[Surgical indications in asymptomatic internal carotid artery stenosis and in relation to heart surgery interventions]

In the last 30 years, carotid endarterectomy has been employed on a wide-spread basis with the intention of providing surgical prophylaxis of stroke. Currently, however, there is no evidence available from prospective, randomized comparative studies indicating a clear superiority of surgical treatment versus medical treatment with respect to stroke prophylaxis or improvement in survival. Based on recent publications with sufficiently large patient populations, operative mortality appears to be about 1% and the rate of perioperative stroke about 3.4%. In those with symptomatic internal carotid stenosis, without surgery there is a 5% yearly risk of cerebral infarction such that carotid endarterectomy possibly appears warranted. In contrast, in association with asymptomatic internal carotid stenosis, that is, in the absence of any symptoms indicative of cerebral hypoperfusion, based on several recent prospective studies, the yearly rate of cerebral infarction is 1 to 2% and, consequently, less than that of the prophylactic surgical intervention. Additionally, carotid endarterectomy does not render complete protection against stroke and the follow-up curves for the respective treatments do not differ meaningfully, even during longterm observation. Accordingly, for asymptomatic internal carotid stenosis, the indication for surgery has not been clearly established. Among those with asymptomatic carotid stenosis, there may be a subgroup of individuals with high-grade luminal obstruction or multiple vessel disease, who according to several studies, appear to be at a higher risk of subsequent complications even though this has not yet been confirmed by prospective, randomized studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Intercellular communication-filling in the gaps

Coordination and synchrony of a variety of cellular activities in tissues of plants and animals occur as a consequence of the transfer of low molecular weight biosynthetic and signaling molecules through specialized structures (plasmodesmata in plant cells and gap junctions in mammalian cells) that form aqueous channels between contacting cells. Investigations with rat liver demonstrated that cell-cell communication is mediated by a 32 kilodalton polypeptide that forms a hexameric pore structure in the plasma membrane. Following association with the same structure in a contiguous cell, a trans-double membrane channel is created that has been termed a gap junction. In plant tissue, long tubelike structures called plasmodesmata are suggested to serve a similar cell-cell linking function between cytoplasmic compartments. Although morphologically distinct, dynamic observations suggest similarities in transport properties between gap junctions and plasmodesmata. Recent work now provides evidence that these functional similarities may reflect a more profound identity between the paradigm animal gap junction polypeptide (32 kilodalton rat liver polypeptide) and an immunologically homologous protein localized to plant plasma membrane/cell wall fractions that may be a component of plasmodesmata.

Concentrations of flucloxacillin in heart valves and subcutaneous and muscle tissues of patients undergoing open-heart surgery

Thirty-seven patients were given a single, 2-g intravenous bolus injection of flucloxacillin prior to open-heart surgery. Within 12 h, flucloxacillin concentrations in serum and heart valves declined from 125.2 to 4.4 micrograms/ml and from 16.5 to 3.7 micrograms/g, respectively. Concentrations in subcutaneous tissue and muscle were almost identical, declining from 14.7 or 14.2 micrograms/g to undetectable levels after 8 to 10 h.

Dynamic continuity of cytoplasmic and membrane compartments between plant cells

Fluorescence photobleaching was employed to examine the intercellular movement of fluorescein and carboxyfluorescein between contiguous soybean root cells (SB-1 cell line) growing in tissue culture. Results of these experiments demonstrated movement of these fluorescent probes between cytoplasmic (symplastic) compartments. This symplastic transport was inhibited with Ca2+ in the presence of ionophore A23187, and also with the tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Both of these agents have previously been demonstrated to inhibit gap junction-mediated cell-cell communication in animal cells. In a companion experiment, a fluorescent phospholipid analogue, N-4-nitrobenzo-2-oxa-1,3-diazole phosphatidylcholine (NBD-PC), was incorporated into soybean cell membranes to examine whether dynamic membrane continuity existed between contacting cells, a transport route not existing between animal cells. Photobleaching single soybean cells growing in a filamentous strand demonstrated that phospholipid did exchange between contiguous cells.

Nuclear transport in 3T3 fibroblasts: effects of growth factors, transformation, and cell shape

Nucleocytoplasmic transport of fluorescent-labeled macromolecules was investigated in transformed and nontransformed 3T3 fibroblasts. Insulin and epidermal growth factor enhanced transport three-fold after 1-2-h incubation with nontransformed adhering fibroblasts; no enhancement of transport was observed for spherical unattached fibroblasts. The concentration of growth factor for maximal enhancement was 3-10 nM. Nuclear transport for Kirsten murine sarcoma virus-transformed BALB/c 3T3 fibroblasts, however, was maximally enhanced before addition of growth factors; addition of insulin or epidermal growth factor causes no additional transport enhancement. Transformation also minimizes cell shape effects on macromolecular nuclear transport. These results provide evidence that protein growth factors and oncogenic transformation may use a similar mechanism for activation of nuclear transport.

Endogenous lectins from cultured cells: nuclear localization of carbohydrate-binding protein 35 in proliferating 3T3 fibroblasts

Proliferating 3T3 mouse fibroblasts contain higher levels of the lectin carbohydrate-binding protein 35 (CBP35) than do quiescent cultures of the same cells. An immunofluorescence study was carried out with a rabbit antiserum directed against CBP35 to map the cellular fluorescence distribution in a large population of cells under different growth conditions. This cytometric analysis showed that the lectin is predominantly localized in the nucleus of the proliferating cells. In quiescent 3T3 cultures, the majority of the cells lost their nuclear staining and underwent a general decrease in the overall fluorescence intensity. Stimulation of serum-starved quiescent 3T3 cells by the addition of serum resulted in an increase in the level of CBP35. The percentage of cells showing distinct punctate intranuclear staining reached a maximum at about the same time as the onset of the first S-phase of the cell cycle. All of these results suggest that CBP35 may be a protein whose presence in the nucleus, in discrete punctate distribution, is coordinated with the proliferation state of the cell.

Endogenous lectin from cultured soybean cells. Chemical characterization of the lectin of SB-1 cells

A lectin has been identified in the cell line, SB-1, originally derived from the roots of Glycine max. This lectin, which we shall refer to as SB-1 lectin, was isolated on the basis of its carbohydrate-binding activity (affinity chromatography on Sepharose column derivatized with N-caproyl-galactosamine) and its immunological cross-reactivity (immunoblotting with rabbit antibodies directed against seed soybean agglutinin (SBA]. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting analysis of SB-1 lectin revealed a major polypeptide (Mr approximately equal to 30,000) which co-migrated with seed SBA. This form of the lectin was observed in fractions purified from culture medium of SB-1 cells or supernatant fraction of SB-1 cell suspension after enzymatic removal of cell wall. Extracts of SB-1 cells under some other conditions yielded a major band (Mr approximately equal to 60,000) as revealed by SDS-PAGE and immunoblotting with rabbit anti-seed SBA; prolonged incubation of these samples in the presence of SDS resulted in the appearance of the 30-kDa polypeptide. It appears that the 60-kDa band represented a highly stable, even under SDS-PAGE conditions, dimeric form of the 30-kDa subunit. The SB-1 lectin derived from the culture medium was compared with seed SBA by gel filtration and by peptide mapping after limited proteolysis; no difference between the lectins from the two sources was found. Extracts of soybean roots fractionated on N-caproyl-galactosamine-Sepharose affinity columns yielded, upon elution with galactose, polypeptides of Mr 30,000 and 60,000. These results suggest that soybean roots contain a lectin whose polypeptide composition corresponds to that of seed SBA and SB-1 lectin.

Penetration of ceftazidime into heart valves and subcutaneous and muscle tissue of patients undergoing open-heart surgery

Patients undergoing open-heart surgery were given an intravenous bolus injection of 2 g of ceftazidime as a single dose over a period of 5 min. Within 12 h, ceftazidime concentrations in serum declined from 55.8 to 3.9 mg/liter. Subcutaneous tissue concentrations of the drug decreased from 21.0 to 2.7 micrograms/g, and muscle concentrations decreased from 34.5 to 2.5 micrograms/g. Ceftazidime concentrations in cardiac valvular tissue were even higher than those in muscle or fat, declining from 37.4 to 6.3 micrograms/g within 10 h.

Epidermal growth factor and insulin stimulate nuclear pore-mediated macromolecular transport in isolated rat liver nuclei

Fluorescence photobleaching was used to measure the effect of epidermal growth factor (EGF), insulin, and glucagon on the nuclear transport of fluorescent-labeled dextrans across the nuclear pore complex. EGF and insulin were found to stimulate transport approximately 200%, while boiling these polypeptide growth factors greatly diminished this enhancement activity. Glucagon demonstrated no enhancement effect. The nuclear transport enhancement effects were observed at EGF and insulin concentrations that elicit the various physiological responses, e.g., nanomolar range.

Fluorescence photobleaching analysis of nuclear transport: dynamic evidence for auxiliary channels in detergent-treated nuclei

Nuclear transport experiments were performed on isolated rat liver nuclei to examine the permeability of membrane and detergent-free peripheral nuclear lamina. The transport of 64K molecular weight fluorescent-derivatized dextrans was measured by using the technique of fluorescence redistribution after photobleaching. Results of these experiments provide evidence for transport pathways that appear to be functionally distinct from nuclear pore complex channels. The suggestion is made that these supplemental pathways are embedded in the peripheral nuclear lamina and are normally masked by the inner nuclear membrane.

Pharmacokinetics of vancomycin in serum and tissue of patients undergoing open-heart surgery

Penetration of vancomycin into serum, heart valves, subcutaneous tissue and muscle was determined in 33 adult patients undergoing open-heart surgery. Each patient received 15 mg/kg vancomycin as a 30-min intravenous infusion preoperatively. Within 6 h vancomycin plasma concentrations declined from 28.9 to 4.2 mg/l. Vancomycin concentrations decreased in subcutaneous tissue slowly and varied in muscle between 1.2 and 3.2 mg/kg, in subcutaneous tissue between 1.3 and 4.4 mg/kg and in heart valves between 2.3 and 4.2 mg/kg. Vancomycin concentrations in heart valves are high enough to inhibit most oxacillin-resistant Staphylococcus aureus, and coagulase-negative staphylococci causing postoperative wound infections and endocarditis.

Enucleation of normal and transformed cells

A quantitative analysis based on centrifugal force requirements for enucleation was developed to examine the response of a number of untransformed and transformed cell lines to cytochalasin mediated enucleation. Examination of the extent of cell enucleation as a function of centrifugal force resulted in a series of response curves demonstrating that enucleation g force requirements varied between Balb/c 3T3, Swiss 3T3, and Kirsten sarcoma virus transformed Balb/c 3T3 (3T3-K). A four times greater centrifugal force was required to reach 50% enucleation for transformed Balb/c 3T3-K when compared to Swiss 3T3. A qualitative correlation could be observed between ease of enucleation and the existence of a well-formed stress fiber network. A comparison of cytochalasin B and D suggested that cytochalasin D was far more effective in the enucleation of transformed cells. Experiments with 2-deoxyglucose and monensin provided evidence that decreasing cellular ATP levels, either directly or potentially by uncoupling ion transport from ATP generation, can decrease the efficiency of enucleation. It is suggested that the organization of the cytoskeleton is affected by the altered cellular ATP levels which can affect the centrifugal requirements of enucleation.

A nuclear specific glycoprotein representative of a unique pattern of glycosylation

Whole rat liver nuclei were reacted with UDP-[14C]galactose in the presence of bovine beta(1----4) galactosyltransferase. The reaction mixture was electrophoresed on a reducing sodium dodecyl sulfate-polyacrylamide gel. Autoradiograms of the gel demonstrated a major labeled broad band migrating with an apparent molecular weight of 65,000-66,000. A number of other less prominently labeled bands were also present. The labeled 65,000-66,000 band when cut from the gel and subjected to alkaline reduction while in the gel matrix exclusively yielded a 14C-labeled disaccharide that co-migrated with a [14C]Gal-GlcNAcol standard in descending paper chromatography. Treatment of this disaccharide with beta-galactosidase (beta-D-galactoside galactohydrolase; EC 3.2.1.23) from Aspergillus niger removed all the [14C]galactose label. Treatment of the labeled 65,000-66,000 polypeptide with Endoglycosidase F, however, did not remove the [14C]galactose label. Western transfer blots of sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels performed with horseradish peroxidase-labeled succinyl wheat germ agglutinin, a lectin specific for GlcNAc, on unlabeled nuclei revealed a dominant band at 63,000-64,000. Subjecting 14C-labeled nuclei to this procedure resulted in a shift of the major horseradish peroxidase-labeled succinyl wheat germ agglutinin band to 65,000-66,000. The shifted band was coincident with the [14C]galactose band as visualized on an autoradiogram. A survey of other rat tissue nuclei revealed the same spectrum of [14C]galactose acceptor proteins with a dominant 65,000-66,000 galactose-labeled band.

Immunological evidence for gap junction polypeptide in plant cells

A whole cell homogenate prepared from soybean (Glycine max (L.) Merr. cv. Mandarin) root cells (SB-1 cell line) was electrophoresed on a sodium dodecyl sulfate-polyacrylamide gel and transferred to nitrocellulose paper. The nitrocellulose was probed with a monospecific antibody capable of recognizing the Mr 27,000 polypeptide of rat liver gap junctions; this antibody was prepared from immune serum raised against gap junctions purified from V79 cells (Chinese lung fibroblasts). The immunoblots afforded two polypeptides migrating at Mr 29,000 and 48,000. This pattern of blotting was also observed when homogenates of soybean or poinsettia leaves excised from whole plants were probed with anti-V79 gap junction antiserum. Gap junction purification schemes, developed for rat liver (Hertzberg, E. L. (1984) J. Biol. Chem. 259, 9936-9943), were employed on soybean protoplast homogenates yielding a significant enrichment for the Mr 29,000 and 48,000 polypeptides as judged by Coomassie Blue staining and immunoblotting with anti-V79 gap junction antiserum. These immunological results provide the first reported evidence for a homologous gap junction polypeptide in plant cells.

Endogenous lectins from cultured soybean cells: isolation of a protein immunologically cross-reactive with seed soybean agglutinin and analysis of its role in binding of Rhizobium japonicum

Incubation of Rhizobium japonicum with the cultured soybean cell line SB-1, originally derived from the roots of Glycine max, resulted in specific adhesion of the bacteria to the plant cells. This binding interaction appears to be mediated via carbohydrate recognition, since galactose can inhibit the heterotypic adhesion but glucose cannot. Affinity chromatography, on a Sepharose column derivatized with N-caproyl-galactosamine, of the supernatant fraction of a SB-1 cell suspension after enzymatic removal of cell wall yielded a single polypeptide (Mr approximately 30,000) on immunoblotting analysis with rabbit antibodies directed against seed soybean agglutinin. Fluorescently labeled rabbit anti-seed soybean agglutinin also yielded specific immunofluorescent staining on the cell wall and plasma membrane of the SB-1 cells. These results suggest that one likely candidate that may mediate the recognition between the Rhizobium and the soybean cells is the endogenously produced SB-1 lectin. This notion is supported by the observation that rabbit anti-seed soybean agglutinin blocked the Rhizobium-soybean cell adhesion, whereas control antibodies did not.

A fluorescence photobleaching assay of gap junction-mediated communication between human cells

Gap junction-mediated communication between contiguous cells has been implicated in the regulation of cell proliferation and differentiation. This report describes a new technique to measure cell-cell communication, gap fluorescence redistribution after photobleaching, which is based on the diffusion-dependent return of 6-carboxyfluorescein-mediated fluorescence in a photobleached cell that is in contact with other fluorescently labeled cells. Fluorescence recovery rates are interpreted as dye transport across gap junctions. Results of experiments on normal human fibroblasts and human teratocarcinoma cells show that this technique can measure rapid dye transfer and detect inhibition of communication (between teratocarcinoma cells) by the tumor promoters 12-O-tetradecanoyl-phorbol-13-acetate and the pesticide dieldrin.