Food deprivation decreases vasopressin mRNA in the supraoptic and paraventricular nuclei of the hypothalamus in rats.

We examined the effect of food deprivation for three days on hypothalamic arginine vasopressin (AVP) mRNA in rats. Simultaneously the effect of water deprivation for the same period was examined as a model of dehydration. Levels of AVP mRNA in the supraoptic nucleus (SON) and the paraventricular nucleus (PVN) were determined by semiquantitative in situ hybridization histochemistry. Water deprivation increased AVP mRNA in both nuclei as previously reported. In contrast, food deprivation decreased AVP mRNA in these nuclei. The changes in AVP mRNA levels in the PVN were observed in the magnocellular subdivision of the nucleus. Plasma levels of ACTH and corticosterone were greatly increased in both treated groups of rats. Plasma AVP and osmolality levels were significantly elevated in water-deprived rats but not in food-deprived rats. These observations indicated that both food deprivation and water deprivation stimulated the pituitary-adrenal axis and that a reduction in AVP mRNA levels in food-deprived rats was caused by food deprivation but not by glucocorticoid feedback suppression nor by altered plasma osmolality.</p

Recovery of physiological traits in saplings of invasive Bischofia tree compared with three species native to the Bonin Islands under successive drought and irrigation cycles

Partial leaf shedding induced by hydraulic failure under prolonged drought can prevent excess water consumption, resulting in delayed recovery of carbon productivity following rainfall. To understand the manner of water use of invasive species in oceanic island forests under a fluctuating water regime, leaf shedding, multiple physiological traits, and the progress of embolism in the stem xylem under repeated drought-irrigation cycles were examined in the potted saplings of an invasive species, Bischofia javanica Blume, and three endemic native species, Schima mertensiana (Sieb. Et Zucc, ) Koitz., Hibiscus glaber Matsum, and Distylium lepidotum Nakai, from the Bonin Islands, Japan. The progress of xylem embolism was observed by cryo-scanning electron microscopy. The samples exhibited different processes of water saving and drought tolerance based on the different combinations of partial leaf shedding involved in embolized conduits following repeated de-rehydration. Predawn leaf water potential largely decreased with each successive drought-irrigation cycle for all tree species, except for B. javanica. B. javanica shed leaves conspicuously under drought and showed responsive stomatal conductance to VPD, which contributed to recover leaf gas exchange in the remaining leaves, following a restored water supply. In contrast, native tree species did not completely recover photosynthetic rates during the repeated droughtirrigation cycles. H. glaber and D. lepidotum preserved water in vessels and adjusted leaf osmotic rates but did not actively shed leaves. S. mertensiana exhibited partial leaf shedding during the first cycle with an osmotic adjustment, but they showed less responsive stomatal conductance to VPD. Our data indicate that invasive B. javanica saplings can effectively use water supplied suddenly under drought conditions. We predict that fluctuating precipitation in the future may change tree distributions even in mesic or moist sites in the Bonin Islands

Effect of Hyperosmotic Stimulation and Adrenalectomy on Vasopressin mRNA Levels in the Paraventricular and Supraoptic Nuclei of the Hypothalamus:

The effects of salt loading and adrenalectomy on arginine vasopressin (AVP) mRNA levels in the paraventricular nucleus (PVN) and the supraoptic nucleus (SON) of the hypothalamus were studied by semiquantitative in situ hybridization histochemistry, using a synthetic oligonucleotide probe and a computer-assisted image analysis system. Salt loading (2% NaCl) for 7 days produced marked increases in AVP mRNA levels in the magnocellular neurons of the PVN, SON, and accessory nuclei. Adrenalectomy caused an increase in AVP mRNA expression in the magnocellular part of the PVN and the expansion of hybridization signals into its medial parvocellular region, where the cell bodies of corticotropin-releasing hormone (CRH) neurons are located. No apparent alteration of AVP mRNA levels was observed in the SON following adrenalectomy. These results indicate that hyperosmotic stimulation and the loss of circulating glucocorticoids had differential effects on AVP gene expression in the PVN and SON, and that the magnocellular PVN and SON neurons responded in different manners to the loss of feedback signals.</p

Combined anterior pituitary function test using CRH, GRH, LH-RH, TRH and vasopressin in patients with non-functioning pituitary tumors.

We examined 8 normal subjects and 16 patients with non-functioning pituitary tumors with a combined anterior pituitary test to evaluate the clinical usefulness of the test. Diagnoses included 9 of chromophobe adenoma, 3 of craniopharyngioma, 2 of Rathke's cleft cyst, and 1 each of intrasellar cyst and tuberculum sella meningioma. All subjects received hypothalamic releasing hormones: 1 micrograms/kg corticotropin releasing hormone (CRH), 1 micrograms/kg growth hormone releasing hormone (GRH), 500 micrograms thyrotropin-releasing hormone (TRH), 100 micrograms luteinizing hormone releasing hormone (LH-RH), and a relatively small dose (5 mU/kg) of lysine vasopressin (LVP). In the normal subjects, the addition of LVP potentiated the secretion of adenocorticotropic hormone (ACTH) induced by CRH, but had no significant effect on the secretion of other anterior pituitary hormones. In the combined test with 5 releasing hormones, the plasma ACTH and cortisol responses were not impaired in the majority of the patients before pituitary surgery. Serum thyroid-stimulating hormone (TSH), prolactin (PRL) and follicle-stimulating hormone (FSH) responses were not impaired in 82%, 70% and 67% of the patients, respectively, while the serum LH and GH responses were impaired in 67% and 73% of the patients, respectively. Following pituitary surgery, responses of these hormones to combined testing were similarly impaired in more than 75% of the patients. These results indicate that plasma ACTH, cortisol and serum TSH responses are fairly good before pituitary surgery but are impaired significantly after surgery. No subjects experienced any serious adverse effects related to the testing. These results suggest that combined testing with hypothalamic hormones is a convenient and useful method for evaluating pituitary function.</p

The dynamics of carbon stored in xylem sapwood to drought-induced hydraulic stress in mature trees.

Climate-induced forest die-off is widespread in multiple biomes, strongly affecting the species composition, function and primary production in forest ecosystems. Hydraulic failure and carbon starvation in xylem sapwood are major hypotheses to explain drought-induced tree mortality. Because it is difficult to obtain enough field observations on drought-induced mortality in adult trees, the current understanding of the physiological mechanisms for tree die-offs is still controversial. However, the simultaneous examination of water and carbon uses throughout dehydration and rehydration processes in adult trees will contribute to clarify the roles of hydraulic failure and carbon starvation in tree wilting. Here we show the processes of the percent loss of hydraulic conductivity (PLC) and the content of nonstructural carbohydrates (NSCs) of distal branches in woody plants with contrasting water use strategy. Starch was converted to soluble sugar during PLC progression under drought, and the hydraulic conductivity recovered following water supply. The conversion of NSCs is strongly associated with PLC variations during dehydration and rehydration processes, indicating that stored carbon contributes to tree survival under drought; further carbon starvation can advance hydraulic failure. We predict that even slow-progressing drought degrades forest ecosystems via carbon starvation, causing more frequent catastrophic forest die-offs than the present projection

Water potential at midday and osmotic potential on the last day of each drought periods.

<p>The values of (A) leaf water potential at midday, (B) leaf osmotic water potential at full turgor measured on the last day of each drought period. The measurement (Start) was conducted just before the cessation of irrigation and the measurements (1^st to 3^rd) were conducted on the last day of the lasting drought period in each drought-irrigation cycle. Bars indicate ± 1 standard error of mean. Different letters showed significant differences in each tree species (ns: no significant differences in each species). See the legend of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0135117#pone.0135117.g001" target="_blank">Fig 1</a>. in the numbers of samples.</p