Neurointermediate lobe peptides recruit prolactin-secreting cells exclusively within the central region of the adenohypophysis.

There is strong evidence that the hypophyseal neurointermediate lobe (NIL) mediates 17 beta-estradiol (E2)-induced PRL secretion in rats. Our laboratory has previously demonstrated that E2 stimulates NIL cells to release an activity that acutely increases the relative abundance of PRL-releasing cells in anterior pituitary (AP) cell cultures. We later found that secretory products of the NIL melanotropes, specifically the acetylated forms of alpha MSH and beta-endorphin (beta END), can account for this activity. Given that blood from the NIL initially perfuses the region of the AP proximal to the NIL, we tested the hypothesis that this specific area was preferentially responsive to the lactotrope recruitment activities. AP glands from ovariectomized rats were dissected into an inner zone, proximal to the NIL, and the remaining outer zone of the gland, then dispersed with trypsin. The resulting cells were cultured for 16 h, either alone or in coculture with NIL cells, and subsequently treated with medium alone (control) or with alpha MSH, beta END, or E2 (all at 1 x 10(-7) M) for 3 h and then subjected to reverse hemolytic plaque assays for PRL release. Under control conditions, the proportion of PRL-secreting cells was significantly greater in cultures from the outer zone of the AP than in those from the corresponding inner zone of the gland. Treatment of AP cells from the inner zone with alpha MSH, beta END, or the E2-induced NIL activity significantly increased the percentage of PRL secretors by about 8% of all AP cells. In contrast, the fraction of PRL-secreting cells in cultures from the outer zone was not affected by these treatments. We conclude that the recruitment of PRL-secreting cells in response to products of the NIL occurs only in that region of the AP proximal to the NIL.     

Suckling increases the proportions of mammotropes responsive to various prolactin-releasing stimuli

It is well established that the suckling stimulus sensitizes or primes the anterior pituitary to PRL-releasing stimuli. It is also recognized that PRL-secreting cells from a given animal are not all alike but instead exhibit a considerable degree of functional heterogeneity. The goal of the present study was to determine whether the suckling-induced priming phenomenon is manifest at the cellular level by shifts in the relative abundance of various mammotrope subpopulations. This was accomplished by using reverse hemolytic plaque assays to evaluate the secretory characteristics of individual PRL secretors derived from lactating rats either before or after the transient application of a suckling stimulus. Groups of day 10 lactating rats separated from their litters for 4 h were either killed immediately or were reunited briefly (10 min) with their pups before death. Adenohypophyseal cells obtained after trypsin dispersion were then subjected to plaque assays for PRL. Mammotropes derived from suckled rats were, on average, considerably more responsive to the stimulatory actions of TRH and angiotensin II and less susceptible to inhibition by dopamine. Mammotropes from nonsuckled rats exhibited a bimodal frequency distribution in which plaques from the second mode were roughly 6-8 times larger (released considerably more PRL) than those from the first. Superimposition of suckling (or in vitro treatment with dopamine) caused the second mode to disappear. Suckling also enhanced greatly the fraction of PRL cells that shifted from the first to the second mode (i.e. released more hormone) after treatment with TRH or angiotensin II. Taken together, our results demonstrate that the suckling-induced sensitization of pituitary tissue to PRL-releasing stimuli is manifest at the cellular level as proportional shifts toward those cells most responsive to stimulatory secretagogues and away from those most susceptible to inhibition by dopamine.     

The role of the suckling stimulus in regulating pituitary prolactin mRNA in the rat

Prolactin (PRL) gene expression and the synthesis and secretion of PRL were examined in ovarian-intact lactating rats suckling eight pups on 10 days postpartum. Plasma samples were assayed for PRL concentrations, and pituitary glands were analyzed for total PRL content and PRL mRNA levels. We found that suckling-induced hyperprolactinemia was associated with very high levels of plasma PRL and a doubling in pituitary PRL mRNA levels, whereas pituitary PRL content was not changed. Removal of the suckling pups decreased plasma PRL concentrations 15-fold within 24 h. This decrease in PRL secretion was not accompanied by any significant change in pituitary PRL content. Evidently, both synthesis and secretion of PRL were decreased in the pituitary gland within 24 h following cessation of suckling, as pituitary PRL mRNA content had returned to diestrous levels at this time. To determine whether or not ovarian steroids might have contributed to the changes in PRL synthesis and secretion during lactation and after withdrawal of the suckling stimulus, the experiments were repeated in lactating rats ovariectomized (OVX) on day 2 postpartum. The results in these OVX rats were qualitatively similar to those described in ovarian-intact rats. We concluded from these findings that the stimulus of suckling induces increases in PRL mRNA levels in the pituitary which provides for the increased PRL synthesis accompanying increased PRL secretion. The cessation of suckling led to prompt decreases in PRL synthesis and secretion within 24 h.     

Polymorphism in a second ABC transporter gene located within the class II region of the human major histocompatibility complex.

Recent studies have identified genes within the major histocompatibility complex (MHC) that may play a role in presentation of antigenic peptides to T cells. We have previously described RING4, a gene within the human MHC class II region that has sequence homology with members of the ABC ("ATP-binding cassette") transporter superfamily. We now report the nucleotide sequence of RING11, a second ABC transporter gene located approximately 7 kilobases telomeric to RING4, RING11 is gamma-interferon inducible, a property shared with other genes involved in antigen presentation. Comparison between the amino acid sequences of RING11 and RING4 reveals strong homology. We propose that they form a heterodimer that transports peptides from the cytoplasm into the endoplasmic reticulum. We have identified two RING11 alleles, which differ in the length of their derived protein sequence by 17 amino acids. The more common of these alleles is present in a Caucasoid population at a frequency of 79%.     

Suppression of leptin during lactation: contribution of the suckling stimulus versus milk production.

Lactation in the rat is characterized by the suppression of pulsatile LH secretion, a large increase in food intake, and changes in energy balance due to the metabolic drain of milk production. The change in energy balance may be a major component in altering reproductive function. A number of factors may contribute to changing energy balance of a lactating animal; one is leptin, the product of adipose tissue, which is known to act partly as a satiety factor to decrease food intake. The aims of the present study were to determine whether there are changes in leptin levels during lactation, a state of high energy demand, and during periods of acute suckling in the presence or absence of changes in energy demand. Our goals were to determine whether lactation and the suckling stimulus influenced serum leptin levels and whether there was a potential role for leptin in the suppression of LH secretion during lactation. The first experiment was performed during diestrus of the estrous cycle, and chronic lactation, (day 9 post partum) in animals suckling 8 pups. The results showed that leptin levels were significantly decreased in both ovarian intact or ovariectomized lactators; this decrease parallels the suppression of pulsatile LH secretion. Serum insulin levels were not altered in the lactating animals. The second experiment was performed in ovariectomized lactators whose 8 pup litters were removed for 48 h, starting on day 9. On day 11, mothers received no pups or pups that were either nonfostered (resulting in no milk production) or fostered (resulting in milk production). The pups were allowed to suckle for 24 h. Following 24 h of acute suckling, serum leptin, and insulin levels correlated with the energy drain on the mother. The levels of leptin were normal and of insulin were elevated in mothers producing no milk. Conversely, leptin levels were suppressed and insulin levels normal in mothers producing milk. The third experiment used the same groups as described for the second experiment except that serial blood samples were collected for measurement of pulsatile LH secretion following 24 h of acute suckling. The results showed that regardless of whether leptin levels remained normal or were suppressed in response to acute suckling, pulsatile LH secretion was significantly inhibited compared with the nonsuckled control animals. In summary, these data suggest that the metabolic drain of milk production, and not the suckling stimulus itself, is the most likely factor responsible for the suppression of leptin secretion during lactation. Furthermore, although the decreased levels of leptin may be causally related to the inhibition of pulsatile LH secretion during chronic lactation, changes in leptin are not a prerequisite for the suppression of LH secretion in response to suckling.     

The effect of exteroceptive pup stimuli on the responsiveness of prolactin release mechanisms to suckling stimuli in the lactating rat

In the lactating rat, the neural stimulus of suckling not only acutely releases PRL but also maintains the responsiveness of PRL regulatory mechanisms to subsequent nursing stimuli. Beginning near midlactation exteroceptive pup stimuli (ECS) can acutely release PRL. We have examined the capacity of this signal also to maintain the responsiveness of PRL release mechanisms to subsequent suckling stimuli. On day 14 postpartum lactating rats were either isolated from their young or exposed to ECS (without suckling) for approximately 24 h. When both groups were later nursed, plasma PRL of mothers earlier exposed to ECS rose significantly higher than that of subjects previously isolated from their young. Suckling produced a significant depletion in pituitary PRL and GH concentrations of ECS-exposed mothers; it did not produce a similar depletion in the pituitaries of the previously isolated group. When the pups were returned for suckling, ECS-exposed mothers began to nurse their pups substantially faster than did females of the isolated group. During the 6 h after nursing, the mammary glands of ECS-exposed mothers secreted milk at twice the rate of mammary glands of the isolated females. We conclude that ECS can maintain the capacity of neuroendocrine mechanisms to respond to galactopoetic hormone-releasing stimuli (consequently enhancing milk secretion) and support the maternal behavior pattern necessary for suckling to occur. As a result, ECS may become an important factor during later stages of lactation, compensating for the decline in suckling stimuli known to occur at that time.     

Small cell carcinoma of the lung exclusively localized within the left descending pulmonary artery

We encountered a 69-year-old woman displaying a filling defect within the left descending pulmonary artery (PA) on a chest CT scan and pulmonary angiography. A subsequent 2-[18F]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) scan demonstrated focal uptake in the left hilum. A cytologic examination of transbronchial needle aspiration specimens revealed small cell carcinoma. The patient underwent concurrent radiation therapy and chemotherapy with cisplatin and etoposide, resulting in tumor shrinkage and recanalization of the involved PA. This is the first case of small cell carcinoma localized exclusively within the PA, and positive findings on FDG-PET facilitated the unexpected diagnosis.     

Airway cooling: stimulus specific modulation of airway responsiveness in the canine lung periphery

We used a wedged bronchoscope technique in conjunction with an in situ isolated perfused left lower lobe preparation in anesthetized dogs to examine cold-associated airway modulation of peripheral lung responses to dry airflow, hypocapnia, and aerosols of histamine and hypertonic NaCl. In this preparation, airway wall temperature was rapidly lowered by decreasing the temperature of blood perfusing the wedged sublobar segment. Cooling significantly attenuated responses to dry air, hypertonic NaCl aerosol, and hypocapnic challenge. In contrast, cooling did not affect peripheral lung responses to aerosolized histamine. Thus, cooling per se does not inhibit the responsiveness of smooth muscle. We conclude that, depending on the stimulus, cooling can modulate airway reactivity. We speculate that cooling attenuates hypocapnia, hypertonic aerosol, and dry air-induced bronchospasm via a cold induced reduction in neuronal activity or mediator production and release.     

The dawn and evolution of hormones in the adenohypophysis

The adenohypophysial hormones have been believed to have evolved from several ancestral genes by duplication followed by evolutionary divergence. To understand the origin and evolution of the endocrine systems in vertebrates, we have characterized adenohypophysial hormones in an agnathan, the sea lamprey Petromyzon marinus. In gnathostomes, adrenocorticotropin (ACTH) and melanotropin (MSH) together with beta-endorphins (beta-END) are encoded in a single gene, designated as proopiomelanocortin (POMC), however in sea lamprey, ACTH and MSH are encoded in two distinct genes, proopoicortin (POC) gene and proopiomelanotropin (POM) gene, respectively. The POC and POM genes are expressed specifically in the rostral pars distalis (RPD) and the pars intermedia (PI), respectively. Consequently, the final products from both tissues are the same in all vertebrates, i.e., ACTH from the PD and MSH from the PI. The POMC gene might have been established in the early stages of invertebrate evolution by internal gene duplication of the MSH domains. The ancestral gene might be then inherited in lobe-finned fish and tetrapods, while internal duplication and deletion of MSH domains as well as duplication of whole POMC gene took place in lamprey and gnathostome fish. Sea lamprey growth hormone (GH) is expressed in the cells of the dorsal half of the proximal pars distalis (PPD) and stimulates the expression of an insulin-like growth factor (IGF) gene in the liver as in other vertebrates. Its gene consists of 5 exons and 4 introns spanning 13.6 kb, which is the largest gene among known GH genes. GH appears to be the only member of the GH family in the sea lamprey, which suggests that GH is the ancestral hormone of the GH family that originated first in the molecular evolution of the GH family in vertebrates and later, probably during the early evolution of gnathostomes. The other member of the gene family, PRL and SL, appeared by gene duplication. A beta-chain cDNA belonging to the gonadotropin (GTH) and thyrotropin (TSH) family was cloned. It is expressed in cells of the ventral half of PPD. Since the expression of this gene is stimulated by lamprey gonadotropin-releasing hormone, it was assigned to be a GTHbeta. This GTHbeta is far removed from beta-subunits of LH, FSH, and TSH in an unrooted tree derived from phylogenetic analysis, and takes a position as an out group, suggesting that lampreys have a single GTH gene, which duplicated after the agnathans and prior to the evolution of gnathostomes to give rise to LH and FSH.     

Effect of the suckling stimulus on daily LH surges induced by chronic oestrogen treatment in ovariectomized lactating rats

Effects of the suckling stimulus on the daily LH surge induced by chronic oestrogen treatment were examined in ovariectomized lactating rats. Wistar-Imamichi strain rats were kept under 14 h light:10 h darkness (lights on at 05.00 h). Litter size was adjusted to eight on day 1 (day 0 = day of parturition) and ovariectomy performed on day 2. Lactating rats deprived of their litters on day 0 served as nonlactating controls. Silicone elastomer tubing filled with oestradiol was implanted on day 6 or 15. Blood samples were collected through an indwelling cannula at 10.00 and 17.00 h on each day after implantation to detect daily LH surges. Daily LH surges occurred in the late afternoon in both lactating and non-lactating rats implanted with oestradiol on day 6 or 15. The amplitude of daily LH surges in lactating rats implanted on day 6 declined much more rapidly than in non-lactating rats implanted on day 6, but no significant difference was found in the profile of the LH surge between lactating and non-lactating rats implanted on day 15. Pituitary LH contents just before the daily LH surge (12.00-12.30 h) 4 days after implantation in lactating rats implanted with oestradiol on day 6 were significantly less than those in nonlactating rats implanted with oestradiol on day 6 or 15 and in lactating rats implanted on day 15.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hormonal modulation of the responsiveness of midbrain central gray neurons to LH-RH

The spontaneous firing rate of midbrain central gray (MCG) neurons and the effect of iontophoretically applied prolactin and luteinizing hormone releasing hormone (LH-RH) on the electrical activity of these neurons was studied in untreated and estrogen-progesterone-treated ovariectomized female rats. The spontaneous firing rate of MCG neurons as well as the neuronal membrane responsiveness to iontophoretically applied prolactin was unaffected by the presence or absence of ovarian hormones. In both treated and untreated rats, the majority of neurons were not responsive to prolactin. On the other hand, the responsiveness of MCG neurons to iontophoretically applied LH-RH was influenced by hormonal treatment. A significantly larger number of MCG neurons were inhibited by LH-RH in hormone-treated animals than in untreated rats. The present work provides evidence at the electrophysiological level that ovarian hormones do not affect the firing rate of MCG neurons but do modulate the responsiveness of MCG neurons to LH-RH.     

The effect of bromocriptine on luteinizing hormone levels in the lactating sow: evidence for a suppressive action by prolactin and the suckling stimulus

Lactating sows (5 per group) were given no treatment or 10 mg bromocriptine orally twice daily from day 14 to 22 after parturition. Both groups were weaned at day 22. Frequent bleedings at 10 min intervals for 6 h were performed at 12, 16, 20 and 24 days after parturition. Prolactin and LH levels were measured in the collected blood samples by radioimmunoassays. Reduction of Prl by bromocriptine increased mean LH levels significantly and a further significant increase was observed after weaning. From the results it is concluded that in the lactating sow both Prl per se and the suckling stimulus are involved in suppression of LH levels.     

中心静脉压评估感染性休克患者容量反应性的应用

目的 探讨中心静脉压(CVP)评估感染性休克患者容量反应性的作用.方法 对入选的66例感染性休克患者行容量负荷试验,以提高患者CVP 2 mm Hg(1mm Hg=0.133 kPa)为目标,心脏指数(CI)≥300 ml·min-1·m-2为有反应者(有反应组),CI<300 ml·min-1·m-2为无反应者(无反应组).CVP由上腔静脉导管测量,全心舒张末容积指数(CEDVI)、胸腔内血容量指数(ITBVI)、每搏输出量指数(SVI)、CI经肺热稀释法和脉搏指示连续心排血量技术(PiCCO)测量.结果 (1)初始CVP有反应组明显低于无反应组,初始CVP用于诊断容量反应性有意义(P<0.05),其中CVP=11 mill Hg时敏感度为0.884,特异度为0.601.(2)有反应组与无反应组比较,初始ITBVI、GEDVI、CI、收缩压、舒张压、平均动脉压、心率差异无统计学意义.容量负荷试验前后,有反应组与无反应组比较,△ITBVI、△GEDVI、△CI、△SVI差异有统计学意义,△ITBVI、△GEDVI用于诊断容量反应性有意义.(3)CVP≤11 mm Hg者与CVP>11 mm Hg者比较,初始ITBVI、GEDVI差异无统计学意义.容量负荷试验前后,CVP≤11 mm Hg者与CVP>11 mm Hg者比较,△ITBVI、△GEDVI差异有统计学意义.结论 (1)用CVP评估感染性休克患者容量反应性有指导意义,但CVP >11 mm Hg时患者对容量负荷试验有反应的可能性较小;(2)与CVP相比,初始ITBVI、GEDVI评估感染性休克患者容量反应性无明确优势,当CVP无法良好预测容量反应性时△ITBVI、△GEDVI有指导意义.