Organization of neurons labeled by antibodies to gamma-aminobutyric acid (GABA) in the superior colliculus of the Rhesus monkey

The inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is found in the superior colliculus (SC) of many mammalian species. In cat, several distinct classes of putative GABAergic neuron have been identified using antibodies directed against the neurotransmitter. It is not known whether these classes are found in other species. To study this, we examined the distribution, morphology, ultrastructure, and synaptic organization of GABA immunoreactive neurons in the SC of the Rhesus monkey (Macaca mulatta). Antibody-labeled neurons were distributed throughout the monkey SC, but were most densely concentrated within the zonal and superficial gray layers (32.5% of the total). These neurons were all small cells ranging from 6.6-16.3 microns in average diameter, and had granule, pyriform, and horizontal morphologies. Four types of labeled profile were identified in single ultrathin sections with the electron microscope. Presynaptic dendrites (PSDs) contained pleomorphic vesicles, received synaptic input from unlabeled axon terminals, and sometimes formed symmetric synaptic contacts with postsynaptic profiles. Two subtypes were found. One type contained loose accumulations of synaptic vesicles throughout the profile and had a distinctive varicose shape. The other type contained small discrete clusters of synaptic vesicles near the site of synaptic apposition. The former were much more common. Profiles with typical axon terminal morphology were also found. These profiles usually contained numerous flattened vesicles and formed symmetric synapses with postsynaptic profiles, both dendrites and cell bodies. Some conventional dendrites and myelinated axons were also labeled. Serial ultrathin section reconstructions revealed that PSDs formed complex synaptic relationships with other elements. Retinal terminals, identified by their characteristic pale mitochondria, established synaptic contacts with both types of PSD. These PSDs also established contact with each other, providing a possible anatomical substrate for disinhibition. We conclude that the monkey SC has multiple GABAergic cell types, similar to those found in cat, and may represent an organization common to both mammals and some other vertebrate species. The circuitry established by these cell types may provide a mechanism for disinhibition as well as inhibition in the mammalian SC.     

A phase I study of prolonged infusion 5-fluorouracil and concomitant radiation therapy in patients with squamous cell cancer of the head and neck

The radiosensitization properties of 5-FU are well documented, and clinical trials have suggested improved local control and survival in head and neck cancer. Clinical trials to date have used bolus injection or short term (less than or equal to 5 days) 5-FU infusions. To determine the maximum tolerated dose (MTD) of 5-FU given as continuous intravenous infusion for 12 weeks concomitant with conventional radiation therapy, 18 patients with advanced inoperable head and neck cancers were treated with conventional irradiation and 100, 200, 250, or 300 mg/m2/day of 5-FU. A dose of 250 mg/m2/day was determined to be the maximum tolerated dose and is recommended for Phase II studies.     

Deterioration following delay in performing femoral angioplasty

It is not uncommon for a delay to occur between assessment arteriography and angioplasty attempt. We reviewed retrospectively the arteriograms of 61 patients where such a delay occurred to assess progression of superficial femoral artery (SFA) disease in this interval. A mean delay of 14.6 days (range 2-60 days) occurred between arteriogram and angioplasty attempt. Arteriographic deterioration was found in six of 61 patients (9.8%) and in three this precluded angioplasty. Of the six patients four had initial arteriography via the same side as the SFA disease whilst two had arteriography via the contralateral femoral approach. We discuss the aetiology of this phenomenon and suggestions are made to reduce its incidence.     

Chondroplastic graft augmentation rhinoplasty

A challenging surgical problem is the correction of supra-tip depression of the nose following collapse of nasal septal support. Numerous materials have been used in augmentation rhinoplasties attempting to correct this deformity, all having certain disadvantages. A modified technique is described in which costal cartilage surrounded by perichondrium is grafted in such noses; the results of a small series is discussed. The problems of graft distortion and resorbtion appear to have been satisfactorily overcome by using this procedure.