LOW-PROTEIN DIET IMPAIRS GLUCOSE-INDUCED INSULIN-SECRETION FROM AND CA-45 UPTAKE BY PANCREATIC RAT ISLETS

Glucose-induced insulin secretion rom and Ca-45 uptake by isolated pancreatic islets, derived from rats fed with normal (NPD) or low protein diet (LPD), were studied. Insulin secretion from both types of islets in response to increasing concentrations of glucose followed an S-shaped pattern. However, basal secretion observed at substimulatory concentrations of glucose (0-5.6 mM), as well as maximal release, obtained at 16.7 mM or higher glucose concentrations were significantly reduced in islets from LPD. Furthermore, in LPD rat islets, the dose-response curve to glucose was clearly shifted to the right compared with NPD islets, with the half-maximal response occurring at 8.5 and 14.4 mM glucose for NPD and LPD islets, respectively. In islets from NPD rats, the Ca-45 content, after 5 or 90 min in the presence of 8.3 mM glucose, was higher than that observed for islets kept at 2.8 mM glucose and increased further at 16.7 mM glucose. After 5 min of incubation, the Ca-45 uptake by LPD islets in the presence of 8.3 mM glucose was slightly higher than basal values (2.8 mM glucose); however, no further increase in the Ca-45 uptake was noticed at 16.7 mM glucose. In LPD islets a significant increase in Ca-45 uptake over basal values was registered only at 16.7 mM glucose, after 90 min of incubation. These data indicate that the poor secretary response to glucose observed in islets from LPD rats may be related to a defect in the ability of glucose to increase Ca2+ uptake and/or to reduce Ca2+ efflux from beta-cells.

Structure of human uropepsin at 2.45 angstrom resolution

The molecular structure of human uropepsin, an aspartic proteinase from the urine produced in the form of pepsinogen A in the gastric mucosa, has been determined by molecular replacement using human pepsin as the search model. Crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 50.99, b = 75.56, c = 89.90 Angstrom. Crystallographic refinement led to an R factor of 0.161 at 2.45 Angstrom resolution. The positions of 2437 non-H protein atoms in 326 residues have been determined and the model contains 143 water molecules. The structure is bilobal, consisting of two predominantly beta -sheet lobes which, as observed in other aspartic proteinases, are related by a pseudo-twofold axis. A model of the uropepsin-pepstatin complex has been constructed based on the high-resolution crystal structure of pepsin complexed with pepstatin.

HMB-45 - A review

HMB-45, named for the immunogen used (human melanoma, black) is a monoclonal antibody developed 10 years ago by Gown and colleagues to a whole-cell extract of a human melanoma. Over the years, it has been demonstrated that HMB-45 is a highly sensitive and specific reagent for the identification of melanoma. More recently, it has been found that HMB-45 reacts with a protein designated gp100-cl, which is apparently related to the pmel 17 gene product. Because gp100-cl is a melanosomal matrix protein, HMB-45 is more correctly identified as an organelle-specific rather than tumor-specific reagent. HMB-45 immunoreactivity is seen in normal fetal and neonatal melanocytes but not in adult resting melanocytes. Reactive or proliferating melanocytes present in inflamed adult skin or in skin overlying certain dermal neoplasms, can also ''re-express'' the HMB-45-defined antigen. Whereas the vast majority of melanomas are HMB-45-positive, one important exception is desmoplastic malignant melanoma, which consistently demonstrates a much lower rate of expression of the HMB-45-defined antigen compared with other types of melanoma. In recent years there have been scattered reports of HMB-45 immunoreactivity in nonmelanomatous tumors, such as breast and other carcinomas, but virtually all these reports employed commercial ascites fluid preparations of HMB-45 antibody that were subsequently shown to be contaminated with nonspecific antibodies. Thus, for most practical purposes, a positive reaction with HMB-45 indicates active melanosome formation and, therefore, melanocytic differentiation. There is also a set of HMB-45-positive tumors that consistently manifest HMB-45 immunoreactivity but do not display obvious pigmentation: clear cell ''sugar'' tumor of the lung, angiomyolipoma, and lymphangiomyomatosis. Nonetheless, these lesions are all unified by recent ultrastructural studies that confirm the presence premelanosomes. Curiously, all three lesions also manifest evidence for simultaneous smooth-muscle differentiation. HMB-45 remains, therefore, a reliable marker of melanoma but may also provide insights into a rare group of tumors.

Lesões do trato gastrointestinal na síndrome da imunodeficiência adquirida: estudo de 45 necrópsias consecutivas.

This study was designed to evaluate retrospectively the frequency and etiology of the gastrointestinal (GI) lesions in 45 consecutive necropsies of adult patients with Acquired Immunodeficiency Syndrome (AIDS). Gross descriptions and histological sections of the GI tract, from mouth to anus, were reviewed. The slides were H&E stained, and when necessary special stains and immunohistochemical methods were also employed. There were lesions in GI tract in 37 (82.3%) patients; the mouth was the segment most frequently involved (73.3% of the cases), followed by the colon (55.5%). Multiple lesions occurred in 17 (37.7%) cases. Cytomegalovirus caused colonic lesions in 35.7% of the cases. Candidiasis was observed in 26.6% mainly in the mouth and herpes simplex (8.8%) was the important agent of esophageal lesions. Oral hairy leukoplasia associated with HPV was found in 16 (35.5%) cases. Neoplasia was diagnosed in 7 (15.5%) cases: four Kaposi's sarcoma, two anal intramucosal carcinomas and one gastric lymphoma. Our data confirm the high frequency and variety of GI tract alterations in AIDS.

Acta resumida de la 49a sesión celebrada en Río de Janeiro el jueves 23 de abril de 1953 a las 16.45 horas

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Acta resumida de la 70a sesión celebrada La Paz el miércoles 29 de mayo a las 11.45 horas

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