Comparison of the Efficacy of HSK3486 and Propofol for Induction of General Anesthesia in Adults: A Multicenter, Randomized, Double-blind, Controlled, Phase 3 Noninferiority Trial.

BACKGROUND: Propofol is an intravenous anesthetic associated with hypotension, respiratory depression, and injection-site pain. HSK3486 injectable emulsion (ciprofol) is a 2,6-disubstituted phenol derivative with fast onset and quick, stable recovery. Previous studies support HSK3486 as an effective, safe anesthetic with substantially less injection-site pain than propofol. The primary objective of this study was to investigate the noninferiority of HSK3486 compared with propofol in successful general anesthesia induction. METHODS: Two hundred fifty-five participants were enrolled in HSK3486-304, a multicenter, randomized (2:1), double-blind, propofol-controlled, phase 3 study evaluating HSK3486 for general anesthesia induction in adults undergoing elective surgery with tracheal intubation. The primary endpoint was successful anesthesia induction, defined as 1 or less on the Modified Observer's Assessment of Alertness/Sedation scale. Key secondary endpoints were proportion of participants with injection-site pain on the Numerical Rating Scale of 1 or greater and a composite endpoint, including the proportion of participants successfully induced while maintaining the desired anesthetic depth and without substantial cardiac and respiratory events. Safety endpoints included adverse events, abnormal vital signs, and injection-site pain. RESULTS: Two hundred fifty-one participants (HSK3486, n = 168; propofol, n = 83) were included in the analyses. General anesthesia was successfully induced in 97.0% versus 97.6% of participants with HSK3486 and propofol, respectively. The difference in success rate was -0.57% (95% CI, -5.4 to 4.2%); the noninferiority boundary of -8% was not crossed. Thirty participants (18.0%) had injection-site pain with HSK3486 versus 64 (77.1%) with propofol (P < 0.0001). Eighty-one participants (48.2%) with HSK3486 versus 42 (50.6%) with propofol (P = 0.8780) satisfied the composite endpoint. When injection-site pain was excluded, the incidence of treatment-emergent adverse events related to study drug was 17.9% for HSK3486 and 14.5% for propofol. CONCLUSIONS: The study met its primary objective and endpoint, demonstrating noninferiority of HSK3486 compared with propofol in successful anesthetic induction. Substantially less injection-site pain was associated with HSK3486 than with propofol.

Henoch-Schönlein purpura in the setting of COVID-19 infection: Two pediatrics cases and review of the literature.

Henoch-Schönlein purpura (HSP) is the most common systemic vasculitis in children, often following a viral infection. Various types of rashes attributed to COVID-19 infection have been described in the literature; however, HSP has rarely been reported. We report two children with HSP associated with acute COVID-19 infection with a review of the available literature. We highlight the clinical presentation, medical management, outcome and age-related difference of reported patients. A limitation of this article is the retrospective nature, limiting full patient history and associated conditions. The findings of this review show that HSP in the setting of COVID-19 is more common in children than adults, with a male predominance, involving various body systems creating a constellation of presentations. Given that HSP can have long-term morbidity from renal disease if untreated, this review may help guide the practitioner's approach to HSP and recognition in the setting of COVID-19 infection.

Early death from childhood cancer: First medical record-level analysis reveals insights on diagnostic timing and cause of death.

BACKGROUND: Approximately 7.5% of pediatric cancer deaths occur in the first 30 days post diagnosis, termed early death (ED). Previous database-level analyses identified increased ED in Black/Hispanic patients, infants, late adolescents, those in poverty, and with specific diagnoses. Socioeconomic and clinical risk factors have never been assessed at the medical record level and are poorly understood. METHODS: We completed a retrospective case-control study of oncology patients diagnosed from 1995 to 2016 at Children's Hospital Colorado. The ED group (n = 45) was compared to a non-early death (NED) group surviving >31 days, randomly selected from the same cohort (n = 44). Medical records and death certificates were manually reviewed for sociodemographic and clinical information to identify risk factors for ED. RESULTS: We identified increased ED risk in central nervous system (CNS) tumors and, specifically, high-grade glioma and atypical teratoid/rhabdoid tumor. There was prolonged time from symptom onset to seeking care in the ED group (29.4 vs. 9.8 days) with similar time courses to diagnosis thereafter. Cause of death was most commonly from tumor progression in brain/CNS tumors and infection in hematologic malignancies. CONCLUSIONS: In this first medical record-level analysis of ED, we identified socioeconomic and clinical risk factors. ED was associated with longer time from first symptoms to presentation, suggesting that delayed presentation may be an addressable risk factor. Many individual patient-level risk factors, including socioeconomic measures and barriers to care, were unable to be assessed through record review, highlighting the need for a prospective study to understand and address childhood cancer ED.

Integration of Gross Anatomy, Histology, and Pathology in a Pre-matriculation Curriculum: A Triple-Discipline Approach.

In recent years, many schools have cut back on their teaching and laboratory hours, and courses in the anatomical sciences are more integrated into the horizontal and longitudinal curriculums. Traditionally, teaching in anatomical science classes consists of lectures and laboratory sessions. Usually, gross anatomy and histology are the two main courses in pre-matriculation programs. The summer pre-matriculation program at the University of Mississippi Medical Center (UMMC) was designed to better prepare students for success in their first year of medicine and dentistry. The course provided these students with an opportunity to study gross anatomy and histology ahead of time and develop their learning skills for the coming academic year. Historically, gross anatomy and histology courses have been taught separately with a different emphasis. We have designed a new approach to implement gross anatomy, histology, and pathology-all three disciplines-in a single lecture in the organ section of the histology course. This triple-discipline (triple lecture) approach allows three professors in anatomy, histology, and pathology to work together in a two-and-a-half-hour review lecture. This approach allows students to develop their critical thinking skills and better prepares them to transfer basic anatomic knowledge into their future clinical practice. Students indicated this was their first experience with the triple-discipline approach, and they remarked that it helped them integrate anatomy and histology as well as demonstrate the clinical importance of the structures and organs. This approach can be used at different stages of medical education and helps faculty and students better integrate various disciplines and is more suitable in the modern curriculum. A similar approach was used in our fourth year course in medical histology.

A phase 2 study of interleukin-22 and systemic corticosteroids as initial treatment for acute GVHD of the lower GI tract.

Graft-versus-host disease (GVHD) is a major cause of morbidity and mortality following allogeneic hematopoietic transplantation. In experimental models, interleukin-22 promotes epithelial regeneration and induces innate antimicrobial molecules. We conducted a multicenter single-arm phase 2 study evaluating the safety and efficacy of a novel recombinant human interleukin-22 dimer, F-652, used in combination with systemic corticosteroids for treatment of newly diagnosed lower gastrointestinal acute GVHD. The most common adverse events were cytopenias and electrolyte abnormalities, and there were no dose-limiting toxicities. Out of 27 patients, 19 (70%; 80% confidence interval, 56%-79%) achieved a day-28 treatment response, meeting the prespecified primary endpoint. Responders exhibited a distinct fecal microbiota composition characterized by expansion of commensal anaerobes, which correlated with increased overall microbial α-diversity, suggesting improvement of GVHD-associated dysbiosis. This work demonstrates a potential approach for combining immunosuppression with tissue-supportive strategies to enhance recovery of damaged mucosa and promote microbial health in patients with gastrointestinal GVHD. This trial was registered at www.clinicaltrials.gov as NCT02406651.

Role of macrophages in HIV pathogenesis and cure: NIH perspectives.

Macrophages play a significant role in HIV infection and contribute to pathogenesis of comorbidities as well as establishment of the viral reservoir in people living with HIV. While CD4+ T cells are considered the main targets of HIV infection, infected macrophages resist the cytopathic effects of infection, contributing to the persistent HIV reservoir. Furthermore, activated macrophages drive inflammation and contribute to the development of comorbidities, including HIV-associated CNS dysfunction. Better understanding the role of macrophages in HIV infection, persistence, and comorbidities can lead to development of innovative therapeutic strategies to address HIV-related outcomes in people living with HIV. In October 2021, the National Institute of Mental Health and the Ragon Institute of MGH, MIT, and Harvard conducted a virtual meeting on role of macrophages in HIV infection, pathogenesis, and cure. This review article captures the key highlights from this meeting and provides an overview of interests and activities of various NIH institutes involved in supporting research on macrophages and HIV.

Small intestinal immunopathology and GI-associated antibody formation in hereditary alpha-tryptasemia.

BACKGROUND: Hereditary alpha-tryptasemia (HαT) is characterized by elevated basal serum tryptase due to increased copies of the TPSAB1 gene. Individuals with HαT frequently present with multisystem complaints, including anaphylaxis and seemingly functional gastrointestinal (GI) symptoms. OBJECTIVE: We sought to determine the prevalence of HαT in an irritable bowel syndrome cohort and associated immunologic characteristics that may distinguish patients with HαT from patients without HαT. METHODS: Tryptase genotyping by droplet digital PCR, flow cytometry, cytometry by time-of-flight, immunohistochemistry, and other molecular biology techniques was used. RESULTS: HαT prevalence in a large irritable bowel syndrome cohort was 5% (N = 8/158). Immunophenotyping of HαT PBMCs (N ≥ 27) revealed increased total and class-switched memory B cells. In the small bowel, expansion of tissue mast cells with expression of CD203c, HLA-DR, and FcεRI, higher intestinal epithelial cell pyroptosis, and increased class-switched memory B cells were observed. IgG profiles in sera from individuals with HαT (N = 21) significantly differed from those in individuals with quiescent Crohn disease (N = 20) and non-HαT controls (N = 19), with increased antibodies directed against GI-associated proteins identified in individuals with HαT. CONCLUSIONS: Increased mast cell number and intestinal epithelial cell pyroptosis in the small intestine, and class-switched memory B cells in both the gut and peripheral blood associated with IgG reactive to GI-related proteins, distinguish HαT from functional GI disease. These innate and adaptive immunologic findings identified in association with HαT are suggestive of subclinical intestinal inflammation in symptomatic individuals.

Factors Associated with Knee Arthroplasty in a Knee Osteoarthritis Patient Cohort Treated with Intra-articular Injections of Hylan G-F 20.

Hylan G-F 20 viscosupplementation can be used to treat knee osteoarthritis pain. This study evaluated time to knee arthroplasty (KA), KA risk factors, and health care resource utilization in patients aged ≥18 years with claims in the Optum Clinformatics Data Mart database (2006-2016) for knee osteoarthritis treated with at least one course of hylan G-F 20. Kaplan-Meier analysis estimated KA risk from osteoarthritis diagnosis and first hylan G-F 20 treatment. KA risk factors were determined using multivariate Cox regression. Among 62,033 patients treated with hylan G-F 20 and/or hylan G-F 20 single intra-articular injection, 60 to 64% did not undergo KA 8 years following first injection. KA risk factors from time of osteoarthritis diagnosis and first hylan G-F 20 treatment were similar: increased age, fewer comorbidities, fewer hylan G-F 20 treatments, female sex, and no ultrasound/fluoroscopy for injection guidance. Patients who underwent KA versus those who did not had more office visits and claims for opioids, nonsteroidal anti-inflammatory drugs, and physical therapy. Patients less likely to undergo KA were younger (<40 years), had more comorbidities, received more courses of hylan G-F 20, were males, or received ultrasound/fluoroscopic injection guidance. Patients who did not receive KA versus those who did used fewer health care resources.

An Open-Label, Dose-Escalation Study to Assess the Safety and Efficacy of IL-22 Agonist F-652 in Patients With Alcohol-associated Hepatitis.

BACKGROUND AND AIMS: Interleukin-22 has beneficial effects on inflammation and impaired hepatic regeneration that characterize alcohol-associated hepatitis (AH). F-652 is a recombinant fusion protein of human interleukin-22 and immunoglobulin G2 fragment crystallizable. This study aims to assess the safety and efficacy signals of F-652 in patients with moderate and severe AH. APPROACH AND RESULTS: A phase-2 dose-escalating study was carried out. F-652 (10 µg/kg, 30 µg/kg, or 45 µg/kg) administered on days 1 and 7 was tested in 3 patients each with moderate (Model for End-Stage Liver Disease [MELD] scores: 11-20) and severe AH (MELD scores: 21-28). Safety was defined by absence of serious adverse events and efficacy was assessed by Lille score, changes in MELD score, and serum bilirubin and aminotransferases at days 28 and 42. Three independent propensity-matched comparator patient cohorts were used. Plasma extracellular vesicles and multiplex serum cytokines were measured to assess inflammation and hepatic regeneration. Eighteen patients (9 moderate and 9 severe AH) were enrolled, 66% were male, and the mean age was 48 years. The half-life of F-652 following the first dose was 61-85 hours. There were no serious adverse events leading to discontinuation. The MELD score and serum aminotransferases decreased significantly at days 28 and 42 from baseline (P < 0.05). Day-7 Lille score was 0.45 or less in 83% patients as compared with 6%, 12%, and 56% among the comparator cohorts. Extracellular vesicle counts decreased significantly at day 28 (P < 0.013). Cytokine inflammatory markers were down-regulated, and regeneration markers were up-regulated at days 28 and 42. CONCLUSIONS: F-652 is safe in doses up to 45 µg/kg and associated with a high rate of improvement as determined by Lille and MELD scores, reductions in markers of inflammation and increases in markers of hepatic regeneration. This study supports the need for randomized placebo-controlled trials to test the efficacy of F-652 in AH.

Inadequacy of current pediatric epinephrine autoinjector needle length for use in infants and toddlers.

BACKGROUND: Epinephrine injection represents the standard of care for anaphylaxis treatment. It is most effective if delivered intramuscularly, whereas inadvertent intraosseous injection may be harmful. The needle length in current pediatric epinephrine autoinjectors (EAIs) is 12.7 mm; however, the ideal needle length for infants and toddlers weighing less than 15 kg is unknown. OBJECTIVE: To determine the skin-to-bone distance (STBD) and skin-to-muscle distance (STMD) at baseline and after simulated EAI application in infants and toddlers (weighing 7.5-15 kg). METHODS: Study participants recruited from 2 North American allergy clinics underwent baseline and compression (10-lb pressure) ultrasonography of the anterolateral thigh with a modified ultrasound transducer mimicking the footprint and maximum pressure application of an EAI device. Ultrasound images, with clinical data masked, were analyzed offline for STBD and STMD in short-axis approach. RESULTS: Of 53 infants (mean age, 18.9 months; 54.7% male; 81.1% white; mean weight, 11.0 kg), 51 had adequate images for short-axis STBD measurements. In these infants, the mean (SD) baseline STBD was 22.4 (3.8 mm), and the mean (SD) STMD was 7.9 (1.7) mm. With 10-lb compression, the mean (SD) STBD was 13.3 (2.1) mm, and the mean (SD) STMD was 6.3 (1.2) mm. An EAI with a needle length of 12.7 mm applying 10-lb pressure could strike the bone in 43.1% of infants and toddlers in this cohort. CONCLUSION: Our data suggest that the optimal EAI needle length for infants and toddlers weighing 7.5 to 15 kg should be shorter than the needle length in currently available pediatric EAIs to avoid accidental intraosseous injections.

Btbd7 is essential for region-specific epithelial cell dynamics and branching morphogenesis in vivo.

Branching morphogenesis of developing organs requires coordinated but poorly understood changes in epithelial cell-cell adhesion and cell motility. We report that Btbd7 is a crucial regulator of branching morphogenesis in vivo. Btbd7 levels are elevated in peripheral cells of branching epithelial end buds, where it enhances cell motility and cell-cell adhesion dynamics. Genetic ablation of Btbd7 in mice disrupts branching morphogenesis of salivary gland, lung and kidney. Btbd7 knockout results in more tightly packed outer bud cells, which display stronger E-cadherin localization, reduced cell motility and decreased dynamics of transient cell separations associated with cleft formation; inner bud cells remain unaffected. Mechanistic analyses using in vitro MDCK cells to mimic outer bud cell behavior establish that Btbd7 promotes loss of E-cadherin from cell-cell adhesions with enhanced migration and transient cell separation. Btbd7 can enhance E-cadherin ubiquitination, internalization, and degradation in MDCK and peripheral bud cells for regulating cell dynamics. These studies show how a specific regulatory molecule, Btbd7, can function at a local region of developing organs to regulate dynamics of cell adhesion and motility during epithelial branching morphogenesis.

Patterned cell and matrix dynamics in branching morphogenesis.

Many embryonic organs undergo branching morphogenesis to maximize their functional epithelial surface area. Branching morphogenesis requires the coordinated interplay of multiple types of cells with the extracellular matrix (ECM). During branching morphogenesis, new branches form by "budding" or "clefting." Cell migration, proliferation, rearrangement, deformation, and ECM dynamics have varied roles in driving budding versus clefting in different organs. Elongation of the newly formed branch and final maturation of the tip involve cellular mechanisms that include cell elongation, intercalation, convergent extension, proliferation, and differentiation. New methodologies such as high-resolution live imaging, tension sensors, and force-mapping techniques are providing exciting new opportunities for future research into branching morphogenesis.

A new leukocyte hyperadhesion syndrome of delayed cord separation, skin infection, and nephrosis.

Leukocyte adhesion deficiency (LAD) I is a well-described genetic disorder in which leukocytes are unable to migrate to sites of inflammation due to mutations in the ITGB2 gene coding for the ß subunit of ß2 (CD18) leukocyte integrins. The classic symptoms of the disease present in the newborn period as failure of separation of the umbilical cord and recurrent bacterial infections, which continue throughout life. We report on a patient with these clinical manifestations but with normal ITGB2 gene sequencing excluding LAD-I, normal carbohydrate-deficient transferrin testing excluding LAD-II, and normal platelet function excluding LAD-III. With testing for CD18 integrin function by flow cytometry, adhesion assay analysis, and time-lapse microscopy, we found the patient's T lymphocytes to express normal levels of ß1 and ß2 integrins but to be highly adhesive to integrin ligands and to display decreased migration compared with control T lymphocytes. The hyperadhesiveness of the cells suggests that they might be prevented from reaching infected tissues. Interestingly, administration of glucocorticoids, for the patient's nephrotic syndrome, alleviated the patient's chronic diarrhea and decreased the incidence of skin infections. The hyperadhesiveness rather than adhesion deficiency of the patient's leukocytes suggests that a novel lesion in a pathway regulating integrin adhesion is responsible for the patient's unique LAD-I-like symptoms.

ECM-modulated cellular dynamics as a driving force for tissue morphogenesis.

The extracellular matrix (ECM) plays diverse regulatory roles throughout development. Coordinate interactions between cells within a tissue and the ECM result in the dynamic remodeling of ECM structure. Both chemical signals and physical forces that result from such microenvironmental remodeling regulate cell behavior that sculpts tissue structure. Here, we review recent discoveries illustrating different ways in which ECM remodeling promotes dynamic cell behavior during tissue morphogenesis. We focus first on new insights that identify localized ECM signaling as a regulator of cell migration, shape, and adhesion during branching morphogenesis. We also review mechanisms by which the ECM and basement membrane can both sculpt and stabilize epithelial tissue structure, using as examples Drosophila egg chamber development and cleft formation in epithelial organs. Finally, we end with an overview of the dynamic mechanisms by which the ECM can regulate stem cell differentiation to contribute to proper tissue morphogenesis.

Bilateral adrenal myelolipomas in a woman with chronic anticoagulation, postmenopausal uterine bleeding, primary hyperparathyroidism and hyperthyroidism.

Adrenal myelolipomas are rare, usually benign unilateral tumors. Their management has controversially been discussed. The authors here present a 53-year-old African American female Jehovah's witness with postmenopausal uterine bleeding on chronic anticoagulation and episodic right flank pain who was found to have bilateral myelolipomas in addition to primary hyperparathyroidism. In collaboration with gynecology, midline laparotomy was performed to remove uterus and both ovaries in addition to the right adrenal gland for a 62 × 79 mm myelolipoma. An open biopsy of the left adrenal mass measuring 42 × 43 mm revealed myelolipoma and ruled out malignancy. Pathology confirmed bilateral myelolipomas, endometrial polyps, and leiomyomata uteri. After an uneventful recovery, the patient then underwent a right inferior parathyroidectomy for parathyroid adenoma. This case illustrates the challenges in deciding when to surgically intervene for bilateral adrenal myelolipoma and, for the first time, associates various other endocrinopathies, although no known endocrine neoplasia syndrome variant was present.

Report of four new patients with protein-truncating mutations in C6orf221/KHDC3L and colocalization with NLRP7.

To date, two maternal-effect genes have been shown to have causative roles in recurrent hydatidiform moles (RHMs); NLRP7 that is mutated in 48-60% of patients with RHMs and C6orf221 (HUGO-approved nomenclature is now KHDC3L), a recently identified gene, that is mutated in 14% of patients with RHMs who are negative for NLRP7 mutations. We sequenced KHDC3L in 97 patients with RHMs and reproductive loss who are mostly negative for NLRP7 mutations. We identified three unrelated patients, each homozygous for one of the two protein-truncating mutations, a novel 4-bp deletion resulting in a frameshift, c.299_302delTCAA, p.Ile100Argfs*2, and a previously described 4-bp deletion, c.322_325delGACT, p.Asp108Ilefs*30, transmitted on a shared haplotype to three patients from different populations. We show that five HM tissues from one of these patients are diploid and biparental similar to HMs from patients with two defective NLRP7 mutations. Using immunofluorescence, we show that KHDC3L protein displays a juxta perinuclear signal and colocalizes with NLRP7 in lymphoblastoid cell lines from normal subjects. Using cell lines from patients, we demonstrate that the KHDC3L mutations do not change the subcellular localization of the protein in hematopoietic cells. Our data highlight the similarities between the two causative genes for RHMs, KHDC3L and NLRP7, in their subcellular localization, the parental contribution to the HM tissues caused by them, and the presence of several founder mutations and variants in both of them indicating positive selection and adaptation.

Multiscale feature analysis of salivary gland branching morphogenesis.

Pattern formation in developing tissues involves dynamic spatio-temporal changes in cellular organization and subsequent evolution of functional adult structures. Branching morphogenesis is a developmental mechanism by which patterns are generated in many developing organs, which is controlled by underlying molecular pathways. Understanding the relationship between molecular signaling, cellular behavior and resulting morphological change requires quantification and categorization of the cellular behavior. In this study, tissue-level and cellular changes in developing salivary gland in response to disruption of ROCK-mediated signaling by are modeled by building cell-graphs to compute mathematical features capturing structural properties at multiple scales. These features were used to generate multiscale cell-graph signatures of untreated and ROCK signaling disrupted salivary gland organ explants. From confocal images of mouse submandibular salivary gland organ explants in which epithelial and mesenchymal nuclei were marked, a multiscale feature set capturing global structural properties, local structural properties, spectral, and morphological properties of the tissues was derived. Six feature selection algorithms and multiway modeling of the data was performed to identify distinct subsets of cell graph features that can uniquely classify and differentiate between different cell populations. Multiscale cell-graph analysis was most effective in classification of the tissue state. Cellular and tissue organization, as defined by a multiscale subset of cell-graph features, are both quantitatively distinct in epithelial and mesenchymal cell types both in the presence and absence of ROCK inhibitors. Whereas tensor analysis demonstrate that epithelial tissue was affected the most by inhibition of ROCK signaling, significant multiscale changes in mesenchymal tissue organization were identified with this analysis that were not identified in previous biological studies. We here show how to define and calculate a multiscale feature set as an effective computational approach to identify and quantify changes at multiple biological scales and to distinguish between different states in developing tissues.

ROCK1-directed basement membrane positioning coordinates epithelial tissue polarity.

The basement membrane is crucial for epithelial tissue organization and function. However, the mechanisms by which basement membrane is restricted to the basal periphery of epithelial tissues and the basement membrane-mediated signals that regulate coordinated tissue organization are not well defined. Here, we report that Rho kinase (ROCK) controls coordinated tissue organization by restricting basement membrane to the epithelial basal periphery in developing mouse submandibular salivary glands, and that ROCK inhibition results in accumulation of ectopic basement membrane throughout the epithelial compartment. ROCK-regulated restriction of PAR-1b (MARK2) localization in the outer basal epithelial cell layer is required for basement membrane positioning at the tissue periphery. PAR-1b is specifically required for basement membrane deposition, as inhibition of PAR-1b kinase activity prevents basement membrane deposition and disrupts overall tissue organization, and suppression of PAR-1b together with ROCK inhibition prevents interior accumulations of basement membrane. Conversely, ectopic overexpression of wild-type PAR-1b results in ectopic interior basement membrane deposition. Significantly, culture of salivary epithelial cells on exogenous basement membrane rescues epithelial organization in the presence of ROCK1 or PAR-1b inhibition, and this basement membrane-mediated rescue requires functional integrin ß1 to maintain epithelial cell-cell adhesions. Taken together, these studies indicate that ROCK1/PAR-1b-dependent regulation of basement membrane placement is required for the coordination of tissue polarity and the elaboration of tissue structure in the developing submandibular salivary gland.