"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.

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.

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.

Listeriosis in renal transplant recipients: report of an outbreak and review of 102 cases

We observed six renal transplant recipients with listeriosis during a 10-week period in the autumn of 1979. Investigation of this outbreak established that the first four cases wer close contacts, all infected by Listeria monocytogenes serotype 1b. The source of infection and route of spread were not identified. A total of 102 renal transplant recipients with listeriosis have now been reported. The major manifestation of disease was meningitis in 50% of the patients, parenchymal disease of the central nervous system in 10%, both meningitis and parenchymal disease of the central nervous system in 9%, and primary bacteremia in 30%. The overall mortality rate was 26%. Pneumonia due to L. monocytogenes, a previously neglected finding, was present in seven patients (7%); five of the seven died. The route of transmission may sometimes be respiratory. Special techniques for isolation of L. monocytogenes from sputum are usually required but not complicated. We recommend that individual renal transplant patients with listeriosis be cared for with secretion and excretion precautions and that they be treated with ampicillin and gentamicin. We advocate the serotyping of all isolates and a careful case-control analysis of all epidemics, but we do not support the use of serologic testing or surveillance cultures.

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.

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.

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.

Medical records. V: A 4 record system and all that

Images

Three-dimensional reconstruction from images of tilted specimens: the paramyosin filament

The three-dimensional structure of the paramyosin filament has been reconstructed from images obtained when the specimen is tilted at different angles about its long axis. The micrographs were correlated spatially using gold marker beads and digitized. The different views contained in each micrograph were combined using a computational technique involving Fourier transforms and the resulting three-dimensional images are presented as various sets of serial sections. The results confirm that the Bear-Selby (1956) net can be seen at all levels in the specimen.

The structure of the paramyosin core in molluscan thick filaments

The thick filaments of molluscan muscles have been examined by electron microscopy and X-ray diffraction in order to test whether the structure of the paramyosin core is crystalline and not helicoidal. In accurately cut transverse sections of the white adductor muscle of the oyster the thick filaments are uniformly stained but, when the sections are titled, parallel striations are revealed. Essentially all the filaments can be shown to exhibit striations which can only be explained in terms of a crystalline structure. The crystallinity is, however, not perfect since the striations although often straight are more frequently curved. Two sets of striations of different spacing can be detected in each filament on tilting to either side of the filament axis. Their spacings when compared to the Bear-Selby net a spacing obtained from X-ray diffraction patterns of the embedded muscle indicate that the striations are seen when the filaments are viewed down the 201 and 301 planes of the Bear-Selby net. Striations have been observed in thick filaments from other catch muscles, the white adductor of the clam, the smooth adductor of the scallop and the anterior byssus retractor of the mussel as well as in a non-catch muscle, the red adductor of the clam. In all cases the spacing striations was similar indicating that, contrary to previous reports, when the conditions are the same the a spacing of the Bear-Selby net is approximately constant from one muscle to another and hence that the paramyosin structure in all these muscles is similar.

Assessment of function of contractile segments in patients with left ventricular aneurysms by quantitative first pass radionuclide ventriculography. Haemodynamic correlation at rest and exercise

Thirteen patients with left ventricular aneurysms complicating myocardial infarction were studied by contrast angiography and by first pass radionuclide ventriculography. The ejection fraction of the contractile segment (EFCS) was measured from both studies using a double hemishperoid model, and the values correlated closely. There was a monotonic relation between EFCS and stroke volume index measured from thermodilution cardiac outputs carried out simultaneously with the radionuclide study. When radionuclide ventriculography was performed at submaximal supine exercise, changes in EFCS paralleled changes in the total left ventricular ejection fraction in 10 of the 13 cases. In nine patients, changes in EFCS paralleled changes in stroke volume index and the relation between EFCS and stroke volume index was maintained at exercise. After administration of the vasodilator isosorbide dinitrate to 12 patients, repeat exercise radionuclide ventriculography showed an improvement in left ventricular ejection fraction and in eight patients EFCS improved. First pass radionuclide ventriculography can accurately estimate EFCS, which may be an important factor in predicting the likely response to aneurysmectomy. Changes in EFCS on exercise are reflected in changes in total left ventricular ejection fraction and stroke volume index. Isosorbide dinitrate may improve contractile segment function on exercise.

District nurse training

Training for district nursing is being reviewed. By 1981 district nurses will have a new administrative structure, a new curriculum, and a new examination. Training for nursing, like that for general practice, is to become mandatory. The history of the development of district nurse training is briefly described.

An evaluation of the A4 folder system in general practice

All 63 general practices known to have introduced the A4 folder system were asked to complete questionnaires comparing A4 records with the traditional medical records envelope system. Of the 77 per cent who replied, an overwhelming majority favoured the A4 system and felt that it helped them to obtain higher standards of care for patients.

Neutron uniformity studies related to clinical total body in vivo neutron activation analysis

Methods of assessing the uniformity of thermal and fast neutron fluence in relation to total body in vivo neutron activation analysis are described. Results are presented for 14 MeV neutrons emitted by sealed tube generators housed in a massive concrete shield, representing a substantial source of neutrons degraded in energy. Optimisation of conditions for patient irradiations is discussed and it is shown that acceptable uniformity of fluence can be achieved with little or no premoderation of the incident neutrons.

Concurrent estimation of total body and exchangeable body sodium in hypertension

1. Total-body neutron-activation analysis in vivo was carried out in 11 hypertensive subjects to measure simultaneously the total body content of sodium, chlorine, calcium, phosphorus and nitrogen. 2. There was a highly significant correlation between total body sodium measured by activation analysis and total exchangeable sodium measured by a standard isotope-dilution technique (r = 0.92, P less than 0.001). Exchangeable sodium averaged 80.3% of total body sodium. 3. The measured values of chlorine, calcium, phosphorus and nitrogen were similar to those for healthy subjects reported by others. 4. Activation analysis in vivo appears promising as an additional tool for investigating sodium metabolism in hypertension, as it is the only method available for determining the total body content of this element. The radiation dose (1 rem) is sufficiently low to permit repeated measurements in the same subject.

Can a myosin molecule bind to two actin filaments?

It is suggested that in striated muscles the two heads of one myosin molecule are able to interact with different actin filaments. This would provide a simple explanation for the appearance and arrangement of cross-bridges in insect flight muscle in rigor.

The instantaneous monitoring of polyacrylamide gels during electrophoresis

The advantages of being able to see protein zones in a gel during electrophoresis (and hence before staining) are pointed out, and a method is described which depends on local increments of refractive index in these zones. The use of local increments of refractive index in polyacrylamide gels for measuring protein concentrations in zones during electrophoresis is briefly considered; it is found that such increments are greater than would be expected from the amount of protein when sodium dodecyl sulphate is present. The enhancement depends on conditions and time of running. This makes quantitative estimates difficult, but the sensitivity of detection of protein zones by observations based on refractive-index changes is greatly increased by this property of sodium dodecyl sulphate. Methods are described for making optically uniform gels (both with uniform and with graded concentrations of polyacrylamide), necessary for observation of small changes in refractive index. A simple dark-field system of observation is described. Examples are given showing protein samples observed with the system during electrophoresis and compared with the same gel stained with Coomassie Blue after completion of the run. Under optimal conditions the optical method is comparable in sensitivity with staining. With the proteins of lower mol.wt. (approx. 15000), the optical method is not so sensitive, becoming less sensitive with longer running time. This loss of sensitivity is greatly decreased by using more concentrated polyacrylamide gels, and graded gels are therefore more suitable for optical observation than are uniform gels. The observation of protein zones during electrophoresis adds nothing to the time needed for making a stained gel and gives much information long before it can be obtained from the stained gel.

A study of changes in whole-body calcium, phosphorus, sodium and nitrogen by neutron activation analysis in vivo in rats on a calcium-deficient diet

1. A method of measuring changes in the total body content of calcium, phosphorus, nitrogen and sodium in rats by activation analysis in vivo is described. 2. The change in the body content of the elements has been measured in rats on a calcium-deficient diet and in control animals, the body nitrogen being used to represent lean body mass for normalization. 3. There were siginificant differences in Ca/N and P/N but not in Ca/P ratios between the animals on a deficient diet and control animals at the end of the dietary period.

Electron microscopy of myosin molecules from muscle and non-muscle sources

Myosin molecules from adult and embryonic vertebrate skeletal muscle, vertebrate cardiac muscle, vertebrate smooth muscle, invertebrate muscle, blood platelets and brain have been examined by a modification of Hall’s mica-replication technique in which droplets of myosin in ammonium formate and glycerol solution are sprayed on a mica substrate at low temperature and then dried in vacuum prior to uni-directional shadowing with platinum. Myosin molecules from all these sources are morphologically indistinguishable and have two globular heads joined to a tail whose length does not differ by more than 10 nm from species to species. The absolute value of the tail length is 150 ± 20 nm (a larger error is given because of the difficulty in defining the point where the tail divides to give the two heads).

A high sensitivity dual-detector shadow-shield whole-body counter with an 'invariant' response for total body in vivo neutron activation analysis

The development of a dual-detector shadow-shield whole-body counting system of high sensitivity is described. The sensitivity and performance of the counter are analysed, with specific references to total body in vivo neutron activation analysis, and shown to be at least comparable with those of many conventional shielded-room counters.

The arrangement of myosin on the surface of paramyosin filaments in the white adductor muscle of Crassostrea angulata

Observations of the surface of intact thick filaments from the oyster Crassostrea angulata have been made in the electron microscope. The surface structure has been revealed by metal shadowing and by a negative staining technique in which aqueous uranyl acetate solution is applied to filaments which have been rendered impervious to this solution. Both methods reveal a regular arrangement of round objects on the filament, interpreted as groups of myosin heads. The arrangement is that of the Bear-Selby net, probably with two or three myosin molecules per node. The possibility is discussed that the helical strands which give rise to the Bear-Selby net may occur in right- and left-handed forms in different filaments.