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PubMed1993

[Physiopathology of the autonomous thyroid nodule].

"Autonomous" thyroid nodule is a localized nodular lesion of the thyroid gland characterized by growth, iodine uptake and function, all independent from TSH control. These nodules represent a heterogeneous anatomic and clinical entity. The clinical diagnosis is based upon a negative suppression of nodule iodine uptake and scan imaging by T3 administration. The nodule function is determined by high serum thyroid hormone levels and/or low TSH (measured by ultrasensitive assay). Etiology and pathogenesis of these nodules is not yet completely clarified. Both genetic and environmental factors determine nodule growth and function: thyroid cells, in fact, are genetically heterogeneous and may have intrinsic (congenital) characteristics that may promote the growth of cellular clones having mitotic and functional activity that is partially independent of TSH. In these particular cell clones, environmental factors like iodine deficiency or other goitrogens may favour the growth of autonomous nodules and also, by activating their function, may induce toxicity. The autonomous thyroid nodules need to be treated only when they become toxic: in this case both surgical excision or radioiodine may be used.

Humans↗

PubMed1993

Incidence and types of non-palpable thyroid nodules in thyroids removed for palpable disease.

The purpose of this study was to determine the number, size and types of non-palpable and ultrasound undetected thyroid nodules in thyroid glands removed for a single palpable nodule. Twenty patients undergoing partial (hemi- and subtotal) thyroidectomy and 40 patients having a total thyroidectomy were analyzed. Patients had no more than one palpable nodule, no cervical adenopathy and no history of previous thyroid surgery. An ultrasound was performed routinely within four months of surgery. Forty-six nodules were detected by final pathology in the partial thyroidectomy group but only 42% were detected by palpation and 59% by ultrasound. The median diameter of non-palpable and ultrasound undetected partial thyroidectomy nodules was 0.5 cm and all were benign except for one case of lymphoma. Pathology detected 186 nodules in the total thyroidectomy group although palpation only detected 22% of these and ultrasound 42%. The median diameters of the benign and malignant non-palpable nodules were 0.4 cm and 0.25 cm respectively. Most of the undetected nodules in the total thyroidectomy group were benign but there were 20 non-palpable and 18 ultrasound undetected papillary carcinomas.

Adolescent↗

PubMed1996

[Cytological diagnosis of thyroid nodules. Comparison of results obtained with guided echography with those from of a "blind" biopsy].

The goal of the study was to verify if echographic fine needle biopsy (US-FNB) improved the diagnostic accuracy of thyroid nodules with respect to a "blind" technique (B-FNB). The study group involved 6,693 patients who underwent aspiration biopsies (989 males and 5,704 females; mean age 46.3 +/- 13.7; range 5-88 years). Total biopsies were 7,952 as some patients underwent two or more biopsies in different nodules. 7,324 nodules with B-FNB and 628 nodules with US-FNB were studied; in this latter cases 136 nodules were not palpable. The diagnosis of malignancy was higher in US- FNB than B-FNB. However, non-diagnostic samples were more prevalent in US-FNB with respect to B-FNB. A histological diagnosis was available in 27 patients with US-FNB and 379 with B-FNB. In US-FNB, accuracy was 81.8%, sensitivity 86.6% and specificity 77.7%. In B-FNB, accuracy was 80.6%, sensitivity 85.1% and specificity 78.1%. These data show that US-FNB diagnostic accuracy was not better than B-FNB. The higher incidence of malignancy found in US-FNB was not dependent on better accuracy, sensitivity or specificity of the US-FNB technique with respect to the B-FNB examination. It is possible that the higher number of malignancies in patients studied with US-FNB was due to the fact that the US-FNB technique aspirated smaller nodules and particular areas of echographic suspicion, thus increasing the possibility of finding a malignancy. Based on our data, we feel that US-FNB results in a greater number of diagnostically inadequate samples. This may depend in part on the smaller size of the biopsied nodules (which are relatively more vascular than larger nodules) and in part on the greater difficulty in carrying-out this technique which directed towards particular echographic areas of suspicion resulting in greater biopsy blood contamination. The authors feel that US-FNB should be carried-out in all cases of non-palpable nodes found incidentally so as to rule out malignancy.

Adolescent↗

PubMed1997

Effectiveness of the thyroid scan in evaluation of the solitary thyroid nodule.

Solitary, palpable thyroid nodules are common, but only a small percentage are malignant. It is important to evaluate these nodules in a cost-efficient manner that avoids missing a cancer. Historically, radioisotope imaging has played a major role in the workup of thyroid nodules; however, with the advent of fine needle aspiration biopsy (FNAB), this role has become less clear. From 1974 to 1994, 770 patients with a solitary nodule underwent thyroidectomy. Preoperatively, 471 had thyroid scans, and 149 had FNAB. The incidence of carcinoma in nodules excised on the basis of thyroid scan was 23 per cent, whereas the incidence of carcinoma was 37 per cent when FNAB was used (P = 0.003). Fine needle aspiration was a significantly better predictor of malignancy than thyroid scan and resulted in a smaller proportion of excisions for benign nodules. Thyroid scan provided little additional information in those patients who underwent FNAB. Because thyroid scans add little in determining which nodules require surgical excision, they should no longer be a routine part of the evaluation of a solitary thyroid nodule.

Adolescent↗

PubMed1997

[Thyroid nodules: assay of serum thyrotropin and cytopuncture versus scintigraphy as first-line tests. Prospective study with 150 cases].

OBJECTIVE: Fine-needle aspiration (FNA) is now considered as the first-line investigation for the diagnosis of thyroid nodules. We searched for a more accurate and cost-effective methodology as this technique fails to recognized hot nodules, frequent in certain countries. PATIENTS AND METHODS: A prospective study was conducted in 150 patients to compare two diagnostic procedures: scintigraphy first combined with FNA in case of cold nodules versus TSH measurement plus FNA when TSH measurement plus FNA when TSH was not depressed. The results were subjected to cost/benefit analysis. RESULTS: Cystic nodules were found in 28 cases (including 3 hyperfunctionning nodules, with 5 suspicious smears (1 carcinoma). FNA was non-diagnostic in 26 patients; 12 were operated on (1 carcinoma), 14 had further FNA (5 suspicious, 9 benign). Altogether 56 nodules were removed, for toxic adenoma (n = 5), for suspicious (n = 21) or malignant (n = 12) smear, or on personal (n = 18) demand; 16 carcinomas were found (2 medullary, 13 capillary, 1 follicular carcinomas). With scintigraphy first, the cost was 787 French francs (FF) per patient. With TSH measurement and FNA, the cost was 554 FF per patient. In both cases, the same number of carcinomas were removed, and all the hot nodules (11 including 5 toxic adenomas) were detected. CONCLUSION: Serum TSH measurement, with scintigraphy if TSH is low, and FNA in all the other cases, is accurate and more cost-effective than scintigraphy as a first-line investigation for the diagnosis of thyroid nodule.

Biopsy, Needle↗

PubMed1997

[Hormonal suppressive therapy of thyroid nodules].

We studied 426 patients in order to analyse the effectiveness of levothyroxine in treating patients with cold thyroid nodules. Nodule volume ranged initially from 0.1 to 10 mL and was measured over a 3 to 18 month-period of treatment using ultrasonography. Nodule variation was studied in each case according to levels of TSH and others factors (age, sex, familial thyroid history, initial volume of nodule and of thyroid gland, date of diagnosis, ultrasonic findings, duration of treatment). Nodule volume increased in 32.6% and significantly decreased (> 50%) in 35.8%. In 2.8% the nodule disappeared. No correlation was found between variation of thyroid nodules and TSH levels under treatment. Similarly no relationship was found between volume variation and other criteria. These results suggest that TSH suppressing doses of levothyroxine are of no advantage in reducing the volume of cold thyroid nodules compared to lower doses.

Adolescent↗

PubMed1998

[Prevalence of thyroid cancer in hot nodules].

The prevalence of thyroid cancer is not nodules is low, as it is estimated to be between 0 and 4% in adults. In order to more accurately estimate this prevalence and to recommend optimal treatment, 93 hot nodules operated between 1976 and 1995 were reviewed. 52 of these subjects (56%) were euthyroid, 11 (12%) suffered from clinical hyperthyroidism and 30 (32%) a presented subclinical hyperthyroidism. All patients were operated for a hot nodule, 1.5 to 6 cm in diameter. Two groups of patients were considered on the basis on the histological examination. Group I consisted of 47 patients (39 F, 8 M, mean age: 44 years +/- 15) with multinodular goitre; 16 (34%) of them underwent total thyroidectomy. Group II was composed of 46 patients (38 F, 8 M, mean age: 44 years +/- 15) with a solitary hot nodule; 39 (85%) patients underwent unilateral lobectomy. Microscopic carcinoma (diameter less tha 1 cm) ws discovered in 2(4%) patients of group 1 and 5 (11%) patients of group 11, corresponding to a total prevalence of 7/93 (7.5%). The microscopic carcinoma was located in the nodule or in the capsule in four cases, and away from the nodule but in the ipsilateral lobe in three cases. In every case, this was an incidental finding and no clinical features distinguished patients with or without microscopic carcinoma. This study suggests that the probability of discovering a microscopic carcinoma associated with a hot nodule is considerable. However, microscopic carcinoma is an incidental discovery in a number of subjects undergoing thyroidectomy and is present in 10 to 20% of autopsied thyroids. As surgical treatment is devoid of risks, it appears indicated, particularly when the nodule exceeds 3 cm in diameter.

Adolescent↗

PubMed2005

Eicosanoids mediate the laminarin-induced nodulation response in larvae of the flesh fly, Neobellieria bullata.

Insects have a highly developed innate immune system, including humoral and cellular components. The cellular immune responses refer to hemocyte-mediated processes such as phagocytosis, nodulation, and encapsulation. Nodulation is considered the predominant defense reaction to infection in insects. Treating third instar larvae of the grey flesh fly, Neobellieria bullata, with laminarin (beta-1,3-glucan, a typical component of fungal cell walls) induced nodulation in a dose-dependent manner. This reaction was initiated very soon after injection and reached its maximal response level after 4 h. The nodules were not randomly distributed in the hemocoel, but were concentrated around the crop. The possible role of eicosanoids in this nodulation process was determined by treating larvae with the phospholipase A(2) inhibitor, dexamethasone, the cyclooxygenase inhibitor, naproxen, and the lipoxygenase inhibitor, esculetin. Both dexamethasone and naproxen significantly impaired the ability of N. bullata larvae to form nodules in response to laminarin. Supplying dexamethasone-treated larvae with the eicosanoid precursor, arachidonic acid, restored the full response. On the other hand, treating larvae with esculetin did not influence the formation of nodules in response to laminarin. This is the first study that demonstrates the occurrence of a laminarin-induced nodulation response in Diptera. Phospholipase A(2) and cyclooxygenase activities, both involved in prostaglandin biosynthesis, appear to play an important role in the regulation of this process.

Animals↗

PubMed1993

Roles of plant homologs of Rab1p and Rab7p in the biogenesis of the peribacteroid membrane, a subcellular compartment formed de novo during root nodule symbiosis.

The peribacteroid membrane (PBM) in legume root nodules is derived from plasma membrane following endocytosis of Rhizobium by fusion of newly synthesized vesicles. We studied the roles of plant Rab1p and Rab7p homologs, the small GTP-binding proteins involved in vesicular transport, in the biogenesis of the PBM. Three cDNAs encoding legume homologs of mammalian Rab1p and Rab7p were isolated from soybean (sRab1p, sRab7p) and Vigna aconitifolia (vRab7p). sRab1p was confirmed to be a functional counterpart of yeast Ypt1p (Rab1p) by complementation of a yeast ypt1-1 mutant. Both srab1 and vrab7 genes are induced during nodulation with the level of vrab7 mRNA being 12 times higher than that in root meristem and leaves. This induction directly correlates with membrane proliferation in nodules. Antisense constructs of srab1 and vrab7, under a nodule-specific promoter (leghemoglobin, Lbc3), were made in a binary vector and transgenic nodules were developed on soybean hairy roots obtained through Agrobacterium rhizogenes-mediated transformation. Both antisense srab1 and vrab7 nodules were smaller in size and showed lower nitrogenase activity than controls. The antisense srab1 nodules showed lack of expansion of infected cells, fewer bacteroids per cell and their frequent release into vacuoles. In contrast, antisense vrab7 expressing nodules showed accumulation of late endosomal structure and multivesicular bodies in the perinuclear region. These data suggest that both Rab1p and Rab7p are essential for the development of the PBM compartment in effective symbiosis.

Amino Acid Sequence↗

PubMed2002

Developmental genetics and evolution of symbiotic structures in nitrogen-fixing nodules and arbuscular mycorrhiza.

Genetic and molecular mechanisms of development are compared for two major plant-microbe endosymbioses: N(2)-fixing nodules (with rhizobia or actinomycetes Frankia) and arbuscular mycorrhiza (with Glomales fungi). Development from the primordia formed de novo in root tissues is common for all known types of N(2)-fixing nodules. However, their structure varies greatly with respect to: (i) tissue topology (location of vascular bundles is peripherical in legumes or central in non-legumes); (ii) position of nodule primordium (inner or outer cortex in legumes, pericycle in non-legumes); (iii) stability of apical meristem (persistent in the indeterminate nodules, transient in the determinate ones). In addition, legumes vary in ability to form compartments harboring endosymbiotic rhizobia and located intercellularly (infection threads) and intracellularly (symbiosomes). Using pea (Pisum sativum) symbiotic mutants, the nodule developmental program is dissected into a range of spatially and temporarily differentiated steps comprising four sub-programs (development of endosymbiotic compartments; nodule histogenesis; autoregulation of nodulation; bacteroid differentiation). The developmental mutations are suggested in some cases to reverse the endosymbiotic system into the morphologically simpler forms some of which may correspond to the ancestral stages of nodule evolution. The origin of legume-rhizobial and actinorhizal symbioses is suggested to be based on a set of preadaptations many of which had been evolved in angiosperms during coevolution with arbuscular mycorrhizal fungi (e.g., inter- and intracellular maintenance of symbionts, their control via defence-like reactions and recognition of chitin-like molecules). An analysis of parallel morphological variation in symbiotic mutants and wild-growing legume species enables us to reconstruct the major stages of evolution for N(2)-fixing symbioses.

Actinomycetales↗

PubMed1987

Biological significance of AFP-positive cells in rat livers with hyperplastic nodules induced by 3'-Me-DAB; combined immunocytochemical and radioautographical studies.

We investigated alpha-fetoprotein (AFP)-positive cells in 3'-Me-DAB hepatocarcinogenesis. In the early stage of 3'-Me-DAB hepatocarcinogenesis immunoreaction of AFP was detected in proliferating cholangiolar "oval" cells and in the late stage, AFP-positive cells, differing from oval cells, were detected in clusters in rat liver with hyperplastic nodules. The clusters of AFP-positive cells were morphologically classified into two different types of foci and one type of nodule. The combined techniques of immunocytochemistry and ratioautography revealed that AFP-positive foci and nodule had more 3H-thymidine labeling index than did areas without AFP-positive cells in liver with hyperplastic nodules; also one type of AFP-positive foci had a higher labeling index than the other type and in AFP-positive nodules there was active cell proliferation; but AFP-positive foci or nodules had less 3H-thymidine labeling than AFP-positive hepatoma cells. These findings suggested that AFP-positive foci and nodule had different biological significance in development of hepatocellular carcinoma and that AFP-positive foci with higher labeling index and AFP-positive nodule should be surveyed as preneoplastic population.

Animals↗

PubMed1992

Incidental adrenal nodules: association with exaggerated 17-hydroxyprogesterone response to adrenocorticotropic hormone.

The etiology of incidentally discovered, nonfunctional adrenal nodules was evaluated by using the 17-hydroxyprogesterone (17-OHP) response to synthetic adrenocorticotrophin (cosyntropin) (ACTH) administration. Patients who were discovered to have adrenal nodules and age-matched volunteers were studied. A total of 12 patients with adrenal nodules and 10 control subjects were studied. None of the patients with adrenal nodules had any evidence of hormonal hypersecretion consistent with pheochromocytoma, Cushing's syndrome or hyperaldosteronism. All subjects had serum 17-OHP and cortisol responses measured at baseline and at 30 and 60 min following the intravenous administration of 250 micrograms of ACTH. Baseline 17-OHP levels in patients with adrenal nodules were not significantly different from those of the normal controls (adrenal nodules 17-OHP: 75 +/- 13 vs control 68 +/- 11 ng/dl). After stimulation with ACTH, both 30 min and 60 min 17-OHP levels in patients with adrenal nodules (322 +/- 47 and 361 +/- 54 ng/dl, respectively) were significantly elevated over the responses seen with the controls (169 +/- 29 ng/dl at 30 min, p < 0.015, and 158 +/- 20 ng/dl at 60 min, p < 0.004). Baseline and post-ACTH serum cortisol levels were similar in both groups. Out of these twelve patients with adrenal nodules, nine were reevaluated twelve months later. In this group the basal 17-OHP remained comparable to normal levels (72 +/- 8.4 ng/dl) whereas the post-ACTH levels still remained exaggerated (30 and 60 min values 327 +/- 37 and 373 +/- 39 ng/dl).(ABSTRACT TRUNCATED AT 250 WORDS)

17-alpha-Hydroxyprogesterone↗

PubMed2000

Development of mineralized nodules in fetal rat mandibular osteogenic precursor cells: requirement for dexamethasone but not for beta-glycerophosphate.

We have reported that a cell population obtained from fetal rat mandible with neutral protease (Pro I) has a unique differentiation sequence in which the elevation of alkaline phosphatase (ALPase), calcium accumulation, and collagen synthesis occurs simultaneously. In this report, we further characterized Pro I-released population of cells by studying the effect of dexamethasone (Dex) or beta-glycerophosphate (beta-GP) on the formation of bone nodules. The formation of bone nodules in Pro I-released population of cells (ProIRPC) was augmented by the addition of Dex (10(-7) M) from days 3 to 14, suggesting that Pro IRPC contained osteoprogenitor (OP) cells. A 24-hour pulse treatment of ProIRPC released population of cells with Dex on days 9 and 12 resulted in an increase in the number of nodules but treatment on days 3, 6, or 15 did not. The number of bone nodules formed in Pro IRPC pulse treated with Dex on day 9 was comparable with that in Pro IRPC treated with Dex from days 3 to 14. Dex caused an earlier elevation of ALPase, in which maximal expression was observed on day 10. beta-GP caused a prolonged elevation of ALPase, but did not affect the formation of bone nodules. Unlike Pro I-released population of cells, rat calvarial cells did not form mineralized nodules without beta-GP, and showed that a Dex-responsive period on bone nodule formation in rat calvarial cells was at preconfluency (days 0 and 1). Thus, it appeared that the Dex-induced differentiation of early OP cells in Pro IRPCs occurred during the limited period from day 9 to day 12. Pro IRPC was found to have an unique characteristic that bone nodule formation was not affected by beta-GP.

Alkaline Phosphatase↗

PubMedDate not supplied

Focal hepatic nodules after transcatheter oily chemoembolization; detection with spiral CT versus conventional CT.

BACKGROUND: The objective of this study was to determine if spiral computed tomography (CT) results in increased rate of detection of focal hepatic nodules containing iodized oil after transcatheter oily chemoembolization when compared with conventional CT. METHODS: Spiral CT with single 24-s breath-hold technique was compared with conventional sequential CT in 42 patients with suspected hepatocellular carcinomas. Two sets of CT scans obtained after transcatheter oily chemoembolization were independently reviewed by two radiologists. The slice thickness was 10 mm for both data sets. The number and sizes of focal hepatic nodules containing iodized oil were documented. All 42 patients had at least hepatic nodule. The lesion size varied from 2 mm to 12 cm. RESULTS: In six of the 42 patients, more hepatic nodules could be identified on spiral CT compared with conventional CT. When scans with spiral CT were used, 107 nodules were detected, whereas 98 nodules were detected with conventional CT. Overall, nine (9%) more nodules were detected with spiral CT (p = .002). If lesions larger than 2 cm are excluded, nine (15%) more lesions were detected with spiral CT (p = .002). CONCLUSION: Spiral CT results in increased rate of detection of focal hepatic nodules after transcatheter oily chemoembolization, particularly in lesions smaller than 2 cm.

Antibiotics, Antineoplastic↗

PubMed2001

Detection of pulmonary nodules at spiral CT: comparison of maximum intensity projection sliding slabs and single-image reporting.

The aim of this study was to compare numbers of pulmonary nodules detected with maximum intensity projections using a slab thickness of 15 mm (MIP 15) and 30 mm (MIP 30) with single image (SI) presentation of chest CT scans. Two readers reviewed MIP 15, MIP 30, and SI presentations of 10-mm (n = 8) and 5-mm collimation (n = 10) helical CT scans and recorded size, location, and diagnostic confidence (definite, probable) of pulmonary nodules. Readers 1 and 2 recorded more nodules with MIP 15 than with SI: 10-mm collimation, 77/64 and 60/56; 5-mm collimation, 64/60 and 40/36; and more "definite" nodules (10-mm collimation: 68/57 and 51/42; 5-mm collimation: 43/36 and 34/30). MIP 15 also detected more nodules than MIP 30 at 10-mm collimation: 77/72 and 60/50; with no major differences at 5-mm collimation: 64/66 and 40/38; and more "definite" nodules (10-mm collimation: 68/58 and 51/36; 5-mm collimation: 43/39 and 34/29). There were only minor differences between SI and MIP 30. Reading time and image number per study were reduced with MIP presentations by a factor of 1.4-5.3. There were no significant differences in the number of nodules detected with SI, MIP 15, and MIP 30, but MIP presentation reduced reporting time and filming cost when compared with SI reporting. For detection of nodules MIP 15 was slightly superior to MIP 30.

Adolescent↗

PubMed1999

Detection of pulmonary nodules with overlapping vs non-overlapping image reconstruction at spiral CT.

The aim of this study was to analyze whether overlapping image reconstruction increases numbers of pulmonary nodules detected at helical CT. Forty-eight helical CT scans (21 with a slice thickness of 10 mm; 27 with a slice thickness of 5 mm) of patients with known pulmonary nodules were reconstructed both with overlapping and non-overlapping image reconstruction. Two readers recorded number and size of pulmonary nodules as well as diagnostic confidence. With overlapping image reconstruction each reader diagnosed more pulmonary nodules (slice thickness 10 mm: +24.0 and +26.7%, both p < 0.01; slice thickness 5 mm: +9.5 and +11.9%, both not significant) and more "definite" nodules (slice thickness 10 mm: +20.3%, p < 0.05, and +30.8%, p < 0.005; slice thickness 5 mm: +18.0 and +17.0%, both p < 0.05). Nodules diagnosed with overlapping image reconstruction only were almost exclusively smaller than the slice thickness. The increase in number of nodules detected was not associated with a decrease in diagnostic confidence. Overlapping image reconstruction improves detection of pulmonary nodules smaller than the slice thickness at spiral CT.

Adolescent↗

PubMed2003

Regulatory regions and nuclear factors involved in nodule-enhanced expression of a soybean phosphoenolpyruvate carboxylase gene: implications for molecular evolution.

We have determined the genomic organization of two closely related phosphoenolpyruvate carboxylase genes in soybean, GmPEPC7, which is expressed at high levels in root nodules, and the housekeeping gene GmPEPC15. Their nucleotide sequences, including most introns and 5;-flanking regions within 600 bp upstream from the transcription start sites, are well conserved, suggesting that they were duplicated quite recently. To gain insights into the process of evolution of the tissue-specifically expressed GmPEPC7gene, we produced chimeric constructs carrying either the GmPEPC7or GmPEPC15promoter fused to the beta-glucuronidase gene. The expression patterns of the reporter observed in nodules that developed on transgenic hairy roots reflected the levels of mRNA levels produced by the genes in wild-type soybean plants, indicating that the GmPEPC7promoter directs nodule-specific expression. Loss-of-function experiments showed that the segment of GmPEPC7between -466 and -400, designated as the "switch region" (SR), was necessary for expression in nodules, although proteins that bind to SR were not detectable in a gel-retardation assay. Another gel-retardation assay indicated that putative nodule nuclear proteins bind specifically to the region of GmPEPC7between -400 and -318, designated as the "amplifier region" (AR). Both SR and AR have characteristic sequences that are not found in the GmPEPC15promoter. Furthermore, experiments using hybrid promoters derived from GmPEPC15demonstrated that AR confers high-level expression in nodules only in combination with SR. When wild-type soybean plants were subjected to prolonged darkness and subsequently illuminated, the level of GmPEPC7mRNA in nodules decreased and then recovered. This study suggests that the acquisition of two interdependent cis-acting elements resulted in molecular evolution of the nodule-enhanced GmPEPC7gene.

Base Sequence↗

PubMed1980

Identification of "nodule-specific" host proteins (nodoulins) involved in the development of rhizobium-legume symbiosis.

Infection of legume roots with Rhizobium species results in the development of a root nodule structure in which the bacteria form an intracellular symbiosis with the plant. We report here that the infection of soybean (Glycine max L.) roots with Rhizobium japonicum results in the synthesis by the plant of at least 18-20 polypeptides other than leghemoglobin during the development of root nodules. Identification of these "nodule-specific" host polypeptides (referred to as nodulins) was accomplished by two-dimensional gel analysis of the immunoprecipitates formed by a "nodule-specific" antiserum with in vitro translation products of root-nodule polysomes that are free of bacteroidal contaminations. Nodulins account for 7-11% of the total 35S-methionine-labeled protein synthesized in the host cell cytoplasm, and the majority of them are of 12,000-20,000 molecular weight. These proteins are absent from the uninfected roots, bacteroids and free-living Rhizobium, and appear to be coded for the plant genes that may be obligatory for the development of symbiosis in the legume root nodules. Analysis of nodulins in ineffective (unable to fix nitrogen) nodules developed due to Rhizobium strains SM5 and 61A24 showed that their synthesis is reduced and their expression differentially influenced by mutations in rhizobia. Two polypeptides of bacterial origin were also found to be cross-reactive with the "nodule-specific" antiserum, suggesting that they are secreted by Rhizobium into the host cell cytoplasm during symbiotic nitrogen fixation.

Fabaceae↗