Biomedical subjects

C E Hayes

Publications and source records attributed to C E Hayes.

At least 37 records · Page 2Linked to original sources

PubMed1998

The Drug Evaluation Classification Program: using ocular and other signs to detect drug intoxication.

BACKGROUND: A systematic approach to determining drug intoxication has been developed for use by police officers. By considering specific physiological signs, trained officers can detect the effects of seven major drug types. METHODS: Officers follow a 12-step testing sequence and evaluate signs such as pupil sizes and responses, eye movements, heart rate, body temperature, mental timing, and balance. A matrix is then used to compare that subject's signs to those that would be produced by the seven types of drugs. If a pattern match is found, the officer concludes that the subject is under the influence of a drug and specifies the drug type. RESULTS: Several field and laboratory validation studies have been conducted using these procedures. In general, officers were 70% to 90% accurate in determining intoxication status and drug classification, but poly-drug use and drug rebound effects can sometimes cause problems in interpretation. CONCLUSION: Ocular and other physiological signs can be used to detect drug intoxication and classify the type of drug taken. Knowledge of the procedures used in the Drug Recognition Program can enable optometrists to serve as consultants to the police and as expert witnesses in cases involving the use of ocular signs that indicate illicit drug use.

Body Temperature↗

PubMed1997

A model of the inversion process in an arterial inversion experiment.

A model of the behavior of spins moving through spatially varying gradient and B1 fields is presented. The model simulates the adiabatic behavior of flowing arterial water during a two-coil arterial inversion experiment. Predictions of the degree of inversion generated by the model are compared with flow phantom results for a wide range of gradient magnitudes, nominal B1 magnitudes, and flow velocities. The high level of agreement between the model and the flow phantom results indicates that the model can be used to help select efficient pulse sequence parameters when setting up an in vivo arterial inversion experiment. In addition, the model provides valuable insights into the adiabatic behavior of arterial spins. These insights could be useful in selecting an efficient surface coil geometry which achieves maximum inversion with a minimum B1 magnitude.

Arteries↗

PubMed1997

Brachial plexus: MR imaging with a dedicated phased array of surface coils.

A phased array of surface coils was constructed for magnetic resonance imaging in three different regions in the brachial plexus. Four-coil subsets of the six-coil array were activated at any given time during imaging in three volunteers. An in vivo estimate of the signal-to-noise ratio (S/N) at three locations in the brachial plexus indicated that the phased-array coil provided a signal-to-noise ratio that was three to six times higher than that of the body coil.

Adult↗

PubMed1997

19F magnetic resonance spectroscopy investigation in vivo of acute and steady-state brain fluvoxamine levels in obsessive-compulsive disorder.

OBJECTIVE: The purpose of this study was to investigate the pharmacokinetics of fluvoxamine in the human brain by using fluorine-19 magnetic resonance spectroscopy (19F MRS) and to assess the relationships among fluvoxamine brain levels, fluvoxamine plasma levels, and clinical efficacy. METHOD: Eight subjects with DSM-IV obsessive-compulsive disorder were entered into a prospective, open-label treatment trial of fluvoxamine. 19F MRS measurements of whole brain drug and metabolite concentrations and spin-lattice (T1) relaxation times were performed serially in seven subjects for up to 5 months. A psychiatric determination of clinical response and a blood sample for plasma fluvoxamine measurement were obtained at each 19F MRS session. RESULTS: The subjects achieved steady-state brain concentrations of fluvoxamine within 30 days after consistent daily dosing, as determined by stabilization of brain fluvoxamine concentrations. The mean brain-to-plasma ratio at steady state was 24 to 1. Brain fluvoxamine T1 values from 140 to 230 msec were observed. All but one subject experienced substantial improvement in symptoms. The one nonresponder exhibited several-fold higher plasma and brain fluvoxamine levels. CONCLUSIONS: Brain fluvoxamine levels were substantially higher than plasma levels. Steady-state brain levels correlated to plasma levels but not to dose. Systematic assessment of treatment response in relation to brain or plasma fluvoxamine level was not feasible because of the marked and rapid clinical response during open-label treatment. These data suggest that fluvoxamine attains brain steady-state levels substantially faster than fluoxetine, with corresponding clinical implications.

Adolescent↗

PubMed1997

Vitamin D and multiple sclerosis.

Recently, it has been clearly demonstrated that exogenous 1,25-dihydroxyvitamin D3, the hormonal form of vitamin D3, can completely prevent experimental autoimmune encephalomyelitis (EAE), a widely accepted mouse model of human multiple sclerosis (MS). This finding has focused attention on the possible relationship of this disease to vitamin D. Although genetic traits certainly contribute to MS susceptibility, an environmental factor is also clearly involved. It is our hypothesis that one crucial environmental factor is the degree of sunlight exposure catalyzing the production of vitamin D3 in skin, and, further, that the hormonal form of vitamin D3 is a selective immune system regulator inhibiting this autoimmune disease. Thus, under low-sunlight conditions, insufficient vitamin D3 is produced, limiting production of 1,25-dihydroxyvitamin D3, providing a risk for MS. Although the evidence that vitamin D3 is a protective environmental factor against MS is circumstantial, it is compelling. This theory can explain the striking geographic distribution of MS, which is nearly zero in equatorial regions and increases dramatically with latitude in both hemispheres. It can also explain two peculiar geographic anomalies, one in Switzerland with high MS rates at low altitudes and low MS rates at high altitudes, and one in Norway with a high MS prevalence inland and a lower MS prevalence along the coast. Ultraviolet (UV) light intensity is higher at high altitudes, resulting in a greater vitamin D3 synthetic rate, thereby accounting for low MS rates at higher altitudes. On the Norwegian coast, fish is consumed at high rates and fish oils are rich in vitamin D3. Further, experimental work on EAE provides strong support for the importance of vitamin D3 in reducing the risk and susceptibility for MS. If this hypothesis is correct, then 1,25-dihydroxyvitamin D3 or its analogs may have great therapeutic potential in patients with MS. More importantly, current research together with data from migration studies opens the possibility that MS may be preventable in genetically susceptible individuals with early intervention strategies that provide adequate levels of hormonally active 1,25-dihydroxyvitamin D3 or its analogs.

Animals↗

PubMed1997

Functional MR spectroscopy of the auditory cortex in healthy subjects and patients with sudden hearing loss.

PURPOSE: To use MR spectroscopy to study the biochemical changes produced by auditory stimuli in patients with sudden sensorineural hearing loss and to compare these findings with the biochemical changes seen in healthy volunteers. METHODS: Single-voxel MR spectroscopy was used to study biochemical changes in the auditory cortex in 11 control subjects and 19 patients with sudden sensorineural hearing loss. MR spectroscopic signals were measured during three different sound conditions (scanner noise, music, and sirens). RESULTS: A lower MR spectroscopic lactate signal was observed in control subjects during the music stimulus than during the other sound conditions. This music-induced lactate change was not observed in patients with hearing loss. The other proton metabolites (choline, creatine, N-acetylaspartate [NAA]) remained stable during the different auditory stimuli. However, the NAA/creatine ratio was higher in the auditory cortex of patients than in the control subjects, and was not dependent on the sound condition. CONCLUSION: The detection of stimulus-induced and stable biochemical MR spectroscopic changes in patients with hearing loss may be useful in assessing disease activity.

Acoustic Stimulation↗

PubMed1996

1,25-Dihydroxyvitamin D3 reversibly blocks the progression of relapsing encephalomyelitis, a model of multiple sclerosis.

Experimental autoimmune encephalomyelitis (EAE) is an autoimmune disease believed to be a model for the human disease multiple sclerosis (MS). Induced by immunizing B10.PL mice with myelin basic protein (MBP), EAE was completely prevented by the administration of 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]. 1,25-(OH)2D3 could also prevent the progression of EAE when administered at the appearance of the first disability symptoms. Withdrawal of 1,25-(OH)2D3 resulted in a resumption of the progression of EAE. Thus, the block by 1,25-(OH)2D3 is reversible. A deficiency of vitamin D resulted in an increased susceptibility to EAE. Thus, 1,25-(OH)2D3 or its analogs are potentially important for treatment of MS.

Animals↗

PubMed1996

Bcmd governs recruitment of new B cells into the stable peripheral B cell pool in the A/WySnJ mouse.

The A/WySnJ mouse provides a genetic model for studying new B cell selection into the stable peripheral B cell pool. Unlike the related A/J strain, the A/WySnJ has a single, autosomal codominant gene defect, Bcmd, resulting in a profound peripheral B cell deficiency. Here, continuous in vivo bromodeoxyuridine labeling and immunofluorescence analysis showed normal bone marrow B cell genesis but excessive B cell loss from the marrow and each peripheral pool in A/WySnJ. The A/WySnJ immature B220low/HSAhigh splenic B cell pool was 79% smaller, had a 69% slower renewal rate, and its cells had a 29% shorter average half-life than A/J. The A/WySnJ mature B220high/HSAlow splenic B cell pool was 92% smaller, had an 83% slower renewal rate, and its cells had a 56% shorter average half-life. In reciprocal chimeras, the A/WySnJ marrow failed to repopulate the peripheral B cell pool in A/J mice, whereas the A/J marrow fully reconstituted the A/WySnJ mice. Histochemistry revealed disordered splenic architecture in A/WySnJ, with few primary lymphoid follicles and a second abnormal phenotype, mastocytosis. There was no common genetic basis for B cell deficiency and mastocytosis in the F2 progeny of an (A/WySnJ x CAST/Ei)F1 intercross. We conclude that Bcmd is expressed in bone marrow cells, most likely B cells, where it hinders short-lived B cell maturation to a long-lived phenotype with the potential to form memory B cells.

Animals↗

PubMed1996

Vitamin A down-regulation of IFN-gamma synthesis in cloned mouse Th1 lymphocytes depends on the CD28 costimulatory pathway.

Some infections deplete serum retinol, low retinol reduces immunity, and reduced immunity establishes susceptibility to further infection in a cyclical relationship that is poorly understood. We showed that when retinol was low, there was excessive Th1 cell IFN-gamma synthesis and inadequate Th2 cell IL-4 and IL-5 synthesis. The retinol metabolite retinoic acid inhibited the IFN-gamma stimulatory activity of APCs, enhanced Th2 cell differentiation, and inhibited Th1 cell IFN-gamma synthesis. Here we focus on the mechanism for retinoic acid inhibition of IFN-gamma synthesis in myelin basic protein-specific MM4 Th1 cells. Physiologic amounts of all-trans-retinoic acid directly and specifically down-regulated the MM4 Th1 cell IFN-gamma secretion rate in vitro without affecting cell growth, viability, or overall protein synthesis. All-trans-, 9-cis-, and 13-cis-retinoic acid, and the synthetic retinoid Ch55, inhibited IFN-gamma synthesis effectively, whereas retinaldehyde, retinol, and retinyl acetate did not. This pattern suggests retinoic acid receptor involvement in the inhibition mechanism. Retinoic acid did not inhibit when Th1 cells were activated only through the TCR/CD3 complex, with or without IL-2 costimulation. Retinoic acid inhibited IFN-gamma synthesis when the CD28 costimulatory pathway was activated in addition to the TCR/CD3 pathway, suggesting it blocks some step in the CD28 pathway. Retinoid probably acted to decrease IFN-gamma transcript accumulation by decreasing transcription because it did not decrease transcript stability. We suggest that unrestrained IFN-gamma synthesis is one key immunobiologic mechanism that accounts for poor antibody-mediated immunity in hypovitaminosis A, since IFN-gamma in relatively small amounts can limit Th2 cell growth and interfere with the B cell stimulatory functions of Th2 cell cytokines.

Animals↗

PubMed1996

Intensity correction of phased-array surface coil images.

Phased-array coils distribute the high signal-to-noise ratio (SNR) performance of their small component surface coils over the larger area covered by the entire array. The inhomogeneous sensitivity profiles of the component surface coils result in images with very high signal near the phased-array and decreased signal far from the array. This paper presents a postprocessing algorithm for correcting these coil-related intensity variations. The algorithm's performance was evaluated by correcting images of volunteers acquired with several different receive-only phased-array surface coils.

Algorithms↗

PubMed1996

Magnetic resonance imaging to study lesions of atherosclerosis in the hyperlipidemic rabbit aorta.

We have developed a high resolution magnetic resonance (MR) imaging technique to serially assess lesions of atherosclerosis in a rabbit model. A volume phased array coil was designed and used to image the abdominal aortas of six atherosclerotic rabbits and two age-, sex-, and weight-matched controls. Lesions of atherosclerosis were induced by a combination of repeat balloon injury and a hyperlipidemic diet. All animals were imaged on at least two occasions 9-16 months after initiation of atherosclerosis. In addition, animals were imaged immediately after sacrifice. Anatomic dissection and histology were performed to verify the MR findings. The volume phased array coil improves the image signal-to-noise ratio over existing extremity coils and resulted in higher resolution images of the abdominal aorta. Proton density-weighted images acquired with 2D/3D fast spin-echo are the most useful sequence to outline the vessel wall and to differentiate wall from lumen and background. Progressive wall thickening and lumen stenosis were observed in the serial images of the diseased rabbits. Wall thickness and lumen area derived noninvasively from the in vivo MR images correlate with postmortem MR images and sections of aorta examined by dissection microscopy and histology. Spin-echo and fast spin-echo imaging with a phased array body coil can be used to accurately assess plaque dimensions, and potentially can be used to image intraplaque features and to monitor lesion progression or regression. It should also be possible to adapt these techniques to assess human disease, especially for peripheral vascular problems.

Animals↗

PubMed1996

Vitamin A deficiency exacerbates murine Lyme arthritis.

Vitamin A deficiency predisposes the host for a strong inflammatory response, suggesting that it may foster susceptibility to diseases, such as Lyme arthritis, in which activated macrophage and inflammatory cytokine production are pathogenic. Infected mice had a rapid serum retinal decline that correlated with the onset of arthritis. The mice with the least retinol developed acute arthritis earlier and more severely than those with the highest retinol. Earlier and stronger interleukin (IL)-12, interferon-gamma (IFN)-gamma, and tumor necrosis factor responses were found in Borrelia burgdorferi-infected, vitamin A-deficient mice compared with controls. The spirochetes induced IFN-gamma secretion from unprimed cells, and retinoid addition in vitro inhibited IFN-gamma synthesis. Vitamin A deficiency may exacerbate acute Lyme arthritis by enhancing an acute arthritogenic inflammatory response initiated by spirochete-driven IFN-gamma secretion. Conversely, vitamin A may lessen acute Lyme arthritis pathology by blocking IFN-gamma and IL-12 synthesis.

Animals↗

PubMed1996

Magnetic resonance neurography for cervical radiculopathy: a preliminary report.

Magnetic resonance neurography was used to directly image cervical spinal nerves in patients with clinical and radiographic evidence of cervical radiculopathy. A magnetic resonance imaging phased-array coil system was used to obtain high-resolution coronal T1-weighted spin echo, coronal/axial T2-weighted fast spin echo with fat saturation, and coronal/axial fast short tau inversion recovery weighted images of the cervical spine and spinal nerves. Three patients with neck and upper extremity pain and one asymptomatic volunteer were studied. The T2-weighted and the fast short tau inversion recovery images demonstrated markedly increased signal in the proximal portion of the affected spinal nerves. In two patients, contrast-to-noise measurements of the affected spinal nerves showed a markedly increased intensity compared with that of the noninvolved spinal nerves. Our findings demonstrate that phased-array coils used in conjunction with magnetic resonance neurography sequences can detect signal abnormalities within compressed cervical spinal nerves in patients with corresponding radicular symptoms and findings. This technique may prove to be helpful in evaluating patients with multilevel disc and/or spondylotic disease of the cervical spine.

Adult↗

PubMed1996

Magnetic resonance neurography of peripheral nerve lesions in the lower extremity.

OBJECTIVE: We describe the clinical application and utility of high-resolution magnetic resonance neurography (MRN) techniques to image the normal fascicular structure of peripheral nerves and its distortion by mass lesions or trauma in the lower extremity. METHODS: MRN images were obtained using a standard 1.5 Tesla magnet and custom built phased-array coils. Patients were imaged using T1-weighted spin echo without and with gadolinium, T2-weighted fast spin echo with fat peripheral nerve tumors (three neurofibromas and one schwannoma), two with intraneural cysts, and three with traumatic peripheral nerve lesions. Six patients with peripheral nerve mass lesions underwent surgery, thereby allowing MRN images to be correlated with intraoperative and pathological findings. RESULTS: Preoperative MRN accurately imaged the normal fascicular anatomy of peripheral nerves and precisely depicted its relation to tumor and cystic lesions. Increased signal on T2-weighted fast spin-echo and short tau inversion recovery fast spin-echo pulse sequences was seen in the peripheral nerve fascicles of patients with clinical and electrodiagnostic evidence of nerve injury. CONCLUSION: MRN proved useful in the preoperative evaluation and planning of surgery in patients with peripheral nerve lesions.

Adult↗

PubMed1996

Sacral plexus: optimal imaging planes for MR assessment.

PURPOSE: To identify the optimal imaging planes for magnetic resonance (MR) evaluation of the sacral plexus (SP) and proximal sciatic nerve (SN). MATERIALS AND METHODS: The SPs of 10 health adult volunteers were prospectively studied with T1-weighted MR imaging with custom-built pelvic phased-array coils. The conspicuity of 12 anatomic characteristics (comprising the SP and their relationship to normal pelvic anatomy) on a series of coronal, axial, and oblique images was graded. Results were evaluated with the Kruskal-Wallis and Wilcoxon signed rank tests. RESULTS: At least two planes were necessary to assess the anatomy of the SP and SN. Analysis of average conspicuity scores showed that the direct coronal and direct axial planes were the best overall and were superior to other imaging planes in the demonstration of the L-4 and L-5 ventral rami, the lumbosacral trunk, the S-1 contribution to the SN, and the SN in the greater sciatic foramen. The sacral coronal plane was best for the visualization of the bony sacrum, sacral foramina, and proximal S-1 to S-4 nerve roots. The remaining imaging planes had limited utility. CONCLUSION: MR imaging with a combination of direct coronal and direct axial planes enables thorough evaluation of all components of the SP and proximal SN.

Adult↗

PubMed1996

Application of magnetic resonance neurography in the evaluation of patients with peripheral nerve pathology.

Currently, diagnosis and management of disorders involving nerves are generally undertaken without images of the nerves themselves. The authors evaluated whether direct nerve images obtained using the new technique of magnetic resonance (MR) neurography could be used to make clinically important diagnostic distinctions that cannot be readily accomplished using existing methods. The authors obtained T2-weighted fast spin-echo fat-suppressed (chemical shift selection or inversion recovery) and T1-weighted images with planes parallel or transverse to the long axis of nerves using standard or phased-array coils in healthy volunteers and referred patients in 242 sessions. Longitudinal and cross-sectional fascicular images readily distinguished perineural from intraneural masses, thus predicting both resectability and requirement for intraoperative electrophysiological monitoring. Fascicle pattern and longitudinal anatomy firmly identified nerves and thus improved the safety of image-guided procedures. In severe trauma, MR neurography identified nerve discontinuity at the fascicular level preoperatively, thus verifying the need for surgical repair. Direct images readily demonstrated increased diameter in injured nerves and showed the linear extent and time course of image hyperintensity associated with nerve injury. These findings confirm and precisely localize focal nerve compressions, thus avoiding some exploratory surgery and allowing for smaller targeted exposures when surgery is indicated. Direct nerve imaging can demonstrate nerve continuity, distinguish intraneural from perineural masses, and localize nerve compressions prior to surgical exploration. Magnetic resonance neurography can add clinically useful diagnostic information in many situations in which physical examinations, electrodiagnostic tests, and existing image techniques are inconclusive.

Adolescent↗

PubMed1995

Vitamin A deficiency results in a priming environment conducive for Th1 cell development.

Certain infections, like that with the human immunodeficiency virus-1, deplete vitamin A, and when vitamin A levels are low, immune dysfunctions establish susceptibility to further infection. Our research has focused on the immune dysfunctions that are a consequence of vitamin A deficiency and that predispose to further infection. We previously studied a helminth infection in mice, and showed that when vitamin A levels are low, the immune response develops a strong regulatory T cell imbalance with excessive T helper type-1 cell interferon (IFN)-gamma synthesis and insufficient T helper type-2 cell development and function. Here, we studied the T cell priming environment in vitamin A-deficient mice to learn how that priming environment might produce a regulatory T cell imbalance and consequently distort the ability of the immune system to respond to an infection. Our results show that during vitamin A deficiency, the priming environment included constitutive interleukin (IL)-12 and IFN-gamma transcripts, but it was devoid of constitutive IL-4 and IL-10 transcripts. Dietary all-trans-retinoic acid supplementation down-regulated the level of constitutive IL-12 and IFN-gamma transcripts. Furthermore, when T cells from naive vitamin A-deficient animals were stimulated through the T cell receptor, they produced excess IFN-gamma protein compared to T cells from control animals. In contrast, T cell stimulation failed to induce IL-4 or IL-10 secretion. The inducible IFN-gamma was largely from CD8+ T cells and all-trans-retinoic acid addition in vitro inhibited IFN-gamma production at the transcript level. Retinoic acid addition in vitro also decreased natural killer cell IFN-gamma synthesis at the transcript level. Taken together, the distorted constitutive and inducible cytokine gene expression patterns that occurred when vitamin A levels were low would be expected strongly to favor T helper type-1 development and limit T helper type-2 cell growth and differentiation, thereby limiting the animal's humoral immune response capability.

Animals↗

PubMed1995

Serial magnetic resonance imaging of experimental atherosclerosis detects lesion fine structure, progression and complications in vivo.

A major problem in the study of lesions of atherosclerosis is the difficulty of imaging noninvasively the lesions and following their progression in vivo. To address this problem, we have developed advanced magnetic resonance techniques to noninvasively and serially image advanced lesions of atherosclerosis in the rabbit abdominal aorta. Both lumen and wall were imaged with high resolution. Progression of disease, resulting in increase in lesion mass, decrease in arterial lumen, or stenosis, and intralesion complications, can be detected. Images acquired in vivo correlate with the fine structure of the lesions of atherosclerosis, including the fibrous cap, necrotic core, and lesion fissures, as verified by gross examination, dissection microscopy, and histology. The ability to noninvasively identify the features of atherosclerotic plaques, has significant implications for determining risks and benefits associated with different therapeutic approaches.

Animals↗