The microsecond rotational motions of eosin-labelled fatty acids in multilamellar vesicles.

The rotational properties of two eosin-labelled fatty acids of different alkyl chain length have been studied in large multilamellar dimyristoylphosphatidylcholine vesicles. The location of the probes at the surface region were ascertained by quenching experiments using a hydrophilic divalent cation solubilized in the aqueous phase (Cu2+) and a hydrophobic aromatic aniline (N,N-dimethylaniline) associated with the lipid. Phosphorescence anisotropy measurements reveal that above the phospholipid phase transition the polarization of eosin luminescence decays monoexponentially in the micro-to-millisecond time range, while below the phase transition a biexponential decay is observed. A model is proposed which attributes the time constants to two separate motions, discrete jumps or 'flipping' of the eosin moiety within restricted boundaries and long-axis rotation. The value of the time-independent term changes with probe position and temperature and reflects orientational constraints imposed by lipid-chromophore interactions. The implications of these results for the study of protein rotations in membranes are discussed.

The association of acrylamide with proteins. The interpretation of fluorescence quenching experiments.

The association properties of acrylamide with a number of proteins in aqueous solution have been investigated by a fluorescence-quenching method previously used in micelles and lipid bilayers (Blatt, E., Chatelier, R.C. and Sawyer, W.H. (1984) Chem. Phys. Lett. 108, 397-400). At pH 7.0, acrylamide partitions between the bulk aqueous phase and the proteins, human serum albumin, monellin and ovalbumin. Comparison with an earlier method of analysis (Sikaris, K.A., Thulborn, K.A. and Sawyer, W.H. (1981) Chem. Phys. Lipids 29, 23-36) confirms the data quantitatively. For human serum albumin at pH 2.2, acrylamide associates according to both partition and binding processes. Equilibrium dialysis experiments performed for the latter system verify that acrylamide associates with proteins.

The effects of Ca2+ on lipid diffusion.

The effects of Ca2+ on rotational and translational diffusion of lipids in multilamellar dimyristoylphosphatidylcholine (DMPC)-water systems were investigated by time-resolved phosphorescence anisotropy steady-state fluorescence polarization and fluorescence recovery after photobleaching (FRAP) experiments. Above the phase transition temperature (Tm), addition of Ca2+ caused a steady increase in the segmental motion of the phosphorescent probe, but resulted in slower diffusion of the fluorescent and lateral diffusion probes. The former result is attributed to changes in the structure of the lipid/water interface that affects the chromophore mobility on the phosphorescence time scale but does not reflect lipid motion. Below the phase transition temperature, slower diffusion of all probes were observed with increasing concentrations of Ca2+, with sudden large changes occurring at [Ca2+] approximately 500 mM. This behaviour is attributed to association of Ca2+ with the lipid phosphate groups and the exclusion of water molecules which results in tighter packing of lipids and smaller segmental motion, leading eventually to the immobilization of lipid molecules.

Cholinergic agents and delay-dependent performance in the rat.

We tested cholinergic agents in delayed matching and nonmatching to position. Each task had a delay between the presentation of information and the chance to act on it later. We used a titrating procedure, new to experiments with rats, to determine the delay. Linopirdine (0.1 mg/kg), which releases acetylcholine, and physostigmine (0.1 mg/kg), a cholinesterase inhibitor, ameliorated the impairment of accuracy produced by scopolamine hydrobromide (0.1 mg/kg). In some cases, scopolamine hydrobromide decreased the number of trials, but physostigmine and linopirdine did not ameliorate that impairment. Both the muscarinic receptor antagonist, scopolamine hydrobromide (0.1 and 0.3 mg/kg), and its peripherally acting analog, scopolamine methylbromide (0.1 and 0.3 mg/kg), decreased accuracy. The impairment produced by scopolamine methylbromide suggests that the deficit produced by muscarinic receptor antagonism may have both a central and peripheral component. At the highest dose, scopolamine hydrobromide decreased the number of trials completed. Thus, some of the effects of scopolamine hydrobromide involve nonmnemonic performance factors. The performance deficits produced by scopolamine hydrobromide suggest that it may be necessary to qualify drug effects in terms of their action on both memorial and nonmemorial aspects of performance.

Environmental influences on incidents of alleged child abuse and neglect in New York State psychiatric facilities: toward an etiology of institutional child maltreatment.

In order to gain a better understanding of the etiology of institutional child maltreatment, 232 allegations of child abuse and neglect in New York State Office of Mental Health operated facilities were investigated with the hypothesis that environmental stresses placed on professional child care workers can precipitate incidents of child maltreatment in institutional settings in the same way that stress and anxiety experienced by a parent can contribute to incidents of abuse in the home. The study focused on administrative policy decisions, patient census and admissions, seasonal influences, staffing levels and identifiable one-time disruptions in daily routines as potential contributors to institutional abuse. A multivariate regression analysis revealed a significant four-variable model for predicting the number of reports of abuse and neglect per month, R2 = .585, F(4,21) = 7.41, p less than .01. Potential preventive measures based on this model were suggested.

Triplet-state detection of labeled proteins using fluorescence recovery spectroscopy.

The experimental procedures for detecting the triplet states of chromophores in solutions (cuvettes) by fluorescence recovery spectroscopy (FRS) are described in detail, together with applications in studies of protein structure and protein-cell interactions in the microsecond to millisecond time domain. The experimental configuration has been characterized by measuring the emission intensities and anisotropies of eosin and erythrosin immobilized in poly(methyl methacrylate). The fluorescence data are compared with those from phosphorescence emission measurements and with theoretical predictions. Triplet-state lifetimes were obtained in 5 mM phosphate buffer, pH 7.0, of concanavalin A labeled with eosin, tetramethylrhodamine, and fluorescein and of alpha 2-macroglobulin labeled with the first two probes. In the case of labeled concanavalin A, iodide quenching measurements gave bimolecular rate constants of approximately 10(9) M-1 s-1. The usefulness of FRS for studying protein-cell interactions is exemplified with eosin-labeled concanavalin A bound to living A-431 human epidermoid carcinoma cells. Finally, the advantages and disadvantages of the technique are compared to those of the alternative phosphorescence emission method.

Effects of quenching mechanism and type of quencher association on stern-volmer plots in compartmentalized systems.

Fluorescence quenching techniques have been used extensively in recent years to examine reaction rates and the compartmentalization of components in lipid micelles and membranes. Steady-state fluorescence methods are frequently employed in such studies but the interpretation of the resulting Stern-Volmer plots is often hampered by uncertainties regarding the mode of association of the quencher with the lipid structure and the nature of the quenching mechanism. This paper presents a method for simulating steady-state Stern-Volmer plots in two phase systems, and shows how the forms of such plots are influenced by the type of association of the quencher with the membrane or micelle (partition and/or binding) and by the type of quenching mechanism (dynamic and/or static). Comparisons of simulated plots with experimental data must take into account the possible combinations of quencher association(s) and quenching mechanism(s). The methods presented are applicable to synthetic and natural membranes and provide a basis for comparing the quenching of fluorescent molecules in biological membranes of differing composition.

Computed tomographic identification of calcified optic nerve drusen.

Four cases of optic disk drusen were accurately diagnosed with orbital computed tomography (CT). The radiologist should be aware of the characteristic CT finding of discrete calcification within an otherwise normal optic disk. This benign process is easily differentiated from lesions such as calcific neoplastic processes of the posterior globe. CT identification of optic disk drusen is essential in the evaluation of visual field defects, migraine-like headaches, and pseudopapilledema.

Rotational dynamics of actin.

The rotational diffusion of actin was studied with the technique of time-resolved phosphorescence anisotropy using actin labeled at Cys-374 with erythrosin iodoacetamide. Immediately after the polymerization of actin was initiated, the correlation time increased sharply, passing through a maximum at 5 min and then declined to low values. F-Actin at equilibrium showed no anisotropy decay. The results were interpreted as indicating the initial formation of short mobile filaments which became increasingly immobile as elongation proceeded, leaving a decay which was dominated by shorter filaments. Some of these short filaments could have arisen by fragmentation of longer filaments. Eventually, the shorter filaments themselves became immobilized by entanglement within the gel matrix. The infinite-time anisotropy increased during polymerization, reflecting a smaller range of angular motion of the probe brought about by restricted torsional motion on the submicrosecond time scale. The results were compared with the length distribution of actin filaments revealed by electron microscopy [Kawamura, M., & Maruyama, K. (1970) J. Biochem. (Tokyo) 67, 437-457]. Polymerization in the presence of 1 microM cytochalasin B abolished the maximum in the correlation time profile and tended to prevent the immobilization of filaments by favoring shorter capped filaments which retained considerable rotational freedom. Addition of spectrin dimer to F-actin caused an increase in the time-invariant anisotropy. Subsequent additions of spectrin-binding proteins (erythrocyte bands 2.1 and 4.1) caused further increases in the anisotropy in a concentration-dependent manner, suggesting additional restriction of submicrosecond torsional motions. The results suggest that actin filaments within nonmuscle cells are rotationally immobile particularly if they are cross-linked by actin-binding proteins.

[Two-year clinical experience with Mevamatic 3--development of a verification and protocol system for irradiation units]. / Zweijährige klinische Erfahrungen mit der Mevamatic 3--Weiterentwicklung eines Verifikations- und Protokolliersystems für Bestrahlungsanlagen.

Since 1983 the computerized record and verify system Mevamatic 3 was tested in connection with the linear accelerator Mevatron 77 (Siemens Company). In consequence of the software development the handling of the system was improved for the clinical routine with the result of a fully utilizable system. The topics of this report are the description of the hardware, the functions of the system, the software development and some possibilities for improvements in the future.

Intraosseous pneumatocysts of the ilium. Findings on radiographs and CT scans.

CT scans demonstrated a localized collection of gas adjacent to a normal sacroiliac joint in 5 patients. In each case the lesion was sharply demarcated by a thin sclerotic rim. A benign bone cyst was confirmed histologically in 2 cases. The radiologist should be aware of this appearance so as to avoid invasive procedures based on a misdiagnosis of infection or neoplasm.