Improvement of microbial strains and fermentation processes.

Improvement of microbial strains for the overproduction of industrial products has been the hallmark of all commercial fermentation processes. Conventionally, strain improvement has been achieved through mutation, selection, or genetic recombination. Overproduction of primary or secondary metabolites is a complex process, and successful development of improved strains requires a knowledge of physiology, pathway regulation and control, and the design of creative screening procedures. In addition, it requires mastery of the fermentation process for each new strain, as well as sound engineering know-how for mediaoptimization and the fine-tuning of process conditions. This review focuses on the various options that may be employed to improve microbial strains and addresses the complex problems of screening, the tools and technology behind the selection of targeted organisms, and the importance of process optimization. Furthermore, this review discusses new and emerging technologies and designing optimized media for tracking mutants with enhanced productivity or other desired attributes.

Serotonergic stimulation of the genioglossus and the response to nasal continuous positive airway pressure.

In obstructive sleep apnea (OSA), abnormal pharyngeal collapsibility may be offset by increased mechanoreflex-mediated activity of dilator muscles while awake, but this reflex is inhibited during sleep and during application of nasal continuous positive airway pressure (CPAP). Direct activation of upper airway (UA) motor neurons in the hypoglossal nucleus by a selective serotonin reuptake inhibitor (SSRI), paroxetine hydrochloride, may increase genioglossal electromyographic (EMG) activity (EMGgg) in a manner resistant to mechanoreflex inhibition. We studied the effects of paroxetine on EMGgg using an intraoral surface electrode during eupnea or room air breathing (RA), hypercapnia (HYP), and CPAP application in the presence of hypercapnia (CPAP + HYP) in 11 normal volunteers, using a double-blind, placebo-controlled crossover design. After 5 d of paroxetine, EMGgg activity increased significantly within each condition (p = 0.02). EMGgg during the conditions of HYP and HYP + CPAP were significantly greater than during RA for both placebo and paroxetine treatments (p = 0.006). EMGgg activity in HYP persisted during HYP + CPAP on paroxetine (183% versus 182% of placebo, respectively). We conclude that paroxetine produces an augmentation in EMGgg in normal subjects during wakefulness and that this effect persists during mechanoreflex inhibition. This is consistent with a central serotonergic effect.

Force production of the genioglossus as a function of muscle length in normal humans.

Resting muscle length affects both maximum force production and force maintenance. The strength and force maintenance characteristics of the genioglossus as a function of resting muscle length have not been described. We hypothesized that genioglossus optimum length (L(o)) could be defined in vivo and that the ability of the genioglossus to sustain a given workload would decrease as resting length deviated from L(o). To test this, 11 normal men repeated maximal isometric genioglossus protrusions at different muscle lengths to determine L(o). L(o) was also obtained by using submaximal efforts while simultaneously recording electromyographic activity of the genioglossus, with L(o) defined as the length at which the force-to-genioglossus electromyographic activity ratio was maximum. Both methods provided similar results. Force maintenance was measured at four muscle lengths on separate days. Target efforts representing 60% of each subject's maximum at L(o) and lasting 5 s were performed at 12-s intervals. Time limit of endurance of the genioglossus was defined as the time from trial onset at which 90% of the target could not be maintained for three consecutive efforts. Time limit of endurance was greatest at L(o) and fell to 47.5% at L(o) + 1 cm, 53.8% at L(o) - 1 cm, and 47.4% at L(o) - 1.5 cm. We conclude that L(o) of the genioglossus can be determined in vivo and that force maintenance of the genioglossus is decreased when operating length deviates from L(o).

Novel naphthoquinones from a Streptomyces sp.

Cdc25A assay-guided fractionation of a fermentation broth derived from a Streptomyces sp. resulted in the isolation of four novel naphthoquinones 1-4. Structures of these compounds were deduced by NMR and mass spectrometry. Two of them, 3 and 4, incorporate a modified cysteine residue which is observed for the first time in this class of natural products. Naphthoquinones 1-4 showed weak activity against cdc25A phosphatase.

Obesity and weight loss in obstructive sleep apnea: a critical review.

Clinic-based and epidemiological studies demonstrate a strong association between obesity and obstructive sleep apnea. However, defining the causal relationship between excess body weight and sleep-disordered breathing remains difficult. Potential mechanisms to be considered include: (1) alterations in upper airway structure; (2) alterations in upper airway function; (3) alterations in the balance between ventilatory drive and load and (4) obesity-induced hypoxemia. Additional evidence for the role of obesity in obstructive sleep apnea comes from clinical studies of weight loss in patients with sleep-disordered breathing. Significant weight loss has been reported in most studies, which has been associated with varying degrees of improvement in sleep-disordered breathing, oxygen hemoglobin saturation, sleep architecture and daytime performance. Surgical and nonsurgical approaches to weight loss have been evaluated, although most studies to date suffer from methodological limitations including lack of random assignment to treatment groups, confounding of treatment interventions, absence of untreated controls and lack of adequate follow-up assessment. Implications for research and clinical practice are discussed.

Early and late respiratory-related cortical potentials evoked by pressure pulse stimuli in humans.

Although respiratory-related cortical evoked potentials (CEPs) have been obtained in humans, early-latency responses have been obtained only with direct electrical stimulation of respiratory afferents. We have recorded both early and late cortical activity in response to a relatively novel stimulus consisting of a 300-ms negative pressure pulse applied to the mouth near the start of selected inspirations, when mouth pressure attained a predetermined threshold. This stimulus caused highly reproducible and rapid changes in mouth pressure and was effective in eliciting CEPs to a wide range of applied pressures. Using pulses of approximately -2 to -25 cmH2O, we obtained an early positive component with a mean latency of approximately 20 ms and a subsequent negative component at approximately 30 ms in normal subjects. Peak-to-peak amplitude varied directly, and component latencies inversely, as a function of pulse magnitude. Using -5- to -10-cmH2O stimuli, we also measured a later positive-negative-positive response with mean component latencies of 96.7 +/- 15.1, 147 +/- 14.8, and 237.6 +/- 23.5 ms, respectively. The early-latency activity was resistant to manipulations of stimulus predictability, whereas the later waves were attenuated or disappeared when load presentation was made completely predictable. We validated our method by eliminating the possibility of tactile stimulation of the lips and teeth as the origin of the evoked responses. We propose that early-latency activity derives from precortical structures and may provide a window on the functioning of respiratory afferents in normal subjects and in patients with respiratory disease.

Nasal and pharyngeal resistance after topical mucosal vasoconstriction in normal humans.

Phenylephrine, an alpha-adrenergic agonist, increases pharyngeal cross-sectional area when applied topically to the nasal and pharyngeal mucosa, as determined by magnetic resonance imaging. In this study, we examined the possibility that the increase in area results from either a decrease in transmural collapsing pressure, as a result of a decrease in upstream (nasal) resistance, or an increase in upper airway muscle activity. In eight normal, awake men we measured inspiratory pharyngeal and nasal resistance and the electrical activity of the genioglossus (EMGGG) and alae nasi (EMG(AN) before and after pharyngeal and nasal + pharyngeal instillation of 1 ml of either 0.25% phenylephrine or normal saline; phenylephrine and saline were tested on separate days. Under control eucapnic conditions, pharyngeal resistance was 0.43 +/- 0.03 cm H2O/L/s, and nasal resistance was 2.43 +/- 0.14 cm H2O/L/s. Pharyngeal resistance was 0.29 +/- 0.03 cm H2O/L/s after nasal + pharyngeal instillation of phenylephrine and 0.98 +/- 0.13 cm H2O/L/s after saline; nasal resistance was 2.18 +/- 0.13 cm H2O/L/s after nasal + pharyngeal instillation of phenylephrine and 3.15 +/- 0.21 cm H2O/L/s after saline. Thus, phenylephrine decreased both nasal and pharyngeal inspiratory resistance. The change in pharyngeal resistance was not dependent on the change in nasal resistance. Eucapnic EMGGG and EMGAN activities did not change after phenylephrine or saline. We conclude that phenylephrine decreased pharyngeal resistance independent of a change in nasal resistance of upper airway muscle activity, and we believe that the changes in resistance we observed reflect a direct effect of phenylephrine on the pharyngeal mucosa and a consequent enlargement of pharyngeal size.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro analytical system for determining the ability of antibiotics at residue levels to select for resistance in bacteria.

An analytical procedure, based on the concept that exposure of bacteria to antibiotics will result in the selection of a resistant population, was developed. Two strains of enteric bacteria, Escherichia coli CS-1 and Enterobacter cloacae B520, which are sensitive to a wide variety of antibiotics, were used as the test organisms. E. coli CS-1 were exposed to 1.00 micrograms antibiotic or antimicrobial/mL; E. cloacae B520 were exposed to 0.01, 0.10, 0.50, 1.00, and 5.00 micrograms/mL. Both organisms developed increased resistance to other antibiotics after exposure to chlortetracycline and oxytetracycline, as measured by the minimum inhibitory concentration (MIC). E. cloacae B520 showed increased resistance to ampicillin, oxytetracycline, and chloramphenicol after exposure to levels as low as 0.10 microgram/mL. Exposure to streptomycin, sulfamethazine, tylosin, bacitracin, flavomycin, virginiamycin, and monensin at levels of 1.00 microgram/mL did not increase the MIC. Exposure to 5.00 micrograms streptomycin, sulfamethazine, tylosin, and monensin/mL increased the MIC of E. cloacae to one of the antibiotic markers. These increased MICs exceeded the 95% confidence limits of the MIC values of the unexposed organisms.

Chromosome 15 abnormalities and the Prader-Willi syndrome: a follow-up report of 40 cases.

High-resolution chromosome analysis and multiple banding techniques were performed on blood samples from 40 patients with Prader-Willi syndrome (PWS) as a follow-up to our recent report in which we found interstitial deletions of 15q in four of five patients with this syndrome. Of the 40 new patients, 19 had interstitial del(15q), one had an apparently balanced 15;15 translocation, and one was mos46,XX/47,XX+idic(15) (pter leads to q11::q11 leads to pter). These data confirm our previous report and demonstrate that half of all patients with the clinical diagnosis of PWS have chromosome abnormalities involving chromosome 15 detectable by high-resolution methods. Although the majority of these involve a specific deletion of bands 15q11-q12, other alterations of chromosome 15 may be present.

NOR lateral asymmetry and its effect on satellite association in BrdU-labeled human lymphocyte cultures.

Second generation BrdU-labeled acrocentric chromosomes exhibit NOR lateral asymmetry (NLA) in metaphases that have been sequentially stained with silver and the Hoechst-Giemsa sister chromatid differential (SCD) technique. The NLA presumably results from suppression of NOR activity in the doubly-substituted chromatid. Examination of single chromatid (NOR) associations in pairs of acrocentrics reveals that light chromatids associate less frequently than dark chromatids and that the frequency distribution of dark and light alignment configurations can be explained by this differential tendency to associate. Thus, it appears that a hypothesis of non-random chromatid segregation as an explanation for non-random chromatid alignments in associating acrocentric chromosomes is unwarranted.

Duplication 11p11.3 leads to 14.1 to meiotic crossing--over.

An infant with macular dysfunction, cleft lip and palate, and developmental delay was shown to have an inverted duplication of 11p11.3 leads to p14.1 on the basis of meiotic recombination subsequent to an intrachromosomal "shift" in his mother. A half-sister had previously been shown [3] to have the reciprocal recombinant with resultant deletion of 11p11.3 leads to 11p14.1.