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L Marzella

Publications and source records attributed to L Marzella.

At least 37 records · Page 2Linked to original sources
PubMed1989

Morphologic characterization of acute injury to vascular endothelium of skin after frostbite.

Cyclo-oxygenase inhibitors and free-radical scavengers protect the skin against necrosis induced by frostbite. However, the tissue component(s) that determine the evolution of skin necrosis and the mechanism of this pharmacologic protection are not precisely defined. We have studied freezing injury to rabbit ears by serial biopsies examined by light and electron microscopy. The morphologic evidence of skin injury due to freezing was localized exclusively in the endothelial cells, particularly in the arterioles. Within 1 hour, the entire microvasculature demonstrated endothelial damage. Intravascular platelet aggregation occurred just after thawing and closely paralleled the endothelial cell injury. Very few neutrophils were seen initially (at 10 minutes). By 1 hour, leukocyte aggregates were present, and they further increased at 6 hours. Swelling of the interstitium started 10 minutes after thawing, while extravasation of erythrocytes began to appear by 6 hours. Parenchymal elements of skin were relatively free of damage. In the ear cartilage, the chondrocytes showed evidence of damage immediately after freezing. The administration of superoxide dismutase (SOD) during thawing (reperfusion) did not qualitatively alter any of the initial morphologic changes induced by freezing. We conclude that the endothelial cell is the initial target of injury induced by freezing, an initial injury that is mediated by a non-free-radical-mediated mechanism. It is likely that this acute injury ultimately compromises blood flow and leads to skin necrosis.

Animals↗
PubMed1989

Hyperoxia and the antimicrobial susceptibility of Escherichia coli and Pseudomonas aeruginosa.

We have tested the ability of hyperoxia (98% O2-2% CO2 at 2.8 atmospheres absolute [ca. 284.6 kPa]) to enhance killing of Escherichia coli (serotype O18 or ATCC 25922) by nitrofurantoin, sulfamethoxazole, trimethoprim, gentamicin, and tobramycin. We have also looked for interactions between hyperoxia and the aminoglycosides against Pseudomonas aeruginosa ATCC 27853. Hyperoxia significantly enhanced bacteriostatic activity of nitrofurantoin and trimethoprim as measured by MIC testing. The possibility exists that these effects might be due to the method required to tests MICs under hyperoxic conditions rather than to the effect of hyperoxia itself. In addition, hyperoxia enhanced killing of bacteria by trimethoprim as measured by MBC testing. Hyperoxia decreased numbers of E. coli by 1.3 log10 and P. aeruginosa by 2.7 log10 in cation-supplemented Mueller-Hinton broth medium. The bacteriostatic effects of hyperoxia did not affect MICs of gentamicin or tobramycin. The lack of interaction between hyperoxia and gentamicin or tobramycin was confirmed by determining the number of viable bacteria remaining after 24 h of exposure to hyperoxia by using a pour plate method. We conclude that hyperoxia potentiates the antimicrobial activity of the reduction-oxidation-cycling antibiotic tested (nitrofurantoin) and of one of the antimetabolites tested (trimethoprim). Hyperoxia does not enhance the bactericidal effects of gentamicin and tobramycin, which require oxidative metabolism for transport into bacterial cells.

Anti-Bacterial Agents↗
PubMed1989

Splanchnic blood flows in a rat model of antibiotic-controlled intra-abdominal abscess during normoxia and hyperoxia.

We have characterized splanchnic blood flows in a rat model of antibiotic-controlled, intra-abdominal abscess (ACIA) in normoxic and hyperoxic environments. Abscesses (1.5 ml average volume) were established by implanting a fecal-agar pellet containing known numbers and strains of live Escherichia coli and Bacteroides fragilis into the peritoneal cavity of rats via a midline incision. Sham-operated rats (SR) served as controls. Cannulas (PE-50) were placed into the left ventricle of both SR and ACIA rats for injection of tracer microspheres (MS) and into the tail artery for a reference withdrawal site. Blood flow measurements were made in conscious unrestrained rats before, during, and after hyperoxic exposure by using MS labelled with either 51Cr or 85Sr or 141Ce. No change in cardiac output (CO), heart rate (HR), or mean arterial pressure (MAP) was seen between ACIA and SR groups. The administration of hyperoxia diminished the fractional distribution of CO to the liver (portal), stomach, cecum, colon, and pancreas in both groups. The percent CO to the liver (arterial), small intestine, and spleen did not change in either group. The blood flow to all splanchnic organs, except liver (arterial), was diminished during hyperoxia in both groups and recovered after hyperoxia. In conclusion, central hemodynamics and splanchnic blood flows are not altered by the presence of a large intra-abdominal abscess controlled by antibiotics. Splanchnic blood flows are diminished by hyperoxia.

Abscess↗
PubMed1988

Response of human hepatocyte lysosomes to postmortem anoxia.

We studied the ultrastructure and degradative activity of lysosomes in human livers after somatic death due to cerebral necrosis secondary to shock and/or head trauma. The livers were obtained at autopsy after varying postmortem intervals. Liver ultrastructure was studied in intact liver, in hepatocyte suspension obtained by collagenase perfusion of the liver, and in cultured hepatocytes. Lysosomal protein degradation was measured in a case 24 hours after hepatocyte isolation. By standard ultrastructural criteria, all the livers demonstrated typical reversible manifestations of cell injury. Most hepatocytes demonstrated varying degrees of irreversible cell injury. The ultrastructural alterations were less severe in the isolated hepatocytes in suspensions, and further improvement in morphologic appearance occurred in the cultured monolayers. The most striking alteration in the liver lysosomes was the increase in the numbers of lipofuscin granules (a type of residual body) compared with control liver. The hepatocyte lysosomes constituted an average 3.1% of cytoplasmic volume. There was no correlation between the volume density of lysosomes and either the duration of postmortem anoxia, clinical course, or patient's age. There was no increase in the number of autophagic vacuoles or of secondary lysosomes in postmortem liver. Autophagic vacuoles were more frequently seen in isolated and cultured hepatocytes. Cultured hepatocytes isolated within one hour of clinical death and tested 24 hours later degraded cell proteins at a rate of 1.7% per hour. Protein degradation was stimulated by a physiologic signal (Dibutyryl cAMP, 1 mmol/L) and was inhibited by microtubule poison (vinblastine). We conclude that (1) viable hepatocytes can be isolated even after prolonged postmortem intervals (range, 30 minutes to seven hours), (2) trauma and shock cause an expansion of hepatocyte lysosomes due to accumulation of lipofuscin, and (3) autophagy is blocked by postmortem anoxia and resumes in the recovery phase from anoxic injury in hepatocyte suspensions and in culture.

Cell Survival↗
PubMed1988

Functional and structural evaluation of the vasculature of skin flaps after ischemia and reperfusion.

Free radicals and other toxic oxygen species play a role in the pathogenesis of ischemic organ damage. The abdominal skin flap has been used as a model to study the effects of superoxide dismutase on the survival of ischemic skin. We have evaluated the evolution of functional and structural injury to the vasculature after ischemic injury in superoxide dismutase-treated and control skin flaps. Ischemia was induced by creating abdominal skin flaps and occluding either the venous or both the venous and arterial blood supplies. Superoxide dismutase was administered immediately after the occlusion was released. At 1 hour of reflow, erythrocyte stasis, platelet deposition, neutrophil adherence, and injury to the endothelium of the large vessels and of the microvasculature were evident. The blood flow in the ischemic skin was only 3 percent of normal. Superoxide dismutase caused no change in the ultrastructure of the vasculature and a marginal decrease in vascular permeability in the ischemic skin at 1 hour of reflow. Increased fluorescent staining of the skin was evident after 24 hours of reflow in the superoxide dismutase-treated flaps. These findings indicate that injury to vascular endothelium by ischemia and reperfusion plays a role in the evolution of skin necrosis.

Abdominal Muscles↗
PubMed1988

Response of autophagic protein degradation to physiologic and pathologic stimuli in rat hepatocyte monolayer cultures.

The lysosomes of hepatocytes increase in numbers and size during acute cell injury in vivo. To elucidate the mechanism of this change, we have studied in vitro the response of the autophagic lysosomal system to several physiologic mediators of autophagy, and to agents known to induce injury and/or the accumulation of lysosomes in vivo. To this end, monolayer cultures of rat hepatocytes were labeled with [14C]leucine to measure hepatocyte protein degradation; ultrastructural analyses were carried out to measure the volume fraction of lysosomes in the hepatocytes. Dibutyryl cyclic AMP increased protein degradation in the hepatocytes either in the presence or absence of serum and insulin. Deprivation of serum and insulin also increased hepatocyte protein degradation. Morphometric analysis indicated parallel increases in the volume fraction of lysosomes in the hepatocytes. The calcium ionophore ionomycin (5 microM), in the presence of 1.3 mM extracellular calcium, increased protein degradation (but not the volume fraction of lysosomes), and this increase was abolished by the addition of ethyleneglycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid. On the other hand, vasopressin (5 nM) caused an increase in protein degradation coupled with an increase in volume fraction of lysosomes. The microtubule depolymerizer vinblastine decreased protein degradation. The microtubule stabilizer taxol did not prevent the inhibitory effects caused by vinblastine. Parallel decreases in the lysosomal compartment were found in the hepatocytes exposed to vinblastine or taxol. Dimethylnitrosamine inhibited protein degradation as well as decreased the volume fraction of lysosomes. Finally, carbon tetrachloride also decreased protein degradation. These data indicate that in physiologic conditions, increases in numbers of hepatocyte lysosomes reflect increased sequestration and degradation of cytoplasmic proteins in response to changes in the levels of hormones, serum factors and nutrients as well as cyclic AMP. The induction of acute cell injury in vitro by calcium ionophore, microtubule active agents, and hepatotoxins inhibits lysosomal proteolysis and causes a decrease in the volume fraction of lysosomes. We conclude that the increase in lysosomal size and numbers occurring in acutely injured hepatocytes in vivo is induced primarily by altered levels of nutritional and hormonal regulators of lysosomal protein degradation.

Animals↗
PubMed1986

Effect of hyperoxia on liver necrosis induced by hepatotoxins.

We have tested the effects of hyperbaric oxygen on necrosis of rat liver induced by the administration of several toxins. The extent of liver necrosis was determined 24 h after the administration of the toxins by measurement of serum levels of alanine and aspartate amino-transferases and by histologic and ultrastructural analyses. Treatment with hyperbaric oxygen decreases carbon tetrachloride (CCl4)-induced necrosis in a manner dependent upon duration and pressure of oxygen exposure. Pretreatment of rats with phenobarbital diminishes this protective effect. Hyperbaric oxygen treatment before or immediately after CCl4 intoxication is protective. Loss of protection is rapid; hyperbaric oxygen treatment 6 h after CCl4 intoxication augments the liver necrosis. No delayed necrogenic effects of CCl4 are seen in the animals treated with hyperbaric oxygen immediately. Hyperbaric oxygen augments the liver necrosis induced by acetaminophen, bromobenzene, dimethylnitrosamine or thioacetamide. This augmented necrosis is averted by prolonged treatment with hyperbaric oxygen. Hyperbaric oxygen has no effect on liver injury induced by galactosamine or lipopolysaccharide. We conclude that hyperoxia decreases the hepatic necrosis induced by compounds which undergo reductive biotransformation by the cytochrome P-450 monooxygenase system; hyperoxia augments the necrosis induced by compounds which undergo oxidative biotransformation by this system. Biotransformation of toxins appears to be nonspecifically inhibited by hyperoxic exposure of long duration.

Acetaminophen↗
PubMed1986

Modification of lysosomal proteolysis in mouse liver with taxol.

Perturbation of lysosomal degradation pathways by drugs such as chloroquine and vinblastine has given us important insights into the means for segregation and degradation of cytoplasm by the lysosomes. Vinblastine (VBL) is a microtubule depolymerizer which increases the number of autophagosomes and also impairs the maturation of the autophagosomes into secondary lysosomes. The authors have tested the effects of the microtubule stabilizer taxol on the proteolytic activity of the lysosomal system in VBL-treated mice. Liver proteins of CD-1 mice were radioisotopically labeled. Taxol and/or vinblastine were subsequently administered. Proteolysis in liver homogenates was determined during in vitro incubation by measuring the release of trichloroacetic acid-soluble radioactivity over time. Taxol enhanced proteolysis in homogenates from VBL-treated mice. The site of the enhanced proteolysis was lysosomal, because it was demonstrated in a crude lysosomal fraction, it manifested an acid pH optimum, and it could be suppressed with cycloheximide. Morphometric analysis indicated that taxol caused a shift in hepatocyte lysosomes of VBL-treated mice toward the later stages of the degradation cycle, coupled with a decrease in the number of small dense body profiles. The results indicate that taxol enhances the maturation of the autophagosomes into proteolytically active secondary lysosomes. It is concluded that the microtubule stabilizer taxol enhances fusion between VBL-induced autophagosomes and lysosomes (small dense bodies) and does not affect the segregation of cytoplasm into autophagosomes.

Alkaloids↗
PubMed1985

What's new in in vitro studies of exocrine pancreatic cell injury?

Exocrine pancreas in vitro models are useful for the study of pancreatic differentiation, secretion mechanisms, cell injury, and lysosomal processing of secretory product. Syrian hamster pancreas in explant organ culture undergoes a series of morphologic changes which parallel in vitro acinar cell injury, differentiation, and phenotypic alteration. Within 48 hours, the cultured acinar cells show morphologic evidence of sublethal cell injury. Autophagy and crinophagy are particularly striking. The autophagic processes can be inhibited by the addition of the protein synthesis inhibitor cycloheximide or by culture at lowered temperatures (20 degrees C). Acinar cells lethally damaged show pyknotic nuclei, high amplitude swelling, and necrosis. Approximately 25% of each explant is viable after 72 hr in culture and the viability remains constant at 25-35% for up to 60 days of culture. The morphological changes of the explants are consistent with many of the features of pancreatitis and carcinoma of the exocrine pancreas. There is an increase in the ductal elements and a decrease in acini over time in culture. This may be due to: (a) an increased replication of ductal epithelial cells concomitant with necrosis of acinar epithelial cells and/or (b) phenotypic alteration of acinar cells to ductal cells. Acinar cell necrosis and phenotypic alterations may in part be due to the activation of lysosomal degradation pathways. Processes which inhibit lysosomal activation proved protective against these alterations, while processes which promote zymogen activation were deleterious.

Animals↗
PubMed1984

Unbuffered osmium staining of cell organelles: alterations induced by cell injury.

We have studied the localization of osmium reduction products to investigate the functional state of organelles as well as organelle interrelationships during cell injury. In normal hepatocytes osmium deposits of variable intensity are seen in nuclear envelope, endoplasmic reticulum. Golgi cisternae and vesicles and lysosomes. Buffering of osmium with s- collidine (pH 7.4) prevents the deposition of osmium. Reversible (30 min) and irreversible (60 min) ischemia without reflow causes no change in the pattern of osmium deposition. Irreversible ischemia followed by reflow causes decreased staining of endoplasmic reticulum (ER) and redistribution of the osmium deposits through the cytoplasm. Reversibly injured pancreatic acinar cells in cultured explants manifest a similar loss of osmium staining in the endoplasmic reticulum cisternae. The administration of antimicrotubule drugs induces an accentuation of osmium staining in localized cisternal elements of hepatocytes. These heavily stained cisternae appear to give rise to the bounding membranes of drug-induced autophagic vacuoles. Cytoplasmic organelles sequestered inside the autophagic vacuoles acquire intense staining when they begin to undergo degradation. In homogenized liver tissue all the subcellular organelles show osmium deposits. The deposits are preferentially localized along the organelle membranes. In particular the dense deposits in the ER lumen are not seen in the subcellular fractions. Phospholipase A2 (3 units/mg protein) enhances the deposition of osmium in the lumen of microsomal vesicles, whereas the presence of detergent has no such effect. Addition of EDTA to the homogenizing medium enhances the ultrastructural preservation of the subcellular fractions but has little effect on the deposition of osmium. OsO4 deposition occurs at acid pH and the intensity and pattern of the stain can be modified in vivo and in vitro. Osmium tetroxide deposition is induced at sites of membrane transformation (autophagic vacuoles) and degradation (lysosomes). Calcium influx and phospholipase activation (ischemia, tissue homogenization, phospholipase addition) enhance osmium deposition and/or influence the localization of the staining pattern.

Animals↗
PubMed1984

Protection of hepatocytes with hyperoxia against carbon tetrachloride-induced injury.

Hyperbaric oxygen (HPO) was administered to rats (100% O2 at 2.8 atm for 90 min) immediately or 1 hr after severe carbon tetrachloride (CCl4) intoxication in order to study the mechanisms of protection against hepatocellular injury by hyperoxia. Slight to moderate hepatocellular injury was observed, particularly by morphologic criteria, 4 hr after CCl4 intoxication. Little cell death was observed; 24 hr after CCl4, 20% of the untreated animals died. In the survivors, the following typical changes occurred in the liver: extensive hepatocellular swelling, vacuolization and necrosis; severe ultrastructural alterations; binding of CCl4 to microsomal lipids; elevation of lipid peroxidation products (conjugated dienes); little decrease in cytochrome b5 and severe decrease in cytochrome P-450 levels. Serum transaminase (alanine aminotransferase and aspartate aminotransferase) levels were elevated. Immediate treatment with HPO prevented the mortality and markedly decreased the hepatocellular necrosis 24 hr after intoxication. Immediate HPO treatment did not lower the levels of free CCl4 in the liver. However, the rise in lipid peroxidation products caused by CCl4 intoxication at 4 hr was reduced. Delayed treatment with HPO (1 hr after CCl4) prevented the mortality but was less effective in preventing necrosis. Some hepatocellular protection was still demonstrable. In particular, the rise in lipid peroxidation products was reduced. Hyperoxia protects hepatocytes against CCl4 toxicity. The rapid decline in protective effect within 60 min of intoxication suggests that hyperoxia inhibits CCl4 activation and/or damage from molecular intermediates. Hyperoxia has little effect on the progression of sublethal injury to cell death in the livers of CCl4-intoxicated rats.

Alanine Transaminase↗
PubMed1984

Degradation of zymogen granules by lysosomes in cultured pancreatic explants.

Pancreatic explants from Syrian hamsters were maintained in culture for determination of the fate of the zymogen granules in the acinar cells. By 6 hours of culture the zymogen granule matrix in many cells becomes nonhomogeneous, and electron-lucent spaces appear. Autoradiography performed 48 hours after pulse labeling shows that several of the altered zymogen granules contain radioactively labeled proteins. Hence these altered granules are mature zymogen granules undergoing regression. Ultrastructural analyses indicate that the zymogen granules are degraded intracellularly in the lysosomes by autophagy, by direct fusion between the lysosomes and the zymogen granules, as well as by engulfment of intact zymogen granules by the lysosomes. Budding of cytoplasm into zymogen granules is also frequently observed. Acid phosphatase histochemistry and anti-amylase immunohistochemistry were used for demonstration of presence of hydrolases and of secretory material in the degenerating zymogen granules. Cycloheximide and low temperature inhibit the degradation of zymogen granules and enhance the short-term viability of the explant. Secretagogues stimulate secretion but have little or no effect on the degradation of zymogen granules or on explant viability. The lysosomes participate in the intracellular degradation of zymogen granules in acinar cells of pancreatic explants. The induction of these lysosomal catabolic processes correlates with the structural alteration of pancreatic acinar cells. The intracellular degradation of secretory membranes and products by the lysosomes may play a role in the adaptation of pancreatic acinar cells to injury.

Acid Phosphatase↗
PubMed1984

Hepatic and systemic metabolic responses to aerobic and anaerobic intra-abdominal abscesses in a highly reproducible chronic rat model.

A single, uniform abscess was formed in 100% of the animals inoculated with a fecal pellet made of sterile rat feces, agar, and a known number and strain of bacteria. The effects of monoclonal Escherichia coli abscess (83 rats) were compared to those of sterile abscess (34 rats) and sham operation (35 rats without abscess). Bacteroides fragilis was added to the sterile pellet to study the effect of an anaerobic monoclonal abscess (16 rats) or of a biclonal abscess containing both aerobes and anaerobes (32 rats). After inoculation, a peritonitis stage with leucopenia, hypoglycemia, body weight loss, and slight fever was followed by the abscess stage with leucocytosis and a slight hyperglycemia. Mild hepatic energy charge deficiency and hepatic lactic acidosis were observed in sterile abscess rats, and slightly enhanced energy charge was seen in monoclonal E. coli abscess rats. The addition of B. fragilis to the sterile pellet, alone or together with E. coli, produced hepatic energy charge deficiency and hepatic lactic acidosis, which were significantly enhanced compared with the monoclonal E. coli abscess rats. The greatest effect was seen in the biclonal E. coli plus B. fragilis abscess, suggesting that anaerobic or combined aerobe and anaerobe abscesses may produce a greater hepatic injury than an aerobic organism abscess alone. This may account for the apparent synergic interaction between aerobic and anaerobic organisms.

Abdomen↗
PubMed1984

Evaluation of injured intestine with the aid of fluorescein.

In an animal model, a new diagnostic use for fluorescein as an aid in determining intestinal viability after blunt trauma, has been evaluated. Areas of traumatized intestine that do not fluoresce are invariably necrotic; fluorescing tissue is always viable. Fluorescein is a simple and rapid means of evaluating traumatized intestine, and it may prove to be a useful adjunct to the clinical examination.

Animals↗