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Biomedical subjects

J B White

Publications and source records attributed to J B White.

At least 19 recordsLinked to original sources
PubMed2001

Reproducible high efficiency gene transfer into Y79 retinoblastoma cells using adenofection.

Several photoreceptor-specific genes are actively transcribed in Y79 retinoblastoma (Rb) cells, making this cell line potentially useful for the study of photoreceptor metabolism. The utility of these cells is limited because commonly used methods of gene transfer into Y79 cells are inefficient and lack reproducibility. In contrast, we found that adenovirus transduction yields high efficiency gene transfer, however, generation of recombinant adenovirus is lengthy and time consuming. Here, we show that adenofection, a method of coupling adenovirus to plasmid DNA for improved gene transfer, is efficient for gene delivery into Y79 cells. Recombinant adenovirus expressing bacterial lacZ was noncovalently complexed to GFP or luciferase reporter plasmids with polyethylenimine. Efficiency of plasmid gene delivery was determined by monitoring GFP fluorescence. For comparison, calcium phosphate-mediated or cationic lipid transfection was performed in Y79 and HEK293 cells using standard protocols. The adenofection protocol yielded significantly higher efficiencies in Y79 cells than that obtained in these cells with calcium phosphate or cationic lipids. This method will facilitate any experiment requiring reproducible high-level gene transfer. Here, we show that adenofection can be used to analyze activity of the rod photoreceptor PDE6A gene promoter.

Adenoviridae↗
PubMed2001

Reduction in atrial defibrillation threshold by a single linear ablation lesion.

INTRODUCTION: This study investigated a hybrid approach to reduce the atrial defibrillation threshold (ADFT) by determining the effect of a single linear radiofrequency ablation (RFA) lesion on both the ADFT and activation patterns during atrial fibrillation (AF). METHODS AND RESULTS: In 18 open chest sheep (45 to 57 kg), coil defibrillation electrodes were placed in a superior vena cava/right ventricular configuration. AF was induced by burst pacing and maintained with acetyl beta-methylcholine (2 to 42 microL/min). ADFTs were obtained before and after a linear RFA lesion was created in the left atrium (LAL; n = 6), right atrium (RAL; n = 6), or neither atrium as a control (n = 6). In animals receiving an LAL, a 504-unipolar-electrode plaque was sutured to the LA. For animals receiving an RAL, two 504-electrode plaques were placed, one each on the LA and RA. From each plaque, activations were recorded before and after ADFT shocks, and organizational characteristics of activations were analyzed using algorithms that track individual wavefronts. In sham-treated controls, the ADFT did not change. In contrast, LAL reduced ADFT energy 29%, from 4.5 +/- 2.3 J to 3.2 +/- 2.0 J (P < 0.05). RAL reduced ADFT energy 25%, from 2.0 +/- 0.9 J to 1.5 +/- 0.7 J (P < 0.05). AF activation was substantially more organized after RFA than before RFA for both the RAL- and LAL-treated animals. CONCLUSION: A single RFA lesion in either the RA or LA reduces the ADFT in this sheep model. This decrease is associated with an increase in fibrillatory organization.

Animals↗
PubMed2000

Pacing after shocks stronger than the upper limit of vulnerability: impact on fibrillation induction.

BACKGROUND: After upper-limit-of-vulnerability (ULV) shocks of the same strength and coupling interval (CI) during the T wave, (1) the epicardial activation pattern (EAP) for the first postshock cycle is indistinguishable between shocks that do (VF) and do not (NoVF) induce ventricular fibrillation (VF) and (2) >/=3 cycles in rapid succession always occur during VF but not during NoVF episodes. To study the role of these rapid cycles, rapid pacing was performed after a shock stronger than the ULV that by itself did not induce rapid cycles and VF. METHODS AND RESULTS: A 504-electrode sock was sutured to the heart in 6 pigs to map EAPs. The S2 shock strength and S1-S2 CI at the ULV were determined by T-wave scanning with an up/down protocol. Ten shocks 50 to 100 V above the ULV (aULV) were delivered at the same S1-S2 CI to confirm that VF was not induced. Then, the postshock interval after aULV shocks was scanned with an S3 pacing stimulus from the LV apex until the shortest S2-S3 CI that captured was reached. This was repeated for S4, S5, etc, until VF was induced. To induce VF, 3 pacing stimuli (S3-S5) with progressively shorter CIs were required; S3 or S3, S4 never induced VF. After cycle S5, which induced VF, 2 EAP types occurred: focal (74%) and reentrant (26%). CONCLUSIONS: At least 3 cycles with short CIs are necessary for VF induction after aULV shocks. Cycles S3-S4 may create the substrate for cycle S5 to initiate VF.

Animals↗
PubMed1999

Predicting the relative efficacy of shock waveforms for transthoracic defibrillation in dogs.

STUDY OBJECTIVE: Previous work has shown that a passive membrane model using a parallel resistor-capacitor circuit is capable of predicting optimal waveforms for transvenous defibrillation. This study tested the ability of that model to predict optimal waveforms for transthoracic defibrillation. METHODS: This study was divided into 3 parts, each of which determined transthoracic defibrillation thresholds (DFTs) in 6 dogs for several different waveform shapes and durations. For each part, strength-duration relationships were determined from both experimental and model data and then compared with test model predictions. Part 1 DFTs were determined at various durations for 3 different monophasic waveforms-the ascending ramp, descending ramp, and square waveform. Part 2 DFTs were determined for 3 biphasic waveforms. Phase 1 was a 30-ms ascending ramp, and phase 2 was an ascending ramp, a descending ramp, or a square waveform. Part 3 DFTs were determined for 3 biphasic waveforms with very short second-phase durations. Phase 1 was a 30-ms ascending ramp, and phase 2 was a descending ramp. RESULTS: For part 1, the model was able to predict the relative defibrillation efficacy of the 3 monophasic waveforms ( P < .05). For parts 2 and 3, the model was able to predict the biphasic waveforms with the lowest DFTs. These predictions were based on the criterion that the model response at the end of the second phase should return to or slightly pass the model response value at the beginning of the first phase. CONCLUSION: The resistor-capacitor model successfully predicted the relative defibrillation efficacy of several different waveforms delivered transthoracically.

Analysis of Variance↗
PubMed1999

Comparison of pentastarch and Hartmann's solution for volume preloading in spinal anaesthesia for elective caesarean section.

We studied 160 patients undergoing elective Caesarean section under spinal anaesthesia who received a preloading volume of 15 ml kg-1 of 10% pentastarch in 0.9% saline, or Hartmann's solution, in a prospective, randomized, double-blind study. We compared the incidence of spinal-induced hypotension in each group. Hypotension was defined as a decrease in systolic arterial pressure to less than 70% of baseline values or < or = 90 mm Hg, whichever was the greater. The groups were comparable in physical characteristics and there was no serious morbidity. Fetal outcome was similar in both groups. Significantly more patients in the Hartmann's group (n = 38, 47.5%) developed hypotension than in the pentastarch group (n = 10, 12.5%) (P < 0.0001). Linear regression analysis showed that the only significant variable was type of fluid used. Blood glucose concentrations were not related to the presence of hypotension. We conclude that starches may be suitable for preloading in Caesarean section under spinal anaesthesia and provide an alternative to the aggressive use of vasoconstrictors.

Adolescent↗
PubMed1999

The effects of managed care on the quality of dental hygiene care.

PURPOSE: This study examined whether patients insured by a managed dental care plan receive lower quality dental hygiene care than those not enrolled in a managed dental care plan. METHODS: Questionnaire data were gathered from 193 dental hygienists in the Chicago, Illinois area. Managed care was measured by a questionnaire item that assessed the proportion of managed care patients treated by the subject; quality of dental hygiene care was measured by items that assessed the extent to which the subject performed each of 23 dental hygiene tasks. RESULTS: A factor analysis of the 23 items assessing the quality of dental hygiene care indicated four meaningful factors named: periodontal procedures, appointment time, visual examinations, and oral examinations. Measures based on these factors were the dependent variables in regression analysis that included managed care as the primary independent variable and demographic characteristics of the subjects and their practices as control variables. Managed care had a significant (p < .05) negative relationship with appointment time, but did not have a significant relationship with periodontal procedures, visual examinations, or oral examinations. CONCLUSION: This study suggests that managed dental care program patients may have inadequate appointment time with a dental hygienist, which may affect whether they receive important services, such as oral health education. Dental hygienists in managed-care environments should be certain they are making effective use of the scheduled appointment time and procedures to ensure managed-care patients receive adequate time for dental hygiene care.

Chicago↗
PubMed1998

Myocardial discontinuities: a substrate for producing virtual electrodes that directly excite the myocardium by shocks.

BACKGROUND: Theoretical models suggest that an electrical stimulus causes regions of depolarization and hyperpolarization on either side of a myocardial discontinuity. This study determined experimentally whether an artificial discontinuity gives rise to an activation front in response to an electrical stimulus, consistent with the creation of such polarized regions. METHODS AND RESULTS: After a thoracotomy in six dogs, a 504-unipolar-electrode plaque was sutured to the right ventricular epicardium to map activations. From a line electrode parallel to one side of the plaque, 10 S1 stimuli were delivered, followed by S2 and S3 stimuli (S1S1, S1S2, S2S3 interval=300 ms). S1 and S3 stimuli were 25 mA; 5-ms S2 stimuli of both polarities were initially 25 mA and increased in 25 mA increments. The plaque was removed, and a transmural incision was made through the ventricular wall in the middle of the mapped region and sutured closed. The plaque was replaced and the stimulation protocol repeated. Before the incision, S2 stimuli directly activated tissue only near the stimulation site. An activation front arose at the border of the directly activated region and propagated across the plaque. As the S2 stimulus strength was increased, the size of the directly activated region increased. After the incision, sufficiently large S2 stimuli caused direct activation of tissue adjacent to the transmural incision as well as at the stimulation site. Activation fronts that arose adjacent to the transmural incision either propagated proximally toward the stimulation site and collided with the activation front originating from the stimulation wire or propagated distally away from the incision. Minimum S2 stimulus strengths activating areas adjacent to the incision were only 45+/-14% (cathode) and 39+/-18% (anode) of the strengths required to directly activate the same area before the incision was formed (P<.05). CONCLUSIONS: Myocardial discontinuities can give rise to activation fronts after a stimulus, suggesting the presence of polarized regions adjacent to the discontinuity.

Animals↗
PubMed1997

Effect of alpha-tomatine and tomatidine on membrane potential of frog embryos and active transport of ions in frog skin.

alpha-Tomatine, a glycoside in which four carbohydrate residues are attached to the 3-OH group of the aglycone tomatidine, occurs naturally in tomatoes (Lycopersicon esculentum). The glycoalkaloid is reported to be involved in host-plant resistance against phytopathogens and to have a variety of pharmacological and toxicological properties in animals and humans. As part of an effort designed to establish the mechanism of action of glycoalkaloids in cells, frog embryos and frog skin were exposed to varying concentrations of alpha-tomatine and tomatidine. alpha-Tomatine increased the fluorescence-measured membrane permeability of frog embryos by about 600% compared with control values; the corresponding value for tomatidine was about 150%. alpha-Tomatine also diminished sodium-active transport in frog skin by about 16% compared with control values, as estimated from the change in the interstitial short-circuit current. Tomatidine had no effect on frog skin. As these findings complement similar results with glycoalkaloids from potatoes and eggplants, the fundamental mechanism governing their action both against fungi, insects and other phytopathogens and in animal and human cells may be disruption of cell membranes and changes in ion fluxes and interstitial currents of the membranes. The described methodologies should make it possible to define the relative potencies of both adverse and beneficial effects of glycoalkaloids and metabolites in cell membranes without the use of animals.

Animals↗
PubMed1995

Evaluating nurse turnover: comparing attitude surveys and exit interviews.

High turnover rates among hospital nurses demand rigorous and valid processes of research to determine the reasons motivating such attrition. In most hospitals, the exit interview often provides the only relevant data. The case study reported here examines the relative effectiveness of exit interviews and an employee attitude survey in generating data that are useful in managing nurse retention. The conclusion reached is that the attitude survey generates more data and higher-quality data. Further, the study shows that the use of open-ended questions can provide useful information and probably should be the starting point in developing or supplementing an attitude survey for nurses. Recommendations for improving the usefulness and validity of nurse attitude surveys and exit interviews in managing nurse retention are provided.

Attitude of Health Personnel↗
PubMed1992

Two gap junction genes, connexin 31.1 and 30.3, are closely linked on mouse chromosome 4 and preferentially expressed in skin.

Two new gap junction genes isolated from the mouse genome code for connexin homologues of 271 and 266 amino acids, designated here Cx31.1 and Cx30.3, respectively. The two open reading frames, oriented in the same direction, are only 3.4 kb apart on mouse chromosome 4. Within the connexin family, these two proteins are most closely related to one another (70% amino acid sequence identity) and to Cx31 (65 and 68% identity, respectively). Comparison of the Cx31.1 mouse gene with a Cx31.1 cDNA showed a similar genomic organization to that found with other members of the connexin gene family, i.e. the coding and 3'-untranslated regions are contained within a single exon, which is preceded by an intron, less than 25 bases upstream of the ATG start codon. Northern blot hybridization revealed highly tissue-specific coexpression of the 1.6-kb Cx31.1 mRNA and two Cx30.3 transcripts of 1.9- and 3.2-kb size, predominantly in skin and two related mouse keratinocyte cell lines. Minor levels of Cx31.1 mRNA were detected in testis. Microinjection of Cx30.3, but not Cx31.1 cRNA, into Xenopus oocyte pairs induced formation of functional gap junction channels with unique voltage-gated parameters compared to other connexins expressed similarly.

Amino Acid Sequence↗
PubMed1991

In search of service quality measures: some questions regarding psychometric properties.

Confirmatory factor analysis was used to evaluate the construct validity of SERVQUAL, an instrument intended to measure consumer-reported service quality. Results indicate the hypothesized conceptualization of service quality was not valid in a health care setting. It is suggested that additional measurement attention to consumer perceptions may provide further insight into subjective health care service quality evaluation. Implications of failing to consider the measurement properties of this and other constructs are discussed.

Consumer Behavior↗
PubMed1990

Evaluating sources of indoor air pollution.

Evaluation of indoor air pollution problems requires an understanding of the relationship between sources, air movement, and outdoor air exchange. Research is underway to investigate these relationships. A three-phase program is being implemented: 1) Environmental chambers are used to provide source emission factors for specific indoor pollutants; 2) An IAQ (Indoor Air Quality) model has been developed to calculate indoor pollutant concentrations based on chamber emissions data and the air exchange and air movement within the indoor environment; and 3) An IAQ test house is used to conduct experiments to evaluate the model results. Examples are provided to show how this coordinated approach can be used to evaluate specific sources of indoor air pollution. Two sources are examined: 1) para-dichlorobenzene emissions from solid moth repellant; and 2) particle emissions from unvented kerosene heaters. The evaluation process for both sources followed the three-phase approach discussed above. Para-dichlorobenzene emission factors were determined by small chamber testing at EPA's Air and Energy Engineering Research Laboratory. Particle emission factors for the kerosene heaters were developed in large chambers at the J. B. Pierce Foundation Laboratory. Both sources were subsequently evaluated in EPA's IAQ test house. The IAQ model predictions showed good agreement with the test house measurements when appropriate values were provided for source emissions, outside air exchange, in-house air movement, and deposition on "sink" surfaces.

Air Pollution↗
PubMed1989

Interrelations among children, parents, premedication, and anaesthetists in paediatric day stay surgery.

OBJECTIVE: To investigate the incidence of difficulties associated with parental presence during the induction of anaesthesia in children and the influence of premedication with special reference to vomiting after papaveretum. DESIGN: Mixed factual and multiple choice questionnaire completed by medical and nursing staff and parents during and after admission. SETTING: Teaching hospital with regional paediatric general surgical unit where parental presence during induction of anaesthesia is long established. PATIENTS: 151 Children aged 1-14 years who had not previously undergone surgery attending with parents for day stay general surgical procedures. INTERVENTION: Children were randomly allocated to receive no premedication (group 1), oral diazepam elixir (0.3 mg/kg) (group 2), or intramuscular papaveretum with hyoscine (0.3 mg/kg with 0.006 mg/kg) (group 3). No other modification to established day stay routine was made. RESULTS: No major problems were associated with the presence of parents during the induction of anaesthesia. Only 10 of the 141 parents who accompanied their child caused some difficulty, and five became distressed. Premedication with both diazepam and papaveretum resulted in sedation but did not ease induction of anaesthesia. Papaveretum greatly reduced pain and distress immediately after the operation, pain and discomfort being observed in only 15% of children (7/48) compared with 66% (27/41) in group 1 and 49% (22/45) in group 2. Papaveretum, however, must be given intramuscularly, and nurses observed that the children preferred being given premedication orally to intramuscularly. In addition, the incidences of nausea and vomiting were significantly higher in the postoperative ward and at home with papaveretum, although no patient who had been given the drug was nauseous or vomited in the recovery area. The incidences of nausea in group 3 were 62% (31/50) and 57% (27/47) in the postoperative ward and at home, respectively, v 21% (7/33) and 14% (4/29) in group 1 and 13% (5/38) and 14% (5/37) in group 2; the incidences of vomiting in group 3 were 60% and 43% in the postoperative ward and at home, respectively, v 18% and 7% in group 1 and 11% and 11% in group 2. Finally, neither the administration or otherwise of premedication nor the drug given affected the children's or parents' perception of day care surgery. CONCLUSIONS: Difficulties with parents in anaesthetic rooms were not common or severe. Premedication provides preoperative sedation and papaveretum improves the immediate postoperative course but the incidences of nausea and vomiting after operation are higher with its use than without.

Ambulatory Surgical Procedures↗
PubMed1989

Analgesia following inguinal herniotomy or orchidopexy in children: a comparison of caudal and regional blockade.

The effectiveness of postoperative analgesia was compared in 44 children undergoing inguinal surgery, 19 of whom received caudal analgesia (1 ml 0.2% bupivacaine/kg) and 25 ilioinguinal block (0.25 ml 0.5% bupivacaine/kg). The requirement for supplementary analgesia (intramuscular morphine) was less in the caudal group, although this did not reach statistical significance in the number studied. Ilioinguinal and caudal blockade both provide useful postoperative analgesia for children following ilioinguinal surgery.

Analgesia↗
PubMed1988

Plasma bupivacaine concentrations during caudal analgesia and ilioinguinal-iliohypogastric nerve block in children.

Plasma bupivacaine concentrations were measured in 27 children aged 3-7 years who received one of two analgesic regimens for herniotomy or orchidopexy. Analgesia was provided either by caudal epidural bupivacaine 0.2% 2 mg/kg (n = 14) or by ilioinguinal-iliohypogastric nerve block with bupivacaine 0.5% 1.25 mg/kg (n = 13). Mean (SD) peak venous bupivacaine concentrations were 0.57 (0.17) microgram/ml and 0.79 (0.38) microgram/ml respectively. Time to peak plasma concentrations were 29.6 (7.9) and 22.3 (10.9) minutes respectively. These concentrations are well below the potentially toxic level of 4.0 micrograms/ml, but suggest that uptake of bupivacaine is more rapid after ilioinguinal-iliohypogastric nerve block than during caudal analgesia.

Anesthesia, Caudal↗
PubMed1988

Cardiac tamponade: a review of diagnosis and anaesthetic and surgical management illustrated by three case reports.

Cardiac tamponade is an uncommon problem in a district general hospital. Three patients were admitted to the intensive therapy unit at Northampton General Hospital with tamponade in a 7-week period, each with a different underlying aetiology. Their case histories are presented and the management in the light of these described. The aetiology, physiology, clinical signs and investigations leading to the diagnosis are considered. In the discussion the opportunity is taken to review the recent literature on the subject.

Adult↗