Prenatal diagnosis of fragile X syndrome by direct detection of the unstable DNA sequence.
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Base Sequence↗
Biomedical subjects
M Lynch
Publications and source records attributed to M Lynch.
A wavelength dependent mechanism for rose bengal-sensitized photoinhibition of red cell acetylcholinesterase.
A 2-fold enhancement in the efficiency of rose bengal-photosensitized inhibition of red cell acetylcholinesterase activity was observed upon excitation of the dye in the ultraviolet (UV) (313 nm) compared to irradiation in the visible (514 or 550 nm). The measurements of efficiency of photosensitized enzyme inhibition were based on the effect produced when the same number of photons are absorbed by rose bengal (RB) at each wavelength. The mechanism for this unexpected enhancement of RB photosensitization upon UV excitation was investigated. The yield of singlet oxygen (O2(1 delta g], detected by time-resolved luminescence at 1270 nm, was independent of excitation wavelength for RB. Radicals were produced upon irradiation of RB at 313 nm but not at 514 nm as detected by bleaching of N,N-dimethylnitrosoaniline (RNO). Irradiation of RB at 313 nm but not at 514 nm appeared to cause homolytic cleavage of carbon-iodine bonds in the dye because iodine radicals, I, detected as I2 were produced with a quantum yield of 0.0041 +/- 0.0005 upon excitation in the UV. Photolysis of I2 in the presence of RNO caused bleaching of the RNO absorption at 440 nm, apparently resulting from reaction of I with RNO. Thus, the enhanced photosensitization upon UV excitation of RB is attributed to formation of I and/or RB. These results indicate that radicals, produced with low relative yield but having high reactivity compared to O2(1 delta g), can contribute to photosensitized enzyme inhibition and may represent an alternative mechanism for photodynamic therapy.
Acetylcholinesterase↗
Hereditary unstable DNA: a new explanation for some old genetic questions?
Fragile X syndrome, associated with the fragile X chromosome, is the most common cause of familial mental retardation. The condition is characterised by a heritable DNA sequence that consists of an abnormal number of CCG repeats, and which is unstable in both mitosis and meiosis. We suggest that such heritable unstable DNA sequences could be present in other parts of the genome and that these might explain a number of genetic events that are not well understood in terms of classic genetic mechanisms. Such poorly explained observations include anticipation, incomplete penetrance, variable expression, and possibly imprinting, variegation, and multifactorial inheritance.
Chromosome Fragility↗
Mapping of DNA instability at the fragile X to a trinucleotide repeat sequence p(CCG)n.
The sequence of a Pst I restriction fragment was determined that demonstrate instability in fragile X syndrome pedigrees. The region of instability was localized to a trinucleotide repeat p(CCG)n. The sequence flanking this repeat were identical in normal and affected individuals. The breakpoints in two somatic cell hybrids constructed to break at the fragile site also mapped to this repeat sequence. The repeat exhibits instability both when cloned in a nonhomologous host and after amplification by the polymerase chain reaction. These results suggest variation in the trinucleotide repeat copy number as the molecular basis for the instability and possibly the fragile site. This would account for the observed properties of this region in vivo and in vitro.
Base Sequence↗
Fragile X genotype characterized by an unstable region of DNA.
DNA sequences have been located at the fragile X site by in situ hybridization and by the mapping of breakpoints in two somatic cell hybrids that were constructed to break at the fragile site. These hybrids were found to have breakpoints in a common 5-kilobase Eco RI restriction fragment. When this fragment was used as a probe on the chromosomal DNA of normal and fragile X genotype individuals, alterations in the mobility of the sequences detected by the probe were found only in fragile X genotype DNA. These sequences were of an increased size in all fragile X individuals and varied within families, indicating that the region was unstable. This probe provides a means with which to analyze fragile X pedigrees and is a diagnostic reagent for the fragile X genotype.
Chromosome Mapping↗
Molteno implants and operating microscope-induced retinal phototoxicity. A clinicopathologic report.
The right eye of a 75-year-old man with a history of cataract extraction, three penetrating keratoplasties, laser trabeculoplasty, two Molteno implants, and an operating microscope-induced retinal phototoxic lesion was studied post mortem. Histopathologic examination of the anterior segment showed evidence of penetrating keratoplasty, cataract surgery, and two Molteno implants with minimal associated tissue response. Ultrastructural examination showed a loose collagenous matrix surrounding the Molteno reservoirs, suggesting aqueous percolation from the reservoirs into the conjunctiva. Posteriorly, in the area of the phototoxic operating microscope-induced lesion, a nodule of retinal pigment epithelial hyperplasia with overlying atrophy of the photoreceptor cell layer of the neurosensory retina was noted. The retina also contained cystoid macular edema and an extensive preretinal membrane that was clinically unexpected.
Aged↗
Analysis of population genetic structure by DNA fingerprinting.
DNA fingerprint similarity is now being used widely to make inferences about the genetic structure of natural and domesticated populations, often with little regard to the limitations of such data. This paper provides an overview of the statistical theory of DNA fingerprint analysis with special focus on applications to natural populations for which little if anything is known about the detailed genetics of the DNA profiles. Approaches to estimating individual and population homozygosity, effective population size, population subdivision, and relatedness are reviewed, and issues concerning the biases and sampling properties of the statistics are discussed.
DNA Fingerprinting↗
Histopathology of antitrochanteric degeneration in adult female turkeys of four strains of different mature size.
The left and right antitrochanters of 80 female turkeys of four strains were examined for histopathological changes at sexual maturity. Ten birds of each strain were fed ad libitum and 10 restricted to achieve 0.6 of the bodyweight of the ad libitum fed birds at 24 weeks old when the birds were photostimulated. Bodyweights at sexual maturity (28 to 31 weeks) for the four strains were 5.4, 6.5, 7.6 and 13.2 kg for restricted and 7.5, 9.0, 11.1 and 17.1 kg for ad libitum fed birds. The prevalence and severity of cartilage change increased with mature size and was lower in restricted turkeys then in turkeys fed ad libitum. The results showed that abnormal cartilage changes forming the basis of clinical disease occur in females. The prevalence and severity of lesions were directly related to bodyweight and were not limited to particular genotypes. Lesions were more severe in the centre of the antitrochanter, possibly because of forces exerted by the trochanter. Concentrations of basophilic cells in the hyaline cartilage were associated with the increased prevalence and severity of lesions in large turkeys and may be of significance in the development of osteochondrotic lesions in the antitrochanter.
Animals↗
Haematology and histopathology of seven-week-old broilers after early food restriction.
The haematology and histopathology of seven-week-old broilers were examined after periods of early food restriction, for six, 10 or 14 days from six days old. After several weeks on an ad libitum diet the birds failed to compensate for the weight lost during early food restriction. Immediately after the periods of food restriction, the birds demonstrated significantly increased heterophil/lymphocyte ratios, reduced eosinophils and slightly raised basophil counts. At seven weeks old, a significant reduction was seen in red and white blood cells and thrombocyte numbers together with significant increases in mean cell haemoglobin and mean cell volume. The haematological profile demonstrated a macrocytic normochromic anaemia caused possibly by a folic acid deficiency as a result of the food restriction. Histopathological lesions were seen in the heart, lungs and liver from birds on all diets but there were more lesions the longer the food had been restricted. Lung disease was more marked where there was inadequate ventilation. Cartilaginous and osseous lung nodules were significantly fewer after food restriction. It was postulated that the increase in pathological lesions in the food-restricted birds may be associated with a stress response.
Animals↗
Modulation by oestrogen and progestins/antiprogestins of alpha interferon receptor expression in human breast cancer cells.
Human breast cancer ZR-75-1 cells expressed 1516 (105) (mean [S.D.]) interferon (IFN) receptors (IFNR) per cell with Kd of 0.61 (0.15) nmol/l. Oestrogen independent ZR-PR-LT and tamoxifen resistant ZR-75-9a1 8 mumol/l cells expressed similar numbers of IFNR. ZR-75-9a1 cells, which had been maintained in the absence of tamoxifen or known oestrogenic activity for 46 weeks, expressed a significantly higher number of IFNR (3170 [315]). Exposure of ZR-75-1 cells to 10(-9) mol/l 17 beta-oestradiol (E2) led to a consistent reduction in IFNR numbers whilst 10(-6) mol/l tamoxifen slightly increased IFNR expression. Since IFN increases oestrogen receptors in this cell line, IFN and E2 appear to have opposite effects on expression of each others' receptor. 10(-9) mol/l medroxy progesterone acetate and mifepristone significantly increased IFNR numbers whilst ORG 2058 decreased IFNR expression and ZK 98.299 had no effect. Progestin/antiprogestin induced IFNR increase in this cell line correlated with down-regulation of progesterone receptor (PR). Thus an IFN/ER/PR axis may exist in ZR-75-1 cells and variants.
Breast Neoplasms↗
Purinergic modulation of field stimulation responses of rat and human vas deferens smooth muscle.
1. Guanethidine at 5 x 10(-6) M strongly inhibited rat prostatic but not epididymal vas deferens, reflecting differences in innervation and the neurogenic field stimulation responses of these tissues. 2. Adenosine and ATP inhibited the field stimulation responses of rat prostatic vas deferens by 56 and 50% respectively. A 10-min pretreatment with 10(-4) M caffeine partly reversed this inhibition, by 55% in the case of adenosine and 60% for ATP. 3. Pretreatment for 10 min with 5 microM quinidine failed to significantly alter the extent of either adenosine or ATP inhibition of the field stimulation responses of rat prostatic vas deferens. 4. 8-Phenyltheophylline, the selective blocker of the A1 subtype of the P1 receptor, partly reversed adenosine-induced inhibition of the vas deferens FS responses. NECA, the selective agonist of the A2 subtype of the P1 receptor, very strongly inhibited vas deferens FS responses. 5. Field stimulation responses of human vas deferens were also inhibited by both adenosine and ATP but to a lesser extent and more variably than in rat tissue. 6. Adenosine and ATP inhibition was reversed by caffeine pretreatment, but far more variably than in rat tissue, and quinidine was without significant effect on inhibition of the responses. 7. It is concluded that in these tissues adenosine and ATP may operate via a P1 type receptor of both A1 and A2 subtypes and that a P2 type receptor may be lacking.
Adenosine↗
A possible role for abscisic acid analogues as calcium channel blockers in mammalian smooth muscle.
1. The abscisic acid (ABA) analogue SD217595 at 10 microM caused inhibition of K(+)-induced phasic and tonic contractions of rat bladder detrusor smooth muscle strips. 2. This attenuation of contraction was a dual effect: the inhibition of phasic contractions was irreversible whereas that of the tonic contractions was readily reversed. 3. The dual inhibition is possibly due to blockade of two subtypes of voltage-operated calcium channels with T- and L-type characteristics. 4. The inhibition of contraction induced by SD217595 is in stark contrast to the potentiation of smooth muscle contraction reported previously with the parent molecule ABA. 5. Two other ABA analogues studied (WL019376 and WL019377) showed neither inhibitory or excitatory effects upon K(+)-induced smooth muscle contraction after short exposures of 10 min.
Abscisic Acid↗
Pulmonary oedema following relief of upper airway obstruction in the Pierre-Robin syndrome: a consequence of early palatal repair?
Pulmonary oedema occurred following relief of an acute upper airway obstruction in an infant with Pierre-Robin syndrome undergoing cleft palate repair. We anticipate an increased prevalence of this phenomenon in view of the present trend for early palatal repair, and would advocate the routine use of a nasopharyngeal airway after operation in infants with severe micrognathia.
Airway Obstruction↗
Immunoglobulin response to intravenous streptokinase in acute myocardial infarction.
OBJECTIVE: To devise assays to assess and follow the specific antibody response in patients treated with streptokinase for acute myocardial infarction. DESIGN: Venous blood samples were collected before treatment with streptokinase started and subsequently at regular intervals over one year. Specific IgG and subclass IgG1 were assessed by an enzyme linked immunosorbent assay. SETTING: Coronary care unit in a general hospital. PATIENTS: 48 patients with acute myocardial infarction: 22 patients had venous blood samples taken at presentation only; serial blood samples were taken from 20 patients who then received thrombolytic therapy with streptokinase and six patients who were unsuitable for thrombolytic therapy. RESULTS: Titres of antibodies to streptokinase were low at presentation in 36 (75%) of the 48 patients. Serial measurements made in 20 patients showed the virtual disappearance of antibody within the first 24 hours. This was followed by a steady increase in the specific IgG1 titre, which peaked at day 14 before gradually declining. Values at one year remained significantly higher than baseline values. There was no evidence of an IgM response in the patients studied. CONCLUSION: Low titres of antibodies to streptokinase were widespread in the population. Antibody was consumed after treatment and the subsequent immunoglobulin rise suggested a secondary immune responses; the recently described neutralising capacity to streptokinase is probably related to this antibody.
Acute Disease↗
Fragile X syndrome: genetic localisation by linkage mapping of two microsatellite repeats FRAXAC1 and FRAXAC2 which immediately flank the fragile site.
We report the genetic localisation of the fragile site at Xq27.3 associated with fragile X syndrome. The position of the fragile site within the multipoint linkage map was determined using two polymorphic microsatellite AC repeat markers FRAXAC1 and FRAXAC2. These markers were physically located within 10 kilobases and on either side of the p(CCG)n repeat responsible for the fragile site. FRAXAC1 has five alleles with heterozygosity of 44% and is in strong linkage disequilibrium with FRAXAC2 which has eight alleles and a heterozygosity of 71%. No recombination was observed either between these markers in 40 normal CEPH pedigrees or with the fragile X in affected pedigrees. These markers provide the means for accurate diagnosis of the fragile X genotype in families by rapid polymerase chain reaction analysis and were used to position the fragile X within the multipoint map of the X chromosome to a position 3.7 cM distal to DXS297 and 1.2 cM proximal to DXS296.
Base Sequence↗
Differentiation of cancellous bone and medullary bone in laying hens: a novel technique for image analysis.
A selective staining technique for the identification and differentiation of cancellous bone from medullary bone of the laying hen by image analysis is described. Undecalcified Polymaster resin sections were oxidized in acidified potassium permanganate and oxalic acid before being immersed in an ammoniacal silver solution. The sections were reduced in formalin, fixed in sodium thiosulfate and counterstained in naphthalene black 10B which was dissolved in picric and acetic acids. Intensely stained cancellous bone was prominent with this technique compared with a paler medullary bone component which permitted the former to be easily recognized and measured by image analysis.
Animals↗
Some but not all benefits of intravenous immunoglobulin therapy after marrow transplantation appear to correlate with IgG trough levels.
Multiple benefits of intravenous immunoglobulin (IVIG) therapy after marrow transplantation have been reported, including decreased incidence of acute graft-versus-host disease (GVHD), infection, sepsis, cytomegalovirus (CMV) pneumonitis and platelet use. To test the hypothesis that the observed beneficial effects of IVIG are related to the serum IgG levels achieved, we followed IgG levels (pre-infusion, 1 h and 24 h post-infusion) in 45 consecutive marrow transplant recipients. IVIG 500 mg/kg was given weekly for six doses starting day -8 pre-transplant, then every other week for a total of 11 doses. Forty-one patients (22 allogeneic, 17 autologous, two syngeneic) were evaluable. Patients with acute GVHD had significantly lower serum IgG trough levels (less than 1200 mg/dl) noted at day +20 post-transplant and afterwards than patients without GVHD (greater than or equal to 1200 mg/dl). Pharmacokinetic modeling of the data indicates that IgG half-life between day -8 and day +6 may predict which recipients are at increased risk of acute GVHD. Allogeneic recipients in the group with trough levels less than 1200 mg/dl required more platelet transfusions. Although there was no significant difference in fungal infection rates or bacteremia, sepsis was noted in only two recipients (one allogeneic, one autologous), both with serum IgG trough levels less than 1200 mg/dl. In addition, three allogeneic recipients had cytomegalovirus pneumonitis, all in the group with lower IgG trough levels. Thus, while serum IgG trough levels less than 1200 mg/dl appear to be strongly associated with acute GVHD, low levels may also be associated with increased platelet utilization, with cytomegalovirus pneumonitis, and sepsis, but not with the overall incidence of infection.
Adolescent↗
Isolation of a human DNA sequence which spans the fragile X.
To identify the sequences involved in the expression of the fragile X and to characterize the molecular basis of the genetic lesion, we have constructed yeast artificial chromosomes (YACs) containing human DNA and have screened them with cloned DNA probes which map close to the fragile site at Xq27.3. We have isolated and partly characterized a YAC containing approximately 270 kb of human DNA from an X chromosome which expresses the fragile X. This sequence in a yeast artificial ring chromosome, XTY26, hybridizes to the two closest DNA markers, VK16 and Do33, which flank the fragile site. The human DNA sequence in XTY26 also spans the fragile site on chromosome in situ hybridization. When a restriction map of XTY26, derived by using infrequently cutting restriction enzymes, is compared with similar YAC maps derived from non-fragile-X patients, no large-scale differences are observed. This YAC, XTY26, may enable (a) the fragile site to be fully characterized at the molecular level and (b) the pathogenetic basis of the fragile-X syndrome to be determined.
Chromosome Mapping↗