Machine learning algorithms in sepsis

Sepsis remains a significant global health challenge due to its high mortality and morbidity, compounded by the difficulty of early detection given its variable clinical manifestations. The integration of machine learning (ML) into laboratory medicine for timely sepsis identification and outcome forecasting is an emerging field of interest. This comprehensive review assesses the current body of research on ML applications for sepsis within the realm of laboratory diagnostics, detailing both their strengths and shortcomings. An extensive literature search was performed by two independent investigators across PubMed and Scopus databases, employing the keywords "Sepsis," "Machine Learning," and "Laboratory" without publication date limitations, culminating in January 2023. Each selected study was meticulously evaluated for various aspects, including its design, intent (diagnostic or prognostic), clinical environment, demographics, sepsis criteria, data gathering period, and the scope and nature of features, in addition to the ML methodologies and their validation procedures. Out of 135 articles reviewed, 39 fulfilled the criteria for inclusion. Among these, the majority (30 studies) were focused on devising ML algorithms for diagnosis, fewer (8 studies) on prognosis, and one study addressed both aspects. The dissemination of these studies across an array of journals reflects the interdisciplinary engagement in the development of ML algorithms for sepsis. This analysis highlights the promising role of ML in the early diagnosis of sepsis while drawing attention to the need for uniformity in validating models and defining features, crucial steps for ensuring the reliability and practicality of ML in clinical setting.

Validation, performance, and reliability of two automated tests for vitamin B12 and folate assay

Background

Deficiency of Vitamin B12 and folate may determine hematological, neurological, and metabolic alterations; therefore, an accurate quantification of their serum levels is required, especially in the presence of symptoms that might suggest a deficiency. CHORUS VIT B12 and CHORUS FOLATE are two automated immunoassays, developed to quantify vitamin B12 and folate, respectively, in human serum.

Design and methods

This single-center, non-pharmacological, diagnostic study described the validation and characterization of CHORUS VIT B12 and CHORUS FOLATE, with a specific focus on performance, precision, and reliability. For each assay, 500 serum samples were analyzed. A comparison between CHORUS assays and commercially available kit was also performed.

Results

For CHORUS VIT B12 the lower limit of quantification (LLoQ) was 165.0 pg/mL and the upper LoQ (ULoQ) was 1846.8 pg/mL. The assay was linear within the calibration range (150-2000 pg/mL) and the accuracy was described with the International Standard Vitamin B12, Serum Folate, HOLO TC (NIBSC code: 03/178), with a mean recovery on two lots of 111%. For CHORUS FOLATE (calibration range of 2.0-20.0 ng/mL), LLoQ was 2.0 ng/mL and ULoQ 19.6 ng/mL. The linearity was demonstrated from 2.4 to 20.0 ng/mL; the accuracy was described with the International Standard mentioned above, achieving a mean recovery on three lots of 92%. The lowest and highest values of both CHORUS and COBAS kits were similar and the median values did not significantly vary.

Conclusion

CHORUS VIT B12 and CHORUS FOLATE performed well, accurately, and reliably in quantifying vitamin B12 and folate in human serum.

A survey on Artificial Intelligence and Big Data utilisation in Italian clinical laboratories

OBJECTIVES

The Italian Society of Clinical Biochemistry and Clinical Molecular Biology (SIBioC) Big Data and Artificial Intelligence (BAI) Working Group promoted a survey to frame the knowledge, skills and technological predisposition in clinical laboratories.

METHODS

A questionnaire, focussing on digitization, information technology (IT) infrastructures, data accessibility, and BAI projects underway was sent to 1,351 SIBioC participants. The responses were evaluated using SurveyMonkey software and Google Sheets.

RESULTS

The 227 respondents (17%) from all over Italy (47% of 484 labs), mainly biologists, laboratory physicians and managers, mostly from laboratories of public hospitals, revealed lack of hardware, software and corporate Wi-Fi, and dearth of PCs. Only 25% work daily on clouds, while 65%-including Laboratory Directors-cannot acquire health data from sources other than laboratories. Only 50% of those with access can review a clinical patient's health record, while the other access only to laboratory information. The integration of laboratory data with other health data is mostly incomplete, which limits BAI-type analysis. Many are unaware of integration platforms. Over 90% report pulling data from the Laboratory Information System, with varying degrees of autonomy. Very few have already undertaken BAI projects, frequently relying on IT partnerships. The majority consider BAI as crucial in helping professional judgements, indicating a growing interest.

CONCLUSIONS

The questionnaire received relevant feedback from SIBioC participants. It highlighted the level of expertise and interest in BAI applications. None of the obstacles stands out more than the others, emphasising the need to all-around work: IT infrastructures, data warehouses, BAI analysis software acquisition, data accessibility and training.

A computer model for professional competence assessment according to ISO 15189

Background As defined by ISO 15189 competence is the "demonstrated ability to apply knowledge and skills" thus, its assessment is fundamental for ensuring the quality of the total testing process in order to reduce the risk for the patient. We have developed a functional software for the measurement of professional competences in order to standardize the procedure and to collect all the data in a single platform, avoiding redundancy and dispersion. Methods Our model objectively assesses the skills, as they become measurable and comparable with appropriate standards and involves both managers and operators, to increase their active engagement. The assessment concerns everyone, but the standards to be met (numerical values) can vary according to the responsibilities. Several subjective and objective criteria are evaluated: each parameter can contribute in a variable proportion to the total skills measured according to the needs of the organization. Results The data are automatically analyzed and can be easily monitored in real time in the form of indicators, thanks to dashboards. The comparison between the skills required and those measured allows highlighting the gap useful for planning personalized training paths. Conclusions Our tool is reliable and highly adaptable to laboratories about competences to track criteria, standards and monitored indicators. The computerized management is a strategic action as it fulfills the requirements of registration, traceability, communication, data analysis and indicators development, which are the tenets of continuous improvement, and allows planning to be made on the basis of the actual training needs.

Methodology to Evaluate Clinical Impact of 0/3 Hour High-Sensitivity Cardiac Troponin T Protocol on Managing Acute Coronary Syndrome in Daily Emergency Department Practice

OBJECTIVE

Sex-/age-differentiated cutoffs and the magnitude of serial changes in high-sensitivity cardiac troponins (hs-cTn) for acute coronary syndrome (ACS) diagnosis algorithms are still under discussion. This study presents a methodology to evaluate decision-making limits and to assess whether sex-specific cutoffs could improve diagnostic accuracy.

METHODS

A high-sensitivity cardiac troponin T (hs-cTnT) 0-/3-hour protocol was adopted, applying the 2015 European Society of Cardiology Guidelines. Decision-making limits (99th percentile: 14 ng/L; delta change ≥ 30%) were agreed upon with the emergency department (ED) at the University Hospital of Siena in Siena, Italy. One-year requests (5177) for hs-cTnT serial determination were compared with the final International Classification of Diseases, 9th revision, clinical modifications diagnosis (contingency tables; receiver operating characteristic curves).

RESULTS

The algorithm's capability to exclude or confirm ACS was verified by remarkable negative predictive value (97%) and high areas under the curve for the first troponin sampling (0.712), troponin sampling at 3 hours (0.789), and delta (0.744). The clinical utility for the general population-even those with comorbidities-accessing the ED was verified. Our data did not support a sex-differentiated cutoff utility because it would not have affected patient management.

CONCLUSION

This methodology allowed us to confirm the effectiveness of our decision-making limits.

Defining and Managing the Preanalytical Phase With FMECA: Automation and/or "Human" Control

OBJECTIVE

Our scope is to provide methodological elements on how to manage effectively the preanalytical phase in the laboratory testing process, by objectively measuring the risk connected to the phases handled by man with respect to those managed by machines.

BACKGROUND

Preanalytical errors account for most of the mistakes related to laboratory testing and can affect patient care. Hence, it is necessary to manage the risk connected to the preanalytical phase, as required by certification and accreditation bodies. The risk assessment discloses the steps at greater risk and gives indications to make decisions.

METHOD

We have reviewed the state of art in the automation of the preanalytical phase, addressing needs and problems. We have used the proactive risk assessment methodology FMECA (Failure Mode, Effects, and Criticality Analysis) to identify the most critical phases in our preanalytical process and have calculated the risk associated.

RESULTS

The most critical phases were the human controlled ones. In particular, the highest risk indexes were associated to manual acceptance of test orders, identification of the patients, tube labeling, and sample collection.

CONCLUSION

Automation in the preanalytical phase is fundamental to replace, support, or extend the human contribution. Nevertheless each organization is different about workloads and competencies, so the most suitable management must be tailor-made in each context.

APPLICATION

We present a method by which each organization is able to find its best balance between automation and human contribution in the control of the preanalytical phase.

Brain protein changes in Mecp2 mouse mutant models: Effects on disease progression of Mecp2 brain specific gene reactivation

Rett syndrome (RTT) is a leading cause of severe intellectual disability in females, caused by de novo loss-of function mutations in the X-linked methyl-CpG binding protein 2 (MECP2). To better investigate RTT disease progression/pathogenesis animal models of Mecp2 deficiency have been developed. Here, Mecp2 mouse models are employed to investigate the role of protein patterns in RTT. A proteome analysis was carried out in brain tissue from i) Mecp2 deficient mice at the pre-symptomatic and symptomatic stages and, ii) mice in which the disease phenotype was reversed by Mecp2 reactivation. Several proteins were shown to be differentially expressed in the pre-symptomatic (n = 18) and symptomatic (n = 20) mice. Mecp2 brain reactivated mice showed wild-type comparable levels of expression for twelve proteins, mainly related to proteostasis (n = 4) and energy metabolic pathways (n = 4). The remaining ones were found to be involved in redox homeostasis (n = 2), nitric oxide regulation (n = 1), neurodevelopment (n = 1). Ten out of twelve proteins were newly linked to Mecp2 deficiency. Our study sheds light on the relevance of the protein-regulation of main physiological process in the complex mechanisms leading from Mecp2 mutation to the RTT clinical phenotype. SIGNIFICANCE: We performed a proteomic study of a Mecp2^stop/y mouse model for Rett syndrome (RTT) at the pre-symptomatic and symptomatic Mecp2 deficient mice stage and for the brain specific reactivated Mecp2 model. Our results reveal major protein expression changes pointing out to defects in proteostasis or energy metabolic pathways other than, to a lesser extent, in redox homeostasis, nitric oxide regulation or neurodevelopment. The Mecp2 mouse rescued model provides the possibility to select target proteins more susceptible to the Mecp2 gene mutation, potential and promising therapeutical targets.

Proteomic analysis of the Rett syndrome experimental model mecp2Q63X mutant zebrafish

Rett syndrome (RTT) is a severe genetic disorder resulting from mutations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene. Recently, a zebrafish carrying a mecp2-null mutation has been developed with the resulting phenotypes exhibiting defective sensory and thigmotactic responses, and abnormal motor behavior reminiscent of the human disease. Here, we performed a proteomic analysis to examine protein expression changes in mecp2-null vs. wild-type larvae and adult zebrafish. We found a total of 20 proteins differentially expressed between wild-type and mutant zebrafish, suggesting skeletal and cardiac muscle functional defects, a stunted glycolysis and depleted energy availability. This molecular evidence is directly linked to the mecp2-null zebrafish observed phenotype. In addition, we identified changes in expression of proteins critical for a proper redox balance, suggesting an enhanced oxidative stress, a phenomenon also documented in human patients and RTT murine models. The molecular alterations observed in the mecp2-null zebrafish expand our knowledge on the molecular cascade of events that lead to the RTT phenotype.

BIOLOGICAL SIGNIFICANCE

We performed a proteomic study of a non-mammalian vertebrate model (zebrafish, Danio rerio) for Rett syndrome (RTT) at larval and adult stages of development. Our results reveal major protein expression changes pointing out to defects in energy metabolism, redox status imbalance, and muscle function, both skeletal and cardiac. Our molecular analysis grants the mecp2-null zebrafish as a valuable RTT model, triggering new research approaches for a better understanding of the RTT pathogenesis and phenotype expression. This non-mammalian vertebrate model of RTT strongly suggests a broad impact of Mecp2 dysfunction.

Inflammatory protein response in CDKL5-Rett syndrome: evidence of a subclinical smouldering inflammation

BACKGROUND

Mutations in the cyclin-dependent kinase-like 5 gene cause a clinical variant of Rett syndrome (CDKL5-RTT). A role for the acute-phase response (APR) is emerging in typical RTT caused by methyl-CpG-binding protein 2 gene mutations (MECP2-RTT). No information is, to date, available on the inflammatory protein response in CDKL5-RTT. We evaluated, for the first time, the APR protein response in CDKL5-RTT.

METHODS

Protein patterns in albumin- and IgG-depleted plasma proteome from CDKL5-RTT patients were evaluated by two-dimensional gel electrophoresis/mass spectrometry. The resulting data were related to circulating cytokines and compared to healthy controls or MECP2-RTT patients. The effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) were evaluated.

RESULTS

CDKL5-RTT mutations resulted in a subclinical attenuated inflammation, specifically characterized by an overexpression of the complement component C3 and CD5 antigen-like, both strictly related to the inflammatory response. Cytokine dysregulation featuring a bulk increase of anti-inflammatory cytokines, predominantly IL-10, could explain the unchanged erythrocyte sedimentation rate and atypical features of inflammation in CDKL5-RTT. Omega-3 PUFAs were able to counterbalance the pro-inflammatory status.

CONCLUSION

For the first time, we revealed a subclinical smouldering inflammation pattern in CDKL5-RTT consisting in the coexistence of an atypical APR coupled with a dysregulated cytokine response.

Proteomic analysis of 4-hydroxynonenal and nitrotyrosine modified proteins in RTT fibroblasts

Rett syndrome (RTT) is a pervasive developmental disorder, primarily affecting girls with a prevalence of 1 in every 10,000 births. A clear etiological factor present in more than 90% of classical RTT cases is the mutation of the gene encoding methyl-CpG-binding protein 2 (MECP2). Recent work from our group was able to shown a systemic oxidative stress (OxS) in these patients that correlates with the gravity of the clinical features. Using freshly isolated skin fibroblasts from RTT patients and healthy subjects, we have performed a two-dimensional gel electrophoresis in order to evidence the oxidative modifications of proteins with special focus on the formation of protein adducts with 4-hydroxynonenal (4-HNE PAs)-a major secondary product of lipid peroxidation- and Nitrotyrosine, a marker derived from the biochemical interaction of nitric oxide (NO) or nitric oxide-derived secondary products with reactive oxygen species (ROS). Then, oxidatively modified spots were identified by mass spectrometry, LC-ESI-CID-MS/MS. Our results showed that 15 protein spots presented 4-HNE PAs and/or nitrotyrosine adducts in fibroblasts proteome from RTT patients compared to healthy control cells. Post-translationally modified proteins were related to several functional categories, in particular to cytoskeleton structure and protein folding. In addition, clear upregulated expression of the inducible NO synthase (iNOS) with high nitrite levels were observed in RTT fibroblasts, justifying the increased nitrotyrosine protein modifications. The present work describes not only the proteomic profile in RTT fibroblasts, but also identifies the modified proteins by 4-HNE and nitrotyrosine. Of note, for the first time, it appears that a dysregulation of NO pathway can be associated to RTT pathophysiology. In conclusion, the evidence of a wide range of proteins able to forms adducts with 4-HNE, Nitrotyrosine or with both confirms the possible alteration of several aspects of cellular functions that well correlates to the complex clinical features of RTT patients.

Expression and oxidative modifications of plasma proteins in autism spectrum disorders: Interplay between inflammatory response and lipid peroxidation

PURPOSE

A role for inflammation and oxidative stress is reported in autism spectrum disorders (ASDs). Here, we tested possible changes in expression and/or oxidative status for plasma proteins in subjects with ASDs.

EXPERIMENTAL DESIGN

To evaluate protein expression and protein adducts of lipid peroxidation-derived aldehyde, analysis of plasma proteins was performed in 30 subjects with ASDs and compared with 30 healthy controls with typical development, using a proteomic approach.

RESULTS

Significant changes were evidenced for a total of 12 proteins. Of these, ten were identified as proteins involved in the acute inflammatory response including alpha-2-macroglobulin, alpha-1-antitrypsin, haptoglobin, fibrinogen, serum transferrin, prealbumin, apolipoprotein A-I apolipoprotein A-IV, apolipoprotein J, and serum albumin. In addition, significant changes occurred for two immunoglobulins alpha and gamma chains.

CONCLUSIONS AND CLINICAL RELEVANCE

Our present data indicate that an inflammatory response, coupled with increased lipid peroxidation, is present in subjects with ASDs. This information can provide new insight into the identification of potential plasma protein biomarkers in autism.

Synthetic Gel of Carotid Artery Plaque

Atherosclerosis is a complex disease that affects medium and large arteries, leading to the formation and progression of plaque. In this process the proteins play an essential role and as a consequence, proteomic-based strategies examining the protein content of cells or tissues could offer a useful approach for the study of plaque proteins. Due to the heterogeneous cell composition of plaque, proteome analysis of whole lesions is difficult, besides being also complicated by the presence of plasma proteins that cannot be completely eliminated. A good way to study variations in protein expression among series of gels is to construct a synthetic gel. This type of gel is obtained by averaging the positions, shapes and optical densities of spots in a given set of gels. To be included in the synthetic gel, spots must be found in at least three gels. To obtain a profile representative of the proteome of atherosclerotic plaque, canceling its high variability, we constructed a synthetic gel using an average of ten carotid plaque samples. We then compared it with an equivalent synthetic gel constructed using ten plasma samples from the same carotid surgery patients. For the comparison of two synthetic gels (plasma/plaque) we could discriminate plasma proteins from plaque proteins. Besides analysis of spots common to plasma, the synthetic gel is useful to detect spots exclusive to plaque, thus simplifying a very complex mixture.

MECP2 Duplication Syndrome: Evidence of Enhanced Oxidative Stress. A Comparison with Rett Syndrome

Rett syndrome (RTT) and MECP2 duplication syndrome (MDS) are neurodevelopmental disorders caused by alterations in the methyl-CpG binding protein 2 (MECP2) gene expression. A relationship between MECP2 loss-of-function mutations and oxidative stress has been previously documented in RTT patients and murine models. To date, no data on oxidative stress have been reported for the MECP2 gain-of-function mutations in patients with MDS. In the present work, the pro-oxidant status and oxidative fatty acid damage in MDS was investigated (subjects n = 6) and compared to RTT (subjects n = 24) and healthy condition (subjects n = 12). Patients with MECP2 gain-of-function mutations showed increased oxidative stress marker levels (plasma non-protein bound iron, intraerythrocyte non-protein bound iron, F₂-isoprostanes, and F₄-neuroprostanes), as compared to healthy controls (P ≤ 0.05). Such increases were similar to those observed in RTT patients except for higher plasma F₂-isoprostanes levels (P < 0.0196). Moreover, plasma levels of F₂-isoprostanes were significantly correlated (P = 0.0098) with the size of the amplified region. The present work shows unique data in patients affected by MDS. For the first time MECP2 gain-of-function mutations are indicated to be linked to an oxidative damage and related clinical symptoms overlapping with those of MECP2 loss-of-function mutations. A finely tuned balance of MECP2 expression appears to be critical to oxidative stress homeostasis, thus shedding light on the relevance of the redox balance in the central nervous system integrity.

Erectile dysfunction and diabetes: Association with the impairment of lipid metabolism and oxidative stress

OBJECTIVES

To test the hypothesis that exists an association of non-diabetic and diabetic patients suffering from erectile dysfunction (ED) with lipid metabolism and oxidative stress.

DESIGN AND METHODS

Clinical and laboratory characteristics in non-diabetic (n = 30, middle age range: 41–55.5 years; n = 25, old age range: 55.5–73), diabetic ED patients (n = 30, age range: 55.5–75 years) and diabetic patients (n = 25, age range: 56–73.25), were investigated. Proteomic analysis was performed to identify differentially expressed plasma proteins and to evaluate their oxidative posttranslational modifications.

RESULTS

A decreased level of high-density lipoproteins in all ED patients (P < 0.001, C.I. 0.046–0.10), was detected by routine laboratory tests. Proteomic analysis showed a significant decreased expression (P < 0.05) of 5 apolipoproteins (i.e. apolipoprotein H, apolipoprotein A4, apolipoprotein J, apolipoprotein E and apolipoprotein A1) and zinc-alpha-2-glycoprotein, 50% of which are more oxidized proteins. Exclusively for diabetic ED patients, oxidative posttranslational modifications for prealbumin, serum albumin, serum transferrin and haptoglobin markedly increased.

CONCLUSIONS

Showing evidence for decreased expression of apolipoproteins in ED and the remarkable enhancement of oxidative posttranslational modifications in diabetes-associated ED, considering type 2 diabetes mellitus and age as independent risk factors involved in the ED pathogenesis, lipid metabolism and oxidative stress appear to exert a complex interplay in the disease.

Altered erythrocyte membrane fatty acid profile in typical Rett syndrome: effects of omega-3 polyunsaturated fatty acid supplementation

This study mainly aims at examining the erythrocyte membrane fatty acid (FAs) profile in Rett syndrome (RTT), a genetically determined neurodevelopmental disease. Early reports suggest a beneficial effects of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) on disease severity in RTT. A total of 24 RTT patients were assigned to ω-3 PUFAs-containing fish oil for 12 months in a randomized controlled study (average DHA and EPA doses of 72.9, and 117.1mg/kgb.w./day, respectively). A distinctly altered FAs profile was detectable in RTT, with deficient ω-6 PUFAs, increased saturated FAs and reduced trans 20:4 FAs. FAs changes were found to be related to redox imbalance, subclinical inflammation, and decreased bone density. Supplementation with ω-3 PUFAs led to improved ω-6/ω-3 ratio and serum plasma lipid profile, decreased PUFAs peroxidation end-products, normalization of biochemical markers of inflammation, and reduction of bone hypodensity as compared to the untreated RTT group. Our data indicate that a significant FAs abnormality is detectable in the RTT erythrocyte membranes and is partially rescued by ω-3 PUFAs.

The Magic Velvet Bean of Mucuna pruriens

Mucuna pruriens (Fabaceae) is an established herbal drug used for the management of male infertility, nervous disorders, and also as an aphrodisiac. It has been shown that its seeds are potentially of substantial medicinal importance. The ancient Indian medical system, Ayurveda, traditionally used M. pruriens, even to treat such things as Parkinson's disease. M. pruriens has been shown to have anti-parkinson and neuroprotective effects, which may be related to its anti-oxidant activity. In addition, anti-oxidant activity of M. pruriens has been also demonstrated in vitro by its ability to scavenge DPPH radicals and reactive oxygen species. In this review the medicinal properties of M. pruriens are summarized, taking in consideration the studies that have used the seeds extracts and the leaves extracts.

Beta-actin deficiency with oxidative posttranslational modifications in Rett syndrome erythrocytes: insights into an altered cytoskeletal organization

Beta-actin, a critical player in cellular functions ranging from cell motility and the maintenance of cell shape to transcription regulation, was evaluated in the erythrocyte membranes from patients with typical Rett syndrome (RTT) and methyl CpG binding protein 2 (MECP2) gene mutations. RTT, affecting almost exclusively females with an average frequency of 1∶10,000 female live births, is considered the second commonest cause of severe cognitive impairment in the female gender. Evaluation of beta-actin was carried out in a comparative cohort study on red blood cells (RBCs), drawn from healthy control subjects and RTT patients using mass spectrometry-based quantitative analysis. We observed a decreased expression of the beta-actin isoforms (relative fold changes for spots 1, 2 and 3: −1.82±0.15, −2.15±0.06, and −2.59±0.48, respectively) in pathological RBCs. The results were validated by western blotting and immunofluorescence microscopy. In addition, beta-actin from RTT patients also showed a dramatic increase in oxidative posttranslational modifications (PTMs) as the result of its binding with the lipid peroxidation product 4-hydroxy-2-nonenal (4-HNE). Our findings demonstrate, for the first time, a beta-actin down-regulation and oxidative PTMs for RBCs of RTT patients, thus indicating an altered cytoskeletal organization.

Proteomic profiling and post-translational modifications in human keratinocytes treated with Mucuna pruriens leaf extract

ETHNOPHARMACOLOGICAL RELEVANCE

Mucuna pruriens (Mp) is a plant belonging to the Fabaceae family, with several medicinal properties among which its potential to treat diseases where reactive oxygen species (ROS) play an important role in the pathogeneses. The aim was to investigate the effects of Mp leaf methanolic extract (MPME) on human keratinocytes protein expression and its role in preventing proteins oxidation after oxidative stress (OS) exposure.

MATERIAL AND METHODS

The effects of MPME on HaCaT cells protein expression were evaluated treating cells with different concentrations of MPME, with glucose oxidase (GO, source of OS) and with MPME subsequently treated with GO. The protein patterns of treated HaCaT cells are analyzed by two-dimensional gel electrophoresis (2-DE) and compared with that of untreated HaCaT. Immunoblotting was then used to evaluate the role of MPME in preventing the 4-hydroxynonenal protein adducts (4-HNE PAs) formation (marker of OS).

RESULTS

Eighteen proteins, identified by mass spectrometry (LC-ESI-CID-MS/MS), were modulated distinctly by MPME in HaCaT. Overall, MPME counteract GO effect, reducing the GO-induced overexpression of several proteins involved in stress response (T-complex protein 1, Protein disulfide-isomerase A3, Protein DJ-1, and Stress-induced-phosphoprotein 1), in cell energy methabolism (Inorganic pyrophosphatase, Triosephosphate isomerase isoform 1, 2-phosphopyruvate-hydratase alpha-enolase, and Fructose-bisphosphate aldolase A isoform 1), in cytoskeletal organization (Cytokeratins 18, 9, 2, Cofilin-1, Annexin A2 and F-actin-capping protein subunit beta isoform 1) and in cell cycle progression (Eukaryotic translation initiation factor 5A-1 isoform B). In addition, MPME decreased the 4-HNE PAs levels, in particular on 2-phosphopyruvate-hydratase alpha-enolase and Cytokeratin 9.

CONCLUSIONS

Our findings show that MPME might be helpful in the treatment of OS-related skin diseases by preventing protein post-translational modifications (4-HNE PAs).

Effects of Mucuna pruriens protease inhibitors on Echis carinatus venom

The medicinal plant Mucuna pruriens, with reputed anti-snake venom properties has been reported to contain a kunitz-type trypsin inhibitor. This study was undertaken to further evaluate the protease inhibitory potential of gpMuc, a multiform glycoprotein, and other protein fractions from M. pruriens seeds against trypsin, chymotrypsin, Echis carinatus snake venom, ecarin and thrombin. The results showed that gpMuc inhibited both trypsin and chymotrypsin activities and was thermally stable, maintaining its trypsin inhibitory activity at temperatures of up to 50°C. Its structural conformation was also maintained at pH ranges of 4-7. Immunoreactivity study confirms that it contains protease-recognizing epitope on one of its isoforms. The whole protein extract of M. pruriens seeds inhibited prothrombin activation by ecarin and whole E. carinatus venom, and also thrombin-like activity using chromogenic assay.

Erythrocyte sedimentation rate measurement by VES Matic Cube 80 in relation to inflammation plasma proteins

Westergren method is considered as the reference procedure to measure Erythrocyte Sedimentation Rate (ESR) by the International Council for Standardization in Haematology. However, a closed automated method, VES Matic Cube 80 (DIESSE S.p.A., Siena, Italy), has been introduced as a new ESR measurement instrument. In this article, we report two different studies: first, we compared the two methods (Westergren and VES Matic Cube 80) and second, we correlated the inflammatory state of 248 patients with their ESR values. Total protein, albumin, C-reactive protein, and other inflammatory proteins were detected in each sample. The results obtained using VES Matic Cube 80 demonstrated a good correlation with those obtained using the Westergren method (Ordinary linear regression: y=0.955x-0.205, r(2) =0.816, P<0.05; Passing-Bablock regression equation: y=0.9153x-0.5763; Bland-Altman analysis: bias 1.2; limits of agreement -17.4-19.9) and with the inflammatory protein levels (CRP: r=0.554 and r=0.498 and Fibrinogen: r=0.699 and r=0.663 for Ves Matic Cube 80 and Westergren, respectively), supporting the hypothesis that VES Matic Cube 80 offers a fast and safe ESR determination, ensuring precision and a very good correlation with the reference method.

The belonging of gpMuc, a glycoprotein from Mucuna pruriens seeds, to the Kunitz-type trypsin inhibitor family explains its direct anti-snake venom activity

In Nigeria, Mucuna pruriens seeds are locally prescribed as an oral prophylactic for snake bite and it is claimed that when two seeds are swallowed they protect the individual for a year against snake bites. In order to understand the Mucuna pruriens antisnake properties, the proteins from the acqueous extract of seeds were purified by three chromatographic steps: ConA affinity chromatography, tandem anionic-cationic exchange and gel filtration, obtaining a fraction conventionally called gpMucB. This purified fraction was analysed by SDS-PAGE obtaining 3 bands with apparent masses ranging from 20 to 24 kDa, and by MALDI-TOF which showed two main peaks of 21 and 23 kDa and another small peak of 19 kDa. On the other hand, gel filtration analysis of the native protein indicated a molecular mass of about 70 kDa suggesting that in its native form, gpMucB is most likely an oligomeric multiform protein. Infrared spectroscopy of gpMucB indicated that the protein is particularly thermostable both at neutral and acidic pHs and that it is an all beta protein. All data suggest that gpMucB belongs to the Kunitz-type trypsin inhibitor family explaining the direct anti-snake venom activity of Mucuna pruriens seeds.

Mucuna pruriens Linn. seed extract pretreatment protects against cardiorespiratory and neuromuscular depressant effects of Naja sputatrix (Javan spitting cobra) venom in rats

Mucuna pruriens has been used by native Nigerians as a prophylactic for snakebite. The protective effects of M. pruriens seed extract (MPE) were investigated against the pharmacological actions of N. sputatrix (Javan spitting cobra) venom in rats. The results showed that MPE-pretreatment protected against cardiorespiratory and, to a lesser extent, neuromuscular depressant effects of N. sputatrix venom. These may be explained at least in part by the neutralisation of the cobra venom toxins by anti-MPE antibodies elicited by the MPE pretreatment.

In vitro effects of Echis carinatus venom on the human plasma proteome

Echis carinatus venom (EV) is a complex mixture of toxins that contribute to its lethality. EV proteolytic activity was analyzed by zymography, chromogenic assays, and SDS-PAGE. To understand the molecular mechanism of the envenomation, we investigated the in vitro effect of EV on human plasma proteins. We looked for EV protein substrates and their proteolytic fragments. We analyzed EV proteolytic activity on standard proteins such as prothrombin or fibrinogen. To set up the optimal EV:plasma protein ratio conditions, plasma was incubated with EV (treated plasma), depleted of abundant proteins, and subjected to SDS-PAGE. Samples from control and treated plasma were also analyzed by 2-DE/MALDI-TOF MS, leading to the identification of four classes of plasma proteins cleaved by EV: proteases, protease inhibitors, binding proteins, and transporters. EV mainly proteolyzes entire proteins but can also act on physiological fragments. In summary, the physiological effects of EV proteases involve other important processes in addition to blood coagulation; complement activation and hemoglobin metabolism are also affected. In particular, the cleavage of protease inhibitors appears to be the mechanism through which the venom neutralizes the body's defenses.

Serum Proteome of Patients with Systemic Sclerosis: Molecular Analysis of Expression and Prevalence of Haptoglobin Alpha Chain Isoforms

Haptoglobin (Hpt) is an acute phase protein characterized by three major phenotypes (Hpt 1-1, Hpt 2-1 and Hpt 2-2). The Hpt 2-2 phenotype is associated with increased prevalence of various systemic diseases, including autoimmune disorders. Moreover, the Hpt 2-2 phenotype induces a shift from Th1 to Th2 response and increases fibrotic processes. On this basis, we performed serum proteomic analysis of with Systemic Sclerosis (SSc), a connective tissue disorder associated with Th2-type immune response and characterized by interstitial and perivascular fibrosis due to different factors (including genetic, environmental, immunological and microchimeric factors). Serum of 23 SSc outpatients (4 males, 19 females, mean age 54±5.3 years) diagnosed according to the American Rheumatism Association (ARA) criteria, were considered for the proteomic analysis and compared to serum of 21 control subjects. Serum depleted of HAP was analyzed by 2-DE, and Hpt chain spots were identified by WB. The expression frequency of each Hpt a chain in SSc patients and controls was compared and quantitative analysis of spot expression (% Vol) was performed. Above all, our study amplifies the limited data in the literature on proteomic analysis in SSc, also confirming previous data that revealed a significant increase of haptoglobin type 2-2 and a concomitant decrease of the 1-1 phenotype in SSc patients. Moreover, our results demonstrate that c spots are more prevalent in SSc patients than in controls (91.3% vs 55.5%, p<0.05), while the expression frequency of a and b spots does not change. In patients Hpt 2-1 or Hpt 1-1 e spot is less abundant. According to our results, the c and e spots can be considered markers for SSc and thus be of use for the early diagnosis of connective tissue disorders and in establishing appropriate treatment.

Ultrastructural and biochemical investigations of protein mobilization of Mucuna pruriens (L.) DC. cotyledons and embryo axis

The mobilization of storage reserves, with particular emphasis on storage proteins of Mucuna pruriens (L.) DC., cotyledons, and embryo was investigated from the ultrastructural and biochemical points of view. Proteins and starch were the two main storage substances in cotyledons, and proteins and lipids were the main ones in the embryo. Embryo protein bodies were smaller and fewer in number than those of cotyledons. Structural and ultrastructural data determined between 24 and 48 h after imbibition and between 48 and 72 h after imbibition, the end of significant embryo and cotyledon protein mobilization, respectively, indicating more precocious storage protein mobilization in the axis than cotyledons. Moreover, storage protein mobilization in embryo and cotyledons occurred before the end of germination. Water soluble proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, producing 29 bands with molecular weights from 14 to 90 KDa. Embryo extract contained more proteins than cotyledon extract, contained seven characteristic bands, and showed a higher variability of the optical density trend than cotyledon.

The protective effect of Mucuna pruriens seeds against snake venom poisoning

ETHNOPHARMACOLOGICAL RELEVANCE

The seed, leaf and root of Mucuna pruriens have been used in traditional medicine for treatments of various diseases. In Nigeria, the seed is used as oral prophylactics for snakebite.

AIM OF THE STUDY

To study the protective effects of Mucuna pruriens seed extract against the lethalities of various snake venoms.

MATERIALS AND METHODS

Rats were pre-treated with Mucuna pruriens seed extract and challenged with various snake venoms. The effectiveness of anti-Mucuna pruriens (anti-MPE) antibody to neutralize the lethalities of snake venoms was investigated by in vitro neutralization.

RESULTS

In rats, MPE pre-treatment conferred effective protection against lethality of Naja sputatrix venom and moderate protection against Calloselasma rhodostoma venom. Indirect ELISA and immunoblotting studies showed that there were extensive cross-reactions between anti-MPE IgG and venoms from many different genera of poisonous snakes, suggesting the involvement of immunological neutralization in the protective effect of MPE pre-treatment against snake venom poisoning. In vitro neutralization experiments showed that the anti-MPE antibodies effectively neutralized the lethalities of Asiatic cobra (Naja) venoms, but were not very effective against other venoms tested.

CONCLUSIONS

The anti-MPE antibodies could be used in the antiserum therapy of Asiatic cobra (Naja) bites.

Proteomic analysis of the pathophysiological process involved in the antisnake venom effect of Mucuna pruriens extract

Previously, we reported the antisnake venom properties of a Mucuna pruriens seed extract (MPE) and tested its in vivo efficacy against Echis carinatus venom (EV) in short- (1 injection) and long-term (three weekly injections) treatments. The aim of the present study was to investigate plasma proteome changes associated with MPE treatments and identify proteins responsible for survival of envenomated mice (CHALLENGED mice). Six treatment groups were studied. Three control groups: one saline, one short-term and one long-term MPE treatment. One group received EV alone. Two test groups received EV with either a short-term or long-term MPE treatment (CHALLENGED mice). The plasma from each group was analysed by 2-DE/MALDI-TOF MS. The most significant changes with treatment were: albumin, haptoglobin, fibrinogen, serum amyloid A and serum amyloid P. Most of these changes were explained by EV effects on coagulation, inflammation and haemolysis. However, MPE treatments prevented the EV-induced elevation in HPT. Consequently, HPT levels were similar to controls in the plasma of CHALLENGED mice. The plasma of CHALLENGED mice showed substantial proteomic modifications. This suggests the mechanism of MPE protection involves the activation of counterbalancing processes to compensate for the imbalances caused by EV.

Simultaneous determination of serum concentrations of levodopa, dopamine, 3-O-methyldopa and alpha-methyldopa by HPLC

Levodopa is the medication of choice for Parkinson's disease. The biological complexity of levodopa and of its main derivatives makes their determination important in the clinical field. The aim of this study was to develop an HPLC method for the simultaneous determination of serum concentrations of levodopa, dopamine, 3-O-methyldopa and alpha-methyldopa. We compared UV and fluorimetric detection of native and derivatised compounds. Though less sensitive than other methods, UV detection is important to exclude naturally fluorescent, interfering substances. Fluorimetric detection of derivatised compounds is more sensitive than UV detection. Since 3-O-methyldopa does not react with the derivatising agent 1,2-diphenylethylenediamine, it cannot be detected. For simultaneous determination of the four compounds after pharmacological treatment of patients we therefore advise fluorimetric detection of the native compound.

Increased serum lactate dehydrogenase isoenzymes in Ph-negative chronic myeloproliferative diseases: a metabolic adaptation?

We evaluated the significance of lactate dehydrogenase (LDH) isoenzymes in chronic myeloproliferative disorders (CMDs) by studying LDH isoenzymes in the serum of patients with secondary polycythemia (SP), polycythemia vera (PV), essential thrombocythemia (ET) and idiopathic myelofibrosis (IMF) in different disease status. LDH activity and isoenzymes were evaluated retrospectively in serum samples from four groups of patients and compared with a control group. LDH activity and isoenzyme distributions of patients with SP and PV did not reveal significant variations with respect to controls. In the ET and IMF group LDH isoenzyme revealed significant variations: IMF showed significant increase of LDH2 and significant reduction of LDH5 isoenzyme, whereas ET showed significant decrease in LDH1 and increase of LDH3. These data suggest that LDH isoenzyme patterns may be a useful marker of CMDs, but this enzymatic pattern could be expression of a metabolic adaptation.

Structural characterization of the N-glycans of gpMuc from Mucuna pruriens seeds

Mucuna pruriens seeds are used in some countries as a human prophylactic oral anti-snake remedy. Aqueous extracts of M. pruriens seeds possess in vivo activity against cobra and viper venoms, and protect mice against Echis carinatus venom. It was recently demonstrated that the seed immunogen generating the antibody that cross-reacts with the venom proteins is a multiform glycoprotein (gpMuc), and the immunogenic properties of gpMuc seemed to mainly reside in its glycan chains. In the present study, gpMuc was found to contain only N-glycans. Part of the N-glycans could be released with peptide-(N (4)-(N-acetyl-beta -glucosaminyl)asparagine amidase F (PNGase F-sensitive N-glycans); the PNGase F-resistant N-glycans were PNGase A-sensitive. The oligosaccharides released were analyzed by a combination of MALDI-TOF mass spectrometry, HPLC profiling of 2-aminobenzamide-labelled derivatives and (1)H NMR spectroscopy. The PNGase F-sensitive N-glycans comprised a mixture of oligomannose-type structures ranging from Man(5)GlcNAc(2) to Man(9)GlcNAc(2), and two xylosylated structures, Xyl(1)Man(3)GlcNAc(2) and Xyl(1)Man(4)GlcNAc(2). The PNGase A-sensitive N-glycans, containing (alpha 1-3)-linked fucose, were identified as Fuc(1)Xyl(1)Man(2)GlcNAc(2) and Fuc(1)Xyl(1)Man(3)GlcNAc(2). In view of the determined N-glycan ensemble, the immunoreactivity of gpMuc was ascribed to the presence of core (beta 1-2)-linked xylose- and core alpha (1-3)-linked fucose-modified N-glycan chains.

Antidiabetic oligocyclitols in seeds of Mucuna pruriens

Using a combination of chromatographic and NMR techniques, the presence of D-chiro-inositol and its two galacto-derivatives is demonstrated in Mucuna pruriens seeds. The quantities detected explain the well-established antiglycaemic effect of Mucuna pruriens seeds.

Serum folate and vitamin B12 levels in children from Mozambique

In order to investigate the behaviour of biochemical parameters in children from Mozambique, we have determined the serum levels of folic acid and vitamin B12, two well known markers of nutritional anemia. We have correlated their values with other blood parameters and have evidenced potential interesting relationship between folate content and platelets count.

Protection of Mucuna pruriens seeds against Echis carinatus venom is exerted through a multiform glycoprotein whose oligosaccharide chains are functional in this role

In a previous paper we demonstrated that extracts of Mucuna pruriens seeds (MPE) protect mice against Echis carinatus venom (EV) by an immunological mechanism. In this paper we demonstrate that the MPE immunogen generating the antibody that cross-reacts with the venom proteins is a multiform glycoprotein (gpMuc) whose immunogenic properties mainly reside in its glycan-chains. The glycoprotein was purified from the protein extract of M. pruriens seeds using Concanavalin A affinity chromatography. Using 2-D gel electrophoresis it separated into seven isoforms having MWs in the range from 20.3 to 28.7 kDa and pIs from 4.8 to 6.5. N-terminal sequencing of these spots revealed close similarity since all of them contained the consensus sequence DDREPV-DT found in soybean Kunitz-type trypsin inhibitor. We suggest that gpMuc contains both N- and O-glycans. Mild alkaline treatment but not PNGase F led to loss of reactivity, indicating that O-glycans are probably involved in the antigenicity of gpMuc.

Proteins from Mucuna pruriens and enzymes from Echis carinatus venom: characterization and cross-reactions

Mucuna pruriens seeds have been widely used against snakebite in traditional medicine. The antivenin property of a water extract of seeds was assessed in vivo in mice. The serum of mice treated with extract was tested for its immunological properties. Two proteins of Echis carinatus venom with apparent molecular masses of 25 and 16 kDa were detected by Western blot analysis carried out using IgG of mice immunized with extract or its partially purified protein fractions. By enzymatic in-gel digestion and electrospray ionization-mass spectrometry/mass spectrometry analysis of immunoreactive venom proteins, phospholipase A(2,) the most toxic enzyme of snake venom, was identified. These results demonstrate that the observed antivenin activity has an immune mechanism. Antibodies of mice treated with non-lethal doses of venom reacted against some proteins of M. pruriens extract. Proteins of E. carinatus venom and M. pruriens extract have at least one epitope in common as confirmed by immunodiffusion assay.

Blood chemistry of rats pretreated with Mucuna pruriens seed aqueous extract MP101UJ after Echis carinatus venom challenge

The effect of a lethal Echis carinatus venom on serum enzyme levels and blood plasma coagulation parameters in rats pretreated with Mucuna pruriens seed aqueous extract MP101UJ (21 mg/kg body wt) 24 h and 3 wk before i.p venom injection (0.50 mg/kg rat) and rats injected with venom alone (0.50 mg/kg body wt) was investigated. The enzyme levels and coagulation parameter levels were measured 4 h after venom administration. The results showed that the increased enzymes lactate dehydrogenase (LDH), glutamic pyruvic transaminase (SGPT), creatinine kinase (CK) and changed coagulation parameters D-Dimer and Quick levels due to the venom effect were inhibited by M. pruriens seed aqueous extract MP101UJ in pretreated rats. Rats pretreated with a single dose (21 mg/kg and multiple doses 21 mg/kg rat) of extract MP101UJ maintained the normal enzyme levels and showed an anticoagulant effect as evidenced by the high PTT level which was also observed in venom treated animals. D-Dimer and Quick values were normal. However, the extract MP101UJ appeared to significantly inhibit the lethal venom induced myotoxic, cytotoxic and coagulation activities in experimental animals.

Inhibition and regulation of rat liver L-threonine dehydrogenase by different fatty acids and their derivatives

Rat liver L-threonine dehydrogenase is a mitochondrial enzyme which transforms L-threonine either into aminoacetone or into acetyl-CoA. We show that it is inhibited by several fatty acids and their derivatives: short chain fatty acids, L-2-hydroxybutyrate and D-3-hydroxybutyrate, long chain fatty acids, such as lauric acid, myristic acid, palmitic and stearic acids, bicarboxylic acids such as malonic acid and its derivatives methyl- and hydroxymalonic acids. The inhibition occurs at low and physiological concentrations of such compounds, which are normally present and metabolized in mitochondria. It presumably plays a role in the physiology of acetyl-CoA-dependent formation of fatty acids and ketobodies, in L-threonine-dependent gluconeogenesis, and in the regulation of L-threonine metabolism by L-threonine dehydrogenase and L-threonine deaminase.

Determination, activity and biological role of adenylosuccinate lyase in blood cells

Adenylosuccinate lyase deficiency, which is associated with severe mental retardation and autistic features, was discovered in 1984. Since then this enzyme has been analyzed in many human tissues and it is now generally agreed that screening for this enzyme defect should be performed in all unexplained neurological diseases. The aim of the present study was to analyze adenylosuccinate lyase activity in blood cells by a fast simple method adaptable to screening purposes. The activity was also analyzed in B-lymphocytes from patients with B-cell chronic lymphocytic leukemia. The biological role of adenylosuccinate lyase and its importance in regulating cellular levels of AMP is discussed.

Effects of Mucuna pruriens extract on activation of prothrombin by Echis carinatus venom

Mucuna pruriens (L.) DC has long been used as a medicinal plant by traditional healers. The validity of the claims made for this plant has also been tested scientifically. Some of its properties are probably linked to high concentrations of dopa since it is useful in the treatment of Parkinson's disease. The antisnake properties of an extract of Mucuna pruriens' seeds (MP101UJ) in vivo were recently demonstrated and one is now investigating its biochemical mechanism. Echis carinatus venom (EV) contains a mixture of proteins that affect the coagulative cascade, causing severe bleeding and haemorrhage. Here the effect of an extract of MP101UJ in prothrombin activation by EV in vitro by clotting and chromogenic assay is studied. An increase in procoagulant activity was found. This could explain the protective effect in vivo.

Determination of urinary methylated purine pattern by high-performance liquid chromatography

We describe the group selective separation and quantification of unmodified and modified purines in human urine by high-performance reverse phase liquid chromatography. The pattern of oxypurines and methylated purines: hypoxanthine (Hx), xanthine (X), 1-methyl hypoxanthine (1-MHx), 1-methyl guanine (1-MG), 3-methyl guanine (3-MG), 7-methyl guanine (7-MG), 1-methyl xanthine (1-MX), 3-methyl xanthine (3-MX), 7-methyl xanthine (7-MX), 1,7-dimethyl guanine (1,7-dMG), 1,3-dimethyl xanthine (1,3-dMX), 1,7-dimethyl xanthine (3,7-dMX) and 1,3,7-trimethyl xanthine (1,3,7-tMX) were determined in a single run in urine of a healthy subject and a gout patient before and after treatment with allopurinol. This method may be useful to investigate the urinary pattern of methylated bases in diseases involving purine metabolism.

Purine nucleotide catabolism in rat liver: labelling of uric acid and allantoin after treatment with oxonic acid and allopurinol

In our previous experiments on rat liver we found that 15' after intraperitoneal administration of 14C-formate the specific radioactivity of allantoin was always higher than that of uric acid. The present experiments have been carried out to interpret this unexpected result, which was only observed in liver and we studied: a) the incorporation of 14C-glycine into uric acid and allantoin; b) the effects of two competitive inhibitors of xanthine oxidase and uricase, oxonic acid and allopurinol respectively, on levels of uric acid and allantoin in liver and on their specific radioactivity after administration of labelled precursor. The results suggested: a) that under normal conditions, the formation of allantoin is so fast that it exceedes export from liver to serum, and thus the radioactivity of labelled precursors accumulates in allantoin; b) that when allopurinol or oxonic acid are administered, the rate of export exceeds that of allantoin formation and the incorporation of radioactivity into allantoin is lower; c) that not all the data, however, could be interpreted on this basis, but seems to require the existence of different pools of uric acid, which are transformed separately into allantoin.

Fatty acid composition of phospholipids, triglycerides and cholesterol in serum of castrated and estradiol treated rats

We have studied the levels of phospholipids, triglycerides, cholesterol esters, and their fatty acid composition in serum for normal, castrated and estradiol treated rats. The sex hormones did not greatly affect the levels of the various lipid fractions which did not undergo great significant variations, under the different treatments. More evident variations occurred in the percent composition of fatty acid and in the content of the various saturated (SAT), unsaturated (UNSAT), essential (EFA) and non essential fatty acids (NEFA). We studied the most important ratios: EFA/NEFA; UNS/SAT; 16:0/16:1; 18:0/18:1, 18:2/18:3; 18:2/20:4. 16:0/16:1; 18:0/18:1 represent the delta9 desaturase, one specific for palmitic, the other for stearic acid. 18:2/18:3 ratio is an index of the delta6 desaturase activity: 18:2/20:4 ratio of delta5 desaturase-elongase. Most changes were evident in triglycerides. We observed a different behaviour of the UNS/SAT and EFA/NEFA ratios in phospholipids and cholesterol esters, which may reflect either an effect of the sex hormones on the exchange of fatty acids between the same lipid fractions, or a redistribution of lipids among different tissues. Great variations were observed of the ratios 16:0/16:1; 18:0/18:1; 18:2/18:3; 18:2/20:4, which are ascribed a different effect of the sex hormones of delta9, delta6, delta5 desaturases.

Restoration of rat liver L-threonine dehydratase activity by pyridoxamine 5'-phosphate: the half-transaminating activity of L-threonine dehydratase and its regulatory role

When a highly purified preparation of rat liver l-threonine deaminase (l-TDH, EC 4.2.1.16) was 99% inactivated by dialysis, removing bound pyridoxal 5'-phosphate (PLP), the apoenzyme was reactivated not only by PLP but also by pyridoxamine 5'-phosphate (PMP). When purified by HPLC, the commercial PMP used in the incubation mixture was found to contain only extremely small amounts of PLP, which could not account for restoration of l-threonine dehydratase activity. HPLC analysis of the assay mixtures showed that during incubation, sufficient PLP had been formed for reactivation of the apoenzyme. The apoenzyme evidently bound PMP and triggered transamination between PMP and the keto acids, which either contaminated, or were formed by the minimal amount of PLP-holoenzyme always present even in the dialyzed preparation. When sufficient PLP was formed, the PLP-holoenzyme and the original 'true' l-threonine dehydratase activity were restored. When PMP was incubated with the apoenzyme in the presence of small quantities of keto acids (pyruvate or 2-oxobutyrate) small amounts of l-alanine or l-aminobutyrate were formed. The reaction was not reversible; l-alanine and l-aminobutyrate did not react with the PLP-holoenzyme. No transaminating activity occurred with other amino acids. These results show that l-threonine dehydratase exists in two forms: the well known stable apoenzyme-PLP (hydrolase deaminating) and the transient apoenzyme-PMP (non-reversible half-transaminating). Half-transamination has the biological role of keeping the activity of the 'true' l-TDH constant and of regulating intracellular levels of pyruvate, alanine, oxobutyric acid, l-aminobutyric acid, l-threonine and l-serine.