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Emr-2 is an emetine-resistant (Emr) Chinese hamster ovary cell mutant that contains a single electrophoretically altered ribosomal protein, a component of its 40S ribosomal subunit [Boersma, D., McGill, S., Mollenkamp, J. & Roufa, D.J. (1979) J. Biol. Chem. 254, in press]. This report describes a genetic experiment designed to test linkage between the genes that specify the altered ribosomal protein, S20*, and emetine resistance in Emr clones that segregated from cultures of Emr-2 cells hybridized with emetine-sensitive cells. The data described indicate that Emr and S20* phenotypes are due to mutations linked to the same chromosome in the Chinese hamster genome; most likely they are due to the same mutation. The data also confirm earlier speculations by others that the Emr locus in Chinese hamster cells is hemizygous.

TE146, a large transposing element of Drosophila melanogaster, carries two copies of the white and roughest genes in tandem. In consequence, z(1)w( 11E4); TE146(Z)/+ flies have a zeste (lemon-yellow) eye color. However, one in 10(3)TE146 chromosomes mutates to a red-eyed form. The majority of these "spontaneous red" (SR) derivatives of TE146 have only one copy of the white gene and are, cytologically, two- to three-banded elements, rather than six-banded as their progenitor. The SR forms of TE146 are also unstable and give zeste-colored forms with a frequency of about one in 10(4). One such "spontaneous zeste" (SZ) derivative carries duplicated white genes as an inverted, rather than a tandem, repeat. The genetic instability of this inverted repeat form of TE146 is different from that of the original tandem repeat form. In particular, the inverted repeat form frequently produces derivatives with internal rearrangements of the TE and gives a much lower frequency of SR forms. In addition, two novel features of the interaction between w(+) alleles in a zeste background have been found. First, copies of w( +) can become insensitive to suppression by zeste even when paired. Second, an inversion breakpoint may disrupt the pairing between two adjacent w(+) alleles, necessary for their suppression by zeste, without physically separating them.

Diphtheria toxin B-fragment binds to cell-surface receptors and facilitates translocation of the enzymatically active A-fragment to the cytosol. In this process the B-fragment inserts into the plasma membrane and induces formation of cation-selective channels. We examined the ability of a number of diphtheria toxin-derived molecules translated in vitro to permeabilize cells. Two proteins consisting of the whole B-fragment and small parts of the A-fragment, and one protein comprising most of the B-fragment alone, were more efficient than full-length toxin in permeabilizing the plasma membrane to monovalent cations. Two shorter B-fragment-derived proteins, with 3 and 10 kd N-terminal deletions, permeabilized the cells to sulfate and sucrose in addition to monovalent cations. The relationship between channel formation and toxin translocation is discussed.

We have developed a system to study the interactions of diphtheria toxin with the cell surface using non-toxic mutant proteins synthesized in vitro. Proteins obtained by N-terminal deletions containing the whole B fragment bound strongly to cells. Deletions extending into the B fragment did not yield an autonomous binding domain. Loss of only the N-terminal 3 kd of the B fragment significantly impaired the ability to recognize the receptor. This, together with previous reports that the C-terminal end of the B fragment is required for binding, suggests that both ends of the B fragment are necessary for receptor recognition. Receptor bound diphtheria toxin undergoes a conformational change at pH less than 5.3 that results in translocation of the A fragment to the cytosol and the appearance of a B fragment-derived 25 kd polypeptide (P25) resistant to externally applied protease. Only the B fragment was required for generation of P25. N-terminal deletions of 130 amino acids or more resulted in proteins that gave rise to P25 at higher pH than full length toxin. Furthermore, a second protease-inaccessible polypeptide of 18 kd (P18) was observed.

The kinetics and kinematics of swing-through crutch gait in children were investigated assisted by the development of a computer package to aid in data analysis. Eight volunteer subjects ambulated with crutches of various lengths as cinefilm, axial crutch, and foot contact forces were recorded. Instantaneous segment energies and powers were calculated from digitized, filtered, cinefilm data. Values of internal mechanical work expenditure were also calculated using 9-segment and 10-segment models of the body. Mechanical inefficiencies in individual gait patterns were identified by abnormalities in the instantaneous energy and power traces augmented by force information. Although crutch length was found to be a critical determinant of efficient gait, the formula to find correct length varied among individuals. Normalized work output values for children, corrected for body weight and distance covered per stride, were found to be much greater than those found in adults.

Pain in the sacroiliac region is often referred to by the non-specific term sacro-iliac syndrome. Quite often there is dull pain accompanied with local tenderness over the sacrum and posterior superior iliac spines. The hypothesis of this work is that the pain may result from surprisingly large stresses within the extensor aponeurosis and other extensor forces directly transmitted to the sacro-iliac region. The forces in 48 muscles were estimated from a detailed, anatomic computer model of the trunk. Forces in muscles that originate from the sacral and posterior superior iliac spine region were summated. For sagittal plane lifts involving relatively light loads of 27·3 kg, nearly 7 kN of force was transmitted to the extensor origins of the sacro-iliac region. A large proportion of this force was produced by the longissimus thoracis pars lumborum and iliocostalis lumborum pars lumborum complex. These predicted high stresses are discussed as possible factors in clinically observed sacroiliac trauma and pain., (Copyright © 1987. Published by Elsevier Ltd.)

We evaluated the noise level of fourteen air-driven handpieces, six low speed (less than 20,000 rev/min) and eight high speed (greater than 160,000 rev/min), with respect to a three-directional co-ordinate system and distances of 6, 12 and 18 in. in each chosen direction. A two-way analysis of variance of the noise level between handpieces and positions indicates that large significant differences exist amongst handpieces and in different positions, and that interaction is just barely significant. The ranking and least significant differences for the mean of all handpieces v. position and for the mean of all positions v. handpiece were compared with the results for the ranking and significances from the one-way ANOVAS for each handpiece v. position and for each position v. handpiece. A trend exists with some of the handpieces of straight design (all low speed) for increased noise levels in a direction perpendicular to the handpieces and decreased levels in a direction parallel to the handpieces. For handpieces of angled design (all high speed) both directions parallel and perpendicular (the perpendicular to the longitudinal turbine axis) to the rotor axis indicate increased noise levels. The parallel direction includes the exiting air from the exhaust port. The perpendicular direction can be indicative of an aerodynamic factor associated with the established air flow patterns. The extremes in noise level were 56.8 dBA for a low-speed handpiece of straight design at the 18 in. distance in a direction parallel to the handpiece, and 87.3 dBA for a high speed handpiece at the 6 in. distance in a perpendicular direction.

A mutant Chinese hamster cell clone has been isolated from an S phase culture. This clone, ts154, could not replicate DNA at nonpermissive temperature (39 degrees C), although it synthesized DNA normally at permissive temperature (33 degrees C). After transfer to 39 degrees, ts154 cells replicated DNA semiconservatively through precisely two complete rounds and divided twice before they ceased DNA synthesis and further growth. The mutation in ts154 affects DNA replication specifically, as its rates of cellular transcription, its ability to support growth of vesicular stomatitis virus, and its ribo- and deoxyribonucleoside triphosphate pools were normal at 39 degrees. Cultures of ts154 resumed DNA replication within 6h when shifted from 39 degrees to 33 degrees, even after 78 h at the nonpermissive temperature. Upon return to 33 degrees, mutant cells achieved a normal steady-state rate of DNA synthesis by 10 h, suggesting that they had come to rest within G1 phase at 39 degrees. Resumption of DNA synthesis and growth after a shift-down to 33 degrees were sensitive to cycloheximide in ts154, and thus likely required synthesis of new protein.

Eyeglasses with protective filters are recommended for users of visible light-curing units to decrease the intensity of blue light reaching the eyes. The transmission curves of 20 commercially available filter glasses are obtained. The irradiance from eight curing units through these glasses is measured. The reduction in irradiance through the filter glasses is related to the transmission curves.

The TE1 family of transposable elements (TEs) of Drosophila consists of unusually large transposons, cytologically visible in larval polytene chromosomes as one or more bands. They are composite elements, as their termini consist of foldback (FB) sequences which are themselves transposable. The location of FB elements at the termini of transposable elements suggests that these sequences have a direct role in the genetic instability of TEs. To investigate the structural and phenotypic consequence of TE excision, we have cloned genomic DNA required for the expression of the no-ocelli (noc) gene of Drosophila; this gene has been mutated by the insertion of TE146, a member of the TE1 family carrying six polytene chromosome bands including functional copies of the white (w+) and roughest (rst+) genes. As reported here, our experiments indicate that the spontaneous excision of TE146, which results in the loss of the w+ and rst+ markers, can occur either as a single-step event or following a partial internal deletion. In either case, the end product is an imprecise excision in which a residual portion of the element, varying in size from 3 to 10 kilobases (kb), is left at the insertion site. These residual sequences share homology with the FB family. Furthermore, despite their imprecise nature, all these spontaneous excisions restore a wild-type noc+ phenotype.

A screen is described that will select for breakpoints within a restricted chromosomal region in Drosophila. The aberrations recovered can be used to construct chromosomes carrying synthetic duplications and deletions. Such chromosomes have applications in the mapping of complementation groups at both the genetic and molecular level. In particular, breakpoints recovered after P element hybrid dysgenesis tend to be associated with P element insertion sites. Such aberration breakpoints can be genetically mapped, as synthetic deletions, and then used as transposon-tagged sites for the recovery of genomic clones.

An intact gene coding for wild type diphtheria toxin was reconstituted in vitro from fragments of cloned inactive diphtheria toxin mutants with defects in different parts of the gene. The reconstituted DNA template was amplified using the Taq DNA polymerase chain reaction, providing a virtually unlimited supply. The toxin was expressed in vitro by transcription from a T3 RNA polymerase promoter, followed by translation of the mRNA in a rabbit reticulocyte lysate system. Diphtheria toxin synthesised in this manner was shown to be as toxic as natural toxin and behaved like natural toxin in every way tested. This can serve as a general approach for study of toxic proteins, opening up the possibility of in vitro gene manipulation. Reconstitution of the wild type gene from fragments followed by polymerase chain reaction amplification bypasses the hazards of cloning protein toxins.

This work describes a dynamic model of the low back that incorporates extensive anatomical detail of a three-dimensional musculo-ligamentous-skeletal system. The reactive moment about L4-L5, determined from sagittal plane lifts, was partitioned into restorative components provided by the disc in bending, ligament strain, and active muscle contraction. Skeletal kinematics were obtained from cine analysis of markers on the rib cage and pelvis. The musculature was driven from surface EMG collected from six sites. When compared with past models, features of this model included improved anatomical modeling, improved monitoring of vertebral motion unit kinematics, improved estimation of neural activation of the musculature, and consideration of the effects of muscle length, velocity, cross-sectional area and passive elasticity in force estimation. Estimations of L4-L5 disc compression and shear were, on average, 16.2% and 42.5% lower, respectively, than those calculated from a simple 5 cm erector tissue moment arm length. There was no need to invoke intra-abdominal pressure or other contentious compression-reducing mechanisms. Muscle activity, particularly that of the sacrospinalis, dominated the generation of the restorative moment. Ligaments played a very minor role in the lifts studied. High muscle loads are consistent with the common clinical observation of muscle strain often produced by load handling.

Four two-dimensional polyacrylamide gel electrophoresis systems were used to identify 78 Chinese hamster cell ribosomal proteins by the uniform nomenclature based on rat liver ribosomal proteins. The 40S ribosomal subunit protein affected by Chinese hamster ovary (CHO) cell one-step emetine resistance mutations is designated S14 in the standard nomenclature. To seek unambiguous genetic evidence for a cause and effect relationship between CHO cell emetine resistance and mutations in the S14 gene, we mutagenized a one-step CHO cell mutant and isolated second-step mutant clones resistant to 10-fold-higher concentrations of emetine. All of the highly resistant, two-step CHO cell mutants obtained displayed additional alterations in ribosomal protein S14. Hybridization complementation tests revealed that the two-step CHO cell emetine resistance mutants were members of the same complementation group defined by one-step CHO cell mutants, EmtB. Two-step mutants obtained from a Chinese hamster lung cell emetine-resistant clone belong to the EmtA complementation group. The two-step and EmtB mutants elaborated 40S ribosomal subunits, which dissociated to 32S and 40S core particles in buffers containing 0.5 M KCl at 4 degrees C. In contrast, 40S ribosomal subunits purified from all EmtA, one-step EmtB EmtC mutants, and wild-type CHO and lung cells were stable at this temperature in buffers containing substantially higher concentrations of salt. Thus, two-step emtB mutations affect the structure of S14 protein directly and the stability of the 40S ribosomal subunit indirectly.

The lumbodorsal fascia (LDF) has been implicated in numerous biomechanical interpretations of low back mechanics as a tissue that provides support to the lumbar spine during demanding load bearing. One hypothesis is that oblique abdominal muscle forces contribute to trunk extensor moment by transforming lateral abdominal tension into longitudinal tension via the LDF. However, a review of the anatomical literature supports the hypothesis that extensor forces in the LDF result from tension within the latissimus dorsi muscle. The purpose of our work was to evaluate the potential of the LDF to generate trunk extensor moment using two mathematical models: one that activated the LDF with the abdominals and another that activated the LDF with the latissimus dorsi. Efforts were made to represent the anatomy as accurately as possible. The results from three subjects performing six squat lifts each, suggested that the potential of the LDF to contribute significant extensor moment has been overestimated. In fact, the issue of whether the LDF is activated by the abdominals or the latissimus dorsi is irrelevant because neither strategy appeared able to generate sizable extensor moments in the type of lift studied.

Most biomechanical models of the trunk and limb system represent the segments as rigid links joined with pins. The implication of this simplifying assumption is that dynamic loads applied to the body are instantaneously transmitted through the linkage with no distortion of the applied force-time waveform. The purpose of this study was to determine whether this assumption was justifiable for loads applied to the hands or shoulders and transmitted through the trunk to the bottom of the pelvis. If not, the intent was to find a transfer function relating load inputs applied to the top of the trunk and outputs measured at the bottom of the trunk. Loads were manually applied to a force transducer attached to a shoulder yoke or to a hand-held loading pan mounted on three subjects. The subjects sat both erect and slouched and also varied the trunk stiffness by voluntarily changing trunk muscle activation. Subjects sat on a rigid steel stool mounted on a force plate from which force outputs were recorded. In addition, a few case studies were performed; some trials utilized light impacts by a hammer to the transducer mounted on the crown of the bare head and in other trials the body was in a standing (lifting) posture. The results indicated that the mechanical response is indeed time dependent. For applied forces with a rise time less than 20 ms (hammer impact) the trunk system reduced the magnitude of the force peaks by up to 40%. However, for applied loads with rise times from about 30 to 300 ms the peak output force was larger than the applied force peak. This was due to inertial effects of the upper body mass as it 'rebounded' from the applied load. During these conditions of biologically generated applied forces, the output could be reasonably reconstructed by processing the input signal through a Butterworth second order low pass filter with a cutoff frequency of 7·5 Hz, a gain and in some cases, a shift in time up to 20 ms. The assumption of rigid body segments in these experiments appeared reasonably justified when the rise time of the applied force was greater than approximately 300 ms. However, for input signals that had a shorter rise time the trunk did not behave rigidly., (Copyright © 1989. Published by Elsevier Ltd.)

The purpose of this study was to add to the growing database of cross-sectional areas and moment arm lengths of trunk musculature using the methods of computerized tomographic scanning. An attempt was also made to estimate muscle force and moment generating capacity under various reported values of muscle force per unit cross-sectional area. The data were obtained on 13 active men 40.5 +/- 11.9 years of age, 173.8 +/- 5.9 cm tall and 89.1 +/- 11.7 kg body mass. Transverse CT scans were taken at the level of the L4/L5 disc with the subjects supine. Muscle cross-sectional areas were measured from 35 mm slides of the scans using a planimeter and moment arm length in the transverse plane were taken from the centroid of the L4/L5 disc to the centroid of the muscle section. Prior to estimating force and moment generating capacity, areas were corrected, where necessary, for fibre pennation angle to produce a physiological cross-sectional area. The physiological cross-sectional areas (cm2) for one side of the body were (mean +/- S.D.): sacrospinalis (SS) 15.9 +/- 2.5; multifidus (Mu) 4.2 +/- 0.7; psoas (Ps) 17.6 +/- 4.0; rectus abdominis (RA) 7.9 +/- 2.5; external oblique (EO) 9.4 +/- 2.7; internal oblique (IO) 8.1 +/- 2.3; transverse abdominus (TA) 2.9 +/- 1.3. The anterior posterior moment arm lengths were: erector mass (SS and Mu combined) 5.90 +/- 0.52; Ps 0.58 +/- 0.40; R.A. 10.28 +/- 2.07; E.O. (anterior portion) 5.94 +/- 1.39; E.O. (posterior portion) 2.08 +/- 1.39; I.O. (anterior portion) 6.92 +/- 1.63; I.O. (posterior portion) 3.85 +/- 1.54. The corresponding lateral moment arm lengths were: 3.26 +/- 0.36; 4.88 +/- 0.36; 4.35 +/- 1.31; 12.86 +/- 1.93; 13.95 +/- 1.16; 10.77 +/- 2.02; 12.52 +/- 1.26. The maximum force per unit cross-section that human muscles are capable of generating is not well defined. However, assuming an intermediate value of 50 N cm-2 of physiological cross-section, the erector musculature observed at the L4/L5 level should be capable of generating an extensor moment of about 118 N.m. At a muscle stress of 30 or 90 N cm-2, values also reported on human muscle, the moment would be 71 and 213 Nm, respectively. It must be remembered, however, that muscles not observable at the L4/L5 level can create moments around that center of rotation.(ABSTRACT TRUNCATED AT 400 WORDS)