Seasonal variations of semen quality in male goats: Study of sperm abnormalities

The type, frequency and seasonal variation of sperm abnormalities in male goats inhabiting in Mediterranean region were evaluated. Semen was collected twice a week with an artificial vagina from 9 10-month-old Murciano-Granadina male goats weighing 41 to 48 kg. Distal cytoplasmic droplets and acrosomal damage were the predominant abnormalities. Increase in age (10 to 27 months) did not reveal itself as a main effect on the occurrence of sperm abnormalities. All types of sperm abnormalities studied showed significant (P<0.01) seasonal variation. The poorest quality semen was collected during winter and spring. In spite of a seasonal variation in sperm quality, semen of Murciano-Granadina goats in the Mediterranean area is good all year long, since the proportion of abnormal spermatozoa was well within the accepted range for normal fertility.

[Ruptured aneurysm of the aortic sinus of Valsalva: clinical course, diagnosis, and treatment]

The authors present the clinical cases of 5 patients, with rupture of the aortic Valsalva's sinus aneurysm open to the right chambers, diagnosed clinically, echocardiographically and hemodynamically in the past eight months. Among them, four were males, and one female. Three were treated surgically successfully, one patient refused surgery and another had a sudden death before surgery. The patients showed arteriovenous blood flow shunt, three from the aorta to the right ventricle, and two to the right atrium. One case was associated to an atrial septal defect, and tricuspid insufficiency in another. The authors added a sixth case: a woman, with rupture of the aortic Valsalva's sinus open to the right ventricle, aortic insufficiency and diaphragmatic subaortic stenosis. The authors discuss the embryologic origin of the formation and rupture of the Valsalva's sinus aneurysm as well as the factors that contribute to it's rupture, the natural history of the illness, it's classification, association with other heart disease as well as diagnosis and treatment.

abaA, a new pleiotropic regulatory locus for antibiotic production in Streptomyces coelicolor

Production of the blue-pigmented antibiotic actinorhodin is greatly enhanced in Streptomyces lividans and Streptomyces coelicolor by transformation with a 2.7-kb DNA fragment from the S. coelicolor chromosome cloned on a multicopy plasmid. Southern analysis, restriction map comparisons, and map locations of the cloned genes revealed that these genes were different from other known S. coelicolor genes concerned with actinorhodin biosynthesis or its pleiotropic regulation. Computer analysis of the DNA sequence showed five putative open reading frames (ORFs), which were named ORFA, ORFB, and ORFC (transcribed in one direction) and ORFD and ORFE (transcribed in the opposite direction). Subcloning experiments revealed that ORFB together with 137 bp downstream of it is responsible for antibiotic overproduction in S. lividans. Insertion of a phi C31 prophage into ORFB by homologous recombination gave rise to a mutant phenotype in which the production of actinorhodin, undecylprodigiosin, and the calcium-dependent antibiotic (but not methylenomycin) was reduced or abolished. The nonproducing mutants were not affected in the timing or vigor or sporulation. A possible involvement of ORFA in antibiotic production in S. coelicolor is not excluded. abaA constitutes a new locus which, like the afs and abs genes previously described, pleiotropically regulates antibiotic production. DNA sequences that hybridize with the cloned DNA are present in several different Streptomyces species.

Changes in polyamine levels in rat brain after systemic kainic acid administration: relationship to convulsant activity and brain damage

We have examined the effects of systemic kainic acid (KA) administration (9 mg/kg, i.p.) on rat behavior, brain damage, and polyamine levels and the action of the specific ornithine decarboxylase inhibitor alpha-difluoromethylornithine (DFMO) on these effects. KA elicited convulsant activity in 63% of the animals. In the acute convulsant phase (1-3 h after KA), a rapid decline (-39% at 3 h) of spermidine content in frontal cortex was found. After the acute convulsant phase, levels of hippocampal spermidine and spermine were reduced (-70 and -66%, respectively, at 8 h). A dramatic increase of putrescine content (68.1, 1,382, and 336% at 8 h, 24 h, and 9 days, respectively, after KA) was found, associated with histological signs of cortical brain damage (ischemia and necrosis). There was a close relationship between the concentration of putrescine and signs of delayed toxicity (body weight losses) 24 h and 9 days after KA. DFMO partially antagonized the convulsant activity and reduced the increased putrescine levels to approximately 50% of values in KA-treated animals at 24 h but did not change the pattern of histological damage. The role of polyamines in the early and late phases of KA-induced neurotoxicity is discussed.

Construction and properties of a family of pACYC184-derived cloning vectors compatible with pBR322 and its derivatives

A family of cloning vectors derived from plasmid pACYC184 and, therefore, compatible with pBR322 and its derivatives (especially the pUC family of vectors), is described. They all contain a multiple cloning site (MCS) and the lacZ alpha reporter gene for easy cloning. They have been grouped in three sets: (i) six of the vectors contain a chloramphenicol-resistance (CmR)-encoding gene and each a different MCS with 16 unique restriction sites overall; (ii) another six vectors contain a kanamycin-resistance (KmR)-encoding gene and the same six MCS; and (iii) two CmR vectors that contain the SP6 and T7 promoters flanking the MCS and lacZ alpha reporter gene of pUC18/19.

Differential response of rat brain polyamines to convulsant agents

The polyamines putrescine (PUT), spermidine (SD) and spermine (SM) have been studied in rat brain after treatment with several convulsant agents. Kainic acid (10 mg/kg), picrotoxinin (1.5 mg/kg), pentylenetetrazol (60 mg/kg) and lindane (gamma-hexachlorocyclohexane) (60 mg/kg) were given to male Wistar rats. Twenty-four hours later, the animals were sacrificed and their brains removed. Cortical polyamines were analyzed by HPLC with fluorimetric detection of their respective dansyl derivatives, using 1,6-diaminohexane as internal standard for the measurements. Polyamine levels are not affected by short periods of time (30 min) of brain exposure to room temperature before freezing the samples, as compared to a quick procedure (less than 40 s from animal death). Kainic acid induced a 14-fold increase of cortical PUT with respect to control values, leaving unchanged the other polyamines. Lindane also increased cortical PUT (4-fold) without affecting SM or SD. Neither picrotoxinin, nor pentylenetetrazol groups were different from controls for any of the polyamines assayed. The results are discussed in relation to the possible mechanism of action of these convulsant agents and the role of the polyamines in cell injury.

Non-specific inhibition of imipramine binding argues against an endogenous ligand

We have attempted to characterize the product(s) inhibiting [3H]imipramine binding from rat cortical membranes. Fractions inhibiting [3H]imipramine binding were analysed by gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography-mass spectrometry (HPLC-MS). Tissue extracts showed marked inhibitory activity (two different peaks); however, extracts containing no brain tissue (blanks) also exhibited inhibitory activity (one peak after HPLC pre-purification). The chemical composition of the compound that inhibited [3H]imipramine binding was identical in both cases (tissue and blank extracts) and consisted of zinc chelates, probably formed by the use of zinc sulfate during the extraction procedure. The second inhibitory peak in the tissue extracts was 5-hydroxytryptamine (serotonin, 5-HT). These results suggest that the inhibitory activity on [3H]imipramine binding attributed to a low-molecular weight putative endacoid is non-specific and due to ions introduced in the sample during purification.

Relationship between serotoninergic measures in blood and cerebrospinal fluid simultaneously obtained in humans

The relationships between the concentration of serotonin (5-HT) and related metabolites in human blood and CSF have been studied. Plasma tryptophan (TP), 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), and indoleacetic acid (IAA), whole-blood 5-HT, and CSF TP, 5-HT, 5-HIAA, IAA, homovanillic acid, and 3-methoxy-4-hydroxyphenylethylene glycol were determined in 35 unmedicated outpatients who underwent minor surgical operations and had no history of psychiatric or neurological illnesses. Significant correlations were found between the serotoninergic parameters analyzed in blood and CSF. Plasma free 5-HT correlated significantly with CSF 5-HT (r = 0.411, p less than 0.02), and plasma 5-HIAA correlated with the CSF 5-HIAA/5-HT ratio (r = 0.508, p less than 0.004). The concentration of 5-HIAA in CSF correlated with the plasma 5-HIAA/5-HT ratio (r = 0.405, p less than 0.026) (which can be taken as an index of monoamine oxidase type A activity in peripheral tissues) and with the platelet 5-HT/plasma 5-HT ratio (r = 0.375, p less than 0.05). The concentrations of IAA in CSF and plasma were strongly correlated (r = 0.899, p less than 0.001). The significance of these results and their relationship to the use of "in vivo" measures of 5-HT and related metabolites in plasma and platelets as an index of serotoninergic function in affective disorders are discussed.

Rapid non-enzymatic HPLC determination of total MHPG in human plasma

We have previously reported a method for the determination of total 3-methoxy-4-hydroxy phenylethylene glycol (MHPG) in brain, based on a simple acid-catalyzed hydrolysis. Now we extend this procedure to the determination of plasma total MHPG. The method involves the deproteinization of plasma with perchloric acid, followed by 3 minutes of an acid-catalyzed step. The hydrolysates are injected into the HPLC system, using a formic acid/methanol eluent with fluorimetric detection. Sample detection limit is below 1 ng MHPG/mL of plasma. This procedure has been used for the determination of plasma total MHPG from 109 healthy individuals of both sexes. Mean value was: 5.4 + 2.3 ng total MHPG/mL of plasma (means +/- S.D., N = 109). No sex differences were observed, and a slight correlation with age (r = 0.24, p less than 0.02) has been found. Plasma-free MHPG was also determined in a subgroup of 15 randomly chosen individuals (3.0 +/- 1.2 ng free MHPG/mL plasma, means +/- S.D.). A significant correlation was obtained with plasma total MHPG (r = 0.77, p less than 0.001, N = 15). The main advantage of the present method lays in its simplicity, since no enzymatic hydrolysis or extraction procedures are needed, being its reliability fully proven through 109 plasma total MHPG determinations.

[Neoplasm of the rhinopharynx: our experience]

We present 87 patients with cancer of the nasopharynx treated in the Fundación "Jiménez Díaz" de Madrid, in the last fifteen years. The clinical aspects of the illness, the therapeutic techniques and the results are analyzed. The global survival and the disease free survival at 5 years were 34 and 22% respectively. Survival in patients with squamous cell carcinoma was somewhat better. Distant metastases was presented in 30% of patients. At present 16 patients are alive and free of disease.

Seasonal changes of plasma serotonin and related parameters: correlation with environmental measures

Seasonal changes of several serotonin-related measures in plasma and whole blood of healthy individuals were determined every 4 weeks. Plasma serotonin (5-HT) shows very marked changes throughout the year, with maximum values during the summer and lowest values in the fall, whereas its metabolite 5-hydroxyindoleacetic acid (5-HIAA) follows a somewhat contrary pattern. The sum of 5-HT plus 5-HIAA in plasma thus does not change significantly during the year and follows the evolution of total plasma tryptophan (TP). The difference of 5-HIAA minus 5-HT in plasma, which is indicative of the efficacy of degradative processes of 5-HT in the periphery, is strongly dependent on the season and suggests a higher degradation of 5-HT during fall-winter. Unlike plasma TP and whole blood 5-HT, significant correlations among plasma 5-HT, 5-HIAA, and the ambient temperature were found. The possible significance and relationship of these findings to the seasonality of major depression is discussed.

[Bone marrow autotransplant: preliminary results in 20 patients with acute leukemia]

The results of bone marrow autograft (BMAG) in 20 patients with acute leukemia (AL) consecutively treated from October 1985 and May 1988 are reported. The follow up was continued until November 1988. The mean age of the patients was 20 years (range 10-48) and their diagnoses were acute myeloblastic leukemia (AML) in 12 and acute lymphoblastic leukemia (ALL) in 8. The preparation for BMAG included cyclophosphamide and whole body radiation in all cases. The procedure was carried out in the first complete remission (CR-1) in 5 patients, in CR-2 in 11, in CR-3 in 2, and in CR-4 in another 2. Two patients died as a direct consequence of BMAG, 11 relapsed and 7 are alive and free from relapse. The likelihood of survival free from prolonged illness was calculated as 24% for the whole series, 60% for the cases of BMAG in CR-1 and 50% for the group of patients with AML. The results were poor in the cases of BMAG carried out for AL in an advanced stage. On the basis of these results the experience of other authors with this therapeutic modality is reviewed, and its current indications are discussed.

[Simultaneous bilateral testicular tumors]

Simultaneous bilateral testicular neoplasia is exceptional and its diagnosis in stage I is of extraordinary interest, especially when they are not marker producers. Echography has currently become the simplest, most effective and economic method of presumptive diagnosis of testicular tumours and the most important for detecting bilaterality when one of them may be present subclinically.

[Epidemiologic monitoring and decentralized planification: the use of sentinel sites in Guerrero]

With the current decentralization of health care in the Mexican state of Guerrero, there is need for detailed but inexpensive information for the planning of health services. A cyclical process of measurement is proposed using sentinel sites, characterized as places of concentration of measurement resources, which are not special intervention areas or health facilities. The sites in Guerrero were selected to be representative of the health conditions in the state. During the first two years, study cycles were carried out regarding acute respiratory infections and diarrhoeas in infants, the risk factors associated with these afflictions and the attention paid to them within the community. Later cycles focussed on the importance of scorpion stings and Chagas' disease, the impact of measles vaccination and the prevalence of tuberculosis. Three types of community-based data are considered in each cycle, to optimize their use in planning (impact, coverage and costs) which, in summary formats, facilitate rapid analysis and presentation.

[Our experience in the treatment of superficial cancer of the bladder with BCG]

We report on our experience with 21 patients with superficial bladder cancer who were treated with intravesical BCG instillation. The BCG vaccine was effective in the treatment of carcinoma in situ. Tumor regression was achieved in 83.3% at 3 months, and 61.1% at 24 months. It is advisable to follow patients closely because of the possibility of tumor progression.

Increased plasma free serotonin but unchanged platelet serotonin in bipolar patients treated chronically with lithium

The effect of lithium salts administered chronically to bipolar patients on peripheral measures of the serotoninergic system has been studied. Plasma free serotonin (5HT), whole blood 5HT, plasma 5-hydroxyindoleacetic acid (5HIAA) and plasma total tryptophan (TP) have been analyzed in 22 patients treated with lithium carbonate (mean daily dose: 1280 mg, mean serum concentration: 0.73 mmol/l) and compared to 14 healthy controls and 11 patients treated chronically with antipsychotic drugs. Lithium salts induced significant increases in plasma free 5HT (+159% with respect to control values) and in plasma 5HIAA (+39%) without affecting 5HT contained in platelets. Plasma TP was also unchanged by chronic lithium treatment. The ratio between 5HT stored in platelets and 5HT free in plasma, a variable reduced after uptake inhibitors like clomipramine, was decreased in lithium-treated patients (-50%). These results are compatible with an enhanced synthesis of 5HT in the periphery (mainly enterochromaffin cells) as well as with an inhibition of platelet 5HT uptake (or increased 5HT efflux from intracellular stores) induced by lithium. The lack of effect of several antipsychotic drugs upon these variables is consistent with their predominant effect on the dopaminergic system and reinforces the specificity of the effect observed with lithium salts. Taken together, these results support the usefulness of using this "in vivo" 5HT peripheral model for the study of the actions elicited by drugs acting on the presynaptic components of the 5HT system.

Organochlorine pesticides by negative ion chemical ionization. Brain metabolites of lindane

A gas chromatographic/mass spectrometric technique for the analysis of organochlorine compounds using negative ion chemical ionization is presented. Detection limits for some compounds (penta- and hexachlorobenzene and p,p'-DDE) are of the order of 60-120 fg injected, while others (lindane, aldrin, etc.) are in the low picogram range (1.0 pg for lindane). The extreme selectivity for chlorine-containing compounds enables the direct analysis of homogenates of biological samples without any extraction or purification step. Metabolic studies can thus be remarkably simplified. Results are presented on the application of this technique to the analysis of lindane metabolites found in rat brain after treatment with this pesticide.

The effect of non-convulsant doses of lindane on temperature and body weight

The effect of lindane (gamma-HCH) on temperature, food intake and body weight was studied in male and female rats after single or repeated non-convulsant oral doses. A single dose of 30 mg/kg induced a significant decrease of core temperature (0.4 degrees C in males and 0.66 degrees C in females) 5 h after administration when compared to the control value. Lindane-induced hypothermia was strongly potentiated (1.45 degrees C) by cold stress when rats were kept at 4 degrees C. The same dose of lindane produced a significant decrease in body weight gain (-85% in males and -219% in females compared to the control gain), accompanied by a diminution of food intake, 24 h after administration. No decrease in both parameters was observed when alpha- or delta-HCH isomers 30 mg/kg were tested. After daily administration with 10 mg/kg lindane for 7 days, no hypothermic effects were observed. However, a slight but significant decrease in body weight gain was recorded over the treatment period. This effect was also accompanied by a reduced food intake. The observed stereoselective effects of HCH isomers on core temperature and body weight could be a useful model to study the mechanisms of lindane neurotoxicity at low subconvulsant doses.

Cerebral glucose uptake in lindane-treated rats

The pesticide and ectoparasiticide lindane, gamma-isomer of hexachlorocyclohexane, is a powerful CNS-stimulant inducing convulsions and other signs of hyperexcitability in mammals. The present work was carried out to investigate the effect of lindane on brain regional glucose uptake at convulsant and non-convulsant doses. Local glucose uptake was measured in male Wistar rats using a modification of the 2-deoxyglucose (2-DG) method. Animals received i.p. [3H]2-DG and the amount of label in different brain structures of control and lindane-treated animals was assayed by a liquid scintillation counting of 18 dissected regions. Lindane at single convulsant dose (150 mg/kg, p.o.) increased 2-DG uptake in olfactory tubercules, hypothalamus, hippocampus, parafloculi and hypophysis. The uptake was decreased in parietal cortex, thalamus and pons-medulla. The pattern of 2-DG uptake after a single non-convulsant dose of 30 mg/kg p.o. was not so modified. After 1 week of treatment with 10 mg/kg per day p.o., increased 2-DG uptake was observed in superior colliculi while it was decreased in parietal cortex. The increase of 2-DG uptake in limbic regions observed at the convulsive dose agrees with the experimental association between poisoning signs induced by lindane and damage in the limbic system.

Synthesis and utilization of neurotransmitters: actions of subconvulsant doses of hexachlorocyclohexane isomers on brain monoamines

We have developed a model for the treatment of data of concentration of brain neurotransmitters (particularly serotonin and the catecholamines), in which the changes induced by any given treatment on the neurotransmitter (NT) and its main metabolite (ME) are converted into 2 new parameters named S and U, that are related to the modifications in the synthesis (S) and utilization (U) of the neurotransmitter elicited by the treatment. Using this model we have studied the effect of subconvulsant doses of lindane and other hexachlorocyclohexane isomers (alpha, beta and delta) on brain monoaminergic systems. The results obtained indicate that serotonergic activity is increased in cell bodies (dorsal raphe) as well as in regions rich in nerve terminals after treatment with lindane. Also, the activity of dopaminergic neurons is increased in the substantia nigra. These results are in agreement with the proposed role of lindane as a "picrotoxinin-like" substance acting as an antagonist at the GABA-A receptor complex and thus impairing the inhibitory tone exerted by GABA on a variety of neurons (serotonin in raphe nuclei and dopamine in substantia nigra).

Brain metabolites of lindane and related isomers: identification by negative ion mass spectrometry

The application of a new method of gas chromatography-mass spectrometry (GC-MS) to the study of some aspects of the metabolism of hexachlorocyclohexanes is presented. Instead of the classical mode of ionization (Electron Impact, EI), this method uses chemical ionization, recording only the negative ions produced. This enables a tremendous enhancement of the signal when chlorinated compounds elute from the chromatographic column. The mass spectra obtained consist generally in the ions corresponding to the molecular weight of the compound analyzed. The sensitivity of the method is higher than any other GC method described: the limit of detection of several organochlorine compounds can be as low as 60 femtograms. Using this method we have been able to identify several Lindane metabolites (tetra-, penta- and hexachlorocyclohexenes, tetra- and pentachlorobenzene) in rat brain homogenates without any purification step. Using this method, a quantitative study of the main metabolites found in brain after treatment with 4 different HCH isomers has been performed. This study reveals that the HCH isomers are cleared from the brain via different metabolic pathways, with a rate of production of metabolites which is inversely correlated to their half lives in brain.

Regional distribution of lindane in rat brain

Lindane distribution in brain areas after oral (30 mg/kg) and i.v.(0.3 mg/kg) administration was studied using autoradiography-imaging analysis and dissection-liquid scintillation counting techniques. Both experimental approaches gave similar results. An heterogeneous distribution of lindane-label in brain regions was observed. Radiolabel concentration in white matter was higher than in grey matter and the concentration ratio was time increasing. Higher concentrations of lindane-label were found in thalamus, mid-brain and pons-medulla at different times after administration when compared to the whole brain mean value. Pretreatment with 300 mg/kg of the alpha-HCH isomer did not induce significant modification in the pattern of lindane radioactivity distribution in brain. Lindane affinity for white matter and myelinated structures could be related to its lipophilic behaviour and is not in disagreement with the current proposed mechanism of action for this xenobiotic.

Genomic instability in Rhizobium phaseoli

Experience from different laboratories indicates that Rhizobium strains can generate variability in regard to some phenotypic characteristics such as colony morphology or symbiotic properties. On the other hand, several reports suggest that under certain stress conditions or genetic manipulations Rhizobium cells can present genomic rearrangements. In search of frequent genomic rearrangements, we analyzed three Rhizobium strains under laboratory conditions that are not considered to cause stress in bacterial populations. DNAs from direct descendants of a single cell were analyzed in regard to the hybridization patterns obtained, using as probes different recombinant plasmids or cosmids; while most of the probes utilized did not show differences in the hybridization patterns, some of them revealed the occurrence of frequent genomic rearrangements. The implications and possible biological significance of these observations are discussed.

Hormone release by primary amniotic fluid cell cultures

Amniotic fluid cells have been widely used in prenatal diagnosis; however, there is great heterogeneity of the cells and their origin. In this study we analyze the karyotype and release of human chorionic gonadotropin (hCG), human chorionic somatomammotropin (hCS), free estriol (E 3), prolactin (PRL) and progesterone (P) of amniotic fluid cells from primary cultures of six normal and two anencephalic fetuses. In all the amniotic fluid samples there was release of hCG; in one amniotic fluid, in which several tetraploid colonies were found. PRL and P were also released. The heterogeneity of amniotic fluid cell morphology and their hormone release in culture was confirmed. The presence of hormones like hCG supports the trophoblastic origin of some amniotic fluid cells from normal and anencephalic fetuses. Other hormones, such as PRL and P could be used in the differential diagnosis between the karyotype of fetal membranes and the true fetal karyotype. Amniotic fluid cell cultures used in prenatal diagnosis yielded second trimester placental cells without any elaborate methods that could be used as cell models for hormone studies.

Percutaneous transuretero-ureterostomy in situ

Endourological techniques allow one to postpone a second, planned intervention--urinary diversion to the intestine--in radical cystectomies with a high surgical risk. PTU consists in introducing one nephrostomy tube percutaneously through one kidney and replacing it by the definitive drainage tube during the surgical procedure after suturing both ureters together.

Decreased plasma serotonin in melancholic patients: a study with clomipramine

Eighteen unmedicated patients suffering from major depressive disorder with melancholia (DSM-III) were examined for abnormalities in peripheral serotonin (5-HT) and related metabolites. Serotonin in platelet-free plasma and in platelets from melancholics was significantly reduced to 30% and 60% of their respective control values. Plasma 5-hydroxyindoleacetic acid was also found to be reduced, but not significantly. Other plasma compounds related to 5-HT (indoleacetic acid, total tryptophan, and free tryptophan) were found to be unchanged in these patients. Of all variables, only platelet 5-HT was affected while patients were on clomipramine (CIM) treatment. After 2 weeks on CIM (100-150 mg/day, orally), platelet 5-HT was reduced to 8% of pretreatment values, but plasma 5-HT did not change and continued to be reduced upon clinical recovery. The existence of a distinct pool of plasma 5-HT that is clearly independent of the platelet pool is indicated by the differences observed in plasma and platelet 5-HT during CIM treatment, as well as by previous data from this laboratory. The very marked decrease in plasma 5-HT levels may be in accord with the central nervous system changes reported in depression and suggests the possibility of using plasma 5-HT as a peripheral indicator of abnormal serotonin function in melancholia.

Reiterated DNA sequences in Rhizobium and Agrobacterium spp

Repeated DNA sequences are a general characteristic of eucaryotic genomes. Although several examples of DNA reiteration have been found in procaryotic organisms, only in the case of the archaebacteria Halobacterium halobium and Halobacterium volcanii [C. Sapienza and W. F. Doolittle, Nature (London) 295:384-389, 1982], has DNA reiteration been reported as a common genomic feature. The genomes of two Rhizobium phaseoli strains, one Rhizobium meliloti strain, and one Agrobacterium tumefaciens strain were analyzed for the presence of repetitive DNA. Rhizobium and Agrobacterium spp. are closely related soil bacteria that interact with plants and that belong to the taxonomical family Rhizobiaceae. Rhizobium species establish a nitrogen-fixing symbiosis in the roots of legumes, whereas Agrobacterium species is a pathogen in different plants. The four strains revealed a large number of repeated DNA sequences. The family size was usually small, from 2 to 5 elements, but some presented more than 10 elements. Rhizobium and Agrobacterium spp. contain large plasmids in addition to the chromosomes. Analysis of the two Rhizobium strains indicated that DNA reiteration is not confined to the chromosome or to some plasmids but is a property of the whole genome.

Nitrogen-fixing nodules induced by Agrobacterium tumefaciens harboring Rhizobium phaseoli plasmids

Rhizobium phaseoli CFN299 forms nitrogen-fixing nodules in Phaseolus vulgaris (bean) and in Leucaena esculenta. It has three plasmids of 185, 225, and 410 kilobases. The 410-kilobase plasmid contains the nitrogenase structural genes. We have transferred these plasmids to the plasmid-free strain Agrobacterium tumefaciens GMI9023. Transconjugants containing different combinations of the R. phaseoli plasmids were obtained, and they were exhaustively purified before nodulation was assayed. Only transconjugants harboring the 410-kilobase plasmid nodulate P. vulgaris and L. esculenta. Nodules formed by all such transconjugants are able to reduce acetylene. Transconjugants containing the whole set of plasmids from CFN299 nodulate better and fix more nitrogen than the transconjugants carrying only the Sym plasmid. Microscopic analysis of nodules induced by A. tumefaciens transconjugants reveals infected cells and vascular bundles. None of the A. tumefaciens transconjugants, not even the one with the whole set of plasmids from CFN299, behaves in symbiosis like the original R. phaseoli strain; the transconjugants produce fewer nodules and have lower acetylene reduction (25% as compared to the original R. phaseoli strain) and more amyloplasts per nodule. More than 2,000 bacterial isolates from nodules of P. vulgaris and L. esculenta formed by the transconjugants were analyzed by different criteria. Not a single rhizobium could be detected. Our results show that R. phaseoli plasmids may be expressed in the A. tumefaciens background and direct the formation of effective, differentiated nodules.