Situating the parietal memory network in the context of multiple parallel distributed networks using high-resolution functional connectivity.

A principle of brain organization is that networks serving higher cognitive functions are widely distributed across the brain. One exception has been the parietal memory network (PMN), which plays a role in recognition memory but is often defined as being restricted to posteromedial association cortex. We hypothesized that high-resolution estimates of the PMN would reveal small regions that had been missed by prior approaches. High-field 7T functional magnetic resonance imaging (fMRI) data from extensively sampled participants was used to define the PMN within individuals. The PMN consistently extended beyond the core posteromedial set to include regions in the inferior parietal lobule; rostral, dorsal, medial, and ventromedial prefrontal cortex; the anterior insula; and ramus marginalis of the cingulate sulcus. The results suggest that, when fine-scale anatomy is considered, the PMN matches the expected distributed architecture of other association networks, reinforcing that parallel distributed networks are an organizing principle of association cortex.

In situ stimulation of aerobic PCB biodegradation in Hudson River sediments.

A 73-day field study of in situ aerobic biodegradation of polychlorinated biphenyls (PCBs) in the Hudson River shows that indigenous aerobic microorganisms can degrade the lightly chlorinated PCBs present in these sediments. Addition of inorganic nutrients, biphenyl, and oxygen enhanced PCB biodegradation, as indicated both by a 37 to 55 percent loss of PCBs and by the production of chlorobenzoates, intermediates in the PCB biodegradation pathway. Repeated inoculation with a purified PCB-degrading bacterium failed to improve biodegradative activity. Biodegradation was also observed under mixed but unamended conditions, which suggests that this process may occur commonly in river sediments, with implications for PCB fate models and risk assessments.

A simple and efficient procedure for saturation mutagenesis using mixed oligodeoxynucleotides.

A method is described for the efficient saturation mutagenesis of a segment of DNA. A pool of mixed oligodeoxynucleotides (oligos) is generated in a single synthesis by deliberately contaminating each nucleotide reservoir with a low concentration of the other three monomers. The concentration at which a particular level of substitution (i.e. single, double, etc.) is favored can be calculated from simple probability. The pool of single-stranded, mixed oligos is then cloned directly into a double-stranded vector. This is achieved by designing the oligo such that it has ends which are complementary to those left by restriction enzymes generating 5' and 3' overhanging ends. The efficiency of the cloning procedure that we describe is greater than 90%. As a result, direct sequence analysis of transformant clones is justified. In the example described, 2/3 of M13 plaques containing an inserted oligo carried one or more mutations. Mutations generated by this method are randomly distributed throughout the inserted DNA and include all types of substitution. The ease and efficiency of the procedure eliminate any requirement for genetic selection of mutants and thus allow phenotypically silent mutations to be obtained.

Changing U.S. immigration law and the occupational selectivity of Asian immigrants.

PIP: This study explored the relationship between US immigration laws and their impact on the immigration of Asian professionals. The article relied on a 1996 Population Association presentation. Data were obtained from the US Immigration and Naturalization Service on legally admitted immigrants to the US. The authors describe the paths to admission, trends in immigration of professionals during 1972-94, and the Immigration Act of 1965 and its 4 amendments. Standardization-decomposition techniques are used to explain the relative differences in professional immigration across 1972-77, 1978-91, and 1992-94. The crude professional rate for all Asians declined by 19% during 1972-91. 62% of the decline was due to changes in the class of admission composition, and 25% was due to a decline in the class-specific professional rates. During 1992-94, the Asian crude professional rate increased 7%, most of which was due to changes in class composition, with the exception of Korean rates. Only the Vietnamese experienced a decline in rates. The 1965 law allowed for equity between countries in admission. The paths of immigration were family ties, job skills, or refugee status. During 1972-77, Chinese took advantage of family reunification, and Indians entered on employment preferences. The legal changes affected the size and share of each class of admission. The revisions indirectly affected the occupational selectivity of immigrant groups. 27% of the flow of Asians during 1972-77 was accounted for by employment preferences. Professionals were 44% of Asian immigrants during 1972-77, 26% during 1978-91, and 33% during 1992-94.^ieng

The gamma delta resolvase bends the res site into a recombinogenic complex.

We have characterized complexes between the gamma delta resolvase and its recombination site, res, using both a gel retardation assay and DNase I cleavage. The mobility of resolvase-res complexes in polyacrylamide gels is sensitive to the location of res within the DNA fragment and is at a minimum when res is at its center. This behavior is characteristic of a protein-dependent bend. By the same assay we have found that bends are induced upon the binding of resolvase to each of the three individual binding sites that constitute res. In the wild-type res, the centers of binding sites I and II are 53 bp apart and the central section of the intersite DNA is sensitive to DNase I cleavage. We find that insertions of 10 or 21 bp (one or two turns of the DNA helix) have no discernible effect on the ability of res to recombine or to form complexes with resolvase. However, insertions of short segment (e.g. 6 or 17 bp) equivalent to nonintegral numbers of helical turns, inhibit recombination and prevent the formation of the normally compact resolvase-res complex. Complexes of resolvase with res containing 10 or 21 bp insertions exhibit a pattern of enhanced and suppressed DNase I cleavages that suggest that the intersite segment is curved. This curvature requires both that site I and II are appropriately spaced, and that site III is also present and occupied.

Isolation and Characterization of Sexual Spore Pigments from Aspergillus nidulans.

The homothallic ascomycete Aspergillus nidulans produces two types of pigmented spores: conidia and ascospores. The synthesis and localization of the spore pigments is developmentally regulated and occurs in specialized cell types. On the basis of spectroscopic evidence, we propose that the major ascospore pigment of A. nidulans (ascoquinone A) is a novel dimeric hydroxylated anthraquinone. The structure of ascoquinone A, as well as a comparison to model compounds, suggests that it is the product of a polyketide synthase. Previous studies have revealed that the conidial pigments from A. nidulans and a related Aspergillus species (A. parasiticus) also appear to be produced via polymerization of polyketide precursors (D. W. Brown, F. M. Hauser, R. Tommasi, S. Corlett, and J. J. Salvo, Tetrahedron Lett. 34:419-422, 1993; M. E. Mayorga and W. E. Timberlake, Mol. Gen. Genet. 235:205-212, 1992). The structural similarity between the ascospore pigment and the toxic anthraquinone norsolorinic acid, the first stable intermediate in the aflatoxin pathway, suggests an evolutionary relationship between the respective polyketide synthase systems.

Helical phasing between DNA bends and the determination of bend direction.

The presence and location of bends in DNA can be inferred from the anomalous mobility of DNA fragments or protein-DNA complexes during electrophoresis in polyacrylamide gels. Direction of bending is not so easily determined. We show here that a protein-induced bend, when linked to a protein-independent DNA bend by a segment of variable length, exhibits an electrophoretic mobility that varies in a sinusoidal manner with the length of the linker. Mobility minima occur once for each addition to the linker of one helical turn of DNA. Since minima should occur when two bends reinforce one another, the direction of one bend relative to the other can be determined from the distances between the two centers of bending at which minima occur. Our results strongly support the idea that the A5-6 tracts in kinetoplast DNA bend towards the minor groove while the bend at the recombination site of the gamma delta resolvase (binding site I of the gamma delta res site) bends towards the major groove.

Immigration to New York City in the '90s: the saga continues.

PIP: The author examines recent immigration flows to New York City, with a focus on their impact on the city's population. Information is included on immigrants by area of the world and country of birth, demographic characteristics, and migration law.^ieng

Resurgent Irish immigration to the U.S. in the 1980s and early 1990s: a socio-demographic profile.

PIP: "This article uses U.S. immigration data to assess how the occupational characteristics of recent Irish immigrants compare with prior immigrant cohorts and also examines how Irish immigrants are incorporated into the U.S. economy. Recent Irish immigrants to the U.S. spanned the occupational spectrum.... While the number of entering Irish professionals increased, flows of the less skilled increased even more dramatically, resulting in an overall decline in the occupational selectivity of Irish immigrants." (EXCERPT)^ieng

Reconceptualizing migration as a household phenomenon: outmigration from New York City by race and Hispanic origin.

"This paper proposes a conceptual framework for analyzing migration as a household event and presents two public use microdata applications of this approach for out-migrants from New York City. The distribution of single- and multi-origin households by race and Hispanic origin permits a more rigorous analysis of household migration differentials....and the disaggregation of household members by migration status provides insight into the household outcomes of the migration process...." (SUMMARY IN FRE AND SPA)

Contraceptive use and sterilization among Puerto Rican women.

A comparison of contraceptive use in the early to mid-1980s among married Puerto Rican women aged 15-49 in the New York City area reveals that island-born Puerto Rican women living in New York rely on female sterilization to nearly the same extent as do women living in Puerto Rico (45% and 41%, respectively) and that mainland-born Puerto Rican women use sterilization as much as do all women in the United States (19% for both groups). Puerto Rican women in New York use reversible methods to a greater extent than do women in Puerto Rico (22% v. 16%), but to a lesser extent than do all women in the United States (37%). Although mainland-born Puerto Rican women in New York use reversible methods more than do island-born women in New York (42% v. 23%), they tend not to adopt these methods to the same extent as do all U.S. women during the early reproductive years, when education and employment are critical to socioeconomic attainment.

PIP: Researchers compared data from 1985 on 1998 15-49 year old Puerto Rican women living in the greater New York City area with data from 1982 on 3174 15-49 year old women living in Puerto Rico and with data from 1982 on 7969 15-44 year old women living in the US to examine their contraceptive practices. Women who were born in Puerto Rico and later lived in New York City had almost the same sterilization rate as those women still living in Puerto Rico (44.7% vs. 40.5%). On the other hand, about the same proportion of Puerto Rican women born and raised in New York City used reversible methods (42.1%), especially oral contraceptives (18.5%) and the IUD (11%). Only 18.5% of the US-born Puerto Rican women had undergone female sterilization which basically equalled that for all US women (18.7%). A higher proportion of Puerto Ricans in New York City used reversible methods than did those in Puerto Rico (21.7% vs. 15.7%), but not as high a proportion as all US women (36.8%). US-born Puerto Ricans did not accept reversible methods as early in the reproductive years as did all US women (42.2% vs. 58.4% for 15-24 year olds). Puerto Rican women, regardless of residence or place of birth, reported fewer male sterilizations and less condom use by their partners than all US women (0% male sterilizations for all Puerto Rican women in New York City, 4.6% for those in Puerto Rico vs. 10.8% and 2.8% of partners using condoms for island-born Puerto Ricans, 5.1% for US-born Puerto Ricans, and 4.4% for those in Puerto Rico vs. 9.8%). These findings on partner responsibility for contraception may reflect the cultural definition of women as rearers of children. The researchers hoped that the results of this descriptive study would motivate others to conduct further research to determine socioeconomic correlates of contraceptive practice and cultural and religious variables.

Transposon-mediated site-specific recombination: identification of three binding sites for resolvase at the res sites of gamma delta and Tn3.

The tnpR gene product, resolvase, of the transposable element gamma delta mediates site-specific recombination between two copies of gamma delta directly repeated on the same replicon, and it negatively regulates transcription of the tnpA (transposase) gene and its own gene. The recombinational site, res, and the regulatory region both are located in the tnpA-tnpR intercistronic region. In studying the interaction of purified resolvase with DNA fragments derived from gamma delta and the related transposon, Tn3, that span this region, we have demonstrated that three sites specifically bind resolvase. Site I overlaps the recombinational crossover point and both transcriptional promoters. Sites II and III cover most of the DNA between the crossover point and the translational start of the tnpR gene. These are the only binding sites we have detected in a region of about 400 base pairs centered on the crossover point. Studies of cointegrates that contain only part of the region that binds resolvase indicate that site I is not sufficient for efficient site-specific recombination and suggest that all three sites are probably required.