Imaging diagnosis of schistosomiasis japonica--the use in Japan and application for field study in the present endemic area

For detecting lesions-related schistosomiasis japonica, X-rays, scintillation scanning, ultrasonography (US), computed tomography (CT), magnetic resonance (MR) and endoscopic examinations with biopsies have been used in Japan. Liver fibrosis and calcified changes are detected by US and CT. Most of the lesions that are detected by endoscopic examinations are due to deposited ova of Schistosoma japonicum. Portal hypertension is detected by US, CT and gastroscopic examination. Because schistosome infection decreased rapidly in Japan, most of the studies on imaging diagnosis were performed on chronic lesions or sequelae of schistosomiasis. Most of the techniques were used on admitted patients in well-equipped hospitals. US was introduced in the 1970s as a safe, rapid, non-invasive and inexpensive technique and has been used for diagnosis in hospitals and screening in the fields. As a typical US image of the liver, septal formation by high echogenic bands like mosaic was described, and this network pattern was reported in the other endemic countries; China and Philippines. As an appropriate technique, US has been broadly used in developing countries. Not only for diagnosis in a hospital, but also for monitoring changes of morbidity, US is used in the community level. Network pattern related to the severity of S. japonicum infection, has not been described in S. mansoni or S. haematobium infection. Appearance of network pattern depends on pathological changes such as periportal fibrosis, postnecrotic fibrosis and calcified ova. For advanced studies on morbidity of schistosomiasis japonica, further research on pathological basis of network pattern and standardization of US diagnosis are necessary.     

Ultrasound versus biological markers in the evaluation of periportal fibrosis in human Schistosoma mansoni

In this paper, the authors review the literature and share their experience of the principal biological markers of fibrosis for the evaluation of periportal fibrosis (PPF) caused by mansoni schistosomiasis. These biological markers are compared to diagnostic ultrasound (US) scans as means of grading PPF. We also review procollagen type I and III, collagen type IV, laminin, hyaluronic acid (HA), immunoglobulin G, platelets, aspartate aminotransferase to platelet ratio index (APRI) and gamma-glutamyl transpeptidase as markers of the disease. Although there are several good markers for evaluating PPF and portal hypertension, such as HA, platelets or APRI, none can yet replace US. These markers may, however, be used to identify patients at greater risk of developing advanced disease in endemic areas and determine who will need further care and US studies.     

Cytokine regulation of periportal fibrosis in humans infected with Schistosoma mansoni: IFN-gamma is associated with protection against fibrosis and TNF-alpha with aggravation of disease

Hepatic periportal fibrosis, which affects 5-10% of subjects infected by Schistosoma mansoni, is caused by the T cell-dependent granuloma that develop around schistosome eggs. Experimental models of infection have shown that granuloma and fibrosis are tightly regulated by cytokines. However, it is unknown why advanced periportal fibrosis occurs only in certain subjects. The goal of the present study was to evaluate the cytokine response of S. mansoni-infected subjects with advanced liver disease in an attempt to relate susceptibility to periportal fibrosis with an abnormal production of cytokines that regulate granuloma and fibrosis. Fibrosis was evaluated by ultrasound on 795 inhabitants of a Sudanese village in which S. mansoni is endemic: advanced periportal fibrosis was observed in 12% of the population; 35% of the affected subjects exhibited signs of portal hypertension. Age (odds ratio (OR), 11.5), gender (OR, 4.2), and infection levels (OR, 2.2) were significantly (p < or = 0.01) associated with hepatic fibrosis. Cytokines produced by egg-stimulated blood mononuclear cells from 99 subjects were measured (75 with no or mild fibrosis; 24 subjects with advanced fibrosis). Multivariate analysis of cytokine levels showed that high IFN-gamma levels were associated with a marked reduction of the risk of fibrosis (p = 0.01; OR, 0.1); in contrast, high TNF-alpha levels were associated with an increased risk (p = 0.05; OR, 4.6) of periportal fibrosis. Moreover, infection levels were negatively associated with IFN-gamma production. These results with observations in experimental models strongly suggest that IFN-gamma plays a key role in the protection of S. mansoni-infected patients against periportal fibrosis, whereas TNF-alpha may aggravate the disease.     

Chronic hepatosplenomegaly in African school children: a common but neglected morbidity associated with schistosomiasis and malaria

Chronic hepatosplenomegaly, which is known to have a complex aetiology, is common amongst children who reside in rural areas of sub-Saharan Africa. Two of the more common infectious agents of hepatosplenomegaly amongst these children are malarial infections and schistosomiasis. The historical view of hepatosplenomegaly associated with schistosomiasis is that it is caused by gross periportal fibrosis and resulting portal hypertension. The introduction of ultrasound examinations into epidemiology studies, used in tandem with clinical examination, showed a dissociation within endemic communities between presentation with hepatosplenomegaly and ultrasound periportal fibrosis, while immuno-epidemiological studies indicate that rather than the pro-fibrotic Th2 response that is associated with periportal fibrosis, childhood hepatosplenomegaly without ultrasound-detectable fibrosis is associated with a pro-inflammatory response. Correlative analysis has shown that the pro-inflammatory response is also associated with chronic exposure to malarial infections and there is evidence of exacerbation of hepatosplenomegaly when co-exposure to malaria and schistosomiasis occurs. The common presentation with childhood hepatosplenomegaly in rural communities means that it is an important example of a multi-factorial disease and its association with severe and subtle morbidities underlies the need for well-designed public health strategies for tackling common infectious diseases in tandem rather than in isolation.     

Periportal fibrosis in human Schistosoma mansoni infection is associated with low IL-10, low IFN-gamma, high TNF-alpha, or low RANTES, depending on age and gender

Schistosoma mansoni infection is highly endemic in parts of Uganda, and periportal fibrosis is common in communities along the shore of Lake Albert. In this study, we have identified cellular immune responses associated with fibrosis. A cohort of 199 individuals aged 6-50, resident in the village for at least 10 years or since birth, were examined for evidence of periportal fibrosis by ultrasound using the Niamey protocol. Whole-blood samples were assayed for levels of nine cellular immune molecules (IL-3, IL-4, IL-5, IL-10, IL-13, TNF-alpha, IFN-gamma, IL-1beta, and RANTES) in the absence of in vitro Ag stimulation, and after stimulation with egg and worm Ags. A lack of Ag specificity allowed the number of variables in the analysis to be reduced by factor analysis. The resulting factor scores were then entered into a risk analysis using a classification tree algorithm. Children, adult males, and adult females had different factors associated with fibrosis. Most cases of fibrosis in children (eight of nine) were associated with low (<47th percentile) IL-10 factor scores. Adult females at lowest risk had relatively high IFN-gamma factor scores (>83rd percentile), whereas those at highest risk had a combination of intermediate (32nd to 83rd percentile) IFN-gamma and relatively high (>60th percentile) TNF-alpha factor scores. Adult males at lowest risk of fibrosis had moderate TNF-alpha factor scores (55th to 82nd percentile), and a high risk was associated with either high TNF-alpha factor scores (>82nd percentile), or intermediate TNF-alpha combined with low RANTES factor scores (<58th percentile). These results demonstrate that periportal fibrosis is associated with cytokine production profiles that vary with both age and gender.     

Severe hepatic fibrosis in Schistosoma mansoni infection is controlled by a major locus that is closely linked to the interferon-gamma receptor gene.

Lethal disease due to hepatic periportal fibrosis occurs in 2%-10% of subjects infected by Schistosoma mansoni in endemic regions such as Sudan. It is unknown why few infected individuals present with severe disease, and inherited factors may play a role in fibrosis development. Schistosoma mansoni infection levels have been shown to be controlled by a locus that maps to chromosome 5q31-q33. To investigate the genetic control of severe hepatic fibrosis (assessed by ultrasound examination) causing portal hypertension, a segregation analysis was performed in 65 Sudanese pedigrees from the same village. Results provide evidence for a codominant major gene, with.16 as the estimated allele A frequency predisposing to advanced periportal fibrosis. For AA males, AA females, and Aa males a 50% penetrance is reached after, respectively, 9, 14, and 19 years of residency in the area, whereas for other subjects the penetrance remains <.02 after 20 years of exposure. Linkage analysis performed in four candidate regions shows that this major locus maps to chromosome 6q22-q23 and that it is closely linked (multipoint LOD score 3.12) to the IFN-gammaR1 gene encoding the receptor of the strongly antifibrogenic cytokine interferon-gamma. These results show that infection levels and advanced hepatic fibrosis in human schistosomiasis are controlled by distinct loci; they suggest that polymorphisms within the IFN-gammaR1 gene could determine severe hepatic disease due to S. mansoni infection and that the IFN-gammaR1 gene is a strong candidate for the control of abnormal fibrosis observed in other diseases.     

Ultrasonography in the study of hepatocellular carcinoma in woodchucks chronically infected with WHV

The woodchuck hepatitis virus (WHV)/woodchuck system is studied as animal model of human hepatocellular carcinoma (HCC) induced by chronic hepatitis B virus infection. The aim of the present study was the evaluation of ultrasound (US) liver examination in woodchuck as a routine method to detect HCC nodules and to follow their growth. Sixteen woodchucks were included in the study. US liver examination was carried out in all animals using a 5 MHz convex scanner. Macroscopic and microscopic examinations were performed to evaluate the US findings. The lower limit of nodule detection by US examination was a diameter of 5 mm. Macroscopic and microscopic examinations confirmed US findings in 14 of 16 animals (86.6%). No false negative results were obtained. Increase of nodule size was faster in the early phase of tumour growth. Small nodules (16 +/- 5 mm) appeared as hypoechoic lesions with well-defined margins and homogeneous structure. Large nodules (42 +/- 19 mm) appeared as hyperechoic lesions with irregular margins, heterogeneous or of mixed pattern; microscopical examination showed different degrees of necrosis, inflammation and fibrosis inside these latter neoplasms. The hepatitis reaction was conspicuously more severe around HCC nodules. No fibrosis and/or cirrhosis were found in normal liver parenchyma surrounding tumour nodules. On the whole, US appears to be helpful in the diagnosis of woodchuck HCC even at an early stage. Serial US evaluation can be used to study the growth rate of tumour nodules during natural history or experimental HCC treatments in woodchuck.     

Hyperplasia of elastic tissue in hepatic schistosomal fibrosis.

Elastic tissue hyperplasia, revealed by means of histological, immunocytochemical and ultra-structural methods, appeared as a prominent change in surgical liver biopsies taken from 61 patients with schistosomal periportal and septal fibrosis. Such hyperplasia was absent in experimental murine schistosomiasis, including mice with "pipe-stem" fibrosis. Displaced connective tissue cells in periportal areas, such as smooth muscle cells, more frequently observed in human material, could be the site of excessive elastin synthesis, and could explain the differences observed in human and experimental materials. Elastic tissue, sometimes represented by its microfibrillar components, also appeared to be more condensed in areas of matrix (collagen) degradation, suggesting a participation of this tissue in the remodelling of the extracellular matrix. By its rectratile properties elastic tissue hyperplasia in hepatic schistosomiasis can cause vascular narrowing and thus play a role in the pathogenesis of portal hypertension.     

Serum zinc as a factor predicting response to interferon-alpha2b therapy in children with chronic hepatitis B

Although it has been unclear why more than 50% of children with chronic hepatitis B virus infection do not respond to interferon therapy, in some instances resistance to interferon probably is caused by an inability to stimulate appropriately cellular immune responses to hepatitis B virus. It is known that immune integrity is tightly linked to zinc status. We examined the relationship between serum zinc levels and response to interferon (INF)-α therapy in children with chronic hepatitis B. Twenty-five children with chronic hepatitis B infection were injected with 5 × 10⁶ units/m² recombinant IFN-α 2b subcutaneously three times weekly for 9 mo. Children were followed for at least 9 mo after the end of therapy. Sustained response was obtained in eight (32%) patients. Although initial serum zinc and alanine aminotransferase levels were significantly higher; initial hepatitis B Virus (HBV)-DNA values, hepatic activity index, periportal necrosis, and fibrosis scores were significantly lower in sustained responders than in nonresponders. Mean baseline serum zinc, alanine aminotransferase and HBV-DNA values, histologic activity index, periportal necrosis, and fibrosis scores were predictive of response to IFN-α 2b therapy. These findings suggest that serum zinc levels might be used as a factor predicting response to interferon-α 2b therapy, and so may help in identifying those children with a better chance of response.     

The 434(G>C) polymorphism within the coding sequence of Eosinophil Cationic Protein (ECP) correlates with the natural course of Schistosoma mansoni infection

Schistosomiasis is a chronic parasitic infection with over 200 million people infected worldwide. In Schistosoma mansoni infections, parasite-derived eggs get trapped in the liver, causing the formation of granulomas, which may develop into periportal fibrosis and portal hypertension, and thus severe morbidity. Eosinophil cationic protein (ECP) is a secretory protein of eosinophil granulocytes that efficiently kills the larval stage of S. mansoni, but also affects fibroblast functions. We have investigated the prevalence of the ECP gene polymorphism 434(G>C) in two African populations, from an S. mansoni endemic area in Uganda (n=297) and from a non-endemic area in Sudan (n=78), and also compared these with a Swedish population (n=209). The genotype frequencies in the Ugandan population differed significantly from both the Sudanese and Swedish populations (P<0.001). In the Ugandan population there was a significant association between genotype and prevalence of infection (P=0.03), with lower prevalence in subjects with the GG genotype compared with GC (P=0.02) and CC (P=0.03). There was also a trend towards an association with periportal fibrosis (P=0.08) in the Ugandan population. This suggested association was confirmed when the predominant tribe (n=212) was analysed separately (P=0.004). Our results suggest that ECP may be an important protein, both in the immune response against S. mansoni and in the development of periportal fibrosis. The results also suggest genetic selection towards the ECP 434CC genotype in populations living in S. mansoni endemic areas.     

Hemostatic Dysfunction Is Increased in Patients with Hepatosplenic Schistosomiasis Mansoni and Advanced Periportal Fibrosis

Background

Schistosomiasis mansoni is an endemic parasitic disease and a public health problem in Northeast Brazil. In some patients, hepatic abnormalities lead to periportal fibrosis and result in the most severe clinical form, hepatosplenic schistosomiasis. This study aimed to evaluate whether abnormal blood coagulation and liver function tests in patients with hepatosplenic schistosomiasis (n = 55) correlate with the severity of their periportal fibrosis.

Methodology/Principal Findings

Blood samples were used for liver function tests, hemogram and prothrombin time (International Normalized Ratio, INR). The blood coagulation factors (II, VII, VIII, IX and X), protein C and antithrombin IIa (ATIIa), plasminogen activator inhibitor 1 (PAI-1) and D-dimer were measured by photometry or enzyme linked immunosorbent assay. Hyperfibrinolysis was defined on the basis of PAI-1 levels and a D-dimer concentration greater than a standard cut-off of 483 ng/mL. Standard liver function tests were all abnormal in the patient group compared to healthy controls (n = 29), including raised serum transaminases (p<0.001) and lower levels of albumin (p = 0.0156). Platelet counts were 50% lower in patients, while for coagulation factors there was a 40% increase in the INR (p<0.001) and reduced levels of Factor VII and protein C in patients compared to the controls (both p<0.001). Additionally, patients with more advanced fibrosis (n = 38) had lower levels of protein C compared to those with only central fibrosis (p = 0.0124). The concentration of plasma PAI-1 in patients was one-third that of the control group (p<0.001), and D-dimer levels 2.2 times higher (p<0.001) with 13 of the 55 patients having levels above the cut-off.

Conclusion/Significance

This study confirms that hemostatic abnormalities are associated with reduced liver function and increased liver fibrosis. Of note was the finding that a quarter of patients with hepatosplenic schistosomiasis and advanced periportal fibrosis have hyperfibrinolysis, as judged by excessive levels of D-dimer, which may predispose them to gastrointestinal bleeding.     

Effects of a gamma-secretase inhibitor of notch signalling on transforming growth factor β1-induced urethral fibrosis

Urethral stricture (US) is a common disorder of the lower urinary tract in men caused by fibrosis. The recurrence rate of US is high; however, there are no effective therapies to prevent or treat urethral fibrosis. The pathogenesis of urethral fibrosis involves myofibroblast activation and excessive extracellular matrix (ECM) deposition. The molecular mechanisms underlying this pathological activation are not completely understood. It has been demonstrated that Notch signalling contributes to the development of fibrosis and inflammation. However, whether this contributes to urethral fibrosis remains unclear. In this study, activation of Notch signalling was observed in patients with US. Additionally, it was noted that activation of Notch signalling promoted ECM production and myofibroblast activation in human urethral scar fibroblasts (HUSFs) treated with transforming growth factor (TGF) β1. However, the Notch inhibitor N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) suppressed activation of Notch signalling as well as proliferation and migration of the TGFβ1-treated HUSFs. Additionally, DAPT ameliorated TGFβ1-induced urethral fibrosis in Sprague Dawley rats by suppressing ECM production, myofibroblast activation and the TGFβ signalling pathway. These findings demonstrate that Notch signalling may be a promising and potential target in the prevention or treatment of urethral fibrosis.     

Pathogenesis of pipe-stem fibrosis of the liver (experimental observation on murine schistosomiasis)

Mice infected with 30 cercariae of Schistosoma mansoni developed portal and septal fibrosis due to the massive and concentrated deposition of eggs in the periportal areas which occurred following the 16th week after infection. The lesion resembled pipe-stem fibrosis seen in human hepatosplenic schistosomiasis in the following characters: portal fibrosis interconnecting portal spaces as well as portal spaces and central canals; portal inflammation; periovular granulomas; vascular obstruction and telangiectasia. The liver parenchyma maintained its normal architecture. Vascular injection techniques with Indian ink and vinylite revealed that the portal system developed numerous dilated collateral venules coming from the large and medium-sized portal branches, about 10 weeks after schistosome infection. The lodging of schistosome eggs into these collaterals resulted in granulomatous inflammation and fibrosis along all the portal tracts, thus forming the pipe-stem lesion. Although not readily demonstrable grossly, the pipe-stem fibrosis of murine schistosomiasis has many similarities with the human lesion and can be considered to have the same basic pathogenesis.     

Formalin-induced experimental sclerosing cholangitis in the rat

The few reported cases of sclerosing cholangitis following removal of an echinococcus cyst are thought to be a consequence of the chemical action of formalin used for sterilization of the residual cavity. The aim of this study was to assess this hypothesis. We injected 0.15ml of 2% buffered formalin solution into the central hepatic lobe of five rats, after a midline laparotomy. At 6, 12, 18 and 24 weeks after formalin injection all rats were reoperated upon and a sample of hepatic parenchyma from both the central and the left hepatic lobe was obtained for microscopic evaluation. Our findings, dilatation of portal tracts and bile canaliculi, thickening of the pericanalicular cytoplasm, portal and periportal inflammatory cell infiltration and fibrosis and enlargement of the perisinusoidal space of Disse, suggest that 2% formalin solution leads to the development of essential phenomena of cholestasis and sclerosing cholangitis in the rat, so thus it should be avoided in liver hydatid disease surgery.     

Long-Term Selenium-Deficient Diet Induces Liver Damage by Altering Hepatocyte Ultrastructure and MMP1/3 and TIMP1/3 Expression in Growing Rats

The effects of selenium (Se)-deficient diet on the liver were evaluated by using growing rats which were fed with normal and Se-deficient diets, respectively, for 109 days. The results showed that rats fed with Se-deficient diet led to a decrease in Se concentration in the liver, particularly among male rats from the low-Se group. This causes alterations to the ultrastructure of hepatocytes with condensed chromatin and swelling mitochondria observed after low Se intake. Meanwhile, pathological changes and increased fibrosis in hepatic periportal were detected by hematoxylin and eosin and Masson’s trichrome staining in low-Se group. Furthermore, through immunohistochemistry (IHC) staining, higher expressions of metalloproteinases (MMP1/3) and their tissue inhibitors of metalloproteinases (TIMP1/3) were observed in the hepatic periportal of rats from the low-Se group. However, higher expressions of MMP1/3 and lower expressions of TIMP1/3 were detected in hepatic central vein and hepatic sinusoid. In addition, upregulated expressions of MMP1/3 and downregulated expressions of TIMP1/3 at the messenger RNA (mRNA) and protein levels also appeared to be relevant to low Se intake. In conclusion, Se-deficient diet could cause low Se concentration in the liver, alterations of hepatocyte ultrastructure, differential expressions of MMP1/3 and TIMP1/3 as well as fibrosis in the liver hepatic periportal.     

The Value of MRI in the Diagnosis of Primary Biliary Cirrhosis and Assessment of Liver Fibrosis

Objectives

To evaluate MRI findings in patients with primary biliary cirrhosis (PBC) and to determine the value of MRI in the diagnosis of PBC and assessment of liver fibrosis.

Materials and Methods

This study reviewed the prevalence of MRI abnormalities seen in 45 PBC patients in the past four years, including 33 patients who underwent liver biopsy. Correlation between the MRI findings and the pathological stage was determined.

Results

There were 33 patients who underwent liver biopsy. Twenty-five patients (75.8%) had non-homogeneous changes in the liver signal intensity, 25 (75.8%) had a periportal halo sign, and 29 (87.9%) had lymphadenopathy. The short axis of the enlarged lymph nodes was a mean of 1.2±0.3 cm. A strong positive correlation was observed between histological stage and the inhomogeneity of liver signal intensity (P<0.001). There were significant differences among the four histological stages based on the periportal halo sign (P=0.034), and the grading of the periportal halo sign was found to be significantly correlated with the histological stage (P<0.001). Grading of the periportal halo sign was significantly different at stage II versus III, and stage III versus IV; no significant difference was found between stages I and II. There were also no significant differences among the four histological states in the occurrence and size of enlarged lymph nodes (P=0.674 and P=0.394).

Conclusion

MRI is valuable in the diagnosis of PBC, and the periportal halo sign and liver signal intensity help to evaluate the degree of liver fibrosis.     

Contributions to the biology of the hypoxic liver. Note I. Histological and electronmicroscopical aspects of the liver in chronic congestive heart failure

A study was carried out on the histological and ultrastructural aspects of liver fragments harvested from 62 patients with acquired or congenital heart disease before open heart surgery under extracorporeal circulation. Against a background of passive congestion in the pericentrolobular and mediolobular areas, various mitochondrial lesions and dilation of the endoplasmic reticulum with a reduced number of ribosomes, the presence of microbodies, biliary pigments, lipid vacuoles, lysosomol hyperplasia and activation, glycogen depletion could be seen, as well as extensive collagenization of Disse's spaces, fibroblast hyperplasia and Kupffer cell activation. These lesions are more reduced in the periportal zones. In the advanced stages of heart failure, there appeared a cirrhogenic organization due to extensive pericentrolobular and periportal fibrosis.     

Utility of a simplified ultrasound assessment to assess interstitial pulmonary fibrosis in connective tissue disorders - preliminary results

Introduction  

Interstitial pulmonary fibrosis (IPF) is a frequent manifestation in patients with connective tissue disorders (CTD). Recently the ultrasound (US) criterion validity for its assessment has been proposed; however, the US scoring systems adopted include the study of several lung intercostal spaces (LIS), which could be time-consuming in daily clinical practice. The aim of this study was to investigate the utility of a simplified US B-lines scoring system compared with both the US comprehensive assessment and the high-resolution computed tomography (HRCT) findings of IPF in CTD patients.     

Capillaria hepatica (Nematoda) infections in human-habituated mountain gorillas (Gorilla gorilla beringei) of the Parc National de Volcans, Rwanda

Habituation to humans of free-ranging populations of endangered mountain gorillas (Gorilla gorilla beringei) raised concern of anthropozoonotic transmission of parasitic helminths and protozoans. Examinations of liver tissue of 19 gorillas found dead in the Parc National de Volcans, Rwanda, revealed 10 cases of hepatic nematodiasis due to Capillaria hepatica. Identifiable C. hepatica eggs were present in the liver of 4 gorillas (3 juveniles, 1 adult), and nematode cross-sections were found in 1 juvenile gorilla. Six other adult gorillas had areas of periportal and subcapsular fibrosis with calcified eggs. Histologically, the lesions surrounded by the areas of mild inflammatory reaction were characterized by subcapsular, periportal foci of fibrosis in which were embedded numerous C. hepatica eggs. Control of hepatic capillariasis in the remaining populations of mountain gorillas should be focused on eradication or control of populations of rodent pests (i.e., mice and rats) that sustain the reservoir of C. hepatica in habitats shared by gorillas and humans.     

Hepatic zonation of carbon and nitrogen fluxes derived from glutamine and ammonia transformations

Background  

Glutaminase predominates in periportal hepatocytes and it has been proposed that it determines the glutamine-derived nitrogen flow through the urea cycle. Glutamine-derived urea production should, thus, be considerably faster in periportal hepatocytes. This postulate, based on indirect observations, has not yet been unequivocally demonstrated, making a direct investigation of ureogenesis from glutamine highly desirable.