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Biomedical subjects

A Lewis

Publications and source records attributed to A Lewis.

At least 19 recordsLinked to original sources
PubMed1992

Borna disease virus, a negative-strand RNA virus, transcribes in the nucleus of infected cells.

Borna disease virus, an unclassified infectious agent, causes immune-mediated neurologic disease in a wide variety of animal hosts and may be involved in pathogenesis of selected neuropsychiatric diseases in man. Initial reports suggested that Borna disease virus is a single-stranded RNA virus. We describe here a method for isolation of viral particles that has allowed definitive identification of the genome as containing a negative-polarity RNA. Further, we show that the viral mRNAs are transcribed in the nucleus.

Borna disease virus↗
PubMed1992

Decreased (3H) quinuclidinyl benzilate binding to lymphocytes in Gilles de la Tourette syndrome.

In spite of an unknown pathophysiology, it has been suggested that central dopaminergic hyperactivity exists in Gilles de la Tourette syndrome (TS). Cholinergic influences have also been postulated as a dopaminergic-cholinergic balance seems to be important in other movement disorders. If TS is due to alterations of cholinergic activity, this may also be expressed at postsynaptic levels. Recently, we showed that circulating lymphocytes may serve as useful peripheral markers reflecting induced alterations or inherent changes in muscarinic receptors in the central nervous system (CNS). In the present study, we compared the muscarinic binding characteristics in peripheral lymphocytes as measured by (3H) quinuclidinyl benzilate [(3H)-QNB] in 27 unmedicated TS patients, against 22 healthy (age and gender-matched) controls. B(max) and Kd values were determined using Lineweaver-Burke plots. The mean B(max) values in nontreated TS patients was markedly and significantly lower than in controls (10.59 +/- 8.4 versus 40.16 +/- 9.2 fmole/10(6) cells, p less than 10(-6), while Kd values were similar in both groups. Our findings suggest that changes in cholinergic receptors may play a role in the pathophysiology of Tourette syndrome.

Adolescent↗
PubMed1992

Participation of bacteriorhodopsin active-site lysine backbone in vibrations associated with retinal photochemistry.

Bacteriorhodopsin (bR) has been biosynthetically prepared with lysine deuterated at its alpha carbon (C alpha--H). The labeled membranes containing bR were investigated by difference Fourier transform infrared (FTIR) spectroscopy. It has been derived from K/bR and M/bR difference spectra (K and M are photocycle intermediates) that several bands previously assigned to the retinal chromophore are coupled to the C alpha--H. The vibrational modes that exhibit this coupling are principally associated with C15--H and N--H vibrations. [C alpha--2H]Lysine-labeled bR was fragmented enzymatically, and bR structures were regenerated with the C alpha--2H label either on lysine-216 and -172 or on the remaining five lysine residues of the protein. FTIR studies of the regenerated bR system, together with methylation of all lysines except the active-site lysine, reveal that the changes observed due to backbone labeling arise from the active-site lysine. The intensity of the C15--H out-of-plane wag is interpreted as a possible indication of a twist around the C15 = N bond.

Bacteriorhodopsins↗
PubMed1992

Photoacoustic injury and bone healing following 193nm excimer laser ablation.

The argon-fluoride excimer laser was investigated as a cutting-ablating tool for bone surgery. A total of 52 rats were divided into two experimental groups and two control groups. In one experimental group cortical bone defects were made; in another experimental group defects penetrating into the medullary space were performed. In the two control groups similar defects were achieved using water-cooled carbide burs. The rats were sacrificed on each of the 3, 7, 10, 20, 30, and 40 postoperative day. The cortical bone, the medullary space, and the extrabony tissue were examined by means of light microscopy. In both experimental groups, bone damage, represented by osteocyte destruction, extended to 1,050-1,450 microns ahead from the irradiated site, and bone healing was very much impaired. In the control groups no histological changes could be identified and bone healing appeared to be within normal limits. We believe this extensive bone damage, following 193 nm irradiation, to be a result of photoacoustic waves propagating in the bone following each pulse. In view of our results we feel that excimer lasers presently in use are not suitable for bone surgery. This problem of photoacoustic damage can be overcome in one of two ways: by designing a CW excimer laser or by reducing the pulse width to the picosecond regime.

Animals↗
PubMed1992

Effect of the ArF excimer laser on human enamel.

Human enamel surface was irradiated with ArF excimer laser and examined under light microscopy and scanning electron microscopy (SEM). Enamel surface was irradiated at three different areas with different energy fluences. It is demonstrated that the ArF excimer laser causes ablation of the calcified hard enamel tissue. Ablation curves were measured. There was no significant difference found in the etch depth between the three different areas of enamel surface. The morphology of the irradiated areas seen under the SEM was found to be dependent on energy fluence. It changed with increase in energy fluence from being etched to forming a smooth, fused, glaze-like surface and then at very high energy fluences producing a rough surface. The influence of the laser irradiation was confined to the irradiated area only, with no visible heat damage to the surroundings. These results suggest that excimer laser could be applied in a controlled and defined manner for tooth enamel treatments in dentistry.

Dental Enamel↗
PubMed1992

HLA-DR1 is not a sign of poor prognosis for the development of multiple basal cell carcinomas.

BACKGROUND: HLA-DR1 is associated with the development of multiple basal cell carcinomas (BCC). However, the association is weak. OBJECTIVE: The purpose of our study was to determine whether HLA-DR1 is a marker for susceptibility to the development of many BCCs during a lifetime. METHODS: Persons with multiple BCCs were placed into two groups: those with less than 10 and those with 20 or more. In addition, the HLA-DR1 frequencies were analyzed. RESULTS: HLA-DR1 was associated with multiple BCCs in the group with less than 10 BCCs but not with the other group. These patients were significantly younger on average than those with 20 or more BCCs. CONCLUSION: HLA-DR1 is associated with the development of multiple BCCs at an early age but it is not associated with development of large numbers of BCCs. The amount of UV light a person receives appears to be more important.

Age Factors↗
PubMed1992

Functionally crossed pipelines. An intermittent condition by a faulty ventilator.

Unexpectedly high blood oxygen tension in intensive care patients occurring over a 5-year period were found to have been caused by an apparently normally functioning ventilator which was intermittently acting as a conduit between the oxygen and air pipelines. Responses to a circular letter sent to Quality Control Pharmacists in England and Wales suggest that similar faults may have occurred at least five times in the past 10 years. Recommendations are given for the prevention of this problem, including monitoring of gas pipeline composition.

Accident Prevention↗
PubMed1992

Subcutaneous fat necrosis of the newborn complicated by hypercalcaemia and thrombocytopenia.

Subcutaneous fat necrosis of the newborn is an uncommon but distinctive condition which appears in the first six weeks of life, associated with variable degrees of hypercalcaemia and which resolves spontaneously over months. We report a case of subcutaneous fat necrosis of the newborn following perinatal distress and complicated by thrombocytopenia and hypercalcaemia.

Fat Necrosis↗
PubMed1992

A comparison of patient risk for pressure ulcer development with nursing use of preventive interventions.

OBJECTIVE: (1) Determine if the Braden scale or Norton scale predicted the same patients to be at risk for pressure ulcer development as were receiving preventive nursing interventions. (2) Identify the items on the Braden and Norton risk assessment scales that the nurses used intuitively to determine a patient's need for a preventive intervention. DESIGN: Cross-sectional study. SETTING: Six hundred-bed, state-supported, long-term care facility. PATIENTS: War veterans who were 82% male and 97% caucasian, mean age 73. MEASUREMENTS: (1) Patients were categorized as at-risk or not-at-risk by the Norton and Braden scales. (2) The presence of a preventive nursing intervention was noted. Agreement in assignment of at-risk status among the two assessments and presence of a preventive intervention was analyzed using Cohen's Kappa. (3) The staff nurses' use of preventive interventions was modeled using stepwise logistic regression. The items from the Braden and Norton risk assessment scales were used as independent variables with staff nurse implementation of a preventive intervention as the dependent variable. RESULTS: Nurse preventive interventions were found on 45% of patients. The Norton scale identified 38% and the Braden scale identified 27% of patients as at-risk. Agreement among the three methods was 0.53. Agreement between the Braden and Norton scales was 0.73. Agreement between use of a preventive intervention and a classification as at-risk by the Braden or Norton scale was 0.41 and 0.43, respectively. Stepwise logistic regression revealed that low Braden mobility scores (Odds Ratio: 2.74) and low Braden friction/shear scores (Odds Ratio: 3.29) were associated with an increased likelihood of a patient receiving a preventive nursing intervention. CONCLUSIONS: The overall level of agreement among the two scales predicting risk and the presence of a preventive intervention was not high. Agreement, however, between the two risk assessment scales was close. The staff nurses apparently relied on a patients' mobility, their exposure to friction/shear, and additional unidentified factors to guide implementation of a preventive intervention. Further study is needed to define the cost, efficacy, and related cost effectiveness of routine pressure ulcer risk assessment.

Aged↗
PubMed1992

Temporal structure model of binaural masking level difference.

It is shown that a simple cross-correlation model is not adequate to explain both binaural masking level difference (MLD) and spatial selective attention. The reason is that for a low-intensity signal in NoS(pi) condition the maximal activity in the binaural analyzer as a function of interaural delay in single spectral channel is independent of signal intensity. On the other hand, if detection ability is associated with the isolation of tonically firing units, MLD is simply explained as the increase in firing synchronization as a function of the signal's interaural phase difference (IPD). Quantitatively results are presented based on numerical solutions of the model.

Attention↗
PubMed1992

Brain neurotransmitter changes in human narcolepsy.

We measured the concentrations of the three major monoamine neurotransmitters noradrenaline, dopamine, and serotonin, their metabolites, and receptor binding sites in autopsied brain of three patients with narcolepsy. As compared with the controls, concentrations of the noradrenaline and serotonin metabolites MHPG and 5-HIAA, respectively, were markedly elevated in cerebral cortical subdivisions of the narcolepsy patients together with a trend for above-normal neurotransmitter/metabolite "turnover" ratio. A moderately reduced number of alpha 1-adrenoceptors, as judged by the reduced levels of 3H-prazosin binding, was observed in cerebral cortex of two of the three patients with narcolepsy. Mean striatal levels of dopamine and its metabolite homovanillic acid were normal, whereas the concentration of dopamine's second metabolite, dihydroxyphenylacetic acid, was markedly reduced by 50% or greater. This was accompanied by a marked increase (+125%) in mean 3H-spiperone binding to the D2 dopamine receptor in both caudate and putamen; in contrast, the levels of 3H-SCH 23390 binding to the striatal D1 dopamine receptor were in the normal range. Our data provide evidence for altered brain monoaminergic neurotransmitter function in human narcolepsy.

Adult↗
PubMed1992

Microsurgery of the retina with a needle-guided 193-nm excimer laser.

This article presents a method used to guide the beam from an argon fluoride excimer laser to make it suitable for microsurgical purposes and confine it to areas that can be varied in dimension from 1 micron to tens or hundreds of microns. This approach guides the excimer laser beam with an articulated mechanical arm and confines it with variable-diameter tapered tubes, possibly allowing the use of this laser in in vitro retinal surgery with endolaser techniques. Currently, because of the lack of a delivery and focusing system for the 193-nm argon fluoride beam and its absorption by biologic liquids, this laser is used exclusively in ophthalmology for topical applications, such as corneal sculpting. This new method resolves these problems in a unique way with impressive results. Specifically, it was shown that, with this needle-guided excimer laser, it is possible to remove retinal tissue accurately without detectable damage to surrounding cells. Applications of this new technique in retinal surgery are discussed.

Animals↗
PubMed1991

Interleukin-5, interleukin-3, and granulocyte-macrophage colony-stimulating factor cross-compete for binding to cell surface receptors on human eosinophils.

Human interleukin (IL)-5 receptors were characterized by means of binding studies using bioactive 125I-labeled IL-5. Of purified primary myeloid cells, eosinophils and basophils but not neutrophils or monocytes expressed surface receptors for IL-5. Binding studies showed that eosinophils expressed a single class of high affinity receptors (Ka = 1.2 x 10(10) M-1) with the number of receptors being small (less than 1000 receptors/cell) and varying between individuals. Among several cell lines examined only HL-60 cells showed detectable IL-5 receptors which were small in numbers (200 receptors/cell) and also bound 125I-IL-5 with high affinity. The binding of IL-5 was rapid at 37 degrees C while requiring several hours to reach equilibrium at 4 degrees C. Specificity studies revealed that the two other human eosinophilopoietic cytokines IL-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF) inhibited the binding of 125I-IL-5 to eosinophils. No competition was observed by other eosinophil activating or nonactivating cytokines. The inhibition of 125I-IL-5 binding by IL-3 and GM-CSF was partial up to a concentration of competitor of 10(-7) M with GM-CSF consistently being the stronger competitor. Converse experiments using IL-5 as a competitor revealed that this cytokine inhibited the binding of 125I-IL-3 and of 125I-GM-CSF in some but not all the individuals tested, perhaps reflecting eosinophil heterogeneity in vivo. Cross-linking experiments on HL-60 cells demonstrated two IL-5-containing complexes of Mr 150,000 and Mr 80,000 both of which were inhibited by GM-CSF. The competition between IL-5, IL-3, and GM-CSF on the surface of mature eosinophils may represent a unifying mechanism that may help explain the common biological effects of these three eosinophilopoietic cytokines on eosinophil function. This unique pattern of competition may also be beneficial to the host by preventing excessive eosinophil stimulation.

Binding, Competitive↗
PubMed1991

193 nm excimer laser ablation of bone.

The argon fluoride excimer laser is investigated as a cutting-ablating tool for bone surgery. Quantitative measurements are presented for various fluences of laser energy and number of pulses. Histological data are presented that demonstrate the minimal damage to the surrounding material from the laser interaction. Comparisons are made for non-decalcified and decalcified bone. The differences observed, as a function of decalcification in the fluences required for specified depth penetration, are noted and a possible explanation is suggested.

Animals↗
PubMed1991

Technique for cellular microsurgery using the 193-nm excimer laser.

A new cell surgery technique has been developed to produce well-defined alterations in cells and tissue without detectable heating and/or other structural damage in the surroundings. The technique involves the use of an argon fluoride excimer laser, in the deep ultraviolet (UV) region of the spectrum at 193 nm, which is guided through a glass pipette filled with a positive air pressure. To demonstrate the method, holes were drilled in the zona pellucida of mouse oocytes. The diameter of the drilled hole was determined by the pipette tip size, and its depth by an energy emitted per pulse and number of pulses. Scanning electron microscopy of the drilled mouse oocytes showed uniform, round, well-circumscribed holes with sharp edges. Oocytes that had their zona pellucida drilled with this new method fertilized in vitro and developed to the blastocyst stage in a rate similar to that of control group. These results demonstrate the nonperturbing nature of this cold laser microsurgical procedure. In addition to the extension of our results for clinical in vitro fertilization purposes, such as enhancement of fertilization and embryo biopsy, there are wide-ranging possible uses of our method in fundamental and applied investigations that require submicron accuracy in cellular alteration.

Animals↗
PubMed1991

Racial differences in affirmation of personal habit change to prevent HIV infection.

METHODS: In the context of an epidemiological investigation of AIDS-related knowledge, attitudes, and practices, 2,006 employees of the Tennessee Mental Health and Mental Retardation residential facilities were surveyed to test the hypothesis that blacks have been differentially sensitized to their disproportionate level of HIV vulnerability. RESULTS: We found that blacks were significantly more likely than whites to affirm personal habit changes to prevent HIV infection (P less than 0.00001) and significantly more likely to reject the notion that AIDS is not a threat to rural areas of the United States (P less than 0.00001). CONCLUSION: These data were interpreted to be suggestive evidence that blacks have been effectively sensitized to the disproportionate threat of AIDS to the black community and may represent an increased receptivity of blacks to the adoption of HIV preventive practices.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Multiple basal cell carcinomas and HLA frequencies in southern Australia.

An association between HLA-DR1 and the development of multiple basal cell carcinomas was detected in southern Australia. A reduction in HLA-DR4 was found in patients with basal cell carcinoma compared with a local control group. The relative risk for HLA-DR1 was 2.1, which was lower than that for persons in farther countries from the equator.

Adult↗