Infection of catheterised patients: bacterial colonisation of encrusted Foley catheters shown by scanning electron microscopy

Summary The surfaces of 32 encrusted urinary catheters were examined by scanning electron microscopy to investigate the association of bacteria with the encrusting deposits. Deposits consisted of struvite crystals surrounded by aggregates of very small crystallites of hydroxyapatite. Underneath these minerals there was a layer of closely packed bacteria. Impressions of bacteria were also observed in hydroxyapatite. Crystals were often engulfed by the bacterial layer, which thus appeared to bind the crystals to each other and to the catheter surface. This thick layer of bacteria associated with crystals may protect both the bacteria from antibiotics and the crystals from acidic bladder washout solutions intended to dissolve them. Furthermore, the existence of this sessile population explains why urease-producing bacteria are not invariably detected in the urine of patients with encrusted catheters. The observation of this bacterial layer (or biofilm) by scanning electron microscopy provided direct evidence for infection being implicated in catheter encrustation.     

'Breaking' position-invariant object recognition

While it is often assumed that objects can be recognized irrespective of where they fall on the retina, little is known about the mechanisms underlying this ability. By exposing human subjects to an altered world where some objects systematically changed identity during the transient blindness that accompanies eye movements, we induced predictable object confusions across retinal positions, effectively 'breaking' position invariance. Thus, position invariance is not a rigid property of vision but is constantly adapting to the statistics of the environment.     

Distribution of glucose incorporated into macromolecular material by treponema pallidum.

Treponema pallidum was observed to incorporate glucose carbons into lipids, ribonucleic acid, deoxyribonucleic acid, and protein. Only the glycerol portions of phosphatidylcholine and phosphatidylglycerol contained glucose-derived carbons. Incorporation of exogenous choline into phosphatidylcholine was detected. Glucose was incorporated into only the pentoses of nucleic acids. About 50% of the glucose incorporated into protein was present in only one amino acid, aspartate. Evidence suggests that aspartate synthesis could follow the conversion of phosphoenolpyruvate to oxalacetic acid by a guanosine 5'-diphosphate-dependent phosphoenolpyruvate carboxykinase.     

Arterial wall properties and dietary atherosclerosis in the racing greyhound.

The effects of experimental (dietary) atherosclerosis on arteries from racing greyhounds were studied. Measurements of pressure and external diameter were made on islated carotid and iliac arteries under active (norepinephrine, 5 microgram/ml) and passive (zero Ca2+ and 2 mM EGTA) smooth muscle conditions. Iliac arteries from diet-fed animals demonstrated substantial intimal lesions, but the carotid arteries were usually grossly involved. Arteries from atherosclerotic animals were stiffer during passive conditions, with the iliac arteries having the greater changes. In iliac arteries from treated animals, collagen and elastin contents were decreased, and the collagen-to-elastin ratio was increased; in carotid arteries from treated animals, elastin content was increased and the collagen-to-elastin ratio was decreased. The maximum range of control of arterial wall mechanics by smooth muscle was diminished in treated iliacs but unchanged in carotids. Both force development and constriction responses associated with smooth muscle activation were diminished in treated iliacs but unchanged in treated carotids. Mechanical properties of series elastic elements in treated iliacs were stiffer, but treated carotids were unchanged.     

Genome-wide linkage analysis of families with obsessive-compulsive disorder ascertained through pediatric probands

The goal of this study was to identify chromosomal regions likely to contain susceptibility alleles for early-onset obsessive-compulsive disorder (OCD). A genome scan was done in 56 individuals from seven families ascertained through pediatric OCD probands; 27 of the 56 subjects had a lifetime diagnosis of definite OCD. Denser mapping of regions on chromosomes 2, 9, and 16 was subsequently done with those subjects and ten additional subjects from the largest family in the study. Direct interviews were completed with 65 of the 66 genotyped individuals. Relatives were interviewed blind to proband status. Of the 65 interviewed individuals, 32 had a lifetime diagnosis of definite OCD. Three of the seven probands had a history of Tourette disorder. Two of the 25 relatives with OCD had a tic history, whereas none of the 33 relatives without OCD had tics. The genome scan consisted of 349 microsatellite markers with an average between-marker distance of 11.3 centiMorgan (cM). Fine mapping was done with 24 additional markers at an average spacing of 1.6 cM. Parametric and nonparametric linkage analyses were conducted using GENEHUNTER(+). The maximum multipoint LOD score with a dominant model was 2.25 on 9p. However, with fine mapping and additional subjects, that LOD score decreased to 1.97. The maximum multipoint nonparametric LOD* score was 1.73 on 19q. The maximum multipoint LOD score with a recessive model was 1.40 on 6p. The results provide suggestive evidence for linkage on 9p and identify regions requiring further study with much larger samples.     

Malaria transmission and naturally acquired immunity to PfEMP-1

Why there are so few gametocytes (the transmission stage of malaria) in the blood of humans infected with Plasmodium spp. is intriguing. This may be due either to reproductive restraint by the parasite or to unidentified gametocyte-specific immune-mediated clearance mechanisms. We propose another mechanism, a cross-stage immunity to Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP-1). This molecule is expressed on the surface of the erythrocyte infected with either trophozoite or early gametocyte parasites. Immunoglobulin G antibodies to PfEMP-1, expressed on both life cycle stages, were measured in residents from an area where malaria is endemic, Papua New Guinea. Anti-PfEMP-1 prevalence increased with age, mirroring the decline in both the prevalence and the density of asexual and transmission stages in erythrocytes. These data led us to propose that immunity to PfEMP-1 may influence malaria transmission by regulation of the production of gametocytes. This regulation may be achieved in two ways: (i) by controlling asexual proliferation and density and (ii) by affecting gametocyte maturation.     

Vascular lesions in testes associated with male infertility in Cameroon

Summary Testicular biopsies in 40 of 41 infertile males with severe oligospermia in Cameroon presented massive subendothelial fibrinoid deposits in the small and medium sized vessels. Fibrinogen, complement and IgM were demonstrated in these deposits by immunofluorescence. Evidence strongly suggestive of parasitic testicular involvement was also observed in 2 cases.It is postulated that the fibrinoid deposits are the result of repeated formation and deposition of circulating immune complexes by reaction of antibodies with antigens. These antigens could be of various origins and in the cases described here they could be derived from living or dying parasites in the region. The accumulation and incorporation of the fibrinoid deposits may lead to vascular stenosis resulting in chronic ischaemia, tubular atrophy and fibrosis, and finally oligospermia.     

Improved chamber for the isolation of anaerobic microorganisms.

A small portable chamber for the recovery of anaerobic bacteria is described. This rigid chamber is constructed of clear acrylic with dimensions of 30 inches (ca. 76.2 cm) wide, 18 inches (ca. 44.7 cm) deep, and 18 inches (ca. 44.7 cm) high. Conventional bacteriological techniques can be used inside the chamber to efficiently isolate strict anaerobic organisms. An adapter allows the attachment of a standard anaerobic jar to the outside of the chamber. The jar can be used to store reduced media. Once the jar is attached to the chamber and the media is removed to the interior of the chamber, the jar is available to receive inoculated media. The anaerobic jar can then be removed from the chamber, without contaminating the jar or chamber with oxygen, and be placed in a conventional 37degreesC incubator. This chamber also allows the microbiologist to process cultures without wearing gloves as was necessary with previous anaerobic chambers. Air-tight latex rubber sleeves seal around the microbiologists arms and to the armport flange of the chamber to prevent the introduction of oxygen into the chamber. Anaerobic conditions are maintained by circulating a 80% N2, 10% H2, 10% CO2 gas mixture through alumina pellets coated with palladium. This study indicates that anaerobic conditions obtained in this chamber are sufficient for recovery of obligate anaerobes.     

Homozygosity for the predominant Cys282Tyr mutation and absence of disease expression in hereditary haemochromatosis.

A candidate gene for hereditary haemochromatosis, HLA-H, has recently been presented. Two missense mutations in the HLA-H gene sequence are predicted to account for nearly 90% of all cases of the disease. The aim of this study was to correlate the presence of these missense mutations with the expressivity of the disease, as assessed by standard biochemical evaluation of serum iron parameters. Detection of the known mutations in haemochromatosis, Cys282Tyr and His63Asp, was undertaken in a large pedigree showing variable expression of the disease in successive generations. In three sibs with overt disease (one male, two female, aged 50 to 53 years), homozygosity for the predominant G to A transition (Cys282Tyr) in HLA-H was detected. However, homozygosity for this mutation was also detected in an asymptomatic male sib, aged 50, harbouring an identical genotype. The finding of an asymptomatic homozygous Cys282Tyr subject, haplo-identical to affected sibs, indicates that clinical expression of symptomatic disease is variable, even in middle aged Cys282Tyr homozygotes. This has profound implications for the future use of genetic screening for haemochromatosis.