Allergic rhinitis due to house dust mites: evaluation of the efficacy of specific sublingual immunotherapy

BACKGROUND

The efficacy and safety of sublingual immunotherapy (SLIT) in patients with chronic rhinitis related to sensitization to house dust mites are still controversial.

METHODS

After application of an anti-mite mattress cover, patients were only included in the study when the cumulative symptom score over a fortnight was greater than 70 out of a possible total of 168. Thirty-two of the 120 patients selected were randomized to receive SLIT for 2 years: 17 received placebo and 15 received the Dermatophagoides pteronyssinus and D. farinae 50/50 allergen extract.

RESULTS

Significant between-group differences were observed after 1 year and persisted at the end of the second year for the rhinitis total score (P < 0.02), blocked nose score (P < 0.01) and nasal itching score (P < 0.01). Skin reactivity to house dust mites was significantly reduced in the group receiving house dust mite extract (P < 0.03). No statistical difference was observed between the two groups for medication scores, but a low medication consumption was observed in all patients. No serious and no systemic adverse reactions were reported.

CONCLUSION

This study indicates the superiority of active treatment vs. placebo, evaluated on efficacy criteria (rhinitis score) or objective criteria (skin reactivity). The availability of a solid form (tablet) could represent a progress in terms of patient acceptability.

A consensus protocol for the determination of the threshold doses for allergenic foods: how much is too much?

BACKGROUND

While the ingestion of small amounts of an offending food can elicit adverse reactions in individuals with IgE-mediated food allergies, little information is known regarding these threshold doses for specific allergenic foods. While low-dose challenge trials have been conducted on an appreciable number of allergic individuals, a variety of different clinical protocols were used making the estimation of the threshold dose very difficult.

OBJECTIVE

A roundtable conference was convened to develop a consensus clinical protocol for low-dose challenge trials for the estimation of threshold doses for specific allergenic foods.

METHODS

In May 2002, 20 clinical allergists and other interested parties were invited to participate in a roundtable conference to develop consensus of the key elements of a clinical protocol for low-dose challenge trials.

RESULTS

A consensus protocol was developed. Patients with convincing histories of food allergies and supporting diagnostic evidence including past challenge trials or high CAP-RAST scores can be enrolled in low-dose challenge trials. Care must be taken with younger patients to assure that they have not outgrown their food allergy. An approach was developed for the medication status of patients entering such trials. Challenge materials must be standardized, for example, partially defatted peanut flour composed of equal amounts of the three major varieties of peanuts (Florunner, Virginia, Spanish). Challenge materials must be appropriately blinded with sensory evaluation used to confirm the adequacy of blinding. A double-blind, placebo-controlled design should be used for low-dose challenge trials. Low-dose challenge trials would begin at doses of 10 microg of the allergenic food and would continue with doses of 100 microg and 1 mg followed by specific higher doses up to 100 mg depending upon the expert judgement of the physician; even higher doses might be applied to assure that the patient is indeed reactive to the particular food. A 30-min time interval would be used between doses, and reactive doses would be expressed as both discrete and cumulative doses. The goal of each challenge would be to develop objective symptoms; trials should not be discontinued on the basis of subjective symptoms only. Statistically, a minimum of 29 patients would be enrolled in low-dose challenge trials for each allergenic food because 0 reactors out of 29 patients at a particular dose allow the conclusion that there is 95% certainty that 90% of allergic individuals will not react to that dose.

CONCLUSION

A consensus protocol was developed. Using this protocol, it will be possible to estimate threshold doses for allergenic foods, the lowest amount that elicits mild, objective symptoms in highly sensitive individuals.

Chromatographic determination of the association constant between 8-methoxypsoralen and modified β-cyclodextrin: protective effect of hydroxypropyl-β-cyclodextrin on 8-methoxypsoralen toxicity in human keratinocytes

The retention of 8-methoxypsoralen (8-MOP) on an immobilised hydroxypropyl-beta-cyclodextrin (HP-beta-CD) column was analysed in HPLC by the determination of its Langmuir distribution isotherm. A such method was used to confirm the potential drug complexing role of this cyclodextrin. The 8-MOP/HP-beta-CD association constant (K) was equal to 29.5 and 18.7 M-1, respectively, at a temperature equal to 5 and 25 degrees C, respectively. These association constant values were used to determine the cytotoxicity profile of human keratinocyte cell line (HaCaT) in relation to the complex concentration. It was showed through these data that HP-beta-CD had a cytoprotective since a reverse effect of HP-beta-CD on 8-MOP cytotoxicity was observed.

Diagnosis of cypress pollen allergy: in vivo and in vitro standardization of a Juniperus ashei pollen extract

BACKGROUND

Cypress pollen allergy is a major cause of rhinoconjunctivitis and asthma in the Mediterranean area. The nonstandardized cypress allergen extracts currently available for the diagnosis of cypress allergy have a low level of activity. The search for an active material has led to the selection of Juniperus ashei (Ja) pollen because of its very high cross-reactivity with cypress extracts and its superior allergenic activity. The aim of this study was to characterize in vitro and calibrate in vivo an in-house reference extract (IHRS) of J. ashei pollen and determine the specificity and sensitivity of a standardized Ja extract for the prick test diagnosis of cypress allergy.

METHODS

Juniperus ashei pollen extract was analysed by 2-D electrophoresis. The IHRS Ja extract was calibrated by skin prick testing in 28 cypress-allergic patients. The sensitivity and specificity of cypress allergy diagnosis using a standardized Ja extract was studied by skin prick test in 42 cypress-allergic patients and 53 nonallergic patients. Jun a 1 content of the IHRS was determined by a monoclonal antibody-based electrophoretic technique.

RESULTS

The Jun a 1 content of the 100 IR/ml Ja IHRS extract was 180 microg/ml. For in vivo diagnosis of cypress allergy, Ja pollen extract demonstrated a sensitivity of 95%, a specificity of 100%, a negative predictive value of 96%, and a positive predictive value of 100%.

CONCLUSION

Standardized Ja pollen extract is therefore a very appropriate tool for the in vivo diagnosis of cypress pollen allergy and good candidate for specific immunotherapy.

Comparison of MultiMap and TSP/CONCORDE for constructing radiation hybrid maps

Radiation hybrid (RH) map construction allows investigators to locate both type I and type II markers on a given genome map. The process is composed of two steps. The first consists of determining the pattern distribution of a set of markers within the different cell lines of an RH panel. This is mainly done by polymerase chain reaction (PCR) amplification and gel electrophoresis, and results in a series of numbers indicating the presence or the absence of each marker in each cell line. The second step consists of a comparison of these numbers, using various algorithms, to group and then order markers. Because different algorithms may provide (slightly) different orders, we have compared the merits of the MultiMap and TSP/CONCORDE packages using a data set of information currently under analysis for construction of the canine genome RH map.

SHV-16, a beta-lactamase with a pentapeptide duplication in the omega loop

A clinical isolate of Klebsiella pneumoniae was found to be resistant to ampicillin (MIC of 128 microg/ml), ticarcillin (MIC of 512 microg/ml), and ceftazidime (MIC of 128 microg/ml) and susceptible to all other beta-lactams; a synergistic effect between clavulanate and ceftazidime suggested the presence of an extended-spectrum beta-lactamase (ESBL). Transconjugants in Escherichia coli were obtained at low levels (10(-7) per donor cell) and exhibited a similar beta-lactam resistance pattern (resistant to ampicillin, ticarcillin, and ceftazidime at 64 microg/ml). The ESBL, pI 7.6, was encoded by a large plasmid (>100 kb) which did not carry any other resistance determinant. The ESBL-encoding gene was amplified by PCR using bla(SHV)-specific primers and was sequenced. The deduced amino acid sequence of the SHV-16 ESBL showed that it differed from SHV-1 by only a pentapeptide insertion (163DRWET167) corresponding to a tandem duplication in the omega loop. The implication of the 163a-DRWET163b-DRWET sequence in ceftazidime resistance was confirmed by cloning either bla(SHV-1) or bla(SHV-16) in the same vector, subsequently introduced in the same E. coli strain. Under these isogenic conditions, SHV-16 conferred a 32-fold increase in ceftazidime MIC compared to that with SHV-1. Furthermore, site-directed mutagenesis experiments modifying either E166aA or E166bA revealed that the functional glutamic residue was that located in the first copy of the duplicated sequence. But surprisingly, the second E166b also conferred a low-level resistance to ceftazidime. This work is the first description of a class A enzyme exhibiting an extended substrate specificity due to an insertion instead of a nucleotide substitution(s) in a clinical isolate.

Nosocomial outbreak due to a multiresistant strain of Pseudomonas aeruginosa P12: efficacy of cefepime-amikacin therapy and analysis of beta-lactam resistance

Over a 3-year period, 67 patients of the Hospital of Pau (Pau, France), including 64 patients hospitalized in the adult intensive care unit (ICU), were colonized and/or infected by strains of Pseudomonas aeruginosa P12, resistant to all potentially active antibiotics except colistin. Most patients were mechanically ventilated and presented respiratory tract infections. Since cefepime and amikacin were the least inactive antibiotics by MIC determination, all ICU patients were treated with this combination, and most of them benefited. Cefepime-amikacin was found highly synergistic in vitro. Ribotyping and arbitrary primer-PCR analysis confirmed the presence of a single clonal isolate. Isoelectrofocusing revealed that the epidemic strain produced large amounts of the chromosomal cephalosporinase and an additional enzyme with a pI of 5.7, corresponding to PSE-1, as demonstrated by PCR and sequencing. Outer membrane protein profiles on sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed the absence of a ca. 46-kDa protein, likely to be OprD, and increased production of two ca. 49- and 50-kDa proteins, consistent with the outer membrane components of the efflux systems, MexAB-OprM and MexEF-OprN. Thus, we report here a nosocomial outbreak due to multiresistant P. aeruginosa P12 exhibiting at least four mechanisms of beta-lactam resistance, i.e., production of the penicillinase PSE-1, overproduction of the chromosomal cephalosporinase, loss of OprD, and overexpression of efflux systems, associated with a better activity of cefepime than ceftazidime.

[Antibiotic resistance of Staphylococcus aureus in urban experience: 6 month study in Aquitaine]

Antibiotic resistance of Staphylococcus aureus has been surveyed by eight city laboratories of the Aquitaine area, during a six month-period (january to june 1998). Antibiotic susceptibility testing has been performed by the disk diffusion method, and the results have been collected and analysed using the SIRscan system. After elimination of the redundant strains, a total of 747 isolates has been retained. They were mainly isolated from pus (64%) collected from patients of the community (40%) or hospitalized in 30 private clinics or nursing homes. The percentages of resistant strains (community/institutions) were: benzylpenicillin: 90% (87/92%), oxacillin: 39% (23/50%), kanamycin: 37% (22/47%); gentamicin: 13% (8/16%), tobramycin: 37% (21/47%), amikacin: 21% (13/27%); netilmicin: 6% (5/7%), erythromycin: 33% (30/35%), spiramycin: 72% (77/69%), lincomycin: 24% (17/29%), pristinamycin: 2% (1/2%), tetracycline: 17% (14/19%); pefloxacin: 40% (25/50%), fosfomycin: 9% (6/12%), rifampicin: 10% (7/13%), fusidic acid: 14% (11/15%), cotrimoxazole and vancomycin: 0%. Meticillin-susceptible strains of S. aureus were mostly sensitive to other antibiotics (< or = 6% resistant strains, except for erythromycin: 22%). Among meticillin-resistant S. aureus, heterogeneous strains with a KT phenotype, and various resistance patterns to the remaining antibiotics were predominant (61%), compared to the homogeneous strains with a KTG phenotype and multiresistant to the other antibiotics (32%). The frequencies of resistant strains were highly variable depending on the specimen, the laboratory and the health care institution, except for cotrimoxazole and vancomycin which were always active.

Specific immunotherapy with a standardized latex extract versus placebo in allergic healthcare workers

BACKGROUND

The prevalence of allergy to natural rubber latex proteins has increased over recent years among healthcare professionals but also in children undergoing multiple operations. Exposure to the antigen mainly occurs through the respiratory mucosa and the percutaneous route. Clinical manifestations range from urticaria to angioedema, rhinoconjunctivitis, bronchial asthma, or anaphylactic shock. Preventive measures have been proposed to reduce the risk of sensitization by using only powder-free or synthetic gloves and latex-free material in operating units, but this is not always possible.

OBJECTIVE

The aim of this study was to investigate the efficacy and safety of specific immunotherapy in sensitized workers.

METHODS

Seventeen patients with latex skin allergy and rhinitis (9 of whom also had asthma) were included in this randomized, double-blind, placebo-controlled trial (9 in the active group and 8 in the placebo group) for 1 year. Treatment started with a 2-day course of rush immunotherapy in hospital. Treatment efficacy was assessed after 6 and 12 months by means of symptom and medication scores recorded on diary cards. Conjunctival provocation tests were also performed.

RESULTS

Patients in the active treatment group had a significantly lower total rhinitis score after 6 (P <. 04) and 12 months (P <.05), conjunctivitis score after 6 months (P <. 02), and cutaneous score after 12 months (P <.03) than in the placebo group. Asthma symptoms after 6 or 12 months of treatment were not significantly different between the two groups after adjustment for baseline values. The global medication score was markedly decreased in the latex-treated group. A significant difference in conjunctival reactivity was observed in favor of the active group: the number of patients for whom the threshold dose was increased after 12 months of treatment was significantly greater in the active group than in the placebo group (P <.02). Most injections were well tolerated, but several adverse effects, including hypotension, urticaria, wheezing, and pharyngeal edema, were observed.

CONCLUSION

The clinical benefits observed during the present study included a significant improvement of rhinitis, conjunctivitis, and cutaneous symptoms. Immunotherapy also decreased allergen-specific conjunctival reactivity. Latex-specific immunotherapy may allow sensitized personnel to remain at work, but further trials need to be conducted in a larger number of patients.

Spaceflight inhibits bone formation independent of corticosteroid status in growing rats

Bone formation and structure have been shown repeatedly to be altered after spaceflight. However, it is not known whether these changes are related to a stress-related altered status of the corticosteroid axis. We investigated the role of corticosteroids on spaceflight-induced effects in rat pelvis and thoracic vertebrae. Thirty-six male Sprague-Dawley rats were assigned to a flight, flight control, or vivarium group (n = 12/group). Bilateral adrenalectomy was performed in six rats per group, the additional six rats undergoing sham surgery. Adrenalectomized (ADX) rats were implanted with corticosteroid pellets. On recovery from spaceflight, thoracic vertebrae and the whole pelvis were removed and processed for biochemistry, histomorphometry, or bone cell culture studies. The 17-day spaceflight resulted in decreased bone volume (BV) in the cotyle area of pelvic bones (-12%; p < 0.05) associated with approximately 50% inhibition of bone formation in the cancellous area of pelvic metaphyses and in thoracic vertebral bodies. The latter effect was associated with a decreased number of endosteal bone cells isolated from the bone surface (BS) in these samples (-42%; p < 0.05). This also was associated with a decreased number of alkaline phosphatase positive (ALP+) endosteal bone cells at 2 days and 4 days of culture, indicating decreased osteoblast precursor cell recruitment. Maintaining basal serum corticosterone levels in flight-ADX rats did not counteract the impaired bone formation in vertebral or pelvic bones. Moreover, the decreased ex vivo number of total and ALP+ endosteal bone cells induced by spaceflight occurred independent of endogenous corticosteroid hormone levels. These results indicate that the microgravity-induced inhibition of bone formation and resulting decreased trabecular bone mass in specific areas of weight-bearing skeleton in growing rats occur independently of endogenous glucocorticoid secretion.

Construction and optimization of a dog whole-genome radiation hybrid panel

A dog whole-genome radiation hybrid (WGRH) panel including 126 clones was constructed by fusing dog fibroblasts irradiated at 5000 rads with thymidine kinase-deficient hamster cells. The average retention frequency of the panel designated as RHDF5000 is 21%, and its resolution power is estimated at 600 kb. The data provided by typing 400 markers were used to estimate linkage power changes subsequent to panel reduction. These changes were analyzed by recomputing typing data from five reduced panels. From these simulations, the parameters allowing investigation of the evolution of the linkage power in the course of panel reduction were determined. Guidelines for constructing a WGRH panel are proposed.

[Biology of social phobia]

Until recently, social phobia had not been extensively investigated. Social phobia is a relatively common anxiety disorder and a number of studies reporting efficacy in treatment medication have been reported. Biological studies have used neuroendocrine, naturalistic and chemical challenges, pharmacological probes, neurotransmitter system measures, brain imaging techniques. In summary, these studies provide some neurobiological basis for separating social phobia from others anxiety disorders (specifically panic disorder) and non psychiatric healthy controls.

Expression of inducible nitric oxide synthase during rat brain inflammation: regulation by 1,25-dihydroxyvitamin D3

This study, based on in situ hybridization and immunolabeling experiments, presents the time-course and cellular distribution of inducible NO synthase (iNOS) expression in a rat model of brain inflammation. Both intrahippocampal injection of lipopolysaccharide (LPS) or of buffer (stab lesion) induce an early, transient, and restricted expression of iNOS mRNA and immunoreactivity in the rat CNS. The topographic and phenotypic characteristics of iNOS-producing cells are distinct. After stab lesion, iNOS mRNAs, expressed at 5 h mainly in cells in the interventricular junction and in a few cells in brain parenchyma, were no more detectable from 15 h onwards, whereas the protein was faintly expressed in parenchymal cells at 15 h and 24 h. In contrast, after LPS injection, iNOS-mRNAs were detected from 5 to 24 h. iNOS-immunoreactivity was highly induced and sequentially observed first in choroid plexus and ependymal cells at 5 h, in monocytes and activated/reactive microglia at 15 h and 24 h, and finally in astrocytes at 72 h. In order to investigate potential regulatory effects of 1,25-dihydroxyvitamin D3 (1,25-D3) on iNOS expression, we have delivered this hormone with LPS or buffer into the rat hippocampus. 1,25-D3 significantly inhibits iNOS expression, at both the mRNA and immunoreactive protein levels, 15 h and 24 h after LPS injection, in the cells of the monocyte lineage. Moreover, 72 h after LPS injection, the addition of 1,25-D3 leads to a 6-fold increase in the number of macrophages around the lesion site, that correlates with a decrease in the proportion of apoptotic cells. Since 1,25-D3 can be produced by activated macrophages/microglia and since NO stimulates 1,25-D3 synthesis by macrophages, our results support the hypothesis that this hormone might be synthesized endogenously during CNS inflammatory reactions, thus explaining the transient and restricted iNOS expression observed after LPS intracerebral injection.

TGF-beta2 prevents the impaired chondrocyte proliferation induced by unloading in growth plates of young rats

Growth plate width and cartilage organization are altered during skeletal unloading in growing rats. Immunohistochemical studies have identified TGF-beta in calcified cartilage, and TGF-beta is known to induce mitogenic effects on chondrocytes in vitro. On the other hand, IGF-1 was shown to be expressed in the proximal tibial growth plate and to mediate GH-induced longitudinal bone growth in rats. We therefore investigated the effect of recombinant human (rh) IGF-1 and rhTGF-beta2 infusion on the changes induced by unloading in the cellular organization of the growth plate in growing rats. Hindlimb unloading for 14 days induced a 13% reduction in growth cartilage height in the proximal tibia. This effect was mostly related to a 17% and 14% decrease in the proliferative zone height and chondrocyte number, respectively. In unloaded rats treated with a systemic infusion of rhTGF-beta2 (2microg/kg/day) the number of chondrocytes in the proliferative zone was not different from those of normal loaded animals. In contrast, rhIGF-1 treatment at a 2mg/kg/day dose was not effective in counteracting the effects of unloading on growth plate height and chondrocyte number. These results show that systemic administration of rhTGF-beta2 prevents in large part the reduced growth of chondrocytes in the proliferative zone and the reduced epiphyseal growth plate growth induced by unloading in rats.

Sequencing of the cholesteryl ester transfer protein 5' regulatory region using artificial transposons

We have isolated and sequenced genomic clones encompassing more than 5 kb of the 5' flanking region of the cholesteryl ester transfer protein gene. This region contains multiple Alu repeats, a Mermaid repeat, and an extensive GA repeat, which made sequencing exceedingly difficult. To circumvent the problems that these repeats posed to traditional sequencing methodologies, we employed a novel transposon-facilitated technique, which greatly simplified sequencing of regions that had been difficult to accomplish otherwise. We utilized the artificial transposon, AT-2, a Bluescript derivative containing the dhfr gene and unique primer sites at both ends of the insertion DNA. Integration of the transposon occurred efficiently and covered the entire region of interest. Analysis of the sequence indicates a number of potential regulatory factor binding sites upstream of the previously characterized minimal promoter. The 5.7-kb regulatory region confers significant transcriptional activation in a conditionally transformed mouse hepatocyte line as compared to a minimal 137-bp promoter fragment. In addition, a tetranucleotide repeat of variable length that may provide a useful genetic marker has been identified 2 kb upstream of the CETP transcriptional start site.

Sequence analysis of two genomic regions containing the KIT and the FMS receptor tyrosine kinase genes

The KIT and FMS tyrosine kinase receptors, which are implicated in the control of cell growth and differentiation, stem through duplications from a common ancestor. We have conducted a detailed structural analysis of the two loci containing the KIT and FMS genes. The sequence of the approximately 90-kb KIT locus reveals the position and size of the 21 introns and of the 5' regulatory region of the KIT gene. The introns and the 3'-untranslated parts of KIT and FMS have been analyzed in parallel. Comparison of the two sequences shows that, while introns of both genes have extensively diverged in size and sequence, this divergence is, at least in part, due to intron expansion through internal duplications, as suggested by the discrete extant analogies. Repetitive elements as well as exon predictions obtained using the GRAIL and GENEFINDER programs are described in detail. These programs led us to identify a novel gene, designated SMF, immediately downstream of FMS, in the opposite orientation. This finding emphasizes the gene-rich characteristic of this genomic region.

The PML and PML/RARalpha domains: from autoimmunity to molecular oncology and from retinoic acid to arsenic

Acute promyelocytic leukemia (APL) is specifically associated to a t(15; 17) translocation which fuses a gene encoding a nuclear receptor for retinoic acid, RARalpha, to a previously unknown gene PML. The PML protein is localized in the nucleus on a specific domain of unknown function (PML nuclear bodies, NB) previously detected with autoimmune sera from patients with primary biliary cirrhosis (PBC). These bodies are nuclear matrix-associated and all of their identified components (PML, Sp100, and NDP52) are sharply upregulated by interferons. We show that autoantibodies against both PML and Sp100 are usually associated in sera with multiple nuclear dot anti-nuclear antibodies and demonstrate that PML is an autoantigen, not only in PBC, but also in other autoimmune diseases. In APL, the PML/RARalpha fusion interferes with both the retinoic acid (RA) response and PML localization on nuclear bodies, but the respective contribution of each defect to leukemogenesis is unclear. RA induces the terminal differentiation of APL blasts, yielding to complete remissions, and corrects the localization of NB antigens. Arsenic trioxide (As2O3) also induces remissions in APL, seemingly through induction of apoptosis. We show that in APL, As2O3 leads to the rapid reformation of PML bodies. Thus, both agents correct the defect in NB antigen localization, stressing the role of nuclear bodies in the pathogenesis of APL.

Effects of spaceflight and recovery on rat humeri and vertebrae: histological and cell culture studies

Skeletal changes associated with spaceflight in the rat have been well documented, but few data are available on bone tissue and bone cell metabolism after subsequent on-Earth recovery. We therefore investigated the effects of microgravity and subsequent recovery on trabecular bone morphology and cellular activities in rat humeri and thoracic vertebrae and compared histomorphometric parameters in caudal vertebrae with the behavior of vertebral osteoblastic cells in culture. We report here that humeral weight showed normal growth during the experiment but was unaffected by spaceflight or recovery from spaceflight. However, the 14-day spaceflight resulted in inhibition of static indexes of bone formation in humeral proximal metaphyses and thoracic vertebral bodies. This was associated with a decrease in bone volume in humeral metaphyses. After 14 days of on-Earth recovery, osteoblastic and osteoid surfaces returned toward normal and bone volume was normalized in humeri, whereas the static bone formation parameters were not restored in thoracic vertebrae. In addition, histological indexes of bone formation and osteoblastic cell growth in vitro were not affected by spaceflight in caudal vertebrae. This study shows that rat humeri and thoracic and caudal vertebrae exhibit different patterns of response to spaceflight and subsequent on-Earth recovery, which could be due, at least in part, to the different loading pattern of these bones, and also to differences in bone turnover rate.

Hypervariable microsatellites provide a general source of polymorphic DNA markers for the chloroplast genome

BACKGROUND

The study of plant populations is greatly facilitated by the deployment of chloroplast DNA markers. Asymmetric inheritance, lower effective population sizes and perceived lower mutation rates indicate that the chloroplast genome may have different patterns of genetic diversity compared to nuclear genomes. Convenient assays that would allow intraspecific chloroplast variability to be detected are required.

RESULTS

Eukaryote nuclear genomes contain ubiquitous simple sequence repeat (microsatellite) loci that are highly polymorphic in length; these polymorphisms can be rapidly typed by the polymerase chain reaction (PCR). Using primers flanking simple mononucleotide repeat motifs in the chloroplast DNA of annual and perennial soybean species, we demonstrate that microsatellites in the chloroplast genome also exhibit length variation, and that this polymorphism is due to changes in the repeat region. Furthermore, we have observed a nonrandom geographic distribution of variations at these loci, and have examined the number and location of such repeats within the chloroplast genomes of other species.

CONCLUSIONS

PCR-based analysis of mononucleotide repeats may be used to detect both intraspecific and interspecific variability in the chloroplast genomes of seed plants. The analysis of polymorphic microsatellites thus provides an important experimental tool to examine a range of issues in plant genetics.