Normal Healthy Human Volunteers Research Articles

Rational Modification of Human Gut Microbiome and Metabolites By Dietary Resistant Starch in Allogeneic Hematopoietic Stem Cell Transplantation: A Feasibility Study

Allogeneic hematopoietic stem cell transplantation (allo-HCT) is limited by acute graft versus host disease (GVHD). GVHD is the principal cause of non-relapse mortality (NRM) and a major cause of morbidity after allo-HCT. Recent published experimental data demonstrated that altering the microbiome-metabolite axis regulates acute GVHD severity. Specifically, short chain fatty acid (SCFA) butyrate was significantly decreased in the intestinal epithelial cells (IECs) of mice experiencing GVHD, while restoring butyrate levels by increasing intestinal butyrate-producing bacteria, reduced experimental acute GI GVHD severity and mortality. Prebiotics usually refer to indigestible carbohydrates that are metabolized by the intestinal microbiota to produce microbial metabolites, such as SCFAs, that serve as nutrients for IECs. Administration of defined quantities of resistant potato starch (RPS), as a prebiotic, to normal healthy human volunteers promoted increase in butyrogenic bacteria and increased intestinal levels of SCFA butyrate to a greater extent than other commercially available resistant starch preparations tested. These data form the rationale for this study and led to prospectively study the clinical feasibility and impact of the administration of RPS as a prebiotic dietary intervention on the intestinal microbiota and its dependent metabolites in allo-HCT recipients. Adults undergoing human leukocyte antigen-matched, related-donor myeloablative allo-HCT were recruited and received RPS orally daily from day -7 to day 100 after allo-HCT. Stool samples were collected in the OMNIgene-Gut® (DNA Genotek) collection kit. Fecal samples were subjected to 16S rRNA gene sequencing to determine microbiota composition and quantification of fecal SCFAs was performed by liquid chromatography. Blood specimens were collected using standardized protocols. The effect of RPS on plasma SCFAs and > 200 other metabolites was longitudinally assessed using targeted and global metabolomic analyses. Mass spectrometry was utilized for quantification of plasma metabolites. The primary objective was to assess the feasibilty and test the effect of RPS on the structure of the patients' intestinal microbiome. Metrics for the feasibility of this dietary intervention were prespecified by setting a target for ≥ 60 % of patients to adhere to ≥ 70% of scheduled doses. We hypothesized that RPS would be feasible and increase stool butyrate levels as a byproduct of microbial metabolism. Key secondary objectives were to longitudinally evaluate plasma metabolites in recipients of RPS compared to historical controls as well as assess tolerability of RPS in allo-HCT recipients. Ten subjects were enrolled. The primary endpoint was met. Feasibility exceeded the preset goal of ≥ 70% adherence to scheduled dosages in ≥ 60 % of patients as 8 of the 10 patients (80%) received ≥ 70 % of scheduled doses. Intestinal butyrate levels were significantly higher while participants were on RPS as compared to when they were not on RPS (p < 0.0001) (fig. 1A). We observed longitudinal changes in plasma metabolites post allo-HCT compared to baseline independent of whether allo-HCT recipients received RPS (p < 0.0001) (fig. 1B). In RPS recipients, the dominant plasma metabolites were, however, much more stable across timepoints when compared to historic controls suggesting a greater equilibrium in their production and consumption (fig. 1C). The median age of participants was 57 years (range 52-62 years). All subjects received standard GVHD prophylaxis with tacrolimus and methotrexate as well as standard antibiotic prophylaxis with levaquin, and standard neutropenic fever treatment with IV cefepime (90%) or IV vancomycin, No adverse effects/toxicities attributed to RPS were observed and longitudinal specimens were collected successfully (table 1). This study showed that a dietary intervention using RPS in allo-HCT recipients is feasible, and was able to rationally alter the salutary intestinal microbial metabolite SCFA butyrate, despite the utilization of several HCT related medications, including antibiotics. These data demonstrate translation of fundamental discoveries in mouse allo-HCT studies, to testing RPS in healthy humans, to showing that RPS is a feasible microbiome-modifying intervention in allo-HCT recipients, and that a prebiotic strategy can now be applied and tested to mitigate acute GVHD in allo-HCT.

Comparative immunogenicity of decellularized wild type and alpha 1,3 galactosyltransferase knockout pig lungs

Decellularized pig lungs recellularized with human lung cells offer a novel approach for organ transplantation. However, the potential immunogenicity of decellularized pig lungs following exposure to human tissues has not been assessed. We found that exposure of native lungs from wildtype and transgenic pigs lacking alpha (1,3)-galactosyltransferase (α-gal KO) to sera from normal healthy human volunteers demonstrated similar robust IgM and IgG immunoreactivity, comparably decreased in decellularized lungs. Similar results were observed with sera from patients who had previously undergone transcutaneous porcine aortic valve replacement (TAVR) or from patients with increased circulating anti-α-gal IgE antibodies (α-gal syndrome). Depleting anti-α-gal antibodies from the sera demonstrated both specificity of α-gal immunoreactivity and also residual immunoreactivity similar between wildtype and α-gal KO pig lungs. Exposure of human monocytes and macrophages to native wildtype lungs demonstrated greater induction of M2 phenotype than native α-gal KO pig lungs, which was less marked with decellularized lungs of either type. Overall, these results demonstrate that native wildtype and α-gal KO pig lungs provoke similar immune responses that are comparably decreased following decellularization. This provides a further platform for potential use of decellularized pig lungs in tissue engineering approaches and subsequent transplantation schemes but no obvious overall immunologic advantage of utilizing lungs obtained from α-gal KO pigs.

Development of Pharmacodynamic Assays to Assess Ex Vivo Masp-2 Inhibition and Their Use to Characterize the Pharmacodynamics of Narsoplimab (OMS721) in Humans and Monkeys

Introduction Narsoplimab (OMS721) is a fully human monoclonal antibody that binds to and inhibits mannan-binding lectin-associated serine protease 2 (MASP-2). MASP-2 is the key enzyme responsible for activation of the lectin pathway of the complement system. The lectin pathway is activated when plasma is exposed to molecular patterns present on microbes and injured host cell surfaces, initiating a proteolytic cascade that results in the activation of complement components C4, C2, C3 and C5 to yield multiple biologically active products. Inhibiting MASP-2 activity prevents lectin-mediated generation of complement activation products, thereby reducing inflammation and tissue injury. Narsoplimab is the first lectin pathway-specific complement inhibitor in clinical development. In published clinical studies and case reports, improvement has been observed in narsoplimab-treated patients with hematopoietic stem cell transplant-associated thrombotic microangiopathy, immunoglobulin A (IgA) nephropathy and atypical hemolytic uremic syndrome. Here we describe the development of pharmacodynamic (PD) assays to quantify MASP-2 inhibition ex vivo and their use to study duration of action and to establish the pharmacokinetic (PK)/PD relationship of narsoplimab in monkeys and humans. Methods PD assays to measure lectin pathway activity, a measure of MASP-2 activity, in minimally diluted (90%) serum from human and monkey were developed using immobilized mannan as a lectin pathway-specific complement activator with C4b as the activation endpoint. ELISA and flow cytometry assay platforms were employed to assess the PD response of monkeys or normal healthy human volunteers administered narsoplimab, respectively. The PD response was used to characterize the time-course and dose-response of lectin pathway inhibition by narsoplimab. Drug concentration data obtained from matched serum samples were used to estimate the ex vivo EC50 of lectin pathway inhibition in monkeys and humans. Lectin pathway-specific complement activation assays applicable to minimally diluted serum samples were developed by evaluating the time-course of lectin-induced complement activation response under varying reaction temperatures and selecting optimized test conditions within the dynamic range of the assay platform. The test methods were used to characterize monkey and human lectin pathway inhibition profiles of narsoplimab in vitro, and the flow cytometric method was validated for analysis of human serum samples. Results The PD assays were used to characterize the PD response of monkeys administered a single intravenous (IV) bolus injection of narsoplimab at 0.05, 0.15, 0.5, 1.5 or 5 mg/kg, and of normal human healthy volunteers administered a single IV infusion of the drug at 0.25, 0.625 or 2 mg/kg, or 6 weekly IV infusions at 2 or 4 mg/kg. A clear, dose-dependent initial PD response was observed in monkeys in the dose range of 0.5 mg/kg to 5 mg/kg, which subsequently declined over time. In humans, a minimal PD response was observed at 0.025 mg/kg. A near maximal initial PD response was seen at 0.675 mg/kg or higher, followed by a decline over time. In the 6-week repeat-dose study, once-weekly dosing of narsoplimab at 2 mg/kg resulted in a mean trough PD response of ~55% lectin pathway inhibition, which increased to an ~80% mean trough response with once-weekly dosing of 4 mg/kg. PK sample analysis revealed a clear PK/PD relationship in monkeys and humans. Modeling of the PK/PD relationship in monkeys indicated an EC50 value of ~7 µg/mL (~ 46 nM), which is comparable to the IC50 value of lectin pathway inhibition in vitro (33 nM). In humans, modeling of the PK/PD relationship data indicated an EC50 value of ~500 ng/mL (3.3 nM), again very similar to the IC50 value of lectin pathway inhibition in vitro (3.4 nM). Conclusion We successfully developed PD assays to monitor blockade of lectin pathway activation in monkeys and humans administered narsoplimab. Using a validated PD assay, we demonstrate that a high level of lectin pathway blockade can be maintained in normal human healthy volunteers by once-weekly administration of narsoplimab at 4 mg/kg IV. We also demonstrate a consistent PK/PD relationship across the study population, indicating that narsoplimab concentration ranges can be used to target the desired level of lectin pathway inhibition. Figure 1 Disclosures Freeman: Omeros Corporation: Current Employment. Cummings:Omeros Corporation: Current Employment. Chuidian:Omeros Corporation: Current Employment. Dudler:Omeros Corporation: Current Employment.

Human Adenovirus Serotype 3 Vector Packaged by a Rare Serotype 14 Hexon.

Recombinant adenovirus serotype 3 (rAd3), which infects cells through the receptor desmoglein 2 (DSG2), has been investigated as a vector for gene therapy or vaccination. However, pre-existing anti-vector immunity may limit the practical application of rAd3. In this study, we investigated the seroprevalence and neutralizing antibody (NAb) titers to Ad3 and alternate serotypes in normal healthy adults in southern China. Sera samples had a high seroprevalence (80.00%) against Ad3 and Ad7 (85.83%), compared with Ad14 (22.50%). Furthermore, 19.17% and 25.83% of samples had high-titer neutralizing antibodies to Ad3 and Ad7, respectively, compared with 3.33% against Ad14. We constructed a chimeric adenovirus, rAd3H14, designed to evade anti-vector immunity by replacing the enhanced green fluorescent protein (EGFP)-expressing hexon of the rAd3EGFP vector with a hexon from Ad14. The chimeric vector rAd3H14 was not neutralized in vitro efficiently by Ad3 NAbs using sera from mice and normal healthy human volunteers. Furthermore, in contrast to the unmodified vector rAd3EGFP, rAd3H14 induced robust antibody responses against EGFP in mice with high levels of pre-existing anti-Ad3 immunity. In conclusion, the chimeric vector rAd3H14 may be a useful alternative vector in adult populations with a high prevalence of Ad3 NAbs.

Supplementation of oil palm phenolics in normal healthy human volunteers

In comparison to the lipid‐soluble antioxidants (vitamin E and carotenoids), it has been less known that the oil palm fruit also contains potent water‐soluble antioxidants. MPOB has developed a breakthrough technology in harvesting a substantial amount of phenolic acids from the bio‐aqueous co‐product of oil palm fruit. Based on several emerging evidences from in‐vitro and animal studies postulating the antioxidant effectiveness of oil palm phenolics (OPP), a Phase 1 Clinical Trial was conducted to evaluate physiological effects of the OPP. In this single‐blind, cross‐over design trial, 25 healthy human volunteers were supplemented with 150 mL of control or OPP (concentration at 1500 ppm Gallic acid equivalent, GAE) treatments, twice per day for 60 days recruitment period. Fasting blood and urine samples were collected at day 1, 30 and 60, and medical examination was performed during the trial interventions. All clinical biochemistry profiles values observed throughout the OPP trial recruitment period were in normal range and no major adverse effect occurred. Additionally, OPP supplementation resulted in significantly improving total cholesterol and LDL‐C levels, compared to the control treatment. These current evidences have provided investigators with several outcomes that justify the needs to continue the investigation with the dose‐exploration and phase 2 clinical trials of OPP in the near future.

An impression cytology based study of ocular surface in an urban population

To assess the health of ocular surface in a defined urban population, conjunctival goblet cell density and degree of surface squamous metaplasia were utilized as study tools. Two thousand names of those aged between 20 and 79 years from the 2006 electoral register in ward number 63 of Kolkata Corporation area were initially selected. Normal healthy human volunteers without any history of ocular surface disorder were recruited and divided into five age-groups. Impression cytology samples were obtained from interpalpebral part of bulbar conjunctiva from all the participants fixated and stained by a single observer. A stratified, clustered, disproportionate, random sampling method was used. The software used in the statistical analysis was EPI Info. The tests applied were t test and ANOVA. A variation in the number of goblet cells according to gender (women having less cells) and age (20-30 years group having the highest number of cells) was found. Those working outdoors were found to have fewer goblet cells compared to those who stay indoors. The majority of the people had grade 1 cytological appearance in both males and females. There was no statistically significant difference in Nelson's grading with age. People using coal and kerosene to cook were found to have a smaller goblet cell density than those who cooked on LPG or those who did not cook at all. Besides age and sex, environmental factors like the method of cooking and occupational variables (like outdoor activity, prolonged period of computer use, etc.) modify the health of the ocular surface. The results of this study will help put these findings into perspective as public health problems.

Development of a simple radiant heat induced experimental pain model for evaluation of analgesics in normal healthy human volunteers

Objective:Human experimental pain models help to understand the mechanism of the painful conditions and can also be adopted to test analgesic efficacy of drugs. In early phases, the clinical development of new analgesics is hindered due to the lack of reliable tests for the experimental pain models. In the present study, we have developed and validated a simple radiant heat pain model which can be used for future screening of various analgesic agents.Materials and Methods:We have standardized the thermal pain model by recording pain threshold and pain tolerance time in seconds at three different intensities and levels in 24 healthy subjects. Reproducibility of the test procedure was evaluated by recording the pain parameters by two observers on three consecutive days. Validity of model was further tested by evaluating the analgesic effect of tramadol.Results and Conclusions:Use of radiant heat pain model with high intensity and short level was found to produce low variability with coefficient of variation less than 5%. Interobserver and interperiod reproducibility was very good as shown by Bland - Altman plot; with most of the values within ± 2SD. Tramadol produced statistically significant increase in pain threshold time. The newly developed pain model produces a type of experimental pain which is responsive to analgesic effects of tramadol at clinically relevant doses.

Antigen Specificity in Subsets of Mucous Membrane Pemphigoid

Mucous membrane pemphigoid (MMP) has several subsets based on target antigens recognized by their sera. MMP and ocular cicatricial pemphigoid (OCP) sera recognize beta4 integrin subunit, oral pemphigoid sera recognize alpha6 integrin subunit, and anti-epiligrin cicatricial pemphigoid sera recognize laminin 5. Our aim is to determine if autoantibodies in the sera of patients with MMP, OCP, and oral pemphigoid (OP) recognize only their target antigens, and to see if this specificity is maintained throughout the clinical course. An immunoblot assay using bovine gingival lysate was used as substrate. Fifteen MMP patients, eight with OCP, and 15 OP patients were studied before therapy and at multiple intervals during the clinical course. Absorption and blocking studies were performed to determine binding specificity. Sera of patients with MMP and OCP recognize only beta4 integrin subunit, and sera of OP patients recognize alpha6 integrin throughout the clinical course. The sera of patients in the subsets of MMP described in this report show adherence and selectivity to target antigen during the entire clinical course, without crossover, interaction, or change. Hence, these subsets of MMP provide an excellent model to study clinical correlation with antigen and antibody specificity, in autoimmunity.

Beneficial role of amino acids in mitigating cytoskeletal actin glycation and improving F-actin content: in vitro.

The actin filaments present in circulating leukocytes facilitate their passage through microvenules and capillaries by helping in their deformability. Decreased deformability of granulocytes is now known to cause occlusion of the retinal microcapillaries leading to hypoxia and the subsequent development of diabetic retinopathy. Structural and functional loss of proteins, due to non-enzymatic glycation and glycoxidation, has been reported to cause diabetic pathogenesis. As amino acids have been earlier reported to have antidiabetic properties, the present study involves the investigation of the susceptibility of the cytoskeletal actin to glycation and its mitigation by free amino acids. This study also involves quantifying F-actin in cultured mononuclear cells obtained from diabetic and normal healthy volunteers and on the effect of glucose and free amino acids on F-actin content. Commercial non-muscle actin and actin immuno-pre-cipitated from granulocytes obtained from (a) normal healthy human volunteers and (b) patients with type 2 diabetes mellitus were subjected to glycation studies using [U] (14)C glucose. The effect of free amino acids, as antiglycating agents, was determined using various concentrations of lysine, arginine, alanine, aspartic acid and glutamic acid. F-actin content in cultured mononuclear cells was estimated by flow cytometry using fluorescein isothiocynate (FITC)-Phalloidin. Commercial actin at physiological conditions of pH and temperature was found to undergo non-enzymatic glycation. The extent of in vitro glycation was significantly low (P<0.001) in actin isolated from patients with type2 diabetes when compared to the non-diabetic group, suggesting an increased in vitro structural modification of actin in patients with diabetes. All the free amino acids tested were found to have varying degrees of antiglycating effect. The F-actin content in the intact mononuclear cells obtained from diabetic patients was found to be low when compared with normal healthy volunteers (P<0.001). Similarly the F-actin content was significantly low when the normal mononuclear cells were incubated with glucose. This effect was reversed upon the addition of free amino acids to the incubation mixture. Free amino acids can play a positive role in improving leukocyte deformability by mitigating cytoskeletal actin glycation and improving F-actin content.

PET Studies of the Effect of the Antidepressant Drugs Nefazodone or Paroxetine on [ 11C]Raclopride Binding in Human Brain

Serotonin modulates dopamine release in the striatum. In this study we set out to determine whether nefazodone and paroxetine, two antidepressant drugs that interact with the brain serotonin system, produce detectable changes in synaptic dopamine in vivo in the human brain using positron emission tomography (PET) and [ 11C]raclopride, a dopamine D-2 receptor specific radiotracer that is sensitive to changes in synaptic dopamine. Three normal healthy human volunteers had 4 PET/[ 11C]raclopride scans each in 2 sessions. In the first session, subjects had a baseline [ 11C]raclopride scan and a second scan 1 hour following the oral administration of either nefazodone (200 mg PO) or paroxetine (20 mg PO). Four to 6 weeks later, in a second PET/[ 11C]raclopride session, the same subjects received the other drug for comparison. Neither nefazodone nor paroxetine produced significant changes in [ 11C]raclopride binding. This and other reports in the literature indicate that different drugs that affect the serotonin system do not produce consistent and predictable changes in [ 11C]raclopride binding and that a full understanding of their actions on serotonin and the associated changes in dopamine requires further investigation.

The role of reactive oxygen species (ROS) in the effector mechanisms of human antimycobacterial immunity.

The aim of this study was to determine the role of reactive oxygen species (ROS) in checking the growth of intracellular mycobacteria within human phagocytes. Peripheral blood-derived neutrophils and monocyte-derived macrophages were isolated from Chronic Granulomatous Disease (CGD) patients and normal healthy human volunteers. CGD patients are known to have a defect in the NADPH oxidase pathway, resulting in their neutrophils and monocyte-derived macrophages being unable to generate oxygen radicals which are required to kill intracellular bacteria. The cells were then infected with Bacille Calmette Guerin (BCG) or Mycobacterium avium, and the bacterial growth in each cell type determined by Colony Forming Units (CFU) estimate. The results obtained indicate that there was no demonstrable inhibition in the intracellular mycobacterial growth within neutrophils or macrophages derived from either Chronic Granulomatous Disease (CGD:deficient in NADPH oxidase pathway) or normal healthy volunteers. Macrophage treatment with either IFN-gamma or TNF-alpha had no effect.

Low levels of serum ionized magnesium are found in patients early after stroke which result in rapid elevation in cytosolic free calcium and spasm in cerebral vascular muscle cells

Ninety-eight patients admitted to the emergency rooms of three urban hospitals with a diagnosis of either ischemic stroke or hemorrhagic stroke exhibited early and significant deficits in serum ionized Mg 2+ (IMg 2+), but not total Mg, as measured with a unique Mg 2+-sensitive ion-selective electrode. Twenty-five percent of these stroke patients exhibited >65% reductions in the mean serum IMg 2+ found in normal healthy human volunteers or patients admitted for minor bruises, cuts or deep lacerations. The stroke patients also demonstrated significant elevation in the serum ionized Ca 2+ (ICa 2+)/IMg 2+ ratio, a sign of increased vascular tone and cerebrovasospasm. Exposure of primary cultured canine cerebral vascular smooth muscle cells to the low concentrations of IMg 2+ found in the stroke patients, e.g. 0.30–0.48 mM, resulted in rapid and marked elevations in cytosolic free calcium ions ([Ca 2+] i) as measured with the fluorescent probe, fura-2, and digital image analysis. Coincident with the rise in [Ca 2+] i, many of the cerebral vascular cells went into spasm. Reintroduction of normal extracellular Mg 2+ ion concentrations failed to either lower the [Ca 2+] i overload or reverse the rounding-up of the cerebral vascular cells. These results suggest that changes in Mg 2+ metabolism play important roles in stroke syndromes and in the etiology of cerebrovasospasm associated with cerebral hemorrhage.

The UVR wavelength dependence for lomefloxacin photosensitization of human skin

Lomefloxacin is a new fluoroquinolone with effective broad-spectrum antimicrobial activity. However, in common with other structurally related drugs, skin photosensitization reactions have been reported. The wavelength dependence for such photosensitization has been investigated on the previously unexposed buttock skin of 12 normal healthy human volunteers of skin type I and II. Using geometric ∼2 dose increments, baseline 24 h minimal erythema doses were assessed at 300, 320, 330, 340, 350 and 360 nm, with broad-band UVA. In addition, dose-response curves were constructed for erythema as measured by a reflectance device. Subjects received single daily oral doses of 400 mg lomefloxacin at specified times for 4 days. At 2 h after the final dose, new areas of buttock skin were irradiated to assesse changes in minimal erythema dose and erythemad dose-response. Convolution of the erythema action spectra obtained pre and on-drug with a terrestrial solar spectrum showed that, although the UVA sensitivity on-drug was enhanced, most of the erythemally effective solar energy was still in the UVB region. An action spectrum derived for lomefloxacin skin photosensitization showed peak activity at 320 nm, the same spectral region as that for maximal absorption of the drug. Ther was no evidence of skin photosensitization at 300 nm.

Buccoadhesive Tablets of Nifedipine: Standardization of A Novel Buccoadhesive-Erodible Carrier

AbstractBuccoadhesive tablets of nifedipine were obtained by incorporation of nifedipine in suitable carrier systems standardised based on bioadhesion and dissolution. The carrier systems were formulated using sodium alginate as the bioadhesive. Mannitol, lactose, polyethylene glycol 6000 and polyethylene glycol 4000 were incorporated as solubilisers, singly or in combination. Carrier systems having a diameter of 11 mm and weighing about 200 mg were obtained by standard tabletting techniques using polyvinylpyrolidone as the binder. The systems were evaluated for bioadhesion and dissolution, 'in vitro' and 'in vivo' in seven normal healthy human volunteers. Based on these studies, nifedipine (5 mg) was incorporated in selected carrier systems to obtain buccoadhesive tablets of nifedipine. These tablets exhibited rapid 'in vitro' drug release.

Gastrointestinal motor effects of erythromycin in humans

The effects of an antibacterially effective IV dose of erythromycin on gastrointestinal motor activity were investigated in eight normal healthy human volunteers in the fasted state and the fed state. Motor activity was recorded by a multilumen manometric tube. Data were analyzed visually and by a computer method. Blood samples were obtained for erythromycin and motilin assays. In the gastric antrum, erythromycin significantly increased the total duration, amplitude, and area under contractions from 0 to 60 minutes and frequency of contractions from 0 to 30 minutes from the start of its infusion in the fasted state. A similar response in the fed state occurred mostly from 0 to 30 minutes after the start of erythromycin infusion. By contrast, erythromycin inhibited the frequency and decreased the duration of small intestinal contractions in the fed state but had no effect in the fasted state. The gastric motor response was related to the plasma concentration of erythromycin, but not to plasma motilin. Erythromycin significantly shortened the duration of migrating motor complex disruption by a meal. Erythromycin also induced symptoms of upper abdominal pain, bloating, and nausea. Abdominal pain was related to strong antral contractions in both fasted and fed states; bloating occurred only in the fed state. Nausea occurred in both fasted and fed states, but it was not related to any specific pattern of motor activity. It is concluded that the strong antral contractions induced by erythromycin may accelerate the rate of gastric emptying, but they may also be responsible for causing the sensations of upper abdominal pain and bloating. The motor response to erythromycin is less during the fed than during the fasted state. The strong antral contractions induced by erythromycin are not mediated by the release of motilin.

Conversion of ABO Blood Groups

Progress is being made toward producing erythrocytes similar to native group O cells from A and B donors. Blood group A and B antigens are known to be carbohydrate in nature. The antigenicity is conferred by different terminal sugars. Removal of these sugars by specific exoglycosidases produces the H antigenic structure that is the determinant found on group O cells. Conditions have been developed that allow for the removal of these antigens while maintaining the metabolic and membrane viability of the red cell. Following successful autologous transfusions with gibbons, appropriately treated human group B erythrocytes are now being used in preclinical studies with normal healthy human volunteers. Results indicate that such treated cells have normal in vivo life spans in both group A and O recipients. However, the latter exhibit a transitory increase in anti-B antibody titer, the significance of which is not yet known. Similar exoglycosidic treatment of group A erythrocytes does not remove all serologically detectable A antigens. This is probably due to the presence of a second internal A antigenic site adjacent to the usual terminal A antigen on some structures. Several approaches are being used to address this problem, including projected treatment with a combination of pertinent exoglycosidases and a search for an endoglycosidase that will cleave the polysaccharide chain at a site upstream from both A antigens.

Regional cerebral blood volume and hematocrit measured in normal human volunteers by single-photon emission computed tomography.

Single-photon emission computed tomography (SPECT) was used for the measurement of regional cerebral blood volume (CBV) and hematocrit (Hct) in normal healthy human volunteers (mean age 30 +/- 8 years). Regional cerebral red blood cell (RBC) volume and plasma volume were determined separately and their responses to carbon dioxide were investigated. Ten right-handed healthy volunteers were the subjects studied. SPECT scans were performed following intravenous injection of the RBC tracer (99mTc-labeled RBC) and plasma tracer (99mTc-labeled human serum albumin) with an interval of 48 h. Regional cerebral Hct was calculated as the regional ratio between RBC and plasma volumes and then was used for calculating CBV. Mean regional CBV in the resting state was 4.81 +/- 0.37 ml/100 g brain, significantly greater in the left hemisphere compared with the right by 3.8% (p less than 0.01). Mean regional RBC volumes (1.50 +/- 0.09 ml/100 g brain) were less than mean regional plasma volumes (3.34 +/- 0.28 ml/100 g brain), and mean regional cerebral Hcts were 31.3 +/- 1.8%, which was 75.9 +/- 2.1% of the large-vessel Hct. During 5% CO2 inhalation, increases in plasma volume (2.48 +/- 0.82%/mmHg PaCO2) were significantly greater than for RBC volume (1.46 +/- 0.48%/mmHg PaCO2). Consequently, the cerebral-to-large-vessel Hct ratio was reduced to 72.4 +/- 2.2%. Results emphasize the importance of cerebral Hct for the measurement of CBV and indicate that regional cerebral Hcts are not constant when shifted from one physiological state to another.