Reduction of the onset response in kilohertz frequency alternating current nerve block with amplitude ramps from non-zero amplitudes.

BACKGROUND: Kilohertz frequency alternating current (KHFAC) waveforms reversibly block conduction in mammalian peripheral nerves. The initiation of the KHFAC produces nerve activation, called the onset response, before complete block occurs. An amplitude ramp, starting from zero amplitude, is ineffective in eliminating this onset activity. We postulated that initiating the ramp from a non-zero amplitude would produce a different effect on the onset. METHODS: Experiments were conducted in an in vivo rat model. KHFAC was applied at supra block threshold amplitudes and then reduced to a lower sub block amplitude (25, 50, 75 and 90% of the block threshold amplitude). The amplitude was then increased again to the original supra block threshold amplitude with an amplitude ramp. This ramp time was varied for each of the amplitude levels tested. RESULTS: The amplitude ramp was successful in eliminating a second onset. This was always possible for the ramps up from 75 and 90% block threshold amplitude, usually from 50% but never from 25% of the block threshold amplitude. CONCLUSIONS: This maneuver can potentially be used to initiate complete nerve block, transition to partial block and then resume complete block without producing further onset responses.

Relating surface roughness and magnetic domain structure to giant magneto-impedance of Co-rich melt-extracted microwires.

Understanding the relationship between the surface conditions and giant magneto-impedance (GMI) in Co-rich melt-extracted microwires is key to optimizing their magnetic responses for magnetic sensor applications. The surface magnetic domain structure (SMDS) parameters of ~45 µm diameter Co69.25Fe4.25Si13B13.5-xZrx (x = 0, 1, 2, 3) microwires, including the magnetic domain period (d) and surface roughness (Rq) as extracted from the magnetic force microscopy (MFM) images, have been correlated with GMI in the range 1-1000 MHz. It was found that substitution of B with 1 at. % Zr increased d of the base alloy from 729 to 740 nm while retaining Rq from ~1 nm to ~3 nm. A tremendous impact on the GMI ratio was found, increasing the ratio from ~360% to ~490% at an operating frequency of 40 MHz. Further substitution with Zr decreased the high frequency GMI ratio, which can be understood by the significant increase in surface roughness evident by force microscopy. This study demonstrates the application of the domain period and surface roughness found by force microscopy to the interpretation of the GMI in Co-rich microwires.

Fate of sympathetic trunk ganglia after cutting in German meat plants.

To minimize risks from pathogenic prion proteins, particular tissues from bovines and other ruminants have been declared specified risk materials (SRMs), which are required to be removed from the food chain. However, in particular for the sympathetic trunk (ST) as a part of the autonomous nervous system (ANS), which represents a potential transfer route for abnormal prion proteins (PrP(Sc)), this is not the case. Consequently, its destination during cutting procedures deserves attention. In this survey, the handling of the ST in beef cutting plants was recorded during ongoing work. To ease these observations, the ST was separated into five parts, and eight destinations for cuts were identified. By means of an observation sheet, the destination of the respective tissue was recorded. About one-third of the ST went into human consumption, another one-third was disposed of as SRMs, and the last one-third was used for nonfood purposes or disposed of. The rear thoracic and sacral ganglia primarily remained naturally connected to the bones going as SRMs. The stellate, front thoracic, and lumbar ganglia went in a different percent into the food chain. Frequently, workers in the same plant decided differently, even from case to case, on the destination of the tissue, which indicates a lack of standardization.

Autonomous nervous system with respect to dressing of cattle carcasses and its probable role in transfer of PrP(res) molecules.

Pathogen prions are widely recognized as the causative agent in bovine spongiform encephalopathy (BSE) and other transmissible spongiform encephalopathies. However, more research on the possible transmission mutes of this agent once it has reached the host is needed. There is evidence based on the anatomy and physiology of the autonomous nervous system (ANS), as well as observations for different animal species, that the ANS might be involved in the axonal drainage of pathogen prions toward the central nervous system. In this context, more attention should be paid to the cranial cervical ganglion, the stellate ganglion, the chain of paravertebral ganglia next to the first six thoracic vertebrae, the chain of the paravertebral ganglia next to loin vertebrae 1 through 6, the vagus nerve in the neck region and in the mediastine, and the esophagus (because of its close connection to the vagus nerve). For a more detailed risk analysis with respect to these tissues, the ANSs of animals having shown clinical signs of BSE might be examined to corroborate the evidence presented here. In the meantime, as a precautionary measure, the tissue addressed should be taken out of the human food chain, taken out of animal feed, and handled as if it were specified risk material. It is technically possible to remove these parts during cutting and dressing.

Impacts of soil faunal community composition on model grassland ecosystems.

Human impacts, including global change, may alter the composition of soil faunal communities, but consequences for ecosystem functioning are poorly understood. We constructed model grassland systems in the Ecotron controlled environment facility and manipulated soil community composition through assemblages of different animal body sizes. Plant community composition, microbial and root biomass, decomposition rate, and mycorrhizal colonization were all markedly affected. However, two key ecosystem processes, aboveground net primary productivity and net ecosystem productivity, were surprisingly resistant to these changes. We hypothesize that positive and negative faunal-mediated effects in soil communities cancel each other out, causing no net ecosystem effects.

[Technical construction, calibration and results with a new intraocular pressure sensor with telemetric transmission]. / Technischer Aufbau, Kalibrierung und Ergebnisse mit einem neuen intraokularen Drucksensor mit telemetrischer Ubertragung.

BACKGROUND: Presently intraocular pressure is measured indirectly by applanation or impression of the cornea. Only isolated values are available with this method. We present a new implantable system for direct and continuos measurement of the intraocular pressure. METHODS: An implantable system consisting of a miniaturized sensor and a telemetric unit was integrated in an intraocular lens. The eye pressure is determined by the sensor, modulated and transduced by the telemetric system. By an extracorporal receiver the signal is demodulated. The electric supply of the intraocular system is achieved by external electromagnetic induction. RESULTS: The telemetric transmission of the intraocular pressure can be achieved with an accuracy of +/- 1 mm Hg and a frequency of registration of 3 values per second. CONCLUSION: Clinical application necessitates further animal trials in vivo.

The Royal Women's Hospital Family Birth Centre: the first 10 years reviewed.

In reviewing the first 10 years experience of the Royal Women's Hospital Family Birth Centre (FBC), we examined the outcomes of pregnancy and labour in a group of women who requested alternative birthing care and who were identified antenatally as being a 'low-risk' population. This study is a retrospective analysis of 5,365 women booked with the birth centre between 1980 and 1989. Over 16% of women developed antenatal complications precluding further care there, while a further 16% developed complications in labour requiring transfer out to conventional labour wards. Thus 67% of those originally booked delivered in the FBC. The instrumental delivery rate was 11%, and the Caesarean section rate was 4%. Of the women who delivered in the FBC, 3.1% had a postpartum haemorrhage and 1.8% required manual removal of placenta. Approximately 4% of babies born in the FBC required some resuscitation, and 0.8% needed admission to the neonatal nursery. Two perinatal deaths occurred in women admitted in labour to the FBC with a live baby, whilst 2 other women presented in labour with a fetal death in utero (perinatal mortality 0.89 per 1,000).

Family births at the Royal Women's Hospital, Melbourne.

A controlled study comparing clinical aspects of birthing unit confinement with orthodox obstetric care in a major obstetric hospital is detailed. The results confirm that this centre provides an acceptable and safe alternative for those who desire such an environment.

The relationship between gestational age and birth-weight in twin pregnancy.

Analysis is made of fetal growth in 563 twin pregnancies. The birth-weight of a twin is affected by the duration of pregnancy and zygosity. Intrauterine growth and weight is the same as a singleton pregnancy up to a gestational age of 32 weeks. After this stage fetal growth slows markedly. The growth curves of both twins are similar with an increasing tendency towards growth retardation in twin 2 after 39 weeks' gestation. Intrauterine growth retardation, as represented by the 10th percentile line, for twin 1 joins 1,094g at 31 weeks, 1,836g at 36 weeks and 2,428g at 40 weeks' gestation. The corresponding figures for twin 2 are 1,131g, 1,875g and 2,337g respectively.

Betamethasone, albuterol, and threatened premature delivery: benefits and risks. Study of 469 pregnancies.

This report details the outcome of pregnancy in 469 patients admitted before 34 weeks' gestation with premature labor with intact membranes (253 patients) or premature rupture of the membranes (PROM) but no labor (216 patients). Betamethasone significantly reduced the incidence of severe respiratory distress syndrome (RDS) both in patients with intact membranes and in those with PROM. PROM had a significant beneficial effect on the incidence of RDS in both groups of patients, those who had received betamethasone and those who had not. Fetal sex did not significantly influence the respiratory response to either PROM or betamethasone administration, except that betamethasone treated female fetuses showed a significantly better response to PROM than similarly treated males. Except in patients with PROM associated with a cervical suture, betamethasone administration did not increase the risk of perinatal or maternal infection.

Premature rupture of the membranes, oligohydramnios and pulmonary hypoplasia.

The clinical and pathological features of oligohydramnios associated with severe pulmonary hypoplasia are described in 10 infants without renal anomalies. In 8 patients the condition was associated with prolonged premature rupture of the membranes at 16 and 36 weeks of gestation in a study of 244 patients (3.3%). Seven of the infants died of respiratory failure within 24 hours of delivery; the other infant survived. In the remaining 2 patients with severe oligohydramnios at term, but unassociated with premature rupture of the membranes, both infants succumbed. Problems with resuscitation should be anticipated in pregnancies complicated by prolonged leakage of amniotic fluid or oligohydramnios, and pulmonary hypoplasia should be recognized as a cause of respiratory distress. Apart from the ultrasonic predelivery confirmation of normal kidneys to exclude Potter's syndrome it is recommended that ultrasonic assessment of thoracic cage volume should be made before delivery.

Premature rupture of the membranes.

In a consecutive series of 93 patients with premature rupture of the membranes at 20 to 34 weeks of gestation, the perinatal mortality was 23.7%. One-quater of the deaths were due to lethal congenital abnormalities, 18% were due to intrauterine infection, and 36% resulted from severe respiratory distress syndrome (RDS). Corticosteroid therapy increased the risk of incompetence, and did not reduce the incidence or severity of RDS. Almost one-third of the patients were delivered within 48 hours of membrane rupture; however, short-term treatment with salbutamol was able to delay the delivery for at least six days in 5 of the 13 patients to whom it was given. As postponement of delivery for days or weeks after the membranes have ruptured reduces the incidence and severity of Rds, this therapy may well have a place in the treatment of this condition.

Premature labour.

Intravenously administered salbutamol inhibited premature labour for at least 48 hours in 49 of 76 patients (64%), but was more effective (89%) when the cervical dilatation was less than 2 cm, and no apparent cause for the premature labour was evident. Even when premature labour complicated multiple pregnancy, hydramnios, or followed a small antepartum haemorrhage, suppression of labour could often be achieved for at least 48 hours, thus following the administration of betamethasone or the transfer of the patient to a hospital with intensive care facilities for both mother and child. Treatment with betamethasone, in addition to salbutamol, was associated with a less severe form of respiratory distress syndrome, and did not increase the risk of maternal or fetal infection, except in patients with cervical incompetence when 46.2% of such patients were infected.

Water intoxication and Syntocinon infusion.

A case of severe water intoxication with convulsion and prolonged coma, following the use of a high dose Syntocinon infusion is described. The pathogenesis and treatment of the condition are discussed.