[Effects of thoracic epidural administration of lidocaine on hemodynamic and arousal responses of double lumen tracheal intubation during induction of anesthesia]

OBJECTIVE

To compare the effects of thoracic epidural administration of lidocaine on hemodynamic and arousal responses of double lumen tracheal intubation during induction of anesthesia.

METHODS

In the study, 40 patients with American Society of Anesthesiologists (ASA) physical statuses I-II, aged 19-66 years, scheduled for elective thoracic surgeries under general anesthesia requiring orotracheal intubation were allocated to either the double-lumen endobronchial intubation (T group) or double-lumen endobronchial intubation after epidural administration of lidocaine (E group). After an intravenous anesthetic induction, the orotracheal double-lumen intubation was performed using a Macintosh direct laryngoscopy (MDLS), respectively. Invasive blood pressure (BP), heart rate (HR) and bispectral index (BIS) were recorded before and after anesthetic induction, immediately after intubation and 5 minutes after intubation with 1-minute interval and the intubation time also noted. The rate pressure product (RPP) was calculated.

RESULTS

After anesthetic induction, BP and RPP in the two groups decreased significantly compared with their preinduction values. In comparison with their postinduction values, the orotracheal intubation in the two groups caused significant increases in BPs, HRs and RPP. In comparison with their preinduction values, BPs decreased significantly in E group, systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial pressure (MAP) increased significantly and lasted for 1 min in T group. The HRs of both groups after intubation were significantly higher than their baseline values , and increased in HR and lasted for 1 min and 4 min in E group and T group, respectively. SBP, DBP, MAP, HR and RPP after intubation in T group were significantly higher than those of E group during the observation period. The values of BIS were similar between both the groups. In T group, the incidences of SBP percent increased>30% of the baseline value and RPP more than 22 000 were significantly higher than in E group. None of the patients in group E had SBP more than 130% of the baseline value and RPP more than 22 000.

CONCLUSION

During double-lumen endobronchial intubation, epidural administration of lidocaine can provide less hemodynamic response and similar arousal response.

Balance control, agility, eye-hand coordination, and sport performance of amateur badminton players: A cross-sectional study

In this study, balance performance, agility, eye-hand coordination, and sports performance were compared between amateur badminton players and active controls.Thirty young adult badminton players and 33 active controls participated in the study. Static single-leg standing balance (with eyes closed) was measured using a force platform, and dynamic balance was measured using the Y Balance Test (lower quarter). Agility was measured using a hexagon agility test, and eye-hand coordination was measured using a computerized finger-pointing task. Sports performance was quantified by the number of times a shuttlecock fell in a designated area following a badminton serve.The badminton players had superior accuracy in badminton serving (P < .001) relative to the active controls. However, no significant between-group differences were noted in all other outcome variables (P > .05).Amateur badminton players had more favorable sports performance, but not balance performance, agility, or eye-hand coordination, than controls.

A comparison of shoulder muscular performance and lean mass between elite and recreational swimmers: Implications for talent identification and development

This study compared the shoulder muscular performance and lean mass between elite and recreational swimmers.Thirty elite swimmers (mean age ± standard deviation = 23.1 ± 3.5 years) and 21 recreational swimmers (mean age ± standard deviation = 20.8 ± 2.1 years) participated in the study. Maximum muscle strength and time to maximum muscle strength of shoulder flexor, extensor, abductor, and adductor muscles were measured using a handheld dynamometer. Lean mass of the arms and body (excluding the head) were measured using dual-energy x-ray absorptiometry (DXA).Results revealed that compared with recreational swimmers, elite swimmers had higher maximum muscle strength of the shoulder flexor, extensor, abductor, and adductor muscles (all P < .001). The time to reach maximum muscle strength of all shoulder muscles showed no significant difference between the 2 groups (P > .05). The lean mass values in the left arm (P = .037), right arm (P < .001), and whole body (P = .014) were higher in elite swimmers than recreational swimmers.Elite swimmers had greater shoulder maximum muscle strength compared with recreational swimmers though the time taken to reach maximum muscle strength was similar between the 2 groups. Elite swimmers also showed a higher lean mass in both arms and their entire body when compared with recreational swimmers. The results may be useful for recreational swimmers who intend to advance to professional level, and for talent identification and early development of elite swimmers.

Clinicopathologic risk factors for right paraesophageal lymph node metastasis in patients with papillary thyroid carcinoma

OBJECTIVES

To investigate risk factors associated with right paraesophageal lymph node (RPELN) metastasis in patients with papillary thyroid carcinoma (PTC) and to determine the indications for right lymph node dissection.

METHODS

Clinicopathologic data from 829 patients (104 men and 725 women) with PTC, operated on by the same thyroid surgery team at the First Affiliated Hospital of Harbin Medical University from January 2013 to May 2017, were analyzed. Overall, 309 patients underwent total thyroidectomy with bilateral lymph node dissection, 488 underwent right thyroid lobe and isthmic resection with right central compartment lymph node dissection, and 32 underwent near-total thyroidectomy (ipsilateral thyroid lobectomy with contralateral near-total lobectomy) with bilateral lymph node dissection.

RESULTS

The overall rate of central compartment lymph node metastasis was 43.5% (361/829), with right central compartment lymph node and RPELN metastasis rates of 35.5% (294/829) and 19.1% (158/829), respectively. Tumor size, number, invasion, and location, lymph node metastasis, right central compartment lymph node metastasis, and right lateral compartment lymph node metastasis were associated with RPELN in the univariate analysis, whereas age and sex were not. Multivariate analysis identified tumors with a diameter ≥ 1 cm, multiple tumors, tumors located in the right lobe, right central compartment lymph node metastasis, and right lateral compartment lymph node metastasis as independent risk factors for RPELN metastasis.

CONCLUSIONS

Lymph node dissection, including RPELN dissection, should be performed for patients with PTC with a tumor diameter ≥ 1 cm, multiple tumors, right-lobe tumors, right central compartment lymph node metastasis, or suspected lateral compartment lymph node metastasis.

Benign mixed tumor of the vagina

Mixed tumor of the vagina is a rare benign tumor containing both epithelial and mesenchymal components. The authors report the case of a 35-year-old woman who presented with a painless mass that had descended from the vagina in the last six months. Physical examination showed the presence of a solitary, non-tender nodule that was 3x3x2 cm in size and seemed to originate from the posterior wall of the lower vagina. The tumor was removed and pathologically examined. The findings were indicative of a mixed tumor of the vagina, and were in agreement with previous cases. No recurrence or progression occurred during the ten-month follow-up. As this tumor shares common features with some other tumors, its differential diagnosis is very important. Moreover, due to the rarity of this disease, gynecologists and pathologists need to familiarize themselves with the features in order to avoid a misdiagnosis.

Effectiveness of a Multifaceted Cognitive Training Programme for People with Mild Cognitive Impairment: A One-Group Pre- and Posttest Design

Objectives

The effectiveness of a cognitive training programme in enhancing the functional abilities of elderly persons with mild cognitive impairments was tested in an integrated home and institutional training programme focused on performing daily tasks.

Methods

Twenty elderly participants were taught cognitive stimulation and memory encoding strategies for 10 weeks by an occupational therapist, or by nonprofessionals and community caregivers. The programme consisted of attention and memory stimulation, association-based and imagery-based strategies. Functional assessment (Chinese version of the disability assessment for dementia instrument and the instrumental activities of daily living scale) and neuropsychological tests (digit span forward test, word list memory subtest of the neuropsychological test battery developed by the Consortium to Establish a Registry for Alzheimer's Disease, Cognistat) were administered before and after the programme.

Results

After the 10-week programme the participants showed significant improvements in average attention and memory. The participants showed improved memory (word list memory: p ≤ .001) and other cognitive function as measured by the naming (p ≤ .001), construction (p ≤ .001), memory (p ≤ .001) and similarities (p ≤ .001) subtests of the Cognistat.

Conclusion

These results provide initial evidence supporting the use of daily tasks as the context in teaching cognitive stimulation and memory encoding strategies to mildly impaired elderly people.

Different small-dose remifentanil blunting the cardiovascular response to laryngoscopy and intubation in children: a randomized double-blind comparison

BACKGROUND

The available data provide inconsistent results on the efficacy of small-dose remifentanil attenuating the cardiovascular response to intubation in children. Therefore, this randomized double-blind study was designed to assess the ability of different small doses of remifentanil on the cardiovascular intubation response in children, with the aim of determining the optimal dose of remifentanil for this purpose.

METHODS

One hundred and twenty-four children aged 3-9 yr were randomized to one of four groups to receive the following in a double-blind manner: normal saline (Group 1), remifentanil 0.75 microg kg(-1) (Group 2), remifentanil 1 microg kg(-1) (Group 3) and remifentanil 1.25 microg kg(-1) (Group 4). Non-invasive blood pressure and heart rate were recorded before anaesthesia induction (baseline value), immediately before intubation (postinduction values), at intubation and at 1 min intervals for 5 min after intubation.

RESULTS

Tracheal intubation caused significant increases in systolic blood pressure and heart rate in Groups 1-3 compared with the baseline values. The maximum percent increases of systolic blood pressure and heart rate were 10% and 26% of the baseline values, respectively, in Group 2; 5% and 14% in Group 3; and 1% and 8% in Group 4 compared with 27% and 37% in Group 1. Except for the Group 3 vs. Group 4 comparison, there were significant differences among the four groups in the maximum percent increases of systolic blood pressure and heart rate.

CONCLUSIONS

When used as part of anaesthesia induction with propofol and vecuronium in children, bolus administration of remifentanil resulted in a dose-related attenuation of the cardiovascular intubation response.

The circulatory responses to tracheal intubation in children: a comparison of the oral and nasal routes

The circulatory responses to laryngoscopic tracheal intubation in 62 healthy children undergoing surgery requiring tracheal intubation were studied. They were randomly assigned to receive either the oral or nasal route for intubation. Baseline non-invasive blood pressure and heart rate were recorded following induction of anaesthesia, at intubation and then every minute for 5 min. The percentage changes of systolic blood pressure and heart rate during the measurement period were calculated. The results demonstrated that intubation time was significantly longer in the nasal group. Both oral and nasal intubation caused significant increases in blood pressure and heart rate compared to baseline and postinduction values. However, there were no significant differences found between the two groups in relation to blood pressure and heart rate. The two groups were similar with respect to the percentage changes of systolic blood pressure and heart rate during the observation period. It is concluded that oral and nasal intubation using a direct laryngoscopy can result in a similar circulatory response in anaesthetised children.

The circulatory responses to fibreoptic intubation: a comparison of oral and nasal routes

The circulatory responses to fibreoptic intubation under general anaesthesia were studied in 60 adult female patients who were randomly assigned to receive either the oral or nasal route for insertion. Non-invasive blood pressure and heart rate were recorded before anaesthesia induction (baseline values), immediately after anaesthesia induction (post-induction values), at intubation and every minute for a further 5 min. The product of heart rate and systolic blood pressure (rate pressure product) at every time point was also calculated. The results showed that both fibreoptic orotracheal intubation and fibreoptic nasotracheal intubation resulted in significant increases in blood pressure, heart rate and rate pressure product compared to baseline and post-induction values. The times required to reach the maximum values of systolic blood pressure and heart rate were significantly longer in the fibreoptic nasotracheal intubation group than in the fibreoptic orotracheal intubation group. There were no significant differences between the two groups in blood pressure, heart rate and rate pressure product at any measuring point, or in the maximum values during observation. The time required for recovery of systolic blood pressure to the post-induction value was not significantly different between the two groups, but the time required for recovery of heart rate to post-induction value was significantly longer in the fibreoptic orotracheal intubation group than in the fibreoptic nasotracheal intubation group. It was concluded that both fibreoptic orotracheal and fibreoptic nasotracheal intubations could cause a similar magnitude of circulatory responses in general anaesthetised, female adults, but the tachycardic response to fibreoptic orotracheal intubation lasted longer than that to fibreoptic nasotracheal intubation.

A comparative study of hemodynamic responses to orotracheal intubation with fiberoptic bronchoscope and laryngoscope in children

BACKGROUND

The purposes of this study were to further identify the hemodynamic responses to orotracheal intubation in children, using a fiberoptic bronchoscope (FOB) and a direct laryngoscope (DLS), and to validate whether the FOB can attenuate the hemodynamic response to orotracheal intubation compared with the DLS.

METHODS

Forty-three children, ASA PS I-II scheduled for elective plastic surgery under general anesthesia requiring orotracheal intubation were randomly allocated to either the DLS group (n = 20) or the FOB group (n = 23). Noninvasive systolic blood pressure (SBP) and heart rate (HR) were recorded before (baseline values) and after anesthesia induction (postinduction values), at intubation and every minute for the first 5 min after intubation. The maximal values of SBP and HR during the observation were also recorded. The product of HR and SBP [rate pressure product (RPP)] at each time point was calculated.

RESULTS

In the DLS group, SBP, HR, and RPP at intubation and 1 min after intubation were significantly higher than postinduction values, but did not exceed baseline values. In the FOB group, SBP, HR, and RPP at intubation increased significantly compared with baseline and postinduction values. In the two groups, the maximal values of SBP, HR, and RPP during the observation were significantly higher than baseline values. Except for the HR at intubation, there were no significant differences in other hemodynamic parameters during the observation and the time required to reach maximal values of SBP, HR, and RPP between the two groups.

CONCLUSIONS

Orotracheal intubation using FOB and DLS in children may cause similar increases in SBP and HR. Compared with the DLS, the FOB had no advantage in attenuating the hemodynamic responses to orotracheal intubation.

Blood pressure and heart rate changes during fibreoptic orotracheal intubation: a comparison of children and adults

BACKGROUND AND OBJECTIVES

Autonomic circulatory regulation and airway anatomy in children are significantly different from those in adults. There is no available published data to compare whether there is a clinically relevant difference in the haemodynamic responses to fibreoptic orotracheal intubation (FOI) under the same conditions between children and adults. In this randomized clinical study, we compared the blood pressure (BP) and heart rate (HR) changes during FOI in 40 children aged 3.5-9 yr and 40 adults aged 21-57 yr, ASA 1 scheduled for elective plastic surgery under general anaesthesia requiring orotracheal intubation.

METHODS

Anaesthesia was induced with intravenous (i.v.) injection of fentanyl and propofol, and face mask inhalation of isoflurane before FOI. Noninvasive BP and HR were recorded before induction (baseline values), after induction (postinduction values), at intubation and for 5 min after intubation at 1-min intervals. The percentage changes of BP and HR at each time point were calculated.

RESULTS

In children and adults, HR at intubation and 1-3 min after intubation were significantly higher than baseline and postinduction values. In adults, BP at intubation increased significantly compared to the postinduction values but did not exceed baseline values. In children, BP at intubation and 1 min after intubation were significantly higher than postinduction and baseline values. As compared to adults, FOI caused a more significant pressor response in children. The percentage changes of BP at intubation and 1 min after intubation were larger in children than in adults. However, there was no significant difference in the percentage change of HR during the observation between children and adults.

CONCLUSIONS

Under general anaesthesia, FOI might cause a more significant pressor response in children than in adults.

Blood pressure and heart rate changes during intubation: a comparison of direct laryngoscopy and a fibreoptic method

Blood pressure and heart rate changes during nasotracheal intubation under general anaesthesia were studied in 100 patients who were randomly allocated to fibreoptic bronchoscope or direct laryngoscopy intubation. Noninvasive blood pressure and heart rate were recorded before and immediately after anaesthesia induction, at anaesthesia intubation and every minute thereafter for 5 min. Nasotracheal intubation was accompanied by significant increases in blood pressure and heart rate compared to baseline values in both groups. Blood pressure and heart rate at intubation, and the maximum values of blood pressure during the observation were significantly higher in the fibreoptic bronchoscope group. However, the maximum values of heart rate were not significantly different between the two groups. Fibreoptic nasotracheal intubation may result in more severe pressor and tachycardiac responses than direct laryngoscopic nasotracheal intubation.

The clinical observation of difficult laryngoscopy and difficult intubation in infants with cleft lip and palate

BACKGROUND

The aims of this study were to evaluate the incidence of difficult laryngoscopy in infants with cleft lip and palate and to observe its relationships with age, sites, and degrees of deformities.

METHODS

A total of 985 infants aged 1 month to 3 years, undergoing repair of cleft lip and palate were included in this study. The infants suffering from unilateral cleft lip, simple cleft palate, and combined bilateral cleft lip and palate were 465, 421, and 79 respectively. They were divided into three groups according to age; 1-6 months group, 6-12 months group and 1-3 years group.

RESULTS

The total incidence of difficult laryngoscopy was 4.77%. The incidence of difficult laryngoscopy was closely related to age, sites and degrees of deformities, and micrognathia. The incidence of difficult laryngoscopy was 7.06% in 1-6 months group, 2.90% in 6-12 months group, and 3.13% in 1-3 years group, and was greatest for infants with combined bilateral cleft lip and palate, less for those with left cleft lip and least for those with right cleft lip and simple cleft palate. The incidences of difficult laryngoscopy in infants with and without micrognathia were 50% and 3.83% respectively. The incidences of moderately difficult, difficult, and failed intubations were 1.02%, 0.91%, and 0.102% respectively.

CONCLUSIONS

Infants with cleft lip and palate, left cleft lip and alveolus, combined bilateral cleft lip and palate, micrognathia, and age <6 months were the important risk factors for difficult laryngoscopy. Difficult intubation occurred mainly in infants with laryngoscopic views of grade III and IV.

Mechanism of extracellular Ca2+ receptor-stimulated hormone release from sheep thyroid parafollicular cells

1. Expression of receptors to extracellular calcium enables parafollicular cells of the thyroid gland (PF cells) to release calcitonin (CT) and serotonin (5-HT) in response to increased external Ca2+. Recently, a calcium-sensing receptor (CaR), similar to the G protein-coupled receptor for external Ca2+ cloned from parathyroid gland, was shown to be expressed in PF cells. Using a highly purified preparation of sheep PF cells, we have examined the electrical and biochemical processes coupling CaR activation to hormone release. 2. Whole-cell recordings in the permeabilized-patch configuration show that elevated extracellular Ca2+ concentration ([Ca2+]0) depolarizes these cells and induces oscillations in membrane potential. In voltage clamp, high [Ca2+]0 activates a cation conductance that underlies the depolarization. This conductance is cation selective, with a reversal potential near -25 mV indicating poor ion selectivity. 3. The CaR expressed in these cells is activated by other multivalent cations with a rank order potency of Gd3+ > Ba2+ > Ca2+ > > Mg2+. The insensitivity of these cells to high external Mg2+ contrasts with the reported sensitivity of the cloned CaR from parathyroid. 4. Elevation of [Ca2+]0 also stimulates increases in intracellular Ca2+ concentration ([Ca2+]i) and this effect is largely inhibited by the Ca2+ channel blocker nimodipine, indicating that L-type voltage-gated Ca2+ channels contribute to the response to elevated [Ca2+]0. 5. Elevated [Ca2+]0 induces an inward current under conditions where the only permeant external cation is Ca2+, indicating that influx via the cation conductance is another source of the increases in [Ca2+]i. 6. Extracellular Ca2+ stimulates 5-HT release with an EC50 of 1.5 mM. Nimodipine blocks 90% of the Ca2+0-induced 5-HT release, while other inhibitors of voltage-gated calcium channels had no effect. These data support an important role for L-type Ca2+ channels in CaR-induced hormone secretion. Although earlier studies indicate that high [Ca2+]0 induces release of Ca2+ from intracellular stores, thapsigargin-induced depletion of these stores did not affect secretion from these cells, indicating that Ca2+ influx is necessary and sufficient for the Ca2+0-induced 5-HT secretion. 7. Inhibition of protein kinase C (PKC) using chelerythrine, staurosporine, or calphostin C inhibited Ca2+0-induced 5-HT release by 50% while phorobol ester-induced 5-HT secretion was completely inhibited. Thus, PKC is an important component of the pathway linking CaR activation to hormone release. However, another as yet unknown second messenger also contributes to this pathway. 8. We tested the contribution of two different phospholipases to the CaR responses to determine the source of the PKC activator diacylglycerol (DAG). Selective inhibition of phosphatidylinositol-specific phospholipase C (PI-PLC) with U73122 had no effect on the response to elevated [Ca2+]0. However, pretreatment with D609, a selective inhibitor of phosphatidylcholine-specific phospholipase C (PC-PLC), inhibited Ca(2+)-induced 5-HT release to 50% of control indicating that phosphatidylcholine is a likely source of DAG in the response of PF cells to elevated [Ca2+]0.

Expression and development of a functional plasmalemmal 5-hydroxytryptamine transporter by thyroid follicular cells

5-Hydroxytryptamine (5-HT) is synthesized and secreted by thyroid parafollicular (PF) cells. As all PF granules contain 5-HT, it is released whenever PF cells secrete. Because 5-HT stimulates follicular (F) cells and can modulate their response to TSH, 5-HT has been proposed to be a paracrine PF to F cell transmitter. This role would require a thyroid mechanism to rapidly inactivate 5-HT. A 5-HT transporter (SERT) in the plasma membrane of serotonergic neurons inactivates neuronal 5-HT. We thus tested the hypothesis that this molecule is expressed in the thyroid. Messenger RNA encoding SERT was demonstrated in both the human thyroid and a rat F cell line (FRTL-5). SERT immunoreactivity was detected in rat F, but not PF, cells. Transporter-mediated uptake of [3H]5-HT by F cells arose early in development (E13 in mice) and was maintained in adult life in mice, guinea pigs, bats, and rats (FRTL-5 cells). These observations indicate that a functional SERT is expressed in the thyroid, not by the 5-HT-secreting PF cells, but by their putative F cell targets.

Acidification of serotonin-containing secretory vesicles induced by a plasma membrane calcium receptor

Parafollicular (PF) cells secrete 5-hydroxytryptamine in response to increased extracellular Ca2+ ([Ca2+]e). This stimulus causes Cl- channels in PF secretory vesicles to open, leading to vesicle acidification. PF cells express a plasmalemmal heptahelical receptor (CaR) that binds Ca2+, Gd3+, and Ba2+. We now report that the CaR mediates vesicle acidification. Ca2+, Gd3+, and Ba2+ induced vesicle acidification, which was independent of channel-mediated Ca2+ entry. Agonist-induced vesicle acidification was blocked by pertussis toxin, inhibitors of phosphatidylinositol-phospholipase C, calmodulin, NO synthase, guanylyl cyclase, or protein kinase G. PF cells contained NO synthase immunoreactivity, and vesicles were acidified by NO donors and dibutyryl cGMP. [Ca2+]e, and Gd3+ mobilized thapsigargin-sensitive internal Ca2+ stores. [35S]G alpha i and [35S]G alpha q were immunoprecipitated from PF membranes incubated with agonists in the presence of [35S]adenosine 5'-O-(thiotriphosphate). Labeling of G alpha i but not G alpha q was antagonized by pertussis toxin. Vesicles acidified in response to activation of protein kinase C; however, protein kinase C inhibition blocked calcium channel- but not CaR-dependent acidification. We propose the following signal transduction pathway: CaR -> Gi -> phosphatidylinositol-phospholipase C -> inositol 1,4,5-trisphosphate -> [Ca2+]i -> Ca2+/calmodulin -> NO synthase -> NO -> guanylyl cyclase -> cGMP -> protein kinase G -> opens vesicular Cl- channel.

Secretogogue-induced gating of chloride channels in the secretory vesicles of parafollicular cells

Thyroid parafollicular (PF) cells are neural crest-derived endocrine cells that secrete serotonin and calcitonin. The secretory vesicles of PF cells acidify when secretion is induced by increased extracellular Ca2+ or TSH. We tested the hypothesis that acidification is regulated by secretogogue-gated Cl- channels in vesicular membranes. Cl- channel (p64) immunoreactivity was enriched in purified PF vesicles. X-Ray microanalysis showed a change in chlorine level in PF vesicles in response to secretogogue-stimulation of isolated cells. Secretogogue stimulation also altered the degree of p64 channel phosphorylation. Protein kinase and phosphatase inhibitors antagonized secretogogue-induced vesicle acidification and secretion; however, secretion could occur even when acidification was blocked. We conclude that acidification of PF vesicles is regulated by a gatable Cl- channel in vesicle membranes and that protein phosphorylation and dephosphorylation are involved in channel activation. Acidification of vesicles is not required for exocytosis.

Serotonin binding protein: synthesis, secretion, and recycling

Serotonin binding protein (SBP) is present in all neurectodermally derived cells that store serotonin (5-HT). Three forms of SBP have been detected (68, 56, and 45 kDa), and antibodies to SBP that interfere with the binding of 5-HT react with each of these proteins. The current experiments test two hypotheses: (a) that the 56- and 45-kDa forms of SBP are produced by posttranslational cleavage of a 68-kDa precursor molecule; and (b) that 45-kDa SBP is a constituent of serotonergic secretory vesicles. Pulse-chase experiments were carried out using medullary thyroid carcinoma cells as a model. These neurectodermally derived cells produce 5-HT and all three forms of SBP. Following pulse labeling for 20 min with L-[35S]methionine, the cells were incubated in the presence of an excess of unlabeled L-methionine for 0, 30, 60, or 90 min at 37 degrees C. Alternatively, the chase was performed under conditions (20 degrees C, inhibition of ATP generation) that delay or stop transport of newly synthesized proteins from the rough endoplasmic reticulum through the Golgi apparatus. Following incubation, the cells were washed and solubilized, and SBP was immunoprecipitated. Radioactive proteins in the immunoprecipitate were electrophoretically resolved and quantified. Immediately after the pulse, each of the three forms of SBP was found to be labeled with 35S. The relative proportions of 35S-labeled 68-, 56-, and 45-kDa SBP remained the same at each interval of chase. These proportions were not changed when the chase was carried out at 20 degrees C or under conditions that blocked the biosynthesis of ATP. These observations suggest that each form of SBP is a primary product of translation, that the smaller forms of SBP are not produced by cleavage from a larger molecule, and that the size of the primary products of translation is not altered by passage to the Golgi apparatus or a post-Golgi compartment. When secretion was induced, 45-kDa SBP, but not 56- or 68-kDa SBP, was released to the medium. When antibodies to 45-kDa SBP were added to the medium at the time secretion was induced, antibody binding sites appeared as patches on the cell surfaces. Because of these sites, cells were lysed when they were stimulated to secrete in the presence of antibodies to 45-kDa SBP and guinea pig complement.(ABSTRACT TRUNCATED AT 400 WORDS)

Serotonergic signalling between thyroid cells: protein kinase C and 5-HT2 receptors in the secretion and action of serotonin

Parafollicular (PF) cells of the thyroid gland are neural crest derivatives, which costore the neurotransmitter, 5-hydroxytryptamine (5-HT) with calcitonin. PF cells are located adjacent to follicular (F) cells within the basement membrane of thyroid follicles. It has been proposed that 5-HT serves an intercellular signalling function in the thyroid and that F cells are its target. This proposal was tested by using cell lines derived from PF (medullary thyroid carcinoma [MTC]) and F (FRTL-5) cells to study the mechanisms that mediate the secretion and action of 5-HT. Secretion of 5-HT by MTC cells was evoked by thyroid stimulating hormone, thyrotropin (TSH), elevated extracellular calcium (increases [Ca2+]e), or by agents that increase intracellular cAMP (increases [cAMP]i). When protein kinase C (PKC) was down-regulated by prolonged treatment of MTC cells with phorbol 12-myristate 13-acetate (PMA), or PKC was inhibited by staurosporin, the TSH- or PMA-evoked secretion of 5-HT was blocked; however, interference with PKC function did not affect 5-HT secretion evoked by increases [Ca2+]e or increases [cAMP]i. In the putative targets, FRTL-5 cells, 5-HT increased the turnover of phosphoinositides (PI), cytosolic calcium (increases [Ca2+]i), increases [cAMP]i, and biphasically modified the effect of TSH on cAMP. All of these 5-HT effects were inhibited by 5-HT2 receptor antagonists (spiperone and ketanserin) and by pertussis toxin (PTx), suggesting that the actions of 5-HT are mediated by 5-HT2 receptors, which are coupled to a G protein. This suggestion was supported by the following additional observations: FRTL-5 membranes bound the 5-HT2 agonist, [125I]2,5-dimethoxy-4-iodophenylisopropylamine ([125I]-DOI), and anti-idiotypic antibodies, which recognize 5-HT2 receptors. [125I]-DOI binding was inhibited by guanosine-5'-O-(3-thiotriphosphate) (GTP-gamma-S) and the antibodies were displaced by spiperone. Data are consistent with the hypothesis that 5-HT serves as a PF to F cell messenger.

Identification of serotonin receptors recognized by anti-idiotypic antibodies

Anti-idiotypic antibodies were generated by immunizing rabbits with affinity-purified antibodies to serotonin (5-hydroxytryptamine; 5-HT). Anti-5-HT activity was removed from the resulting antisera by chromatography through a 5-HT affinity column. The anti-idiotypic antibodies were demonstrated by enzyme-linked immunosorbent assay to bind to affinity-purified whole anti-5-HT antibodies and their Fab fragments. Anti-idiotypic antibodies, purified by affinity chromatography on columns to which antibodies to 5-HT were coupled, competed with 5-HT (covalently bound to protein) for the binding sites on anti-5-HT antibodies and serotonin binding protein. The anti-idiotypic antibodies antagonized the binding of [3H]5-HT to membranes isolated from the cerebral cortex, striatum, and raphe area more than to membranes from hippocampus or cerebellum. The anti-idiotypic antibodies also blocked the binding of the 5-HT1B-selective ligand (-)-[125I]iodocyanopindolol (in the presence of 30 microM isoproterenol) to cortical membranes. In contrast, anti-idiotypic antibodies failed to inhibit binding of the 5-HT1A-selective ligand 8-hydroxy-2-(di-n-[3H]propylamino)-tetralin [( 3H]8-OH-DPAT) to raphe area membranes or hippocampal membranes. These observations suggested that the anti-idiotypic antibodies may recognize some 5-HT receptor subtypes but not others. This hypothesis was tested by ascertaining the ability of anti-idiotypic antibodies to immunostain cells transfected in vitro with cDNA encoding the 5-HT1C or 5-HT2 receptor or with a genomic clone encoding the 5-HT1A receptor. Punctate sites of immunofluorescence were found on the surfaces of fibroblasts that expressed 5-HT1C and 5-HT2 receptors, but not on the surfaces of HeLa cells that expressed 5-HT1A receptors. Immunostaining of cells by the anti-idiotypic antibodies was inhibited by appropriate pharmacological agents: immunostaining of cells expressing 5-HT1C receptors was blocked by mesulergine (but not ketanserin, 8-OH-DPAT, or spiperone), whereas that of cells expressing 5-HT2 receptors was blocked by ketanserin or spiperone (but not mesulergine or 8-OH-DPAT). The anti-idiotypic antibodies failed to inhibit the uptake of [3H]5-HT by serotonergic neurons. It is concluded that the anti-idiotypic antibodies generated with anti-5-HT serum recognize the 5-HT1B, 5-HT1C, and 5-HT2 receptor subtypes; however, neither 5-HT1A receptors nor 5-HT uptake sites appear to react with these antibodies.

Multiple signal transduction mechanisms leading to the secretion of 5-hydroxytryptamine by MTC cells, a neurectodermally derived cell line

Parafollicular (PF) cells of the thyroid gland are neural crest derivatives. These cells remain plastic even in adult animals and can be induced to exhibit neural properties when exposed to NGF in vitro. A human cell line derived from PF cells, medullary thyroid carcinoma (MTC), has previously been shown to synthesize and store 5-HT, a serotonin-binding protein (SBP), and several neuropeptides; moreover, when grown in impoverished media, MTC cells display neural properties. The purpose of the current study was to utilize MTC cells as a neurally relevant model system to investigate factors involved in mediating 5-HT secretion. Electron microscopic immunocytochemistry revealed that secretory vesicles of MTC cells costore immunoreactive 5-HT with SBP and calcitonin. The cAMP derivative, N6-2'-O-dibutyryl-adenosine 3',5'-cyclic monophosphate (dibutyryl-cAMP; 1.0 mM) increased the concentration of 5-HT in MTC cells and almost doubled the rate of synthesis of 5-HT from L-tryptophan. Dibutyryl-cAMP also significantly increased the secretion of 5-HT. Cycloheximide (20 micrograms/ml) and anisomycin (20 microM) inhibited the dibutyryl-cAMP-induced increase of 5-HT release, suggesting that this action of dibutyryl-cAMP requires protein synthesis. Cholera toxin (1.0 microgram/ml) and forskolin (0.05 mM) in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (1.0 mM) both increased 5-HT biosynthesis and secretion. Attempts were made to identify a ligand that stimulates cAMP-mediated secretion of 5-HT. Both thyroid-stimulating hormone (TSH: 50 mU/ml) and elevated [Ca2+]e (7.0 mM), each of which acts as a secretogogue for PF cells, stimulated the secretion of 5-HT. The effect of TSH was Ca2(+)-dependent. Immunocytochemistry with monoclonal antibodies to the TSH receptor confirmed that these receptors are present on MTC cells. Neither TSH nor elevated [Ca2+]e elevated cAMP levels. Measurements of Fura-2 fluorescence, however, indicated that both TSH and elevated [Ca2+]e increased cytosolic calcium ([Ca2+]i), as did elevation of [K+]e. It is concluded that exocytosis can be triggered in MTC cells by multiple signal transduction mechanisms. Either cAMP or elevated [Ca2+]i can stimulate secretion; however, a secretogogue that increases cAMP has yet to be identified.

Preparation and characterization of monoclonal antibodies to serotonin binding protein

Serotonin binding protein (SBP) is a constituent of the synaptic vesicles of serotonergic neurons. Two types of SBP, with molecular masses of 45 kDa and 56 kDa, have been purified. To determine whether there are shared epitopes between the two forms of SBP, we raised and tested for cross-reactivity monoclonal antibodies (MAbs) against each form of SBP. We obtained 12 MAbs, all of which recognize both forms of SBP. Hybridoma clones were produced by fusing P3 X 63Ag8.653 mouse myeloma cells with spleen cells from a mouse that had been immunized with 45-kDa or 56-kDa SBP. Culture supernatants were screened for the presence of anti-SBP antibodies. MAb isotypes were determined by immunodiffusion, using immunoglobulin type-specific antisera. Each antibody to SBP consisted of only a single subclass of immunoglobulin (IgM). We obtained 12 MAbs, each of which interacted with both forms of SBP, as judged by enzyme-linked immunosorbent assay and immunoblot analysis. Ascites fluid to one clone (44-10) was obtained and affinity-purified. In the presence of goat anti-mouse IgM, the partially purified 44-10 antibodies quantitatively immunoprecipitated SBP from crude brain extracts. Immunoblotting revealed two major bands corresponding to 45 kDa and 56 kDa and a minor band corresponding to 68 kDa. MAb 44-10 blocked the binding of [3H]serotonin ([3H]5-HT) to 45-kDa and 56-kDa SBP in a concentration-dependent manner. The 68-kDa protein was found to bind [3H]5-HT. Sites reacting with MAB 44-10 were located immunocytochemically in sections of rat brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Photoaffinity labeling of the two forms of serotonin binding protein: peptide mapping of the binding sites

Serotonin binding protein (SBP) is a vesicular protein found in neurectoderm-derived cells that store 5-hydroxytryptamine (5-HT, serotonin), such as central and peripheral serotonergic neurons and paraneurons (parafollicular cells of the thyroid). 5-HT is stored as a complex with SBP in vivo. Two forms of the protein are found. These differ in molecular mass: one is 45 kDa and the other 56 kDa. It has been suggested that the 56-kDa form of SBP may be the precursor of the 45-kDa form. To study the relationship between these two proteins, we have used a covalently bound radiolabeled probe to analyze their binding domains. A photoaffinity reagent, N-(4-azido-2-nitrophenyl)-5-hydroxytryptamine (NAP-5-HT), was synthesized and characterized by nuclear magnetic resonance spectroscopy, mass spectra, and UV-visible absorption spectra. A 1 M excess of NAP-5-HT inhibited the binding of [3H]5-HT to SBP by 50%. NAP[3H]5-HT was also synthesized and attached to both high- and low-affinity binding sites on both forms of SBP. The high-affinity constants for 45-kDa and 56-kDa proteins were 0.8 nM and 0.02 nM, respectively, whereas the low-affinity constants were 0.3 microM and 0.15 microM. When the high-affinity site of partially purified SBP was photoaffinity-labeled with the reagent, two covalently labeled proteins (45 kDa and 56 kDa) were found by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Inhibition of the labeling of both proteins by 50% was observed in the presence of a 15-fold molar excess of 5-HT.(ABSTRACT TRUNCATED AT 250 WORDS)

Human medullary thyroid carcinoma: characterization of the serotonergic and neuronal properties of a neurectodermally derived cell line

Parafollicular (PF) cells have been found to be a good model system for the study of serotonergic cellular mechanisms relevant to neurons. PF cells are derived from the same region of the neural crest that gives rise to the neurons of the gut and are capable of extending neurofilament-bearing neuritic processes. PF cells also synthesize 5-hydroxytryptamine (5-HT) and costore 5-HT in the same vesicles as the specific 5-HT-binding protein, 45 kDa SBP. A hypothesis has been advanced that PF cells and enteric neurons share a common developmental precursor. The present investigation was undertaken in order to determine whether a human medullary thyroid carcinoma (MTC) cell line, which is derived from PF cells, sufficiently mimics PF cells that it can be substituted for them in investigations of serotonergic cellular biology. In contrast to PF cells, MTC cells can be propagated in vitro to provide adequate amounts of material for biochemical studies. MTC cells were found to contain neuropeptides, including calcitonin, calcitonin gene-related peptide, and somatostatin, which have also been reported to be present in PF cells and enteric neurons. MTC cells also were observed to store endogenous 5-HT, to be able to synthesize 3H-5-HT from 3H-L-tryptophan, and to take up 3H-5-HT from the ambient medium by a carrier-mediated mechanism very similar to that of serotonergic neurons. In addition, the longterm accumulation of 3H-5-HT in MTC cells was antagonized by reserpine, suggesting that the cells contain 5-HT storage vesicles that, like the synaptic vesicles of serotonergic neurons, are characterized by a reserpine-sensitive transporter of biogenic amines. MTC cells also contain type A, but not type B, monoamine oxidase. Finally, MTC cells were found to contain both 45 and 56 kDa SBP. MTC cells thus retain a great many of the properties of PF cells, and, like PF cells, they are serotonergic cells with characteristics similar to serotonergic neurons. Substantial differences were found in the content of immunoreactive 5-HT and neuropeptides in individual MTC cells. Moreover, the release of newly synthesized 5-HT to the medium exceeded the ability of the cells to store the amine. Studies of the ultrastructure of the MTC cells revealed a limited and highly variable number of secretory granules, probably accounting for their limited 5-HT storage capacity and for the heterogeneity of immunostaining with antisera to 5-HT or neuropeptides.(ABSTRACT TRUNCATED AT 400 WORDS)

Costorage of serotonin binding protein with serotonin in the rat CNS

Previous studies have identified two neurectoderm-specific serotonin binding proteins (SBP), one with an apparent Mr of 45 kDa, and one of 56 kDa. The current experiments were undertaken to test the hypothesis that these proteins are specific components of serotonergic neurons. Since actin has been found to bind serotonin, the relationship of the 2 forms of SBP to actin was also investigated. Antisera against purified 45 and 56 kDa SBP were raised in rabbits and shown by analyses of immunoblots and differential absorption to be monospecific and not cross-reactive. Neither antiserum reacted with purified actin and none of 3 different anti-actin sera reacted with purified 45 or 56 kDa SBP. The antisera to 45 and 56 kDa were used for immunocytochemical localization of the proteins, which was compared to that of serotonin. SBP immunoreactivity was found in rat brain and spinal cord; however, no significant differences were observed in the pattern of distribution of 45 and 56 kDa SBP-immunoreactive structures. Immunostaining of neuronal perikarya by either SBP antiserum required pretreatment of animals with colchicine. The distribution of neurons and terminals labeled by each antiserum to SBP was similar to that of neurons and terminals labeled by anti-5-HT sera. SBP-immunoreactive neuronal perikarya were present in the nuclei raphe dorsalis, raphe centralis superior, raphe medianus, raphe magnus, raphe obscurus, raphe pallidus, dorsal to the medial lemniscus in the region of the B9 cell group, near the interpeduncular nucleus, in the area postrema, the pars compacta of the substantia nigra, the dorsomedial nucleus of the hypothalamus, and the arcuate nucleus. SBP-immunoreactive fibers and terminals were present in many additional areas of the brain, as well as the spinal cord, where they paralleled those that were immunostained with antibodies to 5-HT. When double-immunostaining was used, serotonin and 45 and 56 kDa SBP immunoreactivities were found to be colocalized in both the brain and spinal cord. Cells and fibers found to be stained by one immunoreagent were also stained by the others; therefore, serotonergic neurons of the CNS probably contain both 45 and 56 kDa SBP. Moreover, it also seems likely that nonserotonergic neurons contain neither form of SBP. These data strongly suggest that SBP is an intrinsic and specific component of serotonergic neurons that can serve as a serotonergic marker.

A Ca2+-dependent protein kinase activity associated with serotonin binding protein

The endogenous phosphorylation of serotonin binding protein (SBP), a soluble protein found in central and peripheral serotonergic neurons, inhibits the binding of 5-hydroxytryptamine (5-HT, serotonin). A protein kinase activity that copurifies with SBP (SBP-kinase) was partially characterized and compared with calcium/calmodulin-dependent protein kinase II (CAM-PK II). SBP itself is not the enzyme since heating destroyed the protein kinase activity without affecting the capacity of the protein to bind [3H]5-HT. SBP-kinase and CAM-PK II kinase shared the following characteristics: (1) size of the subunits; (2) autophosphorylation in a Ca2+-dependent manner; and (3) affinity for Ca2+. In addition, both forms of protein kinase phosphorylated microtubule-associated proteins well and did not phosphorylate myosin, phosphorylase b, and casein. Phorbol esters or diacylglycerol had no effect on either of the protein kinases. However, substantial differences between SBP-kinase and CAM-PK II were observed: (1) CAM enhanced CAM-PK II activity, but had no effect on SBP-kinase; (2) synapsin I was an excellent substrate for CAM-PK II, but not for SBP-kinase; (3) 5-HT inhibited both the autophosphorylation of SBP-kinase and the phosphorylation of SBP, but had no effect on CAM-PK II. These data indicate that SBP-kinase is different from CAM-PK II. Phosphopeptide maps of SBP and SBP-kinase generated by digestion with S. aureus V8 protease are consistent with the conclusion that these proteins are distinct molecular entities. It is suggested that phosphorylation of SBP may regulate the transport of 5-HT within neurons.

Proteins that bind serotonin in the nervous system of Aplysia californica

The central nervous system of Aplysia has been found to contain two forms of proteins that bind serotonin with high affinity. These proteins share several similarities with the serotonin binding proteins that have been isolated from the vertebrate nervous system. Their ability to bind serotonin is enhanced by Fe2+ and inhibited by Na+,-SH reagents as well as reserpine and N-acetyl-5-hydroxytryptophyl-5-hydroxytryptophanamide.

Prenatal development of serotonin binding protein in relation to other transmitter-related characteristics of central serotonergic neurons

Serotonin binding protein (SBP) is a neuron-specific protein that binds serotonin (5-HT) with high affinity and is concentrated in synaptic vesicles. 5-HT has been shown to be stored in situ in a macromolecular complex with SBP. We have now investigated the ontogeny of SBP in the rat CNS. The time course of the appearance of SBP was related to the appearance of tryptophan hydroxylase, endogenous 5-HT and monoamine oxidase (MAO; types A and B). Binding of [3H]5-HT by SBP was assayed using molecular sieve chromatography. SBP had appeared by day E16; its activity then rose rapidly and reached adult levels (150 nmol [3H]5-HT/g protein) at days E18-E19. Tryptophan hydroxylase activity was measured by following the accumulation in vivo (30 min) of 5-hydroxytryptophan (5-HTP) in the brains of rat embryos whose mothers were treated with the aromatic L-amino acid decarboxylase inhibitor, NSD-1015, (100 mg/kg; i.p.). Tryptophan hydroxylase activity was first detectable at E15, remained present but at a low level through day E20 and then rapidly increased to reach 75% of the adult level at birth (747 pmol/g brain wet wt.). The development of stores of endogenous 5-HT paralleled the time course of development of tryptophan hydroxylase rather than that of SBP. 5-HT was first detected at E15, remained low until the end of intrauterine life and at birth was 50% of the adult level (2640 pmol/g brain wet wt.). MAO activity was determined in crude mitochondrial fractions by measuring 5-hydroxyindoleacetic acid produced from 5-HT as substrate. This activity was already present prior to day E15 (the activity of type B MAO was higher than that of type A) and reached adult levels at day E20 (55 pmol/mg protein/min; A, B). It is concluded that the potential of neurons to store 5-HT, as measured by the activity of SBP, develops more rapidly than their ability to produce 5-HT. Moreover, although the ratio of its two forms changes, MAO activity appears very early in development.

Serotonin depletion induced by reserpine is attenuated by prophylactic administration of lithium

Prophylactic administration of lithium significantly attenuated the serotonin depleting effects of reserpine. In rat brain, lithium did not change the capacity of the storage protein, serotonin binding protein to bind the amine either in vivo or in vitro nor did it change its sensitivity to reserpine. However, the chronic administration of lithium significantly decreased reserpine levels in plasma and brain tissue of treated rats compared with rats which were treated only with reserpine. It is concluded that the antagonism between reserpine and lithium does not involve the serotonin binding protein but may be due to the lithium-induced reduction of reserpine levels.

Identification, purification, and characterization of two forms of serotonin binding protein from rat brain

Serotonin binding protein (SBP) is found in synaptic vesicles of mammalian central and peripheral serotonergic neurons. 5-Hydroxytryptamine (5-HT, serotonin) is physiologically stored as a complex with SBP in vivo. Two forms of SBP have been detected with apparent molecular weights of 45,000 and 56,000 (45K and 56K). To understand the relationship between the two forms more fully, we purified the two proteins to homogeneity and partially characterized them. Purification steps included (NH4)2SO4 fractionation and chromatography on Sepharose 4-B, Affi-Gel-Blue, hydroxylapatite, and phosphocellulose. The 45K from of SBP was obtained pure, whereas the 56K form of SBP was obtained about 90% pure by these methods. To isolate pure 56K SBP for induction of antibodies, the protein was further purified by sodium dodecyl sulfate-gel electrophoresis followed by electroelution. The 56K form of SBP was thus isolated, but in a denatured state; its purity was established by two-dimensional gel electrophoresis. The two forms of SBP (pure 45K and 90% pure undenatured 56K SBP) were similar in their 5-HT binding capacity; the enhancement of 5-HT binding by Fe2+; and inhibition by--SH reagents, chelators, and sodium salts. Antibodies raised against the pure 56K form of SBP cross-reacted with the 45K SBP. The two forms of SBP differed in the following properties: (1) dissociation constants--56K form showed higher affinity for 5-HT (KD1 = 0.4 nM; KD2 = 32 nM), whereas the 45K form showed lower affinity (KD1 = 9.7 nM; KD2 = 120 nM); (2) ratio of number of 5-HT binding sites with low affinity to those with high affinity--56K (19:1), 45K (10:1); (3) isoelectric point--the 56K form of SBP is more acidic (5.6 and 5.9) than the 45K form (6.1); (4) binding enhancement by gangliosides and bicarbonate. To establish whether the 45K form of SBP is found in vivo or is produced by proteolysis during isolation, two additional experiments were carried out. (1) We added a mixture of proteolytic enzyme inhibitors to our homogenization buffer; this addition did not change the ratio of the two forms of SBP. (2) We mixed regions of the CNS enriched in the 45K form of SBP (spinal cord) with regions rich in the 56K form of SBP (raphe nuclei) and homogenized them together. Again, this procedure failed to change the ratio of the two forms of SBP as judged by polyacrylamide gel electrophoresis.(ABSTRACT TRUNCATED AT 400 WORDS)

Human serotonectin: a blood glycoprotein that binds serotonin and is associated with platelets and white blood cells

A glycoprotein that circulates in blood, binds to the surface of platelets, and also binds serotonin with high avidity and specificity, has previously been found in rats. This glycoprotein has been called serotonectin. We now report the purification and characterization of a similar circulating glycoprotein in human blood that we propose be called human serotonectin, to distinguish it from the rat protein. Human serotonectin binds serotonin with high affinity (Kd1 = 36 nM; Kd2 = 1.1 microM). Monospecific antisera were raised in rabbits to purified human serotonectin. These antibodies were used to locate human serotonectin immunocytochemically, for quantitative estimation of the glycoprotein, and for rapid preparation of material purified by affinity chromatography. Evidence was obtained that indicated that human serotonectin circulates in plasma and also binds to the surfaces of white blood cells and platelets but not to red blood cells. In bone marrow it is found on megakaryocytes and on developing white cells of the eosinophil line. The protein can be completely removed by washing with isotonic sucrose or salt solutions from the surfaces of white cells but similar treatment only partially (63% sucrose wash/73% salt wash) removes human serotonectin from platelets. Antibodies to human serotonectin antagonize the uptake of serotonin by platelets but do not inhibit platelet aggregation. These data show that humans, like rats, have a circulating serotonin-binding glycoprotein that is also present as a peripheral membrane protein on platelets. The human also differs from the rat serotonectin in binding to white cells. The material may function in platelet serotonin uptake in both humans and rats; however, its function, if any, with respect to white cells is obscure.

Storage of serotonin in vivo as a complex with serotonin-binding protein in central and peripheral serotonergic neurons

Serotonin-binding protein (SBP) is a soluble protein found in synaptic vesicles of central and peripheral serotonergic neurons. Experiments were undertaken to determine whether serotonin (5-HT) is physiologically stored as a complex with SBP in vivo. [3H]5-HT was used as a probe. Neurons were allowed to specifically take up the labeled amine and attempts were made to recover the in vivo formed [3H]5-HT X SBP complex. Rats were perfused intraventricularly (3 hr) with [3H]5-HT. Strips of rabbit enteric nervous system (ENS) were incubated with [3H]5-HT in the presence of desipramine. The tissues were then homogenized so as to disrupt synaptic vesicles; protein-bound [3H]5-HT was obtained from the 100,000 X g supernatant by filtration on Sephadex G-50 and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Studies with [3H]5-HT added just prior to homogenization indicated that the [3H]5-HT X SBP complex had formed intraneuronally, prior to homogenization. The protein X [3H]5-HT complexes from brain and gut migrated on the gels with apparent molecular weights of 45,000 and 56,000, corresponding to those measured by SDS-PAGE for purified SBP; however, the 45-kilodalton (kd) molecule predominated when the SBP complex was formed in vivo, whereas the 56-kd molecule predominated when the SBP X [3H]5-HT complex was formed with extracted SBP. It is possible that the 56-kd SBP is characteristic of the molecule in perikarya or nonterminal axons, whereas the 45-kd molecule is characteristic of terminal varicosities because radioautographic results show that in both the central nervous system and ENS, [3H]5-HT is mostly concentrated in terminals. In any case, newly taken up [3H]5-HT preferentially labels 45-kd SBP. Depletion of endogenous 5-HT by placing animals on a tryptophan-deficient diet increased the amount of exogenous [3H]5-HT bound to SBP in vivo. This suggests that endogenous 5-HT is normally bound to SBP and competes with the [3H]5-HT probe for available binding sites. The binding of 5-HT to SBP within vesicles may be important to reduce the osmotic pressure that would build up in synaptic vesicles if 5-HT were free in solution.

Synthesis of the apoprotein of cytochrome b in heme-deficient yeast cells

The presence of the apoprotein of cytochrome b has been demonstrated in a mutant of Sacchromyces cerevisiae lacking delta-aminolevulinic acid synthase and, hence, devoid of heme. The apoprotein of cytochrome b present in the mutant was identical with cytochrome b of control cells (mutant cells grown in the presence of delta-aminolevulinic acid) by the following criteria: similar apparent molecular weights in dodecyl sulfate-polyacrylamide gel electrophoresis; anomalous migration behavior during electrophoresis in polyacrylamide gels of different porosities; identical gel pattern obtained after immunoprecipitation with specific antiserum against cytochrome b; and identical fingerprints obtained after limited proteolysis with Staphylococcus aureus V8 protease. The kinetics of incorporation in vivo of [35S]methionine into apoprotein of cytochrome b in the mutant suggested that heme deficiency may affect assembly into the membrane of subunits of the cytochrome b.c1 complex rather than synthesis of cytochrome b.

Yeast mutants deficient in heme biosynthesis and a heme mutant additionally blocked in cyclization of 2,3-oxidosqualene

Mutants of Saccharomyces cerevisiae were isolated which were blocked in heme biosynthesis and required heme for growth on a nonfermentable carbon source. They were rho+, and grew fermentatively on ergosterol or cholesterol and Tween 80, as a source of oleic acid. Cells grown on ergosterol and Tween 80 lacked cytochromes and catalase which were restored by growth on heme. The mutants comprised five nonoverlapping complementation groups. Tetrad analysis showed that the pleiotropic properties of each of the mutants resulted from a single mutation in one of five unlinked loci (hem1 to hem5) affecting heme biosynthesis. Biochemical studies confirmed that each mutation resulted in loss of a single enzyme activity. hem1 mutants grew on delta-aminolevulinate and lacked delta-aminolevulinate synthase activity, hem2 mutants lacked delta-aminolevulinate dehydratase, and hem3 mutants uroporphyrin I synthase. Mutants in hem1, hem2, and hem3 had an additional requirement for methionine on synthetic medium supplemented with either heme or ergosterol and Tween 80, owing to a lack of sulfite reductase which contains siroheme, a modified uroporphyrin III. Since hem4 and hem5 mutants have sulfite reductase activity under all growth conditions, they are blocked after uroporphyrin III. Cell extracts of a hem4 mutant incubated with delta-aminolevulinate accumulated coproporphyrin III suggesting a block in coproporphyrinogenase, the enzyme which converts coproporphyrinogen III to protoporphyrinogen. Cells and extracts of a hem5 mutant accumulated protoporphyrin IX. Since it was the only mutant that grew on heme but not on protoporphyrin IX, a block in ferrochelatase was suggested for this strain. Mutant strains grown on heme had the sterol composition of wild type cells, whereas without heme only squalene, small amounts of lanosterol, and added sterol was observed. A heme product therefore participates in the transformation of lanosterol to ergosterol. A hem3 mutant was isolated which was also blocked between 2,3-oxidosqualene and lanosterol (erg12). When grown on lanosterol or ergosterol (with Tween 80) it accumulated a compound which was identified as 2,3-oxidosqualene by comparison with the synthetic compound in thin layer and gas-liquid chromatography, and by proton magnetic resonance and mass spectroscopy. Supplementation with heme did not remove the requirement for sterol, but it enabled the mutant to convert lanosterol to ergosterol.

tyrR, a regulatory gene of tyrosine biosynthesis in Salmonella typhimurium

4-Fluorophenylalanine-resistant mutants of Salmonella typhimurium were isolated in which tyrosine pathway enzymes were not repressed by l-tyrosine. The mutants produced elevated levels of 3-deoxy-d-arabinoheptulosonic acid 7-phosphate (DAHP) synthetase (tyr) and chorismate mutase T-prephenate dehydrogenase, and these enzymes as well as transaminase A were not repressed by high concentrations of tyrosine. Genetic analysis revealed that a mutation in a gene designated tyrR was responsible for the constitutivity of the tyrosine pathway enzymes in strains SG1, SG7, and SG9, and that tyrR was linked to pyrF. In strain SG1 a mutation had also occurred in aroF, the structural gene for DAHP synthetase (tyr), resulting in loss of sensitivity of this enzyme to end-product inhibition. There appeared to be no relationship between loss of feedback inhibition and loss of end-product repression, since derivative strains of SG1 that carried only the tyrR mutation behaved like the singly mutated tyrR strains, SG7 and SG9, in showing high constitutive levels of tyrosine-specific enzymes that were not repressed by tyrosine.

Regulatory gene of phenylalanine biosynthesis (pheR) in Salmonella typhimurium

4-Fluorophenylalanine-resistant mutants of Salmonella typhimurium were isolated in which synthesis of chorismate mutase P-prephenate dehydratase (specified by pheA) was highly elevated. Transduction analysis showed that the mutation affecting pheA activity was not linked to pheA, and conjugation and merodiploid analysis indicated that it was in the 95- to 100-min region of the Salmonella chromosome. Evidence is presented for the hypothesis that the mutation responsible for constitutivity of chorismate mutase P-prephenate dehydratase occurred in pheR, a gene specifying a cytoplasmic product that affected pheA. pheR mutants were found to carry a second mutation, tyrO. The tyrO mutation acts cis to cause increased levels of the tyrosine biosynthetic enzymes 3-deoxy-d-arabinoheptulosonate 7-phosphate synthetase (tyr) and prephenate dehydrogenase, but it has no effect on regulation of pheA.