The dielectric properties of aqueous solutions of poly(ethylene glycol) and their influence on membrane structure

The dielectric constant of water is reduced drastically on addition of poly(ethylene glycol). The behaviour is not described by a linear mixture equation. The decreased dielectric constant can lead to the general perturbation of the membrane structure which is necessary in such a manner that a strong aggregation of membranes would lead to their fusion. The changed cation permeability in the presence of poly(ethylene glycol) can explained as the effect of the lowered dielectric constant on the transfer energy.     

Comparison of the nucleotide sequence of soybean 18S rRNA with the sequences of other small-subunit rRNAs

Summary We present the sequence of the nuclearencoded ribosomal small-subunit RNA from soybean. The soybean 18S rRNA sequence of 1807 nucleotides (nt) is contained in a gene family of approximately 800 closely related members per haploid genome. This sequence is compared with the ribosomal small-subunit RNAs of maize (1805 nt), yeast (1789 nt),Xenopus (1825 nt), rat (1869 nt), andEscherichia coli (1541 nt). Significant sequence homology is observed among the eukaryotic small-subunit rRNAs examined, and some sequence homology is observed between eukaryotic and prokaryotic small-subunit rRNAs. Conserved regions are found to be interspersed among highly diverged sequences. The significance of these comparisons is evaluated using computer simulation of a random sequence model. A tentative model of the secondary structure of soybean 18S rRNA is presented and discussed in the context of the functions of the various conserved regions within the sequence. On the basis of this model, the short basepaired sequences defining the four structural and functional domains of all 18S rRNAs are seen to be well conserved. The potential roles of other conserved soybean 18S rRNA sequences in protein synthesis are discussed.     

Clinical, genetic, and epidemiological factors in neural tube defects.

We examined clinical, genetic, and epidemiologic factors among 512 probands with nonsyndromal neural tube defects (NTDs). Data were analyzed after grouping the probands in four different ways with respect to pathological features and putative pathogenic mechanisms. Apparently unrelated congenital anomalies occurred more frequently among probands with craniorachischisis (62%), encephalocele (30%), or multiple NTDs (25%) than among probands with anencephaly (14.7%) or spina bifida (10.1%) (P much less than .0001). Unrelated congenital anomalies occurred less often among probands with low spina bifida (6.7%) than among probands with high spina bifida (19.5%). NTDs were seen in 7.8% of the siblings of probands with high spina bifida but in only 0.7% of the siblings of probands with low spina bifida, in 2.2% of the siblings of anencephalic probands, and in none of the siblings of probands with craniorachischisis, encephalocele, or multiple NTDS (P less than .001). In all 16 families in which two siblings had NTDs, both had either defects of the type associated with abnormal primary neurulation or defects of the type associated with abnormal canalization. High spina bifida and multiple NTDs were found more frequently than expected among the Sikh probands (P less than .02). The frequency of non-NTD congenital anomalies was higher among siblings of Sikh probands (8.8%) than among siblings of other probands (2.4%) (P less than .05). This excess was due to the occurrence of hydrocephalus without spina bifida in four of 68 siblings of Sikh probands.     

The acid phosphatases of Thermoascus crustaceus, a thermophilic fungus

Thermoascus crustaceus, a filamentous, thermophilic ascomycete with pathogenic potential was cultured on Sabouraud's liquid medium at temperatures from 27 to 47 degrees C for periods up to 7 days. Growth rate and yield were optimal at 37 degrees C. Morphological changes were confined to the cell walls, the thickness being greatest at 47 degrees C, which were also more resistant to mechanical disruption. Significant amounts of acid phosphatase (EC 3.1.3.2) activity occurred in the spent media of all cultures but were greatest at 37 degrees C. The proportions of acid phosphatase activity which were operationally defined as soluble or bound were also documented; the optimum pH for acid phosphatase activity in all fractions was 5.0. Extracts were subjected to polyacrylamide gel electrophoresis under non-denaturing conditions and the gels were stained for acid phosphatase activity. This revealed four electrophoretically distinct acid phosphatases which had different susceptibilities to inhibition by fluoride, phosphate, or tartrate. Effects of growth temperature, or phosphate supplement in the culture medium, on the acid phosphatase isoenzyme pattern were judged to be minor. Cytochemistry at the electron microscope level indicated acid phosphatase activity on the surface, in the periplasmic space, and in the cytoplasm, but no trends with regard to growth conditions. A substantial temperature range can be tolerated by this species but it is concluded that neither the general shape of the cells nor the acid phosphatase isoenzyme pattern changes substantially; this contrasts with previously documented differences for this class of enzyme in dimorphic Sporotrix schenckii.     

Targeted inactivation of the muscle regulatory gene Myf-5 results in abnormal rib development and perinatal death.

The Myf-5 gene, a member of the myogenic basic HLH factor family, has been inactivated in mice after homologous recombination in ES cells. Mice lacking Myf-5 were unable to breathe and died immediately after birth, owing to the absence of the major distal part of the ribs. Other skeletal abnormalities, except for complete ossification of the sternum, were not apparent. Histological examination of skeletal muscle from newborn mice revealed no morphological abnormalities. Northern blot analysis demonstrated normal levels of muscle-specific mRNAs including MyoD, myogenin, and Myf-6. However, the appearance of myotomal cells in early somites was delayed by several days. These results suggest that while Myf-5 plays a crucial role in the formation of lateral sclerotome derivatives, Myf-5 is dispensable for the development of skeletal muscle, perhaps because other members of the myogenic HLH family substitute for Myf-5 activity.     

Establishment and characterization of hybrid rat mast cells

Rat peritoneal mast cells (RPMC) and rat basophilic leukemia (RBL) cells are representative of connective tissue-type (CTMC) and mucosal-type (MMC) mast cells, respectively. Using polyethylene glycol, we have fused RPMC with 6-thioguanine resistant, HAT (hypoxanthine, aminopterin, thymidine) sensitive RBL-CA10.7 or RBL-CK2 cells, yielding several hybrid rat mast cell lines (HRMC). The hybridomas exhibited different size and cytoplasmic granularity when compared with parental cell lines. Analysis of both high (Fc epsilon RI) and low affinity (Fc epsilon RL) receptors for IgE revealed that the hybrid lines had more variable receptor patterns than the parent lines. Three hybridoma lines were chosen for further study. Differential histochemical staining with alcian blue and safranin O dyes indicated the hybrids to be predominantly of the MMC type: however, a few cells of one of these uncloned hybridomas were found to be of the CTMC type. Attempts to isolate the CTMC hybridomas yielded one culture which was predominantly of the CTMC phenotype and in a number of other cultures, cells were found expressing simultaneously both the CTMC and the MMC phenotype. After 3 weeks in culture, however, all hybridomas, including those which were cloned further, expressed only the MMC histochemical phenotype. This was found to correlate with the presence of rat mast cell protease II (RMCPII) and the absence of RMCPI in all hybridomas, as detected by Western blot analysis. In addition, the histamine content of all cells was significantly lower than that of the parent RPMC. Most hybrid mast cells expressed both Fc epsilon RI and Fc epsilon RL which in some cases exhibited significant variations in the Mr. These results indicate that somatic cell hybrids expressing the MMC and CTMC phenotype can be produced by the fusion of RBL and RPMC. The CTMC phenotype, however, is unstable, and possible reasons for this are discussed.     

Functional differences in human neutrophils isolated pre- and post-prandially.

Activated polymorphonuclear leukocytes have been associated with neoplasia, atherogenesis and reperfusion injury. Since some of these conditions are also correlated with dietary fat, we examined the functional characteristics of leukocytes isolated from subjects before and after consumption of a lipid-rich meal. There was up to 2-fold greater superoxide generation in response to agonists in leukocytes obtained post-prandially; the maximum increase was observed about 4 h after eating and followed the peak (2-4 h) in serum triglycerides. Neutrophils isolated post-prandially also exhibited impaired chemotaxis and defective bacterial killing, but normal phagocytosis. These findings provide a new variable that should be considered in studies of leukocytes.     

Structure-activity relationships in sweeteners. I. Nitroanilines, sulphamates, oximes, isocoumarins and dipeptides

Besides the hydrophilic AH-B moiety in sweeteners, the morehydrophobic ‘third binding sites’ play an essentialrole in inducing sweetness. The distances between these molecularfunctions seem to be very critical, but exact data are lacking.To describe stereochemical requirements more precisely, newconceptual parameters were introduced, namely , and (minimum,optimum and maximum distances between these third binding sitesand the atoms A, H and B of the AH-B moieties respectively,especially appropriate for homologous series) and the S value(shortest distance between the position of an atom and the planeformed by the atoms A, H and B of the AH-B moiety). The dimensionsof the relevant side chains of five homologous series of sweeteners– sulphamates, oximes, nitroanilines, isocoumarins anddipeptides — were determined. We calculated that the positionsof the , and parameters with regard to the AH-B moieties arelocated around two main axes forming 95? angles with the H-Baxis in the AH-B moieties for sulphamates and isocoumarins and125? angles for oximes, nitroanilines and dipeptides. The positionsof are, for all potent sweeteners, situated at 70—85%of the maximum distance of viewed from the centre of the Aatom, while for , this value was found to be 15% for oximes,25% for nitroanilines, 40% for sulphamates, 50—70% fordipeptides and 65% for isocoumarins. The results indicate thereare at least three — but a maximum of four — differentreceptor sites. They have very narrow site clefts with maximumheights of -0.6 nm.     

Problems in prenatal diagnosis of the ichthyosis congenita group

Summary The late onset of normal keratinization after week 24 menstrual age (MA) of fetal life is the cause of considerable problems with the prenatal diagnosis of congenital ichthyosis. This paper summarizes the experiences with prenatal diagnosis in nine pregnancies at risk of congenital ichthyosis and one at risk of chondrodysplasia punctata, rhizomelic type. An important prerequisite—and the main problem—is the manifestation of the mutant genes early enough in fetal life to allow a safe exclusion. Continuous precocious keratinization of the interfollicular epidermis, hyperkeratosis, and/or specific markers of congenital ichthyosis such as various types of lipid inclusions had been expected. With a normal ultrastructure and development of fetal epidermis no evidence of ichthyosis was present in eight cases; all eight children were born healthy. Regional variations of the onset of keratinization of the interfollicular epidermis, observed in one of these eight fetuses as well as in one fetus at risk (but normal for) recessive dystrophic epidermolysis bullosa, posed considerable problems and might lead to a false-positive diagnosis. Examination after birth allowed one to localize these regions to areas close to the mamillae. Regional variations in addition to the well-known cranio-caudal gradient thus are normal findings: both children have normal skin. One fetus at risk of nonbullous congenital ichthyosiform erythroderma (type II) was involved without prenatal manifestation of interfollicular keratinization, specific markers, or increased numbers of cornified cells in the pilosebaceous follicles at 20 weeks MA. A slightly more irregular pattern of the horn cell contents was not regarded as sufficient evidence alone to indicate congenital ichthyosis. A severely affected boy was born in week 34 MA. Similarly the fetus at risk of chondrodysplasia punctata showed no skin abnormalities, neither at fetoscopy (week 22 MA) nor after abortion (week 24 MA) although based on other clinical features it was clearly affected. Thus, this genodermatosis cannot be diagnosed prenatally by its keratinization disturbances. In future cases, precocious keratinization and hyperkeratosis cannot be expected to be expressed before week 24 MA, and minor signs, such as irregularities of horn cell contents, have to be taken as an indication of involvement. Multiple biopsies are required, and a safe exclusion may be impossible before week 22 MA.     

The influence of gramicidin S on hydrophobicity of germinating Bacillus brevis spores

Gramicidin S is known to prolong the outgrowth stage of spore germination in the producing culture. Bacillus brevis strain Nagano and its gramicidin S-negative mutant, BI-7, were compared with respect to cell-surface hydrophobicity and germination of their spores. Parental spores were hydrophobic as determined by adhesion to hexadecane, whereas mutant spores showed no affinity to hexadecane. Addition of gramicidin S to mutant spores resulted in a high cell surface hydrophobicity and a delay in germination outgrowth. The hydrophobicity of parental spores was retained throughout most of the germination period. Hydrophobicity was lost as outgrowing spores entered into the stage of vegetative growth. The data indicate that gramicidin S is responsible for the hydrophobicity of B. brevis spores. It is suggested that in making spores hydrophobic, the antibiotic plays a role in concentrating the spores at interfaces where there is a higher probability of finding nutrients for germination and growth.Abbreviation GS Gramicidin S