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Biomedical subjects

J C Haselgrove

Publications and source records attributed to J C Haselgrove.

At least 55 records · Page 3Linked to original sources
PubMed1985

A rapid, inexpensive, quantitative, general-purpose densitometer and its application to one-dimensional gel electrophoretograms.

We describe the construction of a densitometer based on a TV camera linked to an IBM personal computer (PC) using commercially available components. We discuss some of the problems of accurate quantitative densitometry using low-cost video systems, and describe the manner in which absolute optical density values may be recorded. We describe a digital analysis routine designed to quantitate unresolved bands on noisy one-dimensional electrophoretograms.

Costs and Cost Analysis↗
PubMed1985

High spatial resolution readout of 3-D metabolic organ structure: an automated, low-temperature redox ratio-scanning instrument.

Intraorgan compartmentation of metabolic processes plays an important role in the understanding of the physiological function of the integrated organ under normal as well as under pathological conditions. We describe here a technique by which 3-D information on tissue redox state may be obtained by means of automated scanning of surface fluorescence. The instrument allows for serial scanning of frozen tissue. A typical scan of a tissue volume of 3 X 3 X 2 mm at a linear resolution of 50 micron and a spatial resolution of ca. 3 X 10(-7) ml includes 144,000 single-point measurements of pyridine nucleotide and flavoprotein fluorescence within the tissue block. The scanning process is fully computerized and programs have been developed which allow 2- or 3-D reconstruction of the data in terms of "redox ratio models," exemplified here by a 3-D model of a spreading depression wave in the cerebral cortex of a gerbil.

Animals↗
PubMed1985

In vivo nuclear magnetic resonance imaging of lithium.

Magnetic resonance imaging techniques have previously been applied to 1H, 23Na, 31P, and 19F nuclei. This is the first report of application of these techniques to 7Li. Lithium images of both aqueous phantoms and a rat abdomen are presented. Applications of this technique to humans are discussed.

Animals↗
PubMed1984

Geometrical constraints affecting crossbridge formation in insect flight muscle.

Computer-modelling studies have explored how rigor crossbridge interactions in insect flight muscle are affected by using a four-stranded helical thick filament and by restricting each myosin to forming one crossbridge with only one actin filament. Crossbridges searching over an axial range of +/- 7.2 nm, and within an azimuthal range around actin of +/- 45 degrees, can simulate the actin-labelling patterns observed in thin electron microscope sections well. However, the number of crossbridges attached between any myosin filament and an adjacent actin filament depends on their relative axial and azimuthal positions, and can vary by a factor of two. The relative position that maximized the number of attached bridges also produced the best modelling of the 'double chevron' appearance of two crossbridge pairs attaching within target zones every 38.6 nm, as seen in thin longitudinal sections, and the 'flared X' of crossbridges extending to four out of six surrounding actins at each crossbridge level seen in thin cross-sections. Micrographs show that excellent lattice register of rigor crossbridges in longitudinal sections does not depend on lateral register of thick or thin filament ends. Our modelling suggests how the crossbridge lattice may be generated by filaments becoming mutually annealed to the axial and azimuthal positions at which most crossbridges can attach, at which time the actin filaments are arranged at the diad positions on the P64 crystalline lattice. When the actin filaments are so oriented, in a P64 lattice, two crossbridges on adjacent actin filaments will slew toward the same point on the myosin filament, producing the flared X appearance of origin from a common stem and a single myosin, even if they originate from distinct points and separate molecules.

Actins↗
PubMed1984

The structure and disposition of crossbridges in deep-etched fish muscle.

Deep-etching and rotary-shadowing techniques were used to describe crossbridges in fish (Chanda ranga) muscle, relaxed and in iodoacetate rigor conditions. Three major fracture planes from rigor muscle were studied using stereomicroscopy and Fourier image analysis. The 1,0 plane reveals alternating thick and thin filaments with the thick filaments frontmost in the fracture and the thin filaments in the recessed plane. All crossbridges coming from the frontmost thick filaments are visible on actin filaments in the 1,0 plane. Fourier transforms of digitized images from these fracture planes exhibit axial periodicities of 14 and 36 nm. The actin layer, a fracture plane just below the myosin filaments in the 1,0 plane, shows end-on views of crossbridges projecting out of the fracture plane and limited transverse alignment of crossbridges. Actin layer Fourier transforms demonstrate a 14 nm reflection associated with the attachment of crossbridges with a mean axial periodicity determined by their myosin origins. The 1,1 lattice direction shows pairs of thin filaments alternated with single thick filaments. In this view, all crossbridges coming from three adjacent myosins are visible. In all fracture planes, decoration of individual thin filaments by crossbridges is variable, but usually one (singlet) or two (doublet) closely spaced crossbridges mark each actin target zone, at intervals of 35-38 nm. Counts of crossbridges decorating actin filaments give an average of four every three target zones. The anticipated stagger of target zones for crossbridges from two adjacent myosin filaments is observed. Alignment of actin target zones across the sarcomere is good. We can distinguish two distinct shapes for rigor crossbridges: a narrow, straight bridge and a wider bridge with a triangular shape. We interpret these as being the appearance of crossbridges with one or two S1 subfragments (single and double headed) respectively. Comparison between rigor and relaxed structures indicates attachment of all crossbridges in rigor.

Actins↗
PubMed1983

In vivo one-dimensional imaging of phosphorus metabolites by phosphorus-31 nuclear magnetic resonance.

A phosphorus-31 nuclear magnetic resonance imaging technique has been used to obtain information on phosphorus metabolites from different spatial regions of tissues in vivo. The technique for selection of planes through the tissue is based on phase-encoding of spin echoes and was used to obtain one-dimensional discrimination of phosphorus-31 spectra from different parts of the tissue simultaneously. Specimens were resolved into 16 distinct slices and a signal-to-noise ratio of about 20 to 1 was obtained in 1/2 hour. Results are presented for phantoms, rat legs, and gerbil heads.

Adenosine Triphosphate↗
PubMed1980

A model of myosin crossbridge structure consistent with the low-angle x-ray diffraction pattern of vertebrate muscle.

Low-angle X-ray diffraction patterns have been taken of relaxed frog sartorius muscles stretched to destroy the lattice sampling in the pattern and the observed layer line pattern has been interpreted with model-building studies. The modelling calculations indicate that each crossbridge cannot be represented by a single cylindrical shape, but that the two S-1 heads of the crossbridge are tilted in opposite directions along the filament while twisted the same way round it so that the crossbridge lies wrapped round the filament backbone. The radial position derived for the crossbridge depends on how many strands the filament is assumed to have. If the filament is 2, 3 or 4 stranded then the centre of mass of the crossbridge lies at about 9.5, 12.5, or 15.5 nm respectively from the filament axis.

Actins↗
PubMed1979

Fluorescence mapping of mitochondrial redox changes in heart and brain.

Fluorescence techniques may be utilized to map changes in the distribution of mitochondrial redox states in heart and brain during ischemic or hypoxic stress. The basis of these techniques is the intrinsic fluorescence of reduced NADH and oxidized flavoprotein in mitochondria which respond to changes in critical oxygen supply. Ischemic areas in rabbit hearts induced by coronary ligation were detected and mapped based on the increase in NADH fluorescence in the ischemic zone. The width of the jeopardized normoxic tissue surrounding the ischemic area (less than 50--350 mu) was measured by combination of fluorescein angiography and NADH fluorescence. Areas of increased NADH fluorescence in gerbil brains after carotid artery ligation or induction of spreading depression were mapped in a similar manner. Intraoperative monitoring of flavoprotein fluorescence from human cerebral cortex after superficial temporal artery middle cerebral artery (STA-MCA) anastomoses demonstrated increased rates of cortical oxidative metabolism after the surgical procedures.

Animals↗
PubMed1978

Modeling rigor cross-bridge patterns in muscle I. Initial studies of the rigor lattice of insect flight muscle.

We have undertaken some computer modeling studies of the cross-bridge observed by Reedy in insect flight muscle so that we investigate the geometric parameters that influence the attachment patterns of cross-bridges to actin filaments. We find that the appearance of double chevrons along an actin filament indicates that the cross-bridges are able to reach 10--14 nm axially, and about 90 degrees around the actin filament. Between three and five actin monomers are therefore available along each turn of one strand of actin helix for labeling by cross-bridges from an adjacent myosin filament. Reedy's flared X of four bridges, which appears rotated 60 degrees at successive levels on the thick filament, depends on the orientation of the actin filaments in the whole lattice as well as on the range of movement in each cross-bridge. Fairly accurate chevrons and flared X groupings can be modeled with a six-stranded myosin surface lattice. The 116-nm long repeat appears in our models as "beating" of the 14.5-nm myosin repeat and the 38.5-nm actin period. Fourier transforms of the labeled actin filaments indicate that the cross-bridges attach to each actin filament on average of 14.5 nm apart. The transform is sensitive to changes in the ease with which the cross-bridge can be distorted in different directions.

Actins↗