Online Maintenance of Minimal Directed Hypergraphs

In this paper we deal with directed hypergraphs, a generalization of directed graphs previously introduced in the literature. In particular, we investigate the problem of maintaining efficiently information about minimal hyperpaths while new hyperarcs are inserted. We consider several definitions of minimal hyperpath and we prove that accordingly to some of such definitions the problem of finding the minimal hyperpath is NP-complete, while hyperpaths with minimal GAP and minimal RANK can be found in polynomial time. We deal with this problem in an online fashion, by allowing insertions of hyperarcs in the hypergraphs. We present data structures and algorithms which allow to return a hyperpath with minimal GAP or RANK between an arbitrarily given pair of nodes in a time which is linear in its size. The total time required to maintain the data structure during the insertion of new hyperarcs is (9(m n2) for min-GAP and (9(m n2 log n) for min-RANK (where m is the total size of the description of the hyperarcs and n is the number of nodes). These results are useful in applications where directed hypergraphs are known to be a suitable model (e.g. transition networks, rewriting systems, database schemes, logic programming and problem solving)

Dynamic Data Structures for Series Parallel Digraphs

We consider the problem of dynamically maintaining general series parallel directed acyclic graphs (GSP dags), two-terminal series parallel directed acyclic graphs (TTSP dags) and looped series parallel directed graphs (looped SP digraphs). We present data structures for updating (by both inserting and deleting either a group of edges or vertices) GSP dags, TTSP clags and looped SP digraphs of m edges and n vertices in O( log n) worst-case time. The time required to check whether there is a path between two given vertices is O(log n), while a path of length k can be traced out in O(k + log n) time. For GSP and TTSP dags, our data structures are able to report a regular expression describing all the paths between two vertices x and y in O(h + log n), where h ≤ n is the total number of vertices which are contained in paths from x to y. Although GSP dags can have as many as O(n2) edges, we use an implicit representation which requires only O(n) space. Motivations for studying dynamic graphs arise in several areas, such as communication networks, Incremental compilation environments and the design of very high level languages, while the dynamic maintenance of series parallel graphs is also relevant in reducible flow diagrams

Renal metabolism and urinary excretion of platelet-activating factor in the rat.

The origin of platelet-activating factor (PAF) in the urine remains ill defined. The present study documents that [3H]PAF (3.5 mu Ci) injected into the renal artery of isolated control rat kidney preparations perfused at constant pressure with a cell-free medium containing 1% bovine serum albumin (BSA) was excreted in negligible amounts (0.034%) in the urine, whereas 6% was retained by the kidney. When kidneys were perfused with a BSA-free medium, 0.029 and 71% of the total radioactivity added to the perfusate was recovered in the urine and in the renal tissue, respectively. [3H]PAF urine excretion in proteinuric kidneys from adriamycin-treated rats was still negligible (0.015%). Analysis of the renal tissue-retained radioactivity in control and proteinuric kidneys perfused with 1% BSA indicated metabolism into long chain acyl-sn-glycero-3-phosphorylcholine species, lyso-PAF, glycerols, and intact PAF. Thin layer chromatography analysis of [3H]glycerol fraction in these renal extracts showed two major components comigrating with 1-O-alkylglycerol and 1-O-alkyl-2-fatty acylglycerol. Isolated proximal tubules, but not glomeruli from nephrotic rats exposed to increasing concentrations of BSA (0-4%), had a higher PAF uptake than control tubules for BSA concentrations ranging from 0 to 0.1%. Our findings in the isolated perfused kidneys indicate that, in normal conditions, circulating PAF is excreted in the urine in negligible amounts and that the altered glomerular permeability to proteins does not affect this excretion rate. Moreover, analysis of renal tissue radioactivity documented that the renal metabolism of PAF is comparable in control and nephrotic kidneys

Solitary Peutz-Jeghers Polyp in a Paediatric Patient

Hamartomatous polyps of Peutz-Jeghers are mostly found in patients affected by Peutz-Jeghers syndrome (PJS), but they can be rarely encountered in the general population. It is unclear whether a solitary Peutz-Jeghers polyp (PJP) is an incomplete form of PJS or a separate entity. We report a case of solitary PJP in a paediatric patient in whom the other features of PJS were absent. The patient underwent laparotomy due to small bowel intussusception secondary to an ileac polyp. Histological examination showed the characteristic features of PJP, but the patient did not fulfill the WHO criteria for PJS diagnosis (negative family history for PJS and absence of mucocutaneous pigmentation); moreover analysis of the STK11/LKB1 gene did not reveal any genomic abnormality. The clinical and investigative findings in our case suggest that the solitary PJP can be considered a different clinical entity from PJS

Predictors of weight loss and reversal of comorbidities in malabsorptive bariatric surgery

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Massive Weight Loss Decreases Corticosteroid-Binding Globulin Levels and Increases Free Cortisol in Healthy Obese Patients An adaptive phenomenon?

OBJECTIVE—Obesity, insulin resistance, and weight loss have been associated with changes in hypothalamic-pituitary-adrenal (HPA) axis. So far, no conclusive data relating to this association are available. In this study, we aim to investigate the effects of massive weight loss on cortisol suppressibility, cortisol-binding globulin (CBG), and free cortisol index (FCI) in formerly obese women. RESEARCH DESIGN AND METHODS—Ten glucose-normotolerant, fertile, obese women (BMI >40 kg/m2, aged 38.66 ± 13.35 years) were studied before and 2 years after biliopancreatic diversion (BPD) when stable weight was achieved and were compared with age-matched healthy volunteers. Cortisol suppression was evaluated by a 4-mg intravenous dexamethasone suppression test (DEX-ST). FCI was calculated as the cortisol-to-CBG ratio. Insulin sensitivity was measured by an euglycemic-hyperinsulinemic clamp, and insulin secretion was measured by a C-peptide deconvolution method. RESULTS—No difference was found in cortisol suppression after DEX-ST before or after weight loss. A decrease in ACTH was significantly greater in control subjects than in obese (P = 0.05) and postobese women (P ≤ 0.01) as was the decrease in dehydroepiandrosterone (P ≤ 0.05 and P ≤ 0.01, respectively). CBG decreased from 51.50 ± 12.76 to 34.33 ± 7.24 mg/l (P ≤ 0.01) following BPD. FCI increased from 11.15 ± 2.85 to 18.16 ± 6.82 (P ≤ 0.05). Insulin secretion decreased (52.04 ± 16.71 vs. 30.62 ± 16.32 nmol/m−2; P ≤ 0.05), and insulin sensitivity increased by 163% (P ≤ 0.0001). Serum CBG was related to BMI (r0 = 0.708; P = 0.0001), body weight (r0 = 0.643; P = 0.0001), body fat percent (r0 = 0.462; P = 0.001), C-reactive protein (r0 = 0.619; P = 0.004), and leptin (r0 = 0.579; P = 0.007) and negatively to M value (r0 = −0.603; P = 0.005). CONCLUSIONS—After massive weight loss in morbidly obese subjects, an increase of free cortisol was associated with a simultaneous decrease in CBG levels, which might be an adaptive phenomenon relating to environmental changes. This topic, not addressed before, adds new insight into the complex mechanisms linking HPA activity to obesity