Dysregulation of Kappa Opioid Receptor Neuromodulation of Lateral Habenula Synaptic Function following a Repetitive Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI) increases the risk of cognitive deficits, affective disorders, anxiety and substance use disorder in affected individuals. Substantial evidence suggests a critical role for the lateral habenula (LHb) in pathophysiology of psychiatric disorders. Recently, we demonstrated a causal link between persistent mTBI-induced LHb hyperactivity due to synaptic excitation/inhibition (E/I) imbalance and motivational deficits in self-care grooming behavior in young adult male mice using a repetitive closed head injury mTBI model. One of the major neuromodulatory systems that is responsive to traumatic brain and spinal cord injuries, influences affective states and also modulates LHb activity is the dynorphin/kappa opioid receptor (Dyn/KOR) system. However, the effects of mTBI on KOR neuromodulation of LHb function is unknown. To address this, we first used retrograde tracing to anatomically verify that the mouse LHb indeed receives Dyn/KOR expressing projections. We identified several major KOR-expressing and Dyn-expressing synaptic inputs projecting to the mouse LHb. We then functionally evaluated the effects of in vitro KOR modulation of spontaneous synaptic activity within the LHb of male and female sham and mTBI mice at 4week post-injury using the repetitive closed head injury mTBI model. Similar to what we previously reported in the LHb of male mTBI mice, mTBI presynaptically diminished spontaneous synaptic activity onto LHb neurons, while shifting synaptic E/I toward excitation in female mouse LHb. Furthermore, KOR activation in either mouse male/female LHb generally suppressed spontaneous glutamatergic transmission without altering GABAergic transmission, resulting in a significant reduction in E/I ratios and decreased excitatory synaptic drive to LHb neurons of male and female sham mice. Interestingly following mTBI, while responses to KOR activation at LHb glutamatergic synapses were observed comparable to those of sham, LHb GABAergic synapses acquired an additional sensitivity to KOR-mediated inhibition. Thus, in contrast to sham LHb, we observed a reduction in GABA release probability in response to KOR stimulation in mTBI LHb, resulting in a chronic loss of KOR-mediated net synaptic inhibition within the LHb. Overall, our findings uncovered the previously unknown sources of major Dyn/KOR-expressing synaptic inputs projecting to the mouse LHb. Further, we demonstrate that an engagement of intra-LHb Dyn/KOR signaling provides a global suppression of excitatory synaptic drive to the mouse LHb which could act as an inhibitory braking mechanism to prevent LHb hyperexcitability. The additional engagement of KOR-mediated modulatory action on LHb GABAergic transmission by mTBI could contribute to the E/I imbalance after mTBI, with Dyn/KOR signaling serving as a disinhibitory mechanism for LHb neurons in male and female mTBI mice.

AKAP150-anchored PKA regulates synaptic transmission and plasticity, neuronal excitability and CRF neuromodulation in the mouse lateral habenula

The scaffolding A-kinase anchoring protein 150 (AKAP150) is critically involved in kinase and phosphatase regulation of synaptic transmission/plasticity, and neuronal excitability. Emerging evidence also suggests that AKAP150 signaling may play a key role in brain's processing of rewarding/aversive experiences, however its role in the lateral habenula (LHb, as an important brain reward circuitry) is completely unknown. Using whole cell patch clamp recordings in LHb of male wildtype and ΔPKA knockin mice (with deficiency in AKAP-anchoring of PKA), here we show that the genetic disruption of PKA anchoring to AKAP150 significantly reduces AMPA receptor-mediated glutamatergic transmission and prevents the induction of presynaptic endocannabinoid-mediated long-term depression in LHb neurons. Moreover, ΔPKA mutation potentiates GABAA receptor-mediated inhibitory transmission while increasing LHb intrinsic excitability through suppression of medium afterhyperpolarizations. ΔPKA mutation-induced suppression of medium afterhyperpolarizations also blunts the synaptic and neuroexcitatory actions of the stress neuromodulator, corticotropin releasing factor (CRF), in mouse LHb. Altogether, our data suggest that AKAP150 complex signaling plays a critical role in regulation of AMPA and GABAA receptor synaptic strength, glutamatergic plasticity and CRF neuromodulation possibly through AMPA receptor and potassium channel trafficking and endocannabinoid signaling within the LHb.

Effects of prenatal opioid exposure on synaptic adaptations and behaviors across development

In this review, we focus on prenatal opioid exposure (POE) given the significant concern for the mental health outcomes of children with parents affected by opioid use disorder (OUD) in the view of the current opioid crisis. We highlight some of the less explored interactions between developmental age and sex on synaptic plasticity and associated behavioral outcomes in preclinical POE research. We begin with an overview of the rich literature on hippocampal related behaviors and plasticity across POE exposure paradigms. We then discuss recent work on reward circuit dysregulation following POE. Additional risk factors such as early life stress (ELS) could further influence synaptic and behavioral outcomes of POE. Therefore, we include an overview on the use of preclinical ELS models where ELS exposure during key critical developmental periods confers considerable vulnerability to addiction and stress psychopathology. Here, we hope to highlight the similarity between POE and ELS on development and maintenance of opioid-induced plasticity and altered opioid-related behaviors where similar enduring plasticity in reward circuits may occur. We conclude the review with some of the limitations that should be considered in future investigations. This article is part of the Special Issue on 'Opioid-induced addiction'.

Involvement of Lateral Habenula Dysfunction in Repetitive Mild Traumatic Brain Injury-Induced Motivational Deficits

Affective disorders including depression (characterized by reduced motivation, social withdrawal, and anhedonia), anxiety, and irritability are frequently reported as long-term consequences of mild traumatic brain injury (mTBI) in addition to cognitive deficits, suggesting a possible dysregulation within mood/motivational neural circuits. One of the important brain regions that control motivation and mood is the lateral habenula (LHb), whose hyperactivity is associated with depression. Here, we used a repetitive closed-head injury mTBI model that is associated with social deficits in adult male mice and explored the possible long-term alterations in LHb activity and motivated behavior 10-18 days post-injury. We found that mTBI increased the proportion of spontaneous tonically active LHb neurons yet decreased the proportion of LHb neurons displaying bursting activity. Additionally, mTBI diminished spontaneous glutamatergic and GABAergic synaptic activity onto LHb neurons, while synaptic excitation and inhibition (E/I) balance was shifted toward excitation through a greater suppression of GABAergic transmission. Behaviorally, mTBI increased the latency in grooming behavior in the sucrose splash test suggesting reduced self-care motivated behavior following mTBI. To show whether limiting LHb hyperactivity could restore motivational deficits in grooming behavior, we then tested the effects of Gi (hM4Di)-DREADD-mediated inhibition of LHb activity in the sucrose splash test. We found that chemogenetic inhibition of LHb glutamatergic neurons was sufficient to reverse mTBI-induced delays in grooming behavior. Overall, our study provides the first evidence for persistent LHb neuronal dysfunction due to an altered synaptic integration as causal neural correlates of dysregulated motivational states by mTBI.

Repetitive mild traumatic brain injury induces persistent alterations in spontaneous synaptic activity of hippocampal CA1 pyramidal neurons

Mild traumatic brain injury (mTBI) or concussion is the most common form of TBI which frequently results in persistent cognitive impairments and memory deficits in affected individuals [1]. Although most studies have investigated the role of hippocampal synaptic dysfunction in earlier time points following a single injury, the long-lasting effects of mTBI on hippocampal synaptic transmission following multiple brain concussions have not been well-elucidated. Using a repetitive closed head injury (3XCHI) mouse model of mTBI, we examined the alteration of spontaneous synaptic transmission onto hippocampal CA1 pyramidal neurons by recording spontaneous excitatory AMPA receptor (AMPAR)- and inhibitory GABA_AR-mediated postsynaptic currents (sEPSCs and sIPSCs, respectively) in adult male mice 2-weeks following the injury. We found that mTBI potentiated postsynaptic excitatory AMPAR synaptic function while depressed postsynaptic inhibitory GABA_AR synaptic function in CA1 pyramidal neurons. Additionally, mTBI slowed the decay time of AMPAR currents while shortened the decay time of GABA_AR currents suggesting changes in AMPAR and GABA_AR subunit composition by mTBI. On the other hand, mTBI reduced the frequency of sEPSCs while enhanced the frequency of sIPSCs resulting in a lower ratio of sEPSC/sIPSC frequency in CA1 pyramidal neurons of mTBI animals compared to sham animals. Altogether, our results suggest that mTBI induces persistent postsynaptic modifications in AMPAR and GABA_AR function and their synaptic composition in CA1 neurons while triggering a compensatory shift in excitation/inhibition (E/I) balance of presynaptic drives towards more inhibitory synaptic drive to hippocampal CA1 cells. The persistent mTBI-induced CA1 synaptic dysfunction and E/I imbalance could contribute to deficits in hippocampal plasticity that underlies long-term hippocampal-dependent learning and memory deficits in mTBI patients long after the initial injury.

Lateral Habenula Beyond Avoidance: Roles in Stress, Memory, and Decision-Making With Implications for Psychiatric Disorders

In this Perspective review, we highlight some of the less explored aspects of lateral habenula (LHb) function in contextual memory, sleep, and behavioral flexibility. We provide evidence that LHb is well-situated to integrate different internal state and multimodal sensory information from memory-, stress-, motivational-, and reward-related circuits essential for both survival and decision making. We further discuss the impact of early life stress (ELS) on LHb function as an example of stress-induced hyperactivity and dysregulation of neuromodulatory systems within the LHb that promote anhedonia and motivational deficits following ELS. We acknowledge that recent technological advancements in manipulation and recording of neural circuits in simplified and well-controlled behavioral paradigms have been invaluable in our understanding of the critical role of LHb in motivation and emotional regulation as well as the involvement of LHb dysfunction in stress-induced psychopathology. However, we also argue that the use of ethologically-relevant behaviors with consideration of complex aspects of decision-making is warranted for future studies of LHb contributions in a wide range of psychiatric illnesses. We conclude this Perspective with some of the outstanding issues for the field to consider where a multi-systems approach is needed to investigate the complex nature of LHb circuitry interactions with environmental stimuli that predisposes psychiatric disorders.

Potentiation of glutamatergic synaptic transmission onto lateral habenula neurons following early life stress and intravenous morphine self-administration in rats

Early life stress presents an important risk factor for drug addiction and comorbid depression and anxiety through persistent effects on the mesolimbic dopamine pathways. Using an early life stress model for child neglect (a single 24 h episode of maternal deprivation, MD) in rats, recent published works from our lab show that MD induces dysfunction in the ventral tegmental area and its negative controller, the lateral habenula (LHb). MD-induced potentiation of glutamatergic synaptic transmission onto LHb neurons shifts the coordination of excitation/inhibition (E/I) balance towards excitation, resulting in an increase in the overall spontaneous neuronal activity with elevation in bursting and tonic firing, and in the intrinsic excitability of LHb neurons in early adolescent male rats. Here, we explored how MD affects intravenous morphine self-administration (MSA) acquisition and sucrose preference as well as glutamatergic synaptic function in LHb neurons of adult male rats self-administering morphine. We found that MD-induced increases in LHb neuronal and glutamatergic synaptic activity and E/I ratio persisted into adulthood. Moreover, MD significantly reduced morphine intake, triggered anhedonia-like behaviour in the sucrose preference test and was associated with persistent glutamatergic potentiation 24 h after the last MSA session. MSA also altered the decay time kinetics of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor (AMPAR) currents in LHb neurons of control rats during this time period. Our data highlight that early life stress-induced glutamatergic plasticity in LHb may dampen the positive reinforcing and motivational properties of both natural rewards and opioids, and may contribute to the development of anhedonia and dysphoric states associated with opioids.

Characterization of proinflammatory markers in the ventral tegmental area across mouse models of chronic stress

Despite the high prevalence of major depressive disorder (MDD), understanding of the biological underpinnings remains limited. Rodent models suggest that changes in activity and output of dopamine (DA) neurons in the ventral tegmental area (VTA) are important for depressive-like phenotypes. Additionally, brain inflammatory processes are thought to contribute to MDD pathology and inflammation in the VTA has been linked to changes in VTA DA neuronal activity. Thus, we sought to determine whether there is increased inflammatory signaling in the VTA following forms of chronic stress that induce depressive-like symptoms. First, we subjected male mice to either physical or vicarious chronic social defeat stress (CSDS), paradigms known to induce long-term depressive-like behavior and changes in VTA signaling. Second, we subjected male and female mice to subchronic variable stress (SCVS), a paradigm that induces depressive-like behavior only in female mice. We then isolated mRNA from the VTA and assessed proinflammatory gene regulation via RT-PCR. Our results show that physical, but not vicarious, CSDS increases interleukin 1β (IL-1β) mRNA expression and this inversely correlates with social interaction score. In contrast, IL-1β expression was unchanged in male or female mice following SCVS. No significant increases in VTA ionized calcium binding adapter molecule 1 (Iba1) and glial fibrillary acidic protein (GFAP) immunochemistry were detected following CSDS that would be indicative of a robust inflammatory response. In conclusion, we show that chronic stressors distinctively alter expression of proinflammatory genes in the VTA and changes may depend on the severity and time-course of the stress exposure.

Early life stress dysregulates kappa opioid receptor signaling within the lateral habenula

The lateral habenula (LHb) is an epithalamic brain region associated with value-based decision making and stress evasion through its modulation of dopamine (DA)-mediated reward circuitry. Specifically, increased activity of the LHb is associated with drug addiction, schizophrenia and stress-related disorders such as depression, anxiety and posttraumatic stress disorder. Dynorphin (Dyn)/Kappa opioid receptor (KOR) signaling is a mediator of stress response in reward circuitry. Previously, we have shown that maternal deprivation (MD), a severe early life stress, increases LHb spontaneous neuronal activity and intrinsic excitability while blunting the response of LHb neurons to extrahypothalamic corticotropin-releasing factor (CRF) signaling, another stress mediator. CRF pathways also interact with Dyn/KOR signaling. Surprisingly, there has been little study of direct KOR regulation of the LHb despite its distinct role in stress, reward and aversion processing. To test the functional role of Dyn/KOR signaling in the LHb, we utilized ex-vivo electrophysiology combined with pharmacological tools in rat LHb slices. We show that activation of KORs by a KOR agonist (U50,488) exerted differential effects on the excitability of two distinct sub-populations of LHb neurons that differed in their expression of hyperpolarization-activated cation currents (HCN, Ih). Specifically, KOR stimulation increased neuronal excitability in LHb neurons with large Ih currents (Ih+) while decreasing neuronal excitability in small/negative Ih (Ih-) neurons. We found that an intact fast-synaptic transmission was required for the effects of U50,488 on the excitability of both Ih- and Ih+ LHb neuronal subpopulations. While AMPAR-, GABAAR-, or NMDAR-mediated synaptic transmission alone was sufficient to mediate the effects of U50,488 on excitability of Ih- neurons, either GABAAR- or NMDAR-mediated synaptic transmission could mediate these effects in Ih+ neurons. Consistently, KOR activation also altered both glutamatergic and GABAergic synaptic transmission where stimulation of presynaptic KORs uniformly suppressed glutamate release onto LHb neurons while primarily decreased or in some cases increased GABA release. We also found that MD significantly increased immunolabeled Dyn (the endogenous KOR agonist) labeling in neuronal fibers in LHb while significantly decreasing mRNA levels of KORs in LHb tissues compared to those from non-maternally deprived (non-MD) control rats. Moreover, the U50,488-mediated increase in LHb neuronal firing observed in non-MD rats was absent following MD. Altogether, this is the first demonstration of the existence of functional Dyn/KOR signaling in the LHb that can be modulated in response to severe early life stressors such as MD.

Pubertal Testosterone Programs Adult Behavioral Adaptations to Sexual Experience through Infralimbic Cortex ΔFosB

Acquisition of social proficiency entails behavioral adaptations to social experience, including both behavioral flexibility and inhibition of behaviors inappropriate in specific social contexts. Here, we investigated the contributions of testosterone and ΔFosB, a transcription factor linked to experience-dependent neural plasticity, to the adolescent maturation of social proficiency in male-female social interactions. To determine whether pubertal testosterone organizes circuits underlying social proficiency, we first compared behavioral adaptations to sexual experience in male Syrian hamsters that were deprived of testosterone during puberty (prepubertal castration; NoT@P) to those of males deprived of testosterone for an equivalent period of time in adulthood (postpubertal castration; T@P). All males were given testosterone replacement in adulthood for two weeks before sexual behavior testing, where males were allowed to interact with a receptive female once per week for five consecutive weeks. T@P males showed the expected decrease in ectopic (mis-directed) mounts with sexual experience, whereas NoT@P males did not. In addition, sexual experience induced FosB gene products expression in the infralimbic cortex (IL) in T@P, but not NoT@P, males. Overexpression of ΔFosB via an adeno-associated viral (AAV) vector in the IL of NoT@P males prior to sexual behavior testing was sufficient to produce a behavioral phenotype similar to that of experienced T@P males. Finally, overexpression of ΔFosB in IL increased the density of immature spines on IL dendrites. Our findings provide evidence that social proficiency acquired through sexual experience is organized by pubertal testosterone through the regulation of ΔFosB in the IL, possibly through increasing synaptic lability.

Determination of circuit-specific morphological adaptations in ventral tegmental area dopamine neurons by chronic morphine

Chronic opiate exposure induces neuroadaptations in the mesocorticolimbic system including ventral tegmental area (VTA) dopamine (DA) neurons, whose soma size is decreased following opiate exposure. Yet it is now well documented that VTA DA neurons are heterogeneous, with notable differences between VTA DA neurons based on their projection target. Therefore, we sought to determine whether chronic morphine induced similar changes in the morphology of VTA DA neurons that project to the nucleus accumbens (NAc) and prefrontal cortex (PFC). We utilized Cre-dependent retrograde viral vectors in DA Cre driver lines to label VTA DA neurons that projected to NAc and PFC and assessed neuronal soma size. Consistent with previous data, the soma size of VTA DA neurons that projected to the NAc medial shell was decreased following morphine exposure. However, soma size of VTA DA neurons that projected to the NAc core was unaltered by morphine. Interestingly, morphology of PFC-projecting VTA DA neurons was also altered by morphine, but in this case soma size was increased compared to sham controls. Differences in basal soma size were also noted, suggesting stable differences in projection-specific morphology in addition to drug-induced changes. Together, these data suggest morphine-induced changes in VTA DA morphology occur within distinct VTA DA populations and that study of opiate-induced structural plasticity of individual VTA DA subcircuits may be critical for understanding addiction-related behavior.

Perception of the medical risk of spaceflight

We conducted an opinion survey to improve the characterization of medical risk during spaceflight, using a questionnaire designed to elicit space medicine experts' perceptions of the probability, health effect, and mission impact of selected medical events occurring during spaceflight missions of 30-90 d. This questionnaire was directed toward those events about which little data currently exist, therefore medical events that have occurred during spaceflights with some frequency, such as space motion sickness, were excluded from the questionnaire. The questionnaire was mailed to 99 clinical and research professionals involved with NASA medical programs; 65 responses were returned, of which 60 could be analyzed. The experts rated skin disorders as the most likely to occur, but which would have little effect on mission completion or astronaut health. Circulatory diseases were rated as having the lowest probability of occurrence, but the highest effect on the mission or on a crewmember's health. The results of this survey will be combined with data from analogous populations and existing astronaut health data to establish a data set to support decisions about allocation of health care resources.

Severe open tibial fractures. Results treating 202 injuries with external fixation

Grade III open tibial fractures are known for frequent complications and poor clinical results, yet published series are few and cite conflicting results. To address this dilemma, the authors report a prospective study of 202 consecutive Grade III tibial fractures. All injuries were treated under protocol at the authors' university with primary external fixation and serial debridement. Equinus deformity was prevented with a new tibiometatarsal frame extension. Severe injuries crossing the ankle or knee were temporarily stabilized with external fixation across these joints. Staged reconstruction of soft tissue and then bone was undertaken for 176 of these tibias in patients who survived their multiple injuries. Reconstructive procedures included skin grafts in 57%, muscle flaps in 32%, and bone grafts in 28%. Gastrosoleus myocutaneous flaps were successful in 92% of cases versus 66% for free flaps. Late follow-up data were obtained for 171 (97%). Infection occurred in 15% and led to amputation in 7%. The infection rate was reduced to 9% in the second half of the series largely by removal of all necrotic bone prior to wound coverage. Angulation (greater than 10 degrees) in 9% and delayed union were lessened with early posterolateral grafting followed by progressive fracture loading in the fixator. A 9% incidence of pin tract drainage or loosening was reduced with predrilling and diaphyseal half pins. The time to fixator removal averaged 87 days. Ninety-three percent of the fractures united (median time, nine months) but healing times varied widely according to the amount of tissue injury and bone loss. Eighty-nine percent had satisfactory late clinical function. Results from this study, the largest series of open Grade III tibial fractures reported to date, suggest that successful staged reconstruction is now a reasonable expectation for most of these severe injuries.

External fixation arthrodesis of the ankle joint following trauma

Arthrodesis is currently the treatment of choice for symptomatic degenerative arthropathy of the ankle. Thirty-seven patients underwent arthrodesis for post-traumatic disorders using either a Hoffmann external fixator or a Calandruccio frame. There was degenerative joint disease in 19 (51%), septic arthritis in 11 (30%), severe comminution in five (14%), and uncontrollable equinus in two (5%). The patients were divided into two groups. Twenty-six (70%) were considered to have sustained high energy open or comminuted injuries and 11 (30%), low energy injuries. Twenty-nine (78%) achieved a radiologic fusion following one operation. Four eventually united with further surgery for a final arthrodesis rate of 89%. In the high energy group 18 of 26 (69%) achieved primary fusion. Four united with additional surgery for a final arthrodesis rate of 85%. Two of these required subsequent amputations and two others, a triple arthrodesis which also failed to control chronic pain. Thus, a total of 18 of the 26 patients (69%) achieved a successful result. Also included in the high energy group were three patients with uncontrolled sepsis who underwent amputation before union occurred and one with a painful non-union. All 11 of the patients (100%) who originally sustained low energy injuries achieved a successful arthrodesis. The most common complication was in pin tract infection requiring incision, drainage, and oral antibiotics in 16 patients (43%). None of these progressed to chronic osteomyelitis.

The symphysis pubis. Anatomic and pathologic considerations

The symphysis pubis is a nonsynovial amphiarthrodial joint that is situated at the confluence of the two pubic bones. A thick intrapubic fibrocartilaginous disc is sandwiched between thin layers of hyaline cartilage. The inferior pubic ligament provides most of the joint's stability. Anatomic sections demonstrate a symphysis by the end of the second month of gestation. Thick cartilaginous end-plates are present at birth but become thin by the time of skeletal maturity. Congenital diseases resulting in failure of symphysis formation include exstrophy of the bladder and cleidocranial dysostosis. Both pyogenic and tuberculous infectious diseases involve the symphysis. Metabolic disease, such as renal osteodystrophy, produces widening, while ochronosis results in calcific deposits in the symphysis. Inflammatory disease, such as ankylosing spondylitis, results in bony fusion of the symphysis. Osteitis pubis, the most common inflammatory disease, is treated with anti-inflammatory medication and rest. Degenerative joint disease of the symphysis, which can cause groin pain, results from instability or from abnormal pelvic mechanics. As is the case with most joints, the symphysis serves as a barrier to tumor invasion. The patterns of trauma include diastasis, straddle fracture, intraarticular fracture and overlapping dislocation, and combinations of injuries.

Fetal cardiac arrhythmia: antepartum diagnosis of a case of congenital atrial flutter

A case of antepartum atrial tachyarrhythmia was detected in the 36th week of pregnancy. Cardiotocograph recordings done twice daily enabled close surveillance of the fetal condition after oxytoxin challenge testing had failed to show evidence of hypoxia. After a diagnosis of fetal cardiac arrhythmia had been made, elective caesarean section in the 40th week of pregnancy resulted in delivery of an infant in atrial flutter and cardiac failure. Both these problems were soon resolved by cardioversion and subsequent treatment with digoxin. Cardiac catheterisation showed no underlying cardiac abnormality. Increasing use of antenatal cardiotocography may show that intrauterine tachyarrhythmias are more common than had generally been believed.

The use of the amniotic fluid lecithin/sphingomyelin (L/S) ratio, creatinine concentration and nile blue sulphate tests, individually and in combination, in the assessment of fetal lung maturity

The lecithin-sphingomyelin (LS) ratio is a good, but not absolute, test of fetal lung maturity. A total of 373 infants was delivered within 72 hours of amniotic fluid collection for assessment of the L/S ratio. Five of 43 infants (11-6 per cent) with an L/S ratio of 2-2 or less developed the respiratory distress syndrome (RDS), whereas only one of 320 infants (0-31 per cent) with a higher L/S ratio developed RDS. The risk of RDS could be further defined by using the creatinine concentration (critical value 19 mg/1) and the Nile blue sulphate test (critical value 4 per cent) in combination with the L/S ratio. All three tests were performed in 320 pregnancies and in each instance delivery took place within 72 hours. When all three test results were low, 3 of 5 infants (60 per cent) developed RDS, whereas when all three results were high, none of 175 infants developed RDS. When one or two results were low, 2 of 140 infants (1-4 per cent) developed RDS.

The benefits and risks of amniocentesis for the assessment of fetal lung maturity

Amniocentesis for estimation of the lecithin: sphingomyelin (L/S) ratio was performed on 483 patients on 552 occasions. The introduction of this test has been associated with a highly significant (p less than 0-001) decrease of 59 per cent in the incidence of respiratory distress syndrome. The finding of a low L/S ratio (less than 2-0) enabled delivery to be deferred until lung maturity had been reached in 43 (10-3 per cent) of the 419 patients who had successful amniocentesis. Fetal death occurred after amniocentesis in two patients (0-41 per cent). One fetus died after haemorrhage occurred behind an anterior placenta and the other died of exsanguination. Failed amniocentesis occurred in 64 patients (13-2 per cent), and was more common when the placenta was anterior or was not located before the procedure and when fetal growth was retarded. Fetal distress in labour occurred more commonly after failed amniocentesis. Spontaneous labour followed amniocentesis in 47 patients (9-7 per cent) and was significantly more prone to occur after 38 weeks gestation. Rhesus isoimmunization did not occur in any of the rhesus-negative patients who delivered rhesus-positive babies and who were screened six or more months after amniocentesis, although anti-D immunoglobulin was not given routinely after amniocentesis. Suggestions are made as to how the success rate of this valuable procedure can be improved and how some of the serious fetal and maternal sequelae can be avoided.

Routine induction of labour by amniotomy and simultaneous Syntocinon (synthetic oxytocin) infusion

Of 2,272 deliveries between 1 October, 1967 and 31 December, 1968 290 were induced by simultaneous intravenous Syntocinon (synthetic oxytocin) at amniotomy. The hazards of induction of labour are greatly reduced when this method is used routinely. Only 4 of the 13 caesarean sections were thought to be due to failure of method. Within 12 hours 221 patients were delivered, and this short induction-delivery interval resulted in an extremely low maternal and fetal morbidity. It is believed that with proper safeguards and in the light of present knowledge this is the method of choice.

Foetal blood sampling in the regional hospital

Several difficulties arise in the introduction of foetal blood sampling in a regional hospital. Ideally there should be a unit sufficient to provide continuous registrar cover (anaesthetic cover and medical cover) of the labour suite. In our hospital duties have been reallocated in an attempt to attain this standard. Both consultant and registrar staff must take adequate study leave to understand the principle and practice of blood sampling. Regular lectures and demonstrations must be given to nursing and resident staff. The cost of the initial equipment is abut pound1,000.double daggerFoetal blood sampling has been employed in the unit since January 1968. Its principal use has been the assessment of "foetal distress" Except for one case no low pH value has been found in a "high risk" patient unless the foetus showed signs of clinical distress.