Quaternary structure regulates hemin dissociation from human hemoglobin

Rate constants for hemin dissociation from the alpha and beta subunits of native and recombinant human hemoglobins were measured as a function of protein concentration at pH 7.0, 37 degrees C, using H64Y/V68F apomyoglobin as a hemin acceptor reagent. Hemin dissociation rates were also measured for native isolated alpha and beta chains and for recombinant hemoglobin tetramers stabilized by alpha subunit fusion. The rate constant for hemin dissociation from beta subunits in native hemoglobin increases from 1.5 h-1 in tetramers at high protein concentration to 15 h-1 in dimers at low concentrations. The rate of hemin dissociation from alpha subunits in native hemoglobin is significantly smaller (0.3-0.6 h-1) and shows little dependence on protein concentration. Recombinant hemoglobins containing a fused di-alpha subunit remain tetrameric under all concentrations and show rates of hemin loss similar to those observed for wild-type and native hemoglobin at high protein concentration. Rates of hemin dissociation from monomeric alpha and beta chains are much greater, 12 and 40 h-1, respectively, at pH 7, 37 degrees C. Aggregation of monomers to form alpha1beta1 dimers greatly stabilizes bound hemin in alpha chains, decreasing its rate of hemin loss approximately 20-fold. In contrast, dimer formation has little stabilizing effect on hemin binding to beta subunits. A significant reduction in the rate of hemin loss from beta subunits does occur after formation of the alpha1beta2 interface in tetrameric hemoglobin. These results suggest that native human hemoglobin may have evolved to lose heme rapidly after red cell lysis, allowing the prosthetic group to be removed by serum albumin and apohemopexin.     

Age, testosterone, and behavior among female prison inmates

Stereotactically directed needle biopsy of central nervous system lesions is a widely used diagnostic procedure with low morbidity and mortality. Diagnostic tissue is obtained in most instances. As a part of the College of American Pathologists Practical Topics in Neuropathology series, the following report summarizes the pathologist's role in the procurement, preparation, and interpretation of these important specimens.     

Standards of weight and height for Holstein heifers

To develop a modern appraisal of growth of Holstein dairy heifers, height at withers and heart girth (body weight) data were collected for 5723 heifers representing 163 commercial Holstein dairy herds from October 1983 through May 1985. Quadratic regression equations of height and weight on age were computed for each herd. Estimated weight and height of heifers at 24 mo from these equations were found to be correlated with herd variables such as herd average milk production and age at first calving. Means and standard deviations for height and weight were determined for each age (1 through 24 mo). Third order regressions on age were fitted to the means to describe height and weight. Estimated height (cm) and weight (kg) at 6, 12, 18, and 24 mo were 101.0, 167.2; 117.6, 299.1; 127.4, 420.6; and 132.7, 516.2. A subset of data containing heifers in 89 herds that had a herd average milk production of greater than 7264 kg were also fitted to third order regression on age. Weight and height of dairy heifers are moderately larger in herds with greater than 7264 kg average milk production. Based on the entire data set, commercial Holstein herds in Pennsylvania have heifers somewhat larger than those used to develop National Research Council recommendations.     

The effects of electrode size and orientation on the sensitivity of myoelectric pattern recognition systems to electrode shift

Myoelectric pattern recognition systems for prosthesis control are often studied in controlled laboratory settings, but obstacles remain to be addressed before they are clinically viable. One important obstacle is the difficulty of maintaining system usability with socket misalignment. Misalignment inevitably occurs during prosthesis donning and doffing, producing a shift in electrode contact locations. We investigated how the size of the electrode detection surface and the placement of electrode poles (electrode orientation) affected system robustness with electrode shift. Electrodes oriented parallel to muscle fibers outperformed electrodes oriented perpendicular to muscle fibers in both shift and no-shift conditions (p < 0.01). Another finding was the significant difference (p < 0.01) in performance for the direction of electrode shift. Shifts perpendicular to the muscle fibers reduced classification accuracy and real-time controllability much more than shifts parallel to the muscle fibers. Increasing the size of the electrode detection surface was found to help reduce classification accuracy sensitivity to electrode shifts in a direction perpendicular to the muscle fibers but did not improve the real-time controllability of the pattern recognition system. One clinically important result was that a combination of longitudinal and transverse electrodes yielded high controllability with and without electrode shift using only four physical electrode pole locations.     

Effect of automatic backflushing on number of new intramammary infections, bacteria on teatcup liners, and milk iodine

Effect of an automatic iodine (15 ppm) backflushing system on incidence of new intramammary infections, teatcup liner bacterial populations, and milk iodine was tested in a herd free of Streptococcus agalactiae and with a low prevalence of Staphylococcus aureus. In an 11-mo trial, backflushing was applied to teatcups that milked the right half of the udder; the left half served as control. Clawpieces were divided into left and right halves with each having a milk outlet. Postmilking teat dipping was discontinued. All lactating cows in the University herd were used, averaging 154 with normal attrition and additions of new individuals as they calved. Backflushing reduced numbers of staphylococci recovered from liners by 98.5% and Gram-negative bacteria by 99.5% as compared with unflushed liners. Backflushing significantly reduced new infections caused by Corynebacterium bovis. However, there was no effect on incidence of new infections by staphylococci, streptococci, or coliforms. Iodine concentrations averaged 243 micrograms per liter in milk from control quarters and 486 micrograms from backflushed udder halves. Interior surface cracking was more severe in backflushed teatcup liners than in control liners. These results do not justify the use of backflushing in a herd with low prevalence of contagious pathogens.     

Improving myoelectric pattern recognition robustness to electrode shift by changing interelectrode distance and electrode configuration

Pattern recognition of myoelectric signals for prosthesis control has been extensively studied in research settings and is close to clinical implementation. These systems are capable of intuitively controlling the next generation of dexterous prosthetic hands. However, pattern recognition systems perform poorly in the presence of electrode shift, defined as movement of surface electrodes with respect to the underlying muscles. This paper focused on investigating the optimal interelectrode distance, channel configuration, and electromyography feature sets for myoelectric pattern recognition in the presence of electrode shift. Increasing interelectrode distance from 2 to 4 cm improved pattern recognition system performance in terms of classification error and controllability (p < 0.01). Additionally, for a constant number of channels, an electrode configuration that included electrodes oriented both longitudinally and perpendicularly with respect to muscle fibers improved robustness in the presence of electrode shift (p < 0.05). We investigated the effect of the number of recording channels with and without electrode shift and found that four to six channels were sufficient for pattern recognition control. Finally, we investigated different feature sets for pattern recognition control using a linear discriminant analysis classifier and found that an autoregressive set significantly (p < 0.01) reduced sensitivity to electrode shift compared to a traditional time-domain feature set.     

Managing Diversity in a Technical Environment

ABSTRACT

A landmark study completed by a public policy research organization concluded that American technical businesses can expect a heterogeneous labor force in the future. To maximize productivity, it is crucial that managers tap the potential of all employees, no matter how diverse employee backgrounds might be. A major change in attitudes and behaviors is necessary so that no employee may be limited by the barriers of organizational structure, whether formal or informal. This article recognizes some of the companies that are pioneers in their efforts toward diversity education, and presents a model approach for planning diversity in a technical environment. The model approach was developed by the author by careful review of current diversity programs in the literature.     

Relationships among severity and duration of clinical mastitis and sire transmitting abilities for somatic cell score,udder type traits,productive life,and protein yield

The objective of this study was to determine the relationships among severity and duration of clinical mastitis during first and second lactation and sire transmitting abilities for somatic cell score, udder type traits, productive life, and protein yield. Recording of clinical episodes began at first parturition for 1704 Holstein cows (in six Pennsylvania herds and one Nebraska herd) and continued into second lactation for 1055 of these cows. A total of 456 cows (sired by 168 bulls) had at least one clinical episode during first lactation, and 230 cows (sired by 100 bulls) had at least one clinical episode during second lactation. A severity code from 1 (normal milk) to 5 (acute systemic mastitis) was assigned daily (for up to 30 d after detection) to all quarters that had clinical mastitis. Only the severity codes for the first clinical episode to occur during first and second lactation are considered here. The initial and maximum severity codes, as well as the natural logarithms of both the sum of severity codes that were above normal (> 1) and the total days severity codes were above normal were regressed on herd (a classification variable), age at first calving, days in milk at clinical detection, and sire transmitting abilities taken one at a time. Linear and nonlinear effects were estimated for sire transmitting abilities. Separate analyses were conducted on dependent variables that considered severity and duration of clinical mastitis from: all organisms, coagulase-negative staphylococci, coliform species, streptococci other than Streptococcus agalactiae, and the most common environmental organisms (coliform species and streptococci other than Streptococcus agalactiae). Daughters of sires that transmit the lowest somatic cell score had the least severe and shortest clinical episodes from environmental organisms during first lactation. Selection for lower somatic cell score may reduce the severity and duration of clinical episodes from environmental organisms during first lactation.     

Composition and properties of whey protein concentrates from ultrafiltration

Chemical and nutrient composition and functional properties of whey protein concentrates from ultrafiltration of sweet and acid wheys were studied for potential food uses. Vitamins passed readily through the membrane; thus, vitamin content was slightly higher than in whey. Amino acid values were considerably higher, increasing in direct proportion to increases in protein. Lysine availability was not significantly affected by fractionation or by subsequent beat treatment. Since this process results in substantial removal of minerals along with the permeate, the protein to ash ratio of the protein concentrate increased. Unlike most other methods of recovering protein from whey, solubility was not adversely affected by ultrafiltration. However, protein concentrates were susceptible to heat; normal pasteurization temperatures resulted in approximately 20% denaturation. Whey protein exhibited excellent water retention. Addition of 1.5% protein to skim milk followed by heating formed a custard-like gel with sufficient body to stand alone without leakage. Approximately twice as much egg albumin was required to achieve comparable results. Whipping properties were very good when butterfat content was less than 2%. Excellent stable whips could be produced by a combination of heat and pH adjustment.