Low dosage of native allogeneic bone morphogenetic protein in repair of sheep calvarial defects

A sheep skull trephine defect model was used to test the efficacy of allogeneic partially purified sheep bone morphogenetic protein (sBMP), extracted using a low-cost alternative technique based on 60% ammonium sulphate saturation of the guanethidine-HCI extract of pulverized bone matrix. Eight mg of partially purified sBMP was implanted in six 22-mm right-side sheep calvarial critical-size defects trephined in the diploë area using a midline incision; left-side defects implanted with an equal amount of type IV collagen served as controls. After 16 weeks the sheep were killed and the defects removed. Formation of new bone was evaluated using radiomorphometry and histomorphometry. The healing percentage in sBMP-implanted defects was 60.8 +/- 8.1% and in controls 49.8 +/- 6.7% (P < 0.05) as assessed by radiomorphometry. In cross-sectional histomorphometry, newly formed bone regenerated 50.9 +/- 15.1% in the defects with sBMP and 16.1 +/- 10.6% in controls (P < 0.01). The good result, considering the low dosage of sBMP, can be explained by the strong osteoinductivity and low immunogenicity of native allogeneic sBMP.

Treatment of algodystrophy using intravenous guanethidine regional block

25 cases of algodystrophy of the hand have been treated by regional intravenous guanethidine block. Pain relief was noticed in over 2/3 of the algodystrophies in stages 1 and 2, and the patients could carry on their rehabilitation. The treatment is immediately effective easy to use, without side effects and inexpensive. Unfortunately, it is not effective on the third stage of the disease. Hannington-Kiff has reported that the treatment could also be used neuro-algodystrophy of lower limbs. The authors briefly review here the pathogenesis and the clinical findings in neuro-algodystrophy.

Regional intravenous sympathetic nerve blocks

The assessment of the possible efficacy of regional intravenous blocks or sympathetic blocks, in general, raises a number of questions that may be answered after studying the techniques of regional pharmacologic segmental blocks and their effects on the sympathetic system. The authors present an original clinical study evaluating the capacity of regional intravenous guanethidine to induce a sympathetic blockade compared with other techniques.

The sympathetic nervous system is involved in the maintenance but not initiation of the hypertension induced by N(omega)-nitro-L-arginine methyl ester

Studies in anesthetized animals have advanced the theory that there is an important neurogenic component to the hypertension caused by pharmacological inhibition of nitric oxide, but studies in conscious animals have produced conflicting evidence for and against this theory. To try to reconcile the seemingly contradictory data, we hypothesized that the neurogenic component of this hypertension is time dependent such that the sympathetic nervous system is involved primarily in the maintenance, rather than the initiation, of the hypertension. We measured intra-arterial pressure in conscious, unrestrained rats with and without guanethidine-induced sympathectomy during varying durations of intravenous N(omega)-nitro-L-arginine methyl ester (L-NAME). The major new finding is that sympathectomy had no effect on the hypertensive response to bolus injections of L-NAME but in the same rats it produced a greater than 50% attenuation in the hypertension seen after 6 days of continuous L-NAME (change in mean arterial pressure, 23+/-4 versus 55+/-4 mm Hg, P<.01, sympathectomy versus control). Using 8-hour infusions of L-NAME, we found that 60 minutes was the minimum time required for detecting a sympathectomy-sensitive component of L-NAME-induced hypertension. Furthermore, we demonstrate that the magnitude of this component increases further between 8 hours to 6 days of continuous L-NAME: it accounted for only 18% of the total hypertensive response at 8 hours but 61% after 6 days. From these experiments, we conclude that the importance of the sympathetic system in the pathogenesis of L-NAME-induced hypertension accrues slowly over hours and days, and thus its importance can be overlooked by focusing on the initial phase of the hypertension.

Ovarian granulosa and theca interstitial cells: a morphological and physiological analysis in guanethidine denervated rats at pre-puberty

Since ovary denervation causes delayed puberty, we investigated the relative importance of ovary innervation on the morphology and physiology of theca interstitial cells (TIC) and granulosa cells (GC) in female rats at pre-puberty. Elimination of the sympathetic innervation was performed by long term post natal treatment with guanethidine (GD), an adrenergic blocking agent. The sympathectomized rats exhibited: reductions in follicular volume (40%), granulosa cells area (43%) and theca interstitial cell volume (50%). Ovarian concentrations of pregnenolone (P5) and progesterone (P4) were decreased whereas no differences were observed in androstenedione (A) and estradiol (E2). The intensity of the immunocytochemical reaction for 3 beta hydroxysteroid dehydrogenase (3 beta-HSD) detected only in interstitial cells, did not show any difference. These in vivo results include the TIC in the bulk of ovarian structures affected by GD denervation at pre-puberty as it was already observed for GC. The reduced area/volume occupied by these cells in the GD treated ovary is associated to a blockade of the initial steps of the steroidogenic pathway, probably at the level of the cholesterol side chain cleavage enzyme (P450 s.c.c.), previously to P5 synthesis, since P5 is reduced. Similar intra ovarian concentrations of androgens are discussed in terms of possible pineal deafferentation promoted by GD at high doses.

[The bioavailability of endogenous calcitonin under selective pharmacological sympathectomy]

The serum concentrations of calcitonin (CT) and sublemmal granule numerical density in the thyroid C-cell basal polus cytoplasm were measured in guanethidine-sympathectomized rats aged 2 weeks. Based on the previously proposed procedure [Krasnoperov et al. 1997], the confidence interval of endogenous CT bioavailability was found to be 52-100% (p > or = 0.95). It significantly differed from the similar control parameter (73-100%). The findings suggest that it cannot be excluded that unlike normal animals, sympathectomized 2-week rats may have CT retention at the transinterstitial and/or transmural stages of hemato-C-cellular mass-transfer.

[The postnatal development of the hemato-C-cellular system in the thyroid of rats sympathectomized with guanethidine]

We used ultrastructural morphometry to examine submicroscopical organization of spatial contacts between the C-cells and perifollicular hemocapillaries in the thyroid gland of 2-, 4-, 12-, 26-, and 52-week-old rats desympathized with guanetidine. We found that desympathization does not affect typology of ultrastructural elements of the hemato-C-cellular complex, and predominant coupling of the vascular pole of the C-cell with peripheral zone of endotheliocyte highly effective in terms of transport. Postnatal changes of certain parameters of the hemato-C-cellular system, however, undergo some statistically significant changes. Under experimental conditions, we observed the formation of hemato-C-cellular contacts simultaneously involving two C-cells.

EFFECT OF SOME BLOCKING DRUGS ON THE PRESSOR RESPONSE TO PHYSOSTIGMINE IN THE RAT

Bretylium and guanethidine blocked the pressor effect of physostigmine and potentiated the responses to adrenaline and noradrenaline on the blood pressure of the rat. Morphine and atropine in small doses blocked the pressor effect of physostigmine without interfering with the actions of adrenaline and noradrenaline. Chlorpromazine in small doses (0.5 to 2.5 mg/kg) blocked the pressor effect of physostigmine and potentiated the responses to noradrenaline whilst those to adrenaline remained unaltered. 3,6-Di(3-diethylaminopropoxy)pyridazine di(methiodide) (Win 4981) blocked the pressor effect of physostigmine and, in its early stages, this block was partially reversed by choline chloride. N-Diethylaminoethyl-N-isopentyl-N'N'-diisopropylurea (P-286), in a dose that reduced the effect of dimethylphenylpiperazinium, had no effect on the pressor response to physostigmine or on the responses to adrenaline and noradrenaline. Hexamethonium, even in large doses (100 mg/kg), only blocked partially the effect of physostigmine while mecamylamine produced a complete block; the responses to adrenaline and noradrenaline were potentiated in both instances.

THE EFFECTS OF DRUGS ON THE UPTAKE OF AMINES BY MAST CELLS

Neoplastic mast cells, taken from an ascitic tumour in mice and incubated in vitro, took up (14)C-labelled 5-hydroxytryptamine and histamine from the medium. Uptake during the first hour gave an approximate measure of the initial rate. The amount of each amine taken up in this time was determined by bioassay and by radioactivity, the two methods giving similar results. The curves obtained by plotting initial rate of uptake against concentration in the medium suggested that the uptake of 5-hydroxytryptamine was by an active process and also by diffusion, whereas uptake of histamine was by diffusion only. The cells also took up (14)C-labelled (+/-)-noradrenaline and tryptamine, apparently by diffusion. The active uptake of 5-hydroxytryptamine was inhibited by lowering the temperature to 25 degrees C or by increasing the pH to 8.9, procedures which had little effect on histamine uptake. The effects of cocaine, imipramine, chlorpromazine, mepyramine, promethazine, phenoxybenzamine, lysergic acid diethylamide, bromolysergic acid diethylamide, methysergide, guanethidine, dichloroisoprenaline and pronethalol on the uptake of amines were examined. In general, any antagonist which inhibited uptake of 5-hydroxytryptamine had little effect on uptake of histamine, and vice versa. Possible ways in which these antagonists produce their effects on amine uptake are discussed. A high concentration of 5-hydroxytryptamine, of tryptamine or of noradrenaline inhibited uptake of histamine, but only tryptamine decreased uptake of 5-hydroxytryptamine. These results, together with those from experiments with antagonists, suggest that there are specific binding sites for 5-hydroxtryptamine in these cells.

THE EFFECTS OF GUANETHIDINE ON THE NORADRENALINE CONTENT OF THE HYPOTHALAMUS IN THE CAT AND RAT

Single injections of guanethidine 15 mg./kg. i.p. did not lower the hypothalamic noradrenaline in cats, but, daily injections of 15 mg./kg. s.c. over a 7 day period consistently produced a decrease in the hypothalamic noradrenaline. Attempts to lower the hypothalamic noradrenaline in rats after single injections or daily injections of guanethidine were unsuccessful.