Triterpene saponins from Aster yunnanensis

Four new triterpene saponins, asteryunnanosides A, B, C and D, have been isolated from Aster yunnanensis and their structures deduced as 2 alpha,3 beta,23-trihydroxyolean-12-en-28-oic acid-28-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranoside, 2 alpha,3 beta,23-trihydroxyolean-12-en-28-oic acid-28-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranoside, 2 alpha,3 beta-dihydroxyolean-12-en-28-oic acid-28-O-alpha-L-rhamnopyranosyl-(1-->2)-beta-D-glucopyranoside and 2 alpha,3 beta-dihydroxyolean-12-en-28-oic acid-28-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucopyranoside, respectively, by means of spectral and chemical data.

Triterpenoid saponins from Aster batangensis

Four novel triterpenoid saponins named asterbatanoside F, G, H and I were isolated from the roots of Aster batangensis and their structures elucidated as 3-O-beta-D-glucopyranosyl-23-O-acetyl-bayogenin-28-O-beta-D-glu cop yranosyl- (1-->6)-[alpha-L-rhamnopyranosyl-(1-->2)]-beta-D-glucopyranoside, 3-O-beta-D-glucopyranosyl-bayogenin-28-O-beta-D-glucopyranosyl-(1- ->6)-[alpha-f1p4amnopyranosyl-(1-->2)]-beta-D-glucopyranoside, 3-O-beta-D-glucopyranosyl- (1-->3)-beta-D-glucopyranosyl-bayogenin-28-O-beta-D-glucopyranosyl -(1-->6)-beta-D-glucopyranoside, and 3-O-beta-D-glucopyranosyl-(1-->3)-beta-D- glucopyranosyl-23-O-acetyl-bayogenin-28-O-beta-D-glucopyranosyl-(1 -->6)-beta-D- glucopyranoside by means of spectral data, especially NMR including COSY, HETCOR, COLOC, HOHAHA, ROESY and selective INEPT techniques, and chemical evidence.

Receptor-mediated calcium signals in astroglia: multiple receptors, common stores and all-or-nothing responses

Calcium signals following activation of P2Y purinergic, alpha 1 adrenergic, and muscarinic cholinergic receptors were examined in individual astroglial cells. ATP, phenylephrine and carbachol, each increased intracellular calcium levels ([Ca2+]i) to similar amplitudes in the presence or absence of extracellular Ca2+. The dose-response relationship showed that less than an order of magnitude increase in ligand concentration led to maximal increase in [Ca2+]i from basal levels. Simultaneous application of multiple ligands did not produce additive effects on [Ca2+]i. These data suggested that different ligands released Ca2+ from common stores and that each of the ligands could cause maximal release. Application of a second ligand immediately after the first ligand produced an additional Ca2+ rise, suggesting that the Ca2+ stores were rapidly refilled and that receptor desensitization rather than Ca2+ depletion accounted for the rapid decline of the Ca2+ peak. Caged IP3 produced Ca2+ signals similar to those produced by ligands. For a given cell, both caged IP3 and ligands sometimes produced only one level of partial Ca2+ increases, suggesting the presence of a pool of high IP3-sensitive stores. Together, our results indicate that neuroligands tend to generate an all-or-nothing Ca2+ release from IP3 sensitive stores. The interactions between different receptor systems most likely occur at the level of IP3 accumulation.

Disparate effects of early pressure overload hypertrophy on velocity-dependent and force-dependent indices of ventricular performance in the conscious baboon

BACKGROUND

The effects of early pressure overload on left ventricular (LV) chamber mechanics in the primate heart are poorly understood.

METHODS AND RESULTS

To test the hypothesis that early LV pressure overload hypertrophy is associated with depression of velocity-dependent indices of LV systolic (LV dP/dt) and diastolic function (time constant of relaxation, tau) but unchanged systolic elastance (Ees), we studied six conscious baboons instrumented with LV micromanometers and LV dimension and wall thickness sonomicrometers. Loading conditions were altered by pharmacological angiotensin II generation both before and 12 weeks after producing renovascular hypertension (2 kidney, 1 clip). The LV systolic pressure (149 +/- 11 [SD] versus 114 +/- 5 mm Hg) and LV mass (125 +/- 25 versus 91 +/- 20 g) were greater 12 weeks after than before (both P < .05). Both Ees and Ees normalized for LV mass were similar before versus 12 weeks after (23.0 +/- 9.6 versus 22.3 +/- 9.8 mm Hg/mL and 26.5 +/- 14.5 versus 19.8 +/- 12.5 mm Hg/mL, respectively; both P = NS). At matched LV systolic and diastolic pressures, LV fractional shortening was similar (18.6 +/- 6.8% versus 21.6 +/- 4.9%), but the time constant of LV isovolumic relaxation was significantly longer (42.3 +/- 5.3 versus 31.4 +/- 7.0 ms, P < .05) and LV dP/dt and Vcf were significantly less (1891 +/- 352 versus 2342 +/- 284 mm Hg/s and 0.9 +/- 0.4 versus 1.1 +/- 0.3 circ/s, respectively; both P < .05) 12 weeks after than before.

CONCLUSIONS

In conscious baboons with systemic arterial hypertension and early LV hypertrophy, there is depression of velocity-dependent indices of LV contraction and relaxation but unaltered force-dependent measures of contractility.

Glycosides from Aster yunnanensis

A new oleanane-type triterpene saponin named asteryunnanoside E and a new acetylene glycoside named asteryunnanoside I have been isolated from the roots of Aster yunnanensis, and their structures elucidated as 3-O-beta-D-glucopyranosyl-bayogenin-28-O-beta-D- glucopyranosyl-(1-->2)-beta-D-glucopyranoside and 2Z,8E-decadiene-4,6-diyn-1-O-beta-D-glucopyranos yl-(1-->2)-beta-D- glucopyranoside by means of 1D and 2D NMR techniques (COSY, HETCOR, COLOC, HOHAHA and ROESY) and chemical transformations.

Enhancement of the antineoplastic effect of mitomycin C by dietary fat

In the present study, we investigated the effects of high dietary fat on the growth of MX-1 heterotransplanted in athymic mice and its response to mitomycin C (MC) treatment. We found that high fat intake (25% corn oil, w/w) significantly increased tumor growth, but at the same time it also increased the tumor response to MC treatment compared to the control low fat diet (5% corn oil, w/w). In the tumors from mice fed either low (5% w/w) or high (25% w/w) fat, MC treatment induced oxidative challenge, indicated by significantly increased tumor total superoxide dismutase, catalase, glutathione peroxidase, and glutathione S-transferase peroxidase activities, as well as increased tumor lipid peroxidation. On the other hand, glutathione reductase activity was inhibited by MC treatment. Some of the enzymes which are known to activate MC, such as cytochrome b5 reductase and DT-diaphorase, were also induced in the tumor by high dietary fat intake. The enzyme activities in hepatic tissues were also altered by dietary fat and MC treatment but to a lesser extent. We conclude that high dietary fat intake could enhance the chemotherapeutic effect of MC by increasing MC-activating enzyme activities. The observed increase in lipid peroxidation after MC treatment in MX-1 human mammary carcinoma implanted in the nude mice could result from the observed inhibited glutathione reductase activity. It is tempting to speculate that this might be another antineoplastic mechanism for MC in addition to its known role as a bioreductive alkylating agent. Alternatively, glutathione reductase may be a target for bioreductive alkylation.

Protein splicing: an analysis of the branched intermediate and its resolution by succinimide formation

Protein splicing involves the excision of an internal domain from a precursor protein and the ligation of the external domains so as to generate two new proteins. Study of this process has recently been facilitated by the isolation of a precursor and a branched intermediate from a thermophilic protein splicing element expressed in a foreign protein context. Two aspects of protein splicing are examined in this paper. We demonstrate a succinimide at the C-terminus of the spliced internal protein, implicating cyclization of asparagine in resolution of the branched intermediate, and we identify an alkali-labile bond in the branched intermediate. A revised protein splicing model based on these experimental results is presented.

Influence of acutely altered loading conditions on left atrial appendage flow velocities

OBJECTIVES

The purpose of this study was to identify the effects of altered loading conditions on left atrial appendage flow velocities.

BACKGROUND

Although studies have suggested that Doppler analysis of left atrial appendage blood flow may have clinical utility, the hemodynamic and cardiac mechanical determinants of left atrial appendage flow are poorly understood.

METHODS

Transesophageal Doppler echocardiography was performed in eight atrially paced anesthetized dogs instrumented with sonomicrometers on the left atrial appendage and the left ventricular minor axis and with left atrial and left ventricular micromanometers. Left atrial appendage emptying and filling velocities corresponding to early and late ventricular diastole, respectively, were measured using volume expansion and phenylephrine infusion.

RESULTS

Volume infusion caused a significant decrease in the early to late emptying and filling ratios (mean +/- SD 0.85 +/- 0.24 vs. 0.46 +/- 0.17 and 0.80 +/- 0.50 vs. 0.40 +/- 0.20, both p < 0.05). By contrast, phenylephrine infusion did not significantly alter either filling or emptying ratio. The independent determinants of each flow wave were identified with multiple regression analysis: early emptying velocity--time constant of left ventricular relaxation, left ventricular end-systolic dimension and aortic pressure (r = 0.75, p < 0.001); late emptying velocity--left ventricular peak positive time derivative of left ventricular pressure (dP/dt) and fractional shortening (r = 0.74, p < 0.001); early filling velocity--left atrial appendage shortening fraction (r = 0.45, p = 0.01) and late filling velocity--left atrial appendage lengthening rate and left ventricular fractional shortening (r = 0.56, p < 0.01).

CONCLUSIONS

These results indicate that 1) both the magnitude and the pattern of left atrial appendage emptying and filling velocities are dependent on loading conditions, and 2) left atrial appendage velocities are influenced to a greater extent by changes in left ventricular than in left atrial appendage function. These findings may have implications for the pathogenesis of left atrial appendage thrombi.

Plasticity of astrocytes

It is becoming apparent that astrocytes carry out a large number of different functions in brain and are able to modify their characteristics throughout life, that is they exhibit a high degree of plasticity in their phenotype. For example, the morphology of astrocytes changes markedly during neuronal migration, maturation, and degeneration. It is conceivable that these cells must constantly adjust their abilities to meet changes in brain environment. Several examples of astrocytic plasticity are presented in this review. First, the ability of astrocytes to recognize neuronal signals can change qualitatively as well as quantitatively; evidence suggests that the expression of glial receptors may be developmentally regulated by both intrinsic and extrinsic signals. Second, the expression of adrenergic receptors by astrocytes in adult brain can change in response to neuronal degeneration. The up-regulation of beta-adrenergic receptors in this case suggests that these receptors play a role in function of reactive astrocytes. Finally, glial morphology can be reciprocally regulated by neurotransmitters such as norepinephrine and glutamate. This reciprocal regulation may be significant since both beta-adrenergic receptors and glutamate transporters are found predominantly in astrocytes in the brain. The change in glial morphology may also affect neuronal activity by changing the volume of the extracellular space.

Glutamate blocks astroglial stellation: effect of glutamate uptake and volume changes

Neurotransmitters which increase intracellular cAMP levels can cause cultured astroglia to change from a flat, polygonal shape to a stellate morphology. Little is known about how glial stellation can be regulated by other transmitters. In the present study, we demonstrated that L-glutamate blocked isoproterenol (ISO) or dibutyryl-cAMP induced stellation in astroglia. The glutamate inhibition was concentration dependent, with its maximal effect on > 90% of cells at 500 microM. Glutamate also reversed glial stellation within a short period (< 30 min). Glutamate uptake analogues, D-glutamate and D-aspartate, rather than receptor agonists, kainate and quisqualate, mimicked the glutamate effect. Likewise, the glutamate uptake blocker, D-thero-beta-hydroxyaspartate, blocked the glutamate effect. The glutamate inhibition was not a result of inhibition of cAMP formation, since norepinephrine, which inhibited 80% of ISO-stimulated cAMP, also caused glial stellation. Increases in extracellular K+ to 50 mM also reduced glial stellation, whereas 25 mM K+ had little effect. Since 25 mM K+ caused much greater depolarization than 400 microM glutamate, it was unlikely that the effects of both glutamate and high [K+] on glial stellation were due to membrane depolarization. Hypotonic treatment (120 mOsm) enhanced, whereas hypertonic treatment (520 mOsm) prevented, the glutamate reversal of glial stellation. Thus, glial swelling appeared to be a primary mechanism for the inhibitory effect of glutamate and high [K+] on glial stellation. This mechanism could also explain the observation that glutamate inhibited stellation induced by PMA, a PKC activator. Our data suggest that glutamate released from neurons during neuronal activity or pathology can be taken up by astrocytes and alter their morphology. Changes in glial morphology may in turn affect the volume and composition of the extracellular space and, as a result, neuronal activity.

In vivo assessment of left atrial contractile performance in normal and pathological conditions using a time-varying elastance model

BACKGROUND

Contractile function of the ex vivo, isolated left atrium (LA) has been described by a time-varying elastance, but this atrial chamber property has not been shown in vivo.

METHODS AND RESULTS

Instantaneous LA pressure-volume (P-V) relations were studied in 12 anesthetized, autonomically blocked, atrially paced dogs. LA volume was calculated from orthogonal sonomicrometer pairs using a cast-validated formula. Data were collected during increases in LA pressure produced by a phenylephrine bolus (200 to 400 micrograms IV). Isochronal P-V points from 5 beats, representing a wide range of atrial pressures, were fitted by linear regression analysis (range of R2, .92 to .99). There were significant time-dependent increases in the slopes [E(t)] and small but statistically insignificant decreases in the volume axis intercepts [VO(t)] of the instantaneous LA P-V relations during atrial contraction; maximal elastance (Emax) occurred 29 +/- 16 milliseconds before atrial end systole (minimal LA volume). Emax was not significantly different than the slopes of either the nonisochronal end-systolic P-V relation (Ees) or the nonisochronal maximal P-to-V relation (EmaxPV): 5.5 +/- 2.8, 4.3 +/- 1.5, and 5.4 +/- 4.2 mm Hg/mL, respectively. In 7 dogs, data were collected both before and after a rapid infusion of calcium gluconate (1 to 2 g IV). Emax increased significantly with a calcium-induced increase in inotropic state (4.5 +/- 1.6 to 5.7 +/- 1.8 mm Hg/mL, P < .01), but the volume axis intercept was unchanged (3.6 +/- 0.7 versus 3.4 +/- 1.9, P = NS). In 4 additional dogs with heart failure (mean LA pressure, 26 +/- 6 mm Hg) produced by 3 weeks of rapid right ventricular pacing, LA stroke volume was significantly greater than and elastance determinations were similar to those of normal dogs. However, the effects of calcium infusion on LA function were attenuated in these animals.

CONCLUSIONS

We conclude that (1) in the intact heart, LA contraction may be approximated by time-varying elastance with time-dependent changes in E(t) and that (2) LA systolic P-V relations using either the nonisochronal maximum P-to-V ratio or end systole may be useful as an estimate of Emax, are highly linear and sensitive to calcium-induced changes in inotropic state, and may be useful in identifying LA chamber adaptation to chronic hemodynamic loads.

[A primary clinical trial of genital warts treated with domestic highly purified podophyllotoxin]

Genital warts (condyloma accunimata) are a kind of sexually transmitted disease (STD) caused by human papillomavirus (HPV). In this article, we report 75 cases of genital warts treated with highly purified podophyllotoxin. All volunteers were selected in our clinic and diagnosed according to typical skin lesions and positive 0.5% acetic acid test. Of the 74 cases 48 were male and 26 were female, with a mean age of 28.4 years (21-54). The average duration of disease was 4.4 months (2 weeks-3 years). All lesions were treated with 0.5% podophyllotoxin-ethanal solution topically 2 times per day for 3 successive days. The treatment was repeated if any warts persisted, but not more than 3 therapies in total were applied. The results showed that 41/48 (85.4%) of male and 23/26 (88.5%) of female patients were cured, the overall cure rate was 86.5% and the effectiveness rate (more than 50% lesions disappeared) was 96.15%. During another 3 months of follow-up, 9 male and 4 female patients (17.6% in total) experienced relapsed warts; these were cured with another treatment. Side effects including slight local irritation and erythema or superficial erosions were common, but 3 male and 2 female patients complained of sever pain and local swelling. All side effects were tolerable. It is concluded that our domestically produced highly purified podophyllotoxin is an effective, comparatively safe drug for the treatment of genital warts. It is also very simple to apply, and can be used for self-treatment.

Use of bremsstrahlung radiation to monitor Y-90 tumor and whole body activities during experimental radioimmunotherapy in mice

BACKGROUND

Large differences in uptake between tumors, even for the same size, frequently observed in clinical and experimental radioimmunotherapy (RAIT), make monitoring of uptake in individual tumors imperative in comparing protocols. 90Y, widely-used for RAIT, emits no gamma radiation and absorption of the beta particle in tissue makes its detection unsuitable for in vivo monitoring. We tested whether bremsstrahlung radiation, produced when betas are decelerated by nuclei, could be used to monitor tumor uptake.

METHODS

Subcutaneous human LS174T colon carcinoma tumors were grown in the upper thigh of nude mice and labeled antibody injected intracardially. With the tumor placed in the 2 cm-diameter aperture in a lead collimator, photons with energies from 100 to 200 keV transmitted through plastic, which absorbed the beta particles, were counted to maximize shielding from the rest of the body. The contribution of the normal tissues was subtracted by counting the non-tumor-bearing leg in the same position. Excretion was calculated from whole body activity determined by removing the collimator, placing the mouse in a syringe surrounded by tissue-equivalent material 10 cm from the detector, and counting photons between 200 and 740 keV to minimize the effect of tissue attenuation.

RESULTS

For tumors larger than 0.14 gm, a good correlation was obtained between the in vivo bremsstrahlung measurements and the measurements on excised tumors in a calibrated well counter. Similar excretion rates observed in all the animals suggested that the whole body counting was accurate.

CONCLUSIONS

Bremstrahlung detection appears feasible and reliable for monitoring both tumor and whole body activities.

A new method for determining dose rate distribution from radioimmuno-therapy using radiochromic media

PURPOSE

To describe and evaluate a new, simple, inexpensive method for directly measuring the radiation dose and its spatial distribution generated from explanted tissues of animals previously injected with radiolabeled immunoconjugates or other agents.

METHODS AND MATERIALS

This technique uses the newly developed radiochromic dye medium (Gafchromic) which responds reproducibly for therapeutic dose exposures, has high spatial resolution, does not require film processing, and is relatively insensitive to ambient light. We have evaluated the dose distribution from LS174T tumors and selected normal tissues in nude mice previously injected with 90Y labeled anti-carcinoembrionic antigen antibodies. Individual tissues from sacrificed animals are halved and the flat section of the tissue is placed onto the dosimetry media and then frozen. The dosimetry medium is exposed to beta and Bremsstrahlung radiation originating from the frozen tissues. The relative darkening of the dosimetry medium depends on the dose deposited in the film. The dosimetry medium is scanned with a commercial flatbed scanner and the image intensity is digitally stored and quantitatively analyzed. Isodose curves are generated and compared to the actual tissue outline.

RESULTS

The absorbed dose distribution due to 90Y exposure show only slight gradients in the interior of the tissue, with a markedly decreasing dose near the edges of the tissue. In addition, the isodose curves follow the tissue outline except in regions having radii of curvature smaller than the range of the beta-particle (R90 = 5 mm). These results suggest that the shape of the tumor, and its curvature, are important in determining the minimum dose delivered to the tumor by radiation from 90Y monoclonal antibodies, and hence in evaluating the tumor response to the radiation. The dose and spatial dose distribution were calculated assuming that the total 90Y activity is distributed uniformly throughout a half ellipsoid. The calculated spatial dose distributions for the half ellipsoids were similar to those observed from the dosimetry media that had been exposed to radioactivity contained in the tumors.

CONCLUSION

This method provides direct dose evaluation without elaborate summary calculations based on activity measurements from serial slices. The measured radiation dose actually indicates the dose rate at the time of animal sacrifice. Quantitative analysis of radiation emitted from the tissues is relatively fast, making it feasible to examine a number of tissues under a variety of conditions.

Terpenoid glycosides from the roots of Aster tataricus

A new monoterpene glycoside, shionoside C, and a new oleanane-type triterpene glycoside, aster saponin G, were isolated from the roots of Aster tataricus. Their structures were elucidated on the basis of spectral and chemical methods. Shionoside C is L-endo-camphanol-8-3,5-isopropylidene-beta-D- apiofuranosyl-(1-6)-beta-D-glucopyranoside, aster saponin G is 3-O-[O-alpha-L-arabinopyranosyl-(1-6)-beta-D-glucopyranosyl]-2 beta, 3 beta, 16 alpha-trihydroxyolean-12-en-28-oic acid (asterogenic acid) 28-[O-beta-D-xylopyranosyl-(1-4)-alpha-L- rhamnopyranosyl-(1-2)-beta-D-xylopyranosyl]ester.

Regulation of astroglial responsiveness to neuroligands in primary culture

Previous studies from this laboratory indicate that type-1 astroglia in primary culture are pharmacologically heterogeneous. Two competing hypotheses were proposed to explain the development of glial heterogeneity. First, that the heterogeneity may reflect stable subclasses of astroglia that express a set of receptor-signalling systems. Second, that astroglia can undergo qualitative changes in their expression of receptor-signalling systems with time in vitro. To distinguish between these two hypotheses, experiments were designed to examine neuroligand-evoked calcium responses within clones of type-1 astroglia. If stable and distinct subsets of astroglia were present, a clone derived from a single cell would exhibit uniform responses to a given set of neuroligands. Alternatively, if the pharmacological properties of astroglia underwent qualitative changes, astroglial clones should contain pharmacologically distinct cells. A video-based imaging system and the Ca2+ indicator dye Fura-2 were used to monitor receptor-mediated increases in Cai2+ upon receptor activation. Interestingly, only a fraction of the cells within a given clone responded to carbachol or histamine with an increase in Cai2+, whereas treatment with a P2Y purinergic receptor agonist generally increased Cai2+ in 100% of the cells within the clone. To examine the stability of the receptor signalling over time, individual astroglia within a number of clones were tested on different days for their ability to respond to neuroligands. The results of these experiments indicated that individual astroglial cells tended to lose their responsiveness to certain ligands such as carbachol and histamine as they developed responsiveness to others such as norepinephrine. Our data indicate that during development neurotransmitter receptors on astroglial cells are regulated by both internal and external mechanisms. Glial proliferation produces a variety of pharmacologically distinct astroglial cells. Exposure to neurotransmitters can qualitatively turn off some, but not all, astroglial receptor systems.

Quantitative relationship between alpha 1-adrenergic receptor density and the receptor-mediated calcium response in individual astroglial cells

alpha 1-Adrenergic receptor (alpha 1-AR) agonists elevate the intracellular calcium concentration ([Ca2+]i) in 60-80% of astroglia in vitro. Likewise, 60-70% of astroglia exhibit specific binding sites for the alpha 1-AR-selective antagonist (+-)-125I-[beta-(4-hydroxyphenyl)-ethylaminomethyl]tetralone. The density of alpha 1-AR binding sites varies markedly on individual cells, ranging from a few to > 2000 binding sites/1000 microns 2 of surface area. In the present study, we examined the relationship between the density of alpha 1-AR binding sites on astroglia and their ability to respond to alpha 1-AR agonists with a rise in [Ca2+]i. A video-based imaging system was used to monitor calcium responses in individual astroglial cells, which were subsequently assessed for their expression of alpha 1-ARs using receptor binding autoradiography. The ability of a given concentration of phenylephrine (PE) to elicit a calcium response correlated well with alpha 1-AR density (r = 0.94), i.e., the higher the receptor density the greater the probability that a given astroglial cell would respond to alpha 1-AR agonists. However, the amplitude of the calcium response did not correlate with the alpha 1-AR density. Cells with low alpha 1-AR density (< 10 binding sites/1000 microns 2) could generate a response with an amplitude comparable to that seen in cells with high alpha 1-AR density (> 1000 binding sites/1000 microns 2). To evaluate the relationship between receptor occupancy and calcium response, PE concentrations and alpha 1-AR density were varied while the calcium response in individual cells was monitored. Interestingly, for a given cell the amplitude of calcium response reached its maximum with a small step increase in the concentration of PE (< 5-fold), whereas the latency of the response decreased when PE concentrations were increased. Irreversible inactivation of alpha 1-ARs by phenoxybenzamine reduced the potency of PE but not the maximal calcium response. Cells that responded to 100 nM PE were able to generate a comparable response to 10 microM PE after inactivation of 90% of the total alpha 1-AR binding sites with phenoxybenzamine treatment. In summary, our results indicate that most astroglial cells express a substantial level of "spare" alpha 1-ARs that increase the sensitivity of these cells to alpha 1-AR agonists. Once activated, individual astroglial cells tend to generate a maximal [Ca2+]i elevation that is independent of the total alpha 1-AR density or the concentration of ligand.

Preclinical evaluation of intravenously administered 111In- and 90Y-labeled B72.3 immunoconjugate (GYK-DTPA) in beagle dogs

B72.3, a monoclonal antibody with reactivity against human adenocarcinomas was obtained from the Cytogen Corporation in the form of an immunoconjugate coupled with linker-chelator GYK-DTPA by using proprietary carbohydrate directed site specific chemistry. The immunoconjugate was radiolabeled with indium-111 or yttrium-90. A preclinical analysis was performed in 10 normal beagle dogs. The pharmacokinetics of intravenously administered indium- and yttrium-labeled immunoconjugates were compared serially in blood, bone marrow and urine samples. Compared to 90Y less of the 111In label ended up in urine and more was found in blood and bone marrow. Indium-labeled B72.3 GYK-DTPA had relatively higher uptake in most glandular tissues than 111In-labeled antiferritin immunoconjugate. Bone marrow toxicity was the dose limiting side effect after intravenous infusion of 90Y-labeled B72.3 GYK-DTPA. Toxicity was also observed in the liver but not in other organ systems. Recently other investigators obtained similar results with these immunoconjugates in human patients. A preclinical pharmacokinetic analysis of radioimmunoconjugates in beagle dogs provided useful information regarding bone marrow toxicity, liver toxicity and in vivo instability of the immunoconjugate. Data suggest that for future trials in human patients, a more stable chelated immunoconjugate for yttrium is needed to achieve less liver uptake and a better correlation with the 111In-labeled product than the 90Y-labeled B72.3 GYK-DTPA used in this investigation.