Timing to First Whole Blood Transfusion and Survival Following Severe Hemorrhage in Trauma Patients

Importance

Civilian trauma centers have revived interest in whole-blood (WB) resuscitation for patients with life-threatening bleeding. However, there remains insufficient evidence that the timing of WB transfusion when given as an adjunct to a massive transfusion protocol (MTP) is associated with a difference in patient survival outcome.

Objective

To evaluate whether earlier timing of first WB transfusion is associated with improved survival at 24 hours and 30 days for adult trauma patients presenting with severe hemorrhage.

Design, Setting, and Participants

This retrospective cohort study used the American College of Surgeons Trauma Quality Improvement Program databank from January 1, 2019, to December 31, 2020, for adult patients presenting to US and Canadian adult civilian level 1 and 2 trauma centers with systolic blood pressure less than 90 mm Hg, with shock index greater than 1, and requiring MTP who received a WB transfusion within the first 24 hours of emergency department (ED) arrival. Patients with burns, prehospital cardiac arrest, deaths within 1 hour of ED arrival, and interfacility transfers were excluded. Data were analyzed from January 3 to October 2, 2023.

Exposure

Patients who received WB as an adjunct to MTP (earlier) compared with patients who had yet to receive WB as part of MTP (later) at any given time point within 24 hours of ED arrival.

Main Outcomes and Measures

Primary outcomes were survival at 24 hours and 30 days.

Results

A total of 1394 patients met the inclusion criteria (1155 male [83%]; median age, 39 years [IQR, 25-51 years]). The study cohort included profoundly injured patients (median Injury Severity Score, 27 [IQR, 17-35]). A survival curve demonstrated a difference in survival within 1 hour of ED presentation and WB transfusion. Whole blood transfusion as an adjunct to MTP given earlier compared with later at each time point was associated with improved survival at 24 hours (adjusted hazard ratio, 0.40; 95% CI, 0.22-0.73; P = .003). Similarly, the survival benefit of earlier WB transfusion remained present at 30 days (adjusted hazard ratio, 0.32; 95% CI, 0.22-0.45; P < .001).

Conclusions and Relevance

In this cohort study, receipt of a WB transfusion earlier at any time point within the first 24 hours of ED arrival was associated with improved survival in patients presenting with severe hemorrhage. The survival benefit was noted shortly after transfusion. The findings of this study are clinically important as the earlier timing of WB administration may offer a survival advantage in actively hemorrhaging patients requiring MTP.

A tale of two cities: Policing and firearm homicides in Boston and Philadelphia

BACKGROUND

Recent political movements have raised questions about the effectiveness of police funding, but the impact of law enforcement budgets on firearm violence is unknown. We hypothesized that department funding and measures of police activity would be associated with decreased shootings and firearm homicides (FHs) in two major cities with different police funding patterns.

METHODS

We collected data from the following sources: district attorney's offices, police departments, Federal Bureau of Investigation Uniform Crime Reporting program, the Centers for Disease Control, the Annual Survey of Public Employment and Payroll, and the American Community Survey. Data included demographics, police department budgets, number of officers, homicide clearance rates, firearms recovered, shootings, and FHs, 2015 to 2020. Totals were normalized to population and number of shootings. We used panel linear regression to measure associations between policing variables, shootings, and FHs while adjusting for covariates.

RESULTS

Firearm homicides significantly increased in Philadelphia. In Boston, the trend was less clear, although there was an increase in 2020. Police budget normalized to shootings trended toward a decrease in Philadelphia and an increase in Boston. The number of firearms recovered annually appeared to increase in Boston but peaked midstudy in Philadelphia. In multivariable analyses, police budget was associated with neither shootings nor FHs. However, increased firearm recovery was associated with lower shooting ( β = -0.0004, p = 0.022) and FH ( β = -0.00005, p = 0.004) rates.

CONCLUSION

Philadelphia and Boston demonstrated differences in police funding, 2015 to 2020. While budget is not associated with shootings or FHs, firearm recovery is suggesting that removal of firearms from circulation remains key. The impact this has on vulnerable populations requires further investigation.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level IV.

The evolution and development of a robotic acute care surgery program

BACKGROUND

Acute care surgeons perform more than 850,000 operations annually on emergency general surgery patients in the United States. Emergency general surgery conditions are associated with a disproportionate excess of patient complications and death. Innovative quality improvement strategies have focused on addressing the excess morbidity and mortality among this patient population. Minimally invasive surgical techniques have been shown to reduce the burden experienced by emergency general surgery patients. Still, limited adoption by acute care surgeons has restricted this application's potential. An institutional robotics acute care surgery program provides acute care surgeons additional opportunities to expand minimally invasive surgery access to emergency general surgery patients irrespective of the time or day of the week.

METHODS

A robotics acute care surgery program was developed and implemented at a high-volume academic institution within the division of trauma and acute care surgery.

RESULTS

Three attending surgeons and two fellows within the trauma and acute care surgery division had successfully completed a defined robotics clinical pathway. As a result, around-the-clock use of a robotic surgical platform for emergency general surgery cases was implemented with routine use by trained robotic acute care surgeons and practicing fellows.

CONCLUSION

The advancement of robotic surgical technology has opened new avenues for surgical application in the emergency setting. The development of a robotic acute care surgery program allows acute care surgeons to diversify their practice while providing greater access to minimally invasive approaches for emergency general surgery patients.

Association of Whole Blood With Survival Among Patients Presenting With Severe Hemorrhage in US and Canadian Adult Civilian Trauma Centers

Importance

Whole-blood (WB) resuscitation has gained renewed interest among civilian trauma centers. However, there remains insufficient evidence that WB as an adjunct to component therapy-based massive transfusion protocol (WB-MTP) is associated with a survival advantage over MTP alone in adult civilian trauma patients presenting with severe hemorrhage.

Objective

To assess whether WB-MTP compared with MTP alone is associated with improved survival at 24 hours and 30 days among adult trauma patients presenting with severe hemorrhage.

Design, Setting, and Participants

This retrospective cohort study using the American College of Surgeons Trauma Quality Improvement Program databank from January 1, 2017, and December 31, 2018, included adult trauma patients with a systolic blood pressure less than 90 mm Hg and a shock index greater than 1 who received at least 4 units of red blood cells within the first hour of emergency department (ED) arrival at level I and level II US and Canadian adult civilian trauma centers. Patients with burns, death within 1 hour of ED arrival, and interfacility transfers were excluded. Data were analyzed from February 2022 to September 2022.

Exposures

Resuscitation with WB-MTP compared with MTP alone within 24 hours of ED presentation.

Main Outcomes and Measures

Primary outcomes were survival at 24 hours and 30 days. Secondary outcomes selected a priori included major complications, hospital length of stay, and intensive care unit length of stay.

Results

A total of 2785 patients met inclusion criteria: 432 (15.5%) in the WB-MTP group (335 male [78%]; median age, 38 years [IQR, 27-57 years]) and 2353 (84.5%) in the MTP-only group (1822 male [77%]; median age, 38 years [IQR, 27-56 years]). Both groups included severely injured patients (median injury severity score, 28 [IQR, 17-34]; median difference, 1.29 [95% CI, -0.05 to 2.64]). A survival curve demonstrated separation within 5 hours of ED presentation. WB-MTP was associated with improved survival at 24 hours, demonstrating a 37% lower risk of mortality (hazard ratio, 0.63; 95% CI, 0.41-0.96; P = .03). Similarly, the survival benefit associated with WB-MTP remained consistent at 30 days (HR, 0.53; 95% CI, 0.31-0.93; P = .02).

Conclusions and Relevance

In this cohort study, receipt of WB-MTP was associated with improved survival in trauma patients presenting with severe hemorrhage, with a survival benefit found early after transfusion. The findings from this study are clinically important as this is an essential first step in prioritizing the selection of WB-MTP for trauma patients presenting with severe hemorrhage.

Regenerative Medicine: lessons from Mother Nature

Regenerative medicine strategies for the restoration of functional tissue have evolved from the concept of ex vivo creation of engineered tissue toward the broader concept of in vivo induction of functional tissue reconstruction. Multidisciplinary approaches are being investigated to achieve this goal using evolutionarily conserved principles of stem cell biology, developmental biology and immunology, current methods of engineering and medicine. This evolution from ex vivo tissue engineering to the manipulation of fundamental in vivo tenets of development and regeneration has the potential to capitalize upon the incredibly complex and only partially understood ability of cells to adapt, proliferate, self-organize and differentiate into functional tissue.

Sensitivity analysis in a life cycle assessment of an aged red wine production from Catalonia, Spain

Sustainability in agriculture and food processing is an issue with a clear growing interest; especially in products were consumers have particular awareness regarding its environmental profile. This is the case of wine industry depending on grape production, winemaking and bottling. Also viticulture and generally agricultural production is significantly affected by climate variations. The aim of this article is to determine the environmental load of an aged red wine from a winery in Catalonia, Spain, over its entire life cycle, including sensitivity analysis of the main parameters related to the cultivation, vinification and bottling. The life cycle assessment (LCA) methodology is used for the environmental analysis. In a first step, life cycle inventory (LCI) data were collected by questionnaires and interviews with the winemaker, all data are actual operating data and all the stages involved in the production have been taken into account (viticulture, vinification, bottling and the disposal subsystem). Data were then used to determine the environmental profile by a life cycle impact assessment using the ReCiPe method. Annual variability in environmental performance, stresses the importance of including timeline analysis in the wine sector. Because of that this study is accompanied with a sensitivity analysis carried out by a Monte Carlo simulation that takes into account the uncertainty and variability of the parameters used. In this manner, the results are presented with confidence intervals to provide a wider view of the environmental issues derived from the activities of the studied wine estate regardless of the eventualities of a specific harvesting year. Since the beverage packaging has an important influence in this case, a dataset for the production of green glass was adapted to reflect the actual recycling situation in Spain. Furthermore, a hypothetical variation of the glass-recycling rate in the glass production completes this article, as a key variable of sensitivity analysis, in order… in order to show the potential reduction of total greenhouse gas emissions. It was found that in almost all categories the production of the glass bottles has the highest environmental impact (10%-80% depending on the impact category) followed by the viticulture stage, i.e. the agricultural activities (17%-84% depending on the impact category). The vinification step, i.e. the winemaking itself, has an almost negligible effect on the overall load (1%-5%). The sensitivity analysis showed that the results do not differ by more than ±4% from the expected values except for the water depletion indicator. With the variation of the recycling rate, it could be shown that an increase in the rate from 60% to 85% allows for a reduction of 102gCO2eq. per bottle (-11.1%). The results show that glass production causes the highest environmental load. The key parameters that determine the impact are the recycling rate and the bottle weight. A glass container deposit legislation might be a promising way to enhance the glass recycling. Lightweight bottles and alternative packaging should also be considered.

Altered action potential of myocardial cells from mouse fetuses with trisomy 16: a model of Down syndrome

BACKGROUND

Trisomy 21 in humans and trisomy 16 in mice (a model of Down syndrome) are associated with increases in rates of depolarization and repolarization and decreases in duration of action potential of neurons, due to overexpressing protein subunits of Na(+) and K(+) channels in a gene dose-dependent manner. These chromosomes also have genes for voltage-gated Na(+) and K(+) channels expressed by myocardial cells. Thus, it would be expected that heart cells would have alterations in their action potentials similar to those found in neurons in both aneuploidies.

METHODS

Myocardial cells from normal and trisomy 16 mouse fetuses were compared in relation to their electrical membrane properties using intracellular microelectrodes.

RESULTS

At 13 and 17 days of gestation, trisomic cells, as compared with control cells, had higher amplitude and rates of depolarization and repolarization, with lower duration of plateau of action potential at 25, 50, and 75% of repolarization. This suggests that Ca(2)+ influx is reduced in trisomic cells, which could impair Ca(2)+-dependent fetal myocardial functions (i.e., contractility or matrix secretion).

CONCLUSIONS

Myocardial cells of Ts-16 mice showed electrophysiologic alterations qualitatively similar to those observed in trisomic neurons, in agreement with the gene dose-dependent hypothesis (see Introduction).

Ahaustral colonic segment following trauma: a possible sign of seromuscular tear

Although traumatic seromuscular tears of the colon are often managed conservatively, it is pertinent to detect the tear since it poses a risk for acute or delayed perforation. Unfortunately, clinical findings are inadequate for detecting and monitoring this lesion. Therefore, this complication has not been recognized prior to laporatomy. We have noted that an ahaustral colonic segment following trauma may be a potential marker for seromuscular tear.

Preoperative chemoradiotherapy alters the expression and prognostic significance of adhesion molecules in Barrett's-associated adenocarcinoma

A variety of prognostic markers have been related to decreased patient survival in patients with epithelial malignancies. These include expression of the homotypic adhesion molecule E-cadherin (ECAD) and the hyaluronic acid receptor CD44. Expression of ECAD and CD44 was evaluated in Barrett's-associated adenocarcinoma (BAd) from 67 patients. Expression was determined by immunoperoxidase staining and graded semiquantitatively based on the proportion of positively stained cells. These data were then correlated with clinical and pathological parameters, including the presence or absence of chemoradiotherapy (chemrad) and patient survival. There were 56 men and 11 women (mean age, 62 years). Thirty-nine (58%) patients received preoperative chemrad. ECAD expression was detected in all (100%) tumors. The ECAD staining grade did not correlate with other pathological features of the tumors. However, ECAD staining was significantly increased in BAd of patients who received chemrad (P = .003), in comparison with those who did not, and in individual patients when prechemrad biopsies and postchemrad resection specimens were compared (P = .04). In terms of prognosis, increased ECAD expression was associated with shortened patient survival only in BAd patients who had received chemrad (univariate analysis of chemrad patients with stage I and II BAd, P = .02). ECAD expression was not significantly associated with survival in BAd patients who did not receive chemrad. CD44 expression was detected in 88% of cases. CD44 expression did not correlate with any of the pathological features of the tumors or with chemrad status. Increased expression of CD44 was significantly associated with shortened patient survival in chemrad patients only (univariate analysis P = .03, multivariate analysis P = .04), although a strong trend was observed when all patients were analyzed regardless of chemrad status (P = .07). The results of this study indicate that chemrad alters the expression of ECAD in BAd. Thus, the prognostic utility of ECAD expression must be evaluated in the context of chemrad status. CD44 also may be a valuable prognostic marker in BAd.

Protein kinase C ligands based on tetrahydrofuran templates containing a new set of phorbol ester pharmacophores

A series of substituted tetrahydrofurans with an embedded glycerol backbone carrying additional tetrahydrofuranylideneacetate or tetrahydrofuranylacetate motifs were grouped into four distinct templates (I-IV) according to stereochemistry. The compounds were designed to mimic three essential pharmacophores (C(3)-C=O, C(20)-OH and C(13)-C=O) of the phorbol esters according to a new, revised model. The tetrahydrofuran ring was constructed from glycidyl 4-methoxyphenyl ether, and the structures of the isomeric templates were assigned by NMR spectroscopy, including NOE. The binding affinity for protein kinase C (PKC) was assessed in terms of the ability of the ligands to displace bound [(3)H-20]phorbol 12, 13-dibutyrate (PDBU) from a recombinant alpha isozyme of PKC. Geometric Z- and E-isomers (1 and 3, respectively) containing a tetrahydrofuranylideneacetate motif were the most potent ligands with identical K(i) values of 0.35 microM. Molecular modeling studies of the four templates showed that the rms values when fitted to a prototypical phorbol 12,13-diacetate ester correlated inversely with affinities in the following order: I approximately II > III > IV. These compounds represent the first generation of rigid glycerol templates seeking to mimic the binding of the C(13)-C=O of the phorbol esters. The binding affinities of the most potent compounds are in the same range of the diacylglycerols (DAGs) despite the lack of a phorbol ester C(9)-OH pharmacophore surrogate. This finding confirms that mimicking the binding of the C(13)-C=O pharmacophore of phorbol is a useful strategy. However, since the C(9)-OH and C(13)-C=O in the phorbol esters appear to form an intramolecular hydrogen bond that functions as a combined pharmacophore, it is possible the lack of this combined motif in the target templates restricts the compounds from reaching higher binding affinities.

Pathologic prognostic factors in esophageal squamous cell carcinoma: a follow-up study of 74 patients with or without preoperative chemoradiation therapy

One of the primary goals of pathologic examination of esophageal squamous cell carcinoma resection specimens is to provide information regarding morphologic features which can help prognosticate and guide management of affected patients. The purpose of this study was to determine the prognostic utility of a variety of histopathologic prognostic factors in patients with esophageal squamous cell carcinoma with and without preoperative chemotherapy and radiotherapy (chemrad). Multiple clinical and histologic features such as peri-tumoral lymphocytic infiltrate, Crohn's-like lymphoid reaction, degree of residual tumor, mitosis per 1000 cells, tumor differentiation, lymphatic/vascular invasion, perineural invasion, desmoplastic reaction, and tumor growth pattern were evaluated in patients with (53) and without (21) preoperative chemrad and correlated with survival (mean follow-up, 25 mo). Data were analyzed for the entire cohort and for each separate treatment group by univariate and multivariate analysis. Patients who received chemrad showed no significant survival benefit (hazard ratio = 2.5, P = .10). In the whole cohort of patients, higher pathologic stage (P = .04), poor tumor differentiation (P = .003), increased mitotic count (P = .005), perineural invasion (P = .01), lymphatic/vascular invasion (P = .002), tumor size (P = .05), and absence of a Crohn's-like lymphoid reaction (P = .05) were significantly associated with poor survival by univariate analysis. In multivariate analysis, poor tumor differentiation (P = .005), high mitotic count (P = .01), and vascular invasion (P = .03) were important prognostic features, independent of pathologic stage, for the entire cohort. In the chemrad group only, tumor size (in patients with macroscopic residual tumor) (P = .05), lymph node metastasis (P = .03), mitotic count (P = .01), and lymphatic/vascular invasion (P = .02) were significant prognostic indicators by univariate analysis. Upon multivariate analysis, only lymphatic/vascular invasion (P = .02) and mitotic rate (P = .01) were independent predictors of survival. In the nonchemrad group, only tumor differentiation was significant by both univariate (P = .008) and multivariate analysis (P = .03). The differences in pathologic prognostic factors between chemrad and nonchemrad treated cases suggests that chemrad has a significant effect on the biologic properties of these tumors.

P53 and beta catenin expression in chronic ulcerative colitis--associated polypoid dysplasia and sporadic adenomas: an immunohistochemical study

In patients with chronic ulcerative colitis (CUC), polypoid dysplastic lesions (PDLs) are morphologically similar to sporadic adenomas (SAs), but may be biologically distinct from them and are managed differently. p53 mutations have been shown to occur at an earlier phase in the progression of CUC-associated neoplasia when compared with sporadic colon carcinogenesis. In contrast, APC gene mutations are common and occur at an earlier stage in the development of SA. beta catenin is a cell membrane protein that accumulates in the nucleus of colon cancer cells in response to APC gene mutations. This study was performed to test the hypothesis that CUC-associated PDLs have a different molecular profile than do CUC-associated SAs and therefore may be distinguished on this basis. Mucosal biopsy specimens of 38 benign polypoid epithelial neoplasms (17 CUC-associated PDLs and 21 CUC-associated SAs) from 33 patients with CUC and 13 SAs from patients without CUC (controls) were immunohistochemically stained for p53 and beta catenin and graded as follows: 0 = no staining, 1+ = <50% of cells positive, and 2+ = > or =50% of cells positive. The results were correlated with the clinical and histologic features and compared between the two CUC-associated polyp subgroups. Overall, six (16%) polyps were p53-positive, of which five were CUC-associated PDLs (one 1+ and four 2+) and one was a CUC-associated SA (1+) (p = 0.05). Strong (2+) p53 positivity was detected, however, in only CUC-associated PDLs (4 of 5; 80%). Nine of 32 polyps evaluated for beta catenin were positive and included 1 (8%) of 12 CUC-associated PDLs and 8 (40%) of 20 CUC-associated SAs (p = 0.06). Two of the nine beta catenin polyps were strongly positive, and both were CUC-associated SAs. Non-CUC-associated (control) SAs were positive for p53 and beta catenin in 2 (15%) of 13 and 6 (46%) of 13 cases, but none in a strong (2+) fashion. No differences were observed in p53 or beta catenin staining, between CUC-associated and non-CUC-associated SAs. Neither p53 nor beta catenin expression correlated with any clinical or pathologic features, including size and degree of dysplasia of the polyps. CUC-associated PDLs and CUC-associated SAs may have a different molecular genotype. In patients with CUC, the combination of strong p53 expression and absent or weak beta catenin expression is evidence in favor of a CUC-associated PDL in diagnostically difficult lesions. Furthermore, CUC-associated and non-CUC-associated SAs have a similar P53 and beta catenin immunophenotype and thus provide evidence that they are pathogenetically related neoplasms regardless of the presence or absence of colitis.

Evaluation of organophosphorus pesticide residues in citrus fruits from the Valencian community (Spain)

Approximately 200 citrus samples from markets of the Valencian Community (Spain) were analyzed to establish their residue levels in 12 organophosphorus pesticide residues during the 1994-1995 campaign. The organophosphorus pesticides carbophenothion, chlorpyriphos, chlorfenvinphos, diazinon, ethion, fenitrothion, malathion, methidation, methylparathion, phosmet, quinalphos, and tetradifon were simultaneously extracted by matrix solid-phase dispersion and determined by gas chromatography-mass spectrometry using selected ion monitoring mode. A total of 32.25% contained pesticide residues and 6.9% exceeded the European Union Maximum Residue Levels (MRLs). The pesticides found in the samples with residues above MRLs were carbophenothion, ethion, methidathion, and methyl parathion. Lower level residues of these and the other pesticides studied (except diazinon) were frequently found. The estimated daily intake of the 12 organophosphorus pesticide residues during the studied period was 4.87 x 10(-4) mg/kg body weight/day. This value is lower than the provisional tolerances dairy intakes proposed by the Food and Agriculture Organization and the World Health Organization.

Comparison of octadecylsilica and graphitized carbon black as materials for solid-phase extraction of fungicide and insecticide residues from fruit and vegetables

Methods for the determination of thirteen fungicide and insecticide residues by solid-phase extraction with C18 and graphitized carbon black (GCB) were evaluated. The extraction of the residues was achieved by using matrix solid-phase dispersion (MSPD) and more conventional polar solvent extraction followed by liquid-solid phase partitioning. Determination was carried out by capillary gas chromatography with electron-capture and mass spectrometry detectors. The recoveries were determined by fortifying six different crops (apples, oranges, pears, tomatoes, lettuces and paprikas) with the pesticides studied (bromopropylate, chlorpyrifos methyl, cypermethryn, deltamethryn, fenarimol, fenvalerate, imazalil, lindane, permethryn, phentoate, procymidone, propiconazole and vinclozoline). Although, the data showed that the two extraction methods and both sorbents were able to isolate the pesticide residues from fruit and vegetables, the best results were obtained using MSPD with C18 which gave recoveries ranging from 70 to 105% and practical detection limits between 5.0 and 50.0 micrograms/kg for all the compounds. Ten of these pesticides have been detected in samples taken from Valencia markets, at levels of 0.02-20.50 mg/kg using the described methodology.

Determination of pesticide residues in fruit and vegetables

A review concerning the determination of pesticide residues in fruit and vegetables is presented. The basic principles and recent developments in the extraction and quantitation of pesticides are discussed. Consideration is given to solid phase and supercritical extraction techniques, automation and robotic systems, and immunoassay procedures.

Matrix solid-phase dispersion extraction procedure for multiresidue pesticide analysis in oranges

A multiresidue extraction method based on matrix solid-phase dispersion (MSPD) is optimized for the extraction and gas chromatographic screening of eighteen insecticides (aldrin, carbophenothion, captafol, chlorpyriphos, chlorfenvinphos, diazinon, dicofol, alpha-endosulfan, beta-endosulfan, ethion, fenitrothion, folpet, methidathion, malathion, methyl-azinphos, methyl-parathion, phosmet, and tetradifon) from oranges. After optimization of different parameters, such as type of solid phase used and the amount of solid phase or eluent, recoveries ranged from 67 to 102% with relative standard deviations ranging from 2 to 10%. The limits of detection, calculated as 3 times the baseline noise ranged from 2 to 171 micrograms/kg. These limits of detection were about 10 times lower than the maximum residue levels established by the European Community. Compared with classical methods, the described procedure is simple, less labour intensive and does not require preparation and maintenance of equipment. Troublesome emulsions, such as those frequently observed in liquid-liquid partitioning did not occur.

Proteolytic Activity in Soybean Root Nodules : Activity in Host Cell Cytosol and Bacteroids throughout Physiological Development and Senescence

Root nodules were harvested from chamber-grown soybean (Glycine max L. Merrill cv Woodworth) plants throughout development. Apparent nitrogenase activity (acetylene reduction) peaked before seeds began to develop, but a significant amount of activity remained as the seeds matured. Nodule senescence was defined as the period in which residual nitrogenase activity was lost. During this time, soluble protein and leghemoglobin levels in the host cell cytosol decreased, and proteolytic activity against azocasein increased. Degradative changes were not detected in bacteroids during nodule senescence. Total soluble bacteroid protein per gram of nodule remained constant, and an increase in proteolytic activity in bacteroid extracts was not observed. These results are consistent with the view that soybean nodule bacteroids are capable of redifferentiation into free-living bacteria upon deterioration of the legume-rhizobia symbiosis.