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T Mayer

Publications and source records attributed to T Mayer.

At least 73 records · Page 4Linked to original sources
PubMed1995

Nucleotide induced conformation determines posttranslational isoprenylation of the ras related rab6 protein in insect cells.

Small GTP binding proteins of the rab/YPT family are essential regulators of vectorial transport in the eukaryotic cell. Members of the rab/YPT1 family are found on the cytoplasmic surface of distinct intracellular membrane compartments. Membrane attachment is facilitated by a C-terminal geranylgeranyl moiety. In this report we investigated posttranslational modification and membrane binding of the rab6 protein, a member of the rab/YPT family located on the Golgi apparatus. A set of point mutations, which simulate the GDP or GTP bound conformation, was introduced into the rab6 cDNA. The mutated cDNAs were expressed in insect cells and the ability of the protein products to undergo geranylgeranyl modification and membrane association was assessed by Triton X-114 partition and cell fractionation. We report here that the modification of rab6 in insect cells depends on protein conformation. Only the GDP bound form, but not the GTP bound form is isoprenylated and subsequently membrane bound.

Amino Acid Sequence↗
PubMed1995

Isolation of a hyperthermophilic archaeum predicted by in situ RNA analysis.

A variety of hyperthermophilic bacteria and archaea have been isolated from high-temperature environments by plating and serial dilutions. However, these techniques allow only the small percentage of organisms able to form colonies, or those that are predominant within environmental samples, to be obtained in pure culture. Recently, in situ 16S ribosomal RNA analyses of samples from the Obsidian hot pool at Yellowstone National Park, Wyoming, revealed a variety of archaeal sequences, which were all different from those of previously isolated species. This suggests substantial diversity of archaea with so far unknown morphological, physiological and biochemical features, which may play an important part within high-temperature ecosystems. Here we describe a procedure to obtain pure cultures of unknown organisms harbouring specific 16S rRNA sequences identified previously within the environment. It combines visual recognition of single cells by phylogenetic staining and cloning by 'optical tweezers'. Our result validates polymerase chain reaction data on the existence of large archael communities.

Archaea↗
PubMed1995

Trunk muscle endurance measurement. Isometric contrasted to isokinetic testing in normal subjects.

STUDY DESIGN: This cohort study examined a sample (n = 152) of subjects tested for isokinetic lumbar strength and endurance, using novel endurance measures. OBJECTIVES: To validate a new lumbar sagittal isokinetic endurance testing protocol comparing reliability in a normal subject cohort with strength test reliability to include presentation of a gender-specific normative database, and then correlating the results to a Sorenson isometric endurance protocol. SUMMARY OF BACKGROUND DATA: The isometric Sorenson test has been virtually the only validated clinical tool for lumbar extensor trunk muscle endurance testing, using an exercise chair and permitting the subject to maintain the trunk horizontal against gravity for a single timed contraction. Alternative isokinetic sagittal lumbar performance measurement methodology has been developed recently to measure trunk muscle endurance by determining declining work performance on repeated, reciprocal dynamic contractions. METHOD: We compared protocols, performance measures, normative data, and reliability for the static isometric Sorenson test to three different isokinetic endurance measurements: the endurance ratio, final fatigue ratio, and recovery ratio. Subjects were tested on a sagittal Cybex TEF (Lumex, Inc., Ronkonkoma, NY) unit for a strength trial followed by an endurance trial. Subgroups also performed reliability and isometric endurance protocols. RESULTS: We found an extremely low test-retest correlation for the isometric Sorenson trunk extension test. All test-retest correlations for the corresponding isokinetic endurance measures were significant and markedly higher. Extensor muscle performance declined more substantially on all endurance measures than flexors and showed more variability. In contrast, trunk strength measures were more reliable and less variable than corresponding endurance measures. Moreover, correlations between the isometric Sorenson test and the isokinetic endurance measures were all negative; i.e., increases in Sorenson time are moderately correlated to greater decline in work performance. CONCLUSIONS: Reliability of the Sorenson isometric endurance test is unacceptably low, showing negative correlations to all isokinetic endurance tests for lumbar extensors. Isokinetic strength and endurance tests are far more reliable than isometric tests, with normative data showing more consistent results from men than women. Both genders display more substantial fatigue (and greater variability) in extensor endurance compared with flexor testing. Endurance measures are identified as human performance cognitive constructs, and reasons for greater variability than usually shown by trunk strength measurements are discussed.

Adult↗
PubMed1995

Case report RS: guided tissue regeneration precedes tooth movement and crossbite correction.

This patient presented with a Class III malocclusion and an anterior crossbite. Although spaces were present distal to the mandibular canines, the alveolar ridges were greatly atrophied. New bone was acquired through guided tissue regeneration. The alveolar ridges were augmented, followed by successful orthodontic tooth movement and correction of the Class III relationship and the anterior crossbite.

Alveolar Process↗
PubMed1995

[The microstructure and materials properties of provisional crown and bridge materials].

The fracture resistance, surface hardness and microstructure of different manually and automatically mixed temporary crown and bridge resins and two light cured materials were examined in this study. The materials on butylmethacrylate (BMA) based showed low transverse strength compared to the materials on urethanmethacrylate (UDMA) and Bis-GMA base. Their values corresponded to the transverse strength of a manually mixed, chemically cured resin on PMMA base. The automatically mixed material on Bis-GMA base had lower strength values and surface hardness but fewer macroporosities compared to the manually mixed resins. The light cured material on UDMA base showed a transverse strength and surface hardness, which were higher than the values of the materials on Bis-GMA base. The strength values of the light cured material on PMMA base decreased within 7 days and were already after 24 h in the range of the materials on BMA base.

Crowns↗
PubMed1994

A male incumbent worker industrial database. Part I: Lumbar spinal physical capacity.

STUDY DESIGN: A group of 160 incumbent male railroad workers volunteered for a study of lumbar spine physical capacity. METHODS: They were initially subjected to inclinometric measurements of sagittal and coronal regional mobility (T12-S1). They also were tested on isokinetic trunk strength measurement devices for sagittal (bending) and axial (twisting) trunk strength at multiple speeds. RESULTS: Results showed that they demonstrated mild deficits of lumbar sagittal extension mobility, trunk extensor strength, and sagittal/axial high speed (150-180 degrees/sec) trunk strength when compared with population averages from a previously derived normative database of a nonhomogeneous male population (matched for age and body weight). CONCLUSIONS: It was hypothesized that instructions about "correct lifting techniques," uniformly provided to these workers, may have resulted in an unintended decrement in trunk mobility and strength.

Adult↗
PubMed1994

A male incumbent worker industrial database. Part II: Cervical spinal physical capacity.

STUDY DESIGN: Quantified cervical physical examination data are provided for a group of 160 incumbent railroad workers from four laboring crafts. OBJECTIVES: The subjects were tested for cervical mobility and strength, according to standardized protocols as part of a comprehensive physical examination and functional testing procedure to establish normative data associated with the axial musculoskeletal system. RESULTS: Tri-planar cervical inclinometric mobility norms are provided, as are sagittal and coronal isometric cervical strength data.

Adult↗
PubMed1994

A male incumbent worker industrial database. Part III: Lumbar/cervical functional testing.

STUDY DESIGN: A group of 160 incumbent male railroad workers was administered a battery of isokinetic and isoinertial lumbar/cervical lifting tests that served as a paradigm for whole-person functional testing of manual handling tasks. RESULTS: Results demonstrated that the workers' performance was near normal or somewhat above population averages according to previously derived heterogeneous normative samples. However, there were some differences among the four laboring crafts that made up the present incumbent worker sample. CONCLUSIONS: The implications of these differences are discussed.

Activities of Daily Living↗
PubMed1994

Physical progress and residual impairment quantification after functional restoration. Part I: Lumbar mobility.

Quantification of human performance in chronic low back pain (CLBP) patients is essential to initiate effective treatment and guide progress in a disability-oriented functional restoration program, as well as to objectively evaluate impairment and functional limitations at the time of maximum medical improvement. One such important measure of physical ability is range of motion. Patients who suffer from CLBP almost invariably have some disturbance of mobility. The major goals of the present study were to: 1) develop a database of anticipated range of motion levels at different points in time in a representative sample of CLBP patients; 2) within the sample, determine any gender or spinal surgery-induced differences; 3) evaluate change in range of motion produced by participation in a comprehensive functional restoration treatment program; and 4) identify residual impairment of regional range of motion. Four separate groups of CLBP patients were evaluated: Group 1 (n = 92), unoperated men; Group 2 (n = 26), postdiscectomy men; Group 3 (n = 59), unoperated women; and Group 4 (n = 17) postdiscectomy women. Patients in each group were assessed for spinal range of motion measures at three points in time, for sagittal/coronal motion and validity (employing the relationship between pelvic motion and supine leg raising). Results demonstrated dramatic patient improvements in range of motion from initial referral to program completion. The most significant gains were made in pelvic motion, which returned to near normal levels, indicating that the vast majority overcame low effort or movement inhibition produced by pain or fear of injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Physical progress and residual impairment quantification after functional restoration. Part II: Isokinetic trunk strength.

The current study evaluated human skeletal muscle performance through isokinetic trunk strength testing before and after a comprehensive functional restoration program for a group of 191 chronic low back pain (CLBP) patients. Four groups of patients were identified: 1) postdiscectomy men (n = 26); 2) unoperated men (n = 90); 3) postdiscectomy women (n = 17); and 4) unoperated women (n = 58). Patient test scores were expressed as work normalized to body weight at 60 and 150 degrees/second. The absolute scores were also expressed as "percent normal" relative to a population average normative database (specific to age and gender). An "effort factor" based on the average points variance (APV) of computer-generated curves was also calculated. Results demonstrated improvements in trunk strength measures at all speeds in flexion and extension for all groups. All groups also demonstrated a decrease in APV mean scores after functional restoration, with only 1 of 191 patients remaining in the POOR effort (strength inhibited) group after treatment. The postoperative men showed the greatest effort improvement, with APV scores in the "good" range increasing from 57% to 91% of the group over the course of treatment. There was virtually no difference in gender-specific trunk strength scores between postdiscectomy and unoperated patients, either at program entry or program discharge. However, compared with the normative database of program completion, even in the presence of good effort, persistent residual (and, possibly, permanent) strength impairment was identified.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Removal of Rab GTP-binding proteins from Golgi membranes by GDP dissociation inhibitor inhibits inter-cisternal transport in the Golgi stacks.

Rab proteins are a family of Ras-like GTPases involved in intracellular membrane traffic. Rab GDI, a cytosolic protein which inhibits the dissociation of GDP from various Rab proteins, is required to maintain a pool of Rab proteins in the cytosol. We describe the purification of a cytosolic factor from bovine liver that inhibits intra-cisternal transport between the Golgi stacks. We identify this factor as a Rab GDI. Half-maximal inhibition of transport was observed in the presence of the same concentration of GDI that is required for removal of Rab proteins from the Golgi.

Amino Acid Sequence↗
PubMed1994

History of anthropogenic activities in Hamilton Harbour as determined from the sedimentary record.

Bottom sediment cores collected from two closely spaced locations in the depositional basin of Hamilton Harbour (Lake Ontario, Canada) were analyzed for organic matter, bulk density, heavy metals and phosphorus concentrations. Combined data on dredging and steel production records in relation to core composition, together with (210)Pb dating were used to develop core chronology. Identification and enumeration of chironomid taxa and molluscs in both cores were carried out to interpret the paleoenvironmental conditions in the harbour. Chemical, geochronological and paleolimnological profiles of investigated cores indicate perturbation of the natural sedimentation processes by dredging and spoil disposal, with definite evidence of an infill of extrinsic littoral sediments. Decreasing metal concentrations in sediments reflect a positive response of sediments to decreased metal loadings to the harbour. The recent sediment accumulation rates, estimated from the (210)Pb profiles of the two cores, are 38 and 97 mg cm(-2) year(-1). Mass sedimentation rates of the pre-dredging era were higher (189 and 142 mg cm(-2) year(-1)) due to intensive harbour activities, municipal development and intensive crop production in the late 1800s.

Journal Article↗
PubMed1994

Localized alveolar ridge augmentation before orthodontic treatment. A case report.

Extraction spaces are usually characterized by narrow, atrophic alveolar ridges, which make it difficult to move teeth orthodontically within these areas. Guided tissue regeneration is often used for alveolar ridge augmentation in implantology. In the case presented, localized alveolar ridge augmentation was performed as a preliminary procedure before orthodontic closure of an edentulous space. Guided tissue regeneration enhances the possibilities of orthodontic treatment in adult patients.

Adult↗
PubMed1994

Identifying members of the domain Archaea with rRNA-targeted oligonucleotide probes.

Two 16S rRNA-targeted oligonucleotide probes were designed for the archaeal kingdoms Euryachaeota and Crenarchaeota. Probe specificities were evaluated by nonradioactive dot blot hybridization against selected reference organisms. The successful application of fluorescent-probe derivatives for whole-cell hybridization required organism-specific optimizations of fixation and hybridization conditions to assure probe penetration and morphological integrity of the cells. The probes allowed preliminary grouping of three new hyperthermophilic isolates. Together with other group-specific rRNA-targeted oligonucleotide probes, these probes will facilitate rapid in situ monitoring of the populations present in hydrothermal systems and support cultivation attempts.

Archaea↗
PubMed1993

SNAP family of NSF attachment proteins includes a brain-specific isoform.

The soluble NSF attachment proteins (SNAPs) enable N-ethyl-maleimide-sensitive fusion protein (NSF) to bind to target membranes. Here we report the cloning and sequencing of complementary DNAs encoding alpha-, beta- and gamma-SNAPs. Two of these proteins, alpha and gamma, are found in a wide range of tissues, and act synergistically in intra-Golgi transport. The third, beta, is a brain-specific isoform of alpha-SNAP. Thus, NSF and SNAPs appear to be general components of the intracellular membrane fusion apparatus, and their action at specific sites of fusion must be controlled by SNAP receptors particular to the membranes being fused, as described in the accompanying article.

Amino Acid Sequence↗
PubMed1993

Lumbar muscle usage in chronic low back pain. Magnetic resonance image evaluation.

Methods for detecting recruitment patterns of the lumbar muscles during exercise in patients with chronic low back pain are limited. This article discusses the use of magnetic resonance imaging with Roman chair extension exercise to examine lumbar muscle usage in five normal volunteers, five chronic low back pain patients without surgery, and five chronic low back pain patients with surgery. Changes in signal intensities of psoas, multifidus, and longissimus/iliocostalis with graded exercise were measured at three lumbar disc levels. At rest, there was a difference between multifidus and longissimus/iliocostalis signal intensity in chronic low back pain subjects without surgery (P = 0.0162) and in chronic low back pain subjects with surgery (P = 0.0036), but not in normal subjects. At peak exercise, there was a difference in signal intensities between multifidus and longissimus/iliocostalis in all groups (normal volunteers, P = 0.0069; chronic low back pain patients without surgery, P = 0.0125; chronic low back pain patients with surgery, P = 0.0060). The exercise response was attenuated in chronic low back pain patients with surgery. Thus, MRI demonstrates static and dynamic differences in lumbar paraspinal musculature in chronic low back pain subjects compared to normal subjects.

Exercise↗
PubMed1993

Noninvasive measurement of cervical tri-planar motion in normal subjects.

An electronic digital inclinometer was used to obtain normative data on cervical mobility from 58 normal subjects. They consisted of 28 males (age range, 17-61) and 30 females (age range, 19-62). The measurements were taken from occiput to T1 in flexion-extension, lateral bend, and axial rotation, isolating the regional motion by measuring simultaneously the upper and lower margins of the eight mobile segments. A comparison of radiographs and inclinometer measures showed excellent correlations (r < 0.9997, P < 0.05). Normative data are presented. Gender-specific regional mobility differences occurred only in cervical extension, whereas no consistent age-related differences were found. Stiffer individuals could be found in either gender or any age group, but rigidity in one plane did not necessarily predict rigidity in another.

Adult↗