Design of a proteolytic module for improved metabolic modeling of Bacteroides caccae

The gut microbiota plays a crucial role in health and is significantly modulated by human diets. In addition to Western diets which are rich in proteins, high-protein diets are used for specific populations or indications, mainly weight loss. In this study, we investigated the effect of protein supplementation on Bacteroides caccae, a Gram-negative gut symbiont. The supplementation with whey proteins led to a significant increase in growth rate, final biomass, and short-chain fatty acids production. A comprehensive genomic analysis revealed that B. caccae possesses a set of 156 proteases with putative intracellular and extracellular localization and allowed to identify amino acid transporters and metabolic pathways. We developed a fully curated genome-scale metabolic model of B. caccae that incorporated its proteolytic activity and simulated its growth and production of fermentation-related metabolites in response to the different growth media. We validated the model by comparing the predicted phenotype to experimental data. The model accurately predicted B. caccae's growth and metabolite production (R2 = 0.92 for the training set and R2 = 0.89 for the validation set). We found that accounting for both ATP consumption related to proteolysis, and whey protein accessibility is necessary for accurate predictions of metabolites production. These results provide insights into B. caccae's adaptation to a high-protein diet and its ability to utilize proteins as a source of nutrition. The proposed model provides a useful tool for understanding the feeding mechanism of B. caccae in the gut microbiome.IMPORTANCEMicrobial proteolysis is understudied despite the availability of dietary proteins for the gut microbiota. Here, the proteolytic potential of the gut symbiont Bacteroides caccae was analyzed for the first time using pan-genomics. This sketches a well-equipped bacteria for protein breakdown, capable of producing 156 different proteases with a broad spectrum of cleavage targets. This functional potential was confirmed by the enhancement of growth and metabolic activities at high protein levels. Proteolysis was included in a B. caccae metabolic model which was fitted with the experiments and validated on external data. This model pinpoints the links between protein availability and short-chain fatty acids production, and the importance for B. caccae to gain access to glutamate and asparagine to promote growth. This integrated approach can be generalized to other symbionts and upscaled to complex microbiota to get insights into the ecological impact of proteins on the gut microbiota.

Modelling the growth of Staphylococcus aureus on cooked broccoli under isothermal conditions

In this study, we developed predictive models describing the growth of Staphylococcus aureus on cooked broccoli florets. A pool of 3.5 log CFU/g of five S. aureus strains were inoculated on 10 g broccoli portions. The samples were then stored at 10, 20, 30 and 37 °C, and colonies were enumerated at different time intervals. Baranyi and Roberts model was fitted to the data using a Bayesian Adaptive Markov Chain Monte Carlo for estimation of the growth parameters. S. aureus showed low growth at 10 °C on broccoli samples and at 20-37 °C interval, Baranyi and Roberts model fitted well to the experimental data (R²>0.97). Estimated growth parameters were correlated with the possibility of toxin production and indicate the potential presence of these biological hazards on contaminated broccoli after heat treatment. Additionally, linear regression was performed for growth rate as storage temperature function. This secondary model followed a linear tendency with R²=0.997 and was compared with two tertiary models (ComBase Predictor and Pathogen Modeling Program) and literature data, demonstrating similar growth rate values of both. These results can be helpful for food services and managers to establish food safety standards for S. aureus growth on cooked broccoli.

Exploring the Bacterial Impact on Cholesterol Cycle: A Numerical Study

High blood cholesterol levels are often associated with cardiovascular diseases. Therapeutic strategies, targeting different functions involved in cholesterol transport or synthesis, were developed to control cholesterolemia in human. However, the gut microbiota is also involved in cholesterol regulation by direct biotransformation of luminal cholesterol or conversion of bile salts, opening the way to the design of new strategies to manage cholesterol level. In this report, we developed for the first time a whole-body human model of cholesterol metabolism including the gut microbiota in order to investigate the relative impact of host and microbial pathways. We first used an animal model to investigate the ingested cholesterol distribution in vivo. Then, using in vitro bacterial growth experiments and metabolite measurements, we modeled the population dynamics of bacterial strains in the presence of cholesterol or bile salts, together with their bioconversion function. Next, after correct rescaling to mimic the activity of a complex microbiota, we developed a whole body model of cholesterol metabolism integrating host and microbiota mechanisms. This global model was validated with the animal experiments. Finally, the model was numerically explored to give a further insight into the different flux involved in cholesterol turn-over. According to this model, bacterial pathways appear as an important driver of cholesterol regulation, reinforcing the need for development of novel "bacteria-based" strategies for cholesterol management.

Analysis and numerical simulation of an inverse problem for a structured cell population dynamics model

In this work, we study a multiscale inverse problem associated with a multi-type model for age structured cell populations. In the single type case, the model is a McKendrick-VonFoerster like equation with a mitosis-dependent death rate and potential migration at birth. In the multi-type case, the migration term results in an unidirectional motion from one type to the next, so that the boundary condition at age 0 contains an additional extrinsic contribution from the previous type. We consider the inverse problem of retrieving microscopic information (the division rates and migration proportions) from the knowledge of macroscopic information (total number of cells per layer), given the initial condition. We first show the well-posedness of the inverse problem in the single type case using a Fredholm integral equation derived from the characteristic curves, and we use a constructive approach to obtain the lattice division rate, considering either a synchronized or non-synchronized initial condition. We take advantage of the unidirectional motion to decompose the whole model into nested submodels corresponding to self-renewal equations with an additional extrinstic contribution. We again derive a Fredholm integral equation for each submodel and deduce the well-posedness of the multi-type inverse problem. In each situation, we illustrate numerically our theoretical results.

Signatures of ecological processes in microbial community time series

BACKGROUND

Growth rates, interactions between community members, stochasticity, and immigration are important drivers of microbial community dynamics. In sequencing data analysis, such as network construction and community model parameterization, we make implicit assumptions about the nature of these drivers and thereby restrict model outcome. Despite apparent risk of methodological bias, the validity of the assumptions is rarely tested, as comprehensive procedures are lacking. Here, we propose a classification scheme to determine the processes that gave rise to the observed time series and to enable better model selection.

RESULTS

We implemented a three-step classification scheme in R that first determines whether dependence between successive time steps (temporal structure) is present in the time series and then assesses with a recently developed neutrality test whether interactions between species are required for the dynamics. If the first and second tests confirm the presence of temporal structure and interactions, then parameters for interaction models are estimated. To quantify the importance of temporal structure, we compute the noise-type profile of the community, which ranges from black in case of strong dependency to white in the absence of any dependency. We applied this scheme to simulated time series generated with the Dirichlet-multinomial (DM) distribution, Hubbell's neutral model, the generalized Lotka-Volterra model and its discrete variant (the Ricker model), and a self-organized instability model, as well as to human stool microbiota time series. The noise-type profiles for all but DM data clearly indicated distinctive structures. The neutrality test correctly classified all but DM and neutral time series as non-neutral. The procedure reliably identified time series for which interaction inference was suitable. Both tests were required, as we demonstrated that all structured time series, including those generated with the neutral model, achieved a moderate to high goodness of fit to the Ricker model.

CONCLUSIONS

We present a fast and robust scheme to classify community structure and to assess the prevalence of interactions directly from microbial time series data. The procedure not only serves to determine ecological drivers of microbial dynamics, but also to guide selection of appropriate community models for prediction and follow-up analysis.

Inferring Aggregated Functional Traits from Metagenomic Data Using Constrained Non-negative Matrix Factorization: Application to Fiber Degradation in the Human Gut Microbiota

Whole Genome Shotgun (WGS) metagenomics is increasingly used to study the structure and functions of complex microbial ecosystems, both from the taxonomic and functional point of view. Gene inventories of otherwise uncultured microbial communities make the direct functional profiling of microbial communities possible. The concept of community aggregated trait has been adapted from environmental and plant functional ecology to the framework of microbial ecology. Community aggregated traits are quantified from WGS data by computing the abundance of relevant marker genes. They can be used to study key processes at the ecosystem level and correlate environmental factors and ecosystem functions. In this paper we propose a novel model based approach to infer combinations of aggregated traits characterizing specific ecosystemic metabolic processes. We formulate a model of these Combined Aggregated Functional Traits (CAFTs) accounting for a hierarchical structure of genes, which are associated on microbial genomes, further linked at the ecosystem level by complex co-occurrences or interactions. The model is completed with constraints specifically designed to exploit available genomic information, in order to favor biologically relevant CAFTs. The CAFTs structure, as well as their intensity in the ecosystem, is obtained by solving a constrained Non-negative Matrix Factorization (NMF) problem. We developed a multicriteria selection procedure for the number of CAFTs. We illustrated our method on the modelling of ecosystemic functional traits of fiber degradation by the human gut microbiota. We used 1408 samples of gene abundances from several high-throughput sequencing projects and found that four CAFTs only were needed to represent the fiber degradation potential. This data reduction highlighted biologically consistent functional patterns while providing a high quality preservation of the original data. Our method is generic and can be applied to other metabolic processes in the gut or in other ecosystems.

Challenges in microbial ecology: building predictive understanding of community function and dynamics

The importance of microbial communities (MCs) cannot be overstated. MCs underpin the biogeochemical cycles of the earth's soil, oceans and the atmosphere, and perform ecosystem functions that impact plants, animals and humans. Yet our ability to predict and manage the function of these highly complex, dynamically changing communities is limited. Building predictive models that link MC composition to function is a key emerging challenge in microbial ecology. Here, we argue that addressing this challenge requires close coordination of experimental data collection and method development with mathematical model building. We discuss specific examples where model–experiment integration has already resulted in important insights into MC function and structure. We also highlight key research questions that still demand better integration of experiments and models. We argue that such integration is needed to achieve significant progress in our understanding of MC dynamics and function, and we make specific practical suggestions as to how this could be achieved.

The heat treatment and the gelation are strong determinants of the kinetics of milk proteins digestion and of the peripheral availability of amino acids

This study aimed to determine the kinetics of milk protein digestion and amino acid absorption after ingestion of four dairy matrices by six minipigs: unheated or heated skim milk and corresponding rennet gels. Digestive contents and plasma samples were collected over a 7 h-period after meal ingestion. Gelation of milk slowed down the outflow of the meal from the stomach and the subsequent absorption of amino acids, and decreased their bioavailability in peripheral blood. The gelled rennet matrices also led to low levels of milk proteins at the duodenum. Caseins and β-lactoglobulin, respectively, were sensitive and resistant to hydrolysis in the stomach with the unheated matrices, but showed similar digestion with the heated matrices, with a heat-induced susceptibility to hydrolysis for β-lactoglobulin. These results suggest a significant influence of the meal microstructure (resulting from heat treatment) and macrostructure (resulting from gelation process) on the different steps of milk proteins digestion.

Kinetic modelling of lactate utilization and butyrate production by key human colonic bacterial species

Butyrate is the preferred energy source for colonocytes and has an important role in gut health; in contrast, accumulation of high concentrations of lactate is detrimental to gut health. The major butyrate-producing bacterial species in the human colon belong to the Firmicutes. Eubacterium hallii and a new species, Anaerostipes coli SS2/1, members of clostridial cluster XIVa, are able to utilize lactate and acetate via the butyryl CoA : acetate CoA transferase route, the main metabolic pathway for butyrate synthesis in the human colon. Here we provide a mathematical model to analyse the production of butyrate by lactate-utilizing bacteria from the human colon. The model is an aggregated representation of the fermentation pathway. The parameters of the model were estimated using total least squares and maximum likelihood, based on in vitro experimental data with E. hallii L2-7 and A. coli SS2/1. The findings of the mathematical model adequately match those from the bacterial batch culture experiments. Such an in silico approach should provide insight into carbohydrate fermentation and short-chain fatty acid cross-feeding by dominant species of the human colonic microbiota.

Mathematical modelling of carbohydrate degradation by human colonic microbiota

The human colon is an anaerobic ecosystem that remains largely unexplored as a result of its limited accessibility and its complexity. Mathematical models can play a central role for a better insight into its dynamics. In this context, this paper presents the development of a mathematical model of carbohydrate degradation. Our aim was to provide an in silico approach to contribute to a better understanding of the fermentation patterns in such an ecosystem. Our mathematical model is knowledge-based, derived by writing down mass-balance equations. It incorporates physiology of the intestine, metabolic reactions and transport phenomena. The model was used to study various nutritional scenarios and to assess the role of the mucus on the system behavior. Model simulations provided an adequate qualitative representation of the human colon. Our model is complementary to experimental studies on human colonic fermentation, which, of course, is not meant to replace. It may be helpful to gain insight on questions that are still difficult to elucidate by experimentation and suggest future experiments.

Procalcitonin and calcitonin gene-related peptide decrease LPS-induced tnf production by human circulating blood cells

The pathogenesis of septic shock is mainly due to unregulated tumour necrosis factor-alpha (TNF-alpha) production. Procalcitonin (PCT) and calcitonin gene-related peptide (CGRP) are alternative transcription products of the calcitonin gene. Since high PCT levels have been described in human sepsis, and since CGRP inhibits TNF synthesis in rats, we examined the role of these peptides in the regulation of the inflammatory response during septic shock. LPS-induced TNF production was assessed using a human whole blood model. In this model, PCT (10(-7) M) and CGRP (10(-6) M) significantly inhibit TNF production by 27 and 24 % respectively. The effect of CGRP was reversed by CGRP 8-37 (10 microM), an antagonist of CGRP receptor. No effect on interleukin (IL)-1, IL-6 and IL-8 was found. This is the first description of an anti-inflammatory role for PCT and CGRP in humans.

Procalcitonin is not produced by circulating blood cells

A large number of clinical studies has described procalcitonin (ProCT) as a marker of bacterial infection and a good predictor of disease severity and antibiotherapy efficacy. Nevertheless, the mechanism of ProCT synthesis remains unclear. The aim of this study was to demonstrate potential ProCT production by peripheral blood mononuclear cells as is the case for cytokines involved in sepsis. In a whole blood model, LPS (10 micrograms/ml) stimulation on blood samples from healthy volunteers (n = 14) was tested. Early (TNF-alpha and IL1-beta) and late (IL-6 and IL-8) cytokines were produced in large amounts in contrast to the absence of ProCT. Additional experiments with nitric oxide or detection of intra-cellular ProCT (cell lysis, flow cytometry) had negative results. It was concluded that ProCT is not produced in this model. Data are still needed to investigate the cellular origin of ProCT in order to better define its clinical usefulness.

Total androgen ablation: Canadian experience

A multicenter randomized, double-blind trial comparing total androgen blockade obtained by the use of castration with a pure anti-androgen (nilutamide) with simple castration was begun. One hundred and five patients received the combined treatment and 103 the orchiectomy plus placebo. Several features were used to evaluate the efficacy. Bone pain responded better to combined treatment at 6 months (P = 0.042). The number of favorable responses, as evaluated by the NPCP criteria, was 61% with simple castration and 78% with the combined treatment (P = 0.013). There was no statistically significant difference between the two groups in time to progression (logrank test P = 0.462) or survival (logrank test P = 0.137) despite an increase in median survival of 5.4 months. All other measures showed no difference between the two treatments. With total androgen blockade, 50% of the patients had disease progression at 1 year, and 45% were dead at 2 years. A review of the results of similar reported studies suggests no improvement or very modest improvement with total androgen blockade over testicular androgen ablation alone.

A controlled trial of castration with and without nilutamide in metastatic prostatic carcinoma

A randomized double-blind trial in patients with disseminated, previously untreated prostate cancer (Stage D2) was conducted in eight Canadian centers. All 203 patients enrolled in this study underwent bilateral orchiectomy and were randomized to receive either the nonsteroidal anti-androgen nilutamide or a placebo. Patient responses were graded according to the criteria of the National Prostatic Cancer Project (NPCP). Patients treated with nilutamide had a significantly greater number of positive objective responses (partial and complete regression) than did the patients treated with castration alone (46% versus 20%, P = 0.001). Progression-free survival was improved initially in the nilutamide group, but the median time to progression was 12 months for both groups. Despite an increase in the median length of survival from 18.9 to 24.3 months with the nilutamide, the survival time was not significantly longer in the nilutamide group (log = rank test, P = 0.048). Although minor side effects were frequent, adverse effects related to the medication and leading to discontinuation of treatment were observed in 9% of cases. These results suggest some benefit of the combined treatment (orchiectomy + nilutamide) over orchiectomy alone in the treatment of metastatic prostatic carcinoma.

Scintigraphic evaluation of renal function after extracorporeal shock-wave lithotripsy

We evaluated renal function within 48 hours after extracorporeal shock-wave lithotripsy (ESWL) as well as 1 month and up to 6 months later employing technetium-99m dimercaptosuccinic acid and iodine-131-labelled ortho-iodohippurate. All 17 patients displayed abnormal renal function immediately after ESWL. The abnormalities identified included focal cortical lesions, diffuse reduction of renal function, increased kidney volume, and diffusely and focally increased parenchymal transit times. The follow-up scintigraphic studies indicated that the great majority of the lesions had been temporary.

The assessment of disease aggressivity in stage D2 prostate cancer patients (review)

Suppression of androgen levels in blood of stage D2 prostate cancer patients has been the prominent treatment for advanced prostate cancer. However, the duration of hormone sensitivity of prostate tumor is variable. The type of initial response to hormonal treatment, the length of response and patient's survival are in direct association with disease aggressiveness. Recently, an arithmetic formula expressing disease aggressivity was computed using pretreatment values of prostatic acid phosphatase (P.A.P.), alkaline phosphatase (A.P.), degree of tumor differentiation and number of bone metastases. This aggressiveness score was related to disease response and patients outcome receiving hormonal treatments. The use of an arithmetic formula to express disease aggressivity could result in a subdivision of the disease. The identification of the subgroup of stage D2 patients destined not to benefit from hormonal manipulation could change the strategies employed up until today for the treatment of advanced prostate cancer.

[Lithotripsy of biliary calculi: evaluation of ultrasonography as a method to guide treatment by extracorporeal shock waves]

Extracorporeal shock-wave lithotripsy is a procedure recently introduced to treat gallstone disease. According to the literature, 15% to 25% of symptomatic persons will be candidates for this procedure if it proves effective. Currently, sonography is one of the best methods for monitoring the performance of lithotripsy. The authors have confirmed this. They have designed an in-vitro model which allows comparison between what is actually happening during gallstone lithotripsy and what is being seen by real-time sonography. The sonographic characteristics of the different phases of gallstone lithotripsy are presented.

Total androgen blockade for metastatic cancer of the prostate

This randomized, double-blind study comparing orchiectomy plus placebo to orchiectomy plus a nonsteroid antiandrogen (Anandron) shows that total androgen blockade for metastatic cancer of the prostate provides a significantly better early objective response when compared to castration alone. This response, however, is less apparent at 18 months. The study also suggests a longer survival for the patients with total androgen blockade.

Objective response and disease outcome in 59 patients with stage D2 prostatic cancer treated with either Buserelin or orchiectomy. Disease aggressivity and its association with response and outcome

A comparative study was done in 59 recently diagnosed Stage D2 prostatic cancer patients treated with either long-term GnRH-A (Buserelin) (N = 42) or with orchiectomy (N = 17) and followed up for three years. The suppressed limits of plasma testosterone and estradiol levels after eight-week follow-up as well as the objective clinical response and disease outcome were found to be similar with either treatment. Hot flushes and loss of libido were noticed in both groups throughout the follow-up period; however, there were no other side effects. Analysis of Stage D2 patients based on their time of death enables us to identify nonhormonal variables which, in the form of an aggressiveness score, correlated well with both clinical response and disease outcome. These data confirm that (1) Buserelin is an effective and safe alternative to orchiectomy in advanced prostatic cancer, and (2) in clinical studies a multifactor aggressiveness score is useful for analyzing clinical efficacy data. Prospective application of that score may enable predictability of patient response and influence patient management.

Preliminary results on the clinical efficacy and safety of androgen inhibition by an LHRH agonist alone or combined with an antiandrogen in the treatment of prostatic carcinoma

We have used the paradoxical antigonadal effects of LHRH agonists as a chemical castration in advanced prostatic cancer. We report early results of a phase II study on the clinical efficacy of the LHRH agonist D-Ser (TBU)6, des-Gly-NH2(10) LHRH administered to patients with stage D prostatic carcinoma. Following dose-range finding studies using either intranasal (IN) (200 micrograms twice/day or 500 micrograms twice/day) or subcutaneous (SC) administration (50 micrograms once/day, we developed a sequential combination of SC (500 micrograms three times/day for seven days) and IN regimen that was administered for 3 to 16 months to a group of 23 patients with stage D prostatic carcinoma. Initiation of therapy was associated with a clinical flare in one patient during the first week of treatment. Mean serum testosterone levels were already decreasing at one week and remained inhibited to levels inferior to 1 ng/ml after the first four weeks of treatment. Overall assessment shows that within the first six months of treatment, 26% patients were improved, 39% were stabilized, and 35% were nonresponders. Fourteen patients were followed during the next six months: 29% continued to respond, 29% escaped, 21% remained stable, and 21% were nonresponders. Histologic studies from castrated patients showed changes in spermatogenesis correlating to the degree and duration of suppression of testicular steroidogenesis without signs of toxicity. Preliminary observations on the combination of the pure antiandrogen RU 23908 with Buserelin (n = 5) or castration (n = 3) suggest that the addition of an antiandrogen does not seem to improve the patients nonresponding to other hormonal suppressive therapy (Buserelin) administered before (n = 3) or concomitantly with the antiandrogen (n = 2). Three relapsing castrate patients responded to the antiandrogen, but the response was temporary in two (eight to nine months of therapy). No side effects other than hot flashes and decreased potency are related to LHRH agonist alone or to the low-dose antiandrogen. Multicenter trials will be necessary to delineate the place of LHRH agonist alone or LHRH agonist combined with an antiandrogen in the treatment of prostatic cancer.

Inhibition of serum androgen levels by chronic intranasal and subcutaneous administration of a potent luteinizing hormone-releasing hormone (LH-RH) agonist in adult men

The effect of chronic treatment with the luteinizing hormone-releasing hormone (LH-RH) agonist Buserelin (Hoechst AG, Frankfurt/Main, West Germany) ([D-Ser(TBU)6,des-Gly-NH2(10)]LH-RH ethylamide) administrered by nasal spray (200 or 500 micrograms, twice daily) or subcutaneously (50 micrograms daily) for periods of 1 to 8 months was studied on serum sex steroids and LH levels in 18 patients with cancer of the prostate. Basal serum testosterone concentration decreases to 71.1 +/- 18.3 (NS) and 28.6 +/- 9.3%, (P less than 0.01) of control in patients receiving the 200-micrograms and 500-micrograms dose by nasal spray, respectively. In patients treated subcutaneously, a more rapid inhibition of serum testosterone levels to 19.6 +/- 6.4% of control (P less than 0.01) is observed. The finding of decreased levels of 17-OH-progesterone, testosterone, and dihydrotestosterone in the presence of unchanged pregnenolone concentration indicates that the decrease in androgen biosynthesis induced by Buserelin treatment is due to a blockage at the level of 17-hydroxylase and 17,20-desmolase activities. The present data indicate that chronic administration of Buserelin could be a safe and effective means of reducing serum androgens in patients with cancer of the prostate.

[Analysis of silicone testicular implants after explantation]

Two juvenile size silicone testicular prostheses were analyzed following replacement by adult size devices after 72 and 99 months in situ. Scanning electron microscopy and electron microprobe studies were carried out on the explanted silicone prostheses and their attached tissue capsules. The material at the surface of the prostheses gave no evidence of biodeterioration. However, localized sites of calcification were observed. The adjacent tissue capsule consisted of two distinct concentric layers with different morphologies; the one adjacent to the prosthesis consisted of dense arrays of collagen fibres oriented parallel to the silicone surface and extending outward to a thickness of 100-120 microns. The outer layer was less dense, more disordered and was uneven in thickness. It contained numerous discrete particles of silicon-rich material. Technical and clinical implications of these results are discussed.

[Myocardial protection of the homograft. III - Evaluation of ventricular fibrillations with hypothermic coronary perfusion (author's transl)]

The homotransplanted heart is in severe failure in the immediate post-operative period, secondary to ischemia inherent to the technic of orthotopic transplantation. The present work was carried out to investigate if ventricular fibrillation followed by cold coronary perfusion could protect the homograft during implantation by evaluating the post-operative cardiac performance. In the control group, 7 hearts were excised, immediately immersed in physiological saline at 5 degrees C, and homotransplanted. In a second group of 4 grafts, ventricular fibrillation was induced and the coronary bed was perfused immediately with cold (5 degrees C) extracellular solution for a period of 10 minutes before orthotopic implantation. All animals were prepared at the end of surgery for hemodynamic studies to be carried out 3, 24 and 48 hours post-operatively in the resting state. In group I, the myocardial temperature dropped to 13.5 degrees C in 14.5 minutes. In group II, the hypothermia by perfusion was more rapid and deeper (11 degrees C within 10 minutes). Three hours post-operatively, cardiac function of group II was superior to that of group I as demonstrated by the increase of cardiac index (39%), stroke volume index (41%) mean systolic ejection rate index (44%), maximum systolic flow index (58%), maximum acceleration index (36%), stroke power index (88%), stroke work index (67%). Twenty-four and forty-eight hours post-operatively the cardio-vascular function improved in both groups but remained superior in group II. These results demonstrate that ventricular fibrillation followed by cold coronary perfusion increases protection of the homograft during the initial period of implantation.

[Evaluation of the acute effect of a converting enzyme inhibitor, captopril, in normal and hypertensive subjects]

The response to acute oral administration of 50 mg of Captopril was assessed in 17 normal volunteers and 47 patients with hypertension; 17 had renovascular (RVH) abnormalities and 30 patients had essential hypertension (EH). All patients were maintained on ad libitum sodium intake. The effect of Captopril on mean arterial pressure (MAP) was rapid a maximal within 60 minutes. The converting enzyme inhibitor induced a similar decrease in MAP in normal subjects (-5.1 +/- I mm Hg) and patients with EH (-7.2 +/- I mm Hg). Control plasma renin activity (PRA) was similar in both groups; however, the increase in PRA following Captopril was more marked in normals (8.1 +/- 1.7 ng/ml/h) than in EH (1.7 +/- 0.7 ng/ml/h). In patients with RVH a marked fall in MAP occurred (-25.4 +/- 4 mm Hg). A fall in MAP higher than 20 mm Hg was observed in 65% of patients with RVH and none of the EH group. A negative correlation between log PRA and the change in MAP induced by Captopril was obtained (r = 0.65). Assessment of the response to acute administration of Captopril may be useful for screening patients with RVH.

Protection of the myocardial homograft. 1. The cooling bag

Because severe cardiac insufficiency follows orthotopic heart transplantation, the authors have evaluated protection of the homograft provided by a cooling and isolating bag during the operative period of ischemia and subsequently its effect on cardiac function. In one group or four dogs hearts were transplanted without using hypothermia. In the second group, seven hearts were excised, immediately cooled by immersion in saline at 4 degrees C and orthotopically homotransplanted. In the third group, six hearts were immersed in saline and then isolated in a cooling bag until transplantation had been completed. Cardiac function in all animals was evaluated at rest, 3, 24 and 48 hours after operation. In group 1, lowering of the temperature was minimal and all animals died immediately after operation. In group 2, the myocardial temperature, which had been lowered to 13 degrees C by immersion, had risen to 25 degrees C after 17 minutes. In group 3, the myocardial temperature was maintained at 13 degrees C up to the time the aortic clamp was removed. Three hours after operation, the cardiac performance of group 3 was much better than that of group 3 was much better than that of group 2 as demonstrated by an increase of cardiac output (39%), stroke volume (44%), mean systolic ejection rate (25%), maximum systolic flow (28%), peak velocity (26%), maximum acceleration (20%), left ventricular power (32%) and left ventricular work (47%). In the following days, cardiac function of groups 2 and 3 improved and the disparity between then decreased. These results demonstrate that the cooling bag, while offering technical advantages, maintains profound hypothermia in the donor heart and substantially improves the performance of the homograft in the immediate postoperative phase.

[Effect of captopril in essential hypertension (author's transl)]

The angiotensin I-converting enzyme inhibitor, captopril (SQ 14225) was proposed as first treatment in 12 cases of uncomplicated essential hypertension maintained on unrestricted sodium intake (group I). Arterial pressure was normalized in 7 patients (subgroup Ia) whilst hydrochlorothiazide was added to captopril in 5 patients (subgroup Ib). A significant dose-response curve between the dose of captopril (range 75 to 450 mg/day) and the antihypertensive effect was obtained with a maximum at 300 mg/day. In 8 patients (group II) hydrochlorothiazide was proposed first and the addition of captopril was necessary in 4 cases. No relationship between pretreatment PRA and the maximum effect of captopril was observed (r = -0.34, NS). No disturbance of upright blood pressure regulation was noted. Adverse reaction consisted of 4 cases of benign and spontaneously regressive skin rash or pruritus.

The antihypertensive effect of captopril. Evidence for an influence of kinins

The acute effect of the orally-active converting enzyme inhibitor, captopril, was compared to that of saralasin in 13 patients with various forms of hypertension on ad libitum sodium intake. A significant difference between the effects of the two drugs on mean arterial pressure (MAP) was found (-11 +/- 3 mm Hg with saralasin, -24 +/- 4.5 mm Hg after captopril). This difference was not correlated with control plasma renin activity (PRA). To determine the influence of the endogenous kallikrein-kinin system in the antihypertensive action of captopril, the effect of aprotinin (Apro), an inhibitor of kinin generation, on the MAP level achieved by captopril was assessed in five normal subjects and 15 patients with hypertension on ad libitum sodium intake. In normal subjects, captopril did not alter MAP, nor did Apro have any effect. In six patients with essential hypertension and normal PRA, MAP decreased by 5.5 +/- 2 mm Hg following captopril, and Apro did not modify this level. In nine patients with renovascular hypertension (RVH), MAP fell by 22 +/ 3 mm Hg after captopril administration, and Apro infusion induced a rise in MAP of 13 +/- 1.7 mm Hg. A positive correlation between log control PRA and the effect of aprotinin was obtained ( r = 0.63, p less than 0.005). Apro had no effect in two patients with RVH who experiences a large drop in MAP during salasin. These results suggest that endogenous kinins as well as other substances, the generation of which is inhibited by aprotinin, may participate to the antihypertensive effect of captopril in patients with angiotensin-dependent hypertension. The lack of an aprotinin effect on the MAP level achieved during saralasin infusion suggests that the influence of the kallikrein-kinin system is related to the effect of captopril rather than the fall in arterial pressure resulting from angiotensin blockade.

[Renal and perinephritic abscesses in children]

One child with a pure perinephric abscess and three with renal abscesses, one of which had perinephric extension, are described. All presented with a long course of subacute infection leading to localizing symptoms or signs in the flank. The diagnosis was confirmed by radiologic examination. All the abscesses were surgically drained at various intervals after diagnosis, while the patients were receiving antibiotic therapy. Salvage of renal function was possible in all cases. A rational approach to the diagnosis and management of such abscesses is emphasized.