The comparison of effectivity in breast cancer prevention between skin sparing and subcutaneous mastectomy - 20 years of experience

INTRODUCTION

Breast cancer is the leading cause of neoplasm mortality among women. Several prevention strategies have been implemented to early detect and prevent the cancer occurrence. The most effective protocol includes prevention mastectomy for the high-risk patients. In our study, we have compared the efficacy of subcutaneous mastectomy (SCM) and skin sparing mastectomy (SSM) in long-term follow up.

METHODS

We have included 201 female patients who have been treated at our department over the course of 20 years between 2000 and 2019. All the patients were at high risk of developing breast cancer and therefore were indicated for the prophylactic mastectomy. The main indication was the presence of the mutation in the BRCA1 or BRCA2 cluster, however, even in the lack of such mutation, the family history was sufficient for the mastectomy indication. Patients underwent either SCM, SSM or areola sparing mastectomy (ASM), and were allocated to aforementioned groups, respectively. We have collected the data regarding the reconstruction method along with age, weight, height, body mass index (BMI) and presence of predisposing genetic mutations such as BRCA positivity.

RESULTS

The patients who underwent SSM compared to those who underwent SCM were of higher age, with higher BMI and body mass. The patients in SSM group had statistically significantly higher BMI than in ASM. There was no difference in efficacy between patients who underwent SSM and SCM. The majority of patients (91.5%) were positive for BRCA1 or BRCA2 mutation. In our study, only four patients were tested negative for known breast cancer inducing mutation (three in SCM and one in SSM). The most common reconstruction method was an abdominal flap and breast implant.

CONCLUSIONS

Prophylactic mastectomy is a reliable strategy for significantly reducing the number of breast cancer incidence in high-risk patients regardless of the selected method of mastectomy. These operations allow for the subsequent reconstruction with the whole spectrum of reconstructive options.

Dysfunction of calcium-regulated exocytosis at a single-cell level causes catecholamine hypersecretion in patients with pheochromocytoma

Neuroendocrine tumors constitute a heterogeneous group of tumors arising from hormone-secreting cells and are generally associated with a dysfunction of secretion. Pheochromocytoma (Pheo) is a neuroendocrine tumor that develops from chromaffin cells of the adrenal medulla, and is responsible for an excess of catecholamine secretion leading to severe clinical symptoms such as hypertension, elevated stroke risk and various cardiovascular complications. Surprisingly, while the hypersecretory activity of Pheo is well known to pathologists and clinicians, it has never been carefully explored at the cellular and molecular levels. In the present study, we have combined catecholamine secretion measurement by carbon fiber amperometry on human tumor cells directly cultured from freshly resected Pheos, with the analysis by mass spectrometry of the exocytotic proteins differentially expressed between the tumor and the matched adjacent non-tumor tissue. In most patients, catecholamine secretion recordings from single Pheo cells revealed a higher number of exocytic events per cell associated with faster kinetic parameters. Accordingly, we unravel significant tumor-associated modifications in the expression of key proteins involved in different steps of the calcium-regulated exocytic pathway. Altogether, our findings indicate that dysfunction of the calcium-regulated exocytosis at the level of individual Pheo cell is a cause of the tumor-associated hypersecretion of catecholamines.

BILOBED FLAP IN FACIAL RECONSTRUCTION

INTRODUCTION

The bilobed flap was first described by Esser in 1918. He used it to reconstruct the defects of the nose. It has been used in the reconstructions of trunk and feet defects by many authors since then. Its principle is also advantageous in reconstructions of larger facial defects. Successful reconstruction of problematic suborbital area using the bilobed flap was reported by Yenidunya in 2007. The design of the flap can be successfully used in other atypical facial defects.

MATERIAL AND METHODS

The bilobed flap was used to cover facial defects of 199 patients who underwent 203 tissue reconstructions from 1st January 2007 to 31st December 2016 at the Department of Plastic and Aesthetic Surgery St. Anne´s University Hospital in Brno.

RESULTS

The flaps were equally distributed between the genders, men 101 and women 98. Ages of patients ranged from 39 to 98 years (mean 76 years). It was used in the reconstruction of the tip and alars defects of the nose 159 times, in the reconstruction of periorbital defects 16 times and in other atypical facial areas 28 times. The excision of malignant tumours of the face (basal cell carcinoma, squamous cell carcinoma, SSM) were usually the causes of the defects (89.7%). There were 80 cases with defects of the nasal tip and ala in men and 79 cases in women. Complications occurred 41 times of all reconstructions (20.2%). The most common complication was abundance of the flap (4.9%). The postoperative results were favourable due to the preservation of colour, texture and function of the reconstructed areas.

CONCLUSION

Bilobed flap in different modifications should always be considered in the reconstruction of extensive defects of the face, because unlike other techniques, it preserves good texture and colour of facial skin with minimal donor site morbidity.

INTRAOPERATIVE FAT GRAFTING INTO THE PECTORALIS AND LATISSIMUS DORSI MUSCLES-NOVEL MODIFICATION OF AUTOLOGOUS BREAST RECONSTRUCTION WITH EXTENDED LATISSIMUS DORSI FLAP

BACKGROUND

The latissimus dorsi flap is a reliable and one of the most commonly used methods of both immediate and delayed breast reconstruction. Its disadvantage is the limited volume of transferred tissue. The authors present their experience with the use of extended latissimus dorsi flap associated with immediate fat grafting into the pectoralis and latissimus dorsi muscles for secondary breast reconstruction.

METHODS

From 2013 to 2016, 14 patients underwent secondary unilateral total breast reconstruction with extended latissimus dorsi flap associated with primary fat grafting into the pectoralis major and latissimus dorsi muscles. Fat was injected under visual control between muscle fibers. Fat injected into the pectoralis muscle formed an apparent bulging - autoprosthesis.

RESULTS

Mean patient age was 48.2 years (range, 34 to 64 years). Mean injected fat volume was 86.4 ml (range, 50 to 160 ml) and majority of this volume was injected into the pectoralis muscle. All flaps healed uneventfully and no fat grafting-related complications were observed. The most common complication was donor site seroma, which occurred in 57.1%. Results of postoperative ultrasound examination were evaluated. Incidence and the size of oil cysts and fat necroses were significantly lower in muscular layer in comparison with the subcutaneous layer of the reconstructed breast.

CONCLUSIONS

Immediate fat transfer into the pectoralis and latissimus dorsi muscle increases the breast volume during the reconstruction with extended latissimus dorsi flap avoiding implant-related complications when abdominal tissue is not available. Pectoralis and latissimus dorsi muscles were shown as reliable and safe recipients for fat grafting.

Reconstruction of large facial and orbital defects by combining free flap transfer with craniofacial prosthesis

The reconstruction of complex craniofacial and orbital defects should satisfactorily restore functional and aesthetic integrity. Autologous reconstruction of nasal, periorbital and auricular facial subunits as a whole using a locoregional or a free flap is very challenging and the results are not sometimes ideal. With advanced technologies that are currently available it is possible to plan and produce authentic facial prosthesis that can satisfactory substitute these facial subunits. We demonstrate an alternative reconstructive concept for complex craniofacial defects based on a free flap combined with a facial prosthesis for the replacement of periorbital or auricular facial subunits. This approach was used in two patients with very satisfactory results. Combination of a free flap with a facial prosthesis may become a preferable approach for the reconstruction of complex craniofacial defects. Clinical outcomes of the reconstructions may be enhanced respecting the principle of aesthetic facial subunits.

OUR PRELIMINARY EXPERIENCE WITH A NEW METHOD OF DIEAp FLAP DISSECTION

BACKGROUND

The abdominal tissue is an ideal source for autologous breast reconstruction. We propose a new approach for intramuscular dissection of a DIEP flap in this paper.

METHODS

A total of 84 women underwent breast reconstruction after mastectomy. From this group, 49 patients were treated with traditional DIEP flap of which 21 had unilateral procedure and 28 had bilateral procedure. This new type of dissection was performed in 35 women, with unilateral approach in 14 cases and bilateral approach in 21 cases.

RESULTS

The statistical differences are not significant in the two groups with regards to complications (p > 0.1). Mean operative time in this new approach was 3 hours and 10 minutes per flap. Mean operative time in the traditional dissection of DIEP was 3 hours and 41 minutes per flap. The operative time of the new approach is significantly shorter than the dissection of the traditional DIEP flap (p < 0.01).

CONCLUSION

The approach to DIEP flap dissection proposed by the authors is a new concept in autologous breast reconstruction. In this type of dissection no fascia is resected and it is more reliable than a traditional DIEP flap for the ease of dissection and for the presence of a small protective cuff of muscle around the vessel with a lower risk of perforator injury.It is a reproducible option of dissection, useful also in less experienced hands and it is a time reducing technique compared with the traditional DIEP flap.

Lipomodelling - advanced technique for the correction of Congenital hypoplastic breast malformations and deformities

A variety of surgical techniques has been used to correct hypoplastic breast malformations and deformities, including tissue expanders, breast implants, custom chest wall implants, mammary gland remodelling, as well as locoregional or free flap. Case series of successful breast reconstruction using lipomodelling technique in one patient with severe Polands syndrome and two patients with tuberous breasts are reported together with literature review. No surgical complications were observed and ultrasound examination did not reveal any pathology in breast tissue other than oil pseudocysts postoperatively. In both malformations, submammary fold was moved downwards. Moreover, the lower part of the breast and areolar herniation was corrected in tuberous breast, and in Polands syndrome, the areolar complex was significantly shifted downwards and laterally. In comparison with other reconstructive techniques, lipomodelling allows for the breast correction to begin in early adolescence. Further growth of the unaffected breast may be effectively corrected by subsequent lipomodelling session. This technique appears to change the overall approach to the management of hypoplastic breast and chest wall malformations.

TWISTED DISTAL LATERAL ARM FLAP FOR IMMEDIATE RECONSTRUCTION OF THUMB AVULSION INJURY

BACKGROUND

Replantation is a complicated procedure in avulsion injuries in majority of the cases. When replantation of an avulsed thumb is not feasible, it is mandatory to find an appropriate reconstruction choice as soon as possible due to the importance of the thumb function in the dynamics of the handgrip.

MATERIALS AND METHODS

Three patients with skin avulsion injury underwent immediate reconstruction by twisted lateral arm flap in our department since 2004.

RESULTS

No infection, hematoma, partial or complete flap necrosis were observed after the procedure. All of the flaps healed without complications.

CONCLUSION

Although the gold standard in reconstruction of these trauma defects is the use of local skin flaps or distant inguinal flap, these reconstructive choices have multiple drawbacks such as the loss of sensibility and they are thicker. In thispaper we propose a modification of distally planned lateral arm flap design and a new technique of its spiral shaping for immediate thumb reconstruction.

Dorsoradial forearm flap with silicone bone spacer in reconstruction of A combined THUMB injury - case report

Osseous reconstruction of the thumb following traumatic bone loss can be approached through a variety of techniques. The use of a silicone spacer with secondary bone grafting is a valid therapeutic option. In case of combined injuries, simultaneous immediate reconstruction of missing soft tissues over the spacer by well-vascularised skin cover is essential. Dorsoradial forearm flap has recently been described as distally based cutaneous pedicled flap on the dorsoradial artery, a constant branch of the radial artery. A case of a 52-year-old male patient with a combined injury of the thumb with bone loss of the proximal phalanx and with the loss of dorsal skin reconstructed primarily with bone silicon spacer and together with emergency dorsoradial forearm flap is reported together with a brief literature review.

VASOSPASM OF THE FLAP PEDICLE--MAGNESIUM SULPHATE RELIEVES VASOSPASM OF AXIAL FLAP PEDICLE IN PORCINE MODEL

BACKGROUND

The effect of magnesium sulphate on mechanically provoked vasospasm of the flap pedicle on porcine model was not studied yet. Positive effect of magnesium sulphate on vasospasm was proved in previous studies on rat.

METHODS

The bilateral pedicled flaps based on the caudal superficial epigastric arteries were raised on 8 pigs. Flaps on the right side were the treatment group; flaps on the left side were the control group. The vasospasm was provoked by the tension applied on the pedicle in the axial direction using 160g weight. The blood perfusion of the flap was monitored using laser-Doppler. The duration of the vasospasm was defined as the time from the release of the tension until the blood flow began to rise. These times were detected using an automated computerized detection. In the treatment group, magnesium sulphate was given topically on the vessel; saline was used in the control group.

RESULTS

The duration of the vasospasm in the treatment group was significantly shorter than in the control group (P = 0.024).

CONCLUSION

Magnesium sulphate 10% shortened significantly the mechanically provoked vasospasm on caudal superficial epigastric flap in a porcine model. Further clinical studies are needed to prove the effect in humans.

The use of medicinal leeches in fingertip replantation without venous anastomosis - case report of a 4-year-old patient

Replantation of amputated fingertip is a technical challenge to the microsurgeons. The success rate depends directly on the availability and the size of preserved vessels and on the degree of their damage. In distal digital amputations, veins are usually not easily recovered or even absent, and thus high number of replantation procedures fails because of the venous congestion. The use of medicinal leeches is a treatment option for venous congestion of replanted fingers. A case report of a 4-year-old patient after fingertip replantation without venous anastomosis when temporary venous drainage was provided by an application of medicinal leeches is reported together with literature review. We observed an unusually short duration of venous congestion (48 hours) and there was no need of blood transfusion.

Vasospasm of the flap pedicle - the new experimental model on rat

BACKGROUND

An experimental model for testing vasodilating drugs on vasospasm caused by standardized traumatisation of a pedicle has not been described yet. The aim of this study was to develop such model and to compare the effects of different types of surgical manipulations that can provoke vasospasm during flap dissection.

MATERIAL AND METHODS

The pedicled groin flap was dissected in 185 male Wistar rats under standardised conditions. The blood perfusion curves of the flap were obtained using the Laser Doppler flow-meter. The vasospasm was provoked by the following manoeuvres: pulling on the pedicle; compression of the pedicle by vascular clamps; dissection of the vessels and by presence of blood around the pedicle. The perfusion recording curves were processed and two important time periods describing the progress of spasm were extracted. Combined non-parametrical ANOVA and WILCOXON tests were used to compare the time parameters between the groups. On the basis of statistical evaluation, we divided the factors responsible for vasospasm into categories labelled as strong and weak. The strong stimuli included dissection of the vessels; pulling on the pedicle using 15g, 20g and 25g weights and presence of blood around the pedicle. The weak stimuli included compression of the pedicle using vascular clamps and pulling on the pedicle using 10g weight. Pulling on the pedicle using 15g weight was chosen as the most appropriate stimulus for the experimental model.

RESULTS

A new experimental model for studying vasospasm caused by tension on the pedicle was developed. This model is well defined, easily repeatable and reproducible, produces vasospasm of appropriate duration and permits standardized topical application of vasodilating drugs.

DISCUSSION AND CONCLUSION

The finding that certain kind of surgical traumatisation causes vasospasm that is longer than the others may help microsurgeons to review their methods of surgical manipulation.

Lipomodelling: an important advance in breast surgery

Based on long-term experiences, the authors consider lipomodelling to be a major advance in plastic, reconstructive and aesthetic surgery of the breast. The technique is now well established and the complication rate is very low. The risk of focal fat necrosis is around 3%. Oncological follow-up (now 14 years for the first patients) shows no increased risk of local recurrence or development of a new cancer. 30-40% of the injected fat is absorbed. Volume of the breast becomes stable in 3 to 4 months and remains definitive if the patient maintains constant weight. Because of very good results obtained and excellent acceptance of the procedure by the patients, this technique has completely modified our indications. In breast reconstruction, lipomodelling with autologous latissimus dorsi flap enables obtaining an entirely autologous breast in the majority of the patients. Analogically, lipomodelling can improve results of implant reconstructions, especially if the expander or the implant is planned to be exchanged. Lipomodelling is an effective tool for correction deformities especially in the décolleté after breast reconstruction with abdominal flap (DIEP, SIEA and TRAM). Lipomodelling is also progressively used in the correction of breast and chest wall deformities. In Poland syndrome, this technique appears to be a major advance that will probably revolutionize the treatment of severe cases. This is mainly due to its ability to achieve previously unachievable quality of reconstruction with minimal scaring. The application of lipomodelling in the treatment of pectus excavatum deformities is promising. Lipomodelling represents an advanced therapeutic alternative for tuberous breasts without the need to use an implant, as well as for breast asymmetry due to unilateral hypoplasia. Lipomodelling is an ideal option for cosmetic breast augmentation in patients who wish to achieve moderate, natural enlargement of breasts and who have considerable fat deposits.

The effect of blood around a flap pedicle on flap perfusion in an experimental rodent model

BACKGROUND

The vasospasm has been studied to a considerable extent in the neurosurgical literature. Little experimental and basic scientific literature about vasospasm of flap pedicle is available in the field of reconstructive microsurgery. The purpose of the study was to investigate the effect of presence of blood around the pedicle on a flap perfusion.

MATERIAL AND METHODS

Blood flow through a right groin flap was continuously measured using Laser Doppler flowmetry on 40 male Wistar rats. A segment of the flap's pedicle was surgically cleared of adventitia and bathed in blood. The blood used was either collected from the tail of the rat (group A) or from the bleeding branch of the pedicle itself (group B). The differences between the signal amplitudes before and after exposure of the pedicle to blood were recorded.

RESULTS

The presence of blood around the pedicle resulted in a significant decrease in perfusion of the flap in both groups. However, no significant differences in the duration of impaired blood flow between the groups were observed.

CONCLUSIONS

In conclusion, the presence of blood around the vascular pedicle may cause a significant decrease in the perfusion of a flap, while the origin of the blood does not appear to be an important factor.

The efficacy of magnesium sulfate on resolving surgically provoked vasospasm of the flap pedicle in an experiment

BACKGROUND

Vasospasm frequently accompanies manipulation of small vessels during free flap surgeries and replantations. The purpose of this experimental study was to evaluate the effect of magnesium sulphate on vasospasm provoked by surgical manipulation (axial tension) on the flap pedicle. This kind of surgical manipulation of the vessel cannot be studied in a clinical environment without putting flap viability into risk.

MATERIAL AND METHODS

Forty male Wistar rats weighing around 300 g each were classified in two experimental groups (n=20 in each). In the treatment group (group A) Magnesium Sulphuricum 10% (Biotika, Czech Republic) was applied; the second group (group B) served as a control. The vasopasm was provoked by pulling the pedicle of the right groin flap of the rat. The peripheral blood perfusion of the flap was continuously measured using laser-Doppler recording. In the study group, magnesium sulphate was applied topically on the flap pedicle to relieve vasospasm, and duration of the vasospasm was compared to the control group.

RESULTS

A statistically significant difference (p=0.01) between the groups was found. The duration of vasospasm was significantly shorter in the treatment group A.

CONCLUSIONS

We conclude that in an experimental environment magnesium sulphate is effective in relieving surgically provoked vasospasm of the flap pedicle. This finding is in accordance with our clinical observations.

Feruloylputrescine and Caffeoylputrescine Are Not Involved in Growth and Floral Bud Formation of Stem Explants from Nicotiana tabacum L. var Xanthi nc

The role of feruloylputrescine (FP) and of caffeoylputrescine (CP) was investigated in an explant system of stem explants from day-neutral Nicotiana tabacum L. var Xanthi nc. Previously, a correlation between cortical callus formation and increase in FP content, as well as between in vitro flower formation and increase in CP content had been shown. During the explant growth in vitro, the increase of both FP and CP was inhibited by 4-fluor-(1-amino-2-phenylethyl)phosphonic acid and 2-amino-indene-2-phosphonic acid, both inhibitors of phenylalanine ammonia-lyase (EC 4.3.1.5). dl-alpha-difluoromethylarginine, an inhibitor of arginine decarboxylase (ADC, EC 4.1.1.19), prevented only the increase in FP, while dl-alpha-difluoromethylornithine, an inhibitor of ornithine decarboxylase (EC 4.1.1.17), reduced only that of CP. Increase in dry weight and the formation of cortical callus and of floral buds of explants were not affected by any of the inhibitors. We conclude, in contrast to earlier hypotheses, that FP and CP do not trigger growth and differentiation in the explants. It seems more likely that FP and CP increase in response to auxin and cytokinin in the media.

A method for the separation and partial purification of the three forms of nitrate reductase present in wild-type soybean leaves

A rapid and simple purification method was used to separate and purify nitrate reductases (NR) from Williams soybean leaves. Blue Sepharose columns were sequentially eluted with 50 millimolar NADPH and 50 millimolar NADH, thus separating NAD(P)H:NR from NADH:NRs. Subsequent purification of the collected peaks on a fast protein liquid chromatography-Mono Q column enabled separation of two NADH:NRs. Sodium dodecyl sulfate polyacrylamide gel electrophoresis revealed that the subunit relative molecular mass for all three NR forms (constitutive NAD(P)H:NR [pH 6.5], EC 1.6.6.2; constitutive NADH:NR [pH 6.5], EC not assigned; and inducible NADH:NR [pH 7.5], EC 1.6.6.1) was approximately 107 to 109 kilodaltons. All three NRs showed similar spectra with absorption maxima at 413 and 273 nanometers in the oxidized state, and with the characteristics of a cytochrome b type heme upon reduction with NADH (absorption maxima at 556, 527, and 424 nanometers). The technique developed provides an improved separation of the three NR forms from soybean leaves. The similarity of the NRs with regard to their cytochrome b(556) type heme content and in relative molecular mass indicated that other differences must exist to account for the different kinetic and physical properties previously reported.

Biochemical Characterization of Soybean Mutants Lacking Constitutive NADH:Nitrate Reductase

Two nitrate reductase (NR) mutants were selected for low nitrate reductase (LNR) activity by in vivo NR microassays of M(2) seedlings derived from nitrosomethylurea-mutagenized soybean (Glycine max [L.] Merr. cv Williams) seeds. The mutants (LNR-5 and LNR-6) appeared to have normal nitrate-inducible NR activity. Both mutants, however, showed decreased NR activity in vivo and in vitro compared with the wild-type. In vitro FMNH(2)-dependent nitrate reduction and Cyt c reductase activity of nitrate-grown plants, and nitrogenous gas evolution during in vivo NR assays of urea-grown plants, were also decreased in the mutants. The latter observation was due to insufficient generation of nitrite substrate, rather than some inherent difference in enzyme between mutant and wild-type plants. When grown on urea, crude extracts of LNR-5 and LNR-6 lines had similar NADPH:NR activities to that of the wild type, but both mutants had very little NADH:NR activity, relative to the wild type. Blue Sepharose columns loaded with NR extract of urea-grown mutants and sequentially eluted with NADPH and NADH yielded a NADPH:NR peak only, while the wild-type yielded both NADPH: and NADH:NR peaks. Activity profiles confirmed the lack of constitutive NADH:NR in the mutants throughout development. The results provide additional support to our claim that wild-type soybean contains three NR isozymes, namely, constitutive NADPH:NR (c(1)NR), constitutive NADH:NR (c(2)NR), and nitrate-inducible NR (iNR).

Nitrate Reductases from Wild-Type and nr(1)-Mutant Soybean (Glycine max [L.] Merr.) Leaves : II. Partial Activity, Inhibitor, and Complementation Analyses

Soybean (Glycine max [L.] Merr.) leaves have been shown to contain three forms of nitrate reductase (NR). Two of the forms, which are present in leaves of wild-type (cv. Williams) plants grown in the absence of NO(3) (-), are termed constitutive and designated c(1)NR and c(2)NR. The third form, which is present in NO(3) (-)-grown mutant (nr(1)) plants lacking the constitutive forms, is termed inducible and designated iNR. Samples of c(1)NR, c(2)NR, and iNR obtained from appropriately treated plants were analyzed for the presence of partial activities, response to inhibitors, and ability to complement a barley NR which lacks the molybdenum cofactor (MoCo) but is otherwise active.The three forms were similar to most assimilatory NR enzymes in that they (a) exhibited NADH-cytochrome c reductase, reduced flavin mononucleotide-NR, and reduced methyl viologen-NR partial activities; (b) were inhibited by p-hydroxymercuribenzoate at the site of initial electron transport through each enzyme; (c) were more inhibited by CN(-) in their reduced enzyme state as compared with their oxidized state; and (d) complemented a MoCo-defective NR (e.g. contained cofactors with characteristics similar to the MoCo found in barley NR and commercial xanthine oxidase). However, among themselves, they showed dissimilarities in their response to treatment with HCO(3) (-) and CN(-), and in their absolute ability to complement the barley NR. The site of effect for these treatments was the terminal cofactor-containing portion of each enzyme. This indicated that, although a terminal cofactor (presumably a MoCo) was present in each form, structural or conformational differences existed in the terminal cofactor-protein complex of each form.

Nitrate Reductases from Wild-Type and nr(1)-Mutant Soybean (Glycine max [L.] Merr.) Leaves : I. Purification, Kinetics, and Physical Properties

NADH:nitrate reductase (EC 1.6.6.1) and NAD(P)H:nitrate reductase (EC 1.6.6.2) were purified from wild-type soybean (Glycine max [L.] Merr., cv Williams) and nr(1)-mutant soybean plants. Purification included Blue Sepharose- and hydroxylapatite-column chromatography using acetone powders from fully expanded unifoliolate leaves as the enzyme source.Two forms of constitutive nitrate reductase were sequentially eluted with NADPH and NADH from Blue Sepharose loaded with extract from wild-type plants grown on urea as sole nitrogen source. The form eluted with NADPH was designated c(1)NR, and the form eluted with NADH was designated c(2)NR. Nitrate-grown nr(1) mutant soybean plants yielded a NADH:nitrate reductase (designated iNR) when Blue Sepharose columns were eluted with NADH; NADPH failed to elute any NR form from Blue Sepharose loaded with this extract. Both c(1)NR and c(2)NR had similar pH optima of 6.5, sedimentation behavior (s(20,w) of 5.5-6.0), and electrophoretic mobility. However, c(1)NR was more active with NADPH than with NADH, while c(2)NR preferred NADH as electron donor. Apparent Michaelis constants for nitrate were 5 millimolar (c(1)NR) and 0.19 millimolar (c(2)NR). The iNR from the mutant had a pH optimum of 7.5, s(20,w) of 7.6, and was less mobile on polyacrylamide gels than c(1)NR and c(2)NR. The iNR preferred NADH over NADPH and had an apparent Michaelis constant of 0.13 millimolar for nitrate.Thus, wild-type soybean contains two forms of constitutive nitrate reductase, both differing in their physical properties from nitrate reductases common in higher plants. The inducible nitrate reductase form present in soybeans, however, appears to be similar to most substrateinduced nitrate reductases found in higher plants.

Immunochemical Characterization of Nitrate Reductase Forms from Wild-Type (cv Williams) and nr(1) Mutant Soybean

Soybean (Glycine max L. Merr.) leaves contain two forms of nitrate reductase (NR)-NAD(P)H:NR and NADH:NR. Wild-type (cv Williams), nr(1) mutant and an unrelated cultivar (Prize) were grown with either no N source or with nitrate. Crude extracts were assayed for NR activities and the enzyme forms were purified on blue Sepharose. Analyses were done by polyacrylamide gel electrophoresis and ;Western blotting' using antibodies specific for NR. NAD(P)H:NR was identified as the constitutive NR present in wild-type and Prize, but was absent from the mutant. All three soybean lines contained nitrate-inducible NADH:NR with highest activity at pH 7.5. The results showed that NAD(P)H:NR and constitutive NR were one in the same and confirmed the presence of NADH:NR with pH 7.5 optimum.