Synaptic transmission between rat superior cervical ganglion neurons in dissociated cell cultures.

The principal neurons of the rat superior cervical ganglion (SCGN) when established as dissociated cells in tissue culture form synapses among themselves. In the present study we have examined this synaptic interaction when these neurons are co-cultured with several other types of tissues. Dissociated SCGN were prepared from perinatal rats and studied, after 3-4 weeks maturation, with intracellular recording techniques. Synaptic interactions between sympathetic neurons were demonstrated when these cells were: (a) grown with explants from newborn rat thoracic spinal cord, (b) when the SCGN had survived for several weeks subsequent to removal of the spinal cord explants, and (c) when the SCGN were grown in the presence of an adrenergic target (interscapular brown fat cells). Unidirectional, reciprocal, recurrent and complex chemical synaptic networks, consisting of convergence and divergence, characterized connections between SCGN. All synaptic responses were cholinergic since they were reversibly blocked by hexamethonium or mecamylamine but were not sensitive to 10(-5) M phenoxybenzamine. Removal of the spinal cord explants did not significantly alter the proportion of chemical synaptic interactions between SCGN (more than 25%) from matched cultures. Anatomical observations established that in cultures with brown fat, innervating neurites appeared on the fat cells; these neurites frequently expanded to form varicosities that resembled the adrenergic terminals normally seen on brown fat in the animal. Synaptic profiles also occurred on the neurons in these cultures and some of these were shown to be cholinergic. The proportion of neuronal interactions in the combined SCGN + fat cultures was low, however, suggesting that co-culture with target tissue might influence the frequency of interconnections developed between SCGN in culture. Other factors, such as the presence of non-neuronal cells, degree of dissociation, cellular density, culture age and the survival of certain types of SCGN in culture are discussed as variables related to the formation of synapses between SCGN. Non-rectified electrical coupling between SCGN was also observed in 17 out of 679 pairs (2.5%) of neurons. Attenuation factor for electrically coupled action potentials ranged between 1 and 43.5.     

Changes in the caries experience of 12-year-old Sydney schoolchildren between 1963 and 1982

A study of the caries experience of 12-year-old children attending public high schools in the northern suburbs of Sydney was undertaken in 1982. The data obtained were compared with those from a similar study conducted in the same area in 1963. In the period between the two examinations, Sydney's water supply was fluoridated and fluoride toothpastes became widely available. There was a major improvement in dental health in the 19-year interval between the surveys. The mean number of decayed, missing, and filled teeth (DMFT) per child declined from 8.49 in 1963 to 1.37 in 1982, a reduction of 84%. An analysis of the DMFT index showed that the greatest reductions occurred in the decayed tooth (DT), and missing tooth (MT) components (95% and 94%, respectively). In 1982, in contrast to the situation in 1963, the backlog of unmet restorative dentistry needs was low.     

Successful treatment of functional amblyopia associated with juvenile glaucoma

Twelve patients with either unilateral or bilateral juvenile glaucoma underwent standard amblyopia management for the treatment of suspected functional amblyopia secondary to their glaucoma. Despite the presence of glaucomatous cupping or corneal changes, the amblyopia therapy was successful in ten patients.Dedicated to Dr. G.K. von Noorden on the occasion of his 60th birthday     

Hearing preservation after removal of acoustic neurinoma

Between January 1, 1978, and July 1, 1983, 149 patients underwent acoustic ncurinoma rcmovnl (151 procedures). Of these, 119 ears (118 patients) had had some degree of hearing on the affected side preoperatively, and in all of them the tumors had been removed by a posterior cranial fossa approach. Fourteen (12%) had measurable hearing preserved postoperatively — serviceable in eight cars and poor in six. The patients with preserved hearing had had their hearing loss for a shorter period, slightly better preoperative hearing levels, and a smaller tumor. The complications, morbidity, and mortality in this group were comparable to those in other series. It is concluded that preservation of hearing is a worthwhile goal that can be achieved without increased risk.