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PubMed2000

Free flow electrophoresis device for continuous on-line separation in analytical systems. An application in biochemical detection.

A free flow electrophoresis (FFE) device was developed for continuous electrophoretic separation of charged compounds and implemented in a continuous flow biochemical detection (BCD) system. These continuous separation characteristics make FFE well suitable for online implementation in a chromatographic or flow injection analysis system, in which an additional separation step of charged compounds is desired. In a heterogeneous biochemical flow assay for the determination of biotin, an analyte zone reacts with an excess of an affinity protein. Subsequently, the free binding sites of the affinity protein react with an excess of fluorescein-labeled ligand. Free and affinity protein-bound label are separated on the FFE device prior to fluorescence detection of the separated fractions. Biotin and streptavidin were chosen as, respectively, model ligand and affinity protein. Since all the compounds that are involved possess different electrophoretic properties, quantitative analysis is performed after completely separating the fluorescent affinity complex and labeled biotin in the FFE device within 2 min. Since the device is optically transparent, the separated zones can be detected in the separation compartment, using laser-induced fluorescence. The applicability of the BCD-FFE system in combination with a HPLC separation is demonstrated in the bioanalysis of biotin in human urine at the micromole per liter level.

Biotin↗
PubMedDate not supplied

Separation characteristics of liquid nematode cultures and the design of recovery operations.

Production of nematode-based pesticides involves the recovery of a viable nematode life stage known as the infective juvenile (IJ) from fermentation broth. Waste components to be separated from the IJs include non-IJ life stages, dead nematodes, nematode debris, spent media, and the nematode's associated bacteria. This paper reports separation characteristics of liquid cultures and suspensions of the nematodes Phasmarhabditis hermaphrodita, Steinernema feltiae, and Heterorhabditis megidis measured at small scale. Separation characteristics were determined for dead-end filtration, gravity settling and flotation. Results were used to identify large-scale recovery procedures. Separation of culture liquid by dead-end filtration of the crude fermentation broth was not possible due to rapid blinding of filters. However, nematode-water suspensions prepared by gravity settling could be concentrated using this separation method. Settling tests indicated that IJs could be efficiently separated from culture liquid by centrifugation but not by gravity settling. Examination of the effects of nematode concentration indicated an optimum concentration for gravity settling that may entail modest dilution of the fermentation broth. Flocculation of insoluble spent media in suspensions of P. hermaphrodita prevented its separation from nematodes by gravity settling. However, attachment of air bubbles to spent media allowed removal by flotation. Finally, adjustment of continuous phase density using sucrose allowed separation of non-IJ life stages, dead nematodes, and discarded cuticles from the IJs by flotation. The efficiency of this separation decreased with increasing nematode-solute contact time.

Animals↗
PubMed2005

Microfluidic system for dielectrophoretic separation based on a trapezoidal electrode array.

This paper presents a novel microfluidic device for dielectrophoretic separation based on a trapezoidal electrode array (TEA). In this method, particles with different dielectric properties are separated by the device composed of the TEA for the dielectrophoretic deflection of particles under negative dielectrophoresis (DEP) and poly(dimethylsiloxane)(PDMS) microfluidic channel with a sinuous and expanded region. Polystyrene microparticles are exposed to an electric field generated from the TEA in the microfluidic channel and are dielectrophoretically focused to make all of them line up to one sidewall. When these particles arrive at the region of another TEA for dielectrophoretic separation, they are separated having different positions along the perpendicular direction to the fluid flow due to their different dielectrophoretic velocities. To evaluate the separation process and performance, both the effect of the flow rate on dielectrophoretic focusing and the influence of the number of trapezoidal electrodes on dielectrophoretic separation are investigated. Now that this method utilizes the TEA as a source of negative DEP, non-specific particle adhering to the electrode surface can be prevented; conventional separation approaches depending on the positive DEP force suffer from this problem. In addition, since various particle types are continuously separated, this method can be easily applicable to the separation and analysis of various dielectric particles with high particle recovery and selectivity.

Dimethylpolysiloxanes↗
PubMed2003

The contribution of modern imaging to planning separation strategies in conjoined twins.

BACKGROUND/AIM: An accurate knowledge of the often complex and unexpected anatomy of conjoined twins is required in order to devise appropriate surgical strategies for separation. The recent progress of imaging techniques prompts an assessment of their contribution to planning separation strategies. MATERIAL AND METHODS: From 1990, we treated 8 consecutive sets of conjoined twins: 1 acardiac-acephalus, 1 epigastric heteropagus, 2 omphalopagus, 2 omphalothoracopagus, 1 ischiopagus tetrapus and 1 parapagus tripus. The first two sets were separated straightforwardly after birth and were excluded. Ultrasonographic and plain and contrast X-ray studies were used in all the remaining sets, angiography in 5, CT in 4, and MRI in 4. Helical CT and magnetic resonance angiography (MRA) were used in 3 sets. RESULTS: Two sets of omphalopagus twins and one of omphalothoracopagus twins were separated after birth due to brain damage of one twin, cloacal exstrophy and large arterial shunting, respectively. They were assessed using barium studies (3 sets), IVP (3), angiography (2), CT (2) and MRI (1). Three of six babies survived after separation. In the second set of omphalothoracopagus ecocardiography and MRA revealed that the extent of cardiovascular sharing precluded separation. In the remaining two sets of twins respectively ischiopagus and parapagus, the extent of organ sharing was depicted using three-dimensional helical CT and MRI; the four babies are alive after separation. CONCLUSIONS: Conventional imaging contributes only modestly to separation planning. In contrast, advanced imaging techniques are amazingly efficient in depicting complex fusions that have to be accurately recognised when planning realistic separation strategies.

Female↗
PubMed2002

Separation of motile populations of spermatozoa prior to freezing is beneficial for subsequent fertilization in vitro: a study with various mouse strains.

Success with in vitro fertilization (IVF) using inbred strains of mice varies considerably and appears to be related to the proportion of motile spermatozoa present in epididymal sperm samples of different strains. In this study, motile spermatozoa were separated from the original samples using a column of Sephadex G25. IVF rates were compared between separated and nonseparated samples of epididymal spermatozoa before and after cryopreservation. Oocytes and spermatozoa were obtained from FVB, DBA/2, C57BL/6J, and BALB/c inbred mice; and from F1 (C57BL/6J;ts DBA/2) hybrid mice, and isogenic gametes were used for IVF. These strains of mice were chosen because of their common use in transgenesis and mutagenesis studies. Dulbecco PBS was used for sperm separation on Sephadex, 18% raffinose, and 3% skim milk for cryopreservation; T6 medium for IVF; and mKSOM(AA) for embryo culture. There was a marked improvement in the rate of fertilization using fresh spermatozoa after motile spermatozoa were separated in C57BL/6J and BALB/c strains (92% vs. 58%, 79% vs. 44%) but no differences were found in fertilization rates between separated and nonseparated spermatozoa in F1, FVB, and DBA/2 strains (99% vs. 83%, 95% vs. 93%, 86% vs. 87%, respectively). After cryopreservation, higher rates of fertilization were obtained with separated motile samples in all strains; the greatest improvements were obtained with spermatozoa from C57BL/6J and BALB/c strains (40% vs. 16% and 51% vs. 14% for separated and nonseparated spermatozoa, respectively). No differences were found between the proportions of 14.5-day fetuses developing from embryos derived from separated and nonseparated spermatozoa with or without cryopreservation (33% to 46%). In conclusion, the fertility of frozen-thawed mouse epididymal spermatozoa improves significantly when highly motile populations of spermatozoa are separated for freezing.

Animals↗
PubMed2001

Artery-vein separation via MRA--an image processing approach.

This paper presents a near-automatic process for separating vessels from background and other clutter as well as for separating arteries and veins in contrast-enhanced magnetic resonance angiographic (CE-MRA) image data, and an optimal method for three-dimensional visualization of vascular structures. The separation process utilizes fuzzy connected object delineation principles and algorithms. The first step of this separation process is the segmentation of the entire vessel structure from the background and other clutter via absolute fuzzy connectedness. The second step is to separate artery from vein within this entire vessel structure via iterative relative fuzzy connectedness. After seed voxels are specified inside artery and vein in the CE-MRA image, the small regions of the bigger aspects of artery and vein are separated in the initial iterations, and further detailed aspects of artery and vein are included in later iterations. At each iteration, the artery and vein compete among themselves to grab membership of each voxel in the vessel structure based on the relative strength of connectedness of the voxel in the artery and vein. This approach has been implemented in a software package for routine use in a clinical setting and tested on 133 CE-MRA studies of the pelvic region and two studies of the carotid system from six different hospitals. In all studies, unified parameter settings produced correct artery-vein separation. When compared with manual segmentation/separation, our algorithms were able to separate higher order branches, and therefore produced vastly more details in the segmented vascular structure. The total operator and computer time taken per study is on the average about 4.5 min. To date, this technique seems to be the only image processing approach that can be routinely applied for artery and vein separation.

Algorithms↗
PubMed1993

The effect of phase separation on biphasic waveform defibrillation.

It has been hypothesized that the defibrillation efficacy of a biphasic shock is caused by the large change in voltage between the two phases. This study examined the effects of separating the two phases in time thus splitting in half the rapid voltage change at phase reversal. The study was performed in three parts each using six dogs. Part I determined defibrillation thresholds (DFTs) for two exponentially truncated biphasic waveforms (3.5/2 msec and 6/6 msec) with interphase time delays of 0, 1, 2, 3, 4, 6, 8, and 10 msec. In Part II, probability of success curves were generated using an up down method with 15 shocks for each delay for the 3.5/2 msec biphasic waveform with interphase delays of 0, 2, 3, 4, and 5 msec. In Part III, DFTs were determined using a 3.5/2 msec and 6/6 msec biphasic as well as a third waveform that consisted of two sequential 6-msec pulses of the same polarity with interphase delays of 0, 5, 10, 15, 20, 25, 50, and 100 msec. In all three parts the defibrillating cathode was a 6.17 cm2 transvenous spring electrode positioned in the RV apex and the anode was a 113 cm2 cutaneous left chest wall electrode patch. With all waveforms, the trailing edge voltage of the first phase was equal to the negative of the leading edge voltage of the second phase. There was no statistical difference in DFTs or in 50% successful defibrillation points for phase separations from 0 to 6 msec and 0 to 5 msec for Parts I and II, respectively. In Part I there was a significant increase in DFTs for phase separations of 8 and 10 msec compared to a phase separation of 0 msec. In Part III there was no significant difference for separations of 0 and 5 msec; however, there was a significant increase in DFT requirements for separations from 5 to 50 msec, which then decreased with a separation of 100 msec for all three waveforms tested. In conclusion, defibrillation efficacy was unchanged with phase separations up to 6 msec. With phase separation, the rapid voltage change during phase reversal is split in half and, thus, cannot explain the improved efficacy of biphasic waveforms.

Animals↗
PubMed2006

Maternal separation and handling affects cocaine self-administration in both the treated pups as adults and the dams.

Repeated maternal separation of pups from dams is often used as an early life stressor that causes profound neurochemical and behavioral changes in the pups that persist into adulthood. The effects of maternal separation on both the dams and the treated pups as adults on cocaine self-administration were examined using four separation conditions: 15- or 180-min separation (MS15 and MS180), brief handling without separation (MS0), and a nonhandled group (NH). The separations and handling occurred daily on postnatal days 2 to 15. The acquisition of cocaine self-administration (0.0625-1.0 mg/kg/infusion) was evaluated in the treated pups as adults. The MS180 group acquired cocaine self-administration at the lowest dose tested (0.0625 mg/kg/infusion), whereas the MS15s did not respond for cocaine at rates greater than that seen with saline administration. The NH group received the greatest number of infusions and intake at the highest doses. After self-administration, no differences were observed between groups in activity of two liver carboxylesterases involved in the inactivation of cocaine, ES10 and ES4. Maternal separation affected cocaine self-administration in the dams as well. Although there was an overall significant affect of treatment on cocaine self-administration, the length of separation (15 or 180 min) did not affect cocaine self-administration on the dams. The MS0 dams averaged a greater number of infusions per session than NH group during the 1st week of acquisition. These data suggest that in addition to the profound changes that occur in pups as result of maternal separation, the dams are also susceptible to alterations in behaviors.

Aging↗
PubMed1981

Sequence of centromere separation: an analysis of mitotic chromosomes from long-term cultures of Potorus cells.

The sequence of centromere separation in late metaphase/anaphase cells from a long term culture of cells from a male rat-kangaroo, Potorus tridactylus, was studied. The karyotype of the PTK-1 line has five pairs of autosomes, one modified No. 1 (M1), and X, Y1 and Y2. In 87% of the cells the centromeres of No. 4 or 5 were among the first to separate. Y1, Y2, X, or the marker, M1, were not the earliest chromosomes to separate. Y2 separated last most frequently (59%), followed by X, M1 and Y1. The overall relative averages for the sequence of separation in the entire genome (centromere separation index or CSI) are 1.52, 1.40, 1.11, 0.92, 0.88, 0.86, 0.68, 0.56, and 0.27 for 5, 4, 2, 1, Y1, 3, M1, X, and Y2, respectively (the average for the whole genome is 1). The data indicate that the centromeres of the chromosomes of potorus separate in a specific, genetically controlled, non-random sequence. The chromosomes separating late have larger amounts of centromeric heterochromatin; all of this or part of it may be the controlling element for the sequence of separation.

Animals↗
PubMed2002

Laboratory evaluation of amalgam separators.

BACKGROUND: Amalgam in dental wastewater is receiving increasing scrutiny from regulators because of national, state and local initiatives to reduce or virtually eliminate the discharge of mercury and mercury-containing items into the environment. Amalgam separators are considered to be one means of reducing the amount of amalgam that dental offices discharge into sewers. The purpose of this study was to evaluate the amalgam removal efficiency of commercially available amalgam separators and the total mercury concentration in the effluent from laboratory testing. METHODS: The authors evaluated the amalgam removal efficiency of 12 amalgam separators according to International Organization for Standardization, or ISO, Standard 11143 for Amalgam Separators. Total mercury concentration in the effluent was calculated using the mass of amalgam particles larger than 1.2 micrometers and the volume of effluent, together with U.S. Environmental Protection Agency, or EPA, Method 245.1 for amalgam particles smaller than 1.2 microm. Total dissolved mercury also was determined. RESULTS: The results show that all 12 amalgam separators exceeded the ISO 11143 requirement of 95 percent amalgam removal efficiency. Statistical differences were found in the efficiencies of the separators. Both the total mercury concentration and total dissolved mercury concentration in the effluent demonstrated large variations. CONCLUSIONS AND CLINICAL IMPLICATIONS: This laboratory evaluation shows that amalgam separators removed at least 96.09 percent of the amalgam in samples with particle-size distribution as specified in ISO 11143. Total mercury concentration and total dissolved mercury concentration in the effluent varied widely for each amalgam separator. Additional research is needed to develop test methods to evaluate the efficiency of amalgam separators in removing small amalgam particles, colloidal amalgam particles and ionic mercury in solution.

Dental Amalgam↗
PubMed2001

The anterior iliac separation: alternative index for pelvic morphometry in fetuses with Down syndrome.

OBJECTIVE: The goal of this study was to assess the diagnostic use of an anterior iliac separation measurement as an alternative index for the iliac angle in the assessment of fetal pelvic morphometry. SUBJECTS AND METHODS: In 358 fetuses, the anterior iliac separation, iliac length, and iliac angle were prospectively measured on antenatal sonography. All measurements were obtained at two axial levels (superior and inferior). The gestational age of the fetus was recorded. The anterior iliac separation was normalized by iliac length, and coefficients of variation were calculated for all measurements. The effects of axial level and gestational age were assessed in a linear regression model. The diagnostic use of the anterior iliac separation relative to that of the iliac angle was assessed in a comparison of 24 fetuses with Down syndrome and 247 non-Down syndrome fetuses. RESULTS: The anterior iliac separation was less variable than the iliac angle at both superior and inferior levels. There were statistically significant effects for gestational age and axial level on both the anterior iliac separation and the iliac angle, but there was no significant effect for either factor when the anterior iliac separation was normalized by the iliac length. Comparing Down and non-Down syndrome fetuses, we found that the normalized anterior iliac separation had discriminating power similar to the iliac angle. CONCLUSION: The linear measurement of the anterior iliac separation has diagnostic properties similar to the iliac angle and is subject to less measurement variability. This simpler measurement may be particularly useful when normalized by the iliac length.

Down Syndrome↗
PubMed1990

A comparison of the effects of spatial separation on apparent motion in the auditory and visual modalities.

In the present investigation, the effects of spatial separation on the interstimulus onset intervals (ISOIs) that produce auditory and visual apparent motion were compared. In Experiment 1, subjects were tested on auditory apparent motion. They listened to 50-msec broadband noise pulses that were presented through two speakers separated by one of six different values between 0 degrees and 160 degrees. On each trial, the sounds were temporally separated by 1 of 12 ISOIs from 0 to 500 msec. The subjects were instructed to categorize their perception of the sounds as "single," "simultaneous," "continuous motion," "broken motion," or "succession." They also indicated the proper temporal sequence of each sound pair. In Experiments 2 and 3, subjects were tested on visual apparent motion. Experiment 2 included a range of spatial separations from 6 degrees to 80 degrees; Experiment 3 included separations from .5 degrees to 10 degrees. The same ISOIs were used as in Experiment 1. When the separations were equal, the ISOIs at which auditory apparent motion was perceived were smaller than the values that produced the same experience in vision. Spatial separation affected only visual apparent motion. For separations less than 2 degrees, the ISOIs that produced visual continuous motion were nearly equal to those which produced auditory continuous motion. For larger separations, the ISOIs that produced visual apparent motion increased.

Adult↗
PubMed1998

[Study on the enantiomeric separation of adrenalines by capillary zone electrophoresis].

Capillary zone electrophoresis (CZE) has been used for the enantiomeric separation of the racemic isoprenaline, noradrenaline and adrenaline with bare fused silica capillary and employing beta-cyclodextrin(beta-CD) and beta-cyclodextrin derivatives as the chiral selectors. Both the complexion and enantiomeric resolution were influenced by the temperature, beta-CD type, CD concentration and pH of background electrolyte (BGE). The effects of the BGE types and concentrations on the enantiomeric separation were also investigated. The results showed that 2,6-di-O-carboxymethyl-beta-cyclodextrin (CM-beta-CD) has stronger recognition than that of beta-CD for the chiral separation of the basic drugs under study. The CD concentrations and pH of BGE have strong influence on the efficiency of chiral separation. The adsorption of the basic compound on the surface of bare fused silica capillary is a disadvantage to the chiral separation while the use of beta-CD as the chiral selector and the addition of an amphiphile, such as tetraethylammonium bromide (TEA+) or tetrabutylammonium bromide (TBA+) to the BGE could improve the resolution of the enantiomers due to the reduction of the adsorption of the basic compound on the silica surface by the strong electrostatic force between the positively charged amphiphile and the silica surface. It was also found that as CM-beta-CD was used as the chiral selector there was no influence on the chiral separation of the basic compound whether the amphiphile was added to BGE or not. Lower temperature was favorable to improve the efficiency of the chiral separation. CM-beta-CD gave a baseline enantiomeric separation for isoprenaline, while beta-CD, under the same experimental conditions, gave an incomplete chiral separation. Both CM-beta-CD and beta-CD could not give enantiomeric resolution for noradrenaline and adrenaline.

Electrophoresis, Capillary↗
PubMed1998

[The preparation of chiral column of cellulose triacetate coated on small pore silica gel and the separation of enantiomers].

The cellulose triacetate (CTA) prepared by heterogeneous acetylation and coated on small pore 3-aminopropyl silica gel (10 nm) was used as chiral stationary phase for HPLC (OA column). The racemes of three drugs, two fulvenes and one dazine, were separated on this column. Among these racemes, timolol maleas was separated using 1.0 mol/L NaClO4:95% ethanol = 10:90 as mobile phase. Without NaClO4 in mobile phase, the resolution of timolol maleas can not occur. Ethanols of 95%-98% were used as mobile phase for other racemes. The influence of the content of water in mobile phase on the chiral separation of praziquentelum, the retention time and separation factor (alpha) were reduced with the increase of water content in mobile phase. When the content of water in the mobile phase was 13%, praziquentelum could not be separated. It was found that in the case of samples No. 1 and No. 2, when the substituents R1 and R2 or R'1 and R'2 of fulvenes are 4-methoxybenzoyl and 4-methoxyphenyl, the chiral separations of fulvenes can be obtained. For sample No. 4 when R1 and R2 of fulvenes are 2-methylbenzoyl and 2-methylphenyl or in the case of No. 5, when R1 and R2 are 5-bromo-2-furoyl and 5-bromo-2-furan, the chiral separations of fulvenes can not be achieved. For sample No. 6 and No. 7, when R'1 are 4-chlorobenzoyl and benzoyl or R'2 are 4-chlorophenyl and phenyl, the chiral separation also can not be achieved. The column performance and separation factor were not obviously reduced after used for four months.

Cellulose↗
PubMed2000

[The development of a static water/gas separator].

Objective. To develop a device for separating water from gas in small flow rate under zero "G". Method. Beginning with the study of surface characteristic of materials, a capillary material was developed according to the requirement and the water/gas separator using this single separating material was designed. Result. The water/gas separator worked well in the range of gas flow below 10.0 L/min and water flow below 10.0 ml/min. No gas was found in the separated water and no water was found in the separated gas. Conclusion. The structure of the separator was reasonable and the water/gas separating method using a single separating material was feasible.

Air Conditioning↗
PubMed1985

Structural details of boundary layer separation in a model human carotid bifurcation under steady and pulsatile flow conditions.

We have used a dye-flow visualization technique to analyze the substructure of flow separation in a plastic model of the human carotid bifurcation under steady and pulsatile flow. Under steady conditions at a physiologic flow split (Q external carotid/Q common carotid = 0.30) and Reynolds number (500), a large region of separated fluid developed along the outside wall of the sinus, opposite the flow divider. Yellow dye injected into the boundary layer upstream from the bifurcation traveled slowly along the wall of the common carotid and entered directly into the separation. Blue dye injected into the central, high-velocity streamlines in the common carotid impacted on the flow divider, then traveled circumferentially and entered the separation. Mixing of these two sources was documented by the appearance of green fluid, which lingered in the region of separation. Pulsatile flow resulted in a smaller region of separation; mixing still occurred. Flow separation at the carotid bifurcation is a site of mixing of fluids previously subjected to prolonged low-shear wall contact and brief high-shear wall contact. Separation is itself a site of low shear, but this study reveals a mechanism whereby low and high shear may act independently or synergistically to explain the link between flow separation and atherogenesis.

Carotid Arteries↗
PubMed1994

An experimental model of affinity cell separation.

Cell affinity separations are based on the selective attachment of cell phenotype using antibody or lectins specific for cell surface markers. The major physicochemical factors which influence ligand-mediated cell adhesion dynamics and the efficiency of cell affinity separation have been examined. Uniform cell detachment forces were generated with a parallel-plate flow cell (plate separation 100 microns, surface area 3 cm2). Hydrodynamic shear stress was used to measure cell adhesion strength and to separate cells on the basis of surface affinity. Human cell lines grown in tissue culture were separated on a flat derivatised glass immunoadsorbent which formed the floor of the flow chamber. Flow-cell residence time, detachment shear stress, temperature, and ligand density were shown to influence cell attachment probability. An understanding of the physical basis of ligand-mediated cell adhesion provided a rationale for optimisation of affinity cell separation. At room temperature attachment of positive cells was rapid (< 2 min) and adhesion strength was directly related to immunoadsorbent ligand density. Purity and recovery of enriched fractions were dependent on the separation shear stress and could be optimised using this parameter. Enrichment factors were greater than 100-fold, with at least 90% of positive cells recovered in enriched fractions. Enrichment purity and yields did not decline at higher loading densities (10(5) cells/cm2). Selective immunoadsorbent surface chemistry is a prerequisite for efficient affinity cell separation. Purity and recovery may be optimised by fractionating enriched and depleted cell populations with uniform fluid shear stress.

Antibody Affinity↗
PubMed1992

Mutation affecting cell separation and macronuclear resorption during conjugation in Tetrahymena thermophila: early expression of the zygotic genotype.

A new recessive conjugation lethal mutation was found in Tetrahymena thermophila which was named mra for macronuclear resorption arrest. Other events affected by the mra mutations are separation of pairs, DNA replication in the macronuclear anlagen, and resorption of one of the two micronuclei. In wild-type crosses 50% of the pairs had separated by 12 hr after mixing two mating types and had completed resorption of the old macronucleus 1-2 hr later. In contrast most mra conjugants did not separate even by 24 hr after mixing and the old relic (condensed) macronucleus was seen in over 90% of them. After addition of 10 mM calcium to the conjugation medium, the mra conjugants did separate but they still failed to complete resorption of the old macronucleus and to replicate macronuclear anlagen DNA in the exconjugants. The calcium induced separation of the mra conjugants occurred later than the separation of control pairs. During normal conjugation cell separation occurs before the first expression of known macronuclear genes and prior to processing of the macronuclear DNA. Therefore, the mra phenotype infers that separation of conjugants requires a signal which is produced by the macronuclear anlagen at an unusually early time.

Animals↗