Biomedical subjects

A Lewis

Publications and source records attributed to A Lewis.

At least 145 records · Page 8Linked to original sources

PubMed1993

The efficacy and safety of zona pellucida drilling by a 193-nm excimer laser.

OBJECTIVE: To examine the efficiency of argon fluoride excimer laser drilling of the zona pellucida of mouse oocytes in improving in vitro fertilization (IVF) at low sperm concentrations and to assess its safety. DESIGN: Oocytes obtained from (Balb/c x C57BL6)CB6F1 female mice were drilled by laser and divided into two groups: group I (89 oocytes) were inseminated with 10(5) sperm cells/mL, and group II (94 oocytes) were inseminated with 10(6) sperm cells/mL. Both groups' fertilization rate and development in vitro was compared with control oocytes that underwent the same preparation steps but no drilling (94 and 88 oocytes for group I and group II, respectively). MAIN OUTCOME MEASURES: The fertilization rate and the development in vitro of the laser-drilled groups is compared with that of the control. In addition, in vivo development of embryos generated from laser-drilled oocytes after transfer to pseudopregnant recipients is assessed. RESULTS: For both sperm concentrations, laser drilling significantly enhanced fertilization over control (67% versus 31% at 10(5) sperm cells/mL and 90% versus 54% at 10(6) sperm cells/mL). The development into the blastocyst stage after 96 hours of incubation was similar for both the laser-drilled and control groups at any sperm cell concentration. However, complete hatching at this point was significantly enhanced by the drilling procedure. Normal litters were obtained from the transfer of embryos developed from zona-drilled oocytes into pseudopregnant recipients. CONCLUSIONS: Excimer laser drilling enhanced IVF at low sperm cell concentration. The procedure is safe and did not interfere with embryo development in vitro or in vivo.

Animals↗

PubMed1993

Interaction between human sperm cells and hamster oocytes after argon fluoride excimer laser drilling of the zona pellucida.

OBJECTIVES: To provide conclusive evidence that sperm cells gain access to the perivitelline space exclusively through a laser-drilled opening. To assess the optimal size of the hole and to evaluate the efficacy of laser drilling in comparison with that of mechanical zona dissection. DESIGN: An interspecies model of human sperm cell that interacts with a laser-drilled or partially zona-dissected hamster oocytes. MAIN OUTCOME MEASURES: Penetration rate into the perivitelline space as related to the size of the opening (group A [5 microns], group B [10 microns], and group C [15 microns]) and to the sperm cell concentrations (1 x 10(6), 5 x 10(6), and 10 x 10(6) cells/mL) used for insemination. RESULTS: For each sperm cell concentration, the penetration rate into the perivitelline space was lowest for group A followed by group C and highest for group B. When penetration was compared for each hole size, it was found that sperm concentration had no effect on the rate of penetration in groups A and C but significantly affected this rate in group B. The highest penetration rate of 73% was observed with a concentration of 10 x 10(6) cell/mL and declined to 58% and 23% at 5 x 10(6) cell/mL and 1 x 10(6) cell/mL, respectively. Oocytes drilled by laser (10-microns hole) demonstrated a significantly higher penetration rate when compared with those treated by partial zona dissection (73% versus 20% and 58% versus 21% for sperm densities of 10 x 10(6) cells/mL and 5 x 10(6) cells/mL, respectively). CONCLUSION: Human sperm cells gain access into the perivitelline space of hamster oocytes exclusively through a hole drilled by an argon fluoride excimer laser. An opening of 10 microns was found to yield optimal results. Laser drilling of the zona pellucida seems to be superior to that of mechanical slitting in terms of sperm oolema interaction.

Animals↗

PubMed1993

Too many managers: major threat to CQI in hospitals.

Some hospitals are rushing into continuous quality improvement (CQI) without understanding the pitfalls, one of which is the issue of empowerment. To prevent middle managers from inappropriately reinvolving themselves in the activities of empowered front-line workers, empowerment of employees must be accompanied by a substantial decrease in the number of middle managers. Despite its importance, however, this move is rarely undertaken for two reasons: first, a failure to analyze management "spans of control" in the context of empowerment; second, the fear that staff reductions will imperil the CQI implementation. This article presents case studies of effective and ineffective management to demonstrate that without span of control adjustments, empowerment will fail, whereas appropriate adjustments will allow it to succeed even beyond expectations.

Decision Making, Organizational↗

PubMed1993

Analysis of interferon-alpha 2 sequences in human genomic DNA.

We have analyzed the genomic DNA sequence corresponding to the human interferon-alpha 2 (IFN-alpha 2) gene locus. In human lymphoblastoid Namalwa cells, we have detected sequences corresponding to IFN-alpha 2b and -2c, while in human KG-1 cells both IFN-alpha 2a and -2b were present. However, in 100 independent IFN-alpha 2 clones derived from 20 unrelated Caucasian volunteers, we found only sequences corresponding to IFN-alpha 2b. Statistical analysis of this result suggests that the sequences corresponding to IFN-alpha 2a and -2c are either rare allelic variants of this gene, occurring in only a minority of the Caucasian population, or are restricted to transformed cell lines.

Amino Acid Sequence↗

PubMed1993

Service guarantees in outpatient clinics: a case study.

It is very difficult to receive specific, actionable, constructive feedback systematically in health care delivery. This case study describes a service guarantee tool that does exactly that, at very low cost. As additional benefits, thoughtful use of service guarantees can raise morale, channel complaints that might otherwise go to the "wrong" people, and provide a unique marketing edge.

Ambulatory Care Facilities↗

PubMed1993

Referral physician marketing.

Marketing of specialist services to referring physicians can be highly effective at influencing referral patterns if the referring physician's needs are taken into account. Furthermore, it is possible to generate referrals from nonreferring physicians by approaching them correctly. The ideal approach is for a specialist to treat non-referring physicians as though they referred the patient, even when they didn't. This practice allows the specialist to demonstrate communications service quality in a non-aggressive, non-sales context. The United Weight Control case study summarizes the impact of a referral-generation strategy with "before" and "after" analyses of the strategy's cost and effectiveness.

Ambulatory Care Facilities↗

PubMed1993

Permeabilizing millions of cells with single pulses of an excimer laser.

Poration of millions of cells with single laser pulses of an argon fluoride excimer laser is developed and demonstrated on plant cells. The essence of the technique is to use the large beam size (10 x 25 mm) of the excimer laser and to split it using an appropriate mask into millions of micron- or submicron-sized beams of 193-nm radiation with enough energy to perforate cell membranes and walls. The extremely small depth of penetration of the 193-nm radiation in biological tissue (< 1 microns) is used to great advantage in this technique to provide for a gentle method that does not lead to cell death. This is the first laser-based method that has enough throughput to make it viable for biotechnological applications. Of considerable significance is that the method is applicable not only in the case of the single cells in suspension, but also for cells growing on the leaves of living plants.

Allium↗

PubMed1993

Neuropathologic diagnosis of Alzheimer disease: interrater reliability in the assessment of senile plaques and neurofibrillary tangles.

A diagnosis of definite Alzheimer disease (AD) is made when there is a history of progressive dementia combined with the pathologic findings of numerous senile plaques and neurofibrillary tangles in neocortex. Recent studies have shown, however, that there may be significant interrater variability in the quantitation of these histopathologic lesions. In the present two-center study, interrater reliability and test-retest reliability for plaque and tangle counts were examined when histologic staining and sampling were controlled. We report similar levels of reliability for plaque and tangle counts in 35 cases of AD, nine normal elderly controls and six non-AD dementias: Pearson correlations for interrater reliability ranged from 0.68 to 0.88, and from 0.97 to 0.99 for test-retest reliability. Using quantitative cut-points, concordance between laboratories for experimental diagnoses of AD versus non-AD made on the basis of these lesion counts ranged from 84 to 92% (kappa scores: 0.69-0.84). The agreement between these experimental diagnoses and the clinicopathologic diagnoses of record ranged from 74 to 86% (kappa scores: 0.50-0.71). Thus, under optimal conditions, a moderate to substantial degree of interrater reliability can be attained in the pathologic diagnosis of AD.

Aged↗

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↗