Cardiac murmurs: echocardiography in the assessment of patients requiring antibiotic prophylaxis for dental treatment

BACKGROUND

Traditionally patients who indicate that they have a heart murmur or who indicate that they have had rheumatic fever are given antibiotic prophylaxis for dental treatment. This is commonly done without further assessment of the patient's actual endocarditis risk. Echocardiography is a non-invasive method of assessing cardiac valve function and haemodynamics.

METHODS

Consecutive patients who were referred to a private practice oral and maxillofacial surgeon for dentoalveolar surgery and indicated that they had a cardiac problem and usually had antibiotic prophylaxis, were evaluated. Those with a clear indication for prophylaxis, for example had prosthetic heart valves or previous infective endocarditis, received antibiotic prophylaxis. Where there was uncertainty, they were referred for an echocardiogram, and if abnormal, a formal cardiology review.

RESULTS

Three hundred and seventy patients out of approximately 20 000 (1.85 per cent) indicated that they had a cardiac murmur and usually received antibiotic prophylaxis for dental treatment between 1 February 1997 and 1 February 2005. Two hundred and sixty-two (71 per cent) were female and 108 (29 per cent) were male; age range 0.7 to 98 years, average 37.6 years. Two hundred and seventy (72 per cent) had normal hearts with no indication for antibiotic prophylaxis. Of the 100 (28 per cent) patients with abnormal findings, they were on average older; 49.5 years, range 0.7 to 87 years. Of these, 50 (14 per cent) met current indications for antibiotic prophylaxis.

CONCLUSION

Patients who present for dental treatment indicating that they require antibiotic prophylaxis for cardiac condition need to be fully evaluated. In this study only 50 of 370 patients (14 per cent) required antibiotic prophylaxis. The remaining 320 (86 per cent) would have no benefit but a risk of adverse reaction to the antibiotic.

Contemporary therapy: aromatherapy in the management of acute pain?

Recent surveys indicate that people are increasingly using complementary therapies as an adjunct or alternative to conventional treatment options as well as for general health and well being. Whilst complementary therapies such as aromatherapy have been utilised in clinical settings as diverse as long term care facilities and palliative care, its application to the acute care setting has not been explored in depth. The changes in contemporary health care practices such as post-operative pain management and length of hospital admissions have provided nurses with the challenge of examining the range of therapeutic interventions that can be applied to their practice. The purpose of this paper is to examine critically the potential uses of aromatherapy in the management of acute post-operative pain. The concept of aromatherapy will be explored in relation to its effects on the pain pathways, methods of administration and therapeutic effects. Specific reference will be made to Lavender (Lavandula angustifolia) and its use in aromatherapy. A review of the literature points to gaps in the knowledge related to the clinical application of aromatherapy in relation to issues of dosage, methods of administration and therapeutic effects. The relatively small number of studies that have looked at aromatherapy in the acute care setting supports the literature reviewed. Issues such as small sample sizes and the difficulty in replicating these studies make it difficult to generalize the findings. In order to achieve best practice, further research is necessary to explore the use of aromatherapy in the management of acute post-operative pain.

Estrogen improves abnormal norepinephrine-induced vasoconstriction in postmenopausal women

OBJECTIVE

An exaggerated blood pressure response to mental stress in postmenopausal women has been reported but the underlying mechanism is not clear. In the present study, we examined the role of estrogen in the blood pressure response to mental stress.

SUBJECTS AND METHODS

Hemodynamic responses to mental stress and constrictor responses to norepinephrine were compared in 18 premenopausal (mean +/- SD age 33 +/- 5 years), 22 postmenopausal women (62 +/- 7 years) and 13 postmenopausal women with estrogen replacement therapy (58 +/- 8 years). Premarin was infused in 10 postmenopausal women to determine whether estrogen attenuates norepinephrine-induced vasoconstriction. The hemodynamic responses to a standard mental arithmetic test were measured. Norepinephrine (12.5, 25, 50, 100 ng/min) was infused at 0.5 ml/min for 5 min via the dorsal hand vein. Norepinephrine (100 ng/min) combined with premarin (200 microg/min) was infused into the dorsal hand vein of postmenopausal women. Changes in venous diameter were measured by ultrasonography using a 7.5 MHz transducer.

RESULTS

All study subjects were healthy, normotensive and had normal lipid profiles. The postmenopausal women showed a significantly greater blood pressure response to the mental arithmetic test than the premenopausal women or those taking estrogen replacement therapy (P < 0.01). Norepinephrine induced significant dose-dependent vasoconstriction in all three groups (P < 0.001). The postmenopausal women showed significantly greater constriction in response to norepinephrine than the premenopausal women and those taking estrogen replacement therapy (P = 0.02). Premarin significantly attenuated the norepinephrine-induced vasoconstriction in the postmenopausal women (P< 0.001).

CONCLUSION

Healthy, normotensive postmenopausal women showed an exaggerated blood pressure response to mental stress. An increased vasoconstriction in response to norepinephrine and loss of estrogen-mediated vasodilation may contribute to the increased blood pressure response to stress in postmenopausal women without estrogen replacement therapy.

Complementary therapies: research, education and practice in nursing

There has been an increase in interest in complementary therapies amongst the general public and health care practitioners in recent years. Nurses integrating complementary therapies into their practice are not always adequately prepared due to the diversity of the therapies and the duration of the courses. Guidelines are broad and general, and there is no set standard nor minimum educational requirements related to the therapies in which nurses can integrate in their practice. This paper aims to raise awareness of nurses practising complementary therapies the need for research into practice and efficacy, education and policy development.

Insulin-mediated venodilation is impaired in patients with high cholesterol

Recently we have reported that insulin attenuates norepinephrine (NE)-induced vasoconstriction via a cyclic GMP-NO synthase pathway. Because hypercholesterolemia has been associated with abnormal endothelial function, we investigated whether insulin-mediated vasodilation is impaired in hypercholesterolemia. To assess vasoreactivity, NE (12.5, 25, 50, and 100 ng/min), NE (100 ng/min) combined with insulin (8, 16, 24, and 32 microU/min), and NE (100 ng/min) combined with sodium nitroprusside (0.01, 0.1, 1, 10, and 100 ng/min) were infused into dorsal hand veins. Changes in venous diameter were measured by ultrasonography, using a 7.5-MHz transducer. Twenty-two healthy, normotensive hypercholesterolemic subjects (HC; mean total cholesterol 6.93 mmol/L, HDL 1.45 mmol/L, LDL 4.81 mmol/L) and 18 age-matched normal control subjects (NC; mean total cholesterol 4.81 mmol/L, HDL 1.16 mmol/L, LDL 3.18 mmol/L) were studied. All HC had normal glucose tolerance test results. Baseline vein diameters were similar between groups, and the vasoconstrictor response to NE was not significantly different between HC and NC. Insulin significantly attenuated NE-induced vasoconstriction in NC but not in HC (P<0.01). Both groups were able to venodilate with sodium nitroprusside. To investigate the effects of cholesterol reduction on vascular reactivity, venoreactivity studies were repeated in 12 HC after treatment with 20 to 40 mg/d lovastatin for 6 weeks. There were no significant venoreactivity changes with the treatment. Plasma LDL cholesterol concentration was inversely correlated to venodilator effect of insulin (r=-0.42, P<0.02). In conclusion, insulin-mediated vasodilation is impaired in patients with high cholesterol. Absence of normal insulin-mediated but not sodium nitroprusside-induced venodilation in hypercholesterolemia suggests that insulin-mediated vasodilation is endothelium dependent.

Allergy to gloves. Case report

The risk of contracting infectious diseases from patients with either serious or even fatal consequences has led to considerable changes in dental practice in the last few years. A key step in infection control is to prevent contact between the dentist's skin and the patient's blood and saliva by wearing gloves. The practice initially requires some patients and tolerance but then has few disadvantages. This paper reports a case where there were adverse effects to the patient from the dentist wearing gloves.

Ethanol acutely reduces LH and prolactin secretion: possible involvement by dopamine

Ethanol (ETOH) administered acutely to castrate male rats caused a decline in pituitary luteinizing hormone (LH) and prolactin (PRL) secretion. This was associated with an elevation in hypothalamic and median eminence stores of dopamine (DA) that was related to the dose of alcohol given. Pituitary stalk transection (PST) resulted in a significant rise in plasma PRL levels compared to sham control animals, which suggests that DA in the hypophysial portal blood exerted an inhibitory influence on pituitary PRL secretion. The DA agonist bromocriptine failed to alter mean plasma LH levels in stalk-transected rats. The ETOH-treated castrated rats showed a significant rise in circulating PRL after injection of the DA receptor antagonist haloperidol metabolite II (HAL), but the administration of the DA receptor agonist R(-)-apomorphine HCL (APO) caused plasma PRL to decline to near undetectable levels. Plasma LH levels remained unchanged in the HAL- and APO-treated rats and were similar to those of sham controls. These results suggest that lactotroph DA receptors were still functional. Thus our previous finding of ETOH-induced reduction on LH secretion may be attributable to an inhibitory effect by DA on the luteinizing hormone-releasing hormone (LHRH) peptidergic neurons rather than a direct inhibition by DA on the pituitary gonadotroph.

The use of touch in nursing practice

This paper examines the types of touch used in nursing practice and the effects of touch on the body and mind. The effects of two types of touch, therapeutic touch and massage, are evaluated by reviewing research studies conducted by nurses.

Differential effects of estrogen, tamoxifen and the pure antiestrogen ICI 182,780 in human drug-resistant leukemia cell lines

ICI 182,780, a potent, new steroidal antiestrogen without apparent agonist activity, appears to be a potent modulator of the classic multidrug resistance (MDR) phenotype in the CEM/A7, CEM/VLB100 and K562/VIN100 MDR cell lines. This reagent had no effect on the respective parental CCRF-CEM and K562 cell lines. The use of 1.25 microM ICI 182,780 resulted in a 6- to 7-fold decrease in doxorubicin resistance in the CEM/A7 and CEM/VLB100 cell lines. A dose-response effect was observed at ICI 182,780 concentrations of up to 5 microM. As compared with tamoxifen (TAM), ICI 182,780 was 2 and 4 times more effective in the K562/VIN100 and CEM/A7 cell lines, respectively. ICI 182,780 at 0.625 microM increased [3H]-daunomycin uptake (P < 0.0001) as effectively as 5 microM TAM in the resistant CEM/A7 line. Drug-efflux studies showed that 5 microM ICI 182,780 significantly decreased drug efflux as compared with 5 microM TAM (P < 0.0001). Estradiol (EST) at 10 microM increased doxorubicin resistance by 1.2-1.3 times in the CEM/A7 and CEM/VLB100 cell lines and significantly decreased drug accumulation (P = 0.002) and retention (P < 0.001) in the CEM/A7 cell line. However, the addition of 10 microM EST to 1-2 microM ICI 182,780 did not inhibit the ability of ICI 182,780 to modulate doxorubicin resistance in the two resistant cell lines. Using reverse-phase high-performance liquid chromatography (HPLC) to measure lipophilicity, we found no apparent association between the ability of ICI 182,780, TAM or EST to modulate resistance and their relative hydrophobicity.

Galanin: a hypothalamic-hypophysiotropic hormone modulating reproductive functions

Galanin (GAL) is widely distributed in the peripheral and the central nervous systems. In the brain, the highest GAL concentrations are observed within the hypothalamus and, particularly, in nerve terminals of the median eminence. This location, as well as GAL actions on prolactin, growth hormone, luteinizing hormone (LH), and LH-releasing hormone (LHRH) secretion, suggest the possibility that GAL may act as a putative hypothalamic-hypophysiotropic hormone. To establish this, GAL and LHRH levels were measured in hypophyseal portal plasma samples using specific radioimmunoassays. Rat galanin (rGAL) concentrations in portal blood were approximately 7-fold higher than those observed in peripheral plasma in male and female (estrus, diestrus) rats, indicating an active secretory process of rGAL into the portal vasculature. Frequent (10 min) sampling revealed that rGAL and LHRH were secreted into the portal circulation in a pulsatile manner with a pulse frequency of one pulse per hour. Interestingly, both hormone series depicted a high degree of coincident episodes. In fact, the probability of random coincidence, calculated by the algorithm HYPERGEO, was less than 0.01. Moreover, the retrograde tracer Fluoro-Gold, when given systemically, was taken up by GAL neurons in the hypothalamus, including a subset of neurons expressing rGAL and LHRH, strengthening the notion of the existence of a GAL neuronal system connected to the hypophyseal portal circulation. These observations reinforce the concept that GAL regulates pituitary hormone secretion. To analyze this in further detail, the effects of rGAL on LH secretion were evaluated under basal and stimulated conditions. rGAL induced a small but dose-dependent increase in LH secretion from cultured, dispersed pituitary cells. Interestingly, rGAL enhanced the ability of LHRH to stimulate LH release. The tight link between GAL and LHRH neuronal systems is strengthened by the observation that during the estrous cycle of the rat, rGAL and LHRH contents in the median eminence show an identical profile (r = 1.00). These data indicate that GAL should be considered as a hypothalamic-hypophysiotropic hormone and as an important neuromodulator of LHRH secretion and action. The colocalization and cosecretion of GAL and LHRH and the cooperative action at the level of the anterior pituitary afford important evidence for the functional significance of coexistence of neurotransmitters in neurons of the central nervous system.

Acute ethanol treatment lowers hypophyseal portal plasma luteinizing hormone-releasing hormone (LH-RH) and systemic plasma LH levels in orchidectomized rats

Acute ethanol (EtOH) treatment resulted in a significant decline in hypophyseal portal plasma levels of luteinizing hormone-releasing hormone (LH-RH) in orchidectomized rats. This was accompanied by a similar decrement in circulating luteinizing hormone (LH) without, however, modifying plasma follicle-stimulating hormone (FSH) levels at time when peak blood alcohol concentrations occurred. Thus, acute alcohol intoxication lowers circulating LH levels primarily by impairing hypothalamic neuronal secretion of LH-RH into the portal blood.

Evidence for a negative ultrashort loop feedback mechanism operating on the luteinizing hormone-releasing hormone neuronal system

The present studies were designed to determine whether an ultrashort loop feedback mechanism is involved in the regulation of LHRH secretion. Daily administration of a highly potent LHRH agonist (LHRH-AGO; [D-Ala6,Des-Gly10] LHRH ethylamide) immediately after orchidectomy (ORDX) significantly attenuated the rise of plasma LH from days 2 through 10 after ORDX. Concomitantly with the diminished LH rise after ORDX, a significant increase in LHRH content in the arcuate nucleus was observed in LHRH-AGO-treated rats. Measurement of LHRH levels in hypophyseal portal blood in rats 10 days after ORDX combined with daily agonist treatment revealed a significant decrease in LHRH values in portal plasma compared with those in orchidectomized controls. Arcuate nuclei-median eminence (ME) fragments obtained from ORDX rats treated in vivo with LHRH-AGO for 5 days showed a decreased basal secretion of LHRH and a diminished response to K+ stimulation compared with the release from fragments obtained from ORDX saline-treated controls. To evaluate whether a tonic LHRH inhibitory activity operates within the ME, additional experiments were performed in which ME fragments were incubated in vitro in the presence of a potent LHRH antagonist [( D-pGlu1,D-Phe2,D-Trp3,6]LHRH). The antagonist significantly enhanced the basal secretion of LHRH in a dose-dependent manner. The latter results suggest that LHRH antagonists may enhance LHRH release, perhaps by interacting with LHRH receptors playing an inhibitory role on the endogenous secretion of the decapeptide. These observations strongly suggest a tonic inhibitory or modulatory role of LHRH neurons in the regulation of their own function.

Comparison of panoramic and standard radiographic radiation exposures in the diagnosis of mandibular fractures

Radiological examination of the maxillofacial region is required to confirm fractures and to identify lesions that are present in the jaws. The complex anatomy of the area necessitates multiple radiographic views with standard projections. The accuracy of diagnosis is at times suspect. An orthopantomogram, which is supplemented by a posteroanterior projection of the lower jaw where required, allows a more accurate diagnosis. This pilot study was designed to compare the radiation dosage that is delivered after a standard hospital series of films and an orthopantomogram. The results demonstrate the significant reduction in irradiation to patients who undergo orthopantomography.

Norepinephrine stimulates LH-RH secretion into the hypophysial portal blood of the rat

The present study was designed to investigate the effect of intracerebroventricular infusion of norepinephrine (NE) on the secretion of luteinizing hormone-releasing hormone (LH-RH) into the hypophysial portal blood of steroid-primed ovariectomized rats. Saline infusion into the third ventricle caused no significant change in LH-RH levels. NE infusion (20 micrograms) resulted in a significant release of LH-RH (p less than 0.05) into the portal blood 10-30 min later. This endogenous LH-RH was similar to synthetic LH-RH when characterized by thin-layer chromatography. LH secretion in similarly treated rats but with intact portal vessels, also was significantly elevated (p less than 0.05) at 20 and 40 min after the start of NE infusion. These results show that NE stimulated the secretion of LH-RH into the hypophysial portal blood and this correlated with an enhanced release of LH.

Neuroleptic drug-induced alterations on neonatal growth and development. I. Prenatal exposure influences birth size, mortality rate, and the neuroendocrine system

Subcutaneous injection of codeine or phenobarbital, and feeding amphetamine to rats during gestation and lactation caused irregularities in mortality rates, growth, development, and associated neuroendocrine events within the newborns. Most striking was the subnormal birth size, increased mortality rate, and decreased hypothalamic growth hormone-releasing activity of neonates of mothers fed the highest dose of amphetamine.

Inhibition of gonadotropin-releasing hormone release as the basis of pituitary-gonadal dysfunction during treatment with 4-aminopyrazolo-(3,4-d)-pyrimidine

The inhibitor of hepatic lipoprotein release, 4-aminopyrazolo-(3,4-d)-pyrimidine (4-APP), has been shown to reduce testosterone production via impairment of pituitary gonadotropin secretion rather than through decreased cholesterol availability. It was previously shown that serum LH levels were reduced by more than 75% in male rats treated with 4-APP, but pituitary stores of LH and the gonadotropin response to exogenous GnRH were maintained. Also, there was a reduction in pituitary GnRH receptors which was consistent with hypothalamic GnRH deficiency. The present studies were undertaken to examine the mechanism by which 4-APP inhibits GnRH synthesis and/or release. Intact, adult male or 2-week ovariectomized female rats were treated daily with 25 mg/kg 4-APP for 3 days. Both sexes showed lowered basal serum levels of LH and absence of the elevations in serum LH normally elicited by the opiate antagonist, naloxone. In pituitary portal plasma collected from normal male rats, GnRH was significantly elevated by naloxone treatment, confirming that naloxone acted at the level of hypothalamic GnRH release. However, naloxone stimulation of GnRH secretion into portal blood was absent in rats treated with 4-APP. In vitro, the potassium-induced release of GnRH from perifused medial hypothalami was reduced by 60% in 4-APP-treated male rats while hypothalamic GnRH content remained unchanged. These data indicate that 4-APP has an inhibitory effect on the mechanism of GnRH release, and that analysis of its actions should clarify the processes involved in neurohormone secretion.

Comparison of the effects of Althesin, chloralose-urethane, urethane, and pentobarbital on mammalian physiologic responses

Physiological responses to anesthetic doses of four chemically dissimilar agents, namely, Althesin, urethane, chloralose-urethane, and pentobarbital sodium were compared in rats. The tail-flick test revealed Althesin had greater antinociceptive potency than urethane, chloralose-urethane, and pentobarbital, but its duration of action was shorter than that of chloralose-urethane. Althesin produced minimal or no suppression of core body temperature and mean arterial pressure, and only moderate reduction of mean pulse pressure. The heart rate and respiratory rate of Althesin-treated rats were slower than those of chloralose-urethane and urethane-treated counterparts, respectively, but were not significantly decreased from normal controls. It is concluded that Althesin is a suitable anesthetic for short-term surgery and for studies of body temperature, heart rate, and mean arterial pressure. Because release of gonadotropin-releasing hormone into hypophysial portal blood can be observed under Althesin but is suppressed or blocked by chloralose-urethane, urethane, and pentobarbital, Althesin is the anesthetic of choice in studies concerned with the neural control of ovulatory hormone release.

Morphine suppresses the proestrous surge of GnrH in pituitary portal plasma of rats

Virgin proestrous rats were acutely treated with 2 doses of morphine sulfate (MS) (5-8 and 40 mg/kg BW) or naloxone HCl (NH) (10 mg/kg BW) co-administered with the high dose of MS, and the pituitary portal plasma concentrations of gonadotropin releasing hormone (GnRH) were compared with those of untreated proestrous (PE) and diestrous (DE) control animals. LH and FSH were measured in systemic plasma obtained by venipuncture just prior to the collection of portal blood. Both doses of MS severely diminished the PE surges of LH and FSH, but NH reversed the effect of MS and restored the circulating gonadotropins to PE levels. However, only PE rats treated with the high dose of MS exhibited significantly reduced GnRH concentrations in portal plasma. This suggests that the reduction of gonadotropin concentrations is not due merely to reduced GnRH secretion by the hypothalamus but may involve other mechanism(s) as well. However, in rats given the high dose of MS the severe reduction in pituitary gonadotropin secretion is attributable in large part to the corresponding decrease in hypothalamic GnRH release, since NH restored the GnRH and LH/FSH plasma concentrations to PE levels.

Correlative surges of LHRH, LH and FSH in pituitary stalk plasma and systemic plasma of rat during proestrus. Effect of anesthetics

An effective recovery procedure has been utilized for determining luteinizing hormone-releasing hormone (LHRH) concentrations in rat pituitary stalk plasma. With this new recovery protocol it was revealed that stalk plasma immunoreactive LHRH concentrations increased 5-fold to 206 pg/ml during proestrus(p less than 0.001) and decreased to diestrous levels during estrus. In contrast, the LHRH concentration in systemic plasma extracts remained unchanged throughout the estrous cycle and did not exceed 4 pg/ml. The stalk plasma: systemic plasma ratio increased from 12:1 at diestrus to 76:1 at proestrus; it then decreased to 22:1 at estrus (p less than 0.001). Correlative luteinizing hormone (LH) and follicle-stimulating hormone (FSH) surges of statistically significant magnitudes were observed in the systemic plasma of nonanesthetized cardiac-catheterized rats during proestrus. When administered before the onset of the critical period, Althesin and other anesthetic agents suppressed but did not completely inhibit the peripheral LH surge in cardiac-catheterized rats. The FSH surge was suppressed also but to a lesser degree. These results indicate that the brain triggers the preovulatory surge of LH and FSH via massive secretion of LHRH into the pituitary portal circulation. They also reveal that, aside from any dosage considerations, the type of anesthetic used and the time of administration in relation to the critical period, can significantly affect the magnitude of pituitary LH and FSH secretion.

Differential effect of althesin versus chloralose-urethane anesthesia on in vivo LHRH and LH release in the proestrous rat

Anesthetic doses of Althesin and chloralose-urethane were compared as to their effects on neuroendocrine reproductive processes in diestrous and proestrous rats. Proestrous rats treated with Althesin experienced a 5-fold increase in immuno-reactive luteinizing hormone releasing hormone (LHRH) concentration in methanolic extracts of pituitary stalk plasma. This LHRH increase was 67% greater than that of proestrous rats administered chloralose-urethane. Moreover, Althesin given before the onset of the critical period did not suppress the proestrous surge of LHRH in stalk plasma. The Duncan's multiple range test indicated stalk plasma LHRH activity was significantly elevated in proestrous rats anesthetized with Althesin (p less than 0.05) but not with chloralose-urethane. However, the luteinizing hormone (LH) concentration in peripheral plasma increased 14 to 18-fold in all proestrous rats, including those anesthetized with chloralose-urethane. Evidently, in chloralose-urethane-treated rats, the smaller LHRH surge during proestrus is sufficient to elicit maximum release of LH from the anterior pituitary gland. This suggest that under normal conditions the amount of LHRH secreted into portal blood during proestrus is approximately 2-fold greater than that necessary to elicit maximum secretion of LH. The results also show that picogram concentrations of LH in the stalk plasma will stimulate the release of nanogram quantities of LH into the peripheral plasma of the same rats. Moreover, the sensitivity of the pituitary gland to LHRH stimulation via the portal circulation increases nearly 3-fold between diestrus and proestrus.

Effect of barbital on the pituitary-thyroid axis

Barbital (diethylbarbituric acid), administered via the drinking water (0.1% solution), elicited mild goitrogenic responses in rats (p less than 0.05), accompanied by a slight depression in serum T4 titers (p less than 0.02). The goitrogenic responses appeared to be the result of slight elevations in the serum TSH levels and in the case of neonate rats, whose mothers were fed barbital during pregnancy and lactation, the elevations of TSH in the circulation were pronounced (p less than 0.01). However, continuation of barbital treatment beyond puberty resulted in mean serum TSH titers declining to twice the mean control values so that only the variances between the data were different(p less than 0.05). This group of young adults showed endocrine profiles which resembled those of more mature rats. The latter group included the mothers of these young adults and of the neonates. In contrast to the action of barbital, feeding rats 0.05% propylthiouracil (PTU) in the drinking water caused substantial increases in mean serum levels of TSH (p less than 0.001) and goiter size (p less than 0.001). Moreover, the precipitous declines in serum T4 elicited by PTU were of far greater magnitude than that caused by barbital (p less than 0.001).

Regarding the validity of the endpoint response of the mouse (McKenzie) bioassay for thyrotrophin (TSH)

The release of radiolabelled thyroid hormone into the circulation in low iodine fed mice has been used extensively as a bioassay for thyroid stimulating hormone (TSH). However, the specificity of several bioassays of pituitary hormones have been subject to question. Consequently, the validity of the assay endpoint for TSH in the mouse was re-evaluated with respect to the effect of luteinizing hormone (LH) whose chemical composition closely resembles that of TSH. Mice, prepared for bioassay of TSH received injections of purified LH or α or β subunits of LH. Identical doses of LH and LH subunits were quantified by LH and TSH radioimmunoassays and the results compared with those obtained by the bioassay. Microgram quantities of LH and subunits of LH elicited appreciable responses in the TSH bioassay but produced only negligible effects in the TSH radioimmunoassay. The response of the TSH bioassay of LH and α or β subunits of LH was 40–56% that obtained with LH radioimmunoassay. However, the pituitary concentrations obtained by TSH bioassay when compared with those obtained by radioimmunoassays for TSH, LH, or growth hormone (GH) paralleled closely the TSH radioimmunoassay data, although in terms of quantitative estimates, there was a 15-fold discrepancy between the TSH assays. Estimations of pituitary concentrations of LH lead to the conclusion that, at the doses normally employed, most crude rat pituitary extracts do not contain sufficient quantities of LH to alter significantly bioassayable (McKenzie) estimates of TSH.

Does-related effect of growth hormone on thyroidal radioiodine uptake

Even though growth hormone was reported to play a role in mammalian calorigenesis, few studies have examined its effect on thyroid function. Consequently, the modulatory effect of bovine growth hormone (BGH) on thyroid incorporation of 131I was studied in hypophysectomized (H) rats. Not surprisingly, H recipients fed a low iodine diet consistently displayed greater thyroidal uptakes of radioactive iodine than recipients given regular diets. Furthermore, thyroid radioactive counts increased predictably in direct proportion to the quantity of bovine thyrotropin administered. Larger doses of BGH suppressed the thyroidal uptake of 131I whereas smaller doses either had no effect or enhanced thyroidal activity. Thus, these results affirm that radiolabelled and non-radiolabelled iodine compete in thyroid metabolic processes and furthermore demonstrate that high doses of BGH inhibit thyroid activity.

A re-assessment of the effect of thyrotrophin (TSH) on the tibial plate bioassay for growth hormone (GH)

The claim has been made that thyrotrophin (TSH) can augment the action of growth hormone (GH) to stimulate growth of the epiphysial cartilage plate of the hypophysectomized rat's tibia. The TSH induces its effect via secretion of thyroid hormones which in turn enhance the stimulatory action of GH. If this is true then the employment of the tibia test, whose endpoint is the increase in thickness of the epiphysial cartilage plate in response to GH present either in crude pituitary extracts or relatively purified preparations, which also are likely to contain modest or appreciable quantities of TSH, requires further examination. The present study utilized various fractions of crude pituitary extracts from intact and thyroidectomized rats that respectively contained appreciable quantities of GH or essentially no GH. Fractional aliquots of pituitary extracts from thyroidectomized rats were administered concomitantly with graded doses of exogenous GH to hypophysectomized rats to determine the point at which TSH in the extracts was sufficiently able to stimulate significant tibial plate growth when compared to recipients given GH alone. Purified GH and TSH were also administered in various doses to hypophysectomized recipients in a further attempt to delineate the dose range at which TSH augments the action of GH to promote significant chondrogenesis of the epiphysial plate. The results indicate that the enhancement of the GH effect on the cartilage plate by TSH was evident only when quantities above 100 microng bovine GH were co-administered with 100 mU bovine TSH. As little as 40 mU TSH augmented the growth effect of 400 microng GH on the cartilage plate, demonstrating that smaller quantities of TSH could potentiate larger quantities of GH. These data, therefore, suggest that extracts equivalent to not more than one-half of a normal adult rat's anterior pituitary gland should be administered to hypophysectomized rats for bioassay of GH. Fractions of glands greater than this may contain sufficient amounts of TSH to augment the appreciable quantities of GH already present.

TRH-degrading enzyme activity in peripheral and pituitary-portal plasma of the rat

The enzymatic degradation of TRH was measured in peripheral and pituitary-portal plasma. Enzyme activity in peripheral plasma was 3.20 pg/min/mug plasma protein; in pituitary-portal plasma the rate of degradation was only 0.83 pg/min/mug protein. After dialysis, which removed virtually all endogenous TRH and LHRH, enzyme activity in peripheral and portal plasma was 2.24 and 0.60 pg/min/mug respectively. These data suggest that portal plasma contains large concentrations of unidentified substances which are competitive inhibitors or substrates for the enzyme or that portal plasma contains less TRH-degrading enzyme.

Inconsistency of the tibia test for estimating growth hormone in crude pituitary extracts

The complement fixation immunoassay (CFIA) was used for quantitating growth hormone (GH) in crude anterior pituitary extracts from rats subjected to thyroidectomy with or without cortisol and exogenous GH administration. The results obtained from this study were compared with pertinent bioassay (tibia test) results or correlated with the pituitary acidophil cell counts. Whereas it has been reported that pituitary GH levels are normal by the tibia test at 2 weeks after thyroidectomy, the highly specific CFIA method showed an actual 87% decrement which correlated well with the reduction in acidophilis. In addition, the apparently normal content of GH after cortisol administration to thyroidectomized rats, as measured by the tibia test, was contradictory to the very low acidophil population and to the marked reduction in pituitary GH content as measured by the CFIA. Furthermore, theoretical tibia responses illustrate the inconsistency of the bioassay in different experimental conditions. If, as previously suggested, the content of thyrotrophin (TSH) in the crude pituitary extracts renders the bioassay of GH a dubious procedure, then the superiority of immunoassay is obvious.

A re-examination of the tadpole in metamorphic stasis as a recipient in a bioassay for thyroid-stimulating hormone

The tadpole, in metamorphic stasis, has been used as a bioassay recipient for thyroid-stimulating hormone (TSH). The validity of its use for this purpose, however, has not been tested critically, particularly with respect to the effect of other hormones, most notably, growth hormone (GH) and luteinizing hormone (LH). Growth hormone has been shown to influence thyroid function and LH is a common contaminant of pituitary TSH preparations. Tadpoles of Rana pipiens, arrested at a particular metamorphic stage, received various concentrations of LH alone, a combination of doses of GH and TSH, or GH and rat anterior pituitary extract. Growth hormone was ineffective in re-inducing metamorphosis in 78% of cases, whereas LH stimulated metamorphosis in the tadpoles.

Pituitary thyrotroph function in hypothyroid rats

The suggestion has been made that the substantial increases in pituitary thyrotrophin (TSH) concentration reported in hypothyroid rats by some workers might be attributable to incomplete surgical thyroidectomy or partial goitrogen block. An attempt, therefore, was made to correlate the severity of hypothyroidism with the storage and release rate of TSH. Female and male Long-Evans rats were made hypothyroid either by surgical thyroidectomy or by administration of propylthiouracil (PTU). Rats were also surgically or chemically thyroidectomized and injected daily with subnormal doses of thyroxine (T4) so as to ameliorate the hypothyroidism. Pituitary and serum levels of TSH were quantified, both by bioassay (stasis tadpole), and radioimmunoassay. The results showed TSH reduced in the pituitary of the severely hypothyroid rat. In both females and males, amelioration of the hypothyroidism with small chronic doses of T4 did not increase bioassayable or immunoassayable TSH stores. Paradoxially, bioassay showed serum TSH titers increased in females inversely proportional to the apparent severity of the hypothyroidism. However, radioimmunoassay of the sera of males, whose hypothyroidism was ameliorated by T4, revealed no significant increases in TSH over thyroidectomy controls. Therefore, the results were unclear as to whether subnormal quantities of T4 increase TSH release from the pituitary. The differences in serum TSH concentration between hypothyroid-ameliorated females and males are not attributable to sex or to differences in the reliability between the bioassay and immunoassay. However, bioassayable increases in TSH stores may perhaps reflect an influence exerted by pituitary gonadotrophins or sex steroids.