Stimulus-secretion coupling of arginine-induced insulin release. Resistance of arginine- and ornithine-stimulated glucagon and insulin release to D,L-alpha-difluoromethylornithine

In the isolated perfused rat pancreas, D,L-difluoromethylornithine, tested at a concentration of 3 mmol/L, failed to affect the release of glucagon and insulin caused, over 15 min stimulation, by either L-arginine or L-ornithine (2.0, 5.0 or 10.0 mmol/L) in the presence of either 3.3 or 5.6 mmol/L D-glucose. The inhibition of ornithine decarboxylase also failed to affect the release of glucagon provoked by either L-leucine (2 or 3 mmol/L) or L-glutamine (2 mmol/L) and the secretion of insulin stimulated by a rise in glucose concentration from 5.6 to 10.6 mmol/L. These data are interpreted to suggest that the rapid generation of polyamines from either L-arginine or L-ornithine does not play any significant role in the immediate glucagonotropic and insulinotropic action of these cationic amino acids.     

Both alpha- and beta-adrenoreceptors contribute to the central depressor effect of catecholamines

We compared the effects of alpha 2- and beta-adrenoreceptor blockade on the central actions of catecholamines and metabolites of alpha-methyldihydroxyphenylalanine, epinephrine, alpha-methylnorepinephrine, and alpha-methylepinephrine were studied. I.c.v. and nucleus tractus solitarii (NTS) injections were carried out under anesthesia. Following i.c.v. injection, both epinephrine and methylepinephrine rapidly reduced blood pressure and heart rate, but the effects of methylnorepinephrine occurred somewhat later. Following microinjection into the nucleus of the solitary tract, epinephrine, methylepinephrine, and methylnorepinephrine all caused hypotension and bradycardia. The hypotensive effects of all 3 amines in the NTS were attenuated in additive fashion by yohimbine, an alpha 2 adrenoreceptor antagonist, and timolol, a beta-adrenoreceptor antagonist, whereas only yohimbine attenuated the bradycardia. The combination of yohimbine and timolol abolished the effects of the amines. These data suggest that in the NTS both alpha 2 and beta adrenoreceptor stimulation contribute to the hypotensive effects of these amines, but that only alpha 2 adrenoreceptors are principally involved in the heart rate response.     

The difference in blood pressure between upper arm and finger during physical exercise

Summary. A new apparatus which measures the blood pressure in the finger continuously and yet not invasively was tested for its usefulness during exercise. It was compared with upper arm measurements in 23 volunteers during prolonged bicycle ergometry. Simultaneously, a pulse plethysmogram was recorded from another finger of the same arm, whereas in six additional volunteers Doppler measurements were carried out on the radial artery. The results show that finger systolic pressure ceased to rise at about 40% of maximal exercise; the difference with the continuously rising systolic pressure in the upper arm becoming significant at 140 W. At the same time the amplitude of the finger plethysmogram became significantly higher than its initial value, indicating distinct cutaneous vasodilation, whereas the volunteers also became hot and started to perspire. However, the radial artery ‘flow’, deduced from the Doppler measurements, did not change significantly during exercise. It increased sharply and markedly in the cooling down period. Simultaneously with this increase in flow, HR and both systolic blood pressures fell drastically whereas the plethysmography amplitude remained about stable at its raised level. The results fit in with the idea that a compromise is achieved between the need for muscle activity and the need for temperature regulation. It is concluded that the Finapres functions well during exercise, but that the systolic pressure in the finger is not representative for its more central counterpart during cutaneous vasodilation. It is argued that opening up of AVAs may contribute to this pressure effect.     

The binding of blood-borne estrogens in normal vegetarian and omnivorous women and the risk of breast cancer

Serial blood samples were taken at two-hour intervals over a 24-hour period from 25 premenopausal vegetarians (12 vegans and 13 ovolactovegetarians) and from 21 omnivorous controls. All members of the former group had been on a vegetarian diet for a minimum of three years. The mean proportion of estradiol unbound to blood proteins was similar in both vegetarians (1.26%) and meat eaters (1.16%). However, the amount bound to albumin was significantly raised in vegetarians (50.1% vs. 43.1%, p less than 0.009), whereas that bound to sex hormone-binding globulin (SHBG) was correspondingly lower (48.7% vs. 55.8%, p = 0.01). Mean levels of SHBG were similar in vegetarians (59.9 nmole/l) and omnivores (62.0 nmole/l), as was the total amount of free fatty acid (0.42 mmole/l for both). Within the vegetarian group, no differences were detected between vegans and ovolactovegetarians.     

Pressure suppresses serotonin release by guinea pig striatal synaptosomes

Exposure to high pressure produces neurologic changes in humans which manifest as tremor, EEG changes, and convulsions. Since previous studies have implicated the involvement of the serotoninergic system in these symptoms, it was of interest to study serotonin release at high pressure. Synaptosomes isolated from guinea pig striatum were used to follow serotonin efflux at 68 ATA. The major observation was a decrease in [3H]serotonin release from depolarized striatal synaptosomes at 68 ATA. In view of the role of serotonin as an inhibitory neurotransmitter in this area, the observed decrease in synaptic release leads us to conclude that decreased serotoninergic activity in striatal neurons probably is contributing to the hyperexcitability associated with HPNS.     

Spontaneous transpyloric passage and performance of 'fine bore' polyurethane feeding tubes: a controlled clinical trial

Certain groups of patients requiring enteral nutritional support are at increased risk of regurgitation and pulmonary aspiration of feed. Positioning of enteral feeding tubes distal to the pylorus has been advocated as a method of reducing such complications. Various techniques have been suggested to achieve postpyloric siting. Reports have indicated that lengthening the tube or altering the distal end tip configuration, by varying the tip profile or by the addition of a weight, may facilitate spontaneous transpyloric passage of the tube. This prospective controlled clinical study using three new polyurethane tubes demonstrates that the frequency of spontaneous transpyloric passage of the tube is not affected by tip profile or by the addition of a weight. Indeed, with all three tube designs only about one-third had passed spontaneously through the pylorus at 24 hr. Once through the pylorus the unweighted tube stayed in position significantly longer than the weighted tubes (p less than 0.005). We suggest that in those patients requiring post-pyloric feeding, endoscopic or fluoroscopic techniques should be used to position the tubes at the time of insertion, and that an unweighted tube should be used to prolong tube usage.     

Non-A,Non-B hepatitis; Factors involved in progression to chronicity

A cross-sectional, longitudinal study was undertaken on a group of acute non-A, non-B hepatitis patients, as well as on a control group of hepatitis B patients, in order to assess both the prevalence of the most important factors favoring infection, and the relevance of these factors in promoting evolution towards chronic liver disease. Exposures to unknown risk factors were present in 47.4% of acute non-A, non-B infections, followed by blood transfusions (17.9%), sporadic exposures (17.9%) and drug addiction (16.6%). Unknown as well as sporadic exposures showed a greater prevalence in control population if compared to non-A, non-B cases, while drug addiction was equally represented in the two groups, and blood transfusion nearly absent from control group. The risk of evolution to chronic liver disease was about 13 times greater in non-A, non-B group than in controls, with the greatest risk for drug addicts and the lowest for patients with unknown exposures. Among patients with known exposures, the lowest risk of chronic hepatitis was observed in post-transfusion and in sporadic cases, while the greatest was observed in drug addicts.Corresponding author.