Antibodies against Pax6 immunostain amacrine and ganglion cells and neuronal progenitors, but not rod precursors, in the normal and regenerating retina of the goldfish

Pax6 is a developmental regulatory gene that plays a key role in the development of the embryonic brain, eye, and retina. This gene is also expressed in discrete groups of neurons within the adult brain. In this study, antibodies raised against a fusion protein from a zebra fish pax6 cDNA were used to investigate the expression of the pax6 gene in the mature, growing, and regenerating retina of the goldfish. On western blots of retinal proteins, the pax6 antibodies recognize a single band at the approximate size of the zebra fish pax6 protein. In retinal sections, the antibodies label the nuclei of mature amacrine and some ganglion cells. At the retinal margin, where neurogenesis and cellular differentiation continually occur in goldfish, the antibodies label neuronal progenitors and the newly postmitotic neurons. Following injury and during neuronal regeneration, the antibodies label mitotically active progenitors of regenerating neurons. Rod precursors, proliferating cells that normally give rise solely to rod photoreceptors and are the presumed antecedents of the injury-stimulated neuronal progenitors, are not immunostained by antibodies to the pax6 protein. The results of this study document the identity of pax6-expressing cells in the mature retina and demonstrate that in the goldfish pax6 is expressed in neuronal progenitors during both retinal growth and regeneration.

Ototoxicity of carboplatin: comparing animal and clinical models at the Hospital for Sick Children

Carboplatin was introduced to the paediatric population as an alternative chemotherapeutic agent in the management of various malignant neoplasms, including sarcomas of the head and neck, in the hope that it would have fewer side effects than pre-existing agents. While many investigators have considered the ototoxicity of this drug only incidentally, others have presumed it to be of negligible importance. A recent animal model of its use has demonstrated damage to the inner hair cells of the cochlea, particularly at the basal turn, with a corresponding high incidence of hearing loss. Similarly, 11 of 22 patients who received this agent at the Hospital for Sick Children over the past 2 years demonstrated a sensorineural hearing loss in the 4 to 12 kHz range. This complication occurred as early as after the first dose and was generally progressively worse with subsequent doses. Consequently, we recommend careful audiologic monitoring of children receiving this agent.

Isolated sphenoid sinusitis: the Toronto Hospital for Sick Children experience and review of the literature

Isolated sphenoid sinusitis is often misdiagnosed because of its rarity and varied clinical presentation. Presentation is often both subtle and suggestive of other intracranial etiologic sites, as determined by the anatomic relationships of the sphenoid sinus. As well, the microbiology of acute sphenoid sinusitis has not yet been clearly defined. We present three cases of acute sphenoid sinusitis and a review of the English medical literature. We isolated Staphylococcus aureus in two of our three patients at the Hospital for Sick Children and also found it to be the predominant organism in 48% of positive cultures in the literature. All three patients presented were initially misdiagnosed, as were 78% of cases in the literature.

Prostaglandin synthetase and prostacyclin synthetase in mature rat skeletal muscles: immunohistochemical localisation to arterioles, tendons and connective tissues

Mature skeletal muscles produce appreciable quantities of prostacyclin (PGI2) and smaller amounts of PGF2 alpha and PGE2, but the sources of these prostaglandins within skeletal muscle are unknown. Monoclonal antibodies to prostaglandin synthetase and prostacyclin synthetase were used to determine which muscle cells produce prostaglandins. The antibody to prostacyclin synthetase stained the tendon, fascia, epimysium and the arteries leading to the muscles. The endothelia of arterioles were also stained in the tibialis anterior and cremaster but not in the soleus muscles. Only trace levels of immunoreactivity were observed with the antibody to prostaglandin synthetase in normal muscles. However, immunoreactivity was observed in the muscles of rats that had been pretreated with aspirin, a drug that inhibits and stabilises prostaglandin synthetase. In muscles of the aspirin-treated rats, all cell types that were stained by the antiprostacyclin synthetase also reacted weakly with the antibody to prostaglandin synthetase. In addition, some cells in the endomysium were strongly stained with the antiprostaglandin synthetase but not with the antiprostacyclin synthetase. We conclude that (1) at least one aspect of the regulation of blood flow in the microcirculation of slow muscles is different from that of fast muscles, (2) that the tendon and connective tissue is the major source of PGI2 in mature skeletal muscles, and (3) that the prostaglandin-dependent effects of insulin and some other stimuli on skeletal muscle may be mediated by the muscle's arterioles or connective tissue.

The management of otolaryngological problems in the mucopolysaccharidoses: a retrospective review

The mucopolysaccharidoses are rare, genetically transmitted metabolic disorders that affect children early in life. These potentially life-threatening diseases almost invariably involve the auditory apparatus and the upper respiratory tract. Thus, the otolaryngologist is frequently involved in the care of these patients. This paper presents a 10-year retrospective review of the management of these patients at the Hospital for Sick Children. Data concerning auditory and upper respiratory pathology are presented. Results indicate that persistent serous otitis, sensorineural hearing loss, and upper respiratory obstruction leading to sleep apnea, are frequent findings in these patients. Specific recommendations are made with regard to appropriate otolaryngologic intervention in children affected with these diseases.