Linda T. Archer

Mechanisms of impaired cardiac function by vasopressin.

The mechanisms by which elevated levels of vasopressin (ADH) in man and animals cause serious myocardial dysfunction, evidenced by arrhythmias, reduction in cardiac output and coronary blood flow, are not settled. Experiments were conducted in 16 isolated working left ventricles to examine their metabolic and hemodynamic responses to the infusion of vasopressin and the combination of vasopressin and epinephrine. Contractile performance was evaluated by analysis of positive dP/dt, contractile element velocities, and ventricular work-curves using stroke work/end-diastolic pressure. Relaxation parameters, including negative dP/dt and the early diastolic relaxation time constant, were also studied. Coronary blood flow was reduced 22% or less by vasopressin while cardiac output was maintained at a constant level. Myocardial oxygen consumption, lactate and potassium balances were determined from arterial and coronary sinus concentrations. Vasopressin produced myocardial dysfunction indicated by decrements in contractile and relaxation indices, without evidence of global ischemia. Epinephrine restored the mechanical performance to normal without significant change in coronary blood flow, myocardial oxygen consumption, or lactate and potassium balance.

Increased survival with methylprednisolone treatment in canine endotoxin shock

Abstract The use of corticosteroids has been intensively studied for the treatment of endotoxin shock; however, there still remains much controversy over their use. This study was designed to determine the therapeutic value of treatment with methylprednisolone sodium succinate in the awake and anesthetized canine receiving LD 100 of Escherichia coli endotoxin by either intravenous slow infusion or bolus injection. Methylprednisolone (30 mg/kg) was administered initially at 15 min following the onset of endotoxin infusion and then at 90 min given a maintenance infusion of 15 mg/kg for 120 min. It was found that treatment with methylprednisolone significantly increased survival rate (83%) in dogs receiving LD 100 E. coli endotoxin by slow infusion in either the awake or anesthetized state. Both the 5-hr infusion and bolus injection of endotoxin produced a 100% mortality if steroid was not administered. Treatment with methylprednisolone did not alter the 100% mortality in the canine bolus-injected endotoxin shock model. Survival was associated with a normoglycemia and stabilized hematocrit, while death was accompanied by hypoglycemia and severe hemoconcentration.

Effectiveness of Steroid/Antibiotic Treatment in Primates Administered LD100 Escherichia coli.

Early aggressive therapy with maintenance infusions of methylprednisolone sodium succinate and gentamicin sulfate significantly increases the probability for survival of baboons given LD100 Escherichia coli. The present study was designed to determine if baboons would recover when initiation of treatment was delayed until they had sustained E. coli-induced systemic hypotension for a period of approximately three hours. Sixteen adult baboons were each administered a two-hour infusion of LD100 E. coli. All eight untreated animals died within 42 hours. Five of the eight baboons treated after approximately three hours of hypotension with methylprednisolone sodium succinate and gentamicin sulfate survived. Treated animals had significantly higher blood glucose and insulin levels and lower blood urea nitrogen concentrations than baboons receiving E. coli alone. E. coli blood concentrations were lower in the treated than in the untreated baboon group by the sixth hour (less than 0.02). Heart rates increased in all animals but were not as high in the treated baboons. Both groups experienced similar decreases in mean systemic arterial pressure, PCO2, base excess, leukocyte, lymphocyte, and platelet concentrations, and increases in creatinine and lactate concentrations. Data from the present study indicate that the probability of recovery from shock is significantly increased even when initiation of steroid/antibiotic therapy is postponed until baboons have experienced sustained systemic hypotension.

Genistein induces enhanced growth promotion in ER-positive/erbB-2-overexpressing breast cancers by ER–erbB-2 cross talk and p27/kip1 downregulation

Genistein is a major isoflavone with known hormonal and tyrosine kinase-modulating activities. Genistein has been shown to promote the growth of estrogen receptor positive (ER+) MCF-7 cells. In ER-negative (ER-)/erbB-2-overexpressing (erbB-2+) cells, genistein has been shown to inhibit cell growth through its tyrosine kinase inhibitor activity. The effects of genistein on cell growth and tamoxifen response in ER+/erbB-2-altered breast cancers (known as luminal type B and noted in approximately 10 to 20% of breast cancers) have not been well explored. Using erbB-2-transfected ER+ MCF-7 cells, we found that genistein induced enhanced cellular proliferation and tamoxifen resistance when compared with control MCF-7 cells. These responses were accompanied by increased phosphorylation of ERalpha and ER signaling, without increase in ER protein levels. Genistein-treated MCF-7/erbB-2 cells also showed enhanced activation/phosphorylation of erbB-2, Akt and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase. Blockade of the phosphatidylinositol 3-kinase and/or MAPK pathways abrogated genistein-induced growth promotion, suggesting that genistein effects involve both critical signaling pathways. We also found that p27/kip1 was markedly downregulated in genistein-treated MCF-7/erbB-2 cells. Overexpression of p27/kip1 attenuated genistein-mediated growth promotion. In aggregate, our data suggest that the concomitant coexpression of ER and erbB-2 makes breast cancers particularly susceptible to the growth-promoting effects of genistein across a wide range of doses. The underlying mechanisms involve enhanced ER-erbB-2 cross talk and p27/kip1 downregulation.

Hypoglycemic response of blood to live Escherichia coli organisms and endotoxin

Abstract Progressively developing lethal hypoglycemia in dogs and baboons subjected to endotoxin or live E. coli shock has recently been reported by this laboratory. The purpose of the present study was to explore the possibility that accelerated glycolysis in blood might contribute to the hypoglycemia of shock. Experiments were carried out on canine heparinized blood drawn from nonfasted unanesthetized animals and maintained in vitro under controlled temperature conditions. Plasma glucose was determined with a Beckman glucose analyzer. LD100 to LD0 doses of E. coli endotoxin or live E. coli organisms, as estimated from parallel in vivo studies, were incubated with blood during a 6- to 7-hr period. Glucose blood concentrations, cumulative glucose utilization, and dose-response studies with endotoxin and live organisms were carried out. Paired control blood samples received equal volumes of saline in place of endotoxin or organisms. All studies were conducted on the blood from a colony of seven adult mongrel donor animals. Results demonstrated consistent accelerated glucose disappearance at all doses of endotoxin and organisms, in comparison to the controls with saline only added. LD100 experiments resulted in significantly greater disappearance rates of glucose as compared to LD0 studies, during the first 2 hr. Minimal threshold responses for accelerated glucose utilization were observed at levels above 104 organisms/ml of blood, while those for endotoxin were less than 10−6 mg/ml, both concentrations being sublethal when applied to the whole animal. At glucose concentrations less than 20 mg%, control and experimental curves tended to converge with the achievement of minimal values of about 10 mg%. Positive correlations were seen between rates of glucose disappearance, pH, and pCO2, suggesting accelerated metabolic activities by certain formed elements of the blood during the process of phagocytosis. Findings in in vitro studies were compared to those in eviscerated, nephrectomized dogs in which all sources for new glucose were eliminated, and similar accelerated rates of cumulative glucose utilization were observed between the animal and test tube experiments. Findings suggest that the excessive demand for glucose by certain blood components may explain in part the development of lethal hypoglycemia and acidemia in animals subjected to endotoxin- or live bacterial organism-induced shock.

Dose-response effect of In Vivo administration of endotoxin on polymorphonuclear leukocytes oxidative burst

In vitro, endotoxin primes polymorphonuclear leukocytes (PMNs) to respond with a greateroxidative burst. The purpose of the present study was to investigate the In vivo effect of a wide range ofsingle endotoxin bolus doses using a rat model. PMNs were subsequently challenged In vitro with phorbolester to produce reactive oxygen intermediates (ROI). Flow cytometric determination of ROI production byPMNs using the dichlorofluorescin conversion assay showed that although low doses induced priming,large doses induced a decrease in ROI production by the few PMNs that remained in the circulation. By 6 hafter injection, ROI production had returned to basal levels after a high dose, and was still increasing aftera low dose. Neutropenia occurred immediately after endotoxin injection. After 6 h, PMN counts returned toalmost normal levels with a high dose, but rebound neutrophilia occurred with a small dose. In contrast toin vitro studies, in vivo injection showed a response pattern that varied widely with dose and time ofobservation.

Effects of glucose or insulin on myocardial performance in endotoxin shock.

Summary Past studies reported by this laboratory have documented myocardial dysfunction and progressively developing hypoglycemia in canine endotoxin shock. The purpose of the present study was to determine the effects of glucose concentrations and insulin infusions on myocardial performance following endotoxin administration. Experiments were carried out on isolated, working canine left ventricular heart preparations exchanging blood with intact dogs. Myocardial function was evaluated following endotoxin and correlated with concentrations of glucose and effects of insulin infusion. Cardiac dysfunction occurred within 2–4 hr postendotoxin and the degree of malfunction was not related to arterial blood glucose concentrations. Maintaining blood glucose at control, preshock, levels by infusion of 50% glucose did not prevent myocardial dysfunction as evidenced by elevations of left ventricular end diastolic pressure, and depressed power. Infusions of insulin reversed cardiac failure and maintained normal performance in spite of wide ranges in glucose concentration (5-120 mg%). Findings suggest that myocardial dysfunction is not precipitated or enhanced by the hypoglycemia of endotoxin shock. The beneficial actions of infused insulin on cardiac performance appear to be elicited on the basis of mechanisms other than myocardial glucose transport. Appreciation is expressed to Beverly Beller for technical assistance.

Myocardial performance in splanchnic arterial occlusion shock

Abstract The adverse combined effects of mesenteric ischemia and the subsequently precipitated lethal shock after restoration of mesenteric blood flow have implicated direct or indirect roles of the heart in the pathogenesis of shock. The present experiments were carried out to assay the role of the heart in splanchnic arterial occlusion (SAO) shock. Studies were designed to evaluate the combined effects of SAO shock and diminished coronary perfusion pressure on the performance of a stressed heart. Experiments were carried out on isolated hearts exchanging blood with an intact dog subjected to 2 hr of splanchnic arterial occlusion. Release of the occlusion did not result in any measurable detrimental effect on the heart: LVEDP and cardiac power were maintained in the normal range at mean aortic pressures (afterloads) between 34 and 125 mm Hg at all times during the postocclusion period. dP/dt was elevated, possibly as a result of increased coronary blood flow and decreased coronary vascular resistance. Myocardial oxidative metabolic characteristics were unchanged from control preocclusion values. Normal myocardial function was observed after the release of a lethal period of splanchnic arterial occlusion during both early and terminal periods of shock. Results, though not revealing the cause of SAO shock, suggest that diminished cardiac performance resulting from the actions of blood-borne substances released from the ischemic splanchnic region is not a significant factor in the development of systemic hypotension and death.

Associated leukocyte responses in the lethal aspects of E. coli shock.

Dogs administered lethal injections of E. coli endotoxin or E. coli organisms develop systemic hypotension, hypoglycemia, and hepatosplanchnic dysfunction (1-4). Progressively decreasing blood glucose levels after endotoxin or E. coli administration are due in large part to depressed hepatic function, particularly gluconeogenesis (4-7). Accelerated glucose uptake has been reported following in vitro incubation of either endotoxin or live E. coli organisms in blood, and white blood cell (WBC) phagocytic activity has been implicated as the primary responsible factor (2). Increased phagocytic activity of the blood after endotoxin (8) has been traced to the buffy coat (9) and the leukocyte (10). Recent reports have shown circulating neutrophils to be of major importance in the clearance of bacterial organisms (11) or endotoxin (12) from the blood, while others have described beneficial effects of transfused WBCs in patients and animals in septic shock (13, 14). The purpose of the present study was to explore the responses of canine blood to the separate effects of E. coli organisms and E. coli endotoxin, particularly emphasizing the role of the WBC in the uptake of glucose in vitro and its possible relationship to survival in vivo. Materials and methods. In vivo experiments were carried out on 12 awake adult mongrel dogs during a 4-day period. On the fourth day, venous blood was drawn from each animal and additionally studied in the in vitro state. Animals, selected for robust health and absence of heart worms, were treated for intestinal parasites and conditioned in the animal facility for 3-6 weeks prior to use. Dogs with initial WBC counts between 7000 and 20,000/mm3 and hema-tocrits exceeding 37% were utilized in the experiments. In vivo studies. Unanesthetized, gently restrained animals were divided into paired control and experimental groups which were studied simultaneously.

Tobramycin therapy for lethal sepsis in the dog.

Antimicrobial effectiveness and effect on survival of single-dose vs. multiple-dose aminoglycoside antibiotic therapy (with and without steroid) for lethal sepsis were evaluated. Adult dogs of either sex were anesthetized, divided into five groups, and infused iv for one hour with Escherichia coli. Group A was given no drug. Group B was given a 45-mg/kg, 10-min iv injection of tobramycin (TOB) at 65 min, Group C was given a 3-mg/kg, 10-min TOB injection at 65 min, followed by an 8.25-mg/kg iv infusion for 285 min, and three 11.25-mg/kg intramuscular injections at 6, 12, and 18 h (total 45 mg/kg). Group D was given the same TOB regimen as B, plus a 30-mg/kg iv injection and 30-mg/kg iv infusion of methylprednisolone sodium succinate (MPSS) from 15 to 360 min. Group E was given the same TOB regimen as C, plus the same MPSS regimen as D. Treated dogs also received 11.25 mg/kg of TOB daily for 4 days. The percent surviving more than 7 days was 0, 0, 17%, 83%, and 83%, for groups A through E, respectively. By 4 h, TOB-treated groups had significantly (p < .05) lower E. coli blood levels than group A. Also E. coli levels in group B were significantly (p < .05) lower than those in groups C, D, or E. High trough serum TOB concentrations were associated with death and very low levels with recovery. Serum urea nitrogen and creatinine concentrations increased in all groups, but returned to normal by 7 days in survivors. BP decreased in all groups, but began to recover by 3 h in groups D and E. Serum glucose levels of groups D and E did not decrease. Serum cortisol levels increased in all groups, but were lower than normal from 48 to 168 h in groups D and E. In summary, single-dose TOB was an effective antimicrobial agent. However, recovery from E. coli sepsis was dependent on TOB plus MPSS and was not achieved with TOB alone.