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Biomedical subjects

R Henderson

Publications and source records attributed to R Henderson.

At least 145 records · Page 8Linked to original sources
PubMed1989

Purple membrane: color, crystallinity, and the effect of dimethyl sulfoxide.

In an effort to understand the nature of chromophore-protein interactions in bacteriorhodopsin (bR), we have reinvestigated dimethyl sulfoxide (DMSO)-induced changes in bR [Oesterhelt et al. (1973) Eur. J. Biochem. 40, 453-463]. We observe that dark-adapted bR (bR560) in aqueous DMSO undergoes reversible transformation to a species absorbing maximally at 480 nm (bR480). Beginning at 40% DMSO, this change results in complete conversion to bR480 at 60% DMSO. The kinetics of the reaction reveal that this transformation takes place predominantly through the all-trans isomeric form of the pigment. Thermal isomerization of the 13-cis chromophore to the all-trans form is, therefore, the rate-limiting step in the formation of bR480 from the dark-adapted bR. As in native bR, the chromophore in bR480 is linked to the protein via a protonated Schiff base, and its isomeric composition is predominantly all-trans. The formation of bR480 is associated with minor changes in the protein secondary structure, and the membrane retains crystallinity. These changes in the protein structure result in a diminished chromophore-protein interaction near the Schiff base region in bR480. Thus, we attribute the observed spectroscopic changes in bR in DMSO to structural alteration of the protein. The 13-cis chromophoric pigment appears to be resistant to this solvent-induced change. The changes in the protein structure need not be very large; displacement of the protein counterion(s) to the Schiff base, resulting from minor changes in the protein structure, can produce the observed spectral shift.

Bacteriorhodopsins↗
PubMed1989

Comparison of eleven external fixators for treatment of unstable wrist fractures.

We compared 11 external fixators for treatment of wrist fractures on the basis of rigidity, weight, cost, design characteristics, and provision for allowing wrist motion, and found important differences between them such as rigidity varying as much as 11 times. The Roger Anderson, Hanson Baylor Mini Hoffman, Rectangular Mini Hoffman, and Ace Colles external fixators are lightweight and have low rigidity. The C-series Hoffman unilateral frame and the A.O. have intermediate rigidity. The newly developed methylmethacrylate fixator, the regular Hoffman, the C-series Hoffman bilateral frame, and the Clyburn are more rigid. Although both the Clyburn and the Orthofix allow wrist flexion and extension, the Clyburn is lightweight and the Orthofix has the highest rigidity. These factors are analyzed and reported in a format that will guide the surgeon in the selection of an appropriate fixator for his patient with an unstable wrist fracture.

Humans↗
PubMed1989

An improved retinal densitometer: design concepts and experimental applications.

A photon-counting retinal densitometer is described that has been designed optically and electronically for improved sensitivity and reliability. The device allows measurement of visual pigments through the undilated natural pupils of subjects at relatively low levels of measuring lights, and serves also as an adaptometer for direct comparisons between pigment bleaching or regeneration and light or dark adaptation. Instrumental control and data collection are by computer to permit rapid and simple data analysis and comparisons between subjects. The methods by which the sensitivity and reliability have been enhanced are described in detail, and some examples of experimental results are presented.

Dark Adaptation↗
PubMed1988

Images of purple membrane at 2.8 A resolution obtained by cryo-electron microscopy.

Improvements in technique have produced electron micrographs of purple membrane that provide, after computer analysis, reproducibly measurable diffraction peaks extending to 2.8 A (1 A = 0.1 nm). The improvements include better specimen preparation, a more stable cryo-electron microscope with better alignment and the addition of an image-processing step, which gives weights to local areas of the image according to the local strength of the periodic component of the image. These improvements have enabled the calculation of a directly phased projection map at 2.8 A resolution.

Bacteriorhodopsins↗
PubMed1987

Management of intrinsic spasticity in the hand with phenol injection or neurectomy of the motor branch of the ulnar nerve.

Thirty-nine adults with acquired spastic disorders who had 21 phenol injections and 21 neurectomies of the motor branch of the ulnar nerve in Guyon's canal for control of intrinsic spasticity in the hand were reviewed. Follow-up averaged 25.8 months for the patients with phenol blocks and 24.3 months for those who had a neurectomy. Intrinsic spasticity was relieved in all hands postoperatively. After the phenol block, which is a temporizing procedure, 13 hands had return of spasticity in 6 months. Eight hands had little or no return of spasticity and required no further treatment. Neurectomy was performed in predominantly nonfunctional hands with severe hygiene problems and with no potential for further neurologic recovery. Hand function was improved in six hands after phenol block and in one hand after neurectomy. Hygiene was improved in all hands after phenol block and in all except one hand after neurectomy. Two wound infections and one wound dehiscence occurred.

Adolescent↗
PubMed1987

Noninvasive quantification of left ventricular myocardial mass by gated proton nuclear magnetic resonance imaging.

The validity of cardiac nuclear magnetic resonance imaging for determination of left ventricular myocardial mass was evaluated in nine dogs. A gated spin echo-pulsing sequence was used for in vivo imaging, obtaining 0.7 cm thick slices of the heart spaced by 1 cm. On each imaged slice, the left ventricular surface area was reproducibly determined by planimetry and was multiplied by slice spacing and specific gravity of the myocardium (1.05) to obtain slice mass. Total left ventricular mass was calculated by adding slice masses in short-axis (method I), transaxial (method II) and vertical long-axis (method III) orientations using Simpson's rule. With each method, masses of the portions of the left ventricle subject to partial volume effect either were not accounted for or alternatively were estimated from the same or an orthogonal imaging plane. Calculated left ventricular mass was compared with the actual excised left ventricular weight. With NMR imaging of in situ nonbeating hearts, best results were obtained when either method I or method II was used and partial volume effect was estimated either from the same or an orthogonal plane. With in vivo NMR imaging, best results were noted when method I was used and mass of the partial volume apex was calculated from transaxial slices: Y (in vivo NMR image) = 8.3 + 0.99X, r = 0.996, SEE = 3.14. For this method, the interobserver reliability coefficient and standard error of the measurement were 0.97 and 5.4, respectively. Compared with method I, in vivo methods II and III were associated with larger errors (SEE ranging from 13.03 to 19.03) regardless of the approach used to estimate partial volume effect. It is concluded that NMR imaging is a highly accurate noninvasive method for in vivo measurement of left ventricular mass in dogs and offers promise for accurate measurement of left ventricular mass in patients.

Animals↗