Effects of long-term dehydration on oxidative stress, apoptotic markers and neuropeptides in the gastric mucosa of the dromedary camel.

We investigated the effects of 20 days of dehydration and 20 days of dehydration followed by 72 h of rehydration on the gastric mucosa of the one-humped dromedary camel. The parameters addressed include biomarkers of oxidative stress, apoptosis, gastric epithelial histology, gastric neuropeptides, and their receptors. Nineteen clinically healthy, 4-5 year-old male dromedary camels were divided into three groups (five control camels, eight dehydrated for 20 days, six dehydrated for 20 days and then rehydrated for 72 h). Dehydration affected the oxidative stress biomarkers causing a significant increase in malondialdehyde, glutathione, nitric oxide, and catalase values compared with controls. Also the results revealed that dehydration caused different size cellular vacuoles and focal necrosis in the gastric mucosa. Rehydration for 72 h resulted in improvement in some parameters but was not enough to fully abolish the effect of dehydration. Dehydration caused significant increase in apoptotic markers; tumor necrosis factor α, caspases 8 and 3, BcL-x1 and TGFß whereas caspase 9, p53, Beclin 1, and PARP1 showed no significant change between the three groups indicating that apoptosis was initiated by the extrinsic pathway. Also there were significant increases in prostaglandin E2 receptors and somatostatin in plasma and gastric epithelium homogenate, and a significant decrease in cholecystokinin-8 receptors. A significant decrease of hydrogen potassium ATPase enzyme activity was also observed. Pepsinogen C was not affected by dehydration. It is concluded that long-term dehydration induces oxidative stress and apoptosis in camel gastric mucosa and that camels adjust gastric functions during dehydration towards water economy. More than 72 h are needed before all the effects of dehydration are reversed by rehydration.

Distribution of atrial natriuretic peptide and its effects on contraction and intracellular calcium in ventricular myocytes from streptozotocin-induced diabetic rat.

The distribution of atrial natriuretic peptide (ANP) in blood plasma and cardiac muscle and its effects on ventricular myocyte contraction and intracellular free calcium concentration [Ca2+]i in the streptozotocin (STZ)-induced diabetic rat have been investigated. Blood plasma concentration and heart atrial and ventricular contents of ANP were significantly increased in STZ-treated rats compared to age-matched controls. STZ treatment increased the number of ventricular myocytes immunolabeled with antibodies against ANP. In control myocytes the percentage of cells that labeled positively and negatively were 17% versus 83%, respectively. However, in myocytes from STZ-treated rat the percentages were 52% versus 53%. Time to peak (TPK) shortening was significantly and characteristically prolonged in myocytes from STZ-treated rats (360+/-5 ms) compared to controls (305+/-5 ms). Amplitude of the Ca2+ transient was significantly increased in myocytes from STZ-treated rats compared to controls (0.39+/-0.02 versus 0.29+/-0.02 fura-2 RU in controls) and treatment with ANP reduced the amplitude of the Ca2+ transient to control levels. ANP may have a protective role in STZ-induced diabetic rat heart.

Control of porcine lacrimal gland secretion by non-cholinergic, non-adrenergic nerves: effects of electrical field stimulation, VIP and NPY.

This study employs the technique of electrical field stimulation (EFS) to characterise the effects of endogenous neurotransmitters on protein secretion in the in vitro pig lacrimal gland. The effects of exogenous applications of neurotransmitters on protein output and peroxidase secretion were also investigated for comparative purposes. EFS evoked frequency-dependent (5-20 Hz) increases in protein secretion. The EFS-evoked protein output was abolished with the nerve blocking drug tetrodotoxin (10(-6) M, TTX). Elevated potassium (100 mM KCl) can stimulate protein output in the presence of TTX. Exogenous application of either acetylcholine (ACh, 10(-9)-10(-4) M) or noradrenaline (NA, 10(-8)-10(-4) M) can also result in protein secretion, but they have no detectable effect on peroxidase secretion. In the presence of the cholinergic antagonist, atropine (10(-5) M) the EFS-induced protein output was reduced but not abolished. This atropine-resistant and non-cholinergic nerve-mediated component was further reduced in the combined presence of atropine, phentolamine, and propranolol (all 10(-5) M). When vasoactive intestinal polypeptide (VIP) receptor antagonist (10(-6) M [4-Cl-D-Phe6-Leu17]-VIP) was combined with the cholinergic and adrenergic antagonists, EFS caused a small but detectable increase in protein output. Exogenous application of either 10(-9) M VIP or 10(-9) M neuropeptide-Y (NPY) resulted in protein secretion. Combination of both VIP and NPY only induced an additive effect on protein output. Theophylline (10(-4) M), a phosphodiesterase inhibitor, evoked a small increase in protein output and had no significant effect on the secretory responses elicited by either VIP or NPY. In contrast, theophylline potentiated the non-cholinergic, non-adrenergic EFS-induced protein secretion. The results indicate that protein secretion from the porcine lacrimal gland may be controlled by cholinergic, adrenergic and non-cholinergic, non-adrenergic nerves. The peptidergic neurotransmitters may be VIP and other related neuropeptide(s). In addition to these neurophysiological studies, our results confirm previous findings that the porcine lacrimal nerves contain abundant quantity of NPY and VIP.

Evidence to suggest morphological and physiological alterations of lacrimal gland acini with ageing.

This study investigates changes in the morphology and physiology of lacrimal gland acinar cells with age. Changes in microstructural appearance of the acinar cells, the type and distribution of the different acini in glands and the secretory granules within the acini were examined in glands from animals of 3-5, 9, 12, 20, 24 and 28 month old rats. Differences in the secretory capacity of the acinar cells were also examined in animals of each age-group, with the exception of 28 months. The typical acini of young glands (3-5 months) were of the serous type. This was also true of 9 month glands, although there was a significant reduction in their overall distribution compared to young glands. The acini in the 12 month glands were predominantly of the seromucous type and appeared to be at the expense of the serous acini which were further significantly reduced compared to 3-5 and 9 month glands. This remained the prevalent acini type in 20 month glands, however by 24 months there was a significant increase in the occurrence of mucous acini and this time appeared to be at the expense of the seromucous acini which were significantly reduced in glands of this age-group. The predominant acinar cell in 28 month glands, like 24 month glands, was of the mucous variety. Qualitative EM studies revealed a progressive change in the secretory products of the lacrimal gland acini, strongly correlating to changes in acinar cell type. Typical acini of both 3-5 and 9 month glands contained numerous protein secretory granules. The seromucous acini also of these age groups contained both protein and mucous secretory granules, with the protein secretory granules in higher abundance. By 12 months the typical seromucous acini was packed with both protein and mucous secretory granules of equal proportions. However, by 20 months the predominant seromucous acini contained fewer protein secretory granules and elevated occurrence of mucous secretory granules. By 24 and 28 months the acini contained even fewer protein secretory granules and the typical acinar cell was of the mucous type containing exclusively mucous secretory granules. The secretory capacity of the acini was also altered with age. Maximum protein output in response to cholinergic stimulation resulted in an initial significant increase with ageing from 3-5 months to 9 and 12 months followed by a later significant age-dependent reduction in output. However, maximal peroxidase release from acinar cells of 3-5 and 9 month glands was the same. This was followed by a significant age-dependent reduction in peroxidase release. Furthermore, the concentrations required to evoke these responses differed with age. These results present evidence to suggest that acinar cells of the lacrimal gland undergo progressive alterations with age. The type of acini changing initially from serous to seromucous acini (intermediate phase) followed by a gradual transformation of the seromucous acini to mucous acini. This in turn changes the properties of the acini from protein producing and secreting acini to mucous producing and secreting acini. The results also suggest a reduction in the ability of the acini to synthesise proteins with age and altered responsiveness to cholinergic stimulation to secrete proteins. These findings may help in explaining the occurrence of altered protein/tear secretion with ageing.