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Biomedical subjects

J C Haselgrove

Publications and source records attributed to J C Haselgrove.

At least 37 records · Page 2Linked to original sources
PubMed1997

Left-sided congenital diaphragmatic hernia: value of prenatal MR imaging in preparation for fetal surgery.

PURPOSE: To evaluate the usefulness of prenatal magnetic resonance (MR) imaging in determination of the position of the fetal liver and amount of lung tissue in left-sided congenital diaphragmatic hernia. MATERIALS AND METHODS: In three pregnant women, MR imaging was performed with a 1.5-T magnet and fast gradient-echo, half-Fourier single-shot turbo spin-echo, and echo-planar sequences. MR imaging findings were compared with those from ultrasound (US) performed the same day. The fetuses were 20, 23, and 32 weeks gestational age. RESULTS: The fetal liver was demonstrated in the chest in all three fetuses with MR imaging and in only one fetus with US. The best images of the fetal liver were obtained with a T1-weighted gradient-echo sequence. The best images of the entire fetus were obtained with a half-Fourier single-shot turbo spin-echo sequence. CONCLUSION: In these fetuses, MR imaging proved important by clearly demonstrating herniation of fetal liver into the chest, thereby changing family counseling and prenatal care.

Counseling↗
PubMed1996

Correction for distortion of echo-planar images used to calculate the apparent diffusion coefficient.

An algorithm for correcting the distortions that occur in diffusion-weighted echo-planar images due to the strong diffusion-sensitizing gradients is presented. The dominant distortions may be considered to be only changes of scale coupled with a shear and linear translation in the phase-encoding direction. It is then possible to correct for them by using an algorithm in which each line of the image in the phase-encoding direction is considered in turn, with only one parameter (the scale) to be found by searching.

Algorithms↗
PubMed1995

Three-dimensional reconstruction of fibrin clot networks from stereoscopic intermediate voltage electron microscope images and analysis of branching.

Fibrin polymerizes to produce branching fibers forming a three-dimensional network, which has been difficult to visualize by conventional microscopy. Three-dimensional images of whole clots at high resolution were obtained from stereo-pair intermediate-voltage electron micrographs. Computer software was developed to produce three-dimensional reconstructions of the networks in the form of a pattern of links that connect branching junctions. Network parameters were measured and analyzed to characterize the clots quantitatively. Models in which all links were moved to the origin, while preserving their orientation, allowed visualization of some network parameters and facilitated comparison of networks. Fibrin clots formed in three different conditions were analyzed and compared by these methods. Clots formed in 0.20 M saline buffer consist of fibers of uniform size, and most of the branching junctions consist of three links. Fibrin clots formed in 0.05 M saline buffer are made up of very large diameter fiber bundles with far fewer branching junctions and correspondingly longer links. Clots formed in 0.40 M saline buffer consist of very fine fibers with numerous branching junctions and very short links. In summary, the extent of lateral aggregation is directly related to the distance between branching junctions and inversely related to the total number of branching junctions. These observations must be considered in defining possible mechanisms of fibrin branching.

Biophysical Phenomena↗
PubMed1995

Proton MR spectroscopy of pediatric cerebellar tumors.

PURPOSE: To investigate the role of proton MR spectroscopy in pediatric cerebellar tumor diagnosis. METHODS: Single voxel pulse sequences with long echo time (135 or 270 milliseconds, voxel size 8 to 19 cm3), were used to obtain proton spectra of primary pediatric cerebellar tumors. Eleven primitive neuroectodermal tumors (patient age, 2 to 12 years; mean, 7 years), 11 low-grade astrocytomas (age, 2 to 16 years; mean, 9 years), 4 ependymomas (age, 1 to 6 years; mean, 4 years), 1 mixed glioma ependymo-astrocytoma (age, 11 years), 1 anaplastic ependymoma (age, 7 years), 1 ganglioglioma (age, 14 years), and 1 malignant teratoma (age, 6 days) were studied. Control cerebellum spectra were acquired from five patients without abnormality in cerebellum (age, 2 to 15 years; mean, 8 years). The signal intensities from choline-containing compounds (Cho), creatine/phosphocreatine (Cr), N-acetyl-aspartate (NAA), and lactate (Lac) were quantified. The mean and standard deviation of metabolite ratios were calculated. RESULTS: The control spectra ratios (NAA:Cho = 1.49 +/- 0.36, Cr:Cho = 1.13 +/- 0.23) were distinct from the tumor spectra (NAA:Cho = 0.41 +/- 0.27 and Cr:Cho = 0.37 +/- 0.23). Most of primitive neuroectodermal tumors had low NAA:Cho (0.17 +/- 0.09) and Cr:Cho (0.32 +/- 0.19). Compared with primitive neuroectodermal tumors, low-grade astrocytomas and ependymomas had higher NAA:Cho ratio (0.63 +/- 0.19 and 0.39 +/- 0.12). The Cr:Cho ratio was higher for ependymomas (0.60 +/- 0.20) than for astrocytomas (0.27 +/- 0.12) and primitive neuroectodermal tumors. No NAA was found in the malignant teratoma. Lac:Cho ratio was 0.66 +/- 0.40, 0.58 +/- 0.30, and 0.08 +/- 0.12 for astrocytoma, ependymoma, and primitive neuroectodermal tumor, respectively. Lactate was elevated in the mixed glioma ependymo-astrocytoma, ganglioglioma, and teratoma. The NAA and lactate signals were sometimes obscured by lipids in the spectra. Discriminant analysis was carried out using NAA:Cho and Cr:Cho ratios to differentiate the three major tumor types. The sensitivity/specificity values for diagnosing astrocytoma, ependymoma, and primitive neuroectodermal tumor were found to be 0.91/0.84, 0.75/0.92, and 0.82/0.89, respectively, based on this study. CONCLUSION: In many cases, proton MR spectroscopy can be used to help differentiate cerebellar primitive neuroectodermal tumor, low-grade astrocytoma, and ependymoma.

Adolescent↗
PubMed1994

A MRI bolus tagging method for observing helical flow in the descending aorta.

We present a MRI bolus tagging method for exploring the helical nature of blood flow in the aorta. Two image series are collected, the first to quantify longitudinal flow (coronal/sagittal imaging plane-transverse saturation plane), the second to measure rotational flow (transverse imaging plane-coronal/sagittal saturation plane). The experimental protocol has been established in healthy adult volunteers and children with normal vasculature. Our results permit immediate visualization of the unique nature of helical flow in each volunteer. We demonstrate evidence of rapid helical twist, no helical twist, and reversal of twist.

Adult↗
PubMed1993

Resorption of peritumoural oedema in cerebral gliomas during dexamethasone treatment evaluated by NMR relaxation time imaging.

Peritumoural brain oedema is a prominent feature of malignant brain tumours. Glucocorticoids diminish the neurological symptoms and signs caused by the oedema and reduce the abnormally high cerebral water content. The exact mechanisms of action of the glucocorticoids are unknown. The present study investigates the influence of dexamethasone on NMR relaxation time T1 in peritumoural oedema in 13 patients with gliomas. It is shown that NMR T1 images can be used as a potent monitor of brain oedema, and that dexamethasone significantly reduces mean T1 after 1, 3, and 7 days of treatment by 2%, 6%, and 13% respectively. Using an image histogram analysis technique the term "super-oedema" was defined as the 50% of the total oedema area with the highest T1, corresponding to the highest water content. It is shown, that with this technique the treatment effect of steroids on super-oedema was a reduction of 13%, 33%, and 57% after 1, 3, and 7 days of treatment respectively. The mean change after 24 hours of treatment was statistically significant (p < 0.01). The method can be used in all situations where the anti-oedematous effect of a given treatment is to be monitored.

Aged↗
PubMed1993

Spectral localization of arbitrarily shaped regions of interest (SLASH) using single voxel signals.

A method for obtaining localized spectra from arbitrarily shaped regions of interest is described. When a sample consists of homogeneous compartments or domains, spectra localized in each compartment can be obtained from signals of single voxels with regular shapes by solving a set of simultaneous linear equations. Experimental demonstrations on a phantom and on human brain in vivo for a two compartment, two voxel case are presented. The issue of signal-to-noise ratio is also discussed.

Brain↗
PubMed1993

Computer modeling of the oxygen supply and demand of cells of the avian growth cartilage.

We have used computer modeling studies to investigate the oxygen supply to the prehypertrophic and hypertrophic regions of avian growth plate. We measured experimentally the characteristics of the oxygen consumption of chondrocytes at different oxygen tensions. The oxygen consumption decreases at low oxygen tensions. This relation between oxygen tension and oxygen consumption serves as a protective mechanism that prevents the cells in the prehypertrophic zone from becoming anoxic in the regions farthest from the blood vessels. The results of the calculations, when combined with redox measurements of the cells in the growth plate, indicate that the metabolism of the chondrocytes is not controlled simply by the available oxygen supply.

Animals↗
PubMed1993

Measurement of metabolic events in the avian epiphyseal growth cartilage using a bioluminescence technique.

We developed a technique to map the distribution of selected metabolites in the growth cartilage in situ using luciferase-NAD(P)H:FMN oxidoreductase. Chick tibial epiphyses were freeze-trapped, sectioned, and freeze-dried. For evaluating lactate, luciferase was suspended in a buffer containing polyvinylalcohol, gelatin, NAD, FMN, and lactic dehydrogenase (LDH). The buffer was frozen into a layer 800 microns thick and placed in contact with the tissue section. The temperature of the frozen reagent mixture was then allowed to increase; the emitted light was focused through a photographic lens and collected on film. We found that lactate was synthesized by cells in all regions of the growth plate. The highest concentration of the metabolite was observed in the calcified hypertrophic region. Substantial levels of lactate were also present in articular cartilage. By modifying the composition of the buffer solution, we were able to map the distribution of glucose and glucose-6-phosphate and the activity of LDH. Maximal levels of each of the three components were present in hypertrophic cartilage. Chemical analysis of the tissue section confirmed the luminographic studies and provided further evidence that there was reliance on glycolytic metabolism in terminally differentiated chondrocytes. Use of enzyme couples similar to those described above should permit the technique to be used to study most, if not all, of the major metabolic components of cartilage.

Animals↗
PubMed1992

Sensitivity of in vivo MRS of the N-delta proton in proximal histidine of deoxymyoglobin.

The sensitivity of in vivo MRS of the N-delta proton of the proximal histidine of deoxymyoglobin in human skeletal muscles is discussed. Longitudinal relaxation time T1 of this deoxymyoglobin signal was measured in cuffed human forearms at 1.5 T and found to be 9.9 ms. Deoxymyoglobin spectra can be obtained from a forearm in seconds. The detection sensitivity of deoxymyoglobin in fully ischemic skeletal muscles and that of 31P MRS of PCr in normal resting muscles are compared.

Adult↗
PubMed1990

Time resolved 3-dimensional recording of redox ratio during spreading depression in gerbil brain.

Optical fluorescence and reflectance measurements have been used to map the distribution of metabolic states in three dimensions in the gerbil brain with a spatial resolution of 200 microns an a time resolution of 4-6 s. In Mongolian gerbils anesthetized with pentobarbital, the redox states of the nicotinamide adenine dinucleotide (NADH) and flavoprotein components of the electron transport chain exhibit two distinct phases during the wave of spreading depression: (1) a transient period of oxidation and (2) a prolonged period of reduction, during which the cytochromes are reduced, and the hemoglobin is predominantly in the deoxy form. These data are interpreted as indicating that the energy demand placed on the gerbil brain during such spreading depression wave is sufficient to drive the brain temporarily hypoxic.

Animals↗
PubMed1990

Scanning microfluorimetric measurements of redox status in the rat dento-alveolar tissues.

The oxidative state of periodontal tissues in situ is not known. Scanning microfluorimetry uses NADH fluorescence readings to provide a measure of a tissue's oxidative metabolic activity. Digitally recorded fluorescence signals were compiled to create a distribution map for this reduced pyridine nucleotide in the periodontal structures, which was then related to the morphology as seen by SEM. To distinguish between NADH fluorescence and intrinsic fluorescence of collagen, as well as to study the effect of oxygen deprivation, mitochondrial oxidative activity was inhibited by CO in some animals. Oxidative status and sensitivity to changes in cellular energy metabolism in the dento-alveolar complex were tissue specific; differences between tissues may play a part in the differential remodelling of the periodontium.

Alveolar Process↗
PubMed1988

Linkage between energy status of perivascular cells and mineralization of the chick growth cartilage.

The objective of this investigation was to investigate the relationship between the energy status of epiphyseal chondrocytes of the chick growth cartilage and the development of mineralization. A microfluorimetric scanning technique was used to measure the reduced pyridine nucleotide content of transverse sections of freeze-trapped cartilage; these measurements were related to tissue structure by scanning electron microscopy. The results of this study show that the energy status of cells in the hypertrophic region of the growth cartilage is more complex than was previously believed. In hypertrophic cartilage, most chondrocytes are in a reduced state. However, in the early hypertrophic region, the vascular channels that penetrate the cartilage from the metaphysis exert a profound local effect on the energy metabolism of perivascular chondrocytes. Thus, around each of the channels, there exists a zone of chondrocytes about 40-60 micron wide which exhibits a low fluorescence yield. The fluorescence level suggests that these perivascular cells have a higher level of oxidative metabolism than hypertrophic chondrocytes that are a distance (greater than 150 micron) from the vascular channels. This finding, in conjunction with our earlier observation that mineralization is first seen in the perivascular region, leads us to the conclusion that mineralization is associated with cellular oxidative activity. We now reject the long-held concept that in cartilage the development of mineralization is entirely due to tissue hypoxia.

Animals↗
PubMed1987

Multinuclear MR imaging: a technique for combined anatomic and physiologic studies.

With the use of specially designed multiple-tuned probes for magnetic resonance (MR) imaging, data collection schemes can be developed for obtaining images of different nuclei simultaneously. Both phantom and in vivo MR images of two nuclei (either hydrogen-1, phosphorus-31, lithium-7, or fluorine-19) were obtained in the time span necessary to collect the image of the less sensitive nuclei. This technique offers a means by which physiologic and anatomic information can be gathered in a highly efficient fashion.

Animals↗
PubMed1986

Redox studies of the epiphyseal growth cartilage: pyridine nucleotide metabolism and the development of mineralization.

The objective of this investigation was to examine the redox status of chondrocytes in normal and rachitic growth cartilages and to relate energy metabolism to cell maturation and the initiation of mineralization. The redox status was evaluated by chemical analysis and by microfluorimetric scanning of rapidly frozen, freeze-fractured tibial growth cartilages. In the normal epiphysis, the redox pattern of both avian and lagomorph cartilages were very similar. Thus, in the proliferative tissue zone the NAD/NADH ratio was high; in the hypertrophic zone, the cells appeared to be reduced. The sharp border between the two zones suggested that the redox shift may be associated with development of hypoxia. Induction of rickets resulted in a fivefold decrease in the total concentration of pyridine nucleotides in the proliferating and hypertrophic zones. Furthermore, the NAD/NADH ratio was profoundly disturbed. In the mineralizing zone, there was an accumulation of reduced pyridine nucleotide. Healing, initiated by administration of vitamin D to the rachitic birds, caused a rapid increase in NAD and NADH in all zones of the growth cartilage. It was concluded that vitamin D deficiency leads to changes in the energy metabolism of growth cartilage and that these changes were related to the defective mineralization of the rachitic tissue.

Animals↗
PubMed1986

Relaxation and imaging of lithium in vivo.

It has recently been demonstrated that NMR imaging can be used to record the distribution of lithium. We now report on the parameters pertinent to this imaging. Specifically, the relaxation of Li in aqueous solution, in agarose gel, and in vivo has been investigated. In the latter case, both the longitudinal and transverse relaxations were biexponential, consistent with the behavior expected for a spin 3/2 quadrupole relaxed nucleus. The overall relaxation rate was quite slow in vivo with T'1 = 3.5 sec and T''1 = 6.6 sec.

Animals↗