Most of the genetic covariation between major depressive and alcohol use disorders is explained by trait measures of negative emotionality and behavioral control.

BACKGROUND: Mental health disorders commonly co-occur, even between conceptually distinct syndromes, such as internalizing and externalizing disorders. The current study investigated whether phenotypic, genetic, and environmental variance in negative emotionality and behavioral control account for the covariation between major depressive disorder (MDD) and alcohol use disorder (AUD). METHOD: A total of 3623 members of a national twin registry were administered structured diagnostic telephone interviews that included assessments of lifetime histories of MDD and AUD, and were mailed self-report personality questionnaires that assessed stress reactivity (SR) and behavioral control (CON). A series of biometric models were fitted to partition the proportion of covariance between MDD and AUD into SR and CON. RESULTS: A statistically significant proportion of the correlation between MDD and AUD was due to variance specific to SR (men = 0.31, women = 0.27) and CON (men = 0.20, women = 0.19). Further, genetic factors explained a large proportion of this correlation (0.63), with unique environmental factors explaining the rest. SR explained a significant proportion of the genetic (0.33) and environmental (0.23) overlap between MDD and AUD. In contrast, variance specific to CON accounted for genetic overlap (0.32), but not environmental overlap (0.004). In total, SR and CON accounted for approximately 70% of the genetic and 20% of the environmental covariation between MDD and AUD. CONCLUSIONS: This is the first study to demonstrate that negative emotionality and behavioral control confer risk for the co-occurrence of MDD and AUD via genetic factors. These findings are consistent with the aims of NIMH's RDoC proposal to elucidate how transdiagnostic risk factors drive psychopathology.

Impact of an experimental PRRSV and Streptococcus suis coinfection on the pharmacokinetics of ceftiofur hydrochloride after intramuscular injection in pigs.

This study determined the impact of porcine reproductive and respiratory syndrome virus (PRRSV) and Streptococcus suis coinfection on the pharmacokinetic (PK) profile of ceftiofur hydrochloride in pigs after intramuscular (i.m.) injection. Eighteen clinically normal crossbred gilts were assigned by weight into a challenge group (10 pigs) and control group (eight pigs). Pigs in both groups received a single i.m. injection of ceftiofur hydrochloride (Excenel RTU Sterile Suspension; Zoetis) at a 5 mg/kg BW dose. Serial blood samples were collected to characterize the plasma concentration curve. After a 10 days drug washout period, the challenge group was inoculated with 2 mL of PRRSV isolate VR-2385 (10(5.75) 50% tissue culture infective doses per mL) intranasally and 8 days later inoculated S. suis. When clinical disease was evident, the second PK assessment began in both challenge and control groups. Coinfected pigs demonstrated lower values of AUC and CMAX , but higher values of Cl/F and Vz/F indicating drug kinetics were altered by infection. The data from this study have implications on ceftiofur treatment regimens in diseased pigs.

Disentangling the relationships between maternal smoking during pregnancy and co-occurring risk factors.

BACKGROUND: Maternal smoking during pregnancy (SDP) has been studied extensively as a risk factor for adverse offspring outcomes and is known to co-occur with other familial risk factors. Accounting for general familial risk factors has attenuated associations between SDP and adverse offspring outcomes, and identifying these confounds will be crucial to elucidating the relationship between SDP and its psychological correlates. METHOD: The current study aimed to disentangle the relationship between maternal SDP and co-occurring risk factors (maternal criminal activity, drug problems, teen pregnancy, educational attainment, and cohabitation at childbirth) using a population-based sample of full- (n=206 313) and half-sister pairs (n=19 363) from Sweden. Logistic regression models estimated the strength of association between SDP and co-occurring risk factors. Bivariate behavioral genetic models estimated the degree to which associations between SDP and co-occurring risk factors are attributable to genetic and environmental factors. RESULTS: Maternal SDP was associated with an increase in all co-occurring risk factors. Of the variance associated with SDP, 45% was attributed to genetic factors and 53% was attributed to unshared environmental factors. In bivariate models, genetic factors accounted for 21% (non-drug-, non-violence-related crimes) to 35% (drug-related crimes) of the covariance between SDP and co-occurring risk factors. Unshared environmental factors accounted for the remaining covariance. CONCLUSIONS: The genetic factors that influence a woman's criminal behavior, substance abuse and her offspring's rearing environment all influence SDP. Therefore, the intergenerational transmission of genes conferring risk for antisocial behavior and substance misuse may influence the associations between maternal SDP and adverse offspring outcomes.

Detection of Mycobacterium avium subspecies paratuberculosis: comparing fecal culture versus serum enzyme-linked immunosorbent assay and direct fecal polymerase chain reaction.

Mycobacterium avium ssp. paratuberculosis (MAP) is the etiologic agent of Johne's disease in cattle. The disease causes diarrhea, reduced milk production, poor reproductivity, emaciation, and eventually death. Culture on Herrold's egg yolk agar is considered to be the definitive test for diagnosis of Johne's in cattle. This method has moderate sensitivity (30 to 50%) and is 100% specific; however, it can take up to 16 wk due to the slow growth of MAP. Currently, serum ELISA is used to screen herds for Johne's disease, but positive tests must be confirmed culturally or by PCR. The current research sought to evaluate an in-house direct fecal PCR procedure and directly compare it to ELISA using culture as the gold standard. Serum and fecal samples were collected from cows (n = 250) with unknown Johne's status. Fecal samples were processed for culture on Herrold's egg yolk agar and direct PCR. Serum samples were tested using the Parachek serum ELISA. Overall, 67/250 [26.8%, 95% confidence interval (CI) 21.4 to 32.8] animals were culturally confirmed to be shedding MAP. The PCR and ELISA detected 74/250 (29.6%, 95% CI 24 to 35.7) and 25/250 (10%, 95% CI 6.6 to 14.4), respectively. Culture and PCR were able to detect more positive animals than ELISA. Overall, direct fecal PCR was 70.2% sensitive and 85.3% specific when using culture as the gold standard. The ELISA method was 31.3% sensitive and 97.8% specific. When culture reported <10 cfu, the sensitivity and specificity of PCR and ELISA were 57.1 and 85.3%, and 4.8 and 97.8%, respectively. When culture reported 10 to <40 cfu, the sensitivity of PCR and ELISA were 75 and 50%, respectively. When culture reported > or =40 cfu, the sensitivity of PCR and ELISA were 100 and 88.2%, respectively. Specificity could not be calculated at these levels because there were no negative samples. The direct PCR outperformed the ELISA in detecting animals potentially infected with MAP and was not significantly different when compared with culture. The direct fecal PCR method described here provides faster results than traditional culture and is more sensitive than ELISA at detecting animals suspected of Johne's disease. These data support the use of PCR as an alternative method for screening herds for prevalence and diagnosis of Johne's disease.

Detection of Mycobacterium avium subspecies paratuberculosis in free-ranging bison (Bison bison) by PCR.

Bacterial culture is the 'gold standard' for detecting Mycobacterium avium subspecies paratuberculosis (MAP) infection, but is time consuming, laborious, and recovery of organism varies with species of animal tested. PCR has been used for detection of MAP DNA in feces and tissues. We used PCR to detect MAP DNA isolated from tissues from 25 free-ranging North American bison (Bison bison), each with clinical signs compatible with Johne's disease. We report the performance of PCR to detect MAP DNA in both frozen and paraffin-embedded ileum, jejunum, and ileocecal lymph node samples collected at the time of slaughter. Specific oligonucleotide primers for PCR amplification were derived from 16S rRNA sequence M. avium subspecies (MAs) and insertion elements IS1245 (MAs avium), IS901 (MAs avium), IS900 (MAP), and hspX (MAP). Genomic DNA samples were prepared three different ways; crude DNA from frozen tissues, crude DNA from paraffin-embedded tissues, and purified DNA from paraffin-embedded tissues. An animal was considered infected if MAP DNA was detected in at least two separate tissues using the IS900 primer set. Using these criteria, 25 of 25 bison tested were positive for MAP. The data indicate that these free-ranging bison have been infected by MAP.

Ethanol exerts different effects on myelin basic protein and 2',3'-cyclic nucleotide 3'-phosphodiesterase expression in differentiating CG-4 oligodendrocytes.

Evidence suggests that abnormal myelination is one factor contributing to the neuoropathology associated with fetal alcohol syndrome. We investigated the potential teratogenic effects of ethanol (EtOH) on myelin formation by determining its effects on the developmentally regulated increased expression of myelin basic protein (MBP) and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) in differentiating CG-4 oligodendrocytes (OLGs). By using CG-4 OLGs in vitro we identified processes altered by ethanol actions exerted directly on OLGs. During the first 8 days of development, EtOH decreased the expression of the major structural 18.5 and 14 kDa MBP isoforms by at least 40% at 4 days of development. EtOH concentrations between 25 and 75 mM inhibited MBP expression in a dose-dependent manner. Adding or withdrawing EtOH on specific days of differentiation reversibly modulated the expression of MBP, and the degree of inhibition was directly related to the length of ethanol exposure. As little as two consecutive days of EtOH exposure either early or late during development caused at least a 20% inhibition, however, no short critical time window of EtOH vulnerability for the inhibition was observed. The ethanol effect was selective for MBP expression, as EtOH did not alter the developmentally-regulated increased expression of CNP isozymes or enzyme activity. The results indicate that one factor contributing to the development of fetal alcohol syndrome may be defective myelination resulting from delayed and decreased MBP expression.

High-stakes testing in employment, credentialing, and higher education. Prospects in a post-affirmative-action world.

Cognitively loaded tests of knowledge, skill, and ability often contribute to decisions regarding education, jobs, licensure, or certification. Users of such tests often face difficult choices when trying to optimize both the performance and ethnic diversity of chosen individuals. The authors describe the nature of this quandary, review research on different strategies to address it, and recommend using selection materials that assess the full range of relevant attributes using a format that minimizes verbal content as much as is consistent with the outcome one is trying to achieve. They also recommend the use of test preparation, face-valid assessments, and the consideration of relevant job or life experiences. Regardless of the strategy adopted, it is unreasonable to expect that one can maximize both the performance and ethnic diversity of selected individuals.

Investigating the influence of social desirability on personality factor structure.

This study provides a comprehensive investigation into whether social desirability alters the factor structure of personality measures. The study brought together 4 large data sets wherein different organizational samples responded to different personality measures. This facilitated conducting 4 separate yet parallel investigations. Within each data set, individuals identified through a social desirability scale as responding in an honest manner were grouped together, and individuals identified as responding in a highly socially desirable manner were grouped together. Using various analyses, the fit of higher order factor structure models was compared across the 2 groups. Results were the same for each data set. Social desirability had little influence on the higher order factor structures that characterized the relationships among the scales of the personality measures.

Effects of transient ethanol exposure on the incorporation of [(3)H]ethanolamine into plasmalogen in the differentiating CG-4 oligodendrocyte cell line.

We investigated the potential teratogenic effects of ethanol (EtOH) on myelination by monitoring its effects on the labeling of the myelin-typical lipid, ethanolamine plasmalogen (EPl), in the CG-4 cell line of differentiating oligodendrocytes (OLGs). On 5 different days during the first 8 days of OLG development, cells were labeled for 24 hr with [(3)H]ethanolamine to label EPl and diacyl-ethanolamine phosphoglycerols (diacyl-EPG), and the amount of labeled lipid expressed on each day was determined in the presence and absence of 25-120 mM EtOH. At early stages of development, a lower amount of [(3)H]EPl per cell was found in cells exposed to EtOH. The ratio of [(3)H]EPl to [(3)H]diacyl-EPG in cells exposed to 25, 50, or 120 mM EtOH was decreased by 50% after 4 days of differentiation compared with that in control cells. By adding or withdrawing EtOH at specific days of differentiation, we showed that EtOH inhibited the increased labeling of EPl if it was present for the first 48 hr of differentiation, and subsequent withdrawal failed to relieve the inhibition. Addition of EtOH anytime after the first day of differentiation did not inhibit the increased labeling of EPl. The results show that the increased labeling of EPl in differentiating OLGs resulted from an EtOH-sensitive, developmentally programmed, transient process active only during the first 2 days of differentiation.

Potent inhibition of the aortic smooth muscle maxi-K channel by clinical doses of ethanol.

We investigated the effects of clinically relevant ethanol concentrations (5-20 mM) on the single-channel kinetics of bovine aortic smooth muscle maxi-K channels reconstituted in lipid bilayers (1:1 palmitoyl-oleoyl-phosphatidylethanolamine: palmitoyl-oleoyl-phosphatidylcholine). Ethanol at 10 and 20 mM decreased the channel open probability (P(o)) by 75 +/- 20.3% mainly by increasing the mean closed time (+82 to +960%, n = 7). In some instances, ethanol also decreased the mean open time (-40.8 +/- 22. 5%). The P(o)-voltage relation in the presence of 20 mM ethanol exhibited a rightward shift in the midpoint of voltage activation (DeltaV(1/2) congruent with 17 mV), a slightly steeper relationship (change in slope factor, Deltak, congruent with -2.5 mV), and a decreased maximum P(o) (from approximately 0.82 to approximately 0. 47). Interestingly, channels inhibited by ethanol at low Ca(2+) concentrations (2.5 microM) were very resistant to ethanol in the presence of increased Ca(2+) (>/= 20 microM). Alcohol consumption in clinically relevant amounts may alter the contribution of maxi-K channels to the regulation of arterial tone.

Evaluation of the accuracy and reproducibility of a practical PCR panel assay for rapid detection and differentiation of Mycobacterium avium subspecies.

The Mycobacterium avium subspecies (MAs) include the closely related MAs avium and MAs paratuberculosis. This study was conducted to evaluate the performance of a PCR panel assay as a diagnostic tool to detect and differentiate MAs avium and MAs paratuberculosis infection. Specific oligonucleotides primers derived from the 16 S rRNA (MAs) sequence, insertion elements IS 901 (MAs avium), IS 1245 Mycobacterium avium complex (MAC), IS 900 (MAs paratuberculosis), and the hspX (MAs paratuberculosis) gene sequences were synthesized and used in preassembled PCR reaction mixtures. These five primer sets made up the PCR panel assay. To determine the accuracy of the PCR panel assay for MAs avium and MAs paratuberculosis strain detection and differentiation, lysates of mycobacterial DNA from 120 (n=120) strains were tested with the PCR panel assay by one laboratory (#1). The PCR panel assay specifically detected and differentiated 91/91 (100%) of MAs avium and MAs paratuberculosis strains tested in this study. The PCR panel assay also specifically differentiated all MAs avium and MAs paratuberculosis strains from all but one (M. intracellulare, serovar 23) of the other mycobacterial strains tested. To confirm the accuracy and evaluate the reproducibility of the PCR panel assay, samples were numbered and given to a different laboratory (#2) as 'unknowns' for identification by the PCR panel assay. In this study, the overall accuracy for strain identification using the PCR panel assay was 99.2% (119/120). The reproducibility of the PCR panel assay when comparing data from laboratory #1 with laboratory #2 was found to be 100% (120/120). These results indicate that this 'easy-to-use', rapid PCR method can accurately and reliably detect and differentiate closely related MAs avium and MAs paratuberculosis from each other and from other mycobacterial species. The PCR panel assay can also differentiate mixed cultures of MAs. The simplicity of this PCR method could be beneficial to laboratories that test for members of MA.

General anesthetic action at an internal protein site involving the S4-S5 cytoplasmic loop of a neuronal K(+) channel.

The structural bases of general anesthetic action on a neuronal K(+) channel were investigated using the series of homologous 1-alkanols, electrophysiology, and mutational analysis. Domain swapping between dShaw2 (alkanol-sensitive) and hKv3.4 (alkanol-resistant) and site-directed mutagenesis demonstrated that a 13-amino acid cytoplasmic loop (S4-S5) determines the selective inhibition of native dShaw2 channels by 1-alkanols. The S4-S5 loop may contribute to a receptor for both 1-alkanols and the inactivation particle, because the enhanced 1-alkanol sensitivity of hKv3.4 channels hosting S4-S5 mutations correlates directly with disrupted channel inactivation. Evidence of a discrete protein site was also obtained from the analysis of the relationship between potency and alkyl chain length, which begins to level off after 1-hexanol. Rapid application to the cytoplasmic side of inside-out membrane patches shows that the interaction between dShaw2 channels and 1-alkanols equilibrates in <200 ms. By contrast, the equilibration time is >1000-fold slower when the drug is applied externally to outside-out membrane patches. The data strongly favor a mechanism of inhibition involving a discrete internal site for 1-alkanols in dShaw2 K(+) channels. A new working hypothesis proposes that 1-alkanols lock dShaw2 channels in their closed conformation by a direct interaction at a crevice formed by the S4-S5 loop.

Temporal and quantitative expression of the myelin-associated lipids, ethanolamine plasmalogen, galactocerebroside, and sulfatide, in the differentiating CG-4 glial cell line.

We determined the expression of three myelin-typical lipids in the continuous CG-4 glial cell line of oligodendrocyte progenitor cells, as the cells differentiated into oligodendrocytes. On 6 different days during the first 9 days of oligodendrocyte development, cells were labeled for 24 h with [3H]ethanolamine to label ethanolamine plasmalogens or with [3H]galactose to label the galactocerebroside and sulfogalactocerebroside; and the amount of labeled lipid expressed on each day was determined. Each labeled lipid was expressed with its own specific time course and in a defined amount on each day of differentiation. Increased labeling of plasmalogens and sulfogalactocerebroside started at early developmental stages, and increased labeling of galactocerebroside started at later stages. The results indicate that the differentiating CG-4 cell line provides a valuable system to investigate factors affecting the early time course of myelin-lipid expression and the amounts expressed.

Polymerase chain reaction identification of Mycobacterium avium in formalin-fixed, paraffin-embedded animal tissues.

A PCR procedure previously developed for identification of Mycobacterium bovis in formalin-fixed tissues was used to identify mycobacteria of the M. avium complex. Tissues were examined from 100 culture-positive cases of M. avium complex infection, including 86 in which the subspecies was not identified and 14 that had been identified as M. avium subsp. paratuberculosis. Each sample was tested with 5 primer sets, 16S ribosomal RNA (rRNA), IS900, IS901, IS1245, and a heat shock protein (hspX), that detect 1 or both M. avium subspecies. The success rate of PCR detection varied with the primers used and the animal species tested. Among the 86 cases with no M. avium subspecies designation, primers for the 16S rRNA gene were clearly the most efficient because they produced amplicons from all samples that reacted with any other primer set. The overall detection rate in this group of samples was 71%: highest in avian tissues (89%) followed by swine (72%) and ruminants (57%) None of the avian or swine tissues reacted with primers for IS900 or hspX, which identify M. a. paratuberculosis. In contrast, 7 of the 12 ruminant samples that were 16S rRNA positive reacted with 1 or both of these primers. All of the 14 cases shown by culture to be M. a. paratuberculosis infections were positive with IS900 primers, whereas only 11 were positive for 16S rRNA. These results indicate that 16S rRNA primers are the most useful for PCR identification of M. avium in formalin-fixed tissues of nonruminant species. However, IS900 primers should also be used when ruminant tissues are examined because these primers provide the greatest sensitivity for detection of M. a. paratuberculosis infections.

The effects of chronic ethanol consumption on the formation of phosphatidylethanolamine molecular species and their appearance at the plasma membrane.

The purpose of our study was to determine whether chronic ethanol consumption affected membrane assembly by altering the formation of specific molecular species of phosphatidylethanolamine (PE) and their subsequent incorporation into the plasma membrane (PM). We investigated the effects on the PE species made by the two major pathways in hepatocytes: (1) from CDP-ethanolamine in the endoplasmic reticulum, and (2) by the decarboxylation of phosphatidylserine (PS) in the mitochondria. Ethanol consumption exerted significant effects on the formation of ethanolamine-derived PE species and affected mainly two species, the 16:0/22:6 and 18:0/20:4 species. In cultured hepatocytes from ethanol-fed rats labeled with [3H]ethanolamine for 0.25 to 4 hr, the amount of the [3H]16:0/22:6 PE species was decreased compared with that in control cells, whereas the amount of [3H]18:0/20:4 species was increased. The amount of the [3H]16:0/22:6 PE species on the cell surface was also decreased in hepatocytes from ethanol-fed rats, whereas the amount of [3H]18:0/20:4 species was increased. In contrast, the profile of [3H]PE species formed in cells treated with [3H]serine exhibited minor alterations, and the profile of the serine-derived [3H]PE species on the cells surface was not altered after 4 hr of labeling. The changes in ethanolamine-derived species were apparently caused by time-dependent alterations in the metabolic processes, because the presence of 110 mM ethanol in the culture media did not affect the profiles of [3H]PE species in cells from control or ethanol-fed rats and was not required to sustain the altered profiles. The results indicate that the synthesis of specific PE molecular species and their appearance on the PM may occur by compartmentalized processes which are distinguishable by different sensitivities to ethanol consumption. The results indicate that ethanol consumption may contribute alcoholic hepatic injury by interfering with the metabolism of specific PE molecular species and their assembly into the PM.

Identification of a gene unique to Mycobacterium avium subspecies paratuberculosis and application to diagnosis of paratuberculosis.

Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) is the etiologic agent of paratuberculosis (Johne's disease), a chronic granulomatous enteritis in ruminants. Currently, there is a need for improved diagnostic tests because of the lack of methods for accurate, rapid and reliable detection of M. paratuberculosis infection. A M. paratuberculosis gene (hspX) was cloned, sequenced, and a 30 bp species-specific oligonucleotide was synthesized. As an internal control to identify mycobacterial strains, a 33 bp Mycobacterium genus-specific oligonucleotide was synthesized based on the conserved 5' terminus of the mycobacterial recA gene. Dioligonucleotide hybridization (dOH) analysis identified 28/28 (100%) mycobacterial strains and specifically identified 14/14 (100%) reference (ATCC 19698), bovine, ovine and human isolates of M. paratuberculosis. The M. paratuberculosis-specific oligonucleotide distinguished M. paratuberculosis isolates from related mycobacteria, including all closely related members of the Mycobacterium avium complex (MAC) tested in this study. The members of MAC tested in this study included Mycobacterium avium subspecies avium (M. paratuberculosis, Mycobacterium avium subspecies silvaticum (M. silvaticum) and Mycobacterium intracellulare strains. Hybridization was not observed with DNA extracted from a selected group of other bacterial pathogens. The experiments indicate that the dOH analysis is a useful diagnostic tool to detect mycobacterial infection, specifically M. paratuberculosis. The dOH method could be a good alternative to existing assays and will be adapted for specific identification of M. paratuberculosis from faecal samples, mixed bacteriologic cultures, tissue specimens and whole blood.

Visual pigments and spectral sensitivity of the diurnal gecko Gonatodes albogularis.

The visual pigments and oil droplets in the retina of the diurnal gecko Gonatodes albogularis were examined microspectrophotometrically, and the spectral sensitivity under various adapting conditions was recorded using electrophysiological responses. Three classes of visual pigments were identified, with lambda max at about 542, 475, and 362 nm. Spectral sensitivity functions revealed a broad range of sensitivity, with a peak at approximately 530-540 nm. The cornea and oil droplets were found to be transparent across a range from 350-700 nm, but the lens absorbed short wavelength light below 450 nm. Despite the filtering effect of the lens, a secondary peak in spectral sensitivity to ultraviolet wavelengths was found. These results suggest that G. albogularis does possess the visual mechanisms for discrimination of the color pattern of conspecifics based on either hue or brightness. These findings are discussed in terms of the variation in coloration and social behavior of Gonatodes.

High-performance liquid chromatographic method for determination of the metabolism of polyunsaturated molecular species of phosphatidylserine labeled in the polar group.

A reversed-phase HPLC method to monitor the incorporation of radiolabeled precursors into the polar group of individual polyunsaturated molecular species of phosphatidylserine (PS) is presented. PS labeled in the polar group was decarboxylated and subsequently converted to trinitrophenyl-phosphatidylethanolamine (Tnp-PE), which was separated into its molecular species by reversed-phase HPLC within 90 min, using a gradient of acetonitrile-methanol and ammonium acetate. A major feature of the method is the complete resolution of the stearoyl species, 18:0/20:4 and 18:0/22:6, at ambient temperature. By determining the amount of radioactivity incorporated into each fraction, the metabolism of individual molecular species of PS, and also of PE, labeled in the polar group can be investigated.

A small family of elements with long inverted repeats is located near sites of developmentally regulated DNA rearrangement in Tetrahymena thermophila.

Extensive DNA rearrangement occurs during the development of the somatic macronucleus from the germ line micronucleus in ciliated protozoans. The micronuclear junctions and the macronuclear product of a developmentally regulated DNA rearrangement in Tetrahymena thermophila, Tlr1, have been cloned. The intrachromosomal rearrangement joins sequences that are separated by more than 13 kb in the micronucleus with the elimination of moderately repeated micronucleus-specific DNA sequences. There is a long, 825-bp, inverted repeat near the micronuclear junctions. The inverted repeat contains two different 19-bp tandem repeats. The 19-bp repeats are associated with each other and with DNA rearrangements at seven locations in the micronuclear genome. Southern blot analysis is consistent with the occurrence of the 19-bp repeats within pairs of larger repeated sequences. Another family member was isolated. The 19-mers in that clone are also in close proximity to a rearrangement junction. We propose that the 19-mers define a small family of developmentally regulated DNA rearrangements having elements with long inverted repeats near the junction sites. We discuss the possibility that transposable elements evolve by capture of molecular machinery required for essential cellular functions.

The selective use of stearoyl-polyunsaturated molecular species of phosphatidylcholine and phosphatidylethanolamine for the synthesis of phosphatidylserine.

In rat liver microsomes, [3H]serine was incorporated primarily into the two most abundant molecular species of microsomal phosphatidylserine (PS), 18:0/20:4 and 18:0/22:6, by Ca(2+)-dependent base exchange. The pattern of PS molecular species synthesized was very similar to the species composition of PS and markedly different from the species composition of either microsomal precursor, phosphatidylcholine (PC) or phosphatidylethanolamine (PE). The data indicated that the enrichment of rat liver PS in mainly three fatty acids--stearic, arachidonic, and docosahexaenoic acids, occurred by (1) the preference by PS synthases for the stearoyl-polyunsaturated molecular species, 18:0/20:4 and 18:0/22:6, of PC and PE and (2) a discrimination against the use of the palmitoyl-polyunsaturated species, 16:0/20:4 and 16:0/22:6, and the stearoyl-diunsaturated species, 18:0/18:2. The preferential use of the two species of PC and PE, based on their acyl chain content and not on their relative abundance, demonstrates that an individual molecular species can be selected out of the total pool for a defined function.