Rhodospirillum rubrum: utilization of condensed corn solubles for poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) production.

AIMS: This study sought to develop a less expensive medium for growth of the polyhydroxyalkanoate-producing bacterium Rhodospirillum rubrum from the ethanol production coproduct, condensed corn solubles (CCS). METHODS AND RESULTS: Small-scale trials using R. rubrum were performed in aerated or anaerobic stoppered serum bottles filled with media. The CCS (240 g l(-1)) achieved a maximum cell density and growth rate comparable with the defined supplemented malate-ammonium medium (mSMN) or tryptic soy broth. Microaerophilic solubles medium cultures exhibited significantly higher maximum cell densities and growth rates than did strictly anaerobic cultures; while illumination, nickel or biotin addition had no effect. Growth of R. rubrum in a pH controlled bioreactor was significantly better in CCS (240 g l(-1)) than in mSMN medium and supported production of 0.36% (cell dry weight) poly-(3-hydroxybutyrate-Co-3-hydroxyvalerate) after 24 h. CONCLUSIONS: A CCS medium was devised that supported R. rubrum growth for biopolymer production as effective as the defined medium. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrates that a more economical medium can be developed for biopolymer production using a low value coproduct from ethanol production. The impact is that this inexpensive solubles medium may make it more economical to produce the biopolymer on a commercial scale.

Safety evaluation of natural flavour complexes.

Natural flavour complexes (NFCs) are chemical mixtures obtained by applying physical separation methods to botanical sources. Many NFCs are derived from foods. In the present paper, a 12-step procedure for the safety evaluation of NFCs, 'the naturals paradigm', is discussed. This procedure, which is not intended to be viewed as a rigid check list, begins with a description of the chemical composition of the commercial product, followed by a review of the data on the history of dietary use. Next, each constituent of an NFC is assigned to one of 33 congeneric groups of structurally related substances and to one of three classes of toxic potential, each with its own exposure threshold of toxicological concern. The group of substances of unknown structure is placed in the class of greatest toxic potential. In subsequent steps, for each congeneric group the procedure determines the per capita intake, considers metabolic pathways and explores the need and availability of toxicological data. Additional toxicological and analytical data may be required for a comprehensive safety evaluation. The procedure concludes with an evaluation of the NFC in its entirety, also considering combined exposure to congeneric groups. The first experiences with the use of this procedure are very promising. Future safety evaluations of larger numbers of NFCs will indicate the usefulness of the system, either in its present form or in a form modified on the basis of experience.

ClC-2 chloride channels contribute to HTC cell volume homeostasis.

Membrane Cl(-) channels play an important role in cell volume homeostasis and regulation of volume-sensitive cell transport and metabolism. Heterologous expression of ClC-2 channel cDNA leads to the appearance of swelling-activated Cl(-) currents, consistent with a role in cell volume regulation. Since channel properties in heterologous models are potentially modified by cellular background, we evaluated whether endogenous ClC-2 proteins are functionally important in cell volume regulation. As shown by whole cell patch clamp techniques in rat HTC hepatoma cells, cell volume increases stimulated inwardly rectifying Cl(-) currents when non-ClC-2 currents were blocked by DIDS (100 microM). A cDNA closely homologous with rat brain ClC-2 was isolated from HTC cells; identical sequence was demonstrated for ClC-2 cDNAs in primary rat hepatocytes and cholangiocytes. ClC-2 mRNA and membrane protein expression was demonstrated by in situ hybridization, immunocytochemistry, and Western blot. Intracellular delivery of antibodies to an essential regulatory domain of ClC-2 decreased ClC-2-dependent currents expressed in HEK-293 cells. In HTC cells, the same antibodies prevented activation of endogenous Cl(-) currents by cell volume increases or exposure to the purinergic receptor agonist ATP and delayed HTC cell volume recovery from swelling. These studies provide further evidence that mammalian ClC-2 channel proteins are functional and suggest that in HTC cells they contribute to physiological changes in membrane Cl(-) permeability and cell volume homeostasis.

Ethylamine in human urine.

The urinary excretion of ethylamine has been measured in 200 unrelated healthy volunteers (100 male, 100 female) who maintained their normal diet. The average daily output was 7.82+/-7.03 mg (mean+/-S.D.) (8.01+/-7.40 male; 7.64+/-6.67 female) with a range of values spreading from 0.22 to 35.27 mg. Dietary studies investigating 41 food substances did not highlight any major sources of this amine, except that drinking tea increased subsequent urinary ethylamine levels.

Bridging the gap between managed care and academic medicine: an innovative fellowship.

Numerous challenges face academic medicine in the era of managed care. This environment is stimulating the development of innovative educational programs that can adapt to changes in the healthcare system. The U.S. Quality Algorithms Managed Care Fellowship at Jefferson Medical College is one response to these challenges. Two postresidency physicians are chosen as fellows each year. The 1-year curriculum is organized into four 3-month modules covering such subjects as biostatistics and epidemiology, medical informatics, the theory and practice of managed care, managed care finance, integrated healthcare systems, quality assessment and improvement, clinical parameters and guidelines, utilization management, and risk management. The fellowship may serve as a possible prototype for future post-graduate education.

Cloning of the mgtE Mg2+ transporter from Providencia stuartii and the distribution of mgtE in gram-negative and gram-positive bacteria.

The MM281 strain of Salmonella typhimurium possesses mutations in each of its three Mg2+ transport systems, requires 100 mM Mg2+ for growth, and was used to screen a genomic library from the gram-negative bacterium Providencia stuartii for clones that could restore the ability to grow without Mg2+ supplementation. The clones obtained also conferred sensitivity to Co2+, a phenotype similar to that seen with the S. typhimurium corA Mg2+ transport gene. The sequence of the cloned P. stuartii DNA revealed the presence of a single open reading frame, which was shown to express a protein with a gel molecular mass of 37 kDa in agreement with the deduced size of 34 kDa. Despite a phenotype similar to that of corA and the close phylogenetic relationship between P. stuartii and S. typhimurium, this new putative Mg2+ transporter lacks similarity to the CorA Mg2+ transporter and is instead homologous to MgtE, a newly discovered Mg2+ transport protein from the gram-positive bacterium Bacillus firmus OF4. The distribution of mgtE in bacteria was studied by Southern blot hybridization to PCR amplification products. In contrast to the ubiquity of the corA gene, which encodes the dominant constitutive Mg2+ influx system of bacteria, mgtE has a much more limited phylogenetic distribution.

Cloning and characterization of MgtE, a putative new class of Mg2+ transporter from Bacillus firmus OF4.

The MM281 strain of Salmonella typhimurium which possesses mutations in each its three known Mg2+ transport systems and requires 100 mM Mg2+ for growth was used to screen a genomic library from the gram-positive alkaliphilic bacterium Bacillus firmus OF4 for clones that could restore the ability to grow without Mg2+ supplementation. Of the clones obtained, five also conferred sensitivity to Co2+, similar to the phenotype of mutants with mutations in the S. typhimurium corA Mg2+ transport locus. All five contained identical inserts by restriction analysis. Using 63Ni2+ as a surrogate for the unavailable 28Mg2+, the plasmid insert was shown to restore cation uptake with properties similar but not identical to those of the S. typhimurium CorA Mg2+ transporter. Sequence analysis of one clone identified a single open reading frame with multiple possible initiation sites. Deletion and mutation analysis identified a minimum open reading frame of 939 bp encoding a polypeptide with a predicted molecular mass of 34 kDa. Disruption of the open reading frame eliminated cation influx activity and restored resistance to Co2+. This putative transporter, designated MgtE, has no sequence similarity to any known protein including CorA and appears to represent a new class of Mg2+ transport system.

A comparison of N1 of the whole nerve action potential and wave i of the brain-stem auditory evoked response in Mongolian gerbil.

The present study seeks to provide empirical support for the assumption that wave i of the gerbil brain-stem auditory evoked response (BAER) corresponds to N1 of the whole nerve action potential (WNAP) by comparing the latency and amplitude of BAER wave i and WNAP N1. Fourteen 3-month old gerbils were anesthetized with Nembutal and Urethane-Dial. Normothermia was maintained by a homeothermic blanket system. BAERs were recorded with Grass needle electrodes placed subdermally. The WNAP was recorded with a silver wire placed in the round window niche. WNAP and BAER were simultaneously recorded with a passband of 100-10,000 Hz. Responses consisted of 500 sweeps, and two responses were obtained for each condition. Clicks were 25-microseconds electrical pulses. Tonebursts were shaped with a Hanning window, with 1-ms rise and fall times. Toneburst frequencies included 1, 2, 4, 8, and 16 kHz. For each stimulus, responses were obtained at levels of 30, 50, 70, and 90 dB pSPL. SPL was measured near the entrance to the ear canal with an Etymotic ER-7C probe microphone. Dependent variables were the latency and amplitude of N1 of the WNAP and wave i of the BAER. The latencies of wave i and N1 were very similar. Mean (across animal) latencies of N1 and wave i were within 70 microseconds for all six stimuli (clicks, tonebursts) and all four levels. Latency/intensity function slopes for N1 and wave i were also very similar, with both dependent variables showing an increasing latency/intensity function slope with decreasing toneburst frequency. The N1/wave i amplitude ratio was computed.(ABSTRACT TRUNCATED AT 250 WORDS)

Encoding of amplitude modulation in the gerbil cochlear nucleus: I. A hierarchy of enhancement.

The main goal of the present study was to investigate the encoding of a biologically-relevant acoustic feature--amplitude modulation (AM)--in single neurons of the auditory nerve and ventral cochlear nucleus (VCN). In the anesthetized gerbil auditory-nerve fibers and VCN units show strong synchronous responses to low-intensity, low-frequency AM. As frequency increases, the strength of the synchronous response decreases. In the auditory nerve the strength of the synchronous response is substantially less at high intensities than at low intensities and does not change significantly with AM frequency at high intensities. In contrast to the auditory nerve, VCN units show strong responses at high intensities. They have a particular AM frequency to which they are maximally responsive, and this frequency varies from unit to unit. Therefore, VCN units transform their ascending inputs by enhancing the synchronous response to AM. A correlation exists between a unit's ability to encode AM and its responses to simple sounds. Specifically, onset units show the strongest synchronous responses, followed in order by chopper, primarylike-with-notch and primarylike units. This enhancement is greatest at high intensities and can occur up to 90 dB above a unit's threshold. Thus, a hierarchy of enhancement for AM processing exists in the most peripheral nucleus of the central auditory system.

Effects of pulsing electromagnetic fields on bone growth and articular cartilage.

Observations made during treatment of juvenile pseudarthrosis by pulsing electromagnetic fields (PEMF) suggested that bone growth might be altered. PEMF applied to immature rabbits under conditions of continuous stimulation (24 hours/day for 8 weeks) produced no major changes in bone growth. Continuous stimulation by PEMF induced a statistically significant increase (22%) in femoral articular cartilage glycosaminoglycan. Intermittent PEMF stimulation (12 hours with stimulation/12 hours without stimulation) for 18 weeks produced no significant change in bone growth or time of epiphyseal plate closure. No significant changes in the physical characteristics of growing bone were observed with any treatment.

Comparison of cartilage destruction between infectious and adjuvant arthritis.

The timing and molecular profile of cartilage destruction in Escherichia coli and Staphylococcus aureus infectious arthritis and killed Mycobacterium butyricum adjuvant arthritis are presented. Infectious arthritis was studied for 3 weeks; cartilage samples were analyzed at 2, 10, and 21 days. At 48 h postinfection, glycosaminoglycan content was reduced by 20% (p less than 0.05) in E. coli infected knees and by 42% (p less than 0.05) in tibial plateau cartilage of S. aureus infected knees. By the 3rd week of infection, glycosaminoglycan losses amounted to as much as 73% (p less than 0.005). In comparison, collagen losses were not significant prior to the 3rd week of infection, at which time 42% (p less than 0.05) was lost. Adjuvant arthritic tibial plateau cartilage was examined at 1, 3 and 12 weeks. Glycosaminoglycans decreased by 42% the 1st week, plateauing at 62% by the 3rd and 12th weeks. Collagen degradation began at 3 weeks (28% loss, p less than 0.10) and by the 12th week was reduced by 49% (p less than 0.005). Analysis of the individual species of glycosaminoglycan showed a parallel loss of chondroitin sulfate and keratan sulfate. Fractionation of glycosaminoglycans with respect to size produced no evidence of shortened chains in cartilage from infected joints. Hyaluronic acid losses were greatest when collagen was significantly decreased. The pattern by which chondroitin and keratan sulfates are lost demonstrates that a prominent feature of infectious and noninfectious inflammatory arthritis is a rapid loss of proteoglycan subunits that precedes collagen loss.