Fetal cardiac diagnosis and its influence on the pregnancy and newborn--a tertiary centre experience.

OBJECTIVES: To evaluate the impact of an abnormal fetal cardiac scan on the management of the pregnancy and the outcome of the newborn. METHODS: We reviewed all pregnancies that were referred to the Fetal Cardiac Unit for assessment to determine if the finding of a cardiac abnormality influenced the pregnancy and fetus, timing and mode of delivery, the treatment and outcome of the newborn. Diagnoses were confirmed by echocardiography following the baby's delivery. RESULTS: Between January 2005 and July 2006, there were 251 detailed fetal cardiac scans carried out on at risk pregnancies or those with suspected abnormal scans in 127 fetuses. Seven of the 92 mothers with abnormal fetal cardiac scans opted for termination. Two were successfully treated during the pregnancy for hydrops fetalis arising from a tachyarrhythmia. One was induced early because of deterioration of fetal well-being and increasing cardiac size. Twenty-six infants required a prostaglandin infusion prior to surgery. Two required intensive care for associated malformations. There were 24 survivors following complex surgery, and 2 deaths. Two infants with severe tricuspid valve incompetence from a dysplastic valve died, one associated with a septicaemia and the other where surgery was delayed because of prematurity and low birth weight. There was no maternal morbidity or mortality. CONCLUSIONS: Early detection of fetal cardiac malformation allows for careful counselling of the parents, ongoing antenatal review with a planned site and timing of delivery, and anticipatory postnatal care for optimum outcomes. The importance of careful screening is emphasized to allow for referral of mothers with potentially abnormal scans to an appropriate tertiary centre for confirmation and management.

P1 and NR1 plasmid replication during the cell cycle of Escherichia coli.

Replication patterns of the miniP1 plasmid pZC176, the miniNR1 plasmid pRR933, and the high-copy miniNR1 derivative pRR942 were examined during the Escherichia coli cell division cycle and compared to the cycle-specific replication pattern of a minichromosome and the cycle nonspecific pattern of pBR322. In E. coli cells growing with doubling times of 40 and 60 min, the miniP1 plasmid was found to replicate with a slight periodicity during the division cycle. The periodicity was not nearly as pronounced as that of the minichromosome, was not affected by the presence of a minichromosome, and was not evident in cells growing more rapidly with a doubling time of 25 min. Both miniNR1 plasmids, pRR933 and pRR942, replicated with patterns indistinguishable from that of pBR322 and clearly different from that of the minichromosome. It is concluded that both P1 and NR1 plasmids can replicate at all stages of the cell cycle but that P1 displays a slight periodicity in replication probability in the cycle of slower growing cells. This periodicity does not appear to be coupled to a specific age in the cycle, but could be associated with the achievement of a specific cell mass per plasmid. During temperature shifts of a dnaC(Ts) mutant, the miniP1 plasmid and pBR322 replicated with similar patterns that differed from that of the minichromosome, but were consistent with a brief eclipse between rounds of replication.

IHF redistributes bound initiator protein, DnaA, on supercoiled oriC of Escherichia coli.

In Escherichia coli, initiation of chromosome replication requires that DnaA binds to R boxes (9-mer repeats) in oriC, the unique chromosomal replication origin. At the time of initiation, integration host factor (IHF) also binds to a specific site in oriC. IHF stimulates open complex formation by DnaA on supercoiled oriC in cell-free replication systems, but it is unclear whether this stimulation involves specific changes in the oriC nucleoprotein complex. Using dimethylsulphate (DMS) footprinting on supercoiled oriC plasmids, we observed that IHF redistributed prebound DnaA, stimulating binding to sites R2, R3 and R5(M), as well as to three previously unidentified non-R sites with consensus sequence (A/T)G(G/C) (A/T)N(G/C)G(A/T)(A/T)(T/C)A. Redistribution was dependent on IHF binding to its cognate site and also required a functional R4 box. By reducing the DnaA level required to separate DNA strands and trigger initiation of DNA replication at each origin, IHF eliminates competition between strong and weak sites for free DnaA and enhances the precision of initiation synchrony during the cell cycle.

The utilisation of nuchal translucency as a prenatal marker of Down syndrome, 1993-1999.

A sample of 6,038 obstetric ultrasound referrals and reports between January 1993 and June 1999 in a single Melbourne private ultrasound practice was reviewed to determine whether the referral and reporting pattern for nuchal translucency (NT) measurement has changed. The proportion of both 10-14 week ultrasound scans and mid trimester fetal anatomy scan referrals increased significantly over the study period (p < 0.001 and p < 0.001, respectively). There was also a significant increase in NT reporting and the number of specific referrals for an NT measurement over the study period (p = 0.01 and p < 0.001, respectively). If current trends continue it is likely that the 10-14 week scan for NT measurement will become a routine component of antenatal care. Therefore, as a matter of urgency, it is imperative that the best and most cost-effective screening strategy for Down syndrome in an Australian population is defined.

Drunken-cell footprints: nuclease treatment of ethanol-permeabilized bacteria reveals an initiation-like nucleoprotein complex in stationary phase replication origins.

The nucleoprotein complex formed on oriC, the Escherichia coli replication origin, is dynamic. During the cell cycle, high levels of the initiator DnaA and a bending protein, IHF, bind to oriC at the time of initiation of DNA replication, while binding of Fis, another bending protein, is reduced. In order to probe the structure of nucleoprotein complexes at oriC in more detail, we have developed an in situ footprinting method, termed drunken-cell footprinting, that allows enzymatic DNA modifying reagents access to intracellular nucleoprotein complexes in E.coli, after a brief exposure to ethanol. With this method, we observed in situ binding of Fis to oriC in exponentially growing cells, and binding of IHF to oriC in stationary cells, using DNase I and Bst NI endonuclease, respectively. Increased binding of DnaA to oriC in stationary phase was also noted. Because binding of DnaA and IHF results in unwinding of oriC in vitro, P1 endonuclease was used to probe for intracellular unwinding of oriC. P1 cleavage sites, localized within the 13mer unwinding region of oriC ', were dramatically enhanced in stationary phase on wild-type origins, but not on mutant versions of oriC unable to unwind. These observations suggest that most oriC copies become unwound during stationary phase, forming an initiation-like nucleoprotein complex.

Replication and segregation of a miniF plasmid during the division cycle of Escherichia coli.

Replication of the miniF plasmid pML31 was examined during the division cycle of Escherichia coli growing with doubling times between 40 and 90 min at 37 degrees C and compared to the replication of plasmid pBR322 and the minichromosome pAL70. The replication pattern of pML31 was indistinguishable from that of pBR322 at all growth rates and very different from the cell-cycle-specific replication of the minichromosome. It is concluded that both pML31 and pBR322 plasmids can replicate at all stages of the division cycle, with a probability of replication that increases gradually, but perhaps not exponentially, during the cycle. In contrast, the modes of segregation of pML31 and pBR322 plasmids into daughter cells at division appeared to differ, raising the possibility that pML31 may segregate in a nonrandom fashion similar to that of chromosomes and minichromosomes.

Metabolites from an Antarctic sponge-associated bacterium, Pseudomonas aeruginosa.

In an ongoing survey of the bioactive potential of microorganisms associated with marine invertebrates, the culture media of a sponge-associated bacterial strain of Pseudomonas aeruginosa was found to contain metabolites which inhibit the growth of several Gram-positive microorganisms. A series of diketopiperazines (1-6) including a new natural product (6) and two known phenazine alkaloid antibiotics (7 and 8) were isolated from the culture broth of this bacterium.

Cell cycle-specific changes in nucleoprotein complexes at a chromosomal replication origin.

Initiation of DNA synthesis is triggered by the binding of proteins to replication origins. However, little is known about the order in which specific proteins associate with origin sites during the cell cycle. We show that in cycling cells there are at least two different nucleoprotein complexes at oriC. A factor for inversion stimulation (FIS)-bound nucleoprotein complex, present throughout the majority of the cell cycle, switches to an integration host factor (IHF)-bound form as cells initiate DNA replication. Coincident with binding of IHF, initiator DnaA binds to its previously unoccupied R3 site. In stationary phase, a third nucleoprotein complex forms. FIS is absent and inactive oriC forms a nucleoprotein structure containing IHF that is not observed in cycling cells. We propose that interplay between FIS and IHF aids assembly of initiation nucleoprotein complexes during the cell cycle and blocks initiation at inappropriate times. This exchange of components at replication origins is reminiscent of switching between pre- and post-replicative chromatin states at yeast ARS1.

Correlation of gene transcription with the time of initiation of chromosome replication in Escherichia coli.

Transcriptional levels of the Escherichia coli mioC and gidA genes, which flank the chromosomal origin of replication (oriC) and the dnaA gene, were correlated with the time of initiation of chromosome replication. The transcripts were measured either in dnaC2(ts) mutants that had been aligned for initiation of chromosome replication by a temperature shift or in synchronous cultures of cells obtained using the baby machine technique. In both types of experiments, mioC transcription was inhibited prior to initiation of chromosome replication and resumed several minutes after initiation. Conversely, gidA and dnaA transcription were both inhibited after initiation of replication, coincident with the period of hemimethylation of oriC DNA. It is proposed that mioC transcription prevents initiation of chromosome replication, and must terminate before replication can begin. It is further proposed that the eclipse period between rounds of replication, i.e. the minimum interval between successive initiations, encompasses the time required to methylate GATC sequences in newly replicated oriC plus the time required to terminate mioC transcription. Conversely, the active transcription of gidA and dnaA prior to initiation is consistent with their positive effects on initiation, and their shutdown after initiation could serve to limit premature reinitiation.

Relationships between chromosome segregation, cell shape and temperature in Escherichia coli.

The partitioning of chromosomes into daughter cells during the division of Escherichia coli is non-random. As a result, the chromosome containing the older template DNA strand has a higher probability of segregating toward the old cell pole than toward the new cell pole. The numerical value of this probability is a function of the incubation temperature. It is shown here that a recent model for explaining the physiological basis for non-random chromosome segregation also explains the temperature dependence of the segregation process.

Improved bacterial baby machine: application to Escherichia coli K-12.

Exponentially growing derivatives of Escherichia coli K-12 were immobilized onto the surfaces of nitrocellulose membrane filters which had been coated with poly-D-lysine. The cells attached firmly to the surfaces, and when flushed with culture medium, the immobilized cells continued to divide and newborn cells were released into the effluent. Cell cycle parameters were examined with the technique, and it was found that K-12 derivatives possessed differing values for interdivision times, C, D, and average cell sizes when grown in the same culture media. It was also found that the cells released from immobilized populations of one culture consisted of two predominant size classes: newborn cells of unit size with single nucleoids and newborn cells of double this unit size. The results demonstrated that K-12 derivatives can be used in the baby machine culture technique to examine all aspects of the cell cycle of this organism. Furthermore, the yield of newborn cells was about fivefold greater than that obtained previously with cultures of strain B/r immobilized onto uncoated membranes.

Expression of two mRNAs encoding EGF-related proteins identifies subregions of sea urchin embryonic ectoderm.

Many proteins containing domains related to epidermal growth factor (EGF) function in intercellular interactions that mediate specification of cell fate. We have used in situ hybridization to show that the expression of two EGF-related genes (SpEGF I and SpEGF II) is restricted to the same subset of ectodermal cells in sea urchin pluteus larvae. However, the concentration of EGF I mRNA in different epithelial cells of aboral ectoderm and postoral facial epithelium is constant while that of EGF II mRNA is highly modulated. RNase protection assays show that both genes are activated during the period when ectoderm funder cells are established, i.e., between fourth and fifth and between fifth and sixth cleavages for EGF I and EGF II, respectively. By mesenchyme blastula stage EGF I mRNA reaches maximum abundance (800-1000 copies/expressing cell) as a result of a high transcription rate, while EGF II mRNA peaks at about half that concentration by gastrula stage. EGF I expression begins at early stages of oogenesis while EGF II expression appears to be confined to embryogenesis.

Neocarzinostatin and auromomycin preferentially cleave simian virus 40 DNA and chromosomes at a number of discrete locations.

Neocarzinostatin and auromomycin were shown to cleave simian virus 40 (SV40) DNA with preference for distinct regions of the viral genome. The positions cut by neocarzinostatin and auromomycin were similar, while micrococcal nuclease cleaved at positions other than those recognized by neocarzinostatin and auromomycin. Breaks were distributed throughout the viral genome and were not associated with any single type of genetic element. The limited number of locations in SV40 DNA that were preferentially cut by neocarzinostatin and auromomycin suggests that drug attack is directed by DNA structures other than the known trinucleotide sequence specificity of the drugs. Neocarzinostatin and auromomycin cut purified, cell-free, nuclear and intracellular chromosomal SV40 DNA at similar regions. The data indicate that there are regions in DNA that are hypersensitive to the drugs; the hypersensitivity may be determined by the microstructure of the DNA. The conformational change associated with the packing of the DNA into nucleosomes did not affect the microstructure of the sensitive region, nor did the shielding effect of nuclear proteins affect the drug's access to it. In addition, intracellular drug metabolism or other cellular factors did not alter the ability of drugs to interact at these sensitive regions.

Site specificity of bleomycin cleavage in purified and intracellular simian virus 40 DNA.

The sites of bleomycin-induced cleavage of purified and intracellular simian virus 40 DNA were examined. Breaks in purified DNA were mapped to several discrete sites that were distributed throughout the viral genome, but were not associated with a common genetic element. Double-stranded breaks were made in positions of the first single-stranded nick, and regions of cuts were unaffected by changes in DNA superhelicity. Bleomycin cut intracellular chromosomes at the same sites that were cleaved in purified DNA. These results indicate that SV40 DNA contains DNA secondary structures that are highly preferred sites for BLM cleavage. These conformations appear to be unaffected by nucleoproteins bound to DNA.

Measurement of bleomycin, neocarzinostatin, and auromomycin cleavage of cell-free and intracellular simian virus 40 DNA and chromatin.

Simian virus 40 (SV40) was used as a model for eukaryotic chromatin to allow analysis of strand scission drug action on DNA of the same nucleotide sequence in different environments. Cleavage of purified DNA, cell-free chromatin, and intracellular chromatin by the antitumor drugs bleomycin, neocarzinostatin, and auromomycin was assayed. Comparison of total (single-and double-stranded) drug-induced cutting of purified SV40 DNA and isolated viral minichromosomes, as measured by the conversion of supercoiled DNA to the nicked circular form, revealed that a 2-3-fold higher concentration of all three drugs is required to cut minichromosomes as extensively as naked DNA. In addition, differences in drug activity on cell-free nuclear viral chromatin and intracellular SV40 chromatin were measured. Three times more auromomycin was needed to cut intracellular SV40 DNA as extensively as the viral DNA in isolated nuclei, whereas, surprisingly, the increases in bleomycin and neocarzinostatin concentrations were 200-fold and 1000-fold respectively. When the drugs were used to treat SV40-infected cells, no repair of strand scissions was detected. Formation of double-stranded breaks by bleomycin, neocarzinostatin, and automomycin, measured at equivalent levels of total cleavage, was also examined to provide information on the distribution of strand scissions in different environments. Nucleoproteins were found to cause a 3-fold higher level of neocarzinostatin-induced double-stranded breaks to be made on isolated minichromosomes than on purified DNA, but they had no effect on double-stranded break formation by either bleomycin or auromomycin. In contrast, auromomycin made twice as many double-stranded breaks on intracellular SV40 DNA as on minichromosomes in isolated nuclei. However, neither bleomycin- nor neocarzinostatin-induced double-stranded breaks on intracellular SV40 DNA were significantly different from those made on SV40 in isolated nuclei.

Clinical features of eight pregnancies resulting from in vitro fertilization and embryo transfer.

In vitro fertilization (IVF) and embryo transfer (ET) have resulted in the birth of nine babies, including twins. One of the twins had a congenital cardiac malformation and seven of the nine babies were girls. Labor occurred preterm in two pregnancies; and in six delivery was by cesarean section. Plasma human chorionic gonadotropin (hCG), progesterone (P), and estriol (E3) measurements and ultrasonic scans showed no obvious differences from pregnancies resulting from natural conception. Cytogenetic studies from cord blood and histologic examination of the placentas were unremarkable. The theoretic risks of pregnancy following IVF and ET are discussed. Definite conclusions cannot be drawn until a large number of babies are delivered and a long-term follow-up is completed. Initial results from the current small sample are encouraging.

A case of benign intracranial hypertension in pregnancy.

We describe a 30-year-old patient who developed benign intracranial hypertension at 34 weeks in her second pregnancy and was treated both medically and by decompression of the perioptic meninges; her visual symptoms and signs remained static and she was delivered at 35 weeks by Caesarean section for poor progress in an induced labour.