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Open Access Publications from the University of California

Scholarly Works (4 results)

  • Thesis
  • Peer Reviewed
UC Berkeley Electronic Theses and Dissertations (2013)

This thesis consists of two empirical studies of the industrial organization of food retailing.

Chapter 1 investigates consumer behavior in response to changes in variety in grocery store offerings. Using a rich panel dataset of consumer purchases from one national retailer, we measure the effects of changes in product variety on sales of ice cream, where the assortment changes were gradually introduced to stores. We use a difference in differences approach to measure treatment effects against trends in stores prior to treatment. Our results show an adjustment to product variety causes consumers to alter their purchasing behavior, at least in the subsequent eight weeks of the change. When the rearrangement consisted of adding additional products, consumers purchased more on average in the immediate term, but sales increases mitigated over time, with smaller magnitude increases in variety experiencing sales reductions in later weeks. Product groups treated with reduced variety experienced decreased sales both in the immediate and longer term. We find that extending and reducing assortment have asymmetric effects, with a marginal change to increased variety boosting sales less than a marginal change in decreased variety. Larger magnitude reductions perform poorly in the short run, but actually perform better than both smaller variety reductions and small variety increases in later weeks.

In Chapter 2, I investigate the following question: do firms respond to quality disclosure by nearby competitors? This paper utilizes exogenous variation provided by Los Angeles County's introduction of restaurant hygiene grade cards to explore inter-firm responses in markets for differentiated goods. Under this program, a subset of cities adopted mandatory grade card posting, requiring restaurants to disclose hygiene. This study demonstrates that restaurants under a voluntary hygiene disclosure policy improved hygiene more when located closer to restaurants in mandatory disclosure areas. The proximity effect implies that mandatory disclosure policies influenced restaurant hygiene in nearby voluntary disclosure areas, thus providing direct evidence that quality-disclosure regulations affect non-targeted firms.

    Cover page: Essays on the Industrial Organization of Food Retailing
    • Article
    • Peer Reviewed
    UC San Francisco Previously Published Works (2013)
    The cell-autonomous role of synaptic transmission in the regulation of neuronal structural and electrical properties is unclear. We have now employed a genetic approach to eliminate glutamatergic synaptic transmission onto individual CA1 pyramidal neurons in a mosaic fashion in vivo. Surprisingly, while electrical properties are profoundly affected in these neurons, as well as inhibitory synaptic transmission, we found little perturbation of neuronal morphology, demonstrating a functional segregation of excitatory synaptic transmission from neuronal morphological development.
      Cover page: The Cell-Autonomous Role of Excitatory Synaptic Transmission in the Regulation of Neuronal Structure and Function
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2014)
      The spatiotemporal activities of astrocyte Ca²⁺ signaling in mature neuronal circuits remain unclear. We used genetically encoded Ca²⁺ and glutamate indicators as well as pharmacogenetic and electrical control of neurotransmitter release to explore astrocyte activity in the hippocampal mossy fiber pathway. Our data revealed numerous localized, spontaneous Ca²⁺ signals in astrocyte branches and territories, but these were not driven by neuronal activity or glutamate. Moreover, evoked astrocyte Ca²⁺ signaling changed linearly with the number of mossy fiber action potentials. Under these settings, astrocyte responses were global, suppressed by neurotransmitter clearance, and mediated by glutamate and GABA. Thus, astrocyte engagement in the fully developed mossy fiber pathway was slow and territorial, contrary to that frequently proposed for astrocytes within microcircuits. We show that astrocyte Ca²⁺ signaling functionally segregates large volumes of neuropil and that these transients are not suited for responding to, or regulating, single synapses in the mossy fiber pathway.
        Cover page: Conditions and constraints for astrocyte calcium signaling in the hippocampal mossy fiber pathway.
        • Article
        • Peer Reviewed
        UC San Diego Previously Published Works (2014)
        It is generally accepted that healthy cells degrade their own mitochondria. Here, we report that retinal ganglion cell axons of WT mice shed mitochondria at the optic nerve head (ONH), and that these mitochondria are internalized and degraded by adjacent astrocytes. EM demonstrates that mitochondria are shed through formation of large protrusions that originate from otherwise healthy axons. A virally introduced tandem fluorophore protein reporter of acidified mitochondria reveals that acidified axonal mitochondria originating from the retinal ganglion cell are associated with lysosomes within columns of astrocytes in the ONH. According to this reporter, a greater proportion of retinal ganglion cell mitochondria are degraded at the ONH than in the ganglion cell soma. Consistently, analyses of degrading DNA reveal extensive mtDNA degradation within the optic nerve astrocytes, some of which comes from retinal ganglion cell axons. Together, these results demonstrate that surprisingly large proportions of retinal ganglion cell axonal mitochondria are normally degraded by the astrocytes of the ONH. This transcellular degradation of mitochondria, or transmitophagy, likely occurs elsewhere in the CNS, because structurally similar accumulations of degrading mitochondria are also found along neurites in superficial layers of the cerebral cortex. Thus, the general assumption that neurons or other cells necessarily degrade their own mitochondria should be reconsidered.
          Cover page: Transcellular degradation of axonal mitochondria
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