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Biomedical subjects

S Dixon

Publications and source records attributed to S Dixon.

At least 73 records · Page 4Linked to original sources
PubMed1996

High cellular concentration of peripheral blood progenitor cells during cryopreservation adversely affects CFU-GM but not hematopoietic recovery.

The effects of bone marrow (BM) and peripheral blood progenitor (PBPC) concentration during cryopreservation on subsequent hematopoietic engraftment following high-dose chemotherapy were studied in 24 patients. Seventeen BM harvests and 71 PBPC collections were performed between July 1991 and June 1994. The PBPC were frozen at significantly higher cellular concentrations than the BM (medians of 243 x 10(6)/ml versus 73 x 10(6)/ml respectively, p = 0.0003). The recovery of committed progenitor cell colonies (CFU-GM) was significantly lower from PBPC frozen at concentrations above the median, compared with 116% from those frozen at concentrations below the median (p = 0.0467). This phenomenon was not seen in BM, which was generally frozen at a threefold lower concentrations. Despite the lower recovery of CFU-GM when PBPC were frozen at a higher concentration, the patients receiving these grafts achieved good hematopoietic recovery. The higher number of PBPC probably compensated for the loss, and the patients still received a substantial number of clonogenic hematopoietic precursors.

Adolescent↗
PubMed1995

Flow cytometric determination of pre-transfusion red cell volume in fetuses and neonates requiring transfusion based on RhD+ dilution by transfused D- red cells.

We report a case of feto-maternal haemorrhage and describe a new flow-cytometric method of determining a fetus's or infant's pre-transfusion red cell volume (RCV). We validate this method against an established technique, employing fetal haemoglobin (HbF) dilution, for determining the RCV in fetuses and neonates requiring intravascular transfusion. We discuss advantages and other potential applications of this new method.

Blood Transfusion, Intrauterine↗
PubMed1995

Introduction of computer assisted control of oral anticoagulation in general practice.

The number of patients referred to hospital clinics for monitoring of oral anticoagulation continues to rise rapidly. Introduction of computer programs for the control of oral anticoagulation improves the quality of anticoagulant control in hospital clinics. This approach has now been extended to include patients managed in general practice. Results confirm that the quality of anticoagulation can also be improved in these patients. A standard approach to anticoagulation for hospital and community based patients has also facilitated the transfer of patients on warfarin from the hospital anticoagulant clinics to the community with no deterioration in the quality of anticoagulant control. As a result, the workload in the hospital anticoagulant clinic has fallen for the first time.

Anticoagulants↗
PubMed1994

Lactation management education for physicians.

All health professional groups support breastfeeding as the ideal way to nourish an infant, but numerous surveys have shown that, in general, even perinatal health professionals are not prepared to provide lactation management as part of routine care. Integration of lactation topics into current medical curriculum, whether traditional or problem-based, is the ideal and is possible. Faculty are encouraged to assess the current program for signs of "curriculosclerosis," a prevalent disease characterized by Abrahamson as "hardening of the categories," to look for ways to elasticize the relevant departments, and to integrate lactation management topics at the appropriate place in the larger educational plan. Faculty leadership is crucial. Remedial work, in terms of continuing education, will be necessary for perinatal health professionals until the curriculum model has been in place in preservice and postgraduate programs sufficiently long. Breastfeeding as a primary health care strategy, with its clear health and economic benefits, must be a part of any health care reform and, as such, will be a service expected to be provided by perinatal health professionals.

Education, Medical↗
PubMed1993

Effect of neonatal diethylstilbestrol exposure on volume of the sexually dimorphic nucleus of the preoptic area of the hypothalamus and pituitary responsiveness to gonadotropin-releasing hormone in female rats of known anogenital distance at birth.

The effects of neonatal diethylstilbestrol (DES) exposure on the volume of the sexually dimorphic nucleus of the preoptic area of the hypothalamus (SDN-POA) and on GnRH-stimulated LH secretion were investigated in castrated female rats of known anogenital distance (AGD) at birth. The AGD was measured in females on the day of birth, and 0.1 microgram DES or corn oil was injected from Days 1 through 10 of life. The volume of the SDN-POA was significantly larger in animals that had received DES than in those that had received corn oil. The largest SDN-POA volumes were seen in DES-treated animals that had long (> 1.4 mm) AGDs, and smallest volumes in corn oil-treated females that had short (< or = to 1.4 mm) AGDs. Within treatment groups, animals with longer AGDs had significantly larger SDN-POA volumes than those with short AGDs. Within AGD subgroups, the effect of DES was similar in that the percentage increase in SDN-POA volume was equivalent. Pituitary responsiveness to GnRH was greater in corn oil-treated females with long AGD than in similarly treated females with short AGD. DES treatment blunted LH secretion in both AGD subgroups, but the increased LH secretion was preserved in rats with long AGD. The results indicate that the individual effects of the postnatal environment depend on the androgenicity of the intrauterine microenvironment. Further, variations in the individual's response to potential environmental hazards may be predicted by antecedent intrauterine events.

Anal Canal↗
PubMed1991

Water movement in the rabbit eye.

The intraocular distribution of topically applied D2O was quantified using deuterium nuclear magnetic resonance (NMR) spectroscopy. D2O appeared in all tissues with the highest concentration in the aqueous humor (1.2 M); however, it rapidly dissipated from the eye. Surface coil NMR spectroscopy on D2O-treated eyes in vivo showed that the flow pattern was best described by a single exponential decay plus a constant. This suggests that the D2O flow consisted of a flow component representing vascular circulation (with a flow rate constant of 0.101 min-1), and a reservoir-like component. Topical D2O in conjunction with the surface-coil NMR technique can be used to examine the movement of water in the anterior segment of the living eye.

Animals↗
PubMed1991

A comparative study of carvedilol, slow-release nifedipine, and atenolol in the management of essential hypertension.

Carvedilol is a novel treatment for hypertension, having a balanced pharmacology of vasodilation and beta-receptor blockade. We present here the results of a three-way, multicenter, comparative study on the use of carvedilol, slow-release nifedipine, and atenolol in the management of essential hypertension. A total of 311 patients was entered into the study, of which 293 were randomized to one of the three treatment regimens. Full data are available on 255 patients. Systolic and diastolic blood pressure measurements, in both sitting and standing positions, were taken, together with the heart rate. There was no consistently significant difference between treatments with respect to blood pressure control. Differences in heart rate were more pronounced, with the reduction due to carvedilol being generally intermediate between nifedipine and atenolol. Further studies of carvedilol in hypertension, as well as other indications, are warranted.

Adolescent↗
PubMed1987

The relationship between glucagon receptors and metabolic profile in two strains of rats: Wistar-Furth and Sprague-Dawley.

We studied glucagon and insulin binding to isolated hepatocyte receptors in Wistar-Furth (WF) and Sprague-Dawley (SD) rats, using 125I-labeled hormones. Hepatocytes from WF rats bound more glucagon than hepatocytes from SD rats. There were no differences in insulin binding. These observations prompted us to investigate other strain differences. Fasting and nonfasting serum glucose, glucagon, insulin, and growth hormone were measured. WF animals had a lower fasting glucose and higher fasting glucagon than SD animals, while SD rats had higher nonfasting insulin levels and a higher hepatic glycogen content. Total hepatic glucose production in response to glucagon (10(-8) M) was greater in WF than in SD rats, while glucagon-stimulated gluconeogenesis from alanine was the same in the two groups of animals. We concluded that the decreased glucagon binding does not play a significant role in the maintenance of serum glucose or in the gluconeogenetic response glucagon, and that neither these responses nor the serum glucagon levels appears to be correlated with the number of glucagon receptors. We conclude further that different animal strains of the same species may differ in their biologic responses.

Animals↗
PubMed1985

Increased glucagon receptors in chronically hypersomatotrophic and hyperglucagonemic rats.

The effect of increased levels of growth hormone on glucagon binding by isolated hepatocytes and on the cellular cyclic AMP response to glucagon was evaluated in rats bearing growth hormone-secreting tumor (Mt-T-W15) and in rats treated with rat growth hormone. An increased binding, due to an increased number of receptors, was observed in both groups of animals. Glucagon binding did not correlate with plasma glucagon levels, suggesting a failure of down regulation, possibly due to an effect of growth hormone and insulin on the number of receptors. Tumor-bearing and growth hormone-treated rats had larger hepatocytes so that, when hormone binding was expressed in terms of square micrometer of membrane surface, it appeared decreased. When the tumor was removed the increase in the number of glucagon receptors per cell persisted, even though the average cell size returned toward normal. It is suggested that this retention of the receptors may have been the result of continuing hyperinsulinism. Basal cAMP levels were elevated in hepatocytes of tumor-bearing and growth hormone-treated animals, possibly due to cell hypertrophy. On the other hand, the maximum cAMP response to glucagon was not altered by the experimental procedures. A negative effect of insulin on cAMP accumulation may explain this apparent paradox. Indeed, hepatocytes isolated from rats following tumor removal, but with continuing hyperinsulinemia, had a lower maximum cAMP response, even though the glucagon binding per cell or per unit of cell surface was increased.

Animals↗
PubMed1984

Behavioral effects of circumcision with and without anesthesia.

The behavior of full-term neonates undergoing circumcision with and without local anesthesia was examined using the Brazelton Neonatal Assessment Scale (BNAS). Evaluations were done blindly pre-and postcircumcision and on the day following the procedure. Infants receiving lidocaine in a dorsal penile nerve block (DPNB) remained more attentive to animate and inanimate stimuli following circumcision and demonstrated a greater ability to quiet themselves when disturbed. The smoothness and maturity of motor behaviors showed the expected rate of improvement or recovery curve in the anesthetized group, while the control group's behavior did not. Behavioral differences were still evident on the day following the procedure. This report adds to the growing body of data that indicate that circumcision is a painful procedure that disrupts the course of behavioral recovery following birth. These disruptions can be lessened by the use of local anesthesia to relieve pain and stress during the procedure without any additional morbidity. These data support the use of DPNB during anesthesia for routine neonatal circumcisions still requested by the majority of parents in the country.

Anesthesia, Local↗