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PubMedDate not supplied

Quantifying the 'appleness' or 'pearness' of the human body by subcutaneous adipose tissue distribution.

To quantify subcutaneous adipose tissue topography (SAT-Top) describing individual SAT distribution for a subject or even a group we measured subcutaneous adipose tissue thickness at 15 specified body sites of 303 healthy women aged 20-69 yrs and 20 women with proven non-insulin-dependent diabetes mellitus (NIDDM) by the optical device 'LIPOMETER'. The type of upper-body- and lower-body-fat pattern, (apples or pears), was determined by factor analysis of the data. Upper body sites were highly loaded in factor 1, whereas factor 2 included highly loaded body sites from the lower extremities. For an individual, factor 1 scores > factor 2 scores, was described as an 'apple'-type, while factor 2 > factor 1 was described as a 'pear'-type. We found about 80% 'pears' and 20% 'apples' in 20-29 year olds and 20% 'pears' and 80% 'apples' in 60-69 year old women. Women with NIDDM tended to be 'super-apples'. SAT-Top provides a useful differentiation between apples and pears and we recommend this approach as a screening method.

Adipose Tissue↗
PubMedDate not supplied

Control and assessment of the uterus and cervix during pregnancy and labour.

Preterm labour and resultant preterm birth are the most important problems in perinatology. Countless efforts have failed to establish a single effective treatment of preterm labour, partly because the mechanisms regulating the uterus and cervix during pregnancy are not well understood. New knowledge is needed to inhibit early progression of labour (uterine contractility and cervical ripening), and adequate quantitative tools to evaluate the uterus and cervix during pregnancy are lacking. In this review, we outline studies showing that the uterus (myometrium) and cervix pass through a conditioning step in preparation for labour. This step is not easily identifiable with present methods to assess the uterus or cervix. In the uterus, this seemingly irreversible step consists of changes in the electrical properties to make muscle more excitable and responsive to produce forceful contractions. In the cervix, the step consists of softening of the connective tissue components. Progesterone appears to have a dominant role in controlling both the uterus and cervix, as antiprogestins induce early, preterm conditioning leading to preterm labour. Apparently, nitric oxide (NO) also controls conditioning of the uterus and cervix. In the uterus, NO, in concert with progesterone, inhibits uterine contractility. At term, NO production by the uterus and placenta are decreased and allow labour to progress. In contrast, NO in the cervix increases at the end of pregnancy and it may be the final pathway for stimulating cervical ripening by activation of metalloenzymes. The progress of labour can be assessed non-invasively using electromyographic (EMG) signals from the uterus (the driving force for contractility) recorded from the abdominal surface. Uterine EMG bursts detected in this manner characterize uterine contractile events during human and animal pregnancy. A low uterine EMG activity, measured transabdominally throughout most of pregnancy, rises dramatically during labour. EMG activity also increases substantially during preterm labour in humans and rats. This method may be used one day to predict impending preterm labour and identify control steps and treatments. A quantitative method also assesses the cervix, using an optical device which measures collagen fluorescence in the cervix. The collascope estimates cervical collagen content from a fluorescent signal generated when collagen cross-links are illuminated with excitation light of about 340 nm. The system has proved useful in rats and humans at various stages of pregnancy, and indicates that cervical softening occurs progressively in the last one-third of pregnancy. In rats, collascope readings correlate with resistance measurements made in the isolated cervix, which may help to assess cervical function during pregnancy, and indicate control and treatments.

Animals↗
PubMed2001

Efficacy and safety of haemodialysis treatment with the Hemocontrol biofeedback system: a prospective medium-term study.

BACKGROUND: Hypovolaemia has been implicated as a major causal factor of morbidity during haemodialysis (HD). A model biofeedback control system for intra-HD blood volume (BV) changes modelling has been developed (Hemocontrol), Hospal Italy) to prevent destabilizing hypovolaemia. It is based on an adaptive controller incorporated in a HD machine (Integra), Hospal Italy). The Hemocontrol biofeedback system (HBS) monitors BV contraction during HD with an optical device. HBS modulates BV contraction rates by adjusting the ultrafiltration rate (UFR) and the refilling rate by adjusting dialysate conductivity (DC) in order to obtain the desired pre-determined BV trajectories. METHODS: Nineteen hypotension-prone uraemic patients (seven males, 12 females; mean age 64.5+/-3.0 SEM years; on maintenance HD for 80.5+/-13.2 months) volunteered for the present prospective study that compared the efficacy and safety of bicarbonate HD treatment equipped with HBS, as a whole, with the gold-standard bicarbonate treatment equipped with a constant UFR and DC (BD). The study included three phases: Medium-term studies started with one period of 6 months of BD and always had a follow-up period of HBS treatment ranging from 14 to 30 months (mean 24.0+/-1.6); short-term studies started in September 1999, when all patients went back to BD treatment for a wash-out period of 4 weeks and a short-term study period of a further 3 weeks (phase A). Afterwards, they once again started HBS treatment for a wash-out period of 4 weeks and a short-term study period of a further 3 weeks (phase B). Every patient underwent acute studies during a single HD run, once during phase A and once in phase B. Resistance (R) and reactance (Xc) measurements were obtained utilizing a single-frequency (50 kHz) tetrapolar bioimpedance analysis (BIA). Extracellular fluid volume (ECV) was calculated from R, Xc, and height and body weight measurements using the conventional BIA regression equations. RESULTS: The overall occurrence of symptomatic hypotension and muscle cramps was significantly less in HBS treatment in both medium- and short-term studies. Self-evaluation of intra- and inter-HD symptoms (worst score=0, best score=10) revealed a statistically significant difference, as far as post-HD asthenia was concerned (6.2+/-0.2 in HBS treatment vs 4.3+/-0.1 in BD treatment, P<0.0001). No difference was observed between the two treatments when comparing pre- and post-HD lying blood pressure, heart rate, body weights and body weight changes in medium- and short-term studies. The residual BV%/ Delta ECV% ratio, expression of the vascular refilling, was significantly higher during HBS treatment in acute studies. CONCLUSIONS: HBS treatment is effective in lowering hypovolaemia-associated morbidity compared with BD treatment; this could be related to a greater ECV stability. Furthermore, HBS is a safe treatment in the medium-term because these results are not achieved through potentially harmful changes in blood pressure, body weight, and serum sodium concentration.

Aged↗
PubMed2005

Haemodialysis with on-line monitoring equipment: tools or toys?

BACKGROUND: On-line monitoring of chemical/physical signals during haemodialysis (HD) and bio-feedback represents the first step towards a 'physiological' HD system incorporating adaptive and logic controls in order to achieve pre-set treatment targets. METHODS: Discussions took place to achieve a consensus on key points relating to on-line monitoring and bio-feedback, focusing on the clinical applications. RESULTS: The relative blood volume (BV) reduction during HD can be monitored by optic devices detecting the variations in concentration of haemoglobin/haematocrit. BV changes result from an equilibrium between ultrafiltration and the refilling capacity. However, BV reduction has little power in predicting intra-HD hypotensive episodes, while the combination of the patient-dialysate sodium gradient, the relative BV reduction between the 20th and 40th minute of HD, the irregularity of the profile of BV reduction over time and the heart rate decrease from the start to the 20th minute of HD predict intra-HD hypotension with a sensitivity of 82%, a specificity of 73% and an accuracy of 80%. A bio-feedback system drives the relative BV reduction according to desired values by instantaneously changing the ultrafiltration rate and the dialysate conductivity. This system has proved to reduce the incidence of intra-HD hypotension episodes significantly. Ionic dialysance and the patient's plasma conductivity can be calculated easily from on-line inlet and outlet dialysate conductivity measurements at two different steps of dialysate conductivity. Ionic dialysance is equivalent to urea clearance corrected for recirculation and is a tool for continuously monitoring the dialysis efficiency and detecting early problems with the delivery of the prescribed dose of dialysis. Given the strict and linear relationship between conductivity and sodium content, the conductivity values replace the sodium concentration values and this permits the development of a conductivity kinetic model, by means of which sodium balance can be achieved at each dialysis session. The conductivity kinetic model has been demonstrated to improve intra-HD cardiovascular stability in hypotension-prone patients significantly. Ionic dialysance is also a useful tool to monitor vascular access function, as it can be used to obtain serial measurements of vascular access blood flow. On-line urea monitors provide detailed information on intra-HD urea kinetics and delivered dialysis dose, but they are not in widespread use because of the costs related to the disposable materials (e.g. urease cartridge). The body temperature monitor measures the blood temperature at the arterial and venous lines of the extra-corporeal circuit and, thanks to a bio-feedback system, is able to modulate the dialysate temperature in order to influence the patient's core body temperature, which can be kept at constant values. This is associated with improved intra-HD cardiovascular stability. The module can also be used to quantify total recirculation. CONCLUSIONS: On-line monitoring devices and bio-feedback systems have evolved from toys for research use to tools for routine clinical application, particularly in patients with clinical complications. Conductivity monitoring appears the most versatile tool, as it permits quantification of delivered dialysis dose, achievement of sodium balance and surveillance of vascular access function, potentially at each dialysis session and without extra cost.

Biofeedback, Psychology↗
PubMed2006

Sensory impairment in older adults: part 2: Vision loss.

A decline in vision occurs naturally with age; more severe impairment can result from medical conditions such as age-related macular degeneration, cataracts, glaucoma, and diabetic retinopathy. Nurses can pick up signs of visual impairment and suggest certain environmental modifications to prevent injury, such as keeping floors free of clutter and rooms well lit. Although assistive technologies such as optical devices, magnifiers, telescopes, and electronic magnification can help, some forms of impairment, such as that caused by cataracts and uncorrected refractive error, can be corrected.

Aged↗
PubMedDate not supplied

Continuous monitoring of plasma, interstitial, and intracellular fluid volumes in dialyzed patients by bioimpedance and hematocrit measurements.

Bioimpedance spectroscopy (BIS) permits evaluation of extra- and intracellular fluid volumes in patients. We wished to examine whether this technique, used in combination with hematocrit measurement, can reliably monitor fluid transfers during dialysis. Ankle to wrist BIS measurements were collected during 21 dialysis runs while hematocrit was continuously monitored in the blood line by an optical device. Extracellular (ECW) and intracellular (ICW) water volumes were calculated using Hanai's electrical model of suspensions. Plasma volume variations were calculated from hematocrit, and changes in interstitial volume were calculated as the difference between ECW and plasma volume changes. Because accuracy of ICW was too low, changes in ICW were calculated as the difference between ultrafiltered volume and ECW changes. Total body water (TBW) volumes calculated pre- and postdialysis were, respectively, 3.25+/-3.2 and 1.95+/-2.5 liters lower on average than TBW given by Watson et al.'s correlation. Average decreases in fluid compartments expressed as percentage of ultrafiltered volume were as follows: plasma, 18%; interstitial, 28%, and ICW, 54%. When the ultrafiltered volume was increased in a patient in successive runs, the relative contributions of ICW and interstitial fluid were augmented so as to reduce the relative drop in plasma volume.

Adult↗
PubMed1999

Monitoring for compartmental syndrome using near-infrared spectroscopy: a noninvasive, continuous, transcutaneous monitoring technique.

BACKGROUND: The diagnosis of compartmental syndrome (CS) may be delayed because current monitoring techniques are invasive and intermittent and the compartment pressure (CP) that predicts ischemia is variable. Fiber-optic devices using near-infrared (NIR) wavelength reflection can determine the redox state of light-absorbing molecules and have been used to monitor venous hemoglobin saturation to detect ischemia during low-flow states. The purpose of this study was to determine if NIR spectroscopy can provide continuous, transcutaneous, noninvasive monitoring for muscle ischemia in an animal model of CS. METHODS: Nine swine were anesthetized and a 20-mm NIR probe was placed over the anterolateral compartment of the hind leg to provide continuous determination of muscle oxyhemoglobin level. Needles were inserted into the compartment to measure CP. A nerve stimulator was placed over the peroneal nerve to induce dorsiflexion twitch. Albumin was infused into the muscle to incrementally increase CP until there was complete loss of dorsiflexion, then after 20 minutes fasciotomy was performed. RESULTS: All animals lost dorsiflexion at CP of 43+/-14 mm Hg. There was a significant inverse correlation between CP and oxyhemoglobin level (r = -0.78; p < 0.001) and a correlation between oxyhemoglobin and perfusion pressure (mean arterial pressure minus CP) (r = 0.66; p < 0.001). Redox state was a more consistent predictor of twitch loss than perfusion pressure. CONCLUSION: Muscle oxyhemoglobin level measured by NIR spectroscopy strongly reflected CP, perfusion pressure, and loss of dorsiflexion twitch. Currently available portable NIR devices may provide the benefit of continuous, noninvasive monitoring for CS. Further studies to determine the role of this technology in the detection of compartmental syndrome are warranted.

Animals↗
PubMed2001

Relationship between subcutaneous fatness and leptin in male athletes.

PURPOSE: Circulating leptin is low in trained subjects and closely related to body fat content. However, data are scarce as to whether differences exist in the relationship between different estimates of adiposity, metabolic parameters, and leptin in endurance- and resistance-trained male athletes. We investigated this relationship with special emphasis on subcutaneous fatness and its distribution. METHODS: 20 endurance (ET) and 17 resistance (RT) athletes recruited from different kind of sports were studied. Fat-free mass (FFM) was estimated by means of impedance and fat mass (FM) was calculated. Subcutaneous fat (SAT) and its distribution was measured by means of the optical device Lipometer at 15 body sites (SAT-layers; from 1-neck to 15-calf) on the right side of the body. Fifteen SAT-layers were summed to calculate SAT. Blood samples were obtained for determination for leptin, insulin, and glucose. Insulin resistance was calculated through the fasting insulin resistance index (FIRI; [insulin x glucose/25]). RESULTS: RT-athletes had a greater body mass and body fat content than ET-athletes, but no differences were found for leptin and metabolic parameters. In all athletes, estimates of adiposity were correlated to leptin. However, in ET-athletes FM (P < 0.05), FFM (P < 0.05), and SAT (P < 0.001) but not metabolic parameters were correlated to leptin. In RT-athletes, SAT (P < 0.0001), metabolic parameters (all P < 0.05), but not FM and FFM were in significant relationship with leptin. Stepwise regression revealed SAT as the main determinant for the variation in leptin in all athletes (adj. R(2 )= 0.52, P < 0.0001). CONCLUSION: The results suggest that estimates of adiposity and metabolic parameters are associated with leptin in a sport-specific manner. Whereas leptin might be regulated by overall subcutaneous fatness in athletes, our study does not imply a main influence of fat patterning on leptin in this group of trained subjects.

Adipose Tissue↗
PubMed1977

A field expander for patients with retinitis pigmentosa: a clinical study.

An inexpensive, commercially available optical device was tested on 10 patients with retinitis pigmentosa to determine its value as a field expander for scanning and as an aid to mobility. Visual acuity and visual fields were measured with and without the expander, and the patients' subjective responses were monitored by a questionnaire that was administered at regular intervals during a 2- to 4-week period between test sessions. Six of the 10 subjects considered the device helpful in at least 1 important visual task and planned to continue using it.

Adult↗
PubMed1993

Low-vision aids in age-related macular degeneration.

In spite of the many patients with low vision due to age-related macular degeneration, the year's publications on their rehabilitation are few. The most common complaint of these patients is their inability to read. For this purpose, simple optical devices, eg, overcorrection in reading glasses, hand-held or stand magnifiers, are usually best. With closed-circuit television systems, reading speed may be faster and reading time may be longer but these systems are still too expensive for most users. Results on bifocal intraocular lenses used as a Galilean telescopic system are still unconfirmed. New ideas for many technical devices suitable also for elderly patients have been presented.

Aged↗
PubMed2004

A novel laparoscopic technique for removal of foreign bodies from the urinary bladder using carbon dioxide insufflation.

We describe a new technique for extraction of complex foreign bodies from the urinary bladder which cannot be removed through the conventional pediatric cystoscope, thereby avoiding an open cystotomy and the morbidity associated with it. Using cystoscopy as the optical device through the urethra, a 10-mm laparoscopic port can be introduced suprapubically under vision for extraction of complex foreign bodies while the bladder remains insufflated with carbon dioxide at a pressure of 12 mm mercury.

Adolescent↗
PubMed2000

Farey sequences of spatiotemporal patterns in video feedback.

In this paper we present an experimental and theoretical description of the dynamic of spatial patterns obtained in a video feedback loop. A video camera monitors the screen to which it is connected and can turn around its optical axis at an angle alpha. Under certain conditions of brightness and magnification, this optoelectronic system produces spatiotemporal patterns in the form of spots located on a circle on the screen. These patterns are very similar to the spatial transverse modes obtained in other optical devices such as lasers or photorefractive media. It is possible to generate stationary patterns of n-fold symmetries for angles alpha=2pi/n. When the angle alpha varies around 2pi/n, the pattern rotates with a certain frequency proportional to the difference between 2pi/n and alpha. We discover more general patterns at angles 2pi/(p/k) with p-fold symmetry, following the hierarchy of the Farey algorithm which theoretically can produce stationary patterns at any angle alpha. Very accurate experiments were performed to observe these patterns up to the level k=6. This is the first time a Farey tree has been observed as a sequence of spatial patterns to our knowledge. Previous observations of this hierarchy were made only in the temporal domain.

Animals↗
PubMed2002

Measuring and modeling thermal fluctuations at nanometer length scales.

The size of mechanical, electrical, and optical devices continues to be reduced. As the length scales of such devices decrease, coupling to the external environment greatly increases. Thermal fluctuations due to momentum exchange between air molecules and micron scale devices under ambient conditions can effect the dynamics of a system. To illustrate this we use an atomic force microscope cantilever and detection system to measure background noise and thermal fluctuations of a micron size beam. The beam is modeled by a Langevin-type equation that is externally forced by a white-noise spectrum having an analytic as opposed to a statistical form. This model is compared with experimental data. It is found that at higher frequencies, a white-noise spectrum is not sufficient to model such a system. We modify the forcing spectrum so that it decays at higher frequencies and subsequently achieve closer agreement between the model and the experimental observations.

Journal Article↗
PubMed2000

Beam splitter for guided atoms.

We have designed and experimentally studied a simple beam splitter for guided atoms realized with a current carrying Y-shaped wire nanofabricated on a surface (atom chip). Such a Y-configuration beam splitter has many advantages compared to conventional designs based on tunneling, especially that it will enable robust beam splitting. This and other similar designs can be integrated into more sophisticated surface-mounted atom optical devices at the mesoscopic scale.

Journal Article↗
PubMed2002

Suppression of spatial chaos via noise-induced growth of arrays of spatial solitons.

Domain walls with oscillatory tails are commonplace in models of spatially extended nonlinear optical devices. Their interaction and locking at discrete distances lead to asymptotically stable spatial disorder. We show that noise in the presence of domain walls with oscillatory tails can suppress spatial disorder by privileging highly correlated dynamical states consisting of arrays of spatial solitons.

Journal Article↗
PubMed2005

Terahertz response of a microfabricated rod-split-ring-resonator electromagnetic metamaterial.

The first electromagnetic metamaterials (EM3) produced by microfabrication are reported. They are based on the rod-split-ring-resonator design as proposed by Pendry et al. [IEEE Trans. Microwave Theory Tech. 47, 2075 (1999)] and experimentally confirmed by Smith et al. [Phys. Rev. Lett. 84, 4184 (2000)] in the GHz frequency range. Numerical simulation and experimental results from far infrared (FIR) transmission spectroscopy support the conclusion that the microfabricated composite material is EM3 in the range 1-2.7 THz. This extends the frequency range in which EM3 are available by about 3 orders of magnitude well into the FIR, thereby widely opening up opportunities to verify the unusual physical implications on electromagnetic theory as well as to build novel electromagnetic and optical devices.

Journal Article↗
PubMed2006

Coherence in the B800 ring of purple bacteria LH2.

We study the quantum coherence in the B800 ring and how it affects the dynamics of excitation energy transfer (EET) in photo-synthetic light-harvesting systems. From an analysis of the spectrum, we determine the disorder parameters for the B800 ring and show that the relatively weak electronic coupling between B800 pigments subtly changes the dynamics of EET and improves the uniformity and robustness of B800 --> B850 EET at room temperature, an example of how a multichromophoric assembly can exploit coherence to optimize the efficiency of photosynthesis. A molecular-level description for the dynamics of EET in the light-harvesting system may prove useful for understanding other nanoscale molecular assemblies and designing efficient nanoscale optical devices.

Bacterial Proteins↗
PubMed2006

Colossal light-induced refractive-index modulation for neutrons in holographic polymer-dispersed liquid crystals.

We report strong diffraction of cold neutrons from an only 30 micro m thick holographic polymer-dispersed liquid crystal (H-PDLC) transmission grating. The light-induced refractive-index modulation for neutrons is about 10(-6), i.e., nearly 2 orders of magnitude larger than in the best photo-neutron-refractive materials probed up to now. This makes H-PDLCs a promising candidate for fabricating neutron-optical devices.

Journal Article↗