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J A Medina

Publications and source records attributed to J A Medina.

At least 19 recordsLinked to original sources
PubMed1992

[Biliary calculi resistant to dissolution with bile acids: their heterogeneous composition and diversity of treatment response].

We have studied thirteen biliary stones resistant to biliary acids, using technical methods of stereomicroscopy, scanning electronic microscopy and EDX analyses. We have investigated changes on surface. Three biliary stones did not change and were considered resistant. Seven biliary stones appear partially dissolved and we observed many irregularities on surface and/or concentric dips in relation with cholesterol dissolution. In six cases, biliary pigment alternates with cholesterol. In three cases we observed a calcium carbonate coat on surface. One case included organic fibers. One biliary stone showed cholesterol with spherical bodies of calcium carbonate and pigment. It was a relapsed case of combined treatment. Three stones are composed of small black portions of polymerized calcium bilirubinate, rich in copper and iron. Our results demonstrate that biliary stones previously selected for treatment are a heterogeneous group. Because of this fact we get variable and unpredictable results.

Bile Acids and Salts↗
PubMed1990

Structure and composition of canine urinary calculi.

The chemical constituents of 171 specimens of canine urinary calculi have been analysed by infrared spectroscopy. The analysis revealed that 46 per cent of the total contained struvite as the major component; 26 per cent contained cystine; 16 per cent were found to be composed of whewellite and, or, weddellite; 8 per cent of urates; 3 per cent of calcium phosphate (apatite and, or, brushite) and 1 per cent of silica. A series of selected samples was also studied by scanning electron microscopy and energy dispersive X-ray analysis (EDAX). This examination revealed structures similar to human stones. Potassium and complex urates containing two or more cations were commonly found in many areas of ammonium urate and sodium urate calculi. Moreover, EDAX analysis detected a calcium enriched urate in several zones of urate calculi.

Age Factors↗
PubMed1989

Foreign body.

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Child↗
PubMed1987

The morphological changes of the pancreas in hypovolemic shock and the effect of pretreatment with steroids.

Previous reports from this laboratory have described the effect of hypovolemic shock of varying duration on the exocrine function of the pancreas, and the ability of steroids to reverse the inhibition of secretion observed. This report is a study of pancreatic morphology in prolonged hypovolemia, as well as the effect of steroid pretreatment on the pathology observed. Twelve mongrel dogs were divided into two groups, one with and one without steroid pretreatment. The animals were bled until at least 30-35% of their blood had been withdrawn, or until mean blood pressure (BP) dropped to around 60 mmHg. When BP dropped to 80-90% mmHg, six animals received intravenous (i.v.) prednisolone in 50 cc of 0.9% NaCl, at the rate of 10 cc/min, for a dosage of 30 mg/kg. Of the twelve dogs, six were exposed to 120 min of hypovolemia, and six to 180 min. At the end of the observed hypovolemic period, the blood withdrawn was quickly retransfused. After an hour of recovery, the animals were killed and their pancreases removed. The pancreases were weighed, fixed and examined by light microscopy. Three pancreases were obtained as control from animals not subjected to shock or steroids. The steroid-treated animals displayed an insignificant (5%) increase in pancreatic weight following prolonged hypovolemia. Untreated canine pancreases, on the other hand, showed a significant weight gain (37%, P less than 0.001) after 3 h of hypovolemia. Microscopically, the untreated group revealed marked interstitial edema, hemorrhage and inflammation, as well as focal acinar cell necrosis and fat necrosis, while in the steroid group only very mild edema and inflammatory changes were seen. This study indicates a beneficial effect of steroids on the morphological changes seen in shock-induced pancreatitis in canines and a possible use in the therapy of acute pancreatitis in man.

Animals↗
PubMed1987

New studies on papillary calculi.

Five hundred spontaneously passed stones were collected during a three-year period in an outpatient clinic. They were studied under a stereoscopical optical microscope. Complementary analyses were performed with infrared spectroscopy, scanning electron microscopy and EDAX. There were 142 true papillary stones (28.4%). The rest (71.6%) showed different non-papillary patterns. Papillary stones, type 1 (61 calculi), had an apatite plaque of intrapapillary origin of which 14 showed calcified tubules. Type 2 showed other substances, presumably due to crystalluria but not to an interstitial papillary process (28 stones). Type 3 showed no plaques in their concave faces (53 stones). In types 1 and 2 whewellite is a secondary growth, the plaque acting as a trigger for the development of calcium oxalate. The possibility of hidden Randall's plaques is discussed. Stones with papillary patterns are not as rare as hitherto considered and merit microscopical study.

Electron Probe Microanalysis↗
PubMed1987

Effect of partial versus complete pancreatic denervation on pancreatic secretion.

The aim of this study is to compare the effect of various stimuli on pancreatic secretion in two groups of dogs, one undergoing interruption of the cholinergic and adrenergic branches to the pancreas (long arc reflexes), and the second group undergoing total denervation of the pancreas by its isolation from stomach and duodenum (short arc reflexes). Stimulation of pancreatic secretion was accomplished by (a) hormonal, by i.v. secretin and CCK/PZ and (b) reflex stimulation by intraduodenal administration of fat (Na oleate) or amino acids (Aminosyn). After a few weeks of collected data in stimulated controls, the dogs were divided into two groups: (A) Four dogs underwent proximal truncal vagotomy, celiac ganglionectomy, and stripping of the common hepatic and gastroduodenal arteries for 2-3 cm. (B) Four dogs underwent the same procedures, but in addition the pancreas was dissected away from its vascular and nervous attachments to the duodenal wall and pyloric region, as well as from its mesenteric and peritoneal attachments. All animals were then tested with secretin, Cholecystokinin/pancreozymin (CCK/PZ), intraduodenal fat, and intraduodenal amino acids. The data obtained indicate that secretion of pancreatic bicarbonate is dependent on intact local duodeno-pancreatic nervous reflexes. Fat and amino acids stimulate the secretion of bicarbonate only when the attachments of the pancreas to the stomach and duodenum are intact. Stimulation by secretion or CCK, being humoral-hormonal mediators, appears not to be affected by the local denervation.

Amino Acids↗
PubMed1986

The effect of hypovolemic shock on pancreatic secretion.

A vascular pathogenesis of pancreatitis has been postulated in diabetics, the aged, Ortner's Syndrome, and various low-flow states. This report studies canine pancreatic secretion in a preparation of hypovolemic shock produced by controlled hemorrhage maintained for varying durations. Pancreatic secretion was collected by cannulation of the main pancreatic duct in anesthetized dogs. Secretin was administered by continuous intravenous (i.v.) infusion of 4 U/kg/h. Four 15-min samples of pancreatic juice were collected. Then the dogs were bled by arterial line withdrawing 25-30% of total blood volume or until the mean blood pressure dropped to about 60 mmHg. Blood was collected in heparinized containers for reinfusion. Blood samples for amylase and 15-min samples of pancreatic juice for volume, bicarbonate, and enzymes were obtained during hypovolemia as well as during and following restoration of the blood volume. Hypovolemia induced significant decreases in pancreatic flow, bicarbonate and amylase secretion, parameters which increased after reinfusion but never returned to pre-shock levels. Increasing the period of hypovolemia increased the inhibition of pancreatic flow, increased blood amylase elevation, and resulted in visible pancreatic edema. We conclude that pancreatic secretion is diminished by hypovolemia, that this is initially reversible when hypovolemia is brief, but that the disturbance of function progresses to inflammatory pathology when hypovolemia is prolonged.

Amylases↗
PubMed1986

The effect of steroid administration on pancreatic secretion during and after hypovolemic shock.

In a previous report from this laboratory, 1 h of hypovolemia induced a significant decrease in pancreatic flow, bicarbonate and enzyme secretion. These parameters recover after restoration of blood volume, but never return to pre-shock levels. Furthermore, increasing the period of hypovolemia produced further decreases in pancreatic flow and bicarbonate secretion only. Enzyme secretion, however, rose significantly, probably due to leakage of protein through damaged cell membranes. Prolonged hypovolemia was also accompanied by visible edema. This model of secretory changes induced by fixed periods of hypovolemic shock is ideal to study the effect of steroids on secretion and to assess its possible cytoprotective properties against early induced ischemia pancreatic pathology. Pancreatic secretion was collected by cannulation of the main pancreatic duct in 12 anesthetized dogs. Secretin was administered by continuous intravenous (i.v.) infusion at 4 U/kg/h. Four 15-min samples of pancreatic juice were collected. Then the dogs were bled, withdrawing 25-30% of total blood volume or until the mean blood pressure dropped to about 60 mmHg. At this point, 30 mg/kg of methyl prednisolone were given in 50 cm3 of NaCl i.v. to six animals. Blood samples for amylase and 15-min collections of pancreatic juice for volume, bicarbonate and enzymes were obtained during hypovolemia, as well as during and following the restoration of blood volume. The responses of the two groups differed as follows: (1) Instead of the increase in protein enzyme secretion seen in the non-steroid group with increased duration of hypovolemia, steroid-treated dogs displayed a significant decrease in protein output.(ABSTRACT TRUNCATED AT 250 WORDS)

Amylases↗
PubMed1985

Papillary stones: calcified renal tubules in Randall's plaques.

Papillary stones are small, rounded concretions with one smooth convex face and one concave face which corresponds to its implantation on the papilla and in which a whitish Randall's plaque is often present. Eighty-seven papillary stones were studied with stereoscopic, scanning electron microscopic and x-ray dispersive energy analysis. Sixty-three stones had a plaque and 13 of these showed calcified renal tubules that demonstrated their intrapapillary origin and a link between partial papillary nephrocalcinosis and renal stones.

Calcinosis↗