Biomedical subjects
R L Thompson
Publications and source records attributed to R L Thompson.
Herpes simplex virus type 1 dUTPase mutants are attenuated for neurovirulence, neuroinvasiveness, and reactivation from latency.
Herpes simplex virus type 1 (HSV-1) encodes a dUTPase which has been shown to be dispensable for normal viral replication in cultured cells (S. J. Caradonna and Y. Cheng, J. Biol. Chem. 256:9834-9837, 1981; F. B. Fisher and V. G. Preston, Virology 148:190-197, 1986). However, the importance of this enzyme in vivo has not been determined. In this report, HSV-1 strain 17 syn+ and two isogenic engineered dUTPase-negative mutants were characterized in the mouse model. Both mutants replicated with wild-type kinetics and achieved wild-type titers in cultured cells. The mutants were 10-fold less neurovirulent than 17 syn+ following intracranial inoculation and more than 1,000-fold less virulent following footpad inoculation. The dUTPase- mutants replicated with wild-type kinetics in the footpad and entered and replicated efficiently in the peripheral nervous system of the mouse. However, their replication in the central nervous system was significantly reduced. The dUTPase- strains established latent infections but displayed a greatly reduced reactivation frequency in vivo. Neurovirulence, neuroinvasiveness, and reactivation frequency were all restored by recombination with wild-type dUTPase sequences. These results have important implications with regard to anti-herpesvirus therapeutic strategies.
Rapid in vivo reactivation of herpes simplex virus in latently infected murine ganglionic neurons after transient hyperthermia.
A rapid and physiologically relevant hyperthermia-based induction procedure has been utilized to develop an in vivo model of induced herpes simplex virus (HSV) reactivation in outbred Swiss Webster mice. This procedure was found to efficiently reactivate latent virus from both trigeminal and lumbosacral ganglia. Examination of the time between hyperthermia and virus production demonstrated that detectable levels of infectious virus were present in ganglia as soon as 14 h posttreatment, with peak percent recoveries at 24 h. These data indicated that the switch from latent to active viral gene transcription occurred rapidly following treatment. Immunohistochemical staining for HSV type 1 antigens revealed rare antigen-positive ganglionic neurons 24 h postinduction. HSV antigens were not detected in any other cell type, and lateral spread of the infection was not observed. This is the first report of the detection of HSV antigens in vivo following induced reactivation in the intact nervous system and demonstrates that the neuron is the site of infectious virus production. In addition, our data strongly suggest that at least some neurons in which HSV antigens are detected during reactivation do not survive. Because the temporal and spatial characteristics of HSV reactivation have been clearly defined, this model is uniquely suited for the molecular dissection of the reactivation process.
Herpes simplex virus type 1 latency-associated transcription unit promotes anatomical site-dependent establishment and reactivation from latency.
Defined herpes simplex virus type 1 (HSV-1) mutants KOS/1 and KOS/62 (positive and negative, respectively, for latency-associated transcripts [LATs]) express the Escherichia coli beta-galactosidase (beta-Gal) gene during latency. These mutants were employed to assess the functions of the latency-associated transcription unit on establishment and maintenance of and reactivation from the latent state. It was found that in the trigeminal ganglia, the frequencies of hyperthermia-induced reactivation of KOS/62 and an additional LATs- mutant (KOS/29) were reduced by at least 80%. Quantification of latently infected neurons expressing the beta-Gal gene revealed that the LATs- mutant KOS/62 established approximately 80% fewer latent infections in the trigeminal ganglia than did KOS/1 (LATs+). This reduction in establishment which is evident in the trigeminal ganglia could account for the reduced frequency of reactivation from this site. In striking contrast, both LATs- mutants reactivated with wild-type frequencies from lumbosacral ganglia. Quantification of beta-Gal-positive neurons at this site revealed that KOS/62 established as many as or more latent infections than the LATs+ virus, KOS/1. Colocalization of HSV antigen and beta-Gal suggested that the decreased establishment by LATs- mutants in trigeminal ganglia was the result of inefficient viral shutoff. Thus, one function of the HSV-1 LATs transcription unit is to promote the establishment of latency in trigeminal but not lumbosacral ganglia. Such a function may be relevant to understanding the distinct clinical recurrent disease patterns of HSV-1 and HSV-2.
1987 to 1991 cost and utilization of Class IV HIV patients.
The 1987 to 1991 direct medical costs and service utilization of Class IV Human Immunodeficiency Virus (HIV) patients cared for at a Group Health Cooperative of Puget Sound (GHC) are described and compared across four time periods: 1987-'88, 1989, 1990, and 1991. Cost and utilization information for an age- and sex-matched control group of GHC enrollees not having Class IV HIV conditions are also compared to those of the Class IV HIV group. Data are presented on pharmacy, inpatient care, outpatient visits by physician specialty, laboratory, radiology, home health/hospice and other costs. The costs of the Class IV HIV population are, on average, 20 times those of the control group. The percent distribution of the control group's costs did not experience much change from 1989 to 1991. Conversely, the Class IV HIV group experienced a shift in costs from the inpatient to outpatient setting from 1987-'88 to 1989. This shift was temporary, as the locus of care shifted back to the inpatient setting over the following 2 years. Anecdotal evidence suggests that antiretroviral treatment may have led to a period in which patients required less intensive settings to manage their illness. Inpatient costs may have increased as the initial benefit of zidovudine treatment began to wane. The Class IV HIV population had greater percent of total expenses in pharmacy, laboratory, radiology, and home health/hospice services, and lower percent of total expenses in outpatient primary and specialty care than the control group.
Plasma factor VII is activated by postprandial triglyceridaemia, irrespective of dietary fat composition.
Nine adults took two 7-day diets of standardised energy and total fat content, but with a dietary polyunsaturated/saturated fat ratio of less than 0.3 and greater than 3.0 respectively, while adhering to their daily routine. Blood was drawn on 6 occasions between 09.00 and 22.45 h on the final day of each dietary period for factor VII activity (VIIc), factor VII antigen (VIIag) and lipoprotein lipid concentrations. Diurnal variation was described for each variable in terms of its deviation from the individual's daily mean value at each time point across the day. Plasma triglyceride remained low until after the midday meal, whereafter a marked rise was sustained into the later evening. Plasma VIIc declined until early afternoon, but showed a marked rise in the late afternoon. Plasma VIIag showed no significant diurnal variation. Changes in plasma triglyceride concentration during the day were related positively to changes in VIIc about 160 min later, but not to VIIc at other time points. This effect of postprandial triglyceridaemia on VIIc persisted after allowance for the effect of VIIag on VIIc. Dietary fat composition did not influence VIIc or VIIag. The results suggested an acute but evanescent effect of triglyceride-rich lipoproteins on the reactivity of factor VII, irrespective of their lipid core composition.
Singlet and triplet reactivity in the photoreduction of oxonine(3,7-diaminophenoxazin-5-ium chloride) by iron (II).
The oxazine dye, oxonine (3,7-diaminophenoxazin-5-ium chloride), 1, is photoreduced by Fe (II) sulfate in dilute sulfuric acid. The reaction mechanism is analogous to that for the photo-reduction of thiazine dyes by Fe (II), the most important difference being that reduction of oxonine occurs predominantly from its excited singlet state, S1, rather than from the triplet state, T1. The latter is formed with an intersystem crossing (isc) quantum yield of ca 1.7 x 10(-3). The quenching of S1 by Fe (II) has a rate constant kSQ = 2.2 +/- 0.1 x 10(9) M-1 s-1 and affords the one electron reduced product, semioxonine (R), with a limiting quantum yield, phi SR, of 0.26 +/- 0.02. In contrast, quenching of T1, generated by bromide ion quenching of S1 or by diacetyl sensitization, occurs with KTQ approximately 1.2 x 10(6) M-1 s-1, extrapolated to zero ionic strength, and affords R with a limiting probability, phi TR = 1.1 +/- 0.2. Three possible reasons for the lower quantum yield of the more exothermic S1 reduction are discussed. These are energy transfer from S1 to Fe (II), different rates of escape of R from the encounter complex as a consequence of the different states of protonation of R as initially formed from S1 and T1, and spin allowed back electron transfer in an exciplex formed between S1 and Fe (II). Evidence is also presented for a very low probability (ca 1%) induced isc from the encounter of S1 with paramagnetic Fe (II). Rate parameters for other processes important to the overall reduction mechanism such as disproportionation of R to leucooxonine L and oxonine, k(R)DIS = 1.7 +/- 0.2 x 10(9) M-1 s-1, oxidation of R by Fe (III), k(R)OX = 1.5 +/- 0.1 x 10(5) M-1 s-1, and oxidation of L by Fe (III), kLOX = 1.1 +/- 0.1 x 10(3) M-1 s-1, have also been measured. These results are contrasted with those for the closely related thionine/Fe(II) photoredox reaction, the most well understood system for photogalvanic energy conversion.
A novel comprehensive DUE program--five years of experience.
A comprehensive program has been developed to evaluate prescribing practices in diverse drug therapy categories and in all areas of the institution. Input for topic selection comes not only from the pharmacy department, but also from QA, medical staff, and nursing. The development of monitoring criteria and review of the results by the P&T Committee, Medical Executive Committee, and other key medical staff members, promotes ownership of the program by the medical staff. The benefit of this ownership is active support for the program and participation in peer review. Overall, the results of this cost-effective program include limited use of broad spectrum antibiotics, select prescribing of high-risk drugs, and focused educational efforts to improve quality of patient care. The primary goal for the future of the program is to develop criteria and documentation mechanisms for reporting measurable clinical outcomes. In making the transition, it is important to use the success and impact of the current program as the foundation. This is particularly true for the concurrent monitoring program and its immediate feedback mechanism. The major challenge will be evaluating negative clinical outcomes and developing corrective actions as well as documenting the positive outcomes and the avoidance of negative outcomes of the current program. To meet this challenge, the DUE program must be integrated with all other institutional QA programs. Although a difficult task, this is a significant yet necessary step in the right direction for assuring optimal patient care.
Surgical training posts in Northern Ireland: assessment by surgeons in training.
Northern Ireland has one of the largest surgical training programmes in the United Kingdom. The surgical trainees' assessment of the quality of training provided has been collated prospectively since 1983, and provides a useful insight into the strengths and weaknesses of the programme, as well as the training value of individual posts. The overall quality of clinical training in surgery was considered to be well above average, but some registrars felt that supervision of operative surgery could be improved. Clinical research was considered to be of average quality in the teaching hospitals but below average in district general hospitals. In the current climate of restriction of the number of training posts in general surgery, the views of the trainees should not be neglected in assessing which posts are best suited for training.
Development and reversibility of T lymphocyte dysfunction in experimental obstructive jaundice.
This study evaluates the effect of experimental biliary obstruction by bile duct ligation (BDL) and biliary drainage on cell-mediated immunity in Wistar rats. Immune status has been assessed by a mitogen stimulation test of T lymphocytes with phytohaemagglutinin. Animals were followed for up to 35 days after BDL. Regression analysis showed a significant negative correlation between lymphocyte function and the period of jaundice (correlation coefficient -0.57, P less than 0.001). Following BDL for 21 days, groups of animals had internal biliary drainage for 7, 14 and 28 days, and external drainage for 14 days. Compared with obstructed animals, 14 days internal drainage was required to improve lymphocyte function (P less than 0.05). Animals which had 14 days of external drainage had significantly lower lymphocyte stimulation than internal drainage animals (P less than 0.05). The results demonstrate that obstructive jaundice produces a progressive reduction of T lymphocyte function. This can be reversed by biliary drainage, internal drainage being more effective than external drainage.
Infections related to central venous catheters.
Infection is a potentially life-threatening complication of central venous catheterization. Although line-related bacteremias and sepsis are relatively uncommon, the frequent use of central lines in the intensive-care unit makes these infections a common consideration. Semiquantitative culture techniques for analysis of the catheter tip provide evidence for the diagnosis of catheter-related infections. Bacterial growth of more than 15 colony-forming units/plate is typically considered significant. Preventive measures include using sterile insertion techniques, providing meticulous care for the local site, and minimizing the duration of catheter use. The practice of changing lines over a guidewire is controversial. For treatment of most catheter-related infections, the catheter should be removed and antibiotics should be administered if associated systemic infection occurs.
Development and reversal of endotoxemia and endotoxin-related death in obstructive jaundice.
Gut-derived endotoxemia has been implicated in postoperative complications in patients with jaundice. It is thought that absence of bile in the gut predisposes to portal absorption of endotoxin and endotoxemia is reversed by oral bile salt replacement or internal biliary drainage and return of bile to the gut, but not by external drainage. We believe that the importance of gastrointestinal bile flow has been overestimated and biliary obstruction and the integrity of hepatocyte and Kupffer cell function are more important in the development and reversal of endotoxemia. In experiment 1, serum endotoxin concentrations were measured in control rats (n = 10) after choledochovesical fistula (n = 15) and bile duct ligation (n = 15) and after relief of biliary obstruction by internal drainage (choledochoduodenostomy; n = 8) and sterile external drainage (choledochovesical fistula; n = 8), with a quantitative limulus assay. In experiment 2, mortality rates were measured in similar groups 48 hours after administration of oral endotoxin (5 mg/100 gm) and intravenous lead acetate (5 mg/100 gm). Bilirubin levels were elevated in bile duct ligation (192 +/- 13 mumols/L) compared with control animals and those with choledochovesical fistula, internal drainage, and external drainage (10.6 +/- 1.5 mumols/L). In experiment 1, significant portal endotoxemia and systemic endotoxemia occurred in bile duct ligation (portal, 130.4 +/- 12.9 pg/ml; systemic, 91.8 +/- 11.0 pg/ml) but not in choledochovesical fistula (portal, 49.3 +/- 17.1 pg/ml; systemic, 27.2 +/- 11.5 pg/ml). Relief of obstruction by both internal and external drainage reversed endotoxemia. In experiment 2, significant death occurred in bile duct ligation (13 of 15) but not in choledochovesical fistula (3 of 15), and relief of obstruction by both internal and external drainage prevented death. These results confirm that biliary obstruction is a more important factor than is gastrointestinal bile flow in the development and reversal of endotoxemia.
Differential distribution and non-collateralization of central amygdaloid neurons projecting to different medullary regions.
The distributions of central amygdaloid nucleus (Ce) neurons projecting to different medullary regions were investigated using the retrograde transport of iontophoretically applied Fast Blue or bisbenzimide. Neurons projecting to the nucleus of the solitary tract were located throughout the medial, lateral and ventral subdivisions of the Ce whereas cells projecting to the parvicellular reticular formation and ventrolateral medulla were confined to the medial subdivision of the Ce. Combined injections of fluorescent dyes into these medullary areas resulted in only occasional double-labelled cells. The results suggest that Ce projections to a variety of medullary sites arise from separate populations of neurons with partially overlapping distributions in the medial Ce.
Fat consumption and factor VII coagulant activity in middle-aged men. An association between a dietary and thrombogenic coronary risk factor.
Diet was measured by 5-day weighed inventory to search for an association between fat intake in the general population and factor VII coagulant activity (VIIc), a strong predictor of coronary heart disease. Of 275 men aged 40-59 years registered with a medical practice, 203 (74%) participated and 170 (62%) provided a satisfactory record. After allowance for the increase in fat intake with body size, a statistically significant and positive association was found between dietary fat and VIIc (r = 0.18; P less than 0.05). The correlation coefficient was increased to 0.24 when adjusted for the effect of day-to-day variability in individual fat intake, thereby providing an improved estimate of the true strength of association. The mean difference in VIIc of 12% of standard between men in the highest and lowest quarters of the distribution of fat intake was similar to that reported between men experiencing coronary heart disease and those remaining free. The results support previous experimental fat-feeding studies and suggest that a high fat diet has adverse consequences for blood coagulability and coronary thrombosis.
Herpes simplex virus neurovirulence and productive infection of neural cells is associated with a function which maps between 0.82 and 0.832 map units on the HSV genome.
A herpes simplex virus (HSV) intertypic recombinant (RE6) has been shown to be completely and specifically non-neurovirulent in mice. Direct intracranial inoculation of 10(8) PFU of RE6 does not result in a lethal encephalitis. Neurovirulent recombinant viruses were generated by cotransfection of RE6 DNA with DNA fragments cloned from the pathogenic HSV-1 strain 17 syn+. It was found that a 1.6-kb fragment mapping between 0.82-0.832 m.u. could restore the neurovirulent phenotype. Recombinants which incorporated at least part of this fragment were at least 100,000-fold more neurovirulent than RE6. The recombinants displayed a greatly enhanced capacity to replicate in mouse brain in vivo, but did not display enhanced replication over that of RE6 in cultured mouse cells at 38.5 degrees. Immunohistochemical analysis of infected mouse brain tissue revealed that the permissive host cell range of the recombinants was dramatically altered from that of RE6. While antigen positive cells were extremely rare in mouse brain tissue infected with RE6, the neurovirulent recombinants produced antigens in many cell types including neurons. Thus, wild-type HSV-1 sequences mapping between 0.82-0.832 m.u. can donate a highly neurovirulent phenotype to RE6.
Limited usefulness of quantitative culture of blood drawn through the device for diagnosis of intravascular-device-related bacteremia.
The use of a differential quantitative blood culture technique (Isolator) to diagnose intravascular-device-related bacteremia (IDRB) was studied prospectively. During septic episodes in 44 patients, blood was obtained simultaneously through the suspected infected device and from a peripheral venipuncture. The blood samples were processed by the Isolator technique, which enables easy quantification of microorganisms. The cannula was removed, and its tip was cultured semiquantitatively. Of the 52 cannulas studied, 15 were the cause of IDRB, but only 7 of these showed a significantly higher bacterial count in blood obtained through the device compared with peripheral blood. The bacterial count was higher in blood drawn through the device than in peripheral blood in four of six cases that did not fulfill the definition of IDRB. Some blood cultures obtained through the device were positive despite negative cultures of peripheral blood and cannula tips (six cannulas). Quantitative blood cultures were not useful in diagnosing IDRB in this study.
Dietary intake of men in Wembley, London, by weighed inventory: comparison with national recommendations, with particular emphasis on fat intake.
To assess the extent to which current dietary habits conform with the national nutritional guidelines aimed at reducing the high national mortality from coronary heart disease (CHD), 203 of 275 men (74 per cent) aged 40-59 years in a London community provided a weighed record of all food and drink consumed over 5 d. Satisfactory records were returned by 170 men weighing at least 75 per cent of their intakes, including 43 on medical or self-imposed diets. Mean (s.d.) energy intake was 2476 (590) kcal (10.38 MJ), comprising 37 per cent fat, 42 per cent carbohydrate, 14.7 per cent protein and 6.3 per cent alcohol. Butter or butter spreads were used by 53 per cent, sunflower margarine by 29 per cent and low fat spreads by 13 per cent; lard or dripping was used by 23 per cent of households as the main cooking fat. Intakes of vitamins and trace elements were generally above recommended amounts. These results are closely comparable with the only similar studies for the UK undertaken in Wales and Scotland. Compared with national guidelines, only 32 per cent of men met the short-term goals for fat intake, and even fewer the long-term goals. Carbohydrate and fibre intake remained too low. Alcohol intake exceeded the short-term goal (5 per cent of energy of less) in 36 per cent of men. Greater public health effort will be needed to reduce fat intake further for primary prevention of CHD, particularly as habitual intake is probably underestimated by the weighed dietary record.
Movable finite automata (MFA) models for biological systems. II: Protein biosynthesis.
A recently introduced class of models, the Movable Finite Automata (MFA) models, are used for simulating the elongation of the polypeptide chain in protein biosynthesis. The results of these simulations, all carried out on a microcomputer, are given.