Optimization of Time- and Code-Division-Multiplexed Readout for Athena X-IFU.

Readout of a large, spacecraft-based array of superconducting transition-edge sensors (TESs) requires careful management of the layout area and power dissipation of the cryogenic-circuit components. We present three optimizations of our time- (TDM) and code-division-multiplexing (CDM) systems for the X-ray Integral Field Unit (X-IFU), a several-thousand-pixel-TES array for the planned Athena-satellite mission. The first optimization is a new readout scheme that is a hybrid of CDM and TDM. This C/TDM architecture balances CDM's noise advantage with TDM's layout compactness. The second is a redesign of a component: the shunt resistor that provides a dc-voltage bias to the TESs. A new layout and a thicker Pd-Au resistive layer combine to reduce this resistor's area by more than a factor of 5. Third, we have studied the power dissipated by the first-stage SQUIDs (superconducting quantum-interference devices) and the readout noise versus the critical current of the first-stage SqUIDs. As a result, the X-IFU TDM and C/TDM SQUIDs will have a specified junction critical current of 5 µA. Based on these design optimizations and TDM experiments described by Durkin, et al. (these proceedings), TDM meets all requirements to be X-IFU's backup-readout option. Hybrid C/TDM is another viable option that could save spacecraft resources.

Demonstration of Athena X-IFU Compatible 40-Row Time-Division-Multiplexed Readout.

Time-division multiplexing (TDM) is the backup readout technology for the X-ray Integral Field Unit (X-IFU), a 3,168-pixel X-ray transition-edge sensor (TES) array that will provide imaging spectroscopy for ESA's Athena satellite mission. X-0IFU design studies are considering readout with a multiplexing factor of up to 40. We present data showing 40-row TDM readout (32 TES rows + 8 repeats of the last row) of TESs that are of the same type as those being planned for X-IFU, using measurement and analysis parameters within the ranges specified for X-IFU. Singlecolumn TDM measurements have best-fit energy resolution of (1.91 ± 0.01) eV for the Al Kα complex (1.5 keV), (2.10 ± 0.02) eV for Ti Kα (4.5 keV), (2.23 ± 0.02) eV for Mn Kα (5.9 keV), (2.40 ± 0.02) eV for Co Kα (6.9 keV), and (3.44 ± 0.04) eV for Br Kα (11.9 keV). Three-column measurements have best-fit resolution of (2.03 ± 0.01) eV for Ti Kα and (2.40 ± 0.01) eV for Co Kα. The degradation due to the multiplexed readout ranges from 0.1 eV at the lower end of the energy range to 0.5 eV at the higher end. The demonstrated performance meets X-IFU's energy-resolution and energy-range requirements. True 40-row TDM readout, without repeated rows, of kilopixel scale arrays of X-IFU-like TESs is now under development.

Capacity of human subjects to utilize keto analogues of valine and phenylalanine.

Three adult human subjects were maintained for 7 days (period I) on a protein-free formula diet containing the minimum daily requirements of the eight essential amino acids plus 40 g glycine. During the last 5 days of this period, the average daily nitrogen balances for the three subjects were +0.52, +0.71, and +0.30 g, respectively. During the next 7 days (period II), valine was withdrawn from the diet, and the glycine ration increased by an equimolar amount. During the last 5 days of period II, average daily nitrogen balances declined to -1.82, -1.61, and -1.87 g, respectively. In the final period of 7 days (period III), the keto analogue of valine, alpha-ketoisovaleric acid, was added to the diet in a quantity equimolar to the minimum daily requirement of valine. During the last 5 days of this period, average daily nitrogen balances improved to -0.02, -0.18, and -0.83 g, respectively. Analogous experiments in three subjects involved the withdrawal from the diet of phenylalanine (period II) and replacement by its keto analogue, phenylpyruvic acid (period III). The average daily nitrogen balances were as follows: period I: +1.04, +0.96, and +0.53 g; period II: -1.45, -1.83, and -1.94 g; period III: +0.07, +0.11, and -0.52 g. The data demonstrate that man can convert alpha-ketoisovaleric acid and phenylpyruvic acid to the corresponding essential amino acids, valine and phenylalanine. The efficiency of these conversions is considerably less than 100%.

Utilization of alpha-keto and alpha-hydroxy analogues of valine by the growing rat.

When 70-80-g male albino rats eat a diet furnishing daily requirement of valine for optimal growth (70 mumol/g) and all other nutrients ("complete diet"), they gain weight at an average rate of 3.0 g/100 g body wt/day. When valine is removed, they lose weight at an average 2.1 g/100 g body wt/day. The growth retardation is improved or corrected by adding valine to the diet, daily weight gain being proportional to dietary valine content over a range of 0-70 mumol/g. Addition of alpha-ketoisovaleric acid instead of valine to the valine-free diet also improves or corrects the growth failure. Percent efficiency of alpha-ketoisovaleric acid as a substitute for valine was calculated as: 100 x (micromole valine per gram diet required to produce specified growth response)/(micromole alpha-ketoisovaleric acid per gram diet required to produce the same response). Efficiency of the substitution is inversely related to dietary content of the keto analogue, being 80% when diet contains 17.5 mumol/g (molar equivalent of (1/4) the daily requirement of valine), and 37% when diet provides 140 mumol/g (molar equivalent of twice the daily requirement of valine).alpha-Hydroxyisovaleric acid also substitutes for valine. Efficiency of the substitution at the single ration tested, 70 mumol/g diet, is 45%, similar to that for the keto analogue under the same conditions. When [1-(14)C]alpha-ketoisovaleric acid is injected intravenously, 30-80% of the administered radioactivity is exhaled as (14)CO(2) within 24 h. This finding suggests that inefficiency of alpha-ketoisovaleric acid as a substitute for valine results in part from degradation of the keto acid to isobutyric acid by branched chain dehydrogenase-decarboxylase. Oral administration of neomycin, polymyxin, and bacitracin reduces efficiency of alpha-ketoisovaleric acid as a substitute for valine by (1/4)-(1/2). This effect suggests that transamination of the keto acid may be performed in part by gastrointestinal microbes.

Responsiveness of growth hormone-deficient children to human growth hormone. Effect of replacement therapy for one year.

Previous studies have shown that growth hormone (GH)-deficient children are more responsive to exogenous human growth hormone (HGH) than non-GH-deficient children. In six GH-deficient children, velocity of linear growth was less than 2.5 cm/yr. By the metabolic balance study technique, anabolic responses (increments in elemental balances) were measured to a 7 day course of 0.0532 U HGH/kg body weight (BW)(3/4) per day (dose B) and to 0.168 U/kg BW(3/4) per day (dose C). They were then treated for 1 yr with HGH at a dose intermediate between B and C. Velocity of linear growth accelerated to 15-25 cm/yr for the first 4-7 mo, then declined to 0-8 cm/yr. At 12 mo, responsiveness to doses B and C was measured again; the responses were only 20-60% as great as before treatment. After 3 mo without HGH treatment, responsiveness to the anabolic effects of doses B and C returned to the magnitudes observed before treatment. A low titer of plasma antibodies to HGH was detected in two of the six children at the end of the year's treatment; these titers showed little change after 3 mo without HGH. Thus the hyperresponsiveness of GH-deficient subjects to exogenous HGH, compared to non-GH-deficient individuals, declines during long-term HGH treatment and is restored by 3 mo interruption of treatment. These changes in peripheral responsiveness may be related to the decline in velocity of linear growth which occurs after 4-7 mo of continuous treatment. When HGH was withdrawn after 12 mo, all six patients exhibited negative balances of N, P, Na, and K and loss of BW. Ratios of elemental balances showed about half the weight loss to represent protoplasm, and about half extracellular fluid. These observations indicate a role of GH in the continuing regulation of nitrogen and mineral metabolism in addition to its function as a growth-promoting hormone.

A new method for isolating the nonidentical protein subunits of human plasma alpha-lipoprotein.

Human plasma alpha lipoprotein (alphaLP) was totally delipidated by gel filtration on Sephadex LH-20 in a medium of 2 butanol:acetic acid:H(2)O, 4:1:5. The resulting alpha protein (alphaP) exhibited two major bands, labeled C and D, on acrylamide-gel electrophoresis in 5.0 M urea at pH 8.8 or 4.0. Minor bands labeled A and B, also present, were shown to be aggregates of C which form when the latter is lyophilized. The C and D components were isolated in pure form from alphaP (prepared by LH-20 chromatography of alphaLP) by gel filtration of this protein on Sephadex G-200 in a medium of 1.0 N acetic acid: the C component emerged with a distribution coefficient (K(d)) of 0.4, and the D component with a coefficient of 0.7. From each 100 mg of alphaP, 68 mg of C and 22 mg of D were isolated. 3 mg of a minor fraction with K(d) 0.1, containing A and B components as well as C, were also obtained. D but not C reacts with rabbit antiserum to human alphaLP. C and D differ substantially in content of arginine, histidine, (1/2)-cystine, isoleucine, and tryptophan.

Deficiency of carnitine in cachectic cirrhotic patients.

Carnitine is synthesized from lysine and methionine. In the rat, inadequate intake of either of these essential amino acids causes carnitine depletion. Inasmuch as protein deficiency is common in the hospital population, we have investigated the possible occurrence of nosocomial carnitine deficiency. Fasting serum carnitine concentration was measured in 16 normal and 247 patients in 16 disease groups. Normal range of carnitine was 55-103 muM. Only the cirrhotic group showed significant (P < 0.05) hypocarnitinemia. 14 of 36 hospitalized cirrhotics had subnormal values for serum carnitine. The creatinine/height index, midarm muscle circumference, and triceps skin-fold thickness indicated protein-calorie starvation in the 14 hypocarnitinemic liver patients. In six of the hypocarnitinemic cirrhotics (average serum level 50% of normal), spontaneous dietary intakes of carnitine, lysine, and methionine were measured and found to be only 5-15% as great as in six normocarnitinemic, healthy controls. When these six cirrhotic and six normal subjects were given the same lysine-rich, methionine-rich, and carnitine-free nutritional intake, the normals maintained normal serum carnitine levels and excreted 100 mumol/day, whereas the cirrhotics' serum level fell to 25% of normal, and urinary excretion declined to 15 mumol/day. Seven hypocarnitinemic cirrhotics died. Postmortem concentrations of carnitine in liver, muscle, heart, kidney, and brain averaged only one-fourth to one-third those in corresponding tissues of eight normally nourished nonhepatic patients who died after an acute illness of a 1-3-day duration. THESE DATA SHOW THAT CARNITINE DEPLETION IS COMMON IN PATIENTS HOSPITALIZED FOR ADVANCED CIRRHOSIS, AND THAT IT RESULTS FROM THREE FACTORS: substandard intake of dietary carnitine; substandard intake of lysine and methionine, the precursors for endogenous carnitine synthesis; and loss of capacity to synthesize carnitine from lysine and methionine.

Effects of melanotropic peptides on fetal adrenal gland.

Adrenal glands from early, mid, and late fetuses of rabbit, guinea pig, and rat, and from newborn animals of each species, were incubated for 1-4 h with and without 0.1 nM-1 microM ACTH, alpha- or beta-melanocyte-stimulating hormone (alpha MSH or beta MSH). The effects of the peptides were measured on production of glucocorticoids, and on incorporation of labeled thymidine or leucine into DNA or protein, respectively. The findings were similar in all three species. ACTH stimulated synthesis of glucocorticoids throughout fetal life. Potency increased progressively, as reflected by declining minimal effective dose and rising maximal response. In early and mid fetus alpha MSH and beta MSH caused a modest glucocorticoid steroidogenic effect. ACTH and alpha MSH stimulated DNA and protein synthesis in the early and mid fetal gland. alpha MSH was more potent than ACTH in these respects, minimal effective dose being generally 10 times less and maximal response 25-200% greater. The effects diminished or disappeared in the late fetal and newborn gland. These data indicate that alpha- and beta MSH possess steroidogenic or growth-promoting properties, or both, for the fetal adrenal gland.

Isolation of a novel glycoprotein from the urine of a patient with chronic myelocytic leukemia.

Patient B. J. with chronic myelocytic leukemia excreted 0.5-1.1 g protein per day in the urine. Gel filtration on Sephadex G-75 showed about one-third of this protein to be in molecular weight range 20,000-40,000 (fraction BJC). BJC, prepared from 9 liters of urine by gel filtration, was chromatographed on carboxymethylcellulose. Two proteins were eluted from the resin in pure form (as shown by zone and immunoelectrophoresis) in yields representing 8 and 3 mg/liter of urine: BJC1 and BJC2. Their amino acid compositions were identical. BJC1 contained 61% carbohydrate (33% hexose, 11% sialic acid, 13% glucosamine, 5% galactosamine). BJC2 contained one-fourth to one-half as much of each carbohydrate. Molecular weight of BJC1 was estimated at 29,000 by gel filtration. Neither glycoprotein reacted with rabbit antiserum to normal human serum.Antiserum to BJC1 was made in the rabbit. Immunoelectrophoresis with this antiserum showed a faint precipitin line, corresponding in mobility to BJC1, in normal human plasma, and a stronger line in most leukemic plasmas. By immunodiffusion, BJC1 was not detectable in normal human urine, but a positive reaction occurred in the following conditions: leukemia, 64-72%; other types of disseminated neoplastic disease, 36-78%; regional ileitis, 45%; ulcerative colitis, 38%; tuberculosis, 33%; during the 1st wk after major surgery, 33%.BJC2 was found in the urine by immunoelectrophoresis in 10% of patients with neoplastic disease and was not observed in urine of other patients or in human plasma. Amino acid composition, carbohydrate content, and antigenic specificity indicate BJC1 is a previously unrecognized member of the system of normal human plasma glycoproteins. Like certain other glycoproteins, its plasma concentration frequently increases in patients with neoplastic disease, chronic inflammatory disease, or tuberculosis and after surgery. Because molecular weight is 29,000, increased plasma concentration readily causes its appearance in the urine.

Diurnal variation in the responsiveness of human subjects to human growth hormone.

The objective of this study was to compare the responsiveness of human subjects to the anabolic effects of human growth hormone (HGH) administered at 8 a.m. or at 11 p.m. Three doses of HGH were used: A, 0.0168 U/kg body weight (BW)(3/4) per day; B, 0.0532 U/kg BW(3/4) per day; C, 0.168 U/kg BW(3/4) per day. The effect of each dose on daily balances of N, P, Na, and K and on BW was measured. The subjects were of two groups: (a) seven GH-deficient children, of whom three were deficient in ACTH; and (b) three patients with limb-girdle dystrophy. ACTH-deficient patients in group (a) received exogenous cortisol at 7 a.m. In all 10 subjects, the anabolic effects of dose C, and sometimes of B and A, administered at 11 p.m. were significantly (P < 0.05) greater than when administered at 8 a.m. In these experiments plasma cortisol concentration averaged 3 times greater at 8 a.m. than at 11 p.m. In the next experiments, exogenous cortisol was administered to the three ACTH-deficient patients at 10 p.m. and the responsiveness to HGH injected at 11 p.m. vs. 8 a.m. was again compared. Under these conditions, when plasma cortisol concentration averaged 3 times greater at 11 p.m. than at 8 a.m., HGH injected at 8 a.m. caused significantly greater anabolic responses than HGH injected at 11 p.m. These findings indicate that the magnitude of the anabolic response to exogenous HGH is inversely related to the plasma cortisol concentration at the time of HGH injection.

Distribution of branched-chain alpha-keto acid dehydrogenases in primate tissues.

The specific activity of the branched-chain alpha-keto acid (BCKA) dehydrogenases was measured in normal tissues of the rat, monkey, and man, and in cirrhotic human liver. In the rat, specific activity of the dehydrogenases in liver, kidney, and muscle averaged 33, 26, and 0.4 U/g wet tissue, respectively; proportion of the body's content of the enzyme located in these three organs was 70, 12, and 10%. In the monkey, specific activities in liver and kidney were only one-half to one-third as great as in the rat, whereas activity in muscle was the same; the monkey's body content of dehydrogenase was distributed 50% in liver, 13% in kidney, and 20% in muscle. In man, specific activities in liver and kidney were only 1/15th to 1/25th as great as in the rat, but activity in skeletal muscle was the same. Distribution of the dehydrogenases in man was 30% in liver, 2% in kidneys, and 60% in muscle. In six patients with alcoholic cirrhosis, specific activity of the dehydrogenase in liver was reduced to 20-50% of normal (average, 32%). This reduction may alter the efficiency of BCKA as substitutes for branched-chain amino acids when BCKA are administered orally, but will have little influence on efficiency when they are given intravenously.

Abnormal polyamine metabolism in hereditary muscular dystrophies: effect of human growth hormone.

Previous studies showed hyperre-sponsiveness to human growth hormone (hGH) in men with myotonic or limb girdle dystrophies (MMD or LGD). Because polyamines may mediate some actions of hGH, we have now investigated polyamine metabolism in these and other dystrophies. Under metabolic balance study conditions, serum and urine levels of putrescine (Pu), spermidine (Sd), spermine (Sm), and cadaverine (Cd) were measured in six normal men (36-44 yr), four men with MMD (38-44 yr), and three men with LGD (30-36 yr), before and during treatment with 0.532 U/kg body wt ((3/4)/d) of hGH. Daily balances of N, P, and K were also monitored. In the normal subjects, hGH did not influence elemental balances or serum and urine polyamines. In MMD, hGH caused significant retention of N, P, and K (P < 0.005). Basal levels of Sm and Cd were significantly elevated above normal (P < 0.005), and Pu, Sm, and Cd increased two- to fourfold above basal during hGH treatment (P < 0.005). In LGD, hGH also caused retention of N, P, and K. Basal levels of nearly all the polyamines (not serum Pu) were significantly above normal in serum and urine (P < 0.05). During hGH treatment, all four polyamines rose significantly above basal (P < 0.005). Serum and urine polyamine levels in five boys with Duchenne muscular dystrophy, age 8-13, did not differ from those in five age-matched normal boys. Skeletal muscle polyamines were measured in five men (31-40 yr) without muscle disease and in three men with LGD (30-38 yr). Average concentrations of Pu, Sd, Sm, and Cd were 46, 306, 548, and 61 nmol/g wet wt in LGD and 1, 121, 245, and 14 in the normal subjects, respectively (P < 0.05 in each instance). Polyamines were determined in skeletal muscle, liver, kidney, and brain of male mice with hereditary muscular dystrophy and in age- and sex-matched normal controls. Pu, Sd, Sm, and Cd levels were two to three times higher than normal in muscle, but did not differ in liver, kidney, and brain. Similar findings were made in male hamsters with hereditary dystrophy and in their controls. The abnormality in hamster muscle polyamines appeared between 1 and 6 wk of age and persisted or intensified until 30 wk. These data reveal abnormalities of polyamine metabolism in men with MMD, in men with LGD, and in mice or hamsters with hereditary muscular dystrophy. The polyamine disorder could be related to dystrophic patients' hyperresponsiveness to hGH.

Elemental balances during intravenous hyperalimentation of underweight adult subjects.

Intravenous hyperalimentation was done in 11 underweight adults whose body weight (body wt) was less than 85 percent of ideal. For the first 6 days, "complete formula" was infused furnishing per kilogram ideal body wt per day: 15 g glucose, 0.40 g N, 0.018 g P, 2.4 meq K, 3.0 meq Na, 2.3 meq C1, 0.5 meq Mg, 0.45 meq Ca, and 50 ml H20. Patients gained weight at an average rate of 9.0 g/kg ideal body wt/day and showed average balances/kilogram ideal body wt/day as follows: plus 0.14 g N; plus 0.012 g P; plus 0.43 meq K; plus 0.49 meq Na; plus 0.37 meq Cl; and plus 0.085 meq Ca. Application of standard equations to the elemental balances indicated weight gain consisted of 35-50 percent protoplasm, 35-50 percent extracellular fluid, 5-25 percent adipose tissus, and less than 1 percent bone. Withdrawas of N, P, Na, or K impaired or abolished retention of other elements. Removal of N halted retention P, K, Na and C1; withdrawal of K stopped retention of N and P; and removal of Na or P interrupted retention of all other elements. Weight gain continued at a rate of 1.4-3.1 g/kg ideal body wt/day despite zero or negative elemental balances of N, K, P, and sometimes Na and C1. Calculations showed that weight gain during infusion of fluids lacking N, P, K, or Na consisted largely of adipose tissue, with little or no contribution by protoplasm or extracellular fluid. Data show that repletion of protoplasm and extracellular fluid of wasted adults by intravenous hyperalimentation is retarded or abolished if N, P, Na, or K is lacking. Repletion of bone mineral does not occur in absence of Na or P but proceeds in absence of N, P, K, or Na. Thus, quality of weight gained by underfed adult patients during hyperalimentation depends on elemental composition of the infusate.

Serum and urine polyamines in normal and in short children.

The serum and urine polyamines putrescine, spermidine, and spermine were measured in 112 normal subjects from 0 to 70 yr of age, and in three groups of short children from 7 to 20 yr: 21 growth hormone (GH) deficient patients, 20 normal variant short stature children, and 9 girls with 45, X Turner's syndrome. Urine polyamines were expressed as micromoles per gram of creatinine or per kilogram body weight, and serum polyamines were expressed as nanomoles per milliliter. In normals, the three polyamines were highest in urine and serum at birth. The mean levels declined progressively with age, the rate of change decreasing with age. The mean for the normal subjects, and its 95% confidence and prediction intervals, were estimated from birth to age 70 for each serum and urine polyamine. In GH-deficient children, serum and urine values were significantly lower (P < 0.05) than the age-specific normal values (with the exception of serum spermidine and spermine), averaging 25-55% below normal. This abnormality was corrected during 1 wk of treatment with human GH. In Turner's syndrome, serum and urine values were significantly reduced (P < 0.05), averaging 35-80% below age-specific normals. GH treatment had no corrective effect. In 6 of 20 normal variant short stature children, polyamine levels were significantly (P < 0.01) subnormal, averaging 50-80% below age-specific normals in both serum and urine. Treatment with GH had no corrective effect. These data show that levels of polyamines in serum and urine are correlated with linear growth primarily during the first decade of life. Subnormal polyamine levels are generally associated with growth retardation.

Orosomucoid content of pleural and peritoneal effusions.

22 nonneoplastic, noninflammatory effusions (cirrhosis and congestive heart failure), 12 non-neoplastic inflammatory effusions (tuberculosis, lupus erythematosus, rheumatoid arthritis, and idiopathic pleuropericarditis), and 58 neoplastic effusions (cancer of lung, breast, ovary, and pancreas, and lymphoma) were analyzed by radial immunodiffusion for orosomucoid concentration. The average concentration +/-SE was 35+/-4, 65+/-17, and 130+/-13 mg/100 ml in the three types of effusion, respectively. By gel filtration and ion exchange chromatography, orosomucoid was isolated from 12 nonmalignant and 14 malignant fluids. The orosomucoid preparations reacted as single components in acrylamide gel electrophoresis at pH 9.0, and in immunodiffusion and immunoelectrophoresis against antisera to human serum and to human plasma orosomucoid. In radial immunodiffusion, the slope of the line relating concentration to the square of the diameter of the precipitate area was identical for orosomucoid isolated from normal human plasma and from nonneoplastic effusions, but was subnormal for orosomucoid isolated from neoplastic fluids. All orosomucoid preparations had normal amino acid composition. Orosomucoid from the nonmalignant effusions had normal carbohydrate content. 11 of 14 samples of orosomucoid isolated from neoplastic fluids had abnormalities in carbohydrate composition, consisting of subnormal content of sialic acid (11 of 14), hexose (10 of 14), and hexosamine (3 of 14), and abnormally high content of hexosamine (4 of 14). Discriminant analysis showed that concentration of orosomucoid distinguished between neoplastic and nonneoplastic noninflammatory effusions more effectively than concentration of total protein, albumin, alpha(1), alpha(2), beta, or gamma-globulin.

Maximal rates of excretion and synthesis of urea in normal and cirrhotic subjects.

When normal individuals eat 0.33 g protein N/kg body weight (BW)((3/4)) per day, they excrete 10-15 mg urea N/h per kg BW((3/4)). If they now ingest (at 0 h) 0.27 (dose A), 0.40 (dose B), 0.53 (dose C), 0.94 (dose D), or 1.33 (dose E) g protein N/kg BW((3/4)) (in the form of casein, ovalbumin, or lactalbumin), the rate of urea N excretion accelerates within 4 h. At dose C a maximal rate of urinary urea N excretion (MRUE) is reached, which averages 55 mg urea N/h per kg BW((3/4)) and which persists for 16 h. Higher doses of protein do not further accelerate urea excretion, but prolong the duration of MRUE to 28 h (after dose E). Blood urea N (BUN) rises by 7-20 mg/100 ml during the first 8 h after dose C to E, and remains stable within +/-5 mg/100 ml during the ensuing 8-28 h of MRUE. Each increment of protein above dose C causes a further increment in plasma alpha-amino N. During infusion of free amino acids at a rate of 110 or 165 mg amino acid N/h per kg BW((3/4)) for 12 h, rate of urea excretion increases to the MRUE value produced by dose C-E of oral protein.These findings indicate that MRUE corresponds to a period of maximal rate of urea synthesis (MRUS). MRUS is greater than MRUE because one fraction of newly formed urea is hydrolyzed in the gastrointestinal tract, and another fraction may accumulate temporarily in body water during the MRUE period. Oral neomycin reduces the proportion of urea hydrolyzed in the gut to less than 20%; its extent is measured by recovery in the urine of a tracer dose of [(14)C]urea injected intramuscularly during determination of MRUE. Accumulation of urea in body water is estimated from increment in BUN during the period of MRUE measurement (8-24 h after dose E of casein) and from body water measured with (3)H(2)O. Then MRUS is calculated as: ([mg urea N excreted between 8 and 24 h after dose E] + [BUN at 24 h - BUN at 8 h] x [body water]) x (100/% recovery [(14)C]urea) x (1/kg BW((3/4))) x (1/16 h).MRUS in 10 normal subjects averaged 65 mg urea N/h per kg BW((3/4)) (range 55-76), and in 34 cirrhotics 27 mg urea N/h per kg BW((3/4)) (range 6-64). Among 19 cirrhotic patients fed 40, 60, 80, or 100 g protein daily for successive 10 day periods, the occurrences of hyperammonemia, hyperaminoacidemia, and encephalopathy at each level of protein intake were inversely related to MRUS value.

Metabolic effects of plasmin digests of human growth hormone in the rat and man.

As a first step in our study of structure-function relationships among primate and non-primate growth hormones, human growth hormone (hGH) was subjected to the limited digestive activity of human plasmin. The lyophilized whole digest, containing less than 2% of unchanged hormone, had an average of 2.3 new amino-terminal groups per mole. The digest had the same potency as the native hormone (a) in causing weight gain in hypophysectomized rats; (b) in stimulating somatomedin production in hypophysectomized rats; (c) in stimulating upake of [(3)H]leucine into isolated diaphragm of hypophysectomized rats; (d) in accelerating transport of [(14)C]alpha-aminoisobutyric acid into isolated diaphragm of hypophysectomized rats; (e) in stimulating uptake of [3-0-methyl-(14)C]glucose by isolated adipose tissue of hypophysectomized rats; (f) in accelerating conversion of [(14)C]glucose to (14)CO(2) by isolated epididymal adipose tissue of hypophysectomized rats. The digest also caused glucosuria in partially pancreatectomized rats treated with dexamethasone. These metabolic actions of plasmin-digested hGH in the array of animal tests were confirmed by comparable effects elicited in 11 human subjects (nine pituitary-deficient children and adolescents and two nondeficient adults). A single injection of the plasmin digest caused an increase in plasma free fatty acids and a fall in plasma amino acids. Seven daily injections caused positive balances of nitrogen, phosphorous, sodium, and potassium, gain in body weight, and in two of three subjects impairment of glucose tolerance. The potency of the plasmin digest in producing these metabolic effects in man was comparable to that of native hGH.Thus, 2-3 bonds in the hGH molecule can be cleaved by plasmin without impairing the hormone's growthpromoting, anabolic, diabetogenic, and adipokinetic actions for rat and man.

Impaired growth hormone secretion in the adult population: relation to age and adiposity.

Growth hormone (GH) release was studied in adults of normal stature, ages 21-86 yr. The subjects were 85-115% of ideal body weight, between the 5th and 95th percentiles in height, and free of active or progressive disease. 9 to 12 individuals in each decade from thirds to ninth were evaluated. The following criteria of GH status were measured: serum GH concentration, analyzed by radioimmunoassay at half-hour intervals for 4 h after onset of sleep, and at 1-h intervals from 8 a.m. to 4 p.m. in 52 subjects; daily retention of N, P, and K in response to 0.168 U human (h)GH/kg body wt3/4/day in 18 subjects; and plasma somatomedin C (SmC) level before and during exogenous hGH treatment in 18 subjects. All 10 individuals, 20-29 yr old, released substantial amounts of endogenous GH during both day and night (average peak serum GH obtained during day and night was 7.3 and 20.3 ng/ml, respectively); average plasma SmC was 1.43 U/ml (95% tolerance limits, 0.64-2.22 U/ml). There was no significant effect of exogenous hGH on elemental balances or on plasma SmC. In contrast, 6 of 12 individuals 60-79 yr old showed the following evidences of impaired GH release; peak waking and sleeping serum GH less than 4 ng/ml; plasma SmC less than 0.38 U/ml; a significant retention in N, P, and K; and a significant rise in plasma SmC, in response to exogenous hGH. Plasma SmC, serum GH during sleep, serum GH during the day, retentions of N, P, and K in response to exogenous hGH, and rise in plasma SmC in response to hGH were all intercorrelated (P less than 0.05). Plasma SmC less than 0.38 U/ml corresponded to peak nocturnal serum GH less than 4 ng/ml. The prevalence of plasma SmC less than 0.38 U/ml increased progressively from age 20 to 90: third decade, 0%; fourth, 11%; fifth, 20%; sixth, 22%; seventh, 42%; eight, 55%; and ninth, 55%. Within each decade, plasma SmC was inversely related to adiposity.

Tyramine kinetics and metabolism in cirrhosis.

Hypertyraminemia is common in hepatic cirrhosis and correlates in severity with encephalopathy. The mechanism of cirrhotic hypertyraminemia has not been established. The alternative possibilities are increased production from tyrosine and impaired degradation by monoamine oxidase. This investigation determined the pharmacokinetics of tyramine after an intravenous bolus injections of [3H]-tyramine (180--200 muCi 12 Ci/mmol sp act) in 13 cirrhotics and 9 controls. In normals, [3H]tyramine levels initially declined rapidly (alpha-phase) followed by a slower decline (beta-phase) with an average t 1/2 of 20.8 min. Average normal metabolic clearance rate and production rate were 13.2 liters/min and 15.4 microgram/min, respectively. In cirrhotic patients, the plasma disappearance curve for [3H]tyramine was qualitatively similar to that of the control subjects with no apparent different in beta-t 1/2 (17.2 min). The hypertyraminemia of cirrhosis resulted primarily from overproduction of tyramine, as the production rate (32.0 microgram/min) in these patients was significantly greater (P less than 0.05) than in controls, whereas the metabolic clearance rate remained normal (average 12.2 liters/min). A difference in ratio of tyramine metabolic products was noted as well. Cirrhotics had a high ratio of plasma 4-hydroxyphenylethanol:4-hydroxyphenylacetic acid (60:40 vs. 30:70) as compared with normals. Although the tyramine clearance rates are similar in normals and cirrhotics, different mechanisms may be responsible for catabolism.

Anabolic actions of reduced and S-carbamidomethylated human growth hormone and its plasmin digest in man.

Six children aged 12-15 yr, deficient in endogenous growth hormone, were each treated, after a 7-day control period, for 7 days with 0.0168, 0.052, and 0.168 U/kg body wt3/4 human growth (hGH) (doses A, B, and C, respectively) in separate metabolic balance studies. Doses B and C caused a dose-related retention of N, P, K, Na, and Cl in ratios of 1/0.069/4.5/7.5/5.6. These ratios indicate increments in masses of protoplasm/extracellular fluid (ECF)/bone in ratios of 1/2.0/ less than 0.001. Three of the children were also treated with doses A, B, and C of reduced and carbamidomethylated hGH (RCAM-hGH). Doses B and C caused 1.2-2.8 times as much retention of N, P, and K, and 0.3-0.5 times as much retention of Na and Cl, as did the corresponding doses of hGH. The plasmin digest of RCAM-hGH gave results generally similar to RCAM-hGH. For RCAM-hGH and its plasmin digest, N, P, K, Na, and Cl were retained in ratios of about 1/0.14/5.4/2.2/2.1, indicating increments of protoplasm/ECF/bone of about 1/0.8/0.05. These findings indicate that reduction and carbamidomethylation alter the anabolic actions of hGH in man in both quantitative and qualitative manner. RCAM-hGH is more potent in stimulating enlargement of protoplasm and bone, and less potent in stimulating expansion of ECF, than is the native hormone. The profile of anabolic actions of RCAM-hGH in man does not appear to be further altered by digestion with plasmin.