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Biomedical subjects

G Meyer

Publications and source records attributed to G Meyer.

At least 19 recordsLinked to original sources
PubMed1992

Effectiveness and safety of bolus administration of alteplase in massive pulmonary embolism.

Animal studies have demonstrated that thrombolysis with recombinant tissue-type plasminogen activator (rt-PA) is accelerated and that bleeding is reduced when rt-PA is infused over a short period. Previous clinical studies in patients with venous thromboembolism have shown that rt-PA is an effective thrombolytic agent when administered by continuous infusion over 2 to 24 hours. Clinical experience of bolus rt-PA administration in patients with massive acute pulmonary embolism (PE) is, however, limited. A prospective open study was conducted in which 54 patients with massive PE (Miller index > or = 20 of 34) received a 10-minute infusion of rt-PA at a dose of 1 mg/kg. Perfusion lung scanning was used to assess the change in pulmonary perfusion after drug administration. At 48 hours and 10 days, the mean absolute improvements in the perfusion defect were 11 and 31%, respectively. In addition, a significant clinical improvement occurred within 2 hours in 11 of the 15 shocked patients. Five patients died (9%) as a result of persistent shock (3 patients), neurologic damage (1 patient) or intracranial bleeding (1 patient). Major bleeding occurred in 8 patients (15%). Long-term follow-up information was available for 44 of the 49 discharged patients: 2 had died and 12 (27%) complained of persistent exertional dyspnea, 7 of whom had an associated heart or lung disease or chronic thromboembolism at admission. These results suggest that a bolus regimen of rt-PA could provide a convenient approach to thrombolytic therapy in patients with massive PE.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Early development of the human area postrema and subfornical organ.

The first appearance and early development of two circumventricular organs, the area postrema (AP) and the subfornical organ (SFO), were investigated in human embryos and fetuses from the 4th to the 40th gestational weeks (GW). The AP appears very early in development, during the GW 10; its high vascularization can be seen from GW14, and differentiated neurons are observed from GW 16. The SFO is characterized by a late onset of development. It can first be distinguished at GW 17, but it does not attain cytological differentiation until the last weeks of gestation. It is suggested that the AP has important functions during fetal life, which are related to normal fetal weight and growth; in contrast the SFO, which is connected with drinking behavior and salt/water balance, seems to play a less essential role in early fetal life.

Body Weight↗
PubMed1992

Laminar distribution and morphology of NADPH-diaphorase containing neurons in the superior colliculus and underlying periaqueductal gray of the rat.

We have studied the laminar distribution of reduced nicotinamide dinucleotide phosphate diaphorase (NADPH-d) activity and the morphology of positive neurons in the superior colliculus (SC) and the underlying periaqueductal gray (PAG) of the rat. The morphology of NADPH-d-positive neurons has been compared to that of Golgi-impregnated cells. The highest activity occurs in the stratum zonale and stratum griseum superficiale, contrasting with the pale neuropil in the stratum opticum, where only a few positive neurons are found. In the stratum griseum intermedium positive neurons are grouped in patches separated by narrow, NADPH-d-negative bands. In the deeper layers, the neuropil is NADPH-d-negative, and few neurons show enzymatic activity. In contrast, numerous neurons in the dorsolateral part of the PAG are intensely positive. They are continuous with the positive neurons in the stratum album profundum, with no clear border between the two centers. In both SC and PAG, only small and medium sized neurons are NADPH-d-positive. In comparison with Golgi material, all types of small neurons in the superficial layers show NADPH-d activity; NADPH-d histochemistry, however, does not visualize the characteristic dendritic appendages of these neurons. The large neurons of the SC and PAG, probably representing the long-projecting neurons of these centers, do not contain the enzyme.

Animals↗
PubMed1992

Nature of the neutral Na(+)-Cl- coupled entry at the apical membrane of rabbit gallbladder epithelium: IV. Na+/H+, Cl-/HCO3- double exchange, hydrochlorothiazide-sensitive Na(+)-Cl- symport and Na(+)-K(+)-2Cl- cotransport are all involved.

Transepithelial fluid transport was measured gravimetrically in rabbit gallbladder (and net Na+ transport was calculated from it), at 27 degrees C, in HCO(3-)-free bathing media containing 10(-4) M acetazolamide. Whereas luminal 10(-4) M bumetanide or 10(-4) M 4-acetamido-4'-iso-thiocyanostilbene-2,2'-disulfonate (SITS) did not affect fluid absorption, 25 mM SCN- abolished it; hydrochlorothiazide (HCTZ) in the luminal medium reduced fluid absorption from 28.3 +/- 1.6 (n = 21) to 8.6 +/- 1.6 microliters cm-2 hr-1 (n = 10), i.e., to about 30%. This maximum effect was already obtained at 10(-3) M concentration; the apparent IC50 was about 2 x 10(-4) M. The residual fluid absorption, again insensitive to SITS, was completely inhibited by SCN- or bumetanide. Cl- influx at the luminal border of the epithelium, measured under the same conditions and corrected for the extracellular space and paracellular influx, proved insensitive to 10(-4) M bumetanide, but was slowly inhibited by 10(-3) M HCTZ, with maximum inhibition (about 54%) reached after a 10-min treatment; it subsequently rose again, in spite of the presence of HCTZ. However, if the epithelium, treated with HCTZ, was exposed to 10(-4) M bumetanide during the measuring time (45 sec), inhibition was completed and the subsequent rise of Cl- influx eliminated. Intracellular Cl- accumulation with respect to the predicted activity value at equilibrium decreased significantly upon exposure to 10(-3) M HCTZ, reached a minimum within 15-30 min of treatment, then rose again significantly at 60 min. Simultaneous exposure to HCTZ and bumetanide decreased the accumulation to a significantly larger extent as compared to HCTZ alone, already in 15 min, and impeded the subsequent rise. Intracellular K+ activity rose significantly within 30 min treatment with HCTZ; the increase proved bumetanide dependent. The results obtained show that Na(+)-Cl- symport, previously detected under control conditions, is the HCTZ-sensitive type; its inhibition elicits bumetanide-sensitive Na(+)-K(+)-2Cl- cotransport. Thus, the three forms of neutral Na(+)-Cl(-)-coupled transport so far evidenced in epithelia, Na+/H+, Cl-/HCO3- double exchange (in the presence of exogenous bicarbonate), HCTZ-sensitive Na(+)-Cl- symport and bumetanide-sensitive Na(+)-K(+)-2Cl- cotransport, are all present in the apical membrane of rabbit gallbladder.

Animals↗
PubMed1992

Morphology of neurons in the white matter of the adult human neocortex.

Neurons in the human cerebral cortical white matter below motor, visual, auditory and prefrontal orbital areas have been studied with the Golgi method, immunohistochemistry and diaphorase histochemistry. The majority of white matter neurons are pyramidal cells displaying the typical polarized, spiny dendritic system. The morphological variety includes stellate forms as well as bipolar pyramidal cells, and the expression of a certain morphological phenotype seems to depend on the position of the neuron. Spineless nonpyramidal neurons with multipolar to bitufted dendritic fields constitute less than 10% of the neurons stained for microtubule associated protein (MAP-2). Only 3% of the MAP-2 immunoreactive neurons display nicotine adenine dinucleotide-diaphorase activity. The white matter pyramidal neurons are arranged in radial rows continuous with the columns of layer VI neurons. Neuron density is highest below layer VI, and decreases with increasing distance from the gray matter. White matter neurons are especially abundant below the primary motor cortex, and are least frequent below the visual cortex area 17. In contrast to other mammalian species, the white matter neurons in man are not only present during development, but persist throughout life.

Adult↗
PubMed1992

Effects of intravenous urokinase versus alteplase on total pulmonary resistance in acute massive pulmonary embolism: a European multicenter double-blind trial. The European Cooperative Study Group for Pulmonary Embolism.

Twelve centers participated in a double-blind study in which 63 patients with angiographically documented acute massive pulmonary embolism were randomly assigned to treatment with either urokinase (4,400 U/kg as an intravenous bolus infusion, then 4,400 U/kg per h over 12 h; n = 29) or alteplase (10 mg as an intravenous bolus infusion, then 90 mg over 2 h) followed by heparin (n = 34). The primary objective was to compare the resolution of pulmonary embolism as judged by the change in total pulmonary resistance over the initial 2 h. Further objectives were to evaluate the changes in total pulmonary resistance over the next 10 h and the degree of angiographic resolution at 12 to 18 h. At 2 h, total pulmonary resistance decreased by 18 +/- 22% in the urokinase group and by 36 +/- 17% in the alteplase group (p = 0.0009). Continuous monitoring of pulmonary artery mean pressure, cardiac index and total pulmonary resistance revealed that these variables improved faster in the alteplase group, with consistently significant intergroup differences from 30 min up to 3 to 4 h. After 12 h, the decrease in total pulmonary resistance was 53 +/- 19% in the urokinase group compared with 48 +/- 17% in the alteplase group and the reduction in the angiographic severity score was 30 +/- 25% compared with 24 +/- 18%, respectively, with no significant intergroup differences. Bleeding was equally frequent in the two treatment groups, except that more urokinase-treated patients experienced hematomas at puncture sites.

Double-Blind Method↗
PubMed1992

Effects of simulated microgravity (HDT) on blood fluidity.

Exposures to microgravity and head-down tilt (HDT) produce similar changes in body fluid. This causes an increase in hematocrit that significantly affects hemorheological values. Lack of physical stimulation under bed rest conditions and the relative immobility of the crew during spaceflight also affects the blood fluidity. A group of six healthy male subjects participated as volunteers, and blood samples were collected 10 days before, on day 2 and day 9, and 2 days after the HDT phase. Blood rheology was quantified by plasma viscometry, red cell aggregability, and red cell deformability. A reduced red cell deformability, an indication of the diminished quality of the red blood cells, was measured under HDT conditions that finally led to the so-called "space flight anemia." Enhanced red cell membrane fragility induced by diminished physical activity and an increase in hemoglobin concentration are responsible for this effect. Plasma viscosity is reduced as a result of diminished plasma proteins. However, despite the reduction in plasma proteins, including fibrinogen, alpha 2-macroglobulin, and immunoglobulin M, red cell aggregation was enhanced, principally because of the increase in hematocrit. Our results of hemorheological alterations under HDT conditions may help to elucidate the formerly documented hematologic changes during spaceflight.

Adult↗
PubMed1992

Randomized trial of subcutaneous low-molecular-weight heparin CY 216 (Fraxiparine) compared with intravenous unfractionated heparin in the curative treatment of submassive pulmonary embolism. A dose-ranging study.

BACKGROUND: We compared the efficacy and safety of different dosages of a low-molecular-weight heparin, CY 216 D (Fraxiparine), in the treatment of submassive pulmonary embolism with unfractionated heparin in a prospective, randomized, dose-finding study. METHODS AND RESULTS: The primary outcome was the evolution of pulmonary vascular obstruction. We enrolled 101 patients. Four patient groups were formed: standard heparin by continuous intravenous infusion (group 1) and Fraxiparine subcutaneously 400, 600, and 900 anti-Xa Institute Choay units/kg, respectively (groups 2, 3, and 4). Inclusions were stopped prematurely in groups 3 and 4 because of the incidence of major bleedings. At day 8, the improvement of the pulmonary vascular obstruction and the major bleedings were similar in groups 1 and 2. CONCLUSIONS: The Fraxiparine dosage of 400 anti-Xa Institute Choay units/kg is as effective and safe as unfractionated heparin in the treatment of submassive pulmonary embolism.

Analysis of Variance↗
PubMed1992

["A life threatening event" in infants. Results of polysomnography and examination of a group of 122 infants].

Survivors of an "apparent-life-threatening-event" subsequently more often die from sudden infant death syndrome than others. The aim of this study was to find out abnormal clinical symptoms and/or polysomnographic patterns in this group of patients. Between January 1989 and September 1990 122 infants (mean age 13.98 weeks) were examined after a life threatening event (mean age 9.3 weeks at the event). In total, 222 polysomnographic studies were performed. In 46 cases additional esophageal pH-metric measurements, and in 26 cases a Holter 24 hours monitoring were done. Seven infants were premature and had been ventilated, and 6 were siblings of sudden-infant-death-syndrome victims. Pulmonary problems were identified in 7 (6%), cardiac problems in 17 (14%), 18 (15%) had neurological problems, and 40 (33%) showed a gastroesophageal reflux. In 14 (11%) other diseases were found. Only 43 (35%) infants were without pathologic findings and were classified as having had an "idiopathic" event. The polysomnographic studies showed that obstructive apnea occurred significantly more often, the maximal duration of apnea was longer, and the number of sudden pO2 decreases was significantly higher than in a group of 188 normal infants. Thus, patients having had an "apparent-life-threatening-event" showed a broad spectrum of abnormal clinical symptoms and some respiration disturbances compared to a reference group of infants.

Cerebral Cortex↗
PubMed1992

[High-conductance K+ channels in guinea pig gallbladder epithelium].

Since secretion of electrolytes may be regulated by membrane potential difference, ion channels were studied using patchclamp technique. We have identified, in cell-attached configuration, inward-rectifying channels: the zero-current potential corresponded to the K+ equilibrium potential calculated from intracellular K+ activity. Using inside-out configuration and symmetric 145 mM KCl salines, i/V curve was linear, channel conductance was about 170 pS and the reversal potential 0 mV. The channels were selective for K+ over Na+, N-methylglucamine and anions and were activated by membrane depolarization.

Animals↗
PubMed1992

[Minimally invasive interventions in solitary liver cysts].

Large intrahepatic cysts need surgical intervention when becoming symptomatic. In case of non-parasitic solitary cysts different surgical treatments are available. We performed three different minimal-invasive procedures in 8 patients. Good results were obtained by laparoscopic extended deroofing of the cyst. Indications and technical performance are presented.

Adult↗
PubMed1991

Cytoplasmic phosphorylating domain of the mannitol-specific transport protein of the phosphoenolpyruvate-dependent phosphotransferase system in Escherichia coli: overexpression, purification, and functional complementation with the mannitol binding domain.

The cytoplasmic C-terminal domain, residues 348-637, and the membrane-bound N-terminal domain, residues 1-347, of EIImtl have been subcloned and expressed in Escherichia coli. The N-terminal domain, IICmtl, contains the mannitol binding site, and the C-terminal domain, IIBAmtl, contains the activity-linked phosphorylation sites, His-554 and Cys-384. Overexpression of the BA domain was achieved by a translational in-frame fusion of the gene with the cro ATG start codon, downstream of the strong PR promoter of phage lambda. The domain has been purified and characterized in in vitro complementation assays. It possessed no mannitol phosphorylation activity itself but was able to restore the phosphoenolpyruvate-dependent phosphorylation activity of two EIImtl phosphorylation site mutants, lacking His-554 or Cys-384. The complementary N-terminal domain was also expressed. Membranes possessing IICmtl were unable to phosphorylate mannitol at the expense of phosphoenolpyruvate. However, when the membranes were combined with the purified C-terminal domain, mannitol phosphorylation activity was restored. Mannitol transport and phosphorylation were also restored in vivo when the two plasmids encoding the N- and C-terminal domains were expressed in the same cell. These data demonstrate the existence of structurally and functionally distinct domains in EIImtl: a cytoplasmic domain with phosphorylating activity and a membrane-bound N-terminal domain which, in the presence of the cytoplasmic domain, is able to actively transport and phosphorylate mannitol. The ability to separate, overproduce, and purify structurally stable, enzymatically active domains opens the way for 3D structural studies as well as complete kinetic analysis of the activities of the individual domains and their interactions.

Base Sequence↗