Kinetic characterization of human immunodeficiency virus type-1 protease-resistant variants

Passage of human immunodeficiency virus type-1 (HIV-1) in T-lymphocyte cell lines in the presence of increasing concentrations of the hydroxylethylamino sulfonamide inhibitor VX-478 or VB-11328 results in sequential accumulation of mutations in HIV-1 protease. We have characterized recombinant HIV-1 proteases that contain these mutations either individually (L10F, M46I, I47V, I50V) or in combination (the double mutant L10F/I50V and the triple mutant M46I/I47V/I50V). The catalytic properties and affinities for sulfonamide inhibitors and other classes of inhibitors were determined. For the I50V mutant, the efficiency (kcat/Km) of processing peptides designed to mimic cleavage junctions in the HIV-1 gag-pol polypeptide was decreased up to 25-fold. The triple mutant had a 2-fold higher processing efficiency than the I50V single mutant for peptide substrates with Phe/Pro and Tyr/Pro cleavage sites, suggesting that the M46I and I47V mutations are compensatory. The effects of mutation on processing efficiency were used in conjunction with the inhibition constant (Ki) to evaluate the advantage of the mutation for viral replication in the presence of drug. These analyses support the virological observation that the addition of M46I and I47V mutations on the I50V mutant background enables increased survival of the HIV-1 virus as it replicates in the presence of VX-478. Crystal structures and molecular models of the active site of the HIV-1 protease mutants suggest that changes in the active site can selectively affect the binding energy of inhibitors with little corresponding change in substrate binding.     

Oesophagostomum spp. in pigs: resistance to reinfection

For a study on the occurrence of resistance to reinfection with porcine nodular worm species, pigs were infected twice weekly with 1,000 infective larvae (L3) of Oesophagostomum quadrispinulatum for 8 weeks. All pigs, including noninfected controls, were then treated with fenbendazole. At 10 days after treatment, all pigs received a single challenge inoculation of 5,000 L3 of either O. dentatum or O. quadrispinulatum, respectively. Pigs were slaughtered at 6 weeks after the challenge infection for determination of their worm burdens. The pigs trickle- and challenge-infected with O. quadrispinulatum had significantly lower egg excretion levels (P < 0.01) and worm burdens (P < 0.05) than challenge control pigs, thus indicating some degree of host immunity against the homologous challenge infection. No resistance to reinfection was evident for the heterologous challenge infection. This study elucidates further aspects of the interaction between nodular worm species in the pig.     

5-Benzylidene 1,2-dihydrochromeno[3,4-f]quinolines, a novel class of nonsteroidal human progesterone receptor agonists

A novel series of nonsteroidal progestins, 5-benzylidene-1, 2-dihydrochromeno[3,4-f]quinolines (2), was discovered, and a preliminary structure-activity relationship study around the 5-benzylidene ring generated several potent human progesterone receptor agonists (compounds 8, 16). These new progestins showed biological activities (EC50 = 5.7 and 7.6 nM) similar to progesterone (EC50 = 2.9 nM) in the cotransfection assay with high efficacy (132% and 166%) and binding affinity (Ki = 0.66 and 0.83 nM) similar to medroxyprogesterone acetate (MPA) (Ki = 0.34 nM). A representative analogue, 8, demonstrated similar oral potency to MPA in the uterine wet weight/mammary gland morphology assay in ovariectomized rats.     

Relationship between intracranial pressure and the development of vasospasm after aneurysmal subarachnoid hemorrhage

The relationship between intracranial pressure (ICP) and the development of vasospasm after subarachnoid hemorrhage caused by the rupture of an intracranial aneurysm was investigated. Eleven patients were divided into high (6 cases) and low (5 cases) ICP groups based on ICP data obtained during the perioperative period by continuous ICP monitoring. Transcranial Doppler ultrasonography was performed every 24 hours for 7 days and the severity, distribution, and duration of vasospasm were assessed. The high ICP group tended to have severe, prolonged, and diffuse vasospasm compared with the low ICP group. However, only duration of vasospasm was statistically different. The relationship between cerebral perfusion pressure (CPP) and the development of vasospasm was also examined. CPP had a less significant effect than ICP although similar tendencies for high ICP and low CPP were observed. High ICP worsens vasospasm and treatment for decreasing ICP with perioperative ICP monitoring has potential for avoiding the development of vasospasm.     

A process for identifying marginal performers among students in a clerkship

PURPOSE: To evaluate a review process for identifying marginal performers among students in a clerkship. METHOD: To better identify the marginal performers among the students participating in the medicine clerkship at the University of Minnesota Medical School--Minneapolis, the Medicine Clerkship Committee reviewed in 1990-91 and 1991-92 all students rated by faculty or housestaff as below expectations for any of nine areas of clinical performance (27 students of 890, 3%). (In the past, a student was considered to be a marginal performer only if he or she was assigned an unsatisfactory numerical grade, calculated from the nine ratings, or if written comments by housestaff and faculty and the opinions of the attending faculty and clerkship site coordinator indicated that the student should fail.) Chi-square analysis was used to compare the number of students judged to be marginal performers under the review process with the number of marginal performers in 1988-89 and 1989-90. The two groups were also compared based on their preclerkship performances on standardized examinations. RESULTS: Ten of those reviewed (37%) were judged to have performed marginally. Although the study group's performance on standardized examinations was not different from that of students during the previous two years, significantly fewer students were identified as marginal performers before the review process began than afterwards (2 of 867, 0.2%, versus 10 of 890, 1.1%, p < .05). CONCLUSION: Without changing the way in which faculty and housestaff evaluated students, the review process improved the medicine clerkship evaluation system by identifying significantly more students who were marginal performers.     

Morphologic changes in age-related maculopathy

Age-related maculopathy (ARM) is a degenerative disorder of the central part of the retina with a rising prevalence in patients 50 years of age and older, and comprises different histopathological changes. The morphologic changes in ARM are described and illustrated with light-microscopical, electron microscopical, and fundus pictures. Furthermore, the most important biochemical data are given. The most prominent aging changes in early stages of ARM are drusen and basal laminar deposit (BLD), both extracellular deposits, that are assumed to be important in the development of ARM. Drusen accumulate within Bruch's membrane, whereas BLD is present between Bruch's membrane and the retinal pigment epithelium. Although the histopathologic characteristics of the deposits are well documented, the chemical composition has only been partly resolved. Biochemical analysis of these deposits is necessary to determine the source of the deposits and to find possible ways to avoid or treat them. The late stages of ARM, geographic atrophy, and neovascular (disciform) degeneration, are called age-related macular degeneration (AMD), and result in severe and irreversible visual impairment. Since there is still no adequate therapy for the majority of people disabled by AMD, and because of the aging population resulting in even more patients with this disease, it is necessary to intensify the research on ARM in order to prevent AMD or find a therapy for it.     

Development of fatigue lifetime predictive test methods for hip implants: part I. Test methodology

The fatigue failure of hip joint prostheses will be expected to assume more importance in second generation implants aimed at younger, more active patients. Furthermore, new designs and material combinations including coatings (e.g. hydroxyapatite) may introduce fatigue problems that as yet have not been considered. The current research makes an initial attempt to develop accelerated fatigue testing procedures to enhance the methodology of hip implant lifetime prediction. Tests conducted on a 'model' four point bendbar testpiece (mill-annealed Ti-6A1-4V) highlighted that the accelerated test must be conducted in a physiological solution such as Ringer's at 37 degrees C. The introduction of superimposed block overloads (50 cycles) to signify stair ascent/descent or fast walking and single overloads to signify sit/stand movements or stumbling were found to reduce fatigue life by > 50%. The findings of this fatigue study were combined with biomechanics studies to construct a variable amplitude 'in-service' load spectrum for testing hip implants. Using ambulatory trial data, a simple load sequence was designed containing 4 single (sit/stand movements) and 3 block (stair ascent/descent) overloads that repeated ten times gave one days activity; single overloads repeated every 110 base cycles (normal walking) and block overloads 80, 110 (morning/evening) and 250 (daytime) base cycles.     

Incidental acantholysis

The incidental finding of microscopic foci of acantholytic dyskeratosis, reproducing the histological pattern of Darier's disease, has been the subject of a number of papers in the last few years. In contrast, the incidental finding of other types of acantholysis has not been mentioned in the literature. In the last 5 years, we have noticed such a microscopic finding in 14 biopsy specimens (0.15% of our cutaneous specimens). they were from 13 patients (7 men and 6 women); their ages ranged from 37 to 79 years (mean, 63). Three lesions were located on the head, 7 on the trunk, and 4 on the limbs. The histological diagnoses were basal cell carcinoma (6 cases), keratoacanthoma (2 cases), psoriasis (2 cases), elastolytic granuloma, acral arteriovenous angioma, tinea corporis, and leukocytoclastic vasculitis (1 case each). The histological patterns of the acantholytic foci simulated pemphigus vulgaris (9 cases), superficial pemphigus (1 case), Hailey-Hailey disease (3 cases), and unclassifiable acantholysis (1 case). None of the patients had familial or personal history of acantholytic disorders. We propose a classification of the primary acantholytic disorders based on both their acantholytic pattern and their clinical extent.