Cation-exchange displacement chromatography for the purification of recombinant protein therapeutics from variants

Removal of low level impurities that are closely related to the bioproduct is a commonly encountered challenge in the purification of biopharmaceuticals. These separations are typically carried out by using shallow linear salt gradients at relatively low column loadings, significantly limiting the throughput of the purification process. In this manuscript we examine the utility of displacement chromatography for the purification of recombinant human brain-derived neurotrophic factor, rHuBDNF. The utility of displacement chromatography is compared to gradient elution for the removal of variants of the rHuBDNF. The results demonstrate that displacement chromatography is capable of achieving high yields and purity at high column loadings. Displacements developed on 20 microns and 50 microns cation-exchange resins are shown to provide 8-fold and 4.5-fold increases in production rates, respectively, when compared to an existing linear gradient elution operation. These results demonstrate the efficacy of displacement chromatography for the purification of therapeutic proteins from complex feed streams.

Regionalized lipid diffusion in the plasma membrane of mammalian spermatozoa

The plasma membrane of mammalian spermatozoa shows pronounced lateral asymmetry with many glycoproteins restricted to specific domains. Some of these antigens are freely diffusing throughout the membrane whereas others appear static in position. It is not clear whether these concepts also apply to membrane lipids. In this investigation we have used fluorescence recovery after photobleaching (FRAP) techniques to spatially resolve lipid dynamics in various surface domains of 5 species of mammalian spermatozoa (bull, boar, ram, mouse, and guinea pig). Sperm plasma membranes were loaded with 5-(N-octadecanoyl)aminofluorescein (ODAF) reporter probe, and its diffusion was measured in various domains by FRAP analysis. Results showed that in live bull, boar, ram, and mouse spermatozoa, diffusion coefficients (D) were significantly higher over the acrosome and postacrosome than on the midpiece and principal piece of the tail. In dead or permeabilized cells, on the other hand, large immobile phases developed, particularly on the sperm tail, that severely reduced D values. ODAF diffusion was also sensitive to temperature and cross-linking of protein components within the membrane with paraformaldehyde. Guinea pig spermatozoa were different in almost all respects from those of the other species tested. It is concluded that lipid diffusion in the plasma membrane of live spermatozoa varies significantly between surface domains, because of either compositional heterogeneity, or differences in bilayer disposition, or the presence of intramembranous barriers that impede free exchange between domains. This study emphasizes the important role of membrane lipids in regulating polarized migration of sperm surface antigens during developmental processes such as maturation and capacitation.

Perception of risk, sexual behaviour and STD/HIV prevalence in western Kenya

OBJECTIVE

To determine the feasibility and acceptability of collecting data on sexual practices, knowledge, attitudes and perception of risk with regard to HIV and STD infection in two clinic populations.

DESIGN

A cross sectional survey carried out between June and July 1992.

SETTING

An urban and a rural health centre in western Kenya.

SUBJECTS

One hundred and sixty women attending Maternal Child Health (MCH) and Family Planning Clinics (FP).

INTERVENTIONS

Screening STDs including N. gonorrhoea, C. trachomatis, T. vaginalis and syphilis. In addition subjects were interviewed about sexual practices, knowledge, attitudes and perception of risk with regard to HIV and STD infection.

RESULTS

The presence of any STD including HIV was detected in 36.2% of women at the urban clinic and 21.2% of women at the rural clinic. The demographics of the two populations were similar with respect to age but were significantly different for several variables including marital status, ethnicity and education. Knowledge of STDs and HIV was nearly universal in both clinic populations with > 96% of patients being aware of the existence of such diseases. 76.3% of women at the urban clinic felt they could get an STD as compared to 48.8% at the rural clinic (p < 0.02). This awareness of vulnerability among the urban population was also seen for HIV.

CONCLUSION

It appears to be feasible to conduct studies of sexual practices and perceptions of risk for STD/HIV acquisition in women attending health centres in Kenya.

Ranolazine Roche Bioscience

Ranolazine is a metabolic modulator developed by Syntex (Roche) and is in phase III clinical trials as an anti-anginal agent and for the treatment of peripheral arterial disease, particularly intermittent claudication. It allows maintenance of energy output by muscle cells under hypoxic conditions. Ranolazine may be especially useful in angina patients in whom other therapies are ineffective. The licensee, CV Therapeutics (CVT), began a pivotal placebo-controlled, phase III clinical trial of ranolazine in October 1997 enrolling 150 angina patients [265551]. CVT plans to begin a second phase III trial in 350 to 400 angina patients receiving other anti-anginal medications during 1998 [279177]. Clinical studies suggest that ranolazine lowers the heart's demand for oxygen by increasing its ability to use carbohydrate, rather than fat, as a fuel. This is thought to be due to activation of pyruvate dehydrogenase and modulation of the activities of L-type calcium channels. This is achieved without reducing heart rate or blood pressure, or impairing pumping ability [253375,247228]. Ranolazine has been tested in more than 1300 US and European patients in phase I and phase II clinical trials, and is now being evaluated in a placebo-controlled, double-blind multicenter study to determine its effectiveness in treating stable angina. Phase II trials, in over 1200 patients with ischemic heart disease, were completed by Syntex. They demonstrated increased exercise times to onset of angina or electrocardiographic change associated with insufficient blood flow to the heart with three times daily dosing of ranolazine [224364]. Roche Bioscience claims that in the US and Western Europe approximately 1.4 million angina patients are not adequately treated with existing therapies and some 5 million patients suffer from intermittent claudication [166817]. In August 1998, CV Therapeutics signed an agreement with Catalytica Pharmaceuticals, which will manufacture specified quantities of ranolazine</ulink> for use in clinical trials [293333].

The role of level, spectral, and temporal cues in children's detection of masked signals

Preschool-aged children and adults were asked to detect masked signals in four conditions that evaluated the role of level, spectral, and temporal cues on performance. Psychometric functions fitted to percent correct data at several signal-to-noise ratios showed higher thresholds and shallower slopes for the children in all conditions. Performance was similar in fixed and roving level conditions for both age groups suggesting use of level-invariant cues. When the signal was moved to the spectral edge of the masker the performance of the adults improved but that of the children did not. This suggested that children did not benefit from the additional cues provided by the off-center signal. Children's performance worsened when the signal was a narrow-band noise rather than a pure tone but the adults' did not, suggesting children's reliance on temporal changes in the masker with the introduction of the signal. Analyses of the stimuli suggested that the children's thresholds corresponded to signal-to-noise ratios at which multiple cues were present at magnitudes that were great enough to be discriminable.

Functional differences between BHRF1, the Epstein-Barr virus-encoded Bcl-2 homologue, and Bcl-2 in human epithelial cells

BHRF1, a component of the restricted early antigen complex of the Epstein-Barr virus lytic cycle, encodes a 17-kDa protein with both sequence and functional homology to the antiapoptotic Bcl-2 oncogene. Recent work has suggested that BHRF1 behaves like Bcl-2 in protecting cells from apoptosis induced by a range of stimuli. In this study, the effect of BHRF1 and Bcl-2 on the growth and differentiation of the SCC12F human epithelial cell line was examined. The levels of stable transfected BHRF1 expression achievable in SCC12F cells was consistently lower than that obtained with Bcl-2. While both BHRF1 and Bcl-2 inhibited epithelial differentiation, the effect of Bcl-2 was more pronounced, resulting in an almost complete blockade of differentiation in organotypic raft cultures. However, BHRF1-expressing SCC12F cells proliferated at a much higher rate than SCC12F cells expressing Bcl-2, and this effect was supported by cell cycle analysis which demonstrated that BHRF1, but not Bcl-2, promotes rapid transit through the cell cycle. These data highlight important differences between BHRF1 and Bcl-2 and suggest that BHRF1 may function to promote the survival and proliferation of lytically infected cells. The proliferative properties of BHRF1 described in this study, together with the demonstration that other oncogenic gamma herpesviruses encode Bcl-2 homologues, suggests that these proteins may serve to increase the susceptibility of virus-infected cells to oncogenic transformation, thereby contributing to the development of virus-associated tumors.

Site-directed mutagenesis of boar proacrosin reveals residues involved in binding of zona pellucida glycoproteins

Proacrosin, the zymogen form of the serine protease beta-acrosin, is thought to function as a secondary binding molecule between mammalian gametes during fertilization (Jansen et al., 1995: Int J Dev Biol 39, 501-510). The interaction involves strong ionic bonds between positively charged amino acids on proacrosin and negatively charged polysulphate groups on zona pellucida glycoproteins. In this investigation, we identified the basic residues on proacrosin that are important for this binding. Site-directed mutagenesis shows that two groups of amino acids comprising His47, Arg50, and Arg51 together with Arg250, Lys252, and Arg253 are crucial because their deletion or replacement severely reduces affinity for zona glycoproteins. Molecular models of proacrosin reveal that these residues are located along one face of the protein on two exposed surface loops that project over and around the catalytic site. These findings support the hypothesis that polysulphate binding sites on proacrosin are formed by a restricted number of basic amino acids on the surface of the protein, presenting a specific orientation that is complementary to negatively charged sulphate groups on zona glycoproteins. Identification and elucidation of the stereochemistry of these charged moieties will aid design of new kinds of nonsteroidal antifertility agents.

Differential expression of fibroblast growth factor receptors 1 to 4 and ligand genes in late fetal and early postnatal rat lung

To characterize fibroblast growth factor (FGF) gene expression in the late fetal (days E18 to E22) and early postnatal lung (days P0 to P28), when the alveolar region undergoes extensive growth and reorganization, we analyzed the expression of four FGF receptors and six ligands. FGF receptor 1 (FGFR1) RNA levels were first low (E18) before rising late in the postnatal period (P28). FGFR2 RNA levels were detected early (at E18) and then increased (E20-P0) before falling (P2) to below later postnatal levels (P6 to P28). FGFR3 RNA levels were low at first (E18) and then increased, with peak levels in the days after birth (P2 to P10). FGFR4 RNA levels, barely detected in fetal lung (E18 to E22), increased at birth (P0) and remained high postnatally (P2 to P28). In fetal lung, FGF2 (basic FGF) RNA expression levels were low and FGF1 (acidic FGF) RNA levels were not detected: low RNA levels of each ligand were detected postnatally (P7 to P28). FGF3 to 5 and FGF7 RNA were not detected in fetal or postnatal lung. With in situ hybridization, predominantly the smooth muscle cells of large vessels expressed FGFR1 and 4 mRNA; the epithelial cells of large airways expressed FGFR1, 2, and 4; and alveolar cells expressed FGFR2, 3, and 4. Analysis of protein expression first identified FGF2 localized to the basement membrane of large airways and branching epithelial buds, to mesenchymal cells associated with buds, to the putative smooth muscle cells of large airways and vessels, and to pleural- and mesenchymal-associated cells (E18). Immediately before birth, this pattern of expression persisted (E20 to E22), with FGF2 also being expressed by putative smooth muscle cells of smaller airways and vessels (E22). After birth (P0 to P28), FGF2 expression remained relatively high in the smooth muscle cells of large and small vessels and in pleural cells; in airway smooth muscle cells and in most cells in the alveolar region, however, although FGF2 expression persisted in some cells, its intensity decreased with time.

Maternal serum inhibin A can predict pre-eclampsia

OBJECTIVE

To compare median levels of maternal serum inhibin A in the second trimester blood samples of women who subsequently develop pre-eclampsia and those who do not.

DESIGN

Retrospective analysis of 13 18 week samples from a bank of serum stored at -40 degrees C, originally taken for Down's syndrome screening.

SETTING

Antenatal clinics in a teaching hospital.

SAMPLE

Twenty-eight pregnancies with pre-eclampsia and 701 controls. Samples were taken, on average, 22 weeks before the diagnosis.

MAIN OUTCOME MEASURE

Median inhibin A level.

RESULTS

The median inhibin A level in the cases was 2.01 multiples of the gestation-specific median in the controls, a statistically significant elevation (P < 0.001). Twenty-three (82%) had levels above the normal median; 19 (68%), 15 (54%), and 11 (39%) exceeded the normal 75th, 90th and 95th centiles, respectively.

CONCLUSIONS

In pre-eclampsia the maternal serum inhibin A level can be increased months before the onset of symptoms. This provides an opportunity to study the early natural history of the disease and possibly to conduct treatment trials.

Standardizing the classification and description of follicular unit transplantation and mini-micrografting techniques. The American Society for Dermatologic Surgery, Inc

Previous attempts at classifying small graft transplants have focused mainly upon graft size and have not taken into consideration other technical factors involved in graft production that may influence the outcome of the surgery. The proposed classification attempts to consider these factors by including various technical aspects of harvesting, dissection, and placement, all of which impact the quality and quantity of the small grafts used in the procedure. By standardizing the nomenclature, as well as the description of the other factors involved in the surgery, communication between physicians and patients may be facilitated. In addition, different procedures may be more accurately studied and compared.

The effect of forced vergence on retinal correspondence

The spatial characteristics of the changes in retinal correspondence produced by forced convergence were studied. The vertical extent of lateral shifts in binocular correspondence were quantified by comparing the convergence of the eyes measured with binocular search coils to the convergence of the eyes as determined using nonius lines having vertical separations (gaps) between the nonius lines of 0.5-4.8 degrees. Lateral shifts in binocular correspondence only occurred for nonius gaps < 3-4 degrees. The effects of horizontal retinal eccentricity on lateral shifts in correspondence were determined by measuring the nonius horopter of the subject under forced convergence, using 11 nonius line eccentricities between 4.5 degrees left and right. The nonius horopter was shifted toward the fusion target maximally near the fixation point. There was no shift beyond 3 degrees of eccentricity. We conclude that the nonius horopter is 'dimpled' vertically and horizontally, facilitating local fusion by shifting the line horopter and the region of single binocular vision toward the point of regard over a region of 3 degrees around the fixation point.

Surveillance for Creutzfeldt-Jakob disease among persons with hemophilia

BACKGROUND

Although Creutzfeldt-Jakob disease (CJD) has been shown to be transmissible through blood components in rodent models, no human blood-to-blood transmission has been documented. If blood transmission were possible in humans, persons with hemophilia in the United States would be at higher risk of contracting CJD, because they receive large numbers of blood components. Nearly one-half of the hemophilia population contracted HIV in the 1980s, and many of these people have since died with neurologic complications. This study investigated whether some hemophilia patients with neurologic disorders may have died with CJD.

STUDY DESIGN AND METHODS

Hemophilia treatment Centers across the United States were invited to participate in this retrospective surveillance study. The centers were asked to send any available formalin-fixed paraffin block brain samples from hemophilia decedents. Slides were prepared at the Centers for Disease Control and Prevention and reviewed by three expert neuropathologists. Two slides were stained for the prion protein at the request of one of the neuropathologists.

RESULTS

Specimens from 24 decedents with genetic bleeding disorders were collected and reviewed.The panel found no evidence of CJD in any of the specimens.

CONCLUSIONS

Although the study sample is small, these results support the growing evidence that CJD is not being transmitted in the nation's blood supply.

A trypanosome oligopeptidase as a target for the trypanocidal agents pentamidine, diminazene and suramin

African trypanosomes contain a cytosolic serine oligopeptidase, called OP-Tb, that is reversibly inhibited by the active principles of three of the five most commonly used trypanocidal drugs: pentamidine, diminazene and suramin. OP-Tb was inhibited by pentamidine in a competitive manner, and by suramin in a partial, non-competitive manner. The inhibition of OP-Tb by a variety of suramin analogues correlated with the trypanocidal efficacy of these analogues (P=0.03; by paired Student's t-test). Since intracellular (therapeutic) concentrations of pentamidine and suramin are reported to reach approximately 206Ki and 15Ki respectively, we suggest that these drugs may exert part of their trypanocidal activity through the inhibition of OP-Tb.

Cardiac output and mixed venous O2 content measurements by a tracer bolus method: animal validation study

A bolus method for noninvasive measurement of cardiac output (CO) and mixed venous oxygen content (O2) has been tested against absolute CO and O2 standards in dogs. No statistical differences in CO were found between bolus method and electromagnetic flowmeter measurement comparisons in an 18-dog study in which CO varied from 0. 5 to 3.0 l/min. The SD for all paired differences was 0.14 l/min; however, data averaging over 10-min intervals were found to reduce the CO measurement uncertainty to <0.08 l/min. The ability of the bolus method to follow rapid CO changes, experimentally produced by control of a pump (surgically placed between the superior and inferior vena cava and the right atrium), was documented and found to satisfy CO monitoring requirements of unstable subjects. O2 bolus values were found to be statistically equivalent to reference measurements.

Methylephedrine concentrations in blood and urine specimens

Methylephedrine is a sympathomimetic amine that appears in many over-the-counter cough and cold medications throughout the world. The abuse of methylephedrine-containing medications has been reported in Japan. Although methylephedrine is not available in the United States, it was identified in 15 cases received by the Forensic Toxicology Laboratory, Division of Forensic Toxicology, Office of the Armed Forces Medical Examiner, Armed Forces Institute of Pathology over a two-year period; 12 of the 15 cases were collected from patients or decedents located within the confines of the continental United States. Methylephedrine was identified in each case by gas chromatography-nitrogen-phosphorus detection following an alkaline extraction and subsequently confirmed using full scan electron impact mass spectrometry. Quantitation of underivatized methylephedrine was performed using the same technique. Blood methylephedrine concentrations ranged from less than 0.05 to 0.28 mg/L (n = 14), and the mean methylephedrine concentration in urine was 1.6 mg/L (range, 0.15-6.8, n = 11 [excluding case 6]). A literature search revealed little information pertaining to the interpretation of methylephedrine concentrations in the blood. Six of the 15 cases presented here were positive for methylephedrine in the blood. Three of these cases were postmortem cases, and the other three cases were nonfatal aircraft mishaps. There is no evidence in any of these cases that methylephedrine was present at toxic concentrations; therefore, it appears from the cases reviewed in this study that blood methylephedrine concentrations less than 0.3 mg/L are not associated with significant toxicity.

Comparative effects of schizophrenia and temporal lobe epilepsy on memory

The goal of this study was to further characterize episodic memory functioning in schizophrenia. This study compared verbal and visual learning and memory performance in (1) patients with schizophrenia (N = 35), (2) patients with temporal lobe epilepsy (TLE; N = 30), and (3) normal controls (N = 25). Results indicated significant memory impairments in patients with schizophrenia and TLE. "Savings" score measures of memory decay showed that the loss of information in schizophrenia and TLE was approximately equal, and quantitatively mild compared to that found in most neurologic groups with memory disorders. The severe difficulty shown by the schizophrenia group on a task of incidental recall suggested that the absence of instructional set added to a vulnerability to memory deficit. In contrast, relatively mildly impaired performance on paired associate learning suggested that patients with schizophrenia benefited from retrieval cues, multiple trials, and short (nonsupraspan) informational loads. Because patients with schizophrenia consisted of a relatively nonchronic sample with a mean IQ of 99.7, their memory disorder could not be attributed to schizophrenic dementia, nor was it accounted for by other potential confounds. Patients with schizophrenia, even those relatively early in the course of illness, have a mild episodic memory disorder.