The silver bullet that wasn't: Rapid agronomic weed adaptations to glyphosate in North America

The rapid adoption of glyphosate-resistant crops at the end of the 20th century caused a simplification of weed management that relied heavily on glyphosate for weed control. However, the effectiveness of glyphosate has diminished. A greater understanding of trends related to glyphosate use will shed new light on weed adaptation to a product that transformed global agriculture. Objectives were to (1) quantify the change in weed control efficacy from postemergence (POST) glyphosate use on troublesome weeds in corn and soybean and (2) determine the extent to which glyphosate preceded by a preemergence (PRE) improved the efficacy and consistency of weed control compared to glyphosate alone. Herbicide evaluation trials from 24 institutions across the United States of America and Canada from 1996 to 2021 were compiled into a single database. Two subsets were created; one with glyphosate applied POST, and the other with a PRE herbicide followed by glyphosate applied POST. Within each subset, mean and variance of control ratings for seven problem weed species were regressed over time for nine US states and one Canadian province. Mean control with POST glyphosate alone decreased over time while variability in control increased. Glyphosate preceded by a labeled PRE herbicide showed little change in mean control or variability in control over time. These results illustrate the rapid adaptation of agronomically important weed species to the paradigm-shifting product glyphosate. Including more diversity in weed management systems is essential to slowing weed adaptation and prolonging the usefulness of existing and future technologies.

Is the Peritoneum a Significant Transport Barrier in Peritoneal Dialysis?

Objectives

The anatomic peritoneum is often considered equivalent to the barrier between the dialysate and the blood, and is also called “the peritoneal membrane.” Our hypothesis is that the normal peritoneum is not a significant barrier to solute or water flow. The goal of this study was to explore the effects of alteration of the anatomic peritoneum on the transperitoneal transport of water and solute.

Design

In vivo transport experiments were carried out in control and treated rats. Treatments consisted of frequent mixing of the peritoneal solution versus no mixing, drying the peritoneum prior to the experiment, or selective removal of the entire peritoneum. Transport experiments were carried out via a plastic chamber affixed to the parietal peritoneum. After measuring solute transport or osmotically induced filtration, the tissue underlying the chamber was collected and stained for histology.

Results

Mixing the chamber solution every 5 minutes versus no mixing over 90 minutes did not result in a significant change in the mass transfer coefficient for mannitol (MTCmannitol, n = 14, p > 0.25). Drying the peritoneum prior to the transport experiment did not significantly alter the MTC of albumin or mannitol ( n = 17, p > 0.6; n = 19, p > 0.1, respectively). Manual drying did not remove or significantly alter the apparent peritoneal coating on the surface of the mesothelium. Removal of the entire peritoneum did not significantly alter the osmotically induced volume flux from the tissue, nor did it change the MTCmannitol( n = 9, p > 0.9; n = 9, p > 0.4, respectively).

Conclusions

Mixing of the solution directly over the tissue, manual drying of the peritoneum, or removal of the entire peritoneum does not result in significant alterations in transport. We conclude that the anatomic peritoneum is relatively unimportant as a physical transport barrier in peritoneal dialysis.

Clinical Characteristics and Treatment Patterns of Children and Adults With IgA Nephropathy or IgA Vasculitis: Findings From the CureGN Study

Introduction

The Cure Glomerulonephropathy Network (CureGN) is a 66-center longitudinal observational study of patients with biopsy-confirmed minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, or IgA nephropathy (IgAN), including IgA vasculitis (IgAV). This study describes the clinical characteristics and treatment patterns in the IgA cohort, including comparisons between IgAN versus IgAV and adult versus pediatric patients.

Methods

Patients with a diagnostic kidney biopsy within 5 years of screening were eligible to join CureGN. This is a descriptive analysis of clinical and treatment data collected at the time of enrollment.

Results

A total of 667 patients (506 IgAN, 161 IgAV) constitute the IgAN/IgAV cohort (382 adults, 285 children). At biopsy, those with IgAV were younger (13.0 years vs. 29.6 years, P < 0.001), more frequently white (89.7% vs. 78.9%, P = 0.003), had a higher estimated glomerular filtration rate (103.5 vs. 70.6 ml/min per 1.73 m², P < 0.001), and lower serum albumin (3.4 vs. 3.8 g/dl, P < 0.001) than those with IgAN. Adult and pediatric individuals with IgAV were more likely than those with IgAN to have been treated with immunosuppressive therapy at or prior to enrollment (79.5% vs. 54.0%, P < 0.001).

Conclusion

This report highlights clinical differences between IgAV and IgAN and between children and adults with these diagnoses. We identified differences in treatment with immunosuppressive therapies by disease type. This description of baseline characteristics will serve as a foundation for future CureGN studies.

Acculturation and chronic kidney disease in the Hispanic community health study/study of Latinos (HCHS/SOL)

Hispanics/Latinos are burdened by chronic kidney disease (CKD). The role of acculturation in this population has not been explored. We studied the association of acculturation with CKD and cardiovascular risk factor control. We performed cross-sectional analyses of 13,164 U.S. Hispanics/Latinos enrolled in the HCHS/SOL Study between 2008 and 2011. Acculturation was measured using the language and ethnic social relations subscales of the Short Acculturation Scale for Hispanics, and proxies of acculturation (language preference, place of birth and duration of residence in U.S.). CKD was defined as estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m² or urine albumin-to-creatinine ratio ≥ 30 mg/g. On multivariable analyses stratified by age, lower language subscale score was associated with higher odds of CKD among those older than 65 (OR 1.29, 95% CI, 1.03, 1.63). No significant association was found between proxies of acculturation and CKD in this age strata. Among individuals aged 18–44, a lower language subscale score was associated with lower eGFR (β = −0.77 ml/min/1.73 m², 95% CI −1.43, −0.10 per 1 SD increase) and a similar pattern was observed for ethnic social relations. Among those older than 65, lower language subscale score was associated with higher log-albuminuria (β = 0.12, 95% CI 0.03, 0.22). Among individuals with CKD, acculturation measures were not associated with control of cardiovascular risk factors. In conclusion, lower language acculturation was associated with a higher prevalence of CKD in individuals older than 65. These findings suggest that older individuals with lower language acculturation represent a high risk group for CKD.

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Among Hispanics/Latinos, lower language acculturation was associated with a higher prevalence of chronic kidney disease in older individuals.

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Based on our findings, older individuals with lower language acculturation represent a high-risk group for chronic kidney disease.

NFAT5 and SLC4A10 Loci Associate with Plasma Osmolality

Disorders of water balance, an excess or deficit of total body water relative to body electrolyte content, are common and ascertained by plasma hypo- or hypernatremia, respectively. We performed a two-stage genome-wide association study meta-analysis on plasma sodium concentration in 45,889 individuals of European descent (stage 1 discovery) and 17,637 additional individuals of European descent (stage 2 replication), and a transethnic meta-analysis of replicated single-nucleotide polymorphisms in 79,506 individuals (63,526 individuals of European descent, 8765 individuals of Asian Indian descent, and 7215 individuals of African descent). In stage 1, we identified eight loci associated with plasma sodium concentration at P<5.0 × 10^-6 Of these, rs9980 at NFAT5 replicated in stage 2 meta-analysis (P=3.1 × 10^-5), with combined stages 1 and 2 genome-wide significance of P=5.6 × 10^-10 Transethnic meta-analysis further supported the association at rs9980 (P=5.9 × 10^-12). Additionally, rs16846053 at SLC4A10 showed nominally, but not genome-wide, significant association in combined stages 1 and 2 meta-analysis (P=6.7 × 10^-8). NFAT5 encodes a ubiquitously expressed transcription factor that coordinates the intracellular response to hypertonic stress but was not previously implicated in the regulation of systemic water balance. SLC4A10 encodes a sodium bicarbonate transporter with a brain-restricted expression pattern, and variant rs16846053 affects a putative intronic NFAT5 DNA binding motif. The lead variants for NFAT5 and SLC4A10 are cis expression quantitative trait loci in tissues of the central nervous system and relevant to transcriptional regulation. Thus, genetic variation in NFAT5 and SLC4A10 expression and function in the central nervous system may affect the regulation of systemic water balance.

Cerebrospinal Fluid Absorption Revisited: Do Extracranial Lymphatics Play a Role?

It would seem heretical to suggest that extracranial lymphatic vessels play a major role in the volumetric clearance of cerebrospinal fluid (CSF) from the cranial vault. It is well established that there are no lymphatics within the brain parenchyma, and it has been assumed that the drainage of CSF into the venous system occurs predominantly through the arachnoid villi and granulations. Nonetheless, a physiological association between extracellular fluid in the brain and extracranial lymph has been appreciated for more than 100 years. More important, recent studies in adult experimental animals have demonstrated that on average, one-half of the total volume of CSF absorbed from the cranial compartment was removed by extracranial lymphatics. Our objective in writing this review is to outline the experimental data that support the hypothesis that extracranial lymphatic vessels play an important role in CSF transport in the adult. Additionally, we will develop the hypothesis that lymphatic vessels may provide the primary route through which CSF is cleared from the cranial subarachnoid space in the fetus. With this new conceptual framework, we will reassess hydrocephalus from a lymphatic perspective to determine if impaired CSF transport through extracranial lymphatics might contribute to the development of this disease.

Dialysis therapies: a National Dialogue

The National Institute of Diabetes, Digestive, and Kidney Diseases-supported Kidney Research National Dialogue asked the scientific community to formulate and prioritize research objectives that would improve our understanding of kidney function and disease. Kidney Research National Dialogue participants identified the need to improve outcomes in ESRD by decreasing mortality and morbidity and enhancing quality of life as high priority areas in kidney research. To reach these goals, we must identify retained toxins in kidney disease, accelerate technologic advances in dialysate composition and devices to remove these toxins, advance vascular access, and identify measures that decrease the burden of disease in maintenance dialysis patients. Together, these research objectives provide a path forward for improving patient-centered outcomes in ESRD.

Stretch of human mesothelial cells increases cytokine expression

Peritoneal dialysis requires large solution volumes that increase abdominal girth and stretch the mesothelial cells of the abdominal wall. To address the hypothesis that stretch stimulates those cells to increase synthesis and production of inflammatory cytokines, we grew MeT-5A human mesothelial cells to confluence and placed the cells in growth arrest on BioFlex Collagen membranes (Flexcell International Corporation, Hillsborough, NC, U.S.A.). After 48 hours, cells were either left stationary (STA) or cycled using a 3000T system (Flexcell International Corporation) with a sinusoidal stretch (STR) frequency of 10 cycles per minute and an amplitude of 30%. The supernatant and cells of individual wells were removed at 0, 4, 12, 24, 48, 72, and 96 hours. Supernatant was assayed by ELISA for transforming growth factor beta (TGF-beta), interleukin 6 (IL-6), and vascular endothelial growth factor (VEGF). After trypsinization, the total number of viable cells in each well was estimated from the lack of trypan blue staining. Total RNA from the cells was extracted, and real-time reverse-transcriptase polymerase chain reaction was used to determine messenger RNA (mRNA) for IL-6, TGF-beta, VEGF, TGF-beta receptors 2 and 3 (TGF-beta-R2, -R3), kinase insert domain receptor (KDR), and FMS-related tyrosine kinase 1 (Flt1). Because of decline of cell numbers and viability, results for STR were compared with those for STA at each time interval up to 72 hours. The mRNA for TGF-beta, VEGF, TGF-beta-R3, and KDR were significantly higher in the STR group throughout the 72 hours, and STR IL-6 mRNA declined nonsignificantly. Normalized to the number of viable cells, supernatant IL-6, TGF-beta, and VEGF were not significantly different between the groups. We conclude that mechanical stress from mesothelial stretch does not enhance mesothelial cell secretion oflL-6, TGF-f, or VEGF, but does increase expression ofTGF-P, VEGF, and their corresponding cell receptors TGF-f-R3 and KDR.

Inhibition of ovarian cancer cell metastasis by a fusion polypeptide Tat-ELP

Tumor cell metastasis is a complex, multi-step process that is a major cause of death and morbidity amongst cancer patients. Cell adhesion plays a critical role in the development of metastatic cancer, and it is mediated by interactions between receptors on the cell surface and ligands of the extracellular matrix or other surfaces. Therefore, inhibition of the cell adhesion process appears to be an effective method of preventing metastasis. This work describes a genetically engineered polypeptide with the potential to prevent cell adhesion and inhibit metastasis. We have found that the cell penetrating peptide Tat, fused with elastin-like polypeptide (ELP) inhibited adhesion, spreading, invasion and migration of SKOV-3 ovarian cancer cells in cell culture. Furthermore, we have also confirmed that Tat-ELP has anti-metastatic potential in an experimental ovarian cancer metastasis model in vivo, causing approximately 80% reduction in the tumor burden. Since cell attachment is an important step in tumor cell invasion and metastasis, these results suggest a novel role of Tat-ELP as a therapeutic intervention in cancer metastasis.

Water-only pores and peritoneal dialysis

The article by Ni et al. solidifies the important role of aquaporin-1 in the process of fluid removal from anephric patients treated with peritoneal dialysis. The presence of the water-only channel in the subperitoneal endothelia provides the mechanism for solute-free ultrafiltrate observed early in dialysis and accounts for approximately half of all the filtration observed in dialysis.

Is the peritoneum a significant transport barrier in peritoneal dialysis?

OBJECTIVES

The anatomic peritoneum is often considered equivalent to the barrier between the dialysate and the blood, and is also called "the peritoneal membrane." Our hypothesis is that the normal peritoneum is not a significant barrier to solute or water flow. The goal of this study was to explore the effects of alteration of the anatomic peritoneum on the transperitoneal transport of water and solute.

DESIGN

In vivo transport experiments were carried out in control and treated rats. Treatments consisted of frequent mixing of the peritoneal solution versus no mixing, drying the peritoneum prior to the experiment, or selective removal of the entire peritoneum. Transport experiments were carried out via a plastic chamber affixed to the parietal peritoneum. After measuring solute transport or osmotically induced filtration, the tissue underlying the chamber was collected and stained for histology.

RESULTS

Mixing the chamber solution every 5 minutes versus no mixing over 90 minutes did not result in a significant change in the mass transfer coefficient for mannitol (MTCmannitol, n = 14, p > 0.25). Drying the peritoneum prior to the transport experiment did not significantly alter the MTC of albumin or mannitol (n = 17, p > 0.6; n = 19, p > 0.1, respectively). Manual drying did not remove or significantly alter the apparent peritoneal coating on the surface of the mesothelium. Removal of the entire peritoneum did not significantly alter the osmotically induced volume flux from the tissue, nor did it change the MTCmannitol (n = 9, p > 0.9; n = 9, p > 0.4, respectively).

CONCLUSIONS

Mixing of the solution directly over the tissue, manual drying of the peritoneum, or removal of the entire peritoneum does not result in significant alterations in transport. We conclude that the anatomic peritoneum is relatively unimportant as a physical transport barrier in peritoneal dialysis.

Relationship between pericardial pressure and lymphatic pericardial fluid transport in sheep

We investigated the relationship between pericardial pressure and the volumetric lymphatic clearance rate of pericardial fluid in sheep. A single catheter perfusion system was established to deliver tracer to the pericardial cavity and control pericardial pressure. In addition, catheters were placed into the thoracic duct and into the jugular vein at the base of the neck. (125)I-human serum albumin (HSA) was administered into the pericardial perfusate to serve as the lymph flow marker and its concentration monitored in the effluent from the outflow end of the perfusion system. (131)I-HSA was injected intravenously to permit calculation of plasma tracer loss and tracer recirculation into lymphatics. From mass balance equations, estimates of total pericardial clearance into lymphatics increased significantly as pericardial pressures were elevated in 2. 5 cm H(2)O increments from 2.5 to 12.5 cm H(2)O (P = 0.018). Pericardial lymph transport ranged from 0.89 +/- 0.10 to 3.09 +/- 0. 66 ml/h at 2.5 and 12.5 cm H(2)O pericardial pressure, respectively. The majority of transport occurred through mediastinal vessels with a small proportion (10.3 to 23.9%) being cleared into lymphatics leading to the thoracic duct. We conclude that lymphatic pericardial fluid transport increases approximately 3.5-fold over a pericardial pressure range that encompasses the transition between the shallow and steep portions of the pericardial pressure-volume relationship.

Pericardial fluid absorption into lymphatic vessels in sheep

We estimated the volumetric lymphatic clearance rate of pericardial fluid in sheep. In the first group of studies, 125I-human serum albumin (HSA) was injected into the pericardial cavity and after 4 h, various lymph nodes and tissues were excised and counted for radioactivity. Several lymphatic drainage pathways existed defined by elevated 125I-HSA in the middle and caudal mediastinal, intercostal, and the cardiac nodes located near the root of the aorta. In a second group of experiments, the plasma recovery of intrapericardially administered tracer was compared in sheep with intact lymphatics and in animals in which thoracic duct lymph was diverted and other relevant lymphatics ligated. The 4-h plasma recoveries were reduced significantly from an average of 12.2 +/- 3. 4% injected dose in the lymph-intact group to 3.0 +/- 1.1% injected dose in the diverted/ligated group (an inhibition of approximately 75%). In order to estimate the volumetric clearance of pericardial fluid through lymphatics in conscious sheep, 125I-HSA was administered into the pericardial cavity to serve as the lymph flow marker. 131I-HSA was injected intravenously to permit calculation of plasma tracer loss and tracer recirculation into lymphatics. From mass balance equations, total pericardial clearance into lymphatics averaged 1.50 +/- 0.43 ml/h or approximately 1.13 ml/h if one was to assume that the average 25% recovered plasma tracer in lymph diverted/ligated animals was due to nonlymphatic transport. In conclusion, mediastinal lymphatic pathways remove a volume equivalent to the pericardial volume (8.1 +/- 1.1 ml) every 5.4 to 7. 2 h.

Contribution of extracranial lymphatics and arachnoid villi to the clearance of a CSF tracer in the rat

The objective of this study was to determine the relative roles of arachnoid villi and cervical lymphatics in the clearance of a cerebrospinal fluid (CSF) tracer in rats. 125I-labeled human serum albumin (125I-HSA; 100 micrograms) was injected into one lateral ventricle, and an Evans blue dye-rat protein complex was injected intravenously. Arterial blood was sampled for 3 h. Immediately after this, multiple cervical vessels were ligated in the same animals, and plasma recoveries were monitored for a further 3 h after the intracerebroventricular injection of 100 micrograms 131I-HSA. Tracer recovery in plasma at 3 h averaged (%injected dose) 0.697 +/- 0.042 before lymphatic ligation and dropped significantly to 0.357 +/- 0. 060 after ligation. Estimates of the rate constant associated with the transport of the CSF tracer to plasma were also significantly lower after obstruction of cervical lymphatics (from 0.584 +/- 0. 072/h to 0.217 +/- 0.056/h). No significant changes were observed in sham-operated animals. Assuming that the movement of the CSF tracer to plasma in lymph-ligated animals was a result of arachnoid villi clearance, we conclude that arachnoid villi and extracranial lymphatic pathways contributed equally to the clearance of the CSF tracer from the cranial vault.

Raised intracranial pressure increases CSF drainage through arachnoid villi and extracranial lymphatics

We demonstrated previously that about one-half of cerebrospinal fluid (CSF) removed from the cranial vault was cleared by extracranial lymphatic vessels. In this report we test the hypothesis that lymphatic drainage of CSF increases as intracranial pressure (ICP) is elevated in anesthetized sheep. Catheters were inserted into both lateral ventricles, cisterna magna, cervical lymphatics, and jugular vein. A ventriculocisternal perfusion system was employed to regulate CSF pressures and to deliver a protein tracer (125I-labeled human serum albumin) into the CSF compartment. 131I-labeled human serum albumin was injected intravenously to permit calculation of plasma tracer loss and tracer recirculation into lymphatics. ICP was controlled by adjusting the height of the inflow reservoir and the cisterna magna outflow catheter appropriately. The experimental design consisted of a 3-h period of lower pressure followed by a 3-h period of higher pressure in the same animal (10-20 or 20-30 cmH2O). We determined that incremental changes in ICP were associated with higher CSF transport through lymphatic and arachnoid villi routes in all eight animals tested (P = 0.004).

Determination of volumetric cerebrospinal fluid absorption into extracranial lymphatics in sheep

We estimated the volumetric clearance of cerebrospinal fluid (CSF) through arachnoid villi and extracranial lymphatics in conscious sheep. Catheters were inserted into both lateral ventricles, the cisterna magna, multiple cervical lymphatics, thoracic duct, and jugular vein. Uncannulated cervical vessels were ligated. 125I-labeled human serum albumin (HSA) was administered into both lateral ventricles. 131I-HSA was injected intravenously to permit calculation of plasma tracer loss and tracer recirculation into lymphatics. From mass balance equations, total volumetric absorption of CSF averaged 3.37 +/- 0.38 ml/h, with 2.03 +/- 0.29 ml/h (approximately 60%) removed by arachnoid villi and 1.35 +/- 0.46 ml/h (approximately 40%) cleared by lymphatics. With projected estimates for noncannulated ducts, total CSF absorption increased to 3.89 +/- 0.33 ml/h, with 1.86 +/- 0.49 ml/h (48%) absorbed by lymphatics. Additionally, we calculated total CSF drainage to be 3.48 +/- 0.52 ml/h, with 54 and 46% removed by arachnoid villi and lymphatics, respectively, using previously published mass transport data from our group. We employed estimates of CSF tracer concentrations that were extrapolated from relationships observed in the study reported here. We conclude that 40-48% of the total volume of CSF absorbed from the cranial compartment is removed by extracranial lymphatic vessels.

Lymphatic drainage of the CNS: effects of lymphatic diversion/ligation on CSF protein transport to plasma

The plasma recovery of an intraventricularly administered protein was compared before and after lymph diversion/ligation in the same conscious sheep to determine the relative roles of arachnoid villi and lymphatics in the clearance of a cerebral spinal fluid tracer. 125I-human serum albumin was injected into both lateral ventricles, and venous blood was sampled. One day later, multiple cervical vessels and the thoracic duct were cannulated for lymph collection. Uncannulated vessels were ligated. The experiment was repeated with 131I-human serum albumin as the tracer. Before lymph diversion/ligation, the time-averaged tracer transport into the plasma was 6.4 +/- 1.0%/h, with an average 6-h plasma recovery of 38.2 +/- 5.7% (percentage of injected dose). After lymph diversion/ligation, the values dropped to 2.9 +/- 0.5%/h and 17.7 +/- 2.7%, respectively. The collected lymph contained 8.7 +/- 2.6% of the tracer. No significant differences were observed in sham-operated animals. In conclusion, extracranial lymphatic vessels in sheep transport approximately one-half of the protein tracer from the cerebral spinal fluid compartment into plasma.

Drainage of CSF through lymphatic pathways and arachnoid villi in sheep: measurement of 125I-albumin clearance

We investigated lymphatic drainage pathways of the central nervous system in conscious sheep and quantified the clearance of a cerebrospinal fluid (CSF) tracer into lymph and blood. In the first group of studies, 125I-HSA was injected into the lateral ventricles of the brain or into lumbar CSF and after 6 h, various lymph nodes and tissues were excised and counted for radioactivity. Multiple lymphatic drainage pathways of cranial CSF existed in the head and neck region defined by elevated 125I-HSA in the retropharyngeal/cervical, thymic, pre-auricular and submandibular nodes. Implicated in spinal CSF drainage were mainly the lumbar and intercostal nodes. In a second group of experiments, multiple cervical vessels and the thoracic duct were cannulated and lymph diverted from the animals. Transport of tracer through arachnoid villi was taken from recoveries in venous blood. Following intraventricular administration, the 6 h recoveries of 125I-HSA in the lymph (sum of cervical and thoracic duct) and blood were 8.2% +/- 3.0 and 12.5% +/- 4.5 respectively and at 22 h, 25.1% +/- 6.9 and 20.8% +/- 4.1 respectively. When 125I-HSA was injected into lumbar CSF, the 6 h recoveries of tracer in thoracic duct and blood were 11.6% +/- 2.7 and 16.3% +/- 3.7 respectively. Total lymph and blood recoveries were not significantly different in any experiment. We conclude that the clearance of 125I-HSA from the CSF is almost equally distributed between lymphatic and arachnoid villi pathways.