Beyond cyclopamine: Targeting Hedgehog signaling for cancer intervention

Hedgehog (Hh) signaling plays a significant role in embryogenesis and several physiological processes, such as wound healing and organ homeostasis. In a pathological setting, it is associated with oncogenesis and is responsible for disease progression and poor clinical outcomes. Hedgehog signaling mediates downstream actions via Glioma Associated Oncogene Homolog (GLI) transcription factors. Inhibiting Hh signaling is an important oncological strategy in which inhibitors of the ligands SMO or GLI have been looked at. This review briefly narrates the Hh ligands, signal transduction, the target genes involved and comprehensively describes the numerous inhibitors that have been evaluated for use in various neoplastic settings.

The Effect of Botanical Pesticides Azadirachtin, Celangulin, and Veratramine Exposure on an Invertebrate Species Solenopsis invicta (Hymenoptera: Formicidae)

The injudicious and excessive use of synthetic pesticides has deleterious effects on humans, ecosystems, and biodiversity. As an alternative to traditional crop-protection methods, botanical pesticides are gaining importance. In this research endeavor, we examined the contact toxicity, knockdown time, lethal time, and toxicity horizontal transmission of three natural pesticides from plants (azadirachtin, celangulin, and veratramine) on red imported fire ants (RIFA; Solenopsis invicta). Our research findings indicated that azadirachtin and celangulin exhibited relatively high toxicity, with median lethal dose (LD50) values of 0.200 and 0.046 ng/ant, respectively, whereas veratramine exhibited an LD50 value of 544.610 ng/ant for large workers of S. invicta at 24 h post-treatment. Upon treatment with 0.125 mg/L, the (median lethal time) LT50 values of azadirachtin and celangulin were determined to be 60.410 and 9.905 h, respectively. For veratramine, an LT50 value of 46.967 h was achieved after being tested with 200 mg/L. Remarkably, azadirachtin and celangulin were found to exhibit high horizontal transfer among RIFA, with high secondary mortality (100%) and tertiary mortalities (>61%) after 48 h of treatment with 250 mg/L, as well as with their dust formulations for 72 h. However, veratramine did not exhibit significant toxicity or horizontal transfer effects on RIFA, even at high concentrations. These findings suggest that azadirachtin and celangulin are likely to have a highly prominent potential in the management of S. invicta.

Antihypertensive activity of different components of Veratrum alkaloids through metabonomic data analysis

BACKGROUND

Hypertension is a serious global public health issue. Blood pressure (BP) is still not effectively controlled in about 20 - 30% of hypertensive patients. Therefore, it is imperative to develop new treatments for hypertension. Veratrum alkaloids were once used for the clinical treatment of hypertension, the mechanism of which is still unclear. It was gradually phased out due to adverse reactions.

PURPOSE

This study aimed to investigate the short-term and long-term hypotensive profiles of different components of Veratrum alkaloids in spontaneously hypertensive rats (SHRs) to unveil their mechanisms of action.

RESULTS

Total Veratrum alkaloid (V), component A (A), and veratramine (M) quickly decreased BP within 30 min of treatment, reduced renal and cardiovascular damage, and improved relevant biochemical indicators (nitric oxide [NO], endothelin-1 [ET-1], angiotensin II [Ang II)], noradrenaline [NE], etc) in SHRs to delay stroke occurrence. Thereinto, A exhibited excellent protective effects in cardiovascular disease. The metabolomic profiles of SHRs treated with V, A, and M were significantly different from those of SHRs treated with vehicle. Thirteen metabolites were identified as potential pharmacodynamic biomarkers. Through Kyoto Encyclopedia of Genes and Genomes analysis, V, A, and M-induced hypotension was mainly related to alterations in nicotinate and nicotinamide metabolism, GABAergic synapses, linoleic acid metabolism, ketone body synthesis and degradation, arginine and proline metabolism, and urea cycle, of which nicotinate and nicotinamide metabolism was the key metabolic pathway to relieve hypertension.

CONCLUSION

This work shows that A is an effective and promising antihypertensive agent for hypertension treatment to reduce BP and hypertensive target organ damage, which is mainly mediated through modulating nicotinate and nicotinamide metabolism, RAS, and NO-ET homeostasis.

Convergent Total Synthesis of (-)-Cyclopamine

A concise and enantioselective total synthesis of the Veratrum alkaloid cyclopamine is disclosed. This highly convergent synthesis with a 16-step longest linear sequence (LLS) was enabled by a de novo synthesis of the trans-6,5-heterobicycle via a strain-inducing halocyclization process, a key Tsuji-Trost cyclization to construct the fully substituted, spirocyclic THF motif with exquisite diastereocontrol, and a late-stage ring-closing metathesis (RCM) reaction to forge the central tetrasubstituted olefin.

Hardening of Respiratory Syncytial Virus Inclusion Bodies by Cyclopamine Proceeds through Perturbation of the Interactions of the M2-1 Protein with RNA and the P Protein

Respiratory syncytial virus (RSV) RNA synthesis takes place in cytoplasmic viral factories also called inclusion bodies (IBs), which are membrane-less organelles concentrating the viral RNA polymerase complex. The assembly of IBs is driven by liquid-liquid phase separation promoted by interactions between the viral nucleoprotein N and the phosphoprotein P. We recently demonstrated that cyclopamine (CPM) inhibits RSV multiplication by disorganizing and hardening IBs. Although a single mutation in the viral transcription factor M2-1 induced resistance to CPM, the mechanism of action of CPM still remains to be characterized. Here, using FRAP experiments on reconstituted pseudo-IBs both in cellula and in vitro, we first demonstrated that CPM activity depends on the presence of M2-1 together with N and P. We showed that CPM impairs the competition between P and RNA binding to M2-1. As mutations on both P and M2-1 induced resistance against CPM activity, we suggest that CPM may affect the dynamics of the M2-1-P interaction, thereby affecting the relative mobility of the proteins contained in RSV IBs. Overall, our results reveal that stabilizing viral protein-protein interactions is an attractive new antiviral approach. They pave the way for the rational chemical optimization of new specific anti-RSV molecules.

Veratrum parviflorum poisoning: identification of steroidal alkaloids in patient blood and breast milk

INTRODUCTION

The Veratrum genus is composed of plants containing a diverse set of steroidal alkaloids. Veratrum plant material has been utilized for centuries as herbal medicines, however the alkaloids have such a low therapeutic index that they are not used in modern medicine. Here we report an incident of inadvertent ingestion of V. parviflorum by hikers in Georgia that allowed detection, and in several instances identification of alkaloids from the plant, and correlated their presence within patient blood and breast milk specimens.

CASE HISTORY

Eight patients, three male and five female, presented in the spring of 2020 and 2021 with symptoms requiring emergent medical attention after ingestion of Veratrum parviflorum. All patients believed the plants to be a local native species of wild leek, Allium tricoccum, locally known as ramps. Plants were identified using photographs as well as fresh and cooked plant material provided by patients, in consultation with botanists at the University of Georgia Herbarium. Written consent was obtained from all patients for collection of blood and breast milk specimens for laboratory identification of Veratrum alkaloids.

METHODS

V. parviflorum plant material, and patient serum and breast milk were analyzed by high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (HPLC-QTOF) to identify steroidal alkaloids.

RESULTS

The V. parviflorum extract was confirmed to contain cyclopamine, veratramine, jervine, and muldamine. Two out of the eight patients had detectable concentrations of Veratrum alkaloids. Of the alkaloids identified in the plant, cyclopamine and jervine were detected within patient serum, and cyclopamine and veratramine were observed to be present in breast milk.

DISCUSSION

Toxicity resulting from Veratrum steroidal alkaloids has primarily been reported from V. album and V. viride. This is the second report of V. parviflorum poisoning. The present work reports for the first time the presence of muldamine and jervine within V. parviflorum. This work provides the first instance of identification of Veratrum alkaloids in breast milk. Thus, the findings presented herein add to literature record causative agents contributing to the toxicity of V. parviflorum when ingested and potential for secondary poisoning through breastfeeding.

CONCLUSION

V. parviflorum toxicity was observed to cause nausea, vomiting, hypotension, bradycardia, abdominal pain, light-headedness, blurred vision, and tingling in the arms. Patients experiencing mild symptoms improved with supportive care, IV fluids, and antiemetics, but hemodynamically unstable patients required atropine and vasopressors. This study demonstrated that more lipophilic Veratrum alkaloids can be passed along in breast milk, which suggests additional precautions may be critical to limit further poisonings.

Tumor Microenvironment Modulation by Cyclopamine Improved Photothermal Therapy of Biomimetic Gold Nanorods for Pancreatic Ductal Adenocarcinomas

Due to the rich stroma content and poor blood perfusion, pancreatic ductal adenocarcinoma (PDA) is a tough cancer that can hardly be effectively treated by chemotherapeutic drugs. Tumor microenvironment modulation or advanced design of nanomedicine to achieve better therapeutic benefits for PDA treatment was widely advocated by many reviews. In the present study, a new photothermal therapy strategy of PDA was developed by combination of tumor microenvironment modulation and advanced design of biomimetic gold nanorods. On one hand, biomimetic gold nanorods were developed by coating gold nanorods (GNRs) with erythrocyte membrane (MGNRs). It was shown that MGNRs exhibited significantly higher colloidal stability in vitro, stronger photothermal therapeutic efficacy in vitro, and longer circulation in vivo than GNRs. On the other hand, tumor microenvironment modulation by cyclopamine treatment successfully disrupted the extracellular matrix of PDA and improved tumor blood perfusion. Moreover, cyclopamine treatment significantly increased the accumulation of MGNRs in tumors by 1.8-fold and therefore produced higher photothermal efficiency in vivo than the control group. Finally, cyclopamine treatment combined with photothermal MGNRs achieved the most significant shrinkage of Capan-2 tumor xenografts among all the treatment groups. Therefore, with the integrated advantages of tumor microenvironment regulation and long-circulation biomimetic MGNRs, effective photothermal therapy of PDA was achieved. In general, this new strategy of combining tumor microenvironment modulation and advanced design of biomimetic nanoparticles might have great potential in PDA therapy.

Chevron formation of the zebrafish muscle segments

The muscle segments of fish have a folded shape, termed a chevron, which is thought to be optimal for the undulating body movements of swimming. However, the mechanism shaping the chevron during embryogenesis is not understood. Here, we used time-lapse microscopy of developing zebrafish embryos spanning the entire somitogenesis period to quantify the dynamics of chevron shape development. By comparing such time courses with the start of movements in wildtype zebrafish and analysing immobile mutants, we show that the previously implicated body movements do not play a role in chevron formation. Further, the monotonic increase of chevron angle along the anteroposterior axis revealed by our data constrains or rules out possible contributions by previously proposed mechanisms. In particular, we found that muscle pioneers are not required for chevron formation. We put forward a tension-and-resistance mechanism involving interactions between intra-segmental tension and segment boundaries. To evaluate this mechanism, we derived and analysed a mechanical model of a chain of contractile and resisting elements. The predictions of this model were verified by comparison with experimental data. Altogether, our results support the notion that a simple physical mechanism suffices to self-organize the observed spatiotemporal pattern in chevron formation.

Characterization of subtle brain abnormalities in a mouse model of Hedgehog pathway antagonist-induced cleft lip and palate

Subtle behavioral and cognitive deficits have been documented in patient cohorts with orofacial clefts (OFCs). Recent neuroimaging studies argue that these traits are associated with structural brain abnormalities but have been limited to adolescent and adult populations where brain plasticity during infancy and childhood may be a confounding factor. Here, we employed high resolution magnetic resonance microscopy to examine primary brain morphology in a mouse model of OFCs. Transient in utero exposure to the Hedgehog (Hh) signaling pathway antagonist cyclopamine resulted in a spectrum of facial dysmorphology, including unilateral and bilateral cleft lip and palate, cleft of the secondary palate only, and a non-cleft phenotype marked by midfacial hypoplasia. Relative to controls, cyclopamine-exposed fetuses exhibited volumetric differences in several brain regions, including hypoplasia of the pituitary gland and olfactory bulbs, hyperplasia of the forebrain septal region, and expansion of the third ventricle. However, in affected fetuses the corpus callosum was intact and normal division of the forebrain was observed. This argues that temporally-specific Hh signaling perturbation can result in typical appearing OFCs in the absence of holoprosencephaly--a condition classically associated with Hh pathway inhibition and frequently co-occurring with OFCs. Supporting the premise that some forms of OFCs co-occur with subtle brain malformations, these results provide a possible ontological basis for traits identified in clinical populations. They also argue in favor of future investigations into genetic and/or environmental modulation of the Hh pathway in the etiopathogenesis of orofacial clefting.

prdm12b specifies the p1 progenitor domain and reveals a role for V1 interneurons in swim movements

Proper functioning of the vertebrate central nervous system requires the precise positioning of many neuronal cell types. This positioning is established during early embryogenesis when gene regulatory networks pattern the neural tube along its anteroposterior and dorsoventral axes. Dorsoventral patterning of the embryonic neural tube gives rise to multiple progenitor cell domains that go on to differentiate unique classes of neurons and glia. While the genetic program is reasonably well understood for some lineages, such as ventrally derived motor neurons and glia, other lineages are much less characterized. Here we show that prdm12b, a member of the PR domain containing-family of transcriptional regulators, is expressed in the p1 progenitor domain of the zebrafish neural tube in response to Sonic Hedgehog signaling. We find that disruption of prdm12b function leads to dorsal expansion of nkx6.1 expression and loss of p1-derived eng1b-expressing V1 interneurons, while the adjacent p0 and p2 domains are unaffected. We also demonstrate that prdm12b-deficient fish exhibit an abnormal touch-evoked escape response with excessive body contractions and a prolonged response time, as well as an inability to coordinate swimming movements, thereby revealing a functional role for V1 interneurons in locomotor circuits. We conclude that prdm12b is required for V1 interneuron specification and that these neurons control swimming movements in zebrafish.

[Indian Hedgehog signaling is involved in the stretch induced proliferation of osteoblast]

OBJECTIVE

To observe the role of the Hedgehog (Hh) genes in the proliferation of osteoblasts upon mechanical tensile strains.

METHODS

Primary osteoblasts harvested from newborn rat calvarial bone were subjected to 3% and 6% elongation of tensile stretches using Flexcell 4000 strain unit. The cultures were also treated with either recombinant N-terminals Sonic Hedgehog (N-Shh) or cyclopamine (cy), a Hh inhibitor or gadolinium (GdCl3), an inhibitor of stretch-activated channels. The proliferation of osteoblasts was quantified by cell counting, methyl thiazolyl tetrazolium (MTT) and cell cycle detection via flow cytometry. Statistical analysis was performed using SAS 8.0 software package.

RESULTS

The tensile strain, especially under 6% elongation, promoted osteoblast proliferation. Stretching force could also promote the proliferation even when the cells were treated with cy, but this effect was suppressed by GdCl3.

CONCLUSION

The induced proliferation of osteoblasts by mechanical stretched is mediated at least in part by Indian Hedgehog (Ihh) signaling.

The side population in human lung cancer cell line NCI-H460 is enriched in stem-like cancer cells

Lung cancer is among the most lethal malignancies with a high metastasis and recurrence rate. Recent studies indicate that tumors contain a subset of stem-like cancer cells that possess certain stem cell properties. Herein, we used Hoechst 33342 dye efflux assay and flow cytometry to isolate and characterize the side population (SP) cells from human lung cancer cell line NCI-H460 (H460). We show that the H460 SP cells harbor stem-like cells as they can readily form anchorage-independent floating spheres, possess great proliferative potential, and exhibit enhanced tumorigenicity. Importantly, the H460 SP cells were able to self-renew both in vitro and in vivo. Finally, we show that the H460 SP cells preferentially express ABCG2 as well as SMO, a critical mediator of the Hedgehog (HH) signaling, which seems to play an important role in H460 lung cancer cells as its blockage using Cyclopamine greatly inhibits cell-cycle progression. Collectively, our results lend further support to the existence of lung cancer stem cells and also implicate HH signaling in regulating large-cell lung cancer (stem) cells.

[Hedgehog pathway is associated with the proliferation and differentiation of osteoblasts]

PURPOSE

The purpose of this study was to evaluate the effects of Hedgehog signaling pathway on osteoblast proliferation and differentiation.

METHODS

Primary osteoblasts harvested from newborn rat calvarial bone were cultured for 21 days. The temporary expression of Shh and Ihh was detected by RT-PCR. The culture medium was then treated with either a recombinant Shh N-terminals protein (N-Shh) or cyclopamine (cy), a Hedgehog inhibitor. The proliferation of osteoblasts was quantified by MTT and FCM. The osteoblast differentiation and matrix mineralization were evaluated by ALP and Alizarin-Red staining. The expression of Ptch and Smo was quantified by real-time PCR.SAS 8.0 software package was used for statistical analysis.

RESULTS

Osteoblast expressed both Shh and Ihh. The expression level of Shh decreased with culture time while the amount of Ihh expression increased. N-Shh treatment increased the cell population and the number of cells in S phase (P<0.05. N-Shh also promoted ALP activities (P<0.05) and bone matrix calcification. Moreover, N-Shh application led to an increase in Ptch and Smo mRNA level (P<0.05). Treatment with cy, on the other side, inhibited osteoblast proliferation and differentiation(P<0.05).

CONCLUSION

Heghehog signaling pathway is actively involved in regulating osteoblast proliferation and differentiation.

Transgenic zebrafish line with over-expression of Hedgehog on the skin: a useful tool to screen Hedgehog-inhibiting compounds

We generated a transgenic line Tg(k18:shh:RFP) with overexpression of Sonic hedgehog in the skin epidermis. By 5 day-post-fertilization (dpf), many epidermal lesions were clearly observed, including a swollen yolk sac, epidermis growth malformation around the eyes and at the basement of the pectoral fins. Skin histology revealed embryos derived from Tg(k18:shh:RFP) displayed an elevated Nuclear/Cytoplasmic ratio and pleomorphic nuclei compared to their wild type littermates, suggesting the abnormal growth pattern on the epidermis of Tg(k18:shh:RFP) embryos were dysplasia. Later (by 7 dpf), Tg(k18:shh:RFP) embryos displayed broader pectoral fins which are similar to the polydactyly phenotypes of Nevoid basal cell carcinoma syndrome (NBCCS)/Gorlin patients and polydactylous mice. In addition, treatment with cyclopamine is able to enhance and prolong the survival rates and survival durations of Tg(k18:shh:RFP) embryos. In conclusion, this unique Tg(k18:shh:RFP) fish line, should be an excellent experimental animal for screening for a lower toxicity level of the new Hh-inhibitor and can even be used as a new anti-cancer drug-screening platform.

Gli function is essential for motor neuron induction in zebrafish

The Gli family of zinc-finger transcription factors mediates Hedgehog (Hh) signaling in all vertebrates. However, their roles in ventral neural tube patterning, in particular motor neuron induction, appear to have diverged across species. For instance, cranial motor neurons are essentially lost in zebrafish detour (gli1(-)) mutants, whereas motor neuron development is unaffected in mouse single gli and some double gli knockouts. Interestingly, the expression of some Hh-regulated genes (ptc1, net1a, gli1) is mostly unaffected in the detour mutant hindbrain, suggesting that other Gli transcriptional activators may be involved. To better define the roles of the zebrafish gli genes in motor neuron induction and in Hh-regulated gene expression, we examined these processes in you-too (yot) mutants, which encode dominant repressor forms of Gli2 (Gli2(DR)), and following morpholino-mediated knockdown of gli1, gli2, and gli3 function. Motor neuron induction at all axial levels was reduced in yot (gli2(DR)) mutant embryos. In addition, Hh target gene expression at all axial levels except in rhombomere 4 was also reduced, suggesting an interference with the function of other Glis. Indeed, morpholino-mediated knockdown of Gli2(DR) protein in yot mutants led to a suppression of the defective motor neuron phenotype. However, gli2 knockdown in wild-type embryos generated no discernable motor neuron phenotype, while gli3 knockdown reduced motor neuron induction in the hindbrain and spinal cord. Significantly, gli2 or gli3 knockdown in detour (gli1(-)) mutants revealed roles for Gli2 and Gli3 activator functions in ptc1 expression and spinal motor neuron induction. Similarly, gli1 or gli3 knockdown in yot (gli2(DR)) mutants resulted in severe or complete loss of motor neurons, and of ptc1 and net1a expression, in the hindbrain and spinal cord. In addition, gli1 expression was greatly reduced in yot mutants following gli3, but not gli1, knockdown, suggesting that Gli3 activator function is specifically required for gli1 expression. These observations demonstrate that Gli activator function (encoded by gli1, gli2, and gli3) is essential for motor neuron induction and Hh-regulated gene expression in zebrafish.

Staggered cell-intrinsic timing of ath5 expression underlies the wave of ganglion cell neurogenesis in the zebrafish retina

In the developing nervous system, progenitor cells must decide when to withdraw from the cell cycle and commence differentiation. There is considerable debate whether cell-extrinsic or cell-intrinsic factors are most important for triggering this switch. In the vertebrate retina, initiation of neurogenesis has recently been explained by a 'sequential-induction' model--signals from newly differentiated neurons are thought to trigger neurogenesis in adjacent progenitors, creating a wave of neurogenesis that spreads across the retina in a stereotypical manner. We show here, however, that the wave of neurogenesis in the zebrafish retina can emerge through the independent action of progenitor cells--progenitors in different parts of the retina appear pre-specified to initiate neurogenesis at different times. We provide evidence that midline Sonic hedgehog signals, acting before the onset of neurogenesis, are part of the mechanism that sets the neurogenic timer in these cells. Our results highlight the importance of intrinsic factors for triggering neurogenesis, but they also suggest that early signals can modulate these intrinsic factors to influence the timing of neurogenesis many cell cycles later, thereby potentially coordinating axial patterning with control of neuron number and cell fate.

Multiple muscle cell identities induced by distinct levels and timing of hedgehog activity in the zebrafish embryo

BACKGROUND

In the zebrafish embryo, the differentiation of distinct muscle fiber types has been shown to require the activity of members of the Hedgehog (Hh) family of secreted proteins. Evidence from other systems suggests that Hh behaves as a morphogen, inducing cell fates in a concentration-dependent manner. Exactly how Hh signaling contributes to the generation of the correct pattern of cells within the zebrafish myotome, however, has remained obscure.

RESULTS

Here, we distinguish four distinct myotomal cell identities in the zebrafish embryo on the basis of their position, morphology, and gene expression patterns. Using morpholino oligonucleotides (MOs) to diminish the activities of the Hh pathway components Patched (Ptc), Fused (Fu), and Suppressor of Fused (Su(fu)), and the teratogen cyclopamine to inhibit the Hh transducer Smoothened (Smo), we show that the appropriate differentiation of each cell type depends upon the levels and range of Hh signaling within the myotome. In addition, by transiently modulating Hh activity by using cyclopamine and a heat-inducible transgene, we demonstrate that the competence of myotomal cells to respond to Hh changes with time. Finally, we show that the Gli1 and Gli2 transcription factors mediate most of the response of myotomal cells to Hh.

CONCLUSIONS

Hh signaling acts in a dosage-dependent manner to specify cell fate in the zebrafish myotome. Allocation of the correct number of cells to a specific fate depends upon the range of Hh activity. The timing of exposure to Hh determines the response of cells to the signal.

A hedgehog homolog regulates gut formation in leech (Helobdella)

Signaling by the hedgehog (hh)-class gene pathway is essential for embryogenesis in organisms ranging from Drosophila to human. We have isolated a hh homolog (Hro-hh) from a lophotrochozoan species, the glossiphoniid leech, Helobdella robusta, and examined its expression by reverse transcription polymerase chain reaction (RT-PCR) and whole-mount in situ hybridization. The peak of Hro-hh expression occurs during organogenesis (stages 10-11). No patterned expression was detected within the segmented portion of the germinal plate during the early stages of segmentation. In stage 10-11 embryos, Hro-hh is expressed in body wall, foregut, anterior and posterior midgut, reproductive organs and in a subset of ganglionic neurons. Evidence that Hro-hh regulates gut formation was obtained using the steroidal alkaloid cyclopamine, which specifically blocks HH signaling. Cyclopamine induced malformation of both foregut and anterior midgut in Helobdella embryos, and no morphologically recognizable gonads were seen. In contrast, no gross abnormalities were observed in the posterior midgut. Segmental ectoderm developed normally, as did body wall musculature and some other mesodermal derivatives, but the mesenchymal cells that normally come to fill most of the coelomic cavities failed to develop. Taken with data from Drosophila and vertebrates, our data suggest that the role of hh-class genes in gut formation and/or neural differentiation is ancestral to the bilaterians, whereas their role in segmentation evolved secondarily within the Ecdysozoa.

Interactions of veratrum alkaloids, procaine, and calcium with monolayers of stearic acid and their implications for pharmacological action

The interactions of veratridine, cevadine, veracevine, and veratramine with monolayers of stearic acid show marked differences. Veratridine and cevadine, at concentrations that are known from potential, ionic flux, and other measurements to affect living membranes, react strongly with the film and appear to cause an "interfacial dissolution" whereby both the alkaloid and the stearate leave the surface. Veracevine at the same concentration does not interact with the film. The veratramine reaction is weak, much like that of the local anesthetic procaine. The veratridine and cevadine effects are antagonized by 10^-3M Ca⁺⁺, low pH, and 3.7 and 7.4 x 10^-3M procaine. These differences among the veratrum alkaloids and the antagonisms parallel effects observed in living systems. Such parallelism suggests that similar physical interactions are involved in the stearate film and in natural membranes.

Cyclopamine-induced holoprosencephaly and associated craniofacial malformations in the golden hamster: anatomic and molecular events

Holoprosencephaly is a complex congenital malformation of the brain and is often associated with a spectrum of facial anomalies ranging from normocephaly or nondiagnostic changes to cleft lip/palate (premaxillary dysgenesis), cebocephaly, ethmocephaly, and cyclopia. The primary insult is thought to occur during gastrulation, when prechordal mesenchyme and overlying anterior neural plate undergo complex developmental interactions. Exposure to cyclopamine, a steroid isolated from the desert plant Veratrum californicum, causes holoprosencephaly in mammalian embryos. We have begun to study the pathogenesis of cyclopamine-induced holoprosencephaly and associated craniofacial anomalies in Syrian golden hamsters (Mesocricetus auratus). Embryos were exposed to a single maternal dose of cyclopamine during gastrulation on embryonic day (E) 7.0. By E13.0, 62% of fetuses showed craniofacial malformations, including premaxillary dysgenesis, ocular hypotelorism, and cebocephaly. Facial anomalies were associated with absence of the premaxilla and abnormalities of the midline cranial base, particularly the ethmoid and sphenoid bones. Histological sections from cyclopamine-treated embryos at earlier stages showed marked deficiency of cranial mesenchyme derived from the rostral neural crest. Expression of two transcription factors, HNF-3 beta and Hox-b5, which have been implicated in specification of rostral and caudal neural crest cells, respectively, were examined immunohistochemically. Treatment with cyclopamine caused a transient loss of HNF-3 beta immunoreactivity in prechordal mesenchyme, but had no effect on Hox-b5 expression. The findings suggest that an early event in the pathogenesis of cyclopamine-induced holoprosencephaly may be altered expression of selected proteins in the prechordal mesenchyme and floor plate with secondary impaired development of the adjacent neural plate and cranial neural crest.