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Biomedical subjects

D H Miller

Publications and source records attributed to D H Miller.

461 records · Page 26Linked to original sources
PubMed1968

Effects of Light on the Growth and Development of the Liverwort, Sphaerocarpos donnellii Aust.

Fragments of thalli of the liverwort, Sphaerocarpos donnellii Aust., inoculated into liquid medium containing sucrose and mineral salts, attain a much greater dry weight after 9 days growth in continuous white light than in darkness. Light causes this difference by increasing the rate of growth of the plants. This growth response is mediated by the pigment systems of photosynthesis and phytochrome. An inhibitor of photosynthesis, DCMU, at concentrations which inhibit light-mediated CO(2) fixation, decreases the growth rate of light-grown but not dark-grown plants. Light still slightly increases the growth rate of plants in the presence of DCMU. This latter response is mediated by phytochrome, since it can be effected by a 2 minute exposure to low intensity red light every 12 hours, and far-red light reverses the effect of red. The increased growth rate effected by red light is related to a change in the morphology of the plants. Dark-grown plants form compact balls of tissue consisting of lobes. These lobes are rounded and thick and exhibit an abnormal callus-type growth, with few well-defined meristematic regions. Plants grown in red light form fluffy balls of tissue. The lobes of these plants have a morphology more typical of Sphaerocarpos in nature. They are 2 cell layers thick, flattened, and have numerous well-defined meristematic areas. The greater number of meristems allows for the increased growth rate of the plants grown in red light.

Journal Article↗
PubMed1968

Light Mediated Changes in the Chloroplasts of the Liverwort, Sphaerocarpos donnellii Aust.

Dark-grown plants of Sphaerocarpos, incubated in a liquid medium containing sucrose and mineral salts, have a much lower chlorophyll and nitrogen content than do light-grown plants. Two minutes of red light per 12 hours is about two-thirds as effective in increasing chlorophyll and nitrogen content as is continuous white light. These red light-induced increases are mediated by phytochrome, as they are reversible by alternating exposures to red and far-red light. They appear to be related to differences in the ultrastructure of the chloroplasts. Plastids from dark-grown plants are full of starch and develop few lamellae, while light-grown plastids contain little starch and have many lamellae. The ultrastructural studies are supported by starch determinations which revealed a phytochrome-mediated decrease in starch content. The effect of white light in increasing the chlorophyll and nitrogen content above the level attained in red light-treated plants is not mediated by photosynthetic activity. These results are related to similar responses in other archegoniates and angiosperm seedlings.

Journal Article↗
PubMedDate not supplied

Macroscopic and microscopic assessments of disease burden by MRI in multiple sclerosis: relationship to clinical parameters.

We have evaluated macroscopic white matter abnormalities (visible lesions) together with microscopic abnormalities in the normal appearing white matter (NAWM) of patients with multiple sclerosis (MS) to determine their relative contributions to the development of disability. The total visible lesion volume (TLV) was computed as a measure macroscopic changes, whereas both texture analysis and T2 were used as possible indicators of diffuse disease in the NAWM. Dual echo T2-weighted SE images were obtained from 41 patients with definite MS: 10 primary progressive (PP), 11 secondary progressive (SP), 10 benign (BE), 10 early relapsing remitting (ERR), as well as from 10 healthy controls. Calculation of T2 and texture parameters were performed in a region of frontal NAWM of patients and controls. The TLV of each patient was measured using a semiautomated lesion detection program. No significant differences were found between the controls and the patients for all texture parameters examined. However, NAWM T2 was longer in the patients than in the controls (P = .02). Mean TLV was highest for SP and lowest for BE and ERR patients. A significant correlation was found between TLV and EDSS (P < .01) but not between NAWM T2 or texture and expanded disability status score (EDSS). Our study suggest that: (a) diffuse changes are present in NAWM, (b) texture analysis is unable to detect any subtle structure in the NAWM abnormalities, possibly because of the limited image resolution; (c) in the development of disability in MS, macroscopic lesions are more important than microscopic abnormalities in the NAWM.

Adult↗
PubMedDate not supplied

Lesion volume measurement in multiple sclerosis: how important is accurate repositioning?

This study was designed to estimate the contribution of repositioning inaccuracies to measured intracranial lesion volumes in multiple sclerosis (MS). Five patients with MS were each scanned 10 times, using spin-echo imaging (2,000/34/90), contiguous 5-mm slices, and different scanning positions. The maximum displacements from baseline were +/-4 degrees (AP rotation) and 3 mm (slice offset). Lesion volume was measured twice for each scan using a semiautomated contour technique. Measured lesion volumes ranged from 4,328 mm3 to 164,831 mm3. The mean intrarater coefficient of variation (CV) calculated for individual patients ranged from 1.1 to 4% (median, 1.7%). Using analysis of variance, the overall variance and CV due to altered scan position were greater than that due to rater error (repositioning CV 4.0%, intrarater CV 3.5%). The worst-case difference between volumes in the same patient ranged from 8.9 to 32% (median, 9.9%). Both rater and repositioning errors were greater for smaller lesion volumes. The maximum potential error due to repositioning inaccuracies is of a similar magnitude to the 5 to 10% expected change in lesion volume over 1 year. This study justifies continued careful attention to accuracy in repositioning for serial MR studies in patients with MS.

Brain↗
PubMedDate not supplied

A reproducible repositioning method for serial magnetic resonance imaging studies of the brain in treatment trials for multiple sclerosis.

Serial MRI is an important measure of disease progression in evaluating the treatment of multiple sclerosis (MS). Accurate comparisons of scans for lesion activity and lesion volume require precise repositioning of patients. A simple, reproducible repositioning method is described. In a multicenter treatment trial of MS using beta-interferon-1b, this method has been successful, with only 1.1% of scans being rejected because of poor repositioning.

Adjuvants, Immunologic↗
PubMedDate not supplied

Correction of nonuniformity in images of the spine and optic nerve from fixed receive-only surface coils at 1.5 T.

OBJECTIVE: Our goal was to analyze the sources of nonuniform image intensity of two surface coil configurations used on a General Electric 1.5 T Signa scanner and to correct the major source. MATERIALS AND METHODS: Correction of receive coil nonuniform sensitivity is achieved using division by images of a uniform phantom. Patient images are transferred to a network of Sun workstations for routine correction by technologists. Spinal cord images, originally 512 x 512, are truncated to 128 x 512 to allow four slices to be copied onto one X-ray film. RESULTS: Images of the spinal cord, collected using a four coil multiarray, show marked coil-to-coil nonuniformity and a high signal level from subcutaneous tissue near the coils. After correction the cord has uniform intensity, with improved visualization in the posterior fossa and upper thoracic region, enabling more reliable detection of small intrinsic lesions as occur in multiple sclerosis. Images of the optic nerves, collected using a two coil array, show bright signal in the brain and subcutaneous tissue. After correction the images are more uniform. CONCLUSION: Nonuniformity in images of the spine can be corrected using division by a phantom image. Water phantoms must be restricted in size to avoid standing wave effects; for the optic nerves a cylindrical oil phantom 20 cm in diameter was used.

Artifacts↗
PubMedDate not supplied

Complying with Joint Commission nursing standards: practical documentation tools.

The need for accurate and complete documentation of nursing care has grown as hospitals seek to comply with the new requirements of the Joint Commission on Accreditation of Healthcare Organizations. As of January 1991, the Joint Commission implemented standards for nursing services that include documentation of the planning and delivery of nursing care. While the new JCAHO standards do not call for a separate nursing care plan, they nevertheless involve enough changes to require modification of most currently used documentation forms. This article describes the methods used to design new forms at the Carl T. Hayden Veterans Affairs Medical Center in Phoenix, AZ. The newly developed forms are reviewed and compared with the Joint Commission's new standards and scoring guidelines.

Arizona↗
PubMedDate not supplied

Multiple sclerosis and its treatment.

Multiple sclerosis (MS) is a common neurological disorder responsible for substantial neurological morbidity. Although it is considered to be an autoimmune demyelinating disease of the central nervous system (CNS), mediated by antigen-specific CD4+ T helper (Th1) T-cells, therapeutic strategies aimed at generalised immunosuppression have been disappointing. Recently, immunomodulatory therapies like interferon (IFN)-beta and glatiramer acetate have proved more effective. They reduce the rate and severity of clinical relapses and, in the case of IFN-beta, delay the rate of disease progression. Symptomatic therapies and rehabilitation, however, remain the mainstay of treatment for the majority of patients with MS. The immunopathogenesis of MS and its treatments, both disease modifying and symptomatic, are reviewed below.

Disease Progression↗