Serum lipids during the first year following acute spinal cord injury.

Patients with chronic spinal cord injury (SCI) have low levels of high-density lipoprotein (HDL) cholesterol. The cause of this abnormality and its relation to SCI are unknown. We studied 100 consecutively admitted males with acute SCI prospectively for 1 year to determine changes in serum lipids following acute SCI and the relation of these changes to the level of injury and physical activity. Low-density lipoprotein (LDL), HDL, and total cholesterol and triglycerides were all decreased following acute SCI and gradually increased toward normal by 1 year. Serum HDL, LDL, and total cholesterol levels correlated with the level of SCI: levels were lower in quadriplegic compared with paraplegic patients. Serum HDL showed the greatest change following SCI, increasing by 26% in quadriplegic and 18% in paraplegic patients. These changes in serum lipid levels could not be explained by changes in alcohol consumption or body weight. We estimated that only 44% of the increase in HDL following SCI was associated with an increase in physical activity. We postulate that interruption of the autonomic nervous system influences lipid metabolism and serum lipid levels.

Induction of physiological acrosome reactions in caput epididymal spermatozoa of mice.

Mouse caput spermatozoa are considered immature and thus unable to fertilize oocytes. In this study, we determined whether washing mouse caput spermatozoa increased their ability to acrosome react in response to a physiological stimulus. The results obtained showed that mouse caput spermatozoa incubated in Earles' modified medium containing calcium chloride and supplemented with BSA and pyruvate for 1 h at 37 degrees C and then washed acrosome reacted in response to both solubilized zonae and immunoaggregation of a zona binding site. In addition, the material removed from caput spermatozoa by washing blocked induced acrosome reactions of cauda spermatozoa. The data indicate that mouse caput epididymal spermatozoa, if incubated and washed, can undergo physiological acrosome reactions.

Survival from sepsis. The significance of altered protein metabolism regulated by proteolysis inducing factor, the circulating cleavage product of interleukin-1.

Amino acid (AA) arterial blood plasma concentrations, K1 (peripheral production + infusion rates), and central plasma clearance rates (K1 divided by arterial concentration) (CPCR-AA) were measured in 70 seriously septic patients. All of these people were in the "hyperdynamic" state at the time of observation. Thirty-seven recovered and 33 died. In addition, 10 noninfected, nontraumatized patients about to undergo laparotomy were studied. In 31 patients receiving parenteral alimentation, CPCR-AA was 326 +/- 38 in survivors and 160 +/- 17 ml/M2/min in the deaths (p less than 0.005). In 58 patients studied, while fasted with no intravenous amino acid infusion, values for CPCR-AA were: survivors 202 +/- 22 (28) and deaths 112 +/- 16 (30) ml/M2/min (p less than 0.002). The CPCR-AA in 10 noninfected patients was only 68 +/- 11 ml/M2/min. CPCR-AA in 19 patients correlated with hepatic protein synthetic rates in liver biopsies obtained simultaneously (r = 0.658, p less than 0.01), which shows that CPCR-AA is an indicator of visceral protein synthesis. To study the regulation of amino acid metabolism by synthesis. To study the regulation of amino acid metabolism by proteolysis inducing factor (PIF), the proteolysis inducing activity (PIA) of the plasma fraction (0-50,000 D) was measured 55 times in conjunction with metabolic studies. No significant differences existed in PIA between survivors and deaths. However, in those patients who recovered, PIA was significantly correlated to both peripheral amino acid production (r = 0.773, p less than 0.001) and to CPCR-AA (r = 0.721, p less than 0.001). This observation demonstrates the presence of one or more circulating agents affecting amino acid flux. PIA measured simultaneously in vivo correlated with in vitro protein synthetic rate in incubated liver biopsies (r = 0.653, p less than 0.01). PIF (4,000 D), isolated by chromatography, in patients without amino acid infusion was 35 +/- 3% in survivors and 33 +/- 6% in deaths (N.S.) and only 9 +/- 3% over control in noninfected patients. In patients who recovered, PIF titre was strongly correlated with peripheral amino acid production (r = 0.798, p less than 0.001) and with CPCR-AA (r = 0.835, p less than 0.001). However, values for patients who later died were significantly less for a given PIF titre. Thus, it is concluded that survival from sepsis is, in part, dependent on a significantly elevated CPCR-AA and hepatic protein synthesis, both of which appear to be related to the blood plasma PIF titre.

Induction of hepatic protein synthesis by a peptide in blood plasma of patients with sepsis and trauma.

Accelerated release of amino acids from muscle and their uptake for protein synthesis by liver and other visceral tissues are characteristic of trauma or sepsis. Experimentally, this response is induced by interleukin-1 (IL-1) generated by activated macrophages in vitro. However, IL-1 has not been demonstrated in human blood. A small 4000-dalton peptide recently isolated from plasma of patients with sepsis and trauma induces muscle proteolysis and is called "proteolysis-inducing factor" (PIF). To test whether this agent has the ability also to induce hepatic protein synthesis, a series of animal experiments and clinical observations were undertaken. The structural and secretory (acute-phase reactants) in vitro protein synthesis in livers of normal rats injected intraperitoneally with IL-1 or PIF was significantly greater than that of normal rats or those injected with Ringer's lactate (p less than 0.01). In patients with sepsis and trauma the central plasma clearance rate of amino acids, a measure of visceral (principally hepatic) amino acid uptake, was elevated and correlated with the rates of protein synthesis in incubated liver slices obtained by biopsy at operation from the same patients (p less than 0.05). Both in vivo measured central plasma clearance rate of amino acids and in vitro measured hepatic protein synthesis correlated with plasma levels of PIF in the same patients (p less than 0.01 and p less than 0.05, respectively). We conclude that since PIF, and not IL-1, is present in human plasma and both are produced by activated macrophages, PIF seems to be the stable circulating cleavage product of IL-1, which induces not only muscle proteolysis but also hepatic protein synthesis, principally in the form of acute-phase reactants during infection and other states in which inflammation is present.

Muscle proteolysis induced by a circulating peptide in patients with sepsis or trauma.

Accelerated proteolysis of muscle is characteristic in patients with trauma or sepsis, but its cause is not well understood. Using rat muscle in vitro, we developed a bioassay to compare the proteolytic activity of plasma from 50 patients with trauma or sepsis with that of plasma from 14 normal volunteers and from 15 patients who had undergone "clean" elective surgical procedures. The mean proteolytic activity in the plasma of patients with trauma or sepsis was found to be 190 +/- 8.0 per cent of the control value (rat muscle incubated in medium alone), whereas the activity in normal plasma was 124 +/- 4.5 per cent (P less than 0.001). The activity in the plasma of patients who had undergone elective surgery was slightly elevated at 142 +/- 2.5 per cent (P less than 0.005). In 25 of the patients with trauma or sepsis the rate of amino acid release from one leg was measured by subtracting the concentration of tyrosine plus phenylalanine in the femoral artery plasma from that in the femoral vein; this rate correlated well with the bioactivity of the plasma in the bioassay system (r = 0.67, P less than 0.001). By means of ultrafiltration and chromatography, the plasma factor inducing proteolysis was isolated and found to be a peptide, probably containing sialic acid, with a chain of 33 amino acids and a molecular weight of approximately 4274 daltons.

Exchange of amino acids by muscle and liver in sepsis.

The amino acid "central fractional clearance rate" (CFCR), the ratio of the rate of amino acid entry into the extracellular pool to the size of the pool, is a measure of amino acid uptake and clearance by liver and other visceral tissues. In nine normal postabsorptive persons, the mean CFCR was 5%, compared with 21% in 31 seriously infected patients. For comparative purposes, biopsy specimens of liver and muscle were obtained for incubation. In infected patients, the rate of hepatic incorporation of tyrosine into protein was three times that in noninfected patients and correlated well with the CFCR. There was no significant difference in hepatic tyrosine oxidation. In muscle from infected patients, net protein degradation was six times that in noninfected patients. Incubated tissues from rats behaved similarly. Thus, accelerated transfer of amino acid from muscle to viscera for protein synthesis occurs in humans with sepsis, as it does in animals. The CFCR demonstrated the importance to survival of visceral amino acid uptake; it was 35% in surviving patients, and only 19% in those who died.

Persisting structural abnormalities in liver, kidney, and muscle tissues following hemorrhagic shock.

Hemorrhagic shock-induced abnormalities of liver, kidney, and muscle morphology were studied sequentially for eight days following shock and resuscitation in rabbits. The findings revealed marked structural changes, some of which became more pronounced between one and three days after shock and all of which persisted for at least three days. All of the tissue changes reverted to near normal by eight days. The specific findings included hepatic sinusoidal compression with cellular swelling and vacuolization one day after shock; renal vacuolization and swelling of proximal tubular convolutions, culminating in widespread cellular damage three days after shock; and separation of myofibrils and disruption of the band pattern in muscle tissue. These findings demonstrated the prolongation of the morphological abnormalities induced by shock, previously observed only in the acute phase, and the capacity for structural repair by the tissues after reversible hemorrhagic shock.

Endocrine activation and altered muscle metabolism after hemorrhagic shock.

Studies were conducted to examine glucose and amino acid metabolism by skeletal muscle isolated from rhesus monkeys before and sequentially after an episode of resuscitated hemorrhagic shock. After shock and reinfusion, the tissue exhibited decreased effect of insulin on glucose utilization increased leucine oxidation, and a reduced rate of leucine incorporation into protein. These changes were observed 15 min after reinfusion and persisted in part for at least 3 days. All of the observed abnormalities were more pronounced 24 h after shock and reinfusion than 15 min after and returned to normal by 2-4 wk. The shock-induced metabolic abnormalities in skeletal muscle occurred in spite of prevention of shock-induced adrenal steroid and catecholamine secretion and of changes in blood insulin concentration using adrenalectomized-streptozotocin diabetic monkeys receiving replacement cortisol and insulin infusions. This study thus demonstrated that hemorrhagic shock in rhesus monkeys was followed by insulin resistance plus abnormalities of glucose and amino acid metabolism by skeletal muscle that were not dependent on the concurrent changes in plasma levels of adrenal steroids or catecholamines or on altered circulating insulin levels associated with shock.

Chronic tissue insulin resistance following hemorrhagic shock.

Metabolism of fat and muscle tissue was measured for 30 days following shock and reinfusion in rabbits. Tissue insulin resistance in the post-shock period was demonstrated by decreased oxidation of glucose and decreased incorporation of glucose into neutral lipid or glycogen during incubation with insulin. In addition, the insulin stimulated incorporation of amino acids into muscle protein was markedly reduced after shock. Conversely, the capacity of muscle to oxidize leucine was enhanced by shock, even in the presence of insulin. Tissue insulin resistance and increased leucine catabolism are likely to contribute to the general metabolic response to shock and trauma.

Increased plasma arginine vasopressin in clinical adrenocortical insufficeincy and its inhibition by glucosteroids.

Trichloroacetic acid extracts of plasma were fractionated on a CG-50 resin column and the 50% acetic acid eluents chromatographed on silicic acid-impregnated glass paper in butanol-acetic acid-water. The specific arginine vasopressin (AVP) zone was eluted and assayed for antidiuretic activity in the diuretic rat. Thioglycolate inactivation was used to confirm AVP activity. Recovery of as little as 4 muU AVP per ml plasma ranged between 80 and 90%. In normal subjects after an overnight fast, plasma AVP ranged between 2.5 and 10.0 muU per ml. AVP secretion was inhibited by hemodilution and stimulated with nicotine and hypertonic saline. Plasma AVP was absent in patients with diabetes insipidus even after neurohypophyseal stimulation. Plasma AVP was abnormally elevated during mild dehydration and remained above the normal range despite hemodilution in patients with untreated adrenocortical insufficiency demonstrating a delayed water diuresis. Glucosteroid therapy lowered plasma AVP to normal in dehydrated patients. A normal diuretic response to hydration was accompanied by a fall in plasma AVP to zero in steroid-treated patients. These findings suggest that hypersecretion of AVP may play an important role in the abnormal water metabolism of adrenocortical insufficiency and that the glucosteroids promote normal water diuresis by inhibiting the secretion of AVP from the neurohypophysis.