Nemaline myopathy caused by absence of alpha-skeletal muscle actin.

OBJECTIVE: To investigate seven congenital myopathy patients from six families: one French Gypsy, one Spanish Gypsy, four British Pakistanis, and one British Indian. Three patients required mechanical ventilation from birth, five died before 22 months, one is ventilator-dependent, but one, at 30 months, is sitting with minimal support. All parents were unaffected. METHODS: The alpha-skeletal muscle actin gene (ACTA1) was sequenced. Available muscle biopsies were investigated by standard histological and electron microscopic techniques. The expression of various proteins was determined by immunohistochemistry, western blotting, or both. RESULTS: Three homozygous ACTA1 null mutations were identified: p.Arg41X in the French patient, p.Tyr364fsX in the Spanish patient, and p.Asp181fsX10 in all five British patients. An absence of alpha-skeletal muscle actin protein but presence of alpha-cardiac actin was shown in all muscle biopsies examined, with more alpha-cardiac actin in the biopsy from the child with the greatest muscle function. Muscle biopsies from all patients exhibited nemaline bodies whereas three also contained zebra bodies. INTERPRETATION: The seven patients have recessive nemaline myopathy caused by absence of alpha-skeletal muscle actin. The level of retention of alpha-cardiac actin, the skeletal muscle fetal actin isoform, may determine alpha-skeletal muscle actin disease severity. This has implications for possible future therapy.

Phenotypic mapping of human mesothelial cells.

In recent years it has become clear that the mesothelium plays a prominent homeostatic role in the peritoneum, and can be profoundly altered in disease and during peritoneal dialysis. The cell-surface phenotype of the mesothelial cell has not been thoroughly investigated. This study begins to identify cell surface molecules which may be important in mesothelial functions such as adhesion and interaction with cells of the immune system. The expression of adhesion structures on mesothelial cells such as CD44, the beta integrin chain CD29, the beta 3 integrin chain CD61 and alpha chains CD49 alpha (alpha 1), CD49b (alpha 2), CD49c (alpha 3), CD49e (alpha 5), and CD51 (alpha v) is described. In addition, a wide range of novel molecules including CD90, CD105, CD140b, CD142, CD147, CD151, CD157, CD165, and CD166 are identified. The role and function of such molecules in mesothelial biology and their significance for peritoneal dialysis is discussed.

Sphingosine and sphinganine levels in human mesothelial cells in vitro as a potential index of signal transduction pathways impacted by microbes and osmolality.

Sphingolipids are emerging as important regulators of mammalian cell biology. In this study, the contents of six separate preparations of human omental mesothelial cells in vitro were examined for free sphingosine and sphinganine, and for the total levels of these sphingoid bases in ceramide-containing sphingolipids. Two high-performance liquid chromatography (HPLC) methods for determination of sphingoid base levels in cultured cells were compared. The rapid-HPLC method was found to yield the highest recovery of internal standard. Mesothelial cells initially isolated by collagenase digestion of the omentum were found to have higher free- and total-sphingoid base levels than cells isolated by trypsin-EDTA digestion. Use of sphingoid base levels to gain insights into the status of cellular nutrition, inflammation, programmed cell death, exposure to microbial toxins, cytokines, and growth factors within the peritoneum will require a systematic description of sphingolipids in normal, diseased, and dialyzed mesothelium.

New principles, better practices, and clearer perceptions in intraperitoneal chemotherapy: clinical experience using icodextrin 20 as a carrier solution.

The rationale for using intraperitoneal chemotherapy is based on three phenomena: certain types of tumor are confined to the abdominal cavity for many years; the ability to deliver the drug directly to the surface of tumor deposits; the pharmacological advantage of attaining high local concentrations of the drug within the cavity. Current techniques of intraperitoneal chemotherapy do not use a specially designed carrier solution, which greatly restricts flexibility and does not permit continuous ambulatory intraperitoneal chemotherapy necessary for optimal use of cell cycle-specific antitumor agents. Using icodextrin 20 as a carrier solution containing 50% of the dose of 5-fluorouracil in a 24-hour dwell, simultaneously with a 24-hour elastomeric infusor device containing 50% of the dose, we have succeeded in carrying out continuous ambulatory intraperitoneal chemotherapy, 5 days out of 7 for up to 12 weeks, exposing the peritoneal contents to drug concentrations a thousand-fold greater than attained in the serum in a Phase I clinical trial. These studies have for the first time demonstrated that it is possible to expose continuously for long periods intraperitoneal tumor deposits to sustained high levels of cell cycle-specific cytotoxic agents.

Prolonged intraperitoneal infusion of 5-fluorouracil using a novel carrier solution.

A novel peritoneal carrier solution, Icodextrin 20 (7.5%), has allowed exploration of prolonged, intraperitoneal (i.p.) infusion of the cytotoxic drug 5-fluorouracil (5-FU). A phase I and pharmacokinetic study was performed to determine the toxicities and maximum tolerated dose of prolonged and continuous intraperitoneal 5-FU in patients with peritoneal carcinomatosis. Seventeen patients were entered into this study. Each patient had a Tenckhoff catheter placed into the peritoneal cavity under general anaesthetic. After initial flushing and gradual increase in exchange volumes with Icodextrin 20, 5-FU was administered daily from Monday to Friday, 50% as a bolus in the exchange bag and 50% in an elastomeric infusor device delivering continuous 5-FU to the peritoneal cavity at 2 ml h-1. Treatment was continued for 12 weeks or until intolerable toxicity developed. Abdominal pain and infective peritonitis proved to be the main dose-limiting toxicities. Initial problems with infective peritonitis were overcome by redesign of the delivery system, and it proved possible to deliver 300 mg m-2 5-FU daily (5 days per week) for 12 weeks. Pharmacokinetic studies showed i.p. steady-state 5-FU concentrations (mean 47 500 ng ml-1) that were > 1000-fold higher than systemic venous levels (mean 30 ng ml-1).

Surfactant protein A and lamellar bodies: a homologous secretory function of peritoneum, synovium, and lung.

OBJECTIVE: To review recent discoveries on the existence of lamellar body secreting cells in extrapulmonary sites with respect to their constitution as a previously unrecognized coherent biological system and to evaluate the role of mesothelial research in peritoneal dialysis in initiating this new field of medical research. DATA SOURCES: Studies in the literature on the production and metabolism of pulmonary surfactant with respect to lamellar bodies and surfactant protein A (SP-A). Published investigations on the identification of lamellar bodies and SP-A in extrapulmonary sites and their possible role in systemic expression of autoimmune disorders. RESULTS: It is now established that lamellar bodies of identical periodicity and ultrastructural geometry are present in lung (type II pneumocytes), serosal mesothelium (peritoneum, pleura, and pericardium), and joints (type A and type B synoviocytes). Not only pulmonary lamellar bodies but those at extrapulmonary sites are found in association with SP-A, while SP-A or SP-A-like proteins are present in measurable quantities in normal serosal fluids. These findings have disclosed totally new avenues of research into multisystem disorders, where for the first time an organelle and associated protein provide a link between diverse tissues affected by rheumatoid disease. Evidence of shared epitopes between SP-A and mycobacterial 65-kD heat shock protein indicates a possible etiologic mechanism. CONCLUSIONS: A hitherto ultrastructurally hidden system of lamellar body secretion is now being revealed as a major biological system which appears to subserve surfactant, lubricant, surface protection, and sealant functions in body surfaces and tissue interfaces. This new frontier was born out of investigations into the hitherto neglected biology of peritoneal mesothelium, research which was vital for advancing the therapy of peritoneal dialysis and for preservation of the dialyzing membrane.

Ultrastructure, distribution, and density of lamellar bodies in human peritoneum.

OBJECTIVE: To determine the ultrastructure, relative density, and location of lamellar bodies in the various regions, structures, cells, and intercellular matrix in normal human peritoneum; to carry out engineering analysis of the role of lamellar structures in serosal lubricancy and deduce what effect this system may have on the process of peritoneal dialysis. DESIGN: Five samples of normal human parietal peritoneum obtained at elective operation were fixed in a tannic acid-glutaraldehyde mixture and submitted to examination by transmission electron microscopy. Detailed analysis using reconstruction of serial electron micrographs and tracings of montages were employed in determining location, disposition, density, and geometric patterns of lamellar bodies in all levels of the peritoneal membrane. RESULTS: Lamellar profiles were found in greatest density enmeshed in surface microvilli and in mesothelial cytoplasm. Lamellar bodies were frequently observed capping the external portion of mesothelial junctional complexes, and within intercellular junctions. Lamellar bodies were also encountered in macrophages, both in the peritoneal cavity and submesothelial tissue, and also in fibroblasts. Lamellar bodies were present in low density in the matrix ground substance of submesothelial connective tissue, in blood vessel walls between smooth muscle, in endothelial cell cytoplasm, and in vascular lumina. CONCLUSION: Three-dimensional analysis of lamellae on mesothelial surfaces indicates that an arrangement of constantly changing microscopic spheres and cylinders would act as "ball and roller bearings" among the microvilli for the lubrication of opposing surfaces. The entrapment of fluid in lamellar bubbles, which in normal peritoneum fill the microvillous layer, would, if maintained in peritoneal dialysis, constitute a stagnant layer of considerable stability and inertia.

Ultrastructure, distribution, and density of lamellar bodies in human peritoneum.

OBJECTIVE: To determine the ultrastructure, relative density, and location of lamellar bodies in the various regions, structures, cells, and intercellular matrix in normal human peritoneum; to carry out engineering analysis of the role of lamellar structures in serosal lubricancy and deduce what effect this system may have on the process of peritoneal dialysis. DESIGN: Five samples of normal human parietal peritoneum obtained at elective operation were fixed in a tannic acid-glutaraldehyde mixture and submitted to examination by transmission electron microscopy. Detailed analysis using reconstruction of serial electron micrographs and tracings of montages were employed in determining location, and disposition, density, and geometric patterns of lamellar bodies in all levels of the peritoneal membrane. RESULTS: Lamellar profiles were found in greatest density enmeshed in surface microvilli and in mesothelial cytoplasm. Lamellar bodies were frequently observed capping the external portion of mesothelial junctional complexes, and within intercellular junctions. Lamellar bodies were also encountered in macrophages, both in the peritoneal cavity and submesothelial tissue, and also in fibroblasts. Lamellar bodies were present in low density in the matrix ground substance of submesothelial connective tissue, in blood vessel walls between smooth muscle, in endothelial cell cytoplasm, and in vascular lumina. CONCLUSIONS: Three-dimensional analysis of lamellae on mesothelial surfaces indicates that an arrangement of constantly changing microscopic spheres and cylinders would act at "ball and roller bearings" among the microvilli for the lubrication of opposing surfaces. The entrapment of fluid in lamellar bubbles, which in normal peritoneum fill the microvillous layer, would, if maintained in peritoneal dialysis, constitute a stagnant layer of considerable stability and inertia.

Multiple drug classes and hyperosmolarity alter binding of muscarinic drugs to mesothelial cells in vitro.

Mesothelial cells in vitro exhibited binding sites for L-quinuclidinyl[phenyl-4-3H]-benzilate ([3H]-QNB), but not [3H]-N-methylscopolamine (NMS), a cell-impermeable ligand. [3H]-QNB binding demonstrated a biphasic pattern of binding in living cells: a maximum after 15 min at 37 degrees C was followed by a decrease out to 90 min. [3H]-QNB binding was blocked by increasing concentrations of atropine; WIN35428 and GBR12909, dopamine transport inhibitors also decreased binding. Pretreatment of cells for 18 hours with atropine, QNB, or WIN35428 resulted in enhanced [3H]-QNB binding, but coexposure to cycloheximide blocked this increase. Hyperosmolarity caused by NaCl or mannitol decreased binding of [3H]-QNB to living cells. Thus rabbit peritoneal mesothelial cells possess binding sites for [3H]-QNB that are influenced by other drugs and osmolarity.

The biology of the mesothelium during peritoneal dialysis.

Substantial derangements of mesothelial biology are observed during experimental simulations of dialysis conditions, inferred from the content of human dialysis effluent and visualized by microscopy of human mesothelial biopsies. Can osmotically active solutions be made biocompatible with the osmoregulatory system of the mesothelium? Can the contributions of the mesothelium to host defenses against inflammation and/or infection be supported during CAPD? Do underlying metabolic derangements present in various kidney diseases and end-stage renal disease, regardless of cause, require customized CAPD protocols and solutions? Use of dialysis solutions less directly toxic to the mesothelium is a necessary step toward some day manipulating peritoneal biology by pharmacological and therapeutic modalities.

Lamellar body secretion: ultrastructural analysis of an unexplored function of synoviocytes.

The intra- and extracellular distribution and relative density of lamellar bodies (LBs) were determined by electron microscopy in synovial biopsies from 20 non-rheumatoid arthritis (RA) patients. LBs were found on the synovial surface, in intimal cells, throughout intimal matrix, in blood vessel walls, in endothelial cytoplasm and within vascular lumena. Lamellar profiles were observed in type B synoviocytes within rough endoplasmic reticulum (RER), in association with the Golgi apparatus, and embedded in electron dense matrix (projection cores) in multivesicular bodies. Exocytotic release of mature LBs into intimal matrix was observed. In type A synoviocytes the outer lamellae of LBs were frequently found in contiguity with the limiting membrane of lysosomes. An in vitro investigation of the ultrastructural features of LB formation in cultured type B synoviocytes (from 3 non-RA patients) gave results similar to those obtained in biopsies. These studies provide ultrastructural evidence of synoviocyte activity in secreting and degrading phospholipid lubricant in a sophisticated system whose function and pathological derangements are largely unknown.

Pharmacokinetic study of 5-fluorouracil in a novel dialysate solution: a long-term intraperitoneal treatment approach for advanced colorectal carcinoma.

Five patients with advanced colorectal and gastric carcinoma with peritoneal deposits were treated by continuous weekdays intraperitoneal (i.p.) instillation of 5-fluorouracil (5-FU) 200 mg m-2 day-1 in a novel dialysate solution that ensures maximal exposure of peritoneal areas liable to bear tumours for 24 h. A solution of icodextrin, a glucose polymer, in a 21 twin-bag delivery system allowed a single daily exchange and demonstrated the feasibility of long-term continuous ambulatory treatment with up to 17.4 g of 5-FU, delivered intraperitoneally, in this initial study. During the entire study, there were 235 fluid exchanges or 470 connections and disconnections and no bacterial peritonitis or exit site infection were observed. There was no treatment-associated toxicity worse than WHO grade 2. Drug concentrations in both peritoneal and plasma compartments followed a first-order model with similar half-life value of 1.3 h. 5-FU pharmacokinetic parameters (half-life values, total body clearance, peritoneal clearance and pharmacological advantage of the i.p. route) with this novel icodextrin carrier solution were similar to those obtained in other referenced pharmacokinetic studies with other carrier solutions (dextrose dialysate and lactated Ringer's solutions). This confirms that icodextrin solution is physiologically neutral, drug compatible and allows adequate dwell times with constant fluid balance for long-term continuous intraperitoneal chemotherapy. The pharmacokinetic parameters from this study will be used to design a loading dose infusion schedule in an attempt to maintain steady-state i.p. 5-FU levels in a new multicentre phase I trial.

Lamellar bodies in synoviocytes, mesothelium and specific epithelia as possible site of auto-antigen in rheumatoid disease.

Intracytoplasmic lamellar organelles identical in ultrastructure to surfactant-containing lamellar bodies found in type II pneumocytes, have been demonstrated in other tissues, in synoviocytes and mesothelial cells, in a distribution pattern which reflects the systemic expression of rheumatoid disease. Antibodies raised against surfactant protein A (SP-A), exhibit a ranking of tissue reactivity in area, intensity and density of cells which also parallels the frequency and degree of pathological involvement characteristic of rheumatoid disease, showing in ascending order of immunopositivity, lacrymal and salivary epithelia, pulmonary parenchyma, mesothelium and synoviocytes. Maximal tissue reactivity to anti-SP-A antibodies was found in the synovium of 55 rheumatoid patients exhibiting classical histopathological appearances of RA, in a pattern of immunostaining identical to that obtained with ML30, an antibody to mycobacterial heat shock protein 65kDa which, in turn, cross-reacted with SP-A in dot blot testing.