Search PubMed⌕ Search

Biomedical subjects

L Day

Publications and source records attributed to L Day.

At least 55 records · Page 3Linked to original sources
PubMed1992

Fetal catecholamine, cardiovascular, and neurobehavioral responses to cocaine.

OBJECTIVE: Although maternal cocaine administration results in fetal cardiovascular and behavioral alterations, these responses have been attributed to hypoxia resulting from reduced uteroplacental blood flow. We studied the fetal catecholamine, cardiovascular, and neurobehavioral responses to direct fetal cocaine administration. STUDY DESIGN: Cardiovascular, electrocortical, and electroocular responses and plasma catecholamines were monitored in chronically catheterized fetal sheep (n = 7), 127 +/- 2 days' gestation, during a control period and after intravenous fetal injections of cocaine 0.5 and 1.0 mg/kg. RESULTS: Intravenous cocaine caused prompt increases in fetal plasma norepinephrine (372 +/- 73 to 531 +/- 112 and 842 +/- 233 pg/ml), epinephrine (27 +/- 7 to 46 +/- 13 and 49 +/- 11 pg/ml), and systolic blood pressure (46 +/- 2 to 53 +/- 2 and 55 +/- 2 mm Hg). Low-voltage electrocortical activity decreased from 61.7% +/- 3.0% to 38.4% +/- 3.9% in the first hour after the cocaine 0.5 mg/kg dose but recovered to baseline values during the second hour. After the cocaine 1.0 mg/kg dose, low-voltage electrocortical activity decreased to 40.7% +/- 2.0% and did not recover thereafter. Fetal blood gas values did not change. CONCLUSION: Direct fetal cocaine administration increases fetal plasma catecholamine levels and fetal blood pressure and suppresses low-voltage electrocortical activity. Chronic cocaine exposure may hamper central nervous system maturation and alter postnatal development.

Animals↗
PubMed1992

Concentration thresholds for fetal swallowing and vasopressin secretion.

In adults, plasma osmolality thresholds for hypernatremia-induced arginine vasopressin (AVP) secretion are similar or less than thresholds for stimulation of thirst. In the fetus, the thresholds for swallowing stimulation and AVP secretion have not been defined. Fetal swallowing and AVP secretory responses to hypertonic NaCl and urea were determined in six fetuses (130 +/- 1 1 days) chronically prepared with thyrohyoid, nuchal and thoracic esophagus, and diaphragm electromyograms (EMG), an esophageal flow probe, and vascular catheters. Fetuses received intracarotid injections (0.15 ml/kg) of increasing concentrations of NaCl (0.15, 0.30, 0.45, 0.60, 0.75, and 0.90 M), administered at 2-min intervals. A swallow was defined as a coordinated time-sequence of fetal thyrohyoid, nuchal esophagus, and thoracic esophagus EMG activity. The threshold saline concentration for swallowing was defined as the minimum NaCl dose eliciting swallow responses (within 20 s) after four of five injections at each dose. During a 2-h control period swallowing averaged 25.0 +/- 10.1 ml/h and 39.4 +/- 14.6 swallows/h. The mean NaCl threshold concentration for swallowing stimulation was 0.56 +/- 0.06 M. Fetal plasma AVP (2.6 +/- 0.9 pg/ml) increased significantly at the maximum subthreshold (7.6 +/- 4.0 pg/ml) and the threshold NaCl concentration (8.2 +/- 4.0 pg/ml) that stimulated swallowing. On a subsequent day, equiosmolar urea injections increased plasma AVP (from 2.2 +/- 0.7 to 7.6 +/- 2.6 pg/ml) but had no effect on swallowing activity. Fetal mean arterial blood pressure increased after injections of threshold saline and urea concentrations. Fetal arterial blood osmolality and sodium concentration did not change during any study.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Marketing: Part 1 of 4. Promoting the health visiting profession.

Despite its long history, health visiting still suffers a low public and professional profile; few people know what health visitors do. In the first of a four-part series LIZ DAY argues that health visitors should adopt commercial marketing strategies to 'sell' their services to the public, to NHS managers and to primary health care colleagues. She suggests ways to adapt these commercial sales techniques to an NHS context.

Community Health Nursing↗
PubMed1991

Intraruminal rehydration of ovine fetuses.

During oral rehydration of adult mammals, oropharyngeal stimulation, the act of swallowing, and/or gastric factors contribute to a rapid decrease in plasma arginine vasopressin (AVP) that precedes plasma osmolality changes. To determine whether similar mechanisms are present in the developing fetus, six chronically prepared ovine fetuses were rehydrated with intraruminal (IR) distilled water infusions (1 ml.kg-1.min-1 for 60 min) after 43 +/- 3 h of maternal water deprivation. In response to maternal dehydration, significant increases were noted in maternal and fetal mean plasma osmolalities, sodium and AVP concentrations, and fetal urine osmolality. As estimated by hematocrit, fetal intravascular volume decreased by 11%. Fetal rehydration via IR distilled water infusion evoked a significant decrease in fetal plasma osmolality but no change in urine osmolality. Unexpectedly, fetal arterial blood pressure increased and arterial PO2 decreased while fetal hematocrit indicated a further 7% decrease in intravascular volume after the IR infusion. There was a nonsignificant trend toward increased fetal glomerular filtration rate, urine volume, and plasma AVP concentrations. Identical IR water infusions to five euhydrated fetuses resulted in significant decreases in fetal plasma osmolality and increases in glomerular filtration rate, urine flow, and osmolar excretion. The euhydrated fetuses also exhibited significant increases in mean arterial blood pressure and hematocrit and decreased fetal arterial PO2. These results indicate that IR water does not suppress AVP secretion in the dehydrated ovine fetus. Rather, both euhydrated and dehydrated fetuses exhibit an idiosyncratic vasoconstrictive response to IR water.

Animals↗
PubMed1991

Fetal swallowing: response to graded maternal hypoxemia.

A computer-based system, incorporating electromyography (EMG) and esophageal fluid flow measurement, was used to determine fetal breathing and swallowing responses to graded maternal hypoxemia. Five chronically prepared ewes with singleton fetuses at a gestational age of 130 +/- 2 (SE) days were subjected to successive 30-min periods of mild and moderate hypoxemia (inspired O2 fraction = 0.16 and 0.13, respectively). Mild and moderate maternal hypoxemia evoked significant reductions in fetal arterial PO2 (21 +/- 1 to 17 +/- 1 and 13 +/- 1 Torr, respectively), while fetal arterial pH, hematocrit, plasma osmolality, heart rate, and mean blood pressure did not change. Moderate hypoxemia was associated with significant increases in fetal plasma arginine vasopressin and renin activity and significant reductions from basal values in percent time breathing (53 +/- 4 to 25 +/- 12%), percent time swallowing (11.5 +/- 3.1 to 1.3 +/- 0.7%), and volume swallowed (21.3 +/- 2.1 to 4.8 +/- 2.7 ml/30 min). Fetal swallowing activity was better correlated with arterial PO2 (r = 0.8) than breathing activity (r = 0.45). We conclude that fetal swallowing is suppressed during mild and moderate hypoxemia. It is suggested that several sites and/or mechanisms may account for the hypoxemic inhibition of fetal activities.

Animals↗
PubMed1991

Ovine fetal breathing and swallowing activity in response to plasma glucose changes.

Fetal swallowing activity generally occurs simultaneously with fetal breathing movements (FBM) in sheep. The present study investigated the FBM and swallowing responses to altered fetal plasma glucose. Fetal lambs were chronically prepared with laryngeal, esophageal and diaphragm electromyogram (EMG) wires, an esophageal flow probe and vascular catheters. Beginning at 138 +/- 1 day, FBM and swallowing were monitored during control periods and in response to intravenous glucose infusions (14 mg/kg/min for 120 min) to fetuses of fed and fasted ewes. Glucose infusions to fetuses of fed ewes resulted in significant increases in fetal plasma glucose (21.2 +/- 0.7 to 40.5 +/- 1.9 mg/dl) and time breathing (46.2 +/- 6.3 to 60.0 +/- 9.5 min/2 h). In response to maternal fasting, fetal glucose levels (13.4 +/- 1.0 mg/dl) and time breathing (23.0 +/- 7.2 min/2 h) decreased significantly. Glucose infusion to fetuses of fasted ewes resulted in significant increases in time breathing (50.3 +/- 13.4 min/2 h) and diaphragmatic EMG activity (1,295 +/- 654 to 3,012 +/- 1,182 spikes/2 h). There was no change from basal levels of fetal EMG swallows (83.2 +/- 4.3 swallows/2 h) or esophageal flow (40.8 +/- 7.9 ml/2 h) in response to maternal fasting or fetal glucose infusions.

Animals↗
PubMed1991

Fetal rehydration via intraamniotic fluid: contribution of fetal swallowing.

Amniotic fluid volume is regulated by a balance of fetal fluid production and resorption. Although fetal swallowing is believed to be a major site of fluid resorption, additional routes of fluid exchange also may contribute. In our present study, five chronically prepared, water-restricted, pregnant ewes with singleton fetuses (128 +/- 1 d) were rehydrated via an intraamniotic infusion (100 mL/h over 90 min) of 0.075 M saline. In response to the maternal water restriction, significant increases were noted in maternal and fetal plasma osmolalities (306.6 +/- 1.2 to 315.4 +/- 2.4; 300.5 +/- 1.5 to 311.0 +/- 1.6 mosmol/kg, respectively) and arginine vasopressin concentrations (1.9 +/- 0.2 to 22.6 +/- 5.0; 1.5 +/- 0.1 to 8.5 +/- 2.2 pg/mL, respectively). After the intraamniotic infusion, fetal plasma osmolality (311.0 +/- 1.6 to 303.0 +/- 1.2 mosmol/kg) and hematocrit (36.7 +/- 1.9 to 33.8 +/- 1.4%) significantly decreased although there was no change in maternal arterial blood values. Fetal swallowing averaged 0.39 +/- 0.10 mL/min during the basal period and 0.34 +/- 0.17 mL/min at maximum dehydration, and decreased significantly to 0.19 +/- 0.07 mL/min in response to the intraamniotic infusion. These results indicate the rapid absorption of intraamniotic fluid by the dehydrated ovine fetus, despite the suppression of fetal swallowing. The volume swallowed during and after the intraamniotic infusion was insufficient to account for the observed changes in fetal plasma osmolality and hematocrit. Thus, alternative routes of fluid absorption (i.e. intramembranous flow) likely predominate under conditions of increased fetal plasma to amniotic fluid osmotic gradients.

Absorption↗
PubMed1990

Fetal swallowing: response to systemic hypotension.

The fetal swallowing and endocrine responses to systemic hypotension were studied in five chronically instrumented ovine fetuses (125 +/- 2 days). Fetuses were prepared with bipolar electrodes inserted in the thyrohyoid muscle, nuchal esophagus, and thoracic esophagus, a flow probe surrounding the thoracic esophagus, and arterial and venous catheters. In response to an intravenous infusion of sodium nitroprusside, fetal mean arterial blood pressure decreased from 50.8 +/- 3.6 to 41.7 +/- 3.8 mmHg. Fetal plasma renin activity (5.0 +/- 1.4-25.1 +/- 10.3 ng.ml-1.h-1) and arginine vasopressin (5.6 +/- 4.5-26.3 +/- 21.0 pg/ml) increased, while fetal swallowing electromyogram activity (7.3 +/- 1.1-1.9 +/- 0.3 swallows/10 min) and esophageal flow (5.5 +/- 3.1-1.2 +/- 0.9 ml/10 min) significantly decreased during the nitroprusside infusion. These results indicate a suppression of fetal swallowing in response to systemic hypotension despite stimulation of the renin-angiotensin system.

Animals↗
PubMed1990

Fetal swallowing: correlation of electromyography and esophageal fluid flow.

Patterns of fetal drinking behavior were quantified in five singleton fetuses (128 +/- 1 days gestation) by computer analysis of laryngeal-esophageal electromyography (EMG) and thoracic esophageal fluid flow. Esophageal flow was noted to be bidirectional with an average antegrade flow-to-retrograde flow ratio of 4.4 +/- 1.5. Retrograde esophageal flow coincided with diaphragmatic contractions, suggesting that inspiratory gastroesophageal pressure gradients may be operative. The regurgitated fluid was returned to the fetal rumen by thoracic esophageal contractions. Significant net fluid intake was noted during periods of primarily unidirectional antegrade esophageal flow. Fetuses swallowed an average of 35 +/- 9 ml/h during the 12-h study, extrapolating to an average daily volume of 840 +/- 224 ml. An EMG "propagated swallow" representing coordinated contractions of the thyrohyoid, nuchal esophagus, and thoracic esophagus averaged 43 +/- 3 swallows/h and was highly correlated with net esophageal flow. Nearly 60% of the total fluid intake occurred during "bouts" of propagated swallows, which represented only 8% of the study period. Bouts averaged 11.7 +/- 0.4 propagated swallows, lasted 2.1 +/- 0.2 min, and occurred every 27.6 +/- 1.7 min. Although EMG swallowing activity was similar, there were significant differences among fetuses in net esophageal fluid flow and volume per propagated swallow. We speculate that fetal fluid intake is dependent on the availability and physical properties of the swallowed fluid, whereas swallowing activity is primarily related to cortical maturation and thirst stimulation.

Animals↗
PubMed1990

Maternal dehydration: impact on ovine amniotic fluid volume and composition.

Maternal dehydration consistent with mild water deprivation or moderate exercise results in maternal and fetal plasma hyperosmolality and increased plasma arginine vasopressin (AVP). Previous studies have demonstrated a reduction in fetal urine and lung fluid production in response to maternal dehydration or exogenous fetal AVP. As fetal urine and perhaps lung liquid combine to produce amniotic fluid, maternal dehydration may affect the amniotic fluid volume and/or composition. In the present study, six chronically-prepared pregnant ewes with singleton fetuses (128 +/- 1 day) were water deprived for 54 h to determine the effect on amniotic fluid. Maternal plasma osmolality (306.5 +/- 0.9 to 315.6 +/- 1.9 mOsm/kg) and AVP (1.9 +/- 0.2 to 22.2 +/- 3.2 pg/ml) significantly increased during dehydration. Similarly, fetal plasma osmolality (300.0 +/- 0.9 to 312.7 +/- 1.7 mOsm/kg) and AVP (1.4 +/- 0.1 to 10.4 +/- 2.4 pg/ml) increased in parallel to maternal values. Amniotic fluid osmolality (276.8 +/- 5.7 to 311.6 +/- 6.5 mOsm/kg) and sodium (139.8 +/- 4.8 to 154.0 +/- 5.4 mEq/l) and potassium (9.1 +/- 1.3 to 13.9 +/- 2.4 mEq/l) concentrations increased while a significant (35%) reduction in amniotic fluid volume occurred (871 +/- 106 to 520 +/- 107 ml). These results indicate that maternal dehydration may have marked effects on maternal-fetal-amniotic fluid dynamics, possibly contributing to the development of oligohydramnios.

Amniotic Fluid↗
PubMed1989

The human mannose-binding protein gene. Exon structure reveals its evolutionary relationship to a human pulmonary surfactant gene and localization to chromosome 10.

The human mannose-binding protein (MBP) plays a role in first line host defense against certain pathogens. It is an acute phase protein that exists in serum as a multimer of a 32-kD subunit. The NH2 terminus is rich in cysteines that mediate interchain disulphide bonds and stabilize the second collagen-like region. This is followed by a short intervening region, and the carbohydrate recognition domain is found in the COOH-terminal region. Analysis of the human MBP gene reveals that the coding region is interrupted by three introns, and all four exons appear to encode a distinct domain of the protein. It appears that the human MBP gene has evolved by recombination of an ancestral nonfibrillar collagen gene with a gene that encodes carbohydrate recognition, and is therefore similar to the human surfactant SP-A gene and the rat MBP gene. The gene for MBP is located on the long arm of chromosome 10 at 10q11.2-q21, a region that is included in the assignment for the gene for multiple endocrine neoplasia type 2A.

Acute-Phase Proteins↗
PubMed1989

Education matters.

Explore the source record for details and available documents.

Community Health Nursing↗
PubMed1989

Stimuli for fetal swallowing: systemic factors.

Although the fetal gastrointestinal tract is believed to be a major site of amniotic fluid absorption, there is little information with regard to the acute regulation of fetal swallowing. A model for the study of ovine fetal swallowing was developed to incorporate electromyograms, an esophageal flow probe, and a computer data acquisition and analysis program. The fetal swallowing responses to two primary thirst stimuli, plasma hyperosmolality and angiotensin II, were studied. On alternate days, chronically prepared fetal lambs (131 +/- 2 days) received an intravenous infusion of angiotensin II (100 ng/kg per minute) or bolus injections (3 ml) of 0.15 and 3.97 mol/L saline solution. In response to the angiotensin II infusion, fetal systolic (49.3 to 64.7 mm Hg; p less than 0.05) and diastolic (31.1 to 40.5 mm Hg; p less than 0.05) blood pressures significantly increased. However, fetal swallowing did not change from basal rates of 0.85 swallows per minute and a net esophageal flow of 0.98 ml/min. In response to the injection of 3.97 mol/L saline solution, fetal plasma osmolality increased (292 to 306 mOsm; p less than 0.05) and subsequently decreased to 300 mOsm at 15 minutes after the injection. Within 1 minute after injection of the hypertonic saline solution, fetal swallowing activity (6.0 swallows per minute; p less than 0.05) and net esophageal flow (2.4 ml/min; p less than 0.05) significantly increased. Swallowing returned to basal values within 5 minutes after the injection. The data indicate that ovine fetal responses to osmolar thirst challenges are intact at 130 days' gestation. Fetal swallowing and thus amniotic fluid volume may be affected by fetal responses to in utero stimuli.

Angiotensin II↗