Chemically induced metamorphosis of polychaete larvae in both the laboratory and ocean environment

Planktonic larvae of the marine polychaetePhragmatopoma californica preferentially attach to substrata and metamorphose to the adult form upon contact with cement in tubes built by conspecifics. This gregarious settlement and metamorphosis contributes to the formation of large aggregations or reefs. Larvae also metamorphose upon contact with 2,6-di-tert-butyl-4-methylphenol (DBMP), a possible aromatic analog of cross-linked dihydrox-yphenylalanine (DOPA) residues (present in the polyphenolic protein cement as 2.6% of the amino acid residues). Morphogenesis occurs in the laboratory when larvae are exposed to DBMP either adsorbed to solid surfaces or when dissolved in dimethyl sulfoxide (DMSO) to render it soluble in seawater. Larvae in the ocean were induced to settle and metamorphose on plates coated with DBMP prior to their deployment in the ocean. This is the first report in which a defined organic molecule, identified as an inducer (or precursor to an inducer) of larval settlement and metamorphosis in the laboratory, has been shown to induce these processes in the ocean. Both forskolin and isobutylmethylxanlhine (IBMX) induce metamorphosis ofP. californica larvae, presumably by causing increases in intracellular cyclic AMP (cAMP). A discussion of the pathway controlling chemically mediated metamorphosis and evidence suggesting the possible role of cAMP in the process are presented. Other compounds known to increase intracellular cAMP levels, including arachidonic, linoleic, and palmitoleic acids, found by other workers to induce settlement and metamorphosis ofP. californica, may exert this activity by direct modification of internal cAMP levels in the larvae.

G protein and diacylglycerol regulate metamorphosis of planktonic molluscan larvae

The regulatory guanine nucleotide binding protein (G protein) activators cholera toxin and the GTP analog 5-guanylyl imidophosphate, the second messenger diacylglycerol, and certain diamino acids all facilitate (amplify) the settlement and metamorphic responses of planktonic larvae of Haliotis rufescens (marine mollusc) to morphogenetic chemical stimuli. In contrast, the G protein-inhibiting analog guanosine 5'-O-[beta-thio]diphosphate inhibits facilitation by L-alpha,beta-diaminopropionic acid but does not block facilitation by diacylglycerol. Diacylglycerol, cholera toxin, and the guanine nucleotide analogs alone neither induce the settlement and metamorphosis of the larvae nor do they inhibit induction of metamorphosis by gamma-aminobutyric acid. These results thus establish the existence of separate regulatory and inductive pathways controlling larval metamorphosis in response to two classes of exogenous chemical signals from the environment. The regulatory pathway, operating independently through a G protein-diacylglycerol cascade apparently controlled by facilitating diamino acids in the water column, can amplify the larval responsiveness to inducers of metamorphosis. This mechanism may have adaptive significance in the recognition and selection of favorable habitats for metamorphosis of the larvae. Similar regulatory pathways, based on exogenous control of a G protein-diacylglycerol cascade, may govern responsiveness to stimuli in other sensory and developmental systems.

Manifestations of cardiovascular toxicity associated with the approved tyrosine kinase inhibitors

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Background: Since 2001, 5 tyrosine kinase inhibitors (TKi’s; imatinib, erlotinib, sorafenib, sunitinib and dasatinib) have been approved for hematologic and solid tumor indications including, CML, ALL, GIST, RCC, pancreatic and NSCLC. While individual agents are designed to inhibit the TK activity of specific targets, “cross-talk” with non-target TKs (e.g., ABL, EGFR, VEGFRs, KIT, KDR, CSF1R, PDGFRs, RET, the SRC family, EPHA2, RAF, and FLT3) is extensive. The relationship between inhibition of individual kinases and the toxicity profile of each drug is unclear. Methods: Following from the observation of cardiovascular (CV) toxicity in clinical settings (pre- and post- marketing) and from the original non-clinical toxicologic evaluations, a new “class-related” review of non-clinical toxicological findings was conducted. To compare the non-clinical and clinical CV findings, the Adverse Event Reporting System (AERS) was searched for all events, excluding those of non-CV nature and those unlikely to be drug-related (e.g. hemorrhagic events were excluded from the initial analyses). Individual patient reports were not reviewed in full, therefore definitive attribution of disease related events can not be made. Results: While variable in expression, the non-clinical signs of toxicity included cardiac and vascular inflammation, cardiac degeneration and hypertrophy, decreased cardiac function (e.g. LVEF decreases), alterations in blood pressure, and QT prolongation. Clinical reports for the TKi’s have included hypo- and hypertension, conduction abnormalities and arrhythmias, cardiac hypertrophy and changes in cardiac function (LVEF and CHF). Conclusions: It is not possible at this time to relate the CV toxicities associated with the TKi’s to a specific pattern of TK inhibition. CV toxicity has been observed both clinically and non-clinically and warrants further investigation.

No significant financial relationships to disclose.

In situ observation of fluoride-ion-induced hydroxyapatite-collagen detachment on bone fracture surfaces by atomic force microscopy

The topography of freshly fractured bovine and human bone surfaces was determined by the use of atomic force microscopy (AFM). Fracture surfaces from both kinds of samples exhibited complex landscapes formed by hydroxyapatite mineral platelets with lateral dimensions ranging from ∼90 nm × 60 nm to ∼20 nm × 20 nm. Novel AFM techniques were used to study these fracture surfaces during various chemical treatments. Significant topographical changes were observed following exposure to aqueous solutions of ethylenediaminetetraacetic acid (EDTA) or highly concentrated sodium fluoride (NaF). Both treatments resulted in the apparent loss of the hydroxyapatite mineral platelets on a timescale of a few seconds. Collagen fibrils situated beneath the overlying mineral platelets were clearly exposed and could be resolved with high spatial resolution in the acquired AFM images. Time-dependent mass loss experiments revealed that the applied agents (NaF or EDTA) had very different resulting effects. Despite the fact that the two treatments exhibited nearly identical results following examination by AFM, bulk bone samples treated with EDTA exhibited a ∼70% mass loss after 72 h, whereas for the NaF-treated samples, the mass loss was only of the order of ∼10%. These results support those obtained from previous mechanical testing experiments, suggesting that enhanced formation of superficial fluoroapatite dramatically weakens the protein-hydroxyapatite interfaces. Additionally, we discovered that treatment with aqueous solutions of NaF resulted in the effective extraction of noncollagenous proteins from bone powder.

Atomic force microscopy study of living diatoms in ambient conditions

We present the first in vivo study of diatoms using atomic force microscopy (AFM). Three chain-forming, benthic freshwater species -Eunotia sudetica, Navicula seminulum and a yet unidentified species - are directly imaged while growing on glass slides. Using the AFM, we imaged the topography of the diatom frustules at the nanometre range scale and we determined the thickness of the organic case enveloping the siliceous skeleton of the cell (10 nm). Imaging proved to be stable for several hours, thereby offering the possibility to study long-term dynamic changes, such as biomineralization or cell movement, as they occur. We also focused on the natural adhesives produced by these unicellular organisms to adhere to other cells or the substratum. Most man-made adhesives fail in wet conditions, owing to chemical modification of the adhesive or its substrate. Diatoms produce adhesives that are extremely strong and robust both in fresh- and in seawater environments. Our phase-imaging and force-pulling experiments reveal the characteristics of these natural adhesives that might be of use in designing man-made analogues that function in wet environments. Engineering stable underwater adhesives currently poses a major technical challenge.

Bone indentation recovery time correlates with bond reforming time

Despite centuries of work, dating back to Galileo, the molecular basis of bone's toughness and strength remains largely a mystery. A great deal is known about bone microsctructure and the microcracks that are precursors to its fracture, but little is known about the basic mechanism for dissipating the energy of an impact to keep the bone from fracturing. Bone is a nanocomposite of hydroxyapatite crystals and an organic matrix. Because rigid crystals such as the hydroxyapatite crystals cannot dissipate much energy, the organic matrix, which is mainly collagen, must be involved. A reduction in the number of collagen cross links has been associated with reduced bone strength and collagen is molecularly elongated ('pulled') when bovine tendon is strained. Using an atomic force microscope, a molecular mechanistic origin for the remarkable toughness of another biocomposite material, abalone nacre, has been found. Here we report that bone, like abalone nacre, contains polymers with 'sacrificial bonds' that both protect the polymer backbone and dissipate energy. The time needed for these sacrificial bonds to reform after pulling correlates with the time needed for bone to recover its toughness as measured by atomic force microscope indentation testing. We suggest that the sacrificial bonds found within or between collagen molecules may be partially responsible for the toughness of bone.

A novel fluorescent silica tracer for biological silicification studies

BACKGROUND

Biological silica production has drawn intense attention and several molecules involved in biosilicification have been identified. Cellular mechanisms, however, remain unknown mainly due to the lack of probes required for obtaining information on live specimens.

RESULTS

The fluorescence spectra of the compound 2-(4-pyridyl)-5-((4-(2-dimethylaminoethylaminocarbamoyl)methoxy)phenyl)oxazole (PDMPO) are affected by the presence of >3.2 mM silicic acid. Increase in intensity and shift in the fluorescence coincide with the polymerization of Si. The unique PDMPO-silica fluorescence is explored here to visualize Si deposition in living diatoms. The fluorophore is selectively incorporated and co-deposited with Si into the newly synthesized frustules (the outer silica shells) showing an intense green fluorescence.

CONCLUSIONS

We suggest that a fluorescence shift is due to an interaction between PDMPO and polymeric silicic acid. PDMPO is an excellent probe for imaging newly deposited silica in living cells and has also a potential for a wide range of applications in various Si-related disciplines, including biology of living organisms as diatoms, sponges, and higher plants, clinical research (e.g. lung fibrosis and cancer, bone development, artificial bone implantation), and chemistry and physics of materials research.

Annual per capita apparent consumption of tobacco products in the United States: 1900-1990

BACKGROUND

Analyses of secular trends in tobacco consumption can provide evidence of potential tobacco-disease relationships and have utility in terms of public health projections and policy. The purpose of this project was to provide a unique set of continuous apparent tobacco product consumption estimates for the United States over the period spanning 1900 through 1990.

METHODS

Two U.S. Department of Agriculture data sources provide information on long-term apparent tobacco consumption in the United States; however, differences exist between these data sets. The consumption estimates in these reports were adjusted to a common population base. A 9-year overlap of the data sets was then used to calibrate one data series to the other using inverse regression. Predicted tobacco consumption estimates for the years 1900 through 1944 were then combined with the adjusted 1945-1990 data.

RESULTS

Inverse regression showed a strong linear relationship between the two U.S. Department of Agriculture summaries for each tobacco product during the 9-year overlap period. A continuous set of annual per capita tobacco consumption estimates is reported by product for the United States.

CONCLUSIONS

The two U.S. Department of Agriculture reports can be combined to provide a history of tobacco product consumption in the United States over the period 1900-1990.

Direct observation of the transition from calcite to aragonite growth as induced by abalone shell proteins

The mixture of EDTA-soluble proteins found in abalone nacre are known to cause the nucleation and growth of aragonite on calcite seed crystals in supersaturated solutions of calcium carbonate. Past atomic force microscope studies of the interaction of these proteins with calcite crystals did not observe this transition because no information about the crystal polymorph on the surface was obtained. Here we have used the atomic force microscope to directly observe changes in the atomic lattice on a calcite seed crystal after the introduction of abalone shell proteins. The observed changes are consistent with a transition to (001) aragonite growth on a (1014) calcite surface.

Food group intake and the risk of oral epithelial dysplasia in a United States population

OBJECTIVES

Oral epithelial dysplasia (OED) is a histopathologic diagnosis associated with an increased risk of oral cancer. The paper explores the relationship between OED risk and food group intake.

METHODS

In this case-control study, incident cases of OED were identified through two oral pathology laboratories. Controls, pair-matched 1:1 to cases on age (+/- 5 years), gender, appointment date (+/- 1 year), and surgeon, were identified through the office in which the respective case was biopsied. Exposure data were obtained via a telephone interview and mailed food-frequency questionnaire. Conditional logistic regression was used to obtain odds ratio point estimates.

RESULTS

Based upon 87 matched pairs and after controlling for smoking, drinking, and other potential covariates there was an apparent inverse relationship between OED risk and the consumption of fruits and vegetables, with the intake of these foods being associated with a strong attenuating effect among smokers. OED risk decreased with increased poultry consumption, but increased modestly with bread/cereal and dairy food intake.

CONCLUSIONS

This investigation provides evidence that some aspects of diet may be associated with the risk of OED. It also suggests that in oral carcinogenesis the role of diet is not simply one of a late effect.

Expression of a Scr/Hox5 gene in the larval central nervous system of the gastropod Haliotis, a non-segmented spiralian lophotrochozoan

Hox genes encode a set of evolutionarily conserved transcription factors that regulate anteroposterior patterning mechanisms in insects and vertebrates and are expressed along this axis in a range of bilaterians. Here we present the developmental expression of a Scr/Hox5 gene in the gastropod mollusc Haliotis. In Haliotis, embryogenesis yields a non-feeding trochophore larva that subsequently develops into the veliger larva, which possesses many of the characteristics of the adult body plan. Quantitative RT-PCR analysis reveals that this gene, which is called Hru-Hox5, is first expressed in the trochophore larva. Hru-Hox5 transcript prevalence increases continually through larval development until metamorphic competence develops in the veliger and then again over the first four days of metamorphosis. In situ hybridization reveals that larval expression of Hru-Hox5 is restricted primarily to the primordial and newly formed branchial ganglia, located between the anterior cerebral-pleuropedal ganglionic complex and the posterior visceral ganglia. The expression of Hru-Hox5 in the central region of the abalone CNS is similar to that observed for its orthologue (Lox20) in the leech, suggesting that Hox5 genes were used, along with other Hox genes, to pattern the CNS of the ancestral spiralian lophotrochozoan.

Head and neck in situ carcinoma: incidence, trends, and survival

This analysis describes the epidemiology of in situ head and neck carcinomas (anatomic sites of lip, oral cavity, pharynx, larynx) about which there is limited knowledge. Data were derived from nine population-based cancer registries participating in the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) Program. SEER annual age-adjusted incidence rates for in situ head and neck carcinomas increased from 6.33/1,000,000 person-years (PY) in 1976 to 8.04/1,000,000 PY in 1995 [percent change (PC)=35%, P<0. 001]. From 1976 to 1995 age-adjusted changes in incidence by anatomic site ranged from 53% PC (larynx) to -11% PC (lip) (both P<0. 005). Incidence and survival associated with in situ head and neck carcinomas varied by anatomic site, age, sex, and race and did so in a pattern similar to that seen for invasive carcinomas of this region. However, the climbing incidence of in situ carcinoma, which may be related to increased surveillance, contrasts sharply with the declining incidence of invasive carcinoma.

Biomimetic synthesis of ordered silica structures mediated by block copolypeptides

In biological systems such as diatoms and sponges, the formation of solid silica structures with precisely controlled morphologies is directed by proteins and polysaccharides and occurs in water at neutral pH and ambient temperature. Laboratory methods, in contrast, have to rely on extreme pH conditions and/or surfactants to induce the condensation of silica precursors into specific morphologies or patterned structures. This contrast in processing conditions and the growing demand for benign synthesis methods that minimize adverse environmental effects have spurred much interest in biomimetic approaches in materials science. The recent demonstration that silicatein-a protein found in the silica spicules of the sponge Tethya aurantia--can hydrolyse and condense the precursor molecule tetraethoxysilane to form silica structures with controlled shapes at ambient conditions seems particularly promising in this context. Here we describe synthetic cysteine-lysine block copolypeptides that mimic the properties of silicatein: the copolypeptides self-assemble into structured aggregates that hydrolyse tetraethoxysilane while simultaneously directing the formation of ordered silica morphologies. We find that oxidation of the cysteine sulphydryl groups, which is known to affect the assembly of the block copolypeptide, allows us to produce different structures: hard silica spheres and well-defined columns of amorphous silica are produced using the fully reduced and the oxidized forms of the copolymer, respectively.

Silicatein filaments and subunits from a marine sponge direct the polymerization of silica and silicones in vitro

Nanoscale control of the polymerization of silicon and oxygen determines the structures and properties of a wide range of siloxane-based materials, including glasses, ceramics, mesoporous molecular sieves and catalysts, elastomers, resins, insulators, optical coatings, and photoluminescent polymers. In contrast to anthropogenic and geological syntheses of these materials that require extremes of temperature, pressure, or pH, living systems produce a remarkable diversity of nanostructured silicates at ambient temperatures and pressures and at near-neutral pH. We show here that the protein filaments and their constituent subunits comprising the axial cores of silica spicules in a marine sponge chemically and spatially direct the polymerization of silica and silicone polymer networks from the corresponding alkoxide substrates in vitro, under conditions in which such syntheses otherwise require either an acid or base catalyst. Homology of the principal protein to the well known enzyme cathepsin L points to a possible reaction mechanism that is supported by recent site-directed mutagenesis experiments. The catalytic activity of the "silicatein" (silica protein) molecule suggests new routes to the synthesis of silicon-based materials.

Trends in the incidence of lip, oral, and pharyngeal cancer: Connecticut, 1935-94

Using Connecticut Tumor Registry data we explored trends in age-adjusted (AARs) and age-specific (ASRs) incidence rates for lip, oral, and pharyngeal cancer over the 60-year period 1935-94. Particular attention was given to findings from the most recent series of 5-year periods that have not been previously analyzed. There was a long-term decline in lip cancer AARs by period, and ASRs generally fell over time and with successive birth cohorts. This notable decrease in rates continued through 1990-94 and with the more recent cohorts, particularly among males. Oral cancer AARs for males peaked in the early 1960s and the late 1970s while rates for pharyngeal cancer increased into the late 1970s. For each of these sites, rates began to decline in 1980-84 and have continued to fall into the first half of the 1990s. Among females AARs for oral and pharyngeal cancer increased more than threefold between 1935-39 and 1980-84; however, encouragingly, and in sharp contrast to the earlier trend, rates fell during the most recent 10-year period. ASRs for oral and pharyngeal cancer were increasing by the birth cohort of 1900 and tended to increase through the cohort of 1920 for males and the cohorts of 1920-30 for females. ASRs for subsequent cohorts have remained relatively unchanged or decreased modestly. It is doubtful that the observed trends in lip, oral and pharyngeal cancer incidence are primarily artifactual, but more likely represent secular changes in exposure to environmental risk factors.

Silicatein alpha: cathepsin L-like protein in sponge biosilica

Earth's biota produces vast quantities of polymerized silica at ambient temperatures and pressures by mechanisms that are not understood. Silica spicules constitute 75% of the dry weight of the sponge Tethya aurantia, making this organism uniquely tractable for analyses of the proteins intimately associated with the biosilica. Each spicule contains a central protein filament, shown by x-ray diffraction to exhibit a highly regular, repeating structure. The protein filaments can be dissociated to yield three similar subunits, named silicatein alpha, beta, and gamma. The molecular weights and amino acid compositions of the three silicateins are similar, suggesting that they are members of a single protein family. The cDNA sequence of silicatein alpha, the most abundant of these subunits, reveals that this protein is highly similar to members of the cathepsin L and papain family of proteases. The cysteine at the active site in the proteases is replaced by serine in silicatein alpha, although the six cysteines that form disulfide bridges in the proteases are conserved. Silicatein alpha also contains unique tandem arrays of multiple hydroxyls. These structural features may help explain the mechanism of biosilicification and the recently discovered activity of the silicateins in promoting the condensation of silica and organically modified siloxane polymers (silicones) from the corresponding silicon alkoxides. They suggest the possibility of a dynamic role of the silicateins in silicification of the sponge spicule and offer the prospect of a new synthetic route to silica and siloxane polymers at low temperature and pressure and neutral pH.

The relationship between bottle usage/content, age, and number of teeth with mutans streptococci colonization in 6-24-month-old children

OBJECTIVES

Mutans streptococci (MS) are the primary pathogens involved in the development of early childhood caries. However, factors that may affect their acquisition in the mouths of young children are not well understood, and the period of initial colonization remains controversial. This study investigated the relationship of age, number of teeth, and bottle usage/content with regard to the isolation of MS in 6-24-month-old children.

METHODS

A total of 122 children from low-income families attending a nutritional supplement program, and their mothers, participated in this study. Children were examined for dental caries and number of erupted teeth and were sampled for MS. Mothers were administered a questionnaire to obtain details of baby bottle use, including what food items were put in the bottle during the last week.

RESULTS

MS was detected in more than one-third of the 6-24-month-olds. Unlike some studies that suggest a later period of infectivity, approximately 20% of children under 14 months of age, including 4 of 22 infants aged 6-9 months, were colonized with MS. When examined separately, age, number of teeth, and bottle usage/content were each found to be related to the presence of MS. Mutans streptococci colonization was more likely with increasing age and number of teeth, and children whose bottles contained sweetened beverages were more likely to be colonized than children whose bottles contained milk. Logistic regression models that controlled for both age and number of teeth indicated that children who consumed sweetened beverages in their baby bottle had a statistically significant, four-fold increase in the odds of colonization by MS relative to children who consumed milk.

CONCLUSIONS

The finding that approximately 20% of the children under 14 months of age were infected with MS indicates that colonization in this sample of low-income preschool children may begin earlier than suggested by some investigations. Additionally, the risk of MS colonization appears lower among infants who consume milk rather than sweetened beverages in the bottle.

Molecular cloning and characterization of lustrin A, a matrix protein from shell and pearl nacre of Haliotis rufescens

A specialized extracellular matrix of proteins and polysaccharides controls the morphology and packing of calcium carbonate crystals and becomes occluded within the mineralized composite during formation of the molluscan shell and pearl. We have cloned and characterized the cDNA coding for Lustrin A, a newly described matrix protein from the nacreous layer of the shell and pearl produced by the abalone, Haliotis rufescens, a marine gastropod mollusc. The full-length cDNA is 4,439 base pairs (bp) long and contains an open reading frame coding for 1,428 amino acids. The deduced amino acid sequence reveals a highly modular structure with a high proportion of Ser (16%), Pro (14%), Gly (13%), and Cys (9%). The protein contains ten highly conserved cysteine-rich domains interspersed by eight proline-rich domains; a glycine- and serine-rich domain lies between the two cysteine-rich domains nearest the C terminus, and these are followed by a basic domain and a C-terminal domain that is highly similar to known protease inhibitors. The glycine- and serine-rich domain and at least one of the proline-rich domains show sequence similarity to proteins of two extracellular matrix superfamilies (one of which also is involved in the mineralized matrixes of bone, dentin, and avian eggshell). The arrangement of alternating cysteine-rich domains and proline-rich domains is strikingly similar to that found in frustulins, the proteins that are integral to the silicified cell wall of diatoms. Its modular structure suggests that Lustrin A is a multifunctional protein, whereas the occurrence of related sequences suggest it is a member of a multiprotein family.

Mouthwash use and dentures in relation to oral epithelial dysplasia

This case-control study investigated the potential association between oral epithelial dysplasia (OED) and both mouthwash and denture use. Incident OED cases aged 20-79 years were identified through two oral pathology laboratories. Controls were pair-matched (1:1) to cases on age (+/- 5 years), gender, appointment date and surgeon. A telephone interview was used to obtain exposure information. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were generated using conditional logistic regression. Based upon 127 case-control pairs and after adjusting for smoking, drinking, education and either denture or mouthwash use, the OR for OED and regular mouthwash use (1+ uses/week for 6+ months) was 0.8 (95% CI, 0.4-1.5) while the OR for OED and wearing a denture was 0.7 (95% CI, 0.4-1.3). There were no clear trends of increased OED risk with increased mouthwash use or years of denture wearing. Our findings suggest that neither mouthwash nor denture use are associated positively with OED risk.

A Mox homeobox gene in the gastropod mollusc Haliotis rufescens is differentially expressed during larval morphogenesis and metamorphosis

We have isolated a homeobox-containing cDNA from the gastropod mollusc Haliotis rufescens that is most similar to members of the Mox homeobox gene class. The derived Haliotis homeodomain sequence is 85% identical to mouse and frog Mox-2 homeodomains and 88.9% identical to the partial cnidarian cnox5-Hm homeodomain. Quantitative reverse transcription-polymerase chain reaction analysis of mRNA accumulation reveals that this gene, called HruMox, is expressed in the larva, but not in the early embryo. Transcripts are most prevalent during larval morphogenesis from trochophore to veliger. There are also transient increases in transcript prevalence 1 and 3 days after the intitiation of metamorphosis from veliger to juvenile. The identification of a molluscan Mox homeobox gene that is more closely related to vertebrate genes than other protostome (e.g. Drosophila) genes suggests the Mox class of homeobox genes may consist of several different families that have been conserved through evolution.

Modification of calcite crystal growth by abalone shell proteins: an atomic force microscope study

A family of soluble proteins from the shell of Haliotis rufescens was introduced over a growing calcite crystal being scanned in situ by an atomic force microscope (AFM). Atomic step edges on the crystal surface were altered in shape and speed of growth by the proteins. Proteins attached nonuniformly to the surface, indicating different interactions with crystallographically different step edges. The observed changes were consistent with the habit modification induced by this family of proteins, as previously observed by optical microscopy. To facilitate further studies in this area, AFM techniques and certain AFM imaging artifacts are discussed in detail.

Effects of ddC and AZT on locomotion and acoustic startle. I: Acute effects in female rats

Several synthetic nucleoside analogues, including AZT(RETROVIR), ddC (HIVID), ddI (VIDEX), and d4T (ZERIT), are currently being used in the treatment of HIV infection. Unfortunately, in clinical use the appearance of severe and sometimes debilitating peripheral neuropathy and pain has been associated with the long-term use of several of these drugs (i.e., ddC, ddI and d4T), although not with AZT. To date, standard pre-clinical animal toxicity studies have failed to reveal any adverse neurologic effects of these compounds. However, previously reported preliminary findings suggest that ddC may alter several neuro-behavioral parameters (including locomotor activity, acoustic startle responding, and aggression) in rats and mice following presentation in the animals' drinking water for 7 days. The current series of experiments examined effects of acutely administered ddC and AZT on spontaneous locomotor activity and acoustic startle responses (with and without pre-pulse) in female Sprague-Dawley rats. Following intragastric administration, ddC reduced locomotion at all but the highest dose, whereas AZT had no significant effect on locomotor activity. Acutely administered ddC had no effect on ASR, whereas AZT increased ASR at the highest stimulus intensity. These data support the use of behavioral testing in the development of the antiviral nucleoside analogues, as behavioral testing may be more effective in identifying the neurologically active agents than is standard toxicity testing.

Smoking and drinking in relation to oral epithelial dysplasia

Oral epithelial dysplasia (OED) is a histopathological diagnosis that is associated with an increased risk of oral cancer. The purpose of this case-control study was to measure the association between OED and the use of smoking tobacco and alcoholic beverages. Incident cases of OED (n = 127) were identified through two oral pathology laboratories. Controls, pair-matched 1:1 to cases on age (+/- 5 years), gender, appointment date (+/- 1 year), and surgeon, were identified through the office in which the respective case had been biopsied. Exposure information regarding smoking, drinking, and other potential risk factors was obtained through a standardized telephone interview. Conditional logistic regression was used to calculate measures of association and statistical significance. The odds ratio (OR) for current smoking adjusted for drinking, mouthwash use, denture status, and education was 4.1 (95% confidence interval, 2.1-7.9) relative to never/ex-smokers. The risk of OED increased with increasing levels of smoking and declined following smoking cessation, with ex-smokers of 15+ years demonstrating no excess risk relative to never smokers. Individuals drinking 7+ drinks/week, relative to less than that amount, had over twice the risk of OED (OR, 2.4; 95% confidence interval, 1.2-4.8) after controlling for smoking, mouthwash use, denture status, and education. Adjusted ORs tended to increase with increasing levels of alcohol intake. An exploratory analysis suggests that the joint effect of smoking and drinking may be more than additive as regards the risk of OED. The findings of this case-control study implicate smoking and drinking as important risk factors for OED.

Risk factors for enamel fluorosis in a nonfluoridated population

The purpose of this case-control investigation was to investigate the possible association between mild-to-moderate enamel fluorosis and exposure during early childhood to fluoride supplements, fluoride toothpaste, and/or infant formula use in nonfluoridated communities. Analysis was performed on 460 10- to 13-year-old children, born after 1979, who were residents of six nonfluoridated communities in Massachusetts and Connecticut. The fluorosis status of the subjects was determined on the basis of a clinical dental examination using the Fluorosis Risk Index (FRI). Risk factor exposure was ascertained via a mailed questionnaire with a response rate of 90% and a questionnaire reliability of 87%. Logistic regression analyses revealed a moderate association between mild-to-moderate enamel fluorosis on early forming (FRI classification I) enamel surfaces and both fluoride supplement use (odds ratio (OR) = 2.25, 95% confidence interval (CI) 1.08-4.69) and early toothbrushing habits (OR = 2.56, 95% CI 1.34-4.88). There was a strong association between mild-to-moderate fluorosis on later forming (FRI classification II) enamel surfaces and both supplement use (OR = 7.97, 95% CI 2.98-21.33) and early toothbrushing habits (OR = 4.23, 95% CI 1.72-10.41). Infant formula was not found to be associated with fluorosis on either FRI classification I or II surfaces.

Interdisciplinary Research at the Nation's Coastal Laboratories

The nation's coastal (i.e., marine and Great Lakes) laboratories and programs of aquatic research face serious challenges for survival in the decades to come. Although research in these institutions is strongly interdisciplinary, this characteristic and its effect are not widely recognized. Examples of successful interdisciplinary research are many, encompassing a wide range of scales of operation, from the varied technical approaches taken in individual laboratories to multi-laboratory, multi-institutional and multi-platform programs of very large scale. Our survey of interdisciplinary research in the nation's marine and coastal laboratories leads to three conclusions: (1) The trend toward collaboration in marine research is scientist-driven, rapid, and inexorable. It is driven by problems of increasing complexity, and the recognition that multiple approaches are synergistic and powerful, producing answers where single approaches cannot. (2) This trend is rapidly increasing the diversity of expertise and technical competence among coastal laboratories. (3) And the research community and its support agencies must therefore find new ways of representing this rapidly increasing diversity within the country's marine laboratories and their programs. Given past successes, we may be tempted to push forward with large multidisciplinary programs, but we should not neglect the funding required by innovative individual scientists. The marine and aquatic research community and its funding agencies face a major challenge in the years ahead: they must develop a publicly recognizable, national agenda for marine and coastal research that adequately represents the broad spectrum of interdisciplinary research entailed, while ensuring that nonconventional work and innovative "individual" science be effectively funded. Such a balanced approach is most likely to effect a sustained economic development of the nation's coastal zone.

An assessment of oral cancer underregistration at the Connecticut Tumor Registry

The purpose of this study was to investigate whether and to what extent cases of oral cancer diagnosed through the University of Connecticut Health Center Oral Pathology Biopsy Service went unregistered by the Connecticut Tumor Registry during the period 1984 to 1988. All Oral Pathology Biopsy Service pathology reports generated from 1984 to 1988 were reviewed to identify diagnosed oral cancer cases (International Classification of Diseases, 9th revision codes 140, 141, 143 to 145). The names of all identified patients were computer-linked to previously registered cases. Nineteen (8.6%) of the 221 reportable cases of oral cancer diagnosed through the Oral Pathology Biopsy Service from 1984 to 1988 went unregistered. The 19 unregistered cases represented 1.6% of all known Connecticut oral cancer cases diagnosed during the period. The finding of a past, albeit small, "gap" in oral cancer cases registered with the Connecticut Tumor Registry suggests that oral pathologists should confirm that cases of oral cancer diagnosed through their pathology services are being registered by their regional tumor registries.

Fluoride supplement use by children in fluoridated communities

OBJECTIVES

The purpose of this study is to describe patterns of inappropriate fluoride supplementation among a sample of Connecticut schoolchildren living in optimally fluoridated areas.

METHODS

Fluoride exposure histories were obtained via a written questionnaire with a response rate of 89 percent and an overall reliability of 87 percent agreement.

RESULTS

A total of 575 subjects lived the entire first eight years of life in a fluoridated community. Of these, 26.1 percent had a history of inappropriate supplementation sometime during that period, including 31.8 percent of subjects with mild to moderate fluorosis and 22.8 percent of subjects without fluorosis. There were no significant supplement history differences related to current age, sex, or socioeconomic status. Overall, 71 percent of these subjects used only vitamins with fluoride, while only 14 percent were reported to have used fluoride supplements alone. Sixty-eight percent of the subjects who were supplemented while breast feeding, continued supplementation after cessation of breast feeding.

CONCLUSIONS

These findings reinforce the need for health professionals to be targeted more aggressively at the school, residency, and private practice levels to better promote a full understanding of the proper utilization of fluoride supplements.

Arterial supply to the human anterior cruciate ligament

The arterial supply to the anterior cruciate ligament (ACL) was prepared for study by injecting a fresh cadaver knee with an epoxy lead-oxide solution and subsequently immersing it in 10% formalin for a 2-week period. The vasculature of the ACL was exposed through dissection for examination. A second specimen was prepared similarly and was evaluated by a CAT scan. ACL vascularization arises from the middle genicular artery and vessels of the infrapatella fat pad and adjacent synovium. The artery gives rise to periligamentous vessels which form a web-like network within the synovial membrane. These periligamentous vessels give rise to penetrating branches which transversely cross the ACL and anastomose with a network of longitudinally oriented endoligamentous vessels. Terminal branches of the inferior medial and lateral genicular arteries supply the distal portion of the ACL directly. The extremities of the ACL seem to be better vascularized than the middle part, and the proximal portion seems to have a greater vascular density than the distal portion. The arteries at the ligamentous-osseous junctions of the ACL do not significantly contribute to the ligament's vascularity. Ramifications concerning the ACL's blood supply as it relates to athletic training is also discussed.

A hox/hom homeobox gene in sponges

The hox/hom homeobox genes code for DNA-binding proteins that confer positional information during animal development; these genes have been found in a wide range of triploblasts and in cnidarians. We report here the identification of a hox/hom gene and two other homeobox genes in the genomes of sponges. This finding extends the detection of hox/hom genes to the lowest metazoan phylum and suggests a monophyletic origin of the kingdom Animalia. Because, in culture, sponge cells quickly reaggregate, differentiate and construct tissue after disaggregation, they can provide a useful model system for characterization of the basic roles of homeobox genes in the control of cellular differentiation.

Inorganic Overgrowth of Aragonite on Molluscan Nacre Examined by Atomic Force Microscopy

The nacre (mother-of-pearl) that forms the irridescent inner layers of mollusc shells is a highly ordered microlaminate composite of aragonite crystals and biopolymers with a strength and fracture resistance that far exceed those of the mineral crystals themselves. The processes governing the biofabrication of this material by the secretory cells of the mantle are complex and only partially understood. We have used the atomic force microscope (AFM) to investigate the aqueous solution conditions under which mineral growth can occur on the nacreous layer of the shell of the bivalve mollusc Atrina sp. In situ imaging of the mature nacre surface exposed to a pH-controlled environment of natural seawater with added carbonate ions reveals that inorganic overgrowth of aragonite can occur within the ranges of pH and inorganic ion concentrations found in the molluscan extrapallial fluid from which the mineral is produced during biological shell growth. Thus, we posit that once nucleation has occurred, nacreous tablets could grow inorganically in the extrapallial space; the role of proteins and other macromolecules may be limited to initiating growth or controlling morphology through selective adsorption and spatial constraint on the growing crystal.

Sequence-independent detection of gene family homologs: identification of a transcript encoding a molluscan serine protease homologous to the pancreatic enzymes of vertebrates

Autoradiography of 32P-labeled cDNA, fractionated at high resolution by electrophoresis through thin (0.8-1.5 mm) vertical alkaline agarose gels, provides a sequence-independent screening procedure for gene family homologs. A screen of tissues of a marine mollusc revealed a prominent intestine-specific cDNA encoding a pancreatic serine protease homolog, which was not detectable as a discrete poly(A)+ RNA species on formaldehyde agarose gels. Discrete cDNA products are authentic, non-truncated transcripts of tissue-specific mRNA. A band-sharpening effect is imparted to cDNA products due to (a) substitution of a uniform length 5'-oligo(dT) terminus for heterogeneous 3'-poly(A) termini and (b) the inherent superior resolution of alkaline-denatured DNA.

Risk factors for enamel fluorosis in a fluoridated population

The purpose of this case-control investigation was to investigate the possible association between mild-to-moderate enamel fluorosis and exposure during early childhood to infant formula, fluoride toothpaste, and/or fluoride supplements. Analysis was performed on 401 residents of fluoridated communities in Connecticut, who were 12-16 years old and born prior to 1980. The case and control subjects for this study were selected on the basis of a clinical examination given in 1991. Subject fluorosis status was determined using the Fluorosis Risk Index. Risk factor exposure was ascertained via a mailed questionnaire with a response rate of 89% and a questionnaire reliability of 87%. Logistic regression analyses, which adjusted for confounding variables, revealed that mild-to-moderate enamel fluorosis on early forming (Fluorosis Risk Index (FRI) classification I) enamel surfaces was strongly associated with both milk-based (odds ratio (OR) = 3.34, 95% confidence interval (CI) 1.38-8.07) and soy-based (OR = 7.16, 95% CI 1.35-37.89) infant formula use, as well as with frequent brushing (OR = 2.80, 95% CI 1.15-6.81). A very strong association was observed with inappropriate fluoride supplement use (OR = 23.74, 95% CI 3.43-164.30). Respectively similar associations were observed between mild-to-moderate enamel fluorosis on later forming (FRI classification II) enamel surfaces and frequent brushing and fluoride supplement use, but not with infant formula use.

Myogenesis in primary cell cultures from larvae of the abalone, Haliotis rufescens

Myogenesis culminating in the differentiation of contracting myocytes occurs in primary cell cultures derived from premyogenic trochophore and early veliger larvae of Haliotis rufescens (red abalone, gastropod mollusc). No detectable muscle cells were present at the start of the primary cultures. Onset and organization of myofibrillogenesis in culture (revealed by histochemical and immunohistochemical detection of filamentous actin, myosin, and desmin) generally paralleled those of smooth muscle development in vivo, although development of cells with striated sarcomeres was occasionally observed in culture, but not in the intact larvae. Most of the muscle cells that developed in culture were mononucleate, although some multinucleate syncytia were observed. Dissociated larval cells remained viable up to 12 weeks, exhibiting an average of one to two divisions in the first six days, and attachment of approximately 6 to 8% of the original population. Cell culture and in vitro myogenesis of Haliotis myoblasts and myocytes will facilitate studies of the molecular mechanisms controlling early muscle development, and should provide a useful model system for biotechnological improvement of the abalone.

Morphogen-Based Chemical Flypaper for Agaricia humilis Coral Larvae

Larvae of the scleractinian coral Agaricia humilis settle and metamorphose in response to chemosensory recognition of a morphogen on the surfaces of Hydrolithon boergesenii and certain other crustose coralline red algae. The requirement of the larva for this inducer apparently helps to determine the spatial pattern of recruitment in the natural environment. Previous research showed that the inducer is associated with the insoluble cell wall fraction of the recruiting algae or their microbial epibionts, and that a soluble but unstable fragment of the inducing molecule can be liberated by limited hydrolysis, either with alkali or with enzymes specific for cell wall polysaccharides. We now show that the parent morphogen can be solubilized by gentle decalcification of the algal cell walls with the chelators EGTA or EDTA, suggesting that the morphogen may be a component of the calcified recruiting alga itself, rather than a product of any noncalcified microbial epibionts. The solubilized inducer is subsequently purified by hydrophobic-interaction and DEAE chromatography. The purified, amphipathic morphogen retains activity when tightly bound to beads of a hydrophobic-interaction chromatography resin, and this activity (tested with laboratory-reared larvae) is identical in the ocean and the laboratory. We have attached the purified, resin-bound inducer to surfaces coated with a silicone adhesive and thus produced a potent artificial recruiting substratum--i.e., a morphogen-based chemical "flypaper" for A. humilis larvae. This material should prove useful in resolving the role of chemosensory recognition of morphogens in the control of substratum-specific settlement, metamorphosis, and recruitment and in the maintenance of species isolation mechanisms in the natural environment.

Nicotine increases sensory gating measured as inhibition of the acoustic startle reflex in rats

Chronic nicotine administration has been reported to increase acoustic startle response (ASR) amplitude in rats, which has been offered as evidence that some dosages of nicotine can enhance attention. The present experiments examined effects of acutely administered nicotine on amplitude and pre-pulse inhibition (PPI) of acoustic startle in rats. PPI, the decrease in ASR amplitude by a stimulus preceding the startle-eliciting event, reflects pre-attentive neural processes underlying sensory gating. Nicotine had a biphasic dose effect on startle amplitude, with increases at lower dosages (0.01 mg/kg) and decreases at higher dosages (0.5-5.0 mg/kg SC). Lower dosages of nicotine (0.001-0.01 mg/kg) increased PPI and the increase at 0.001 mg/kg occurred independently of changes in ASR amplitude. These results confirm that increases in PPI are not dependent upon changes in ASR amplitude. Results are consistent with nicotine's enhancements of performance on cognitive tasks in humans and are the first reported use of the PPI paradigm to model such effects. These findings indicate that ASR paradigms are useful to study effects of nicotine.

Smoking, gender, and age as risk factors for site-specific intraoral squamous cell carcinoma. A case-series analysis

BACKGROUND

Studies assessing risk factors for oral cancer do not generally report results for specific oral sites. The purpose of the current study was to examine differences in the distribution of age, gender, and tobacco use by intraoral site in a series of oral cancer cases.

METHODS

Information on gender, age at diagnosis, and lesion location was obtained for all incident cases of oral squamous cell carcinoma diagnosed through the University of Connecticut Oral Pathology Biopsy Service during the period 1987-1991 (N = 150). Information on tobacco use was obtained through a telephone interview or from medical or dental records.

RESULTS

The tongue, floor of the mouth (FOM), and gingiva, respectively, were the most commonly affected sites. The male-to-female ratio was greatest for FOM cancer (3.4) and lowest for gingival cancer (0.5). The mean age at diagnosis did not differ significantly by site. The percentage of smokers among cases of FOM, tongue, and gingival cancer was 97%, 64%, and 50%, respectively. When multiple logistic regression was used to compare FOM and gingival cancer, gender and smoking remained significant predictors. The odds of smoking among patients with FOM cancer were 32 times the odds of smoking among patients with gingival cancer (odds ratio for age, gender adjusted = 32.6, 3.3-323.5).

CONCLUSIONS

The findings suggest that cancer of the FOM is more strongly associated with smoking than is cancer of the gingiva and, perhaps, the tongue. The reported results should be interpreted cautiously in light of study limitations, which include the absence of information on alcohol consumption and lack of a noncancer control group.

Calcium control of metamorphosis in polychaete larvae

The importance of Ca2+ in the control of metamorphosis of a marine invertebrate larva was investigated. An excess of [Ca2+] in the external medium induced metamorphosis of Phragmatopoma californica (polychaete) larvae in a concentration-dependent manner. This effect is specific for calcium, and not simply the result of osmotic changes, as an excess of Mg2+ did not induce metamorphosis. Consistent with this finding, the calcium ionophore, A23187, also induced metamorphosis in a concentration-dependent manner. Paradoxically, however, the aromatic compounds diltiazem, verapamil, D600, and nifedipine, known to block Ca2+ channels in other systems, also induced metamorphosis. When exposed to diltiazem for only 20 h and subsequently washed free of this compound, 95% of the larvae metamorphosed and developed normally. Previous studies have demonstrated that the induction of metamorphosis in Phragmatopoma californica is controlled by chemosensory recognition of an exogenous morphogen and mediated by an excitatory pathway that involves adenyl cyclase and cyclic AMP. Because cellular excitation and cyclic AMP-dependent signal transduction generally involve the participation of calcium ion, the most parsimonious explanation for the results reported here include (1) direct control of the morphogenetic pathway by calcium ion, and (2) complexities of the calcium regulation of this process, or a functional similarity between the structurally related aromatic effectors tested and the natural inducer of metamorphosis.

Molluscan chymotrypsin-like protease: structure, localization, and substrate specificity

A messenger RNA encoding a chymotrypsin-like preproprotease is expressed abundantly and specifically in the distal quarter of the intestine of the mollusc Haliotis rufescens (red abalone). Consistent with this finding, a chymotrypsin-like activity was detected at highest concentration in the lumen of this segment of the intestine. Because the complexity of total protein in the distal intestinal fluid was low and the chymotrypsin-like protease was highly expressed, purification of the enzyme to near homogeneity was achieved by a single passage over an anion-exchange resin. The primary specificity of the protease, predicted from homology of the key amino acid residues (Ser189, Gly216, and Ser226) in the substrate binding site with similar residues lining the S1 subsites of other chymotrypsin-like enzymes, was confirmed by hydrolysis of a family of tetrapeptide substrates with different P1 amino acids. The optimal P1 residues include those with bulky, gamma-branched side chains (phenylalanine and leucine) similar to the side chain of the asparagine residue at P1 of the activation peptide of the proenzyme. Thus, unlike zymogens of the pancreatic serine proteases, which are activated by the common tryptic mechanism, the zymogen of the molluscan enzyme appears to be activated by an autocatalytic mechanism, i.e., by cleavage with active chymotrypsin-like protease. Additional unique properties of the enzyme predicted from the primary sequence include an unpaired cysteine, with the potential for internal thiol-disulfide isomerization between two different conformers of the protease.

The ets multigene family is conserved throughout the Metazoa

This study provides the first empirical evidence for the conservation of the ets proto-oncogene transcription factor family throughout the Metazoa. Using the polymerase chain reaction with degenerate primers corresponding to conserved sequences within the ETS DNA-binding domain, we have detected ets genes in a range of lower metazoans, including sponges, ctenophores, anemones, flatworms and nematodes, and in several higher invertebrate metazoans. Many of these sequences are significantly divergent from the original v-ets-1 oncogene, although most can be aligned with recently defined groups within the ets gene family. Multiple ETS domain sequences were detected in a number of the lower metazoan species, providing evidence for the existence of an ets multigene family at the earliest stages of metazoan evolution. In contrast, we were unable to detect any ETS sequences in fungal, plant or several protozoan DNAs. Our findings suggest that the duplication and divergence of ets proto-oncogenes responsible for generating the multigene family occurred concomitantly with the development of metazoan animals. In addition, these data corroborate other recent molecular evidence in providing strong support for the monophyletic origin of all multicellular animals, including sponges.

Isolation of full-length RNA templates for reverse transcription from tissues rich in RNase and proteoglycans

RNA isolated by conventional guanidinium isothiocyanate methods from tissues of a mollusc (red abalone: Haliotis rufescens) is largely degraded and discolored by contaminants. These contaminants are associated with inhibition of reverse transcriptase, prevent accurate spectrophotometric determination of RNA concentration, and impart undesirable viscosity to the preparations. A cold two-step method of RNA isolation was devised which provides high yields of full-length RNA templates from these tissues and eliminates the discolored contaminant. Immediately following homogenization of tissues at ca. 5 degrees C, which proved crucial for the recovery of high-molecular weight species, the RNA is isolated from the bulk of the RNase by a single acid-phenol-chloroform extraction at 0 degrees C. The inhibitor of reverse transcriptase, suspected to be a proteoglycan (or a similar high-molecular-weight polyanion) component of the intestinal mucus, is eliminated only by a second purification step employing ultracentrifugation through a dense cushion of CsCl. This cold two-step method should prove useful for providing full-length RNA templates relatively free of polysaccharide, a common contaminant of RNA preparations, from both plant and animal tissues.

Identification of eight homeobox-containing transcripts expressed during larval development and at metamorphosis in the gastropod mollusc Haliotis rufescens

The red abalone, Haliotis rufescens, is an especially tractable experimental model for studying molecular and cellular changes that occur at metamorphosis, because synchronous settlement and metamorphosis of the planktonic larvae can be induced in the laboratory. Using reverse transcription-polymerase chain reaction with degenerate primers based on the Drosophila Antennapedia-class homeodomain consensus sequence, eight differentially transcribed homeoboxes were identified from Haliotis larvae prior to and during metamorphosis. These are the first homeoboxes isolated from the phylum Molusca. Five of the partial homeobox sequences presented appear to represent Antennapedia-like genes of the putative Haliotis HOM-C/Hox complex; the remainder show similarity to homeoboxes of divergent classes. Analysis of RNA from a range of early developmental, larval, and metamorphic stages revealed that Antennapedia-like homeobox transcripts are present in trochophore and veliger larvae and in settled individuals undergoing metamorphosis, but not in the egg or early embryo.

Specific Inhibitors of Protein Synthesis Do Not Block RNA Synthesis or Settlement in Larvae of a Marine Gastropod Mollusk (Haliotis rufescens)

Antibiotic inhibitors of protein synthesis were tested for their effectiveness in larvae of the red abalone, Haliotis rufescens (gastropod mollusk). Emetine and anisomycin proved highly effective in this system, while cycloheximide, fusidic acid, puromycin, and tetracycline were less effective. Emetine and anisomycin specifically inhibited protein synthesis but not RNA synthesis. The contribution to protein synthesis by chloramphenicolsensitive prokaryotic contaminants was found to be undetectable, except following the onset of symptoms of toxicity resulting from prolonged exposure to emetine or anisomycin. The induction of larval settlement and plantigrade attachment by γ-aminobutyric acid (GABA), a functional analog of the natural inducer of settlement, occurred even under conditions in which most protein synthesis was inhibited, as expected for a chemosensory system response, whereas subsequent developmental metamorphosis was completely blocked. Because emetine and anisomycin block protein synthesis--including the synthesis of new transcription factors--but do not block early transcription, treatment of marine invertebrate embryos and larvae with these inhibitors can be used to obtain a selective enrichment in the mRNA population of "early gene" transcripts induced directly by GABA and other morphogenetic signals, without dilution by new mRNAs, the appearance of which is dependent on the synthesis of new protein transcription factors.

Organization, expression and nucleotide sequence of the operon encoding R-phycoerythrin alpha and beta subunits from the red alga Polysiphonia boldii

The characterization of the operon encoding the alpha and beta subunits of rhodophytan (R)-phycoerythrin (PE) from the macrophytic red alga Polysiphonia boldii is reported. This plastid-encoded operon was cloned, its nucleotide sequence determined, and its expression characterized by northern and primer extension analyses. The arrangement and expression of the PE alpha and beta genes, named rpeA and rpeB, are similar to those of the cyanobacterial (C)-PE genes: rpeB is located 5' of rpeA, with an intergenic region of 64 nucleotides. The two genes are transcribed on a 1.25 kb dicistronic transcript, and each coding region is preceded by a prokaryotic ribosome binding site consensus sequence. Transcription is initiated 95 nucleotides upstream of the initiating methionine codon of rpeB. The promoter region resembles that of prokaryotic genes, with an AT-rich -10 sequence. A direct pentanucleotide repeat (5'-TGTTA-3') was found in the -35 region. This pentanucleotide is present upstream of all PE operons that have been characterized thus far. An extensive inverted repeat is present 3' of rpeA; inverted repeats are found downstream of all PE operons sequenced to date, although the sequence is not conserved. The deduced amino acid sequences from these genes provide complete sequences for an R-PE. Of the amino acid residues 85% are identical to those of bangeophycean (B)-PE from the unicellular red alga Porphyridium cruentum. Conserved residues include cysteines at the bilin attachment sites of C- and B-PEs, aspartates at positions postulated to interact with bilin chromophores, and an apparent consensus sequence for N-methylation of an asparagine residue in C-PEs.

Cilia from Abalone Larvae Contain a Receptor-Dependent G Protein Transduction System Similar to that in Mammals

Lysine and related diamino acids amplify (facilitate) the response to inducers of metamorphosis in larvae of the marine mollusk Haliotis rufescens. Previous studies showed that a cholera toxin-sensitive G protein transduces the lysine signal via a diacylglycerol-dependent pathway. We have isolated and partially purified larval cilia that may be involved in recognizing the facilitating chemical signals. These isolated cilia provide an open or porous membrane-associated sensory system that is uniquely tractable for in vitro analyses of chemosensory signal transduction. The cilia contain receptors that exhibit sodium-independent binding of the facilitating diamino acids. The binding strength for lysine and related diamino acids in vitro is correlated with the effectiveness of these ligands as facilitators in vivo. The cilia contain a cholera toxin-sensitive G protein functionally coupled to the lysine receptor. The receptor and the G protein reciprocally regulate one another, suggesting that the chemosensor may be a member of the rhodopsin-like, G proteincoupled transmembrane receptor superfamily. Previous analyses of mRNAs from the larval cilia revealed a sequence coding for a G protein with high homology to Gq from mammalian brain, and another sequence coding for a protein homologous to Gi/Go. Similarities between this system, other chemosensory signal transduction pathways, and mechanisms of neuronal long-term potentiation are evident. Because the receptors and transducers controlling settlement and metamorphosis in Haliotis and other marine invertebrate larvae appear homologous to components controlling neuronal activity, cellular proliferation, and differentiation in mammals, characterization of the molecules controlling metamorphosis may help in the design of new regulators useful in medicine.

Cement precursor proteins of the reef-building polychaete Phragmatopoma californica (Fewkes)

Two distinctive 3,4-dihydroxyphenyl-L-alanine-(DOPA-) containing proteins (Pc-1 and Pc-2) have been isolated and partially characterized from the thorax of the reef-building sabellariid Phragmatopoma californica. They are the first such reported from the phylum Annelida. The proteins are presumed to be soluble precursors of the quinone-tanned cement used to bind particulate materials in the construction of the tubes that serve as habitats for the worms. The proteins have apparent molecular weights ranging from 18,000 to 20,000 and isoelectric point greater than or equal to 8.0. Both proteins consist of repeated sequence motifs in their primary structure. Pc-1 has repeats of (XGGY*GY*GAK) where X = V, L, I, AA, or KV, and Y* is DOPA or tyrosine. Pc-2, in contrast, appears to have repeats of (X1-[GGY*]n-[GA]m-X2-[HP(A)V]p-HK) where X1 can be AL, A, or F; X2 can be WG or absent; n and m can be 1 or 2, and p = 0-2. Both protein families appear to share the same C-terminal sequence ALGGY*GAGA. Of the DOPA-containing proteins characterized from other phyla, Phragmatopoma cement precursors most resemble those from the liver fluke Fasciola hepatica and the mussel Trichomya hirsuta.