Early Aseptic Failure of the Tibial Component-Cement Interface in ATTUNE® Total Knee Arthroplasty: A Report of Three Cases

Total knee arthroplasty (TKA) systems are designed to maximize the longevity of the implant. However, an unusually high rate of aseptic tibial tray loosening was observed in the DePuy ATTUNE^® total knee arthroplasty system (DePuy Synthes, Warsaw, USA). Affected patients noted symptoms of instability and reproducible pain at the bone-implant interface. However, there was no radiographic evidence of lucency or implant failure. Intra-operatively, the tibial component was grossly loose and lacked adhered cement. We hypothesize that the loosening is due to the smooth architecture of the undersurface of the tibial component, lacking either grit blasting or porous coating.

Two-Stage Total Knee Arthroplasty Revision With Extended Antibiotic Spacer Use

Despite the many benefits of total knee arthroplasty (TKA) in the treatment of degenerative arthritis, infection of the total knee prosthesis presents a dangerous post-operative complication affecting 0.5-1.9% of all cases. Infection after the first three post-operative weeks is treated with either one or two-stage revision operations involving the removal of all prosthetic components. Two-stage revision operations are more commonly used and involve the removal of prosthetic components followed by the implantation of a cement mold infused with antibiotics (antibiotic spacer) as well as systemic antibiotic treatment for four to six weeks before prosthetic reimplantation. This case report details a TKA revision in a patient with osteoarthritis of the knee. The patient presented with an elevated erythrocyte sedimentation rate, C-reactive protein, and white blood cell count nearly two years after the primary operation and was found to have an infected total knee prosthetic. A two-stage revision was planned but due to scheduling disruption by the coronavirus disease 2019 pandemic, the second stage of the operation was delayed until 12 months after the stage one operation. The patient ambulated without pain on an antibiotic spacer for 12 months, providing information about the long-term use of spacers. This case also offers a look at a potential benefit to one-stage operations, which have been shown in the literature to have similar outcomes as two-stage operations. The patient had a medical history of psoriasis and immunosuppressive treatment with methotrexate, two risk factors for prosthetic joint infection, and may have benefited from prophylactic antibiotic therapy extending beyond the perioperative period. The goal of this case report is to detail the prolonged use of an antibiotic spacer, examine the risks and benefits of one and two-stage total knee revisions, and discuss prophylactic antibiotic use in high-risk patients following TKA.

Comparision of atrazine and metolachlor affinity for bermudagrass ( Cynodon dactylon L.) and two soils

Given that bermudagrass is being used as one of the grasses of choice in grass filter strip plantings as an acceptable grass to reduce off-target losses of herbicides, laboratory experiments were conducted to determine and compare the relative affinity of bermudagrass, a Weswood soil, and a Houston Black soil for atrazine (6-chloro- N-ethyl- N-isopropyl-1,3,5-triazine-2,4-diamine) and metolachlor (2-chloro- N-(2-ethyl-6-methylphenyl)- N-(2-methoxy-1-methyethyl) acetamide). Experiments were also conducted to determine if the presence of one herbicide affects the relative affinity of the other compound to these sorbents. The experiments were carried out using radiolabeled atrazine and metolachlor. Results were reported in disintegrations min(-1) (dpms) and converted to K(d) to determine and compare relative affinity. Both K(d) values for relative affinity of atrazine (86.2) and metolachlor (131.5) to bermudagrass were significantly greater than those of the two soils, Weswood (atrazine, 20.0 and metolachlor, 28.4) and Houston Black (atrazine, 35.8 and metolachlor, 33.5). The two compounds were also mixed together to mimic the common practice of applying atrazine and metolachlor simultaneously as a tank mix. Relative affinity of atrazine to any of the sorbents was not affected by the presence of metolachlor. Similarly, when comparing the affinity of metolachlor alone to that of metolachlor with atrazine present in the solution, no significant differences were observed for bermudagrass or the Weswood soil. However, on the Houston Black soil, the presence of atrazine significantly increased the soil's affinity for metolachlor.

Aspergillus fumigatus infection in a mega prosthetic total knee arthroplasty: salvage by staged reimplantation with 5-year follow-up

Fungal infection after total joint arthroplasty is an extremely serious complication and a challenge to the treating physician. When a fungal infection is compounded by a massive allograft or a metallic segmental replacement of the femur or other long bone, treatment options become increasingly limited and commonly have led to arthrodesis or amputation of the infected limb. We present the first case report of a low-grade osteosarcoma treated with a segmental distal femoral allograft prosthetic composite knee arthroplasty, which was complicated by infection with Aspergillus fumigatus. This complication was treated successfully with a staged reimplantation procedure, intravenous amphotericin, and oral fluconazole suppression. At 5 years after reimplantation, the patient has had no evidence of infection, no pain, and excellent range of motion without extensor lag. The Knee Society knee score improved from 50 to 100, and the function score improved from 40 to 100 (for both scores, 100 is the maximum).

Total knee arthroplasty in an adult with congenital dislocation of the patella

This article reports the use of total knee arthroplasty with release of the lateral retinaculum, proximal extensor mechanism realignment, and patellar resurfacing as a valid treatment option for adult patients with congenital dislocation of the patella who have absence of the femoral sulcus and associated osteoarthritis. The patient presented in this case report had improvement of his Knee Society knee score and function score from preoperative levels of 8 and 45 to 77 and 80 postoperatively.

Morpholin-2-yl-phosphinic acids are potent GABA(B) receptor antagonists in rat brain

The pharmacological properties of morpholin-2-yl-phosphinic acids were evaluated on GABA(B) receptors. In rat neocortical slices maintained in Mg2+-free Krebs medium, baclofen, a GABA(B) receptor agonist, produced a concentration-dependent depression of the frequency of spontaneous discharges with an EC50 of 14 +/- 5.5 microM, which was antagonised reversibly by the morpholin-2-yl-phosphinic derivatives. The order of potency was 3-[(3S,6R)-6-[(cyclohexylmethyl)hydroxyphosphinoylmethyl- morpholin-3-yl]benzoic acid (CGP 76290A) (pA2 = 7.1 +/- 0.05) > its enantiomer 3-[(3R,6S)-6-[(cyclohexylmethyl)hydroxyphosphinoylmethyl]-++ +morpholin-3-yl]benzoic acid (CGP 76291A) (pA2 = 6.8 +/- 0.1) > cyclohexylmethyl-[(2R',5S')-5-(3-nitrophenyl)-morpholin-2-++ +ylmethyl]phosphinic acid (CGP 71978) (pA2 = 6.5 +/- 0.05) > cyclohexylmethyl-[(2R,5S)-5-phenyl-morpholin-2-ylmethyl++ +]phosphinic acid (CGP 71980) (pA2 = 6.3 +/- 0.15) > its enantiomer cyclohexylmethyl-[(2S,5R)-5-phenyl-morpholin-2-ylmethyl++ +]phosphinic acid (CGP 71979) (pA2 = 5.8 +/- 0.1). An open chain analogue of CGP 76290A, CGP 56999A (3-[1(R)-[(3-cyclohexylmethyl-hydroxyphosphinoyl)-2(S)-hydro xypropyl-amino]-ethyl]benzoic acid lithium salt) gave a pA2 of 6.6 +/- 0.2. In GABA(B) receptor binding assays, CGP 71982 (the racemic mixture of CGP 76290A and CGP 76291A), CGP 76290A, CGP 76291A, CGP 71978, CGP 71980 and CGP 71979 had IC50 values against [3H]CGP 27492 binding of 8, 1.85, 69, 124, 326 and 1460 nM, respectively. In electrically-evoked [3H]GABA release from rat cortical slices, CGP 71982, CGP 71978, CGP 71980 and its enantiomer CGP 71979, antagonised GABA(B) autoreceptors with EC150 values of 2.5, 33, 181 and 474 nM, respectively. These compounds form a novel class of potent GABA(B) receptor antagonists.

Effects of the putative P-type calcium channel blocker, R,R-(-)-daurisoline on neurotransmitter release

The alkaloid and medicinal herb constituent, R,R-(-)-daurisoline, was originally reported to be a N-type Ca2+ channel blocker, but newer evidence indicates that it is a blocker of P-type Ca2+ channels. To clarify its specificity with respect to N- and P-channels, we compared its effects on the electrically induced release of endogenous glutamate, 3H-GABA and 3H-noradrenaline, from brain slices with those of omega-agatoxin IVA and omega-conotoxin GVIA. Like omega-agatoxin IVA (but with about 1000-fold lower potency), and unlike omega-conotoxin GVIA, R.R-(-)-daurisoline inhibited the release of 3H-GABA and glutamate, with IC50 values of 8 and 18 microM. However, inhibition particularly of 3H-GABA release was more complete than by omega-agatoxin IVA, indicating interaction with one or more additional voltage-sensitive Ca2+ channels, possibly the Q-type. Its potency to inhibit glutamate release elicited either electrically, by veratrine or by high concentrations of K+ was similar, in contrast to sodium channel blockers. The effects of R,R-(-)-daurisoline on the release of 3H-noradrenaline, 3H-dopamine and 3H-acetylcholine were in agreement with previous knowledge from experiments with omega-agatoxin IVA suggesting an involvement of P-channels. A weak inhibition of 3H-noradrenaline release at 10 microM, similar to that by omega-agatoxin IVA at 0.03 microM, was occluded by alpha 2-antagonistic properties and could be unmasked in presence of rauwolscine. At 10 microM, it also inhibited electrically evoked 3H-dopamine and 3H-5-hydroxytryptamine release and caused a marked spontaneous release of all three monoamines in a reserpine-like manner. Spontaneous and evoked release of 3H-acetylcholine was inhibited by about 25% at 10 microM. In radioligand binding studies, R,R-(-)-daurisoline interacted with alpha 1- and alpha 2-adrenoceptors, 5-HT2 and muscarinic cholinergic receptors with IC50 values close to 1 microM, and with mu opiate receptors even with 0.18 microM. Atropine reduced the weak inhibitory effect of R,R-(-)-daurisoline on 3H-acetylcholine release somewhat, suggesting that it was brought about by both P channel blockade and cholinergic agonist activity. The effect on 3H-GABA release was unaffected by naloxone, indicating that the interaction of R,R-(-)-daurisoline with mu opiate receptors is antagonistic. The pattern of effects on neurotransmitter release observed with R,R-(-)-daurisoline resembles that of omega-agatoxin IVA and supports previous electrophysiological data suggesting that the compound blocks P-type voltage-sensitive Ca2+ channels. However, the more complete blockade of amino acid release by R,R-(-)-daurisoline suggests interaction with additional Ca2+ channel subtypes. Although it does also possess other pharmacological properties, we think that the compound is suitable to test whether blockade of glutamate release via voltage-sensitive Ca2+ channels is a viable concept to obtain novel neuroprotective and/or anticonvulsant compounds.

Similar potency of carbamazepine, oxcarbazepine, and lamotrigine in inhibiting the release of glutamate and other neurotransmitters

We compared the effects of the antiepileptic drugs carbamazepine, oxcarbazepine, and lamotrigine on the release from rat brain slices of endogenous glutamate, [3H]-GABA, and [3H]-dopamine, elicited by the Na+ channel opener, veratrine, and of the same transmitters as well as [3H]-noradrenaline, [3H]-5-hydroxytryptamine, and [3H]-acetylcholine, elicited by electrical stimulation. The three antiepileptic drugs inhibited veratrine-induced release of endogenous glutamate, [3H]-GABA, and [3H]-dopamine, with IC50 values between 23 and 150 microM, in or near the concentration range in which they interact with Na+ channels, and there was little difference between the compounds. They were five to seven times less potent in inhibiting electrically as compared with veratrine-stimulated release of [3H]-GABA and [3H]-dopamine; similarly, carbamazepine and tetrodotoxin were more potent in inhibiting veratrine-induced as compared with electrically induced release of endogenous glutamate. Carbamazepine, oxcarbazepine, and lamotrigine also inhibited electrically stimulated release of [3H]-5-hydroxytryptamine (IC50 values, 150 to 250 microM) and [3H]-acetylcholine (IC50 values, 50 to 150 microM); [3H]-noradrenaline release was affected to a lesser degree. The active concentration ranges of these drugs with respect to inhibition of veratrine-stimulated neurotransmitter release matched the therapeutic plasma and brain concentrations. It is uncertain whether these effects are relevant in vivo at anticonvulsant doses, because the drugs are markedly less potent in inhibiting the more physiologic release elicited by electrical stimulation. Therefore, the hypothesis that inhibition of glutamate release is the mechanism of anticonvulsant action of lamotrigine (or carbamazepine and oxcarbazepine) is doubtful. Other consequences of Na+ channel blockade may have an important role.

Phosphinic acid analogues of GABA. 1. New potent and selective GABAB agonists

The antispastic agent and muscle relaxant baclofen 1 is a potent and selective agonist for bicuculline-insensitive GABAB receptors. For many years efforts to obtain superior GABAB agonists were unsuccessful. We describe the syntheses and biological properties of two new series of GABAB agonists, the best compounds of which are more potent than baclofen in vitro and in vivo. They were obtained by replacing the carboxylic acid group of GABA or baclofen derivatives with either the phosphinic acid or the methylphosphinic acid residue. Surprisingly, ethyl- and higher alkylphosphinic acid derivatives of GABA yielded novel GABAB antagonists, which are described in part 2 of this series. Structure-activity relationships of the novel GABAB agonists are discussed with respect to their affinities to GABAB receptors as well as to their effects in many functional tests in vitro and in vivo providing new muscle relaxant drugs with significantly improved side effect profiles.

Phosphinic acid analogues of GABA. 2. Selective, orally active GABAB antagonists

In 1987, 25 years after the synthesis of the potent and selective GABAB agonist baclofen (1), Kerr et al. described the first GABAB antagonist phaclofen 2. However, phaclofen and structurally similar derivatives 3-5 did not cross the blood-brain barrier and hence were inactive in vivo as central nervous system agents. As a consequence, the therapeutic potential of GABAB antagonists remained unclear. In exploring GABA and baclofen derivatives by replacing the carboxylic acid residue with various phosphinic acid groups, we discovered more potent and water soluble GABAB antagonists. Electrophysiological experiments in vivo demonstrated that some of the new compounds were capable of penetrating the blood-brain barrier after oral administration. Neurotransmitter release experiments showed that they interacted with several presynaptic GABAB receptor subtypes, enhancing the release of GABA, glutamate, aspartate, and somatostatin. The new GABAB antagonists interacted also with postsynaptic GABAB receptors, as they blocked late inhibitory postsynaptic potentials. They facilitated the induction of long-term potentiation in vitro and in vivo, suggesting potential cognition enhancing effects. Fifteen compounds were investigated in various memory and learning paradigms in rodents. Although several compounds were found to be active, only 10 reversed the age-related deficits of old rats in a multiple-trial one-way active avoidance test after chronic treatment. The cognition facilitating effects of 10 were confirmed in learning experiments in Rhesus monkeys. The novel GABAB antagonists showed also protective effects in various animal models of absence epilepsy.

GABA and glutamate release affected by GABAB receptor antagonists with similar potency: no evidence for pharmacologically different presynaptic receptors

1. The effects of a series of nine GABAB receptor antagonists of widely varying potencies on electrically stimulated release from cortical slices of [3H]-GABA in the absence or presence of 10 microM of the GABAB agonist, (-)-baclofen and of endogenous glutamate in the presence of (-)-baclofen were compared. 2. The concentrations of the compounds half maximally increasing [3H]-GABA release (EC50's) at a stimulation frequency of 2 Hz correlated well with the IC50 values obtained from the inhibition of the binding of the agonist, [3H]-CGP 27492, to GABAB receptors in rat brain membranes (rank order of potency: CGP 56999 A > or = CGP 55845 A > CGP 52432 > or = CGP 56433 A > CGP 57034 A > CGP 57070 A > or = CGP 57976 > CGP 51176 > CGP 35348). 3. Likewise, the concentrations causing half-maximal increases of [3H]-GABA in the absence or presence of (-)-baclofen, and of endogenous glutamate in the presence of (-)-baclofen, correlated well with each other. Reports in the literature suggesting the CGP 35348 exhibits a 70 fold preference for inhibition of (-)-baclofen's effects on glutamate over [3H]-GABA release, and that CGP 52432 shows a 100 fold preference in the opposite sense, could not be confirmed in our model. 4. Therefore, our results suggest that, if there are pharmacological differences between GABAB autoreceptors and GABAB heteroreceptors on glutamatergic nerve endings in the rat cortex, they are not revealed by this series of compounds of widely different potencies. 5. In particular, our results with CGP 35348 and CGP 52432 do not support the hypothesis that GABAB autoreceptors and GABAB heteroreceptors on glutamatergic nerve endings represent subtypes with different pharmacology.

A role for computer simulation in solving the riddles of autoreceptor-mediated regulation of GABA release

The autoreceptor-mediated control of GABA release was simulated on a personal computer using commercially available software (STELLA/ITHINK). The experimental data to be matched were taken from previous publications. A basic model was able to fairly accurately reproduce frequency dependencies of GABA release in the presence and absence of uptake inhibition as well as concentration-response curves for changes in release produced by the agonist, (-)-baclofen, or by relatively low concentrations of the antagonists, phaclofen and CGP 35348. Obvious mismatch was observed at high concentrations of a potent antagonist, at a stimulation frequency of 2 Hz. Whereas the experimental data indicate a 3-fold increase in release as compared to controls, simulation predicts a 7-fold increase. By adaptation of the model, simulation data were obtained indicating that this mismatch was not due to (a) the autoreceptor occurring as two subtypes with different affinities for antagonists, (b) the occurrence of an agonist and antagonist state of the autoreceptor, with the latter prevailing at low synaptic concentrations of endogenous GABA, and (c) overruling of uptake inhibition by markedly elevated synaptic GABA concentrations. On the other hand, a simple restriction of the amount of transmitter able to be released per time unit produced much better matching data. A refined model assuming a restricted replacement capacity for exocytotically emptied synaptic vesicles at their docking sites gave similar results. As a consequence, we shall attempt to address this possibility experimentally. Simulation can never prove a case in the positive sense. It can, however, help to exclude ill-matching solutions of a problem and to prioritize among possible ones, which then must be experimentally addressed. We found simulation with this user-friendly software extraordinarily useful, also and not least because it necessitates and stimulates very intense dealing with a subject.

Autoreceptor-mediated regulation of GABA release: role of uptake inhibition and effects of novel GABAB antagonists

While the role of GABAB autoreceptors in the regulation of GABA release in synaptosomes and brain slices is well established, little is known about their role in vivo. Doubts have arisen because there is an apparent discrepancy between the frequencies at which GABA neurons fire and the frequency range within which autoreceptor regulation is observed in vitro. To see whether this apparent mismatch could be due to the use of a GABA uptake inhibitor in the release experiments in slices, we have compared the frequency dependencies of GABA release in the presence and absence of uptake inhibition. Before-hand, the previously incomplete frequency curve in the presence of uptake inhibition was extended at the lower end. To achieve this, stimulation was performed by means of groups of 4 pseudo-one-pulses (POP's) at inter-POP intervals corresponding to frequencies of 0.015625-0.5 Hz. It could be shown that activation of the GABAB autoreceptor by endogenously released GABA begins at a stimulation frequency as low as 0.0625 Hz. Experiments with the antagonist, CGP 35348, at inter-POP intervals of 1 min, at which the preceding POP has no longer an effect on GABA release during the next one, showed that basal release alone already substantially activated the autoreceptor. The frequency dependence in the absence as compared to the presence of uptake inhibition was shifted towards higher frequencies by a factor of 4. We do not consider this enough to remove our doubts about the in vivo operativity of GABAB autoreceptors.(ABSTRACT TRUNCATED AT 250 WORDS)

CGP 28014, a new inhibitor of cerebral catechol-O-methylation with a non-catechol structure

CGP 28014 (N-(2-pyridone-6-yl)-N',N'-di-n-propylformamidine) or its methanesulfonate salt CGP 28014 A was suspected to be a catechol-O-methyl-transferase (COMT) inhibitor because it was found to reduce the levels of homovanillic acid (HVA) and to increase those of 3,4-dihydroxyphenylacetic acid (DOPAC) in the rat striatum, after oral or intraperitoneal administration. These effects were maintained after repeated administration. The compound was only weakly active as a COMT inhibitor in vitro. However, its effect on striatal HVA and DOPAC was not prevented by pretreatment with the inhibitor of microsomal drug metabolizing enzymes in the liver, proadifen, indicating that, if CGP 28014 acts as a prodrug, its conversion to the active compound is not by oxidative metabolism in the liver. Also, there was no evidence that conversion to 2-amino-6-hydroxypyridine could explain its effects. The in vivo effect of CGP 28014 was substantiated in two additional in vivo test systems. Thus, it inhibited the accumulation of 3-methoxytyramine in the rat striatum after MAO inhibition by clorgyline, and the formation of O-methyl-DOPA from exogenously administered DOPA. It proved to be equipotent or nearly so with tropolone, and also showed a similar duration of action. Similar to tropolone, it increased S-adenosylmethionine levels in the striatum. Pyrogallol, on the other hand, decreased them, because being a substrate of COMT, it consumes methyl groups. This suggests that CGP 28014 does not inhibit COMT because it is a substrate of the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

Investigations on GABAB receptor-mediated autoinhibition of GABA release

In this study, we have investigated the effects of phaclofen on the [3H] overflow from [3H]GABA prelabelled rat cortical slices and its interaction with the effects of (-)-baclofen in dependence of the stimulation frequency. (-)-Baclofen strongly depressed the [3H] overflow in the frequency range of 0.125 to 4 Hz to a constant residual level (IC50 = 0.37 micromol/l at 0.125 Hz), but became inactive above. The potency of the (+)-enantiomer was considerably weaker by a factor of nearly 1000. The GABAB antagonist, phaclofen, increased [3H] overflow at 300 micromol/l and, more-markedly, at 3 and 1 mmol/l, respectively. However, the increase was virtually independent of the frequency between 0.125 and 16 Hz. If the compound interacted only with the putative GABAB autoreceptor involved in the regulation of GABA release, the extent of the enhancing effect should increase with increasing frequency because of the concomitant rise in synaptic GABA concentration. In order to further investigate this phenomenon, the IC50 of (-)-baclofen and antagonism of phaclofen against (-)-baclofen were determined at 0.125 Hz and 2 Hz, respectively. Whereas the IC50 of (-)-baclofen was 0.63 +/- 0.04 micromol/l at 0.125 Hz, it increased to 4.88 +/- 0.45 micromol/l at 2 Hz. The pA10-values of phaclofen were about the same at both frequencies, whereas the pA2-values differed by a factor of 2.3.(ABSTRACT TRUNCATED AT 250 WORDS)

Release of endogenous GABA from the substantia nigra is not controlled by GABA autoreceptors

The characteristics of the release of GABA from slices of the rat substantia nigra, elicited by electrical stimulation at frequencies of 0.5-48 Hz and by elevated K+ concentrations ranging from 15-35 mmol/l, was studied. Comparisons were made with cortical slices where the data were not available from previous studies. No GABA release could be evoked from rat nigral slices by electrical stimulation between 0.5 and 4 Hz, in contrast to cortical slices, in which this pool is sensitive towards inhibition by (-)-baclofen. Also, comparatively less GABA release could be evoked from nigral than from cortical slices by K+ concentrations between 15 and 25 mmol/l. While (-)-baclofen at 10 mumol/l inhibited release caused by 15 mumol/l K+ in cortical, it did not in nigral slices. GABA release caused by higher frequencies (8-48 Hz) or 30 mmol/l K+ concentrations was Ca2+-dependent and in the former case also tetrodotoxin-sensitive. It had similar characteristics as in cortical slices and was insensitive towards (-)-baclofen, muscimol and bicuculline. Even more markedly than in the cortex, 30 mmol/l K+ released greater amounts of GABA than electrical stimulation at 24 Hz of a similar duration, suggesting the existence of one or several additional pool(s) of lesser excitability.(ABSTRACT TRUNCATED AT 250 WORDS)

Ca2+-dependent release of endogenous GABA from rat cortical slices from different pools by different stimulation conditions

The previously reported inhibitory effect of (-)-baclofen on the electrically evoked release of endogenous GABA from rat brain slices indicated the possibility of existence of GABAB autoreceptors. In this study, we have tested an alternative explanation, i.e. the possibility that (-)-baclofen reduced an excitatory glutamatergic input to GABAergic neurons by inhibiting glutamate release, by investigating the interaction of 1 mmol/l L-glutamate with the inhibitory effect of 10 mumol/l (-)-baclofen. L-Glutamate did not affect the electrically evoked release of GABA on its own and did not abolish the effect of (-)-baclofen, suggesting that the latter was not secondary to a reduction of glutamate release. On the other hand, it greatly increased the basal release of GABA and more than doubled the GABA content of the slices at the end of the perfusion, indicating a marked enhancement of GABA synthesis. This additional GABA, apparently formed from exogenous L-glutamate, was not releasable by electrical stimulation at 0.5 or 24 Hz, but at least in part by stimulation with 30 mmol/l K+. The previously reported increase of GABA release at 12 Hz as compared to 4 Hz was studied in more detail. GABA released by electrical stimulation at 8-48 Hz was Ca2+-dependent and tetrodotoxin-sensitive. No evidence was obtained for a decrease of the amount of GABA released per impulse with increasing frequency in this range.(ABSTRACT TRUNCATED AT 250 WORDS)

Interactions of isamoltane (CGP 361A), an anxiolytic phenoxypropanolamine derivative, with 5-HT1 receptor subtypes in the rat brain

Isamoltane (CGP 361A; (1-(2-(1-pyrrolyl)-phenoxy)-3-isopropylamino-2-propanol hydrochloride), a beta-adrenoceptor ligand (IC50 = 8.4 nmol/l) which has reported activity as an anxiolytic in man was found to be a reasonably active inhibitor of the binding of [125I]ICYP to 5-HT1B recognition sites in rat brain membranes with 27-fold selectivity (IC50 = 39 nmol/l) as compared to the inhibition of binding of [3H]8-OH-DPAT to 5-HT1A receptors (IC50 = 1070 nmol/l). This selectivity was considerably greater than that observed for other beta-adrenoceptor ligands including propranolol (5-HT1A/5-HT1B ratio = 2), oxpenolol (3.5) and cyanopindolol (8.7). The 5-HT1B activity of the compound resided in the (-)-enantiomer. (-)-Isamoltane had weak activity (IC50 3-10 mumol/l) at 5-HT2 and alpha 1-adrenoceptors. The compound was devoid of activity at a number of other central neurotransmitter recognition sites including the 5-HT1C site. Isamoltane increased the electrically evoked release of [3H]5-HT from prelabeled rat cortical slices in a manner similar to that of cyanopindolol. While both compounds were similar in potency to methiothepin, they had lower efficacy. Oxprenolol was less potent that both isamoltane and cyanopindolol while propranolol was essentially inactive. The effects of the compounds on 5-HT release appeared to be correlated with their 5-HT1B rather than 5-HT1A activity. In vivo, isamoltane increased 5-HTP accumulation in rat cortex following central decarboxylase inhibition at doses of 1 and 3 mg/kg i.p. At higher doses this effect was gradually diminished. Similar, but less clearcut results were obtained with cyanopindolol and oxprenolol, but propranolol was ineffective. No changes in brain tryptophan levels were associated with the isamoltane-evoked changes in brain 5-HTP levels. In reserpinized animals, isamoltane reduced 5-HTP accumulation even at doses which enhanced accumulation of this metabolite when given alone. The effects of the putative 5-HT1B agonist, m-trifluoromethylphenylpiperazine (TFMPP), the mixed 5-HT autoreceptor agonist/antagonist/beta-adrenoceptor antagonist, pindolol, the 5-HT uptake inhibitor, CGP 6085A and the MAO-A inhibitor, brofaromine, were not antagonized by pretreatment with isamoltane. The possibility that isamoltane and the other beta-adrenoceptor antagonists are antagonists at 5-HT1B receptors and that their effect on 5-HT synthesis in vivo is the net result of their agonist/antagonist effects at 5-HT1A and 5-HT1B receptors is discussed in relation to the potential mechanism of the anxiolytic activity of isamoltane.

Potential involvement of a baclofen-sensitive autoreceptor in the modulation of the release of endogenous GABA from rat brain slices in vitro

The effects of the GABAA agonist, muscimol, and of the enantiomers of the GABAB agonist, baclofen, on the release of endogenous GABA from slices of the rat cerebral cortex, striatum and hippocampus were measured by means of a HPLC method with electrochemical detection. Moreover, the effect of the GABAA antagonist, bicuculline, and of the frequency of stimulation were studied in cortical slices. The amount of endogenous GABA released per impulse from cortical slices decreased by about 50% when the frequency was increased from 0.25 Hz to 1 Hz. This might indicate that GABA inhibited its own release (-)-Baclofen at 1 and 10 microM, but not its (+)-enantiomer, markedly inhibited the release of endogenous GABA, to a similar extent in all 3 areas investigated. The effect of (-)-baclofen was dependent on the frequency of stimulation: at lower frequencies (0.25 and 0.5 Hz) it was more marked than at a higher one (4 Hz). This would be expected from the results showing that the release of endogenous GABA decreases with increasing frequency, which suggests that this amino acid inhibits its own release. Muscimol at 10 microM, on the other hand, was ineffective in all 3 areas at a stimulation frequency of 0.5 Hz. Bicuculline (10 microM) at 4 Hz, at which autosuppression of GABA release is maximal did not enhance the release of endogenous GABA from cortical slices. With cerebellar or nigral slices, no adequate stimulation-induced release of endogenous GABA could be obtained under comparable conditions. These data are compatible with, but do not prove the existence of GABAB-type presynaptic autoreceptors modulating the release of this amino acid. More definite conclusions may possibly be drawn when a GABAB antagonist becomes available, which is expected to enhance GABA release under appropriate conditions.

The measurement of the release of endogenous GABA from rat brain slices by liquid chromatography with electrochemical detection

A method for the determination of GABA by derivatization with 2,4,6-trinitrobenzenesulphonic acid and subsequent separation and quantitation by HPLC with electrochemical detection was characterized with respect to specificity, reproducibility and sensitivity. No other amino acid occurring in significant amounts in the brain was found to interfere; however, adequate separation of the derivatives of GABA and tryptophan must be carefully checked in each experiment. The sensitivity of the method is essentially determined by baseline noise, which mainly depends on the quality of the HPLC pump; under our conditions, it was about 2 ng/ml analyte. The coefficients of variation determined at two different concentrations relevant for the subsequent experiments were well below 10%. The method proved useful for the assessment of endogenous release of GABA from superfused rat cortical slices by electrical stimulation, which, in contrast to the basal release, was found to be completely calcium-dependent at stimulation frequencies of 5 and 12 Hz, under our conditions. Both stimulated and basal release of GABA was enhanced 4-5-fold by the inhibitor of GABA uptake, SK&F 89976 (10 microM).

Ifoxetine, a compound with atypical effects on serotonin uptake

Ifoxetine (CGP 15210 G; (+/-)-bis-[cis-3-hydroxy-4-(2,3-dimethyl-phenoxy)]-piperidine sulfate) prevented the depletion of serotonin (5-HT) induced by H 75/12 and p-chloromethamphetamine in the rat brain, and that caused by endogenously released dopamine after the combined administration of haloperidol and amfonelic acid in the rat striatum. These effects are typically caused by compounds that inhibit 5-HT reuptake. Unexpectedly, ifoxetine only weakly inhibited the uptake of radiolabelled 5-HT into rat brain synaptosomes in vitro or ex vivo, the human thrombocytes in vitro or into rat thrombocytes after pretreatment. The following, among the possible explanations for this apparent discrepancy, were considered and regarded as unlikely: the involvement of an active metabolite; the possibility that ifoxetine accumulates in the brain to an extent sufficient to cause in vivo uptake inhibition; a pharmacokinetic interaction with the depleting agents. The possibility that the depletor tests give false positives was also considered. However, ifoxetine lowered brain 5-hydroxyindoleacetic acid and reduced the accumulation of 5-hydroxytryptophan after central decarboxylase inhibition. This suggests that it also interferes with 5-HT metabolism in the absence of depleting agents, which means that it interacts in some way with serotonergic transmission. Ifoxetine displayed weak or no interactions with 5-HT1, 5-HT2, alpha 1-, alpha 2- and beta-noradrenoceptors, histamine H1, muscarinic acetylcholine, opiate, GABA A, and benzodiazepine receptors in vitro, and with dopamine and 5-HT2 receptors in vivo. It did not antagonize the noradrenaline (NA) depletion induced by H 77/77 in rat brain and only weakly interfered with the uptake of i.v. injected radiolabelled NA into the rat heart. This suggests that its interaction with the 5-HT system is specific. Due to its atypical properties, among which the rather weak potentiation of the neurological effects of 5-hydroxytryptophan is also important, ifoxetine may exhibit a therapeutic and/or side-effect profile which differs from that of classical 5-HT uptake inhibitors.

CGP 4718 A, a new potential antidepressant with a dual mode of action

CGP 4718 A (4-[5-chloro-benzofuranyl-2-]-1-methylpiperidine HCl) was found to inhibit MAO A preferentially in vitro in a competitive manner. Assessment of its in vivo effects by an ex vivo approach showed it to be a relatively weak, reversible inhibitor of MAO A. There were also effects on MAO B but they were inferior by a factor of about 10. The onset of the inhibitory effects in rat liver and brain was rapid, being maximal in about 1 h following administration of CGP 4718 A p.o. The inhibition was of relatively short duration with the effects being undetectable 24 h after treatment. CGP 4718 A also inhibited the reuptake of serotonin (5-HT) in synaptosomes in vitro and ex vivo. Evidence for 5-HT uptake inhibition was also found by using the H 75/12 depletor model. Its in vitro and in vivo potency as a 5-HT uptake inhibitor was approximately the same as that of imipramine. The effects on MAO A and on 5-HT uptake occurred over a similar dose range (above 10 mg/kg p.o.) and also had a similar time course. No evidence for inhibitory effects on noradrenaline uptake was found in vivo.

Carbamazepine decreases catecholamine turnover in the rat brain

The anticonvulsant carbamazepine (100 mg/kg i.p.) increased the levels of 3-methoxy-4-hydroxyphenylglycol sulfate in the rat brain as well as its accumulation after inhibition of acid transport by probenecid. It did not interfere with 3-methoxy-4-hydroxyphenylglycol sulfation in vivo. However, this was not corroborated by the results of turnover studies. The depletion of brain norepinephrine after inhibition of tyrosine hydroxylase or dopamine (DA) beta-hydroxylase rather tended to be decreased and the accumulation of DA in the rat heart after DA beta-hydroxylase inhibition was diminished. Carbamazepine also reduced the depletion of striatal DA after tyrosine hydroxylase inhibition and the accumulation of striatal dopa after central decarboxylase inhibition, but did not affect the levels of the deaminated DA metabolites, homovanillic acid and 3,4-dihydroxyphenylacetic acid, even after pretreatment with probenecid. Therefore, carbamazepine seems to reduce catecholamine turnover in spite of its enhancing action on the firing of norepinephrine and DA neurons reported in the literature. These apparently paradoxical effects might be explained by an interference with the catecholamine storage mechanism. Two other anticonvulsants, diphenylhydantoin and phenobarbital, in doses approximately equieffective to that of carbamazepine with respect to their anticonvulsant action, showed similar although somewhat weaker effects on DA, but not on norepinephrine turnover. Within the catecholamine hypothesis of affective disorders, the reduction of catecholamine turnover by carbamazepine might explain the reported antimanic and antipsychotic effects in patients.

Negative feedback control of serotonin release in vivo: comparison of 5-hydroxyindolacetic acid levels measured by voltammetry in conscious rats and by biochemical techniques

All evidence that serotonin release from central neurones is controlled by a negative feedback mechanism comes from in vitro studies. To study this problem in vivo we performed differential pulse voltammetry in conscious rats, in which carbon fibre electrodes had been implanted 2-15 weeks previously. The effects of monoamine oxidase inhibition (which decreases the amount of 5-hydroxyindoleacetic acid), as well as that of probenecid (which increases 5-hydroxyindoleacetic acid), suggests that 5-hydroxyindoleacetic acid rather than serotonin is measured. Blockade of the presynaptic serotoninergic autoreceptors by methiothepin, metergoline or quipazine led to an increase in differential current of the peak attributed to 5-hydroxyindoleacetic acid in hippocampus, hypothalamus and striatum. Stimulation of these receptors by m-chlorophenylpiperazine, MK-212 or LSD decreased the signal attributed to 5-hydroxyindoleacetic acid. A decrease in the signal was also seen with cinanserin. Stimulation of presynaptic alpha 2-adrenoreceptors by clonidine decreased the signal. Metergoline, quipazine and cinanserin showed biphasic effects, and no effect was observed with methysergide. In general, a reasonable agreement with the results of Baumann & Waldmeier obtained in vitro with electrically stimulated [3H]serotonin prelabelled cortex slices was achieved with differential pulse voltammetry. Only partial agreement with the results of voltammetry was obtained if 5-hydroxyindoleacetic acid was determined biochemically under comparable conditions. Qualitatively, the effects observed with methiothepin, m-chlorophenylpiperazine, clonidine and LSD were in good agreement with those measured with voltammetry as well as with the in vitro effects obtained in electrically stimulated cortex slices. No, or only partial correlation with the results obtained with voltammetry was found with MK 212, cinanserin, metergoline and quipazine. It is concluded that voltammetry preferentially measures extraneuronal 5-hydroxyindoleacetic acid rather than overall changes of this metabolite.

Effects of CGP 11305 A, a new reversible and selective inhibitor of MAO A, on biogenic amine levels and metabolism in the rat brain

CGP 11305 A [4-(5-methoxy-7-bromo-benzofuranyl-2)piperidine HCl), a reversible, selective inhibitor of MAO A, increased the levels of rat brain noradrenaline, dopamine, and serotonin dose-dependently and to approximately the same extent. Concomitantly, it lowered the levels of their metabolites, MHPG-SO4, HVA, DOPAC, and 5-HIAA. When compared with the irreversible MAO A inhibitor clorgyline, the effects of CGP 11305 A were of much shorter duration. Moreover, the increases of noradrenaline and serotonin and the decreases of their metabolites MHPG-SO4 and 5-HIAA were smaller after CGP 11305 A than after clorgyline in equieffective doses for MAO A inhibition. CGP 11305 A decreased the synthesis of catecholamines and serotonin less markedly than clorgyline. This is probably due to the reversibility of the interaction of the compound with MAO A. In contrast to CGP 11305 A, clorgyline increased the level of dopamine less than those of noradrenaline and serotonin. This is explained by assuming that dopamine synthesis is particularly sensitive to end product inhibition. CGP 11305 A also exhibited some inhibitory properties on the uptake of serotonin and, to a lesser degree, of noradrenaline in vitro and in vivo. Compared with MAO inhibition, however, uptake inhibition required 30-100 times higher doses.

Feedback control of noradrenaline release as a function of noradrenaline concentration in the synaptic cleft in cortical slices of the rat

Cortical slices incubated with [3H]noradrenaline (NA) were used to study quantitatively the infelucne of the NA concentration in the synaptic cleft on electrically induced release of [3H]NA from adrenergic nerve terminals. Stimulation-induced [3H]-overflow was regarded to be proportional to the NA concentration in the synaptic cleft. High concentrations of piperoxan or clonidine were used to block, or maximally stimulate, respectively, the presynaptic alpha-receptors and thus to eliminate feedback control. These two extreme conditions were thought to delineate maximal feedback range. With alpha-receptors not artifically manipulated, [3H]overflow increased with stimulus intensity, yet not in proportion to the [3H]-overflow when the presynaptic alpha-receptors were blocked, demonstrating increasing feedback inhibition with increasing NA concentrations in the synaptic cleft. Feedback inhibition of NA release was shown to depend in an exponential fashion on NA concentration in the synaptic cleft. The slope of the regression line indicated that maximal inhibition of NA release occurred with NA concentrations in the synaptic cleft 65,000--700,000 times higher than threshold concentration. Data from experiments with different stimulus rates also supported the notion of feedback control of NA release.

Neurobiochemical aspects of maprotiline (Ludiomil) action

In the first part of the paper a short review of the neurobiochemical effects of the antidepressant drug maprotiline is given. Its most obvious effect is the inhibition of noradrenaline uptake in peripheral and central neurones. The peculiarity of this action consists in its high degree of selectivity, as no inhibition of serotonin uptake could be demonstrated in vivo. In the second part, the results of new experiments are described. These show that serotonin uptake is not diminished in rat mid-brain synaptosomes even after treatment with very high doses of maprotiline (600 mg/kg p.o.). In addition, the influence of the antidepressant on noradrenaline and serotnin uptake was studied in rat cerebral cortex, cerebellum, hypothalamus and pons-medulla. Dopamine and serotonin uptake were measured in the corpus striatum. Again, only the uptake of noradrenaline was found to be inhibited. There was not even a slight tendency towards inhibition of serotonin uptake. This high degree of selectivity distinguishes maprotiline from the tricyclic antidepressants and thus makes it an intersting 'extreme-type' uptake inhibitor.

Preliminary report of the M. D. Anderson Hospital/Texas A & M variable energy cyclotron fast-neutron therapy pilot study

The records of 248 patients treated with fast neutrons and of 102 comparable but nonrandomized control patients treated conventionally with photons, surgery, or combined surgery and photon irradiation were reviewed. Fast neutron therapy included treatment with neutrons alone, a neutron boost after photon therapy, or a schedule of alternating neutron and photon treatments (mixed beam). The results with mixed beam irradiation were superior to those obtained with the other neutron therapy techniques, and compared favorably with the results of standard treatment methods. However, the lack of a conclusive advantage for neutron therapy in this pilot study illustrates the need for on-going randomized clinical trials.

Selective inhibition of noradrenaline and serotonin uptake by C 49802-B-Ba and CGP 6085 A

The effects of two new compounds, 1-(1-methylamino-2-hydroxy-3-propyl)-dibenzo[b,e]bicyclo[2,2,2]octadiene-HCl (C 49802-B-Ba) and 4-(5,6-dimethyl-2-benzofuranyl) piperidine HCl (CGP 6085 A), on noradrenaline (NA) and serotonin (5-HT) uptake were investigated in different test systems, CGP 6085 A is a very potent and selective inhibitor of 5-HT uptake in rat brain (ED50 1-4 mg/kg p.o., depending on test system). Doses up to 1000 mg/kg p.o. did not inhibit NA uptake. C 49802-B-Ba is a potent and selective inhibitor of NA uptake in rat brain (ED50 5-10 mg/kg p.o. depending on test system) and heart (ED50 1.5 mg/kg p.o.). At 300 mg/kg p.o., this compound caused no inhibition of 5-HT uptake.

Metaraminol uptake by human thrombocytes: a poor model for neuronal noradrenaline uptake

The IC50 of a number of antidepressants and related drugs on the uptake of 1-metaraminol and serotonin into human thrombocytes, and of noradrenaline and serotonin into rat midbrain synaptosomes were compared. In accordance with previous reports, it was found that platelets provide a good model for the study of neuronal uptake of serotonin. Platelet uptake of 1-metaraminol, although correlated to some extent with noradrenaline uptake into synaptosomes, seems to be an unsatisfactory model for the neuronal uptake of the latter amine.

Achondroplasia: clinical radiologic features with comment on genetic implications

"I have been associated with the Little People of America, a national organization of dwarfs, for five years, and have been running a registry for bone dysplasias at the University of Minnesota for two years. On the basis of this experience, I know that many individuals with other conditions are given the diagnosis of achondroplasia and that the implications of this diagnosis are often not recognized, or at least not trans mitted to the patient. 1 believe it is safe to say that a number of teachers of pediatrics consider achondroplasia as a broad category rather than a specific condition. I think this is wrong for the reasons stated in the pa per. Also, it seems to me, if this idea is abandoned more of an effort may be made to find out about conditions which are now considered 'atypical achondroplasia.'" —From the submission letter by the author.