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Biomedical subjects

P Herman

Publications and source records attributed to P Herman.

At least 19 recordsLinked to original sources
PubMed2006

The modified Beer-Lambert law revisited.

The modified Beer-Lambert law (MBLL) is the basis of continuous-wave near-infrared tissue spectroscopy (cwNIRS). The differential form of MBLL (dMBLL) states that the change in light attenuation is proportional to the changes in the concentrations of tissue chromophores, mainly oxy- and deoxyhaemoglobin. If attenuation changes are measured at two or more wavelengths, concentration changes can be calculated. The dMBLL is based on two assumptions: (1) the absorption of the tissue changes homogeneously, and (2) the scattering loss is constant. It is known that absorption changes are usually inhomogeneous, and therefore dMBLL underestimates the changes in concentrations (partial volume effect) and every calculated value is influenced by the change in the concentration of other chromophores (cross-talk between chromophores). However, the error introduced by the second assumption (cross-talk of scattering changes) has not been assessed previously. An analytically treatable special case (semi-infinite, homogeneous medium, with optical properties of the cerebral cortex) is utilized here to estimate its order of magnitude. We show that the per cent change of the transport scattering coefficient and that of the absorption coefficient have an approximately equal effect on the changes of attenuation, and a 1% increase in scattering increases the estimated concentration changes by about 0.5 microM.

Absorption↗
PubMed2006

Modified pharyngogastrostomy by a stapler technique.

Pharyngolaryngoesophagectomy is the gold standard treatment for the majority of larynx, pharynx and cervical esophagus advanced tumours. Reconstruction of these pharyngoesophageal defects is complex, and implicates additional time, morbity and mortality to the procedure. Gastric pull up and pharyngogastrostomy with hand sewing technique is the commonest way of doing it. The authors describe a modified technique to execute it using a stapler device.

Anastomosis, Surgical↗
PubMed2005

Electroporative adjustment of pH in living yeast cells: ratiometric fluorescence pH imaging.

A number of vital cell functions including modulation of signaling pathways and regulation of the cellular transport critically depends on the cytoplasmic pH. Many pathological cellular changes are related to the abnormal cytosolic pH as well. Reliable and well-calibrated methods for quantification of the cytosolic pH are therefore of high importance. The pH calibration is particularly difficult in walled cells since standard methods fail. In this report we evaluated the new electroporative calibration method of the cytosolic pH in yeasts by the fluorescence microscopy. The calibration was done on living cells using pyranine as a ratiometric pH-sensitive probe. The probe was electroporatively delivered to the cytosol. We have shown that unlike the measurements in suspension the fluorescence microscopy reveals cell subpopulations with different sensitivity to the pH calibration. While the majority of the cells were well calibrated, there was found subpopulation of uncalibrated cell as well as singular cells exhibiting anomalous pH calibration due to the staining of acidic organelles. Resolution of cell subpopulations helps to achieve better pH calibration compared to the calibration in cuvette on a cell suspension.

Arylsulfonates↗
PubMed2005

Enhanced sodium absorption in middle ear epithelial cells cultured at air-liquid interface.

CONCLUSION: As we demonstrated previously that transcription of alpha-ENaC was correlated with oxygen tension in the culture medium, this study suggests that the increase in alpha-ENaC expression observed under ALI conditions may result from greater oxygenation of ME cells. OBJECTIVE: The physiology of the middle ear (ME) is primarily concerned with keeping the cavities fluid-free, to allow transmission of sound vibrations from the eardrum to the inner ear. ME epithelial cells are thought to play a key role in this process as they actively absorb sodium and water in order to clear any excess fluid present in the cavities. MATERIAL AND METHODS: As an air-liquid interface (ALI) model has been shown to improve differentiation and enhance sodium absorption in other respiratory epithelia, we established an ALI model for ME cells. RESULTS: ME cells cultured under ALI conditions exhibited a fourfold increase in sodium absorption, which was not related to either a metabolic effect or to enhanced morphological differentiation, but instead to an increase in expression of the alpha-subunit of the epithelial sodium channel (alpha-ENaC).

Absorption↗
PubMed2004

A simple technique for removal of the gallbladder during microlaparoscopic cholecystectomy.

With the advent of mini-instruments, laparoscopic cholecystectomies have been performed with two or three trocars instead of the standard four ports. However, removal of the gallbladder is a difficult aspect with these microlaparoscopic techniques. To remove the gallbladder through the 11-mm umbilical port, a 5-mm telescope should be used. However this telescope is not always available. Other techniques are suitable only for patients with limited or no inflammation of the gallbladder. An efficient, simple, and inexpensive technique is described that allows removal of the gallbladder through an 11-mm trocar without the need for a 5-mm telescope. It permits removal of the specimen in acute suppurative or thick-wall cholecystitis independently of the technique used.

Cholecystectomy, Laparoscopic↗
PubMed2004

Pseudo real-time method for monitoring of the limiting anisotropy in membranes.

Data acquisition and analysis of the time-resolved fluorescence anisotropy is typically a time consuming process preventing usage of this experimental method for monitoring of time-dependent phenomena. We describe a method for pseudo real-time monitoring of the limiting fluorescence anisotropy r(infinity) allowing to track changes of the membrane order occurring on the time scale of minutes. Principle and performance of the method is demonstrated in the time domain with the time-correlated single photon counting detection. DMPC liposomes stained with 1,6-diphenyl-1,3,5-hexatriene (DPH) have been used to test influence of the diffusion membrane potential on the membrane order during the temperature-induced phase transition in DMPC membranes. It has been found that the transmembrane field of the order of -70 mV increases the phase transition temperature by about 1.5 degrees C-2 degrees C. It is proposed that the full advantage of the method can be utilized with a gated detection, which besides a faster data acquisition brings additional advantage of excitation light suppression. The method can be also used for imaging.

Dimyristoylphosphatidylcholine↗
PubMed2004

[Duration of induced seizures during selective pharyngeal brain cooling].

Whole body hypothermia can be used to treat the injured brain (e.g. after hypoxic events). Side effects include hemodynamic instability, coagulopathy and infection. Because of these side effects it appears reasonable to cool the brain selectively (selective brain cooling, SBC) without changing the core temperature. A new animal model was used to demonstrate SBC from the pharynx and to examine effects of SBC on the duration of pharmacologically induced seizure activity. Sprague-Dawley rats (n=18, 12 successful experiments) were sedated and mechanically ventilated. Invasive blood pressure monitoring was instituted and blood gases were drawn to evaluate the arterial blood gas status. Electrical brain activity was recorded using a microneedle in the extracellular compartment of the rat brain cortex. Cooled water was circulated through a small tubing into and out of the pharynx of the animals. The cortical as well as the rectal temperature were recorded. After the injection of a single dose of bicuculline (1 mg/kg i.v.) per animal the duration of the induced seizure activity was measured and compared with the temperature prior to the induction of seizure activity. The cortical blood flow (CBF) was detected using intra tissue Doppler signals in the rat cortex in the same location as the EP-study. The influence of a brain temperature reduction between 36.5 degrees to 31.5 degrees C on the seizure duration was examined. There was a positive correlation between the seizure duration and the cortical temperature (r=0.64). Also the CBF was increased during seizure activity (p=0.02) and the increase correlated weakly with cortical temperature (r=0.18). The core temperature remained in the normothermic range (36.9+/-0.7 degrees C) Conclusion: The duration of induced seizures correlates with local brain temperature. In the future further studies should examine the efficiency of induced (selective) brain cooling to treat prolonged seizure activity.

Animals↗
PubMed2003

Breast cancer and serum organochlorine residues.

BACKGROUND: Controversy still exists about the breast carcinogenic properties in humans of environmental xenoestrogens (organochlorines), justifying new investigations. AIMS: To compare the blood levels of total dichlorodiphenyltrichloroethane (DDT) and hexachlorobenzene (HCB) in samples collected at the time of breast cancer discovery, in order to avoid the potential consequences of body weight change (after chemotherapy or radiotherapy) on the pesticide residue levels. METHODS: Blood levels of HCB and total DDT (we calculated total DDT concentrations by adding all DDT and DDE isomers) were compared in 159 women with breast cancer and 250 presumably healthy controls. Risk of breast cancer associated with organochlorine concentration was evaluated. RESULTS: Mean levels of total DDT and HCB were significantly higher for breast cancer patients than for controls. No differences in serum levels of total DDT or HCB were found between oestrogen receptor positive and oestrogen receptor negative patients with breast cancer. CONCLUSIONS: These results add to the growing evidence that certain persistent pollutants may occur in higher concentrations in blood samples from breast cancer patients than controls.

Breast Neoplasms↗
PubMed2003

[Selective pharyngeal brain cooling].

Whole-body cooling can be used in the treatment of various brain pathologies, for example, after hypoxic events. Potential complications include haemodynamic instability, coagulation disorders and infection. Selective brain cooling (SBC) would therefore appear to make good sense. In an animal model a new approach to SBC was therefore evaluated. A rat weighing 350 g was sedated with alpha-chloralose (40 mg/kg/h) and d-tubocurarine (4.05 mg/kg/h), mechanically ventilated and placed on a heating pad. A thermocouple was introduced into the somatosensory cortex to a depth of 2.5 mm. SBC was achieved using a novel approach: PTFE tubing (ID 100 microns) with an inlet and an outlet was wrapped around and glued to a piece of wood, and introduced non traumatically into the pharynx. The tubing was perfused with cold water (+4 degrees C). Under SBC the cortical temperature dropped from 38.4 degrees C to 27.7 degrees C while the core temperature remained stable. In an animal model SBC was successfully accomplished via the pharynx. Further studies should now be done to evaluate the effectiveness of this approach in larger animals with potentially different anatomical features.

Animals↗
PubMed2003

[Endoscopic resection of the frontal sinus floor following the Draf procedure: long term results and therapeutic algorithm].

OBJECTIVES: Endoscopic resection of the frontal sinus floor is a minimally invasive and functional surgical procedure designed for the treatment of inflammatory sinus diseases, which avoids the side-effects of external osteoplastic obliteration. The aim of the study was to evaluate long term results and to determine computed tomographic criteria predictive of success. PATIENTS AND METHODS: Our study reports the results of 20 patients operated for nasofrontal stenosis associated or not with osteitis or secondary mucocele. RESULTS: A successful result was obtained in 90% with a mean follow-up of 3.5 years. Failures (2) were attributed to insufficient resection and to frontal sinus osteogenesis. CONCLUSION: Endoscopic frontal sinusotomy is a safe and effective procedure for large sinuses with large distance between nasion and cribriform plate, but not in case of osteogenesis and multiple mucoceles. In case of unfavourable anatomy, or for the aforementioned pathologies, the obliteration procedure should be preferred.

Adolescent↗
PubMed2003

[Benefits and limitations of mammography].

The literature on screening mammography provides ample opportunity for doubt (the sceptics) and dogma (the screening zealots), and can be interpreted to prove both benefit and harm. The benefit of mammography screening, if any, is modest and the balance between beneficial (potentially, a 20% relative reduction in breast cancer mortality with no significant benefit on all-cause mortality) and harmful (physical and psychological morbidity related to the 15-40% missed cancers and the 80-90% false-positive diagnoses) effects is still delicate. The mammogram alone is a modest weapon. Concurrent clinical breast examination is mandatory. Women that are concerned about breast cancer should be fully informed of the potential benefits and risks of screening mammography. These women should benefit from mammography with concurrent clinical breast examination, and possible whole-breast ultrasound in heterogeneously dense and extremely dense breast patterns.

Age Factors↗
PubMed2002

Fractal characterization of complexity in temporal physiological signals.

This review first gives an overview on the concept of fractal geometry with definitions and explanations of the most fundamental properties of fractal structures and processes like self-similarity, power law scaling relationship, scale invariance, scaling range and fractal dimensions. Having laid down the grounds of the basics in terminology and mathematical formalism, the authors systematically introduce the concept and methods of monofractal time series analysis. They argue that fractal time series analysis cannot be done in a conscious, reliable manner without having a model capable of capturing the essential features of physiological signals with regard to their fractal analysis. They advocate the use of a simple, yet adequate, dichotomous model of fractional Gaussian noise (fGn) and fractional Brownian motion (fBm). They demonstrate the importance of incorporating a step of signal classification according to the fGn/fBm model prior to fractal analysis by showing that missing out on signal class can result in completely meaningless fractal estimates. Limitation and precision of various fractal tools are thoroughly described and discussed using results of numerical experiments on ideal monofractal signals. Steps of a reliable fractal analysis are explained. Finally, the main applications of fractal time series analysis in biomedical research are reviewed and critically evaluated.

Algorithms↗
PubMed2002

[Is sudden sensorineural hearing loss a therapeutic emergency? Early results in a prospective cohort of 136 patients].

Idiopathic sudden sensorineural hearing loss is one of the most controversial issues in otology. A prospective cohort study including 136 sudden hearing losses seen at the ENT emergency referral center of Lariboisiere Hospital during an 18-month period was conducted. Patients were hospitalized and a corticotherapy course was administered, eventually associated with an antiviral treatment, low molecular weight dextran or sedative. At the end of the 5-day hospitalization, 74% of the patients had recovered, at least partially, with a mean gain of 22 dB. The outcome was considered satisfactory, i.e. superior to 50% of the initial loss, in 30% of the patients. After 1 month, 86% of the patients recovered at least partially with a mean gain of 30 dB. The outcome was considered satisfactory in 44% of the patients. A prognosis analysis showed that vertigo, age of the patient and anacusis are pejorative factors. Ascending audiogram shapes seem to involve a better prognosis. The therapeutic delay is not correlated with the quality of the outcome, which questions the classical notion of therapeutic emergency.

Adrenal Cortex Hormones↗