Changes in blood plasma volume in rats during ontogenesis

The dynamics of blood plasma volume were studied for the first time in rats during ontogenesis. The significance of blood plasma volume is estimated in the transport of physiologically active substances to cells and target organs during development. The blood plasma volume was measured in male and female rats during embryogenesis on day 18 (E18), perinatal development on E21 and day of postnatal development (P3), and postnatal development on P15 and P30. Body mass was determined in the same animals and correlation was estimated between the blood plasma volume and body mass. The plasma volume increased 1.9-fold from E18 to E21, 1.4-fold from E21 to P3, 2.1-fold from P3 to P15, and 3.4-fold from P15 to P30. The body mass increased 5-fold from E18 to E21, 2-fold from E21 to P3, 2.3-fold from P3 to P15, and 3.2-fold from P15 to P30. The ratio of blood plasma to body mass was the highest on E18 (19%) and decreased twice by E21. This index varied from 5.4 to 4.8% during postnatal development. No sex-related differences in these indices were found in rats. The results obtained make it possible to determine the total content of physiologically active substances on the basis of their plasma concentration and, thereby, estimate the efficiency of secretory organs.     

Changes in blood plasma volume in rats during ontogenesis

The dynamics of blood plasma volume were studied for the first time in rats during ontogenesis. The significance of blood plasma volume is estimated in the transport of physiologically active substances to cells and target organs during development. The blood plasma volume was measured in male and female rats during embryogenesis on day 18 (E18), perinatal development on E21 and day 3 of postnatal development (P3), and postnatal development on P15 and P30. Blood plasma volume was measured using Evans Blue dye method. Body mass was determined in the same animals and correlation was estimated between the blood plasma volume and body mass. The plasma volume increased 1.9-fold from E18 to E21, 1.4-fold from E21 to P3, 2.1-fold from P3 to P15, and 3.4-fold from P15 to P30. The body mass increased 5-fold from E18 to E21, 2-fold from E21 to P3, 2.3-fold from P3 to P15, and 3.2-fold from P15 to P30. The ratio of blood plasma to body mass was the highest on E18 (19%) and decreased twice by E21. This index varied from 5.4 to 4.8% during postnatal development. No sex-related differences in these indices were found in rats. The results obtained make it possible to determine the total content of physiologically active substances on the basis of their plasma concentration and, thereby, estimate the efficiency of secretory organs.     

Changes in regional blood volume and blood flow during static handgrip

Increased blood pressure (BP) and heart rate during exercise characterizes the exercise pressor reflex. When evoked by static handgrip, mechanoreceptors and metaboreceptors produce regional changes in blood volume and blood flow, which are incompletely characterized in humans. We studied 16 healthy subjects aged 20-27 yr using segmental impedance plethysmography validated against dye dilution and venous occlusion plethysmography to noninvasively measure changes in regional blood volumes and blood flows. Static handgrip while in supine position was performed for 2 min without postexercise ischemia. Measurements of heart rate and BP variability and coherence analyses were used to examine baroreflex-mediated autonomic effects. During handgrip exercise, systolic BP increased from 120 +/- 10 to 148 +/- 14 mmHg, whereas heart rate increased from 60 +/- 8 to 82 +/- 12 beats/min. Heart rate variability decreased, whereas BP variability increased, and transfer function amplitude was reduced from 18 +/- 2 to 8 +/- 2 ms/mmHg at low frequencies of approximately 0.1 Hz. This was associated with marked reduction of coherence between BP and heart rate (from 0.76 +/- 0.10 to 0.26 +/- 0.05) indicative of uncoupling of heart rate regulation by the baroreflex. Cardiac output increased by approximately 18% with a 4.5% increase in central blood volume and an 8.5% increase in total peripheral resistance, suggesting increased cardiac preload and contractility. Splanchnic blood volume decreased reciprocally with smaller decreases in pelvic and leg volumes, increased splanchnic, pelvic and calf peripheral resistance, and evidence for splanchnic venoconstriction. We conclude that the exercise pressor reflex is associated with reduced baroreflex cardiovagal regulation and driven by increased cardiac output related to enhanced preload, cardiac contractility, and splanchnic blood mobilization.     

Effect of blood volume on plasma volume shift during exercise

To assess the relationship between blood volume (BV) and the reduction in plasma volume (PV) during exercise in individual variations, we measured BV and changes in PV in thirteen male volunteers during treadmill exercise until exhaustion. The lactate threshold (LT), as a predictor of aerobic exercise capacity, was calculated from the exercise intensity at the point of plasma lactate concentration buildup to 4 mmol. The relationship of peak VO₂ with BV indicated a significant positive correlation. The strong positive relation between the shifts in PV and total PV, and resulted in a maintenance of the circulating BV.     

Changes in plasma volume during hypohydration and rehydration in subjects from the tropics

Plasma volume (PV) at different levels of hypohydration was determined using radio-iodinated serum albumin-125 in 28 heat acclimated male volunteers in hot dry condition in a climatic chamber. The heat acclimated subjects were hypohydrated to varying degrees i.e. 1%, 2%, 3% and 4% body mass deficit by moderate work in hot conditions in a climatic chamber maintained at 45 degrees C dry bulb temperature and 30% relative humidity. A rehydration study was carried out in only those subjects who were hypohydrated to 3% and 4% body mass and they were brought back to a 2% level of hypohydration by giving a calculated amount of water. A significant decrease in PV was observed at 3% and 4% hypohydration only. The magnitude of the decrease was the same in both the groups and not related to the level of hypohydration. With partial rehydration in the 3% hypohydrated group PV was restored fully, while in the 4% hypohydrated group restoration was incomplete, indicating that at this hypohydration level some of the replenished water that entered in plasma may have moved to the intracellular compartment which may have contributed more at 4% hypohydration. It is suggested that with higher levels of thermal hypohydration significant reduction in the intracellular compartment may result in accentuated physiological strain during work in the heat.     

Changes in plasma volume and haematocrit in intact and splenectomized sheep during feeding.

Changes in jugular haematocrit during daily 2-h feeding periods in trained sheep with and without spleens were compared with changes in the concentration of the plasma tracer radio-iodinated human serum albumin. Jugular haematocrit was increased by 16% in intact sheep and 9% in splenectomized sheep 20 min after they started to eat dry rations. The dilution of tracer in plasma, studied after mixing in the vascular system had been completed, showed four phases. Phase 1 was the rate of removal of tracer in the period before eating began. Phase 2 was the sudden increase in plasma radioactivity that occurred in the first 20 min of eating, indicating a loss of plasma from the circulation. Phase 3 was the decrease in tracer concentration during the remaining feeding period and phase 4 was a post-feeding phase, characterized by a slower rate of decrease of tracer than during phase 3, implying that there was significant recycling of tracer during this phase. The sudden increase in plasma radioactivity, initiated by the onset of feeding, represented a reduction in plasma volume of 10-12%. Minimum plasma volume coincided with peak haematocrit values. The reduced plasma volume accounted for the increased haematocrit in splenectomized sheep, but only accounted for about half of the increase in intact sheep. The residual increase in haematocrit in intact sheep was most likely the result of splenic contraction.     

Suppression of a thioesterase gene expression and the disappearance of short chain fatty acids in the preen gland of the mallard duck during eclipse, the period following postnuptial molt

Wax esters of short chain acids (monomethyl-C6) constitute the major products of the uropygial gland of mallard ducks. During eclipse, the period (June and July) immediately following postnuptial molt, the production of short chain acyl groups is severely curtailed and longer chain acyl groups become the dominant components; after this period the composition reverts. These changes in composition were accompanied by corresponding changes in the level of S-acyl fatty acid synthase thioesterase activity, and the level of the immunologically detectable amount of this enzyme. In vitro translation of the poly(A)+ RNA from the gland produced a 30-kDa protein which cross-reacted with rabbit antibodies prepared against this enzyme. The level of translatable mRNA for the thioesterase in the gland dramatically decreased as the birds went into eclipse and all of these changes reverted when the eclipse period was over. These results strongly suggest that the thioesterase is involved in the production of the short chain fatty acids in vivo and that during eclipse the expression of the thioesterase gene is suppressed.     

Changes in plasma thyroid hormones, luteinizing hormone (LH), estradiol, progesterone and corticosterone of laying hens during a forced molt

1. Circulating concentrations of iodothyronines, luteinizing hormone(LH), estradiol(E2), progesterone and corticosterone were measured in hens before, during, and after a forced molt induced by fasting. 2. Corticosterone increased at the onset of molt, peaked at the maximal molt and returned to pre- and post-molt levels. LH, E2 and progesterone declined during the molt, and the decline was coincident with the cessation of egg production. 3. Thyroxine(T4), triiodothyronine (T3) and reverse triiodothyronine(rT3) increased during the molt. The increases of T4 and T3 were not abolished even if the forced molt was conducted in mild weather.     

Haste makes waste: accelerated molt adversely affects the expression of melanin-based and depigmented plumage ornaments in house sparrows

Background

Many animals display colorful signals in their integument which convey information about the quality of their bearer. Theoretically, these ornaments incur differential production and/or maintenance costs that enforce their honesty. However, the proximate mechanisms of production costs are poorly understood and contentious in cases of non-carotenoid-based plumage ornaments like the melanin-based badge and depigmented white wing-bar in house sparrows Passer domesticus. Costly life-history events are adaptively separated in time, thus, when reproduction is extended, the time available for molt is curtailed and, in turn, molt rate is accelerated.

Methodology/Principal Findings

We experimentally accelerated the molt rate by shortening the photoperiod in order to test whether this environmental constraint is mirrored in the expression of plumage ornaments. Sparrows which had undergone an accelerated molt developed smaller badges and less bright wing-bars compared to conspecifics that molted at a natural rate being held at natural-like photoperiod. There was no difference in the brightness of the badge or the size of the wing-bar.

Conclusions/Significance

These results indicate that the time available for molt and thus the rate at which molt occurs may constrain the expression of melanin-based and depigmented plumage advertisements. This mechanism may lead to the evolution of honest signaling if the onset of molt is condition-dependent through the timing of and/or trade-off between breeding and molt.     

Changes in blood plasma osmolality and states of mania

Manic patients were studied systematically over a period of months. Fluctuations in their blood plasma osmolality were observed and these correlated significantly and inversely with undulations in their mania, rating scores. Successful treatment of patients with lithium carbonate was correlated with increasing levels of their plasma osmolality and with a significant remission of mania symptomatology. Animal studies have shown that adaptations to altered blood plasma osmolalities are accompanied by profound metabolic changes in tissues of the central nervous system. A similar relationship is likely to exist in man. We suggest, therefore, that an altered plasma osmolality is linked to changes in manic symptomatology, through osmotically regulated metabolic changes in the central nervous system.     

Changes in plasma volume in submaximal exertion of short duration

Changes in plasma fluid volume and hyperlactacidemia were measured in nine healthy young men who had been running 10 min on a motor-driven treadmill (work rate from 40 to 90% V0, max). Our results show that there is a linear relationship between reduction of plasma fluid volume and intensity from 50% of max. For a given intensity the reduction of plasma fluid volume is a function of hyperlactacidemia.     

Comparison of adrenocortical responses to acute stress in lowland and highland Eurasian tree sparrows (Passer montanus): similar patterns during the breeding, but different during the prebasic molt

Previous studies indicate most free-living avian species in both extreme and temperate environments seasonally modulate the adrenocortical responses to acute stress, and those breeding in harsh environments always express reduced adrenocortical responses, which may allow them to obtain maximal reproductive success. However, recent investigations showing a human commensal species, house sparrows (Passer domesticus), expressed similar corticosterone (CORT) responses in both benign and harsh environments. In this study, focusing on another human commensal species, Eurasian tree sparrows (P. montanus), we examined the adrenocortical response to acute stress in lowland populations, among the early and late breeding, the prebasic molt, and the wintering stages, and compared them with previously published data from populations on the Tibetan Plateau. Our results show: (1) similar to highland Eurasian tree sparrows, lowland populations show no differences in baseline CORT levels among life history stages, and the stress-induced CORT (maximal CORT, total and corrected integrated CORT) levels are lower during the early breeding and the prebasic molt stages than those in the late breeding and the wintering stages; (2) highland Eurasian tree sparrows show stronger adrenocortical responses during the prebasic molt stage than lowland populations, whereas there are no differences between the early and the breeding stages (except for maximal CORT). Our results suggest that Eurasian tree sparrows from both harsh and benign environments have similar patterns of adrenocortical responses in the breeding stage, whereas they are different in the prebasic molt stage. In highland birds, the increased maximal CORT levels during the late breeding and the small increases in adrenocortical responses during the prebasic molt are interesting but remain unexplained.     

Changes in regional myocardial volume during the cardiac cycle: implications for transmural blood flow and cardiac structure

Although previous studies report a reduction in myocardial volume during systole, myocardial volume changes during the cardiac cycle have not been quantitatively analyzed with high spatiotemporal resolution. We studied the time course of myocardial volume in the anterior mid-left ventricular (LV) wall of normal canine heart in vivo (n = 14) during atrial or LV pacing using transmurally implanted markers and biplane cineradiography (8 ms/frame). During atrial pacing, there was a significant transmural gradient in maximum volume decrease (4.1, 6.8, and 10.3% at subepi, midwall, and subendo layer, respectively, P = 0.002). The rate of myocardial volume increase during diastole was 4.7 +/- 5.8, 6.8 +/- 6.1, and 10.8 +/- 7.7 ml.min(-1).g(-1), respectively, which is substantially larger than the average myocardial blood flow in the literature measured by the microsphere method (0.7-1.3 ml.min(-1).g(-1)). In the early activated region during LV pacing, myocardial volume began to decrease before the LV pressure upstroke. We conclude that the volume change is greater than would be estimated from the known average transmural blood flow. This implies the existence of blood-filled spaces within the myocardium, which could communicate with the ventricular lumen. Our data in the early activated region also suggest that myocardial volume change is caused not by the intramyocardial tissue pressure but by direct impingement of the contracting myocytes on the microvasculature.