Spatiotemporal self-organization in a surface reaction: from the atomic to the mesoscopic scale

Scanning tunneling microscopy data revealed the atomic processes in propagating reaction fronts that occur in the catalytic oxidation of hydrogen on Pt(111). The fronts were also characterized on mesoscopic length scales with respect to their velocity and width. Simulations on the basis of a reaction-diffusion model reproduce the experimental findings qualitatively well. The quantitative comparison reveals the limitations of this traditional approach to modeling spatiotemporal pattern formation in nonlinear dynamics.

Identification and characterization of a gene cluster involved in manganese oxidation by spores of the marine Bacillus sp. strain SG-1

The marine Bacillus sp. strain SG-1 forms spores that oxidize manganese(II) as a result of the activities of uncharacterized components of its spore coat. Nucleotide sequence analysis of chromosomal loci previously identified through insertion mutagenesis as being involved in manganese oxidation identified seven possible genes (designated mnxA to mnxG) in what appears to be an operon. A potential recognition site for the sporulation, mother-cell-specific, RNA polymerase sigma factor, sigmaK, was located just upstream of the cluster, and correspondingly, measurement of beta-galactosidase activity from a Tn917-lacZ insertion in mnxD showed expression at mid-sporulation to late sporulation (approximately stage IV to V of sporulation). Spores of nonoxidizing mutants appeared unaffected with respect to their temperature and chemical resistance properties and germination characteristics. However, transmission electron microscopy revealed alterations in the outermost spore coat. This suggests that products of these genes may be involved in the deposition of the spore coat structure and/or are spore coat proteins themselves. Regions of the deduced protein product of mnxG showed amino acid sequence similarity to the family of multicopper oxidases, a diverse group of proteins that use multiple copper ions to oxidize a variety of substrates. Similar regions included those that are involved in binding of copper, and the addition of copper at a low concentration was found to enhance manganese oxidation by the spores. This suggests that the product of this gene may function like a copper oxidase and that it may be directly responsible for the oxidation of manganese by the spores.

Nonrandom 4p13 rearrangements of the RhoH/TTF gene, encoding a GTP-binding protein, in non-Hodgkin's lymphoma and multiple myeloma

We recently isolated the RhoH/TTF gene by its fusion to the LAZ3/BCL6 gene, in a non-Hodgkin's lymphoma (NHL) cell line, which bore a t(3;4)(q27;p11-13) translocation. This gene encodes a novel Rho GTP-binding protein and is specifically expressed in hematopoietic tissues. We made its precise mapping at band 4p13, and described its partial genomic structure. Using fluorescence in situ hybridization and molecular analyses, we report here on the rearrangement of the RhoH/TTF gene, at band 4p13, in four cases of NHL with t(3;4)(q27;p13) translocation and its fusion to the LAZ3/BCL6 gene at band 3q27, in three of these cases. RT-PCR analysis of two cases allowed the detection of variable fusion transcripts emerging from the rearranged alleles, and in one case, a deregulated expression of both RhoH/TTF and LAZ3/BCL6 genes, by promoter substitution, was observed. We also show here another rearrangement of the RhoH/TTF gene in a patient with multiple myeloma and t(4;14)(p13;q32) translocation, with breakage within the IGH gene. It is the first report which describes the recurrent chromosomal alteration of a GTP-binding protein encoding gene, in patients with hematopoietic malignancies.

Characterization of a silicon transporter gene family in Cylindrotheca fusiformis: sequences, expression analysis, and identification of homologs in other diatoms

The transport of silicon is an integral part of the synthesis of the silicified cell wall of diatoms, yet knowledge of the number, features, and regulation of silicon transporters is lacking. We report the isolation and sequence determination of five silicon transporter (SIT) genes from Cylindrotheca fusiformis, and examine their expression patterns during cell wall synthesis. The encoded SIT amino acid sequences are highly conserved in their putative transmembrane domains. Nine conserved cysteines in this domain may account for the sensitivity of silicon uptake to sulfhydryl blocking agents. A less conserved C-terminal domain is predicted to form coiled-coil structures, suggesting that the SITs interact with other proteins. We show that SIT gene expression is induced just prior to, and during, cell wall synthesis. The genes are expressed at very different levels, and SIT1 is expressed in a different pattern from SIT 2-5. Hybridization experiments show that multiple SIT gene copies are present in all diatom species tested. From the data we infer that individual transporters play specific roles in silicon uptake, and propose that the cell regulates uptake by controlling the amount or location of each. The identification of all SIT genes in C. fusiformis will enhance our understanding of the mechanism and control of silicon transport in diatoms.

Trans-splicing in chloroplasts: the rps 12 loci of Nicotiana tabacum

The rps12 gene in tobacco chloroplasts consists of three exons that code for a polypeptide with homology to Escherichia coli ribosomal protein S12. C-terminal exons 2 and 3 of rps12 are located in the inverted repeat regions of the tobacco chloroplast genome. Exon 1 of rps12 is 29 kilobase pairs downstream of the nearest copy of exons 2 and 3 and 69 kilobase pairs away from the distal copy of exons 2 and 3. RNA gel blot hybridization analysis and primer extension sequencing of cDNA to rps12 encoding RNAs indicate that exon 1 and exons 2 and 3 are encoded on separate transcripts. Exon 1 and exons 2 and 3 are covalently ligated in the correct reading frame in rps12 mRNA. These results indicate that a bimolecular (trans-) splicing event occurs during the formation of mature rps12 mRNA.

Energy of the oscillating legs of a fast-moving cheetah, pronghorn, jackrabbit, and elephant

Lifelike models of the oscillating legs treated as three-segment systems show the course of kinetic and potential energy over the locomotor cycle for a cheetah, pronghorn, jackrabbit, and elephant running at speeds approaching their maxima. The models can be adjusted to eliminate differences among the animals in time intervals, mass or length of limb, and joint angles. This facilitates analysis of the influence on total energy of each of these variables and of the distribution of mass among leg segments. Fast-cycling legs of the carnivore type have significantly more energy than those of the hoofed type. This may contribute to the lesser endurance that is usual for carnivores that hunt using a high-speed dash.

Silicon-responsive cDNA clones isolated from the marine diatom Cylindrotheca fusiformis

In organisms ranging from single-celled algae to mammals, including humans, silicon is essential for, and actively participates in, a variety of life processes. It has become clear that silicon (i) acts as a metabolite affecting a variety of cellular processes, and (ii) regulates gene expression. However, the mechanisms by which silicon (i.e., Na2SiO3.9H2O, in the present study) acts are not clear, due to inherent methodological difficulties. As part of our program to understand how silicon acts in biological systems, we present the first isolation of cDNA clones derived from silicon-responsive mRNAs, from the marine diatom Cylindrotheca fusiformis. We distinguish between clones responding only to silicon starvation and replenishment, and those also responding to other cellular conditions. Some of the clones can be identified by similarity to other genes, and should be useful as probes to isolate genes from other organisms. Isolation of these clones provides the means to (i) identify metabolic pathways affected by silicon, and (ii) investigate the mechanism(s) of silicon-regulated gene expression.

Coronary thrombolysis with Desmodus salivary plasminogen activator in dogs. Fast and persistent recanalization by intravenous bolus administration

BACKGROUND

DSPA (Desmodus salivary plasminogen activator) is a new thrombolytic agent corresponding to a natural plasminogen activator discovered in the saliva of the vampire bat Desmodus rotundus. Compared with tissue plasminogen activator (TPA), DSPA, produced in a recombinant cell line, is more fibrin cofactor dependent than TPA.

METHODS AND RESULTS

The thrombolytic properties of DSPA and TPA were compared in a canine model of copper coil-induced coronary thrombosis. All dogs received heparin 200 IU/kg IV and SC. Whereas controls did not reperfuse within 180 minutes (none of six), intravenous bolus administration of DSPA at 25, 50, and 100 micrograms/kg resulted in a 100% incidence (6 of 6) of recanalization within 37, 23, and 18 minutes, respectively. TPA at 63 and 125 micrograms/kg reopened the coronaries in 33% (two of six) and 50% (three of six) of cases within 40 minutes. Eighty-three percent (5 of 6) of the arteries were still patent 3 hours after 50 and 100 micrograms/kg DSPA, whereas only 20% (one of five) of all coronaries originally recanalized with both doses of TPA were still open at 3 hours. Plasma levels of alpha 2-antiplasmin decreased significantly only with 125 micrograms/kg TPA. The clearance of DSPA (2.3 to 3.5 mL.min-1.kg-1) was lower compared with TPA (11.4 to 20 mL.min-1.kg-1) due to a prolonged terminal half-life.

CONCLUSIONS

In a canine coronary thrombosis model, DSPA exhibited higher potency and recanalized coronary arteries faster and with a lower incidence of reocclusion than TPA. Its properties may translate into a higher efficacy in patients compared with available thrombolytic agents. The long half-life of DSPA may allow for single bolus administration in the treatment of acute myocardial infarction.

Determination of dextromethorphan metabolizer phenotype in healthy volunteers

The dextromethorphan metabolizer phenotype in 450 healthy volunteers (299 men, 151 women) was determined after oral administration of a 15 mg dose. In 8 h-postdose urine samples the ratio of dextrorphan (DOP) to dextromethorphan (DMP) was measured by HPLC. Urinary excretion of DMP and DOP within 8 h after the dose varied greatly between individuals, ranging from 0-11% and 0.04-100% of dose, respectively. In 143 test subjects the fraction of the dose of DMP in urine was below the detection limit. In the remaining 307 volunteers the metabolic ratio (MR) of DOP to DMP varied from 0.07 to 2906. In 404 test subjects the MR was greater than 10 and they were classified as extensive metabolizers (90% of the entire group). Of the entire group 5% had MRs of 1-10 and less than 1, respectively. Depending on the limit for classification of poor metabolizers, their frequency was 5-10% in the Caucasian population studied. The present data are in agreement with previous findings that the oxidative metabolic polymorphisms of debrisoquin and DMP co-segregate; the frequency of the PM phenotype of dextromethorphan in Caucasian populations varies between 5 and 10%.

Patient-informant concordance on the Structured Clinical Interview for DSM-III-R personality disorders (SCID-II)

In the assessment of personality disorders, patients reports can be questioned for several reasons, such as lack of insight, shame, and acute psychiatric state. High concordance between patient-based and informant-based diagnoses would be an indication of the validity of patient reports (convergent validity). The present study examined the concordance between 42 psychotherapy outpatients and their informants (intimates) on the Structured Clinical Interview for DSM-III-R Personality Disorders (SCID-II). Similar to prior studies, low or only modest levels of agreement were found. In comparison with evaluations of the personality of the patient by the therapist, patient interviews seemed to be more valid than informant interviews. Furthermore, couples with high intensity and intimacy in the contact generally showed higher agreement than couples with low intensity and intimacy. In conclusion, the data slightly suggest that patient reports are more valid than informant reports. However, the lack of a golden standard forces us to find more evidence before concluding that patient reports on personality result in valid diagnoses.

Molecular comparison of pathogenic bacteria from pear trees in Japan and the fire blight pathogen Erwinia amylovora

Several strains of the genus Erwinia, which were isolated in Japan from pear trees with necrotic symptoms that resembled fire blight, and tentatively identified as Erwinia amylovora, were reinvestigated for their relationship to the fire blight pathogen. These isolates produced ooze on slices of immature pears and were mucoid on MM2Cu agar plates, but did not synthesize levan and did not give the expected PCR signals with several primer pairs specific for Erwinia amylovora. The isolates tested positive with PCR primers designed to detect the novel pear pathogen Erwinia pyrifoliae, which was isolated from Nashi pear trees in South Korea. The nucleotide sequence analysis of a DNA fragment preceding the gene cluster for exopolysaccharide synthesis revealed a closer relationship to Erwinia pyrifoliae than to Erwinia amylovora. Plasmid profiles, protein patterns and genomic DNA analysed by PFGE after XbaI and SpeI digestion were different than Erwinia amylovora. Experiments with strains of Erwinia amylovora isolated from raspberry (Rubus sp.), Erwinia mallotivora and Enterobacter pyrinus also did not reveal a relationship between these bacteria and the Japanese Erwinia strains. The latter are not identical to Erwinia pyrifoliae, but possess many similar features to this pathogen that causes Asian pear blight. It is concluded that pathogenic bacteria isolated in Japan from pear trees with symptoms resembling fire blight are possibly different from Erwinia amylovora.

Overprediction of anxiety, and disconfirmatory processes, in anxiety disorders

The overprediction of anxiety phenomenon and its relationships with fear, dysfunctional and functional beliefs, and emotional experiences during confrontations with feared stimuli were investigated in two studies. Study 1 investigated exposure in vivo exercises executed by anxiety patients during treatment (n = 37). Study 2 investigated behavioural experiments executed by anxiety patients (n = 11) during cognitive treatment. In both studies patients rated various variables just before and immediately after their exercises. The results indicate that anxiety patients tend to overpredict the level of anxiety they are going to experience. There is no evidence that this phenomenon is a statistical artefact, caused for instance by a pre-test response style. There is also no evidence that the observed adjustment of incorrect anxiety predictions is a statistical artefact. A global negative emotional evaluation of the experience appears to have an adverse influence on the reduction of anxiety predictions and on the reduction of fear. Fear, and its reduction after exposure in vivo or after behavioural tests, appears to be influenced by both anxiety predictions and dysfunctional beliefs. Positive emotions and functional beliefs did not appear to play an important role. The interrelationships between these factors are comprised in a path-model which describes how emotional and cognitive information yielded by disconfirmatory experiences influences changes in anxiety predictions and changes in fear. Unexpectedly, change in dysfunctional belief did not relate directly to change in fear, but only indirectly, via change in anxiety predictions. Theoretical and therapeutical implications are discussed.

Instability of short-sequence DNA repeats of pear pathogenic Erwinia strains from Japan and Erwinia amylovora fruit tree and raspberry strains

An array of short-sequence DNA repeats (SSRs) occurs in the plasmid pEA29 of the fire blight pathogen Erwinia amylovora. A large number of "fruit tree" strains, mainly from Central and Western Europe, were screened for their SSR numbers, and the analyses were extended to five raspberry strains from North America and six pear pathogenic Erwinia strains from Japan. The repeat ATTACAGA present in all E. amylovorastrains was found to be reiterated 3 to 15 times. The Japanese strains contained the major repeat sequence GGATTCTG, which was reiterated 16 to 24 times. ATTACAGG, which resembles the SSR of E. amylovora, was reiterated two or three times. In a novel approach, sequencing gels were used to visualize the rare occurrence of shorter arrays (down to three repeats) in E. amylovoraand the Japanese Erwinia strains. Changes in the repeat numbers in E. amylovora were observed repeatedly when the bacteria had been exposed to stress conditions. The repeat structures of homo- and heteroduplices of PCR-amplified repeats were also analyzed by cleavage of annealed molecules with the single-strand-specific endonuclease from bacteriophage T4. Not only heteroduplexes, but also homoduplexes showed non-matching regions in the SSRs, which could arise from transient formation of loops due to strand slippage during the assays.

Weight loss improves endothelial function independently of ADMA reduction in severe obesity

This prospective study was performed in order to establish whether improvement of endothelial function after weight reduction can be explained by a decrease of elevated asymmetric dimethyl arginine (ADMA), an inhibitor of endogenous NO-synthase (eNOS). Therefore, 21 obese subjects (BMI: 41.1±6.4 kg/m(2)) were studied at baseline and after 12 weeks of weight reduction with a very low calorie diet. Biochemical and clinical parameters of endothelial function were assessed before and after weight loss. Biochemical parameters were determined by measurement of ADMA and soluble intercellular adhesion molecule (sICAM). Clinical parameters were assessed by pulse wave analysis (PWA). Weight intervention resulted in a 21.4±6.8 kg reduction of body weight from 119.7±12.8 kg at study start to 98.3±11.6 kg at study end (p<0.001). Accordingly, biochemical markers improved under weight reduction (ADMA from 0.47±0.07 mmol/l to 0.42±0.08 mmol/l; p=0.002; ICAM from 276±42 ng/ml to 236±29 ng/ml; p<0.001). Further, clinical parameters of functional endothelial function improved with an increase of deltaRI after salbutamol inhalation from -1% before to -9% after weight reduction (p=0.02). Interestingly, improvement of endothelial function correlated with improved HOMA index only (r=-0.60, p=0.04) but not with reduced ADMA levels, improved hypertension or reduced body weight. In conclusion, weight reduction with a very low calorie diet improves endothelial function measured by pulse wave velocity. The missing correlation with ADMA suggests possible further mechanisms underlying this observed effect, for example, improvement of insulin resistance.

Characterization of hns genes from Erwinia amylovora

The small basic histone-like protein H-NS is known for bacteria to attenuate virulence of several animal pathogens. An hns homologue from E. amylovora was identified by complementing an E. coli hns-mutant strain with a cosmid library from E. amylovora. A 1.6 kb EcoRI-fragment complemented the mucoid phenotype and repressed the ss-glucosidase activity of E. coli PD32. The open reading frame encoding an H-NS-like protein of 134 amino acid was later shown to be located on plasmid pEA29 (McGhee and Jones 2000). A chromosomal hns gene was amplified with PCR consensus primers and localized near galU of E. amylovora. E. amylovora mutants were created by insertion of a resistance cassette, and the intact gene was inserted into a high copy number plasmid for constitutive expression. Purified chromosomal H-NS protein preferentially bound to a DNA fragment from the lsc region and bending was predicted for an adjacent fragment with the rlsB-promoter. Levan production was significantly increased by hns mutations. Synthesis of the capsular exopolysaccharide amylovoran and of levan were reduced, when hns from the E. amylovora plasmid was overexpressed. A mutation in chromosomal hns of E. amylovora increased amylovoran synthesis, and both mutations retarded symptom formation on immature pears.

Pharmacokinetics and tolerability of oral iloprost in thromboangiitis obliterans patients

OBJECTIVE

Iloprost is a potent PGI2 mimetic, which has been shown to be therapeutically effective in several vascular disorders. Due to its rapid clearance from the central compartment, iloprost is administered mainly by i.v. infusion, which limits its use to hospitalized patients. In order to improve pharmacotherapeutic use of this PGI2 mimetic, an oral extended-release (ER) dosage form has been developed, which should mimic plasma level profiles as observed after i.v. infusion and serve as a therapeutic equivalent.

METHODS

This trial was performed to investigate the tolerability and pharmacokinetics of iloprost administered perorally, compared with i.v. infusion, in 12 patients suffering from thromboangiitis obliterans (TAO). A dose titration was carried out for 1 week with i.v. iloprost, followed by a p.o. titration and treatment phase of 3 weeks' duration. Pharmacokinetics was investigated at the individually tolerated dose levels; i.e., on days 5-7 (i.v. infusion at 2, 2.5 and 3 ng.kg-1.min-1), and twice during p.o. treatment after b.i.d. administration of 50, 100, 150, 200 or 300 micrograms.

RESULTS

Individual tolerability of iloprost varied: 7 patients out of 12 tolerated the maximum i.v. dose of 3 ng.kg-1.min-1; six tolerated the maximum oral dose of 600 micrograms. No patients withdrew from the study due to adverse events. Flush and headache were the most common adverse events and seemed to be related to the study drug. After i.v. infusion of iloprost, dose-normalized (3 ng.kg-1.min-1), steady-state plasma levels were 260 pg.ml-1. Terminal half-life was 0.57 h. Total clearance ranged from 8 to 17 ml.min-1.kg-1. Peroral administration of the ER formulation resulted in dose-dependent Cmax and AUC values. AUC values of the first and second daily dose interval, i.e., 0-5 h and 5-11 h after first dosing, were almost identical. Absolute bioavailability was 24%, with the exception of two patients who tolerated only 50 micrograms b.i.d. and exhibited a bioavailability of approx. 60%. The AUC values observed in weeks 2 and 4 were identical, demonstrating low day-to-day variability of iloprost plasma level profiles in TAO patients.

CONCLUSION

Based upon pharmacokinetic data, the ER formulation provides an equivalent to the i.v. infusion of iloprost and broadens the range of therapy to nonhospitalized patients. The availability of capsules with 50 and 100 micrograms iloprost enables individual dose titration and pharmacotherapy. Beneficial effects, as observed with i.v. iloprost in TAO patients, should therefore be achievable by peroral pharmacotherapy using the new ER formulation.

Pharmacokinetics and pharmacodynamics of cicaprost in healthy volunteers after oral administration of 5 to 20 micrograms

In a Phase I study, the tolerability, pharmacodynamics and pharmacokinetics of cicaprost have been investigated in 6 male volunteers given 5, 10, 15 and 20 micrograms as tablets of the beta-cyclodextrin clathrate. Individual inhibition of platelet aggregation and changes in facial colour (measured by chromametry) were dose-dependent and reached a maximum 30 to 60 min post-dose. The maximum inhibition of platelet aggregation was about 40%. After 3 to 4 h pre-treatment values had returned. Blood pressure remained within the normal range. The peak plasma level of cicaprost was reached within 15 to 90 min after drug intake. Both Cmax- and AUC were individually dose-dependent. The terminal half-life in plasma of cicaprost was approx. 1 h, and its total clearance amounted to 4-7 ml.min-1.kg-1. The time courses of the plasma levels and of the pharmacodynamic actions were in agreement. Interindividual differences were observed in the occurrence of unwanted effects (e.g. headache). Thus, cicaprost is an orally available PGI2-mimetic, for which effects on platelet aggregation and vascular perfusion have been demonstrated in healthy volunteers after doses of 5 to 15 micrograms.

Pharmacokinetics of 3H-cicaprost in healthy volunteers

Cicaprost (5-[(E)-(1S,5S,6S,7R)-7-hydroxy-6-[(3S,4S)-3-hydroxy-4-methylnona- 1,6- diinyl]-bicyclo[3.3.0]octan-3-yliden]-3-oxapentanoic acid, ZK 96 480) is a novel PGI2-derivative, which is chemically stable and not subject to metabolic degradation in rats and cynomolgus monkeys. The pharmacokinetics of Cicaprost were studied in six healthy volunteers (age: 54-74 y) after i.v. infusion (2.1 micrograms over 60 min) and p.o. dosage (7.6 micrograms) of the tritiated compound. All treatments were well-tolerated by the test subjects. At the end of the infusion plasma levels of approximately 100 pg/ml were reached, declining biphasically with half-lives of 3-4 min and 64 +/- 21 min. Total clearance was 3.8 +/- 0.5 ml/min/kg. The oral dosage resulted in peak plasma levels of 251 +/- 90 pg/ml occurring at 23 +/- 5 min post dose. The terminal half-life in the plasma was 115 +/- 30 min. Gastro-intestinal absorption and absolute bioavailability of Cicaprost was complete. After both routes of administration approx. 60% of dose was excreted with the urine within 24 h, whereas fecal 3H-excretion lasted for several days and accounted for approx. 35%. Radiochromatography revealed that Cicaprost was metabolically stable in plasma and urine. In the feces several degradation products were observed apart from approx. 30% of the dose fraction being excreted unchanged by that route. The present results demonstrate that Cicaprost is an orally completely bioavailable, metabolically stable PGI2-mimetic which may be an ideal candidate for oral therapy because of its pharmacokinetic characteristics.

Molecular cloning of a t(11;14)(q13;q32) translocation breakpoint centromeric to the BCL1-MTC

In B-cell malignancies, the t(11;14)(q13;q32) at the 11q13 BCL1 locus is characterized by a scattering of breakpoint sites along a 100 kb genomic region, between the BCL1 major translocation cluster (MTC) and the PRAD1 (also termed cyclin D1 or CCND1) gene. Recently, the 11q13 breakpoint region was extended on both sides, centromeric to the MTC and telomeric to PRAD1. We report here the molecular cloning of a new t(11;14) breakpoint site, 20 kb centromeric to the MTC, from a patient with prolymphocytic leukemia. We subcloned a non-repetitive DNA fragment near the breakpoint and mapped this new 11q13 probe (pHO11c) relative to already identified breakpoint sites, using long- and short-range physical mapping within the BCL1 locus. Rearrangements in the BCL1 locus are associated with deregulation of the PRAD1 gene, which is often overexpressed, particularly in mantle-cell malignancies. The detectable but weak PRAD1 expression in the case we present suggests that this breakpoint centromeric to the MTC still lies inside the BCL1 locus boundaries. We think that attention should be focused on this region centromeric to the BCL1-MTC, where the investigation of previously unidentified translocations may increase understanding of the PRAD1 gene deregulation in t(11;14) associated pathologies.

Characterization of two circular plasmids from the marine diatom Cylindrotheca fusiformis: plasmids hybridize to chloroplast and nuclear DNA

This paper reports the discovery and initial characterization of two small plasmids, pCf1 and pCf2, in the marine diatom Cylindrotheca fusiformis. Extracted diatom DNA separates into two bands in CsCl-Hoechst 33258 dye gradients. Upon agarose gel electrophoresis of a sample of the upper band of the gradient we observed, in addition to high molecular weight (genomic) chloroplast and mitochondrial DNA, pairs of lower molecular weight bands. These bands contained two species of circular plasmid DNA molecules, as shown by electron microscopy. The nucleotide composition of the plasmids, and chloroplast and mitochondrial DNAs is similar, as indicated by their co-banding in the gradients. They were cloned, and their restriction maps determined, showing that pCf1 is 4.27 and pCf2 4.08 kb in size. By hybridization analysis, we showed that pCf1 and pCf2 share regions of similarity, but not identity. Neither plasmid hybridizes with mitochondrial DNA. Both plasmids hybridize with chloroplast DNA, and pCf2 also hybridizes with nuclear DNA.