Identification and characterization of visual pigments in caecilians (Amphibia: Gymnophiona), an order of limbless vertebrates with rudimentary eyes

In comparison with the other amphibian orders, the Anura (frogs) and Urodela (salamanders), knowledge of the visual system of the snake-like Gymnophiona (caecilians) is relatively sparse. Most caecilians are fossorial with, as far as is known any surface activity occurring mainly at night. They have relatively small, poorly developed eyes and might be expected to possess detectable changes in the spectral sensitivity of their visual pigments. Microspectrophotometry was used to determine the spectral sensitivities of the photoreceptors in three species of caecilian, Rhinatrema bivittatum, Geotrypetes seraphini and Typhlonectes natans. Only rod opsin visual pigment, which may be associated with scotopic (dim light) vision when accompanied by other 'rod-specific' components of the phototransduction cascade, was found to be present. Opsin sequences were obtained from the eyes of two species of caecilian, Ichthyophis cf. kohtaoensis and T. natans. These rod opsins were regenerated in vitro with 11-cis retinal to give pigments with spectral sensitivity peaks close to 500 nm. No evidence for cone photoreception, associated with diurnal and colour vision, was detected using molecular and physiological methods. Additionally, visual pigments are short-wavelength shifted in terms of the maximum absorption of light when compared with other amphibian lineages.

Effect of fatigue on performance measured by a driving simulator in automobile drivers

OBJECTIVE

To identify risk factors of performance decrement in automobile drivers.

METHODS

114 drivers (age <30 years, n=57; age > or =30 years, n=57) who stopped at a rest stop area on a freeway were recruited for the study. They filled out a questionnaire on their journey, sleep/wake patterns and performed a 30-min test on a driving simulator. The test evaluates, by computerized analysis, the lateral deviation of a virtual car from an appropriate trajectory on a virtual road. A sex/age matched control group was recruited in the community. Control subjects were studied at the same time of day as the index case driver. Controls had normal sleep wake schedule, absence of long driving and performed the same driving test.

RESULTS

Drivers performed significantly worse than controls on the driving test. Age and duration of driving were the main factors associated with decreased performance.

CONCLUSION

Our driving simulator can identify fatigue generated by driving but results must be considered in relation with age of subjects.

History of water on Mars: a biological perspective

We divide the history of water on the Martian surface into four epochs based upon the atmospheric temperature and pressure. In Epoch 1, during which a primordial CO2 atmosphere was actively maintained by impact and volcanic recycling, we presume the mean annual temperature to have been above freezing, the pressure to have exceeded one atmosphere, and liquid water to have been widespread. Under such conditions, similar to early Earth, life could have arisen and become abundant. After this initial period of recycling, atmospheric CO2 was irreversibly lost due to carbonate formation and the pressure and temperature declined. In Epoch II, the mean annual temperature fell below freezing but peak temperatures would have exceeded freezing. Ice covered lakes, similar to those in the McMurdo Dry Valleys of Antarctica could have provided a habitat for life. In Epoch III, the mean and peak temperatures were below freezing and there would have been only transient liquid water. Microbial ecosystems living in endolithic rock "greenhouses" could have continued to survive. Finally, in Epoch IV, the pressure dropped to near the triple point pressure of water and liquid water could no longer have existed on the surface and life on the surface would have become extinct.

Computer detection and analysis of periodic movements in sleep

Standard polysomnography (PSG) and electromyographic (EMG) recording of the right and left anterior tibial muscles by Medilog 9000 recorder was carried out in 10 patients with periodic movements in sleep (PMS). The analog EMG signals and the sleep data from the Oxford ss90III sleep stager were fed into an IBM compatible personal computer for automatic detection and analysis using specific criteria to define the leg events, the interevent interval, the number of epochs (greater than 30 jerks), and the number of bursts (4 to 29 jerks). The results of automatic analysis were compared with data obtained from visually scored paper PSG. The total number of leg jerks detected by visual scoring was 2,812 and by automatic scoring was 2,789. The mean duration of the leg jerks 2.77 s [standard deviation (SD), 1.22] and the mean inter-interval event duration was 27.3 s (SD, 14.7). The total numbers of epochs scored visually was 35 and scored automatically was 33. The correlation co-efficient to the line of identity was 0.8 (p less than 0.005). The sensitivity of automatic scoring was 94% and the specificity was 85%. Automatic detection and analysis of PMS can provide an objective method for the study of several aspects of this disease that are still not yet fully understood.

An automated interferometer for the analysis of anaesthetic gas mixtures

A microprocessor-controlled interferometer is described. The eyepiece of a conventional Jamin type interferometer has been replaced by an array of photocells which records the intensity across the interference pattern. Mathematical correlation procedures are used to locate the principal interference pattern maximum and, by sequential analysis of a fresh gas mixture followed by fresh gas plus vapour, it is possible to determine both oxygen and vapour concentrations. The instrument was used to analyse mixtures of oxygen and nitrous oxide and also oxygen, nitrous oxide plus halothane. It was found that the oxygen concentration could be determined to an accuracy of +/- 1% v/v and the vapour concentration to +/- 0.1% v/v. The instrument is suitable for monitoring concentrations delivered by an anaesthetic machine and may be included in a microprocessor-controlled anaesthetic machine.

The fetal phonogram: a measure of fetal activity

In 12 pregnant mothers fetal sounds and infrasounds were recorded by means of a new compliance matched transducer and compared with a simultaneous ultrasound record of fetal activity. A defined pattern on the fetal phonograph correlated with 86% of the total fetal breathing detected with ultrasound, and a further distinctive pattern was associated with 90% of fetal movements. Examination of the fetal phonocardiogram when the fetus was breathing showed a significant increase in the short-term variability of both the systolic and diastolic times when compared with non-breathing episodes. The median amplitude variabilities for both the first and the second heart sounds were also significantly increased during fetal breathing. Measurement of fetal sounds and infrasounds with a compliance matched transducer offers a non-invasive method for assessment of fetal activity for long periods of time.

Lower oesophageal contractility: a new monitor of anaesthesia

The value of measuring lower oesophageal contractility (LOC) as a guide to the depth or adequacy of anaesthesia was investigated. Two forms of activity were recorded during light anaesthesia- nonpropulsive tertiary and provoked secondary peristalsis. Deepening anaesthesia resulted in progressive suppression of LOC. The smooth muscles of the lower oesophagus remain active despite the skeletal-muscle paralysis produced by muscle-relaxant drugs. The activity of the lower oesophagus may be a useful guide to the adequacy of anaesthesia.

Regional ischemic ventricular dysfunction in myocardium supplied by a narrowed coronary artery with increasing halothane concentration in the dog

The effects of increasing inspired halothane concentration (0.5, 1.0, 1.5, 2.0 per cent) upon left ventricular myocardium supplied by a critically narrowed coronary artery and a normal coronary artery were studied in 11 open-chested dogs. Regional ventricular function was measured by continuous recording of ventricular segment length using pairs of implanted miniature ultrasonic length detectors in the left anterior descending coronary artery (LAD) and left circumflex coronary artery (LC) territories before and during critical stenosis of the LAD by a micrometer-controlled snare. Critical narrowing was documented by ischemic regional ventricular function (i.e., post-systolic shortening; systolic lengthening) limited to the LAD territory when FIO2 = 0 for 90 seconds. Hemodynamic variables (aortic, left atrial and left ventricular pressure, and heart rate) were measured, ECG lead II was recorded, and the first derivative of left ventricular pressure (LV dP/dt) and coronary perfusion pressure derived for each halothane concentration before and during LAD narrowing. Increasing halothane was associated with equivalent progressive depression of global ventricular function before and during LAD constriction. Prior to LAD constriction, no ischemic changes in regional function occurred. Regional ventricular function was normal during 0.5 percent halothane in the presence of LAD constriction. With increasing halothane during LAD constriction, ischemic regional ventricular function was observed in the LAD territory in eight of eleven hearts, whereas regional ventricular function remained normal in the LC territory. The epicardial ECG was recorded in three dogs and was insensitive as an indicator of ischemia, becoming abnormal only after severe ischemic changes were established. In these studies, in which heart rate remained constant, arterial blood pressure and LV dP/dt decreased, and left ventricular end-diastolic pressure increased, decrease in blood flow and oxygen delivery due to a lower perfusion pressure distal to the coronary artery narrowing appears to be primarily responsible for the observations. The authors hypothesize that clinically unapparent episodes of regional myocardial ischemia distal to narrowed coronary arteries may be an important cause of perioperative myocardial infarction.

A robust respiration follower for studies of diabetic autonomic neuropathy

Studies of diabetic autonomic using the valsalva manoeuvre have previously utilized a strain gauge respiration monitor. The present paper describes a respiration follower for use in such work. This device was designed to be far less fragile and also to give a large, noise-free, output signal suitable for direct connection to a recording device.

Influenza Virus Growth and Antibody Response in Amantadine-Treated Mice

Amantadine (1-adamantanamine), a symmetrical primary amine, reduces the mortality rate and increases the survival time of mice infected with influenza A viruses. Virus production, although not completely prevented, is considerably diminished in treated mice. Treated survivors are generally resistant to challenge with homologous virus when the primary infecting virus inoculum is high. With a low primary virus dose a small percentage of treated mice escape an immunizing infection.