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.

Fractionated intravenous administration of 90Y-labeled B72.3 GYK-DTPA immunoconjugate in beagle dogs

B72.3, a monoclonal antibody with reactivity against human adenocarcinomas, was coupled with linker-chelator GYK-DTPA using carbohydrate mediated conjugation chemistry and radiolabeled with yttrium-90. Single and double intravenous injections of radioimmunoconjugate were compared for acute and late normal tissue toxicity in 15 beagle dogs. The second injection was given 4 or 8 days after the first. Pharmacokinetics of the radioimmunoconjugate in blood, bone marrow and urine were similar for first and second injections. Only bone marrow (acute) and liver (late) toxicity were observed. Both liver and bone marrow toxicity were decreased by fractionation of the injections. After double injections, the total equitoxic dose was 15 and 60% higher for bone marrow and liver toxicity, respectively. The mechanisms of normal tissue protection offered by fractionated radioimmunoglobulin therapy (RIT) remain to be defined. Fractionated RIT will have a better therapeutic ratio than single injection RIT, if antitumor effects appear to be less susceptible to fractionation than normal tissues.

Influence of pericardium on left atrial compliance and pulmonary venous flow

We studied seven open-chest anesthetized dogs to test the hypothesis that left atrial (LA) compliance is increased after pericardiectomy and to determine the effect of pericardiectomy on left atrial reservoir and conduit function. Two orthogonal sonomicrometer crystal pairs were used to estimate LA volume, and LA filling was assessed with a pulmonary vein (PV) flow probe. The left ventricular (LV) systolic (JFTI) and diastolic (KFTI) PV flow integrals were used as indexes of LA reservoir and conduit function, respectively. Diastolic LV transmitral flow was assessed with transesophageal Doppler echocardiography. Data were acquired over a wide range of intracardiac pressures and volumes obtained by intravenous hetastarch infusion both before and after pericardiectomy. The mean dynamic stiffness constant of the LA diastolic pressure-volume relation was significantly greater before pericardiectomy than afterwards (0.15 +/- 0.04 vs. 0.08 +/- 0.03 ml-1, P < 0.05). Data were analyzed before and after pericardiectomy at three matched levels of left atrial pressure (LAP; 7, 13, and 20 mmHg). The J-to-KFTI ratio increased significantly with volume infusion and was significantly less after pericardiectomy than before (1.2 +/- 0.7 vs. 1.2 +/- 0.6, 1.8 +/- 0.6 vs. 2.2 +/- 0.9, and 2.0 +/- 0.8 vs. 2.6 +/- 0.9 at low, mid, and high levels of LAP, respectively; P < 0.05 at mid and high levels of LAP). Peak early transmitral velocity increased with both volume infusion and pericardiectomy. We conclude that pericardiectomy increases LA compliance and early LV filling rate and is accompanied by a relatively greater augmentation in conduit than reservoir function of the left atrium.

Comparative assessment of regional left atrial perfusion by laser Doppler and radionuclide microsphere techniques

OBJECTIVE

The aim was to study the relation between left atrial microcirculatory flux, using laser Doppler flowmetry (LDF), and blood flow, using radiolabelled microspheres (MS).

METHODS

Studies were done in five anaesthetised dogs. LDF probes were sewn to the appendage and body of the left atrium. Radionuclide spheres (15 microns) were used to quantitate blood flow at baseline, and during atrial pacing at 3.5 Hz, atrial fibrillation, and intravenous adenosine infusion (1 mg.kg-1 x min-1).

RESULTS

In the left atrial body, both MS and LDF perfusion increased significantly during pacing and adenosine infusion; only LDF registered significant increases during atrial fibrillation. In the left atrial appendage, MS flow failed to increase significantly with any intervention and LDF perfusion increased significantly only during atrial fibrillation. There was a significant but weak correlation (r = 0.36, p < 0.05) between LDF and MS when data from all sample sites (n = 40) were compared, but good correlation when only baseline and pacing data were compared (r = 0.72, p = 0.0004, n = 20). In four additional dogs with heart failure [mean left atrial pressure 25.3(SD 7.4) mm Hg] produced by three weeks of rapid right ventricular pacing, flux values at baseline were increased significantly compared to control dogs and the responses registered by LDF to pacing, atrial fibrillation, and adenosine infusion were attenuated markedly.

CONCLUSIONS

(1) Microcirculatory flux detected by LDF can identify the direction, and to a lesser extent, the magnitude of changes in regional atrial perfusion; and (2) LDF may be useful in identifying abnormalities of vasodilator reserve that accompany chronic left atrial myocardial dysfunction.

Determination of left atrial volume using sonomicrometry: a cast validation study

We developed a technique for left atrial (LA) volume estimation using two pairs of sonomicrometers sewn to the anteroposterior (LAX) and mediolateral (SAX) LA diameters and validated the method against water displacement of LA casts in 15 dogs. LA pressure was adjusted to a preselected level (5, 10, or 15 mmHg) by dextran infusion and was matched by postmortem infusion of casting resin (Conthane DPEN-18402). LA volume was modeled empirically as an ellipsoid of revolution without regression constants [(SAX)2(LAX)]. There was a strong correlation between the calculated LA volume and water displacement of the LA body [r = 0.87, standard error of estimate (SEE) = 3.3 ml, P = 0.0001] but a weaker correlation against water displacement of the entire LA (body+appendage, r = 0.81, SEE = 3.9 ml, P = 0.0003). The appendage volume fraction (appendage volume/total LA volume), as determined by water displacement of the casts, increased with increasing LA size (r = 0.78, P = 0.001). These data indicate that, in the normal canine heart, LA volume can be estimated accurately with high temporal and spatial resolution sonomicrometry using two atrial dimensions, and the contribution of appendage to total LA volume may become significant as the atrium enlarges.

Surveillance and care of four Chinese hemophiliacs with human immunodeficiency virus (HIV) infection

Four Chinese hemophiliacs with HIV infection have been followed up in Zhejiang Province since 1985. A plan for optimal care of HIV seropositive patients was proposed, including surveillance and care; clinical follow-up and preventive education of asymptomatic HIV seropositive patients; keeping the disease confidential so as not to stir up unnecessary social unease; propaganda and health education about acquired immunodeficiency syndrome (AIDS); treatment with traditional Chinese medicines; and regular surveillance of family members and medical personnel. This plan is regarded as feasible and effective for the prevention and control of AIDS in China.

The effect of cyclosporine treatment on the expression of genes encoding granzyme A and perforin in the infiltrate of mouse heart transplants

Following activation of cytotoxic T cells and NK cells several genes encoding proteins putatively involved in cell-mediated cytotoxicity become expressed. The expression of genes encoding the cytotoxic T cell associated serine protease granzyme A and perforin was analyzed in cellular infiltrates of MHC mismatched (H-2d-->H-2k) heterotopic heart transplants both in immunosuppressed recipients treated with cyclosporine and in untreated recipients. Heart transplants were completely rejected by untreated animals on day 10 post-transplantation, whereas CsA treatment generally prolonged survival of the transplants beyond 30 days. In untreated recipients the number of granzyme A- and perforin-expressing cells in heart transplants increased from approximately 10 granzyme A-positive cells/mm2 and 1 perforin-positive cell/mm2 on day 2 posttransplantation to over 80 positive cells for both genes on day 5 posttransplantation. In contrast, these values remained always below 15 positive cells/mm2 for both genes between day 5 and day 30 posttransplantation in CsA-treated recipients. Comparison of the frequency of CD8+ T cells in the infiltrates showed that lower numbers of perforin and granzyme A-positive cells were mainly due to the immunosuppressive action of CsA rather than to reduced infiltration of transplants. The present study shows that expression of granzyme A and perforin gene can be used to discriminate between quiescent and activated cytotoxic cells also in immunosuppressed animals and further confirms that these can be used as sensitive markers for monitoring the fate of a transplant.

Altered left atrial compliance after atrial appendectomy. Influence on left atrial and ventricular filling

Previous studies have shown regional differences in atrial distensibility. We studied 12 open-chest dogs to test the hypothesis that left atrial compliance is decreased after removal of the left atrial appendage and to determine the effect of altered atrial compliance on atrial reservoir and conduit function. Sonomicrometer crystal pairs were used to measure the long- and short-axis diameters of the left atrium over a wide range of intracardiac pressures and volumes obtained by intravenous hetastarch infusion both before and after suture ligation of the left atrial appendage (appendectomy). Pulmonary venous flow was measured with an ultrasonic flowmeter, and transmitral flow velocities were measured with transesophageal Doppler echocardiography. After appendectomy, the diastolic pressure-volume relation was shifted upward and to the left in six of seven dogs. The mean dynamic stiffness constant of the left atrial diastolic pressure-volume relation was significantly greater after appendectomy than before (0.20 +/- 0.11 [mean +/- SD] versus 0.14 +/- 0.08 ml-1, p < 0.01); the mean y intercept was slightly, but significantly, less after appendectomy (0.6 +/- 0.3 versus 1.3 +/- 0.6 mm Hg, p < 0.05). The left atrial reservoir volume (maximum minus minimum left atrial volume) was significantly less after appendectomy at matched left atrial pressures. The systolic to diastolic flow integral ratio of pulmonary venous flow (JFTI/KFTI), an index of the relative reservoir to conduit functions of the left atrium, increased significantly with volume infusion only before appendectomy; at matched left atrial pressure, JFTI/KFTI was significantly less afterwards.(ABSTRACT TRUNCATED AT 250 WORDS)

Resting and reactive astrocytes express adrenergic receptors in the adult rat brain

Adrenergic receptor subtypes were localized in situ and in cells isolated from the trigeminal motor nucleus and several other brain regions. To study receptor expression in reactive astrocytes, motor neuron degeneration and a glial reaction were induced in the trigeminal motor nucleus by the injection of the toxic lectin Ricin communis into the trigeminal motor root. Autoradiography following incubation of tissue sections in the alpha 1-ligand 125IBE 2254 (HEAT) or the beta-ligand 125Iodocyanopindolol (ICYP) showed a decrease in alpha 1- and an increase in beta-adrenergic receptor binding in the region of neuronal degeneration and gliosis. Glial hypertrophy, rather than hyperplasia, appears to be mainly responsible for the increased beta-binding, since inhibition of mitosis with cytosine arabinofuranoside only partially blocked elevations of beta-adrenergic receptor binding and GFAP immunolabelling in reactive astrocytes. More direct evidence for the expression of adrenergic receptors in normal and reactive astrocytes was obtained by combined autoradiography and immunohistochemistry of cells dissociated from the cerebral cortex, striatum, cerebellum, and trigeminal motor nucleus of adult rats. More than 88% of GFAP-positive astrocytes showed varying densities of beta-adrenergic receptor binding. In each region, the beta 2-subtype was proportionally greater than the beta 1-subtype. Astrocytes also expressed a significant density of alpha 1-receptors. Trigeminal motor neurons did not show beta-receptor binding, but had a density of alpha 1-receptors tenfold greater than astrocytes. A model for the role of astrocytes in adrenergic receptor-mediated modulation of trigeminal motor neuron excitability is discussed.

Influence of loading conditions and contractile state on pulmonary venous flow. Validation of Doppler velocimetry

BACKGROUND

Although recent studies suggest that pulmonary venous flow velocities may be used to evaluate left ventricular diastolic function, the influence of loading conditions and contractile state on the magnitude and pattern of pulmonary venous flow are poorly understood.

METHODS AND RESULTS

Fourteen anesthetized open-chest mongrel dogs were instrumented with pulmonary venous flow probes, atrial sonomicrometer crystal paris, and high-fidelity micromanometers; transesophageal Doppler echocardiography was used to obtain simultaneous pulmonary venous flow velocities. Measurements were made over a wide range of left atrial pressure obtained by either intravascular volume infusion and inferior vena caval balloon inflation (n = 8), halothane inhalation (n = 6), or phenylephrine infusion (n = 5). There was an excellent correlation for pulmonary venous systolic (J) to diastolic (K) time integral between the Doppler and flow probe signal (r = 0.94; SEE, 0.18). When left atrial pressure was increased by volume infusion, there was a significant linear relation between mean left atrial pressure and the Doppler J/K peak (r = 0.64; SEE, 3.4 mm Hg) and flow velocity-time integral ratio (r = 0.75; SEE, 2.9 mm Hg). By contrast, when left atrial pressure was elevated by halothane-induced cardiac depression, there was no correlation. The independent determinants of the pattern of pulmonary venous flow (stepwise multiple linear regression analysis) under all conditions were atrial systolic shortening, aortic systolic pressure, heart rate, and left ventricular end-systolic dimension (cumulative r = 0.80).

CONCLUSIONS

The pattern of pulmonary venous flow can be measured accurately with Doppler velocities and is differentially influenced by loading conditions and myocardial contractile state; in the absence of myocardial contractile dysfunction, the pattern of pulmonary venous flow may provide an estimate of left atrial pressure; and pulmonary venous flow is determined largely by atrial systolic function.

Selection of reagents for human radioimmunotherapy

Promising response rates are noted in patients with refractory Hodgkin's disease after radioimmunoglobulin therapy (RIT) with Yttrium-90 labeled polyclonal antiferritin. To explore the most efficacious selection of RIT reagents for use in humans, experimental animal data are reviewed for radiolabeled antiferritin and B72.3. Nude mice with subcutaneously implanted human malignancies provide an excellent primary screen for radiolabeled antibodies under consideration for use in humans. They provide information on the potential of a new reagent to target a human malignancy in vivo. The other determinant of the therapeutic ratio of RIT reagents--normal tissue toxicity--is best analyzed in large animals, such as dogs. Hematologic toxicity is dose limiting in all species and best predicted by a prescription of radiolabeled antibodies in mCi per kilogram body weight and the presence or absence of bone marrow targeting. Per cGy, RIT is more effective in causing BM damage in dogs than in rats. In dogs, bone marrow transplantation with autologous cryopreserved bone marrow cells or G-CSF treatment can accelerate hemopoietic recovery and granulopoiesis, respectively, after RIT. When dose escalation beyond bone marrow toxicity is performed, the liver (dog) or the intestinal tract (rat) become the next dose limiting tissue in dose escalation studies. Significant improvement in RIT results will be achieved when the normal liver uptake of chelated monoclonal antibody in dogs and in human patients can be prevented. The described animal models and continued investigations of RIT in patients with endstage Hodgkin's disease will allow for further improvement in the therapeutic ratio of RIT and the applicability of RIT in humans.

Expression of adrenergic receptors in individual astrocytes and motor neurons isolated from the adult rat brain

Attempts to show the distribution of adrenergic receptors (ARs) in autoradiographs of a brainstem motor nucleus following elimination of motor neurons yielded the unexpected result of an increase in beta-AR density. This increase was related to the gliosis accompanying the motor neuron degeneration. To determine the cells on which the AR subtypes were located, we dissociated cells from various regions of the adult rat brain and subsequently identified astrocytes by glial fibrillary acidic protein (GFAP) immunofluorescence. Slides containing the astrocytes were prepared for autoradiography using the nonselective beta ligand 125I-iodocyanopindolol (125ICYP) or the alpha 1 ligand 125IBE 2254 (125I-HEAT). The addition of the selective beta 1 blocker betaxolol or the beta 2 blocker ICI 118.551 to the incubation medium to displace 125ICYP binding was used to determine the binding of beta-AR subtypes. The great majority (greater than 88%) of isolated astrocytes sampled from the trigeminal motor nucleus, cerebral cortex, striatum, and cerebellum showed beta-AR binding. Astrocytes from the first three regions had similar average densities of beta-ARs, whereas the density in cerebellar astrocytes was 2- to 3-fold greater. The beta 2-AR subtype was proportionally greater than the beta 1 subtype in each region. Reactive astrocytes isolated from the trigeminal motor nucleus after degeneration of motor neurons showed a beta-AR density nearly 2-fold greater than resting astrocytes from the same region, with the beta 1 subtype showing the greater proportional increase. There was no beta-AR binding on trigeminal motor neurons. Astrocytes also showed a significant level of alpha 1-AR binding. No differences in alpha 1-AR binding were found in normal astrocytes isolated from the different regions, nor was there an increase in reactive astrocytes. In contrast, trigeminal motor neurons had an alpha 1-AR density nearly 10 times greater than astrocytes. In terms of the NE modulation of synaptic responses in motor neurons, the distribution of ARs would permit NE to act indirectly through alpha 1 and beta receptors on astrocytes and directly through alpha 1 receptors on motor neurons.

A clinical and laboratory study of ciclopirox olamine (8% Batrafen) in the treatment of onychomycosis

Ciclopirox olamine, a new synthetic substituted pyridone derivative, is an antimycotic agent with activity against a broad spectrum of pathogenic and nonpathogenic fungi. The clinical efficacy and safety of 8% ciclopirox olamine nail liquor were evaluated in 100 cases with finger (or great toe) onychomycosis. After 16 weeks and 24 weeks of treatment for finger and great toe onychomycosis, respectively, the overall therapeutic results were excellent in 36 cases, good in 17, fair in 24, and poor in 23. The period of treatment was extended in 31 cases; among them, 10 cases showed further improvement. As for in vitro inhibitory activity, the MIC of ciclopirox olamine against T. rubrum and C. albicans was 1 to 4 mg/L and 1 to 16 mg/L, respectively. This study indicates that 8% ciclopirox olamine nail liquor, with its satisfactory efficacy and lack of side effects, is a good remedy for onychomycosis.

[Isolation of human immunodeficiency virus (HIV) in epidemic area of HIV infection in Yunnan Province]

Blood were collected from HIV infected persons in epidemic area of HIV infection in Yunnan province for isolation of HIV. The coculture method was used for cultivating the virus and reverse transcriptase assay (RT) was the main method for detection of HIV. Of 25 seropositive, 24 asymptomatic and one PGL, 10 showed positive RT activity (greater than 5,000 cpm/ml and with a steadily increase, some to more than 40,000 cpm/ml). The results were confirmed by the detection of HIV1 p24 Ag (ELISA) and HIV1 POL and GAG gene sequence (PCR]. In accordance with the reports from other labs, the viruses isolated from these group of persons infect only PMCs, grew slowly with gradual increase of RT activity and caused no CPE. Efforts are making, at present, to rise the virus titer with better culture system. The amplified gene sequence of the isolates are under investigating.