Acoustic properties of polyvinyl chloride gelatin for use in ultrasonography

Visualization of superficial structures with conventional rapid scanners has been difficult. A solid flexible polyvinyl chloride (PVC) gelatin slab used as a stand-off material can provide a constant scan distance and thus overcome the problem of poor near field resolution. PVC gelatin expands the capability of the 3-4 MHz transducer to delineate superficial structures. We report on the acoustic properties of the PCV gelatin, including the values of velocity and attenuation as a function of both frequency and temperature, and the comparison of data with published values of velocity and attenuation for water, soft tissue, and a phantom material.

Specific binding of vasoactive intestinal peptide to human circulating mononuclear cells

The interaction of the neuropeptide vasoactive intestinal peptide with human circulating mononuclear cells has been studied. Mononuclear cells were able to bind radiolabelled vasoactive intestinal peptide; the binding was rapid, reversible, saturable, and specific for vasoactive intestinal peptide. A fragment of vasoactive intestinal peptide (10-28) was 25-fold less effective than intact peptide as a competitor for the binding of the tracer. Secretin was 100-fold less effective as a competitor and glucagon competed poorly even at concentrations 10 000 times greater than that of the tracer molecule. In tracer dilution studies, the binding suggested a single class of binding sites with an apparent dissociation constant (Kd) of 2.4 X 10(-10) M and a capacity of 2 000 sites per cell. In the presence of vasoactive intestinal peptide, there was a dose-dependent augmentation of cyclic AMP in the mononuclear cells. The concentration of vasoactive intestinal peptide which produced a half-maximal effect was the same as the Kd for the peptide binding. We conclude that mononuclear cells have specific high-affinity binding sites for vasoactive intestinal peptide. Interactions between mononuclear cells and vasoactive intestinal peptide may be an important mechanism modulating local immune responses within tissues innervated by vasoactive intestinal peptide containing neurons.

Partial purification of [3H]mianserin binding sites

Frontal cortex membranes were solubilized with digitonin, prelabelled with 4 nM [3H]mianserin, and partially purified by isoelectric focussing. Bound [3H]mianserin separated from free [3H]mianserin as a single radioactive peak with a pI value of 5.03. A 14-fold purification was achieved. Focussing in the presence of 1 microM ketanserin (R 41468) or 1 microM chlorpyramine (a histamine H1-antagonist) or 10 microM spiperone (an S2-antagonist) completely abolished the peak of radioactivity at pH 5. Pharmacological characterization of the eluted radioactive peak revealed both histaminergic and serotonergic binding properties. The data suggest that the serotonergic and histaminergic components of [3H]mianserin binding to frontal cortex are not separable by solubilization, gel filtration or isoelectric focussing.

[3H]Mianserin binding to solubilized membranes of frontal cortex

[3H]Mianserin binding sites were characterized in membranes of dog frontal cortex and solubilized with digitonin. The solubilized [3H]mianserin binding sites retained the binding characteristics of the membrane preparation. The dissociation constant (KD) for the soluble material was 2.2 nM which compared closely to that of the membrane-bound site (1.1 nM). Drug binding profiles indicated that the solubilized sites were both serotonergic and histaminergic in nature. Drugs active both H1- and S2-receptors potently displaced [3H]mianserin with Hill slopes close to 1. More selective serotonergic drugs such as LSD and spiperone competed for [3H]mianserin binding with shallow displacement curves. Of the neurotransmitters tested, serotonin was the most potent for both preparations. Because all the components of [3H]mianserin binding co-solubilize, the soluble material can be used to isolate individual sites.

Ascorbate injury and EDTA (or manganese) protection of D2-dopamine receptors

Ascorbic acid, EDTA, and Mn2+ modulated neuroleptic binding to membrane receptors but not to solubilized receptors. Preincubation with ascorbic acid at 22 degrees C produced a profound time-dependent decline in [3H]spiperone binding to membrane receptors (prepared in Tris-ascorbate buffer). Ascorbate had minimal effect if introduced simultaneously with [3H]spiperone in the incubation medium, and receptor binding was performed and assayed at 0 degrees C. Binding to the solubilized receptor was not ascorbate sensitive. Both EDTA and Mn2+ blocked the ascorbate effect on membrane receptors but were without effect on solubilized receptors. The preparation and incubation buffers used for [3H]spiperone binding studies should include EDTA if ascorbate is present in the buffer.

Assay for soluble dopamine receptors by the precipitation method

Receptors with high affinity for neuroleptics (D2-type dopamine receptors) were solubilized from dog striatum using 1% digitonin. Soluble receptors were labelled using [3H]spiperone, and the bound 3H-ligand was separated from the free [3H]spiperone by molecular sieving on the Sephadex G-50 columns. This paper presents a polyethylene glycol (PEG) precipitation method designed to replace this column method. IC50 values for both neuroleptics and dopamine agonists, as well as dissociation constants for [3H]spiperone were similar for both methods. The precipitation method yielded a receptor density of 64 fmol/mg protein whereas the molecular sieving technique yielded a value of 194 fmol/mg protein. The qualitative similarities between the methods validates using the rapid precipitation method for monitoring the receptor during various stages of its purification.

Irradiation of choroidal melanoma with iodine 125 ophthalmic plaque

Radioactive iodine 125 is a low-energy gamma isotope with physical characteristics suitable for irradiation of intraocular tumors. Metal ophthalmic applicators have been designed to shield vital ocular structures while allowing irradiation of the tumor. We compared the radiation effects of iodine 125 and cobalt 60. The Greene melanoma was transplanted into the suprachoroidal space of rabbits. The tumor then grew as an intraocular mass, was irradiated, and was followed up for two months before enucleation. Histopathologic examination defined the extent of the radiation damage to the tumor and other ocular structures from the iodine 125 and from the cobalt 60. The eye irradiated with iodine 125 suffered minimal radiation damage, whereas the tumor was sterilized. The eye irradiated with cobalt 60 showed substantial radiation damage, and the melanoma was incompletely treated. Our results support the use of iodine 125 in treating intraocular tumors. More research is needed as to optimum total dose and dose rate.

Interactions of Human Fibrinogen with Glass Surface

Plasma protein adsorption is an important effect in thrombosis at artificial surfaces. A study was made of interactions between human fibrinogen and glass. Three types of information were developed: (1) rates of adsorption and equilibrium surface conc. (mass/area). (2) reversibility properties of the adsorbed layer, e.g. exchange between surface and solution; (3) molecular changes in fibrinogen after desorption. Kinetics of adsorption, exchange and desorption were studied in tris buffer, using Kabi fibrinogen labelled with iodine (125 or 131). Changes in desorbed fibrinogen were assessed by circular dichroism and SDS-acrylamide gel electrophoresis. It is found that adsorption is limited to a monolayer over conc, range 50 to 300mg%. Desorption into original buffer does not occur, but rapide exchange between solution and surface is observed. Exchange increases in rate and extent with increasing protein conc, but a residue of 20% of the layer remains unexchangeable. Adsorption decreases with increase in conc, of tris at constant pH. Also treatment of adsorbed layers with tris of higher conc, than was used for adsorption results in desorption, with 20% remaining nondesorbable. Desorbed fibrinogen has a greatly reduced α-helix content and exhibits only one band (compared to 3 originally) in SDS-acrylamide gels, intermediate between Bβ and γ bands. Since 20% of bound radioactivity resides in v-chains these data may indicate that fibrinogen adsorption on glass involves preferential binding of γ-chains. Solution-surface exchange may analogously involve subchains as opposed to whole molecules. Such phenomena may play a role in blood-surface contact situations.

Radiation therapy of choroidal melanoma

During the past 8 years, 32 patients with melanoma of the choroid have been treated with cobalt-60 ophthalmic applicators. Excluding three patients lost to follow-up, 24 patients who have now been observed for at least 3 years after treatment form the subject of this study. Each application but two delivered 8,500 to 10,000 rads to the tumour apex. A second application was performed in large tumours showing a poor response to the initial plaque treatment. The factors affecting results include age of the patient, tumour size, total dose delivered, and dose rate. Three out of seventeen patients with tumour diameters greater than 12 mm died of their disease with pulmonary and/or liver metastasis. Three eyes required enucleation and no residual tumour was found in two specimens. Three patients, average age 76 years, died from causes other than melanoma. An 83 per cent relative survival, excluding the three patients lost to follow-up, compares favourably with enucleation. The low incidence of metastasis after radiotherapy suggests augmentation and/or continuation of the host's immune response. Low energy radiation using Iodine-125, with its unusual protective characteristics is ideal for treatment of choroidal melanoma.

Effectiveness of lead lenses in reducing radiation exposure

Optically ground prescription lenses of glass, leaded glass, and plastic were exposed to radiations that simulated routine angiography. Radiations transmitted through the lenses were measured. Plastic provided no protection, regular glass provided moderate protection, and high lead content glass reduced radiation transmission by approximately 70%. A brief review of the literature concerning the biological effects of radiations to the eye is included.

Electron microscopy of magnesium-depleted bacteria

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