Use of a perfusion technique for measurements of respiratory activity in cultured cells

Summary A method for measuring respiratory activity in anchorage-dependent cultured cells has been developed. This method is based on a technique that permits the perfusion of standard plastic culture dishes with attached cells. Basal respiratory activities were studied in two continuous cell lines of neural origin, neuroblastoma C1300 clone 41A₃ and glioma 138MG. As compared to traditional measurements on detached cells, a fourfold increase in value was obtained. Investigations on membrane permeability suggested that the observed difference could be attributed to alterations in cell membrane integrity. Pretreatment with dibutyryl cyclic AMP, known to induce a morphological and biochemical differentiation in C1300 and 138MG cells, caused in both cell lines an enhanced respiration. This work was supported by grants from the National Swedish Board for Technical Development (grant 82-5025).     

Generation of optimum pseudorandom signals for respiratory impedance measurements

Spontaneous breathing may impair the reliability of forced oscillatory impedance estimates at low frequencies, especially when the oscillatory power is distributed among many frequency values. Since the amplitude of the external forcing is limited to avoid non-linearities, it is suggested that the total energy of a composite electrical signal driving the loudspeaker be maximized at a given amplitude by finding the optimum phase relationships of the signal components, and that the low-frequency components increase in energy at the expense of the less disturbed high-frequency region. In healthy children and adults and in obstructed patients, the coherences and the coefficients of variation of the respiratory system impedance (Z_rs) at 2 and 3 Hz were studied in the case of three test signals of 2–15 Hz bandwidth. Signals T1 and T2 had a flat power spectrum, whereas the components of T3 decreased sharply between 2 and 5 Hz; T1 was generated by simple random selection of phase angles, while optimization for maximum energy was done for T2 and T3. Optimization alone (T2) increased the reliability of the Z_rs estimates at all frequencies, whereas enhancement of the low-frequency power (T3) resulted in a radical improvement of the estimates at 2 and 3 Hz, without loss in reliability at higher frequencies.     

Isolation and respiratory measurements on a single large mitochondrion

Mitochondria ranging in size from 5–8 μm were produced by feeding Cuprizone to mice weaned at 17 days. A small piece of liver was disrupted and a single large mitochondrion isolated with a suction capillary and a micromanipulator and placed in a microchamber attached to a sensitive oxygen electrode. The mitochondrion showed a respiratory rate of 1.4 × 10^?10 μatoms 0/min and a respiratory ratio with and without ADP of 3.7 with succinate. The respiratory ratio is the same as that obtained with normal mitochondria measured in the same apparatus. The respiratory rate of a 7 μm mitochondrion is estimated to be 1.3 × 10^?4 μatoms 0/min/cm² of inner membrane surface area which is very similar to the rate of 0.7 × 10^?4 μatoms 0/min/cm² estimated for a normal mitochondrion.     

Use of a heat transfer analogy for a mathematical model of respiratory tract deposition

Mathematical models predicting the aerosol deposition in the respiratory tract are reviewed. Data in the literature indicated not only that the air flow in the trachea and major bronchi may not be laminar, but also that the entrance effect of the tube or airway has not been considered. A new approach to a mathematical model of respiratory tract deposition, based on the analogy of the heat and mass transfer, is discussed.     

Nonrebreathing valve system for small animal respiratory measurements.

Flow resistence, frequency response, and backflow characteristics of a nonrebreathing valve system applicable to measuring small animal respiratory volumes are described. Unidirectional valves, molded from liquid resin, were fitted into a modified Y tube for direct use on an endotracheal tube or face mask. Valve size and dead space volume can be scaled to fit several small animal species. In this system, valve resistance was 2.0 and 5.6 mm of water for steady flow rates of 0.5 and 3.0 1/min, respectively.     

Use of personal protective equipment for respiratory protection

Management of hazards in biomedical research facilities requires the application of the traditional industrial hygiene responsibilities of anticipation, recognition, evaluation, and control to characterize the work environment, evaluate tasks and equipment, identify hazards, define exposure groups, and recommend controls. Generally, the diversity and unique characteristics of hazards faced by laboratory and animal facility employees and the short-term and low-level nature of the exposures factor into the selection of proper exposure control measures in the laboratory. The proper selection of control measures is based on a hierarchy of elimination and minimization by engineering controls, followed last by personal protective equipment when exposures cannot be eliminated. Once it is decided that personal protective equipment is needed, specific regulations and guidelines define safety standards for research facilities, including the elements of a sound respiratory protection program. These elements include respirator selection (including appropriate protection factors), medical evaluation, fit testing, training, inspection, maintenance and care, quality, quantity and flow of breathing air, and routine and emergency use procedures.     

Temperature as a predictive tool for plantar triaxial loading

Diabetic foot ulcers are caused by moderate repetitive plantar stresses in the presence of peripheral neuropathy. In severe cases, the development of these foot ulcers can lead to lower extremity amputations. Plantar pressure measurements have been considered a capable predictor of ulceration sites in the past, but some investigations have pointed out inconsistencies when solely relying on this method. The other component of ground reaction forces/stresses, shear, has been understudied due to a lack of adequate equipment. Recent articles reported the potential clinical significance of shear in diabetic ulcer etiology. With the lack of adequate tools, plantar temperature has been used as an alternative method for determining plantar triaxial loading and/or shear. However, this method has not been previously validated. The purpose of this study was to analyze the potential association between exercise-induced plantar temperature increase and plantar stresses. Thirteen healthy individuals walked on a treadmill for 10 minutes at 3.2 km/h. Pre and post-exercise temperature profiles were obtained with a thermal camera. Plantar triaxial stresses were quantified with a custom-built stress plate. A statistically significant correlation was observed between peak shear stress (PSS) and temperature increase (r=0.78), but not between peak resultant stress (PRS) and temperature increase (r=0.46). Plantar temperature increase could predict the location of PSS and PRS in 23% and 39% of the subjects, respectively. Only a moderate linear relationship was established between triaxial plantar stresses and walking-induced temperature increase. Future research will investigate the value of nonlinear models in predicting plantar loading through foot temperature.     

Use of prodigiozan for preventing acute respiratory viral diseases in a children's collective]

The epidemiological efficacy of 0.02 per cent solution of prodigiosan, a bacterial polysaccharide was used for the treatment of children in an area with acute respiratory infections, such as influenza and parainfluenza. The drug was administered intranasally by means of a dosing sprayer in the amounts of 0.2 ml once in 4 days for 4 months. Among the children treated with prodigiosan the rate of the acute respiratory viral infections was 2 times lower and the average duration of the disease was 2.4 times lower as compared to the control group. After 4 months of the drug use the average value of the "skin autoflora" test was much lower than that in the control group which testified to an increase in the non-specific immunobiological reactivity of the children under the effect of prodigiosan.     

Use of spot measurements for assessing residential ELF magnetic field exposure: a validity study

The purpose of this study was to evaluate residential short term "spot" measurements as surrogates for long term personal magnetic field (MF) exposure. In an epidemiological study on birth weight and pregnancy delay, MF exposure was assessed by taking five spot measurements in each room. For a subsample of 30 subjects 24 h personal MF measurements were made, and the following exposure metrics were calculated: 24 h arithmetic mean, 24 h median, percentage of time above 0.15 microT, and percentage of time above 0.29 microT. The 24 h exposure metrics were used as gold standards, when evaluating the validity of various summary measures calculated from spot measurements for assessing personal exposure. Based on Spearman correlation coefficient (r), specificity and sensitivity, the average of the spot measurements of a residence resulted in least exposure measurement error (misclassification). Also the above bed spot value correlated better with the 24 h metrics than any room average. Spot measurements performed about equally well in predicting different types of exposure metrics.     

The osmotic magnetometer: a new model for magnetite-based magnetoreceptors in animals

Homing pigeons and migratory birds are well known examples for animals that use the geomagnetic field for their orientation. Yet, neither the underlying receptor mechanism nor the magnetoreceptor itself is known. Recently, an innervated structure containing clusters of magnetite nanocrystals was identified in the upper beak skin of the homing pigeon. Here we show theoretically that such a cluster has a magnetic-field-dependent shape, even in fields as weak as the Earth's magnetic field; by converting magnetic stimuli into mechanical strain, the clusters can be assumed as primary units of magnetoperception in homing pigeons. Since the orientation of the strain ellipsoid indicates the direction of the external magnetic field, a cluster of magnetite nanocrystals also has the potential to serve as the basis of the so-called inclination compass of migratory birds. It is quantitatively demonstrated that the magnetic-field-induced shape change of a cluster can be amplified as well as counterbalanced by means of osmotic pressure regulation, which offers an elegant possibility to determine the magnetic field strength just by measuring changes in concentration. Received: 18 May 1998 / Revised version: 11 February 1999 / Accepted: 11 February 1999     

Use of liposomes for correction of respiratory hypoxia in experimental pneumonia

White laboratory rats, weighted 100-160 g, with acute pneumonia, inhale (from 4-th to 8-th days of developing the disease) liposomes. It was shown, that introduction of liposomes promoted normalization of external breath, acid-base state of blood, increased diffusion ability of lung for O2 and decreased arterial hypoxia. It was noted, that liposomes are an effective antihypoxant, inhibited the process of lipid peroxidation and, evidently, the destruction of cell membranes.