Back injury in municipal workers: a case-control study.

OBJECTIVES: The purpose of this study was to identify factors associated with acute low back injury among municipal employees of a large city. METHODS: For each of 200 injured case patients, 2 coworker controls were randomly selected, the first matched on gender, job, and department and the second matched on gender and job classification. In-person interviews were conducted to collect data on demographics, work history, work characteristics, work injuries, back pain, psychosocial and work organization, health behaviors, and anthropometric and ergonomic factors related to the job. Psychosocial work organization variables were examined with factor analysis techniques; an aggregate value for job strain was entered into the final model. Risk factors were examined via multivariate logistic regression techniques. RESULTS: High job strain was the most important factor affecting back injury (odds ratio [OR] = 2.12, 95% confidence interval [CI] = 1.28, 3.52), and it showed a significant dose-response effect. Body mass index (OR = 1.54, 95% CI = 1.08, 2.18) and a work movement index (twisting, extended reaching, and stooping) (OR = 1.42, 95% CI = 0.97, 2.08) were also significant factors. CONCLUSIONS: Results suggest that increasing workers' control over their jobs reduces levels of job strain. Ergonomic strategies and worksite health promotion may help reduce other risk factors.

An ergonomic characterization of work in concrete form construction.

Concrete formwork construction was identified as the area of greatest ergonomic risk in unionized carpentry by both managers and unionized carpenters. Ergonomic risks were identified and characterized using (a) 1220 randomized work samples from videotape, (b) 82 worker discomfort surveys, (c) on-site observation, and (d) labor-management focus group discussions. Results showed that carpenters spent over 40% of the day in a forward torso flexion posture and over one-third of the day working at or below knee level. Hammering was the single most frequently performed activity at approximately 17% of the day. The body location with the highest reported prevalence of symptomatic disorders was the lower back at 48% followed by the forearms/wrist at 37%. It was concluded that carpenters are exposed to significant hazards in formwork construction, and that opportunities exist for the implementation of ergonomic interventions.

Assisted hatching with or without bovine oviductal epithelial cell co-culture for poor prognosis in-vitro fertilization patients.

Older patients and those who consistently return for embryo transfer but without implantation were studied to see if a combination of day 3 assisted hatching and co-culture (AH+CC) might be beneficial compared to assisted hatching alone (AH-alone). Female patients of > or = 38 years and couples who had previously failed to implant embryos three times or more were prospectively and randomly assigned to either an experimental or a control group. In the experimental group all embryos were co-cultured on partial monolayers of bovine oviductal epithelial cells for 2 days followed by assisted hatching by zona drilling (AH+CC). All control embryos were cultured by standard procedures until day 3 when they also underwent zona drilling prior to uterine transfer (AH-alone). With 50 cycles in each group there was unfortunately a marginal bias against the AH+CC group in that these patients had undergone a higher number of previous transfer cycles. There was a marginally lower percentage of fragmentation and a significantly higher degree of zona thickness variability in the AH+CC embryo group. Embryonic implantation was significantly increased (P < 0.05) in the AH+CC group (18%) when compared to the AH-alone group (10%). This difference was reflected in a significantly higher (P < 0.05) initial pregnancy rate (52 versus 32%) in the AH+CC group, and a higher (not significant) viable pregnancy rate (38 versus 22%).

The human/robot interface.

NASA: The use of telerobotic technology in space exploration is examined. Early aspirations for anthropomorphic designs and advances in the field are reviewed. The application of human factors engineering to robotics design and the human-machine interface are examined. New strategies in design and automation are presented.^ieng

Treatment of male infertility and idiopathic failure to fertilize in vitro with under zona insemination and direct egg injection.

OBJECTIVE: Failure to fertilize eggs in vitro may be countered by micromanipulation of gametes to place selected spermatozoa underneath the zona pellucida of the egg or directly into the egg, thereby improving chances of fertilization and production of viable embryos. Analysis of our clinical data for assisted fertilization was undertaken to assess those factors of relevance in this therapy, and a description of our procedures are given. STUDY DESIGN: Retrospective analysis of 85 cycles (73 couples) of in vitro fertilization and embryo transfer performed at a private infertility clinic, in which micromanipulation for assisted fertilization was used to overcome either severe male factor infertility or idiopathic failure to fertilize, was performed. RESULTS: In 60 cycles where only embryos from under zona insemination were available for uterine transfer, 15 singleton and two twin pregnancies occurred (28.3% viable pregnancy rate per transfer, 14.1% embryonic implantation). In 14 of these cycles embryos arose only after repeated under zona insemination adding more spermatozoa; this accounted for four of the singleton and one of the twin pregnancies (38.5% pregnancy rate, 22.2% embryonic implantation). No embryos arose from partial zona dissection performed in five cycles on sibling eggs. However, in 16 cycles conventional insemination yielded fertilization in six cycles, and mixed transfer of these embryos and sibling embryos from under zona insemination gave rise to one pregnancy from four transfers (pregnancy rate 25%, embryonic implantation 7.1%). Likewise, in nine cycles donor spermatozoa yielded fertilization in eight cycles, and mixed transfer with sibling embryos fertilized by under zona insemination with partner's spermatozoa gave rise to two pregnancies from five transfers (pregnancy rate 40%, embryonic implantation 15.8%). Fertilization and pregnancy rates did not differ whether couples suffered either from male factor infertility or from previous idiopathic fertilization failure. Direct egg injection of a single spermatozoon into 105 eggs gave an 88.6% egg survival and 32.3% fertilization. Mixed transfers with sibling embryos from conventional and under zona insemination yielded one triplet, one twin, and three singleton pregnancies. CONCLUSIONS: Overall, a 24.7% (21/85) viable pregnancy rate per cycle initiated occurred when only embryos from assisted fertilization were available. This strongly indicates that assisted fertilization made a real contribution in cases where either insufficient spermatozoa were available for conventional insemination or in cases where previous fertilization failure had arisen. The wide range of seminal parameters were found to be unhelpful in defining chances of success with assisted fertilization.

The effects of Vero (green monkey kidney) cell coculture on the motility patterns of cryopreserved human spermatozoa.

OBJECTIVE: To determine the effects of Vero (a primate, urogenital epithelium-derived cell line) cell monolayer coculture on cryopreserved human sperm function in vitro. DESIGN: Prospective, controlled investigation in which cryopreserved semen specimens were thawed, processed, and then simultaneously exposed to control media (Dulbecco's modified Eagle's medium with either 10% heat-inactivated fetal bovine serum [FBS] or 10% heat-inactivated pooled human sera [PHS]) or the same media with the addition of confluent Vero cell monolayers. A second series of investigations was also performed to study the effect of Vero cell conditioned media (CM). SETTING: In vitro fertilization/andrology service of tertiary center. PATIENTS: Donors with normal semen parameters. INTERVENTIONS: Coculture of human spermatozoa with Vero cell monolayers or Vero cell CM. MAIN OUTCOME MEASURES: General and hyperactivated (HA) motility patterns, multifactor, repeated measures ANOVA. RESULTS: General sperm motility parameters, including percentage motility, mean velocity, and mean amplitude of lateral head displacement were significantly greater than controls in the Vero cell monolayer-FBS group at 6 hours and in both the Vero cell monolayer-FBS and Vero cell monolayer-PHS groups by 24 hours. Hyperactivated motility was increased after 3 hours in the Vero cell monolayer-FBS coculture group. A significant decrease in the total sperm concentration over the time course of the study in the Vero cell monolayer, but not the control or Vero CM groups, was also noted. Vero CM did not exert significant effects on any sperm motility parameter, in spite of a sample size sufficient to detect relevant increases with a power of 0.80. CONCLUSIONS: Vero cell monolayers have a positive influence on cryopreserved sperm function as assessed by general and HA motility patterns. Epithelial cell to spermatozoon contact seems to be important in this process.

Chemical removal of the outside of the zona pellucida of day 3 human embryos has no impact on implantation rate.

Two hundred eighteen consenting patients entered a randomized study of the application of chemical zona pellucida thinning on their day 3 embryos, prior to uterine transfer. Of those control patients (n = 108), whose embryos remained unmanipulated, 40 (37.0%) have ongoing/delivered pregnancies, while in the experimental group (n = 110), whose embryos had their zonae pellucidae chemically thinned, there are 49 patients (44.6%) who have ongoing/delivered pregnancies. Although this difference is not significant, clearly the application of this micromanipulative intervention has not been detrimental, and this bodes well for routine application of embryonic micromanipulation procedures in general. Certain patient subgroups were studied including older women, those with elevated basal follicle stimulating hormone levels, patients with embryos of differing zona thickness, and patients with embryos of differing uniformity of zona thickness. No significant influence of chemical removal of the outside of the zona on the implantation rate of embryos in any of these subgroups was observed other than a marginally significant (P = 0.095) improvement of implantation of embryos with less than 4.0 microns variation in zona thickness when chemical zona thinning was applied. Failure of chemical zona thinning to enhance human embryo implantation significantly, compared to assisted hatching by complete zona drilling, strongly suggests that the bilayered human zona pellucida needs to be fully breached, unlike that of the mouse.

Repeated sperm injection under the zona following initial fertilization failure.

When fertilization fails following micromanipulative under-zona insemination, it is possible to repeat the procedure adding more spermatozoa to achieve fertilization, embryonic development and pregnancy. We report on 18 human in-vitro fertilization cycles where this approach was used. In nine cycles only late-fertilized embryos were available for transfer, and these gave rise to two viable pregnancies (22.2% per transfer). In six cycles, where a mixture of late- and timely fertilized embryos were available for transfer, two viable pregnancies arose (33.3% per transfer). In three cycles no fertilization was achieved even after reinsemination by repeated under-zona insemination.

Electroejaculation in combination with in vitro fertilization and gamete micromanipulation for treatment of anejaculatory male infertility.

OBJECTIVE: Failure to ejaculate may be overcome by use of electroejaculation. However, such semen samples are often unsuitable for therapies like intrauterine insemination. The combination of electroejaculation with in vitro fertilization, including gamete micromanipulation, should improve chances of fertilization and pregnancy in such cases. STUDY DESIGN: Within a private infertility clinic electroejaculation in combination with intrauterine insemination was carried out in 18 cycles (10 couples). Four couples went on to receive therapy by electroejaculation plus in vitro fertilization, along with six other couples (15 cycles total) with semen too poor for intrauterine insemination. RESULTS: One term pregnancy arose in the electroejaculation-intrauterine insemination group, and one term pregnancy plus one continuing pregnancy arose from two couples (three cycles) who underwent in vitro fertilization with conventional insemination after electroejaculation. Six couples (nine cycles) had embryos arising only from gamete micromanipulation transferred, and this yielded two term pregnancies, one spontaneous abortion, and a biochemical pregnancy. Two couples (three cycles) failed to achieve fertilization even with micromanipulation; however, donor-inseminated eggs gave rise to two term pregnancies and one continuing pregnancy in these patients. CONCLUSIONS: This report confirms the feasibility of in vitro fertilization in conjunction with electroejaculation and extends the therapy to incorporate gamete micromanipulation.

Partial dissection of the zona pellucida of frozen-thawed human embryos may enhance blastocyst hatching, implantation, and pregnancy rates.

The rate of successful implantation after replacement of frozen-thawed embryos in in vitro fertilization is commonly only 5% to 10% per embryo. A limiting factor may be inability of otherwise viable embryos to be released from the intact zonae pellucidae. Culture conditions and/or cryopreservation in in vitro fertilization may affect the zona and impair blastocyst hatching. Therefore opening of the zona by partial slicing by means of micromanipulation before replacement of early cleaved embryos may improve chances of eventual hatching (referred to as assisted hatching). In 65 thawed embryo replacement cycles methyl-prednisolone and antibiotics were given for 4 days mid cycle. Assisted hatching was performed in 32 cycles, with 33 cycles left as controls. Patient's age, infertility, cycle supplementation, and number of thawed and replaced embryos did not differ significantly between the two groups. Rates of viable embryonic implantation were 16% (10/63) and 9% (6/64) in the assisted hatching and control groups, respectively. Group sizes need approximately to double before this trend toward improved implantation with the use of assisted hatching reaches statistical significance.

Routine application of partial zona dissection for male factor infertility.

Partial zona dissection (PZD) increases the chances of fertilization by improving the access of spermatozoa to the perivitelline space (PVS) helping those spermatozoa unable to penetrate the zona pellucida (ZP) and possibly those poorly able to penetrate the oolemma. Problems arise in assessing semen to decide which parameters might indicate defects of this nature. PZD, by circumventing the ZP, may also increase the rate of polyspermy, especially in infertility where ZP and oolemmal penetration are not defective. Given these drawbacks, we performed PZD as routine treatment for male infertility in 70 in-vitro fertilization cycles. In three different groups, PZD proved to be either effective, ineffective or unnecessary. In the first group of 35 cycles, fertilization was 23% with initial PZD and 33% with PZD reinsemination (36% and 41% polyspermy respectively). No fertilization occurred following conventional insemination (CONV). Four pregnancies occurred in this group. In a second group of 19 cycles, fertilization did not occur with either PZD or CONV. In the final group of 16 cycles, fertilization was similar following both PZD and CONV, but polyspermy was 48% in the PZD category. Transfer of mixed PZD and CONV embryos in this group yielded 10 pregnancies. Assessment of all patient and seminal profiles, and those in an oligozoospermic subcategory, revealed no parameters of relevance to success or failure with PZD. However, one subgroup in the group of total failure to fertilize did have a significantly lower percentage of normal morphology (P less than 0.005), suggesting that degree of teratozoospermia may be a prognosticator of success using PZD.

Recognition of paternal pronuclei in human zygotes.

The possibility of pronuclear gender determination using morphological criteria only was investigated in 140 two-pronucleate and 39 tripronucleate zygotes. Zygotes were videotaped on different focal points and the positions of the polar bodies, pronuclear diameters, number and distribution of nucleoli, and presence of sperm tail remnants were indicated on diagrams. The three known criteria used for recognition of the paternal pronucleus in rodent zygotes were investigated. These criteria are (a) the presence of sperm tail remnants, (b) an increased pronuclear diameter, and (c) the farthest distance from the second polar body. Sperm tail remnants were observed in only 3/342 (1%) of the pronuclei. Pronuclear diameters and positions of the largest pronuclei did not reveal any trends. Pronuclei of tripronucleate zygotes were frequently smaller than those of two-pronucleate ones. The parental origin of human pronuclei cannot be determined morphologically using standard light optics. Microsurgical removal of paternal pronuclei from polyspermic zygotes should therefore be implemented with caution.

Observations on the morphology of pronuclei and nucleoli in human zygotes and implications for cryopreservation.

The effects of cryopreservation on human zygotes at various stages between the appearance of pronuclei and their close association were investigated. Pronuclear zygotes (n = 233) from 101 patients were frozen using propanediol 21-35 h following egg collection. The incidence of implantation of thawed pronuclear zygotes frozen 29-35 h following oocyte collection was significantly higher than that of younger pronuclear zygotes (28 versus 10%, respectively). Zygote age did not affect cell survival following cryostorage. The diameter and association of pronuclei and the number and distribution of nucleoli were determined from video tape recordings of 140 fresh zygotes. Pronuclear migration continued after pronuclear enlargement. The number of nucleoli remained constant during pronuclear migration, but their random distribution within the pronucleus diminished. Strongly adhered pronuclei had significantly more aligned nucleoli on adjacent sides than pronuclei which were still visually separated by ooplasm. This equatorial distribution of nucleoli was noted in the majority of zygotes older than 26 h. The findings suggest that zygote cryopreservation should be initiated when pronuclear migration is completed. This moment can be determined accurately by studying pronuclear association and nucleolar alignment.

Coculture of human zygotes on fetal bovine uterine fibroblasts: embryonic morphology and implantation.

Zygotes from in vitro fertilization patients (n = 116) were randomly allocated to culture in either conventional plastic petri dishes or coculture on a monolayer of fetal bovine uterine fibroblasts. Embryos (n = 288) remained 26 to 32 hours in these culture systems. Video tape recording for later morphological analysis (11 parameters) was performed on 117 conventionally cultured and 104 cocultured embryos, shortly before replacement, by an independent observer, unaware of the culture conditions for each embryo. A significantly greater number of cocultured embryos (52%) had "good" morphology (zero or only one abnormal characteristic) as compared with conventionally cultured embryos (30%). The most outstanding morphological characteristic of cocultured embryos was the expanded appearance of their blastomeres. The incidence of implantation per embryo increased from 13% to 19% when the coculture rather than conventional culture system was used, and the incidence of ongoing pregnancy per patient after coculture doubled to 35%.

Arm posture and human movement capability.

Many workers perform manual assembly tasks or use hand tools while the hands are postured above the shoulders or to the side of the body. Experiments were conducted to study the sensitivity of speed-accuracy movement performance to a wide range of hand locations around the shoulder under various levels of hand loads, ratios of work to rest, and task durations. Subjects performed a spatially constrained stylus-to-hole Fitts reciprocal movement task designed to simulate high-incentive manual assembly operations while providing basic information regarding changes in human move and positioning capabilities. Significant decrements in movement performance occurred when hands were postured above shoulder level. Move and positioning times increased 15.3% and 26.5%, respectively, with elevation of the hand from -15 to 60 deg respective to shoulder level. Posturally based decrements in movement capability were unrelated to differences in subject strength capability found among test postures. The consequences of elevated arm postures on human move and positioning capability are presented along with workplace design and methods recommendations for job designers facing work-height decisions in manual assembly environments.

In-vitro development and implantation of human embryos following culture on fetal bovine uterine fibroblast cells.

Human zygotes resulting from IVF were placed in two different culture systems to evaluate in-vitro development and to establish pregnancies in patients following embryo replacement. Treatment A (control) consisted of culturing zygotes in a modified Earle's Balanced Salt solution while treatment B consisted of culturing zygotes on a monolayer of fetal bovine uterine fibroblasts in this same culture medium. At the time of embryo replacement, embryos within treatments A and B had 3.7 and 4.3 blastomeres present, respectively. After 24 h in culture, the cellular fragmentation rate for treatment A embryos was 0.85 which was greater (P less than 0.05) than the fragmentation rate of 0.40 for embryos within treatment B. The incidence of implantation for patients whose embryos were given treatment A was 17.0% which was lower (P less than 0.05) than 35% for those given treatment B. Implantation rates increased with time in culture (43%) for treatment B embryos. Culture by treatment B of three-pronucleate zygotes resulted in 7/9 and 4/9 reaching the blastocyst and expanded blastocyst stages, respectively, whereas only 1/26 three-pronucleate zygotes cultured using treatment A reached either of these stages.

Videocinematography of fresh and cryopreserved embryos: a retrospective analysis of embryonic morphology and implantation.

Eleven morphologic criteria were studied from videotapes of 323 fresh and 103 thawed embryos. The proportion of thawed embryos (30/39; 77%) with more than one abnormality was (P = 0.03) higher than that of fresh embryos (5/13; 38%), despite similar implantation rates (18% and 15%, respectively). The best predictor of thawed embryo implantation was cell-cell adherence: when scored "positive," 11 of 17 women (65%) became pregnant, whereas none became pregnant (0/15; P = 0.0002) when blastomeres did not adhere. The total number of abnormalities for thawed embryos was an important prognostic. An increased percentage variation of zona pellucida thickness was the most important prognostic for fresh embryos. When the "best" embryo had a zona pellucida that varied more than 25%, 24 of 60 (40%) resulted in pregnancy; pregnancies were not induced (0/21) when the "best" embryo had less than 10% variation (P = 0.0003).

Shoulder posture and localized muscle fatigue and discomfort.

In many industries workers perform manual assembly tasks with hands postured above the shoulders. Awkward shoulder and arm postures are often viewed as acceptable given costs of workplace modification, postural exertions which are in compliance with current design recommendations, ready availability of strong workers, and numbers of electromyographic studies which fail to detect significant signs of localized muscle fatigue (LMF). An experiment was conducted to: (a) study the onset and severity of (LMF) in the shoulder when performing a stylus-to-hole Fitts reciprocal movement task under a range of postures, hand loads, ratios of work-to-rest, and task durations, and (b) to evaluate the efficacy of three techniques (i.e., changes in EMG behaviour, postural tremor, and cross-modal matching estimates) in detecting and monitoring posturally-based LMF and discomfort in the shoulder complex. Experimental findings showed that posturing hands above shoulder level significantly increased the risk of LMF and postural discomfort even in light-weight manual assembly environs where postural exertions are small, and that cross-modal matching estimates and postural tremor were more sensitive metrics of LMF in the shoulder complex than EMG RMS voltage and mean spectral power frequency metrics. The basis for experimental findings, as well as potential application of LMF metrics in future postural stress investigations, are discussed. Recommendations for workplace posture are provided for job designers facing work height decisions in manual assembly environs.

Duration of storage of cryopreserved human embryos.

The incidence of cell injury, embryo survival, and implantation following cryopreservation of zygotes and two- to five-cell embryos was studied in 100 patients in order to evaluate the effect of duration of storage. The incidence of individual cell survival was 58% regardless of the length of time kept in liquid nitrogen or the stage of the embryo at freezing. There were 104 of 208 (50%) thawed embryos that survived completely intact, and of those, 24 implanted successfully. Twenty-one (21%) patients had a clinical pregnancy; two of them miscarried Neither the survival of zygotes or cleaved embryos upon thawing nor the incidence of implantation was affected by the duration of cryostorage.