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M Melnick

Publications and source records attributed to M Melnick.

At least 37 records · Page 2Linked to original sources
PubMed1996

Glucocorticoids, tumor necrosis factor-alpha, and epidermal growth factor regulation of pulmonary morphogenesis: a multivariate in vitro analysis of their related actions.

The mouse lung commences development on embryonic day 11 as an epithelial evagination from the posterior pharyngeal wall into undifferentiated mesenchyme, this epithelium bifurcating to form the lung primordium. Branching morphogenesis, as well as terminal differentiation, requires epithelial-mesenchymal interactions utilizing precise regulatory controls. Not surprisingly, specific hormones and growth factors appear to play a key role in this regulation. We report here a series of experiments designed to investigate morphodifferentiation (epithelial branching number, generation number, and fractal dimension) and histodifferentiation (cell morphology and SP-A immunolocalization), as they relate to glucocorticoid (CORT)-regulation of growth factor function and expression (Northern analysis). These experiments were conducted in embryonic lung primordia (E11.5-E12) cultured under defined conditions in the presence of single or combined CORT, TNF-alpha, and EGF supplementation. EGF supplementation enhances branching morphogenesis, but not immunodetectable SP-A expression, in embryonic lung primordia cultured for 4 or 7 days. TNF-alpha supplementation also enhances branching morphogenesis on days 4 or 7 in vitro; on day 7, SP-A expression is also enhanced. By contrast, the introduction of exogenous CORT to embryonic explants cultured 4 or 7 days markedly alters morphodifferentiation and histodifferentiation. Early on it would appear to enhance morphodifferentiation by changing the process of branching, while contemporaneously initiating precocious SP-A expression; later on, it alters morphogenesis by continued terminal differentiation of normal lung epithelium and a singular transdifferentiation of lung mesenchyme into an epithelioid morphotype expressing SP-A. This is correlated with a CORT-induced, highly significant, down-regulation of TGF-beta 2 and TGF-beta 3 transcripts. Explants supplemented with CORT + TNF-alpha or CORT + EGF.demonstrate a microanatomy and SP-A expression pattern identical to that seen with CORT supplementation alone. EGF inhibits the accelerated lung maturation normally seen in the presence of exogenous TNF-alpha alone, suggesting a relationship between these two seemingly disparate regulatory pathways.

Animals↗
PubMed1996

Developmental expression of insulin-like growth factor II receptor (IGF-IIR) in congenic mouse embryonic lungs: correlation between IGF-IIR mRNA and protein levels and heterochronic lung development.

Embryonic lung maturation in the H-2 congenic pair, B10.A and B10, proceeds at different rates. The dependence of this heterochronic development on maternal haplotype suggests the involvement of a parentally imprinted gene. Since B10.A (H-2a) and B10 (H-2b) mice are genetically identical except for a 3-18 cM region of chromosome 17 that includes the H-2 complex, we sought a promising candidate gene(s) involved in regulating the rate of lung development from genes encoded in this region. The best candidate is the gene encoding the type II insulin-like growth factor receptor (IGF-IIR), whose ligand is the growth factor IGF-II. Only the maternal copy of this gene is expressed in postimplantation embryos. This receptor does not appear to transduce mitogenic signals; instead, IGF-IIR appears to regulate the levels of its ligand available to the growth-promoting type I IGF receptor (IGF-IR). Using in situ hybridization and indirect immunofluorescence, we demonstrate that IGF-IIR mRNA and protein are localized throughout the pulmonary mesenchyme, as well as in branching epithelia of the pseudoglandular and canalicular stages. We also examined the levels of IGF-IIR mRNA and protein expression by RNase protection assay and ligand blotting during the embryonic period of lung development in B10.A and B10 mice, and found that there is a highly significant positive correlation of IGF-IIR levels with progressive development in both strains. Further, slower-developing B10.A lungs contain significantly higher levels of IGF-IIR mRNA and protein than the more rapidly developing B10 lungs. These results suggest that haplotype-dependent elevation of IGF-IIR levels reduces the available concentration of IGF-II, resulting in a decreased rate of morphogenesis in B10.A mice. Heterochronic lung maturation, then, appears consequent to variable extracellular levels of this important growth factor. These results may be of clinical importance to predicting susceptibility to Respiratory Distress Syndrome in prenatal newborns.

Animals↗
PubMed1996

The glucocorticoid-glucocorticoid receptor signal transduction pathway, transforming growth factor-beta, and embryonic mouse lung development in vivo.

Lung morphogenesis has been shown to be regulated by glucocorticoids (CORT). Because CORT has been primarily thought to affect fetal lung development, previous studies have focused on the role of CORT receptor (GR)-mediated regulation of fetal lung development. Although endogenous CORT increases during embryonic and fetal stages and exogenous CORT treatment in vivo and in vitro clearly accelerates embryonic lung development, little is known about the morphoregulatory role of the embryonic CORT-GR signal transduction pathway during lung development. In this study, we characterize the embryonic mouse CORT-GR pathway and demonstrate: stage-specific in situ patterns of GR immunolocalization; similarity in GR relative mobility with progressive (E13 --> E17) development; that embryonic GR can be activated to bind a GR response element (GRE); significantly increasing levels of functional GR with increasing lung maturation; and the presence of heat shock protein (hsp) 70 and hsp90 from early (E13) to late (E17) developmental stages. These results support the purported importance of the embryonic CORT-GR signal transduction pathway in progressive lung differentiation. To demonstrate that the embryonic CORT-GR directed pathway plays a role in lung development, early embryonic (E12) lungs were exposed to CORT in utero and surfactant-associated protein A (SP-A) expression was analyzed; CORT treatment up-regulates SP-A mRNA expression and spatiotemporal protein distribution. Finally, to determine whether CORT-GR-directed pulmonary morphogenesis in vivo involves the modulation of growth factors, we studied the effect of CORT on TGF-beta gene expression. Northern analysis of TGF-beta 1, TGF-beta 2, and TGF-beta 3 transcript levels in vivo indicates that CORT regulates the rate of lung morpho- and histodifferentiation by down-regulating TGF-beta 3 gene expression.

Animals↗
PubMed1996

The neurogenic genes egghead and brainiac define a novel signaling pathway essential for epithelial morphogenesis during Drosophila oogenesis.

Notch (N) and other neurogenic genes have been implicated in two fundamental processes, lateral specification of cell fates, and epithelial development. Previous studies have suggested that the neurogenic gene brainiac (brn) is specifically required for epithelial development (Goode, S., Morgan, M., Liang, Y-P. and Mahowald, A. P. (1996). Dev. Biol. 178, 35-50). In this report we show that egghead (egh), a gene with phenotypes identical to brn, encodes for a novel, putative secreted or transmembrane protein. We describe the role of egh and brn germline function in the morphogenesis of the follicular epithelium from the time it is born through the time that it migrates towards the oocyte late in oogenesis. By comparing the function of germline egh and brn to N during oogenesis, we have obtained direct evidence for the involvement of Notch in maintenance of the follicle cell epithelium, and the specificity of brn and egh in epithelial development during oogenesis. The most striking phenotype observed for all three genes is a loss of apical-basal polarity and accumulation of follicular epithelial cells in multiple layers around the oocyte. The spatiotemporal onset of this adenoma-like phenotype correlates with the differential accumulation of egh transcripts in the oocyte at stage 4 of oogenesis. In contrast to N, we find that brn and egh are essential for the organization, but not specification, of stalk and polar cells. The expression patterns and functional requirements of brn, egh, and N lead us to propose that these genes mediate follicular morphogenesis by regulating germline-follicle cell adhesion. This proposal offers explanations for (1) the involvement of egh and brn in N-mediated epithelial development, but not lateral specification, (2) why brn and egh embryonic neurogenic phenotypes are not as severe as N phenotypes, and (3) how egh and brn influence Egfr-mediated processes. The correlation between the differential expression of egh in the oocyte and the differential requirement for brn, egh, and N in maintaining the follicular epithelium around the oocyte, suggests that Egghead is a critical component of a differential oocyte-follicle cell adhesive system.

Amino Acid Sequence↗
PubMed1996

Facial growth after primary periosteoplasty versus primary bone grafting in unilateral cleft lip and palate.

A cephalometric evaluation of long-term changes resulting from two different surgical techniques for the correction of unilateral cleft lip and palate (UCLP) was undertaken on a sample of 19 males with primary bone grafting, and 42 males with primary periosteoplasty from the Science Academy of the Czech Republic, Prague. Lateral cephalometric radiographs collected at approximately 10 and 15 years of age were traced, digitized, and analyzed using the finite-element method. Facial growth and development between the two groups were compared. Significant differences between the two groups were found in the upper face, the posterior part of the maxilla, the anterior bony chin, and nasal bone areas. The periosteoplasty group demonstrated significantly greater vertical development between anterior cranial base and the maxilla. The bony chin was larger and a greater inferior displacement of the posterior palate were found in the periosteoplasty group. An increased proclination in the nasal bone was observed in the bone graft group. This investigation both confirms the findings of a previous study of these sample populations, and provides additional important details regarding the differences between the groups.

Adolescent↗
PubMed1996

Sensory dysfunction associated with repetitive strain injuries of tendinitis and focal hand dystonia: a comparative study.

Repetitive strain injuries are reaching epidemic levels among workers who perform heavy schedules of rapid alternating movements (eg., computer programmers, data entry workers) or repetitive, sustained, coordinated movements (eg., editors, writers, salespeople). The purpose of this study was to determine if patients with repetitive strain injury demonstrated degraded sensory motor performance with their hands. Sixty age-matched adults were recruited, with 15 each assigned to a healthy adult control group, a healthy musician control group, a tendinitis group, or a focal dystonia group. Four sensory motor subtests from the Sensory Integration and Praxis Test were given to the subjects according to a standardized protocol. Using multiple one-factor analyses of variance in the parametric or nonparametric mode followed by post hoc pairwise testing, no significant differences were found between the healthy controls and the musician controls. On the test of kinesthesia, using the left hand, subjects with tendinitis performed significantly worse than controls and subjects with focal dystonia. Compared with controls, subjects with focal dystonia did significantly worse on graphesthesia and manual form perception (part 1 and part 2). Subjects with focal dystonia also did significantly worse than subjects with tendinitis when using the left hand on graphesthesia and manual form perception (part 2). When treating patients with repetitive strain injury, discriminative sensory motor skills must be carefully assessed and may need to be addressed as part of an effective treatment program.

Adult↗
PubMed1995

Protein structure-based design of potent orally bioavailable, nonpeptide inhibitors of human immunodeficiency virus protease.

A class of potent nonpeptidic inhibitors of human immunodeficiency virus protease has been designed by using the three-dimensional structure of the enzyme as a guide. By employing iterative protein cocrystal structure analysis, design, and synthesis the binding affinity of the lead compound was incrementally improved by over four orders of magnitude. An inversion in inhibitor binding mode was observed crystallographically, providing information critical for subsequent design and highlighting the utility of structural feedback in inhibitor optimization. These inhibitors are selective for the viral protease enzyme, possess good antiviral activity, and are orally available in three species.

Administration, Oral↗
PubMed1994

Effect of in ovo retinoic acid exposure on forebrain neural crest: in vitro analysis reveals up-regulation of N-CAM and loss of mesenchymal phenotype.

In a prior study of in ovo exogenous retinoic acid (RA) exposure, we observed a prolonged expression of cell surface N-CAM in cranial neural crest (NC) cells exhibiting migratory failure. In the present studies, we employed an experimental strategy in which embryos were first exposed to exogenous RA in ovo and incubated for 45-60 hr; this was followed by extirpation and in vitro culturing of these same RA-exposed cranial neural tubes. NC cell outgrowth from the explant was assayed, as was the immunohistochemical localization of HNK-1 and N-CAM antigens. In RA-exposed explants, the size of the NC cell outgrowths were comparable to controls. However, almost all NC cells lost their mesenchymal phenotype and were arranged in an "epithelioid" pattern of tightly packed polygonal cells that expressed N-CAM at adjacent cell boundaries. By contrast, control NC cells were flattened and multipolar in shape and expressed HNK-1, rarely co-expressing N-CAM. These observations indicate that RA modulates NC cell N-CAM expression and microanatomical phenotype, a finding consistent with prior in ovo studies of RA-exposure. Several possible explanations are considered.

Animals↗
PubMed1994

Tumor necrosis factor-alpha and embryonic mouse lung morphogenesis.

The ontogeny of the embryonic and fetal lung involves complex interactions between epithelial and mesenchymal primordia which require a specific program of gene regulation and signal transduction. Past studies in our laboratory using congenic mouse strains indicate that one or more genes which map to the H-2 region of chromosome 17 regulate the rate of lung morphogenesis, defined in this context as differentiative heterochrony among strains. Since hormones and growth factors are the messengers of morphogenesis, it was logical to propose that tumor necrosis factor-alpha (TNF-alpha), a well-characterized cytokine whose gene maps to the D-region of the H-2 complex, is a putative mediator of lung morphogenesis. We investigated this proposition using immunochemical methods and a serumless, chemically defined in vitro model system. Our results demonstrate that: (1) TNF-alpha has a specific spatiotemporal localization, in vivo and in vitro; (2) TNF-alpha receptor, in vivo and in vitro, is localized throughout the embryonic lung; (3) TNF-alpha supplementation in vitro of embryonic lung primordia has a marked dose-dependent, stimulatory effect on branching morphogenesis and surfactant-associated protein (SP-A) expression; (4) multiple immunoreactive proteins, including 17, 26, and 68 kDa species, are expressed during development in vivo, and a subset of these are expressed in vitro; and (5) both time- and glucocorticoid-dependent changes occur in the in vivo expression pattern of TNF-alpha immunoreactive proteins after 4 and 7 days in vitro, including the up-regulation of a novel 40 kDa protein. Given that glucocorticoids (CORT) regulate TNF-alpha expression and TNF-alpha's ability to stimulate pulmonary morphodifferentiation and histodifferentiation, we conclude that TNF-alpha is an autocrine/paracrine pulmonary cytokine, probably a component of the lung morphogenesis pathway regulated by CORT.

Animals↗
PubMed1994

Finite element-based cephalometric analysis.

The finite element method has proven to be a useful tool for morphometric analysis in craniofacial biology. However, few attempts have been made to adapt this method for routine use by clinicians. The CEFEA program incorporates the advanced features of the finite element method but bypasses the detailed understanding of the engineering and mathematics previously required to interpret results. The program uses the color graphics display of common personal computers to show size change, shape change, and angle of maximum change. These are pictured as colored triangles of clinically relevant regions between pre- and mid- or posttreatment lateral headfilms. The program is designed to have features of interest in both clinical practice and research.

Cephalometry↗
PubMed1993

Raphe of the posterior neural tube in the chick embryo: its closure and reopening as studied in living embryos with a high definition light microscope.

Chick embryos cultured on a curved substratum show a transient enlargement of the posterior neuropore (PN), mimicking the temporary delay of PN closure as seen in the curly tail (ct) mouse mutant (van Straaten et al. [1993] Development 117:1163-1172). In the present study the PN enlargement in the chick embryo was investigated further with a high definition light microscope (HDmic), allowing high resolution viewing of living embryos in vitro. The temporary PN enlargement appeared due to considerable reopening of the raphe of the posterior neural tube, which was followed by reclosure after several hours. The raphe was subsequently studied in detail. It appeared very irregular, with small zones of apposed, open and fused neural folds. During closure, these raphe features shifted posteriorly. A distinct fusion sequence between surface epithelium and neuroepithelium was not seen. During experimental reopening of the raphe in vitro, small bridges temporarily arose, broke and disappeared quickly; they likely represented the first adhesion sites between the neural folds. More prominent adhesion sites partly detached, resulting in bridging filopodia-like connections; they probably represented the first anteroposterior locations of neural fold fusion. Our observations in the living chick embryo in vitro thus show that the caudal neural tube has an irregular raphe with few adhesion sites, which can be readily reopened. As a result of the irregularity, the PN does not close zipper-like, but button-like by forming multiple closure sites.

Animals↗
PubMed1993

H-2 gene complex and corticosteroid responsiveness: evidence that the corticosteroid hormone signal transduction pathway in the adult mouse lung is not associated with haplotype-specific responses to corticosteroids.

Differential responsiveness to corticosteroids (CORT) has been shown to be related to HLA haplotype. A strong association between the mouse homolog to the human HLA complex, the H-2 complex, and intrauterine responses to CORT have also been demonstrated; haplotype differences alter CORT-induced susceptibility to cleft palate and temporal differences in lung maturation. Since variation in the glucocorticoid receptor (GR) is associated with tissue specific responses to CORT, we hypothesize that haplotype-specific CORT responsiveness may be regulated by H-2 associated modification of GR expression and/or function. Given that H-2 congenic mice are genetically identical except at the H-2 complex on mouse chromosome 17 and the GR structural gene is encoded on chromosome 18, the GR gene is identical in these mice. However, any step in the GR signal transduction pathway may be regulated by gene(s) at or near the H-2 complex and result in haplotype-specific differences in CORT responsiveness. We have investigated differences in qualitative and quantitative characteristics of the adult B10 (H-2b) and B10.A (H-2a) pulmonary GR by Scatchard analysis, immunochemical and biochemical assays. No differences in the GR binding parameters (BMAX and Kd), receptor form and level, or ligand-GR complex binding to glucocorticoid response element (GR-GRE) were detected, leading us to conclude that H-2 associated factors do not regulate the relative intrauterine responses to CORT by modulating the adult GR.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Cortex Hormones↗
PubMed1992

Genetic analysis of cleft lip with or without cleft palate in Madras, India.

We performed a genetic analysis of 331 non-syndromic cleft lip with or without cleft palate (CL +/- P) proband families ascertained in Madras, India. Predictions of the multifactorial threshold (MF/T) model are tested; goodness-of-fit tests of the MF/T model and complex segregation analysis are also utilized to clarify the genetic etiology of CL +/- P in this study population. There was little evidence for the MF/T model. The most reasonable conclusion from mixed model analysis is that of a major locus with reduced transmission probability. This is not altogether surprising if manifestation of CL +/- P also depends on in utero exposure to harmful environmental agents during the critical period of facial development, as suggested by Melnick et al. [1980] and demonstrated in an animal model of CL +/- P [Melnick et al., 1981]. Further the results in the Madras population are quite similar to those in other populations of Europe and Asia.

Cleft Lip↗
PubMed1992

Cleft lip with or without cleft palate in Shanghai, China: evidence for an autosomal major locus.

Orientals are at higher risk for cleft lip with or without cleft palate (CL +/- P) than Caucasians or blacks. We collected demographic and family data to study factors contributing to the etiology of CL +/- P in Shanghai. The birth incidence of nonsyndromic CL +/- P (Shanghai 1980-87) was 1.11/1,000, with a male/female ratio of 1.42. Almost 2,000 nonsyndromic CL +/- P probands were ascertained from individuals operated on during the years 1956-83 at surgical hospitals in Shanghai. Detailed family histories and medical examinations were obtained for the probands and all available family members. Genetic analyses of the probands' families were performed under the mixed model with major locus (ML) and multifactorial (MFT) components. The hypotheses of no familial transmission and of MFT alone could be rejected. Of the ML models, the autosomal recessive was significantly most likely and was assumed for testing three complex hypotheses: (1) ML and sporadics; (2) ML and MFT; (3) ML, MFT, and sporadics. None of the complex models were more likely than the ML alone model. In conclusion, the best-fitting, most parsimonious model for CL +/- P in Shanghai was that of an autosomal recessive major locus.

Asian People↗
PubMed1991

Neural tube and neural crest: a new view with time-lapse high-definition photomicroscopy.

The dynamic process of neural tube formation and neural crest migration in live, unstained cultured avian embryos at Hamburger-Hamilton (H.H.) stages 8-11 was investigated by time-lapse cinematography using a high-definition microscope. These studies have demonstrated that neural tube closure in the trunk region differs from that observed in the head. The cephalic neural folds elevate slowly, then make contact rapidly. Following this initial apposition, they gradually "zip-up" in the rostrad and caudad direction. In the trunk region where the neuroepithelium bulges adjacent to the somites, the edges of the folds pulsate and forcefully touch-retract-touch in these bulging regions; the intersomitic epithelia retract, remain open even after more posterior somitic regions have apposed, and then close slowly. Epithelial blebs and N-CAM antibody were observed at the leading edges of the neuroepithelia. Between the open folds only a few bridging cells were seen; they probably represent the sites of initial cell adhesion following epithelial retraction. Focusing into the developing embryo shows that neuroepithelial fusion occurs prior to surface epithelial fusion. A meshwork of synchronously pulsating neural crest cells was identified below the surface epithelium and a preliminary investigation of their initial migration was conducted.

Animals↗
PubMed1991

Mouse major histocompatibility complex and lung development: haplotype variation, H-2 immunolocalization, and progressive maturation.

The association of the mouse major histocompatibility complex (H-2), lung maturation, and corticosteroid responsiveness has recently been demonstrated in congenic B10 (H-2b) and B10.A (H-2a) mice (Hu et al.: American Journal of Medical Genetics 35:126-131, 1990). We have investigated additional haplotypes [B10.BR (H-2k) and B10.D2 (H-2d)] to confirm that there is a strong association between H-2 haplotype variation and the degree of pulmonary maturation. Lungs of B10.D2, B10.BR, B10, and B10.A congenic mice achieve haplotypic specific maturation: B10.D2 lungs greater than B10 lungs = B10.BR lung greater than B10.A lungs. It appears that the expression of these developmental potentials is under corticosteroid regulation. Further, to test the hypothesis that H-2 antigens would be expressed earlier in embryonic lungs with the H-2b (B10) or H-2k (B10.BR) haplotype than with the H-2a (B10.A) haplotype, we investigated the spatiotemporal patterns of H-2 antigen localization in B10, B10.BR, and B10.A congenic mouse strains with and without corticosteroid treatment. The spatial patterns of H-2 antigen localization was similar in the B10, B10.BR, and B10.A mouse lungs; however, these patterns appeared earlier in both untreated and treated B10 and B10.BR mice as compared with untreated B10.A mice, suggesting an H-2 haplotype associated rate of pulmonary maturation. Following corticosteroid treatment, all congenic strains had a temporally comparable spatial distribution of H-2 antigens. Our results provide preliminary evidence suggesting that both a lung "developmental gene(s)" and a "glucocorticoid responsiveness gene(s)" are most likely outside the K-D subregions of the H-2 complex. A model of the H-2 regulation of lung maturation and corticosteroid responsiveness is discussed.

Animals↗
PubMed1991

Bone remodeling in W/Wv mast cell deficient mice.

Strong experimental evidence exists for a relationship between mast cells and bone disease, but the role of mast cells in the regulation of bone remodeling is unknown. In order to address this question, mast cell deficient mice (W/Wv) were paired with their mast cell sufficient (+/+) littermates and evaluated for differences in response to an induced cycle of bone remodeling. This was achieved using a tooth egression protocol, in which a synchronous cycle of bone remodeling was induced in the mandibular buccal alveolar periosteum by extraction of the opposing dentition. Quantitative histomorphometric changes during the activation, resorption, reversal, and formation phases of bone remodeling were documented using standard techniques. Most cell deficient mutants exhibited the following defects in response to an induced cycle of bone remodeling: (a) the onset of the remodeling cycle was delayed by a prolonged activation phase, (b) the duration and extent of the active formation phase was decreased, and (c) the amount of new bone matrix synthesized was diminished while mineralization rates were found to be normal. These results suggest that mast cells and their mediators provide a paracrine mechanism which influences the recruitment of osteoclast and osteoblast progenitors and their participation in bone remodeling. Nonetheless, since bone remodeling occurs in mast cell deficient mice, albeit less efficiently, this mechanism is most likely one of several redundant mechanisms that provide for adequate skeletal homeostasis.

Animals↗