A molecular biology approach to the mechanism of T-cell-mediated cytotoxicity.
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Cloning, Molecular↗
Biomedical subjects
W R Clark
Publications and source records attributed to W R Clark.
The inducible cytotoxic T-lymphocyte-associated gene transcript CTLA-1 sequence and gene localization to mouse chromosome 14.
Classical phenomenological approaches to the study of the mechanism of T-cell-mediated cytotoxicity have now given way to a search for molecules involved in this function; this is attempted either by subcellular and biochemical fractionation of material from cytotoxic cells, or through the characterization of molecules recognized by cytotoxicity-inhibiting monoclonal antibodies Molecules having a role in cytotoxicity may also be identified by detecting the corresponding messenger RNA transcripts. Such an approach may include, as a first step, the search for transcripts as specific as possible to cytotoxic T cells; only secondarily can their actual relevance to cytotoxicity be investigated. We report here the preparation and systematic screening of a differential complementary DNA bank, in which we detected three distinct messenger RNA transcripts (CTLA-1, CTLA-2 and CTLA-3) present in various cytotoxic T cells but not (or less so) in a range of non-cytotoxic lymphoid cells. We describe the co-inducibility of these transcripts and of cytotoxicity in thymocytes and hybridoma cells, the sequence of CTLA-1 cDNA, its protein homology with serine esterases and the localization of the corresponding gene to mouse chromosome 14.
Amino Acid Sequence↗
Cytotoxic T lymphocyte mediated lysis without release of serine esterase.
Cloned cytotoxic T lymphocytes (CTL) can lyse target cells in a Ca2+-dependent or Ca2+-independent fashion, depending on the target cell used. We have used these Ca2+-free assay conditions to determine whether there is serine esterase release in the absence of extracellular Ca2+. We find that under conditions where there is significant target cell killing in the absence of Ca2+, there is no detectable serine esterase release. To the extent that serine esterase and perforin-like molecules reside in the same granules, these results also suggest that target cell killing may occur in the absence of degranulation. Our results provide an example of target cell killing without serine esterase release, and the first indication that lysis and degranulation can be functionally dissociated.
Animals↗
Hemodialyzer membranes and configurations: a historical perspective.
The principle of hemodialysis (HD) was first described over a century ago while the first human HD treatment was performed in 1923 with collodion tubes. Since that time, a variety of different hemodialyzer configurations and membranes have been used. The purpose of this article is to provide a historical review of these various configurations and membranes. The rotating drum, coil, parallel flow, and hollow fiber artificial kidneys are discussed. Emphasis is placed on the factors that have influenced the shaping of the contemporary HD market.
Equipment Design↗
Quantitative characterization of hemodialyzer solute and water transport.
Clinicians are frequently faced with the task of selecting a hemodialyzer for a dialysis-dependent patient. Several quantitative dialyzer parameters, such as clearance, sieving coefficients, and ultrafiltration coefficient, are routinely used in this selection process. However, the quantitative basis and exact meaning of these indices are often unclear or misinterpreted. The purpose of this article is to provide a detailed description of several of these parameters with the hope that this information will enable clinicians to make dialyzer selection from a more quantitative perspective.
Equipment Safety↗
What clinically important advances in understanding and improving dialyzer function have occurred recently?
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Biocompatible Materials↗
Quantification of middle molecular weight solute removal in dialysis.
The pioneering work of Gotch emphasized the critical need to be quantitative with respect to treatment prescription. Through his meticulous derivations and analyses regarding Kt/V(urea), he has provided powerful insight into the standard therapy prescriptions that we now employ clinically. However, time has seen the proliferation of treatment techniques, most of which are too "young" to have been characterized with respect to clinical outcomes. Further, the relationship between removal of urea and removal of middle molecular size solutes associated with these newer techniques deviates from that associated with conventional, clinically qualified techniques. In this article we examine the solute clearance profile of some of these new methodologies and their relationship to current criteria for treatment adequacy. Our approach is to discuss components of the overall transport process and then utilize modeling of surrogate molecules over the size range of interest whose transport characteristics are known. Alteration in the solute clearance profile of these surrogate markers in response to changes in prescription variables will thus offer insight into the spectrum of toxic middle molecules that are removed when size, space of distribution, and generation rate are known.
Humans↗
Reconciling differences in effective solute removal between intermittent and continuous therapies.
Solute removal by various forms of renal replacement therapy (RRT) differs from that occurring in the native kidney in several ways. Among the dialytic therapies, the relationship between clearance and mass removal rate may differ substantially. The purpose of this article is to review the various approaches that have been proposed to account for this differing relationship among the various types of RRT. Specific quantitative approaches along with clinical applications are provided.
Humans↗
Urea kinetics during continuous hemofiltration.
Urea kinetic analysis allows for the calculation of the urea distribution volume and urea generation rate. This method was employed in patients with acute renal failure managed by continuous venovenous hemofiltration (CVVH). Based on serial serum urea nitrogen concentration measurements, each patient's treatment course consisted of both steady state and non-steady state periods. Thirteen data sets were obtained from 11 critically ill patients treated with CVVH. The duration of therapy was 9.5 +/- 7.5 days (mean +/- SD). Serum urea nitrogen concentration fell from 114 +/- 32 mg/dl to a steady state value of 79 +/- 17 mg/dl (p < 0.0005). The urea distribution volume was 0.55 +/- 0.11 L/kg (range 0.29-0.73), and the urea generation rate 11.7 +/- 3.1 mg urea N/min (range 7.1-17.3). The steady state serum urea nitrogen concentration had a linear relationship to the rate of urea generation (r = 0.92). Urea kinetic analysis permitted the simultaneous determination of the urea generation rate and distribution volume, on an individualized basis, in patients with acute renal failure treated with CVVH.
Acute Kidney Injury↗
Clinical evaluation of a new high efficiency hemodialyzer: polysynthane.
Two increasingly common characteristics of the American chronic hemodialysis (HD) population, high hematocrit and large body size, may render the currently recommended adequacy targets difficult to achieve, even with very efficient dialyzers. In a group of patients with these characteristics, we assessed the ability of a new high efficiency dialyzer (PSN210; Baxter Healthcare Corporation) to achieve the currently recommended adequacy targets. Six patients (mean pre-HD weight and hematocrit, 90.3 +/- 18.0 kg and 0.40 +/- 0.03 kg, respectively) were evaluated. At prescribed blood and dialysate flow rates of 400 and 800 ml/min, respectively, and a mean treatment duration of 4 hrs, mean delivered urea Kt/V and reduction ratio (URR) were 1.38 +/- 0.25 and 0.73 +/- 0.07, respectively. For the same flow rates, whole blood clearances for urea, creatinine, and phosphate were 315 +/- 13, 246 +/- 28, and 260 +/- 27 ml/min, respectively. These data indicate this dialyzer has an efficient mass transfer design allowing adequate dialysis to be delivered even to very large patients under high efficiency conditions.
Adult↗
Smoke inhalation and airway management at a regional burn unit: 1974-1983. Part I: Diagnosis and consequences of smoke inhalation.
Victims of smoke inhalation with and without burns and burn patients with respiratory insufficiency for reasons other than smoke at a regional burn unit are profiled in terms of age, burn size, length of stay, and mortality. The diagnostic characteristics of patients with an inhalation injury (N = 108) are listed; 7% of all patients (N = 52) have known smoke exposure with equivocal evidence for injury to the airway or pulmonary parenchyma. The degree of respiratory (visceral) failure experienced by patients with inhalation injury is not uniformly severe. Many of the clues to this diagnosis are indirect and not always related to the severity of pulmonary injury. Timing and degree of visceral failure control the severity of the injury, which increases progressively from that in patients with a burn only (parietal injury) through those with a visceral injury only (smoke without burn), those with both smoke and burn, to those with a burn and uniformly severe respiratory failure on the basis of sepsis.
Adult↗
Smoke inhalation and airway management at a regional burn unit: 1974 to 1983. II. Airway management.
According to criteria established to define patients with smoke inhalation, the airway management of all victims of smoke and burns (1974 to 1984; n = 805) was reviewed. Fourteen percent of all patients were intubated (n = 117); patients intubated on the day of injury (n = 41) were more likely to extubate themselves or have technical problems with the endotracheal tube. Twelve percent of patients with smoke inhalation without burns required endotracheal intubation versus 62% of those with burns. An endotracheal tube was required for a median of 5 days. Tracheotomies were performed in 48 patients: 40% of those intubated and 6% of all patients. The mean postburn day for tracheotomy was day 15. There was no difference in the mortality rate for patients with an endotracheal tube only and those who had a tracheotomy as well: 42% and 37%, respectively. The prolonged length of stay for patients with a tracheotomy relates to the severity of the burn. Tracheotomy was not the cause of death in any patient. The strategy of grafting the neck before tracheotomy was used successfully in eight patients.
Adolescent↗
Impact of the nutritional regimen on protein catabolism and nitrogen balance in patients with acute renal failure.
BACKGROUND: Patients with acute renal failure are in substantial negative nitrogen balance as a result of their extremely high protein catabolic rates. We prospectively evaluated a series of patients with acute renal failure managed with continuous venovenous hemofiltration to determine which nutritional and nonnutritional variables might influence protein catabolism and nitrogen balance. METHODS: Forty consecutive patients (aged 52 +/- 20 years; mean +/- SD) were monitored for 357 treatment days (average treatment duration 8.9 +/- 8.6 days). All data (including nutritional regimen, laboratory values, APACHE II score, administered blood products, hemofiltration parameters, and medications) were collected daily. RESULTS: For all patients, the mean normalized protein catabolic rate was 1.4 +/- 0.5 g/kg per day. The rate did not differ between those who received nutrition support and those who did not. The net nitrogen deficit was less in those patients receiving nutrition support (-6.0 +/- 5.2 vs -14.0 +/- 5.6 g N/d; p = .02). Using regression techniques (adjusted for the within-person correlation and the previous day's normalized protein catabolic rate), the level of protein and energy provision and the interaction between protein and energy provision were predictive of the normalized protein catabolic rate. Predicted values, using this equation, suggest that at low protein administration rates (< 1 g/kg per day), increasing energy provision may reduce the protein catabolism. However, at this level of protein provision, patients remain in negative nitrogen balance. At protein administration rates necessary to achieve nitrogen balance (approximately 1.5 to 1.8 g/kg per day), protein catabolism may increase. Providing relatively low levels of energy may diminish the magnitude of this increase. CONCLUSION: These results suggest that the optimal nutritional regimen for patients with acute renal failure may require a high-protein (approximately 1.5 to 1.8 g/kg per day) and a relatively low-energy (approximately 25 to 35 kcal/kg per day) content.
Acute Kidney Injury↗
Effect of acute smoke inhalation on angiotensin converting enzyme, plasminogen activator, and angiotensin-II in the dog.
Smoke inhalation injuries in humans are associated with many uncontrolled variables which impact on the lung and make the cause of the pulmonary response difficult to assess. In this report, an established model of smoke inhalation injury in the dog was used to study the early responses of tissue and serum angiotensin-converting enzyme (ACE), tissue plasminogen activator (PLA), and plasma angiotensin II. Animals were exposed to smoke from burning sawdust and kerosene for five minutes. The hemodynamic and pulmonary mechanical responses were typical with a rise in pulmonary artery pressure, pulmonary vascular resistance, and venous admixture (shunt fraction) while dynamic compliance fell. Within five minutes of smoke exposure, lung ACE declined without any change in serum ACE. Lung PLA dropped one hour after injury. Plasma angiotensin II increased within 30 minutes without evidence for systemic hypertension. These early enzymatic changes substantiate the presence of pulmonary endothelial damage known to occur in this form of chemical injury. These changes may condition the lung's physiologic response to the injury and to additional stresses which are multiple when smoke inhalation occurs in conjunction with a cutaneous burn.
Angiotensin II↗
Regional anesthesia in a patient with epidermolysis bullosa.
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Brachial Plexus↗
Effects of dialysis membrane on intradialytic vancomycin administration.
STUDY OBJECTIVE: To quantify the influence of hemodialyzers on vancomycin removal when the drug was infused during hemodialysis. DESIGN: Prospective, controlled, crossover study with three arms. SETTING: A university-affiliated medical center. PATIENTS: Eight subjects receiving outpatient hemodialysis. INTERVENTIONS: The three treatment arms were vancomycin 1000 mg infused after dialysis was completed (control), and the same dosages infused during the last hour of hemodialysis with a cellulose triacetate (CT) and a cellulose acetate (CA) hemodialyzer. MEASUREMENTS AND MAIN RESULTS: The areas under the curve from time zero to 44 hours (AUC0-44 hrs) for the three study arms were significantly different (p < 0.05), with the mean vancomycin AUC0-44 hrs being significantly lower when administered during CT and CA dialysis (73.7% and 87.2% of control; p < 0.05 vs control). The mean vancomycin peak concentration achieved during CT dialysis was significantly lower than for the CA and control arms (20.5, 23.9, 27.0 mg/L, respectively). Forty-four-hour postinfusion concentrations were similarly lower. CONCLUSION: Clinicians should recognize that the composition of the hemodialyzer significantly influences vancomycin serum concentrations when the drug is administered during hemodialysis.
Anti-Bacterial Agents↗