Effects of 24-hour starvation period on metabolic parameters of 20-day-old rats

The effects of a 24-hour starvation period upon 20-day-old rat pups were studied both in animals kept in the presence of their starved dams and in their absence. The relative loss of body weight was more intense in the rats that received no milk, being however, severe in both groups. There was a significant maintenance of both plasma glucose levels and total amino acids, with differences in blood glucose compartmentation and a remarkable uniformity in the effects of starvation upon individual amino-acid concentrations. A significant increase in plasma urea was observed, higher in the rats kept in the presence of the dam. Ketone bodies increased with starvation but their final levels were lower than in adults. The general pattern of metabolic change observed suggests a situation, after 24-h food deprivation, similar to that of long term starvation in adults; with an active protein amino-acid catabolism but with a remarkable maintenance of circulating foodstuff levels.     

Variation of visual detection over the 24-hour period in humans

A circadian rhythm for visual sensitivity has been intensively assessed in animals. This rhythm may be due to the existence of a circadian clock in the mammalian eye, which could account for fluctuating sensitivity to light over the day in certain species. However, very few studies have been devoted to the human visual system. The present experiment was designed to assess a possible rhythm of visual sensitivity using a psychophysical method over the whole 24h period. Twelve subjects underwent visual detection threshold measures in a protocol that allowed one point every 2h. The results show that the visual detection threshold changes over the 24h period, with high thresholds in the morning, a progressive decrease over the day and the early night, and an increase during the last part of the night. These data suggest that a circadian rhythm influences visual sensitivity to mesopic luminance in humans. (Chronobiology International, 17(6), 795-805, 2000)     

Irregular 24-hour activity rhythms and the metabolic syndrome in older adults

Circadian rhythms – near 24?h intrinsic biological rhythms – modulate many aspects of human physiology and hence disruption of circadian rhythms may have an important impact on human health. Experimental work supports a potential link between irregular circadian rhythms and several key risk factors for cardiovascular disease including hypertension, obesity, diabetes and dyslipidemia, collectively termed the metabolic syndrome. While several epidemiological studies have demonstrated an association between shift-work and the components of the metabolic syndrome in working-age adults, there is a relative paucity of data concerning the impact of non-occupational circadian irregularity in older women and men. To address this question, we studied 7 days of actigraphic data from 1137 older woman and men participating in the Rush Memory and Aging Project, a community-based cohort study of the chronic conditions of aging. The regularity of activity rhythms was quantified using the nonparametric interdaily stability metric, and was related to the metabolic syndrome and its components obesity, hypertension, diabetes and dyslipidemia. More regular activity rhythms were associated with a lower odds of having the metabolic syndrome (OR?=?0.69, 95% CI?=?0.60–0.80, p?=?5.8?×?10^?7), being obese (OR?=?0.73, 95% CI?=?0.63–0.85, p?=?2.5?×?10^?5), diabetic (OR?=?0.76, 95% CI?=?0.65–0.90, p?=?9.3?×?10^?4), hypertensive (OR?=?0.78, 95% CI?=?0.66–0.91, p?=?2.0?×?10^?3) or dyslipidemic (OR?=?0.82, 95% CI?=?0.72–0.92, p?=?1.2?×?10^?3). These associations were independent of differences in objectively measured total daily physical activity or rest, and were not accounted for by prevalent coronary artery disease, stroke or peripheral artery disease. Moreover, more regular activity rhythms were associated with lower odds of having cardiovascular disease (OR?=?0.83; 95% CI?=?0.73–0.95, p?=?5.7?×?10^?3), an effect that was statistically mediated by the metabolic syndrome. We conclude that irregular activity rhythms are associated with several key components of the metabolic syndrome in older community-dwelling adults, and that the metabolic syndrome statistically partially mediates the association between activity rhythms and prevalent cardiovascular disease. Although additional longitudinal and experimental studies are needed to conclusively delineate the causal relationships underlying these associations, these findings are consistent with preclinical data, and add further support for investigations of the irregularity of activity rhythms as a potential therapeutic target to decrease the burden of cardiovascular disease in older adults.     

Metabolic level and the function of the peripheral catecholaminergic systems in immobilization hypothermia in rats

Metabolic peculiarities were studied on the model of prolonged immobilization hypothermia in rats (body temperature +20 degrees C for 24 h). Stress reactions and the state of peripheral catecholaminergic systems were compared in hypo- and normothermia. A direct correlation was established between the intensity of metabolism and the mediator activity in adrenergic nerve structures.     

Posthypoxic changes in the cerebral cortex of dogs in the late recovery period after 4-hour hypovolemic hypotension]

On the 14th-21st day of the restorative period after four-hour hypovolemic hypotension the level of total RNA decreased in the tissue of the gray matter of the brain by 20.9%, and of DNA-by 13%. In the postmitochondrial supernatant the concentration of prealbumins was reduced by 26.5%, alpha-globulins--19.2%, gamma-globulins--by 59.8%; the concentration of albumins and beta-globulins was increased by 12.6% and 50.0%, respectively. The activity of acid cathepsins rose by 50%, and of acid phosphatase--by 44%. The activity of total lactic dehydrogenase (LDH) and glutamic dehydrogenase failed to differ essentially from the control level. However, LDH isoenzyme spectrum changes towards the reduction of LDH3+4+5 from 31.9 to 14.2%. Analysis of densitograms of electrophoresis in polyacrylamide gel showed physico-chemical changes in the protein molecules similar in nature to the denaturation phenomenon. The Purkinje's cell count decreased in the cerebellum by 41.3% in comparison with control.     

Ultrastructure of the cerebral cortex of the cat in the early recovery period after short-term anoxia

The ultrastructure of cat sensomotor cortex has been studied during a 15-minute recovery after 2.5-6-minute oxygen supply cessation. An increase of osmopholia of free and endoplasmic reticulum bound ribosomes was detected in addition to a great number of altered mitochondria with longitudinal crystal arrangement. Besides, numerous activated synapses, local destructive changes of membrane complexes in dendrite and myelinated axons cytoplasm and glycogen granule accumulation in neuroglia were noticed. During the recovery period more prominent changes were shown after a 6-minute anoxia than after a 2.5-minute one.     

Dissociation between plasma adrenocorticotropin and serum cortisol level during the early postoperative period after gastrectomy

We demonstrated the dissociation between plasma adrenocorticotropin (ACTH) and serum cortisol levels during the early recovery period after radical gastrectomy in 9 of 31 patients with gastric adenocarcinoma. Patients with the dissociation between plasma ACTH and serum cortisol levels (DAC) showed a sustained elevation of serum cortisol level on the first or second postoperative day, while the plasma ACTH level returned to its preoperative state. These patients also had more advanced cancers (p < 0.05) and suffered from more postoperative complications (p < 0.05) than those without DAC. In these patients with DAC, serum cortisol and interleukin (IL)-6 levels remained higher on the second postoperative day than in those of the patients without DAC (21.80 +/- 1.57 vs. 13.68 +/- 0.72 microg/dl, p < 0.001, and 74.31 +/- 15.65 vs. 18.75 +/- 3.14 pg/ml, p < 0.001, respectively). On the second postoperative day, serum IL-6 levels showed a significant correlation with serum cortisol levels in all patients (r = 0.511, p < 0.01). These results suggest that the DAC during the early postoperative period after radical gastrectomy is associated with advanced stage of cancer and postoperative complication, and that the increased serum IL-6 level is at least in part responsible for maintaining the elevated serum cortisol.     

Fluctuation of the plasma TRH level in normal subjects in a 4-hour observation period

Radioimmunoassayable TRH and TSH were measured in plasma samples taken at 5 min intervals for 4 hr (2100-0200 hr) from 4 normal male subjects. Three subjects showed a TSH surge at 2135 hr, 2455 hr and 0150 hr, respectively. The mean plasma TRH level of the 4 subjects was 10.3-11.7 pg/ml. Plasma TRH showed random fluctuation, which did not coincide with the nocturnal increase in plasma TSH.     

Day-to-day alteration of 24-hour sleep pattern immediately before and after giving birth

Sleep and Biological Rhythms - The current literature suggests that nighttime sleep is compromised during late pregnancy and early postpartum periods, but little is known about the 24-hour sleep...     

Comparison of early passive motion and immobilization after flexor tendon repairs

Thirty-one flexor tendon repairs in 30 patients managed by early passive motion were retrospectively compared with 31 flexor tendon repairs in 30 patients managed by 3 weeks of postoperative immobilization. Repairs were performed by several surgeons, including plastic surgical residents. There were no statistically significant differences between the two groups comparing age, zone of injury, number of tendons repaired, nature of injury, or associated injuries. No statistically significant difference was found between the two groups when total active and total passive range of motion were compared for repairs in zone I, zone II, zones III and IV, and all zones combined. In the early passive motion group in zone II, there were 12 percent excellent results, 15 percent good results, 23 percent fair results, and 50 percent poor results. In the immobilization group, there were 18 percent excellent results, 8 percent good results, 23 percent fair results, and 53 percent poor results. There was no significant difference between the two groups (p less than 0.05).     

Effects of cold immobilization and recovery period on honeybee learning, memory, and responsiveness to sucrose

In addition to human error and variation in laboratory conditions, there are numerous factors that can complicate comparisons among studies. Furthermore, differences in how experimental methods are executed can make it difficult to distinguish between effects of focal versus extraneous variables. Insect neural function is commonly evaluated using Pavlovian conditioning techniques; learning and memory in many species can be assessed using the proboscis extension reflex (PER). However, there are significant inconsistencies in methods used to immobilize insects prior to PER tests. We compared responses of honeybees immobilized in a refrigerator, on ice, and in a freezer, and evaluated influence of recovery interval before testing. Ice-chilling weakly decreased learning (response to an originally neutral odor) more so than refrigeration or freezing, but not 24-h recall of odor. We found no significant differences in responsiveness to sucrose relative to cooling method, but responsiveness was significantly lower among honeybees left to recover for only 0.75 h versus 1.5 or 3 h. Finally, we observed increased responsiveness to sucrose and geraniol between June and August. Our results suggest that inconsistencies in cold immobilization methods could confound interpretation and comparison of results from a large body of work on honeybee learning and memory.     

A morphometric study of the 24-hour variations in subcellular structures of rat pancreatic acinar cells during the periweaning period

Summary Pancreatic acinar cells of rats obtained before (21 days of age) and after (31 and 42 days) weaning were morphometrically examined at six evenly spaced times during 24 h.Morphometric analysis demonstrated clear-cut variations in the average volume of the cell and nucleus, the incidence of binucleate acinar cells, and the volume and numerical densities of various cytoplasmic organelles during 24 h, at each stage. The daily mean values and variation of these parameters at 21 days clearly differed from those at 31 and 42 days. In particular, changes in the volume densities of rER and zymogen granules were bimodal at 21 days, whereas they were unimodal at 31 and 42 days. Moreoever, some parameters also differed between 31 and 42 days, the main difference being an 8 h time shift in the variation curves of the volume densities of rER and zymogen granules.These findings indicate that morphometric analysis of the subcellular structures of pancreatic acinar cells during 24 h can be used to determine their developmental stage.     

Neural substrates for the motivational regulation of motor recovery after spinal-cord injury

It is believed that depression impedes and motivation enhances functional recovery after neuronal damage such as spinal-cord injury and stroke. However, the neuronal substrate underlying such psychological effects on functional recovery remains unclear. A longitudinal study of brain activation in the non-human primate model of partial spinal-cord injury using positron emission tomography (PET) revealed a contribution of the primary motor cortex (M1) to the recovery of finger dexterity through the rehabilitative training. Here, we show that activity of the ventral striatum, including the nucleus accumbens (NAc), which plays a critical role in processing of motivation, increased and its functional connectivity with M1 emerged and was progressively strengthened during the recovery. In addition, functional connectivities among M1, the ventral striatum and other structures belonging to neural circuits for processing motivation, such as the orbitofrontal cortex, anterior cingulate cortex and pedunculopontine tegmental nucleus were also strengthened during the recovery. These results give clues to the neuronal substrate for motivational regulation of motor learning required for functional recovery after spinal-cord injury.     

Effect of stress on the cardiomyocyte transmembrane potential of the working heart and its recovery after hypothermia

Emotional-painful stress in rats was shown to decrease insignificantly transmembrane cardiomyocyte potential (TCP) measured in isolated hearts. The recovery of TCP following its depression due to the preparation cooling was twice slower in stress-exposed than in control animals. This is in keeping with the data on stress-induced disturbances of Na, K-ATPase activity (an enzyme playing a leading role in TCP maintenance). It is suggested that the disturbance in cation pump function activity plays a certain role in the onset of arrhythmias and cardiac fibrillation during stress.     

Characteristics of proteolysis in the gastrointestinal tract in the early postnatal period

The activity of proteinases was increased, when we used experimental casein for artificial feeding of newborn rats. Control casein contained in milk substitutes delayed protein evacuation from the stomach. The activity of intestine pancreatic proteinases was increased when we used experimental casein and decreased, for control casein. When the activity of pancreatic proteinases increased, lysosomal intestine activity decreased.