Different subjects: the health care system's participation in the differential construction of the cultural citizenship of Cuban refugees and Mexican immigrants

This paper explores the public health system's differential construction of Mexican and Cuban immigrants' "deservingness" of citizenship benefits and its preparation of them for different roles in U.S. society. Civic institutions such as the public health care system are charged with inculcating normative behavior in immigrants and instilling in them different conceptions about their rights and responsibilities. Faced with limited resources under the implementation of Medicaid managed care, hospital administrators created new categories of "deserving" and "undeserving" immigrants based on neoliberal standards of individual responsibility and self-discipline. As a result, hospital policies construct different types of "cultural citizenship" for Cuban and Mexican immigrants, preparing the former to be active citizens and discouraging the latter from pressing demands on American civil institutions. I show that this negative construction of Mexican immigrants' moral worth leads to unmet health needs and poor health outcomes.     

Deletions in the transmembrane domain of a sindbis virus glycoprotein alter virus infectivity, stability, and host range

The alphaviruses are composed of two icosahedral protein shells, one nested within the other. A membrane bilayer derived from the host cell is sandwiched between the protein shells. The protein shells are attached to one another by protein domains which extend one of the proteins of the outer shell through the membrane bilayer to attach to the inner shell. We have examined the interaction of the membrane-spanning domain of one of the membrane glycoproteins with the membrane bilayer and with other virus proteins in an attempt to understand the role this domain plays in virus assembly and function. Through incremental deletions, we have reduced the length of a virus membrane protein transmembrane domain from its normal 26 amino acids to 8 amino acids. We examined the effect of these deletions on the assembly and function of virus particles. We found that progressive truncations in the transmembrane domain profoundly affected production of infectious virus in a cyclic fashion. We also found that membrane composition effects protein-protein and protein-membrane interactions during virus assembly.     

Aging alters circadian and light-induced expression of clock genes in golden hamsters

Aging alters numerous aspects of circadian biology, including the amplitude of rhythms generated by the suprachiasmatic nuclei (SCN) of the hypothalamus, the site of the central circadian pacemaker in mammals, and the response of the pacemaker to environmental stimuli such as light. Although previous studies have described molecular correlates of these behavioral changes, to date only 1 study in rats has attempted to determine if there are age-related changes in the expression of genes that comprise the circadian clock itself. We used in situ hybridization to examine the effects of age on the circadian pattern of expression of a subset of the genes that comprise the molecular machinery of the circadian clock in golden hamsters. Here we report that age alters the 24-h expression profile of Clock and its binding partner Bmal1 in the hamster SCN. There is no effect of age on the 24-h profile of either Per1 or Per2 when hamsters are housed in constant darkness. We also found that light pulses, which induce smaller phase shifts in old animals than in young, lead to decreased induction of Per1, but not of Per2, in the SCN of old hamsters.     

Twenty-four-hour profiles of serum leptin in siberian and golden hamsters: photoperiodic and diurnal variations

Serum leptin concentrations were obtained from male Siberian hamsters (Phodopus sungorus) and golden hamsters (a.k.a. Syrian, Mesocricetus auratus) housed on long [light:dark (LD) 16:8] and short (LD 6:18) photoperiods for 10-11 weeks. Blood samples were collected at 45-min intervals for 24 h from individual animals using an in-dwelling atrial catheter. In Siberian hamsters, exposure to short photoperiods as compared to long photoperiods reduced body weight (32.5 +/- 1.5 vs 47.7 +/- 1.1 g) and leptin (24-h mean: 5.3 +/- 0.4 ng/ml vs 18.6 +/- 2.1 ng/ml). Although photoperiod influenced the temporal distribution of leptin in golden hamsters, the main effect of photoperiod on leptin levels in golden hamsters did not reach significance (24-h mean: 7.1 +/- 1.0 ng/ml vs 5.1 +/- 0.8 ng/ml.). Body weights of golden hamsters did not vary significantly following exposure to short photoperiod for 11 weeks (178.3 +/- 3.6 g in LD 6:18 vs 177.8 +/- 7.3 g in LD 16:8). There was no nocturnal increase in serum leptin in either species. Marked interindividual differences were apparent in individual leptin profiles. Periodogram analysis revealed that only a few animals exhibited 24-h periodicities; the presence of a significant 24-h periodicity was more common in hamsters exposed to short days. Photoperiod-associated differences in the 24-hour profile of leptin secretion may be the result of photoperiod-associated changes in feeding behavior or metabolism. A full understanding of the regulation of leptin secretion in multiple time domains may enhance our understanding of the function of leptin.     

Chlorophyll fluorescence quenching in isolated light harvesting complexes induced by zeaxanthin

Non-photochemical quenching of chlorophyll fluorescence in plants occurs in the light harvesting antenna of photosystem II and is regulated by the xanthophyll cycle. A new in vitro model for this process has been developed. Purified light harvesting complexes above the detergent critical micelle concentration have a stable high fluorescence yield but a rapidly inducible fluorescence quenching occurs upon addition of zeaxanthin. Violaxanthin was without effect, lutein and antheraxanthin induced a marginal response, whereas the violaxanthin analogue, auroxanthin, induced strong quenching. Quenching was not caused by aggregation of the complexes but was accompanied by a spectral broadening and red shift, indicating a zeaxanthin-dependent alteration in the chlorophyll environment.     

Adaptive response to cold temperatures and characterization of cspA in Salmonella typhimurium LT2

Salmonella typhimurium is a major foodborne microbial pathogen which primarily contaminates poultry products causing salmonellosis in humans. S. typhimurium LT2 cultures, when transferred from 37 °C to 5 °C or 10 °C, showed an initial lag period in growth with an approximate generation time of 10–25 h. Western blot assay using E. coli CS7.4 antibody and analysis of radiolabeled total cellular proteins from S. typhimurium cultures after exposure to 10 °C or 5 °C showed elevated expression of a major cold shock protein, CS7.4. Identification of a decreased level of CS7.4 at 37 °C suggests that the expression of this protein may require a large temperature downshift. Putative regulatory protein binding segment on the 5-untranslated region referred as Fragment 7 in S. typhimurium exhibited a 90.6% and a 56.25% nucleotide sequence identity when compared with the Fragment 7 of E. coli and S. enteritidis, respectively. The differences in the nucleotide sequence within the Fragment 7 between S. typhimurium and S. enteritidis may explain the differential expression of CspA at 37 °C. The nucleotide sequence of the open reading frame of S. typhimurium cspA gene showed a single base difference at 816 bp position from a G to a C which altered the amino acid residue from a glycine to an alanine. In addition to CspA, an elevated expression of a 105 kDa, and decreased expression of 6 proteins were evidenced when cultures of S. typhimurium were exposed to 10 °C or 5 °C. Differential expression of the CspA and other proteins in S. typhimurium following exposure to cold temperatures suggest that adaptation and continued growth and survival at cold temperatures in this pathogen may be aided by these cold-responsive proteins.     

Electron acceptors in isolated intact spinach chloroplasts act hierarchically to prevent over-reduction and competition for electrons

Electron fluxes in isolated intact spinach chloroplasts were analyzed under saturating light and under optimal CO₂ and P_i supply. When CO₂ assimilation was the only ATP- and NADPH-consuming reaction, the ΔpH decreased and the chloroplasts showed clear evidence of over-reduction. This suggested that additional electron flow is required in order to maintain the ΔpH and the stromal NADPH/ATP ratio. The additional electron flow may be cyclic electron transport around Photosystem I and linear electron transport towards either oxaloacetate or O₂. The contributions of, and the interrelationships between, these three electron transfer pathways were analyzed by following the reactions of chloroplasts in their presence or absence, and by monitoring to what extent they were able to compensate for each other. Inhibition of cyclic electron flow by antimycin A caused strong over-reduction and decreased the ΔpH. Only oxaloacetate, but not O₂, was able to restore photosynthesis. In the presence of H₂O₂, there was a rapid build-up of a high ΔpH, and the reduction of any other electron acceptor was prevented. It is concluded that the different electron acceptors in the stroma are organized in a hierarchical manner; this allows electron flux towards CO₂ and nitrite reduction to proceed without any competition for electrons, and any excess electrons to be taken by these additional non-assimilatory pathways. Hence, the ΔpH is maintained at the required level and over-reduction of the electron transport chain and the stromal redox components is avoided. This revised version was published online in June 2006 with corrections to the Cover Date.     

Growth plate formation and development in alligator and mouse metapodials: evolutionary and functional implications

Mammalian metapodials (metacarpals and metatarsals), unlike most long bones, form a single growth plate, and undergo longitudinal growth at only one end. The growth dynamics of non-mammalian tetrapod metapodials have not been systematically examined in order to determine if unidirectional growth is unique to mammals. Here we compare murine metapodial ossification in growth stages that parallel those of embryonic, juvenile and subadult American alligators (Alligator mississippiensis). Safranin O staining was used for qualitative histology, and chondrocyte differentiation and proliferation were assessed via immunohistochemistry for type X collagen and proliferative cell nuclear antigen (PCNA). We establish that growth plates form at both ends of alligator metapodials and are maintained in the subadult. PCNA results show that alligators and mice share common patterns of chondrocyte proliferation during growth plate formation. In addition, while alligators and mice differ initially in the degree of organization and pace of chondrocyte differentiation, these parameters are largely similar in established growth plates. However, the replacement of cartilage by bone is highly irregular throughout growth in the alligator, in contrast to the more uniform process in the mouse. These results indicate that while alligators and mammals share common mechanisms of chondrocyte regulation, they differ substantially in their processes of ossification. Phylogenetic analysis indicates that the direct ossification of one epiphysis and reliance on a single growth plate is a derived character (synapomorphy) in therian mammals and likely indicates an adaptation for erect quadrupedal gait.