A standardized method for measuring the force required to join wire harnesses and sparkplugs.

Understanding the forces required to insert a sparkplug wire (wire) onto a sparkplug (plug), independent of worker variation, is important for ergonomists, engineers, and designers. This paper describes a methodology for measuring the forces required to seat a wire onto a plug. A three-axis programmable mill was used to insert wires onto plugs mounted on a force transducer. Inflection points and slopes of the force-displacement curves were found to correspond to mechanical events as the plug and wire were joined. These events were further isolated by dissecting the wires to better understand the force contribution of each wire component. Liner superposition was then used to show that each of these force elements may be added to estimate the total force required to seat a wire onto a plug. This methodology may be used to quantify the effects of design choices, lubricants (wet and dry), and pre-working on axial insertion forces associated with sparkplugs and other insertions. This paper does not address worker abilities or variation, however, the methodology and equipment described may provide a foundation for the exploration of worker ability, variation and work techniques.

Investigation of flexible hose insertion forces and selected factors.

Flexible hoses are widely used in automobiles. Understanding the force required to insert a hose, independent of worker variation, is important for engineers, designers and health professionals. Various parameters affect the insertion forces including the interference between the hose and flange. Also, it has been observed that workers often add motions during the insertion process, including rotation and oscillation. This paper describes the effects of these parameters on axial insertion forces. A programmable mill was used to isolate the effects of four variables on hose insertion force: fit, insertion speed, rotational velocity and oscillation magnitude. The results show that the magnitude of the interference of the 19 mm inside diameters (ID) heater hose and the flange, and the insertion technique affect the insertion forces; resulting in a range of insertion forces from 11.1+/-0.2 to 128.4+/-11.3N.

An alteration of human immunodeficiency virus gp41 leads to reduced CCR5 dependence and CD4 independence.

Human immunodeficiency virus (HIV) type 1 infection requires functional interactions of the viral surface (gp120) glycoprotein with cell surface CD4 and a chemokine coreceptor (usually CCR5 or CXCR4) and of the viral transmembrane (gp41) glycoprotein with the target cell membrane. Extensive genetic variability, generally in gp120 and the gp41 ectodomain, can result in altered coreceptor use, fusion kinetics, and neutralization sensitivity. Here we describe an R5 HIV variant that, in contrast to its parental virus, infects T-cell lines expressing low levels of cell surface CCR5. This correlated with an ability to infect cells in the absence of CD4, increased sensitivity to a neutralizing antibody recognizing the coreceptor binding site of gp120, and increased resistance to the fusion inhibitor T-20. Surprisingly, these properties were determined by alterations in gp41, including the cytoplasmic tail, a region not previously shown to influence coreceptor use. These data indicate that HIV infection of cells with limiting levels of cell surface CCR5 can be facilitated by gp41 sequences that are not exposed on the envelope ectodomain yet induce allosteric changes in gp120 that facilitate exposure of the CCR5 binding site.

Characterization of a simian human immunodeficiency virus encoding the envelope gene from the CCR5-tropic HIV-1 Ba-L.

The tat, rev, vpu, and env genes from the monocytotropic CCR5-dependent HIV-1 Ba-L isolate were substituted for homologous simian immunodeficiency virus (SIV) sequences in the SIV genome. The resultant SHIV (SHIV Ba-L) replicated in CCR5-positive PM-1 cells but not in CCR5-negative CEMX174 cells. Infection of HOS cells expressing different co-receptors showed SHIV Ba-L to be strictly CCR5-dependent. Infection of PM-1 cells and rhesus peripheral blood mononuclear cells (PBMCs) was highly sensitive to RANTES but not to SDF-1. Although SHIV Ba-L infected rhesus and pigtail macaques intravenously or rectally, plasma viremia was controlled after 3 weeks. After serial passage through 4 pigtails by blood and bone marrow transfer, virus from pigtail PBMCs had higher in vitro infectious titers on rhesus PBMCs and was efficiently transmitted vaginally in rhesus and cynomolgus macaques. Plasma viremia generally persisted longer than after infection with unpassaged virus but was eventually controlled with no significant decrease in CD4+ T-cell counts in peripheral blood. The envelope gene of SHIV Ba-L revealed a very little genetic drift during in vivo passage. SHIV Ba-L provides a potentially useful model for R5 HIV-1 infection of humans.

Activation of NF-kappaB by the human herpesvirus 8 chemokine receptor ORF74: evidence for a paracrine model of Kaposi's sarcoma pathogenesis.

Infection with human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma (KS)-associated herpesvirus, is necessary for the development of KS. The HHV-8 lytic-phase gene ORF74 is related to G protein-coupled receptors, particularly interleukin-8 (IL-8) receptors. ORF74 activates the inositol phosphate/phospholipase C pathway and the downstream mitogen-activated protein kinases, JNK/SAPK and p38. We show here that ORF74 also activates NF-kappaB independent of ligand when expressed in KS-derived HHV-8-negative endothelial cells or primary vascular endothelial cells. NF-kappaB activation was enhanced by the chemokine GROalpha, but not by IL-8. Mutation of Val to Asp in the ORF74 second cytoplasmic loop did not affect ligand-independent signaling activity, but it greatly increased the response to GROalpha. ORF74 upregulated the expression of NF-kappaB-dependent inflammatory cytokines (RANTES, IL-6, IL-8, and granulocyte-macrophage colony-stimulating factor) and adhesion molecules (VCAM-1, ICAM-1, and E-selectin). Supernatants from transfected KS cells activated NF-kappaB signaling in untransfected cells and elicited the chemotaxis of monocytoid and T-lymphoid cells. Expression of ORF74 conferred on primary endothelial cells a morphology that was strikingly similar to that of spindle cells present in KS lesions. Taken together, these data, demonstrating that ORF74 activates NF-kappaB and induces the expression of proangiogenic and proinflammatory factors, suggest that expression of ORF74 in a minority of cells in KS lesions could influence uninfected cells or latently infected cells via autocrine and paracrine mechanisms, thereby contributing to KS pathogenesis.

An HIV-1 transgenic rat that develops HIV-related pathology and immunologic dysfunction.

We report, to our knowledge, the first HIV type 1 (HIV-1) transgenic (Tg) rat. Expression of the transgene, consisting of an HIV-1 provirus with a functional deletion of gag and pol, is regulated by the viral long terminal repeat. Spliced and unspliced viral transcripts were expressed in lymph nodes, thymus, liver, kidney, and spleen, suggesting that Tat and Rev are functional. Viral proteins were identified in spleen tissue sections by immunohistochemistry and gp120 was present in splenic macrophages, T and B cells, and in serum. Clinical signs included wasting, mild to severe skin lesions, opaque cataracts, neurological signs, and respiratory difficulty. Histopathology included a selective loss of splenocytes within the periarterial lymphoid sheath, increased apoptosis of endothelial cells and splenocytes, follicular hyperplasia of the spleen, lymphocyte depletion of mesenteric lymph nodes, interstitial pneumonia, psoriatic skin lesions, and neurological, cardiac, and renal pathologies. Immunologically, delayed-type hypersensitivity response to keyhole limpet hemocyanin was diminished. By contrast, Ab titers and proliferative response to recall antigen (keyhole limpet hemocyanin) were normal. The HIV-1 Tg rat thus has many similarities to humans infected with HIV-1 in expression of viral genes, immune-response alterations, and pathologies resulting from infection. The HIV-1 Tg rat may provide a valuable model for some of the pathogenic manifestations of chronic HIV-1 diseases and could be useful in testing therapeutic regimens targeted to stages of viral replication subsequent to proviral integration.

Motion times, hand forces, and trunk kinematics when using material handling manipulators in short-distance transfers of moderate mass objects.

The risk of musculoskeletal injury associated with manual materials handling tasks has led in part to the use of material handling manipulators, yet there is limited empirical data to facilitate selection, design, and evaluation of these devices. A laboratory study of two types of mechanical manipulators (articulated arm and overhead hoist) was conducted of short-distance transfers of moderate loads, and the influence of various task parameters and transfer method on motion times, peak hand forces, and torso kinematics was obtained. Use of manipulators increased elemental motion times for symmetric sagittal plane transfers by 36-63%, and asymmetric transfers (in the frontal plane) by 62-115%, compared to similar transfers performed manually. Peak hand forces were significantly lower with both manipulators (40-50%), and approximately 10% higher for asymmetric versus symmetric transfers. Overall torso kinematics were grossly similar with and without a manipulator. These results suggest that for self-paced job tasks, moderate mass objects will be transferred slower over short distances and with lower levels of external (hand) forces when using mechanical aids. These simple effects, however, were influenced by object mass and transfer height.

Muscle responses to simulated torque reactions of hand-held power tools.

The aim of this work was to investigate physiological responses to torque reaction forces produced by hand-held power tools used to tighten threaded fasteners. Such tools are used repetitively by workers in many industries and are often associated with upper limb musculoskeletal complaints. The tools considered for stimulation in this study had straight handles and required from 100 to 400 ms to tighten fasteners to a peak torque of 1.0 to 2.5 Nm and from 50 to 150 ms for the torque to decay to zero. A tool stimulator was constructed to apply a programmed torque profile to a handle similar to that of a straight in-line power screwdriver. Wrist flexor and extensor surface EMGs and handle position were recorded as subjects held handles subjected to controlled torque loads that tended to flex the wrist. It was found that: (1) very high EMG values occurred even though torques were of short duration (50 to 600 ms) and the peak torques were low (7-28% of maximum strength); (2) high EMGs in anticipation of torque are directly related to torque build-up rate and peak torque; (3) high peak flexor and extensor EMGs during and following torque onset are related to torque build-up rate and peak torque; (4) minimum time of peak EMGs of 72-87 ms following the onset of torques with 50 ms build-up suggests the contribution of an extensor muscle stretch reflex component; delayed peak for longer build-ups suggests a central control of muscle force in response to torque; (5) angular excursions of handles increase with decreasing torque build-up time and increasing torque magnitude causes increasing eccentric work; (6) the results show that the slow torque build-up times (450 ms) correspond to minimum peak EMGs; and (7) accumulated EMGs increase with increasing torque and torque build-up times. Further studies are needed to evaluate fatigue and musculoskeletal injuries associated with prolonged periods of tool use.

The effect of keyboard keyswitch make force on applied force and finger flexor muscle activity.

The design of the force-displacement characteristics or 'feel' of keyboard keyswitches has been guided by preference and performance data; there has been very little information on how switch 'feel' alters muscle activity or applied force. This is a laboratory-based repeated measures design experiment to evaluate the effect of computer keyboard keyswitch design on applied finger force and muscle activity during a typing task. Ten experienced typists typed on three keyboards which differed in keyswitch make force (0.34, 0.47 and 1.02 N) while applied fingertip force and finger flexor electromyograms were recorded. The keyboard testing order was randomized and subjects typed on each keyboard for three trials, while data was collected for a minimum of 80 keystrokes per trial. No differences in applied fingertip force or finger flexor EMG were observed during typing on keyboards with switch make force of 0.34 or 0.47 N. However, applied fingertip force increased by approximately 40% (p < 0.05) and EMG activity increased by approximately 20% (p < 0.05) when the keyswitch make force was increased from 0.47 to 1.02 N. These results suggest that, in order to minimize the biomechanical loads to forearm tendons and muscles of keyboard users, keyswitches with a make force of 0.47 N or less should be considered over switches with a make force of 1.02 N.

Development and evaluation of an observational method for assessing repetition in hand tasks.

Several physical stressors, including repetitive, sustained, and forceful exertions, awkward postures, localized mechanical stress, highly dynamic movements, exposures to low temperatures, and vibration have been linked to increased risk of work-related musculoskeletal disorders. Repetitive exertions have been among the most widely studied of these stressors, but there is no single metric for assessing exposure to repetitive work. A new methodology enables repetitive hand activity to be rated based on observable characteristics of manual work. This method uses a series of 10-cm visual-analog scales with verbal anchors and benchmark examples. Ratings for repetition reflect both the dynamic aspect of hand movements and the amount of recovery or idle hand time. Trained job analysis experts rate the jobs individually and then agree on ratings. For a group of 33 jobs, repetition ratings using this system were compared to measurements of recovery time within the cycle, exertion counts, and cycle time. Amount of recovery time within the job cycle was found to be significantly correlated with the analysis ratings (r2 = 0.58), as were the number of exertions per second (r2 = 0.53). Cycle time was not related to the analyst ratings. Repeated analyses using the new method were performed 1 1/2 to 2 years apart on the same jobs with the same group of raters. Ratings for repetition differed less than 1 point (on the 10-cm scale), on average, among the different sessions. These results indicate that the method is sensitive to exertion level and recovery time, and that the decision criteria and benchmark examples allow for a consistent application of these methods over a period of time. This method of rating repetition can be combined with similar scales for other physical stressors.

Keyboard reaction force and finger flexor electromyograms during computer keyboard work.

This study examines the relationship between forearm EMGs and keyboard reaction forces in 10 people during keyboard tasks performed at a comfortable speed. A linear fit of EMG force data for each person and finger was calculated during static fingertip loading. An average r2 of .71 was observed for forces below 50% of the maximal voluntary contraction (MVC). These regressions were used to characterize EMG data in force units during the typing task. Averaged peak reaction forces measured during typing ranged from 3.33 N (thumb) to 1.84 N (little finger), with an overall average of 2.54 N, which represents about 10% MVC and 5.4 times the key switch make force (0.47 N). Individual peak or mean finger forces obtained from EMG were greater (1.2 to 3.2 times) than force measurements; hence the range of r2 for EMG force was .10 to .46. A closer correspondence between EMG and peak force was obtained using EMG averaged across all fingers. For 5 of the participants the force computed from EMG was within +/-20% of the reaction force. For the other 5 participants forces were overestimated. For 9 participants the difference between EMG estimated force and the reaction force was less than 13% MVC. It is suggested that the difference between EMG and finger force partly results from the amount of muscle load not captured by the measured applied force.

Effects of key stiffness on force and the development of fatigue while typing.

An experiment was conducted to investigate the effect of key stiffness on the development of fatigue, keyboard reaction forces, and muscle electromyography (EMG) responses. Six subjects typed continuously for 2 hours on each of two keyboards (0.28 N or 0.83 N resistance keys, presented in random order). Keyboard reaction force and root mean square finger flexor and extensor EMG were recorded for 2 minutes at 250 Hz for every 10 minutes subjects typed. After typing for 2 hours subjects were given a 2-hour rest break and then typed on the remaining keyboard for an additional 2 hours Fifty-four percent more peak force, 34% more peak finger flexor EMG, and 2% more peak finger extensor EMG were exerted while using the 0.83 N keyboard. Peak and 90th percentile values showed similar trends and were well correlated for force and finger flexor and extensor EMG. Subjects typed much harder than necessary (4.1 to 7.0 times harder on the 0.28 N keyboard and 2.2 to 3.5 times harder on the 0.83 N keyboard) to activate the keys. Fatigue was observed on the 0.83 N keyboard during 2 hours of continuous typing, but the trends were mild. It appears that the ratio of typing force to flexor EMG may not be a sensitive enough indicator of fatigue for low-force high repetition work.

Integrative Cloning, Expression, and Stability of the cryIA(c) Gene from Bacillus thuringiensis subsp. kurstaki in a Recombinant Strain of Clavibacter xyli subsp. cynodontis.

A bacterial endophyte was engineered for insecticidal activity against the European corn borer. The cryIA(c) gene from Bacillus thuringiensis subsp. kurstaki was introduced into the chromosome of Clavibacter xyli subsp. cynodontis by using an integrative plasmid vector. The integration vectors pCG740 and pCG741 included the replicon pGEM5Zf(+), which is maintained in Escherichia coli but not in C. xyli subsp. cynodontis; tetM as a marker for selection in C. xyli subsp. cynodontis; and a chromosomal fragment of C. xyli subsp. cynodontis to allow for homologous recombination between the vector and the bacterial chromosome. Insertion of vector DNA into the chromosome was demonstrated by DNA hybridization. Recombinant strains MDR1.583 and MDR1.586 containing the cryIA(c) gene were shown to produce the 133,000-kDa protoxin and several smaller immunoreactive proteins. Both strains were equally toxic to insect larvae in bioassays. Significant insecticidal activity was demonstrated in planta. The cryIA(c) gene and the tetM gene introduced into strain MDR1.586 were shown to be deleted from some cells, thereby giving rise to a noninsecticidal segregant population. In DNA hybridization experiments and insect bioassays, these segregants were indistinguishable from the wild-type strain. Overall, these results demonstrate the plausibility of genetically engineered bacterial endophytes for insect control.

Investigation of applied forces in alphanumeric keyboard work.

This paper considers one way that occupational health professionals can assess the force exerted by keyboard users and the possible relationship between that force and the key force-displacement relationship. First, three personal-computer keyboards with the standard QWERTY layouts were tested as described by the American National Standard for Human Factors Engineering of Visual Display workstations (ANSI/HFS 100-1988) to determine the peak forces, 0.47-0.89N; displacements prior to the "breakaway" force that acknowledges key registration, 2.0-2.5 mm; and total key travel, 3.3-4.3 mm. Second, keyboard reaction forces were recorded while 10 subjects typed 4 alphanumeric sentences on the keyboards. It was found that the peak forces corresponding to each keystroke were 2.5 to 3.9 times the required activation forces, indicating that the subjects consistently displaced the keys to their limits. The average of the peak forces for all keystrokes was lowest for the keyboard with the lowest required activation force. It was concluded that keyboard reaction forces can be used as an index of finger forces for keying tasks. Further studies are necessary to evaluate the relationship between keyboard reaction forces, fatigue, and chronic muscle, tendon, and nerve disorders.

Utilization of an Epstein-Barr virus replicon as a eukaryotic expression vector.

Epstein-Barr virus (EBV) replicons which include the genetic element oriP and a functional gene for Epstein-Barr nuclear antigen (EBNA-1) can be maintained episomally in a variety of mammalian cell lines [Yates et al., Nature 313 (1985) 812-815]. We have assessed the application of an EBV replicon for foreign gene expression. Two cDNAs, human interferon-gamma (IFN-gamma) and the extracellular domain of the human epidermal growth factor receptor (EGF-Rex), cloned in an EBV replicon, were efficiently expressed and the protein was secreted into the extracellular media. Expression in human embryonic 293 cells was approximately ten-fold higher than in CV-1 cells. The expression of the human protein is dependent upon the orientation of the IFN-gamma transcriptional cassette relative to the other genetic elements within the vector.

Computerized spirometry using a portable microcomputer.

The reliable conduct of pulmonary function studies, while in the field, is increasingly important as various standards mandate this activity. Versatile, portable and accurate equipment is required. A lightweight and computerized portable spirometer system is discussed, PSPIRO, which uses a standard volumetric spirometer and a briefcase-sized microcomputer. The system, compact enough to be easily moveable by one person, performs tests for FVC, FEV(1), FEV(3), the percentage of predicted pulmonary function for each, and the ratio of FEV(1)/FVC. Back extrapolation is used to establish the start of each forced expiratory maneuver, reproducibility checks are performed, and accuracy is within acceptable epidemiologic standards. A small, portable analog to digital interface (PLAD) was developed for performing A/D conversions through the RS-232C port of the portable microcomputer.

Investigation of cumulative trauma disorders in a poultry processing plant.

Cumulative trauma disorders such as carpal tunnel syndrome and tenosynovitis can be caused, precipitated, or aggravated by repeated exertions with the hand. This paper describes a study in a poultry processing factory that proceeds from an analysis of health records to an analysis of work methods, postures and forces. Alternative work procedures and knife designs are recommended to reduce stressful work postures and forces.