Antiviral therapy in a child with pediatric human immunodeficiency virus (HIV): case study of audiologic findings.

Over the past decade, much research has been conducted to determine the auditory consequences of human immunodeficiency virus (HIV) infection and acquired immune deficiency syndrome (AIDS). This research, primarily using adult patients, has focused on the involvement of the central auditory nervous system (CANS). Measures of auditory evoked potentials, particularly the auditory brainstem response (ABR), can document changes in the CANS as the disease progresses and during treatment with antiviral therapies such as zidovudine (AZT) and didanosine (ddI). This case study presents the audiologic findings for a child with HIV infection. Evaluations were performed over a 2-year period prior to the initiation of antiviral therapy and following treatment. Audiologic measures included behavioral audiometry, tympanometry, otoacoustic emissions, and ABR latency/intensity functions and rate studies. Findings indicated a gradual shortening of all ABR component latencies following the initiation of antiviral therapy. In addition, a high-frequency hearing loss was detected during the final evaluation subsequent to 19 months of treatment with AZT and ddI.

A model culture system with human gingival fibroblasts for evaluating the cytotoxicity of dental materials.

A model experimental culture system and protocol are described to screen polymerized dental materials for diffusible toxic products. The system employs cultures of human gingival fibroblasts grown in plates containing immobilized samples of polymerized resins. Comparative cytoxicity is evaluated by counting viable cells with the aid of phase optics at several time periods up to 48 h. To achieve adequate statistical sampling, multiple counts are made in four different zones at 90 degrees angles from each sample and at three distances from the centers of samples. The most significant data were generated during a 24 to 48 h test period in climate. This cytotoxicity test measured cell death as a function of time of exposure and distance from the sample (24 h, 0 to 3 mm; 48 h, 3 to 6 mm) and permitted a calculation of the relative cytoxicity for each material, which is termed the viability index (VI). This can be expressed as a percentage related to the control, which is called the time-distance cytotoxicity index (TDCI). This method is simple to carry out because it used basic laboratory equipment, is rapid, and has a sound scientific basis. It focuses on times and distances when or where, or both, the greatest cellular changes are taking place. Some data illustrated are based on the screening of eight different restorative resins. The literature of cell culture testing of dental materials is reviewed. It is concluded that biotoxicity studies ideally should employ diploid human target cells from the oral cavity because the cells retain specialized features. Secondary cultures or strains of human diploid gingival fibroblasts, which are relatively easy to obtain and maintain, are recommended as cells of choice for screening dental restorative materials in vitro.

Inhibition of axoplasmic transport in the developing visual system of the rat-L Structural changes in the retina and optic nerve with graded doses of intraocular colchicine.

In order to study the role of axonal transport in the mediation of transneuronal metabolic stimulations upon a population of differentiating neurons, colchicine, a potent inhibitor of rapid and slow phases of axonal transport, was injected into the eye of albino rats at 1, 3, 5, 10, 15 and 20 days postnatal in concentrations ranging from 10-5 M to 2 X 10-2 M and in quantities of 0.3 to 0.5 microliter. Quantitative light and electron microscopy were subsequently employed to assess reactive alterations in the developing retina and optic nerve. Application of colchicine severely retarded the development of the sensory elements, with disappearance of synaptic ribbons of sensory cell axons, a significant reduction in the thickness of the inner plexiform layer, due to the presence of numerous shruken synaptic elements and the appearance of rosettes of sensory cells displaced to the inner nuclear layer. These alterations were found to be dose-dependent. Counts of ganglion cell populations at various times after application of colchicine demonstrated optimal concentrations which could be injected at each postnatal age without causing ganglion cell degeneration. Ultrastructural examination of such cells revealed varying degrees of disorganization and dissolution of the endoplasmic reticulum with the formation of occasional small cytoplasmic vacuoles. Higher concentrations of colchicine caused extensive vacuole formation in all classes of retinal neurons, scattered hyperchromic cells and widespread degeneration and autolysis. The diameter of the optic nerve was reduced to 60-95% of normal following intraocular colchicine, depending on the concentration employed, but electron microscopy revealed normal patterns of distribution of axoplasmic microtubules and filaments in control and experimental animals and quantitative analysis revealed no significant loss of axons. While no reactive changes took place in individual elements, the periphery of the nerve was often indented by a highly-folded glia limitans. Maximal doses of intraocular colchicine for each age level were established by this study. These were: 1 day. 10-3 M: 5 days, 5 x 10-3 M; 10 days, 5 X 10-3 M; 15 and 20 days, 10-2 M. The information derived from this morphological analysis provides the foundation for subsequent measurements of axonal transport inhibition in the developing visual system to be reported in the second article of this series.