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Biomedical subjects

J Aiken

Publications and source records attributed to J Aiken.

12 recordsLinked to original sources
PubMed1998

Reversibility of scrapie inactivation is enhanced by copper.

The only known difference between the cellular (PrPC) and scrapie-specific (PrPSc) isoforms of the prion protein is conformational. Because disruption of PrPSc structure decreases scrapie infectivity, restoration of the disease-specific conformation should restore infectivity. In this study, disruption of PrPSc (as monitored by the loss of proteinase K resistance) by guanidine hydrochloride (GdnHCl) resulted in decreased infectivity. Upon dilution of the GdnHCl, protease resistance of PrP was restored and infectivity was regained. The addition of copper facilitated restoration of both infectivity and protease resistance of PrP in a subset of samples that did not renature by the simple dilution of the GdnHCl. These data demonstrate that loss of scrapie infectivity can be a reversible process and that copper can enhance this restoration of proteinase K resistance and infectivity.

Animals↗
PubMed1995

Repeatability of nutrient intakes estimated by a semiquantitative food frequency questionnaire in elderly subjects.

In order to evaluate the repeatability of nutrient values estimated from a semiquantitative food frequency questionnaire being used in a longitudinal study of the relationships between diet, hemostatic factors, and stroke risk in the elderly in Western Sydney, a subsample of 62 participants (24 men, 38 women) completed a repeat questionnaire approximately 1 month after baseline data were collected. The mean age was 78 years (range, 65 to 88; median, 78). Nutrient values calculated from the repeat questionnaire were not significantly different from the baseline results by paired t test. Intraclass correlation coefficients ranged from 0.63 for beta carotene to 0.82 for saturated fat. Quadratic weighted kappa values were calculated for quintile categories and these ranged from 0.50 for fiber to 0.86 for ethanol. These values are comparable to previously published results in elderly subjects and confirm that repeatability of nutrient intakes estimated using semiquantitative food frequency questionnaires is very high in the elderly. Older subjects may be more established in their dietary habits than younger subjects, so any tendency for repeatability to decrease due to impaired memory associated with advanced age is offset by a lower intraindividual variability in dietary habit.

Aged↗
PubMed1994

Surgical implications of genitourinary tract anomalies in patients with imperforate anus.

Genitourinary anomalies in patients with imperforate anus are a frequent source of significant morbidity. We report a retrospective study of 64 genitourinary procedures performed on 23 patients. Renal, collecting system, bladder and perineal anomalies were encountered in 65%, 83%, 87% and 65% of these complex cases, respectively. A total of 70% of the patients required intermittent catheterization due to bladder dysfunction. Surgical alternatives, complications of management and functional outcomes are reviewed in detail. Genitourinary reconstruction is best undertaken as an integral part of imperforate anus reconstruction. Failure to do so results in the loss of surgical alternatives, unnecessary reoperative procedures and compromised outcomes.

Abnormalities, Multiple↗
PubMed1994

Analysis of the extent to which sperm movement can predict the results of ionophore-enhanced functional assays of the acrosome reaction and sperm-oocyte fusion.

This study has examined the extent to which the information generated by ionophore-enhanced bioassays of the acrosome reaction and sperm-oocyte fusion might be predicted from the computer-aided analysis of sperm motility. Strong correlations (r approximately 0.7) were observed between specific components of sperm movement in semen and the potential for A23187-induced sperm-oocyte fusion, generating a stepwise regression coefficient of R = 0.663 on the bais of two criteria, percentage progressive motility and amplitude of sperm lateral head displacement (ALH). The movement characteristics of the spermatozoa recovered from the Percoll gradients gave an even higher R value of 0.838 on the basis of four variables (percentage rapid, average path velocity, straightness and ALH). In contrast, the ability of human spermatozoa to undergo acrosome reaction in response to A23187 exhibited a limited correlation with sperm movement, whether these measurements were made in the original semen sample or following Percoll purification (R approximately 0.4). These results have diagnostic implications, since sperm-oocyte fusion and the acrosome reaction clearly differ in their relative dependence on sperm motility. In practical terms, it should be noted that the computer-aided analysis of sperm movement was shown to provide up to 70% of the information generated by the more laboured assessment of sperm-oocyte fusion.

Acrosome↗
PubMed1994

Amphotericin B delays both scrapie agent replication and PrP-res accumulation early in infection.

Amphotericin B delays the onset of clinical symptoms in hamsters infected with scrapie agent strain 263K. Here we show that accumulation of a scrapie-specific isoform of the prion protein (PrP-res) and agent replication were delayed early in amphotericin B-treated animals. By 8 weeks postinfection, only untreated animals exhibited clinical symptoms of scrapie infection whereas PrP-res levels and titers were similar in treated and untreated animals. This suggests that although PrP-res accumulation and agent replication are linked, they are not the sole factors required for the onset of clinical disease.

Amphotericin B↗
PubMed1993

Persistence of viral RNA in the central nervous system of mice inoculated with MHV-4.

In order to study the role that viral persistence may play in chronic central nervous system (CNS) disease induced by murine coronaviruses, we have used the reverse transcriptase-polymerase chain reaction (RT-PCR) to study viral RNA in the brains of mice after intracerebral inoculation of JHM virus (JHMV or MHV-4). Quantitative RT-PCR showed that JHMV RNA decreased from approximately 2 ng/ug total brain RNA at day 6 post-inoculation (PI) to 0.1 pg/ug total brain RNA at 360 days PI. Double-stranded viral RNA could be detected up to day 20 PI. By the selective use of upstream or downstream primers during the RT step, it was possible to measure negative sense and positive sense JHMV RNA respectively, and we found that there was a marked rise in the ratio of positive to negative sense JHMV RNA after day 13 PI. Analysis of amplified products by dideoxy DNA sequencing showed that the characteristic mutation of our input virus (at position 3340 of gene 3) is maintained to at least day 42 PI. Taken together, these results favor a model of JHMV persistence in vivo in which viral RNA is present as double stranded forms initially and predominantly as single stranded, positive sense forms at late timepoints. Further analysis of this model in quantitative terms may contribute to our understanding of the biological significance of coronavirus persistence in the CNS.

Animals↗
PubMed1990

Studies in rat liver perfusion for optimal harvest of hepatocytes.

Pediatric liver transplantation is successful but donor scarcity is a major limitation. We are studying hepatocyte transplantation as an alternative to provide functional hepatic replacement. This report details the study of rat liver perfusion for optimal harvest of hepatocytes and cell implantation. We performed 128 rat liver perfusions using a technique modified from the two-step enzymatic perfusion described by Seglen. We examined variations in the perfusion, rate, time, antegrade versus retrograde, pulsatile versus continuous flow, temperature, collagenase type, and variables of buffer composition. We have found optimal cell yield and viability under the following conditions: in situ perfusion, continuous flow at 25 cc/min, retrograde perfusion via the inferior vena cava, water bath temperature 38 degrees C, Boerhinger-Mannheim collagenase using a nonoxygenated HEPES based perfusion buffer, pH 7.4, for the initial perfusion and the same buffer with 4.8 mmol/L CaCl2 for the collagenase perfusion. These conditions consistently generate cell harvests of 500 to 700 x 10(5) cells/g of liver tissue with cell viability between 85% and 95%.

Animals↗
PubMed1990

Detection of bovine viral diarrhea virus genome in leukocytes from persistently infected cattle by RNA-cDNA hybridization.

A bovine viral diarrhea virus (BVDV) cDNA library was constructed. One cloned complementary DNA sequence was used as a probe to detect BVDV RNA by hybridization in infected cell cultures and in mononuclear leukocytes from persistently infected cattle by dot blot and in situ hybridization. The cDNA probe hybridized with all cytopathic and noncytopathic BVDV isolates tested. The hybridization results were consistent with results obtained using conventional subculturing and immunofluorescent staining methods and by inoculation of seronegative test cattle.

Animals↗
PubMedDate not supplied

The mesentery as a laminated vascular bed for hepatocyte transplantation.

The small bowel mesentery provides a unique structure of a large vascularized surface area to support hepatocyte transplantation. Cell-seeded polymeric matrices can be juxtaposed in a relatively atraumatic manner between leaves of mesentery such that adequate exchange of nutrients and diffusion of gases can proceed in the interim while neovascularization occurs. Hepatocytes obtained from (RHA) Wistar rats by collagenase perfusion were seeded onto non-woven filamentous sheets of polyglycolic acid 1 x 3 cm in size and 2 mm thickness to a density of 500,000 cells/cm2. Twenty-six recipient Gunn rats (UDP-glucuronyl transferase deficient) underwent laparotomy. Hepatocyte-ladened polymer sheets were placed between leaves of mesentery. Eight sheets were placed per animal and the leaves were approximated, creating a functional implant 1 x 3 x 2 cm. Biopsies between 5-99 days after implantation revealed neovascularization, moderate inflammatory reaction and the presence of viable hepatocytes in 96% (25/26). Immunoperoxidase studies using anti-albumin antibody substantiated hepatocyte specific function in implants. HPLC profiles of bile from Gunn rats transplanted with hepatocytes from congeneic (RHA) rats demonstrated the presence of bilirubin conjugates. There were no conjugation fractions seen in control gunn rats without hepatocyte transplantation. Although total serum bilirubin did not significantly decrease, conjugated bilirubin was identified in 46% (12/26) animals after transplantation with congeneic hepatocytes. We conclude that the mesentery of the small bowel provides a large vascularized surface for cell transplantation. Large numbers of metabolically active hepatocytes can engraft, vascularize, and show function. The mesentery may be a potential bed for clinical hepatocyte transplantation.

Animals↗