Non-linear effects of non-host diversity on the removal of free-living infective stages of parasites.

Among the ecological functions and services of biodiversity is the potential buffering of diseases through dilution effects where increased biodiversity results in a reduction in disease risk for humans and wildlife hosts. Whether such effects are a universal phenomenon is still under intense debate and diversity effects are little studied in cases when non-host organisms remove free-living parasite stages during their transmission from one host to the next by consumption or physical obstruction. Here, we investigated non-host diversity effects on the removal of cercarial stages of trematodes, ubiquitous parasites in aquatic ecosystems. In laboratory experiments using response surface designs, varying both diversity and density at same time, we compared three combinations of two non-hosts at four density levels: predatory crabs that actively remove cercariae from the water column via their mouth parts and gills, filter feeding oysters that passively filter cercariae from the water column while not becoming infected themselves, and seaweed which physically obstructs cercariae. The addition of a second non-host did not generally result in increased parasite removal but neutralised, amplified or reduced the parasite removal exerted by the first non-host, depending on the density and non-host combination. These non-linear non-host diversity effects were probably driven by intra- and interspecific interactions and suggest the need to integrate non-host diversity effects in understanding the links between community diversity and infection risk.

The relationship between working in the "gig" economy and perceived subjective well-being in Western Balkan countries.

The combination of accelerated digitalization and the recent COVID-19 crisis has increased the number of remote workers worldwide to unimaginable proportions. Among the large number of remote workers that execute their projects from home, there is a significant number of permanently self-employed remote workers, usually referred to as freelancers. Despite the importance of this kind of business activity for modern project management society, perceived drivers of freelancing are still unknown. The goal of this paper was to shed some light on the general subjective well-being of freelancing activity and investigate differences concerning gender, age, and education. The study was performed in late 2020 and included 471 freelancers from Serbia, Bosnia and Herzegovina, Macedonia, and Montenegro that participated in an online questionnaire evaluating their subjective well-being while participating in the "gig" economy. Factor analysis was used as a primary statistical method and two major groups were identified: (1) Impact of working from home on a freelancer's personal life and health and (2) Fulfillment of expectations in the economic and professional sense. Gender was found not to be significant for overall work satisfaction. However, older freelancers proved to be more satisfied with the fulfillment of economic and professional expectations, which correlate with years of professional experience. Another conclusion is that more educated freelancers are generally less satisfied with both groups of drivers - fulfillment of personal life and professional expectations. Understanding how the combination of occupations, technological infrastructure, and demographic characteristics in the region has affected the well-being of freelancers may help policymakers and organization owners, as well as future entrepreneurs, better prepare for this model of work in the future. It also increases the possibility of exploring individual dimensions of wellbeing useful for targeting interventions at the level of each country separately. In line with this, the present study contributes to the existing body of knowledge and the impact of hybrid models of work on the subjective well-being of workers in the "gig" economy.

Soil humic acid and arsenite binding by isothermal titration calorimetry and Dynamic Light Scattering: Thermodynamics and aggregation.

The arsenite-humic acid binding process was investigated using Isothermal Titration Calorimetry (ITC), Dynamic Light Scattering and Laser Doppler Electrophoresis techniques. The ITC data were successfully (R2 = 0.996-0.936) interpreted by applying the MNIS model, enabling thermodynamic parameters to be determined. The MNIS model was adjusted to the arsenite-HA binding process assuming that hydrogen bonding is the dominant type of interaction in the system. Negative enthalpy change values indicated the arsenite-HAs binding as an exothermic process. Negative ΔG values (-(26.83-27.00) kJ mol-1) pointed out to spontaneous binding reaction, leading to the formation of the arsenite-HA complexes. The binding constant values ((7.57-5.02) 105 M-1) clearly demonstrate pronounced binding affinity. As ΔS values are obviously positive but close to zero, and ΔH>ΔS, the reaction can be considered enthalpy driven. Reaction heats and ΔH values (-(18.96-15.64) kJ mol-1) confirmed hydrogen bonds as the most ascendant interaction type in the arsenite-HA complex. Negative zeta potential values (-45 to -20 mV) had shown that arsenite-HA aggregates remained negatively charged in the whole molar charge ratio range. The HAs' aggregate size change is evident but not particularly pronounced (Zav = 50-180 nm). It can be speculated that aggregation during the titration process is not expressive due to repulsive forces between negatively charged arsenite-HA particles. Thermodynamic and reaction parameters clearly indicated that arsenite-HA complexes are formed at common soil pH values, confirming the possible influence of humic acids on increased As mobility and its reduced bioavailability.

Development of genistein-loaded gold nanoparticles and their antitumor potential against prostate cancer cell lines.

Soy isoflavone genistein (Gen) exerts beneficial effects against prostate cancer cells in vitro and in vivo. However, its use as a chemoprevention/therapeutic agent is largely limited due to its low bioavailability. In this study we synthesized two variants of a new delivery system, genistein-gold nanoparticles conjugates Gen@AuNPs1 and Gen@AuNPs2, by an environmentally friendly method, using a dual role of Gen to reduce Au3+ and stabilize the formed AuNPs, with no additional component. The formation of Gen@AuNPs was confirmed via UV-Vis spectroscopy, FTIR, and Raman spectra measurements. The spherical shape and uniform size of Gen@AuNPs1 and Gen@AuNPs2 (10 ± 2 and 23 ± 3 nm, respectively), were determined by transmission electron microscopy. The nano-conjugates also varied in hydrodynamic diameter (65.0 ± 1.7 and 153.0 ± 2.2 nm) but had similar negative zeta potential (-35.0 ± 2.5 and -37.0 ± 1.6 mV), as measured by dynamic light scattering. The Gen loading was estimated to be 46 and 48%, for Gen@AuNPs1 and Gen@AuNPs2, respectively. The antiproliferative activities of GenAuNPs were confirmed by MTT test in vitro on three malignant prostate carcinoma cell lines (PC3, DU 145, and LNCaP), while selectivity toward malignant phenotype was confirmed using non-cancerous MRC-5 cells. Flow cytometric analysis showed that the inhibition on cell proliferation of more potent Gen@AuNPs1 nano-conjugate is comparable with the effects of free Gen. In conclusion, the obtained results, including physicochemical characterization of newly synthesized AuNPs loaded with Gen, cytotoxicity, and IC50 assessments, indicate their stability and bioactivity as an antioxidant and anti-prostate cancer agent, with low toxicity against human primary cells.

How invasive oysters can affect parasite infection patterns in native mussels on a large spatial scale.

There are surprisingly few field studies on the role of invasive species on parasite infection patterns in native hosts. We investigated the role of invasive Pacific oysters (Magallana gigas) in determining parasite infection levels in native blue mussels (Mytilus edulis) in relation to other environmental and biotic factors. Using hierarchical field sampling covering three spatial scales along a large intertidal ecosystem (European Wadden Sea), we found strong spatial differences in infection levels of five parasite species associated with mussels and oysters. We applied mixed models to analyse the associations between parasite prevalence and abundance in mussels and oysters, and 12 biological and environmental factors. For each parasite-host relationship, an optimal model (either a null, one-factor or two-factor model) was selected based on AIC scores. We found that the density of invasive oysters contributed to three of the 12 models. Other biological factors such as host size (six models), and the density of target or alternative host species (five models) contributed more frequently to the best models. Furthermore, for parasite species infecting both mussels and oysters, parasite population densities were higher in native mussels, attributed to the higher densities of mussels. Our results indicate that invasive species can affect parasite infection patterns in native species in the field, but that their relative contribution may be further mediated by other biological and environmental parameters. These results stress the usefulness of large-scale field studies for detailed assessments of the mechanisms underlying the impacts of invasive species on native host communities.

Consumer and host body size effects on the removal of trematode cercariae by ambient communities.

Parasite transmission can be altered via the removal of parasites by the ambient communities in which parasite-host interactions take place. However, the mechanisms driving parasite removal remain poorly understood. Using marine trematode cercariae as a model system, we investigated the effects of consumer and host body size on parasite removal rates. Laboratory experiments revealed that consumer or host body size significantly affected cercarial removal rates in crabs, oysters and cockles but not in shrimps. In general, cercarial removal rates increased with consumer (crabs and oysters) and host (cockles) body size. For the filter feeding oysters and cockles, the effects probably relate to their feeding activity which is known to correlate with bivalve size. Low infection levels found in cockle hosts suggest that parasite removal by hosts also leads to significant mortality of infective stages. The size effects of crab and shrimp predators on cercarial removal rates were more complex and did not show an expected size match-mismatch between predators and their cercarial prey, suggesting that parasite removal rates in predators are species-specific. We conclude that to have a comprehensive understanding of parasite removal by ambient communities, more research into the various mechanisms of cercarial removal is required.

Double screening for dual disorder, alcoholism and depression.

Comorbidity of alcohol use disorder and major depressive disorder has been reported in samples. The aim of this study was to examine the relationship between alcoholism and depression in undiagnosed patients by simultaneously applying screening tests for both disorders. A total of 421 subjects were included in the study, of which 246 were female. Two screening tests, the Michigan Alcoholism Screening Test and the Beck Depression Inventory, were used. In the total sample, 28.03% of the respondents engaged in some type of harmful alcohol use and 55.82% experienced some level of depression; 24.70% of the respondents had both at the same time, some type of harmful alcohol use and some level of depression. Results of statistical analysis showed that a more problematic alcohol use type was associated with a more severe level of depression, with a greater positive association between problematic alcohol use and severity of depressive symptoms among females and more harmful alcohol consumption among males. This study points to the importance of screening for alcoholism and depression, because their timely detection and treatment improves the quality of life in newly diagnosed individuals and reduces the economic burden on society for health services due to greater use if a greater severity of dual disorder is reached.

Liver elastography malignancy prediction score for noninvasive characterization of focal liver lesions.

BACKGROUND & AIMS: To analyse elastographic characteristics of focal liver lesions (FLL)s and diagnostic performance of real-time two-dimensional shear-wave elastography (RT-2D-SWE) in order to differentiate benign and malignant FLLs. METHODS: Consecutive patients diagnosed with FLL by abdominal ultrasound (US) underwent RT-2D-SWE of FLL and non-infiltrated liver by intercostal approach over the right liver lobe. The nature of FLL was determined by diagnostic work-up, including at least one contrast-enhanced imaging modality (MDCT/MRI), check-up of target organs when metastatic disease was suspected and FLL biopsy in inconclusive cases. RESULTS: We analysed 196 patients (median age 60 [range 50-68], 50.5% males) with 259 FLLs (57 hepatocellular carcinomas, 17 cholangiocarcinomas, 94 metastases, 71 haemangiomas, 20 focal nodular hyperplasia) of which 70 (27%) were in cirrhotic liver. Malignant lesions were stiffer (P < .001) with higher variability in intralesional stiffness (P = .001). The best performing cut-off of lesion stiffness was 22.3 kPa (sensitivity 83%; specificity 86%; positive predictive value [PPV] 91.5%; negative predictive value [NPV] 73%) for malignancy. Lesion stiffness <14 kPa had NPV of 96%, while values >32.5 kPa had PPV of 96% for malignancy. Lesion stiffness, lesion/liver stiffness ratio and lesion stiffness variability significantly predicted malignancy in stepwise logistic regression (P < .05), and were used to construct a new Liver Elastography Malignancy Prediction (LEMP) score with accuracy of 96.1% in validation cohort (online calculator available at http://bit.do/lemps). CONCLUSION: The comprehensive approach demonstrated in this study enables correct differentiation of benign and malignant FLL in 96% of patients by using RT-2D-SWE.

Design and preparation of 90Y-labeled imidodiphosphate- and inositol hexaphosphate-coated magnetic nanoparticles for possible medical applications.

Radiolabeled magnetic nanoparticles (MNPs) coated with hydrophilic phosphate ligands, i.e., imidodiphosphate (IDP) and inositol hexaphosphate (IHP), were developed as multifunctional agents to localize both radioactivity and magnetic energy at a tumor site. The coating of MNPs with phosphates made them biocompatible, increased their colloidal stability and allowed binding of the radionuclide 90Y to the available functional groups on the surface of the MNPs. IDP and IHP have not hitherto been used for the coating of MNPs and the results of this study of the functionalized MNPs showed that the phosphate groups influenced the modification of the surface of MNPs. Characterization of the MNPs was performed using X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, dynamic light scattering and laser Doppler electrophoresis. The specific power absorption values obtained for MNPs (46.95-80.76 W g-1) in different physiological media indicated their possible application in hyperthermia treatment. Both types of coated MNPs were 90Y-labeled in a reproducible high yield (>98%). In vitro studies of 90Y-MNPs in saline and human serum showed their high stability after 72 h. The biodistribution pattern of the MNPs after intravenous administration to healthy Wistar rats was followed by the radiotracer method, revealing that 90Y-Fe3O4-IDP and 90Y-Fe3O4-IHP MNPs were predominantly found in the liver (85.21% ID and 86.22% ID), followed by the spleen (9.23% ID and 8.82% ID) and the lungs (1.53% ID and 1.53% ID). The results of this comprehensive study showed that radiolabeled biocompatible phosphate magnetic complexes hold great promise for therapeutic uses combining magnetic hyperthermia and radiotherapy.

Subtypes and clinical significance of common bile duct varices in portal vein thrombosis: diagnosis and follow-up by Doppler US and EUS.

PURPOSE: To investigate (1) diagnostic performance of transabdominal color doppler ultrasound (US) and endoscopic ultrasound (EUS) for detection and sub-classification of common bile duct varices (CBDV) in patients with portal vein thrombosis (PVT), and (2) clinical significance and natural history of CBDV subtypes. PATIENTS AND METHODS: During a 4-year period, 56 patients with PVT underwent US and EUS for the presence and subtypes of CBDV. Natural history was analyzed for patients who attended control visits. RESULTS: CBDV were diagnosed in 57 and 59 % of patients with US and EUS, respectively. In 19 % of patients, EUS revealed different CBDV subtypes than previously seen by US. The most common were paracholedochal (PCV), while the least common were epicholedochal (ECV) and Submucosal varices (SMV). Nine patients had obstructive jaundice and underwent ERCP which was complicated by hemobilia in two patients with SMV. Among eight patients who underwent control EUS (median follow-up 60 months), the form of CBDV remained unchanged. Two patients bled from esophageal varices, both with ECV. CONCLUSION: While abdominal US and EUS are equally sensitive for detection of CBDV, EUS allows more precise determination of CBDV subtype. Patients with SMV might be at increased risk of bleeding upon ERCP.

Insecticidal potential of natural zeolite and diatomaceous earth formulations against rice weevil (Coleoptera: Curculionidae) and red flour beetle (Coleoptera: Tenebrionidae).

Insecticidal potential of natural zeolites and diatomaceous earths originating from Serbia against Sitophilus oryzae (L.) and Tribolium castaneum (Herbst) was evaluated. Two natural zeolite formulations (NZ and NZ Modified) were applied to wheat at rates of 0.50, 0.75, and 1.0 g/kg, while two diatomaceous earth (DE) formulations (DE S-1 and DE S-2) were applied at rates of 0.25, 0.50, 0.75, and 1.0 g/kg. A bioassay was conducted under laboratory conditions: temperature of 24 +/- 1 degrees C, relative humidity in the range 50-55%, in tests with natural zeolites, and 60-65%, in tests with DEs, and in all combinations for progeny production. Mortality was assessed after 7, 14, and 21 d of insect contact with treated wheat, and the total mortality after an additional 7-d recovery on untreated broken wheat. Progeny production was also assessed after 8 wk for S. oryzae and 12 wk for T. castaneum. The highest mortality for S. oryzae and T. castaneum was found after the longest exposure period and 7 d of recovery, on wheat treated with NZ at the highest rate and DEs at rates of 0.50 -1.0 g/kg. Progeny reduction higher than 90% was achieved after 14 and 21 d of contact of both beetle pests with wheat treated with DE S-1 at 0.50-1.0 g/kg and DE S-2 at 0.75-1.0 g/kg, while the same level of reduction was achieved only for T. castaneum after its contact with the highest rate of NZ formulation. NZ Modified, applied even at the highest rate, revealed much lower insecticidal potential.

90Y-labeled tin fluoride colloid as a promising therapeutic agent: preparation, characterization, and biological study in rats.

In this study, tin fluoride colloid (SnF-c) was prepared, labeled with yttrium-90 ((90)Y), and characterized with respect to its physicochemical properties and biological behavior in an animal model. Particle size of SnF-c, at constant concentration of SnF(2), was dependent on pH, concentration of sodium fluoride (NaF), temperature, and time. The particle size of SnF-c decreased with an increase in NaF concentration and a decrease in reaction mixture pH. Radiolabeling yield of (90)Y-SnF-c at higher temperature increased and it was greater than 98% for the preparation at 95 °C. The (90)Y-SnF-c demonstrated high in vitro stability both in human serum and human synovial fluid at 37 °C up to 7 days. In vivo distribution studies in healthy male Wistar rats of (90)Y-SnF-c (particles <1 µm), following intravenous administration, revealed that the localization takes place preferably in the liver. The (90)Y-SnF-c (particles >1 µm) was well retained in the synovial space for 96 h after intra-articular injection, whereas leakage of (90)Y from the joint was 1.96% over this period. Because of high labeling yield and stability, (90)Y-SnF-c might be a promising agent for radiosynovectomy or therapy of liver malignancies.

Isolated splenic metastasis from colorectal carcinoma in a high risk patient: a case report.

Isolated splenic metastasis arising from a colorectal carcinoma is a rare finding. We report a case of 74-year-old man with a medical history of diabetes type II and paroxysmal atrial fibrillation, who underwent a right hemicolectomy for an adenocarcinoma of caecum in August 2004. In June 2007 the patient was diagnosed with high grade aortic valve stenosis as well as long segment stenosis of the first obtuse marginal branch of left coronary artery. He was suggested aortic valve replacement with coronary artery bypass grafting but he refused the surgery. In October 2007 the patient underwent alpha 18FDG - PET scanning, due to increasing values of CEA serum level, which showed a 5 cm big isolated hypermetabolic lesion in the spleen. Due to operative risk, splenectomy was refused by surgeons. The patient underwent a chemotherapy with capecitabine in total of 8 cycles before his CEA level began to rise and MSCT showed a progression in size of splenic metastasis. The patients condition was reevaluated by a team of experts and splenectomy was performed in September 2008. In May 2009 during the postoperative follow up, MSCT scanning revealed enlarged lymph nodes in celiac region and hepatic lesion suspicious of metastasis and the patient was admitted for further chemotherapy treatment. There is still no standardized treatment for this condition due to small number of cases reported in literature. Splenectomy followed by chemotherapy seems to be an optimal treatment but still no final conclusions can be made.

Placental growth factor as short-term predicting biomarker in acute coronary syndrome patients with non-ST elevation myocardial infarction.

OBJECTIVES: The relevance of placental growth factor was analyzed at the admission of patients with acute coronary syndrome (ACS) without ST elevation in prognosis of fatal outcome after 30 days. METHODS: We collected blood samples from 102 ACS patients admitted to the coronary unit with acute chest pain manifesting within the last 12 hours. RESULTS: In all 102 admitted patients, higher values of placental growth factor (PLGF; >13.2 ng/L, average value) indicated a higher risk of fatal outcome (hazard ratio [HR] 2.28, 95% confidence interval [CI] 1.21- 4.76, P = 0.0125). PLGF is an important independent prognostic marker (adjusted HR 2.35, 95% CI 1.98-4.61, P = 0.1338), and this was shown in a multiparameter model, which involved other statistically important markers of relative risk (age >65, gender, and estimated glomerular filtration rate [eGFR]). CONCLUSION: PLGF levels measured at 12 hours of symptom onset and 30 days later may independently predict fatal outcome in patients with ACS without ST elevation.

Utility of placental growth factor for prediction of 30-day adverse event in emergency department population with non-ST elevation acute coronary syndrome.

BACKGROUND: Placental growth factor (PIGF) belongs to the vascular endothelial growth factor family and seems to be an independent biomarker for plaque disruption, ischemia, and thrombosis. Plasma PIGF is rapidly produced in infarcted myocardial tissue during the acute phase of myocardial infarction. In this study, the relevance of PIGF was analyzed at the admission of patients with acute coronary syndrome (ACS) without ST elevation for the prognosis of fatal outcome after 30 days. METHODS: We collected blood samples from 102 ACS patients admitted to the coronary unit with manifesting acute chest pain within the previous 12 hours and measured the levels of PIGF, high-sensitivity C-reactive protein (hsCRP), and cardiac markers: troponin T (cTnT), B-type natriuretic peptide, creatine kinase-MB (CKMB) and CK activity. RESULTS: PIGF, troponin T, and hsCRP levels were significantly higher in non-survivors than in survivors. ROC analysis showed that PIGF had the highest area under ROC curve (AUC, 0.713), but it was not significantly different from AUCs for cTnT and hsCRP. Higher values of PIGF (>13.2 ng/L) pointed towards a higher risk of fatal outcome (HR 2.28; 95 % CI 1.21-4.76; P=0.0125). The multivariable proportional hazards analysis, which had involved other statistically significant markers of relative risk (age and gender), showed that PIGF was an independent prognostic marker (adjusted HR 2.14; 95 % CI 1.08-4.22). CONCLUSIONS: These results confirmed that PIGF is an independent biomarker of short-term adverse outcome in patients with ACS without ST elevation and that plaque instability, represented by PIGF elevation, has an important role in the pathogenesis of future coronary events.

Endoscopic ultrasound in solid pancreatic masses--current state and review of the literature.

Some 25 years ago endoscopic ultrasound (EUS) was introduced in clinical practice for better visualization of pancreas. At the time of introduction EUS was superior to other methods in detection of pancreatic masses allowing tissue diagnosis by later introduced EUS-guided fine needle aspiration (FNA). During the time EUS was improved, electronic probes replaced mechanical probes adding ability of color Doppler, power Doppler, contrast enhanced endosonography as well as EUS elastography analysis. Meanwhile, CT technology has also experienced significant improvements raising the question whether EUS has lost ground in diagnostics of solid pancreatic masses. The aim of this review was to discuss the current evidence of clinical impact of EUS and EUS-FNA in evaluation of solid pancreatic masses with special emphasis on differentiation between benign and malignant pancreatic lesions. According to the literature, the detection of small pancreatic tumors, preoperative localization of pancreatic endocrine tumors and tissue sampling by fine-needle aspiration of pancreatic masses in cases with therapeutic consequences are considered firm indications for EUS. Cytological tissue analysis remains undisputed in differentiation benign from malignant lesions, but the question when FNA is needed is discussed. Color Doppler, power Doppler, contrast enhanced endosonography and especially elastography are also discussed as tools that are bringing additional information in evaluation of pancreatic masses, however insufficient for definitive judgment of the lesion's nature. Pancreatic cancer staging as indication for EUS is discussed controversially, inconsistent results and conflicting evidence in literature making adequate conclusion impossible. However, this indicates that at least the role of EUS is no longer undisputed in this matter. Resuming the role of EUS we can state that despite some controversies EUS is very valuable method in evaluation of solid pancreatic masses and with EUS guided FNA is nowadays by far the best method for obtaining tissue diagnosis.

Assessment of heavy metal and pesticide levels in soil and plant products from agricultural area of Belgrade, Serbia.

This study was aimed to assess the levels of selected heavy metals and pesticides in soil and plant products from an agricultural area of Belgrade, Serbia and to indicate possible sources and risks of contamination. Soil, vegetable, and fruit samples from the most important agricultural city areas were collected from July to November of 2006. Metal contents were determined by atomic absorption spectrometry, whereas pesticide residues were analyzed by gas chromatography-mass spectrometry after extraction performed using solid-phase microextraction technique. Soil characterization based on the determination of selected physical and chemical properties revealed heterogeneous soils belonging to different soil groups. The concentrations of lead, cadmium, copper, and zinc in soil samples do not exceed the limits established by national and international regulations. Residues of the herbicide atrazine were detected in three soil samples, with levels lower than the relevant limit. The presence of other herbicides, namely prometryn, chloridazon, acetochlor, flurochloridone, and napropamide, was registered in some soil samples as well. Among the insecticides investigated in the soil, fenitrothion and chlorpyrifos were the only ones detected. In most of the investigated vegetable samples from the Obrenovac area, Pb and Cd contents are higher in comparison with the maximum levels, indicating the emission of coal combustion products from local thermal power plants as a possible source of contamination. Residue levels of some herbicides and insecticides (metribuzin, trifluralin, pendimethalin, bifenthrin, chlorpyrifos, and cypermethrin) determined in tomato, pepper, potato, and onion samples from Slanci, Ovca, and Obrenovac areas are even several times higher than the maximum residue levels. Inappropriate use of these plant protection products is considered to be the most probable reason of contamination. Because increased levels of heavy metals and pesticide residues found in plant products could pose a risk to consumers' health, their continual monitoring before product distribution to city markets is indispensable.