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Biomedical subjects

S Hagan

Publications and source records attributed to S Hagan.

27 records · Page 2Linked to original sources
PubMed1994

Quantum optical coherence in cytoskeletal microtubules: implications for brain function.

'Laser-like,' long-range coherent quantum phenomena may occur biologically within cytoskeletal microtubules. This paper presents a theoretical prediction of the occurrence in biological media of the phenomena which we term 'superradiance' and 'self-induced transparency'. Interactions between the electric dipole field of water molecules confined within the hollow core of microtubules and the quantized electromagnetic radiation field are considered, and microtubules are theorized to play the roles of non-linear coherent optical devices. Superradiance is a specific quantum mechanical ordering phenomenon with characteristic times much shorter than those of thermal interaction. Consequently, optical signalling (and computation) in microtubules would be free from both thermal noise and loss. Superradiant optical computing in networks of microtubules and other cytoskeletal structures may provide a basis for biomolecular cognition and a substrate for consciousness.

Animals↗
PubMed1992

The feasibility of a public-private long-term care financing plan.

In this study, the feasibility of a public-private long-term care (LTC) financing plan that would combine private LTC insurance with special Medicaid eligibility requirements was assessed. The plan would also raise the Medicaid asset limit from the current $2,000 to the value of an individual's insurance benefits. After using benefits the individual could enroll in Medicaid. Thus, insurance would substitute for asset spend-down, protecting individuals against catastrophic costs. This financing plan was analyzed through a computer model that simulated lifetime LTC use for a middle-income age cohort beginning at 65 years of age. LTC payments from Medicaid, personal income and assets, Medicare, and insurance were projected by the model. Assuming that LTC use and costs would not grow beyond current projections, the proposed plan would provide asset protection for the cohort without increasing Medicaid expenditures. In contrast, private insurance alone, with no change in Medicaid eligibility, would offer only limited asset protection. The results must be qualified, however, because even a modest increase in LTC cost growth or use of care (beyond current projections) could result in substantially higher Medicaid expenditures. Also, private insurance might increase personal LTC expenditures because of the added cost of insuring.

Aged↗
PubMed1991

Medicaid spenddown among nursing home residents in Wisconsin.

We examined Medicaid spenddown among nursing home residents from 72 facilities in Wisconsin during 1988. Results indicate that only a small proportion (12%) of discharges from these facilities had spent down to Medicaid eligibility. This represents about one-fourth (23%) of persons who had been admitted private pay. Moreover, we estimated that over 40% of those who spent down to Medicaid did so within 6 months, 58% spent down within a year, and 76% spent down within 2 years. Even though a relatively small percentage of residents spent down, this group had very long stays (median stay greater than 3 years) and thus contributed quite heavily to nursing home days.

Aged↗
PubMed1987

Tissue specific methylation of c-myc in adult chickens.

Methylation of cytosine in DNA has long been correlated with modulation of specific gene expression in eukaryotes. Methylation of the c-myc locus was examined in six tissues from adult Leghorn chickens. The c-myc locus was found to be variably methylated in all examined tissues, except blood, where erythrocytic DNA showed no evidence of significant methylation of c-myc. This is contrasted with the observed sever methylation of the beta actin locus and the generally high methylation patterns found in avian erythrocytic DNA.

Actins↗
PubMed1986

Oral nicotine induces an atherogenic lipoprotein profile.

Male squirrel monkeys were used to evaluate the effect of chronic oral nicotine intake on lipoprotein composition and metabolism. Eighteen yearling monkeys were divided into two groups: 1) Controls fed isocaloric liquid diet; and 2) Nicotine primates given liquid diet supplemented with nicotine at 6 mg/kg body wt/day. Animals were weighed biweekly, plasma lipid, glucose, and lipoprotein parameters were measured monthly, and detailed lipoprotein composition, along with postheparin plasma lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) activity, was assessed after 24 months of treatment. Although nicotine had no effect on plasma triglyceride or high density lipoproteins (HDL), the alkaloid caused a significant increase in plasma glucose, cholesterol, and low density lipoprotein (LDL) cholesterol plus protein while simultaneously reducing the HDL cholesterol/plasma cholesterol ratio and animal body weight. Levels of LDL precursors, very low density (VLDL) and intermediate density (IDL) lipoproteins, were also lower in nicotine-treated primates while total postheparin lipase (LPL + HTGL) activity was significantly elevated. Our data indicate that long-term consumption of oral nicotine induces an atherogenic lipoprotein profile (increases LDL, decreases HDL/total cholesterol ratio) by enhancing lipolytic conversion of VLDL to LDL. These results have important health implications for humans who use smokeless tobacco products or chew nicotine gum for prolonged periods.

Administration, Oral↗
PubMedDate not supplied

Cultured human retinal pigment epithelial cells differentially express thrombospondin-1, -2, -3, and -4.

Thrombospondins are a family of at least five proteins (TSP-1 to -4 and cartilage oligomeric matrix protein or COMP) whose functions are indeterminate. Distribution differences between family members suggest each protein may have some distinct functions. The retinal pigment epithelium (RPE) has divers unusual roles for an epithelia and can produce TSP-1. However, the wide range of RPE activities suggests that, if different thrombospondin family members do have different functions, RPE may express thrombospondins additional to TSP-1. Therefore, we analysed expression of thrombospondin isoforms by RPE using reverse-transcription-linked polymerase chain reaction. Cultured cells exhibited differential expression of TSP-1 to -4; TSP-2 and TSP-4 appearing later in culture than TSP-1 and TSP-3. In situ RPE expressed mRNA for TSP-1 to -4. No COMP mRNA was detected in RPE. These observations suggest that thrombospondin isoforms are regulated differently by the cells and that these proteins may have different functions in the RPE.

Adult↗