Altered defaecatory behaviour and faecal incontinence in a video-tracked animal model of pudendal neuropathy.

AIM: The aim was to develop a behavioural animal model of faecal continence and assess the effect of retro-uterine balloon inflation (RBI) injury. RBI in the rat causes pudendal neuropathy, a risk factor for obstetric related faecal incontinence in humans. METHOD: Video-tracking of healthy rats (n = 12) in a cage containing a latrine box was used to monitor their defaecatory behaviour index (DBI) over 2 weeks. The DBI (range 0-1) was devised by dividing the defaecation rate (pellets per hour) outside the latrine by that of the whole cage. A score of 0 indicates all pellets were deposited in the latrine. Subsequently, the effects of RBI (n = 19), sham surgery (n = 4) and colostomy (n = 2) were determined by monitoring the DBI for 2 weeks preoperatively and 3 weeks postoperatively. RESULTS: The DBI for healthy rats was 0.1 ± 0.03 with no significant change over 2 weeks (P = 0.71). In the RBI group, 13 of 19 rats (68%) showed no significant change in DBI postoperatively (0.08 ±  -0.05 vs 0.11 ±  -0.07) while in six rats the DBI increased from 0.16 ±  -0.09 to 0.46 ± 0.23. The negative control, sham surgery, did not significantly affect the DBI (0.09 ± 0.06 vs 0.08 ± 0.04, P = 0.14). The positive control, colostomy, increased the DBI from 0.26 ± 0.03 to 0.86 ± 0.08. CONCLUSIONS: This is the first study showing a quantifiable change in defaecatory behaviour following injury in an animal model. This model of pudendal neuropathy affects continence in 32% of rats and provides a basis for research on interventions for incontinence.

Methods of applying the 1994 case definition of chronic fatigue syndrome - impact on classification and observed illness characteristics.

BACKGROUND: Multiple case definitions are in use to identify chronic fatigue syndrome (CFS). Even when using the same definition, methods used to apply definitional criteria may affect results. The Centers for Disease Control and Prevention (CDC) conducted two population-based studies estimating CFS prevalence using the 1994 case definition; one relied on direct questions for criteria of fatigue, functional impairment and symptoms (1997 Wichita; Method 1), and the other used subscale score thresholds of standardized questionnaires for criteria (2004 Georgia; Method 2). Compared to previous reports the 2004 CFS prevalence estimate was higher, raising questions about whether changes in the method of operationalizing affected this and illness characteristics. METHODS: The follow-up of the Georgia cohort allowed direct comparison of both methods of applying the 1994 case definition. Of 1961 participants (53 % of eligible) who completed the detailed telephone interview, 919 (47 %) were eligible for and 751 (81 %) underwent clinical evaluation including medical/psychiatric evaluations. Data from the 499 individuals with complete data and without exclusionary conditions was available for this analysis. RESULTS: A total of 86 participants were classified as CFS by one or both methods; 44 cases identified by both methods, 15 only identified by Method 1, and 27 only identified by Method 2 (Kappa 0.63; 95 % confidence interval [CI]: 0.53, 0.73 and concordance 91.59 %). The CFS group identified by both methods were more fatigued, had worse functioning, and more symptoms than those identified by only one method. Moderate to severe depression was noted in only one individual who was classified as CFS by both methods. When comparing the CFS groups identified by only one method, those only identified by Method 2 were either similar to or more severely affected in fatigue, function, and symptoms than those only identified by Method 1. CONCLUSIONS: The two methods demonstrated substantial concordance. While Method 2 classified more participants as CFS, there was no indication that they were less severely ill or more depressed. The classification differences do not fully explain the prevalence increase noted in the 2004 Georgia study. Use of standardized instruments for the major CFS domains provides advantages for disease stratification and comparing CFS patients to other illnesses.

Effects of stimulation frequency and intensity in sacral neuromodulation on anorectal inputs to the somatosensory cortex in an experimental model.

INTRODUCTION: Although sacral neuromodulation (SNM) is an established treatment for faecal incontinence, stimulation parameters have been derived empirically and only one frequency (14 Hz) is employed clinically. The aim of this study was to test a range of stimulation frequencies to establish an optimal frequency of SNM for maximum augmentation of anal canal cortical evoked potentials (EPs) in an animal model. METHODS: In female Wistar rats, anal canal EPs were recorded over the primary somatosensory cortex using a flexible multielectrode array, and the effect of SNM was studied. SNM was applied at 0·1-100 Hz and a frequency response curve plotted. The data were fitted to a quadratic equation. RESULTS: The magnitude of potentiation of anal canal EPs caused by SNM depended significantly on stimulation frequency (P < 0·001). The frequency-potentiation relationship was parabolic in form, with a clear optimum at 2 Hz. The SNM must be applied for at least 3 min. The theoretical maximal potentiation predicted by the model was not found to be statistically different to actual data recorded (P = 0·514-0·814). The response depended on stimulation amplitude in an 'all-or-nothing' fashion. EPs were augmented when the SNM intensity was 0·5 times the motor threshold to tail twitch or greater, but values below this intensity failed to affect the EPs. CONCLUSION: The effect of SNM in this animal model is governed principally by frequency, with an optimum of 2 Hz. If animal data can be translated to humans, optimization of SNM frequency may offer a clinically relevant improvement in the efficacy of SNM. Surgical relevance Sacral neuromodulation (SNM) for faecal incontinence currently employs stimulation parameters that have been derived empirically and may not be optimal. This study used an animal model of SNM and focused on its acute effect on anal canal cortical evoked potentials (EPs). It was found that SNM potentiated EPs, with a clear optimum at a frequency of 2 Hz. If this finding is applicable to the mechanism of action of human SNM, this suggests that there may be a clinically relevant improvement by reducing stimulus frequency from its typical value of 14 Hz to 2 Hz.

Is there a nitrergic modulation of the rat external anal sphincter?

Nitric oxide is known to relax the internal anal sphincter, but its effect on the external anal sphincter (EAS) is unknown. The aim of this study was to investigate whether there is a nitrergic nerve plexus that modulates the EAS, similar to that found in oesophageal striated muscle. An in vitro ring preparation of rat anal canal was used to evaluate the effects of the nitric oxide synthase inhibitor N(ω)-nitro-L-arginine (L-NNA) and the NO donor sodium nitroprusside (SNP) on the EAS in conditions of neuromuscular blockade and the effect of SNP on nerve-evoked contractions. Immunohistological experiments were conducted to determine whether the neuronal isoform of nitric oxide synthase (nNOS) is present in the EAS. During direct muscle stimulation neither L-NNA (P = 0.32) nor SNP (P = 0.19) significantly changed the EF(50), which is the frequency at which 50% of maximal contraction is reached, compared with a time-dependent control. Nerve-evoked contractions were also not altered by addition of SNP to the tissue bath. Immunohistohistological experiments clearly showed co-localization of nNOS-positive nerve fibres at motor endplates of the oesophagus but not in the EAS. The internal anal sphincter was richly innervated by nitrergic fibres, but these did not extend into the EAS. In conclusion, there are no nitrergic motor fibres innervating the EAS, neurotransmission at the motor endplates is not affected by NO, and NO does not affect muscle force directly in conditions of neuromuscular blockade. There is, therefore, no evidence that EAS contraction is directly modulated by NO or by pudendal nitrergic fibres or diffusion from neighbouring nitrergic plexuses of the anal canal.

Combined ischemic and neuropathic insult to the anal canal in an animal model of obstetric-related trauma.

BACKGROUND: Childbirth, in particular, when it involves instrumental vaginal delivery, can result in direct trauma to the external anal sphincter muscle. In addition, a global injury to the pelvic floor, including neurovascular injury to the anal sphincter complex, may occur. OBJECTIVE: The aims of this study were to determine whether sensory drive from the anal canal and oxygenation of the external anal sphincter were compromised during simulated labor in a validated animal model of obstetric trauma. DESIGN: Fifteen female Wister rats were operated on. Group 1 (n = 5) underwent pelvic balloon compression for 1 hour to simulate increased pelvic pressure during childbirth. Somatosensory cortical potentials, evoked by electrically stimulating the anal canal, were tracked. In group 2 (sham), the balloons were not inflated. In group 3, tissue PO2 values of the external anal sphincter and femoral arterial blood flow were measured simultaneously during the period of balloon inflation. RESULTS: The peak amplitude of cortical evoked potentials was reduced (from 11.8 ± 1.5 µV to 3.1 ± 1.1 µV) during pelvic compression (p = 0.002, ANOVA). During this period, arterial blood flow to the hindlimb and the external anal sphincter tissue PO2 decreased by 20% (p < 0.001) and 60% (p < 0.001). CONCLUSION: Pelvic compression that mimics obstetric trauma is associated with diminished anocortical drive. This neural insult may be compounded by concomitant ischemia of the external anal sphincter.

Chronic hypoxia increases rat diaphragm muscle endurance and sodium-potassium ATPase pump content.

The effects of chronic hypoxia (CH) on respiratory muscle are poorly understood. The aim of the present study was to examine the effects of CH on respiratory muscle structure and function, and to determine whether nitric oxide is implicated in respiratory muscle adaptation to CH. Male Wistar rats were exposed to CH for 1-6 weeks. Sternohyoid and diaphragm muscle contractile properties, muscle fibre type and size, the density of fibres expressing sarco/endoplasmic reticulum calcium-ATPase (SERCA) 2 and sodium-potassium ATPase (Na+,K+-ATPase) pump content were determined. Muscle succinate dehydrogenase (SDH) and reduced nicotinamide adenine dinucleotide phosphate (NADPH) dehydrogenase activities were also assessed. Acute and chronic blockade of nitric oxide synthase (NOS) was employed to determine whether or not NO is critically involved in functional remodelling in CH muscles. CH improved diaphragm, but not sternohyoid, fatigue tolerance in a time-dependent fashion. This adaptation was not attributable to increased SDH or NADPH dehydrogenase activities. The areal density of muscle fibres and relative area of fibres expressing SERCA2 were unchanged. Na+,K+-ATPase pump content was significantly increased in CH diaphragm. Chronic NOS inhibition decreased diaphragm Na+,K+-ATPase pump content and prevented CH-induced increase in muscle endurance. This study provides novel insight into the mechanisms involved in CH-induced muscle plasticity. The results may be of relevance to respiratory disorders characterised by CH, such as chronic obstructive pulmonary disease.

Effect of injury on S1 dorsal root ganglia in an experimental model of neuropathic faecal incontinence.

BACKGROUND: An experimental model of neuropathic faecal incontinence has recently been established. This study aimed to quantify and compare the effect of crush and compression injury on first-order sensory neurones of the inferior rectal nerve (IRN) using a nuclear marker of axonal injury, activating transcription factor (ATF) 3. METHODS: Eighteen Wistar rats were allocated to three groups: an unoperated control group, an IRN crush group (positive control) and a retrouterine balloon compression group. Five days after surgery, all animals were anaesthetized and perfused with fixative, and S1 dorsal root ganglia (DRG) were harvested. The tissue was sampled and neuronal nuclear ATF-3 expression calculated. RESULTS: Estimated total S1 DRG ATF-3 nuclear labelling was higher in the nerve crush (median (interquartile range) 171 (60-824) cells) and balloon compression (59 (20-274) cells) groups, compared with that in the unoperated control group (9 (3-24) cells) (P = 0.001 and P = 0.008 respectively). In all groups, most neurones displaying the marker of injury were of the C-fibre class. CONCLUSION: This study confirmed the presence of axonal injury in a pelvic compression model of obstetric injury. C-fibre afferent pathways appeared to be most vulnerable. Neuromodulation may function through augmentation of residual C-fibre pathways.

Sacral nerve stimulation increases activation of the primary somatosensory cortex by anal canal stimulation in an experimental model.

BACKGROUND: Sacral and posterior tibial nerve stimulation may be used to treat faecal incontinence; however, the mechanism of action is unknown. The aim of this study was to establish whether sensory activation of the cerebral cortex by anal canal stimulation was increased by peripheral neuromodulation. METHODS: A multielectrode array was positioned over the right primary somatosensory cortex of anaesthetized rats. A brief burst of electrical stimulation was applied to either the left sacral root or the left posterior tibial nerve, and evoked potentials from anal canal stimulation were signal-averaged at intervals over 1 h. At the end of the experiment, the cerebral cortex was removed and probed for polysialylated neural cell adhesion molecule (PSA-NCAM). RESULTS: Sacral nerve root and posterior tibial nerve stimulation significantly increased the peak amplitude of primary cortical evoked potentials by 54.0 and 45.1 per cent respectively. This change persisted throughout the period of observation. The density of PSA-NCAM-positive cells in the somatosensory cortex underlying the electrode array was increased by approximately 50 per cent in the sacral nerve-stimulated group. CONCLUSION: Brief sacral neuromodulation induces profound changes in anal canal representation on the primary somatosensory cortex, providing a plausible hypothesis concerning the mechanism of action of neuromodulation in the treatment of faecal incontinence.

Atrophy of the sphincters of continence in an experimental model.

BACKGROUND: Pudendal nerve injury during childbirth may result in external anal sphincter (EAS) atrophy. Recently, balloon compression of the pelvic side wall has been shown to result in EAS atrophy in an experimental model. The aim of this study was to determine whether other sphincters of continence are similarly affected. METHOD: Sixteen adult female virgin Wistar rats (eight controls) were studied 4 weeks after surgery. Anal and urethral canals were dissected, snap frozen and sectioned using a cryostat (100 microm thickness). Masses of EAS, internal anal sphincter (IAS) and external urethral sphincter (EUS) were calculated stereologically and stained with succinate dehydrogenase histochemistry to differentiate striated from smooth muscle. Sphincter length was determined and total sphincter mass calculated. Data were analysed with an unpaired Student's t-test. RESULTS: Atrophy of EAS (30.9 +/- 1.7 to 21.3 +/- 1.7 mg/ kg, P = 0.001), IAS (98.1 +/- 11.3 to 67.1 +/- 5.0 mg/kg, P = 0.01) and EUS (9.6 +/- 0.98 to 7.4 +/- 0.8 mg/kg, P = 0.05) was found 4 weeks after the injury. CONCLUSION: In an experimental model of obstetric pudendal nerve injury, significant atrophy of striated and smooth muscle sphincters of continence occurs and may contribute to altered continence following vaginal childbirth.

Experimental models of neuropathic fecal incontinence: an animal model of childbirth injury to the pudendal nerve and external anal sphincter.

PURPOSE: Childbirth is the most common cause of fecal incontinence and damage to the pudendal nerve is a major component of childbirth injury. This study was designed to develop an acute animal model of injury to the innervation of the external anal sphincter. METHODS: Forty-eight female virgin wistar rats were studied. Two models of neuropathic injury were developed. Bilateral inferior rectal nerve crush (Group A) acted as a positive control. Prolonged intrapelvic retrouterine balloon inflation (Group B) simulated the pelvic compressive forces of labor. Quantitative analysis of external anal sphincter muscle function was performed by using electromyography, external anal sphincter specific force production, and stereologic calculation of external anal sphincter mass. RESULTS: Injury in both groups caused significant atrophy of the external anal sphincter (P = 0.002, ANOVA) and electromyographic evidence of reinnervation at one week. Specific force (mN force per mg mass) was not altered. External anal sphincter muscle mass recovered after four weeks in Group B. CONCLUSIONS: Balloon dilation within the boney pelvis results in denervation of the external anal sphincter and offers an experimental model of the effects of childbirth on the continence mechanism in humans.

The role of 3D printing in preoperative planning for heart transplantation in complex congenital heart disease.

BACKGROUND: The presence of a structural cardiac defect in the setting of dextrocardia is extremely rare. Graspable models allow enhanced appreciation of aberrant structures and vascular relations, particularly in rare and complex cases. This is the first case report of the use of a replica of a patients' anatomy to plan the surgical strategy in the setting of dextrocardia. AIMS: We intend to demonstrate the benefit of three-dimensional printing to enhance preoperative planning in complex congenital heart disease undergoing heart transplantation. The anomalous structures encountered include situs inversus dextrocardia, transposition of the great vessels, a single atrium and a dilated double-outlet single right ventricle. METHODS: Computed Tomography acquisition was performed with the use of ECG multiphase gating technology and contrast enhancement. The structures of interest were segmented and the generated 3D mesh was exported as a stereolithographic (STL) file. The model was printed on a Z-Corp 250 binder jetting printer. Post processing techniques were used to enhance model strength. RESULTS: Pre-operative 3D visualisation of the patients' anatomy allowed for a more comprehensive surgical strategy to be planned, thus reducing the intra-operative duration and cross-clamp time which are recognised to correlate with reduced patient morbidity. CONCLUSION: The ongoing advances in medical image procurement and 3D processing software and printing technology will continue to enhance preoperative planning and thereby improve patient care. We demonstrate the pivotal role played by such technologies in advancing spatial comprehension of complex aberrant anatomy.

Acute lumbosacral nerve stimulation does not affect anorectal motor function in a rodent model.

BACKGROUND: Sacral nerve stimulation has become a first line treatment for fecal incontinence, however, its effect on the motor function of the anorectum is uncertain. The aim of this study was to apply acute lumbosacral nerve stimulation in an animal model and to determine its effect on the external and internal anal sphincter forces, the rectoanal inhibitory and excitatory reflexes, and the slow wave frequency of the internal anal sphincter. METHODS: Lumbosacral nerve stimulation was applied to 16 nulliparous female rats. A novel in vivo preparation was designed to allow simultaneous monitoring of external and internal anal sphincter forces. The effect of rectal distension on the two anal sphincters was also studied. KEY RESULTS: Lumbosacral nerve stimulation delivered at either S1 or L6 in rodents did not affect sphincter forces, rectoanal reflexes or slow wave frequency of anal canal smooth muscle. CONCLUSIONS & INFERENCES: The absence of effect on the motor pathways of continence suggests that the mechanism of action is predominantly on sensory feedback mechanisms from the anorectum, thereby increasing cortical awareness of the pelvic floor.

Reversal of sensory deficit through sacral neuromodulation in an animal model of fecal incontinence.

BACKGROUND: Sacral neuromodulation (SNM) is a treatment option for intractable fecal incontinence. The mechanism of action is unclear, however, increasing evidence for afferent somatosensory effects exists. This study's aim was to elucidate effects of acute SNM on the cerebral cortex in a rodent model of pudendal nerve injury. METHODS: The effects of 14 Hz and 2 Hz SNM on sensory cortical activation were studied. In 32 anesthetized rats, anal canal evoked potentials (EPs) were recorded over the primary somatosensory cortex. Pudendal nerve injury was produced by 1-hour inflation of two intra-pelvic balloons. Four groups were studied: balloon injury, balloon injury plus either 14 Hz or 2 Hz SNM, sham operation. Immunohistochemistry for the neural plasticity marker polysialylated neural cell adhesion molecule (PSA-NCAM) positive cells (numerical density and location) in the somatosensory cortex was performed. KEY RESULTS: Anal EP amplitudes diminished during balloon inflation; 14 Hz SNM restored diminished anal EPs to initial levels and 2 Hz SNM to above initial levels. Evoked potential latencies were prolonged during balloon inflation. The numerical density of PSA-NCAM positive cells increased in the SNM groups, but not in sham or balloon injury without SNM. Stimulated cortices showed clusters of PSA-NCAM positive cells in layers II, IV, and V. Post SNM changes were similar in both SNM groups. CONCLUSIONS & INFERENCES: Sacral neuromodulation augments anal representation in the sensory cortex and restores afferent pathways following injury. PSA-NCAM positive cell density is increased in stimulated cortices and positive cells are clustered in layers II, IV, and V.

Antibodies to Epstein-Barr virus-specific DNase and DNA polymerase in the chronic fatigue syndrome.

In an attempt to examine further the association between active Epstein-Barr virus (EBV) infection and the chronic fatigue syndrome (chronic EBV syndrome, or chronic or atypical mononucleosis), antibodies acting against EBV-specific DNase and DNA polymerase, which are expressed only during virus replication, were assayed. Serum samples from 25 healthy EBV-seropositive individuals neutralized 3.5 +/- 5.1 U (mean +/- SD) of DNase activity and 14.7 +/- 8.5 U of DNA polymerase activity. From these values were selected upper limits of anti-EBV enzyme activity of 17.9 and 31.3 U neutralized in normal individuals, respectively (representing the 95% confidence limit). Serum samples from six groups of subjects representing a variety of EBV-related illnesses were then studied. Only patients with notably elevated anti-EBV antibody titers to viral capsid antigen (VCA) (greater than 10,000) had elevated levels of anti-EBV DNase (38 to 56 U neutralized) and anti-EBV DNA polymerase (72 to 106 U neutralized). Three additional patients and two geriatric controls with average anti-EBV early antigen/VCA titers had slightly elevated levels of antibody to EBV DNA polymerase. IgA anti-VCA, anti-early antigen antibodies, or both, were also detected in the same patients who had high EBV DNase and polymerase antibody levels. These antibody profiles are similar to those in patients with nasopharyngeal carcinoma. Since three of the six patients with elevated anti-EBV enzyme antibody levels developed fatal lymphomas, patients with chronic EBV and this antibody profile might be in another illness category at risk for malignant disease.

Mechanically evoked cortical potentials: A physiological approach to assessment of anorectal sensory pathways.

BACKGROUND: Normal defaecation involves activation of anorectal mechanoreceptors responsive to pressure and stretch. The aim of this study was to develop selective anal and rectal mucosal light-touch stimulation suitable for measurement of cortical evoked potentials (EPs) in order to explore the sensory arm of these pathways. NEW METHOD: A novel device was manufactured to deliver selective rectal and/or anal light-touch stimulation using a shielded inter-dental brush mounted on a rotating stepper motor (1Hz, 1ms, 15° rotation). Resultant somatosensory EPs recorded with a 32-channel cortical multi-electrode array were compared to those elicited by electrical anorectal stimulation (2mm anal plug electrode [1Hz, 1ms, 10V]). RESULTS: Eighteen anaesthetized female Wistar rats (body mass 180-250g) were studied. Electrical and mechanical stimulation provoked similar maximal response amplitudes (electrical anorectal 39.0µV[SEM 5.5], mechanical anal 42.2µV[8.1], mechanical rectal 45.8µV[9.0]). Response latency was longer following mechanical stimulation (electrical anorectal 8.8ms[0.5], mechanical anal 16.4ms[1.1], mechanical rectal 18.3ms[2.5]). The extent of activated sensory cortex was smaller for mechanical stimulation. Sensory inferior rectal nerve activity was greater during anal compared to rectal mechanical in a subgroup of 4 rats. Evoked potentials were reproducible over 40min in a subgroup of 9 rats. COMPARISON WITH EXISTING METHODS: Cortical EPs are typically recorded in response to non-physiological electrical stimuli. The use of a mechanical stimulus may provide a more localized physiological method of assessment. CONCLUSIONS: To the authors' knowledge these are the first selective brush-elicited anal and rectal EPs recorded in animals and provide a physiological approach to testing of anorectal afferent pathways.

Core body temperature is normal in chronic fatigue syndrome.

BACKGROUND: Subjects with chronic fatigue syndrome (CFS) frequently report symptoms of subnormal body temperature and low-grade fever. We conducted a study to determine whether CFS subjects manifest any abnormality of core body temperature (CBT) that might help explain their fatigue. METHODS: Continuous 24-hour recordings of CBT measured every 5 min were performed in 7 subjects meeting the Centers for Disease Control definition of CFS. Three additional groups were studied: normal controls, subjects with seasonal allergy, and subjects with major depression. Subjects (n = 7) in each group were age-, sex-, and weight-matched to the CFS group and had normal basal metabolic rates, thyroid function, and 24-hour urinary free cortisol excretions. CBT was measured with an ingestible radio frequency transmitter pill and a belt-worn receiver-logger. Each pill was factory-calibrated to +/- 0.1 degree C and field-calibrated with a water bath calibration prior to use. RESULTS: The 24-hour mean calibration-adjusted CBTs of each group were not significantly different (control: 37.00 +/- 0.17 degrees C; CFS: 37.04 +/- 0.31 degrees C; allergy: 37.15 +/- 0.18 degrees C; depression: 37.16 +/- 0.18 degrees C). Similarly, the mean peak and trough circadian temperatures were not statistically different. The mean 24-hour profile of CBT for each group showed a similar circadian rhythm. In simultaneously collected blood samples, each group showed a similar circadian profile of serum cortisol with a peak occurring at 08:00. CONCLUSIONS: Subjects with CFS have normal CBT despite frequent self-reports of subnormal body temperature and low-grade fever.

Postnatal endocardial fibroelastosis of the valve of the foramen ovale.

The valve of the foramen ovale of the heart changes at birth from a prenatal shunting device for the transseptal flow of systemic venous return to a postnatal active barrier to backflow of left atrial blood at higher pressure. To investigate the morphologic response to this functional change in the valve of the foramen ovale, we examined 200 hearts from embryos, fetuses and autopsy patients spanning over a millionfold range of heart weights (0.001 to 1,230 g). The relation of valve thickness to log heart weight was studied by a stepwise linear regression procedure that fitted the data to two linear regressions, one including observations made before birth and the other including observations made after birth. Analysis of variance tables demonstrated that the data are significantly better explained (p < 0.001) by two linear regressions that abruptly separate from one another at the time of birth than by a single linear regression. Histologic study showed that the prenatal valve consists of a thin myocardial layer with delicate endocardium. The postnatal thickening of the valve tissue occurs mainly by fibroelastotic thickening of the endocardium. The endocardial fibroelastosis of the valve develops after it closes and becomes a component of the left atrial wall. The observations support the concept that fibroelastosis is a nonspecific response of the lining of the cardiovascular system to increased mural tension.

Effects of 5-HT and 5-HT1A receptor agonists and antagonists on dorsal vagal preganglionic neurones in anaesthetized rats: an ionophoretic study.

1. Effects of ionophoretic administration of 5-hydroxytryptamine (5-HT) and selective 5-HT1A receptor agonists and antagonists on identified dorsal vagal preganglionic and dorsal raphe neurones were studied in pentobarbitone sodium or chloral hydrate-anaesthetized rats, respectively. 2. Extracellular recordings were made from 176 preganglionic neurones in the dorsal vagal nucleus (DVN). Application of 5-HT at low currents (< or = 10 nA) increased the activity of these neurones. However, at increased currents (10-60 nA), it had a predominantly depressant effect. Application of selective 5-HT1A receptor antagonists, (+/-)-pindolol or WAY-100635, attenuated the excitatory responses evoked by 5-HT. 3. Ionophoresis of the 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (5-30 nA) increased the firing rate of 19 and decreased that of 67 of the 104 vagal neurones tested. Other 5-HT1A receptor agonists, flesinoxan and N,N-di-n-propyl-5-carboxamidotryptamine (DP-5-CT) also had predominantly depressant effects. 4. (+/-)-Pindolol attenuated excitations but not inhibitions evoked by 8-OH-DPAT. Surprisingly, WAY-100635 and 8-OH-DPAT produced the same effect on these neurones and when applied together, WAY-100635 failed to attenuate the 8-OH-DPAT responses. 5. Dorsal raphe neurones were identified by their low, regular firing rate and their subsequent histological localization. 8-OH-DPAT reversibly reduced the activity in all 7 neurones tested and this was antagonized by WAY-100635 in all 3 neurones tested. 6. In conclusion, 5-HT applied to vagal preganglionic neurones evokes excitatory and inhibitory responses. The excitatory, but not the inhibitory responses may be mediated, at least in part, by activation of 5-HT1A receptors.

Evidence that 5-HT1D receptors mediate inhibition of sympathetic ganglionic transmission in anaesthetized cats.

In anaesthetized cats, 5-carboxamidotryptamine (5-CT) or 5-hydroxytryptamine (5-HT) (0.3-300 micrograms kg-1,i.v.) inhibited the postganglionic compound action potential evoked by preganglionic electrical stimulation (0.5 Hz) with a similar potency in the stellate and splanchnic ganglia. In the 5-HT experiments transmission thorough the inferior mesenteric ganglia was also recorded. The maximal inhibitory effect of 5-HT was greater on the stellate and splanchnic ganglia (60 +/- 4 and 52 +/- 5%) than on the inferior mesenteric (15 +/- 2%). The effects of 5-HT were unaffected by pretreatment with antagonists (1 mg kg-1;i.v.) for 5-HT2 (BW501C67), 5-HT1A (WAY-100635) and 5-HT3 receptors (ondansetron). However, responses to both 5-HT and 5-CT were attenuated significantly by GR127935 (1 mg kg-1) except the responses to 5-HT at the inferior mesenteric ganglia. These results are consistent with the involvement of 5-HT1D receptors mediating inhibition of sympathetic ganglionic transmission in vivo.

Deficiency of UV-induced excision repair in human thymocytes.

The capacity of human thymocytes and of differentiated lymphocytes circulating in peripheral blood to perform unscheduled DNA synthesis (a measure of nucleotide excision repair) after UV irradiation was measured by radioautographic analysis. Only 4% of immature T lymphocytes, but 68% of circulating lymphocytes exhibited unscheduled DNA synthesis. When UV sensitivity of peripheral blood lymphocytes and thymocytes from the same donor were compared, the thymocytes, in each case, were significantly more UV sensitive than were the circulating lymphocytes. Peripheral blood lymphocytes from subjects undergoing halothane and morphine anesthesia during surgery showed 56% less excision repair capacity than those from unanesthetized donors. The difference occurred in the number of cells capable of repair rather than in the extent of repair synthesis per cell. Ultraviolet-induced unscheduled DNA synthesis occurred in only 3% of the thymocytes removed from rats killed by cervical dislocation. Therefore, the deficiency of excision repair was observed in rat thymocytes which had not been affected by anesthesia or surgical trauma. Since the thymus contains more than 90% immature T-cells, our results indicate that immature T-cells are deficient in nucleotide excision repair whereas the majority of mature peripheral blood lymphocytes exhibit such repair.