The impact of improved glycaemic control with GLP-1 receptor agonist therapy on diabetic retinopathy

Rapid improvement in glycaemic control with GLP-1 receptor agonist (RA) therapy has been reported to be associated with significant progression of diabetic retinopathy. This deterioration is transient, and continuing GLP-1 RA treatment is associated with reversal of this phenomenon. Pre-existent maculopathy, higher grade of retinopathy and longer duration of diabetes may be risk factors for persistent deterioration.

GLP-1 agonist treatment: implications for diabetic retinopathy screening

Rapid improvement in glycaemic control induced by GLP-1 agonist therapy could be yet another illustration of transient or permanent progression of diabetic retinopathy, similar to documented examples such as pregnancy and continuous subcutaneous insulin infusion. Specific guidelines would be needed to monitor this paradoxical phenomenon during treatment with GLP-1 agonists.

Molecular studies of hemichordate development: a key to understanding the evolution of bilateral animals and chordates

Using the Hawaiian acorn worm, Ptychodera flava, we began molecular studies on the development of hemichordates, a phylum previously unstudied at this level. Here we review results garnered from the examination of a few specific genes selected to help understand the evolution of vertebrate structures. These studies suggest new ideas about the evolution of developmental mechanisms in the deuterostomes. In a seminal observation, we noted an unexpected zone of expression of the Brachyurygene in the early anterior embryonic ectoderm where the mouth will form. Typically, the Brachyury gene is closely linked to development of the notochord and is expressed around the blastopore and in the posterior mesoderm in most animals. This first expression of Brachyury at the blastopore may represent a regulatory program associated with organizing the original animal head and gut opening, as suggested by the expression of Brachyury during hypostome formation in hydra. We believe that the anterior expression of Brachyury in deuterostomes represents the cooption of the program for organizing the original animal gut opening to form the deuterostome mouth. Recent data from the trochophore larva of a polychaete show that an anterior zone of expression of Brachyury is produced in this protostome by splitting of the Brachyury field during the formation of a gut with a mouth and anus by the lateral fusion of the sides of the blastopore. The ability to initiate independently a secondary regulatory program to organize the new mouth leading to an anterior field of Brachyury expression may be a signal event in the evolution of the deuterostomes. We also noted that the P. flava homolog of T-brain/Eomes, a gene closely related by sequence and expression around the blastopore to Brachyury and associated with development of the vertebrate brain, also exhibits early posterior expression around the blastopore and a field of de novo anterior ectoderm expression during later embryogenesis. The tissue in the zone of de novo anterior ectoderm expression of Pf-Tbrain produces the apical organ, a larval neural structure that has been touted as an evolutionary precursor of the chordate dorsal brain. The gene regulatory mechanisms responsible for initiating the anterior zone of de novo expression of T-brain may represent a cooption to specify early neuroectoderm of the regulatory program evolved first to drive anterior Brachyury expression for deuterostome mouth formation. It will be interesting to examine the possibilities that an ability to initiate the de novo anterior expression of the program that includes T-brain may be a key event in the evolution of the developmental mechanisms leading to the chordate dorsal nervous system.

T-Brain expression in the apical organ of hemichordate tornaria larvae suggests its evolutionary link to the vertebrate forebrain

T-box genes encode a novel family of sequence-specific activators that appear to play crucial roles in various processes of animal development. Although most of the T-box genes are involved in the mesoderm formation of chordate embryos, mammalian T-Brain is expressed in the developing central nervous system, and defines molecularly distinct domains within the cerebral cortex. Here we report the first invertebrate T-Brain homologue from the hemichordate acorn worm, Ptychodera flava, which we designate Pf-Tbrain. Developmental expression of Pf-Tbrain was examined by whole mount in situ hybridization to various stages of P. flava embryos. A weak, broad in situ hybridization signal of the Pf-Tbrain transcript is first detected during gastrulation in cells around the archenteron, but this signal disappears as gastrulation proceeds. At mid-gastrula an intense signal appears in several apical ectoderm cells of the gastrula. This signal becomes restricted to the apical region, where the eyespots or the light-sensory organ of the tornaria larva form. Expression of Pf-Tbrain in the apical sensory organ of the tornaria and vertebrate T-Brain in the forebrain suggests an evolutionary relationship between the non-chordate deuterostome larval apical sensory organ and the chordate forebrain.

Characterization of gill-specific genes of the acorn worm Ptychodera flava

Acorn worms are hemichordate deuterostomes that have remarkable gills thought to be homologous to pharyngeal gills in urochordates and cephalochordates, and pharyngeal pouches in vertebrates. In search of molecular keys to analyzing the origin and evolution of the anterior gut and neck region of the chordate body, the present study isolated cDNA clones for six gill-specific genes, designated PfG1 to PfG6, from Ptychodera flava using differential screening of a cDNA library of RNA from gills. Northern blotting confirmed that these genes were all expressed only in the gills. In situ hybridization showed that the expression of these genes is limited to the endodermally derived columnar epithelium of the pharynx. PfG1 encodes a 42-kDa polypeptide containing sequence similar to D-domains, protein domains characteristic of extracellular proteins. Expression of PfG1 is localized in a delimited pattern along the columnar epithelium of the inner gill apparatus. Expression in the epibranchial ridge appears as two stripes running longitudinally in the epithelium just lateral of the midline. A stripe of expression also appears in a slightly posterior portion on the curve of each band of columnar epithelium on the pharyngeal surface of the secondary gill bars. The five other gill-specific genes, PfG2 to PfG6, encode a family of C-type lectin polypeptides that appear to be secreted proteins. PfG2 to PfG6 are also expressed in the columnar epithelium of the epibranchial ridge as two parallel stripes, but at the lateral margin of the ridge. One of the genes, PfG6, is additionally expressed in the innermost curve of the epithelium on the pharyngeal surface of each secondary gill bar. The localization of expression of PfPax1/9, a gill-specific transcription factor gene, was examined and shown to also be primarily in the endodermal columnar epithelium on the pharyngeal faces of the gill bars. On the secondary gill bars, where PfG1 and PfG6 are also expressed in the columnar epithelium, PfPax1/9 is expressed in the anterior and posterior portions but signal is not evident in the epithelium on the central, innermost curve of the gill bar. The anterior domain of PfPax1/9 expression is more extensive but overlaps the anterior domain of PfG1 expression, whereas its posterior domain of expression is more posterior and complementary to that of PfG6.

Developmental expression of the hemichordate otx ortholog

The phylogenetic location of hemichordates is unique because they seem to fill an evolutionary gap between echinoderms and chordates. We report here characterization of Pf-otx, a hemichordate ortholog of otx, with its embryonic and larval expression pattern. Pf-otx is initially expressed in the vegetal plate of the blastula. Expression remains evident in the archenteron through gastrulation and then disappears. A new expression domain appears near the mouth along the preoral and postoral ciliated bands in the early tornaria larva.

Molecular characterization of TgHBox4, a Drosophila Abd-B homolog found in the sea urchin Tripneustes gratilla

We have isolated and sequenced a cDNA clone that, as judged by the sequence of the homeobox region, encodes a sea urchin homolog of the homeobox containing the gene Abdominal-B of Drosophila. The total length of the cDNA is 3634 nucleotides and includes an open reading frame, which encodes a protein that is 32,321 Da. The N-terminal region of the homeodomain includes consensus sequences found in some of TgHBox4's Abdominal-B relatives. A genomic clone representing the 5' part of the message was also isolated. This clone and a previously isolated clone were found to represent the full-length cDNA sequence. We have also raised antibodies against a bacterially expressed portion of the TgHBox4 protein and used them to determine the location of TgHBox4 proteins during development. The protein displays ubiquitous expression early in development but becomes more restricted, to posterior regions, late in embryogenesis. Thus, in contrast to its Abd-B homologs in bilateral metazoans, TgHBox4 is probably not involved in pattern formation but may have a posterior-defining role late in embryogenesis.

Characterization of a hemichordate fork head/HNF-3 gene expression

Based on anatomical and developmental similarities, hemichordates are thought to be most closely related to chordates. However, so far very few developmental genes have been characterized from hemichordates. To gain molecular insight into the developmental mechanisms involved in the origin and evolution of chordates, we investigated the expression of a fork head/HNF-3 (PfHNF3) gene in the acorn worm embryo. Chordate fork head genes are implicated in the formation of endoderm, notochord and floor plate. We found that a PfHNF3 transcript was first detected at the early blastula stage; the signal of in situ hybridization was found in the vegetal plate cells, invaginating endoderm and then in the archenteron. By the late gastrula and into the early tornaria larva stages, an intense signal remained in the anterior region of the archenteron, while the expression in the other regions of archenteron decreased. The intense signal was retained in the pharynx of the tornaria larva. A comparison of the pattern of PfHNF3 with that of HNF-3 genes of sea urchin, ascidian, amphioxus and vertebrate suggests a possible acquisition of new functions of the gene during deuterostome evolution.

Novel pattern of Brachyury gene expression in hemichordate embryos

Together with echinoderms and chordates, hemichordates constitute the third major group of the deuterostomes, which share a number of common developmental features. The Brachyury gene is responsible for the formation of notochord, the most defining feature of chordates. Therefore, isolation and characterization of the hemichordate homolog of Brachyury is key to understand the origin and evolution of chordates. Here we show that the hemichordate Brachyury gene (PfBra) is expressed in two regions of the gastrula and young tornaria larva, the archenteron invagination region and the stomodeum invagination region.

Acute Cytotoxic Allogeneic Histoincompatibility Reactions Involving Gray Cells in the Marine Sponge, Callyspongia diffusa

A variety of procedures were used in a study of the histoincompatibility reactions of Callyspongia diffusa. Rejection reactions as traditionally tested between laterally apposed intact fingers cut from two different sponges require about a week of contact to exhibit cytotoxicity. In a miniaturized assay involving reactions between small pieces of tissue snipped from sponges with scissors and pushed together on an insect pin, cytotoxicity is evident within 48 hours of contact. Reactions of cells dissociated by divalent cation removal and allowed to reaggregate in seawater were also studied. Aggregates produced from allogeneic mixtures of cells from two individuals were killed by internal cytotoxic reactions within 36 hours of the initiation of aggregation. After only one hour of aggregation, aggregates from allogeneic mixtures were significantly smaller than aggregates of cells from a single individual. This rapid slowing of aggregation is the earliest response to allogeneic contact that we noted and does not appear to reflect early cytotoxic processes. Apposition of an aggregate containing cells from one sponge to an aggregate containing cells from a second individual leads to mutual destruction. Aggregates harvested and apposed 4 hours after initiation of aggregation begin to show mutual cytotoxicity at 36 hours of contact. Aggregates placed in contact 48 hours after the initiation of aggregation exhibit cytotoxicity within 8 hours. These rapidly reacting 48-hour aggregates exhibit a pronounced accumulation of gray cells at the boundary of allogeneic contact by 8 hours. These results are interpreted as indicating at least five steps in the histoincompatibility reactions of C. diffusa: (1) recognition soon after allogeneic contact; (2) generation of signals that suppress cell aggregation and cell movement and attract gray cells to the boundary of contact; (3) acceleration of the sponge immune response--including the responsiveness of gray cells to accumulate at the boundary of allogeneic contact--by tissue trauma produced when the tissue is cut or dissociated it into individual cells; (4) arrival of gray cells at the boundary of allogeneic contact; and (5) initiation of cytotoxic processes.

Security standards for medical information systems

This paper has provided an overview of some of the aspects of medical information systems security and the standards that are available to implement security solutions. There is a need to address a complete solution for the security of medical information systems: technical, procedural and legal protection of medical records, databases, applications, hardware and software, networks and the management of the system. The existing standards cover some of these topics but not all. There is still room for further work and the development of standardised technological solutions supported by legal and procedural measures.

Distinct pattern of embryonic expression of the sea urchin CyI actin gene in Tripneustes gratilla

Cloning and sequencing of Tripneustes gratilla genomic DNA and cDNA encoding a developmentally regulated, embryonic messenger RNA, referred to as Tg616, revealed an actin-encoding gene orthologous to the CyI actin gene described from Strongylocentrotus purpuratus. Tg616 and SpCyI share: (1) 150 nucleotides of highly conserved sequence 5' of the transcription start site, (2) 95% nucleotide sequence identity in the protein encoding regions, which specify identical amino acid residues in 375 of 377 positions, and (3) extensive nucleotide sequence identity in the 3' untranslated region of their messenger RNAs. Tg616 was therefore designated TgCyI. In situ hybridization shows sequential activation of TgCyI in various cells of the embryo. TgCyI mRNA becomes abundant in primary and secondary mesenchyme cells as they prepare to enter the blastocoel, in prospective aboral ectoderm cells at blastula stage, in gut cells during gut differentiation, and in oral ectoderm at pluteus stage. This pattern of embryonic gene expression is more complex than any of the major patterns of developmentally upregulated genes observed in S. purpuratus embryos and is distinct from SpCyI expression which is progressively restricted to the gut and oral ectoderm.

Invertebrate immune recognition, natural immunity and the evolution of positive selection

Invertebrate immunity exhibits immediate recognition without prior contact. Here, Tom Humphreys and Ellis Reinherz propose that receptors capable of actively recognizing self histocompatibility antigens could be generated by a process similar to positive selection, and that these could guide 'natural immunity' to foreign cells. These ideas provide a conceptual basis for invertebrate immunity and for understanding the evolutionary precedents for T-cell-mediated antigen recognition.

Natural history of dysplastic nevi

BACKGROUND

Dysplastic nevi are markers of melanoma risk and potential precursors of melanoma. Few studies have addressed the natural history of dysplastic nevi.

OBJECTIVE

Our purpose was to describe the changes observed in nevi over time in a cohort of our patients with dysplastic nevi.

METHODS

We used a historical cohort design to study 153 patients with dysplastic nevi observed for a minimum of 5 years. Physical examination at completion of the study was compared with baseline overview and close-up photographs. Lesions excised during the study interval were assessed for history of change.

RESULTS

Fifty one percent of all evaluated nevi (297 of 593) showed clinical signs of change during an average follow-up of 89 months. New nevi were common in adulthood and continued to form in more than 20% of patients older than 50 years of age. Nevi were observed to become more clinically atypical, less clinically atypical, and disappear in all age groups. In this small cohort rates of nevus change were not correlated with personal or family history of melanoma, sex, or total number of nevi. Total nevus counts and rates of nevus change were correlated with age.

CONCLUSION

Dysplastic nevi remain clinically dynamic in adulthood. Our data suggest that the decrease in counts of dysplastic nevi associated with increasing age is only partly explained by the disappearance of nevi over time and probably reflects a tendency to larger numbers of nevi among more recent birth cohorts.

Multiple copies of a DNA sequence from Pseudomonas syringae pathovar phaseolicola abolish thermoregulation of phaseolotoxin production

Phaseolotoxin, a phytotoxin of Pseudomonas syringae pv. phaseolicola, is produced at 18 degrees C but not at 28 degrees C. Here we report that a fragment (24.4 kb) cloned from the wild-type strain, which does not harbour a gene(s) involved in phaseolotoxin biosynthesis, abolishes this thermoregulation in the wild type and suppresses a Tox- mutant at both temperatures. A subclone harbouring a 485 bp fragment contains motifs that are characteristic of DNA-binding sites. In mobility shift assays we have detected a protein(s) from the wild-type and the mutant strains, grown at appropriate temperatures, that specifically binds to the fragment containing the DNA-binding motifs. We propose that the binding protein is a repressor which is 'titrated' by this fragment when it is present in the cell on a multiple copy plasmid, thus allowing expression of phaseolotoxin genes.

N-(4'-hydroxyphenylacetyl)palytoxin: a palytoxin prodrug that can be activated by a monoclonal antibody-penicillin G amidase conjugate

Palytoxin (PTX), one of the most toxic nonprotein molecules known, is cytotoxic at picomolar concentrations against a wide variety of cell types. In contrast to most cytotoxins, PTX exerts its activity extracellularly. A method for targeting PTX to tumor cells is described in which a monoclonal antibody-enzyme conjugate activates a PTX prodrug at surfaces of tumor cells. The prodrug, N-(4'-hydroxyphenylacetyl)palytoxin (NHPAP), was prepared by reacting PTX with an active ester of 4-hydroxyphenylacetic acid. NHPAP was 1000 times less toxic than PTX to a panel of carcinoma and lymphoma cell lines. The cytotoxic activity of the combination of penicillin G amidase from Escherichia coli with NHPAP was equal to PTX. Two cell lines that were multidrug resistant showed no enhanced resistance to NHPAP +/- penicillin G amidase. Immunologically specific activation of NHPAP took place when H2981 cells (L6 antigen positive) were treated with the monoclonal antibody conjugate L6-penicillin G amidase followed by NHPAP. This system is distinguished from other prodrug activation schemes, since the released drug exerts its activity extracellularly, has high potency, and may be able to overcome the multidrug resistant phenotype.

Preformatted charts improve documentation in the emergency department

STUDY OBJECTIVES

To determine if the use of programmed charts with complaint-specific entry criteria results in improved documentation of patient encounters and better clinical outcome.

DESIGN

Prospective study.

SETTING

Emergency department of an urban university hospital.

TYPE OF PARTICIPANTS

Female patients presenting to the emergency department with gynecologic complaints of abdominal pain, bleeding, or vaginal discharge.

INTERVENTIONS

Programmed and blank charts were provided randomly for physicians in the ED.

MEASUREMENTS

Chart scores based on documentation criteria for patient history, physical examination, laboratory studies, diagnosis, and discharge instructions and patient outcome scores of 0% to 100% based on the persistence of their complaints at the time of the follow-up interview.

MAIN RESULTS

Overall documentation of history, physical examination, and laboratory studies was more complete on programmed charts than on blank charts (81.1% vs 71%, P less than .0001). The patient history portion of the charts was found to benefit the most from the use of programmed charts (74.8% vs 60.1%, P less than .0001). Although programmed charts demonstrated better documentation, there was no statistically significant correlation with patient outcome parameters or with patient satisfaction with the quality of medical care. However, more patients whose physicians used programmed charts were satisfied with their physicians' explanations of their problem (chi 2 = 5.2, P less than .02).

CONCLUSION

Programmed charts improve documentation by facilitation of the documentation process and allow more time for patient-physician interaction. Quality of documentation alone, however, is not a reliable indicator of patient outcome or of the quality of care received.

Comparison of Restriction Fragment Length Polymorphisms of Proto-Oncogenes in Native Hawaiians and Other Ethnic Groups in Hawaii

The relative genetic diversity of selected proto-oncogenes in the native Hawaiian gene pool was examined by comparing the restriction fragment length polymorphisms of these genes in a group of 23 individuals with at least part Hawaiian ancestry, and in 20 individuals from other ethnic groups. Twenty-one combinations of the proto-oncogenes, c-fms, c-myc, L-myc, c-Ha-ras, and c-Ki-ras, tested with 1 or more of the restriction enzymes Bam HI, Eco RI, Hind III, Pst I, Pvu I and Kpn I were examined. Sixteen of these did not exhibit RFLPs in Hawaiians or in other ethnic groups. Four of the combinations exhibiting RFLPs in native Hawaiians exhibited similar-sized restriction fragments in the other ethnic groups. Only in the case of c-myc digested with Pst I were 5 individuals of Hawaiian ancestry found to have an RFLP which has not been detected in other ethnic groups. These 5 cases exhibited a 13-kb c-myc fragment in addition to the 5.5-kb fragment found in most Hawaiians and always present in other ethnic groups. The presence in Hawaiians of most RFLPs found in other ethnic groups indicates that the genetic diversity of proto-oncogenes in the gene pool of native Hawaiians is not substantially less than that of other ethnic groups.

Activation of the L1 late H2B histone gene in blastula-stage sea urchin embryos by Antennapedia-class homeoprotein

The L1 late H2B histone gene of the sea urchin Strongylocentrotus purpuratus is transcriptionally activated in late blastula stage embryos by a mechanism that depends on an enhancer element located 3' of the gene (Zhao et al., 1990). A protein factor, designated H2B abp 1, binds this element at a site that resembles the consensus recognition sequence of Antennapedia-class homeodomain proteins. We demonstrate here that Antennapedia (Antp) and Hbox4 proteins, members of the Antennapedia class of homeoproteins from Drosophila and sea urchin respectively, bind the L1 H2B abp 1 site, and that the Drosophila Antp protein acts through this site to trans-activate the L1 H2B gene, in vivo. In addition, RNA gel blot analysis demonstrated that Hbox4 transcripts accumulate in developing embryos with a time course that closely resembles that of H2B adp 1 DNA binding activity and the activity and the transcription rate of the L1 late H2B gene. Finally, we show that antibody prepared against the sea urchin Hbox4 protein, a member of the Abd-B subclass of the Antennapedia class, specifically inhibits binding of the H2B abp 1 factor to the L1 H2B enhancer, suggesting that H2B abp 1 is encoded by Hbox4 or a closely related gene.

The transposable element Uhu from Hawaiian Drosophila--member of the widely dispersed class of Tc1-like transposons

We report the complete nucleotide sequence of the transposable element Uhu from the vicinity of the alcohol dehydrogenase (Adh) gene of Drosophila heteroneura (an endemic Hawaiian Drosophila). The complete element is about 1650 base-pairs (bp) long, has 46-50 base-pair inverse imperfect repeats at it's ends, and contains a large open reading frame potentially encoding a 192 amino acid protein. We demonstrate that Uhu belongs to a class of transposable elements which includes Tc1 from Caenorhabditis elegans, Barney from Caenorhabditis briggsae, and HB1 from Drosophila melanogaster. All of these elements share significant sequence similarity, are approximately 1600 base pairs long, have short inverse terminal repeats (ITRs), contain open reading frames (ORFs) with significant sequence identity, and appear to insert specifically at TA sequences generating target site duplications.

Characterization and expression of two sea urchin homeobox gene sequences

We describe two homeobox sequences, TgHbox5 and TgHbox6, isolated from the Hawaiian sea urchin Tripneustes gratilla using a Drosophila Sex combs reduced probe. Sequence analysis shows that the encoded TgHbox5 homeodomain shares only 30-52% amino acid identity with homeodomains encoded by previously characterized genes, establishing that it is a divergent homeobox that is not in any known class of homeoboxes. TgHbox5 is expressed in the embryo as two major developmentally regulated transcripts. one at 5.0 kilobase (kb) appearing by blastula stage and the other at 2.7 kb appearing at pluteus stage. Multiple transcripts from TgHbox5 are present at a much lower level in adult tissues and are predominantly expressed in small and large intestines. The TgHbox6 homeobox is an Antenna-pedia-class homeobox, which appears not to be expressed during embryogenesis but produces abundant 3.6 and 3.2 kb transcripts in the six adult tissues examined.

Progressively restricted expression of a homeo box gene within the aboral ectoderm of developing sea urchin embryos

A homeo box-containing gene, Hbox1 is expressed in an unusual and highly conserved spatial pattern in embryos of two different species of sea urchin, Tripneustes gratilla and Strongylocentrotus purpuratus. Hybridization in situ shows that this mRNA accumulates initially throughout the aboral ectoderm; however, between blastula and pluteus stages, the region containing Hbox1 mRNA retracts gradually until only a small area around the vertex is labeled in pluteus larvae. Aboral ectoderm appears cytologically uniform and also accumulates uniform levels of other tissue-specific mRNAs. Therefore, the Hbox1 pattern reveals a previously unsuspected heterogeneity of aboral ectoderm cells and a polarity within this tissue. In S. purpuratus, the Hbox1 gene product probably is not involved in initial specification of cell fate, as this message does not achieve a significant fraction of its peak abundance until almost hatching blastula stage, well after the time aboral ectoderm cells have initiated a tissue-specific program of gene expression. RNA blot and RNase protection analyses revealed low levels of Hbox1 mRNA in all adult tissues examined. However, this message was not detectable in mature eggs, suggesting that the Hbox1 gene does not have a maternal function. In addition to highly conserved spatial and temporal patterns of expression, the homeo box genes of these two urchin species also are conserved highly in sequences outside the homeo domain, despite the divergence of these two species (30-45 my). Two notable features of the protein shared with several vertebrate homeo proteins are a short conserved sequence encoded by an exon upstream of that encoding the homeo domain and a large region of high serine and proline content.

Stage- and tissue-specific expression of two homeo box genes in sea urchin embryos and adults

We report the isolation of two different homeo box genes, HB3 and HB4, from the Hawaiian sea urchin Tripneustes gratilla. DNA sequencing revealed a definitive Antennapedia (Antp) class homeo box in each gene. Southern transfer hybridizations showed the genes to be single-copy. A 5.7-kb transcript of the HB3 gene was found in ovary, testis, small intestine and gastrula poly(A)+ RNA. The HB4 gene produces three transcripts. A 3.7-kb and a 4.4-kb transcript are expressed during embryogenesis. A 3.5-kb transcript appears in each of the adult tissues studied. The HB4 gene appears to be the sea urchin cognate of the Drosophila infrabdominal-7 (iab-7) gene, the mouse Hox 1.7 and Hox 3.2 genes and the Xenopus X1Hbox 6 gene. An examination of Antp class homeo box genes in deuterostomes indicates that a chromosomal duplication has taken place in the evolutionary line leading to the vertebrates after the divergence of the echinoderms. Thus, the sea urchin represents the primitive condition.

Sea urchin morphogenesis and cell-hyalin adhesion are perturbed by a monoclonal antibody specific for hyalin

We have generated and characterized a monoclonal antibody (McA Tg-HYL) that recognizes sea urchin hyalin as evidenced by immunofluorescence staining of the hyaline layer (HL) and immunoblot staining of the hyalin protein band. On immunoblots of HL extracts only the hyalin protein reacted with McA Tg-HYL. Immunoprecipitates of radioactive proteins from embryos incubated with [35S]methionine yielded radioactive hyalin and 190, 140 and 105 × 10(3) Mr proteins associated with hyalin. McA Tg-HYL was generated against Tripneustes gratilla embryos but reacts with hyalin from the distantly related sea urchin species, Colobocentrotus atratus, Strongylocentrotus purpuratus, Arbacia punctulata, Lytechinus variegatus and Lytechinus pictus. Developing embryos of the above-mentioned six species were treated with McA Tg-HYL and did not gastrulate or form arms. Observations of treated embryos revealed areas of separation of the hyaline layer from the underlying embryonic cells, suggesting that McA Tg-HYL was interfering with binding of the cells to the HL. Using the centrifugation-based adhesion assay of McClay et al. (Proc. natn. Acad. Sci. U.S.A. 78, 4975–4979, 1981), Fab' fragments of McA Tg-HYL were found to inhibit cell-hyalin binding. McA Tg-HYL did not inhibit hyalin gelation in vitro or the reaggregation of dissociated blastula cells. We postulate that McA Tg-HYL recognizes an evolutionarily conserved hyalin domain involved in cell-hyalin binding and required for normal epithelial folding.

A gene expressed in the endoderm of the sea urchin embryo

Using a previously cloned, developmentally regulated mRNA sequence expressed predominantly in the endoderm of sea urchin pluteus larvae, we isolated genomic clones and additional cDNA clones to define the gene and the protein it encodes. Nucleic acid sequencing revealed that the gene consists of four exons interrupted by three introns and spans approximately 3600 bp. It encodes a low-molecular-weight protein with polar ends. A stretch of Glu and Asp residues at its carboxyl terminus suggests that it is a nucleic acid-binding protein and a stretch of four Lys residues near the amino terminus suggests a nuclear localization signal.

An engrailed class homeo box gene in sea urchins

The homeo box, a conserved DNA element first recognized in Drosophila development-controlling genes, is present in the genomes of many higher metazoan species and provides a valuable probe for the isolation of regulatory genes from diverse phylogenetic groups. We have employed these probes to isolate and study the homeo-box genes in sea urchins. As in other species, the sea urchin homeo boxes fall into at least two classes defined by nucleotide sequence similarity to the homeo boxes of the Drosophila Antennapedia (Antp) and engrailed (en) genes. In this study, we characterize the only detectable sea urchin en class homeo box. Its nucleotide sequence similarity and lack of an intron indicate that it is more closely related to the two mouse en class homeo boxes than to the two Drosophila en class homeo boxes. These relationships are most parsimoniously explained if the single sea urchin en class homeo-box gene represents the primitive condition and the two mouse and the two Drosophila en class homeo-box genes represent independent duplications which occurred in the evolutionary lines leading to the vertebrates and arthropods, respectively. The most abundant en class gene transcripts detected by gel transfer analysis of RNA extracted from sea urchin tissues were found in Aristotle's lantern. Rare transcripts were present in ovary, testis and coelomocytes.

Tumor promoters and diacylglycerol activate the Na+/H+ antiporter of sea urchin eggs

Various tumor promoters (TPA, lyngbyatoxin and aplysiatoxin) and diacylglycerol induced cytoplasmic alkalinization of sea urchin eggs independently of intracellular Ca2+ release. This response stimulated protein synthesis and was blocked by amiloride or a lack of extracellular Na+, procedures which inhibit the Na+/H+ antiporter. These results suggest that the antiporter which is responsible for cytoplasmic alkalinization in sea urchin eggs is activated directly or indirectly by protein kinase C in a Ca2+-independent manner.

Length and sequence polymorphisms in the ribosomal gene spacer of the Hawaiian sea urchin, T. gratilla

Blot-hybridization of sea urchin (Tripneustes gratilla) genomic DNA with a cloned rDNA probe revealed individual variation in the length of the rDNA repeat unit and also in the non-transcribed spacer sequences. The number of distinct rDNA repeat subclasses distinguishable within any one sea urchin was limited and usually 2 to 3. However, examination of a number of sea urchins indicated a large number of distinct rDNA repeat types in the population as a whole; all of the rDNA repeat types in nine individuals were different. The presence of limited heterogeneity in the rDNA repeats of single individuals, with may different repeat types in the population as a whole, suggests that rDNA variants can be rapidly and selectively propagated within a chromosomal lineage.

Stage-specific expression of a homeo box-containing gene in the non-segmented sea urchin embryo

Hybridization of Drosophila homeo box DNA probes to Southern transfers of genomic DNA from the Hawaiian sea urchin Tripneustes gratilla has revealed that the sea urchin genome contains at least five homeo boxes. Examination of the DNA from several individuals shows that the sequences flanking these homeo boxes exhibit little restriction fragment length polymorphism, indicating they are more highly conserved than the majority of sea urchin DNA. Several clones in a T. gratilla genomic DNA library which hybridized with Drosophila homeo box probes were identified, and one found to be transcribed during embryogenesis was selected for further study. Southern transfer hybridizations showed the cloned gene to be single-copy. DNA sequencing of the sea urchin gene defined a homeo box 70-73% homologous to the Drosophila homeo box probes and an encoded homeo domain 78-88% homologous to those encoded by the probes. Hybridization of DNA probes from the sea urchin homeo box-containing gene to Northern transfers of embryonic RNA demonstrated that the gene produces two transcripts of 6.9 kb and 7.7 kb. Transcripts first accumulate at blastula stage and increase to a maximum level at gastrula stage before decreasing considerably in abundance by pluteus stage.

Effects of bepridil on force development and transmembrane electrical activity of adult canine Purkinje strands: comparison with nisoldipine and lidocaine

Superfusion of a bepridil containing normal Tyrode solution produced a concentration-dependent decrease in force development and shortening of action potential duration in isolated Purkinje strands. At a concentration close to the 50% inhibitory concentration for effects on force development and action potential duration, bepridil blocked 'slow' action potentials in potassium depolarized, isoproterenol-restored Purkinje strands. When the concentration-response relations for decreasing force development and shortening action potential duration were compared to those of nisoldipine and other calcium entry inhibitors, bepridil was the least potent. Bepridil also showed a concentration-dependent effect on the maximum rate of rise of the Purkinje fiber action potential upstroke similar to, though less potent than that of lidocaine. In addition, like lidocaine, bepridil shifted the membrane responsiveness curve of the Purkinje strands to the left. These findings indicate that bepridil produced effects that are consistent with its classification as a calcium entry inhibitor (class IV antiarrhythmic), as well as effects that are 'lidocaine-like' (class I antiarrhythmic).

Characterization of toposomes from sea urchin blastula cells: a cell organelle mediating cell adhesion and expressing positional information

Cell adhesion in the sea urchin blastula is mediated by a 22S genus-specific glycoprotein complex consisting initially of six 160-kDa subunits that are processed proteolytically as development proceeds. Noncytolytic removal of the 22S particle from the surface with either 2.5% butanol or trypsin renders dissociated cells reaggregation incompetent, and addition restores reaggregation and development. Polyclonal antibodies against the 22S complex prevent reaggregation in a genus-specific manner while monoclonal antibodies stain cell surface structures in a pattern consistent with a code that specifies the position of a cell in the embryo by a unique combination of subunits in its cell adhesion particles. The existence of similar particles in Drosophila and amphibian embryos suggests that these glycoprotein complexes are a general class of organelles, the toposomes, that in the embryo mediate cell adhesion and express positional information.

Structural analysis of ribosomal RNA genes from the Hawaiian sea urchin species, Tripneustes gratilla

Ribosomal gene sequences (rDNA) were isolated from the genomic DNA of the Hawaiian sea urchin Tripneustes gratilla by cloning in plasmid and phage vectors. The rRNA coding regions in four clones were localized by hybridizing Southern transfers of endonuclease-digested DNA with 32P-labeled 26S rRNA and 32P-labeled 18S rRNA. Three of the rDNA clones were isolated from a library of DNA from a single sea urchin and represent the two major types of rDNA repeats present in that individual's genome. Both repeat types appear identical within their rRNA coding regions but are dissimilar in an area of the nontranscribed spacer (NTS) adjacent to the 3' end of the 26S coding region. The cloned rDNA repeats were shorter than their genomic counterparts due to deletions occurring within internally repetitious NTS domains, probably as a result of unequal recombination during phage propagation.

Transcription of similar sets of rare maternal RNAs and rare nuclear RNAs in sea urchin blastulae and adult coelomocytes

We studied the sequences transcribed in the rare class of hnRNA and the rare maternal RNA set in blastula embryos and a tissue of adult sea urchins, coelomocytes. About 26% of labelled single-copy DNA formed hybrids which bound to hydroxyapatite after three cycles of hybridization with nuclear RNA from blastulae and coelomocytes. This corresponds to transcription of about 50% of the single-copy genome by both cell populations. To compare the rare hnRNA sequences synthesized by blastulae and coelomocytes directly, labelled single-copy DNA was hybridized with blastula nuclear RNA to high RNA C0t, fractionated into sequences complementary and non-complementary to blastula nuclear RNA by chromotography on hydroxyapatite, and then each fraction was rehybridized with nuclear RNA from blastulae and coelomocytes. About 62% of the labelled DNA complementary to blastula nuclear RNA and about 1.5% of the labelled DNA non-complementary to blastula nuclear RNA hybridized with nuclear RNA from both cell populations. Thus, coelomocytes and blastula embryos transcribe essentially the same single-copy sequences in the rare hnRNA class. A probe for the rare maternal RNA set was isolated by hybridizing single-copy DNA with total egg RNA to high RNA C0t. 65-67% of this probe hybridized with whole-cell RNA from eggs, blastulae, plutei and coelomocytes demonstrating that essentially all rare maternal RNAs are present, and presumably transcribed, in blastulae, plutei and coelomocytes.

The poly(A)(+)RNA sequence complexity is also represented in poly(A)(-)RNA in sea-urchin embryos

The extent to which the poly(A)(+)RNA sequence complexity from sea-urchin embryos is also represented in poly(A)(-)RNA was determined by cDNA cross-hybridization. Eighty percent or more of both the cytoplasmic poly(A)(+)RNA and polysomal poly(A)(+)RNA sequences appeared in a poly(A)(-) form. In both cases, the cellular concentrations of the poly(A)(-)RNA molecules that reacted with the cDNA were similar to the concentrations of the homologous poly(A)(+) sequences. Additionally, few, if any, abundant poly(A)(+)mRNA molecules were quantitatively discriminated by polyadenylation, since the abundant poly(A)(+)sequences were also abundant in poly(A)(-)RNA. Neither degradation nor inefficient binding to oligo (dT)-cellulose can account for the observed cross-reactivity. These data indicate that, in sea-urchin embryos, the poly(A) does not regulate the utilization of mRNA by demarcating an mRNA subset that is specifically and completely polyadenylated.

Calcium dependent aggregation of marine sponge cells is provoked by leukotriene B4 and inhibited by inhibitors of arachidonic acid oxidation

Dissociated cells of the marine sponge, Microciona prolifera, aggregate in response to a species-specific aggregation factor (MAF) and Ca ionophores. We now report that leukotriene B4, a 5-lipoxygenase product, also causes aggregation of sponge cells. No other lipoxygenase products provoked aggregation. However, nordihydroguaiaretic acid (NDGA), colchicine, indomethacin, piroxicam and ibuprofen inhibited MAF-induced aggregation; the latter three agents inhibited Ca movements. Inhibition of prostaglandin release cannot be the mechanism whereby these agents inhibit aggregation of sponge cells, since the cells do not respond to exogenous cyclooxygenase products.

Molecular cloning of five individual stage- and tissue-specific mRNA sequences from sea urchin pluteus embryos

Five developmentally regulated sea urchin mRNA sequences which increase in abundance between the blastula and pluteus stages of development were isolated by molecular cloning of cDNA. The regulated sequences all appeared in moderately abundant mRNA molecules of pluteus cells and represented 4% of the clones tested. There were no regulated sequences detected in the 40% of the clones which hybridized to the most abundant mRNA, and the screening procedures were inadequate to detect possible regulation in the 20 to 30% of the clones presumably derived from rare-class mRNA. The reaction of 32P[cDNA] from blastula and pluteus mRNA to dots of the cloned DNAs on nitrocellulose filters indicated that the mRNAs complementary to the different cloned pluteus-specific sequences were between 3- and 47-fold more prevalent at the pluteus stage than at the blastula stage. Polyadenylated RNA from different developmental stages was transferred from electrophoretic gels to nitrocellulose filters and reacted to the different cloned sequences. The regulated mRNAs were undetectable in the RNA of 3-h embryos, became evident at the hatching blastula stage, and reached a maximum in abundance by the gastrula or pluteus stage. Certain of the clones reacted to two sizes of mRNA which did not vary coordinately with development. Transfers of RNA isolated from each of the three cell layers of pluteus embryos that were reacted to the cloned sequences revealed that two of the sequences were found in the mRNA of all three layers, two were ectoderm specific, and one was endoderm specific. Four of the regulated sequences were complementary to one or two major bands and one to at least 50 bands on Southern transfers of restriction endonuclease-digested total sea urchin DNA.

Two Ca2+ functions are demonstrated by the substitution of specific divalent and lanthanide cations for the Ca2+ required by the aggregation factor complex from the marine sponge, Microciona prolifera

Multivalent cations were tested for their ability to replace the Ca2+ requirements of aggregation factor (AF) complex in activity, stability, and integrity assays. The ability of each cation to replace the Ca2+ required for the cell aggregation-enhancing activity of AF was examined by replacing the usual 10 mM Ca2+ with the test cation at various concentrations in the serial dilution assay of the AF. The other alkaline earth cations, Mg2+, Sr2+, and Ba2+, could not replace Ca2+; two transition elements, Mn2+ and Cd2+, partially replaced calcium. All 15 of the available lanthanides (including La3+ and Y3+) produced normal activity but only at 10-400-fold lower cation concentrations than Ca2+. An AF preparation is stable and remains active for months in 1 mM Ca2+ but decays rapidly when Ca2+ is lowered. Sr2+ and Ba2+ at 20 mM but not at 1 mM could replace 1 mM Ca2+ and give long term stability. AF was not stable in the presence of Mg2+, even at 100 mM. High Mn2+ concentrations did not stabilize AF even though AF was partially active in Mn2+. Cd2+ gave full stability at 75 mM and La3+ at about 0.1 mM. When Ca2+ is chelated, the macromolecular subunits of the AF slowly dissociate. Permeation chromatography and analytical ultracentrifugation showed that the cations that stabilized activity maintained the integrity of AF complex while those that failed to stabilize activity allowed the complex to dissociate into subunits, indicating that these two Ca2+ requirements are related. The cation specificities for activity and for stability-integrity are different indicating that these are separate Ca2+-dependent functions.

Oligo(U) sequences present in sea urchin maternal RNA decrease following fertilization

Oligo(U) tracts were identified and measured in RNA from sea urchin eggs and embryos using a quantitative assay based on the amount of [3H]poly(A) protected from RNase T2 in duplexes with the oligo(U). The oligo(U) amounted to 0.0035% of egg RNA (0.063 X 10(-12) g/egg) and decreased to 0.0015% (0.027 X 10(-12) g/embryo) by 2 hr after fertilization. The oligo(U) tracts had a maximum size of 15-30 nucleotides and were associated with two size classes of RNA. In eggs about half were in 100 to 200 nucleotide RNA and half in mRNA-sized molecules. After fertilization, the oligo(U) in the population of large-mRNA-sized molecules was greatly reduced.

Organization and polysaccharides of sponge aggregation factor

Aggregation factor, the macromolecular complex which mediates species-specific aggregation of dissociated sponge cells, was isolated from several species, partially characterized, and visualized by electron microscopy. All factors were large fibrous complexes with a backbone and side chains or arms. In some factors, the backbone is linear. In others it is circular and the complex appears as a sunburst with arms extending like rays from the circle. The size and location of the polysaccharide chains have been studied using purified preparations of Microciona prolifera. "Sunbursts" treated with ethylenediaminetraacetate (EDTA) for 4 weeks at 0 degrees C dissociate into 3 protein- and polysaccharide-containing components. Sodium dodecyl sulfate does not cause the sunburst to dissociate nor does it inhibit dissociation in the presence of EDTA suggesting that dissociation is not due to hydrolytic enzymes. The dissociation products were fractionated on a 977-A pore size micropore glass column. Fifteen percent of the material is excluded and appears in the electron microscope as the central circle of the sunburst. Digestion of the circles with 10(-3) M dithiothreitol (DTT) and 0.5 mg/ml proteinase K for 72 h at 37 degrees C produces 2 polysaccharide chains of 65,000 and 6,000 daltons as fractionated and sized on a 233-A pore size micropore glass column using Pharmacia dextrans as standards. The included fractions of the EDTA-treated material are subunits of the arms which contain 70% of the polysaccharide. A single polysaccharide of 6,000 daltons as measured on 233-A size glass beads and Sephadex G-75 is released from these subunits by proteinase digestion. Pharmacia dextrans are used as standard on both columns. We calculate that there would be four 65,000-dalton chains and one hundred 6,000-dalton chains per circle and fifty 6,000-dalton chains per arm. The third component of the EDTA-treated preparation is partially included on the column. It appears as linear fibrils in the electron microscope and contains polydisperse polysaccharides of several-hundred-thousand daltons. It may be an impurity since there is apparently less than 1 of the large polysaccharide chains per sunburst.