Visualisation of the medial longitudinal fasciculus using fibre tractography in multiple sclerosis patients with internuclear ophthalmoplegia.

BACKGROUND: This study investigates the use of fibre tractography to facilitate visualisation of the medial longitudinal fasciculus (MLF) and the impact of internuclear ophthalmoplegia (INO) causing lesions on these reconstructions of the tract. Improved visualisation of such tracts may improve knowledge, understanding and confidence related to neurological conditions. AIMS: To explore the use of fibre tractography for the visualisation of the MLF in patients with INO. METHODS: Twelve MS subjects with clinical evidence of INO and 12 matched controls underwent magnetic resonance imaging (MRI), including diffusion tensor imaging (DTI), of the brain. Fibre tractography reconstructions were then evaluated and validated by an experienced neuroanatomist. RESULTS: The evaluating neuroanatomist confirmed that the MLF had been reproduced in all of the reconstructed cases (fibre tractography was unsuccessful in five cases). The sensitivity of fibre tractography to MLF pathology was 58.3 % while the specificity was much higher at 85.7 % with a positive predictive value of 87.5 % and a negative predictive value of 54.6 %, with excellent intra-reader reliability. CONCLUSION: This study demonstrates that fibre tractography of the MLF can potentially be performed with a view to facilitating improved visualisation of the tract and associated pathology in cases of INO. This may help explain the association between lesion type and location with clinical symptomatology and may assist in monitoring disease progression. These reconstructions may provide a valuable addition to the teaching and understanding of clinical signs related to subtle pathology.

Stereology of the placenta in type 1 and type 2 diabetes.

OBJECTIVE: To assess by stereology the placental structure in type 1 (T1DM) and type 2 (T2DM) diabetic pregnancies compared to normal non-diabetic (ND) controls. STUDY DESIGN: Prospective case control study. Placentae were sampled in a systematic random fashion. Stereological analysis was performed using a computerised stereology programme (Image Pro 6.2, Media Cybernetics, Inc, Silver Spring MD, USA). Participants were matched for gender of infant and mode of delivery. MAIN OUTCOME MEASURES: Volume, length and surface area of placental components; clinical outcome. RESULTS: Ten ND, eight T2DM and ten T1DM women consented to the study. There was no difference between the groups regarding maternal age, neonatal birth weight, or placental weight. On stereological examination, terminal villous volume was significantly increased in both diabetic groups compared to ND controls. Capillary volume and length was increased in T1DM pregnancies compared to ND and T2DM. Capillary length was increased in both diabetic groups compared to ND. When all diabetic groups were compared based on severity of glycaemia those with poor glycaemic control (HbA1c>7%) had higher placental capillary volume than those with good glycaemic control. CONCLUSIONS: This study demonstrates an association between maternal diabetes and increased terminal villous volume. Additionally capillary volume and length is increased in the placentae of normally grown infants of T1DM diabetic mothers compared to non-diabetic controls. Maternal glycaemia appears to influence capillary, but not stromal, development. This suggests that factors other than glycaemia have a role in placental development in pre-gestational diabetes.

The Adriamycin rat/mouse model and its importance to the paediatric surgeon.

The teratogenic effect of Adriamycin (doxorubicin) in the rat model, and more recently in the mouse, has provided paediatric surgeons with a reliable, easily reproducible method of studying the embryology and molecular biology for a range of complex congenital anomalies. Concomitantly these animal models have stimulated interest among embryologists for the effect on the notochord, shedding more light on the important organizational role of this structure in the developing embryo. Finally, as more is learnt of the pathogenesis of the various malformations induced by Adriamycin, future therapeutic interventions involving gene therapy, drugs or surgery may arise. This article reviews the establishment of the Adriamycin rat and mouse models, examines their impact on various congenital malformations, and suggests targets for further research.

Differences in nitrergic innervation of the developing chick cloaca and colorectum.

The intrinsic innervation of the developing gut has long been a subject of investigation, but little is known regarding that of the embryonic cloaca. The cloaca, like the rest of the gastrointestinal tract, is intrinsically innervated by the enteric nervous system. Nitrergic neurons and fibres make up a large part of this system, thus, their distribution provides us with a useful insight into its development. Cloacal and colorectal tissue specimens were removed from chick embryos at embryonic days 11 (E11), E15 and E19. NADPH-diaphorase (NADPH-d) histochemistry was carried out using whole mount tissue preparations. Ganglia density, the number of NADPH-d-positive cells per ganglia in the myenteric plexus and cell size were calculated and statistical analysis was performed to compare both regions of the gut (P<0.001). There were significant differences in the ganglia density in the cloaca compared to the colorectum at E11 (P<0.05) and E15 (P<0.01), with the colorectum having a much denser network. In both the cloaca and the colorectum, ganglia density significantly decreased with age (P<0.001), while significant differences were observed in the number of NADPH-d-positive cells per ganglia in both regions through development. Total cell size was similar in both the cloaca and colorectum at each stage and increased in both regions through development, predominantly due to an increase in the cytoplasm. Results reveal striking differences in innervation between the chick embryo cloaca and colorectum. The sparse network of innervation evident within the cloaca in contrast to the dense network within the colorectum emphasizes the individuality of both regions. These results highlight the need for a further in-depth analysis of the enteric nervous system's development within the embryonic cloaca.

The effect of vagal neural crest ablation on the chick embryo cloaca.

The cloaca, the caudal limit of the avian gastrointestinal tract, acts as a collecting chamber into which the gastrointestinal, urinary, and genital tracts discharge. It is intrinsically innervated by the enteric nervous system, which is derived from neural crest emigres that migrate from the vagal and sacral regions of the neural tube. Abnormal cloacal development can cause a number of anorectal anomalies, including persistent cloaca. Ablation of the vagal neural crest has previously been shown to result in an aganglionic hindgut to the extent of the colorectum. The aim of our study was to investigate the effect of vagal neural crest ablation on the cloaca, the limit of the hindgut in the developing chick embryo. Chick embryos were incubated until the 10-12 somite stage. The vagal neural tube corresponding to the level of somites 3-6 was then ablated, and eggs were incubated until harvested on embryonic day 11 (E11). Whole chick embryos were fixed, embedded in paraffin, and sectioned. Immunohistochemistry was then carried out using the HNK-1 monoclonal antibody to label neural crest cells, and results were assessed by light microscopy. Vagal neural crest ablation resulted in a dramatic decrease in the number of neural crest cells colonizing the chick embryo cloaca compared with control embryos. Ablated embryos contained only a small number of HNK-1-positive neural crest cells, which were scattered within the myenteric plexus in a disorganised pattern. Hypoganglionosis was also evident in other regions of the hindgut in ablated embryos. Ablation of the vagal neural crest results in a hypoganglionic cloaca in addition to hypoganglionosis of the hindgut. These results suggest that the cloaca is largely innervated by vagal neural crest emigres. Further studies involving quail-chick chimeras to investigate the exact contribution provided by both vagal and sacral neural crest cells to the cloaca should increase our understanding of the pathophysiology of conditions like persistent cloaca.

Adriamycin induces notochord hypertrophy with conservation of sonic hedgehog expression in abnormal ectopic notochord in the adriamycin rat model.

BACKGROUND/PURPOSE: The Adriamycin rat model (ARM) is a well-established model of the Vertebral, Anorectal, Cardiac, Tracheoesophageal, Renal, Limb (VACTERL) association. The notochord, which expresses Sonic Hedgehog (Shh), has been found to be grossly malformed with ventral ectopic branches in the foregut region of embryos in the ARM. The authors designed this study to test the hypothesis that Shh-expressing ectopic notochord could contribute to an increased volume of notochord relative to total embryo volume, resulting in an increased concentration of Shh in the notochord of affected embryos. METHODS: Adriamycin was administered intraperitoneally to rats on days 7 (E7), E8, and E9 of gestation and saline to control animals. Embryos recovered at E12 and E14 were examined immunohistochemically for Shh expression. Quantitative morphology using the Cavalieri technique was performed to determine embryo and notochord volume. RESULTS: Embryos in both Adriamycin and control groups at E12 and E14 showed comparable levels of Shh expression in notochord at all locations. The percentage of notochord per embryo was significantly increased in Adriamycin embryos at E12 and E14 compared with equivalent controls. CONCLUSIONS: These data suggest that Adriamycin induces notochord hypertrophy. With all regions of the notochord secreting Shh, this could result in a higher concentration gradient of Shh in close abnormal proximity to the foregut, possibly contributing to the malformations found in the VACTERL association.

Increased fibronectin expression in developing embryos is associated with abnormal notochord in the Adriamycin rat model.

BACKGROUND: The VACTERL association is a spectrum of clinical conditions, including esophageal atresia (EA) and tracheoesophageal fistula (TEF), which affects approximately 1 in 5,000 live human births. The administration of intraperitoneal Adriamycin to pregnant rats reliably induces anomalies, such as EA and TEF, in their offspring, in what is known as the Adriamycin rat model (ARM). In affected embryos the presence of gross notochord abnormalities is commonly found, with typical features being ectopic ventral branches and adherence of the notochord to the foregut. Fibronectin (FN) is an extracellular matrix (ECM) glycoprotein present on most cell surfaces, in extracellular fluids and in plasma. FN is involved in various functions, including cell adhesion, cell motility and wound healing. Previous studies in rats have shown that a single dose of Adriamycin can produce an appreciable rise in FN levels in various organs such as kidney and heart. We hypothesised that Adriamycin administration could promote upregulation of FN expression contributing to increased gut-notochord adherence and the development of abnormal ventral notochordal branching in the ARM. This study was designed to investigate FN expression in ARM embryos. METHODS: Adriamycin (1.75 mg/kg) was administered intraperitoneally to pregnant rats on days 7,8 and 9 of gestation (E7, E8 and E9 respectively). Control animals were given saline. Embryos recovered on E10-E14 were fixed, embedded in paraffin and sectioned. Immunohistochemistry using an anti-FN rabbit polyclonal antibody was performed. RESULTS: FN expression in both Adriamycin and control embryos on E10, E11 and E12 was comparable. However, the levels of FN expression in Adriamycin embryos on E13 and E14 were significantly greater in embryos with abnormal notochords than in equivalent control embryos. CONCLUSION: Adriamycin-induced increased expression of FN, in the ARM, may contribute to abnormal notochord development leading to the VACTERL association.

The timing of enteric neural crest cell colonisation of the chick embryo cloaca.

Neural crest cell (NCC) migration and formation of the enteric nervous system (ENS) is an essential process in the development of the normal human gut. Abnormalities of the ENS lead to a number of neurochristopathies. In avian embryos, the cloaca acts as a common chamber into which gastrointestinal, urinary and genital tracts emerge. Previous studies have elucidated the specific timeframes at which NCCs reach the various regions of the developing chick gut but, to date, none have looked at NCC colonisation of the cloaca. The aim of our study was to investigate the exact timing of the appearance of NCCs in the cloaca of chick embryos. Chicken embryos were harvested on embryonic days (E) 8-12. Whole embryos were fixed, embedded in paraffin and sectioned. Fluorescent immunohistochemistry, using an anti-HNK-1/N-CAM monoclonal antibody, was performed and images were obtained by confocal microscopy. There was no evidence of NCCs in the cloaca of embryos from E8 to E11. Intense immunoreactivity to HNK-1 first appeared in the cloaca of E12 embryos, demonstrating a profuse circumferential colonisation by NCCs at this time. Our study is the first to show the exact timing of enteric NCC colonisation of the chick embryo cloaca. Further studies, involving quail-chick chimeras, are required to establish the true origin of cloacal NCCs and to establish the relationship between NCCs and persistent cloaca.

Adriamycin effects on the chick embryo.

Adriamycin is an anthracycline, anti-neoplastic drug with known teratogenic effects on foetal rats in what is known as the Adriamycin rat model (ARM). This includes conditions similar to those in newborn humans, known collectively as the VACTERL association. This comprises vertebral (V), anorectal (A), cardiac (C), tracheoesophageal (TE), renal (R) and limb (L) anomalies. We designed this study to test the hypothesis that the administration of Adriamycin to chick embryos would cause similar anomalies to those in the VACTERL association seen in the ARM. Fertilized Ross eggs received Adriamycin doses from 2-50 microg into the air sac and from 0.9-6 microg into the albumin. Administration varied from day 0-3 (D(0-3)) with D(0) being the first day of incubation. Control eggs received saline. Embryos were incubated at 38 degrees C and a relative humidity of 70%. Embryos were recovered on D(14), paraffin-embedded and transverse sections studied for morphological abnormalities. In the air sac group ( n=142), 71% of Adriamycin embryos survived versus 86% of controls (n=29). In the albumin group (n=121), 42% of Adriamycin embryos survived versus 55% of controls (n=69). No embryos demonstrated anomalies consistent with the VACTERL association. Ventral defects affected 1% of surviving Adriamycin embryos versus 4% of controls in the air sac group. In the albumin group, 19.8% of surviving Adriamycin embryos had ventral defects compared to 15.7% of surviving controls. Anophthalmia affected 1% of the surviving embryos in the Adriamycin air sac group and 2% of the Adriamycin albumin group. No controls developed anophthalmia. Exencephaly affected 2% of the survivors in the Adriamycin air sac group but none of the albumin group or controls. The administration of Adriamycin to chick embryos in comparable doses and times to those used in the ARM does not appear to produce comparable effects in relation to developmental anomalies, such as the VACTERL association. Despite examining different administration routes and mimicking the ARM, by giving Adriamycin to embryos at gastrulation, we were unable to re-create the anomalies seen in the ARM.

Notochord anomalies in the adriamycin rat model: A morphologic and molecular basis for the VACTERL association.

BACKGROUND/PURPOSE: The Adriamycin rat model (ARM) is a reliable model of the VACTERL association. The notochord is structurally abnormal in the region of the foregut, midgut, and hindgut in the ARM. The authors hypothesised that notochord anomalies allow ectopic expression of molecular signals in the developing embryo and thus lead to VACTERL malformations. This study was designed to investigate this hypothesis. METHODS: Adriamycin (1.75 mg/kg) was administered intraperitoneally to pregnant rats on days 7, 8, and 9 of gestation. Control animals were given saline. Embryos were recovered on gestational days 10.5 to 14 at (1/2)-day intervals and at full term. The first group of embryos were embedded in resin, and sagittal sections stained with Toluidine blue were studied for morphologic abnormalities. The second group of embryos were examined using in situ hybridization for the expression of Sonic Hedgehog (Shh), a patterning gene implicated in the etiology of the VACTERL association. RESULTS: Twenty-seven of the 28 (96.4%) full-term embryos showed VACTERL anomalies. Forty-five of the 50 (90%) experimental embryos (gestational days 10.5 to 14) showed notochord abnormalities. Abnormal ventral branches from the notochord toward the gut were a commonly observed abnormality. These were seen to impinge on the developing foregut, midgut, dorsal aorta, and kidney. In situ hybridization for Shh showed that these branches from the notochord expressed Shh in 66.6% of experimental embryos. This abnormal Shh expression was not seen in the control embryos. CONCLUSIONS: Adriamycin diffusely induces altered notochord morphology in the rat embryo. The abnormal notochord morphology may allow ectopic expression of Sonic Hedgehog, and, thus, contribute to the malformations found in the VACTERL association.

Cell death in the early adriamycin rat model.

The adriamycin rat model (ARM) exhibits many features of the VACTERL association. Adriamycin is a cytotoxic drug used in cancer chemotherapy. Although its exact mode of action is not clear, it is presumed to have a similar cytotoxic role in the developing embryo. Lysotracker red (LT) is a dye that stains phagolysosomes and apoptotic bodies and allows entire rodent embryos to be stained for apoptosis. We hypothesised that there was increased cell death in adriamycin-exposed embryos. To investigate this hypothesis, adriamycin (1.75 mg/kg) was given intraperitoneally to rats on days 7, 8, and 9 of pregnancy. A control group was given saline on the same schedule. Embryos were recovered at 3, 12, 24, and 48 h following the last dose and also at term (21 days) to confirm that the usual incidence of congenital anomalies found in the ARM was obtained in our animal model. Embryos were embedded in resin, sectioned, and studied by light microscopy. Embryos from the 3-h and 24-h groups were studied using LT and confocal microscopy to search for evidence of apoptosis. All term newborns (100%) from the adriamycin-treated group demonstrated the typical abnormalities found in the ARM, i.e., oesophageal atresia, multiple gastrointestinal atresias, vertebral malformations, absent tails, ureterohydronephrosis, etc. In the 9.5-day adriamycin group there was no difference in appearance between the experimental and control embryos. Specifically, no cellular debris or increased cell turnover indicative of adriamycin cytotoxicity was observed in the experimental group. At day 10.5, 90% of embryos from two separate litters had evidence of notochordal distortion and tethering to the gut or gut-tube abnormalities. These findings were not observed in the control embryos. Confocal microscopy and LT examination of the embryos from litters killed at 3 and 24 h following the last dose of adriamycin demonstrated no evidence of increased cell death in adriamycin-exposed embryos compared to control embryos. The absence of significant apoptosis in the developing embryos in the immediate period following administration of adriamycin suggests that the teratogenic effect of adriamycin is not caused by cell death.

Effects of cadmium on formation of the ventral body wall in chick embryos and their prevention by zinc pretreatment.

BACKGROUND: Cadmium (Cd) is an established experimental teratogen whose effects can be reversed by pretreatment with zinc. Mesodermal development is a frequently reported target for Cd teratogenicity. The aim of this study was to examine the mechanisms of Cd induced body wall defects in chick embryos. METHODS: Chick embryos in shell-less culture were treated with 50 microl of cadmium acetate (8.9 x 10(-5) M Cd(2+)) at 60-hr incubation (H.-H. stages 16-17). Controls received equimolar sodium acetate. Other embryos were treated with various concentrations of zinc acetate and then with Cd or NaAc 1 hrs later. Development was evaluated 48 hrs later. Resin-embedded 1-microm sections were examined at earlier stages. RESULTS: Cd caused embryolethality (35%), ventral body wall defect with malpositioned lower limbs (40%), and weight reduction in survivors. After 4-hr treatment with Cd, breakdown of junctions between peridermal cells with rounding up and desquamation occurred. Shape changes were also seen in the basal layer of the ectoderm. At 4 hr, cell death was evident in lateral plate mesoderm, somites, and neuroepithelium; the lateral plate mesoderm began to grow dorsally, carrying the attached limb buds with it. Zn pretreatment protected against the lethal, teratogenic, and growth-retarding effects of Cd, as well as ectodermal changes and cell death. CONCLUSIONS: Cd disrupts peridermal cell adhesion and induces cell death in the mesoderm. This may result in abnormal growth of lateral plate mesoderm and in a body wall defect. Zn pretreatment prevents both the gross teratogenic effects and the cellular changes, most likely by competition with Cd.

Evaluation of a miniature antimony electrode for measurement of myocardial pH.

Myocardial pH reflects the metabolic status of the heart and pH monitoring is an invaluable way to monitor the efficacy of myocardial protection during cardiac surgery. We developed a miniature antimony electrode for pH measurement in the heart. We examined the sensitivity, accuracy and the effects of temperature and oxygen tension on pH readings with this electrode in standard buffers and in anaesthetized dogs. In buffers the antimony electrode exhibited a gradient of -50.3 +/- 1.8 mV pH-1 at 25 degrees C, close to the Nernstian slope and showed a high correlation with conventional glass electrode readings (mean difference 0.027 +/- 0.0035 pH, r2 = 0.97). With increasing temperature the antimony electrode pH readings increased by 0.03 +/- 0.002 pH degree C(-1). With increasing PO2 the pH reading decreased (-0.73 pH/log PO2 mm Hg, r2 = 0.96). In the dog heart the antimony electrode showed a decrease in myocardial pH with increasing PCO2, and an increase in pH when NaHCO3 was given intravenously. Coronary occlusion resulted in paradoxically higher pH readings with the antimony electrode due to the effect of lowered myocardial PO2 interfering with pH measurement. The dissolution of antimony from the electrode in blood plasma was tested and found to be low. These studies suggest that antimony electrodes have low toxicity and provide accurate pH determinations under conditions of constant PO2. For more widespread clinical application, the problem of oxygen interference needs to be solved.

Enhanced expression of inducible nitric oxide synthase without vasodilator effect in chronically infected lungs.

We hypothesized that abnormal ventilation-perfusion matching in chronically infected lungs was in part due to excess nitric oxide (NO) production after upregulation of inducible NO synthase (iNOS) expression. Rats were anesthetized and inoculated intratracheally with Pseudomonas aeruginosa incorporated into agar beads (chronically infected) or with sterile agar beads (placebo inoculated) and killed 10-15 days later. Immunohistochemistry demonstrated increased expression of iNOS and reduced expression of endothelial NOS (eNOS) in chronically infected compared with placebo-inoculated or noninoculated lungs. In isolated lungs from chronically infected rats, NOS inhibition with N(omega)-nitro-L-arginine methyl ester increased the mean perfusion pressure (14.4 +/- 2.7 mmHg) significantly more than in the placebo-inoculated (4.8 +/- 1.0 mmHg) or noninoculated (5.3 +/- 0.8 mmHg) lungs (P < 0.01). Although the chronically infected lungs were more sensitive to NOS inhibition, further evidence suggested that the increased iNOS expression was not associated with enhanced iNOS activity. Selective inhibitors of iNOS did not produce an increase in vascular resistance similar to that produced by nonselective inhibitors. Accumulation of nitrate/nitrite in the perfusate of isolated lungs was unchanged by chronic infection. Thus although iNOS expression was increased in chronic pulmonary infection, iNOS activity in the intact lung was not. Nonetheless, endogenous NO production was essential to maintain normal vascular resistance in these lungs.

The effects of lithium on vascular development in the chick area vasculosa.

The effects of lithium on vascular development were examined using the chick embryo area vasculosa in shell-less culture as an experimental model. Embryos were explanted after 48 h in ovo and LiC1 (50, 100, 150 and 200 microg in 10 microl water) was applied to the centre of the blastodisc. Controls were untreated or given equimolar amounts of NaCl. At 24 h and 48 h after treatment, untreated and NaCl controls were identical, having well developed extraembryonic vessels. At doses of 100 microg and greater, LiCl significantly inhibited normal vascular development and expansion of the area vasculosa in the majority of explants. In many specimens blood islands continued to form but their assembly into primitive vessels was prevented, indicating that lithium affects the mechanism regulating the assembly of vascular endothelium. At the same time the embryos were alive but retarded in development compared with controls. When LiCl (150 microg) was applied to cultures explanted after 72 h in ovo (when the primary vascular network had already formed through vasculogenesis) no adverse effects were seen. This suggests that lithium affects vasculogenesis but not angiogenesis. Treatment with myo-inositol completely reversed the effects of lithium in a time dependent manner indicating that the phosphatidylinositol second messenger cycle may be involved in the cellular events of vasculogenesis. Finally the results of this study show that the yolk sac vasculature is particularly vulnerable to lithium and the consequent effects of this interference on embryonic development are discussed.

The effects of lithium on neurulation stage mouse embryos.

The aim of this study was to evaluate the maternal toxicity and teratogenicity of lithium following intraperitoneal injection (i.p.) with lithium carbonate (Li2CO3) in pregnant CD-1 mice at the developmental stage of neurulation (E8; day of vaginal plug, E0). Light (LM) and electron (TEM) microscopic studies were also done to document the tissue and cellular changes occurring in embryonic tissues during the 48 h following treatment with 300 mg/kg body wt. Li2CO3. Controls were untreated or given equimolar amounts of NaCl or Na2CO3. A pharmacokinetic study showed that lithium was rapidly absorbed from the peritoneal cavity after the above-stated dose, achieved peak serum levels of 9.8 mmol/l within 1 h, had a half-life in the blood of 5 h and was completely cleared by 16 to 24 h after injection. Doses of Li2CO3 > 300 mg/kg body wt. were toxic to adult CD-1 mice. The latter dose had no detectable maternal toxicity but caused a 19% resorption rate and 2% incidence of open cranial neural tube defect in gestations terminated on E18. The malformation and resorption rates in gestations terminated on E11, E12 and E14 were not significantly different from those of E18. A strong litter effect was seen both for the resorption and malformation rates at all stages examined. At 3 h after treatment cell death became evident in the neuroepithelium. Cells continued to die for approximately 17 h and all necrotic debris had been cleared by 48 h. Also at 3 h after treatment small densely stained inclusions began to appear in mesodermal cells. TEM showed these to be non-membrane bound with an irregular shape and variable size; the lack of staining for acid phosphatase indicated a non-lysosomal structure; the ultrastructural features suggested a lipoid basis. At 24 h after treatment vascular ruptures and surface ectodermal ruptures were seen in the cranial mesoderm. These ruptures with extravascated blood were also seen at 48 h after treatment. A litter effect was also noted with respect to the tissue and cellular changes. These experiments suggest that the developing vascular system may be a target for lithium. In addition, the possibility is discussed that lithium induced cell death in the neuroepithelium may lead to neural tube defects.

Anatomy of the extraneural blood supply to the intracranial oculomotor nerve.

AIMS: An anatomical study was undertaken to determine the extraneural blood supply to the intracranial oculomotor nerve. METHODS: Human tissue blocks containing brainstem, cranial nerves II-VI, body of sphenoid, and associated cavernous sinuses were obtained, injected with contrast material, and dissected using a stereoscopic microscope. RESULTS: Eleven oculomotor nerves were dissected, the intracranial part being divided into proximal, middle, and distal (intracavernous) parts. The proximal part of the intracranial oculomotor nerve received extraneural nutrient arterioles from thalamoperforating arteries in all specimens and in six nerves this blood supply was supplemented by branches from other brainstem vessels. Four nerves were seen to be penetrated by branches of brainstem vessels and these penetrating arteries also supplied nutrient arterioles. The middle part of the intracranial oculomotor nerve did not receive nutrient arterioles from adjacent arteries. The distal part of the intracranial oculomotor nerve received nutrient arterioles from the inferior cavernous sinus artery in all 11 nerves and in seven nerves this was supplemented by a tentorial artery arising from the meningohypophyseal trunk. The inferior hypophyseal artery arose from the meningohypophyseal trunk in all 11 cavernous sinuses dissected. CONCLUSION: This study shows a constant pattern to the blood supply of the intracranial oculomotor nerve. It also highlights the close relation between the blood supplies to the intracavernous oculomotor nerve and the pituitary gland.

Early changes in the choroidal vasculature of rats occurring with experimentally induced hypertension.

We investigated the early changes in the choroidal vasculature in rats following surgically induced renovascular hypertension. Renovascular hypertension was induced in a group of 12 male Wistar rats using a modified Goldblatt procedure. The rats were divided into four groups, each being sacrificed at weekly intervals, the first group being sacrificed 1 week following the procedure. Vascular casts were prepared of the choroidal circulation using acyl resin (mercox). These were then studied using the scanning electron microscope. No abnormality of the choroidal circulation was noted for the first 2 weeks. At 3 weeks, when a rise in the average mean arterial pressure was noted, nodular lesions were seen in the choroidal arteries and choriocapillaris. These lesions were present in far greater numbers by 4 weeks. It seems likely that the nodular lesions described are microaneurysms and may contribute to the pathogenesis of the clinically described Elschnig spot.

A non-invasive photographic modification for recording early vascular development in the chick.

The chick embryo shell-less culture technique allows continuous observation and access to the developing vessels of the area vasculosa (AV); hence, its value as an angiogenesis assay system. The main drawback of the method is that adequately contrasted photographs cannot be achieved without injection of a contrast medium which kills the embryo making further observation of the same specimen impossible. Furthermore, injection prior to 72 h incubation has a high failure rate. In an attempt to overcome these problems, we explored the possibility of using a high-contrast photographic process. Embryos were explanted into shell-less culture after 48 h incubation and photographed through a stereo microscope. After trials with different films we found that Kodalith ortho Type 3 (Kodak) and Technical Pan film (Kodak) produced images of the vasculature which were identical in contrast and detail to India-ink-injected specimens photographed with conventional film. In addition, excellent images could be recorded as early as 48 h of incubation.