FLT3 tyrosine kinase inhibition modulates PRC2 and promotes differentiation in acute myeloid leukemia

Internal tandem duplication mutations in fms-like tyrosine kinase 3 (FLT3-ITD) are recurrent in acute myeloid leukemia (AML) and increase the risk of relapse. Clinical responses to FLT3 inhibitors (FLT3i) include myeloid differentiation of the FLT3-ITD clone in nearly half of patients through an unknown mechanism. We identified enhancer of zeste homolog 2 (EZH2), a component of polycomb repressive complex 2 (PRC2), as a mediator of this effect using a proteomic-based screen. FLT3i downregulated EZH2 protein expression and PRC2 activity on H3K27me3. FLT3-ITD and loss-of-function mutations in EZH2 are mutually exclusive in human AML. We demonstrated that FLT3i increase myeloid maturation with reduced stem/progenitor cell populations in murine Flt3-ITD AML. Combining EZH1/2 inhibitors with FLT3i increased terminal maturation of leukemic cells and reduced leukemic burden. Our data suggest that reduced EZH2 activity following FLT3 inhibition promotes myeloid differentiation of FLT3-ITD leukemic cells, providing a mechanistic explanation for the clinical observations. These results demonstrate that in addition to its known cell survival and proliferation signaling, FLT3-ITD has a second, previously undefined function to maintain a myeloid stem/progenitor cell state through modulation of PRC2 activity. Our findings support exploring EZH1/2 inhibitors as therapy for FLT3-ITD AML.

miR-196b-TLR7/8 Signaling Axis Regulates Innate Immune Signaling and Myeloid Maturation in DNMT3A-Mutant AML

PURPOSE

DNMT3A mutations confer a poor prognosis in acute myeloid leukemia (AML), but the molecular mechanisms downstream of DNMT3A mutations in disease pathogenesis are not completely understood, limiting targeted therapeutic options. The role of miRNA in DNMT3A-mutant AML pathogenesis is understudied.

EXPERIMENTAL DESIGN

DNA methylation and miRNA expression was evaluated in human AML patient samples and in Dnmt3a/Flt3-mutant AML mice. The treatment efficacy and molecular mechanisms of TLR7/8-directed therapies on DNMT3A-mutant AML were evaluated in vitro on human AML patient samples and in Dnmt3a/Flt3-mutant AML mice.

RESULTS

miR-196b is hypomethylated and overexpressed in DNMT3A-mutant AML and is associated with poor patient outcome. miR-196b overexpression in DNMT3A-mutant AML is important to maintain an immature state and leukemic cell survival through repression of TLR signaling. The TLR7/8 agonist resiquimod induces dendritic cell-like differentiation with costimulatory molecule expression in DNMT3A-mutant AML cells and provides a survival benefit to Dnmt3a/Flt3-mutant AML mice. The small molecule bryostatin-1 augments resiquimod-mediated AML growth inhibition and differentiation.

CONCLUSIONS

DNMT3A loss-of-function mutations cause miRNA locus-specific hypomethylation and overexpression important for mutant DNMT3A-mediated pathogenesis and clinical outcomes. Specifically, the overexpression of miR-196b in DNMT3A-mutant AML creates a novel therapeutic vulnerability by controlling sensitivity to TLR7/8-directed therapies.

KAT6A and ENL form an epigenetic transcriptional control module to drive critical leukemogenic gene expression programs

Epigenetic programs are dysregulated in acute myeloid leukemia (AML) and help enforce an oncogenic state of differentiation arrest. To identify key epigenetic regulators of AML cell fate, we performed a differentiation-focused CRISPR screen in AML cells. This screen identified the histone acetyltransferase KAT6A as a novel regulator of myeloid differentiation that drives critical leukemogenic gene expression programs. We show that KAT6A is the initiator of a newly-described transcriptional control module in which KAT6A-catalyzed promoter H3K9ac is bound by the acetyllysine reader ENL, which in turn cooperates with a network of chromatin factors to induce transcriptional elongation. Inhibition of KAT6A has strong anti-AML phenotypes in vitro and in vivo, suggesting that KAT6A small molecule inhibitors could be of high therapeutic interest for mono or combinatorial differentiation-based treatment of AML.

Single-cell mutation analysis of clonal evolution in myeloid malignancies

Myeloid malignancies, including acute myeloid leukaemia (AML), arise from the expansion of haematopoietic stem and progenitor cells that acquire somatic mutations. Bulk molecular profiling has suggested that mutations are acquired in a stepwise fashion: mutant genes with high variant allele frequencies appear early in leukaemogenesis, and mutations with lower variant allele frequencies are thought to be acquired later1-3. Although bulk sequencing can provide information about leukaemia biology and prognosis, it cannot distinguish which mutations occur in the same clone(s), accurately measure clonal complexity, or definitively elucidate the order of mutations. To delineate the clonal framework of myeloid malignancies, we performed single-cell mutational profiling on 146 samples from 123 patients. Here we show that AML is dominated by a small number of clones, which frequently harbour co-occurring mutations in epigenetic regulators. Conversely, mutations in signalling genes often occur more than once in distinct subclones, consistent with increasing clonal diversity. We mapped clonal trajectories for each sample and uncovered combinations of mutations that synergized to promote clonal expansion and dominance. Finally, we combined protein expression with mutational analysis to map somatic genotype and clonal architecture with immunophenotype. Our findings provide insights into the pathogenesis of myeloid transformation and how clonal complexity evolves with disease progression.

miR-196b target screen reveals mechanisms maintaining leukemia stemness with therapeutic potential

We have shown that antagomiR inhibition of miRNA miR-21 and miR-196b activity is sufficient to ablate MLL-AF9 leukemia stem cells (LSC) in vivo. Here, we used an shRNA screening approach to mimic miRNA activity on experimentally verified miR-196b targets to identify functionally important and therapeutically relevant pathways downstream of oncogenic miRNA in MLL-r AML. We found Cdkn1b (p27Kip1) is a direct miR-196b target whose repression enhanced an embryonic stem cell-like signature associated with decreased leukemia latency and increased numbers of leukemia stem cells in vivo. Conversely, elevation of p27Kip1 significantly reduced MLL-r leukemia self-renewal, promoted monocytic differentiation of leukemic blasts, and induced cell death. Antagonism of miR-196b activity or pharmacologic inhibition of the Cks1-Skp2-containing SCF E3-ubiquitin ligase complex increased p27Kip1 and inhibited human AML growth. This work illustrates that understanding oncogenic miRNA target pathways can identify actionable targets in leukemia.

DNMT3A Haploinsufficiency Transforms FLT3ITD Myeloproliferative Disease into a Rapid, Spontaneous, and Fully Penetrant Acute Myeloid Leukemia

Cytogenetically normal acute myeloid leukemia (CN-AML) represents nearly 50% of human AML. Co-occurring mutations in the de novo DNA methyltransferase DNMT3A and the FMS related tyrosine kinase 3 (FLT3) are common in CN-AML and confer a poorer prognosis. We demonstrate that mice with Flt3-internal tandem duplication (Flt3(ITD)) and inducible deletion of Dnmt3a spontaneously develop a rapidly lethal, completely penetrant, and transplantable AML of normal karyotype. AML cells retain a single Dnmt3a floxed allele, revealing the oncogenic potential of Dnmt3a haploinsufficiency. FLT3(ITD)/DNMT3A-mutant primary human and murine AML exhibit a similar pattern of global DNA methylation associated with changes in the expression of nearby genes. In the murine model, rescuing Dnmt3a expression was accompanied by DNA remethylation and loss of clonogenic potential, suggesting that Dnmt3a-mutant oncogenic effects are reversible. Dissection of the cellular architecture of the AML model using single-cell assays, including single-cell RNA sequencing, identified clonogenic subpopulations that express genes sensitive to the methylation of nearby genomic loci and responsive to DNMT3A levels. Thus, Dnmt3a haploinsufficiency transforms Flt3(ITD) myeloproliferative disease by modulating methylation-sensitive gene expression within a clonogenic AML subpopulation.

SIGNIFICANCE

DNMT3A haploinsufficiency results in reversible epigenetic alterations that transform FLT3(ITD)-mutant myeloproliferative neoplasm into AML. Cancer Discov; 6(5); 501-15. ©2016 AACR.This article is highlighted in the In This Issue feature, p. 461.

Recombineering-based dissection of flanking and paralogous Hox gene functions in mouse reproductive tracts

Hox genes are key regulators of development. In mammals, the study of these genes is greatly confounded by their large number, overlapping functions and interspersed shared enhancers. Here, we describe the use of a novel recombineering strategy to introduce simultaneous frameshift mutations into the flanking Hoxa9, Hoxa10 and Hoxa11 genes, as well as their paralogs on the HoxD cluster. The resulting Hoxa9,10,11 mutant mice displayed dramatic synergistic homeotic transformations of the reproductive tracts, with the uterus anteriorized towards oviduct and the vas deferens anteriorized towards epididymis. The Hoxa9,10,11 mutant mice also provided a genetic setting that allowed the discovery of Hoxd9,10,11 redundant reproductive tract patterning function. Both shared and distinct Hox functions were defined. Hoxd9,10,11 play a crucial role in the regulation of uterine immune function. Non-coding non-polyadenylated RNAs were among the key Hox targets, with dramatic downregulation in mutants. We observed Hox cross-regulation of transcription and splicing. In addition, we observed a surprising anti-dogmatic apparent posteriorization of the uterine epithelium. In caudal regions of the uterus, the normal simple columnar epithelium flanking the lumen was replaced by a pseudostratified transitional epithelium, normally found near the more posterior cervix. These results identify novel molecular functions of Hox genes in the development of the male and female reproductive tracts.

MicroRNAs in the midst of myeloid signal transduction

MicroRNA (miRNA) play important roles in the development and physiological function of hematopoietic stem/progenitor and mature cell lineages. In addition, deregulated miRNA expression and subsequent gene expression changes are associated with hematologic diseases including myelodysplastic syndromes and acute myeloid leukemia. This review focuses on myelopoiesis as a model to highlight the involvement of miRNA in the regulation of normal and malignant cellular signaling pathways. By incorporating miRNA regulation into well-established myeloid signal transduction pathways, we hope to shed light on targetable factors both upstream and downstream of miRNA signaling. These pathway-specific miRNA functions suggest scenarios wherein miRNA-based therapeutics may be beneficial either alone or in combination with current therapies.

Chk2*1100delC Acts in synergy with the Ron receptor tyrosine kinase to accelerate mammary tumorigenesis in mice

The CHEK2 (Chk2 in mice) polymorphic variant, CHEK2*1100delC, leads to genomic instability and is associated with an increased risk for breast cancer. The Ron receptor tyrosine kinase is overexpressed in a large fraction of human breast cancers. Here, we asked whether the low penetrance Chk2*1100delC allele alters the tumorigenic efficacy of Ron in the development of mammary tumors in a mouse model. Our data demonstrate that Ron overexpression on a Chk2*1100delC background accelerates the development of mammary tumors, and shows that pathways mediated by a tyrosine kinase receptor and a regulator of the cell cycle can act to hasten tumorigenesis in vivo.

Kruppel-like factor 5 is not required for K-RasG12D lung tumorigenesis, but represses ABCG2 expression and is associated with better disease-specific survival

K-RAS mutations are found in approximately 30% of lung cancers. The transcription factor Krüppel-like Factor 5 (KLF5) has been shown to mediate cellular transformation signaling events downstream of oncogenic RAS in other cancers, but a role for KLF5 in lung tumorigenesis has not been defined. We show here that knockdown of KLF5 expression significantly decreased anchorage-independent growth, but did not affect proliferation of human lung adenocarcinoma cells. Moreover, Klf5 is not required for lung tumor formation in an inducible oncogenic K-Ras(G12D) mouse model of lung tumorigenesis, and non-small cell lung cancer patients expressing high levels of KLF5 (21/258) have a significantly better disease-specific survival than those with intermediate to no KLF5 expression. Further, KLF5 knockdown in K-RAS-mutant human lung cancer cells resulted in a fivefold increase in ATP-binding cassette, subfamily G (WHITE), member 2 (ABCG2), an anthracycline drug transporter, which lead to significantly increased resistance to doxorubicin treatment, a chemotherapeutic agent clinically used to treat lung cancer. In summary, while KLF5 is not required for oncogenic mutant K-Ras-induced lung tumorigenesis, KLF5 regulation of ABCG2 expression may be important for chemotherapeutic resistance and patient survival.

First Report of Pyrenophora seminiperda in Turkey and Greece

Pyrenophora seminiperda (Brittleb. & D.B. Adam) Shoemaker (anamorph Drechslera campanulata (Lév.) B. Sutton) is a generalist seed pathogen that can cause high mortality in the seed banks of annual and perennial grasses and a minor leaf spot disease. Its current reported distribution is mainly temperate grasslands, deserts, and winter cereal-growing regions in Argentina, Australia, Canada, Egypt, New Zealand, South Africa, and the United States (2). P. seminiperda was originally described in France in the mid-1800s, but there are no recent reports from eastern Europe or Asia (2). In May of 2008, we observed what appeared to be P. seminiperda on seeds from seed bank samples collected in Turkey. Evidence of disease was observed as macroscopic black stromata protruding from the seed. The characteristic club-shaped stromata were collected from a Taeniatherum caput-medusae seed near Pamukkale, Turkey and six Bromus tectorum seeds in Love Valley near Goreme, Turkey. An additional collection from a single undispersed B. tectorum seed was obtained from Perissa, Greece. Identity of the pathogen was tentatively established by evaluating morphological characteristics for nine isolates in V8 agar culture. After 4 days of incubation at 20°C with a 12-h photoperiod, the cultures produced white mycelium. Following wounding, the mycelium produced black, club-shaped stromata (2 to 8 × 0.4 to 0.9 mm) in a radial pattern. These produced branched conidiophores bearing crescent-shaped, multicellular conidia (79 to 125 μm long). These attributes are consistent with those of the anamorph of P. seminiperda as described by Shoemaker (4) and Campbell et al. (1). The teleomorph was not observed. The identity of the isolates as P. seminiperda was confirmed with ribosomal DNA internal transcribed spacer (ITS) genetic sequencing analysis. ITS sequences obtained were identical to sequences for North American haplotypes of this species. Four of the Love Valley isolates, (representative isolate: GQ168725, BPI 879142, NRRL 54032) matched the HTA haplotype (GQ168724), while the other four (representative isolate: GQ168736, BPI 879143, NRRL 54033) matched the HTJ haplotype (GQ168735). The isolate from Perissa, Greece (GQ168728, BPI 879144, NRRL 54034) matched the HTC haplotype (GQ168727). Pathogenicity of several Love Valley isolates was confirmed by producing conidia in culture, dusting nondormant B. tectorum seeds with 0.003 g of conidial inoculum per 50 seeds, and incubating for 14 days at 10/20°C with a 12-h photoperiod. Stromata developed on >90% of inoculated seeds and mortality as high as 34% was observed. Morphological similarities combined with ITS sequence data provide conclusive evidence that P. seminiperda occurs in Turkey and Greece. The discovery of this pathogen in these countries indicates that it may be widespread in Eurasia and that it could have arrived in North America on seeds of B. tectorum (3) rather than representing a novel pathogen for this important weed in its North American range. References: (1) M. A. Campbell et al. Plant Pathol. 52:448, 2003. (2) R. W. Medd et al. Australas. Plant Pathol. 32:539, 2003. (3) S. E. Meyer et al. Can J. Plant Pathol. 30:525, 2008. (4) R. A. Shoemaker. Can. J. Bot. 44:1451, 1966.

The Ron receptor tyrosine kinase is not required for adenoma formation in Apc(Min/+) mice

The Ron receptor tyrosine kinase is overexpressed in approximately half of all human colon cancers. Increased Ron expression positively correlates with tumor progression, and reduction of Ron levels in human colon adenocarcinoma cells reverses their tumorigenic properties. Nearly all colon tumors demonstrate loss of the adenomatous polyposis coli (APC) tumor suppressor, an early initiating event, subsequently leading to beta-catenin stabilization. To understand the role of Ron in early stage intestinal tumorigenesis, we generated Apc-mutant (Apc(Min/+)) mice with and without Ron signaling. Interestingly, we report here that significantly more Apc(Min/+) Ron-deficient mice developed higher tumor burden than Apc(Min/+) mice with wild-type Ron. Even though baseline levels of intestinal crypt proliferation were increased in the Apc(Min/+) Ron-deficient mice, loss of Ron did not influence tumor size or histological appearance of the Apc(Min/+) adenomas, nor was beta-catenin localization changed compared to Apc(Min/+) mice with Ron. Together, these data suggest that Ron may be important in normal intestinal tissue homeostasis, but that the expression of this receptor is not required for the formation and growth of adenomas in Apc(Min/+) mice.

Major depression and the stress system: a life span perspective

From a transactional developmental perspective, the authors review findings from studies of animals and humans regarding a proposed relation between stress system abnormalities and major depression. The stress system has evolved to promote successful adaptation across the life span, but disruptions in its functioning may increase the risk of pathological outcomes. Emphasis is placed on the role of prenatal and early postnatal experience in contributing to individual differences in postnatal stress reactivity, which may interact with cognitive and psychosocial vulnerabilities to increase susceptibility to later onset of depression. Findings regarding cognitive, psychosocial, and medical sequelae of depression are also reviewed, with a focus on the possible mediating role of the stress system. The authors highlight the importance of multidisciplinary, longitudinal studies in attempting to gain a deeper understanding of the complex developmental processes involved in the onset and course of depression.

Patients' perceived outcomes after stapedectomy for otosclerosis

We conducted a retrospective study of 29 patients who had undergone stapedectomy for otosclerosis to determine how well their subjective perceptions of hearing improvement correlated with objective audiometric measurements. Patients expressed their assessments of hearing function by completing two versions of the Hearing Disability and Handicap Scale (HDHS). One version of the HDHS was based on patients' retrospective recollections of their hearing impairment prior to surgery, and the other reflected their assessment of their current function. We evaluated these HDHS data both separately and in conjunction with pre- and postoperative audiometric findings. Following surgery, the group's mean pure-tone average improved significantly, from 58 to 27 dB--that is, the average patient had a moderately severe hearing loss preoperatively and only a mild hearing loss postoperatively. Significant improvement was also reflected in the difference between the mean pre- and postoperative HDHS scores, although some patients indicated that they experienced almost no improvement. Overall, our findings indicated that there was a relationship between objective and subjective assessments of hearing improvement following surgery, but that it was weak. Although most patients perceived significant improvement, the degree of that perceived improvement cannot be predicted from the pure-tone audiogram. We conclude, therefore, that a significant difference between audiometric findings and HDHS self-assessments is useful in identifying patients who might benefit from additional counseling and/or aural rehabilitation.

Bipolar disorder in youth

The debate regarding the possible existence of prepubertal bipolar illness has surfaced at various points in history. In its most recent incarnation, proponents of a childhood bipolar diagnosis argue that there is an early-onset form of bipolar illness that is highly comorbid and characterized by simultaneous irritability and depression. Others have suggested that childhood manic symptoms are more likely a nonspecific indicator of risk, or may be the result of symptom overlap with various other forms of childhood pathology. This article briefly reviews pertinent findings from epidemiologic, developmental, family, and treatment studies that shed light on the etiology, phenomenology, and developmental significance of manic symptoms in young people.

The effect of stapes surgery on high frequency hearing in patients with otosclerosis

OBJECTIVE

To assess the effect of stapedectomy on high frequency hearing.

STUDY DESIGN

A retrospective, one-group, pretest-posttest case review was performed of the audiometric data of patients who underwent stapedectomy at a tertiary referral center.

PATIENTS

Thirty-eight patients (40 ears) with primary uncomplicated surgery were selected. Twenty-two of the patients were older than 40 years. Preoperative and postoperative audiograms were analyzed.

RESULTS

Preoperative and postoperative audiograms exhibited a down-sloping configuration toward the high frequencies. Surgery resulted in a significant improvement (p < 0.05) from 500 to 4000 Hz in air conduction and 500 to 2000 Hz in bone conduction. Analysis of variance showed that age had no bearing on preoperative audiometric results (p < 0.05) for air conduction, bone conduction, and the air bone gap. Postoperatively, younger patients' 4000 to 8000 Hz (air conduction) and 4000 Hz (bone conduction) were better than those of the older patients (p < 0.05), but the high frequency range was still poorer than age-matched controls in the younger patients.

CONCLUSION

Stapedectomy resulted in significant closure of the air bone gap between 500 to 4000 Hz, but failed to influence hearing above 4000 Hz. Age appears to be an important variable; poorer results in the high frequency range were seen in the older patients who underwent stapes surgery. These findings, together with the residual postoperative hearing loss in the high frequency range in young patients, may reflect disease-specific injury resulting from cochlear otosclerosis.

Are social supports in late midlife a cause or a result of successful physical ageing?

BACKGROUND

Many studies have noted a strong association between poor social support and premature mortality. A limitation of such studies has been their failure to control adequately for confounders that damage both social supports and physical health.

METHODS

A 50-year prospective multivariate study of 223 men was used to examine the possible causal relationships between social supports and health. Alcohol abuse, prior physical health and mental illness prior to age 50 were controlled. Relative social supports were quantified over the period from age 50 to 70.

RESULTS

Adequacy of social supports from age 50 to 70 was powerfully correlated with physical health at age 70 (P < 0.001). However, such social supports were also powerfully predicted by alcohol abuse (P < 0.001), smoking (P < 0.001) and indicators of major depressive disorder (P < 0.01) assessed at age 50. When prior smoking, depression and alcohol abuse were controlled, then the association of physical health with social supports was very much attenuated. Some facets of social support like religion and confidantes were unassociated with health even at a univariate level. Surprisingly, in this sample friends seemed more important for sustained physical health than closeness to spouse and to children.

CONCLUSIONS

While social supports undoubtedly play a significant role in maintaining physical well-being in late life, much of the association between poor social supports and mortality may be mediated by alcoholism, smoking and pre-morbid psychopathology.

Developmental changes in tympanometry: a case study

The use of 226 Hz tympanometry in neonates and infants has been controversial due to the large number of false negative responses for middle ear pathology. A review of the literature highlights several anatomical differences between this population and that of the adult, which is not recognized during interpretation of their tympanograms. The aim of the study was to document tympanometric changes in a single child using 226 Hz, 1000 Hz and sweep frequency probe tones until she was 6.5 months old. Both 226 Hz and 1000 Hz tympanograms show a maturational change in middle ear resonance from a mass to a stiffness-dominated system, which was corroborated by sweep frequency probe tones. It is suggested that high-frequency probe tones were able to increase test sensitivity to the mechanics of the middle ear when it was mass-dominated, as in this infant. Due to the large intersubject variability reported in the literature, it is recommended that both high and conventional probe tone tympanograms are performed in infants under 6 months of age to increase diagnostic accuracy. Middle ear resonance can also be determined for each individual enabling more appropriate selection of probe tones for Y, B and G tympanometry.

Binaural unmasking returns to normal in teenagers who had otitis media in infancy

Several studies have shown that the binaural masking level difference (MLD) is reduced in children who have a history of recurrent otitis media (OM) in infancy. In this prospective study we have retested the MLD in two groups of teenagers who were originally tested 6 years ago. Members of one of these groups (OM group; n = 26) had at least 5 recorded episodes of OM before the age of 5 years. The other group (controls; n = 17) had no known history of OM. The mean MLD (500-Hz tone in a narrow band noise masker) of the OM group was, at 6-12 years of age, significantly lower than that of the controls. In this study (at ages 12-18 years), we found no difference between the mean MLDs of the OM and control groups. These results show that the reduced MLD that occurs following OM in infancy can recover in later childhood.

1995 IPA/Bayer Research Awards in Psychogeriatrics. Late-life consequences of affective spectrum disorder

Recent research suggests that affective disorder is associated with increased mortality and physical morbidity, but the reasons for this association remain uncertain. This report describes a 50-year prospective study of 240 men evaluated from the time they were university students in 1940-1942. A family history of mental illness was obtained and the men's habits, psychological adjustment, and marital and occupational satisfaction were followed every 2 years and their objective physical health was tracked every 5 years until age 70. Twenty-five men were identified as having affective spectrum disorder prior to age 53. Of the variables studied, the presence of affective spectrum disorder was the most powerful predictor of poor psychosocial outcome at age 65 and one of the most powerful predictors of poor physical health. Alcohol abuse and cigarette abuse accounted for the observed increased rates of heart disease and cancer. When alcohol abuse, smoking, and suicide were controlled for, affective disorder made a significant contribution to physical morbidity by age 70, but not to mortality from natural causes. Affective spectrum disorder, even in an educated population without antisocial trends, carries a profound negative risk to late-life physical and social adjustment.

The intron of Arabidopsis thaliana polyubiquitin genes is conserved in location and is a quantitative determinant of chimeric gene expression

We have isolated and determined DNA sequence for the 5'-flanking regions of three Arabidopsis thaliana polyubiquitin genes, UBQ3, UBQ10, and UBQ11. Comparison to cDNA sequences revealed the presence of an intron in the 5'-untranslated region at the same position immediately upstream of the initiator methionine codon in each of the three genes. An intron at this position is also present in two sunflower and two maize polyubiquitin genes. An intron is also found in the 5'-untranslated regions of several animal polyubiquitin genes, although the exact intron position is not conserved among them, and none are in the same position as those in the higher plant polyubiquitin genes. Chimeric genes containing the 5'-flanking regions of UBQ3, UBQ10, and UBQ11 in front of the coding regions for the reporter enzyme Escherichia coli beta-glucuronidase (GUS) were constructed. When introduced transiently into Arabidopsis leaves via microprojectile bombardment, all resulted in readily detectable levels of GUS activity that were quantitatively similar. The introns of UBQ3 and UBQ10 in the corresponding promoter fragments were removed by replacement with flanking cDNA sequences and chimeric genes constructed. These constructs resulted in 2.5- to 3-fold lower levels of marker enzyme activity after transient introduction into Arabidopsis leaves. The UBQ10 promoter without the 5' intron placed upstream of firefly luciferase (LUX) resulted in an average of 3-fold lower LUX activity than from an equivalent construct with the UBQ10 intron. A UBQ3 promoter cassette was constructed for the constitutive expression of open reading frames in dicot plants and it produced readily detectable levels of GUS activity in transient assays.

Binaural masking level differences in infants with and without otitis media with effusion

The binaural masking level difference (MLD) was measured in two groups of infants (aged 7-10 months) who either had or did not have a documented history of otitis media with effusion (OME). Subjects were trained to detect a 500 Hz signal (either in or out-of-phase between the ears) against an in-phase, narrow band noise masker centred at 500 Hz. Non-OME infants had elevated masked thresholds and reduced MLDs compared with normal-hearing older (7-12 years) children and adults (20-27 years). OME infants also had elevated masked thresholds and reduced MLDs but, in contrast to studies using older subjects, their results were similar to those of the non-OME infants. These results suggest that, during at least the first year of life, infants are disadvantaged compared with adults or children when listening in noisy environments. They also suggest that OME does not further compromise infants' ability to detect sounds in those environments.

Binaural masking level differences in children with a history of otitis media

The binaural hearing of children with and without a history of otitis media (OM) was assessed by determining their binaural masking level differences (BMLDs). The test was also administered to a group of adults. BMLDs for the non-OM children were not significantly different from those of adults. However the mean BMLD of the OM children was significantly lower than that of non-OM children. Some children in the OM group had small (15-25 dB HL) sensitivity deficits in one or both ears. However, no correlation was found between BMLD and hearing level in cases of either symmetric or asymmetric loss. Exclusion of OM children with residual middle ear abnormalities did not abolish the significant difference between the OM and non-OM groups. We suggest that the small BMLDs in the OM group may be associated with these children having difficulties detecting and attending to signals in noisy environments.

Osmotic regulation of PhoE porin synthesis in Escherichia coli

In Escherichia coli, adaptation to hyperosmotic conditions alters the expression of the outer membrane porins OmpF and OmpC. The amount of PhoE porin, which is normally induced by phosphate deprivation, was greatly reduced in cells adapted to high-osmolarity conditions. Osmoregulation of PhoE operated independently of the activity of the PhoR phosphate sensor and did not involve cross-talk from the homologous osmosensor EnvZ. PhoE synthesis was partially restored by additional copies of the positive regulator phoB+ and by the osmoprotectant glycine betaine.

[A contribution to series sectioning of larynx (author's transl)]

A histological method for large series sectioning of larynx is described. The decalcification consists of 5% HNO3, absolute alcohol and 0,5 chromic trioxide. The larynx is imbedded in paraplast. Sections of 6--10 micron in thickness can be cut from blocs 8 X 6 X 5 cm and stained by general histological methods. The complete procedure took only six to seven weeks.