Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography

The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study.     

Paediatric dacryocystorhinostomy

Of 258 cases of dacryocystorhinostomy performed on children in the period September 1981 to September 1991, 130 were for simple, unresolved congenital nasolacrimal duct obstruction. Other indications for surgery included punctal agenesis, lacrimal fistula, post-traumatic and post-inflammatory canalicular obstruction. Of 177 children without canalicular pathology, 171 (96%) were relieved of symptoms with one operation, without canalicular intubation. Of 81 cases with canalicular disease, 55 of 70 (79%) who underwent DCR plus canalicular intubation, and 10 of 11 who underwent DCR plus Lester-Jones tube, were substantially improved with one operation. No child required peroperative or postoperative blood transfusion. Dacryocystorhinostomy in childhood, in experienced surgical hands, is a safe procedure, achieving relief of symptoms in most cases, particularly in the absence of canalicular disease.     

Food intolerance: our practice

This paper describes the clinical presentation of food allergy and/or intolerance (F.A.I.). The role of a diagnostic dietary trial is reviewed. Finally dietary management is discussed.     

Epidermal growth factor concentrations in pig tissues and body fluids measured using a homologous radioimmunoassay.

A homologous radioimmunoassay for the measurement of epidermal growth factor (EGF) levels in pig tissues and body fluids has been developed using an antiserum to recombinant porcine EGF. The assay is highly specific, showing no cross-reactivity with a variety of other polypeptides including the structurally related protein, transforming growth factor-alpha. Furthermore, < 1% cross-reactivity was observed with mouse EGF emphasizing the necessity for homologous assays for EGF measurement. Immunoreactive EGF was present in extracts of pig kidney and pancreas (3.44 +/- 0.43 and 0.76 +/- 0.13 (S.E.M.) pmol/g wet weight respectively), but was not detected in extracts of submaxillary gland or liver. Although immunoreactive EGF was not detectable in uterine, allantoic or ovarian follicular fluids, colostrum contained EGF at biologically active concentrations (0.84 +/- 0.15 nmol/l). Immunoreactive EGF was also present in pig urine, with similar concentrations in samples from male or female animals. In addition, pig urine inhibited the binding of 125I-labelled EGF to 3T3 fibroblasts and stimulated DNA synthesis in quiescent monolayers of these cells, indicating that the immunoreactive material in urine is biologically active. Quantitative comparisons of the data presented here with that published previously indicate considerable species variation in the EGF levels of various tissues and body fluids.     

Distribution and structure of identified tonic and phasic synapses between L-neurones in the locust ocellar tract.

The ultrastructures and distributions of the discrete anatomical synapses which constitute two distinct types of output connections made by individual ocellar L-neurons, L1-3, are described. Outputs to neurones L4-5 are excitatory and transmit tonically, whereas reciprocal connections among the three L1-3 neurones are inhibitory and incapable of transmission for longer than a few milliseconds. The tonically transmitting synapses are located in the lateral ocellar tract and are made between the axons of L1-3, which do not receive inputs, and short branches of L4-5, which make no outputs. Each excitatory connection is composed of a few hundred discrete anatomical synapses, each characterised by a bar-shaped presynaptic density which is 0.15-1.5 microns in length and associated with a large number of round synaptic vesicles. Two postsynaptic profiles are apposed to each presynaptic density. Associated with tonic synapses are abundant invaginations of the presynaptic membrane. Synapses of the reciprocal, inhibitory, phasic connections occur in the protocerebral arbors of L1-3, among numerous output synapses of these neurones. Each phasic connection is composed of a few tens of discrete anatomical synapses. Each bar-shaped presynaptic density is associated with two postsynaptic profiles, and is 0.1-1.0 microns long. Compared with the tonic, excitatory connection, there are fewer vesicles and fewer invaginations of the presynaptic membrane associated with each synapse.