Serum thyroid hormones and tissue 5'-monodeiodinase activity in acutely thyroidectomized newborn lambs

1986 ◽  
Vol 251 (2) ◽  
pp. E151-E155 ◽  
Author(s):  
D. H. Polk ◽  
S. Y. Wu ◽  
D. A. Fisher
Keyword(s):  
Sham Operation ◽  
Fetal Sheep ◽  
Arterial Blood Gas ◽  
Arterial Blood ◽  
Brown Adipose ◽  
Serum T3 ◽  
Serum T4 ◽  
Serum Thyroid Hormones ◽  
Metabolic Significance

After either total thyroidectomy or sham operation in full-term fetal sheep, fetuses were delivered and serial blood samples were obtained for measurements of thyroxine (T4), triiodothyronine (T3), and catecholamines. Despite comparable serum T4 values (T4 means +/- SE, sham 7.1 +/- 0.6 micrograms/dl, thyroidectomized 6.8 +/- 0.7 micrograms/dl at 60 min after birth), serum T3 values were lower in the thyroidectomized animals (T3 means +/- SE, thyroidectomized 39 +/- 4.8 ng/dl, sham 153 +/- 20.1 ng/dl at 60 min after birth). Four hours after birth, the animals were killed with an intravenous overdose of barbiturate. Brain, thyroid, liver, kidney, and brown adipose tissues were dissected and analyzed for thyroxine 5'-monodeiodinase (5'-MDI) activity in vitro. 5'-MDI activity was comparable in all tissues from sham-operated and thyroidectomized lambs. Plasma epinephrine and norepinephrine concentrations, mean arterial pressure, mean pulse, rectal temperature, and arterial blood gas values were similar in the two groups of animals. These data support the hypothesis that the thyroid gland is the major source of T3 for the T3 surge in the immediate newborn period. They also indicate that the neonatal T3 surge has limited immediate metabolic significance in euthyroid newborns.

Cold-induced increase in brown fat thyroxine 5'-monodeiodinase is attenuated in Zucker obese rat

1987 ◽  
Vol 252 (1) ◽  
pp. E63-E67 ◽  
Author(s):  
S. Y. Wu ◽  
J. S. Stern ◽  
D. A. Fisher ◽  
Z. Glick
Keyword(s):  
Cafeteria Diet ◽  
Treatment Groups ◽  
Brown Adipose ◽  
Obese Rats ◽  
Serum T3 ◽  
Serum T4 ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

In this study we examined the possibility that the reduced brown adipose tissue (BAT) thermogenesis in the Zucker obese rat may result from a limited capacity for enzymic conversion of thyroxine (T4) to triiodothyronine (T3) in BAT. A total of 34 lean and obese rats, approximately 4 mo old were divided into three treatment groups: group 1 (5 lean and 6 obese) was fed Purina rat chow for 21 days, and group 2 (5 lean and 6 obese) was fed a cafeteria diet for 21 days, and group 3 (6 lean and 6 obese) was fed Purina rat chow and maintained in the cold (8 +/- 1 degrees C) for 7 days. The lean and obese rats in all three groups of animals were matched closely for age and respective body weight. Activity of T4 5'-deiodinase was determined as the rate of T3 production from added T4 under controlled in vitro conditions. Serum T4 and T3 were determined by radioimmunoassay. The rate of T4-to-T3 conversion in BAT was similar in the lean and obese rats maintained at room temperature, whether fed rat chow or a cafeteria diet (approximately 40-50 pmol T3/scapular BAT depot per h). However, expressed per scapular BAT depot, lean rats exposed to cold displayed about a fivefold increase in BAT T3 production (P less than 0.0001), whereas only a small increase was observed in the cold-exposed obese rats. Serum T3 levels tended to be reduced in the Zucker obese rats. Our data indicate a reduced capacity for T3 production in Zucker rat BAT exposed to cold.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Inhibition of pituitary type 2 deiodinase by reverse triiodothyronine does not alter thyroxine-induced inhibition of thyrotropin secretion in hypothyroid rats

2005 ◽  
Vol 153 (3) ◽  
pp. 429-434 ◽  
Author(s):  
P Cettour-Rose ◽  
T J Visser ◽  
A G Burger ◽  
F Rohner-Jeanrenaud
Keyword(s):  
Specific Inhibitor ◽  
Adult Rats ◽  
Reverse T3 ◽  
Brown Adipose ◽  
Tsh Secretion ◽  
Serum T3 ◽  
Serum T4 ◽  
Serum Tsh ◽  
Tsh Levels

Objectives: Intrapituitary triiodothyronine (T3) production plays a pivotal role in the control of TSH secretion. Its production is increased in the presence of decreased serum thyroxine (T4) concentrations and the enzyme responsible, deiodinase type 2 (D2), is highest in hypothyroidism. In order to document the role of this enzyme in adult rats we developed an experimental model that inhibited this enzyme using the specific inhibitor, reverse T3 (rT3). Methods: Hypothyroidism was induced with propylthiouracil (PTU; 0.025 g/l in drinking water) which in addition blocked deiodinase type 1 (D1) activity, responsible for the rapid clearance of rT3 in vivo. During the last 7 days of the experiment, the hypothyroid rats were injected (s.c.) for 4 days with 0.4 or 0.8 nmol T4 per 100 g body weight (bw) per day. For the last 3 days, the same amount of T4 was infused via s.c. minipumps. In additional groups, 25 nmol rT3/100 g bw per day were added to the 3-day infusion of T4. Results: Infusion of 0.4 nmol T4/100 g bw per day did not affect the high serum TSH levels, 0.8 nmol T4/100 g bw per day decreased them to 57% of the hypothyroid values. The infusions of rT3 inhibited D2 activity in all organs where it was measured: the pituitary, brain cortex and brown adipose tissue (BAT). In the pituitary, the activity was 27%, to less than 15% of the activity in hypothyroidism. Despite that, serum TSH levels did not increase, serum T4 concentrations did not change and the changes in serum T3 were minimal. Conclusions: We conclude that in partly hypothyroid rats, a 3-day inhibition of D2 activity, without concomitant change in serum T4 and minimal changes in serum T3 levels, is not able to upregulate TSH secretion and we postulate that this may be a reflection of absent or only minimal changes in circulating T3 concentrations.

scholarly journals Desensitization of Adrenaline-Induced Red Blood Cell H+ Extrusion in Vitro After Chronic Exposure of Rainbow Trout to Moderate Environmental Hypoxia

1991 ◽  
Vol 156 (1) ◽  
pp. 233-248 ◽  
Author(s):  
S. THOMAS ◽  
R. KINKEAD ◽  
P. J. WALSH ◽  
C. M. WOOD ◽  
S. F. PERRY
Keyword(s):  
Rainbow Trout ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Whole Blood ◽  
Inverse Correlation ◽  
Adrenergic Stimulation ◽  
Plasma Adrenaline ◽  
Arterial Blood Gas ◽  
Arterial Blood

The sensitivity of red blood cell Na+/H+ exchange to exogenous adrenaline was assessed in vitro using blood withdrawn from catheterized rainbow trout (Oncorhynchus mykiss) maintained under normoxic conditions [water PO2, (PwO2)=20.66 kPa] or after exposure to moderate hypoxia (PwO2=6.67-9.33 kPa) for 48 h, which chronically elevated plasma adrenaline, but not noradrenaline, levels. Peak changes in whole-blood extracellular pH over a 30 min period after adding 50–1000 nmoll−1 adrenaline were employed as an index of sensitivity; the blood was pre-equilibrated to simulate arterial blood gas tensions in severely hypoxic fish (PaO2=2.0 kPa, PaCO2=0.31 kPa). Blood pooled from normoxic fish displayed a dose-dependent reduction in whole-blood pH after addition of adrenaline. Blood pooled from three separate groups of hypoxic fish, however, displayed diminished sensitivity to adrenaline, ranging from complete desensitization to a 60%reduction of the response. Subsequent experiments performed on blood from individual (i.e. not pooled) normoxic or hypoxic fish demonstrated an inverse correlation between the intensity of H+ extrusion (induced by exogenous adrenaline addition) and endogenous plasma adrenaline levels at the time of blood withdrawal. However, acute increases in plasma adrenaline levels in vitro did not affect the responsiveness of the red blood cell to subsequent adrenergic stimulation. The intensity of H+ extrusion was inversely related to the PaO2in vivo between 2.67 and 10.66 kPa, and directly related to the logarithm of the endogenous plasma adrenaline level. The results suggest that desensitization of Na+/H+ exchange in chronically hypoxic fish is related to persistent elevation of levels of this catecholamine. This desensitization can be reversed in vitro as a function of time, but only when blood is maintained under sufficiently aerobic conditions.

Ultrasound guided blood sampling from fetal sheep

1989 ◽  
Vol 40 (2) ◽  
pp. 401 ◽  
Author(s):  
JP Newnham ◽  
RW Kelly ◽  
P Boyne ◽  
SE Reid
Keyword(s):  
Ultrasound Guidance ◽  
Needle Aspiration ◽  
Blood Sampling ◽  
Ultrasound Guided ◽  
Fetal Sheep ◽  
Arterial Blood Gas ◽  
Operator Experience ◽  
Arterial Blood ◽  
Fetal Death Rate ◽  
Repeated Sampling

The feasibility of obtaining fetal blood samples by needle aspiration under ultrasound guidance was assessed in 32 fetal sheep from 101-1 36 days' gestation. Seventy-six attempts at blood sampling were made, of which all but two were successful. The overall fetal death rate resulting from this procedure was 9.2%. However, with increasing operator experience and with advancing gestational age, 95.5% of fetuses survived the procedure. Repeated sampling from individual fetuses had minimal effects on arterial blood gas values. Ultrasound guided blood sampling now provides an alternative to chronic catheterization as a basis for some types of research with fetal sheep.

Umbilical cord occlusion stimulates breathing independent of blood gases and pH

1991 ◽  
Vol 70 (4) ◽  
pp. 1796-1809 ◽  
Author(s):  
S. L. Adamson ◽  
I. M. Kuipers ◽  
D. M. Olson
Keyword(s):  
Prostaglandin E2 ◽  
Umbilical Cord ◽  
Blood Gases ◽  
High Frequency Oscillation ◽  
Breathing Rate ◽  
Fetal Sheep ◽  
Arterial Pco2 ◽  
Arterial Blood Gas ◽  
Arterial Blood

The role of umbilical cord occlusion in the initiation of breathing at birth was investigated by use of 16 unanesthetized fetal sheep near full term. Artificial ventilation with high-frequency oscillation was used to control fetal arterial blood gas tensions. At baseline, PCO2 was maintained at control fetal values and PO2 was elevated to between 25 and 50 Torr. In the first study on six intact and four vagotomized fetuses, arterial PCO2 and PO2 were maintained constant during two 30-min periods of umbilical cord occlusion. Nevertheless, the mean fetal breathing rate increased significantly when the umbilical cord was occluded. In the second study on six intact fetuses, hypercapnia (68 Torr) was imposed by adding CO2 to the ventilation gas. When the umbilical cord was occluded, there was a significantly greater stimulation of breathing (rate, incidence, and amplitude) in response to hypercapnia than in response to hypercapnia alone. During cord occlusion, plasma prostaglandin E2 concentration decreased significantly. Results indicate that cord occlusion stimulates breathing possibly by causing the removal of a placentally produced respiratory inhibitor such as prostaglandin E2 from the circulation.

scholarly journals Effectiveness of Nurse Led Intervention on Respiratory Parameters and Cholinesterase among Organophosphorus Compound Poisoning Patients Admitted in Dhanvantri Critical Care Centre at Erode – A Historical Comparison

1970 ◽  
Vol 1 (2) ◽  
Author(s):  
Aruna Devi. G
Keyword(s):  
Partial Pressure ◽  
Organophosphorus Compound ◽  
Serum Cholinesterase ◽  
Control Group ◽  
Care Centre ◽  
Arterial Blood Gas ◽  
Historical Comparison ◽  
Arterial Blood ◽  
Respiratory Parameters

Context: Nurses play a vital role in the management of poisoning,as it demands close observation, timely administration of antidotes in adequate doses and skilful nursing interventions. Methods:Quasi experimental design- A historical comparison was adopted.Total 30 organophosphorus compound poisoning patients, out of which 15 participants were in experimental group and 15 participants were in control group. Purposive sampling technique was used to select the participants admitted in Dhanvantri Critical Care Centre at Erode. The level of respiratory parameters were assessed by adopting in vitro ABG (Arterial Blood Gas) analysis which constitutes pH (acidity), pCO2 (partial pressure of carbon dioxide), pO2 (partial pressure of oxygen) and HCO3 (bicarbonate). Serum cholinesterase estimation level was measured from the vein by adopting in vitro method.

Infusion of ACTH stimulates expression of adrenal ACTH receptor and steroidogenic acute regulatory protein mRNA in fetal sheep

2006 ◽  
Vol 291 (2) ◽  
pp. E214-E220 ◽  
Author(s):  
Luke C. Carey ◽  
Yixin Su ◽  
Nancy K. Valego ◽  
James C. Rose
Keyword(s):  
Regulatory Protein ◽  
Late Gestation ◽  
Mrna Levels ◽  
Acth Stimulation ◽  
Fetal Sheep ◽  
Fetal Plasma ◽  
Arterial Blood ◽  
Acth Receptor ◽  
Underlying Mechanisms

The late-gestation plasma cortisol surge in the sheep fetus is critical for stimulating organ development and parturition. Increased adrenal responsiveness is one of the key reasons for the surge; however, the underlying mechanisms are not fully understood. Our recent studies suggest that ACTH-mediated increased expression of ACTH receptor (ACTH-R) and steroid acute regulatory protein (StAR) may play a role in enhancing responsiveness. Hence, we examined effects of ACTH infusion in fetal sheep on mRNA expression of these two mediators of adrenal responsiveness and assessed the functional consequences of this treatment in vitro. Fetuses of ∼118 and 138 days of gestational age (dGA) were infused with ACTH-(1–24) for 24 h. Controls received saline infusion. Arterial blood was sampled throughout the infusion. Adrenals were isolated and analyzed for ACTH-R and StAR mRNA, or cells were cultured for 48 h. Cells were stimulated with ACTH, and medium was collected for cortisol measurement. Fetal plasma ACTH and cortisol concentrations increased over the infusion period in both groups. ACTH-R mRNA levels were significantly higher in ACTH-infused fetuses in both the 118 and 138 dGA groups. StAR mRNA increased significantly in both the 118 and 138 dGA groups. Adrenal cells from ACTH-infused fetuses were significantly more responsive to ACTH stimulation in terms of cortisol secretion than those from saline-infused controls. These findings demonstrate that increases in circulating ACTH levels promote increased expression of ACTH-R and StAR mRNA and are coupled to heightened adrenal responsiveness.

Effects of in vivo metabolic acidosis on midcortical bone ion composition

1999 ◽  
Vol 277 (5) ◽  
pp. F813-F819 ◽  
Author(s):  
David A. Bushinsky ◽  
Jan M. Chabala ◽  
Konstantin L. Gavrilov ◽  
Riccardo Levi-Setti
Keyword(s):  
Metabolic Acidosis ◽  
Bone Mineral ◽  
Calcium Absorption ◽  
Urinary Calcium ◽  
Calcium Excretion ◽  
Ion Composition ◽  
Arterial Blood Gas ◽  
Arterial Blood

Chronic metabolic acidosis increases urine calcium excretion without altering intestinal calcium absorption, suggesting that bone mineral is the source of the additional urinary calcium. During metabolic acidosis there appears to be an influx of protons into bone mineral, lessening the magnitude of the decrement in pH. Although in vitro studies strongly support a marked effect of metabolic acidosis on the ion composition of bone, there are few in vivo observations. We utilized a high-resolution scanning ion microprobe with secondary ion mass spectroscopy to determine whether in vivo metabolic acidosis would alter bone mineral in a manner consistent with its purported role in buffering the increased proton concentration. Postweanling mice were provided distilled drinking water with or without 1.5% NH4Cl for 7 days; arterial blood gas was then determined. The addition of NH4Cl led to a fall in blood pH and [Formula: see text] concentration. The animals were killed on day 7, and the femurs were dissected and split longitudinally. The bulk cortical ratios Na/Ca, K/Ca, total phosphate/carbon-nitrogen bonds [(PO2 + PO3)/CN], and[Formula: see text]/CN each fell after 1 wk of metabolic acidosis. Because metabolic acidosis induces bone Ca loss, the fall in Na/Ca and K/Ca indicates a greater efflux of bone Na and K than Ca, suggesting H substitution for Na and K on the mineral. The fall in (PO2 + PO3)/CN indicates release of mineral phosphates, and the fall in[Formula: see text]/CN indicates release of mineral[Formula: see text]. Each of these mechanisms would result in buffering of the excess protons and returning the systemic pH toward normal.

scholarly journals Continuous Measurement of Arterial Blood Gas Status during Total Hip Replacement: A Prospective Study

1996 ◽  
Vol 24 (3) ◽  
pp. 334-341 ◽  
Author(s):  
B. Venkatesh ◽  
D. W. Pigott ◽  
A. Fernandez ◽  
S. P. Hendry
Keyword(s):  
Total Hip Replacement ◽  
Hip Replacement ◽  
Blood Gases ◽  
Blood Gas ◽  
Arterial Blood Gas ◽  
Total Hip ◽  
Arterial Blood ◽  
The Mean ◽  
A Prospective Study

The arterial blood gas chemistry was measured continuously in ten patients during primary cemented total hip replacement in order to define more precisely the patterns of changes in blood gases during various stages of the operation. All ten patients demonstrated significant drops in PaO2 after femoral cement implantation and nine of the ten after acetabular cement implanation. The mean drop in PaO2 following acetabular cement expressed as mean ± SD was 18±8 mmHg (16±6%) (P<0.05) and femoral cement application was 25±11 mmHg (23±9%) (P<0.05). For changes in PaO2 there were corresponding drops in SpO2 in all patients with the femoral cement and in eight patients with the acetabular cement. The mean drop in SpO2 following the application of acetabular and femoral cements respectively were 1.7±1.5% and 3±2.45%. No changes in blood PaO2 were observed during dislocation of the hip joint or reaming of acetabulum and femur. In vitro studies revealed no effect of the liquid monomer or the cured cement on the performance of the Clark electrode of the sensor. We suggest that significant drops in PaO2 occur with both acetabular and femoral cement implantation and that the derangements in blood PaO2 last longer than detected by pulse oximetry following cement implantation.

Sign in / Sign up

Export Citation Format

Share Document