Rate of oxygen consumption by parotid atrophic acinar cells from rats fed liquid diet.

Adult male rats were maintained on a nutritionally adequate liquid-diet or laboratory chow and water (control), for 9 days. They were then killed and the parotid glands removed. Enzymatically dispersed acinar-cell preparations were used to study rates of oxygen consumption (QO2) using a Clark oxygen electrode. For both CON and LD cell preparations the basal QO2 was 0.132 (+/- 0.03-0.05) nmol O2 per microgram DNA per min and in each case this was increased approx. 2.4-fold under stimulation by carbachol (10 microM) and approx. 3.1-fold by adrenaline (10 microM). Isoprenaline (10 microM) elicited no significant increase in QO2. Addition of ouabain (2.5 mM) or removal of Ca2+ from the extracellular medium prevented the action of carbachol to increase QO2 over a sustained period. There were no significant differences in the basal, agonist-stimulated, or ouabain-sensitive QO2 by dispersed acinar cells from liquid-diet rats compared to control. The results are consistent with the notion that liquid diet-induced atrophy represents a physiological adaptation rather than a pathological change. Nevertheless, they also indicate that in the acinar cells from liquid-diet rats the Na+/K+ ATPase is required to operate at normal levels of energy consumption despite the reduced acinar-cell volume and consequently lower levels of agonist-elicited transepithelial ion movements known to occur in these cells.

Functional characteristics of atrophic parotid acinar cells from rats after liquid feeding.

Rat parotid atrophy, induced by liquid feeding over 10 days, was manifested as gland weight loss (40%) and histologically as acinar shrinkage. Acinar secretory function was investigated in the same glands using enzymatically dispersed cell preparations and superfused gland slices. Results were normalized for the acinar proportional volume, determined by stereological analysis. Although total amylase activity was significantly lower in liquid-fed (LD) rats, the percentage amylase releases elicited by isoproterenol (10 mumol/L) and carbachol (10 mumol/L) were unchanged from controls (CON). Superfused gland slices from LD and control (CON) rats exhibited increases in membrane permeability (86Rb+ efflux) and in the efflux and re-uptake of K+ in response to acetylcholine (10 mumol/L). However, the recorded maxima were significantly lower in LD than in CON (86Rb+, 27% lower; K+ efflux, 35% lower; K+ re-uptake, 35% lower). Similarly, after 60-minute equilibration, the 36Cl- content of cells from LD rats was 57% lower than that from CON. Carbachol (10 mumol/L), acting for 1 min with bumetanide (100 mumol/L), elicited an efflux of 36Cl- from cells from LD rats, but this was significantly lower (32.2%) in LD than in CON (49.9%). The reduced levels of ion movement are probably commensurate with the reduced acinar cell volume occurring in LD rats. These results show that mechanisms for the formation of primary saliva (exocytosis and transepithelial ion movements) are substantially preserved in the altered acinar cells of LD rats. Thus, in salivary disorders, severe morphological acinar atrophy may not inevitably signify exhausted secretory function.

Binding of a novel radioiodinated thromboxane A2/prostaglandin H2 antagonist to guinea pig lung membranes.

The utilization of a novel radioiodinated TXA2/PGH2 receptor antagonist, ISAP (7-[(1R,2S,3S,5R)-6,6-dimethyl-3(4- iodobenzenesulfonylamino)-bicyclo[3.1.1]-hept-2-yl]-5(Z)-heptenoic acid) to characterize TXA2/PGH2 receptors from guinea pig lung parenchymal membranes in radioligand binding assays is described. [125I]ISAP binding was saturable, displaceable, and dependent upon protein concentration. The time course of binding yielded k1 = 2.12 x 10(8) M-1 min-1, k1 = 4.46 x 10(-3) min-1, Kd = k-1/k1 = 17.8 pM. Equilibrium binding studies indicated a single class of high affinity binding sites with a Kd of 52.7 +/- 1.9 pM and a Bmax of 92.7 +/- 7.2 fmoles/mg protein (n = 4). Binding was inhibited by a series of structurally diverse mimetics and antagonists with the rank order of potency IBOP greater than ONO11113 = SQ26655 greater than U46619 (mimetics) and (d)-S-145 greater than ISAP greater than (1)-S-145 greater than SQ29548 greater than BM13505 = I-PTA-OH (antagonists), with entantioselectivity of binding demonstrated by (d) and (1) S-145. Binding was also inhibited by prostanoids (PGD2, PGF2 alpha, and 9 alpha, 11 beta-PGF2) thought to act at the airway TXA2/PHH2 receptor, but not by histamine or carbachol, and only weakly by LTB4 and LTD4, consistent with specific binding to the lung TXA2/PGH2 receptor.

A comparative quantitative histological investigation of atrophic changes in the major salivary glands of liquid-fed rats.

Adult male rats were maintained on a wholly liquid diet for 9 days. The three pairs of major glands were removed, weighed, histologically sectioned and examined by stereological and morphometric techniques. The results were compared with the same glands from control rats maintained on normal hard diet and water, and the extent of the differences was compared between the three different types of gland. Up to 50% of the serous acinar volume in the parotid glands, but only 15% in the submandibular glands, was lost after liquid feeding. There was no loss of the mucous acinar tissue in the sublingual gland. Mean acinar diameters were reduced by 33% in parotids and 15% in submandibular glands after liquid feeding, whereas the mucous acini of the sublingual gland remained unaltered. The results point to varying levels of susceptibility to the loss of masticatory reflexes between the parotid serous acini and the submandibular serous acini, and show that the morphology of the sublingual mucous acini is independent of masticatory reflex stimulation. The reductions in acinar diameters suggest that most of the glandular atrophy after liquid feeding is due to acinar cell shrinkage rather than to losses of acinar cell numbers in both parotid and submandibular glands.

The effects of a liquid diet on initial and sustained, stimulated parotid salivary secretion and on parotid structure in the rat.

Adult male rats were maintained on a nutritionally adequate liquid diet, or laboratory chow and water (controls), for 7 days. They were then anaesthetized and parotid flow was recorded after isoprenaline or pilocarpine stimulation, each collected over two, timed sampling periods--an initial 5 min and a subsequent 15 min. The isoprenaline-induced flow rates in liquid diet rats were reduced to 45 and 30% of those in control rats for the first and subsequent samples respectively (p less than 0.02). After pilocarpine stimulation there were no significant differences in the first samples, but in the subsequent samples the flow rate in liquid diet rats was reduced to 54% of that in controls (p less than 0.001). The parotid gland weights were reduced by 35% in liquid diet rats compared to controls (p less than 0.05). On computerized planimetric analysis, parotids (from rats that had not been given secretagogues) had significantly smaller mean acinar areas, mean acinar profile perimeters and mean acinar transection diameters after liquid feeding (p less than 0.001). The findings support the notion that there is a functional reserve capacity available in atrophied glands to support the relatively fast flow that occurs on initial stimulation but which becomes exhausted during sustained stimulation. This exhaustion occurs more severely and more rapidly in the low-volume, protein-rich saliva elicited by sympathomimetic stimulation than in the high-volume, low-protein saliva formed in response to parasympathomimetic stimulation.

Strategies, systems, value judgements and dieldrin in control of locust hoppers.

The physiology and field biology of locusts have been extensively studied, and ecological control of Red Locusts has been investigated by field experiment. No fruitful or even promising non-insecticidal method of control has emerged. An effective and economical system requires an insecticide that is: (i) effective at very small area dosages, as a stomach poison placed on the natural vegetation can be, if it is also cumulative; (ii) persistent enough in sunshine and rain to retain effectiveness over the locust's non-feeding periods; (iii) capable of being well distributed by well-tried methods; and (iv) not dangerous to users or consumers and posing a minimal overall risk. Only one insecticide, dieldrin, satisfies all these requirements. Dieldrin is not in the small class of insecticides that are dangerous to man by skin absorption (such as parathion, arsenicals, DNC) and, at the area dosages needed for locust control, is not dangerous to stock. The Sayer exhaust sprayer in a Land Rover, with work rates of the order of square kilometres per hour is excellent for many situations; aircraft spraying at he rate of square kilometres per minute is quicker and less subject to difficulties of terrain, but requires trained and appropriately directed aircrew. Apart from checking, aircraft methods require no party on the ground to find, assess and control locust hoppers. Several ideas about dieldrin are found to be based on insufficient evidence and are probably not true: for example that dieldrin in the atmosphere at a few parts in a million million (10(12)) becomes concentrated in a food web and harmful to man, or that dieldrin is carcinogenic in man. It is noteworthy, however, that one species of antelope in South Africa is exceptionally susceptible to dieldrin poisoning, though harm occurs at area dosages considerably greater than are required in the method of aircraft spraying of Courshee & McDonald (1963). To attack tsetse flies, emissions two orders of magnitude greater have been used. Care must be taken with any insecticide, but the risks of using dieldrin as properly used in locust hopper control have been exaggerated by propaganda. If harm is to be expected, then a quantitative comparison of that with the undoubted benefits of locust control is required to enable one to make a value judgement.

The meaning of the term "klinokinesis".

The original definition of the term klinokinesis was based on an account by Ullyott (1936) of the behaviour of the flatworm, Dendrocoelum lacteum, an account recently shown to be unsound. Recently, the behaviour of Escherichia coli and of Salmonella typhimutium in chemical gradients has been found to conform to the definition, so the term can continue in use. But no uncomplicated case has been found in metazoans, though the manoeuvres of klinokinesis may make large contributions to the behaviour of some of them, even though it may be complicated and obscured by other types of reaction, such as orthokinesis. What is needed is mathematical treatment sufficiently thorough to enable the existence of the reaction in metazoans to be ascertained. There may well be other systems of manoeurvres using random changes of direction and these should be sought and investigated.