Postnatal growth of gut and muscle: competitors or collaborators.
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Animal Nutritional Physiological Phenomena↗
Biomedical subjects
T A Davis
Publications and source records attributed to T A Davis.
Amino acid compositions of body and milk protein change during the suckling period in rats.
The amino acid concentrations of rat body protein and rat milk protein were measured at 1, 6, 10 and 16 d of age to determine whether the concentration of each amino acid in proportion to the concentration of total recovered amino acids (amino acid composition) in the body changes during early growth and development and whether parallel changes occur in the amino acid composition of milk. The ratio of essential to nonessential amino acids in bodies decreased 10% during the suckling period (P < 0.05). The ratio of essential to nonessential amino acids in milk proteins decreased by 6% (P < 0.05). With the exception of threonine, the body to milk ratio for each essential amino acid seemed similar to that for the other essential amino acids, implying that most essential amino acids are equally limiting for the synthesis of body protein in exclusively milk-fed pups. Measurements of milk intake and milk composition were used to determine amino acid intakes and hence the efficiency with which milk amino acids were used for body protein deposition. The efficiency of essential amino acid utilization was 75% between 1 and 6 d, 86% between 6 and 10 d, and 62% between 10 and 16 d of age. Although the overall efficiency of nonessential amino acid utilization showed a similar pattern, the results suggested the need for a high degree of glycine and arginine synthesis.
Amino Acids↗
Enhanced response of muscle protein synthesis and plasma insulin to food intake in suckled rats.
To compare the sensitivity of muscle protein synthesis to food intake in neonatal and weaned rats, 5- and 16-day-old suckled rats and 28-day-old weaned rats were either fed, fasted for 8-10 h, or refed for 1-4 h after an 8-h fast. Protein synthesis was measured in vivo in soleus and plantaris muscles with a large dose of L-[4-3H]phenylalanine. In fed rats, fractional rates of protein synthesis (KS) decreased with age. Fasting decreased KS, and refeeding increased KS most in 5-day-old animals, less in 16-day-old rats, and least in 28-day-old rats. In 5-day-old rats, there were no differences in KS between soleus and plantaris muscles in the fed state and after fasting and refeeding; at 28 days, KS was higher in soleus than in plantaris in fed rats, and the soleus did not respond to fasting and refeeding. In rats at all three ages, the concentration of most plasma amino acids decreased during fasting; when 5-day-old rats were refed, plasma amino acid concentrations increased, but not to the levels in the fed state. Plasma insulin concentrations increased with age. Plasma insulin concentrations decreased more rapidly with fasting and increased more extensively with refeeding in 5-day-old rats than in older rats. These results suggest that muscle protein synthesis is more responsive to food intake in young suckled rats than in older suckled or weaned rats; this increased responsiveness is accompanied by greater changes in circulating insulin concentrations.
Aging↗
Invariant chain peptides in most HLA-DR molecules of an antigen-processing mutant.
Class II major histocompatibility complexes bind peptides in an endosome-like compartment. When the class II null cell line 721.174 was transfected with class II DR3 genes, DR molecules were produced in normal amounts. However, the DR molecules were abnormally conformed and unstable because deletion of an antigen-processing gene had impaired intracellular formation of most class II-peptide complexes. Yet, 70 percent of the DR molecules still bore peptides, 80 percent of which were 21- to 24-amino acid fragments of the class II-associated invariant chain. These peptides were rare on DR3 from control cells. Thus, a defect in the main antigen-processing pathway revealed a process in which DR molecules bind long peptides derived from proteins present in the same compartment.
Amino Acid Sequence↗
A comparison of therapeutic schedules for administering granulocyte colony-stimulating factor to nonhuman primates after high-dose chemotherapy.
Granulocyte colony-stimulating factor (G-CSF) has been shown to be effective in clinical trials for reducing the period of neutropenia after chemotherapy. In this study, we compared the timing for initiating G-CSF administration after chemotherapy with the duration of neutropenia and hematopoietic regeneration. Nonhuman primates treated with high-dose chemotherapy (mechloroethamine, 1.5 mg/kg, intravenously) and not administered G-CSF therapy experienced 8 days of neutropenia (absolute neutrophil count [ANC] less than 1,000/mm3) and had an ANC nadir of 124 +/- 64/mm3 at day 7. Monkeys receiving G-CSF (5 micrograms/kg/d, subcutaneously) began treatment on either days 1, 3, 5, or 7 after chemotherapy. Monkeys treated with G-CSF had an earlier ANC recovery and the number of days with an ANC less than 500/mm3 and ANC less than 1,000/mm3 was reduced by approximately 50% in all treatment strategies. All G-CSF-treated animals, irrespective of the time that G-CSF was initiated, reached an ANC of 10,000/mm3 on day 13 +/- 1 day after chemotherapy. These results demonstrated that the duration of G-CSF therapy was almost twice as long for monkeys treated on day 1 as it was for monkeys that received therapy beginning on day 7. A comparison of the results for all treated monkeys identified a distinct difference in the responses of monkeys treated on day 1 from that of animals treated with G-CSF at later times. G-CSF initiated 1 day after chemotherapy led to an earlier onset of neutropenia and a more rapid and augmented recovery of myeloid progenitor cells in the peripheral blood when compared with control and delayed therapy groups. This study demonstrates that neutropenia due to a single dose of mechloroethamine can be equally reduced with both early and delayed initiation of G-CSF. Further, initiating G-CSF therapy after 7 days required approximately 50% less days of therapy to reach an appropriate termination point. The applicability of these findings to other chemotherapy regimens and for repeated cycles is uncertain and needs to be further evaluated. This is a US government work. There are no restrictions on its use.
Animals↗
Peripheral blood hematopoietic progenitor/stem cells proliferate to form colonies in liquid culture but require contact with vascular endothelial cells and GM-CSF.
To test the hypothesis whether peripheral blood hematopoietic progenitor/stem cells (PBSCs) interact with vascular endothelial cells during events leading to extramedullary hematopoiesis, we cocultured T-cell depleted, peripheral blood mononuclear cells obtained from cytokine treated primates in liquid culture containing a monolayer of porcine aortic endothelial cells (PAECs) for 7 days. Recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) added to cocultures of PBSC-PAEC stimulated colony formation, while only a few clusters were observed in cultures without GM-CSF. In contrast, colony formation was not stimulated when either interleukin 1 (IL-1) or IL-3 were added to the cultures. Colony and cluster formation in response to GM-CSF was dose dependent; 20 +/- 5 colonies/5,000 cells were formed at 3 U/ml, and optimal colony formation of 42 +/- 11/5,000 cells occurred at 100 U/ml. Colonies formed in the presence of GM-CSF were large, and most contained greater than 200 cells. Morphological and phenotypical characterization of cells from isolated colonies suggested that the majority of cells were predominantly immature myeloid elements. However, there was also a low but consistent frequency of megakaryocytic lineage cells. Thus, PBSCs interact with non-bone marrow--derived vascular endothelial cells and proliferate, but only in the presence of GM-CSF, suggesting that PBSC interaction with vascular endothelial cells in vivo could lead to extramedullary hematopoiesis.
Animals↗
Therapeutic evaluation of interleukin-1 for stimulation of hematopoiesis in primates after autologous bone marrow transplantation.
A multiple dose IL-1 therapy was evaluated for its capability to stimulate hematopoiesis in normal primates and to restore hematopoiesis after autologous bone marrow transplantation. The administration of IL-1 to normal animals over a dose range of 0.5 to 10 micrograms/kg/d led to a 7-12 fold increase in peripheral blood neutrophil and monocyte counts after 24 hours. This increase in the mature peripheral blood myeloid cells was followed by changes in the myeloid composition of the bone marrow, where the percentage of myeloid elements increased along with a transient increase in myeloid progenitor cell activity. IL-1 treatment also led to an initial decrease in platelet counts of 10-30% during the first 3 days of treatment. However, a striking finding was a significant and long lasting stimulation of increased platelet production with platelet counts increasing to 77% of baseline 3 days after cessation of treatment and remaining elevated for the next 10 days. The therapeutic potential of the IL-1 regimen to restore hematopoiesis was further evaluated in an established autologous bone marrow transplantation model. In monkeys receiving IL-1 doses, 1.0 and 5.0 ug/kg/d, neutrophil counts recovered to greater than 0.5 x 10e9/1 on day 16, one day earlier than control, but the recovery to baseline neutrophil counts occurred 5 days sooner than control. IL-1 therapy had its greatest effect on the restoration of platelet counts after transplantation, reaching greater than 100 x 10e9/1 by day 21, two weeks earlier than control. This work demonstrates that IL-1 therapy stimulates myelopoiesis but its most promising clinical application is the stimulation of platelet production.
Animals↗
Porcine colostrum and milk stimulate visceral organ and skeletal muscle protein synthesis in neonatal piglets.
Our objective was to determine the relative contributions of protein synthesis and protein absorption in the rapid accretion of gastrointestinal protein in suckling piglets during the early neonatal period. We measured the rates of tissue protein synthesis using a flooding dose of L-[4-3H]phenylalanine in various visceral and peripheral tissues of neonatal piglets fed water, mature milk or colostrum for 6 h. The jejunal and ileal protein synthesis rates in piglets fed either colostrum or milk were three- to fourfold higher than in piglets fed water. The increased jejunal and ileal protein synthesis could not, however, account for the differences in protein mass between the colostrum-fed and water-fed groups. The relative abundance of IgG, a major porcine colostral protein, in jejunal tissue was markedly higher in piglets fed colostrum than in piglets fed either milk or water. The fractional protein synthesis rates in liver, kidney, spleen and skeletal muscle and the absolute protein synthesis rates in liver and spleen were also greater in piglets fed colostrum than in those fed milk or water. Increased endogenous protein synthesis made only a minor contribution to the increased intestinal protein accretion in neonatal piglets fed colostrum. A much larger proportion of this increase seemed to be a result of absorption and retention of ingested immunoglobulins.
Animals↗
Effects of intravenous saline infusion on fetal ovine lung liquid secretion.
These studies were designed to investigate the relationship between body fluid volume expansion and secretion of lung liquid in fetal sheep. Twelve fetal animals were used for saline infusion studies after providing them with indwelling vascular catheters and an exteriorized tracheal loop. An additional 10 animals were used as controls. Lung liquid production was measured using an impermeant tracer technique (Blue Dye Dextran). Saline infusion at 1.6, 4.0, 15.6, and 19.2 ml.kg-1.h-1 did not alter significantly lung liquid secretion rates. These results demonstrate that 1) intravenous infusion of saline at relatively high rates in the ovine fetus does not affect net fetal lung liquid formation rate, and 2) the lungs of chronically catheterized, unanesthetized fetal sheep probably do not participate in regulation of excess fluid and electrolytes.
Animals↗
Hepatic protein synthesis in suckling rats: effects of stage of development and fasting.
We studied the developmental changes in hepatic protein synthesis in suckling rats between postpartum d 1 and 28 and investigated the effect of fasting for 10 or 18 h on hepatic protein turnover at postpartum d 5, 10, 16, and 28. Fractional protein synthesis rates (KS, %/d) were measured in vivo using a flooding dose of L-[4-3H]phenylalanine. Although hepatic KS and translation efficiency (protein synthesis/unit RNA) were significantly higher at postpartum d 28 than d 1, the pattern of change was biphasic: KS and translational efficiency were higher at d 10 and 28 than at d 5 and 16. The largest increase in KS and translational efficiency occurred during the period normally associated with weaning (between postpartum d 16 and 28). At all stages of development, the KS and translational efficiency in fasted rats were significantly lower than those in control (fed) rats, although the relative decline in both measurements was largest at postpartum d 10. The absolute rates of hepatic protein synthesis declined to similar levels on d 5, 10, and 16 after 10 h of fasting and changed little after 18 h of fasting; this level was significantly higher at postpartum d 28. Our results suggest that postnatal development in suckling rats was marked by a biphasic pattern in the rates of hepatic protein synthesis, which increased during the neonatal and weaning periods. The relative changes in the synthesis and loss of hepatic protein in response to fasting were greater during the neonatal than during the late suckling and weaning periods.
Age Factors↗
Stage of development and fasting affect protein synthetic activity in the gastrointestinal tissues of suckling rats.
We studied suckling rats from 1 to 28 d of age to determine the normal developmental changes in the protein synthetic activity of gastrointestinal tissue. We also studied the changes that occurred in response to 10 or 18 h of fasting at 5, 10, 16 and 28 d of age. Protein synthesis was measured in vivo using a flooding dose of L-[4-3H]phenylalanine. Fractional protein synthesis rates (FSR, %/d) of stomach and small intestines increased nearly 80% during the period normally associated with weaning (d 18 to 28). Between birth and 28 d, the pancreas FSR increased approximately 6.5-fold from 46 to 302%/d. The increases in stomach, small intestinal and pancreatic FSR were largely due to increases in translational efficiency (gram protein synthesized per gram RNA). At 5, 10, 16 and 28 d postpartum, both the FSR and translational efficiency in pancreatic and small intestinal tissues were decreased after 10 h of fasting; however, measures in stomach tissue were largely unaffected. The magnitude of decline in FSR and translational efficiency in response to fasting was greater during the earlier than in the later stages of development. The results suggest that the FSR in the pancreas, small intestines and stomach of suckling rats increase during the period of development associated with weaning. Fasting affected protein synthetic activity more profoundly in pancreatic and small intestinal tissue in the early stages of development.
Aging↗
Response of muscle protein synthesis to fasting in suckling and weaned rats.
Protein synthetic efficiency (KRNA) is low in immature skeletal muscle of suckling rats and increases toward the end of the suckling period. To determine whether immature skeletal muscle is able to further reduce KRNA in response to fasting, suckling (5, 10, and 16 days of age) and weaned (28 days of age) rats were fed, fasted for 10 h, or fasted for 18 h and injected with a flooding dose of L-[4-3H]phenylalanine for measurement of muscle protein synthesis in vivo. In fed rats, fractional rates of protein synthesis (KS) and protein synthetic capacity decreased during the suckling period. KRNA increased toward the end of the suckling period. In 5-day-old rats, fasting for 10 h produced a 50% decline in KS of extensor digitorum longus and plantaris muscles, but KS did not change further after 18 h of fasting. In older suckled and weaned rats, 10 h of fasting decreased KS of extensor digitorum longus and plantaris muscles 30%; after 18 h of fasting, values had declined to 50% of those in fed animals. The reductions in KS in soleus muscles with 10 and 18 h of fasting were similar to those in other muscles at 5 and 10 days but were less than those in other muscles at 16 and 28 days. Changes in KRNA were similar to those for KS in all muscles from all age groups fasted for 10 and 18 h. Protein synthetic capacity decreased approximately 12% after 18 h of fasting, but this effect did not differ between age groups or muscle types.(ABSTRACT TRUNCATED AT 250 WORDS)
3-Hydroxybutyric Acid↗
In vivo stimulation of platelet production in a primate model using IL-1 and IL-3.
The in vivo administration of various cytokines for hematopoietic stimulation has led primarily to the enhancement of the myeloid response with an insignificant contribution toward stimulating any increase in platelet production. Current studies have suggested that interleukin 1 (IL-1) and interleukin 3 (IL-3) are two of several factors that have an effect on either megakaryocyte formation or platelet production. The objective of our research was to investigate how the in vivo administration of IL-1 or IL-3 or a combination could be used to regulate megakaryocytopoiesis and platelet production in nonhuman primates. A single dose of IL-1 was able to stimulate an increase in platelet production for 3 weeks. The response was shown to be biphasic, with increased platelet counts of 46% and 49% above baseline on days 8 and 17, respectively. In contrast, the administration of IL-3 for 6 days led to an increase of 29% above baseline on day 17. An interesting observation was that the increased platelet counts were accompanied by a transient increase in the peripheral blood of a highly proliferative megakaryocyte colony-forming cell (MK-CFC), which attained a maximum concentration on day 7. The administration of a sequential combination of IL-1, then IL-3, was further evaluated to elucidate a possible potentiation on platelet production. The result was a similar increase in platelets to that observed in IL-1-only-treated monkeys for the first 7 days. However, the most significant effect was observed on day 17, when the 85% increase in platelets was demonstrated to be additive of the single-agent effects on that day. A reversal in the order of cytokine administration did not affect platelet production in this manner. In IL-1, then IL-3-treated monkeys, the increased platelet counts were also accompanied by an increase in the concentration of the peripheral blood MK-CFC from days 7 through 14. These results demonstrate that a combination of factors may be required to enhance platelet production, stimulating not only the formation of megakaryocytes but also stimulating the production and release of platelets into the peripheral blood.
Animals↗
Structural characterization of the isoenzymatic forms of human myeloperoxidase: evaluation of the iron-containing prosthetic group.
Myeloperoxidase (MPO) from human neutrophils has been purified and found to exist in three isoenzymatic forms, resolved by ion exchange chromatography. In addition to differences in subunit size and cellular compartmentalization of the isoenzymes, differences have been reported in their activity and susceptibility to inhibition. The structural basis of these isoenzymes is unclear; we attempted to further define their functional characteristics and structural identity. First, we measured respective enzymatic activity using a panel of substrates; MPO I was found to have lower activity with some substrates (pyrogallol, guaiacol, potassium iodide [KI]), but similar activity to the other isoenzymes with 4-aminoantipyrine. These studies confirm that MPO I is enzymatically distinct from MPO II and MPO III. Next, we examined the structural basis of these differences by evaluating the iron-containing prosthetic group in each form using electron paramagnetic resonance (EPR) and determination of the pyridine hemochrome. No significant difference between the isoenzymes was noted in these parameters, suggesting that the prosthetic group is the same in each protein. The cause for any difference in enzymatic activity must lie then in variations extrinsic to the heme, and based on previous studies of the gene and protein analysis, the posttranslational modification of MPO must account for these isoenzymatic species.
Electron Spin Resonance Spectroscopy↗
Granulocyte-macrophage colony-stimulating factor: more than a hemopoietin.
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Bone Marrow Cells↗
Induction of the heat shock response in rats modulates heart rate, creatine kinase and protein synthesis after a subsequent hyperthermic treatment.
STUDY OBJECTIVE - The aim of the study was to examine the effect of prior induction of the heat shock response on heat shock protein synthesis and physiological variables relevant to the shock response. DESIGN - Synthesis of heat shock protein (SP71, molecular mass 71,000) was induced in rats by 15 min hyperthermia (42 degrees C). Protein synthesis, heart rate, blood pressure and creatine kinase activity were determined in comparison with controls (no heat shock) and a group receiving two heat shock treatments 24 h apart (prior induction group). SUBJECTS - 24 male Sprague-Dawley rats (125-150 g) were used, divided into three groups: controls (n = 4), heat shock X 1 (HS, n = 11), heat shock X 2 (2 X HS, n = 9). Heat shock was induced under anaesthesia on a heating pad. MEASUREMENTS and RESULTS - Blood pressure and heart rate were measured at the beginning of the hyperthermia period, when body temperature first reached 42 degrees C (t = 0 min) and at the end of the hyperthermia treatment (t = 15 min). At t = 0 min systolic blood pressure and heart rate were increased compared to the control values in both HS and 2 X HS groups. At t = 15 min heart rate in the HS group was increased to 554 (SEM21) beats.min-1 v control 465(19) (p less than 0.05). In the 2 X HS group, heart rate of 494(14) beats.min-1 at t = 15 min was not significantly different from control. At t = 15 min, creatine kinase values in the hyperthermia treatment groups were not different from control. However at 2.5 h after hyperthermic treatment plasma creatine kinase was increased in the HS group to 481(83) mU.ml-1 (n = 6) v 223(20) in controls, but was not increased in the 2 X HS group [178(64), n = 4]. Rats were radiolabelled for 2 h with 1.0 mCi of [35S]-methionine 30 min after hyperthermic treatment in HS group and 30 min after the second hyperthermic treatment in 2 X HS group. Following the 2 X HS treatment, synthesis of SP71, though increased above control values, was lower than in the HS group. CONCLUSIONS - The reduction in heart rate, plasma creatine kinase and synthesis of SP71 following a second hyperthermic exposure could be caused by a protective influence of the first exposure.
Animals↗
Differential augmentation of in vivo natural killer cytotoxicity in normal primates with recombinant human interleukin-1 and granulocyte-macrophage colony-stimulating factor.
The effect of recombinant human interleukin-1 (IL-1) alpha, granulocyte-macrophage colony-stimulating factor (GM-CSF), and combined factor therapy (CFT) on Rhesus monkey peripheral blood natural killer (NK) activity in vivo was compared. During a 14-day treatment period, IL-1-treated animals demonstrated a 170% increase in NK activity against K562 target cells by day 4, reaching maximal levels (300%) at day 16, and returning to baseline by day 30. NK activity of GM-CSF-treated monkeys increased slightly (60-100%) during days 4-12, as did saline-treated monkeys, but returned to baseline values by day 16. A delayed increase in NK activity resulted after GM-CSF treatment, reaching a peak (260%) on day 23 and remaining elevated through day 39. CFT resulted in a bimodal response pattern, with two peaks of NK activity: one at day 16 and a second at day 39. The first peak of activity (223%) was significantly less than the activity attained with IL-1 alone; the second peak (300%) was of greater duration and occurred later than the peak observed in GM-CSF-treated monkeys. Unlike IL-1, GM-CSF treatment did not lead to a immediate stimulation of NK activity; augmentation was delayed by more than 7 days post treatment. CFT results suggest that GM-CSF reduced the direct NK response to IL-1; while IL-1 led to an enhanced delayed NK response. Therefore, IL-1 and GM-CSF augment NK activity through different but interrelated pathways.
Animals↗
Protein turnover in skeletal muscle of suckling rats.
To determine the normal changes in protein turnover of skeletal muscle in vivo during the suckling period of rats, protein synthesis was measured in soleus, plantaris, anterior tibialis, and extensor digitorum longus (EDL) muscles of 1- to 28-day-old rats using a flooding dose of L-[4-3H]phenylalanine. Protein mass of hind-limb muscles increased nearly 100-fold, and RNA increased approximately 20-fold between 1 and 28 days of age. The total amount of protein synthesized per day increased 34-fold. Fractional protein synthesis rates (Ks) decreased two- to threefold between 1 and 28 days postpartum as a result of a decrease in protein synthetic capacity (RNA/protein). Protein synthetic efficiency (total protein synthesized/RNA) increased during this period. Ks were similar among the four muscles at 1-10 days. At 16 days, Ks increased in soleus and plantaris as a result of increases in protein synthetic efficiency; Ks did not increase in anterior tibialis and EDL. These data suggest that, during the suckling period, protein synthetic capacity in skeletal muscles of rats declines, while protein synthetic efficiency increases. The increase in translational efficiency occurred earlier in weight-bearing muscles (soleus, plantaris) than in non-weight-bearing muscles (anterior tibialis and EDL) and was associated with the appearance of mobility.
Aging↗