Construction of a model of the human proximal colon

The objective of the present study was to construct a system that re-creates the conditions of fermentation and absorption of the human proximal colon. The model was constructed using a glass tube with an internal dialysis membrane tube. The food substrate was fed into the dialysis membrane three times a day simulating a typical human feeding. The substrate contained 58% carbohydrates, 35% proteins, 3% fiber, 3% starch, and 1% lipids on dry weight base, with 90% moisture. The inoculum was a fecal culture propagated in TSB. The intestinal absorption was simulated using a polyethylene glycol (PEG) solution running continuously outside the dialysis membrane. All microorganisms increased their counts after inoculation, and reached higher counts generally after substrate feed. The most important short chain fatty acids (SCFA: acetic, propionic and butyric acids) were analyzed, and their concentrations inside and outside the membrane were significantly different due to the extraction efficiency of the PEG solution. The greatest production occurred at 48 h. SCFA ratios showed that at the beginning, acetate was the predominant compound, but after 12 h the proportion of butyrate increased and the acetate was decreased. This SCFA production pattern is similar to that reported for the proximal colon in live systems. Continuous operation of the colon model for 48 h was enough to reveal the development of microorganisms and SCFA production. This model reproduced the conditions of the human proximal colon adequately and can be used to study the development of colonic microbiota.     

Age at death determination by means of femoral frequency of secondary osteons

A statistical model for the estimation of the age at death is defined and tested to evaluate its performance. It is characterized by the probability of the femoral frequency of secondary osteons for any given age, that we compute by means of 28 scheletons of Italian subjects. In a standard case we obtain good evalutations of the methods, while in practice it can be used according to the objectives of the particular investigation. Moreover other surveys could easily be added to our data in order to obtain a more powerfool tool.     

Apoptosis and cell proliferation in proximal tubular cells exposed to apoptotic bodies. Novel pathophysiological implications in cisplatin-induced renal injury

The therapeutic efficacy of the antineoplastic drug cisplatin is limited by its nephrotoxicity, which affects particularly to proximal tubular cells (PTC). Cisplatin-induced cytotoxicity appears to be multifactorial and involves inflammation, oxidative stress as well as apoptosis. We have recently shown that the cyclo-oxygenase-2 (COX-2)/intracellular prostaglandin E₂ (iPGE₂)/EP receptor pathway mediates the apoptotic effect of cisplatin on human proximal tubular HK-2 cells. Here, we studied the effects on HK-2 cells of apoptotic bodies (ABs) generated after treatment of HK-2 cells with cisplatin. We found that ABs inhibited cell growth, induced apoptosis and increased COX-2 expression and iPGE₂ in ABs-recipient HK-2 cells. Inhibition of the COX-2/iPGE₂/EP receptor pathway in these cells prevented the effects of ABs without interfering with their internalization. Interestingly, 2nd generation ABs (i.e. ABs released by cells undergoing apoptosis upon treatment with ABs) did not trigger apoptosis in naïve HK-2 cells, and stimulated cell proliferation through the COX-2/iPGE₂/EP receptor pathway. These results suggest that ABs, through iPGE₂-dependent mechanisms, might have a relevant role in the natural history of cisplatin-induced acute kidney failure because they contribute first to the propagation of the noxious effects of cisplatin to non-injured PTC and then to the promotion of the proliferative tubular response required for proximal tubule repair. Since iPGE₂ also mediates both cisplatin-induced HK-2 cell apoptosis, intervention in the COX-2/iPGE₂/EP receptor pathway might provide us with new therapeutic avenues in patients with cisplatin-induced acute kidney injury.     

Regional permeability differences between the proximal and distal portions of the isolated salmonid posterior intestine

The objective of this study was to assess regional variations in the permeability of the salmon posterior intestine and to evaluate the effect of permeability enhancers as a basis for oral delivery of biologically active peptides. Proximal and distal portions of the posterior intestine of the chinook salmon (Oncorhynchus tshawytscha) were removed, mounted as flat sheets in Ussing chambers and superfused with trout Ringer's. Intestinal permeability was assessed under short-circuit conditions by measurement of ¹⁴C-mannitol (mucosal to serosal) flux. Tissues were treated either with the mucolytic agent dithiothreitol (10 mmol · l⁻¹), the permeability enhancer sodium deoxycholate (5.0 mmol · l⁻¹) or both and compared to untreated controls. Both proximal and distal control tissues had low permeabilities, but the distal region had a lower transepithelial electrical resistance and produced significantly less mucus. Treatment with either dithiothreitol or sodium deoxycholate alone reduced mucus adhering to tissue in both regions but did not increase permeability or change transepithelial electrical resistance. In the distal region, sequential treatment with both agents significantly reduced adhering mucus, decreased transepithelial electrical resistance, and increased tissue permeability. The salmon posterior intestine can be divided into proximal and distal regions. The distal region is more likely to have the necessary permeability and responsiveness to enhancement for the successful delivery of peptides or polar drugs. Accepted: 14 January 1997     

Studies of the regulation of renal gluconeogenesis in normal and Pi depleted proximal tubule cells

Pi depletion of proximal tubule cells isolated from mouse kidney results in a decrease in the cell content of fructose-2,6-bisphosphate and an increase in the rate of gluconeogenesis from pyruvate, malate and succinate. Gluconeogenesis from glycerol is unaffected by Pi depletion. Introduction of fructose-2,6-bisphosphate into the cytosol of ATP-permeabilized cells is accompanied by a fall in gluconeogenesis. The presence of external Ca2+ stimulates gluconeogenesis. When cytosolic Ca2+ is raised to 1.8 microM by permeabilization, the resealed cells still require 2.5 mM Ca2+ in the bathing medium in order to perform gluconeogenesis at the maximum rate. Cells permeabilized in the presence of cAMP show a decreased rate of glucose production. Phorbol ester stimulates gluconeogenesis provided that the phorbol treatment is performed in the absence of Ca2+ ions. It is suggested that Pi depletion may stimulate pyruvate carboxylase activity and facilitate the entry of certain gluconeogenic substrates into mitochondria. It is also proposed that important aspects of the control of renal gluconeogenesis by parathyroid hormone are mediated by protein kinase C.