The aging gut

1986 ◽  
Vol 64 (1) ◽  
pp. 30-38 ◽  
Author(s):  
A. B. R. Thomson ◽  
M. Keelan
Keyword(s):  
Fatty Acids ◽  
Gastrointestinal Tract ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Physiological Function ◽  
Normal Function ◽  
Membrane Composition ◽  
Form And Function ◽  
Age Related ◽  
And Function

A spectrum of changes occurs in the function of the gastrointestinal tract throughout the life of the animal. With aging, there is a decline towards newborn levels of the villus surface area and brush border membrane markers, but the absorption of some nutrients continues to increase (such as glucose and vitamin), whereas the absorption of some nutrients falls (such as cholesterol and fatty acids). Clearly there is a distinction between age-related alterations in intestinal form and function, and some of the enzyme- or carrier-mediated changes are substrate specific. With aging, the structure and brush border membrane composition of the intestine tends to regress towards newborn levels. It remains to be clarified whether these changes are a benefit to the animal, whether they represent a degeneration of normal function, and whether these changes are the cause or the effect of various age-related alterations in metabolic and physiological function.

Resection of rabbit ileum: effect on brush border membrane enzyme markers and lipids

1985 ◽  
Vol 63 (12) ◽  
pp. 1528-1532 ◽  
Author(s):  
M. Keelan ◽  
K. Walker ◽  
A. B. R. Thomson
Keyword(s):  
Fatty Acids ◽  
Total Cholesterol ◽  
Bile Acids ◽  
Chain Length ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Composition ◽  
Rabbit Ileum ◽  
Ileal Resection ◽  
Distal Small Intestine

Alterations in transport function have been described 6 weeks after surgical resection of 50% of the distal small intestine. Previous studies demonstrated a modest increase in the jejunal uptake of medium chain length fatty acids following resection, while the uptake of many other lipids (cholesterol, bile acids, fatty alcohols, short and long chain length fatty acids) appears to be unaffected. Marked changes in the kinetic constants for the carrier-mediated uptake of four sugars and leucine were observed following resection, but the changes in transport were not associated with changes in the mucosal surface area. This study was undertaken to examine the possible adaptive mechanisms that occur with ileal resection in the rabbit. A 29% increase in the wet weight of jejunal mucosal scrapings and a 53% increase in jejunal brush border membrane (BBM) protein was observed following resection. The jejunal BBM sucrase (S) was unchanged following ileal resection, but alkaline phosphatase (AP) total activities were increased in the resected rabbits. This resulted in a 45% increase in the ratio of AP/S with resection. The lipid composition (total free fatty acids, total bile acids, total cholesterol, total phospholipids, individual phospholipids, and the ratio of total phospholipids/total cholesterol) of BBM was similar in control and resected rabbits. This suggests that quantitative rather than qualitative changes in the membrane composition may be responsible for the transport changes observed in resected animals.

scholarly journals A developmental biologist’s journey to rediscover the Zen of plant physiology

F1000Research ◽  
2015 ◽  
Vol 4 ◽  
pp. 264 ◽  
Author(s):  
José R. Dinneny
Keyword(s):  
Plant Physiology ◽  
Human Population ◽  
Holistic Approach ◽  
Normal Function ◽  
Plant Biology ◽  
Form And Function ◽  
Adaptive Mechanisms ◽  
Basic Concepts ◽  
Living Organisms ◽  
And Function

Physiology, which is often viewed as a field of study distinct from development, is technically defined as the branch of biology that explores the normal function of living organisms and their parts. Because plants normally develop continuously throughout their life, plant physiology actually encompasses all developmental processes. Viewing plant biology from a physiologist’s perspective is an attempt to understand the interconnectedness of development, form, and function in the context of multidimensional complexity in the environment. To meet the needs of an expanding human population and a degrading environment, we must understand the adaptive mechanisms that plants use to acclimate to environmental change, and this will require a more holistic approach than is used by current molecular studies. Grand challenges for studies on plant physiology require a more sophisticated understanding of the environment that plants grow in, which is likely to be at least as complex as the plant itself. Moving the lab to the field and using the field for inspiration in the lab need to be expressly promoted by the community as we work to apply the basic concepts learned through reductionist approaches toward a more integrated and realistic understanding of the plant.

Developmental maturation of Na(+)-H+ exchange in rat renal tubular brush-border membrane

1991 ◽  
Vol 261 (6) ◽  
pp. F1017-F1025 ◽  
Author(s):  
I. Zelikovic ◽  
E. Stejskal ◽  
P. Lohstroh ◽  
A. Budreau ◽  
R. W. Chesney
Keyword(s):  
Brush Border ◽  
Brush Border Membrane ◽  
Initial Rate ◽  
Neonatal Rat ◽  
Adult Rats ◽  
Luminal Membrane ◽  
Age Related ◽  
Proximal Tubular ◽  
Na Uptake ◽  
Developmental Maturation

The developmental maturation of the Na(+)-H+ exchanger present in the proximal tubular luminal membrane of the rat was investigated. An overshoot of 1 mM Na+ uptake was evident in brush-border membrane vesicles derived from the renal cortex of 7- and 21-day-old and adult rats in the presence of an outwardly directed H+ concentration ([H+]) gradient [intravesicular pH (pHi) = 5.5; extravesicular pH (pHo) = 7.5]. Na+ uptake was amiloride sensitive at all ages examined. Significantly higher initial rate (3 s) Na+ uptake and peak accumulation (60 s) in the presence of a [H+] gradient were found in vesicles from 7-day-old rats compared with adult animals. Significantly enhanced initial rate Na+ uptake by neonatal vesicles was also evident under pH-equilibrated conditions (pHi = pHo = 7.5). An age-related decrease in amiloride-sensitive Na+ accumulation by vesicles was found. Kinetic analysis of Na(+)-H+ exchange in voltage-clamped vesicles, in the presence of dimethylamiloride (DMA), and calculating 5-s Na+ uptake values showed a maturational decrease in capacity (decreasing Vmax) coupled with a maturational increase in affinity (decreasing Km) of Na(+)-H+ antiport. These data suggest that an enhanced amiloride-inhibitable Na(+)-H+ exchange activity due to increased capacity of exchange exists in the proximal tubular luminal membrane of the neonatal rat. This increased Na(+)-H+ exchange may potentially contribute to positive Na+ balance in the growing organism and may rapidly dissipate the electrochemical Na+ gradient across the luminal membrane necessary for Na(+)-solute contransport, thereby contributing to glycosuria and aminoaciduria of early life.

Effects of dietary n−3 polyunsaturated fatty acids on T-Cell membrane composition and function

Lipids ◽  
2004 ◽  
Vol 39 (12) ◽  
pp. 1163-1170 ◽  
Author(s):  
Kirsten C. Switzer ◽  
David N. McMurray ◽  
Robert S. Chapkin
Keyword(s):  
Fatty Acids ◽  
T Cell ◽  
Cell Membrane ◽  
Polyunsaturated Fatty Acids ◽  
Membrane Composition ◽  
And Function ◽  
T Cell Membrane
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