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Biomedical subjects

M D Phillips

Publications and source records attributed to M D Phillips.

At least 19 recordsLinked to original sources
PubMed2001

Characterization of a novel autosomal dominant bleeding disorder in a large kindred from east Texas.

A large east Texas family with autosomal dominant inheritance of a novel bleeding disorder has been identified. The disorder is characterized clinically by easy bruising, life-threatening bleeding with trauma or surgery, and menorrhagia in affected women. Laboratory studies demonstrated prolongation of the prothrombin time and activated partial thromboplastin time in affected individuals. Paradoxically, assays of known coagulation factors are all within normal limits. To determine the molecular basis of this disease, a candidate gene linkage analysis in this kindred was done. Initially it was hypothesized that the cause of the disease in this family could be an antithrombin III (AT3) mutation that resulted in a constitutively active AT3 in the absence of heparin binding. Linkage studies using DNA from the family and an intragenic polymorphic marker within the AT3 gene showed that the disease mapped to this locus. The coding region and intron/exon junctions of AT3 were sequenced using the proband's DNA, but this analysis failed to identify a mutation. Additional family members were recruited for the study, and 16 polymorphic markers around the AT3 gene were analyzed. Using 2 recombinants, the critical interval for the defective gene was narrowed to approximately 1.5 Mb, centromeric to AT3. The factor V (FV) gene was mapped into the disease interval and sequenced; there were no mutations found. Elucidation of the genetic defect causing the bleeding disorder in this family may reveal a novel protein involved in the coagulation cascade.

Adult↗
PubMed2001

Improving clinical histories on radiology requisitions.

PURPOSE: The Health Care Financing Administration (HCFA) regards billing for radiologic examinations without an appropriate indication as unlawful, and both the referring physician and the radiologist are liable. HCFA regulations are interpreted as requiring that all requisitions for radiologic examinations include a current diagnosis and appropriate indication for the study. The purpose of this investigation was to determine the rates at which requisitions currently meet these criteria and to assess the effectiveness of a simple intervention designed to improve them. MATERIALS AND METHODS: One hundred fifty consecutive chest radiography requisitions were examined to determine the rate at which current diagnoses and appropriate indications were present. An intervention was then implemented that included a month-long effort to inform referring physicians and radiologists of HCFA regulations, followed by a 1-week period during which requested examinations were not performed unless accompanied by a clinical diagnosis and appropriate indication. Another 150 consecutive chest radiography requisitions were then assessed to determine the effect of the intervention. A 3-month follow-up sample of a third set of 150 consecutive requisitions was then obtained. RESULTS: The intervention produced a 69% decrease in the rate at which current diagnoses were missing from requisitions, and a 61% decrease in the corresponding rate for appropriate indications. Both results are significant with chi2 analysis at the P = .001 level. After 3 months with no additional intervention, rates decayed back toward baseline, with only a 35% remaining decrease for current diagnosis and an 18% decrease for appropriate indication. CONCLUSION: The intervention performed in this study significantly reduces the rate of noncompliance with HCFA regulations. However, this improvement decays over time if it is not reinforced.

Centers for Medicare and Medicaid Services, U.S.↗
PubMed2001

Temporal lobe activation demonstrates sex-based differences during passive listening.

PURPOSE: To evaluate potential sex differences in temporal lobe activation during the performance of a functional magnetic resonance (MR) imaging passive-listening paradigm. MATERIALS AND METHODS: Twenty strongly right-handed volunteers (10 men, 10 women) underwent imaging with a 1.5-T machine by using a gradient-echo echo-planar sequence. The task consisted of passive listening to simple narrative text interleaved with same-narrative text played backward. Volumes of interest were drawn around anterior and posterior areas of activation in bilateral temporal lobes. The peak percentage of activation and the percentage of activated voxels at single-voxel significance levels of 10(-2), 10(-3), and 10(-4) within each volume of interest were measured. An asymmetry index A was then calculated for both anterior and posterior volumes of interest such that A = (L - R)/(L + R), where R is either the peak percentage activation or the percentage of activated voxels within the right volume of interest and L is either the peak percentage activation or the percentage of activated voxels within the left volume of interest. The asymmetry indexes were compared between men and women by using a standard t test. RESULTS: Men showed a significantly higher degree of asymmetric activation than did women in both the anterior and posterior volumes of interest by using peak percentage activation and at all single-voxel significance levels. The degree of activation asymmetry was greater by using single-voxel significance measurements, compared with peak percentage activation measures. CONCLUSION: Women demonstrate a higher degree of bilateral language representation in temporal lobe regions than do men during passive listening. These findings, combined with the variable results of prior functional MR imaging language studies of sex differences, suggest that they may be task specific.

Adult↗
PubMed2001

Approach to functional magnetic resonance imaging of language based on models of language organization.

Functional MR imaging (fMRI) has been a useful tool in the evaluation of language both in normal individuals and patient populations. The purpose of this article is to use various models of language as a framework to review fMRI studies. Specifically, fMRI language studies are subdivided into the following categories: word generation or fluency, passive listening, orthography, phonology, semantics, and syntax.

Brain Mapping↗
PubMed2001

Diffusion-weighted imaging of white matter abnormalities in patients with phenylketonuria.

Phenylketonuria (PKU) is an autosomal recessive disorder caused by a deficiency of the enzyme phenylalanine hydroxylase (EC 1.14.16.1). Affected patients develop elevated plasma and tissue levels of phenylalanine and its related ketoacids. Untreated patients usually exhibit severe mental retardation and poor motor function, with characteristic T2 white matter signal abnormalities on conventional MR images. In the present study, we performed diffusion-weighted imaging in three PKU patients. All three patients demonstrated significantly restricted diffusion in all white matter areas examined.

Adult↗
PubMed2000

Correlations in low-frequency BOLD fluctuations reflect cortico-cortical connections.

Cross-correlation of low-frequency temporal fluctuations (<0.08 Hz) was used to correlate widely separated anatomic regions during continuous performance of a spatial working memory task. The regions of highest correlation to right-hemisphere dorsolateral prefrontal cortex correspond to the regions of largest baseline signal change in a conventional block-style functional MRI paradigm. Additionally, it is shown that the correlations between elements of the functional network increase during performance of a task that activates the network when compared to a task that does not directly stimulate the functionally connected network.

Attention↗
PubMed2000

Quantitative comparison of functional contrast from BOLD-weighted spin-echo and gradient-echo echoplanar imaging at 1.5 Tesla and H2 15O PET in the whole brain.

Spin-echo and gradient-echo echoplanar functional magnetic resonance imaging (fMRI) studies at 1.5 Tesla (T) were used to obtain blood oxygenation level-dependent (BOLD) contrast images of the whole brain in seven strongly right-handed women during execution of a complex motor task. Five subjects underwent subsequent H215O positron emission tomography (PET) studies while performing the same task. Group-averaged results for changes in the MRI relaxation rates R2* and R2 at 1.5T in response to neuronal activation in nine cortical, subcortical, and cerebellar motor regions are reported. Results for each method are grouped according to tissue type-cerebral cortex (precentral gyrus and supplementary motor area), subcortical regions (thalamus and putamen), and cerebellar cortex (superior lobule). The observed changes in R2* from activation-induced oxygenation changes were more variable across brain regions with different tissue characteristics than observed changes in R2. The ratio of deltaR2* to deltaR2 was 3.3 +/- 0.9 for cerebral cortex and 2.0 +/- 0.6 for subcortical tissue. deltaR2*, deltaR2, and relative blood flow changes were deltaR2* = -0.201 +/- 0.040 (s-1), deltaR2 = -0.064 +/- 0.011 s(-1), and deltaf/f = 16.7 +/- 0.8% in the cerebral cortex; deltaR2* = -0.100 +/- 0.026 s(-1), deltaR2 = -0.049 +/- 0.009 s(-1), and deltaf/f = 9.4 +/- 0.7% in the subcortical regions; and deltaR2* = -0.215 +/- 0.093 s(-1), deltaR2 = -0.069 +/- 0.012 s(-1), and deltaf/f = 16.2 +/- 1.2% in the cerebellar cortex.

Adult↗
PubMed2000

Postexercise rehydration: effect of Na(+) and volume on restoration of fluid spaces and cardiovascular function.

Our purpose was to study the interaction between Na(+) content and fluid volume on rehydration (RH) and restoration of fluid spaces and cardiovascular (CV) function. Ten men completed four trials in which they exercised in a 35 degrees C environment until dehydrated by 2. 9% body mass, were rehydrated for 180 min, and exercised for an additional 20 min. Four RH regimens were tested: low volume (100% fluid replacement)-low (25 mM) Na(+) (LL), low volume-high (50 mM) Na(+) (LH), high volume (150% fluid replacement)-low Na(+) (HL), and high volume-high Na(+) (HH). Blood and urine samples were collected and body mass was measured before and after exercise and every hour during RH. Before and after the dehydration exercise and during the 20 min of exercise after RH, cardiac output was measured. Fluid compartment (intracellular and extracellular) restoration and percent change in plasma volume were calculated using the Cl(-) and hematocrit/Hb methods, respectively. RH was greater (P < 0.05) in HL and HH (102.0 +/- 15.2 and 103.7 +/- 14.7%, respectively) than in LL and LH (70.7 +/- 10.5 and 75.9 +/- 6.3%, respectively). Intracellular RH was greater in HL (1.12 +/- 0.4 liters) than in all other conditions (0.83 +/- 0.3, 0.69 +/- 0.2, and 0.73 +/- 0.3 liter for LL, LH, and HH, respectively), whereas extracellular RH (including plasma volume) was greater in HL and HH (1.35 +/- 0.8 and 1.63 +/- 0.4 liters, respectively) than in LL and LH (0.83 +/- 0.3 and 1.05 +/- 0.4 liters, respectively). CV function (based on stroke volume, heart rate, and cardiac output) was restored equally in all conditions. These data indicate that greater RH can be achieved through larger volumes of fluid and is not affected by Na(+) content within the range tested. Higher Na(+) content favors extracellular fluid filling, whereas intracellular fluid benefits from higher volumes of fluid with lower Na(+). Alterations in Na(+) and/or volume within the range tested do not affect the degree of restoration of CV function.

Adult↗
PubMed1999

Differences between relapsing-remitting and chronic progressive multiple sclerosis as determined with quantitative MR imaging.

PURPOSE: To investigate the cross-sectional relationships among multiple quantitative brain magnetic resonance (MR) imaging measurements in patients with relapsing-remitting versus chronic progressive multiple sclerosis (MS). MATERIALS AND METHODS: Thirty-eight patients with MS (relapsing-remitting, 26, chronic progressive, 12) were examined. Lesion volume on T2-weighted MR images, contrast material-enhancing lesion volume, percentage of brain parenchymal volume (brain volume/[brain volume + cerebrospinal fluid volume), and magnetization transfer ratio histogram peak height for the whole brain were calculated. RESULTS: Significant negative correlation was noted between volume on T2-weighted images and magnetization transfer ratio histogram peak height for both the relapsing-remitting and chronic progressive groups (P < .001 for both). A positive correlation was demonstrated for lesion volume on T2-weighted images and enhancing lesion volume in the relapsing-remitting group (P < .01) but not in the chronic progressive group. Negative correlations were demonstrated for enhancing lesion volume and magnetization transfer ratio histogram peak height (P = .02), for Expanded Disability Status Scale score and magnetization transfer histogram peak height (P = .02), and for Expanded Disability Status Scale score and percentage of brain parenchymal volume in the relapsing-remitting group (P = .004) but not in the chronic progressive group. CONCLUSION: The cross-sectional relationships among multiple quantitative brain MR imaging measurements are different between relapsing-remitting and chronic progressive MS.

Adult↗
PubMed1999

Diffusion imaging in pediatric hypoxic ischemia injury.

This article is a brief review on the physics of diffusion imaging as well as the pertinent adult literature regarding stroke and diffusion imaging. The remainder of the article focuses on the potential uses of diffusion imaging for the evaluation of hypoxic ischemia injury in pediatric populations. In particular, diffusion changes in hypoxic ischemia injury in newborns are reviewed as the diffusion abnormalities in immature brain may behave in a manner different from adults.

Adolescent↗
PubMed1998

Multidisciplinary gastrointestinal cancer clinic: abdominal radiologist as active participant.

RATIONALE AND OBJECTIVES: Abdominal radiologists actively participated and provided subspecialty radiologic expertise in a multidisciplinary gastrointestinal cancer clinic that served a tertiary referral center. The purpose of this study was to evaluate the feasibility and nonradiologists' opinions of this new approach to radiologic consultation. MATERIALS AND METHODS: One of four subspecialty-trained abdominal radiologists joined physicians from four other subspecialties in staffing weekly 4-hour clinic sessions. Images were reviewed, opinions on test selection and interventional options rendered, and patients met with when interventional options were considered. Radiologists were compensated a fixed sum for each session. A survey of nonradiologists' opinions about the radiologists' active participation was conducted after 15 months (61 clinic sessions). RESULTS: Abdominal radiologists' active participation was feasible and highly regarded by nonradiologist physicians. Specific benefits cited in the survey included improved interpretation, more efficient use of nonradiologist physician time, and improved rapport between radiologists and nonradiologists. Nonradiologist physicians believed that patient care was improved and that the radiologists' participation should continue. CONCLUSION: The active participation of abdominal radiologists in a multidisciplinary gastrointestinal cancer clinic is feasible and highly regarded by nonradiologists.

Attitude of Health Personnel↗
PubMed1998

von Willebrand disease: recent advances in pathophysiology and treatment.

This review focuses on new developments in the pathophysiology and treatment of von Willebrand disease (vWd). New aspects of the cell biology, gene control, and structure-function correlates of von Willebrand factor (vWf) are reviewed. vWd is more prevalent than previously recognized, affecting up to 1% of the population; this is particularly evident in women's health. Blood group is an important determinant of von Willebrand factor levels; individuals of blood group O tend to have lower plasma levels of vWf than those in other blood groups. Currently available blood tests of vWf quantity and function are discussed, in addition to newer tests undergoing validation. Treatment of classical vWd with desmopressin acetate and plasma derivatives is discussed, as is the potential for intravenous immunoglobulin and corticosteroids in acquired vWd. Special situations, such as the management of vWd in pregnancy, are also discussed.

ABO Blood-Group System↗
PubMed1998

Percutaneous abdominal biopsy: cost-identification analysis.

PURPOSE: To determine the difference in cost to providers of percutaneous abdominal biopsy as the first strategy versus surgical biopsy. MATERIALS AND METHODS: Cost of tissue diagnosis determination with percutaneous biopsy as the first strategy in 439 patients with an abdominal mass was estimated. Costs included direct hospital costs and professional costs of initial and repeat biopsy, follow-up imaging and clinic visits, surgical biopsy (when needed), and treatment of complications. The sum of these costs was compared with the estimated cost had the same patients undergone surgical biopsy instead, with no complications or need for follow-up or repeat biopsy. RESULTS: The total estimated cost of percutaneous biopsy as the first strategy ($543,245) was less than the cost had surgical biopsy been used alone ($1,919,867). The average per patient direct hospital cost of percutaneous biopsy ($800) was lower than that of surgical biopsy ($3,419). The average per patient professional cost of percutaneous biopsy ($438) was also lower than that of surgical biopsy ($955). Savings averaged $3,136 per patient, or $1,376,622 for the study period. CONCLUSION: Substantial health care cost savings may result by using a diagnostic algorithm in which percutaneous biopsy is the first strategy for establishment of a diagnosis in patients suspected of having abdominal malignancy.

Abdominal Neoplasms↗
PubMed1998

Negative predictive value of imaging-guided abdominal biopsy results: cytologic classification and implications for patient management.

OBJECTIVE: Our purpose was to assess the negative predictive value of imaging-guided abdominal biopsy results and correlate it with cytology classification, lesion size, needle gauge, and cancer history. MATERIALS AND METHODS: A retrospective study was performed of 100 patients with proven diagnoses who had undergone imaging-guided abdominal biopsies showing no cells that were malignant or suspicious for malignancy. Specimens were classified as normal or benign, nondiagnostic, or atypical. Negative predictive value was calculated for each cytologic category, lesion size, needle gauge, and cancer history. Logistic regression analysis was performed to allow us to identify predictors of false-negative results. RESULTS: Overall negative predictive value was 67%. Other negative predictive values were normal or benign result, 78%; nondiagnostic result, 66%; and atypical result, 29%. Negative predictive value was greater when the lesion was large (> or =3 cm) (p = .031). Logistic regression analysis allowed us to predict a 9.3% chance of a false-negative result for a specimen of normal or benign cytology that was taken from a large lesion in a patient with no cancer history but an 87% chance of a false-negative when a specimen of atypical cytology was taken from a small (<3 cm) lesion in a patient with a cancer history. CONCLUSION: Imaging-guided abdominal biopsy specimens containing atypical cells should be viewed with caution. In patients without cancer, if a lesion is large and the specimen contains normal target organ or benign cells, the likelihood of a false-negative result may be low enough that imaging surveillance at appropriate intervals may be sufficient.

Abdominal Neoplasms↗
PubMed1997

Successful treatment of acquired hemophilia with oral immunosuppressive therapy.

BACKGROUND: Acquired autoantibodies to factor VIII in patients without hemophilia are rare, but they cause severe illness and death if not eradicated. OBJECTIVE: To examine daily therapy with oral cyclophosphamide and prednisone for acquired hemophilia. DESIGN: Case series. SETTING: Academic medical center. PATIENTS: Nine consecutive patients without hemophilia who had severe hemorrhage caused by high titers of factor VIII inhibitors. INTERVENTIONS: Daily oral cyclophosphamide and prednisone. Coagulation factors were used only for bleeding. MEASUREMENTS: Plasma titers of factor VIII inhibitor, factor VIII activity, and clinical evidence of bleeding. RESULTS: All patients achieved complete remission, which was defined as loss of residual inhibitor activity and return to a normal titer of factor VIII. Therapy lasted a median of 12 weeks (range, 3 to 37 weeks). Bleeding resolved in a median of 3 weeks (range, 2 to 10 weeks). Median follow-up after discontinuation of therapy was 91 weeks (range, 61 to 164 weeks). CONCLUSION: Daily administration of oral cyclophosphamide and prednisone without empirical factor VIII therapy seems to be an effective and well-tolerated treatment for acquired hemophilia.

Administration, Oral↗