Fitness landscapes for effects of shape on chemotaxis and other behaviors of bacteria

Data on the shapes of 218 genera of free-floating or free-swimming bacteria reveal groupings around spherical shapes and around rod-like shapes of axial ratio about 3. Motile genera are less likely to be spherical and have larger axial ratios than nonmotile genera. The effects of shape on seven possible components of biological fitness were determined, and actual fitness landscapes in phenotype space are presented. Ellipsoidal shapes were used as models, since their hydrodynamic drag coefficients can be rigorously calculated in the world of low Reynolds number, where bacteria live. Comparing various shapes of the same volume, and assuming that departures from spherical have a cost that varies with the minimum radius of curvature, led to the following conclusions. Spherical shapes have the largest random dispersal by Brownian motion. Increased surface area occurs in oblate ellipsoids (disk-like), which rarely occur. Elongation into prolate ellipsoids (rod-like) reduces sinking speed, and this may explain why some nonmotile genera are rod-like. Elongation also favors swimming efficiency (to a limited extent) and the ability to detect stimulus gradients by any of three mechanisms. By far the largest effect (several hundred-fold) is on temporal detection of stimulus gradients, and this explains why rod-like shapes and this mechanism of chemotaxis are common.     

Hearing loss in community-dwelling older persons: national prevalence data and identification using simple questions

OBJECTIVE: To estimate the prevalence of hearing loss among community-dwelling older persons according to clinical criteria and to develop a brief self-report screening instrument to detect hearing loss. DESIGN: Survey. SETTING: National probability sample of noninstitutionalized older persons. PARTICIPANTS: A total of 2506 persons aged 55 to 74 who participated in the National Health and Nutrition Examination Survey. MAIN OUTCOME MEASURES: Hearing loss as defined by Ventry and Weinstein (VW) criteria and by the High Frequency Pure-Tone Average (HFPTA) scale. RESULTS: Hearing loss by VW criteria was present in 14.2% and by HFPTA criteria in 35.1% of those surveyed. The prevalence increased with advancing age and was higher among men and those with less education. A logistic regression model identified six independent factors for hearing loss by VW criteria: age > or = 70 years (adjusted odds-ratio (AOR) 2.7, 95% confidence interval (95% CI) 1.6, 4.4), male gender (AOR 3.0, 95% CI 1.9, 4.8), < or = 12th grade education (AOR 3.8, 95% CI 1.8, 7.7), having seen a doctor for deafness or hearing loss (AOR 8.9, 95% CI 5.3, 14.9), unable to hear a whisper across a room (AOR 3.2, 95% CI 2.0, 5.1), and unable to hear a normal voice across a room (AOR 6.2, 95% CI 2.6, 14.9). A clinical scale based on the logistic model had 80% sensitivity and 80% specificity in predicting hearing loss using VW criteria and 59% sensitivity and 88% specificity in predicting hearing loss using HFPTA criteria. CONCLUSIONS: Hearing loss, as defined by two clinical criteria, is common and can be screened for accurately using simple questions that assess sociodemographic and hearing-related characteristics.     

Safety and immunogenicity of HIV-1 DNA constructs in chimpanzees

A global effort to control the HIV epidemic is likely to rely heavily on immunization strategies. As our closest genetic relative, the chimpanzee provides the most important model for preclinical safety and immunogenicity studies. We have immunized adult, pregnant and infant chimpanzees with our plasmid vaccines. We have found these vaccines to be safe and well tolerated in all of these groups. The same vaccines have induced both humoral and cellular immunity in each instance.     

Infection of human marrow stroma by human immunodeficiency virus-1 (HIV-1) is both required and sufficient for HIV-1-induced hematopoietic suppression in vitro: demonstration by gene modification of primary human stroma

Patients with human immunodeficiency virus-1 (HIV-1) infection often present with bone marrow (BM) failure that may affect all hematopoietic lineages. It is presently unclear whether this failure reflects a direct viral impairment of the CD34+ hematopoietic progenitor cells or whether the virus affects the BM microenvironment. To study the effects of HIV-1 on the BM microenvironment, we examined the stromal cell monolayers in long-term BM culture (LTBMC), which are the in vitro equivalent of the hematopoietic microenvironment. We assessed the hematopoietic support function (HSF) of human stromal layers by determining the cellular proliferation and colony-forming ability of hematopoietic progenitors from BM cells grown on the stromal layers. We show that the HSF is reduced by in vitro infection of the human stromal cell layer by a monocytotropic isolate of HIV-1 (JR-FL). There is no loss of HSF when the stromal cell layer is resistant to HIV-1 replication, either using murine stromal cell layers that are innately resistant to HIV-1 infection or using human stromal cells genetically modified to express a gene that inhibits HIV-1 replication (an RRE decoy). Decreased HSF was seen using either human or murine hematopoietic cells, if the stromal cells were human cells that were susceptible to HIV-1 infection. These in vitro studies implicate HIV-1 replication in the stroma as the essential component causing decreased hematopoietic cell production in HIV-1 infection.     

Coupling of skeletal muscle to a prosthesis for circulatory support

A durable bond between the end of skeletal muscles and prosthetic structures could, with appropriate linkage, allow circulatory support power by synchronous and/or sequential contraction of several in situ conditioned muscles. Potential advantages relative to a myoplasty wrap involve 1) less traumatic dissection, 2) efficient linear force development, 3) selectable contraction rate, 4) greater stroke work, 5) independent control of muscle pre-load and end diastolic pressure, and 6) independent control of duration of muscle tension and ejection time. However, no existing means of tissue-prosthetic bonding appears adequate. Practicality would demand that full tension bearing capacity by the bond take no longer than muscle conditioning. A prosthesis was developed to achieve those goals. As scaled for this study, it is made of 7,200-7,800 unspun, unplaited, 22 to 26 microns diameter polyester fibers swaged into four taper needles for weaving through distal muscle. The other end is formed into a polyurethane sheathed kernmantel cord for distal fixation. Devices were implanted in six 3 to 4 kg rabbits (unilateral posterior tibial tendon replacement, random side selection with contralateral dissection/closure controls), and their tensile strength was tested at 30 days. All healed well; leg movements were normal after 1 week. Limbs were frozen at -70 degrees C between death and testing. Control failure occurred at 243 +/- 94 N and experimental at 163 +/- 44 N (p = 0.065, t-test); highest estimated requirement was 17.2 N. Interface strength was adequate by 30 days. Continued investigations, addressing other questions, are warranted.     

Remote recollection of preoperative pain in patients undergoing excision of endometriosis

To determine the accuracy of postoperative recall of preoperative pain, this prospective, longitudinal study was conducted by a general gynecologist in private practice at a referral center. Before excision of endometriosis at laparoscopy or laparotomy and again at 6 to 18 months after surgery, 168 patients completed a 5-point scale assessing 11 symptoms that may be related to endometriosis. For 6 of the 11 symptoms, over 50% of patients had exact recall of pain level. For 10 symptoms, over 80% recalled their preoperative pain level within +/-1 point. Patients requiring reoperation were most likely to recall preoperative pain levels accurately. Those not requiring reoperation tended to inflate slightly their remote assessment of preoperative pain, indicating that successfully treated patients tend to forget how much they formerly hurt.     

Gray-scale ultrasound: utility preoperatively and postoperatively in a patient with obstructive jaundice

We present a case of obstructing calculi of the common bile duct diagnosed by ultrasonography. Postoperatively, a sterile abscess due to bile leakage at the distal common bile duct developed, and was also diagnosed by ultrasound Ultrasonography was useful in following the course of clearing of the bile collection. Preoperative ultrasound evaluation of the jaundiced patient should be followed by postoperative sonography, especially if complications occur.     

Adaptive sidelobe nulling using digitally controlled phase-shifters

Adaptive null-steering arrays which use phase-only weights are examined. The optimal phase weightings are developed and the mathematical equations are reduced to a simplified computational form. Approximations for low sidelobe arrays allow more efficient computations and demonstrate the decomposition of the antenna pattern into a sum of patterns which place gain towards each directional emitter. Computer simulations and breadboard array measurements substantiate the mathematical development and indicate the practicality of the method.