Heikki J. Aho

Disc degeneration in magnetic resonance imaging : a comparative biochemical, histologic, and radiologic study in cadaver spines

Magnetic resonance imaging (MRI) findings of 89 autopsied intervertebral discs from 22 cadaveric lumbar spines were correlated with biochemical composition, conventional radiography, and histologic structure to study the nature of disc intensity changes seen in MRI. Discs with a low signal intensity on T2-weighted MRI were characterized by shortening of relaxation times, dehydration, and decreases in total proteoglycan content and chondroitin-keratan sulfate ratios in the nucleus pulposus. This corresponded well with previously published studies. In histologic structure, no obvious differences between MRI findings were found. In conclusion, a low signal intensity in a lumbar disc on T2-weighted MRI probably reflects a true biochemical disc degeneration, but its relation to structural degenerative changes is uncertain. Therefore, MRI seems to be a sensitive and a specific imaging modality for detecting pathologic biochemical disc changes in the spine of a young adult.

In situ localization of collagen production by chondrocytes and osteoblasts in fracture callus.

An experimental model of fracture-healing was used to study the production of types-I and II collagen by in situ hybridization. The distribution of cartilage matrix in callus was determined by histochemical staining. Messenger RNA (mRNA) for cartilage-specific type-II collagen was detectable as early as the fifth day in a small number of cells that had acquired a chondrocyte phenotype but that also contained type-I collagen mRNA, suggesting an ongoing change in the expression of collagen genes. The location of the first chondrocytes, which were adjacent to cortical bone, suggested that they originated from cells that had derived from the periosteum by differentiation. On the seventh day of callus formation, the presence of both type-I and type-II collagen mRNA in chondrocytes of expanding cartilage suggested that most growth occurred by differentiation of mesenchymal cells and less by proliferation of differentiated chondrocytes. Expansion continued until the tenth to fourteenth day, after which the cartilage was replaced by woven bone. This was characterized by the presence of osteoblasts that were active in the synthesis of type-I collagen.

Malignant rhabdoid tumor of the prostatic region

We describe a malignant rhabdoid tumour of the prostatic region in a 14-year old boy. The tumour showed positive immunoreactivity for epidermal prekeratin, monoclonal cytokeratin, epithelial membrane antigen, carcinoembryonic antigen and monoclonal vimentin but was negative for myoglobin, alfa-fetoprotein and lysozyme. Electron microscopy revealed pleomorphic cells with collections of paranuclear intermediate filaments, sheaves of tonofilaments and abundant microvilli in some tumour cells. Epithelial derivation was also suggested by occasional intracytoplasmic lumina and rare cell junctions.

Evidence for insufficient chondrocytic differentiation during repair of full-thickness defects of articular cartilage

The main objective of this study was to characterize the cellular phenotypes in the repair tissue of full-thickness defects of articular cartilage by histologic and molecular biologic techniques. Healing of the defects in the articular cartilage of the knee joints of 12 rabbits was analyzed at days 3, 7, 14, 28 and 50 using histology and Northern analysis of mRNA levels for type I, II and III collagens and osteonectin. The cellular source of each mRNA was determined by in situ hybridization. Two novel cDNA clones for rabbit type II and III collagen mRNAs were constructed to obtain species-specific hybridization probes. The repair tissue of full-thickness defects consisted of two types of tissue. At the bottom of the defect, bone-derived cells with high levels of type I collagen and osteonectin mRNA were actively producing new osteoid, while superficially a slow transition from a fibrin clot into undifferentiated mesenchyme with cells containing type III collagen mRNA was observed. This tissue subsequently became fibrocartilaginous, with small groups of cells turning on the transcription of the type II collagen gene and acquiring a phenotype typical for hyaline cartilage. The data suggest that small clusters of cells in the repair tissue of full-thickness articular cartilage defects are capable of turning on an apparently correct chondrocytic phenotype. The low transcription level of the type II collagen gene suggests, however, that insufficient amounts of fundamentally important regulatory factors or progenitor cells are present in the repair tissue. In the future, such factors should be administrable into the joint by novel therapeutic means.

Quantitation of Schwann cells and endoneurial fibroblast-like cells after experimental nerve trauma

SummarySchwann cells and endoneurial fibroblastlike cells were quantitatied for 30 weeks in both nonregenerating and freely regenerating, transected rat sciatic nerve. Immunocytochemical recognition of S-100 protein was used as a marker for Schwann cells and other immunocytochemical and histological methods in the differentiation of S-100 protein-negative endoneurial cells in cross sections of the distal stump 10 mm distal to the site of transection. A marked increase in the total number of cells was observed during the first 4 weeks after the injury in both operative groups. The quantitative relationships between cell populations remained essentially the same as in normal nerves, although the proliferation of the S-100 protein-negative cell population was proportionately slightly stronger when compared to the number of these cells in normal nerves. After the initial proliferation, a gradual decrease occurred in the total number of cells per cross section. This was most marked in the non-regenerating nerves, whereas in the regenerating nerves the decrease in cell number ceased at 16 weeks. The number of Schwann cells was 3.5 times as high as in the control nerves in this phase. The method used in the present study is less laborious than morphometry employing electron microscopy. Furthermore, electron microscopic characteristics of endoneurial cells are not always reliable after nerve trauma, because normal anatomical relationships have become disturbed. This study demonstrates that S-100 protein immunocytochemistry is useful in the study of traumatic lesions of peripheral nerve.

Human acute pancreatitis: a light and electron microscopic study.

The histology and ultrastructure of resected pancreas from seven patients suffering from acute haemorrhagic pancreatitis were studied. Special attention was paid to necrotic acini and zymogen granules. Acinar cells in the border of necrotic and non-necrotic parenchyma contained lipid droplets, autophagic vacuoles, bundles of intermediate filaments and degenerated cell organelles, including zymogen granules, PAS-positive material derived from secretory proteins was situated in dilated acinar lumina and in the interstitium, and proved to be fibrillar in fine structure. There were thrombosed vessels and extravasated erythrocytes at the border of the parenchymal necrosis. Bundles of intermediate filaments were often the only identifiable structures in the severely necrotic acinar cells. The amount of lipid was decreased in damaged fat cells. Older fat necroses were surrounded by myofibroblasts. It was concluded that acinar and fat cells undergo concomitant necrosis in the inflamed pancreas, zymogen granules degenerate in the acinar cells at the border of necrotic and non-necrotic areas, and secretory proteins may be displaced in the interstitium outside acinar lumina. Myofibroblasts participate in the healing of autodigestive injuries.

Experimental pancreatitis in the rat. Development of pancreatic necrosis, ischemia and edema after intraductal sodium taurocholate injection.

Acute hemorrhagic pancreatitis was induced in rats by injecting sodium taurocholate into the common biliopancreatic duct. The extent of pancreatic necrosis was quantified in histological sections during the course of the disease. The proportion of necrotic acini was low, although the amount of necrosis increased from 3.3% of pancreatic parenchyma at 15 min to 10.5% at 12 h. The degree of ischemia in the inflamed pancreas was estimated by extracting intravenously injected toluidine blue from the gland. The amount of the dye in the gland decreased progressively during 12 h to 58.8% of the amount in normal pancreas. The development of pancreatic edema was studied by recording the water content of the gland. The edema was maximal at 3 h and resolved partly in 12 h after the induction of the disease. Necrosis and ischemia become progressively more pronounced in the edematous pancreas during sodium taurocholate-induced acute hemorrhagic pancreatitis. This kind of pathophysiologic course is also thought to characterize human pancreatitis. The present simple model of acute hemorrhagic pancreatitis in the rat is suitable for quantitative observations on the development of pancreatic damage under various experimental conditions.

Human Meconium Has High Phospholipase A2 Activity and Induces Cellular Injury and Apoptosis in Piglet Lungs

Aspiration of meconium produces an inflammatory reaction resulting in necrotic changes in lung tissue. To further investigate the mechanisms of the meconium-induced early pulmonary injury, twenty 10–12-d-old piglets were studied for lung tissue ultrastructural and apoptotic changes and phospholipase A2 activity. Twelve piglets received an intratracheal bolus (3 mL/kg) of a 20-mg/mL (thin, n= 6) or 65-mg/mL (thick, n= 6) mixture of human meconium, and control piglets (n= 5) received the same amount of intratracheal saline. Three ventilated piglets with no aspiration were also studied. Pulmonary hemodynamics and systemic oxygenation were followed for 6 h after meconium or saline insufflation. In the control groups, the pulmonary tissue showed open alveolar spaces and intact vascular walls, whereas meconium administration resulted in severe pneumonitis, with alveolar spaces filled with inflammatory exudate. Meconium instillation additionally resulted in edematous changes in the vascular walls and alveolar epithelium, whereas type II pneumocytes were intact. The amount of apoptotic cells was increased, especially in the respiratory epithelium, and the catalytic activity of phospholipase A2 in lung tissue samples was significantly elevated after thick meconium instillation. This activity rise proved to be mainly because of human group I phospholipase A2, introduced by meconium. Our data thus show that aspiration of meconium leads to severe lung tissue inflammation with early ultrastructural changes in the pulmonary alveolar walls and is associated with apoptotic cell death in the epithelium, already during the first hours after the insult. These results further suggest that high phospholipase A2 activity, mainly introduced into the lungs within the meconium, may have an important role in the initiation of these alterations in neonatal lungs.

Pulmonary alveolar proteinosis and glomerulonephritis in lysinuric protein intolerance: Case reports and autopsy findings of four pediatric patients

Lysinuric protein intolerance is an autosomal recessive disease caused by defective transport of cationic amino acids. Of the 38 lysinuric protein intolerance patients diagnosed in Finland since 1965, four pediatric patients have died. We describe the clinical courses and autopsy findings for these patients. All patients developed acute respiratory insufficiency. In addition to pulmonary hemorrhages, three of the patients had pulmonary alveolar proteinosis and one had cholesterol granulomas. Three patients had a clinically obvious renal insufficiency, but all four showed histologic signs of immune complex-mediated glomerulonephritis. The patients also developed hepatic insufficiency with fatty degeneration or cirrhosis. All patients showed anemia, thrombocytopenia, and a severe bleeding tendency. The bone marrow of three patients was hypercellular, but the amount of megakaryocytes was decreased in two cases. Amyloid was present in the lymph nodes and the spleen. Bone specimens showed osteoporosis. We conclude that pediatric patients with lysinuric protein intolerance are predisposed to develop pulmonary alveolar proteinosis and glomerulonephritis. They are also at risk of protein malnutrition in the active growth phase, probably due to higher requirements for total nitrogen and amino acids.

Compound Heterozygous Desmoplakin Mutations Result in a Phenotype with a Combination of Myocardial, Skin, Hair, and Enamel Abnormalities

Desmoplakin (DP) anchors the intermediate filament cytoskeleton to the desmosomal cadherins and thereby confers structural stability to tissues. In this study, we present a patient with extensive mucocutaneous blisters, epidermolytic palmoplantar keratoderma, nail dystrophy, enamel dysplasia, and sparse woolly hair. The patient died at the age of 14 years from undiagnosed cardiomyopathy. The skin showed hyperplasia and acantholysis in the mid- and lower epidermal layers, whereas the heart showed extensive fibrosis and fibrofatty replacement in both ventricles. Immunofluorescence microscopy showed a reduction in the C-terminal domain of DP in the skin and oral mucosa. Sequencing of the DP gene showed undescribed mutations in the maternal and paternal alleles. Both mutations affected exon 24 encoding the C-terminal domain. The paternal mutation, c.6310delA, leads to a premature stop codon. The maternal mutation, c.7964 C to A, results in a substitution of an aspartic acid for a conserved alanine residue at amino acid 2655 (A2655D). Structural modeling indicated that this mutation changes the electrostatic potential of the mutated region of DP, possibly altering functions that depend on intermolecular interactions. To conclude, we describe a combination of DP mutation phenotypes affecting the skin, heart, hair, and teeth. This patient case emphasizes the importance of heart examination of patients with desmosomal genodermatoses.