Systematic review: emotion dysregulation and challenging behavior interventions for children and adolescents on the autism spectrum with graded key evidence-based strategy recommendations

Challenging behavior, such as aggression, is highly prevalent in children and adolescents on the autism spectrum and can have a devastating impact. Previous reviews of challenging behavior interventions did not include interventions targeting emotion dysregulation, a common cause of challenging behavior. We reviewed emotion dysregulation and challenging behavior interventions for preschoolers to adolescents to determine which evidence-based strategies have the most empirical support for reducing/preventing emotion dysregulation/challenging behavior. We reviewed 95 studies, including 29 group and 66 single case designs. We excluded non-behavioral/psychosocial interventions and those targeting internalizing symptoms only. We applied a coding system to identify discrete strategies based on autism practice guidelines with the addition of strategies common in childhood mental health disorders, and an evidence grading system. Strategies with the highest quality evidence (multiple randomized controlled trials with low bias risk) were Parent-Implemented Intervention, Emotion Regulation Training, Reinforcement, Visual Supports, Cognitive Behavioral/Instructional Strategies and Antecedent-Based Interventions. Regarding outcomes, most studies included challenging behavior measures, while few included emotion dysregulation measures. This review highlights the importance of teaching emotion regulation skills explicitly, positively reinforcing replacement/alternative behaviors, using visuals and metacognition, addressing stressors proactively, and involving parents. It also calls for more rigorously designed studies and for including emotion dysregulation as an outcome/mediator in future trials.

A Digital Mental Health App Incorporating Wearable Biosensing for Teachers of Children on the Autism Spectrum to Support Emotion Regulation: Protocol for a Pilot Randomized Controlled Trial

BACKGROUND

As much as 80% of children on the autism spectrum exhibit challenging behaviors (ie, behaviors dangerous to the self or others, behaviors that interfere with learning and development, and behaviors that interfere with socialization) that can have a devastating impact on personal and family well-being, contribute to teacher burnout, and even require hospitalization. Evidence-based practices to reduce these behaviors emphasize identifying triggers (events or antecedents that lead to challenging behaviors); however, parents and teachers often report that challenging behaviors surface with little warning. Exciting recent advances in biometric sensing and mobile computing technology allow the measurement of momentary emotion dysregulation using physiological indexes.

OBJECTIVE

We present the framework and protocol for a pilot trial that will test a mobile digital mental health app, the KeepCalm app. School-based approaches to managing challenging behaviors in children on the autism spectrum are limited by 3 key factors: children on the autism spectrum often have difficulties in communicating their emotions; it is challenging to implement evidence-based, personalized strategies for individual children in group settings; and it is difficult for teachers to track which strategies are successful for each child. KeepCalm aims to address those barriers by communicating children's stress to their teachers using physiological signaling (emotion dysregulation detection), supporting the implementation of emotion regulation strategies via smartphone pop-up notifications of top strategies for each child according to their behavior (emotion regulation strategy implementation), and easing the task of tracking outcomes by providing the child's educational team with a tool to track the most effective emotion regulation strategies for that child based on physiological stress reduction data (emotion regulation strategy evaluation).

METHODS

We will test KeepCalm with 20 educational teams of students on the autism spectrum with challenging behaviors (no exclusion based on IQ or speaking ability) in a pilot randomized waitlist-controlled field trial over a 3-month period. We will examine the usability, acceptability, feasibility, and appropriateness of KeepCalm as primary outcomes. Secondary preliminary efficacy outcomes include clinical decision support success, false positives or false negatives of stress alerts, and the reduction of challenging behaviors and emotion dysregulation. We will also examine technical outcomes, including the number of artifacts and the proportion of time children are engaged in high physical movement based on accelerometry data; test the feasibility of our recruitment strategies; and test the response rate and sensitivity to change of our measures, in preparation for a future fully powered large-scale randomized controlled trial.

RESULTS

The pilot trial will begin by September 2023.

CONCLUSIONS

Results will provide key data about important aspects of implementing KeepCalm in preschools and elementary schools and will provide preliminary data about its efficacy to reduce challenging behaviors and support emotion regulation in children on the autism spectrum.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05277194; https://www.clinicaltrials.gov/ct2/show/NCT05277194.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/45852.

Systematic Review: Emotion Dysregulation and Challenging Behavior Interventions for Children andAdolescents with Autism with Graded Key Evidence-Based Strategy Recommendations

Challenging behavior, such as aggression, is highly prevalent in children and adolescents with autism and can have a devastating impact. Previous reviews of challenging behavior interventions did not include interventions targeting emotion dysregulation, a common cause of challenging behavior. We reviewed emotion dysregulation and challenging behavior interventions for preschoolers to adolescents to determine which evidence-based strategies have the most empirical support for reducing/preventing emotion dysregulation/challenging behavior. We reviewed 95 studies, including 29 group and 66 single-case designs. We excluded non-behavioral/psychosocial interventions and those targeting internalizing symptoms only. We applied a coding system to identify discrete strategies based on autism practice guidelines with the addition of strategies common in childhood mental health disorders, and an evidence grading system. Strategies with the highest quality evidence (multiple randomized controlled trials with low bias risk) were Parent-Implemented Intervention, Emotion Regulation Training, Reinforcement, Visual Supports, Cognitive Behavioral/Instructional Strategies and Antecedent-Based Interventions. Regarding outcomes, most studies included challenging behaviors measures while few included emotion dysregulation measures. This review highlights the importance of teaching emotion-regulation skills explicitly, positively reinforcing replacement/alternative behaviors, using visuals and metacognition, addressing stressors proactively, and involving parents. It also calls for more rigorously-designed studies and for including emotion dysregulation as an outcome/mediator in future trials.

Risk of Poor Neonatal Adaptation Syndrome Among Infants Exposed to Second-Generation Atypical Antipsychotics Compared to Antidepressants: Results From the National Pregnancy Registry for Psychiatric Medications

Objective: While poor neonatal adaptation syndrome (PNAS) has been particularly well described among infants exposed to antidepressants, specifically selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs), this is not the case for second-generation antipsychotics (SGAs). In 2011, the US Food and Drug Administration (FDA) issued a drug safety warning regarding fetal antipsychotic exposure and risk for PNAS and extrapyramidal symptoms (EPS). The primary objective of this study was to examine the risk for PNAS among infants exposed to SGAs compared to SSRI/SNRI-exposed infants, leveraging the prospective, longitudinal design of the National Pregnancy Registry for Psychiatric Medications (NPRPM). Methods: The NPRPM is a prospective pharmacovigilance program in which pregnant women, aged 18-45 years, are enrolled and followed prospectively. Medical records were systematically reviewed and data abstracted using a checklist of PNAS and EPS symptoms specifically outlined in the FDA drug safety warning. The two study groups included infants exposed to an SGA during pregnancy and infants exposed to an SSRI/SNRI during pregnancy. The primary outcome was the presence of at least one or more PNAS symptoms during the first month of life. Other neonatal outcomes following exposure to the medication of interest, including preterm birth, neonatal intensive care unit (NICU) admission, rates of EPS, and whether infants were discharged home with their mothers, are also reported. Results: Of the 2,145 women enrolled in this study as of December 16, 2020, a total of 373 women and their infants (n = 384) were eligible for inclusion (n = 193 SGA-exposed infants and 191 SSRI/SNRI-exposed infants). Among SGA-exposed infants, 32.6% (63/193) experienced at least 1 PNAS sign compared to 34.6% of infants (66/191) in the SSRI/SNRI-exposed group. The majority of infants in each group showed no symptoms of PNAS. No differences were observed between the two groups with respect to rates of preterm birth, NICU admission, prevalence of EPS, and timing of infants being discharged home with their mothers. Conclusions: PNAS symptomatology was comparable among infants exposed prenatally to an SGA or to an SSRI/SNRI. These preliminary findings provide an estimated risk of PNAS among infants exposed to SGAs of roughly 30%. Interestingly, these findings are also consistent with estimates in the literature of PNAS in SSRI/SNRI-exposed infants, suggesting a possible common pathway underlying this phenomenon. Trial Registration: ClinicalTrials.gov identifier: NCT01246765.

Correction. Reproductive Safety of Second-Generation Antipsychotics: Updated Data From the Massachusetts General Hospital National Pregnancy Registry for Atypical Antipsychotics

This corrects the article DOI: 10.4088/JCP.20m13745.

Reproductive Safety of Second-Generation Antipsychotics: Updated Data From the Massachusetts General Hospital National Pregnancy Registry for Atypical Antipsychotics

Objective: Second-generation antipsychotics (SGAs) are prescribed for a wide range of indications in women of reproductive age. The National Pregnancy Registry for Atypical Antipsychotics (NPRAA) was established to determine the risk of major malformations among infants exposed to these medications during the first trimester relative to a comparison group of unexposed infants of mothers with histories of psychiatric morbidity. Methods: Women, aged 18-45 years, with histories of psychiatric illness were prospectively followed through pregnancy and during the postpartum period. Pediatric and maternal medical records were obtained and screened for evidence of major malformations. Potential cases were adjudicated by a dysmorphologist who was blinded to drug exposure.. Recruitment to the Registry, which is based at the Ammon-Pinizzotto Center for Women's Mental Health at Massachusetts General Hospital (MGH), includes nationwide provider referral, self-referral, and advertisement through the MGH Center for Women's Mental Health website. Results: As of April 9, 2020, 1,906 women had enrolled, including 889 in the exposure group and 1,017 controls. A total of 1,311 women completed the study and were eligible for inclusion in the analysis. Medical records were obtained for 81.3% of participants. Among 640 live births in the exposure group, 16 (2.50%) had confirmed major malformations reported, and among 704 live births in the control group, 14 (1.99%) had confirmed major malformations reported. The estimated odds ratio for major malformations comparing exposed and unexposed infants was 1.48 (95% CI, 0.625-3.517). Conclusions: Data from the Registry assessing SGAs as a class indicate that they are unlikely to have a major teratogenic effect. These findings provide pertinent information for women and their health care providers regarding decisions about atypical antipsychotic use during pregnancy. Trial Registration: ClinicalTrails.gov identifier: NCT01246765.

Reproductive safety of aripiprazole: data from the Massachusetts General Hospital National Pregnancy Registry for Atypical Antipsychotics

Aripiprazole has become one of the most commonly prescribed psychotropics, making a more comprehensive understanding of its reproductive safety profile a priority. The goal of the current analysis was to determine the risk of major malformations in infants exposed during the first trimester of pregnancy to aripiprazole compared to infants whose mothers had psychiatric diagnoses but did not use an atypical antipsychotic during pregnancy. The National Pregnancy Registry for Atypical Antipsychotics is a prospective pharmacovigilance program in which pregnant women are enrolled and interviewed during pregnancy and the postpartum period. Medical records are assessed to confirm presence or absence of major malformations. Pregnant women ages 18-45 with psychiatric diagnoses are enrolled. As of April 2020, N = 848 women who had delivered infants were eligible for analyses. A total of 158 women with first trimester exposure to aripiprazole were compared to 690 controls. For 163 infants born to women in the exposed group, seven major malformations were confirmed (4.29%), compared to fourteen of the 690 unexposed infants (1.99%). The unadjusted odds ratio for major malformations between aripiprazole-exposed and unexposed infants was 2.21 (95% confidence interval [CI] = (0.88, 5.57) The adjusted odds ratio for major malformations was 1.35 (95% confidence interval [CI] = (0.43, 4.20). After adjustment for confounding variables, the risk of major malformations after first trimester exposure to aripiprazole was not significant compared to controls. While these results are reassuring, they are limited by relatively small numbers of participants. Future analyses with larger numbers are expected to provide more of a complete and precise reproductive safety profile regarding aripiprazole use during pregnancy. Trial registration: clinicaltrials.gov NCT01246765.

In vivo and in vitro assessment of mitogen activated protein kinase involvement during quail secondary palate formation

Spatiotemporally regulated cell proliferation and differentiation are crucial for the successful completion of morphogenesis of the vertebrate secondary palate. An understanding of the mechanisms by which these cellular phenomena are regulated during palate development involves the identification of the various signal transduction pathways. In the present study, the presence and activation of mitogen-activated protein (MAP) kinases were investigated during the development of quail secondary palate. The palatal shelves were dissected on days 5-9 of incubation, homogenized, and centrifuged, after which the samples were separated by anion exchange fast protein liquid chromatography. The fractions were analyzed for myelin basic protein (MBP) phosphorylation. In addition, primary cultures of quail palate mesenchymal cells (QPMCs) were treated with epidermal growth factor (EGF) and prepared for MBP phosphorylation assays. A temporally regulated pattern of phosphotransferase activity, characterized by a three-fold increase in phosphotransferase activity toward MBP between days 5 and 8 of incubation, was observed during quail palate development. Western blotting, using MAP kinase antibodies, demonstrated the presence of a 42-kDa isoform between days 5 and 9 of incubation, during which the level of protein remained constant. Antityrosine immunoblotting with 4G10 also detected a 42-kDa protein. Phosphotransferase assays, using either a MAP kinase-specific substrate peptide (S5) or a protein kinase C inhibitor (R3), further confirmed the presence of a MAP kinase in the developing palate of quail. Because diverse biological processes occur concurrently during in vivo palate morphogenesis, the involvement of MAP kinase was explored further in primary cell culture. The data showed that EGF stimulated proliferation and activated 42-kDa MAP kinase in QPMCs. It is suggested that MAP kinase cascade may be involved in growth factor-regulated cell proliferation during morphogenesis of quail secondary palate.

The activation of MAP kinase during vertical palatal shelf development in hamster

Mitogen-activated protein (MAP) kinase has been implicated in signal transduction pathways that regulate cell cycle progression during the proliferation of eukaryotic cells. Previous studies have shown that a rapid burst of cell proliferation is a major event of the development of mammalian palatal shelves in a vertical direction. The present study analyzed the involvement of MAP kinase during the vertical development of the secondary palate in hamster. Palates were dissected at various times between days 10:00 and 12:00 of gestation, homogenized, centrifuged and fractionated on a Mono Q column by fast protein liquid chromatography. The fractions were assayed for phosphotransferase activity toward myelin basic protein, and also toward a synthetic peptide APRTPGGRR (S5), which was more specifically utilized by MAP kinase. The data showed that MAP kinase activity increased during the initial phase, i.e., between days 10:00 and 11:12, and then decreased during the latter half of vertical palate development, i.e., between days 11:12, and 12:00 of gestation. Western blotting studies, using antibodies raised against the subdomain I ATP binding sequence (GEGA), subdomain III (ERK1-III), and the C-terminus (ERK1-CT) of MAP kinases, demonstrated the presence of both the 42-kDa and 44-kDa MAP kinase isoforms between days 10:12 and 12:12 of gestation. A monoclonal antibody (4G10), which detects phosphotyrosine, demonstrated phosphorylation of both the 42-kDa and 44-kDa isoforms. The amount of protein remained constant during vertical palatal shelf development indicating that the differential activity of MAP kinase was most likely due to post-translational modification (i.e., phosphorylation). There was a good correlation between the temporal expression of MAP kinase activity and the rates of cell proliferation in the developing vertical palate suggesting a possible involvement of MAP kinase in regulation of cell proliferation during secondary palate development.

Developmental alterations in casein kinase 2 activity during the morphogenesis of quail secondary palate

BACKGROUND

During the progression of avian secondary palate morphogenesis, the rate of cell proliferation declines, whereas the production and accumulation of extracellular matrices increases. To investigate the regulation of these events, we examined the quail secondary palate for the activity of casein kinase 2 (CK 2), a pleiotropic serine/threonine second messenger independent enzyme implicated in cell growth and differentiation.

METHODS

Quail palatal shelves were dissected between days 5 and 9 of incubation, which is the period of palate morphogenesis in quail, and prepared either for light microscopic observations or homogenized, cleared by ultracentrifugation, and then subjected to fractionation on a MonoQ column by fast protein liquid chromatography and Western immunoblotting.

RESULTS

Histological examination showed that the palatal shelves appeared on day 5 of incubation and approximated by day 8 of incubation. Fractionation of palate extract using a Mono-Q column revealed the presence of a major peak of phosvitin phosphotransferase activity which eluted with 0.5 M NaCl. This activity peak coincided with the presence of a 42 kDa subunit of CK 2 as determined by Western blotting with a CK 2 specific antibody. The CK 2 activity towards phosvitin was elevated on days 5 and 6 and then rapidly declined by day 9. The decrease in CK 2 activity did not correlate with a decrease in CK 2 protein during palate development indicating that the differential activity of the CK 2 enzyme observed during quail palate development may be due to post-translational modifications of the enzyme. A high positive correlation was found between the CK 2 phosphotransferase activity and both the proliferation index and DNA synthesis during palate development.

CONCLUSION

On the basis of literature analysis and the results of the present study, it was suggested that the activity of CK 2 may be regulated along with protein kinase A to coordinate cell proliferation and the synthesis of extracellular matrices during palate development in quail.

Changes in casein kinase 2 activity during development of the secondary palate in the hamster

BACKGROUND

Casein kinase 2 (CK 2) is a serine/threonine kinase that has been ubiquitously conserved in all eukaryotic cells. The exact functions of this enzyme have not yet been clarified; however, studies have repeatedly suggested that it may play crucial roles in the regulation of cell proliferation. During the formation of the secondary palate in the hamster, bursts of cell proliferation occur during the initial half of vertical shelf development, which decrease during the subsequent steps of palate morphogenesis, thus indicating that the cell cycle in the developing vertical palate may be tightly regulated.

METHODS

In the present study, palatal shelves were dissected at 12-hour intervals between days 10 and 12 of gestation, which is the period of vertical shelf development in the hamster. The palates were homogenized and cleared by ultracentrifugation and the resultant supernatants were fractionated on a Mono Q column by fast protein liquid chromatography.

RESULTS

Using phosvitin as a substrate, the phosphotransferase activity in the fractionated samples decreased steadily from days 10 to 11, increased to a fivefold peak on day 11:12, and then decreased on day 12 of gestation. Western blot analysis using two CK 2 specific antibodies demonstrated that both the 42-kDa (alpha) and the 38-kDa (alpha') subunits of the CK 2 holoenzyme were found throughout the formation of the vertical palatal shelves in the hamster. The amount of alpha and alpha' subunits appears to remain constant, which suggested that the differential activity of the CK 2 enzyme may be due to posttranslational modifications. CK 2 activity correlated well with DNA synthesis (i.e., cell proliferation) rates from days 10 to 11, but not from days 11 to 12 of gestation.

CONCLUSIONS

It is proposed that the activity of CK 2 may regulate the rate of cell proliferation by stimulation of progression through G1 phase of the cell cycle and may also relate to the effects of various growth factors during the vertical development of mammalian palate.

In vivo/in vitro studies on the effects of cyclophosphamide on growth and differentiation of hamster palate

A study was undertaken to examine the effects of cyclophosphamide (CP) on growth and differentiation of palatal tissues. An in vivo/in vitro approach was designed to analyze (1) whether the damage caused by in vivo administration of CP in the developing palate can be altered in vitro, and (2) to determine the effects of CP on the synthesis of collagen and glycosaminoglycan (GAG), which are essential for proper palate development. In addition, effects of vitamin B1 and/or B6 on in vivo modulation of CP teratogenicity was evaluated. Pregnant hamsters were given 30 mg/kg CP or 1 ml saline on day 10 of gestation. Control and CP-treated embryonic palates were dissected on day 11 of gestation and incubated in vitro in the presence or absence of CP. In order to allow metabolic activation of CP in vitro, either a slice of hamster liver or microsomal S9 fraction of liver was added to the culture medium. To study collagen and GAG synthesis, palates were obtained between days 10 and 13 of gestation, and incubated in growth medium supplemented with [14C]proline or [3H]glucosamine, as appropriate. The rates of collagen and GAG synthesis were determined. The results showed that, in the controls, the presence of a liver slice or S9 fraction in the culture medium had no effects on in vitro closure of palate. In vivo CP exposed palates did not fuse in vitro. When drug was given in vitro, or both in vivo and in vitro, palatal closure did not occur. CP reduced synthesis of both collagen and GAG in the vertically developing palate. The drug-treated shelves reoriented only after the rates of collagen and GAG synthesis were restored to the levels comparable to the control counterparts. Co-administration of vitamin B1 and B6 did not interfere with the teratogenicity of CP. It was suggested that CP treatment affected DNA synthesis and injured growing cells, which in turn reduced the synthesis of GAG and collagen and affected the expansion of shelf volume to delay the reorientation of the palatal shelves. Furthermore, it appears that in vivo treatment with CP changes the programming of palatal tissues to prevent the fusion process in vivo, which could not be altered in vitro.

Analysis of cell proliferation kinetics during the secondary palate development in quail

A study was undertaken to analyze the spatio-temporal pattern of mesenchymal cell proliferation in the developing palate of quail. Quail embryos were grown in shell-less culture. The developing palates were labelled with 3H-thymidine between culture days 2-6 (which corresponded in vivo incubation days 5-9), and processed for light microscopic autoradiography. Percent labelled mesenchymal cells were determined. The data showed that, as in mammals, a high rate of random cell proliferation in mesenchyme was a major component of early palate development in quail. As the palate morphogenesis advanced, the rate of cell proliferation declined. Segmental analysis, however, indicated that, in contrast to mammals, the mesenchymal cell proliferation rates continually changed in various regions of quail palate during morphogenesis. It was suggested that the spatio-temporal changes in the distribution of dividing cells may reflect differences in the timings of cell cycles between various segments, thus resulting in a heterogeneous population of cells in the developing palate of quail. Further, the differences in the segmental pattern of cell proliferation between birds and mammals may form the basis for differences in the morphogenesis of their palates.

A novel approach to the growth analysis of hamster secondary palate by histone 3 mRNA in situ hybridization

A study was undertaken to determine the cell proliferation kinetics during the development of hamster vertical palatal shelf ad initium. Hamster embryo heads, obtained at different times between days 10 and 12 of gestation (which is the period of vertical shelf development) were processed and sectioned to localize histone 3 mRNA, a cell cycle specific gene, by in situ hybridization. Sense and antisense 35S-labelled histone 3 riboprobes were used as hybridization probes. Percent labelled cells were determined. The results showed that a high rate of random proliferation of both epithelial and mesenchymal cells was a major component of early vertical palatal growth. Subsequently, during the latter half of vertical shelf development, the proliferation rates of the epithelial and mesenchymal cells were different in a region specific manner. It was suggested that the spatio-temporal changes in the distribution of cycling mesenchymal and epithelial cells during vertical palate development may indicate their heterogeneity for subsequent segregation into appropriate phenotypes.

A comparative study on the effects of 5-fluorouracil on glycosaminoglycan synthesis during palate development in quail and hamster

A comparative study was undertaken to investigate the effects of 5-fluorouracil (FU) on glycosaminoglycans (GAG) synthesis during morphogenesis of the secondary palate in birds (where, unlike mammals, palate morphogenesis begins in a horizontal direction ad initium and lacks mammalian-type shelf reorientation) and mammal. Previous studies have shown that FU induces cleft palate in both birds and mammals. Air sacs of quail eggs were injected with 100 micrograms FU in 0.1 ml saline or 0.1 ml saline only. Hamsters were given intramuscular injection of 81 mg/kg FU in 1 ml saline or 1 ml saline only. Total GAG synthesis was measured by incorporation of 3H-glucosamine. Sulfated and non-sulfated GAGs were identified by Alcian Blue histochemistry combined with the use of GAG-degrading enzymes. The results indicated that a continuous synthesis of GAG at a steady rate was associated with normal palate morphogenesis in both quail and hamster. The amount of GAG synthesized in hamster palate was four-fold higher than in quail palate. In contrast to the developing hamster palate where the predominant GAG was hyaluronate, the major GAGs present during quail palate development were sulfated and were concentrated on the nasal side. FU treatment did not affect the rate of GAG synthesis in the developing palate of quail. In contrast, FU administration altered the rates of GAG synthesis, and affected hyaluronate accumulation, during palate morphogenesis in hamster.(ABSTRACT TRUNCATED AT 250 WORDS)

Genesis of hadacidin-induced cleft palate in hamster: morphogenesis, electron microscopy, and determination of DNA synthesis, cAMP, and enzyme acid phosphatase

A morphological, electron microscopic, and biochemical study was undertaken to analyze the genesis of hadacidin-induced cleft palate in hamster fetuses. Gross and light microscopic observations indicated that hadacidin affected the growth of vertical palatal shelves to induce cleft palate. Electron microscopic observations showed that initial hadacidin-induced changes were seen in the mesenchymal cells. Within 12 hr of drug administration, the perinuclear space was swollen and a lysosomal response injury was evident in the mesenchymal cells. Subsequently, 24 hr after hadacidin treatment, lysosomes appeared in the epithelial cells; changes were also seen in the basal lamina which included separation of the lamina densa from the basal cells, duplication of lamina densa, and complete loss of basal lamina. Between 36 and 42 hr post-treatment, the cellular and basal lamina changes subsided, and the epithelium of vertical shelves underwent stratification. Biochemical determination of enzyme acid phosphatase indicated that the levels of enzyme activity in both the control and treated palatal tissues corresponded to the appearance of lysosomes. Measurement of cAMP levels suggested that the peak activity of cAMP corresponded to that of enzyme acid phosphatase and cell injury. The cAMP activity in hadacidin-injured cells, however, was significantly lower in comparison to that of the dying cells of control palates. Hadacidin treatment also affected DNA synthesis in the developing primordia of the palate. It was suggested that hadacidin injures the precursor cells of the palate prior to the appearance of the primordia, and subsequently affects their proliferative behavior, stunting the vertical growth of the palatal shelves and inducing a cleft palate.