Effects of endothelin-1 on release of adrenomedullin and C-type natriuretic peptide from individual human vascular endothelial cells

Regulation of cardiovascular system activity involves complex interactions amongst numerous factors. Three of these vasoactive factors are adrenomedullin, C-type natriuretic peptide (CNP) and endothelin-1 (ET-1), each of which is claimed to have important local effects. To investigate paracrine/autocrine regulation of the secretion of these peptides we used a cell immunoblot method. We postulated that basal release of adrenomedullin and CNP by endothelial cells is modulated by ET-1. Dispersed human aortic endothelial cells were attached to a protein binding membrane and incubated for 1 or 4 h with control medium or with ET-1, endothelin receptor antagonists or antibody to ET-1, and then submitted to immunohistochemical staining. Peptides (adrenomedullin, CNP and ET-1) within individual cells were stained, as was peptide secreted and adjacent to the cell. It was demonstrated that adrenomedullin, CNP and ET-1 can be contained within the same cell. In addition, we observed that individual endothelial cells can secrete all three peptides. The endothelin ET-A/ET-B receptor antagonist, bosentan, the ET-B receptor antagonist, BQ-788, and anti-ET-1 serum decreased the percentage of endothelial cells that secreted adrenomedullin and CNP relative to control. Conversely, the addition of ET-1 induced an increase in the number of endothelial cells that secreted adrenomedullin and CNP. These results provide strong evidence that endogenous ET-1, from human vascular endothelial cells, acts in a paracrine/autocrine manner to modulate the basal release of adrenomedullin and CNP. Our observations of this modulation suggest that vascular endothelial cells of humans constitute an important component of a self-responsive vasoregulatory system.

Brief report: prevalence of post-traumatic stress disorder symptoms after severe traumatic brain injury in a representative community sample

PRIMARY OBJECTIVE

In this study, the authors investigated the prevalence of symptoms of post-traumatic stress disorder (PTSD) in a community sample of 66 survivors of severe traumatic brain injury (TBI). RESEARCH DESIGN, METHODS AND PROCEDURES: A representative sample of survivors of TBI were selected on the basis of having suffered significant disturbance in consciousness following their trauma event in the form of coma and/or post-traumatic amnesia. Neuropsychological testing confirmed that participants had suffered cognitive deficits consistent with severe brain injury. Participants were administered the Impact of Events inventory for symptoms of PTSD.

MAIN OUTCOMES AND RESULTS

The authors found a prevalence rate of 18% for moderate-to-severe PTSD symptoms.

CONCLUSIONS

PTSD symptoms are common following severe TBI. Further research is needed to establish protective and predictive factors for PTSD in TBI groups.

Peptides interact in gonadotrophin regulation

The regulation of luteinizing hormone (LH) activity is vital to normal reproductive functioning of the female. Although gonadotrophin-releasing hormone (GnRH) has a prominent role in the regulation of LH it is now believed that other peptides are also involved. Among these peptides is oxytocin. The addition of oxytocin to cultures of pituitary cells from female rats elicited a concentration-dependent secretion of LH. This secretion was enhanced in an oestrogenised environment and was inhibited by progesterone and testosterone. Oxytocin administered to female rats at pro-oestrus advanced the endogenous LH surge that occurs on the evening of pro-oestrus. Conversely oxytocin receptor antagonist suppressed the production of the LH surge in a dose-dependent manner, indicating that endogenous oxytocin is a crucial component of LH regulation. In the human female, oxytocin administered during the late follicular phase advanced the onset of the midcycle LH surge. Oxytocin added to rat pituitary cells in vitro induced LH synthesis. Furthermore rats administered oxytocin on pro-oestrus had higher LH pituitary content following development of the LH surge than did rats administered saline. Thus oxytocin promoted synthesis and replacement in the pituitary of LH released into the circulation. Incubation of pituitary pieces with oxytocin plus GnRH induced secretion of amounts of LH greater than the sum of the amounts released by oxytocin and GnRH separately. Additionally the increased LH levels observed in the peripheral circulation of pentobarbitone-anaesthetised rats administered GnRH were enhanced if the rats received oxytocin prior to the GnRH. Thus oxytocin synergised with GnRH in stimulating LH release. Addition of diBucAMP reduced the oxytocin-mediated augmentation and dideoxyadenosine enhanced the augmentation, suggesting that oxytocin worked most efficiently in a milieu low in cAMP activity. The use of a cell immunoblot assay revealed that individual cells responded differently to oxytocin and to GnRH and that the two peptides could act on the same cell. Perifusion studies performed on hemipituitaries demonstrated that a LH response could be determined by the presence of three peptides, oxytocin, neuropeptide Y and GnRH. Hence oxytocin is potentially involved also in multiple interactions during the process of LH regulation. LH regulation is therefore apparently the result of a community of peptides acting in a co-operative network.

The circus in the pituitary

Actions and Interactions at the Pituitary was a Satellite Meeting of the 34th Congress of the International Union of Physiological Sciences held in Christchurch, New Zealand from 24-25 August 2001.

High-performance liquid chromatographic separation of the enantiomers of organophosphorus pesticides on polysaccharide chiral stationary phases

High-performance liquid chromatographic separation of the individual enantiomers of 12 organophosphorus pesticides (OPs) was obtained on polysaccharide enantioselective HPLC columns using alkane-alcohol mobile phase. The OP pesticides were crotoxyphos, dialifor, fonofos, fenamiphos, fensulfothion, isofenphos, malathion, methamidophos, profenofos, crufomate, prothiophos and trichloronate. The enantiomers of fenamiphos, fensulfothion, profenofos and crufomate were separated on CHIRALPAK AD; the enantiomers of fenamiphos were also separated on CHIRALPAK AS; the enantiomers of methamidophos, crufomate and trichloronate were separated on CHIRALCEL OD; the enantiomers of crotoxyphos, dialifor, fonofos, malathion, prothiophos and trichloronate were separated on CHIRALCEL OJ; and the enantiomers of isofenphos were separated on CHIRALCEL OG. Baseline or partial separation of the enantiomers of six of these OP pesticides was obtained on CHIRALCEL OJ. In continued method development, the separation of the enantiomers of the 12 OPs was investigated more extensively on CHIRALCEL OJ to determine whether the mobile phase composition, flow-rate and column temperature could be optimized to yield at least partial separation of the enantiomers. Chromatographic conditions were found that gave either baseline or near baseline separations of the enantiomers of the 12 OPs on the CHIRALCEL OJ column.

Determination of perchlorate in tobacco plants and tobacco products

Previous field and laboratory studies with vascular plants have shown that perchlorate is transported from perchlorate fortified soils and is accumulated in the plant tissues and organs. This paper contains results of preliminary investigations on the occurrence of perchlorate in tobacco plants grown in soils amended with a fertilizer whose nitrogen content is derived from naturally occurring sodium nitrate (Chile saltpeter). Ion chromatography (IC) and capillary electrophoresis (CE) were used for quantitative analysis, while nuclear magnetic resonance (NMR) spectroscopy was used for qualitative analysis of perchlorate. Results show that perchlorate is accumulated by tobacco plants into the leaves from soils amended with fertilizers that contain perchlorate. Also, perchlorate can persist over an extended period of time and under a variety of industrial processes as shown by its presence in off-the-shelf tobacco products including cigarettes, cigars, and pouch and plug chewing tobaccos in concentrations ranging from nd to 60.4 +/- 0.8 mg/kg on a wet weight basis.

Release of luteinizing hormone from the anterior pituitary gland in vitro can be concurrently regulated by at least three peptides: gonadotropin-releasing hormone, oxytocin and neuropeptide Y

Normal action of the female ovulatory cycle is dependent on a surge of luteinizing hormone (LH) from the pituitary. Regulation of the levels of LH is therefore vital to reproductive function. It has long been established that gonadotropin-releasing hormone (GnRH) is an important component of the regulatory processes. Other peptides, including oxytocin and neuropeptide Y (NPY), have also been observed to affect LH activities. However, the possibility of the concurrent actions of these peptides has rarely been considered despite their documented presence in the hypophyseal blood during pro-oestrus. In this study, the direct effects of oxytocin and NPY on LH release were studied, as well as the effects of both peptides simultaneously. Also, pituitaries were stimulated with GnRH, and the effects of pre-exposure of the pituitary tissue to oxytocin or NPY were investigated. Further, the effect of oxytocin and NPY together on GnRH stimulation of LH release was determined. Anterior pituitaries were collected from adult female rats on the morning of pro-oestrus. Hemipituitaries were cut in two and placed in a chamber of a perifusion system. The pituitary tissue was perifused with medium alone, oxytocin and NPY, separately or in combination, for 2 h after an initial 100-min equilibration period with no peptide present. Fractions of eluate were collected and LH was measured by radioimmunoassay. LH output was stimulated by both oxytocin (p < 0.01) and NPY (p < 0.02). Furthermore, the addition of NPY to oxytocin during the perifusion elicited a further increase in LH release (p < 0.05). The pituitary tissue was exposed to a 4-min pulse of GnRH after 220 min. Stimulation of LH release by GnRH was synergistically augmented by exposure of the tissue to either oxytocin (p < 0.01) or NPY (p < 0.05) for the immediately preceding 2 h. When NPY was added to oxytocin in the perifusion medium, stimulation of LH release by GnRH was increased even further (p < 0.05). Oxytocin also synergistically enhanced the effect of a second, primed GnRH pulse, whereas the effect of NPY was less robust. This study therefore demonstrated that LH release is modified in the presence of oxytocin, NPY or GnRH alone, and also that combinations of the peptides produce further variations in LH output. Therefore, the concentrations of LH that are present in vivo are likely to be at least partly the result of the co-ordinated effects of combinations of peptides acting on the pituitary.

Reducing everyday memory and planning problems by means of a paging system: a randomised control crossover study

OBJECTIVES

To evaluate a paging system designed to improve independence in people with memory problems and executive deficits.

METHODS

After a successful pilot study, a randomised control trial was conducted involving a crossover design with 143 people aged between 8 and 83 years. All had one or more of the following: memory, planning, attention, or organisation problems. Most had sustained a traumatic head injury or a stroke although a few had developmental learning difficulties or other conditions. The crossover design ensured that some people received a pager after a 2 week baseline whereas others were required to wait for 7 weeks after the baseline before receiving the pager. Participants were assessed at three time periods-namely, at baseline, 7 weeks, and at 14 weeks postbaseline.

RESULTS

More than 80% of those who completed the 16 week trial were significantly more successful in carrying out everyday activities (such as self care, self medication, and keeping appointments) when using the pager in comparison with the baseline period. For most of these, significant improvement was maintained when they were monitored 7 weeks after returning the pager.

CONCLUSIONS

This particular paging system significantly reduces everyday failures of memory and planning in people with brain injury.

Prevalence of Streptococcus iniae in tilapia, hybrid striped bass, and channel catfish on commercial fish farms in the United States

OBJECTIVE

To determine the prevalence of Streptococcus iniae in tilapia (Oreochromis spp), hybrid striped bass (Morone chrysops X M saxatilis), and channel catfish (Ictalurus punctatus) on commercial fish farms in the United States.

ANIMALS

1,543 fish (970 tilapia, 415 hybrid striped bass, and 158 channel catfish).

PROCEDURES

The dry-swab technique was used for collection of specimens for streptococcal isolation. Specimens were shipped by overnight delivery and processed by use of standard bacteriologic techniques.

RESULTS

Streptococcus iniae was not isolated from market-size channel catfish. Prevalence in tilapia and hybrid striped bass was 37 of 970 (3.81%) and 30 of 415 (7.23%), respectively. Prevalence by farm ranged from 0.0 to 27.4% for tilapia and 0.0 to 21.6% for hybrid striped bass. In tilapia, prevalence was lowest in market-size and nursery fish (4 of 239 [1.67%] and 3 of 339 [0.88%], respectively), with an increase in prevalence for fish in the grow-out stage (30 of 337 [7.96%]). For hybrid striped bass, prevalence was lowest in nursery and market-size fish (3 of 96 [3.12%] and 1 of 47 [2.12%], respectively) and highest in fish in the grow-out stage (26 of 272 [9.56%]). Prevalence in market-size tilapia and hybrid striped bass was 5 of 286 (1.75%).

CONCLUSIONS AND CLINICAL RELEVANCE

Results of this study do not support the contention that S iniae is a serious public health threat associated with commercially raised fish; rather, it represents a limited risk for older or immunocompromised people who incur puncture wounds while handling and preparing fish.

Delays in thrombolytic therapy for acute myocardial infarction: association with mode of transportation to the hospital, age, sex, and race

BACKGROUND: Although increased myocardial salvage and reduced mortality are associated with timely thrombolytic therapy for acute myocardial infarction, some patients still experience delays in treatment. OBJECTIVES: To examine treatment times in patients with acute myocardial infarction treated with thrombolytic therapy and to determine whether delays in treatment are associated with mode of transportation to the hospital, age, sex, or race. METHODS: Medical records of 176 patients with acute myocardial infarction treated with thrombolytic therapy at a community hospital were reviewed and analyzed retrospectively. RESULTS: Median times for the interval between arrival at the hospital and acquisition of a diagnostic electrocardiogram (door-to-electrocardiography time) and the interval between arrival and start of thrombolytic therapy (door-to-drug time) were 6 minutes and 34 minutes, respectively. However, 76.1% of the patients met the recommendation of the American College of Cardiology/American Heart Association of door-to-electrocardiography time of 10 minutes, and 47.2% met the recommendation of door-to-drug time of 30 minutes or less. Door-to-drug times did not differ significantly according to race or mode of transportation to the hospital. Door-to-electrocardiography and electrocardiography-to-drug times were significantly longer for older patients than for younger patients (P = .005 and P &lt; .001, respectively), and electrocardiography-to-drug times were significantly longer for females than for males (P = .01). CONCLUSIONS: With increased emphasis on recognition and rapid treatment of patients with acute myocardial infarction at highest risk for delays in treatment, that is, women and the elderly, benefits of thrombolytic therapy might be maximized.

Molecular alterations in the neurofibromatosis type 2 gene and its protein rarely occurring in meningothelial meningiomas

OBJECT

The neurofibromatosis Type 2 (NF2) gene is the only tumor suppressor gene that has been clearly implicated in the development of benign meningiomas. Interestingly, previous data obtained by the authors indicate that reduced NF2 protein expression seldom occurs in meningothelial meningiomas, the most common histological type of meningioma. The goal of the current study was to explore further the hypothesis of NF2 gene-independent tumorigenesis of meningothelial meningiomas.

METHODS

The authors performed a mutational analysis of all 17 exons of the NF2 gene by using single-stranded conformational polymorphism (SSCP). In addition, expression levels of the NF2 protein and mu-calpain, a protease suggested to inactivate the NF2 protein, were determined by immunoblotting analysis of 27 meningiomas (20 meningothelial and seven nonmeningothelial). Mutations of the NF2 gene were found in only one (5%) of 20 meningothelial meningiomas and three (43%) of seven nonmeningothelial tumors (Fisher's exact test, p = 0.042). The levels of NF2 protein were severely reduced in six (28.5%) of 21 meningothelial meningiomas, in contrast to six (86%) of seven nonmeningothelial meningiomas (Fisher's exact test, p = 0.023). Activation of IL-calpain did not correlate with the status of NF2 protein expression in the meningiomas analyzed, demonstrating that mu-calpain activation does not account for the loss of NF2 protein in meningiomas with apparently normal NF2 genes.

CONCLUSIONS

These results clearly demonstrate that NF2 gene mutations and decreased NF2 protein expression rarely occur in meningothelial meningiomas compared with other histological types of meningiomas. The clinical behavior of meningothelial meningiomas, however, is similar to that of other benign meningiomas. It is likely, therefore, that the tumorigenesis of meningothelial meningiomas is the result of deleterious alterations of genes that have final phenotypical effects similar to inactivation of the NF2 gene.

Delays in thrombolytic therapy for acute myocardial infarction: association with mode of transportation to the hospital, age, sex, and race

BACKGROUND

Although increased myocardial salvage and reduced mortality are associated with timely thrombolytic therapy for acute myocardial infarction, some patients still experience delays in treatment.

OBJECTIVES

To examine treatment times in patients with acute myocardial infarction treated with thrombolytic therapy and to determine whether delays in treatment are associated with mode of transportation to the hospital, age, sex, or race.

METHODS

Medical records of 176 patients with acute myocardial infarction treated with thrombolytic therapy at a community hospital were reviewed and analyzed retrospectively.

RESULTS

Median times for the interval between arrival at the hospital and acquisition of a diagnostic electrocardiogram (door-to-electrocardiography time) and the interval between arrival and start of thrombolytic therapy (door-to-drug time) were 6 minutes and 34 minutes, respectively. However, 76.1% of the patients met the recommendation of the American College of Cardiology/American Heart Association of door-to-electrocardiography time of 10 minutes, and 47.2% met the recommendation of door-to-drug time of 30 minutes or less. Door-to-drug times did not differ significantly according to race or mode of transportation to the hospital. Door-to-electrocardiography and electrocardiography-to-drug times were significantly longer for older patients than for younger patients (P = .005 and P < .001, respectively), and electrocardiography-to-drug times were significantly longer for females than for males (P = .01).

CONCLUSIONS

With increased emphasis on recognition and rapid treatment of patients with acute myocardial infarction at highest risk for delays in treatment, that is, women and the elderly, benefits of thrombolytic therapy might be maximized.

Determination of perchlorate at parts-per-billion levels in plants by ion chromatography

A method for the analysis of perchlorate in plants was developed, based on dry weight, and applied to the analysis of plant organs, foodstuffs, and plant products. The method reduced greatly the ionic interferences in water extracts of plant materials. The high background conductivity, due to the plant matrix, was reduced sufficiently to allow quantitation of perchlorate with little or no matrix interference. Ion chromatography (IC) on a microbore AS16 anion-exchange column and a conductivity detector was used for separation and detection of perchlorate from the ionic plant extract. The extract was heated to precipitate proteins, centrifuged, exposed to alumina, and filtered through a cartridge filled with divinylbenzene to yield a water clear extract for IC analysis, even from highly colored solutions. Heating the extract and treatment with alumina reduced substantially the ionic content of the extracts without loss of perchlorate.

In vivo and in vitro effects of benzothiazole on sheepshead minnow (Cyprinodon variegatus)

Benzothiazole, a common chemical associated with tire manufacturing and industrial wastewater, is a principal component of both fresh water and estuarine tire leachate, a neurotoxicant to larval sheepshead minnows (Cyprinodon variegatus) in in vivo estuarine studies. The neurotoxic potential of benzothiazole was investigated following in vivo and in vitro exposure of sheepshead minnows to 3.75, 7.5, 15, 30 and 60 mg/l benzothiazole. Following benzothiazole exposure, fish were evaluated for survival, growth and histological alterations. Fish mortality occurred after 5 days of exposure to 60 mg/l (LC50 = 41.9). Significant decreases in larval growth were noted at all concentrations. Histologically, gills had cellular alterations but the central nervous system lacked the severe cellular damage seen in previous tire leachate exposure studies. Benzothiazole cytotoxicity to primary cultures of brain cells from sheepshead minnow and tilapia (Oreochromis niloticus) and two epithelial cell lines was evaluated using a tetrazolium salt assay (MTT) at 1 and 4 days. In vitro results indicate primary cultures of brain cells are less sensitive to benzothiazole than epithelial cell lines. Significant cytotoxicity to the epithelial cell lines was noted at 30 and 60 mg/l concentrations. Histologically and cytotoxicologically, the present study indicates that benzothiazole is a gill toxicant and not a neurotoxicant.

Improvement or simply practice? The effects of twenty repeated assessments on people with and without brain injury

Measuring recovery of function may mean testing the same individual many times, a procedure that is inevitably open to improvement due to learning on the specific tests rather than recovery per se. This is particularly likely to be an issue with measures of memory performance. We therefore studied the performance of normal and brain-injured people across 20 successive test sessions on measures of orientation, simple reaction time, forward and backward digit span, visual and verbal recognition, word list learning and forgetting, and on three semantic memory measures, namely, letter and category fluency and speed of semantic processing. Differences in overall performances between the two groups occurred for all tests other than orientation, digit span forward, and simple reaction time, although the tests differed in their degree of sensitivity. The tests varied in the presence or absence of practice effects and in the extent to which these differed between the two groups. Data are presented that should allow investigators to select measures that are likely to optimize sensitivity while minimizing possible confounding due to practice effects.

Regulation of C-fos protein in gonadotrope cells by oxytocin and gonadotropin-releasing hormone

The integrated regulation of luteinizing hormone (LH) from the anterior pituitary gland is vital to the functioning of the ovulatory cycle in the female and consists of several components acting at different time points. The best-studied is the rapid release of LH elicited by gonadotropin-releasing hormone (GnRH). The so-called primary (immediate early) response genes (PRGs), including c-fos, regulate relatively long-term activities, such as mitosis, protein synthesis, protein release and cell differentiation. Regular ovulatory cycles occur as a result of interaction of several peptide factors including the primary factor, GnRH and oxytocin, although GnRH and oxytocin do not have identical activities. We wished to determine whether oxytocin could mediate changes in expression of c-fos protein and compare its effects with those of GnRH. Anterior pituitary glands were collected from female rats at proestrus and a single-cell suspension prepared. Cells were incubated with oxytocin or GnRH at selected concentrations for various times. C-fos protein was extracted and submitted to Western blot analysis. Other cells were stained immunohistochemically for c-fos and LH following incubation with the peptides and fixation. There was an increase in c-fos protein from 15 to 60 min in Western blots of cells from all incubations. After immunohistochemistry, it was observed that both oxytocin (100 nM) and GnRH (100 nM) increased the percentage of cells that expressed c-fos protein (p < 0.001) and of cells that expressed LH (p < 0.001). The responses to the peptides were concentration dependent. We found that neither all LH-containing cells expressed c-fos, nor all c-fos-containing cells immunostained for LH. The effects of the peptides were not the same. High concentrations of GnRH (1 microM) induced the appearance of a higher percent of LH-containing cells having c-fos than did 10 nM GnRH (p < 0.01), whereas a lower percent of LH-containing cells with c-fos were observed when the oxytocin concentration was raised from 10 nM to 1 microM (p < 0.02). It appears, therefore, that the two peptides have different regulatory effects on LH-containing cells, indicating the possibility of specialized function. The results emphasize the suggestion that stimulation of LH secretion is not the sole index of gonadotrope-directed activity by a peptide. Collectively, these results indicate that the peptides oxytocin and GnRH are able to modulate processes that are associated with longer-term activities of gonadotropes and also demonstrate that specific subpopulations of LH-containing gonadotropes are stimulated to express c-fos.

Pre- versus post-anterior clinoidectomy measurements of the optic nerve, internal carotid artery, and opticocarotid triangle: a cadaveric morphometric study

OBJECTIVE

Published morphometric data supporting the microsurgical advantages of anterior clinoidectomy are scant. The goal of this study was to quantify, with direct measurements, the improved exposure of the optic nerve, internal carotid artery (ICA), and opticocarotid triangle (OCT) after extradural removal of the anterior clinoid process.

METHODS

Ten formalin-fixed adult cadaver heads were dissected bilaterally, and measurements were made both before and after anterior clinoidectomy. Twenty sets of pre- and post-anterior clinoidectomy measurements were collected, consisting of: 1) optic nerve length from the optic chiasm to the optic canal (pre) and to the anulus of Zinn (post); 2) ICA length from the ICA bifurcation to the distal limit of the anterior clinoid process (pre) and to the ICA distal dural ring (post); 3) OCT width, the widest in situ distance between the optic nerve and the ICA (pre) and the analogous measurement with allowable retraction on the mobilized ICA and optic nerve (post); and 4) OCT length from the point where the A1 segment crosses the optic chiasm to the optic canal (pre) and to the anulus of Zinn (post).

RESULTS

The right and left combined mean values +/- standard error of the mean before and after removal of the anterior clinoid process, respectively, were: optic nerve length, 10.28 +/- 2.30 mm and 22.83 +/- 2.54 mm; ICA length, 10.48 +/- 2.39 mm and 14.78 +/- 3.02 mm; OCT width, 3.93 +/- 1.16 mm and 12.95 +/- 2.61 mm; and OCT length, 10.38 +/- 2.84 mm and 23.55 +/- 2.79 mm.

CONCLUSION

Anterior clinoidectomy can provide a twofold increase in exposure of the optic nerve length and the OCT length, as well as a three- to fourfold increase in the maximum OCT width. This dramatically improves surgical exposure in the suprasellar and periclinoid regions.

Implantable defibrillator event rates in patients with unexplained syncope and inducible sustained ventricular tachyarrhythmias: a comparison with patients known to have sustained ventricular tachycardia

OBJECTIVES

To assess the clinical significance of inducible ventricular tachyarrhythmias among patients with unexplained syncope.

BACKGROUND

Induction of sustained ventricular arrhythmias at electrophysiology study in patients with unexplained syncope and structural heart disease is usually assigned diagnostic significance. However, the true frequency of subsequent spontaneous ventricular tachyarrhythmias in the absence of antiarrhythmic medications is unknown.

METHODS

In a retrospective case-control study, the incidence of implantable cardiac defibrillator (ICD) therapies for sustained ventricular arrhythmias among patients with unexplained syncope or near syncope (syncope group, n = 22) was compared with that of a control group of patients (n = 32) with clinically documented sustained ventricular tachycardia (VT). Sustained ventricular arrhythmias were inducible in both groups and neither group received antiarrhythmic medications. All ICDs had stored electrograms or RR intervals. Clinical variables were similar between groups except that congestive cardiac failure was more common in the syncope group.

RESULTS

Kaplan-Meier analysis of the time to first appropriate ICD therapy for syncope and control groups produced overlapping curves (p = 0.9), with 57 +/- 11% and 50 +/- 9%, respectively, receiving ICD therapy by one year. In both groups, the induced arrhythmia was significantly faster than spontaneous arrhythmias, but the cycle lengths of induced and spontaneous arrhythmias were positively correlated (R = 0.6, p < 0.0001). During follow-up, three cardiac transplantations and seven deaths occurred in the syncope group, and two transplantations and five deaths occurred in the control group (36-month survival without transplant 52 +/- 11% and 83 +/- 7%, respectively, p = 0.03).

CONCLUSIONS

In patients with unexplained syncope, structural heart disease and inducible sustained ventricular arrhythmias, spontaneous sustained ventricular arrhythmias occur commonly and at a similar rate to patients with documented sustained VT. Thus, electrophysiologic testing in unexplained syncope can identify those at risk of potentially life-threatening tachyarrhythmias, and aggressive treatment of these patients is warranted.

GnRH and oxytocin have nonidentical effects on the cellular LH response by gonadotrophs at pro-oestrus

For full fertility in the female ovulation is necessary, which is dependent on the production of a surge of LH. An understanding of the processes which result in the high levels of LH requires delineation of the activities of individual component cells. In this study the responses of gonadotrophs to two signalling hypothalamic peptides, GnRH and oxytocin, were investigated. A cell immunoblot method was used to identify and distinguish between cells which secrete LH and those which contain LH but do not secrete the glycohormone. Rats were killed on the morning of pro-oestrus, the pituitary collected and the cells dispersed onto a protein-binding membrane for study. Cells were then incubated with GnRH and oxytocin, after which the membranes including the attached cells were stained by immunocytochemistry for LH. GnRH increased the total number of immunopositive cells which were present in a concentration-dependent manner. The most prominent change after 2 h incubation was in the number of secreting cells, whereas after 4 h there was also a marked increase in numbers of nonsecreting cells. Oxytocin also increased the total number of immunopositive cells in a concentration-responsive manner, however the profile of action of oxytocin was different from that observed for GnRH. Oxytocin had a relatively greater effect on numbers of immunopositive nonsecreting cells. Thus, the results reveal the potential for gonadotrophs to be flexibly and appropriately modulated by selected hypothalamic peptides. When cells were preincubated with oxytocin prior to GnRH there was not an additive increase in the numbers of immunopositive cells, suggesting that the two agonists act, in a nonidentical manner, on similar cells. The increase in the total number of immunopositive cells implies that there was a production of LH or post-translational processing, induced by exposure to GnRH or oxytocin. The results confirmed the heterogeneity of gonadotrophs and the existence of functionally distinguishable subpopulations, and revealed a difference between the effects of GnRH and oxytocin on expression and secretion of LH.

In vitro basal and GnRH-stimulated secretion of gonadotrophins reflects long-lasting modulatory effects, and peripheral levels are not predicted by pituitary responsiveness to GnRH

OBJECTIVE

Production of the appropriate pattern of gonadotrophin levels is crucial to proper functioning of the female reproductive system. We aimed to establish whether the pituitary has invariant secretory characteristics when isolated from in vivo controls. We aimed to obtain information during both the rising and declining phases of the gonadotrophin surge.

DESIGN

This study investigated factors that are directed at the pituitary by isolating it from the acute influences of the in vivo environment and studying gonadotrophin secretion in vitro.

METHODS

Pituitaries of adult female rats were collected at selected times during the day of pro-oestrus and incubated in vitro, and at the same time blood was collected. Peripheral levels of LH and FSH were measured over the whole day of pro-oestrus, basal in vitro secretions of LH and FSH from pituitaries were measured, GnRH-stimulated LH and FSH secretion were assessed, and the responsiveness of LH and FSH secretion to GnRH were calculated.

RESULTS

Peripheral levels of LH peaked at 1800 h (P<0.02) followed by a subsequent decline. In contrast, although FSH had a peak at 1800 h (P<0.01), serum levels were also high at the end pro-oestrus. The profile of basal LH and FSH secretion from the pituitary in vitro, in the absence of added secretagogue, resembled that of the peripheral blood levels of each gonadotrophin. Pituitaries collected at 1800 h secreted most LH (P<0. 02). FSH secretion was low early on the day of pro-oestrus and then increased to and was maintained at high levels in the last quarter of the day (P<0.01). When the pituitaries were stimulated with GnRH the patterns of LH release and FSH release approximated those observed for basal release. Responsiveness of the pituitaries to GnRH was calculated by determining the ratio of GnRH-stimulated release to basal release. However, low levels of gonadotrophin were secreted even from pituitaries which were highly responsive as determined from consideration of percentage increase in secretion induced by GnRH.

CONCLUSIONS

The secretory activity was dependent on the time of day the pituitaries were collected. Since the secretion occurred after the tissue had been removed from the direct influence of the in vivo environment, the variations in secretion must reflect long-lasting components of the mechanism that regulate gonadotrophin concentrations. There were changes in both LH and FSH responsiveness to GnRH stimulation over the day of pro-oestrus. Delineation of the time courses and changing predominance of multiple processes is needed to assist understanding the mechanisms underlying the female reproductive cycle.

Measuring recovery from post traumatic amnesia

Three groups of participants were assessed. Each participant was tested on 20 occasions. The groups comprised people (i) in post traumatic amnesia (PTA) following severe head injury (n=9), (it) with severe head injury but not in PTA (n=10), and (iii) with no history of head injury or other neurological condition (n=13). Subjects were given several tests of memory, attention and learning in order to determine which tests were good at (a) distinguishing people in PTA from those not in PTA, and (b) monitoring recovery over time. The results indicate that people in PTA have a wide range of deficits and their cognitive recovery is a gradual process rather than an all-or-none phenomenon. In terms of measurement, the study suggests that a good test of PTA should include orientation questions, together with a reaction time measure, a visual recognition test and a speed of information processing measure. Most of the tests administered were good at distinguishing between brain-injured and nonbrain-injured people, although only two tests distinguished between the two brain-injured groups, i.e. those in PTA and those out of PTA. Almost all tests were good at monitoring recovery from PTA.

Modulation of gonadotropin levels by peptides acting at the anterior pituitary gland

There are several lines of evidence that point to peptides participating in the regulation of LH and/or FSH levels by action at the pituitary. This evidence includes altered secretion of gonadotropins from the anterior pituitary cells or tissue in vitro when exposed to the peptide. Additionally, modification of GnRH-stimulated LH/FSH secretion has been observed. Furthermore, there is potential for a separately modulated interaction with the primed response. Another potential of action is by interaction among non-GnRH peptides on gonadotropin-regulating processes, although there are no good data available on this aspect. Other observations, consistent with a pituitary role for the peptides in modulation of LH, include detection of the peptides in portal blood, detection of high-affinity receptors or receptor mRNA in the pituitary, and detection of intrapituitary peptide or peptide mRNA in the pituitary. The modulation by steroids of both concentrations and type of activities provides a further level of physiological refinement. There is, however, some confusion regarding the involvement of these peptides in gonadotropin control. The reasons can be seen by considering aspects of investigations. There are experimental variations such as 1) species studied, e.g., NPY has been reported to have an effect on LH secretion from rat cells (168) but not on sheep anterior pituitary tissue (64), and substance P inhibits GnRH-stimulated release from rat cells (182) but potentiates the response in prepubertal porcine cells (92); 2) the steroidal conditions under which the study is performed, e.g., NPY has opposite effects in certain endocrine environments, augmenting GnRH-stimulated LH release in proestrus-like conditions (168), and inhibiting in metestrus-like environment (66); 3) the type of cell preparation, e.g., responsiveness to substance P might depend on whether cells in overnight culture were in separated or clustered state (91); 4) the time course considered, e.g., oxytocin that might induce marked LH release from pituitary cells after a longer length of incubation than GnRH requires (68); 5) length of exposure to peptide, e.g., endothelin that augmented or inhibited GnRH-stimulated LH release (50); 6) In addition, it is possible that the traditional endpoint selected in such studies, namely, observation of gonadotropin secretion, is not necessarily the most important for these peptides (56, 81, 117). Unfortunately, at this stage a definitive answer to the question "What do the peptides actually do?" cannot be provided and we remain tantalized by the glimpses of potential roles. Perhaps in a few years an updated review will be able to include a more complete answer. It is necessary for the full understanding of LH control that not only the properties of the peptides in isolation be characterized but also their interactions.