Rapamycin-sensitive phosphorylation of PKC on a carboxy-terminal site by an atypical PKC complex.

BACKGROUND: The protein kinase C (PKC) family has been implicated in the control of many cellular functions. Although PKC isotypes are characterized by their allosteric activation, phosphorylation also plays a key role in controlling activity. In classical PKC isotypes, one of the three critical sites is a carboxy-terminal hydrophobic site also conserved in other AGC kinase subfamily members. Although this site is crucial to the control of this class of enzymes, the upstream kinase(s) has not been identified. RESULTS: A membrane-associated kinase activity that phosphorylates the hydrophobic site in PKCalpha was detected. This activity was suppressed when cells were pretreated with the immunosuppresant drug rapamycin or the phosphoinositide (Pl) 3-kinase inhibitor LY294002. These pretreatments also blocked specifically the serum-induced phosphorylation of the hydrophobic site in PKCdelta in vivo. The most highly purified hydrophobic site kinase preparations ( approximately 10,000-fold) reacted with antibodies to PKCzeta/iota. Consistent with this, rapamycin and LY294002 reduced the recovery of PKCzeta from the membrane fraction of transfected cells. An activated mutant of PKCzeta, but not wild-type PKCzeta, induced phosphorylation of the PKCdelta hydrophobic site in a rapamycin-independent manner, whereas a kinase-dead PKCzeta mutant suppressed this serum-induced phosphorylation. The immunopurified, activated mutant of PKCzeta could phosphorylate the PKCdelta hydrophobic site in vitro, whereas wild-type PKCzeta could not. CONCLUSIONS: PKCzeta is identified as a component of the upstream kinase responsible for the phosphorylation of the PKCdelta hydrophobic site in vitro and in vivo. PKCzeta can therefore control the phosphorylation of this PKCdelta site, antagonizing a rapamycin-sensitive pathway.

Pheochromocytomas: can malignant potential be predicted?

OBJECTIVES: The presence of metastatic lesions is the only acceptable fact to confirm malignant pheochromocytoma. Patients with malignant pheochromocytomas, however, have a very poor survival rate. The aim of our study was to postulate predictive values for malignant pheochromocytomas. METHODS: We evaluated symptoms, diagnostic modalities, treatment, and long-term follow-up of 86 patients with 85 benign and 10 malignant pheochromocytomas. Parameters from the benign were compared with those of the malignant pheochromocytomas. RESULTS: Preoperative 24-hour urinary dopamine was in the normal range for benign pheochromocytomas but increased in malignant pheochromocytomas (P<0.0001). Vanillylmandelic acid was elevated in both benign and malignant pheochromocytomas but higher in malignant than in benign tumors (P = 0.01). No differences could be shown in urinary epinephrine and norepinephrine samplings. Tumor location was divided into 77 adrenal (81%) and 18 extra-adrenal (19%) sites. Malignant pheochromocytomas were located more often at extra-adrenal sites (P = 0.03). There was no increased incidence of malignancy in patients with familial bilateral pheochromocytomas or multiple endocrine neoplasia. Tumors greater than 80 g in weight corresponded to malignancy (P<0.0001). Dopamine tumor concentration was higher in malignant than in benign pheochromocytomas (P = 0.01). Persistent arterial hypertension occurred in 9 (13%) of 72 benign and 6 (60%) of 10 malignant pheochromocytomas (P = 0.001). The 10-year survival rate was 94% for benign pheochromocytomas. All patients with malignant pheochromocytomas died within this period (P = 0.0001). CONCLUSIONS: High preoperative 24-hour urinary dopamine levels, extra-adrenal tumor location, high tumor weight, elevated tumor dopamine concentration, and postoperative persistent arterial hypertension are all factors that increase the likelihood of malignant pheochromocytoma. Patients with these characteristics should have more frequent follow-up evaluations to identify malignancy at earlier states.

Protein kinase C isotypes controlled by phosphoinositide 3-kinase through the protein kinase PDK1.

Phosphorylation sites in members of the protein kinase A (PKA), PKG, and PKC kinase subfamily are conserved. Thus, the PKB kinase PDK1 may be responsible for the phosphorylation of PKC isotypes. PDK1 phosphorylated the activation loop sites of PKCzeta and PKCdelta in vitro and in a phosphoinositide 3-kinase (PI 3-kinase)-dependent manner in vivo in human embryonic kidney (293) cells. All members of the PKC family tested formed complexes with PDK1. PDK1-dependent phosphorylation of PKCdelta in vitro was stimulated by combined PKC and PDK1 activators. The activation loop phosphorylation of PKCdelta in response to serum stimulation of cells was PI 3-kinase-dependent and was enhanced by PDK1 coexpression.

Interaction between grapefruit juice and midazolam in humans.

OBJECTIVE: To investigate the effects of grapefruit juice on the pharmacokinetics and dynamics of midazolam. METHODS: Eight healthy male subjects participated in this open crossover study. Intravenous (5 mg) or oral (15 mg) midazolam was administered after pretreatment with water or grapefruit juice. We measured the pharmacokinetics and pharmacodynamics (reaction time, Digit Symbol Substitution Test [DSST], general impression judged by the investigators, and drug effect judged by the subjects) of midazolam and the pharmacokinetics of alpha-hydroxymidazolam. RESULTS: In comparison to water, pretreatment with grapefruit juice did not change the pharmacokinetics or pharmacodynamics of intravenous midazolam. After oral administration, pretreatment with grapefruit juice led to a 56% increase in peak plasma concentration (Cmax), a 79% increase in time to reach Cmax (tmax), and a 52% increase in the area under the plasma concentration-time curve (AUC) of midazolam, which was associated with an increase in the bioavailability from 24% +/- 3% (water) to 35% +/- 3% (Grapefruit juice; mean +/- SEM, p < 0.01) After oral administration of midazolam, pretreatment with grapefruit juice was associated with a 105% increase in tmax and with a 30% increase in the AUC of alpha-hydroxymidazolam. For oral midazolam, pretreatment with grapefruit juice led to significant increases in tmax for all dynamic parameters and in the AUC values for the reaction time and DSST, whereas the maximal dynamic effects remained unchanged. CONCLUSIONS: Pretreatment with grapefruit juice is associated with increased bioavailability and changes in the pharmacodynamics of midazolam that may be clinically important, particularly in patients with other causes for increased midazolam bioavailability such as advanced age, cirrhosis of the liver, and administration of other inhibitors of cytochrome P450.

Pain assessment after intramuscular injection.

Several parameters (pH, osmotic pressure) influencing the local tolerance of injectable drugs have been well-documented; however, little attention has been paid to pain following an injection--a common problem in clinical practice. A pain questionnaire was used to record pain up to 24 h after a deep ventrogluteal injection. Two groups of healthy volunteers were recruited: the first group (n = 6) received 3 different cotrimoxazole preparations and placebo and the second group (n = 10) received 4 different multivitamin preparations and placebo (double-blind, cross-over). Parameters monitored during and after injection included pain localization (line drawing), pain intensity (visual-analog scale: VAS) and verbal description of pain (pain rating index: PRI). In both groups, the equality of pain (VAS, PRI) induced by the preparations was rejected in all cases (Friedman's test, p < or = 1%). The pairwise comparisons of the groups showed significant differences (p < or = 5%) between various preparations. The correlation (Spearman's rank correlation) between pain parameters VAS and PRI was high. The present investigations have shown that the pain questionnaire is a valuable tool to investigate the subjective pain symptoms during and after the injection of different preparations.

Hyperventilation-induced changes of blood cell counts depend on hypocapnia.

Voluntary hyperventilation for 20 min causes haemoconcentration and an increase of white blood cell and thrombocyte numbers. In this study, we investigated whether these changes depend on the changes of blood gases or on the muscle work of breathing. A group of 12 healthy medical students breathed 36 l.min-1 of air, or air with 5% CO2 for a period of 20 min. The partial pressure of CO2 decreased by 21.4 mmHg (2.85 kPa; P < 0.001) with air and by 4.1 mmHg (0.55 kPa; P < 0.005) with CO2 enriched air. This was accompanied by haemoconcentration of 8.9% with air (P < 0.01) and of 1.6% with CO2 enriched air (P < 0.05), an increase in the lymphocyte count of 42% with air (P < 0.001) and no change with CO2 enriched air, and an increase of the platelet number of 8.4% with air (P < 0.01) and no change with CO2 enriched air. The number of neutrophil granulocytes did not change during the experiments, but 75 min after deep breathing of air, band-formed neutrophils had increased by 82% (P < 0.025), whereas they were unchanged 75 min after the experiment with CO2 enriched air. Adrenaline and noradrenaline increased by 360% and 151% during the experiment with air, but remained unchanged with CO2 enriched air. It was concluded that the changes in the white blood cell and platelet counts and of the plasma catecholamine concentrations during and after voluntary hyperventilation for 20 min were consequences of marked hypocapnic alkalosis.(ABSTRACT TRUNCATED AT 250 WORDS)

A reversible form of apical left ventricular hypertrophy associated with pheochromocytoma.

A patient with pheochromocytoma was found to have typical features of apical left ventricular hypertrophy similar to apical hypertrophic cardiomyopathy of the Japanese type. The electrocardiogram showed giant negative T waves (1.0 mV), and echocardiography as well as angiographic examination revealed left ventricular hypertrophy confined to the apex. Surgical removal of the tumor resulted in striking regression of apical hypertrophy and essential normalization of the electrocardiogram within 1 year of operation. These findings emphasize the possible role of catecholamines in the cause of apical hypertrophic cardiomyopathy and illustrate the potential reversibility of this condition in association with pheochromocytoma. It is suggested that patients with signs of apical left ventricular hypertrophy should undergo thorough screening for a pheochromocytoma.

Effect of head-down tilt bedrest (10 days) on lymphocyte reactivity.

Immunological responses of six healthy males to 10 days of head-down tilt bedrest (HDT) were assessed. Lymphocyte responsiveness was severely reduced immediately before, during, and immediately after the HDT, even though the lymphocyte numbers did not change. By contrast, delayed-type hypersensitivity was not affected. No dramatic changes were found in WBC counts and lymphocyte subpopulations, with the only exception of natural killer (NK) cells which transiently decreased immediately after HDT. Plasma cortisol levels were elevated above normal immediately before and during the HDT. The data suggest that the mitogenic response of lymphocytes was affected by psychological and fluid shift stress. These results are compared with data obtained during and after spaceflight. We conclude that the stress of HDT induces changes in immunological responsiveness that are strikingly similar to those arising from the stress of spaceflight.

Intercostal nerve block for minor breast surgery.

Two anesthetic procedures, intercostal nerve block (ICNB) and general anesthesia, were evaluated in 45 female patients scheduled for minor breast surgery. The study was designed to compare ICNB with general anesthesia for breast surgery with respect to efficacy, surgical stress and postoperative analgesia and to evaluate epinephrine and ornipressin as vasoconstrictors in the local anesthetic solution. Thirty patients received ICNB of T3-T7 unilaterally using 2% lidocaine plus epinephrine (15 patients, Group A) and 2% lidocaine plus ornipressin (15 patients, Group B). The control group consisted of 15 patients receiving a general anesthetic. The highest median lidocaine plasma level was 2.8 micrograms/ml in those patients who received epinephrine and 5.3 micrograms/ml in those who received ornipressin. There were statistically significantly higher lidocaine plasma levels in Group B than in Group A after 10, 30 and 60 minutes from injection while the two groups did not differ significantly at the 20- and 90-minute time intervals. Before and during surgery, epinephrine and norepinephrine plasma levels were highest in the epinephrine group, whereas, postoperatively, the plasma levels of both catecholamines were highest in the patients receiving general anesthesia. The latter patients experienced significantly more nausea and vomiting than the regional anesthesia groups. Patients with regional anesthesia required significantly less analgesics postoperatively than the patients receiving general anesthesia.

Cardiovascular regulation during angiotensin converting enzyme inhibition with captopril in diabetes-associated hypertension.

Diabetes-associated hypertension is accompanied by high levels of body sodium and cardiovascular hyper-reactivity to noradrenaline. Captopril, a promising drug for the treatment of hypertension in diabetics, may influence sodium metabolism and adrenergic pathways. This possibility was investigated in 11 patients with non-azotaemic diabetes mellitus and hypertension, studied after a 3-week placebo phase and after an 8-week phase of captopril treatment (50-100 mg/day). Blood pressure, exchangeable body sodium, blood volume, plasma renin activity, angiotensin II (Ang II), aldosterone, catecholamine levels and the pressor reactivity to infused Ang II or noradrenaline were measured. Compared with placebo, captopril caused a significant decrease in arterial pressure and stimulation of plasma renin activity. Exchangeable sodium, blood volume, plasma Ang II, aldosterone, noradrenaline and adrenaline levels, the pressor and aldosterone responsiveness to infused Ang II and the pressor response to infused noradrenaline (alone or combined with atropine) were not modified. These findings suggest that in hypertensive diabetics angiotensin converting enzyme inhibition causes a marked decrease in blood pressure. The mechanism of action is unrelated to changes in body sodium or noradrenergic-dependent pressor reactivity. In the stable phase of therapy, Ang II-dependent pathways are left unaltered when captopril is administered twice a day.

Effect of a herbal yeast food supplement and long-distance running on immunological parameters.

The effect of a food supplement on immunological parameters of 16 long-distance runners was tested in a randomized, double-blind and placebo-controlled trial. The supplement comprised plasmolysed herbal yeast, malt, honey, and orange juice. No statistically significant differences between the two groups regarding the following variables were detected at three sessions at rest and immediately after a 21 km run: total and differential white blood cell counts, numbers of B- and T-cells and T-subpopulations, concanavalin-A-induced lymphocyte proliferation, serum levels of immunoglobulins, neopterin, IL-2 receptors, beta 2-microglobulin, complement factor b, c4 and c3c, and c1-inactivator. These findings suggest that the effects of the tested food supplement on these parameters are negligible with respect to improvements in the immunological status of long-distance runners. The changes observed immediately after the run had a transient character. In both groups, however, low lymphocyte counts, IgG subclass 2 levels and c1-inactivator levels were noted at rest, which indicate that the immune status of endurance athletes may be affected by training.

Application of linked DNA markers to screening families with multiple endocrine neoplasia type 2A.

There now exists a set of tightly linked markers to the gene causing multiple endocrine neoplasia type 2A. In this report we discuss the use of these markers for early and accurate prediction of gene carrier status in three different families. Factors that influence the probability of obtaining useful information with DNA markers are available family size, in particular the number of available affected individuals, and the extent of clinical and biochemical screening in the family. At present, DNA analysis has about a 3% risk of misdiagnosis; this risk is even lower if it is used in conjunction with the pentagastrin stimulation test for C-cell hyperplasia. With the combined tests, an individual at age 20 years may be scored as carrier or not with an estimated accuracy of 99%.

Biochemical changes in the mother and the fetus during labor and its significance for the management of the second stage.

In 69 patients with uneventful pregnancies, term labor was studied prospectively with respect to length of second stage, number of bearing down efforts, maternal and fetal levels of lactate, epinephrine and norepinephrine. Maternal venous blood concentrations were measured in early labor and at the time of delivery while samples from umbilical artery and vein provided fetal blood. There was a significant rise of lactate and catecholamines in maternal blood during labor and at delivery fetal lactate concentration was lower than the maternal level while for epinephrine and norepinephrine fetal levels were higher. For all three compounds umbilical artery concentrations were higher than umbilical venous levels. While there was no correlation between the biochemical parameters in maternal blood and length of second stage maternal lactate and norepinephrine concentration at the time of delivery significantly correlated with the number of bearing down efforts. Umbilical artery lactate correlated with both, length of second stage and number of bearing down efforts.

Biotransformation of moclobemide in humans.

The structure of the urinary metabolites formed after moclobemide administration in human was elucidated, and the pattern compared with that in the plasma. The metabolic pathways of moclobemide were also compared with those of structurally related substances. After oral moclobemide administration, on average 95% of the dose was recovered in the urine within 4 days, with a mean of 92% being excreted during the first 12 h. The drug is extensively metabolized: less than 1% of the dose was excreted unchanged. A total of 19 metabolites, accounting together for about 64% of the dose, was isolated and all metabolites accounting for more than 1% of the dose were identified. Consistent with other morpholine-containing compounds, metabolic pathways of moclobemide include mainly oxidative attack on the morpholine moiety, leading to a multitude of oxidation products. Four primary metabolic reactions were identified: morpholine N-oxidation, aromatic hydroxylation, morpholine C-oxidation and deamination. The major metabolites in urine are 4 carboxylic acids (M7A and M7B, M8, M9) that account for 49% of the dose. Only 2 metabolites (M3, M10) were found to be hydroxylated on the aromatic nucleus. They were excreted completely as conjugates of glucuronic and/or sulfuric acid. Conjugation in general, however, seems to be of minor importance in the overall biotransformation of the drug. The metabolite pattern in plasma was found to be qualitatively but not quantitatively similar to that observed in urine. Almost all of the main urinary metabolites were found in plasma as well. The unchanged parent compound and 2 primary oxidation products of the morpholine ring (M1, M15), which were present in urine only in trace amounts, could easily be detected in plasma.

[Permeability pulmonary edema in pheochromocytoma]. / Permeabilitäts-Lungenödem bei Phäochromozytom.

We describe two patients with pheochromocytoma who developed pulmonary edema of rapid onset. The edema occurred spontaneously in the first case and during surgery for the tumor in the second patient. Since left ventricular function was normal in both patients and the protein content of the edema fluid was elevated in one patient, the conditions involved were permeability edemas.

Effects of the benzodiazepine receptor antagonist flumazenil in hepatic encephalopathy in humans.

If increased gamma-aminobutyric acid (GABA)-mediated neurotransmission contributes to the mediation of hepatic encephalopathy, it may be possible to induce ameliorations of the syndrome by pharmacologically antagonizing a component of the GABA/benzodiazepine receptor complex. To test this possibility we administered the benzodiazepine receptor antagonist flumazenil by intravenous injection to 14 patients with hepatic encephalopathy complicating cirrhosis. Flumazenil administration induced variable and transient, but distinct, improvements of the mental status in 71% of the patients. The degree of encephalopathy improved from stage IV to stage II in 4 patients and from stage IV to stage III in 2 patients. The mental status of all patients with less advanced encephalopathy (3 with stage III, 1 with stage II) also improved, but these responses were clinically less impressive. The arousal effect occurred within minutes after the injection and lasted for 1 to 2 h. Furthermore, it was associated with a significant increase of the mean electroencephalographic frequency from 4.2 to 5.2 cycle/s. Of the 8 patients who were ultimately discharged from the hospital, 7 had responded to flumazenil. No patient who died within 48 h of receiving flumazenil had shown any arousal effect. These findings strongly favor a prominent pathogenetic role of increased GABAergic tone in hepatic encephalopathy in humans and suggest that a positive response to flumazenil might be of prognostic value in predicting short-term survival in encephalopathic patients with liver disease.

[Drug therapy of pain]. / Medikamentöse Schmerztherapie.

Pain represents the most frequent complaint for which patients ask for medical help. Successful treatment of acute and chronic pain syndromes largely depends on the knowledge and the therapy of the underlying disease process and on the rational use of analgesics, such as the nonnarcotic analgesic-antipyretics, the anti-inflammatory agents and the opioid analgesics. In addition, so-called 'adjuvant' analgesics of different chemical structures can be used in special clinical conditions to increase the efficacy of the common analgesics. For optimal therapy, the selection and dosing of a specific agent has to be tailored to the individual needs of the patient. For this purpose it is important to follow some general principles of pain management and to consider the relevant pharmacokinetic and pharmacodynamic properties of the various analgesics. This overview summarizes the most important pharmacological properties of the widely used analgetic drugs, with special emphasis on their risk-benefit ratio in various clinical situations.

Mechanism of action of ketanserin: studies on cardiovascular reactivity in essential and diabetes-associated hypertension.

Ketanserin is a selective serotonin-S2 receptor antagonist with alpha 1-adrenoceptor inhibiting activity. The relative contribution of the latter mechanism to antihypertensive efficacy was studied in a group comprising eight normal subjects, 10 patients with essential hypertension and eight diabetics with arterial hypertension. Ketanserin treatment administered over a period of 8 weeks, decreased arterial pressure in patients with essential hypertension and, to a lesser extent, in diabetics, but not in normal subjects. In all three groups, exchangeable sodium, blood volume, the activity of the adrenergic and renin-angiotensin-aldosterone systems and the pressor responsiveness to norepinephrine (NE) or angiotensin II (Ang II) were unaltered, while the pressor reactivity to phenylephrine showed a significant decrease in normal subjects only. This suggests that the antihypertensive mechanism of ketanserin does not involve a modification of the physiological relationship between endogenous noradrenergic and pressor reactivity to NE. Moreover, ketanserin does not interfere with Ang II-dependent mechanisms.

Experimental model for the investigation of kinetic and/or dynamic interactions between drugs and ethanol in humans.

This study was performed to establish an experimental method for the investigation of interactions between ethanol and drugs under predictable and controlled conditions. The model was tested with flumazenil (Ro 15-1788), a short-acting benzodiazepine antagonist with an elimination half-life of 1 h. Six healthy volunteers (5 males, 1 female) were administered ethanol by intravenous infusion with stepwise changing rates. The infusion rates were adapted to each subject on the basis of individual disposition parameters of ethanol, which were derived from preceding short-term infusions of 120 min duration (1.0 mg/kg in males, 0.8 mg/kg in the female). This two-step procedure led to individual ethanol plasma levels between 1.47 +/- 0.04 and 1.71 +/- 0.03 g/L, which were reached after 2.5 h and thereafter maintained over another 6 h. Within the period of constant ethanol levels, single doses of flumazenil and placebo, respectively, were injected intravenously as a bolus (2 min) in a double-blind fashion according to a randomized two-way crossover design. Three subjects received a dose of 0.10 mg/kg of flumazenil, and the remaining three subjects received a dose of 0.20 mg/kg. Evaluation of the plasma concentration time curves of flumazenil did not reveal evidence of an effect of ethanol on the pharmacokinetics of this drug.

[Benzodiazepine--practice and problems of its use]. / Benzodiazepine--Praxis und Probleme ihrer Anwendung.

Benzodiazepines are the most frequently prescribed drugs in the Western world. About 3% of the adult Swiss population regularly use benzodiazepines for the treatment of anxiety states or for induction of sleep. All benzodiazepine agonists available exert qualitatively similar pharmacodynamic actions. They commonly activate central GABAergic neuroinhibition, thereby inducing anxiolysis, sedation/hypnosis, anticonvulsion and muscle relaxation. However, various derivatives differ in their physicochemical and pharmacokinetic properties such as lipophilicity, rate of gastrointestinal absorption, hepatic biotransformation and elimination half life. These differences among individual substances can be used clinically to optimize therapy for the individual patient. For example, the elimination half life greatly influences the frequency, intensity and type of adverse reactions such as hangover, rebound insomnia, development of tolerance and dependence as well as withdrawal symptoms. It is estimated that "low-dose dependency" develops in as many as 30 to 45% of chronically treated patients. Low-dose dependency is mainly characterized by the appearance of withdrawal symptoms after cessation of therapy. Since management of the withdrawal state is difficult and especially troublesome for the patient it is best to prevent the development of benzodiazepine dependence by prescribing these drugs less and restricting them to short-term use (7-14 days).