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PubMed2000

Redox status of plasma homocysteine and other plasma thiols in stroke patients.

Despite the growing evidence that plasma homocysteine is a cardiovascular risk factor, the mechanism behind the vascular injuries is still unknown. Studies are difficult as a result of the fact that little is known about the formation of different homocysteine species in vivo. Since extracellular glutathione and cysteine may influence the formation of different homocysteine species, we have in the present study investigated the different fractions of homocysteine and their relation to the different fractions of glutathione and cysteine in stroke patients and control subjects. We found a ratio of about 32-33% between reduced and total plasma glutathione concentrations and 2.6 3.0% between reduced and total plasma cysteine concentrations both in patients and in healthy control subjects. We noted an elevated concentration of total plasma homocysteine in stroke patients, but no difference in the ratio between reduced and total plasma homocysteine concentrations in patients and control subjects (mean value 1.20 and 1.10%, respectively). However, in a subgroup of patients with higher concentrations of total plasma homocysteine, we observed a significantly lower ratio of reduced to total plasma homocysteine compared to a subgroup of patients with lower concentration of total plasma homocysteine. A low reduced/total ratio of plasma homocysteine in combination with elevated plasma homocysteine concentrations might reflect an increased pro-oxidant activity in plasma from these patients. Thus, increased pro-oxidant activity in plasma might be one factor, besides genetic and nutritional factors, that could explain hyperhomocysteinemia. Since substantial evidence indicates that progression of atherosclerosis is related to enhanced pro-oxidant activity, the premature vascular disease associated with increased plasma homocysteine concentration might be as a result of increased pro-oxidant activity and the elevated plasma homocysteine concentration may only reflect the increased oxidative stress.

Aged↗
PubMed2003

High plasma homocysteine concentrations are associated with plasma concentrations of thrombomodulin in patients with type 2 diabetes and link diabetic nephropathy to macroangiopathy.

In type 2 diabetic patients with or without nephropathy, we examined relationships between plasma concentrations of total homocysteine (tHcy) and clinical macroangiopathy, as well as endothelial dysfunction indicated by plasma thrombomodulin (TM) concentrations. We studied 103 type 2 diabetic patients including 26 with macroangiopathy (12 patients with coronary artery disease [CAD], 10 with stroke, and 4 with peripheral vascular disease [PVD]). Plasma tHcy was measured by high-performance liquid chromatography. Plasma TM was determined by enzyme immunoassay. As an index of glomerular filtration rate, creatinine clearance (Ccr) also was determined in a 24-hour urine collection. Considering all diabetic patients, plasma tHcy concentrations were significantly higher in those with macroangiopathy than in those without (10.4 +/- 3.7 v 8.5 +/- 2.8 micromol/L, P=.0077). By univariate and multivariate analyses, plasma tHcy was correlated inversely with Ccr. Plasma tHcy concentrations were significantly higher in the patients with overt albuminuria than in those with normoalbuminuria or microalbuminuria. After exclusion of patients with renal insufficiency (Ccr<60 mL/min), differences in plasma tHcy concentrations between patients with and without macroangiopathy were abolished. By multivariate analysis, total cholesterol, urinary albumin, Ccr, C-peptide, and tHcy retained significant influence on the plasma TM. Even in patients with normal renal function (Ccr > or = 80 mL/min), plasma tHcy was correlated positively with plasma TM. In conclusions, diabetic nephropathy is a main determinant of plasma tHcy elevation in type 2 diabetic patients. Since plasma TM is independently associated with plasma tHcy, in diabetic patients with overt nephropathy, elevation of tHcy reflecting reduced clearance is a likely cause of endothelial dysfunction, resulting in the atherosclerosis underlying development of cardiovascular disease.

Aged↗
PubMed2007

Plasma 1,25-dihydroxyvitamin D levels in primary hyperparathyroidism depend on sex, body mass index, plasma phosphate and renal function.

BACKGROUND: Primary hyperparathyroidism (PHPT) is characterized by elevated plasma levels of PTH and calcium with reduced plasma phosphate. Physiologically, renal 1alpha,25-dihydroxyvitamin D [1,25(OH)(2)D] production is stimulated by PTH and phosphate deprivation, and inhibited by 1,25(OH)(2)D itself and calcium. AIM: To investigate relations between circulating levels of 1,25(OH)(2)D, 25-dihydroxyvitamin D (25OHD), PTH, calcium, phosphate, renal function and skeletal complications in patients with PHPT. DESIGN: Cross-sectional study. MATERIAL: Two hundred and fifty-two consecutive hypercalcaemic Caucasian patients aged 24-91 (median 65.9) years (85.3% females) with PHPT. RESULTS: In patients with PHPT, plasma 1,25(OH)(2)D was increased by 27%[107 (9-250) pmol/l, median (range)] compared to controls [84 (18-172) pmol/l, P < 0.001]. In univariate models, plasma 1,25(OH)(2)D depended inversely on age (r = -0.23, P < 0.001) and plasma phosphate (r = -0.23, P < 0.001) and positively on plasma calcium (r = 0.14, P < 0.05), plasma 25OHD (r = 0,15, P < 0.05) and creatinine clearance rate (r = 0.32, P < 0.001). In the final multiple regression model, plasma 1,25(OH)(2)D depended positively on renal function (r(p) = 0.43, P < 0.001) and female sex (r(p) = 0.15, P < 0.05) but inversely on body mass index (BMI; r(p) = -0.23, P < 0.005) and plasma phosphate (r(p) = -0.18, P < 0.05). Plasma 1,25(OH)(2)D correlated positively with renal calcium excretion and inversely with lumbar spine bone mineral density (BMD) but was not associated with risk of fractures or renal stones. CONCLUSION: Patients with PHPT have elevated plasma 1,25(OH)(2)D levels but, to a large extent, individual values overlap controls. The increase in plasma 1,25(OH)(2)D depends on renal function, hypophosphataemia and the female sex and is attenuated by high BMI. High plasma 1,25(OH)(2)D is associated with higher plasma calcium levels.

Adult↗
PubMed2004

Changes in plasma non-esterified fatty acids, glucose and alpha-amino nitrogen and their relationship with body weight and plasma growth hormone in growing buffaloes (Bubalus bubalis).

A study was undertaken to investigate the changes of plasma non-esterified fatty acids (NEFA), glucose and alpha-amino nitrogen and their relationship with age, body weight (BW) and plasma growth hormone (GH) in growing buffaloes. For the purpose, six growing female Murrah buffalo calves of 6-8 months of age were selected on the basis of their BW and fed according to Kearl standard (Nutrient Requirements of Ruminants in Developing Countries, International Feedstuffs Institute, Utah State University, Utah, USA, 1982, p. 89) for growing buffaloes (target growth rate 500 g/day) to meet energy and protein requirement of the animals. Blood samples collected at fortnight intervals for 1 year were analysed for plasma NEFA, glucose, alpha-amino nitrogen and GH. The animals were also weighed at fortnight intervals. Plasma NEFA and glucose levels were found to decrease (p < 0.01) with age. Unlike plasma NEFA and glucose, plasma alpha-amino nitrogen level increased (p < 0.01) as the buffaloes become older. Plasma NEFA and glucose concentrations in growing buffaloes were found to be positively correlated with plasma GH (r = 0.379 and 0.420 respectively), but these were non-significant (p > 0.01). However, plasma NEFA and glucose showed a good correlation (p < 0.01; r = 0.780 and 0.652 respectively) with plasma GH per 100 kg live weight. Plasma alpha-amino nitrogen exhibited non-significant (p > 0.01) negative correlation (r = -0.295) with plasma GH but a negative correlation (p < 0.01; r = -0.641) with GH per 100 kg BW. So, plasma metabolites showed a definite pattern of change during growth and these have a significant (p < 0.01) correlation with plasma GH per 100 kg BW than GH.

Age Factors↗
PubMed1982

Contribution of plasma protease inhibitors to the inactivation of kallikrein in plasma.

Although Cl-inhibitor (Cl-INH) and alpha(2)-macroglobulin (alpha(2)M) have been reported as the major inhibitors of plasma kallikrein in normal plasma, there is little quantitative support for this conclusion. Thus, we studied the inactivation of purified kallikrein in normal plasma, as well as in plasma congenitally deficient in Cl-INH, or artificially depleted of alpha(2)M by chemical modification of the inhibitor with methylamine. Under pseudo-first-order conditions, the inactivation rate constant of kallikrein in normal plasma was 0.60 min(-1). This rate constant was reduced to 0.35, 0.30, and 0.06 min(-1), in plasma deficient respectively in Cl-INH, alpha(2)M, or both inhibitors. Thus Cl-INH (42%) and alpha(2)M (50%) were found to be the major inhibitors of kallikrein in normal plasma. Moreover all the other protease inhibitors present in normal plasma contributed only for 8% to the inactivation of the enzyme. To confirm these kinetic results, (125)I-kallikrein (M(r) 85,000) was completely inactivated by various plasma samples, and the resulting mixtures were analyzed by gel filtration on Sepharose 6B CL for the appearance of (125)I-kallikrein-inhibitor complexes. After inactivation by normal plasma, 52% of the active enzyme were found to form a complex (M(r) 370,000) with Cl-INH, while 48% formed a complex (M(r) 850,000) with alpha(2)M. After inactivation by Cl-INH-deficient plasma, >90% of the active (125)I-kallikrein was associated with alpha(2)M. A similar proportion of the label was associated with Cl-INH in plasma deficient in alpha(2)M. After inactivation by plasma deficient in both Cl-INH and alpha(2)M, (125)I-kallikrein was found to form a complex of M(r) 185,000. This latter complex, which may involve antithrombin III, alpha(1)-protease inhibitor, and/or alpha(1)-plasmin inhibitor, was not detectable in appreciable concentrations in the presence of either Cl-INH or alpha(2)M, even after the addition of heparin (2 U/ml). These observations demonstrate that Cl-INH and alpha(2)M are the only significant inhibitors of kallikrein in normal plasma confirming previous predictions based on experiments in purified systems. Moreover, in the absence of either Cl-INH or alpha(2)M, the inactivation of kallikrein becomes almost entirely dependent on the other major inhibitor.

Angioedema↗
PubMed1977

The effects of temperature and plasma cortisol on distribution of aldosterone between plasma and red blood cells: influence on metabolic clearance rate and on hepatic and renal extraction of aldosterone.

Aldosterone enters red blood cells (RBC) to a greater extent at 37 C than at lower temperatures. The ratio of 3H-aldosterone concentration in RBC to that in plasma increases from 0.2 at 4 C to 0.7 at 37 C when cortisol concentration is low. Increasing plasma cortisol increases the RBC/plasma aldosterone ratio. When plasma transcortin (CBG) is saturated with cortisol, the RBC/plasma ratio of 3H-aldosterone approaches 0.93, the ratio observed in RBC incubated in 4% albumin solution. The effects of plasma cortisol and temperature on the RBC/plasma ratio reflect an affinity of aldosterone for plasma CBG greater than the affinity for plasma albumin or RBC. Hepatic extraction averages 92% of plasma and RBC aldosterone. Neither hepatic extraction nor renal extraction (less than or equal to 20%) is significantly altered by changing plasma cortisol concentration. Whole blood MCR of aldosterone is unaffected by redistribution of aldosterone from plasma to RBC when plasma cortisol increases, but both plasma cortisol and the temperature at which blood is separated affect the RBC/plasma ratio of 3H-aldosterone and thus change the calculated plasma MCR. The RBC transport of aldosterone, and its dependence on temperature and plasma cortisol, must be taken into account in the evaluation of plasma aldosterone concentration.

Aldosterone↗
PubMed1997

Plasma protein abnormalities in nephrotic syndrome: effect on plasma colloid osmotic pressure and viscosity.

The concentrations of 25 plasma proteins were measured in 22 patients with membranous nephropathy. For some large proteins, the plasma concentrations were increased; there were also large proteins with low plasma concentrations, but small or medium-sized proteins showed uniformly lower plasma concentration than the controls. Plasma colloid osmotic pressure (pi) and viscosity (eta) were not interrelated but showed positive and significant correlations with plasma concentrations of small and medium-sized proteins (pi) and plasma concentrations of large proteins (eta), respectively. Nephrotic plasma is not efficient in maintaining plasma pi but highly efficient in maintaining plasma eta. High plasma fibrinogen concentrations and low antithrombin III concentrations may predispose to thrombosis, and low IgG concentrations may account for the higher predisposition to bacterial infection. The relative composition of nephrotic plasma is heavily dependent on the size of the different proteins. Plasma pi and eta are also maintained by the relative preponderance of different plasma proteins.

Adult↗
PubMed1998

The use of plasma as a replacement fluid in plasma exchange. Canadian Apheresis Group.

BACKGROUND: The Canadian Apheresis Group has maintained a national registry of apheresis activities for the past 16 years. Since 1991, the use of plasma as a replacement fluid in plasma exchange has been recorded. STUDY DESIGN AND METHODS: Six years of data from the registry on the use of plasma as a replacement fluid were analyzed. RESULTS: Plasma was used in more than 25 percent of all plasma exchange procedures. Of 41,519 plasma exchange procedures reported, 11,970 used plasma alone or in combination with albumin. In 1991, 1026 (78%) of these procedures used plasma appropriately for either thrombotic thrombocytopenic purpura (TTP) or adult hemolytic uremic syndrome (HUS); between 1992 and 1996, these numbers were 1043 (81%), 1570 (86%), 1171 (87%), 2192 (92%), and 2741 (90%), respectively. In the remaining procedures, frozen or cryosupernatant plasma was administered to 326 patients for a total of 40 diseases other than TTP or HUS. CONCLUSIONS: In those diseases for which plasma was administered as the sole replacement fluid, no disease appears to justify such treatment without the existence of an associated condition requiring specific replenishment of some plasma component. Further evaluation of the specific indications for the use of plasma as a replacement fluid in plasma exchange is required for diseases other than TTP or HUS.

Adult↗
PubMed1999

Cost-effectiveness of transfusing virus-inactivated plasma instead of standard plasma.

BACKGROUND: Virus inactivation of plasma intended for transfusion avoids the transmission of hepatitis B virus, hepatitis C virus, and HIV. However, because most plasma recipients also receive other blood components concomitantly, the procedure reduces but cannot eliminate the risk of transfusion-transmitted infection. As virus-inactivated plasma has just been licensed in the United States and other countries, a cost-effectiveness analysis is pertinent. STUDY DESIGN AND METHODS: A Monte Carlo simulation of a Markov model representing the possible outcomes of plasma recipients was used to derive costs and utilities of transfusing virus-inactivated plasma instead of standard plasma. Probability distributions for patients' age and sex and for the number of blood components transfused per case were determined in 924 plasma recipients in a tertiary-care hospital. Other values were obtained from the medical literature. Results of the baseline and sensitivity analyses are the mean (+/- SD) of 10 simulations with 10(7) patients per simulation. RESULTS: In the baseline analysis, transfusing virus-inactivated plasma instead of standard plasma prolonged the quality-adjusted survival by 1 hour and 11 minutes per patient, at a cost-effectiveness ratio of $2,156,398 +/- $257,587 per quality-adjusted life year gained. Cost-effectiveness was most sensitive to the patients' mean age, the incremental cost per unit of virus-inactivated plasma, the HIV and hepatitis C virus transmission rates, and the short-term mortality of plasma recipients due to their underlying diseases. CONCLUSIONS: Compared to most accepted medical procedures, the transfusion of virus-inactivated plasma produces little health benefit at a very high cost. This poor cost-effectiveness ratio is due to the low current risk of infection with transfusion-transmitted viruses and to the greater age and poor short-term prognosis of most plasma recipients.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Correlation between changes in plasma HIV RNA levels and in plasma infectivity in response to antiretroviral therapy.

We evaluated the degree of correlation between the variation of different HIV-1 viral load measures in response to antiretroviral therapy. A quantitative reverse transcriptase polymerase chain reaction (RT-PCR) for plasma HIV-RNA, and HIV plasma infectivity titration, were performed on prospective samples obtained from 86 antiretroviral-naive patients with symptomatic infection and CD4+ < 300/mm3, enrolled in a randomized double-blind trial of the HIV protease inhibitor saquinavir (SQV) in combination with zidovudine (ZDV). Subjects were stratified according to plasma virus infectivity and examined for correlations between distinct response categories with respect to CD4 count and HIV RNA copy number changes. Infectious virus could be titrated in 72% of patients at baseline. A significant reduction (< 1 log10) in HIV plasma infectivity titer was observed during the study in 69% of these patients. The reduction in plasma infectivity was a good predictor of sustained CD4+ cell increases and of sustained decrease in HIV RNA plasma copies. A decrease of at least 0.5 log10 in HIV RNA copy number was observed in 82% of the treated patients. A good correlation was found between HIV plasma infectivity titer and plasma HIV RNA copy number variations (p < 0.001). However, 10 of 17 patients with unchanged plasma infectivity titer showed a significant reduction in HIV RNA copies. While a good correlation was found between plasma infectivity and RNA plasma copies variations, only a minor correlation was found between CD4+ cell count variation and plasma infectivity titer variation. However, reduction in plasma infectivity was a very good predictor of high CD4 changes.

Anti-HIV Agents↗
PubMed1985

Changes in plasma fibronectin during donor apheresis and therapeutic plasma exchange.

Changes in plasma levels of the opsonic glycoprotein fibronectin were studied during machine apheresis in 32 healthy plasma donors and 18 patients undergoing a total of 86 therapeutic plasma exchanges. Donation of 500 ml of plasma at 3-monthly intervals produced a 10% immediate decrease in plasma fibronectin with no evidence of a long-term affect on levels of this protein. One plasma volume exchange with fibronectin-poor plasma protein fraction produced subnormal plasma fibronectin levels in 98% of post-exchange samples. Efficiency of exchange was significantly lower in patients with paraproteinaemia, probably reflecting increased plasma volume in such patients. Daily plasma exchange produced progressive depletion of plasma fibronectin (index of recovery 0.68) whereas levels were maintained close to the initial value with longer exchange intervals, except in the more severely ill patients. Reduction of plasma fibronectin by plasma exchange may increase susceptibility to infection and reduce the efficacy of this procedure when the object of exchange is to reverse reticuloendothelial blockade.

Adult↗
PubMed1980

A technique developed for isolated canine papillary muscle function in various plasmas; and utility ascertained with plasma containing myocardial depressant factors.

Isolated papillary muscles from young dogs were studied to determine the feasibility of utilizing plasma, without added foam depressants, as a test solution to support muscle function. Diluted canine plasma, undiluted canine plasma, plasma with adjusted protein content, monkey plasma, and plasma containing myocardial depressant factors (MDF) were evaluated. For each test, each papillary muscle served as its own control, with either Krebs-Henseleit solution or a control plasma to establish a basis for evaluation of the test plasma. A technique was implemented to oxygenate the muscle, in plasma, without foam production and to monitor pH continuously. These studies indicated that plasma (diluted, undiluted, or with protein adjustments to accommodate experimental procedural requirements) was a satisfactory test solution. Furthermore, plasma from species unrelated to the dog could be utilized. In utilizing plasma, it was essential to establish or adjust the pH and osmolarity for normal muscle function. These studies with plasma containing MDF indicated that MDF depressed canine papillary muscle function. The Vmax values and Po values were decreased and latency was increased. The effects of MDF in canine papillary muscle preparations were completely reversible in short-term studies (up 10 10 hours' duration).

Animals↗
PubMed1975

[Plasma aldosterone and plasma renin activity in patients with essential and renal hypertension under acute stimulation with saline depletion and acute suppression with saline infusion].

Plasma aldosterone, plasma renin activity, sodium and potassium in the plasma and the urine were determinated under acute stimulation with saline-depletion (furosemide) and under acute suppression with saline infusion in 40 patients with primary hypertension stage I, 19 patients with primary hypertension stages II and III, and 11 patients with renal hypertension (chronic glomerulonephritis and chronic pyelonephritis). The majority of the patients with primary hypertension stage I showed a good stimulation of the plasma aldosterone and the plasma renin activity under acute salt depletion. Three out of the 40 patients with primary hypertension stage I, and 13 of the 19 patients with primary hypertension stages II and III did not show any stimulation of the renin secretion ("low renin hypertension"). In all these patients the plasma aldosterone stimulation remained intact. With infusion of saline all the groups showed suppression of the plasma aldosterone and the plasma renin activity. A good stimulation of the plasma renin activity, demonstrates that in our experiments the renin-angiotensin system cannot be responsible for the increase in aldosterone secretion under salt depletion. Most likely the increase of the plasma aldosterone, in spite of the fixed renin activity, is stimulated by the sodium depletion due to diuretics. In all patients with primary hypertension we did not find an inadequate reaction of the aldosterone secretion under saline infusion. The patients with renal hypertension showed a minimal stimulation and suppression of the plasma renin activity. The plasma aldosterone secretion increased only slightly under sodium depletion and the decrease under saline infusion was statistically not significant. Thus we conclude that these patients show an inadequate reaction of the plasma aldosterone and renin secretion under salt infusion and depletion.

Adult↗
PubMed1992

A marked molecular heterogeneity of growth hormone (GH) detected in the plasma but not pituitary of a patient with acromegaly: comparison with other acromegalics and an implication for discrepant plasma levels of GH and insulin-like growth factor.

We experienced a 41-year-old acromegalic male (Case 1) in whom the basal plasma GH was extremely high (320-450 ng/mL) but plasma IGF-I was only slightly elevated (2.0-2.8 U/mL). His nutritional condition and associated diabetes mellitus did not appear to be responsible for the relatively low IGF-I level, and a GH-autoantibody in the plasma was absent. We thus performed gel filtration analyses of his plasma and somatotroph adenoma to determine elution patterns of immunoreactive (IR) and receptor active (RA) GH. For comparison, the same studies were carried out on plasmas and somatotroph adenomas obtained from three other acromegalics (Cases 2-4) whose basal plasma GH and IGF-I levels were 22-45 ng/mL and 3.5-6.0 U/mL, respectively. IR GH in Case 1's plasma distributed over an extremely wide range keeping similar titers rather than showing three discernible components (big-big, big, and little GH) as did plasmas and adenomas from Cases 2-4. And, most of the IR GH in Case 1's plasma was eluted in such fractions that contained low levels of RA GH, indicating a minor proportion of biologically active GH. However, interestingly, the chromatographic profile and total GH content of Case 1's adenoma were similar to those of Cases 2-4's adenomas. These results may, at least in part, explain the discrepancy between the plasma GH and IGF-I levels of Case 1. The unexpectedly different GH elution patterns between the plasma and adenoma from this patient, may suggest a contribution of certain plasma factor(s) to the unusual chromatographic profile of plasma GH.

Acromegaly↗
PubMed1993

Determination of GABA and vigabatrin in human plasma by a rapid and simple HPLC method: correlation between clinical response to vigabatrin and increase in plasma GABA.

The novel antiepileptic drug vigabatrin (Sabril) acts by inhibiting degradation of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), increasing the GABA concentrations in the brain. Because the GABA degrading enzyme GABA aminotransferase (GABA-T) is also present in peripheral tissues, including blood platelets, measurement of plasma GABA levels might be a useful indication of the pharmacological response to vigabatrin during therapeutic monitoring. However, because of the very low concentrations of GABA in plasma, the few methods available for plasma GABA analysis are time-consuming, difficult to perform and/or not selective enough because of potential interference with other plasma constituents. In the present study, a rapid, selective and sensitive amino acid analysis HPLC method has been developed for plasma GABA determination with fluorescence detection, using o-phthaldialdehyde as a precolumn derivatizing agent. By employing a 3 microns particle size reversed-phase column and a multi-step gradient system of two solvents, the very low endogenous concentration of GABA in human plasma could be reproducibly quantitated without interference of other endogenous compounds. Incubation of human plasma samples with GABA degrading enzyme(s) resulted in an almost total loss of the GABA peak, thus demonstrating the specificity of the method for GABA analysis. In addition to GABA and other endogenous amino acids, the HPLC method could be used to quantitate plasma levels of vigabatrin. Thus, this improved HPLC amino acid assay might be used to examine whether concomitant monitoring of plasma GABA and vigabatrin is useful for clinical purposes. This was examined in 20 epileptic patients undergoing chronic treatment with vigabatrin. The average plasma GABA level of these 20 patients did not differ significantly from non-epileptic controls. However, when epileptic patients were subdivided according to their clinical response to vigabatrin, vigabatrin responders had significantly higher GABA levels than nonresponders or controls. In contrast to the difference in plasma GABA, vigabatrin responders and nonresponders did not differ in dose or plasma level of vigabatrin. These data may indicate that determination of plasma GABA is a valuable non-invasive method for therapeutic monitoring in patients on medication with vigabatrin.

Adult↗
PubMed2000

Plasma HIV-1 copy number and in vitro infectivity of plasma prior to and during combination antiretroviral treatment.

Some studies on untreated patients have shown a general correlation between plasma HIV copy number and plasma infectivity in in vitro models. Recent observations also indicate that HIV-RNA level is an important predictor of perinatal transmission and may also have a role in heterosexual transmission. To further analyse the correlation between HIV viral load and plasma infectivity, we studied the relationship between HIV-1 plasma copy number and plasma infectivity prior to and during treatment with antiretroviral combination regimens in HIV-1 infected adults. Plasma infectivity was assessed in vitro by coculture of plasma from HIV-positive patients with PHA-stimulated fresh PBMC from uninfected donors. A positive plasma isolation, in almost all cases (43/45) and irrespective of treatment status, was associated with an HIV viral load higher than 100000 copies per ml, with higher plasma HIV-1 RNA values in isolation-positive samples compared with isolation-negative samples (median values, 710000 vs. 37500 copies per ml, respectively). SI and NSI strains had similarly high viral load values (470000 vs. 790000 copies per ml), but CD4 counts were lower in the SI phenotype group. Our data indicate that low levels of viral load are only exceptionally associated with isolation from plasma in the in vitro model we used. This observation confirms indirectly the presence of an association between viral load and infectivity. The requisite of a high plasma viral load in order to obtain infectivity (i.e. positivity of HIV isolation from plasma) also seems maintained under antiretroviral treatment, adding confidence in the conclusion that reductions in viral load translate into reduction of plasma infectivity. Due to the extreme complexity of factors determining transmission, a very prudent interpretation of the results is essential when information from experimental studies has to be transferred to clinical situations requiring assessment of risks or clinical decisions.

Adult↗
PubMed1996

Comparison of lyophilized plasmas with fresh plasmas for calibration of thromboplastin reagents in oral anticoagulant control.

In a multicentre study of four thromboplastin reference materials (three from rabbit brain and one from bovine brain combined with adsorbed bovine plasma), three types of lyophilized plasmas were included. One was a pooled normal plasma, another was made by pooling plasmas of coumarin-treated patients, and the third was prepared by adsorption of vitamin K dependent clotting factors (artificially depleted). The purpose of this study was to investigate whether these lyophilized plasmas could be used for reliable calibration of the four thromboplastins. Calibration line slopes were calculated for the lyophilized plasmas and compared to the slopes based on fresh plasmas. When a rabbit thromboplastin was calibrated against a similar but not identical reagent (like-to-like comparison), the slopes for lyophilized plasmas and for fresh plasmas were the same. However, significant differences between lyophilized and fresh plasmas were observed in the calibration of unlike thromboplastins. The deviation of the slope with artificially depleted plasma was greater than that with lyophilized coumarin plasma. Indiscriminate use of these lyophilized plasmas for thromboplastin calibration should be avoided.

Administration, Oral↗
PubMedDate not supplied

Evaluation of factor VIII-rich cryoprecipitate and the plasma fibronectin-rich, heparin-precipitable fraction prepared from single-donor plasma units.

A plasma fibronectin-rich component was prepared by heparin-induced 4 degrees C precipitation of fresh or stored (21 days at 4 degrees C), single-donor plasma. The recovery of plasma fibronectin was 45 percent at a concentration of 0.05 mg heparin per ml (7.5 units/ml) and 75 percent at 0.1 mg per ml (15 units/ml). The biologic activity of plasma fibronectin, as assessed by the spreading of Chinese hamster ovary cells or attachment of monocytes to gelatin-coated surfaces, was similar to that of plasma fibronectin concentrates made from fresh or stored plasma. Only 20 to 30 percent of the factor VIII activity in fresh plasma was recovered in cryoprecipitate produced after the heparin-induced precipitate containing fibronectin was removed. Cryoprecipitate prepared from the supernatant plasma that remains after heparin-induced cold precipitation in the presence of CaCl2 (5 mM) contained approximately 50 percent less factor VIII. The relatively low recovery of factor VIII in cryoprecipitate prepared from fibronectin-depleted plasma makes cryoprecipitation an unsuitable method of producing fibronectin-rich and factor VIII-rich components effectively from a single unit of fresh plasma. However, heparin-induced cold precipitation provides an efficient method for preparing plasma fibronectin concentrates from small plasma pools or single units of stored or fresh plasma.

Blood Preservation↗