Mechanisms of depolymerization and activation of a polysialic acid and its tetramer by hydrogen peroxide

Naturally occurring polysialic acid (PSA), appropriately functionalized, has been widely used in different biological products. The present paper describes an original approach which enables to both activate and depolymerize the PSA, by reacting with hydrogen peroxide. In order to understand the mechanisms, we investigate the course of H2O2 reactions with the native PSA and with a simpler model, the tetrasialic acid (4SA). Three recurrent reactions were observed. First, we detected a very fast and irreversible decarbonylation at the reducing end of the polysaccharide. Then, the hydroxyl radicals (generated via the Fenton reaction) were responsible for the depolymerization of glycosidic linkages by substitution reactions. Finally, the oxidation of hydroxyl groups led to the formation of carbonyl groups and the carbohydrate's activation.

Oxidation of sialic acid using hydrogen peroxide as a new method to tune the reducing activity

Functionalized sialic acids are useful intermediates to prepare a wide range of biological products. As they often occur at a non-reducing terminal of oligosaccharides, the most used technique to activate them is by periodate-mediated oxidation of their glycerol side chain. Here, we describe an alternative, non toxic, and environmentally-friendly method to activate the sialic acid residues by hydrogen peroxide oxidation. Four oxidative systems involving H2O2, EDTA, iron chloride, and UV light were studied and the products obtained were analyzed by LC-MS and NMR, before and after a derivatization reaction. At first, we observed, for each system, an irreversible decarbonylation reaction at the reducing end. Then, the decarbonylated sialic acid (DSA) was oxidized and fragmented into a mix of carbonyls and carboxyl acids, more or less fast according to the experimental conditions. Analysis of the reaction indicated an apparent radical mechanism and heterolytic alpha-hydroxy-hydroperoxide cleavages. The modest reducing activity was mainly explained as a consequence of over-oxidation reactions.

Clinical features and therapeutic outcomes of patients with acromegaly: single-center experience

The aim of this study was to review the outcome of acromegaly treatment, as well as co-morbidity and mortality in a series of patients with acromegaly attending a single center in the last 10 yr. In that period, 53 patients were treated for acromegaly. Transsphenoidal operation was applied as the first-line therapy in 94.3% of patients and it led to disease remission in 59.2% of them. The remission criteria included a nadir GH<1 μg/l after glucose load, and normal age-related IGF-I levels. The remission rate after transsphenoidal surgery was significantly higher in the group of patients with microadenoma (76.9%), than in the group of patients with macroadenoma (52.8%). Patients with invasive tumors had remission rate of 16.7% after transsphenoidal surgery. There were no perioperative deaths. As the second-line treatment somatostatin analogues, radiotherapy, and dopaminergic agonists were used. Hypertension and diabetes were the most frequent co-morbidities in the group of patients. After successful treatment, 30% of patients with diabetes or impaired glucose tolerance had significant improvement of glycemic control. Transsphenoidal surgery is the appropriate firstline therapy in patients with somatotropinoma. Medical and radio-therapy should be reserved as the second-line therapy after surgery failure.

The Language of Caring: Quantitating Medical Practice Patterns using Symbolic Dynamics

Real-world medical decisions rarely involve binary sole condition present or absent-patterns of patient pathophysiology. Similarly, provider interventions are rarely unitary in nature: the clinician often undertakes multiple interventions simultaneously. Conventional approaches towards complex physiologic derangements and their associated management focus on the frequencies of joint appearances, treating the individual derangements of physiology or elements of intervention as conceptually isolated. This framework is ill suited to capture either the integrated patterns of derangement displayed by a particular patient or the integrated patterns of provider intervention. Here we illustrate the application of a different approach-that of symbolic dynamics-in which the integrated pattern of each patients derangement, and the associated provider response, are captured by defining words based on the elements of the pattern of failure. We will use as an example provider practices in the context of mechanical ventilation- a common, potentially harmful, and complex life support technology. We also delineate other domains in which symbolic dynamics approaches might aid in quantitating practice patterns, assessing quality of care, and identifying best practices.

The keyhole concept in aneurysm surgery--a comparative study: keyhole versus standard craniotomy

OBJECTIVE

The purpose of the study is to compare the results of minimally invasive keyhole craniotomy and standard larger craniotomies in the surgical treatment of patients with intracranial aneurysms.

METHODS

In the past eight years 628 patients were operated by two experienced neurosurgical teams. The first group of 482 patients with 565 aneurysms were operated through a small keyhole craniotomy, using the eyebrow keyhole approach in particular. The remaining 146 patients with 167 aneurysms were operated using a standard craniotomy that included pterional/frontotemporal, frontoparietal parasagittal, and retrosigmoid suboccipital craniotomies. All operations were performed in the standard microsurgical technique using intraoperative evoked potential monitoring and endoscopic assistance in selected cases.

RESULTS

Most supratentorial aneurysms and basilar tip aneurysms were successfully operated through an eyebrow keyhole craniotomy. Distal MCA aneurysms as well as aneurysms on the MCA with a long M1 segment were operated through a temporal keyhole, and aneurysms of the distal PCA (P2-P3) segment subtemporally. The frontoparietal parasagittal keyhole approach was used only for pericallosal artery aneurysms. Infratentorial aneurysms of the VA/PICA complex were operated via a retrosigmoid approach. On comparing the surgery results in patients with a keyhole craniotomy and those with standard craniotomy, similar outcomes were found for both groups, with excellent or very good outcomes (GOS 5 and 4) in 398 (82.57%) patients from the keyhole craniotomy group, and in 116 (79.45%) patients from the standard craniotomy group. The mortality rate in the keyhole group was 0.83% (4 patients) and 2.05% (3 patients) in the standard craniotomy group.

CONCLUSION

Parallel treatment results in using two options--keyhole craniotomy and standard larger craniotomy--were analysed in the past eight years. Two experienced neurosurgical teams in performing both surgical approaches have reached almost similar morbidity and mortality rates, and overall surgical results. The type of craniotomy is selected according to the experience of the surgical team, and familiarity with certain approach. The authors have good experience with the minimally invasive approach for different intracranial pathology and recommend it especially in neurovascular surgery.

[Importance of the CRH (corticotropin releasing hormone) test in the differential diagnosis of Cushing's syndrome]

In the group of 13 patients with Cushing's syndrome (CS) CRH test was performed by sampling the blood from peripheral vein and in eight patients also after inferior petrosal sinus catheterization (IPSC) to resolve the disease etiology. In the group of patients with Cushing's disease (CD, n = 11), which was proven by surgery and adenoma immunohistochemistry, 10/11 had in CRH test the significant increase of cortisol and ACTH in the peripheral blood. Among two patients with ectopic ACTH syndrome one had the significant increase of both hormones in CRH test. After IPSC the ratio of ACTH in the petrosal sinus and in the peripheral vein was significant in 4/8 patients before, and in 6/8 after CRH administration. The intersinus gradient was significant in 3/8 patients before, and in 4/8 after CRH test. According to our results we can conclude that the determination of ACTH in the blood from peripheral veins after CRH administration is a very sensitive method for differential diagnosis of CS, while the results after IPSC were less sensitive in our conditions than those described in the literature.

Minimally invasive treatment of cavernous angioma of the optic chiasm: case report

Cavernous angioma of the optic chiasm or optic nerve is extremely rare. We report the case of a 58-year-old woman with cavernous angioma of the optic chiasm. The lesion was totally removed through the eyebrow keyhole approach, which allowed appropriate intraoperative exploration of the optic chiasm and related structures. The present case confirms that a cavernous angioma located in the optic chiasm can be totally resected without further impairment of visual function.

The Croatian telemedicine

Telemedicine developed in Croatia in two phases. The first phase during the 1970s was limited because of insufficient technology and scarce resources. But that phase was important as a learning process and the preparatory stage for the promising future. The communications infrastructure was heavily destroyed during the 1991-92 war but it was reconstructed and rebuilt as a modern technology based on optical fibres. The new technical and technological infrastructure was the base for the development of CARNet (Croatian Academic and Research Network). CARNet was linked to the Internet and enabled the international exchange of information for the scientific community. Telemedicine projects started firstly as pilot projects around the same time as in other countries. They were financially covered mostly by the Ministry of Science either directly or through the CARNet. The telemedicine projects, like telepathology, teleradiology, teleneurosurgery, teleeducation, developed in a very sophisticated way and are now in the phase of implementation into the routine health practice. Some projects are still in the pilot phase, but thanks to highly trained professionals, they are promising and it can be expected that with the growing economic stuation they will be implemented soon.

Growth promoting effect of human plasma ultrafiltrate bioactive fraction (TBP) for human non-functioning pituitary adenoma cells in vitro

We described before that the chromatographically purified "human plasma ultrafiltrate bioactive fraction" (humoral factor tentatively denoted as tumor basic protein--TBP) regulates in vitro release of ACTH from pituitary adenomas stimulating the hormone release from the tumors showing low hormonal activity in vitro and inhibiting ACTH production in vitro by highly hormonally active pituitary tumors. In this study we describe growth promoting effects (determined by 3H-TdR incorporation assay) of TBP (5 microg/l, i.e. 10% w/v plasma equivalent concentration) for 10 non-functioning pituitary tumors. The effects of TBP appeared to negatively correlate with the in vitro growth abilities of the tumors that were otherwise dependent on the duration of the clinical symptoms of the tumor presence. Hence, similar to its effects on hormonal activity of the pituitary tumors, TBP stimulated the growth of the tumors which did not express high spontaneous 3H-TdR intensity, but did not stimulate the cells with high capacity of spontaneous 3H-TdR incorporation. Moreover, all the tumors that were stimulated by TBP were nononcocytic adenomas while oncocytoma cells were not stimulated at all. Thus, TBP shows activity of humoral (plasma) factor involved in the growth regulation of pituitary adenomas that might be used to define the growth abilities of these tumors, especially in case of null cell adenomas and oncocytomas as were the tumors used in this study.

Evolution of clinical symptoms in a young woman with a recurrent gonadotroph adenoma causing ovarian hyperstimulation

OBJECTIVE

To demonstrate the clinical course in a young female with gonadotroph adenoma causing ovarian stimulation.

PATIENT AND METHODS

Our patient was a 23-year-old woman with a history of oligomenorrhea who had previously undergone bilateral ovarian wedge resection owing to the clinical appearance of polycystic ovaries. Two years later, she sought treatment for headache, galactorrhea, history of spotting and lower abdominal distension. FSH, LH, beta-LH, inhibin A and B, estradiol, prolactin (PRL), and beta-chorionic gonadotrophin (beta-CG) were measured, and the responses of FSH, LH and beta-LH to thyrotrophin-releasing hormone (TRH) were documented. Immunohistochemical analysis of the tumor tissue was performed after surgery. Five years after the trans-sphenoidal surgery, the patient again became oligomenorrheic. A large recurrent adenoma was diagnosed on CT one year later. Transvaginal ultrasound showed ovaries of normal size with multiple small cystic formations simulating a polycystic pattern, While the patient was awaiting surgery, a pituitary apoplexy occurred. Emergency decompressive surgery was performed and the patient fully recovered.

RESULTS

Enlarged ovaries were found on ultrasound examination simulating a hyperstimulation-like pattern. At that time, elevated levels of FSH (13.4IU/l) and marginally elevated levels of beta-LH (1.43ng/ml) were found, whereas the level of LH (0.5IU/l) was subnormal. Plasma estradiol was markedly supranormal (6150pmol/l). Levels of inhibin A and B were elevated (326pg/ml and 588pg/ml respectively). The prolactin level (70ng/ml) was increased, whereas beta-chorionic gonadotrophin (beta-CG) was normal. Significantly increased FSH, LH, and beta-LH responses to TRH stimulation were documented. Pituitary macroadenoma was found on MRI scan and removed by trans-sphenoidal surgery. Immunohistochemical examination showed high positivity for beta-CG and LH, and slight positivity for FSH. Five years after the surgery, estradiol was elevated (1160pmol/l), whereas basal levels of LH (4.65IU/l) and FSH (3.98IU/l) were not suppressed. After the second operation, immunostaining of the adenoma tissue confirmed the previous findings.

CONCLUSIONS

Measurement of gonadotrophins in our case did not prove to be a method for identifying a large recurrent gonadotroph pituitary adenoma. The sonographic ovarian imaging varied from a polycystic- to an ovarian hyperstimulation-like pattern during the evolution of the tumour.

Endoscopic third ventriculostomy with ultrasonic contact microprobe

The authors describe their first clinical experiences in endoscopic third ventriculostomy (ETV) with the original ultrasonic contact microprobe (UCM) designed at the Department of Neurosurgery in Zagreb. The analysis includes the clinical course of disease in eight patients submitted to surgery from May to September 1999 (3 men and 5 women, from 14 to 61 years of age). Surgery was performed in patients with neurological symptoms of elevated intracranial pressure and neuroradiological evidence of non-communicating hydrocephalus caused by mesencephalic aqueduct stenosis. The perforation in the base of the third brain ventricle made by the ultrasonic contact microprobe was widened by a balloon catheter. The authors have come to conclusion that the ETV when performed by contact ultrasonic microprobe is a small risk procedure in case of non-communicating hydrocephalus. For its small diameter (1.6 mm) and simple handling the newly designed contact ultrasonic microprobe is very suitable for use in neuroendoscopy as it enables fenestration of the third brain ventricle with minimal thermal and ultrastructural damage to the adjacent neurovascular structures. Further research will be focused on defining indications for the use of the device in other neuroendoscopic procedures as well.

Ultrasonic contact microprobe: experimental results

At the Department of Neurosurgery, School of Medicine, University of Zagreb, the original ultrasonic contact microprobe (UCM) was designed. The efficacy of the instrument was tested on 120 brains of Wistar strain rats. The authors have been investigating the possibility of transferring high-energy ultrasound through the titanium wire probe of the device and the efficacy of UCM in controlled punctiform destruction of brain tissue. Light and electron microscope assessed the lesions made in the brains of experimental rats. Histological findings in the preparations showed the zone of thermal injuries from 100 to 200 microm and the zone of ultrastructural changes from 200 to 300 microm, indicating the sparing effect of the microprobe with regard to the adjacent neurovascular structures. The small dimensions of the ultrasonic contact microprobe (1.6 mm) enable its introduction through the operating canal of a ventriculoscope. Further research is expected to show the efficacy of the ultrasonic contact microprobe in endoscopic neurosurgery.

[Endoscopic ventriculocisternostomy of the third cerebral ventricle]

Endoscopic third ventriculocisternostomy (ETV) is a minimally invasive technique that establishes a communication between third ventricle and interpeduncular cistern. We analyzed clinical files of eleven patients (7 males and 4 females) operated on between September 1996 and February 1998. Patients' age ranged from 3 to 61 years. ETV was performed in hydrocephalic patients with neurological signs of increased intracranial pressure (ICP) and CT or MRI diagnosed noncommunicating hydrocephalus (aqueductal stenosis). The fenestration instrument was a monopolar coagulation wire and dilation instrument was a balloon catheter. Post-operative decrease in the third ventricle diameter is the most reliable neuroradiological sign of successful operation. All patients, but one, were able to remain independent of the shunt system after the ETV. ETV is a low-risk neurosurgical technique that should be considered as the initial treatment of noncommunicating hydrocephalus. Features that increase ETV probability of success include age over 1-year, relatively recent obstruction, no meningitis or subarachnoid haemorrhage history and normal ventricular anatomy. ETV excludes mechanical complications and lowers the risk of biological complications which are characteristic for CSF drainage operations. Economic aspect is also very important because drainage devices are very expensive.

Clinical and morphological features of undifferentiated monomorphous GH/TSH-secreting pituitary adenoma

A 41-year-old male presented with progressive visual defects, acromegaly and hyperthyroidism. After clinical evaluation a giant GH/TSH-secreting pituitary adenoma was diagnosed. Administration of the somatostatin analog octreotide at doses of 150 microg s.c. per day inhibited the secretion of both GH and TSH. A three-week treatment with octreotide prior to surgery led to slight visual improvement and CT scan showed some new necrotic areas within the tumor mass. Transcranial surgery was performed. By immunohistochemical analyses of the adenoma tissue GH, prolactin and beta-chorionic gonadotropin were detected; TSH was negative. Electron microscopy revealed an undifferentiated, monomorphous adenoma with morphological features of an acidophil stem cell adenoma such as the presence of misplaced exocytoses, fibrous bodies and mitochondrial gigantism. However, the tumor cells contained small secretory granules (up to 250 nm) accumulated along the cell membrane characteristic of thyrotrope cells. Furthermore, some adenoma cells were fusiform with long cytoplasmic processes resembling thyrotropes. Two months after the operation CT scan revealed a large residual tumor. Serum GH and TSH levels had increased again and the TSH level was even higher than before the treatment. The patient died suddenly, most probably of lethal arrhythmia. Specimens of the adenoma tissue obtained at autopsy confirmed the previous findings with the exception of positive immunostaining for TSH which was found in less than 1% of the adenoma cells. This undifferentiated, monomorphous GH/TSH-secreting pituitary adenoma represents an entity that is unusual both in its ultrastructural features and clinical manifestations suggesting a cytogenesis from an early, undifferentiated stem cell.

Radical surgery of a giant Galen's vein aneurysm using total circulatory arrest: case report

BACKGROUND

Arteriovenous malformations of Galen's vein are a rare type of vascular anomaly. The complex anatomy of these lesions creates an extremely difficult management dilemma. We report successful surgical treatment of a 7-year-old patient with a Galen's vein aneurysm.

METHODS AND RESULTS

A 7-year-old patient with slowly progressing gait disturbance, emotional instability, and strange behaviour is presented. A computed tomography scan revealed a high-density mass in the pineal region and cerebral angiography showed an aneurysm of Galen's vein. We decided to perform surgical excision of the aneurysm. The operation was performed under hypothermic circulatory arrest with barbiturate cerebral protection. The patient had no signs of postoperative ischemic deficits, hemorrhage, or neurologic deterioration.

CONCLUSIONS

Various techniques have been described for the obliteration of Galen's vein aneurysms, including direct surgical approach, staged operation, and transarterial, transvenous or transtorcular embolization. We present this patient to illustrate the use of hypothermic circulatory arrest and barbiturate cerebral protection for successful surgical excision of this complex vascular lesion. The combination of these techniques allowed us, in this case, to operate with reasonable safety on otherwise, difficult to treat aneurysm of Galen's vein.

Eyebrow keyhole approach in vascular neurosurgery

The authors review their experience in the surgery of intracranial aneurysms via an eyebrow keyhole approach. The eyebrow keyhole approach presumes a skin incision in the lateral two-thirds of the eyebrow followed by small supraorbital craniotomy (15 x 25 mm). Using this approach and an intraoperative endoscope for better visualisation of the aneurysmal neck, the authors operated on thirty-seven patients with forty intracranial aneurysms. There was no mortality, postoperative recovery was fast, and the cosmetic effect was excellent. Advantages and possibilities of this approach are discussed and results are presented. The authors recommend this approach as a minimal invasive surgery procedure in the treatment of intracranial aneurysms. When performed by experienced vascular neurosurgeons this approach is neither more difficult for the surgeon nor more dangerous for the patient than any other standard craniotomy procedure. According to the authors' present results, surgery of intracranial aneurysm via an eyebrow keyhole approach is the method of choice when performed by an experienced vascular neurosurgeon.

Neuroendoscopic fenestration of arachnoid cysts

The authors report 6 patients with arachnoid cysts treated endoscopically. The series includes 6 patients with temporobasal arachnoid cysts. The age of the patients at the time of diagnosis ranged from 5 to 71 years. The patients' symptoms included headache, seizures, vomiting, nausea, dizziness, and problems with balance. The authors performed cystocisternostomies via burr holes with the aid of a universal neuroendoscopic system. In 4 cases the endoscopic fenestration was a unique treatment which enabled the avoidance of a definitive cystoperitoneal shunt. In the two cases treated subsequently, cystoperitoneal shunts were performed. The surgical endoscopic technique and the postoperative radiological findings which indirectly confirm the patency of the fenestration are discussed. The authors conclude that endoscopic fenestration of intracranial fluid cysts represents the treatment of preference. In cases where the endoscopic procedure fails a microneurosurgical procedure or cystoperitoneal shunting is recommended to avoid exposing the patient to additional risk.

[Use of intraoperative ultrasound in neurosurgery]

Intraoperative ultrasound (US) is a device which is a great help to neurosurgeon in intracerebral lesions localization, in the definition of inner tumors structure, in its relation to the surrounding structures, as well as during stereotaxic operations. We report our experiences with US in more than 500 operations. Its maximum usage is during gliomas and metastases operations because of their subcortical localization. Choosing this optimal approach to the tumor, the surrounding brain is minimally damaged. Using modern devices we are able to distinguish edema from infiltrative gliomas, which was not possible using former devices (both edema and gliomas are hyperechoic). In vascular neurosurgery we use US mostly in the localization of small arteriovenous malformations (AVMs). In pediatric neurosurgery the usage is very often in drainage operations for ventricular catheter placement control. The main US shortage is lower image resolution, and the basic advantage is real time imaging. It enables our prompt intervention in every unfavorable situation.

Reducing the incidence of infection in pediatric cerebrospinal fluid shunt operations

We reviewed our experience with shunt implantation during two time periods. From June 1985 to December 1990, 201 children with hydrocephalus underwent 382 operations. Among these children 36 (18%) developed a proven shunt infection, with an incidence rate per procedure of 9.4%. As a result of this study, a new effective protocol for shunt procedures involving modifications to the perioperative (antibiotic prophylaxis) and intraoperative management (meticulous surgical technique, complete shunt revision) of children undergoing initial shunt implantation or revision was initiated. With this new protocol 75 children underwent a total of 112 procedures between January 1991 and December 1995. The incidence of shunt infection decreased, with a per patient rate of 8% and a per procedure rate of 5.3%. The majority of infections in our study were caused by Staphylococcus epidermidis, which was found in 22 (52.3%) patients.

Analysis of the in vitro secretory activity of human pituitary adenomas: modification of corticotropin release from adenoma tissue explant cultures by addition of a human plasma ultrafiltrate bioactive fraction

The lack of control of tumour behaviour is manifested in different ways, depending primarily on the type of tumour. This results in numerous problems of tumour diagnosis and therapy. In the case of "benign" tumours, like pituitary adenomas, in vitro studies are often used for evaluation of the tumour. The use of tissue explant cultures of human pituitary adenomas and the comparison of the feature of cultured tumours with their behaviour in vivo showed that corticotropin is released not only from the tumours associated with Cushing's disease, but also from clinically non-functioning tumours. Hence, it was supposed that the release of corticotropin in vivo from non-secreting tumours is probably under the influence of certain neuroendocrine and/or systemic humoral factors. To test this possibility, samples of 22 tumours were cultured in plain culture medium or in the presence of the "human plasma ultrafiltrate bioactive fraction" (tentatively termed as TBP) prepared by anion-exchange chromatography. In the presence of TBP the release of corticotropin was strongly inhibited in adenomas showing relatively high spontaneous secreting activity in vitro (> 200 ng/l in 24 hours), while immunohistochemistry of these tumours indicated accumulation of corticotropin inside the cells. In contrast, TBP stimulated corticotropin release from tumours that showed relatively low basic corticotropin release (< 200 ng/l in 24 hours), with no obvious change in cellular corticotropin immunoreactivity. Such a dual activity of TBP was not observed for 8 samples of adenomas cultured in the presence of surrounding pituitary tissue, probably because TBP did not affect corticotropin secretion by the normal pituitary cells (as indicated by immunohistochemistry). From these results, it appears that TBP could be one of the humoral factors involved in the regulation of corticotropin release from pituitary adenoma tissue. Its possible involvement in the regulation of corticotropin release from normal pituitary tissue, however, is uncertain.

Extended anterior subcranial approach for skull base tumors: long-term results

The extended anterior subcranial approach differs significantly from more traditional surgical approaches to the skull base in that it allows a broad inferior access to the anterior skull base planes with tumor exposure from below rather than via the transfrontal route. The authors initially used the subcranial approach in 1978 for the treatment of high-velocity skull base trauma and certain craniofacial anomalies. In 1980 they expanded the indications to include the combined neurosurgical-otolaryngological resection of various skull base tumors. Osteotomy of the frontonasoorbital external skeletal frame provides optimum anterior access to the orbital and sphenoethmoidal planes as well as to the nasal and paranasal cavities while avoiding frontal lobe retraction and the external facial incisions characteristic of transcranial and transfacial approaches. The improved visualization of the anterior skull base and clival-sphenoidal region facilitates en bloc tumor removal, optic nerve decompression, exposure of the medial aspect of the cavernous sinus, and watertight realignment of the anterior cranial base dura. In this report the authors present their experience over the past 13 years with 104 patients who underwent operation via the extended subcranial approach. Because extensive frontal lobe manipulation and external facial incisions are avoided with this approach, intensive care unit and overall hospital stay are reduced, related complications are minimized, and postoperative cosmetic appearance is enhanced. The extended anterior subcranial method is therefore an excellent alternative to traditional transfacial-transcranial skull base approaches for the removal of selected skull base tumors.

Estimation of blood levels of endothelin and neurokinin receptor antagonists at the rat portal and jugular veins after oral administration as a tool in peptide drug design

The blood concentration of three representative endothelin and four neurokinin receptor antagonists were monitored both at the portal and jugular vein of rats 30, 60 and 90 min after oral administration. Peptide-derived structures, in the size range tetra-pentapeptides, were shown to be absorbed in the reverse order of their log P values, to be weakly metabolized in the first hepatic transit and to maintain high blood levels during the observation time. These interesting results obtained by a simple and convenient UV assay, stress once again the importance of monitoring oral absorption early in the process of peptide drug design.

New N alpha-guanidinobenzoyl derivatives of hirudin-54-65 containing stabilized carboxyl or phosphoryl groups on the side chain of phenylalanine-63

We report on the synthesis and pharmacological properties of a new series of thrombin inhibitors derived from hirudin carboxyl-terminal fragments. Two (arylphosphono)phenylalanines, p-PO3H2-L-Phe1 and m-PO3H2-L-Tyr, and one (carboxymethyl)phenylalanine, p-CH2COOH-L-Phe, were prepared and incorporated into position 63 of the modified hirudin's C-terminal dodecapeptide using the Fmoc solid-phase synthesis strategy. Substitution by any one of the residues led to very active analogs which doubled the thrombin time at low micromolar concentration (Ctt2) in vitro (1 microM < Ctt2 < 3 microM) and potently increased the activated partial thromboplastin time (APTT) ex vivo. These compounds displayed a higher potency in vitro and a longer duration of action in vivo than both the corresponding sulfated or phosphorylated tyrosine counterparts.

Synthesis and in vitro activities of new tryptophan-modified and thiomethylene-containing pseudopeptide antagonists of the neurokinins

A series of pseudopeptide analogs of the substance P-like hexapeptide Ava-Phe-Phe-Gly-Leu-Met-NH2 was produced by N alpha-protection, introduction of the thiomethylene bond, of D- and non-proteinogenic amino acids, and alteration of the side chain of tryptophan. Synthesis of the pseudopeptides on a solid phase was successfully improved by direct formation of the CH2-S bond on the resin. However, while thiomethylene formation between leucine and norleucine led to the expected SS diastereoisomer, the major product of the similar coupling between two phenylalanines was the SR isomer. An improved resistance of the analogs to proteolysis was observed, which could be related to the structural changes. Interestingly, these modifications led to three water-soluble and potent neurokinin antagonists on classical in vitro bioassays.

Tetrapeptide tachykinin antagonists: synthesis and modulation of the physicochemical and pharmacological properties of a new series of partially cyclic analogs

We report on the synthesis and the pharmacological properties of a new series of tachykinin antagonists based on the pseudopeptide pharmacophore cyclo[-Abo-Asp(D-Trp-Phe-N(Me)Bzl)-] which contains the 2-azabicyclo[2.2.2]octane-3(S)-carboxylic acid (Abo) residue. Variation of the substituents on the tryptophan indole nitrogen was shown to modulate water solubility and transport properties of the analogs as well as potency in classical in vitro response and binding assays. One water-soluble compound, 16, in which the substituent was 3-carbonylpropionate, strongly prolonged the reaction time in the mouse hot-plate test both after iv or oral administration and was devoid of degranulating activity in rat peritoneal mast cells.