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Biomedical subjects

B Horowitz

Publications and source records attributed to B Horowitz.

At least 91 records · Page 5Linked to original sources
PubMed1995

Inactivation of Trypanosoma cruzi trypomastigote forms in blood components by photodynamic treatment with phthalocyanines.

Three phthalocyanine dyes HOSiPcOSi(CH3)2(CH2)3N(CH3)2 (Pc 4), HOSiPcOSi(CH3)2(CH2)3N+(CH3)3I- (Pc 5) and aluminum tetrasulfophthalocyanine hydroxide (AlOHPcS4) were evaluated for their ability to inactivate the trypomastigote form of Trypanosoma cruzi in fresh frozen plasma (FFP) and red blood cell concentrates (RBCC). The compound Pc 4 was found to be highly effective in killing T. cruzi, Pc 5 less effective and AlOHPcS4 ineffective. With FFP as the medium, a complete loss of parasite infectivity in vitro (> or = 5 log10) was found to occur with 2 microM Pc 4 after irradiation with red light (> 600 nm) at a fluence of 7.5 J/cm2, while with RBCC as the medium, a complete loss was found to occur at a fluence of 15 J/cm2. Even without illumination, Pc 4 at 2 microM also killed about 3.7-4.1 log10 of T. cruzi in FFP during 30 min. Observed differences in T. cruzi killing by the various phthalocyanines may related to differences in binding; Pc 4 binds to the parasites about twice as much as Pc 5. Ultrastructural analysis of treated parasites suggests that mitochondria are a primary target of this photodynamic treatment. The data indicate that Pc 4 combined with exposure to red light could be used to eliminate bloodborne T. cruzi parasites from blood components intended for transfusion. The inactivation of T. cruzi by Pc 4 in the dark suggests a possible therapeutic application.

Animals↗
PubMed1995

Psoralen-mediated virus photoinactivation in platelet concentrates: enhanced specificity of virus kill in the absence of shorter UVA wavelengths.

Treatments with psoralens and long-wavelength ultraviolet radiation (UVA, 320-400 nm; PUVA) have shown efficacy for virus sterilization of platelet concentrates (PC). Our laboratory has employed the psoralen derivative 4'-aminomethyl-4,5',8-trimethylpsoralen (AMT), and we have found that platelet integrity is best preserved when rutin, a flavonoid that quenches multiple reactive oxygen species, is present during AMT/UVA treatment of PC. In this report, we examine the effects of different UVA spectra under our standard PC treatment conditions (i.e. 50 micrograms/mL AMT, 0.35 mM rutin and 38 J/cm2 UVA). Added vesicular stomatitis virus (VSV; > or = 5.5 log10) was completely inactivated with the simultaneous maintenance of the platelet aggregation response (> 90% of control) when a UVA light source with transmission mainly between 360 and 370 nm (narrow UVA1) was used. In contrast, with a broad-band UVA (320-400 nm; broad UVA) light source, the aggregation response was greatly compromised (< 50% of control) with only a minor increase in the rate of VSV kill. With this lamp, platelet function could be improved to about 75% of the control by adding a long-pass filter, which reduced the transmission of shorter (< or = 345 nm) UVA wavelengths (340-400 nm; UVA1). At equivalent levels of virus kill, aggregation function was always best preserved when narrow UVA1 was used for PUVA treatment. Even in the absence of AMT, and with or without rutin present, narrow UVA1 irradiation was better tolerated by platelets than was broad UVA.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗
PubMed1995

MR imaging of the eyelids: normal and pathologic findings.

MR imaging is commonly used to evaluate orbital and facial soft-tissue disease. Although the eyelids are visible on these images, the radiographic appearance and the detailed anatomy of these structures has received little attention in the literature [1-4]. Anatomic correlation with MR images may be extremely helpful in the accurate interpretation and staging of eyelid malignancies and infections.

Adult↗
PubMed1995

Suppression of two cloned smooth muscle-derived delayed rectifier potassium channels by cholinergic agonists and phorbol esters.

Functional coupling between muscarinic (m3) receptors and two voltage-gated K+ (Kv) channels (Kv1.2 and Kv1.5) cloned originally from canine colonic smooth muscle was studied using the Xenopus oocytes expression system and a mammalian cell line (COS cells). Oocytes were coinjected with cRNAs encoding the human m3 receptor and the Kv channel clones. COS cells were stably transfected with the hm3 cDNA and the cDNA encoding Kv1.5 channels. In oocytes coexpressing hm3 receptors and Kv channels, acetylcholine (ACh, 100 microM) decreased the whole-oocyte Kv channel current (IKv) by 72% over 20 min. ACh was equally effective at suppressing IKv1.2 as IKv1.5. In oocytes expressing only Kv channels phorbol esters (phorboldibutyrate) and phorbol dideconoate (10-30 nM) mimicked the action of ACh on IKv in oocytes coexpressing hm3 receptors. At the single-channel level, both ACh and phorbol dibutyrate applied to the extra-patch membrane reduced the open probability of Kv channels in the cell-attached patches without affecting single-channel conductance. In cotransfected COS cells, over a similar time course as in oocytes ACh suppressed whole-cell IKv1.5, but only by 30% and the effect was not reversible. These data indicate that stimulation of m3 receptors in cells that express Kv1.2 and Kv1.5 channels causes a poorly reversible decrease in the open probability of these channels.

Acetylcholine↗
PubMed1994

Block by 4-aminopyridine of a Kv1.2 delayed rectifier K+ current expressed in Xenopus oocytes.

1. The blocking action of 4-aminopyridine (4-AP) on a delayed rectifier Kv1.2 K+ channel expressed in oocytes was investigated at room temperature (22 degrees C) and physiological temperature (34 degrees C) using the double-electrode voltage clamp and patch clamp techniques. 2. At room temperature, 4-AP (100 microM) inhibition occurred only after activation of current. The rate of onset of block was dependent upon the length of time current was activated by a depolarizing step. Similarly, removal of block required current activation. The degree of steady-state block by 4-AP was not reduced by increasingly more depolarized step potentials. The degree of steady-state block also did not change over the duration of a 1 s step. 3. When channels were nearly fully inactivated, 4-AP produced no additional block of a subsequent depolarizing step, suggesting that 4-AP did not bind when channels were in the inactivated state. In single channel experiments, 4-AP decreased the mean open time in a dose-dependent manner but did not alter the single-channel current amplitude. 4. At 34 degrees C the I-V relationship and inactivation curve shifted to more negative potentials. Increasing the temperature to 34 degrees C did not alter the degree of block by 4-AP, although the rate of onset of block was greatly enhanced. 5. Results suggest that 4-AP binds to the open state of the Kv1.2 channel and is trapped when the channel closes. 4-AP cannot bind when the channel is closed or inactivated prior to the addition of the drug. C-type inactivation and 4-AP binding to the channel are mutually exclusive. A model for the proposed mechanism of action of 4-AP on the Kv1.2 channel is proposed based on experimental data.

4-Aminopyridine↗
PubMed1994

Removal/neutralization of hepatitis A virus during manufacture of high purity, solvent/detergent factor VIII concentrate.

Recent reports have suggested an increased risk of type A viral hepatitis in hemophilic patients treated with high purity factor VIII concentrates prepared using ion exchange chromatography coupled with solvent/detergent treatment for inactivation of viruses. To determine the capacity for removal or inactivation of hepatitis A virus during the factor VIII manufacturing process, human plasma and various factor VIII production intermediates were spiked with cell culture-propagated virus and subjected to scaled down conditions mimicking the manufacture of solvent/detergent factor VIII. The combination of antibody-mediated neutralization, cryoprecipitation, anion exchange chromatography, and lyophilization in the absence of sucrose resulted in a minimal reduction of 5.5 to 8.55 log10 in the infectivity of hepatitis A virus.

Animals↗
PubMed1994

Quencher-enhanced specificity of psoralen-photosensitized virus inactivation in platelet concentrates.

BACKGROUND: Treatment with psoralens and UVA (PUVA) has been shown to be efficacious in eliminating the risk of virus transmission by platelet concentrates (PCs). It has previously been demonstrated that, during the inactivation of cell-free vesicular stomatitis virus (VSV) by aminomethyltrimethylpsoralen (AMT) and UVA in PCs, platelet function could be protected either by oxygen removal before irradiation or by inclusion of a type I free radical quencher, such as mannitol. STUDY DESIGN AND METHODS: Under previous PUVA treatment conditions for PCs (25 micrograms/mL AMT; 30 min UVA at 7 mW/cm2; 2 mM [2 mmol/L] mannitol), more than 6 log10 of added cell-free VSV was completely inactivated. In the current study, various PUVA conditions are evaluated for efficacy in inactivating other viral forms that could be present in PCs. Maintenance of platelet integrity (i.e., platelet number, solution pH, and aggregation response during initial storage after treatment) and kill of cell-associated VSV are examined. RESULTS: While cell-free viruses were inactivated efficiently under previous PUVA conditions, cell-associated VSV and the non-lipid-enveloped bacteriophage M13 were not. Effective inactivation of these viruses was achieved by raising the concentration of AMT to 50 micrograms per mL and extending the period of irradiation to 90 minutes (39 J/cm2). However, for maintenance of platelet integrity under these conditions, the prior removal of oxygen or the inclusion of compounds known to quench both type I and type II photoreactants (e.g., flavonoids such as rutin) was required. CONCLUSION: These findings suggest that the viral safety of PCs may be enhanced through treatment with AMT and UVA in the presence of flavonoids, and that flavonoid use may prove beneficial in other systems where oxygen-mediated damage occurs.

Antiviral Agents↗
PubMed1994

Viral safety of solvent/detergent-treated blood products.

Laboratory research that began in 1982 led to the licensing in the USA of a solvent/detergent (SD)-treated factor VIII concentrate in 1985. The licence was granted on the basis of several factors. First, studies had demonstrated the inactivation of several marker viruses (vesicular stomatitis virus, Sindbis virus, Sendai virus) and other viruses such as human immunodeficiency virus (HIV), hepatitis B virus (HBV), and non-A, non-B hepatitis virus (NANBHV; now known principally to be hepatitis C virus) added to the factor VIII concentrate just before treatment. Secondly, it had been realized that the relevant viruses in transfusion (e.g. HIV, HBV, NANBHV) all had lipid envelopes. Finally, laboratory, preclinical and clinical evidence indicated that factor VIII and other proteins present in the preparation were unaffected by SD treatment. The applicability of the SD method to a wide range of products and preparations, high process recoveries and a growing body of viral safety information linked with the failure of several other virus-inactivation methods to eliminate hepatitis transmission fostered the adoption of SD technology by more than 50 organizations worldwide. SD mixtures are now used in the preparation of a diverse array of products. Numerous laboratory and clinical studies suggest that coagulation-factor concentrates and other SD-treated products prepared from plasma pools are now safer than the individual units from which they were derived. Also, a large body of evidence indicates that hepatitis A virus (HAV) is not typically transmitted by blood and blood products.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

New phthalocyanines for photodynamic virus inactivation in red blood cell concentrates.

Cationic phthalocyanines with either aluminum or silicon as the central metal were evaluated for their ability to inactivate viruses in red blood cell concentrates (RBCC) photodynamically. In addition, the virucidal potential of a substituted anionic phthalocyanine, aluminum dibenzodisulfophthalocyanine hydroxide (A1N2SB2POH) was evaluated and compared with that of the much studied anionic aluminum tetrasulfophthalocyanine hydroxide (A1PcS4OH). Based on the rate of inactivation of the lipid-enveloped vesicular stomatitis virus (VSV), the virucidal potential of these phthalocyanines was: HOSiPcOSi(CH3)2(CH2)3N+(CH3)3I- (Pc 5) = SiPc[OSi(CH3)2-(CH2)3N+(CH3)3I-]2 (Pc 6) > A1PcOSi(CH3)2(CH2)3N+(CH3)2(CH2)11CH3I- (Pc 21) = A1N2SB2POH = A1PcS4 > HOSiPc[OSi(CH3)2(CH2)3N+(CH3)2(CH2)11CH3I-]2 (Pc 14) > A1PcOSi(CH3)2(CH2)3N+(CH3)3I- (Pc 2). Phthalocyanine ligand 14 and Pc 21 are new phthalocyanines, made by quaternizing known amino analogues. Compared to VSV, the rate of inactivation of Sindbis virus (another model lipid-enveloped virus) was identical when treated in red blood cells (RBC) with Pc 5 and slightly higher when treated with Pc 6 and A1PcS4OH. Treatment of RBCC containing cell-free human immunodeficiency virus (HIV-1) with Pc 5 or A1PcS4OH required 15 min of irradiation to inactivate (> 5 log10 reduction) the virus. The extent of HIV-1 inactivation with A1N2SB2POH was 3.7 log10 after 60 min of red light exposure. The RBC integrity after photosensitization was measured by the ability of the cells to bind to plates coated with poly-L-lysine, (which reflects the retention of the RBC surface negative charges) and hemolysis of the cells over a 7 day storage period.(ABSTRACT TRUNCATED AT 250 WORDS)

Erythrocyte Transfusion↗
PubMed1994

The photochemical properties of fluoroaluminum phthalocyanine.

Fluoride is known to inhibit the photodynamic activity of aluminium phthalocyanine in a variety of biological systems. In order to gain insight into this phenomenon, the effect of fluoride on the photophysical properties of free and albumin-bound chloroaluminum phthalocyanine sulfonate (AlPcSn) were studied. The association constant of NaF with AlPcSn in aqueous solution was measured as 500 +/- 20 M-1. This binding affects the photophysical properties of the dye: the absorption bands in the visible range are blue-shifted by 6-8 nm, and this effect is mirrored in the fluorescence emission spectrum. Human serum albumin significantly quenched the dye fluorescence independent of the presence of fluoride ion. The transient absorption spectrum of the excited dye triplet is unchanged by NaF, but the quantum yield for its generation is increased by 50%, with no decrease in its lifetime. Formation of fluoroaluminum phthalocyanine complexes was also observed in tetrabutylammonium fluoride-assisted solutions in wet acetonitrile. The fluoro-AlPcSn complex is a better photosensitizer for generation of singlet oxygen than the original dye-hydroxyl ion complex, as confirmed using the imidazole-N,N-dimethyl-4-nitrosoaniline method. On the other hand, the fluoro-AlPcSn complex exhibits an intense inhibitory effect on photohemolysis of red blood cells (RBC) even after the cells are washed to remove free dye and fluoride prior to irradiation, indicating that once the dye is attached to the cellular site, the fluoride ligand is no longer prone to displacement (by hydroxyl ion, for example). Nonetheless, it is clear from the spectroscopic data that the new fluoro complex is an efficient sensitizer for photooxidation.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗
PubMed1994

Cloning and characterization of a Kv1.5 delayed rectifier K+ channel from vascular and visceral smooth muscles.

We have cloned and characterized the expression of a Kv1.5 K+ channel (cKv1.5) from canine colonic smooth muscle. The amino acid sequence displayed a high level of identity to other K+ channels of the Kv1.5 class in the core region between transmembrane segments S1-S6; however, identity decreased to between 74 and 82% in the NH2 and COOH terminal segments, suggesting that cKv1.5 is a distinct isoform of the Kv1.5 class. Functional expression of cKv1.5 in oocytes demonstrated a channel highly selective for K+, which activates in a voltage-dependent manner on depolarization to membrane potentials positive to -40 mV. At room temperature the channel showed fast activation (time to half of peak current, 5.5 ms) and slow inactivation that was incomplete after 20-s depolarizations. Single channel analysis of the channel expressed in oocytes displayed a linear current-voltage curve and had a slope conductance of 9.8 +/- 1.1 pS. Northern blot analysis demonstrated differential expression of cKv1.5 in smooth muscles of the gastrointestinal tract and abundant expression in several vascular smooth muscles. We propose that cKv1.5 represents a component of the delayed rectifier current in both vascular and visceral smooth muscles.

Amino Acid Sequence↗
PubMed1994

Heterotetramer formation and charybdotoxin sensitivity of two K+ channels cloned from smooth muscle.

Delayed rectifier K+ channels are involved in the electrical activity of all excitable cells. The relationship between native K+ currents recorded from these cells and cloned K+ channel cDNAs has been difficult to ascertain partly because of contradictions in pharmacological characteristics between native and expressed currents. Through the study of the charybdotoxin (CTX) pharmacology of two cloned smooth muscle delayed rectifier K+ channels (cKv 1.2 and cKv1.5) expressed in oocytes, evidence for heterotetramer formation was obtained. We have shown that the presence of even a single CTX-insensitive subunit renders the heterotetrameric channel insensitive to CTX. The two K+ channel clones differ in an amino acid at the mouth of the pore region, which may be in a position to block the access of CTX to its binding site and hence determine CTX sensitivity of the heterotetrameric channel. These results may explain discrepancies reported between native and cloned smooth muscle K+ channels.

Amino Acid Sequence↗
PubMed1994

Cost and intensity of care in case managers' referrals to psychiatric day programs.

OBJECTIVE: The purpose of the study was to determine whether case managers referred clients with different needs to programs with different goals and levels of intensity, and thus with different costs. METHOD: A total of 150 case managers were asked to select one of three day programs--day treatment, clubhouse, or supported employment--for four hypothetical clients described in case vignettes. They also were asked to choose any or all of three types of concurrent services for these clients, including a medication clinic, outpatient counseling, and a social club. They listed the five most important criteria for making their decisions. RESULTS: The 70 case managers who responded to the survey consistently referred the most functionally impaired clients to day treatment programs and recommended fewer support services for those clients. The least impaired clients were referred to clubhouse or supported employment programs, and many support services were recommended. The most important decision-making criteria cited were clients' motivation, problem-solving ability, and history. CONCLUSIONS: Case managers differentially select day programs based on clients' functional ability. Clients referred to vocationally oriented programs are also referred to concurrent services that increase the cost of the total service package.

Adult↗
PubMed1994

Molecular physiology of CFTR Cl- channels in heart.

Recent electrophysiological data suggests a number of similarities in the properties of cAMP-dependent Cl- channels in heart and cAMP-dependent Cl- channels encoded by the cystic fibrosis transmembrane conductance regulator (CFTR) gene product in various epithelial cells. We tested the hypothesis that cAMP-dependent Cl- channels in heart may be due to cardiac expression of CFTR by amplification and sequencing of several regions of CFTR from myocardial tissue derived from various species and areas of the heart. Regions corresponding to the first nucleotide binding domain (NBD1), transmembrane segments I-VI (TS I-VI), transmembrane segments VII-XII (TS VII-XII), and the regulatory domain (R domain) were amplified and sequenced from rabbit ventricle (see Fig. 1). Comparison of the known amino acid sequence of human epithelial CFTR with the deduced sequence from rabbit heart indicated deletion of exon 5 in the first cytoplasmic loop of TS I-VI suggesting that CFTR is an alternatively spliced isoform in rabbit ventricle. Outside of the alternatively spliced region, the heart CFTR Cl- channel isoform displayed greater than 95% identity to human epithelial CFTR Cl- channels. We have also compared the molecular distribution of the CFTR gene product to the distribution of cAMP-dependent Cl- channels in native cardiac myocytes derived from various species and areas of the heart. Amplification of regions corresponding to NBD1, R domain, and TS VII-XII from atrium and ventricle of guinea pigs, rabbit, and dog hearts exhibited a distribution which closely matched the distribution of cAMP-dependent Cl- channels assessed using electrophysiological techniques.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Removal and inactivation of hepatitis A virus (HAV) during processing of factor VIII concentrates.

Although hepatitis A virus (HAV) transmission by single donor blood products is a rare event, recent reports have raised concerns about the potential for HAV transmission by pooled plasma products. In this study the removal and inactivation of HAV during production of a factor VIII concentrate, which included solvent-detergent treatment and anion-exchange chromatography steps, was assessed at 5 distinct stages of production using infectivity and, in some cases, isotopic assays. The results of these 'spiking' studies revealed an overall HAV clearance of > 8 log with appreciable contributions from antibody neutralisation, cryoprecipitation, lyophilization and possibly chromatography, but not filtration. In addition it was shown that neither solvent detergent treatment or ion-exchange chromatography reversed or impeded the neutralisation of HAV by antibody.

Drug Contamination↗
PubMed1993

Cloning and expression of a Kv1.2 class delayed rectifier K+ channel from canine colonic smooth muscle.

A cDNA (CSMK1) encoding a delayed rectifier K+ channel of the Kv1.2 class was cloned from canine colonic circular smooth muscle and expressed in Xenopus oocytes. These channels appear to be uniquely expressed in gastrointestinal muscles and may participate in the electrical slow wave activity. Functional expression of CSMK1 in Xenopus oocytes demonstrated a K+ current that activated in a voltage-dependent manner upon depolarization. This current was highly sensitive to 4-aminopyridine (IC50, 74 microM). A low-conductance K+ channel was identified in inside-out patches from oocytes injected with CSMK1. This channel displayed a linear current-voltage relation with a slope conductance of 14 pS. The channels were blocked in a concentration-dependent manner by 4-aminopyridine. Northern blot analysis demonstrated that CSMK1 is expressed in a wide variety of gastrointestinal smooth muscles. Portal vein, renal artery, and uterus do not express CSMK1, suggesting that, among smooth muscles, expression of this K+ channel may be restricted to gastrointestinal smooth muscles. CSMK1 is 91% homologous to RAK, a delayed rectifier K+ channel cloned from rat heart, but displays unique pharmacological properties and tissue distribution.

4-Aminopyridine↗
PubMed1993

Enhancement in the safety of immune globulins prepared from high-risk plasma.

Hyperimmune gamma-globulins have proven efficacious in the prevention and treatment of viral infections, including those caused by hepatitis A and B viruses, cytomegalovirus, parvovirus. Interest in the prevention and/or treatment of infections caused by human immunodeficiency virus (HIV) has led to clinical trials with anti-HIV immune plasma and purified immune globulin prepared from donors who are actively infected with HIV. The handling and fractionation of this or other infectious plasma requires the construction and operation of virus containment facilities designed to protect fractionation employees and the immediate environment. This requirement would be reduced substantially by applying virucidal procedures prior to or during plasma pooling. We have shown that heating plasma at 56 degrees C for 1 h followed by treatment with 1% tri(n-butyl) phosphate (TNBP) and 1% Triton X-100 for 4 h at 30 degrees C resulted in the inactivation of > or = 10(12.1) tissue culture infectious doses (TCID50) of HIV. With this treatment, the recovery of IgG was 87 +/- 3%. Fractionation of treated plasma by cold ethanol precipitation proceeded normally, and overall recovery, purity, and potency against selected viral markers were unaffected. The additional treatment of plasma with 15 g/l Aerosil for 4 h at 45 degrees C removed 10(4.5) TCID50 of HIV but resulted in substantial IgG losses both prior to and following fractionation. We conclude that potentially infectious plasma can be treated at 56 degrees C for 1 h and by TNBP/Triton X-100 at 30 degrees C for 4 h prior to fractionation. These steps appear sufficient to assure safety and to permit routine fractionation of plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Adsorption↗