Arsenic-containing hydrocarbons disrupt a model in vitro blood-cerebrospinal fluid barrier

Lipid-soluble arsenicals, so-called arsenolipids, have gained a lot of attention in the last few years because of their presence in many seafoods and reports showing substantial cytotoxicity emanating from arsenic-containing hydrocarbons (AsHCs), a prominent subgroup of the arsenolipids. More recent in vivo and in vitro studies indicate that some arsenolipids might have adverse effects on brain health. In the present study, we focused on the effects of selected arsenolipids and three representative metabolites on the blood-cerebrospinal fluid barrier (B-CSF-B), a brain-regulating interface. For this purpose, we incubated an in vitro model of the B-CSF-B composed of porcine choroid plexus epithelial cells (PCPECs) with three AsHCs, two arsenic-containing fatty acids (AsFAs) and three representative arsenolipid metabolites (dimethylarsinic acid, thio/oxo-dimethylpropanoic acid) to examine their cytotoxic potential and impact on barrier integrity. The toxic arsenic species arsenite was also tested in this way and served as a reference substance. While AsFAs and the metabolites showed no cytotoxic effects in the conducted assays, AsHCs showed a strong cytotoxicity, being up to 1.5-fold more cytotoxic than arsenite. Analysis of the in vitro B-CSF-B integrity showed a concentration-dependent disruption of the barrier within 72 h. The correlation with the decreased plasma membrane surface area (measured as capacitance) indicates cytotoxic effects. These findings suggest exposure to elevated levels of certain arsenolipids may have detrimental consequences for the central nervous system.

Effects of arsenolipids on in vitro blood-brain barrier model

Arsenic-containing hydrocarbons (AsHCs), a subgroup of arsenolipids (AsLs) occurring in fish and edible algae, possess a substantial neurotoxic potential in fully differentiated human brain cells. Previous in vivo studies indicating that AsHCs cross the blood-brain barrier of the fruit fly Drosophila melanogaster raised the question whether AsLs could also cross the vertebrate blood-brain barrier (BBB). In the present study, we investigated the impact of several representatives of AsLs (AsHC 332, AsHC 360, AsHC 444, and two arsenic-containing fatty acids, AsFA 362 and AsFA 388) as well as of their metabolites (thio/oxo-dimethylpropionic acid, dimethylarsinic acid) on porcine brain capillary endothelial cells (PBCECs, in vitro model for the blood-brain barrier). AsHCs exerted the strongest cytotoxic effects of all investigated arsenicals as they were up to fivefold more potent than the toxic reference species arsenite (iAs^III). In our in vitro BBB-model, we observed a slight transfer of AsHC 332 across the BBB after 6 h at concentrations that do not affect the barrier integrity. Furthermore, incubation with AsHCs for 72 h led to a disruption of the barrier at sub-cytotoxic concentrations. The subsequent immunocytochemical staining of three tight junction proteins revealed a significant impact on the cell membrane. Because AsHCs enhance the permeability of the in vitro blood-brain barrier, a similar behavior in an in vivo system cannot be excluded. Consequently, AsHCs might facilitate the transfer of accompanying foodborne toxicants into the brain.

Necrotizing fasciitis: treatment concepts and clinical results

BACKGROUND

Necrotizing fasciitis is a life-threatening soft tissue infection characterized by a rapid spreading infection of the subcutaneous tissue and in particular the fascia. The management of infected tissues requires a rapid diagnosis, immediate aggressive surgical management and an extended debridement. In some cases early amputations of the affected tissues and maximum intensive care treatment, in case of sepsis, are required. Due to a rising number of cases we aimed to evaluate our patients in a retrospective review.

METHOD

All patients diagnosed with necrotizing fasciitis from 2014 to 2016 (21 months) in our level one trauma center were identified. Their charts were reviewed and data were analyzed in terms of demographic and social information, microbiological results, therapeutic course, socio-economic outcome and mortality.

RESULTS

We found 15 patients with necrotizing fasciitis. None of these died in the observation period. The mean number of surgical interventions was seven. Two patients underwent limb amputation; diabetes mellitus was assigned with a significant higher risk for amputation. The mean hospitalization was 32 days, including 8 days on intensive care unit. Of the discovered bacteria 93% were sensitive to the initial antibiotic treatment with Ampicillin, Clindamycin and Clont.

CONCLUSION

Surgical therapy is indicated if necrotizing fasciitis is suspected. Diabetes mellitus was a clinical predictor of limb amputation in patients with necrotizing fasciitis in our cohort. Aminopenicillin ± sulbactam in combination with clindamycin and/or metronidazole is recommended as initial calculated antibiotic treatment.

In vitro toxicological characterisation of arsenic-containing fatty acids and three of their metabolites

Arsenic-containing fatty acids are bioavailable and toxic to human liver cells in culture.

Arsenic-containing fatty acids are a group of fat-soluble arsenic species (arsenolipids) which are present in marine fish and other seafood. Recently, it has been shown that arsenic-containing hydrocarbons, another group of arsenolipids, exert toxicity in similar concentrations comparable to arsenite although the toxic modes of action differ. Hence, a risk assessment of arsenolipids is urgently needed. In this study the cellular toxicity of a saturated (AsFA 362) and an unsaturated (AsFA 388) arsenic-containing fatty acid and three of their proposed metabolites (DMA^V, DMAPr and thio-DMAPr) were investigated in human liver cells (HepG2). Even though both arsenic-containing fatty acids were less toxic as compared to arsenic-containing hydrocarbons and arsenite, significant effects were observable at μM concentrations. DMA^V causes effects in a similar concentration range and it could be seen that it is metabolised to its highly toxic thio analogue thio-DMA^V in HepG2 cells. Nevertheless, DMAPr and thio-DMAPr did not exert any cytotoxicity. In summary, our data indicate that risks to human health related to the presence of arsenic-containing fatty acids in marine food cannot be excluded. This stresses the need for a full in vitro and in vivo toxicological characterisation of these arsenolipids.

[Outcome after Implantation of the Aptis Total Distal Radioulnar Joint Replacement Prosthesis]

BACKGROUND

To date, the Aptis distal radioulnar joint (DRUJ) prosthesis by Scheker is the only total, bipolar prosthesis available. In the literature, only few data exist concerning the prosthesis and its surgical technique. Aim of the present study was the evaluation of the medium-term clinical and radiological outcome following implantation of the Aptis DRUJ prosthesis.

METHODS AND PATIENTS

5 patients (4 women and 1 man) with mean age of 40.2 (30-65) years underwent secondary implantation of the Aptisprosthesis between February 2006 and May 2013. The average date of the follow-up was after 36 (24-48) months. Besides the complications, the wrist range of motion (ROM) and the strength in grip were measured. The quality of pain was determined using a visual analogue pain scale from 0-10. In follow-up X-ray controls, bone resorption and bony abnormalities were evaluated. The DASH score as well as the postoperative subjective satisfaction of the patients were recorded.

RESULTS

No patient required removal of the prosthesis. Only 1 patient underwent secondary surgery in which debridement of the screw tip over the radius was required. The postoperative range of motion in pronation and supination was measured with 78 (70-90)° and 82 (70-90)°. The average grip strength amounted to 29 (24-32) kg. This represented 85 (76-100)% of the value of the contralateral side. Postoperative pain symptoms on the visual analogue pain scale were measured with 0 points at rest and with 1.2 (0-2) points under strain. Radiological evaluation showed bone resorption at the radial peg in 2 patients, but without evidence of implant loosening. The DASH score was recorded with 37 (13-75) points. All patients were satisfied or very satisfied after the surgical treatment.

CONCLUSION

The Aptis prosthesis is a safe and efficient treatment option for previously failed surgery of the DRUJ.

In vitro toxicological characterisation of three arsenic-containing hydrocarbons

Arsenic-containing hydrocarbons are one group of fat-soluble organic arsenic compounds (arsenolipids) found in marine fish and other seafood. A risk assessment of arsenolipids is urgently needed, but has not been possible because of the total lack of toxicological data. In this study the cellular toxicity of three arsenic-containing hydrocarbons was investigated in cultured human bladder (UROtsa) and liver (HepG2) cells. Cytotoxicity of the arsenic-containing hydrocarbons was comparable to that of arsenite, which was applied as the toxic reference arsenical. A large cellular accumulation of arsenic, as measured by ICP-MS/MS, was observed after incubation of both cell lines with the arsenolipids. Moreover, the toxic mode of action shown by the three arsenic-containing hydrocarbons seemed to differ from that observed for arsenite. Evidence suggests that the high cytotoxic potential of the lipophilic arsenicals results from a decrease in the cellular energy level. This first in vitro based risk assessment cannot exclude a risk to human health related to the presence of arsenolipids in seafood, and indicates the urgent need for further toxicity studies in experimental animals to fully assess this possible risk.

Arsenic-containing hydrocarbons are toxic in the in vivo model Drosophila melanogaster

Arsenic-containing hydrocarbons cause developmental toxicity in Drosophila melanogaster.

Correlation between dynamical heterogeneities, structure and potential-energy distribution in a 2D amorphous solid

We investigate the collective properties of particles in a 2D experimental system which consists of a bi-disperse mixture of colloidal particles confined at an air/water interface. We find a direct correlation between structure and dynamical heterogeneities in this system: particles belonging to locally ordered structures have lower potential energy and are slower than other particles. In a more general way we show that particles with high potential energy are dominating the dynamics especially in the α-relaxation regime.

Crystal nuclei and structural correlations in two-dimensional colloidal mixtures: experiment versus simulation

We examine binary mixtures of superparamagnetic colloidal particles confined to a two-dimensional water-air interface both by real-space experiments and Monte Carlo computer simulations at high coupling strength. In the simulations, the interaction is modelled as a pairwise dipole-dipole repulsion. While the ratio of magnetic dipole moments is fixed, the interaction strength governed by the external magnetic field and the relative composition is varied. Excellent agreement between simulation and experiment is found for the partial pair distribution functions including the fine structure of the neighbour shells at high coupling. Furthermore local crystal nuclei in the melt are identified by bond-orientational order parameters and their contribution to the pair structure is discussed.

The experimental realization of a two-dimensional colloidal model system

We present the technical details of an experimental method to realize a model system for two-dimensional (2D) phase transitions and the glass transition. The system consists of several hundred thousand colloidal superparamagnetic particles confined by gravity at a flat water-air interface of a pending water droplet where they are subjected to Brownian motion. The dipolar pair potential and, therefore, the system temperature are not only known precisely but also directly and instantaneously controllable via an external magnetic field H. In the case of a one-component system of monodisperse particles the system can crystallize upon application of H whereas in a two component system it undergoes a glass transition. Up to 10,000 particles are observed by video microscopy and image processing provides their trajectories on all relative length and time scales. The position of the interface is actively regulated thereby reducing surface fluctuations to less than 1 microm and the setup inclination is controlled to an accuracy of +/-1 murad. The sample quality being necessary to enable the experimental investigation of the 2D melting scenario, 2D crystallization, and the 2D glass transition, is discussed.

Partial clustering prevents global crystallization in a binary 2D colloidal glass former

A mixture of two types of super-paramagnetic colloidal particles with long-range dipolar interaction is confined by gravity to the flat interface of a hanging water droplet. The particles are observed by video microscopy and the dipolar interaction strength is controlled via an external magnetic field. The system is a model system to study the glass transition in 2D, and it exhibits partial clustering of the small particles (N. Hoffmann et al., Phys. Rev. Lett. 97, 078301 (2006)). This clustering is strongly dependent on the relative concentration [Formula: see text] of big and small particles. However, changing the interaction strength [Formula: see text] reveals that the clustering does not depend on the interaction strength. The partial clustering scenario is quantified using Minkowski functionals and partial structure factors. Evidence that partial clustering prevents global crystallization is discussed.

Local crystalline order in a 2D colloidal glass former

A mixture of two types of super-paramagnetic colloidal particles with long-range dipolar interaction is confined by gravity to a flat interface of a hanging water droplet. The particles are observed by video microscopy and the dipolar interaction strength is controlled by an external magnetic field. The local structure as obtained by pair correlation functions and bond order statistics is investigated as a function of system temperature and relative concentration. Although the system has no long-range order and exhibits glassy dynamics, different types of stable crystallites coexist. The local order of the globally disordered structure is explained by a small set of specific crystal structures. The statistics of crystal unit cells show a continuous increase of local order with decreasing system temperature as well as a dependence on sample history and local composition.

Dynamic glass transition in two dimensions

The question of the existence of a structural glass transition in two dimensions is studied using mode coupling theory (MCT). We determine the explicit d dependence of the memory functional of mode coupling for one-component systems. Applied to two dimensions we solve the MCT equations numerically for monodisperse hard disks. A dynamic glass transition is found at a critical packing fraction phi(c)d=2 approximately equal 0.697 which is above phi(c)d=3 approximately equal 0.516 by about 35%. Phi(c)d scales approximately with phi(rcp)d, the value for random close packing, at least for d=2, 3. Quantities characterizing the local, cooperative "cage motion" do not differ much for d=2 and d=3, and we, e.g., find the Lindemann criterion for the localization length at the glass transition. The final relaxation obeys the superposition principle, collapsing remarkably well onto a Kohlrausch law. The d=2 MCT results are in qualitative agreement with existing results from Monte Carlo and molecular dynamics simulations. The mean-squared displacements measured experimentally for a quasi-two-dimensional binary system of dipolar hard spheres can be described satisfactorily by MCT for monodisperse hard disks over four decades in time provided the experimental control parameter Gamma (which measures the strength of dipolar interactions) and the packing fraction phi are properly related to each other.

Complement sensitivity of Entamoeba histolytica and various nonpathogenic amoeba species

Culture forms of the potentially pathogenic Entamoeba histolytica were compared to those of the nonpathogenic species of E. dispar, E. hartmanni, E. coli, Endolimax nana, and E. moshkovskii regarding the sensitivity to lysis by human complement activated through the alternative pathway. E. dispar was found unique in its complement resistance; all other nonpathogenic isolates resembled E. histolytica in that they were complement sensitive. Thus, a state of complement sensitivity is not a particular property of potentially pathogenic amoebae.

Spinal narcotics for postoperative analgesia in total joint arthroplasty. A prospective study

Sixty patients who were scheduled to have an elective total hip or knee arthroplasty were randomly assigned to one of three groups of twenty patients each before operation with spinal anesthesia. A double-blind technique was used throughout the study. The patients in Group I (control group) received hyperbaric 1 per cent tetracaine with epinephrine as the subarachnoid spinal anesthetic; the patients in Group II (morphine group), hyperbaric 1 per cent tetracaine with epinephrine and a single subarachnoid dose of Duramorph (morphine sulphate), 0.5 milligram; and those in Group III (Dilaudid group), hyperbaric 1 per cent tetracaine with epinephrine and a single subarachnoid dose of Dilaudid (hydromorphone hydrochloride), 0.002 milligram per kilogram of body weight. During the first twenty-four hours after the operation, the patients in Group II and Group III had significantly less pain compared with those in Group I. This was shown by the use of a visual linear-analog pain scale (p less than 0.05), the patients' ratings of the quality of relief of pain (p less than 0.02), and comparative measurements of the pain-altering medications that were used (p less than 0.05). The patients in Group II and Group III did not have any more complications or side effects than those in Group I. There was no significant difference in the quality and duration of analgesia between Group II and Group III.

Isoenzymes of the lung fluke Paragonimus uterobilateralis from Liberia

The enzymes of 35 adult Paragonimus uterobilateralis were analysed using thin-layer starch gel electrophoresis. From a total of 21 enzyme systems studied, 15 proved to be useful for the description and recognition of this species. All individuals were identical concerning 11 enzymes. In four remaining enzymes, alanine aminotransferase (ALAT, hexokinase, aspartate aminotransferase and phosphogluconate dehydrogenase, two or three variants, also being partly typical for this species were observed. In a comparison involving seven different enzymes, there were no differences between the electrophoretic patterns of 35 adult and 24 juvenile P. uterobilateralis. Additional examinations of 30 adult P. uterobilateralis with isoelectric focusing on ultrathin-layer polyacrylamide gels revealed clearer separations of enzymes. The method showed corresponding results or identiy of all individuals tested with three representative enzymes (ALAT, glucosephosphate isomerase and adenylate kinase).

Isoenzymes of Trypanosoma rangeli stocks and their relation to other trypanosomes transmitted by triatomine bugs

Culture forms of three trypanosome species, Trypanosoma rangeli, T conorhini and T. cruzi, have been compared isoenzymatically by isoelectrofocusing. Of 9 enzymes examined, three: nonspecific esterase (NSE), phosphoglucomutase (PGM) and glucosephosphate isomerase (GPI), showed species specific enzyme profiles. Little isoenzymatic variation was found amongst the 14 T. rangeli stocks examined. Two of them were identified as T. cruzi of Group I demonstrating the necessity of a clear identification of trypanosome populations isolated from bugs in areas endemic for T. rangeli and T. cruzi. In extracts of artificially mixed cultures of T. rangeli and T. cruzi only the patterns of NSE showed clearly the specific bands of both species. The NSE should be tested for the detection of mixed infections under natural conditions.

Further isoenzymatic studies on Trypanosoma cruzi stocks from Brazil, Colombia and Chile

Eighteen stocks of T. cruzi from Brazil, Colombia and Chile were compared by five isoenzyme patterns of isoelectrofocusing with the three principal Brazilian zymodemes (Z1, Z2, Z3). The two main Groups I and II found confirmed the zymodemes 1 and 2. However, in some cases new isoenzyme types of the enzymes GPI and PGM in the Groups I and II have been seen. Stocks typed as Z3 did not show homogeneous enzyme patterns. A clear differentiation from the Z1 and Z2 or an association with a third group was not possible. The results of Chilean stocks showed the predominance of the Group II in the domestic cycle of T. cruzi, whereas the results of the Colombian stocks typed as Group I pointed out that in countries north of the Amazon basin only Group I of T. cruzi exists.

Comparative characterization of Venezuelan Trypanosoma cruzi stocks by electron microscopy, isoelectrofocusing and lectin typing

The intraspecific variation among culture forms of 14 Venezuelan Trypanosoma cruzi stocks were examined by kDNA configuration, isoenzymes, and agglutination behaviour of lectins. The results have shown that in all of the stocks the central band of kDNA is present, showing that the stocks are parasites of the subgenus Schizotrypanum. By isoenzymes and lectin typing it has been found that the stocks belong to the isoenzyme group I and the lectin-type PNA which were already described for other Venezuelan stocks. The homogeneous results of intraspecific characterization contrast to those found in other countries in South America south of the Amazon basin and seem to be a further evidence that in countries north of the Amazon basin mainly on T. cruzi-type exists.

Semiautomated Fluorometric Method for Determination of Vitamin C in Foods: Collaborative Study

Continuous flow automation of the microfluorometric procedure compares favorably with the manual method in sensitivity, specificity, and generality, and reduces the cost of routine vitamin C assay. Fifteen samples of 12 different products of ready-to-eat cereals, fruit juices, and infant formula were sent to 6 collaborators; one sample in each category was sent as blind duplicates. The within-laboratory standard deviations for 5 collaborators on the 3 sets of blind duplicates were 1.23, 0.87, and 3.64 mg/100 g, respectively. Overall, the average relative standard deviation between laboratories was 11.1% (range 4.5-16.6%) for the manual method and 4.99% (range 1.5-12.6%) for the semiautomated method. The method has been adopted official first action.

The characterization of Trypanosoma cruzi stocks by starch-gel electrophoresis, comparison of results with those of isoelectric focusing

The culture forms of 30 T. cruzi stocks originating from different parts of Brazil and Venezuela were screened by starch-gel electrophoresis for the isoenzyme patterns of 9 enzymes: glucose-6-phosphate dehydrogenase (G6PD), phosphoglucomutase (PGM), glucosephosphate isomerase (GPI), aspartate aminotransferase (ASAT), "malic" enzyme (ME), alanine aminotransferase (ALAT), peptidases (PEP 1, PEP 2) and malate dehydrogenase (MDH). G6PD, PGM, GPI to some extent also ASAT, ME patterns divide 25 stocks into two distinct main groups A and B. The Brazilian stocks of group A originated from different wild animal species only, those of group B were with one exception isolated from human patients, or domestic hosts. In contrast all stocks from Venezuela regardless of their original host belonged to group A. The results of all enzymes showed group A (16 stocks and 7 profiles) to be more homogeneous than group B (9 stocks and 7 profiles). Comparison of these results with previous results of isoelectric focusing of the same stocks shows both methods to be complementary. The two methods gave identical classification of stocks with G6PD, PGM and GPI, both methods dividing most stocks into two main groups. The enzymes ALAT and ASAT confirmed this grouping to some extent in the starch-gel electrophoresis. For both starch-gel and isoelectric focusing ME was of only limited value because of variable enzyme activities in the trypanosome extracts. For the enzymes PEP 1, and PEP 2 and MDH neither method was useful in demonstrating intraspecific variation within the T. cruzi complex.

Comparison of isoenzymes of some species of the subgenus schizotrypanum from bats by isoelectrofocusing

Culture forms of bat-trypanosomes of the species T. dionisii, T. vespertilionis and T.c. marinkellei were compared isoenzymatically by isoelectrofocusing. The enzymes tested were: nonspecific esterase (NSE, E.C.3.1.1.), phosphoglucomutase (PGM, E.C. 2.7.5.1), glucose-6-phosphate dehydrogenase (G-6-PD, E.C. 1.1.1.49), glucosephosphate isomerase (GPI, E.C. 5.3.1.9), malate dehydrogenase (MDH, E.C. 1.1.1.37), alcohol dehydrogenase (NADP+) (ADH, E.C. 1.1.1.2). Their enzyme types were related to those of T. cruzi. The comparison of enzyme patterns of the six enzymes has shown that each species was characterized by species-specific enzyme profiles. Among the stocks of the European species, T. dionisii, and T. vespertilionis, variations of the enzyme patterns of PGM, G-6-PD and GPI suggesting that the final status of this subspecies is probably not yet established. In relation to T. cruzi it has been found that T. dionisii showed identical enzyme profiles with group II of T. cruzi. For T. vespertilionis no enzyme types identical with T. cruzi were detectable. T.c. marinkellei showed only identical enzyme patterns to T. cruzi-group I by the enzymes NSE and GPI.

The characterization of Chilean and Bolivian Trypanosoma cruzi stocks from Triatoma infestans by isoelectrofocusing

Culture forms of 12 Chilean and 9 Bolivian Trypanosoma cruzi stocks were compared isoenzymatically by the following enzymes: non-specific esterase, phosphoglucomutase, glucose-6-phosphate dehydrogenase, glucosephosphate isomerase, and alcohol dehydrogenase. On the basis of the electrophoretic mobility of these enzymes the stocks were classified into two main groups. Ten Chilean stocks were characterized as group II; two stocks showed enzyme patterns of group I. In contrast, five Bolivian stocks were classified as belonging to group I, the other four to group II. The results show that the two groups of T. cruzi overlap in Triatoma infestans suggesting that both groups of T. cruzi are infective for man. The classification of stocks into two groups is discussed in the light of published results of Brazilian T. cruzi stocks. A strong association of groups with the transmission cycles as it seems to be in Brazil does not exist in Chile and Bolivia.

The identification of two main-groups of Trypanosoma cruzi stocks from Brazil by their isoenzyme patterns of isoelectrofocusing

The isoelectrofocusing of seven enzymes was studied using extracts of 40 Brazilian stocks of T. cruzi culture forms. Four enzymes showed intraspecific variation in enzyme profiles and were selected for characterization of T. cruzi. These enzymes are: nonspecific esterase (E.C.3.1.1), phosphoglucomutase (E.C. 2.7.5.1), glucose-6-phosphate dehydrogenase (E.C. 1.1.1.49) and glucosephosphate isomerase (E.C. 5.3.1.9). The parasite stocks were isolated from endemic areas in the States: Rio Grande do Sul, Sao Paulo, Espirito Santo, Minas Gerais and Bahia. By combining the electrophoretic patterns of the four enzymes concerned the stocks have been classified into two main-groups. Stocks of group I were exclusively isolated from wild animal reservoirs, whereas group II was mainly composed of stocks from human cases and domestic hosts. Only three "sylvatic" stocks have been found in group II. The enzymes glucose-6-phosphate dehydrogenase and glucosephosphate isomerase showed further subtypes within both groups I and II; their significance is not yet clear. The results are in support of the existence of a domestic and a sylvatic transmission cycles in Brazil which are either clearly distinct or overlapping in some areas.

The use of isoelectrofocusing in thin layer polyacrylamide and agarose gels as a method for the characterization of Venezuelan Trypanosoma cruzi stocks

The technique of isoelectrofocusing has been used to compare culture forms of 12 stocks of T. cruzi isolated in different regions of Venezuela. The following seven enzymes have been used for the characterization: unspecific esterase (E.C.3.1.1), malate dehydrogenase (E.C.1.1.1.37), "malic enzyme" (E.C.1.1.1.40), hexokinase (E.C.2.7.1.1), phosphoglucomutase (E.C.2.7.5.1), glucosephosphate isomerase (E.C.5.3.1.9) and glucose-6-phosphate dehydrogenase (E.C.1.1.1.49). The isoelectrofocusing method allows to determine reproducible enzyme patterns of high selectivity and with a number of bands. This permits to recognize possible differences within the T. cruzi-complex much easier than previous methods. The Venezuelan T. cruzi stocks showed a remarkable homogenous behaviour concerning the enzyme profiles. Most of them were identical. Different types seen for "malic enzyme", phosphoglucomutase, and glucose-6-phosphate dehydrogenase were observed in only three stocks, It was not possible to find a clear relationship between the types and the histories of stocks.