PubMed Health⌕ Search

Biomedical subjects

R David

Publications and source records attributed to R David.

At least 127 records · Page 7Linked to original sources
PubMed1988

Coagulation activities of plasma microparticles.

An evaluation of the effect of plasma microparticles (MP) on in vitro coagulation has been undertaken using platelet rich (PRP), platelet poor (PPP) and platelet free (PFP) plasmas prepared by differential centrifugation. MP provide coagulant material which shortens the activated partial thromboplastin time (APTT) and dilute simplastin time (DSTT) which is different from that contributed by commercial phospholipid preparations. The amount of platelet factor three (PF3) available in plasma is directly correlated with the centrifugal force used in its preparation and is present in large amounts in the MP pellet remaining after preparation of PFP. Factor VIII (F.VIII:C) and von Willebrand factor (vWf) were associated with the MP fraction but could be separated from MP on sucrose gradients. The effect of MP on the APTT was independent of the F.VIII:C/vWf and was not solely due to their PF3 content. Plasma prepared for routine coagulation assays contains MP which contribute to the APTT and DSTT and should be considered in their assessment. High speed centrifugation of plasma reduces the F.VIII:C/vWf:Ag/RCoF levels and this may contribute to losses of these proteins during preparative procedures utilising high speed centrifugation.

Adult↗
PubMed1988

Anterior dynamic imaging of the liver and spleen.

Anterior dynamic imaging of the abdomen was performed in 870 patients using a large field-of-view (LFOV) gamma camera. Sequential images were obtained immediately after the injection of Tc-99m sulfur colloid (Tc-99m SC) in an antecubital vein for liver-spleen imaging and was followed by standard planar images. This provided additional information in 172 cases (20%), including such findings as determination of the lesion's vascularity in 76 (9%), visualization of abnormal portal blood flow in 53 (6%), and detection of abnormalities in the aorta, inferior vena cava, iliac vessels, or kidneys in 43 (5%) of these patients. This procedure is recommended in all patients undergoing liver-spleen imaging.

Adult↗
PubMed1988

Platelet-associated immunoglobulins G, A and M are secreted during platelet activation: normal levels but defective secretion in grey platelet syndrome.

Platelet-associated (PA) IgG is known to be released from normal human platelets when they are stimulated by aggregating agents. We have studied whether PA-IgA and PA-IgM are also secreted during platelet activation or during blood collection and processing and whether their levels are related to those in serum. Processing of platelets from normal donors in the presence of secretion inhibitors prostaglandin E1 (PGE1) and theophylline increased levels of both surface and total PA-immunoglobulins (Ig) in intact and lysed platelets respectively, with increases being significant for surface PA-IgA and PA-IgM and total PA-IgM. About 50% of total PA-IgM, 40% PA-IgA and 20% PA-IgG was detectable on intact platelets. All three PA-Ig and PA-albumin were secreted in response to thrombin and this release was inhibited by PGE1. The platelet:serum ratio of each Ig and albumin were similar. In grey platelets deficient in alpha-granules, PA-Ig and PA-albumin levels were raised per platelet but when increased platelet size was taken into account PA-Ig were normal and PA-albumin just below normal. Although thrombin caused release of most of the small amounts of beta-thromboglobulin present, PA-Ig and PA-albumin were not released. This suggests that PA-Ig and albumin from plasma may enter a pool of secretory proteins in normal platelets, but in grey platelets they remain in some other site.

Alprostadil↗
PubMed1988

Expansile bone lesions of the vertebra.

Vertebral expansion may be caused by both benign and malignant disease processes. Recognition of such lesions on radiographs facilitates accurate diagnosis in many cases.

Bone Cysts↗
PubMed1988

Adrenal androgens in children with short stature.

Recent data suggest that adolescent individuals with growth hormone (GH) deficiency have subnormal levels of adrenal androgens (AA). In order to determine the developmental pattern of AA in GH deficiency and to assess whether AA levels can help identify children with GH deficiency, we measured plasma concentrations of dehydroepiandrosterone (DHEA), DHEA sulfate (DHEA-S), delta 4-androstenedione (delta 4A), and cortisol in the basal state and during prolonged adrenocorticotropin (ACTH) infusion (8 h) in a group of 34 individuals, 26 males and 8 females, with short stature. Their chronological ages (CA) ranged from 1.75 to 17.5 years (median 10.35 years). The subjects were grouped into two categories according to the results of pituitary testing: group 1 = short, non-GH-deficient (n = 16), and group 2 = GH-deficient, ACTH-sufficient (n = 18). Patients in groups 1 and 2 had similar bone ages (BA: 7.2 +/- 0.7 vs. 7.5 +/- 1.0 years) and Z scores for height (-3.0 +/- 0.2 vs. -3.2 +/- 0.3 units) and height velocity (-2.5 +/- 0.4 vs. -2.6 +/- 0.2 units). For both groups there were significant increases from basal to peak levels for DHEA, DHEA-S, delta 4A and cortisol following prolonged ACTH infusion. Although both basal and peak levels of DHEA-S overlapped in groups 1 and 2 for all CA and BA, levels in group 2 tended to be lower, especially for BA greater than 10 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Effect of changing medication regimens in glaucoma patients.

When glaucoma medication fails to adequately control intraocular pressure (IOP), a second medication is frequently added. Before adding a second drug to patients whose IOP was no longer controlled by 0.5% timolol, we tested the effect of switching to another beta blocker, levobunolol (0.5 or 1%). We also evaluated the effect of study participation on compliance in the control group continuing to receive 0.5% timolol. In each treatment group, the IOP of approximately 30-40% of the patients was successfully controlled for the 3-month study period. The remaining patients did not exhibit significant pressure reductions and were dropped from the study within 2 weeks. We concluded that (1) the results of 'switch' studies without a control group must be interpreted carefully, and (2) the initiation of a 'new regimen' with an equieffective beta blocker may be sufficient to increase compliance and thereby control IOP.

Aged↗
PubMed1988

Epidemiology of retinal vein occlusion and its association with glaucoma and increased intraocular pressure.

A population-based study found an overall incidence rate of symptomatic retinal vein occlusion (RVO) in a 4-year period to be 2.14 per 1,000 in the 40 years and over age group. When cases found among glaucoma clinic patients were separated from the remainder of the population there was marked difference in the incidence rate of RVO in the same time period (1.85 and 17.3 per 1,000, respectively). The rate of RVO increased significantly (p less than 0.001) with age in the general population from 0.93 per 1,000 among persons under 64 years of age to 5.36 per 1,000 among persons over 65. The increase in the rate of RVO by age was less dramatic in the glaucoma clinic population. The two populations also differed in the frequency of the occlusion type: the ratio of the rate of branch vein occlusion to central vein occlusion was 3.2:1 in the general population, but equally distributed in the glaucoma clinic population. Persons with increased intraocular pressure and/or glaucoma were found to have a higher prevalence of RVO than persons with no history of elevated intraocular pressure.

Adult↗
PubMed1988

Presence of immunoreactive corticotropin-releasing factor in rat testis.

We attempted to demonstrate the presence of immunoreactive (ir) CRF in rat testis by RIA, and by an immunocytochemical technique. The RIA was performed on 27,000 x g supernatants of phosphate buffer extracts of adult rat testes, and revealed a high concentration of irCRF (51 - 74 ng/g testis), with a clear parallelism to the standard curve prepared with synthetic rat CRF. In contrast, the peripheral blood level of irCRF was extremely low (less than 0.05 ng/ml). Immunocytochemical studies of irCRF revealed strong specific staining in the Leydig cells and germ cells in normal adult rat testis. Epididymal spermatozoa also stained positive. Testicular irCRF fluctuated significantly with age. The levels (mean +/- SD) assayed in 10, 20, 60 and 90-day-old rats were 41.6 +/- 4.7, 8.7 +/- 0.2, 55.5 +/- 3.3 and 71.3 +/- 3.4 ng/g testis, respectively (P less than 0.01). The level was drastically reduced after abdominal translocation of a testis (9.6 +/- 1.3 ng/g testis), and after hypophysectomy (16.7 +/- 1.6 ng/g testis) in adult rats. However, neither hemicastration nor unilateral cryptorchidism influenced the irCRF levels in the contralateral testis. These data suggest a local production of irCRF which may play a role in regulation of Leydig cell function and sperm maturation in testis and epididymis.

Animals↗
PubMed1988

Closed chest cardiac massage in the newborn infant.

The recommended techniques for external cardiac compression during cardiopulmonary resuscitation of the newborn are reviewed. The American Heart Association advises the rescuer to depress the infant's midsternum with the index and forefingers. An alternative recommendation is to encircle the chest with both hands and appose the thumbs on the midsternum. The cases reported here prove the superiority of the latter maneuver over the former in improving cardiac output and systemic blood pressures. The history of external cardiac compression in infants and children is briefly reviewed, further supporting the conclusion that the technique of encircling the chest with thumbs at midsternum is more efficacious and hence the preferred approach to closed chest cardiac massage in the newborn.

Blood Pressure↗