Dose-effect relationship of adenosine provoked angina pectoris-like pain--a study of the psychophysical power function

In an analysis of the psychophysical power function of chest pain induced by adenosine, this agent was repeatedly given in increasing doses into a peripheral vein to six healthy volunteers (five men) aged 23-44 years. On the first day the maximum tolerable dose was determined. On the second day seven doses of adenosine (20, 30, 40, 50, 60, 80 and 100% of the maximum dose) were given single blind in randomized order followed by another seven doses in reversed order. The heart rate was calculated from electrocardiographic recordings. Chest pain was continuously rated according to the CR-10 scale. Before the adenosine test, the perception of sourness was tested similarly with six concentrations of citric acid (1-100 mM). The psychophysical power functions were similar for the perception of sourness provoked by citric acid and chest pain provoked by adenosine, with exponents of 0.69 +/- 0.21 and 0.60 +/- 0.32, respectively. The two modalities showed the same high goodness of fit to the power function (rxy being 0.965 +/- 0.030 and 0.967 +/- 0.033, respectively). For adenosine the group mean relation was R = 1.66(S-2.36)0.6, rxy = 0.999. No signs of tolerance were observed for the chest pain provoked by adenosine. In conclusion, chest pain provoked by adenosine follows a psychophysical power function as with other sensory modalities.

Polymorphism of HLA and insulin gene is correlated to type I diabetes

A polymorphic locus flanking the 5'-end of the insulin gene was studied by means of the recombinant DNA technique in 62 diabetic and nondiabetic subjects. The small allele predominantly was found with the following frequencies: 28 insulin-dependent diabetics 0.89; 6 probands of a family with one type I diabetic member 0.92; 10 patients with a non-insulin-dependent diabetes mellitus 0.55; 18 control probands (normal glucose tolerance) 0.64. --Because of the relatively high number of all probands with the small allele we assume that the presence of this allele on both chromosomes increases the susceptibility but is not sufficient for the onset of an insulin-dependent diabetes mellitus. By a correlation of the polymorphic region of the insulin gene with other DNA regions (in particular with the major histocompatibility complex) the susceptibility may be further increased. Therefore, the HLA-DR gene polymorphism of type I diabetes is of interest.

Adenosine-provoked angina pectoris-like pain--time characteristics, influence of autonomic blockade and naloxone

In a study to characterize the time characteristics and the influence of blockade of beta, cholinergic and opioid receptors on the chest pain induced by adenosine, this agent was given as a bolus into a peripheral vein of six healthy volunteers (4 men) 24-45 years of age. On the first day the maximum tolerable dose was determined in each case. On the second day three doses of adenosine (1/3, 2/3, and a full maximum tolerable dose) and three doses of placebo were given as single blind doses in randomized order. Thereafter metoprolol (10 mg to males, 8 mg to females), followed by 1 mg atropine and then 0.4 mg naloxone were given intravenously. After each agent the test procedure was repeated. Heart rate and atrio-ventricular blocks were recorded by electrocardiography and respiration by dynamic spirometry. One minute after each dose of adenosine, the chest pain was scored. The maximum tolerable dose of adenosine was 8.0-15.9 mg. All subjects experienced angina pectoris-like pain. Following injection, onset of respiratory stimulation, AV-block and chest pain occurred after 14 +/- 4.0, 19 +/- 5.4 and 21 +/- 6.4 s, the differences being highly significant. Maximal respiratory stimulation occurred after 18 +/- 4.6, not statistically different from the onset of AV-block which in its turn occurred earlier (P less than 0.005) than the time for maximal central chest pain, 29 +/- 7.8 seconds. Metoprolol induced a 20% slowing of heart rate. After atropine there was a 30% faster heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of mixed micelles formed from glycocholic acid and lecithin with the protein binding of various drugs

Mixed micelles (MM) formed from glycocholic acid and lecithin are suited to solubilize lipophilic drugs for intravenous use. To test for possible drug-drug interactions, the protein binding of a series of agents known to bind to different sites on albumin (diazepam, warfarin, ketoprofen, frusemide, probenecid) and additionally (prazosin, quinidine, propranolol) or exclusively (disopyramide) to alpha 1-acid glycoprotein or to transcortin (prednisolone) was determined in the presence and absence of MM. Concentrations of MM, corresponding to the maximum possible plasma concentration achieved by injecting the highest clinical doses of MM into the systemic circulation, had little or no effect on the unbound fractions of drugs known to bind exclusively to albumin. Only at five times higher MM concentrations were the free fractions substantially increased (by up to 45%). Unbound fractions of drugs bound with high affinity but low capacity to alpha 1-acid glycoprotein were increased between 50-85% even at 'therapeutic' doses of MM. The present study suggests that drugs solubilized by MM should be given by slow injection or infusion to patients already receiving drugs which are highly bound to alpha 1-acid glycoprotein.

The major histocompatibility complex and diabetes mellitus

Recent studies have greatly increased the knowledge of the genetics of diabetes mellitus. At present several markers of the disease are under discussion. For insulin-dependent diabetes mellitus there is an association between markers of the histocompatibility complex and the incidence of the disease. The genes of the human histocompatibility complex code for at least three different classes of polymorphic proteins involved in the immune response. Two of them, the class I and the class II antigens are described in the article. The class II antigens are primarily expressed on special cells of the immune system. A typical feature of these antigens is their extensive polymorphism, which is the result of their genetic organization. The occurrence of insulin-dependent diabetes mellitus is more or less strongly associated with the class II antigen types DR3 and/or DR4. Using recombinant DNA technology it is possible to further characterize these and other class II specificities at genetic level. There are data on the occurrence of some class II antigen related DNA restriction fragments. They are much more strongly associated with the susceptibility to the disease than other markers found so far.

A convenient radiometric assay for hyaluronan

Hyaluronan-binding proteins (HABP) isolated from bovine cartilage have been utilized in a radiometric assay for determination of hyaluronan (hyaluronic acid; HA) in serum. The samples to be analysed are preincubated with iodinated HABP. After 60 minutes the protein that is not bound to hyaluronan, in the solution, is recovered on HA-Sepharose in a 45-min incubation. Hyaluronan can be determined in the range from 10 to 1,000 micrograms/l. The sample size is 100 microliter and the intra-assay and inter-assay coefficients of variations are less than 10% and less than 10%, respectively for samples containing hyaluronan concentrations in the range 10-200 micrograms/l. Detection limit is 4 micrograms/l.

A competitive enzyme immunoassay of human beta 2-microglobulin based on separation by filtration

A competitive enzyme immunoassay has been developed for the determination of beta 2-microglobulin in undiluted human serum. In the assay a beta 2-microglobulin-beta-galactosidase conjugate competes with beta 2-microglobulin from the sample for the binding to anti-beta 2-microglobulin antibodies bound to small size agarose particles (micro-Sepharose) via a double antibody. The conjugate is made by providing beta 2-microglobulin with 'reactive disulphide structures.' This is achieved by the heterobifunctional reagent SPDP and the subsequent linkage of the formed derivative to beta-galactosidase by a thioldisulphide exchange reaction. This procedure gives conjugates with high immunoreactivity and enzyme activity. The assay is fast and simple. The reagents are incubated together for 60 min in the wells of a Millititer plate and separation is performed by filtration. Bound enzyme-labelled beta 2-microglobulin is measured by incubation with substrate for 15 min. Both incubations are performed at room temperature without agitation. Due to the high capacity of the micro-Sepharose no sample predilution is needed. The use of the Millititer filtration system gives a rapid and efficient separation and the advantages of access to equipment for dispensing and reading adapted to the microtitre format.

Angina pectoris-like pain provoked by intravenous adenosine in healthy volunteers

In a study to characterise the chest pain induced by adenosine this agent was given as a bolus into a peripheral vein to six healthy volunteers (five men) aged 30-44. On the first day the maximum tolerable dose was determined in each case. On the second day three doses of adenosine (one third, two thirds, and the full maximum tolerable dose) and three doses of saline were given single blind in randomised order. Thereafter aminophylline 5 mg/kg was given and the procedure repeated in a different randomised order. On the third day between two thirds and the full maximum tolerable dose was given followed by 10 mg dipyridamole intravenously and a second injection of the same dose of adenosine. Heart rate and atrioventricular blocks were recorded by electrocardiography. One minute after each dose of adenosine the chest pain was scored. The maximum tolerable dose of adenosine ranged from 10.6 to 37.1 mg. All subjects experienced uneasy central chest pain provoking anxiety. The pain radiated to the shoulders, ulnar aspect of the arms, epigastric area, back, and into the throat. The pain began about 20 seconds after the injection and lasted 10-15 seconds. Increasing the dose of adenosine increased the intensity of the pain. Administration of aminophylline reduced the pain significantly. Second degree heart block was recorded in five of the six subjects during the time that the pain was experienced. After aminophylline no block was observed. Dipyridamole increased the intensity of pain. The duration of second degree heart block increased in four of the subjects, and in two of these third degree heart block occurred. These findings suggest that adenosine released from the myocardium during ischaemia induces angina pectoris by stimulating theophylline sensitive receptors.

The human insulin gene and diabetes mellitus

The recombinant DNA technology is a useful tool to characterize the insulin gene and adjacent areas. A highly polymorphic region near the human insulin gene was detected and its possible relation to certain types of diabetes mellitus is discussed. In three cases the synthesis of a structurally abnormal insulin of lower biological activity leads to hyperglycemia. These mutant insulin gene sequences can be identified with the help of restriction endonuclease cleavage analysis. Insulin gene expression is regulated mainly at translational level. Elements near or within the insulin gene seem to be required for a sufficient and cell-specific expression. But the role of the polymorphic locus is not yet clear. First results on gene transplantation by administration of liposome entrapped insulin gene sequences are surprising, but at this time only of speculative value for medical research.

Effect of nicotine on prostacyclin formation in human endocardium in vitro

The effect of nicotine on the formation of prostacyclin by human endocardium was studied in vitro. Slices of cardiac valve cusps were incubated in a saline medium and the prostacyclin-like activity generated spontaneously by the tissue specimens was assessed in terms of its capacity to inhibit ex vivo platelet aggregation. In separate experiments supernatants of valvular tissue homogenates were incubated with [14C]arachidonate. This resulted in the appearance of labelled 6-keto-prostaglandin F1 alpha in the radiochromatograms, indicating the formation of prostacyclin in the homogenates. Nicotine inhibited dose-dependently the spontaneous generation of prostacyclin-like activity (I50 approximately equal to 2 X 10(-4) M), as well as the formation of 6-keto-prostaglandin F1 alpha (I50 approximately equal to 2 X 10(-5) M), indicating an inhibitory effect of the drug on endocardial prostacyclin production.

Stimulatory cholinergic effect on the release of antiaggregatory activity into the circulation of cat and man and its modification by beta-adrenergic antagonists

The release of PGI2-like activity into the circulation in response to cholinergic agonists and modification of this response by beta-adrenergic antagonists was investigated in anaesthetized cats and healthy humans. Antiaggregatory activity in the arterial blood was continuously assayed by measuring platelet aggregation on blood superfused collagen strip. In some of the human experiments, after the administration of the drugs, the conversion of [14C]-arachidonate to [14C]-prostaglandins in the pulmonary vascular bed was studied. Cholinergic agonists stimulated the release of PGI2-like activity into the circulation, which effect was potentiated in cats by beta-adrenergic antagonists. In humans the latter agents did not stimulate the conversion of [14C]-arachidonate to prostaglandins in the pulmonary circulation and, moreover, inhibited the stimulatory cholinergic effect. The results suggest that an interplay between cholinergic and beta-adrenergic mediators may be involved, although in a different way in cats and in humans, in the release of PGI2-like activity into the systemic circulation.

The effect of stress hormones on the interorgan flux of amino acids and on the concentration of free amino acids in skeletal muscle

Plasma concentrations of free amino acids have previously been found to decrease posttraumatically and this decrease can be reproduced by infusion of stress hormones. The mechanisms underlying this effect has not been investigated and therefore 14 healthy subjects were studied by infusing adrenaline alone or a combination of adrenaline, glucagon, and cortisol, in dosages giving pathophysiological plasma concentrations of the hormones. The influence on the interorgan fluxes of free amino acids and on the concentrations of free amino acids in skeletal muscle were determined. During hormone infusion splanchnic oxygen consumption doubled, indicating an increase in metabolic activity. There was a significant decrease in the arterial plasma level of all amino acids except alanine. Significant increases in alanine flux was noted, the release from one leg doubled and the splanchnic uptake increased by 60%. After only 1 h all essential amino acids showed a significantly decreased concentration in muscle while the level of alanine was increased. There were no differences between the two hormone groups. The results indicate that stress hormones can initiate an increased formation of alanine in skeletal muscle and an increase in alanine transport from the periphery to the splanchnic area.

Is hyperventilation a physiologically significant stimulus for prostaglandin release in the human pulmonary vascular bed?

The influence of hyperventilation on the pulmonary prostaglandin (PG) release was studied in healthy volunteers. Hyperventilation was forced by adding 8% CO2 to the inhaled air and arterial and mixed venous blood was sampled for radioimmunoassays of 6-keto-PGF1 alpha and PGE2. The increased ventilation did not alter the arterio-venous PG concentration differences suggesting that hyperventilation accompanying the activation of chemoreceptors is not a physiologically significant stimulus for the pulmonary PG release in man.

Effect of propranolol, practolol and atenolol on human platelet thromboxane formation and plasma levels of prostaglandins 6-keto-F1 alpha and E2

The effects of three different beta-adrenergic blocking drugs, propranolol, practolol and atenolol on platelet thromboxane production and the release of prostacyclin and prostaglandin E2 into the circulation were investigated in healthy volunteers. The beta-adrenergic antagonists were administered intravenously at equipotent doses. The serum TxB2 levels after whole blood clotting and the arterial and venous plasma concentrations of 6-keto-PGF1 alpha and PGE2 were measured before and during a 60 min period after the administration of the drugs, using radioimmunoassay. Practolol and atenolol elicited a significant decrease in platelet thromboxane formation but remained without effect on plasma 6-keto-PGF1 alpha and PGE2 levels. In contrast, propranolol did not influence serum TxB2 concentrations but induced a significant increase in plasma content of 6-keto-PGF1 alpha and PGE2. The results indicate that beta-adrenergic antagonists alter the balance between the proaggregatory, vasoconstricting and antiaggregatory, vasodilating prostanoids in the human cardiovascular system. Although the direction of the action of these drugs seems to differ depending on the selectivity of the beta-adrenoceptor blocking properties the net effect of this action should be beneficial.

Mapping of cysteine genes on the chromosome of Pseudomonas aeruginosa PAO

Three loci coding for different steps in the pathway of cysteine biosynthesis have been mapped by R68.45-mediated coconjugation analysis. The cysteine auxotrophic mutants could be subdivided into sulfite and sulfide-requiring mutants. Sulfide-requiring mutants (cysIV group) were localized at a single position between pyrF and pur-67, while sulfite-requiring mutants (cysI and cysII) mapped at two different regions. The cysI group was also localized between pyrF and pur-67, although more distal to pyrF than the cysIV group. This group included the cys-54 marker, which has been mapped previously. The second group of sulfite-requiring mutants, designated as cysII, was cotransducible with hisI and localized at the end of the PAO chromosomal map. This location was also confirmed for the marker cys-59. The marker cys-59 (which was cotransducible with hisI) was cotransferred by R68.45-mediated conjugations with both the late marker pur-67 and the early marker ilv-226. As the late marker hisI was positioned at about 60-65 min (Herrmann and Günther, in press) the length of the PAO chromosome was estimated to be about 70 min.

Prostaglandin formation from exogenous precursor in homogenates of human cardiac tissue

The ability of some different components of human cardiac tissue to synthesize prostaglandins (PGs) from exogenous precursor was investigated. Fractions of the cardiac tissue containing either parts of valve cusps and the papillary musculature or some selected tissue components such as myocytes, endocardial elements, endothelial cells and connective tissue were prepared and homogenized. Low-speed supernatants of the various homogenates thus obtained were incubated with [14C]-labelled arachidonate [( 14C]-AA]. [14C]-PGs formed in the incubates were extracted, separated by thin-layer chromatography and quantified using liquid scintillation spectrometry. In the incubates of all the fractions [14C]-AA was converted to [14C]-PGs with a time-dependent yield, most effectively at 3 minutes' incubation time. The "endocardial" and "endothelial" fractions were found to exhibit the highest cyclo-oxygenase activity, the [14C]-AA conversion rate in these incubates being twice as high as in the others. [14C]-labelled PGF2, PGE2 alpha and 6-keto-PGF1 alpha were found to be the principal PG products and there was no evidence of TxB2 formation in any of the incubates. [14C]-6-keto-PGF1 alpha was the main PG formed, constituting about 40% or more of the [14C]-PG activity in the incubates of all the fractions, whereas labelled PGE2 and PGF2 alpha were observed in considerably smaller and nearly equal amounts. The results demonstrate a considerable ability of human cardiac tissue to synthesize prostacyclin (PGI2) and, at the same time, the existence of local differences in tissue cyclo-oxygenase activity, which appears to be significantly higher in the endocardial layer than in the myocardium itself.

Pharmacokinetics of tenoxicam in healthy human volunteers

Tenoxicam, a thieno-thiazine derivative, belongs to a new chemical class of non-steroidal anti-inflammatory drugs. Single dose kinetics was investigated after intravenous and oral administration to define the disposition and general absorption characteristics of the drug. After intravenous administration of 20 mg tenoxicam to 12 volunteers the time course of the plasma concentrations of unchanged drug followed two-compartment model characteristics. The area under the plasma-concentration time curve in the distribution phase contributed however only 3% or less to the total area. The plasma clearance was low with values ranging from 1.3 to 4.2 ml/min and the volume of distribution Vss was small averaging at 20 to 40% of the total body weight. The median half-life of elimination from the body was found to be 72 hours (range 42 to 100 hours). The disposition was not influenced by sex. Tenoxicam is highly bound to plasma albumin. At pH 7.4 the fraction bound exceeded 99% but was highly dependent on the pH. Plasma protein binding in patients with rheumatic disease was not different from that measured in healthy volunteers. The partitioning of tenoxicam into red blood cells was limited. Erythrocyte concentrations were only 20-30% of the corresponding plasma concentrations. After oral administration of a 20-mg tablet complete and rapid absorption of the drug was observed with maximum plasma levels of 1.7 to 3.6 micrograms/ml reached within 0.5 to 2 hours. Due to the rapid absorption and terminal half-life of the drug its plasma concentration profile after oral administration was very similar to that following intravenous dosing. The pharmacokinetic characteristics of tenoxicam offers a rationale to administer the entire dose in one single portion.

Release of prostacyclin from the human pulmonary vascular bed in response to cholinergic stimulation

The ability of the human pulmonary vascular bed to synthesize prostaglandins (PGs) in response to cholinergic stimulation was investigated in healthy male volunteers. In all of them, except controls, carbaminoylcholine (CCh) was injected subcutaneously at a dose of 5 micrograms/kg. In 3 subjects [1-14C]-labelled arachidonate was then infused at a constant rate into the right atrium between 10 and 15 min after the administration of the drug and the blood from the subclavian artery was sampled simultaneously. The arterial content of [14C]-labelled metabolites was extracted, separated by thin-layer chromatography and quantified using liquid scintillation spectrometry. In 8 other subjects PGI2-like activity after the administration of CCh was assayed in the arterial blood and in 1 subject in the venous blood, using a technique for continuous measurement of platelet aggregation on blood-superfused collagen strip. The major portion of [14C]-activity in the radiochromatograms migrated in parallel with the 6-keto-PGF1 alpha standard. No early defined peaks corresponding to any of the unlabelled PGs D2, E2 or F2 alpha, appeared, but in one chromatogram a minor radiopeak corresponding to authentic thromboxane B2 was observed. Also in the platelet aggregation experiments, 5-15 min after the administration of CCh, a significant increase in the PGI2-like activity was observed in the arterial as well as in the peripheral venous blood, which effect of the drug was abolished by pretreatment with atropine and acetylsalicylic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of beta-blockade on glycogen metabolism in human subjects during exercise

The effect of beta-blockade on glycogen metabolism during isometric and dynamic exercise in humans has been investigated. Isometric exercise increased the glycogenolytic rate in muscle but had no effect on the cAMP content. Neither the metabolic pattern nor the time of contraction was affected by beta-blockade. Dynamic exercise increased the cAMP content in muscle by about 100%. The cAMP content at rest was significantly reduced after propranolol infusion and did not increase during exercise. Total hexosemonophosphates increased sixfold during exercise but little or no increase occurred after administration of propranolol. The accumulation of lactate in muscle was slightly reduced during exercise following beta-blockade. The fraction of phosphorylase in the alpha form was 22.5% of the total at rest but decreased to 16% at exhaustion. Synthetase I was similarly decreased. During exercise with propranolol phosphorylase alpha decreased further to 3%, whereas synthetase I was unchanged. It is concluded that beta-blockade has no effect on muscle glycogenolysis during isometric contraction but decreases the rate of glycogen degradation during dynamic exercise at high work loads due to changes in the phosphorylase-synthetase system.

The effect of physical training in elderly subjects with special reference to energy-rich phosphagens and myoglobin in leg skeletal muscle

Energy-rich phosphagens and myoglobin were determined in leg skeletal muscles of seven, 61- to 80-year-old, apparently healthy male subjects. The study repeated after the participants had been exercising on an ergometer bicycle twice weekly for 6 weeks. Before training, myoglobin and all intramuscular energy-rich phosphagens were within the range recorded for a larger series of subjects of similar age. When re-examined after training the myoglobin level remained the same but creatine decreased significantly and the ratio between phosphocreatine and total creatine increased. A slight but significant rise was also observed for the ATP/ADP ratio. It is concluded that age-related changes of intramuscular phosphagens in elderly subjects in part might be due to physical inactivity.

Effect of posttraumatic epidural analgesia on the cortisol and hyperglycaemic response to surgery

Plasma cortisol and glucose were measured in 36 patients undergoing abdominal hysterectomy under either general anaesthesia (Group I), epidural analgesia (T4-S5) effective before surgery (Group II) or general anaesthesia plus epidural analgesia (T4-S5) effective from 30 min after initiation of surgery. The results confirmed that epidural analgesia effective before skin incision (Group II) prevented the normal per-and postoperative increase in plasma cortisol and glucose. Patients receiving posttraumatic epidural analgesia (Group III) showed the normal initial increase in plasma cortisol and glucose, but initiation of epidural analgesia immediately broke the stress-response and prevented any further increase in plasma cortisol and glucose. However, although posttraumatic neurogenic blockade inhibited a major part of the stress-response, resting endocrine-metabolic activity was not reestablished, suggesting that once released the endocrine-metabolic response to trauma leads to persistent changes even if further afferent stimuli from the traumatized area are prevented.

Hepatic gluconeogenesis during halothane anaesthesia in man

It is known that hepatic gluconeogenesis from lactate and aminoacids is inhibited by halothane in in vitro studies on isolated, perfused livers. In the present work, the effect of halothane anaesthesia on hepatic gluconeogenesis was studied in three volunteers during a constant amino-acid infusion and compared with three control subjects who did not receive any halothane during the amino-acid infusion. Prior to the investigation, all the subjects were on a carbohydrate-poor diet in order to deplete hepatic glucogen stores. During the investigation, hepatic gluconeogenesis was stimulated by a constant amino-acid infusion which caused a slight rise in total hepatic blood flow (THBF), a marked increase in splanchnic oxygen consumption and oxygen extraction, elevation in blood glucose and urea levels and in splanchnic glucose and urea releases. Halothane anaesthesia administered during continued amino-acid infusion caused a reduction in THBF to sub-control values, while the increased oxygen consumption was only slightly reduced, thereby further increasing splanchnic oxygen extraction. Blood glucose and urea levels of the anaesthetized subjects were consistent with those of the control subjects. Splanchnic release of glucose was reduced almost to control values during halothane. However, the release of urea was only slightly reduced. It is concluded that the stimulating effect on hepatic gluconeogenesis caused by the amino-acid infusion was inhibited during halothane anaesthesia, while metabolization of the amino-acids, other than through gluconeogenesis, proceeded without any major changes.

On stability of scintillation detectors

This paper describes how a photomultiplier tube in a scintillation detector changes pulse height with time, when the detector is exposed to a gamma-emitting source and high dynode voltage. The change in pulse height causes a "drift" of the spectral peaks out of the preadjusted energy window, and errors in counting rate of about 20% are detected. The drift is dependent on the photon flux, the level of the high voltage, and the energy of the source. The effect was not present in all detectors studied. It is thus important to check the stability properties of a detector before use.

Effects of concentration-dependent plasma protein binding on ceftriaxone kinetics

The kinetics of ceftriaxone, a cephalosporin, was studied in six healthy subjects who received bolus injections of 150, 500, and 1,500 mg intravenously in a random crossover fashion. Although total drug concentration time profiles after all doses could be described by biexponential equation, simple compartment analysis was inappropriate because a disproportional increase in the area under the total drug concentration time curves occurred with dose. This resulted in a dose-dependent increase in total systemic clearance (ClTS) from 9.7 ml/min at the 150-mg dose to 13 ml/min at the 1500-mg dose. The dose-dependent changes in ClTS could be explained in terms of the concentration-dependent plasma protein binding of ceftriaxone (fplasma ranging from 0.04 to 0.167), because the area under the free drug concentration time curves (AUCFO-infinity) increased proportionately to dose. Mean total clearance with reference to free (unbound) ceftriaxone (ClFS) was constant at 255 ml/min. Calculated mean renal clearance with reference to free ceftriaxone (ClFR) was 173 ml/min, or slightly more than the average glomerular filtration rate in humans. Mean plasma ceftriaxone t1/2 was not influenced by dose and averaged 8 hr. This biological t1/2 is by far the longest ever for a cephalosporin in healthy subjects.

[The diagnostic significance of microcalcifications in testicular tumors (author's transl)]

The evaluation of total orchiectomy tissue specimens with malignant testicular tumors shows that microcalcifications can be found in a surprisingly high percentage by radiological and histological examinations. Small, often in several groups located calcifications in the parenchyma neighbouring the tumor are typical for seminoma, whereas in teratoma solitary microcalcifications and polymorphic types can also be seen. Microcalcifications are also present in not neoplastic testicular diseases but in a much smaller percentage and with a different type of calcification. The preoperative radiographic examination of testicular tumors of unknown origin seems to be indicated as a non-invasive method able to provide further information about the presence of a malignant germ cell tumor. Regarding the genetic risks of the method, there is hope to avoid other more invasive examinations with their danger of tumor spreading and to enable a radical resection of the primary tumor before its metastic formation by the mean of preoperative orchioradiography.

Intracellular pH and bicarbonate concentration in human muscle during recovery from exercise

Eight subjects exercised on an ergometer until exhaustion. Femoral venous blood was analyzed for lactate, pyruvate, protein, electrolytes, and acid-base parameters. Muscle samples taken during the recovery period from m. quadriceps femoris were analyzed for water, electrolytes, lactate, and acid-labile CO2. Water content in the muscle biopsy sample was increased after exercise to 78.7 +/- 0.5% compared with the normal 76.7 +/- 0.8% at rest. The distribution of water between the extra- and intracellular space was calculated by the chloride method. In spite of elevated PCO2 in femoral venous blood the content of acid-labile CO2 was decreased in muscle after exercise. One minute after termination of exercise muscle CO2 was about half of the normal content at rest. During the recovery period muscle CO2 increased but was 20 min after termination of exercise still significantly below the value at rest. Intracellular pH (pHi) and bicarbonate concentration ([HCO3-]i) in muscle have been calculated. The validity of the assumptions underlying the calculations are thoroughly discussed. pHi decreased from the normal value at rest, 7.00 +/- 0.06 (mean +/- SD), to about 6.4 after exercise. [HCO3-] decreased from 10.2 +/- 1.2 mmol/l at rest to about 3 mmol/l after exercise. The changes are the greatest so far reported for an in vivo situation. After 20 min recovery pHi was almost the same as at rest, whereas bicarbonate was still well below.

The registration of slow ERG potentials of the perfused extracorporeal bull's eye

Enucleated bull's eyes were perfused with blood and ERG recorded, with special attention paid to the slow components. When the blood flow was interrupted, the ERG components vanished in the following order: b wave, c wave, off-effect (d wave), and a wave. When the perfusion was continued afterward, we saw a variation in the standing potential that hinted at the biochemical activities causing slow electrical potentials of the retina.

Urinary glucose and vitamin C

The recent popularization of self-prescribed large doses of vitamin C has increased the possibility for erroneous conclusions to be drawn from standard clinical methods used in urinary glucose monitoring, due to interference with these methods by the greatly elevated excretion of vitamin C. The coupled-enzyme-chromogen strip tests showed erroneously negative glucose levels in urines of both a diabetic individual and a subject with a genetic low renal threshold for glucose when they were supplementing their normal diets with 1-2 g vitamin C per day. With this regimen, their urinary vitamin C levels reached 200 mg/dl (11.4 mmol/l). For normal urine with vitamin C added, false-positive tests for glucose were found using Benedict's reagent when vitamin C was present at 250 mg/dl (14.3 mmol/l) or higher concentrations. In diabetic individuals consuming large quantities of vitamin C, this interference with standard coupled-enzyme-chromogen strip tests or Benedict's test could present a significant problem in diagnosis and clinical management of the disease. A simple anion exchange method of treating the urine was used to correct the false results.