Palatal cytosol cortisol-binding protein associated with cleft palate susceptibility and H-2 genotype

Significant association of HLA-B and HLA-DRB1 alleles with cleft lip with or without cleft palate

Nucleotide sequence level typing of HLA-B, -DRB1, and -DPB1 alleles was performed on Japanese patients with cleft lip with or without cleft palate (CL/P). Two HLA-B alleles, B*1501 and B*5101, showed a significant positive association with CL/P. The increase of B*1501 was evident in female patients (OR=3.6, Pc=0.003), whereas the increase of B*5101 was evident in male patients (OR=3.7, Pc < 0.001). One HLA-DRB1 allele, HLA-DRB1*0802 also showed an increase in CL/P patients. Conversely, HLA-B*4403 and DRB1*1302 were not observed in the patient group (Pc=0.01 and Pc=0.02, respectively). No HLA-DPB1 alleles showed significant association with CL/P. Thus, the present study indicates that HLA alleles, or closely linked loci, may be involved in the pathogenesis of CL/P.

The effects of the glucocorticoid, dexamethasone, on the development of the Drosophila embryo

We have investigated the effects of the glucocorticoid, dexamethasone, and five structural analogs on Drosophila development in an effort to identify steroid ligands that may play a role in the embryogenesis of this organism. Embryos were exposed to glucocorticoids either by direct culture in supplemented medium, or by examining embryos from adult flies raised on supplemented fly food. After exposure, embryos were examined for developmental defects. At a morphological level, exposure to dexamethasone disrupts the dorsolateral folding of the amnioserosa during germ band extension. In addition, germ band retraction and dorsal closure is also disrupted. The phenocritical period of these effects is within the first 4 h of embryogenesis. This response is dosage sensitive, with embryos responding to concentrations of dexamethasone ranging from 10^-6 to 10^-3M. Furthermore, glucocorticoids which are closely related structural analogs of dexamethasone also disrupt germ band retraction and dorsal closure, while other tested steroids had no effect on embryonic development. At a molecular level, expression of the gene, Krüppel, is absent from the amnioserosa of dexamethasone-treated embryos. The cuticular phenocopy resulting from exposure to dexamethasone and related glucocorticoids is morphologically similar to the mutant phenotype associated with four genes required for germ band retraction, namely hindsight, serpent, tail-up and u-shaped. The results of this study represent the first association of a glucocorticoid with dose, stage and tissue specific effects on Drosophila development at both morphological and molecular levels.

Comparison of dexamethasone-induced embryotoxicity in vitro in mouse and rat embryos

Previous work demonstrated that rat embryos were more susceptible to the growth retardation effect of the synthetic glucocorticoid dexamethasone (DEX) in vivo than were mouse embryos. The purpose of this study was to examine this species difference using an in vitro system. Embryos of CD rats and CD-1 mice were cultured in a whole embryo culture system with concentrations of DEX from 5 to 250 micrograms/ml. Rat embryos were explanted on day 9 of gestation (GD 9: plug day = GD 0), while mouse embryos were removed on GD 8. After 48 h in culture, each viable embryo was evaluated for morphological score, and the number of somite pairs, crown-rump, and head lengths, as well as DNA and protein concentrations were determined. A reduced morphological score was observed for mouse embryos at 5 micrograms DEX/ml, but a significant decrease in this parameter was only observed at DEX concentrations of > or = 100 micrograms/ml in rat embryos. Significant reductions in the number of somite pairs were observed at 25 micrograms/ml for mouse embryos and 100 micrograms/ml for rat embryos. Crown-rump and head lengths as well as DNA and protein concentrations were significantly decreased at 100 micrograms/ml in mouse embryos and 150 micrograms/ml in rat embryos. Therefore, in vitro mouse embryos were adversely affected by lower concentrations of DEX than were rat embryos for each of the six end points examined in this study. This species sensitivity in vitro could be due to inherent genetic differences or to the slightly different developmental stages evaluated using the culture system.(ABSTRACT TRUNCATED AT 250 WORDS)

Messenger RNA phenotyping for semi-quantitative comparison of glucocorticoid receptor transcript levels in the developing embryonic mouse palate

A specific complex of glucocorticoid and receptor interacts with responsive genes in target tissues of developing palate and controls its morphogenesis. In order to examine developmental changes in glucocorticoid receptor gene expression during embryonic palate formation, variations in transcript levels have been determined using a simple semi-quantitative reverse transcription-polymerase chain reaction (PCR) procedure. Oligo (dT)16 was used as the primer for reverse transcription, and the amount of PCR product for glucocorticoid receptor was normalized against those for glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and beta-actin. We found that either GAPDH or beta-actin were suitable internal standards, and that the mRNA levels of glucocorticoid receptor undergoes a significant decrease of 30% at the developmental stage of embryonic mouse palatal shelf re-orientation. Immunolocalization of the receptor demonstrated a significant change in the distribution pattern of glucocorticoid receptor during the re-orientation stage of secondary palate formation. Our present data suggest that developmental variations in glucocorticoid receptor level control morphogenetic events of secondary palate formation.

Drug administration to the pregnant or lactating woman: a reference guide for dermatologists

Dermatologists are occasionally faced with the problem of appropriate systemic drug administration to the lactating or pregnant woman. The physician's responsibility is to be aware of the potential risk of prescribing a specific therapeutic agent, to inform the mother of this risk, and to administer an alternate, less deleterious drug, if available. The purpose of this review is to provide guidelines for dermatologists who must consider the risks to the fetus or neonate of drug administration to the pregnant woman or lactating mother.

Inhibition of palatal fusion in vitro by indomethacin in two strains of mice with different H-2 backgrounds

Susceptibility to glucocorticoid-induced cleft palate in mice has been related to the H-2 histocompatibility complex on chromosome 17. Indomethacin administered in vitro to palatal processes from 13.5-day-old mouse embryos inhibited palatal fusion. Strains with the A background and the H-2a haplotype had significantly higher rates of inhibition than their partners with the H-2b haplotype. The inhibition was prevented in both strains by the addition to the media of prostaglandin E2, but this corrective effect was greater in the A strain with the H-2a haplotype. Thus, blockade of palatal fusion involves prostaglandins, suggesting a similar genetic and biochemical pathway for the different susceptibilities to cleft palate induced by both indomethacin and glucocorticoids.

Genetic regulation of testosterone-induced immune suppression

Genes in the major histocompatibility complex (H-2) of the mouse control several immune functions as well as various facets of testosterone (Te) physiology. In order to study the genetic control of Te-induced immune suppression, complete Freund's adjuvant (CFA; containing Mycobacteria tuberculosis) was administered parenterally to several mouse strains differing at the H-2 complex which were either sham- or Te-treated. The specific lymphocyte proliferative response to purified protein derivative (PPD) was measured in draining lymph node cells. The response to PPD in strains bearing H-2b (B6 and B10) but not H-2d (B10.D2 and DBA/2) or H-2k (B10.BR and AKR) haplotypes was markedly lower in Te-implanted compared to sham-implanted controls. This result suggests that the ability of Te to dampen the immune response to PPD is regulated by H-2-linked gene(s).

Murine glucocorticoid receptors: new evidence for a discrete receptor influenced by H-2

The glucocorticoid receptor contents in the lungs of females of two congenic strains of mice, B10.A (H-2a) and B10 (H-2b), differing only in the H-2 histocompatibility region of chromosome 17, have been measured by the dextran-charcoal method and by our previously described methods of molecular sieving and ion exchange chromatography [M. Katsumata, C. Gupta, and A. S. Goldman (1985) Arch. Biochem. Biophys. 243, 385-395]. As reported, two receptors, II and IB, are demonstrable by each column chromatographic method, and 5,5-diphenylhydantoin binds to receptor IB but not to receptor II. Receptor IB cannot be detected unless molybdate is added in cytosols prepared with hypotonic buffer [10 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid and 10 mM dithiothreitol, pH 7.35) according to S. L. Liu, J. F. Grippo, R. P. Erickson, and W. B. Pratt (1984) J. Steroid Biochem. 21, 633-637], a method which has been reported to give maximal receptor levels. Using hypotonic buffer containing 10 mM molybdate we observed a small but significantly higher content of receptor IB in B10.A mice than that in B10 mice, but no significant difference in receptor II or total receptor content. On the other hand, cytosols prepared with isotonic buffer (50 mM Tris-HCl, 120 mM NaCl, 1 mM EDTA, 10 mM dithiothreitol, and 10 mM molybdate, a modification of the buffer used in our previous report) contained significantly higher levels of receptor IB and of total binding in pulmonary cytosols of B10.A as compared to those of B10. There was no difference in receptor II content. Molybdate stabilizes receptor IB in both buffers. These results explain the apparent contradiction between our results and those of Liu et al. by showing that the hypotonic buffer used by them allows for determination of maximal levels of receptor II, but permits selective destruction of receptor IB. However, the use of isotonic buffer gives maximal values of both receptors II and IB. With isotonic buffer, it is demonstrated that only the level of receptor IB is influenced by H-2-linked genes.

Partial characterization and ontogeny of renal cytosolic glucocorticoid receptors in mouse kidney

The glucocorticoid receptor (GR) was partially characterized in mouse renal cytosol. A sensitive and reproducible [3H]dexamethasone binding assay suitable for use with small quantities of cytosolic protein, was developed. Studies defined the optimal equilibrium binding conditions, metabolism of [3H]dexamethasone in adult renal cytosol, specificity of binding of the GR, and molecular weight of the GR-[3H]dexamethasone complex by gel filtration chromatography. The assay was subsequently used to measure the renal GR during different stages of foetal and postnatal development, as well as in glomerular and renal tubular preparations from adult mice. An almost linear increase in GR occurred from day 13 to day 18 of gestation with levels rising from 100 to 201 fmol/mg cytosol protein; this was followed by a sharp rise in receptor concentration just after birth to 343 fmol/mg cytosol protein. Adult levels, 410-433 fmol/mg cytosol protein, were reached by 2 weeks after birth. The equilibrium dissociation constants (Kd) of the [3H]dexamethasone-receptor complex were similar in adult and in embryonic cytosols (range, 2.8-11.8 nM; mean +/- SD = 6.5 +/- 2.9 nM). Specific binding was assessed to be 3- to 5-fold greater in tubular than in glomerular preparations. These data on the localization and ontogeny of GR during murine metanephric development provide a basis for study of glucocorticoid-mediated effects on various models of congenital and acquired renal disease.

Murine glucocorticoid receptors and the H-2 locus--a reappraisal

It has been demonstrated that susceptibility to glucocorticoid-induced formation of cleft palate is regulated by the mouse histocompatibility complex (H-2). This has encouraged us to examine H-2 effects on glucocorticoid binding in tissues of adult animals which would provide sufficient material with which to study the biochemical mechanism of the H-2 effect. Although it has been reported that cytosol prepared from lungs of adult mice with a high susceptibility to steroid-induced cleft palate formation have a higher level of glucocorticoid binding than lung cytosol prepared from a low-susceptibility strain, we are unable to demonstrate any influence of H-2 on binding capacity in this tissue from adult animals when glucocorticoid receptors are assayed in the presence of receptor reducing and stabilizing agents that maximize binding capacity. Cytosol prepared from rat liver contains an endogenous receptor-reducing system composed of NADPH and thioredoxin. It has also been reported that the murine H-2 complex contains a gene(s) that regulates the level of a modifier(s) in fetal hepatic cytosol that affects the binding of glucocorticoids to the receptor. Of two known low molecular weight modifiers that could account for this effect, we have previously established that the heat-stable, steroid receptor "modulator" is not regulated by the H-2 complex. In the present work we have assayed thioredoxin, a second potential modifier, in liver cytosols prepared from adults of two pairs of two H-2 congenic mouse strains. Our results show that the amount of thioredoxin is the same in all four mouse strains and that it is not regulated by the H-2 locus. At this time, we are unable to identify a system in adult mice in which the widely reported regulation of glucocorticoid binding by the mouse histocompatibility locus can be submitted to definitive biochemical study.

Biochemical mechanism of glucocorticoid-and phenytoin-induced cleft palate

The production of cleft palate by glucocorticoids and phenytoin is a complicated interference in a complex developmental program involving many genetic and biochemical processes. The H-2 histocompatibility region includes genes which affect (1) susceptibility to glucocorticoid- and phenytoin-induced cleft palate; (2) glucocorticoid receptor level in a variety of tissues including maternal and embryonic palates, adult thymuses, and lungs; and (3) the degree of inhibition of prostaglandin and thromboxane production by glucocorticoids and phenytoin in thymocytes. A gene linked to a minor histocompatibility locus (H-3) on the second chromosome also influences susceptibility to glucocorticoid- and phenytoin-induced cleft palate. Phenytoin is an alternate ligand for the glucocorticoid receptor affecting prostaglandin and/or thromboxane production. The capacity of glucocorticoids to induce cleft palate is correlated with their anti-inflammatory potency. At least some of the anti-inflammatory effects of glucocorticoids can be explained by the inhibition of prostaglandin and/or thromboxane release, which in turn could be caused by inhibition of arachidonic acid release from phospholipids. Similar mechanisms may be involved in cleft palate induction, as exogenous arachidonic acid injected into pregnant rats and mice at the same time as glucocorticoids reduces the teratogenic potency of the steroids, and indomethacin, an inhibitor of cyclooxygenase, blocks the corrective action of arachidonic acid. Glucocorticoids and phenytoin cause a delay in shelf elevation, and this delay is promoted by fetal membranes and the tongue. However, the cells of the medial edge epithelium are programmed to die whether contact is made with the apposing shelf or not. Glucocorticoids and phenytoin interfere with this programmed cell death, and this interference by both drugs seems to be glucocorticoid receptor mediated, to require protein synthesis, and to be related to arachidonic acid release.

Role of glucocorticoids and epidermal growth factor in normal and abnormal palatal development

The purpose of this chapter has been to discuss glucocorticoid and EGF involvement in normal and abnormal palatal development. It is to be hoped that we have made clear the important point that these hormone/growth factors and their receptors are present during normal embryonic palatal development to provide for regulation of growth and cellular differentiation. When these hormone/growth factors are administered in pharmacological or large doses that result in teratogenesis, these potent chemicals and their receptors then become inducers of cleft palate. The primary reason for this is that the hormone/growth factor receptors have unique and special areas of localizations in target (embryonic and fetal) tissues, e.g., glucocorticoids in the palate. Therefore, large amounts of these chemicals are specifically bound to receptors in these target tissues and these high levels of hormone/growth factor-receptor complexes result in aberrant development, e.g., glucocorticoids cause inhibition of palatal mesenchymal cell growth. These effects are distinct from the interactions of physiological levels of these hormone/growth factors with their receptors in these target tissues during development, e.g., glucocorticoids cause induction of key enzymes and modulation of EGF receptor levels. The exact molecular mechanism(s) by which high levels of hormone/growth factors--receptor complexes exert harmful effects on embryos or fetuses is (are) unknown and remain(s) a challenge for the future. Interaction of hormone/growth factors and their receptors certainly cannot provide an explanation for the mechanism of all types of craniofacial teratogenesis, but this concept certainly appears capable of providing important information relating to the mechanisms of many animal and human teratogens. The fact that these chemicals and their receptors are involved in normal development makes them all the more important since subtle alterations in their levels or activities could result in teratogenesis without an exposure to pharmacological levels of these hormone/growth factors. It seems that progress in this area will develop quickly since the techniques of recombinant DNA research are available in conjunction with responsive in vitro cell systems such as the established line of human embryonic palatal mesenchymal cells. Clearly, the future looks very exciting for understanding the role that these hormone/growth factors and their receptors play in normal and abnormal palate development.

Segregation of HLA in families with oral clefts: evidence against linkage between isolated cleft palate and HLA

In an earlier study of families with two or more sibs affected with a cleft of the lip with or without clefts of the palate, we found no evidence for close linkage of HLA with this malformation. In the present study, we confine our attention to isolated cleft palate, an entity that is genetically distinct from cleft palate associated with cleft lip. In 15 sibships with two or more affected sibs, cleft palate, and parental HLA haplotypes assorted independently in the affected sibs, providing evidence against close linkage of this phenotype.

Corticosteroid-induced abnormality in fetal mice and H-2 haplotype: evidence of a cytoplasmic effect

Different strains of H-2 congenic mice have different susceptibilities to corticosteroid-induced fetal loss and cleft palate. Applying this knowledge, we tested the null hypothesis, which assumes that there are no statistically significant differences in the frequency of abnormality among various types of treated backcross offspring and, thus, no evidence of a cytoplasmic effect. In the present study this null hypothesis was frequently, but not consistently, rejected. Therefore, there was some evidence of a cytoplasmic effect. One possible explanation of these results is seen when one considers the phenotypic effects of "gene-gene interaction" between variant H-2 genotypes and an invariant mitochondrial genotype.

Distribution and metabolism of triamcinolone acetonide in the rat embryomaternal unit during a teratogenically sensitive period

The distribution and metabolism of triamcinolone acetonide (TAC) in the rat embryomaternal unit were investigated during a teratogenically sensitive period. Pregnant rats (Day 12 of gestation) were injected im with 0.125 or 0.5 mg/kg [3H]TAC. Maternal plasma and embryos were collected at selected time points and analyzed by HPLC and liquid scintillation counting. No significant differences in the percentage of total radioactivity representing unchanged TAC, concentration of TAC, or its elimination half-life were detected in either plasma or embryos of the two dose groups. These results provide evidence that the metabolism and distribution of TAC in the rat embryomaternal unit are dose independent over this known teratogenic dose range. To determine whether multiple administration of TAC resulted in any alterations in maternal or embryonal exposure, the same parameters were evaluated following one (Day 12), two (Days 12 and 13), or three (Days 12, 13, and 14) injections of [3H]TAC (0.5 mg/kg, im). The only alterations detected were an increase in the percentage of total radioactivity in maternal plasma representing unchanged TAC at 1 hr following the second or third injection and an increase in the embryonal concentration of TAC at the same time points.

Diphenylhydantoin: an alternative ligand of a glucocorticoid receptor affecting prostaglandin generation in A/J mice

Evidence for the binding of 5,5-diphenylhydantoin and glucocorticoids to a common receptor is presented for pulmonary and hepatic cytosols and thymocytes of A/J female mice. The 5,5-diphenylhydantoin-protein complex is absorbed by DNA cellulose, and is incorporated into nuclei, 5,5-Diphenylhydantoin, like glucocorticoids, inhibits the production of prostaglandins in thymocytes. Thus a common receptor is probably responsible for the inhibitory and teratogenic effects of these drugs.

H-2 histocompatibility region: influence on the murine glucocorticoid receptor and its response

The influence of the H-2 histocompatibility complex on glucocorticoid receptor levels, and the biochemical response of glucocorticoid action measured as the degree of inhibition of prostaglandin production, has been studied in the mouse thymus and lung. The B10A (H-2a) strain of mice has significantly higher glucocorticoid receptor levels and a significantly greater biochemical response to glucocorticoid than the B10 (H-2b) strain, which differs from B10A within the H-2 complex only. Thus, the anti-inflammatory hormone response of glucocorticoids is correlated to hormone receptor level, both of which are influenced by the H-2 locus.

Susceptibility to cleft palate and the major histocompatibility complex (H-2) in the mouse

The congenic mouse strains B10 and B10.A differ genetically only at the H-2 locus, B10 having the H-2b and B10.A the H-2a haplotype. The two strains also differ in susceptibility to cortisone-induced cleft palate, B10 being more resistant than B10.A. Since stage of palate closure is also associated with susceptibility to cortisone-induced cleft palate it was postulated that the H-2 haplotype may affect the cortisone-induced cleft palate susceptibility by altering the stage of palate closure. The present study shows that palate closure occurs at the same stage in the two strains, so this hypothesis must be rejected.

The susceptibility to cortisone-induced cleft palate of recombinant inbred strains of mice: lack of association with the H-2 haplotype

Recombinant-inbred (RI) strains of mice derived from the cross of strains C57BL/6J and DBA/2J were used to study the inheritance of susceptibility to cortisone-induced cleft palate. Most of the RI strains could be classified as either resistant, like C57BL/6J, or susceptible, like DBA/2J, suggesting the segregation of a major locus. An association with the phosphoglucomutase-1 locus (Pgm-1) on Chromosome 5 was observed. There was no association with the H-2 locus on Chromosome 17 as had been reported in previous studies utilizing different strains. We conclude that susceptibility to cortisone-induced cleft palate may be determined by different loci depending on the strains studied.

Glutamine synthetase activity in the developing secondary palate and induction by dexamethasone

Glutamine synthetase (EC 6.3.1.2) (GS) and glutamyltransferase (EC 2.3.2.1) (GT) specific activity were examined in developing A/Jax and C57BL/6J (C57) mouse fetal secondary palates. In addition, the induction of palatal GS was also examined after maternal injection of dexamethasone. Palatal GT activity was uniformly higher in A/J than C57 palates with both strains showing highest activity late on day 13 of gestation and a drop in activity by early day 14. In contrast, A/J palatal GS activity peaked transiently late on day 13, dropped by early day 14 and remained lower throughout the remaining period of palatal development. Palatal GS activity in C57 mouse fetuses, although failing to show a discrete transient peak of activity, remained at a constant elevated level from early day 13 to late day 14 and did not decrease until day 15 of gestation. These elevated levels of palatal GS and GT activity correspond to the gestation period of maximal palatal glycoconjugate biosynthesis. Thus, palatal GS activity may play an important regulatory role in the synthesis of these macromolecules. A/J and C57BL/6J mice exhibit different susceptibilities to glucocorticoid-induced cleft palate. However, maternal administration of a non-teratogenic dose of dexamethasone on either late day 12 or late day 13 resulted in a dramatic stimulation of both A/J and C57 fetal palatal GS but not GT activity when assay 18 h later. A/J palatal tissue responded to dexamethasone with greater induction of palatal GS activity than enzyme activity in C57 palates. Palatal GS, sensitive to glucocorticoid stimulation, may thus be an important link in expressing hormonal control of normal palatal differentiation.

Genes in mice that affect susceptibility to cortisone-induced cleft palate are closely linked to Ir genes on chromosomes 2 and 17

Inbred and congeneic strains of mice have been examined for susceptibility to cortisone-induced cleft palate, and the role of genes linked to H-2 on chromosome 17 has been confirmed. Increasing degrees of susceptibility were associated with the H-2d, H-2b, H-2k, and H-2a haplotypes, respectively, with H-2q and H-2s also being associated with fairly high levels of susceptibility. Evidence was obtained that suggests that one gene maps within the B region of H-2, and that a second H-2 linked gene which acts by complementation maps to the right of E. Another gene affecting this trait is closely linked to the H-3 and Ir-2 loci on the second chromosome.

An unusual symmetric recombinant between adenovirus type 12 DNA and human cell DNA

On purification of human adenovirus type 12 (Ad12) by equilibrium sedimentation in CsCl density gradients, two bands of particles, Ad12-3 and Ad12-3a, are observed. The particles from band Ad12-3a contain a recombinant of human host cell DNA and of Ad12 DNA. The human cell DNA sequences contain repetitive DNA recurring 200 to 500 times in cellular DNA. Ad12 DNA and the recombinant genomes exhibit the same or similar lengths. This finding suggests that a constant amount of DNA is packaged into complete Ad12 particles. On cleavage of KB cellular DNA with EcoRI, BamHI, HinfI, Msp I, Mbo I Pst I, or Bgl II, the (32)P-labeled cellular DNA from Ad12-3a particles hybridizes on Southern blots to distinct bands of KB DNA. There is also less-specific background hybridization that is not observed in the control. The cellular DNA from Ad12-3a particles is not methylated, whereas the same cellular sequences in KB cell DNA appear to be extensively methylated. On denaturation and renaturation, the recombinant DNA molecules are converted to molecules half as long as Ad12 DNA, as determined by gel electrophoresis and electron microscopy. The recombinant DNA molecules were terminally labeled by exonuclease III treatment and subsequent refilling of the depleted segments with [(32)P]dNTPs by using DNA polymerase I (Klenow fragment). When these molecules were cleaved with EcoRI, BamHI, Msp I, or Pst I, only one terminal DNA fragment was found to be labeled. The results of partial digestion experiments using Msp I, HinfI, or Mbo I are consistent with a model in which 700-1150 base pairs from the left terminus of Ad12 DNA are linked to host cell DNA containing repetitious sequences, and this structure is symmetrically duplicated as a large inverted repeat of the type ABCDD'C'B'A'. The Ad12 DNA sequences are flanking the entire molecule, which consists mainly of human KB cell DNA. The recombinants appear to be stable on serial passage of the virus preparation for many years, although variations in the sequence of the recombinants occur. These symmetric recombinant (SYREC) molecules suggest a way to use adenovirus DNA as a eukaryotic vector. Their occurrence provides further evidence for the generation of virus-host DNA recombinants and may help elucidate the role this interaction may have in adenovirus replication and oncogenesis.

Corticosteroid-induced cleft palate in mice and H-2 haplotype: maternal and embryonic effects

This report confirms and expands on the original preliminary observations made by Bonner and Slavkin that corticosteroid-induced cleft palate in mice is associated with H-2 haplotype. Using three congenic strains, B10, B10.A, and B10.D2, our studies demonstrate that B10.A (H-2a) is most susceptible and B10.D2(H-2d) is least susceptible, B10(H-2b) being intermediate. Variation in fetal loss among strains accounts for less than 1 percent of the variation in cleft-palate frequency among strains; variation in H-2 haplotype, however, accounts for more than 60 percent of the variation in cleft-palate frequency. With regard to all possible reciprocal F1 hybrids, our results indicate that while there is a significant maternal effect, maternal haplotype can account for only 11 percent of the variation in cleft-palate frequency among crosses. Embryonic haplotype accounts for 17 percent of the variation, which is indicative of an important embryonic effect. Finally, our studies suggest that susceptibility to corticosteroid-induced cleft palate is associated with the K end of the H-2 complex.

Cortisone-induced cleft palate in the brachymorphic mouse

Previous studies have shown that the autosomal recessive gene brachymorphic (bm/bm), which is maintained on a C57BL/6J (C57) background, reduces limb growth and sulfation of cartilage proteoglycans. Hydrocortisone administered on gestational days 11-14 resulted in 20% CP in the C57 mouse, but 95% CP in the bm/bm mouse. The bm/bm mouse had a median effective dose for CP of 45 mg/kg, compared to 325 mg/kg for C57 and 40 mg/kg for A/J. Morphometric analysis indicated that the time of palatal elevation was delayed in the bm/bm relative to the C57 mouse both with and without hydrocortisone treatment. The amount of cytoplasmic glucocorticoid receptor protein present in the bm/bm palate on day 14 was the same as the amount found in the C57 palate, and was not elevated as it is in the A/J palate. The levels of cyclic AMP in the bm/bm palate on day 14 were 30-70% higher than that found in the C57 palate with or without hydrocortisone. These results suggest that both bm/bm and A/J exhibit a delay in palatal shelf rotation and elevated levels of cyclic AMP, which appear to be predisposing factors for cortisone-induced cleft palate. These strains differ in that elevated levels of steroid receptors are present in A/J palate, whereas lower levels are found in the C57 and bm/bm mice.

Influence of H-2-linked genes on glucocorticoid receptors in the fetal mouse palate

The binding of 3H-dexamethasone to cytosolic receptors in fetal jaws and in cytosols and nuclei of primary cell cultures of fetal palates was studied in various congenic strains of mice. The amount of specific binding was greater in palatal tissues from B10.A and B10.A(2R) mice than in B10 or B10.A(5R) preparations. These differences were not observed in the liver. Since the strains with higher levels of glucocorticoid receptor are known to be more susceptible to cortisone-induced cleft palate than the strains with low receptor levels, it is suggested that quantitative variation in receptor levels may be involved in determining H-2-linked differences in cleft-palate susceptibility. Whether or not this is the case, it appears that an H-2-linked gene affects the quantity of a cytosolic glucocorticoid-binding protein which translocates to the nucleus.

Masseter myopathy following systemic corticosteroid administration: an experimental study

Immature A/J mice were treated with a series of alternate (every 4 days) doses of triamcinolone hexacetonide, a long-acting synthetic analogue of cortisol, and their masseter muscles were studied ultrastructurally. Various degrees of degenerative changes were found in most myofibers of triamcinolone-treated animals. These changes ranged from local alterations in the configuration of the Z discs to a complete disarray of the myofibrilar architecture. Severely affected myofibers revealed areas with total disintegration of myofilaments, loss of mitochondria, and an almost total depletion of glycogen. In addition, some nuclei were centrally located and an obvious enhancement of collagen fibrillogenesis was found in the endomysial spaces. The latter comprised a mixture of banded collagen fibrils and slender filaments which lacked any specific orientation of organization. Endothelial cells of intramuscular capillaries were hypertrophic, thus evoking a marked occlusion of the vascular lumen. Ultrastructural changes were also noted in axon terminals and in the sole-plate sarcoplasm: loss of synaptic vesicles along with shrinkage of axon terminals, partial loss of postsynaptic folds, and a decrease in the number of mitochondria within the sole-plate sarcoplasm. It is proposed that triamcinolone, even if administered on an alternate schedule, promotes myopathic changes in the masseter muscles of immature mice which, in turn, might possibly contribute to the hormone-retardive effect upon the growth potential of the developing mandible.

A glucocorticoid receptor in fetal mouse: its relationship to cleft palate formation

Fetal mouse tissue was investigated for a glucocorticoid binding receptor which might be responsible for cleft palate formation. Fetal mouse heads contain a soluble component which binds the glucocorticoid triamcinolone acetonide in vitro with high affinity. This binding component is present in small finite amounts. Other glucocorticoids compete with triamcinolone acetonide for the binding site in a manner consistent with their potency ranking as cleft palate teratogens. Several mineralocorticoids and progestins also compete when administered in vitro but not when administered in vivo. Triamcinolone acetonide binding was determined in three mouse strains, A/J, C3H, and C57BL, which are listed in decreasing order of cleft palate susceptibility to cortisone. No positive correlation was found between cortisone cleft palate susceptibility and either triamcinolone acetonide binding affinity or binding amount in fetuses from these strains. Cleft palate dose response curves for triamcinolone acetonide were determined in these strains, but they were not parallel to each other as they were for cortisone. This suggests that triamcinolone acetonide may cause cleft palate by different mechanisms in these strains. Thus, fetal mouse tissue contains an apparent glucocorticoid receptors, but its relationship to cleft palate formation in mice is not clear.

Neural tube defects in curly-tail mice. I. Incidence, expression and similarity to the human condition

The incidence of neurovertebral defects in mutant mice of the curly-tail strain was investigated and found to be similar to that observed in the same mice twenty-five years ago. The results of breeding experiments support the hypothesis of Grüneberg that the defects in these mice are probably caused by a recessive gene, the expression of which is markedly affected by the genetic background. Selection against the curly-tail phenotype for six generations did not affect the incidence of abnormalities. A marked excess of females was found among exencephalic mice, as among humans with neural tube defects. Similarly, polyhydramnios, hydrocephaly, high levels of amniotic fluid alphafoetoprotein and distinctive, rapidly adhering cells in the amniotic fluid also occurred in these mice, as in humans. The curly-tail mice thus provide a useful model for the investigation of neural tube defects in man.

The major histocompatibility complex (HLA) as a genetic marker in human craniofacial anomalies

Study of the incidence and segregation of the serologically detectable A and B products of the HLA complex in 140 family units in which one or more offspring was afflicted with a developmental craniofacial anomaly has uncovered no evidence of an association between HLA-A or B antigens or haplotypes and the malformations under study. Further analysis of HLA-D products in the same family units by the mixed leukocyte culture (MLC) technique has, however, uncovered a relatively high incidence of non-reactivity between the cells of one (or both) parent(s) and cells of some offspring in 41 of the 140 families included in this study. The parent couples involved in this finding were unrelated and generally did not share any HLA-SD haplotypes. When this finding was studied further by Primed LD Typing techniques, the results in six families suggested that such MLC non-reactivity is a consequence of the sharing of LD alleles by each pair of parents in these families. The known polymorphism of the HLA-D locus (or loci) and the low incidence of comparable findings in the normal population suggest that LD allele sharing in this particular population may be related to the selection of certain particular HLA-D products in families afflicted with developmental craniofacial anomalies. This result may be relevant to the possible existence in man of an analogue of the murine T/t complex which may occur in linkage with the HLA complex, in the same manner as the linkage disequilibrium which is been documented between the t complex and H-2 in chromosome 17 of the mouse.

Long bone growth during prolonged intermittent corticosteroid treatment and subsequent rehabilitation

Immature A/J mice were treated for up to 7 weeks intermittent doses of triamcinolone hexacetonide and were thereafter allowed to recover for 7 weeks. Qualitative and quantitative morphological measurements were performed on the epiphyseal cartilage plate and diaphyseal bone of the humerus. By the third injection significant structural changes were noted in the cartilaginous tissue followed by a complete cessation of bone growth. The hormonal inhibitory effect on long bone growth lasted throughout the experimental period. However, at the end of the recovery period the length of the humerus was 96% of the normal. In contrast, the humeral width at midshaft and the width of its medullary cavity revealed slower recovery, achieving only 80% of the control values. Following rehabilitation, the growth of experimental epiphyseal plates exceeded that of nontreated animals as their width and the number of hypertrophic chondrocytes were 131% and 125% of their controls respectively. Thus, in A/J mice (a highly susceptible inbred strain of mice) intermittent (every four days) administration of a long-acting corticosteroid hormone arrested endochondral and periosteal bone formation; the former, however, underwent full recovery following the termination of the hormonal treatment.

Estrogen receptor in uteri of mice of different H-2 genotypes

A relationship between the amount of available estradiol receptors in uteri of inbred mice and their H-2 genotype is suggested by study in congenic animals.

H-2 and non-H-2 determined strain variation in palatal shelf and tongue adenosine 3':5' cyclic monophosphate: a possible role in the etiology of steroid-induced cleft palate

The concentration of cAMP was measured in palatal shelves and tongues of 14.5-day old foetuses, 14.5-day old foetuses from steroid treated mothers, and 15.5-day old foetuses from four inbred lines of mice which represent the four possible combinations of two H-2 alleles and two residual genetic backgrounds. The incidence of spontaneous and steroid-induced cleft palate in these four strains was also determined. Analyses of variance of the cAMP data reveal that both the H-2 region and residual genetic background determine cAMP concentrations in both tissues and on both days of development. Similar analyses of cAMP concentrations after steroid treatments of the mother indicate that the interaction between H-2 and residual genetic background is significantly different in the injected than in the uninjected mice in both palatal shelves and tongues. The incidence of steroid-induced cleft palate parallels the palatal shelf concentration of cAMP before steroid treatment of the mother with one exception. These data suggest that a portion of the H-2 controlled component of susceptibility to steroid-induced cleft palate is mediated through alterations in the metabolism of cAMP.

Involvement of glucocorticoids in the development of the secondary palate

Genetic differences between various inbred strains of mice in the levels of glucocorticoid receptors embryonic in maxillary mesenchyme cells appear to be reflected in the magnitude of the responses to steroids in these cells. High levels of glucocorticoids cause significant growth inhibition in maxillary mesenchyme cells with subsequent alterations in the production of extracellular matrix components. The presence of higher levels of cytoplasmic glucocorticoid receptor proteins may be one factor which could predispose those strains such as A/J to a greater inhibition of craniofacial growth in vivo by glucocorticoids and therefore increase the frequency of cleft palate production. Furthermore, women with infertility treated with glucocorticoids to support pregnancy give birth to infants with a marked decrease in birth weight [98]. Pharmacologic doses of glucocorticoids can also cause a dramatic reduction in the growth of a number of fetal tissues in mice and humans. In fact, there is evidence that glucocorticoids may be a causative factor in the production of cleft palate in primates [52]. The nature of the molecular elements which determine the biochemical and physiologic responses to glucocorticoids in the palate still remains largely unknown. Although in the mouse there is some evidence to suggest that the major histocompatibility locus (H-2) might be involved, the level(s) at which this control is exerted is unknown. It is possible that this locus may regulate in some manner the level of glucocorticoid receptors and the response to glucocorticoids in the secondary palate. Moreover, there is evidence to suggest that other genes distinct from, but closely linked to the H-2 locus may be important in determining both the strain-dependent differences in susceptibility to glucocorticoid-induced cleft palate and the intracellular levels of cyclic AMP in the secondary palate. It is also apparent that glucocorticoids in conjunction with other hormones or growth factors such as epidermal growth factor and agents which regulate cyclic nucleotide metabolism are essential for the normal development of the secondary palate. Excesses or deficiencies in either the level of these growth regulators and/or in their receptors in specific fetal tissues at defined periods in development are likely to lead to certain fetal malformations. Definition and integration of the genetic, biochemical, and endocrine factors which are involved in the control of cellular growth as influenced by alterations in the composition of cell surface and extracellular matrix components should provide some insights into the events associated with normal palatogenesis.

Glucocorticoid receptors

Glucocorticoid receptors are found in most mammalian tissues and have been studied in detail in a number of tissue culture systems. With cells that have not been exposed to steroids, the receptors are found in the cytoplasmic fraction from which they can be isolated and studied. Methods for studying glucocorticoid receptors depend on their high-affinity specific binding of radioactive steroids. The reversible interaction is intracellular. It follows Michaelian kinetics, at least in cell-free cytosol, and involves a thermodynamically homogeneous population of about 10 000 sites per cell. The receptor is an asymmetric, slightly acidic protein of about 100 000 daltons. It is very labile, especially in the unbound form. Binding activity depends on the integrity of thiol groups and perhaps on phosphorylation of amino acid residues. Although indirect, the evidence is overwhelmingly convincing that this protein is the physiologic glucocorticoid receptor. The time-kinetics of binding and dissociation are consistent with the sequence of events in glucocorticoid action. Various steroid analogs display binding characteristics predictable from their glucocorticoid activity. Loss of the binding protein from certain cultured cell lines is accompanied by unresponsiveness to glucocorticoids. The extensive tissue distribution of receptors parallels the extensive role of glucocorticoids in regulation. Finally, there is a strong correlation between nuclear binding of receptors and nuclear effects of the steroid. The glucocorticoid receptor can be distinguished from other glucocorticoid-binding proteins, based on their steroid specificity and physicochemical properties. There is no clear-cut demonstration that the receptor differs from tissue to tissue, and it is in fact very similar in various species. Unlike in other systems, receptor concentration does not seem to be regulated by its ligand or by other hormones. However, certain cases of hypo- as well as hypersensitivity to glucocorticoids appear to result from changes at the receptor level. The data indicate that the receptor can exist in inactive and active forms. The former predominate in the absence of steroid or when an angatonist is bound. Glucocorticoid agonists bind the active form, allowing it to be "activated" and subsequently bound to the nucleus. All of the receptors in isolated cytosol do not appear to be available for immediate occupancy by an agonist and this may be due to the time required for conversion of the receptors from inactive to active forms. The correlations between receptor binding and the glucocorticoid response indicate that the receptor is a rate-limiting factor in the magnitude and kinetics of the response, and this finding has important implications regarding mechanisms.