摘要:

Phenylhydrazine (PHZ) exposure is used to studyin vitrored cell aging mechanisms dependent on Hb oxidation. The effect of PHZ on normal neonatal red blood cells was studied in unseparated blood and after separation into light and heavy cells. PHZ caused more extensive morphologic changes in neonatal than in adult red blood cells. PHZ exposure of neonatal cells caused less reduced glutathione depletion than in adult cells. Although we found the same total amount of oxidized Hb in both cells, a well defined oxidation product of Hb was demonstrated by Mössbauer spectra only in neonatal cells. This oxidation product was not methemoglobin but a trivalent, high-spia iron compound. All neonatal cell populations were more sensitive to PHZ than were adult ones, as demonstrate by the presence of Heinz bodies at low PHZ concentration, which did not affect adult cells. These studies demonstrate greater sensitivity of neonatal cells to PHZ in all densityseparated populations.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Immunomodulating agents are being investigated for treatment of infection in newborn infants where morbidity and mortality remain high despite the continued development of new antibiotics. We studied the effect of the methylxanthine pentoxifylline on polymorphonuclear leukocyte (PMN) chemotaxis, F-actin content, and phagocytic activity as measured by nitroblue tetrazolium reduction and H2O2production in neonates and adults to determine whether pentoxifylline might be useful in augmenting PMN function. The drug was found to have a dose-dependent effect on both neonatal and adult PMN function with enhancement at lower concentrations and suppression at higher concentrations. PMN chemotaxis increased 42% (p < 0.01) in neonates and 16% (p< 0.05) in adults at 100 μg/mL of pentoxifylline and it decreased 4 and 25%, respectively, at 4000 μg/mL. PMN nitroblue tetrazolium reduction increased by 34% in neonates and 23% (p< 0.05) in adults at 100 μg/mL of pentoxifylline and decreased by 52 (p< 0.01) and 74% (p< 0.01), respectively, at 2000 μg/mL. Similar dose-dependent responses were noted with F-actin content and H2O2production. These and other observations support the hypothesis that pentoxifylline has a broad range of effects on PMN but that a primary effect is alteration of PMN deformability. Pentoxifylline has potential clinical use as an immunomodulator in augmenting impaired PMN function in neonates and other immunocompromised hosts or in suppressing excessive PMN activity in certain disease processes. (Pediatr Res29:123–127, 1991)

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Volume and deformability of blood cells are important determinants of the microcirculation. Leukocytes are larger and considerably less deformable than erythrocytes. In our study, volume and deformability of polymorphonuclear neutrophils (PMN), lymphocytes, and monocytes in adults and full-term neonates were studied by means of a micropipette system. Neonatal immature granulocytes were also investigated. Membrane cytoplasm tongues were aspirated into 2.5-pm (diameter) micropipettes over a period of 1 min. Adult and neonatal PMN were totally aspirated into 5-μm micropipettes. Tongue growth and final tongue length of PMN were about twice those of monocytes and lymphocytes. At a pressure of −2 cm H2O, tongue growth of lymphocytes and monocytes was similar. At a pressure of −4 cm2O, however, tongue growth of monocytes was faster and the final tongue was longer than those of lymphocytes (p < 0.05). Cellular volume and deformation behavior of the different leukocyte subpopulations (PMN, monocytes, and lymphocytes) were similar in neonates and adults. Compared to mature neonatal PMN, immature neonatal neutrophilic granulocytes were significantly less deformable (final tongue length of 5.4 ± 1.52 versus 9.3 ± 1.48 pm at −2 cm H2O) and larger (421 ± 68 versus 360 ± 38 fL). The entry time of PMN into 5-pm micropipettes was similar in neonates and adults at aspiration pressures of −2, −3, and −4 cm H2O. We conclude that the deformability of neonatal and adult leukocytes is not different despite functional differences and that immature granulocytes may contribute to impaired microcirculation in neonates with severe septicemia or hypoxemia.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The net balance of neutrophil elastase and its inhibitor, α1-antitrypsin (α1-AT), is a critical determinant of connective tissue turnover during homeostasis and in disease states. In addition to liver-derived á1-AT, which translocates from blood to tissues, this elastase-α1-AT balance is maintained by expression of α-AT at the local tissue level in resident mononuclear phagocytes. Our previous studies have shown that this elastase-α1-AT balance is also tightly controlled at a cellular level in that addition of exogenous neutrophil elastase (serpine-type elastase) to cultured mononuclear phagocytes is associated with an increase in expression of the α1-AT gene. Subsequent studies have demonstrated that this novel regulatory loop involves interaction between exogenous neutrophil elastase and endogenous α1-AT inducing a structural rearrangement in the α1-AT molecule and exposing highly conserved conformation-specific domain of α1-AT, which can then be recognized by a specific cell surface receptor, the serpinenzyme complex receptor. In the following study, we examined the effect of a bacterial metalloelastase,Pseudomonas aeruginosaelastase, on expression of α1-AT in human mononuclear phagocytes. We show that pseudomonas elastase inactivates monocyte-derived α1-AT by limited proteolysis but, in so doing, á1-AT becomes recognized by the serpin-enzyme complex receptor and mediates an increase in de novo synthesis of á1-AT in these cells. However, the concentrations of pseudomonas elastase needed to proteolytically inactivate á1-AT in monocyte culture fluid are higher than those required for inactivation of purified plasma á1-AT. Results of experiments in this report show that this can be explained, at least in part, by binding of pseudomonas elastase to another endogenous protease inhibitor, α2-macroglobulin. Thus, the results of this study further define the elaborate mechanisms by which the host mononuclear phagocyte controls the elastase-α1-AT balance and, in turn, connective tissue turnover. (Pediatr Res29:133–140, 1991)

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

The primary genetic defect of Zellweger syndrome may be related to defective synthesis or impaired import of peroxisomal proteins. We analyzed the presence and measured the abundance of the 22-kD peroxisomal integral membrane protein (PMP) in patients with Zellweger syndrome. We determined the intracellular localization of the 22-kD PMP and compared it with the localization of a peroxisomal 44-kD thiolase precursor protein. The 22-kD PMP was quantified by immunoblot analyses in liver tissue (n= 7 patients). Immunoblot signals were evaluated using transmission photometry. The intracellular localization of the 22-kD PMP and the peroxisomal 44-kD thiolase precursor protein were determined by immunoblot analyses on fibroblast subcellular fractions prepared by Nycodenz (n= 5 patients) or sucrose density gradient centrifugation (n= 2 patients). The 22-kD PMP was present and associated with membrane fractions in all patients. Its abundance varied in patients as compared with normal human liver controls. The 22-kD PMP was located in subcellular membrane fractions having a lower density than normal peroxisomes or mitochondria. Using two different gradient techniques, the 22-kD PMP and the peroxisomal 44-kD thiolase precursor protein were found in the same low-density gradient fractions. These results suggest that in Zellweger syndrome peroxisome-like elements containing both the 22-kD PMP and a 44-kD thiolase precursor protein are formed. Globally defective synthesis or import of peroxisomal proteins is therefore unlikely to be the primary genetic defect in the patients we studied.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Phenylacetylglutamine (PAG), the amino acid acetylation product of phenylacetate (or phenylbutyrate after β-oxidation) was evaluated as a waste nitrogen product in patients with inborn errors of urea synthesis. A boy with carbamyl phosphate synthetase deficiency receiving a low nitrogen intake excreted SO-90% of administered phenylacetate or phenylbutyrate as PAG. The amount of PAG nitrogen excreted varied from 38–44% of his dietary nitrogen, similar to the relationship between urea nitrogen and dietary nitrogen found in normal subjects receiving low dietary nitrogen. With few exceptions, neither phenylacetate nor phenylbutyrate accumulated in plasma. Treatment with relatively high dose phenylacetate or phenylbutyrate (0.5–0.6 g/kg/d) resulted in normal daytime levels of glutamine. These data suggest that PAG may replace urea as a waste nitrogen product when phenylbutyrate is administered at a dose that yields PAG nitrogen excretion equal to 40–44% of a low nitrogen intake.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID

摘要:

Argininosuccinate synthetase and argininosuccinate lyase catalyze the conversion of citrulline to arginine in kidney. Immunohistochemical staining of mouse kidney sections with antibodies to these two enzymes, compared with the staining patterns of known markers for proximal tubules, demonstrated that these enzymes are localized within the proximal tubules. The relative abundance of mRNA encoding argininosuccinate synthetase and argininosuccinate lyase during fetal and postnatal development of mouse kidney was also determined. Changes in relative abundance of these mRNA in kidney are coordinate during development, paralleling the developmental profile of phosphoenolpyruvate carboxykinase mRNA, which is also expressed in proximal tubules. Although relative abundances of the mRNA are comparable in liver and kidney of adult mice, the profiles of mRNA abundance during development of these two organs are distinct. The results indicate that these enzymes and their corresponding mRNA can serve as useful markers for examining the differentiation and development of renal proximal tubules in vivo and in cultured explants.

ISSN:0031-3998    

出版商:OVID    

年代:1991

数据来源: OVID