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PubMed1981

[The variability of fetal heart rate response to the reduction of uterine blood flow in anaesthetized and unanaesthetized pregnant sheep].

The variation of the fetal heart rate (FHR) and blood pressure (BP) response to a definite hypoxic stress has been investigated in 3 unanaesthetized and 8 anaesthetized near term pregnant sheep. Uterine blood flow (UBF) was reduced by inserting an inflatable balloon into the maternal aorta in 33 experiments. By inflation of the balloon blood flow was reduced to zero for 5-60 sec. The response on fetal heart rate an systolic and diastolic blood pressure has been measured. The lag time of the response was estimated. Following the reduction of uterine blood flow fetal heart rate fell and the blood pressure rose. The fall of FHR and the rise of fetal systolic and diastolic BP was correlated to the duration of flow reduction. There was however a wide variation of the FHR and BP response to a definite duration of flow reduction which was also dependent on the application of anaesthesia. A relationship between the oxygen saturation at control and the FHR and BP response could not be established. From this experiment it may concluded that the application of anaesthetics reduce the FHR and BP response. In addition the duration and the fall of the FHR is not good measure for estimating the severity of fetal hypoxia.

Anesthesia↗
PubMed1995

[Conduction anesthesia and the newborn infant].

The placental transfer of local anaesthetics (LA) depends on maternal, placental and fetal factors. The assessment of effects of LA and epidural anaesthesia (EA) on the fetus is based on the monitoring of fetal heart rate (FHR) and the measurement of the fetal pH. Apgar score and neurobehavioral tests allow an evaluation of the neonatal effects of the drugs used. Direct effects of LA: a diminution of variability of FHR was observed shortly after the beginning of an EA using lidocaine but there was no modification of FHR after EA using bupivacaine or lidocaine with epinephrine. Fetal neurological toxicity is rare and there are very few alterations of neurobehavioral scores after EA. Indirect effects on uteroplacental blood flow (UBF): in high concentration, LA can induce vasoconstriction of uterine arteries but maternal arterial hypotension that impedes directly uteroplacental blood flow is the main effect. Prevention of aortocaval compression is essential because it allows better Apgar scores and arterial pH at birth. Use of colloids has not a better preventive efficacy than an equal volume of cristalloids while dextrans are formally contra-indicated because of serious fetal accidents. Large iv infusion of dextrose solutions are responsible for maternal and fetal hyperglycemia and hyperinsulinemia leading to neonatal hypoglycemia. The utilization of IM prophylactic ephedrine is not useful while the therapeutic administration of ephedrine to treat maternal arterial hypotension is efficient. Phenylephrine used in case of maternal arterial hypotension seems as efficient as is ephedrine. Epidural narcotics: the use of morphine by epidural route can induce neonatal respiratory depression and low neurobehavioral scores. The epidural administration of fentanyl does not alter the variability of the FHR and does not modify neither Apgar or neurobehavioral scores, nor respiratory adaptation of the newborn. Use of epidural alfentanil or sufentanil does not lead to low neurobehavioral scores unless very high doses are used. For elective caesarean section, newborns present a lower Apgar score at 1 min and necessitate respiratory assistance more frequently after general anaesthesia (GA) than after EA. Neurobehavioral scores are better after EA than after GA. For emergency caesarean section, the percentage of newborns with an Apgar score < 4 or necessitating a respiratory assistance is more important after GA than after EA. However, the perinatal mortality is not more important after GA than after EA.

Adult↗
PubMed1977

[The effect of local anaesthetics on uterine blood flow and O2-consumption in pregnant sheep (author's transl)].

The local anesthetics bupivacaine, etidocaine, lignocaine and chloroprocaine were infused intravenously for 30 min to pregnant sheep, prepared for chronic studies. The amide compounds reached highere plasma concentrations than chloroprocaine. All local anaesthetics decreased uterine blood flow and O2 consumption without marked alterations of arterial or uterine venous blood gases. These changes were within the wide physiological range of variation, which was established in controls during 24 h. The findings may be of significance during paracervical block or pathological states of UBF or fetal homeostasis.

Anesthetics, Local↗
PubMed2025

Chromosome-specific epigenetic control and transmission of ribosomal DNA arrays in Hominidae genomes.

Ribosomal RNA (rRNA) genes are organized in tandem arrays known as ribosomal DNA (rDNA) on multiple chromosomes in Hominidae genomes. We measured copy number and transcriptional activity status of rRNA gene arrays across multiple individual genomes, revealing an identifiable fingerprint of rDNA copy number and activity. In some cases, entire arrays were transcriptionally silent, characterized by high DNA methylation across the rRNA gene, inaccessible chromatin, and the absence of transcription factors and transcripts. Silent arrays showed reduced association with the nucleolus and decreased interchromosomal interactions, consistent with the model that nucleolar organizer function depends on transcriptional activity. Removing rDNA methylation activated silent arrays. Array activity status remained stable through induced pluripotent stem cell reprogramming and differentiation into cerebral and intestinal organoids. Haplotype tracing in two unrelated family trios showed paternal transmission of silent arrays. We propose that the epigenetic state buffers rRNA gene dosage, specifies nucleolar organizer function, and can propagate transgenerationally.

Epigenesis, Genetic↗