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Growth of microorganisms in total nutrient admixtures.

It has been reported that intravenous fat emulsions, because of their isotonicity and neutral pH, support microbial growth, but traditional parenteral nutrition solutions, being hypertonic and more acidic, are not as supportive. To date, few studies have documented microbial growth in total nutrient admixtures (TNA) containing dextrose, amino acids, fat, electrolytes, vitamins, and trace elements. This study was undertaken to analyze the growth of Staphylococcus aureus, Candida albicans and four gram-negative enteric bacilli in three different nutrient admixtures, with and without the inclusion of 5% fat emulsion. The composition of the admixtures was either 5, 10, or 25% dextrose; either 0 or 5% fat; and 3% amino acids, electrolytes, vitamins, and trace elements. All admixtures were innoculated with 100 colony-forming units per milliliter, incubated at room (25 degrees C) or refrigerated (4 degrees C) temperature, with samples withdrawn at 0, 3, 6, 12, 24, and 48 hours and plated in triplicate. Only C. albicans demonstrated any significant growth regardless of fat content. The pH of the admixtures was similar (acidic), and all solutions were hypertonic and found to inhibit bacterial growth. Conclusions suggest that TNA, when formulated with normal concentrations of additives, is no more likely to support growth of contaminant organisms than the traditional solutions. This contradicts the notion that the addition of fat to total parenteral nutrition will enhance the ability of these admixtures to support microbial growth.

Candida albicans↗
PubMed1982

Evidence for genetic admixture as a determinant in the occurrence of insulin-dependent diabetes mellitus in U.S. blacks.

In recent years, it has been proposed that genetic admixture may have played a role in the increased frequency of insulin-dependent diabetes mellitus (IDDM) in young U.S. blacks relative to African blacks. In support of this proposal, the similar associations of specific markers of the major histocompatibility complex (MHC) with IDDM in U.S. blacks with respect to U.S. whites have been cited. To determine whether racial admixture was a factor in the increased prevalence, we did three analyses of admixture. In the first we used nine genetic markers (ABO, Rh, Fy, Hp, Gc, Pl, OR, Tfr, and Gm) and determined that there was significantly greater than zero genetic contribution from whites in our sample of U.S. black IDDM patients (9.6 +/- 2.3%, P less than 0.01) when a sample of U.S. blacks without IDDM was used as one "parental" population. In the next two analyses, we estimated the amounts of genetic contribution from whites in the U.S. blacks with and without IDDM using reported gene frequencies for West African blacks for four genetic markers (ABO, Rh, Fy, and Hp). The estimate of admixture (21.4 +/- 2.8%) for the black IDDM sample was greater than that for the U.S. black controls (17.9 +/- 2.3%), although the difference was not significant. Our estimate of genetic contribution from whites, 21.4% for black IDDM patients, supports the assumptions of 20% admixture which MacDonald and Rotter and Hodge used to test their respective models for the inheritance of IDDM. These results support the hypothesis that admixture with the white population is, in part, responsible for the increase in prevalence of IDDM seen in U.S. blacks.

Black People↗
PubMed2002

A comparative evaluation of the effects of oral lorazepam, alprazolam and diazepam on venous admixture.

OBJECTIVE: To compare the effects of oral diazepam, lorazepam and alprazolam premedication on venous admixture. MATERIAL AND METHODS: One hundred fifty patients divided in three groups were included in the study. The venous admixture was determined using the ISO-shunt nomogram. The values obtained 90 minutes after administration of the drugs were compared with the values before the drug administration. The Student's t-test was applied to find out the significance. RESULTS: These were highly significant change in increase in venous admixture (Qs/Qt) in group I patients 90 minutes after premedication as compared to premedication values. There was statistically insignificant difference in venous admixture (Qs/Qt) in group II and group III patients 90 minutes after premedication as compared to premedication values. CONCLUSION: From the present study it can be concluded that 2 mg of oral lorozepam given 90 minutes before surgery to healthy patients have significant effects on venous admixture. However, the effects of alprazolam and diazepam had no significant effect on venous admixture.

Administration, Oral↗
PubMed1975

Intropin (dopamine hydrochloride) intravenous admixture compatibility. Part 1: stability with common intravenous fluids.

The stability of dopamine hydrochloride (Intropin) in several large-volume parenteral solutions was studied. Admixtures of dopamine were assayed by colorimetric and chromatographic procedures. Admixtures (800 mug dopamine per ml) in the following intravenous fluids in glass bottles at pH 6.85 or below were found to be chemically and physically stable for at least 48 hours at room temperature: dextrose 5%, dextrose 5% and sodium chloride 0.9%, 5% dextrose in 0.45% sodium chloride, dextrose 5% in lactated Ringer's solution, lactated Ringer's injection, 0.9% sodium chloride, 1/6 molar sodium lactate, and 20% mannitol. The admixture of dopamine in 5% dextrose was stable for a minimum of seven days at 5 C. A 5% dextrose-dopamine admixture in a polyvinylchloride bag was stable for at least 24 hours at room temperature. The admixture of dopamine in 5% sodium bicarbonate solution produced an unstable solution of pH 8.20. A chemical and physical change (development of a pink color) was observed in this admixture. It is recommended that dopamine not be added to 5% sodium bicarbonate solution or any alkaline intravenous solution.

Chemical Phenomena↗
PubMed1986

Compatibility of aminophylline and methylprednisolone sodium succinate intravenous admixtures.

The stability of aminophylline and methylprednisolone sodium succinate in admixtures containing both drugs was studied. Admixtures containing aminophylline 1.0 mg/mL and methylprednisolone sodium succinate 2.0 and 0.5 mg/mL were prepared in both 5% dextrose injection and 0.9% sodium chloride injection. Each admixture was prepared in triplicate and samples were kept at room temperature in glass. Immediately after admixture and at one, two, and three hours, samples were visually inspected, tested for pH, filtered, and assayed in duplicate by high-performance liquid chromatography for theophylline concentration and for both methylprednisolone sodium succinate and methylprednisolone alcohol. Control solutions containing only one of the two drugs were also tested. No visual changes were observed. The admixtures had higher pH values after aminophylline was added, but pH of the samples did not change significantly. Aminophylline concentrations did not change significantly throughout the study period. In 0.9% sodium chloride admixtures with methylprednisolone sodium succinate 0.5 mg/mL, less than 90% of the initial methylprednisolone concentration remained at two hours at the 2.0 mg/mL initial concentration, less than 90% remained at three hours. However, methylprednisolone alcohol (a pharmacologically active form of methylprednisolone sodium succinate) was detected in increasing concentrations after the first hour. Aminophylline in a final concentration of 1.0 mg/mL or less can be mixed with methylprednisolone sodium succinate in a final concentration of 2.0 mg/mL or less in 5% dextrose injection or 0.9% sodium chloride injection and administered intravenously within three hours after mixing.

Aminophylline↗
PubMed1986

Interaction of aztreonam with nafcillin in intravenous admixtures.

An interaction between aztreonam and nafcillin sodium in 0.9% sodium chloride injection or 5% dextrose injection stored in glass or plastic containers is reported. During preliminary experiments, admixtures of aztreonam 10 or 20 mg/mL and nafcillin sodium 10 or 20 mg/mL in 0.9% sodium chloride injection or 5% dextrose injection prepared in glass flasks became cloudy and showed evidence of a fine precipitate. Drug concentrations were measured with a stability-indicating high-performance liquid chromatographic (HPLC) assay. Admixtures of aztreonam 20 mg/mL and nafcillin sodium 20 mg/mL in 5% dextrose injection or 0.9% sodium chloride injection were prepared in polyvinyl chloride bags and stored at room temperature (23-25 degrees C) for 48 hours. The admixtures were assayed at 0, 24, and 48 hours with the same HPLC procedure used during the pretesting experiments. The precipitates were isolated, washed, and centrifuged; the supernatant was analyzed by HPLC assay, and the final residue was analyzed by nuclear magnetic resonance (NMR) spectroscopy. The initial recoveries of drug from the pretesting experiments ranged from 99.2 to 102.4%. Analysis of the precipitates indicated that the precipitate was neither a salt nor a complex formed by the physical interaction of aztreonam and nafcillin sodium, but probably a high-molecular-weight polymer formed by the covalent bonding of subunits of the formulation components. Substantial losses of both drugs from the admixtures were evident after 48 hours of storage. The precipitate was observed sooner in the admixtures containing 0.9% sodium chloride injection than in the admixtures prepared in 5% dextrose injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Aztreonam↗
PubMed1986

Stability of intravenous admixtures of doxorubicin and vincristine.

The stability of doxorubicin and vincristine in admixtures containing both drugs in 0.9% sodium chloride injection, 0.45% sodium chloride and Ringer's acetate injection, and 0.45% sodium chloride and 2.5% dextrose injection was studied. Doxorubicin hydrochloride was added to 30-mL quantities of each base solution to achieve initial doxorubicin concentrations of 1.40 mg/mL and to 0.9% sodium chloride injection to achieve concentrations of 1.88 and 2.37 mg/mL. Vincristine sulfate was added to each doxorubicin admixture to achieve vincristine concentrations of 0.033 and 0.053 mg/mL. All admixtures were protected from light and stored in polysiloxan bags that are used with portable delivery devices. Admixtures were kept at temperatures of 25, 30, and 37 degrees C. Samples withdrawn immediately after preparation and at 1, 2, 4, 7, 10, and 14 days were analyzed by high-performance liquid chromatography for content of each drug. The stability of doxorubicin was dependent on temperature and composition of the base solution. Analysis of data from the samples containing 0.45% sodium chloride and Ringer's acetate injection showed that doxorubicin concentrations were less than 90% of the initial concentration by 12 hours at 37 degrees C, 35 hours at 30 degrees C, and 62 hours at 25 degrees C, and visual changes occurred in all of these admixtures over the course of the study. Vincristine degradation also was most rapid in 0.45% sodium chloride and Ringer's acetate admixtures. Data analysis showed that concentrations of vincristine were less than 90% of initial after eight days at 25 degrees C, five days at 30 degrees C, and three days at 37 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, High Pressure Liquid↗
PubMed1985

Stability of intravenous admixtures of aztreonam and ampicillin.

The stability of aztreonam and ampicillin in intravenous admixtures containing both drugs was studied. Each of the following drugs and combinations of drugs was added to both 5% dextrose injection and 0.9% sodium chloride injection: aztreonam 10 and 20 mg/mL, ampicillin sodium 5 and 20 mg/mL, aztreonam 20 mg/mL and ampicillin sodium 20 mg/mL, aztreonam 20 mg/mL and ampicillin sodium 5 mg/mL, aztreonam 10 mg/mL and ampicillin sodium 20 mg/mL, and aztreonam 10 mg/mL and ampicillin sodium 5 mg/mL. One of each of these admixtures was stored at 25 degrees C for 48 hours and 4 degrees C for seven days. At various storage times the admixtures were inspected for visual changes and 2-mL samples were examined microscopically for crystalline and particulate matter, tested for pH, and assayed by high-performance liquid chromatography. No visual changes were observed. In the two-drug solutions, pH was influenced by concentrations of the two drugs and stability of the drugs was influenced by the solution pH. The pH of single-drug aztreonam admixtures did not change during storage, but the pH of single-drug and two-drug admixtures containing ampicillin decreased. In single-drug admixtures, aztreonam loss under both storage conditions was less than 10% but ampicillin loss was more than 10% in 0.9% sodium chloride injection and more than 50% in 5% dextrose injection. The stability of ampicillin was increased in the presence of aztreonam, and the stability of aztreonam was decreased in the presence of ampicillin.(ABSTRACT TRUNCATED AT 250 WORDS)

Ampicillin↗
PubMed1979

Assuring the quality of intravenous admixture programs.

Several aspects of quality assurance (QA) methods in i.v. admixture programs are discussed, and a basic framework for developing QA programs for admixture services is presented. The objective of QA is to insure that admixture products: (1) are therapeutically and pharmaceutically appropriate to the patient; (2) are free from microbial and pyrogenic contaminants; (3) are free from undesirable levels of particulate or toxic contaminants; (4) contain drugs in correct amounts; and (5) are labeled, stored and distributed under principles of good drug control. Three types of QA criteria bases which may be used as indicators of quality are discussed (resources, facilities and organization; required procedures; end-products or results). Because end-product monitoring has certain limitations in the admixture setting, QA must rely heavily on procedure-centered review methods. General guidelines for developing QA programs are outlined. Adherence to procedure is the key to assuring the quality of admixture products. In developing a QA program, the highest priority should be given to the education and training of admixture personnel, particularly with respect to aseptic technique and pharmaceutical calculations.

Drug Combinations↗
PubMed1983

Lorazepam solubility in and sorption from intravenous admixture solutions.

The solubility of lorazepam in aqueous i.v. solutions and the potential for lorazepam sorption from i.v. admixtures in flexible polyvinyl chloride (PVC) bags and tubing were determined. The solubility of triplicate samples containing 15 mg of lorazepam and 20 ml of deionized water, 5% dextrose, lactated Ringer's, or 0.9% sodium chloride injections was determined. The decrease in lorazepam concentration from a 40-micrograms/ml admixture solution in 5% dextrose injection stored in PVC bags was calculated. Duplicate samples of (1) 50 ml in 50-ml PVC bags, (2) 100 ml in 50-ml PVC bags, and (3) 100 ml in 250-ml PVC bags were laid flat to approximate surface areas of 80, 160, and 270 sq cm, respectively, to determine sorptive loss. The continuous flow sorption of lorazepam from duplicate admixtures was tested at three rates through 180- and 350-cm PVC tubing. The solubility of lorazepam in deionized water, 5% dextrose, lactated Ringer's, and 0.9% sodium chloride injections was 0.054, 0.062, 0.055, and 0.027 mg/ml, respectively. Lorazepam solubility was pH dependent. The decrease in lorazepam concentration from the admixture solution stored in PVC bags for up to 121 hours followed biexponential kinetics that account for both the sorptive loss of the drug and the increasing ratio of bag surface area to solution volume. At least 90% of the initial concentration was maintained for five and two hours when the ratio was less than 2.0 and 2.7-2.8 sq cm/ml, respectively. The admixture solution retained a minimum of 95% of initial concentration when 50-ml aliquots were delivered at 600, 200, and 100 ml/hr through both sizes of PVC tubing. Because of its adequate aqueous solubility and slow sorption by PVC delivery components, lorazepam is suited for dilution in i.v. admixtures for treating conditions with intermittent or continuous infusions.

Adsorption↗
PubMed1982

Physiochemical properties of aminophylline-dextrose injection admixtures.

The compatibility and stability of aminophylline-dextrose injection admixtures were investigated. Aliquots of 5% dextrose injection, 0.9% sodium chloride injection, and 5% dextrose and 0.9% sodium chloride injection were studied for these physiochemical properties: pH, color, clarity, absorbance in a spectrophotometer at 400 nm, and hydroxymethylfurfural (HMF) content. Aminophylline injection was added to the solutions, and aliquots were withdrawn after 0, 6, 24, and 48 hours of storage at 5, 25, 35, and 55 degrees C for testing of the physiochemical properties and aminophylline content. An aminophylline admixture in 5% dextrose injection was passed through an in-line filter (IVEX-2), and eluents were collected for aminophylline assay and for testing the above physiochemical properties. HMF and theophylline were assayed to high-pressure liquid chromatography (HPLC). The aminophylline concentration remained constant in all admixtures studied. A yellow color developed in dextrose-containing aminophylline admixtures stored at 25, 35, and 55 degrees C for 48, 24, and 6 hours, respectively. HMF concentration, pH, and clarity remained within compendial limits. The in-line filter did not retain active ingredients or alter the physiochemical properties of the admixture. Solutions that were yellow showed additional peaks on HPLC. HMF seemed to be a precursor for this yellow color, inasmuch as HMF concentration increased with increasing color intensity. It is concluded that aminophylline-dextrose admixtures are visually and chemically stable for 48 hours when stored under refrigeration or at room temperature.

Aminophylline↗
PubMed2025

Nested Admixture During and After the Trans-Atlantic Slave Trade on the Island of São Tomé.

Human genetic admixture, involving the contact between two or more previously isolated populations, can be a complex process influenced by social dynamics. In this study, we aim to reconstruct complex admixture histories in São Tomé, an island in the Gulf of Guinea where the Portuguese established one of the first plantation-based slave societies. Since the 15th century, migration waves from Africa and Europe, slavery, marooning, and indentured labour led to profound demographic shifts and social stratification on the island. Examining 2.5 million SNPs newly genotyped in 96 São Toméans, we observed patterns of genetic differentiation that were more complex than those of other populations descended from enslaved Africans on either side of the Atlantic. Using local ancestry inference and Identical-by-Descent methods, we identified five genetic clusters in São Tomé and reconstructed shared ancestries between each cluster and 70 African and European population samples, including an extensive sample from the Cabo Verde archipelago. Our findings align with historical records, retracing the major slave trade routes and labour-driven migrations after the abolition of slavery. We also identified gene flow between recently admixed groups that were previously isolated on the island. We call this process, creating multiple layers of genetic ancestry in admixed genomes, nested admixture. We suggest that changing social structures in São Tomé transformed the genetic structure of its population and influenced the admixture process. This study demonstrates how successive admixture and isolation events during and after the Trans-Atlantic Slave Trade shaped extant genetic diversity patterns at local scale in Africa.

Humans↗
PubMed1997

Mitochondrial versus nuclear admixture estimates demonstrate a past history of directional mating.

Six blood group antigens (ABO, RH, MNS, KK, KP, FY) and five plasma proteins (HP, GC, APOA4, FXIIIB, C1R) were typed in 790 individuals, and 12 mtDNA RFLP and deletion polymorphisms were typed in 657 individuals from the San Luis Valley, Colorado. The 790 nuclear typings were conducted on 399 Anglos and 391 Hispanics, while the 657 mitochondrial haplotypes were generated from 207 Anglos and 450 Hispanics. Chakraborty's ADMIX2 FORTRAN program was used to estimate the average Amerindian admixture using all nuclear loci simultaneously. Since there is no recombination in mtDNA, the sum of the frequencies of the Amerindian/Asian-specific mitochondrial haplotypes represents the level of Amerindian admixture. The nuclear estimates of Amerindian admixture were 33.15 +/- 2.41% for the Hispanics and 9.72 +/- 1.90% for the Anglos, while the strictly maternally inherited mtDNA estimates of Amerindian admixture were 85.11% for the Hispanics and 0.97% for the Anglos. This dramatic difference in estimated levels of admixture between the biparentally derived nuclear estimates and the uniparentally derived mtDNA estimates is indicative of past directional matings between Hispanic males and Amerindian females.

Blood Group Antigens↗
PubMed2001

Ancestral proportions and admixture dynamics in geographically defined African Americans living in South Carolina.

We analyzed admixture in samples of six different African-American populations from South Carolina: Gullah-speaking Sea Islanders in coastal South Carolina, residents of four counties in the "Low Country" (Berkeley, Charleston, Colleton, and Dorchester), and persons living in the city of Columbia, located in central South Carolina. We used a battery of highly informative autosomal, mtDNA, and Y-chromosome markers. Two of the autosomal markers (FY and AT3) are linked and lie 22 cM apart on chromosome 1. The results of this study indicate, in accordance with previous historical, cultural, and anthropological evidence, a very low level of European admixture in the Gullah Sea Islanders (m = 3.5 +/- 0.9%). The proportion of European admixture is higher in the Low Country (m ranging between 9. 9 +/- 1.8% and 14.0 +/- 1.9%), and is highest in Columbia (m = 17.7 +/- 3.1%). A sex-biased European gene flow and a small Native American contribution to the African-American gene pool are also evident in these data. We studied the pattern of pairwise allelic associations between the FY locus and the nine other autosomal markers in our samples. In the combined sample from the Low Country (N = 548), a high level of linkage disequilibrium was observed between the linked markers, FY and AT3. Additionally, significant associations were also detected between FY and 4 of the 8 unlinked markers, suggesting the existence of significant genetic structure in this population. A continuous gene flow model of admixture could explain the observed pattern of genetic structure. A test conditioning on the overall admixture of each individual showed association of ancestry between the two linked markers (FY and AT3), but not between any of the unlinked markers, as theory predicts. Thus, even in the presence of genetic structure due to continuous gene flow or some other factor, it is possible to differentiate associations due to linkage from spurious associations due to genetic structure.

Africa↗
PubMed2005

Admixture analysis of a rural population of the state of Guerrero, Mexico.

We studied 156 individuals of Native American descent from the city of Tlapa in the state of Guerrero in western Mexico. Most individuals' ethnicity was either Nahua, Mixtec, or Tlapanec, but self-identified Mestizos and individuals of mixed ethnicities were also included in the sample. We typed 24 autosomal, one Y-chromosome, and four mitochondrial ancestry-informative markers (AIMs) to estimate group and individual admixture proportions, and determine whether the admixture process involved directional gene flow between parental groups. When genetically defined (GD) Mestizos were excluded from the analysis, Native American ancestry represented approximately 98% of the population's gene pool, while European and West African ancestry represented approximately 1% each. Maternally inherited markers also showed an exceptionally high Native American contribution (98.5%), as did the paternally inherited marker, DYS199 (90.7%). We did not detect genetic structure in this population using these AIMs, which appears consistent with the homogeneity of the sample in terms of admixture proportions. The addition of GD Mestizos to the sample did not produce a considerable change in admixture estimates, but it had a major effect on population structure. These results show that the population of Tlapa in Guerrero, Mexico, has experienced little admixture with Europeans and/or West Africans. They also show that the impact of a small number of admixed individuals on an otherwise homogeneous population might have profound implications on subsequent ancestry/phenotype analysis and mapping strategies. We suggest that heterogeneity is a major characteristic of Mexican populations and, as a consequence, should not be disregarded when designing epidemiological studies of Mexican and Mexican American populations.

Black People↗
PubMed2006

Phenotypic evolution of human craniofacial morphology after admixture: a geometric morphometrics approach.

An evolutionary, diachronic approach to the phenotypic craniofacial pattern arisen in a human population after high levels of admixture and gene flow was achieved by means of geometric morphometrics. Admixture has long been studied after molecular data. Nevertheless, few efforts have been made to explain the morphological outcome in human craniofacial samples. The Spanish-Amerindian contact can be considered a good scenario for such an analysis. Here we present a comparative analysis of craniofacial shape changes observed between two putative ancestor groups, Spanish and precontact Aztecs, and two diachronic admixed groups, corresponding to early and late colonial periods from the Mexico's Central Valley. Quantitative shape comparisons of Amerindian, Spanish, and admixed groups were used to test the expectations of quantitative genetics for admixture events. In its simplest form, this prediction states that an admixed group will present phenotypic values falling between those of both parental groups. Results show that, in general terms, although the human skull is a complex, integrated structure, the craniofacial morphology observed fits the theoretical expectations of quantitative genetics. Thus, it is predictive of population structure and history. In fact, results obtained after the craniofacial analysis are in accordance with previous molecular and historical interpretations, providing evidence that admixture is a main microevolutionary agent influencing modern Mexican gene pool. However, expectations are not straightforward when moderate shape changes are considered. Deviations detected at localized structures, such as the upper and lower face, highlight the evolution of a craniofacial pattern exclusively inherent to the admixed groups, indicating that quantitative characters might respond to admixture in a complicated, nondirectional way.

Biological Evolution↗
PubMed1986

Effect of lipid admixtures on the L-dipalmitoylphosphatidylcholine subtransition.

The effect of lipid admixtures on the properties of the L-dipalmitoylphosphatidylcholine (L-DPPC) subtransition is investigated by using high-sensitivity differential scanning calorimetry. The four admixtures used are D-DPPC, L-dipalmitoylphosphatidylethanolamine (L-DPPE), cholesterol, and palmitic acid. In all cases the subtransition decreases in enthalpy until disappearance with increase of the admixture concentrations. About 5-7 mol% of D-DPPC or palmitic acid are sufficient for abolishment (without position shifts) of the subtransition, while, on addition of L-DPPE or cholesterol, it persists up to about 20 mol% of the admixture and its disappearance is accompanied by a slight shift to higher temperatures. These data are tentatively interpreted in terms of lateral mixing of L-DPPC and admixture as indicating compound formation with D-DPPC and palmitic acid, and clustering of L-DPPE and cholesterol.

Calorimetry, Differential Scanning↗
PubMed1991

The effects of admixture and population subdivision on cytonuclear disequilibria.

We examine the generation of cytonuclear disequilibria by admixture and continued gene flow. General formulas analogous to the nuclear case are first derived showing that the allelic and genotypic disequilibria from admixture or population subdivision equal their expected value across the contributing (sub) populations plus the covariance across these sources between the cytoplasmic gene frequency and the relevant nuclear frequency. A detailed study is then presented of the cytonuclear dynamics, in a random-mating population under two different migration scenarios. In both cases closed-form solutions are given for all variables as a function of the initial conditions and relevant migration parameters. The dynamics of the gene frequencies and allelic disequilibria, which dominate each system, are the same as those involving two unlinked nuclear loci, while the dynamics of the genotypic disequilibria and cytonuclear frequencies have no nuclear counterpart. The continent-island formulation focuses on a population receiving continued immigration from a large source of constant composition. A major discovery is that cytonuclear disequilibria can transiently build up on the "island" to levels far exceeding those found at equilibrium. In contrast, the admixture formulation focuses on the dynamics within two populations undergoing continued intermigration. Although in this case all cytonuclear associations must ultimately decay to zero, long-term transient disequilibria can develop which are many times their initial admixture values. For both migration scenarios it is shown that the time of population censusing relative to migration and reproduction dramatically affects both the amount and pattern of the nonrandom associations produced. The empirical relevance of these models is discussed in light of nuclear-mitochondrial data from a hybrid zone between European and North American eels and from a zone of racial admixture in humans.

Alleles↗