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PubMed2001

Trueness-to-type and agronomic characteristics of Coffea arabica trees micropropagated by the embryogenic cell suspension technique.

Trueness-to-type and agronomic characteristics of trees of four coffee (Coffea arabica L.) F(1) hybrid clones derived from embryogenic cell suspensions were compared with those of trees produced from in vitro microcuttings. Three types of variants were observed among the 644 trees derived from embryogenic suspensions. Total frequency of the variants was 2.1% for trees originating from embryogenic cell suspensions, whereas no variant was found among the trees produced from microcuttings. The variant known as "thick leaf" had thick leaves, many abnormally starry flowers and low yields of large fruit. The "dwarf" variant was characterized by slow growth and small fruit. The "dwarf peaberry" variant had abnormal seeds in a single cavity, in addition to the "thick leaf" and "dwarf" characteristics. Compared with normal trees, the variants differed in leaf density and number of chloroplasts per guard cell. The variants aside, there were no differences in the main agronomic characteristics between trees produced from embryogenic suspensions and those produced from microcuttings. For all four clones, the trees had vegetative characteristics, productivity, fertility, and bean biochemical, mineral and organoleptic characteristics that were identical to those of the controls. We conclude that it is possible to generate coffee trees commercially with normal agronomic performance from embryogenic suspensions, because the frequency with which somaclonal variants occur is limited.

Agriculture↗
PubMed1999

The long-term effect of epidural administration of butamben suspension on nerve injury-induced allodynia in rats.

UNLABELLED: Although local anesthetics can, in some situations, alleviate neuropathic pain, currently available preparations are short-acting and nonselective, producing, for example, motor dysfunction. Clinical studies report that a novel suspension preparation of butamben has the advantage of a prolonged duration of action, and it can be used epidurally, without impairment of motor function. In this behavioral study, we investigated the effect of the epidural administration of a 5% butamben suspension on nerve injury-induced allodynia. Behavioral studies were performed using an established animal model of neuropathic pain, which involves a partial ligation of the sciatic nerve. Nociceptive thresholds to mechanical stimulation were determined by the paw withdrawal method. The allodynia to mechanical stimulation induced by partial nerve ligation was significantly attenuated by daily injections, for 5 days, of 10 microL of butamben suspension. The analgesia lasted at least 7 days after the final injection. Daily injections of 10 microL of vehicle, for 5 days, had no significant effect on allodynia. During the period of daily injections, both the butamben and vehicle treated rats had temporary impairment of motor coordination compared with untreated controls. Motor function recovered after the final injection. Neither daily injections of butamben for 2 or 3 days, nor smaller volumes for 5 days (2.5-5 microL), had a long-lasting effect. We conclude that repeated epidural administration of butamben suspension for several days provides long-lasting analgesia in rats with nerve injury-induced allodynia to mechanical stimulation. IMPLICATIONS: In this animal behavioral study, using rats with nerve injury-induced pain, we examined the possible long-term analgesic effects of epidural administration of a suspension of the local anesthetic, butamben. We found that multiple doses for several days were required to provide a prolonged analgesia.

Analgesia, Epidural↗
PubMed2001

Atovaquone suspension for treatment of Pneumocystis carinii pneumonia in HIV-infected patients.

OBJECTIVE: To describe clinical experience with atovaquone suspension for the treatment of Pneumocystis carinii pneumonia (PCP) in HIV-infected patients. DESIGN: A retrospective chart review. METHODS: The medical records of 54 HIV-infected patients with PCP treated with atovaquone were examined. The outcomes of 34 patients treated with atovaquone suspension (750 mg twice a day) were compared with those of 20 patients treated with atovaquone tablets (750 mg three times a day). RESULTS: The proportion of patients successfully treated was similar with the suspension (74%) and tablet (70%) formulations of atovaquone. The proportion of patients with an inadequate response to therapy was lower for patients treated with atovaquone suspension (15%) than tablets (30%). Both formulations were well tolerated. CONCLUSION: Atovaquone suspension is effective and well tolerated for the treatment of PCP.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Sprayed keratinocyte suspensions accelerate epidermal coverage in a porcine microwound model.

Keratinocyte suspensions can potentially treat a variety of epidermal defects, but the mechanism of action has not been fully determined. We developed a porcine model to study the effect of sprayed cell suspensions delivered on small wounds within a meshed autograft. Paired full-thickness surgically excised wounds were covered with a fully expanded 3:1 meshed split-thickness autograft. A keratinocyte cell suspension was sprayed onto half of the wounds at a seeding density of 2.8 x 10(3) cells/cm2; the remaining wounds were sprayed with cell culture medium alone. Histologic analysis at days 5 and 8 showed an increase in average epidermal thickness, confluence, keratin cysts, and blood vessels in the keratinocyte cell suspension group compared with the cell culture medium control group. Wounds sprayed with the cell suspension showed faster and better quality of epithelialization than wounds sprayed with cell culture medium alone.

Animals↗
PubMed1998

Single pericytes and pericytes in suspension are stimulated in a similar way by low-density lipoprotein.

BACKGROUND: Pericytes are regarded as the microvascular counterpart of smooth muscle cells and implicated in the regulation of blood pressure at the microvascular level. Ca2+ plays an important role in biochemical processes involved in blood pressure regulation and can be activated by low-density lipoprotein (LDL) cholesterol. OBJECTIVE: To determine whether stimulation either of single cells or of cells in suspension by LDL would produce any difference in the increase in cytosolic free calcium levels ([Ca2+]i). DESIGN AND METHODS: Single pericytes were loaded with 2 micromol/l of the Ca2+-sensitive dye Indo-1/AM. The Indo-1 fluorescence was recorded at 405 nm (Ca2+-bound) and 485 nm (Ca2+-free) after stimulation with LDL. Pericytes in suspension were loaded with 2 micromol/l of the Ca2+-sensitive dye FURA-2/AM. The FURA-2 fluorescence kinetics were recorded at 340-380 nm. Ratios of fluorescence at the two wavelengths were transformed to [Ca2+]i. RESULTS: Basal [Ca2+] levels appeared to be higher in single cells (148+/-13 nmol/l, n = 20) than they were in cells in suspension (128+/-8 nmol/l, n = 25; P= 0.0078). After stimulation with LDL the increase in [Ca2+]i in both systems was about 220% above baseline. A clear dose dependency was seen for both systems. CONCLUSIONS: Single pericytes and pericytes in suspension increase their [Ca2+]i after stimulation with LDL dose-dependently. Even though single-cell measurements revealed some technical limitations, their responses were comparable to those obtained in a cell suspension. In analogy to aortic smooth muscle cells, our results indicate that LDL might also play a blood-pressure-regulatory role in the microvasculature.

Animals↗
PubMed2003

Granular dynamics of density profiles in a suspension interface.

The temporal evolution of the density profiles at the interface of a Rayleigh-Taylor instability in a sedimenting suspension is experimentally investigated. It is found that the sand-glycerin density gradients within the interface change with time, and that the evolution of the gradients differs significantly, depending on the location: The density profiles become steeper in the regions where the suspension flows downwards, whereas the profiles become flatter in the regions where the fluid flows upwards. This observation shows that there is a motion of the sand grains relative to the carrier fluid and hence reveals the prevailing granular dynamics in the suspension interface. It shows a behavior of the suspension which is different from the behavior of a homogeneous Newtonian one-component fluid whose density profiles do not change in time. Another interesting result is that the slopes of the profiles differ already at the very beginning (t=0) of the evolution of the instability, indicating that the suspension might have self-structured prior to instability onset.

Journal Article↗
PubMed2005

Brownian dynamics simulation of orientational behavior, flow-induced structure, and rheological properties of a suspension of oblate spheroid particles under simple shear.

Brownian dynamics (BD) simulations were carried out for suspensions of oblate spheroid particles interacting via the Gay-Berne (GB) potential. The oblate spheroid particles were applied as a model of disc-like particles and the system of suspension of the particles was considered. Numerically analyzed were both the change in phase with the number density of the particles at equilibrium state and the behavior of the particles in simple shear flows. The system changed from isotropic phase to nematic one with increasing the particle concentration. In the simulation of shear flows, the shear was imposed upon the systems in nematic phase at equilibrium. The systems exhibited various motions of the director depending on the shear rate, e.g. the continuous rotation of director at low shear rates, the wagging at moderate shear rates, and the flow aligning at high shear rates. Temporal change in inner structure of suspensions was also analyzed and collapse of initial particle configurations due to shear was found. Moreover, rheological properties of the suspension were investigated. The numerical simulation predicted the shear-thinning in viscosity, negative first normal stress difference, and positive second normal stress difference, and these results qualitatively agreed with the predictions using a constitutive equation for discotic nematics. The present study proved that the BD simulation using spheroid particles interacting via the GB potential is an effective approach for investigating the flow behavior and flow-induced structure of suspensions of disklike particles at a particulate level.

Journal Article↗
PubMed2002

Hydrodynamic fluctuations and instabilities in ordered suspensions of self-propelled particles.

We construct the hydrodynamic equations for suspensions of self-propelled particles (SPPs) with spontaneous orientational order, and make a number of striking, testable predictions: (i) Nematic SPP suspensions are always absolutely unstable at long wavelengths. (ii) SPP suspensions support novel propagating modes at long wavelengths, coupling orientation, flow, and concentration. (iii) In a wave number regime accessible only in low Reynolds number systems such as bacteria, polar-ordered suspensions are invariably convectively unstable. (iv) The variance in the number N of particles, divided by the mean , diverges as (2/3 ) in polar-ordered SPP suspensions.

Animals↗
PubMed2004

High-frequency transformation of undeveloped plastids in tobacco suspension cells.

Although leaf chloroplast transformation technology was developed more than a decade ago, no reports exist of stable transformation of undeveloped plastids or other specialized plastid types, such as proplastids, etioplasts, or amyloplasts. In this work we report development of a dark-grown tobacco suspension cell model system to investigate the transformation potential of undeveloped plastids. Electron microscope analysis confirmed that the suspension cells carry plastids that are significantly smaller (approximately 50-fold less in volume) and have a very different subcellular localization and developmental state than leaf cell chloroplasts. Using antibiotic selection in the light, we demonstrated that both plastid and nuclear transformation of these cell suspensions is efficient and reproducible, with plastid transformation frequency at least equal to that of leaf chloroplast transformation. Homoplasmic plastid transformants are readily obtained in cell colonies, or in regenerated plants, providing a more consistent and versatile model than the leaf transformation system. Because of the uniformity of the cell suspension model, we could further show that growth rate, selection scheme, particle size, and DNA amount influence the frequency of transformation. Our results indicate that the rate-limiting steps for nuclear and plastid transformation are different, and each must be optimized separately. The suspension cell system will be useful as a model for understanding transformation in those plant species that utilize dark-grown embryogenic cultures and for characterizing the steps that lead to homoplasmic plastid transformation.

Cell Nucleus↗
PubMed1996

Growth Inhibition in Suspension-Cultured Rice Cells under Phosphate Deprivation Is Mediated through Putrescine Accumulation.

The effects of phosphate deprivation on the growth and polyamine levels of suspension-cultured rice (Oryza sativa) cells were investigated. When rice suspension cells were deprived of phosphate, cell growth was markedly inhibited. Phosphate deprivation resulted in a higher putrescine level and lower spermidine and spermine levels in rice suspension cells. The growth of rice cells cultured in the absence of phosphate did not recover as a result of spermidine and spermine addition. D-Arginine and [alpha]-methylornithine, inhibitors of putrescine biosynthesis, caused a reduced level of putrescine in rice suspension cells cultured under phosphate deprivation. The growth of rice cells cultured in the absence of phosphate was completely recovered after the addition of D-arginine but not [alpha]-methylornithine. Our results indicate that putrescine accumulation is a factor causing growth inhibition of suspension-cultured rice cells under phosphate deprivation.

Journal Article↗
PubMed1987

Kinetics of l-Valine Uptake in Suspension-Cultured Cells and Protoplast-Derived Cells of Tobacco: Comparison of Wild-Type and the Val-2 Mutant.

A kinetic analysis was made of l-valine uptake in protoplast-derived cells (mesophyll protoplasts cultured for 6 days) and in suspension-cultured cells of tobacco (Nicotiana tabacum L., cv Xanthi). Cells from wild-type and Val(r)-2 mutant plants were compared. A low-K(m) component was found in protoplast-derived cells (K(m) = 45 +/- 5 micromolar) as well as in suspension-cultured cells (K(m) = 84 +/- 21 micromolar). In the mutant cells the V(max) of this component was 12- to 14-fold less than in wild-type cells. A second component (K(m) = 2.4 +/- 0.7 millimolar) was found in suspension-cultured cells but not in protoplast-derived cells; its V(max) was the same in wild-type and mutant cells. A third component was apparently unsaturable (linear component). It was present in protoplast-derived cells but not in suspension-cultured cells, and had the same magnitude in wild-type and mutant cells. The results are discussed with reference to the uptake of l-valine in leaf tissue, in which the three kinetic components have been found simultaneously. The reduced V(max) of the low-K(m) component in the Val(r)-2 mutant, and the differential expression of the other two components in suspension-cultured cells and protoplast-derived cells indicate that the kinetically distinguishable components represent physically distinct transport systems.

Journal Article↗
PubMed1994

High-pressure freezing of cell suspensions in cellulose capillary tubes.

A procedure for efficient cryoimmobilization of large volumes of cell suspensions or micro-organisms by high-pressure freezing is described. This procedure uses transparent, porous cellulose capillary tubes with an inner diameter of 200 microns, into which the suspensions are drawn by capillary action. The tubes are processed by high-pressure freezing and freeze-substitution as if they were tissue samples. Centrifugation of suspensions at low temperatures is no longer necessary and cryopreparation is greatly facilitated. A very high yield of adequately frozen specimens is obtained due to the constant, defined sample geometry. This approach can also be used to process suspensions by conventional chemical fixation, eliminating the need to embed pellets in low-melting-point agarose, for example, prior to chemical fixation. The preparation procedure is demonstrated with suspensions of nematodes, paramecia and bacteria.

Animals↗
PubMed1997

Optimal seat suspension design based on minimum "simulated subjective response".

This work addresses a method for improving vertical whole body vibration isolation through optimal seat suspension design. The primary thrusts of this investigation are: (1) the development of a simple model that captures the essential dynamics of a seated human exposed to vertical vibration, (2) the selection and evaluation of several standards for assessing human sensitivity to vertical vibration, and (3) the determination of the seat suspension parameters that minimize these standards to yield optimal vibration isolation. Results show that the optimal seat and cushion damping coefficients depend very much on the selection of the vibration sensitivity standard and on the lower bound of the stiffnesses used in the constrained optimization procedure. In all cases, however, the optimal seat damping obtained here is significantly larger (by than a factor of 10) than that obtained using existing seat suspension design methods or from previous optimal suspension studies. This research also indicates that the existing means of assessing vibration in suspension design (ISO 7096) requires modification.

Automobile Driving↗
PubMed2000

Attenuation and dispersion of sound in dilute suspensions of spherical particles

This paper considers sound propagation in dilute suspensions of constant-mass particles that can translate and pulsate under the effects of a small amplitude sound wave. A new theory for sound attenuation and dispersion is developed on the basis of the changes of the suspension's compressibility produced by the relative motions between host fluid and particles. The approach, used earlier to treat propagation in rigid-particle suspensions, decouples the propagation problem from the more difficult problem of obtaining accurate descriptions for the fluid-particle interactions. In this work the role of the pulsational motion is included in the theoretical framework. The resulting theory is thus applicable to aerosols, bubbly liquids, emulsions, and hydrosols composed of elastic particles, and includes, as a special limit, rigid-particle suspensions. The results are expressed in terms of three complex quantities that describe, respectively, the particles' translational velocity, temperature, and pressure, relative to their counterparts in the fluid. Theoretical results for these quantities, applicable in wide frequency ranges, are available from previous studies [Temkin and Leung, J. Sound Vib. 49, 75-92 (1976), Temkin, J. Fluid. Mech. 380, 1-38 (1999)]. Together with the compressibility theory presented here, they provide a more general description of propagation in dilute suspensions than presently available. In the case of aerosols and hydrosols, the theory produces known results for the attenuation and the sound speed. For bubbly liquids and emulsions the new results presented here differ from those available in the literature. The differences are traced to the neglect in the existing theories of the acoustic pressure disturbance produced by the pulsations of the particles.

Journal Article↗
PubMed1967

Production of rubella hemagglutinating antigen in suspension cultures.

Rubella virus specific hemagglutinating antigen was prepared in the fluid phase of suspension cultures. Systems employing baby hamster kidney culture adapted inocula, nonadapted inocula, and cells derived from long-term infected suspension cultures were evaluated. Optimal specific hemagglutinating titers were obtained when kaolin-treated fetal bovine serum was used in the media and when the incoulum had previously been adapted in a suspension culture system. When cultures derived from long-term infected suspension systems were studied, the number of daily harvests in which acceptable titers were present was prolonged. However, titers were generally higher in suspension systems employing cells which had recently been infected.

Animals↗
PubMed1991

Suitability of infection of cells in suspension for detection of herpes simplex virus.

Detection of herpes simplex virus in clinical specimens by the suspension-infection technique was compared with detection by conventional cell culture. The sensitivity and specificity of the suspension-infection technique compared with those of conventional culture were 95.9 to 98.2% and 97.5 to 100%, respectively, depending on the cell line used in the tests. The mean time to diagnosis by the suspension-infection technique was 1 day, compared with 4.8 days by conventional culture. Comparable detection of low-level positive specimens was observed with the methods. In a clinical setting, the isolation rates obtained by suspension-infection and conventional culture were indistinguishable. These results indicate that the suspension-infection method can be used for the detection of herpes simplex virus and can yield rapid diagnostic results without a time-consuming centrifugation step.

Animals↗
PubMed1990

Age effects on rat hindlimb muscle atrophy during suspension unloading.

Disuse can induce numerous adaptive alterations in skeletal muscle. In the present study the effects of hindlimb unloading on muscle mass and biochemical responses were examined and compared in adult (450 g) and juvenile (200 g) rats after 1, 7, or 14 days of whole body suspension. Quantitatively and qualitatively the soleus (S), gastrocnemius (G), plantaris (P), and extensor digitorum longus (EDL) muscles of the hindlimb exhibited a differential sensitivity to suspension and weightlessness unloading in both adults and juveniles. The red slow-twitch soleus exhibited the most pronounced atrophy under both conditions, with juvenile responses being greater than adult. In contrast, the fast-twitch EDL hypertrophied during suspension and atrophied during weightlessness, with no significant difference between adults and juveniles. Determination of biochemical parameters (total protein, RNA, and DNA) indicated a less rapid rate of response in adult muscles. This was corroborated by assessment of muscle alpha-actin mRNA levels, which indicated a rapid (within 1 day) and significant (P less than 0.05) effect in juveniles but not in adults. The results of this investigation indicate 1) a qualitatively similar differential effect of unloading on muscles of adults and juveniles, 2) a quantitatively reduced and less rapid effect of suspension on adult muscles, and 3) a close similarity of adult and juvenile muscle responses during suspension and spaceflight, suggesting that this ground-based model simulates many of the unloading effects of weightlessness.

Age Factors↗
PubMed1995

Cardiovascular variability and baroreceptor reflex sensitivity over a 14-day tail suspension in rats.

To verify whether a long-term weightlessness simulation was associated with development of cardiovascular deconditioning, male Wistar rats were tail suspended for 13 days and then removed for a 24-h recovery. Blood pressure (BP) and heart rate (HR) responses, their spectral properties, and the pharmacologically tested baroreceptor reflex sensitivity were studied throughout the suspension period and after removal from the tail suspension device. BP, HR, and their variability were not altered over the experimental period, and there were no indications of orthostatic intolerance on release from head-down suspension. Spectral properties of BP and HR were unchanged during the experiment, and tail suspension did not induce modifications in the baroreceptor reflex sensitivity. These results taken together suggest that cardiovascular deconditioning may not be developed even after long-term hindlimb suspension in rats, in contrast to humans exposed to actual or simulated weightlessness. Our results raise issue with the use of tail-suspended rats as a valid model for the study of alterations in cardiovascular function induced by spaceflight in humans.

Animals↗