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L Sperling

Publications and source records attributed to L Sperling.

At least 37 records · Page 2Linked to original sources
PubMed1995

A large multigene family codes for the polypeptides of the crystalline trichocyst matrix in Paramecium.

The secretory granules (trichocysts) of Paramecium are characterized by a highly constrained shape that reflects the crystalline organization of their protein contents. Yet the crystalline trichocyst content is composed not of a single protein but of a family of related polypeptides that derive from a family of precursors by protein processing. In this paper we show that a multigene family, of unusually large size for a unicellular organism, codes for these proteins. The family is organized in subfamilies; each subfamily codes for proteins with different primary structures, but within the subfamilies several genes code for nearly identical proteins. For one subfamily, we have obtained direct evidence that the different members are coexpressed. The three subfamilies we have characterized are located on different macronuclear chromosomes. Typical 23-29 nucleotide Paramecium introns are found in one of the regions studied and the intron sequences are more variable than the surrounding coding sequences, providing gene-specific markers. We suggest that this multigene family may have evolved to assure a microheterogeneity of structural proteins necessary for morphogenesis of a complex secretory granule core with a constrained shape and dynamic properties: genetic analysis has shown that correct assembly of the crystalline core is necessary for trichocyst function.

Amino Acid Sequence↗
PubMed1994

Antibodies that can discriminate between dynein heavy chains and their HUV1 photoproducts.

Dyneins are multi-subunit enzymes that transduce chemical energy into the mechanical energy that makes cilia and flagella beat and moves organelles towards the minus end of microtubules. The ATPase activity is borne by heavy chains, and recent molecular analysis indicates that dynein heavy chain genes form an ancient multigene family: the similarity between the same isoform of two distantly related species is greater than that between different isoforms of the same species. We have exploited sequence identities between a Paramecium axonemal dynein heavy chain gene cloned in our laboratory and sequences of dynein heavy chains from other species to prepare antibodies against active-site peptides capable of recognizing dynein heavy chains regardless of species or isoform. One of the antibodies is perfectly specific for the larger product of V1 photolysis (HUV1) and thus incorporates a unique property of the hydrolytic ATP binding site of all known dynein heavy chains, the capacity for photocleavage in the presence of micromolar vanadate. Our characterization of these reagents suggests that they will be useful for biochemical and in situ studies of known dyneins as well as identification of potential new members of the family.

Amino Acid Sequence↗
PubMed1994

Protein processing and morphogenesis of secretory granules in Paramecium.

The ciliated protozoan Paramecium provides a model system for the study of regulated secretion, featuring architecturally complex secretory storage granules-trichocysts-docked at the plasma membrane, ready to respond to an exocytotic stimulus. The trichocysts are characterized by crystalline contents that confer upon the organelle a defined shape which can be altered by single gene mutation. The crystalline trichocyst contents are built up from a heterogeneous set of small acidic polypeptides generated by proteolytic maturation of a family of precursor molecules, suggesting an important role for protein processing in this system. We have recently shown that the primary defect in several secretory mutants lacking functional trichocysts is in intracellular trafficking rather than protein processing. However, analysis of how these defects lead to altered trichocyst shape supports the notion that the protein processing is essential for morphogenesis. Preliminary results of a cloning project reveal that an extensive multigene family (approximately 100 genes) codes for the trichocyst matrix proteins. Deduced amino acid sequences of putative processing sites indicate that (at least) two distinct processing reactions are probably involved in the maturation of these proteins, and allow us to speculate that each reaction may control a key event of trichocyst biogenesis.

Amino Acid Sequence↗
PubMed1994

Evidence for defects in membrane traffic in Paramecium secretory mutants unable to produce functional storage granules.

The ciliated protozoan Paramecium has a regulated secretory system amenable to genetic analysis. The secretory storage granules, known as trichocysts, enclose a crystalline matrix with a genetically determined shape whose biogenesis involves proteolytic maturation of a family of precursor molecules into a heterogeneous set of small acidic polypeptides that crystallize within the maturing vesicles. We have developed an original pulse-chase protocol for monoxenic Paramecium cultures using radiolabeled bacteria to study the processing of trichocyst matrix proteins in wild-type and mutant cells. In wild-type cells, proteolytic processing is blocked in the presence of monensin and otherwise rapidly completed after approximately 20 min of chase, suggesting that the conversion occurs in the trans-Golgi and/or in small vesicles soon after sorting to the regulated pathway, probably before crystallization begins. In trichless mutant cells, which contain no visible trichocysts, secretory proteins are synthesized but not processed and we report constitutive secretion of the uncleaved precursor molecules. The mutation thus appears to affect sorting to the regulated pathway and should prove useful for analysis of the sorting machinery and of the relationship between sorting and proteolytic processing of secretory proteins. In mutants bearing misshapen trichocysts with poorly crystallized contents (tam33, tam38, stubbyA), the proteolytic processing of the trichocyst matrix proteins appears to be normal, while both pulse-chase and morphological data indicate that intracellular transport is perturbed, probably between ER and Golgi. Precursor molecules are present in the mutant trichocysts but not in wild-type trichocysts and may account for the defective crystallization. Our analysis of these mutants suggests that the temporal coordination of intracellular traffic plays a regulatory role in granule maturation.

Animals↗
PubMed1994

Cesarean section in twin pregnancies in two Danish counties with different cesarean section rates.

OBJECTIVE: Based on a comparison of the clinical indications for cesarean section (CS) in two Danish counties and a review of the literature regarding this issue the aim of this study was to discuss possible explanations for variations in CS rates in twin pregnancies. The comparison of indications for CS in twin pregnancies was made between two Danish counties, one with a high and one with a low overall CS rate in twin deliveries, taking into account the distribution of parity, mother's age, gestational age at birth, and birth weight. DESIGN: A population based, historic follow-up study based on antecedent data. SETTING: Two Danish counties, with a CS rate in twin pregnancies of 57% and 28%, respectively. SUBJECTS: All women with twin pregnancies who delivered in 1989 in the two counties. MAIN OUTCOME MEASURES: Comparison of the CS rates in the two counties according to indications and fetal presentation. SECONDARY MEASURES: Perinatal and maternal outcome. RESULTS: The difference in CS rates between the two counties could not be explained by different distributions of background characteristics. Different attitudes were found towards CS in cases with previous CS, with twin A in breech presentation and in cases with vertex-breech deliveries. These differences could explain less than two thirds of the overall 29% (CI: 12-46%) difference in risk of CS between the two counties, indicating more subtle reasons for the discrepancy. No difference between the two counties in perinatal morbidity and mortality was seen. CONCLUSION: In order to understand and discuss regional variations in the use of CSs in twin deliveries the subjects must be addressed in different ways: the unequivocal indications related to fetal presentations and previous CS can be subjected to randomised controlled trials or large scaled follow-up studies regarding maternal and perinatal morbidity and mortality. Other more subtle determinants of the physicians' and the pregnant women's attitude towards CS, however, seem quantitatively important, and these can only be evaluated in observational studies and through discussions.

Adult↗
PubMed1993

An approach to ergonomics evaluation of hand tools.

Based on current knowledge of cumulative trauma disorders in the hand and forearm, related to the use of hand tools, an analysis was undertaken of variables to be considered in ergonomics evaluation of hand tools. Measurement methods were developed and an evaluation station was implemented. Measurement methods are physical, physiological or psychophysical. They focus on the tool, and on the effect of typical use of the tool on the operator. The evaluation station serves as a resource in the development, selection, and testing of tools for a given purpose.

Journal Article↗
PubMed1993

A cube model for the classification of work with hand tools and the formulation of functional requirements.

In an interdisciplinary research project, a model, visualized as a cube, was developed for the classification and analysis of work with hand tools and for communication of different ways of solving problems related to manual handling. The dimensions of the cube are demands of force, precision and time. Each dimension is divided into three levels of low, moderate and high demands respectively. Preliminary limits are proposed for acceptable and non-acceptable use situations and for situations that have to be investigated further. Using a case study of plate shears as a starting point, various measures of improving the position in the cube are discussed. The hand tool, the workplace, the work organization as well as the user of the hand tool are included in the analysis.

Journal Article↗
PubMed1993

Tool design, user characteristics and performance: a case study on plate-shears.

Performance, grip forces and fatigue were studied in six male and six female subjects while cutting with plate-shears. Three types of plate-shears were used, one standard and two modified, either with a spring grip, or with a spring grip in combination with a reduced grip span. In addition, three types of plate - easy, moderately difficult and difficult to cut - were used. Male subjects used around 40% of their maximal grip force and female subjects around 60% with the moderately difficult plate; the male subjects produced more than twice as long a cutting distance as the females. Neither EMG analysis (frequency shifts) nor subjective exertion or reduction of handgrip MVC indicated a more pronounced fatigue in women than in men, probably because the female subjects used about a 50% lower cutting rate than the men. Productivity (in cm cut per min) was strongly related to measures of hand size and to the relative grip force used. Thus in a multiple regression analysis using metacarpal hand circumference and relative grip force as independent variables, R2 was 0.77. The two types of modified plate-shears were preferred by all and gave a roughly 30% higher productivity in the male subjects but did not improve productivity in the females. However, with a spring grip and reduced grip span, the female subjects reduced the relative grip forced used from around 65 to 50%. The total work (force-time integral) per cm cut was not influenced by type of plate-shear.

Journal Article↗
PubMed1991

Cortical morphogenesis in Paramecium: a transcellular wave of protein phosphorylation involved in ciliary rootlet disassembly.

In Paramecium, the morphogenesis of the cortex at cell division, which assures reconstruction of shape and surface pattern, has been shown to involve transcellular signals which spread across the cortex like a wave, originating principally from the oral apparatus. One of the events these signals control is the reorganization of the ciliary rootlets through a cycle of regression and regrowth. The ciliary rootlets are nucleated on the ciliary basal bodies and form a scaffold extending over the entire cell surface that is important in aligning the basal bodies and the unit territories organized around them in longitudinal rows. We present evidence that the mechanism underlying their reorganization is cell-cycle-dependent phosphorylation of the structural proteins which compose the ciliary rootlets. We have isolated the rootlets and prepared a polyclonal antibody against them. In situ immunofluorescence of dividing cells with the anti rootlet antibody, and with the monoclonal antibody MPM-2 specific for phosphoproteins shows that a wave of phosphorylation of the ciliary rootlets spreads across the cell at division and just precedes their regression. Two-dimensional Western blot analysis of cytoskeleton and isolated rootlets along with alkaline phosphatase treatment demonstrates that the rootlets are composed of phosphoproteins, while experiments with interphase and dividing cells provide direct evidence that hyperphosphorylation of these proteins at division brings about disassembly of the structure.

Animals↗
PubMed1991

Salpingitis isthmica nodosa in female infertility and tubal diseases.

Salpingitis isthmica nodosa (SIN) is a condition of nodular thickening of the proximal Fallopian tube. The purpose of this study was to investigate the occurrence, distribution and frequency of SIN in Danish women salpingectomized because of tubal pregnancy or salpingitis and to correlate SIN with infertility, pregnancies, outcome of pregnancies, births, pelvic inflammatory disease and salpingitis. Sections from the isthmus were present in the specimens from 223 tubes from 193 patients and were analysed by the same pathologist. Originally, SIN was found in 12 patients but on re-examination, it was found in 24 patients. Ten women with SIN were bilaterally salpingectomized. Only one woman had SIN in both tubes. Women with SIN gave birth to as many children as women without SIN. After SIN had been diagnosed, no children were born, but this was not statistically different from the frequency of births in the non-SIN group after salpingectomy. Women with SIN had histological signs of salpingitis more often than women without SIN, but SIN complicated with salpingitis did not influence the number of children or tubal pregnancies. Women with SIN had a greater risk of two or more tubal pregnancies than women without SIN.

Adult↗
PubMed1989

Clothing fasteners for long-term-care patients: evaluation of standard closures and prototypes on test garments.

For the elderly long-term-care patient it is of great psychological and practical importance to be able to dress and undress without assistance. However, the design and position of clothing fasteners often lead to a restriction of the functional capacity of the patient. The aim of this study was to facilitate a more independent daily life for long-term care patients. New fasteners were developed in accordance with a user-oriented product development process where a detailed knowledge of the final users and their capacity and limitations, problems, needs and wishes form the basis for further development. In an initial experimental study (I) the practical use of different standard clothing fasteners (button, hook and eye, nylon pressure tape and zipper) was evaluated. Different fasteners and positions are favourable to different patient groups. Wrist angle in different hand positions is crucial for the function of fasteners for persons with reduced hand function. User demands on clothing fasteners were specified and prototypes developed. In a subsequent study (II) an adapted oval button and a 'finger strap' alternative to hook-and-eye were designed and evaluated, together with a standard button. The oval button in combination with a vertical buttonhole improved the function for most patients, and the front position for the fasteners was superior to a diagonal or lateral position on the chest. The finger strap was of advantage to patients with hemiplegia and joint complaints but was difficult for many of the subjects to understand, being a technical innovation.

Journal Article↗
PubMed1987

The crystal lattice of Paramecium trichocysts before and after exocytosis by X-ray diffraction and freeze-fracture electron microscopy.

Paramecium trichocysts are unusual secretory organelles in that: (a) their crystalline contents are built up from a family of low molecular mass acidic proteins; (b) they have a precise, genetically determined shape; and (c) the crystalline trichocyst contents expand rapidly upon exocytosis to give a second, extracellular form which is also an ordered array. We report here the first step of our study of trichocyst structure. We have used a combination of x-ray powder diffraction, freeze-etching, and freeze-fracture electron microscopy of isolated, untreated trichocysts, and density measurements to show that trichocyst contents are indeed protein crystals and to determine the elementary unit cell of both the compact intracellular and the extended extracellular form.

Animals↗
PubMed1984

Tissue-specific expression is conferred by a sequence from the 5' end of the rat albumin gene.

We have constructed a transient expression vector containing 400 bp of rat albumin gene immediate 5'-flanking sequences inserted 5' to the bacterial enzyme chloramphenicol acetyl transferase (CAT). We have transfected various clones of rat hepatoma cells representing different states of expression of the liver phenotype with this vector (pALB-cat) and also with two control vectors containing viral promoters (pSVE-cat and pRSV-cat), and measured activity of the bacterial enzyme CAT in cellular extracts 48 h later. The albumin flanking sequences are able to direct highly efficient CAT expression, compared with the control vectors, only in cells which express their own albumin gene: the albumin-negative hepatoma cells are at least 100 times less efficient in expressing CAT after transfection with the pALB-cat plasmid than are the albumin-positive ones. An unexpected result of our study is the total inability of the rat albumin flanking sequences to direct expression in albumin-producing mouse hepatoma cells.

Acetyltransferases↗
PubMed1984

Albumin extinction without methylation of its gene.

In earlier work we identified at the 5' end of the rat albumin gene an Msp I site whose undermethylation appears to be necessary but not sufficient for stable expression of the gene in rat hepatoma cells. Here, we ask whether the block to expression of albumin production, which occurs when rat hepatoma cells are hybridized with cells that do not produce the protein, could be the result of de novo methylation of this site. In two types of somatic hybrids, rat hepatoma-mouse L cell fibroblasts, and rat hepatoma-dedifferentiated variant rat hepatoma cells, extinction occurs and is maintained during the first 5-15 generations after fusion. During this time the Msp I site of the now inactive rat albumin gene remained unmethylated.

Albumins↗
PubMed1983

Muscle function in 75-year-old men and women. A longitudinal study.

Nine-teen men and twenty-one women, regarded as representative for the healthy seventy-five-year-old urban population were subjected to tests of lower and upper extremity function. The results were compared with those in the same probands at the age of 70. The investigation included tests of muscular isometric and isokinetic strength in knee-extension and flexion, isometric strength in key-grip, transversal volar grip, elbow-extension and flexion. Furthermore muscular coordination in hand and arm and submaximal endurance in hand-grip were measured. The subjects were classified with regard to physical activity. Between the age of 70 and 75 there was a significant decline in muscle strength in both sexes in the knee-extensors and a somewhat smaller in isometric than in isokinetic strength, and a decline also in the elbow-extensors and flexors. In a test of muscular coordination of the upper extremities and of maximal strength and submaximal endurance in hand-grip the results did not differ significantly between the age of 70 and 75. Isokinetic muscle strength in the knee-extensors and flexors was higher in men with a higher level of physical activity than in those with a lower activity. The results may indicate that the decrement of muscle strength in this age in part may be based on a changed activity pattern (note lack of change in hand-grip strength) with lack of fast and forceful movements in the daily living and speaks for the desirability that elderly people be physically active and that this may prevent disability.

Aged↗