Prospective assessment of the impact of intraoperative diuretics in kidney transplant recipient surgery.

BACKGROUND: The use of intraoperative diuretics, such as furosemide or mannitol, during kidney transplantation has been suggested to reduce the rate of delayed graft function (DGF). The evidence base for this is sparse, however, and there is substantial variation in practice. We sought to evaluate whether the use of intraoperative diuretics during kidney transplantation translated into a reduction in DGF. METHODS: We conducted a cohort study evaluating the use of furosemide or mannitol given intraoperatively before kidney reperfusion compared with control (no diuretic). Adult patients receiving a kidney transplant for end-stage renal disease were allocated to receive furosemide, mannitol, or no diuretic. The primary outcome was DGF; secondary outcomes were graft function at 30 days and perioperative changes in potassium levels. Descriptive and comparative statistics were used where appropriate. RESULTS: A total of 162 patients who received a kidney transplant from a deceased donor (either donation after neurologic determination of death or donation after circulatory death) were included over a 2-year period, with no significant between-group differences. There was no significant difference in DGF rates between the furosemide, mannitol, and control groups. When the furosemide and mannitol groups were pooled (any diuretic use) and compared with the control group, however, there was a significant improvement in the odds that patients would be free of DGF (odds ratio 2.10, 95% confidence interval 1.06-4.16, 26% v. 44%, p = 0.03). There were no significant differences noted in any secondary outcomes. CONCLUSION: This study suggests the use of an intraoperative diuretic (furosemide or mannitol) may result in a reduction in DGF in patients undergoing kidney transplantation. Further study in the form of a randomized controlled trial is warranted.

A Prospective Study of the Effect of Gastroduodenal Artery Reconstruction on Duodenal Oxygenation and Enzyme Content After Pancreas Transplantation.

BACKGROUND: Whole pancreas transplantation provides durable glycemic control and can improve survival rate; however, it can carry an increased risk of surgical complications. One devastating complication is a duodenal leak at the site of enteroenteric anastomosis. The gastroduodenal artery (GDA) supplies blood to the donor duodenum and pancreas but is commonly ligated during procurement. Since we have not had expressive changes in pancreatic back table surgical techniques in the recent decades, we hypothesized whether back table GDA reconstruction, improving perfusion of the donor duodenum and head of the pancreas, could lead to fewer surgical complications in simultaneous pancreas-kidney (SPK) transplants. MATERIAL AND METHODS: Between 2017 and 2021, we evaluated demographic information, postoperative complications, intraoperative donor duodenum, recipient bowel O2 tissue saturation, and patient morbidity through the Comprehensive Complication Index (CCI®). RESULTS: A total of 26 patients were included: 13 underwent GDA reconstruction (GDA-R), and 13 had GDA ligation (GDA-L). There were no pancreatic leaks in the GR group compared to 38% (5/13) in the GDA-L group (p = 0.03913). Intraoperative tissue oxygen saturation was higher in the GDA-R group than in the GDA-L (95.18 vs.76.88%, p < 0,001). We observed an increase in transfusion rate in GDA-R (p < 0.05), which did not result in a higher rate of exploration (p = 0.38). CCI® patient morbidity was also significantly lower in the GDA-R group (s < 0.05). CONCLUSIONS: This study identified improved intraoperative duodenal tissue oxygen saturation in the GDA-R group with an associated reduction in pancreatic leaks and CCI® morbidity risk. A larger prospective multicenter study comparing the two methods is warranted.

Anatomy of a Neotropical insect radiation.

BACKGROUND: Much evolutionary theory predicts that diversity arises via both adaptive radiation (diversification driven by selection against niche-overlap within communities) and divergence of geographically isolated populations. We focus on tropical fruit flies (Blepharoneura, Tephritidae) that reveal unexpected patterns of niche-overlap within local communities. Throughout the Neotropics, multiple sympatric non-interbreeding populations often share the same highly specialized patterns of host use (e.g., flies are specialists on flowers of a single gender of a single species of host plants). Lineage through time (LTT) plots can help distinguish patterns of diversification consistent with ecologically limited adaptive radiation from those predicted by ecologically neutral theories. Here, we use a time-calibrated phylogeny of Blepharoneura to test the hypothesis that patterns of Blepharoneura diversification are consistent with an "ecologically neutral" model of diversification that predicts that diversification is primarily a function of time and space. RESULTS: The Blepharoneura phylogeny showed more cladogenic divergence associated with geography than with shifts in host-use. Shifts in host-use were associated with ~ 20% of recent splits (< 3 Ma), but > 60% of older splits (> 3 Ma). In the overall tree, gamma statistic and maximum likelihood model fitting showed no evidence of diversification rate changes though there was a weak signature of slowing diversification rate in one of the component clades. CONCLUSIONS: Overall patterns of Blepharoneura diversity are inconsistent with a traditional explanation of adaptive radiation involving decreases in diversification rates associated with niche-overlap. Sister lineages usually use the same host-species and host-parts, and multiple non-interbreeding sympatric populations regularly co-occur on the same hosts. We suggest that most lineage origins (phylogenetic splits) occur in allopatry, usually without shifts in host-use, and that subsequent dispersal results in assembly of communities composed of multiple sympatric non-interbreeding populations of flies that share the same hosts.

Structural characterization of the nitrogenase molybdenum-iron protein with the substrate acetylene trapped near the active site.

The biological reduction of dinitrogen (N2) to ammonia is catalyzed by the complex metalloenzyme nitrogenase. Structures of the nitrogenase component proteins, Iron (Fe) protein and Molybdenum­iron (MoFe) protein, and the stabilized complexes these component proteins, have been determined, providing a foundation for a number of fundamental aspects of the complicated catalytic mechanism. The reduction of dinitrogen to ammonia is a complex process that involves the binding of N2 followed by reduction with multiple electrons and protons. Electron transfer into nitrogenase is typically constrained to the unique electron donor, the Fe protein. These constraints have prevented structural characterization of the active site with bound substrate. Recently it has been realized that selected amino acid substitutions in the environment of the active site metal cluster (Iron­molybdenum cofactor, FeMo-co) allow substrates to persist even in the resting state. Reported here is a 1.70Å crystal structure of a nitrogenase MoFe protein α-96Arg➔Gln variant with the alternative substrate acetylene trapped in a channel in close proximity to FeMo-co. Complementary theoretical calculations support the validity of the acetylene interaction at this site and is also consistent with more favorable interactions in the variant MoFe protein compared to the native MoFe protein. This work represents the first structural evidence of a substrate trapped in the nitrogenase MoFe protein and is consistent with earlier assignments of proposed substrate pathways and substrate binding sites deduced from biochemical, spectroscopic, and theoretical studies.

Light-driven dinitrogen reduction catalyzed by a CdS:nitrogenase MoFe protein biohybrid.

The splitting of dinitrogen (N2) and reduction to ammonia (NH3) is a kinetically complex and energetically challenging multistep reaction. In the Haber-Bosch process, N2 reduction is accomplished at high temperature and pressure, whereas N2 fixation by the enzyme nitrogenase occurs under ambient conditions using chemical energy from adenosine 5'-triphosphate (ATP) hydrolysis. We show that cadmium sulfide (CdS) nanocrystals can be used to photosensitize the nitrogenase molybdenum-iron (MoFe) protein, where light harvesting replaces ATP hydrolysis to drive the enzymatic reduction of N2 into NH3 The turnover rate was 75 per minute, 63% of the ATP-coupled reaction rate for the nitrogenase complex under optimal conditions. Inhibitors of nitrogenase (i.e., acetylene, carbon monoxide, and dihydrogen) suppressed N2 reduction. The CdS:MoFe protein biohybrids provide a photochemical model for achieving light-driven N2 reduction to NH3.

Fe protein-independent substrate reduction by nitrogenase MoFe protein variants.

The reduction of substrates catalyzed by nitrogenase normally requires nucleotide-dependent Fe protein delivery of electrons to the MoFe protein, which contains the active site FeMo cofactor. Here, it is reported that independent substitution of three amino acids (ß-98(Tyr→His), α-64(Tyr→His), and ß-99(Phe→His)) located between the P cluster and FeMo cofactor within the MoFe protein endows it with the ability to reduce protons to H2, azide to ammonia, and hydrazine to ammonia without the need for Fe protein or ATP. Instead, electrons can be provided by the low-potential reductant polyaminocarboxylate-ligated Eu(II) (Em values of -1.1 to -0.84 V vs the normal hydrogen electrode). The crystal structure of the ß-98(Tyr→His) variant MoFe protein was determined, revealing only small changes near the amino acid substitution that affect the solvent structure and the immediate vicinity between the P cluster and the FeMo cofactor, with no global conformational changes observed. Computational normal-mode analysis of the nitrogenase complex reveals coupling in the motions of the Fe protein and the region of the MoFe protein with these three amino acids, which suggests a possible mechanism for how Fe protein might communicate subtle changes deep within the MoFe protein that profoundly affect intramolecular electron transfer and substrate reduction.

Development and validation of a Haitian Creole screening instrument for depression.

Developing mental health care capacity in postearthquake Haiti is hampered by the lack of assessments that include culturally bound idioms Haitians use when discussing emotional distress. The current paper describes a novel emic-etic approach to developing a depression screening for Partners in Health/Zanmi Lasante. In Study 1 Haitian key informants were asked to classify symptoms and describe categories within a pool of symptoms of common mental disorders. Study 2 tested the symptom set that best approximated depression in a sample of depressed and not depressed Haitians in order to select items for the screening tool. The resulting 13-item instrument produced scores with high internal reliability that were sensitive to culturally informed diagnoses, and interpretations with construct and concurrent validity (vis-à-vis functional impairment). Discussion focuses on the appropriate use of this tool and integrating emic perspectives into developing psychological assessments globally. The screening tool is provided as an Appendix.

The UPD3 cytokine couples environmental challenge and intestinal stem cell division through modulation of JAK/STAT signaling in the stem cell microenvironment.

In Drosophila, the replacement of spent enterocytes (ECs) relies on division of intestinal stem cells (ISCs) and differentiation of their progeny, the enteroblasts (EBs). Recent studies have revealed a role for JAK/STAT signaling in the modulation of the rate of ISC division in response to environmental challenge. Here, we demonstrate the critical role of the UPD3 cytokine in the JAK/STAT-dependent response to enteric infection. We show that upd3 expression is activated in ECs and in EBs that massively differentiate in response to challenge. We show that the UPD3 cytokine, which is secreted basally and accumulates at the basement membrane, is required for stimulation of JAK/STAT signaling in EBs and visceral muscles (VMs). We further show that stimulation of ISC division requires active JAK/STAT signaling in EBs and VMs, but apparently not in ISCs. Our results suggest that EBs and VMs modulate the rate of the EGFR-dependent ISC division through upd3-dependent production of the EGF ligands Spitz and Vein, respectively. This study therefore supports the notion that the production of the UPD3 cytokine in stem cell progeny (ECs and EBs) stimulates intestinal stem cell division through modulation of JAK/STAT signaling in the stem cell microenvironment (EBs and VMs).

Claudin-4 forms a paracellular barrier, revealing the interdependence of claudin expression in the loose epithelial cell culture model opossum kidney cells.

The effect of claudins on paracellular fluxes has been predominantly studied in either Madin-Darby canine kidney (MDCK) or LLCPK cells. Neither model system has a very low transepithelial resistance (TER) as observed in leaky epithelia. Moreover, results from one model system are not always consistent with another. Opossum kidney (OK) cells form tight junctions yet have a very low TER. We therefore set out to characterize the paracellular transport properties of this cell culture model. Ussing chamber dilution potential measurements revealed that OK cells exhibit a very low TER (11.7 ± 1.4 Ω·cm(2)), slight cation selectivity (P(Na)/P(Cl) = 1.10 ± 0.01), and the Eisenman permeability sequence IV; the permeability of monovalent cations ranking K(+) > Cs(+) > Rb(+) > Na(+) > Li(+). Quantitative real-time PCR studies found that OK cells endogenously express claudin-4 > -1 > -6 > -20 > -9 > -12 > -11 > -15. Overexpression of claudin-4 significantly increased TER, decreased Na(+) and Cl(-) permeability, and increased levels of claudin-1, -6, and -9 mRNA. Knockdown of claudin-4 in the overexpressing cells significantly decreased TER without altering claudin expression; thus claudin-4 forms a barrier in OK cells. Knockdown of endogenous claudin-4 decreased claudin-1, -9, and -12 expression without altering TER. Claudin-2 overexpression decreased TER, significantly increased Na(+) and Cl(-) permeability, and decreased claudin-12 and -6 expression. Together these results demonstrate that claudin expression is tightly coupled in OK cells.

Factor structure of PTSD symptoms among West and Central African refugees.

Although trauma is widespread in Africa, Africans are unrepresented in the literature on posttraumatic stress disorder (PTSD). The authors used confirmatory factor analysis of responses to the Harvard Trauma Questionnaire to model PTSD symptom structure in a sample of African refugees presenting at a U.S. torture treatment clinic. They tested four models that are proposed in the literature and one based on their clinical experience in which some symptoms of hyperarousal were integrated into intrusion. Their findings support a preference for a 4-factor aroused intrusion model. Discussion focuses on interpretation of models, the role of numbing and avoidance, and the limitations of Euro American symptoms in non-Euro American populations.

Resistance of neisseria meningitidis to the toxic effects of heme iron and other hydrophobic agents requires expression of ght.

Several genetic systems that allow the use of iron-protoporphyrin IX (heme) have been described for the pathogenic bacterium Neisseria meningitidis. However, many questions about the process of heme acquisition and utilization remain to be answered. To isolate and analyze unidentified genes that play a role in heme iron uptake and utilization, a Himar1 transposon mutant library was screened in N. meningitidis serogroup A strain IR4162. One locus identified by transposon mutagenesis conferred protection against heme toxicity. A mutant with a deletion in a gene termed ght (gene of hydrophobic agent tolerance) within this locus was susceptible to heme and other hydrophobic agents compared to the parental strain. Transcriptional analysis indicated that ght is cotranscribed with an upstream open reading frame NMA2149. Uncharacterized orthologues of ght were identified in many other gram-negative bacteria. We present genetic evidence for the importance of ght in resistance to hydrophobic agents and its potential role in interaction with other hydrophobic agent resistance mechanisms within N. meningitidis.