James T. McMahon

Hydroxyapatite-coated femoral stems. Histological analysis of components retrieved at autopsy.

Plasma-sprayed coating of hydroxyapatite are biocompatible and, because of their osteoconductive properties, may contribute to the early fixation of total joint prostheses. To evaluate this interface, we histologically analyzed five hydroxyapatite-coated femoral stems which, along with the surrounding bone, were retrieved from three humans at autopsy. The five femoral components had been in situ for a mean duration of twelve months (range, almost five to twenty-five months) and had been inserted for osteonecrosis (two), osteoarthrosis (two), and as an uncermented revision for failure of a cemented stem. The three patients had had a good or excellent clinical result and had died of causes unrelated to the joint arthroplasty. A coating of hydroxyapatite was identified on each stem. There was a variable amount of apposition of bone (32 to 78 per cent of available surface per section). The deposition of bone was most prominent on the surface of the prosthesis that was close to the endosteal surface of the bone, especially in areas that are predicted by Wolffs law (anterior and medial aspects of the implant, and at lateral-oblique corners). There were occasional foci of bone-remodeling around the implant, including osteoclast-mediated removal of the coating of hydroxyapatite along with adjacent bone. Occasional particles of ceramic were present within macrophages in the adjacent bone marrow. Other areas showed formation of new bone with a few areas of bone directly against the metal substrate. The over-all histological features suggest mechanically stable implants with bone-remodeling at the surface of the bone-implant interface.

Isolation and characterization of debris in membranes around total joint prostheses.

Particles of wear debris have been implicated in osteolysis around and aseptic loosening of total joint prostheses, but the number and size distribution of particles present in periprosthetic tissues are unknown. A method of particle assay was developed, consisting of nitric-acid digestion of tissue followed by collection of particles, electronic quantitation, and parallel morphological and chemical characterization. Nitric acid had minimum deleterious effects on control samples of titanium, cobalt-chromium alloy, and polyethylene particles, as determined by atomic absorption spectroscopy, scanning electron microscopy, and electronic measurements of the sizes of the particles. Acid digestion of twelve control samples of tissue, including tissue rich in hemosiderin, resulted in particle counts that were no higher than that in the digestion solution background. Other digestion preparations, including hydrochloric acid and sodium hypophosphate, were not as effective as nitric acid. With the low size limit of detection of approximately 0.58 micrometer, particle analysis of tissue adjacent to twenty retrieved total joint implants indicated a range of concentration of 0.85 to 141.85 x 10(9) particles per gram of tissue (dry weight). Although a few particles of more than 100 micrometers were detected, the mode of particle diameter from each sample ranged from the lower limit of detection (approximately 0.58 micrometer) to 0.79 micrometer. The findings of morphological studies and x-ray spectroscopy of isolated particles corresponded with those of light microscopy of the fibrous membranes. These data indicate that most of the particles in implant membranes are smaller than the resolution of the light microscope and that tissue digestion is necessary for quantitation and characterization.

Chronic Propionibacterium Endophthalmitis After Extracapsular Cataract Extraction and Intraocular Lens Implantation

We studied six cases of chronic, indolent intraocular inflammation that occurred after extracapsular cataract extraction and posterior chamber intraocular lens implantation. The inflammation was characterized by a delayed onset, and in three cases had the clinical appearance of a granulomatous iridocyclitis. Cultures of intraocular specimens obtained from six eyes yielded Propionibacterium; five yielded P. acnes. Pleomorphic gram-positive bacilli consistent with Propionibacterium were identified in cytologic or histopathologic studies in four of the six culture-positive cases. After surgical and medical therapy, the inflammation resolved. Postoperative Propionibacterium endophthalmitis may masquerade as a chronic iridocyclitis.

SF3B1 haploinsufficiency leads to formation of ring sideroblasts in myelodysplastic syndromes

Whole exome/genome sequencing has been fundamental in the identification of somatic mutations in the spliceosome machinery in myelodysplastic syndromes (MDSs) and other hematologic disorders. SF3B1, splicing factor 3b subunit 1 is mutated in 60%-80% of refractory anemia with ring sideroblasts (RARS) and RARS associated with thrombocytosis (RARS-T), 2 distinct subtypes of MDS and MDS/myeloproliferative neoplasms (MDSs/MPNs). An idiosyncratic feature of RARS/RARS-T is the presence of abnormal sideroblasts characterized by iron overload in the mitochondria, called RS. Based on the high frequency of mutations of SF3B1 in RARS/RARS-T, we investigated the consequences of SF3B1 alterations. Ultrastructurally, SF3B1 mutants showed altered iron distribution characterized by coarse iron deposits compared with wild-type RARS patients by transmission electron microscopy. SF3B1 knockdown experiments in K562 cells resulted in down-regulation of U2-type intron-splicing by RT-PCR. RNA-sequencing analysis of SF3B1 mutants showed differentially used genes relevant in MDS pathogenesis, such as ASXL1, CBL, EZH, and RUNX families. A SF3B pharmacologic inhibitor, meayamycin, induced the formation of RS in healthy BM cells. Further, BM aspirates of Sf3b1 heterozygous knockout mice showed RS by Prussian blue. In conclusion, we report the first experimental evidence of the association between SF3B1 and RS phenotype. Our data suggest that SF3B1 haploinsufficiency leads to RS formation.

Autophagy inhibition and antimalarials promote cell death in gastrointestinal stromal tumor (GIST)

Although gastrointestinal stromal tumors (GISTs) harboring activating KIT or platelet-derived growth factor receptor A (PDGFRA) mutations respond to treatment with targeted KIT/PDGFRA inhibitors such as imatinib mesylate, these treatments are rarely curative. Most often, a sizeable tumor cell subpopulation survives and remains quiescent for years, eventually resulting in acquired resistance and treatment failure. Here, we report that imatinib induces autophagy as a survival pathway in quiescent GIST cells. Inhibiting autophagy, using RNAi-mediated silencing of autophagy regulators (ATGs) or antimalarial lysosomotrophic agents, promotes the death of GIST cells both in vitro and in vivo. Thus, combining imatinib with autophagy inhibition represents a potentially valuable strategy to promote GIST cytotoxicity and to diminish both cellular quiescence and acquired resistance in GIST patients.

Light chain nephropathy

In 13 specimens of renal tissue from 11 patients, deposits of monoclonal immunoglobulin light chains and continuous granular electron-dense material within tubular basement membranes and in association with the glomerular basement membrane were identified. All but one patient were men n the fifth to seventh decades of life, and each presented with azotemia and features of glomerular rather than tubulointerstitial disease. Osteolytic bone lesions occurred in only three patients, and a bone marrow plasmacytosis greater than 30 percent consistent with plasma cell myeloma was identified in only four patients. Light chain distribution in the nephron was confirmed with immunoelectron microscopy and was not associated with deposition of other serum proteins such as immunoglobulin heavy chains, complement, transferrin, alpha 2 macroglobulin and albumin. The electron dense deposits differed in distribution and character from those associated with membranoproliferative glomerulonephritis type II (dense deposit disease), amyloidosis, cryoglobulinemia, macroglobulinemia and benign monoclonal gammopathy. Serum from six of these patients did not bind to normal human or rat renal parenchyma in vitro. Kappa light chain nephropathy was characterized by predominant linear tubular basement membrane kappa deposits, and nodular mesangial and linear glomerular basement membrane kappa immunostaining. Lambda light chain nephropathy was characterized by linear lambda glomerular basement membrane and tubular basement membrane immunostaining. Manifestations of glomerular dysfunction dominated the clinical presentation of light chain nephropathy, and most patients did not have typical features of multiple myeloma. The diagnosis was predicated upon thorough immmunohistologic assessment of renal biopsy material.

Diagnosis of chloroquine cardiomyopathy by endomyocardial biopsy.

CHLOROQUINE and hydroxychloroquine are antimalarial agents that are often used in the treatment of collagen vascular diseases. However, both drugs can cause a toxic skeletal-muscle myopathy, the hi...

Infectious Crystalline Keratopathy

In three patients (three men, 44, 67, and 83 years old) an unusual keratopathy characterized by white, branching, crystalline stromal opacities produced lesions that were insidious, that increased in size slowly, and that were clinically and histopathologically associated with little corneal inflammation. Intraocular inflammation eventually became evident in two of the patients. The keratopathy developed while the patients were using topical corticosteroids. In two cases, histopathologic studies disclosed accumulations of gram-positive cocci in the corneal stroma; a viridans streptococcus agent was isolated on culture. In one case, the viridans streptococcus was determined to be a dextran producer, which may have contributed to the pathogenesis of the keratopathy. Despite aggressive treatment with a variety of drugs, epithelial healing, and resolution of the corneal infiltrate, residual scarring persisted in two cases and neovascularization and graft edema in one case each.

Minocycline-related cutaneous hyperpigmentation as demonstrated by light microscopy, electron microscopy and X-ray energy spectroscopy

Argenyi ZB, Finelli L, Bergfeld WF, Tuthill RJ, McMahon JT, Ratz JL, Pefroff N. Minocycline‐related cutaneous hyper‐pigmentation as demonstrated by light microscopy, electron microscopy and X‐ray energy spectroscopy.

Effects of Hyperoxia on Nitric Oxide Synthase Expression, Nitric Oxide Activity, and Lung Injury in Rat Pups

Although hyperoxic exposure is an important contributor to the development of bronchopulmonary dysplasia and nitric oxide (NO) has been implicated in the pulmonary response to oxygen, the role of NO in mediating chronic neonatal lung injury is unclear. Therefore, rat pups were exposed to normoxia or hyperoxia (>95% O2) from d 21 to 29. After the rats were killed, their lungs were removed for analysis of nitric oxide synthase (NOS) expression, NO activity as measured by 3′,5′-cyclic guanosine monophosphate (cGMP) assay, and lung pathology. Hyperoxia caused 5-fold and 2-fold increases in inducible (i) NOS and endothelial (e) NOS levels, respectively. NO activity was assessed by measuring cGMP levels after normoxic or hyperoxic exposure in the presence and absence of NOS blockade with either aminoguanidine (AG) or Nω-nitro-L-arginine (L-NNA). cGMP levels were elevated in hyperoxic versus normoxic rats (287 ± 15 versus 106 ± 9 pmol/mg protein, respectively, p < 0.001), and this increase in cGMP was attenuated after NOS blockade with either AG or L-NNA. Hyperoxic exposure significantly increased lung/body weight ratios and induced histologic changes of interstitial and alveolar edema; however, these hyperoxia-induced histologic changes were not altered by NOS blockade with AG or L-NNA. We conclude that hyperoxic exposure of rat pups up-regulated both iNOS and eNOS and increased NO activity as measured by cGMP levels derived from both iNOS and eNOS. Blockade of NOS reduced cGMP levels in the hyperoxic rat pups; however, it did not seem to reverse the pathologic consequences of hyperoxic exposure.