Dissociation of maximal O2 uptake from O2 delivery in canine gastrocnemius in situ

To test the hypothesis that maximal O2 uptake (VO2max) can be limited by O2 diffusion in the peripheral tissue, we kept O2 delivery [blood flow X arterial O2 content (CaO2)] to maximally contracting muscle equal between 1) low flow-high CaO2 and 2) high flow-low CaO2 conditions. The hypothesis predicts, because of differences in the capillary PO2 profile, that the former condition will result in both a higher VO2max and muscle effluent venous PO2 (PVO2). We studied the relations among VO2max, PVO2, and O2 delivery during maximal isometric contractions in isolated, in situ dog gastrocnemius muscle (n = 6) during these two conditions. O2 delivery was matched by varying arterial O2 partial pressure and adjusting flow to the muscle accordingly. A total of 18 matched O2 delivery pairs were obtained. As planned, O2 delivery was not significantly different between the two treatments. In contrast, VO2max was significantly higher [10.4 +/- 0.5 (SE) ml.100 g-1.min-1; P = 0.01], as was PVO2 (25 +/- 1 Torr; P less than 0.01) in the low flow-high CaO2 treatment compared with the high flow-low CaO2 treatment (9.1 +/- 0.4 ml.100 g-1.min-1 and 20 +/- 1 Torr, respectively). The rate of fatigue was greater in the high flow-low CaO2 condition, as was lactate output from the muscle and muscle lactate concentration. The results of this study show that VO2max is not uniquely dependent on O2 delivery and support the hypothesis that VO2max can be limited by peripheral tissue O2 diffusion.     

Effect of hemoglobin concentration on maximal O2 uptake in canine gastrocnemius muscle in situ

O2 delivery to maximally working muscle was decreased by altering hemoglobin (Hb) concentration and arterial PO2 (PaO2) to investigate whether the reductions in maximal O2 uptake (VO2max) that occur with lowered [Hb] are in part related to changes in the effective muscle O2 diffusing capacity (DmO2). Two sets of experiments were conducted. In the initial set (n = 8), three levels of Hb [5.8 +/- 0.3, 9.4 +/- 0.1, and 14.4 +/- 0.6 (SE) g/100 ml] in the blood were used in random order to pump perfuse, at equal muscle blood flows and PaO2, maximally working isolated dog gastrocnemius muscle. VO2max declined with decreasing [Hb], but the relationship between VO2max and both the effluent venous PO2 (PvO2) and the calculated mean capillary PO2 (PcO2) was not linear through the origin and, therefore, not compatible with a single value of DmO2 (as calculated by Bohr integration using a model based on Fick's law of diffusion). To clarify these results, a second set of experiments (n = 6) was conducted in which two levels of Hb (14.0 +/- 0.6 and 6.9 +/- 0.6 g/100 ml) were each combined with two levels of oxygenation (PaO2 79 +/- 8 and 29 +/- 2 Torr) and applied in random sequence to again pump perfuse maximally working dog gastrocnemius muscle at constant blood flow. In these experiments, the relationship between VO2max and both PvO2 and calculated PcO2 for each [Hb] was consistent with a constant estimate of DmO2 as PaO2 was reduced, but the calculated DmO2 for the lower [Hb] was 33% less than that at the higher [Hb] (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Women's status and infant mortality in rural Colombia

This paper investigates the effects of maternal demographic characteristics and social and economic statuses on infant mortality in rural Colombia. Demographic characteristics include the age of the mother, parity and length of preceding interbirth interval, and sex of infant. Measures of women's status at the time of birth include education, wage labor and occupation, economic stratum, place of residence, and whether the mother is living with a husband. The life history data for the study (involving 4,928 births) were collected in 1986 from a representative sample of two cohorts of women resident in rural central Colombia. Overall differentials in infant mortality by measures of women's status are small and are in good part associated with the differing reproductive behaviors of the women and variations in breastfeeding practices. The sharp declines in infant mortality recorded in rural Colombia in recent years appear less related to improved status of women than to reductions in fertility that enhance infant survivorship and to public health interventions shared by all segments of the population.     

Family networks in prenatal and postnatal health

This paper examines the effects of kin access on prenatal health practices, birth outcome, and postnatal health practice for infants born to black and white mothers ages 21 to 28 in the U.S. during 1984-86. The data used for this research were compiled from three sources: (1) The National Longitudinal Survey of Youth; (2) The Children of the National Longitudinal Survey of Youth; (3) special kin access data files, which were created specifically for this study. Logistic regression procedures are used to assess the effects of kin proximity, maternal grandmother proximity, and presence of the child's father on health practices (N = 1,030) and birth outcome (N = 1,385), controlling for the mother's educational attainment, work experience, poverty, presence of the child's father, and birth order of the child. We find no evidence supporting the notion that kin access positively affects the prenatal and postnatal health practices of young mothers. The results suggest that young mothers who reside with their mothers or other adult kin, and those who are in close proximity to them, are no more likely to seek prenatal care during the first trimester, or to avoid smoking or drinking during pregnancy. Mothers who live with a sexual partner or husband are, however, somewhat more likely to seek prenatal care and to avoid alcohol use during pregnancy. Closer kin access is associated with a lower probability of breastfeeding. These results suggest that it will not be adequate to rely on kin networks or kin assistance to improve the prospect of healthy birth outcomes.     

Development of mammary hyperplasia and neoplasia in MMTV-TGF alpha transgenic mice

To study the role of transforming growth factor alpha (TGF alpha) in normal mammary development and mammary neoplasia in vivo, we have generated transgenic mice in which a human TGF alpha cDNA is expressed under the control of the MMTV enhancer/promoter. Overexpression of TGF alpha in the mammary epithelium, as confirmed by in situ hybridization and immunohistochemistry, is associated with hyperplasia of alveoli and terminal ducts in virgin female and pregnant transgenic mice. A range of morphologic abnormalities including lobular hyperplasia, cystic hyperplasia, adenoma, and adenocarcinoma is seen in mammary tissue of transgenic females. In contrast, no morphologic abnormalities are seen in transgenic males in spite of TGF alpha overexpression in salivary glands and reproductive organs. TGF alpha can therefore act as an oncogene in vivo and appears to predispose mammary epithelium to neoplasia and carcinoma.     

Assessment of methods to determine minimal cellulase concentrations for efficient hydrolysis of cellulose

Summary The enzyme loading needed to achieve substrate saturation appeared to be the most economical enzyme concentration to use for hydrolysis, based on percentage hydrolysis. Saturation was reached at 25 filter paper units per gram substrate on Solka Floc BW300, as determined by studying (a) initial adsorption of the cellulase preparation onto the substrate, (b) an actual hydrolysis or (c) a combined hydrolysis and fermentation (CHF) process. Initial adsorption of the cellulases onto the substrate can be used to determine the minimal cellulase requirements for efficient hydrolysis since enzymes initially adsorbed to the substrate have a strong role in governing the overall reaction. Trichoderma harzianum E58 produces high levels of -glucosidase and is able to cause high conversion of Solka Floc BW300 to glucose without the need for exogenous -glucosidase. End-product inhibition of the cellulase and -glucosidase can be more effectively reduced by employing a CHF process than by supplemental -glucosidase.Offprint requests to: C. M. Hogan     

Giving between generations in American families

This paper documents the types and amounts of aid exchanged between adults and their non-coresidential parents. Data for the study are drawn from a representative national sample survey of Americans age 19 and older conducted in 1987–1988. Exchanges of monetary and material resources, childcare, household assistance, and companionship and advice are considered. Patterns of intergenerational exchange are found to differ by gender, family structure, age, ethnicity, and socioeconomic situation. Differences in exchange between males and females and between whites and Mexican-Americans are related to other life-course characteristics, and to the availability and proximity of kin. Blacks and persons living in poverty are shown to be less involved than other groups in intergenerational exchanges. Finally, patterns of prior assistance and the available needs and resources of the respondents and their parents are found to influence current patterns of exchange. Support for this research was provided by NICHD Grant No. 1 R01 HD26070-01, “Intergenerational Exchanges in Families with Children,” Dennis P. Hogan, Principal Investigator. Funds for the computer analysis were provided by the Pennsylvania State University Intercollege Research Programs. David Eggebeen is an Assistant Professor of Human Development in the Department of Human Development and Family Studies and a research associate at the Population Issues Research Center at Pennsylvania State University. He trained in sociology and demography at the University of North Carolina. His current research interests, besides those related to intergenerational relations, are the recent changes in the demographic structure of childhood in America and their implications for children’s social and economic well-being. Dennis P. Hogan is a professor of sociology and the director of the Population Issues Research Center at Pennsylvania State University. His current research interests, besides those related to intergenerational relations, are in the interrelation of social structures and the demographic life course. He is coauthor with David I. Kertzer ofFamily, Political Economy, and Demographic Change: The Transformation of Life in Casalecchio, Italy, 1861–1921, University of Wisconsin Press, 1989.     

A Common Region of Deletion on Chromosome 17q in Both Sporadic and Familial Epithelial Ovarian Tumors Distal to BRCA1

Linkage analysis in familial breast and ovarian cancer and studies of allelic deletion in sporadic ovarian tumors have identified a region on chromosome 17q containing a candidate tumor-suppressor gene (referred to as BRCA1) of likely importance in ovarian carcinogenesis. We have examined normal and tumor DNA samples from 32 patients with sporadic and 8 patients with familial forms of the disease, for loss of heterozygosity (LOH) at 21 loci on chromosome 17 (7 on 17p and 14 on 17q). LOH on 17p was 55% (22/40) for informative 17pl3.1 and 17pl3.3 markers. When six polymorphic markers flanking the familial breast/ovarian cancer susceptibility locus on 17ql2-q21 were used, LOH was 58% (23/40), with one tumor showing telomeric retention. Evaluation of a set of markers positioned telomeric to BRCA1 resulted in the highest degree of LOH, 73% (29/40), indicating that a candidate locus involved in ovarian cancer may reside distal to BRCA1. Five of the tumors demonstrating allelic loss for 17q markers were from individuals with a strong family history of breast and ovarian cancer. More important, two of these tumors (unique patient number [UPN] 57 and UPN 79) retained heterozygosity for all informative markers spanning the BRCA1 locus but showed LOH at loci distal to but not including the anonymous markers CMM86 (D17S74) and 42D6 (D17S588), respectively. Deletion mapping of seven cases (two familial and five sporadic) showing limited LOH on 17q revealed a common region of deletion, distal to GH and proximal to D17S4, that spans −25 cM. These results suggest that a potential tumor-suppressor gene involved in both sporadic and familial ovarian cancer may reside on the distal portion of chromosome 17q and is distinct from the BRCA1 gene.