Biomedical subjects

U Keller

Publications and source records attributed to U Keller.

At least 19 recordsLinked to original sources

PubMed2006

Menstrual cycle symptoms are associated with changes in low-grade inflammation.

BACKGROUND: A close link between mood, low-grade inflammation and obesity has been demonstrated even in healthy subjects. We investigated the relationship between changes in physical and psychological symptoms and inflammatory markers during the menstrual cycle both in normal weight and in overweight women. MATERIALS AND METHODS: Eight healthy normal weight (body mass index 21.6 +/- 1.9 kg m(-2)) and seven overweight (body mass index 30 +/- 2.4 kg m(-2)) young women with normal ovarian function and with no premenstrual syndrome were assessed 15 times throughout their menstrual cycle. At each time point fasting blood was drawn and symptoms were recorded using the Freeman Daily Symptom Record. RESULTS: Independent of weight status, the serum concentrations of highly sensitive C-reactive protein (hs-CRP) and the total scores, in addition to the individual four factors (mood, behaviour, pain and physical symptoms), of the Daily Symptom Record varied significantly during the menstrual cycle (all P < or = 0.04) and paralleled each other. During the menstrual cycle, repeated hs-CRP serum concentrations correlated to the corresponding total symptom score and the factors mood, behaviour and physical symptoms, independent of both weight status and changes in circulating gonadal steroids (all P < or = 0.04). These associations were not observed for tumour necrosis factor-alpha serum levels. The mean hs-CRP concentrations were associated with the mean total symptom score, independent of weight status (r = 0.56, P = 0.04). CONCLUSION: Healthy young women showed psychological and physical symptoms during the menstrual cycle which changed in association with alterations in low-grade inflammation and which were independent of body weight or plasma levels of gonadal steroids.

Adult↗

PubMed2006

Women with polycystic ovary syndrome are sensitive to the TNF-alpha-lowering effect of glucose-induced hyperinsulinaemia.

BACKGROUND: Restoration of near-euglycaemia by intensive insulin therapy results in decreased serum levels of inflammatory mediators. The authors investigated whether the anti-inflammatory effect of insulin was independent of its glucose-lowering action and if this effect was intact in insulin-resistant women with the polycystic ovary syndrome (PCOS) characterized by low-grade chronic inflammation. MATERIALS AND METHODS: Blood was drawn on the third and sixth days after progestin-induced withdrawal bleeding in 20 young non-diabetic women with PCOS and once between the third and sixth days of the menstrual cycle in 21 age-matched lean healthy control women during a 75-g oral glucose tolerance test (oGTT). Serum insulin, glucose and tumour necrosis factor alpha (TNF-alpha) concentrations were measured after 0, 30, 60, 90 and 120 min. RESULTS: The increase in insulin and glucose concentrations during the oGTT was significantly more pronounced in patients with PCOS (one patient with impaired fasting glucose, one patient with impaired glucose tolerance, three patients with both) compared with healthy controls. The TNF-alpha serum concentrations decreased in patients with PCOS (mean of both days, P = 0.004). In patients and in controls, there was an inverse correlation between the serum concentrations of insulin and of TNF-alpha during oGTT (for patients, a mean of both days, P = 0.009; for controls, P = 0.047), but not between the serum concentrations of glucose and TNF-alpha. CONCLUSIONS: The decrease in TNF-alpha concentrations during oGTT and the inverse correlation between endogenous hyperinsulinaemia and serum TNF-alpha concentrations suggested an anti-inflammatory effect of moderately-high insulin concentrations. This occurred despite the presence of moderate hyperglycaemia. These findings also demonstrated a preserved responsiveness of inflammatory mediators to insulin in PCOS.

Adult↗

PubMed2006

Effect of sibutramine and of cognitive-behavioural weight loss therapy in obesity and subclinical binge eating disorder.

AIM: In this randomized, double-blind, placebo-controlled study, the effect of sibutramine and cognitive-behavioural weight loss (cognitive-BWL) treatment was assessed in obese subjects with and without subclinical binge eating disorder (sBED). METHODS: Seventy-three obese participants were recruited from the community, 29 with and 44 without sBED. Subjects were randomly assigned to a 16-week treatment with either sibutramine or placebo while simultaneously participating in a cognitive-behavioural weight loss treatment. RESULTS: Intent-to-treat analysis showed moderate weight loss after treatment in all subject groups. Treatment with BWL programs and sibutramine leads to a higher weight loss in all subjects compared with that in patients who had undergone BWL programs alone. Subjects with sBED significantly reduced their binge episodes during treatment, but with no augmenting effect of sibutramine. DISCUSSION: Our results yield further evidence that sBED is associated with characteristics comparable with full-syndrome BED, significantly differing from those of obesity alone. These findings call for a systematic assessment of eating behaviour before starting obesity treatment.

Adolescent↗

PubMed2005

Phyllosilicates on Mars and implications for early martian climate.

The recent identification of large deposits of sulphates by remote sensing and in situ observations has been considered evidence of the past presence of liquid water on Mars. Here we report the unambiguous detection of diverse phyllosilicates, a family of aqueous alteration products, on the basis of observations by the OMEGA imaging spectrometer on board the Mars Express spacecraft. These minerals are mainly associated with Noachian outcrops, which is consistent with an early active hydrological system, sustaining the long-term contact of igneous minerals with liquid water. We infer that the two main families of hydrated alteration products detected-phyllosilicates and sulphates--result from different formation processes. These occurred during two distinct climatic episodes: an early Noachian Mars, resulting in the formation of hydrated silicates, followed by a more acidic environment, in which sulphates formed.

Aluminum Silicates↗

PubMed2005

Pulse self-compression to the single-cycle limit by filamentation in a gas with a pressure gradient.

We calculate pulse self-compression of a 30 fs laser pulse traversing gas with different pressure gradients. We show that an appropriate density profile brings significant improvement to the self-compression by filamentation. Under an optimal pressure gradient, the pulse duration is reduced to the single optical cycle limit over a long distance, allowing easy extraction into an interaction chamber.

Journal Article↗

PubMed2005

Frequency-sheared, time-delayed extreme-ultraviolet pulses produced by high-harmonic generation in argon.

We report the production of frequency-sheared high harmonics in argon by control of the envelope and chirp of the electric field of the femtosecond driving laser pulse. Using the classic three-step model of high-harmonic generation, we established a direct link between the properties of the harmonics and the fully characterized driving pulses. A simulation of the single-atom response in the strong-field approximation confirms the simple picture and shows good agreement with the experimental results.

Journal Article↗

PubMed2005

Nearly quantum-noise-limited timing jitter from miniature Er:Yb:glass lasers.

We report on nearly quantum-limited timing-jitter performance of two passively mode-locked Er:Yb:glass lasers with a repetition rate of 10 GHz. The relative timing jitter of both lasers was measured to be 190 fs (100 Hz-1.56 MHz) root mean square. The remaining cavity-length fluctuations are below 7.5 pm in the 6 Hz-8 kHz frequency range, indicating the stability of a rugged miniature cavity setup. By actively controlling the cavity length we reduced the timing jitter to 26 fs (6 Hz-1.56 MHz). We also discuss the influence of cavity length on the practically achievable timing jitter.

Journal Article↗

PubMed2005

Validity of wave-front reconstruction and propagation of ultrabroadband pulses measured with a Hartmann-Shack sensor.

Wave-front reconstruction for ultrabroadband laser pulses is verified by use of a Hartmann-Shack sensor. We estimate the accuracy of numerical wave-front propagation by comparing numerical with experimental results and verify that wave fronts of ultrabroadband laser pulses from a hollow fiber can be propagated correctly by a single polychromatic wave-front measurement to a place where detection is not practicable, e.g., inside a vacuum chamber or laser focus.

Journal Article↗

PubMed2005

Femtosecond pulse generation with a diode-pumped Yb3+:YVO4 laser.

A diode-pumped Yb:YVO4 laser has been passively mode locked for the first time, to our knowledge. 120 fs pulses with an average output power of 300 mW and a peak power as high as 14.5 kW are obtained by use of a semiconductor saturable-absorber mirror for passive mode locking. The optical spectrum has a 10 nm bandwidth (full width at half-maximum) and is centered at 1021 nm.

Journal Article↗

PubMed2005

Soliton mode-locked Er:Yb:glass laser.

We report on a simple diode-pumped passively mode-locked Er:Yb:glass laser generating transform-limited 1536-nm solitons of 255-fs duration with a repetition rate of 50 MHz and average power of 58 mW. We also discuss timing jitter and the trade-off between short pulses and high output power in these lasers.

Journal Article↗

PubMed2005

2.1-W picosecond passively mode-locked external-cavity semiconductor laser.

We demonstrate an optically pumped passively mode-locked external-cavity semiconductor laser generating 4.7-ps pulses at 957 nm with as much as 2.1 W of average output power and a 4-GHz repetition rate. Compared with earlier results, the chirp of the pulses has been greatly reduced by use of an intracavity etalon. Apart from restricting the bandwidth, the etalon also helps optimize wavelength-dependent gain parameters and dispersion.

Journal Article↗

PubMed2005

Passively mode-locked 914-nm Nd:YVO4 laser.

We demonstrate what is to our knowledge the first mode-locked Nd:YVO4 laser operating on the 4F3/2-4I9/2 transition at 914 nm. Using a semiconductor saturable-absorber mirror for passive mode locking, we have obtained 3-ps pulses at a repetition rate of 233.8 MHz. The laser is based on a standard delta cavity and is pumped by a Ti:sapphire laser. We obtained an average output power of 42 mW through one mirror and an accumulated output power of approximately 150 mW (through all cavity mirrors) at a pump power of 1.4 W.

Journal Article↗

PubMed2005

[Low-carbohydrate diets for obesity].

Low-carbohydrate diets for the treatment of obesity are currently receiving widespread popularity, mainly in Anglo-Saxan countries. Several controlled trials have demonstrated larger weight loss (3-6 kg) during these diets compared to conventional low-fat diets. The weight differences between these diets were statistically significant after 6 months but not any more after 12 months. Possible reasons for the increased weight loss may be the initial loss of body water, later on the diminishment of food choices, the satiating properties of proteins and the anorectic effect of ketosis. Controlled studies have not demonstrated any increase in LDL-cholesterol but a favorable increase in HDL-C and a lowering of serum triglycerides. Even if these diets "work" in selected patients, they are problematic because the increase in protein ingestion may lead to increased intake of saturated fat, and intake of water soluble antioxidants, vitamins and of fiber may be too low. For these reasons, their protective effect on the "major killers " atherosclerotic diseases, hypertension, diabetes type 2 and some forms of cancer is questionable. Moreover, these diets are unpleasant on the long run, and social eating is impaired. For all these reasons they should not be generally recommended. Reasonable nutritional changes for the treatment of obesity should be suitable for lifelong use, and they should always be combined with increased physical activity and with behavioral measures.

Diet, Reducing↗

PubMed2005

X-PERT: weight reduction with orlistat in obese subjects receiving a mildly or moderately reduced-energy diet: early response to treatment predicts weight maintenance.

AIM: To determine the effect of two different levels of energy deficit on weight loss in obese patients treated with orlistat. METHODS: Patients (n=430) were randomized in a 1-year, multicentre, open-label, parallel group study conducted at 23 hospital centres and university medical departments worldwide. Obese outpatients (body mass index 30--43 kg/m(2)) aged 18--70 years with a body weight of >or=90 kg and a waist circumference of >or=88 cm (women) or >or=102 cm (men) were treated with orlistat 120 mg three times daily plus a diet that provided an energy deficit of either 500 or 1,000 kcal/day for 1 year. Orlistat treatment was discontinued in patients who did not achieve >or=5% weight loss after assessment at 3 and 6 months. The primary outcome measure was change in body weight from baseline at week 52. RESULTS: Reported mean difference in energy intake between the two groups (500-1,000 kcal/day deficit) at weeks 24 and 52 was actually 111 and 95 kcal/day respectively. Of the 430 patients involved in the study, 295 achieved >or=5% weight loss at both 3 and 6 months. In this population, at week 52, weight loss from baseline was similar for patients randomized to either the 500 or the 1,000 kcal/day deficit diet (-11.4 kg vs. -11.8 kg, respectively; p=0.778). After 12 months of treatment with orlistat, 84% (n=118/141) and 85% (n=131/154) of patients in the 500 and 1,000 kcal/day deficit groups, respectively, achieved >or=5% weight loss, and 50% (n=70/141) and 53% (n=82/154) of patients, respectively, achieved >or=10% weight loss. Patients in both the diet treatment groups showed similar significant improvements in blood pressure, lipid levels and waist circumference at week 52. CONCLUSIONS: Treatment with orlistat was associated with a clinically beneficial weight loss, irrespective of the prescribed dietary energy restriction (-500 or -1000 kcal/day). Patients who achieved >or=5% weight loss at 3 months achieved long-term, clinically beneficial weight loss with orlistat plus either diet. Therefore, identifying patients who lose at least 5% weight after 3 months and who maintain this weight loss up to 6 months is a valuable treatment algorithm to select patients who will benefit most from orlistat treatment in combination with diet.

Adolescent↗

PubMed2004

Nutritional fats and the risk of type 2 diabetes and cancer.

Dietary factors are important predictors for the risk of diabetes type 2. Increased consumption of fibre-rich foods, fruits and vegetables as well as limited amounts of total and saturated fats are essential elements in the prevention of diabetes type 2. The association between these dietary factors and the appearance of diabetes was not only present in cohort studies but were also major elements in the dietary part of the two large diabetes prevention trials (Finnish Diabetes Prevention Study, Diabetes Prevention Program). There is also strong evidence for a relation between obesity and total fat intake and the incidence of certain types of cancers. There is a significant correlation between total fat intake and the risk of cancer; however, it is much weaker than that of the effect of red meat. Recommendations to decrease red meat intake, particularly processed meat, may decrease the risk of colorectal and prostate cancer and may have beneficial effects on breast cancer as well, although this evidence is less compelling. Overall, recommendations focused on controlling or reducing body weight by regular physical activity and avoidance of excessive energy intake from all sources, particularly from fat and saturated fats, by increasing consumption of fibre-rich carbohydrates, vegetables and fruits are effective in decreasing the risk for type 2 diabetes by more than 50% in high-risk individuals. Similar dietary patterns are likely to diminish the manifestation of certain forms of cancers. These conclusions are in agreement with current recommendations for cancer prevention as propagated by the American Cancer Society.

Diabetes Mellitus, Type 2↗

PubMed2004

Compact 10-GHz Nd:GdVO4 laser with 0.5-W average output power and low timing jitter.

We demonstrate a compact, diode-pumped Nd:GdVO4 laser with a repetition rate of 9.66 GHz and 0.5-W average output power. The laser is passively mode locked with a semiconductor saturable absorber mirror (SESAM), yielding 12-ps-long sech2-shaped pulses. For synchronization of the pulse train to an external reference clock, the SESAM is mounted on a piezoelectric transducer. With an electronic feedback loop of only a few kilohertz loop bandwidth we achieved a rms timing jitter of 146 fs (integrated from 10 Hz to 10 MHz). This is an upper limit because it is mostly limited by the measurement system. The laser setup with a simple linear cavity has a footprint of only 130 mm x 30 mm.

Journal Article↗

PubMed2004

Diabetes mellitus in Tropical Chronic Pancreatitis Is Not Just a Secondary Type of Diabetes.

AIMS: In chronic calcific pancreatitis of the tropics, etiology and relationship to developing diabetes mellitus are unknown. Some consider these cases a straightforward secondary type of diabetes, while others suggest selective beta-cell impairment. Testing pancreatic function, we investigated whether selective beta-cell impairment triggers diabetes associated with tropical pancreatitis. METHODS: At a Bangladeshi research institute, 8 chronic tropical pancreatitis and no diabetes mellitus subjects, 14 fibrocalculous pancreatic diabetics and 27 matched healthy controls underwent arginine (endocrine pancreatic function) and secretin (exocrine pancreatic function assessment) stimulation tests. RESULTS: All patients with clinically-diagnosed, chronic pancreatitis demonstrated pronounced exocrine pancreatic dysfunction with beta-cell functioning differing significantly between the two groups. Compared to controls, patients having tropical pancreatitis and no diabetes showed normal plasma C-peptide values at baseline and after arginine stimulation, while fibrocalculous pancreatic diabetics demonstrated a typical diabetic pattern for plasma C-peptide levels. In contrast, pancreatic alpha-cell functioning (glucagon response to arginine) was preserved in both pancreatitis groups. CONCLUSION: A preserved pancreatic alpha-cell function in diabetics with advanced chronic pancreatitis of the tropics supports the concept of two different pathogenic mechanisms, one eliciting chronic pancreatitis and the other selective pancreatic beta-cell impairment and subsequent diabetes mellitus.

Adult↗

PubMed2004

Phase-preserving chirped-pulse optical parametric amplification to 17.3 fs directly from a Ti:sapphire oscillator.

Phase-stabilized 12-fs, 1-nJ pulses from a commercial Ti:sapphire oscillator are directly amplified in a chirped-pulse optical parametric amplifier and recompressed to yield near-transform-limited 17.3-fs pulses. The amplification process is demonstrated to be phase preserving and leads to 85-microJ, carrier-envelope-offset phase-locked pulses at 1 kHz for 0.9 mJ of pump, corresponding to a single-pass gain of 8.5 x 10(4).

Journal Article↗