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Biomedical subjects

D T Miller

Publications and source records attributed to D T Miller.

At least 55 records · Page 3Linked to original sources
PubMed1989

Metabolic status of platelet concentrates during extended storage: improvement with pharmacological inhibitors and reduced surface-to-volume ratio.

The depletion of plasma nutrients and buffering capacity may present a potential barrier to the long-term liquid storage of platelet concentrates (PC). We have found that PC prepared with reversible inhibitors of platelet activation added to the citrate anticoagulant and stored at a reduced surface-to-volume (S/V) ratio have a much slower rate of lactate build-up (p less than 0.01), slower consumption of glucose (p = 0.05), and more stable pH (p less than 0.01) than controls. By pO2 and pCO2 measurements, PC prepared with inhibitors showed evidence of continued respiration and responsiveness even after storage at 22 degrees C for 15 days. In addition, these PC released only 11% of the total cellular LDH during the storage period as compared to the release of 43-67% of the total LDH in control PC. Maximum benefit of the inhibitors was seen after reduction of the S/V ratio of the storage container, which was made possible by the reduced metabolic demands of platelets stored in the unactivated state. These data suggest that the fall in pH and loss of platelet integrity associated with the platelet storage lesion are correlated with a high metabolic rate which can be controlled by inhibiting the activation of platelets during preparation and storage. The use of these inhibitors and reduced bag surface area may make prolonged liquid storage of platelets feasible.

Alprostadil↗
PubMed1989

Sex steroids and bone density in premenopausal and perimenopausal women.

Bone density begins to decline in women before menopause, and the degree of bone loss is variable. We performed a cross-sectional analysis on the entry data of a 5-yr prospective study of risk factors for osteoporosis to determine the correlation of bone density with serum sex steroid concentrations and body weight. We studied 292 healthy white women, aged 35-50 yr, who were menstruating regularly or had had menses in the past 12 months. Blood samples were drawn in the early follicular phase for estradiol (E2), testosterone (T), dehydroepiandrosterone sulfate, and sex hormone-binding globulin (SHBG). Free levels of E2 (FE2) and T (FT) were calculated based on total T and E2, SHBG, and albumin levels. Women were classified as premenopausal (FSH, less than 12 U/L) and perimenopausal (FSH greater than or equal to 12 U/L; n = 46; 16%). Bone density was measured by dual photon absorptiometry of the lumbar spine (L2-L4) and hip and by single photon absorptiometry of the wrist. Perimenopausal women were older than premenopausal women (45.5 +/- 3.5 and 41.0 +/- 3.9 yr, respectively), but did not differ in height or weight. While bone density did not correlate with age in each group, perimenopausal women had significantly lower bone density at the L2-L4 and femoral neck (L2-L4, 1.18 +/- 0.14 in perimenopausal and 1.24 +/- 0.12 g/cm2 in premenopausal women; femur, 0.84 +/- 0.11 in perimenopausal and 0.90 +/- 0.11 g/cm2 in premenopausal women; P less than 0.005). Body weight showed the strongest positive correlation with bone density. Log FT, percent FT, and FE2 percent correlated positively with bone density, even after controlling for weight. Log SHBG was negatively correlated with bone density in premenopausal women at the hip and wrist after controlling for weight. FSH was inversely correlated with bone density, and E2 and T were lower in perimenopausal than premenopausal women. These data suggest that women who are still menstruating may have relative deficiencies in both E2 and T, with reduced bone densities as a consequence.

Adult↗
PubMed1989

The use of thrombin inhibitors and aprotinin in the preservation of platelets stored for transfusion.

We have evaluated the use of several thrombin inhibitors (heparin, Fragmin, hirudin, and Thromstop) in combination with cyclic adenosine 3',5'-monophosphate-active agents (prostaglandin E-1 [PGE-1] plus theophylline) and aprotinin for preparation and extended storage of platelet concentrates. Replacement of citrate with heparin resulted in accelerated clumping of platelets during storage. Fragmin, a low molecular weight heparin fraction, induced a high degree of platelet clumping, even in the presence of a standard amount of citrate (citrate-phosphate-dextrose-adenine formula 1 [CPDA-1]) plus PGE-1 and theophylline. The best anticoagulant formulation appeared to be CPDA-1 containing PGE-1 plus theophylline plus aprotinin, plus either hirudin or Thromstop for preservation of platelet responsiveness and structural integrity by in vitro markers. In eight platelet concentrates prepared with these inhibitors and stored for 15 days, the plasma pH was 6.50 +/- 0.15, the PO2 was 94 +/- 29 mm Hg, the PCO2 was 27 +/- 4 mm Hg, and the hypotonic shock response was 76% +/- 25% of the initial value recorded at Day 1 (all values expressed as mean +/- SD). Only 11% +/- 3% of the cellular lactate dehydrogenase was released, 69% +/- 8% of the platelets appeared to be in a discoid shape, and the response to 20 mumol/L adenosine 5'-diphosphate remained at 50% +/- 17% of the initial value. These results were all significantly different (p less than 0.01) from data obtained for concentrates prepared without aprotinin. The use of a factor Xa inhibitor (diamidino-benzofuranyl ethane) in place of Thromstop or hirudin did not provide substantial improvement over controls without inhibitors.

Aprotinin↗
PubMed1989

Dreaming: the impact of life stress events.

The impact of life stress on dreaming continues to be an area of clinical and research significance. Examined is recent research addressing sleep- and dream-related activity within the context of life stress events. Attention to dream activity as a function of maintaining psychological health and the therapeutic issues involved in health maintenance are discussed. Import for further clinical research is explored.

Adaptation, Psychological↗
PubMed1989

Plasmin activity and complement activation during storage of citrated platelet concentrates.

Platelet concentrates were studied for evidence of plasmin activity and complement activation during a 7-to-10-day storage period. When measured by an amidolytic activity assay, plasmin reached a level of 845 +/- 540 nkats/L on day 7 (n = 9). Fibrin(ogen) degradation product (FDP) levels became markedly elevated on the tenth day of storage, rising to 45 +/- 22 micrograms/ml (n = 5). Antiplasmin levels decreased in platelet concentrates by 18% +/- 6% (n = 5) over 7 days, but there was no significant decrease in stored platelet-poor plasma (-1.7%, n = 5, p = 0.5). The amount of plasminogen in platelet concentrate converted to plasmin was estimated to be less than 3% by assay of total plasminogen. Supernatant plasma from stored platelet concentrates was examined for the presence of the complement activation peptides C3a and C5a. From day 0 to day 10 of storage, mean C3a levels rose from 327 ng/ml to 6690 ng/ml. An equivalent increase in C3a levels, from 336 ng/ml at day 0 to 6866 ng/ml at day 10, was also observed in stored platelet-poor plasma. C5a was not detected (less than 10 ng/ml) at any point during the storage period; however, we noted a small decrease of borderline significance (p = 0.04) in total C5 from day 0 (117 micrograms/ml) to day 10 (108 micrograms/ml). Only trace amounts of C3 fragments were found on stored platelets, and there was no evidence of the membrane attack complex. These findings indicate the presence of plasmin activity and conversion of C3 during storage of platelet concentrates.

Blood Platelets↗
PubMed1989

An improved radioimmunoassay of C-peptide and its application in a multiyear study.

A commercial radioimmunoassay (RIA) for human proinsulin C-peptide was modified to improve its ruggedness and specificity, to decrease the influence of specimen matrix, and to shorten "hands-on" time. In the new protocol, we prepare calibrators in a C-peptide-free serum pool, prepared by treatment with activated charcoal (biological matrix), instead of in a defined matrix. This yielded essentially 100% analytical recoveries for C-peptide concentrations up to 300 pmol/L, a broader analytical range. We also corrected calibrators and unknown samples for nonspecific binding (NSB). Decreasing the concentration of ethanol (from 950 to 880 mL/L) for differential precipitation of the antigen-antibody complex resulted in an NSB of less than 10%, while maintaining high bound/total count percentages for samples and calibrators. C-peptide is thermally unstable without aprotinin at -20 degrees C and with or without aprotinin at 4 degrees C or above, but multiple freeze-thaw cycles do not affect C-peptide in serum. The modified C-peptide assay was applied to plasma from a multiyear study (fasting and post-carbohydrate-challenge subjects). During the four years of the study CVs ranged from 1.9% to 8.6% for replicate analyses of C-peptide in samples with concentrations less than or equal to 500 pmol/L. Between-run CVs were 3.8% to 8.2%, total CVs 3.8% to 10.7%.

Buffers↗
PubMed1988

Preservation of in vitro function of platelets stored in the presence of inhibitors of platelet activation and a specific inhibitor of thrombin.

We prepared platelet concentrates (PCs) in an experimental anticoagulant consisting of citrate-phosphate-dextrose-adenine formula 1 (CPDA-1) containing inhibitors of platelet activation (prostaglandin E1 and theophylline) and a specific thrombin inhibitor (hirudin or D-phenylalanyl-L-prolyl-L-arginine-chloromethyl ketone-2HCl). Over a 15-day storage period, these PCs showed by in vitro markers (pH, lactic dehydrogenase, PO2, PCO2, glucose consumption, morphology, and hypotonic shock recovery) greatly improved function and integrity relative to PCs in CPDA-1 only. At day 10 of storage, the experimental PCs had higher pH (P = 0.02), better morphology scores (P less than 0.001), more rapid recovery from hypotonic shock (P = 0.03), and higher PCO2 levels (P less than 0.001) than controls in CPDA-1 only. Additional storage time increased these differences to a significance level of p less than 0.01 in all tests. The experimental anticoagulant was less effective when hirudin was absent. Plasma pH was well maintained, and less glucose was consumed in the experimental anticoagulant without the aid of an increase of buffering capacity or gas transport. These findings indicate that thrombin and platelet activation play a major role in the development of the platelet storage lesion.

Adenine↗
PubMed1987

Prolonged neonatal alloimmune thrombocytopenic purpura associated with anti-Bak(a). Two cases in siblings.

Two cases of prolonged neonatal alloimmune thrombocytopenic purpura in siblings due to anti-Bak(a) are reported. The first case was complicated by an intracranial hemorrhage due to severe thrombocytopenia, but the second case had no untoward complications. Delivery by cesarean section and immediate platelet support from "compatible" (nonmaternal) donors may have contributed to the more favorable outcome in the second case. An analysis of the gene frequencies of platelet-specific antigens suggests that factors other than the potential for maternal exposure to antigen determine the incidence of affected births. Knowledge of gene frequencies may, however, permit a priori prenatal calculation of the probability of an affected birth for couples with a previously affected child even if the genotype of the father is unknown.

Acute Disease↗
PubMed1987

Interpretation of red cell survival data for in vivo compatibility testing: a normal value study.

Short-term survival studies are sometimes required to determine the compatibility of donor red cells. The results of these studies are generally expressed as per cent survival at 60 min. The present study was undertaken to investigate the potential for more sophisticated data analytical techniques to improve sensitivity. In one group of eight healthy male volunteers, autologous red cells were labelled with 51chromium and injected immediately, while in a second group, red cells were stored for 5 d prior to injection. In both groups, eight to 10 samples were collected in the first 6 h and another 10-12 samples over the next 4 weeks. Estimation of the 60 min per cent survival was insufficiently sensitive to detect 'physiological' haemolysis following injection of 5-d-old autologous blood. Regression analysis of 6 h survival data, however, demonstrated significantly higher red cell clearance rates in these cases than in those receiving fresh cells, with a mean 24 h loss of 3.3% of activity. The upper limit for the 6 h red cell clearance rate was 1.63%/h after fresh autologous blood and 2.43%/h after 5-d-old blood. The significance of these findings is discussed and a protocol suggested for the analysis of short-term red cell survival data.

Adult↗
PubMed1986

Effects of polychlorinated biphenyls and lipemia on serum analytes.

Twelve serum analytes [triglycerides, cholesterol, total and conjugated bilirubin, high-density-lipoprotein cholesterol (HDL-C), alkaline phosphatase (AP), gammaglutamyl transferase (GGT), aspartate aminotransferase (AST), alanine aminotransferase (ALT), beta-glucuronidase (beta-glu), alanine aminopeptidase (AAP), and 5'-nucleotidase (5'nuc)] were measured to investigate their correlation with exposure to polychlorinated biphenyls (PCBs) and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT). The relationship between serum lipids, lipophilic toxicants, and the analytes was also evaluated. The beta-glu, 5'nuc, triglycerides, cholesterol, and total bilirubin correlated positively and significantly with log concentrations of serum total PCBs and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), a metabolite of DDT. The more highly chlorinated PCBs (Aroclor 1260) had significant, positive correlations with several serum analytes, but the less chlorinated PCBs (Aroclor 1242) correlated significantly and negatively only with HDL-cholesterol. Triglyceride- and cholesterol-rich lipoproteins were added to serum to determine the effects of lipids on these assays. Several were spuriously elevated. AP and beta-glu were not affected by lipoprotein addition with the methods used in this study. AAP was increased significantly only at triglyceride concentrations exceeding 400 mg/dl. Lipoproteins may be elevated because of deranged lipid metabolism in response to PCBs, or PCBs may be elevated because elevated lipoproteins are present, as in familial triglyceridemia, a relatively common dyslipoproteinemia. Because this relationship is not well understood with respect to cause and effect, we propose the further use in epidemiological investigations of assay methods that are little affected by blood lipids yet are correlated with PCB concentrations. Congener-specific quantification of PCBs would help elucidate the effects of PCBs on assays used to monitor health effects.

5'-Nucleotidase↗
PubMed1986

Generation and degradation of fibrinopeptide A in stored platelet concentrate.

The levels of fibrinopeptide A (FPA) were measured in samples from stored platelet concentrates (PC) by radioimmunoassay. In 27 standard, citrated PC, the mean FPA was 13.6 ng/ml, which is elevated 5-6X over background levels. This value did not change significantly over a 7-day storage period. Addition of PGE-1 and theophylline resulted in higher initial levels of FPA (18.0 ng/ml) and a pronounced rise during the storage period (to 43.4 ng/ml by day 10). In contrast, addition of a thrombin inhibitor, D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone-2 HCl (PPACK) or hirudin, resulted in lower initial levels of FPA relative to standard, citrated PC and a slow increase over time. Introduction of exogenous FPA into citrated PC resulted in a predicted elevation of FPA levels followed by a rapid loss of immunoreactivity (t1/2 = 18 h). Addition of PPACK did not affect this fall-off. However, PC prepared and stored in the presence of PGE-1 and theophylline showed a much slower fall-off of exogenous FPA (t1/2 = 38 h). These data indicate that FPA levels in samples from citrated PC represent a dynamic balance between generation and degradation processes and, thus, the data above underestimate the amount of thrombin activity present in stored, citrated PC.

Amino Acid Chloromethyl Ketones↗
PubMed1986

Analysis of platelet factor 3 in platelet concentrates stored for transfusion.

The amount of platelet factor 3 (PF3) activity expressed in stored platelet concentrates (PC) was measured in conjunction with extracellular LDH levels. Standard manual techniques for preparation of PC resulted in PF3 and LDH levels remarkably higher than those observed in PC prepared by apheresis or special manual plateletpheresis. During storage of PC, PF3 activity rose 2- to 10-fold, while LDH levels rose less than 2-fold over starting values. Loss of LDH and appearance of PF3 expressed as a percent of total per platelet were significantly correlated only in standard, manual PC. Approximately half of the PF3 activity observed in any type of PC remained in the supernatant plasma after centrifugation. Upon gel filtration, the supernatant PF3 activity eluted in a high molecular weight peak containing phosphate and light-scattering material. Our findings indicate that platelets in standard, citrated PC express PF3 in amounts that approach that of frozen-thawed (lysed) platelets; however, the manner in which the PF3 activity appears suggests that stored platelets undergo a combination of activation and damage processes.

Blood Coagulation Factors↗
PubMed1985

A four-year experience with donor blood transfusion protocols for living-donor renal transplantation.

Our experience over the last 4 years with HLA-identical, donor-specific transfusion (DST), and Imuran (IM) + DST living-donor transplants in 206 patients is presented. Transplants from 8 completely incompatible sibling donors, 4 distantly related donors, and 7 unrelated donors are included. Except for a slightly higher average serum creatinine, and a markedly reduced rate of donor-specific sensitization in the IM + DST group when compared with the DST group (14% vs. 31%, P less than .005), the results of transplantation using these 3 protocols have been equivalent. Actuarial one-year survival was 97% for patients and 93% for grafts for the combined group of 206 patients. Of the 44 patients who entered the DST or IM + DST protocols but were not transplanted, 31 patients (70%) have subsequently been transplanted, and all 5 recipients of living-donor kidneys and 20 of 26 recipients of cadaveric kidneys (77%) have functioning grafts. Because it optimizes the availability of transplantable living-donor kidneys, gives results equivalent to those obtained with HLA-identical donors and the DST protocol, and is not associated with clinically apparent adverse effects, we now use the IM + DST protocol for all living-donor transplants except those between HLA-identical donor-recipient pairs.

Adolescent↗
PubMed1983

Beneficial effects of adenosine and phosphate in kidney preservation.

A new perfusate developed in the animal laboratory has been used in our clinical transplantation program in the last year. This perfusate provides excellent clinical results even with less-than-ideal kidneys, as manifested by an 83% immediate function rate and a 96.5% one-month graft survival. Optimum utilization of all donors referred to a transplant center may lessen the problem of insufficient donor organs. Continued basic research in the laboratory to optimize perfusion preservation may produce even better perfusates that can be adapted to the clinical situation and further improve graft survival.

Adenosine↗
PubMed1983

Comparative analysis of the DST and Imuran-plus-DST protocols for live donor renal transplantation.

We have done a comparative analysis of two consecutive clinical trials at our center: the first in 56 patients who received blood transfusions from their prospective donors (DST group), and the second in 36 patients who received such transfusions while they were taking Imuran in an attempt to reduce the incidence of sensitization against the donor (IM + DST group). The major findings of our study are: (1) Imuran significantly (P less than .05) reduced the rate of sensitization from 27% to 11%; (2) Patients who had prolonged dialysis before entering one of these protocols were significantly more likely to become sensitized against their living donors, and had significantly higher sensitization against the leukocyte panel, although panel-reactive antibodies were not significantly changed by transfusions from the live donor; (3) MLC reactivity against the living donor was not significantly altered by donor transfusions, and was also not different for sensitized and transplanted patients; (4) Results of transplantation were excellent in both patient groups, with only two grafts and two patients lost in 68 transplants (actuarial one-year survival of 97% and 93% of patients alive and with functional grafts at one year in the DST and IM + DST groups, respectively); (5) Rejection episodes occurred in about 50% of each group, but were of a special type (DST-type rejection) in about 30% of the DST patients and 10% of the IM + DST patients (P = .07); (6) The probability of transplantation, and the results of transplantation after unsuccessful entry into one of these protocols was not adversely affected. We think that primarily because of the low rate of sensitization the IM + DST protocol is superior to the DST protocol. Both, however, are established clinical tools that have increased our clinical transplant volume by a large number of highly successful transplants.

Azathioprine↗