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Biomedical subjects

A R Williams

Publications and source records attributed to A R Williams.

At least 109 records · Page 6Linked to original sources
PubMed1990

Effects of ultrasound on placental transfer during the last third of gestation in the rat.

The effect of ultrasound on placental transfer in the rat has been measured in vivo. At 15, 18, 21 and 22 days of gestation one uterine horn of each anaesthetized rat was exposed, after laparatomy, to ultrasound. The control horn was effectively shielded. Radio-labelled tracers were then injected into the maternal circulation via a jugular vein cannula and fetuses removed simultaneously from both experimental and control horns at times predetermined to ensure minimal backflux from fetus to mother. Samples of maternal plasma were also taken at suitable intervals. The radioactive content of fetuses and plasma were measured and a unidirectional materno-fetal clearance value (Kmf) for each fetus calculated. It was shown that in rats whose body temperature was accurately maintained at 37 degrees C, ultrasound at the level used in the present study had no effect on placental clearance. However, in rats whose body temperature was allowed to fall to 32 degrees C, a 3 min exposure to 1.1 MHz continuous wave ultrasound at 1 W cm-2 caused a significant (p less than 0.001) decrease in the placental clearance of 22Na (by 55%) and 51Cr-EDTA (by 45%) in rats at 15 days of gestation. These effects showed no dose response and were not observed in rats at any of the other stages of gestation which we investigated. However, in rats at 21 days of gestation the clearance of 45Ca2+ was significantly (p less than 0.01) reduced (by 30%) by a similar exposure to ultrasound. It is concluded that although an interesting biological effect of ultrasound at low body temperatures has been observed, it has little relevance for the normal use of ultrasound in obstetrics.

Animals↗
PubMed1990

Chronic cancer pain management with the Du Pen epidural catheter.

Chronic epidural administration of narcotics and/or local anesthetics is sometimes required in those few patients where utilization of systemic narcotics and appropriate adjuvant medications is unsuccessful in controlling intractable cancer pain. The Du Pen epidural catheter (Davol, Inc.) a silicone-based tunneled catheter modeled after the Hickman central venous catheter, has provided a safe, reliable means of long-term administration of drugs to the epidural space in over 400 patients to date. A systematic approach to the pharmacology of epidural pain control includes drug choice, bolus dosing versus infusion, volume guidelines, and titration protocols. Utilization of local anesthetics in combination with narcotics allows for enhanced pain relief in those patients refractory to narcotics as is frequently the case with neurogenic involvement. Follow-up care of patients receiving epidural narcotic with or without local anesthetic can be accomplished by a trained home cae team. Successful epidural pain management requires thorough patient and caregiver education, frequent pain assessment, and monitoring of side effects, with close collaboration between patient/family, pharmacist, home care nurse, and physician.

Analgesia, Epidural↗
PubMed1990

Low dose rate teletherapy using a telecaesium 137 unit radiobiological, physical and clinical considerations.

Low dose rate teletherapy aims to combine the supposedly superior results obtained with low dose rate implants with the convenience and staff protection characteristics of external beam therapy. Previous investigators have used telecobalt units to produce dose rates of 1.1 to 1.8 Gy/hr to treat in daily sessions lasting 6-10 hours to total doses of 60-70 Gy. These studies have not discounted the possibility that much of the advantage of interstitial implants results from the low dose rates used per se, and from the fact that the total dose is delivered in a short overall time. The relationship between total dose, dose rate and volume giving normal tissue and anit-tumour effects, however, remains ill-defined. At the Newcastle Mater Misericordiae Hospital a Caesium teletherapy unit has been modified to treat at low dose rates and a study has been designed with a view to establish which permutations of total dose and dose rate are isoeffective for acute mucosal and acute skin reactions in the dose rate range between 0.8 and 9.6 Gy/hr (1.3 and 16 cGy/min).

Cesium Radioisotopes↗
PubMed1990

Effects of cavitational activity on the root surface of teeth during ultrasonic scaling.

It is recognised that roughness of the root surface will occur during ultrasonic scaling and this has been attributed to the vibrating scaling tip. Although the presence of cavitational activity and acoustic microstreaming forces have been described their effects on the root surface have not been fully evaluated. Utilising an in vitro system of polished gold, it was possible to demonstrate an indentation produced by the scaling tip. However cavitational activity around the tip within the water supply appeared to produce an area of erosion (0.66 +/- 0.3 mm2, 1 SD, n = 10), and the surface appeared pitted. A scanning electron microscope study (SEM) of root surfaces following ultrasonic scaling showed similar areas of erosion. A replica technique was utilised so that control and experimental root surfaces could be observed. Cavitational activity and acoustic microstreaming resulted in a superficial removal of root surface constituents, and this area of removal was measured as 0.7 +/- 0.3 mm2 (1 SD, n = 10), which was not significantly different from that area observed with the gold surface system (p greater than 0.1). It may be concluded that cavitational activity within the cooling water supply of the ultrasonic scaler results in a superficial removal of root surface constituents.

Dental Prophylaxis↗
PubMed1990

Two-, three- and four-breed rotational crossbreeding of beef cattle: reproductive traits.

Reproductive data were collected on 4,596 cow exposures in a rotational crossbreeding study that spanned four generations (1970 through 1988). Angus (A), Brahman (B), Charolais (C) and Hereford (H) breeds were included in three two-breed (A-B, C-B and H-B), three three-breed (A-B-C, A-B-H and C-H-B) and one four-breed (A-B-C-H) rotational mating system. Contemporary straightbreds were produced each generation. Reproductive traits of interest were calving rate, calf survival, weaning rate, calf birth date and calving assistance. Overall means and standard errors for calving rate, calf survival, weaning rate, calf birth date and calving assistance were 82.1 +/- .6%, 92.8 +/- .4%, 76.2 +/- .6%, 50.4 +/- .3 d and 4.2 +/- .3%, respectively. Rotational mating systems had similar calving and calf survival rates that were greater (P less than .01) than those of straightbreds. Three- and four-breed rotation systems had similar weaning rates (81.5 +/- 1.1 and 80.8 +/- 2.0%) that were higher than those for two-breed rotations (77.1 +/- 1.2%). Two- and three-breed rotation systems had fewer assisted births (3.5 +/- .6 and 2.2 +/- .6%) than straightbreds (5.5 +/- .6%) and the four-breed rotation (5.4 +/- 1.0%). Three-breed rotation calves were born earlier in the calving season (46.8 +/- .6 d; P less than .05) than straightbred, two-breed or four-breed rotation calves (51.8 +/- .6, 52.1 +/- .6 and 51.1 +/- 1.0 d). Hereford-Brahman two-breed rotation cows had higher (P less than .05) calving and weaning rates than A-B or C-B two-breed rotation cows (87 +/- .4 vs 81.9 +/- 1.9 and 81.5 +/- 1.8%; 81.7 +/- 2.0 vs 76.4 +/- 2.1 and 74.1 +/- 2.0%). All three-breed rotation combinations had similar calving, calf survival and weaning rates, assistance at calving and calf birth dates. Rotational combinations tended to be more superior (P less than .05) to weighted purebred means for calving, calf survival and weaning rates than for calf birth date and calving assistance.

Analysis of Variance↗
PubMed1990

Children at home on mechanical assistive devices and their families: a retrospective study.

Few assessments have been done of the influence of caregiver and family interactions on the developmental status of children discharged on mechanical assistive devices. The ages of the 25 children in this study ranged from 2-30 months. Seven were on apnea monitors at the time of the home interviews, and 18 had been off the monitors for 18 months or more. Mothers were administered six questionnaires: Family Adaptability and Cohesion Evaluation Scales (FACES III), Duke-UNC Functional Social Support Questionnaire, Families Coping Strategies (FCOPES), Self-Esteem Scale, Home Observation for Measurement of the Environment, and the Receptive-Expressive Emergent Language Scale (REEL). Results on the FACES III revealed that families were not rigid in adaptability; 61% were chaotic, and 33% were balanced. On the cohesion scale, 25% were disengaged, 30% were enmeshed, and 45% were balanced. On the FCOPES, and it's subscales, 36-40% of the respondents scored below the established norms. Social support was strongly correlated with Cohesion and Adaptability (r = .47, .67), HOME scores correlated with Self-Esteem (r = .47) and FCOPES Reframe scale (r = .45), and REEL scores correlated with Social Support (r = .47, .52). Path-analysis revealed two paths: help-seeking behaviors of the mother and the child-mother interactions.

Adaptation, Psychological↗
PubMed1989

Measurement of anomalously high hydration of (dA)n.(dT)n double helices in dilute solution.

Different DNA sequences have different physical properties, which seem to be important for their biological function. In particular, (dA)n.(dT)n has many unusual features, which include resistance to conformational changes in a variable chemical environment, an unusual thermodynamics of interaction with ligands, and the inability to reassociate into nucleosomes. Short A.T base-pair runs also play a critical role in DNA bending. It is believed that hydration of DNA is an important factor in determining the physical chemical and biological properties of different regions of DNA. Until now, however, it has not been possible to study the details of the hydration of DNA in dilute solution with sufficient sensitivity and precision. Moreover, it was not known if different base sequences differ in the extent of their hydration. Indirect evidence that (dA)n.(dT)n can be hydrated to a greater extent than other DNA sequences may be inferred from a recent study of the binding of drugs to polynucleotides. Here we used a novel high-precision technique measuring ultrasonic velocity to obtain direct estimates of the extent of hydration of various oligo- and polynucleotides in dilute solution. We report that different DNA sequences differ in their hydration, and that (dA)n.(dT)n in particular has an anomalously high level of hydration.

Base Sequence↗
PubMed1989

Infectious and noninfectious exposures in the etiology of light chain myeloma: a case-control study.

Sixty-nine subjects with light chain myeloma were interviewed in a multicenter case-control study, and their responses were compared to those of 1683 controls selected from the general population of the same geographic areas. The interview was directed at the subject's history of exposure to a variety of chemical and infectious agents. Persons with a history of a medical implant had 2.2 times the risk of other persons (95% confidence interval = 0.9-5.8), a relative risk that increased with increasing time that the implant had been present. Alkali exposure that was deemed by the subject to be unusually heavy was associated with a relative risk of light chain myeloma of 7.8 (95% confidence interval = 1.7-35.3), while similarly defined exposure to carbon monoxide increased the risk by 6.1 times (95% confidence interval = 2.0-18.2). These findings differ from those obtained in our study of the more common forms of multiple myeloma and, while the differences are plausibly due only to chance given the large number of exposures investigated, they could be an indication that light chain myeloma is an etiologically distinct entity.

Bacterial Infections↗
PubMed1989

Factors influencing performance of chronically ill children on a developmental screening test.

The Metro-Manila Developmental Screening Test (MMDST) is a Philippine version of the Denver Developmental Screening Test (DDST) for which norms were developed in 1980 on 6006 Filipino children. The MMDST was administered in homes and out-patient clinics to children with chronic illness such as cardiac, neurologic, metabolic and others (n = 405). A discriminant analysis using 16 variables was carried out to compare the characteristics of chronically ill children with abnormal scores of the MMDST (n = 130) and those with normal scores (n = 183). Eleven variables with significant standardized discriminant function coefficients formed three clusters: a child variable cluster (age, -0.31; sex, 0.23; present weight, 0.25; and "only" child, 0.17); a parent variable cluster (mother's education, 0.43; place of longest residence of father, 0.38 and of mother, -0.28; and father's education, 0.17); and a situational variable cluster (number of children in the family, -0.23; current place of residence, 0.25; and working mother, 0.17). Children who tended to have abnormal MMDST scores were older, female, with low present weights, large families, living in rural areas, with mothers not working outside the home (hence, lower family incomes). Additionally, the mothers and fathers of these children had lower educations and fathers had resided in rural areas for a major portion of their lives.

Child↗
PubMed1989

Investigation of cavitation in flowing media by lithotripter shock waves both in vitro and in vivo.

Cavitation produced by lithotripter shock waves was characterized in vitro in water and blood, and in vivo in aortic blood by means of a 1.6 MHz resonant bubble detector. This system was readily able to detect bubbles resulting from shock-wave induced cavitation in both water and blood flowing through plastic tubes in vitro, and even in blood pumped by the heart through a plastic arterio-venous shunt. However, this system was unable to detect evidence of shock-wave induced cavitational activity occurring within the intact vascular systems of dogs in vivo.

Animals↗
PubMed1989

Bubble cycling as the explanation of the promotion of ultrasonic cavitation in a rotating tube exposure system.

The cavitation-promotion effect of rotating a sample tube during ultrasound exposure is not yet fully understood. Cavitation-induced hemolysis was observed in 0.5% hematocrit suspensions of erythrocytes exposed for 5 min at 37 degrees C. For 1.61 MHz unfocused exposure an apparent threshold of 4 W/cm2 spatial-peak intensity was obtained for hemolysis in a 72 rpm rotating exposure chamber which was made of dialysis tubing. If the tube was not rotated, then no hemolysis was observed up to 16 W/cm2. Creation of standing waves in the sample by using a thick-walled culture tube, or by placing a styrofoam reflector behind the dialysis tube did not change the apparent threshold. Focused 1.45 MHz exposure gave the same apparent threshold in a rotating dialysis tube, but this increased to about 128 W/cm2 for the nonrotating case. When the focused ultrasound was turned on for half a rotation and off for half, results were similar to those for a nonrotating CW case, while on-off cycles synchronized to a quarter rotation gave results similar to the rotating CW case. A plausible explanation of the rotation effect, given these results, is that rotation brings bubbles on the rear wall, where the beam exits the tube, back around to the front again, where the bubbles may then re-nucleate the suspension, and thereby promote cavitation bioeffects in the rotating tube.

Animals↗
PubMed1989

EFSUMB position.

Explore the source record for details and available documents.

Animals↗
PubMed1989

Effects of constraint on the oscillatory pattern of endosonic files.

When operated in air, the transverse oscillation of the endosonic file exhibits a series of nodes and antinodes along its length with the greatest displacement amplitude occurring at the unconstrained tip. Endosonic files of varying design, length, and thickness exhibit differences in their oscillation. Preliminary work has revealed that the endosonic file is susceptible to constraint when working within the root canal and a model system was designed to investigate this problem. The constraining influence was found to be greatest when it was applied at those antinodes nearest the tip. This effect was further enhanced if the file was angled. Furthermore, constraint applied at the nodes also influenced the file oscillation. Such results may explain in situ observations on the occasional inefficiency of the system, especially when negotiating the apical third of a curved root canal. Clinical techniques utilizing an endosonic file may require reappraisal in order to minimize such constraint.

Root Canal Therapy↗
PubMed1989

The role of non-acoustic factors in the induction and proliferation of cavitational activity in vitro.

It is well known that a liquid exposed to relatively low intensities of MHz ultrasound may or may not cavitate depending upon a variety of non-acoustic factors. This paper shows that in some cases the material used as the acoustically transparent window and even the length of the sample chamber may also be important factors. Cling film, dialysis membrane and Parafilm are all equally acceptable as acoustically transparent windows for ultrasound, whereas glass cover slips or 'soft' surfaces (in which active bubbles may embed themselves) are not. All the results obtained confirm the validity of bubble recycling as being the dominant mechanism responsible for the enhancement of cavitational activity commonly observed when the sample chamber is rotated.

Acoustics↗
PubMed1988

Optimal preservation of p21 ras immunoreactivity and morphology in paraffin-embedded tissue.

Specific immunostaining of p21 ras protein by the well-characterized pan-ras antibody Y13-259 is achieved in paraffin sections of human and animal tissues fixed in periodate-lysine-paraformaldehyde-dichromate (PLPD). Intensity of staining is as good as in cryostat sections, with superior histological detail. Localization to plasma membrane is demonstrated in rodent cells genetically manipulated to express abundant p21 ras (the FHO5T1 cell line), both in preparations suspended in agar after culture in vitro and in those growing as tumour in vivo. Strong positive staining is observed in neoplasms of human breast and colon, tissues in which there is independent evidence of elevated ras gene expression. The superior morphology afforded by this technique allows clear characterization of p21 ras expression in small premalignant lesions for which other methods of detection of oncogene expression are not appropriate.

Animals↗