Browsing by Author "Vitzthum, Virginia J"

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Calculations of analyte loss in experiments conducted by Banerjee et al. (1985, Table 2)
Vitzthum, Virginia J
Banerjee, Levitz, and Rosenberg (Steroids 46, 967, Dec 1985) investigated the stability of salivary progesterone in glass, polypropylene, and polyethylene storage vials. Occasionally, Banerjee et al. are misquoted as having stated that polypropylene tubes are not suitable for storing saliva intended for progesterone assays. This is not the case: Banerjee et al extoled the use of glass vials for untreated saliva samples kept at room temperature for 72 hours, showed that polyethylene tubes were particularly poor for such storage (approximately 45% loss of analyte), and showed that polypropylene tubes had a much smaller analyte loss (approximately 17%). Banerjee et al also showed that for storage at -20C, polypropylene tubes had only very small losses (2%). Here we present Banerjee et al's results in a convenient and readily-understandable form.
data set for article "Links among inflammation, sexual activity and ovulation: Evolutionary trade-offs and clinical implications"
Lorenz, Tierney K; Worthman, Carol M; Vitzthum, Virginia J
How It Works: The Biological Mechanisms that Generate Demographic Diversity
Vitzthum, Virginia J
Tinbergen (1963) proposed that a complete understanding of any behavior requires knowledge of its function, evolutionary history, developmental history, and mechanism of operation. This chapter is largely concerned with gaining some insight into the nature of the biological mechanisms generating variation in human fertility and, consequently, demographic diversity within and across populations. My inquiry is informed by life history theory, an analytical framework within evolutionary theory for studying maturation, reproduction, and aging and the associated behavioral and physiological mechanisms underlying the allocation of resources to these processes. Different allocation patterns are referred to as life history strategies (LHSs) and are subject to natural selection. Biological mechanisms can be usefully conceptualized as a set of suitably timed strategic responses to signals. I discuss this and other ideas about the mechanisms that underlie the implementation of LHSs, and introduce the concepts of "ecomarkers" and "the physiological fallacy." Drawing on empirical studies and theoretical models, I examine some intriguing features of human reproductive physiology that are directly relevant to demographic research in both low- and high-fertility populations. Several points, some contrary to common assumptions, emerge from this inquiry. For example: (1) The marked within- and between-population variation in many features of female reproductive functioning challenges the widespread assumption that there is a universal "normal" human biology. (2) The most likely outcome of a human conception is early loss. This unseen natural selection in the production of offspring may hamper investigations of hypothesized associations of post-natal reproductive success with resources or with offspring quality, even in low fertility populations. (3) Competition between incompatible but essential functions shape the timing and operation of various mechanisms. Some biological, psychological and behavioral functions cannot readily co-occur. Of necessity, successful LHSs must juggle such incompatibilities regardless of the abundance of energy and other resources, therefore some reproductive mechanisms may not depend upon (or be responsive to) energy availability. (4) Biomedically, the absence of ovulation is typically considered a pathology (and in some cases it may be). But from a life history perspective, each option of ovulating/not ovulating is a fork in the reproductive road at which there is a strategic decision to continue engaging in the possibility of reproduction or to forego the current opportunity. Not ovulating in a given cycle can be the best strategy for optimizing lifetime reproductive success.
Protocol for extraction and enzyme immunosorbent assay (ELISA) of progesterone or estradiol from human salivary samples preserved with or without sodium azide (protocol v1.0).
Chester, Emily M; Vitzthum, Virginia J
Field research in remote areas presents many challenges, often including a lack of facilities and resources for maintaining a cold chain to preserve samples at low temperatures until they can be assayed in a laboratory. Cold-chains are necessary for the storage and transport of many types of biological samples (e.g., blood, urine and saliva) in order to reduce degradation and inhibit bacterial and fungal growth. One alternative to a cold chain is to add sodium azide, a potent antimicrobial, to each biological sample. However, sodium azide is incompatible with commercial enzyme immunoassay (EIA) kits that use horseradish peroxidase, an enzyme inactivated by sodium azide. To address this problem, we tested and validated EIA protocols that use an alternative enzyme, alkaline phosphatase. These protocols can be used for the measurement of steroid hormones in salivary samples that have been preserved with sodium azide, thus eliminating the trouble and expense of maintaining a cold chain from the field to the lab.