Shwachman's syndrome: pathomorphosis and long-term outcome

BACKGROUND

Shwachman's syndrome is the second most common cause of inherited/congenital pancreatic insufficiency after cystic fibrosis. The main associated features are usually cyclic neutropenia, metaphyseal dysostosis, and growth retardation. Other organs or functions may be involved in this syndrome, showing a wide range of abnormalities and symptoms. There are reports of Shwachman's syndrome in childhood, but little is known about the long-term clinical course of these patients. This article reports on the pathomorphosis and long-term follow-up of 13 patients with Shwachman's syndrome diagnosed in infancy focusing, in particular, on modifications of the exocrine pancreatic function over time.

METHODS

Exocrine pancreatic function was evaluated by duodenal intubation followed by a pancreatic stimulation test. Nutritional, biochemical, hematologic, radiologic, and psychological evaluations were performed at various intervals. Six patients were included in long-term follow-up evaluation.

RESULTS

At diagnosis, growth retardation was present in all patients, and all subjects showed pancreatic insufficiency. Hematologic features (intermittent neutropenia, anemia and thrombocytopenia), respiratory infection during the first years of life, and skeletal abnormalities were also frequently observed. Other associated features at diagnosis included hepatic involvement and occasional renal dysfunction. In the six patients followed up, a significant growth improvement was observed. In five of them the pancreatic stimulation test showed values of lipase within reference range outputs, whereas fat balance or fecal fat losses were normal in all but one subject. Of seven subjects assessed by psychological evaluation, IQ test results were markedly abnormal in one and bordered on abnormality in the others.

CONCLUSIONS

The present data on Shwachman's syndrome diagnosed in infancy underline the possibility of improvement or normalization of exocrine pancreatic function with age, suggesting the need for periodic checks on pancreatic activity in these subjects. It also indicates the possibility of diagnosis of this syndrome in the absence of pancreatic insufficiency; decreasing frequency of infections over time; and the usefulness of early neuropsychological evaluation.

Antioxidants and blockers of arachidonate metabolism inhibit the mitogenic effects of TPA in hepatocytes: differences in the operative mechanisms according to the cell cycle setting

A single exposure to a low concentration (10(-10) mol/l) of TPA doubled the size of the fraction of neonatal rat hepatocytes flowing into DNA synthesis within 24 hours in 4-day-old primary cultures kept in low-calcium (0.01 mmol/l) HiWoBa2000 synthetic medium, thereby evoking a phenotypically neoplastic feature in normal, i.e. non-initiated cells. Inhibition kinetics studies, in which several antioxidants and blockers of the arachidonate cascade were given, each by itself, simultaneously with or at various time intervals after TPA, showed that the early mitogenic effects of TPA, i.e. the commitment of GO hepatocytes to grow and the reactivation of hepatocytes poised at the G1/S boundary required oxygen radicals and all the main metabolites of arachidonate. Instead, the subsequent flow into S phase of TPA-committed hepatocytes was not controlled by oxygen radicals and prostaglandins but by retinoid-modulable activities and by products of the lipoxygenase and thromboxane synthase pathways of arachidonate metabolism.

Growth stimulation and apoptosis induced in cultures of neonatal rat liver cells by repeated exposures to epidermal growth factor/urogastrone with or without associated pancreatic hormones

In untreated primary cultures of neonatal rat liver kept in high-calcium (1.8 mmol/l), foetal bovine serum (10% v/v)- containing minimal essential medium (FBS-MEM), the absolute numbers of hepatocytes did not change between day 4 and day 9 because ongoing cell loss was counterbalanced by proliferation of a discrete sub-population of the cells. By contrast, the number of stromal cells increased linearly with time. Growth of hepatocytes and stromal cells was differently affected by the daily addition, between day 4 and day 8 of culture, of fresh medium to which peptide mitogen(s) in concentrations ranging from 10(-14) to 10(-8) mol/l had been added. Epidermal growth factor/urogastrone (EGF/URO) with or without equimolar mixtures of glucagon and insulin, induced first hyperplasia of hepatocytes and stromal cells and then apopotosis (degeneration and death) of the progeny of the stimulated cells. By contrast, equimolar mixtures of glucagon and insulin caused a progressive increase in the number of hepatocytes and stromal cells unbalanced by any increase in cell death. At subphysiological concentrations glucagon, in synergism with EGF/URO and/or some other unknown heat-stable component of serum, acted as a trophic factor for hepatocytes. By contrast, insulin alone did not enhance growth of hepatocytes, but rather blocked the mitogenic effects of EGF/URO. The three hormones exerted neither mitogenic nor apoptotic effects when administered in a low calcium (0.01 mmol/l) FBS-MEM medium. These results reveal that EGF/URO may control the size of cell populations in neonatal liver by calcium-dependent mechanisms that make it unlikely to be a promoter of hepatocyte tumours. They also show that glucagon acts as a positive trophic regulator for hepatocytes.

Studies on the mechanisms by which tumor promoters stimulate the growth of primary neonatal rat hepatocytes

A single exposure to a low concentration (10(-10) mol/L) of several tumor promoters, namely 12-O-tetradecanoylphorbol-13-acetate (TPA), phenobarbital (PB), nafenopin, saccharin, teleocidin, benzoyl peroxide, butylated hydroxytoluene (BHT), dichlorodiphenyltrichloroethane (DDT), lindane, clofibrate, and melittin significantly stimulated DNA synthesis of neonatal rat hepatocytes in 4-day-old primary cultures. These cultures were kept in low-calcium (0.01 mmol/L) HiWoBa2000 synthetic medium, thereby evoking a neoplastic phenotype in otherwise normal (i.e., non-initiated) cells. The simultaneous addition of a single dose of alpha-tocopherol (10(-4) mol/L) or selenous acid (10(-5) mol/L), just as that of exogenous superoxide dismutase (SOD) (4), together with each of the above agents fully suppressed the stimulation of hepatocytic DNA synthesis by the xenobiotics. Hence, these findings strengthen the view that superoxide anions (or some other oxidizing compounds) act as the common mediators of the mitogenic effects of various tumor promoters in hepatocytes. Inhibition kinetics studies, in which TPA in a single dose (10(-10) mol/L) was used as the paradigmatic compound together with several kinds of inhibitors of its activity showed that the early mitogenic effects of TPA, i.e., the commitment of quiescent (G0) hepatocytes and the reentry into active cycling of hepatocytes spontaneously poised at the G1/S boundary, required oxidizing compounds, arachidonate metabolism derivatives, and plasmalemmal calcium-binding sites and transmembrane calcium fluxes. Instead, a later TPAs effect, the flow into DNA synthesis of hepatocytes previously committed to cycle, was shown to be controlled by retinoid-modulable activities, by some product(s) of the lipoxygenase pathway, and again by plasmalemmal calcium-binding sites and transmembrane calcium fluxes. Such results reveal that in the neonatal rat hepatocyte the ability to answer to a single mitogenic stimulus and the metabolic pathways by which this answer is enacted depend upon the mitotic cycle setting of the hepatocytes at the moment of the experimental treatment.