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Biomedical subjects

D Holbrook

Publications and source records attributed to D Holbrook.

13 recordsLinked to original sources
PubMed1999

Increased susceptibility to erythrocyte C5b-9 deposition and complement-mediated lysis in chronic renal failure.

BACKGROUND: Decreased red blood cell survival contributes to the anemia of chronic renal failure patients. Because patients on chronic dialysis therapy are frequently exposed to excessive complement activation, we investigated the susceptibility of this patient population to erythrocyte C5b-9 deposition, complement-mediated lysis, and ghost formation. METHODS: We developed a flow cytometric assay using antibodies to both glycophorin and the C5b-9 complex to detect C5b-9 deposition on intact erythrocytes and erythrocyte ghosts. Serum C5b-9 levels and C5b-9 deposition on erythrocyte ghosts were measured by enzyme-linked immunosorbent assay. RESULTS: A significant increase in C5b-9 deposition on intact erythrocytes was demonstrated in patients with advanced chronic renal failure (2.2 +/- 0.5%) and in patients on chronic maintenance hemodialysis (2.3 +/- 0.4%) compared with normal volunteers (0.9 +/- 0.1%, P = 0.005 vs. chronic renal failure, P < 0.001 vs. chronic hemodialysis patients). There was also a significantly higher percentage of C5b-9-positive erythrocyte ghosts in patients with advanced chronic renal failure (20.6 +/- 5%) and in chronic hemodialysis patients (15.5 +/- 3.1%) compared with normal controls (2.6 +/- 0.9%, P < or = 0.001 vs. advanced chronic renal failure and chronic hemodialysis patients). Treatment of erythrocyte preparations with cobra venom factor, which activates the complement cascade, resulted in dramatic increases in the percentages of C5b-9-positive erythrocyte ghosts in patients with chronic renal failure (49.9 +/- 6.9%) and in chronic hemodialysis patients (45.0 +/- 4.2%) compared with normal volunteers (22.3 +/- 2.7%, P < 0.001 vs. chronic renal failure and chronic hemodialysis patients). Erythrocyte membrane expression of the complement regulatory proteins CD59 and CD55 did not significantly differ between normal controls and hemodialysis patients. Plasma C5b-9 levels after cobra venom factor stimulation were higher in chronic renal failure patients (538 micrograms/ml) compared with normal controls (345 micrograms/ml, P < 0.001). CONCLUSIONS: Patients with chronic renal failure and on hemodialysis therapy are susceptible to erythrocyte C5b-9 deposition with subsequent lysis and ghost formation. Susceptibility to complement-mediated erythrocyte injury may contribute to the anemia of chronic renal disease.

Cell Survival↗
PubMed1998

Elevated plasma glycocalicin levels and decreased ristocetin-induced platelet agglutination in hemodialysis patients.

A bleeding diathesis caused by platelet dysfunction is a major cause of morbidity and mortality in patients with uremia. Platelet adhesion to vascular subendothelium is defective in uremia and depends on the interactions of the platelet glycoprotein (GP) Ib/IX complex with the vascular wall. We measured levels of platelet surface GPIb, platelet surface GPIX, plasma glycocalicin (a product of enzymatic cleavage of GPIb), and ristocetin-induced platelet agglutination (RIPA) in patients undergoing chronic hemodialysis compared with patients undergoing peritoneal dialysis and healthy controls. Patients undergoing chronic maintenance hemodialysis have higher levels of platelet surface expression of GPIb (187+/-10 fluorescent units; P < 0.001) than either healthy controls (120+/-4 fluorescent units; P < 0.001) or patients undergoing peritoneal dialysis (127+/-5 fluorescent units; P < 0.001). Similar changes were observed in platelet surface GPIX. Plasma glycocalicin levels were elevated in chronic hemodialysis patients (71+/-5 nmol/L) compared with healthy controls (36+/-3 nmol/L; P < 0.001). Plasma glycocalicin levels also increased progressively throughout the hemodialysis procedure. The slope of RIPA was significantly lower in chronic hemodialysis patients (46+/-3) than in either healthy controls (67+/-4; P < 0.05) or peritoneal dialysis patients (62+/-2; P < 0.05). In conclusion, patients undergoing chronic maintenance hemodialysis have increased plasma glycocalicin levels and decreased RIPA, which may contribute to diminished platelet adhesion to vascular subendothelium and increased bleeding associated with uremia.

Blood Platelets↗
PubMed1997

Increased reticulated platelets in dialysis patients.

The purpose of this study was to measure the percent reticulated platelets and platelet counts in patients on chronic hemodialysis, peritoneal dialysis and normal volunteers. The relationship between the percent reticulated platelets and the platelet count can then be used to determine the rate of platelet turnover. Platelet rich plasma was obtained, platelets were fixed and incubated with thiazole orange and analyzed for the percent reticulated platelets by flow cytometry. Normal controls had a mean of 2.77 +/- 0.17% reticulated platelets while peritoneal dialysis patients had a mean percent reticulated platelets of 6.92 +/- 0.68 (P < 0.00001). Chronic hemodialysis patients had a mean percent reticulated platelets of 8.21 +/- 0.36 (P < 0.00001 vs. normal controls and P = 0.05 vs. peritoneal dialysis patients). Platelet counts did not differ significantly among the three groups. The identity of reticulated platelets was confirmed in experiments measuring platelet specific glycoproteins, experiments using RNase, and in mixing experiments with normal and uremic platelets and plasma. We conclude that dialysis patients have a marked increase in circulating reticulated platelets compared to normal controls, indicating accelerated platelet turnover. Increased platelet activation and turnover may contribute to the qualitative platelet dysfunction observed in dialysis patients.

Blood Platelet Disorders↗
PubMed1995

Soluble complement receptor 1 inhibits both complement and granulocyte activation during ex vivo hemodialysis.

Hemodialysis with cellulosic membranes results in both complement and granulocyte activation. We investigated the effects of soluble complement receptor 1 (sCR1), a potent complement inhibitor, on both complement and granulocyte activation in an ex vivo model of dialysis. Measurements were made of complement activation (radioimmunoassay for C3a desArg) as well as granulocyte activation (flow cytometric measurements of reactive oxygen species production, granulocyte CD11b/CD18 (MAC-1) expression and CD62L (L-selectin) expression). sCR1 completely abolished the generation of plasma C3a desArg during ex vivo hemodialysis. Without sCR1, C3a desArg levels rose from 968 +/- 373 ng/ml to 4961 +/- 40 ng/ml by the end of the ex vivo procedure (p < 0.001). sCR1 also completely inhibited MAC-1 upregulation and L-selectin shedding from granulocytes during ex vivo hemodialysis. With sCR1 there was still a statistically significant increase in granulocyte reactive oxygen species production (from 2.42 +/- 0.1 fluorescence channels to 6.47 +/- 0.7 fluorescence channels, p < 0.01) but a 50% inhibition when compared with experiments without sCR1 (3.15 +/- 0.5 to 11.2 +/- 1.9, p < 0.01). We conclude that sCR1 completely abolishes complement activation and changes in granulocyte cell adhesion molecules during ex vivo hemodialysis with cellulosic membranes. sCR1 partially inhibits granulocyte reactive oxygen species formation.

Anaphylatoxins↗
PubMed1994

Kt/V, nutritional parameters, serum cortisol, and insulin growth factor-1 levels and patient outcome in hemodialysis.

Despite many technical advances in dialysis care, morbidity and mortality in chronic hemodialysis patients in the United States remains high. In this study, we analyzed the effects of Kt/V, nutritional parameters (serum albumin level, triceps skin-fold thickness, mid-arm muscle circumference, and normalized protein catabolic rate), and predialysis serum cortisol and insulin growth factor-1 levels on predicting morbidity and mortality. The cohort studied consisted of 52 patients recruited from a single outpatient dialysis facility. Cox proportional hazards modeling indicated that only Kt/V predicted subsequent mortality (P = 0.02), while both predialysis cortisol levels (P = 0.03) and Kt/V (P = 0.03) predicted hospitalization. Kaplan-Meier analysis demonstrated that the ability of cortisol levels to predict hospitalization was largely confined to the group with values greater than 22 micrograms/dL predialysis. High serum cortisol levels were correlated with low serum albumin levels and a trend toward low triceps skin-fold thickness and higher normalized protein catabolic rate, suggesting a catabolic state. Both predialysis serum cortisol and insulin growth factor-1 levels were higher than those in age- and sex-matched normal human controls. These results demonstrate the importance role of Kt/V in predicting subsequent hospitalization rates and mortality, and that high predialysis serum cortisol levels correlate with a high hospitalization rate.

Adult↗
PubMed1994

Effects of aprotinin on complement and granulocyte activation during ex vivo hemodialysis.

Hemodialysis with cellulosic membranes results in complement activation, granulocytopenia, and granulocyte activation. To further investigate the relationship between complement activation and granulocyte activation, we developed a model of ex vivo hemodialysis with blood flow, dialysate flow, and dialysate composition similar to in vivo hemodialysis. We used this model to investigate the effects of aprotinin, a potent serine protease inhibitor frequently used as an anti-inflammatory agent during cardiopulmonary bypass surgery, on both complement and granulocyte activation. Seven normal human volunteers were phlebotomized for ex vivo hemodialysis on two occasions each, one with and once without 800,000 kallikrein inhibitor units of aprotinin added to the circuit. Measurements were made of complement activation (radioimmunoassay for C3a desArg and C5a desArg), as well as granulocyte activation (flow cytometric measurements of reactive oxygen species (ROS) production, granulocyte CD11b-CD18 [MAC-1, CR3] expression, and CD62-L [L-selectin] expression). Statistically significant elevations in C3a desArg levels occurred by 10 minutes and reached a maximum of 5,367 +/- 712 ng/mL by 60 minutes after the initiation of ex vivo hemodialysis. Plasma C5a levels were elevated to 236 +/- 32 ng/mL at 60 minutes compared with 45 +/- 15 ng/mL predialysis. Aprotinin was able to significantly inhibit dialysis-induced C3a generation (peak 2,456 +/- 572 ng/mL at 60 minutes) as well as C5a generation (86 +/- 23 ng/mL at 60 minutes). During ex vivo hemodialysis, there was also a significant increase in granulocyte ROS production, MAC-1 upregulation, and L-selectin downregulation. Changes in granulocyte activation were not affected by the administration of aprotinin.(ABSTRACT TRUNCATED AT 250 WORDS)

Aprotinin↗
PubMed1993

Intradialytic granulocyte reactive oxygen species production: a prospective, crossover trial.

By the use of flow cytometric techniques, this prospective, randomized crossover study was designed to analyze intradialytic granulocyte reactive oxygen species (ROS) formation in whole blood with complement-activating and noncomplement-activating hollow fiber membranes. Dialysis with a complement-activating membrane resulted in a 6.5-fold increase in granulocyte hydrogen peroxide production 15 min after dialysis initiation and remained significantly elevated (P < 0.01) through the first 30 min with this membrane in comparison to both predialysis values and simultaneous values with a noncomplement-activating membrane. Further studies demonstrated that blood obtained at 15 min with a complement-activating membrane generated significantly less granulocyte ROS production in response to Staphylococcus aureus incubation than blood obtained either predialysis or at the same time in dialysis with a noncomplement-activating membrane. Both complement-activating and noncomplement-activating dialysis membranes caused slightly decreased granulocyte responsiveness to phorbol myristate acetate. It was concluded that hemodialysis with complement-activating membranes results in increased granulocyte ROS production and decreased responsiveness to S. aureus challenge during the dialysis procedure. These results document the potential role of ROS in hemodialysis-associated pathology and susceptibility to infection.

Adult↗
PubMed1988

Psychiatric interviewing techniques. A second experimental study: eliciting feelings.

The effects of two experimental interview styles, designed to differ in the extent of their use of active feeling-oriented techniques but similar in their use of active fact-oriented techniques, were compared in initial diagnostic interviews with the mothers of children referred to a psychiatric clinic. The style that employed a higher level of actively responsive feeling-oriented techniques elicited more emotional expression and more often obtained certain feelings of potential diagnostic significance. The actively responsive style was more effective in increasing the amount of feeling expressed if mothers' spontaneous rate of expression was relatively low.

Adolescent↗
PubMed1981

Psychiatric interviewing techniques. IV. Experimental study: Four contrasting styles.

The development and definition of four contrasting interview styles is described. The four styles were designed using different permutations of techniques which, on the basis of an earlier naturalistic study, appeared to be most effective in eliciting either factual information or feelings. A 'sounding board' style utilized a minimal activity approach; an 'active psychotherapy' style actively sought to explore feelings and to bring out emotional links and meanings; a 'structured' style adopted an active cross-questioning approach, and a 'systematic exploratory' style aimed to combine a high use of both fact-oriented and feeling-oriented techniques. Quantitative measures based on video-tape and audio-tape analysis showed that two experienced interviewers could be trained to adopt these four very different styles and yet remain feeling and appearing natural. An experimental design to compare the four styles is described.

Attitude↗
PubMed1981

Psychiatric interviewing techniques V. Experimental study: eliciting factual information.

Four experimental interview styles, each recommended by experts in the field, were compared for their efficiency in eliciting factual information during the initial diagnostic interviews with the mothers of children referred to a psychiatric out-patient clinic. If encouraged to talk freely, mothers tended to mention most (but not all) key issues without the need for standardized questioning on a pre-determined range of topics. However, systematic questioning was essential in order to obtain good quality factual data. Better data were obtained when interviewers were sensitive and alert to factual cues and chose their probes with care. Clinically significant factual information, idiosyncratic to the family and outside the range of standard enquiry was common, but was obtained satisfactorily with all four styles. No one style was generally preferred by informants. The advantages of systematic questioning for obtaining factual information were not associated with any disadvantages with respect to the eliciting of emotions and feelings.

Attitude to Health↗
PubMed1981

Psychiatric interviewing techniques. VI. Experimental study: eliciting feelings.

Four experimental interview styles, designed to differ in the extent of their use of active fact-oriented and active feeling-oriented techniques, were compared in relation to their use in the initial diagnostic interviews with the mothers of children referred to a psychiatric clinic. All four styles proved to be effective in eliciting emotions and feelings, but the findings suggested that each was effective for different reasons. It appeared that emotional expression could be encouraged by the interviewer's response to emotional cues, by a reflective style with little factual cross-questioning, by the use of direct requests for self-disclosures, by the optimal (but not necessarily maximal) use of interpretations. and expressions of sympathy, and by direct requests for feelings.

Emotions↗