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)

Group 3 LEA Gene HVA1 Regulation by Cold Acclimation and Deacclimation in Two Barley Cultivars with Varying Freeze Resistance

The level of expression of the group 3 late embryogenesis abundant abscisic acid-regulated gene (HVA1) to cold treatment has been studied in winter barley (Hordeum vulgare) seedling tissue. The cDNA clone (pHVA1) encoding this late embryogenesis abundant protein was used as a hybridization probe to detect the corresponding mRNA. Expression of the HVA1 gene was determined after the tissue had been subjected to a regimen of 2 degrees C exposure (cold acclimation), followed by a return to 25 degrees C growth conditions (deacclimation). Accumulation of HVA1 mRNA occurred upon cold acclimation of the tissue and disappeared as early as 2 hours after exposure to deacclimation conditions. A comparison of the response to cold acclimation and deacclimation was made between seedling tissue of a freeze-resistant and less freeze-resistant cultivar. In both cultivars, the HVA1 gene was expressed and modulated by cold treatment. Within 2 hours of deacclimation HVA1 mRNA was no longer detectable in either cultivar independently of freeze resistance. The level of expression of HVA1 appeared to be greater in the less freeze-resistant cultivar (Winter Malt).

[The clinical use of sodium hyaluronate eyedrops as a substitute for tears]

The present paper reports on the curative effect of the 0.1% Sodium hyaluronate (Na-HA) eyedrops jointly manufactured by Guangzhou Red Cross Hospital and Guangzhou Institute of Medical & Pharmaceutical Industry. 70 cases were studied. There were kerato-conjunctivitis sicca, lagophthalmos corneal fluorescein diffuse punctate epithelial lesion caused by contact lens, and keratitis punctata superficialis. The results showed effective treatment which occupied 95.7%. In the discussion, the authors point out that Na-HA has the same stagnatisity and elasticity as biotears because of its adhesion to the corneal epithelium. Moreover, it has the water-retaining microsponge action similar to that of mucopolysaccharide. Hence, Na-HA has protective effects on corneal epithelium. Finally, the authors conclude that Na-HA eyedrop is so far the most ideal substitute for tears and superior to other artificial tears.

[Chemical constituents of the leaves of Crataegus pinnatifida Bge. var. major N. E. Br]

Compounds were isolated from the aqueous extract of the leaves of Crataegus pinnatifida var. major and seven of them were identified as 2-(4-hydroxybenzyl)malic acid, quercetin, hyperin, vitexin, rhamnosylvitexin, diethylamine hydrochloride and sorbitol respectively by UV, IR, NMR, MS, some chemical techniques by comparison with the standard spectra of known compounds.

Mössbauer studies on the metal-thiolate cluster formation in Fe(II)-metallothionein

The stepwise 57Fe(II)-thiolate cluster formation in rabbit liver metallothionein-2 (MT) has been followed at pH 8.5 using Mössbauer spectroscopy. The zero-field spectra recorded at 4.2 K exhibit at all stages of filling one virtually identical single quadrupole splitting delta EQ and isomer shift delta as found for reduced rubredoxin (Rdred) or the model compound [Fe(II)(SPh)4]2-, thus indicating an Fe(II)-tetrathiolate coordination. A similar conclusion was reached also in previous electronic absorption studies [M. Good and M. Vasák (1986) Biochemistry 25,8353--8356]. The Mössbauer spectra obtained in the presence of a magnetic field were analyzed on the basis of a spin-Hamiltonian formalism resulting in Mössbauer parameters similar to those for Rdred and the inorganic model compound [Fe(II)(SPh)4]2-. The identity of the Mössbauer parameters of partially and fully metal-occupied MT suggests that a comparable distortion of the metal binding sites must exist. Simulation of the spectra revealed that the Fe(II) ions in the partially metal-occupied 57Fe(II)4-MT form appear to be magnetically isolated, whereas in the fully metal-saturated 57Fe(II)7-MT form a ratio of 3:4 of paramagnetic to diamagnetic subspectra was obtained. The latter result suggests the existence of three isolated metal binding sites and a metal-thiolate cluster containing four metal ions. In the light of structure determinations of MT containing Zn(II) and/or Cd(II) [W. Braun et al. (1986) J. Mol. Biol. 187, 125-129, and W. F. Furrey et al. (1986) Science (Wash. DC) 231, 704-710], which revealed two metal-thiolate clusters containing three and four metal ions, respectively, and involving all 20 cysteine residues in metal binding, the appearance of Mössbauer parameters characteristic of three isolated Fe(II) sites in 57Fe(II)7-MT is peculiar and deserves further studies. It is concluded, moreover, that the four-metal cluster is diamagnetic with the four Fe(II) ions being antiferromagnetically coupled. The appearance of magnetic coupling above four Fe(II) equivalents bound to apoMT indicates that the cluster formation occurs in a two-step process.