Monomeric, monovalent derivative of Maackia amurensis leukoagglutinin. Preparation and application to the study of cell surface glycoconjugates by flow cytometry

A stable subunit of Maackia amurensis leukoagglutinin (MMAL) was prepared by the selective reduction of disulfide bridges between the subunits followed by alkylation with 4-vinylpyridine. MMAL failed to precipitate fetuin, whereas it retained its ability to bind to the same glycoprotein coated on a plastic plate, indicating the monovalency of this derivative. This binding to immobilized fetuin was inhibited by a haptenic sugar, Neu5Ac alpha 2-3lactose, with the same inhibitory potency as against the native M. amurensis leukoagglutinin. Microscopic observation as well as flow cytometric analyses showed that Chinese hamster ovary cells were clearly stained with fluorescein isothiocyanate-labeled MMAL without any detectable agglutination. This staining was inhibited by the addition of fetuin or by the sugar chains of fetuin. Differences in the types of sialylated glycoconjugates on the cell surface of several cell lines were detected by the combined use of fluorescein isothiocyanate-labeled MMAL and the monomeric derivative of elderberry bark lectin (specific for the Neu5Ac alpha 2-6Gal/GalNAc sequence) by flow cytometry. These results demonstrate the usefulness of these monovalent derivatives of sialylated oligosaccharide-specific lectins as probes for the analysis of cell surface glycoconjugates containing sialic acid by the technique of flow cytometry.     

Value of transcranial Doppler indices in predicting raised ICP in infantile hydrocephalus. A study with review of the literature

Cerebral hemodynamic changes in infants with progressive hydrocephalus have been studied with the transcranial Doppler (TCD) technique. Several authors have referred to the correlation between the hemodynamic changes and increased intracranial pressure (ICP). Despite conflicting conclusions on the value of pulsatility index (PI) and resistance index (RI) measurements for monitoring infantile hydrocephalus, these pulsatility indices are the most commonly used for this purpose. Although clinical signs of raised ICP are highly variable and unreliable in infants, assumptions have been made in most of the studies about the presence of elevated ICP on the basis of the patient's clinical state. Few studies have reported on actual ICP values, however, and a direct relationship between ICP and TCD changes has never been adequately demonstrated. In the present study, this relationship was investigated in long-term simultaneous TCD/ICP measurements, in an attempt to develop a noninvasive method of monitoring the effect of ICP on intracranial hemodynamics. Two groups of data sets were established. Group I consisted of pre- and postoperative (shunt implantation) TCD/ICP measurements. Group II were long-term simultaneous TCD/ICP recordings showing significant ICP variations. In most of the postoperative measurements there was a decrease in the average PI and RI values. The correlation between PI or RI and ICP in the long-term simultaneous recordings, however, was generally poor. The risk of obtaining false positive or false negative PI or RI values in short-term measurements was also demonstrated. It can be concluded from our results, besides the wide range of reference values for the Doppler indices and extracranial influences upon them, that the present Doppler indices are inadequate for monitoring the complex intracranial dynamic responses in patients with raised ICP.     

An efficient method of FIR filtering based on impulse responserounding

A new method of implementing efficient FIR filters is presented. It involves approximation of an equiripple FIR by a rounding operation and application of the derived impulse response by a simple recursive equation. The technique is extremely efficient for lowpass, highpass, bandpass, and bandstop filters with sharp transitions and low edge frequencies     

Systemic aluminum toxicity: effects on bone, hematopoietic tissue, and kidney

Although the full mechanisms are not yet elucidated, research into the mechanism of toxicity of aluminum (Al) on bone formation and remodeling and on hematopoietic tissue is ongoing. In contrast little information exists on the interactive effects of systemic Al and the kidney. In bone, both clinically and experimentally, high doses of Al inhibit remodeling, slowing both osteoblast and osteoclast activities and producing osteomalacia and adynamic bone disease. In contrast, while very low levels of Al are mitogenic in bones of experimental animals, the effect of low levels of Al in humans is unknown. Aluminum has been shown to have its mitogenic action at the osteoblast, but whether the effect on resorption is viz osteoblast-directed changes in osteoclast activity has not yet been determined. Parathyroid hormone (PTH) levels are disrupted by Al in humans and animals. Whether altered PTH levels play a major or even a minor role in Al-dependent osteotoxicity requires clarification. In hematopoietic tissue, Al causes a microcytic anemia, not reversible by iron. Friend leukemia cells treated with Al have been reported to accumulate excess iron, without incorporating it into ferritin or heme. It is not yet known which steps in iron metabolism are disrupted by Al, if they involve a single mechanism of action, or even if this disruption in iron metabolism accounts for the anemia seen in Al toxicosis. In kidney, research is needed to evaluate Al nephrotoxicity; there are almost no studies in this area. Furthermore, research is needed to evaluate mechanisms of renal Al excretion, presently shown by one study to occur at the distal tubule. Such studies might well throw light on whether Al plays a role in aggravating renal insufficiency, or whether the role of the kidney in Al toxicosis is limited to the causative effect of renal compromise on Al accumulation. In summary, while a number of mechanisms have been proposed for the toxic action of Al, no single mechanism emerges to explain these diverse effects of systemic Al. Recommendations for future research are presented and summarized in Table 1.     

A comparison of leaf-spring with aircushion trailer suspensions in the transport environment

Packaging engineers need to be able to accurately determine the forces present in the shipping environment in order to protect packaged goods. The purpose of this study was to determine the vertical vibration levels measured in three separate truck-trailer suspension systems; conventional leaf-spring, conventional air-ride and damaged air-ride. The main conclusion reached in this study is that the air-ride suspension when maintained gives lower power density (PD) levels on all road surfaces studied. A damaged air-ride suspension and leaf-spring suspension are very similar in response frequencies, although the damaged air-ride produces higher vibration levels at lower frequencies.     

Sexual dimorphism of circulating somatotropin, insulin-like growth factor I and II, insulin-like growth factor binding proteins, and insulin: relationships to growth rate and carcass characteristics in growing lambs

The effects of sex and age on patterns of circulating somatotropin (ST) concentration and plasma IGF-I, IGF-II, insulin, and IGF binding protein-3 (IGFBP-3) were studied in ram, wether, and ewe lambs (n = 7 or 8) sampled at mean ages of 81 (I1) and 158 d (I2). Between 81 and 158 d of age, rams grew more rapidly than wethers (P < .01), and wethers grew more rapidly than ewes (P < .01). The sex differences in growth were reflected in empty body weight at slaughter: rams > wethers > ewes (P < .05). Mean plasma ST concentrations, ST pulse amplitude, and integrated plasma ST concentrations were greater (P < .05) in rams than in ewes at I1 and I2. Characteristics of the ST plasma profile in wethers were generally intermediate between those of rams and ewes. The interpulse interval was greater in ewes than in wethers at I2. The IGF-I and IGFBP-3 concentrations were greater in rams than in ewes at both sampling times. Plasma IGF-II was greater in ewes than in rams at I2. Mean plasma ST was approximately two thirds less at I2 than at I1 regardless of sex. Mean plasma ST and IGF-I at both ages were positively correlated with growth. Mean plasma ST at I2 was negatively correlated with fatness at slaughter. Sex and age significantly affected patterns of circulating ST and concentrations of IGF-I and IGFBP-3 in prepubertal growing lambs, under conditions for which growth rates and composition were also sexually dimorphic.     

Purification and characterization of a NADP+/NADPH-specific flavoprotein that is overexpressed in FdI- strains of Azotobacter vinelandii

Earlier studies have established that mutant strains of Azotobacter vinelandii that do not synthesize ferredoxin I (AvFdI) overexpress another protein designated Protein X (Morgan, T. V., Lundell, P. J., and Burgess, B. K. (1988) J. Biol. Chem. 263, 1370-1375). This protein has now been purified using two-dimensional gel electrophoresis as an assay. The purified protein is a monomer with M(r) approximately 29,000 which degrades slowly to a specific M(r) approximately 22,000 form when stored in solution. The native protein is bright yellow and contains noncovalently attached FAD that is reduced by either dithionite or NADPH without formation of a stable semiquinone. Titration with NADP+/NADPH gives an E0' value of approximately -327 mV versus SHE. Because this E0' is so close to that of the NADP+/NADPH couple it is not clear if Protein X is an NADPH oxidase or an NADP+ reductase in vivo. Comparison of the NH2-terminal sequence and other properties of Protein X with those of other proteins, suggests that it is likely to be related to the Escherichia coli ferredoxin NADP+ reductase (the fpr gene product), and affinity chromatography shows that Protein X binds specifically to AvFdI.     

p-aminohippurate uptake by syncytial microvillous membrane vesicles of human term placenta

The mechanism of uptake of p-aminohippurate (PAH) by syncytial microvillous membrane vesicles of human term placenta was investigated. Initial PAH uptake and efflux were increased in the presence of a pH-gradient and a Cl(-)-gradient, respectively. Forced negative and positive membrane potentials did not influence the uptake, which indicated that the transport is not electrogenic. The pH-dependent increase is probably the result of a higher rate of diffusion due to a lower degree of dissociation of PAH. Because several organic anions failed to transstimulate PAH uptake and FCCP did not decrease the uptake in the presence of an inwardly directed H(+)-gradient, ruling out a PAH/OH- antiport, an anion exchange system does not appear to be present in these membranes. Since electrogenicity and anion exchange seem not to be involved in the Cl(-)-dependent increase, an allosteric effect of Cl- on the transporter might be possible. Various organic anions were able to inhibit pH-stimulated PAH uptake significantly. Kinetic analysis of the probenecid sensitive part of uptake provided further evidence for mediated transport of PAH (Km = 7.4 +/- 2.6 mM and Vmax = 2.0 +/- 0.4 nmol/mg/15 s). Non-inhibitable diffusion accounted for the main part of total transport. Concentration dependent inhibition of PAH transport by probenecid showed a Ki of 2.5 +/- 0.9 mM. It is concluded that human placental syncytial microvillous membrane vesicles possess a low affinity transport mechanism for PAH with low specificity. The importance of this system, for placental excretion of anionic drugs, will depend on the intrasyncytial concentration of these drugs, caused by the transport across the basal membrane.     

GaAs pHEMT-based technology for microwave applications in a volume MMIC production environment on 150-mm wafers

The establishment of a 150-mm (6-in) gallium arsenide (GaAs) facility is described together with the development of very high yielding and cost-effective semiconductor device technologies and a manufacturing capacity of over 40000 wafers/annum. The background to the demand for very high volumes of RF products for this market is discussed, together with the prospects for future growth. The paper describes recent process development by the utilization of a data-driven yield management system to support the delivery of high-quality RF products to customers. Finally, "end of line" DC and RF testing of finished 150-mm GaAs pHEMT foundry wafers is described, enabling scalar measurements of power, noise, and intermodulation products as well as vector measurements of S-parameters and noise parameters at frequencies of up to 40 GHz.