Continued development of the Nimbus/University of Pittsburgh (UOP) axial flow left ventricular assist system

Nimbus and the University of Pittsburgh (UOP) have continued the development of a totally implanted axial flow blood pump under the National Institutes of Health (NIH) Innovative Ventricular Assist System (IVAS) program. This 62 cc device has an overall length of 84 mm and an outer diameter of 34.5 mm. The inner diameter of the blood pump is 12 mm. It is being designed to be a totally implanted permanent device. A key achievement during the past year was the completion of the Model 2 pump design. Ten of these pumps have been fabricated and are being used to conduct in vitro and in vivo experiments to evaluate the performance of different materials and hydraulic components. Efforts for optimizing the closed loop speed control have continued using mathematical modeling, computer simulations, and in vitro and in vivo testing. New hydraulic blade designs have been tested using computational fluid dynamics (CFD) and flow visualization. A second generation motor was designed with improved efficiency. To support the new motor, a new motor controller fabricated as a surface mount PC board has been completed. The program is now operating under a formal QA system.     

Nitrite levels in breath condensate of patients with cystic fibrosis is elevated in contrast to exhaled nitric oxide

BACKGROUND: Nitric oxide (NO) is released by activated macrophages, neutrophils, and stimulated bronchial epithelial cells. Exhaled NO has been shown to be increased in patients with asthma and has been put forward as a marker of airways inflammation. However, we have found that exhaled NO is not raised in patients with cystic fibrosis, even during infective pulmonary exacerbation. One reason for this may be that excess airway secretions may prevent diffusion of gaseous NO into the airway lumen. We hypothesised that exhaled NO may not reflect total NO production in chronically suppurative airways and investigated nitrite as another marker of NO production. METHODS: Breath condensate nitrite concentration and exhaled NO levels were measured in 21 clinically stable patients with cystic fibrosis of mean age 26 years and mean FEV1 57% and 12 healthy normal volunteers of mean age 31 years. Breath condensate was collected with a validated method which excluded saliva and nasal air contamination and nitrite levels were measured using the Griess reaction. Exhaled NO was measured using a sensitive chemiluminescence analyser (LR2000) at an exhalation rate of 250 ml/s. Fourteen patients with cystic fibrosis had circulating plasma leucocyte levels and differential analysis performed on the day of breath collection. RESULTS: Nitrite levels were significantly higher in patients with cystic fibrosis than in normal subjects (median 1.93 microM compared with 0.33 microM). This correlated positively with circulating plasma leucocytes and neutrophils (r = 0.6). In contrast, exhaled NO values were not significantly different from the normal range (median 3.8 ppb vs 4.4 ppb). There was no correlation between breath condensate nitrite and lung function and between breath condensate nitrite and exhaled NO. CONCLUSIONS: Nitrite levels in breath condensate were raised in stable patients with cystic fibrosis in contrast to exhaled NO. This suggests that nitrite levels may be a more useful measure of NO production and possibly airways inflammation in suppurative airways and that exhaled NO may not reflect total NO production.     

The endogenous agonist quinolinic acid and the non endogenous homoquinolinic acid discriminate between NMDAR2 receptor subunits

The polysialic acid (polySia) capsule of Escherichia coli K1 is a key virulence determinant of the organism, allowing it to evade host defenses. The proteins necessary for expression of the capsule are encoded by the 17 kb kps gene cluster. This cluster contains two genes, kpsM and kpsT, that are required for polySia transport across the cytoplasmic membrane. KpsM is a hydrophobic integral inner membrane protein, while KpsT is a peripheral inner membrane protein that binds ATP. They belong to the ATP-binding cassette (ABC) superfamily of transporters. To study the role of KpsT in polySia translocation, we used PCR mutagenesis to isolate dominant negative mutations of plasmid-encoded kpsT. All mutations mapped to the same glutamic acid residue at position 150, adjacent to Walker motif B of KpsT. Wild-type (kps+) cells harboring one such allele, E150G, did not transport polySia to the cell surface but accumulated intracellular polysaccharide and produced small colonies containing cells that grew as long filaments. The E150G protein still bound ATP as shown by 8-azidoATP photolabeling assays. We combined the E150G allele with each of five mutations isolated previously in kpsT. Mutations that disrupt ATP-binding (K44E) or alter regions of the protein thought to interact with KpsM (G84D, S126F) suppressed the dominant negative phenotype while mutations in the C-terminal portion of the protein (C163Y, H181Y) did not suppress. These studies have allowed the development of a working model for the role of KpsT in polySia chain translocation.     

Ultrastructural evidence for intra- and extranuclear projections of GABAergic neurons of the suprachiasmatic nucleus

GABAergic projections of the suprachiasmatic nucleus (SCN) were demonstrated in a double-labelling ultrastructural study which visualised the efferents of the SCN by PHA-L tracing, diaminobenzidine (DAB) immunocytochemistry, and GABA with immunogold postembedding staining. The results show a strong contralateral projection of the SCN that is partly GABA-containing. In addition, ipsilateral SCN projections to the dorsomedial hypothalamus and periventricular part of the paraventricular nucleus and sub-paraventricular nucleus were shown to contain GABA. The present results indicate that the SCN may utilize this inhibitory neurotransmitter to regulate and organize its own circadian rhythm as well as using GABA to transmit its diurnal information to other regions of the brain.     

Relation between the space flight-induced frequency of dominant lethal mutations and the level of allozyme heterozygosity in Drosophila melanogaster populations

Currently, the treatment of falciparum malaria is seriously compromised by spreading drug resistance. We studied the effects of camptothecin, a potent and specific topoisomerase I inhibitor, on erythrocytic malaria parasites in vitro. In Plasmodium falciparum, camptothecin trapped protein-DNA complexes, inhibited nucleic acid biosynthesis, and was cytotoxic. These results provide proof for the concept that topoisomerase I is a vulnerable target for new antimalarial drug development.     

Increased immune activation precedes the inflection point of CD4 T cells and the increased serum virus load in human immunodeficiency virus infection

In sickness-conditioned learning, animals become ill after sampling a new substance and develop an aversion that is expressed as avoidance of that substance in subsequent presentations. We examined the parameters of a one-trial, nongustatory, sickness-conditioned learning task in day-old chicks. Chicks pecked a bead and were made ill by i.p. injection of lithium chloride (LiCl). Both 0.5 and 1.0 M LiCl (0.1 ml) produced reliable avoidance at test. Chicks injected with LiCl between 15 and 45 min after training avoided the bead at test, whereas those injected within 5 or 10 min or more than 45 min after training did not. Avoidance was present until 24 h posttraining and absent after 48 h. Therefore, robust learning of the sickness-conditioned learning task occurs in one trial without the need for gustatory cues, and memory for the task lasts at least 24 h. Uses of this task to study memory formation in the day-old chick are discussed.     

Design and evaluation of a device for measuring three-dimensional micromotions of press-fit femoral stem prostheses

Implant micromotion is considered to be a major factor in the loosening of cementless total hip replacements. Translational micromotion at the bone-implant interface generally occurs in all three spatial directions. Under physiological loading, the interfacial micromotion consists of a cyclic amplitude and changes in the mean, which, in the cranio-caudal direction, represents subsidence of the prosthesis. Existing measurement strategies, which are based on dial gauges, extensometers, LVDTs, hall-effect transducers or strain gauge techniques provide information about only one component of the general three-dimensional micromovement. Moreover, in the majority of the studies, the data are difficult to interpret due to the measured motions being composed of interfacial micromotion and femoral strains. A new transducer was designed that allows the accurate measurement of all three isolated components of micromotion. An optoelectronic approach, based on silicon position-sensitive detectors (PSD) in combination with high precision mechanical parts, was chosen. To exclude thermodrifts during long-term testing, a thermistor was integrated in the sensor. Validation experiments on a precision positioning table indicated the high precision and resolution of the developed sensors. Furthermore, in-vitro tests on a standard press-fit prosthesis demonstrated the easy handling and reliability of the system.     

Expression of an antigen homologous to the human CO17-1A/GA733 colon cancer antigen in animal tissues

The CO17-1A/GA733 antigen is associated with human carcinomas and some normal epithelial tissues. This antigen has shown promise as a target in approaches to passive and active immunotherapy of colorectal cancer. The relevance of animal models for studies of immunotherapy targeting this antigen in patients is dependent on the expression of the antigen on normal animal tissues. Immunohistoperoxidase staining with polyclonal rabbit antibodies to the human antigen revealed the human homologue on normal small intestine, colon and liver of mice, rats and non-human primates, whereas mouse monoclonal antibodies to the CO17-1A or GA733 epitopes on the human antigen did not detect the antigen. Polyclonal rabbit antibodies, elicited by the murine antigen homologue derived from recombinant baculovirus-infected insect cells, immunoprecipitated the antigen from mouse small intestine, colon, stomach, kidney and lung. The isolated recombinant murine protein bound polyclonal, but not monoclonal, antibodies to the human CO17-1A/GA733 antigen, and recombinant human antigen bound polyclonal antibodies elicited by the murine antigen homologue. Thus, the antigen homologue expressed by animal tissues is similar, but not identical, to the human antigen. These results have important implications for experimental active and passive immunotherapy targeting the CO17-1A/GA733 antigen.     

Relationships between left hemisphere predominance and disturbances of lipid metabolism in different ethnic groups

In neonates and infants, hearing impairment leads to impaired language and cognitive development. For that reason, early detection of this sensory deficit is of outstanding importance, particularly in pre-term neonates, who constitute a high risk population in regard to very early acquired hearing loss. Evoked (EOAE) and spontaneous otoacoustic emission (SOAE) recording in 93 pre-term and full-term neonates revealed that this technique is potentially useful for auditory screening in neonatology units. EOAEs and SOAEs can be recorded successfully from 30 weeks of conceptional age. SOAEs were found to be prevalent in females and presented higher peak numbers in right than in left ears. Furthermore, SOAE incidence in pre-term and full-term neonates was found to be high in EOAE positive ears, associated with strong and robust EOAEs.