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Biomedical subjects

A J Gordon

Publications and source records attributed to A J Gordon.

At least 19 recordsLinked to original sources
PubMed1997

A p53-independent pathway for induction of p21waf1cip1 and concomitant G1 arrest in UV-irradiated human skin fibroblasts.

Largely on the basis of studies using the potent clastogen ionizing radiation, it has been widely assumed that up-regulation of the cyclin-dependent kinase inhibitor p21(waf1cip1) in cultured cells exposed to DNA-damaging agents is contingent upon the presence of functional p53 tumor suppressor protein. Nevertheless, we demonstrate here that the model mutagen 254-nm UV light induces p21(waf1cip1) protein and concomitant G1 arrest in normal human skin fibroblasts, as well as in p53-deficient fibroblasts derived from cancer-prone Li-Fraumeni syndrome patients. However, as expected, following exposure to ionizing radiation, elevated p21(waf1cip1) protein levels and G1 arrest were observed only in normal fibroblasts. These data provide a prominent and clinically relevant example in which p21(waf1cip1)-mediated growth arrest occurs independently of p53 in human cells treated with a model DNA-damaging agent.

Aneuploidy↗
PubMed1995

Isolation of an ubiquitously expressed cDNA encoding human dynamin II, a member of the large GTP-binding protein family.

Dynamin (Dyn) is a member of a novel group of GTPases which was initially identified as a microtubule-binding protein with a role in vectorial movement. Three distinct Dyn-encoding genes (DYN I, II and III), with a neuronal-, ubiquitous or testis-specific expression, respectively, have been identified in rat. In man, only DYN I has so far been characterized. We have previously isolated a genomic DNA fragment implicated in the correction of mitomycin C hypersensitivity of cells from a Fanconi anemia patient belonging to genetic complementation group D (FA(D)). Using this probe, we have cloned a human complementary DNA designated hDYN II encoding a ubiquitous Dyn isoform. The predicted protein consists of 866 amino acids (97.5 kDa). Dyn proteins exhibit a high degree of evolutionary conservation: hDyn II is 98% identical to rat Dyn II and 73% identical to hDyn I. A unique 3.6-kb transcript is found in all human tissues examined and it is more abundant in skeletal muscle and heart. This transcript is also expressed in tissue-culture cells. The hDYN II message is present and not mutated in the FA(D) patient studied. In addition to the GTP-binding domain and motifs associated with regulatory function, the hDyn II protein contains a noticeable number of concensus motifs for p34Cdc2 kinase phosphorylation which may indicate a potential role at the G2/mitosis transition. The sequence reported here should allow a more complete analysis of Dyn function(s) in man.

Amino Acid Sequence↗
PubMed1995

Inversions with deletions and duplications.

Complex mutational events, including de novo inversion with deletion and duplication of sequence, have been observed but are difficult to model. We propose that nascent leading-strand misalignment upon the lagging-strand template during DNA replication can result in the inversion of sequence. The positioning of this misalignment and of the realignment of the leading strand back into the leading-strand template will determine if the inversion is accompanied by deletion and duplication of sequence. We suggest that such strand misalignment-realignment events may occur at the replication fork during concurrent DNA replication.

Base Sequence↗
PubMed1994

Antenatal screening for cystic fibrosis: a trial of the couple model.

OBJECTIVE: To assess the delivery and acceptability of antenatal couple screening for cystic fibrosis. Carrier status was notified only when both members of a partnership had cystic fibrosis alleles and therefore a one in four risk of having an affected child. DESIGN: Mouthwash samples were tested when both partners participated. Results were returned only to positive couples. SETTING: Two large maternity hospitals in Edinburgh. SUBJECTS: Screening was offered to all couples who booked at one of the two hospitals. MAIN OUTCOME MEASURES: (a) The take up of screening, carriers and carrier couples identified, take up of prenatal diagnosis, and numbers of affected fetuses detected; (b) questionnaire measures of patient satisfaction and stress. RESULTS: Screening was offered to 8536 couples. 714 (8.4%) were regarded as ineligible, usually because of late booking or absence of a partner. 1900 (24.3%) of the remainder declined screening. Among the 5922 screened couples, four tested positive--that is, both partners were cystic fibrosis heterozygotes. All four elected to have prenatal diagnosis. There were three terminations of pregnancy because of an affected fetus, one couple having two successive pregnancies with affected fetuses. The participation rate was 76% for eligible couples (5922/7822) and 69% for all couples (5922/8536). Only 89 screened couples (1.5%) requested information on individual carrier status. No anxiety was detected among a cohort of the screened population, and 99% of questioned participants expressed satisfaction with the concept of couple screening. CONCLUSIONS: Antenatal couple screening is a satisfactory and acceptable way of screening for cystic fibrosis and has been adopted as routine in the two trial hospitals.

Anxiety↗
PubMed1994

Fluorescein angiographic characteristics of macular holes before and after vitrectomy with transforming growth factor beta-2.

We evaluated the fluorescein angiographic features of full-thickness macular holes before and after vitrectomy, fluid-gas exchange, and instillation of transforming growth factor beta-2 in 43 eyes in a masked fashion to evaluate the angiographic characteristics of macular holes preoperatively and the changes that occur with successful and unsuccessful closure of the macular hole. Hyperfluorescence was present in the base of the macular hole preoperatively in 34 of 43 eyes (79.1%), was questionable in eight of 43 eyes (18.6%), and was definitely absent in only one of 43 eyes (2.3%). The hyperfluorescence in the base of the macular hole disappeared in 19 of 20 eyes (95%) with successful closure of the macular hole (P < .00001) and appeared to be caused by blocked fluorescence at the site of the macular hole. The photographic features of eyes with unsuccessful closure of the macular hole changed little, except that the size of the cuff of neurosensory detachment around the hole increased and was associated with decreased postoperative visual acuity. These angiographic changes support the presence of a glial tissue plug bridging a small defect in the fovea of eyes with successful closure of a macular hole.

Combined Modality Therapy↗
PubMed1993

The effect of pars plana vitrectomy and transforming growth factor-beta 2 without epiretinal membrane peeling on full-thickness macular holes.

PURPOSE: Surgical techniques for the treatment of macular holes generally include removal of the overlying cortical vitreous and/or epiretinal membranes. The authors demonstrate that by using vitrectomy, posterior hyaloid removal, fluid-gas exchange, and transforming growth factor-beta 2 (TGF-beta 2), a growth factor that modulates the wound healing process, epiretinal membrane peeling can be avoided and the surgical procedure thereby simplified without compromising results. METHODS: A total of 24 eyes of 24 patients with stage 2, 3, or 4 full-thickness macular holes were treated. Of 24 patients, 1 was lost to follow-up after suffering a stroke; the remaining 23 (17 females and 6 males) (age range, 11-81 years; mean, 64 years) were followed for 5 to 16 months (mean, 12 months). Preoperative best-corrected visual acuity ranged from 20/50 to 20/400 (mean, 20/125). A standardized vitrectomy was performed with posterior hyaloid removal and, after a near-complete fluid-air exchange, 0.1 ml of a solution containing 1330 ng of TGF-beta 2 was instilled over the macular hole. No attempts were made to peel epiretinal membranes or drain fluid from the macular hole. RESULTS: Of 23 eyes, 22 (96%) had resolution of the surrounding subretinal fluid and flattening of the macular hole (1 patient required a second procedure, in which visual improvement of 20/30 was achieved); 11 (48%) had visual acuities of 20/40 or better, 19 (85%) had visual acuities of 20/60 or better, and 19 (85%) showed an improvement in visual acuity of at least two lines (mean, 3.8 lines). The authors saw no retinal pigment epithelial mottling. CONCLUSION: The authors' results demonstrate that treatment of macular holes using vitrectomy, fluid-gas exchange, and the instillation of a solution containing TGF-beta 2, without epiretinal membrane peeling, maintains efficacy while simplifying surgery.

Adolescent↗
PubMed1993

Spontaneous mutagenesis in Escherichia coli harbouring plasmid pKM101: DNA sequence analysis of forward lacI- mutations.

To investigate the influence of plasmid pKM101 on spontaneous mutagenesis, 198 lacI- mutations generated in Escherichia coli harbouring pKM101 were characterized at the DNA sequence level. pKM101 by itself did not enhance the lacI- forward mutation frequency. In general, the resultant distribution of mutation highlights particular sequences at which a variety of mutational events repeatedly occur, including 5'-(G/C)TGG-3', 5'-CCAGG-3', 5'-GATC-3' and 5'-TCGCG-3' sequences. Specifically, the distribution of mutation within base substitution and deletion classes distinguishes the pKM101 spectrum from the wild-type distribution (i.e. absence of pKM101). An even distribution amongst base substitutions was observed which corresponds to a 2.9- to 6.3-fold increase in occurrence of low frequency events (A-->G,T,C; G-->C); high frequency events in the wild-type distribution (G-->A,T) were not influenced by the presence of pKM101. One complex event was recovered which was comprised of two base substitutions separated by 4 bp. An 11-fold increase in small deletion events (3-6 bp) was also observed. The observed pKM101 spectrum does not closely resemble the mutational consequences of SOS induction in the absence of mutagenic treatment (recA441 spectrum) but does return a distribution like that obtained in E. coli deficient in polymerase I activity (polA1 spectrum).

Amino Acid Sequence↗
PubMed1992

Influences on biomedicine in rural Dominican Republic: an analysis of process.

This paper, based on fieldwork among agrarian reform beneficiaries in the Dominican Republic, examines the utilization of health care. Specific attention is given to the consumption of private medical care and its relationship to changes in the system of land tenure, policy in the agrarian reform, and the roles of physicians. A principal concern of the paper is the examination of the adaptive strategies of beneficiaries of the reform in light of political and economic influences. A second concern is the consideration of the integration of critical medical anthropology's perspectives on the political economy with a perspective on decision-making and adaptive strategies.

Agriculture↗
PubMed1992

The influence of local DNA sequence and DNA repair background on the mutational specificity of 1-nitroso-8-nitropyrene in Escherichia coli: inferences for mutagenic mechanisms.

We have examined the mutational specificity of 1-nitroso-8-nitropyrene (1,8-NONP), an activated metabolite of the carcinogen 1,8-dinitropyrene, in the lacI gene of Escherichia coli strains which differ with respect to nucleotide excision repair (+/- delta uvrB) and MucA/B-mediated error-prone translesion synthesis (+/- pKM101). Several different classes of mutation were recovered, of which frameshifts, base substitutions, and deletions were clearly induced by 1,8-NONP treatment. The high proportion of point mutations (> 92%) which occurred at G.C sites correlates with the percentage of 1,8-NONP-DNA adducts which occur at the C(8) position of guanine. The most prominent frameshift mutations were -(G.C) events, which were induced by 1,8-NONP treatment in all strains, occurred preferentially in runs of guanine residues, and whose frequency increased markedly with the length of the reiterated sequence. Of the base substitution mutations G.C-->T.A transversions were induced to the greatest extent by 1,8-NONP. The distribution of the G.C-->T.A transversions was not influenced by the nature of flanking bases, nor was there a strand preference for these events. The presence of plasmid pKM101 specifically increased the frequency of G.C-->T.A transversions by a factor of 30-60. In contrast, the -(G.C) frameshift mutation frequency was increased only 2-4-fold in strains harboring pKM101 as compared to strains lacking this plasmid. There was, however, a marked influence of pKM101 on the strand specificity of frameshift mutation; a preference was observed for -G events on the transcribed strand. The ability of the bacteria to carry out nucleotide excision repair had a strong effect on the frequency of all classes of mutation but did not significantly influence either the overall distribution of mutational classes or the strand specificity of G.C-->T.A transversions and -(G.C) frameshifts. Deletion mutations were induced in the delta uvr, pKM101 strain. The endpoints of the majority of the deletion mutations were G.C rich and contained regions of considerable homology. The specificity of 1,8-NONP-induced mutation suggests that DNA containing 1,8-NONP adducts can be processed through different mutational pathways depending on the DNA sequence context of the adduct and the DNA repair background of the cell.

Base Sequence↗
PubMed1992

Resolution and characterization of polymorphic DNA by SSCP and chemical cleavage methodologies.

A variety of techniques have been developed to detect single-base changes for the two different purposes. One is the detection of mutational events without phenotypic selection, and another is the rapid and conventional identification of mutations such as the specific base changes related to activation of oncogene, genetic diseases, etc. In this study, the utility of the two methods, single strand conformation polymorphism (SSCP) and chemical cleavage, was explored using 13 E. coli lacI- mutations cloned onto M13 phase. The 167 base region encompassing mutations was amplified by PCR as dsDNA. Following denaturation, these PCR products were analyzed by non-denaturing polyacrylamide gel electrophoresis (SSCP) and the separation of the ssDNA fragment carrying the altered sequence from the original sequence was found to be dependent on the location and type of the change. Hetero duplexes of changed/original sequences were also prepared by hybridization of the above PCR products. Mismatched C and T bases were modified by hydroxylamine and osmium tetroxide, respectively, and subsequently treated with piperidine to analyze the cleaved DNA fragments on a polyacrylamide gel (Chemical Cleavage). The cleavage efficiency was also found to be influenced by the type of mismatch and its surrounding sequence. Such observed characteristics should contribute to a better appreciation for these types of mutational systems, which in turn should lead to insight into the mechanisms of mutagenesis.

Base Sequence↗
PubMed1991

Spontaneous and 9-aminoacridine-induced frameshift mutagenesis: second-site frameshift mutation within the N-terminal region of the lacI gene of Escherichia coli.

A novel forward mutational system, based on the acquisition of an Iq-d dominant phenotype from an initial Iq- recessive state, was used to identify second-site frameshift mutation [+/- 1(+/- 3n) events] within the N-terminal region of the lacI gene of Escherichia coli. The DNA sequences are described of forty-six spontaneous and twenty 9-aminoacridine(9-AA)-induced second site mutations. Although -1 frameshift events dominate both spectra, the nature and site specificity of these events clearly distinguish two mutational distributions. The spontaneous distribution contains two -(A:T) frameshift hotspots; one within a monotonic A5 run (9 occurrences), the other at a 5'-CACAACAAC-3' sequence (12 occurrences). In contrast 17 of the 20 mutations recovered after 9-AA treatment involve the loss of a G:C pair, 14 of which occur at a single site (5'-CGGGC-3'). The striking specificity of the observed mutational hotspots is of interest since this open genetic target contains similar sequences which were infrequently recovered.

Aminacrine↗
PubMed1991

Social networks and recovery: one year after inpatient treatment.

In an effort to understand the effect of social networks on outcome for treatment of alcoholism, a 1-year follow-up prospective study of 156 inpatients was undertaken. Treatment outcome was associated with diverse aspects of the social network: whether individuals were family, friends, or co-workers; the type of relationship--whether or not drinking together was part of social interaction; and the presence of social support, both perceived support and support through participation in treatment. Hierarchical path analysis using Lisrel 6 was used to analyze the data. The active support of co-workers not regularly drinking with the patient and the perceived support of co-workers without respect to their drinking were influential in recovery, exerting positive and negative effects, respectively. The indirect effect of other variables indicates that nondrinking and drinking family and friend relationships also exert positive and negative effects, respectively. The authors suggest that a major factor in recovery is the ability to elicit and receive support. Improving this ability may be a fruitful objective in treatment.

Adolescent↗
PubMed1991

Complex choristoma of the eyelid containing ectopic cilia and lacrimal gland.

A 2-year-old girl was born with an aggregate of ectopic cilia in the right upper eyelid that intermittently produced tears. During elective excision, the cilia were found to be clustered tightly with prominent bulb-like follicles. A separate lobe of lacrimal gland tissue was adjacent to the roots of the cilia just posterior to the orbital septum with no direct communication with the lacrimal gland. Histopathologically, the lesion contained multiple large hair follicles in the dermis with accompanying adnexal structures. Large ectopic lobules of lacrimal gland tissue also were present. Postoperatively, the child had a good cosmetic result and has remained asymptomatic over an 18-month follow-up period. To our knowledge, this is the first reported case of an eyelid choristoma containing ectopic cilia and lacrimal gland. Ectopic cilia alone is a very rare anomaly of the lashes, with only nine cases reported in the literature.

Child, Preschool↗
PubMed1991

The mutational specificity of 2-(2-furyl)-3-(5-nitro-2-furyl)-acrylamide (AF2) in the lacI gene of Escherichia coli.

We have determined the mutational specificity of the 5-nitrofuran derivative furylfuramide (AF2) in the lacI gene of Escherichia coli. Treatment of a delta uvrB, pKM101 strain with 1 M AF2 yielded a mutation frequency approximately 300 times greater than that of untreated controls. Of the 165 AF2-induced mutants analysed by DNA sequencing, 145 were base substitution mutations, 11 were frameshifts, and the remainder small deletions, tandem base substitutions and complex mutations. Base substitution occurred primarily (greater than 93%) at G:C base pairs. The proportions of the various mutations are very similar to those that have been reported for AP sites. We suggest that the principal mechanism for AF2 mutagenesis is the formation of an adduct which depurinates to yield AP sites that serve as a substrate for error-prone repair. Seventy-two of the mutations occurred at four 5'-TGC-3' sites. The majority (10/11) of the frameshift mutations occurred at one such hotspot and could have been templated by an inverted repeat less than 100 bp removed from the site of the mutation.

Base Sequence↗
PubMed1991

The action of 1-nitroso-8-nitropyrene in Escherichia coli: DNA adduct formation and mutational consequences in the absence of nucleotide excision-repair.

To study the mechanisms of mutagenesis by the carcinogen 1,8-dinitropyrene we have determined the DNA adducts formed and mutations induced by its partially activated metabolite 1-nitroso-8-nitropyrene (1,8-NONP) in an Escherichia coli strain deficient in nucleotide excision-repair. Using DNA sequence analysis we have characterized a collection of 159 lacI- mutations recovered following treatment with 1,8-NONP. The mutational spectrum was dominated by -1 frameshifts (110 events) in runs of contiguous G or C residues. Frameshift frequency was observed to increase with the length of the reiterated sequence. Two mutations involved the loss of GpC from alternating (GpC)n sequences. The ratio of -1:-2 events observed following 1,8-NONP treatment was markedly different from that induced by N-acetoxy-N-acetyl-2-aminofluorene in the same genetic target. Other mutational classes recovered included 'spontaneous' hotspot mutations (19 events), base substitutions (12 events), deletions (7 events), one duplication, one + (A:T) frameshift and one mutation containing closely juxtaposed -(G:C) events. Of the 125 point mutations characterized, 124 occurred at G:C sites. The site specificity of mutation was consistent with the 32P-postlabeling profile of 1,8-NONP-DNA adducts which showed that 95% of the adducts migrated to the same position on the TLC plates as the guanine C(8) adduct 1-N-(2'-deoxyguanosin-8-yl)-amino-8-nitropyrene. Two minor 1,8-NONP-DNA mutations were also detected, one at dG/dC sites, and the other at dA/dT sites.

Animals↗
PubMed1990

Mutational specificity of alkylating agents and the influence of DNA repair.

Alkylating treatments predominantly induce G: C = greater than A:T transitions, consistent with the predicted significance of the miscoding potential of the O6-alG lesion. However, the frequency and distribution of these events induced by any one compound may be diagnostic. SN1 agents that act via an alkyldiazonium cation, such as the N-nitroso compounds, preferentially generate G: C = greater than A:T transitions at 5'-RG-3' sites, while the more SN2 alkylsulfates and alkylalkane-sulfonates do not. The precise nature of this site bias and the possibility of strand bias are target dependent. The extent of this site bias and the contribution of other base substitutions are substituent size dependent. A similar 5'-RT-3' effect is seen for A:T = greater than G:C transitions, presumably directed by O4-alT lesions. The 5'-RG-3' effect, at least, likely reflects a deposition specificity arising from some aspect of helix geometry, although it may be further exaggerated by alkylation-specific repair. Excision repair appears to preferentially reduce the occurrence of ethylation-induced G:C = greater than A:T and A:T = greater than G:C transitions at sites flanked by A:T base pairs. This may be due to an enhancement of the helical distortion imposed by damage at such positions. A similar effect is not seen for methylation-induced mutations and in the case of propyl adducts, the influence of excision repair on the ultimate distribution of mutation cannot be as easily defined with respect to neighbouring sequence.

Alkylating Agents↗