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Biomedical subjects

W Nelson

Publications and source records attributed to W Nelson.

At least 37 records · Page 2Linked to original sources
PubMed1997

Cytokine mRNA expression in the B/W mouse model of systemic lupus erythematosus--analyses of strain, gender, and age effects.

To gain a better understanding of inherent gender-related effects on autoimmunity, cytokine genes were examined in female and male New Zealand Black X New Zealand White (B/W) mice, which are a murine model of systemic lupus erythematosus (SLE). In preliminary studies, semiquantitative reverse transcriptase-polymerase chain reaction analysis showed a trend for B/W spleen cell interferon gamma (IFN-gamma) mRNA in B/W female spleen cells to exceed that of males. This difference was obliterated following concanavalin A (Con A) stimulation. Spleen cells from B/W mice of both sexes were then examined at 6, 18, and 27 weeks of age, and results were compared with matched groups of nonautoimmune DBA/2 mice. Pooled splenocytes from all 12 groups of animals were compared simultaneously for expression of mRNA specific for IFN-gamma, interleukin 4 (IL-4) and interleukin 6 (IL-6). Strain was a potent influence on cytokine transcripts. In unstimulated splenocytes from female and male B/W mice, there was a notable trend for IFN-gamma and IL-6 mRNA expression to exceed transcripts from nonautoimmune DBA/2 mice. When comparisons were carried out by gender, a highly significant increase of IFN-gamma transcripts was apparent in B/W females compared to B/W males at the age of 27 weeks. Following Con A incubation, strain and gender differences were eliminated. IL-4 transcript expression was similar in all pools of cells, and age was not an important factor in expression of any transcript. This study represents the first examination of multiple cytokine transcripts in lymphoid cells from B/W mice. In this hormone-sensitive model of SLE, strain and gender determined in vivo expression of IFN-gamma and IL-6 mRNA.

Age Factors↗
PubMed1995

It is not necessary to administer more than 10 micrograms.kg-1 of atropine to older children before succinylcholine.

It is common practice at the Hospital for Sick Children, Toronto, to administer atropine 20 micrograms.kg-1 prior to succinylcholine in infants and children. It is unclear whether "prophylactic" administration of this dose of atropine to older children (6-16 yr) is necessary. This study was designed to compare the changes in heart rate, rhythm and mean arterial pressure after administration of either atropine 10 or 20 micrograms.kg-1 with succinylcholine or vecuronium (control group) to older children anaesthetized with thiopentone. Thirty-six ASA I or II patients (6-16 yr) were studied. Anaesthesia was induced with thiopentone 5 mg.kg-1. Patients were randomly assigned to receive: (a) atropine 10 micrograms.kg-1 and succinylcholine 1.5 mg.kg-1 (n = 12), (b) atropine 20 micrograms.kg-1 and succinylcholine 1.5 mg.kg-1 (n = 13) or (c) vecuronium 0.1 mg.kg-1 (n = 11) to facilitate tracheal intubation. Heart rate and rhythm were recorded continuously using a computerised analogue interface whereas blood pressure was monitored non-invasively before induction of anaesthesia, immediately before and at one and three minutes after laryngoscopy. No difference was observed between patients who received atropine 10 or 20 micrograms.kg-1 prior to succinylcholine. No episode of sinus bradycardia occurred. Premature atrial contractions were observed in two patients (one succinylcholine/atropine 20 micrograms.kg-1, one vecuronium). Administration of atropine 20 micrograms.kg-1 prior to succinylcholine provides no advantage over atropine 10 micrograms.kg-1 in older children in terms of cardiovascular stability.

Adolescent↗
PubMed1994

A rapid method for detection and identification of flaviviruses by polymerase chain reaction and nucleic acid hybridization.

A polymerase chain reaction (PCR) technique was developed and evaluated for the detection of flaviviruses. A set of sense and antisense oligomeric DNA primers were constructed from nucleotide sequences of the conserved region of the genome of several different flaviviruses. Virus specific complementary DNA (cDNA) was prepared by reverse transcription of total RNA extracted from infected cell cultures. Amplified cDNA was identified by nucleic acid hybridization with specific oligomeric internal probes. Various conditions, such as number of cycles and annealing temperature were examined to optimize the detection of viral RNAs from infected cell cultures. Slot blot hybridization with a radioactive probe was used to evaluate the sensitivity of PCR amplification. The PCR amplified RNA sequences of dengue 2 (DEN-2), West Nile (WN), St. Louis encephalitis (SLE) and Kunjin (KUN) virus and detected 0.1 to 1 pg of viral RNA. Japanese encephalitis (JE), Yellow Fever virus (YF), DEN-1, 3, and 4 viruses were not amplified. The more frequent occurrence of mismatches in the 3' primer binding site may explain the failure to amplify cDNA of these viruses.

Aedes↗
PubMed1994

Postanesthesia nursing care for ambulatory surgery patients post-spinal anesthesia.

There has been a renewed interest in spinal anesthesia in recent years. However, its use for ambulatory surgery patients has not been as well accepted as its use for inpatients because of the high incidence of postdural puncture headache (PDPH) and uncertain patient recovery time before hospital discharge. Recently, studies indicate that the incidence of PDPH can be lowered to an acceptable level by applying improved techniques such as the use of a 27-g spinal needle or a needle with a tip designed like a pencil point, such as a Whitacre (Becton-Dickinson, Rutherford, NJ) or Sprotte (Pajunk, Geisingen, Germany) needle. Also, by using xylocaine or bupivacaine, which are short- or intermediate-acting local anesthetics, rather than tetracaine, a long-acting anesthetic, patients can be safely discharged from the hospital within 4 to 6 hours from the induction of anesthesia. These improved techniques have allowed spinal anesthesia to be a valid, even desirable, option for selected patients undergoing ambulatory surgery. When considering spinal anesthesia for ambulatory surgery patients, it is important that the postanesthesia care staff be knowledgeable, because nursing care is one of the three integral parts of total patient care that makes ambulatory surgery successful. The other two components are surgery and anesthesia management. This presentation reviews the history, indications, benefits, and complications of spinal anesthesia and recommends nursing care for patients undergoing ambulatory surgery.

Adult↗
PubMed1993

Detection of West Nile virus by the polymerase chain reaction and analysis of nucleotide sequence variation.

A polymerase chain reaction (PCR) assay was developed to rapidly detect and identify West Nile (WN) virus. The RNA from seven isolates of WN virus from six countries and four other flaviviruses (Kunjin, Japanese encephalitis, St. Louis encephalitis, and yellow fever viruses) was reverse-transcribed (RT) and amplified by PCR. The nucleotide sequences of the amplified products were determined by a rapid, automated DNA sequencing method. The WN virus RT/PCR assay detected the target gene segment of sequencing method. The WN virus RT/PCR assay detected the target gene segment of isolates from both the African-Middle Eastern group and the Indian group with a sensitivity of approximately 0.05 pg of viral RNA. Kunjin virus was the only other flavivirus tested that produced a band of the appropriate size. Five of seven WN virus isolates showed 92-98% homology in the nucleotide sequence of their PCR products. The sequence of one isolate was virtually identical to the published sequence of the Nigerian isolate (99.5% homology). No correlation was established between the degree of nucleotide homology, geographic location, time of isolation, or source of the isolates.

Amino Acid Sequence↗
PubMed1991

The Los Angeles TEAM Study: personal exposures, indoor-outdoor air concentrations, and breath concentrations of 25 volatile organic compounds.

The U.S. Environmental Protection Agency and the California Air Resources Board studied the exposures of 51 residents of Los Angeles, California, to 25 volatile organic chemicals (VOCs) in air and drinking water in 1987. A major goal of the study was to measure personal, indoor, and outdoor air concentrations, and breath concentrations of VOCs in persons living in households that had previously been measured in 1984. Other goals were to confirm the marked day-night and seasonal differences observed in 1984; to determine room-to-room variability within homes; to determine source emission rates by measuring air exchange rates in each home; and to extend the coverage of chemicals by employing additional sampling and analysis methods. A total of 51 homes were visited in February of 1987, and 43 of these were revisited in July of 1987. The results confirmed previous TEAM Study findings of higher personal and indoor air concentrations than outdoor concentrations of all prevalent chemicals (except carbon tetrachloride); higher personal, indoor, and outdoor air concentrations in winter than in summer; and (in winter only) higher outdoor concentrations at night than in the daytime. New findings included the following: (1) room-to-room variability of 12-hour average concentrations was very small, indicating that a single monitor may be adequate for estimating indoor concentrations over this time span; (2) "whole-house" source emission rates were relatively constant during both seasons, with higher rates for odorous chemicals such as p-dichlorobenzene and limonene (often used in room air fresheners) than for other classes of chemicals; (3) breath concentrations measured during morning and evening were similar for most participants, suggesting the suitability of breath measurements for estimating exposure in the home; (4) limited data obtained on two additional chemicals-toluene and methylene chloride-indicated that both were prevalent at fairly high concentrations and that indoor air concentrations exceeded outdoor concentrations by a factor of about three.

Adolescent↗
PubMed1990

Amplification, detection, and automated sequencing of gibbon interleukin-2 mRNA by Thermus aquaticus DNA polymerase reverse transcription and polymerase chain reaction.

Reverse transcription-polymerase chain reaction (RT-PCR) is a gene expression assay by which messenger RNA (mRNA) production can be measured. This technique involves three steps: isolation of RNA from cells or tissues, the creation of a DNA copy of the desired message (cDNA) by viral reverse transcriptase enzymes (RT), and amplification of this DNA segment by the polymerase chain reaction (PCR) for subsequent quantitation and analysis. Here we describe a one-enzyme, one-step method combining the RT and PCR steps of conventional RT-PCR by exploiting the recently documented RT properties of Taq polymerase, the thermostable enzyme used for PCR amplification of DNA. RNA was extracted from gibbon T-cells (MLA144), reverse transcribed and amplified with oligonucleotide primers (specific for the 5' portion of a spliced interleukin-2 (IL-2) messenger RNA) by Taq polymerase. A discrete fragment of correct length for IL-2 cDNA was detected. Experiments showed that this product was RNA-dependent and specific for IL-2. This fragment was sequenced by automation employing a biotin primer-streptavidin magnetic bead protocol which confirmed its origin as processed IL-2 mRNA. The modification of the RT-PCR procedure using a thermostable enzyme speeds up reaction time and increases stringency. This method should make the diagnostic screening of cells for gene expression more efficient and practical.

Animals↗
PubMed1989

Particulate and nicotine sampling in public facilities and offices.

The purpose of this study was to characterize and measure indoor air quality in public facilities and office buildings. The pollutants of interest were particulate matter smaller than 2.5 microns in diameter, PM-2.5, and environmental tobacco smoke (ETS). Integrated PM-2.5 samples were taken on Teflon membrane filters using Harvard Aerosol Impactors as a pre-size selector. Filters were analyzed by gravimetric analysis. Nicotine, which was used as a marker for ETS, was collected on sodium-bisulfate-impregnanted, glass-fiber filters and was analyzed by gas chromatography. Twenty-one structures were monitored in Metropolitan Boston. Measured particle concentrations ranged from 6.0 micrograms/m3 to about 550 micrograms/m3. Nicotine concentrations were as high as 26 micrograms/m3 in a designated smoking room. Real-time measurements were also taken using two types of nephelometers; a Handheld Aerosol Monitor (HAM) and a Miniature Real-Time Aerosol Monitor (MINIRAM). Short-term field measurements with these instruments correlated better with the integrated PM-2.5 concentrations in smoking locations than with concentrations in non-smoking areas.

Nicotine↗
PubMed1988

Food restriction, circadian disorder and longevity of rats and mice.

Evidence that food restriction alters circadian rhythms as it prolongs the healthful life of rats and mice is reviewed. Because rhythms in different variables are changed in different ways, the circadian organization that is characteristic of freely feeding animals is disrupted. In the case of daily food restriction (meal feeding), the extent of disruption depends on the timing of the meal in relation to the daily light-dark schedule. Recent studies indicate that the extension of life span by a given level of food restriction is similar regardless of mealtime, whether fixed or shifted at weekly intervals throughout life. Such results suggest that the effects of food restriction on circadian organization are not involved in the effect on survival. On the other hand, changes in any given rhythm (such as an increased amplitude and a decreased overall average of body temperature) could point to the mechanism by which longevity is increased.

Animals↗
PubMed1988

Coagulation of sheep intestinal and prefemoral lymph.

We have determined the most suitable method for the automated analysis of the clotting parameters in sheep intestinal and prefemoral lymph as defined by the Activated Partial Thromboplastin Times (APTT; measure of intrinsic coagulation pathway) and the Prothrombin Times (PT; measure of extrinsic coagulation pathway). As opposed to optical density systems, the use of a Fibro-System Fibrometer was found to provide the most consistent assessment of coagulation with the endpoint being the time to fibrin strand formation. We measured APTT in sheep intestinal and prefemoral lymph of 59.78 +/- 7.69 seconds and 51.03 +/- 10.49 seconds respectively. These values were more prolonged than those obtained from sheep blood plasma but only in the case of intestinal lymph were the differences significant (p less than 0.025). Human blood APTT values were significantly less than both sheep blood (p less than 0.05) and sheep intestinal (p less than 0.001) and prefemoral lymph (p less than 0.01). PT values were found to be 21.56 +/- 1.14 seconds in intestinal and 22.00 +/- 1.88 seconds in prefemoral lymph. These values were also significantly greater than those obtained from sheep blood (both p less than 0.001). Human blood PTs were significantly less than both sheep blood (p less than 0.001) and intestinal and prefemoral lymph (both p less than 0.001). Measurement of APTT and PT values in intestinal lymph and PT determinations in prefemoral lymph were not affected by storage in the refrigerator or freezer. There was some indication that APTT values in prefemoral samples were susceptible to storage artifacts; however, the differences in coagulation times were not significant.

Animals↗
PubMed1987

Decreased lymphatic pumping after intravenous endotoxin administration in sheep.

The effects of endotoxin on the ability of lymphatic vessels to pump fluid in vivo have been assessed with the use of a sheep model system that permits analysis of lymph pumping in sheep without the complication of variable lymph inputs. This involved the isolation of intestinal lymphatic vessels from all lymph input, with saline or lymph provided from a reservoir. The blood and nerve supplies to the vessel were left intact. With no net driving pressure, but with a transmural pressure applied to the vessel to initiate spontaneous contractions and fluid pumping, the intravenous administration of endotoxin (3.3 micrograms/kg in anesthetized sheep and 33 micrograms/kg in nonanesthetized animals) reduced fluid propulsion in both groups of animals (P less than 0.02 and P less than 0.03, respectively). Comparisons with animals that did not receive endotoxin revealed maximum inhibition greater than 90% in anesthetized and 50% in nonanesthetized sheep. Normal pulsatile lymphatic pressures (produced from lymphatic contractions) were reduced in frequency and amplitude after endotoxin administration. Endotoxin itself had no effect on the vessels when added to the fluid in the reservoir, suggesting that the inhibition of the "lymph pump" was mediated through the interaction of endotoxin with cellular or humoral elements in the host. In addition to suppression of lymphatic contractile activity, the intravenous injection of endotoxin enhanced lymph formation as indicated by the 3- to 10-fold increases in lymph flow rates in the two groups. We conclude that, for a given transmural pressure, the systemic administration of endotoxin reduces lymphatic pumping activity. We speculate that this effect may be important in the pathogenesis of the edema associated with sepsis.

Anesthesia↗
PubMed1987

Increased intrinsic pumping of intestinal lymphatics following hemorrhage in anesthetized sheep.

The return of fluid and protein to the bloodstream by the lymphatic circulation may play an important role in reconstituting intravascular volume following hemorrhage. In this study, we have defined the lymph-flow changes that occur in cannulated mesenteric lymphatics following a 25% blood loss in anesthetized sheep and investigated the effects of hemorrhage on the intrinsic contractile activity (lymph pumping) of these vessels in vivo using a new model system. The removal of 25% of the calculated blood volume resulted in increases in lymph flow over a 6-hour period, with peak changes to 3.5 times the prebleed levels. Systemic arterial pressures dropped to roughly 50% of control values immediately following the bleed and returned to control in 3 hours. To directly assess the effects of hemorrhage on lymphatic pumping, a segment of intestinal lymphatic was isolated from all lymph input and supplied with fluid from a reservoir. While there was no net pressure driving fluid through the duct, a transmural distending pressure was applied to the vessel, which stimulated resting lymphatic contractions and fluid pumping. A 25% blood loss resulted in increased activity of the lymph pump; up to 6 times more fluid was propelled through this "isolated" vessel in vivo than in similar preparations in sheep that were not bled (p less than 0.01). Measurements of fluid pulse pressures in this preparation indicated increased pumping frequency and/or force after hemorrhage compared with prebleed levels. We conclude that lymphatic contractile activity is stimulated after a blood loss independent of changes in lymph formation and speculate that this mechanism may play an important role in the reexpansion of the vascular space.

Animals↗
PubMed1986

Schedule-shifts, circadian rhythms and lifespan of freely-feeding and meal-fed mice.

Mice feeding ad lib were subjected to weekly 12-hr shifts of the daily light-dark (LD) schedule beginning at either 7, 20 or 52 weeks of age and continuing until death. Other mice were meal-fed and, from 7 weeks of age until death, experienced weekly 12-hr shifts of the LD schedule alone (with mealtime fixed) or of both the LD schedule and mealtime. Telemetered core temperature data indicated marked differences in response to the different shift conditions and suggested, in the case of meal-fed animals, involvement of a food-anticipatory rhythm. Shifting of the LD schedule had no statistically significant effect on the mean survival time of mice feeding ad lib, regardless of when shifting began. While meal-feeding in itself prolonged life, the added imposition of schedule-shifting had no statistically significant effect on mean survival time, regardless of whether the meal schedule reinforced or opposed shifts of the LD schedule. In the latter case, tenth-decile survival time may have been increased.

Aging↗
PubMed1986

Meal-timing, circadian rhythms and life span of mice.

The possibility that circadian rhythm alteration may contribute to the life-prolonging effect of food restriction was investigated in female CD2F1 mice housed in a room with a 12-h span of fluorescent lighting daily. A control group was allowed to feed ad libitum throughout life while three other groups began lifelong restriction to about 75% of ad libitum intake when 6 wk old. The daily schedule of food accessibility differed among these three groups: a single meal during early darkness; a single meal during early light; six smaller meals at about 2-h intervals during darkness. Food restriction as such clearly prolonged life, but there were no statistically significant differences in overall mean life span or in 10th-decile life span among the three restricted groups. Telemetered body temperature data confirmed marked differences in the effects of these different restricted feeding schedules on circadian rhythms. The effect of food restriction on survival is probably not due to altered relations among circadian rhythmic variables. Possible contributing factors suggested by the results are a lower body temperature, a reduced overall metabolic rate and an increased circadian amplitude.

Animals↗