Testing the Drosophila maternal haploid gene for functional divergence and a role in hybrid incompatibility

Crosses between Drosophila simulans females and Drosophila melanogaster males produce viable F1 sons and poorly viable F1 daughters. Unlike most hybrid incompatibilities, this hybrid incompatibility violates Haldane's rule, the observation that incompatibilities preferentially affect the heterogametic sex. Furthermore, it has a different genetic basis than hybrid lethality in the reciprocal cross, with the causal allele in Drosophila melanogaster being a large species-specific block of complex satellite DNA on its X chromosome known as the 359-bp satellite, rather than a protein-coding locus. The causal allele(s) in Drosophila simulans are unknown but likely involve maternally expressed genes or factors since the F1 females die during early embryogenesis. The maternal haploid (mh) gene is an intriguing candidate because it is expressed maternally and its protein product localizes to the 359-bp repeat. We found that this gene has diverged extensively between Drosophila melanogaster and Drosophila simulans. This observation led to the hypothesis that Drosophila melanogaster mh may have coevolved with the 359-bp repeat and that hybrid incompatibility thus results from the absence of a coevolved mh allele in Drosophila simulans. We tested for the functional divergence of mh by creating matched transformants of Drosophila melanogaster and Drosophila simulans orthologs in both Drosophila melanogaster and Drosophila simulans strains. Surprisingly, we find that Drosophila simulans mh fully complements the female sterile phenotype of Drosophila melanogaster mh mutations. Contrary to our hypothesis, we find no evidence that adding a Drosophila melanogaster mh gene to Drosophila simulans increases hybrid viability.

Differences in Comorbidities Explain Black-White Disparities in Outcomes After Femoropopliteal Endovascular Intervention

BACKGROUND

Black adults have a higher incidence of peripheral artery disease and limb amputations than White adults in the United States. Given that peripheral endovascular intervention (PVI) is now the primary revascularization strategy for peripheral artery disease, it is important to understand whether racial differences exist in PVI incidence and outcomes.

METHODS

Data from fee-for-service Medicare beneficiaries ≥66 years of age from 2016 to 2018 were evaluated to determine age- and sex-standardized population-level incidences of femoropopliteal PVI among Black and White adults over the 3-year study period. Patients' first inpatient or outpatient PVIs were identified through claims codes. Age- and sex-standardized risks of the composite outcome of death and major amputation within 1 year of PVI were examined by race.

RESULTS

Black adults underwent 928 PVIs per 100 000 Black beneficiaries compared with 530 PVIs per 100 000 White beneficiaries (risk ratio, 1.75 [95% CI, 1.73-1.77]; P<0.01). Black adults who underwent PVI were younger (mean age, 74.5 years versus 76.4 years; P<0.01), were more likely to be female (52.8% versus 42.7%; P<0.01), and had a higher burden of diabetes (70.6% versus 56.0%; P<0.01), chronic kidney disease (67.5% versus 56.6%; P<0.01), and heart failure (47.4% versus 41.7%; P<0.01) than White adults. When analyzed by indication for revascularization, Black adults were more likely to undergo PVI for chronic limb-threatening ischemia than White adults (13 023 per 21 352 [61.0%] versus 59 956 per 120 049 [49.9%]; P<0.01). There was a strong association between Black race and the composite outcome at 1 year (odds ratio, 1.21 [95% CI, 1.16-1.25]). This association persisted after adjustment for socioeconomic status (odds ratio, 1.08 [95% CI, 1.03-1.13]) but was eliminated after adjustment for comorbidities (odds ratio, 0.96 [95% CI, 0.92-1.01]).

CONCLUSIONS

Among fee-for-service Medicare beneficiaries, Black adults had substantially higher population-level PVI incidence and were significantly more likely to experience adverse events after PVI than White adults. The association between Black race and adverse outcomes appears to be driven by a higher burden of comorbidities. This analysis emphasizes the critical need for early identification and aggressive management of peripheral artery disease risk factors and comorbidities to reduce Black-White disparities in the development and progression of peripheral artery disease and the risk of adverse events after PVI.

Intravascular ultrasound in peripheral venous and arterial interventions: A contemporary systematic review and grading of the quality of evidence

Although angiography has been the primary imaging modality used in peripheral vascular intervention, this technique has major limitations due to the evaluation of three-dimensional vessels in two dimensions. Intravascular ultrasound (IVUS) is an important adjunctive tool that can address some of these limitations. This systematic review assesses the appropriateness of IVUS as an imaging modality for guiding peripheral intervention through evidence collection and clinical appraisal of studies. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a cohort of 48 studies (29 arterial; 19 venous) detailing IVUS use in peripheral vascular intervention were extracted. Qualitative assessment of the studies evaluated pre- and postprocedure efficacy of IVUS and revealed that IVUS-guided peripheral intervention in arterial and venous diagnosis and treatment was superior to other imaging techniques alone. Each study in the cohort was further assessed for reliability and validity using the Oxford Centre for Evidence Based Medicine (CEBM) level of evidence scale. The majority of both arterial (79.3%) and venous (73.7%) studies received a 2b rating, the second highest level of evidence rating. The evidence to date indicates that IVUS results in better clinical outcomes overall and should be more widely adopted as an adjunctive imaging modality during peripheral intervention. (PROSPERO Registration No.: CRD42021232353).

Regulation of dopaminergic function: an [18F]-DOPA PET apomorphine challenge study in humans

Dopaminergic function has a key role in normal brain function, dopaminergic dysfunction being implicated in numerous neuropsychiatric disorders. Animal studies show that dopaminergic stimulation regulates dopaminergic function, but it is not known whether this exists in humans. In the first study (study 1), we measured dopamine synthesis capacity (indexed as K_i^cer) to identify the relationship between baseline and change in K_i^cer under resting conditions for comparison with effects of dopaminergic stimulation. In the second study (study 2), we used a within-subjects design to test effects of dopaminergic stimulation on dopamine synthesis capacity. In study 1, eight volunteers received two ¹⁸F-DOPA scans on separate days, both at rest. In study 2, 12 healthy male volunteers received two ¹⁸F-DOPA positron emission tomographic (PET) scans after treatment with either the dopamine partial agonist apomorphine (0.03 or 0.005 mg kg^-1) or placebo. In study 1, no significant correlation was found between baseline and change in dopamine synthesis capacity between scans (r=-0.57, n=8, P=0.17, two-tailed). In study 2, a significant negative correlation was found between baseline dopamine synthesis capacity and percentage change in dopamine synthesis capacity after apomorphine challenge (r=-0.71, n=12, P=0.01, two-tailed). This correlation was significantly different (P<0.01) from the correlation between baseline and change in dopamine synthesis capacity under unstimulated conditions. One-way repeated-measures analysis of variance showed a significant group (study 1/study 2) × time interaction (F(1,18)=11.5, P=0.003). Our findings suggest that regulation of dopamine synthesis capacity by apomorphine depends on baseline dopamine function, consistent with dopamine stimulation stabilizing dopaminergic function. Loss of this autoregulation may contribute to dopaminergic dysfunction in brain disorders such as schizophrenia, substance dependence, and Parkinson's disease.

Chronic exposure to haloperidol and olanzapine leads to common and divergent shape changes in the rat hippocampus in the absence of grey-matter volume loss

BACKGROUND

One of the most consistently reported brain abnormalities in schizophrenia (SCZ) is decreased volume and shape deformation of the hippocampus. However, the potential contribution of chronic antipsychotic medication exposure to these phenomena remains unclear.

METHOD

We examined the effect of chronic exposure (8 weeks) to clinically relevant doses of either haloperidol (HAL) or olanzapine (OLZ) on adult rat hippocampal volume and shape using ex vivo structural MRI with the brain retained inside the cranium to prevent distortions due to dissection, followed by tensor-based morphometry (TBM) and elastic surface-based shape deformation analysis. The volume of the hippocampus was also measured post-mortem from brain tissue sections in each group.

RESULTS

Chronic exposure to either HAL or OLZ had no effect on the volume of the hippocampus, even at exploratory thresholds, which was confirmed post-mortem. In contrast, shape deformation analysis revealed that chronic HAL and OLZ exposure lead to both common and divergent shape deformations (q = 0.05, FDR-corrected) in the rat hippocampus. In particular, in the dorsal hippocampus, HAL exposure led to inward shape deformation, whereas OLZ exposure led to outward shape deformation. Interestingly, outward shape deformations that were common to both drugs occurred in the ventral hippocampus. These effects remained significant after controlling for hippocampal volume suggesting true shape changes.

CONCLUSIONS

Chronic exposure to either HAL or OLZ leads to both common and divergent effects on rat hippocampal shape in the absence of volume change. The implications of these findings for the clinic are discussed.

Leveraging Industry-Academia Collaborations in Adaptive Biomedical Innovation

Despite the rapid pace of biomedical innovation, research and development (R&D) productivity in the pharmaceutical industry has not improved broadly. Increasingly, firms need to leverage new approaches to product development and commercial execution, while maintaining adaptability to rapid changes in the marketplace and in biomedical science. Firms are also seeking ways to capture some of the talent, infrastructure, and innovation that depends on federal R&D investment. As a result, a major transition to external innovation is taking place across the industry. One example of these external innovation initiatives is the Sanofi-MIT Partnership, which provided seed funding to MIT investigators to develop novel solutions and approaches in areas of interest to Sanofi. These projects were highly collaborative, with information and materials flowing both ways. The relatively small amount of funding and short time frame of the awards built an adaptable and flexible process to advance translational science.

Effect of chronic antipsychotic treatment on striatal phosphodiesterase 10A levels: a [¹¹C]MP-10 PET rodent imaging study with ex vivo confirmation

A number of phosphodiesterase 10A (PDE10) inhibitors are about to undergo clinical evaluation for their efficacy in treating schizophrenia. As phosphodiesterases are in the same signalling pathway as dopamine D2 receptors, it is possible that prior antipsychotic treatment could influence these enzyme systems in patients. Chronic, in contrast to acute, antipsychotic treatment has been reported to increase brain PDE10A levels in rodents. The aim of this study was to confirm these findings in a manner that can be translated to human imaging studies to understand its consequences. Positron emission tomography (PET) scanning was used to evaluate PDE10A enzyme availability, after chronic haloperidol administration, using a specific PDE10A ligand ([(11)C]MP-10). The binding of [(11)C]MP-10 in the striatum and the cerebellum was measured in rodents and a simplified reference tissue model (SRTM) with cerebellum as the reference region was used to determine the binding potential (BPND). In rats treated chronically with haloperidol (2 mg kg(-1) per day), there was no significant difference in PDE10A levels compared with the vehicle-treated group (BPND±s.d.: 3.57 ± 0.64 versus 2.86 ± 0.71). Following PET scans, ex vivo analysis of striatal brain tissue for PDE10A mRNA (Pde10a) and PDE10A enzyme activity showed no significant difference. Similarly, the PDE10A protein content determined by western blot analysis was similar between the two groups, contrary to an earlier finding. The results of the study indicate that prior exposure to antipsychotic medication in rodents does not alter PDE10A levels.

Haloperidol and olanzapine mediate metabolic abnormalities through different molecular pathways

The pathogenesis of antipsychotic-induced disturbances of glucose homeostasis is still unclear. Increased visceral adiposity has been suggested to be a possible mediating mechanism. The aim of this study was to investigate, in an animal model, the differential effects of olanzapine and haloperidol on visceral fat deposition (using magnetic resonance imaging(MRI)) and on critical nodes of the insulin signaling pathway (liver-protein levels of IRS2 (insulin receptor substrate 2), GSK3α (glycogen synthase kinase-3α), GSK3β, GSK3α-Ser21, GSK3β-Ser9). To this end, we studied male Sprague-Dawley rats treated with vehicle (n=8), haloperidol (2 mg kg(-1) per day, n=8), or olanzapine (10 mg kg(-1)per day, n=8), using osmotic minipumps, for 8 weeks. The haloperidol group showed a higher percentage of visceral fat than both the olanzapine group and the vehicle group, whereas there was no difference between the olanzapine and the vehicle group. In terms of insulin signaling pathway, the olanzapine group showed significantly reduced IRS2 levels, reduced phosphorylation of GSK3α and increased phosphorylation of GSK3β, whereas there was no difference between the haloperidol and the vehicle group. Our data suggest that different molecular pathways mediate the disturbances of glucose homeostasis induced by haloperidol and olanzapine with a direct effect of olanzapine on the insulin molecular pathway, possibly partly explaining the stronger propensity of olanzapine for adverse effects on glucose regulation when compared with haloperidol in clinical settings.

Antimicrobial effect and mode of action of terpeneless cold-pressed Valencia orange essential oil on methicillin-resistant Staphylococcus aureus

AIMS

The objectives of this study were to evaluate the antistaphylococcal effect and elucidate the mechanism of action of orange essential oil against antibiotic-resistant Staphylococcus aureus strains.

METHODS AND RESULTS

The inhibitory effect of commercial orange essential oil (EO) against six Staph. aureus strains was tested using disc diffusion and agar dilution methods. The mechanism of EO action on MRSA was analysed by transcriptional profiling. Morphological changes of EO-treated Staph. aureus were examined using transmission electron microscopy. Results showed that 0·1% of terpeneless cold-pressed Valencia orange oil (CPV) induced the cell wall stress stimulon consistent with the inhibition of cell wall synthesis. Transmission electron microscopic observation revealed cell lysis and suggested a cell wall lysis-related mechanism of CPV.

CONCLUSIONS

CPV inhibits the growth of Staph. aureus, causes gene expression changes consistent with the inhibition of cell wall synthesis, and triggers cell lysis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Multiple antibiotics resistance is becoming a serious problem in the management of Staph. aureus infections. In this study, the altered expression of cell wall-associated genes and subsequent cell lysis in MRSA caused by CPV suggest that it may be a potential antimicrobial agent to control antibiotic-resistant Staph. aureus.

Compensatory changes in enzymes of arginine metabolism during renal hypertrophy in mice

The present study investigates enzyme activities of the urea cycle, transamidinase and ornithine-proline inter-conversion in the hypertrophied kidney after unilateral nephrectomy in mice. Surgical removal of the left kidney in mice led to compensatory enlargement of the right kidney after 1 and 14 days. This renal growth was associated with an increase in glomerular volume (but not number) and enlargement of the proximal convoluted tubules. The total renal protein content increased in proportion to the increase in kidney weight, but the protein per gram weight of kidney did not change. The specific activity of only ornithine aminotransferase (OAT), the rate-limiting enzyme in the conversion of ornithine to proline, increased in 2 weeks of hypertrophy. The specific activity of all other enzymes was unchanged. However, the total enzyme activity per kidney of all the enzymes, without exception, was elevated in the hypertrophied kidney. While the increase in total OAT activity was much more than the increase in kidney weight, all other enzymes increased more or less in proportion to the increase in renal mass. The results suggest that compensation in OAT activity to chronic reduction in renal mass was complete, but only partial in the case of other enzymes.

Delivery of a stringent dimerizer-regulated gene expression system in a single retroviral vector

Small molecule-regulated transcription has broad utility and would benefit from an easily delivered self-contained regulatory cassette capable of robust, tightly controlled target gene expression. We describe the delivery of a modified dimerizer-regulated gene expression system to cells on a single retrovirus. A transcription factor cassette responsive to the natural product dimerizer rapamycin was optimized for retroviral delivery by fusing a highly potent chimeric activation domain to the rapamycin-binding domain of FKBP-rapamycin-associated protein (FRAP). This improvement led to an increase in both the potency and maximal levels of gene expression induced by rapamycin, or nonimmunosuppressive rapamycin analogs. The modified transcription factor cassette was incorporated along with a target gene into a single rapamycin-responsive retrovirus. Cell pools stably transduced with the single virus system displayed negligible basal expression and gave induction ratios of at least three orders of magnitude in the presence of rapamycin or a nonimmunosuppressive rapamycin analog. Levels of induced gene expression were comparable to those obtained with the constitutive retroviral long terminal repeat and the single virus system performed well in four different mammalian cell lines. Regulation with the dimerizer-responsive retrovirus was tight enough to allow the generation of cell lines displaying inducible expression of the highly toxic diphtheria toxin A chain gene. The ability to deliver the tightly inducible rapamycin system in a single retrovirus should facilitate its use in the study of gene function in a broad range of cell types.

The positive role of voids in the plasma membrane in growth and energetics of Escherichia coli

Bacterial respiration, endogenous as well as induced respiration by glucose, lactose and glycine betaine, was found to be sensitive to external solute concentration. Permeability of hydrogen peroxide, a non-electrolyte of molecular size between water and urea, through the bacterial membranes changed directly with the rate of respiration (an activity residing in the bacterial plasma membrane) in E. coli and the enhanced permeability and respiratory activity were highly correlated. Hydrogen peroxide permeability and induction of voids (spaces in the matrix of the bilayer into which hydrophobic fluorescent probes partition, which in turn were used to assess the modulation of these cavities) were shown to be a direct and excellent measure of leak conductance. Fluorescence intensity and anisotropy of the extrinsic fluorescent probes (incorporated by growing bacteria in their presence) decreased with increased respiration in bacteria, consistent with lowered molecular restriction and enhanced hydration in the membrane phase for these probes as seen in dimyristoylphosphatidylcholine bilayers due to phase transition. The physical basis of osmotic phenomena, as a relevant (thermodynamic) volume, could relate to water exchange or compression, depending on the osmotic domain. In the domain of compression in bacteria, i.e. well above the isotonic range, the computed activation volume was consistent with voids in the membrane. This study emphasises a major role of leak conductance in bacterial physiology and growth.

A general strategy to enhance the potency of chimeric transcriptional activators

Efforts to increase the potency of transcriptional activators are generally unsuccessful because poor expression of activators in mammalian cells limits their delivery to target promoters. Here we report that the effectiveness of chimeric activators can be dramatically improved by expressing them as noncovalent tetrameric bundles. Bundled activation domains are much more effective at activating a reporter gene than simple monomeric activators, presumably because, at similar expression levels, up to 4 times as many the activation domains are delivered to the target promoter. These bundled activation domains are also more effective than proteins in which activation domains are tandemly reiterated in the same polypeptide chain, because such proteins are very poorly expressed and therefore not delivered effectively. These observations suggest that there is a threshold number of activation domains that must be bound to a promoter for activation, above which promoter activity is simply a function of the number of activators bound. We show that bundling can be exploited practically to enhance the sensitivity of mammalian two-hybrid assays, enabling detection of weak interactions or those between poorly expressed proteins. Bundling also dramatically improves the performance of a small-molecule-regulated gene expression system when the expression level of regulatory protein is limiting, a situation that may be encountered in gene therapy applications.

Proteasome-mediated degradation of transcriptional activators correlates with activation domain potency in vivo

We show that the intracellular concentration of transcriptional activator proteins is regulated by the proteasome-mediated protein degradation pathway. The rate of degradation of activators by proteasomes correlates with activation domain potency in vivo. Mutations either in the activation domain residues involved in target protein interaction or in the DNA-binding domain residues essential for DNA binding abolish the transcriptional activation function in vivo and render the activator resistant to degradation by proteasomes. Finally, using a rapamycin-regulated gene expression system, we show that recruiting activation domains to DNA-bound receptor proteins greatly enhanced the rate of degradation of reconstituted activators. These observations suggest that in mammalian cells efficient recruitment of activator-target protein complexes to the promoter means that they are subjected to rapid degradation by proteasomes. We propose that proteasome-mediated control of the intracellular levels of transcriptional activators could play an important role in the regulation of gene expression.

A versatile synthetic dimerizer for the regulation of protein-protein interactions

The use of low molecular weight organic compounds to induce dimerization or oligomerization of engineered proteins has wide-ranging utility in biological research as well as in gene and cell therapies. Chemically induced dimerization can be used to activate intracellular signal transduction pathways or to control the activity of a bipartite transcription factor. Dimerizer systems based on the natural products cyclosporin, FK506, rapamycin, and coumermycin have been described. However, owing to the complexity of these compounds, adjusting their binding or pharmacological properties by chemical modification is difficult. We have investigated several families of readily prepared, totally synthetic, cell-permeable dimerizers composed of ligands for human FKBP12. These molecules have significantly reduced complexity and greater adaptability than natural product dimers. We report here the efficacies of several of these new synthetic compounds in regulating two types of protein dimerization events inside engineered cells--induction of apoptosis through dimerization of engineered Fas proteins and regulation of transcription through dimerization of transcription factor fusion proteins. One dimerizer in particular, AP1510, proved to be exceptionally potent and versatile in all experimental contexts tested.

A humanized system for pharmacologic control of gene expression

Gene therapy was originally conceived as a medical intervention to replace or correct defective genes in patients with inherited disorders. However, it may have much broader potential as an alternative delivery platform for protein therapeutics, such as cytokines, hormones, antibodies and novel engineered proteins. One key technical barrier to the widespread implementation of this form of therapy is the need for precise control over the level of protein production. A suitable system for pharmacologic control of therapeutic gene expression would permit precise titration of gene product dosage, intermittent or pulsatile treatment, and ready termination of therapy by withdrawal of the activating drug. We set out to design such a system with the following properties: (1) low baseline expression and high induction ratio; (2) positive control by an orally bioavailable small-molecule drug; (3) reduced potential for immune recognition through the exclusive use of human proteins; and (4) modularity to allow the independent optimization of each component using the tools of protein engineering. We report here the properties of this system and demonstrate its use to control circulating levels of human growth hormone in mice implanted with engineered human cells.

YY1 facilitates the association of serum response factor with the c-fos serum response element

YY1 is a multifunctional transcription factor that acts as an activator or repressor in different contexts. YY1 binds to multiple sites in the mouse c-fos promoter, inducing at each site a sharp DNA bend. Binding of YY1 to a site situated between the cyclic AMP response element (CRE) and the TATA box bends the DNA in a way that interferes with the interaction of proteins bound at the CRE and TATA elements, resulting in repression of transcription. Here, we show that binding of YY1 to a different site in the c-fos promoter has a different result. Binding of YY1 to the c-fos serum response element (SRE) enhances the binding of serum response factor (SRF). This enhancement requires the binding of YY1 to SRE DNA. YY1 and SRF can cooccupy the SRE at least transiently. In the region of overlapping contact, YY1 contacts DNA in the major groove, while SRF contacts DNA in the minor groove. YY1 also enhances the association of SRF with the SRE in transfected insect cells. Thus, although YY1 induces similar structural changes in DNA at different binding sites, it can have distinct local effects on protein-DNA and protein-protein interactions. These data support a general role for YY1 in the building of highly organized promoter complexes.

DNA bending and orientation-dependent function of YY1 in the c-fos promoter

The assembly of multicomponent complexes at promoters, enhancers, and silencers likely entails perturbations in the path of the DNA helix. We present evidence that YY1, a ubiquitously expressed DNA-binding protein, regulates the activity of the c-fos promoter primarily through an effect on DNA structure. YY1 binds to and induces a phased DNA bend at three sites in this promoter. By use of a truncated c-fos promoter activity containing a single functional YY1 site, we show that YY1 represses promoter activity but that repression does not appear to be an intrinsic property of the protein in this context. Moreover, when the orientation of the YY1 site is reversed, YY1 activates the same promoter. Repression by YY1 is also alleviated by changing the relative phasing of factor-binding sites on either side of YY1. We conclude that the principal function of YY1 in this promoter is to bend DNA to regulate contact between other proteins. Thus, YY1 represents a new class of transcription factors that influences promoter function by affecting promoter structure rather than by directly contacting the transcriptional machinery. We provide evidence that the product of the male sex determination gene SRY may also belong to this class of structural factors.

Human and Drosophila homeodomain proteins that enhance the DNA-binding activity of serum response factor

Cells with distinct developmental histories can respond differentially to identical signals, suggesting that signals are interpreted in a fashion that reflects a cell's identity. How this might occur is suggested by the observation that proteins of the homeodomain family, including a newly identified human protein, enhance the DNA-binding activity of serum response factor, a protein required for the induction of genes by growth and differentiation factors. Interaction with proteins of the serum response factor family may allow homeodomain proteins to specify the transcriptional response to inductive signals. Moreover, because the ability to enhance the binding of serum response factor to DNA residues within the homeodomain but is independent of homeodomain DNA-binding activity, this additional activity of the homeodomain may account for some of specificity of action of homeodomain proteins in development.

Presence of a partial urea cycle in the leech, Poecilobdella granulosa

Ornithine carbamoyltransferase (OCT) and arginase, but not arginine synthetase (AS), were detected in the body wall and gut tissues of the leech. The activities of these enzymes were not altered by starvation. The high activity of arginase in body wall is probably due to the association of the latter with botryoidal tissue. Hirudineans, which evolved from oligochaete ancestors, appear to have lost the citrulline-arginine segment of the urea cycle due to their ammonotelic mode of nitrogen excretion.

Allantoin excretion in snakes

Allantoin, which is generally regarded as absent in the excreta of snakes, has been demonstrated in the urinary deposits of 7 species of snakes by a sensitive paper chromatographic method. It appears that allantoin is the end product of purine catabolism in these animals.

The expression of sequences similar to the human c-erb-A oncogene are regulated in a tissue and stage specific manner in Drosophila melanogaster

The gene encoding the human thyroid hormone receptor, c-erb-A, is hypothesized to be a member of a superfamily of genes, which originated from a primordial receptor encoding gene. To trace the molecular evolutionary background of this gene, we initiated the search for it in the genome of Drosophila melanogaster by using low stringency hybridization analysis. We report here the presence of more than one gene in Drosophila with varying degrees of sequence similarity. By RNA blot hybridization analyses utilizing both wild type and a temperature sensitive ecdysone deficient mutant strain, ecd1, with a human c-erb-A probe, we show that a single high molecular weight RNA of 6.8kb in size is recognized by human c-erb-A, is regulated in a stage and tissue specific manner, and is also inducible in organisms of the ecd1 mutant strain in the presence of exogeneous ecdysone.