Internal radiotherapy for hepatic metastases I: The homogeneity of hepatic arterial blood flow

Internal radiotherapy, in the form of arterially infused yttrium-90-labeled microspheres, theoretically appears encouraging as a method of treatment for hepatic metastases. Previous investigators have assumed a homogeneous distribution of these microspheres and given dosages of isotope based solely on an estimated liver mass. The purpose of this study has been to establish the homogeneity of isotope distribution in liver substance when 15 μm microspheres are arterially injected. This has been done in three mammalian species, with the results expressed as a mean percentage coefficient of variation of 28 ± 5%. Also demonstrated is the fact that 15 μm particles, while not penetrating to the venous circulation, achieve a more homogeneous spread throughout the liver than larger particles. It has been demonstrated that to achieve this maximum homogeneity distribution, 4000 beads/g of liver tissue are required. This equates in the therapeutic situation to a maximum activity of 4 Ci/g of infused microspheres. These results are considered significant in that they indicate criteria necessary to achieve the maximum homogeneity of therapeutic agent within liver substance when it is administered by this method, and will allow confidence limits to be attached to direct in vivo measurement of hepatic irradiation.     

Prostacyclin increases gastric mucosa blood flow via cyclic AMP

Although prostacyclin has been shown to inhibit stress-induced gastric mucosal ulceration, the mechanism for this cytoprotection is unknown. This experiment measures the effect of intravenous prostacyclin on gastric mucosal blood flow and any modification of this effect by pretreatment with the phosphodiesterase inhibitor, theophylline. Miniature swine were anesthetized, intubated, and ventilated. Three groups of six animals each were studied: (1) theophylline, (2) prostacyclin, and (3) prostacyclin plus theophylline. After stabilization, baseline gastric mucosal blood flow was measured with radioactive spheres. Theophylline (or vehicle) was then infused at 50 mg/kg/hr × 15 min followed by 2 mg/kg/hr thereafter. After 30 min prostacyclin (or vehicle) was infused at 0.005, 0.05, and 0.5 μg/kg/min for three consecutive 15-min periods, each followed by measurement of gastric mucosal blood flow. Results: At 0.5 μg/kg/min, prostacyclin increased gastric mucosal blood flow despite a drop in mean arterial pressure (50.1 ± 8.4 vs 17.4 ± 4.1 ml/100 g/min). Significant differences in cardiac index were not seen among the three groups. Pretreatment with theophylline potentiated prostacyclin's effect on gastric mucosal blood flow suggesting that prostacyclin increases gastric mucosal blood flow by a mechanism dependent on cyclic AMP (113.2 ± 23.3 vs 50.1 ± 8.4 ml/100 g/min). Since mucosal ischemia is an accepted prerequisite for stress-induced ulceration, prostacyclin's effect on blood flow may contribute to its protective effect on gastric mucosa.     

Tumor stasis factor (TSF): a possible mechanism for the regulation of tumor cell proliferation

A new class of factors that regulates tumor cell division in vitro can be isolated from fresh and cultured tumor cells by 3 M KCl extraction. Tumor stasis factors (TSF) inhibiting cultured tumor cell proliferation were extracted from 8 of 11 fresh human tumors and 2 cultured tumor cell lines. TSF inhibited [3H]Tdr incorporation by allogeneic and autologous cultured tumor cells in a dose-dependent manner. Extracts of normal human tissues and benign tumors did not demonstrate inhibition with the exception of liver. The mechanism of inhibition was cytostatic and not cytotoxic as demonstrated with trypan blue exclusion by tumor cells following TSF treatment, maintenance of intact tumor cell monolayers following addition of TSF, and lack of inhibition of Con A-mediated lymphocyte proliferation by TSF. TSF activity could be reversed by washing for up to 48 hr of incubation and was resistant to heat, pH alterations, reducing agents, proteases, and glycosidases. However, the active moiety bound to lentil lectin and could be purified 80-fold by preparative isoelectric focusing. These factors may represent a novel regulatory mechanism for tumor cell proliferation.     

Small bowel transplantation in the rat: The adverse effect of increased pressure during the flushing procedure of the graft

The influence of the pressure during the flushing procedure on the results of the subsequent transplantation was investigated in a model of heterotopic functional small bowel transplantation in the outbred Wistar rat. In this model insufficient small bowel preservation will result in a lethal shock, soon after revascularization. If the size of the small bowel graft was reduced to a 15-cm segment of the proximal jejunum, improper preservation did not lead to lethal shock, but to histological changes of the graft. The influence of high flushing pressure (80 cm), medium flushing pressure (50 cm), low flushing pressure (35 cm), and no flushing procedure at all, was investigated in different groups of rats. Flushing was performed by gravity using chilled Ringer's lactate solution (4°C), buffered with NaHCO₃ at a pH of 7.4. The results were evaluated histologically as well as clinically. Results indicated flushing of the graft to be superior to a nonflushing procedure. A flushing pressure of 80 cm and even 50 cm proved to be harmful to the jejunal graft. Flushing pressure of 35 cm resulted in successful segmental (jejunal) and subtotal (minus 5- to 7-cm distal ileum) small bowel transplantation. However, survival of a total small bowel graft could not be achieved with the optimal flushing procedure indicating that the functional integrity of a small bowel graft also depends on conditions other than the method of short-term preservation.     

The contractile properties of wound granulation tissue

A systematic examination of the contractile properties of wound granulation tissue is presented. Shortening of and tension generated by granulation tissue in the presence of 30 mM diphenhydramine HCl have been measured. Analysis of the stress (load per unit area)/strain (extent of shortening) results from isotonic shortening studies showed that over the range of 0 to 2.5% shortening there was an approximately linear relationship between stress and strain with a high modulus of elasticity. At lower stresses, wide variations in the amount of shortening occurred with little change in stress. Our interpretation of these findings is that diphenhydramine HCl caused an active shortening of the granulation tissue by 2.5% of its length and contractions greater than this were the result of secondary effects such as coiling and bending of the strips. It is shown that the granulation tissue would have to shorten by 2% once every 3 days to account for observed in vivo rates of contraction for large human wounds and once every 13 hr for rapidly contracting experimental rabbit wounds. The time course of the development of isometric tension by the granulation tissue is shown to be consistent with the proposal that each contractile cell contributes equally to the overall tension developed and that each cell is individually activated by a critical concentration of diphenhydramine HCl which is transported through the tissue by diffusion.     

Reduction of the drug-induced nephrotoxicity by ATP-MgCl2. II. Effects on gentamicin-treated isolated perfused kidneys

Drug-induced nephrotoxicity (NT) has become an increasingly significant clinical problem. An in vitro model of drug-induced NT was therefore developed using gentamicin and the effects of ATP-MgCl2 on reduction or prevention of NT were determined. To study this, non-pulsatile perfusion in isolated rat kidneys was maintained at 100 mm Hg during 2 hr of perfusion at 37 degrees C. The oxygenated Krebs-HCO3 perfusate contained 7.5 g/dl albumin as colloid, glucose, creatinine, amino acids, trace amounts of [3H]inulin and 125I-lysozyme, and either 0, 0.4, 0.8, or 1.2 mg/ml of gentamicin. In some studies, 2 mM ATP-MgCl2 was added with 0.8 mg/ml of gentamicin at 0 and 60 min of perfusion. During each 10-min clearance period, glomerular filtration rates, sodium absorption, water absorption, and fractional clearance of TCA-precipitable lysozyme were measured. The results indicate that renal perfusate flow, glomerular filtration rate, urinary flow and tubular absorption of protein (a sensitive indicator of tubular function), sodium, and water were affected by gentamicin in a dose-dependent manner. An isolated kidney preparation can therefore be used to study gentamicin-induced NT. Higher in vitro perfusate concentrations of the drug were needed, however, to acutely mimic the in vivo cumulative effects. Nonetheless, renal perfusate flow, glomerular filtration rate, and the depression in protein reabsorption which occurred with gentamicin treatment were markedly improved by simultaneous treatment with ATP-MgCl2. Thus, ATP-MgCl2 may be useful in reducing drug-induced nephrotoxicity.     

The effect of free fatty acids on insulin-mediated glucose uptake

Free fatty acids (FFA) have been shown in vitro to inhibit insulin-mediated glucose uptake by muscle and have been proposed as in vivo mediators of peripheral insulin resistance. Twenty percent fat emulsion and heparin were administered to six awake healthy dogs during 3-hr insulin clamp studies. Lipid infusion resulted in a fivefold increase in FFA concentration over control (2371 ± 331 vs 439 ± 65, P < 0.002), but did not importantly alter glucose and insulin concentrations. No change was observed in glucose disposal (13.30 ± 1.41 vs 13.76 ± 1.51 mg/kg · min control), hindquarter A–V glucose concentration difference (9 ± 2 vs 9 ± 1 mg/dl), or hindquarter glucose uptake (3.42 ± 0.84 vs 3.71 ± 0.65 mg/kg · min). These observations suggest that FFA may not be important mediators of peripheral insulin resistance in critically ill patients.     

The measurement of glucose turnover and oxidation using radioactive and stable isotopes

Isotopes have become the best means for investigating glucose kinetics in vivo. With the recent greater availability of stable isotopes there has developed a need to understand how data may be obtained from the use of both radioactive and stable glucose tracers. Described for the nonexpert is the calculation of glucose appearance and disappearance, clearance and oxidation using both stable and radioactive glucose isotopes, administered both by bolus and primed constant infusion and under both steady and nonsteady state conditions. Other substrates may be studied using similar methodology. The use of stable substrate isotopes will be an expanding field of metabolic research in man.     

Long-term myocardial preservation: thromboxane production and coronary resistance

In a series of 18 experiments on long-term myocardial preservation we evaluated whether vasoactive substances like thromboxane and prostacyclin are associated with the secondary increase in coronary resistance during preservation perfusion of the canine heart. In a control group (n = 12) and in a group treated with a specific thromboxane synthetase inhibitor (OKY 1581) coronary resistance was measured at 10 and 30 min, and at 1, 4, and 24 hr. At the same time intervals thromboxane A2 and prostacyclin (PGI2) production were determined as TXB2 and 6-keto PGF1 alpha, respectively. After OKY 1581 treatment no increase in TXB2 occurred and no secondary increase in coronary resistance was observed, while in the control group both TXB2 levels and resistance increased (P less than 0.01); 6-keto PGF1 alpha levels showed the same increase in control and in treated hearts. From this study it is concluded that during 24-hr myocardial preservation the characteristic secondary increase in coronary resistance is related to thromboxane production in the heart and is prevented by inhibition of thromboxane synthetase.     

The clinical and histopathological effects of pancreatic duct occlusion in experimental acute pancreatitis in dogs

A continuous production of significant pancreatic enzymes, which are thought to be responsible for the maintenance of the digesting process, is frequently found in fulminant necrotizing pancreatitis. Since the medical therapies known to be effective are based upon the rationale of slowing pancreatic secretion, a simple measure which permits the "burning out" of residual pancreatic tissue might therefore have a therapeutic value. In this study, 2 hr after the induction of acute hemorrhagic pancreatitis, 5 dogs (Group I) were treated with 1.5 ml Ethibloc injected into the pancreatic duct; 5 other animals (Group II) were given 1.5 ml saline; Group III (5 dogs) had no treatment. All animals in Group II and 4 of the 5 animals in Group III expired within 8 days postoperatively. In contrast, 4 of 5 animals from Group I survived. Although some of the biochemical parameters showed significant changes after the induction of acute pancreatitis, no differences were seen between the three groups. In the expired animals, the picture of histological examination was that of a fulminant acute hemorrhagic pancreatitis of the left lobe. In the survival dogs although normal pancreatic tissue was present in the right lobe at necropsy at intervals, there was always a pancreatic atrophy of the left lobe and striking adhesions with the surrounding tissues suggesting the severity of the disease in the acute phase. These findings suggest that pancreatic duct occlusion causing the exocrine secretion to stop may have beneficial effects in the treatment of acute fulminant pancreatitis in the acute phase and may improve the survival rate.     

Role of the liver in host defense to pneumococcus following splenectomy

Splenectomy is associated with increased susceptibility to bacterial infection, and this is thought to be primarily due to a decrease in clearance of bacteria from the blood. The purpose of the present study was to determine if splenectomy could increase susceptibility to pneumococcus type 3, which is cleared primarily by the liver in rats, and if hepatic function is altered by splenectomy. Splenectomy increased the mortality of rats challenged iv with pneumococcus. Heat-killed, 51Cr-labeled pneumococci were rapidly cleared by the liver and splenectomy did not alter the initial clearance rate or the initial hepatic uptake of bacteria. Injection of viable pneumococci showed that blood levels were unchanged at 30 min but were much greater 5 hr after challenge in splenectomized animals. Hepatic uptake of viable pneumococcus was also not changed at 30 min after injection but at 5 hr the number of bacteria in the liver was greater in the splenectomized animals. This suggests an impairment in hepatic bactericidal function. Another contributing factor may have been that the hepatic bactericidal capacity was overwhelmed by the pneumococci which would normally have been killed by the spleen. Lung localization of viable bacteria was increased initially but there was no decrease in pulmonary bactericidal function. Thus, splenectomy increased susceptibility to a bacteria cleared primarily by the liver which was attributed to an impairment of hepatic bactericidal function and/or an inability of the liver to compensate for the loss of splenic function due to a saturation of the bactericidal system.     

The hemodynamic effects of intravenous infusions of serotonin in conscious dogs

The effects of exogenously infused serotonin on central and regional hemodynamics were investigated in 14 dogs. Using intravenous doses that mimic postprandial levels of serotonin, we were able to demonstrate no changes in cardiac output or mean arterial pressure. However, there were region-specific changes in blood flow. Blood flow to the fundus, antrum, brain, heart, and skeletal muscle were increased by both the low-dose (4 μ/kg-min) and the high-dose (10 μg/kg-min) infusions. In contrast, blood flow to the kidney, spleen, and liver decreased. Whole blood 5-HT levels were measured in mixed venous blood and systemic arterial blood. Based on the differences between serotonin levels in these two circulations, pulmonary inactivation of exogenously infused serotonin was calculated to be 44%. The half-life of exogenous serotonin was measured at 1.2 min. The data thus suggest that at doses which mimic those released from the intestinal enterochromaffin cells, serotonin may play a role in mediating postprandial hemodynamic responses.     

Intellectual change and carotid endarterectomy,subjective speculation or objective reality: A review

The literature on objective measurement of intellectual changes associated with carotid endarterectomy was reviewed. Studies were assessed methodologically for their ability to provide conclusions concerning three pertinent questions in this area: (1) Do patients with extracranial carotid insufficiency show a consistent intellectual deficit as compared to patients without significant disease? (2) Are there intellectual changes associated with carotid endarterectomy or, more precisely, does the operation serve a restorative or prophylactic function? (3) What, if any, physiological events correlate with these changes? It was suggested that, due to inconsistent results and methodological shortcomings, no satisfactory conclusions can be reached at this point. Further research is required before conclusions can reach acceptable levels of confidence.     

Development of a new miniature method for the study of wound healing in human subjects

A new miniaturized method for evaluation of healing potential in human subjects has been developed. A small, standardized, subcutaneous wound is made in a standard location. Expanded PTFE tubing is placed in the wound and removed at specific intervals. The ingrowth of connective tissue is evaluated by histology and by measurement of hydroxyproline accumulation. Beginning on the fifth day, hydroxyproline accumulation correlates with visual accumulation of tissue in the tubing. Preliminary results show decreased hydroxyproline accumulation in the wounds of patients with preoperative debility. This is to be expected on the basis of previous clinical experience and laboratory studies. This method has the further advantage that the catheters may be placed with local anesthesia in outpatients and therefore may be applied systematically to populations, as well as for observation in patients requiring operation.     

ATP-MgCl2 produces sustained improvement in hepatic mitochondrial function and blood flow after hepatic ischemia

Recent studies have shown that infusion of ATP-MgCl₂ following hepatic ischemia significantly improved mitochondrial function and hepatic blood flow 1 hr after treatment. To determine if the improvement in the above parameters by ATP-MgCl₂ is short-lived or whether it persists for prolonged periods of time after treatment, hepatic ischemia in rats was produced for 90 min followed by reperfusion. The rats then received iv 0.5 ml of saline or ATP-MgCl₂ (12.5 μmole each). Twenty-four hours after reflow, hepatic blood flow was measured by H₂ polarography following which the animals were sacrificed and hepatic mitochondria isolated. The results indicated that 24 hr after reflow, mitochondrial state 3 respiration, respiratory control ratio, adenine nucleotide translocase activity, ATP synthetic activity, and hepatic blood flow were depressed by approximately 50% in animals which were treated with saline after hepatic ischemia. In addition, there was a fourfold increase in mitochondrial free fatty acid levels of such animals. Animals which were treated with ATP-MgCl₂ following hepatic ischemia showed significantly improved mitochondrial function (used as an index of cellular recovery) and hepatic blood flow. These results in conjunction with previous results suggest that infused ATP-MgCl₂ improves mitochondrial function and blood flow and that these effects persist even 24 hr after administration of ATP-MgCl₂. Thus, infusion of ATP-MgCl₂ following severe ischemia produces sustained improvement in cellular function.     

Renal krypton-85 washout in hemorrhage in sinoaortic-denervated dogs

Two groups of dogs, prepared as (a) sham controls and (b) bilaterally carotidsinusectomized and bilaterally-vagotomized experimental animals, were subjected to hemorrhage to study the reflex control of kidney washout compartments. Krypton-85 disappearance curves after renal artery injections of ⁸⁵Kr in saline were obtained and analyzed before bleeding (control), after bleeding to 50 mm Hg blood pressure, and 2.5 hr after hemorrhage. Before hemorrhage, the experimental group exhibited a significantly greater mean blood pressure, component II flow, and total renal blood flow (RBF) than the control group. Although the component I flow rates were not significantly different, the percentage of radioactivity was smaller in the experimental dogs. Immediately after hemorrhage, both groups exhibited a marked tendency toward a single component in place of components I and II. Of primary interest is the fact that both groups of dogs exhibited similar flow components after hemorrhage. Both groups reverted back to three component curves by 2.5 hr after hemorrhage, but the control group had a much greater flow in component I. In addition, the control group took back a significantly larger volume of blood from the hemorrhage bottle. It appears that carotid sinus removal and vagal sectioning resulted in a significant degree of prehemorrhage and renal blood flow redistribution, but not complete redistribution as found in hemorrhagic hypotension. Factors other than the sympathetic nervous system may have been involved.     

Prediction of progressive disease in Zollinger-Ellison syndrome—Comparison of available preoperative tests

Availability of alternative methods of treatment of the Zollinger-Ellison syndrome (ZES) has necessitated a reevaluation of that disease. To evaluate ability of preoperative tests to predict postoperative clinical course, serum samples (frozen since collection) obtained fasting and after calcium stimulation in 18 patients with documented ZES with at least 5 years of postoperative follow-up were reassayed, fractionated into molecular components by gel filtration through a 200 × 1-cm Sephadex G-50 superfine column, and quantitated by assay with an antibody with equimolar recognition of the major C-terminal peptides. Total gastrin immunoreactivity (IRG), response of serum gastrin to calcium stimulation (SIRG), or the combination of these two factors are the most frequent criteria for estimating postoperative course and magnitude of disease. These measurements were compared to the percentage of G-17 (G-17/IRG) by the methods of R. S. Galen and S. R. Gambino (Beyond Normality: The Predictive Value and Efficiency of Medical Diagnoses, New York: Wiley, 1975, pp. 10–14, 50–51) (Sensitivity, Specificity, Predictive value of positive and negative tests, Efficiency). Percentage G-17 > 20% of IRG is the most sensitive (100%) and specific (91%) method of evaluating extent of disease preoperatively in patients with ZES.     

High arginine levels in intravenous hyperalimentation abrogate post-traumatic immune suppression

Trauma victims often suffer immune system failure. Oral arginine has strong immune-enhancing properties. The metabolic, hormonal, and immune effects of increasing concentrations of arginine as part of post-trauma intravenous hyperalimentation (IVH) were studied. Groups of 11-14 rats, 275-350 g, underwent jugular vein catheterization and bilateral closed femoral fractures under anesthesia. IVH was started immediately postinjury at a rate of 0.8-1 ml/100 g body wt/hr and continued for 5 days. Twenty percent dextrose and three different amino acid mixtures were given as follows: (A) FreII (1.55 g ARG/1); (B) FreIII (4.05 g ARG/1); (C) modified FreIII (7.9 g ARG/1). All rats lost weight over the 5-day postinjury period; however, rats in groups B and C lost significantly less weight than rats in group A (-3.4 +/- 0.8% of initial body weight and -3.6 +/- 0.9% vs -6.1 +/- 1.2%, P less than 0.05). Rats in group A had negative cumulative nitrogen balance, while those in groups B and C were in highly positive balance. No significant difference in body weight change or nitrogen balance was noted between groups B and C. Trauma-induced thymic involution as assessed by thymic weight and lymphocyte content was greatest in group A, which received the lowest amount of arginine, and was linearly abrogated by increasing the amount of arginine administered (A less than B less than C). Thymocyte immune responsiveness increased with the amount of arginine given as assessed by mitogenesis in response to Con A (stimulation index: A--151.3 +/- 28.8 vs B--243.6 +/- 29.2, P less than 0.01 vs C--321.8 +/- 22.3, P less than 0.001 vs A and P less than 0.02 vs B) and PHA (A--65.0 +/- 14.3 vs B--67.7 +/- 15.3, NS, vs C--117 +/- 14.0, P less than 0.005 vs A and B).(ABSTRACT TRUNCATED AT 250 WORDS)     

Experimental aortic coarctation in puppies

Coarctation was produced in nine puppies at the age of 2 months with a simple silk ligature on the thoracic aorta. The constriction was standardized by measuring the blood pressure below the coarctation. Two of the operated puppies died. Five puppies were sham operated and they served as a control group. The blood pressure was followed by an indirect ultrasound method. At the end of 7 months of follow-up, when the dogs were 9 months old, the mean blood pressures were $\text{112}\text{76}$ mm Hg in the control group and $\text{193}\text{121}$ mm Hg in the coarctation group. The difference between the groups was highly significant (P < 0.001). A good collateral circulation could be demonstrated in the coarctation group by aortic angiography and it was also demonstrated in the measurements of renal perfusion with an isotope technique. It is suggested that experimental work involving coarctation should be performed in young animals which will develop good collateral circulation during their growth.