The ultrastructure of polyploid B-cells in the islets of normal mice

Neonatal hyperinsulinemic hypoglycemia: heterogeneity of the syndrome and keys for differential diagnosis

The two major forms of infantile persistent hyperinsulinemic hypoglycemia require different treatments, but are difficult to differentiate during surgery. Indeed, one is characterized by focal adenomatous hyperplasia often macroscopically invisible, whereas the other consists of a diffuse, but discreet, beta-cell abnormality. We evaluated, in a large series of persistent hyperinsulinemic hypoglycemia, the reliability of two criteria in differentiating these two forms: the mean beta-cell nuclear radius (MNR) and the beta-cell nuclear crowding, i.e. the number of nuclei per 1000 micron 2 beta-cell (BCNC). The values of the largest MNR and of BCNC in cases bearing a focal lesion (respectively, 3.27 microns +/- 0.25 and 14.62 +/- 1.78) were significantly different from those in the diffuse pathology (4.25 microns +/- 0.43 and 10.00 +/- 1.55). Setting the threshold value of MNR at 3.70 microns and that of BCNC at 12.00 enabled correct classification of 90.9% of the diffuse and 100% of the focal forms. beta-Cell nuclear analysis can thus contribute to a subclassification of the syndrome, not allowed by clinical or biological data. If performed during surgery it could help in determining the extent of pancreatectomy necessary to cure the patient, as the diffuse form, with abnormal nuclei in the whole pancreas, requires subtotal to near-total pancreatectomy, whereas the focal form, devoid of abnormal insular beta-cell nuclei, can be cured by partial pancreatectomy.

Partial or near-total pancreatectomy for persistent neonatal hyperinsulinaemic hypoglycaemia: the pathologist's role

AIMS

To determine whether the presence of abnormal B-cell nuclei predicts the existence of a focal or of a diffuse form of persistent neonatal and infantile hyperinsulinaemic hypoglycaemia in a series of 20 infants.

METHODS AND RESULTS

Intra-operative frozen sections were performed on small specimens from the pancreatic head, isthmus and tail. In 13 cases, abnormal B-cell nuclei were identified, but even a near-total pancreatectomy was insufficient to cure some of these patients, in whom no focal lesion was detected. On the other hand, abnormal insular B-cell nuclei were not found in seven cases; based on the results of selective venous catheterization, a limited resection was performed, sufficient to cure each patient, and a focal adenomatous hyperplasia was found in each resected specimen.

CONCLUSIONS

Intra-operative examination of small pancreatic specimens taken from the different parts of the gland allows one to determine the type of lesion (focal or diffuse) in neonatal onset hyperinsulinaemic hypoglycaemia, and to decide on the most appropriate surgical treatment.

Nesidiodysplasia--a histologic entity?

Five cases of persistent neonatal hyperinsulinemic hypoglycemia (PNHH) were studied by a combined immunofluorescent and Feulgen technique under a computerized microscope which was used to measure the area and absorbance of beta cell nuclei. An increase of 16% was found in the nuclear area and absorbance of the beta cells in PNHH cases, in comparison with age-matched control cases. A smaller increase (9%) was found in nuclear area and absorbance of non-endocrine ductal cells in PNHH cases. In all PNHH and control cases, higher values of nuclear area and absorbance were found for beta cells in the islets of Langerhans than for nesidioblasts. The increase in average size of beta cell nuclei in PNHH can be used as a morphologic criterion for diagnosis in these cases. The increased absorbance of the nuclei stained with the Feulgen reaction is the morphologic expression of polyploidy, and has a correlation to the metabolic activity of beta cells in this disorder. We conclude that, in contrast to the normal postnatal developmental process of nesidioblastosis, nesidiodysplasia is a well-defined histologic entity, manifested by an increase of beta cell nuclear size and its DNA content.

The basic structural lesion of persistent neonatal hypoglycaemia with hyperinsulinism: deficiency of pancreatic D cells or hyperactivity of B cells?

Pancreatic tissue obtained at subtotal pancreatectomy from 15 infants with persistent hypoglycaemia with hyperinsulinism, and autopsy specimens from 23 age-matched normoglycaemic controls, were studied with morphometric methods after immunocytochemical staining of the four main islet cell types (A, B, D and pancreatic polypeptide cells). In three cases, a focal lesion was detected by gross examination. Macroscopic or microscopic examination did not distinguish the 12 other cases from controls. As found previously, nesidioblastosis was not a specific feature of the pancreas in infantile hypoglycaemia, being observed in age-matched controls as well. In cases with hypoglycaemia the volume density of B cells was not significantly increased; that of the A cells was within normal range. The volume density of pancreatic polypeptide cells was markedly augmented and that of somatostatin cells was significantly decreased. The mean nuclear volume of the B cells was increased by 40% in cases with diffuse changes, but in cases with a focal lesion this increase was restricted to the abnormal area. This finding is of decisive importance for diagnosis and has therapeutic implications. The increase in B-cell nuclear size is thought to reflect an enhanced functional activity of these cells. On the other hand, the figures obtained for the volume density of B and D cells must be viewed with some reservation because degranulation may interfere with accurate detection of these cells.

Stereological analysis of normal rabbit pancreatic islets

Stereological methods were applied to obtain morphometric data related to pancreatic islets of Langerhans in the normal rabbit. By light microscopy, it was found that 1 mm3 of pancreatic parenchyma contained 47.7 islets, constituting 2.2% of its volume. Approximately 69% of the islets had diameters less than 80 micrometer; 31% were greater than 80 micrometer. The former group of islets, however, composed only 13% of the volume of the endocrine pancreas and the latter group, 87%. Using electron microscopy, a unit volume of islet tissue was observed to consist of 86% beta cells, 7.7% alpha cells, and 2.2% delta cells. The average beta-cell volume was 1260 micrometer 3 and its cytoplasm consisted of 52.6% matrix, 12.7% rough endoplasmic reticulum, 10.2% secretory granules, 7.8% mitochondria, and 3.3% Golgi apparatus. A typical beta cell contained 662 mitochondria, intermediate (10-nm) filaments whose length totalled 50 mm, and 9,200 secretory granules with a ratio of four mature granules to each immature or "pale" granule. Within alpha and beta cells, three parameters were used for the quantitation of organelles or their component parts: 1) volume; 2) surface; and 3) numerical densities. In the beta cell, the surface densities of rough endoplasmic reticulum and Golgi membranes exceeded, by two- or threefold, their counterparts in alpha cells. Similarly, the number of beta-cell mitochondria exceeded by 30% that of alpha cells; but beta-cell mitochondrial volume was twice that of the alpha cell, as were surface densities of both inner and outer mitochondrial membranes. Volume and surface densities of secretory granules within beta cells were half the values obtained for alpha cells. An alpha cell contained three times the number of granules present in a beta cell.

Polyploidy in islets of normal and diabetic humans

This study was designed as a pilot project to determine whether the increased polyploidization of pancreatic B cells in diabetic mice reported from our laboratory is also characteristic of human diabetes. Nuclei of hematoxylin and eosin stained islets cells were traced by camera lucida and their volumes determined by semiautomatic particle size analysis. Previous studies have confirmed that nuclear volume can be used as an index of polyploidy, since, in mouse and human islets, the nuclear DNA content is directly proportional to the nuclear volume. Five insulin independent and three insulin dependent human diabetic patients and their age and sex matched controls were studied. The percentages of polyploid nuclei in insulin independent diabetic islets were elevated significantly over those in control subjects in four of five cases; the exception was an 85 year old male who was diagnosed as a diabetic only two months prior to death. Of the three insulin dependent diabetics, one, whose islets appeared otherwise normal, had a significantly greater percentage of polyploid nuclei than the controls; the other two, whose islets were markedly hyalinized, exhibited percentages of polyploid nuclei within normal ranges. The implications of relative percentages of polyploid nuclei in normal and diabetic islets and the possible relationship with previous studies of genetically diabetic mice are discussed.

Polyploidy in the pancreas of the normal and diabetic mutant mouse

The DNA content of endocrine and exocrine pancreatic nuclei of normal C57BL/KsJ and diabetic mutant C57BL/Ks-db/db mice was measured by Feulgen microdensitometry. The exocrine and endocrine pancreatic nuclei of the 4-week-old normal, 12-week-old normal, and 4-week-old (prehyperglycaemic) diabetic mutant mice contained diploid and tetraploid cells, while the 12-week-old (established hyperglycaemic) mutant contained diploid, tetraploid, and octaploid nuclei. The polyploidy in the endocrine pancreas of all these mice was confined to the B-cells, while the A-cells were always diploid.