Biological activity of carboxy-terminal gastrin analogs

Amidated forms of gastrin are derived by post-translational processing of a large precursor peptide and stimulate gastric acid secretion via the gastrin/CCK(B) receptor. Non-amidated biosynthetic intermediates may exert biological effects through other mechanisms, but their effect on gastric acid secretion is unclear. Amidated gastrins stimulate acid secretion mainly by releasing histamine from mucosal enterochromaffin-like cells. This study examines the effects on histamine release from the vascularly perfused rat stomach of amidated gastrin-17, COOH-terminal glycine-extended gastrin-17, gastrin-17 extended at the COOH-terminal including the remaining progastrin sequence, and carboxy-terminal progastrin fragments (SAEDEN and GRRSAEDEN). Carboxy-terminal extended gastrins induced histamine release which was inhibited by the gastrin/CCK(B) antagonist L-740,093, but had to be given in concentrations 100-fold higher than amidated gastrin-17 to produce comparable effects. These progastrin-derived peptides are found in high concentrations in some patients with the Zollinger-Ellison syndrome and may contribute to acid hypersecretion and other gastrin/CCK(B) receptor mediated responses.     

Purification and crystallization of complexes modeling the active state of the fragile histidine triad protein

Fragile histidine triad protein (Fhit) is a diadenosine triphosphate (ApppA) hydrolase encoded at the human chromosome 3 fragile site which is frequently disrupted in tumors. Reintroduction of FHIT coding sequences to cancer cell lines with FHIT deletions suppressed the ability of these cell lines to form tumors in nude mice even when the reintroduced FHIT gene had been mutated to allow ApppA binding but not hydrolysis. Because this suggested that the tumor suppressor activity of Fhit protein depends on substrate-dependent signaling rather than ApppA catabolism, we prepared two crystalline forms of Fhit protein that are expected to model its biologically active, substrate-bound state. Wild-type and the His96Asn forms of Fhit were overexpressed in Escherichia coli, purified to homogeneity and crystallized in the presence and absence of ApppA and an ApppA analog. Single crystals obtained by vapor diffusion against ammonium sulfate diffracted X-rays to beyond 2.75 A resolution. High quality native synchrotron X-ray data were collected for an orthorhombic and a hexagonal crystal form.      

Bone marrow mononuclear cell count does not predict neutrophil and platelet recovery following autologous bone marrow transplant: value of the colony-forming unit granulocyte-macrophage (CFU-GM) assay

The common use of the marrow autograft mononuclear cell (MNC) count derives from positive correlative studies following allogeneic transplantation and from earlier conflicting data regarding the value of the bone marrow autograft colony-forming unit granulocyte-macrophage (CFU-GM) assay for prediction hematologic recovery after ABMT. We conducted a retrospective analysis at our institution to determine whether autograft CFU-GM levels predict engraftment of neutrophils and platelets after ABMT in heavily pretreated patients with hematologic malignancies. Between 1 January 1993 and 1 March 1995, 58 heavily pretreated patients received only marrow cells as the autograft product. Patients with Hodgkin's disease (n = 25), acute myeloid leukemia (n = 19), and non-Hodgkin's lymphoma (n = 14) underwent intensive therapy with etoposide and melphalan. Unpurged marrow containing a minimum of 1.5 x 10(8)/kg (range: 1.5-4.8) was infused. Median time to an absolute neutrophil count > or = 0.5 x 10(9)/L was 21 days (range 10-270) and median time to a platelet count > or = 20 x 10(9)/L independent of transfusions was 44 days (range 13-317). There was no correlation between autograft MNC count and neutrophil or platelet engraftment. However, a correlation between autograft CFU-GM and both platelet and neutrophil recovery was demonstrated with a threshold CFU-GM of 3 x 10(4)/kg; delayed neutrophil recovery was observed in 79% of patients below this threshold compared to only 9% in those with an autograft CFU-GM level of more than 3 x 10(4)/kg (p = 0.0001). Similarly, platelet recovery was delayed in 76% of patients below, and 20% of those above this threshold (p = 0.003). We conclude that marrow autograft CFU-GM is predictive of engraftment of both platelets and neutrophils in heavily pretreated patients after ABMT for hematological malignancies.     

Traumatic dental injuries in a cohort of 16-year-olds in northern Sweden

The prevalence and yearly incidence of traumatic tooth injury between 1 and 16 years of age were studied in a cohort of 16-year-olds, born in 1975, and residing in the County of V?sterbotten, northern Sweden. The study comprised 3007 dental records from the public dental health service. The general distribution was 50.3% girls and 49.7% boys. The records showed that 35% of the children on one or more occasions had sustained injury to their primary or permanent dentition. The frequency was nearly twice as high for boys (64%) as for girls (36%). Twenty-five percent of the 16-year-olds had met with tooth injury more than once and this group consisted predominantly of boys. The incidence of injury episodes to primary and permanent teeth was 28 per 1000 per year. The boys had sustained trauma to their teeth most frequently when they were 4 years of age and between the ages of 8 and 11. This was also true for girls at 4 and at 9 years of age, although less evidently so. In the primary dentition, the majority of dental injuries had affected the supporting tissue of the maxillary incisors. In the permanent dentition, 75% of the traumatised teeth were upper incisors. Fractures of varying severity constituted 60% of all registered diagnoses in this dentition, followed by subluxation (19%) and concussion (11%).     

Evaluation of biologic gastrin activity of compound CI-988 in the isolated, vascularly perfused rat stomach

BACKGROUND: The peptoid CI-988 has previously been shown to have high affinity for the cholecystokinin (CCK)-B/gastrin receptor and has been reported to be a powerful CCK antagonist in many systems, although it has agonist activity on histidine decarboxylase in the rat. METHODS: In the present study the effect of CI-988 on acid secretion and histamine release in the totally isolated, vascularly perfused rat stomach was assessed. RESULTS: CI-988 was found to be a gastrin agonist with regard to the stimulation of both histamine release and acid secretion. CONCLUSION: Thus, in this stomach model CI-988 behaved as a CCKB/gastrin agonist. The present study underlines the importance of testing the biologic activity of ligands in models with sufficient sensitivity.