Electromyographic study of the cat''s diaphragm during oesophageal distension

In 10 cats, under acute experimental conditions, the effects of distension of the oesophagus on diaphragmatic activity were studied. Bipolar recording electrodes were implanted in the diaphragmatic dome muscular fibres and crura muscular fibres. Electrodes similar to those in the diaphragm were inserted in the oesophageal muscular wall above the hiatus and in the rectus abdominis muscle. Changes in the intrathoracic pressure and blood pressure were recorded by catheters placed in the pleural cavity and carotid artery respectively. Distension of the lower part of the thoracic oesophagus (at the level between the heart and the hiatus, 5 to 7 cm from the hiatus) by inflating a balloon with 10 to 15 ml of air produced a partial or total inhibition of the inspiratory electrical activity of the inner hiatal muscular fibres, while the inspiratory electrical activity of the dome muscular fibres was generally unchanged. This inhibition was increasingly pronounced as the distension volume increased and as the balloon was positioned nearer to the hiatus. During the distension period, only electrocardiographic potentials were recorded on the oesophageal muscular wall and rectus abdominis muscle traces and no significant changes were observed from intrathoracic pressure or blood pressure channels. Distension by means of a balloon either inflated with up to 5 ml of air when placed 5 to 7 cm cranial to the hiatus or inflated with 15 ml of air when localised in the cervical oesophagus and intrahiatally produced no effect. All areas of the diaphragm were silent during expiration.     

AEOLIAN ADDITIONS TO SOILS AND SEDIMENTS IN THE SOUTH PACIFIC AREA

The particle-size distribution of the whole sample and the content, particle-size distribution, and oxygen-isotope abundance (δ¹⁸O) in quartz were employed to determine the extent to which aeolian materials such as aerosolic dust (10 to I /μm) from Australia, loess (50 to 10μm) in New Zealand, and flöttsand (250 to 20 μm) in Australia have been accreted into soils and sediments in the South Pacific area. Although aeolian material from both local and more distant sources has been deposited on the Franz Josef, Fox, and Tasman glaciers, the extent to which aeolian materials have been added to soils in South Westland, New Zealand, could not be determined because the oxygen-isotope abundance (12.9 to 13.5 0/00 in quartz from the soils was similar to that (13.1 to 13.9 0/00) in quartz from the dust samples. The quartz from loess added to two basaltic soils in North Auckland, New Zealand, had an oxygen-isotope abundance (12.9 to 13.9 0/00) slightly lower than that (15.0 to 15.4 0/00) in quartz from a greywacke-derived soil and the underlying rock also in North Auckland. The oxygen-isotope abundance (13.6 to 15.4 0/00) in quartz from a chronosequence of soils developed in basalt in Victoria, Australia, indicates that the quartz did not originate from the parent basalt, but probably was transported by aeolian processes from stranded beach ridges and dunes and added to the soils in the form of flöttsand, an aeolian material coarser than loess and finer than dune sand. Most particles of the pelagic sediments fell within the aerosolic dust size range. The oxygen-isotope abundance (12.1 to 15.1 0/00) in quartz isolated from several pelagic sediments between latitudes 35 and 45° S. was similar to that (12.9 to 15.4 0/00) in quartz from New Zealand and Australian soils located between these latitudes. An aeolian source of quartz explains the above relationship and also the decreasing delta values of quartz from sediments and soils with increasing latitude in the South Pacific area. Oxygen-isotope abundance in quartz refutes a volcanic origin of quartz in pelagic sediments but supports the deduction of Griffin et al. (1968) from mineralogical analyses that the quartz and associated minerals were transported from lands to seas.     

Veterinary education in the world—changing attitudes

SUMMARY Veterinary educators all over the world are concerned about the explosion in knowledge and about the way veterinary science is taught at present. How can we produce veterinarians who will provide the sort of care that will be expected in the year 2000 and beyond? In the recent past many schools have increased the information presented in their courses without removing any material. Student stress has increased, and undergraduates do not retain what they are taught. The type of assessment that is currently used often requires regurgitation of ‘facts’ rather than the solution of problems. This paper considers some of the issues that are pertinent to the future of veterinary education and suggests ways in which the situation may be improved. There is a need for increased activity by the Australian Veterinary Association to convince government that present funding is inadequate and that increased funding is urgently needed if we are to produce veterinarians of the quality the country will need in the next century.     

Pharmacokinetics of caffeine in the oestrogen-implanted ovariectomized ewe

The disposition kinetics of caffeine and its metabolites theophylline, theobro-mine and paraxanthine in the oestrogen-implanted ovariectomized ewe following single intravenous doses of 5, 10, 15 or 20 mg/kg caffeine are described in this paper. Blood was collected at 5, 30 and 60 min, and at 3, 6, 8, 12, 24, 48, 72, 96, 120, 144, 192 and 240 h after dosing. Caffeine concentrations peaked within 30 min of administration but remained in a plateau phase for 3-6 h before declining over a prolonged period of time. For caffeine the mean elimination half-life was calculated to be 47 h. Detectable caffeine concentrations remained for 10 days after administration in all groups. The area under the plasma concentration-time curve ( AUC ) values were used to compare tissue caffeine exposure and were, approximately, linearly related to dose. Metabolite concentrations were maintained at peak and near peak concentrations for 6-24 h after caffeine administration followed by prolonged elimination. Because of significant species differences in drug elimination rates, it is concluded that the ewe is not a suitable animal model in the clinical context. However, the sheep may well provide insights into caffeine's mechanism of action of relevance to veterinary drug research.     

High night temperature stimulates photosynthesis, biomass production and growth during the vegetative stage of rice plants

The effects of night temperature on biomass accumulation and plant morphology were examined in rice ( Oryza sativa L.) during vegetative growth. Plants were grown under three different night temperatures (17, 22 and 27°C) for 63 days. The day temperature was maintained at 27°C in all treatments. The final biomass of the plants was greatest in the plants grown at the highest night temperature. Total leaf area and tiller number were also the greatest in this treatment. Growth analysis indicated that the relative growth rate in the 27°C night-temperature treatment was maximal between days 21–42 and this was caused by increases in leaf area ratio, leaf weight ratio and specific leaf area. Plant total nitrogen contents did not differ among treatments. However, nitrogen allocation to the leaf blades was highest and the accumulation of sucrose and starch in the leaf blades and sheaths was the lowest in the 27°C night-temperature treatment by day 42. Despite this, dark respiration was also highest, and both the gross and net rates of CO₂ uptake at the level of the whole plant at day 63 were the highest in the 27°C night-temperature treatment. Thus, high night temperature strongly stimulated the growth of leaf blades during the early stage of rice plant growth, leading to increased biomass during the vegetative stage of the rice plants. As the CO₂ uptake rate per total leaf area was higher, photosynthesis at the level of the whole plant was also stimulated by a high night temperature.     

THE USE OF DIFFUSION TENSOR IMAGING TO EVALUATE THE SPINAL CORD IN NORMAL AND ABNORMAL DOGS

Diffusion tensor imaging (DTI) is a specialized magnetic resonance sequence to determine the direction of water molecule motion. Our hypothesis was that information derived from DTI will be significantly different in dogs with a spinal cord lesion compared with a normal dog. Eleven normal dogs and six dogs with a spinal cord lesions were imaged. DTI was performed along with standard T1‐ and T2‐weighted sequences in transverse and sagittal planes. Fractional anisotrophy and apparent diffusion coefficient (ADC) were obtained using regions of interests centered on the cranial aspect, middle cranial, middle caudal, and caudal aspects of the spinal cord. In normal dogs, the DTI sequence was characterized by normal fiber tracking with no statistical difference between the four sections of spinal cord (P>0.05). In the dogs with a spinal cord lesion, there was a significant difference in fractional anisotropy between the two groups (P=0.0003) and the ADC analysis statistical significance (P=0.048) at the caudal most site. Based on these findings, DTI is a potentially useful method to evaluate the spinal cord in dogs.