Search PubMed⌕ Search

Biomedical subjects

J R Weeks

Publications and source records attributed to J R Weeks.

At least 19 recordsLinked to original sources
PubMed1999

Reproductive outcomes among Mexico-born women in San Diego and Tijuana: testing the migration selectivity hypothesis.

Mexican immigrants to the United States have better reproductive outcomes than do U.S.-born non-Latina whites. Explanations offered for this "epidemiologic paradox" include (1) poor outcomes among Mexican women may be hidden by their return to Mexico; (2) Mexican women may have a higher fetal death rate that alters the pattern of live birth outcomes; (3) Mexican women may have socioeconomic characteristics which, if properly measured, would explain the outcome; (4) Mexican women may have personal characteristics which would explain the outcome, if properly measured; (5) there may be ameliorative or salutogenic "protective" effects of culture; and (6) migration may be selective of healthier women who are thus more prone to positive outcomes. We test these explanations, with an emphasis on the last one, using a data set that combines reproductive histories and birth outcomes for Mexico-born women delivering in San Diego, California and Mexican women delivering in Tijuana, Mexico. These data are compared with U.S.-born Latinas and U.S.-born non-Latina Whites. Multivariate logistic regression analysis suggests that when controlling for birth history (stillbirths and miscarriages), socioeconomic characteristics (education and prenatal visits), personal characteristics (age, parity, time in area, history of family problems), and health characteristics (history of smoking, alcohol use, drug use, anemia, vaginal bleeding, urinary infection), the adjusted odds of a positive birth outcome (measured as a live birth of 2500 grams or more) is highest for women delivering in Tijuana, implying that migrants may not be so selective when compared to the country of origin. The number of prenatal visits was an important explanatory variable.

Journal Article↗
PubMed1993

Locus-specific variation in phosphorylation state of RNA polymerase II in vivo: correlations with gene activity and transcript processing.

To investigate functional differences between RNA polymerases IIA and IIO (Pol IIA and Pol IIO), with hypo- and hyperphosphorylated carboxy-terminal repeat domains (CTDs), respectively, we have visualized the in vivo distributions of the differentially phosphorylated forms of Pol II on Drosophila polytene chromosomes. Using phosphorylation state-sensitive antibodies and immunofluorescence microscopy with digital imaging, we find Pol IIA and Pol IIO arrayed in markedly different, locus- and condition-specific patterns. Major ecdysone-induced puffs, for example, stain exclusively for Pol IIO, indicating that hyperphosphorylated Pol II is the transcriptionally active form of the enzyme on these genes. In striking contrast, induced heat shock puffs stain strongly for both Pol IIA and Pol IIO, suggesting that heat shock genes are transcribed by a mixture of hypo- and hyperphosphorylated forms of Pol II. At the insertion sites of a transposon carrying a hybrid hsp70-lacZ transgene, we observe only Pol IIA before heat shock induction, consistent with the idea that Pol II arrested on the hsp70 gene is form IIA. After a 90-sec heat shock, we detect heat shock factor (HSF) at the transposon insertion sites; and after a 5-min shock its spatial distribution on the induced transgene puffs is clearly resolved from that of Pol II. Finally, using antibodies to hnRNP proteins and splicing components, we have discerned an apparent overall correlation between the presence and processing of nascent transcripts and the presence of Pol IIO.

Amino Acid Sequence↗
PubMed1993

Service provider attitudes toward natural family planning.

"Our study...addresses the issue of availability of NFP [natural family planning] within the established family planning provider setting--clinics and private practice.... The data for this study were gathered by means of questionnaires administered by mail to clinic administrators and service providers, OB/GYN physicians in private practice, and NFP-only providers...in Los Angeles and San Diego Counties in California.... The principal analytical goal in this research is to determine the effect that service provider attitudes may have on the availability of NFP....Our research has indicated that the single most identifiable barrier to the availability of NFP is the negative attitude of physicians toward the method, prompted by their skepticism about its use-effectiveness."

Americas↗
PubMed1991

Infant mortality among ethnic immigrant groups.

The numerically large and growing Indochinese refugee population has been little studied with respect to infant health. It is a population that is young, is experiencing high fertility, late onset of prenatal care, and is characterized by low socioeconomic status. Thus, it presents a high risk profile with respect to infant mortality. Using linked birth and infant death records for the San Diego metropolitan area for the period 1978-85 infant mortality rates (IMRs) were calculated for Indochinese refugee groups from Vietnam, Laos and Cambodia in comparison with other ethnic groups. We found, surprisingly, that Indochinese refugees as a group had an IMR below that for non-Hispanic Whites and substantially below that for Blacks. In general, IMRs for Indochinese refugees were similar to those for other Asian groups. These findings held even after controlling for birth weight and onset of prenatal care. The timing and causes of death suggest areas in which the IMR could drop to even lower levels with improved community outreach programs, especially among refugee groups from Laos (Hmong and Lao) who exhibited the unusual pattern of higher post-early neonatal than early neonatal mortality.

Birth Weight↗
PubMed1989

Analysis of the gene encoding the largest subunit of RNA polymerase II in Drosophila.

We have characterized RpII215, the gene encoding the largest subunit of RNA polymerase II in Drosophila melanogaster. DNA sequencing and nuclease S1 analyses provided the primary structure of this gene, its 7 kb RNA and 215 kDa protein products. The amino-terminal 80% of the subunit harbors regions with strong homology to the beta' subunit of Escherichia coli RNA polymerase and to the largest subunits of other eukaryotic RNA polymerases. The carboxyl-terminal 20% of the subunit is composed of multiple repeats of a seven amino acid consensus sequence, Tyr-Ser-Pro-Thr-Ser-Pro-Ser. The homology domains, as well as the unique carboxyl-terminal structure, are considered in the light of current knowledge of RNA polymerase II and the properties of its largest subunit. Additionally, germline transformation demonstrated that a 9.4 kb genomic DNA segment containing the alpha-amanitin-resistant allele, RpII215C4, includes all sequences required to produce amanitin-resistant transformants.

Amino Acid Sequence↗
PubMed1988

The C-terminal repeat domain of RNA polymerase II largest subunit is essential in vivo but is not required for accurate transcription initiation in vitro.

DNA sequence analysis of RpII215, the gene that encodes the Mr215,000 subunit of RNA polymerase II (EC 2.7.7.6) in Drosophila melanogaster, reveals that the 3'-terminal exon includes a region encoding a C-terminal domain composed of 42 repeats of a seven-residue amino acid consensus sequence, Tyr-Ser-Pro-Thr-Ser-Pro-Ser. A hemi- and homozygous lethal P-element insertion into the coding sequence of this domain causes premature translation termination and therefore truncation of the protein, leaving only 20 heptamer repeats. While loss of approximately 50% of the repeat structure in this mutant is a lethal event in vivo, enzyme containing the truncated subunit remains capable of accurate initiation at promoters in vitro. Moreover, treatment of purified intact RNA polymerase II with protease, to remove the entire repeat domain, does not eliminate the enzyme's ability to initiate accurately in vitro. Possible in vivo functions for this unusual protein domain are considered in light of these results.

Amino Acid Sequence↗
PubMed1987

Developmental toxicity of alprostadil in rats after subcutaneous administration or intravenous infusion.

Timed-pregnant Upj:TUC(SD)spf (Sprague-Dawley) rats were dosed with alprostadil (prostaglandin E1), either subcutaneously on Days 6-15 of gestation at 0.0, 0.5, 1.0, or 2.0 mg/kg/day or by iv infusion into the jugular vein (24 hr/day) on Days 7-15 at 0.0, 0.5, 1.0, 2.0, 4.0, or 6.0 mg/kg/day. Maternal toxicity was observed in all dams receiving alprostadil subcutaneously, the severity of which increased in a dose-related manner. Toxicity also was evident in the offspring in the 2.0 mg/kg/day group as evidenced by a significant increase in the percentage of resorptions and a significant decrease in the percentage of live fetuses. Mean fetal weight was significantly depressed in all three alprostadil-treated groups and several skeletal and visceral variations were significantly higher in the 1.0 and 2.0 mg/kg/day groups than in the vehicle control group; in addition, there were two instances of significantly increased frequencies of skeletal variations in the 0.5 mg/kg/day group. Gross, visceral, and skeletal malformations were significantly increased in the high-dose group. During iv infusion of alprostadil more than 50% of the dams in the 6.0 mg/kg/day group died and there was one death in the 4.0 mg/kg/day group. Significant decreases in maternal weight gain between Days 7 and 11 of gestation were observed at doses of 1.0 mg/kg/day and above. However, continuous iv infusion of this prostaglandin, at dosages which were not severely toxic to the dams, was judged not to be teratogenic or otherwise embryotoxic in rats. The increase in uterine contractions, observed at 1.0 and 2.0 mg/kg after sc administration to rats implanted with chronic uterine microballoons, was consistent with the hypothesis that the developmental toxicity observed after bolus sc administration was the consequence of decreased blood flow in the uterus and/or placenta and/or embryos.

Abnormalities, Drug-Induced↗
PubMed1986

Alteration of the growth-rate-dependent regulation of Escherichia coli tyrT expression by promoter mutations.

The growth-rate regulation of transcription of the Escherichia coli tyrT gene depends on sequences in at least two distinct regions of the promoter, the upstream element required for optimal activity and the discriminator adjacent to the transcription start-point. Since mutations in the discriminator also alter the response of the promoter to amino acid starvation, we conclude that growth rate and amino acid control mechanisms share a common target molecule, probably RNA polymerase.

Base Sequence↗
PubMed1986

Fertility and adaptation: Indochinese refugees in the United States.

"Levels of fertility among Indochinese refugees in the United States are explored in the context of a highly compressed demographic transition implicit in the move from high-fertility Southeast Asian societies to a low-fertility resettlement region. A theoretical model is developed to explain the effect on refugee fertility of social background characteristics, migration history and patterns of adaptation to a different economic and cultural environment controlling for marital history and length of residence in the U.S." The chief source for the data and analyses is the Indochinese Health and Adaptation Research Project (IHARP), San Diego State University. "Multiple regression techniques are used to test the model which was found to account for nearly half of the variation in refugee fertility levels in the United States. Fertility is much higher for all Indochinese ethnic groups than it is for American women; the number of children in refugee families is in turn a major determinant of welfare dependency. Adjustments for rates of natural increase indicate a total 1985 Indochinese population of over one million, making it one of the largest Asian-origin populations in the United States."

Acculturation↗
PubMed1986

Teaching international demography.

"I describe a course on international demography in this paper. The course enables students to use demographic concepts to understand the demographics of various countries and regions. The course involves an introduction, examination of specific geographic regions, and a concluding overview. I also describe several student projects and review available course materials."

Demography↗
PubMed1986

Dye-ligand affinity chromatography of RNA polymerase II.

The binding of wheat germ RNA polymerase II to five different dye-ligand chromatography gels (Matrex gels, Amicon Corp.) was tested. A quantitative binding of the enzyme to four of the gels, namely Dyematrex gels Blue A, Blue B, Red A and Green A was observed. Only the Orange A gel column failed to bind the enzyme strongly. Nearly 100% of the activity could be recovered from the Green A column by elution with high salt concentration and high pH. Under these conditions only a part of the activity was eluted from the other three columns since the enzyme bound tightly. Enzyme activity could be removed from the columns by elution with nucleotide substrates, but the yield from the Blue A, Blue B and Red A columns was still low (7 to 42%). The Green A Matrex gel appeared to be useful for the purification and analysis of RNA polymerase.

Chromatography, Affinity↗
PubMed1985

Negative supercoiling induces spontaneous unwinding of a bacterial promoter.

We have examined the influence of negative supercoiling on the DNA structure of a bacterial promoter (tyrT from Escherichia coli), the transcriptional activity of which is strongly enhanced by torsional stress in vitro. Certain regions of this promoter become sensitive to digestion by single-strand-specific S1 nuclease as a consequence of negative superhelicity. These regions occur with high frequency (1 per 30-50 bp) and are normally centered on a TpA doublet. The major positions of cleavage are located in and around the -10 sequence TATGATG, the unwinding of which is a prerequisite for gene expression. An apparently trivial change in the -10 sequence from TATGATG to TATGAAG reduces both transcriptional activity and S1 nuclease sensitivity at least 10-fold. Thus the nuclease sensitivity of the promoter correlates strongly with its biological function; and both of these phenomena correlate with certain sequence-dependent structural properties of the DNA.

DNA Restriction Enzymes↗
PubMed1984

Prediction of abuse liability of drugs using IV self-administration by rats.

A total 31 psychoactive drugs were offered to groups of naive rats for IV self-administration and an injection rate greater than that for rats offered only saline indicated reinforcement. Two protocols were used: in the first, rats were offered drug at a selected dose for 5 days, then the dose was reduced by 1 log unit (to 0.1 the original dose) for an additional 4 days; in the second, rats were offered saline for 3 days as a "prescreen' to eliminate rats with high or low operant-injection rates. Drug was offered to acceptable rats for 5 days, then the dose was reduced 0.5 log unit (to 0.32 the original dose) for 5 more days. A scoring system, based upon the injection rates during the last 3 days of each period, describes the reinforcing action. Scores were dose-related. Tests on both protocols gave similar results. Data from monkey studies have been reported for 27 of the drugs tested. Of these drugs, 18 were reinforcers and six were nonreinforcers in both species, nalorphine and ethylketazocine were reinforcers only in rats, and ethanol was a reinforcer only in monkeys.

Animals↗
PubMed1984

Cyanoacrylate ester adhesive: a versatile tool in experimental surgery.

Cyanoacrylate ester adhesive is useful in experimental surgery in rodents and other animals for closing skin and muscle incisions, securing cannulae in place, and securing dental acrylic to bone. Both laboratories reporting here found independently that the technique used in applying cyanoacrylate for wound closures is important. Very small droplets of adhesive must be applied. A device for this purpose is described.

Animals↗
PubMed1984

Family life education in California ninth and tenth grades.

Superintendents , principals and family life education teachers in all California school districts having a ninth and/or 10th grade were surveyed about their family life education ( FLE ) efforts. Responses were obtained from 80% of the superintendents , 45% of the principals and 39% of the FLE teachers who were sent questionnaires. While most superintendents reported the existence of an FLE program in at least one district school, the surveys revealed that less than one-fourth of ninth graders and less than one-third of 10th graders received such instruction during the 1981-1982 academic year. District decisions to offer FLE were reported to be most strongly influenced by school faculty and administrators while the decision not to offer FLE was most strongly influenced by clergy and special interest groups. More than half of the FLE teachers who returned surveys taught FLE as a unit within another course. Teachers generally covered a variety of curriculum topics, with units/courses most likely to address human development, physiology and sexual disease and least likely to deal with value-laden topics such as premarital intercourse, sexual behavior and sexual preference. However, the greater number of class hours devoted to FLE , the greater the chance that these issues were covered in the curriculum. Finally, the data reveal that evaluation of FLE courses was relatively limited in scope and was largely subjective in many schools.

Adolescent↗