Problems and concerns among medical students--1975

Students at the University of Colorado School of Medicine were surveyed using an inventory of problems and conerns relating to their personal and academic lives. Results were to provide a data base for improvement of their educational environment via the ecosystem design process. The survey revealed that chief among student conerns are a lack of personal freedom, excessive academic pressures, and feelings of dehumanization. A marked trend toward increasing difficulty with thoughts of having chosen the wrong profession is noted over the four class levels. The authors offer several hypotheses relating to the underlying conditions responsible for these findings and discuss their possible relation to the current malpractice insurance crisis.     

Unipolar versus bipolar hemiarthroplasty for the treatment of femoral neck fractures in the elderly

This paper presents the short term results of an ongoing prospective randomized trial comparing a cemented unipolar with a cemented bipolar hemiarthroplasty for the treatment of displaced femoral neck fractures in the elderly. Forty-seven patients with an average age of 77 years completed 6-month followup. Outcomes at 6 weeks, 3 months and 6 months were assessed by completion of a patient oriented hip outcome instrument and by functional tests of walking speed and endurance. No differences in the postoperative complication rates or lengths of hospitalization were seen between the two groups. Patients treated with a bipolar hemiarthroplasty had greater range of hip motion in rotation and abduction and had faster walking speeds. However, no differences in hip rating outcomes were found. These early results suggest that use of the less expensive unipolar prosthesis for hemiarthroplasty after femoral neck fracture may be justified in the elderly.     

Magnetic resonance imaging of elephantiasis neuromatosa

We present the case of a 43-year-old man with neurofibromatosis type 1 who developed elephantiasis neuromatosa of his left leg. The gross limb enlargement was extremely disfiguring, and resulted in such severe disability that he was only able to walk a very short distance using crutches. Previous debulking procedures had resulted in massive blood loss, and prior to attempting further surgical intervention MRI studies were requested. Taking advantage of the excellent tissue characterisation and multiplanar imaging capabilities of MRI, we were able to assess the extent of soft tissue and osseous involvement. The use of recently developed MR angiographic sequences enabled us to non-invasively provide detailed images to assess the relationship of the lesions to the major vessels, as well as the vascular supply and angiographic features of the lesions themselves. This article describes our MRI-based findings, which precluded debulking surgery in this unusual manifestation of neurofibromatosis.     

UV- and gamma-radiation sensitive mutants of Arabidopsis thaliana

Arabidopsis seedlings repair UV-induced DNA damage via light-dependent and independent pathways. The mechanism of the "dark repair" pathway is still unknown. To determine the number of genes required for dark repair and to investigate the substrate-specificity of this process we isolated mutants with enhanced sensitivity to UV radiation in the absence of photoreactivating light. Seven independently derived UV sensitive mutants were isolated from an EMS-mutagenized population. These fell into six complementation groups, two of which (UVR1 and UVH1) have previously been defined. Four of these mutants are defective in the dark repair of UV-induced pyrimidine [6-4]pyrimidinone dimers. These four mutant lines are sensitive to the growth-inhibitory effects of gamma radiation, suggesting that this repair pathway is also involved in the repair of some type of gamma-induced DNA damage product. The requirement for the coordinate action of several different gene products for effective repair of pyrimidine dimers, as well as the nonspecific nature of the repair activity, is consistent with nucleotide excision repair mechanisms previously described in Saccharomyces cerevisiae and nonplant higher eukaryotes and inconsistent with substrate-specific base excision repair mechanisms found in some bacteria, bacteriophage, and fungi.     

Localization of the gene for thiamine-responsive megaloblastic anemia syndrome, on the long arm of chromosome 1, by homozygosity mapping

Thiamine-responsive megaloblastic anemia, also known as "TRMA" or "Rogers syndrome," is an early-onset autosomal recessive disorder defined by the occurrence of megaloblastic anemia, diabetes mellitus, and sensorineural deafness, responding in varying degrees to thiamine treatment. On the basis of a linkage analysis of affected families of Alaskan and of Italian origin, we found, using homozygosity mapping, that the TRMA-syndrome gene maps to a region on chromosome 1q23.2-23.3 (maximum LOD score of 3.7 for D1S1679). By use of additional consanguineous kindreds of Israeli-Arab origin, the putative disease-gene interval also has been confirmed and narrowed, suggesting genetic homogeneity. Linkage analysis generated the highest combined LOD-score value, 8.1 at a recombination fraction of 0, with marker D1S2799. Haplotype analysis and recombination events narrowed the TRMA locus to a 16-cM region between markers D1S194 and D1S2786. Several heterozygote parents had diabetes mellitus, deafness, or megaloblastic anemia, which raised the possibility that mutations at this locus predispose carriers in general to these manifestations. Characterization of the metabolic defect of TRMA may shed light on the role of thiamine deficiency in such common diseases.     

A state observer for the Virgo inverted pendulum

We report an application of Kalman filtering to the inverted pendulum (IP) of the Virgo gravitational wave interferometer. Using subspace method system identification techniques, we calculated a linear mechanical model of Virgo IP from experimental transfer functions. We then developed a Kalman filter, based on the obtained state space representation, that estimates from open loop time domain data, the state variables of the system. This allows the observation (and eventually control) of every resonance mode of the IP mechanical structure independently.     

Trypanosoma cruzi: protective response of vaccinated mice is mediated by CD8+ cells, prevents signs of polyclonal T lymphocyte activation, and allows restoration of a resting immune state after challenge

Currently, there is no vaccine available against Chagas' disease. Immune abnormalities induced by T. cruzi pose particular difficulties for vaccine development, since immunological memory must be able to overcome them to prevent spread of infection/sequelae. We have previously demonstrated that experimental vaccination with live CL-14 trypomastigotes does not induce polyclonal lymphocyte activation, immunosuppression, or pathology and efficiently immunizes against virulent T. cruzi. Herein we show that: (1) expansion of CD4+ and CD8+ subsets peaks 2 weeks after infective challenge in both challenged-vaccinated mice and infected controls, but the former exhibit a smaller increase in blastogenesis and in the numbers of activated CD11a(hi)CD4+ and CD11a(hi)CD8+ cells; (2) in long-term-vaccinated mice, expansion of activated subsets (CD62Llo/- and CD11a(hi)) is accelerated among CD8+ PBL 1 week after challenge; (3) challenged-vaccinated mice retract the CD8+-activated subset 5 weeks after challenge, different from infected controls; (4) protection conferred by CL-14 immunization can be adoptively transferred to na?ve recipients with lymphocyte suspensions, and prior depletion of CD8+ (but not of CD4+) cells abolishes protective immunity. Our findings indicate that protective immunity generated by CL-14 immunization involves a transient CD8+ recall response and is capable of preventing the signs of polyclonal lymphocyte activation induced by virulent challenge.     

A feasibility study of steam-jet refrigeration

In this paper a feasibility study of steam-jet refrigeration is conducted. First and second law analyses as well as the economics of a steam-jet refrigeration system are presented. Thermodynamic parameters investigated include the coefficient of performance (COP), refrigerating effect, condenser heat rejection, motive steam requirements, second law efficiency, and system irreversibility. Economic parameters investigated include equipment costs, space needs, power requirements, and installed and operational costs. © 1998 John Wiley & Sons, Ltd.