Biomedical subjects

T Monk

Publications and source records attributed to T Monk.

7 recordsLinked to original sources

PubMed2001

Baculoviral expression and characterization of rodent cathepsin S.

The cysteinyl proteinase cathepsin S is implicated as a key enzyme in the processing of major histocompatability complex (MHC) class II molecules expressed on antigen presenting cells and thus is a potential therapeutic target for modulation in immune system-based disease. We have identified a form of rat cathepsin S, similar to a published mouse form with an eight-amino acid extended presequence relative to the human enzyme and the previously published rat enzyme. In addition, we have expressed these mouse and rat proteins in baculovirally infected Sf9 insect cells along with "humanized" forms truncated by eight residues at the amino-terminus. All forms of the rodent proteinases were overexpressed and milligram per litre amounts of functional enzyme could be isolated from the cells and/or the cell culture supernatant. Furthermore, addition of a carboxy-terminal hexahistidine purification tag had no effect on the kinetic characteristics of any of the enzyme forms against the Boc-Val-Leu-Lys-AMC peptide substrate (rat k(cat) s(-1) approximately 30; mouse k(cat) s(-1) approximately 65). Differences were seen in the potency of the generic cysteine proteinase inhibitor, E64, against the human, mouse, or rat form of the enzyme (13.3 x 10(4), 43.2 x 10(4), and 25 x 10(4) K(obe)/[I] M(-1) s(-1), respectively). Such data highlights the need for greater awareness of species variation in inhibitor potency. These reagents are vital for confirming inhibitor potency against the endogenous form of the enzyme prior to evaluation of drug candidates in rodent model systems.

Animals↗

PubMed1999

Where does preoperative erythropoietin therapy count? A mathematical perspective.

BACKGROUND: The administration of erythropoietin (EPO) can be used to increase a patient's hematocrit (Hct) in the preoperative period and thus possibly preclude the need for allogeneic red cells. However, the exact effect on the postoperative Hct of a given rise in Hct in the preoperative period (and on the avoidance of allogeneic blood) has not been thoroughly evaluated. STUDY DESIGN AND METHODS: Equations were developed on the basis of previously described relationships that allowed the assessment of the impact of a given preoperative Hct increase on the postoperative Hct under a variety of clinical situations. RESULTS: Equations were derived that related the change in preoperative Hct after the administration of EPO to the final Hct after a given blood loss. In a typical example (blood volume = 5000 mL, pre-EPO Hct of 40%, post-EPO Hct of 45% after blood losses of 1000, 2000, 3000, 4000, 5000, and 6000 mL), an additional 205, 168, 137, 112, 92, and 75 mL of red cells, respectively, would be present postoperatively over the volume in the same patient who did not receive EPO. For a smaller patient, such as a child (blood volume, 2500 mL), an additional 17 mL (5000-mL blood loss) to 83 mL (1000-mL blood loss) of red cells would be present postoperatively. Hemodilution and EPO act synergistically to yield additional postoperative red cell volume. CONCLUSION: The use of preoperative EPO with a preoperative increase in Hct results in an increased postoperative Hct after a surgical blood loss. Such a postoperative increase is a function of the volume of blood lost and the patient's blood volume but is independent of the patient's initial Hct. The final postoperative red cell volume increase associated with a preoperative increase in Hct of 1 to 5 percent is limited, however (generally equivalent to a fraction of 1 unit of allogeneic blood). Much of the increase in the patient's Hct vanishes at higher blood losses, and this therapy is most effective with blood loss of <4000 mL. EPO therapy alone may be most effectively used in patients with mild anemia who are undergoing routine surgical procedures that commonly require blood transfusion.

Blood Loss, Surgical↗

PubMed1999

The value of oxygen-carrying solutions in the operative setting, as determined by mathematical modeling.

BACKGROUND: The use of oxygen carriers (red cell [RBC] substitutes) in acute trauma and in surgery, with or without the use of acute normovolemic hemodilution (ANH), is being investigated. Mathematical modeling was used to assess the impact of RBC substitutes, with or without ANH, in the elective surgical setting. STUDY DESIGN AND METHODS: Mathematical equations and computer models were developed on the basis of previously described mathematical principles, for better understanding of the potential efficacy of RBC substitutes for blood needs with or without ANH. Savings were calculated for a patient with a blood volume of 5000 mL and an initial hematocrit (Hct) of 45 or 30 percent. RESULTS: Substantial increases in the tolerable blood losses (or reduced allogeneic RBC needs) were most evident when the use of an RBC substitute to achieve severe ANH to a Hct that the patient might not otherwise have been able to tolerate was combined with the use of RBC substitutes as replacement for the surgical blood subsequently lost. However, the benefit was greatly dependent on the patient's initial Hct. For example, for a patient with a blood volume of 5000 mL and an initial Hct of 45 percent, a blood loss of approximately 2500 mL resulted in a final Hct of 28 percent without the use of an RBC substitute or ANH. In contrast, with the combined use of staged ANH with an RBC substitute and the RBC substitute for lost surgical blood, a blood loss of up to 14.5 L could be tolerated. However, in an anemic patient (blood volume 5000 mL, initial Hct 30%), a Hct of 28 percent cannot be sustained without the use of allogeneic RBCs for any of the described strategies, even when blood losses were as low as 1 L. CONCLUSION: The use of RBC substitutes has the potential to result in a substantial reduction in allogeneic RBC exposure. This benefit is essentially limited to the nonanemic patient when the use of an RBC substitute is combined with severe ANH and there is concomitant large perioperative blood loss. Anemic patients can be expected to have only limited benefit, because of an inability to sequester an adequate volume of autologous RBCs via ANH.

Blood Substitutes↗

PubMed1997

A standardized method for calculating blood loss.

BACKGROUND: The estimation of blood loss for a surgical procedure is both poorly reproducible and typically underestimated. Therefore, comparison of surgical transfusion outcomes such as blood loss and amount of blood transfused from one institution to another, or from one surgeon to another, is difficult. Recently, mathematical modeling has contributed to our understanding of transfusion strategies. STUDY DESIGN AND METHODS: A mathematical model of blood loss for a surgical hospitalization was developed on the basis of recently described mathematical principles for blood loss and hemodilution. The model was designed so that the calculation of blood loss would be based on easily measured factors such as the patient's blood volume, the number and type of red cell units transfused, the initial hematocrit, the discharge hematocrit, the transfusion trigger, the volume of intraoperatively salvaged blood transfused, and the amount of hemodilution performed. The calculated blood loss was then compared with the intraoperative blood loss actually estimated by the anesthesiologist in 250 consecutive patients who underwent radical retropubic prostatectomy. RESULTS: The mathematical equations were placed in a computer model to allow rapid calculation of a particular patient's blood loss. Figures were derived from the computer modelling to facilitate rapid manual calculation of the blood loss. There was a significant relation (p < 0.001) between the calculated blood loss for the hospitalization and the estimated intraoperative blood loss. However, the calculated blood loss was on average 2.1 times the intraoperative blood loss estimated by the anesthesiologist. CONCLUSION: The use of such mathematical modeling to rapidly estimate a patient's blood loss has the potential to allow ready, objective comparisons between sites and even surgeons. It also allows for a more judicial and informed decision as to what (if any) blood should be available or what blood-conservation techniques should be employed for a specific patient.

Blood Loss, Surgical↗

PubMed1988

Stimulation of mucosal T cells in situ with anti-CD3 antibody: location of the activated T cells and their distribution within the mucosal micro-environment.

Mucosal T cells in explants of human fetal small intestine (17-20 weeks gestation) in organ culture were activated in situ using monoclonal anti-CD3 antibody. Changes in the distribution of T cells within the mucosa, and their phenotype, were monitored by immunohistochemistry on frozen sections. Anti-CD3 stimulated T cells (as determined by expression of CD25) were predominantly in the lamina propria and were rarely seen in the epithelium. In control cultures, after 72 h, CD3+ IEL decreased to low numbers compared to day zero. However, in cultures treated with anti-CD3, IEL numbers were maintained and in some experiments significantly increased compared to day zero levels. At onset of culture 50-60% of CD3+ IEL were CD4-, 8-, and virtually all were HML-1+. The T cell infiltrate into the epithelium induced by activation of lamina propria T cells with anti-CD3 was also mostly CD3+, 4-, 8-, HML-1+. These experiments provide strong evidence that increases in IEL numbers can be a consequence of lamina propria T cell activation.

Antibodies↗

PubMedDate not supplied

Production and systemic absorption of toxic byproducts of tissue combustion during laparoscopic cholecystectomy.

Among the potential hazards of laparoscopic surgery using electrocautery is the release of chemical by-products of incomplete tissue combustion into the pneumoperitoneum with subsequent transperitoneal absorption into the bloodstream and/or release into the operating room. The purpose of this study of patients undergoing laparoscopic cholecystectomy (LC) was twofold: (1) to assess the relationship between intraperitoneal concentration of carbon monoxide (CO) and blood levels of carboxyhemoglobin (COHb) and methemoglobin (MetHb), and (2) to assess the surgeon's inhalation of CO resulting from ambient smoke exposure. During LC with monopolar electrocautery, 21 patients were evaluated intraoperatively for intraperitoneal [CO] by sampling gas from a trocar, whereas arterial [COHb) and [MetHb] were determined perioperatively. The surgeon's venous blood was drawn pre- and postoperatively to assay [COHb] and [MetHb]. Patients completed visual analogue questionnaires 6 hours and 24 hours postoperatively to assess for adverse symptoms. Mean (+/- SEM) patient age and weight were 45 +/- 3 years and 84 +/- 4 kg, respectively. Mean duration of the operation was 69 +/- 5 minutes, and electrocautery was used for 3.0 +/- 0.3 minutes. Intraperitoneal [CO] rose to peak levels of 209 +/- 19 ppm at 50 minutes, whereas systemic [COHb] and [MetHb] were unchanged. The surgeon's systemic [COHb] and [MetHb] did not increase postoperatively. Nausea, abdominal pain, and fatigue scores decreased significantly between 6 and 24 hours postoperatively; however, there were no correlations between these symptoms and peak intraperitoneal [CO]. Although LC using electrocautery increases intraperitoneal [CO] to "hazardous" levels, systemic [COHb] and [MetHb] are not elevated by generation of intraperitoneal smoke. The surgeon's exposure to CO by the evacuation of smoke through laparoscopic ports is negligible. Production of smoke during LC using monopolar electrocautery, therefore, does not appear to pose a threat to either the patient or the surgeon.

Arteries↗

PubMedDate not supplied

Intervention factors for promoting adjustment to nightwork and shiftwork.

This chapter reviews a broad range of factors that, if controlled, might promote adaptation to nightwork, shiftwork, and extended workshifts. Systematic study has begun in four of the areas reported here: work schedule design, napping, bright light stimulation, and drugs. Physical activity, ambient temperature, diet, and individual behaviors have been studied only superficially.

Adaptation, Physiological↗