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S Peterson

Publications and source records attributed to S Peterson.

At least 37 records · Page 2Linked to original sources
PubMed1999

The EPR signals from the S0 and S2 states of the Mn cluster in photosystem II relax differently.

The oxygen evolving complex (OEC) of photosystem II (PSII) gives rise to manganese-derived electron paramagnetic resonance (EPR) signals in the S0 and S2 oxidation states. These signals exhibit different microwave power saturation behavior between 4 and 10 K. Below 8 K, the S0 state EPR signal is a faster relaxer than the S2 multiline signal, but above 8 K, the S0 signal is the slower relaxer of the two. The different temperature dependencies of the relaxation of the S0 and S2 ground-state Mn signals are due to differences in the spin-lattice relaxation process. The dominating spin-lattice relaxation mechanism is concluded to be a Raman mechanism in the S0 state, with a T(4.1) temperature dependence of the relaxation rate. It is proposed that the relaxation of the S2 state arises from a Raman mechanism as well, with a T(6.8) temperature dependence of the relaxation rate, although the data also fit an Orbach process. If both signals relax through a Raman mechanism, the different exponents are proposed to reflect structural differences in the proteins surrounding the Mn cluster between the S0 and S2 states. The saturation of SII(slow) from the Y(D)(ox) radical on the D2 protein was also studied, and found to vary between the S0 and the S2 states of the enzyme in a manner similar to the EPR signals from the OEC. Furthermore, we found that the S2 multiline signal in the second turnover of the enzyme is significantly more difficult to saturate than in the first turnover. This suggests differences in the OEC between the first and second cycles of the enzyme. The increased relaxation rate may be caused by the appearance of a relaxation enhancer, or it may be due to subtle structural changes as the OEC is brought into an active state.

Electron Spin Resonance Spectroscopy↗
PubMed1999

Methanol modification of the electron paramagnetic resonance signals from the S(0) and S(2) states of the water-oxidizing complex of photosystem II

The Mn-derived electron paramagnetic resonance (EPR) multiline signal from the S(0) state of the water-oxidizing complex is observable only in the presence methanol. In the present study, we have characterized the effect of methanol on the EPR signals from the S(0) and S(2) states as well as on the EPR Signal II(slow) originating from the Tyrosine(D)(ox) radical. The amplitudes of the S(0) and S(2) multiline signals increase with the methanol concentration in a similar way, whereas the S(2) g=4.1 excited state signal amplitude shows a concomitant decrease. The methanol concentration at which half of the spectral change has occurred is approximately 0.2% and the effect is saturating around 5%. Methanol has an effect on the microwave power saturation of the S(2) multiline signal, as well. The microwave power at half saturation (P(1/2)) is 85 mW in the presence of methanol, whereas the signal relaxes much slower (P(1/2) approximately 27 mW) without. The relaxation of Signal II(slow) in the presence of methanol has also been investigated. The P(1/2) value of Signal II(slow) oscillates with the S cycle in a similar way as without methanol, but the P(1/2) values are consistently lower in the methanol-containing samples. From the results, we conclude that methanol modifies the magnetic properties of the S(0) and S(2) states in a similar way. The possible site and nature of methanol binding is discussed.

Journal Article↗
PubMed1999

Health care costs associated with chronic hepatitis B.

The long-term health care costs of patients with chronic hepatitis B (CHB) were compared with those of patients without CHB. Patients with laboratory markers for CHB were identified from an HMO database and matched with up to four control patients (either not tested for hepatitis B infection or with negative test results). Cost data were collected retrospectively for both groups of patients for the period up to 30 days before identification of the first marker for hepatitis B (prediagnosis), 30 days before identification of the first marker through 180 days after the identification (peridiagnosis), and 181 days after identification through the end of the six-year study period. Costs were categorized as emergency room, inpatient, short-stay inpatient, laboratory, radiology, office visit, pharmacy, outside claim, or other and were analyzed as ratios of the costs of each patient with CHB to the median of the corresponding control patients. Eighty-eight patients were identified as having CHB; there were 342 control patients. In the seven months surrounding the appearance of their first diagnostic marker, the patients with CHB had costs 3.3 times those of the corresponding control patients and, after the first seven months, 2.9 times those of the control patients per month. Peridiagnosis costs in the categories of laboratory, radiology, office visits, and pharmacy were significantly higher for patients with CHB than for control patients. Except for emergency room costs, postdiagnosis costs per month of the patients with CHB were significantly higher than those of the corresponding control patients. Examination of an HMO database showed that, compared with patients without CHB, patients with CHB had significantly higher health care costs around and after the CHB diagnosis.

Adult↗
PubMed1999

Lipids of the pawpaw fruit: Asimina triloba.

The fatty acid composition and structure of pawpaw fruit (Asimina triloba) triglycerides were examined and found to contain fatty acids ranging from C6 to C20. Octanoate represented 20% of the fatty acids while other medium-chain fatty acids were present in low amounts. Analysis of the intact triglycerides by high-temperature gas-liquid chromatography gave an unusual three-cycle carbon number distribution. Analysis of triglyceride fractions separated according to degree of unsaturation suggested that one octanoate was paired with diglyceride species containing long-chain fatty acids. Determination of the double-bond positions of monoene fatty acids revealed cis delta9 and cis delta11 hexadecenoate and cis delta9, cis delta11, and cis delta13 octadecenoate isomers were present in significant quantities. Octanoate and positional monoene fatty acid isomers were found only in the fruit lipids and not in the seed lipids. Phenacyl esters of fatty acids were found to be useful derivatives for structure determination using multiple types of analyses.

Chromatography↗
PubMed1999

Impact of adopting lower-fat food choices on energy and nutrient intakes of American adults.

OBJECTIVE: To evaluate the energy and nutrient intake of free-living men and women who choose foods consistent with different fat-reduction strategies. DESIGN: For each year of the Continuing Survey of Food Intake by Individuals from 1989 through 1991, food codes were used to sort respondents by type of milk; type of meats; and type of cheese, yogurt, salad dressing, cake, and pudding (i.e., full-fat or fat-modified products) consumed. SUBJECTS: A nationally representative sample of 3,313 men and 3,763 women who completed 3-day intake records and consumed either a reduced-fat or full-fat food from at least 1 of the 3 fat-reduction strategy categories. STATISTICAL ANALYSIS PERFORMED: Analysis of variance with the Scheffé test was used to analyze differences in energy and nutrient intake between exclusive users, mixed users, and nonusers of each strategy or combined strategies. RESULTS: Regardless of fat-reduction strategy, men and women who used them reported significantly lower intakes of total fat (up to 18 g lower), saturated fat (up to 12 g lower), cholesterol (up to 75 mg lower) and energy compared with nonusers. Exclusive users of single strategies met or approached recommendations of the National Cholesterol Education Program for total fat, saturated fat, and cholesterol intake; micronutrient intake varied depending on the strategy used. Skim milk users had the most favorable micronutrient intake, whereas lean meat users reported inadequate intake of zinc (men 63% and women 59% of the Recommended Dietary Allowances [RDAs]) and female users of fat-modified products reported inadequate intakes of vitamin E (64% of RDA) and zinc (65% of RDA). Multiple-strategy users achieved National Cholesterol Education Program goals and reported adequate micronutrient intakes and significantly lower energy intake. Mixed users of fat-modified products compared with nonusers of any fat-modified products had adequate micronutrient intake and lower intakes of total fat (32% vs 36% of energy for men and 32% vs 35% of energy for women) and saturated fat (11% vs 13% of energy for men and 11% vs 12% of energy for women). In addition, nonusers of any fat-modified strategy had the highest cholesterol and energy intake and the lowest intake of many micronutrients. APPLICATIONS: A variety of fat-reduction strategies can be implemented to reduce energy, total fat, saturated fat, and cholesterol intake. Some of the strategies were associated with an inadequate micronutrient intake, so additional dietary guidance is needed to ensure that all nutrient requirements are met. Furthermore, people who do not use any fat-reduction strategy or those who exclusively use lean meats or fat-modified products would benefit from understanding how to balance their food choices.

Adult↗
PubMed1999

Mobilization of blood-derived stem and progenitor cells in normal subjects by granulocyte-macrophage- and granulocyte-colony-stimulating factors.

BACKGROUND: It was previously reported that the combination of granulocyte-macrophage-colony-stimulating factor (GM-CSF) and granulocyte-CSF (G-CSF) for 4 days mobilized more primitive CD34+ subsets than did either G-CSF or GM-CSF alone. STUDY DESIGN AND METHODS: The studies determine the optimal number of days of growth factor dosing for mobilization and collection of peripheral blood progenitor cells, by increasing the days of administration of GM-CSF and/or G-CSF or employing the sequential administration of GM-CSF followed by G-CSF. Sixty normal subjects were given injections of G-CSF or GM-CSF alone; GM-CSF and G-CSF concurrently for 4, 5, or 6 days; or a sequential regimen of GM-CSF for 3 or 4 days followed by G-CSF for 2 or 3 days. A 10-L apheresis was performed 24 hours after the last dose. RESULTS: The three most efficacious mobilization regimens consisted of sequential GM-CSF for 3 days followed by G-CSF for either 2 or 3 days and G-CSF alone for 5 days. Each of these regimens resulted in the collection of significantly greater numbers of CD34+ cells by apheresis than any of the 4-day dosing regimens with G-CSF and/or GM-CSF (sequential GM-CSF/G-CSF: 3 days/2 days = 3.58 +/- 0.53 x 106 CD34+ cells/kg; GM-CSF/G-CSF: 3 days/3 days = 4.45 +/- 1.08 x 10(6) CD34+ cells/kg; G-CSF: 5 days = 3.58 +/- 0.97 x 10(6) CD34+ cells/kg; all p<0.05 vs. G-CSF and/or GM-CSF for 4 days). Clonogenic assays generally paralleled the level of CD34+ cells. Regimens containing GM-CSF resulted in a higher percentage of the cells from primitive CD34+/CD38-/HLA-DR+ subset than G-CSF alone. CONCLUSION: Compared with 4-day dosing regimens with G-CSF and/or GM-CSF, mobilization of CD34+ cells in normal subjects using sequential GM-CSF for 3 days followed by G-CSF for 2 or 3 days or using G-CSF alone for 5 days increased the number CD34+ cells that can be collected by a single 10-L apheresis 24 hours after the last dose of cytokine.

Antigens, CD34↗
PubMed1999

Coverage and cost of iodized oil capsule distribution in Tanzania.

Distribution of oral iodized oil capsules (IOC) is an important intervention in areas with iodine deficiency disorders (IDD) and low coverage of iodized salt. The mean reported coverage of 57 IOC distribution campaigns from 1986-1994 of people aged 1-45 years in 27 districts of Tanzania was 64% (range 20-96%). This declined over subsequent distribution rounds. However, due to delayed repeat distribution, only 43% of person-time was covered, based on the programme objective of giving two IOC (total 400 mg iodine) at 2-year intervals. Three different capsule distribution strategies used in 20 distribution rounds in 1992-1993 were analyzed in depth. Withdrawal of financial support for district distribution expenses under the 'district team' strategy, and the subsequent change to integrated 'primary health care' distribution, increased delays and capsule wastage. The third, more vertical strategy, 'national and district teams', accomplished rapid distribution of IOC about to expire and subsequently a return to the initial 'district team' allowance strategy was made. Annual cost of 'district team' distribution was 26 cents per person (400 mg iodine/2 years). Cost analysis revealed that the IOC itself accounts for more than 90% of total costs at the levels of coverage achieved. IOC will be important in the elimination of IDD in target areas of severe iodine deficiency and insufficient use of iodized salt, provided that high coverage can be achieved. Campaign distribution of medication with high item cost and long distribution intervals may be more cost-effectively performed if separated from regular PHC services at their present resource level. However, motivating health workers and community leaders to do adequate social mobilization remains crucial even if logistics are vertically organized. Insufficient support of distribution expenses and health education may lead to overall wastage of resources.

Adolescent↗
PubMed1999

The population's use of pharmaceuticals.

OBJECTIVES: In this study, population-based analysis is used to study the extent to which characteristics such as age, sex, socioeconomic status, and region of residence are associated with different patterns of pharmaceutical use. It also includes an examination of whether pharmaceutical use is responsive to differential health needs across the population. RESEARCH DESIGN: Indicators of access, intensity of use, and total expenditures are used to describe Manitobans' use of pharmaceutical agents, consistent with the POPULIS framework. MEASURES: Several rate-based measures have been developed for this purpose: the number of residents who are pharmaceutical users; the number of prescriptions dispensed; the number of different drugs dispensed; the total number of defined daily doses (DDDs) dispensed; and expenditures for pharmaceuticals. The DDD measurement provides a cumulative assessment of total drug use (i.e., across multiple drug categories) and is a useful indicator of a population's total drug exposure. RESULTS: Patterns of use of pharmaceuticals follow patterns similar to those patterns in earlier POPULIS studies on health care access, intensity, and expenditures. In areas where health is generally poorer, a greater number of prescriptions are dispensed. The highest use of pharmaceuticals also was found in the lower-income quintiles and among those at greatest socioeconomic risk, traditionally those with the poorest health status. CONCLUSIONS: This kind of population-based pharmaceutical information can help monitor the effectiveness of policy initiatives, as well as serve to better manage pharmaceutical use within the health care system.

Age Factors↗
PubMed1999

Assessing the extent to which hospitals are used for acute care purposes.

OBJECTIVES: The degree to which Manitobans were appropriately hospitalized for medical conditions was assessed using a retrospective chart review of a sample of patients in 26 hospitals. RESEARCH DESIGN: A standardized set of object-based, nondiagnostic criteria (Inter-Qual) was used by trained abstractors to assess the patient at admission and for each day of stay. RESULTS: A high percentage of admissions and days of care were inappropriate. Overall, 49.5% of medical patients were acute at the time of admission, 1.6% required no health care services, and 48.9% could have received care through alternate methods or facilities. Only 33.4% of the subsequent days of stay were appropriate. For patients assessed as acute at the time of admission, by the 8th day of stay, only 47% were still acute and by day 30, only 27% were acute. Patients aged 75 years or older were just as likely to be acute at the time of admission as were younger patients; however, they accounted for 54% of the days in the study, and fewer than 30% of these days were acute. Our data suggest that despite their high use of hospitals, disadvantaged groups (the poor, aboriginal Manitobans), have the same levels of appropriateness as others. CONCLUSIONS: We conclude that alternatives to hospital care must first be established and made known and available before a shift in health care resources can occur.

Acute Disease↗
PubMed1999

Waiting times for surgical procedures.

OBJECTIVES: Polls show that nearly two thirds of Canadians believe that waiting times prior to surgery have increased in recent years. A study was undertaken in Manitoba to determine whether public perceptions about long and increasing waits were valid. RESEARCH DESIGN: Using administrative data, waiting times for 10 types of surgery-ranging from coronary artery bypass surgery and mastectomy to cataract surgery and hernia repairs-were studied over a 5-year period. RESULTS: Using each patient's preoperative visit to the surgeon as the beginning of the waiting time, median waiting times for most of the procedures studied were found to have, in fact, remained stable or fallen slightly over the period studied. CONCLUSIONS: Further, an examination of waiting times for cataract surgery demonstrated that allowing surgeons to practice in both public and private arenas seems to be counterproductive to providing good public service.

Adult↗
PubMed1999

Using population-based data to enhance clinical practice guideline development.

OBJECTIVES: Working with the College of Physicians and Surgeons of Manitoba, and using tonsillectomies as a basis of inquiry, MCHPE examined surgical rates and patterns of practice. This project had three major aims: to review whether current patterns of delivery provide optimal care; to enhance the development of clinical guidelines; and to inform and influence physician practice. RESEARCH DESIGN: Both a population-based method of inquiry (which permits comparisons across population groups) and a provider-based approach (which offers insights into differences in the nature of care offered by different types of hospitals and physicians) were used. MEASURES: Synergies between these two approaches offered useful insight into aspects of quality and efficiency of care. RESULTS: Consistent with other jurisdictions, there was a high degree of variability across regions. However, there were also a number of surprising findings, including high rates of surgery in females, in older children, and among residents of rural areas. Data analysis raised a number of quality-of-care issues related to small caseload volumes, performance of procedures in very young children, and patterns of postoperative care in rural hospitals. The analyses provided impetus for addressing these issues in the guideline and suggested that the target audience for intervention should be rural physicians rather than urban specialists. CONCLUSIONS: This project demonstrated that data analysis can provide a powerful adjunct to the development and implementation of clinical practice guidelines.

Adolescent↗
PubMed1999

Neural evidence linking visual object enumeration and attention.

Visual object enumeration is rapid and accurate for four or fewer items but slow and error-prone for over four items. This dichotomy has recently been linked to visual attentional phenomena by findings suggesting that 'subitizing' of small sets of objects is preattentive whereas 'counting' of over four items demands spatial shifts of attention. We evaluated this link at a neural level, using H2 15-O positron emission tomography to measure changes in regional cerebral blood flow while subjects enumerated the number of target vertical bars that 'popped out' of a 16-bar visual display consisting of both horizontal and vertical bars. Relative to a condition with a single target, subitizing (one to four targets) activated foci in the occipital extrastriate cortex, consistent with involvement of early, preattentive visual processes. Relative to subitizing, counting (five to eight targets) activated a widespread network of brain regions, including multiple foci implicated in shifting visual attention-large regions of the superior parietal cortex bilaterally and a focus in the right inferior frontal cortex. These results offer the first direct neural support for mapping the subitizing-counting dichotomy onto separable processes mediating preattentive vision and shifts of visual attention.

Adolescent↗
PubMed1998

Regulation of NGF responsiveness in human neuroblastoma.

Functional nerve growth factor (NGF) responsiveness was investigated in human neuroblastoma (NB) cell lines in vitro and retinoic acid (RA) was found to transcriptionally enhance expression of the trkA, but not the trkB gene in GOTO cells, while the reverse was found in HTLA230 NB cells. Ciliary neurotrophic factor (CNTF) specifically induced trkA gene transcription in both cell lines. Transcriptional activation of the trkA gene increased total trkA protein and surface bound receptor, which was tyrosine phosphorylated upon NGF stimulation inducing immediate early response gene transcription (i.e. c-fos, Egr-1). Newly synthesized trkA protein had a molecular weight of 110 kDa and was post-translationally modified. Rapid down regulation of the receptor protein occurred upon NGF stimulation, despite the presence of high levels of trkA mRNA, due to an increased rate of receptor degradation. Transient DNA synthesis and cell proliferation upon NGF treatment occurred in GOTO cells with elevated trkA expression. In contrast, NGF induced neuronal differentiation in HTLA230 cells expressing the endogenous trkA receptor gene, despite the lack of p75 expression. Hence, transcriptional activation of trkA gene expression can be achieved by different signal pathways in human NB cells, but NGF can act either as mitogen or inducer of cell differentiation, depending on the tumor from which cells are derived.

Ciliary Neurotrophic Factor↗
PubMed1998

The S0 state EPR signal from the Mn cluster in photosystem II arises from an isolated S = 1/2 ground state.

During oxygen evolution, the Mn cluster in Photosystem II cycles through five oxidation states, S0-S4. S0 and S2 are paramagnetic, and can be monitored by electron paramagnetic resonance (EPR). Recently a new EPR signal from the S0 state was discovered [Ahrling et al. (1997) Biochemistry 36, 13148-13152, Messinger et al. (1997) J. Am. Chem. Soc. 119, 11349-11350]. Here, we present a well-resolved S0 spectrum, taken at high power and low temperature. The spectrum is wider and more resolved than previously thought, with structure over more than 2500 G, and appears to have at least 20 reproducible peaks on each side of g = 2. We also present the temperature dependence of the unsaturated S0 signal amplitude. A linear relationship was found between signal intensity and reciprocal temperature (1/T) in the region 5-25 K, clearly extrapolating to 0. This obeys the Curie law, indicating that the S0 state is a ground S = 1/2 state with no thermally accessible excited state. The data are consistent with a minimum energy gap of 30 cm-1 between the ground and first excited states.

Dimerization↗
PubMed1998

Relationships between brain morphology and behavioral measures of hemispheric asymmetry and interhemispheric interaction.

Thirty adult males identified consonant-vowel-consonant nonword trigrams projected briefly to the left visual field (right hemisphere), the right visual field (left hemisphere) or to both visual fields (and hemispheres) simultaneously. Magnetic resonance images of the brains of these same individuals provided measurements of the length of the Sylvian fissure and surface area of the planum temporale within each hemisphere as well as measurements of the midsagittal area of the corpus callosum. Both behavioral and morphological asymmetries were consistent with those found in previous studies. In addition, there were several relationships between brain morphology and trigram naming. For example, as the length of the right-hemisphere Sylvian fissure increased to become more like the typical length of the left-hemisphere Sylvian fissure, there were fewer errors of trigram identification and attention was distributed more quickly or evenly across the three letters contained in the display. In addition, as the midsagittal area of the corpus callosum increased, the percentage of errors increased on left visual field trials, but not on right visual field or bilateral trials, suggesting that an increase in corpus callosum size may be indicative of greater functional isolation of the two hemispheres.

Adult↗
PubMed1998

Outbreak of sterile peritonitis among continuous cycling peritoneal dialysis patients.

BACKGROUND: Approximately 30,000 patients receive peritoneal dialysis in the United States. In August 1996, several dialysis centers from different states reported sterile peritonitis among CCPD patients using sterile peritoneal dialysis solution (PDS) from a single manufacturer. The manufacturer recalled 53 lots of PDS that had passed established industry guidelines and Food and Drug Administration (FDA) approved quality control tests [including endotoxin levels <0.5 endotoxin units (EU)/ml], but had pre-sterilization bacterial colony counts >1 cfu/ml. METHODS: At one outpatient dialysis center, Hospital of the University of Pennsylvania (HUP), we conducted a retrospective cohort study of all CCPD patients treated during July 15 to August 30, 1996. A case-patient was defined as any HUP patient with culture-negative peritoneal fluid with a white blood cell count >100/mm3, cloudy peritoneal fluid, and/or abdominal pain. PDS and tubing were cultured for bacteria and assayed for endotoxin. RESULTS: Overall, 14 of 28 patients had sterile peritonitis. The only risk factor identified was exposure to > or =1 lot of recalled PDS (14 of 22 vs. 0/6, P = 0.02); the more recalled lots received, the higher the attack rate (P = 0.0001). Five of 47 PDS bags had detectable endotoxin; recalled lots were more likely to have measurable endotoxin than nonrecalled lots (5/19 vs. 0/17, P = 0.05). When case-patients resumed CCPD using PDS from non-recalled lots, no further cases were reported. CONCLUSIONS: Our results suggest that this outbreak was caused by intrinsic PDS contamination with endotoxin. Pre-sterilization colony counts may be an important quality control indicator for CCPD fluids in conjunction with endotoxin levels.

Adult↗