Calcium scoring on coronary computed angiography tomography with photon-counting detector technology: Predictors of performance

INTRODUCTION

Obtaining accurate coronary artery calcium (CAC) score measurements from CCTA datasets with virtual non-iodine (VNI) algorithms would reduce acquisition time and radiation dose. We aimed to assess the agreement of VNI-derived and conventional true non-contrast (TNC)-based CAC scores and to identify the predictors of accuracy.

METHODS

CCTA datasets were acquired with either 120 or 140 ​kVp. CAC scores and volumes were calculated from TNC and VNI images in 197 consecutive patients undergoing CCTA. CAC density score, mean volume/lesion, aortic Hounsfield units and standard deviations were then measured. Finally, percentage deviation (VNI - TNC/TNC∗100) of CTA-derived CAC scores from non-enhanced scans was calculated for each patient. Predictors (including anthropometric and acquisition parameters, as well as CAC characteristics) of the degree of discrepancy were evaluated using linear regression analysis.

RESULTS

While the agreement between TNC and VNI was substantial (mean bias, 6.6; limits of agreement, 178.5/145.3), a non-negligible proportion of patients (36/197, 18.3%) were falsely reclassified as CAC score ​= ​0 on VNI. The use of higher tube voltage significantly decreased the percentage deviation relative to TNC-based values (β ​= ​-0.21 [95%CI: 0.38 to -0.03], p ​= ​0.020) and a higher CAC density score also proved to be an independent predictor of a smaller difference (β ​= ​-0.22 [95%CI: 0.37 to -0.07], p ​= ​0.006).

CONCLUSION

The performance of VNI-based calcium scoring may be improved by increased tube voltage protocols, while the accuracy may be compromised for calcified lesions of lower density. The implementation of VNI in clinical routine, however, needs to be preceded by a solution for detecting smaller lesions as well.

Effect of weight and storage time of broiler breeders' eggs on morphology and biochemical features of eggs, embryogenesis, hatchability, and chick quality

The transfer of hatchability results obtained under experimental conditions to the commercial ground with a positive financial effect proves the value and usefulness of these data. On the other hand, finding results on commercial processes of broiler breeders' egg incubation in the literature is challenging. The presented study aimed to determine the effects of egg weight and storage time on the physical, biochemical characteristics of hatching eggs, embryogenesis and hatchability in Ross 308 broiler breeders. On the laying day, the eggs were divided into four weight groups: S - small eggs (57-61 g), M - medium eggs (62-66 g), L - large eggs (67-71 g), and XL - extra-large eggs (72-76 g). The eggs were then stored for 3, 7, 14, and 21 days under controlled conditions. As the egg storage time increased, a decrease in the yolk quality (lower index) was observed. The highest Haugh units were found in eggs from the S and M groups. The cholesterol content of the M, L, and XL groups was lower on days 7, 14, and 21 as compared to that of eggs only stored for 3 days. Egg weight loss during incubation decreased with an increase in the egg weight. An extension of the egg storage time caused an increase in the loss of egg weight. On the 14th and 18th days of hatching, an increase in the eggshell temperature was noted with an increase in the weight of the egg. The eggs stored for 7 days were characterised by the highest shell temperature on each day. The highest hatchability percentage was recorded for the M group. The hatchability rate decreased with the prolongation of the storage time, while the number of crippled chicks after hatching increased. The results confirmed that the increased weight of the eggs and prolonged storage time (14 and 21 days) increased the weight and decreased the length of the newly hatched chicks, respectively. Chicks from the heaviest eggs and those stored for 14 and 21 days showed poor results on the Pasgar score® test. The observations indicate the need to adopt various (of those available) methods to assess the quality of newly hatched chicks in hatcheries in order to produce high-quality broiler chickens. The results also indicate that prolonged egg storing beyond 14 days may affect the thyroid hormone economy during the hatching of chicks, especially in the XL group.

Altered expression of CYP17A1 and CYP19A1 in undescended testes of dogs with unilateral cryptorchidism

Cryptorchidism is the most common disorder of sex development in dogs and testosterone plays a crucial role in the inguinal phase of the testes descending into the scrotum. The molecular background of impaired testosterone synthesis in the testes of cryptorchid dogs is poorly elucidated. In this study, we analyzed the expression of four genes involved in testicular steroidogenesis (CYP17A1, CYP19A1, HSD3B2 and HSD17B3) in undescended and contralateral scrotal testes from inguinal unilateral cryptorchid dogs (n = 13) and from the scrotal gonads of normal males (n = 15). We found that transcript level of CYP17A1 was significantly increased in inguinal gonads, while the level of CYP19A1 was decreased. For these two genes, we analyzed the methylation level of single CpG sites in the promoter region localized within putative target sites for testicular transcription factors (NUR77, CREB, CAR and HSF2). A correlation between decreased methylation in the promoter of CYP17A1 and its increased transcript level in undescended gonads was observed, but the change in protein level was not significant. We also resequenced the 5'-flanking region of both genes and two known polymorphic sites, SNP in CYP17A1 and an indel in CYP19A1, were found. However, the distribution of the variants in affected (n = 80) and control (n = 75) dogs was not associated with cryptorchidism. We tentatively conclude that the altered expression of CYP17A1 and CYP19A1 in undescended testes could be caused by their exposure to increased temperature in the body. Furthermore, we showed that the identified polymorphisms cannot be considered markers associated with a predisposition to cryptorchidism.

Nanofiltration bei der Herstellung des PPSB-Konzentrates Beriplex® P/N

Nanofiltration, bestehend aus der Kombination von Planova® 75 nm/35 nm Filtern, ist in den Produktionsprozeß des PPSB-Konzentrates Beriplex® P/N integriert. Abreicherungsfaktoren der mit umhüllten Viren versetzten Intermediärprodukte von mehr als 7,2 log10 für HSV-1, mehr als 7,3 log10 für HIV-1, von 3,8 log10 für BVDV und von 4,3 log10 für HBV wurden durch die Filtration erzielt. Durch das PPSB-Reinigungsverfahren, die Pasteurisierung und die Nanofiltration wird ein kumulierter Virusabreicherungsfaktor von mindestens 15 log10 für in Zellkultur titrierbare Viren erzielt. Durch fünf konsekutive Aufarbeitungen im Produktionsmaßstab parallel mit/ohne Nanofiltration wurde die Reproduzierbarkeit und Beibehaltung der Produktqualität gezeigt. Die Einführung der Nanofiltration führte zu keinen nachteiligen Auswirkungen auf Beriplex® P/N; das Produktprofil blieb erhalten.

LITHIUM FLUORIDE CRYSTALS AS FLUORESCENT NUCLEAR TRACK DETECTORS

Radiophotoluminescence signal of LiF crystals was found to be sufficiently strong to visualize tracks of a single charged particle. This was achieved with a wide-field fluorescent microscope equipped with a ×100 objective and LiF single crystals grown with the Czochralski method at IFJ PAN. The tracks of alpha particles, protons, as well as products of 6Li(n,α)3H reaction with thermal neutrons (moderated Pu/Be source), were observed. These encouraging results are the first steps towards practical use of LiF as fluorescent nuclear track detectors. The most promising dosimetric application seems to be neutron measurements.

IMAGING OF PROTON BRAGG PEAKS IN LiF

Lithium fluoride (LiF) is one of the most common thermoluminescent phosphors routinely used in radiation protection services. Another advantageous property of LiF is radiophotoluminescence, whose occurs after its irradiation due to the creation of color centers. Excitation of LiF samples with a blue light causes the emission of photoluminescence, which spectrum consists of two peaks at ~520 and ~670 nm. The work was focused on imaging of Bragg peaks of proton beams routinely applied at the proton eye radiotherapy facility operating at the Institute of Nuclear Physics Polish Academy of Sciences (IFJ PAN) in Krakow by the measurement of the fluorescence light in LiF crystals excited with a 445 nm blue light after their previous irradiation with the proton beams of energies of 28, 30, 40 and 50 MeV. The range of proton beams in LiF crystals for different energies was calculated by Monte Carlo simulations.

Fibrinogen alpha and beta gene polymorphisms in pediatric stroke--case-control and family based study

BACKGROUND/PURPOSE

Data on the role of the -455G > A polymorphism of the gene encoding β fibrinogen subunit (FGB) and the Thr312Ala polymorphism of the gene for the α fibrinogen subunit (FGA) in childhood ischemic stroke are insufficient. Therefore the aim of the study was to evaluate a possible association between these two polymorphisms and arterial ischemic stroke.

METHODS

The study group consisted of 85 children after ischemic stroke, 146 of their parents and 159 controls. Both polymorphisms were genotyped using the restriction fragment length polymorphism method. Two study designs were used: a case-control model and a family-based transmission-disequilibrium test. Statistica 7.1 and EpiInfo 6 softwares were used in all analyses.

RESULTS

In the TDT test, a tendency to a higher transmission of the 312Ala allele of the FGA gene and the -455A allele of the FGB gene was observed, however, it was statistically non-significant. The frequencies of alleles and genotypes of both FGA and FGB genes polymorphisms did not differentiate children from both groups also in the case-control model. Additive or synergistic effects between FGA and FGB genes polymorphisms were not observed.

CONCLUSION

An analysis of the results obtained in this study and a critical review of previously published data indicate that examined gene polymorphisms are not related to ischemic stroke in children.

Resonant third harmonic generation of KrF laser in Ar gas

Investigations of emission of harmonics from argon gas jet irradiated by 700 fs, 5 mJ pulses from a KrF laser are presented. Harmonics conversion was optimized by varying the experimental geometry and the nozzle size. For the collection of the harmonic radiation silicon and solar-blind diamond semiconductor detectors equipped with charge preamplifiers were applied. The possibility of using a single-crystal CVD diamond detector for separate measurement of the 3rd harmonic in the presence of a strong pumping radiation was explored. Our experiments show that the earlier suggested 0.7% conversion efficiency can really be obtained, but only in the case when phase matching is optimized with an elongated gas target length corresponding to the length of coherence.

Thoracal, abdominal and thoracoabdominal aortic aneurysm

AIM

Aortic aneurysm is a complex disease affecting males and females in a different way. We analysed gender specific differences in the abdominal (AAA), thoracal (TAA) and thoraco-abdominal (TA-AA) aortic aneurysm in patients hospitalized for aortic aneurysm (AAA) in Germany.

METHODS

Detailed lists for all patients suffering from AAA, TAA or TA-AA documented in the DRG-System as principal diagnosis in the years 2010 were provided by the Federal Statistical Office.

RESULTS

The total number of cases in males was 17,731. It was more than three time higher than in females with 4657. AAA were 6.2 time more frequent in males than in females, TAA and TA-AA only 1.6 and 1.5 times, respectively. The rates of ruptured aneurysms show a steep increase in the 9th and 10th decade which is more pronounced in females. In males there is an age dependent increase in the rate of endovascular treatment of TAA and AAA. There is no such trend in females. The rate for AAA even decreases with age. The same could be shown for more complex fenestrated or branched endoprotheses. In around 20% of all male cases with TA-AA such a design is used in the 7th to the 9th decade of life. In females such a rate is only reached in the 7th decade. In older females the rate stepwise decreased.

CONCLUSION

There are gender specific differences in the rate of rupture and endovascular treatment of AAA, TAA and TA-AA in males and females in Germany. The reasons for these differences should be elucidated in order to prove whether these differences are due to actual gender specific requirements, or simply a lack of compatibility in awareness and devices.

Gastric electrical stimulation with Enterra therapy improves symptoms of idiopathic gastroparesis

BACKGROUND

Gastric electrical stimulation (GES) is a therapeutic option for intractable symptoms of gastroparesis (GP). Idiopathic GP (ID-GP) represents a subset of GP.

AIMS

A prospective, multicenter, double-blinded, randomized, crossover study to evaluate the safety and efficacy of Enterra GES in the treatment of chronic vomiting in ID-GP.

METHODS

Thirty-two ID-GP subjects (mean age 39; 81% F, mean 7.7 years of GP) were implanted with GES. The stimulator was turned ON for 1½ months followed by double-blind randomization to consecutive 3-month crossover periods with the device either ON or OFF. ON stimulation was followed in unblinded fashion for another 4.5 months. Twenty-five subjects completed the crossover phase and 21 finished 1 year of follow-up.

KEY RESULTS

During the unblinded ON period, there was a reduction in weekly vomiting frequency (WVF) from baseline (61.2%, P < 0.001). There was a non-significant reduction in WVF between ON vs OFF periods (the primary outcome) with median reduction of 17% (P > 0.10). Seventy-five percent of patients preferred the ON vs OFF period (P = 0.021). At 1 year, WVF remained decreased (median reduction = 87%, P < 0.001), accompanied by improvements in GP symptoms, gastric emptying and days of hospitalization (P < 0.05).

CONCLUSIONS & INFERENCES

(i) In this prospective study of Enterra GES for ID-GP, there was a reduction in vomiting during the initial ON period; (ii) The double-blind 3-month periods showed a non-significant reduction in vomiting in the ON vs OFF period, the primary outcome variable; (iii) At 12 months with ON stimulation, there was a sustained decrease in vomiting and days of hospitalizations.

Trends in lower extremity surgical and endovascular revascularization in Germany

BACKGROUND

We analyzed trends in lower extremity endovascular and open surgical procedures in hospitalized patients in Germany.

PATIENTS AND METHODS

We used national statistics (DRG statistics) published by the Federal Statistical Office including data from almost all hospitals in Germany to calculate annual procedure rates of lower extremity endovascular and open surgical procedures in the years 2005 to 2008. Detailed lists of the OPS-codes 8 - 836, 5 - 381, 5 - 393 separated by the 6th number of the code were analyzed regarding procedures representing revascularization of peripheral arteries including the aorta.

RESULTS

Between 2005 and 2008 the total number of endovascular procedures increased from 73,584 to 98,664 and the number of surgical procedures from 74,789 to 86,172 a year. Age-adjusted incidence rates of endovascular procedures in people >= 65 years increased from 325 to 432 per 100,000 while the incidence rates of all open surgical procedures increased from 315 to 351 per 100.000. Looking only at bypass surgery the incidence remained unchanged with 177 and 176 per 100,000 in the same period. Endovascular procedures other than balloon angioplasty including percutaneous atherectomy, laser recanalization or usage of cutting balloon, account for less than 1 % in Germany.

CONCLUSIONS

The numbers of endovascular procedures overweigh the numbers of open surgical procedures for treatment of lower extremity PAD in Germany today. In contrast to data from the USA we could not demonstrate a decrease of open surgical procedures in Germany in recent years.

[Chronically progressive occlusive disease of intestinal arteries - short overview from a vascular surgical perspective]

BACKGROUND

Intestinal ischaemia is quite rare among the cardiovascular diseases. However, it is increasingly diagnosed. The aim of this selective but representative short overview is to assess the impact of intestinal ischaemia in vascular and visceral medicine from a vascularsurgical perspective.

MATERIAL AND METHODS

A literature search and selection in relevant online services of the medical scientific literature was performed, in particular, of the last decade on the competent management of intestinal ischaemia combined with the clinical expertise obtained in daily vascular surgical practice including didactically prepared demonstrable cases / case reports related to typical / specific clinical problems and situations.

RESULTS AND DISCUSSION

Although the superior mesenteric artery (SMA) is most frequently responsible for the clinical presentation, usually 2 or 3  major arterial trunks are involved for a relevant clinical symptomatology. These disorders of the intestinal circulation are most frequently caused by progressive atherosclerotic occlusive disease. In chronic progressive disease, the visceral arteries show the ability to enlarge typical collateral circulation pathways, which may not always lead to a complete compensation. With a degree of stenosis of more than 70 %, mesenteric ischaemic pain and physical prostration are the major clinical findings. Intestinal infarction with a mortality rate of 60-80 % is the endpoint of the chronically progressive intestinal ischaemia. There-fore, an urgent medical treatment is highly required. CT angiography is the diagnostic procedure of choice in patients with suspected chronic intestinal ischaemia. Mesenteric angiography is subject to specific questions and / or to endovascular arteriographic treatment. Duplex scanning has been advocated as a non-invasive method of pre- and post-interventional screening. Treatment is indicated in symptomatic intestinal vascular disease. Due to the high morbidity of the majority of patients and the enormous invasivity associated with conventional surgery, arteriographic intervention is the treatment of choice, even though quality improvement is required. Surgical reconstructions are highly standardised and should be associated with perioperative mortality less than 3 %. We recommended the reconstruction of 2  vessels, for which antegrade supracoeliacal revascularisation techniques are favourable. In (threatening) septic conditions, autologous reconstructions are required. Intestinal infarction is the most serious complication of all visceral revascularisations. In recurrent occlusions of visceral arteries, it is recommended to favour and finally use a different therapeutic modality. Post-therapeutic care includes second-look operation as well as clinical examination and diagnostic imaging. Antithrombotic therapy should be initiated. The further screening of patients after intestinal revascularisation should be performed by duplex scanning.

CONCLUSION

Chronically progressive occlusive disease of intestinal arteries is considered as a complex disease with challenging diagnostic and therapeutic management, in which an interdisciplinary, partly finding- and stage-dependent (also with regard to the frequency and recurrency of the specific local finding) sequential therapeutic approach (e. g., endovascular vs. open procedure; interventionalist / endovascular specialist / vascular surgeon) becomes more and more relevant requiring a competent center of vascular medicine.

Safety and efficacy of ghrelin agonist TZP-101 in relieving symptoms in patients with diabetic gastroparesis: a randomized, placebo-controlled study

BACKGROUND

Gastroparesis, a chronic disorder of abnormal gastric motility, is common in patients with diabetes mellitus. A synthetic, selective ghrelin receptor agonist, TZP-101, is in clinical development for treatment of gastroparesis. This double-blind, randomized, placebo-controlled study evaluated the safety and efficacy of multiple TZP-101 doses in patients with moderate to severe symptomatic diabetic gastroparesis.

METHODS

Patients were admitted to the hospital and adaptively randomized to receive a single 30-min intravenous infusion of 20, 40, 80, 160, 320, or 600 μg kg(-1) TZP-101, (n = 57) or placebo, (n = 19) for four consecutive days. Symptoms were evaluated daily with the patient-rated Gastroparesis Cardinal Symptom Index (GCSI) and Gastroparesis Symptom Assessment (GSA). Clinicians rated gastroparesis symptoms on treatment day 4.

KEY RESULTS

  The 80 μg kg(-1) dose was identified as the most effective dose. On day 4, there was statistically significant improvement compared with placebo in the severity of GCSI Loss of Appetite and Vomiting scores for that dose group (P = 0.034 and P = 0.006). In addition, at the 80 μg kg(-1) dose, the proportion of patients with at least 50% improvement in vomiting score was significantly different (P = 0.019) compared with placebo. Meal-related GSA scores for Postprandial fullness were significantly improved in the 80 μg kg(-1) TZP-101 group compared with placebo (P = 0.012). Clinicians rated the 80 μg kg(-1) group better improved than placebo for overall symptom assessment (P = 0.047). Safety profiles were similar in the placebo and TZP-101 groups and all doses were well-tolerated.

CONCLUSIONS & INFERENCES

TZP-101 appears to be safe, well-tolerated, and effective at acutely addressing several gastroparesis symptoms.

[Amputation of ischaemic extremities--a vascular surgeon's point of view]

The amputation surgery being one of the oldest branches of surgery itself is often times discredited since amputations are frequently considered as a result of failure of alternative therapy options. Worldwide hundreds of thousands amputations are performed annually even though especially in vascular surgery great progress in revascularisation techniques and abilities has been made. Presumably due to rising of life expectancies and increase of diabetes mellitus the number of amputations will in future even rise. Peripheral artery disease and diabetes mellitus which are often associated with a high comorbidity are the most common causes of critical limb ischemia and amputations of the lower extremity. Complications after major amputations like wound infection, development of phantom pain, severe mental distress, myocardial infarction or stroke are frequent. Survival one year after amputation range from 30-50%. The patient collective of amputees is a large group with a high degree of comorbidity in need of special attention and care. The level of amputation ( i.e.: above vs. below knee), postoperative complications, early mobilisation and use of prosthesis are important for the postoperative outcome and the amputees further fate. To regain the independence and mobility in the known social surrounding after amputation is often not to achieve but should be the highest aim of the treating persons.

Crouzon's syndrome: tooth morphological and microanalytical evaluation

AIM

To assess the morphological and microanalytical structure of teeth in Crouzon's Syndrome.

METHODS

A 21 year old patient with this condition was evaluated to demonstrate tooth morphology in this syndrome. Assessment of 4 teeth from this patient consisted of morphological analysis in SEM as well as microanalysis of elements. Sections were created in order to assess any defects of the enamel, dentine, root, and any demineralisation.

RESULTS

Micro-analysis using x-ray techniques revealed lower levels of calcium and magnesium from this patient with Crouzon's as compared with samples from a normal healthy patient of comparable age. Furthermore, in the subject's teeth notable amounts of lead were found.

CONCLUSION

Histological images revealed morphological abnormalities especially in dentine. Furthermore, in the dentine levels of calcium and magnesium were lowered according to the microanalytical tests.

Pituitary function and the somatotrophic system in patients with idiopathic Parkinson's disease under chronic dopaminergic therapy

Idiopathic Parkinson's disease and dopaminergic medication may influence pituitary hormone secretion. The present study aimed to reveal any abnormalities of the somatotrophic system induced by the disease itself and/or the dopaminergic therapy. Investigations of other pituitary hormones under basal and stimulated conditions, as well as an analysis of body composition, were also performed. This was a controlled diagnostic study in which luteinising hormone-releasing hormone, thyroid-releasing hormone, corticotrophin-releasing hormone and arginine hydrochloride were administered to ten patients with idiopathic Parkinson's disease under dopaminergic medication. Basal and stimulated hormone concentrations and bioelectrical impedance analyses were compared with those of healthy, age-matched controls. Basal growth hormone (GH) at -30 and 0 min was higher in Parkinsonian patients (2.74 +/- 3.79 ng/ml versus 0.53 +/- 0.10 ng/ml and 2.12 +/- 2.44 ng/ml versus 0.51 +/- 0.03 ng/ml; P < 0.05). The area under the GH curve after stimulation was greater in Parkinsonian patients (502.4 +/- 202.6 ng x min/ml versus 312.0 +/- 98.5 ng x min/ml; P < 0.05), depending on higher basal GH levels, rather than a greater arginine response. No differences in insulin growth factor (IGF)-1 or IGF-BP3 concentrations were detected. There were no differences between the groups in basal and stimulated gonadotrophic, corticotrophic and thyrotrophic function, or body composition. Prolactin was below the detection limit in the patients during the course of the study. Parkinsonian patients experience marked hypoprolactinaemia and repeated stimulation of GH secretion during chronic dopaminergic therapy. Our findings suggest a peripheral GH resistance in these chronically-treated patients.

[Chronic mesenteric ischemia with consecutive ischemic colitis. Suggestions for diagnosis and therapy]

The incidence of acute mesenteric ischaemia has decreased over the last few years. However, cases of chronic mesenteric ischaemia have grown in number, as this disease is the most frequent disorder of the large intestine in the elderly. The typical clinical presentation of ischaemic colitis develops gradually and only becomes recognisable in the late stage of the disease. We present a 51-year-old woman with a history of unexplained abdominal pain. Multislice CT demonstrated an irregular stenosis of the truncus coeliacus and superior mesenteric artery. A Riolan's anastomosis was present and showed excellent perfusion. After a hemicolectomy 6 years previously, different radiologic procedures and endoscopy revealed a structural tumour at the colon transversum we suspected to be malignant. A sequential procedure was conducted. In a first vascular intervention, the truncus coeliacus was reconstructed with a vein patch, and the mesenteric superior artery was replanted. The second laparotomy was performed for revision of the superior mesenteric artery and resection of the intestinal tumour. However, no carcinoma was found in histological examination. In fact, the individual multidisciplinary considerations play an important role in determining the best treatment strategy, if intervention is warranted. Based on our experience, sequential intervention with a common clinical pathway is the safest and most suitable and economic procedure for curing complex pathologies.

[Cost comparison of different graft materials in femoropopliteal bypass: experience with G-DRG]

BACKGROUND

The German DRG classification refrains from medical accuracy of different surgical procedures by concentrating mainly on economic aspects. The process cost calculation of femoropopliteal bypass should as an example illuminate the charge of a surgical procedure under hospital conditions.

METHODS

From 07/03 to 03/04 we analysed out of 71 peripheral arterial reconstructions 10 alloplastic grafts (PBP) and 10 autologous vein grafts (VBP) for femoropopliteal above-knee bypass through the process cost calculation. This required a classification of the procedure in different diagnostic and treatment sections (ward, intensive care, diagnosis, treatment (surgical procedure)).

RESULTS

The average length of hospitalisation with VBP amounted to 12.2 +/- 3.6 (7-19) days, and with PBP to 14.0 +/- 8.0 (8-35) days. The duration of the surgical procedure was almost identical with 118 +/- 26 minutes (VBP) compared to 110 +/- 31 minutes (PBP), but in average 0.4 more assistants participated in VBP. One bleeding caused revision in VBP; one PBP led to extended length of hospitalisation because of wound complication. We diagnosed one asymptomatic bypass occlusion in VBP. The average total costs in VBP amounted to 4 368.10 euro (profit: 4 468.15 euro), in PBP to 5 069.50 euro (profit: 3 802.94 euro).

CONCLUSION

The reconstruction of the superficial femoral artery with alloplastic or autologous vein graft is profitable in G-DRG. Although less medical staff in required in PBP the price of the prosthesis weakens the profit. The autologous vein graft shows furthermore a shorter length of hospitalisation. Further investigation into cost-effectiveness regarding long-term follow-up and patency rates could lead to consequences for the German health system.

Inhalation dose due to presence of 131I in air above septic tank system of an endocrinology hospital

We present here measurements of the 131I concentration for both: gaseous and aerosol fraction of 131I in the air above the septic tank containing wastes from medical application of this isotope. Aerosols were collected using air filters, whereas gaseous forms of iodine were trapped in KI impregnated charcoal double layer cartridge. Besides an active method (pumping of the air through system of filters) an attempt for using a passive method (charcoal traps) for monitoring of radio-iodine is described. For better characterisation of a site the external kerma was determined by means of G-M and TLD techniques as well as the activity kept in the septic tank was measured by gamma spectrometry. Results show that the activity of the aerosol fraction can be neglected compared to that of the gaseous fraction. He measured activity of air is low, on the level of 1 Bq m(-3), even during simulated failure of the ventilation system. Estimated inhalation dose for the serviceman of septic tanks is low ( approximately 10%) compared with external dose obtained by such person due to gamma radiation from the tank (on the level approximately 500 nSv h(-1)). Therefore, the concept of passive monitoring of the iodine in air was abandoned. Also estimated is the efficiency of 131I reduction by a charcoal filter of the ventilation system and 131I input to the environment by the ventilation chimney.

Plasmids ofStaphylococcus cohnii isolated from the intensive-care unit

Numerous isolates of both subspecies of Staphylococcus cohnii were found in the environment of the intensive-care unit of a pediatric hospital. These isolates carried in their cells many plasmids, up to fourteen, of a wide range of sizes (< 2 to > 56 kb). Striking was the occurrence of large plasmids not very common in staphylococci. These were present in > 80% of S. cohnii isolates. Fifty-two different plasmid profiles were found in 79 investigated isolates belonging to S. cohnii ssp. cohnii and S. cohnii ssp. urealyticus. Isolates similar in plasmid profiles were grouped in antibiotic-resistance clusters established for 9 antibiotics (gentamicin, ciprofloxacin, clindamycin, erythromycin, tetracycline, chloramphenicol, mupirocin, trimethoprim-sulfamethoxazole, vancomycin) using the method of unweighted pair group mathematical averages (UPGMA). Many isolates were multiresistant to antibiotics and produced bacteriocins.

Effects of a combination of recombinant human growth hormone with metformin on glucose metabolism and body composition in patients with metabolic syndrome

Abdominal obesity and insulin resistance are central findings in metabolic syndrome. Since treatment with recombinant human growth hormone (rhGH) can reduce body fat mass in patients with organic GH deficiency, rhGH therapy may also have favourable effects on patients with metabolic syndrome. However, due to the highly increased risk for type 2 diabetes in these patients, strategies are needed to reduce the antagonistic effect of rhGH against insulin. We conducted a 18-month randomised, double-blind, placebo-controlled study to assess the effect of rhGH in combination with metformin (Met) in patients with metabolic syndrome. 25 obese men (55 +/- 6 years, BMI 33.4 +/- 2.9 kg/m (2)) with mildly elevated fasting plasma glucose (FPG) levels at screening (6.1-8.0 mmol/l) were included. All patients received metformin (850 mg twice daily) either alone or in combination with rhGH (daily dose 9.5 microg/kg body weight). An oGTT was performed at baseline, after 6 weeks, and after 3, 6, 12, and 18 months of therapy. Glucose disposal rate (GDR) was measured by euglycemic hyperinsulinemic clamp at 0 and 18 months and body composition was measured by DEXA every 6 months. In the Met + GH group, IGF-I increased from 146 +/- 56 microg/l to 373 +/- 111 microg/l (mean +/- SD) after 3 months and remained stable after that. BMI did not change significantly in either group during the study. Total body fat decreased by -4.3 +/- 5.4 kg in the Met + GH group and by -2.7 +/- 2.9 kg in the Met + Placebo group (differences between the two groups: p = n. s.). Waist circumference decreased in both groups (Met + GH: 118 +/- 8 cm at baseline, 112 +/- 10 cm after 18 months; Met + Placebo: 114 +/- 7 cm vs. 109 +/- 8 cm; differences between the two groups: p = 0.096). In the Met + GH group, FPG increased significantly after 6 months (5.9 +/- 0.7 vs. 6.7 +/- 0.4 mmol/l; p = 0.005), but subsequently decreased to baseline levels (18 months: 5.8 +/- 0.2 mmol/l). FPG remained stable in the Met + Placebo group until 12 months had elapsed, and then slightly decreased (baseline: 6.2 +/- 0.3, 18 months: 5.5 +/- 0.6 mmol/l, p = 0.02). No significant changes were seen in either group regarding glucose and insulin AUC during oGTT or HbA (1c) levels. GDR at 18 months increased by 20 +/- 39% in Met + GH-group and decreased by -11 +/- 25% in the Met + Placebo group (differences between the two groups: p = 0.07). In conclusion, treatment of patients with metabolic syndrome and elevated FPG levels did not cause sustained negative effects on glucose metabolism or insulin sensitivity if given in combination with metformin. However, since our data did not show significant differences between the two treatment groups with respect to body composition or lipid metabolism, future studies including larger numbers of patients will have to clarify whether the positive effects of rhGH on cardiovascular risk factors that have been shown in patients with GH deficiency are also present in patients with metabolic syndrome, and are additive to the effects of metformin.

Dietary origin of mycotoxins with estrogenic potential and possible health implications to female dogs

In Poland, occurrence of toxigenic fungi in cereals, foods, feeds and their components as well as mycotoxins accumulation in such material has been studied by numerous teams including our research group for over thirty years since 1969. Mostly cereal kernels and feeds have been examined for presence of toxigenic fungi, their toxigenic potential and natural contamination with mycotoxins. Ochratoxin A, deoxynivalenol, nivalenol and moniliformin were found to be significant contaminants of agricultural products in high percentage of cereal grain samples. The profile of toxic metabolites was similar but the concentration levels of the toxins were lower when compared to already published data of the same climate zone. Zearalenone (ZEA), a nonsteroidal mycotoxin with estrogen-like activity, is synthesized by molds (Fusarium) commonly contaminating poorly stored agricultural products and foodstuffs. Since in the course of examinations and during surgical procedures performed in dogs, ovarian cysts were detected and because frequently this is the first stage of the endometrica pyometra complex (EPC) found in approximately 30% of the females we assume that both factors, mycotoxins (ZEA) and pathological aberrations are possibly related in these animals. Similar activity of the toxin (possibly present in pelleted dog feed) and effects including infertility of female dogs is speculated with indication and suggestion on necessity of additional studies on the problem.

Transmission of HCV infection among long-term hospitalized onco-haematological patients

Hepatitis C virus (HCV) infection is becoming a substantial problem in long-term hospitalized patients. Onco-haematological patients undergoing chemotherapy are especially prone to HCV infection. These patients are usually immunosuppressed and therefore antibodies to HCV are not produced despite the presence of HCV RNA in peripheral blood. The aim of the study was to see how often long-term hospitalized patients acquired HCV infection, and what were the possible sources and routes of virus transmission. The study involved 129 children with lymphoproliferative diseases, 36 patients with solid tumours, and 61 healthcare workers from onco-haematological wards. All were HCV RNA and anti-HCV negative at the time of first hospitalization. During a two and a half-year follow-up study among 165 onco-haematological patients, HCV RNA appeared in 87 in subsequent hospitalizations. The majority of infections were (82/87) were 1a genotype, 2 were 1b, 1 was 1a + 1b and 1 was 1a + 3a. In an attempt to establish the origin of HCV infection, healthcare workers were screened for HCV genotyping. All HCV-infected staff working on wards had the same genotype (1a). None of the staff was infected with 1b genotype. As the most prevalent genotype in Polish blood donors is 1b, HCV infection in onco-haematological patients is most likely due to horizontal transmission, probably involving genotype 1a, and potential horizontal transmission of HCV is implied by the presence of 1a genotype of HCV in saliva and urine of selected patients. Spread of hospital HCV infection among children may be facilitated by micro-injury of the skin and mucosa. Early detection of HCV RNA is important in such immunosuppressed patients, as they are not able to produce anti-HCV antibodies. This may enable the introduction of prophylactic steps to prevent the spread of HCV infection by horizontal transmission.

Hepatitis G virus co-infection may affect the elimination of hepatitis C virus RNA from the peripheral blood of hemodialysis patients

Hemodialysis patients are at risk for hepatitis C virus (HCV) and hepatitis G virus (HGV) infection. The aim of this study was to investigate the possible influence of HGV co-infection on HCV RNA elimination from the peripheral blood of hemodialysis patients. The study involved 144 persons, all with HCV antibodies and HCV RNA. Among 144 patients 24 (16.7%) were positive for HGV RNA. After 2.5 years of observation 80 patients (55.6%) were still HCV RNA-positive. In the latter group 18 patients were co-infected with HGV and 62 were HGV RNA-negative. During 2.5 years of the follow-up study 64 patients eliminated HCV RNA from the serum. In this group only 6 patients were HGV co-infected. None of the HGV-positive patients eliminated HGV RNA from the serum. The higher incidence of HGV co-infection in the group of patients who remained HCV RNA-positive (18/80, 22.5%), in comparison to the group of HCV antibodies-positive patients who lost HCV in the blood (6/64, 9.4%, P < 0.0001) suggests, that the co-infection with HGV may delay the spontaneous elimination of HCV RNA from the blood.

Thermodynamic linked-function analysis of Mg(2+)-activated yeast pyruvate kinase

Yeast pyruvate kinase (YPK) is regulated by intermediates of the glycolytic pathway [e.g., phosphoenolpyruvate (PEP), fructose 1,6-bisphosphate (FBP), and citrate] and by the ATP charge of the cell. Recent kinetic and thermodynamic data with Mn(2+)-activated YPK show that Mn(2+) mediates the allosteric communication between the substrate, PEP, and the allosteric effector, FBP [Mesecar, A., and Nowak, T. (1997) Biochemistry 36, 6792, 6803]. These results indicate that divalent cations modulate multiligand interactions, and hence cooperativity with YPK. The nature of multiligand interactions on YPK was investigated in the presence of the physiological divalent activator Mg(2+). The binding interactions of PEP, Mg(2+), and FBP were monitored by fluorescence spectroscopy. The binding data were subject to thermodynamic linked-function analysis to determine the magnitudes of the multiligand interactions governing the allosteric activation of YPK. The two ligand coupling free energies between PEP and Mg(2+), PEP and FBP, and FBP and Mg(2+) are 0.88, -0.38, and -0.75 kcal/mol, respectively. The two-ligand coupling free energies between PEP and Mn(2+) and FBP and Mn(2+) are more negative than those with Mg(2+) as the cation. This indicates that the interactions between the divalent cation and PEP with YPK are different for Mg(2+) and Mn(2+) and that the interaction is not simply electrostatic in nature, as originally hypothesized. The magnitude of the heterotropic interaction between the metal and FBP is similar with Mg(2+) and Mn(2+). The simultaneous binding of Mg(2+), PEP, and FBP to YPK is favored by 3.21 kcal/mol compared to independent binding. This complex is destabilized by 3.30 kcal/mol relative to the analogous YPK-Mn(2+)-PEP-FDP complex. Interpretation of K(d) values when cooperative binding occurs must be done with care as these are not simple thermodynamic constants. These data demonstrate that the divalent metal, which activates phosphoryl transfer in YPK, plays a key role in modulating the various multiligand interactions that define the overall allosteric properties of the enzyme.

Kinetic linked-function analysis of the multiligand interactions on Mg(2+)-activated yeast pyruvate kinase

The multiligand interactions governing the allosteric response of Mg(2+)-activated yeast pyruvate kinase (YPK) during steady-state turnover were quantitated by kinetic linked-function analysis. The substrate, PEP, the enzyme-bound divalent metal, Mg(2+), and the allosteric effector, FBP, positively influence each other's interaction with the enzyme in the presence of saturating concentrations of the second substrate, MgADP. The presence of Mg(2+) enhances the interaction of PEP and of FBP with YPK by -2.0 and -1.0 kcal/mol, respectively. The simultaneous interaction of PEP, Mg(2+), and FBP with YPK is favored by -4.1 kcal/mol over the sum of their independent binding free energies. The coupling free energies measured for Mg(2+)-activated YPK are weaker than the corresponding coupling free energies measured for Mn(2+)-activated YPK [Mesecar, A., and Nowak, T. (1997) Biochemistry 36, 6792, 6803], but are consistent with results of thermodynamic measurements with the Mg(2+)-YPK complex [Bollenbach, T. J., and Nowak, T. (2001) Biochemistry 36, 13088-13096]. A comparison of ligand binding data measured by kinetic and thermodynamic linked-function analyses reveals that the MgADP complex modulates both the binding of the other three ligands and the two- and three-ligand coupling interactions between the other three ligands. Enzyme-bound Mg(2+) does not influence the homotropic cooperativity in PEP binding to YPK. It is the MgADP complex that induces homotropic cooperativity in PEP binding. It is the enzyme-bound Mn(2+) that induces homotropic binding of PEP with Mn(2+)-activated YPK. These results lend support to the hypothesis that divalent metals modulate the interactions of ligands on YPK and that divalent metals play a role in regulation of the glycolytic pathway.

Structural investigation of the binding of nucleotide to phosphoenolpyruvate carboxykinase by NMR

The enzyme phosphoenolpyruvate carboxykinase (PEPCK) catalyzes the reversible conversion of oxalacetate and GTP to phosphoenolpyruvate (PEP), GDP, and CO2. PEPCK from higher organisms is a monomer, specifically requires GTP or ITP, and uses Mn2+ as the activating cation. Currently, there is no crystal structure of GTP-utilizing PEPCKs. The conformation of the bound nucleotide was determined from transferred nuclear Overhauser effects (trnOe) experiments to determine internuclear proton distances. At 600 MHz in the presence of PEPCK, nOe effects were observed between nucleotide protons. Internuclear distances were calculated from the initial rate of the nOe buildup. These distance constraints were used in energy minimization calculations to determine the conformation of PEPCK-bound GTP. The bound nucleotide has the base oriented anti to the C2'-endo(2E) ribose ring conformation. Relaxation rate studies indicate that there is an additional relaxation effect on the C1' proton upon nucleotide binding to PEPCK. Nucleotide binding to PEPCK-Mn2+ was studied by 1H relaxation rate studies, but results were complicated by long dipole-dipole distances and the presence of competing complexes. Modification of PEPCK by iodoacetamido-TEMPO leads to an inactive enzyme that is spin-labeled at cys273. The interaction of TEMPO-PEPCK with GTP allows for the measurement of nuclear distances between GTP and the spin label. The results suggest that cys273 lies near the ribose ring of the bound nucleotide, but it is too far to be implicated in direct hydrogen bonding interactions consistent with previous results [Makinen, A. L., and Nowak, T. J. Biol. Chem. (1989) 264, 12148], suggesting that cys273 does not actively participate in catalysis. Modification of PEPCK with several cysteine specific modifying agents causes no change in the ability of the enzyme to bind nucleotide as monitored by fluorescence quenching. A correlation between the size of the modifying agent and the maximal observed quenching upon saturation of the enzyme with nucleotide is observed. This suggests a mechanism for inactivation of PEPCK by cysteine modification due to inhibition of a dynamic motion that may occur upon nucleotide binding.

Dimethylsulfoxide promotes K+-independent activity of pyruvate kinase and the acquisition of the active catalytic conformation

Pyruvate kinase requires K+ for maximal activity; the enzyme exhibits 0.02% of maximal activity in its absence [Kayne, F. J. (1971) Arch. Biochem. Biophys. 143, 232-239]. However, pyruvate kinase entrapped in reverse micelles exhibits an important K+-independent activity [Ramírez-Silva, L., Tuena de Gómez-Puyou, M., & Gómez-Puyou, A. (1993) Biochemistry 32, 5332-5338]. It is possible that the amount of water, as well as interactions of the protein with the micelles, can account for this behavior. We therefore explored the solvent effects on the catalytic properties of muscle pyruvate kinase. The enzyme exhibited an activity of 19.4 micromol x min(-1) x mg(-1) in 40% dimethylsulfoxide, compared with 280 and 0.023 micromol x min(1) x mg(-1) observed with and without K+ in water, respectively. pH activity profiles and kinetic constants for the substrates of pyruvate kinase in dimethylsulfoxide without K+ were similar to those in 100% water with K+, and differed from those in water without K+. The spectral center of mass of the emission spectrum of pyruvate kinase in 100% water exhibited a blue shift of 3.5 nm in the presence of Mg(2+), phosphenolpyruvate, and K+, ligands that induce the active conformation of the enzyme. The spectral center of mass of the apoenzyme in 30-40% dimethylsulfoxide coincided with that of the enzyme-Mg(2+)-phosphenolpyruvate-K+ complex in 100% water. The water relaxation rate enhancement factor and binding of phosphenolpyruvate to the pyruvate kinase-Mn(2+)-(CH3)4N+ complex in 30-40% dimethylsulfoxide were similar to those of the pyruvate kinase-Mn(2+)-K+ complex in water. The aforementioned results indicate that when muscle pyruvate kinase is without K+, 30-40% dimethylsulfoxide induces its active conformation.

[Evaluation of treating head and neck rhabdomyosarcoma in the Pediatric Institute in Poznan in 1973-1997]

In the paper the authors present the evaluation of head and neck rhabdomyosarcoma (RMS) treatment in 14 children admitted to Pediatric Institute in the past 25 years. The treatment was related to the stage of the neoplasm at the time of diagnosis and consisted in the surgical intervention combined with chemo- and radiotherapy. Embryonal stage was diagnosed in 10 children (71.4%) and alveolar stage in 4 children (28.6%). In the analysed material primary neoplastic changes were found: in 6 cases in the orbit, in 2 cases in the maxillary sinus and nasal cavity, in 2 cases in the mandible. We noted also 1 case in each of the following structures: the nasopharynx, the palate, the pterygoideo-palatal fossa, the neck. In the years 1973-1991--7 children were treated according to the IRS I and II projects. Three of the children presented with the third stage of neoplastic disease and the rest with the second. Between the years 1991-1997--7 other children were hospitalized and underwent treatment based on CWS-91 project. Six of them showed the third stage of neoplasm, and only one--the first. The performed analysis revealed the insignificant improvement in the effectiveness of the treatment after the introduction of the CWS-91 project.

Limited pattern of TCR delta chain gene rearrangement on the RNA level in multiple sclerosis

Susceptibility to multiple sclerosis (MS) is most likely affected by a number of genes, including HLA and T-cell receptor (TCR) genes. T cells expressing gamma/delta receptors seem to contribute to autoagression in MS, as evidenced by their localization in the MS plaques in the brain. The aim of this study was to analyse the TCRdelta chain gene rearrangement at the RNA (cDNA) level and compare to the DNA pattern rearrangement. TCRdelta gene rearrangement was analysed in MS patients and healthy individuals with the use of primers specific for Vdelta1-6 and Jdelta1 genes (at the DNA level) and specific for Vdelta1-6 and Cdelta1 genes (at the cDNA level). The size of PCR products was analysed on agarose gel and by ALF-Express (Pharmacia). Additionally, the lymphocyte surface immunophenotype was studied with specific monoclonal antibodies. At the DNA level a restricted pattern of Vdelta3-Jdelta1 and Vdelta5-Jdelta1 was found only in MS patients. Contrary to DNA, mono-, oligoclonal RNA (cDNA) rearrangements were limited to Vdelta1-Cdelta1, Vdelta2-Cdelta1 and Vdelta3-Cdelta1 only in MS patients as well. Surface immunophenotype analysis revealed in MS a much higher frequency of activated gamma/delta T lymphocytes, i.e. expressing HLA-DR and CD25. An elevated level of CD56 positive cells in MS was recorded. Mono-oligoclonal pattern of TCRdelta gene rearrangement at the RNA level, along with increase in activated gamma/delta T cells, strongly argue for a significant role of gamma/delta T lymphocytes in the pathogenesis of MS.

[The role of local surgical and radiological control in the treatment of soft tissue sarcoma sensitive to chemotherapy in children. Report of Polish Pediatric Solid Tumors Treatment Group]

In this paper the role local surgical and radiological control in the treatment of soft tissue sarcomas in children was analyzed. All children were treated according to CWS-91 and SIOP-IV protocols. Eighty three children with RMS A + E, EES/PNET, SS, UDS were included in the analysis. The primary surgery consisted of R0 (5%), R1 (18%) or R2 (16%) resection. In majority of cases (61%) primary surgical intervention was limited to diagnostic biopsy. Conventional or hyperfractionated radiotherapy was performed in 42.8%, 73.8% and 75% of children with disease stage II, III and IV, respectively. Delayed surgery was performed in 20 out of 53 (37.7%) children with stage III of the disease. In 5 patients without primary focus (urinary bladder in 3 and prostate in 2 cases) removed, progression of the disease occurred. In 5 children (stage IV) with progression of the disease no secondary surgery was performed. In 4 of them the primary tumor exceeded 10 cm in diameter. No delayed surgery was performed in 69% of relapsed children with stage III of the disease. Planned radiation therapy was not performed in 15.9% of cases. Primary local surgical control of primary tumor is of great importance for remission duration. In children who underwent delayed surgery the estimated EFS was of 0.7, in comparison with 0.5 EFS of those without secondary surgical treatment.

Characterization of the second metal site on avian phosphoenolpyruvate carboxykinase

Chicken liver phosphoenolpyruvate carboxykinase (PEPCK) requires two divalent cations for activity. One cation activates the enzyme through a direct interaction with the protein at site n(1). The second cation, at site n(2), acts in the cation-nucleotide complex that serves as a substrate. The Co(3+)(n(1))-PEPCK and Cr(3+)(n(1))-PEPCK complexes were used to examine the kinetic, mechanistic, and binding properties of the n(2) metal. EPR studies performed on the Co(3+)(n(1))-PEPCK-GTP complex yielded a stoichiometry of 1 mol of Mn(2+) bound per mole of Co(3+)(n(1))-PEPCK-GTP with a K(D) of 5 microM. PRR studies show a significant enhancement for the Co(3+)(n(1))-PEPCK-Mn(2+)(n(2))-GDP complex. A change in enhancement in the presence of PEP suggests that PEP interacts with the second metal ion. The distance between Mn(2+) at site n(2) on PEPCK and the cis and trans protons and the (31)P of PEP are 7.0, 7.5, and 4.8 A, respectively, as measured by high-resolution NMR. PRR studies of the Co(3+)(n(1))-PEPCK-Mn(2+)(n(2))-GTP and Co(3+)(n(1))-PEPCK-Mn(2+)(n(2))-GDP complexes as a function of frequency (omega(I)) were used to estimate the hydration number of the n(2) metal to be between 0.5 and 0.7. The metal-metal distance for the M(n(1))-PEPCK-M(n(2))-GTP complex is approximately 8.3 A, and the distance for the M(n(1))-PEPCK-M(n(2))-GDP complex is 9.2 A. The change in the metal-metal distance suggests a conformational change at the active site of PEPCK occurs during catalysis. The Co(3+)(n(1))-PEPCK complex was incubated with Co(2+), GTP, and H(2)O(2) to create a doubly labeled and inactive Co(3+)(n(1))-PEPCK-Co(3+)(n(2))-GTP complex. The Co(3+)(n(1))-PEPCK-Co(3+)(n(2))-GTP complex was digested by LysC, and two cobalt-containing peptides were purified using RP-HPLC. Amino acid sequencing of the second cobalt-containing peptide points to the region of Tyr57-Lys76 of PEPCK. Asp66, Asp69, and Glu74 are all feasible ligands to the site n(2) metal.

Role of His159 in yeast enolase catalysis

There are presently several proposed catalytic mechanisms of yeast enolase, all of which have emerged from separate structural investigations of enolase from yeast and lobster muscle. However, the identities of the residues functioning as the general acid/base pair are not yet established unambiguously. In the Mn(2+)-phosphoglycolate complex of lobster muscle enolase, the imidazole group of His157 (His159 in the yeast enolase numbering system) is in van der Waals contact (4.5 A) with the C(2) of the inhibitor [Duquerroy et al. (1995) Biochemistry 34, 12513-12523]. To gain further information about the role played by His159 in the catalytic mechanism of yeast enolase this residue has been mutated to Ala. The gene encoding for the H159A mutation has been constructed and the mutant protein has been expressed in Escherichia coli. The purified mutant protein is folded properly as indicated by near- and far-UV circular dichroism and fluorescence data, and the mutation has no significant effect on the formation of ternary and quaternary enzyme-ligand complexes. In a typical assay, H159A showed 0.01% of wild-type specific activity, which corresponds to a reduction in k(cat) of 4 orders of magnitude. The H159A fails to ionize the C-2 proton of either 2-PGA or phosphoglycolate. These findings are consistent with His159 serving as a potential catalytic base in the enolase reaction. We have suggested that His159 could also serve as a metal ligand at the third, inhibitory, metal binding site. This proposal is consistent with the catalytic mechanism of yeast enolase. Binding of metal ion at site III interferes with His159 reacting as the catalytic base, i.e., abstracting the C(2) proton from 2-PGA. Metal binding studies support the above proposal. Mn(2+) binding at sites I and II for the His159Ala mutant is identical to that of wild type. The binding of Mn(2+) at the third, inhibitory site of H159A is a factor of 3 weaker compared to wild-type enolase. The factor of 3 in binding is reasonable for the contribution to binding strength of a single nondominant ligand in a chelate [Klemba, M., and Regan, L. (1995) Biochemistry 34, 10094-10100. Regan, L. (1993) Annu. Rev. Biophys. Biomol. Struct. 22, 257-281. Cha et al. (1994) J. Biol. Chem. 269, 2687-2694].

Role of lysine 240 in the mechanism of yeast pyruvate kinase catalysis

Site-directed mutagenesis was used to change Lys 240 of yeast pyruvate kinase (Lys 269 in muscle PK) to Met. K240M has an absolute requirement for FBP for catalysis. K240M is 100- and 1000-fold less active than wild-type YPK in the presence of Mn(2+) and Mg(2+), respectively. Steady-state fluorescence titration data suggest that the substrate PEP binds to K240M with the same affinity as it does to wild-type YPK. The rate of phosphoryl transfer in K240M has been decreased >1000-fold compared to wild-type YPK. The detritiation of 3-[(3)H]pyruvate catalyzed by YPK occurs at a rate significantly greater than the spontaneous rate. Detritiation of pyruvate by wild-type YPK occurs as a divalent metal- and FBP-dependent process requiring ATP. There is no detectable detritiation of pyruvate catalyzed by K240M. The solvent deuterium isotope effect on k(cat) is 2.7 +/- 0.2 and 1.6 +/- 0.1 for the wild type and for K240M YPK, respectively. This suggests that the isotope sensitive step in the PK reaction does not involve Lys 240 and that the enolpyruvate intermediate is still protonated by K240M. Isotope trapping was used to characterize enolpyruvate protonation by K240M. While there was enrichment of the methyl protons of pyruvate from labeled solvent formed by catalysis with muscle PK and wild-type YPK, only background levels of tritium were trapped with K240M. In K240M, the proton donor exchanges protons with the solvent at a higher rate relative to turnover than does the proton donor in wild-type YPK. The pH-rate profile of K240M exhibits the loss of a pK(a) value of 8. 8 observed with wild-type YPK. The above data and recent crystal structure data suggest that Lys 240 interacts with the phosphoryl group of phosphoenolpyruvate and helps to stabilize the pentavalent phosphate transition state during phosphoryl transfer. Phosphoryl transfer is highly coupled to proton transfer, or Lys 240 also affects enolate protonation.

Discovery of three novel orphan G-protein-coupled receptors

We have discovered three novel human genes, GPR34, GPR44, and GPR45, encoding family A G-protein-coupled receptors (GPCRs). The receptor encoded by GPR34 is most similar to the P2Y receptor subfamily, while the receptor encoded by GPR44 is most similar to chemoattractant receptors. The receptor encoded by GPR45 is the mammalian orthologue of a putative lysophosphatidic acid receptor from Xenopus laevis. Partial sequence of GPR34 was discovered during a search of the GenBank database of expressed sequence tags (ESTs). This sequence information was used both to isolate the full-length translational open reading frame from a human genomic library and to assemble a contig from additional GPR34 EST cDNAs. Northern blot and in situ hybridization analyses revealed GPR34 mRNA transcripts in several human and rat brain regions. Also, we used polymerase chain reaction (PCR) to amplify human genomic DNA using degenerate oligonucleotides designed from sequences encoding transmembrane domains 3 and 7 of opioid and somatostatin receptors. Two PCR products partially encoding novel GPCRs, named GPR44 and GPR45, were discovered and used to isolate the full-length translational open reading frames from a human genomic library. Both GPR44 and GPR45 are expressed in the central nervous system and periphery. For chromosomal localization, fluorescence in situ hybridization analysis was performed to assign GPR34 to chromosomes 4p12 and Xp11. 3, GPR44 to chromosome 11q12-q13.3, and GPR45 to chromosome 2q11. 1-q12.

pH dependence of the reaction catalyzed by yeast Mg-enolase

The pH dependence of the chemical shifts of the 31P resonances of enzyme-bound substrates 2-phosphoglycerate (PGA) and phosphoenolpyruvate (PEP) were measured to obtain further insight into the catalytic mechanism of yeast enolase. The 31P resonances of PGA and PEP bound to the enolase-Mg complex are individually observed by NMR. The Keq,internal = 1.5 favoring PEP was measured. A pH dependence of the 31P chemical shifts gives pKa values of 5.82 and 6.16 for bound PGA and PEP, respectively, indicating that both ligands bind predominantly with their phosphate groups as the dianionic species and their ionization has been altered. The phosphoryl group of PGA has been suggested as playing a role in catalysis [Nowak, T., Mildvan, A. S., and Kenyon, G. L. (1973) Biochemistry 12, 1690-1701]. The pH dependence of the kinetic parameters for Mg-enolase shows a single break in the plot of pKm, PGA vs pH at pH 6.27 with a pH independence above pH 7. This is consistent with the trianion of PGA preferably binding to the enzyme. The kcat profile gives pKA values of 5.94 and 8.35, and kcat/Km profiles give pKA values of 5.85, 6.25, and 8.39. Activation studies with Mg2+ show a pH independence for the activator constant (Ka), but a pH-dependent inhibition at higher concentrations of Mg2+. The log kcat and kcat/Ka profiles from Mg2+ activation give pKA values of about 5.9 and 8.4. These results confirm the importance of residues with pKA values of about 5.9 and 8.4 (His and Lys residues?) but do not support a function for the phosphoryl group of the substrate. The pH dependence of the Ki,Mg2+ gives pKA fits of 5. 95, 7.13, and 8.35. Data from cation inhibition suggest that the phosphate of the substrate and a His residue on enolase may bind the inhibitory Mg2+.

Chromium(III) modification of the first metal binding site of phosphoenolpyruvate carboxykinase

Chicken liver phosphoenolpyruvate carboxykinase (PEPCK) is activated by Cr2+ as the sole activator under anaerobic conditions. PEPCK was modified with Cr3+, starting with either Cr2+ or Cr3+. Cr3+ has the distinct advantage of being a paramagnetic cation that could serve as a paramagnetic probe. Activators Mn2+, Mg2+, and Co2+ protect against Cr3+ incorporation. EPR, CD, and fluorescence studies indicate that Cr3+ was incorporated into the cation binding site of PEPCK. The water proton relaxation rate (PRR) and fluorescence binding studies showed that Cr3+(n1)-PEPCK forms enzyme-substrate complexes similar to those observed for the Mn2+(n1)-PEPCK complex (n1 represents the metal "enzyme binding site" as opposed to the metal "nucleotide binding site"). Cr3+(n1)-PEPCK requires an additional divalent cation for activity, an indication of two metal sites on PEPCK. Cr3+(n1)-PEPCK retains 15% residual activity as compared to unmodified PEPCK and demonstrates normal Michaelis-Menten kinetics. This is the first report of an active Cr3+-modified enzyme complex.

Conformational changes in yeast pyruvate kinase studied by 205Tl+ NMR

The interaction of the monovalent cation with yeast pyruvate kinase (yPK) has been investigated by 205Tl+ NMR. TlNO3 activates yPK to 80-90% activity compared to KCl with an apparent Ka of 1.00 +/- 0.03 mM in the presence of 4 mM Mn(NO3)2 as the activating divalent cation. At higher concentrations of Tl+, enzyme inhibition is observed with an apparent KI of 180 +/- 10 mM. The extent of inhibition is dependent on the nature and concentration of the divalent cation. The effect of Mn2+ on the 1/T1 and 1/T2 values of 205Tl+ in the presence of yPK was determined at 173.02 MHz (300 MHz, 1H) and 346.03 MHz (600 MHz, 1H). The temperature dependence of the relaxation rates indicates that fast exchange conditions prevail for 205Tl+ longitudinal relaxation rates. The correlation time, tauc, for the Mn2+-205Tl+ interaction was estimated by a frequency dependence of 1/T1m for several enzyme complexes, and an average value of tauc was determined to be 0.91 ns. The distance between Tl+ and Mn2+ at the active site of yPK was calculated from the paramagnetic contribution of Mn2+ to the longitudinal (1/T1m) relaxation rates of Tl+ bound to yPK. For the apo yPK complex, the Tl+ to Mn2+ distance is 6.7 +/- 0.2 A. Upon addition of phosphoenolpyruvate (PEP) to form the yPK-Tl-Mn-PEP complex, the inter-cation distance decreases to 6.1 +/- 0.3 A. The addition of the allosteric activator fructose 1,6-bisphosphate (FBP) to form the yPK-Tl+-Mn2+-PEP-FBP complex gives an intermetal distance of 6.2 +/- 0.2 A. In the yPK-Tl-Mn-FBP complex, a Tl+-Mn2+ distance of 6.0 +/- 0.1 A is observed, indicating that FBP causes a conformational change at the active site in the absence of PEP. Analogous 205Tl NMR experiments with competitive inhibitors of PEP (oxalate, BrPEP) indicate that these ligands do not induce the same conformational changes as do the physiological substrates and activators. Similar experiments with the nonallosteric rabbit muscle PK were also performed and analyzed.

The allosteric regulation of pyruvate kinase by fructose-1,6-bisphosphate

BACKGROUND

Yeast pyruvate kinase (PK) catalyzes the final step in glycolysis. The enzyme therefore represents an important control point and is allosterically activated by fructose-1,6-bisphosphate (FBP). In mammals the enzyme is found as four different isozymes with different regulatory properties: two of these isozymes are produced by alternate splicing. The allosteric regulation of PK is directly related to proliferation of certain cell types, as demonstrated by the expression of an allosterically regulated isozyme in tumor cells. A model for the allosteric transition from the inactive (T) state to the active (R) state has been proposed previously, but until now the FBP-binding site had not been identified.

RESULTS

We report here the structures of PK from yeast complexed with a substrate analog and catalytic metal ions in the presence and absence of bound FBP. The allosteric site is located 40 A from the active site and is entirely located in the enzyme regulatory (C) domain. A phosphate-binding site for the allosteric activator is created by residues encoded by a region of the gene corresponding to the alternately spliced exon of mammalian isozymes. FBP activation appears to induce several conformational changes among active-site sidechains through a mechanism that is most likely to involve significant domain motions, as previously hypothesized.

CONCLUSIONS

The structure and location of the allosteric activator site agrees with the pattern of alternate genetic splicing of the PK gene in multicellular eukaryotes that distinguishes between a non-regulated isozyme and the regulated fetal isozymes. The conformational differences observed between the active sites of inactive and fully active PK enzymes is in agreement with the recently determined thermodynamic mechanism of allosteric activation through a 'metal relay' that increases the affinity of the enzyme for its natural phosphoenolpyruvate substrate.

Closed-loop subcutaneous insulin infusion algorithm with a short-acting insulin analog for long-term clinical application of a wearable artificial endocrine pancreas

Considering the management and safety of the insulin delivery route when a wearable artificial endocrine pancreas is applied to ambulatory diabetic patients on a long-term basis, we developed a s.c. insulin infusion algorithm by analyzing the dynamics of a s.c. injected short-acting insulin analog (Insulin Lispro) by a three-compartment model. Principally the insulin infusion algorithm was developed as a transfer function with the first-order delay in both proportional and derivative actions to blood glucose concentrations. The parameters for this algorithm were calculated to simulate a physiological plasma insulin profile as closely as possible. By applying this algorithm with regular insulin, diabetic patients showed a 2 h postprandial hyperglycemia and a delayed hyperinsulinemia, followed by hypoglycemic episodes 4-5 h after oral glucose load, just as observed in the computer simulation study. However, using Insulin Lispro, a near-physiological glycemic control (postprandial blood glucose of 153.1 +/- 8.3 mg/100 ml at 60 min and 90.3 +/- 7.1 mg/100 ml at 180 min, respectively) could be achieved without showing any delayed hyperinsulinemia or hypoglycemia. Daily glycemic excursions were also controlled near-physiologically and although the daily insulin requirement (731.7 +/- 160.5 mU/kg/day) was slightly higher, it was not significantly different from that with i.v. insulin infusion (622.3 +/- 142.6 mU/kg/day). These results indicate that the application of s.c. insulin infusion algorithm with Insulin Lispro is feasible for long-term glycemic control with a wearable artificial endocrine pancreas in ambulatory diabetic patients.