Tacrolimus-induced thrombotic microangiopathy in orthotopic liver transplant patients: case series of four patients.

Thrombotic microangiopathy (TMA) is a potentially fatal complication in solid organ and bone marrow transplant patients, with reported incidence of 0.5-3% and mortality of about 75%. To emphasise the importance of early diagnosis and prompt commencement of therapy results in improved clinical outcomes. A retrospective study of all patients who underwent orthotopic liver transplantation (OLTX) at the Western Australian Liver Transplantation Service from May 1994 to December 2010 was conducted to identify patients who developed tacrolimus-induced TMA. We identified four patients with tacrolimus-induced TMA post-OLTX, derived from a cohort of 104 patients treated with tacrolimus in our institution. The mean age at diagnosis was 40 years, and the mean time of onset was 63 ± 7.5 weeks after OLTX. The indications for OLTX in the four patients were fulminant hepatic failure in three (Wilson disease, paracetamol overdose and post-partum thrombotic thrombocytopenic purpura) and hepatitis C virus-related cirrhosis. All patients had tacrolimus post-OLTX. At diagnosis, tacrolimus was discontinued in all patients, and three of the four patients underwent plasma exchange and all patients improved clinically. Mean duration of follow up was 15 ± 7.5 months. There was no mortality 6 months post-TMA. Early diagnosis with immediate discontinuation or conversion of calcineurin inhibitors and plasma exchange should be offered to OLTX patients with TMA as it results in good outcomes.

The impact of random natural variability on aspartic acid racemization ratios in enamel from different types of human teeth.

Previous research has indicated that the extent of amino acid racemization in enamel varies systematically between tooth types within the dentition. This phenomenon was suggested to be due to differences in temperature at various locations within the mouth. This paper presents an analysis of aspartic acid racemization in a fraction of the enamel proteins which should be particularly susceptible to deviations in temperature, in order to assess the impact of temperature on variability in racemization values. The acid soluble fraction of the enamel was analysed from 129 human teeth of different tooth types and from both living individuals and archaeological skeletal remains. Samples were collected by acid etching of the enamel to isolate proteins located a small distance below the enamel surface. For each population, the racemization values for different tooth types were compared to identify any possible systematic variation. Where multiple teeth were analysed from the one individual, the age estimates produced for the different teeth were compared to obtain an indication of the overall level of variability in racemization values. No systematic variation in the extent of racemization between different tooth types was observed in any of the populations analysed. There appeared instead to be a high level of random variability in the extent of racemization, with substantial differences observed between age estimates produced from multiple teeth from the one individual. The results of this study suggest that the differences in racemization values observed here are due to random variations and not the temperature at different locations within the mouth.

Assessment of common hyperelastic constitutive equations for describing normal and osteoarthritic articular cartilage.

With the aim of providing information for modelling joint and limb systems, widely available constitutive hyperelastic laws are evaluated in this paper for their ability to predict the mechanical responses of normal and osteoarthritic articular cartilage. Load-displacement data from mechanical indentation were obtained for normal and osteoarthritic cartilage at 0.1 s(-1) and 0.025 s(-1) and converted to the stress-stretch ratio. The data were then fitted to the Arruda-Boyce, Mooney-Rivlin, neo-Hookean, Ogden, polynomial, and Yeoh hyperelastic laws in the MATLAB environment. Although each of the hyperelastic laws performed satisfactorily at the higher rate of loading, their ability to fit experimental data at the lower loading rate varied considerably. For the preferred models, coefficients were provided for stiff, soft, and average tissues to represent normal and degraded tissue at high and low loading rates. The present authors recommend the use of the Mooney-Rivlin or the Yeoh models for describing both normal and degraded articular cartilage, with the Mooney-Rivlin model providing the best compromise between accuracy and required computational power.

Malignant fibrous histiocytoma complicating nephrogenic systemic fibrosis post liver transplantation.

A 46-year-old man with cirrhosis secondary to hepatitis C virus infection and alcohol underwent orthotopic liver transplantation, which required urgent re-grafting because of biliary sepsis from necrosis of the left liver lobe. Recovery was complicated by renal failure and nephrogenic systemic fibrosis (probably related to intravenous gadolinium exposure). He subsequently developed a malignant fibrous histiocytoma. We present this case highlighting the occurrence of two rare conditions in the same patient following liver transplantation. We believe this is the first case of its kind to be reported.

The application of amino acid racemization in the acid soluble fraction of enamel to the estimation of the age of human teeth.

Estimation of age-at-death for skeletonised forensic remains is one of the most significant problems in forensic anthropology. The majority of existing morphological and histological techniques are highly inaccurate, and show a bias towards underestimating the age of older individuals. One technique which has been successful in forensic age estimation is amino acid racemization in dentine. However, this method cannot be used on remains where the post-mortem interval is greater than 20 years. An alternative approach is to measure amino acid racemization in dental enamel, which is believed to be more resistant to change post-mortem. The extent of amino acid racemization in the acid soluble fraction of the enamel proteins was determined for modern known age teeth. A strong correlation was observed between the age of the tooth and the extent of racemization. No systematic bias in the direction of age estimation errors was detected. For the majority of teeth analyzed, the presence of dental caries did not affect the results obtained. In a minority of cases, carious teeth showed a higher level of racemization than would be expected given the age of the individual. These results indicate that amino acid racemization in enamel has the potential to be used in age estimation of skeletal remains.

In vitro degradation of articular cartilage: does trypsin treatment produce consistent results?

It is common practice in laboratories to create models of degraded articular cartilage in vitro and use these to study the effects of degeneration on cartilage responses to external stimuli such as mechanical loading. However, there are inconsistencies in the reported action of trypsin, and there is no guide on the concentration of trypsin or the time to which a given sample can be treated so that a specific level of proteoglycan depletion is achieved. This paper argues that before any level of confidence can be established in comparative analysis it is necessary to first obtain samples with similar properties. Consequently, we examine the consistency of the outcome of the artificial modification of cartilage relative to the effects of the common enzyme, trypsin, used in the process of in vitro proteoglycan depletion. The results demonstrate that for a given time and enzyme concentration, the action of trypsin on proteoglycans is highly variable and is dependent on the initial distribution and concentration of proteoglycans at different depths, the intrinsic sample depth, the location in the joint space and the medium type, thereby sounding a note of caution to researchers attempting to model a proteoglycan-based degeneration of articular cartilage in their experimental studies.

Modelling of the enzymatic kinetically controlled synthesis of cephalexin: influence of diffusion limitation.

In this study the influence of diffusion limitation on enzymatic kinetically controlled cephalexin synthesis from phenylglycine amide and 7-aminodeacetoxycephalosporinic acid (7-ADCA) was investigated systematically. It was found that if diffusion limitation occurred, both the synthesis/hydrolysis ratio (S/H ratio) and the yield decreased, resulting in lower product and higher by-product concentrations. The effect of pH, enzyme loading, and temperature was investigated, their influence on the course of the reaction was evaluated, and eventually diffusion limitation was minimised. It was found that at pH >or=7 the effect of diffusion limitation was eminent; the difference in S/H ratio and yield between free and immobilised enzyme was considerable. At lower pH, the influence of diffusion limitation was minimal. At low temperature, high yields and S/H ratios were found for all enzymes tested because the hydrolysis reactions were suppressed and the synthesis reaction was hardly influenced by temperature. The enzyme loading influenced the S/H ratio and yield, as expected for diffusion-limited particles. For Assemblase 3750 (the number refers to the degree of enzyme loading), it was proven that both cephalexin synthesis and hydrolysis were diffusion limited. For Assemblase 7500, which carries double the enzyme load of Assemblase 3750, these reactions were also proven to be diffusion limited, together with the binding-step of the substrate phenylglycine amide to the enzyme. For an actual process, the effects of diffusion limitation should preferably be minimised. This can be achieved at low temperature, low pH, and high substrate concentrations. An optimum in S/H ratio and yield was found at pH 7.5 and low temperature, where a relatively low reaction pH can be combined with a relatively high solubility of 7-ADCA. When comparing the different enzymes at these conditions, the free enzyme gave slightly better results than both immobilised biocatalysts, but the effect of diffusion limitation was minimal.

Integrated reactor concepts for the enzymatic kinetic synthesis of cephalexin.

Integrated process concepts for enzymatic cephalexin synthesis were investigated by our group, and this article focuses on the integration of reactions and product removal during the reactions. The last step in cephalexin production is the enzymatic kinetic coupling of activated phenylglycine (phenylglycine amide or phenylglycine methyl ester) and 7-aminodeacetoxycephalosporanic acid (7-ADCA). The traditional production of 7-ADCA takes place via a chemical ring expansion step and an enzymatic hydrolysis step starting from penicillin G. However, 7-ADCA can also be produced by the enzymatic hydrolysis of adipyl-7-ADCA. In this work, this reaction was combined with the enzymatic synthesis reaction and performed simultaneously (i.e., one-pot synthesis). Furthermore, in situ product removal by adsorption and complexation were investigated as means of preventing enzymatic hydrolysis of cephalexin. We found that adipyl-7-ADCA hydrolysis and cephalexin synthesis could be performed simultaneously. The maximum yield on conversion (reaction) of the combined process was very similar to the yield of the separate processes performed under the same reaction conditions with the enzyme concentrations adjusted correctly. This implied that the number of reaction steps in the cephalexin process could be reduced significantly. The removal of cephalexin by adsorption was not specific enough to be applied in situ. The adsorbents also bound the substrates and therewith caused lower yields. Complexation with beta-naphthol proved to be an effective removal technique; however, it also showed a drawback in that the activity of the cephalexin-synthesizing enzyme was influenced negatively. Complexation with beta-naphthol rendered a 50% higher cephalexin yield and considerably less byproduct formation (reduction of 40%) as compared to cephalexin synthesis only. If adipyl-7-ADCA hydrolysis and cephalexin synthesis were performed simultaneously and in combination with complexation with beta-naphthol, higher cephalexin concentrations also were found. In conclusion, a highly integrated process (two reactions simultaneously combined with in situ product removal) was shown possible, although further optimization is necessary.

Asymmetric strecker synthesis of alpha-amino acids via a crystallization-induced asymmetric transformation using (R)-phenylglycine amide as chiral auxiliary.

[reaction: see text]. Diastereoselective Strecker reactions based on (R)-phenylglycine amide as chiral auxiliary are reported. The Strecker reaction is accompanied by an in situ crystallization-induced asymmetric transformation, whereby one diastereomer selectively precipitates and can be isolated in 76-93% yield and dr > 99/1. The diastereomerically pure alpha-amino nitrile obtained from pivaldehyde (R1 = t-Bu, R2 = H) was converted in three steps to (S)-tert-leucine in 73% yield and >98% ee.

Modeling of the enzymatic kinetic synthesis of cephalexin--influence of substrate concentration and temperature.

During enzymatic kinetic synthesis of cephalexin, an activated phenylglycine derivative (phenylglycine amide or phenylglycine methyl ester) is coupled to the nucleus 7-aminodeacetoxycephalosporanic acid (7-ADCA). Simultaneously, hydrolysis of phenylglycine amide and hydrolysis of cephalexin take place. This results in a temporary high-product concentration that is subsequently consumed by the enzyme. To optimize productivity, it is necessary to develop models that predict the course of the reaction. Such models are known from literature but these are only applicable for a limited range of experimental conditions. In this article a model is presented that is valid for a wide range of substrate concentrations (0-490 mM for phenylglycine amide and 0-300 mM for 7-ADCA) and temperatures (273-298 K). The model was built in a systematic way with parameters that were, for an important part, calculated from independent experiments. With the constants used in the model not only the synthesis reaction but also phenylglycine amide hydrolysis and cephalexin hydrolysis could be described accurately. In contrast to the models described in literature, only a limited number (five) of constants was required to describe the reaction at a certain temperature. For the temperature dependency of the constants, the Arrhenius equation was applied, with the constants at 293 K as references. Again, independent experiments were used, which resulted in a model with high statistic reliability for the entire temperature range. Low temperatures were found beneficial for the process because more cephalexin and less phenylglycine is formed. The model was used to optimize the reaction conditions using criteria such as the yield on 7-ADCA or on activated phenylglycine. Depending on the weight of the criteria, either a high initial phenylglycine amide concentration (yield on 7-ADCA) or a high initial 7-ADCA concentration (yield on phenylglycine amide) is beneficial.

Choice of treatment improves quality of life. A study on patients undergoing dialysis.

BACKGROUND: Quality of life (QOL) is an important measure of the success of medicine. Choice of treatment is an important variable influencing QOL. We studied QOL in patients undergoing treatment for end-stage renal failure. Until June 1993 our patients needing dialysis could freely choose continuous ambulatory peritoneal dialysis (CAPD); however, since that time most patients have been forced to undergo CAPD because the hemodialysis program is full. METHODS: We compared QOL in patients accepted before or after June 1993. Forty-five patients undergoing CAPD were studied during the period of choice compared with 44 who had no choice. Quality of life was studied by Bradburn Affect Scale, Mental Health Scale, Campbell Life Satisfaction, Perceived Health, Karnofsky Scale, Activity Scale, Physical Symptoms Scale, and desire for treatment change. RESULTS: The patients undergoing CAPD in the no-choice group had a lower score than the choice population in 4 of the 7 QOL scales. The Mental Health Scale mean score was 18.4 compared with 15.5, and the patients ranking highest on the Mental Health Scale decreased from 33% to 18%, while those ranking lowest increased 7-fold from 2% to 14% comparing choice with no-choice group. The Bradburn Affect Scale score was +0.7 in the choice group compared with -0.3 in the no-choice group. There were no differences in age, sex, race, or treatment that explained the difference. Influence of other time-related factors is unlikely as there were no similar lower scores with time in the QOL reported by patients in the in-center or assisted self-care hemodialysis or transplant groups. CONCLUSIONS: Once the freedom of choice of treatment is gone from the patients undergoing CAPD their psychological QOL deteriorates.

Schistosomiasis: collaboration in laboratory diagnosis.

PIP: Harpur Memorial Hospital in Menouf and the Hospital for Tropical Diseases in London have shared a development program through the laboratories for eight years to develop laboratory facilities and organize a diploma course in medical laboratory technical training, in Egypt, with the help of an annual visit by a senior laboratory medical scientist from London. The laboratory in Egypt has been upgraded while the Hospital for Tropical Diseases has benefitted by obtaining valuable teaching material for its training programs in the UK and worldwide. Schistosomiasis is a major health problem in Egypt, with both S. haematobium and S. mansoni common in the Menoufaya district of the Nile delta, requiring significant laboratory time for diagnosis. This article describes the diagnostic procedures used in Harpur Memorial Hospital serving an area of acute schistosomiasis infection with consideration of whether diagnostic tests used in Egypt require further development. The laboratory in London sees mainly expatriate patients with a range of schistosomiasis conditions and has a wider range of diagnostic procedures available. In Menouf, stool and urine samples of all outpatients are routinely examined, with rectal biopsies performed on a proportion of patients with good clinical indication of schistosomiasis. Serodiagnosis for Schistosoma is not currently available at the hospital. Rectal biopsy has, however, proved to be a reliable method of diagnosing schistosomiasis in the difficult cases when urine and stool examinations were negative, with the introduction of the formol ether technique for concentration of faeces having greatly improved the initial detection of ova.^ieng