged population of biologically at-risk neonates.
The study examines the relationships that exist between early recurrent otitis media, language and central auditory processing in children. A retrospective case-control experimental design was employed and ten subjects were allocated to each of the two research groups, namely children with a history of early recurrent otitis media (research group 1) and children without a history of early recurrent otitis media (research group 2). The children in both research groups were in grade one and turning 7 years old. The language and central auditory processing of the subjects were assessed using the Clinical Evaluation of Language Function (Wiig & Semel, 1980) and the Willeford Battery of Central Auditory Function (Willeford, 1974). The results showed that the language and central auditory processing of the children with a history of early recurrent otitis media were significantly poorer than that of their disease-free peers. The results stress the importance of vigorous identification and management programmes for children with a history of early recurrent otitis media.
Profoundly deaf cochlear implant users provide an interesting population in which to assess the role of distorted auditory feedback in speech, since their electrically stimulated hearing is significantly different from normal hearing. The aim of the study was to evaluate, by means of spectrographic and listener analyses, the speech production changes in a postlingually deafened adult with the use of a multichannel cochlear implant over time, compared to that of hearing aids as well as no-amplification. The results indicated significant improvements in the use of suprasegmental speech features as well in the production of specific segmental features of speech.
Decidual transformation of the peritoneum is a frequent occurrence during pregnancy. Incidence and pathogenesis are vague. Complications like bleeding, suspicion of cancer and adhesions are rare. We present a case of mechanical ileus, followed by acute prerenal failure of the kidney caused by decidual transformation of the peritoneum.
This study researches the occurrence of communicative acts of preschool Afrikaans-speaking hearing-impaired children. The relevance of communication and the incidence of verbal versus non-verbal communication behaviour was also measured. To this end communication samples (30 minutes each) were made of ten three-to-five year old severely hearing-impaired Afrikaans-speaking children in interaction with a familiar adult. The main conclusions of this study were: the subjects as a group are able to express a variety of communication acts appropriately, making use of both verbal and non-verbal behaviour. However, non-verbal behaviour predominates in the communicative behaviour of the group. Some of their verbal utterances are produced without voice.
In recent literature otitis media is linked to speech and language problems, behavioural problems and learning disabilities. Until recently limited research has been done in order to determine the influence of otitis media on the central auditory abilities. The aim of this study was to determine whether otitis media has an influence on the central auditory abilities of children with sensory integration problems. Thirteen persons diagnosed as children with sensory integration problems were selected as subjects. They were divided into two groups, namely eight subjects with a history of otitis media (group A) and five subjects without a history of otitis media (group B). A test battery was compiled for evaluation of the central auditory abilities and was used on the subjects. In terms of group A deviating results were obtained on every subtest of the central auditory test battery which indicated a possible brainstem involvement. Group B obtained normal results in more or less all the tests. The results therefore suggest that chronic otitis media has an influence on the central auditory abilities, i.e. in terms of insufficient brainstem functioning. Implications for research and treatment were discussed.