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Biomedical subjects

J K Roberts

Publications and source records attributed to J K Roberts.

At least 19 recordsLinked to original sources
PubMed2001

Development and commercial use of Bollgard cotton in the USA--early promises versus today's reality.

Bollgard cotton is the trademark given to a number of varieties of cotton bio-engineered to produce an insecticidal protein from Bacillus thuringiensis (Bt). When produced by the modified cotton plants, this protein controls certain lepidopterous cotton insect pests. Commercially available since 1996, these cotton varieties are purchased under a license agreement in which the growers pay a fee and agree to abide by the terms, which include a 1-year license to use the technology and agreement to participate in an insect resistance management program. Today, Bollgard cotton is grown on more than one-third of all cotton acreage in the USA. This product has reduced cotton production costs and insecticide use by providing an effective alternative to chemical insecticides for the control of tobacco budworm, Heliothis virescens; cotton bollworm, Helicoverpa zea; and pink bollworm, Pectinophora gossypiella. The specificity and safety profile of the Bt protein produced in planta in cotton was maintained. It has retained its selectivity for lepidopterous insects and lacks the characteristics found in potential allergenic proteins. Fiber quality, the agronomic characteristics of the plant and seed composition remain unchanged. New cotton technology is being developed to provide improved insect control and a wider spectrum of activity. These future products could further reduce insecticide use in the production of cotton, while maintaining the high level of safety and reliability that has been demonstrated by five seasons of Bollgard cotton use.

Agriculture↗
PubMed2001

The effect of changes in the health care environment on rehabilitation research: a survey of rehabilitation physicians.

OBJECTIVE: To assess what effect organizational, funding, and system changes in the health care environment may have on rehabilitation research. DESIGN: National survey. SETTING: Academic and clinical research programs. PARTICIPANTS: A total of 138 physicians participated in the survey. INTERVENTION: Mailed instrument requesting information on demographics, research activities, and indicators of change. MAIN OUTCOME MEASURES: Percentage of respondents reporting specific perceptions on (1) how academic and research programs are affected by organizational changes, (2) availability of research funds, and (3) the overall impact that health care changes have on research; between-group comparisons on survey responses. RESULTS: Usable responses were obtained from 138 physicians (response rate, 42.5%). Responding physicians reported workplace changes that included organizational restructuring (32.6%), affiliation with managed care plans (24%), and staff decreases (45.9%). Over half (54.8%) indicated that facility changes had detracted from their abilities to conduct research. A third (34.8%) reported declines in numbers of inpatient beds, and 89.6% reported decreased length of stay (LOS). Decreased LOS was cited as detracting from ongoing research by 36.6% and as discouraging new research by 33.3% of respondents. Although not reflected in measures of scholarly productivity, 53.6% reported having less time to devote to scholarship and 48.5% reported decreased professional activities. Over two thirds (67.4%) of responding physicians indicated that health care system changes had a negative impact on current research, and 54.5% indicated that such changes made it less likely that they would pursue new research. CONCLUSION: Changes in the health care system have had a dampening effect on rehabilitation physicians' research pursuits.

Attitude of Health Personnel↗
PubMed2001

Contribution of glutamate dehydrogenase to mitochondrial glutamate metabolism studied by (13)C and (31)P nuclear magnetic resonance.

The relative contribution of glutamate dehydrogenase (GDH) and the aminotransferase activity to mitochondrial glutamate metabolism was investigated in dilute suspensions of purified mitochondria from potato (Solanum tuberosum) tubers. Measurements of glutamate-dependent oxygen consumption by mitochondria in different metabolic states were complemented by novel in situ NMR assays of specific enzymes that metabolize glutamate. First, a new assay for aminotransferase activity, based on the exchange of deuterium between deuterated water and glutamate, provided a method for establishing the effectiveness of the aminotransferase inhibitor amino-oxyacetate in situ, and thus allowed the contribution of the aminotransferase activity to glutamate oxidation to be assessed unambiguously. Secondly, the activity of GDH in the mitochondria was monitored in a coupled assay in which glutamine synthetase was used to trap the ammonium released by the oxidative deamination of glutamate. Thirdly, the reversibility of the GDH reaction was investigated by monitoring the isotopic exchange between glutamate and [(15)N]ammonium. These novel approaches show that the oxidative deamination of glutamate can make a significant contribution to mitochondrial glutamate metabolism and that GDH can support the aminotransferases in funneling carbon from glutamate into the TCA cycle.

Aminooxyacetic Acid↗
PubMed2001

The effect of changes in the U.S. health care system on rehabilitation research: the results of a survey of rehabilitation health professionals.

To obtain empirical data on the impact of changes in the health care system on rehabilitation research, physicians, psychologists, nurses, physical therapists, and occupational therapists involved in such research were surveyed to determine: 1) how the changes had affected their research productivity; 2) whether their scholarly activities (e.g., publications) had been affected; and 3) whether working in an academic vs non-academic institution made a difference. There were 438 usable responses (38% response rate) to the survey, which was sent to members of national organizations. Although the results somewhat supported suggestions that changes in the system had had a dampening effect on research, they were ambiguous, failing to clearly demonstrate a negative impact of managed care. More rigorous study is needed to enable firm conclusions and the formulation of actions to address factors that may influence rehabilitation research.

Academic Medical Centers↗
PubMed2000

NMR adventures in the metabolic labyrinth within plants.

The era of metabolic engineering has begun, but there is only limited knowledge about metabolic fluxes and how they are regulated in plants. Particular challenges are the non-linearities between enzyme abundances, metabolite concentrations and metabolic fluxes, and the existence of metabolic networks that provide multiple routes between many important metabolites. NMR offers the means to distinguish and quantitate the fluxes along different routes to key metabolites. NMR can therefore help us understand and resolve the apparent paradox of, on the one hand, great metabolic flexibility evident in the natural responses of plants and, on the other hand, the unpredictable changes in metabolism reported in genetically engineered plants.

Carbohydrate Metabolism↗
PubMed2000

Patterns of protein synthesis and tolerance of anoxia in root tips of maize seedlings acclimated to a low-oxygen environment, and identification of proteins by mass spectrometry.

Tolerance of anoxia in maize root tips is greatly improved when seedlings are pretreated with 2 to 4 h of hypoxia. We describe the patterns of protein synthesis during hypoxic acclimation and anoxia. We quantified the incorporation of [(35)S]methionine into total protein and 262 individual proteins under different oxygen tensions. Proteins synthesized most rapidly under normoxic conditions continued to account for most of the proteins synthesized during hypoxic acclimation, while the production of a very few proteins was selectively enhanced. When acclimated root tips were placed under anoxia, protein synthesis was depressed and no "new" proteins were detected. We present evidence that protein synthesis during acclimation, but not during subsequent anoxia, is crucial for acclimation. The complex and quantitative changes in protein synthesis during acclimation necessitate identification of large numbers of individual proteins. We show that mass spectrometry can be effectively used to identify plant proteins arrayed by two-dimensional gel electrophoresis. Of the 48 protein spots analyzed, 46 were identified by matching to the protein database. We describe the expression of proteins involved in a wide range of cellular functions, including previously reported anaerobic proteins, and discuss their possible roles in adaptation of plants to low-oxygen stress.

Adaptation, Physiological↗
PubMed2000

Subcortical infarction resulting in acquired stuttering.

Stuttering is an uncommon presentation of acute stroke. Reported cases have often been associated with left sided cortical lesions, aphasia, and difficulties with other non-linguistic tests of rhythmic motor control. Three patients with subcortical lesions resulting in stuttering are discussed. In one patient the ability to perform time estimations with a computerised repetitive time estimation task was characterised. One patient had a pontine infarct with clinical evidence of cerebellar dysfunction. A second patient had a left basal ganglionic infarct and a disruption of timing estimation. A third patient had a left subcortical infarct and a mild aphasia. These findings expand the reported distribution of infarction that can result in acquired stuttering. Subcortical mechanisms of speech control and timing may contribute to the pathophysiology of acquired stuttering.

Brain↗
PubMed1999

Identification of a nucleic acid binding domain in eukaryotic initiation factor eIFiso4G from wheat.

Higher plants have two complexes that bind the m7G-cap structure of mRNA and mediate interactions between mRNA and ribosomal subunits, designated eIF4F and eIFiso4F. Both complexes contain a small subunit that binds the 5'-cap structure of mRNA, and a large subunit, eIF4G or eIFiso4G, that binds other translation factors and RNA. Sequence-specific proteases were used to cleave native cap-binding complexes into structural domains, which were purified by affinity chromatography. We show here that eIFiso4G contains a central protease-resistant domain that binds specifically to nucleic acids. This domain spans Gln170 to Glu443 and includes four of the six homology blocks shared by eIFiso4G and eIF4G. A slightly shorter overlapping sequence, from Gly202 to Lys445, had no nucleic acid binding activity, indicating that the N-terminal end of the nucleic acid binding site lies within Gln170 to Arg201. The binding of the central domain and native eIFiso4F to RNA homopolymers and double- and single-stranded DNAs was studied. Both molecules had highest affinity for poly(G) and recognized single- and double-stranded sequences.

Amino Acid Sequence↗
PubMed1999

Does salivary gland scintigraphy predict response to pilocarpine in patients with post-radiotherapy xerostomia?

This study was undertaken to determine whether standard salivary gland scintigraphy may be used for the objective assessment of salivary gland sialogogues, in particular oral pilocarpine, in the treatment of post-radiotherapy xerostomia. Nine patients, with xerostomia following radiotherapy to the head and neck region underwent salivary gland scintigraphy with technetium-99m pertechnetate (40 MBq) both before and following 1 month of oral pilocarpine (5 mg tds). For each scan, the percentage uptake in the first 14 min, the peak uptake, time to peak uptake and the percentage of activity excreted following lemon juice stimulation were calculated. The results were correlated with the subjective response as assessed by questionnaire and visual analogue scale. We found no correlation between subjective response and any of the four scan parameters analysed. We could not identify any parameter that predicted those patients who would respond to pilocarpine. In addition, only one parameter, the percentage of activity excreted following stimulation, correlated with previous dose of radiotherapy to the gland. In conclusion, in this study salivary gland scintigraphy did not appear to correlate with or predict response to oral pilocarpine. However, future studies might consider performing salivary gland scintigraphy prior to radiotherapy as well as at differing time points following the commencement of pilocarpine.

Administration, Oral↗
PubMed1998

Spatio-temporal pattern for expression of galectin-3 in the murine utero-placental complex: evidence for differential regulation.

In mice, immunoreactive galectin-3 protein has previously been localized in uterine epithelial cells adjacent to implanting blastocysts as well as in the decidualized endometrium of implantation sites, uterine natural killer cells, and several types of placental trophoblast cells. Because galectin-3 is a soluble extracellular molecule, protein localization by immunohistochemical methods does not demonstrate its cellular origin. Therefore, the present study was undertaken to determine precisely which cell types in the utero-placental complex express galectin-3 mRNA. In situ hybridization results demonstrated that galectin-3 mRNA was expressed throughout the utero-placental complex in all cell types previously shown to contain immunoreactive protein, including uterine epithelium, decidualized endometrium, uterine natural killer cells, and placental trophoblasts. These results indicate that galectin-3 protein is not synthesized in a restricted cell type and translocated through the extracellular spaces to other tissue compartments. Furthermore, Northern blot analysis of total RNA prepared from separated fetal and maternal components of utero-placental complexes demonstrated different patterns of expression for galectin-3 mRNA in the uterus and placenta. Relative levels of galectin-3 mRNA peak at midgestation in the implantation site and during the second half of gestation remain elevated in the placenta but decline in the uterus. Separate mechanisms for regulating expression of galectin-3 on opposite sides of the feto-maternal interface are indicated.

Animals↗
PubMed1998

Homocysteine as a risk factor for ischemic stroke: an epidemiological story in evolution.

Homocysteine is a metabolite of methionine that may be remethylated by enzymes requiring folate and cobalamin (vitamin B12) to again form methionine or catabolized by the pyridoxine (vitamin B6) dependent enzyme, cystathionine beta synthase (CBS) to form cysteine (fig. 1) [1]. Homocysteine exists as a combination of various free and protein bound forms, but the total amount is what is usually measured and may be reported as homocyst(e)ine [2]. The biological plausibility that elevated homocysteine might lead to vascular disease noted in 1969 by McCully [3]. He reported that a child with abnormal cobalamin metabolism and hyperhomocysteinemia had arterial lesions similar to those seen in children with severe hyperhomocysteinemia from CBS deficiency. These findings led to the idea that moderate elevations in homocysteine, even those still within the so-called normal range, might also lead to vascular pathology through a variety of mechanisms including atherosclerosis and thrombosis [4].

Adult↗
PubMed1997

Valvular strands and cerebral ischemia. Effect of demographics and strand characteristics.

BACKGROUND AND PURPOSE: Valvular strands, thin filamentous material attached to the mitral or aortic valve, are seen during transesophageal echocardiography and have been associated with stroke. Little is known about this association in different age, sex, and race-ethnic subgroups and the effect of various strand characteristics on this association. METHODS: From patients referred for transesophageal echocardiography, 73 patients with recent ischemic stroke (68) or transient ischemic attack (5) were age matched to 73 stroke- and transient ischemic attack-free control subjects. The association between valvular strands and cerebral ischemia was evaluated for the overall group and demographic subgroups. The effect of strand location, length, number, and valve thickness was also determined. RESULTS: An association between cerebral ischemia and valvular strands was observed (odds ratio [OR] = 4.4; 95% confidence interval [CI] = 2.0 to 9.6). The association was found for both men and women and among all three race-ethnic groups. The OR was greater in those who were younger (12.5 [95% CI = 2.4 to 64.5] for age < 60, 4.8 [95% CI = 1.3 to 18.2] for age 60 to 69, and 1.8 [95% CI = 0.5 to 6.4] for age > or = 70 years). Strands on both the mitral (OR = 3.5; 95% CI = 1.5 to 7.9) and aortic (OR = 3.7; 95% CI = 1.1 to 11.9) valve were associated with cerebral ischemia, whereas the number and length of strands were not. The effect of strands was independent of mitral or aortic valve thickness. CONCLUSIONS: Valvular strands, whether mitral or aortic, are associated with ischemic stroke, especially among younger persons.

Aged↗
PubMed1997

Race-ethnicity and determinants of carotid atherosclerosis in a multiethnic population. The Northern Manhattan Stroke Study.

BACKGROUND AND PURPOSE: Risk factors for carotid atherosclerosis have been studied in white populations but infrequently in multiethnic cohorts. The aim of this study was to determine the importance of race-ethnicity and other factors associated with carotid atherosclerosis in a mixed population of Hispanics, blacks, and whites. METHODS: As part of the Northern Manhattan Stroke Study, 526 stroke-free community residents (aged > or = 40 years; 41% men, 59% women; 46% Hispanic, 31% black, 23% white) were recruited through random-digit dialing and had vascular risk factor evaluations. Maximum internal carotid artery plaque thickness (MICPT) was measured with B-mode ultrasound. The frequency distribution of MICPT was examined in the three race-ethnic groups, and multivariate regression was performed to identify factors that were independently associated with MICPT. RESULTS: Mean MICPT in the entire sample was 1.5 +/- 1.4 mm, increased directly with age, and was greater in whites and blacks than Hispanics. Other independent determinants of MICPT included smoking, glucose, LDL cholesterol, and hypertension. After we controlled for these covariates, Hispanic (versus non-Hispanic) race-ethnicity was still an independent determinant of less carotid plaque. There was a significant interaction between race-ethnicity and LDL cholesterol, with a greater effect of increasing LDL cholesterol among Hispanics. CONCLUSIONS: Atherosclerotic risk factors were predictive of MICPT in this mixed-ethnic cohort. Hispanics had significantly less carotid plaque after adjustment for other known risk factors, but they also had a greater impact of increasing LDL cholesterol.

Adult↗