Search PubMed⌕ Search

Biomedical subjects

A Williamson

Publications and source records attributed to A Williamson.

66 records · Page 4Linked to original sources
PubMed1988

Assessment of the use of transfusion therapy perioperatively in patients with sickle cell hemoglobinopathies.

During the period of 1978 to 1986, 66 patients (31 men, 35 women) with a mean age of 28.4 years and various sickle cell hemoglobinopathies underwent 82 surgical procedures; 28 were emergencies. Fifty of the 66 patients had HbSS, 13/66 had HbSC, and 3/66 had HbS-thalassemia. All 66 patients received transfusions, although not for all procedures. In 48 patients, transfusion therapy was only administered preoperatively. Simple transfusions (1 to 10 units) were administered in 31 of 48 procedures. Exchange transfusions (1 to 6 units) were performed in nine of 48 procedures. Preoperative hematocrit ranged from 7.0% to 54.2%; of those receiving transfusions the hematocrit ranged from 22.6% to 53.7%. Intraoperative transfusions (1 to 10 units) were performed in 14 of 82 procedures; postoperative transfusions (1 to 6 units) were performed in 13 of 82 procedures. No advantage was noted in preoperative exchange transfusion as measured by a decrease in postoperative complications; a slight increase was seen in atelectasis in this group of patients with preoperative transfusions. An increase was reported in the complication rate of patients with an hematocrit of less than 30%. The type of transfusion (preoperative, intraoperative, or postoperative) administered did not appear to be related to postoperative morbidity rates. The complication rate for simple transfusions was 51.6% and for multiple transfusions, 55.6%. HbSS hemoglobinopathy had the higher complication rate. The hepatitis B surface antigen was demonstrated in four of 66 (6.1%) patients; ten of 66 (15.2%) developed alloantibodies. The benefits of transfusion therapy should be judged according to clinical needs; not all sickle cell patients need exchange or preoperative transfusion.

Adult↗
PubMed1988

A transient calcium-dependent potassium component of the epileptiform burst after-hyperpolarization in rat hippocampus.

1. The epileptiform burst potential produced by picrotoxin is a model of the interictal spike potential seen in epilepsy. We have studied the epileptiform burst after-hyperpolarization (epileptiform burst AHP) using intracellular recording from rat CA1 hippocampal pyramidal cells in the slice preparation. In most experiments burst potentials were induced by electrical stimulation of afferent fibres, but in some experiments bursts that arose spontaneously were also investigated. 2. Previous evidence suggested that the epileptiform burst AHP has two slow K+-dependent components and that both components would be blocked by phorbol esters that activate protein kinase C. We found that phorbol esters indeed blocked the slow components, but also uncovered a transient hyperpolarizing component of the epileptiform burst AHP. This phorbol-ester-insensitive component (the transient AHP) peaked approximately 65 ms after the onset of the stimulus and lasted approximately 150 ms. The transient AHP is K+ dependent since its reversal potential shifted in elevated [K+]o, whereas Cl- loading of the cell had no effect on either its development or reversal potential. 3. The transient AHP was either greatly reduced or abolished by 5-10 mM-tetraethylammonium (TEA) and by 15-20 nM-charybdotoxin (CTX), both of which block a particular Ca2+-dependent K+ current. Concomitant with the block of the transient AHP was a significant increase in burst duration. The transient AHP was not blocked by up to 1 mM-4-aminopyridine (4-AP), 1 mM-N'-2'-O-dibutyryl-adenosine 3':5'-cyclic monophosphate (dBcAMP) or 50 microM-carbamylcholine (carbachol), and burst duration was relatively unaffected by these agents. 4. The transient AHP is Ca2+ dependent: (1) it was often associated with the occurrence of a slow, Ca2+-dependent spike; (2) its amplitude was increased in either elevated [Ca2+] saline or in (3) Bay K 8644 (5-10 microM), a compound that prolongs the open time of certain Ca2+ channels. 5. We conclude that a Ca2+-dependent K+ conductance is transiently activated by the epileptiform burst potential. Its distinctive pharmacological profile indicates that it is fundamentally different from the slow Ca2+-dependent K+ conductance. The Ca2+-dependent K+ current, IC, may mediate the transient AHP. Our data also suggest that the transient AHP conductance plays an important role in repolarizing the membrane after bursts of action potentials.

Action Potentials↗
PubMed1984

Temperament in Australian infants.

A convenience sample of 240 infants aged 4-8 months was studied to evaluate the suitability of a revised version of Carey's Infant Temperament Questionnaire (ITQ) for an Australian population. Data analyses indicated all item/dimension correlations significant at P less than 0.01 or better, satisfactory internal consistency of the instrument as measured by alpha coefficients, and test retest reliability of 0.79. Infants rated as having a 'difficult' temperament were significantly more likely to be reported as having problem behaviours. Significant differences were found between Australian and American infants on three of the nine temperament dimensions - rhythmicity, activity and intensity. The results of this study indicate that this revised ITQ is suitable for use with Australian infants.

Australia↗
PubMed1982

The ability to see solid form in early infancy.

The perception of three-dimensional attributes of solid objects by twelve-week-old infants was studied. In the first experiment the rates of habituation of fixation to a cube in a fixed orientation, to one which changed in orientation between presentations, and to a sequence of photographs of cubes in different orientations were determined. Habituation rate was also determined for a photograph of a cube in a fixed orientation. No difference was found between the initial fixation times for solids and photographs, or between the habituation curves for the solids in fixed and varying orientation. For the photographs habituation was much greater for the fixed orientation than the varying orientation condition. These data were interpreted as providing strong evidence that the infants were responding to the stimuli on the basis of their three-dimensional attributes. In the second experiment the same discriminations were examined by a recovery-from-habituation technique. One group was habituated to a cube in a fixed orientation and tested for recovery of fixation to a new orientation. A second group was habituated to a photograph of a cube in a single orientation and tested for recovery to a photograph of a new orientation. Both groups showed recovery and the recovery was the same for both conditions. These data demonstrated that the subjects were, after all, capable of discriminating between different orientations of a solid cube, and they provided no further evidence that the infants were perceiving three-dimensional attributes of the stimuli.

Depth Perception↗
PubMedDate not supplied

Establishing community pharmacy-based anticoagulation education and monitoring programs.

OBJECTIVE: To determine the process for establishing community pharmacy-based anticoagulation education and monitoring programs using fingerstick capillary whole blood testing. DESIGN: Pilot community-based intervention study using convenience sample of patients. SETTING: Three community pharmacies with pre-established health education centers and laboratories certified for moderate complexity. PARTICIPANTS: 26 patients were referred to the clinics by 2 primary care physicians for each pharmacy, most with a diagnosis of atrial fibrillation. INTERVENTION: Patient assessment, including adherence to prescribed regimens; changes in medication use, including prescription and nonprescription medications, vitamins, health foods, and nutrition supplements; changes in diet and ethanol consumption; assessment of adverse experiences; and needed changes in warfarin dosage. MAIN OUTCOME MEASURES: Percentage of international normalized ratio (INR) values within therapeutic range, major bleeding events, and thrombotic events. RESULTS: A total of 21 patient charts were available for analysis. More than 80% of patients had INR values within their targeted range (+/- 0.2) 60% or more of the time, comparable with values reported for anticoagulation clinics. Of the 235 INR values obtained during the study, 75% were within the individualized targeted therapeutic range (e.g., 2 to 3 +/- 0.2). One patient experienced a major bleeding event related to an underlying cancer. None of the patients experienced a thrombotic event. CONCLUSION: Community pharmacies can effectively implement an anticoagulation education and monitoring program.

Adult↗
PubMedDate not supplied

Age and sex differences in the cerebellum and the ventral pons: a prospective MR study of healthy adults.

BACKGROUND AND PURPOSE: The human brain exhibits a complex pattern of differential aging. The purpose of this study was to examine whether age differences in the volume of cerebellar regions and the ventral pons are differential or generalized, whether the age-related shrinkage is linear or exponential, and whether there are sex differences in the size of the cerebellum and pons. METHODS: The volumes of the cerebellar hemispheres (excluding the vermis and the peduncles), the vermis, and the ventral pons were estimated from the prospectively acquired MR scans of 190 healthy volunteers (aged 18-81 years). The relation between regional volumes, age, and sex was assessed while taking into account differences in body size (height). RESULTS: We found a moderate age-related reduction in the volume of the cerebellar hemispheres and the cerebellar vermis. In contrast to previous findings that suggested differential vulnerability of the posterior vermis, the age-related shrinkage of the vermian lobules was uniform-about 2% per decade. In accord with all reports in the literature, the size of the ventral pons was unrelated to age. The volume of the cerebellar hemispheres, the vermis, and the ventral pons were larger in men, even after adjustment for height. The magnitude of the sex difference was the largest in the hemispheres and the anterior vermis, and the smallest in the lobules VI-VII (declive-folium-tuber). CONCLUSION: Moderate age-related shrinkage of the cerebellum and lack of age-related differences in the ventral pons are robust phenomena. However, in all likelihood, the effects of age on the cerebellum are not differential but uniform. The cerebellum and the pons are larger in men than in women and the difference is especially pronounced in the cerebellar hemispheres and the anterior vermis.

Adolescent↗