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Biomedical subjects

C A Hernández

Publications and source records attributed to C A Hernández.

8 recordsLinked to original sources
PubMed2004

Proteolytic activities in body and faecal extracts of the storage mite, Acarus farris.

Trypsin, chymotrypsin, cathepsins B and D, aminopeptidase and carboxypeptidases A and B were detected in body extracts of the storage mite Acarus farris (Oudemans) (Astigmata: Acaridae). Faeces-enriched medium exhibited higher (10-50-fold) specific protease activity rates than those measured with mite body extracts for trypsin, chymotrypsin and carboxypeptidases A and B, suggesting that they are involved in mite digestion. However, the activity of cathepsin B was only three-fold higher in faecal than in body extracts, indicating that its presence in the lumen of the digestive tract is low compared to that of serine proteases. The activity of aminopeptidases was higher in mite bodies, indicating that they might be membrane bound. Cathepsin D activity was only detected in body extracts, indicating that this enzyme is not a digestive protease in this species. Zymograms resolved three major bands of gelatinolytic activity, but at least one protease form was only present in body extracts. Protease inhibitors of different specificity were tested in vivo to establish their potential as control agents. The development of A. farris was significantly retarded when the immature stages were fed on artificial diet containing inhibitors of serine and cysteine proteases and aminopeptidases, whereas no such effect was found with inhibitors of aspartyl proteases and carboxypeptidases. Interestingly, the most significant effects on A. farris occurred when a combination of inhibitors targeting different enzyme classes was supplied mixed in the diet, suggesting a synergistic toxicity. Several plant lectins were also tested, but only wheat germ agglutinin and concanavalin-A affected development.

Acaridae↗
PubMed1997

Common biliary-pancreatic conduit stenosis induces pancreobiliary reflux.

A striking pancreatic juice reflux toward the biliary tree (PR) has frequently been found in subjects with common bile-pancreatic conduit (CBPC) and gallstone-induced acute pancreatitis (SAP). Our aim was to determine the role of the CBPC functional diameter as a potential trigger of PR. The CBPC was calibrated in three groups of patients: (A) patients with gallbladder stones using intraoperative direct cholangiometry (n = 24), (B) patients after surgical removal of common bile duct stones using postoperative cholangiometry via T-drain (n = 6), and (C) patients with SAP using the same procedures as in group B (n = 6). In all patients in groups B and C, aliquots of bile were collected and assayed for pancreatic amylase content. The mean functional diameter of the CBPC varied from 0.80 mm in patients in groups A and B to 0.47 mm in group C (p < 0.001). The bile samples of group B contained low concentrations of amylase, whereas high values could be found in all samples of group C. We conclude that PR is a frequent event occurring after bile duct revision concerning small amounts of pancreatic juice. However, CBPC functional stenosis as seen in patients with SAP obviously induces PR with high amounts of pancreatic juice.

Acute Disease↗
PubMed1993

Sphincter stenosis and gallstone migration through the biliary tract.

We have investigated whether stenosis or insufficiency at the duodenal papilla results from the passage of a gallstone through the biliary tract. In three groups of patients after cholecystectomy we studied meal-stimulated pancreatic enzyme activity in T-drain bile from the common bile duct. Group A had gallbladder stones only; group B had gallbladder stones and bile duct stones; and group C had an episode of acute gallstone-induced pancreatitis, which was taken as direct evidence for gallstone migration into the duodenum. Reflux of pancreatic juice into the common bile duct was absent in group A, was occasionally found in group B, and was strikingly increased in group C. We conclude that passage of a gallstone through the biliary tract causes functional stenosis of the sphincter of Oddi and allows for a common channel between the pancreatic duct and the common bile duct. It does not cause sphincter insufficiency as previously assumed.

Biliary Tract↗
PubMed1993

How to choose the training data for neural network medical diagnosis systems.

This paper presents a research work on the generalization capability of Multilayers Feedforward Neural Networks with Backpropagation under the point of view of training data. The research is focused on the case of neural networks medical diagnosis systems and it is shown through 3-D plots of the neural network performance an appropriate way to select the training data distribution which should be used for the design of the neural network. A real world distribution which can be obtained by randomly sampling a medical data base is more appropriate than an equal distribution which is the normally used distribution in the bibliography. The results are presented by using a medical diagnosis data base: different diagnosis of one main symptom: vaginal discharge of non-menstruating women.

Computer Simulation↗
PubMedDate not supplied

Gallstones and acute pancreatitis--mechanisms and mechanics.

The observation that necrotizing pancreatitis and gallstones can be associated is more than 300 years old [1]. Since the beginning of our century, numerous investigations have addressed the question as to how gallstones cause pancreatitis. Despite this effort and many excellent clinical and experimental studies, few pathophysiological issues in gastroenterology have remained so controversial and even fewer have found advocates with such incompatible views and uncompromising convictions. We will review the past and present theories regarding the pathophysiology of gallstone-induced pancreatitis and outline the therapeutic consequences implied by these concepts.

Acute Disease↗