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Biomedical subjects

S E Anderson

Publications and source records attributed to S E Anderson.

At least 55 records · Page 3Linked to original sources
PubMed1997

Hepatic protein synthesis in the sheep: effect of intake as monitored by use of stable-isotope-labelled glycine, leucine and phenylalanine.

Rates of protein synthesis for the liver, plasma albumin and total plasma protein were quantified in sheep either offered a supra-maintenance intake or fasted for 3 d. The technique of continuous infusion over a 12 h period was employed with the simultaneous infusion of [1-13C]glycine, [1-13C]leucine and [2H5]phenylalanine. Blood and plasma samples were removed at timed intervals from the hepatic portal and hepatic veins plus the aorta. Enrichments of the free amino acids (AA) were determined in all blood and plasma samples as was the protein-bound AA in an apolipoprotein B100 extract. Protein-bound phenylalanine enrichments were also measured in albumin and total protein from plasma plus samples from liver biopsies. The apolipoprotein B100 enrichments agreed well with those of the free AA in hepatic (and hepatic portal) plasma but were lower than for arterial free AA and greater than liver homogenate free AA. This adds support to the concept that export proteins may preferentially use AA directly from extracellular sources. Intake had no significant effect on constitutive liver protein synthesis and the values agreed well with those obtained by other isotopic approaches. There were, however, significant declines, based on hepatic venous free phenylalanine enrichment, at the lower intake in both the fractional (3.4 v. 4.7% per d; P = 0.024) and absolute (2.4 v. 4.2 g/d; P = 0.011) synthesis rates of albumin, which matched the estimated decrease in total plasma albumin content (52 v. 67 g, P < 0.01). In contrast, there was a smaller reduction in total plasma protein mass (145 v. 151 g, P = 0.035) with no observed significant difference in kinetic parameters. Albumin synthesis was calculated to account for a maximum of 17% of total liver protein synthesis in the fed condition and this may fall to 8% during moderate fasts.

Amino Acids↗
PubMed1996

Method for the determination of 15NH3 enrichment in biological samples by gas chromatography/electron impact ionization mass spectrometry.

An alternative method for the determination of [15N]ammonia enrichment in biological fluids was developed. It is based on the use of glutamate dehydrogenase of bovine liver (EC 1.4.1.2.) with 2-oxopentanoic acid as substrate, to convert the ammonia present in the sample into norvaline, the enrichment of which can be measured by gas chromatography/mass spectrometry as its tertiary butyldimethylsilyl (TBDMS) derivative under electron impact selective ion recording (SIR) conditions. The principal advantage of the present approach is that it is simpler and quicker than the previously described methods, because the synthetic product, norvaline, is not present in biological fluids and pre-processing of the sample is unnecessary. The procedure includes a pre-incubation stage which allows removal of contaminant ammonia present in the reagents used for the enzyme reaction. The contributions of other sources of nitrogen to norvaline production have been checked and quantified: these may provide limitations of the technique when samples for analysis are low in ammonia (e.g. arterial or hepatic venous blood). To reduce these contributions, short times of incubation are proposed. The results from two experiments in vivo in which two sheep were infused with [15N]ammonium chloride in the mesenteric vein are presented and the biological implications which arise from the results are discussed. The validity of the procedures was demonstrated by the quantitative recovery from the mesenteric and portal veins of [15N]ammonia infused.

Ammonia↗
PubMed1996

Albumin but not fibrinogen synthesis correlates with galactose elimination capacity in patients with cirrhosis of the liver.

Albumin and fibrinogen synthesis rates were measured in 15 subjects with different clinical stages of postviral cirrhosis and compared with galactose elimination capacity and aminopyrin breath test. Forty-three mg per kg body weight [2H5ring]phenylalanine with an isotopic enrichment of 10 atom% were intravenously injected. [2H5ring]phenylalanine enrichments in the plasma-free phenylalanine and the albumin and fibrinogen isolates were measured by gas chromatography-mass spectrometry. Fractional synthesis rates of albumin were normal in Child A cirrhosis (7.6 +/- 2.2%d), but were lower in both Child B (3.5 +/- 0.8%d) and C (4.5 +/- 2.8%d). Absolute rates of albumin synthesis were (103 +/- 30 mg/kg/d) in the child A group and substantially lower in the Child B (50 +/- 3 mg/kg/d) and C (36 +/- 20 mg/kg/d) group. The average fractional synthesis rate of fibrinogen was 16.7 +/- 7.5%d and the absolute synthesis rate 11.6 +/- 6.4 mg/kg/d. The values of the galactose elimination capacity and the aminopyrin breath test were below the normal range in all patients, gradually decreasing with an increase in the severity of the clinical stage of cirrhosis. Albumin synthesis rates significantly correlated with the Child scores, the galactose elimination capacity, and the aminopyrin breath test, whereas fibrinogen synthesis rates showed no such correlations.

Adult↗
PubMed1996

Determination of protein synthesis in lymphocytes in vivo after surgery.

1. The stimulation and depression of peripheral blood lymphocytes has previously been studied in vitro, showing an immune depression postoperatively; however, it is difficult to interpret these in vitro findings. Therefore, an in vivo technique has been established for determination of the fractional protein synthesis rate, as an index of metabolic activity in human peripheral blood lymphocytes, by using a stable isotope technique. 2. The rate of protein synthesis was calculated from the increase in enrichment of L-[2H5]phenylalanine in protein of a mixed population of mononuclear leucocytes, isolated by density gradient, after an intravenous flooding dose of L-[2H5]phenylalanine. A linear time course of isotopic incorporation into the cells was demonstrated. 3. The fractional rate of protein synthesis of a mixed population of mononuclear leucocytes was studied in relation to surgical interventions and to potential modifiers of the response. The fractional synthesis rate increased 24 h after open and laparoscopic cholecystectomy (49 +/- 19% and 40 +/- 14% respectively, P < 0.02), irrespective of postoperative total parenteral nutrition or preoperative glucose infusion. In contrast to surgery, insulin did not stimulate protein synthesis in peripheral mononuclear leucocytes.

Adult↗
PubMed1996

Template-based automatic recognition of birdsong syllables from continuous recordings.

The application of dynamic time warping (DTW) to the automated analysis of continuous recordings of animal vocalizations is evaluated. The DTW algorithm compares an input signal with a set of predefined templates representative of categories chosen by the investigator. It directly compares signal spectrograms, and identifies constituents and constituent boundaries, thus permitting the identification of a broad range of signals and signal components. When applied to vocalizations of an indigo bunting (Passerina cyanea) and a zebra finch (Taeniopygia guttata) collected from a low-clutter, low-noise environment, the recognizer identifies syllables in stereotyped songs and calls with greater than 97% accuracy. Syllables of the more variable and lower amplitude indigo bunting plastic song are identified with approximately 84% accuracy. Under restricted recordings conditions, this technique apparently has general applicability to analysis of a variety of animal vocalizations and can dramatically decrease the amount of time spent on manual identification of vocalizations.

Animals↗
PubMed1996

Effects of Na-K-2Cl cotransport inhibition on myocardial Na and Ca during ischemia and reperfusion.

In the context of the "pump-leak" hypothesis (37), changes in myocardial intracellular Na (Nai) during ischemia and reperfusion have historically been interpreted to be the result of changes in Na efflux via the Na-K pump. We investigated the alternative hypothesis that changes in Nai during ischemia are the result of changes in the Na "leak" rather than changes in the pump. More specifically, we hypothesize that the increase in Nai during ischemia is in part the result of increased Na uptake mediated by Na/H exchange. Furthermore, we present data consistent with the interpretation that the Na-K-2Cl cotransporter is active (or, alternatively, displaced from equilibrium) during ischemia and may contribute an additional Na efflux pathway during reperfusion. Thus inhibition of Na efflux via Na-K-2Cl cotransport during ischemia and reperfusion could result in increased Nai and therefore decreased force driving Ca efflux via Na/Ca exchange and ultimately increased intracellular Ca concentration ([Ca]i). Nai (in meq/kg dry wt) and [Ca]i (in nM) were measured in isolated Langendorff-perfused rabbit hearts using nuclear magnetic resonance spectroscopy. Except, during the 65 min of ischemia, hearts were perfused with N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid-buffered Krebs-Henseleit solution equilibrated with 100% O2 at 23 degrees C and pH 7.4 +/- 0.05. During ischemia, Nai rose from 16.6 +/- 0.3 to 62.9 +/- 5.1 (delta Nai approximately 46) meq/kg dry wt and decreased during subsequent reperfusion (mean +/- SE, n = 3 hearts). To measure Na uptake ("leak") in the absence of efflux via the Na-K pump, in all of the protocols described below, the perfusate was nominally K-free solution containing 1 mM ouabain for 10 min before ischemia and during the 30-min reperfusion. After K-free perfusion, Nai rose from 20.2 +/- 0.5 to 79.1 +/- 5.3 (delta Nai approximately 59) meq/kg dry wt (n = 3) during ischemia and decreased during K-free reperfusion. When amiloride (1 mM) was added to the K-free perfusate to inhibit Na/H exchange, Nai rose from 16.3 +/- 0.9 to 44.7 +/- 5.1 (delta Nai approximately 28) meq/kg dry wt (n = 3) during ischemia; i.e., amiloride decreased Na uptake. When bumetanide (20 microM) was added to the nominally K-free perfusate to inhibit Na-K-2Cl contransport, Nai rose from 22.5 +/- 3.9 to 83.8 +/- 13.9 (delta Nai approximately 61 meq/kg dry wt (n = 3) during ischemia and did not decrease during reperfusion; i.e., bumetanide inhibited Na recovery during reperfusion (P < 0.05 compared with bumetanide free). For the same protocol, the presence of bumetanide resulted in increased [Ca]i during ischemia and reperfusion (P < 0.05); these increases in [Ca]i are interpreted to be the result of increased Nai. Thus the results are consistent with the hypotheses.

Animals↗
PubMed1995

Detection of K-ras oncogene mutations in bronchoalveolar lavage fluid for lung cancer diagnosis.

BACKGROUND: Lung cancer is the leading cause of cancer deaths in the United States. A long-standing goal of cancer researchers has been to develop tests that would facilitate earlier diagnosis and treatment of lung cancer and thereby decrease mortality from this disease. Because cancer results from the accumulation of a variety of genetic events (e.g., mutations, rearrangements, and deletions) in genes controlling cell growth and differentiation, these changes might serve as diagnostically useful molecular markers. Activation of the K-ras oncogene by point mutations in codon 12, which occurs in many cases of lung adenocarcinoma, may serve as one such clinically useful molecular marker. For detection of K-ras point mutations in bronchoalveolar lavage fluid, in which small numbers of malignant cells are mixed with a population of predominantly genetically normal cells, the sensitivity of commonly used assays for ras mutations risks false-negative results. PURPOSE: By applying a highly sensitive assay, we investigated whether detection of K-ras codon 12 mutations in samples of bronchoalveolar lavage fluid could be clinically useful in diagnosing lung cancer. METHODS: We developed a highly sensitive assay for detecting K-ras codon 12 mutations based on an enriched polymerase chain reaction (PCR) technique. This technique was applied to 87 specimens of bronchoalveolar lavage fluid specimens that were obtained from 86 patients, and associated tumor biopsy specimens obtained from 35 of these patients who underwent diagnostic bronchoscopy for clinically suspected lung cancer. Statistical comparisons were performed by using the two-tailed Fisher's exact test [corrected]. RESULTS: Of 52 patients with confirmed lung cancer, samples of bronchoalveolar lavage fluid from 16 patients contained K-ras codon 12 mutations, including 14 (56%) of 25 patients with lung adenocarcinomas, one (33%) of three with bronchoalveolar carcinomas, one (20%) of five with large-cell carcinomas, and none of the 14 with squamous cell carcinomas. Mutations were detected in four additional cases in which cancer was suspected but had not been histologically confirmed. Tissue samples from 35 of the patients all yielded the identical K-ras codon 12 genotype found in the corresponding samples of bronchoalveolar lavage fluid. No mutation was found in any sample from 30 patients with diagnoses other than non-small-cell lung cancer. Thus, for those cases in which tissue was available and tested, the sensitivity and specificity of detecting K-ras mutations in bronchoalveolar lavage fluid for diagnosing K-ras mutation-positive lung cancer were both 100%. For nine patients, K-ras mutations were detected in bronchoalveolar lavage fluid obtained during otherwise nondiagnostic bronchoscopies. CONCLUSIONS: Our data demonstrate that sensitive detection of K-ras codon 12 mutations can serve as an important adjunct to cytology in the diagnosis of lung cancer. IMPLICATIONS: Detection of these mutations could lead to earlier cancer diagnosis and less need for invasive diagnostic procedures.

Bronchoalveolar Lavage Fluid↗
PubMed1995

Personality, appraisal, and adaptational outcomes in HIV seropositive men and women.

A cross-sectional exploratory design was used to assess the relationships of personality, socioeconomic status, and appraisal with functional and emotional outcomes in 77 men and 50 women with HIV infection. Multiple regression analysis showed that, among men, socioeconomic status moderated the negative relationship between self-esteem and disruption in usual activities. Consistent with Lazarus and Folkman's (1984) theory, appraisal of HIV threat mediated the negative relationship between self-esteem and mood disturbance for men and women, and the positive relationship between self-esteem and purpose in life for women. Appraisal did not mediate between personality variables and disruption in usual activities or life satisfaction for men or women.

Activities of Daily Living↗
PubMed1995

Acute stimulation of albumin synthesis rate with oral meal feeding in healthy subjects measured with [ring-2H5]phenylalanine.

1. The short-term effect of oral feeding on albumin synthesis rate was investigated in 12 healthy volunteers using two meal regimens. Albumin synthesis was measured over 90 min after injection of a 'flooding' amount (43 mg/kg body weight) of phenylalanine enriched to 7.5, 10 or 15 atoms % with the stable isotope [ring-2H5]phenylalanine. 2. In one set of subjects, consumption of five small hourly meals resulted in a consistent and significant increase (P < 0.05) in albumin fractional synthesis rate from a mean (+/- SEM) fasting value of 5.8 (+/- 0.4)%/day to 7.1 (+/- 0.4)%/day in the fed state. 3. A second study in which albumin synthesis was measured 30 min after consumption of a single larger meal was carried out in another set of volunteers. The fractional rate of albumin synthesis was again significantly elevated after feeding (P < 0.05), rising from 7.1 (+/- 0.4)%/day in the fasted state to 9.1 (+/- 0.6)%/day in the fed state. In both studies, similar responses were observed in the absolute rate of albumin synthesis (mg day-1 kg-1). 4. Albumin secretion time was significantly shorter (P < 0.05) after feeding in both studies, suggesting that the acute stimulation in albumin synthesis observed after feeding may in part be mediated via a post-transcriptional mechanism. 5. The response of total liver protein synthesis to oral feeding was investigated in an animal model employing adult rats studied with a flooding amount of [2,6-3H]phenylalanine.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Albumin synthesis rates measured with [2H5ring]phenylalanine are not responsive to short-term intravenous nutrients in healthy humans.

The response of albumin synthesis rates to infusion of either an intravenous nutrient mixture containing adequate nitrogen and energy or an isotonic saline infusion was compared in adult men. In a crossover study, nine healthy male subjects received a short-term (13.5-h) infusion of either the nutrient mixture or the saline solution, and albumin synthesis rates were measured by a stable isotope technique employing [2H5ring]phenylalanine. Fractional rates of albumin synthesis did not differ significantly between treatments (saline, 7.3 +/- 1.0%/d; intravenous nutrients, 7.8 +/- 1.0%/d). The secretion time of albumin was significantly lower with intravenous nutrients infusion than with saline infusion. Plasma albumin concentration as well as prealbumin and transferrin concentrations decreased over time when subjects were infused with either saline or the nutrient solution as a result of dilution rather than a change in synthesis. These results suggest that albumin synthesis rate does not respond to short-term intravenous nutrients.

Adult↗
PubMed1995

Chronic metabolic acidosis decreases albumin synthesis and induces negative nitrogen balance in humans.

Chronic metabolic acidosis has been previously shown to stimulate protein degradation. To evaluate the effects of chronic metabolic acidosis on nitrogen balance and protein synthesis we measured albumin synthesis rates and urinary nitrogen excretion in eight male subjects on a constant metabolic diet before and during two different degrees of chronic metabolic acidosis (NH4Cl 2.1 mmol/kg body weight, low dose group, and 4.2 mmol/kg body weight, high dose group, orally for 7 d). Albumin synthesis rates were measured by intravenous injection of [2H5ring]phenylalanine (43 mg/kg body weight, 7.5 atom percent and 15 atom percent, respectively) after an overnight fast. In the low dose group, fractional synthesis rates of albumin decreased from 9.9 +/- 1.0% per day in the control period to 8.4 +/- 0.7 (n.s.) in the acidosis period, and from 8.3 +/- 1.3% per day to 6.3 +/- 1.1 (P < 0.001) in the high dose group. Urinary nitrogen excretion increased significantly in the acidosis period (sigma delta 634 mmol in the low dose group, 2,554 mmol in the high dose group). Plasma concentrations of insulin-like growth factor-I, free thyroxine and tri-iodothyronine were significantly lower during acidosis. In conclusion, chronic metabolic acidosis causes negative nitrogen balance and decreases albumin synthesis in humans. The effect on albumin synthesis may be mediated, at least in part, by a suppression of insulin-like growth factor-I, free thyroxine and tri-iodothyronine.

Acidosis↗
PubMed1994

Response of protein synthesis in human skeletal muscle to insulin: an investigation with L-[2H5]phenylalanine.

The role of insulin in the regulation of muscle protein synthesis in adult humans has been investigated with intravenous infusion of insulin at levels comparable with those observed after normal feeding. Glucose was also infused to maintain euglycemia. Muscle protein synthesis was measured in six healthy subjects before and during insulin and glucose infusion from the incorporation of L-[2H5]phenylalanine into the protein of vastus lateralis sampled by percutaneous biopsy. L-[2H5]phenylalanine was given as a single injection of a flooding amount (45 mg/kg). The relatively low levels of enrichment of phenylalanine in protein (0.005 atom%) were measured by modified gas chromatography-mass spectrometry and verified by comparison with incorporation of L-[2,6-3H]phenylalanine. Similarity of enrichment in tissue-free and plasma pools (flooding) and linear incorporation over the period of measurement were also verified. The fractional rate of muscle protein synthesis in the group of postabsorptive subjects was 1.65 +/- 0.11% (SE)/day. The rate was unaltered by insulin and glucose infusion, 1.66 +/- 0.16%/day.

Adult↗
PubMed1992

The determination of low d5-phenylalanine enrichment (0.002-0.09 atom percent excess), after conversion to phenylethylamine, in relation to protein turnover studies by gas chromatography/electron ionization mass spectrometry.

A gas chromatography/mass spectrometry (GC/MS) method for measuring very low levels of enrichment of d5-phenylalanine (0.002-0.09 atom percent excess) is described. This method makes it possible to determine the enrichment of amino acid incorporated into tissue protein during studies of protein synthesis in man. Phenylalanine is enzymatically converted to phenylethylamine and the d5-enrichment is measured in the heptafluorobutyryl derivative by selective-ion recording under electron ionization conditions. The coefficients of variation for muscle-protein hydrolysate samples enriched with d5-phenylalanine at the 0.005 and 0.05 atom percent excess levels were 6.0 and 1.2%, respectively. This precision at low enrichment and the small amount of protein needed (about 1 mg) provide real advantages for clinical studies of tissue protein synthesis. Moreover, in contrast to the conventional approach which uses GC/MS for plasma amino acids (typically 2-20 atom percent excess) but gas isotope-ratio mass spectrometry for protein-bound amino acids, the enrichment of both plasma-free and protein-bound d5-phenylalanine can be measured with a single instrument.

Gas Chromatography-Mass Spectrometry↗
PubMed1992

Cell volume and pH regulation by the Amphiuma red blood cell: a model for hypoxia-induced cell injury.

The Amphiuma red blood cell is one of the model systems employed early in the study of vertebrate cell volume regulation. Following both cell swelling and shrinkage the Amphiuma red blood cell demonstrates volume regulation to virtual completion in 90-120 min. When swollen the Amphiuma red blood cell loses K, Cl and osmotically obliged water, while following shrinkage volume regulation is the result of Na, Cl and therefore water uptake. The main contribution of the Amphiuma red cell as a model is that it was the first cell in which volume regulation was demonstrated to be electroneutral and more specifically that K/H and Na/H exchangers were responsible for regulation following cell swelling and shrinkage, respectively. Additionally, the Amphiuma red blood cell K/H and Na/H exchangers have been demonstrated to function in a pH regulatory capacity. The latter observation in turn led to the demonstration of the mutually exclusive and contradictory nature of volume and pH regulation predicted upon Na/H exchanger activity. These observations prompted our recent investigations of the Na/H exchanger as a contributor to hypoxia-induced cell damage, using the rabbit heart as a model. These studies illustrated that Na, and Ca imbalances characteristic of hypoxia-induced cell damage are ultimately referable to the Na/H exchanger's function in a pH regulatory capacity, which contributes fundamentally to cell volume and Ca derangement and ultimately cell injury.

Animals↗
PubMed1992

Responses in tissue protein synthesis to sub- and supra-maintenance intake in young growing sheep: comparison of large-dose and continuous-infusion techniques.

In ten lambs (average live weight 33 kg), five offered 300 g/d (approximately 0.6 x maintenance; L) and five 900 g/d (1.8 x maintenance; H), tissue protein synthesis was measured by three procedures simultaneously. The techniques involved continuous infusion of [U-14C]phenylalanine and [1-13C]leucine over 7-8 h followed by a terminal large dose of [15N]phenylalanine during the last 30 or 60 min. Rates of protein synthesis were then calculated based on the free amino acid or oxo-acid isotopic activity in either arterial, iliac venous blood or tissue homogenate for the continuous-infusion studies, or on plasma or tissue homogenate for the large-dose procedure. For muscle (> 99%), and to a lesser extent skin (85-93%), effective flood conditions were achieved with the [15N]phenylalanine but were either not established or maintained for liver and tissues of the gastrointestinal tract (< 50%). The large dose of phenylalanine also caused changes in the concentration and isotopic activity of blood leucine and 4-methyl-2-oxo-pentanoate. Based on the assumption that the large-dose procedure yields the closest value for the true rate of protein synthesis (L 1.97%/d, H 2.85%/d) then, for muscle, only values based on the homogenate as precursor gave comparable results for both leucine (L 1.83%/d, H 3.01%/d) and phenylalanine (L 1.67%/d, H 2.71%/d) continuous infusion. The values based on the arterial or venous amino or oxo-acid were significantly less, more so at the lower intake. In contrast, for skin, a tissue dominated by export protein synthesis, values from the large-dose procedure (L 6.37%/d, H 10.98%/d) were similar to those derived with arterial or venous metabolites as precursor (L 5.23 and 6.93%/d, H 9.98 and 11.71%/d for leucine), but much less than those based on homogenate data. Based on the large-dose technique, protein synthesis increased with intake in muscle (P < 0.001), skin (P = 0.009) and liver (26.7 v. 30.5%/d; P = 0.029). The contributions of muscle and skin to total protein synthesis were approximately equal. The incremental efficiency of conversion for muscle of synthesized protein into deposition appeared to be similar to values reported for rodents.

Animals↗
PubMed1992

Effect of food intake on hind-limb and whole-body protein metabolism in young growing sheep: chronic studies based on arterio-venous techniques.

Whole-body protein synthesis, estimated by the irreversible loss rate procedure, and hind-leg protein metabolism determined by arterio-venous techniques were monitored in response to three nutritional conditions (approximately 0.6, 1.2 and 1.8 x energy maintenance (M)) in ten wether lambs (33 kg average live weight). In all lambs and treatments measurements were based on radiolabelled phenylalanine, but the terminal procedures (five at 0.6 x M and five at 1.8 x M) also included infusion of [1-13C]leucine; this permitted comparison of amino acids catabolized (leucine) and non-metabolized (phenylalanine) by the hind-limb tissues. Whole-body protein synthesis increased with intake and the relationship with energy expenditure was slightly lower than that reported previously for pigs and cattle. The efficiency of protein retention:protein synthesis did not exceed 0.25 between the two intake extremes. Effects of intake on amino acid oxidation were similar to those observed for cattle. Hind-limb protein synthesis also increased significantly (P < 0.001) in response to intake. Estimates of protein gain, from net uptake values, indicated that the tissues made a greater proportional contribution to total protein retention above M and to protein loss below M, emphasizing the role played by muscle tissue in providing mobile protein stores. The rates of protein synthesis calculated depended on the selection of precursor (blood) metabolite, but rates based on leucine always exceeded those based on phenylalanine when precursor from the same pool was selected. The incremental efficiency of protein retained:protein synthesis was apparently unity between 0.6 and 1.2 x M but 0.3 from 1.2 to 1.8 x M. Blood flow through the iliac artery was also proportional to intake. Leucine and oxo-acid catabolism to carbon dioxide increased with intake such that the metabolic fate of the amino acid was distributed in the proportion 2:1 between protein gain and oxidation. The rates of oxidation were only 1-3% the reported capacity of the rate-limiting dehydrogenase enzyme in muscle, but sufficient enzyme activity resides in the hind-limb adipose tissue to account for such catabolism.

Amino Acids↗
PubMed1992

Age-related response of rabbit heart to normothermic ischemia: a 31P-MRS study.

The age-related response of the myocardium to 30 min of 37 degrees C global ischemia and 120 min of 37 degrees C reperfusion, measured by phosphorus-31 magnetic resonance spectroscopy and the recovery of isovolumic function, was evaluated by using perfused neonatal (3-8 days old, n = 10), immature (24-30 days old, n = 10), and adult (2-4 mo old, n = 5) rabbit hearts. Basal intracellular pH (pHi) was highest in neonatal hearts and decreased with age. The basal phosphocreatine (PCr)-to-ATP ratio differed in each group, increasing with age. Rapid depletion of PCr occurred in all groups during ischemia; ATP retention was greater in adults than in neonates. Reperfusion resulted in no measurable recovery of ATP in any group. Postischemic pHi stabilized above preischemic values in neonatal and immature hearts and below preischemic values in adult hearts. Recovery of PCr and cytosolic Pi (Pcyi) content, heart rate, and coronary flow during reperfusion was greater in neonatal and immature than in adult hearts. During the final 20 min of ischemia, pHi was lower in immature than in neonatal or adult hearts. Postischemic recovery of left ventricular maximum rate of pressure rise (+dP/dtmax) was depressed in immature compared with neonatal and adult hearts. These results demonstrate increased tolerance of the neonatal heart and increased susceptibility of the immature heart to unprotected normothermic ischemic injury relative to the adult heart and suggest that maturational changes in myocardial pHi regulation may be responsible for the observed age-related response.

Adenosine Triphosphate↗