New formulation of in situ gelling Metolose-based liquid suppository.

CONTEXT: An in situ gelling liquid suppository is liquid at room temperature but forms a gel at body temperature. In our work, Metolose® SM-4000 (methylcellulose) is studied that basically shows thermal gelation at 68°C (2%, w/w). OBJECTIVE: The objective was to study the potency of different factors (concentration, pH, additives) to change the value of thermal gelation temperature (T (t)) for Metolose® to form an in situ gelling liquid suppository. MATERIALS AND METHODS: We studied the effect of Metolose® concentration, pH, and salts (sodium chloride, potassium chloride, sodium hydrogen carbonate, and sodium monohydrogen phosphate) on T (t) by viscosimetry. To choose the appropriate compound, in vitro drug release was examined. Rectal safety test was performed on rats in vivo after 12-hour application. RESULTS: Increasing the Metolose® concentrations (0.5-4%, w/w), T (t) can be decreased, but it also altered the consistency of gel. pH does not affect the T (t). The water-soluble salts allowed reducing the gelation temperature to 37°C. Sodium monohydrogen phosphate in 4.5% concentration was found to be the most appropriate. The impact of examined factors on in vitro drug release of piroxicam from the in situ-formed gel was characterized according to Fickian diffusion. Metolose® and the chosen salt did not cause any morphological damage on the rectal tissues. DISCUSSION: According to our study, Metolose® has the physical and chemical potential to be used as base for liquid suppositories.

Myeloperoxidase evokes substantial vasomotor responses in isolated skeletal muscle arterioles of the rat.

AIMS: Myeloperoxidase (MPO) catalyses the formation of a wide variety of oxidants, including hypochlorous acid (HOCl), and contributes to cardiovascular disease progression. We hypothesized that during its action MPO evokes substantial vasomotor responses. METHODS: Following exposure to MPO (1.92 mU mL(-1)) in the presence of increasing concentrations of hydrogen peroxide (H2O2), changes in arteriolar diameter of isolated gracilis skeletal muscle arterioles (SMAs) and coronary arterioles (CAs) and in the isometric force in basilar arteries (BAs) of the rat were monitored. RESULTS: Myeloperoxidase increased vascular tone to different degrees in CAs, SMAs and BAs. The mechanism of increased vasoconstriction was studied in detail in SMAs. MPO-evoked vasoconstrictions were prevented by the MPO inhibitor 4-aminobenzhydrazide (50 µM), by endothelium removal in the SMAs. Surprisingly, the HOCl scavenger L-methionine (100 µM), the thromboxane A2 (TXA2) antagonist SQ-29548 (1 µM) or the non-specific cyclooxygenase (COX) antagonist indomethacin (1 µM) converted the MPO-evoked vasoconstrictions to pronounced vasodilations in SMAs, not seen in the presence of H2O2. In contrast to noradrenaline-induced vasoconstrictions, the MPO-evoked vasoconstrictions were not accompanied by significant increases in arteriolar [Ca(2+)] levels in SMAs. CONCLUSION: These data showed that H2O2 -derived HOCl to be a potent vasoconstrictor upon MPO application. HOCl activated the COX pathway, causing the synthesis and release of a TXA2-like substance to increase the Ca(2+) sensitivity of the contractile apparatus in vascular smooth muscle cells and thereby to augment H2 O2 -evoked vasoconstrictions. Nevertheless, inhibition of the HOCl-COX-TXA2 pathway unmasked the effects of additional MPO-derived radicals with a marked vasodilatory potential in SMAs.

The novel cardiac myosin activator omecamtiv mecarbil increases the calcium sensitivity of force production in isolated cardiomyocytes and skeletal muscle fibres of the rat.

BACKGROUND AND PURPOSE: Omecamtiv mecarbil (OM) is a novel cardiac myosin activator drug for inotropic support in systolic heart failure. Here we have assessed the concentration-dependent mechanical effects of OM in permeabilized cardiomyocyte-sized preparations and single skeletal muscle fibres of Wistar-Kyoto rats under isometric conditions. EXPERIMENTAL APPROACHES: Ca2+ -dependent active force production (Factive ), its Ca2+ sensitivity (pCa50 ), the kinetic characteristics of Ca2+ -regulated activation and relaxation, and Ca2+ -independent passive force (Fpassive ) were monitored in Triton X-100-skinned preparations with and without OM (3nM-10 µM). KEY RESULTS: In permeabilized cardiomyocytes, OM increased the Ca2+ sensitivity of force production (ΔpCa50 : 0.11 or 0.34 at 0.1 or 1 µM respectively). The concentration-response relationship of the Ca2+ sensitization was bell-shaped, with maximal effects at 0.3-1 µM OM (EC50 : 0.08 ± 0.01 µM). The kinetics of force development and relaxation slowed progressively with increasing OM concentration. Moreover, OM increased Fpassive in the cardiomyocytes with an apparent EC50 value of 0.26 ± 0.11 µM. OM-evoked effects in the diaphragm muscle fibres with intrinsically slow kinetics were largely similar to those in cardiomyocytes, while they were less apparent in muscle fibres with fast kinetics. CONCLUSIONS AND IMPLICATIONS: OM acted as a Ca2+ -sensitizing agent with a downstream mechanism of action in both cardiomyocytes and diaphragm muscle fibres. The mechanism of action of OM is connected to slowed activation-relaxation kinetics and at higher OM concentrations increased Fpassive production.

Effect of preexisting brain ischemia on sympathetic nerve response to intracranial hypertension.

The performance of the sympathetic nervous system during sustained moderate cerebral ischemia (CI) was examined in the present study. For this purpose, a Cushing response was elicited repeatedly during incomplete global CI in anesthetized artificially ventilated cats after vagotomy and baroreceptor denervation. In control animals without CI, sympathetic activity in response to brief elevation of intracranial pressure (ICP) showed a well-repeatable two-phase reaction. During CI there was a progressive deterioration of background sympathetic nerve discharge (SND) over a period of 30 min. SND response to repeated elevation of ICP was initially similar to control response but later with progression of CI was seriously changed. 1) Instead of the usual hyperactivation, sympathetic nerve activity was depressed during intracranial hypertension. 2) The characteristic desynchronized activity either appeared later during the reperfusion period or remained absent. The progressive loss of SND response to raised ICP in developed CI was compared with the changes seen in experiments in which repeated ICP elevations were superimposed on asphyxia. These findings suggest that the sympathetic component of the Cushing reaction strongly depends on the actual state of brain stem autonomic circuits and may be seriously altered in pathological situations involving ischemic brain injury.

Neuropeptides in the human superior cervical ganglion.

Superior cervical ganglia from 7 human cadavers (3-7 h post mortem) were immunostained for tyrosine hydroxylase (TH), dopamine-beta-hydroxylase (DBH) and 14 different neuropeptides. The results show that ganglionic cells contain TH, DBH, neuropeptide Y (NPY), somatostatin, vasoactive intestinal polypeptide (VIP) and calcitonin gene-related peptide (CGRP). These substances were present predominantly within large ganglionic cells. Inside the ganglion, the number and topographical distribution of various types of immunoreactive cells differed from one another. NPY and CGRP immunoreactivities were found in some TH-positive cells, but that co-localization never exceeded the 30% of the TH cells. Leu-enkephalin showed a weak immunoreactivity, which was restricted to fibers or varicosities. Neuropeptides like substance P, dynorphin A and B, cholecystokinin, galanin, corticotropin-releasing factor, thyrotropin-releasing hormone, angiotensin II and neurotensin showed no immunoreactivity in the human superior cervical ganglion.

Inhibitory effect of hypoxic condition on acetylcholine release is partly due to the effect of adenosine released from the tissue.

Isolated longitudinal muscle strip with Auerbach's plexus attached was used to study the stimulation-evoked release of 3H-acetylcholine (3H-ACh) under normoxic and hypoxic conditions. Hypoxia reduced the release of ACh. Theophylline, a purinoceptor P1 antagonist and vinpocetine, an antiischemic compound partly reversed the effect of hypoxia. Unlike theophylline, the effect of vinpocetine was not mediated via adenosine action, since it failed to affect the presynaptic action of adenosine, and the effect of theophylline and vinpocetine was additive. When they were added together the effect of hypoxia was almost completely antagonized. Dipyridamole, an adenosine uptake inhibitor, potentiated the effect of hypoxia and the presynaptic inhibitory action of adenosine on ACh release. Evidence was obtained that the effect of hypoxia is at least partly due to adenosine formed from purine nucleotides.

Contralateral approach to bilateral and ophthalmic aneurysms.

In a previous survey, we found a high incidence of fatal rupture of an unclipped aneurysm in patients with multiple aneurysms. To deal with this problem, we introduced a more vigorous technique that accesses aneurysms previously considered unapproachable during one operating session. Attempts were made to clip middle cerebral and ophthalmic aneurysms contralateral to the operative exposure. We have successfully clipped contralateral aneurysms of the posterior communicating artery when bilateral aneurysms were present. We have also used this contralateral approach successfully with single ophthalmic and proximal carotid aneurysms that pointed medially. We review the cases of 39 patients with 43 intracranial aneurysms operated from the contralateral side and present the surgical technique in relation to the angiographic findings.

Third ventricle germinoma after total removal of intrasellar teratoma. Case report.

A unique case is presented of a third ventricle germinoma developing 3 years after total removal of an intrasellar teratoma. The third ventricle germinoma was not considered to be a recurrence or dissemination of the mature intrasellar teratoma but to have been transformed from multicenter germ cells present in the midline of the brain with different temporal development. The relevant literature is reviewed and the problems of management of patients with germ-cell tumors are discussed.

Sensitivity of the short-range spinal interneurons of the cat to experimental spinal cord trauma.

The technique of retrograde axoplasmic transport was used to demonstrate the effect of experimental spinal cord injury on the spinal interneurons in the upper lumbar and lower thoracic segments of cats. Force of varied intensity was applied to the dorsal surface of the spinal cord and horseradish peroxidase (HRP) was injected into the next caudal segment. A large impact (250 to 350 gm-cm) inducing permanent paraplegia of the hind legs blocked the axoplasmic transport instantaneously in both cranial and caudal directions. If 1 week elapsed between the trauma and injection, neurons cranial to the trauma did not show any evidence for retrograde axoplasmic transport, while few neurons in the caudal direction were labeled with HRP. A moderate impact (150 gm-cm) which rendered the animals only transiently paraplegic spared the axoplasmic transport in some neurons both cranially and caudally to the injection. No obvious recovery or additional loss in the number of HRP-labeled neurons could be found in the cats if the injections followed the trauma by 1 week. The loss of spinal cord neurons following the injury seems to be the immediate mechanical consequence of the trauma.

Transoral surgery for craniocervical space-occupying processes.

Although the number of reports concerning the transoral approach to anteriorly placed lesions of the craniocervical junction are increasing, the development of this technique is still in its early stages. The indications and surgical methods vary widely, and there is much room for discussion of the technical details. Eight cases operated on via transoral surgery during the last 4 years are presented in support of the transoral approach to tumors in the craniocervical region.

Blood flow and autoregulation in rat pituitary gland.

The authors describe an experimental model that allows dynamic studies of blood flow in the pituitary gland. Twenty-eight male Wistar rats were anesthetized and the pituitary gland was exposed using a parapharyngeal approach. Teflon-coated platinum wire electrodes were placed in the adenohypophysis near the midline and laterally as well as in the parietal cortex and the white matter. Blood flows were measured by the hydrogen clearance method. Baseline values were as follows: 89.9 +/- 22 ml/100 gm/min in the medial adenohypophysis, 55.9 +/- 8 ml/100 gm/min in the lateral adenohypophysis, 59.2 +/- 14 ml/100 gm/min in the parietal cortex, and 28.1 +/- 8.9 ml/100 gm/min in the white matter. Effective autoregulation was demonstrated by altering the blood pressure with metaraminol infusion or blood withdrawal. The range of autoregulation was wider in the adenohypophysis than in the cerebral cortex.

Reduction of blood flow in the adenohypophysis of rats by bromocriptine.

The possibility that bromocriptine has a selective effect on blood flow in the adenohypophysis was examined in rats. Twenty-four anesthetized male Wistar rats underwent measurement of blood flow using the hydrogen clearance method. Intravenous injection of 50 micrograms/kg bromocriptine reduced the blood flow in both the medial and lateral parts of the adenohypophysis to about 70% of the baseline value. Simultaneously measured cerebral cortical and white matter flows were unchanged. Similar results were obtained following administration of a higher dose (500 micrograms/kg) of bromocriptine. This phenomenon cannot be attributed to the decrease in blood pressure. The course of change in blood flow in the medial and lateral adenohypophysis did not follow that of the mean arterial blood pressure, and the alteration of blood pressure remained within the limits of autoregulation in the adenohypophysis. The results indicate that bromocriptine is capable of reducing blood flow selectively in the pituitary region. This mechanism may contribute to the clinical usefulness of this drug.

Comparison of methods eliciting cerebral ischaemic pressor response in the cat.

Three methods of intercepting the blood supply to the brain were tested by means of X-ray angiography and by monitoring the pressor response following cerebral ischaemia. The methods were: (1) occlusion of carotid and basilar artery; (2) occlusion of carotids and vertebral arteries in the cervical canal of the third vertebra; (3) occlusion of carotid and subclavian arteries. The X-ray angiographs showed that in most cases we could close the accessory sources of the cerebral circulation and drastically reduce the blood supply to the brain of the cat. With all three methods the cerebral ischaemia evoked strong blood pressor elevation, which was weaker however when the carotid and basilar artery were clamped, in comparison with the other two methods. This may be explained by the existence of small arteries supplying the lower brain stem and originating intracranially from the vertebral artery near to the junction of the vertebral and anterior spinal artery.

Could craniopharyngiomas produce pituitary hormones?

The authors have studied the endocrinological characteristics of 13 craniopharyngioma biopsy specimens in paraffin embedded histological sections with immunohistochemical methods for pituitary hormones (GH, PRL, ACTH, TSH, FSH and LH). Scattered cell groups with mild to moderate positivity for at least one hormone were found in all but one case. This finding supplies further evidence to the hypothesis which suggests the Rathke's pouch origin of craniopharyngiomas. Beside the hypothalamic-hypophyseal lesion it might explain the endocrinological disturbances accompanying the patients suffering from these tumours.

Management of pineal region tumours.

Pineal region tumours represent a colourful, challenging peculiarity of brain pathology. Views on their management are still much divided and controversial. Data of fifty patients with the whole palette of these tumours seen in the National Institute of Neurosurgery have been analysed in view of the result of management versus histology of these tumours. Findings of tumour marker studies have not at all been conclusive in predicting histology and outcome, however, cytology of the cerebrospinal fluid (CSF), if positive, pointed toward a very gloomy management result in all cases. Merits of infratentorial-supracerebellar, occipito-transtentorial approaches of direct surgery, palliative interventions and their timing, as well as that of irradiation are discussed in comparison with opinions and arguments from the literature. Shunt procedures alone proved to be dangerous in some cases by evoking haemorrhagic complications. In carefully selected cases microsurgical intervention gave the best possible results in expansively growing pineal region tumours. There is still place for irradiation and chemotherapy, again, in certain types of mass lesions.

Experiences in the endovascular treatment of cerebral arteriovenous angiomas.

Percutaneous superselective balloon catheterization for the treatment of large cerebral arteriovenous malformations, for which direct operation is infeasible, is described. Both a detachable balloon technique and a "calibrated leak" free embolization have been applied, based on a new hardening silicone material elaborated by the authors. The experiences of operations performed since 1978 are represented by four selected case studies.

Transformation of a human mixed GH-PRL adenoma cell population in response to long-term bromocriptine treatment.

A child was operated 3 times because of a recurrent growth hormone- and prolactin-producing pituitary adenoma. Between the operations she was treated for five years with bromocriptine. The characteristics of the tumour cell population collected after the last operation was now examined by electron microscopy, immunocytochemistry, and in tissue culture and compared to those of the primary tumour cells reported earlier. A prominent change was the reversal of the proportion of the densely and sparsely granulated cells in favour of the GH-type, densely granulated cells. These cells, some of them coexpressing PRL, did not essentially change their characteristics either in vivo or in culture. On the other hand, pleomorphous cells with smaller cytoplasmic area and prominent lysosomal structures represented the sparsely granulated population containing PRL or both PRL and GH. The morphological alteration of the PRL-type cells was also reflected in vitro. Hence, while GH-type cells prevail, at least a sub-population of PRL-type cells survives long-term bromocriptine administration. A shift in the incidence of the two cell types in favour of the GH-type cells explains the change in the endocrine status of the patient.

Effect of vasoactive intestinal polypeptide (VIP) on growth hormone (GH) and prolactin (PRL) release and cell morphology in human pituitary adenoma cell cultures.

Six GH adenomas and three prolactinomas were investigated by light- and electron-microscopic morphological and immunocytochemical methods and the effect of vasoactive intestinal polypeptide (VIP) on growth hormone (GH) and prolactin (PRL) secretion was tested in vitro. The tumour cells of the acromegalic patients revealed both GH and PRL immunoreactivity while prolactinomas showed only PRL activity. All the adenomas stained immunocytochemically also for VIP. By electron microscopy, the tumours included two densely and two sparsely granulated GH, two mixed GH/PRL, and three sparsely granulated PRL adenomas. The dissociated cells were explanted, and cultured in vitro. The cultures in micro test plates were treated with VIP at different concentrations between 10(-5)-10(-12) M. GH and PRL contents in the culture media were measured by radioimmunoassay. GH release was significantly stimulated by VIP in a dose-dependent manner over the whole concentration range, while VIP was effective on the PRL release only at 10(-6)-10(-7) M concentration. The cells of a mixed adenoma were grown in Petri dishes and used for ultrastructural and immunocytochemical studies. The cytoplasmic structure of the cells treated with VIP corresponded to that of active hormone-secreting cells with large ergastoplasmic fields and Golgi zones containing secretory granules. Massive exocytotic events were encountered mainly in the GH-type cells. GH and PRL double immunocytochemistry showed the predominance of GH cells, many of them containing low amounts of PRL as well. Cells predominantly containing PRL were spread among them, they also might contain GH as well. Some of the cells contained only a single immunoreactive hormone. The intensity of gold labelling of the secretory granules appeared higher in the VIP-treated cells than in the untreated control ones which showed a cytoplasmic structure characteristic of glandular cells with low secretory activity. As all the adenoma cells both contained and reacted to VIP, our results are in agreement with an autocrine or paracrine effect of this peptide. The fine structure of the cells in the cultures treated with VIP supply an additional argument to the assumption that VIP may serve as a growth factor for these cell types.

Transoral approach for epidural craniocervical pathological processes.

Transoral surgery for ventral craniocervical pathology is an integral part of modern neurosurgery. This approach should be considered in many more cases than in current practice. On the basis of our experiences with 15 operations in 13 patients we feel able to improve the surgical technique in some small details, as 1. the double, two flap incision of the posterior wall of the pharynx, 2. the method of "deep" resection of the odontoid in its high upward and backward position, and 3. insertion of bone grafts and chips in the cavity of tumorous vertebrae for fixation. Admittedly, these cases are not encountered every day in neurosurgical units. An exact knowledge of the anatomical, neurological, pathological, radiological and surgical details is of vital importance and constitutes the basis of this account. This method should not be confined to specialised regional neurosurgical centres, but is within the technical capacity of all trained neurosurgeons.

Decompression of vertebral artery in cases of cervical spondylosis.

In four cases with symptoms of vertebral artery insufficiency, compression of the artery was abolished by removing the adjacent cervical osteoarthritic spurs. However, total relief could be achieved only by incision and resection of the constricting fibrotic ring around the vertebral artery. This periarterial fibrotic tissue appears to play a role in the pathogenesis of symptoms.