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Biomedical subjects

G Meyer

Publications and source records attributed to G Meyer.

At least 253 records · Page 14Linked to original sources
PubMed1993

Electrosyntheses of disaccharides from phenyl or ethyl 1-thioglycosides.

Constant current electrolyses of the glycosyl donors phenyl and ethyl 2,3,4,6-tetra-O-benzyl-1-thio-beta-D-glucopyranoside in dry acetonitrile in the presence of various primary and secondary sugar alcohols, performed in an undivided cell, gave beta-linked disaccharide derivatives selectively in good yields. Phenyl 2,3,4,6-tetra-O-benzoyl-1-thio-beta-D-glucopyranoside gave the beta-glucosides exclusively in good to moderate yields.

Carbohydrate Sequence↗
PubMed1993

The effects of chronic administration of captopril on the mouse subfornical organ and area postrema.

We have studied by morphometric procedures the chronic effect of captopril on the subfornical organ (SFO) and area postrema (AP) of the adult mouse. Oral administration of captopril does not produce any change in the size of individual nuclei of the ependymocytes and neurons in both centers. However, there are other quantitative effects of captopril on the global volume of the SFO and on the neuropil and vascular elements of both the SFO and AP which present a significant increase. It is suggested that this increase is due to metabolic processes at the level of both circumventricular organs.

Administration, Oral↗
PubMed1993

[Treatment of venous thromboembolic disease in patients with cancer].

Results of classical anticoagulant therapy in cancer patients with venous thromboembolism (VT) are highly discussed. We retrospectively analysed the outcome of 43 patients with VT and cancer: 32% developed specific complications during either i.v. heparin therapy (10 +/- 0.9 days) or treatment by antivitamin K (106 +/- 14.9 days). Recurrence of thromboembolism (16%) and/or hemorrhages (16%) were much more frequent than in patients without cancer, underlying need for alternative therapy in cancer patients with VT.

Female↗
PubMed1993

Regulation of in vitro capillary tube formation by anti-integrin antibodies.

Human endothelial cells are induced to form an anastomosing network of capillary tubes on a gel of collagen I in the presence of PMA. We show here that the addition of mAbs, AK7, or RMAC11 directed to the alpha chain of the major collagen receptor on endothelial cells, the integrin alpha 2 beta 1, enhance the number, length, and width of capillary tubes formed by endothelial cells derived from umbilical vein or neonatal foreskins. The anti-alpha 2 beta 1 antibodies maintained the endothelial cells in a rounded morphology and inhibited both their attachment to and proliferation on collagen but not on fibronectin, laminin, or gelatin matrices. Furthermore, RMAC11 promoted tube formation in collagen gels of increased density which in the absence of RMAC11 did not allow tube formation. Neither RMAC11 or AK7 enhanced capillary formation in the absence of PMA. Lumen structure and size were also altered by antibody RMAC11. In the absence of antibody the majority of lumina were formed intracellularly from single cells, but in the presence of RMAC11, multiple cells were involved and the lumen size was correspondingly increased. Endothelial cells were also induced to undergo capillary formation in fibrin gels after PMA stimulation. The addition of anti-alpha v beta 3 antibodies promoted tube formation in fibrin gels and inhibited EC adhesion to and proliferation on a fibrinogen matrix. The enhancement of capillary formation by the anti-integrin antibodies was matrix specific; that is, anti-alpha v beta 3 antibodies only enhanced tube formation on fibrin gels and not on collagen gels while anti-alpha v beta 1 antibodies only enhanced tubes on collagen and not on fibrin gels. Thus we postulate that changes in the adhesive nature of endothelial cells for their extracellular matrix can profoundly effect their function. Anti-integrin antibodies which inhibit cell-matrix interactions convert endothelial cells from a proliferative phenotype towards differentiation which results in enhanced capillary tube formation.

Animals↗
PubMed1993

[Laparoscopic cholecystectomy of large gallbladder calculi].

Laparoscopic cholecystectomy is more laborious in patients with large gallbladder stones in that they can only be removed safely after an enlargement of one incision or intraoperative lithotripsy. Preoperative extracorporeal shock-wave lithotripsy (ESWL) might theoretically solve this problem and facilitate the extraction of the gallbladder. Ten patients with minimum one stone > 20 mm of diameter received ESWL treatment within 24 h before operation. Complete pulverization of stones was achieved in only one patient. Additional mechanical fragmentation by forceps was necessary in 7 and an enlargement of the incision in 5 of 10 patients. Compared to 10 patients with corresponding stones and mechanical lithotripsy ESWL showed no advantage and cannot be recommended because of increase of costs.

Adult↗
PubMed1993

[Video-thoracoscopic atypical lung resection].

A new era in thoracoscopy within the framework of minimal invasive thoracic surgery was introduced due to the possibilities of video-endoscopy, the development of an accordingly advanced and suitable instrumentarium as well as the production of an endoscopically applicable linear stapler. The introduction of the endo-staplers has made the thoracoscopic resection even of larger parts of lung parenchyme possible. Just as in laparoscopy a clear reduction of post-operative pain, a reduced impairment of post-operative pulmonary function, a shorter in hospital stay and an earlier return to normal activities are advantages of thoracoscopy when compared to the severely more traumatising thoracotomy. Good indications for this procedure are the spontaneous pneumothorax and the resection biopsy in the quest of finding the diagnosis of unclear pulmonary disease. For the diagnostic and should the situation arise therapeutic resection of solitary pulmonary nodules in contrast a stricter selection and handling of indications is imperative. The method however proved worthwhile under such conditions. The technique and results are reported of video thoracoscopies in 73 patients as well as 51 atypical lung resections carried out thoracoscopically with the Endo-GIA 30. A switch to open thoracotomy became necessary in 16.4%. Indications were pneumothorax (35.6%), hemothorax (1.3%), diagnostic resection of solitary nodule (42.5%), pneumopathy (11.0%), and extrapulmonary tumor (9.6%). Atypical resections were carried out only in the case of solitary nodule (51.7%), pneumothorax (39.7%), and pneumopathy (8.6%). A histological diagnosis was obtained in all cases. The average operating time for solitary nodule and pneumothorax was 1 hour, for pneumopathy 1/2 hour. Chest drains could be removed after 1.6-2.6 days. The postoperative complication rate amounted to 3.9%. There was no mortality. The introduced procedure represents a new and promising alternative in thoracic surgery.

Adult↗
PubMed1993

Laparoscopic stenting for protection of common bile duct sutures.

Laparoscopic common bile duct exploration is comparable with the open operation and it is usually finished with the insertion of external bile drainage such as a T-tube. We performed an antegrade placement of a biliary stent with primary suture of the common bile duct following common bile duct exploration. We thereby avoided the acquisition of the additional expensive equipment required for the transcystic approach and the placement of a T-tube, which in our eyes contradicts the idea of minimized discomfort in minimally invasive surgery.

Adult↗
PubMed1993

Surgical management of CSF otorhinorrhea following retrosigmoid removal of cerebellopontine angle tumors.

Cerebrospinal fluid (CSF) otorhinorrhea continues to be one of the most common complications following surgery for cerebellopontine angle (CPA) tumors. For retrosigmoid approaches, this complication has been reported to occur in 12-19 percent of patients. Nearly all prior surgical attempts at control have included middle ear and eustachian tube obliteration along with packing of the mastoid. This article reviews 165 retrosigmoid procedures (January 1982-December 1990) for removal of CPA tumors, with a leak rate of 9.8 percent (16 cases), 7.2 percent (12 cases) requiring surgical control. An operative technique involving only mastoid obliteration is presented. This approach is less invasive as it limits the scope of the surgical field and also maintains the integrity of the middle ear for potential preservation of hearing. This approach has resulted in control in 100 percent of the patients, without reoperation. The routes of the CSF leak, the technique, and the rationale for its use are presented.

Cerebellar Neoplasms↗
PubMed1993

[Various techniques for laparoscopic small intestinal anastomosis. A preliminary report].

Three groups with n = 6 pigs were subjected to different techniques of endoscopic small bowel anastomosis. In Group I connection of the gut endings was done, using an all layer stapler-device, otherwise employed as hernia-stapler. Two thirds of the circumference became inverted, one third was everted. Anastomosis of Group II was done with the same stapler device, but all clips were set to evert the wound-endings. Group III consisted of triangularly shaped anastomosis, for which a linear stapler device was being used. All animals survived the investigation period (14 days) and were postmortally examined. Technical aspects and clinical results are being discussed.

Anastomosis, Surgical↗
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↗