Nucleotide induced head-head interaction in myosin

Summary In isolated myosin the reaction sequence of essential thiol groups with N-ethylmaleimide was studied using the following five approaches: kinetics of the modification reaction, effects of modification on enzyme properties, affinity chromatography of isolated subfragment-1 stemming from modified myosin, isolation of cyanogen bromide peptides and identification of the tryptic thiol peptides thereof. All techniques involved revealed differences whether the modification was performed in the presence or absence of pyrophosphate on the one hand and in the presence of ADP or ATP on the other. In the former cases the two thiol-1 groups per myosin, one per active site, reacted at an equal rate indicating an equivalent microenvironment of these groups and hence a symmetric site-site relationship. In contrast, the nucleotides induce the sequential modification of thiol-1 on one head followed by the thiol-2 on the other head. This indicates non-equivalence in microenvironment of the essential thiols connected with each active site and hence that a form of asymmetric head-head interaction is operative.     

Elevated troponin T levels in a female carrier of Duchenne muscular dystrophy with normal coronary angiogram: a case report and review of the literature

We present the case of a 48-year-old female carrier of Duchenne muscular dystrophy (DMD) with repeatedly documented levels of elevated troponin T without arguments for cardiac ischaemia. Elevated levels of troponin T are frequently reported in DMD patients and may function as a useful cardiac index to assess dystrophic degeneration of the myocardium in a subclinical stage. Cardiac troponins may help the clinician to diagnose myocardial damage in a very early stage of cardiac impairment independently from skeletal muscle degeneration.     

High definition plus colonoscopy combined with i-scan tone enhancement vs. high definition colonoscopy for colorectal neoplasia: A randomized trial

Background

High definition endoscopy is the accepted standard in colonoscopy. However, an important problem is missed polyps.

Aims

Our objective was to assess the additional adenoma detection rate between high definition colonoscopy with tone enhancement (digital chromoendoscopy) vs. white light high definition colonoscopy.

Methods

In this prospective randomized trial patients were included to undergo a tandem colonoscopy. The first exam was a white light colonoscopy with removal of all visualized polyps. The second examination was randomly assigned in a 1:1 ratio as either again white light colonoscopy (Group A) or colonoscopy with tone enhancement (Group B). Primary endpoint was the adenoma detection rate during the second withdrawal (sample size calculation – 40 per group).

Results

67 lesions (Group A: n = 34 vs. Group B: n = 33) in 80 patients (mean age 61 years, male 64%) were identified on the first colonoscopy. The second colonoscopy detected 78 additional lesions: n = 60 with tone enhancement vs. n = 18 with white light endoscopy (p < 0.001). Tone enhancement found more additional adenomas (A n = 20 vs. B n = 6, p = 0.006) and identified significantly more missed adenomas per subject (0.5 vs. 0.15, p = 0.006).

Conclusions

High definition plus colonoscopy with tone enhancement detected more adenomas missed by white light colonoscopy.     

Age assessment of the Spitalfields cemetery population by rib phase analysis

Accurate paleodemographic reconstruction depends in large part on the ability to estimate age at death from the skeleton. Thus, it is important to evaluate the reliability of standards utilized for this assessment. The rib phase technique has proven to be one of the most consistently reliable means of determining age in modern human adults. A recent study also demonstrated that this method can be applied to Neandertals because they exhibit the same pattern of age-related change. However, the efficacy of the rib phases in aging archaeological populations of anatomically modern humans has not been systematically examined. Therefore, the purpose of this paper is to determine if ribs from the 16th to 18th century Spitalfields cemetery population (with church records of age at death) manifest a morphological aging pattern similar to that found in the recent specimens upon which the rib phase standards are based. Age was assessed on a sample of 87 individuals using only the sternal ends of the ribs without access to the rest of the skeleton or records of age and sex. Results indicated that Spitalfields ribs exhibit essentially the same aging patterns found in the ribs of modern Whites. Overall, the demographic profile generated from the ribs produced a good approximation of this sample in both range and distribution. Error was in the direction of underaging, and results for males were better than for females. The present findings indicate that the rib can be considered a reliable site for age estimation in archaeological populations. © 1995 Wiley-Liss, Inc.     

Action of bencyclane-hydrogen-fumarate on the carbohydrate metabolism of bovine lens homogenates

1-Benzyl-1-(3-dimethylaminopropoxy)cycloheptane (bencyclane-hydrogen-fumarate; Fludilat) in a concentration of 10-2 M effects an increase in the O2 consumption and the formation of CO2 in a 10% bovine lens homogenate. This effect is even increased if the glucose-substrate supply is raised from 25 mM to 37 mM. Investigations on the concentrations at ATP, ADP and AMP show that bencyclane is able to stabilize the physiologic distribution pattern of the three free adenine nucleotides. Further, the observed changes in the distribution pattern indicated that the fumaric acid rest of bencyclane may serve as a substrate for this reaction in the same way as fumarate.     

Characterization of phospholipase A2 activity in aspirates of human pancreatic pseudocysts after isolation by reversed-phase high performance liquid chromatography

Summary Phospholipase A (PLA) is able to attack membrane phospholipids and thereby plays a putative role in the pathogenesis of pancreatic pseudocysts. We looked for PLA₂-like activity in aspirates from human pancreatic pseudocysts. In material originating from one cyst which occurred shortly after an acute pancreatitis attack, hydrolyzing enzymatic activity measured by a sensitive bioassay system for PLA₂ activity was found without prior trypsin activation (67×10³ U/min/100 µl). A biochemical characterization of this hydrolyzing enzymatic activity was provided after resolution of the respective proteins contained in the cyst fluid by HPLC. High hydrolyzing activities were found in correspondence to one specific, early eluting peak. The purified enzyme had pH optima at 3.5 and 6. Addition of EDTA (5 mM) to the test system abolished the enzymatic activity which mirrored the requirement for calcium ions. The activity was optimal at calcium concentrations ranging from 1–2 mM. Higher calcium concentrations reduced the enzymatic activity. The enzyme showed high heat stability. SDS-gel analysis of the peak showed one single band with a molecular weight of about 20,000 Daltons. Our findings demonstrate the possibility of activated, PLA-like activity in human pancreatic pseudocyst fluid. We speculate that an inappropriate activation of this enzyme in peri- or intrapancreatic fluid collections could account for pseudocyst formation after an acute pancreatitis attack.