ADAPTATION TO SUCROSE LOADING IN THE RAT

1966 ◽  
Vol 44 (3) ◽  
pp. 389-400
Author(s):  
Vincent Fiorica ◽  
P. F. Iampietro ◽  
Russell Moses
Keyword(s):  
Body Weight ◽  
Antidiuretic Hormone ◽  
Water Conservation ◽  
Physiological Adaptation ◽  
Loading Conditions ◽  
Adaptive Responses ◽  
Arterial Infusion ◽  
Initial Loading ◽  
Sucrose Solutions ◽  
Sucrose Loading

Four groups of unanesthetized rats were infused with standardized volumes of 1.46 M (50% w/v) sucrose solutions through chronically indwelling arterial catheters. The excretion of water and solutes was measured during the following 6 hours. Five days later, after the animals had returned to their pre-loading weights, each group was infused again with the same load given initially. After the second loading, a pattern of excretion of water and solutes was observed which was different from that elicited by the first loading. The adaptations manifested after a second loading were characterized principally by (a) a smaller total volume excretion of urine (milliliters per 100 g body weight), (b) the excretion of a smaller fraction of the infused load, (c) an earlier inhibition of the initial diuresis, and (d) the production of a more concentrated urine. It is suggested that the initial loading conditions generate a physiological adaptation which promotes the water conservation mechanisms of the animal. This may involve a greater sensitivity of the adapted animal to antidiuretic hormone. It was further observed that the characteristics of the adaptations generated by intra-arterial infusion are qualitatively different from those produced by intraperitoneal infusion. This suggests that the ability of hypertonic solutions to evoke adaptive responses is dependent on the route through which such solutions are given.

Regulation of metabolic rate in Svalbard and Norwegian reindeer

1984 ◽  
Vol 247 (5) ◽  
pp. R837-R841 ◽  
Author(s):  
K. J. Nilssen ◽  
J. A. Sundsfjord ◽  
A. S. Blix
Keyword(s):  
Body Weight ◽  
Critical Temperature ◽  
Food Intake ◽  
Metabolic Rate ◽  
Seasonal Changes ◽  
Serum Levels ◽  
Physiological Adaptation ◽  
Conservation Of Energy ◽  
Winter Food ◽  
Lower Critical Temperature

Food intake, body weight, serum levels of triiodothyronine (T3) and free thyroxine (FT4), and metabolic rate were measured at intervals in Svalbard (SR) and Norwegian (NR) reindeer. From summer to winter food intake decreased 57 (SR) and 55% (NR), while body weight decreased 8.6 (SR) and 3.8% (NR). In SR T3 and FT4 changed seasonally, whereas this was only evident for T3 in NR. Resting (standing) metabolic rate (RMR) in winter was 1.55 (SR) and 2.05 W X kg-1 (NR), lower critical temperature (TLC) being -50 (SR) and -30 degrees C (NR). RMR in summer was 2.15 (SR) and 2.95 W X kg-1 (NR), TLC being -15 (SR) and 0 degrees C (NR). Seasonal changes in T3 and FT4 did not coincide with changes in food intake or RMR in either SR or NR. RMR did, however, correlate with food intake. This indicates that seasonal changes in RMR are due to the thermic effects of feeding and represent no physiological adaptation aimed at conservation of energy during winter.

The Relationship Between Loading Conditions and Fracture Patterns of the Proximal Femur

1996 ◽  
Vol 118 (4) ◽  
pp. 575-578 ◽  
Author(s):  
K. H. Yang ◽  
K.-L. Shen ◽  
C. K. Demetropoulos ◽  
A. I. King ◽  
P. Kolodziej ◽  
...  
Keyword(s):  
Body Weight ◽  
Hip Fracture ◽  
Ultimate Load ◽  
Gluteus Medius ◽  
Muscular Contraction ◽  
Femoral Neck Fractures ◽  
Loading Conditions ◽  
Trochanteric Fractures ◽  
Fracture Patterns ◽  
The Relationship

In an attempt to test the hypothesis of spontaneous hip fracture, seven pairs of femurs, with ages ranging from 59 to 90, were tested under two loading conditions designed to simulate muscular contraction. Simulated iliopsoas contraction produced femoral neck fractures at an average normalized ultimate load of 5.2 ± 0.8 times body weight. Simulated gluteus medius contraction produced sub-/inter-trochanteric fractures at an average normalized ultimate load of 4.1 ± 0.6 times body weight. The average ultimate load for all specimens was 3040 ± 720 N. Fracture patterns produced by both loading conditions were clinically relevant. The results from this study suggest that abnormal contraction produced by major rotator muscles could induce hip fracture.

Development of a New Artificial Knee Joint for an Asian and Middle Eastern Population

2013 ◽  
Author(s):  
Harcharan Singh Ranu
Keyword(s):  
Finite Element ◽  
Body Weight ◽  
Maximum Load ◽  
The Body ◽  
The Other ◽  
Elastic Behavior ◽  
Loading Conditions ◽  
Load Bearing Capacity ◽  
Linear Elastic ◽  
Materials Used

Design of an artificial knee was developed using computer 3-D modeling, the high flexion knee was obtained by using a multi-radii design pattern, The increase of final 20 degrees in flexion was obtained by increasing the condylar radii of curvature. The model of the high flexion knee was developed and one of the models was subjected to finite element modeling and analysis. The compositions of components in the artificial knee were, femoral component and the tibial component were metal, whereas the patellar component and the meniscal insert were made using polyethylene. The metal component used for the analysis in this study was Ti6Al4V and the polyethylene used was UHMWPE. Overall biomaterials chosen were: meniscus (UHMWPE, mass = 0.0183701 kg, volume = 1.97518e-005 m3), tibial component (Ti6Al4V, mass = 0.0584655 kg, volume = 1.32013e-005 m3), femoral component (Ti6Al4V, mass = 0.153122 kg, volume = 3.45742e-005 m3), total artificial assembly (mass = 0.229958 kg, volume = 6.75e-005m3). However, in this design the load had been taken to 10 times the body weight. The weight over single knee is only half the maximum load as the load is shared between the two knee joints. Following were the loading conditions, taking average body weight to be 70Kgs and taking extreme loading conditions of up to 10 times the body weight, i.e. 700Kgs on each of the leg performed the Finite Element Analysis (FEA) over the newly designed knee. The loading was done at an increment of 100 Kgs. The loading conditions and the meshing details for the analysis of the assembly were Jacobian check: 4 points, element size: 0.40735 cm, tolerance: 0.20367 cm, quality: high, number of elements: 80909, number of nodes: 126898. A maximum load of 600 Kgs is optimum for this model. The other components observed linear elastic behavior for the applied loads. Based on these results it was determined that the load bearing capacity of the model were well within the failure levels of the materials used for the analysis. A maximum load of 600 Kgs is optimum for this model. The other components observed linear elastic behavior for the applied loads. Based on these results it was determined that the load bearing capacity of the model were well within the failure levels of the materials used for the analysis. Conclusion drawn from this is that for the first time an innovative new design of an artificial knee joint to suite a segment of some religious population has been developed. This allows them to pray, bend in different positions and squat without too much difficulty.

Lower body negative pressure vs. lower body positive pressure to prevent cardiac atrophy after bed rest and spaceflight. What caused the controversy?

2006 ◽  
Vol 100 (3) ◽  
pp. 1090-1090 ◽  
Author(s):  
Marieta V. Pancheva ◽  
Vladimir S. Panchev ◽  
Adelina V. Suvandjieva
Keyword(s):  
Cardiac Muscle ◽  
Bed Rest ◽  
Left Ventricular ◽  
Physiological Adaptation ◽  
Positive Pressure ◽  
Loading Conditions ◽  
Lower Body ◽  
Cardiac Atrophy ◽  
End Diastolic Volume ◽  
Lv Mass

Cardiac muscle adapts well to changes in loading conditions. For example, left ventricular (LV) hypertrophy may be induced physiologically (via exercise training) or pathologically (via hypertension or valvular heart disease). If hypertension is treated, LV hypertrophy regresses, suggesting a sensitivity to LV work. However, whether physical inactivity in nonathletic populations causes adaptive changes in LV mass or even frank atrophy is not clear. We exposed previously sedentary men to 6 ( n = 5) and 12 ( n = 3) wk of horizontal bed rest. LV and right ventricular (RV) mass and end-diastolic volume were measured using cine magnetic resonance imaging (MRI) at 2, 6, and 12 wk of bed rest; five healthy men were also studied before and after at least 6 wk of routine daily activities as controls. In addition, four astronauts were exposed to the complete elimination of hydrostatic gradients during a spaceflight of 10 days. During bed rest, LV mass decreased by 8.0 ± 2.2% ( P = 0.005) after 6 wk with an additional atrophy of 7.6 ± 2.3% in the subjects who remained in bed for 12 wk; there was no change in LV mass for the control subjects (153.0 ± 12.2 vs. 153.4 ± 12.1 g, P = 0.81). Mean wall thickness decreased (4 ± 2.5%, P = 0.01) after 6 wk of bed rest associated with the decrease in LV mass, suggesting a physiological remodeling with respect to altered load. LV end-diastolic volume decreased by 14 ± 1.7% ( P = 0.002) after 2 wk of bed rest and changed minimally thereafter. After 6 wk of bed rest, RV free wall mass decreased by 10 ± 2.7% ( P = 0.06) and RV end-diastolic volume by 16 ± 7.9% ( P = 0.06). After spaceflight, LV mass decreased by 12 ± 6.9% ( P = 0.07). In conclusion, cardiac atrophy occurs during prolonged (6 wk) horizontal bed rest and may also occur after short-term spaceflight. We suggest that cardiac atrophy is due to a physiological adaptation to reduced myocardial load and work in real or simulated microgravity and demonstrates the plasticity of cardiac muscle under different loading conditions.

THE SECRETION OF ANTIDIURETIC HORMONE IN RESPONSE TO HAEMORRHAGE AND THE FATE OF VASOPRESSIN IN ADRENALECTOMIZED RATS

1954 ◽  
Vol 11 (2) ◽  
pp. 165-176 ◽  
Author(s):  
M. GINSBURG
Keyword(s):  
Body Weight ◽  
Sodium Chloride ◽  
Antidiuretic Hormone ◽  
Intravenous Injection ◽  
Posterior Pituitary ◽  
Arterial Blood ◽  
Adrenalectomized Rats ◽  
Intact Rats

SUMMARY 1. The antidiuretic potency of arterial blood from adrenalectomized rats was greater than that from intact rats, but only if 2 or more ml. of blood were taken from each rat. It is concluded that the amounts of posterior pituitary antidiuretic hormone released during haemorrhage are greater in adrenalectomized than in intact rats. 2. The effect of haemorrhage on the antidiuretic potency of blood in adrenalectomized rats treated with sodium chloride or cortisone was not different from that in intact rats. 3. The disappearance of intravenously injected vasopressin (100 mU/100 g body weight) was retarded after adrenalectomy. Up to 48 hr after adrenalectomy this was due to a reduced capacity of the kidneys to remove vasopressin from the circulation. 4. Treatment with cortisone increased the rate of disappearance of vasopressin in adrenalectomized rats, but the rate was not restored to that observed in intact animals. 5. Treatment with sodium chloride did not affect the rate at which vasopressin was removed from the circulation of adrenalectomized rats. 6. The excretion of an antidiuretic agent in the urine which followed intravenous injection of vasopressin (100 mU/100 g) 48 hr after adrenalectomy was equivalent to 2·1% of the dose. This compared with an excretion of 6·7% of the dose in intact animals.

Physiological effects of short-term water deprivation in the South American sigmodontine rice rat Oligoryzomys nigripes and water rat Nectomys squamipes within a phylogenetic context

2004 ◽  
Vol 82 (8) ◽  
pp. 1326-1335 ◽  
Author(s):  
Martim de França Silveira Ribeiro ◽  
Pedro Luiz Bernardo da Rocha ◽  
Lys Angela Favaroni Mendes ◽  
Steven Franklin Perry ◽  
Elisabeth Spinelli de Oliveira
Keyword(s):  
Body Size ◽  
Water Conservation ◽  
Water Deprivation ◽  
Small Body ◽  
Physiological Adaptation ◽  
Suitable Model ◽  
Arid Environments ◽  
Short Term ◽  
Evaporative Water ◽  
Semi Arid

Ancestrally, oryzomyine rodents have a sylvan habit, but some species have colonized the semi-arid Brazilian Caatinga. Therefore, the clade provides a suitable model for studying adaptation to such environments within a phylogenetic framework. We investigated physiological responses to short-term water deprivation in two oryzomyine rodents kept in captivity. Oligoryzomys nigripes (Olfers, 1818), a small-bodied rodent, occupies the Caatinga, whereas Nectomys squamipes (Brants, 1827), which is larger and semi-aquatic, lives in moist habitats outside this region. Measurements were also carried out in three additional related species of intermediate body size. Neither O. nigripes nor N. squamipes displays exceptional ability to conserve water, and this condition appears to be plesiomorphic for the clade. The results for O. nigripes, such as the great absolute water intake and the high ratio of water ingested to urine voided, probably derive from allometric specializations correlated with its small body size and greater evaporative water loss. In N. squamipes, low urine osmolality and a reduction of food intake during water deprivation may be related to its semi-aquatic lifestyle. Therefore, the Oryzomyini exemplify Neotropical rodents that can occupy semi-arid environments with no remarkable physiological adaptation for water conservation.

scholarly journals Permeability of the Hydrated Shale under Cyclic Loading and Unloading Conditions

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Liu Xianshan ◽  
Li Man ◽  
Xu Ming ◽  
Kang Zhiyong
Keyword(s):  
Cyclic Loading ◽  
Confining Pressure ◽  
Loading Conditions ◽  
Permeability Evolution ◽  
Loading Process ◽  
Cyclic Loading And Unloading ◽  
Initial Loading ◽  
Cyclic Processes ◽  
Loading And Unloading ◽  
Shale Permeability

The hydrated shales under cyclic loading and unloading conditions are common for the shale reservoir development; corresponding mechanical properties and permeability evolution are very significant and should be deeply researched. Firstly, the experiments of the hydrated shales under the above conditions are discussed, showing that the peak strength is lower and corresponding permeability is higher for more days of hydrating treatment. Secondly, the damage theory is proposed to analyze the shale permeability evolution due to hydromechanical damage and get permeability variation under initial loading and unloading conditions, observing that the permeability in the loading process decreases with increasing confining pressure and increases in the unloading process with decreasing confining pressure; however, the former changes much greater than the latter considering the same confining pressure, indicating that the irreversible damage for the hydrated shales in this cyclic condition has resulted in obvious difference of the permeability. Furthermore, the curves between the permeability and confining pressure based on the experimental data are fitted as negative exponential functions under initial loading conditions and power functions under more cyclic loading conditions, showing that more loading process will change the permeability evolution model. However, the permeability while unloading changes smoothly and can be fitted as a power function with the confining pressure. And in addition, the loss ratio and recovery ratio of the permeability have been deeply researched under five cyclic loading and unloading conditions, thoroughly explaining the permeability decreasing variation with more cyclic processes. Finally, the sensitive coefficients of the permeability have been investigated to observe the largest coefficients under initial cyclic conditions and less and less with more cyclic processes, especially the coefficients while loading which are more sensitive to lower confining pressure and smaller while unloading, which is in accordance with the shale permeability loss and recovery variation, revealing the permeability evolution of the hydrated shale under complex extracted environment.

Water Physiology and Nutrition in Fluctuating Populations of Rattus-Colletti in Monsoonal Northern-Territory, Australia

1987 ◽  
Vol 14 (4) ◽  
pp. 443 ◽  
Author(s):  
CK Williams
Keyword(s):  
Body Weight ◽  
Population Decline ◽  
Dry Season ◽  
Social Consequences ◽  
Physiological Adaptation ◽  
Wet Season ◽  
Water Turnover ◽  
Dry Seasons ◽  
Fluctuating Populations ◽  
Wet And Dry Seasons

During wet and dry seasons and transitions of the monsoonal cycle, rates of water turnover and nutritional variables were measured on a population of Rattus colletti which fluctuated between extremes of high and low abundance. Rate of water turnover (RWT in millilitres per day) and body weight ( W, in kilograms) were related allometrically: RWT = aW*O.742 � 0.061, where a varied between seasons and sexes. Seasonal rates of water turnover were consistent with physiological adaptation in R. colletti to seasonal aridity. Rate of water turnover correlated with seasonal hydric regime, varying by a factor of 3.5 between dry and wet seasons. During the wet season, low body weight and lack of breeding seemed to be caused by flooding and its physical and social consequences. During dry season aridity the rats were short of food and water, but not in a dry season when rain fell and breeding ensued. Reproduction increased requirements for food and water in both sexes. Juveniles had relatively high requirements, and shortages appeared to retard growth. Very large populations resulted from prolific breeding after dry season rain had sustained high consumption of food and water on the riverine plains, the dry season habitat. Population decline resulted from very high wet season rainfall followed by a rainless dry season when food and water intakes were depressed, probably because the previous rainfall pattern reduced the availability of sedge corms, the dry season source of food and water. This climatic pattern recurred in the next wet and dry seasons, reinforcing the effects on R, colletti, which became rare for several years on both riverine systems studied.

On the Theory of Bin Loads

1969 ◽  
Vol 91 (2) ◽  
pp. 339-344 ◽  
Author(s):  
A. W. Jenike ◽  
J. R. Johanson
Keyword(s):  
Flow Pattern ◽  
Loading Conditions ◽  
Bulk Solid ◽  
Initial Loading ◽  
Vertical Part ◽  
Concentrated Forces

It is proposed that three loading conditions should be considered in the analysis of loads acting on a bin: Initial loading which occurs when bulk solid is charged without any of it being withdrawn, flow loading which occurs after flow has been established, and switch loading which occurs during the switch from initial to flow loading. The last is transient but, while it acts, it exerts large concentrated forces. The importance of the flow pattern is outlined and an expression is given for the high local force which frequently acts at the transition from the vertical part to the converging part of a bin.

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