The role of epinephrine in the circulatory effects of coffee

The circulatory response to coffee was studied in 10 normotensive, 10 bilaterally adrenalectomized, and 10 hypertensive subjects. In the normotensive group, drinking coffee exerted a rise in blood pressure (+5.1/+11.5 mm Hg), a fall in heart rate (-6.0 bpm), a rise in plasma epinephrine (+257.2%), and no change in plasma norepinephrine. The response to coffee in the hypertensive group was similar or even enhanced. In the patients who had undergone adrenalectomy, the coffee-induced rise of diastolic blood pressure was attenuated (+7.9 mm Hg; P less than 0.05), whereas plasma norepinephrine showed a fall (-20.8%) and plasma epinephrine remained undetectable throughout all tests. Additionally, a fall of plasma renin activity after coffee was observed in all three groups. We conclude that the pressor response to coffee is not purely a result of circulating epinephrine or to stimulation of the renin-angiotensin-aldosterone system. On the other hand, the coffee-induced increase of plasma epinephrine may increase the pressor response to coffee.     

Association between elevated plasma total homocysteine and increased common carotid artery wall thickness

Homocysteine is increasingly recognized as a risk factor for atherothrombotic arterial diseases. We investigated the relation between plasma concentrations of total homocysteine (tHcy) and common carotid artery intima-media wall thickeness, measured by B-mode ultrasonography, in 513 asymptomatic men and women from eastern Finland aged 45–69 years. The subjects were examined in 1994–95 at the baseline of the Antioxidant Supplementation in Atherosclerosis Prevention (ASAP) study, a randomized double-blind placebo-controlled two by two factorial trial on the effect of vitamin E and C supplementation in the prevention of atherosclerotic progression. The subjects were assigned into two categories according to the plasma tHcy concentration; concentration over 11.5 umol/L (highest quartile) or concentration below 11.5 umol/L. In this study population the mean plasma tHcy concentration was 10.0 μmol/L, and the prevalence of plasma tHcy concentration exceeding 11.5 μmol/L was 33% in men and 18% in women. The adjusted mean intima-media thickness of the right and left common carotid arteries was 1.12 mm in men with elevated plasma tHcy concentration and 1.02 mm in men with a plasma tHcy concentration below 11.5 μmol/L (P = 0.029). In women there was no significant difference. We conclude that elevated plasma tHcy concentrations are associated with early atherosclerosis, as manifested by increased common carotid artery intima-media wall thickeness, in middle-aged eastern Finnish men.     

Demonstration of a hormonal inhibitor of proximal tubular reabsorption during expansion of extracellular volume with isotonic saline

Evidence for the elaboration of a hormonal inhibitor of renal tubular reabsorption in response to expansion of extracellular fluid volume was obtained by examining the effects of plasma from rats and dogs undergoing saline diuresis on the rate of proximal tubular reabsorption measured both directly by micropuncture techniques and indirectly by clearance techniques.Intravenous infusion of plasma from salineloaded rats and dogs, but not plasma from control animals, inhibited the intrinsic reabsorptive capacity of the proximal tubule (as estimated from the shrinking-drop technique) by 35%, and reduced fractional reabsorption (as estimated from the tubular fluid-to-plasma ratio) by 20%. In addition the natriuretic plasma increased urine flow, solute-free water clearance, and potassium excretion in rats with hereditary diabetes insipidus, indicating an increase in the delivery of filtrate out of the proximal tubule to the more distal diluting segments of the nephron.The hormonal inhibition of proximal tubular reabsorption had an extremely rapid onset of action (within seconds after instillation into the tubular lumen) and a short duration of action (less than 30 min after cessation of an intravenous infusion). Inhibitory activity was lost from natriuretic plasma upon dialysis and could be recovered in the dialysate. Dialysates of natriuretic plasma, when injected directly into the tubular lumen, also inhibited proximal reabsorption, indicating an action on the luminal side of the cell.     

Neutrophil chemotaxis and adherence in vitro and localization in vivo in rabbits with Staphylococcus aureus abscesses

Decreased neutrophil (PMN) function may contribute to an altered host defense system in hosts with bacterial abscesses but has not been well correlated to in vivo outcome. We have found that blood PMNs from rabbits with chronic (2-week) experimental Staphylococcus aureus abscesses have decreased chemotaxis in response to an S. aureus supernatant (370 +/- 130 microns migration vs 570 +/- 180 microns, p less than 0.05) and decreased adherence (11.5% +/- 13.2% vs 32.9% +/- 18.6%, p less than 0.005) compared with PMNs from animals with acute (24-hour) abscesses. No differences were found in chemokinesis, random migration, and chemotaxis in response to zymosan-activated serum. No plasma inhibitors of PMN chemotaxis or inhibitors of chemotaxins were found. Although animals with chronic abscesses had higher levels of circulating chemotaxins, in both groups of animals abscess chemotaxin levels were greater than the plasma chemotaxin level. Animals with a concomitant chronic abscess had less PMN influx into an acute abscess but also less bacterial growth within the abscess than animals without a concomitant chronic abscess. We conclude that rabbits with chronic staphylococcal abscesses have decreased chemotaxis and adherence measured in vitro and decreased PMN localization in vivo. In this model, these functions were not associated with increased bacterial proliferation in vivo.     

Stimulation of thermogenesis by carbohydrate overfeeding. Evidence against sympathetic nervous system mediation.

Daily carbohydrate intake of seven men with normal weight was limited to 220-265 g/d for 6 d and then increased to 620-770 g/d for 20 d, while intake of protein, fat, and sodium remained constant. Carbohydrate overfeeding increased body weight by 4.8%, basal oxygen consumption (VO2) by 7.4%, BMR by 11.5%, and serum triiodothyronine levels by 32%. Overfeeding did not affect the thermic effect of a standard meal. Intravenous propranolol reduced the thermic effect of a meal by 22% during the base-line feeding period, and by 13% during carbohydrate overfeeding, but did not affect preprandial VO2. Overfeeding attenuated the rise in plasma glucose and FFA levels induced by infusion of norepinephrine, but had no effect on the increase in VO2 induced by norepinephrine. Overfeeding did not alter 24-h urinary excretion of vanillylmandelic acid, supine plasma catecholamine levels (pre- and postprandial), blood pressure, or plasma renin activity, but increased peak standing plasma norepinephrine levels by 45% and resting pulse rate by 9%. Even though short-term carbohydrate overfeeding may produce modest stimulation of sympathetic nervous system activity in man, the increase in thermogenesis induced by such overfeeding is neither suppressed by beta adrenergic blockade nor accompanied by an increased sensitivity to the thermogenic effects of norepinephrine. These data do not support an important role for the sympathetic nervous system in mediating the thermogenic response to carbohydrate overfeeding.     

肺癌患者肿瘤型M2丙酮酸激酶表达水平及临床意义

目的探讨肺癌患者治疗前后血浆中肿瘤型M2丙酮酸激酶（TuM2-PK）的表达水平及其与肿瘤的近期疗效关系。方法用ELISA法分别检测肺癌患者组（n=80）、良性肺部疾病组（n=60）、健康体检组（n=100）血浆中的TuM2-PK的表达水平，并进行比较分析。结果肺癌组TuM2-PK浓度、阳性率（23．1kU／L、69％）明显高于良性肺疾病组（11．5kU／L、5％）和健康对照组（9．1kU／L、3％）（P〈0．01）。经内科治疗后，病情缓解者血浆TuM2-PK浓度（13．1kU／L）与治疗前（21．6kU／L）相比显著下降（P〈0．05）；病情进展者血浆TuM2-PK浓度（63．5ku／L）与治疗前（23．4kU／L）相比显著升高（P〈0．05）；病情稳定者血浆TuM2-PK浓度治疗前后差异无统计学意义（P〉0．05）。手术后TuM2-PK阳性率显著下降，而化疗后阳性率下降不明显。结论TuM2-PK对肺癌的辅助诊断有较高的临床价值，有助于疗效的评估。     

Study of the sorption capacity of red blood cell membranes for the assessment of the pattern of endogenous intoxication in dermatoses

The parameters of the sorption capacity of red blood cell membranes and the level of small and medium molecular weight substances were studied in 53 patients with chronic dermatoses. The plasma accumulation of small and medium molecular weight substances contributes to the altered sorption capacity of red blood cell membranes and to the occurrence of resistance to long used drugs. Biological blood clearance should be performed to enhance the efficiency of therapeutic measures.     

巢式逆转录聚合酶链反应检测冠状病毒的研究

目的 建立一种新的逆转录-聚合酶链反应(RT-PCR)反应模式,以提高传染性非典型肺炎(SARS)冠状病毒检测的阳性率和研究病毒在机体的定位状态和致病机理。方法 采用两种RT-PCR反应模式检测SARS患者血浆、淋巴细胞、粪便以及肺组织中病毒核酸。结果 和常规PCR方法相比,新的PCR反应模式能显著提高标本中病毒的检出率,差别有统计学意义;急性期SARS患者淋巴细胞中病毒阳性率较高(84.6％);血浆中病毒阳性率较低(11.5％)。结论 新RT-PCR反应模式可能有利于早期诊断、筛检SARS病原体;淋巴细胞中病毒的检出率较高,提示此类标本可用于SARS实验室诊断,对分析和阐明SARS的发病机制亦可能有一定的指导作用。     

Pyridostigmine kinetics in healthy subjects and patients with myasthenia gravis

Comparative pyridostigmine kinetics in plasma were measured in 10 healthy subjects given 4 mg iv and 60 mg oral pyridostigmine bromide. As determined from the AUC ratio, oral availability was 11.5% to 18.9% (means = 14.3%). Mean t 1/2 of the plasma level decline after oral dosing was 200 minutes, twice as long as the terminal elimination t1/2 after intravenous infusion (97 minutes). Thus absorption may proceed at a slower rate than elimination. Comparison of intraindividual data revealed strict dependence of the AUC on the infused dose (2, 4, and 8 mg) in one subject and variability in AUC up to a factor of two when two subjects took oral pyridostigmine three times. Patients with myasthenia who were receiving continuous therapy with oral pyridostigmine had AUC values per unit dose corresponding to those in healthy subjects. Storage stability of pyridostigmine in plasma required acidification of samples and storage at -75 degrees C. When native plasma was kept at -20 degrees C, there was appreciable loss of pyridostigmine within 1 to 2 months, the extent of which depended on the initial concentration.     

Multiple oral doses of nicardipine, a calcium-entry blocker: effects on renal function, plasma renin activity, and aldosterone concentration in mild-to-moderate essential hypertension

We studied the effects of nicardipine administered in a 4-week fixed oral maintenance dosage (20 or 40 mg t.i.d.) on renal function, plasma renin activity (PRA), and plasma aldosterone concentration in seven patients with mild-to-moderate essential hypertension. Glomerular filtration rate and renal blood flow were measured by means of sodium thiosulfate and para-aminohippurate, respectively. Nicardipine increased renal blood flow by 11.5% +/- 4.3% (mean +/- SE; P less than 0.05) and glomerular filtration rate by 16.3% +/- 6.4% (P less than 0.05) and decreased total renal vascular resistance by 30.0% +/- 2.7% (P less than 0.05), with a significant (P less than 0.05) reduction in systolic and diastolic blood pressure as compared with placebo values. Nicardipine increased PRA significantly (P less than 0.05), whereas plasma aldosterone concentration remained unchanged. Our results indicate that nicardipine given in a multiple oral dosage has some favorable renal effects with a concomitant hypotensive action in patients with mild-to-moderate essential hypertension. Nicardipine appears to blunt the secretion of aldosterone responding to an increased PRA possibly through its calcium-antagonizing action.     

Serial trough and peak amikacin levels in plasma as predictors of nephrotoxicity.

We studied 113 patients treated with intravenous amikacin to determine the value of determining serial trough and peak amikacin levels in plasma for predicting nephrotoxicity. Thirteen patients (11.5%) developed renal toxicity, with significant increases from 48 to 96 h in both peak and trough amikacin levels (6.7 +/- 4.7 [standard deviation] days before the serum creatinine rose). The nontoxicity group had no change or even showed decrements in amikacin levels in plasma. A higher nephrotoxicity risk was seen in patients with increments greater than 1 microgram/ml between 48 and 96 h, with odds ratios of 16.4 for trough, 8 for peak, and 7.2 for both levels. We suggest that an increment of at least 1 microgram/ml in amikacin levels in plasma from 48 to 96 h may predict the appearance of renal toxicity.     

Determination of histamine concentrations in plasma by liquid chromatography/electrochemistry

Histamine was extracted from deproteinized plasma with Amberlite CG 50 weak cation-exchange resin (analytical recovery of [3H]histamine, 60.5%). The eluate was evaporated and histamine in the redissolved sample was condensed with o-phthalaldehyde and 2-mercaptoethanol at pH 11.5. This adduct was separated by liquid chromatography under isocratic conditions and oxidized on a glassy carbon electrode at +0.4 V for electrochemical detection. 3-Methylhistamine was used as internal standard. As little as 0.45 pmol of standard histamine condensate was detected. The histamine concentration in 88 human plasma samples appeared to be normally distributed; its mean value was 7.20 (SD 2.61) nmol/L. Authentic and extracted histamine produced similar hydrodynamic voltammograms, and exogenous and endogenous histamine gave identical chromatographic characteristics with different mobile phases or different chromatographic columns. Standard and extracted histamine had similar degradation rates when samples were incubated with diamine oxidase (EC 1.4.3.6). Analytical recovery of known amounts of histamine added to pooled plasma was 97.7% (SD 22.3%). The inter- and intra-assay CVs for histamine determinations were 9.0% and 8.6%, respectively.     

A new insulin immunoassay specific for the rapid-acting insulin analog, insulin aspart, suitable for bioavailability, bioequivalence, and pharmacokinetic studies

Objectives: To validate a specific enzyme-linked immunosorbent assay for the rapid-acting human insulin analogue, insulin aspart, in human serum, human plasma, and porcine plasma.

Design and methods: For the enzyme-linked immunosorbent assay, two murine monoclonal antibodies were developed that bind to two different epitopes on the insulin aspart molecule. Key parameters for validation were imprecision, accuracy, matrix effects, dilution-linearity, and cross-reactivity.

Results: No cross-reactivity was found with human and porcine insulin, human proinsulin, or human C-peptide. The assay is sensitive (limit of QUANTIFICATION = 11.5 pmol/L), accurate (95–107% recovery with human serum, human plasma, and porcine plasma in the range 16–800 pmol/L), and has a 14.7% total imprecision within the entire analytical range. Dilution of samples gave linear results with human serum as the diluent.

Conclusions: The insulin aspart-specific enzyme-linked immunosorbent assay described in this study is well suited to study the bioavailability, bioequivalence, and pharmacokinetics of this insulin analogue.     

Predictability of antihypertensive responsiveness and alpha-adrenoceptor antagonism during prazosin treatment

This study investigates concentration-effect relationships in nine patients who had essential hypertension treated with prazosin. Antihypertensive responsiveness was determined for each individual patient in terms of millimeters of mercury of blood pressure reduction per nanogram per milliliter of plasma prazosin concentration. The principal findings were that there was significant attenuation of antihypertensive responsiveness, from 11.5 mm Hg per nanogram per milliter after the first dose to 8.7 mm Hg per ng/ml after 1 week of treatment with prazosin. Correspondingly, there was significant attenuation of the degree of alpha 1-antagonism as assessed by the pressor response to intravenous phenylephrine. However, there was no significant further attenuation of either assessment during continued treatment for up to 3 months. These findings suggest that after an early adaptation, which occurs within the first week of treatment, there is no long-term attenuation of the antihypertensive effect of prazosin. Despite this initial adaptive change, the magnitude of the long-term antihypertensive effect of prazosin was predictable from the first dose response in individual patients.     

Radioimmunoassay for bupropion in human plasma: comparison of tritiated and iodinated radioligands

We evaluated the potential usefulness of 125I-labeled p-hydroxybupropion in a direct radioimmunoassay for bupropion in human plasma as compared with a currently used [3H]bupropion dextran-coated charcoal method. In both radioimmunoassay methods succinoylpropylbupropion antiserum was used that was highly specific for unchanged drug, cross reactivities with known bupropion metabolites being less than 0.3%. However, the use of 125I-labeled p-hydroxybupropion afforded greater sensitivity (0.3 microgram/L vs 0.6 microgram/L with [3H]bupropion) and was readily adaptable to the more convenient polyethylene glycol separation method. Between-assay CVs were 3.8 to 12.2% (mean 7.6%) with the 125I-based radioimmunoassay and 5.1 to 11.5% (mean 7.5%) with the 3H-based assay. Agreement between the two radioimmunoassay determinations of buproprion in human plasma samples collected over a 60-h period after oral drug administration was excellent (slope = 1.086, r = 0.989). We find the 125I-based assay a convenient and suitable alternative to the [3H]bupropion assay in pharmacokinetic studies in humans.     

Cardiovascular reflexes in patients with vascular headache

We have investigated the autonomic function of 75 patients with migraine by examining cardiovascular reflex function. The results were compared with those of 78 healthy volunteers. Measurements were made between attacks. Patients with migraine showed a smaller heart-rate response to deep breathing but a greater heart-rate response and higher blood pressure to standing when compared to controls. Migraine patients had a higher percentage of established sympathetic lesions (51% vs 17%) and severe (25% vs 5%) or atypical (24% vs 11.5%) global autonomic dysfunction. No significant differences were found among patients with migraine with aura, migraine without aura, and migraine with prolonged aura. Our findings indicate that patients with migraine have sympathetic hypofunction.     

Effect of food on blood hydralazine levels and response in hypertension

A study with a nonspecific hydralazine assay reported that food increased hydralazine concentrations in plasma. We used a specific HPLC hydralazine assay to determine the effect of food on hydralazine blood levels and hemodynamic responses after oral hydralazine. Six subjects with uncomplicated essential hypertension were given 1 mg/kg hydralazine solution orally on two occasions at least 3 days apart. On 1 study day subjects fasted and on the other they were given a standard meal 45 min before hydralazine. Mean arterial pressure and heart rate were monitored for 2 hr before and for 4 hr after hydralazine and frequent venous blood samples were drawn for hydralazine assay. Hepatic blood flow was estimated by determination of indocyanine green clearance before food, after food, and 30 min after hydralazine. Peak blood hydralazine concentrations fell in all (46.2% +/- 11.5%; means +/- SE) and areas under the blood hydralazine concentration/time curves fell (45.7% +/- 9.5%) after food. This could not be explained by changes in liver blood flow. Food-related reductions in blood levels of hydralazine were associated with reduced vasodepressor effects (41.5% +/- 5.6%). It is possible that food increases intravascular conversion of hydralazine to hydralazine pyruvic acid hydrazone. The reduction in vasodepressor response suggests that patients with hypertension should take hydralazine at a fixed time in relation to meals.     

An improved approach for the determination of plasma [3H]noradrenaline kinetics using high-performance liquid chromatography

An improved approach for the determination of plasma [3H]noradrenaline ([3H]NA) kinetics in man is described, incorporating the extraction of plasma [3H]catechols on alumina and separation of [3H]NA from [3H]dihydroxymetabolites by high-performance liquid chromatography (HPLC). After a 30 min intravenous infusion, [3H]NA accounted for 57.2 +/- 13.2% of the radioactivity recovered by the procedure, while the dihydroxy-metabolites 3,4-[3H]dihydroxyphenylethylene. glycol ([3H]DHPG) and 3,4-[3H]dihydroxymandelic acid ([3H]DOMA) accounted for 32.3 +/- 11.5% and 4.9 +/- 6.0% respectively. After 90 min of constant infusion the proportion due to [3H]NA fell to 44.4 +/- 10.4%, while that due to [3H]DHPG rose to 45.9 +/- 9.5% because of an increase in the amount of [3H]DHPG at the later time. Plasma [3H]NA radioactivity rose rapidly during the constant infusion and usually reached a plateau by 30 min. However, in individual subjects large variations in plasma [3H]NA radioactivity occurred during the course of the infusion, implying rapid and variable changes in plasma [3H]NA clearance. The inclusion of a step to separate [3H]NA from [3H]dihydroxymetabolites is necessary if the aim is to determine plasma [3H]NA kinetics, as a large proportion of the radioactivity recovered from plasma on alumina is due to the presence of these metabolites.     

The effect of a single dose of propranolol on human erythrocytes in vivo

Abstract. In vitro propranolol has a profound effect on erythrocytes as indicated by a decrease of the packed cell volume and a shift to the right of the oxygen dissociation curve. Because of the lack of satisfactory in vivo studies, the effect of 80 mg propranolol and placebo was compared in twelve volunteers in a double-blind study. Although plasma propranolol concentrations varied greatly from individual to individual, all propranolol subjects demonstrated effective beta-blockade. Packed cell volume, mean cellular volume, plasma trapping after haematocrit centrifugation, P 50, 2,3-DPG, ATP, erythrocyte filterability and blood viscosity at different packed cell volumes (50% and 80%) and shear rates (11.5, 23, 46, 115 and 230 s^-1) did not change significantly following administration of either propranolol or placebo. These findings are of interest in view of the use of betablocking agents in critically ill patients.     

Effect of a common reference plasma on the inter-laboratory variation of the measurement of total and free protein S: a collaborative study of the Dutch Working Group on Haemostasis Laboratory Diagnosis

The comparability of test results for protein S between laboratories is hampered by a high inter-laboratory variability. The effect of the use and type of common reference plasma on the inter-laboratory variability of the total and free protein S measurement was evaluated. The results of 10 plasma samples measured against a centrally distributed frozen plasma and a centrally distributed lyophilized plasma were compared with those of various local reference plasmas regularly used by the 11 participating laboratories. The mean intra-assay coefficient of variation for total protein S in each laboratory varied from 3.8 to 12.8% (mean intra-assay CV of all laboratories: 7.4+/-2.3%); for free protein S this range was 3.1 to 13.3% (mean intra-assay CV of all laboratories: 6.6+/-2.7%). We confirmed the high inter-laboratory coefficient of variation (mean+/-SD) with the several local reference plasmas for both total protein S (13.4+/-5.6%; n = 10) and free protein S (17.1+/-7.5%: n = 11). For total protein S, the inter-laboratory CV was reduced to 11.5+/-4.8%, (p=0.05) by using a common frozen reference plasma, while it was increased to 16.8+/-3.4%, (p=0.022) using a common lyophilized reference plasma. For free protein S, these values decreased only statistically significantly for the common lyophilized reference plasma, to 15.1+/-6.0%, (p = 0.008). For free protein S, the dilution factor used was identified as a factor influencing the inter-laboratory variability. This study shows that, for both types of protein S measurements, using one frozen reference plasma shows a slight decrease in inter-laboratory variability, while a common lyophilized plasma shows inconsistent results. It is concluded that further investigation is necessary to examine other sources of variability to increase the comparability of laboratory results for both total and free protein S.