Intestinal maturation: characterization of mitochondrial calcium transport in the rat

The mitochondria play a major role in the regulation of intracellular calcium. Despite the fact that the enterocytes receive the majority of absorbed calcium, the role of the intestinal mitochondria in calcium transport during maturation is not known. Therefore, the current studies were designed to characterize calcium pump activity of jejunal mitochondria of rats during maturation (suckling, weanling, and adolescent rats). The functional integrity of the intestinal mitochondria of suckling and adolescent rats was determined by oxygen consumption studies demonstrating respiratory control ratios of more than 3 when succinate was used as a test substrate. Ca++ uptake was significantly stimulated by the presence of 3 mM ATP at all age groups studied. Maximal Ca++ uptake in the presence of 3 mM ATP and 2 mM succinate was 31.1 +/- 0.4, 50.2 +/- 4.2, and 94.3 +/- 1.5 nmol/mg protein (mean +/- SE) in suckling, weanling, and adolescent rats, respectively. Rates of ATP hydrolysis were 15.5 +/- 1.5 and 2.9 +/- 0.3 nmol/ATP hydrolyzed/mg protein in adolescent and suckling rats, respectively (p less than 0.001). Ca++ uptake was completely inhibited by 0.25 microM ruthenium red, oligomycin (10 micrograms/mg protein), 0.5 mM dinitrophenol and 1 mM sodium azide at all age groups. Ca++ efflux in the presence of ruthenium red occurred by a Na+-dependent pathway, indicating a Ca++/Na+ exchange mechanism. Kinetic parameters for ATP stimulated Ca++ uptake at 10 s revealed a Km of 0.84 +/- 0.11, 0.65 +/- 0.17, and 0.57 +/- 0.03 microM and Vmax of 1.83 +/- 0.07, 3.62 +/- 0.26 and 14.15 +/- 0.21 nmol/mg protein/10 s in suckling, weanling, and adolescent rats, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of early weaning on the activity of several enzymes in the liver of rat.

In normally weaned rats the activity of two enzymes in rat liver, i.e. ATP citrate lyase and malic enzyme, gradually increases between the end of the third and the beginning of the fourth postnatal week. The activity of mitochondrial alpha-glycerophosphate oxidase remains unchanged during this period. Early weaning on the 18th postnatal day causes a rapid increase in activity of these enzymes. The impulse for this increase is very probably the change from high fat milk diet to high carbohydrate standard laboratory diet, the decrease of blood lipids, the activation of thyroid gland and changes of sensitivity of hepatic cells towards thyroid hormones. These results showed that early weaning modifies to the known picture of physiological weaning to a great extent.     

Development maturation of riboflavin intestinal transport in the rat

The intestinal transport of riboflavin in the immature intestine of the suckling rat (14 day old) and its subsequent maturation in weanling (22 day old) and adult (90 day old) rats were investigated using the intestinal everted sac technique. The mucosal-to-serosal transport of 0.5 microM riboflavin was linear with time for 30-min incubation and occurred at a rate of 4.6, 3.6, and 1.6 pmol/g initial tissue wet wt/min in suckling, weanling, and adult rats, respectively. The transport of 0.5 microM riboflavin was higher in the jejunum than the ileum in all age groups. The transport system of riboflavin in all age groups was saturable, energy-, temperature-, and Na+-dependent. Kinetic parameters of the transport process were different. Apparent Kt of the transport process was the same in suckling and weanling rats (0.12 and 0.11 microM, respectively) but tripled in adult rats (0.35 microM). On the other hand, a progressive decrease in Vmax from 166 to 122 to 54 pmol/g initial tissue wet weight/30 min was observed in the suckling, weanling, and adult rats, respectively. The present study demonstrates that the characteristics of the transport process of riboflavin is similar in suckling, weanling, and adult rats and occurs by an energy-, temperature-, and Na+-dependent carrier-mediated process. However, the affinity and the activity (or the number) of the transport carriers of riboflavin decrease with maturation.     

Development of colonic fluid and electrolyte transport: influence of weaning pattern

The purpose of this study was to investigate the normal postnatal development of electrolyte and water transport in the large intestines of rats aged 10-20 days, to focus on the events taking place around the time of weaning, and to study the influence of different feeding patterns at the time of weaning on the normal development of the transport mechanisms in the large intestine. The net absorption of sodium, potassium, and water was investigated by using in vivo luminal isotonic perfusion in rats aged 12-40 days. The activity of the active transport enzyme Na-KATPase in the colonic mucosa of rats aged 10-40 days was determined. We found a significant decrease in the net absorption of electrolytes and water that was greatest around the time of weaning. Since the NaKATPase activity was lower in 10-16-day-old rats than in 40-day-old rats, we suggest that the high sodium and water uptake in the colon of suckling rats is independent of the sodium pump. Changes in the feeding patterns around the time of weaning, such as prolonged suckling, were associated with a significantly higher net absorption of electrolytes and water than in rats that were normally weaned at 20 days of age. The Na-KATPase activity was not significantly influenced by the weaning pattern.     

Effect of early weaning and prolonged nursing on development of the rat pancreas

Pancreatic development was studied in rats 17-28 days of age. Control pups, weaned naturally at 21-24 days showed a gradual increase in body weight, pancreatic weight, total DNA and protein content with age. Pups weaned at 17 days showed a transient increase in pancreatic weight and protein content only at day 22; at no time did they show a difference in either DNA content or body weight. Pups nursed up to 25 days of age had a smaller body weight, but had DNA and protein content similar to control rats. Control pups showed gradual increases in lipase and trypsinogen with a sharp increase in amylase between days 22 and 25. Pups weaned at 17 days showed a precocious increase in trypsinogen and a sharp increase in amylase between days 19-22, but an immediate decrease in lipase which eventually returned to the control level at day 28. Pups nursed beyond the weaning stage showed an increase in lipase and trypsinogen but no sharp increase in amylase. A significant increase in all pancreatic enzymes, pancreatic mass, pancreatic DNA and protein content was seen in all groups of rats irrespective of their diet. The results suggest an inherent biological program as a basic control of pancreatic ontogeny with diet playing a modifying role.     

Intestinal maturation: characterization of mitochondrial phosphate transport in the rat and its regulation by 1,25-(OH)2 vitamin D3

The mitochondria play a major role in the regulation of oxidative phosphorylation within the cell. Despite the fact that the enterocytes receive the majority of absorbed phosphate and their high metabolic turnover rate, the role of the intestinal mitochondria in phosphate transport system during maturation is not known. Therefore, the current studies were designed to characterize phosphate transport by jejunal mitochondria of rats during maturation (suckling, weanling, and adolescent rats). The functional integrity of the intestinal mitochondria of suckling and adolescent rats was determined by oxygen consumption studies demonstrating respiratory control ratios of more than 3 when succinate was used as a test substrate. Phosphate uptake was significantly stimulated by the presence of 3 mM ATP at all age groups studied. Maximal phosphate uptake in the presence of 3 mM ATP and 2 mM succinate was 16.5 +/- 1.0, 20.5 +/- 1 and 28.7 +/- 0.4 nmol/mg protein (mean +/- SE) in suckling, weanling, and adolescent rats respectively. ATP-dependent phosphate uptake was inhibited by 80% with 100 microM p-MB. Kinetic parameters for ATP stimulated phosphate uptake at 10 s revealed a Km of 4 +/- 0.9, 2.8 +/- 0.4, and 0.9 +/- 0.1 mM and Vmax of 5 +/- 0.7, 9.5 +/- 1, and 11 +/- 0.7 nmol/mg protein per 10 s in suckling, weanling, and adolescent rats, respectively. Phosphate uptake was also stimulated by an inwardly directed pH gradient (pH out less than pH inside) compared to no pH gradient condition suggesting the presence of PO4-/OH- exchange.(ABSTRACT TRUNCATED AT 250 WORDS)     

Divergent membrane maturation in rat kidney: exposure by dietary taurine manipulation

Taurinuria is characteristic of the immature rat. The excessive taurine loss could be the result of brush border or basal lateral membrane immaturity. The beta-amino acid, taurine, and D-glucose were examined using isolated brush border membrane vesicles (BBMV), slices and tubules prepared from 28-day-old rats. In BBMV, taurine accumulation was inversely proportional to osmolarity, indicating uptake rather than binding, and taurine accumulation was Na+-dependent. BBMV from 28-day rats did not accumulate D-glucose to the same degree as in adult BBMV, and the initial rate of uptake was slower. Taurine uptake had a similar Km and Vmax in BBMV from immature rats. Despite similarities in the kinetics of taurine uptake, higher urinary taurine concentrations are found in younger rats. The efflux of taurine from slices and tubules was much slower than in adults and probably accounts for the taurinuria of young animals. A diet low in methionine and taurine (LTD) given for seven days resulted in a lower excretion and fractional excretion of taurine than in animals fed a normal sulfur amino acid diet (NTD). A high-taurine diet (HTD) causes excessive taurinuria. These patterns of excretion are reflected at the brush border membrane surface with greater uptake after the LTD and reduced uptake after the HTD. A kinetic analysis of adult and 28-day-old animal BBMV reveals that the Vmax of accumulation is altered by diet, whereas the Km remains unchanged. The Vmax is higher in BBMV from LTD animals and lower in BBMV from HTD animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

母代大鼠高脂饮食对子代早期肝内脂肪酸代谢相关基因表达的影响

目的探索母代高脂饮食对子鼠早期肝脏病理改变的影响及其可能机制。方法 SD雌性大鼠随机分成高脂饮食组(HF组)和对照组,至交配怀孕产仔,哺乳期母鼠继续原饮食并喂养子鼠至其3周龄,取子鼠肝脏组织,观察肝脏病理变化,并检测肝脏内过氧化物酶体增殖物激活受体α(PPARα)、长链脂酰辅酶A合成酶3(ACSL3)、肉毒碱棕榈酰基转移酶1α(CPT-1α)及3-羟基酰基辅酶A脱氢酶(Ehhadh)的基因表达变化。结果 HF组母鼠所育的子鼠3周龄时肝细胞胞浆内可见弥漫性空泡变性,小叶内可见点灶状坏死;HF组子鼠肝脏组织PPARα和Ehhadh基因表达水平明显高于对照组,而ACSL3基因表达则显著低于对照组,差异均有统计学意义(P0.05);CPT-1α基因表达水平亦高于对照组子鼠,但两组间差异无统计学意义(P=0.19)。结论母鼠孕期持续至哺乳期的高脂饮食可引起子代早期肝内脂肪酸β氧化相关基因PPARα,CPT1α与Ehhadh表达代偿性增加,ACSL3表达降低,但尚不能逆转子代肝脏脂肪变性的发生。     

Mucosal immune activation and maturation of the small intestine at weaning in the hypothymic (nude) rat

Activation of the mucosal immune system peaks at weaning on days 21 and 22 of life in the rat. We have investigated activation in the gut associated lymphoid tissue and maturation of intestinal mucosa in hypothymic (nude) and in phenotypically normal heterozygous CBH rats at 22 days of life. Intestinal maturation, as assessed by villus area, crypt length, crypt cell production rate and disaccharidase activity, was similar in hypothymic and normal rats, and indices of mucosal immune function were elevated in both groups at this time. The proportion of mononuclear cells from the mesenteric lymph node expressing IL-2R was 11% in heterozygous and 14% in hypothymic rats as determined by flow cytometry. Immunoperoxidase staining of MLN sections confirmed the presence of IL-2R+ cells in the T-dependent interfollicular areas. However, the number of T-cells was considerably depleted in hypothymic rats. Intraepithelial lymphocyte counts and serum rat mucosal mast cell protease II concentrations were similar in the two groups, while counts of jejunal mucosal mast cells and eosinophils were paradoxically increased in hypothymic animals. As T lymphocyte function is thought to be impaired in hypothymic rats, the intact mucosal immune activity in hypothymic rats could be due to activation of intrinsic "thymic independent" T lymphocytes in hypothymic rats, or to engraftment with extrinsic maternal milk-derived lymphocytes and their activation in the infant rat gut.     

Combined influence of early sexual maturation and central adiposity on subsequent stature

Introduction Shorter adult stature has been attributed to early sexual maturation, as well as early adiposity, but it is not clear if these factors are interrelated.Results and discussion A number of 1,605 Norwegian adolescents were followed from early (baseline) to late adolescence (follow-up). Maturational timing was assessed by self-reports of pubertal status (pubertal development scale, PDS) in boys and age at menarche (AAM) in girls. Height, weight and waist circumference were measured at baseline and at follow-up. Differences in height at follow-up and height gain related to the timing of sexual maturation and the level of central adiposity (i.e. high or low waist circumference) at baseline were estimated using general linear modelling. At follow-up, the median height was 180 cm in boys and 167 cm in girls. Early maturing boys and girls with relatively high central adiposity at baseline were, on average, 5.7 cm (P value<0.001) and 3.6 cm (P value<0.001) taller than early maturing boys and girls with low central adiposity. Differences in stature related to central adiposity were less pronounced for intermediate and late maturing boys and girls. The height was lowest in boys (176.6 cm) and girls (163.8 cm) who had matured early and had low central adiposity at baseline. Height gain during follow-up was independent of the level of central adiposity, but was closely related to the timing of sexual maturation. The association between the early timing of sexual maturation and subsequent height was modified by the level of central adiposity in early adolescence.Conclusion The results suggest that early maturity combined with adiposity yields higher stature than early maturity and leanness.     

Renal function in preterm infants during the first five days of life: influence of maturation and early colloid treatment.

We measured the influence of maturation and early freshly frozen plasma infusion (FFP) on renal function (day 2 and day 5) in preterm infants in intensive care; they were divided into two groups, those with gestational ages less than 30 weeks (G less than 30) and those with gestational ages of 30-34 weeks (G 30-34). A total of 35 infants was studied. The infants were randomly assigned to one of two treatment groups, one receiving FFP, the other not, yielding four study groups; G less than 30 and no FFP (8 infants), G less than 30 and FFP (8 infants), G 30-34 and no FFP (9 infants) and G 30-34 and FFP (10 infants). The infants in the two FFP groups received FFP 10 ml/kg on days 1-3. FFP did not significantly influence creatinine clearance (CCr) or the urinary sodium excretion rate either in G less than 30 or G 30-34. CCr was significantly lower (p less than 0.001) and fractional urinary sodium excretion significantly higher (p less than 0.002) in infants of G less than 30 than in infants of G 30-34. Infants of G less than 30 had significantly higher plasma potassium concentrations (p less than 0.01) than infants of G 30-34. Despite the low CCr and the high urinary sodium excretion rate, infants of G less than 30 had stable fluid and electrolyte balance.     

Development of cholesterol metabolism: the effect of diet composition at weaning

Wistar rats were weaned on day 18 to a high fat (HF), high carbohydrate (HG) or high cholesterol (HCO 2%) diet. The activities of 3-hydroxy-3-methylglutaryl-CoA-reductase (HMGR), 7 alpha-hydroxylase (7-OHase) and acyl-CoA-cholesterol-acyltransferase (ACAT) were assayed in the liver and small intestinal mucosa on days 21, 25 and 30 and in adult animals. An HF diet raises hepatic ACAT and HMGR activities in young rats but has the opposite effect in the gut. The cholesterol diet also raises hepatic ACAT activity, but less so than the HF diet. In the gut, however, the HCO diet invokes the greatest rise in ACAT of all the diets tested. Except in adult rats, the HG diet always raises hepatic ACAT activity more than the HCO diet or the Purina Chow. In the gut, however, activity is very low for the HG diet, much lower than for the HCO diet. Early feeding of the HCO diet for 12 days (from day 18 to 30) and refeeding the same diet from day 48 to 50 resulted in a subsequent response to the HCO diet. It is concluded that early weaning results in changes in enzyme activities that depend on the composition of the diet fed at weaning and that this may also effect the later response to the same and perhaps other diets.     

Intestinal development in the suckling rat: effects of weaning, diet composition, and glucocorticoids on thymidine kinase activity and DNA synthesis

The present study was designed to determine whether the ontogenic changes in the salvage pathway for DNA synthesis of suckling rat intestine could be causally related to physiologic events during the weaning period. The intestinal activity of soluble thymidine kinase, extremely low in young sucklings (d 11, 0.057 +/- 0.007 nmol X min-1 X g tissue-1), increased dramatically between d 18 and 22 postpartum and reached a plateau (19.8 +/- 0.5 nmol X min-1 X g tissue-1) at the fourth postnatal week. Rat pups prevented from weaning showed an initial rise in the enzyme synthesis by d 18 as did their littermates weaned onto an adult diet. Compared with 22-d-old rats weaned onto chow pellets (14.1 +/- 2.1 nmol X min-1 g tissue-1), thymidine kinase concentration was reduced by one-half in rats of the same age, fed on mother's milk alone (6.5 +/- 0.7 nmol X min-1 X g tissue-1) or on a liquid artificial diet either high in fat (mimicking rat milk, 7.4 +/- 0.6 nmol X min-1 X g tissue-1) or high in carbohydrate mimicking chow, 6.4 +/- 1.3 nmol X min-1 X g tissue-1). The relative proportions of fat and carbohydrate in the diet had little or not effect on growth rate, intestinal wt, and DNA content per centimeter. In a second experiment, 9-d-old sucklings were treated for four consecutive d with either saline or hydrocortisone hemisuccinate at doses assumed to be in the physiologic (0.5 mg/100 g body wt per day) and pharmacologic (2.0 mg/100 g body wt per day) range.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nausea and vomiting in early pregnancy: Effects on food intake and diet quality

Experiences of nausea and/or vomiting in pregnancy (NVP) vary greatly, but the paucity of studies with pre‐pregnancy dietary data mean that little is known about the effects of NVP on diet. Using an administered food frequency questionnaire, diet was assessed before pregnancy and at 11 and 34 weeks' gestation in 2270 participants in a UK birth cohort study (Southampton Women's Survey). Experience of NVP in early pregnancy was graded as none, mild, moderate, or severe. Participants reported their level of food consumption as more, the same, or less than before pregnancy. “Prudent” diet scores (derived using principal component analysis) were used to describe participants' diet quality before, in early and late pregnancy. In early pregnancy, 89% of women were nauseous, although most commonly, the NVP experienced was mild (48%) or moderate (30%); 11% had severe NVP. A total of 39% of women reported an increase in their level of food intake in early pregnancy; 34% reported a reduction. Increasing severity of nausea was associated with changes in intake of a range of foods, most notably reduced consumption of vegetables, tea/coffee, rice/pasta, breakfast cereals, beans/pulses and citrus fruits/fruit juices and increased consumption of white bread, and soft drinks. Increasing severity of nausea was also associated with decreasing prudent diet score from before to early pregnancy, such that women with severe nausea had prudent diet scores 0.29 SDs lower than those with no nausea (P < 0.001). However, this was transient as NVP was not related to change in diet quality from before to late pregnancy.     

Effects of prolactin on Na+K(+)-ATPase activity in the nephron during maturation in the rat.

The effect of prolactin (PRL) on renal Na+K(+)-ATPase was investigated in 7-d-old neonatal rats. Animals were treated by bromocriptine (Br; a blocker of endogenous PRL secretion), and the enzyme activity was compared with that of untreated controls. Na+K(+)-ATPase was determined in renal sections in the medullary thick ascending limb of Henle's loop and in the distal tubule by cytochemistry. In the distal tubule, Na+K(+)-ATPase activity was significantly lower in Br-treated animals than in controls (330 +/- 169 versus 558 +/- 146 pmol inorganic phosphate/mm/h, respectively); values did not differ in the medullary thick ascending limb of Henle's loop between Br-treated and control animals (132 +/- 74 versus 165 +/- 113 pmol inorganic phosphate/mm/h, respectively). In vitro effects of PRL were investigated by determining the enzyme activity after incubation of renal sections from Br-treated and untreated animals with different concentrations of PRL. Results suggest that PRL may affect renal Na+K(+)-ATPase activity in the distal tubule in the neonatal period but do not support a major role of PRL in the enzyme maturation.     

The influence of cortical maturation on the BOLD response: an fMRI study of visual cortex in children

We performed blood oxygenation level-dependent (BOLD) functional MR imaging in 11 children younger than 5 y of age and 10 children older than 5 y of age. All but five of the children in the older age group were tested under light anesthesia. We examined the cerebral oxidative metabolism (CMRO(2)) associated with the processing of a flashed and a reversing checkerboard stimulus. These stimuli had been shown in a previous study to induce identical vascular responses. The reversing checkerboard activated twice the neuronal population of the flashed checkerboard, doubling the CMRO(2) associated with it. We compared the extent of activation for the positive BOLD response and found that it did not differ between the different age groups. We estimated the oxidative metabolism by examining the change in the local deoxyhemoglobin (HbR) concentration using Delta R2*. Because both stimuli induced the same vascular response, any increase in oxygen requirement would have to be met by the identical blood volume. Increasing CMRO(2) will therefore result in an increase in the oxygen extraction fraction (OEF), which raises the local HbR concentration. In the younger children, both checkerboard stimuli produced identical, high HbR concentrations. In the older children, the HbR concentration to the flashed stimulus was significantly lower than to the reversing stimulus. We conclude that, for identical stimuli, the oxidative energy requirement associated with the cortical processing is higher in young children than in older children because the presence of superfluous synaptic connections in the immature visual system activates a larger neuronal population.     

Protein and energy intake during weaning: I. Effects on growth

The growth and food consumption of 30 healthy infants from 4 to 6 months of age have been measured. Two groups were assigned randomly to either a formula with 1.9 g of protein and 72 kcal per 100 ml (F1) or 2.7 g of protein and 69 kcal per 100 ml (F2). A third group of infants were fed breast milk (0.96 g of protein and 65 kcal per 100 ml (HM)). All infants received supplementary food according to the same regimen and were fed ad libitum. The mean protein intake was 1.3, 2.6 and 3.6 g/kg/day in the HM-, F1- and F2-groups respectively. The corresponding mean energy intake was 80, 101 and 94 kcal/kg/day. The formula-fed infants had significantly higher protein and energy intakes when compared to the breast-fed group. No significant differences were found in the rate of growth of crown-heel length, head circumference or in weight gain. The differences in protein intake between the breast- and formula-fed infants without differences in growth indicate that the formulas may provide a protein intake in excess to the needs.     

Effects of an artificial diet on growth of patients with cystic fibrosis.

The effects of an artificial diet on growth were examined in a controlled trial on 43 patients with cystic fibrosis. 28 patients received the diet for 12 months. Comparison was made between their growth before, during, and after dietary treatment. Growth changes were also assessed in 15 other patients who received a conventional diet. Artificial dietary treatment led to some improvement in height, weight, subscapular skinfold thickness, and a disproportionate advance of bone age for the group as a whole. Only 10 (36%) patients had a 'clinically' significant improvement in height, weight, or both--i.e. more than 0.5 standard deviation score. Greatest improvements were in young and mildly affected patients. It is proposed that the future use of such an unpleasant and expensive diet should be restricted to a few selected cases, rather than given as routine treatment.