Diagnostic yield muscle biopsy in patients with clinical evidence of mitochondrial cytopathy.

We retrospectively reviewed 118 muscle biopsy specimens from 113 patients with clinical and/or biochemical evidence of mitochondrial cytopathy. Light microscopic evaluation revealed histologic abnormalities in 65 specimens. The most common histologic findings included angular atrophic esterase-positive muscle fibers, type II muscle atrophy, regenerating muscle fibers, and scattered cytochrome-oxidase deficient fibers. Ragged red fibers were noted in 3 specimens on a Gomori trichrome stain. Electron microscopic evaluation was performed in 113 muscle specimens, and in 34, no abnormalities were identified. Increased numbers of mitochondria, particularly in the subsarcolemmal region, were identified in 54 specimens. Increased mitochondrial size was seen in 8 specimens and paracrystalline mitochondrial inclusions in 3. Other ultrastructural findings included focally increased glycogen deposition, focal Z-band streaming, and focally increased lipid accumulation. For 39 cases, concomitant skin biopsy specimens were available; abnormalities were identified by electron microscopy in 12. The majority of biopsy specimens demonstrated some light or electron microscopic abnormality. Specific histologic findings suggestive of mitochondrial abnormalities (partial cytochrome oxidase deficiency, ragged red fibers) were noted in a minority of cases. Ultrastructural evidence of mitochondrial abnormalities was noted in the majority of cases.

Ultrastructural examination of the axillary skin biopsy in the diagnosis of metabolic diseases.

There is little information in the literature regarding the usefulness of ultrastructural examination of axillary skin biopsies in the evaluation of metabolic diseases. This is a retrospective clinicopathologic review of 143 patients who underwent axillary skin biopsies as part of evaluations for metabolic disease. Twenty-three (16%) had abnormalities, classified as follows: mitochondrial (n = 12), lysosomal (n = 6), increased glycogen (n = 3), nonspecific cytoplasmic inclusions (n = 2), ceroid lipofuscinosis (n = 1), and intradermal giant cells containing vacuoles and tubular inclusions (n = 1). Muscle biopsies were performed in 13 of the 23 patients; 11 showed abnormalities, including those related to mitochondria (n = 4) and other nonspecific changes (n = 7). Two patients underwent postmortem examination. Follow-up was available in 21 patients. A clinical or biochemical diagnosis was reached in 11 patients: metachromatic leukodystrophy (n = 2), electron transport chain abnormalities (n = 2), glutaric aciduria type II (n = 1), Unverricht disease (n = 1), Lennox-Gastaut syndrome (n = 1), ketotic hypoglycemia of childhood (n = 1), probable Leigh disease (n = 1), 5-methyl tetrahydrofolate homocystine methyltransferase deficiency (n = 1), and pyruvate dehydrogenase deficiency (n = 1). Of the 120 patients with negative skin biopsy results, 29 had abnormal findings on muscle (n = 27), nerve (n = 7), or brain (n = 3) biopsies. One patient had an abnormal heart biopsy result, and 3 patients underwent postmortem examinations. Follow-up was obtained in 27 of 29 patients. Diagnoses were achieved in 15 patients: electron transport chain abnormalities (n = 5), cortical dysplasia (n = 3), myoclonic epilepsy (n = 1), leukodystrophy (n = 2), Pallister-Killian mosaic syndrome (n = 1), Rett syndrome (n = 1), Landau-Kleffner syndrome (n = 1), and mitochondrial cardiomyopathy (n = 1). In conclusion, axillary skin biopsy is helpful in the evaluation of some causes of metabolic disease, but often the findings are nonspecific. A negative biopsy result does not rule out the possibility of metabolic disease, but a positive result may provide direction for further evaluation.

Immunohistochemistry in the differential diagnosis of acinar and endocrine pancreatic neoplasms.

Histologic differential diagnosis of acinar cell carcinoma (ACC), mixed acinar-endocrine cell carcinoma (MAEC), and pancreatic endocrine tumors (PET) can be difficult but is important because of differences in their clinical behavior. This study investigates the utility of immunohistochemistry (IHC) in this differential diagnosis using immunohistochemical stains that are available in most laboratories. IHC was performed on paraffin-embedded tissue in ACC (n = 6), MAEC (n = 2), and PET (n = 13), using synaptophysin (SYN), chromogranin (CHR), chymotrypsin (CHY), and alpha-1-antitrypsin (AAT). Electron microscopy (EM) was performed in all cases to confirm the diagnosis. Long-term follow-up and death of disease (DOD) was known in all patients. The ACCs stained as follows: CHY (4/6), AAT (3/6), SYN (4/6); CHR was negative in all cases. Both cases of MAEC stained with CHY, AAT, and SYN (2/2); CHR was negative. PET stained as follows: SYN (13/13), CHR (8/13), CHY (4/13), AAT (5/13). In the ACC/ MAEC group, six of eight patients were DOD at mean follow-up of 11 months. Among the PET, two of 16 patients were DOD at mean follow-up of 37 months. Considerable immunophenotypic overlap exists between ACC, MAEC, and PET. Consequently, one can neither confirm nor rule out a diagnosis of ACC or MAEC using generally available immunohistochemical stains alone. These findings support a role for EM in the evaluation of exocrine and endocrine pancreatic neoplasms.

Laparoscopic aortorenal bypass.

BACKGROUND AND PURPOSE: Open surgical renovascular repair, although producing excellent results, confers significant operative morbidity. As a result, less morbid procedures such as percutaneous balloon angioplasty and stenting have gained increasing acceptance. Laparoscopic techniques have not previously been applied to renal revascularization. The aim of this study was to demonstrate the technical feasibility and the long-term clinical and pathologic outcomes of laparoscopic aorto-left renal artery bypass in a chronic porcine model. MATERIALS AND METHODS: Eight animals were used in the study. All laparoscopic suturing and knot-tying were performed intracorporeally using free-hand techniques. The following operative steps were employed: (1) aortic dissection and cross-clamping; (2) transection and refashioning of the left renal artery ostium; (3) in-situ renal hypothermia; (4) end-to-side aorto-left renal artery anastomosis; and (5) aortic unclamping. In situ renal hypothermia was achieved laparoscopically by infusion of ice-cold heparinized saline into the renal artery through a balloon catheter. RESULTS: All eight pigs underwent laparoscopic aortorenal bypass successfully. The median surgical time was 110 minutes, and the aortic cross-clamping time was 45.5 minutes. The median anastomotic time was 40 minutes, and the renal warm ischemia time was 9 minutes. The median estimated blood loss was 30 mL. An intraoperative complication of suture breakage leading to anastomotic hemorrhage occurred in one animal; the problem was corrected laparoscopically. Postoperatively, one animal died from pneumonia. The remaining seven animals experienced no postoperative complications and were euthanized, one each at postoperative day 0 and 1 and week 1, 2, 3, 4, and 6. The median preoperative and postoperative (at euthanasia) serum creatinine values (1.15 mg/dL v 1.2 mg/dL; P = 0.39) were similar. However, compared with preoperative peripheral renin activity (0.25 microg/L per hour), the postoperative peripheral renin activity was elevated (0.9 microg/L per hour; P = 0.047). Autopsy revealed a grossly normal left kidney, with Doppler confirmation of flow in the repaired renal artery in all seven animals. Ex vivo angiography confirmed a patent anastomosis. On histopathology examination, the early left renal parenchymal specimens revealed transient, mild acute tubular necrosis that resolved over sequential specimens without significant long-term sequelae. Histologic analysis of the aorto-left renal artery anastomotic site revealed gradual endothelialization with time. CONCLUSIONS: Laparoscopic aortorenal artery revascularization is technically feasible. Our chronic animal model has demonstrated durable success over a 6-week follow-up. This study represents the initial report in the literature.

Myofibroblastoma of the ovary: report of a case.

We report an unusual case of an ovarian tumor arising in a 22-year-old female that showed histologic, immunohistochemical, and ultrastructural features of myofibroblastic differentiation. The mass was found incidentally and upon excision was 9.0 cm in its greatest dimension and almost entirely replaced the left ovary. The patient is alive without evidence of disease 21 months after excision. Histologically, the tumor was encapsulated and composed of cytologically bland spindled cells arranged into a variety of patterns, similar to those found in both solitary fibrous tumor and hemangiopericytoma. Immunohistochemically, the cells stained strongly for smooth muscle actin and muscle-specific actin, with only focal and weak staining for CD34. Stains for S-100 protein, desmin, and AE1/AE3 were negative. Ultrastructurally, the neoplastic cells showed clear-cut evidence of myofibroblastic differentiation. The differential diagnostic considerations, including solitary fibrous tumor and hemangiopericytoma, are discussed.

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 Nomega-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.

Role of electron microscopy of sperm in the evaluation of male infertility during the era of assisted reproduction.

OBJECTIVES: To determine whether there are indications for and benefits from electron microscopy (EM) of sperm during the era of assisted reproductive technology. METHODS: The medical history, semen analyses, and EM findings of 55 patients with pure male-factor infertility were reviewed to determine: (1) which semen characteristics (seminal volume, sperm concentration, percent motility, and percent normal morphology) were associated with normal or abnormal ultrastructure as determined by EM, (2) whether EM findings correlated with success or failure of in vitro fertilization (IVF), and (3) whether EM could screen for potentially inheritable genetic disorders. RESULTS: Principal EM diagnoses were normal sperm ultrastructure (11 of 55; 20%), tail abnormalities (21 of 55; 38%), necrospermia (12 of 55; 22%), acrosomal defects (9 of 55; 16%), neck abnormalities (1 of 55; 2%), and incomplete maturation (1 of 55; 2%). Every patient with an abnormal EM study had impaired motility (33% or below) and abnormal morphology (13% or lower normal forms by World Health Organization criteria). The percentage of normal sperm morphology differed significantly across EM diagnoses (P < 0.0001). Differences in motility across the groups could not be detected because EM was only performed on patients with impaired motility. Although the partner of 1 patient with a normal EM study who underwent IVF achieved pregnancy, 11 with abnormal EM studies failed to establish a pregnancy by IVF. Finally, 5 (11%) of 44 patients with abnormal EM findings were diagnosed with primary ciliary dyskinesia directly as a result of EM. In addition, 3 (6.8%) of the 44 patients with abnormal EM findings were diagnosed with complete acrosomal loss. CONCLUSIONS: Patients with severely abnormal motility and morphology on routine semen analysis may benefit from EM study of sperm. Our data indicate that EM findings correlate with success or failure of IVF, and that EM can screen for potentially inheritable genetic disorders.

Obliterative central bronchitis due to mineral dust in patients with pneumoconiosis.

OBJECTIVE: We studied at autopsy a distinctive obliterative bronchitis in three persons with pneumoconiosis and hilar node fibrosis. METHODS: Lungs were evaluated macroscopically, microscopically, and with energy-dispersive spectroscopy. RESULTS: Chest roentgenogram demonstrated right middle lobe syndrome in one patient; bronchostenosis was seen at bronchoscopy in another. The stenotic sites were in perihilar bronchi and showed an upper lobe predominance. Fibrosis with silicotic nodules involved the bronchus, peribronchial tissue, and adjacent lymph nodes. Simple coalworkers' pneumoconiosis was observed in two patients; the third had complicated, mixed dust fibrosis. CONCLUSION: Obliterative bronchitis represents an unusual fibrotic response to free crystalline silica. The process may occur simultaneously in the adjacent lymph node and the bronchial wall; however, it need not be associated with complicated pneumoconiosis. Clinically, obliterative bronchitis may masquerade as bronchogenic carcinoma.

Solitary fibrous tumor of the meninges. Case report and review of the literature.

The authors present the case of a left frontal solitary fibrous tumor of the meninges. The gross appearance of the tumor was very similar to that of a fibroblastic meningioma. Histological examination showed a mixture of spindle-shaped and round cells arranged in a collagen matrix. Immunohistochemical staining of the tumor demonstrated diffuse positive staining for CD34 and vimentin. The tumor displayed no positive staining for markers of muscle, epithelial, glial, or neurocrest differentiation or for estrogen and progesterone receptors. The MIB-1 labeling index (the percentage of positive staining tumor cell nuclei), a marker of cellular proliferation, was 1.1%. Ultrastructural studies support attributing a mesenchymal, rather than meningothelial, nature to the tumor. A differential diagnosis is discussed and a review of the literature on these rare tumors is presented.

Leukocyte adhesion molecules and x-ray energy dispersive spectroscopy in Sturge-Weber disease.

We examined the light microscopic and ultrastructural features associated with Sturge-Weber disease, including x-ray energy dispersive spectroscopy to evaluate the chemical composition of the mineralized deposits and immunofluorescence microscopy with leukocyte adhesion molecules to examine the blood vessel proliferation further. Two patients (a 17-year-old girl and a 9-month-old boy) with Sturge-Weber disease comprise this series. Mineralized deposits stained strongly positive with von Kossa and negative with Prussian blue. Transmission electron microscopy of tissue removed during a functional hemispherectomy procedure in both cases indicated that most concretions were adjacent to or in the basal lamina of parenchymal vessels; no deposits were observed in leptomeningeal vessels. Energy dispersive spectroscopy of the deposits showed emission peaks corresponding predominantly to calcium, with lesser amounts of phosphorus. Fluorescent monoclonal antibodies to leukocyte adhesion molecules (endothelial cell, vascular cell, and intercellular: ELAM-1, VCAM-1, and ICAM-1) demonstrated strong positive staining of the meningeal vessels with all three antibodies. Cortical vessels were positive only for ICAM-1. Findings based on routine staining and energy dispersive spectroscopy indicate that the mineralized deposits detected in Sturge-Weber disease are composed primarily of calcium phosphate and are located primarily in and adjacent to the vascular basal lamina. There is an aberrant expression of ELAM-1 and VCAM-1 in the meningeal vascular proliferation similar to what is observed with other vascular malformations and tumors. Parenchymal vessel changes may be secondary to the meningeal vascular proliferation.

De novo light-chain deposition disease in a cadaver renal allograft.

The deposition of immunoglobulin (Ig) light chains after renal transplantation most commonly occurs as a manifestation of recurrent multiple myeloma or recurrent light chain nephropathy. We report the development of de novo light chain deposition disease (LCDD) in a cadaveric renal transplant recipient 16 years after transplantation with no evidence of prior multiple myeloma or LCDD and no current evidence of myeloma or lymphoproliferative malignancy.

Microsporidial keratoconjunctivitis caused by Septata intestinalis in a patient with acquired immunodeficiency syndrome.

PURPOSE: To examine and treat a patient with acquired immunodeficiency syndrome (AIDS) who had mildly hyperemic conjunctiva and epithelial keratopathy in both eyes. METHODS: The patient underwent conjunctival biopsy. The specimen was examined by transmission electron microscopy. RESULTS: Septata intestinalis was demonstrated to be the cause of keratoconjunctivitis in the patient. The keratoconjunctivitis resolved after three weeks of therapy with topical fumagillin. No organisms were seen on repeat conjunctival biopsy. CONCLUSIONS: Microsporidial keratoconjunctivitis in patients with AIDS can be caused by S. intestinalis. This condition appears to respond to topical fumagillin.

Impact of chlorhexidine-silver sulfadiazine-impregnated central venous catheters on in vitro quantitation of catheter-associated bacteria.

To assess the impact of the antiseptic effects of silver sulfadiazine-chlorhexidine-impregnated central venous catheters on catheter culture systems, a series of in vitro experiments was performed. Segments of antiseptic and non-antiseptic-impregnated catheters were sonicated in thioglycolate broth and removed. After the addition of 10(3) CFU of Staphylococcus epidermidis per ml, aliquots of catheter-exposed broth were subcultured onto blood agar at 15-min intervals. Decreased mean colony counts were noted at 45 min for broth exposed to antiseptic-impregnated catheters compared with the colony counts for broth exposed to non-antiseptic-impregnated catheters (170 versus 540 CFU/ml). These effects, which were also demonstrated by the roll-plate method, were abrogated by the use of medium containing inhibitors of silver sulfadiazine and chlorhexidine. To assess the duration of the antiseptic effects, catheter segments were suspended for up to 14 days in phosphate-buffered saline, incubated with 10(6) CFU of S. epidermidis per ml, and cultured. Inhibition of bacterial growth by antiseptic-impregnated catheters disappeared after 14 days. These studies suggest that antiseptic compounds elute from catheters during broth- and solid medium-based culturing processes, making necessary the addition of inhibitors of these compounds in culture media. They further suggest that the antimicrobial effects of antiseptic-impregnated catheters wane within several days of placement.

Comparison of myocardial cell injury in acute cellular rejection versus acute vascular rejection in cyclosporine-treated heart transplants.

BACKGROUND: Myocyte necrosis has been cited as a key feature in the diagnosis and classification of both moderate and severe acute cellular rejection (International Society for Heart and Lung Transplantation grades 3A to 4). However, our previous work suggests that myocyte necrosis is not a typical feature of cellular rejection. METHODS: To clarify this point and to elucidate differences between cellular rejection and acute vascular rejection, we compared the light and electron microscopic features of 35 consecutive endomyocardial biopsy specimens from six patients with acute vascular rejection diagnosed with positive immunofluorescence, 12 consecutive endomyocardial biopsy specimens from three patients with mixed acute vascular rejection and cellular rejection, and 435 endomyocardial biopsy specimens of International Society for Heart and Lung Transplantation grades 2 to 4 cellular rejection. RESULTS: Endomyocardial biopsy specimens from eight of nine patients with acute vascular rejection and mixed acute vascular rejection/cellular rejection exhibited classic myocyte necrosis as the typical form of myocardial cell injury. Myocyte necrosis was characterized by lysis of the sarcolemma, marked swelling of mitochondria, and intramitochondrial flocculent densities. In contrast, the typical form of myocardial cell injury in cellular rejection was reversible. Reversible cellular rejection was characterized by extensive loss of myosin filaments and Z-lines with subsarcolemmal and intracytoplasmic accumulation of Z-band material. Cell swelling, mitochondrial swelling, intramitochondrial densities, and lysis of sarcolemma were not observed. CONCLUSIONS: We conclude that myocyte necrosis is a characteristic feature of acute vascular rejection, whereas reversible myocardial cell injury is characteristic of cellular rejection, including grade 4. Myocyte necrosis is not a feature of cellular rejection. The presence of true myocyte necrosis in endomyocardial biopsy specimens from cyclosporine-treated heart transplants implicates some process other than cellular rejection. Processes producing myocyte necrosis include acute vascular rejection, peritransplantation ischemia, and accelerated atherosclerosis.

Activation of intravascular macrophages within myocardial small vessels is a feature of acute vascular rejection in human heart transplants.

BACKGROUND: We investigated the pathogenesis of acute vascular rejection by performing immunofluorescent screening on frozen sections for C1q, C3c, and immunoglobulin M in endomyocardial biopsy specimens from all new heart transplants. METHODS: Immunofluorescence for C4c, C5, immunoglobulin G, and immunoglobulin A was performed on all positive endomyocardial biopsy specimens. Twenty-eight positive endomyocardial biopsy specimens from six patients were identified, and 22 of those were studied with transmission electron microscopy. RESULTS: Endothelial hyperplasia and myocyte necrosis were prominent in the five female patients with positive immunofluorescence. In addition, macrophages with ultrastructural cytologic features of activation were seen filling capillaries and venules in intimate contact with endothelium and exiting those vessels. Activated macrophages were large cells with abundant cytoplasm and ruffled borders and contained numerous lysosomes, rough endoplasmic reticulum, and mitochondria. Intravascular activated macrophages were identified in five of six patients with positive immunofluorescence but were not seen in any of the endomyocardial biopsy specimens with negative immunofluorescence, including multiple examples of moderate (grades 2 to 3B) and severe (grade 4) acute cellular rejection. In the five female patients with activated macrophages, acute vascular rejection recurred multiple times with one fatality. Review of the files showed three additional, similar cases. The one male patient with positive immunofluorescence but without activated macrophages had only a single episode of acute vascular rejection. CONCLUSIONS: Complement and antibodies can activate macrophages, so this finding is not surprising. To the best of our knowledge, this is the first report of the intravascular activation of macrophages, and the first association of this process with acute vascular rejection. Activated macrophages may contribute to myocyte necrosis in acute vascular rejection by compromising blood flow in small vessels.

Expression of cell adhesion molecules in an established and characterized new human renal cell cancer line, CCF-RC7.

In order to investigate the importance of cell adhesion molecules (CAMs) in renal cell carcinoma (RCC), a cell line, designated as CCF-RC7, was established from a human RCC of the clear cell type. CCF-RC7 was passaged over 50 times in vitro for 3 1/2 years. The cell line has an epithelial morphology and a doubling time of 30 h, forming colonies in soft agar with an average efficiency of 10.4% and producing clear cell tumors in athymic nude mice. CCF-RC7 cells have an aneuploid-hypotetraploid karyotype with a modal chromosome number of 82 and rearrangements in chromosomes 9, 12 and 14. Immunohistochemical and flow immunocytometric analyses revealed high expression of ICAM-1 (CD54), and Hermes antigen (CD44), which was significantly upregulated by cytokine and PMA treatment. VLA-4 was expressed on approximately 20% of tumor cells and could not be altered by cytokine or PMA stimulation. High expression of sialyl Lewis X was also demonstrated by immunohistological examination. This newly characterized cell line will serve as a useful model for the study of CAMs during hematogenous metastasis and host defense mechanisms in human RCC.

Acute vascular (humoral) rejection in non-OKT3-treated cardiac transplants.

To determine the incidence and morphologic features of acute vascular rejection (AVR) in cardiac transplant patients who have not received OKT3 induction therapy, we performed immunofluorescence (IF) staining for Clq and C3c on 341 endomyocardial biopsies from 135 patients. Each AVR biopsy, defined by positive IF, was further evaluated for C4c, C5, IgG, IgM, and IgA. Light and electron microscopy were also performed. The clinical features of each case were reviewed. A total of 29 biopsies from 6 recently transplanted patients (1993) and 10 biopsies from 4 long-term transplants (pre-1993) had IF evidence of AVR. All patients with AVR had linear vascular deposits of various complement components and immunoglobulins. Of the 6 recently transplanted patients, 4 were multiparous females. The male had a single episode of AVR. IF patterns were variable between and within patients. Clq and C3c were the most consistently detected complement components. IgM was the most frequently detected antibody. Of the 10 cases of AVR, 6 occurred within the first month post-transplant. Myocyte necrosis was present in all cases with cardiac dysfunction. Patients with early onset AVR had more recurrences and one fatality. There was one fatality in the long-term transplant group. Concomitant grades 0 to 4+ cellular rejection did not correlate with results of IF or clinical severity. The incidence of AVR in non-OKT3-treated patients is 7%. Of the early onset patients, 66% are multiparous females, indicating the possible importance of prior sensitization. IF patterns are not predictive of outcome. AVR may be asymptomatic, but early onset predicts a difficult clinical course and is detected only by IF screening.

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.