Effect of chilling on the survival of Bacteroides fragilis.

Factors affecting the susceptibility of Bacteroides fragilis subsp. fragilis to low temperature were examined. Predetermined numbers of cells were spread on agar media or suspended in enriched Trypticase soy broth and exposed to low temperature under both aerobic and anaerobic conditions. Exposure of 18-h growth of a freshly isolated B. fragilis strain to 4 degrees C aerobically or anaerobically resulted in a loss of at least 50% viability after 12 h. B. fragilis cells in early growth (6 h) were more tolerant to exposure at 4 degrees C than older cells (18 h). When the freshly isolated strain was repeatedly subcultured in the laboratory it was uniformly more cold tolerant than fresh clinical isolates. The incorporation of 1.0 M sucrose and 5 mM magnesium chloride into liquid media partially alleviated the lethal effects of cold temperature on B. fragilis subsp. fragilis.     

A bi-allelic VNTR in the human TNFR2 (p75) gene promoter

We describe a bi-allelic VNTR polymorphism within a 42 bp region in the promoter of the tumour necrosis factor receptor 2 gene (TNFR2). Within this region there are one (Allele 1) or two (Allele 2) repeats of a 15 bp sequence, 5'-GCCGGGC AGGTGGAG-3'. Allele frequencies observed in a Caucasian population were 0.3 (Allele 1) and 0.7 (Allele 2).     

Decreased phenylalanine uptake and turnover in patients with vitiligo

The human epidermis has the full machinery for autocrine L-phenylalanine turnover to L-tyrosine in keratinocytes and melanocytes. Phenylalanine hydroxylase (PAH) activities increase linearly with inherited skin colour (skin phototype I-VI, Fitzpatrick classification) yielding eightfold more activities in black skin compared to white skin. Moreover, UVB irradiation (1 MED) significantly increases epidermal PAH activities 24 h after exposure. Importantly, L-phenylalanine uptake and turnover in the pigment forming melanocytes is vital for initiation of melanogenesis. In this context it was shown that the uptake of this amino acid is regulated by calcium. The depigmentation disorder vitiligo provides a unique model to follow impaired L-phenylalanine turnover in the skin as well as in serum because affected individuals hold an impaired epidermal 6BH4 de novo synthesis/recycling and regulation including low epidermal PAH activities. After overnight fasting and oral loading with L-phenylalanine (100 mg/kg body weight), 29.6% of 970 patients tested (n=287/970) yielded serum phenylalanine/tyrosine ratios >or=4 and 35.3% (n=342/970) had mild to moderate hyperphenylalaninaemia (HPA), while 9.3% (n=90/970) had both serum L-phenylalanine levels >or=2.0 mg/dl and phe/tyr ratios >or=4.0. Isolated HPA was found in 26% (n=252/970), whereas 20.3% had only increased ratios (n=197/970). None of the patients had phenylketonuria and the family history for this metabolic disease was negative. The IQ followed normal Gaussian distribution. In vitro L-phenylalanine uptake/turnover studies on primary epidermal melanocytes originating from these patients demonstrated a significantly decreased calcium dependent L-phenylalanine uptake and turnover compared to healthy control cells. Based on our observation, we would like to propose that phenylalanine uptake/turnover is under tight control by calcium which in turn could offer an additional novel mechanism in the aetiology of HPA.     

Computational fluid dynamics modeling of impeller designs for the HeartQuest left ventricular assist device

To finalize the design of the next generation of the HeartQuest left ventricular assist device, a suitable impeller had to be designed and tested. The new prototype was based on calculations and test results of previous designs, but required several changes to decrease the size. For most pump designs, this is a simple matter of altering impeller geometry and rotational speed to achieve the desired pressure rise and flow rate. However, this particular pump was limited by housing geometry and the magnetic bearings that support the impeller. Without much freedom in the overall impeller size, the only parameters open to the designers were the blade profiles and the rotating speed. Rather than build several candidates and test them in a rig at enormous cost, computational models of several designs were tested and analyzed. This not only saved money, but also sped up the development time for the project. The computer models were developed in TASCflow, a computational fluid dynamics software package from AEA Technologies. This paper analyzes the data from several of the selected models, paying close attention to pumping performance and general trends from specific design changes.     

Clonal T-cell populations in lymphomatoid papulosis. Evidence of a lymphoproliferative origin for a clinically benign disease

Lymphomatoid papulosis is a chronic, clinically benign skin disorder that, when examined histologically, is seen to include numerous large, atypical lymphoid cells that display antigenic markers of T lymphocytes. To investigate the disparity between the clinical behavior of this disease and its malignant histologic appearance, we analyzed the DNA from skin lesions of six patients for rearrangements of beta and gamma T-cell receptor genes. Lesions from five of these patients showed between one and three clonal rearrangements for at least one T-cell receptor gene. Three separate biopsy specimens from a single patient showed different patterns of rearrangements for the beta gene in each specimen. Our results indicate that lymphomatoid papulosis is a clonal T-cell lymphoproliferative process that may possibly be multiclonal in origin. We conclude that this disease has both biologic and histologic features consistent with a malignant T-cell neoplasm despite its indolent course.     

Characterization of an inversion duplication of the short arm of chromosome 8 by fluorescent in situ hybridization

A de novo chromosome aberration in a woman with severe mental retardation and minor anomalies has been characterized cytogenetically. The patient's karyotype was described as 46, XX, inv dup (8)(p12 → p23.1). Previous Southern blot dosage studies with the marker locus D8S7 demonstrated that the patient was monosomic for this locus, suggesting that the rearrangement generated a duplication-deficiency chromosome. We have reinvestigated this patient using fluorescent in situ hybridization with chromosome 8 cosmids and an Alu-PCR product specific for 8p. These studies have confirmed directly that the duplicated chromosome also has undergone deletion. © 1992 Wiley-Liss, Inc.