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Biomedical subjects

A Elliott

Publications and source records attributed to A Elliott.

At least 37 records · Page 2Linked to original sources
PubMed1989

Pupil size after extracapsular cataract extraction and posterior chamber lens implantation: a prospective randomized trial of epinephrine and acetylcholine.

The effects of using epinephrine in the irrigating fluid and intracameral acetylcholine were studied by measuring changes in pupil size in the 48 hours following extracapsular cataract extraction and intraocular lens implantation in 39 eyes. Epinephrine reduced peroperative pupil constriction, but its effect was insignificant thereafter. The pupil constriction following acetylcholine was maximal at 2 hours and was still significant at 4 hours, but pupils redilated by 6 hours. Neither drug had any effect after this time. The edge of most lens implants was visible at 6 hours, after which pupils steadily constricted.

Acetylcholine↗
PubMed1985

The structure of C-protein and X-protein molecules and a polymer of X-protein.

C-protein and X-protein are components of the thick filaments in vertebrate skeletal muscles and occupy similar locations in different fibre types. We find that the molecules are both rods about 30 to 40 A wide, but they differ significantly in their lengths, the X-protein molecule being about 350 A long and the C-protein molecule about 280 A. This suggests they are not isoforms. The short length of the C-protein molecule implies that it cannot act in the thick filament as a length-determining agent by a simple vernier mechanism. X-protein associates at low ionic strength (KCl concentration less than 0.07 M) but, unlike C-protein, forms long ordered polymers. These have been examined by electron microscopy to gain information on the molecular shape and on how the molecules interact. The polymers are helically twisted ribbons with a repeat distance along the axis of 660 A. The cross-section of the ribbon is approximately elliptical with major and minor axes of 405 A and 166 A, respectively. From an analysis of the micrographs by optical diffraction, we deduce that the molecules run across the face of the ribbon at an angle of about 15 degrees to the diameter and lie on a two-stranded helix. Models for the polymer are discussed in which the molecules are slightly bowed outwards and bind to each other only at their ends. We suggest that interactions similar to those in the polymer might occur in the thick filaments of muscle, and propose that at each axial position where X-protein attaches along the myosin filament, three X-protein molecules might form an approximately triangular ring around the filament backbone. The appearance of the X-protein polymers is similar to that of the twisted structures called paired helical filaments that make up the neurofibrillary tangles associated with dementia of the Alzheimer type.

Animals↗
PubMed1985

Tuberculin sensitivity in rural Gambian children.

A tuberculin survey was undertaken in 480 Gambian children under the age of 10 years, resident in a group of villages where BCG vaccination, shortly after birth, has been widely practised for about 5 years. Ten tuberculin units of purified protein derivative were given by needle and syringe; reactions of 3 mm or greater were considered positive. An overall tuberculin positivity rate of 59% was found which varied little with age, sex or village size. Among children who had probably not had BCG vaccination the positivity rate was about 20% with an annual increase of approximately 5%. Among children who had probably been vaccinated with BCG the positivity rate was between 60% and 80%. There was a fall in the prevalence of positivity of about 10-20% during the first year after vaccination. Thereafter, positivity rates were well maintained for at least another 5 years.

Age Factors↗
PubMed1985

Serum lactate dehydrogenase and creatine kinase during marathon training.

Serum total creatine kinase (CK) and the lactate dehydrogenase (LDH) isoenzymes were studied in 38 sedentary middle-aged men (aged 35-50 yrs) during a 30 week marathon training programme. Basal CK activity rose by 33% after 15 weeks but a significant rise (27%) in LDH activity took 30 weeks to occur. Post-exercise (maximum test on a bicycle ergometer) CK and LDH activities were higher than pre-exercise levels but the increment in enzyme activity following exercise did not change. LDH1 and LDH2 isoenzyme activity increased by 2.5% and 4% of total LDH respectively while LDH3 and LDH5 decreased by 3.9% and 2.4% respectively over 30 weeks. Post marathon total CK did not correlate with finishing time at 30 mins or 30 hrs post race. The range of CK MB isoenzyme activity at 30 mins post race was 1.8-9.8% of total CK with 11 subjects having a value above 6%. The training programme appears not to have affected muscle CK and LDH release during exercise but isoenzyme distribution changes reflect the adaptations known to occur in muscle during endurance training. Unfortunately only 16 subjects were available for all the investigations, and it is these upon whom most of the data were obtained.

Adult↗
PubMed1984

Molecular organization of paramyosin in the core of molluscan thick filaments.

An arrangement of paramyosin molecules in the polar part of molluscan thick filaments is proposed which accounts for the X-ray diffraction pattern of the smooth adductor muscle (other than the part ascribed to actin) and for the appearance of separated filaments in the electron microscope. The proposed structure is based on the PI arrangement of Cohen et al. (1971), and contains sets of parallel, equidistant molecules with successive molecules displaced along the molecular axis by 72 nm, which we call PI sheets. Every molecule belongs to two PI sheets which are nearly perpendicular. This array is not propagated throughout the filament, but is sheared periodically in the direction of the molecular (filament) axis by 2/5 X 72 nm. The shear occurs along parallel equidistant planes which are inclined to the PI sheets. The analysis of the X-ray data has been made possible by concentrating on those patterns from filaments in which the two sets of PI sheets appear to be mutually perpendicular, a condition brought about by bathing the muscle in aqueous acetone. In one set, there are four intermolecular spaces between shear planes (this appears to be true at least for the smooth adductors of Ostrea edulis, Crassostrea angulata and Mercenaria mercenaria). In the other set, the number varies with species and probably lies between eight and ten in the first two and appears to be six in the last named species. The known paracrystalline nature of paramyosin filaments suggests that this number, though dominant in one species, is not exactly constant.

Animals↗
PubMed1984

"Splicing" of paramyosin filaments.

We have obtained electron micrographs of negatively stained thick filaments from the smooth adductor muscles of the oyster which show in detail the bipolar region of the paramyosin core. The polarity of the filament changes to either side of a line included at only 3 degrees to the filament axis. Along this line the pattern of interactions repeats every 8 X 14.4 nm. A model for the molecular organization is proposed. We conclude that this unusual arrangement occurs in order to maintain the tensile strength of the filament in the same way as the strength of a rope is maintained when joining two ends by a long splice.

Animals↗
PubMed1983

Analysis of surgical versus medical therapy in active complicated native valve infective endocarditis.

From 1972 to 1980, 23 patients (Group A) with native valve infective endocarditis underwent surgical intervention, often for multiple indications, during the active stage of the infective process because of progressive class III and IV (New York Heart Association) heart failure (12 patients), persistent severe hypotension (3 patients), uncontrolled infection for over 21 days (11 patients), aortic root abscess (2 patients), and pericarditis (1 patient). Eighty-five patients (Group B) with active native valve endocarditis, matched for severity of illness, were treated medically. Two patients (9%) in Group A and 43 patients (51%) in Group B died during the hospital admission (p less than 0.001). Any difference in long-term cumulative survival rate between the 2 groups was largely due to the beneficial impact of surgical management on the hospital mortality. Of 23 patients in Group A, 11 (48%) had an entirely uncomplicated postoperative course. Long-term mortality rates in those with aortic valve endocarditis treated medically (79%) were significantly higher than in those with mitral valve involvement (47%) (p less than 0.05). Patients with aortic valve involvement treated surgically had a better hospital (p less than 0.005) and long-term (p less than 0.0005) survival rate than those treated medically. Two groups at risk for postoperative complications were identified; 3 of 11 patients (27%) with uncontrolled infection had an early postoperative recurrence, and 4 of 7 patients (57%) with an aortic root abscess had postoperative prosthetic paravalvular regurgitation. Surgery therefore effects a substantial reduction in hospital mortality in patients with complicated active infective endocarditis (9% versus 51%), but patients with preoperative prolonged periods of uncontrolled infection or with aortic root abscess are liable to postoperative complications.

Adolescent↗
PubMed1982

A rapid quantitative method for the preparation of 123I-iodo-hippuric acid.

The labelling of o-iodo-hippuric acid (hippuran) with 123I by several methods was investigated with a view to producing a simple one-step kit preparation. The requirements for the final product are high labelling efficiency and high radiochemical purity. A method which incorporates CuSO4 . 5H2O as a catalyst was found which gave promising preliminary results. Such variables as pH, mass of CuSO4 . 5H2O, volume of 0.02 N NaOH containing the 123I, reaction temperature and time were investigated in detail and optimum values obtained. The results have led to the production of a kit which can be stored for up to 3 months in liquid form and up to 9 months if freeze-dried. The kit has been used in several thousand patients and has yielded consistently good clinical results.

Humans↗
PubMed1982

Effect of substrate on freeze-dried and shadowed protein structures.

Muscle thick filaments have been prepared for electron microscopy by a method involving freeze-drying and shadowing. The same method applied to filaments on three different substrates gives rise to quite different appearances. The filaments on one of the substrates, hydrophilic carbon, show new detail not previously observed.

Aluminum Silicates↗
PubMed1982

Factors that affect the reproducibility of measurements of left ventricular function from first-pass radionuclide ventriculograms.

To examine which factors affect the reproducibility of ejection fraction (EF), pulmonary transit time (PTT) and segmental wall motion assessed from first-pass radionuclide angiograms (FPRA), 32 patients who had FPRA were randomized for site of injection of isotope (right or left arm) and projection (right or left anterior oblique [RAO or LAO]). The quality of injected bolus was measured from the full width at half maximum (FWHM) of the bolus time-activity curve in the superior vena cava. All patients had two sequential studies on each of two consecutive days, and each study was analyzed independently by two observers. For EF, inter- and intraobserver correlations ranged from 0.94-0.98. EF was higher in the RAO than the LAO projection (mean 47.4% vs 40.3%, p less than 0.001), but neither injection site nor bolus FWHM affected the results. For PTT, interobserver correlations ranged from 0.75-0.93 and intraobserver correlations from 0.61-0.85. Variability in PTT was large, and inter- and intraobserver variabilities were directly related to bolus FWHM (mean 0.60 +/- 0.21 second for interobserver differences in PTT of less than 2.0 seconds, mean 1.55 +/- 0.86 seconds for interobserver differences in PTT of greater than 2 seconds [p less than 0.005]). Differences in FWHM between sequential studies were 0.28 +/- 0.29 second when intraobserver differences in PTT were less than 2 seconds and 1.04 +/- 0.67 seconds when differences in PTT were greater than 2.0 seconds (p less than 0.005). Variations in PTT were not related to differences in projection or injection site. Wall motion was highly reproducible for both projections. In the RAO projection, one of 116 anterior segments (0.9%), one of 116 apical segments (0.9%), and four of 116 inferior segments (3%) were judged normal from one observer's images and abnormal from another. In the LAO view, discrepancies occurred in one of 126 septal segments (0.8%), two of 126 apical segments (1.6%) and four of 126 posterolateral segments (3%). This study shows that EF and wall motion are highly reproducible in any projection, but the choice of projection significantly affects the values for EF from FPRA. PTT measurements are less reliable, highly bolus dependent, and their use in clinical practice depends on quality control of the bolus of injected radionuclide.

Adult↗
PubMed1982

Structure of the thick filaments in molluscan adductor muscle.

Molluscan adductor muscles are in general of two kinds--a slow-acting smooth muscle, which after contraction can go into a catch state, in which tension is maintained for many hours with a small turnover of ATP, and a quicker-acting muscle, usually to some extent striated, which has not the catch property in marked degree, if at all. The thick filaments of both kinds of adductors contain myosin and paramyosin. Those from catch muscles are noteworthy for their high paramyosin content(up to about 90% by weight), which may be correlated with their great length and diameter. The paramyosin forms a core with a surface layer of myosin. Recently, we have shown that the paramyosin core of catch muscles resembles a single crystal in its molecular arrangement, although the degree of regularity varies from one filament to another. The evidence is from electron microscopy both of individual filaments and of pieces of whole muscle embedded and sectioned. Individual negatively stained filaments change greatly in appearance when rotated round their long axes, in a way not compatible with a helical structure. A three-dimensional reconstruction of the filament from micrographs of a rotated filament confirms this. Transverse sections of smooth adductor muscles show no internal features within the thick filaments when viewed accurately along the filament axis. On tilting striations appear on the filaments that may be correlated with the planes of the Bear-Selby net. They are a general feature of the filaments and have been seen in the smooth adductors of P. maximus, O. edulis, Crassostrea gigas, M. mercenaria, of the anterior byssus retractor of M. edulis and in the red (obliquely striated) adductor of M. mercenaria. The arrangement of the myosin on the paramyosin core is not known.

Animals↗
PubMed1981

Structure of filamin and the F-actin-heavy merofilamin complex.

Rotary-shadowed filamin molecules appear as long, highly flexible rods curved into a variety of configurations. The particles observed were 2.7 nm wide but had contour lengths of either 98 nm or 193 nm. The longer particles are probably end-to-end dimers of the shorter but it is not clear how many polypeptide chains these particles contain. Heavy merofilamin, obtained by digestion of filamin with a calcium-activated protease from muscle, has been used to investigate where filamin binds on the actin filaments. Negatively stained filaments of actin plus heavy merofilamin resemble those of pure actin; occasionally rod-shaped material sticking out from the filament is observed suggesting that the elongated shape of filamin is maintained after digestion. Optical diffraction patterns of electron micrographs of paracrystals of actin plus heavy merofilamin indicate that the helical symmetry of the actin filament is unchanged, but the observed interfilament spacing is larger than in F-actin paracrystals. Increased intensity of the second layer-line reflection is observed, suggesting that additional material is lying along the grooves of the actin helix. The elongated shape of filamin and its ability to bind to F-actin in a way similar to tropomyosin suggest a possible role for this protein in regulating the organization and aggregation of actin filaments.

Actins↗