ABSTRACT: Textbooks are an expression of the state of development of a discipline at a given moment in time. By reviewing eight epidemiology textbooks published over the course of a century, we have attempted to trace the evolution of five epidemiologic concepts and methods: study design (cohort studies and case-control studies), confounding, bias, interaction and causal inference. Overall, these eight textbooks can be grouped into three generations. Greenwood (1935) and Hill (first edition 1937; version reviewed 1961)'s textbooks belong to the first generation, "early epidemiology", which comprise early definitions of bias and confounding. The second generation, "classic epidemiology", represented by the textbooks of Morris (first edition 1957; version reviewed 1964), MacMahon & Pugh (first edition 1960; version reviewed 1970), Susser (1973), and Lilienfeld & Lilienfeld (first edition 1976; version reviewed 1980), clarifies the properties of cohort and case-control study designs and the theory of disease causation. Miettinen (1985) and Rothman (1986)'s textbooks belong to a third generation, "modern epidemiology", presenting an integrated perspective on study designs and their measures of outcome, as well as distinguishing and formalizing the concepts of confounding and interaction. Our review demonstrates that epidemiology, as a scientific discipline, is in constant evolution and transformation. It is likely that new methodological tools, able to assess the complexity of the causes of human health, will be proposed in future generations of textbooks.
Sozial- und Präaventivmedizin SPM 02/2004; 49(2):97-104. · 0.82 Impact Factor
ABSTRACT: Hormone levels change significantly with increasing age. These changes may be related to, or be associated with, the emergence of age-related diseases, such as Alzheimer's disease (AD).
Five hundred and seventy-six women over the age of 65 were studied from the Washington Heights-Inwood Columbia Aging Project (WHICAP). These women were selected from a group of healthy Medicare beneficiaries that were aged 65 and older living in the geographically defined area of northern Manhattan in New York City. Serum levels of estrone (E1), estradiol (E2), total testosterone (TT), dehydroepiandosterone (DHEA), luteinizing hormone (LH), follicle stimulating hormone (FSH), and sex-hormone binding globulin (SHBG) were measured.
Significant differences were found between patients with AD and controls only in the level of SHBG, which was 20% higher in patients compared to controls (68.5nmol/l versus 54.7nmol/l, P<0.001). We also estimated levels of total E2 because after menopause, E2 is largely derived from E1. AD patients had significantly lower levels of estimated E2 (AD 0.46 versus controls 0.49, P<0.01). Differences remained significant after adjusting for age, ethnic group, education, and body mass index (BMI).
A marked increase in SHBG levels was found in AD patients. SHBG normally responds to circulating testosterone and estrogen, therefore, elevated SHBG suggests an abnormal increase in its production and regulation. Further work is needed to clarify the cause and consequences of this observation.
Neurobiology of Aging 02/2004; 25(2):141-7. · 6.19 Impact Factor
ABSTRACT: The expression and localization of glucose transporter isoforms play essential roles in the glucoregulatory activities of the hippocampus and ultimately contribute to cognitive status in physiological and pathophysiological settings. The recently identified glucose transporter GLUT8 is uniquely expressed in neuronal cell bodies in the rat hippocampus and therefore may contribute to hippocampal glucoregulatory activities. We show here that GLUT8 has a novel intracellular distribution in hippocampal neurons and is translocated to intracellular membranes following glucose challenge. Immunoblot analysis revealed that GLUT8 is expressed in high-density microsomes (HDM), suggesting that GLUT8 is associated with intracellular organelles under basal conditions. Immunogold electron microscopic analysis confirmed this observation, in that GLUT8 immunogold particles were associated with the rough endoplasmic reticulum (ER) and cytoplasm. Peripheral glucose administration produced a rapid twofold increase in GLUT8 levels in the HDM fraction while decreasing GLUT8 levels in low-density microsomes. Similarly, peripheral glucose administration significantly increased GLUT8 association with the rough ER in the hippocampus. Conversely, under hyperglycemic/insulinopenic conditions, namely, in streptozotocin (STZ) diabetes, hippocampal GLUT8 protein levels were decreased in the HDM fraction. These results demonstrate that GLUT8 undergoes rapid translocation to the rough ER in the rat hippocampus following peripheral glucose administration, trafficking that is impaired in STZ diabetes, suggesting that insulin serves as a stimulus for GLUT8 translocation in hippocampal neurons. Because glucose is liberated from oligosaccharides during N-linked glycosylation events in the rough ER, we propose that GLUT8 may serve to transport glucose out of the rough ER into the cytosol and in this manner contribute to glucose homeostasis in hippocampal neurons.
The Journal of Comparative Neurology 11/2002; 452(2):103-14. · 3.81 Impact Factor
ABSTRACT: Fluorescence immunohistochemistry was performed to characterize the distribution and phenotype of GLUT8-positive neurons in rat brain and to compare the cellular distribution of GLUT8 with GLUT3 in the hippocampus. Based upon the absence of co-localization with the non-neuronal markers GFAP (astroglial) and OX42 (microglial), it appears that GLUT8 is expressed exclusively in neurons. At the cellular level, GLUT8 immunofluorescence was localized to neuronal cell bodies and the most proximal dendrites of inhibitory and excitatory neurons while GLUT3 immunofluorescence was localized to the neuropil in the hippocampus. These results demonstrate that GLUT8 is a neuron-specific glucose transporter expressed in the neuronal cell bodies of excitatory and inhibitory neurons in the rat hippocampus.
Brain Research 05/2002; 932(1-2):129-34. · 2.73 Impact Factor
ABSTRACT: We describe the localization of the recently identified glucose
transporter GLUTx1 and the regulation of GLUTx1 in the hippocampus of
diabetic and control rats. GLUTx1 mRNA and protein exhibit a unique
distribution when compared with other glucose transporter isoforms
expressed in the rat hippocampus. In particular, GLUTx1 mRNA was
detected in hippocampal pyramidal neurons and granule neurons of the
dentate gyrus as well as in nonprincipal neurons. With
immunohistochemistry, GLUTx1 protein expression is limited to neuronal
cell bodies and the most proximal dendrites, unlike GLUT3 expression
that is observed throughout the neuropil. Immunoblot analysis of
hippocampal membrane fractions revealed that GLUTx1 protein expression
is primarily localized to the intracellular compartment and exhibits
limited association with the plasma membrane. In streptozotocin
diabetic rats compared with vehicle-treated controls, quantitative
autoradiography showed increased GLUTx1 mRNA levels in pyramidal
neurons and granule neurons; up-regulation of GLUTx1 mRNA also was
found in nonprincipal cells, as shown by single-cell emulsion
autoradiography. In contrast, diabetic and control rats expressed
similar levels of hippocampal GLUTx1 protein. These results indicate
that GLUTx1 mRNA and protein have a unique expression pattern in rat
hippocampus and suggest that streptozotocin diabetes increases
steady-state mRNA levels in the absence of concomitant increases in
GLUTx1 protein expression.
Proceedings of the National Academy of Sciences 02/2001; 98(5):2820-2825. · 9.68 Impact Factor