Effects of intense exercise training on endothelium-dependent exercise-induced vasodilatation

To determine whether intense exercise training affects exercise-induced vasodilatation, six subjects underwent 4 weeks of handgrip training at 70% of maximal voluntary contraction. Exercise forearm vascular conductance (FVC) responses to an endothelium-dependent vasodilator (acetylcholine, ACH; 15, 30, 60 μg min^?1) and an endothelium-independent vasodilator (sodium nitroprusside, SNP; 1·6, 3·2, 6·4 μg min^?1) and FVC after 10 min of forearm ischaemia were determined before and after training. Training elicited significant (P<0·001) increases in grip strength (43·4 ± 2·3 vs. 64·1 ± 3·5 kg, before vs. after, mean ± SEM), forearm circumference (26·7 ± 0·4 vs. 27·9 ± 0·4 cm) and maximal FVC (0·4630 ± 0·0387 vs. 0.6258 ± 0·0389 units, P<0·05). Resting FVC did not change significantly with training (0·0723 ± 0·0162 vs. 0.0985 ± 0·0171 units, P>0·4), but exercise FVC increased (0·1330 ± 0·0190 vs. 0.2534 ± 0·0387 units, P<0·05). Before and after the training, ACH increased exercise FVC above the control (no drug) exercise FVC, whereas SNP did not. Training increased (P<0·05) the exercise FVC responses to ACH (0·3344 ± 0·1208 vs. 0.4303 ± 0·0858 units, before vs. after training, 60 μg min^?1) and SNP (0·2066 ± 0·0849 vs. 0.3172 ± 0·0628 units, 6·4 μg min^?1). However, these increases were due to the increase in control (no drug) exercise FVC, as the drug-associated increase in exercise FVC above control did not differ between trials (P>0·6). These results suggest that exercise FVC is increased by both exercise training and stimulating the release of endothelium-dependent vasodilators. However, training does not affect the vascular response to these vasodilators.     

Effect of glibenclamide on insulin release at moderate and high blood glucose levels in normal man

Insulin release occurs in two phases; sulphonylurea derivatives may have different potencies in stimulating first- and second-phase insulin release. We studied the effect of glibenclamide on insulin secretion at submaximally and maximally stimulating blood glucose levels with a primed hyperglycaemic glucose clamp. Twelve healthy male subjects, age (mean ± SEM) 22.5 ± 0.5 years, body mass index (BMI) 21.7 ± 0.6 kg m^?2, were studied in a randomized, double-blind study design. Glibenclamide 10 mg or placebo was taken before a 4-h hyperglycaemic clamp (blood glucose 8 mmol L^?1 during the first 2 h and 32 mmol L^?1 during the next 2 h). During hyperglycaemic clamp at 8 mmol L^?1, the areas under the Δinsulin curve (AUC_Δinsulin , mean ± SEM) from 0 to 10 min (first phase) were not different: 1007 ± 235 vs. 1059 ± 261 pmol L^?1 × 10 min (with and without glibenclamide, P = 0.81). However, glibenclamide led to a significantly larger increase in AUC_Δinsulin from 30 to 120 min (second phase): 16 087 ± 4489 vs. 7107 ± 1533 pmol L^?1 × 90 min (with and without glibenclamide respectively, P < 0.03). The same was true for AUC_ΔC-peptide: no difference from 0 to 10 min but a significantly higher AUC_ΔC-peptide from 30 to 120 min on the glibenclamide day (P < 0.01). The M/I ratio (mean glucose infusion rate divided by mean plasma insulin concentration) from 60 to 120 min, a measure of insulin sensitivity, did not change: 0.26 ± 0.05 vs. 0.22 ± 0.03 μmol kg^?1 min^?1 pmol L^?1 (with and without glibenclamide, P = 0.64). During hyperglycaemic clamp at 32 mmol L^?1, the AUC_Δinsulin from 120 to 130 min (first phase) was not different on both study days: 2411 ± 640 vs. 3193 ± 866 pmol L^?1 × 10 min (with and without glibenclamide, P = 0.29). AUC_Δinsulin from 150 to 240 min (second phase) also showed no difference: 59 623 ± 8735 vs. 77389 ± 15161 pmol L^?1 × 90 min (with and without glibenclamide, P = 0.24). AUC_ΔC-peptide from 120 to 130 min and from 150 to 240 min were slightly lower on the glibenclamide study day (both P < 0.04). The M/I ratio from 180 to 240 min did not change: 0.24 ± 0.04 vs. 0.30 ± 0.07 μmol kg^?1 min^?1 pmol L^?1 (with and without glibenclamide, P = 0.25). In conclusion, glibenclamide increases second-phase insulin secretion only at a submaximally stimulating blood glucose level without enhancement of first-phase insulin release and has no additive effect on insulin secretion at maximally stimulating blood glucose levels. Glibenclamide did not change insulin sensitivity in this acute experiment.     

Reduction of the acute bioavailability of metformin by the α-glucosidase inhibitor acarbose in normal man

In a double-blind cross-over study, we investigated a possible influence of the α-glucosidase inhibitor acarbose on the bioavailability of the biguanide compound metformin. Each of the six healthy young male volunteers was randomly allocated during two consecutive 7 day periods to either acarbose (days 1–3: 3 times 50mg day^?1; days 4–7: 3 times 100 mg day^?1) or placebo. At day 7 and 14 of the study, the overnight-fasted subjects ingested 1000mg metformin with the first bite of a standardized breakfast (500kcal; 60 g carbohydrates) and together with either placebo or 100 mg acarbose. Acarbose significantly (P < 0·05) reduced the meal-induced increase in blood glucose and plasma insulin levels. Acarbose induced a significant (P < 0·05) reduction in early (90, 120, 180min) serum levels, peak concentrations (Cmax: 1·22 ± 0·14 vs. 1·87 ± 0·60 mgl^?1) and area under the curve of metformin (AUC 0–540min: 423±55 vs. 652±55 mg minl^?1), but did not diminish its 24 h urinary excretion. In conclusion, acarbose significantly reduces the acute bioavailability of metformin in normal subjects.     

Randomized,double‐blind comparison of effects of abiciximab bolus only vs. on‐label regimen on ex vivo inhibition of platelet aggregation in responders to clopidogrel undergoing coronary stenting

Summary. Background: On top of aspirin, an abciximab bolus‐only regimen results in a 30% drop in platelet inhibition at 6 h as compared with the on‐label regimen. The concomitant administration of high loading dose clopidogrel, by bridging with abciximab bolus, may sustain suppression of platelet activity over time. Objectives: To investigate the non‐inferiority of abciximab bolus‐only and concomitant high loading dose clopidogrel vs. abciximab bolus + infusion with respect to the inhibition of platelet aggregation (IPA) as determined by light transmission aggregometry. Patients/Methods: Seventy‐three patients with non‐ST segment elevation acute coronary syndromes underwent double‐blind randomization to abciximab bolus followed by a 12‐h placebo infusion and concomitant 600‐mg clopidogrel vs. abciximab bolus + a 12‐h infusion and 300 mg of clopidogrel. IPA was determined by light transmission aggregometry throughout 24 h. Clopidogrel poor responsiveness was defined as ≥ 50% 5 μmol L^?1 ADP‐induced maximum platelet aggregation. Results: In clopidogrel responders (n = 68), IPA after 20 μmol L^?1 ADP at 4 h was 89% ± 13% in the bolus‐only arm vs. 92% ± 14% in the bolus + infusion arm (P = 0.011 for non‐inferiority). IPA after 5 or 20 μmol L^?1 ADP and 5 or 15 μmol L^?1 TRAP and the proportion of patients showing ≥ 80% IPA did not differ at any time point, irrespective of clopidogrel responsiveness status. Thirty‐day outcomes were similar, whereas hemoglobin (0.91 ± 0.8 vs. 0.5 ± 0.7 g dL^?1; P = 0.01) and platelet count mean drop (41.7 ± 57 vs. 18.6 ± 34 10⁹ L^?1; P = 0.042) were significantly reduced in the bolus‐only arm. Conclusions: Withholding abciximab post‐bolus infusion in patients receiving high loading dose clopidogrel does not impair platelet inhibition throughout 24 h, and has the potential to improve the safety profile of the drug at reduced costs.     

Influence of portacaval shunt on bile formation in the rat

Abstract. Bile flow and bile acid secretion were measured in rats 21 to 28 days after a portacaval shunt and in sham-operated and normal animals. The following results were obtained. (1) Bile flow was significantly lower (6.65 ± SEM 0.36 μl-min^?1 · 100 g^?1) in the shunted rats than in the sham-operated animals (8.21 ± SEM 0.21 μl · min^?1 · 100 g^?1; P < 0.01). (2) Bile acid excretion was not significantly different in the shunted rats (0.27 ± SEM 0.03 μmol · min^?1 · 100 g^?1) and the sham-operated rats (0.26 ± SEM 0.02 μmol · min^?1 · 100 g^?1; NS). (3) During bile acid infusions, there was a linear relationship between bile flow and bile acid excretion in both groups of animals. The slope of the relationship was similar, suggesting that the osmotic activity of the bile acids was not modified in the shunted animals, and the bile acid-independent flow, estimated by the extrapolation of this relationship to a zero bile acid excretion, was significantly lower in the rats with a portacaval shunt (5.20 ± SEM 0.40 μl · min^?1 · 100 g^?1) than in the sham-operated animals (6.50 ± SEM 0.30 μl · min^?1 · 100 g^?1; P < 0.02). (4) The liver weight was significantly lower in the rats with a portacaval shunt than in the sham-operated animals and there was a parallel decrease of liver weight (-17%) and of the bile acid-independent flow (-22%). No difference was found between the sham-operated rats and the normal rats. It is concluded that portacaval shunt in the rat results in a decreased bile flow, due to a decrease in the bile acid-independent flow. Since bile acid secretion rate remained unchanged, it is suggested that the secretion of bile acids on the one hand and the bile acid-independent flow on the other are regulated by separate mechanisms.     

Surgical removal of insulinoma restores glucose recovery from hypoglycaemia but does not normalize insulin action

Abstract. In the present study we have evaluated the effects of chronic hyperinsulinaemia secondary to insulinoma, on insulin sensitivity and on counter-regulatory responses to hypoglycaemia. We studied six patients (M/F = 3/3; age = 40 ± years), before and 6–9 months after surgical ablation of the neoplasia, by means of an euglycaemic-hyperinsulinaemic clamp (1 mUkg^-1min^-1). Seven normal subjects (M/F = 4/ 3; age = 38 ± 6 years) underwent the same experimental study as the control subjects. In insulinoma patients after 100 min of the euglycaemic-hyperinsulinaemic clamp, glycaemia was allowed to drop to a minimum value of l.9mmol L^-1, and recovery evaluated after interrupting insulin infusion. During the entire study, 3-³H-glucose was infused to determine hepatic glucose production and glucose utilization. Surgical removal of the pancreatic adenoma was followed by a reduction in body weight (BMI=25.7 ±l.9vs. 23.0 ± 1.6 kgm^-2; P?0.005), normalization of fasting plasma levels of glucose (2.94 ±0.16 vs. 4.83± 0.11 mmol L^-1), insulin (162 ± 24 vs. 48 ±12 pmol L^-1) and of basal hepatic glucose production (7.6 ± 0.7 vs. 12.2 ± 1.11μmol kg^-1min^-1). Before the operation, insulin-mediated glucose disposal was significantly lower than in the controls (30.8 ±3.1 vs. 4.91± 3.1 μmol kg^-1min^-1). Six to nine months after surgical removal of the adenoma, glucose utilization was unchanged (30.5 ±3.3 μmol kg^-1min^-1) and still significantly lower than in controls (P<0.0). After the euglycaemic phase, the plasma glucose level dropped to the same hypoglycaemic nadir (2.0±0.1 vs. 2.2 ±0.2 mmol L^-1) in both studies. Upon withdrawal of insulin infusion, recovery from hypoglycaemia was much slower before than after removal of the insulinoma (0.66±0.16vs. 2.50 ± 0.38 μmol min^-1; P<0.01). The impaired recovery from hypoglycaemia was associated with a sluggish rise in plasma glucagon concentration (+ 49 ± 15vs. +95 ±27 ng L^-1), growth hormone (+16±6vs.+ 30±3*mu;g L^-1), and cortisol (+156 ±41 vs. +361 ±62nmol L^-1; all P<0.05–0.005). In contrast to that found after adenoma removal, hepatic glucose production in insulinoma patients remained suppressed even after induction of hypoglycaemia. Our data suggest that in hyperinsulinaemic insulinoma patients restoration of normal insulin levels (a) ameliorates the response of some parameters of the counter-regulation to acute hypoglycaemia; but (b) is not able to restore normal insulin sensitivity.     

Acute saline infusion induces extracellular acidification and activation of the Na+/H+ exchanger in man

The effect of acute expansion of the extracellular fluid volume (ECV) with isotonic (0.9%) saline on the activity of the lymphocyte Na⁺/H⁺ antiport (NHE) was studied in a total of 18 healthy volunteers. Saline was infused at a constant rate so that 4 mmol kg^?1 b.w. was administered over 2 h. NHE activity was measured by quantifying cytosolic pH (pH_i) recovery following acidification of the cells with propionic acid and by pH clamping at various pH_i values between 7.2 and 5.8 using nigericin. Both methods demonstrate NHE activation associated with intravenous saline infusion, the kinetic difference being a marked decrease in the Hill coefficient n from 3.28 ± 0.21 (SEM) to 2.22 ± 0.11 in the absence of changes in baseline pH_i (7.14 ± 0.02 vs. 7.08 ± 0.02; P = 0.15), V_max (42.8 ± 2.7 vs. 48.1 ± 2.8 mmol L^?1 min^?1; P = 0.08) and pK (6.32 ± 0.04 vs. 6.35 ± 0.02). NHE activation was associated with significant decreases in serum chloride (P = 0.016), calcium (P = 0.008), total cholesterol (P = 0.008), low-density lipoproteins (P = 0.016) and high-density lipoproteins (P = 0.008). Moreover, saline infusion induced extracellular acidification with a decrease in pH from 7.39 ± 0.01 to 7.37 ± 0.01 (P = 0.016), HCO₃^? from 23.3 ± 0.43 mmol L^?1 to 21.3 ± 0.25 mmol L^?1 (P = 0.008) and base excess from ?1.03 ± 0.38 mmol L^?1 to ?3.00 ± 0.31 mmol L^?1 (P = 0.008). Our results show for the first time that acute ECV expansion with isotonic saline is followed by an activation of the lymphocyte NHE. The underlying mechanism(s) remain to be investigated. However, the demonstration in our study of marked changes in acid–base balance induced by acute saline points to a possible inter-relationship of antiporter activation and extracellular acidification.     

Acute hyperinsulinaemia decreases cholesterol synthesis less in subjects with non-insulin-dependent diabetes mellitus than in non-diabetic subjects

To investigate the effect of insulin on cholesterol synthesis in vivo we measured plasma mevalonic acid (MVA) concentrations using gas chromatography–mass spectrometry in six non-obese patients with non-insulin-dependent diabetes mellitus (NIDDM) [four men, two women; age 57.5±2.2 years (mean±SEM); glycated haemoglobin (HbA1) 8.5±0.5%; total cholesterol (TC) 5.7±0.5 mmol L^?1, triglyceride (TG) 3.8±0.9 mmol L^?1] and six non-diabetic, sex- and age-matched control subjects (age 55.7±2.8 years; HbA1 6.5±0.1%; TC 5.4±0.3 mmol L^?1, TG 1.2±0.1 mmol L^?1). Subjects were studied twice: during 13-h hyperinsulinaemic (1 mu kg^?1 min^?1), euglycaemic (5 mmol L^?1) clamp and during a saline infusion. Baseline MVA concentration was significantly higher in diabetic patients than in control subjects (9.8±0.7 ng mL^?1 vs. 5.6±0.9 ng mL^?1P=0.004). At the end of each study, MVA concentration, expressed as a percentage of baseline, was significantly lower during the hyperinsulinaemic, euglycaemic clamp than during the saline study in both the diabetic (54.4±5.3% vs. 69.6±6.3%, P=0.036) and control subjects (30.5±3.4% vs. 61.7±6.0%, P=0.01). However, the decrease in MVA during the hyperinsulinaemic clamp study was more marked in the control subjects than in the diabetic subjects (P=0.03). A significant positive correlation was found between percentage decrease of MVA and non-esterified fatty acids following the insulin clamp in NIDDM (r=0.83, P=0.04). We conclude that acute hyperinsulinaemia decreases cholesterol synthesis less in subjects with NIDDM than in non-diabetic subjects and that this phenomenon, together with increased basal cholesterol synthesis in NIDDM, may in part be due to insulin resistance.     

Altered skeletal muscle glucose transport and blood lipid levels in habitual cigarette smokers

We determined whether habitual cigarette smoking alters insulin-stimulated glucose transport and GLUT4 protein expression in skeletal muscle. Vastus lateralis muscle was obtained from 10 habitual cigarette smokers and 10 control subjects using an open muscle biopsy procedure. Basal 3-O-methylglucose transport was twofold higher (P > 0·01) in muscle from habitual smokers (0·05 ± 0·08 vs. 1·04 ± 0·19 μmol ml^?1 h^?1; controls vs. smokers respectively). Insulin (600 pmol l^?1) increased glucose transport 2·6-fold (P > 0·05) in muscle from control subjects, whereas no significant increase was noted in habitual smokers. Skeletal muscle GLUT4 protein expression was similar between the groups. FFA levels were elevated in the smokers (264 ± 49 vs. 748 ± 138 μmol l^?1 for control subjects vs. smokers; P < 0·05), and serum triglyceride levels were increased in the smokers (0·9 ± 0·2 vs. 2·3 ± 0·6 mmol l^?1 for control subjects vs. smokers; P < 0·05). Skeletal muscle carnitine palmitil (acyl) transferase activity was similar between the groups, indicating that FFA transport into the mitochondria was unaltered by cigarette smoking. In conclusion, cigarette smoking appears to have a profound effect on glucose transport in skeletal muscle. Basal glucose transport is markedly elevated, whereas insulin-stimulated glucose transport is impaired. These changes cannot be explained by altered protein expression of GLUT4, but may be related to increased serum FFA and triglyceride levels. These findings highlight the importance of identifying habitual cigarette smokers in studies aimed at assessing factors that lead to alterations in lipid and glucose homeostasis in people with non-insulin-dependent diabetes mellitus (NIDDM).     

Osteocalcin metabolism in the pulmonary circulation

The aim of this study was to evaluate the role of the pulmonary vessel endothelium in the removal of circulating osteocalcin, by measuring the osteocalcin levels in serum from pulmonary and radial artery blood from 39 patients undergoing aorto‐coronary bypass. Because of the discrepancies between methods of measurement, two methods were used. Significant differences were observed in group A (n = 18), tested with heterologous radioimmunoassay (2·85 ± 0·67 μg l^?1 in the pulmonary versus 2·69 ± 0·67 μg l^?1 in the radial artery serum, P<0·001) and in group B (n = 21), tested with a two‐site immunoradiometric assay (5·22 ± 1·46 versus 4·93 ± 1·36 μg l^?1, P<0·01). The percentage differences were –5·54 ± 4·76% (P<0·001) in group A and –4·99 ± 8·13% (P<0·01) in group B; the comparison between the percentage differences was not significant. These different osteocalcin concentrations between the two vascular compartments were considered a marker of osteocalcin degradation. Therefore, the study seems to demonstrate that, as well as kidney, liver and bone, the lung is a relevant site of osteocalcin catabolism. The proteolytic activity of pulmonary vessel endothelium seems to involve about 5% of the circulating peptide.     

Carbonic anhydrase II in the cerebrospinal fluid: its value as a disease marker

Carbonic anhydrase (CA) II is the predominant CA isoenzyme in the brain of mammals. We have recently developed a dual-label time-resolved immunofluorometric assay to quantify minute amounts of CA I and II in the cerebrospinal fluid (CSF). The present study was aimed at elucidating the clinical value of such measurements in the case of neurological disorders. Lumbar CSF samples were obtained from 111 patients suffering from various neurological diseases and from 97 control patients with no specific signs of central nervous system diseases. The highest CA II concentrations were found in patients with brain infarction (median 66.5 μg L^?1, n = 20), whereas the control patients had markedly lower values (median 7.8 μg L^?1, n = 97). Relative to a reference range calculated from the control material (10.2 ± 17.2 μgL ^?1), the sensitivity of CA II measurement in differentiating brain infarction was 100%. Patients with transient ischaemic attack (median 11.2 μg L^?1, n = 9), multiple sclerosis (median 14.7 μg L^?1, n = 18) or epilepsy (median 20.3 μg L^?1, n = 17) usually had CA II concentrations within the normal range, but those with central nervous system infection (n = 14), dementia (n = 19) or trigeminal neuralgia (n = ;6) tended to have higher CA II levels in their CSF, the median values being 39.1 μg L^?1, 45.5 μg L^?1 and 44.0 μg L^?1 respectively. The findings indicate that the concentration of CA II in the CSF marks disease activity in patients with brain damage. This finding could provide a basis for further studies estimating the value of CA II measurement as a new laboratory marker of diseases affecting the brain.     

Effects of a high‐fat meal on resistance vessel reactivity and on indicators of oxidative stress in healthy volunteers

High fat meals postprandially impair macrovascular endothelial function and a link to increased oxidative stress is suggested. Few information, on the other hand, exists on the effect of postprandial hyperlipidaemia on resistance vessel function. Under normal circumstances this vascular bed regulates tissue perfusion and, by controlling flow, impacts on macrovascular nitric oxide formation. The impact of a high fat meal (1200 kcal, 90 g fat, 46 g protein and 47 g carbohydrates) on postprandial resistance vessel reactivity and on indicators of oxidative stress was studied in 11 healthy subjects by venous‐occlusion plethysmography using another six subjects as time control group. Ingestion of the test meal resulted in a pronounced increase of serum triglycerides from 1·05 ± 0·61 mmol l^?1 in the fasting state to peak postprandial values of 1·94 ± 0·41 mmol l^?1 (P < 0·001) reached after 4 h and a return to baseline after 8 h. Fasting peak reactive hyperaemia (RH) was 19·6 ± 2·4 ml min^?1 (100 ml)^?1. Two hours after ingestion of the test meal peak RH was transiently reduced to 16·8 ± 2·2 ml min^?1 (100 ml)^?1 (P < 0·05). No alteration of resting forearm perfusion was observed. The time course of peak RH suggested a potential biphasic effect of the test meal with an early impairment and a late increase of RH. Ingestion of a lipid rich test meal did not exert any influence on either total plasma antioxidant capacity given in trolox equivalents (513 ± 26 μmol l^?1 at baseline) or on plasma peroxides measured as H₂O₂ equivalents (469 ± 117 μmol l^?1). Our results suggest that ingestion of a meal containing 90 g of fat results in a transient impairment of reactive hyperaemia in healthy subjects but these vascular alterations are not accompanied by signs of systemically increased oxidative stress.     

The kinetics of G-CSF mobilization of CD34+ cells in healthy people

When healthy people are given granulocyte colony stimulating factor (G-CSF) for 10 days the number of CD34+ cells in the peripheral blood begins to increase on the fourth day, reaches a maximum on the sixth day and then decreases. In this study, we further define the time and variability of peak mobilization of CD34+ cells. Twenty-two healthy people were given G-CSF (7.5 or 10 μg kg^?1 day^?1) subcutaneously each morning for 5 days and peripheral blood CD34+ cell counts were analysed immediately prior to the fourth (day 4) and fifth (day 5) G-CSF injection and 24 h after the fifth injection (Day 6). White blood cell (WBC) and neutrophil counts were greatest on day 6 [WBC = 43.8 ± 13.9 × 10⁹ L^?1 (mean ± 1 SD) and neutrophils = 36.6 ± 12.8 × 10⁹ L^?1]. In contrast the CD34+ cell counts on day 6 (107 ± 104 × 10⁶ L^?1) were less than on day 5 (128 ± 136 × 10⁶ L^?1) (P= 0.048) but still greater than on day 4 (60.7 ± 40.2 × 10⁶ L^?1) (P < 0.0001). The CD34+ cell counts of 10 donors were measured 2, 4 and 6 h after the fifth injection to determine if the counts increased further between days 5 and 6. The number of CD34+ cells in the blood on day 5 2 h after the fifth injection (193 ± 277 × 10⁶ L^?1) was greater than the number prior to the injection (158 ± 190 × 10⁶ L^?1), 4 h post-injection (139 ± 158 × 10⁶ L^?1) and 6 h post-injection (170 ± 236 × 10⁶ L^?1), but the differences were not significant (P= 0.29, 0.25 and 0.45). The number of CD34+ cells in the blood of 12 people were measured before and after the fourth G-CSF dose. Prior to the day 4 injection the CD34+ count was 61 ± 40 × 10⁶ L^?1. At 2, 4 and 6 h the counts were 60 ± 40, 61 ± 29 and 64 ± 30 × 10⁶ L^?1, respectively, and the differences were not significant (P= 0.99, P= 0.98, and P= 0.73). In conclusion, when healthy volunteers are given daily G-CSF injections, the number of mobilized CD34+ cells was the greatest on day 5, slightly less on day 6 and the least on day 4. If only one PBSC component is needed, PBSCs can be collected on day 5 after only 4 days of G-CSF. If PBSC components are collected on both days 5 and 6, the fifth dose can be given either before or after the collection of the first PBSC component.     

Postprandial chylomicron and plasma vitamin E responses in healthy older subjects compared with younger ones

The effect of ageing on vitamin E bioavailability in humans was assessed by comparing chylomicron and plasma α-tocopherol postprandial concentrations after a dose of vitamin E (432 or 937 IU as dl-α-tocopherol acetate), in eight young (20–30 years old) and eight healthy elderly men (64–72 years old). The fasting plasma α-tocopherol concentration was significantly higher in the elderly (33 ± 2 μmol L^?1) than in the young (22 ± 2 μmol L^?1). In both groups, the plasma and chylomicron α-tocopherol postprandial concentrations were significantly, approximately twofold, higher after the 937-IU meal than after the 432-IU meal. For both test meals, the chylomicron α-tocopherol areas under the curve were significantly lower in the elderly than in the young subjects: 98.9 ± 16.5 (young group) vs. 55.3 ± 7.8 (elderly group) μmol L^?1 h for the 937-IU test meal and 60.4 ± 14.1 (young group) vs. 26.0 ± 7.6 (elderly group) μmol L^?1 h for the 432-IU test meal, whereas the plasma α-tocopherol area under the curve was significantly higher in elderly than in young subjects: 337.56 ± 16.11 (937-IU test meal) vs. 159.81 ± 35.55 (432-IU test meal) μmol L^?1 h in the young group and 709.55 ± 69.33 (937-IU test meal) vs. 436.39 ± 41.08 (432-IU test meal) μmol L^?1 h in the elderly group. We concluded that (a) the amount of vitamin E appearing in plasma is proportional to the dose ingested (up to 937 IU); (b) the intestinal absorption of vitamin E is not increased, even possibly decreased, in the elderly; and (c) the amount of vitamin E transported by non-chylomicron lipoproteins is apparently higher in the elderly. This suggests that vitamin E postprandial transport is affected by ageing, mainly as the consequence of age-related modifications of lipoprotein metabolism.     

Cocaine administration enhances platelet reactivity to subendothelial components: studies in a pig model

Myocardial infarction in cocaine abusers may be related to a direct platelet-activating effect. We analysed this possibility in an experimental model. Studies were carried out in eight normal, anaesthetized pigs with a weight of 30.7 ± 3.7 kg. Blood samples were withdrawn before and 20 min after i.v. administration of cocaine (10 mg kg^?1; at 1 mg kg^?1 every 2 min). Modifications in platelet responses to arachidonic acid (AA; 1.4 mmol L^?1), ADP (1–4 μM), synthetic thromboxane endoperoxide analogue (U46619; 1 μM), collagen (2.5–5 μg mL^?1), adrenaline (10 μM) and ristocetin (0.8–1 mg mL^?1) were tested by conventional aggregometry. Changes in the capacity of platelets to form aggregates on damaged subendothelium were assessed by means of an ex vivo perfusion system in which blood was circulated for 10 min at 800 s^?1, a shear rate similar to that found in normal coronary arteries. The interaction of platelets with perfused denuded arterial segments was morphometrically quantified and expressed as a percentage of damaged vessel surface covered by platelets (%CS). Cocaine administration did not influence platelet aggregation patterns in pigs. However, there was a significant increase in the interaction of pig platelets with subendothelial structures after cocaine infusion (%CS = 40 ± 17% vs. 27 ± 16% baseline; mean ± SD; P < 0.01). Cocaine administration in this animal model increases the reactivity of platelets exposed to subendothelium. These results support the concept that the administration of cocaine to pigs has a prothrombotic effect by facilitating the interaction of platelets with damaged arteries.     

Renal effects of i.v. adenosine infusion in humans

Summary. The effects of systemic intravenous (i.v.) infusion of adenosine on renal blood flow and glomerular filtration in eight healthy, awake females have been examined. In conclusion, i.v. infusion of adenosine in healthy, awake subjects causes a minor increase in total renal blood flow and a marked reduction in glomerular filtration. This shows that adenosine also exerts a vasodilatory effect in the renal circulation, primarily on postglomerular arterioles. In addition, adenosine may produce an aldosterone-like effect on salt excretion, and a reduction in renal oxygen consumption. Renal blood flow and glomerular filtration rate were measured as the clearance of para-aminohippuric acid (PAH) and inulin, respectively. Following basal sampling adenosine was infused i.v. at successive rates of 60 and 80 μg kg^-1 min^-1 for 30 min at each rate. Plasma clearance of PAH showed a minor, but non-significant, increase from 697 ±41 to 775 ±97 ml min^-1. However, the arterial plasma concentration of PAH decreased by 17±4% (P < 00.1), indicating that there was a small increase in renal blood flow. Inulin clearance was reduced from 123±14 to 88±11 ml min^-1 1.73 m^-2 (P < 0.01). The resulting filtration fraction was reduced from 18±1 to 11±1 (P < 0.001). The K⁺/Na⁺ excretion ratio increased from a basal value of 10±1 to 42±11 (P < 0.01) at the highest dose of adenosine, and renal oxygen consumption decreased from 17±2 to 9± 1 ml min^-x (P <0.001).     

Influence of Portacaval Shunt on Bile Formation in the Rat*

Abstract. Bile flow and bile acid secretion were measured in rats 21 to 28 days after a portacaval shunt and in sham-operated and normal animals. The following results were obtained. (1) Bile flow was significantly lower (6.65±SEM 0.36 μl min^-1-100 g^-l) in the shunted rats than in the shamoperated animals (8.21 ± SEM 0.21 μl min^-1 100 g^-1; P < 0.01). (2) Bile acid excretion was not significantly different in the shunted rats (0.27±SEM 0.03μmol-min^-1100g^-1) and the sham-operated rats (0.26±SEM 0.02 μmol-min^-1 -100 g^-1; NS). (3) During bile acid infusions, there was a linear relationship between bile flow and bile acid excretion in both groups of animals. The slope of the relationship was similar, suggesting that the osmotic activity of the bile acids was not modified in the shunted animals, and the bile acid-independent flow, estimated by the extrapolation of this relationship to a zero bile acid excretion, was significantly lower in the rats with a portacaval shunt (5.20±SEM 0.40 μ min^-1 100 g^-1) than in the sham -operated animals (6.50±SEM 0.30 μl min^-1 100 g^-1; P < 0.02). (4) The liver weight was significantly lower in the rats with a portacaval shunt than in the sham-operated animals and there was a parallel decrease of liver weight (–17%) and of the bile acid-independent flow (–22%). No difference was found between the sham-operated rats and the normal rats. It is concluded that portacaval shunt in the rat results in a decreased bile flow, due to a decrease in the bile acid-independent flow. Since bile acid secretion rate remained unchanged, it is suggested that the secretion of bile acids on the one hand and the bile acid-independent flow on the other are regulated by separate mechanisms.     

Increased urinary excretion of a major thromboxane metabolite in early alcohol withdrawal

Summary. Urinary excretion of 2, 3-dinor-thromboxane B2 as a marker of in vivo thromboxane A2 (TXA2) biosynthesis was measured in six alcoholics 1 and 14 days after the cessation of heavy drinking using gas chromatography/mass spectrometry. Six non-alcoholic healthy volunteers served as controls. One day after alcohol withdrawal the excretion of the dinor metabolite was significantly higher (P<0–01) in the alcoholics (408 ± 42 pg mg^-1 creatinine) than in the controls (180 ± 30 pg mg^-1 creatinine) and was accompanied by a significantly reduced platelet count (103–0 ± 20–2×110⁹ 1^-1 vs. 194–0 ± 13–9×10⁹ 1^-1 in controls; P<001). The metabolite excretion fell then significantly (P<0–05) to 245 ± 53 pg mg^-1 creatinine 14 days after alcohol withdrawal and this was paralleled by an increase in platelet count to 453–5 ± 72–0×10⁹ 1^-1 (P<0–05). The present results support the hypothesis that TX-A₂ biosynthesis is increased in early alcohol withdrawal and strongly suggest platelets as a cellular origin of the increased TXA₂ formation.     

Increased serum angiotensin converting enzyme activity in type T insulin—dependent diabetes mellitus: its relation to metabolic control and diabetic complications

Abstract. Serum angiotensin-converting enzyme (ACE) was measured in 150 insulin-dependent diabetes mellitus (IDDM) patients and 72 healthy subjects by radioassay, using [³H]-hippuryl-glycyl-glycine as a substrate. Mean (SD) serum ACE activity in diabetic patients was 120 ± 33 nmol ml^?1 min^?1 (range 46–215) and was significantly increased by 56% compared to control values (77 ± 23 nmol ml^?1 min^?1, range 46–125, P < 0·001). ACE activity > 125 nmol ml^?1 min^?1 was observed in 60 of 150 IDDM patients. 96 IDDM patients were normoalbuminuric (< 22 mg 24 h^?1) and 49 patients were micro- or macroalbuminuric (range 22–6010 mg 24 h^?1). Micro- and macroalbuminuric IDDM patients were found to have significantly greater ACE activity values than normoalbuminuric patients (128 ± 36 vs. 115 ± 30 nmol ml^?1 min^?1, P = 0·025). Metabolically well-controlled IDDM patients (glycosylated haemoglobin ≤ 8%) had lower ACE activity values than the patients with glycosylated haemoglobin greater than 8% (109 ± 20 vs. 127 ± 32 nmol ml^?1 min^?1, P < 0·02). A significant correlation between degree of metabolic control and ACE activity was found (r = 0.435, P < 0·001) so that an increase in one glycosylated quartile unit is accompanied by an increase in ACE activity of 10·5 nmol ml^?1 min^?1. Thus ACE activity in the serum of IDDM patients was increased by 56% in 40% of the patients. It was increased in IDDM patients without complications and in patients with retinopathy or nephropathy. In diabetic patients with nephropathy, ACE activity was greater than in diabetic patients without nephropathy. ACE activity was positively correlated with metabolic control. The role of increased ACE activity in the development of diabetic nephropathy remains to be established.     

Effect of acute acidosis and alkalosis on leucine kinetics in man

Summary. The effects of acute pH changes on whole body leucine kinetics (1-¹³C-leucine infusion technique) were determined in normal subjects. Plasma insulin, glucagon, and growth hormone concentrations were kept constant by somatostatin and replacement infusions of the three hormones. When acidosis was produced by ingestion of NH4CI (4 mmol kg^-1 p. os; n = 8) arterialized pH decreased within 3 h from 7.39±0.01 to 7.31 ±0.01 (P<0.001) and leucine plasma appearance increased by 0.13 ±0.04 μmol kg^-1 min^-1 (P<0.02); in contrast, when alkalosis was produced by intravenous infusion of 4 mmol kg^-1 NaHCO₃ (n= 1, pH 7.47 ±0.01), leucine plasma appearance decreased by -0.09 ± 0.04 (xmol kg^-1 min^-1 (P<0.01 vs. acidosis). Whole body leucine flux also increased during acidosis compared to alkalosis (P<0.05), suggesting an increase in whole body protein breakdown during acidosis. Apparent leucine oxidation increased during acidosis compared to alkalosis (P=0.05). Net forearm leucine exchange remained unaffected by acute pH changes. Plasma FFA concentrations decreased during acidosis by -107 ±67 μmol l^-1 (P<0.05) and plasma glucose increased by 1.90±0.25 mmol l^-1 (P<0.02); in contrast, alkalosis resulted in an increase in plasma FFA by 83 ± 40 (μmol 1^-1 (P<0.02; P<0.01 vs. acidosis), suggesting an increase in lipolysis; plasma glucose decreased compared to acidosis (P<0.01). The data demonstrate that acute metabolic acidosis and alkalosis, as they occur in clinical conditions, influence protein breakdown, and in the opposite direction, lipolysis.