Control of feeding during saline consumption and fluid deprivation in hamsters

Cellular dehydration induced by water deprivation or hypertonic saline injection reduces feeding in a variety of species. Normal feeding in rats is maintained during isotonic saline consumption by increasing the intake of saline compared to the usual intake of water. Hamsters do not show the spontaneous preference for isotonic saline noted in rats, even after adrenalectomy. In the present investigation, feeding by hamsters was depressed during both isotonic and hypertonic saline consumption compared to the usual feeding with water. Saline intakes did not exceed water intakes under similar conditions. When fluid intakes were elevated by prior fluid deprivation, feeding rates increased at all concentrations of saline after a delay proportional to the osmolality of the solution. Positive 24-hr sodium balances were always associated with saline consumption. Water and hypertonic saline injections reduced feeding, and the fluid loads were excreted very slowly. When hamsters were fluid deprived prior to injections, saline totally suppressed feeding, while water increased feeding compared to sham injected controls. It is concluded that cellular dehydration produces a reduction of feeding in hamsters drinking isotonic or hypertonic saline. Reduced feeding with isotonic saline consumption results from the failure of hamsters to increase their ad lib intake of that solution. The prolonged retention of both sodium and fluid after saline consumption or injection suggests that further saline intake may be inhibited by an expansion of the extracellular space.     

Body fluid changes, thirst and drinking in man during free access to water

To investigate whether human thirst and drinking during ad lib access to water occur in response to body fluid deficits, we obtained blood samples and visual analog scale thirst ratings from five healthy, volunteer, young men at hourly intervals and when they were thirsty during a normal working day. Although there were significant increases in ratings of thirst, pleasantness of drinking water, mouth dryness and unpleasantness of the taste in the mouth when subjects were thirsty enough to drink compared with intervening intervals, there were no concomitant changes in body fluid variables (microhematocrit, plasma osmolality and plasma sodium, potassium, protein and angiotensin II concentrations). Subjects drank mainly in association with eating and were not overhydrated as indicated by constantly hypertonic urine and significant tubular reabsorption of free water over the experimental period. The results indicate that during free access to water humans become thirsty and drink before body fluid deficits develop, perhaps in response to subtle oropharyngeal cues, and so provide evidence for anticipatory thirst and drinking in man.     

Drinking to intracellular dehydration following vagotomy in rats

Abdominally vagotomized rats maintained on a solid diet drank less and had longer latencies to drink than sham vagotomized rats following IP injection of an osmotic load (0.75 M NaCl, 1% BW). However, these two groups did not differ in latency or water intake following injection of isotonic saline. Since both vagotomized and control rats drank more water and had shorter latencies following injection of hypertonic saline than after isotonic saline, vagotomy apparently attenuated but did not abolish osmotic drinking. Maintenance on a liquid diet and a brief fast prior to testing (to ensure an empty stomach) did not alter these results, indicating that the impairment of gastric emptying of solid food that accompanies total abdominal vagotomy cannot account for the attenuation of osmotically induced drinking. Furthermore, this deficit was seen even when intracellular dehydration was produced at different times during the circadian cycle and when water presentation was delayed 0.5 hr postinjection. In addition, vagotomized rats drank less than control rats following 16-hr water deprivation and exhibited a lower water-food ratio on ad lib regimen. However, vagotomized and sham vagotomized rats exhibited the same relative day-night difference in water consumption as well as short latency response to thermal pain, which with other results indicates that vagotomy did not result in a general impairment of behavior. These findings suggest that osmotic perturbations are detected by the viscera and the information conveyed to the brain via afferent vagus nerves.     

Reduced thirst in old, thermally dehydrated rats

Water intake and blood parameters of young (7-month) and old (23-month) male Brown Norway rats were assessed following a period of thermal dehydration. Rats of both ages were randomly assigned to one of three groups: (1) Unheated-blood sample, (2) Heated-blood sample, and (3) Heated-water intake. The colonic temperature of heated rats was raised at the rate of 0.05 degrees C/min for 1 h using an infrared heat lamp. Water intake was then measured over the following 2 h. The heating protocol resulted in a similar level of dehydration in both young and old rats; however, plasma osmolality and sodium concentration increased to a significant extent only in the young rats. Old rats drank significantly less water at all time points during the 2 h following the heat stress. While neither group replaced the water lost as a result of the thermal dehydration, the young rats did rehydrate to a greater extent. These results suggest that the diminished level of rehydration in aged rats, following a thermal dehydration, is due to an attenuated rise in plasma osmolality.     

Interaction between the septal area and the subfornical organ in the control of water intake induced by thirst-eliciting procedures

Rats bearing lesions in the septal area followed by lesions in the subfornical organ were submitted to various thirst-eliciting procedures. The rats with hyperdipsia induced by lesions of the septal area drank more water than either during the control period or after lesion of the subfornical organ under the same thirst-eliciting or angiotensin-liberating stimuli (polyethyleneglycol, isoproterenol, water deprivation and ligation of the inferior vena cava). The overdrinking elicited by lesions in the septal area was blocked after lesion of the subfornical organ. Neither hypovolemia, nor hypotension or water deprivation could elicit increased water intake in animals whose subfornical organ had been destroyed. Animals with lesions in the subfornical organ showed decreased water intake after cellular dehydration. The results obtained suggest that the subfornical organ acts as a more important structure than the septal area in the regulation of water intake elicited by angiotensin, with two opposite effects: a direct one facilitating water intake, and an indirect one inhibiting the septal area. The septal area has an inhibitory effect on the subfornical organ and on water intake.     

丹参种子形态结构与吸水萌发特性

目的 :系统研究丹参种子的形态结构与吸水萌发特性 ,为丹参规范化栽培提供理论依据和技术参考。方法 :形态结构研究采用扫描电子显微镜观察并拍照 ;种子吸水 /脱水速率用重量法 ,种子发芽条件研究参照国家农作物种子检验规程和国际标准的有关规定进行。结果 :①通过种子形态结构观察发现 ,在丹参果实的果皮外层有 10～20μm厚度的黏液物质覆盖 ,并形成菱形网纹结构 ,其重量占种子重量的 8%～ 10 % ;②黏液物质能够迅速吸水膨胀 ,2h吸水量可达种子原重的 10倍以上 ,而脱水速率却远低于吸水 ;③丹参种子发芽的最适温度在 25℃左右 ,当年的新种子发芽率可以达到 75%以上 ,在 23℃ ,28℃变温条件下发芽势与活力指数最高。同时发现 ,预先冷冻、PEG引发和GA₃ 浸种等处理技术可以明显提高丹参种子的发芽率。     

The influence of hydration state on thermoregulation during a 161-km ultramarathon

It is advised that individuals should avoid losing >2% of their body mass during exercise in order to prevent hyperthermia. This study sought to assess whether a loss of >2% body mass leads to elevations in core temperature during an ultramarathon. Thirty runners agreed to take part in the study. Body mass and core temperature were measured at the start, at three locations during the race and the finish. Core temperature was not correlated with percent body mass change (p = 0.19) or finish time (p = 0.11). Percent body mass change was directly associated with finish time (r = 0.58, p < 0.01), such that the fastest runners lost the most mass (~3.5–4.0%). It appears that a loss of >3% body mass does not contribute to rises in core temperature. An emphasis on fluid replacement for body mass losses of this magnitude during prolonged exercise is not justified as a preventative measure for heat-related illnesses.     

Use of sodium–glucose cotransporter 2 inhibitors in older patients with type 2 diabetes mellitus

Aim

Sodium–glucose cotransporter 2 (SGLT2) inhibitors are antidiabetic agents that act on the proximal renal tubules to lower blood glucose levels by inhibiting glucose reabsorption and promoting urinary glucose excretion. The present study assessed the long‐term use of SGLT2 inhibitors in older patients with diabetes.

Methods

A total of 117 older patients with type 2 diabetes who were given SGLT2 inhibitors were enrolled from April 2014 to March 2016.

Results

The mean age of the patients was 73.7 ± 10.0 years. During the follow‐up period (mean 289.3 days), there was no event associated with oral administration of SGLT2 inhibitors. These drugs significantly lowered fasting blood glucose and glycosylated hemoglobin levels at 6 months, and did not affect the creatinine level, blood urea nitrogen/creatinine ratio or estimated glomerular filtration rate during treatment. Although the treatment significantly increased hemoglobin and hematocrit levels, it did not affect the ultrasonographically determined diameter of the inferior vena cava, and no signs of intravascular collapse were observed. Changes in brain natriuretic peptide levels during the follow‐up period were assessed in 78 patients with a brain natriuretic peptide level exceeding the normal upper limit before treatment with SGLT2 inhibitors. The brain natriuretic peptide levels significantly decreased after 6 months of treatment.

Conclusions

In older Japanese patients with diabetes, treatment with SGLT2 inhibitors for 6 months exerted a favorable hypoglycemic effect, while no sign of dehydration was observed. Geriatr Gerontol Int 2018; 18: 108–114 .