Atrial fibrillation after resection: a PROGRESS III study.

AIM: Atrial fibrillation (AF) is a common cardiac arrhythmia, and is associated with worsening quality of life and complications such as stroke. Previous work showed that 8% of patients develop new-onset AF following colonic resection and highlighted factors that might predict the development of postoperative AF. The development of a new arrhythmia may have a negative effect on longer-term quality of life as well as cancer survivorship. The aim of this study is to accurately quantify the incidence of AF following colorectal cancer surgery and to validate a model to predict its development. METHOD: The Atrial Fibrillation After Resection (AFAR) study will recruit 720 patients aged 65 or over undergoing resection of colorectal cancer with curative intent. The primary outcome is development of AF within 90 days of surgery. Assessment of cardiac rhythm will be performed using 24-h Holter monitors at baseline, 30 and 90 days after surgery. An electrocardiogram (ECG) will be performed on the day of discharge. Baseline descriptors including model variables and quality of life will be recorded using EQ-5D-5L. The occurrence of complications and other key surgical outcomes will be recorded. An additional blood test for N-terminal pro B-type natriuretic peptide (NT-proBNP) will be performed prior to surgery. Statistical analysis will validate a previously derived model and will test the incremental value of added variables such as NT-proBNP. Finally, an exploratory analysis will assess whether changes in ECG measures between baseline and postoperative ECG can predict subsequent new-onset AF. CONCLUSION: This study will provide data that may allow us to stratify the risk of developing AF following colorectal cancer surgery. This may inform screening or prophylactic approaches.

Non-randomized studies should be considered for assessing surgical techniques in rectal prolapse: prospective cohort study.

AIM: Randomized trials comparing surgical techniques for rectal prolapse are not always feasible. We assessed whether non-randomized comparisons of those who have had surgery with those still waiting would be confounding baseline health status. METHOD: This was a prospective cohort study in seven UK hospitals. Participants were ≥ 18 years and listed for surgical interventions of equivalent intensity for rectal prolapse. They were defined as short or long waiters (≤ 18 or > 18 weeks, respectively). Time on the waiting list was compared with baseline comorbidity (Charlson comorbidity index) and change from baseline in health status (EQ-5D-5L) at the time of surgery. RESULTS: In all, 203 patients were analysed. Median (interquartile range) waiting time was 13.7 weeks (8.1, 20.4) varying across sites. Baseline comorbidity was not an important predictor of waiting time. Median Charlson comorbidity index was 2 (0, 3) for short and 1 (0, 3) for long waiters. A change in waiting time by a week was associated with negligible improvement in the EQ-5D-5L index of 0.001 (95% CI -0.000 to 0.003, P = 0.106). CONCLUSION: Negligible change in patient reported health status while on the waiting list and lack of effect of comorbidities in influencing waiting time support the use of non-randomized pre-/post-studies to compare the effects of surgical interventions for rectal prolapse.

Difficult airway management of a child impaled through the neck.

We report the difficult airway management of a child impaled through the neck by a wooden plant support. The various options are discussed and the involvement of experienced personnel together with a clear preformulated plan of action is stressed.

DGAT2 is a new diacylglycerol acyltransferase gene family: purification, cloning, and expression in insect cells of two polypeptides from Mortierella ramanniana with diacylglycerol acyltransferase activity.

Acyl CoA:diacylgycerol acyltransferase (EC; DGAT) catalyzes the final step in the production of triacylglycerol. Two polypeptides, which co-purified with DGAT activity, were isolated from the lipid bodies of the oleaginous fungus Mortierella ramanniana with a procedure consisting of dye affinity, hydroxyapatite affinity, and heparin chromatography. The two enzymes had molecular masses of 36 and 36.5 kDa, as estimated by gel electrophoresis, and showed a broad activity maximum between pH 6 and 8. Based on partial peptide sequence information, polymerase chain reaction techniques were used to obtain full-length cDNA sequences encoding the purified proteins. Expression of the cDNAs in insect cells conferred high levels of DGAT activity on the membranes isolated from these cells. The two proteins share 54% homology with each other but are unrelated to the previously identified DGAT gene family (designated DGAT1), which is related to the acyl CoA:cholesterol acyltransferase gene family, or to any other gene family with ascribed function. This report identifies a new gene family, including members in fungi, plants and animals, which encode enzymes with DGAT function. To distinguish the two unrelated families we designate this new class DGAT2 and refer to the M. ramanniana genes as MrDGAT2A and MrDGAT2B.

Apparently unstable normal FMR1 alleles in nine developmentally delayed patients: implications for molecular diagnosis of the fragile X syndrome.

The Fragile X syndrome is a common form of X-linked mental retardation, affecting approximately 1 in 4,000 males. Since the discovery of the FMR1 gene responsible for the syndrome, molecular, rather than cytogenetic, diagnosis of Fragile X syndrome has become the gold standard. Numerous molecular diagnostic centers worldwide use PCR and Southern blotting to characterize the size of the CGG repeats within the gene, expansion of which has been shown to be associated with the vast majority of cases of Fragile X syndrome. Instability of this repeat through successive generations has been demonstrated in many patients and has been associated with numerous factors, including repeat length and molecular structure of the repeat. Nine males with normal-size alleles that exhibit repeat length instability by the presence of a second normal length distinct band by repeated PCR analysis from peripheral lymphocytes are reported. Many hypotheses addressing the reason for this apparent instability were tested without elucidating the underlying molecular causes, including cytogenetic analysis, sequence analysis of the repeat locus, and analysis of flanking dinucleotide repeat loci. All patients exhibited a normal complement of sex chromosomes by cytogenetic and molecular analysis. These results from the widely used PCR analysis illustrate an interesting molecular phenomenon and raise many questions relating to the factors and mechanisms involved in trinucleotide instability as well as having implications for the diagnostic testing of the Fragile X syndrome.

Fragile X premutation is a significant risk factor for premature ovarian failure: the International Collaborative POF in Fragile X study--preliminary data.

The preliminary results of an international collaborative study examining premature menopause in fragile X carriers are presented. A total of 760 women from fragile X families was surveyed about their fragile X carrier status and their menstrual and reproductive histories. Among the subjects, 395 carried a premutation, 128 carried a full mutation, and 237 were noncarriers. Sixty-three (16%) of the premutation carriers had experienced menopause prior to the age of 40 compared with none of the full mutation carriers and one (0.4%) of the controls. Based on these preliminary data, there is a significant association between fragile X premutation carrier status and premature menopause.

Characterization of acyl-ACP thioesterases of mangosteen (Garcinia mangostana) seed and high levels of stearate production in transgenic canola.

Acyl-acyl-carrier protein (ACP) thioesterases are, at least in part, responsible for the fatty acyl chain length composition of seed storage oils. Acyl-ACP thioesterases with specificity for each of the saturated acyl-ACP substrates from 8:0 through 16:0 have been cloned, with the exception of 18:0, and are members of the FatB class of thioesterases. The authors have determined that the tropical tree species mangosteen (Garcinia mangostana) stores 18:0 (stearate) in its seed oil in amounts of up to 56% by weight. Acyl-ACP thioesterase activity as measured in crude mangosteen seed extracts showed a preference for 18:1-ACP substrates, but had significant activity with 18:0 relative to that with 16:0-ACP, suggesting a thioesterase might be involved in the production of stearate. Three distinct acyl-ACP thioesterases were cloned from mangosteen seed cDNA; two representative of the FatA class and one representative of the FatB class. When expressed in vitro, the enzyme encoded by one of the FatAs (Garm FatA1) while preferring 18:1-ACP showed relatively low activity with 16:0-ACP as compared to 18:0-ACP, similar to the substrate preferences shown by the crude seed extract. Expression of Garm FatA1 in Brassica seeds led to the accumulation of stearate up to 22% in seed oil. These results suggest that Garm FatA1 is at least partially responsible for determining the high stearate composition of mangosteen seed oil and that FatA as well FatB thioesterases have evolved for specialized roles.

Impact of carrier status determination for Duchenne/Becker muscular dystrophy by computer-assisted laser densitometry.

Carrier status determination for Duchenne and Becker muscular dystrophies (D/BMD), disorders caused by mutations in the dystrophin gene at Xp21, is complicated by a number of factors. These include a high mutation rate and a 5-10% recombination frequency across the dystrophin gene. For these reasons, linkage analysis frequently gives an inconclusive result, and a direct mutation detection method for females at risk is desirable. Because 65% of the mutations that cause D/BMD are deletions of one or more exons of the dystrophin gene, diagnosis in most affected males is relatively easy using multiplex polymerase chain reaction (PCR) analysis. However, deletion analysis in females is more difficult because of the interference of the normal X chromosome in the deletion assay. We have developed a quantitative PCR-based analysis designated computer-assisted laser densitometry (CALD), which uses the automated fluorescent fragment analysis application of the Applied Biosystems (Foster City, California) automated sequencer. This method has proved to be 100% accurate in retrospective blind studies analysing a total of 351 samples. Subsequent analysis of more than 800 women from more than 400 D/BMD families has shown that a highly accurate carrier risk can be given in more than 90% of cases.

Tissue-specific methylation differences and cognitive function in fragile X premutation females.

Tissue-specific variation in (CGG)n repeat size and methylation status of the FMR1 gene was investigated in 17 female premutation carriers. Minor variation in premutation repeat size among leukocyte, lymphoblast, and fibroblast tissues was noted in some subjects. One subject exhibited a premutation size allele of (CGG)64 in leukocyte and fibroblast tissues by polymerase chain reaction analysis but a normal-size allele of (CGG)46 in lymphoblast cells, suggesting low-level mosaicism in blood and clonality of the lymphoblast cell line. Six subjects exhibited differences in methylation pattern between leukocytes and lymphoblasts but not between leukocytes and fibroblasts, whereas 2 subjects showed large differences in methylation pattern between leukocytes and fibroblasts. Cognitive function was studied in 14 subjects using the Wechsler Adult Intelligence Scale-Revised. Mean Verbal and Performance IQs were well within the average range as was the mean Full Scale IQ; nevertheless, a trend toward lower Performance IQ compared with Verbal IQ was observed. No significant correlation was apparent between Full Scale IQ and (CGG)n repeat size; however, a significant positive correlation was observed between Full Scale IQ and the proportion of the active X carrying the normal FMR1 allele in fibroblasts but not in leukocytes or lymphoblasts.

Modification of the substrate specificity of an acyl-acyl carrier protein thioesterase by protein engineering.

The plant acyl-acyl carrier protein (ACP) thioesterases (TEs) are of biochemical interest because of their roles in fatty acid synthesis and their utilities in the bioengineering of plant seed oils. When the FatB1 cDNA encoding a 12:0-ACP TE (Uc FatB1) from California bay, Umbellularia californica (Uc) was expressed in Escherichia coli and in developing oilseeds of the plants Arabidopsis thaliana and Brassica napus, large amounts of laurate (12:0) and small amounts of myristate (14:0) were accumulated. We have isolated a TE cDNA from camphor (Cinnamomum camphorum) (Cc) seeds that shares 92% amino acid identity with Uc FatB1. This TE, Cc FatB1, mainly hydrolyzes 14:0-ACP as shown by E. coli expression. We have investigated the roles of the N- and C-terminal regions in determining substrate specificity by constructing two chimeric enzymes, in which the N-terminal portion of one protein is fused to the C-terminal portion of the other. Our results show that the C-terminal two-thirds of the protein is critical for the specificity. By site-directed mutagenesis, we have replaced several amino acids in Uc FatB1 by using the Cc FatB1 sequence as a guide. A double mutant, which changes Met-197 to an Arg and Arg-199 to a His (M197R/R199H), turns Uc FatB1 into a 12:0/14:0 TE with equal preference for both substrates. Another mutation, T231K, by itself does not effect the specificity. However, when it is combined with the double mutant to generate a triple mutant (M197R/R199H/T231K), Uc FatB1 is converted to a 14:0-ACP TE. Expression of the double-mutant cDNA in E. coli K27, a strain deficient in fatty acid degradation, results in accumulation of similar amounts of 12:0 and 14:0. Meanwhile the E. coli expressing the triple-mutant cDNA produces predominantly 14:0 with very small amounts of 12:0. Kinetic studies indicate that both wild-type Uc FatB1 and the triple mutant have similar values of Km,app with respect to 14:0-ACP. Inhibitory studies also show that 12:0-ACP is a good competitive inhibitor with respect to 14:0-ACP in both the wild type and the triple mutant. These results imply that both 12:0- and 14:0-ACP can bind to the two proteins equally well, but in the case of the triple mutant, the hydrolysis of 12:0-ACP is severely impaired. The ability to modify TE specificity should allow the production of additional "designer oils" in genetically engineered plants.

FRAXE expansion is not a common etiological factor among developmentally delayed males.

Expansion of a (CGG)n trinucleotide repeat unit at FRAXE, a newly defined fragile site distal to FRAXA, at Xq28, is reported to be associated with mild mental retardation. Three hundred developmentally delayed male patients referred for fragile X testing but negative for the FMR-1 gene trinucleotide expansion were screened for the FRAXE expansion. This group of patients had a wide range of intellectual or behavioral problems and included 19 patients who had low-level fragile site expression detected cytogenetically at Xq27-q28. None of the patients tested positive for the FRAXE expansion. These results suggest that FRAXE is not a common etiological factor among this group of patients. The data support the hypothesis that FRAXE is either very rare or a benign fragile site that is not associated with any clinical phenotype, similar to the FRAXF and FRA16A sites.

Heterogeneity in Roberts syndrome.

Roberts syndrome (RS) is a rare, autosomal recessive condition characterized primarily by growth retardation, developmental delay, and limb anomalies. Some RS patients (RS+), but not others (RS-), have an abnormality of their constitutive heterochromatin (the "RS effect"). RS+ patients also show a cellular hypersensitivity to DNA damaging agents such as mitomycin C (MMC). Lymphoblastoid cell lines from 2 unrelated RS+ patients were fused and hybrid cells examined for correction of the RS effect and MMC hypersensitivity. Neither cellular defect was corrected in the 2 hybrid cell lines examined, suggesting that these 2 patients represent a single complementation group. Fusions were also performed between one RS+ cell line and 2 different RS- cell lines. In both fusions, the hybrids demonstrated correction of both the heterochromatin abnormality and MMC hypersensitivity. These observations suggest that RS+ and RS- patients belong to different complementation groups and do not arise from the same single gene mutation.

Changes in oxygen saturation in the 72 hours after hip surgery: the effect of oxygen therapy.

The aim of this study was to investigate changes in oxygen saturation (SpO2) occurring during the three days following hip surgery in patients in this hospital and to determine to what extent SpO2 might be improved by oxygen therapy for 24 or 72 hours. Eighty-three patients (aged 43-96 years) scheduled for elective total hip replacement or emergency surgery for hip fractures were studied. Forty-four patients had 24 hour postoperative oxygen prescribed by their anaesthetist or surgeon; we randomized these to either continue oxygen for a total of three days (Group 1) or to discontinue oxygen after Day 1 (Group 2). Patients not prescribed oxygen by the surgeon or anaesthetist (n = 39) were randomly assigned either to receive oxygen for three days (Group 3) or not to receive oxygen (Group 4). Oxygen was administered through nasal cannulae at a flow of 2 l.min-1. SpO2 was measured every 10 seconds for three days and stored on computer disc. Percentage of time spent with SpO2 below 90% was used as an index of desaturation. Patients receiving oxygen had significantly improved SpO2. In patients not receiving oxygen, desaturation was most severe on Days 1 and 2, improving somewhat on Day 3. On Day 2 desaturation was similar in Groups 2 and 4. When oxygen was not being administered males were significantly more desaturated than females. Our investigations indicate that following hip surgery poor saturation continues for at least two days and can be improved by oxygen therapy.

An automated system for testing the accuracy of patient-controlled analgesia devices.

A system was developed to test the accuracy of patient-controlled analgesia devices in situations simulating clinical use. Bolus requests are made automatically at predetermined intervals, and the infusate delivered is measured and recorded without the need for operator presence. To ensure clinical relevance, the bolus request times used in this study corresponded to a pattern typical of those requested by patients on the ward. Graseby, Abbott Provider 5500 and IVAC patient-controlled analgesia devices were tested and found to deliver reasonably accurately over a 24 h period. However, when an infusion was started in an unprimed system or after a period of no bolus requests in a bolus-only mode the Graseby and IVAC machines under-delivered. This system provides a means of testing patient-controlled analgesia devices operating in any delivery mode.

Fatty acid biosynthesis redirected to medium chains in transgenic oilseed plants.

Medium-chain fatty acids (FAs), found in storage lipids of certain plants, are an important renewable resource. Seeds of undomesticated California bay accumulate laurate (12:0), and a 12:0-acyl-carrier protein thioesterase (BTE) has been purified from this tissue. Sequencing of BTE enabled the cloning of a complementary DNA coding for a plastid-targeted preprotein. Expression of the complementary DNA in the seeds of Arabidopsis thaliana resulted in BTE activity, and medium chains accumulated at the expense of long-chain (greater than or equal to 16) FAs. Laurate became the most abundant FA species and was deposited in the storage triacylglycerols. These results demonstrate a mechanism for medium-chain FA synthesis in plants.

Allene oxide and aldehyde biosynthesis in starfish oocytes.

Allene oxides are a very unusual type of epoxide that, in biological systems, are formed by the enzymic dehydration of fatty acid hydroperoxides (lipoxygenase products). This reaction occurs widely in plants, in which allene oxide synthesis is a key step in the conversion of linolenic acid to jasmonic acid, the plant growth regulator. We report biosynthesis of the allene oxide (8R)-8,9-epoxyeicosa-(5Z,9,11Z,14Z)-tetraenoic acid via the (8R)-lipoxygenase metabolism of arachidonic acid in starfish oocytes. Formation of the allene oxide was deduced from high pressure liquid chromatography, UV, gas chromatography-mass spectrometry and 1H-NMR analyses of the precise structure and mechanism of biosynthesis of its major hydrolysis product, the alpha-ketol 8-hydroxy-9-ketoeicosa-(5Z,11Z,14Z)-trienoic acid. A second enzymic activity detected in the oocytes (hydroperoxide lyase) cleaves specifically the (8R)-hydroperoxy substrate into C7 and C13 fragments, identified as the hydroxyacid, (5Z)-7-hydroxyheptenoic acid, and two aldehydes, (2E,4Z,7Z)-tridecenal and its 4E isomer. Discovery of the allene oxide synthase and hydroperoxide lyase marks the first definitive localization of these enzymic activities to an animal cell. It was established previously that the (8R)-lipoxygenase metabolite (8R)-HETE will activate the maturation (re-initiation of meiosis) of starfish oocytes. The individual 8-lipoxygenase products may be involved at distinct stages of cell development.

Developmental induction, purification, and further characterization of 12:0-ACP thioesterase from immature cotyledons of Umbellularia californica.

The fatty acyl content of developing cotyledons of Umbellularia californica (California Bay) changes from a long-chain composition to a predominance of 10:0 and 12:0 in just 4-5 days at the beginning of an approximately 100-day period of medium-chain deposition. This striking change occurs at the earliest appearance of 12:0-acyl-carrier protein (ACP) thioesterase activity. The coincidence of these rapid events is consistent with the hypothesis that the enzyme plays a major role in medium-chain biosynthesis. The 12:0-ACP thioesterase has been substantially purified; enzyme activity consistently comigrates in chromatographic and electrophoretic systems with a protein or pair of proteins having an apparent molecular weight of approximately 34 kDa. A native molecular weight of approximately 42 kDa has been estimated by gel filtration chromatography, suggesting that the enzyme is a monomer. Affinity chromatography on immobilized ACP is a critical step in the purification procedure, and resolves the 12:0-ACP and 18:1-ACP thioesterases sufficiently to confirm that the medium-chain enzyme has negligible action on 18:1-ACP.

Somatic cell hybridization of Roberts syndrome and normal lymphoblasts resulting in correction of both the cytogenetic and mutagen hypersensitivity cellular phenotypes.

Roberts syndrome (RS) is a rare recessive condition of limb deformities, growth retardation, and developmental delay. Cultured cells from approximately half of RS patients exhibit a "puffing" of the constitutive heterochromatin and a hypersensitivity to mitomycin C (MMC). Patients exhibiting these cellular phenomena are designated RS+. Somatic cell hybridization with normal cells has been shown to correct the heterochromatin abnormality in RS+ cells. To determine if the MMC hypersensitivity could also be corrected by hybridization to normal cells, we fused two different RS+ lymphoblastoid cell lines (LCLs) to a ouabain-resistant, HAT-sensitive, normal LCL. Cytogenetic analyses of hybrid cell lines (HCLs) revealed complete correction of the heterochromatin abnormality. MMC cell killing assays revealed correction of the mutagen hypersensitivity as well. Five of the six HCLs tested exhibited D10 values (the dose at which 10% of the cells survive) that were not significantly lower than that of the normal parent but that were 6- to 18-fold greater than those of the RS+ parents. Correction of both of these cellular phenotypes in RS+ cells by fusion with normal cells supports the hypothesis that both of these phenomena are caused by a common defect in the Roberts syndrome gene (RBS).

A specific acyl-ACP thioesterase implicated in medium-chain fatty acid production in immature cotyledons of Umbellularia californica.

Umbellularia californica (California Bay) seeds accumulate 10:0 and 12:0 as principal reserve fatty acyl groups. An in vitro fatty acid synthesis system from the developing cotyledons produces chiefly 10:0 and 12:0, in approximately the same proportions as the intact tissue. The kinetics of acyl thioester and free fatty acid formation in this system suggest that a medium-chain specific acyl-acyl-carrier protein (ACP) hydrolysis mechanism is responsible for the preponderance of medium-chain products. A crude extract of the developing cotyledons exhibits hydrolytic activity toward acyl-ACPs, with marked preference for 12:0-ACP and 18:1-ACP in the test series 6:0, 8:0, 10:0, 11:0, 12:0, 14:0, 16:0, and 18:1-ACPs. Partial purification of the 12:0-ACP hydrolytic activity has resulted in its separation from the 18:1-ACP hydrolase(s) and the 12:0-coenzyme A hydrolase(s) that are also present, thereby demonstrating its specificity for the 12-carbon acyl chain length and the ACP derivative. During cotyledon development, as the proportion of medium-chain to other fatty acyl groups increases, the extractable yield of this activity also increases substantially. Collectively these results suggest a role for this 12-ACP thioesterase in medium-chain production in vivo.