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Biomedical subjects

N M Wilson

Publications and source records attributed to N M Wilson.

At least 55 records · Page 3Linked to original sources
PubMed1991

Use of transcutaneous oxygen tension, arterial oxygen saturation, and respiratory resistance to assess the response to inhaled methacholine in asthmatic children and normal adults.

Respiratory resistance (Rrs6), transcutaneous oxygen tension (PtcO2), and oxygen saturation (SaO2) were measured during methacholine challenge in 15 asthmatic children and six normal adults. During bronchoconstriction, induced by a wide range of inhaled methacholine concentrations (0.5-256 g/l), the rise in Rrs6 was reflected by a fall in PtcO2 in all subjects. Although there was a significant mean fall in SaO2 at maximum bronchoconstriction there was no consistent relation between changes in SaO2 and Rrs6. The inhaled dose of methacholine causing a 40% increase in Rrs6 (PD40Rrs6) and a 20% fall in PtCO2 (PD20PtcO2) was calculated for each subject. There was no significant difference in mean PD40Rrs6 and PD20PtcO2, and the relation between the two was similar in the asthmatic children and the normal adults. It was therefore concluded that the measurement of PtcO2, but not SaO2, during methacholine challenge can be used for the assessment of bronchial responsiveness, and that it could prove particularly useful for children too young to cooperate with lung function tests.

Administration, Inhalation↗
PubMed1990

Selective induction of cytochrome P450 isozymes in rat liver by 4-n-alkyl-methylenedioxybenzenes.

To examine the structural requirements of cytochrome P450 induction by 4-n-alkyl-substituted methylenedioxybenzenes (MDBs), rats were treated in vivo with a series of MDBs that differed in alkyl carbon side-chain length (0, 1, 2, 3, 4, 5, 6, or 8). Expression patterns of specific P450 isozymes were evaluated with Western and Northern blotting, enzymatic assays, and solution hybridization assays. As determined by carbon monoxide difference spectroscopy, maximal hepatic induction of total P450 content occurred when rats were treated with MDB derivatives with alkyl chain lengths of five or six carbons. However, maximum induction of the specific P450s--P450IA1, P450IIB1, and P450IIB2--occurred with n-hexyl-MDB. In contrast to effects observed with phenobarbital, treatment with MDBs resulted in higher levels of P450IIB2 than of P450IIB1 in rat hepatic microsomes. Western blot quantitation of MDB-induced hepatic P450IIB1 and P450IIB2 apoenzymes did not correlate to measured levels of the corresponding P450 mRNAs. In fact, P450IIB1 and P450IIB2 apoenzyme levels were consistently lower than expected based on Northern blot and solution hybridization measures of the respective mRNAs. These data suggest that the n-alkyl-MDBs effect increases in levels of hepatic P450 in a complex manner, producing accumulation of P450 mRNAs concomitant with alterations in processes regulating steady-state levels of P450 apoenzyme.

Alkylation↗
PubMed1990

Selective expression of cytochrome P450 isozymes by 4-n-alkyl-methylenedioxybenzenes in rat lung cells.

Rat lung preparations were analyzed for cytochrome P450 expression as a function of pretreatment with 1 mmol/kg/day of various substituted n-alkyl-methylenedioxybenzenes (MDBs). Lung P450s were quantitated by Western blotting and visualized by immunocytochemical techniques using polyclonal antibodies directed against P450IA1/IA2 and P450IIB1/IIB2. Results demonstrated that n-hexyl and n-octyl-MDB (but not n-butyl-MDB) increased P450IA1 in lung microsomes (50 pmol/mg microsomal protein) compared to untreated controls and n-butyl-MDB-treated animals (6 pmol/mg). However, treatment with all of these MDBs concomitantly decreased P450IIB1 in rat lung microsomes, from 40 pmol/mg in untreated control lungs to below the detection limit of this method (less than 2 pmol/mg). In vitro metabolism assays with rat lung microsomes, utilizing 7,12-dimethylbenz[a]anthracene as substrate, confirmed the increase in P450IA1 by selected MDBs and the concomitant decrease of catalytically active P450IIB1. Immunocytochemistry of rat lungs with these same IgGs indicated selective cellular responses. n-Hexyl-MDB (but not n-butyl-MDB) increased P450IA1-like immunoreactivity, but the increase was specifically localized to Clara cells. Immunocytochemical results further showed that P450IIB1-like immunoreactivity disappeared entirely from alveolar type II cells, yet appeared unchanged in Clara cells relative to untreated controls. Increases in P450IA1 due to treatment with n-hexyl-MDB were associated with increases in P450IA1 mRNA as indicated by Northern blot experiments. In contrast, the decreased levels of P450IIB1, consequent to treatment with n-alkyl-MDBs, were not associated with altered levels of pulmonary P450IIB1 mRNA as determined by Northern blotting and solution hybridization assays. These results imply that n-alkyl-MDBs regulate pulmonary cytochromes P450 by both transcriptional and post-transcriptional mechanisms.

Alkylation↗
PubMed1990

How much aerosol reaches the lungs of wheezy infants and toddlers?

Using sodium cromoglycate as a non-toxic marker, we assessed the delivery of aerosol to nine wheezy infants and seven healthy adults. The drug was delivered to the infants by face mask and spacer device from a metered dose inhaler, and by face mask and nebuliser to the infants and the adults who breathed though their noses. The concentration of sodium cromoglycate was estimated in timed urine collections to find out how much of the dose was absorbed from the lung. Only 0.13% to 0.61% of the 20 mg nominal dose was detected in the urine, representing an estimated 0.3% to 1.5% deposited in the lung. Nasal filtration of aerosol could be a critical factor in reducing lung deposition.

Absorption↗
PubMed1990

Treatment of acute, episodic asthma in preschool children using intermittent high dose inhaled steroids at home.

In a double blind, controlled trial, the effect of high dose beclomethasone dipropionate (750 micrograms three times daily for five days) administered by metered dose inhaler and valved spacer, was compared with placebo, during 70 paired episodes of acute asthma in 24 preschool children. Treatment commenced at home at the first sign of an attack. Parents' blind preference for active treatment was significant. Data from 17 pairs of treatment, however, were affected by interventions such as hospital admission or oral corticosteroid treatment. These events occurred similarly in active and control periods. An intrasubject comparison was made of diary scores from the 18 pairs of episodes in which no intervention occurred in either the active or placebo treatment. Both daytime and night symptoms over the first week of the attack were significantly reduced by active treatment. Intermittent high dose inhaled beclomethasone dipropionate is beneficial in modifying the severity of acute episodic asthma in preschool children able to use a spacer device.

Acute Disease↗
PubMed1990

Primary restorative colectomy in malignant left-sided large bowel obstruction.

A series of 18 consecutive patients who underwent primary resection and immediate anastomosis as the treatment for malignant left-sided large bowel obstruction are presented. Intraoperative mechanical preparation of the colon was omitted. There was no clinical evidence of anastomotic dehiscence or wound infection. The mean duration of hospital stay was 11 days. It is suggested that colonic continuity can be restored immediately and safely without mechanical bowel preparation, providing attention is directed to constructing an anastomosis that has a good blood supply and is free from tension.

Aged↗
PubMed1989

Xenobiotic microsomal epoxide hydrolase: 5' sequence of the human gene.

A cDNA for human microsomal epoxide hydrolase (mEH) was used to isolate genomic clones representing the 5' portion of the corresponding human gene. A total of 1034 bases of mEH gene sequence were obtained that included exon 1 and 5' flanking information. In contrast to the structure reported for the rat mEH gene (Falany et al. (1987) J. Biol. Chem. 262, 5924-5930), the human mEH gene lacked a CAAT box, but did contain a high-affinity CTF binding site at position -278 and an SV40 core enhancer element at position -525. TATA boxes were identified at positions -32 and -29 for the human and rat genes, respectively. Sequence comparisons between 5' flanking regions of the human and rat mEH genes demonstrated 47% homology, considerably less than the 83% conservation observed in the cDNA coding areas. Primer extension experiments localized the transcription initiation site of the human gene to a position 116 bases 5' from the analogous site in the rat mEH gene.

Base Sequence↗
PubMed1989

A yeast telomere binding activity binds to two related telomere sequence motifs and is indistinguishable from RAP1.

Telomere Binding Activity (TBA), an abundant protein from Saccharomyces cerevisiae, was identified by its ability to bind to telomeric poly(C1-3A) sequence motifs. The substrate specificity of TBA has been analyzed in order to determine whether the activity binds to a unique structure assumed by the irregularly repeating telomeric sequences or whether the activity recognizes and binds to subset of specific sequences found within the telomere repeat tracts. Deletion analysis and DNase I protection assays demonstrate that TBA binds specifically to two poly-(C1-3A) sequences that differ by one nucleotide. The methylation of four guanine residues, located at identical relative positions within these two binding sequences, interferes with TBA binding to the substrates. A synthetic olignucleotide containing a single TBA binding site can function as a TBA binding substrate. The TBA binding site shares homology with the binding sites reported for the Repressor/Activator Protein 1 (RAP1), Translation Upshift Factor (TUF) and General Regulatory Factor (GRFI) transcription factors, and TBA binds directly to RAP1/TUF/GRFI substrate sequences. Yeast TBA preparations and the RAP1 gene product expressed in E. coli cells are both similarly sensitive to in vitro protease digestion. Affinity-purified TBA extracts include a protein indistinguishable from RAP1 in binding specificity, size, and antigenicity. The binding affinity of TBA for the two telomeric poly(C1-3A) binding sites is higher than its affinity for any of the other binding substrates used for its identification. In extracts of yeast spheroplasts prepared by incubation of yeast cells with Zymolyase, an altered, proteolyzed form, of TBA (TBA-S) is present. TBA-S has a faster mobility in gel retardation assays and SDS-PAGE gels, yet it retains the DNA binding properties of standard TBA preparations: it binds to RAP1/TUF/GRFI substrates with the same relative binding affinity and protects poly(C1-3A) tracts from DNase I digestion with a "footprint" identical to that of standard TBA preparations.

Base Sequence↗
PubMed1989

Selective potent restriction of P450b- but not P450e-dependent 7,12-dimethylbenz[a]anthracene metabolism by the microsomal environment.

The prototypic members of the rat liver cytochrome P450IIB subfamily, P450b and P450e, differ by only 13 amino acids and yet purified P450b is considerably more active than P450e for all known substrates. A unique regioselectivity difference between cytochromes P450b and P450e for the metabolism of 7,12-dimethylbenz[a]anthracene (DMBA) and a genetic deficiency in P450e expression in the Marshall (M520/N) rat strain have been exploited to determine the microsomal contributions of the respective forms toward the metabolism of DMBA. The total contribution to metabolism by each isozyme has been assessed based on the sensitivity to rabbit anti-P450b/e IgG and comparison with microsomal P450b and P450e content as measured by Western blots. Liver microsomes from untreated M520/N rats do not express detectable levels of P450e but express P450b at a level that is 2-fold higher than that of P450e in liver microsomes from untreated F344 rats (50 pmol/mg). However, only 4% of the constitutive DMBA metabolizing activity of liver microsomes from the M520/N rat strain could be inhibited by anti-P450b/e IgG. A 30-fold induction of hepatic P450b by phenobarbital (PB) was also completely ineffective in increasing P450b-dependent DMBA metabolism. PB treatment had no appreciable effect on either the levels of expression of P450b protein or P450b-dependent DMBA metabolism, in M520/N lung and adrenal microsomes. In contrast, PB treatment of F344 rats considerably increased P450b/e-dependent metabolism by liver, lung, and adrenal microsomes. The regioselectivity of the anti-P450b/e-sensitive metabolism (predominantly 12-methyl hydroxylation), however, indicated a much greater contribution from P450e than P450b in every tissue examined despite a several fold higher expression of P450b than of P450e. P450b was expressed constitutively in lung microsomes from both strains but again failed to exhibit appreciable DMBA metabolizing activity. Based on these activities and microsomal P450b contents, P450b consistently exhibited turnover numbers (0.02-0.15 nmol/nmol P450b/min) that were at least 10-fold lower than those of pure P450b. In contrast, the calculated turnover numbers for microsomal P450e were consistently comparable to those of pure P450e (approximately 1 nmol/nmol P450e/min).

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

A comparison of primary nursing and team nursing in a geriatric long-term care setting.

The purpose of this study was to evaluate primary and team nursing on two 45-bed geriatric units. A 2 year longitudinal study with a quasi-experimental ABA cross-over design and a staff survey, permitted comparisons of the two nursing systems on indices of patient well-being, nursing practice, staff morale and costs. Differences in nursing practice, in selected measures of patient well-being and in responses to the staff survey were positively associated with primary nursing. No differences emerged in relation to staff morale or costs. The benefits of primary nursing and implications for further research are discussed.

Aged↗
PubMed1988

The expression and metabolic activity of cytochrome P-450 isozymes in control and phenobarbital-induced primary cultures of rat hepatocytes.

The expression and activity of the phenobarbital (PB)-inducible P-450 isozymes, P-450b and P-450e, and the major 3-methylcholanthrene (MC)-inducible form, P-450c, were studied in primary cultures of adult rat hepatocytes in T1, Leibovitz L-15 (L-15), and a modification of Waymouth 752/1 (Way) media. P-450 isozymes in initially isolated hepatocytes and control and PB-treated cultures were quantitated by Western blot analysis, and activity was determined with 7,12-dimethylbenz[a]anthracene (DMBA) as substrate. Data from the Western blot analysis correlated well with the metabolic activity toward DMBA. P-450b was consistently induced by PB in hepatocytes in T1 and to a lesser extent in Way. P-450e protein was constitutive in initially isolated cells, expressed in control cultures at a reduced level, and increased or maintained by PB in all three media. DMBA metabolite formation associated with P-450b and P-450e activity was induced by PB in hepatocytes in T1 and Way and was inhibited by antibodies to P-450b. P-450c was only infrequently expressed in freshly prepared hepatocytes, but was detected in all control and PB-treated cultures although at a much higher level in T1. Thus, the amounts of P-450 isozymes, their inducibility by PB, and their activity toward DMBA were found to be dependent on the medium. We have demonstrated enzyme induction and increased activity of the major PB-inducible isozymes in hepatocytes in T1; these are also associated with a change in the control of P-450c expression leading to enhanced constitutive expression and inducibility by phenobarbital.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1987

Expression and function of three cytochrome P-450 isozymes in rat extrahepatic tissues.

Western blots using a polyclonal and a monoclonal antibody raised against rat liver cytochrome P-450b indicate tissue-specific expression of low levels of cytochrome P-450's b and e. P-450b and P-450e were expressed very selectively in, respectively, lung and adrenal microsomes of untreated rats but neither isozyme was detected in the corresponding kidney or small intestine microsomes. The regioselectivity of microsomal metabolism of 7,12-dimethylbenz[a]anthracene (DMBA) as well as the sensitivity to inhibition by anti P-450b/e IgG established that low levels of "b-like" P-450's are functional in lung and adrenal microsomes from uninduced rats, but not in microsomes from the kidney or small intestine. Functional P-450c was also detected at low levels in liver, lung, kidney, and adrenals of untreated rats. Among the extrahepatic tissues examined, DMBA metabolism was the highest in rat adrenal microsomes. However, only 30% of this activity was due to P-450's b, e, or c. Phenobarbital (PB) treatment of rats increased microsomal DMBA metabolism in all extrahepatic tissues examined. The selectivity of this increase for 12-methyl hydroxylation of DMBA and the near complete inhibition by anti-P-450b/e are consistent with induction of P-450e even though P-450b was preferentially induced in each of the extrahepatic tissues examined. The levels of expression of P-450b were increased by PB in all sets of adrenal, lung, and intestinal microsomes and in three out of six sets of kidney microsomes. The levels of P-450e were also increased by PB in all sets of adrenal microsomes. Following PB treatment, P-450e became immunoquantifiable (greater than 2 pmol/mg protein) in three of six sets of lung and kidney microsomes but remained below detection in all sets of intestinal microsomes. Based on the activity of purified P-450e, undetectable levels (less than 1 pmol/mg protein) could account for increased DMBA metabolism in this tissue. The high constitutive level of P-450b in the lung (approximately 40 pmol/mg), was remarkably inactive in DMBA metabolism and was only slightly increased by PB treatment (50%). In contrast, PB treatment caused a 2.5- to 10-fold increase in 12-methyl hydroxylation of DMBA that was highly sensitive to anti-P-450b/e. A protein comigrating with P-450e was well above detection (6-7 pmol/mg) in two of six preparations of lung microsomes that showed highest induction of this activity.(ABSTRACT TRUNCATED AT 400 WORDS)

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1987

Differential expression and function of three closely related phenobarbital-inducible cytochrome P-450 isozymes in untreated rat liver.

The levels of expression of cytochromes P-450b and P-450e (both inducible by phenobarbital (PB) and differing by only 14 of 491 amino acids) in liver microsomes from untreated male rats were separately quantitated by Western blotting with a polyclonal antibody raised against P-450b that is equally effective against P-450e (anti P-450b/e). A protein with mobility identical to P-450e was detected in all microsomal samples. Microsomes from uninduced livers of individual male rats from five different strains exhibited only minor interstrain and interindividual variability in the expression of P-450e (17 +/- 5 pmol P-450e/mg microsomal protein) with the exception of the Brown Norway strain (8.5 +/- 0.5 pmol P-450e/mg). Expression of P-450b varied widely from undetectable levels (less than 2 pmol/mg) in most Sprague-Dawley rats to about 50% of P-450e levels in Fischer and Brown Norway strains. Anti P-450b/e inhibited total metabolism of 7,12-dimethylbenz[a]anthracene (DMBA) by uninduced microsomes, to an extent dependent on rat strain (15-30%), predominantly through inhibition of formation of 12-hydroxymethyl-7-methyl BA (12HOMMBA) (65-85%), the major metabolite of purified P-450e. A specific activity for P-450e-dependent DMBA metabolism was calculated from four sets of microsomes where the P-450b content was either undetectable or very low (0.7-1.0 nmol/nmol P-450e/min-1). Comparable calculated activities were, however, obtained from other untreated rat liver microsomes where P-450b levels were significant. Polymorphism in P-450b was detected but did not affect total P-450b expression or the sensitivity of DMBA metabolism to anti P-450b/e. A fourth band of greater mobility than P-450b (apparent Mr less than 50,000), was also recognized by anti P-450b/e. The intensity of this band did not vary among individual rats or among the different strains and therefore did not correlate with the sensitivity of microsomal DMBA metabolism to anti P-450b/e. A monoclonal antibody (MAb) against P-450b (2-66-3) recognized P-450's b, b2, and e on Western blots but did not react with this higher mobility band. MAb 2-66-3 and two other MAbs produced against P-450b inhibited 12-methylhydroxylation of DMBA by untreated rat liver microsomes to the same extent as anti P-450b/e. Following PB induction, P-450b was induced to about double the level of P-450e in most rat strains examined.(ABSTRACT TRUNCATED AT 400 WORDS)

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1987

Immunological identification and effects of 3-methylcholanthrene and phenobarbital on rat pulmonary cytochrome P-450.

Rabbit antibodies to the phenobarbital (PB) inducible rat liver microsomal cytochrome P-450s b and e and to 3-methylcholanthrene (MC) inducible P-450c were used to examine the expression of these isozymes in rat lungs. Western blots of total lung microsomes demonstrated that about 40 pmol P-450b/mg protein (and no detectable P-450e) were present in lungs from control or MC treated rats and that pretreatment with PB caused a small but significant (P less than 0.05) increase in the expression of P-450b. Microsomes from control and PB treated lung contained minimal levels of P-450c, and MC induced this isozyme to 185 pmol/mg. Immunocytochemistry was used to demonstrate immunoreactivity to these isozymes in specific cell types. Neither P-450b nor P-450c was detectable in endothelial cells from control or PB treated lungs, but MC increased immunoreactivity to P-450c in pulmonary endothelial cells. Type II alveolar cells showed distinct immunoreactivity to P-450b and weak immunoreactivity to P-450c in control or PB treated rats. Individual Clara cells stained for either P-450c or P-450b in control, MC treated, and PB treated rats, and colocalization was observed in some cells. An increase in type II alveolar cell and Clara cell immunoreactivity to P-450c was observed after MC induction. Mast cells, identified by metachromatic Giemsa staining, appeared to react nonspecifically with both antisera. In conclusion, P-450c is highly inducible by MC in rat lung (detected in microsomes by Western blot), specifically in endothelial cells, Clara cells, and alveolar type II cells (as visualized by immunocytochemistry); and P-450b is present in rat lung microsomes, and immunoreactivity to this isozyme is localized in alveolar type II and Clara cells.

Animals↗