A 0, 1 nanoliter glass capillary electrode

Summary The production and use of a glass microelectrode is described. This electrode can be used to measure pH and sodium concentration in sample volumes as small as 0.1 nl.Supported by the Deutsche Forschungsgemeinschaft.     

A versatile and reproducibly operating microelectrode puller

A microelectrode puller is described with the following properties: reproducibility of pulling; easy adjusting procedure; the possibility of shaping the electrode; and the possibility of intermittent pulling of different types of electrodes. These properties are obtained by: a well phased pulling scheme; nearly frictionless moving parts; symmetrical and vertical pulling; and fully electronic switching.     

A method for single unit recording from the free-moving cat

An implanted microelectrode technique for recording unit activities from the free-moving cat is described. Stainless steel insect pins electrically sharpened to about 10 μ tip, insulated, are soldered to about 10 cm long lead-off wire. After the electrodes are inserted to predetermined regions in the brain, their lead wires are soldered to a modified 9-pin miniature socket. The electrodes, lead wires and socket were then cemented to the skull with acrylic resin. The socket was fitted to 9-pin miniature plug which contained an input FET stage. We could selectively connect it with one of 8 leads from implanted microelectrodes. The input probe was separated from the main amplifier chassis, the connection made by about 50 cm long flexible lead wires so that the animal could move about freely. This input probe greatly reduced the artifact due to animal movement. The device could thus be used for unit recording from operantly behaving cats.     

A simple circuit for filtering single unit action potentials from electrograms

A circuit is described which is able to select single motor unit action potentials from an interference pattern. The differentiator circuit produces its effect in 2 ways: by selecting only those action potentials of fast rise-time, it reduces the number of action potentials in the record; by producing an output of short-duration pulses, the probability of superposition is reduced.     

The preparation and control of reversal movements as a single unit of action

Previous research has demonstrated that movement time and kinematic properties of limb trajectories to the first target of a two-target reversal movement differ to that of single-target responses. In the present study we investigated whether two-target reversal movements are organized as a single unit of action or two separate components by perturbing the number of targets prior to and during movement execution. In one experiment, participants performed single-target movements and on one-third of the trials a second target was presented either at target presentation, movement onset or peak velocity. On those trials in which a second target was presented, participants were required to complete their movement to the first target and then move to the second target. In a second experiment, the reverse was the case with participants performing two-target movements that changed to single-target movement on one-third of the trials. A two-target movement time advantage was observed only when the required response was specified prior to movement initiation. Also, participants failed to prevent movement towards the second target when the requirements of the task changed from a two-target to single-target response at movement onset or later. These results indicate that two-target reversal movements were organized as a single unit of action prior to response initiation.     

A technique for recording local blood flow and neuronal activity with a single microelectrode

A technique is presented for recording both local blood flow, by means of hydrogen clearance method, and neuronal activity of the cat's cortex using a single microelectrode. The requirements of electrodes for recording cerebral blood flow are different from those for recording extracellular spikes. Only electrodes within a small range of impedance (measured at 10 Hz) are suitable to record both. A bridge method is used for the recordings. The bridge signal is split in order to amplify cell activities and H2 responses separately. Three examples demonstrate the method and the importance of appropriately selected electrodes.     

Changes in the interstitial pH of dog myocardium in response to local ischemia,hypoxia, hyper- and hypocapnia,measured continuously by means of glass microelectrodes

Summary In open-chest dogs the pH changes of the myocardial interstitium were measured during local ischemia, hypoxia, hyper- and hypocapnia. Microglasselectrodes (Corning 0150) were inserted into the wall of the left ventricle. Simultaneously we recorded the local myocardial blood flow, the arterial blood pressure, the heart rate and the expiratory CO₂ concentration. Local ischemia was produced by transient occlusion of the left descending coronary artery. In the ischemic region a decrease in pH occurred after 15–30 sec, the magnitude of which depended on the occlusion time, and on the extent of the ischemic region. When the occlusion time was short, the maximum decrease in pH was found after the release of blood flow. Mean values varied from about 0.1 pH (1 min occlusion) to 0.65 pH (30 min occlusion). After fibrillation the pH fell by 1.2 units (mean value) below the initial level. Hypoxia (10% for 5–13 min) was accompanied by an increase in pH by 0.05–0.1 units. After 2–3 min the pH reached a steady state or decreased again. After ventilation with sufficient O₂ concentration an acidotic overshoot occurred (0.03-0.1 pH). When shifts in the interstitial pH similar to those during ischemia and hypoxia were produced by varying the arterialpCO₂, no comparable changes in local blood flow and in the other parameters could be observed.Supported by the Deutsche Forschungsgemeinschaft.     

GABAergic control of rubral single unit activity during a reaction time task

Summary The activity of 61 rubral neurones was recorded in association with microinjections of GABA, muscimol, bicuculline-methiodide or saline, in cat Red Nucleus area, during the performance of a reaction time task. The depressing action of GABA and muscimol on the firing of most neurones (17/23) suggests that, in a behavioural situation, an inhibitory GABAergic control can be exerted on rubral neurones discharging with different patterns during the reaction time task. The motor slowing down induced by GABA and muscimol is in agreement with a general reduction of the rubral output. Injections of bicuculline, whose antagonistic effects on GABA transmission are well established in the Red Nucleus, had various consequences on the firing of rubral neurones: 1) the decreases of activity related to the reaction time task were never suppressed, suggesting that these task-related inactivations are probably not mediated by GABA A receptors; 2) an enhancement of the tonic and phasic discharges was found for 1/4 of the neurones (7/29), which were either activated or not modulated in relation to the reaction time task, suggesting that a sustained GABA A-mediated inhibition, blocked by bicuculline, could be exerted on these neurones; 3) a reduction of the tonic and phasic discharges was observed for other neurones (15/29), which were either activated, inactivated or not modulated in relation to the reaction time task, suggesting that the activity of these neurones could be controlled by inhibitory processes not mediated by GABA A receptors, possibly enhanced or released by bicuculline. The delay in motor triggering induced by bicuculline could be related to the disruption of the pattern or rubral output during the reaction time task, as a result of the opposite changes affecting the firing of rubral neurones. A well-balanced GABAergic activity appears to be critical in the control of rubral firing during the performance of the reaction time task.     

Extra- and intracellular hydrogen ion-selective microelectrode based on neutral carriers with extended pH response range in acid media

A series of new neutral hydrogen ion carriers suitable for application in H⁺-selective microelectrodes is presented. One carrier (ETH 1907) proves to be superior to tridodecylamine currently very much in use. Microelectrodes based on ETH 1907 in an optimized membrane composition exhibit a linear dynamic response function from pH 2 to 9 extended into the acidic range, a response time 5 s, and a resistance of about 35 G for a tip diameter of about 1 m. This makes the electrode suitable for measurements at normal physiological intracellular pH as well as in acid physiological media. Measurements using this microelectrode in proximal tubule cells of isolated perfused frog kidney are presented.     

Cerebral pulsation and single unit recording in the guinea pig's visual cortex

A technique is described for minimizing the difficulties caused by the cerebral pulsation in recording the single units in the guinea pig's visual cortex. This technique is particularly suitable for recording with glass microelectrodes.     

A parent as a vector of Salmonella brandenburg nosocomial infection in a neonatal intensive care unit

A newborn baby was admitted to the Neonatal Intensive Care Unit (NICU) of St Germain en Laye Hospital (France) because of premature birth. On day 12, he contracted gastroenteritis due to Salmonella brandenbourg . The salmonellosis led to a septic shock syndrome with a brief cardiopulmonary arrest. He was treated with intravenous ceftriaxone and gentamicin, and the evolution was favorable. Microbiological investigations revealed that the mother was the vector for this nosocomial infection. S. brandenbourg was isolated from the feces of the baby, despite recent recommendations on managing stool specimens from patients hospitalized for more than three days: according to these recommendations, these stools should be processed for viruses and Clostridium difficile toxin only.     

A method for the manufacture of single barrel liquid ion-selective microelectrodes: an in situ study of ant venom pH

A method for the manufacture of single barrel ion-sensitive microelectrodes, employing liquid ion-selective sensors, is described in detail. This method had proven reliable and repeatable for the manufacture of pH-sensitive microelectrodes using a liquid proton carrier. It is believed that this method has advantages over other published methods since it allows direct visualization and control of major steps during electrode fabrication and overcomes several problems often encountered using more conventional methods. Microelectrodes fabricated using this technique have been used to measure the in situ pH of venom from two myrmicine ants,Tetramorium caespitum (L.) andMyrmica ruginodis (N.).     

A method for recording unit neural activity in unanaesthetized sheep and goats

A chronic preparation has been made in horned sheep and goats for recording unit activity in unanaesthetized animals. The micro-electrode manipulator is supported by means of a metal bar permanently attached to the animal's horns. A perforated lucite block, implanted into the roof of the cranium, rendered a large part of the brain accessible for recording. A brief outline is given of the advantages of sheep and goats for experimental work on brain function and behavior.     

Thermal stress and physiological strain of children exposed to hot environments in a glass bangle factory

Summary A group of 19 male children (mean age 12.1 years SEM 1.6 years) occupationally exposed to an excessively hot environment for an average duration of 2.5 years SEM 1.7 years in the glass bangle factory in Firozabad, India, were studied to evaluate the physiological strain induced by the thermal radiation (mean radiant temperature 46.2° SEM 5.1° C) and high ambient temperature (38.2° SEM 3.4° C) prevailing in the factory. Over a work-shift the mean increase in oral temperature was 0.90° C in the exposed children, in comparison with the 0.40° C increase recorded in the control children (p<0.05). The maximum increase in oral temperature was recorded in ‘gulliwalas’ (0.90° C) and the minimum in ‘battiwalas’ (0.80° C). The mean peak value of oral temperature (37.5° C) was observed at 1600 hours. A significant increase in the pulse rate (25.9 beats·min⁻¹) during the work-shift was observed in the exposed children in comparison with a mean increase of 9.4 beats·min⁻¹ in the control group. Ventilatory studies showed pulmonary hyperventilation in the exposed workers. The increase in pulmonary ventilation was in the form of an increase in tidal volume and respiratory frequency induced by high environmental temperatures and thermal radiation. The cardio-respiratory responses showed physiological strain induced by the high ambient temperature and radiant heat prevailing in the glass bangle factory.     

Association of single nucleotide polymorphisms in interleukin 12 (IL-12A and -B) with asthma in a Chinese population

Increasing evidence has indicated that genetic variants may contribute to immune dysregulation and susceptibility to noninfectious inflammatory diseases. Cytokines, including interleukin 12 (IL-12), play a key role in the regulation of the immune system. The aim of this study was to investigate whether single nucleotide polymorphisms (SNP) in IL-12A and IL-12B were associated with asthma in a Chinese population. Genotype characteristics were determined in 197 asthma patients and 369 controls by the polymerase chain reaction-restriction fragment length polymorphism method and DNA sequencing assay. The genotype and allele frequencies of IL-12A rs568408 demonstrated significant differences between cases and controls (p < 0.001). The AC genotype of rs3212227 was associated with a significantly decreased risk of asthma compared with the AA genotype (p = 0.036). The subjects carrying combined genotypes (rs568408 AG and rs3212227 AC/CC) at both loci had a 2.05-fold increased asthma risk compared with those carrying all other genotypes (p = 0.001). In contrast, individuals carrying combined genotypes of rs568408 GG and rs3212227 AC/CC were associated with a significantly decreased risk of asthma compared with those carrying the combined genotypes of rs568408GG and rs3212227AA (p = 0.009). No significant difference was reported for rs2243115 between cases and controls. These results suggest that the SNPs in IL-12A rs568404 and IL-12B rs3212227 may individually and jointly contribute to the risk of asthma in a Chinese population.     

A functional single nucleotide polymorphism in promoter of ATM is associated with longevity

Although the ‘ataxia telangiectasia mutated’ (ATM) gene plays an important role in physiological processes, such as sensing DNA damage, reducing oxidative stress and protecting telomeres length, little information about ATM and longevity is available. Therefore, we aim to examine the association between genetic variants in promoter of ATM and longevity in Chinese Nonagenarians/Centenarians. Genotyping was performed in 789 long-lived individuals (LLIs) and 886 ethnically matched control subjects. A single nucleotide polymorphism (SNP, rs189037) in the promoter region of ATM gene was identified, and significant association between CT genotype and longevity was observed. Meanwhile, the SNP was able to affect expression of ATM mRNA by differentially binding to AP-2α. The CC genotype strongly bound to AP-2α, and the TT genotype showed less binding affinity to AP-2α. The AP-2α strongly repressed the reporter expression in the CC genotype and showed less repression of the TT genotype driving expression in vitro assay. Accordingly, TT genotype individuals had highest ATM mRNA expression, CT genotype individuals had moderate ATM mRNA expression, and the CC genotype individuals had the lowest ATM mRNA.     

A simple method for measuring oxygen uptake on a single breath basis

Summary A simple method for calculating breath by breath O₂ uptake by the conventional open circuit method is described. Each expiratory volume is collected in a collapsible bag (4 l capacity) surrounded by a rigid box connected to a spirometer. A system of tubes with two solenoid valves operated by a manual switch allows the collection of air into the bag, during expiration, and its emptying by a vacuum pump during inspiration, respectively. The sampling line of a fast responding O₂ and CO₂ analyzer, together with temperature and pressure probes are inserted into the tube connecting the bag to the vacuum. The expired volume is therefore recorded (by the spirometer output) during expiration and its composition analyzed during the immediately following inspiratory phase, thus allowing gas exchange measurements to be performed on each single breath. VO₂ measured by this method at steady state over periods of about 1 min yields substantially the same values as obtained by standard open circuit method (average ratio = 1.01). Ventilations up to 150 l/min (ATPS) and respiratory rates up to 60/min can be easily followed. The simplicity of VO₂ calculation, and the very limited dead space of the system (about 70 ml, downstream the expiratory valve), make this method particularly suitable for determining VO₂ kinetics at the onset and offset of exercise.     

Laser microdissection and pressure catapulting (LMPC) in paraffin sections mounted on glass slides. A methodological report

The technique of laser microdissection together with laser pressure catapulting (LMPC) is demonstrated in paraffin sections obtained from surgical specimens of brain tumors mounted on glass slides. A sufficient and precise application of microdissection techniques in tissue on glass slides is worthwhile, since it offers the possibility of a retrospective analysis of archived paraffin sections in histopathology. We could demonstrate a precise dissection of areas in tissues of different thicknesses (4 microm and 20 microm). Areas of tissue mounted directly on glass need to be dissected in a scanning mode in order to remove the total region in form of small tissue fragments row by row. This mode provided a precise microdissection of tissue areas of different sizes and shapes. A successful molecular biological analysis of the microdissected regions could be demonstrated. As an example for such an analysis, differential-PCR for detecting an amplification of the gene for the epidermal growth factor receptor (EGFR) was performed.