In situ measurements of skeletal muscle power output using new capacitive strain gauge.

Experiments are described in which a fatigue index is determined for the latissimus dorsi muscle of sheep in situ, using capacitive strain gauges. Parallel experiments for invasive and non-invasive measurements are conducted, measuring global contraction and relaxation rates and shortening duration for paced muscle. The results show that, above one pulse per burst (5 V, 100 microseconds pulsewidth), contraction rates (62 +/- 11 mm s-1) and relaxation rates (50 +/- 7 mm s-1) are constant for unloaded muscle. For one animal, fatigue testing with a 2.5 kg load at six pulses per burst shows shortening rates increasing to a maximum (80 mm s-1) after 30 s and reducing to 5 mm s-1 after 150 s. The decrease in shortening amplitude is used as a fatigue index, log displacement against time. Power output is load dependent, measuring 4.7 W kg-1 with a 2.5 kg load. There is good agreement between the invasive and non-invasive measurements, thus providing a method for monitoring changes in muscle parameters non-invasively during future pacing transformation.

Pneumococci causing invasive disease in Britain 1982-1990.

A total of 5348 isolates of Streptococcus pneumoniae was serotyped and screened for insusceptibility to tetracycline, penicillin, erythromycin and chloramphenicol. Of these, 4238 (79%) were isolated from patients who had pneumonia or meningitis or were bacteraemic. Altogether, 3948 (74%) of the isolates belonged to one or other of the serotypes 1, 3, 4, 6, 8, 9, 14, 19 or 23 with serotypes 6, 14, 18, 19 and 23 being frequent causes of invasive disease in young children. Many isolates of type 1 were isolated from pneumonia and few from meningitis. Some 768 (14%) isolates were insusceptible to one or more antibiotic and 591 of these belonged to serotypes 6, 9, 14, 19 or 23. Representatives of type 14 resistant to erythromycin were prominent from 1986 onwards. There was an increase in the number of multi-resistant pneumococci from 1985. Among these were isolates of type 23 insusceptible to penicillin, chloramphenicol and tetracycline and cultures of type 6 resistant additionally to erythromycin.

Information from time-varying vibrotactile stimuli.

Experiments have been carried out to investigate the information transfer available via a single vibrator on the fingertip. In a first experiment, for stimuli with durations 80 to 320 ms, discrimination of a one-octave step change in frequency at the halfway point was investigated. Results were similar for three stimulus types--sinewave, monophasic pulse and tetraphasic pulse--suggesting temporal cues are more important than spectral cues in this task. In a second experiment, subjects were required to perceive changes in a sequence of stimulus elements. A presentation rate of 6.25 elements s-1 was found to give better results than a rate of 12.5 elements s-1. In the former case, the potential information transfer per element was estimated to be approximately 1.0 bits, corresponding to an information transfer rate of around 6 bits s-1. Implications for the design of a tactile aid to lipreading are discussed.

Coding of acoustic features for a single-channel tactile aid.

Measurements have been made on the discrimination of speech contrasts on the basis of single-channel vibrotactile presentation of a variety of speech-derived signals, coded as amplitude- and frequency-modulated pulse trains. Stimulation was at the index fingertip. The signals chosen for tactile presentation were the speech amplitude envelope, the voice fundamental frequency FO and the zero-crossing frequency in the 1.3-6.6 kHz band. "Two-feature' codings, which present two of these signals simultaneously (one coded as stimulus frequency and one coded as stimulus amplitude), were found to be no more effective than "single feature' codings which present only one signal (coded as both amplitude and frequency). Scores for consonant discrimination were highest for the single-feature coding of zero-crossing frequency, although differences between the codings were not, in general, significant. Scores for emphatic-stress discrimination were highest for the single-feature coding of F0, and this coding produced best results overall. A practical wrist-worn device, whose design is influenced by these experimental results is briefly described.

Supramolecular order within the lens: 1H NMR spectroscopic evidence for specific crystallin-crystallin interactions.

alpha-, beta- and gamma-crystallins from bovine lens contain flexible terminal extensions which are readily observed by NMR spectroscopy. By monitoring these resonances, NMR spectroscopy therefore offers a means of examining specific protein-protein interactions in crystallin mixtures. In this paper, a 1H NMR spectroscopic study of bovine lens nuclear and cortical homogenates and various crystallin mixtures is presented. In both homogenates, resonances from the flexible C-terminal extensions of alpha-crystallin and the N-terminal extension of beta B2-crystallin are readily observed suggesting that these regions are not involved in crystallin-crystallin interactions. In the cortical homogenate, resonances from the short N-terminal extension of gamma S-crystallin are also present. The cortical homogenate gives rise to more intense resonances than the nuclear homogenate, suggesting that the cortical region has many more mobile crystallin regions. In both homogenates, the C-terminal extension of beta B2-crystallin and the very short C-terminal extension of gamma B-crystallin are not observed. Thus, the C-terminal regions of these proteins are involved in interactions with other crystallins. Similar effects are observed upon mixing of the individual crystallins, e.g. the C-terminal extension of gamma B-crystallin is absent in spectra of mixtures of total gamma-crystallin and high-molecular-weight beta-crystallin aggregates (beta H). Overall, the results are consistent with a short-range order for the crystallins within the lens.

A 1H NMR spectroscopic comparison of gamma S- and gamma B-crystallins.

Two-dimensional 1H NMR spectroscopic studies are presented on bovine gamma S- and gamma B-crystallin. In gamma S-crystallin, the four N-terminal residues have great flexibility compared with the rest of the molecule and assume a random coil conformation. NMR spectroscopy and electrospray mass spectrometry show that the N-terminal residue is acetylated. Thus, gamma S-crystallin is similar to the acidic beta-crystallins in having a flexible N-terminal extension and an N-terminus that is blocked with an acetyl group but no C-terminal extension. In addition to the short N-terminal extension in gamma S-crystallin, other unassigned resonances are also observed in the NMR spectra. In gamma B-crystallin, however, cross-peaks in the NH to alpha-CH region of the spectrum are essentially restricted to the last three residues of the C-terminal domain. The NMR data imply that gamma S-crystallin has a more flexible structure than gamma B-crystallin. Sedimentation equilibrium studies on gamma S-crystallin are consistent with this proposal. Resonances from the N-terminal extension of gamma S-crystallin are not affected by the presence of alpha-crystallin implying that this region is not involved in interactions between the two molecules. It is concluded that gamma S-crystallin shares structural properties which are intermediate between the beta- and gamma-crystallins.

Vibrotactile and electrotactile perception of time-varying pulse trains.

To establish the best strategy for transmitting speech-derived information via a single tactile channel, measurements were made on the perception of frequency- and/or amplitude-modulated pulse-train stimuli, with a comparison of the electrotactile and vibrotactile modalities. In one experiment, vibrotactile perception of 2-oct step changes in stimulus frequency was found to be significantly better than electrotactile on a time-scale appropriate for the transmission of speech features (e.g., with practiced subjects, information transfer of 69% with 200-ms vibrotactile stimuli, 32% with 200-ms electrotactile stimuli). Perception of step changes in stimulus amplitude was similar in the two modalities when changes in amplitude were tailored to match the different dynamic ranges available. In a second experiment, vibrotactile-perception of voice fundamental frequency with various codings was investigated. Both experiments showed information transfer for vibrotactile stimuli to be greater when frequency and amplitude modulation were used together rather than with one or the other in isolation (sentence-stress identification scores: 66% for FM stimuli, 69% for AM stimuli, 80% for FM/AM stimuli). It is concluded that frequency- and amplitude-modulated vibratory stimulation is a good choice in a practical device for the profoundly hearing impaired.

Alpha-crystallin: molecular chaperone and protein surfactant.

Bovine lens alpha-crystallin has recently been shown to function as a molecular chaperone by stabilizing proteins against heat denaturation (Horwitz, J. (1992) Proc. Natl. Acad. Sci. USA, 89, 10449-10453). An investigation, using a variety of physico-chemical methods, is presented into the mechanism of stabilization. alpha-Crystallin exhibits properties of a surfactant. Firstly, a plot of conductivity of alpha-crystallin versus concentration shows a distinct inflection in its profile, i.e., a critical micelle concentration (cmc), over a concentration range from 0.15 to 0.17 mM. Gel chromatographic and 1H-NMR spectroscopic studies spanning the cmc indicate no change in the aggregated state of alpha-crystallin implying that a change in conformation of the aggregate occurs at the cmc. Secondly, spectrophotometric studies of the rate of heat-induced aggregation and precipitation of alcohol dehydrogenase (ADH), beta L- and gamma-crystallin in the presence of alpha-crystallin and a variety of synthetic surfactants show that stabilization against precipitation results from hydrophobic interactions with alpha-crystallin and monomeric anionic surfactants. Per mole of subunit or monomer, alpha-crystallin is the most efficient at stabilization. alpha-Crystallin, however, does not preserve the activity of ADH after heating. After heat inactivation, gel permeation HPLC indicates that ADH and alpha-crystallin form a high molecular weight aggregate. Similar results are obtained following incubation of beta L- and gamma-crystallin with alpha-crystallin. 1H-NMR spectroscopy of mixtures of alpha- and beta L-crystallin, in their native states, reveals that the C-terminus of beta B2-crystallin is involved in interaction with alpha-crystallin. In the case of gamma- and alpha-crystallin mixtures, a specific interaction occurs between alpha-crystallin and the C-terminal region of gamma B-crystallin, an area which is known from the crystal structure to be relatively hydrophobic and to be involved in intermolecular interactions. The short, flexible C-terminal extensions of alpha-crystallin are not involved in specific interactions with these proteins. It is concluded that alpha-crystallin interacts with native proteins in a weak manner. Once a protein has become denatured, however, the soluble complex with alpha-crystallin cannot be readily dissociated. In the aging lens this finding may have relevance to the formation of high molecular weight crystallin aggregates.

1H-NMR spectroscopy of beta B2-crystallin from bovine eye lens. Conformation of the N- and C-terminal extensions.

1H-NMR spectroscopic studies of a 46-kDa homodimer, beta B2-crystallin, from bovine eye lens are presented. beta B2-crystallin has terminal extensions extending from globular N- and C-terminal domains that are well resolved in the NMR spectra, whereas, in the main, resonances from the bulk of the protein are not observed. Using two-dimensional NMR methods on beta B2-crystallin, its synthesised terminal extensions and a proteolysed sample of beta B2-crystallin with a portion of its C-terminus removed, it was possible to assign resonances to most of the amino acids in the terminal extensions. One-dimensional experiments at various pH values provided H-2 chemical shifts for the three terminal extension histidines from which their pKa values were measured. It is concluded that the terminal extensions appear to be of little ordered conformation, are accessible to solvent and flex freely from the main body of the protein. The results of the NMR spectroscopic studies of beta B2-crystallin are in excellent agreement with those for the X-ray crystal structure [Bax, B., Lapatto, R., Nalini, V., Driessen, H., Lindley, P. F., Mahadevan, D., Blundell, T. L. & Slingsby, C. (1990) Nature 347, 776-780]. No change in the spectrum of beta B2-crystallin was observed in the presence of calcium, suggesting that the termini are not involved in calcium binding.

1H-NMR spectroscopy of bovine lens beta-crystallin. The role of the beta B2-crystallin C-terminal extension in aggregation.

1H-NMR spectroscopic studies of bovine eye lens beta-crystallin aggregates (dimer, trimer and octomer) are presented. The NMR spectra for all three beta-crystallin aggregates are dominated by resonances from the beta B2 subunit, particularly from the N- and C-terminal extensions of this subunit. Resonances from other beta subunits, which all have terminal extensions, are, in general, absent from spectra of the beta-crystallin aggregates. Therefore, the beta B2 subunit and, in particular its terminal extensions, has enhanced flexibility compared to the other beta-crystallin subunits. Furthermore, resonances arising from the C-terminal extension of beta B2-crystallin are not present in the spectrum of the octomer, which is consistent with the C-terminal extension binding in this aggregate and hence being involved in large aggregate formation. A possible interaction between the C-terminal extension of beta B2 and the hydrophobic beta B1 subunit, which is only found in the octomer, is discussed. At higher temperatures (45 degrees C) in the octomer, partial exposure of the C-terminal extension of beta B2 occurs indicating that the octomer may be starting to break up into smaller aggregates.

Antibiotic-resistant pneumococci in the United Kingdom.

Pneumococcal pneumonia and meningitis remain common infections with significant morbidity and mortality. For many years, penicillins or cephalosporins, erythromycin and chloramphenicol have been the mainstay of chemotherapy for these and other pneumococcal infections. Resistance to these antimicrobial agents has increased worldwide and resistant pneumococci are now isolated with increasing frequency in the United Kingdom. This article reviews the results of antimicrobial susceptibility and serotyping studies carried out over the last five years on UK isolates of Streptococcus pneumoniae referred to the Streptococcus and Antibiotic Reference Laboratories of the Division of Hospital Infection for serotyping or confirmation of antibiotic resistance. During this period there has been a marked increase in the referral of pneumococcal isolates resistant to one or more of the antimicrobials commonly used for treatment. The implications for antimicrobial therapy and vaccination policy are discussed.

Cell populations associated with gingival bleeding.

The presence of crevicular bleeding after probing is an objective clinical sign of gingival inflammation. It has been associated with a plasma cell-dominated inflammatory infiltrate in deep pockets and has been suggested as an indication of active periodontitis. The purpose of this study was to characterize the cellular composition of gingival connective tissue associated with shallow pockets which bled after probing. Prior to biopsy, the mid-facial gingiva associated with 30 teeth from 26 patients was assessed for the presence or absence of visual inflammation, pocket depth and bleeding after probing with a standardized force of 25 g. A horizontal reference incision was made on the facial aspect of the gingiva to demarcate for histologic analysis the specific gingival area probed and evaluated for inflammation. Cell populations were determined from histological sections using morphometric point counting techniques in six standard fields at and coronal to the level of the reference incision. The percentage of cell types and the per cent volume densities of all tissue components were compared between clinically normal and inflamed gingiva. In clinically inflamed gingiva there was a significantly greater percentage of lymphocyte/macrophage/monocyte cells and a smaller percentage of fibroblast/endothelial cells. The percentage of plasma cells was only a fraction of that found for other inflammatory cells. The results of this study indicated that a lesion in the gingiva associated with bleeding after probing can consist of an inflammatory infiltrate which is not dominated by plasma cells.

Techniques to increase the response rate in follow-up studies: results of a pilot test.

As a part of the design and implementation of a caseload weighting system, Arkansas Rehabilitation Services is adopting a revised client data system. To assess the validity of the data collected in the new system a follow-up survey for recently closed clients has been designed; and to insure the adequacy of the survey design several issues were considered. These included overall survey and questionnaire design. The process, designed to maximize useful information collected with limited resources, resulted in a telephone survey augmented by mail and personal interviews. The survey procedures and instrumentation were pilot tested for two months with 629 clients. This resulted in major modifications in questionnaire design and brought to light easily adopted procedural improvements resulting in less ambiguity, improved readibility, increased response rate and reduced response bias. Using the described survey methods the investigators observed an overall response rate of 50.8% which compares very favorably with that reported in other studies similar in nature.

Effect of specific teaching techniques on cognitive learning, transfer of learning, and affective behavior of nurses in an in-service education setting.

To test the effects of different teaching techniques on learning, transfer of learning, and affective behavior of nurses, three hypotheses were developed based on Gagne's Theory of Knowledge Acquisition, Ellis' Theory of Transfer of Learning, and Bloom's Theory of Affective Consequences of Knowledge. The hypotheses tested were that an experimental (E) group will learn, transfer, and demonstrate affective behaviors significantly more than control groups. Subjects were 131 staff nurses. The E group (N=36) was taught by means of filmstrip with discussion (FD). Control groups II, III, and IV (N=33, 31, and 31 subjects, respectively) were taught by means of lecture alone (L), lecture with discussion (LD), and filmstrip alone (F), respectively. The content taught was Engel's Theory of Grief and Mourning Process. Pre- and posttests were done to obtain measures on learning and transfer. Results showed that the E group transferred significantly more than the L group; in general, all groups showed significant increases in learning and transfer; film groups transferred significantly more than the lecture groups; subjects preferred LD and FD significantly more than F or L. Implications were made for education of patients, students, and staff.