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G R Douglas

Publications and source records attributed to G R Douglas.

At least 37 records · Page 2Linked to original sources
PubMed1996

Database and software for the analysis of mutations at the lacZ locus in transgenic rodents.

The use of transgenic rodents is becoming increasingly widespread in genetic toxicology. In an effort to centralize and standardize the information regarding mutations in rodents bearing the lacZ transgene, we have created a computerized database that contains published information about DNA sequence alterations on over 100 mutants. Information on the literature citation, mutagenic conditions, organs from specific animals, mutation frequency in each organ, specific mutation, amino acid change, and other data are provided for each mutant. We have also produced a software package for the analysis of the lacZ database. Routines have been developed for the analysis of single base substitutions, including programs to 1) determine whether two mutational spectra are statistically different, 2) determine whether mutations show a DNA strand bias, 3) determine the frequency of transitions and transversions, 4) display the number and kind of mutations observed at each base in the coding region, 5) perform nearest-neighbor analysis, and 6) display mutable amino acids in the lacZ protein. The software runs only on IBM-compatible machines running Microsoft Windows. The software and lacZ database are freely available via the Internet (http:@sunsite.unc.edu/dnam/mainpage.ht ml). These programs simplify the analysis of the rapidly increasing information about lacZ mutation. The programs permit the facile comparison between different lacZ data sets as well as the identification of mutational patterns that may be of importance to experimenters studying the mechanisms of mutation and mutational spectra in transgenic animals.

Amino Acids↗
PubMed1996

Temporal and molecular characteristics of lacZ mutations in somatic tissues of transgenic mice.

In order to help establish criteria for optimizing protocols for in vivo mutation studies, lacZ transgenic mice (Muta mouse) were treated with five consecutive daily doses of ethylnitrosourea (50 mg/kg), sampled at times up to 55 days after treatment, and mutant frequencies and DNA sequences determined for liver and bone marrow. In the bone marrow, the mutant frequency rose very rapidly in the first 5 days after treatment to 34 times the control frequency. Subsequently, there was a brood peak where the mutant frequency did not vary significantly, although it did appear to begin to decline after 45 days. In contrast, in the liver, the peak mutant frequency (11 times the control frequency) was not achieved until 35 days, after which there appeared to be a slow decline up to 55 days, which was not statistically significant. Once the maximum mutant frequency was reached, the mutation spectra in the two tissues were indistinguishable. In contrast to the G:C-->A:T transitions in 5'-CpG sites characteristic of untreated mice, A:T-->T:A transversions and A:T-->G:C transitions were prominent in both liver and bone marrow of ENU-treated mice, suggesting the involvement of unrepaired O2- and O4-ethylthymine adducts. In addition, G:C-->T:A transversions were induced in liver. This study demonstrates the possibility that although tissues may have different mutation fixation times, a single mutation fixation time equal to the longest time may be appropriate for in vivo mutation studies, provided that the mutation frequency does not decline appreciably after the peak is reached. This study also illustrates the necessity of ensuring that mutation characteristics are determined after optimal fixation has occurred.

Animals↗
PubMed1996

Comparison of psychophysical and electrophysiological testing in early glaucoma.

PURPOSE: To compare the sensitivity and specificity of a wide range of psychophysical and electrophysiological tests in the detection of early glaucomatous damage. METHODS: Forty-three normals and 43 patients with early glaucoma, some still without field defects, were tested with differential light threshold perimetry, short-wavelength automated perimetry, high-pass resolution perimetry, motion detection, flicker contrast sensitivity, flickering and isoluminantly matched letter tests, and pattern and flash electroretinography, including photopic, scotopic, oscillatory potentials, and 30 Hz flicker. Receiver operating characteristic analysis was applied to continuous variables derived from each of the tests. RESULTS: Most parameters reflected glaucomatous loss to some degree, even though only single variables were analyzed separately in the receiver operating characteristic analysis. The pattern electroretinogram and some of the letter acuity tests had the best sensitivity and specificity, followed by short-wavelength automated perimetry and high-pass resolution-perimetry. Motion detection, flicker contrast, and flash electroretinogram parameters scored poorly. Six patients with normal results on the Humphrey field test had abnormal results on many of the other tests. CONCLUSIONS: Applying different psychophysical and electrophysiological tests may add to our ability to detect early glaucomatous damage.

Contrast Sensitivity↗
PubMed1995

Temporal and molecular characteristics of mutations induced by ethylnitrosourea in germ cells isolated from seminiferous tubules and in spermatozoa of lacZ transgenic mice.

The lacZ transgenic mouse (Muta mouse) model was used to examine the timing of ethylnitrosourea (ENU)-induced mutations in germ cells. The spectrum of mutations was also determined. Animals received five daily treatments with ENU at 50 mg/kg and were sampled at times up to 55 days after treatment. In mixed germ-cell populations isolated from seminiferous tubules, there was little increase in the mutant frequency 5 days after treatment; subsequently, there was a continuous increase until the maximum (17.5-fold above background) was reached by approximately 35 days. In the spermatozoa, an increase in mutant frequency was not seen until 20 days after treatment, with the maximum (4.3-fold above background) being achieved no sooner than approximately 35 days. Based on the timing of sampling, these data demonstrate the detection of both spermatogonial and postspermatogonial, mutations. The most prominent feature of the ENU-induced base-pair mutations in testicular germ cells sampled 55 days after treatment is that 70% are induced in A.T base pairs, compared to only 16% in spontaneous mutations. These findings are consistent with comparable data from ENU studies using assays for inherited germ-cell mutations in mice. This study has demonstrated the utility and potential of the transgenic mouse lacZ model (Muta mouse) for the detection and study of germ-cell mutations and provides guidance in the selection of simplified treatment and sampling protocols.

Animals↗
PubMed1995

Acrylamide: a review of its genotoxicity and an assessment of heritable genetic risk.

An updated review of the genotoxicity studies with acrylamide is provided. Then, using data from the studies generating quantitative information concerning heritability of genetic effects, an assessment of the heritable genetic risk presented by acrylamide is presented. The review offers a discussion of the reactions and possible mechanisms of genotoxic action by acrylamide and its epoxide metabolite glycidamide. Several genetic risk approaches are discussed, including the parallelogram, direct (actually a modified direct), and doubling dose approaches. Using data from the specific-locus and heritable translocation assays, the modified direct and doubling dose approaches are utilized to quantitate genetic risk. Exposures of male parents to acrylamide via inhalation, ingestion, and dermal routes are also quantitated. With these approaches and measurements and their underlying assumptions concerning extrapolation factors (including germ cell stage specificity, DNA repair variability, locus specificity), number of human loci associated with dominant disease alleles, and spontaneous mutation rates, an assessment of heritable genetic risk for humans is calculated for the three exposure scenarios. The calculated estimates for offspring from fathers exposed to acrylamide via drinking water are up to three offspring potentially affected with induced genetic disease per 10(8) offspring. Estimates for inhalation or dermal exposures suggest higher risks for induced genetic disease in offspring from fathers exposed in occupational settings.

Acrylamide↗
PubMed1995

Ambulatory blood pressure monitoring in glaucoma. The nocturnal dip.

PURPOSE: Hypoperfusion of the optic nerve head may be among the significant factors relating to glaucoma damage. The physiologic nocturnal blood pressure "dip" may be exaggerated in some patients and may compromise local vascular supply. METHODS: Twenty-four-hour ambulatory blood pressure recording was performed on 38 patients with normal-tension glaucoma and on 46 with primary open-angle glaucoma. Eleven control subjects of similar age also were tested. The means of the systolic and diastolic blood pressures, mean arterial pressure, and pulse pressure for 24 hours, taken during the daytime (6 AM-10 PM) and night (10 PM-6 AM) periods were determined. The percentage nocturnal dip for each patient was calculated. A masked assessment of Humphrey visual fields for progression or stability was done on those 52 patients who had numerous fields plotted for more than 2 years. RESULTS: The results of the control subjects confirmed that the authors' technique produces values similar to cardiologic studies from large healthy populations. The mean results from all the authors' patients with glaucoma were within the ranges reported for control subjects in the literature. The blood pressure parameters of the normal-tension glaucoma and primary open-angle glaucoma groups did not differ significantly. All nocturnal pressure parameters (except pulse pressure) were lower in the 37 patients with progressive field defects compared with the 15 patients whose pressure parameters were stable, whereas the systolic, diastolic, and mean arterial pressure dips were significantly larger (systolic dip, P = 0.001). CONCLUSION: The nocturnal reduction in blood pressure may be an additional risk factor in patients with glaucoma.

Aged↗
PubMed1995

Evidence for in vivo non-mutagenicity of the carcinogen hydrazine sulfate in target tissues of lacZ transgenic mice.

Transgenic mouse models permit the confirmation of in vitro mutagenicity in vivo without the constraints in the selection of tissues imposed by other in vivo assays. This feature is of particular importance in the determination of mutagenicity in the target tissues of carcinogens, especially those that are in vitro mutagens. Such information is critical in the determination of whether a chemical is carcinogenic via a genotoxic or non-genotoxic mechanism. Hydrazine sulfate is an in vitro mutagen that induces lung and liver tumours in mice. Transgenic mice from strain 40.6 (Mutamouse) were administered single oral doses up to a toxic concentration (400 mg/kg). No dose induced any lacZ mutations in lung, liver or bone marrow. Since the highest single dose used is higher than the cumulative dose that induced tumours in previous studies, it may be that either hydrazine sulfate is genotoxic in target tissues in vivo only when given in multiple doses or that it is a non-genotoxic carcinogen.

Administration, Oral↗
PubMed1995

Cytogenetic mapping of lambda gt10 lacZ sequences in the transgenic mouse strain 40.6 (Muta Mouse).

The transgenic mouse strain 40.6 (Muta Mouse) was developed for the detection of gene mutations induced in vivo. Strain 40.6 was constructed by microinjecting the shuttle vector lambda gt10 lacZ into the male pronucleus of a single cell embryo resulting from a CD2 (i.e. BALB/c x DBA/2)F1 x CD2F1 cross. Approximately 40 concatenated copies of the shuttle vector were integrated per haploid genome. The resulting mice were bred to disomy for the insert for use in mutagenicity studies. Ultimately, it is hoped that transgenic rodent model systems such as this one will play an important regulatory role in hazard identification. Despite the increasing use of this strain in toxicological studies, relatively little is known about the site of integration of the target gene into the mouse genome. In this study, fluorescence in situ hybridization and DAPI chromosome banding were combined to determine the location of the transgenic element in the mouse genome. The results indicate that the lambda sequences containing the lacZ gene are located in the B region of mouse chromosome 3. No other major chromosomal rearrangements were evident in the genome of this mouse strain.

Animals↗
PubMed1994

Mutagenic activity of 3 industrial chemicals in a battery of in vitro and in vivo tests.

3 chemicals were selected for mutagenicity testing from a priority list, based on production volume and available mutagenicity data. Propargyl alcohol (PA), 2-nitroaniline (2NA), and 5-methyl-1H-benzo-triazole (MBT) were selected for testing using the approach recommended in the Health Protection Branch Genotoxicity Guidelines. The battery of tests included the Salmonella/mammalian microsome mutation assay, the in vitro chromosomal aberration assay, and the bone-marrow micronucleus assay. The results indicate that 2 of the 3 chemicals, PA and 2NA, were clastogenic in vitro. Both PA and 2NA induced chromosomal aberrations in CHO cells in vitro with and without metabolic activation, while none induced reverse mutations detectable with the Salmonella/mammalian microsome assay. Because PA and 2NA were found to be in vitro clastogens, they also were tested in the mouse bone-marrow micronucleus assay. 2NA induced a small increase in micronuclei in males but not females. PA did not induce an increase in micronuclei.

1-Propanol↗
PubMed1994

Sequence spectra of spontaneous lacZ gene mutations in transgenic mouse somatic and germline tissues.

As a critical step in determining whether transgenic mouse gene mutation systems are suitable models for the detection and quantification of induced gene mutations in vivo, spontaneous mutant frequencies and mutation spectra have been characterized for liver, bone marrow, and male germ cells of the lacZ transgenic mouse strain 40.6. The lacZ transgene is carried on a recombinant bacteriophage lambda shuttle vector that is recovered from mouse genomic DNA, and analysed in vitro for mutations that occurred in the mouse tissues. Mutations are detected visually as clear or pale blue plaques when X-gal is the substrate for beta-galactosidase; whereas, the wild-type plaques are dark blue. There was no statistical difference in the mutant frequency among the three tissues studied, the pooled mutant frequency being 2.23 +/- 0.41 per 10(5) pfu. The predominant type of mutation was GC-->AT transitions, with most occurring in 5'-CpG dinucleotides, suggesting that the deamination of 5-methylcytosine is the main mechanism of mutagenesis. There was, however, a statistically significant difference in the base pair substitution mutation spectrum for the liver and bone marrow when mutations were grouped according to GC or AT base-pairs. The proportion of transition versus transversion mutations was also statistically different among the three tissues, resulting mainly from the fact that germ cells were different from both bone marrow and liver. A lower number of spontaneous transitions in male germ cells was accompanied by an increase in transversions, with the proportion of GC-->AT transitions in 5'-CpG sites also declining.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

The effect of lens opacity on the resolution visual field in normal subjects.

The sensitivity of the visual field declines with age. The density of the crystalline lens increases with age and may be partly responsible for the decline in sensitivity. To determine whether lens opacity influences the mean threshold of the visual field, 82 normal subjects were enrolled. All had their lens opacity measured with the Interzeag Lens Opacity Meter 701 and the visual field assessed with the Ring Resolution Perimeter. Lens opacity was highly correlated with age, while mean visual field threshold was also correlated with age but showed much greater variation. Multiple regression failed to show any influence of lens opacity measurements on the mean field threshold after age had been accounted for.

Adult↗
PubMed1992

Induction of chromosomal aberrations in Chinese hamster ovary cells by triethyllead acetate.

Organolead compounds enter the environment primarily through the combustion of leaded gasoline and industrial discharge. Lead and lead-containing compounds have been shown to induce a broad spectrum of toxic effects, including hematopoietic, renal, neurologic, and carcinogenic effects. In this study, the mutagenic activity of triethyllead acetate (Et3PbAc) was determined by measuring the induction of chromosomal aberrations in Chinese hamster ovary cells. The results indicate that Et3PbAc is very cytotoxic and a potent clastogen. In preliminary cytotoxicity studies used to determine appropriate test concentrations for chromosomal aberration analysis, the LC50 of Et3PbAc was approximately 10 microM in the absence of metabolic activation, and 80 microM in the presence of metabolic activation. The maximal response was greater with metabolic activation than without. However, a much higher dose was required to elicit a significant response in the presence of metabolic activation than in its absence.

Animals↗
PubMed1992

Diagnostic concepts in open-angle glaucoma.

Primary open-angle glaucoma is not yet fully understood in terms of its pathophysiologic mechanisms. However, they are being addressed more completely in the recent literature. To the list of known risk factors associated with this disease, systemic influences are now being added. Primary open-angle glaucoma is becoming a much more complex disease as research uncovers associations and relationships that were previously unknown. Without knowledge of these mechanisms, the clinician is unable to adequately diagnose and treat the problem. Advances in computer-based diagnostic tools have been made, and we are now beginning to understand their value and limitations. However, whatever technology has to offer, we must always remember that the ultimate decision on initial diagnosis and further deterioration remains a clinical one.

Glaucoma, Open-Angle↗
PubMed1992

Bilateral malignant glaucoma.

Two cases of bilateral malignant glaucoma are presented. In one case the condition developed sequentially in the two eyes; pars plana vitrectomy was eventually needed in the operated eye, whereas the condition responded to medical treatment in the fellow eye. In the second case the two eyes were involved simultaneously nearly 1 year after surgery, and the glaucoma responded to medical treatment.

Female↗
PubMed1991

Light-sense, flicker and resolution perimetry in glaucoma: a comparative study.

A total of 106 eyes of 106 patients with different types of glaucoma were examined by automated light-sense, flicker and resolution perimetry (Humphrey Field Analyzer, program 30-2; flicker perimeter as described by Lachenmayr [16, 18]; resolution perimeter as devised by Frisén [4, 6, 8-11]). The fields were classified in a masked fashion as being normal or as having purely diffuse loss, purely localized loss or diffuse as well as localized loss. As compared with light-sense perimetry, resolution perimetry had a markedly lower sensitivity in the detection of glaucomatous damage (77%) but a high specificity (93%); the comparison of resolution perimetry with flicker perimetry showed similar results (sensitivity, 75%; specificity, 85%). When flicker perimetry was compared with light-sense perimetry and vice versa, the sensitivity was high (95% and 94%, respectively), but the specificity was low (57% and 62%, respectively). The prevalence of detection of diffuse loss by both light-sense and resolution perimetry was related to visual acuity, whereas flicker perimetry did not show such a relationship.

Adult↗