Problems of Sensing Tachyarrhythmias by an Antitachycardia Pacemaker (Symbios 7008)

Atrial burst pacing is an effective method of terminating supraventricular tachycardia. In the patient presented in this report, a Symbios 7008 pacemaker (Medtronic Inc., Minneapolis, MN, USA) was implanted for two reasons: (1) severe AV conduction defect (AH, 230 msec; HV, 150 msec) and bifascicular block following anterior myocardial infarction; and (2) paroxysmal atrial flutter. The conduction defect ruled out programming other than atrial burst in DDD mode. Activation of burst pacing required appropriate programming of the "tachycardia detection window" on the basis of the cycle length of the flutter waves. In the case reviewed, episodes of atrial flutter with variable cycle lengths of 230 to 280 msec necessitated reprogramming of the AV interval, the refractory period, and the upper rate interval. The use of an antitachycardia device in automatic mode may be limited by variations in tachycardia cycle length.     

Trypanosoma brucei infection in nude mice: B lymphocyte function is suppressed in the absence of T lymphocytes

B lymphocyte function was assessed in outbred nude mice and nu/+controls infected with Trypanosoma brucei brucei. On day 10 of the infection in outbred nu/nu mice in which the initial wave of parasites was strongly controlled, B cell function was unaltered on enhanced compared with uninfected animals or infected nu/+. In other nu/nu mice unable to control the initial parasitaemia, thymidine incorporation and Ig secretion by spleen cells were increased on day 10 and their response to lipopolysaccharide in vitro negated. By day 15 however, even the spleen cells of infected nu/nu which controlled the initial wave of parasites were proliferating and secreting Ig on removal from the mice and they were unable to respond to LPS in vitro. These experiments confirm results of a previous study of B cell function in T cell-depleted mice (Askonas et al. 1979). T. b. brucei infection of mice causes both enhanced Ig production and suppression of the ability of B cells to respond to mitogen even in the absence of T cells, but the presence of T cells may accelerate the changes which occur in B lymphocytes following this infection.     

Project Megapoles: Promoting better health for socially disadvantaged groups across Europe

A new public health network is looking at ways of achievingbetter health and reducing differences in health between Europe'scapital cities. A report from the Socially Disadvantaged Groupssub-network of Megapoles.     

Hand function in relation to brain lesions and corticomotor‐projection pattern in children with unilateral cerebral palsy

Aim To investigate relationships between hand function, brain lesions, and corticomotor projections in children with unilateral cerebral palsy (CP). Method The study included 17 children (nine males, eight females; mean age 11.4 [SD 2.4] range 7–16y), with unilateral CP at Gross Motor Function Classification System level I and Manual Ability Classification System level I or II. Hand function was assessed with the Box and Blocks test and Assisting Hand Assessment (AHA). Conventional structural magnetic resonance images were assessed visually for type, location, and extent of brain lesions. Single‐pulse transcranial magnetic stimulation (TMS) provided information on organization of corticomotor projections. Results The most favourable hand function was seen in children who had white‐matter damage of immaturity with mild white‐matter loss and contralateral motor projections. Children with ipsilateral projections had the most impaired function. Nevertheless, in this subgroup a range of ability was seen (AHA 29–59%). Motor‐projection patterns appeared to be influenced by lesion extent and location, but not by lesion type. Interpretation Combining information from structural magnetic resonance images and TMS can improve prediction of hand function. A wide variation in hand function was seen within all motor‐projection patterns. Although the most impaired hand function was seen in the ipsilateral motor‐projection group, some children in this group had fairly good ability. Such information is important for treatment planning.     

Computerised version of the Chou and Fasman protein secondary structure predictive method

A DEC-SYSTEM 10 FORTRAN computer program to carry out secondary structure prediction of proteins, according to the algorithm of Chou & Fasman (1, 2), is described. Program results are compared with predictions made by Chou & Fasman.     

PRIMARY STRUCTURE OF LOBSTER-MUSCLE ARGININE KINASE: Amino and Carboxyl-terminal Structure of the Enzyme and Complete Alignment of the Cyanogen-Bromide Peptides

The acetylation state of the blocked NH₂-terminal end of arginine kinase was characterized by the occurrence of 1 mol acetyl group/mol protein; a 5-residue segment corresponding to the amino-terminal portion was isolated from a pronase digest of the enzyme and its amino acid sequence determined as N-acetyl Ala-Asx-Ala-Ala-Thr. Arginine kinase is terminated at the carboxyl end by the sequence Lys-Glu-MetOH; this particular 3-residue sequence is repeated three times in the overall structure of the protein and is present in three CNBr fragments. One of these, a peptide of 14 amino acid residues, was identified in the course of this study and its amino acid sequence determined. Its location at the COHO-terminal end of the enzyme was recognized on the basis of investigations carried out with des-MetOH-Glu-arginine kinase, a specific proteolytic derivative. The alignment of the eight CNBr-fragments which constitute the arginine kinase molecule was established according to the sequential and compositional properties of seven unique tryptic methionyl peptides isolated from the whole protein. The alignment was confirmed by using BNPS-skatole fragments of the enzyme as another protein source.     

Synthesis of a metal binding protein designed on the α/β scaffold of charybdotoxin*

The α/β scaffold of the scorpion toxin charybdotoxin has been used for the engineering of a metal binding site. Nine substitutions, including three histidines as metal ligands, have been introduced into the original toxin sequence. The newly designed sequence, 37 amino acids long, has been assembled by solid-phase synthesis and HBTU (2-(1H-benzotriazol-l-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate) coupling of Fmoc-protected amino acids. Formation of the three disulfide bonds occurred efficiently and rapidly in the presence of glutathione, and this post-synthesis modification has facilitated the purification task enormously. The process of synthesis and purification was performed in less than a week with an overall 10.2°, yield. Circular dichroism analysis showed that the newly designed protein is folded in a α/β structure, similarly to the parent toxin. Electronic absorption spectroscopy, circular dichroism and gel filtration experiments have been used to show that Cu²⁺ and Zn²⁺ ions bind with high affinity to the newly engineered protein. These results demonstrate that the α/β fold, common to all scorpion toxins, is a very versatile basic structure, tolerant for substitutions and able to present new sequences in a predetermined conformation. The chemical approach is shown to be effective, rapid and practical for the production of novel designed small proteins. © Munksgaard 1995.     

The efficiency of irrigants in removing root canal debris when used with an ultrasonic preparation technique

Summary. Three types of irrigant, 2.6 per cent sodium hypochlorite, water and Solvidont were compared for their ability to remove debris during root canal preparation with ultrasonically operated K files. Twenty-seven freshly extracted human teeth were divided into three groups, and each group prepared using one of the irrigants. The teeth were sectioned longitudinally, stained and photographed for assessment by a ranking system. Canals prepared with sodium hypochlorite were found to have significantly less debris remaining than those prepared with water or Solvidont. No significant difference was found between preparations with water and Solvidont.