Maternal hemodynamics, fetal biometry and Doppler indices in pregnancies followed up for suspected fetal growth restriction.

OBJECTIVES: To assess whether, in a cohort of patients with a small-for-gestational-age (SGA) fetus with estimated fetal weight ≤ 10th percentile, maternal hemodynamics, fetal biometry and Doppler indices at presentation can predict the subsequent development of an abnormal fetal Doppler index or delivery of a baby with birth weight < 3rd percentile. METHODS: This was a prospective observational cohort study conducted at a specialist clinic for the management of pregnancies with a SGA fetus at King's College Hospital, London, UK. The study population comprised 86 singleton pregnancies with a SGA fetus, presenting at a median gestational age of 32 (range, 26-35) weeks. We measured maternal cardiac function using a non-invasive transthoracic bioreactance monitor, as well as mean arterial pressure, fetal biometry, and umbilical artery (UA), fetal middle cerebral artery (MCA) and uterine artery (UtA) pulsatility indices (PI), and the deepest vertical pool of amniotic fluid. Z-scores of these variables were calculated based on reported reference ranges and the values were compared between pregnancies with evidence of an abnormal fetal Doppler index at presentation (Group 1), those that had developed an abnormal Doppler index at a subsequent visit (Group 2) and those that did not develop an abnormal Doppler index throughout pregnancy (Group 3). Abnormal fetal Doppler was defined as UA-PI > 95th percentile and/or MCA-PI < 5th percentile. Differences in measured variables at presentation were also compared between pregnancies delivering a baby with birth weight < 3rd percentile and those delivering a baby with birth weight ≥ 3rd percentile. Multivariate logistic regression analysis was used to determine significant predictors of birth weight < 3rd percentile and evolution from normal to abnormal fetal Doppler. RESULTS: In the study population, 14 (16%) cases were in Group 1, 19 (22%) in Group 2 and 53 (62%) in Group 3. Birth weight was < 3rd percentile in 39 (45%) cases and ≥ 3rd percentile in 47 (55%). There was decreased cardiac output and stroke volume and increased peripheral vascular resistance compared with a normal population, and the deviations from normal were most marked in Group 1. Pregnancies with birth weight < 3rd percentile, compared with those with birth weight ≥ 3rd percentile, had greater deviations from normal in fetal biometry, maternal cardiac output, stroke volume, heart rate, peripheral vascular resistance and UtA-PI. Multivariate logistic regression analysis demonstrated that, in the prediction of birth weight < 3rd percentile, maternal hemodynamic profile provided significant improvement to the prediction provided by maternal demographics, fetal biometry, UtA-PI, UA-PI and MCA-PI (difference between areas under receiver-operating characteristics curves, 0.18 (95% CI, 0.06-0.29); P = 0.002). In contrast, there was no significant independent contribution from maternal hemodynamics in the prediction of the subsequent development of abnormal fetal Doppler. CONCLUSIONS: In pregnancies with a SGA fetus, there is decreased maternal cardiac output and stroke volume and increased peripheral vascular resistance, and the deviations from normal are most marked in cases of redistribution in the fetal circulation and reduced amniotic fluid volume. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

A demonstration of a 1:1 correspondence between chiasma frequency and recombination using a Lolium perenne/Festuca pratensis substitution.

A single chromosome of the grass species Festuca pratensis has been introgressed into Lolium perenne to produce a diploid monosomic substitution line 2n = 2x = 14. The chromatin of F. pratensis and L. perenne can be distinguished by genomic in situ hybridization (GISH), and it is therefore possible to visualize the substituted F. pratensis chromosome in the L. perenne background and to study chiasma formation in a single marked bivalent. Recombination occurs freely in the F. pratensis/L. perenne bivalent, and chiasma frequency counts give a predicted map length for this bivalent of 76 cM. The substituted F. pratensis chromosome was also mapped with 104 EcoRI/Tru91 and HindIII/Tru91 amplified fragment length polymorphisms (AFLPs), generating a marker map of 81 cM. This map length is almost identical to the map length of 76 cM predicted from the chiasma frequency data. The work demonstrates a 1:1 correspondence between chiasma frequency and recombination and, in addition, the absence of chromatid interference across the Festuca and Lolium centromeres.

Physical and genetic mapping in the grasses Lolium perenne and Festuca pratensis.

A single chromosome of the grass species Festuca pratensis has been introgressed into Lolium perenne to produce a diploid monosomic substitution line 2n = 2x = 14. In this line recombination occurs throughout the length of the F. pratensis/L. perenne bivalent. The F. pratensis chromosome and recombinants between it and its L. perenne homeologue can be visualized using genomic in situ hybridization (GISH). GISH junctions represent the physical locations of sites of recombination, enabling a range of recombinant chromosomes to be used for physical mapping of the introgressed F. pratensis chromosome. The physical map, in conjunction with a genetic map composed of 104 F. pratensis-specific amplified fragment length polymorphisms (AFLPs), demonstrated: (1) the first large-scale analysis of the physical distribution of AFLPs; (2) variation in the relationship between genetic and physical distance from one part of the F. pratensis chromosome to another (e.g., variation was observed between and within chromosome arms); (3) that nucleolar organizer regions (NORs) and centromeres greatly reduce recombination; (4) that coding sequences are present close to the centromere and NORs in areas of low recombination in plant species with large genomes; and (5) apparent complete synteny between the F. pratensis chromosome and rice chromosome 1.

Changes in hippocampal gene expression associated with the induction of long-term potentiation.

The expression of four genes: zif/268, c-fos, tubulin and alpha Ca2+/calmodulin-dependent protein kinase II (alpha CAMKII) was studied following the induction of LTP in Schaffer collateral CA1 neurone synapses in rat hippocampal slices maintained in vitro. Levels of c-fos mRNA and tubulin (T26) mRNA in area CA1 were unchanged after induction of LTP, however, zif/268 and alpha CAMKII mRNA levels showed a significant increase compared to non-potentiated controls. It is possible, therefore, to measure changes in gene expression using in situ hybridisation following induction of LTP in vitro and these results strengthen the theory that zif/268 and alpha CAMKII are involved in some aspect of the induction or maintenance of hippocampal LTP.

Increased expression of dendritic mRNA following the induction of long-term potentiation.

A small number of mRNAs, including Ca2+/calmodulin-dependent protein kinase II alpha-subunit (CamKIIalpha) mRNA and microtubule-associated protein 2 (MAP2) mRNA, are present in the dendrites of neurones as well as in the cell bodies. We show here that the induction of long-term potentiation (LTP) in the hippocampal perforant path/granule cell synapses in anaesthetised rats is associated with increased levels of CamKIIalpha mRNA and MAP2 mRNA in the granule cell dendrites after 2 h. Similarly, induction of LTP in the Schaffer collateral/CA1 pyramidal cell synapses in hippocampal slices maintained in vitro also results in elevated dendritic levels of CamKIIalpha mRNA and MAP2 mRNA 2 h later. In both models, the levels of various other mRNA species restricted to the cell body region were unaffected by the induction of LTP. Increased expression of dendritic CamKIIalpha mRNA and MAP2 mRNA appears to be a general feature of hippocampal plasticity, since it occurs following LTP induction in both the dentate gyrus and the CA1 region. The elevation of mRNA levels in a restricted region close to the afferent synapses would allow a highly-localised enhancement of the synthesis of the corresponding proteins, providing an elegant mechanism for protein-synthesis-dependent synaptic plasticity to maintain a high degree of anatomical specificity.

Thin-film electrode fabrication techniques.

After a long developmental effort, we can now fabricate, using thin-film techniques, both rigid modiolar multielectrodes and flexible scala tympani multielectrodes which we believe appropriate for long-term implantation in human subjects. In vitro and in vivo life tests are in progress to confirm this expectation.

Involvement of two isoforms of SNAP-25 in the expression of long-term potentiation in the rat hippocampus.

Induction of long-term potentiation (LTP) in the hippocampus is associated with changes in expression of a variety of different proteins and is thought to be the mechanism which underlies synaptic plasticity. The 25 kDa synaptosomal-associated protein (SNAP-25) is a presynaptic protein which is involved in neurotransmitter exocytosis at the nerve terminal. Two isoforms of SNAP-25 have so far been identified (a and b) which differ in their distribution and developmental regulation. Using in situ hybridization, we demonstrated that the mRNA levels of the two isoforms of this protein are increased 2 h after the induction of LTP in granule cells of the dentate gyrus following high frequency stimulation of the perforant path in vivo. These observations further demonstrate the involvement of both isoforms of SNAP-25 in functional synaptic plasticity, although their exact roles have yet to be fully determined.

Long-term potentiation in perforant path/granule cell synapses is associated with a post-synaptic induction of proenkephalin gene expression.

Enkephalin peptides released from hippocampal mossy fibres lower the threshold for the generation of long-term potentiation (LTP) at the mossy fibre synapses. High frequency stimulation of the hippocampal dentate gyrus, sufficient to induce mossy fibre LTP, is associated with increased expression of the proenkephalin gene in the granule cells. We show here that a similar elevation in proenkephalin mRNA levels is observed, in anaesthetised rats, following stimulation of the perforant path sufficient to induce LTP in the perforant path/granule cell synapses. This strengthens the evidence implicating granule cell enkephalins as mediators of functional plasticity in the hippocampus. Furthermore. the results hint at a form of 'domino plasticity', where potentiation of transmission at the perforant path/granule cell synapses is subsequently followed by an enkephalin-mediated potentiation of transmission at the mossy fibre synapses.

Hyperalgesia induced by altered glycinergic activity at the spinal cord.

Glycine or its receptor antagonist, strychnine, were administered perispinally to investigate their effect on nociceptive responses elicited by activation of various cutaneous receptors. Strychnine produced dose-dependent sensory and motor disturbances; 1 and 5 micrograms doses were sub-convulsive, eliciting recurrent episodes of coordinated grooming, scratching and biting at the skin, which persisted for approximately 10 minutes post-injection; higher doses (25 and 100 micrograms) increased the intensity and duration of these effects, and produced convulsive motor seizures. Motor disturbances were not elicited by glycine (5, 25, 100 and 400 micrograms). Strychnine treated rats, at all doses, vocalized consistently in response to light cutaneous stimulation; a significant proportion of glycine treated rats also vocalized, but were not as sensitive to mild stimulation. Skin hyperalgesia persisted for at least 30 minutes in both strychnine and glycine treated rats. Both strychnine and glycine significantly reduced vocalization thresholds to tail shock. However, no clear effect on tail flick latency was observed following either strychnine or glycine. These results indicate that glycinergic neurons contribute to the tonic regulation of nociceptive input at the spinal cord.

Strychnine antagonizes vaginal stimulation-produced analgesia at the spinal cord.

Vaginal-cervical mechanostimulation (VS) suppresses vocalization and withdrawal responses to noxious stimulation. To determine whether the inhibitory neurotransmitter, glycine, contributes to the action of VS, strychnine, a specific glycine receptor antagonist was administered perispinally via intrathecal catheter in dosages of 1,5,25 and 100 micrograms. Prior to strychnine administration, VS (400 g force) elevated thresholds to elicit vocalization in response to graded intensities of tail shock, and blocked vocalization elicited by stimulation of a skin area, previously sensitized by intradermal injection of a 20% yeast solution. After strychnine administration the analgesic effects of VS were significantly attenuated. These findings suggest that the analgesic action of VS is partially mediated by glycine at the spinal level.

Nociceptive responses to altered GABAergic activity at the spinal cord.

GABA agonists and antagonists were injected intrathecally at the spinal cord, to determine their effect on nociceptive thresholds. Tactile stimulation, applied against the flank by a medium diameter von Frey fiber (5.5 g force), elicited distress vocalizations after, but not before injection of the GABA antagonists, bicuculline MI or picrotoxin (0.25 and 1 microgram dosages). Vocalization threshold to tail shock was significantly reduced by bicuculline MI or picrotoxin. Tail flick withdrawal latency from radiant heat was not altered by GABA antagonists. The GABA agonist, muscimol, significantly elevated vocalization threshold to tail shock at a 5 micrograms dose. At a lower dose level (1 microgram), muscimol significantly reduced vocalization threshold to tail shock. Tail flick latency was significantly prolonged by the 5 micrograms dose of muscimol; however, flaccid paralysis of the hind limbs was also evident. Nociceptive thresholds were not altered by GABA or saline injection. These findings indicate that GABAergic activity contributes to the tonic modulation of nociception at the spinal cord.

Reaction time during cocaine versus alcohol withdrawal: longitudinal measures of visual and auditory suppression.

Visual and auditory stimulus discrimination tasks, analogous to those used in the Reitan-Klove Sensory Perceptual Examination, were performed by 12 cocaine-dependent and 5 alcohol-dependent patients after 1 week, 3 weeks, and 3 months of verified abstinence. Sixteen control subjects, who were not substance-dependent, performed the same tasks after comparable intervals. During each task, either visual or auditory stimuli were presented in the left, in the right, or in both sensory fields. A simple key press was made to discriminate these conditions. Cocaine-dependent patients responded more slowly than control subjects during both tasks. The reaction-time slowing persisted across all three sessions, spanning a 3-month period of abstinence. There were no significant differences between the cocaine-dependent and control groups in response accuracy. In the context of other findings, these findings are interpreted as reflecting an enduring effect of prior cocaine dependence on motor as opposed to sensory functioning.

Chronotropic effect of alkali metals on spontaneously beating right atria.

The alkali metal ions lithium, potassium, rubidium and cesium depress the rate of spontaneous beating of isolated rabbit right atria. At low concentrations (2 to 4 mM) the negative chronotropic effect was in the order: Cs greater than Rb greater than K or Li; at a higher concentration (12 mM) it was Rb or K greater than Cs or Li. Force of contraction was also depressed by potassium and cesium at all levels, but was stimulated by lithium and by low levels of rubidium (2 mM). Lithium had little chronotropic effect up to relatively high concentrations, decreasing spontaneous beating rate to 80% of control at 100 mM LiCl. The significant positive inotropic effect at 2 mM LiCl (to 120% of control) increased (to 180% of control) at 40 mM LiCl. Rate of beating was significantly depressed by 0.2 mM CsCl. The chronotropic effect of cesium was biphasic; the decrease in SBR at 2 and 4 mM cesium was greater than the negative chronotropic effect at 10 mM CsCl. The effect of rubidium (above 4 mM) closely resembled that of increased potassium in decreasing spontaneous beating rate and contractile force.

A retrospective search for lyssavirus in humans in the Northern Territory.

BACKGROUND: Following the 1996 discovery of a rabies-like lyssavirus in Australian flying foxes, it was unclear whether this was a new epizootic or an unrecognised, previously existing disease. OBJECTIVE: To review cases of unexplained encephalitis in the Northern Territory (NT) to test available clinical specimens for lyssavirus and survey the use of diagnostic tests by clinicians. METHODS: The NT hospital morbidity database was searched from January 1992 to September 1996 for all Royal Darwin Hospital (RDH) cases with an ICD-9 code encompassing encephalitis or viral meningitis. Final diagnoses were determined by hospital record review. For cases of unexplained encephalitis, we assessed the use of diagnostic tests and located clinical specimens for testing for lyssavirus-specific inclusion bodies via immunohistochemistry, immunofluorescence and reverse-transcriptase polymerase chain reaction (RT-PCR). RESULTS: Encephalitis occurred in 34/154 (22%) cases located by the search; 53% (18/34) of encephalitis cases were unexplained. Of these, 24% had no serology performed and 47% had no blood cultures taken. Four (22%) died and two had autopsies. These were the only two cases with clinical specimens available for testing. They were negative for lyssavirus. None of the 71 cases coded as viral meningitis had unexplained encephalitis. CONCLUSION: There was a considerable proportion of unexplained illness among NT cases of encephalitis. IMPLICATIONS: Clinicians should test for lyssavirus in patients with encephalitic symptoms and a postmortem should be sought where death is unexplained. Specimens should be stored to enable testing for emerging infectious diseases.