Physical properties of a single-motif erythrocyte spectrin peptide: a highly stable independently folding unit

Spectrin is a long flexible rod-like actin cross-linking protein mostly comprised of many tandem homologous 106-residue motifs. In this study, the conformational stability and physical properties of a single homologous motif peptide, alpha1, were evaluated and compared to intact spectrin monomers and alphabeta heterodimers. It is interesting that while spectrin dimers elongate by about 3-fold in low ionic strength buffers relative to their size in physiological buffers, the single-motif peptide does not show significant changes in secondary structure in 10 mM phosphate buffer compared with isotonic buffer. This single-motif peptide is monomeric in physiological buffer as demonstrated by equilibrium sedimentation studies, and its hydrodynamic radius determined by gel filtration and dynamic light scattering of about 2.2 nm is consistent with an elongated rod-like shape. Unfolding of the single-motif peptide in urea solutions was similar to unfolding of intact heterodimers. Differential scanning calorimetry analyses showed that this single motif undergoes a reversible two-state transition with a Tm of 53 degrees C and an enthalpy of 65 kcal/mol in physiological buffer. Thermal stability was unaffected by ionic strength changes, but was decreased below physiological pH. These data show that this 13 kDa spectrin motif is a monomeric, highly stable, triple-helical, independently folding protein building block with physical characteristics that define many of the structural properties of the 526 kDa spectrin heterodimer. In contrast, interactions between adjacent motifs are probably responsible for spectrin's molecular flexibility and elasticity.     

Isolation of an amoeba naturally harboring a distinctive Legionella species

There are numerous in vitro studies documenting the multiplication of Legionella species in free-living amoebae and other protozoa. It is believed that protozoa serve as host cells for the intracellular replication of certain Legionella species in a variety of environmental settings. This study describes the isolation and characterization of a bacterium initially observed within an amoeba taken from a soil sample. In the laboratory, the bacterium multiplied within and was highly pathogenic for Acanthamoeba polyphaga. Extracellular multiplication was observed on buffered charcoal yeast extract agar but not on a variety of conventional laboratory media. A 16S rRNA gene analysis placed the bacterium within the genus Legionella. Serological studies indicate that it is distinct from previously described species of the genus. This report also describes methods that should prove useful for the isolation and characterization of additional Legionella-like bacteria from free-living amoebae. In addition, the characterization of bacterial pathogens of amoebae has significant implications for understanding the ecology and identification of other unrecognized bacterial pathogens.     

Electrocardiographically gated myocardial perfusion SPECT: technical principles and quality control considerations

BACKGROUND: Apoptosis in vivo has been identified in developing cartilage from embryonic chick sterna and avian and murine growth plates. To date, no evidence exists that chondrocytes in articular cartilage undergo apoptosis. METHODS: We examined the distribution of cells demonstrating fragmented DNA in the articular knee cartilage of C57BL/6 mice (aged 11, 18, 24, and 30 months) and Wistar rats (aged 6, 12, and 24 months) using a DNA end-labeling technique. RESULTS: Control experiments utilizing retinoic acid-induced apoptosis in a chondrocyte cell line, established that DNA end-labeling correlated with DNA ladder formation. In vivo, apoptotic cells were detected in articular cartilage tissue in both species examined. The percentage of apoptotic cells increased significantly (P < 0.05 with age) for all joint surfaces in both species. No significant difference was found between the medial and lateral or femoral and tibial joint surfaces of the knee. Apoptotic cells were observed in both the calcified and uncalcified regions of the articular cartilage of C57 mice. In the rat, only the calcified region of articular cartilage contained apoptotic cells. CONCLUSIONS: These results suggest that apoptosis plays a role in some aspect of maintenance, remodeling, or turnover of mature articular cartilage. In addition, the increase in apoptosis associated with aging could contribute to the greater risk for cartilage degeneration.     

Heme packing motifs revealed by the crystal structure of the tetra-heme cytochrome c554 from Nitrosomonas europaea

Cytochrome c554 (cyt c554), a tetra-heme cytochrome from Nitrosomonas europaea, is an essential component in the biological nitrification pathway. In N. europaea, ammonia is converted to hydroxylamine, which is then oxidized to nitrite by hydroxylamine oxidoreductase (HAO). Cyt c554 functions in the latter process by accepting pairs of electrons from HAO and transferring them to a cytochrome acceptor. The crystal structure of cyt c554 at 2.6 A resolution shows a predominantly alpha-helical protein with four covalently attached hemes. The four hemes are arranged in two pairs such that the planes of the porphyrin rings are almost parallel and overlapping at the edge; corresponding heme arrangements are observed in other multi-heme proteins. Striking structural similarities are evident between the tetra-heme core of cyt c554 and hemes 3-6 of HAO, which suggests an evolutionary relationship between these redox partners.     

Early high dose antioxidant vitamins do not prevent bronchopulmonary dysplasia in premature baboons exposed to prolonged hyperoxia: a pilot study

The effect of two different types of functional ankle-foot orthosis on the gait of patients with spastic hemiplegia was studied. A gap was cut into the conventional stiff orthosis to allow a limited dorsiflexion of 10-15 degrees, while plantarflexion was blocked (spring type). This gap was bridged by an aluminum bar to stiffen the orthosis for the experiment. Fourteen patients of different ages (6.5-20.1 years) walked barefoot and with the orthosis, once springy and once stiff. Kinetics and kinematics were analyzed. Gait was significantly improved into normal pattern by using any type of ankle-foot orthosis. While walking barefoot with a toe-heel-toe gait, the physiological heel-toe gait was restored with any type of orthosis. The spring type of orthosis was significantly superior to the stiff orthosis. This was most clearly expressed in the general parameters of gait-like cadence, velocity, and step length. Kinetic data gave a significant improvement by using any ankle-foot orthosis. Whereas break force was similar with both types, push-off was further improved with the spring type. Kinematics revealed little statistical difference between the two types, although gait was more dynamic and physiological with the spring type of orthosis. Any functional ankle-foot orthosis ameliorates the gait pattern in patients with spastic hemiplegia, but a spring type of orthosis renders the gait more dynamic and best corrects the pathology of gait.     

Perspectives of patients with terminal renal failure: quality of life and psychological adjustment before and in the first year after heart transplantation

This prospective study was designed to compare quality of life, life satisfaction, and subjective ratings of health before and at variable time intervals after heart transplantation (HTx). 175 patients were included between February 1994 and December 1997. Every six months before and 1 1/2, 3, 6, and 12 months after HTx, they received the following standardized and validated questionnaires: German SF 36, heart failure and specific transplant symptom list, global quality of life assessment, Munich life quality dimension list, expected/experienced life changes after HTx. Inclusion criteria were the acceptance of the patient on the waiting list for HTx, good command of the German language, and a minimum age of 18 years. During data evaluation, median (Me), mean (M), and standard deviation (SD) were created from individual parameters. Quality of life was rated as very poor by 84% of patients with congestive heart failure. Only 6 weeks after HTx, 74% rated their quality of life as significantly better. Before HTx 80% were very unsatisfied about their health status and 87% about physical performance. Six weeks after HTx, this parameter improved significantly and 76% were very satisfied about their health status and 50% about physical performance. While somatic changes expected before HTx corresponded well with experienced ones, psychological improvements were smaller than expected, but one year after HTx they were significant (before: M = 3.66; SD = 0.9; Range (R) = 3.78 vs 12 months postop: M = 4.61; SD = 0.6; R = 2.67; p < 0.05). Quality of life correlated before HTx best with subjectively rated health (r = 0.61, p < 0.01) and 6 months after with satisfaction about health status (r = 0.76, p < 0.01). Only in 25% were expected improvements fulfilled regarding sexual activity/satisfaction, professional situation, and recreational activities. 90% of post-transplant patients reported physical complaints, most by effects of immunsuppression, but were coping well. The study shows that already 6 weeks after successful HTx all quality of life parameters improved significantly. Despite some unfulfilled expectations and complaints, the postoperative life situation of HTx patients appeared significantly improved.     

Evidence of genomic instability in Campylobacter jejuni isolated from poultry

Poultry isolates of Campylobacter jejuni derived from a survey of meat processing batches were genotyped by pulsed-field gel electrophoresis (PFGE) of chromosomal DNA to establish the clonal relationships between single-colony isolates. In the majority of batches studied, one or two genotype patterns predominated. However, in one batch (batch A), 21 single-colony isolates gave 14 different PFGE genotypes. The banding patterns obtained with SmaI were sufficiently different to distinguish between genotypes, although the patterns also produced many common bands. The question of whether these isolates represented different clones or had a common clonal ancestry was addressed by additional genotypic and phenotypic methods. Restriction length polymorphism of PCR products obtained from the flagellin genes showed an identical flagellin genotype for all of these isolates. In contrast, unrelated control isolates resulted in different flagellin genotypes. Moreover, all 14 different PFGE genotypes of batch A had identical Penner serotypes and identical or similar biotypes and phage types. It was concluded that the isolates were of clonal origin and that the diversity in the PFGE banding patterns had most likely originated from genomic rearrangements. However, the PFGE genotypes were shown to be stable upon subculturing in vitro and after in vivo passage in chickens, and natural transformation between isogenic mutants carrying antibiotic markers did not occur in vivo in a chick colonization model. The possible mechanisms for the hypothesized genomic recombinations and the conditions that allow, induce, or select for such events are discussed.     

Skin injury in the operating room

Judge Christian Byk renders service to the Steering Committee on Bioethics of the Council of Europe (CDBI) by proposing a draft of the protocol destined to fill in a gap in international law on the status of the human embryo. This proposal, printed in a previous issue of the Journal of Medical Ethics deserves nevertheless to be questioned on important points. Is Christian Byk proposing to legalise research on human embryos not only in vitro but also in utero?     

Differential dependency of unmyelinated and A delta epidermal and upper dermal innervation on neurotrophins, trk receptors, and p75LNGFR

This study investigates discrepancy and congruence between doctors and patients in their beliefs about the need for medical treatment. One hundred seventy-six outpatients and 337 university students rated each of a set of 35 symptoms on the urgency with which they would seek medical advice were they experiencing that symptom. Sixty-six general practitioners rated the urgency with which a person experiencing that symptom should seek medical advice. These symptoms were classified as relatively serious or nonserious on the basis of ratings by a separate set of doctors. General practitioners perceived a greater overall need for treatment than did patients, but this difference was greater for nonserious than for serious symptoms. In fact patients perceived treatment to be more urgent for three serious symptoms, each potentially indicative of cancer. The observed pattern of doctor-patient discrepancies can be explained in terms of the availability heuristic. The role of this heuristic in the cognitive dynamics of doctor-patient relationships merits future attention.