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Biomedical subjects

J Joseph

Publications and source records attributed to J Joseph.

At least 181 records · Page 10Linked to original sources
PubMed1990

Fracture resistance of dowel channel preparations with various dentin thickness.

This in vitro study consisted of 40 cast dowel core made of technique metal alloy. They were divided into 4 groups of dowel channels with 1 mm facial dentin thickness, 2 mm facial dentin thickness, 1 mm facial dentin thickness with 60 degrees bevel for the metal collar and 2 mm facial dentin thickness with 60 degrees bevel in the metal collar, respectively. The fracture resistance under horizontal force were compared by using Instron machine. From the study, it was found that more than 1 mm thickness of labial dentin wall of post channel is required to prevent root fracture under horizontally directed force and an addition of 2 mm collar in the core around the root enhanced the resistance to root fracture. It was also found that adequate post diameter should be present when technique metal was used to prevent dowel failure due to bending under force.

Analysis of Variance↗
PubMed1989

Molecular dynamics of antitumor ether-linked phospholipids in model membranes: a spin-label study.

We have synthesized a spin-labeled derivative of ET-18-OCH3, a known antitumor ether-linked phospholipid. The spin-labeled analog was shown to be as potent as ET-18-OCH3 in inhibiting 3H-thymidine uptake of HL60 leukemic cells. Electron spin resonance (ESR) studies showed that the mobility of this ether-linked phospholipid in the membrane is more restricted when compared to its ester-linked counterparts. It is probable that the absence of the bulky carbonyl oxygens allows closer packing of the two alkyl chains in the ether-linked phospholipid, thereby reducing the angular amplitude of the motion of the alkyl chains. These findings may be of importance in elucidating mechanisms by which the antitumor ether-linked phospholipids perturb the structure of cellular membranes.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1989

Differential modulation of MHC class I antigen expression on mouse brain endothelial cells by MHV-4 infection.

Virus-induced modulation of mouse cerebral endothelial cell class I and class II antigens by the neurotropic coronavirus, MHV-4 (JHM), was examined by flow cytometry. In susceptible BALB/c, H-2Kd was downregulated, while H-2Dd was upregulated following infection by MHV-4. In contrast, H-2K and H-2D antigens were both upregulated in either MHV-4-susceptible B10.S and (BALB/c x SJL) F1, or MHV-4-resistant SJL-derived cerebral endothelial cells following infection with this virus. Class II antigen expression was unchanged following MHV-4 infection. Virus-induced MHC class I modulation is genetically regulated, and may influence virus clearance by class I-dependent CTL.

Animals↗
PubMed1989

Anesthesia for perinatal surgery.

A 30 year gravida 3 para 2002 woman presented at 28 weeks' gestation with polyhydramnios. Ultrasound revealed a single fetus with a large anterior neck mass. With halothane general anesthesia providing uterine relaxation and maintaining placental and umbilical blood flow, an otolaryngologist attempted to secure the airway. We discuss the rationale for our anesthetic management and suggest its use in similar situations in which surgical intervention may be required in the immediate perinatal period.

Anesthesia, General↗
PubMed1989

HIV-related symptoms and psychological functioning in a cohort of homosexual men.

The authors administered the Center for Epidemiological Studies Depression (CES-D) Scale to 4,954 homosexual men in the Multicenter AIDS Cohort Study. HIV antibody status at enrollment was a less important predictor of psychological distress than were reported physical symptoms. Multivariate analysis showed an association between a high score on each CES-D Scale component and the number of self-reported possible AIDS- or HIV-related symptoms, perceived lymphadenopathy, and absence of "someone to talk to about serious problems." This relationship between self-reported physical symptoms and psychological distress suggests a possible etiologic relationship between perceived AIDS risk and psychological symptoms in men at risk of AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Spin-label assay for phospholipase A2.

A rapid and continuous method for measuring phospholipase A2 activity using electron spin resonance spectroscopy and a spin-labeled phospholipid as a substrate has been developed. The substrate, 1-palmitoyl-2-(4-doxylpentanoyl)glycerophosphocholine, gives rise principally to a broad ESR line in aqueous solution due to strong spin-spin interactions, probably resulting from its micellar formation. Upon addition of bee venom phospholipase A2, the water-soluble product, 4-doxylpentanoic acid, is released which brings about a sharp three-line spectrum. Thus, the kinetics of phospholipase A2 activity can be followed by monitoring the increase in the ESR signal amplitude of the three-line spectrum, which is linearly proportional to the amount of 4-doxylpentanoic acid produced; no separation of the product from the substrate is needed during the measurement. The rate of hydrolysis of 1 nmol min-1 can be accurately measured within a 5-min period of time in a sample volume of 100 microliters. This new method should be useful for assaying phospholipase A2 activities in various biological systems.

Bee Venoms↗
PubMed1988

Exogenous ATP causes the contraction of intact fibroblasts in vitro.

The contraction of intact fibroblasts was investigated in vitro. The addition of ATP to the cells lead to a rapid, reversible reduction of cell area, which appeared to be a contraction. The change of cell area was measured using image analysis. ATP (15 mM) elicited the maximal contraction, with a 50% reduction in area achieved within 90 s. Adenosine was a partial agonist for the contraction. The contraction was dependent on control of the environmental calcium; cells in a calcium- and magnesium-free environment underwent spontaneous contraction. Replenishing the calcium and magnesium lead to stability of the cells. Since fibroblast contraction is involved in wound healing at many sites in the body, this system provides a physiological model for the direct investigation of fibroblasts with intact cell membranes, and allows for the testing of drugs which may influence wound healing in vivo.

Adenosine↗
PubMed1988

Down-regulation of interferon-gamma-induced class II expression on human glioma cells by recombinant interferon-beta: effects of dosage treatment schedule.

We have examined the influence of human recombinant interferon-beta (IFN-beta) and interferon-gamma (IFN-gamma) on class II antigen expression on cultured glioblastoma multiforme cells by flow cytometry. Class II molecules were not constitutively expressed on these cells, nor induced by IFN-beta. IFN-gamma increased class II expression in a dose-dependent fashion. We demonstrate that IFN-beta is either antagonistic or synergistic with IFN-gamma in class II induction depending upon dose and schedule of administration. Both interferons at 100 IU/ml reduce class II expression by 18%, compared to IFN-gamma alone. Pretreatment with IFN-beta for 72 h, followed by both interferons yielded a 90% reduction. In contrast, lower concentrations (10 IU/ml) of both interferons were synergistic.

Drug Administration Schedule↗
PubMed1988

Synthesis of a spin-labeled phospholipid for studying membrane dynamics in intact mammalian cells.

We report here the synthesis of a spin-labeled phospholipid, 1-palmitoyl-2-(4-doxylpentanoyl)glycerophosphocholine. The synthetic route for this probe involves two major steps: 1) the synthesis of 4-doxylpentanoic acid from ethyl levulinate and 2-amino-2-methyl propanol, and 2) the synthesis of the lipid from 4-doxylpentanoic acid and lysolecithin. The efficiency and yield of both steps have been greatly improved. This represents the first instance that the synthesis of this important spin-labeled phospholipid is described in detail. Because it mimics the native lipid molecule and can be readily incorporated into biological membranes, this probe should be extremely useful for studying lipid dynamics in the plasma membrane of intact mammalian cells using electron spin resonance (ESR) spectroscopy.

Animals↗
PubMed1988

Sexual partner selectiveness effects on homosexual HIV transmission dynamics.

Deterministic simulation models are used to show that HIV transmission dynamics in homosexual populations can be strongly affected by sexual partner selectiveness. The type of selectiveness or biased mixing examined is where individuals with similar new partnership formation rates are more likely to form a pair than would be expected by chance. The effect of such selectiveness could be strong even when the total number and distribution of new sexual partnerships and sex acts remains constant. This means that in order to predict the future course of HIV transmission and identify the populations at highest risk, we must have information not only on the frequency of new sexual partnerships and types of sex acts, but also on who has sex with whom. Given high sexual partner selectiveness, some groups of homosexuals with low rates of sex and new sex partners would take many decades before a single introduction would generate an epidemic. Epidemics in these groups can be markedly accelerated by only modest contact with higher risk groups. Even in very low activity groups, which if isolated would have no epidemic, an important proportion of their members can be infected when they are not selective. The relative risks of AIDS in groups making high numbers of new sexual partnerships compared to groups making low numbers are markedly affected by sexual partner selectiveness. The models developed were examined using information collected in 1984 from the Coping and Change Study in collaboration with the Chicago Multicenter AIDS Cohort Study. This population was divided into activity groups by the rate at which individuals established new sexual partnerships and then a structure of new sexual partnerships between these activity groups was defined consistent with available data. Even without introducing any behavior change in the models, the proportion of the homosexual population infected was seen to level off temporarily at around 50% after several years as a consequence of saturation in the high risk groups when lower risk groups were not yet being consumed by the epidemic process. Most sex in the study population is casual or anonymous. The sample selection procedures were biased toward individuals who engage in such sex. There is, however, a large group of individuals that avoids the casual and anonymous sex scene. Simulated epidemics indicated that under a variety of conditions, the population that does not engage in casual and anonymous sex could experience an epidemic of HIV infection quite some time after the epidemic in the population that does has waned.(ABSTRACT TRUNCATED AT 400 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1987

Use of soft contact lenses in an eye casualty department for the primary treatment of traumatic corneal abrasions.

We have assessed the role of bandage contact lenses in the primary treatment of traumatic corneal abrasions. Patients treated with bandage lenses healed more quickly (0.05 greater than p greater than 0.02) and with less discomfort (0.05 greater than p greater than 0.02) than those treated traditionally, with the added advantage of maintaining vision during treatment. Resterilisation of contact lenses reduces the cost and makes the treatment economically viable. Large diameter lenses were fitted satisfactorily without the use of keratometry.

Adult↗
PubMed1986

Haptoglobin phenotypes in dementia of the Alzheimer type.

Previous investigations of the association of haptoglobin (Hp) with dementia of the Alzheimer type (DAT) have reported contradictory results. In the present study, we phenotyped 69 patients clinically diagnosed as having DAT and, for comparison, 64 cognitively intact individuals. We failed to find a significant association between either of the Hp alleles and DAT. Instead, we observed a nonsignificant decrease in the Hp-1 gene frequency in the DAT population (0.34) as compared to our normal elderly comparison group (0.41).

Aged↗