The empty pelvis syndrome: a core data set from the PelvEx collaborative

BACKGROUND

Empty pelvis syndrome (EPS) is a significant source of morbidity following pelvic exenteration (PE), but is undefined. EPS outcome reporting and descriptors of radicality of PE are inconsistent; therefore, the best approaches for prevention are unknown. To facilitate future research into EPS, the aim of this study is to define a measurable core outcome set, core descriptor set and written definition for EPS. Consensus on strategies to mitigate EPS was also explored.

METHOD

Three-stage consensus methodology was used: longlisting with systematic review, healthcare professional event, patient engagement, and Delphi-piloting; shortlisting with two rounds of modified Delphi; and a confirmatory stage using a modified nominal group technique. This included a selection of measurement instruments, and iterative generation of a written EPS definition.

RESULTS

One hundred and three and 119 participants took part in the modified Delphi and consensus meetings, respectively. This encompassed international patient and healthcare professional representation with multidisciplinary input. Seventy statements were longlisted, seven core outcomes (bowel obstruction, enteroperineal fistula, chronic perineal sinus, infected pelvic collection, bowel obstruction, morbidity from reconstruction, re-intervention, and quality of life), and four core descriptors (magnitude of surgery, radiotherapy-induced damage, methods of reconstruction, and changes in volume of pelvic dead space) reached consensus-where applicable, measurement of these outcomes and descriptors was defined. A written definition for EPS was agreed.

CONCLUSIONS

EPS is an area of unmet research and clinical need. This study provides an agreed definition and core data set for EPS to facilitate further research.

ASSESSMENT OF PCXMC MONTE CARLO SIMULATIONS IN SLOT-SCANNING-BASED EXAMINATIONS: COMPARISON WITH IN-PHANTOM THERMOLUMINESCENT DOSIMETRY

Slot-scanning technology is nowadays a valid solution for the follow-up of chronic musculoskeletal disorders on children and adolescent patients, but there is no commercial software designed for simulating this X-ray beam geometry. PC Program for X-ray Monte Carlo (PCXMC) is a widespread Monte Carlo software developed for dose computation in projection radiography. In this study, experimental measurements were performed to evaluate its applicability in examinations with a slit-beam device. Physical phantoms corresponding to an adult and a 5-y-old child with calibrated thermoluminescent dosemeters were used for experiments. Different simulation approaches were investigated. Differences between measured and calculated organ doses ranged from -95 to 67% and were statistically significant for almost all organs. For both patients, PCXMC underestimated the effective dose of about 25%. This study suggests that PCXMC is not suited for organ dose evaluation in examinations with slot-scanning devices. It is still a useful tool for effective dose estimation when a proper correction factor is applied.

Minimum standards of pelvic exenterative practice: PelvEx Collaborative guideline

This document outlines the important aspects of caring for patients who have been diagnosed with advanced pelvic cancer. It is primarily aimed at those who are establishing a service that adequately caters to this patient group. The relevant literature has been summarized and an attempt made to simplify the approach to management of these complex cases.

Radiation exposure during modern therapeutic endoscopic ultrasound procedures and standard alternatives

Background and study aims  Therapeutic EUS (t-EUS) is increasingly being adopted in clinical practice in tertiary referral centers; however, little is known about radiation exposure (RE) metrics and diagnostic reference limits for it. Methods  Kerma-area product (KAP [Gy·cm ² ]), Air Kerma and fluoroscopy time were retrospectively evaluated for all consecutive t-EUS procedures performed in San Raffaele Institute between 2019 and 2021. For EUS-guided choledochoduodenostomies (EUS-CDS) and gastroenterostomies (EUS-GE), an equal number of endoscopic retrograde cholangiopancreatographies (ERCPs) plus metal stenting and duodenal stents were included respectively for comparison. Results  Data from 141 t-EUS procedures were retrieved (49 % pancreatic cancer, 38 % peripancreatic fluid collections). EUS-CDS (N = 44) were mainly performed fluoroless, while ERCPs required a significantly higher RE (KAP = 25 [17-55], P < 0.0001). Fluid collection drainage (EUS-FCD) with lumen apposing metal stents (LAMS, N = 26) were performed fluoroless, while EUS-FCD with double-pigtail plastic stents (DPPS, N = 28) required higher RE (KAP = 23 [13-45]). EUS-guided gallbladder drainage (EUS-GBD, N = 6) required scarce RE (KAP = 9 [3-21]) for coaxial DPPS placement. EUS-GE (N = 27) required higher RE than duodenal stenting (KAP = 44 [28-88] versus 29 [19-46], P = 0.03). EUS-guided hepaticogastrostomies (EUS-HGS, N = 10) had the highest RE among t-EUS procedures (KAP = 81 [49-123]). Procedure complexity or intervening complications were evaluated and resulted in higher RE within each procedure. Conclusions  t-EUS procedures have different RE ( P  < 0.000001). EUS-CDS, EUS-GBD, and EUS-FCD with LAMS can be performed with no-to-mild radioscopy, unlike standard alternatives. However, radioscopy remains essential in case of technical difficulties or complications. EUS-GE and EUS-HGS involve a high RE. Endoscopists involved in t-EUS might experience RE higher than category standards, which indicates a need for increased awareness and personalized preventive measures.

Fabrication of 3D printed patient-derived anthropomorphic breast phantoms for mammography and digital breast tomosynthesis: Imaging assessment with clinical X-ray spectra

PURPOSE

To design, fabricate and characterize 3D printed, anatomically realistic, compressed breast phantoms for digital mammography (DM) and digital breast tomosynthesis (DBT) x-ray imaging.

MATERIALS

We realized 3D printed phantoms simulating healthy breasts, via fused deposition modeling (FDM), with a layer resolution of 0.1 mm and 100% infill density, using a dual extruder printer. The digital models were derived from a public dataset of segmented clinical breast computed tomography scans. Three physical phantoms were printed in polyethylene terephthalate (PET), acrylonitrile-butadiene-styrene (ABS), or in polylactic-acid (PLA) materials, using ABS as a substitute for adipose tissue, and PLA or PET filaments for replicating glandular and skin tissues. 3D printed phantoms were imaged at three clinical centers with DM and DBT scanners, using typical spectra. Anatomical noise of the manufactured phantoms was evaluated via the estimates of the β parameter both in DM images and in images acquired via a clinical computed tomography (CT) scanner.

RESULTS

DM and DBT phantom images showed an inner texture qualitatively similar to the images of a clinical DM or DBT exam, suitably reproducing the glandular structure of their computational phantoms. β parameters evaluated in DM images of the manufactured phantoms ranged between 2.84 and 3.79; a lower β was calculated from the CT scan.

CONCLUSIONS

FDM 3D printed compressed breast phantoms have been fabricated using ABS, PLA and PET filaments. DM and DBT images with clinical x-ray spectra showed realistic textures. These phantoms appear promising for clinical applications in quality assurance, image quality and dosimetry assessments.

Decommissioning procedure and induced activation levels, calculations and measurements in an 18 MeV medical cyclotron

The present article describes the decommissioning of a self-shielded 18 MeV medical cyclotron IBA Cyclone 18/9 after 14 years of operation. A Monte Carlo simulation of the possible nuclear reactions was performed in order to plan the decommissioning activities. During the cyclotron dismantling, the activities of the cyclotron components, concrete wall and floor samples were measured. Residual activities were analysed by means of an HPGe detector and liquid scintillation counting, and compared with simulation data. Dosimetry of the staff involved in the decommissioning procedure was monitored by individual TL dosimeters and/or digital dosimeter. The cyclotron component analysis confirmed the presence of gamma and pure beta emitters,²²Na,⁵⁴Mn,⁶⁰Co,⁶⁵Zn,²⁰⁷Bi,⁵⁵Fe,⁶³Ni at different values of specific activity, depending on the positioning of the sample point and on the alloy of the sampled part. In these components the presence of gamma and pure beta emitters was measured 5 years after the shutdown at levels far above clearance limits as defined by the 'Recommended radiological protection criteria for the recycling of metals from the dismantling of nuclear installations' (RP89) guidelines. The simulation, carried out by FLUKA Code (version 2020.0.5) on the cyclotron components, provided good agreement with measurements, with a maximum discrepancy of the same order as the uncertainties. Four engineers of the cyclotron maintenance staff were involved in the dismounting of the hottest components and rigging of the cyclotron in the deposit 6 months after shutdown and two engineers were involved during the drilling phase 3.5 years after shutdown. The measured dose from external exposure of the involved staff was lower than 100μSv person^-1during the first phase and lower than 20μSv person^-1during the final drilling phase. Measured doses from intake were negligible. In conclusion, the decommissioning of the 18 MeV cyclotron does not represent a risk for the involved staff, but, due to the presence of long-lived radioisotopes, the cyclotron components are to be treated as low level radioactive waste, and stored in an authorised storage area for at least 25 years after shutdown.

Effects of dopamine and nitric oxide on arterial pressure and renal function in volume expansion

1. The aim of the present study was to investigate the role of dopamine (DA) in the hypotensive and renal effects of L-arginine during extracellular fluid volume expansion (10% bodyweight). 2. Animals were randomized to non-expanded and expanded groups. Both groups received different treatments: L-arginine (250 mg/kg, i.v.), N(G)-nitro-L-arginine methyl ester (L-NAME; 1 mg/kg, i.v.), haloperidol (3 mg/kg, i.p.) and L-arginine + haloperidol (n = 8). Mean arterial pressure (MAP), diuresis, natriuresis, kaliuresis, glomerular filtration rate, renal plasma flow (RPF) and nitrite and nitrate (NO(x)) excretion were determined. 3. The increase in MAP induced by L-NAME was greater in expanded than in non-expanded rats (42 +/- 3 vs 32 +/- 3 mmHg, respectively; P < 0.01). Administration of haloperidol did not modify the L-arginine hypotensive effect. 4. Blockade of nitric oxide synthase diminished urine flow in non-expanded (4.15 +/- 0.56 vs 0.55 +/- 0.11 microL/min per 100 g; P < 0.01) and expanded animals (24.42 +/- 3.67 vs 17.85 +/- 2.16 microL/min per 100 g; P < 0.01). Diuresis induced by L-arginine was reduced by DA blockade in both non-expanded (17.15 +/- 2.11 vs 6.82 +/- 0.61 microL/min per 100 g; P < 0.01) and expanded animals (44.26 +/- 8.45 vs 25.43 +/- 5.12 microL/min per 100 g; P < 0.01). 5. Sodium excretion decreased with L-NAME treatment in non-expanded (0.22 +/- 0.03 vs 0.06 +/- 0.01 microEq/min per 100 g; P < 0.01) and expanded animals (3.72 +/- 0.70 vs 1.89 +/- 0.23 microEq/min per 100 g; P < 0.01). Natriuresis induced by L-arginine was diminished by haloperidol both in non-expanded (0.94 +/- 0.13 vs 0.43 +/- 0.04 microEq/min per 100 g; P < 0.01) and expanded rats (12.77 +/- 0.05 vs 3.53 +/- 0.75 microEq/min per 100 g; P < 0.01). Changes in kaliuresis changes seen following treatment with L-arginine, L-NAME and L-arginine + haloperidol followed a pattern similar to that observed for sodium excretion in both groups of rats. 6. L-arginine enhanced RPF in non-expanded animals (11.96 +/- 0.81 vs 14.52 +/- 1.05 mL/min per 100 g; P < 0.01). Glomerular filtration rate was increased by extracellular volume expansion (3.08 +/- 0.28 vs 5.42 +/- 0.46 mL/min per 100 g; P < 0.01). 7. The increase in NOx induced by acute volume expansion (0.18 +/- 0.03 vs 0.52 +/- 0.08 nmol/min per 100 g; P < 0.01) was diminished following the administration of haloperidol (0.52 +/- 0.08 vs 0.26 +/- 0.06 nmol/min per 100 g; P < 0.01). 8. Although DA does not participate in the actions of nitric oxide on vascular tone, both systems would play an important role in renal function adaptation during extracellular fluid volume expansion.

Sequential treatment with lamivudine and interferon monotherapies in patients with chronic hepatitis B not responding to interferon alone: results of a pilot study

Sustained viral suppression using monotherapy with interferon alfa (IFN-alpha) or lamivudine can only be achieved in a small percentage of patients with chronic hepatitis B. The concomitant administration of lamivudine and IFN-alpha does not enhance efficacy. We postulated that the optimal timing of therapy might be sequential treatment with lamivudine and IFN-alpha. The aim of this study was therefore to assess the efficacy of sequential treatment in patients resistant to IFN-alpha alone. Fourteen male patients, with a median age of 40 years, nonresponders to IFN-alpha with hepatitis B virus (HBV) DNA > 100 pg/mL (branched DNA [bDNA] Chiron) and positive hepatitis B e antigen (HBeAg) in 11 of 14 patients, were treated with lamivudine 100 mg/d alone for 20 weeks, then with both IFN-alpha2b 5 MU 3 times per week and lamivudine for 4 weeks, and lastly with IFN-alpha alone for 24 weeks. At the end of lamivudine therapy, all patients had undetectable serum HBV DNA, and none exhibited an emergence of HBV polymerase mutant or breakthrough. Sustained serum HBV-DNA clearance 6 months after the end of sequential treatment was achieved in 8 of 14 patients, HBeAg-to-anti-HBe seroconversion in 5 of 11 patients, and HBeAg and hepatitis B surface antigen (HBsAg) seroconversions in 3 of 14 patients (anti-HBs > 100 IU/mL). All sustained responders had normalized their alanine transaminase (ALT) values and exhibited histologic improvements. In conclusion, the results of this pilot study suggest that sequential treatment with lamivudine and IFN-alpha can induce a sustained virologic response, including HBs seroconversion, in patients with chronic hepatitis B not responding to IFN-alpha alone, without the selection of drug-resistant mutants. This therapeutic schedule warrants further evaluation in clinical trials.

Modular construction for function of a ribonucleoprotein enzyme: the catalytic domain of Bacillus subtilis RNase P complexed with B. subtilis RNase P protein

The bacterial RNase P holoenzyme catalyzes the formation of the mature 5'-end of tRNAs and is composed of an RNA and a protein subunit. Among the two folding domains of the RNase P RNA, the catalytic domain (C-domain) contains the active site of this ribozyme. We investigated specific binding of the Bacillus subtilis C-domain with the B.subtilis RNase P protein and examined the catalytic activity of this C-domain-P protein complex. The C-domain forms a specific complex with the P protein with a binding constant of approximately 0.1 microM. The C-domain-P protein complex and the holoenzyme are equally efficient in cleaving single-stranded RNA (approximately 0.9 min(-1) at pH 7.8) and substrates with a hairpin-loop 3' to the cleavage site (approximately 40 min(-1)). The holoenzyme reaction is much more efficient with a pre-tRNA substrate, binding at least 100-fold better and cleaving 10-500 times more efficiently. These results demonstrate that the RNase P holoenzyme is functionally constructed in three parts. The catalytic domain alone contains the active site, but has little specificity and affinity for most substrates. The specificity and affinity for the substrate is generated by either the specificity domain of RNase P RNA binding to a T stem-loop-like hairpin or RNase P protein binding to a single-stranded RNA. This modular construction may be exploited to obtain RNase P-based ribonucleoprotein complexes with altered substrate specificity.

The 3' substrate determinants for the catalytic efficiency of the Bacillus subtilis RNase P holoenzyme suggest autolytic processing of the RNase P RNA in vivo

We investigated the catalytic efficiency and the specificity of the Bacillus subtilis RNase P holoenzyme reaction with substrates that contain a single strand, a hairpin loop, or a tRNA 3' to the cleavage site. At a saturating ribozyme concentration, RNase P can cleave a single-stranded RNA at approximately 0.6 min(-1) at pH 7.8. Replacing the single-stranded RNA 3' to the cleavage site by a hairpin loop or by the yeast tRNA(Phe) increases the cleavage rate by up to approximately 600-fold and approximately 3,200-fold, respectively. These results show that compared to a single-stranded RNA substrate, the cleavage rate for the holoenzyme reaction is primarily enhanced by an acceptor-stem-like helix. Substrate binding, approximately 7-10 microM for a single-stranded RNA, improves by approximately 1,000-fold upon the addition of the tRNA. The efficiency of the RNase P holoenzyme cleaving a single-stranded RNA is sufficiently high to consider autolytic processing of the RNase P RNA (denoted P RNA) transcript in the cell. The addition of the RNase P protein to a precursor form of the P RNA in vitro results in autolytic processing of the 5' and the 3' end of this precursor in a matter of minutes. Autolytic processing produces the reported 5' end of the mature P RNA. The precise 3' end generated by autolytic processing is different over the course of the reaction and the final product is 4 nt shorter than the reported 3' end of the B. subtilis P RNA. The observed 3' end in vitro is consistent with the property of the holoenzyme reaction with single-stranded RNA substrates. The discrepancy with the reported 3' end may be due to other processing events in vivo or inaccurate determination of the mature 3' end of the P RNA isolated from the cell. We propose that the mature B. subtilis P RNA is generated at least in part by autolytic processing upon the binding of the RNase P protein to the precursor P RNA.

Research trends in mother-child healthcare, 1966-1995

OBJECTIVE

To explore trends in mother-child healthcare (MCHC) research over the past 30 years.

METHODS

Classifications of Medline articles were made at 5-year intervals using Medical Subject Headings (MeSH) as classifiers. Papers were classified in mutually and non-mutually exclusive categories by subject (mother and four age groups of children) and type of research (clinical, basic, epidemiologic, and unclassified) and its various combinations.

RESULTS

The number of MCHC papers increased from 34,110 in 1966 to 65,028 in 1995, but the proportion of all Medline articles (18-21%) was relatively stable. There were remarkable long-term temporal stabilities in the proportions of MCHC papers of mothers and the four age groups of children. Most papers dealt with child (46%) and adolescents (45%), and only 11% studied mother and children together. Regression analysis indicated that a linear increase in number of MCHC papers in Medline (1053/year) was represented largely by single-age and combinations of age children, especially adolescence. However, the slope for mother-plus-children papers (113/year) was substantially higher than for mothers alone (64/year). Clinical papers (52%) were the dominant type of MCHC research, but the proportions of basic and epidemiologic papers and their combinations with clinical papers have increased substantially in the past decade.

CONCLUSIONS

There has been a dominance of clinical and child-related papers in MCHC research, which may be a reflection of restricted outlooks of specialists in the area. This may change soon if the tendency toward increasing numbers of basic and epidemiologic papers holds.

Prevalence of pre-obesity and obesity in urban adult Mexicans in comparison with other large surveys

OBJECTIVE

1. To estimate the prevalence of pre-obesity and obesity in a 1992 to 1993 national survey of the Mexican urban adult population. 2. To compare our findings with other national surveys and with data for Mexican Americans.

RESEARCH METHODS AND PROCEDURES

The national representative sample of the Mexican urban adult population included 8462 women and 5929 men aged 20 to 69 years from 417 towns of >2500 people. Body mass index (BMI), calculated from measured weight and height, was classified using the World Health Organization categories of underweight (BMI < 18.5 kg/m2), normal weight (BMI 18.5 to 24.9 kg/m2), pre-obesity (PreOB = BMI 25 to 29.9 kg/m2) and obesity (OB = BMI 30+ kg/m2). Estimates for Mexican Americans were calculated from U.S. survey data.

RESULTS

Overall, 38% of the Mexican urban adult population were classified as pre-obese and 21% as obese. Men had a higher prevalence of pre-obesity than women did at all ages, but women had higher values of obesity. Both pre-obesity and obesity increased with age up to the age range brackets of 40 to 49 or 50 to 59 years for both men and women. Both pre-obesity and obesity prevalence estimates were remarkably similar to data for Mexican Americans from 1982 through 1984. Comparison with other large surveys showed that countries differed more in the prevalence of obesity than of pre-obesity, leading to differences in the PreOB/OB ratio, and that countries also differed in the gender ratio (female/male) for both pre-obesity and obesity.

DISCUSSION

Pre-obesity and obesity were high in our population and increased with age. Our approach of characterizing large surveys by PreOB/OB and gender ratios appeared promising.

Increasing frequency of gastric lymphoma in two national institutes of health in Mexico

BACKGROUND

Some studies performed in developed countries with caucasian population have suggested an increase in the frequency of primary gastric lymphoma (PGL) in the past two decades.

OBJECTIVE

To establish the frequency of PGL in two National Institutes of Health in Mexico in an interval of 18 years.

METHODS

We reviewed 1,854 gastric malignant neoplasms diagnosed between 1979-1996 in mestizo patients seen at two different institutions. One of them (INC) is an oncological hospital, whereas the other one (INN) is a general hospital which treats patients with benign as well as malignant gastrointestinal diseases.

RESULTS

A hundred and sixty three (8.8%) gastric lymphomas were identified from 1,854 gastric malignant tumors. The incidence of PGL showed a two to three-fold increase in the last years of the study in both institutions. The increased frequency was highly significant when compared to the initial rate. This increase does not appear to be due to patient selection criteria nor to the number of malignant gastric tumors in our institutions.

CONCLUSIONS

Our results indicate an increased frequency of PGL the patient population of two National Institutes of Health in Mexico during the last years. Additional studies are necessary in order to define in the increase in PGL is limited to certain geographical areas or ethnic groups.

Hypertension in urban Mexico: the 1992-93 national survey of chronic diseases

The purpose of this work is to estimate the prevalence of hypertension in the urban population of Mexico. We studied a multistage national sample representative of the urban population in 417 cities of over 2500 people. The blood pressure of 14 657 individuals (6053 men and 8604 women) aged 20-69 years was measured after a 5-min rest using a standard mercury sphygmomanometer. The survey personnel had been previously trained and standardised. The main results show a crude prevalence of hypertension, as defined by the JNC VI, of 28.1% in women and 37.5% in men (27.2% and 37.1% age-adjusted). Both genders exhibited a trend of increasing hypertension with age. In individuals under 50 years of age, women had lower rates than men, but the difference disappeared in the older groups. The awareness of hypertension (28%) as well as the success of treatment (22%) were low in our sample. Our results had more similarities than differences with respect to those observed in other national surveys. It is concluded that hypertension in Mexico is an important public health problem similar to that seen in developing and developed nations. Efforts should be aimed at strengthening measures to prevent and control hypertension in Mexico. More information is needed of the sort obtained from longitudinal studies.

External quality control program of four blood cell counters

OBJECTIVE

To evaluate an internal-external quality control program of four automated counters.

METHODS

Every one or two weeks during 14 months, six direct cell parameters were measured in three fresh blood samples in four Coulter counters. The median per parameter of the working day was used to detect inaccuracies and if the participants' internal control program confirmed it, a recalibration of the parameter was performed.

RESULTS

In 21 of 22 instances, the internal program confirmed an inaccuracy and a recalibration was done (4 leukocyte and 5 erythrocyte counts, 5 hemoglobins, 7 red-cell volumes). In these four parameters there were no large differences between the lowest and highest counter upon analyzing all results whereas all counters differed from one another in the parameters that cannot be recalibrated by the user (platelet volume, red-cell distribution width).

CONCLUSIONS

1. The program contributed to good accuracy and precision within-counters and good concordancy between-counters in the parameters that can be recalibrated. 2. The counter differences in red-cell distribution width were sufficiently large (up to 9%) to affect clinical interpretation. This poses the need of width distribution reference ranges for each counter.

The cleavage step of ribonuclease P catalysis is determined by ribozyme-substrate interactions both distal and proximal to the cleavage site

The cleavage step of bacterial RNase P catalysis involves concentration-independent processes after the formation of the ribozyme-substrate complex that result in the breaking of a phosphodiester bond. The 2'OH group at the cleavage site of a pre-tRNA substrate is an important determinant in the cleavage step. We determined here that in contrast to a tRNA substrate, the 2'OH at the cleavage site of two in vitro selected substrates has no effect, whereas a 2'OH located adjacent to the cleavage site has a similarly large effect on the cleavage step. This result indicates that a unique 2'OH in the vicinity of the cleavage site interacts with the ribozyme to achieve the maximal efficiency of the cleavage step. Individual modifications in a pre-tRNA substrate that disrupt ES interactions proximal to the cleavage site generally have little effect on the usage of this unique 2'OH. Ribozyme modifications that delete the interactions involving the T stem-loop of the tRNA have a large effect on the usage of this unique 2'OH and also alter the location of this 2'OH. We propose a new ES complex prior to the bond-breaking step in the reaction scheme to explain these results. This second ES complex is in fast equilibrium with the initial ES complex formed by bimolecular collision. The ribozyme interaction with this unique 2'OH shifts the equilibrium in favor of the second ES complex. The formation of the second ES complex may require optimal geometry of the two independently folding domains of this ribozyme to precisely position crucial functional groups and Mg2+ ions in the active site. Such a domain geometry is significantly favored by the RNase P protein. In the absence of the protein, spatial rearrangement of these domains in the ES complex may be necessary.

Recognition of a pre-tRNA substrate by the Bacillus subtilis RNase P holoenzyme

The holoenzyme of the bacterial RNase P has broader selectivity for biological substrates compared to the RNA alone (denoted P RNA) reaction. The structural basis of the substrate selectivity is investigated using a pre-tRNA substrate containing single-atom modifications by single turnover kinetics. Hydroxyl radical protection of the holoenzyme in the absence of the substrate shows that the RNase P protein binds to several regions in P RNA. The holoenzyme interacts with a subset of functional groups in the T stem-loop region of a pre-tRNA substrate previously identified to directly contact P RNA. The subtle change in structural recognition allows the holoenzyme to recognize RNA structures with only a small perturbation in an A-form helix at the corresponding position of the T stem-loop. This altered profile may permit the holoenzyme to bind non-tRNA substrates with little change in catalytic efficiency. The holoenzyme recognizes the same set of functional groups as the P RNA reaction in the region around the cleavage site and shows similar cleavage site selection compared to the P RNA reaction. These results suggest that the holoenzyme does not alter the fundamental mechanism of this enzymatic reaction. Rather, the holoenzyme significantly affects the binding affinity of an RNA substrate through additional interactions with the 5' leader [Kurz, C. A., Niranjanakumari, S., and Fierke, C. A. (1998) Biochemistry 37, 2393] and through altered recognition of the substrate structure.

Recognition of the 5' leader and the acceptor stem of a pre-tRNA substrate by the ribozyme from Bacillus subtilis RNase P

The catalysis by the ribozyme from bacterial RNase P involves specific interactions with the structure of the tRNA substrate. Recognition of the T stem-loop by this ribozyme occurs in a groove-like structure dictated by the tertiary folding of tRNA [Loria, A., and Pan, T. (1997) Biochemistry 36, 6317]. Effects of 2'-OH --> 2'-H modifications within the acceptor stem and the 5' leader on substrate binding and catalysis are determined using a tRNAPhe substrate that is significantly cleaved at more than one site. In all but one case, the 2'-deoxy substitution has little effect on binding for cleavage at the correct and incorrect sites. Substitution of the 2'-OH group at the correct site, however, decreases the cleavage chemistry by more than 3.4 kcal/mol for cleavage at both the correct and incorrect sites. Substitutions of the 2'-OH groups at the incorrect sites have no effect for cleavage at the incorrect and correct sites. Truncation of the 5' leader results in differential effects on cleavage at different sites. These observations lead to a model in which cleavage at the correct and incorrect sites involves formation of different ribozyme-substrate complexes depending on binding of specific nucleotides in the 5' leader. Binding of the T stem-loop of tRNA and the 2'-OH group at the correct cleavage site is common for all ES complexes. An A/U-rich 5' leader significantly promotes formation of the ES complex and accelerates the cleavage chemistry over those of a C/G-rich 5' leader, but only moderately enhances cleavage at the correct site over cleavage at the incorrect sites. Since cleavage at different sites requires formation of different ES complexes, cleavage site selection can occur at the level of the ES complex and at the chemical step.

Recognition of the T stem-loop of a pre-tRNA substrate by the ribozyme from Bacillus subtilis ribonuclease P

The ribozyme from bacterial ribonuclease P (denoted P RNA) specifically recognizes the coaxially stacked T stem-loop and the acceptor stem of a tRNA substrate. This recognition is mediated primarily through tertiary interactions. At least four 2'-OH groups in the T stem-loop region have been implicated as direct contacts with Bacillus subtilis P RNA [Pan, T., et al. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 12510]. Effects of six single 2'-OH --> 2'-H substitutions and two base mutants of the G19-C56 tertiary interaction in tRNA on substrate binding (Kd) and the chemical step of the reaction (k2) have been determined using a tRNA(Phe) substrate containing a 2'-deoxy residue at the cleavage site. Our results show that at least five functional groups in the T stem-loop of tRNA directly participate in P RNA binding. They include the 2'-OH groups of residues 54, 56, 61, and 62 and possibly the 4-amino group of the conserved C56. The 2'-OHs of residues 54, 61, and 62 are positioned within the same minor groove due to stacking of the reverse Hoogsteen U54-A58 pair on the G53-C61 Watson-Crick pair in the T stem. This groove is extended to the 4-amino group of C56 through the tertiary structure of tRNA. We use the term "tertiary groove" to describe alignment of functional groups through tertiary folding of an RNA. The binding also includes the 2'-OH of nucleotide C56 which is not located in this tertiary groove. Assuming additivity, these five interactions can contribute 7.4 kcal/mol or 10(5)-fold in binding but only -0.5 kcal/mol or approximately 2-fold in chemistry at 37 degrees C. The P RNA binding site for the T stem-loop includes at least the previously identified A230 as well as the A130 in B. subtilis P RNA. The Kd and k2 data from the A130G mutant of B. subtilis P RNA suggest that A130 may be proximal to residue 56 in tRNA. These results show how the highly structured T stem-loop region in a pre-tRNA substrate is bound by the B. subtilis P RNA. This is among the first examples of how a nonhelical RNA structure can be recognized by another RNA through tertiary interactions.

Domain structure of the ribozyme from eubacterial ribonuclease P

Large RNAs can be composed of discrete domains that fold independently. One such "folding domain" has been identified previously in the ribozyme from Bacillus subtilis ribonuclease P (denoted P RNA). This domain contains roughly one-third of all residues. Folding of an RNA construct consisting of the remaining two-thirds of B. subtilis P RNA was examined by Fe(II)-EDTA hydroxyl radical protection. This molecule folds into the proper higher-order structure under identical conditions as the full-length P RNA, suggesting the presence of a second folding domain in B. subtilis P RNA. Folding analysis of the Escherichia coli P RNA by hydroxyl radical protection shows that this P RNA is completely folded at 5-6 mM Mg2+. In order to analyze the structural organization of folding domains in E. coli P RNA, constructs were designed based on the domain structure of B. subtilis P RNA. Fe(II)-EDTA protection indicates that E. coli P RNA also contains two folding domains. Despite the significant differences at the secondary structure level, both P RNAs appear to converge structurally at the folding domain level. The pre-tRNA substrate, localized in previous studies, may bind across the folding domains with the acceptor stem/3'CCA contacting the domain including the active site and the T stem-loop contacting the other. Because all eubacterial P RNAs share considerable homology in secondary structure to either B. subtilis or E. coli P RNA, these results suggest that this domain structure may be applicable for most, if not all, eubacterial P RNAs. Identification of folding domains should be valuable in dissecting structure-function relationship of large RNAs.

Diagnostic accuracy of hyaluronan and type III procollagen amino-terminal peptide serum assays as markers of liver fibrosis in chronic viral hepatitis C evaluated by ROC curve analysis

Diagnostic accuracy of two serum markers of liver fibrosis, hyaluronan (HA) and amino-terminal peptide of type III procollagen (P-III-P), was studied in a cohort of 326 untreated patients with chronic viral hepatitis C. Both P-III-P (RIA-gnost P-III-P, Behring Diagnostic) and HA (HA-test, Pharmacia) serum concentrations correlated with the histological grades of liver fibrosis (P &lt; 0.001). Receiver-operating characteristic (ROC) curves showed that serum HA had greater diagnostic performance than P-III-P, both for discriminating patients with extensive liver fibrosis from those with no or mild fibrosis (area under the ROC curves: 0.864 vs 0.691, P &lt;0.001) or for discriminating patients with cirrhosis from those without cirrhosis (area under the ROC curves: 0.924 vs 0.734, P &lt;0.001). At cutoff values of 0.8 kU/L for serum P-III-P and 85 micrograms/L for serum HA, sensitivities were 70.0% and 64.5%, and specificities were 63.4% and 91.2%, respectively, for discriminating patients with extensive liver fibrosis from those with no or mild fibrosis. At the cutoff values of 1.0 kU/L for serum P-III-P and 110 micrograms/L for serum HA, sensitivities were 60.0% and 79.2%, and specificities were 74.0% and 89.4%, respectively, for discriminating patients with liver cirrhosis from those without cirrhosis. We conclude that, because the diagnostic accuracy of serum HA is greater than that of serum P-III-P as a marker of liver fibrosis, serum HA should be preferred when monitoring liver fibrosis in patients with chronic viral hepatitis C.

Diagnostic accuracy of hyaluronan and type III procollagen amino-terminal peptide serum assays as markers of liver fibrosis in chronic viral hepatitis C evaluated by ROC curve analysis

Diagnostic accuracy of two serum markers of liver fibrosis, hyaluronan (HA) and amino-terminal peptide of type III procollagen (P-III-P), was studied in a cohort of 326 untreated patients with chronic viral hepatitis C. Both P-III-P (RIA-gnost P-III-P, Behring Diagnostic) and HA (HA-test, Pharmacia) serum concentrations correlated with the histological grades of liver fibrosis (P < 0.001). Receiver-operating characteristic (ROC) curves showed that serum HA had greater diagnostic performance than P-III-P, both for discriminating patients with extensive liver fibrosis from those with no or mild fibrosis (area under the ROC curves: 0.864 vs 0.691, P <0.001) or for discriminating patients with cirrhosis from those without cirrhosis (area under the ROC curves: 0.924 vs 0.734, P <0.001). At cutoff values of 0.8 kU/L for serum P-III-P and 85 micrograms/L for serum HA, sensitivities were 70.0% and 64.5%, and specificities were 63.4% and 91.2%, respectively, for discriminating patients with extensive liver fibrosis from those with no or mild fibrosis. At the cutoff values of 1.0 kU/L for serum P-III-P and 110 micrograms/L for serum HA, sensitivities were 60.0% and 79.2%, and specificities were 74.0% and 89.4%, respectively, for discriminating patients with liver cirrhosis from those without cirrhosis. We conclude that, because the diagnostic accuracy of serum HA is greater than that of serum P-III-P as a marker of liver fibrosis, serum HA should be preferred when monitoring liver fibrosis in patients with chronic viral hepatitis C.

Erythrocyte production in iron deficiency anemia

Erythrocyte production was measured in 21 iron deficiency anemia patients after therapy with parenteral iron. The red cell mass was measured twice with 51Cr and red blood cell survival by labeling with 51Cr. In all cases, erythrocyte production increased in the 12 h following parenteral iron administration (dextran or polysaccharide-iron oxide). Production increased sharply for 3 to 6 days, remained high for 2 or 3 days and fell sharply thereafter. It is suggested that this fall is not due to a lack of available iron.

Probing of tertiary interactions in RNA: 2'-hydroxyl-base contacts between the RNase P RNA and pre-tRNA

A general method has been developed to analyze all 2' hydroxyl groups involved in tertiary interactions in RNA in a single experiment. This method involves comparing the activity of populations of circularly permuted RNAs that contain or lack potential hydrogen-bond donors at each position. The 2' hydroxyls of the pre-tRNA substrate identified as potential hydrogen bond donors in intermolecular interactions with the ribozyme from eubacterial RNase P (P RNA) are located in the T stem and T loop, acceptor stem, and 3' CCA regions. To locate the hydrogen-bond acceptors for one of those 2' hydroxyls in the P RNA, a phylogenetically conserved adenosine was mutated to a guanosine. When this mutant P RNA was used, increased cleavage activity of a single circularly permuted substrate within the population was observed. The cleavage efficiency (kcat/Km) of a singly 2'-deoxy-substituted substrate at this position in the T stem was also determined. For the wild-type P RNA, the catalytic efficiency was significantly decreased compared with that of the all-ribo substrate, consistent with the notion that this 2' hydroxyl plays an important role. For the P RNA mutant, no additional effect was found upon 2'-deoxy substitution. We propose that this particular 2' hydroxyl in the pre-tRNA interacts specifically with this adenosine in the P RNA. This method should be useful in examining the role of 2' hydroxyl groups in other RNA-RNA and RNA-protein complexes.

[Chronic viral hepatitis C. Anatomoclinical and biological correlations]

OBJECTIVES

The relations between the severity of histopathological lesions and epidemiological, clinical and biological data were studied in 86 patients with chronic viral hepatitis C.

PATIENTS AND METHODS

None of the patients had any clinical signs of decompensated liver disease. Three groups of patients were individualized according to histopathological findings: 17 (20%) had chronic persistent hepatitis, 48 (56%) had chronic active hepatitis without cirrhosis, and 21 (24%) had cirrhosis.

RESULTS

Patients with cirrhosis differed significantly from patients in the two other groups for all biological parameters. With multivariate analysis, alkaline phosphatase activity and serum hyaluronic acid were two independent parameters significantly associated with cirrhosis. A serum hyaluronic acid level above 150 micrograms/L or alkaline phosphatase activity above normal were predictive of cirrhosis with a sensitivity of 87% and a specificity of 93%. None of the parameters in this study provided a clear distinction between patients with chronic persistent and chronic active hepatitis.

CONCLUSION

Determination of serum hyaluronic acid and alkaline phosphatase activity as a non invasive index of cirrhosis could be useful for diagnosis and follow-up in patients with chronic viral hepatitis C.

Serum hyaluronan as a marker of liver fibrosis in chronic viral hepatitis C: effect of alpha-interferon therapy

BACKGROUND/AIMS

It has been suggested that increases in serum hyaluronan levels might be a marker of fibrosis in chronic viral hepatitis C. Patients receiving alpha-interferon therapy are an excellent model to determine the relationship between serum hyaluronan and liver fibrosis, since results suggest that alpha-interferon could reduce liver fibrosis.

METHODS

We studied the relationship between serum hyaluronan and histopathological indices of liver fibrosis, inflammation and necrosis, before and after alpha-interferon therapy (3 MU, three times weekly for 6 months), and the effect of treatment on serum hyaluronan and on histological liver fibrosis, in 52 patients. Hyaluronan levels were measured using a radiometric assay and the liver histopathological indices were scored according to the Knodell system.

RESULTS

The serum hyaluronan level correlated with the extent of liver fibrosis both before and after alpha-interferon therapy (p < 0.0001), but not with the histopathological indices of liver inflammation or necrosis. Parallel changes in serum hyaluronan and liver fibrosis occurred: serum hyaluronan levels fell significantly in patients in whom fibrosis improved (p < 0.01, n = 11), increased significantly in patients in whom fibrosis worsened (p < 0.05, n = 10), and did not change significantly in patients in whom fibrosis was unmodified (n = 31). Furthermore, fibrosis improved only when the antiviral effect of alpha-interferon was reflected by persistent normalization of serum alanine aminotransferase, although there was no correlation between serum hyaluronan levels and alanine aminotransferase activities.

CONCLUSION

Serum hyaluronan thus appears to be a non-invasive index of liver fibrosis.

Factors predictive of the response to interferon in patients with chronic hepatitis C

Factors predictive of the response to interferon in patients with chronic hepatitis C remain to be identified. In this study, we investigated factors predictive of the short-term response, defined as a return to normal alanine aminotransferase activity after treatment, and the long-term response defined as normal alanine aminotransferase activity 1 year after completing treatment, in 75 patients with chronic hepatitis C virus treated with recombinant alpha interferon (either 6 MU x 3/week for 3 months then 3 MU x 3/week for 3 months (n = 27) or 3 MU x 3/week for 6 months (n = 48)). At the end of treatment, 42 patients (56%) had normal alanine aminotransferase activity ("responders") and 33 (44%) had high alanine aminotransferase activity ("non-responders"). Twenty (48%) of the 42 responders had normal alanine aminotransferase activity 1 year after treatment ("sustained responders"), while 22 (52%) had high alanine aminotransferase activity ("transient responders"). The dosage of interferon was not predictive of the short-term and the long-term response to treatment. The responders differed significantly from the non-responders in terms of age, i.v. drug abuse, aspartate aminotransferase, gammaglutamyltranspeptidase and alkaline phosphatase activities, bilirubinemia, serum bile acid concentrations, prothrombin time, platelet count, ferritinemia, hyaluronic acid levels, positivity for the antibody to 5.1.1 of the recombinant immunoblot assay band and the histological fibrosis score. The following parameters were independently correlated with the short-term response in a multivariate analysis: gammaglutamyltranspeptidase activity, serum bile acid concentrations and positivity for the antibody to 5.1.1 of the recombinant immunoblot assay band.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of liver transplantation on sex-hormone disorders in male patients with alcohol-induced or post-viral hepatitis advanced liver disease

The effects of liver transplantation on the pituitary-gonadal axis and sex-hormone metabolism were evaluated by studying hormonal status (androgens, oestrogens, and gonadotropins) and sex-hormone-binding globulin levels in men with advanced liver disease of both alcoholic and viral origins. Comparison of the results prior to and 6 months after liver transplantation showed that successful liver transplantation in men induced significant differences in sex-hormone levels and in pituitary-gonadal function in both alcoholic and post-hepatitis patients. Plasma testosterone and dihydrotestosterone levels increased, oestrogen (oestrone and oestradiol) and androstenedione levels fell while gonadotropin (FSH and LH) levels increased. There was also a fall in plasma prolactin levels. Sex-hormone binding globulin plasma levels were elevated prior to transplantation and decreased thereafter. These data show that male patients with advanced liver disease have biological hypogonadism and feminization, irrespective of the aetiology, and that these abnormalities rapidly improve after successful liver transplantation. Therefore in men with advanced liver disease the biochemical signs of sex hormone disturbance are reversible and may be largely related to the liver disease.

[Hepatitis C]

Hepatitis C virus (HCV), identified in 1989, is the main agent of Non-A, Non-B hepatitis. The number of HCV carriers in France is estimated between 500,000 and 2 millions. The main risk factors for HCV infection are blood products transfusion and i.v. drug abuse. Cirrhosis occurs in 30% of cases with a delay ranging from 10 to 30 years, and hepatocellular carcinoma in 2.5% of cases. Interferon is, for instance, the only effective therapy in patients with chronic hepatitis C; however, prolonged response (in terms of transaminase normalization) after stopping treatment occurs only in 20% of patients.

The use of centrally prepared reagents in an external quality experimental trial

The authors provide the results of a short-term experimental trial in external quality assessment in 42 clinical laboratories conducted by the Mexican Ministry of Health. Assay kits for glucose, urea, and creatinine were prepared by the Ministry. The results may prove useful to organizers of external quality assessments in third-world countries who may opt for this strategy to improve performance. The laboratories performed the tests on reconstituted lyophilized control serum, also prepared by the Ministry. All three assays were performed manually using colorimetric methods. On the basis of their intralaboratory precision (coefficients of variation less than 8%, 8-12%, and greater than 12% for high, medium, and low precision, respectively), 12 laboratories demonstrated high precision for all three tests. Eight laboratories showed medium and low precision for different tests, while the other 22 fell in between. The results showed that the strategy of using centrally prepared reagents to improve interlaboratory agreement did not work well for urea and creatinine, but met expectations for glucose. The laboratories achieved an interlaboratory coefficient of variation of 10% for glucose in this first trial.