Morphology and life history of Halopteris filicina (Sphacelariales, Phaeophyceae) from Korea

The vegetative morphology and life history of Halopteris filicina (Grateloup) Kutzing, collected from Korea, were examined in laboratory culture. Field plants attaining 3–5 cm in height were epilithic, tufted, yellowish-brown, and produced numerous erect axes with alternately distichous branches from compact basal discs. They were cultured under a 12:12 h LD photoperiod at 10°-C, 15°C and 20°C to observe the influence of temperature on reproduction. At 10°C plants grew only vegetatively, whereas at 15°C and 20°C they produced unilocular sporangia. Unispores released from sporangia developed into monoecious, anisogamous gametophytes that formed plurilocular female and male gametangia on the same lateral branches. The zygotes, by fusion of female macrogametes and male microgametes, developed into sporophytes bearing unilocular sporangia, whereas the unfused female gametes germinated parthenogenetically. This species was confirmed to have an isomorphic life history, basically similar to the other species of Sphacelariales.     

Rat brain Na channel mRNAs in non-excitable Schwann cells

The expression of rat brain voltage-sensitive Na⁺ channel mRNAs in Schwann cells was examined using in situ hybridization cytochemistry and RT-PCR. The mRNAs of rat brain Na⁺ channel subtype II and III, but not subtype I, were detected in cultured Schwann cells from sciatic nerve and in intact sciatic nerve, which contains Schwann cells but not neuronal cell bodies. These results indicate that rat brain Na⁺ channel mRNAs, which have been considered as mainly neuronal-type messages, are also expressed in glial cells in vitro and in vivo.     

Characterization of the interaction of the glp repressor of Escherichia coli K-12 with single and tandem glp operator variants.

The glp operons of Escherichia coli are negatively controlled by the glp repressor. Comparison of the repressor-binding affinities for consensus and altered consensus operators in vivo showed that all base substitutions at positions 3, 4, 5, and 8 from the center of the palindromic operator caused a striking decrease in repressor binding. Substitutions at other positions had a severe to no effect on repressor binding, depending on the base substitution. The results obtained indicate that the repressor binds with highest affinity to operators with the half-site WATKYTCGWW, where W is A or T, K is G or T, and Y is C or T. Strong cooperative binding of the repressor to tandem operators was demonstrated in vivo. Cooperativity was maximal when two 20-bp operators were directly repeated or when 2 bp separated the two operators. Cooperativity decreased with the deletion of 2 bp or the addition of 4 bp between the individual operators. Cooperativity was eliminated with a 6-bp insertion between the operators.     

Analysis of peptides from known proteins: Clusterization in sequence space

A combinatorial sequence space (CSS) model was introduced to represent sequences as a set of overlapping k-tuples of some fixed length which correspond to points in the CSS. The aim was to analyze clusterization of protein sequences in the CSS and to test various hypotheses about the possible evolutionary basis of this clusterization. The authors developed an easy-to-use technique which can reveal and analyze such a clusterization in a multidimensional CSS. Application of the technique led to an unexpectedly high clusterization of points in the CSS corresponding to k-tuples from known proteins. The clusterization could not be inferred from nonuniform amino acid frequencies or be explained by the influence of homologous data. None of the tested possible evolutionary and structural factors could explain the clusterization observed either. It looked as if certain protein sequence variations occurred and were fixed in the early course of evolution. Subsequent evolution (predominantly neutral) allowed only a limited number of changes and permitted new variants which led to preservation of certain k-tuples during the course of evolution. This was consistent with the theory of exon shuffling and protein block structure evolution. Possible applications of sequence space features found were also discussed.Correspondence to: H.A. Lim     

Rapid screening of an SH2-containing gene using PCR amplification method

Summary To isolate a novel gene that contains an SH2 domain, we devised a rapid and nonradioactive cDNA library screening method using polymerase chain reaction (PCR). For PCR amplification, we designed degenerate oligonucleotide primers from the multialigned DNA sequences of SH2 domains. This method offers an inexpensive and efficient approach for the isolation of clones of interest from cDNA libraries.     

Turnover characteristics in continuous l-lysine fermentation

The turnover characteristics of a microbial bioreactor were comparatively investigated as a closed (batch) and a continuous stirred tank reactor (CSTR) open system, using a 2-l fermentor. Corynebacterium glutamicum (ATCC 21544) was chosen as the microorganism since it has the ability to produce l-lysine. Parameters measured were l-lysine production rates, glucose consumption rates and biomass production rates as a function of dilution rate, bioreactor volume and biomass concentration. The modes of microbial cell behaviour under steady-state and transition-state conditions were examined. Investigations on scaling properties of the CSTR system were also aimed at comparing scaling or allometry of metabolic rates in organisms that are also open energy dissipative systems.This investigation was first presented at the 10th Dechema-Jahrestagung der Biotechnologen, 1–3 June 1992, Karlsruhe, Germany     

Substantial overproduction of antibodies by applying osmotic pressure and sodium butyrate

Much of the current cell technology has enabled increased antibody production levels due to judicious nutrient feeding to raise cell densities and design better bioreactors. This study demonstrates that hybridomas can be hyperstimulated to produce higher immunoglobulin (lg) levels by suppressing cell growth and increasing culture longevity through adaptation to higher osmolarity media and addition of sodium butyrate. Prior to adaptation, cells placed in higher osmotic pressures (350 and 400 mOsm) were severely suppressed in growth down to 25% of the control (300 mOsm), although total lg titers achieved were similar to the control, approximately 140 mg/L. After a week of adaptation to 350 and 400 mOsm media, cell growth was not as dramatically suppressed, but considerably higher lg levels were attained at these elevated osmolarities. The highest yield of 265 mg/L was obtained at 350 mOsm compared to 140 mg/L at 300 mOsm, while maximum viable cell numbers dropped from 35 x 10(5) cells/mL to 31 x 10(5) cells/mL and culture longevity was extended by 20 h more than the control. Sodium butyrate, known to enhance protein production in other cell types, was then supplemented at a range of concentrations between 0.01 and 0.4 mM to the 350 mOsm culture to further enhance the lg levels. Butyrate at a concentration of 0.1 mM, in combination with osmotic pressure at 350 mOsm, further elevated the lg levels to 350 mg/L. Concomitantly, maximum viable cell numbers were reduced to 22 x 10(5) cells/mL, but culture longevity was extended by 40 h in the 0.1 mM butyrate supplemented culture compared to the control condition. Specific antibody productivity, q(Mab), continued to stay high during the stationary phase and was further elevated during the decline phase: thus, overall lg levels can be increased by 2.3 times by combining osmotic pressure and butyrate treatment. (c) 1993 John Wiley & Sons, Inc.