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H Linares

Publications and source records attributed to H Linares.

At least 19 recordsLinked to original sources
PubMed1991

The application of solvent-processed human dura in experimental tracheal reconstruction.

To evaluate the role of solvent-processed human cadaveric dura in experimental tracheal reconstruction, anesthetized piglets underwent an elliptical excision of a four-ring segment of the trachea. Twelve animals were randomly divided into two equal groups: in group I, the resected trachea was rotated 180 degrees and sutured into position; in group II, the resected trachea was replaced with dura. The animals were extubated after the operation, and endotracheal stents were not used. Tracheal dimensions were recorded, and tissues were evaluated for mechanical compliance (percent elongation/displacement). Histology of the grafts was characterized by fibrosis and granulation tissue, and there were no distinguishing features between groups. The data suggest that solvent-processed human dura has compliance and patency comparable to those of autologous free-grafted trachea and that it may prove useful as an adjunct to reconstructive tracheal surgery in infants.

Animals↗
PubMed1990

Endotoxin (LPS) increases mesenteric vascular resistance (MVR) and bacterial translocation (BT).

Endotoxemia is responsible for many of the pathophysiologic alterations that occur with Gram-negative sepsis. We utilized a chronic ovine model to determine the hemodynamic disturbances in the gastrointestinal tract during endotoxemia. Sheep with indwelling arterial, venous, and pulmonary arterial catheters were used. An ultrasonic flow probe was placed on the cephalic mesenteric artery. The animals were subjected to: 1) Ringer's lactate infusion (sham n = 6); or 2) 1.5 mcg/kg E. coli endotoxin (n = 6) over over a period of one half hour and were monitored for 48 hours. They were then sacrificed and specimens of mesenteric lymph node, liver, spleen, kidney, and lung obtained for bacteriologic cultures and histologic analysis. Sheep receiving endotoxin showed more than 50% reduction in the mesenteric blood flow. Mesenteric vascular resistance increased while non-mesenteric systemic vascular resistance decreased. The increase in the total systemic vascular resistance, noted during endotoxemia, was thus likely due to the increase in the mesenteric vascular resistance. At autopsy there were positive cultures for microorganism in the mesenteric lymph nodes in six out of six sheep with endotoxemia as compared to one out of six of control. Thus the vasoconstriction in the mesenteric areas may have resulted in bacterial translocation from the GI tract.

Animals↗
PubMed1987

Failure of TPN supplementation to improve liver function, immunity, and mortality in thermally injured patients.

Hypermetabolism with negative nitrogen balance and immune deficiencies characterize the systemic response to major thermal injury. Patients with burns greater than 50% of the total body surface area (TBSA) initially have poor gastrointestinal function, making it difficult to deliver sufficient enteral calories to meet nutritional requirements. Controversy has developed over whether to supplement oral alimentation with total parenteral nutrition (TPN) early in their treatment. This study randomly assigned 28 patients with burns greater than 50% TBSA to receive TPN supplementation or no TPN supplementation in the first 10 days postburn. Patients receiving TPN supplementation had significantly lower T-cell helper-to-suppressor cell ratios than the unsupplemented group. However, there was no difference in mortality between the groups (eight in each). All patients who died developed hepatomegaly associated with fatty infiltration cholestasis and antemortem liver function abnormalities, indicating that this syndrome is the result of burn injury itself, not TPN.

Adult↗
PubMed1987

Determinants of mortality in pediatric patients with greater than 70% full-thickness total body surface area thermal injury treated by early total excision and grafting.

Recent advancements in burn care have improved the survival rates of victims with severe burn injuries. The total mortality rate in a series of 1,057 pediatric patients admitted to Shriners Burns Institute Galveston Unit between 1982 and 1986 was 2.7%. The burn size resulting in a 50% death rate was 95% of the total body surface area (TBSA). In this study 19 survivors and 13 nonsurvivors with greater than 70% full-thickness TBSA burn injuries were compared. All survivors were adequately resuscitated upon arrival 11% sustained an inhalation injury. Forty-six per cent of the nonsurvivors sustained an inhalation injury; 31% were not initially adequately resuscitated. The presence of preadmission shock and inhalation injury were early determinants of mortality with secondary renal, pulmonary, or cardiovascular collapse being the later predictors of mortality in these massively burned pediatric patients.

Adolescent↗
PubMed1987

Pathways for water absorption and physiological role of the lateral interspaces in the kidney tubule.

Possible routes for water and salt flow and the most likely theories that describe coupling between water and salt flow across leaky epithelia are presented. The osmotic theories seem the most likely ones. However, several of the theories have weaknesses that render them unsatisfactory, in particular because of the possibility of paracellular water flow in these epithelia. Puzzling are the findings that measurements of the cellular water osmotic permeability give figures that are too low for some of the exclusively transcellular theories to work. If these observations hold in the future, it may be shown that part of the water moves through paracellular pathways in these leaky epithelia. This view is supported by the observation that large extracellular markers are dragged by volume flow. Finally, experimental evidence is reviewed indicating that changes in the luminal area concentration may modulate the functional state of the nephron junctional complexes.

Animals↗
PubMed1987

Polymorphic organization of the endoplasmic reticulum of the Malpighian tubule. Evidence for a transcellular route.

Isosmotic fluid absorption carried out by many mammalian epithelia appears to be similar to the isosmotic secretion of insect epithelia such as the Malpighian tubules, which are responsible for urine formation and osmoregulation. We have studied by electron microscopy (80 kV) the three-dimensional characteristics of organelles in the Malpighian tubules of Rhodnius prolixus using thick sections (0.3-0.5 microns) and uranyl and lead impregnation. The ER presents a different organization in the upper (distal) and lower (proximal) segments of the Malpighian tubule. In distal secretory segment, the ER forms a network made of chains of vesicles having irregular shapes (ca. 0.06 micron in diameter) connected to each other by canaliculi while in the lower absorptive segment, the ER is made of parallel saccules arranged in stacks or whorls in the central region of the cytoplasm. In both segments, the ER network extends throughout the cytoplasm from the basolateral infoldings to the apex between the many mitochondria present in these two areas. A unique feature of these cells, revealed by thick sections, is the presence in each microvillus of either a mitochondrion or an ER canaliculus in continuity with the ER network. The ER does not seem to have any specific association with mitochondria or other organelles. As in the mammalian nephron, this ER organization is most likely related to specific segmental functions and adds support to its potential role as a transcellular epithelial route.

Animals↗
PubMed1986

Etiology of the pulmonary pathophysiology associated with inhalation injury.

This study describes an experimental model of smoke inhalation injury in sheep in which the same pathophysiologic alterations occur as with clinical inhalation injury in man. Diffuse pulmonary mucosal sloughing with atelectasis and emphysema with concomitant development of pulmonary edema results in a decrease in arterial oxygen and progressive pulmonary deterioration which results in a substantial mortality. Increased pulmonary edema fluid is shown to be caused by an increased microvascular permeability to protein with pulmonary lymph and tracheobronchial fluid, a filtrate of plasma. Concomitant with this increase in microvascular permeability is an influx of neutrophils, release of proteolytic enzymes and an identified presence of the metabolite of the prostanoid thromboxane A2 which are postulated as contributors to the progressive pulmonary dysfunction post inhalation injury.

Animals↗
PubMed1985

Pathways for volume flow and volume regulation in leaky epithelia.

Continuous pathways must pierce the cell membrane to be used by water during osmotic equilibration between proximal straight tubular cells and the external medium, because a) the water osmotic permeability coefficient of the basolateral plasma membrane, Poscb, is high; b) its activation energy, Ea, is as that of free water movement and c) pCMBS inhibits markedly (but reversibly) Poscb and increases Ea to values similar to those observed in lipid bilayers without pores. d) Preliminary measurements of Pd the water diffusive permeability coefficient using NMR indicate that Poscb/Pd is near 4 - 5. The following two observations indicate that a significant paracellular water flow must exist in leaky epithelia. Namely, a) large extracellular solutes are dragged by water in four leaky epithelia: gall bladder, Necturus proximal tubule, rat proximal tubule and Rhodnius malpighian tubule. b) The transcellular water osmotic permeability coefficient is smaller than the transepithelial values available in the rabbit proximal straight tubule. This requires a significant paracellular permeability.

Animals↗
PubMed1984

Effect of para-chloromercuribenzenesulfonic acid and temperature on cell water osmotic permeability of proximal straight tubules.

The apparent Arrhenius energy of activation (Ea) of the water osmotic permeability (Pcos) of the basolateral plasma cell membrane of isolated rabbit proximal straight tubules has been measured under control conditions and after addition of 2.5 mM of the sulfhydryl reagent, para-chloromercuribenzenesulfonic acid (pCMBS), of mersalyl and of dithiothreitol. Ea (kcal/mol) was 3.2 +/- 1.4 (controls) and 9.2 +/- 2.2 (pCMBS), while Pcos decreased with pCMBS to 0.26 +/- 0.17 of its control value. Mersalyl also decreased Pcos both in vitro and in vivo (using therapeutical doses). These actions of pCMBS and mersalyl were quickly reverted with 5 mM dithiothreitol and prevented by 0.1 M thiourea. Ea for free viscous flow is 4.2 and greater than 10 for non-pore-containing lipid membranes. By analogy with these membranes and with red blood cells, where similar effects of pCMBS on Pos are observed, it is concluded that cell membranes of the proximal tubule are pierced by aqueous pores which are reversibly shut by pCMBS. Part of the action of mercurial diuretics can be explained by their action on Pcos.

Animals↗
PubMed1984

Osmotic water permeability of the apical membrane of proximal straight tubular (PST) cells.

Osmotic steps, delta C, were produced across the apical cell membrane of isolated rabbit PST by perfusing their lumens with double barreled micropipettes at a rate of 0.5-0.8 nl/s. delta C = 15-46 mOsmolar were induced with mannitol. Changes in luminal diameter were recorded as a function of time with a TV camera and an integrator-processor system with space and time resolutions of 0.03 micron and 0.0167 s (3). The tubules were bathed with oil. Outer tubule diameter was time invariant. Pcaos, the apical cell osmotic permeability was therefore calculated from cell volume changes with time in units of 10(-4) cm3/cm2 X s. Osmolar. Pcaos was independent of delta C. The mean is 22.8 +/- 1.3 (n = 55). With a basolateral permeability of 50.4 (3,12), the transcellular permeability is 14 (same units) smaller than the transepithelial values available. This leads to the conclusion that a significant paracellular water osmotic permeability must exist.

Animals↗
PubMedDate not supplied

Increased mortality with intravenous supplemental feeding in severely burned patients.

Patients with large cutaneous burns are characterized by an elevated metabolic rate and lose up to 25% of their body weight within 3 weeks. A previous study suggested that intravenous supplementation to attain nutritional requirements was of no benefit in patients with cutaneous burns covering greater than 50% of their total body surface area. In this study 39 patients with burns greater than 50% of their total body surface area were randomly assigned to receive intravenous supplementation of enteral calories (n = 16) or enteral calories alone (n = 23). Intravenous supplementation decreased the amount of enteral calories that patients with burns could tolerate. The mortality rate was significantly higher (p less than 0.05) in the intravenously supplemented group at 63% as compared with 26% in the group receiving enteral calories alone. Both groups showed significant decrease in natural killer cell activity when compared with controls at both 0 to 7 and 7 to 14 days after injury. T cell helper/suppressor ratios were depressed in both groups when compared with controls; however, the intravenously supplemented group was significantly depressed at 7 to 14 days after burn. Both groups demonstrated hepatomegaly, moderate fatty infiltration, and cholestasis. It is suggested that intravenous supplementation should be carefully evaluated and used only in patients with total enteral failure.

Adult↗