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Biomedical subjects

S Nichols

Publications and source records attributed to S Nichols.

At least 37 records · Page 2Linked to original sources
PubMed1996

Epidemiological, clinical, and neuropathological study of apolipoprotein E genotype in Alzheimer's disease.

Our studies of the APOE genotype in AD confirm a strong association of the epsilon 4 allele with development of AD and a decreased risk associated with epsilon 2. From a clinical/neuropathological perspective, the major effects of APOE epsilon 4 are to lower the age of onset and to increase the amount of A beta deposit in the brain. Neither rate of progression nor number of neurofibrillary tangles were affected. We also carried out a longitudinal population-based assessment of the APOE genotype to determine the risk for developing cognitive impairment of someone in the general population based on APOE genotype. APOE epsilon 4 carried about 1.4-fold increased risk, and APOE epsilon 2 about 1.7-fold decreased risk. Thus, inheritance of APOE epsilon 4 is a major biological risk factor for AD, but it has limited utility as a prognostic indicator for development of dementia in an individual.

Age of Onset↗
PubMed1996

Apolipoprotein E and cognitive change in an elderly population.

The apolipoprotein E (apoE) epsilon 4 allele is overrepresented, and the apoE epsilon 2 allele underrepresented, in Alzheimer's disease. To assess the risk of cognitive impairment in individuals with these genotypes in the general population, we studied a population-based sample of 1,899 individuals 65 years and older as a follow-up to the Iowa 65+ Rural Health Study. Multiple regression and logistic regression analyses demonstrated significant effects of apoE epsilon 4 and apoE epsilon 2 in predicting performance on a delayed recall task over a 4- to 7-year period. The magnitude of this effect was, however, fairly modest, with odds ratios for developing impairment of approximately 1.37 (95% confidence interval: 1.007, 1.850; p = 0.045) for apoE epsilon 4 and 0.53 (95% confidence interval: 0.368, 0.777; p = 0.001) for apoE epsilon 2. These effects were more pronounced in women than men. Importantly, 85% of elderly apoE E4/4 individuals (average age, 81) scored in the unimpaired range on a screening mental status test. Thus, many individuals reach old age without cognitive impair- ment despite inheritance of one or two apoE epsilon 4 alleles. This suggests that apoE genotyping will have limited utility as a diagnostic or prognostic indicator of cognitive decline in individuals.

Aged↗
PubMed1996

Virologic markers of human immunodeficiency virus type 1 in cerebrospinal fluid of infected children.

To identify virologic correlates associated with central nervous system (CNS) abnormalities in children infected with human immunodeficiency virus type 1 (HIV-1), cerebrospinal fluid (CSF) was examined for virologic markers and correlated with neurodevelopmental status and neuroimaging abnormalities. Of 30 children, 18 (60%) had at least 1 culture-positive CSF sample; in total, 21 (55%) of 38 CSF specimens were culture-positive. CSF white blood cell counts were higher in specimens that were culture-positive (P = .01). HIV-1 RNA was detected in 90% of CSF samples, and RNA levels > or = 10,000 copies/mL were found in 6 (75%) of 8 children with severe neurocognitive impairment (P = .08) and 11 (73%) of 15 children with a cognitive index < or = 85 (P = .04). Higher RNA levels were associated with abnormal brain imaging scans (P = .04) and with neurocognitive deficits (P = .04). Thus, HIV-1 is present within the CNS of most infected children, and neurocognitive impairment appears to be associated with increased HIV-1 replication.

Adolescent↗
PubMed1995

Development of a direct viable count procedure for some gram-positive bacteria.

The direct viable count (DVC) is a procedure for enumerating viable-nonculturable cells. It should be noted, however, that bacteria demonstrating the viable but nonculturable phase have to date included only Gram-negative species, mainly because the DVC procedure does not lend itself to the analysis of Gram-positive bacteria since the DVC procedure is dependent on the bacterium being sensitive to nalidixic acid. The authors report here concerning studies on an analogous procedure for the direct enumeration of viable-nonculturable Gram-positive bacteria. To facilitate a differential DVC for Gram-positive bacteria, ciprofloxacin, enoxacin, norfloxacin or isopropyl cinodine were substituted for nalidixic acid. These antibiotics were chosen because, like nalidixic acid, they are DNA gyrase inhibitors. The concentrations used for each antibiotic were 1000 micrograms ml-1, 100 micrograms ml-1. Pure cultures of Staphylococcus aureus, Enterococcus faecalis, Streptococcus agalactiae, Listeria monocytogenes and Bacillus subtilis were obtained from the culture collection at the University of Wyoming and a faecal streptococcus was isolated from the Laramie wastewater treatment plant. An antibiotic and optimal concentration thereof was found which gave enlarged cells for all the organisms except the faecal streptococcus isolated from the wastewater plant for which no enlarged cells were ever seen. The antibiotic and concentration thereof which gave the optimal percent enlarged cells in the DVC procedure varied between organisms.

Anti-Bacterial Agents↗
PubMed1995

Tuberculosis knowledge among New York City injection drug users.

Structured interviews measuring tuberculosis knowledge were administered to 494 New York City injection drug users, 31% of whom reported a history of having a reactive tuberculin skin test. Medical records review of a subsample confirmed the validity of self-reported data. Most respondents understood the mechanisms of tuberculosis transmission. Three fourths of the subjects did not fully understand the distinction between a reactive skin test and active tuberculosis, but those who reported a history of skin test reactivity were twice as likely to understand this distinction. Forty percent of subjects did not understand the importance of medication adherence. Misunderstandings, based on a recent lack of tuberculosis education, may contribute to the fear and confusion that interfere with efforts to control tuberculosis.

Adolescent↗
PubMed1994

Preparations for AIDS vaccine trials. Retention, behavior change, and HIV-seroconversion among injecting drug users (IDUs) and sexual partners of IDUs.

The likelihood that subjects in human immunodeficiency virus (HIV) vaccine efficacy trials will alter their behavioral risks for HIV infection over time must be considered in evaluating the feasibility of such trials and in estimating the necessary sample sizes to be enrolled. Potential subjects for future vaccine efficacy trials include injecting drug users (IDUs) and others who may be difficult to retain in studies and who may alter HIV-risk-related behaviors substantially over time. We have investigated behavior change, retention, and HIV seroconversion among 577 New York City resident IDUs and sexual partners of IDUs enlisted between July 1 and December 31, 1992. We attempted to see all subjects every 3 months for interviews, blood donation and HIV testing. We were able to retain 68% of subjects in the study through the third scheduled recall at 7.5-10.5 months after enlistment. HIV seroconversion through March 1, 1994, was 1.33/100 person-years at risk. There was a significant inverse relationship between HIV seroconversion and retention at the 9-month recall after adjusting for age, gender, and the amount of locator information provided by subjects at enlistment. Among subjects seen at each of the scheduled visits at 3, 6, and 9 months after enrollment, modest but statistically significant behavior changes that reduced risk were observed in self-reported drug injection frequency, heroin injection frequency, sexual contact with IDUs, and sharing of needles/syringes. The magnitude of these changes in risk, however, was small and may be transient. The behavior changes observed to date do not appear to be large enough to substantially alter calculations of sample sizes needed in future HIV vaccine efficacy trials.

AIDS Vaccines↗
PubMed1994

LEEP: early experience with a new approach to cervical lesions.

The loop electrosurgical excision procedure (LEEP) is a new diagnostic and therapeutic approach for the management of cervical lesions found during the evaluation of abnormal findings from Papanicolaou smears. The procedure may be an alternative to laser therapy, cold knife conization, cryotherapy or hot cautery. The first 235 consecutive LEEPs performed at the Gundersen Clinic were reviewed 6 months after the last procedure was done. Twelve of 187 patients with follow up Papanicolaou smears and clinic visits had persistent disease. Nine of 187 patients had a repeat LEEP. LEEP was found to be a highly effective means for diagnosis and treatment as 98% of the patients were free of evidence of recurrent cervical lesions 6 months after the initial LEEP.

Electrosurgery↗
PubMed1993

Transgenic corn plants expressing MDMV strain B coat protein are resistant to mixed infections of maize dwarf mosaic virus and maize chlorotic mottle virus.

The maize dwarf mosaic virus strain B (MDMV-B) coat protein (cp) gene was cloned into a monocot expression cassette and introduced into sweet corn cell suspension cultures via particle bombardment or electroporation. Transformed cells were selected on culture media containing 300 mg/l kanamycin, and plants were regenerated. Cells from all transformed lines expressed the cp gene; and one transgenic line synthesized approximately 100-200 micrograms MDMV-cp per gram fresh weight. Plants regenerated from this line were challenged with a virus inoculum concentration adjusted to produce symptoms in nontransgenic controls at six days post inoculation. In growth chamber studies, the presence of the MDMV-cp provided resistance to inoculations with MDMV-A or MDMV-B and to mixed inoculations of MDMV and maize chlorotic mottle virus.

Base Sequence↗
PubMed1992

Computer-assisted morphometry: point, intersection, and profile counting and three-dimensional reconstruction.

The use of computers in morphometry can involve 1) automated image analysis, semiautomated image analysis and point, intersection, intercept and profile counts of two-dimensional images on tissue sections with mathematical extrapolation to the third dimension, 2) direct measurement of volumes, surfaces, lengths, and curvature using x,y,z coordinates of serial sectioned images, or 3) stereologic techniques and serial sections which is a combination of 1 and 2 above. Automated and semiautomated image analysis are generally restricted to specimens that are characterized by differential contrast such as interalveolar septa in the lung or histochemically stained mucous granules in pulmonary epithelium. Point, intersection, and profile counts using hand-held, notebook PCs, portable PCs, or standard PCs and MS-DOS-based application programs are extremely efficient, precise, affordable, and convenient methods of quantitating average values of a population. When morphometric measurements of individual structures are required, computer-assisted three-dimensional reconstruction using x,y,z coordinates of the surface outline from serial sections is a tedious yet precise method. We describe a computer program that efficiently estimates mean caliper diameter, volume, and surface area with less than five percent error with five sections per structure. We also describe a program that does digital image subtraction on serial sections, superimposes digitally generated test systems on biological images, and accumulates point, intersection, and profile counts using a Macintosh II series computer.

Animals↗
PubMed1992

The role of alterations in free radical metabolism in mediating cognitive impairments in Down's syndrome.

Down's syndrome (DS) is a genetic disorder involving an excess of chromosome 21 (trisomy 21) in approximately 96% of the cases and comprises approximately 15% of the population with mental retardation (Heller, 1969). In addition to the constitutional mental deficiencies associated with the syndrome many DS patients develop dementia associated with Alzheimer's disease (AD) in their later years of life (Thase et al., 1984). The genetic locus for Cu,Zn-superoxide dismutase (SOD1), a key enzyme in free radical metabolism, is located on chromosome 21, and the activity level of this enzyme is elevated by approximately 50% in a variety of cells of DS patients (see Kedziora and Bartosz, 1988; Sinet, 1982). Because alterations in free radical metabolism may be involved in neuronal death and may be associated with a number of pathological manifestations of DS, it is important to understand the role of free radical metabolism in cognitive impairments of DS, the topic discussed in this chapter.

Aging↗
PubMed1991

Pharmacokinetics of cefotaxime and desacetylcefotaxime in patients with liver disease.

The dispositions of cefotaxime and its metabolite desacetylcefotaxime were investigated in patients with different forms of chronic parenchymal liver disease (CPLD). A total of 31 subjects (27 patients and 4 controls) received a single 2-g dose of cefotaxime by infusion, and serial blood samples were drawn. The area under the concentration-time curve ranged from 176 to 241 micrograms.h/ml, the apparent half-life ranged from 1.49 to 2.42 h, and clearance ranged from 2.06 to 3.10 ml/min/kg in patients with four different forms of CPLD. The area under the concentration-time curve and the apparent half-life of desacetylcefotaxime ranged from 72 to 128 micrograms.h/ml and 7.1 to 13.4 h, respectively. Pharmacokinetic parameters were significantly different in patients with CPLD compared with those in control subjects and were related to clinical indices of hepatic impairment. Modest accumulation of cefotaxime in patients with severe hepatic impairment is unlikely to produce toxicity because of its high therapeutic index, and dosing modifications may not be required.

Adult↗
PubMed1991

Sexual behavior, attitudes toward safer sex, and gender among a cohort of 244 recovering i.v. drug users.

Heterosexual contact with drug users is a major route of AIDS transmission. This study of 135 male and 109 female methadone maintenance patients described subjects' sexual behavior, preventive practices and attitudes toward safer sex; explored ethnic-racial differences in high risk sexual behavior and attitudes; and examined the relationship between attitudes toward safer sex and frequency of condom use for men and women. Reported condom use was low, and it correlated with attitudes toward safer sex. Men tended to report higher rates of sexual risk-taking, although women reported more frequent sex with IV drug users. Study findings have implications for developing intervention strategies to reduce risk behavior associated with HIV transmission.

Adult↗
PubMed1990

Distribution and etiology of leishmaniasis in Colombia.

A total of 340 Leishmania strains, isolated from humans, animals, and sand flies from various regions of Colombia, were examined by isozyme electrophoresis. Seven different Leishmania species were identified. Leishmania panamensis and L. braziliensis were the most common, representing 53.8% and 30.3% of the total, respectively. Isolation rates of the other species were as follows: L. chagasi, 9.4%; L. guyanensis, 2.6%; L. amazonensis, 1.8%; L. mexicana, 0.8%; and a new species requiring additional study, 1.2%. Statistical analyses of representative L. panamensis and L. braziliensis isolates indicated that the populations of these 2 species are genetically very similar. L. panamensis may have a continuous distribution in Colombia west of the eastern Andes Mountains and L. braziliensis may have a continuous distribution east of the western Andes Mountains. Information is given on disease manifestations of the parasites in human hosts and on isolation records from sand flies and animals.

Animals↗