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Biomedical subjects

R Little

Publications and source records attributed to R Little.

At least 19 recordsLinked to original sources
PubMed2000

PET measures of benzodiazepine receptors in progressive supranuclear palsy.

OBJECTIVE: To evaluate the integrity of neurons containing benzodiazepine receptors in metabolically affected regions of the brain in patients with clinically diagnosed progressive supranuclear palsy (PSP). METHODS: The cerebral distribution of [11C]flumazenil (FMZ), a ligand that binds to the gamma-aminobutyric acid A (GABAA) receptor, and [18F]fluorodeoxyglucose (FDG), a measure of local cerebral glucose metabolism, was determined with PET in 12 patients with PSP and 10 normal control subjects. Tracer kinetic analysis was applied to quantify data and analysis was performed using three-dimensional stereotactic surface projections and stereotactically determined volumes of interest. RESULTS: There was a global reduction in FMZ binding of 13%, with a reduction in the anterior cingulate gyrus of 20% (p = 0.004), where glucose metabolic rates also showed the greatest reduction. CONCLUSIONS: PSP causes loss of benzodiazepine receptors in the cerebral cortex. Consistent with postmortem studies, the authors did not find significant changes in FMZ binding in subcortical nuclei that exhibit the most pathologic change. This study suggests that both loss of intrinsic neurons containing benzodiazepine receptors and deafferentation of the cerebral cortex from distant brain regions contribute to cerebral cortical hypometabolism in PSP.

Aged↗
PubMed1999

Decreased striatal monoaminergic terminals in multiple system atrophy detected with positron emission tomography.

We examined the density of striatal presynaptic monoaminergic terminals, using a ligand for the type 2 vesicular monoamine transporter, (+)-[11C]dihydrotetrabenazine, with positron emission tomography in 7 normal control subjects, 8 multiple system atrophy (MSA) patients with predominantly parkinsonian features (MSA-P), 8 MSA patients with principally cerebellar dysfunction (MSA-C), and 6 sporadic olivopontocerebellar atrophy (sOPCA) patients. The findings were correlated with the results of neurological evaluations and magnetic resonance imaging studies. Specific binding was significantly reduced in the putamen of all patient groups in the order MSA-P < MSA-C < sOPCA, compared with controls. Mean blood-to-brain ligand transport (K1) was significantly decreased in the putamen of all patient groups and in the cerebellar hemispheres of MSA-C and sOPCA but not MSA-P groups, compared with controls. Significant negative correlations were found between striatal binding and the intensity of parkinsonian features and between cerebellar K1 and the intensity of cerebellar dysfunction. The results suggest fundamental differences between MSA-P and MSA-C groups reflecting differential severity of degeneration of nigrostriatal and cerebellar systems in these two forms of MSA. The findings also show that some sOPCA patients have subclinical nigrostriatal dysfunction and are at risk of developing MSA with disease progression.

Adult↗
PubMed1998

Allelic imbalance, including deletion of PTEN/MMACI, at the Cowden disease locus on 10q22-23, in hamartomas from patients with Cowden syndrome and germline PTEN mutation.

Cowden disease (CD) is a rare, autosomal dominant inherited cancer syndrome characterized by multiple benign and malignant lesions in a wide spectrum of tissues. While individuals with CD have an increased risk of breast and thyroid neoplasms, the primary features of CD are hamartomas. The gene for CD has been mapped by linkage analysis to a 6 cM region on the long arm of chromosome 10 at 10q22-23. Loss of heterozygosity (LOH) studies of sporadic follicular thyroid adenomas and carcinomas, both component tumors of CD, have suggested that the putative susceptibility gene for CD is a tumor suppressor gene. Somatic missense and nonsense mutations have recently been identified in breast, prostate, and brain tumor cell lines in a gene encoding a dual specificity phosphatase, PTEN/MMACI, mapped at 10q23.3. Furthermore, germline PTEN/MMACI mutations are associated with CD. In the present study, 20 hamartomas from 11 individuals belonging to ten unrelated families with CD have been examined for LOH of markers flanking and within PTEN/MMACI. Eight of these ten families have germline PTEN/MMACI mutations. LOH involving microsatellite markers within the CD interval, and including PTEN/MMACI, was identified in two fibroadenomas of the breast, a thyroid adenoma, and a pulmonary hamartoma belonging to 3 to 11 (27%) of these patients. The wild-type allele was lost in these hamartomas. Semi-quantitative PCR performed on RNA from hamartomas from three different tissues from a CD patient suggested substantial reduction of PTEN/MMACI RNA levels in all of these tissues. The LOH identified in samples from individuals with CD and the suggestion of allelic loss and reduced transcription in hamartomas from a CD patient provide evidence that PTEN/MMACI functions as a tumor suppressor in CD.

Chromosomes, Human, Pair 10↗
PubMed1998

A simple high performance liquid chromatography assay for simultaneous determination of omeprazole and metronidazole in human plasma and gastric fluid.

Antibiotics which are actively secreted into gastric fluid may be more efficacious in the eradication of Helicobacter pylori in peptic ulcer disease. Other agents used in the treatment of this disease such as omeprazole or other anti-secretory agents may alter the secretion and/or distribution characteristics of antibiotics. In order to test the applicability of these concepts to metronidazole, a sensitive and specific high performance liquid chromatography (HPLC) assay was developed to quantitate omeprazole in plasma, and metronidazole in plasma and gastric fluid. The HPLC system consisted of a multi-phase column combining anion exchange and reversed phase separation (OmniPac Pax-500, Dionex), and a variable wavelength UV detector set at 254 nm. The mobile phase was a mixture of 0.1 M sodium phosphate buffer:methanol:acetonitrile (60:20:20) with final pH adjusted to approximately 7.0. Metronidazole and omeprazole were extracted by adsorption onto a C2-bonded silica gel solid phase extraction column, and eluted with methanol. The extract was dried, reconstituted in a solution of acetyl salicylic acid (ASA), and then injected into the HPLC system. Under these conditions, metronidazole, omeprazole and ASA were well separated and recoveries in plasma were greater than 80%. Omeprazole could not be measured in gastric fluid because of rapid decomposition. Using 0.3 ml of sample, the assay sensitivity was less than 0.1 microgram ml-1 and linear up to 10 micrograms ml-1. Both intra- and inter-assay CV were greater than 15%. It was applied successfully in determining metronidazole concentrations in clinical samples of plasma and gastric fluid.

Anti-Infective Agents↗
PubMed1998

Successful medical management of isolated renal zygomycosis: case report and review.

We describe the medical management of isolated renal zygomycosis in an adult patient with AIDS during chemotherapy for AIDS-related lymphoma. After initial presentation during the first cycle of chemotherapy, the infection was contained within the kidney following recovery of the neutrophil count without medical or surgical intervention. Since he was not considered to be a candidate for nephrectomy, his infection was treated with amphotericin B lipid complex during subsequent chemotherapy. Neutropenia was minimized by the addition of cytokine support therapy with granulocyte colony-stimulating factor and reduced doses of chemotherapy. Following this strategy, his lymphoma completely resolved, and renal zygomycosis was controlled. At the time of this writing, he had been in complete remission for 18 months without evidence of progressive fungal infection. This report and our literature review indicate that isolated renal zygomycosis can be associated with a favorable prognosis, occurs with greatest frequency in patients with AIDS, is associated with parenteral access, and may be managed by medical therapy alone.

AIDS-Related Opportunistic Infections↗
PubMed1998

Vinblastine for recurrent Hodgkin's disease following autologous bone marrow transplant.

PURPOSE: Bone marrow transplant (BMT) can cure recurrent Hodgkin's disease, but more than half of patients will progress and require additional treatment. When this occurs, there are no curative options and palliative therapy is usually indicated. In such patients, we have routinely used long-term vinblastine therapy because of its relatively low toxicity and high activity. PATIENTS AND METHODS: We retrospectively reviewed the charts of all patients with Hodgkin's disease who relapsed after autologous BMT since 1991. Of 23 patients, 16 received vinblastine; we also include our index case, who began vinblastine following relapse in 1987. Patients received vinblastine 4 to 6 mg/m2 every 1 to 2 weeks, and continued until evidence of disease progression. RESULTS: The 17 patients in this report had a median age of 31 years, performance status of 2, had received a median of three prior regimens, and 12 (71%) patients were advanced stage. Ten (59%) patients had objective responses, of which two (12%) were complete (CR) and eight (47%) were partial (PR). Two additional patients without measurable disease clinically improved for more than 6 months, and 1 patient had stable disease for more than 18 months. With a median follow-up of 20.4 months, the median event-free (EFS) and overall survival were 8.3 and 38.8 months, respectively. The two complete responders remain in remission at 4.6+ and 9+ years. Vinblastine was well tolerated with 3% of cycles associated with fever and neutropenia, and no cumulative or chronic toxicity. CONCLUSION: Vinblastine provides effective palliation with low toxicity in recurrent Hodgkin's disease following transplant. These results suggest that long-term vinblastine therapy may be potentially curative and should be considered as initial therapy for such patients.

Adult↗
PubMed1998

Phase II and dose-escalation with or without granulocyte colony-stimulating factor study of 9-aminocamptothecin in relapsed and refractory lymphomas.

PURPOSE: To assess the efficacy and maximum dose-intensity of a new topoisomerase I (topo I)-targeting agent, 9-aminocamptothecin (9-AC), in patients with relapsed or refractory lymphomas. PATIENTS AND METHODS: Eligible patients had measurable disease and were considered incurable. 9-AC was infused over 72 hours at an initial dose rate of 40 microg/m2/h every 3 weeks with subsequent intrapatient escalations or reductions in 10-microg/m2/h increments based on toxicity. To assess the impact of granulocyte-colony stimulating factor (G-CSF) on dose-intensity, the first 16 patients received no G-CSF and the subsequent 29 patients received G-CSF on all cycles. RESULTS: Forty-five patients received a total of 142 cycles of 9-AC. The patients' median age was 55 years, 73% had stage IV disease, and histologies included indolent and aggressive non-Hodgkin's lymphoma (NHL) in 33% and 58% of patients, respectively, and Hodgkin's lymphoma in 9%. Patients had received a median of two prior chemotherapy regimens, and 67% of patients had chemotherapy-sensitive disease. Of 40 assessable patients, 10 (25%) achieved a partial response (PR). Chemotherapy-sensitive patients had a 32% response rate compared with 8% in chemotherapy-resistant patients. With a median follow-up duration of 35 months, the median event-free survival (EFS) and overall survival times were 1.5 and 12.5 months, respectively, and the median duration of response was 5 months (range, 1 to 10). G-CSF significantly reduced the incidence of neutropenia and diarrhea, but did not permit a significant increase in dose-intensity. CONCLUSION: 9-AC had a reasonable response rate of 25% in heavily pretreated patients. The low response rate in patients with chemotherapy-resistant disease suggests that there is cross-resistance between 9-AC and standard chemotherapy. However, there was no association between 9-AC response and the number of prior regimens. Due to dose-limiting thrombocytopenia, G-CSF support did not increase dose-intensity, although individual patients benefited from the use of G-CSF.

Adult↗
PubMed1998

What is hemoglobin A1c? An analysis of glycated hemoglobins by electrospray ionization mass spectrometry.

Hemoglobin A1c (HbA1c) is a stable minor Hb variant formed in vivo by posttranslational modification by glucose, originally identified by using cation exchange chromatography, and containing primarily glycated N-terminal beta-chains. However, the structure(s) of the quantified species has not been elucidated, and the available methods lack a reference standard. We used electrospray ionization mass spectrometry to determine the extent of glycation of samples separated by boronate affinity and/or cation exchange chromatography. Analyses of clinical samples were consistent with the curvilinear relationship of patient glucose and HbA1c. As glycation increased, the ratio of beta-chain to alpha-chain glycation increased, and the number of glycation sites on the beta-chain increased, although these were relatively minor components. We found several glycated species that cochromatographed with HbA1c on cation exchange, including species with both glycated alpha- and beta-chains, nonglycated alpha- and glycated beta-chains, and multiply glycated beta-chains. The combined use of affinity and cation exchange chromatography with structural confirmation by electrospray ionization mass spectrometry was found to be useful in producing samples of sufficient purity for the standardization of glycohemoglobin clinical assays.

Blood Glucose↗
PubMed1997

Biochemical characterization of recombinant fusions of lipopolysaccharide binding protein and bactericidal/permeability-increasing protein. Implications in biological activity.

The physiological response to endotoxin (lipopolysaccharide (LPS)) can be regulated by two closely related LPS-binding proteins, LPS-binding protein (LBP), which potentiates LPS' inflammatory activity via interaction with the monocytic antigen CD14, and bactericidal/permeability-increasing protein (BPI), which neutralizes LPS. Both proteins bind LPS with high affinity sites in their N-terminal domains, whereas interaction between LBP and CD14 is dependent upon the LBP C-terminal domain. We have created fusions of the N- and C-terminal domains from each protein and compared the functional activities and pharmacokinetics of these fusions, the individual N-terminal domains, and the parent proteins. The N-terminal domains of BPI and LBP bound lipid A with their characteristic apparent affinity constants, regardless of the C-terminal fusion partner. In addition, the C-terminal domain of LBP allowed transfer of LPS to CD14 in conjunction with either N-terminal LPS binding domain. Proteins containing a BPI N-terminal domain had greater heparin binding capacities in vitro and were cleared more rapidly from the plasma of whole animals. Taken together, these data better define how closely related proteins such as BPI and LBP can have opposing effects on the body's response to LPS.

Acute-Phase Proteins↗
PubMed1997

An investigation of the effect of paternal occupation group at conception on birth weight and gestational age. ALSPAC Study Team of Pregnancy and Childhood.

The occupational histories of fathers were collected prospectively as part of the Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC), and were used to investigate the association of paternal job title with a baby's birth weight and gestational age. The analysis cohort consisted of 4,795 singleton live-born babies whose fathers responded fully to questionnaire items regarding occupational history. Jobs were coded using the British Standard Occupational Codes and classified into nine major occupational groups. A 73-gram difference (95% CI: 0.16, 145.17) was found between the mean birth weight of full-term babies born of professional fathers (3,543 gm) and of fathers working in craft and related occupations (3,470 gm). This difference decreased and lost significance after controlling for sociodemographic variables. No difference was found in the mean birth weight of preterm babies, or in the rate of preterm delivery, when analyzed by paternal occupation at conception. Our results suggest that when important sociodemographic variables are known, the father's job title alone may not be a useful predictor of birth weight or preterm delivery.

Birth Weight↗
PubMed1996

Spinocerebellar ataxia type 1 with multiple system degeneration and glial cytoplasmic inclusions.

Spinocerebellar ataxia type 1 (SCA1) is a dominantly inherited progressive neurological disorder characterized by neuronal degeneration and reactive gliosis in the cerebellum, brainstem, spinocerebellar tracts, and dorsal columns. Multiple system atrophy is a sporadic progressive neurological disorder with degeneration and gliosis in the basal ganglia, cerebellum, brainstem, and spinal autonomic nuclei, and with argyrophilic glial cytoplasmic inclusions. We describe 4 members of a family with the SCA1 mutation and a dominantly inherited progressive ataxia in which autopsy examination of 1 member showed neuropathological changes typical of multiple system atrophy, including glial cytoplasmic inclusions. In this patient, magnetic resonance imaging revealed marked brainstem and cerebellar volume loss and mild supratentorial generalized volume loss. Positron emission tomography with [18F]fluorodeoxyglucose revealed widespread hypometabolism in a pattern found in sporadic multiple system atrophy and not in dominantly inherited olivopontocerebellar atrophy. Positron emission tomography with [11C]flumazenil revealed normal benzodiazepine receptor distribution volumes, similar to those seen in sporadic multiple system atrophy. Two other family members still living had similar changes in the imaging studies. The findings in this family suggest that the SCA1 gene mutation can result in a disorder similar to multiple system atrophy, both clinically and neuropathologically.

Adult↗
PubMed1996

Decreased striatal monoaminergic terminals in olivopontocerebellar atrophy and multiple system atrophy demonstrated with positron emission tomography.

We used [11C]dihydrotetrabenazine, a new ligand for the type 2 vesicular monoamine transporter (VMAT2), with positron emission tomography to study striatal monoaminergic presynaptic terminals in 4 patients with multiple system atrophy, 8 with sporadic olivopontocerebellar atrophy, and 9 normal control subjects. Specific binding in the striatum was significantly reduced in the multiple system atrophy patients as compared with the normal control group, with average reductions of 61% in the caudate nucleus (p = 0.002) and 58% in the putamen (p = 0.009). Smaller reductions were found in the sporadic olivopontocerebellar atrophy group, averaging 26% in the caudate nucleus (p = 0.05) and 24% in the putamen (p = 0.11). Mean blood-to-brain [11C]dihydrotetrabenazine transport (K1) was significantly different between groups only in the cerebellum, with values for the sporadic olivopontocerebellar atrophy group diminished compared with the normal control group. Cerebellar K1 was not significantly decreased in the multiple system atrophy group. The finding of reduced striatal VMAT2 in sporadic olivopontocerebellar atrophy patients suggests nigrostriatal pathology, indicating that some may later develop symptomatic extrapyramidal disease.

Adult↗
PubMed1996

The repeatability of self-reported exposure after miscarriage. ALSPAC Study Team. Avon Longitudinal Study of Pregnancy and Childhood.

BACKGROUND: The Avon Longitudinal Study of Pregnancy and Childhood is a prospective study of women who were resident in Avon and who were expected to deliver a baby between April 1991 and December 1992. METHODS: The study provided an opportunity to test the repeatability of responses from 220 women who experienced a miscarriage and who reported exposure to occupational substances and common household products and appliances in two questionnaires. The first questionnaire was completed in the early part of the pregnancy and the second after the miscarriage. Women were asked to score their frequency of exposure on a five-point scale from 'daily' to 'never'. Their responses were analysed to assess the degree of agreement between replies to identical questions in the two questionnaires using the kappa statistic. A new frequency variable was created which compared the replies for the two questionnaires; this was analysed for all exposures by cross-tabulation with possible explanatory variables (age of mother, social class, history of miscarriage and the time lag between questionnaires). RESULTS: In general there was good agreement in the reported exposures to 48 substances and products. The results showed a small and consistent pattern of reporting exposures less frequently in the second questionnaire, i.e. after miscarriage. This was not explained by the analysis of possible confounding variables. Given the literature, the authors had expected to find a shift in the opposite direction. CONCLUSION: The study reinforces the need to be cautious when using the results from single surveys of retrospective self-reported exposure.

Abortion, Spontaneous↗
PubMed1996

Intent-to-treat analysis for longitudinal studies with drop-outs.

We consider intent-to-treat (IT) analysis of clinical trials involving longitudinal data subject to drop-out. Common methods, such as Last Observation Carried Forward imputation or incomplete-data methods based on models that assume random dropout, have serious drawbacks in the IT setting. We propose a method that involves multiple imputation of the missing values following drop-out based on an "as treated" model, using actual dose after drop-out if this is known, or imputed doses that incorporate a variety of plausible alternative assumptions if unknown. The multiply-imputed data sets are then analyzed using IT methods, were subjects are classified by randomization group rather than by the dose actually received. Results from the multiply-imputed data sets are combined using the methods of Rubin (1987, Multiple Imputation for Nonresponse in Surveys). A novel feature of the proposed method is that the models for imputation differ from the model used for the analysis of the filled-in data. The method is applied to data on a clinical trial for Tacrine in the treatment of Alzheimer's disease.

Alzheimer Disease↗
PubMed1995

Perinatal brain injury in premature infants born to mothers using alcohol in pregnancy. Neonatal Brain Hemorrhage Study Team.

OBJECTIVE: Alcohol has been shown to have teratogenic effects on the fetal central nervous system. However, little research has been done to assess the impact of prenatal alcohol exposure on premature infants, a group particularly vulnerable to perinatal brain injury. METHODS: We examined the relation between maternal alcohol use and the most common forms of brain injury in premature infants--germinal matrix/intraventricular hemorrhage (GM/IVH) and white-matter damage--in a large population-based cohort of infants weighing 2000 g or less. The analyses included 349 infants younger than 31 weeks' gestation who received at least one cranial ultrasound scan and whose mothers were queried about prenatal alcohol use in a postpartum interview. RESULTS: Infants of mothers who reported "moderate" alcohol use (fewer than seven drinks per week and fewer than three drinks per occasion) to "high" use (seven or more drinks per week and/or three or more drinks per occasion) before recognized pregnancy, and moderate alcohol use during pregnancy, were not at increased risk for brain injury. However, after controlling for potentially confounding factors, infants of women reporting high alcohol use during pregnancy were at increased risk of developing isolated brain hemorrhage (odds ratio [OR] = 5.5, 95% confidence interval [CI] = 1.2, 24.7), any brain hemorrhage (OR = 6.7, 95% CI = 1.8, 26.4), and white-matter damage (OR = 9.5, 95% CI = 1.9, 46.4). CONCLUSION: Premature infants of women who report consuming seven or more drinks per week and/or three or more drinks per occasion during pregnancy have substantially elevated risks of both of the most common forms of brain injury in premature infants.

Alcohol Drinking↗