[A modified technique of obturator fabrication for cleft palate infants]

Cleft palate is a commonly observed congenital maxillofacial defect. The first problem to be faced is the interference of feeding. It is a hard challenge for both the parents and the dentist. A cleft palate infant is unable to produce negative pressure in the oral cavity, thus resulting in feeding difficulty. The maxillary obturator resolves feeding problem and induces better maxillary growth patterns before operation. The maxillary obturator should be applied as early as possible to avoid the post surgical problems. The material for traditional obturator is tough and often injures the soft tissue. In order not to interfere with the growth of the dental arch, the border of the obturator must be trimmed regularly, until the retention becomes insufficient. In this paper, a modified technique of obturator fabrication was presented. The new method uses silicone relining material instead of ortho resin, as the packing of the obturator. It has been applied to dozens of patients. After a long follow up and comparison with the traditional method, the advantages of the new design can be summarized as follows: (1) Silicone is softer and does not injure the soft tissue. (2) It does not require the trimming of the border of obturator. (3) It has better retention and comfort for the patients.

[Delayed intracranial aneurysm of left atrial myxoma--a case report]

Although embolism is known as a common complication in the early growing stage of atrial myxoma, development of further neurologic disorders after the removal of tumor is rarely encountered. Arterial aneurysm formation and metastatic tumor growth represent the two disorders that had been reported in the literature. Based on the pathogenesis of hematogeneous disseminating, atrial myxoma may lodge its fragment or its adherent thrombus on intracranial vessels to produce cerebral infarct. Besides, several reports have indicated that myxoma emboli in the cerebral vessels may invade the vessel wall to produce delayed disorders. Embolization from atrial myxoma is now recognized as a potentially treatable cause of cerebral infarct. However, the long-term course following resection of the tumor remain complicated, partly due to these inconsistent delayed complications, or the therapeutic dilemma. We report a case with delayed intracranial aneurysm formation and reviewed the literature. A 67-year old woman with a past history of left cerebral infarction was transferred to our hospital for further evaluation of her gross hematuria. Infarction of the left kidney was then demonstrated by angiography. A left atrial myxoma was found in a echocardiographic screen, and the patient received a successful resection of the myxoma subsequently. Unfortunately, three episodes of stroke developed in a half year after the operation of the cardiac myxoma.(ABSTRACT TRUNCATED AT 250 WORDS)

Congenital spinal arachnoid cysts: report of 2 cases with review of the literature

Two cases of congenital spinal arachnoid cysts with paraparesis are presented. Case 1, a 16-year-old male patient, had a 2-year history of progressive weakness of the lower limbs. Postmyelographic axial computed tomography (CT) and myelography revealed a dorsally located extradural mass. The configuration of the mass was further assessed with magnetic resonance imaging (MRI). He underwent laminectomy from T8 to L1 with total excision of an extradural arachnoid cyst. A communication with the subarachnoid space found at the T8 level was surgically closed. The patient made an uneventful recovery. Case 2, a 9-year-old girl, developed paraparesis and the cauda equina syndrome two days prior to admission. Postmyelographic CT and myelography revealed an anteriorly located intradural mass. She underwent laminectomy from C6 to T2 and partial removal of an intradural arachnoid cyst. One week later, her neurological functions had recovered completely. The literature dealing with this rare spinal lesion is also reviewed.

Nucleotide sequence and estrogen induction of Xenopus laevis 3-hydroxy-3-methylglutaryl-coenzyme A reductase

We have isolated and sequenced overlapping cDNA clones encompassing the entire protein coding region of Xenopus laevis 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoA reductase). This 3-kilobase cDNA codes for an 883-amino acid protein, which exhibits extensive amino acid sequence homology to mammalian HMG-CoA reductases. The highly conserved 341-amino acid membrane spanning domain exhibits 89% amino acid sequence identity with hamster HMG-CoA reductase. In contrast to the high degree of homology in the coding regions of the mRNAs, the nucleotide sequences of the 5'- and 3'-untranslated regions of Xenopus and mammalian HMG-CoA reductase mRNAs exhibit negligible homology. Primer extension data suggests that Xenopus HMG-CoA reductase mRNA is transcribed from multiple initiation sites. The Xenopus HMG-CoA reductase cDNA clones were used as hybridization probes to examine estrogen regulation of hepatic HMG-CoA reductase mRNA levels. Northern blot analysis demonstrates that estradiol-17 beta induced HMG-CoA reductase mRNA in livers of male X. laevis 10-fold within 24 h. Reductase mRNA levels reach a plateau 23-fold higher than basal levels between 5 and 8 days after initial estrogen administration. In contrast to the vitellogenin and retinol binding protein genes whose transcription is induced by estrogen in Xenopus liver, the runoff transcription rate of HMG-CoA reductase does not increase significantly on administration of estradiol-17 beta. These data suggest that the estrogen induction of HMG-CoA reductase mRNA may be achieved through posttranscriptional mechanisms.

Conformational changes in ornithine decarboxylase enable recognition by antizyme

Rapid, polyamine-induced degradation of mammalian ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) (ODC) is though to be controlled by the availability of a small, ODC-binding protein termed antizyme. In this study we have investigated the ability of antizyme to bind ODC protein in various altered physiological states. In particular, cold, NaCl, spermidine and deprivation of coenzyme and substrate enhance enzyme-antizyme complex formation and are all found to promote ODC homodimer dissociation. Conversely, conditions that maintain the active ODC homodimer state prevent antizyme binding and inactivation of ODC. Further, covalent modification of ODC near its active site by difluoromethylornithine or phosphate also increases its sensitivity to antizyme. These results suggest that the initial signal in ODC degradation may actually be a subtle conformational change in the enzyme that enables antizyme to bind to the enzyme and may subsequently facilitate its degradation.

Comparison of hemodynamic changes induced by adenosine monophosphate and sodium nitroprusside alone and during dopamine infusion in the anesthetized dog

Adenosine receptor stimulation, such as by adenosine monophosphate (AMP), elicits systemic vasodilation that may be useful to control cardiac afterload during treatment of acute low-output cardiac failure. This study compared the hemodynamic effects of graded doses of sodium nitroprusside (SNP) with those of AMP when infused alone or in combination with the positive inotropic agent dopamine (DA) in anesthetized dogs. Both SNP (2-25 micrograms.kg-1.min-1) and AMP (200-2500 micrograms.kg-1.min-1) were effective vasodilators and reduced systemic vascular resistance and arterial pressure in a dose-dependent manner. Heart rate and cardiac index were increased by both agents. When compared at dosages that caused similar decreases in arterial pressure, cardiac index was increased more by AMP than by SNP. Also, AMP-induced vasodilation was associated with less tachyphylaxis. Sodium nitroprusside and AMP, at the dosages used, did not depress atrioventricular nodal conduction or antagonize DA-induced increases in renal blood flow. At equivalent decreases in mean arterial pressure, the increase from baseline in cardiac and stroke indices observed with AMP alone was further increased by the concomitant administration of DA. These results suggest that AMP and DA-AMP may offer significant advantages over SNP or DA-SNP in situations where elevation of cardiac output and reduction in afterload are required.

Interrelation between the charge isoforms of mammalian ornithine decarboxylase

Ornithine decarboxylase (ODC) isolated from a variety of tissues has been separated, using DEAE ion-exchange chromatography, into multiple peaks of activity that appear to be related to control of this enzyme stability. Reports of these charge isoforms in current literature are generally unclear as to whether these represent a covalent posttranslational modification or merely an alteration in structural conformation or association. In this study we investigated the relationship of this form separation to the degree of enzyme polymerization, interaction with other proteins and buffer components, and the multiple isoelectric forms of this enzyme noted in denaturing concentrations of urea. High-performance chromatography techniques were used to demonstrate that two of the major enzyme forms, ODC I and II, are really monomers of the enzyme, while minor peaks of activity frequently observed to elute after ODC II contain various dimeric enzyme states. Pyridoxal 5'-phosphate (0.05 mM) added to isolated enzyme preparations composed of I and II monomers induced the formation of I and II dimers as well as a mixed I-II dimer. All three dimer forms were observed to be natural components of freshly isolated crude cell homogenates. The charge distinction between the monomer forms I and II was found to be maintained during ion-exchange chromatography in the presence of 8 M urea, and the enzyme isoforms demonstrated distinct bands on isoelectric focusing gels run in the presence of 9 M urea. Thus, although some of the multiple ornithine decarboxylase forms identified by ion-exchange chromatography of crude mammalian cell homogenates are related to enzyme conformation, the two major forms are distinctly charged protein states that can be visualized using two-dimensional gel electrophoresis of highly purified samples.

Meningioma in the anterior III ventricle in a child

A case is described of meningioma in the anterior part of the III ventricle in a 14-year-old girl. The mass was successfully removed through a transcallosal approach.

Mucocele of the sphenoid sinus with the apex orbitae syndrome

A mucocele of the sphenoid sinus with visual impairment and headache is presented. Mucocele of the sphenoid sinus is relatively rare. The preoperative diagnosis was uncertain in this case but sphenoid sinus mucocele was considered. The transnasal surgical approach is considered to be best for treatment.

Temporal difference of thyrotropin-releasing hormone in prevention of testicular regression in golden hamsters exposed to short photoperiods: possible involvement of beta-endorphin

Male golden hamsters were exposed to long photoperiod or short photoperiod (SP) and injected with 1 microgram TRH and/or 1 microgram LHRH at lights on (LO) or lights off (LX) for a total of 8 weeks. Both TRH and LHRH prevented testicular regression if they were injected at LO. Injected at LX, TRH did not prevent testicular regression, and LHRH was only partially effective. Plasma beta-endorphin levels were significantly higher in groups with atrophic testes. These results indicate that TRH like LHRH can prevent SP-induced testicular regression in hamsters by some unknown mechanism and that beta-endorphin may be involved in the control of testicular function in hamsters.

Enzymatic preparation of seasoning 5'-nucleotides from baker's yeast

Chemical phosphorylation with sodium trimetaphosphate (STMP) as a modifying agent was used to prepare functional protein isolate and dissociated nucleic acid (mostly RNA) from baker's yeast. The majority of protein-RNA complex in the disintegrated yeast cells was first extracted with an aqueous alkaline solution (pH 12, 40 degrees C) followed by phosphorylation with STMP under the same condition for 6 hrs. An apparent dissociation of protein-RNA complex occurred due to the covalent attachment of anionic phosphate groups onto yeast protein molecules. The nucleic acid residued in the supernatant after removal of modified protein isolate by isoelectric precipitation was recovered by reprecipitating at pH 2 followed by converting it to 5'-nucleotides with malt rootlets 5'-phosphodiesterase as well as red marine algal adenylate deaminase. This coherent process provided a preparation of food-usable functional protein isolate and 5'-nucleotides from baker's yeast.

Age difference in endogenous opiate modulation of short photoperiod-induced testicular regression in golden hamsters

Effects of age and naloxone on testicular function were studied in golden hamsters exposed to short photoperiods. Subjection of hamsters to short photoperiods of 6 h light: 18 h darkness for 6 weeks led to testicular regression in young adult (5-6 months) or middle-aged (11-12 months) golden hamsters but not in prepubertal hamsters of 1-2 months of age. The middle-aged hamsters had decreased testis width by week 4 of treatment and the young hamsters by week 5. Daily injection of naloxone at the time of 'lights on' partially prevented testicular regression in young and middle-aged hamsters but the extent of regression was significantly greater in the middle-aged animals. Plasma LH and FSH concentrations were significantly reduced in hamsters placed in short photoperiods regardless of age or testicular weight, while naloxone treatment significantly increased the LH concentrations in all age groups. Plasma beta-endorphin-like immunoreactivity was significantly increased by short photoperiod or older age. These results indicated that (a) the sensitivity of the testicular suppression to short photoperiod increases as a function of age, (b) naloxone, a specific opiate receptor blocker, can partially prevent short photoperiod-induced testicular regression and (c) ageing and short photoperiods increase beta-endorphin-like immunoreactivity. It is concluded that the opiate system may be involved in ageing and photoperiod regulation of reproductive function.

Age and sex difference in serum and pituitary thyrotropin concentrations in the rat: influence by pituitary adenoma

Effects of age and sex difference on serum and pituitary thyrotropin (TSH) concentrations were investigated in young (4 to 6 months) and old (28 to 36 months) Long-Evans rats with or without pituitary tumor. Basal and TRH-induced serum TSH concentrations in young males are significantly (P less than .05) higher than in old males, while there is no significant difference in basal TSH between young and old female rats, but young females had greater TSH response to TRH than the old females. Orchidectomy significantly reduced plasma TSH in the young but not in the old male rats. Administration of testosterone propionate reversed the castration effects on TSH in the young male rat. Ovariectomy significantly reduced plasma TSH in the old but not in the young female rats. Estrogen treatment slightly increased basal TSH concentrations in both the young and old rats.

Altered lateralization of cognitive processes in depressed women

Eighteen normal men and women had a left hemisphere advantage for processing a verbal task, but depressed women showed a trend toward right hemisphere superiority. In depression the right hemisphere may share functions performed exclusively by the left hemisphere in normal subjects. Altered laterality may be a trait of depression-prone people or a change related to depressive episodes themselves. In the latter case, the right hemisphere may be compensating for relative deactivation of the dominant left hemisphere.

Extrapolation from concentrated to dilute aqueous acids

The location and the manner of union of the H0 and HR acidity functions with −log [Formula: see text] have been determined for aqueous HClO4, HCl, and H2SO4 (H0 only) through particularly careful and extensive indicator measurements in dilute and moderately concentrated solutions of these acids. These data were also used to evaluate and compare a number of different ways of extrapolating measurements made in concentrated acids down to dilute solution; over the limited range of acidity investigated, the traditional acidity function method, as commonly applied in the absence of an appropriate acidity function (i.e. in the form of mH0), was found to be the least satisfactory of these extrapolative methods, and the Cox–Yates technique was found to be the best.

Luteinizing hormone releasing hormone prevents testicular atrophy in golden hamsters exposed to a short photoperiod: temporal difference in effectiveness of administration of luteinizing hormone releasing hormone

Exposure of male golden hamsters to short photoperiods of 6 h light: 18 h darkness led to testicular and accessory sex organ atrophy in 5 weeks. Short photoperiods also significantly depressed serum levels of LH, FSH, prolactin and testosterone in samples obtained by decapitation, but not in samples collected on the preceding day under ether anaesthesia. Injections of luteinizing hormone releasing hormone (LH-RH) at 09.00 h (lights on) or at 15.00 h (lights off) prevented testicular regression when compared with hamsters receiving injection vehicle only. However, the hamsters receiving LH-RH injections at lights on had significantly greater testicular weight and accessory sex organ (seminal vesicles and coagulating glands) weight and testosterone concentration than those receiving LH-RH at lights off. No increase in testicular weight was observed in hypophysectomized male hamsters given the same LH-RH injections and the same lighting regimen. These results indicate that LH-RH alone can prevent, at least partially, testicular and sex organ atrophy and increase serum testosterone concentration by stimulating release of LH and FSH in hamsters exposed to short photoperiods, involving temporal difference of LH-RH action. Further implications of the results are discussed.

Effects of aging on luteinizing hormone release in different physiological states of the female golden hamster

Effects of aging on estrous cycles and LH release in response to luteinizing hormone releasing hormone (LHRH), castration, and estradiol benzoate were studied in the female golden hamster (Mesocricetus auratus). About 80% to 90% of female golden hamsters still cycled regularly when reaching 19-22 months of age. However, some animals showed age-induced irregularity of the estrous cycle which included an interruption or complete absence of estrous vaginal discharge. Young female hamsters (3-5 months) had significantly (p less than 0.01) higher basal LH concentration than old animals (19-22 months) in the morning of each stage of estrous cycle. LHRH elicited about 20-30 fold increase in serum LH concentrations in both young and old hamsters. No significant difference in LH release was observed between young and old hamsters in response to LHRH. In acyclic hamsters, the peak of LH release in response to LHRH was delayed. LHRH-induced LH release was greater in the morning of proestrus than during diestrus in both young and old hamsters. LH increase was significantly greater in the young than in old hamsters on the 13th and 15th day after castration. However, positive feedback stimulation of LH release by estradiol benzoate was the same in both young and old hamsters. These results indicate that in the female hamster, LH response to acute stimuli such as LHRH and estrogens is the same in the young as in the old animal and that circulating basal LH concentration may decrease or its degradation or clearance may increase during the aging process in female golden hamsters. Irregularity of estrous cycles in aging hamsters may be related to delayed responsiveness of pituitary LH to LHRH stimulation.

Spontaneous and melatonin-induced testicular regression in male golden hamsters: augmented sensitivity of the old male to melatonin inhibition

Effects of aging and melatonin on testicular function of golden male hamsters were investigated. Young (3-4 months) and old (22-26 months) male hamsters were maintained on a long photoperiod (14 h light, 10 h dark) and injected with graded doses of 10, 25, 50 microgram melatonin or injection vehicle, at 17:00 h (3 h before lights off) for a period of 6 weeks. Old male hamsters had significantly decreased testicular weights as compared with the young counterparts, but accessory sex organ (seminal vesicles and accessory glands) weights did not differ between young and old male hamsters. All doses of melatonin suppressed testicular and accessory sex organ weights in the young as well as in the old animals. The percent decrease in testicular weight in response to melatonin treatment was significantly greater (p less than 0.01) in the old than in the young hamsters. Basal plasma prolactin concentration did not differ between young and old male hamsters. Melatonin significantly decreased plasma prolactin concentrations in both age-groups. Young hamsters had greater mean plasma luteinizing hormone concentrations than old hamsters, and melatonin suppressed luteinizing hormone equally in both groups. These results indicate that the testes of the male hamster spontaneously regress during the aging process, and this may be independent of prolactin, since there was no difference in serum prolactin concentrations between young and old hamsters. The finding that melatonin injections brought about a greater percent decrease in testicular weight in the old than in the young hamsters suggests that there is an increased sensitivity of the reproductive system to melatonin inhibition in the old male hamster.

Melatonin given in the morning prevents the suppressive action on the reproductive system of melatonin given in late afternoon

Melatonin administered to female hamsters kept under light:dark cycles of 14:10 (in hours) normally suppresses reproductive processes only if the indoleamine is administered later than 6.5 h after the beginning of the photoperiod. In the present study, we investigated the influence of morning (11.00 h) injections of melatonin on the reproductive inhibitory effects of afternoon (17.00 h) melatonin injections. Adult female hamsters were exposed to light daily from 06.00 to 20.00 h. The animals were divided into the following experimental groups: group 1, injected with vehicle at both 11.00 and 17.00 h; group 2, injected with vehicle at 11.00 h and 25 microgram melatonin at 17.00 h; group 3, injected with 1 mg melatonin at 11.00 h and 25 microgram melatonin at 17.00 h; group 4, injected with 1 mg melatonin at 11.00 h and vehicle at 17.00 h. Control animals injected with vehicle at both 11.00 and 17.00 h had normal 4-day estrous cycles throughout the 8 weeks of the experiment. 100% of the animals injected with vehicle in the morning and melatonin in the afternoon became acyclic within 7 weeks. However, if the afternoon injections of melatonin were preceded by morning injections of the indoleamine, the animals continued to exhibit normal estrous cycles. Also, hamsters injected with melatonin at 11.00 h and vehicle at 15.00 h had normal estrous cycles throughout the study. At the conclusion of the experiment, the uterine weights and plasma prolactin levels in the animals that received vehicle at 11.00 h and malatonin at 17.00 h were depressed compared to those in the vehicle-vehicle injected controls. Again, the morning injections of melatonin prevented the afternoon injections of melatonin from decreasing either the uterine weights or the plasma prolactin levels. It is concluded that the morning injections of melatonin either down-regulated the melatonin receptors or decreased their number and thereby rendered afternoon injections of melatonin incapable of inhibiting reproductive processes.

The combination of twice daily luteinizing hormone-releasing factor administration and renal pituitary homografts restores normal reproductive organ size in male hamsters with pineal-mediated gonadal atrophy

Light deprivation by bilateral orbital enucleation led to testicular and accessory sex organ regression in male hamsters within 12 weeks. Blinding also significantly depressed circulating levels of immunoreactive LH, FSH, and PRL. Twice daily injections of LRF did not prevent atrophy of the testes and accessory sex organs in blind animals even though they stimulated the release of both LH and FSH. Likewise, the restoration of normal plasma levels of PRL, due to the implantation of two pituitary homografts under the kidney capsule of blind hamsters only slightly stimulated testicular and accessory organ growth in the animals. However, twice daily LRF injections into light-deprived hamsters bearing subcapsular pituitary transplants completely restored normal testicular and accessory sex organ sizes. The results suggest that LH, FSH, and PRL act to restore normal testicular function in hamsters suffering from pineal-induced gonadal atrophy due to light deprivation. The possibility that the pituitary homografts secreted hormones in addition to PRL which also assisted in maintaining gonadal size cannot be excluded. Since the LRF injections stimulated the release of both LH and FSH from the pituitary of blind hamsters, it appears that the pineal normally inhibits the secretion of the gonadotropins at a site above the anterior pituitary, i.e. within the brain.

Pituitary prolactin cell hyperplasia

In female Long-Evans rats, development of prolactin cell adenomas is preceded by hyperplasia of prolactin cells, suggesting that factors affecting the endocrine function of prolactin cells might have an important role in the genesis of prolactin-producing pituitary tumors.

Acute effects of arginine vasotocin on plasma and pituitary levels of prolactin in the male rat: influence of urethane anesthesia

The acute effects of arginine vasotocin (AVT), a putative pineal peptide, on plasma levels of prolactin were investigated in the unanesthetized, estrogen-progesterone-treated male rat. A 10-microgram s.c. injection resulted in significantly increased levels of prolactin while a 1-microgram injection depressed plasma levels of this hormone; an inhibition of release was further suggested by increased levels of pituitary prolactin in rats treated with the lower dose. The same dose administered subcutaneously to urethane-anesthetized rats had no significant effect on plasma prolactin titers while a 10-microgram dose was still stimulatory. In anesthetized rats, no dose of the AVT administered (1 ng to 10 micrograms, s.c., or 1 fg to 1 microgram, i.v.) resulted in inhibition of prolactin release. In the unanesthetized normal male rat, 5 micrograms AVT first increased and then decreased levels of prolactin. Urethane anesthesia appears to mask an inhibitory effect of AVT on plasma prolactin levels in these animal preparations. Since AVT is capable of decreasing plasma prolactin levels, this peptide might be involved in the depression of plasma prolactin levels which appears to (at least partially) mediate pineal-induced gonadal degeneration.

Influence of subcutaneous deposits of melatonin on the antigonadotrophic effects of blinding and anosmia in male rats. A dose-response study

23-day-old male rats were left intact, rendered blind and anosmic, pinealectomized together with blinding and anosmia, or subcutaneously implanted with graded doses of melatonin in beeswax immediately following surgical blinding and anosmia. 5 weeks later, blind, anosmic animals were found to have significantly depressed anterior pituitary, testicular, and accessory sex organ weights. Both pituitary and plasma prolactin and luteinizing hormone (LH) concentrations were also significantly suppressed. Pinealectomy of blind, anosmic animals completely restored testicular and accessory organ weights. Likewise, pituitary LH and prolactin and plasma LH levels were also restored to intact control levels by pineal removal. Only the highest dose of melatonin (1 mg) restored the testicular and accessory sex organ weights to those of the intact controls. As little as 1 microgram melatonin restored plasma and pituitary LH concentrations to the levels of the intact controls. However, none of the dosages of melatonin reversed plasma prolactin concentrations to those of the untreated animals. The decrease in pituitary prolactin induced by blinding and anosmia was reversed by pinealectomy or by the lower doses (1, 50 or 100 micrograms) of melatonin. These results indicate that melatonin can reverse the antigonadotrophic effects of blinding and anosmia in male rats. The minimal dose of melatonin required to restore testicular and accessory sex organ weights in blind, anosmic rats is 1 mg implanted subcutaneously in beeswax.

Effects of age and testicular function on the pituitary-thyroid system in male rats

Old male rats of 22–24 months and young ones of 3–5 months were studied to find the effects of ageing, of orchidectomy and of orchidectomy and treatment with testosterone propionate (TP) on the basal serum concentrations of thyrotrophin (TSH) and on the total and free concentrations of tri-iodothyronine (T3) and thyroxine (T4) in the serum. The changes in TSH after treatment with thyrotrophin releasing hormone (TRH) were also observed. Intact old rats had significantly (P < 0·001) lower basal T4 and T3 as well as lower (P < 0·05) testosterone concentrations than were present in young rats. They also had higher basal TSH and per cent free T4 but lower absolute free T3 concentrations than had young rats. Two weeks after orchidectomy, basal TSH concentrations were slightly but significantly (P < 0·05) decreased in both young and old rats while T4 decreased significantly (P < 0·05) only in the young. The responses of TSH to TRH were also reduced by orchidectomy in both age groups with the old rats being less responsive than the young. Orchidectomy and treatment with pharmacological doses of TP produced similar effects on the pituitary-thyrotrophic response for both old and young rats but a greater effect occurred in the basal T4 response in young rats. In all groups basal TSH was influenced by orchidectomy or by treatment with TP but was always higher in the aged rat. Tri-iodothyronine concentration was always lower in the older rat and was not altered by orchidectomy or by treatment with TP in either young or old rats.

These results indicate that (1) in the male rat these age-specific effects on the thyroid–pituitary system are probably due, not only to a reduction in thyroid gland function and plasma T4 protein-binding, but also to a concomitant hyporesponsiveness of the aged male rat pituitary thyrotroph to TRH stimulation and (2) there is probably a significant influence of testicular function on the pituitary–thyroid system of the male rat.

Effects of age and ovarian function on the pituitary-thyroid system in female rats

The effects of ovariectomy and ovariectomy and treatment with oestradiol benzoate (OB) on the basal concentration of thyrotrophin (TSH), the total concentrations and concentrations of free tri-iodothyronine (T3) and thyroxine (T4), and the concentrations of TSH, T3 and T4 observed after treatment with thyrotrophin releasing hormone (TRH) were studied in old (16–17 months of age) constant oestrous and young (3–4 months of age) oestrous rats. The untreated old control rats had significantly (P< 0·001) lower basal total T4 concentrations and percentage and absolute concentrations of free T4 and lower percentage and absolute concentrations of free T3 than untreated young rats. The basal levels of TSH in these two groups were similar and the increases in TSH after injection of TRH were identical. Two weeks after ovariectomy, no significant additional differences in hormone concentrations between old and young rats were observed. However, release of TSH induced by TRH was increased by three- to fourfold in old rats after ovariectomy compared with nine- to tenfold in young ovariectomized rats (P<0·01). Basal T4 concentrations remained unchanged in old ovariectomized rats treated for 7 days with 2 μg OB/day compared with both intact and ovariectomized rats. However, T4 concentrations in OB-treated young rats were significantly (P<0·001) reduced. Treatment with OB significantly increased both basal and TRH-induced T3 and TSH levels in old and young rats although the young rats showed a greater response (P<0·001). Two hours after injection of TRH, serum T3 concentrations in old rats increased only after OB treatment and not after ovariectomy alone or in intact rats, whereas T3 concentrations rose in all three groups of young animals.

These results indicate that (1) older female rats have lower total T4, free T4 and free T3 concentrations and a lower TSH response to TRH, (2) OB treatment in young rats suppresses serum T4 but increases serum T3 and results in a greater TSH response to TRH and (3) at least one of the mechanisms accounting for the alterations in thyroid function observed in the older female rat, in addition to possible concomitant primary thyroid gland hypofunction, is a hyporesponsiveness of pituitary thyrotrophs to both endogenous negative feedback signals from low serum thyroid hormone concentrations and exogenous TRH stimulation.

Stimulation of growth of carcinogen-induced mammary cancers in rats by thyrotropin-releasing hormone

Twice-daily injections of three different doses of synthetic thyrotropin-releasing hormone (TRH), a hormone normally produced by the hypothalamus, produced significant increases in size and number of 7,12-dimethylbenz(a)anthracene-induced mammary cancers over 0.87% NaCl solution-injected control rats. When thyroidectomized rats, bearing 7,12-dimethylbenz(a)anthracene-induced mammary tumors were given the same twice-daily injections of TRH, mammary tumor growth was increased to the same extent as in intact rats given TRH, showing that the effects of TRH were not exerted via stimulation of thyroid function. The TRH-induced increments in mammary tumor growth were accompanied by significant increases in serum prolactin levels over 0.87% NaCl solution-injected controls. A single daily injection of 2-bromo-alpha-ergocryptine (CB-154), a prolactin-release inhibitor completely blocked TRH-induced mammary tumor growth and reduced serum prolactin values. These results indicate that a twice-daily pulse of TRH can stimulate mammary tumor growth by releasing prolactin from the anterior pituitary.

Stimulation of carcinogen-induced mammary tumor growth in rats by adrenalectomy

The effect of adrenalectomy on 7,12-dimethylbenz(a)anthracene-induced mammary tumor growth was studied in Sprague-Dawley female rats. Weekly measurements revealed that adrenalectomy significantly increased both mammary tumor size and number and elevated serum prolactin levels as compared to the intact controls. Daily injection of 1 mg hydrocortisone acetate into the intact 7,12-dimethylbenz(a)anthracene-tumor bearing rats did not significantly alter tumor size, number, or serum prolactin levels but, when injected into adrenalectomized rats, it prevented increased tumor growth and prolactin release. Daily injection of ovine prolactin and hydrocortisone suppressed endogenous prolactin release but significantly increased tumore size and number. Ergocornine, a prolactin-inhibiting drug, blocked adrenalectomy-induced tumor growth and partially blocked prolactin release. These results indicate that adrenalectomy in rats stimulates tumor growth by increasing prolactin release.

Effects of biogenic amines and TRH on release of prolactin and TSH in the rat

The effects of a single injection of drugs on serum prolactin and TSH were determined in male and in estrogen-primed ovariectomized rats. The precursor of serotonin, 5-hydroxytryptophan(5-HTP), produced a significant rise in serum prolactin and TSH, whereas para chloroamphetamine, a depletor of serotonin, elicited a fall in serum prolactin and TSH. alpha-methylmetatyrosine (alpha-MMT) and reserpine, both depressors of brain catecholamine (CA) and serotonin levels, evoked significant increases in serum prolactin and reductions in serum TSH. Injection of alpha-MMT or reserpine together with 5-HTP further elevated serum prolactin but prevented any significant change in serum TSH. This suggests that the ability of alpha-MMT and reserpine to inhibit TSH release is mediated through a reduction in brain serotonin and not via a decrease in CA. alpha methylparatyrosine, which inhibits CA synthesis without altering serotonin, evoked a marked increase in serum prolactin but had no effect on serum TSH. L-dopa administration significantly reduced serum prolactin values but had no significant effect on serum TSH. Synthetic TRH increased both serum prolactin and TSH levels in male rats, but when it was injected after L-dopa administration, it did not elicit any rise in serum prolactin and evoked the same increase in serum TSH. This suggest that L-dopa acts directly or indirectly on the pituitary prolactin cells to inhibit TRH stimulation of prolactin release, but does not influence the action of TRH on pituitary TSH cells. Pilocarpine decreased serum prolactin, but had no significant effect on serum TSH values. The present study suggests that only serotonergic drugs produce similar effects on release of prolactin and TSH, whereas drugs that alter CA and pilocarpine depress prolactin release but have little or no effect of TSH.