Anti-Human Immunodeficiency Virus Activity, Bioavailability and Drug Resistance Profile of the Novel Proteinase Inhibitor MDL 74,695

MDL 74,695, a novel dipeptide-like compound containing the ‘difluorostatone type’ transition state mimic and a potent inhibitor of the human immunodeficiency virus (HIV) proteinase, was investigated for anti-HIV activity in vitro. The compound showed selective inhibition of both HIV-1 and HIV-2 in MT-4 cells. A potent antiviral effect against a range of clinical isolates of HIV-1 cultured in human peripheral blood mononuclear cells and primary monocytes was also demonstrated. The antiviral activity of MDL 74,695 against viruses resistant to a range of reverse transcriptase inhibitors was equivalent to the wild-type. In rats MDL 74,695 (30 mg kg−1) was 4.9% orally bioavailable and maintained levels above the in vitro 50% inhibitory concentration (IC50) for approximately 3 h. Viruses with reduced sensitivity to MDL 74,695 and saquinavir were selected in cell culture by continuous passage in increasing drug concentrations, and first appeared after 20 and 17 passages, respectively. Amino acid changes were identified at positions 48 (glycine to valine), 50 (isoleucine to valine) and 82 (valine to either isoleucine or alanine) in various combinations for MDL 74,695-resistant viruses. For saquinavir-resistant viruses changes were identified at positions 48 (glycine to valine) and 90 (leucine to methionine). Studies using MDL 74,695, saquinavir and a third proteinase inhibitor indinavir, indicated that virus selected in the presence of MDL 74,695, with amino acid exchanges at positions 48 and 82 showed cross-resistance to saquinavir. However, viruses selected in the presence of MDL 74,695 with amino acid exchanges at positions 50 and 82 showed no significant change in sensitivity to saquinavir. Likewise, viruses selected in the presence of saquinavir with amino acid exchanges at positions 48 and 90 remained sensitive to MDL 74,695. All viruses selected after growth in the presence of either MDL 74,695 or saquinavir showed little or no resistance to indinavir.

MDL 74,968, a new acyclonucleotide analog: activity against human immunodeficiency virus in vitro and in the hu-PBL-SCID.beige mouse model of infection

The novel acyclonucleotide derivative of guanine, 9-[2-methylidene-3-(phosphonomethoxy)propyl] guanine (MDL 74,968), had antiviral activity comparable to those of 9-(2-phosphonomethoxyethyl) adenine (PMEA) and 2',3'-dideoxyinosine against laboratory strains of both human immunodeficiency virus (HIV) types 1 and 2 cultured in MT-4 cells and several clinical HIV isolates cultured in human peripheral blood mononuclear cells (PBMCs). MDL 74,968 was at least fourfold less toxic than PMEA to MT-4 cells or PBMCs, thereby producing a more favorable in vitro selectivity index for the former compound. Studies of acute toxicity in CD-1 mice showed that MDL 74,968 was not toxic at doses of 1,600 mg/kg of body weight via the intraperitoneal route or at doses of 500 mg/kg via the intravenous route. Furthermore, no adverse effects of MDL 74,968 were apparent when mice were treated at doses of 200 mg/kg twice daily for 5 days. Treatment by continuous subcutaneous infusion of MDL 74,968 or PMEA at the daily dose of 20 mg/kg in the hu-PBL-SCID.beige murine model of HIV infection significantly reduced the severity of infection compared with that in placebo-treated controls. Quantitation of virus recovery by endpoint titration of spleen cells in coculture with mitogen-activated PBMCs demonstrated that MDL 74,968 as well as PMEA significantly reduced the amount of virus (P < 0.02). Moreover, by using DNA extracted from spleens, the mean HIV:HLA PCR product ratio, which takes into account individual variation in immune system reconstitution, were 0.50 and 0.40 for MDL 74,968 and PMEA treatments, respectively, whereas animals receiving the placebo control had significantly higher levels of HIV proviral DNA (mean 0.78; P < 0.02). Taken together, these promising findings suggest that an orally bioavailable prodrug of MDL 74,968 should be developed for the treatment of HIV infection.

Potent inhibition of human immunodeficiency virus by MDL 101028, a novel sulphonic acid polymer

MDL 101028, a novel biphenyl disulphonic acid urea co-polymer was designed and synthesised as a heparin mimetic. This low molecular weight polymer showed potent inhibition of human immunodeficiency virus type 1 (HIV-1) replication in a number of host-cell/virus systems, including primary clinical isolates of the virus cultured in human peripheral blood mononuclear cells (PBMCs). When compared with the heterogeneous polysulphated molecules, heparin and dextran sulphate, this chemically defined compound showed equivalent antiviral activity with 50% inhibitory concentrations (IC50s) in the range 0.27-3.0 micrograms/ml in the host-cell/virus systems tested. MDL 101028 also inhibited the replication of HIV type 2 and the simian immunodeficiency virus (SIV), as well as HIV-1 variants resistant to reverse transcriptase inhibitors. Virus growth was blocked when exposure of T-lymphocytes to MDL 101028 was restricted to the virus absorption stage, or even in whole blood conditions. MDL 101028 did not irreversibly inactivate virions, and in contrast to heparin, did not inhibit the attachment of radiolabelled HIV-1 to CD4+ T-cells. MDL 101028 blocked HIV-induced cell-to-cell fusion and this activity appears to explain the mechanism of its antiviral action. The antiviral evaluation of discrete oligomer molecules of MDL 101028 showed that a polymer chain length of six repeating units had optimal potency. The lack of anticoagulant properties and significant antiviral activity in whole blood may allow the development of MDL 101028 as a treatment of HIV infections.

The ribonucleotide reductase inhibitor (E)-2'-fluoromethylene-2'-deoxycytidine (MDL 101,731): a potential topical therapy for herpes simplex virus infection

The ribonucleotide reductase inhibitor MDL 101,731 was examined for antiviral activity against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) in vitro and in combination with acyclovir in the murine zosteriform model of HSV-1 infection. The in vitro antiviral activity (IC50) for both serotypes of HSV was similar and in the range 23-98 nM for Vero cells. Comparable activities were obtained against acyclovir-resistant viruses. In the zosteriform model, topical combination therapy of MDL 101,731 with acyclovir (5%:5% w/w) applied 48 h after infection was more effective than acyclovir alone and even appeared to promote lesion resolution.

1988: use of a Bayesian statistical model for risk assessment in coronary artery surgery. Updated in 1995

A computerized statistical model based on the theorem of Bayes was developed to predict mortality after coronary artery bypass grafting. From January, 1984, to April, 1987, at our hospital, 700 patients underwent isolated coronary artery bypass grafting. The presence or absence of 20 risk factors was determined for each patient. The first 300 patients formed the initial database of the Bayesian predictive model, and the remaining 400 patients were prospectively evaluated in four groups of 100 each. Each group was prospectively evaluated and then incorporated into the database to update the model. There was good agreement between predicted and observed results. Bayesian theory is particularly suited to this task because it (1) accommodates multiple risk factors, (2) is tailored to one's specific practice, (3) determines individual, rather than group, prognosis, and (4) can be updated with time to compensate for a changing patient population. These flexible attributes are especially valuable in light of recent changes in the coronary artery bypass graft patient profile.

Antiviral activity and metabolism of the castanospermine derivative MDL 28,574, in cells infected with herpes simplex virus type 2

The 6-O-butanoyl derivative of castanospermine (MDL 28,574: BUCAST), an inhibitor of glycoprotein processing, blocked the growth of herpes simplex virus type-2 with the effect markedly enhanced by exposure of cells to the compound pre- as well as post-infection. The effectiveness of the derivative corresponded to an increased uptake with greatest accumulation after virus infection. Gas chromatography/mass spectrometry identified the predominant component in MDL 28,574 treated cells as castanospermine, an inhibitor of alpha-glucosidase 1. The effects of this compound on the synthesis of viral glycoprotein, gB, was determined with the increased molecular weight of the mannose-rich precursor evidence for the modulation of glycoprotein processing.

Treatment with the alpha-glucosidase 1 inhibitor 6-O-butanoyl castanospermine reduces the detection of LFA-1 (CD18/CD11a) by monoclonal antibodies

The antiviral clinical candidate 6-O-butanoyl castanospermine (MDL 28,574), an alpha-glucosidase 1 inhibitor, was examined for its effect on elementary parameters of immune function. It did not affect the mitogenic response of uninfected human mononuclear leukocytes or the detection of a range of cell surface markers, with the exception of the integrin LFA-1 (CD18/CD11a), which was reduced, after cell growth in vitro. The detection of LFA-1 was also reduced on both human and murine cells after oral administration of the compound to xenochimaeric or normal mice, respectively. Altered LFA-1 expression or function may contribute to reduced cell adhesion and the observed reduction in the in vitro allogeneic response by uninfected cells, as well as the previously described prevention of cell conjugate and HIV-induced syncytium formation.

The effect of oral treatment with 6-O-butanoyl castanospermine (MDL 28,574) in the murine zosteriform model of HSV-1 infection

Oral treatment of mice, cutaneously infected with herpes simplex virus type 1 (HSV-1) (strain SC16), with the alpha-glucosidase 1 inhibitor 6-O-butanoyl castanospermine (MDL 28,574) produced a significant delay in lesion development and reduced the amount of virus recovered from the brain. Virus load in the brains of mice, whose treatment started 2 days prior to infection, was reduced approximately 100-fold when compared to untreated controls. Treatment initiated at the time of infection, while less effective than pre-treatment, nevertheless reduced virus recovery from the brain by 10-fold. Consistent with its antiviral activity, orally administered MDL 28,574 was rapidly incorporated by brain tissue and mice fed with compound over extended periods maintained relatively high levels of drug at this site.

The inhibition of human immunodeficiency virus type 1 in vitro by a non-nucleoside reverse transcriptase inhibitor MKC-442, alone and in combination with other anti-HIV compounds

MKC-442, a derivative of the non-nucleoside reverse transcriptase (RT) inhibitor 1-[(2-hydroxyethoxy)methyl)-6-(phenylthio)thymidine (HEPT), showed potent and selective inhibition of human immunodeficiency virus type 1 (HIV-1) replication in vitro, using a range of host-cell/virus systems including human peripheral blood mononuclear cells infected with primary clinical isolates. MKC-442 was evaluated in combination with the nucleoside analogues AZT, ddI and ddC, the non-nucleoside RT inhibitor nevirapine, the HIV-1 proteinase inhibitor Ro-31-8959, and the alpha-glucosidase 1 inhibitor, MDL-28,574, using a cell viability assay. Drug interactions were evaluated by the isobologram technique and by calculating combination indices. Notable synergistic inhibition of HIV-1 replication was observed when MKC-442 was combined with AZT and MDL-28,574 and moderate synergy with ddI. In combination with ddC, nevirapine or Ro-31-8959, only a slightly better than additive effect was observed. Impressive synergy was seen using the three-drug combinations of MKC-442, AZT and MDL-28,574 or MKC-442, AZT and Ro-31-8959. No additional cytotoxicity was observed as measured by [3H]thymidine incorporation by concanavalin A-stimulated peripheral blood mononuclear cells, when MKC-442 was combined with any of the above-mentioned compounds. The use of MKC-442 in a two- or three-drug combination regimen with other RT inhibitors, a proteinase inhibitor or an alpha-glucosidase 1 inhibitor should be considered for HIV-1-related chemotherapy.

The prevention of cell adhesion and the cell-to-cell spread of HIV-1 in vitro by the alpha-glucosidase 1 inhibitor, 6-O-butanoyl castanospermine (MDL 28574)

The intercellular adhesion molecule (ICAM-1, CD54) and its counter receptor, the integrin leukocyte function associated antigen 1 (LFA-1, CD11a/CD18), have important roles in the immune response. These include guiding leukocytes to sites of inflammation (Issekutz and Issekutz, 1992), enhancement of antigen presentation (Moy and Brian, 1992) and potentiation of cytotoxic cell function (Umehara et al., 1992; Sanchez-Madrid et al., 1982). In addition to these activities LFA-1 and ICAM-1 are implicated in the cell-to-cell transmission of human immunodeficiency virus (HIV-1) since antibodies to CD18, CD54 or synthetic peptide analogs of ICAM-1 antagonise the formation of virus-induced syncytia (Fecondo et al., 1993; Gruber et al., 1991; Hildreth and Orentas, 1989; Valentin et al., 1990). The alpha-glucosidase 1 inhibitor 6-O-butanoyl castanospermine (MDL 28574) has antiviral activity for HIV which is manifested by a decrease in syncytia as well as the production of virus with altered gp120 and a reduced infectivity (Taylor et al., 1991). Previously, it has been shown that the alpha-glucose 1 inhibitor (MDL 28574) treatment of human leukocytes in vitro or mouse lymphocytes in vivo affects the detection of LFA-1 but not domain 1 of CD4 nor several other CD markers (Bridges et al., submitted for publication). Here, we demonstrate that pre-treatment of HIV-permissive CD4+ cells with MDL 28574 substantially reduces their capacity to bind with cells chronically infected with HIV-1 which results in reduced virus production.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of alpha-glucosidase I of the glycoprotein-processing enzymes by 6-O-butanoyl castanospermine (MDL 28,574) and its consequences in human immunodeficiency virus-infected T cells

The 6-O-butanoyl derivative of castanospermine (MDL 28,574) was previously shown to be approximately 30-fold more potent than the naturally occurring molecule at inhibiting the replication of human immunodeficiency virus (HIV) (D. L. Taylor, P. S. Sunkara, P. S. Liu, M. S. Kang, T. L. Bowlin, and A. S. Tyms, AIDS 5:693-698, 1991). We now report that consistent with its improved anti-HIV activity, MDL 28,574 is more effective (50% inhibitory concentration [IC50], 20 microM) than the parent molecule (IC50, 254 microM) at causing the accumulation of glucosylated oligosaccharides in HIV-infected cells by inhibition of glycoprotein processing. These were predominantly of the glucose 3 type, as determined by P4 Bio-Gel analysis after digestion with purified alpha-glucosidase I, indicating that, intracellularly, this enzyme is the major target for inhibition. MDL 28,574, however, was less active (IC50, 1.27 microM) than castanospermine (IC50, 0.12 microM) against the mutual target enzyme, cellular alpha-glucosidase I, in a cell-free assay system. The increased effects of MDL 28,574 against alpha-glucosidase I in cell culture were attributed to the improved cellular uptake of the more lipophilic derivative. Inhibition of this enzyme activity in HIV-infected H9 cells impaired viral glycoprotein processing and resulted in the expression of abnormally configured gp120. This did not affect virus production, but the virions had decreased infectivity which was partially related to a reduced ability to bind to CD4+ T cells.

ACTIVE Na+-, Cl-- AND HCO3--DEPENDENT ACID EXTRUSION IN ATLANTIC COD RED BLOOD CELLS IN WINTER ACTIVATED BY HYPERCAPNIA

The relationship between intracellular pH (pHi) and extracellular pH (pHe) was investigated in red blood cells from the Atlantic cod (Gadus morhua) in carbon dioxide/bicarbonate-buffered salines. In summer animals (August/September), similar transmembrane distribution ratios of chloride ([Cl-]i/[Cl-]e=rCl-) and protons ([H+]e/[H+]i=rH+) suggested a passive Donnan distribution of these ions across the red blood cell membrane at pHe 6.7&shy;8.4. In winter animals (February/March), a marked discrepancy occurred between rH+ and rCl- at low pHe values. The pronounced increase in rH+ resulted in significantly higher pHi values compared with those of red blood cells from summer animals and at pHe 6.7 pHi exceeded pHe by 0.3 units. The increases in rH+ values were completely abolished by cyanide and 2,4-dinitrophenol. The high disequilibrium rH+ values were sodium-, chloride- and bicarbonate-dependent. During hypercapnic acidosis, proton equivalents were extruded from the red blood cell. The resulting high rH+ values were accompanied by a reduced chloride shift into the red blood cell and a ouabain-insensitive net sodium influx. The net sodium influx into red blood cells from winter animals was significantly reduced in the presence of DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid). The results suggest the activation of a Na+-dependent Cl-/HCO3-exchanger at low pHe in the red blood cells of the Atlantic cod in winter.

CATECHOLAMINE-ACTIVATED SODIUM/PROTON EXCHANGE IN THE RED BLOOD CELLS OF THE MARINE TELEOST GADUS MORHUA

The effects of catecholamines on the pH and the cellular ion and water content were investigated in red blood cells from the Atlantic cod (Gadus morhua). Noradrenaline induced a rapid decrease in the extracellular pH (pHe) of red blood cells suspended in a CO2/bicarbonate or in a CO2/bicarbonate-free buffer system. The noradrenaline-induced changes in pHe were a saturable function of the external sodium ion concentration and were inhibited by amiloride but not by DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid, final concentration of both 10(-4) mol l-1). The catecholamine-induced extracellular acidification was accompanied by an intracellular alkalization and protons were moved from their electrochemical equilibrium. Proton extrusion was associated with an increase in the red blood cell sodium and chloride concentrations. In the presence of DIDS, the chloride movements were blocked and the net proton efflux under these conditions matched the net sodium influx. The results strongly suggested the activation of a sodium/proton exchanger by catecholamines in the red blood cells of the Atlantic cod. The red blood cell receptor affinity for adrenaline was three times higher than that for noradrenaline. Comparison with data in the literature for in vivo catecholamine concentrations indicated that adrenaline was more effective than noradrenaline in activating the red blood cell sodium/proton exchanger in the Atlantic cod in vivo.

Latent equid herpesviruses 1 and 4: detection and distinction using the polymerase chain reaction and co-cultivation from lymphoid tissues

The polymerase chain reaction (PCR) and co-cultivation were used to identify the lymphoreticular system as the site of latency of equid herpesvirus I (EHV-1). Primers for PCR were designed from aligned nucleotide sequences of the glycoprotein gB genes to amplify the same region of both the EHV-1 and EHV-4 genomes. Subsequent restriction digests using specific enzymes distinguished the amplified fragments of the EHV-1 genome from those of the EHV-4 genome. Ten weeks following an experimental infection of five ponies with EHV-1, latent virus was detected by PCR and recovered by co-cultivation, predominantly from lymphoid tissues draining the respiratory tract. Significantly, latent EHV-1 also persisted in peripheral blood leukocytes (PBL). Latent EHV-4, presumably from a preceding natural infection, was also detected in some tissues, including PBL, from all animals. Of additional interest was the recovery of EHV-1 and -4 only in the presence of the ubiquitous EHV-2.

Direct measurement of first-pass ileal clearance of a bile acid in humans

The purpose of this study was to develop and validate a method of directly measuring ileal bile acid absorption efficiency during a single enterohepatic cycle (first-pass ileal clearance). This has become feasible for the first time because of the availability of the synthetic gamma-labeled bile acid 75Selena-homocholic acid-taurine (75SeHCAT). Together with the corresponding natural bile acid cholic acid-taurine (labeled with 14C), SeHCAT was infused distal to an occluding balloon situated beyond the ampulla of Vater in six healthy subjects. Completion of a single enterohepatic cycle was assessed by obtaining a plateau for 75SeHCAT activity proximal to the occluding balloon, which prevented further cycles. Unabsorbed 75SeHCAT was collected after total gut washout, which was administered distal to the occluding balloon. 75SeHCAT activity in the rectal effluent measured by gamma counter was compared with that of absorbed 75SeHCAT level measured by gamma camera and was used to calculate first-pass ileal clearance. This was very efficient (mean value, 96%) and showed very little variation in the six subjects studied (range, 95%-97%). A parallel time-activity course in hepatic bile for 14C and 75Se during a single enterohepatic cycle, together with a ratio of unity for 14C/75Se in samples obtained at different time intervals, suggests that 75SeHCAT is handled by the ileum like the natural bile acid cholic acid-taurine. Extrapolation of 75SeHCAT first-pass ileal clearance to that of the natural bile acid therefore seems justifiable. In a subsidiary experiment, ileal absorption efficiency per day for 75SeHCAT was also measured by scanning the gallbladder area on 5 successive days after the measurement of first-pass ileal clearance. In contrast with absorption efficiency per cycle, absorption efficiency per day varied widely (49%-86%), implying a possible wide variation in recycling frequency per day.

Ileal and jejunal absorptive function in patients with AIDS and enterococcidial infection

Small intestinal absorptive function was investigated in six patients with the acquired immunodeficiency syndrome (AIDS) who had diarrhoea and weight loss. Proximal function was assessed by [14C]Triolein test of fat absorption. Distal function was determined by a test of bile acid absorption in which the loss of radio-labelled synthetic bile acid, 75seleno-23-homocholic acid-taurine ([75Se]HCAT), from the enterohepatic circulation was quantified by abdominal gamma-scanning and by a vitamin B12-intrinsic factor absorption test. Concurrently indirect tests of small intestinal bacterial overgrowth ([14C]glycocholate and breath hydrogen) were carried out. In addition, jejunal histological examination and stool microscopy and culture for enteropathogens were performed. Fat absorption was reduced in all six patients, four of whom had jejunal villous atrophy. Bile acid and vitamin B12 absorption were normal in four subjects. Enteropathogens were not detected in any of the four subjects with normal terminal ileal absorptive function. In contrast, reduced bile acid and vitamin B12 absorption were detected in two of six subjects. Both patients had an enteropathogen (Cryptosporidium spp. and Isospora belli) present on stool and jejunal histological examination. Neither subject had evidence of small-intestinal bacterial overgrowth. AIDS patients therefore may have normal ileal absorptive function in the presence of jejunal disease. Infection with Cryptosporidium spp. or I. belli may however, be associated with severe ileal dysfunction.

Olga--oligonucleotide primer design program for the Atari ST

A program to facilitate the design of oligonucleotide primers has been devised. Olga is written in draft ANSI standard 'C' and makes use of the implementation of Digital Research GEM (Graphics Environment Manager) on the Atari ST. Olga is specifically suited to the polymerase chain reaction (PCR) allowing simultaneous analysis of two primer sequences. The advantage of Olga is that it provides in one program analyses for direct repeats, secondary structures and primer dimerization as well as several useful 'finishing' tools for workers engaged in PCR optimization and oligonucleotide syntheses.

One way protection between equid herpesvirus 1 and 4 in vivo

Two groups each of six sibling ponies were exposed to sequential infections with equid herpesvirus 1 or 4 (EHV-1 or EHV-4) at four or five month intervals. Two exposures to EHV-4 did not significantly reduce virus shedding or pyrexia when the ponies were subsequently exposed to EHV-1. However, two sequential infections with EHV-1 completely protected against challenge with EHV-4. Virus neutralising antibody in each group did not increase until 21 days after primary exposure and was subtype specific. However, complement fixing antibody rose within seven days after inoculation with EHV-1, and 14 days after inoculation with EHV-4, and while the latter was subtype specific the former was directed against both EHV-1 and EHV-4. Interpretation of these findings in relation to vaccination is discussed.

An analysis of neural spike-train distributions: determinants of the response of visual cortex neurons to changes in orientation and spatial frequency

A previously unexploited method of examining neural spike-trains was applied to data obtained from cells in the visual cortex. Distributions of interspike intervals recorded extracellularly from cat visual cortex under four conditions were analyzed. Stimuli were gratings differing in orientation and spatial frequency. The probability density function of first passage time for a random walk with drift process, which is defined by its barrier height and drift coefficient, was used to characterize the generating process of axonal discharge under resting and stimulus conditions. Drift coefficient and barrier height were derived from the sample mean and standard deviation of the measured inter-spike intervals. For cells with simple receptive fields, variations in the drift coefficient were produced by changes in orientation and spatial frequency. Variations in barrier height were produced only by changes in orientation of the stimulus.

Further investigations of equine interferons in vitro

Following a published procedure, preparations of equine interferon (EqIFN) were prepared. Equine mononuclear leukocytes were induced with equine influenza virus to yield a preparation designated EqIFN-alpha, or with phytohemagglutinin to yield a preparation designated EqIFN-gamma. A preparation designated EqIFN-beta was obtained from equine embryo kidney cells treated with poly(rI):poly(rC) and DEAE Dextran. The pH and heat stability of these preparations were studied, and also their activity on various equine and ovine cells challenged with difference viruses. Unexpectedly, the EqIFN-gamma preparation was found to be stable at pH 2 and to heat at 60 degrees C for 2 h, whereas the EqIFN-beta preparation was labile under these conditions.

Equine interferons following exposure to equid herpesvirus-1 or -4

When 23 ponies were infected with equid herpesvirus-1 or -4 (EHV-1 or EHV-4), nasal shedding of interferon (IFN) correlated closely with the duration of viral excretion. Equine interferon (EqIFN) was detected in the serum only from animals infected with the EHV-1 virus, and here high levels correlated with clinical symptoms of locomotor disorder and indicated a poor prognosis. Low levels of IFN were detected in explanted mononuclear cells from ponies infected with either virus.

Adolescents and AIDS. Female's attitudes and behaviors toward condom purchase and use

Condom use has been advocated as a method to prevent human immunodeficiency virus (HIV) transmission. Although condoms are not uniformly popular with adolescent males, adolescent females' beliefs about condom use are unclear. To assess the specific health attitudes and behaviors as they relate to condom purchase by adolescents, we surveyed 99 adolescent females between 12 and 19 years of age (50 black, 49 white) who were attending a comprehensive adolescent health clinic. The respondents were from low to middle socioeconomic backgrounds and 85% were sexually active. A 41-item survey was developed and focused on four areas: comfort or embarrassment with menses (EM), basic knowledge of acquired immunodeficiency syndrome (AIDS) (KA); comfort in discussing contraception with partner (CC) and risk of contracting AIDS (AR). Chi-square analyses of the four factors determined that decreased EM was related to increased age (p less than 0.05), sexual activity (p less than 0.05), and CC (p less than 0.05). Older adolescents also demonstrated greater CC (p less than 0.05). Increased KA was related to contraceptive use (p less than 0.02) as well as CC (p less than 0.02). Descriptive analyses showed that 62% of the sample reported that a fear of AIDS had influenced their contraceptive behavior, but only 17% of the females reported purchasing or using a condom to prevent AIDS transmission. These findings suggest that although adolescent females have an awareness about AIDS, their behavior remains unchanged.

Separation of synthetic cycloalkylated bases, nucleosides and nucleotides by reversed-phase high-performance liquid chromatography

Reversed-phase high-performance liquid chromatography was used to determine the elution profiles of a series of synthetic cycloalkylated bases, nucleosides, and their corresponding 5'-monophosphates. A 70% aqueous methanol solution proved to be the most efficient solvent system for the separation of a mixture of the bases, all of which were eluted in times ranging from 3.3 to 4.8 min at a flow-rate of 0.8 ml/min. Subsequently, the same percentage of methanol solvent, at 0.8 ml/min, eluted the nucleoside mixture as well, with retention times ranging from 3.3 to 5.0 min. Optimum separation and resolution were achieved with 70% methanol at a flow-rate of 0.6 ml/min for a mixture of the base and nucleoside series. A phosphate buffer, containing acetonitrile-tetrabutylammonium ion, was used to analyze the 5'-monophosphate derivatives. Elution times ranged from 2.6 to 6.1 min at a flow-rate of 1.0 ml/min. Three variables were considered in order to determine optimum conditions for separation and resolution: (a) the percentage of methanol in the solvent; (b) flow-rate of solvent; and (c) the size of the cycloalkylated group of each synthetic analogue. The procedures and conditions described herein have potential use as a monitoring system to detect modified nucleic acid derivative which are prevalent in the body fluids of patients with certain metabolic disorders.

Kinetics for the synthetic bile acid 75selenohomocholic acid-taurine in humans: comparison with [14C]taurocholate

The "apparent" fractional turnover rate of the gamma-labeled bile acid analogue 75selenohomocholic acid-taurine (75SeHCAT) was assessed from decline in radioactivity over the gallbladder area on 4 successive days using a gamma-camera, and was compared in the same subjects with the fractional turnover rate of the corresponding natural bile acid, cholic acid-taurine, labeled with 14C ([14C]CAT) using the classical Lindstedt technique. Very similar results were obtained in 5 healthy individuals (coefficient of variation 4.8%, medians 0.35 and 0.34, respectively). By contrast, the fractional deconjugation rate assessed from zonal scanning of glycine- and taurine-conjugated bile acids on thin-layer chromatography was much less for 75SeHCAT than for [14C]CAT (0.02 and 0.13, respectively; p less than 0.05). The fractional rate for deconjugation plus dehydroxylation was also determined by zonal scanning, and gave lower values for 75SeHCAT than for [14C]CAT (0.02 and 0.12, respectively; p less than 0.05). There was a striking similarity between the fractional rate for deconjugation alone and that for deconjugation plus dehydroxylation for both bile acids in individual samples (r = 0.999, p less than 0.001), suggesting that these two processes might occur simultaneously and probably involve the same bacteria. We conclude that our scintiscanning technique provides an accurate, noninvasive method of measuring fractional turnover rate of a bile acid in humans, and that the finding that 75SeHCAT remains conjugated with taurine during enterohepatic recycling means that absorption should be specific for the ileal active transport site, thus rendering it an ideal substance for assessing ileal function.

Hepatic handling of a synthetic gamma-labeled bile acid (75SeHCAT)

75Se-homocholic acid-taurine (75SeHCAT) is the first available gamma-labeled bile acid, and should therefore be handled more efficiently and specifically by the liver than previous hepatoscintigraphic agents. We have measured serum and hepatic kinetics for 75SeHCAT, and compared them with those for the conventional hepatobiliary scintigraphic agent 99mTc-hepatoiminodiacetic acid, and with serum kinetics for the corresponding natural bile acid, [14C]cholic acid-taurine. We used a dynamic scintigraphic technique and serial blood sampling in 8 subjects. Initial hepatic uptake rate was identical to initial serum disappearance rate (14% dose/min) for 75SeHCAT, but significantly lower for 99mTc-hepatoiminodiacetic acid (6% vs. 14% dose/min, p less than 0.001). Hepatic transit time was shorter for 75SeHCAT (13 min vs. 22 min, p less than 0.02), net hepatic excretory rate was more rapid (1.4% vs. 0.8% dose/min, p less than 0.001), and urinary excretion was lower (1.0% vs. 9.0% dose, p less than 0.001). Initial and late-plasma disappearance rates were significantly lower for 75SeHCAT (14.3% and 1.5% dose/min) than for [14C]cholic acid-taurine (21.3% and 2.8% dose/min, respectively), and plasma clearance was also lower (275 vs. 670 ml/min). In vitro, 75SeHCAT was bound to serum proteins more completely than [14C]cholic acid-taurine (90.4% vs. 86.5%, p less than 0.005). We conclude that 75SeHCAT provides a hepatoscintigraphic agent that is handled more efficiently and specifically by the liver than the conventionally used agent 99mTc-hepatoiminodiacetic acid. It is not cleared from the serum as rapidly as [14C]cholic acid-taurine, probably due to its stronger protein binding. The clinical value of 75SeHCAT in assessing liver disease should be investigated.

The characterization of equine herpes virus-1-infected cell polypeptides recognized by equine lymphocytes

Ponies, without evidence of previous exposure to Equine herpes virus-1 (EHV-1), were experimentally infected with EHV-1 subtype 2 and investigated for lymphocyte transformation to virus-infected cell polypeptides, as shown by separation with gel electrophoresis. Animals made significant responses to Western blot fractions that corresponded to molecular weights of approximately 30,000, 40,000-45,000, 60,000-65,000, 80,000-95,000 and 100,000-140,000 MW. These molecular weight ranges correlated with the positions of major EHV-1 subtype 2 glycoproteins that were found at migration distances approximating to 137,000, 111,000, 90,000, 65,000 and 47,000 MW. Responses were also made to a subset of similar points on the subtype 1 profile. Hyperimmune equine serum precipitated numerous infected-cell proteins of both subtypes; in particular the recognition of polypeptides with MW of 142,000, 132,000, 114,000, and 46,000 was in agreement with the mitogenic responses. Labelling with 125I indicated that immunoprecipitated greater than 250,000, 182,000, 142,000, 132,000, 75,000, 46,000 and 32,000/34,000 MW products were exposed on the surface of infected cells.

Genetic restriction of cytolysis during equid herpesvirus 1 subtype 2 infection

Six Welsh Mountain pony foals were experimentally infected with a subtype 2 isolate of Equid Herpesvirus 1 (EHV-1) and subsequently examined for T cell mediated cytotoxicity against both subtypes. Cytotoxicity was not observed at 3 or 7 days after primary exposure but virus-specific, and genetically restricted, cytotoxicity of EHV-1-labelled autologous skin fibroblasts could be demonstrated 7 and 21 days after the animals were given a second exposure to live virus. Killing of subtype 2 antigen-labelled targets was more efficient than subtype 1 coated cells. This finding was paralleled by the observation that virus-neutralizing and complement-fixing antibody levels were subtype specific after the primary infection but after secondary exposure were directed against both subtypes. During primary infection the lymphocyte proliferative response to EHV-1 subtype 2 was not evident at 7 days post infection (dpi) but by 18 dpi was present in all animals. The second exposure produced an earlier (3 dpi) and larger proliferative response which was specific to the infecting isolate. The non-specific proliferative response to Concanavalin A mitogen indicated that virus infection induced a state of activation in circulating lymphocytes.

Effects of artificial depletion of the bile acid pool in man

In order to elucidate the relationship between bile acid pool size and cholesterol saturation index of fasting state gall bladder bile, we artificially depleted the bile acid pool in 12 healthy volunteers. Bile acid pool size decreased from 7.6 +/- 0.9 to 5.8 +/- 0.7 mmol (mean +/- SEM, p less than 0.01), and saturation index of fasting state gall bladder bile increased from 0.93 +/- 0.07 to 1.18 +/- 0.07 (p less than 0.001). There was no alteration in saturation index of basal or stimulated hepatic bile. There was no change in gall bladder storage of basal hepatic bile, nor in the proportion of the bile acid pool stored in the gall bladder. The bile acid mass in the gall bladder fell from 4.9 +/- 0.5 to 3.4 +/- 0.4 mmol (p less than 0.05) and phospholipid mass from 1.6 +/- 0.3 to 1.2 +/- 0.2 mmol (p less than 0.05), but there was no change in cholesterol mass. The gall bladder volume fell from 30 +/- 4 to 18 +/- 2 ml (p less than 0.01). These results suggest that artificial depletion of the bile acid pool increased saturation index of fasting state gall bladder bile without altering saturation index of basal or stimulated hepatic bile; it probably increased the ratio of basal: stimulated hepatic bile within the gall bladder by decreasing gall bladder storage of stimulated hepatic bile.

Innate immunity during Equid herpesvirus 1 (EHV-1) infection

Intrinsic phagocytosis and killing of C. albicans by equine monocytes and polymorphonuclear leucocytes (PMN) was examined during Equid Herpesvirus 1 (EHV-1) (subtypes 1 or 2) and Adenovirus infections. Monocyte function increased during EHV-1 subtype 2 and Adenovirus infection. Conversely, there was an impairment of monocyte ingestion during EHV-1 subtype 1 infection which was ascribed to virus replication in peripheral blood mononuclear cells. PMN phagocytosis was not decreased in any of the infections studied. The raised levels of haemolytic complement in animals which subsequently developed EHV-1 subtype 1 induced paresis suggested an abnormality of complement turnover. Increased levels of interferon were evident in the nasal secretions of both subtype 1 and subtype 2 infected animals but only subtype 1 virus induced measurable levels of serum interferon. No intrinsic abnormality of interferon production by monocytes or lymphocytes was found.

Use of a gamma-labeled bile acid (75SeHCAT) as a test of ileal function. Methods of improving accuracy

The object of the present study was to improve the accuracy of measurements of ileal function obtained by abdominal scanning and fecal counting after oral administration of the gamma-labeled bile acid 75seleno-homocholic acid-taurine (75SeHCAT), as current techniques do not distinguish between retention of the bile acid within the enterohepatic circulation from retention within the colon, and are also affected by incomplete stool collection when using the fecal method. We have therefore introduced the following modifications: (a) simultaneous ingestion of 51CrCl3 as a nonabsorbable correction marker for both the abdominal scanning and fecal counting methods; and (b) the use of 75SeHCAT counts over the gallbladder area on abdominal scanning, because these counts should be independent of colonic retention. We have studied 42 subjects, including 6 healthy controls, 6 ileal resection subjects, 15 ulcerative colitis patients, and 15 patients with unresected ileal Crohn's disease. Colonic retention (0%-68% per day) caused a variable overestimate of 75SeHCAT absorption. Corrected measurements of the fecal absorption index determined by a gamma-counter and of the abdominal absorption coefficient determined by a gamma-camera correlated well with each other (r = 0.92, p less than 0.0001), providing an internal validation of the 51CrCl3 modification. The fecal absorption index could also be determined from the carmine-rich stool collection of a single day, and this also correlated well with the abdominal absorption coefficient (r = 0.81, p less than 0.0001). Gallbladder scanning alone was simpler, involving only one isotope, but it correlated less well with the fecal absorption index than did the abdominal absorption coefficient (r = -0.64, p less than 0.001).

Endothelial cell infection and thrombosis in paralysis caused by equid herpesvirus-1: equine stroke

Eight mares were infected with equid herpesvirus-1 subtype 1 isolated from a case of equine paresis. In two mares killed at 4 d.p.i. immunofluorescence showed endothelial cell infection together with thrombosis in the rete arteriosus of the nasal mucosa and also in the spinal cord of one of these mares. Circulating platelet counts in the other six mares fell as early as 2 d.p.i. and remained depressed for seven days. Circulating immune complexes started to appear at 2 d.p.i., reached maximum levels at 10 d.p.i., but were undetectable at 28 d.p.i. Three of the six remaining mares developed varying degrees of inco-ordination at 8 and 9 d.p.i. In the two inco-ordinate mares that were killed at 9 and 10 d.p.i. the haemorrhages in the spinal cord and brain were associated with extensive endothelial cell fluorescence and thrombus formation. Clinical paresis coincided with an increase in circulating complement fixing and neutralising antibodies which in all six mares were higher against the subtype 2 isolate than subtype 1. In five yearlings infected with a subtype 2 isolate of EHV-1 platelet counts remained normal and neither immune complexes nor viraemia, nor inco-ordination were detected.

Experimental reactivation of equid herpesvirus 1 (EHV 1) following the administration of corticosteroids

Eight ponies were experimentally infected with equid herpesvirus 1 (EHV 1) (subtype 1). All animals showed clinical and serological evidence of infection and virus was isolated from nasal swabs and leucocytes. These ponies were kept in isolation for a further three months during which time complement fixing antibody decreased at least four-fold. Following immunosuppression with dexamethasone and prednisolone subtype 1 virus was recovered from six of the eight animals within 14 days. Five of these six ponies were viraemic and three of them shed virus in nasal secretions; only four displayed significant rises in complement fixing antibody and only two in neutralising antibody. Clinical abnormalities were not detected during reactivation.

Quantification of temocillin biliary excretion and gallbladder bile concentration in healthy subjects

The techniques of duodenal perfusion with polyethylene glycol as a nonabsorbable marker, and cholescintiscan using 99Tc HIDA as a gallbladder bile marker, were used to measure the total duodenal output and gallbladder bile concentration of temocillin after administration of an intravenous bolus injection to each of 6 healthy subjects. We carried out 8 studies. 3 with 0.5g temocillin and 5 with 1g temocillin. The plasma half-life of temocillin was 177 (+/- 25) minutes [mean (+/- SD)] and 196 (+/- 29) minutes with the 0.5g and 1g doses, respectively. Urinary excretion accounted for 38% of the total dose given during the study period of 6 hours, and total biliary excretion was recorded as 2.2% of the given dose for both doses. The mean concentration of temocillin in gallbladder bile was 314.7 (+/- 273.2) mg/L after the 0.5g dose and 474.5 (+/- 307.3) mg/L after 1g dose. It was concluded that temocillin is highly concentrated in the normal gallbladder in man.

Further evidence for the procidin function of C3

It was found that heat-inactivated serum supported phagocytosis, but did not promote oxygen consumption or killing of Candida, by human polymorphonuclear leucocytes (PMNs). It was also established that C3 is required for activation of the PMN candidacidal related mechanisms of superoxide anion generation and iodination. Addition of purified C3 to C3 deficient serum restored phagocytic killing. Further evidence for C3 involvement in Candida killing was obtained from studies of PMN ingestion and killing in the presence of trypan blue or heparin. Trypan blue, which antagonises C3 receptors, prevented efficient killing, as did heparin, which affects C3 conversion in normal serum. From these results it is evident that phagocytic killing is not an obligatory consequence of ingestion. The findings also indicate that killing by PMNs is dependent upon the interaction of humoral factors, termed procidins, with receptors responsible for initiation of microbicidal mechanisms. Activation products of C3 may stimulate phagocytic killing by engagement of their counterpart receptors on PMNs.

Assessment of gall-bladder storage function in man

1. We have validated a scintiscanning method for measuring fasting-state gall-bladder (GB) filling in man. 99mTc-labelled diethyl phenylcarbamoylmethyliminodiacetate (Tc-HIDA) was given intravenously, and 90 min later GB and gut activity were measured by using two isosensitive rectilinear scanning heads (anterior and posterior). Studies with a phantom GB in vitro, and studies in man in vivo, showed that the maximum error due to differences in isotope depth was 8%, compared with 300% when only one head was used.

2. By combining this technique with measurement of biliary lipid concentrations of fasting-state GB bile obtained by nasoduodenal intubation and intravenous cholecystokinin infusion, we were able to measure for the first time the total mass of all three biliary lipids in the GB. GB bile samples obtained in this way were divided into three consecutive portions of equal size in order to assess GB mixing. Bile acid pool size was also measured by isotope dilution.

3. We studied 12 healthy non-obese men. Fasting-state GB filling over 90 min (mean ± sem) was 54 ±8%. Biliary lipid mass in GB was 4.9 ±0.5 mmol for bile acids (67 ± 5% of the total bile acid pool), 1.6 ±0.2 mmol for phospholipid and 0.5 ± 0.1 mmol for cholesterol. The three consecutive portions of fasting GB bile gave values of 1.05 ± 0.07, 1.05 ± 0.06 and 1.03 ±0.10 for cholesterol saturation index (SI) and 6.6 ±1.1, 7.4 ± 1.6 and 6.5 ± 1.0 for Tc-HIDA c.p.m. × 1000 per mmol of bile acids.

4. The SI of fasting-state GB bile was significantly correlated with fasting-state GB filling (r = 0.63; P &lt; 0.05). It was also correlated with cholesterol mass in GB (r = 0.64; P &lt; 0.05), but not with bile acid and phospholipid mass.

5. We conclude that: (a) valid measurements of GB filling can be made in man by a simple scintiscanning technique employing 99mTc-HIDA as a biliary marker; (b) biliary lipid mass can also be measured if GB bile is obtained; (c) SI in health is in part determined by the degree of fasting-state GB filling, and in part by cholesterol mass in GB; (d) fasting-state GB content is well mixed in health.

Mechanisms of proteinuria in human glomerulonephritis

We evaluated glomerular barrier function in 28 patients with glomerulonephritis. Neutral dextrans of graded size were used to characterize the size-selective properties of the barrier. Charge selectivity was characterized by electrofocusing excreted urinary proteins. A fractional IgG clearance (relative to freely permeable inulin), smaller or greater than 100 x 10(-5) was used to distinguish patients with minor (group I, n = 13) and major (group II, n = 15) urinary IgG leakage, respectively. Fractional clearances of smaller dextrans (radii 20-50 A) were similar, but those of larger dextrans (radii 52-60 A) were elevated in group II relative to group I patients. A model of solute transport through a bimodal pore size distribution revealed the values for pore radius in the lower mode to approximate 51-55 A in both group I and group II patients. Pore radius in the upper mode, by contrast, was much larger in group II than in group I patients, approximating 87-97 vs. 72-77 A, respectively. Electrofocusing of urinary protein from group I patients revealed mostly albumin (isoelectric point 5.2). In group II patients, however, immunoglobulin excretion was copious. Moreover, the distribution of anionic, neutral, and cationic species (isoelectric points 5.5-8.5) in urinary and plasma eluates of IgG2 and IgG4 was similar. We conclude that when glomerulonephritis is associated with selective albuminuria, as in group I,, there is an isolated reduction of electrostatic retardation of relatively small anionic proteins. Major urinary IgG leakage (group II), however, appears to result from the development in the glomerular membrane of a subpopulation of enlarged pores that are highly permeable towards proteins of large size and varying charge.

Role of pulmonary edema in the acute pulmonary response to sepsis

There is evidence that both bronchoconstriction and accumulation of lung water may contribute to the early alterations in lung function following septicemia. Eigher of these may be mediated by blood components. To assess these proposed mechanisms the changes in hemodynamics, pulmonary mechanics, gas exchange, and gravimetric lung water were measured in the first 4 h after Escherichia coli infusion in the anesthetized dog and baboon. These species were selected because of previously demonstrated differences in the response to gram-negative sepsis. Both species developed systemic hypotension and early hypoxemia. The dogs had early transient increases in venous admixture (Qva/Qt) but not shunt or dead space, while the baboon had a more persistent increase in Qva/Qt and a late increase in dead space, Increases in nonelastic resistance and decreases in lung compliance were preceded or accompanied by decreases in the leukocyte count in both species, but the platelet count, fibrinogen, and total hemolytic complement had different changes in the two species. Postmortem lung analysis revealed increased lung weight in both species but the wet weight-to-dry weight ratio was not increased in either species. The fractional water content of the excess lung mass was less than that of whole blood. Histological examination revealed large numbers of extravasated leukocytes in the lungs, which may be sufficient to explain the increase in lung weight. We conclude that pulmonary edema does not play a role in the early pulmonary response to E. coli bacteremia in either species. The physiological changes observed are more consistent with bronchoconstriction.

A radiometric assay for the combined measurement of phagocytosis and intracellular killing of Candida albicans

A radiometric assay for combined measurement of phagocytosis and intracellular killing of Candida albicans by human polymorphonuclear leucocytes (PMNs) is presented. The assay, based upon the incorporation of 3H-uridine into the micro-organisms, makes it possible to measure phagocytosis and intracellular killing simultaneously but independently in a single sample. Thus it is possible to determine in a single assay whether increased survival of the micro-organism is due to reduced ingestion or reduced ability of the PMN to kill. The assay is objective, quantitative and convenient for clinical application. It is also suitable for analysing the effects of various agents, including serum factors and drugs, on PMN function.