Biomedical subjects

N Katz

Publications and source records attributed to N Katz.

At least 19 recordsLinked to original sources

PubMed2006

Arabinoxylan consumption decreases postprandial serum glucose, serum insulin and plasma total ghrelin response in subjects with impaired glucose tolerance.

OBJECTIVE: Arabinoxylan (AX) consumption is associated with metabolic improvement during diabetes and with modulation of ghrelin, an orexigenic gut hormone. The effect of AX consumption on ghrelin secretion in disturbed metabolic states is unknown. Therefore, we investigated the postprandial responses to AX consumption of serum glucose, insulin and triglycerides and plasma total and acylated ghrelin in subjects with impaired glucose tolerance (IGT). DESIGN: Randomized, single-blind, controlled, crossover intervention trial. SUBJECTS: Seven female and four male adults with IGT, aged 55.5 years, and body mass index (BMI) 30.1 kg/m(2). INTERVENTION: Subjects received either placebo or 15 g AX supplement for 6 weeks with a 6-week washout period in-between. MAIN OUTCOME MEASUREMENTS: Postprandial responses of serum glucose, insulin and triglycerides, and plasma total and acylated ghrelin after a liquid meal challenge test (LMCT) measured at the beginning and at the end of the dietary intervention at -20, -5, 0, 15, 30, 45, 60, 90, 120, 150, 180, 210 and 240 min. RESULTS: After LMCT, AX consumption resulted in lower postprandial responses in serum glucose, insulin and triglycerides (P<0.05). Compared to placebo, total plasma ghrelin was also reduced by 42+/-8 pg/ml (P<0.001) after AX consumption with no difference in plasma acylated ghrelin. CONCLUSION: AX consumption improved postprandial metabolic responses after an LMCT in subjects with IGT and reduced total ghrelin response. However, acylated ghrelin responses were unchanged, suggesting that the acylated ghrelin-mediated orexigenic regulation is not improved as only total plasma ghrelin decreased.

Aged↗

PubMed2006

Measurement of the entanglement of two superconducting qubits via state tomography.

Demonstration of quantum entanglement, a key resource in quantum computation arising from a nonclassical correlation of states, requires complete measurement of all states in varying bases. By using simultaneous measurement and state tomography, we demonstrated entanglement between two solid-state qubits. Single qubit operations and capacitive coupling between two super-conducting phase qubits were used to generate a Bell-type state. Full two-qubit tomography yielded a density matrix showing an entangled state with fidelity up to 87%. Our results demonstrate a high degree of unitary control of the system, indicating that larger implementations are within reach.

Journal Article↗

PubMed2006

State tomography of capacitively shunted phase qubits with high fidelity.

We introduce a new design concept for superconducting phase quantum bits (qubits) in which we explicitly separate the capacitive element from the Josephson tunnel junction for improved qubit performance. The number of two-level systems that couple to the qubit is thereby reduced by an order of magnitude and the measurement fidelity improves to 90%. This improved design enables the first demonstration of quantum state tomography with superconducting qubits using single-shot measurements.

Journal Article↗

PubMed2006

Coherent state evolution in a superconducting qubit from partial-collapse measurement.

Measurement is one of the fundamental building blocks of quantum-information processing systems. Partial measurement, where full wavefunction collapse is not the only outcome, provides a detailed test of the measurement process. We introduce quantum-state tomography in a superconducting qubit that exhibits high-fidelity single-shot measurement. For the two probabilistic outcomes of partial measurement, we find either a full collapse or a coherent yet nonunitary evolution of the state. This latter behavior explicitly confirms modern quantum-measurement theory and may prove important for error-correction algorithms in quantum computation.

Journal Article↗

PubMed2006

Increase in serum resistin during weight loss in overweight subjects is related to lipid metabolism.

OBJECTIVE: Human resistin has been stated to influence preadipocyte cell numbers and to stimulate adipocyte triglyceride lipolysis in vivo and in vitro. However, its role in human obesity remains unclear. DESIGN: Cross-sectional study for comparisons of lean and obese subjects, and subsequent longitudinal 4-month weight loss intervention study in obese subjects. SUBJECTS: Healthy subjects, lean (n=20, BMI<25) and overweight (n=43, BMI>or=25). MEASUREMENTS: Serum resistin, body weight, body fat, waist-to-hip ratio, as well as markers of insulin resistance and lipid metabolism at baseline and after 4 months of intervention. RESULTS: Serum resistin was positively correlated to HOMA-IR (partial r=0.288; P=0.055), serum fructosamines (partial r=0.280; P=0.062), serum NEFA (partial r=0.276; P=0.066) and negatively to age (partial r=-0.349; P=0.019) and serum apolipoprotein A-1 (partial r=-0.363; P=0.014). During the intervention, serum resistin increased significantly (P<0.001). The increase was inversely related to changes in waist-to-hip ratio (P=0.025) and positively to serum apolipoprotein B (P=0.011). In males only, the increase in resistin during weight loss was predicted by total serum cholesterol at baseline (r=0.703, P=0.007). No relation was observed between changes in resistin and changes in HOMA-IR. CONCLUSION: The present study indicates an association between serum resistin and markers of abdominal fat distribution as well as the regulation of lipid metabolism. However, human resistin is unlikely to play an independent role in the regulation of glucose metabolism.

Adult↗

PubMed2006

Selenium and antioxidant vitamin status of elderly German women.

OBJECTIVE: Low antioxidant intake and status have been shown to be associated with an elevated risk for various diseases. Data on the status of antioxidant vitamins, selenium and coenzyme Q10 of younger female seniors are scarce. The aim of this study was to assess the status of these antioxidants, as well as influencing factors such as dietary intake, anthropometric data and educational level in female seniors (60-70 years) in Germany. DESIGN: Dietary intake of alpha-tocopherol, beta-carotene and ascorbic acid was determined by a 3-day diet record. Serum concentrations of alpha-tocopherol, beta-carotene, ascorbic acid, selenium and coenzyme Q10 were measured. Anthropometric measures, socioeconomic and educational status were assessed. SETTING: In total, 178 elderly women without severe diseases in the region of Hannover, Germany, were included in the study. The mean (+/- s.d.) age and BMI of the women was 63.2 (2.73) years and 25.6 (3.77) kg/m2, respectively. The study participants were generally better educated than the overall German female population. RESULTS: Dietary intake of the ascorbic acid and alpha-tocopherol was below RDA in six and 75% of the women, respectively. In comparison to estimated desirable serum concentrations of alpha-tocopherol, ascorbic acid, beta-carotene and selenium, lower concentrations were found in 23, 1, 6, and 39% of the women, respectively. Ascorbic acid (r = 0.205, P = 0.009) and beta-carotene (r = 0.173, P = 0.025) intake were significantly associated with serum concentrations. Beta-carotene concentrations were influenced by the type of diet, BMI, and school education (R2 = 0.128, P < 0.001). Serum selenium was positively associated with alcohol intake (r = 0.229, P = 0.003). Neither employment nor vocational training was predictive for the serum concentrations of antioxidant vitamins, selenium or coenzyme Q10. CONCLUSIONS: Poor status of selenium and alpha-tocopherol is highly prevalent even among younger, well-educated female seniors, whereas ascorbic acid and beta-carotene status seems sufficient in most women.

Aged↗

PubMed2006

Arabinoxylan fibre consumption improved glucose metabolism, but did not affect serum adipokines in subjects with impaired glucose tolerance.

The consumption of arabinoxylan, a soluble fibre fraction, has been shown to improve glycemic control in type 2 diabetic subjects. Soluble dietary fibre may modulate gastrointestinal or adipose tissue hormones regulating food intake. The present study investigated the effects of arabinoxylan consumption on serum glucose, insulin, lipids, leptin, adiponectin and resistin in subjects with impaired glucose tolerance. In a randomized, single-blind, controlled, crossover intervention trial, 11 adults consumed white bread rolls as either placebo or supplemented with 15 g arabinoxylan for 6 weeks with a 6-week washout period. Fasting serum glucose, insulin, triglycerides, unesterified fatty acids, apolipoprotein A1 and B, adiponectin, resistin and leptin were assessed before and after intervention. Fasting serum glucose, serum triglycerides and apolipoprotein A-1 were significantly lower during arabinoxylan consumption compared to placebo (p=0.029, p=0.047; p=0.029, respectively). No effects of arabinoxylan were observed for insulin, adiponectin, leptin and resistin as well as for apolipoprotein B, and unesterified fatty acids. In conclusion, the consumption of AX in subjects with impaired glucose tolerance improved fasting serum glucose, and triglycerides. However, this beneficial effect was not accompanied by changes in fasting adipokine concentrations.

Adiponectin↗

PubMed2005

Collisional decay of a strongly driven Bose-Einstein condensate.

We study the collisional decay of a strongly driven Bose-Einstein condensate oscillating between two momentum modes. The resulting products of the decay are found to strongly deviate from the usual s-wave halo. Using a stochastically seeded classical field method we simulate the collisional manifold. These results are also explained by a model of colliding Bloch states.

Journal Article↗

PubMed2005

Interactive virtual environment training for safe street crossing of right hemisphere stroke patients with unilateral spatial neglect.

PURPOSE: The goal of this study was to determine whether non immersive interactive virtual environments are an effective medium for training individuals who suffer from Unilateral Spatial Neglect (USN) as a result of a right hemisphere stroke, and to compare it to a standard computer visual scanning training. METHOD: Participants included 19 patients with right hemisphere stroke in two groups, 11 in an experimental group were given computer desktop-based Virtual Reality (VR) street crossing training and 8 in a control group who were given computer based visual scanning tasks, both for a total of twelve sessions, 9 hours total, over four weeks. Measures included: 1. Standard USN assessments, paper and pencil and ADL checklist; 2. Test on the VR street program; and 3. Actual street crossing videotaped. Testing was performed pre and post intervention. RESULTS: The VR group achieved on the USN measures results that equaled those achieved by the control group treated with conventional visual scanning tasks. They improved more on the VR test and they did better on some measures of the real street crossing. CONCLUSIONS: Despite several limitations in this study the present results support the effectiveness of the VR street program in the treatment of participants with USN, and further development of the program.

Accidents, Traffic↗

PubMed2005

Optically induced polarons in bose-einstein condensates: monitoring composite quasiparticle decay.

Nonresonant light scattering off atomic Bose-Einstein condensates is predicted to give rise to hitherto unexplored composite quasiparticles: unstable polarons, i.e., local "impurities" dressed by virtual phonons. Optical monitoring of their spontaneous decay can display either Zeno or anti-Zeno deviations from the golden rule, and thereby probe the temporal correlations of elementary excitations in the condensates.

Journal Article↗

PubMed2005

Interference of arachidonic acid and its metabolites with TNF-alpha release by ochratoxin A from rat liver.

We investigated the role of arachidonic acid and its metabolites on the ochratoxin A (OTA) provoked release of proinflammatory and apoptotic cytokine TNF-alpha from blood-free perfused rat liver. OTA induced TNF-alpha release dose- and time-dependently yielding 2600 pg TNF-alpha/ml at 2.5 micromol/l after 90 min without significant release of LDH and lactate. Aristolochic acid, 50 micromol/l, a phospholipase A2 inhibitor, and 10 micromol/l of exogenous arachidonic acid decreased TNF-alpha below normal level. Indomethacin, 10 micromol/l, a potent inhibitor of the cyclooxygenase (COX) pathway, almost doubled TNF-alpha concentrations in the perfusion solution to reach 5500 pg/ml at 90 min. On the other hand, inhibition of lipoxgenase (LPX) by 30 micromol/l nordihydroguaiaretic acid (NDGA) and the cytochrome P-450 (CYP) pathway by 100 micromol/l of metyrapone decreased TNF-alpha below normal levels as well. Concurrent administration of two blockers (COX inhibitor with LPX inhibitor, or COX inhibitor with CYP-450 inhibitor, or LPX inhibitor with CYP-450 inhibitor) blocked TNF-alpha release below normal levels. In addition, 10 micromol/l caffeic acid phenylethyl ester, a NF-(kappa)B inhibitor, blocked OTA mediated TNF-alpha release. In conclusion, arachidonic acid and its cyclooxygenase metabolites are suppressors of OTA mediated TNF-alpha release from liver, whereas LPX and CYP-450-metabolites have the opposite effect. OTA-induced TNF-alpha release is likely to occur via the NF-(kappa)B transcription factor pathway in perfused rat liver.

Animals↗

PubMed2005

Long-term effect of a plant-based diet on magnesium status during pregnancy.

OBJECTIVE: To compare dietary magnesium intake and magnesium concentrations in serum, red blood cells (RBC) and urine during pregnancy of women habitually following a long-term plant-based diet and of women following an average Western (control) diet. DESIGN: Prospective study during pregnancy. SETTING: Giessen, Germany. SUBJECTS: Healthy pregnant women (n=108) in their 9-12th, 20-22nd and 36-38th gestational week habitually following a plant-based diet for more than 3 y or an average Western diet. The vegetarians were subdivided into ovo-lacto vegetarians (n=27) and low-meat eaters (n=43). RESULTS: Significant higher dietary magnesium intakes were observed in pregnant women consuming a plant-based diet (508+/-14 mg/day for ovo-lacto vegetarians, P<0.001 and 504+/-11 mg/day for low-meat eaters, P<0.001) than in pregnant women consuming a control diet (412+/-9 mg/day). Serum magnesium concentrations were similar in all diet groups whereas RBC magnesium was slightly higher in low-meat eaters than in controls (P=0.058). Urinary magnesium excretion was higher in ovo-lacto vegetarians (P=0.023), followed by low-meat eaters (P=0.017) when compared to the control group. During the third trimester of pregnancy, the frequency and the occurrence of calf cramps was lower in the plant-based diet group than in the control group (P=0.004 and 0.008). CONCLUSIONS: Owing to a higher dietary magnesium intake confirmed by higher urinary magnesium excretion, habitual plant-based diets result in a slightly improved magnesium status during pregnancy and reduce the frequency of calf cramps during the third trimester of pregnancy compared to an average Western diet. Therefore, plant-based diets during pregnancy can be recommended with regard to magnesium supply.

Adult↗

PubMed2004

High sensitivity phonon spectroscopy of Bose-Einstein condensates using matter-wave interference.

We study low-momentum excitations of a Bose-Einstein condensate using a novel matter-wave interference technique. In time-of-flight expansion images we observe strong matter-wave fringe patterns. The fringe visibility is a sensitive spectroscopic probe of in-trap phonons and is explained by use of a Bogoliubov excitation projection method applied to the rescaled order parameter of the expanding condensate. Gross-Pitaevskii simulations agree with the experimental data and confirm the validity of the theoretical interpretation. We show that the high sensitivity of this detection scheme gives access to the quantized quasiparticle regime.

Journal Article↗

PubMed2004

[A hierarchical model for analysis of socio-economic variables and water contact patterns associated with the hepatosplenic form of schistosomiasis].

A study of factors associated with the hepatosplenic clinical form of schistosomiasis was carried out in an endemic area (Comercinho, Minas Gerais) where prevalence of Schistosoma mansoni infection was 70.4%. Of the 1,408 inhabitants aged two years and over, 1,162 (82.5%) participated in the study. Socio-demographic characteristics and reasons for water contacts of individuals with the hepatosplenic form (n = 73) were compared to those who did not present splenomegaly and eliminated (positive controls; n + 804) or did not eliminate S. mansoni eggs in stools (negative controls; n = 285). Multivariate analysis was performed, considering the existence of colinearity among socio-economic status of the family, running water in the household, and bathing in streams. The hepatosplenic form in children was strongly associated with occupation of the head of the family (manual workers) (OR = 11.4; 95% CI = 1.4 - 91.8), absence of running water in the household (OR = 7.7; 95% CI = 2.6 - 23.1), and bathing in streams (OR and 95% CI 7.6; 2.5-22.9 and 5.7; 1.3-25.5 for frequencies > weekly and <= weekly, respectively); bathing in streams, which implies intense contacts, was a consequence of the first two factors. Our results suggest that running water in the household can decrease morbidity from schistosomiasis because it reduces the need for intense contacts with streams.

English Abstract↗

PubMed2003

[Environmental and social determinants in schistosomiasis mansoni in Ravena, Minas Gerais, Brazil].

This study identified the role of biological and social determinants in the transmission of schistosomiasis mansoni in Ravena, Minas Gerais, Brazil, in 1980. This data was used to characterize the clinical and epidemiological profiles of the endemic desease in the population, allowing for the determination of the efficacy of the potable water supply and the specific treatment of those infected with S. mansoni. The district contains three locations, Ravenopolis, Ravena and Lavapes, where the prevalence of the endemic disease was, 20.1%, 42.6% and 63.9%, respectively. The prevalence in the district was statistically higher in men. The age brackets that displayed differences by gender were 10-14 and 15-19 years. Severity of infection was statistically different among individuals within the 10-14 year bracket in ali three locations, and in the 15-19 year bracket among individuals from Ravenopolis and Ravena. The hepatointestinal form was associated with age, and individuals under 15 years of age presented risk of infection 8.85 times higher than adults. Multivariable analysis of the factors involved in transmission of the disease showed that Lavapes was independently associated with infection. In that area, poor sanitary conditions and the proximity of houses to streams infested with S. marsoni cercariae facilitated infection of neighborhood women while performing domestic activities, as well as men digging sand from the streams for construction. These results show the focal nature of transmission of the endemic requiring specific intervention for effective control of disease.

English Abstract↗

PubMed2003

Three-wave mixing of bogoliubov quasiparticles in a bose-einstein condensate.

A dressed basis is used to calculate the dynamics of three-wave mixing between Bogoliubov quasiparticles in a Bose condensate. Because of the observed oscillations between different momentum modes, an energy splitting, analogous to the optical Mollow triplet, appears in the Beliaev damping spectrum of the excitations from the oscillating modes.

Journal Article↗

PubMed2003

Bragg spectroscopy of the multibranch Bogoliubov spectrum of elongated Bose-Einstein condensates.

We measure the response of an elongated Bose-Einstein condensate to a two-photon Bragg pulse. If the duration of the pulse is long, the total momentum transferred to the condensate exhibits a nontrivial behavior which reflects the structure of the underlying Bogoliubov spectrum. It is thus possible to perform a spectroscopic analysis in which axial phonons with a different number of radial nodes are resolved. The local density approximation is shown to fail in this regime, while the observed data agree well with the results of simulations based on the numerical solution of the Gross-Pitaevskii equation.

Journal Article↗

PubMed2003

Awareness of disabilities in stroke rehabilitation--a clinical trial.

PURPOSE: To investigate the frequency of unawareness of disabilities after stroke during the rehabilitation stage, the relationship of unawareness with neuroanatomical variables, and the impact of unawareness on functional outcomes. METHOD: Sixty consecutive patients (36 with right, 24 with left hemisphere damage) admitted to rehabilitation hospital with a first, single, unilateral stroke were evaluated at admission, discharge and at 1-year post onset of stroke. Unawareness of disabilities was operationally defined as the discrepancy between therapist and patient's rating on the motor scale of the functional independence measure (FIM). Functional outcomes included FIM, instrumental activities of daily living (IADL) scale, activity card sort (ACS) and safety rating scale. RESULTS: Unawareness of disabilities was found in 44/60 patients at admission and 24/57 at discharge. There was no significant difference between the hemisphere groups in the frequency of unawareness at both times. Discharge unawareness in the right hemisphere group was significantly associated with lesions in the frontal and temporal lobes, and with lesion size. Unawareness in the left hemisphere damaged group was not associated with any neuroanatomical variables. A negative impact of unawareness at admission on functional outcomes was not found, but it was found that unawareness at discharge was a negative predictor of activity level (ACS score) at follow up, after controlling for the severity of initial disability level. CONCLUSIONS: Unawareness of disabilities is a significant issue in stroke rehabilitation. Unawareness that persists to discharge from rehabilitation correlates with neuroanatomical variables in right hemisphere damaged patients, and is a negative predictor for some rehabilitation outcomes at follow-up.

Activities of Daily Living↗