Effects of short-term fasting in male Sprague-Dawley rats

Fasting is a common procedure for animals in experiments. Although fasting may be necessary for scientific reasons, it should be minimized. In the current study, jugular-catheterized male Sprague-Dawley rats in metabolism cages were fasted for 0 to 24 h before measurement of various physiologic markers (serum chemistry, CBC analysis, serum corticosterone). When controlled for cohort, rats fasted for 6 and 16 h had significantly lower serum glucose than did nonfasted rats. Other values did not differ from controls. Only rats fasted for 24 h had elevated serum corticosterone levels. Therefore, fasting for as long as 16 h has fewer effects on rats that does fasting for 24 h. Fasting for 24 h or more therefore should receive appropriate consideration by both scientists and the IACUC in the experimental design and the animal-use protocol.

A blood sampling microsystem for pharmacokinetic applications: design, fabrication, and initial results

This paper describes a microsystem for automated blood sampling from laboratory mice used in pharmacokinetic studies. Intended to be mounted as a "backpack" on a mouse, it uses a microneedle, reservoir, and an actuator to instantaneously prick the animal for a time-point sample, eliminating the need for a tethered catheter with large dead volume. The blood is collected by capillary effect through a 31-33 gauge microneedle (250-210 microm OD) into a approximately 1 microL micromachined steel reservoir. The voice coil actuator provides a peak force of approximately 300 mN, which amply exceeds the measured piercing force of mouse skin (i.e., 60-85 mN for a 31-gauge needle with 12 degrees bevel). The sampling system was tested in vitro using a mock vessel with adjustable pressure; the reservoir was filled in <0.15 s by a combination of the capillary effect and blood pressure. The system may also be used to sample interstitial fluid, but the absence of blood pressure makes it necessary to enhance the capillary effect of the needle. This is accomplished by either electropolishing the inner surface to make it more hydrophilic or using a polymer wire insert to increase the surface area. The steel surface of the reservoir is also coated with silicon oxynitride by plasma-enhanced chemical vapor deposition to improve its hydrophilicity. Blood from fresh bovine tissue was collected into the reservoir to simulate interstitial fluid sampling. In vivo tests on live, anesthetized mice resulted in successful collection of blood into the reservoir. The possible integration of the device in microanalytical systems and the device scalability for multisampling are discussed.

The therapeutic potential of novel anticoagulants

Conventional anticoagulant therapy has been based on indirect inhibition of coagulation factors with heparin and warfarin. These agents display liabilities prompting the development of new anticoagulants over the last two decades. The first to be developed was a series of low molecular weight heparins(LMWHs). Their favourable pharmacokinetic profiles and risk/benefit ratios led to widespread use in Europe and, more recently, approval for their use in the USA. Paralleling the development of LMWHs has been the pursuit of a different strategy focused on direct rather than indirect inhibition of enzymes in the coagulation cascade. In contrast to heparin, LMWHs, or other glycosaminoglycans, direct inhibitors exert their effects independent of either antithrombin III (ATIII) or heparin cofactor II (HCII) and more effectively inhibit clot-bound thrombin or FXa. Highly potent, selective (versus other serine proteases)direct thrombin and FXa inhibitors have been identified and isolated from natural sources, such as leeches, ticks and hookworms. The recombinant forms and analogues of the senatural proteins have been produced using molecular biology techniques, i.e., rHirudin, Hirulogs, recombinant tick anticoagulant peptide (rTAP), recombinant antistasin (rATS) and recombinant nematode anticoagulant peptide-5 (rNAP-5). The design of novel structures or the modification of existing chemicals has led to the synthesis of many non-peptide, low molecular weight inhibitors of thrombin and FXa. Some of them are orally active and may be suitable for long-term clinical use. In addition, considerable progress has been made in developing specific TF/VIIa complex inhibitors. The anticoagulation properties of the new agents are being characterised in experimental studies. Some of them have been advanced to large scale clinical trials and their effectiveness, and sometimes relative ineffectiveness,in arterial and venous thromboembolic disorders has been demonstrated. They are being tested for their potential as new antithrombotic agents that act via direct enzyme inhibition. Thus,the clinician should in future be able to target different thrombotic conditions with proven, specific anticoagulant interventions.

Fluorescence detection of plant extracts that affect neuronal voltage-gated Ca2+ channels

Structurally novel compounds able to block voltage-gated Ca2+ channels (VGCCs) are currently being sought for the development of new drugs directed at neurological disorders. Fluorescence techniques have recently been developed to facilitate the analysis of VGCC blockers in a multi-well format. By utilising the small cell lung carcinoma cell line, NCI-H146, we were able to detect changes in intracellular Ca2+ concentration ([Ca2+](i)) using a fluorescence microplate reader. NCI-H146 cells have characteristics resembling those of neuronal cells and express multiple VGCC subtypes, including those of the L-, N- and P-type. We found that K+-depolarisation of fluo-3 loaded NCI-H146 cells causes a rapid and transient increase in fluorescence, which was readily detected in a 96-well plate. Extracts of Australian plants, including those used traditionally as headache or pain treatments, were tested in this study to identify those affecting Ca2+ influx following membrane depolarisation of NCI-H146 cells. We found that E. bignoniiflora, A. symphyocarpa and E. vespertilio caused dose-dependent inhibition of K+-depolarised Ca2+ influx, with IC(50) values calculated to be 234, 548 and 209 microg/ml, respectively. This data suggests an effect of these extracts on the function of VGCCs in these cells. Furthermore, we found similar effects using a fluorescence laser imaging plate reader (FLIPR) that allows simultaneous measurement of real-time fluorescence in a multi-well plate. Our results indicate that the dichloromethane extract of E. bignoniiflora and the methanolic extract of E. vespertilio show considerable promise as antagonists of neuronal VGCCs. Further analysis is required to characterise the function of the bioactive constituents in these extracts and determine their selectivity on VGCC subtypes.

Prostate brachytherapy: comparison of dose distribution with different 125I source designs

PURPOSE

To evaluate the interchangeability of various commercially available iodine 125 ((125)I) sources and to assess the dosimetric effect of a change in source.

MATERIALS AND METHODS

A modified peripherally loading prostate brachytherapy plan to deliver 145 Gy was devised by using a model (125)I source, which until recently was the only available (125)I source. A dose-volume histogram was generated. By using the available radial dose functions and anisotropy distributions for eight other currently commercially available sources, the same implant placement was planned and dose-volume histogram distributions tabulated. This exercise was performed for 15-, 45-, and 60-cm(3) glands. No implants were placed, and no physical radiation measurements were made. Dose calculations were theoretic: They were generated by using a widely available treatment planning system.

RESULTS

There was little difference in dose distribution to the volume receiving 100% of the prescribed dose (<6%); only one source showed a difference greater than 2%. Large differences, up to -40% to +60%, were seen in the volume of tissue encompassed within internal high-dose regions receiving 150% or 200% of the prescribed dose. These findings held true, irrespective of gland size, within a clinically relevant range (15-60 cm(3)) and for a uniformly loaded radionuclide distribution.

CONCLUSION

Reviewing only peripheral dose at or near the prescription dose of 145 Gy revealed little difference in doses for various source designs. Marked differences in high-dose regions were seen and may affect the dose received by internal sites. Effects of these changes on cure and/or complications remain speculative.

Modulation of in vitro platelet 5-HT release by species of Erythrina and Cymbopogon

Extracts of Australian plants were screened to detect constituents affecting adenosine di-phosphate (ADP) induced platelet aggregation and [14C]5-hydroxytryptamine (5-HT) release. Extracts of four tested plants including, Eremophila gilesii, Erythrina vespertilio, Cymbopogon ambiguus, and Santalum acuminatum, were found to cause significant inhibition of platelet 5-HT release. Inhibition levels ranged from 56-98%, and was not due to the non-specific effects of protein binding tannins. These extracts, and those we have previously identified as being active, were examined further to determine if they affect epinephrine (EPN), arachidonic acid (A.A) or collagen stimulated platelet aggregation and 5-HT release. Among those extracts investigated, we found that both the methanolic extract of E. vespertilio and the dichloromethane (DCM) extract of C. ambiguus were most potent and caused significant inhibition of platelet activation induced by EPN, A.A and to a lesser extent by collagen. Inhibition of ADP induced platelet 5-HT release by both of these extracts, was dose-dependent, with IC50 values for E. vespertilio and C. ambiguus estimated to be 20.4 microl (1.855 mg/ml) and 8.34 microl (0.758 mg/ml), respectively. Overall, C. ambiguus exhibited most activity and also caused dose-dependent inhibition of A.A induced platelet activation. These results indicate that inhibition may occur specifically at a site within the A.A pathway, and suggest the presence of a cyclo-oxygenase inhibitor. Both E. vespertilio and C. ambiguus are reported to be traditional headache treatments, with the present study providing evidence that they affect 5-HT release.

Antithrombotic effect of LB-30057 (CI-1028), a new synthetic thrombin inhibitor, in a rabbit model of thrombosis: comparison with inogatran

LB-30057 (CI-1028) is a novel, orally bioavailable, direct thrombin inhibitor with a Ki of 0.38 nM against human thrombin. The effects of LB-30057 on thrombus formation and hemostasis were evaluated in a veno-venous shunt model of thrombosis in rabbits, and compared with inogatran, another direct inhibitor of thrombin. Each compound was studied at 5 or 6 different doses with 5 or 6 rabbits in each group. After administration as a bolus i.v. injection followed by continuous infusion, both LB-30057 and inogatran dose-dependently inhibited thrombus formation, which was measured as an increase in time to occlusion (TTO) and a decrease in thrombus weight. Both compounds also improved vena caval blood flow and reduced the overall incidence of thrombotic occlusion. LB-30057 significantly prolonged TTO from 23 +/- 4 min (before dose) to 110 +/- 10 min at the highest dose (0.7 mg/kg + 47 microg/kg/min) (p < 0.001), and reduced thrombus weight from 57 +/- 2 mg to 15 +/- 5 mg (p < 0.001). Occlusive thrombus formed in only one of six rabbits that received the highest dose of LB-30057 (vs. 13/13 in the control group, p < 0.01). At the dose that produced the maximum antithrombotic effect (0.7 mg/kg + 47 microg/kg/min), LB-30057 increased aPTT and bleeding time approximately 2-and 2.5-fold above baseline, respectively. On a gravimetric basis, LB-30057 and inogatran displayed comparable in vivo antithrombotic efficacy. When compared to equally effective anti thrombotic doses of inogatran, LB-30057 caused less prolongation in aPTT, had no effect on PT, and tended to have less of effect on bleeding time. These results indicate that LB-30057 is an effective antithrombotic compound and it appears to have a better benefit/risk profile than inogatran in this experimental model.

Inhibition of platelet aggregation and 5-HT release by extracts of Australian plants used traditionally as headache treatments

To identify potential migraine therapeutics, extracts of eighteen plants were screened to detect plant constituents affecting ADP induced platelet aggregation and [14C]5-hydroxytryptamine (5-HT) release. Extracts of the seven plants exhibiting significant inhibition of platelet function were reanalysed in the presence of polyvinyl pyrrolidone (PVP) to remove polyphenolic tannins that precipitate proteins. Two of these extracts no longer exhibited inhibition of platelet activity after removal of tannins. However, extracts of Crataegus monogyna, Ipomoea pes-caprae, Eremophila freelingii, Eremophila longifolia, and Asteromyrtus symphyocarpa still potently inhibited ADP induced human platelet [14C]5-HT release in vitro, with levels ranging from 62 to 95% inhibition. I. pes-caprae, and C. monogyna also caused significant inhibition of ADP induced platelet aggregation. All of these plants have been previously used as traditional headache treatments, except for C. monogyna which is used primarily for protective effects on the cardiovascular system. Further studies elucidating the compounds that are responsible for these anti-platelet effects are needed to determine their exact mechanism of action.

Effects of a factor Xa inhibitor, DX-9065a, in a novel rabbit model of venous thrombosis

The objective of this study was to evaluate the effects of DX-9065a, a nonpeptide, direct inhibitor of factor Xa (FXa), in a novel experimental model of venous thrombosis. The experiments were conducted on anesthetized rabbits in which a veno-venous shunt with cotton threads was inserted into the vena cava. DX-9065a was administered intravenously to the rabbits as an initial bolus followed by a maintenance infusion using the following dosing schedules: DX-I: 0.25 mg/kg + 3 micrograms/kg/min.; DX-II: 0.75 mg/kg + 9 micrograms/kg/min.; DX-III: 1.5 mg/kg + 18 micrograms/kg/min.; DX-IV: 3.0 mg/kg + 36 micrograms/kg/min.; DX-V: 6.0 mg/kg + 72 micrograms/kg/min. DX-9065a induced a dose-dependent increase in the time to occlusion and a dose-dependent decrease in thrombus weight. Because of the unique character of the model, we were also able to show a dose-dependent increase in blood flow through the shunt. In addition, there were dose-dependent increases in prothrombin time (PT) and activated coagulation time (ACT) with more variable responses in the activated partial thromboplastin time (APTT). DX-9065a had little effect on thrombin time (TT) or bleeding time at all doses tested. In conclusion, dose-dependent antithrombotic efficacy was documented with DX-9065a in this new model of venous thrombosis. Although the in vivo potency of the compound was not striking, the results support the utility of FXa inhibition in venous thrombosis and demonstrate the utility of this experimental model for evaluating the efficacy of novel anticoagulants.

Modulation of Bcl-2 expression: a potential component of estrogen protection in NT2 neurons

Neuroprotective effects of estrogen have been demonstrated against a variety of cytotoxic insults. We present data here addressing a possible mechanism of estrogen neuroprotection in the human teratocarcinoma cell line NT2 terminally differentiated to a neuronal phenotype. Cell death induced by H2O2 or glutamate results in a dose-dependent cell death of NT2 neurons, while 24 h of estrogen pretreatment significantly enhances neuronal viability. Bcl-2 expression has been shown to reduce oxidative stress and prevent cell death. In NT2 neurons, Bcl-2 levels are dramatically elevated upon differentiation and are further enhanced with estrogen treatment. These results suggest that neuroprotective effects of estrogen may be related to increases in Bcl-2 expression.

A novel model of venous thrombosis in the vena cava of rabbits

The objective of this study was to develop and validate a new experimental model of venous thrombosis in the rabbit. A 3-cm length of siliconized PE tubing was used as a veno-venous shunt inserted into the abdominal vena cava of anesthetized rabbits. The PE tubing contained six cotton threads which helped to restrict blood flow through the tubing and served as a foreign, thrombogenic surface upon which a thrombus could develop. By continuously measuring blood flow through the vena cava, the rate of thrombus development can be monitored until zero flow is achieved indicating that a completely occlusive thrombus is present. The shunt can be removed making it possible to weigh the thrombus and/or determine its composition. A second shunt can be placed in the vena cava to make a second determination of time to occlusion and thrombus weight, using the data from the first shunt as an internal control standard for comparison. Reproducibility of the technique was demonstrated in a control group (n = 7) in which two successive shunts were used without an antithrombotic intervention. In studies with the first and second shunts, time to occlusion averaged 20.6+/-5.2 min and 20.2+/-5.7 min (pNS), respectively. The net thrombus weights (less the wet weight of the cotton threads) were 49.0+/-3.5 mg and 47.0+/-3.3 mg (pNS). Histologic examination of the thrombi indicated that they were largely composed of fibrin and red blood cells, consistent with the characteristics of venous thrombi. The low molecular weight heparin (LMWH) enoxaparin was used as an antithrombotic intervention to validate the model. Dose-dependent changes in time to occlusion and thrombus weight were achieved which paralleled alterations in coagulation parameters (thrombin time and activated partial thromboplastin time) and bleeding time determined with an ear bleeding technique. The veno-venous shunt model is easy to use, reproducible, and responds appropriately to an antithrombotic intervention, indicating that it should be useful for experimental evaluation of antithrombotic agents designed for venous thromboembolic disorders.

Squamous cell carcinoma of the midventral abdominal pad in three gerbils

Squamous cell carcinoma of the midventral abdominal pad was diagnosed in 3 male gerbils. Two of the gerbils had raised, ulcerated masses on the midventral portion of the abdomen. The first gerbil was 2 years old, and an excisional biopsy was performed. The gerbil survived 23 months after surgery without evidence of metastasis or clinical signs of local recurrence. At necropsy, neoplastic squamous cells were seen on histologic examination of the surgery site. The second gerbil was 4 years old, and surgical excision of the tumor with concurrent castration was curative. The third gerbil was moribund on admission, perhaps because ulceration of the tumor may have allowed bacteria to invade the tissue, resulting in septicemia and disseminated intravascular coagulation. These gerbils illustrated that hematologic, radiographic, and biochemical testing in rodents can be useful and that excision of squamous cell carcinoma tumors of the midventral abdominal pad of gerbils can be an effective treatment.

Estrogen protects primary cortical neurons from glutamate toxicity

The gonadal steroid estrogen has been shown to affect neuronal growth, differentiation and survival. We examined the ability of estrogen to protect primary cortical neurons from toxicity induced by the excitatory neurotransmitter glutamate. In these experiments, a 24-h pretreatment with 15 and 50 nM 17 beta-estradiol significantly reduced cellular lactate dehydrogenase (LDH) release from primary cortical neurons, indicating that neurons treated with 17 beta-estradiol were protected from a toxic glutamate exposure. Pretreatment with related steroids such as progesterone, dihydrotestosterone, dexamethasone or cholesterol did not significantly decrease LDH release. The anti-estrogen tamoxifen blocked the protective effects of 17 beta-estradiol suggesting that a classical steroid hormone receptor may be involved in the mechanism subserving estrogen neuroprotection during glutamate toxicity.

Effect of beta agonists on protein turnover in isolated chick skeletal and atrial muscle

Various beta-adrenergic agonists were found to inhibit rates of protein degradation and net protein breakdown in isolated chick extensor digitorum communis (EDC) and atrial muscles. Rates of protein synthesis were not altered by these compounds. The beta-agonist cimaterol inhibited rates of protein degradation in EDC muscles incubated with or without amino acids and insulin. Cimaterol also inhibited the increased proteolysis induced by injury to muscle or by incubating muscles at body temperature (42 degrees C) versus 37 degrees C. Thus, beta-agonists may help promote skeletal muscle accretion in vivo even under conditions of severe negative nitrogen balance by slowing muscle proteolysis.

K(+)-stimulated amino acid release from cultured cerebellar neurons: comparison of static and dynamic stimulation paradigms

The release of several endogenous amino acids and adenosine from rat cerebellar neuronal cultures following elevated K+ exposure in the presence and absence of added Ca2+ was studied. The amino acids aspartate (ASP), glutamate (GLU) and GABA were released from the cultures in a dose- and Ca(2+)-dependent manner. Taurine (TAU) and the nucleoside adenosine (ADN) efflux rates were dose-dependent but Ca(2+)-independent, and basal levels increased in the absence of Ca2+. The K+ depolarization induced release of serine (SER), alanine (ALA) and proline (PRO), was not dose-dependent and in the absence of extracellular Ca2+ (with added Mg2+) higher basal release of SER and ALA, but not PRO, was noted. These findings demonstrate that in addition to known cerebellar neurotransmitters, other neuroactive and neutral amino acids are released from cultured cerebellar neurons in response to K+ depolarization. Their observed efflux suggests they may have as yet unidentified roles in neuronal function with different classes of efflux corresponding to: neurotransmitter-type release (ASP, GLU, GABA), an osmoregulatory, possibly neuromodulatory-type release (TAU), a Ca(2+)-insensitive, possibly neuromodulatory-type release (ADN), and a depolarization-sensitive release (SER, ALA, PRO) of which SER and ALA are partially Ca(2+)-sensitive.

Effect of beta agonists on protein turnover in adipose tissue

Chronic administration (21 days) of the beta agonist cimaterol to rats decreased epididymal fat by 27%, and inhibited in vitro rates of protein synthesis by 34% and net protein breakdown by 71% in adipose tissue. Likewise, incubation of rat adipose tissue with cimaterol and isoproterenol stimulated lipolysis, and inhibited protein synthesis and degradation. Thus, in addition to affecting muscle mass and lipid metabolism, beta agonists appear to slow rates of protein turnover in adipose tissue.

The synthesis of 3-phosphonoalanine, phosphonopyruvic acid and phosphonolactic acid. Scission of the C-P bond during diazotization of phosphonoalanine

3-Phosphonoalanine has been made by the Strecker synthesis from phosphonoacetaldehyde, which is easily prepared from vinyl acetate. It gives phosphonopyruvate by transamination when treated with glyoxylate. Phosphonolactate, an analogue of phosphoglycerate, is prepared by reducing phosphonopyruvate. Diazotization of phosphonoalanine was investigated as a route for making phosphonolactate: addition of NaNO2 to the isoelectric form of phosphonoalanine gave much scission of the C-P bond with release of phosphate; addition of HBr prevented this release and gave largely the bromo acid. The supplement reports the synthesis of arsonolactate, a similar analogue, by treating chlorolactate with alkaline arsenite.

Glutamate receptor agonists cause efflux of endogenous neuroactive amino acids from cerebellar neurons in culture

Cultured neurons from rat cerebellum were used to examine the effects of glutamate receptor agonists on the release of endogenous amino acids and adenosine. Kainic acid exposure resulted in the release of glutamate, taurine, GABA and alanine in a dose- and calcium-dependent manner. Stimulation with quisqualic acid resulted in the dose- and calcium-dependent release of GABA. N-Methyl aspartic acid did not elicit the release of any neuroactive amino acids. These findings suggest that N-methyl aspartate receptors are not coupled to transmitter release in these cultures, and that kainate and quisqualate receptors may have different neuronal distributions.

Stimulus-coupled taurine efflux from cerebellar neuronal cultures: on the roles of Ca++ and Na+

Primary cultures of cerebellar neurons obtained from 7-9-day-old rats and grown 7-9 days in vitro (DIV) were used to study the effects of Na+ and Ca++ on K+-evoked taurine release. These cultures, made up largely of granule neurons (90%) and inhibitory interneurons (5-7%), produced a dose-dependent, depolarization-evoked taurine release that was Ca++-dependent at 40 mM K+, and Ca++-independent at K+ concentrations above 40 mM. The dihydropyridine Ca++ channel agonist BAY K 8644 (1 microM) augmented 30 mM K+-evoked release, while the antagonist nifedipine (5 microM) abolished both the BAY K 8644- and K+-enhanced release. Depolarization with the Na+ channel agonist veratridine (50 microM) stimulated taurine efflux, which was completely blocked by pretreatment with tetrodotoxin (2 microM). However, 50 mM K+-evoked taurine release was not affected by tetrodotoxin pretreatment. Substitution of choline Cl for NaCl partially antagonized 50 mM K+-evoked release, and by itself, the Na+ ionophore monensin (50 microM) stimulated release. These results suggest that both K+-evoked and basal taurine release from primary cerebellar neuronal cultures are sensitive to the levels of both intracellular and extracellular Na+ and Ca++. In contrast to previous findings using cerebellar astrocytes, neuronal L-type Ca++ channels, but not voltage-dependent Na+ channels, also appear to be necessary. The implications of these results on taurine's status as a putative neurotransmitter are discussed.

K+-evoked taurine efflux from cerebellar astrocytes: on the roles of Ca2+ and Na+

The ionic requirements for K+-evoked efflux of endogenous taurine from primary cerebellar astrocyte cultures were studied. The Ca2+ ionophore A23187 evoked taurine efflux in a dose-dependent fashion with a time-course identical to that of K+-induced efflux. The Ca2+-channel antagonist nifedipine had no effect upon efflux induced by 10 or 50 mM K+. In addition, verapamil did not antagonize 50 mM K+-evoked efflux except at high, non-pharmacological concentrations (greater than 100 microM), and preincubation with 2 microM omega-conotoxin had no effect on 50 mM K+-evoked efflux. Similarly, preincubation with 1 mM ouabain had no effect on the amount of taurine released by K+ stimulation, but did accelerate the onset of efflux by 2-4 min. Although 2 microM tetrodotoxin had no effect on K+-evoked release, replacing Na+ with choline abolished the taurine efflux seen in response to K+ stimulation. Together, these findings suggest that neuronal N- and L-type Ca2+- and voltage-dependent Na+-channels are not involved in the influx of Ca2+ which appears to be necessary for K+-evoked taurine efflux, and that in addition to Ca2+, extracellular Na+ is also required.

Dose-dependent, K+-stimulated efflux of endogenous taurine from primary astrocyte cultures is Ca2+-dependent

The K+-stimulated efflux of endogenous taurine from primary rat cerebellar astrocyte cultures prepared from 7-9-day-old rats was studied at 16-18 days in vitro using HPLC analysis. Taurine efflux was dose-dependent at K+ concentrations between 10 mM and 80 mM, with an EC50 of approximately 50 mM. Maximum stimulation of efflux above basal levels ranged from 56% at 10 mM K+ (204 pmol/min/mg protein) to 470% at 80 mM K+ (960 pmol/min/mg protein). Removal of Ca2+ from the buffer and the addition of either 1 mM EGTA or 10 mM Mg2+ abolished K+-stimulated efflux. Taurine efflux peaked and fell in parallel with the K+ concentration, but with an approximate lag of 3-5 min. The time course and amount of preloaded [3H]taurine released did not differ significantly from that seen for endogenous efflux. Basal taurine efflux varied inversely with the extracellular concentration of Ca2+ over the concentration range 0-5.0 mM. The observed Ca2+ dependence is consistent with a role for Ca2+ in the regulation of taurine release. Furthermore, taurine release from astrocytes in response to elevated K+ may reflect a neuromodulatory role for this amino acid in the CNS.

Rational use of sedative/hypnotics

Among medications targeted at the central nervous system, sedative/hypnotics are the most widely prescribed. The use of sedative/hypnotics is reviewed in the context of historical influences on prescribing practice and from a current neuroscience perspective. Recommendations are made regarding appropriate applications for these drugs, and the principles for choosing one drug over another are emphasized.

HPLC analysis of putative amino acid neurotransmitters released from primary cerebellar cultures

An HPLC method is described that measures amino acids (putative neurotransmitters and/or neuromodulators) released from primary, dissociated cerebellar cells maintained in monolayer culture. Precolumn derivatization with phenylisothiocyanate, followed by reverse phase chromatography with UV detection was used to quantitate the phenylcarbamyl amino acid derivatives in a chemically defined medium. Quantitation was linear, reproducible and sensitive to one picomole. This method is useful for the measurement of putative neurotransmitters GABA, glutamate, aspartate, taurine and adenosine, and can easily be modified to analyze other amino acids in physiological samples.

Possible role of glutathione in the antitumor effect of a copper-containing synthetic superoxide dismutase in mice

The effect of glutathione and a glutathione reductase inhibitor on the antitumor effect of Cu(II)(3,5-diisopropylsalicylate)2 (CuDIPS) was studied. CuDIPS is a low-molecular-weight copper coordination compound that exhibits superoxide dismutase-like activity. CuDIPS had antitumor activity against intraperitoneal Ehrlich ascites carcinoma in Swiss mice. A single ip injection of glutathione partially eliminated the antitumor effect of CuDIPS, whereas a single ip injection of 1,3-bis(2-chloroethyl)-1-nitrosourea enhanced the antitumor effect of CuDIPS. These results are consistent with the hypothesis that CuDIPS exerts part of its antitumor effect by producing H2O2.

Benign X-linked myopathy with acanthocytes (McLeod syndrome). Its relationship to X-linked muscular dystrophy

Two healthy men with McLeod syndrome, a rare X-linked recessive phenotype characterized by acanthocytosis and weakened red blood cell antigenicity in the Kell blood group system, have been investigated. Both men showed raised blood creatine kinase levels, with myopathic EMG abnormalities. Biopsies of the quadriceps muscle showed the features of an active myopathy although there was no clinical evidence of muscular abnormality. The combination of the association of membrane abnormalities in red blood cells and a myopathy in both McLeod phenotype and Duchenne muscular dystrophy suggests that these syndromes may be due to related genetic abnormalities. The genetic locus for McLeod phenotype is situated near the end of the short arm of the X chromosome. The locus for Duchenne muscular dystrophy is unknown but it has been postulated that it is also situated on the short arm of the X chromosome at Xp 21. The occurrence of a subclinical X-linked myopathy with acanthocytosis (McLeod phenotype) thus raises the possibility of a new approach to genetic investigations in Duchenne muscular dystrophy, and in the related milder forms of this disease.

The effect of weight loss and weight maintenance on high density lipoprotein cholesterol and selected tissue cholesterol levels in lean and obese Zucker rats

Obese and lean Zucker rats were studied to compare the effects of a 6-week weight loss regimen (period 1) and a subsequent 4-week weight maintenance period (period 2) on high density lipoprotein (HDL2, d = 1.063-1.125 g/ml) cholesterol, plasma, adipose tissue, liver, and total body cholesterol. The effects of weight loss were compared with animals not subjected to weight reduction (control, period O). Weight loss was achieved by reducing food intake below maintenance levels. Plasma cholesterol did not change significantly among the three periods in obese and lean rats. HDL2 cholesterol was higher (P less than 0.05) in obese and lean rats at period 2 compared with the other periods. Adipose tissue cholesterol (per cell) did not differ among the three periods in obese and lean rats. Liver cholesterol (milligrams/gram liver) decreased significantly (P less than 0.05) at period 1 and sustained this level at period 2 in lean rats, whereas liver cholesterol was unchanged among the three periods in obese rats. Carcass cholesterol (milligrams/gram carcass) in obese rats increased significantly (P less than 0.05) after period 1 and sustained this level after period 2. Carcass cholesterol concentration was unchanged in lean rats. These data suggest that consideration must be given to homeostatic mechanisms of carcass and liver cholesterol concentrations in studies examining changes in plasma HDL2 cholesterol levels.

Prevalence of antichlamydial antibody in London blood donors

The prevalence of type-specific antichlamydial antibody in a population of blood donors in London was studied using a microimmunofluorescence test. Twenty-six (17%) of 150 women and 38 (26%) of 150 men had antichlamydial antibody (IgG at greater than or equal to 1/16 or IgM greater than or equal to 1/8 or both). Of these, five (3%) women had one (0.75%) man had this antibody directed against Chlamydia trachomatis serotypes D-K, responsible for genital infections, and one man had antibody to Chlamydia psittaci agents. The remaining 57 men and women had antibody against an atypical chlamydial isolate designated Chlamydia IOL-207, which is iodine-negative and serologically distinct from both C trachomatis and C psittaci. The nature and location of infection by this agent are obscure. The results of this study suggest that the prevalence of sexually transmitted infection with C trachomatis serotypes D-K in a normal adult population in London is very low.