Upregulation of the secretory pathway in cysteine protease inhibitor-resistant Trypanosoma cruzi

A novel chemotherapy in development for Chagas' disease targets cruzain, the major cysteine protease of Trypanosoma cruzi. Peptidomimetic inhibitors disrupt the intracellular cycle of the parasite and rescue animals from a lethal infection. Inhibitor killing of parasites results from interruption of autocatalytic cruzain processing and transport to lysosomes, and massive accumulation of precursor protein in the Golgi complex. To further understand the mechanisms of protease processing and transport in this primitive eukaryote, and uncover potential mechanisms for resistance to these drugs, we generated cysteine-protease inhibitor (CPI)-resistant epimastigotes in vitro and investigated the mechanisms involved at the biochemical and structural levels. Resistance to 20-fold the lethal CPI concentration, achieved after a year of gradual drug increase, was accompanied by a modest decrease in growth rate. A marked increase in the number of vesicles trafficking from the Golgi complex to the flagellar pocket occurs in resistant cells. No mature protease reaches lysosomes though accumulation of endocytosed gold particles in lysosomes appears to be normal. Higher molecular mass cruzain species, consistent with complexes of cruzain precursors and inhibitor, are secreted by CPI-resistant parasites into the culture supernatant. Release of these cruzain precursors may be facilitated by an enhanced acidification of trans-Golgi cisternae in resistant parasites. The pH within Golgi cisternae is higher in control epimastigotes and most mature cruzain is lysosomal. Cruzain activity is negligible in CPI-resistant epimastigote extracts compared to the parental clone. Activity is restored following withdrawal of the inhibitor. No cross-resistance to the therapeutic drugs nifurtimox and benznidazole occurred and, conversely, parasites resistant to these drugs were sensitive to CPI. Protease inhibitors are thus potential therapeutical alternatives in cases of nifurtimox/benznidazole resistance. Cumulatively, these results suggest that CPI-resistance induces upregulation of Golgi complex function and post-Golgi secretory pathway, and release of precursors before the enzyme reaches its site of biologic activity.

Miniature C-arm imaging: an in vitro study of detecting foreign bodies in the emergency department

STUDY OBJECTIVE

Recently, we have had clinical success detecting foreign bodies (FBs) using a mobile C-arm fluoroscopic device. This study tests its utility to detect FBs of differing densities in soft tissue.

DESIGN

Blinded, randomized, controlled in vitro study.

METHODS

Two physicians used the Xi-scan mini C-arm to image FBs. Five FBs of differing densities were studied: metal, gravel, glass, wood, and plastic. The FBs were placed into the deep muscles of chicken legs. One hundred observations were made: 50 legs with FBs and 50 legs without FBs. The blinded investigators imaged the legs and determined the presence or absence of FBs.

RESULTS

Imaging located 100% of metal, gravel and glass FBs. Plastic and wood could not be consistently detected (sensitivity 0.4, specificity 0.6).

CONCLUSIONS

This device accurately detects metal, gravel and glass. Radiolucent (wood) and semiradiopaque (plastic) FBs could not be located reliably. Clinical trials would define utility of this device in saving time, money and radiation exposure.

Intraosseous needle: use of the miniature C-arm imaging device to confirm placement

Intraosseous infusions are commonly used in pediatric emergencies. Although this technique is often lifesaving, significant complications can develop from incorrect needle placement. Current methods of evaluating needle position rely on the operator's experience with the procedure. We describe the use of a miniature C-arm imaging device to accurately confirm proper needle placement.

Injuries to children related to shopping carts

STUDY OBJECTIVE

To describe the epidemiology of shopping cart-related injuries among children and to consider targeted prevention strategies based on these epidemiologic findings.

DESIGN

A consecutive series of patients.

SETTING

The emergency department of a large, academic children's hospital.

PARTICIPANTS

Sixty-two children treated for shopping cart-related injuries during a 15-month period.

RESULTS

Children ranged in age from 4 months to 10 years (mean, 2.8 years). Thirty-three children (53%) were boys. Twelve patients (19%) arrived via ambulance. Forty-nine children (79%) had injuries to the head, including one child admitted to the hospital. Eleven children (18%) had fractures, including 5 (8%) with skull fractures. Nine patients (14%) had lacerations, and 30 patients (48%) had superficial injuries (ecchymoses or abrasions). The most common mechanism of injury was falling out of the carts (58% of children), followed by cart tip-overs (26% of children). Injuries caused by falls from the carts occurred across the entire age range, whereas injuries caused by cart tip-overs were most frequent among children 1 year of age or younger. The sitting position was associated with tip-over injuries, and standing in the cart basket was associated with falling from the cart.

CONCLUSIONS

Shopping cart-related injuries cause serious pediatric morbidity, especially among children younger than 5 years of age, and are potentially fatal. Based on identified age-specific mechanisms of injury, currently used prevention strategies are not sufficient. The use of infant seats and restraining belts is an inadequate strategy for prevention of shopping cart-related injuries among children 1 year of age or younger, because cart tip-over is an important mechanism of injury in this age group. Shopping carts should be redesigned to decrease the tip-over hazard. Transportation of children in shopping carts of current design should be prohibited.

Epidemiology of shopping cart-related injuries to children. An analysis of national data for 1990 to 1992

OBJECTIVE

To describe the epidemiologic characteristics of shopping cart-related injuries among children in the United States.

DESIGN

A retrospective analysis of data from the National Electronic Injury Surveillance System of the US Consumer Product Safety Commission for 1990 to 1992.

RESULTS

An estimated 75,200 shopping cart-related injuries occurred in children younger than 15 years treated in US emergency departments during 1990 to 1992 (95% confidence interval, 57,500 to 92,900). Children younger than 5 years were at highest risk, accounting for 63,200 (84%) of the injuries. A 20% increase was observed in the number of injuries among 0- to 4-year-old children from 1990 to 1992. Fifty-three percent of injured children were male. The head and neck region was the most common anatomic site of injury, accounting for 74% of injuries among children younger than 15 years. An estimated 2000 children (2.7%) younger than 15 years required hospital admission (1.2% in 1990 compared with 3.5% in 1992). Children aged 0 to 4 years accounted for 93% of these hospital admissions. Among 0- to 14-year-old children, fractures accounted for 45% of hospital admissions, followed by internal injury (22%) and concussion (17%).

CONCLUSIONS

Injuries related to shopping carts are an important cause of pediatric morbidity, especially among children younger than 5 years. These injuries can also result in death. Shopping carts should be redesigned to decrease the risk of injury to children, and transportation of children in shopping carts of current design should be prohibited.

Electrical injuries in a pediatric emergency department

STUDY OBJECTIVE

To examine the spectrum of electrical injuries and develop guidelines for management.

DESIGN

Retrospective review of charts compiled during a 6-year period (1988 through 1993).

SETTING

Pediatric emergency department.

PARTICIPANTS

Seventy-eight patients seen for electrical injuries.

RESULTS

Fifty-four percent of patients were boys, and the mean age of the patients was 5.3 years. Eighty-two percent sustained burns. We divided patients into those who were involved in major electrical current events (n = 8) (water contact and high voltage) and minor electrical current events (n = 70) (injury sustained while placing an object in an outlet or touching/plugging in a cord or during oral contact with a cord). Of the minor events, all burns (n = 61) involved less than 1% of body surface area. Eighteen patients sustained second-degree burns, and 19 sustained third-degree burns. Of the eight major-event patients, one had abnormal ECG/rhythm strip findings, two had abnormal urinalysis results, and six had abnormal levels of creatine phosphokinase. All eight were admitted. Of the 70 minor-event patients, 2 of 53 had abnormal ECG/rhythm strip findings, 1 of 48 had abnormal urinalysis results, and 2 of 40 had abnormal creatine phosphokinase levels. Thirty-six of the 70 minor-event patients were admitted. Patients involved in major events were more likely to undergo studies (P = .002), to have an abnormal result (P = .000008), and to be hospitalized (P = .008). In minor-event patients, hospitalization was limited to observation and the fitting of oral appliances.

CONCLUSION

Children involved in electrical events are usually exposed to low-voltage household current resulting in minor injury. Asymptomatic children with minor electrical injuries do not require laboratory evaluation or hospitalization.

Recombinant endotoxin neutralizing protein improves survival from Escherichia coli sepsis in rats

OBJECTIVE

A recombinant endotoxin neutralizing protein was evaluated for its ability to ameliorate the effects of Escherichia coli sepsis in rats.

DESIGN

Prospective, controlled animal trial.

SETTING

Hospital animal research laboratory.

SUBJECTS

Wistar rats, treated with gentamicin 1 hr after challenge with intraperitoneal E. coli O18ac.

INTERVENTIONS

The animals received a recombinant endotoxin neutralizing protein, in doses of 5, 25, or 50 mg/kg, either 30 or 60 mins after challenge; controls received saline.

MEASUREMENTS AND MAIN RESULTS

Geometric mean serum endotoxin concentrations in endotoxin neutralizing protein-treated animals did not differ from control animals. Tumor necrosis factor concentrations in animals treated with endotoxin neutralizing protein 30 mins after challenge were significantly lower than controls. Animals treated with 25 or 50 mg/kg of endotoxin neutralizing protein 30 mins after E. coli challenge had significant improvements in survival compared with controls. Animals treated with 50 mg/kg of endotoxin neutralizing protein 60 mins after E. coli challenge had significant improvements in survival compared with controls.

CONCLUSION

Endotoxin neutralizing protein significantly reduces mortality from Gram-negative sepsis in an antibiotic-treatment model of E. coli peritonitis and bacteremia in rats, mediated by a neutralization of the biological effects of endotoxin.

Inhibition of 7-bromomethylbenz[a]anthracene-promoted mouse skin tumor formation by retinoic acid and dexamethasone

Retinoic acid, a potent inhibitor of mouse skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate, fails to inhibit tumor formation by the complete carcinogen, 7, 12-dimethylbenz[a]anthracene (DMBA). To obtain further clues about the nature of the mechanism of the carcinogenic process as well as the mechanism of the effect of retinoic acid on tumor promotion, the effect of retinoic acid and two other modifiers (dexamethasone and 7,8-benzoflavone) of tumor formation on tumor promotion by 7-bromomethylbenz[a]anthracene (BrMBA) was determined. BrMBA, a structural analogue of DMBA, is a weak mouse skin tumor-initiating agent but is a good skin tumor promoter. Application of 10, 100, and 200 nmol of BrMBA twice weekly to DMBA-initiated skin resulted in 0, 1.6, and 2.5 papillomas per mouse, and 0, 44, and 60% of mice had papillomas at the 25th week of promotion treatment, respectively. Application of 17 nmol of retinoic acid or 76 nmol of dexamethasone 30 min prior to each twice weekly application of 100 nmol of BrMBA to DMBA-initiated skin inhibited the formation of skin papillomas by 73 and 100%, respectively. 7,8-Benzoflavone, at a 367-nmol dose, did not inhibit tumor promotion by BrMBA. Application of 200 nmol of BrMBA to mouse skin induced epidermal ornithine decarboxylase activity; a peak activity was observed between 8 and 18 hr following BrMBA treatment. Application of 17 nmol of retinoic acid or 76 nmol of dexamethasone inhibited the induction of ornithine decarboxylase activity by BrMBA. 7,8-Benzoflavone did not inhibit the induction of ornithine decarboxylase activity by BrMBA. Retinoic acid and dexamethasone, which inhibit tumor promotion by 12-O-tetradecanoylphorbol-13-acetate, also inhibited tumor promotion by BrMBA, but the nature of the mechanism of tumor promotion by BrMBA is unclear; BrMBA did not inhibit specific binding of 12-O-[3H]tetradecanoylphorbol-13-acetate to the cellular membrane fraction of mouse epidermis.