Accumulation of platelets as a key mechanism of human erection

In this study, the role of platelets in the human erectile response was assessed. Twenty patients with erectile dysfunction were studied by means of (111)In-oxine-platelets and blood pool imaging using 99mTc. Seventeen patients received intracavernously prostaglandin E1, and three patients received papaverine together with phentolamine. In patients who responded with erection, an increase by between 16 to 137% platelets/ml and a rapid platelet accumulation in the penis during the initial phase of erection were observed. In patients without erection, no change in local platelet concentration occurred. It is likely that platelets play a major role in human erection, probably by temporary activation, thereby regulating venous outflow.

Hormonal influences on stress-induced neutrophil mobilization in health and chronic fatigue syndrome

This investigation tested the hypotheses that women diagnosed with chronic fatigue syndrome (CFS) would exhibit significantly greater systemic indices of exercise-induced leukocyte mobilization and inflammation (neutrophilia, lactoferrin release, complement activation) than controls matched for age, weight, and habitual activity and that responses in the luteal phase of the menstrual cycle would be greater than in the follicular phase. Subjects stepped up and down on a platform adjusted to the height of the patella for 15 min, paced by metronome. Blood samples were collected under basal conditions (the day before exercise) and following exercise for determination of circulating neutrophils and plasma concentrations of lactoferrin, C3a des arg, and creatine kinase. Complete, 24-hr urine collections were made for determination of cortisol excretion. For all subjects, circulating neutrophil counts increased 33% (P < 0.0001) and lactoferrin increased 27% (P = 0.0006) after exercise, whereas plasma C3a des arg and creatine kinase did not increase. No indication of an exaggerated or excessive response was observed in the CFS patients compared to the controls. In healthy women, circulating neutrophil numbers exhibited previously described relationships with physiological variables: basal neutrophil counts correlated with plasma progesterone concentrations (R = 0.726, P = 0.003) and the exercise-induced neutrophilia correlated with both urinary cortisol (R = 0.660, P = 0.007) and plasma creatine kinase (R = 0.523, P = 0.038) concentrations. These relationships were not observed in the CFS patients (R = 0.240, P = 0.370; R = 0.042, P = 0.892; and R = 0.293, P = 0.270; respectively). These results suggest that normal endocrine influences on the circulating neutrophil pool may be disrupted in patients with CFS.

Effects of prostaglandin E1 metabolites on the induction of arterial thromboresistance

Prostaglandin (PG) E1 has been shown to induce arterial thromboresistance in experimental animals and in man. It is known to be degraded in vivo to metabolites which have comparable (13,14-dihydro-PGE1) or no (15-keto-PGE1, 15-keto-13,14-dihydro-PGE1) biological activity. It was the goal of this study to examine whether 13,14-dihydro-PGE1 and its derivatives might share biological activity in rendering the arterial wall less thrombogenic. Using a cross-perfusion technique the aorta and iliac artery surface were exposed to a donor rabbits' blood. We examined the intact endothelial lining and a surface which had been deendothelialized before by means of a Fogarty catheter. Donor animals and/or receiver animals were treated daily for 1 week with 13,14-dihydro-PGE1, PGE1, 15-keto-PGE1, 15-keto-13,14-dihydro-PGE1, or the vehicle only, respectively. From the group of the receiver animals, a subgroup of 6 animals each was treated for the same period of time with either 13,14-dihydro-PGE1, PGE1, 15-keto-PGE1, 15-keto-13,14-dihydro-PGE1, or the vehicle. Immediately after the last administration of the respective PG or solvent, native blood from a donor rabbit was circulated [30 mL/min. under in vivo flow conditions (60 Hz)] over an arterial segment of a receiver animal. Deposition of 111Indium-oxine labeled autologous platelets per surface unit was quantitatively assessed. In vitro perfusion data were morphometrically analysed. In animals pretreated with 13,14-dihydro-PGE1 the thromboresistance was almost comparable to that achieved with PGE1. In contrast, pretreatment of the donor animals (platelet) had only minor effects on the thromboresistance. The other compounds showed no effects. In vitro perfusion of human saphenous vein segments revealed PGE1 and 13,14-dihydro-PGE1 again to be of comparable potency, while 15-keto-PGE1 and 15-keto-13,14-dihydro-PGE1 were only active at concentrations being several orders of magnitude higher. Not only PGE1 but also its in vivo formed metabolite PGE0 may play an important role in inducing improvement of haemostatic balance via the vascular wall rather than the platelets. The other metabolites, however, are unlikely to exhibit an effect at biologically relevant concentrations.

Linguistic processing during repetitive transcranial magnetic stimulation

To determine if linguistic processing could be selectively disrupted with repetitive transcranial magnetic stimulation (rTMS), rTMS was performed during a picture-word verification task. Seven right-handed subjects were trained in two conditions: picture-word verification, which required the subject to verify whether the picture of an object matched the subtitle name on the same page, and frame verification, which required subjects to verify whether there was a rectangular frame around the combined object picture and subtitle. Half of the trials were performed during rTMS. The effects of rTMS on performance were evaluated at the following four scalp positions: left anterior (the area where rTMS produced speech arrest), a mirror site on the right, and two positions in the left and right parietal region. Stimulation over the left deltoid muscle served as a control. Subjects had less difficulty in making picture-word matching decisions during unstimulated compared with stimulated trials at the left anterior and posterior positions. No significant difference in accuracy was detected in the frame verification condition, but response times in the frame verification condition were longer with stimulation at the left anterior position. Because rTMS of the dominant hemisphere affected linguistic processing independent of speech motor output, we confirm that rTMS may be used to investigate language and other cognitive functions.

Child fatality associated with pathological features of histiocytic necrotizing lymphadenitis (Kikuchi-Fujimoto disease)

We report a case of histiocytic necrotizing lymphadenitis without granulocytic infiltration (Kikuchi-Fujimoto disease), diagnosed at necropsy in a 19-month-old child dying unexpectedly after a febrile illness. This is the youngest case with this disease that has been thus far reported. It is one of only two reported cases in which the patient died during the acute phase of the illness. Histological findings not unlike those seen in the lymph nodes were present at extranodal sites; this is the first case in which this feature has been described. In keeping with many other reported cases, it was not possible to identify an underlying etiology that might explain the morphologic changes.

Alteration of rat cerebral microvascular eicosanoid formation by isradipine, a calcium channel blocker

We studied the influence of the calcium channel blocker isradipine on cerebral microvascular and aortic eicosanoid synthesis. The rat cerebral microvascular eicosanoid formation was assessed by means of bioassay, radioimmunoassay and radio thin layer chromatography from endogenous as well as from exogenous (20:4) radiolabelled substrate. The in vitro as well as the in vivo (0.3 mg/kg/day for 1 week) effect of isradipine was examined. Isradipine increased significantly (P < 0.01) both conversion to and formation of PGI2 and its derivative 6-oxo-PGF1alpha respectively, as well as PGD2-production, while TXB2-synthesis was diminished. The conversion to the other metabolites was not affected to a significant extent. These findings indicate that isradipine enhances PGI2-generation in aorta and cerebral microvessels from both exogenous and endogenous substrate and PGD2 from endogenous substrate, a phenomenon shown to underlie the antiatherosclerotic actions of this calcium channel blocker.

Randomised trial of efficacy and safety of oral ganciclovir in the prevention of cytomegalovirus disease in liver-transplant recipients. The Oral Ganciclovir International Transplantation Study Group [corrected]

BACKGROUND

Cytomegalovirus (CMV) disease is a frequent cause of serious morbidity after solid-organ transplantation. The prophylactic regimens used to prevent CMV infection and disease have shown limited benefit in seronegative recipients. We studied the safety and efficacy of oral ganciclovir in the prevention of CMV disease following orthotopic liver transplantation.

METHODS

Between December, 1993, and April, 1995, 304 liver-transplant recipients were randomised to receive oral ganciclovir 1000 mg or matching placebo three times a day. Seronegative recipients of seronegative livers were excluded. Study drug was administered as soon as the patient was able to take medication by mouth (no later than day 10) until the 98th day after transplantation. Patients were assessed at specified times throughout the first 6 months after surgery for evidence of CMV infection, CMV disease, rejection, opportunistic infections, and possible drug toxicity.

FINDINGS

The Kaplan-Meier estimate of the 6-month incidence of CMV disease was 29 (18.9%) of 154 in the placebo group, compared with seven (4.8%) of 150 in the ganciclovir group (p < 0.001). In the high-risk group of seronegative recipients (R-) of seropositive livers (D+), incidence of CMV disease was 11 (44.0%) of 25 in the placebo group, three (14.8%) of 21 in the ganciclovir group (p = 0.02). Significant benefit was also observed in those receiving antibodies to lymphocytes, where the incidence of CMV disease was 12 (32.9%) of 37 in the placebo group and two (4.6%) of 44 in the ganciclovir group (p = 0.002). Oral ganciclovir reduced the incidence of CMV infection (placebo 79 [51.5%] of 154; ganciclovir 37 [24.5%] of 150; p < 0.001) and also reduced symptomatic herpes-simplex infections (Kaplan-Meier estimates: placebo 36 [23.5%] of 154; ganciclovir five [3.5%] of 150; p < 0.001).

INTERPRETATION

Oral ganciclovir is a safe and effective method for the prevention of CMV disease after orthotopic liver transplantation.

Development of a humanized monoclonal antibody (MEDI-493) with potent in vitro and in vivo activity against respiratory syncytial virus

Neutralizing polyclonal antibody to respiratory syncytial virus (RSV) has been shown to be an effective prophylactic agent when administered intravenously in high-risk infants. This study describes the generation of a humanized monoclonal antibody, MEDI-493, that recognizes a conserved neutralizing epitope on the F glycoprotein of RSV. The affinity of MEDI-493 was found to be equal to or slightly better than an isotype-matched chimeric derivative of the parent antibody. In plaque reduction, microneutralization, and fusion-inhibition assays, MEDI-493 was significantly more potent than the polyclonal preparation. Broad neutralization of a panel of 57 clinical isolates of the RSV A and B subtypes was demonstrated. Pretreatment of cotton rats with MEDI-493 resulted in 99% reduction of lung RSV titers at a dose of 2.5 mg/kg, corresponding to a serum concentration of 25-30 microg/mL. Further, MEDI-493 did not induce increased RSV infection or pathology in either a primary or a secondary challenge.

Hyperalphalipoproteinemia and prostaglandin I2 stability

PGI2 is a powerful regulator of thromboresistance modulating the local platelet/vessel wall interaction. Beside the amount synthesised the availability of the biologically active compound depends on its half-life at the site of action. Plasmatic half-life of PGI2 is extremely shortened during severe infections, but also in acute myocardial infarction with extremely lowered levels of HDL-c and apoAI, the latter being described as a potential PGI2-stabilising factor. These conditions are characterised by an enhanced thrombophilic risk. This study investigated for the first time whether high levels of HDL-c (mean: 95 +/- 13 mg/dl) and apoAI (mean: 179 +/- 13 mg/dl) which have been shown epidemiologically to protect against coronary heart disease in turn might be associated with an increase in PGI2 half-life. Results were obtained from 31 healthy subjects with hyperalpha-LP as compared with 10 controls. The biological half-life of PGI2 (hyperalpha-LP: mean: 915 +/- 118 sec vs. controls: 714 +/- 70 sec; p = 0.001) was positively related to HDL-c (r = 0.8795, p < 0.001) and apoAI levels (r = 0.8025, p < 0.001). The partial correlation coefficient correcting for the association between HDL-c and apoAI levels was also significant (PGI2 to HDL-c: r = 0.6000, p < 0.001). These results suggest that the antiatherosclerotic properties of HDL might be at least partly due to an increase in PGI2 half-life.

Effect of isradipine on in-vivo platelet function

In animal studies calcium channel blockers (CCB's) and especially isradipine, a second generation dihydropyridine, interrupt the sequence of events culminating in the formation of atherosclerotic lesions. The effect of 4 weeks isradipine treatment (5mg daily) on blood pressure and in-vivo platelet function (measured with 111Indium-oxine labeled autologous platelets) were investigated in a randomized, double-blind and placebo controlled trial in 40 patients with mild to moderate hypertension and scintigraphically diagnosed active atherosclerotic lesions of the carotid arteries. The average supine systolic/diastolic blood pressure was significantly reduced at the end of the treatment period in the isradipine group (group 1; p < 0.0001) but remained unchanged in the placebo group (group P). The heart rate was not significantly altered in either group. There were no serious side effects. The platelet uptake ratio (PUR) measured over the atherosclerotic region of the carotid artery on 4 consecutive days before and after treatment decreased significantly in group I from 1.20 to 1.15 (within groups: p < 0.0001) but remained unchanged in group P. Platelet survival increased significantly in group I (mean 5.70 hours, lower quartile 4.50, upper quartile 4.50 hours, within groups: p < 0.0001) and remained unchanged in group P. Isradipine has a beneficial effect on in-vivo platelet function as evidenced by a decreased platelet deposition on vascular lesion sites and an associated prolonged platelet survival in patients with hypertension and active atherosclerotic lesions.

PGE1-induced arterial thromboresistance is a vascular property as identified by cross-perfusion technique

Prostaglandin (PG) E1 has been shown to improve thromboresistance. This experiment was designed to examine whether an effect on the arterial wall or the platelets is responsible for this phenomenon. Using a cross-perfusion model, the aortic and iliac artery endothelium of rabbits was removed by a balloon catheter before being perfused with blood of donor rabbits. Donor and/or receiver animals were treated with 20 microg PGE1 or vehicle (cyclodextrin) intravenously daily for 1 week. After the last administration of PGE1 or its vehicle, the animals were killed and native blood from a donor rabbit was recirculated (30 ml/min) via a deendothelialized segment of a receiver rabbit. The contact (C) and spread (S) platelets as well as the denuded surface covered with platelet aggregates (> 5 microm in height) were quantified by morphometry. Deposition of (111)In-oxine labeled autologous platelets was quantitatively determined per surface unit. In addition, PGI(2)- and TXB2-formation by the denuded aortic and iliac artery segments was determined. Pretreatment of receiver rabbits with PGE1 resulted in morphometrically assessed decreased platelet adhesion and aggregation, even when the donor rabbit was vehicle-treated. A vehicle-treated receiver rabbit, in contrast, shows platelet deposition comparable to controls, even if the donor rabbit was PGE1-pretreated. Treatment of donor animals with PGE1 did not result in a reduction in thrombogenicity. The beneficial in vivo PGE1 action of decreased arterial thrombogenicity is thus mediated by an effect on the vascular wall rather than on circulating platelets.

PET imaging of maze processing

Covered maze traversal models nonverbal planning, involving sequential execution of moves using learned spatial maps. To determine the neural substrate involved in maze processing, eleven adults underwent [H(2)15O]-PET while performing motor control, following the computer; visual control, choosing the wall with more dead-ends; uncovered maze, traversing fully visible mazes; covered maze, traversing mazes only locally visible. Maze processing lateralizes to the right hemisphere: uncovered maze versus controls revealed area 23 and 29 activation; covered maze versus controls activated areas 8, 10 and 19. The extrastriate region may store path information, evoked by prefrontal areas for spatial planning and navigation.

Epstein-Barr virus-associated Hodgkin's disease: epidemiologic characteristics in international data

Hodgkin's disease (HD) has long been suspected to have an infectious precursor, and indirect evidence has implicated Epstein-Barr virus (EBV), a ubiquitous herpesvirus, as a causal agent. Recent molecular studies using EBER in situ hybridization or latency membrane protein-I (LMP-I) immunohistochemistry have identified EBV latent infection in up to 50% of HD tumors. However, the epidemiologic features of these cases have not been examined in detail. To explore the epidemiology of EBV-positive HD so as to understand the role of EBV in HD etiology more clearly, this project accumulated patient data from 14 studies that had applied these EBV assays to HD tumors. With information on age at diagnosis, sex, ethnicity, histologic subtype, country of residence, clinical stage and EBV tumor status from 1,546 HD patients, we examined risk for EBV-positive disease using logistic regression. Forty percent of subjects had EBV-positive tumors, and EBV prevalence varied significantly across groups defined by the study variables. Odds ratios (OR) for EBV-associated HD were significantly elevated for Hispanics vs. whites (OR = 4.1), mixed cellularity vs. nodular sclerosis histologic subtypes (OR = 7.3, 13.4, 4.9 for ages 0-14, 15-49, 50+ years), children from economically less-developed vs. more-developed regions and young adult males vs. females (OR = 2.5). These findings suggest that age, sex, ethnicity and the physiologic effects of poverty may represent biologic modifiers of the EBV association and confirm that this association is strongly but variably linked to histologic subtype. The data augment biologic evidence that EBV is actively involved in HD pathogenesis in some cases but describe epidemiologic complexity in this process.

Prostaglandin E1 decreases human arterial accumulation of radiolabeled apo B-containing lipoproteins in vivo

OBJECTIVE

An increased apo B-containing lipoprotein influx and cholesterol ester accumulation in arteries are well-known events in human atherogenesis. In vitro and experimental animal studies have provided evidence of a beneficial effect of PGE1 on both vascular apo B-containing lipoprotein accumulation and cholesterol ester content.

METHODS

We examined the effect of PGE1 (administered via an intravenous portable infusion pump at a rate of 5 ng PGE1 kg-1.min-1 for 5 days a week, 6 h daily, over a total of 5 weeks) in ten patients (eight males, two females) on 123I-apo B-containing lipoprotein accumulation into the large arteries in vivo. Apo B-containing lipoprotein isolation was carried out by immunoaffinity chromatography and radiolabeling with the iodine monochloride method. 123I-apo B-containing lipoprotein accumulation was imaged and quantified by means of special computer software before and after 5 weeks of PGE1 therapy.

RESULTS

PGE1 led to a significant decrease in maximal arterial apo B-containing lipoprotein retention. The mean decrease in the carotid and femoral arteries in type I lesions amounted to between 16.9% and 30.4%, and in type II lesions between 22.4% and 30.7%, 20 h after injection of radiolabeled apo B-containing lipoprotein. The type of arterial apo B-containing lipoprotein kinetic curves, however, remained unchanged.

CONCLUSION

These findings indicate that PGE1 decreases the apo B-containing lipoprotein influx in the large arteries and the vascular cholesterol content, suggesting that PGE1 may lead to regression of lipid-rich lesions in human in vivo.

The prostacyclin stimulating plasma factor activity improves thromboresistance only if vascular PGI2-production is intact

PGI2 is important in regulating platelet vessel wall interaction (1). In perfusion chamber experiments the amount of PGI2 formed was inversely related to the amount of platelets deposited (2). In 1978 a plasma factor was described which stimulates vascular PGI2-production (3). In later years, this activity has been monitored in different patient groups (for review see 4). Interestingly, it has been found that diseases associated with an increased bleeding tendency such as uraemia (5) or hepatic failure (6) were associated with an increased PF-activity while others with an enhanced thrombophilia sometimes show an absence of PF-activity (7). Recently, the PGI2 stimulating plasma factor has been purified and cloned (8). It was the aim of these experiments to assess whether PF-activity plays a role in local hemostasis regulation under in-vivo flow conditions and whether this is dependent on the presence of an intact PGI2-formation.

Prevalence of herpesviridae and hepatitis B virus DNA in the liver of patients with non-A, non-B fulminant hepatic failure

Members of the herpes virus family and hepatitis B virus (HBV) have been implicated as etiologic agents in non-A, non-B (NANB) fulminant hepatic failure (FHF), but the frequency of infection with these agents has not been established using appropriate controls. To examine this issue, we studied 50 NANB FHF patients and 104 liver transplant recipients from North America and Europe. Hepatic DNA was analyzed by polymerase chain reaction (PCR) for evidence of Epstein-Barr virus (EBV), cytomegalovirus (CMV), herpes simplex virus I (HSV I) and II (HSV II), varicella-zoster virus (VZV), and human herpes virus-6 (HHV-6) nucleic acid sequences. The prevalence of HBV was assessed in North American subjects only. HSV I, HSV II, VZV, and HHV-6 viral sequences were not observed in any samples. Three of 50 FHF (6%) and 14 of 104 control patients (13%) were positive for CMV DNA. Two of 50 FHF (4%) and 10 of 104 control patients (10%) had EBV DNA, and HBV DNA was observed in 3 of 10 North American FHF patients (30%) and 3 of 59 controls (5%) without serum markers for HBV infection. The finding of HBV DNA in the liver of seronegative controls from North America but not Europe suggests that occult hepatitis B sequences in patients with NANB FHF may simply reflect geographic differences. The majority of cryptogenic FHF cases cannot be attributed to infection with herpes viruses or HBV.

Is a (n inborn) deficiency of prostacyclin synthesis stimulating plasma factor associated with increased lipoprotein(a)?

Patients with the antiphospholipid syndrome as well as those with a lack in the prostacyclin synthesis stimulating plasma factor (PF) are prone to develop thrombophilia and are at a higher clinical risk for vascular disease. As patients with the antiphospholipid syndrome have been reported to show elevated lipoprotein (Lp)(a) levels, we re-examined all our patients known to have an inborn or an acquired persistent deficiency of PF. Their non-affected relatives served as controls. In addition, 36 patients suffering from clinically manifested atherosclerosis as well as 16 healthy adults, all of them having elevated Lp(a) levels (> 30 mg/dl), were screened for a PF deficiency. In fact, all the patients with a deficient PF activity showed elevated Lp(a) values. While the prevalence of PF deficiency ranges about 1-2%, in 7 (19%) patients with clinically manifested atherosclerosis and 3 (19%) healthy adults with elevated Lp(a) this defect was found. The findings demonstrate an association between PF deficiency and Lp(a), indicating a biochemical interaction which needs to be further elucidated.

A finite element analysis of a mandibular canine as a denture abutment

A two dimensional finite element model was made of a mandibular canine and its supporting bone. The model was used to show stress values associated with loading the tooth as a partial denture abutment before and after modification to include rest seat preparations in different positions. Axial load produced a low pattern of stress while load on the unprepared tooth produced a very high pattern of stress. The effectiveness of rest seats in reducing stress in the alveolar bone was confirmed.

Prostaglandin I2-mediated upregulation of 125I-LDL-receptor binding by isradipine in normo- and hypercholesterolemic rabbits in vivo

The in-vivo low-density lipoprotein (LDL)-uptake by the liver was monitored during the initial 60 minutes after injection of radiolabelled LDL. LDL-uptake by the liver as evidenced by the liver/blood pool ratio in normocholesterolemic male New Zealand white rabbits (44.2 +/- 3.1% of whole body activity) was almost double as compared to the ones fed a 1% cholesterol enriched diet (22.5 +/- 3.3%). The blood disappearance of 125I-LDL was significantly faster in normocholesterolemic animals. A 4-week treatment with the dihydropyridine calcium channel blocker isradipine resulted in a significantly enhanced LDL-binding by the liver, both in normo- and hypercholesterolemic animals to a comparable extent. A concomitant acetylsalicylic acid (ASA) treatment completely abolished the benefit induced by isradipine while ASA alone was ineffective. Similarly, 125I-LDL disappearance from blood was improved by isradipine, while ASA neutralizes this effect. Again, ASA alone did not change the kinetics. Plasma cholesterol and high-density lipoprotein (HDL) cholesterol remained unchanged. Isradipine significantly enhanced vascular prostaglandin(PG)I2-generation while concomitant ASA treatment or ASA application alone almost completely depressed PGI2-formation. It is concluded that the improved LDL-binding by the liver is due to an enhanced PGI2-formation evoked by isradipine.

Ex-vivo and in-vivo platelet function in patients with severe hypercholesterolemia undergoing LDL-apheresis

Patients with severe familial hypercholesterolemia (HC) show abnormal platelet function and shortened platelet survival. Atherosclerosis is associated with platelet hyperactivity. Low-density lipoporotein (LDL)-apheresis eliminates the most atherogenic lipid fraction and inhibits the progression of atherosclerosis inducing even regression. In order to assess the influence of LDL-apheresis on platelet function ex-vivo and in-vivo, 6 patients with severe heterozygous HC, all of them being pharmacologically treated with HMG-CoA reductase inhibitors and anion exchange resins were investigated. Ex-vivo platelet function was assessed by the aggregation response to ADP before starting apheresis treatment, as well as after 2 and 24 weeks, respectively. In-vivo platelet function was determined by measuring platelet survival after radiolabeling with 111In-oxine before starting LDL-apheresis and after 24 weeks of twice monthly treatment. LDL-apheresis therapy induced a significant (p < 0.01) drop in cholesterol by 64%, LDL-cholesterol by 77% and in triglycerides by 46% over a period of 24 weeks. ADP-induced platelet aggregation revealed a decreased aggregability of platelets with a decline in the maximal amplitude and the slope of the response curve. Changes in platelet sensitivity to prostaglandins (PG) were significantly for PGI2, but did not reach statistical significance for PGE1. The results revealed a significant (p < 0.001) increase in platelet survival of 111In-oxine-radiolabeled autologous platelets from a mean of 106.50 hours before to 137.50 hours (p < 0.01) after treatment, being accompanied by an increase in labeling efficiency (p < 0.001) and recovery (p < 0.001). These data provide evidence for improved hemostatic regulation in vivo as a result of maintainance of lipid-lowering achieved with LDL-apheresis.

Apolipoprotein A and biological half-life of prostaglandin I2 in HIV-1 infection

Disturbances in lipid and lipoprotein metabolism being reported for HIV-1 infection are a common sign of severe infections. Apolipoprotein A being the main constituent protein of HDL has been described to function as the prostaglandinI2 (PGI2)-stabilising factor. PGI2 is not only one of the most potent biological antiaggregatory substances but seems to exert cell-protective properties in the central nervous system, too. PGI2 half-life as well as lipid [total-cholesterol (total-c), triglycerides] and (apo)lipoprotein [LDL-c, HDL-c and apolipoprotein (apo) AI] levels were investigated in 14 HIV-1 positive patients (13 males, 1 female, aged from 29 to 57 yrs). Patients exhibited decreased levels of total-c, LDL-c, HDL-c and apo AI, respectively, while elevated triglyceride levels were observed. PGI2 half-life was shortened (median 53, range: 15-161 seconds) in the patients' plasma as compared with normal controls ranging from 9-12 minutes. In patients with neurological manifestation (n = 8) the decrease of PGI2 half-life (median: 34 seconds, range: 15-67 seconds) was significantly more pronounced (p < 0.05) than in patients (n = 6) with the absence of any central nervous manifestation (median: 83.5, range: 29-161 seconds). The dramatic changes in both HDL-c and apolipoprotein AI as seen during HIV-1 infection are likely to impair PGI2-stabilisation thus being associated with the presence of peripheral neuropathy, dementia and haemostatic imbalance.