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PubMed2002

Small pulmonary nodules on CT accompanying surgically resectable lung cancer: likelihood of malignancy.

SUMMARY: The aim of this study was to determine the likelihood of malignancy in small nodules in the nonprimary lobe in patients with resectable bronchogenic carcinoma. In 141 patients who underwent curative resection of bronchogenic carcinoma and had adequate follow-up CT examinations, the presence of small nodules in the nonprimary lobe preoperatively and change of preexisting nodules, if any, was assessed. The criteria used to determine benignity of a nodule was stability or decrease in size for 24 months on CT. Histopathology of the nodules was reviewed for an additional 10 patients who underwent surgical biopsy for an accompanying nodule before curative surgery. Sixty-two (44%) of 141 patients had a total of 138 small (< or = 10 mm) nodules in the nonprimary lobes (< 5 mm in 113, 5-10 mm in 25). Of these 138 nodules, 132 were benign with only six nodules malignant (with histopathologic confirmation for the enlarging nodules). The 132 benign nodules showed no change (n = 120), decrease in size (n = 11), or increase in size (n = 1) on follow-up studies, with the single enlarging nodule proved benign on biopsy. In 10 patients who had a preoperative biopsy of a single preexisting nodule in the nonprimary lobe (< 5 mm = 1; 5-10 mm = 5; > 10 mm = 4) two proved to be malignant (both > 10 mm) and eight were benign. Most small (< 10 mm) nodules associated with resectable bronchogenic carcinoma are benign, consistent with published results of other studies. However, a small number of nodules are malignant and CT does not reliably distinguish between benign and malignant nodules.

Adult↗

PubMed2002

Comparison of low-dose and standard-dose helical CT in the evaluation of pulmonary nodules.

The purpose of this study was to investigate the diagnostic accuracy of low-dose helical computed tomography by comparing the number of nodules detected at low- and standard-dose CT. The prospective study included 25 patients who were referred to CT scan for the assessment of pulmonary metastases. All patients underwent CT examinations at both standard- (200 mA, 120 kV, collimation 5 mm, table feed 10 mm per rotation) and low-dose (50 mA, 120 kV, collimation 5 mm, table feed 10 mm per rotation). The number of nodules detected at each protocol was recorded. The size of the nodules was measured electronically and categorized as <3, 3-4.9, 5-6.9, 7-9.9, and >/=10 mm. Finally, the nodules detected at only standard- or low-dose CT were assessed for the underlying causes of discrepancy. In 25 patients, 533 nodules were detected at standard-dose, whereas 518 nodules were observed at low-dose CT. There were no statistically significant differences in the number of nodules detected at standard- or low-dose CT ( p>0.05). Four hundred ninety-one (87.7%) nodules were detected at both standard- or low-dose CT, 42 (7.5%) nodules were observed only at standard-dose CT, and 27 (4.8%) nodules were seen only at low-dose CT. The sensitivity of low-dose CT was 92.5% for all nodules, 88.1% for nodules <5 mm, and 97.4% for nodules >/=5 mm. No significant image artifact interfering with nodule detection was observed at low-dose CT. The low-dose CT protocol used in this study provided images of adequate quality; thus, it can be used reliably in the detection or exclusion of pulmonary nodules.

Female↗

PubMed1991

Management of solitary pulmonary nodules.

The solitary pulmonary nodule (SPN), a single intrapulmonary spherical lesion that is fairly well circumscribed, is a common clinical problem. About half of SPNs seen in clinical practice are malignant, usually bronchogenic carcinomas. Some nodules are primary tumors of other kinds or metastatic. Virtually all benign SPNs are tuberculous or fungal granulomas. The standard management of the SPN of unknown cause is prompt surgical removal unless benignity is established by prior chest roentgenograms showing that the nodule has been stable (i.e., showing no growth) for 2 years or by the presence of a "benign" pattern of calcification. Less universally accepted criteria for benignity include (1) transthoracic needle aspiration biopsy (TNAB) showing a specific benign process, and (2) patient's age under 30 to 35 years. Bronchoscopy has a low diagnostic yield, particularly for benign nodules. SPNs usually grow at constant rates, expressed as the "doubling time" (DT). A nodule with a DT between 20 and 400 days is usually malignant. Benign nodules usually have a DT greater than 400 days. The prospective determination of DT by serial chest roentgenograms (the "wait and watch" strategy) is widely criticized but has clinical utility in special circumstances, particularly if the likelihood of malignancy is low and/or the anticipated surgical mortality is high. The presence and pattern of calcification are best shown by high-resolution thin-section computed tomography (CT). Diffuse, laminated, central or "popcorn" patterns of calcification indicate benignity. An eccentric calcium deposit or a stippled pattern does not rule out malignancy. CT densitometry will often show "occult" calcification in nodules that show no direct visual evidence of calcium deposition. The characteristics of the edge of the nodule correlate with the likelihood of malignancy. Nodules with irregular or spiculated margins are almost always malignant. The probability that the nodule is malignant (pCA) is related to the age of the patient, the diameter of the nodule, the amount of tobacco smoke inhalation, the overall prevalence of malignancy in SPNs, the nature of the edge of the lesion, and the presence or absence of occult calcification. It is possible by Bayesian techniques to combine these factors to calculate a more precise and comprehensive prediction of pCA in any given nodule. The 5-year survival after nodule resection depends on the size of the nodule at the time of surgery; it may be as high as 80% with nodules that are 1 cm in diameter. Lymph node involvement is uncommon with small tumors, and many authorities question the need for CT staging in such cases.(ABSTRACT TRUNCATED AT 400 WORDS)

Biopsy↗

PubMed1998

Thyroid nodules in Graves' disease: classification, characterization, and response to treatment.

Thyroid nodules in patients with Graves' disease are common and raise concern about coexistent thyroid malignancy. Alternative etiologies for such nodules are more frequent, and separation from thyroid malignancy is important for rational management. To characterize the types of thyroid nodules present in patients with Graves' disease, evaluate the response of these nodules to treatment, and stratify the risk of thyroid malignancy, we report on a retrospective single center study in an ambulatory setting of 468 Graves' patients ages (12-75) followed for 1-31 years (mean = 5.1) treated with radioiodine (n = 345), near-total thyroidectomy (n = 19), thionamide antithyroid drugs (n = 88), or observation (n = 18). Sixty patients (12.8% of the total) had nodules and were classified as: (1) Graves' disease with a solitary hypofunctional nodule (n = 27, 5.8%); (2) Graves' disease with multiple nodules (n = 21, 4.5%); (3) Graves' disease with autonomous nodule (n = 4, 1%); or (4) patchy Graves' disease (n = 8, 1.7%). Six patients (1.3% of total or 10% of nodule patients) had cancer: five in group 1 and and one in Group 4. Based on the response to therapy or surgical and fine-needle aspirate pathology, the remaining patients demonstrated pseudo-nodules of autoimmune thyroid disease, autonomous nodules of Marine-Lenhart syndrome, colloid goiter, hyperplastic adenomatous disease, and Hashitoxicosis. In conclusion, Graves, patients commonly present with or may develop nodules (12.6%) and the majority of these are benign expressions of autoimmune changes and coexistent nodular goiter. Thyroid cancer occurs in 10% of all nodules, 19% of palpable solitary cold nodules, and 1.3% of the total patients. If the fine-needle aspiration biopsy (FNAB) cytology is benign, it is reasonable to use nonsurgical therapy. Any single cold nodule that remains or develops after treatment needs careful re-examination due to the high risk of malignancy.

Adolescent↗

PubMed1998

Thyroid nodules in Graves' disease: classification, characterization, and response to treatment.

Thyroid nodules in patients with Graves' disease are common and raise concern about coexistent thyroid malignancy. Alternative etiologies for such nodules are more frequent, and separation from thyroid malignancy is important for rational management. To characterize the types of thyroid nodules present in patients with Graves' disease, evaluate the response of these nodules to treatment, and stratify the risk of thyroid malignancy, we report on a retrospective single center study in an ambulatory setting of 468 Graves' patients ages (12-75) followed for 1-31 years (mean = 5.1) treated with radioiodine (n = 345), near total thyroidectomy (n = 19), thionamide antithyroid drugs (n = 88) or observation (n = 18). Sixty patients (12.8% of the total) had nodules and were classified as: (1) Graves' disease with a solitary hypofunctional nodule (n = 27, 5.8%); (2) Graves' disease with multiple nodules (n = 21, 4.5%); (3) Graves' disease with autonomous nodule (n = 4, 1%); or (4) patchy Graves' disease (n = 8, 1.7%). Six patients (1.3% of total or 10% of nodule patients) had cancer: 5 in group 1 and 1 in group 4. Based on the response to therapy or surgical and fine-needle aspirate pathology, the remaining patients demonstrated pseudo-nodules of autoimmune thyroid disease, autonomous nodules of Marine-Lenhart syndrome, colloid goiter, hyperplastic adenomatous disease, and Hashitoxicosis. In conclusion, Graves' patients present with or may develop nodules commonly (12.6%) and the majority of these are benign expressions of autoimmune changes and coexistent nodular goiter. Thyroid cancer occurs in 10% of all nodules, 19% of palpable solitary cold nodules and 1.3% of the total patients. If the fine-needle aspiration biopsy (FNAB) cytology is benign, it is reasonable to use nonsurgical therapy. Any single cold nodule that remains or develops after treatment needs careful re-examination due to the high risk of malignancy.

Adolescent↗

PubMed1985

Digital synthesis of lung nodules.

Studies evaluating observer accuracy and visual perception of pulmonary nodules usually are based upon test films obtained from clinical practice in patients with proven pulmonary nodules. Unfortunately, such nodules do not always occur in the optimal size and location to facilitate testing. Such studies would be enhanced by the ability to place nodules of desired size and location on chest radiographs. This report describes a method of placing a computer-generated (synthesized) nodule on a digitized chest radiograph. To demonstrate the similarity of these synthesized nodules to real nodules, each digitized radiograph with a computer-generated nodule was paired with a digitized chest radiograph of a patient with a clinically proven pulmonary nodule. A total of 22 pairs of chest radiographs were then shown to 13 radiologists, who were asked to distinguish the synthesized nodule from the real nodule. With this two alternative forced-choice test, the radiologists were only able to distinguish the synthesized nodule in 51% of the cases, strongly suggesting that computer generated nodules may be used to simulate real pulmonary nodules in future tests of nodule detection.

Humans↗

PubMed2006

Detection of small pulmonary nodules using direct digital radiography and picture archiving and communication systems.

PURPOSE: To evaluate the detection of small pulmonary nodules, in the diameter range of 5.4 to 15 mm, using direct digital chest imaging and soft copy interpretation on picture archiving and communication systems. MATERIALS AND METHODS: The results of clinical computed tomography (CT) scans of the thorax were retrospectively reviewed from our radiology information system and picture archiving and communication systems archives. Patients with CT studies containing between 1 and 6 nodules, who also had a digital chest examination within 1 month of the CT scan were selected. Thirty patients with suitable nodules and 30 without nodules were included and form the data base for this study. The nodules were between 5.4 and 15 mm in average diameter. Four separate observers independently viewed the frontal and lateral chest studies of the 60 patients. The presence or absence of nodules was determined. Data were analyzed with Kappa, McNemar and Fischer exact tests for agreement and differences between observers, nodule size, and nodule zone. RESULTS: A total of 42 nodules between 5.4 and 15 mm were present. The overall detection rate for the 4 observers was 41.7%. For nodules between 5.4 and 8 mm the detection rate was 26.2%. Agreement between observer's detection was poor to moderate. Differences between observers for both nodule size and zone were not significant. Only 1 observer had a relationship between nodule detection and nodule size. CONCLUSIONS: Observer detection of pulmonary nodules in the range of 5 to 15 mm using current digital radiography systems is not reliable in the confusing environment of the lung. Additional modification of these systems is required to increase nodule conspicuity.

Adult↗

PubMed2003

Natural history of benign solid and cystic thyroid nodules.

BACKGROUND: Thyroid nodules are common and most often benign. The natural history of benign thyroid nodules, however, is unclear. OBJECTIVE: To determine the natural history of cytologically benign thyroid nodules using ultrasonography. DESIGN: Retrospective case series. SETTING: Single tertiary care clinic. PARTICIPANTS: All patients referred to the Brigham and Women's Hospital Thyroid Nodule Clinic, Boston, Massachusetts, who had benign cytologic results on ultrasonography-guided fine-needle aspiration of a thyroid nodule between 1995 and 2000 and returned for a requested follow-up examination 1 month to 5 years later. MEASUREMENTS: Nodule dimensions were measured at both visits, and growth was defined as an increase in calculated volume of 15% or greater. These results were correlated with the time between examinations, age, sex, baseline serum thyroid-stimulating hormone concentration, and cystic content of each nodule. RESULTS: Nodule volume increased over time (P < 0.001). The estimated proportion of nodules with an increase in volume of 15% or greater after 5 years was 89%. Nodules with greater cystic content were less likely to grow than solid nodules (P = 0.01). Seventy-four of the 330 nodules were reaspirated on the second visit. Despite an average increase in volume of 69%, only 1 of 74 reaspirated nodules was malignant. CONCLUSION: Most solid, benign thyroid nodules grow. Therefore, an increase in nodule volume alone is not a reliable predictor of malignancy.

Biopsy, Needle↗

PubMed1989

Survey of iron-accumulative macroregenerative nodules in cirrhotic livers.

Recently, macroregenerative nodules in cirrhotic livers have been suspected to be among the putative precancerous lesions in human hepatocarcinogenesis. We examined the morphologies of 99 macroregenerative nodules in 44 cirrhotic livers with special emphasis on stainable iron. In 26 macroregenerative nodules (26%), stainable iron selectively accumulated within the macroregenerative nodules themselves, and little or no iron was found in the surrounding regenerative nodules. In nine macroregenerative nodules (9%), an appreciable amount of stainable iron was present in both the macroregenerative nodules and the surrounding regenerative nodules. In the remaining 64 macroregenerative nodules (65%), stainable iron was absent in both the macroregenerative nodules and the surrounding regenerative nodules. Hyperplastic hepatocellular foci were present within 19 (73%) of the 26 iron-accumulative macroregenerative nodules, one (11%) of the nine iron-positive macroregenerative nodules and 20 (31%) of the 64 iron-negative macroregenerative nodules. These findings suggest that iron-accumulative macroregenerative nodules are frequently associated with hyperplastic hepatocellular foci and should be included among the precancerous lesions in human hepatocellular carcinoma.

Adult↗

PubMed1991

Differential regulation of cytochrome(s) P450 2B1/2 by phenobarbital in hepatic hyperplastic nodules induced by aflatoxin B1 or diethylnitrosamine plus 2-acetylaminofluorene in male F344 rats.

Phenobarbital (PB) is an effective growth stimulator of hepatic hyperplastic nodules developed with diethylnitrosamine and 2-acetylaminofluorene plus partial hepatectomy (the Solt-Farber model), but it does not apparently stimulate the growth of preneoplastic lesions produced with aflatoxin B1 (AFB). Some studies have suggested a correlation between the induction of specific cytochrome P450 enzymes and the tumor promoting effects produced by repeated treatment with PB. To examine this hypothesis further, hepatic hyperplastic nodules were produced with AFB (10 ip doses of AFB, 150 micrograms/kg/day, followed by partial hepatectomy) or by a modified Solt-Farber protocol (DEN/AAF), and the effects of PB on nodule growth and expression of cytochrome(s) P450 2B1 and/or P450 2B2 (P450 2B1/2) were determined. Both treatment protocols (without PB) produced multiple, large nodules within 10-17 weeks of carcinogen administration. These nodules stained intensely for glutathione S-transferase p (GST-p; GST7-7) and gamma-glutamyl transpeptidase (GGT) and weakly for P450 2B1/2. Pentoxyphenoxazone dealkylation activity was decreased to less than 50% of the surrounding tissue levels in both types of nodules. PB treatment of animals with DEN/AAF-induced nodules greatly increased P450 2B1/2 expression in surrounding tissues, whereas most, but not all, nodules were not inducible. Pentoxyphenoxazone dealkylation was increased 31- to 35-fold in surrounding tissue, but it was increased only 2-fold in pooled nodular tissue, relative to untreated control liver. In contrast to the DEN/AAF group, immunohistochemical staining and pentoxyphenoxazone dealkylation in the AFB group demonstrated that P450 2B1/2 was equally inducible in nodular and surrounding tissues. Short-term treatment (5 days) with PB produced a 2-fold increase in the number and total area of GGT-positive nodules in the DEN/AAF group, but it had no significant effect on the number, size distribution, or total area of GGT-positive nodules in the AFB group. All large GGT-positive nodules in the DEN/AAF group were nonresponsive to induction of P450 2B1/2, whereas all of the GGT-positive nodules which were responsive to P450 2B1/2 induction by PB in this group were relatively small. The size and area of AFB-induced GGT-positive nodules was not affected by PB treatment, and P450 2B1/2 in all of these nodules was inducible by PB. Although a causal, inverse relationship between the responsiveness of nodules to PB induction of P450 2B1/2 and their reaction to PB growth stimulation cannot be firmly established, these data are consistent with such a hypothesis.

2-Acetylaminofluorene↗

PubMed2003

Example-based assisting approach for pulmonary nodule classification in three-dimensional thoracic computed tomography images.

RATIONALE AND OBJECTIVES: An example-based assisting approach that supports decision making in classifying pulmonary nodules in 3-dimensional (3D) thoracic computed tomography images has been developed. MATERIALS AND METHODS: The example-based assisting approach retrieves and displays nodules that exhibit morphologic and internal profiles consistent to the nodule in question. It uses a 3D computed tomography image database containing 143 pulmonary nodules for which diagnosis is known. The central module makes possible analysis of the query nodule image and extraction of the features of interest: shape, surrounding structure, and internal structure of the nodules. The principal axes and the compactness characterize the nodule shape. The surrounding and internal structures are represented by the distribution pattern of computed tomography density value and 3D curvature indexes. The nodule representation is then used for computing a similarity measure such as a correlation coefficient and a malignant likelihood of the query nodule. The malignant likelihood is estimated by the difference between the representation patterns of the query case and the retrieved lesions. The Mahalanobis distance was adopted as the difference measure. The approach performance was assessed through leave-one-out method by the false-positive rate. RESULTS: Given a query nodule image, the proposed method retrieved benign and malignant images similar to the query case and provided its malignant likelihood. The number of cases that obtained enough number of the retrieved cases for estimating the malignant likelihood was 107 cases (malignant, 70; benign, 37) in our database. Sensitivity was 91.4% (64 of 70 malignant nodules), specificity was 51.4% (19 of 37 benign nodules), and accuracy values were 77.6% (83 of 107 nodules). CONCLUSION: Preliminary assessment of this approach showed that an example-based assisting approach is an effective tool for making the diagnostic decision in the classification of pulmonary nodules using the nodule image database.

Databases, Factual↗

PubMed2004

The potential contribution of a computer-aided detection system for lung nodule detection in multidetector row computed tomography.

RATIONALE AND OBJECTIVES: We sought to evaluate the potential benefits of a computer-aided detection (CAD) system for detecting lung nodules in multidetector row CT (MDCT) scans. METHODS: A CAD system was developed for detecting lung nodules on MDCT scans and was applied to the data obtained from 15 patients. Two chest radiologists in consensus established the reference standard. The nodules were categorized according to their size and their relationship to the surrounding structures (nodule type). The differences in the sensitivities between an experienced chest radiologist and a CAD system without user interaction were evaluated using a chi2 analysis. The differences in the sensitivities also were compared in terms of the nodule size and the nodule type. RESULTS: A total of 309 nodules were identified as the reference standard. The sensitivity of a CAD system (81%) was not significantly different from that of a radiologist (85%; P > 0.05). The sensitivities of the CAD system for detecting nodules < or = 5 mm in diameter as well as detecting isolated nodules were higher than those of a radiologist (83% vs. 75%, P > 0.05; 93% vs. 76%, P < 0.001). The sensitivities of a radiologist for detecting nodules >5 mm and the nodules attached to other structures were higher than those of a CAD system (98% vs. 79%, P < 0.001; 91% vs. 71%, P < 0.001). There were 28.8 false-positive results of CAD per CT study. CONCLUSION: The CAD system developed in this study performed the nodule detection task in different ways to that of a radiologist in terms of the nodule size and the nodule type, which suggests that the CAD system can play a complementary role to a radiologist in detecting nodules from large CT data sets.

Adult↗

PubMed1993

Role of Oxygen in the Limitation and Inhibition of Nitrogenase Activity and Respiration Rate in Individual Soybean Nodules.

Although infected cell O2 concentration (Oi) is known to limit respiration and nitrogenase activity in legume nodules, techniques have not been available to measure both processes simultaneously in an individual legume nodule. Consequently, details of the relationship between nitrogenase activity and Oi are not fully appreciated. For the present study, a probe was designed that allowed open circuit measurements of H2 evolution (nitrogenase activity) and CO2 evolution (respiration rate) in a single attached soybean nodule while simultaneously monitoring fractional oxygenation of leghemoglobin (and thereby Oi) with a nodule oximeter. Compared to measurements of whole nodulated roots, use of the probe led to inhibition of nitrogenase activity in the single nodules. During oximetry measurements, total nitrogenase activity (TNA; peak H2 evolution in Ar/O2) in the single nodules was 16% of that in whole nodulated roots and 48% of nodulated root activity when Oi was not being measured simultaneously. This inhibition did not affect the nodules' ability to regulate Oi, because exposure to Ar/O2 (80:20, v/v) caused nitrogenase activity and respiration rate to decline, and this decline was linearly correlated with a concurrent decrease in Oi. When the nodules were subsequently exposed to a linear increase in external pO2 from 20 to 100% O2 at 2.7% O2/min, fractional leghemoglobin oxygenation first increased gradually and then more rapidly, reaching saturation at a pO2 between 76 and 100% O2. Plots of nitrogenase activity and respiration rate against Oi showed that rates increased with Oi up to a value of 57 nM, with half-maximal rates being attained at Oi values between 10 and 14 nM O2. The maximum nitrogenase activity achieved during the increase in pO2 (potential nitrogenase activity) was 30 to 57% of that measured in intact nodulated roots, showing that O2 limitation of nitrogenase activity could account for a significant proportion of the inhibition of TNA associated with the use of the probe. However, some factor(s) in addition to O2 must have limited the activity of single nodules at both subsaturating and saturating Oi. At Oi values greater than about 57 nM, nitrogenase activity and nodule respiration were inhibited, but, because this inhibition has been shown previously to be readily reversible when the Oi was lowered, it was not attributed to direct O2 inactivation of the nitrogenase protein. These results indicate that maximum nitrogenase activity in legume nodules is supported by a narrow range of Oi values. Possible biochemical mechanisms are discussed for both O2 limitation of nitrogenase activity at low Oi and inhibition of nitrogenase activity at high Oi.

Journal Article↗

PubMed1981

Effect of nitrate in the rooting medium on carbohydrate composition of soybean nodules.

Nodulated soybean plants (Glycine max [L.] Merr) were grown in sand culture. Carbohydrate composition of nodules, roots, and leaf blades was determined and related to the effects of nitrate in nutrient solution on nodule growth and on nitrogenase activity of nodules.When plants were grown without nitrate for 6 weeks and then supplied with 150 milligrams NO(3)-N/liter for 4 or 7 days, there was an 80% decline in acetylene reduction activity of nodulated roots, relative to the 0-N control. The 80% decline in nitrogenase activity was accompanied by a decline in nodule glucose concentration of about 0.15 milligram per gram fresh weight and an increase in nodule sucrose concentration of about 0.23 milligram per gram fresh weight.Plants were grown with 0, 30, or 100 milligrams NO(3)-N/liter for 5 or 6 weeks to study long-term effects of nitrate on nodule growth. The 100-N treatment reduced nodule weight/plant by 70% but reduced the sum of sucrose + glucose + fructose concentration in nodules by only 12%. The ratios of [sucrose] in nodules/[sucrose] in roots and [fructose] in nodules/ [fructose] in roots increased slightly in response to nitrate, indicating that nitrate affects sugar concentration in roots more than sugar concentration in nodules.The effect of nitrate on glucose concentration of nodules was consistently negative. However, if it is assumed that sucrose, glucose, and fructose are equivalent in their ability to support nodule functions, then the overall results are not consistent with the hypothesis that nitrate inhibits nodule growth and activity by reducing the accumulation of carbohydrate in nodules.

Journal Article↗

PubMed1984

Effect of salinity on nodule formation by soybean.

A split-root growth system was employed to evaluate the effect of NaCl on nodule formation by soybean (Glycine max L. Merr. cv Davis). By applying the salinity stress and rhizobial inoculum to only one-half the root system, the effects of salinity on shoot growth were eliminated in the nodulation process. Rhizobium colonization of inoculated root surfaces was not affected by the salt treatments (0.0, 26.6, 53.2, and 79.9 millimolar NaCl). While shoot dry weight remained unaffected by the treatments, total shoot N declined from 1.26 grams N per pot at 0.0 millimolar NaCl to 0.44 grams N per pot at 79.9 millimolar NaCl. The concentration of N in the shoot decreased from 3.75% N (0.0 millimolar NaCl) to 1.26% N at 79.9 millimolar NaCl. The decrease in shoot N was attributed to a sharp reduction in nodule number and dry weight. Nodule number and weight were reduced by approximately 50% at 26.6 millimolar NaCl, and by more than 90% at 53.2 and 79.9 millimolar NaCl. Nodule development, as evidenced by the average weight of a nodule, was not as greatly affected by salt as was nodule number. Total nitrogenase activity (C(2)H(2) reduction) decreased proportionally in relation to nodule number and dry weight. Specific nitrogenase activity, however, was less affected by salinity and was not depressed significantly until 79.9 millimolar NaCl. In a second experiment, isolates of Rhizobium japonicum from nodules formed at 79.9 millimolar NaCl did not increase nodulation of roots under salt stress compared to nodule isolates from normal media (0.0 millimolar NaCl). Salt was applied (53.2 millimolar NaCl) to half root systems at 0, 4, 12, and 96 hours from inoculation in a third experiment. By delaying the application of salt for 12 hours, an increase in nodule number, nodule weight, and shoot N was observed. Nodule formation in the 12- and 96-hour treatments was, however, lower than the control. The early steps in nodule initiation are, therefore, extremely sensitive to even low concentrations of NaCl. The sensitivity is not related to rhizobial survival and is probably due to the salt sensitivity of root infection sites.

Journal Article↗

PubMed1986

Two indirect methods for detecting ureide synthesis by nodulated legumes.

Two methods were developed for the detection of altered ureide metabolism in legume nodules. Both techniques are based on the positive correlation between the presence of high xanthine dehydrogenase (EC 1.2.1.37) specific activity in nodules and the ability of those nodules to produce the ureides, allantoin and allantoic acid. In the first method, nodulated legumes are treated for 2 weeks with a soil drench of allopurinol. After allopurinol treatment, leaves of N(2)-fed, ureide-producing legumes, soybean, cowpea, and lima bean, became very chlorotic. Leaves of KNO(3) (-) or NH(4)Cl-fed ureide-producing legumes were unaffected by the allopurinol treatment. Leaves of the amide-producing legumes, alfalfa, clover, peak, and lupin, were unaffected by the allopurinol treatment with N(2), KNO(3), or NH(4)Cl as nitrogen source. These experiments showed that long-term allopurinol treatments are useful in differentiating between ureide- and amide-producing legumes when effectively nodulated. A second method was developed for the rapid, qualitative estimation of xanthine dehydrogenase activity in legume nodules. This method utilizes pterin, an alternate substrate for xanthine dehydrogenase. Xanthine dehydrogenase hydroxylates pterin in the presence of NAD(+) to produce isoxanthopterin. When exposed to long wave ultraviolet light (365 nanometers), isoxanthopterin emits blue fluorescence. When nodules of ureide-producing legumes were sliced in half and placed in microtiter plate wells containing NAD(+) and pterin, isoxanthopterin was observed after 6 hours of incubation at room temperature. Allopurinol prevented isoxanthopterin production. When slices of amide-producing legume nodules were placed in wells with pterin and NAD(+), no blue fluorescence was observed. The production of NADH by xanthine dehydrogenase does not interfere with the fluorescence of isoxanthopterin. These observations agree with the high specific activity of xanthine dehydrogenase in nodules of ureide-producing legumes and the low activity measured in amide-producing nodules. The wild soybean, Glycine soja Sieb. and Zucc., was examined for ureide synthesis. Stems of wild soybean plants had a high ureide abundance with N(2) as sole nitrogen source when nodulated with either Rhizobium fredii or Bradyrhizobium japonicum. Ureide abundance declined when nitrate or ammonium was added to the nutrient solution. Nodule slices of these plants produced isoxanthopterin when incubated with pterin. Nodule crude extracts of G. soja had high levels of xanthine dehydrogenase activity. Both Glycine max and G. soja plants were found to produce ureides when plants were inoculated with fast-growing R. fredii. The two methods described here can be used to discriminate ureide producers from amide producers as well as detect nitrogen-fixing legumes which have altered ureide metabolism. A nodulated legume that lacks xanthine dehydrogenase activity as demonstrated by the pterin assay cannot produce ureides since ureide synthesis has been shown to require xanthine dehydrogenase activity both in vivo and in vitro. A nodulated legume that remains green during allopurinol treatment also lacks ureide synthesis since the leaves of ureide-producing legumes are very chlorotic following allopurinol treatment.

Journal Article↗

PubMed1997

Hepatic stellate cell activation in dysplastic nodules: evidence for an alternate hypothesis concerning human hepatocarcinogenesis.

We have previously suggested that dysplastic nodules (also referred to as "adenomatous hyperplasia" or "macroregenerative nodules"), likely precursors of hepatocellular carcinoma (HCC), develop as an infiltrating clonal expansion, in advance of or parallel to cirrhosis. As part of this hypothesis, to explain aspects of their gross and microscopic appearance, we suggested that dysplastic nodules are resistant to the scarring process affecting the rest of the liver. We sought to test this hypothesis by examining the distribution of activated hepatic stellate cells (HSCs), the hallmark of hepatic scarring, in cirrhotic nodules, dysplastic nodules and HCC. We immunohistochemically stained 56 cirrhotic nodules, 20 low grade dysplastic nodules, 27 high grade dysplastic nodules, and 20 HCCs with monoclonal antibodies against alpha-smooth muscle actin to identify activated HSCs. Distribution and number of HSCs were graded semiquantitatively (0 to 4+). In our results, HSCs were significantly less widespread in dysplastic nodules than in cirrhotic nodules or in HCCs (both: p < 0.00001). HSCs were also more prominent in the periphery of dysplastic nodules than in the center, though still fewer in number than in cirrhotic nodules. In conclusion, the low number of activated HSCs in dysplastic nodules, compared to both cirrhotic nodules and HCC, supports our hypothesis concerning dysplastic nodule development: that they arise as clonal expansions of neoplastic hepatocytes in advance of, or parallel to, the development of cirrhosis.

Actins↗

PubMed1999

Two-dimensional multi-criterion segmentation of pulmonary nodules on helical CT images.

A multi-criterion algorithm for automatic delineation of small pulmonary nodules on helical CT images has been developed. In a slice-by-slice manner, the algorithm uses density, gradient strength, and a shape constraint of the nodule to automatically control segmentation process. The multiple criteria applied to separation of the nodule from its surrounding structures in lung are based on the fact that typical small pulmonary nodules on CT images have high densities, show a distinct difference in density at the boundary, and tend to be compact in shape. Prior to the segmentation, a region-of-interest containing the nodule is manually selected on the CT images. Then the segmentation process begins with a high density threshold that is decreased stepwise, resulting in expansion of the area of nodule candidates. This progressive region growing approach is terminated when subsequent thresholds provide either a diminished gradient strength of the nodule contour or significant changes of nodule shape from the compact form. The shape criterion added to the algorithm can effectively prevent the high density surrounding structures (e.g., blood vessels) from being falsely segmented as nodule, which occurs frequently when only the gradient strength criterion is applied. This has been demonstrated by examples given in the Results section. The algorithm's accuracy has been compared with that of radiologist's manual segmentation, and no statistically significant difference has been found between the nodule areas delineated by radiologist and those obtained by the multi-criterion algorithm. The improved nodule boundary allows for more accurate assessment of nodule size and hence nodule growth over a short time period, and for better characterization of nodule edges. This information is useful in determining malignancy status of a nodule at an early stage and thus provides significant guidance for further clinical management.

Algorithms↗