Analysis of the structure of photosystem I in cyanobacterial thylakoid membranes

Using electron microscopy of negatively stained specimens, we have investigated the shape and degree of association of photosystem (PS) I complexes in cyanobacterial thylakoid membranes. When incubated at high concentrations of magnesium chloride (greater than 0.15 M), the PSI complexes form small ordered arrays in the membrane composed of monomeric complexes in a P1 square lattice of dimensions a = b = 11 nm. Averaged projections of the complex resemble those found for the purified PSI reaction centre after reconstitution (Ford, R.C, Hefti, A. and Engel, A. (1990) EMBO J. 9, 3067-3075). Some small differences in its shape are discussed, with particular reference to the differences in the polypeptide composition of the 2 preparations. We find that the complex remains in the monomeric form in the thylakoid membrane under all the conditions tested.

Does sport negatively influence joint scores in patients with juvenile rheumatoid arthritis. An 8-year prospective study

The influence of sporting activities performed using joint protective measures on deterioration in hand and lower extremity function was evaluated over 8 years in 62 patients with juvenile rheumatoid arthritis (JRA). Sporting activities usually recommended to patients with JRA, such as cycling and swimming, did not negatively influence hand or lower extremity function as compared to a control group of patients not taking part in sporting activities. Besides cycling and swimming, other sporting activities were only performed by a minority of patients (less than 10%). Decreases in total joint scores of both the hands and lower extremities, showed significant correlations with disease duration in patients taking part and in patients not taking part in sporting activities. Polyarticular onset of disease was associated with higher total joint scores of the hands as compared to pauciarticular onset of disease. In lower extremity function, no difference was found between patients with polyarticular onset and patients with pauciarticular onset. Disease duration of longer than 10 years, accompanied by severe functional deterioration, was followed by low participation in sporting activities. Therefore, we suggest that appropriate sporting activities, such as cycling and swimming, can be advised to patients with JRA regardless of disease duration, since no negative effects were observed in our study over a period of 8 years.

Density determination by analytical ultracentrifugation in a rapid dynamical gradient: application to lipid and detergent aggregates containing proteins

A rapidly developing dynamical gradient can be formed in the analytical centrifuge when a buffer solution prepared in D2O is underlayered under the same buffer solution prepared in H2O in a specially designed double sector cell. In a short time the boundary layer spreads to form the gradient. Heavy particles (S greater than or equal to 10S) will band in the gradient corresponding to their density, which can be determined accurately. To this end, the buffer may contain density adjusting additives such as sucrose. We present results with this technique for lipid vesicles, for a Ca-antagonist bound to vesicles, as well as for a lipoprotein and reconstituted regular membrane protein-lipid arrays.

Scanning transmission electron microscopic mass determination of in vitro self-assembled smooth muscle myosin filaments

We have measured the mass per unit length of in vitro self-assembled smooth muscle myosin filaments, using scanning transmission electron microscope darkfield images of freeze-dried samples. The measured values were integral multiples, usually 1, 2, 3 or 4, of 75 kDa per nm. The data corroborate an earlier proposal, that these filaments are built from monolayer sheets of molecules, each sheet having two antiparallel myosin molecules per 14.3 nm of its length.

In vitro assembly of gap junctions

Gap junction structures were assembled in vitro from octyl-beta-D-glucopyranoside-solubilized components of lens fiber cell membranes. Individual pore structures (connexons), short double-membrane structures, and other amorphous material were evident in the solubilized mixture. Following the removal of the detergent by dialysis, these connexons associated to form single- and double-layered, two-dimensional hexagonal arrays (unit cell size a = b = 8.5 nm). The formation of larger arrays was dependent on the lipid-to-protein ratio and the presence of Mg2+ ions. Crystallographic analysis of electron micrographs revealed that lens junctional connexons consisted of six subunits surrounding a stain-filled channel. Upon further detergent treatment, in vitro assembled gap junctions were insoluble and formed three-dimensional stacks while other components were solubilized. SDS-PAGE and mass data from scanning transmission electron microscopy strongly suggest that a 38-kDa polypeptide, which is a processed form of the lens specific gap junction protein MP70, is a major component of the arrays. The in vitro assembly of gap junctions opens new avenues for the structural analysis of gap junctions and for the study of the intermolecular interactions of connexons during junctional assembly.

[Computed tomography in the diagnosis of popliteal artery entrapment syndrome]

Popliteal artery entrapment syndrome (PAES), a rare cause of lower limb ischemia, is due to an anomalous relationship between the popliteal artery and the gastrocnemius muscle in the popliteal fossa. Hypertrophy of the muscle, or its anomalous insertion, can displace or compress the artery, leading to stenosis or obstruction. It is clinically manifested by intermittent claudication and most often occurs in young, healthy men. Arteriography is the method of choice to demonstrate vascular lesions, but it can only visualize change in the course of vessels or intrinsic lesions. Due to its high spatial and density resolution, CT scan can differentiate between bony structures, vessels, muscles, and fatty tissue in the popliteal fossa. It is therefore a very useful supporting examination in PAES and can demonstrate whether or not stenosis or occlusion of the artery results from causes outside the artery itself.

The structural basis for the intrinsic disorder of the actin filament: the "lateral slipping" model

Three-dimensional (3-D) helical reconstructions computed from electron micrographs of negatively stained dispersed F-actin filaments invariably revealed two uninterrupted columns of mass forming the "backbone" of the double-helical filament. The contact between neighboring subunits along the thus defined two long-pitch helical strands was spatially conserved and of high mass density, while the intersubunit contact between them was of lower mass density and varied among reconstructions. In contrast, phalloidinstabilized F-actin filaments displayed higher and spatially more conserved mass density between the two long-pitch helical strands, suggesting that this bicyclic hepta-peptide toxin strengthens the intersubunit contact between the two strands. Consistent with this distinct intersubunit bonding pattern, the two long-pitch helical strands of unstabilized filaments were sometimes observed separated from each other over a distance of two to six subunits, suggesting that the intrastrand intersubunit contact is also physically stronger than the interstrand contact. The resolution of the filament reconstructions, extending to 2.5 nm axially and radially, enabled us to reproducibly "cut out" the F-actin subunit which measured 5.5 nm axially by 6.0 nm tangentially by 3.2 nm radially. The subunit is distinctly polar with a massive "base" pointing towards the "barbed" end of the filament, and a slender "tip" defining its "pointed" end (i.e., relative to the "arrowhead" pattern revealed after stoichiometric decoration of the filaments with myosin subfragment 1). Concavities running approximately parallel to the filament axis both on the inner and outer face of the subunit define a distinct cleft separating the subunit into two domains of similar size: an inner domain confined to radii less than or equal to 2.5-nm forms the uninterrupted backbone of the two long-pitch helical strands, and an outer domain placed at radii of 2-5-nm protrudes radially and thus predominantly contributes to the outer part of the massive base. Quantitative evaluation of successive crossover spacings along individual F-actin filaments revealed the deviations from the mean repeat to be compensatory, i.e., short crossovers frequently followed long ones and vice versa. The variable crossover spacings and diameter of the F-actin filament together with the local unraveling of the two long-pitch helical strands are explained in terms of varying amounts of compensatory "lateral slipping" of the two strands past each other roughly perpendicular to the filament axis. This intrinsic disorder of the actin filament may enable the actin moiety to play a more active role in actin-myosin-based force generation than merely act as a rigid passive cable as has hitherto been assumed.

Biological structures imaged in a hybrid scanning transmission electron microscope and scanning tunneling microscope

A hybrid scanning transmission electron microscope (STEM) and scanning tunneling microscope (STM) is described which allows simultaneous imaging of biological structures adsorbed to electron-transparent specimen supports in both modes of scanning microscopy, as demonstrated on uncoated phage T4 polyheads. We further discuss the reproducibility and validity of height data obtained from STM topographs of biomacromolecules and present raw data from topographs of freeze-dried, metal-coated nuclear envelopes from Xenopus laevis oocytes.

Mass analysis of bacteriophage T4 proheads and mature heads by scanning transmission electron microscopy and hydrodynamic measurements

Quantitative mass analysis of bacteriophage T4 proheads by scanning transmission electron microscopy (STEM) revealed a mass of 79.5 +/- 0.6 MDa, while hydrodynamic measurements yielded a prohead mass of about 80 MDa. This is 25% less than the prohead mass deduced from its polypeptide composition, and this finding implies that the bacteriophage T4 prohead is built of fewer polypeptide copies than previously reported. In contrast, the mass of mature heads measured by STEM, 194 +/- 2 MDa, is in agreement with previous mass measurements of DNA and protein content, and it is consistent with the previously determined stoichiometry. This good agreement of average STEM values for proheads and mature heads with corresponding hydrodynamic measurements suggests that STEM allows faithful evaluation of the masses of large supramolecular assemblies (i.e., greater than or equal to 200 MDa) such as whole viruses or cellular organelles.

Chiari pelvic osteotomy for osteoarthritis secondary to hip dysplasia. Indications and long-term results

Of 142 Chiari pelvic osteotomies for osteoarthritis in dysplastic hips, most performed by Chiari himself, we were able to review 82 and obtain information about 18 by questionnaire. All patients were over 30 years of age at operation; follow-up averaged 15.5 years. Twenty hips had undergone secondary total hip replacement. The outcome was good in 75%, fair in 9% and poor in 16%. High osteotomies all gave good results, and the result also depended on adequate medialisation. Statistics were worse for patients over 44 years of age at the time of operation. For osteoarthritis secondary to hip dysplasia, the Chiari pelvic osteotomy is an alternative procedure to early hip replacement. In contrast to intertrochanteric osteotomy, it has the advantage of facilitating the implantation of an acetabular prosthesis should arthroplasty become necessary at a later stage.

Bilateral stress fracture of the scaphoid. A case report

Bilateral stress fractures of the scaphoid bones in a gymnast are reported and discussed with special consideration of the possible differential diagnoses; bipartite scaphoid and pseudarthrosis of the scaphoid bone. The relevance of the mechanical factors involved and the abduction and dorsiflexion of the wrist in gymnastics are suggested as likely pathomechanisms.

Imaging biological macromolecules by STM: quantitative interpretation of topographs

Methods are discussed which permit the calibration of x-, y-, z-sensitivities, non-linearities and frequency responses of the scanning device of a scanning tunneling microscope (STM) either by interferometry or directly from STM topographs. A technique is presented to measure the frequency response of the complete STM feedback unit and to derive a maximum speed in z direction which allows one to estimate the maximum scanning speed still permitting one to track surface corrugations. The signal transfer characteristics of a STM are evaluated in a direct comparison with high resolution transmission electron microscopy on an identical specimen area. The various effects of contaminants between tip and specimen and the finite tip radius receive special attention.

[The effect of meniscectomy on the strength of the femoral quadriceps muscle after more than 3 years]

This paper investigates the strength of the quadriceps extensor femoris following partial meniscectomy by means of arthrotomy. Measurements were carried out on 30 patients using a velocity-controlled dynamometer. Follow-up ranged from three to twelve years. On clinical examination 17 patients revealed atrophy of the quadriceps, amounting to 1 cm in 12 patients and up to 2 cm in 5 patients. The average difference in muscular strength between the operated leg and the non-operated one totalled 11% in the cases of 1 cm atrophy and 19% in the 2 cm cases. Those patients who presented with no atrophy on the operated leg had an average loss of 4% in muscular strength, which is within the normal range. In addition, an interrelationship was established between measurements carried out at different angular velocities and the extent of quadriceps atrophy. The high percentage of patients showing a weakness of the quadriceps extensor femoris after a long follow-up period is most likely due to the severing of proprioceptors during surgery and to inadequate or lacking postoperative physiotherapy.

Injury of the Achilles tendon: diagnosis with sonography

We determined the diagnostic accuracy of sonography for the assessment of injury to the Achilles tendon. After anatomic investigations in three human cadavers, we performed a clinical study in 24 healthy volunteers and 73 symptomatic patients referred for achillodynia or signs of heel thickening or both in whom a clinical diagnosis of acute total rupture was excluded. High-resolution real-time sonography was performed and the results were compared with final clinical diagnoses (55 patients) and surgical findings (18 patients). Fifty-two of the patients had been involved in various sporting activities (long-distance runners, jumpers, and basketball players), three patients had familial hypercholesterolemia, five patients had systemic inflammatory disease, and 13 patients had no known underlying cause. Anatomic investigation demonstrated accurate assessment of tendon structure and thickness. Sonograms were abnormal in 53 patients (sensitivity, 0.72; specificity, 0.83), and the extent of structural disorders of the tendon could be assessed properly. Abnormalities occurred in the form of tendon swelling (45%), abnormal tendon structure (42%), rupture (15%), and peritendinous lesions (47%). No changes were detected in low-grade disease of short duration, which suggests symptoms caused by functional disorders. Sonography is valuable in the diagnosis of various lesions of the Achilles tendon and its surrounding tissue. Furthermore, it can be used to estimate the degree of tendon abnormality and to differentiate between functional and morphologic conditions.

[Breast biopsy of nonpalpable lesions after mammography-guided wire localization]

Mammography is used increasingly for diagnosis and screening. Its advantage is its ability to discover very small and often nonpalpable mammary lesions. While its sensitivity in detecting pathological changes in the breast is high, differentiation between benign and malignant lesions is less precise, so biopsy is necessary. To ensure removal of the entire lesion with minimal damage to breast tissue, precise localization is mandatory. The accepted technique is the needle-wire method. 39 of 167 biopsies guided by mammography performed during 3 years for nonpalpable lesions detected by mammography were malignant. In 24 of them the histological diagnosis was atypical epithelial proliferation, considered a transition to carcinoma.

[Isokinetic measurements of the stretch strength of the femoral quadriceps muscle in surfers in comparison to healthy, untrained persons]

The strength of the quadriceps muscle of twelve male surfers who practice their sport for more than 10 years was compared with results of 15 male untrained persons. The concentric peak torque of knee extensors was measured every 10 degrees in a range from 90 to 20 degrees isometrically and dynamically with a constant angle velocity of 10 degrees/sec. The difference in torque between the left and the right leg is not significant, but there is a slight dominance in favour of the standing leg. The body weight related strength of the surfers was 3.2 Nm/kg indicating a higher strength characteristic compared to 2.7 Nm/kg of untrained subjects. Moreover the strength values of our group of athletes were above the value of 3 Nm/kg, which is referred to in the literature as representing a good training status. In view of these results it can be concluded that a long-lasting specific training like surfing will change the strength characteristics of the quadriceps muscles, although none of the surfers had undertaken an extensive strength training for the lower extremity.

Ordered arrays of the photosystem I reaction centre after reconstitution: projections and surface reliefs of the complex at 2 nm resolution

We present an electron microscopical analysis of the photosystem I reaction centre, the membrane complex involved in the second light-driven step of photosynthetic electron transfer in plants and cyanobacteria. To this end, ordered two-dimensional arrays were reconstituted from detergent solubilized photosystem I reaction centres and phospholipids, and studied by electron microscopy and digital image processing. Small (P1) and large (P3) hexagonal lattices obtained with reaction centres of the thermophilic cyanobacterium Phormidium laminosum had unit cell sizes of a = b = 8.8 nm and 15.8 nm, respectively. Reaction centres of a second thermophilic strain, Synechococcus sp. OD24, gave square lattices (a = b = 14.5 nm; P2(1)). Irrespective of the packing arrangement, projections of negatively stained photosystem I complexes showed elongated asymmetric shapes with a large domain at one end which was tilted with respect to a small domain forming the tip of the other end. Such features were also found in averaged projections of solubilized reaction centre trimers. Surface reliefs reconstructed from freeze-dried metal-shadowed P2(1) lattices revealed that reaction centres had a ridge of 2.5 nm height projecting from one side of the membrane while their other side was rather flat and exhibited a shallow, central indentation.

Palmar hyperhidrosis CT guided chemical percutaneous thoracic sympathectomy

Palmar hyperhidrosis or excessive sweating of the hands causes, to those affected, emotional and physical disturbance and impediment in professional and social life. The cause is unknown. Sweat glands are innervated by the sympathetic chain of the autonomous nervous system. The center of sympathetic regulation of the upper extremities is located between the segments of D.2-D.9 of the spinal cord. Accepted treatment consists of surgery aimed to excise the third thoracic sympathetic ganglion. Besides the surgical procedure as such, and its complications, there are complications inherent to the excision of the ganglion. These are Horner's syndrome, compensatory sweating in other parts of the body, and recurrence of sweating. CT guided chemical percutaneous thoracic sympathectomy presents an alternative, which in the event of failure does not prevent ensuing surgery. The preliminary experience with this procedure in 50 patients is presented and discussed.

In vitro uptake 153gadolinium and gadolinium complexes by hyaline articular cartilage

This in vitro study evaluated whether Gadolinium (Gd) penetrates into hyaline cartilage and would be incorporated into vital chondrocytes. Hyaline joint cartilage of rabbits was exposed to radioactive 153GdCl3 and to a radioactive 153Gd-DTPA-BSA-complex (DTPA, diethylene-triaminepentaacetic acid; BSA, bovine serum albumine). In addition an exchange experiment with radioactive 153GdCl3 versus Gd-DTPA-di-N-methylglucamine (Magnevist) was performed. Incorporation of 153GdCl3 into neuroblastoma cells, connective tissue cells and chondrocytes was tested. The results showed that the depth and extent of incorporation of Gd depends on the molecular mass and time of exposure. 153Gd-DTPA-BSA complexes exhibited an incorporation rate of maximal 11% +/- 2.8% up to the middle third of the cartilage within 24 h with almost no incorporation (2 +/- 1.9%) for the deep layer. The exchange experiment revealed no uptake of Gd for the deep layer. The maximal incorporation rate of 153GdCl3 into vital chondrocytes was 6.3%. These data indicate that under the condition of MR-arthrography, Gd-DTPA-di-N-methylglucamine will not be absorbed into the deep layers of hyaline cartilage and will not be incorporated into vital chondrocytes.

Invasive lobular carcinoma. Mammographic pattern

A retrospective study was done on 107 histologically proven cases of invasive lobular carcinoma which represent about 11.5% of the total of 934 cases of cancer of the breast. Age, breast parenchyma pattern and morphology, and radiological signs of malignancy were tabulated and correlated with the same data in ductal carcinoma. The number of false negative cases was almost twice as high as in ductal carcinoma type (19% versus 10%). In the majority of cases the patients presented a glandular or dense type of parenchyma pattern, which reduced the internal visibility. Besides spiculated masses, relatively subtle signs of malignancy, as asymmetric density and architectural distortion were relatively more frequently represented than in the ductal type of breast carcinoma. No clear-cut radiological criteria could be found pointing toward the underlying histology. Discreet clinical signs in younger patients with glandular or dense breast should alert the radiologist to the possible presence of this type of carcinoma. Due attention should be warranted to these less conspicuous signs of malignancy such as asymmetric density and architectural distortion.

Correlation between structure and mass distribution of the nuclear pore complex and of distinct pore complex components

Nuclear pore complexes (NPCs) prepared from Xenopus laevis oocyte nuclear envelopes were studied in "intact" form (i.e., unexposed to detergent) and after detergent treatment by a combination of conventional transmission electron microscopy (CTEM) and quantitative scanning transmission electron microscopy (STEM). In correlation-averaged CTEM pictures of negatively stained intact NPCs and of distinct NPC components (i.e., "rings," "spoke" complexes, and "plug-spoke" complexes), several fine structural features arranged with octagonal symmetry about a central axis could reproducibly be identified. STEM micrographs of unstained/freeze-dried intact NPCs as well as of their components yielded comparable but less distinct features. Mass determination by STEM revealed the following molecular masses: intact NPC with plug, 124 +/- 11 MD; intact NPC without plug, 112 +/- 11 MD; heavy ring, 32 +/- 5 MD; light ring, 21 +/- 4 MD; plug-spoke complex, 66 +/- 8 MD; and spoke complex, 52 +/- 3 MD. Based on these combined CTEM and STEM data, a three-dimensional model of the NPC exhibiting eightfold centrosymmetry about an axis perpendicular to the plane of the nuclear envelope but asymmetric along this axis is proposed. This structural polarity of the NPC across the nuclear envelope is in accord with its well-documented functional polarity facilitating mediated nucleocytoplasmic exchange of molecules and particles.