The effect of ivermectin in seven strains of Aedes aegypti (Diptera: Culicidae) including a genetically diverse laboratory strain and three permethrin resistant strains.

Seven different strains of Aedes aegypti (L.), including a genetically diverse laboratory strain, three laboratory-selected permethrin-resistant strains, a standard reference strain, and two recently colonized strains were fed on human blood containing various concentrations of ivermectin. Ivermectin reduced adult survival, fecundity, and hatch rate of eggs laid by ivermectin-treated adults in all seven strains. The LC50 of ivermectin for adults and the concentration that prevented 50% of eggs from hatching was calculated for all strains. Considerable variation in adult survival after an ivermectin-bloodmeal occurred among strains, and all three permethrin-resistant strains were significantly less susceptible to ivermectin than the standard reference strain. The hatch rate after an ivermectin bloodmeal was less variable among strains, and only one of the permethrin-resistant strains differed significantly from the standard reference strain. Our studies suggest that ivermectin induces adult mortality and decreases the hatch rate of eggs through different mechanisms. A correlation analysis of log-transformed LC50 among strains suggests that permethrin and ivermectin cross-resistance may occur.

A role for endosomal proteins in alphavirus dissemination in mosquitoes.

Little is known about endosomal pathway proteins involved in arthropod-borne virus (arbovirus) assembly and cell-to-cell spread in vector mosquitoes. UNC93A and synaptic vesicle-2 (SV2) proteins are involved in intracellular transport in mammals. They show amino acid sequence conservation from mosquitoes to humans, and their transcripts are highly enriched in Aedes aegypti during arbovirus infection. Transient gene silencing of SV2 or UNC93A in mosquitoes infected with the recombinant alphavirus Sindbis MRE16-enhanced green fluorescent protein (SINV; family Togaviridae) resulted in the accumulation of viral positive- and negative-strand RNA, congregation of virus envelope antigen in intracellular networks, and reduced virus dissemination outside of the midgut. Further, UNC93A silencing, but not SV2 silencing, resulted in a 10-fold reduction in viral titres at 4 days post-infection. Together, these data support a role for UNC93A and SV2 in virus assembly or budding. Cis-regulatory elements (CREs) were identified at the 5'-ends of genes from the original data set in which SV2 and UNC93A were identified. Common CREs at the 5'-end genomic regions of a subset of enriched transcripts support the hypothesis that UNC93A transcription may be co-regulated with that of other ion transport and endosomal trafficking proteins.

Silencing an Anopheles gambiae catalase and sulfhydryl oxidase increases mosquito mortality after a blood meal.

Catalase is a potent antioxidant, likely involved in post-blood meal homeostasis in mosquitoes. This enzyme breaks down H2O2, preventing the formation of the hydroxyl radical (HO*). Quiescins are newly classified sulfhydryl oxidases that bear a thioredoxin motif at the N-terminal and an ERV1-like portion at the C-terminal. These proteins have a major role in generating disulfides in intra- or extracellular environments, and thus participate in redox reactions. In the search for molecules to serve as targets for novel anti-mosquito strategies, we have silenced a catalase and a putative quiescin/sulfhydryl oxidase (QSOX), from the African malaria vector Anopheles gambiae, through RNA interference (RNAi) experiments. We observed that the survival of catalase- and QSOX-silenced insects was reduced over controls following blood digestion, most likely due to the compromised ability of mosquitoes to scavenge and/or prevent damage caused by blood meal-derived oxidative stress. The higher mortality effect was more accentuated in catalase-silenced mosquitoes, where catalase activity was reduced to low levels. Lipid peroxidation was higher in QSOX-silenced mosquitoes suggesting the involvement of this protein in redox homeostasis following a blood meal. This study points to the potential of molecules involved in antioxidant response and redox metabolism to serve as targets of novel anti-mosquito strategies and offers a screening methodology for finding targetable mosquito molecules.

Nuclear magnetic resonance analysis of cell metabolism.

Nuclear magnetic resonance (NMR) continues to be a useful tool for the study of cellular metabolism. A variety of NMR techniques have been developed or newly applied to the analysis of cell systems. Many of these techniques are particularly useful for the analysis of immobilized cell bioreactors. The use of several NMR techniques has been an integral part of recent comprehensive metabolic studies. Novel computer-based models and methods have been developed which may make NMR study of metabolism more accessible and powerful.

Myocardial revascularization for the third time. Clinical characteristics and follow-up.

Twenty-five patients presenting for a third revascularization procedure were retrospectively reviewed at Loyola University Medical Center, Maywood, IL. This represents 0.5 percent of the total revascularization cases over a five-year period extending from 1985 through 1989. Perioperative mortality was none, and seven complications occurred in six patients. Internal mammary arteries were used for revascularization in 60 percent of this group. Follow-up reveals that only one patient has died secondary to an arrhythmia. All patients except one are symptomatically improved, and 18 patients remain angina free at a mean follow-up of 22.3 months. It is therefore concluded that patients are clinically improved with a third revascularization, and this procedure should be offered as an effective means of treatment.

Multivariate discriminant analysis of risk factors for operative mortality following isolated coronary artery bypass graft. Loyola University Medical Center experience, 1970 to 1984.

The Loyola Open-Heart Registry is a fully operational database that contains detailed data on approximately 9,000 patients who have undergone coronary bypass or cardiac valve replacement from January 1970 to December 1984. We analyzed the registry data using multivariate discriminant analysis to identify and quantitate those factors that might predict operative mortality (OM) for patients undergoing coronary artery bypass grafts at Loyola University Medical Center: Operative mortality was defined as death within 30 days following surgery. A total of 50 clinical and angiographic variables were analyzed for possible univariate association with operative mortality. Twenty-two variables were found to have significant univariate association with OM, and these 22 variables were subjected to multivariate discriminant analysis. For patients undergoing isolated, elective coronary artery bypass, the factors found to be predictive of OM are age (greater than 70) (F = 11.57), severe (more than six stenoses) coronary artery disease (F = 5.81), diffuse disease (F = 5.54), positive family history (F = 5.17), and number of coronary arteries bypassed (F = 4.78).

Successful use of the total artificial heart as a bridge to transplantation with no mediastinitis.

UNLABELLED: High rates of infection, especially mediastinitis, have been reported with the use of the total artificial heart (TAH), thereby limiting its usefulness. We have used the TAH as a bridge to transplantation with only minor infectious complications and a zero incidence of mediastinitis. Between February 1988 and August 1990, the TAH was inserted at Loyola University Medical Center in 19 patients, ages 16 to 64 years (mean, 44 years). Seventeen patients (89%) underwent transplantation within 1 to 34 days (mean, 9.8 days). Of the patients who did not undergo transplantation, one was brain dead and the other died of bleeding diathesis. Early (30-day) deaths occurred in two patients (11.7%): acute rejection at 18 days and multiple cerebral infarcts at 14 days. Three late deaths (17.6%) occurred: one patient, cytomegalovirus and pneumocystis pneumonia at 4 months; one patient, bronchopneumonia and multisystem failure at 9 months; and one patient, chronic rejection at 14 months. Minor infectious complications during the TAH implantation included Enterobacter pneumonia treated with antibiotics and positive sputum cultures (Escherichia coli; Candida), with no clinical evidence of infection in two patients. No cases of mediastinitis occurred either while the TAH was implanted or after transplantation. All patients were on antibiotics while the device was in place. CONCLUSION: Our experience with the TAH shows this to be an excellent device for successful bridging of patients for heart transplantation. We have had minimal infectious complications and none directly attributed to the use of this device. This device should continue to be used safely as a bridge to transplantation.

Comparison of results after heart transplantation: mechanically supported versus nonsupported patients.

Between March 1984 and July 1990 our team transplanted 168 hearts. One hundred twelve patients did not require mechanical support (group I). Fifty-six patients required mechanical support (group II). Intraaortic balloon counterpulsation was used in 37 patients (66%). The total artificial heart (TAH) was used in 16 patients (29%), and the ventricular assist device (VAD) was used in three patients (5%). The time spent on the device ranged from 1 to 35 days. No statistical difference was noted on the survival between the two groups. The 30-day and 1-year survival rate was 95% (106 patients) and 71% (79 patients) in group I and 91% (51 patients) and 68% (38 patients) in group II. As of July 31, 1990, 70% in group I and 68% in group II are alive. No significant differences were found between the two groups for the following variables (after heart transplantation): length of stay, 30-day survival, 1-year survival, and complications. The only significant difference found between the two groups was the incidence of infections: group I, 23%; group II, 51.7% (p = 0.001). Mechanical support as a bridge to transplantation provides excellent support until a donor becomes available. No difference was found in the 30-day and 1-year survival between the two groups.

Parathyroid carcinoma: biochemical and pathologic response to DTIC.

Parathyroid carcinoma is a rare cause of hyperparathyroidism. Cure results from successful en bloc resection. However, because of its rarity, the malignant nature may not be appreciated at the initial operative procedure and as a result, definitive resection may not be accomplished. However, even with extensive en bloc resections, local recurrences do occur and patients die of metabolic derangements associated with hypercalcemia. Thus in addition to operative intervention, palliative chemotherapy may be required to control the hypercalcemia. Radiotherapy has been unsuccessful. A single case of nonfunctioning parathyroid carcinoma responding to treatment with methotrexate, Adriamycin, cyclophosphamide, and CCNU has been reported. We report a case of recurrent functioning parathyroid carcinoma treated with dacarbazine (DTIC) in which biochemical and pathologic evidence of at least a partial response was seen. The patient, a 33-year-old woman, had undergone five previous neck explorations during a 26-month period for aggressive locally recurrent disease. Before DTIC therapy the intact parathyroid hormone (PTH) level was 1032 pg Eq/ml (normal 163 to 347 pg Eq/ml) and the serum calcium level was 16.8 mg/dl (normal 8.8 to 10.0 mg/dl). After a course of DTIC there was a marked improvement in her clinical status and biochemical parameters (intact PTH 545 pg Eq/ml; serum calcium 11.8 mg/dl). For 2 months her condition stabilized, with PTH levels between 700 and 760 pg Eq/ml and serum calcium levels between 10.2 and 16.0 mg/dl. With a slowly progressive rise in biochemical parameters a second course of DTIC was initiated and a marked drop in serum calcium levels (5.7 mg/dl) occurred, but PTH levels remained unchanged. A progressive course of septicemia, malnutrition, and disseminated intravascular clotting ultimately lead to her death 4 weeks later. At autopsy examination the tumor was confined to the neck. Grossly and microscopically there was extensive central as well as peripheral necrosis of the tumor, which was thought to be the result of the cytotoxic effect of DTIC. From this experience and because of the grim prognosis in patients with recurring parathyroid carcinoma, it may be that aggressive use of chemotherapy with DTIC early in the course of treatment should be considered.

The use of the Jarvik-7 total artificial heart and the Symbion ventricular assist device as a bridge to transplantation.

The proliferation of transplantation programs has not been paralleled by a similar increase in the availability of organ donors. Between 1984 and 1987, 104 orthotopic heart transplantations were performed at Loyola University Medical Center. During the same period, 25 patients died while awaiting a donor organ. To reduce the mortality, we began using the total artificial heart (TAH) and a ventricular assist device (VAD) as a bridge to transplantation in 1988. Of 29 patients who underwent transplantation, 15 patients required a TAH and three patients required a VAD as a bridge. The underlying heart conditions were ischemic cardiomyopathy (11 patients), dilated cardiomyopathy (5 patients), giant cell myocarditis (1 patient), and allograft failure (1 patient). The average duration of mechanical support was 10 days (range, 1 to 35 days). Of the 17 patients who successfully underwent transplantation, 1 patient died at 17 days because of acute rejection of the transplanted heart, and another patient died at 14 days because of a cerebral vascular event. Fifteen patients (83%) were long-term survivors. Nine patients required reoperation for bleeding. While the mechanical device was in place, the activated clotting time was maintained between 170 and 200 seconds with heparin. Dipyridamole was given. We conclude that the TAH and VAD are excellent mechanical bridges to transplantation.

A device to measure the oxygen uptake rate of attached cells: importance in bioartificial organ design.

Quantification of the dependence of cellular oxygen uptake rate (OUR) on oxygen partial pressure is useful for the design and testing of bioartificial devices which utilize cells. Thus far, this information has only been obtained from suspended cells and from cells attached to microcarriers. In this work, a device was developed to obtain the dependence of OUR on oxygen partial pressure for anchorage-dependent cells cultured in standard culture dishes. The device is placed and sealed on the top of the culture dish, and holds a Clark polarographic mini-electrode flush with the bottom surface of the device. It also houses a motor to spin a magnetic stir bar within the cell chamber to insure that the medium is well-mixed. Several characteristics of the device--such as oxygen leakage into the device chamber, electrode-lag time, and linearity of the electrode at low oxygen partial pressures--were quantified and their potential effect on the values of Vm (maximal OUR) and K0.5 (oxygen partial pressure at which OUR is half-maximal) were evaluated. Comparison of Vm and K0.5 values obtained with this device with previously published values for suspended rat hepatocytes, Bacillus cereus, and E. coli indicated that the technique provides values accurate within 30% as long as the cell under study has a K0.5 greater than approximately 1.0 mmHg. For hepatocytes cultured on 0.05 mm thickness collagen gel for 1 day (n = 4) and 3 days (n = 6), Vm was found to be 0.38 +/- 0.12 and 0.25 +/- 0.09 nmol O2/S/10(6) cells, respectively, and K0.5 was found to be 5.6 +/- 0.5 and 3.3 +/- 0.6 mmHg, respectively. This technique should aid in predicting bioreactor conditions such as flow rate, cell density, distance of cell from flow, and gas phase oxygen partial pressure which can lead to oxygen limitations. In addition, further studies of the effect of factors such as extracellular matrix composition, metabolic substrate, and drugs on the dependence of OUR on oxygen partial pressure for many anchorage-dependent cell types can be pursued with this technique.

A simplified model for predicting malaria entomologic inoculation rates based on entomologic and parasitologic parameters relevant to control.

Malaria transmission intensity is modeled from the starting perspective of individual vector mosquitoes and is expressed directly as the entomologic inoculation rate (EIR). The potential of individual mosquitoes to transmit malaria during their lifetime is presented graphically as a function of their feeding cycle length and survival, human biting preferences, and the parasite sporogonic incubation period. The EIR is then calculated as the product of 1) the potential of individual vectors to transmit malaria during their lifetime, 2) vector emergence rate relative to human population size, and 3) the infectiousness of the human population to vectors. Thus, impacts on more than one of these parameters will amplify each other's effects. The EIRs transmitted by the dominant vector species at four malaria-endemic sites from Papua New Guinea, Tanzania, and Nigeria were predicted using field measurements of these characteristics together with human biting rate and human reservoir infectiousness. This model predicted EIRs (+/- SD) that are 1.13 +/- 0.37 (range = 0.84-1.59) times those measured in the field. For these four sites, mosquito emergence rate and lifetime transmission potential were more important determinants of the EIR than human reservoir infectiousness. This model and the input parameters from the four sites allow the potential impacts of various control measures on malaria transmission intensity to be tested under a range of endemic conditions. The model has potential applications for the development and implementation of transmission control measures and for public health education.

The potential impact of integrated malaria transmission control on entomologic inoculation rate in highly endemic areas.

We have used a relatively simple but accurate model for predicting the impact of integrated transmission control on the malaria entomologic inoculation rate (EIR) at four endemic sites from across sub-Saharan Africa and the southwest Pacific. The simulated campaign incorporated modestly effective vaccine coverage, bed net use, and larval control. The results indicate that such campaigns would reduce EIRs at all four sites by 30- to 50-fold. Even without the vaccine, 15- to 25-fold reductions of EIR were predicted, implying that integrated control with a few modestly effective tools can meaningfully reduce malaria transmission in a range of endemic settings. The model accurately predicts the effects of bed nets and indoor spraying and demonstrates that they are the most effective tools available for reducing EIR. However, the impact of domestic adult vector control is amplified by measures for reducing the rate of emergence of vectors or the level of infectiousness of the human reservoir. We conclude that available tools, including currently neglected methods for larval control, can reduce malaria transmission intensity enough to alleviate mortality. Integrated control programs should be implemented to the fullest extent possible, even in areas of intense transmission, using simple models as decision-making tools. However, we also conclude that to eliminate malaria in many areas of intense transmission is beyond the scope of methods which developing nations can currently afford. New, cost-effective, practical tools are needed if malaria is ever to be eliminated from highly endemic areas.

Kinetic modeling of slow dissociation of bromosulphophthalein from albumin in perfused rat liver: toxicological implications.

Due to strong binding between organic anions and albumin, the kinetics of the binding process must be carefully considered in biologically-based models used for predictive toxicology applications. Specifically, the slow dissociation rate of an organic anion from the protein may lead to reduced availability of free anion in its flow through the capillaries of an organ. In this work, the effect of the dissociation rate of the anion bromosulphophthalein (BSP) from albumin was studied in isolated, perfused rat livers in the presence of albumin concentrations of 0.25, 1, and 4% (w/v) and an initial BSP concentration of 20 microM. The uptake of BSP from the perfusion medium was modeled using a biologically-based kinetic model of the sinusoidal and intracellular liver compartments. The best fit of the model to data resulted in the prediction of a slow dissociation rate constant for the BSP-albumin of between 0.097 and 0.133 s(-1). Assuming BSP and albumin to be in binding equilibrium in the sinusoidal space, with rapid binding-rate constants, as is often done, produced an unacceptable fit. These results indicate that the strong binding interaction between BSP and albumin, beyond keeping the concentration of free chemical low due to a small equilibrium dissociation constant, can also reduce uptake by an organ due to the slow release of BSP from the protein during passage through the capillaries. The implication of this dissociation-limited condition, when extrapolating to other doses and in-vivo situations, is discussed.

Cadmium uptake kinetics in rat hepatocytes: correction for albumin binding.

The relationship between cytotoxicity and kinetics of cadmium uptake was investigated in primary rat hepatocyte cultures. Primary rat hepatocytes were exposed to cadmium concentrations ranging from 1.0 to 80 micro M in albumin-free buffer or 32 to 8,000 microM in buffer containing physiological concentrations of bovine serum albumin (600 micro M) for 1 h, and cellular toxicity was observed at 23 h postexposure. Hepatocytes exposed to cadmium in the presence of albumin appeared less sensitive to cadmium toxicity when compared to cells exposed in the absence of albumin. The experimentally derived 23-h postexposure EC(50)s for hepatocytes exposed to cadmium in both presence and absence of albumin was 65.5 +/- 2.4 and 14.3 +/- 3.9 microM, respectively. A Scatchard plot of cadmium binding to albumin suggested two high-affinity binding sites. The observed uptake of cadmium by hepatocytes in the absence and presence of albumin consisted of a composite fast uptake rate and cell membrane association (Component I), and a slow, sustained uptake rate (Component II). Cadmium uptake rates in hepatocytes, based on total medium cadmium concentrations, indicated that Component II uptake rates were four times faster under albumin-free exposure conditions. However, when uptake rates were evaluated, based on the calculated equilibrium concentration of free cadmium in the exposure buffer, uptake rates in hepatocytes exposed in the presence of albumin were two times as fast. This faster cadmium uptake in the presence of albumin may result from diffusion-limited, nonequilibrium conditions occurring at the cell surface.

Internal mammary artery revascularization in the patient on long-term renal dialysis.

Twenty-six patients on long-term renal dialysis underwent coronary artery bypass grafting. The patients were divided into two groups: group 1, (16 patients) saphenous vein bypass grafts, and group 2, (10 patients) internal mammary artery in combination with saphenous vein bypass grafts. Both groups were similar in terms of cardiac hemodynamics and previous number of myocardial infarctions, though more group 1 patients were in New York Heart Association class III or IV. Patients in group 1 received 2.9 bypass grafts per patient; patients in group 2 received 4.0 bypass grafts per patient (4 with bilateral mammary arteries). No wound healing problems occurred in either group. Blood replacement was similar for both groups (group 1, 5.5 units/patient; group 2, 5.3 units/patient). More platelets were given to group 1 patients (16.2 units/patient) than group 2 patients (3.1 units/patient). We conclude that use of the internal mammary artery in patients on long-term renal dialysis does not alter wound healing or increase blood loss in this subset of patients.

Aortic valve replacement in patients 75 years old and older.

A consecutive group of 100 patients in the eighth decade of life who had aortic valve replacement (AVR) from 1975 through 1986 were retrospectively studied. Eighty-five of them were in New York Heart Association (NYHA) Functional Class III or IV. Isolated AVR was performed in 44 patients and AVR with concomitant procedures, in 56. Perioperative mortality (30 days) was 3%, and perioperative morbidity included 83 complications in 60 patients. Long-term follow-up was available on 93 patients, 71 of whom were alive and 22 of whom were dead. Sixty-eight of the 71 long-term survivors are now in NYHA Class I or II. The low rate of perioperative mortality and the improved quality of life after AVR support the performance of this procedure in this older population.

Early myocardial revascularization for postinfarction angina.

In 1983 and 1984, coronary artery bypass grafting (CABG) was performed on 107 consecutive patients for postinfarction angina. In each instance, CABG was done within 30 days of infarction. Sixty-three patients (59%) required intravenous administration of nitroglycerin and/or the intraaortic balloon pump (IABP) for relief of angina. Oral medications relieved angina in the remaining 44 patients. Thirty-eight patients underwent CABG 7 days or less after the infarction (Group 1), 25 received it between 8 and 15 days later (Group 2), and 44 had CABG between 16 and 30 days later (Group 3). There were 9 in-hospital deaths: 4 in Group 1, 2 in Group 2, and 3 in Group 3. Thirteen patients needed the IABP for hemodynamic stability as well as relief of angina. Even when the patient was stable hemodynamically, death was more likely to occur among these 13 patients if CABG was conducted within 7 days of infarction. Follow-up was 94% complete at 29.4 months. Eighty-six percent of patients were asymptomatic or in New York Heart Association Functional Class I, and 6% were in Class II. There were 2 late deaths. CABG for angina can be accomplished within 30 days of an acute infarction with good results. The exception to this rule is the patient in whom shock develops after a myocardial infarction and who, despite stabilization, receives CABG within 7 days of the infarction.

The CardioWest total artificial heart bridge to transplantation: 1993 to 1996 national trial.

BACKGROUND: We performed a controlled study of a total artificial heart in bridge to transplantation. We hypothesized that the CardioWest total artificial heart used in a selected population of decompensating cardiac transplantation candidates would result in improved survival compared with matched controls. METHODS: The CardioWest trial started in 1993 in six United States institutions under an investigational device exemption from the Food and Drug Administration. Four centers contributed 27 implant and 18 matched retrospective control patients. RESULTS: Of the implant patients, 25 (93%) received a transplant, 24 (89% of the total, 96% of those transplanted) were discharged and are currently surviving. In the control group, 10 patients died awaiting transplantation, 8 received a transplant, and 7 were discharged with 6 surviving (p = 0.00001). All adverse events were documented with respect to time. Thirteen serious adverse events occurred, 11 of which occurred in the 2 patients that died during implant. CONCLUSIONS: In a selected group of patients with endstage heart disease, use of the CardioWest total artificial heart is lifesaving. When compared with the series of matched retrospective controls, a significant improvement in survival was found in the CardioWest implant group.

Ventricular aneurysm due to blunt chest injury.

A left ventricular aneurysm developed in 3 patients sustaining blunt chest injury. Evidence of an acute myocardial infarction on the electrocardiogram and enzyme analysis prompted cardiac catheterization, which revealed total occlusion of the left anterior descending coronary artery in 2 of the 3 patients. Ventricular aneurysmectomy was performed in each patient. A review of the literature revealed 32 previously reported patients with left ventricular aneurysm caused by blunt trauma. Clinical features, catheterization or autopsy findings, and outcome are examined.