Inhaled Silica Nanoparticles Causes Chronic Kidney Disease in Rats

INTRODUCTION

Silica nanoparticles (SiNPs) released during the burning of sugarcane have been postulated to have a role in chronic kidney disease of unknown etiology. We tested the hypothesis that pristine SiNPs of the size present in sugarcane might cause chronic kidney injury when administered through the lung in rats.

METHODS

We administered 200 nm or 300 nm amorphous SiNPs twice weekly (4 mg/dose) or vehicle by oropharyngeal aspiration for 13 weeks to rats followed by sacrifice after an additional 13 weeks (26 weeks total). Tissues were evaluated for presence of SiNPs and evidence of histologic injury.

RESULTS

Both sizes of SiNPs caused kidney damage, with early tubular injury and inflammation (at week 13) that continued to inflammation and chronic fibrosis at week 26 despite discontinuing the SiNP administration. Both sizes of SiNPs caused local inflammation in the lung and kidney and were detected in the serum and urine at week 13, and the 200 nm particles also localized to the kidney with no evidence of retention of the 300 nm particles. At week 26 there was some clearance of the 200 nm silica from the kidneys, and urinary levels of SiNPs were reduced but still significant in both the 200 and 300 nm exposed rats.

CONCLUSIONS

Inhaled SiNPs causes chronic kidney injury that progresses despite stopping the SiNP administration. These findings are consistent with the hypothesis that human exposure to amorphous silica nanoparticles found in burned sugarcane fields could have a participatory role in chronic kidney disease of unknown etiology.

Multisegment Foot Kinematic and Kinetic Compensations in Level and Uphill Walking Following Tibiotalar Arthrodesis

BACKGROUND

Foot and ankle movement alterations following ankle arthrodesis are still not well understood, particularly those that might contribute to the documented increase in adjacent joint arthritis. Generalized tarsal hypermobility has long been postulated, but not confirmed in gait or functional movements. The purpose of this study was to more thoroughly evaluate compensation mechanisms used by arthrodesis patients during level and uphill gait through a variety of measurement modalities and a detailed breakdown of gait phases.

METHODS

Level ground and uphill gait of 14 unilateral tibiotalar arthrodesis patients and 14 matched controls was analyzed using motion capture, force, and pressure measurements in conjunction with a kinetic multisegment foot model.

RESULTS

The affected limb exhibited several marked differences compared to the controls and to the unaffected limb. In loading response, ankle eversion was reduced but without a reduction in tibial rotation. During the second rocker, ankle dorsiflexion was reduced, yet was still considerable, suggesting compensatory talar articulation (subtalar and talonavicular) motion since no differences were seen at the midtarsal joint. Also during the second rocker, subjects abnormally internally rotated the tibia while moving their center of pressure laterally. Third rocker plantarflexion motion, moments, and powers were substantially reduced on the affected side and to a lesser extent on the unaffected side.

CONCLUSION

Sagittal plane hypermobility is probable during the second rocker in the talar articulations following tibiotalar fusion, but is unlikely in other midfoot joints. The normal coupling between frontal plane hindfoot motion and tibial rotation in early and mid stance was also clearly disrupted. These alterations reflect a complex compensatory movement pattern that undoubtedly affects the function of arthrodesis patients, likely alters the arthrokinematics of the talar joints (which may be a mechanism for arthritis development), and should be considered in future arthrodesis as well as arthroplasty research.

LEVEL OF EVIDENCE

Level III, comparative study.

Metallic fragments on the surface of miniplates and screws before insertion

Particulate metal fragments have been identified histologically within the tissues adjacent to miniplates and screws after they have been removed. These were thought to have been caused by corrosion and degradation of the metal. However, the particles may have originated from rough edges or from protuberances left on the metal surface after cutting and machining during manufacture, and subsequently become detached. This study was undertaken to analyse the incidence and distribution of metal fragments on the surface of miniplates and screws before use. Fifteen miniplates and 60 screws were examined by stereomicroscopy and scanning electron microscopy. Rough metal edges or protuberances were identified on over half the samples, mostly in the countersink area of screw holes on the mini-plates. Fragments were detected within some of the cruciform screw heads and on some screw threads. We conclude that metal protuberances are present on the surface of mini-plate components when they are received from the manufacturer. There is a risk that the fragments might be detached and deposited into the tissues during insertion.

Phase I study of (6R)-5,10-dideazatetrahydrofolate: a folate antimetabolite inhibitory to de novo purine synthesis

BACKGROUND

Cancer chemotherapy with folate antimetabolites has been traditionally targeted at the enzyme dihydrofolate reductase and is based on the requirement of dividing tumor cells for a supply of thymidylate and purines. However, a new compound, 5,10-dideazatetrahydrofolate (DDATHF, whose 6R diastereomer is also known as Lometrexol), has become available that prevents tumor cell growth by inhibiting the first of the folate-dependent enzymes involved in de novo purine synthesis, glycinamide ribonucleotide formyltransferase.

PURPOSE

We investigated the toxicity and therapeutic activity of DDATHF in a phase I clinical trial.

METHODS

DDATHF was given at one of the following dose levels to 33 patients (16 females and 17 males) with malignant solid tumors: 3.0 mg/m2 per week (level A) to 10 patients, 4.5 mg/m2 per week (level B) to 13 patients, or 6.0 mg/m2 per week (level C) to 10 patients. Each drug cycle consisted of three weekly injections of DDATHF followed by a 2-week rest prior to redosing in the next cycle.

RESULTS

Of 33 patients, 27 received at least one full cycle of DDATHF. Thrombocytopenia was the major dose-limiting toxicity, and it was severe in one of 10 patients during the first cycle and in two of four patients during the second cycle. Because of cumulative toxicity at 6.0 mg/m2, second or later cycles were abbreviated to two weekly doses. Stomatitis was generally mild, but it was dose-limiting in one patient. Neutropenia was infrequent and mild, and normocytic anemia requiring blood transfusion was common with repeat dosing. Leucovorin was given for grade 2 or greater thrombocytopenia and resulted in hematologic recovery within 1 week in all eight patients so treated. Without leucovorin, the thrombocytopenia lasted from 7 to 49 days in three patients. A partial response was noted in one patient with non-small-cell lung cancer and a minor response in one patient with breast cancer. Three patients with colorectal cancer achieved stable disease for greater than 3 months with improvement in carcinoembryonic antigen levels in one patient.

CONCLUSIONS

DDATHF has an unusual pattern of toxicity with repetitive dosing, and humans with advanced cancer are considerably more sensitive than would be predicted from previous animal studies. Although doses of 6.0 mg/m2 per week on our schedule have been determined to be safe, repeated cycles require careful monitoring because of cumulative toxic effects.

IMPLICATIONS

Additional phase I studies of DDATHF that relate toxicity to folate intake and tissue folate pools appear warranted.

Mixed fusobacterium and actinomyces pulmonary infection. Case report

This is a report of a twelve-year-old black male who presents a history of left neck pain, left shoulder pain, weight loss and minimal fever. The admission diagnosis was a malignancy, supported by radiographic findings of consolidation of left lower and left upper lobes and periosteal new bone formation along the inferior aspects of the left second, third and fourth ribs. Open biopsy of the chest wall revealed a large abscess cavity. Subsequent cultures on anaerobic blood agar plates grew Actinomyces and Fusobacterium. The patient was treated with penicillin and improved clinically. This case emphasizes the need to culture tissue specimens for a wide array of organisms, including those not commonly seen today. A high index of suspicion is required for the diagnosis of anaerobic infections. Mixed anaerobic infections, including actinomyces, although uncommon in children, should be considered in the etiology of an intrathoracic mass.