Effect of venting on myocardial protection by hypothermic cardioplegic arrest

Myocardial rewarming between cardioplegic (CP) infusions is in part attributable to blood circulating through the heart from collateral channels. This experiment was performed to determine if the type of left ventricular (LV) venting affects myocardial temperature (temp) or alters myocardial protection. Twelve dogs underwent cardiopulmonary bypass (CPB) at 37 degrees C and were subjected to 100 min of cardioplegic arrest by intermittent coronary infusion of 300 ml 0-4 degrees C CP solution. Arterial, central venous, left atrial, and LV pressures; cardiac output; systemic, septal (S), right ventricular (RV), and LV temp; myocardial ATP and glycogen were measured; LV pressure/volume curves and LV dp/dt were calculated. Group A (6 dogs) had an LV vent during CPB, and Group B (6 dogs) had the aorta vented via the CP line. CP infusion lowered LV temp to 8 degrees C in Group A vs 13 degrees C in Group B (P less than 0.000002); S temp was lowered to 7 degrees C in Group A vs 11 C in Group B (P less than 0.00007); and RV temp was lowered to 16 degrees C in Groups A and B. Ten minutes after CP, LV and S temp increased to 20-21 degrees C in Groups A and B, and RV temp to 24-25 degrees C in Groups A and B. Twenty minutes after CP all temperatures were the same. Hemodynamics and myocardial metabolic studies were similar in the two groups. CONCLUSIONS: Hearts vented via the LV cooled to a lower temperature vs those vented via the aorta. Venting did not affect myocardial rewarming, myocardial metabolites, or ventricular function.     

Neutrophil function in adults after traumatic splenectomy

The syndrome of postsplenectomy sepsis in both children and adults is receiving increased clinical attention. However, the exact immunologic reasons for the increased susceptibility to bacterial sepsis after splenectomy is unclear. The purpose of the current report is to describe the results of studies of peripheral neutrophil function in 24 healthy adult individuals who had previously undergone incidental or traumatic splenectomy. The patient population studied had their splenectomies performed a mean of 6.8 years prior to the current study to avoid any bias resulting from the acute hospitalization or injury. None of the patients had underlying hematologic or malignant diseases. The results of these experiments indicate that peripheral neutrophil chemotaxis, phagocytosis, and intracellular killing of Staphylococcus are normal in this population, and additionally, that the sera of these patients adequately support the opsonization of S. aureus and generates chemotactic factors normally. No neutrophil defect or impairment of serum opsonic or chemotactic activity after incidental or traumatic splenectomy was identified in the population studied.     

Bacterial adherence to vascular grafts after in vitro bacteremia

All currently used arterial prosthetics have a greater susceptibility to infection following bacteremia than does autogenous tissue. This experiment compares quantitative bacterial adherence to various prosthetic materials after bacteremia carried out in a tightly controlled and quantitative fashion. Ten centimeters long, 4 mm i.d. Dacron, umbilical vein (HUV), and polytetrafluoroethylene (PTFE) grafts, as well as PTFE grafts with a running suture line at the midportion were tested. Each graft was interposed into a pulsatile perfusion system modified from a Waters MOX 100 TM renal transplant pump. Indium-111-labeled Staphylococcus aureus were added to heparinized canine blood to give a mean concentration of 4.7 X 10(6) bacteria/cc. This infected blood was recirculated through each graft for 30 min at a rate of 125 cc/m, 100 Torr (sys), 60 beats/min. The gamma counts/graft were used to calculate the number of bacteria/cm2 of graft surface. After nine experiments, a mean of 9.63 X 10(5) bacteria/cm2 were adherent to the Dacron, 1.04 X 10(5) bacteria/cm2 to the HUV, and 2.15 X 10(4) bacteria/cm2 to the PTFE. These differences were all significant at the 0.05 level. The addition of a suture line increased bacterial adherence to the PTFE graft by 50%. These results suggest that PTFE is the vascular graft material of choice when a prosthetic graft must be implanted despite a high risk of subsequent clinical bacteremia. Our in vitro, pulsatile perfusion model gave accurate and reproducible results, and appears well suited for further studies of bacterial, or platelet adherence to grafts, as well as the biomechanics of vascular conduits.     

Thyroid function and lipid concentration after thyroidectomy in rats

The purpose of this study was to determine whether subjects with high serum thyrotropin (TSH) levels and low-normal serum thyroxine (T₄) levels are euthyroid, as a result of the increased TSH stimulation of the thyroid, or hypothyroid. As a model to study this clinically important problem we analyzed serum cholesterol (Chol), triglyceride (Tg), TSH, T₄, and triiodothyroxine (T₃) before and 7, 10, and 12 weeks after sham operation (SO), hemithyroidectomy (Htx), and total thyroidectomy (Ttx) in 33 male Sprague—Dawley rats. By 7 weeks after Ttx serum TSH levels increased from 861 ± 84 to 9657 ± 644 ng/ml, T₄ decreased from 3.7 ± 0.18 to 0.84 ± 14 ng/ml, and T₃ decreased from 0.317 ± 0.026 to 0.217 ± 0.007 ng/ml (P < 0.001). Serum Chol increased from 69.6 to 112.5 mg/dl, whereas Tg decreased from 70.93 ± 3.56 to 50.54 ± 4.18 mg/dl (P < 0.01). After Htx serum TSH levels were higher than before operation and were higher than in the SO group (P < 0.05); serum T₄ and T₃ levels tended to be lower than before Htx and lower than in the SO group, but this decrease was only significant for both T₄ and T₃ 10 weeks after operation (P < 0.05); serum Chol and Tg levels were the same in Htx and SO animals. Thus, after Ttx (1) serum T₃ and T₄ levels decrease, (2) serum TSH levels increase, (3) serum Chol levels increase, and (4) serum Tg levels decrease. After Htx (1) serum TSH levels increase, (2) serum T₃ and T₄ levels are low-normal or slightly low, (3) serum Chol and Tg levels are normal. It appears that increased TSH stimulation of the thyroid gland can maintain normal serum lipid levels in the presence of low-normal or slightly low thyroid hormone concentrations. Thus, animals with increased serum TSH levels and low-normal or slightly low thyroid hormone levels are either not hypothyroid or serum lipid levels are an insensitive indicator of hypothyroidism.     

Azathioprine and acute pancreatitis: Studies with an isolated perfused canine pancreas

Recent controlled clinical trials have documented the development of acute pancreatitis in 5% of patients receiving azathioprine for Crohn's disease, by far the highest incidence of drug-induced pancreatitis recorded to date. In an effort to evaluate the effects of azathioprine on the pancreas, the isolated ex vivo perfused canine pancreas model was used. No significant changes in gross appearance, weight, or serum amylase occurred in azathioprine-treated glands compared to controls. Azathioprine administration, however, resulted in a significant increase in secretory volume (two fold) and bicarbonate output (two fold), and a profound depression of trypsin output compared to controls. These preliminary studies demonstrate that azathioprine has marked effect on pancreatic function in this model.     

Extraction of glutathione by the isolated perfused rabbit kidney

The effects of adding exogenous reduced glutathione (GSH) to the perfusate were studied in the isolated perfused rabbit kidney. The addition of 500 mg/liter of GSH to the perfusate prevented the depletion of cortical and medullary GSH; perfusion without the addition of GSH consistently resulted in depletion of tissue levels of this tripeptide. In addition, GSH supplementation of the perfusate decreased renal vascular resistance and increased perfusate flow. GSH extraction studies revealed a progressive decrease in renal extraction with time, ranging from complete extraction at 10 min to a value of 38% at 60 min. The fractional clearance of GSH increased from 7.3% at 10 min to 17.9% after 60 min of perfusion. The results indicate a high affinity of the rabbit kidney for GSH and a relatively large net reabsorption of the tripeptide.     

The effect of acute and chronic glucocorticoid excess on leucine kinetics and protein turnover in vivo

The present studies were undertaken to assess the effects of excess cortisol on amino acid exchange in the conscious dog. Three groups of 18-hr fasted dogs with catheters chronically implanted in the femoral artery were studied: Group I (n = 6) received saline; Groups II and III (n = 5, each) received ACTH intravenously (1 U/min) for 7 hr; in addition, Group III received ACTH, 500 U/day intramuscularly for 4 days. Leucine rates of appearance (Ra) and clearance were measured using a constant infusion of L-4,5-[3H]leucine. ACTH treatment resulted in a 9-fold increase in plasma cortisol in Groups II and III (from 2 +/- 1 to 18 +/- 1 and 17 +/- 2 micrograms/dl, in II and III, respectively P less than 0.001), with no effect on either plasma insulin or glucagon. Plasma leucine (mmole/liter) increased from 118 +/- 6 (I) to 153 +/- 6 (II, P less than 0.005) to 275 +/- 35 (III, P less than 0.001). Leucine Ra (micromoles/kilogram/minute) did not change in II, but rose by 39% (P less than 0.005) in III. Clearance (milliliters/kilogram/minute) dropped from 25 +/- 2 (I) to 18 +/- 2 (II, P less than 0.005), to 15 +/- 2 (III, P less than 0.001). It is concluded that acute elevations of cortisol increased plasma leucine only by inhibiting its rate of disposal, whereas chronic elevations had a dual effect; they inhibited leucine disposal and increased its entry into the plasma compartment, suggesting an inhibition of protein synthesis and stimulation of protein breakdown.     

Influence of serum on impaired neutrophil chemotaxis after thermal injury

Impaired neutrophil chemotaxis has been consistently documented after thermal injury but whether this defect is primarily related to an acquired cellular defect or to humoral factors is not clear. To study this question, serial neutrophil chemotaxis measurements using the agarose technique of chemotaxis, were made in 34 patients with a mean burn size of 33%. Eighty-three percent of these patients developed a neutrophil chemotactic defect at some time during their hospital stay. The results of this study indicated that the serum from burn patients did not contain cell-directed inhibitor(s) of chemotaxis (CDI) or chemotactic factor inactivator(s). Furthermore, the chemotactic defect in the burn patient's neutrophils could not be reversed by normal human serum, suggesting that the cause of this defect was not related to the absence of normal circulating humoral substances. Additionally, no suppressive effect of silvadene (10 g/ml) on neutrophil chemotaxis was found. Therefore, we concluded that stable serum factors were not likely to play a major role in the development of the acquired neutrophil defect thermal injury.     

Functional preservation of the mammalian kidney. V. pharmacokinetics of dimethyl sulfoxide (1.4M) in kidneys (rabbit and dog) perfused at 37, 25, or 10 degrees C followed by transplantation (dog).

Rabbit and dog kidneys were perfused for 30 min at 37°C with 1.4 M [³H]Me₂SO in a K⁺-Mg²⁺?rich perfusate. Subsequently the kidneys were perfused for 30 min with Me₂SO-free perfusate. The rate of Me₂SO uptake and washout as well as Me₂SO distribution in the tissue were determined. It was found that equilibrium conditions were achieved within 30 min for both uptake and washout with $\text{T}\text{M}$ ratios approaching 1.0. The amount of Me₂SO in the cortex and medulla of rabbit kidneys was not significantly different. The same experiment was repeated with dog kidneys at 25 and 10°C. At these lower temperatures the rate of uptake and washout was significantly less, but the final concentration achieved within 30 min was the same as at 37°C. Dog kidneys flushed with a K⁺?Mg²⁺?rich solution, with or without 1.4 M dimethyl sulfoxide (Me₂SO), were kept at 10°C, then reimplanted in the autologous host, and an immediate contralateral nephrectomy was performed. Of the dogs receiving kidneys treated with Me₂SO-free solution, 86% survived; of the dogs receiving Me₂SO-treated kidneys, 75% survived. Dog kidneys were perfused for 30 min with a K⁺?Mg²⁺?rich solution, with or without 1.4 M Me₂SO, at 25 or 37°C. All kidneys were then perfused for 30 min with a Me₂SO-free solution at the same temperature used for the first perfusion. All kidneys were then reimplanted in the autologous host and an immediate contralateral nephrectomy was performed. Of the dogs receiving kidneys perfused at 25°C with Me₂SO-free solution, 43% survived; of the dogs receiving kidneys perfused with Me₂SO, 42% survived. Dog kidneys were also treated at 37°C in a manner similar to those at 25°C. Of the dogs receiving kidneys perfused at 37°C with Me₂SO-free solution, 80% survived; of the dogs receiving kidneys perfused with Me₂SO, 67% survived. Other results indicate that perfusion with a closed circuit is superior to perfusion with an open circuit. Also, gradual administration and washout of Me₂SO gives better renal survival than rapid changes in Me₂SO concentration.     

Liver cell membrane alterations during hemorrhagic shock in the rat

Previous studies using the Ling-Gerard microelectrode to measure membrane potential and a muscle biopsy technique to determine water and electrolyte content have established a skeletal muscle cell membrane defect in hemorrhagic shock. The present study was undertaken to compare and contrast changes occurring on a cellular level in the liver and skeletal muscle of the rat during sustained hemorrhagic shock. The liver has been suggested as a possible primary site of organ failure during prolonged shock with a loss of normal liver processes and important hepatic metabolic functions. Thirty-four experiments were performed in rats with 11 experiments in the control group. Skeletal muscle membrane potential as well as liver cell membrane potential was measured after opening the abdomen through a midline incision. The ventral lobe of the liver was exposed and placed on a suspension apparatus to decrease respiratory interference and the liver was impaled with a Ling-Gerard microelectrode. Muscle cell resting membrane potentials were measured in exposed skeletal muscle in the leg of the animals. Biopsy samples were obtained at intervals in both the liver and skeletal muscle. Twenty-three experiments were conducted by producing hemorrhage with the withdrawal of blood over a 5- to 15-min period of time and maintaining a systolic blood pressure of 60 mm Hg for 115 ± 40 min. The distribution of water and electrolytes in intra- and extracellular space in the muscle biopsies as well as in the liver on the basis of chloride distribution was considered to be a passive phenomenon related to the resting cell membrane potential as predicted by the Nernst equation. Correction of the measured water and electrolyte content of the biopsies for residual blood was carried out with the use of chromium-51-tagged red blood cells. The control group of rats did not demonstrate any significant change in membrane potential of either muscle or liver cells during the experiment. The membrane potentials were maintained at normal levels in the muscle ?91.4 ± 2.2 mV; and in the liver at a mean of ?40.3 ± 3.3 mV. The hemorrhagic shock group of animals demonstrated significant changes. Muscle membrane potential decreased to ?80.99 ± 6.3 mV (P < 0.01) while at the same time period the liver membrane potential decreased to ?24.1 ± 4.6 mV (P < 0.001). The results of these experiments give further evidence of a cellular membrane defect in hemorrhagic shock. The liver cell membrane potential changes and accompanying water and electrolyte shifts occurred before any significant changes in the muscle tissue. The data indicate the existence of a major alteration in rat liver cell membrane function early in the shock state.     

The biologic response to standard suture materials in the skin of fetal rabbits

It is thought that wound healing and reaction of tissue to suture materials in the newborn or preterm infant may resemble that of the fetus. Wound healing in fetal experimental animals has been described, but to date no study of reaction to suture material in fetal animals has been performed. Operations on 60 pregnant, New Zealand white rabbits were performed. Hysterotomies were performed, and a variety of sutures were simply placed in the skin in Group I. In Group II, a small skin incision was made, and the wound was closed with the various sutures. The suture materials studied were: silk, Prolene, Ethibond, chromic catgut, and Vicryl. The animals were sacrificed 2 to 5 days postoperatively, and histology and grading of the tissue reaction was carried out. Grading was based on: (1) reactive cellular density, and (2) cellular response dimension. The reaction observed in all fetuses was: (1) mild to moderate by our criteria, (2) identical with or without a wound, and (3) present 2 days after implantation and did not seem to change significantly thereafter. This study demonstrates a similar host-tissue response of the rabbit fetus to a variety of suture materials and suggests that any decision on the choice of suture material in the fetus and possibly the preterm and newborn infant should be based on properties of the suture other than the host-tissue response that the suture produces.     

Detection of intestinal ischemia,I. Microardiological and temperature differences between mesenteric and antimesenteric margin of the small intestine of the rat

Microradiographs were made of the vasculature of the ileum of rats following an injection of micropaque. The radius of vessels entering the mesenteric margin of the rat small intestine decreases significantly during its course toward the antimesenteric margin. The relative lack of vascular supply in the antimesenteric region of bowel was associated with a significant reduction (P < 0.001) of mean surface temperature as compared to its mesenteric surface. Occlusion of the blood supply to the bowel wall abolished this temperature gradient (P < 0.1). Measurement of temperature differences between the mesenteric and antimesenteric margin of the bowel wall of man may prove to be a sensitive indicator of bowel viability in intestinal surgery.     

Interorgan relationships of alanine and glutamine during fasting in the conscious dog

This study was designed to assess the interorgan relationships of glutamine and alanine in the conscious, overnight fasted dog, and to determine changes which occur with progressive fasting. Dogs were fasted for 18 hr (n = 6), 48 hr (n = 6), and 96 hr (n = 6) prior to the study. Catheters had been previously implanted in the femoral artery, renal vein, portal vein, and hepatic vein, and were used for blood sampling at 30-min intervals during the 3-hr experimental period. Hepatic and renal blood flows were determined by indocyanine green and para-aminohippuric acid (PAH) extraction methods, respectively. Balance data (micromoles/kilogram/minute) were estimated by multiplying the appropriate arteriovenous concentration differences by blood flows. Hepatic uptake of glutamine decreased 50% after a 48-hr fast, and by 96 hr, the liver became a net producer of glutamine. Gut utilization remained constant throughout fasting. The kidney's utilization gradually increased with fasting. The hepatic extraction of alanine fell with fasting, declining to 40% of its original uptake at 96 hr. The gut's production of alanine fell during the first 48 hr of fasting, but remained stable thereafter. The kidney's production of alanine increased throughout the period of starvation. The arterial concentration of glutamine rose with fasting, while that of alanine fell even with a 48 hr fast. The liver, by becoming a net producer of glutamine, and the kidney, by increasing its production of alanine, decrease demands for peripheral release of these two amino acids, and thus may have protein-sparing actions during fasting.     

Prostaglandin-induced bicarbonate secretion in the canine stomach: Characteristics and evidence for a cholinergic mechanism

Using a canine chambered stomach preparation, the effect of topical 16,16-dimethyl prostaglandin E₂ (dmPGE₂) in neutral solution (150 mN NaCl) on gastric mucosal bicarbonate (HCO₃^?) secretion was assessed. Compared to control studies in which neutral solution alone bathed the epithelium, dmPGE₂ (0.5, 1.0, 2.0, and 4.0 μg/ml), when applied to gastric mucosa, significantly increased the output of gastric HCO₃^? in a stepwise and dose-related fashion. Accompanying these effects in HCO₃^? output were similar increases in sodium, potassium, chloride, and gastric perfusate volume. In other studies, the effects of intravenous atropine and close intraarterial tetrodotoxin on this PG-induced HCO₃^? secretion were evaluated. Both agents completely prevented the stimulation of HCO₃^? output induced by dmPGE₂ (2 μg/ml). It is concluded that dmPGE₂, when topically applied to canine gastric epithelium, is a potent stimulant of bicarbonate output that is dose-dependent. The ability of atropine and tetrodotoxin to prevent this secretion suggests that a cholinergic mechanism may be involved and that dmPGE₂ mediates its effects on HCO₃^? output through acetylcholine release which in turn stimulates cholinergic nerve endings.     

Penicillin and natural immunity protect against postsplenectomy sepsis

Prophylactic penicillin, splenic autotransplantation, and immunization using pneumococcal vaccine have all been shown to reduce the incidence and mortality of postsplenectomy sepsis. However, little is known regarding the effect of penicillin in established infection or the effect of prior infection in either asplenic controls or animals with autotransplanted splenic tissue. An animal model with bacterial introduction via the lungs was used to investigate the effect of penicillin, splenic autotransplantation, and previous exposure to the infecting organism on the mortality of postsplenectomy sepsis. One hundred fifty-nine rats underwent either sham celiotomy, intraperitoneal splenic autotransplantation, or splenectomy. Twelve weeks postoperatively all animals were challenged using Streptococcus pneumoniae delivered transtracheally. Half of each group received procaine penicillin by intramuscular injection for 5 days beginning 24 hr post bacterial inoculation and mortality was observed. Eight weeks later surviving rats that had received penicillin were reinoculated with the same organism and mortality was again observed. Splenic autotransplantation reduced the early mortality in postsplenectomy sepsis. Prior bacterial exposure reduced the mortality in postsplenectomy sepsis, even in splenectomized animals. Treatment with penicillin produced a marked reduction in mortality even when administration was postponed for 24 hr after bacterial inoculation.     

Role of mitochondrial enhancement in maintaining hepatic energy charge level in endotoxin shock

The purpose of this study is to clarify the nature of apparent abnormalities in fuel substrate utilization which occur during progressive endotoxin shock and to relate these findings with its implications for circulatory behavior. After the administration of endotoxin, marked differences appeared in the time courses of hepatic energy charge and mitochondrial oxidative and phosphorylative activities between the early stage with normal blood pressure and the late stage with low blood pressure. In the early stage, the hepatic energy charge was maintained at near normal levels with a concomitant enhancement in mitochondrial oxidative and phosphorylative activities. In the late stage, this enhancement of mitochondrial oxidative and phosphorylative activities was depressed concomitant with a fall in hepatic energy charge. The mitochondrial enhancement was further associated with a fall in mitochondrial redox state, a rise in ketone body formation, and normoglycemia, indicating an acceleration of free fatty acid β-oxidation and gluconeogenesis at the early stage. In comparison, mitochondrial inhibition was accompanied by a further fall in mitochondrial redox state and hypoglycemia, indicating an inhibition of gluconeogenesis at the late stage. It is suggested that an enhancement in mitochondrial oxidative and phosphorylative activities is a protective mechanism which compensates for the fall in hepatic energy charge, and thus plays an essential role in the survival and recovery.     

Prolongation of intestinal allograft survival without immunosuppressive drug therapy. Transplantation of small bowel allografts

Although survival of small-bowel allografts can be prolonged by immunosuppressive drug therapy, infectious complications have been frequent, and therefore alternate approaches have been sought. The rat model of accessory small-bowel transplantation (LBN-F leads to Lewis rat combination) was used to study the effects upon mean survival time (MST) of conveying the venous effluent from the graft through the liver (porto-portal anastomosis; PP-A) rather than into the central circulation (porto-caval anastomosis; PC-A). Also investigated was the effect of splenectomy of the host. With PC-A, the MST was 12.5 days; with PP-A, the MST was prolonged to 22.9 days (P less than 0.005); and with PC-A or PP-A and simultaneous splenectomy, the MSTs were 22 days (P less than 0.001) and 24.2 days (P less than 0.05), respectively. In the last three groups, rejection was chronic (fibrosis, partial reabsorption of the graft), rather than acute as in rats with PC-A. A rise in antidonor hemagglutinin activity paralleled the rejection process and was delayed in rats with PP-A and those with splenectomy. These results suggest that intestinal transplantation should involve PP-A rather than PC-A. Hepatic filtration or alteration of antigen originating in the graft may be the cause for delayed, chronic graft rejection. Splenectomy, acting on the efferent arm of the rejection process by decreasing the host's immune reactivity, had the same effect on the mode of graft rejection, when combined with PC-A. An enhancing effect of splenectomy, when added to PP-A, could not be elicited.