Muscle wasting in insulinopenic rats results from activation of the ATP-dependent, ubiquitin-proteasome proteolytic pathway by a mechanism including gene transcription

In normal subjects and diabetic patients, insulin suppresses whole body proteolysis suggesting that the loss of lean body mass and muscle wasting in insulinopenia is related to increased muscle protein degradation. To document how insulinopenia affects organ weights and to identify the pathway for accelerated proteolysis in muscle, streptozotocin-treated and vehicle-injected, pair-fed control rats were studied. The weights of liver, adipose tissue, and muscle were decreased while muscle protein degradation was increased 75% by insulinopenia. This proteolytic response was not eliminated by blocking lysosomal function and calcium-dependent proteases at 7 or 3 d after streptozotocin. When ATP synthesis in muscle was inhibited, the rates of proteolysis were reduced to the same level in insulinopenic and control rats suggesting that the ATP-dependent, ubiquitin-proteasome pathway is activated. Additional evidence for activation of this pathway in muscle includes: (a) an inhibitor of proteasome activity eliminated the increased protein degradation; (b) mRNAs encoding ubiquitin and proteasome subunits were increased two- to threefold; and (c) there was increased transcription of the ubiquitin gene. We conclude that the mechanism for muscle protein wasting in insulinopenia includes activation of the ubiquitin-proteasome pathway with increased expression of the ubiquitin gene.

Invasion of minor veins of tobacco leaves inoculated with tobacco mosaic virus mutants defective in phloem-dependent movement

To fully understand vascular transport of plant viruses, the viral and host proteins, their structures and functions, and the specific vascular cells in which these factors function must be determined. We report here on the ability of various cDNA-derived coat protein (CP) mutants of tobacco mosaic virus (TMV) to invade vascular cells in minor veins of Nicotiana tabacum L. cv. Xanthi nn. The mutant viruses we studied, TMV CP-O, U1mCP15-17, and SNC015, respectively, encode a CP from a different tobamovirus (i.e., from odontoglossum ringspot virus) resulting in the formation of non-native capsids, a mutant CP that accumulates in aggregates but does not encapsidate the viral RNA, or no CP. TMV CP-O is impaired in phloem-dependent movement, whereas U1mCP15-17 and SNC015 do not accumulate by phloem-dependent movement. In developmentally-defined studies using immunocytochemical analyses we determined that all of these mutants invaded vascular parenchyma cells within minor veins in inoculated leaves. In addition, we determined that the CPs of TMV CP-O and U1mCP15-17 were present in companion (C) cells of minor veins in inoculated leaves, although more rarely than CP of wild-type virus. These results indicate that the movement of TMV into minor veins does not require the CP, and an encapsidation-competent CP is not required for, but may increase the efficiency of, movement into the conducting complex of the phloem (i.e., the C cell/sieve element complex). Also, a host factor(s) functions at or beyond the C cell/sieve element interface with other cells to allow efficient phloem-dependent accumulation of TMV CP-O.

Baculovirus-mediated expression and characterization of rat CYP2A3 and human CYP2a6: role in metabolic activation of nasal toxicants

Cytochrome P450 2A3 (CYP2A3) was previously identified in rat lung by cDNA cloning and recently found to be expressed at a high level in the olfactory mucosa. In the current study, CYP2A3 was expressed in insect cells lacking endogenous cytochrome P450 (P450) activity, and the substrate specificity of the recombinant cytochrome was characterized and compared with that of CYP2A6, a human ortholog of rat CYP2A3, which has been detected in human olfactory mucosa as well as in liver. The CYP2A3 and CYP2A6 cDNAs were cloned into baculovirus, and recombinant viruses were used to produce active enzymes in Spodoptera frugiperta (SF9) cells. The metabolic activities of S. frugiperta cell microsomal fractions containing CYP2A3 or CYP2A6 were studied in a reconstituted system with purified rabbit NADPH-P450 reductase. CYP2A3 was found to be active toward testosterone, producing 15 alpha-hydroxytestosterone and several other metabolites, but it had only low activity toward coumarin. On the other hand, CYP2A6 was active toward coumarin but not toward testosterone. However, both enzymes were active in the metabolic activation of hexamethylphosphoramide, a nasal procarcinogen, and 2,6-dichlorobenzonitrile (DCBN), a herbicide known to cause tissue-specific toxicity in the olfactory mucosa of rodents at very low doses. In addition, both enzymes were active toward 4-nitrophenol, a preferred substrate for CYP2E1. Consistent with CYP2A3 being a major catalyst in microsomal metabolism of DCBN, the activities of both CYP2A3 and rat olfactory microsomes in DCBN metabolism were inhibited strongly by metyrapone and methoxsalen (ID50 < 1 microM, with DCBN at 30 microM), but only marginally by 4-methylpyrazole, an inhibitor of CYP2E1. In contrast, the activity of CYP2A6 was only weakly inhibited by metyrapone or methoxsalen (ID50 > 50 microM). Thus, rat CYP2A3 and human CYP2A6 have differences in substrate specificity as well as tissue distributor. These findings should be taken into account when assessing the risk of exposure to potential nasal toxicants in humans.

Reverse mutations in the fragile X syndrome

Three females were identified who have apparent reversal of fragile X premutations. Based on haplotype analysis of nearby markers, they were found to have inherited a fragile X chromosome from their premutation carrier mothers, and yet had normal size FMR1 repeat alleles. The changes in repeat sizes from mother to daughter was 95 to 35 in the first, 145 to 43 in the second, and 82 to 33 in the third. In the first family, mutations of the nearby microsatellites FRAXAC2 and DXS548 were also observed. In the other two, only mutations involving the FMR1 repeats were found. We suggest differing mutational mechanisms such as gene conversion versus DNA replication slippage may underlie such reversions. We estimate that such revertants may occur among 1% or less of premutation carrier offspring. Our results indicate that women identified to be carriers by linkage should be retested by direct DNA analysis.

Expression of CYP2A genes in rodent and human nasal mucosa

CYP2A10 and CYP2A11, which are abundant in olfactory microsomes from rabbits, are active in the metabolic activation of a number of nasal toxicants, such as hexamethylphosphoramide and N-nitrosodiethylamine. Previous immunohistochemical studies indicated that CYP2A-related cytochromes P450 may also be present in rodent and human olfactory tissue. In the present study, the expression of cytochromes P450 highly homologous to rabbit CYP2A10/11 in rat, mouse, and human nasal mucosa was studied. In Sprague-Dawley rats, CYP2A3 mRNA was detected in olfactory mucosa at levels much higher than those found in total RNA from lung. Similar observations were made for the level of microsomal CYP2A3 protein with the use of antibodies to rabbit CYP2A10/11. However, mRNAs for two other rat cytochrome P450 genes in the CYP2A subfamily, CYP2A1 and CYP2A2, were not detected in nasal tissue by RNA-polymerase chain reaction analysis. In C57BL/6 mice, both CYP2A4 and CYP2A5 mRNAs were detected in the olfactory mucosa by RNA-polymerase chain reaction, but the CYP2A5 transcript was present at a level much higher than that of CYP2A4. The expression of another mouse gene in CYP2A subfamily, CYP2A12, was not detected in nasal tissue. CYP2A5 protein was also detected in mouse olfactory microsomes at higher levels than in liver, lung, or kidney microsomes. However, no significant sex differences in the levels of CYP2A4/5 mRNA or microsomal coumarin 7-hydroxylase activity were found with the nasal tissue. In addition, consistent with previous immunohistochemical studies, the expression of CYP2A6 in human nasal mucosa was detected by RNA-polymerase chain reaction as well as RNA blot analysis. The identification of CYP2A6 in human nasal tissues may have important implications for risk assessment of potential nasal toxicants, and the abundant expression of the CYP2A genes in rat and mouse olfactory tissue suggests a molecular basis for the known tissue-specific toxicity of numerous inhaled compounds in rodents.

Prenatal diagnosis and carrier screening for fragile X by PCR

During the past three years, we have conducted fragile X DNA studies for carrier screening and prenatal diagnosis using a previously described PCR protocol that accurately resolves normal FMR1 alleles and premutations and detects most full mutations [Brown et al., JAMA 270:1569-1575, 1996]. A total of 344 pregnant women with a family history of mental retardation of unknown cause were screened and 6 fragile X carriers were identified: two had full mutations, and four had premutations. The mentally retarded relatives of two other women were found to be fragile X positive although the women themselves were not carriers. In all, 6 carriers and 8 fragile X families were identified by this screening. We have also screened 40 pregnant women who were members of previously identified fragile X families, but whose carrier status was unknown. Ten were found to be carriers and were offered prenatal diagnosis. Prospective prenatal testing of 84 carrier women correctly detected 31 fetal samples (19 females, 12 males) with full mutations and 6 with premutations (2 females, 4 males). No false positives but one false negative occurred early on due to undetected maternal cell contamination. In addition, screening of 806 males with developmental delays of unknown cause gave positive results in 33 (4.1%). Potential problems and pitfalls of direct DNA testing are discussed. Because of the proven success of fragile X screening with direct molecular analysis, screening of all undiagnosed individuals with mental retardation and at risk pregnant women should now be considered. The identification of fragile X carriers and prenatal diagnosis of their pregnancies should significantly reduce the prevalence of this syndrome.

Modulation of multidrug resistance gene (mdr-1) with antisense oligodeoxynucleotides

1. Multidrug resistance is the major obstacle to successful cancer chemotherapy. Circumventing multidrug resistance therefore represents a high priority for clinical anti-cancer treatment. Among many reversal strategies, antisense oligodeoxynucleotides may offer a molecular targeting tool for overcoming cellular multidrug resistance. 2. Two 17-mer phosphorothioate antisense oligomers, complementary to the 5' end of the ATG initiator codon-containing region and loop-forming site (located at nucleotides 991-1007 from the first ATG codon) in mdr-1 cDNA sequence, were synthesized. The purpose was to study their effects on the function and expression of P-glycoprotein and mdr-1 gene. 3. The results showed that 10 mumol/l antisense oligomers could significantly inhibit the growth of multidrug resistant K562/Adm cells cultured in adriamycin-containing medium. No such effect was observed for parental (sensitive) K562/S cells. Intracellular daunorubicin accumulation increased greatly in the K562/Adm cells after they were treated with oligomers for 48 h and P-glycoprotein synthesis was strikingly reduced. 4. Further investigation with [alpha-32P]dCTP incorporation by the reverse transcriptase-polymerase chain reaction method revealed that antisense oligomers could result in a reduction in the level of mdr-1 mRNA, probably through hindering mdr-1 gene transcription. 5. The high reversal efficiency and specificity of antisense oligomers in regulating mdr-1 gene expression suggest a potential clinical application in gene therapy for drug resistant malignancies.

Metabolic activation of 2,6-dichlorobenzonitrile, an olfactory-specific toxicant, by rat, rabbit, and human cytochromes P450

The herbicide 2,6-dichlorobenzonitrile (DCBN) is known to cause tissue-specific toxicity at very low doses in the olfactory mucosa of rodents. The toxicity of DCBN is reportedly cytochrome P450 (P450) dependent, but the isoforms involved have not been identified, and the effects of this agent on humans are not known. In the present study, DCBN metabolism was examined with microsomes and with purified P450s in a reconstituted system. Rat and rabbit olfactory microsomes act on DCBN to form DCBN-protein adducts as well as two metabolite peaks, designated M1 and M2, identified through high performance liquid chromatography with radiometric detection. The activity of rat olfactory microsomes in DCBN metabolism is much higher than that of liver or lung microsomes. Of seven purified rabbit P450s known to be expressed in the olfactory mucosa, including 1A2, 2A10/11, 2B4, 2E1, 2G1, and 3A6, the 2A10/11 preparation is the most active, producing M2 as well as DCBN-protein adducts; P450 2E1 is the only other active isoform. The addition of purified epoxide hydrolase (EC 4.2.1.63) to the reconstituted enzyme system leads to the formation of M1 and decreased formation of M2. It seems that M1 and M2 are derived from an epoxide intermediate that also forms covalent protein adducts. Gas chromatography- and liquid chromatography-mass spectrometry analyses of nasal microsomal DCBN metabolites and DCBN-glutathione conjugates indicated that the major reactive intermediate may be 2,3-oxo-DCBN and that M1 may be 2,3-dihydroxy-6-chlorobenzonitrile, whereas M2 may correspond to a monohydroxy-DCBN. Interestingly, heterologously expressed human P450s 2A6 and 2E1, but not 1A2, are active in the metabolism of DCBN, forming protein adducts as well as M2. Thus, the preferential expression of P450s of the 2A subfamily in olfactory tissue suggests a molecular basis for the tissue-specific toxicity of the herbicide and may have important implications for risk assessment in humans.

Identification of the primary metal ion-activation sites of the diphtheria tox repressor by X-ray crystallography and site-directed mutational analysis

The diphtheria tox repressor, DtxR, is a 226 amino acid transition metal ion-activated regulatory protein that controls the expression of diphtheria toxin in toxigenic Corynebacterium diphtheriae. The previously solved three-dimensional DtxR structures have identified two potential metal ion binding sites which may play a role in the activation of DNA binding by the repressor. We have used both X-ray crystallographic and site-directed mutational analysis of DtxR(C102D)-Ni2+ complexes and DtxR to identify the metal ion-binding site which results in the activation of the repressor. We demonstrate that DtxR contains both a primary and an ancillary metal ion binding site. The primary site functions directly in the activation of DNA binding. In contrast, the ancillary site contributes weakly, if at all, to activation.

The acidosis of chronic renal failure activates muscle proteolysis in rats by augmenting transcription of genes encoding proteins of the ATP-dependent ubiquitin-proteasome pathway

Chronic renal failure (CRF) is associated with negative nitrogen balance and loss of lean body mass. To identify specific proteolytic pathways activated by CRF, protein degradation was measured in incubated epitrochlearis muscles from CRF and sham-operated, pair-fed rats. CRF stimulated muscle proteolysis, and inhibition of lysosomal and calcium-activated proteases did not eliminate this increase. When ATP production was blocked, proteolysis in CRF muscles fell to the same level as that in control muscles. Increased proteolysis was also prevented by feeding CRF rats sodium bicarbonate, suggesting that activation depends on acidification. Evidence that the ATP-dependent ubiquitin-proteasome pathway is stimulated by the acidemia of CRF includes the following findings: (a) An inhibitor of the proteasome eliminated the increase in muscle proteolysis; and (b) there was an increase in mRNAs encoding ubiquitin (324%) and proteasome subunits C3 (137%) and C9 (251%) in muscle. This response involved gene activation since transcription of mRNAs for ubiquitin and the C3 subunit were selectively increased in muscle of CRF rats. We conclude that CRF stimulates muscle proteolysis by activating the ATP-ubiquitin-proteasome-dependent pathway. The mechanism depends on acidification and increased expression of genes encoding components of the system. These responses could contribute to the loss of muscle mass associated with CRF.

Identification of human genes related to olfactory-specific CYP2G1

CYP2G1, which is uniquely expressed in the olfactory mucosa of rats and rabbits, may have functions important for the olfactory chemosensory system. The aim of the present study is to determine whether CYP2G genes are present in the human genome. Several gene fragments were obtained by PCR amplification of human genomic DNA. One fragment, termed E7, which contained an open reading frame for 44 amino acids, is highly homologous in deduced amino acid sequence to residues 322-375 in rabbit or rat CYP2G1. Three other gene fragment, termed E7-8, H2Gp1 and H2Gp2, respectively, were also obtained and found to have structural homology with coding sequences in the rat CYP2G1 gene. RNA-PCR analysis of human nasal RNA indicated that at least one CYP2G gene is transcribed. Southern blot analysis of human genomic DNA with use of cloned E7 or E7-8 as the probe indicated that more than one CYP2G-related gene may be present in the human genome. These results provide a basis for further characterization of the structure and function of the human CYP2G genes.

[Limbal epithelial autograft transplantation for treatment of unilateral fibrous vascularized cornea caused by chemical burns]

OBJECTIVE

To provide healthy epithelial source for damaged cornea to prevent the invasion of conjunctival tissue for treatment of corneal vascularized opacity after chemical turns.

METHODS

Limbal epithelial autograft transplantation was performed on 17 cases (17 eyes) with vascularized corneal opacity caused by chemical burns.

RESULTS

Of 17 cases, the epithelial healing was stable in 15 cases, and there was corneal graft transparency, improvement of visual acuity and without neovascularization in 13 cases.

CONCLUSION

Limbal epithelial autograft Limbal epithelial autograft transplantation applied for reconstruction of palisades of Vogt to provide new stem cell source for injured limbus is a reasonable therapeutic method for treatment of vascularized corneal opacity caused by chemical burns.

Zonula occludens toxin modulates tight junctions through protein kinase C-dependent actin reorganization, in vitro

The intracellular signaling involved in the mechanism of action of zonula occludens toxin (ZOT) was studied using several in vitro and ex vivo models. ZOT showed a selective effect among various cell lines tested, suggesting that it may interact with a specific receptor, whose surface expression on various cells differs. When tested in IEC6 cell monolayers, ZOT-containing supernatants induced a redistribution of the F-actin cytoskeleton. Similar results were obtained with rabbit ileal mucosa, where the reorganization of F-actin paralleled the increase in tissue permeability. In endothelial cells, the cytoskeletal rearrangement involved a decrease of the soluble G-actin pool (-27%) and a reciprocal increase in the filamentous F-actin pool (+22%). This actin polymerization was time- and dose-dependent, and was reversible. Pretreatment with a specific protein kinase C inhibitor, CGP41251, completely abolished the ZOT effects on both tissue permeability and actin polymerization. In IEC6 cells ZOT induced a peak increment of the PKC-alpha isoform after 3 min incubation. Taken together, these results suggest that ZOT activates a complex intracellular cascade of events that regulate tight junction permeability, probably mimicking the effect of physiologic modulator(s) of epithelial barrier function.

Nature of the inactivation of elastase by N-peptidyl-O-aroyl hydroxylamine as a function of pH

The mechanism of inactivation of porcine pancreatic elastase (PPE) by N-peptidyl-O-aroylhydroxylamine was studied by X-ray crystallography. The inactivator forms a stable complex with the enzyme by means of a covalent attachment to the active site Ser 203(195) O gamma. The nature of the complex is, however, different depending on the pH at which the inactivation reaction occurs. At pH 5, the complex formed is a hydroxylamine derivative of Ser 203(195) in which the O gamma of serine is the oxygen of the hydroxylamine derivative. At pH 7.5, the complex formed is a carbamate derivative at Ser 203(195) O gamma. In both types of complexes, the inactivator binds in the S' subsites of the enzyme instead of forming the usual antiparallel beta-sheet with the S subsites. The implication for the mechanism of inactivation at different pHs is discussed.

Metabolism of aflatoxin B1 by rabbit and rat nasal mucosa microsomes and purified cytochrome P450, including isoforms 2A10 and 2A11

The nasal mucosa of some mammalian species are susceptible to the toxicity of aflatoxin B1 (AFB1), a potent hepatocarcinogen, but little is known about the nasal enzymes involved in the metabolic activation of AFB1 or the metabolites produced. In the present study, the metabolism of AFB1 was studied with nasal microsomes from rats and rabbits and with several purified isozymes of rabbit P450 in a reconstituted enzyme system. The rates of AFB1-N7-guanine DNA adduct formation with rabbit and rat nasal microsomes are over 3- and 10-fold higher, respectively, than with liver microsomes from the same species. On the other hand, the rates of formation of AFM1 (9a-hydroxy-AFB1) and AFQ1 (3-hydroxy-AFB1) products known to be less toxic, are lower with nasal than with liver microsomes. Of particular interest, nasal microsomes produce high levels of six unidentified polar metabolites that are not formed by microsomes from liver or several other tissues. These same products are also generated by P450 NMa purified from rabbit nasal microsomes in a reconstituted system, but not by five other isozymes of cytochrome P450 (1A2, 2B4, 2E1, 2G1, 3A6) that are known to be present in nasal microsomes. AFB1-DNA adducts are formed by P450 NMa at a rate 3-fold higher than that by nasal microsomes. The DNA adducts are formed at much slower rates by P450s 2G1, 2B4, and 1A2, and adducts are not formed at measurable rates by P450s 2E1 and 3A6. Moreover, AFB1-DNA adduct formation is also catalyzed by cDNA-derived, heterologously expressed P450s 2A10 and 2A11, both of which are known to be present in the purified P450 NMa preparation. The Km and Vmax values of the two isozymes for DNA adduct formation are comparable to those for nasal microsomes. Furthermore, the formation of AFB1-DNA adducts by nasal microsomes is decreased by nicotine, a known inhibitor of P450 NMa. These data indicate that members of the P450 2A gene subfamily play an important role in the metabolic activation of AFB1 in rabbit and rat nasal mucosa and suggest a molecular basis for assessing the health risk associated with inhalation exposure to this procarcinogen in humans.

Pulses with fixed magnitude and variable phase response profiles

The Shinnar-Le Roux (SLR) method of pulse envelope design provides for the generation of nearly arbitrary magnitude response profiles with such great efficiency that the pulse envelopes may often be calculated at the time of sequence initiation. A significant limitation of the method is that it provides only limited control of the phase of the response profile. In the current manuscript it is demonstrated that the phase of the response profile can be modulated without affecting the magnitude profile by replacement of some of the roots of the SLR polynomials with one over their complex conjugate. This method allows interactive tailoring of the phase profile to the user's needs. Although the method does not allow for the optimization of arbitrary phase profiles, a variety of pulses, which are of general utility, have been generated. Some of these pulses and their response profiles are presented.

[Full thickness lamellar keratoplasty with viscodelamination of cornea for treatment of bullous keratopathy]

Intrastromal injection of viscoelastic (2% methylcellulose or healon) will facilitate the separation of deep stroma during dissection of recipient stroma. Full thickness lamellar keratoplasty was performed on a smooth graft bed which approached Descemet's membrane. 21 cases with bullous keratopathy were treated and followed up for six months, post-operatively. The symptoms were controlled in all cases and 13 cases were relieved from blindness with corrected visual acuities over 0.05. The safety, efficacy and reoperability of full thickness lamellar keratoplasty with viscodelamination of cornea for treatment of bullous keratopathy make it a promising technique.

Steroid metabolism by rabbit olfactory-specific P450 2G1

Cytochrome P450 2G1 (2G1), which is uniquely expressed in the olfactory mucosa in mammals, may have important physiological functions. In the present study, we have examined the catalytic activity of rabbit 2G1 toward a number of steroid sex hormones, including androstenedione, estradiol, progesterone, testosterone, and 5 alpha-dihydrotestosterone; the purified cytochrome is active toward all of these compounds in a reconstituted enzyme system with turnover numbers of 1.84, 0.34, 1.46, 1.04, and 0.84, respectively, at a substrate concentration of 5 microM. In the presence of cytochrome b5, the turnover numbers are 1.58, 0.66, 1.66, 2.74, and 1.34, respectively. Estradiol is converted to the 2-hydroxy compound (major product) and 4-hydroxy compound (minor product) by 2G1, and progesterone is converted to the 16 alpha-hydroxy derivative as well as the corresponding keto compound as a secondary product. The same products are formed in olfactory microsomal suspensions as major metabolites of progesterone, and the reactions are inhibited strongly by anti-2G1 IgG. In a reconstituted system, 2G1 has an apparent Km of 2.0 microM and a Vmax of 1.8 nmol/min/nmol P450 for the formation of the 16 alpha-hydroxyprogesterone. Of particular interest, 2G1-catalyzed progesterone metabolism is effectively inhibited by the boar pheromones, 5 alpha-androst-16-en-3-one and 5 alpha-androst-16-en-3 alpha-ol, and to a lesser extent by a variety of odorant compounds as well as by known P450 inhibitors, including ketoconazole and alpha-naphthoflavone. The broad substrate specificity and relatively high catalytic efficiency of 2G1 in sex steroid metabolism suggest a role for this unique P450 isozyme in the maintenance of steroid hormone homeostasis in the olfactory mucosa.

Predictors of outcome after anterior temporal lobectomy: positron emission tomography

We assessed the relationship between temporal lobe metabolism measured quantitatively and qualitatively with PET using [18F]-fluorodeoxyglucose (FDG) and postoperative seizure frequency after anterior temporal lobectomy. Forty-three patients with refractory partial epilepsy had anterior temporal lobectomy and preoperative assessment with PET-FDG. Qualitative PET analysis was performed visually by two blinded observers, and quantitative PET analysis was performed using an anatomic template for six control and six temporal lobe subregions, deriving an asymmetry index for each region. Seizure outcome was assessed 1 year after surgery; patients were classified as being seizure-free or as having persistent seizures. Qualitative data were analyzed using Fisher's exact test and the t test, and quantitative data were analyzed using a repeated-measures ANOVA. Thirty-two patients (74%) were seizure-free at follow-up, and 11 had persistent seizures, although most improved. Twenty-nine of 35 patients (83%) with restricted temporal lobe hypometabolism by visual analysis were seizure-free, compared with three of eight patients (37.5%) with normal scans or multilobar hypometabolism. Quantitative analysis revealed that an asymmetry of mesial temporal lobe glucose consumption (uncal region) correlated with improved surgical outcome (p < 0.02). We developed a logistic regression model to predict individual outcome based on the asymmetry in uncal metabolism. Lateral temporal metabolism did not correlate with outcome. We conclude that both visual PET analysis and quantitative PET analysis predict outcome after temporal lobectomy, although quantitative measures offer more precise information.

Sequential three-dimensional time-of-flight MR angiography of the carotid arteries: value of variable excitation and postprocessing in reducing venetian blind artifact

OBJECTIVE

Multiple overlapping three-dimensional (3D) time-of-flight carotid MR angiography potentially combines many of the desirable features of two-dimensional (2D) and single-volume 3D MR angiographic imaging techniques. Yet the maximum-intensity-projection images from such acquisitions are often degraded by artifact due to nonuniform signal intensity of contiguous imaging volumes and inadequate, yet arduous, postprocessing. The former has been termed venetian blind artifact. To date, the severity of the artifact has been minimized by the use of very thin slabs with a large percentage of overlap. However, the artifact typically is still appreciable, and the required acquisition and postprocessing times are increased. The purpose of this study was to examine the value of technical modifications of both the multislab acquisition and postprocessing procedures to reduce this artifact on images of healthy volunteers.

SUBJECTS AND METHODS

Spatially variable RF pulses along the direction of flow were applied as excitation pulses in the multislab time-of-flight MR angiographic acquisitions to compensate for the nonuniform blood signal intensity caused by spin saturation. An automatic postprocessing technique was used to optimally combine the image data in overlapping slices by selecting the higher-intensity pixel of the two on a pixel-by-pixel basis. Ratios of the standard deviation of signal intensity to the mean signal intensity were computed as a function of RF profile and postprocessing method along the long axes of the arteries to measure the uniformity of the signal intensity of the blood. The spatially variable and sinc RF pulse acquisitions, combined with automatic and conventional manual postprocessing, were compared.

RESULTS

Compared with the sinc pulse acquisition, the MR angiograms acquired with spatially variable excitation pulses improved the signal uniformity of the arteries with thicker volumes and less overlap, thereby reducing the acquisition time by 25% for similar spatial coverage. When used with the automatic postprocessing technique, the severity of the venetian blind artifact on maximum-intensity-projection images was minimized and the postprocessing time was reduced by roughly a factor of 5.

CONCLUSION

The combined use of spatially variable excitation pulses and an automatic postprocessing technique can improve the uniformity of the signal from blood across the slab and allow thicker slabs to be acquired with less overlap. Data acquisition and postprocessing times can be reduced significantly. This work suggests it may be possible to easily produce overlapping 3D MR angiograms that should be superior to conventional 2D and 3D studies.

Structure-function analysis of CYP2A10 and CYP2A11, P450 cytochromes that differ in only eight amino acids but have strikingly different activities toward testosterone and coumarin

Cytochrome P450 NMa, which was first identified in this laboratory in rabbit nasal microsomes, is now known to represent two distinct gene products, P450s 2A10 and 2A11. In the present study, chimeric and site-directed mutants of 2A11 were constructed to determine which of the eight different amino acid residues are responsible for the much greater activity of 2A10 toward coumarin and testosterone. Mutation of Arg62 and Asp63 of 2A11 to the corresponding residues in 2A10, or mutation of Thr120 to Ser, as found in 2A10, did not change the activities. However, mutation of Arg62, Asp63, Gln104, Ala117, and Thr120 of 2A11 to the corresponding residues in 2A10 resulted in a protein that is as active as 2A10 in coumarin hydroxylation and approximately half as active as 2A10 in androstenedione formation. Mutation of Arg372 in 2A11 to His, as found in 2A10, resulted in a significant increase in the rate of hydroxylation of testosterone, but not of coumarin. Our findings indicate that the identify of the amino acid at position 104 and/or 117 is important for activity with testosterone and for regioselectivity at the 17 position, as well as for optimal activity with coumarin. In contrast, the identity of the residue at position 372 is important for optimal activity with testosterone but not the regioselectivity at the 17 position and does not influence the activity with coumarin.

Direct structural observation of an acyl-enzyme intermediate in the hydrolysis of an ester substrate by elastase

The method of X-ray crystallographic cryoenzymology has been used to determine the crystal structure of a kinetically significant species on the reaction pathway of a crystalline enzyme. The structure of a specific acyl-enzyme intermediate in the elastase-catalyzed hydrolysis of the N-carbobenzoxy-L-alanine p-nitrophenyl ester has been determined and refined against X-ray diffraction data at 2.3-A resolution. The difference Fourier electron density map clearly shows electron density for the trapped acyl-enzyme. The acyl-enzyme was formed at -26 degrees C and was stabilized at -55 degrees C during data collection, taking advantage of the glass transition in protein dynamics that occurs at around -50 degrees C.

Fragile X induction systems in CVS cultures: effect on cytogenetic, PCR, and genomic Southern Blot DNA analyses of the FMR-1 gene

Low fragile X frequencies have been commonly observed in chorionic villus sample (CVS) cultures, compared to subsequent analysis in whole blood or products of conception (POC). To investigate possible mechanisms for this effect, CVS cultures from a previously identified fragile X positive male, were restudied and compared to subsequent POC cultures from lung, muscle, skin, and thymus. Cultures were exposed, for the last 24 hours before harvesting, to FUdR, excess thymidine, and a combination of both. For CVS, only those cultures that were exposed to a combination of FUdR and excess thymidine showed positive cytogenetic findings (1/90 or 1.1%), agreeing with our original positive cytogenetic results (2/86 or 2.3%) for cultures exposed to excess thymidine. Fragile X frequencies in the POC tissues from this fetus increased to an average of 14%. PCR analyses showed full mutations (> 200 CGG repeats) in uninduced CVS cultures but induced cultures exhibited apparently smaller sizes in the range of 120-180 repeats. The results showed variability. In one instance, the banding pattern from one of the uninduced cultures was similar to the results where cultures were exposed to a double induction system. When PCR analyses were conducted on induced POC cultures, full mutations were observed in virtually all samples. Southern blot genomic analysis using probe StB12.3 showed an unmethylated full mutation in CVS cultures. Southern blot patterns from cultures of muscle revealed size variations of DNA bands in the premutation range representing unmethylated DNA as well as methylated full mutations. Finally, variations were also observed in lung and skin cultures, compared to CVS and muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

SPARC (secreted protein acidic and rich in cysteine) regulates endothelial cell shape and barrier function

SPARC (secreted protein acidic and rich in cysteine) can be selectively expressed by the endothelium in response to certain types of injury and induces rounding in adherent endothelial cells in vitro. To determine whether SPARC might influence endothelial permeability, we studied the effect of exogenous SPARC on the movement of 14C-labeled bovine serum albumin across postconfluent bovine pulmonary artery endothelial cells. SPARC increased (P < 0.02) transendothelial albumin flux in a dose-dependent manner at concentrations > or = 0.5 microgram/ml. At a fixed dose (15 micrograms/ml), exposure times > or = 1 h augmented (P < 0.005) albumin flux by 1.3- to 3.6-fold; this increase was blocked by anti-SPARC antibodies but not by inhibition of protein synthesis. Barrier dysfunction was not associated with loss of cell viability. Monolayers exposed to SPARC exhibited a rounded morphology and intercellular gaps. Prior stabilization of F-actin with phallicidin protected against the changes in barrier function (P = 0.0001) that were otherwise induced by SPARC. Bovine aortic and retinal microvascular endothelia also responded to SPARC. We propose that SPARC regulates endothelial barrier function through F-actin-dependent changes in cell shape, coincident with the appearance of intercellular gaps, that provide a paracellular pathway for extravasation of macromolecules.

[Studies on the induction of L-phenylalanine ammonia lyase(PAL) in Rhodotorula glutinis and transformation of phenylalanine from trans-cinnamic acid]

The induction of PAL in Rhodotorula glutinis and transformation of L-phenylalanine from trans-cinnamic acid were studied. The optimum medium for PAL induction was composed of (g/L) 10.0 yeast extract, 10.0 peptone, 5.0 NaCl, 0.5 KH2 PO4, 0.5 phenylalanine 1.0 (NH4)2SO4 and 5.0 glucose, pH 6.0-6.5. The cultivation temperature was 30.0 degrees C. In the process of transformation, the effect of [NH4]+ on initial velocity was in accordance with Michaelis-Menten rate expression in which Km and Vmax were 16.85 mol/L and 5.96 g.L-1.h-1 for ammonia and the optimum pH was 10.0. Substrate activation and inhibition were observed at low and high concentration of cinnamic acid. The yield of phenylalanine from cinnamic acid reached more than 60.0%.

Lipopolysaccharide (LPS)-binding protein and soluble CD14 function as accessory molecules for LPS-induced changes in endothelial barrier function, in vitro

Bacterial LPS induces endothelial cell (EC) injury both in vivo and in vitro. We studied the effect of Escherichia coli 0111:B4 LPS on movement of 14C-BSA across bovine pulmonary artery EC monolayers. In the presence of serum, a 6-h LPS exposure augmented (P < 0.001) transendothelial 14C-BSA flux compared with the media control at concentrations > or = 0.5 ng/ml, and LPS (10 ng/ml) exposures of > or = 2-h increased (P < 0.005) the flux. In the absence of serum, LPS concentrations of up to 10 micrograms/ml failed to increase 14C-BSA flux at 6 h. The addition of 10% serum increased EC sensitivity to the LPS stimulus by > 10,000-fold. LPS (10 ng/ml, 6 h) failed to increase 14C-BSA flux at serum concentrations < 0.5%, and maximum LPS-induced increments could be generated in the presence of > or = 2.5%. LPS-binding protein (LBP) and soluble CD14 (sCD14) could each satisfy this serum requirement; either anti-LBP or anti-CD14 antibody each totally blocked (P < 0.00005) the LPS-induced changes in endothelial barrier function. LPS-LBP had a more rapid onset than did LPS-sCD14. The LPS effect in the presence of both LBP and sCD14 exceeded the effect in the presence of either protein alone. These data suggest that LBP and sCD14 each independently functions as an accessory molecule for LPS presentation to the non-CD14-bearing endothelial surface. However, in the presence of serum both molecules are required.

Analogous inhibitors of elastase do not always bind analogously

It has been assumed that the structure of a single inhibitor complex is sufficient to define the available subsites of an enzyme that has a unique binding site and a uniquely defined mode for ligand binding--the specificity for these subsites can thus be probed by kinetic experiments. Elastase is an enzyme for which these traditional assumptions, which underlie such structural and kinetic studies, do not hold. Three new crystal structures of elastase complexed to chemically similar inhibitors with similar binding affinities reveal a diversity of binding modes as well as two new subsites on elastase. The existence of multiple binding sites and different binding modes for such similar inhibitors indicates that researchers must proceed with caution when using kinetics to map out protein subsites.

Bioconcentration of cadmium in water hyacinth (Eichhornia crassipes) in relation to thiol group content

To study the bioconcentration of cadmium in water hyacinth, the plants were exposed to water containing 2 microg Cd2+/ml for extended periods of time. Three strains from several exposures during a 30-day period were sampled for the analyses of cadmium and thiol group. The data showed that the plant concentrates cadmium mainly in the roots and that the cadmium uptake is proportional to the increase of the thiol group content. The latter suggests the possibility of using the thiol group content to assess the bioconcentration of heavy metal ions in water hyacinth and as a general parameter for monitoring the heavy metal pollution of water. A simple two-compartmental model was used to simulate the kinetics of cadmium uptake. The calculated bioconcentration factor matches the one derived directly from experimental data, indicating the adequacy of the model.

Relationship of articular soft tissue contour and shape to the underlying eminence and slope profile in young adult temporomandibular joints

This study examined whether the overall shape of the articular soft tissue overlying the posterior slope and articular eminence of the temporal bone could be predicted by the underlying osseous contour in a histologic model of 51 central sagittal sections of young adult temporomandibular joints. Articular soft tissue and bone contours were traced, and osseous landmarks identified on the basis of joint geometry. Soft tissue thickness measurements were made under low power light microscopy. Seven categories of articular soft tissue pattern were identified. The soft tissue uniformly followed the osseous contour in only one (14%). A progressive increase in soft tissue thickness from the middle of the posterior slope to the articular crest was the most common pattern (35%) but did not describe most of the sample that was more asymmetric. Pattern was poorly predicted by the shape and slope of the temporal bone outline or by dental factors that describe anterior guidance and did not relate to disk displacement. The articular soft tissue compensated for flatter eminence slopes and osseous irregularities and maintained an intact surface. This study has clinical implications for radiographic interpretation of disk space, condyle translation pathways, and the integrity of the functional articular surface.

Contour mapping of the TMJ temporal component and the relationship to articular soft tissue thickness and disk displacement

The osseous architecture of central sagittal histologic sections of the temporal component of 51 temporomandibular joints of young adults at autopsy was studied to determine if this predicted the thickness of the overlying articular soft tissue and disk displacement. Geometric groupings of fossa-eminence shapes were generated using a hierarchical cluster analysis of the osseous fossa-eminence sigmoid curve, size, and slope. Six cluster groups were evolved and tested for relationship to soft tissue thickness measured at the eminence crest, mid-point of the eminence slope, closed pack location of the condyle, the inflection point, and the depth of the fossa. Soft tissue thickness at the inflection point and depth of the fossa was remarkably constant between cluster groups. Increased soft tissue thickness at the eminence crest and lower part of the posterior slope was weakly correlated to a flatter eminence slope and curve, explaining 10% to 20% of the variance (r2). There were no relationships between the parameters studied to the fossa curvature. An ANOVA showed no statistical difference in the posterior slope angle between the categories of disk position (p = 0.715) or to the six cluster groupings. The results suggest that the osseous contours seen on radiographs may not accurately predict the actual articular surface of the temporal component.

Rapid fragile X carrier screening and prenatal diagnosis using a nonradioactive PCR test

OBJECTIVE

To develop a rapid, nonradioactive test using the polymerase chain reaction (PCR) capable of detecting full fragile X mutations, premutations, and resolving normal alleles and to apply this to prenatal diagnosis and carrier screening of pregnant women at risk for fragile X carrier status.

DESIGN

Prenatal and blood sample PCR analysis with confirmation by direct Southern blotting and cytogenetic techniques.

SETTING

Samples sent to a DNA diagnostic research laboratory at a tertiary referral center.

PARTICIPANTS

Pregnant women with a family history of undiagnosed mental retardation or known fragile X syndrome and controls.

RESULTS

A rapid, nonradioactive PCR screening protocol for the fragile X mental retardation-1 gene for both normal and mutant alleles was developed. Analysis of 570 control X chromosomes showed a modal number of 30 CGG repeats (range, 12 to 52 repeats) and a calculated heterozygosity of approximately 80%. No excess of homozygosity was found, indicating the test was accurate for normal allele resolution. In addition, 150 unrelated pregnant women were screened. Within known fragile X families, five of 20 pregnant women were diagnosed as carriers. Two new fragile X families were diagnosed among relatives of 130 females with family histories of undiagnosed mental retardation, although no carriers were identified. Prenatal PCR testing of 28 carriers accurately detected nine fetuses with full mutations.

CONCLUSIONS

This rapid, nonradioactive PCR protocol allows accurate resolution of normal alleles as well as simultaneous detection of carrier alleles and full mutations. With this approach, efficient screening of pregnant women at risk for fragile X carrier status, subsequent genetic counseling of identified carriers, and reliable prenatal diagnosis can be offered.

Evidence that methylation of the FMR-I locus is responsible for variable phenotypic expression of the fragile X syndrome

DNA at the FMR-1 locus was analyzed by Southern blot using probe StB12.3 in an unusual fragile X family with six brothers, three of whom are affected with fragile X to varying degrees, two of whom are nonpenetrant carriers, and one of whom is unaffected. Fragile X chromosome studies, detailed physical examinations, and psychological testing were completed on all six. Two of the affected brothers and the two nonpenetrant brothers were found to be methylation mosaics. The three affected males spanned the phenotypic and cognitive spectrum of the fragile X syndrome. A correlation was seen between the degree of methylation and the phenotypic expression identified in the three affected males. The two males initially classified as nonpenetrant were found to have mild phenotypic expression which consisted of minor cognitive deficits and a partial physical phenotype. These two, who were negative on fragile X chromosome studies, were found on DNA analysis to have large broad smears, with approximately 97% of the DNA unmethylated. The results described here indicate that some "nonpenetrant" carrier males may have varying amounts of methylation of the FMR-1 region, which can result in mild expression of the fragile X syndrome. The apparently mild phenotypic and cognitive expression of the fragile X syndrome in the two males, initially classified as nonpenetrant, who are mosaic for hypermethylation of an expansion of the CGG repeat in the premutation range, indicates that expression of the syndrome is not confined to males with large, hypermethylated expansions (full mutation) but has instead a gradient effect with a threshold for the full expression of the phenotype.

Bacterial lipopolysaccharide induces actin reorganization, intercellular gap formation, and endothelial barrier dysfunction in pulmonary vascular endothelial cells: concurrent F-actin depolymerization and new actin synthesis

Bacterial lipopolysaccharide (LPS) influences pulmonary vascular endothelial barrier function in vitro. We studied whether LPS regulates endothelial barrier function through actin reorganization. Postconfluent bovine pulmonary artery endothelial cell monolayers were exposed to Escherichia coli 0111:B4 LPS 10 ng/ml or media for up to 6 h and evaluated for: 1) transendothelial 14C-albumin flux, 2) F-actin organization with fluorescence microscopy, 3) F-actin quantitation by spectrofluorometry, and 4) monomeric G-actin levels by the DNAse 1 inhibition assay. LPS induced increments in 14C-albumin flux (P < 0.001) and intercellular gap formation at > or = 2-6 h. During this same time period the endothelial F-actin pool was not significantly changed compared to simultaneous media controls. Mean (+/- SE) G-actin (micrograms/mg total protein) was significantly (P < 0.002) increased compared to simultaneous media controls at 2, 4, and 6 h but not at 0.5 or 1 h. Prior F-actin stabilization with phallicidin protected against the LPS-induced increments in G-actin (P = 0.040) as well as changes in barrier function (P < 0.0001). Prior protein synthesis inhibition unmasked an LPS-induced decrement in F-actin (P = 0.0044), blunted the G-actin increment (P = 0.010), and increased LPS-induced changes in endothelial barrier function (P < 0.0001). Therefore, LPS induces pulmonary vascular endothelial F-actin depolymerization, intercellular gap formation, and barrier dysfunction. Over the same time period, LPS increased total actin (P < 0.0001) and new actin synthesis (P = 0.0063) which may be a compensatory endothelial cell response to LPS-induced F-actin depolymerization.

Construction of multiple copy of alpha-domain gene fragment of human liver metallothionein IA in tandem arrays and its expression in transgenic tobacco plants

Metallothioneins (MT) are low molecular weight, cysteine-rich, metal-binding proteins. An MT molecule contains two domains which appear to act independently--an alpha-domain, which is characterized by cadmium-binding, and a beta-domain, which binds preferentially to copper. Based on this conception, DNA duplex encoding the alpha-domain (106 bp) of human MT-IA was constructed from a chemically-synthesized oligomer by repair synthesis and enzymatic ligation and cloned into pUC19. The genes cloned were sequenced and found to be in the correct order as designed. Synthetic directional adapters were attached to the terminals of the alpha-domain gene fragment of human MT-IA to establish complete control over fragment orientation during ligation. The use of these directional adapters thereby ensured the production of multiple copies of the alpha-domain in tandem arrays. The successive alpha-domains were linked by a peptide linker consisting of 10 residues. A chimeric gene containing 12 cloned tandemly repeated copies of the 106 bp alpha-domain DNA was introduced into tobacco cells on a disarmed Ti-plasmid of Agrobacterium tumefaciens. A total of 10 different transgenic tobacco plants were generated, of which two showed root and shoot growth unaffected by up to 200 mg/l kanamycin and 100 microM cadmium, whereas root growth of control plants was severely inhibited and leaf chlorosis developed on media containing only 10 microM cadmium.

Isolation and heterologous expression of cloned cDNAs for two rabbit nasal microsomal proteins, CYP2A10 and CYP2A11, that are related to nasal microsomal cytochrome P450 form a

Nasal microsomal P450 form a (NMa), a major cytochrome P450 isozyme in rabbit olfactory and respiratory nasal mucosa with high activity toward a variety of odorants and environmental toxicants, was previously purified to electrophoretic homogeneity from rabbit nasal microsomes. In the present study, a cDNA library constructed from poly(A)+ RNA from rabbit respiratory nasal mucosa was screened with antibodies to P450 NMa, and five immunopositive clones were isolated and characterized. Sequence analysis indicated that the clones encode two highly similar P450s that contain 494 amino acid residues, with the first 20 corresponding to P450 NMa, and differ from each other in only 8 residues scattered throughout the polypeptide chains. On the basis of structural homology the two proteins are designated as CYP2A10 and CYP2A11 and are the first members of the P450 2A subfamily to be identified in nasal tissue. Genomic blot analysis indicated that 2A10 and 2A11 are apparently not allelic variants. Both genes are expressed in liver and lung as well as in nasal tissues, as judged by RNA blot analysis, but the relative levels of the two mRNAs differ. Both enzymes were partially purified after expression of the cDNAs in Escherichia coli and shown to catalyze the oxygenation of a variety of substrates, including ethanol and procarcinogens such as N-nitrosodiethylamine and phenacetin. P450 2A10 is generally more active than P450 2A11 and strikingly so in the conversion of testosterone to androstenedione.

Maturation induced internalization of beta 1-integrin by Xenopus oocytes and formation of the maternal integrin pool

A pool of beta 1-integrin, ready to be inserted into the cleavage membranes, is present in the cytoplasm of the Xenopus egg, while its plasma membrane is devoid of this membrane protein (Gawantka et al., 1992). The underlying mechanisms that lead to this specific pattern of beta 1-integrin distribution in the egg have been investigated. beta 1-Integrin is present on the oocyte membrane throughout oogenesis. During maturation the oocyte membrane is cleared of beta 1-integrin via internalization of the protein by the oocyte. Synthesis of beta 1-integrin precursor is stimulated moderately in the maturing oocyte. At the same time processing of the precursor into the mature form of beta 1-integrin and its complexing with a putative alpha-chain is greatly accelerated. This way a maternal integrin pool accumulates in the mature oocyte. It is localized in conspicuous yolk free patches which contain large amounts of endoplasmic reticulum, Golgi complexes and smooth vesicles. We suggest that membrane vesicles harbouring the beta 1-integrin are generated in these cytoplasmic regions and that this store of vesicles provides the material source for the rapid membrane formation during cleavage.

Immunohistochemical localization of a cytochrome P-450 isozyme in human nasal mucosa: age-related trends

Immunoperoxidase staining with an antibody to cytochrome P-450 (NMa) was used to investigate the localization of this isozyme in the human nasal mucosa. Olfactory mucosa was identified by staining of olfactory receptor cells with an antibody to olfactory marker protein. Immunoreactivity to NMa was localized in sustentacular cells in the olfactory epithelium, and in Bowman's gland acinar cells and vascular endothelial cells in the lamina propria. In the respiratory mucosa, ciliated epithelial cells, as well as serous gland acinar cells and vascular endothelial cells in the lamina propria, were immunoreactive for this isozyme. An age-related decrement in the intensity and extent of immunoreactivity within these cells was noted in nasal tissue from patients 60 years of age and over when compared with that of patients under 60 years of age. These results identify sites of xenobiotic metabolism or activation in human nasal mucosa.

TNF-alpha induces endothelial cell F-actin depolymerization, new actin synthesis, and barrier dysfunction

Tumor necrosis factor-alpha (TNF-alpha) influences pulmonary vascular endothelial barrier function in vitro. We studied whether recombinant TNF-alpha (rTNF-alpha) regulates endothelial barrier function through actin reorganization. Postconfluent bovine pulmonary artery endothelial cell monolayers were exposed to human rTNF-alpha (1,000 U/ml) and evaluated for 1) transendothelial [14C]albumin flux, 2) F-actin organization with fluorescence microscopy, 3) F-actin quantitation by spectrofluorometry, and 4) monomeric G-actin levels by the deoxyribonuclease I inhibition assay. rTNF-alpha induced increments in [14C]albumin flux (P < 0.04) and intercellular gap formation at > or = 2-6 h. During this same time, the endothelial F-actin pool decreased (P = 0.0064), with reciprocal increases in the G-actin pool (P < 0.0001). Prior F-actin stabilization with phallicidin protected against the rTNF-alpha-induced increments in G-actin (P < 0.002) as well as changes in barrier function (P < 0.01). Prior protein synthesis inhibition enhanced the rTNF-alpha-induced decrement in F-actin (P < 0.0001), blunted the G-actin increment (P < 0.002), and increased rTNF-alpha-induced changes in endothelial barrier function (P < 0.003). Therefore, rTNF-alpha induces pulmonary vascular endothelial F-actin depolymerization, intercellular gap formation, and barrier dysfunction. rTNF-alpha also increased total actin (P < 0.02) and new actin synthesis (P < 0.002), which may be a compensatory endothelial cell response to rTNF-alpha-induced F-actin depolymerization.

Flavone improves functional recovery after ischemia in isolated reperfused rabbit hearts

The effects of flavone (2-phenyl-1,4-benzopyrone), a modulator of the cytochrome P-450 monooxygenase system, on myocardial postischemic reperfusion recovery were examined in the present study. Left ventricular functional recovery was evaluated in isolated, crystalloid-perfused rabbit hearts after 2 hours of modestly hypothermic (34 degrees C) global ischemia. Four groups (n = 8 in each group) were studied and compared: a vehicle control group, a second group pretreated with flavone (8 x 10(-6) mol/L) before ischemia, a third group pretreated with flavone followed by SKF 525-A (1.7 x 10(-5) mol/L), an inhibitor of cytochrome P-450, and a fourth group pretreated with flavone followed by indomethacin (1 x 10(-6) mol/L), an inhibitor of cyclooxygenase. At 15, 30, and 45 minutes after reperfusion, recovery of left ventricular developed pressure in the control group averaged (mean +/- standard deviation) only 2.60% +/- 12.7%, 35.5% +/- 15.0%, and 42.9% +/- 13.5% of baseline, respectively. In the flavone-treated group, recovery was significantly better, averaging 67.7% +/- 10.7%, 73.9% +/- 9.3%, and 73.6% +/- 7.6% of baseline at the same time periods. Recovery of peak positive rate of pressure rise in the control group averaged 27.4% +/- 15.2%, 38.6% +/- 19.2%, and 45.4% +/- 18.6% of baseline at 15, 30, and 45 minutes of reperfusion, respectively. In the flavone-treated group recovery values were significantly higher, averaging 67.8% +/- 9.6%, 77.3% +/- 8.5%, and 77.0% +/- 9.0% of baseline. End-diastolic pressures were significantly lower in the flavone-treated group compared with the control group at all reperfusion time points. Myocardial oxygen consumption was significantly higher in the flavone-treated group at 30 and 45 minutes of reperfusion, as well. The improvement resulting from flavone infusion was abolished completely by SKF 525-A, providing support for the interpretation that the effects of flavone were mediated through the cytochrome P-450 system. The cyclooxygenase inhibitor indomethacin midly attenuated the effects of flavone pretreatment, suggesting that the effects of flavone were only minimally related to metabolites of cyclooxygenase. We conclude that pretreatment with flavone represents a promising approach to myocardial protection that may be due to modulation of the myocardial cytochrome P-450 system.

Cytochromes P450 NMa, NMb (2G1), and LM4 (1A2) are differentially expressed during development in rabbit olfactory mucosa and liver

Mammalian olfactory mucosa has a high concentration of cytochrome P450 monooxygenases (P450). The major olfactory P450 isoforms in adult rabbits include P450 NMa, which is found in both olfactory and respiratory mucosa, as well as in liver at a low level, P450 NMb (2G1), which is olfactory specific, and P450 form 4 (1A2), which is found only in liver and olfactory mucosa. In the present study, we have found that the developmental expression of olfactory P450 in rabbits is not coordinated with the ontogenesis of hepatic P450. These three P450 isoforms were detected immunochemically and found to be at a relatively high level in olfactory but not hepatic microsomes in the first 2 weeks after birth. In the liver, NMb is not detectable at any age and NMa is not detectable until the fourth week. P450 1A2 is not detectable until the third week, but its level increases rapidly in the fourth week. These P450 isoforms are also detectable in prenatal olfactory tissue at 2 days before birth, indicating that direct exposure to air is not a prerequisite for their early expression in this tissue and that the early appearance of these enzymes may be controlled by both endogenous and environmental factors. In addition, the developmental expression of 2E1, a minor olfactory P450 isoform, also occurs earlier in olfactory mucosa than in liver, and the same conclusion can be made about the expression of NADPH-P450 reductase, which is detectable in olfactory microsomes but not in hepatic microsomes from prenatal rabbits. Thus, the regulatory mechanisms that control basal prenatal expression in the olfactory tissue may be common for multiple P450 isoforms and perhaps also for other biotransformation enzymes. The tissue-specific early onset of expression of multiple forms of P450 in olfactory tissue suggests that these enzymes may play an important role in the neonatal period, when olfactory ability is vital for the survival of the newborn. The presence of relatively high levels of biotransformation enzymes in the olfactory mucosa may also have important implications for neonatal inhalation toxicology.

Metabolism of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a tobacco-specific carcinogen, by rabbit nasal microsomes and cytochrome P450s NMa and NMb

Rabbit nasal olfactory and respiratory microsomes were found to catalyze the alpha-hydroxylation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) with specific activities of 262 and 136 pmol/min/mg protein in the formation of keto aldehyde, and of 318 and 190 pmol/min/mg protein in the formation of keto alcohol respectively. The formation of NNK-N-oxide was observed in experiments with rabbit olfactory and respiratory microsomes, but not with rat nasal microsomes. However, the rat nasal microsomes had higher activity in catalyzing the alpha-hydroxylation of NNK. In a reconstituted system, rabbit P450NMa, a major constitutive P450 isozyme in nasal microsomes, displayed high activities in the formation of the keto aldehyde and the keto alcohol with apparent Km values of 15 and 9 microM respectively. In comparison, rabbit olfactory specific P450NMb had a low activity in catalyzing the formation of keto aldehyde (Km = 186 microM) and no activity in the formation of keto alcohol. The P450NMa-catalyzed oxidation of NNK was inhibited by nicotine and diallyl sulfide. Kinetic studies indicated that nicotine is a competitive inhibitor. These results demonstrate that enzymes in rabbit nasal microsomes, especially P450NMa, efficiently catalyze the bioactivation of NNK.

Induction of P-450 cytochromes 2E2, 1A1, and 1A2 by imidazole in neonatal rabbits

Cytochrome P-450 2E1 is induced in adult rabbits by treatment with alcohol, imidazole, and a variety of other agents, as shown earlier in this laboratory, but it is not known whether the highly homologous P-450 2E2 is similarly induced. In this study, the effects of imidazole on 2E2 expression were examined in neonatal rabbits, in which 2E1 is not detectable. Treatment of the animals with imidazole on days 8 through 11 after birth caused a 3-fold increase in the content of total P-450 in liver microsomes. In contrast, the microsomal content of cytochrome b5 and NADPH-P450 reductase was not changed. Immunoblot analysis revealed a significant increase in the level of P-450 2E2 (3-fold) as well as 1A1 (> 10-fold) and 1A2 (> 2-fold) in hepatic microsomes from imidazole-treated neonatal rabbits. The rates of microsomal N-demethylation of N-nitrosodimethylamine and O-deethylation of 7-ethoxyresorufin were similarly increased from 1.3 and 0.03 nmol/min/mg protein, respectively, to 5.6 and 0.24 nmol/min/mg protein, respectively, by imidazole treatment. Blot analysis indicated that the levels of 2E2, 1A1, and 1A2 mRNAs are not increased by imidazole treatment and that 2E1 mRNA is not detectable in either untreated or imidazole-treated neonates. The induction of P-450 2E2 was confirmed by NH2-terminal amino acid sequence analysis of immunopurified 2E protein from hepatic microsomes of imidazole-treated neonatal rabbits.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunolocalization of two cytochrome P450 isozymes in rat nasal chemosensory tissue

The NMa and NMb isoforms of cytochrome P450 enzymes are expressed in three nasal chemosensory organs: the olfactory, septal and vomeronasal mucosae. The NMa isoform is widely distributed throughout the nasal mucosa whereas the NMb isoform is present primarily in the chemosensory mucosae. The localization of cytochromes P450 demonstrates that sustentacular cells in the olfactory and septal epithelia, the mucus of the vomeronasal organ and the acinar cells of glands in the lamina propria of all three chemosensory systems engage in xenobiotic metabolism and participate in odorant/pheromone clearance, a perireceptor process associated with chemosensory transduction.

Interleukin-1 alpha and -beta augment pulmonary artery transendothelial albumin flux in vitro

Human recombinant interleukin-1 alpha (rIL-1 alpha) and -beta were studied to determine whether either could alter the permeability of bovine pulmonary artery endothelial cell monolayers. Endothelial cells were grown to confluence on filters mounted in chemotaxis chambers placed in wells. Barrier function of the monolayers was assessed by placing 14C-labeled bovine serum albumin ([14C]BSA) in the upper chamber and sampling the lower well for [14C]BSA. rIL-1 alpha induced a significant (P less than 0.01) dose- and time-dependent increase in transendothelial [14C]BSA flux. rIL-1 alpha exposures as brief as 30 min increased permeability, but the increased albumin transfer could not be demonstrated before 4 h after exposure. Exposures up to 6 h were reversible at 24 h. rIL-1 alpha induced significantly (P less than 0.01) greater increments in [14C]BSA flux than did equivalent exposures to rIL-1 beta. No important differences between bovine and human rIL-1 beta were demonstrated. Increased transendothelial flux could not be ascribed to either endothelial cytotoxicity or growth inhibition. There was no additive or synergistic relationship between rIL-1 alpha and human recombinant tumor necrosis factor-alpha. Our studies suggest that IL-1 alpha and -beta may play a role in the pathogenesis of pulmonary vascular leak.

P-450-dependent arachidonic acid metabolism in rabbit olfactory microsomes

Microsomes isolated from rabbit olfactory epithelium catalyzed the conversion of arachidonic acid to several metabolites at a rate of 692 +/- 106 pmol/min/nmol P-450. The major metabolite was the omega-hydroxylated metabolite, 20-hydroxyeicosatetraenoic acid, accounting for 57% of the total metabolite produced. A putative omega-1 hydroxylated metabolite was also formed to a lesser extent. Epoxyeicosatrienoic acids were not detected with microsomal incubations, although metabolites corresponding to the dihydroxyeicosatrienoic acids were observed and represented about 20% of the total metabolite produced. The metabolism of arachidonic acid was also studied in a reconstituted system with six purified P-450 isoforms that are known to be expressed in rabbit olfactory mucosa. These included P-450NMa, P-450 2G1 (NMb), P-450 1A2, P-450 2B4, P-450 2E1, P-450 3A6 and a partially purified preparation of P-450 4A isoforms. The P-450 4A forms were the only enzymes to produce significant amounts of the omega-hydroxylated metabolite of arachidonic acid. The other isoforms were either inactive (P-450NMa and P-450 3A6) or produced metabolites other than the 20-hydroxyeicosatetraenoic acid and, thus, cannot account for the majority of the miscrosomal metabolism of arachidonic acid. Immunoblot analysis with goat anti-rat P-450 4A1 identified one major and a second minor protein of the P-450 4A gene family in olfactory microsomes. The same antibody identified two proteins in rabbit renal tissue that were significantly induced by pretreatment with clofibric acid and were present in a partially purified preparation of P-450 4A from rabbit renal cortex.(ABSTRACT TRUNCATED AT 250 WORDS)