Development of a miniaturepCO2 electrode for biomedical applications

A miniaturepCO₂ electrode for possible CO₂ measurement in a biological system was constructed and evaluated. ThepCO₂ electrode employed a miniature pH glass electrode and the Severinghaus configuration. The electrode was evaluated in both gas and liquid phases. A good linear relation existed between the measured electrode potential of thepCO₂ electrode and the logarithm of the CO₂ concentration at 20°C in both gas and liquid phases. The temperature dependence of the electrode over the temperature range of 20–60°C was evaluated. From 20 to 40°C, a change of CO₂ of 0·15%/°C at a CO₂ level of 9·6 mole% was observed. The response time,pCO₂ and temperature-hysteresis effects, and long-term stability of thepCO₂ electrode were also investigated and discussed.     

Optimum electrode configuration for detection of arm movement using bio-impedance

A four-channel impedance measurement system, including a two-channel goniometer, to analyse human arm movement, was constructed. Impedances and joint angles were simultaneously measured for wrist and elbow movements. As the impedance changes resulting from wrist and elbow movements depended heavily on electrode placement, the optimum electrode configurations for those movements were determined by searching for high correlation coefficients, large impedance changes and minimum interferences in ten subjects (age: 29±6 years). The optimum electrode configurations showed very strong relationships between the wrist joint elbow joint angle and upper arm impedance (correlation coefficient=−0.97±0.03). Although the measured impedance changes of the wrist (1.1±1.5Ω) and elbow (−5.0±2.9Ω) varied between individuals, the reproducibilities of wrist and elbow impedance changes of five subjects were 5.8±1.8% and 4.6±1.4% for the optimum electrode pairs, respectively. It is proposed that this optimum electrode configuration would be useful for future studies involving the accurate measurement of arm movements by the impedance method.     

Development of a model system for evaluation of human endothelial cell proliferationin Vitro: Possible clinical applications

A system for evaluation of the ability of human blood serum to affect endothelial cell proliferation was developed and tested. The system based on incorporation of³H-thymidine into DNA was used to analyze the effects of hormone replacement therapy on endothelial repair and angiogenesis. Blood serum from 12 menopausal women less effectively activated endothelial proliferation compared to control donor serum. After 6-month hormone replacement therapy with Divina (a combination of estradiol and medroxyprogesterone), this index increased in seven female subjects (58.3%), but remained below the control level. The model proposed by us can be used in clinical practice and drug testing for evaluation of the influence of blood serum on vascular endothelium. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 129, No. 4, pp. 404–407, April, 2000     

An automatically balancing isolation amplifier for the decoupling of measuring systems with high impedances

Summary It is theoretically shown that different conditions of coupling and grounding cause error voltages with the simultaneous use of two high-impedance measuring systems (e.g. pH electrodes). By the use of special amplifiers using optical transmission systems these error voltages are prevented. The transmission characteristics of the couplers are sensitive to changes in temperature due to the incorporation of infrared emitters in the system. An amplifying equipment with high d. c. stability was developed. The temperature drift was suppressed by the use of a special chopper stabilisation.List of Symbols and Constants E _E potential of the galvanic element glass electrode - E _B potential of the galvanic element reference electrode - E _G boundary liquid-wall of the reservoirs - f _o switching frequency of the MOS FET-switches 300 Hz - j Gauss number (j ₂=–1) - K ₁ d. c. voltage gain of the amplifier (V ₁): 36 - K ₂ d. c. voltage gain of the optical transmission system: 0.1 - R _b resistance of the reference electrode - R _e resistance of the glass electrode - R _EE input resistance of the amplifier (input glass electrode): 10¹² - R _EB (input reference electrode): 10¹² - R _1–3,R _K 1–4 electrical resistances of the liquid between the electrodes and the wall of the reservoir - R _G ,R _G 1–2,T ₁ time constant of the operational amplifier (V ₁): 1.6 · 10^–4 s - T ₂ time constant of the optical transmission system: 3 · 10^–6 s - T time constant of the hold elements: 0.1 · 10^–6 s - (l) radian frequency: s^–1 - u(t) time function of the voltage - U complex function of the voltage     

Development of thermal energy storage materials for biomedical applications

Abstract

The phase change materials (PCMs) have been utilized widely for solar thermal energy storage (TES) devices. The quality of these materials to remain at a particular temperature during solid–liquid, liquid–solid phase transition can also be utilized for many biomedical applications as well and has been explored in recent past already. This study reports some novel PCMs developed by them, along with some existing PCMs, to be used for such biomedical applications. Interestingly, it was observed that the heating/cooling properties of these PCMs enhance the quality of a variety of biomedical applications with many advantages (non-electric, no risk of electric shock, easy to handle, easy to recharge thermally, long life, cheap and easily available, reusable) over existing applications. Results of the present study are quite interesting and exciting, opening a plethora of opportunities for more work on the subject, which require overlapping expertise of material scientists, biochemists and medical experts for broader social benefits.     

Evaluating the process of polishing borosilicate glass capillaries used for fabrication of in-vitro fertilization (iVF) micro-pipettes

In this paper we investigate a number of gas flames for fire polishing borosilicate glass capillaries used in the manufacturing of IVF micro-pipettes. Hydrofluoric acid (HF) was also used as an alternative to finish the pipette end. Glass micro tools in the IVF industry are drawn from hollow glass capillaries of diameter 1 mm. These capillaries are cut manually to a length of 100 mm from hollow glass rods resulting in sharp and chipped edges. These capillaries are held in a customised holder having padding of soft silicone or rubber. Sharp and uneven edges of these capillaries pick up particles of rubber or soft silicone shavings, rendering them ineffective for IVF treatments. The working range of borosilicate glass is 800–1,200°C. The experiments involved analysis of fire polishing process for borosilicate glass capillaries using candle, butane, propane, 2350 butane propane, oxyacetylene gas flames, finding the optimum distance of the capillary relative to the flame, optimum time for which the capillary should be held in the flame and optimum region of the flame which gives the required temperature range. The results show that 2350 butane propane gas mix is optimum for fire polishing of borosilicate glass capillaries. The paper is concluded by comparing the results of fire polishing with the results of acid polishing, in which HF of 1.6% concentration is used to etch the ends of the borosilicate glass pipettes.     

Evidence for outcrossing in Phytophthora sojae and linkage of a DNA marker to two avirulence genes

Two genetically different isolates of the homothallic Oomycete, Phytophthora sojae, were demonstrated to outcross and form hybrid oospores after co-culturing in vitro. Random amplified polymorphic DNA (RAPD) markers revealed ten hybrids among 354 oospores analysed. One F₁ hybrid was allowed to self fertilise and produce an F₂ population of 247 individuals. Among 53 F₂ individuals, selected at random, 18 polymorphic RAPD markers were observed to segregate at near 3:1 Mendelian ratios, consistent with segregation for dominant alleles at single loci. Segregation of virulence against soybean resistance genes Rps1a, 3a, and 5 revealed that the avirulence genes Avr1a, 3a and 5 were dominant to virulence. Avirulence against these three resistance genes appeared to be conditioned by one locus for Avr1a and two independent, complementary dominant loci for both Avr3a and Avr5. Segregation of virulence against Rps6 was in the ratio of 1:2:1 (avirulent:mixed reaction:virulent), suggesting a semi-dominant allele at a single locus. Two avirulence genes and one RAPD marker formed one linkage group, in the order Avr3a, OPH4-1, Avr5, each separated by approximately 5 cM. Our results confirm that outcrossing occurred between the parental isolates, and that sexual recombination under field conditions may play an important role in generating and maintaining genetic diversity in populations of P. sojae.     

Construction and performance of a new catheter-tip oxygen electrode

A membrane-covered catheter-tip oxygen-electrode system is described, which gives a linear response in the P_o2 range of 0–350 mm Hg. The system is highly stable, free from drift and mechanically safe for application in man. This is accomplished by using a screw cap for fastening the membrane holder, thus preventing the loss of parts and making the electrolyte chamber really fluidtight. Insulation of the platinum wire with glass precludes the possibility of fluid-bridge contact with the silver anode beyond the measuring site at the tip.     

In vivo measurement of carbon dioxide tension with a miniature electrode

A commercially available catheter type electrode with whichP _CO2 can be continuously measured in vivo and in vitro gave progressively less accurate results the longer the measuring period was extended. This proved to be due to temperature effects and a change in sensitivity with time. A correction procedure for these effects was developed which was based on two observations. 1. The relationship between temperature and the logarithm of the sensitivity of the electrodeamplifier combination was linear and virtually identical for 9 electrodes: 8% change in sensitivity for a deviation of 1° C from the temperature during calibration. 2. The change in sensitivity due to drift of the electrode output is approximately a logarithmic function of time: 1 h after calibration all electrodes exhibited a decreased sensitivity, varying between 0.3 and 16.7%. The drift effect can be dealt with by repeated calibrations, preferably at 1^1/2 h intervals.The adequacy of the correction procedure was assessed in in vivo measurements in cats and dogs. The meanP _CO2 difference between the in vivo measurement, corrected for temperature and drift, and samples analyzed with a conventional electrode, was 0.005 kPa (0.04 mm Hg) with a standard deviation of 0.187 kPa (1.39 mm Hg).     

Fabrication and characterization of oxygen-diffused titanium for biomedical applications

Although titanium has been successful as an orthopedic or dental implant material, performance problems still persist concerning implant–bone interfacial bonding strength. In this study a novel oxygen-diffused titanium (ODTi), fabricated by introducing oxygen into the titanium crystal lattice by thermal treatment, was investigated. The fabricated material is the result of a surface modification made on commercially pure titanium (cp Ti) previously coated with poly(vinyl alcohol) (PVA) by means of a thermal treatment performed at 700 °C in an ultra-pure argon atmosphere. The thermal treatment at 700 °C led to the formation of an anatase TiO₂ film on the cp Ti surface and a concentration gradient of oxygen into titanium. The surface of the fabricated ODTi consisted of an outer nanometric layer of anatase TiO₂ and an inner nanometric layer of Ti₂O_x (x < 1) in which the oxygen is in solid solution with the titanium metal. It was found that ODTi possesses in vitro apatite formation ability after being soaked into simulated body fluid (SBF) solution. This apatite formation ability is attributed to the presence of the anatase TiO₂ outermost surface layer and to abundant hydroxyl groups (–OH) formed on the ODTi surface after immersion in SBF.     

APCO2 surface electrode working on the principle of electrical conductivity

APCO₂ electrode working on the principle of electrical conductivity is described. The calibration curve can be linearized according to the formula . This linearity has been tested in thePCO₂ range of 0.93–9.33 kPa (7–70 Torr). For the experiments electrodes are used which have conductivity values of about 50 nS and drifts of maximally 5%/h at aPCO₂ of 5.33 kPa (40 Torr). The response time (T ₉₀) is about 20 s. The temperature sensitivity is 2.4 nS/1 K between 298K–310K. The standard error of the measurements is =0.33 nS. With these electrodes tissuePCO₂ can be measured on the surface of various organs.     

Effect of a peptide extract of fetal brain tissue on the intracellular pH of mouse peritoneal phagocytes

The intracellular pH (pH_i) of mouse peritoneal neutrophils, initially 0.2 U, drops after a 15-min incubation of these cells with a peptide extract of fetal brain tissue. Treatment with the preparation leads to appreciable changes in the distribution of neutrophils by the examined parameter. For macrophages, the acidifying effect of the agent and its effect on the pattern of cell distribution in terms of pH values are far less expressed. The effects of the agent in dilutions 1∶10² and 1∶10⁴ on the mean pH_i are virtually the same. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 12, pp. 626–630, December, 1995 Presented by V. I. Kulakov, Member of the Russian Academy of Medical Sciences     

Body surface potential mapping system equipped with a microprocessor for the dynamic observation of potential patterns

A body surface potential mapping system equipped with a microprocessor has been developed. It enables high-speed real-time and simultaneous observation of e.c.g. data of 96 lead points in a character display mode. The machine has functions not only to perform basic data processing such as baseline correction and linear interpolation for malfunctioned electrodes but also to generate an isopotential contour map, record data onto a floppy disc, make hard copies of displayed patterns and characters, etc. To increase the operation speed, all the assembler programs were put in one module. Thus, an operator can easily recognise the spatial motion pattern of the body surface potential map and, in addition, find malfunctioned channels by observing the pattern. A belt type electrode system allows quick and adaptable attachment. The practical usefulness of the system has been proved with the co-operation of cardiologists with over 120 cases of cardiac disease.