Outcomes of hyperbaric oxygen treatment for central and branch retinal artery occlusion at a major Australian referral hospital.

Introduction: This study analysed the treatment outcomes of patients that received hyperbaric oxygen treatment (HBOT) for retinal artery occlusion (RAO) at the Royal Brisbane and Women's Hospital in Brisbane, Australia between 2015 and 2021. Methods: Retrospective study from patient records including 22 eyes from 22 patients that received HBOT for either central RAO (17 patients) or branch RAO (five patients). Patients received the Royal Brisbane and Women's Hospital RAO protocol for their HBOT. Analysis included best corrected visual acuity pre- and post-treatment, subjective improvements, side effects and patient risk factors were also recorded. Results: Improvement in best corrected visual acuity was LogMAR -0.2 for central RAO on average with 8/17 (47%) experiencing objective improvement, 5/17 (29%) experienced no change and 4/22 (24%) experienced a reduction in best corrected visual acuity. Subjective improvement (colour perception or visual fields) was reported in an additional 4/17 patients, resulting in 12/17 (71%) reporting improvement either in visual acuity or subjectively. There was no improvement in the best corrected visual acuity of any of the five patients suffering from branch RAO. Cardiovascular risk factors present in the cohort included hypertension, hypercholesterolaemia, previous cardiovascular events, cardiac disease and smoking. Limited side effects were experienced by this patient cohort with no recorded irreversible side effects. Conclusions: Hyperbaric oxygen treatment appears a safe, beneficial treatment for central RAO. No benefit was demonstrated in branch RAO although numbers were small. Increased awareness of HBOT for RAO resulting in streamlined referrals and transfers and greater uptake of this intervention may further improve patient outcomes.

360-Degree laser retinopexy in primary vitrectomy for rhegmatogenous retinal detachment: factors associated with its use and impact on surgical outcomes.

BACKGROUND: To determine patient and surgical factors associated with the use of 360-degree laser retinopexy during primary pars plana vitrectomy (PPV) ± scleral buckle (SB) for rhegmatogenous retinal detachment (RRD) and its impact on surgical outcomes. METHODS: Patients who underwent PPV ± SB for repair of non-complex RRD at a single centre were included in this retrospective study. The primary outcome was single surgery anatomical success (SSAS). Secondary outcomes included visual acuity, epiretinal membrane formation, the presence of cystoid macular oedema, tonic pupil and corneal epithelial defects. Multiple logistic regression and multivariate regression was used. RESULTS: The study included 192 cases, of which 130 received 360-degree laser. Worse preoperative logMAR visual acuity (P = 0.009), male sex (P = 0.060), higher PVR grades, supplemental SB (P = 0.0468) and silicone oil/C3F8 tamponade (P < 0.0001) were associated with 360-degree laser use. No significant associations between 360-degree laser and SSAS (P = 0.079), final logMAR visual acuity (P = 0.0623), ERM development (P = 0.8208), postoperative CMO (P = 0.5946), tonic pupil (P > 0.9999) or corneal epithelial defects (P = N/A) were found. CONCLUSIONS: 360-degree laser retinopexy during primary PPV ± SB for RRD was associated with more complex cases and more extensive operations. Even when accounting for this, there was no difference in surgical outcomes or complication rates.

Therapeutic drug monitoring of meropenem and piperacillin-tazobactam in the Singapore critically ill population - A prospective, multi-center, observational study (BLAST 1).

PURPOSE: To determine percentage of patients with sub-therapeutic beta-lactam exposure in our intensive care units (ICU) and to correlate target attainment with clinical outcomes. MATERIALS AND METHODS: Multi-centre, prospective, observational study was conducted in ICUs from three hospitals in Singapore from July 2016 to May 2018. Adult patients (≥21 years) receiving meropenem or piperacillin-tazobactam were included. Four blood samples were obtained during a dosing interval to measure and determine attainment of therapeutic targets: unbound beta-lactam concentration above (i) minimum inhibitory concentration (MIC) at 40% (meropenem) or 50% (piperacillin) of dosing interval (40-50%fT > MIC) and (ii) 5 × MIC at 100% of dosing interval (100%fT > 5 × MIC). Correlation to clinical outcomes was evaluated using Cox regression. RESULTS: Beta-lactam levels were highly variable among 61 patients, with trough meropenem and piperacillin levels at 21.5 ± 16.8 mg/L and 101.6 ± 81.1 mg/L respectively. Among 85 sets of blood samples, current dosing practices were able to achieve 94% success for 40-50%fT > MIC and 44% for 100%fT > 5 × MIC. Failure to achieve 40-50%fT > MIC within 48 h was significantly associated with all-cause mortality (HR: 9.0, 95% CI: 1.8-45.0), after adjustment for APACHE II score. Achievement of 100%fT > 5 × MIC within 48 h was significantly associated with shorter length of hospital stay. CONCLUSION: Current dosing practices may be suboptimal for ICU patients. Beta-lactam TDM may be useful.

Trichostatin A regulates fibro/adipogenic progenitor adipogenesis epigenetically and reduces rotator cuff muscle fatty infiltration.

Rotator cuff (RC) muscle fatty infiltration (FI) is an important factor that determines the clinical outcome of patients with RC repair. There is no effective treatment for RC muscle FI at this time. The goal of this study is to define the role Trichostatin A (TSA), a histone deacetylase (HDAC) inhibitor in regulating muscle fibro/adipogenic progenitors (FAPs) adipogenesis and treating muscle fatty degeneration after massive RC tears in a mouse model. We hypothesize that TSA reduces muscle FI after massive RC tears. HDAC activity was measured in FAPs in RC muscle after tendon/nerve transection or sham surgery. FAPs were treated with TSA for 2 weeks and FAP adipogenesis was evaluated with perilipin and Oil Red O staining, as well as reverse transcript-polymerase chain reaction for adipogenesis-related genes. About 0.5 mg/kg TSA or dimethyl sulfoxide was administered to C57B/L6 mice with massive rotator cuff tears through daily intraperitoneal injection for 6 weeks. Supraspinatus muscles were harvested for biochemical and histology analysis. We found that FAPs showed significantly higher HDAC activity after RC tendon/nerve transection. TSA treatment significantly reduced HDAC activity and inhibited adipogenesis of FAPs. TSA also abolished the role of bone morphogenetic protein-7 in inducing FAP adipogenesis and promoted FAP brown/beige adipose tissue (BAT) differentiation. TSA injection significantly increased histone H3 acetylation and reduced FI of rotator cuff muscles after massive tendon tears. Results from this study showed that TSA can regulate FAP adipogenesis and promote FAP BAT differentiation epigenetically. HDAC inhibition may be a new treatment strategy to reduce muscle FI after RC tears and repair.

Pharmacodynamic effects of the K+ binder patiromer in a novel chronic hyperkalemia model in spontaneously hypertensive rats.

Currently described hyperkalemia (HK) animal models are typically acute and cause significant distress and mortality to the animals, warranting new approaches for studying chronic HK in a more appropriate clinical setting. Using the spontaneously hypertensive rat (SHR) model as a more relevant disease template, as well as surgical (unilateral nephrectomy), dietary (3% potassium [K+ ] supplementation), and pharmacological (amiloride) interventions, we were able to stably induce HK on a chronic basis for up to 12 weeks to serum K+ elevations between 8 and 9 mmol/L, with minimal clinical stress to the animals. Short-term proof-of-concept and long-term chronic studies in hyperkalemic SHRs showed concomitant increases in serum aldosterone, consistent with the previously reported relationship between serum K+ and aldosterone. Treatment with the K+ binder patiromer demonstrated that the disease model was responsive to pharmacological intervention, with significant abrogation in serum K+ , as well as serum aldosterone to levels near baseline, and this was consistent in both short-term and long-term 12-week chronic studies. Our results demonstrate the feasibility of establishing a chronic HK disease state, and this novel HK animal model may be suitable for further evaluating the effects of long-term, K+ -lowering therapies on effects such as renal fibrosis and end-organ damage.

Pharmacokinetics of Prenylflavonoids following Oral Ingestion of Standardized Epimedium Extract in Humans.

Leaves of the Epimedium plant are traditionally consumed for bone health and other indications. The aim of this study was to establish the safety and pharmacokinetics of the metabolites of prenylflavonoids (icariin, icariside I, icariside II, icaritin, and desmethylicaritin) following single doses of a defined Epimedium prenylflavonoid extract in humans. A single oral dose of 370, 740, or 1110 mg of a standardized Epimedium prenylflavonoid extract was administered to 30 healthy male subjects in a randomized, placebo-controlled trial. Serum samples were collected over a 48-h period and analyzed by liquid chromatography-tandem mass spectrometry and non-compartmental pharmacokinetic modelling. Epimedium prenylflavonoid extracts were well tolerated and no adverse effects were observed. The principle metabolites detected in the serum were icariside II and desmethylicaritin. Icariside II had a T max of between 4.1 - 4.3 h, reaching a maximum AUC0→∞ of 23.0 (17.5, 29.9) h×ng/mL (median [IQR: interquartile range]) with the highest dose of the Epimedium prenylflavonoid. On the other hand, desmethylicaritin had a delayed T max of 24.1 - 24.4 h and reached a maximum AUC0→∞ of 126.1 (62.4, 202.9) h×ng/mL. The median maximum plasma concentration and AUC0→∞ of desmethyliciaritin showed an increase with higher doses of the Epimedium prenylflavonoid (p < 0.05). Icariin, icariside I, and icaritin levels were below detection limits. Levels of Epimedium prenylflavonoid metabolites observed in this study were consistent with levels demonstrated to have anti-osteoporotic effects in cellular and animal studies. Coupled with the favorable safety profile of the extract observed, further studies are required to explore the utility of Epimedium prenylflavonoid extracts to prevent osteoporosis in postmenopausal women.

Adjunctive use of celecoxib with anti-tuberculosis drugs: evaluation in a whole-blood bactericidal activity model.

COX-2 inhibition may be of benefit in the treatment of tuberculosis (TB) through a number of pathways including efflux pump inhibition (increasing intracellular TB drug levels) and diverse effects on inflammation and the immune response. We investigated celecoxib (a COX-2 inhibitor) alone and with standard anti-tuberculosis drugs in the whole-blood bactericidal activity (WBA) model. Healthy volunteers took a single dose of celecoxib (400 mg), followed (after 1 week) by a single dose of either rifampicin (10 mg/kg) or pyrazinamide (25 mg/kg), followed (after 2 or 7 days respectively) by the same anti-tuberculosis drug with celecoxib. WBA was measured at intervals until 8 hours post-dose (by inoculating blood samples with Mycobacterium tuberculosis and estimating the change in bacterial colony forming units after 72 hours incubation). Celecoxib had no activity alone in the WBA assay (cumulative WBA over 8 hours post-dose: 0.03 ± 0.01ΔlogCFU, p = 1.00 versus zero). Celecoxib did not increase cumulative WBA of standard TB drugs (mean cumulative WBA -0.10 ± 0.13ΔlogCFU versus -0.10 ± 0.12ΔlogCFU for TB drugs alone versus TB drugs and celecoxib; mean difference -0.01, 95% CI -0.02 to 0.00; p = 0.16). The lack of benefit of celecoxib suggests that efflux pump inhibition or eicosanoid pathway-related responses are of limited importance in mycobacterial killing in the WBA assay.

Outcomes of Surgical and Chemotherapeutic Treatments of Goblet Cell Carcinoid Tumors of the Appendix.

BACKGROUND: Goblet cell carcinoids (GCCs) of the appendix are rare mucinous neoplasms, for which optimal therapy is poorly described. We examined prognostic clinical and treatment factors in a population-based cohort. METHODS: Patients diagnosed with GCC from 1984 to 2014 were identified from the British Columbia Cancer Agency and the Vancouver Lower Mainland Pathology Archive. RESULTS: Of 88 cases with confirmed appendiceal GCCs, clinical data were available in 86 cases (annual population incidence: 0.66/1,000,000). Median age was 54 years (range 25-91) and 42 patients (49%) were male. Metastasis at presentation was the strongest predictor of overall survival (OS), with median OS not reached for stage I-III patients, and measuring 16.2 months [95% confidence interval (CI) 9.1-29] for stage IV patients. In 67 stage I-III patients, 51 (76%) underwent completion hemicolectomy and 9 (17%) received adjuvant 5-fluorouracil-based chemotherapy. No appendicitis at initial presentation and Tang B histology were the only prognostic factors, with inferior 5-year recurrence-free survival (53 vs. 83% with appendicitis, p = 0.02; 45% Tang B vs. 89% Tang A, p < 0.01). Of 19 stage IV patients, 10 (62.5%) received 5-fluorouracil-based chemotherapy and 11 (61%) underwent multiorgan resection (MOR) ± hyperthermic intraperitoneal chemotherapy (HIPEC). Low mitotic rate and MOR ± HIPEC were associated with improved 2-year OS, but only MOR ± HIPEC remained significant on multivariate analysis (hazard ratio 5.4, 95% CI 1.4-20.9; p = 0.015). CONCLUSIONS: In this population-based cohort, we demonstrate excellent survival outcomes in stage I-III appendiceal GCCs and clinical appendicitis. Hemicolectomy remains the standard treatment. In metastatic disease, outcomes remain poor, although MOR ± HIPEC may improve survival.

Postoperative complications affect long-term outcomes after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy for colorectal peritoneal carcinomatosis.

BACKGROUND AND OBJECTIVES: Morbidity after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (CRS + HIPEC) for colorectal peritoneal carcinomatosis (PC) may negatively affect survival. The objective was to determine the impact of postoperative complications (CX) on survival in patients undergoing CRS + HIPEC for colorectal PC. METHODS: All patients undergoing laparotomy for planned CRS + HIPEC for colorectal PC at a single institution from 1999 to 2014 were included. Patients were divided into three groups: CRS + HIPEC without CX (+HIPEC-CX); CRS + HIPEC with postoperative complication (+HIPEC + CX); and aborted CRS and HIPEC due to unresectable disease (-HIPEC). Postoperative morbidity were defined as Clavien II+ complications. Kaplan-Meier survival analyses and multivariable Cox proportional hazard modeling were used to describe the disease-free (DFS) and overall survival (OS). RESULTS: One hundred and twenty-two patients were included in the analysis (50 +HIPEC - CX, 40 +HIPEC + CX, 32-HIPEC). Overall complication rate was 42%. OS at 1-, 3-, and 5-years in patients undergoing successful CRS + HIPEC were 97%, 67%, and 45%. CX after successful CRS + HIPEC was independently associated with worsened OS (HR1.58, 95%CI, 1.19-1.97) but not DFS (HR1.11, 95%CI, 0.56-2.20). PCI also independently predicted worsened DFS (HR1.12, 95%CI, 1.06-1.18) and OS (HR1.08, 95%CI, 1.04-1.12). Patients with unresectable disease had significantly worse OS (HR6.50, 95%CI, 1.37-7.01). CONCLUSIONS: CX after CRS + HIPEC significantly affect OS. Patient selection and perioperative care are of paramount importance in the management of CRS + HIPEC for colorectal PC.

Impact of electrocautery and hyperthermic intraperitoneal chemotherapy on intestinal microvasculature in a murine model.

BACKGROUND: Electrocautery (EC) is used during cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC). Using a murine model, we studied the effect of HIPEC on small bowel EC lesions and surrounding normal tissues. METHODS: Thirty-two rats were divided into five groups: a control group with EC lesions; EC plus intraperitoneal heated 5% dextrose (D5W); EC plus oxaliplatin (OXA, 460 mg/m(2)); EC plus mitomycin C 10 mg/m(2) (MMC10); EC plus MMC 35 mg/m(2) (MMC35). EC lesions and surrounding tissue microvasculature were analysed after intravenous injection of fluorescein. RESULTS: In the ileum OXA significantly reduced EC lesions microvasculature compared with the control group; MMC10 caused greater reduction than the control, D5W and MMC35 groups. Surrounding tissue microvasculature was significantly reduced by MMC35 exposure when compared to the control, OXA or MMC10 groups. In the jejunum EC injuries exposed to OXA or MMC10 had significantly reduced microvasculature compared to the control, heated D5W and MMC35 groups. Surrounding tissue microvasculature was significantly reduced by MMC35 exposure when compared to the OXA group. There was no significant microvasculature difference between the EC lesions made before or after HIPEC. CONCLUSION: HIPEC with OXA and MMC10 potentiates small bowel wall EC injuries. MMC35 reduces surrounding unharmed tissue microvasculature. There was no effect of hyperthermia alone on microvasculature.

Conferring Phosphorogenic Properties on Iridium(III)-Based Bioorthogonal Probes through Modification with a Nitrone Unit.

The use of bioorthogonal probes that display fluorogenic or phosphorogenic properties is advantageous to the labeling and imaging of biomolecules in live cells and organisms. Herein we present the design of three iridium(III) complexes containing a nitrone moiety as novel phosphorogenic bioorthogonal probes. These probes were non-emissive owing to isomerization of the C=N group but showed significant emission enhancement upon cycloaddition reaction with strained cyclooctynes. Interestingly, the connection of the nitrone ligand to the cationic iridium(III) center led to accelerated reaction kinetics. These nitrone complexes were also identified as phosphorogenic bioorthogonal labels and imaging reagents for cyclooctyne-modified proteins. These findings contribute to the development of phosphorogenic bioorthogonal probes and imaging reagents.

Prehabilitation versus rehabilitation: a randomized control trial in patients undergoing colorectal resection for cancer.

BACKGROUND: The preoperative period (prehabilitation) may represent a more appropriate time than the postoperative period to implement an intervention. The impact of prehabilitation on recovery of function al exercise capacity was thus studied in patients undergoing colorectal resection for cancer. METHODS: A parallel-arm single-blind superiority randomized controlled trial was conducted. Seventy-seven patients were randomized to receive either prehabilitation (n = 38) or rehabilitation (n = 39). Both groups received a home-based intervention of moderate aerobic and resistance exercises, nutritional counseling with protein supplementation, and relaxation exercises initiated either 4 weeks before surgery (prehabilitation) or immediately after surgery (rehabilitation), and continued for 8 weeks after surgery. Patients were managed with an enhanced recovery pathway. Primary outcome was functional exercise capacity measured using the validated 6-min walk test. RESULTS: Median duration of prehabilitation was 24.5 days. While awaiting surgery, functional walking capacity increased (≥ 20 m) in a higher proportion of the prehabilitation group compared with the rehabilitation group (53 vs. 15%, adjusted P = 0.006). Complication rates and duration of hospital stay were similar. The difference between baseline and 8-week 6-min walking test was significantly higher in the prehabilitation compared with the rehabilitation group (+23.7 m [SD, 54.8] vs. -21.8 m [SD, 80.7]; mean difference 45.4 m [95% CI, 13.9 to 77.0]). A higher proportion of the prehabilitation group were also recovered to or above baseline exercise capacity at 8 weeks compared with the rehabilitation group (84 vs. 62%, adjusted P = 0.049). CONCLUSION: Meaningful changes in postoperative functional exercise capacity can be achieved with a prehabilitation program.

Induction of chemoprotective phase 2 enzymes by ginseng and its components.

Phase 2 detoxification enzymes protect against carcinogenesis and oxidative stress. Ginseng ( PANAX spp.) extracts and components were assayed for inducer activity of NQO1 (quinone reductase), a phase 2 enzyme, in Hepa1c1c7 cells. Ginseng extracts were analyzed for ginsenosides and panaxytriol. Korean red PANAX GINSENG extracts demonstrated the most potent phase 2 enzyme induction activity (76,900 U/g dried rhizome powder and 27,800 U/g for two similar preparations). The ginsenoside-enriched HT-1001 American ginseng ( PANAX QUINQUEFOLIUS) extract was the next most potent inducer, with activity of 15,900 U/g, followed by raw American ginseng root with activity of 8700 U/g. Neither a polysaccharide-enriched extract of American ginseng nor a commercial white PANAX GINSENG preparation showed any inducer activity. Pure ginsenosides showed no inducer activity. Protopanaxadiol and protopanaxatriol, deglycosylated ginsenoside metabolic derivatives, showed potent induction activity (approximately 500,000 U/g each). Synthetic panaxytriol was over 10-fold more potent (induction potency 5,760,000 U/g). There was no correlation between ginsenoside content and phase 2 enzyme induction. The most potent inducing red ginseng extract also had the highest panaxytriol content, 120.8 microg/g. We found that ginseng induced NQO1 and that polyacetylenes are the most active components.

Possible differential induction of phase 2 enzyme and antioxidant pathways by american ginseng, Panax quinquefolius.

Human immunodeficiency virus (HIV)-infected patients often take herbal medicines, which may interact with antiretrovirals. American ginseng induces phase 2 and antioxidant enzymes in vitro and might increase the clearance of zidovudine and/or enhance antioxidant activity. Ten healthy volunteers received 300 mg of zidovudine orally before and after 2 weeks of treatment with a ginsenoside-enriched American ginseng extract 200 mg twice daily. This ginseng extract induced the phase 2 enzyme quinone reductase with an average concentration of doubling of enzyme activity of 190 microg/mL. Total ginsenoside content was 8.5 +/- 0.5%. Pharmacokinetic profiles of zidovudine and oxidative stress marker concentrations were measured post-zidovudine dose. American ginseng does not significantly affect the formation clearance of zidovudine to its glucuronide (ratio post- to pre-American ginseng = 1.17; 90% confidence interval: 0.95-1.45; P = .21), total clearance (ratio = 0.97; 0.82-1.14; P = .70), or plasma zidovudine AUC0-8 (ratio = 1.03; 0.87-1.21; P = .77). Oxidative stress biomarkers are reduced post-American ginseng (F2-isoprostane ratio = 0.79; 0.72-0.86; P < .001; 8-hydroxy-deoxyguanosine ratio = 0.74; 0.59-0.92; P = .02). Two weeks of American ginseng does not alter zidovudine pharmacokinetics but reduces oxidative stress markers.

(3R, 9R, 10R)-Panaxytriol: A molecular-based nutraceutical with possible application to cancer prevention and treatment.

Panaxytriol is a nutraceutical-based active constituent of Korean red ginseng and is reported to exhibit potent anti-tumor properties. Its activity may be in part due to its induction of phase 2 chemoprotective enzymes. Its unique properties may have important implications in cancer therapeutics.

Interactions between natural health products and antiretroviral drugs: pharmacokinetic and pharmacodynamic effects.

Concurrent use of natural health products (NHPs) with antiretroviral drugs (ARVs) is widespread among human immunodeficiency virus-infected patients. This article reviews the clinical pharmacokinetic and pharmacodynamic interactions between NHPs and ARVs. Many NHPs are complex mixtures and are likely to contain organic compounds that may induce and/or inhibit drug metabolizing enzymes and drug transporters. Although the weight of evidence for the effects of certain NHPs varies and many studies of these products lack scientific rigor, it has been observed that St. John's wort clearly induces cytochrome P450 3A4 and P-glycoprotein and reduces protease inhibitor and nonnucleoside reverse-transcriptase inhibitor concentrations, thereby increasing the likelihood of therapeutic failure. Limited clinical research suggests that intake of garlic and vitamin C results in reductions in ARV concentrations. The intake of milk thistle, Echinacea species, and goldenseal inhibits cytochrome P450 enzymes in vitro and may increase ARV concentrations, but by clinically unimportant amounts. Intake of fish oil reduces ARV-induced hypertriglyceridemia without significantly affecting lopinavir concentrations. Before recommending the use of NHPs as adjuncts to ARV use, studies should first exclude significant pharmacokinetic interactions and ensure that ARV efficacy is maintained.

Suicide-related perforating injury of globe with nail gun.

A case is reported of nail gun injury due to suicide attempt involving both orbits, frontal lobe and abdomen, which resulted in an unusual posterior perforation of the left globe. Injury was inflicted with a total of eight nails. Three nails entered the left orbit, one of which perforated the posterior aspect of the left globe. One nail entered the right orbit involving the optic nerve and crossed the midline to finish in the left sphenoid sinus. Three nails entered the frontal lobe near the midline and the final nail pierced the left lobe of the liver. The left eye underwent primary repair, lensectomy and vitrectomy with silicone oil and achieved a visual acuity of 6/60, 3 months post removal of oil with sutured posterior chamber intraocular lens. The right eye suffered traumatic optic neuropathy and currently has a visual acuity of 6/36 due to senile cataract formation. No other serious sequelae resulted from the other injuries and the patient has recovered from his episode of depression.

A surface loop of the potato leafroll virus coat protein is involved in virion assembly, systemic movement, and aphid transmission.

Two acidic domains of the Potato leafroll virus (PLRV) coat protein, separated by 55 amino acids and predicted to be adjacent surface features on the virion, were the focus of a mutational analysis. Eleven site-directed mutants were generated from a cloned infectious cDNA of PLRV and delivered to plants by Agrobacterium-mediated mechanical inoculation. Alanine substitutions of any of the three amino acids of the sequence EWH (amino acids 170 to 172) or of D177 disrupted the ability of the coat protein to assemble stable particles and the ability of the viral RNA to move systemically in four host plant species. Alanine substitution of E109, D173, or E176 reduced the accumulation of virus in agrobacterium-infiltrated tissues, the efficiency of systemic infection, and the efficiency of aphid transmission relative to wild-type virus, but the mutations did not affect virion stability. A structural model of the PLRV capsid predicted that the amino acids critical for virion assembly were located within a depression at the center of a coat protein trimer. The other amino acids that affected plant infection and/or aphid transmission were predicted to be located around the perimeter of the depression. PLRV virions play key roles in phloem-limited virus movement in plant hosts as well as in transport and persistence in the aphid vectors. These results identified amino acid residues in a surface-oriented loop of the coat protein that are critical for virus assembly and stability, systemic infection of plants, and movement of virus through aphid vectors.