Measurement of the parity-violating asymmetry in inclusive electroproduction of π- near the Δ0 resonance.

The parity-violating (PV) asymmetry of inclusive π- production in electron scattering from a liquid deuterium target was measured at backward angles. The measurement was conducted as a part of the G0 experiment, at a beam energy of 360 MeV. The physics process dominating pion production for these kinematics is quasifree photoproduction off the neutron via the Δ0 resonance. In the context of heavy-baryon chiral perturbation theory, this asymmetry is related to a low-energy constant d(Δ)- that characterizes the parity-violating γNΔ coupling. Zhu et al. calculated d(Δ)- in a model benchmarked by the large asymmetries seen in hyperon weak radiative decays, and predicted potentially large asymmetries for this process, ranging from A(γ)-=-5.2 to +5.2 ppm. The measurement performed in this work leads to A(γ)-=-0.36±1.06±0.37±0.03 ppm (where sources of statistical, systematic and theoretical uncertainties are included), which would disfavor enchancements considered by Zhu et al. proportional to V(ud)/V(us). The measurement is part of a program of inelastic scattering measurements that were conducted by the G0 experiment, seeking to determine the N-Δ axial transition form factors using PV electron scattering.

Transverse beam spin asymmetries at backward angles in elastic electron-proton and quasielastic electron-deuteron scattering.

We have measured the beam-normal single-spin asymmetries in elastic scattering of transversely polarized electrons from the proton, and performed the first measurement in quasielastic scattering on the deuteron, at backward angles (lab scattering angle of 108°) for Q² = 0.22 GeV²/c² and 0.63 GeV²/c² at beam energies of 362 and 687 MeV, respectively. The asymmetry arises due to the imaginary part of the interference of the two-photon exchange amplitude with that of single-photon exchange. Results for the proton are consistent with a model calculation which includes inelastic intermediate hadronic (πN) states. An estimate of the beam-normal single-spin asymmetry for the scattering from the neutron is made using a quasistatic deuterium approximation, and is also in agreement with theory.

Strange quark contributions to parity-violating asymmetries in the backward angle G0 electron scattering experiment.

We have measured parity-violating asymmetries in elastic electron-proton and quasielastic electron-deuteron scattering at Q2=0.22 and 0.63 GeV2. They are sensitive to strange quark contributions to currents in the nucleon and the nucleon axial-vector current. The results indicate strange quark contributions of approximately < 10% of the charge and magnetic nucleon form factors at these four-momentum transfers. We also present the first measurement of anapole moment effects in the axial-vector current at these four-momentum transfers.

Hormone replacement therapy increases isometric muscle strength of adductor pollicis in post-menopausal women.

A randomized open trial of hormone replacement therapy was used to assess changes in adductor pollicis muscle strength during 6-12 months of treatment with Prempak C 0.625(R) in comparison with an untreated control group. Muscle strength (maximal voluntary force; MVF), muscle cross-sectional area and bone mineral density were measured. Women entering the trial had oestrogen levels below 150 pmol.l-1, confirming their post-menopausal hormonal status. In the treated group, MVF increased by 12.4+/-1.0% (mean+/-S.E.M.) of initial MVF over the duration of treatment, while it declined slightly (2.9+/-0.9%) in the control group. This increase in strength could not be explained by an increase in muscle bulk, there being no significant increase in cross-sectional area during the study. Those subjects who were weakest at enrolment showed the greatest increases in muscle strength after treatment. Bone mineral density in total hip, Ward's triangle and total spine increased in the treated group, in agreement with previous studies. There was no correlation between the individual increases in bone mineral density and those in MVF.

Maternal virus load and perinatal human immunodeficiency virus type 1 subtype E transmission, Thailand. Bangkok Collaborative Perinatal HIV Transmission Study Group.

To determine the rate and risk factors for human immunodeficiency virus (HIV)-1 subtype E perinatal transmission, with focus on virus load, pregnant HIV-infected women and their formula-fed infants were followed prospectively in Bangkok. Of 281 infants with known outcome, 68 were infected (transmission rate, 24.2%; 95% confidence interval, 19.3%-29.6%). Transmitting mothers had a 4.3-fold higher median plasma HIV RNA level at delivery than did nontransmitters (P<.001). No transmission occurred at <2000 copies/mL. On multivariate analysis, prematurity (adjusted odds ratio [AOR], 4.5), vaginal delivery (AOR, 2.9), low NK cell percentage (AOR, 2.4), and maternal virus load were associated with transmission. As RNA quintiles increased, the AOR for transmission increased linearly from 4.5 to 24.8. Two-thirds of transmission was attributed to virus load>10,000 copies/mL. Although risk is multifactorial, high maternal virus load at delivery strongly predicts transmission. This may have important implications for interventions designed to reduce perinatal transmission.

Changes in isometric force of mouse soleus muscle during the oestrous cycle.

Muscles excised from young female mice at known phases of the oestrous cycle were studied in vitro to determine if there are variations in force analogous to those that occur in vivo during the menstrual cycle in women. Oestrous phase was determined from vaginal smears. The maximum isometric and eccentric forces of pairs of isolated soleus muscles were measured. The first muscle was studied immediately after dissection, the second after incubation in Ringer solution for up to 2 h. Normalised isometric muscle force in the first muscle of each pair depended on the oestrous phase, the force being greatest during dioestrus. There was a negative correlation between normalised force and the eccentric/isometric force ratio. Neither of these phenomena was found with the second muscle of each pair. These results show that in mouse soleus muscle cross-bridge function does vary according to the phase of the oestrous cycle. However, the rise in force does not follow the pattern of the rise in blood oestrogen levels as it does in humans, and in the mouse the effect on cross-bridge function washes out after a few hours in vitro.

A study of force and cross-sectional area of adductor pollicis muscle in female hip fracture patients.

OBJECTIVES: To determine the extent of muscle weakness in older female hip fracture patients compared with healthy older and young women; to determine the extent to which this weakness is caused by a decline of the force produced per unit area of muscle rather than by a decline in muscle bulk; and to investigate the mechanism of the decline in force per unit area. DESIGN: This was an open study of three groups of subjects, two age matched older groups and one young group. SETTING: University College London, Royal Free Hospital, and St. Thomas's Hospital, London. PARTICIPANTS: Twenty-nine older female hip fracture patients (mean age 85.6 +/- 0.9 SEM), 18 healthy older women (mean age 84.7 +/- 1.2 SEM), and 43 young women (mean age 28.9 +/- 1.2 SEM). MEASUREMENTS: Adductor pollicis muscle maximum voluntary force (MVF) during isometric and pliometric contractions and cross-sectional area (CSA), body weight, height, and demi-span. RESULTS: Isometric MVF was lowest in the hip fracture group. In both older groups, isometric MVF and CSA were lower than in the young women. Only part of this weakness in the older groups could be explained by the smaller CSAs. The isometric force per unit area (MVF/CSA) was also lower in both older groups, the hip fracture patients again having the lowest values. Analysis of variance showed a significant difference between groups. The age-related declines in pliometric force were much less than the declines in isometric force. This resulted in an increase in the pliometric/isometric force ratio both for the hip fracture patients and for the healthy older women compared with that for young women. CONCLUSION: In comparison with the results from young women, the adductor pollicis muscles of female hip fracture patients were even weaker than those of healthy older women when normalized for muscle size. This decline in isometric MVF/CSA accounted for at least half of the overall weakness in the hip fracture patients. Inasmuch as pliometric force is maintained in situations where weakness is caused by a decline in the force produced per muscle cross-bridge, this is the likely mechanism of the declines in isometric MVF/CSA observed in this study.

Detection of antibodies to human immunodeficiency virus type 1 in oral fluids: a large-scale evaluation of immunoassay performance.

Paired serum and oral-fluid (OF) specimens (n = 4,448) were collected from blood donors and patients attending local sexually transmitted disease clinics in Trinidad and Tobago and the Bahamas and were tested for the presence of human immunodeficiency virus type 1 (HIV-1) antibodies. Sera were tested by Abbott AB HIV-1/HIV-2 (rDNA) enzyme immunoassay (EIA), and positive specimens were confirmed by Cambridge HIV-1 and HIV-2 Western blotting (WB). OF specimens were collected with the OraSure collection device and were tested by Murex GACELISA and by two EIAs from Organon Teknika (the Oral Fluid Vironostika HIV-1 Microelisa System [OTC-L] and the Vironostika HIV-1 Microelisa System [OTC-M]). EIA-reactive OF specimens were confirmed by miniaturized WB (OFWB). GACELISA detected all 474 HIV-1 seropositive specimens (sensitivity, 100%). OTC-L detected 470 positive specimens (sensitivity, 99.2%), while OTC-M detected 468 positive specimens (sensitivity, 98.8%). Specificities ranged from 99.2 to 100% for the three assays. Concordance of OFWB with serum WB was 99.4%, and banding patterns determined by the two methods were similar. The immunoglobulin G (IgG) concentration of OF specimens ranged from 0.21 to 100 microg/ml, with a mean of 17.1 microg/ml. Significant differences in OF IgG concentrations were observed between HIV antibody-positive and HIV antibody-negative persons (31.94 versus 15.28 microg/ml, respectively [P < 0.0001]). These data further confirm the suitability of OF specimens for detection of HIV-1 antibodies. Currently available HIV-1 antibody assays provide sensitivities and specificities with OF specimens comparable to those achieved with serum specimens.

PIP: The use of oral fluid (OF) as a specimen for detecting antibodies to infectious agents has become increasingly popular since the approach was first described in the 1980s. OF is a mixture of saliva, mucosal and bacterial products, and gingival crevicular fluid. 4448 paired serum and OF specimens collected from 4448 blood donors and patients attending 3 sexually transmitted disease clinics in Trinidad and Tobago and the Bahamas were tested for the presence of HIV-1 antibodies. The sera were tested by Abbott AB HIV-1/HIV-2 (rDNA) enzyme immunoassay (EIA), and positive specimens were confirmed by Cambridge HIV-1 and HIV-2 Western blotting (WB). OF specimens were collected using the OraSure collection device and were tested by Murex GACELISA and 2 EIAs from Organon Teknika (OTC-L and OTC-M). EIA-reactive OF specimens were confirmed by miniaturized WB (OFWB). GACELISA detected all 474 HIV-1 seropositive specimens, OTC-L detected 470 positive specimens, and OTC-M detected 468 positive specimens. Specificities were 99.2-100% for the three assays. There was a 99.4% concordance of OFWB with serum WB, and banding patterns determined by the two methods were similar. The immunoglobulin G (IgG) concentration of OF specimens was 0.21-100 mcg/ml, with a mean of 17.1 mcg/ml. Significant differences in OF IgG concentrations were observed between HIV antibody-positive and HIV antibody-negative persons. These data support the suitability of OF specimens for detecting HIV-1 antibodies. Currently available HIV-1 antibody assays provide sensitivities and specificities with OF specimens comparable to those achieved with serum specimens.

Interpreting the relation between force and cross-sectional area in human muscle.

The maximum force a muscle can produce depends on its cross-sectional area (CSA). However, the exact interpretation of this relationship has been a matter of controversy. Recently, the controversy has centered on whether the measurements are best correlated using regression analysis or ratio standards. Applying regression analysis to this problem implies that all the experimental error is in the measurement of force. Thus, confusion may arise by failure to take account of errors in the measurement of CSA. Using a statistical model, we show how regression analysis can be misleading as error is introduced into the measurement of CSA as well as that of force. Because neither the errors in force nor CSA can be quantified in the experimental situation, we conclude that ratio standards are less likely to mislead although the accuracy of the result depends on the degree of correlation between force and CSA in the muscle measured.

Changes in maximal voluntary force of human adductor pollicis muscle during the menstrual cycle.

1. Muscle strength of the adductor pollicis (AP) was studied throughout the menstrual cycle to determine whether any variation in force is similar to the known cyclical changes in ovarian hormones. Three groups of young women were studied: trained regularly menstruating athletes (trained), untrained regularly menstruating (untrained) and trained oral contraceptive pill users (OCU). In addition a group of untrained young men was studied as controls. 2. Maximum voluntary force (MVF) of AP was measured over a maximum period of 6 months. Ovulation was detected by luteinizing hormone measurements or change in basal body temperature. There was a significant increase in MVF (about 10%) during the follicular phase of the menstrual cycle when oestrogen levels are rising, in both the trained and untrained groups. This was followed by a similar in MVF around the time of ovulation. Neither the OCU nor the male subjects showed cyclical changes in MVF.

Oral fluid as a specimen for detection and confirmation of antibodies to human immunodeficiency virus type 1.

Paired serum and oral fluid specimens (n = 287) were collected with the Omni-Sal device and were assayed for the presence of antibodies to human immunodeficiency virus type 1 (HIV-1). Enzyme immunoassays (EIAs)--Abbott 3A11, an Organon Teknika Corporation research-use-only test, and the Murex GACELISA--were used per the manufacturers' inserts or were modified slightly to accommodate the oral fluid specimens. Compared with serum Western blot (immunoblot) results, each EIA had a sensitivity of 100% and the specificities were 89.6% for the Abbott 3A11 EIA, 96.5% for the GACELISA, and 97.8% for the Organon Teknika Corporation EIA. Specificities based on specimens that were repeatedly reactive were 99.3% for all EIAs. A miniaturized Western blot technique used for confirmatory testing of both the serum and oral fluid specimens found 149 of the 287 samples to be HIV-1 antibody positive in both sample types. The Western blot banding patterns observed for the serum and oral fluid specimens were essentially identical. Immunoglobulin G concentrations were determined for all oral fluid specimens and ranged from < 0.5 to > 40.0 micrograms/ml. Immunoglobulin G concentrations did not correlate with the ability of any of the EIAs to detect HIV-1-specific antibody or with the ability of the modified Western blot to detect HIV-1 protein-specific antibodies.

Neither changes in phosphorus metabolite levels nor myosin isoforms can explain the weakness in aged mouse muscle.

1. The contractile force, phosphorus metabolite levels, intracellular pH and myosin isoforms were compared in isolated soleus and extensor digitorum longus (EDL) muscles from young (6 month old) and aged (28 month old) mice, at 23 degrees C. 2. The isometric force per unit cross-sectional area was significantly lower by 21 +/- 5% in soleus muscles from aged mice compared to those from young mice (mean +/- S.E.M., n = 11 and 9 respectively). 3. The EDL muscle contained twice as much total creatine and phosphocreatine as the soleus, 1.7 times as much ATP, and 0.4 times the inorganic phosphate (Pi) per unit weight. The intracellular pH and free ADP levels were not significantly different between these muscle types. 4. There was no significant difference in resting metabolite levels between young and old EDL or soleus despite the difference in mechanical strength. 5. Examination of the expression of myosin isoforms by non-denaturing gel electrophoresis has shown that the percentage of each isoform does not change with respect to age; thus, if there is an atrophic process occurring, it is not fibre type specific. 6. We have determined that neither the Pi levels nor the intracellular pH can explain the differences seen in muscle strength with age. There is also no correlation between muscle weakness and any of the other metabolites responsible for energy transduction (phosphocreatine, ATP or ADP).

The effect of metabolic fuel on force production and resting inorganic phosphate levels in mouse skeletal muscle.

1. The effect of different metabolic fuels (glucose, pyruvate and lactate) and no exogenous metabolic fuel on force production was studied in isolated mouse soleus and extensor digitorum longus (EDL) muscles. Force was measured, at 25 degrees C, during isometric tetanic contractions and during contractions with isovelocity stretching and shortening. In parallel experiments, measurements were made of the resting phosphorus metabolite levels using 31P NMR. 2. In soleus muscles, the isometric tetanic force was potentiated with pyruvate (20 mM) as metabolic fuel, compared with glucose (11 mM), by 17.8 +/- 3.6% (mean +/- S.E.M., n = 6). The force was the same with no exogenous metabolic fuel, with glucose, or with lactate as metabolic fuel. The force exerted during shortening was also potentiated by pyruvate and by the same proportion as isometric force. However, during rapid stretching there was no force enhancement with pyruvate. The changes in the force seen with pyruvate are qualitatively similar to those produced when inorganic phosphate (Pi) is lowered in skinned rabbit psoas muscle fibres. 3. We tested whether the Pi content decreased in the presence of pyruvate by measuring resting Pi using 31P NMR spectroscopy. We found that, in soleus muscles, resting Pi was present with glucose and absent with pyruvate as metabolic fuel, and the effect was reversible. 4. EDL muscles produced the same isometric force whether the metabolic fuel was glucose, pyruvate, lactate or if no exogenous metabolic fuel was supplied. EDL muscles already had Pi levels below detectability at rest in glucose. There were no changes in the 31P NMR spectrum with pyruvate as metabolic fuel. 5. It appears therefore that the force potentiation in soleus muscles with pyruvate is due to a lowering of Pi. EDL muscles, which have a very low resting Pi in glucose, therefore have very little potential for force enhancement by this mechanism.

The time course of phosphate metabolites and intracellular pH using 31P NMR compared to recovery heat in rat soleus muscle.

1. The recovery time course of changes in phosphate metabolites and pH, after tetanic contractions of 6 and 9 s were studied using 31P NMR with 4 and 16 s resolution, in rat soleus muscles at 20 degrees C. Muscles were at a sarcomere length of 3.15 microns (active), being greater than optimum for force which was 2.88 microns (active). 2. The post-contraction recovery of chemical changes was compared with the heat production in parallel experiments. Initial and recovery heat production were measured in tetanically stimulated muscles. 3. During recovery from tetanic contractions the changes in phosphocreatine (PCr) matched the changes in inorganic phosphate (Pi). The change in intracellular pH (pHi) was biphasic. The pHi first became more alkaline after contraction and then decreased until it reached a point below the baseline value. There was then a final recovery. 4. The initial heat and recovery heat production were greater than that expected from the PCr hydrolysis estimated during the tetanus and the PCr resynthesis that follows. 5. These data support the presence of 'unexplained heat' during a contraction and its related recovery processes in rat soleus muscle.

Muscle weakness in women occurs at an earlier age than in men, but strength is preserved by hormone replacement therapy.

1. The time-course of the age-related decline in specific muscle force (maximum voluntary force per cross-sectional area) in men and women was determined by measuring the maximum voluntary force and cross-sectional area of the adductor pollicis muscle in 273 subjects aged 17-90 years (176 men, 30 premenopausal women and 67 peri- or post-menopausal women who were not receiving hormone replacement therapy). 2. To determine whether the loss of specific muscle force is hormone-dependent in women, we studied a further 25 women, aged 42-72 years, who were receiving hormone replacement therapy. 3. There was no significant difference in specific force between young men and pre-menopausal women. Around the time of the menopause there was a dramatic decline in specific force in women which was prevented by the use of hormone replacement therapy. In men the weakness started later (around the age of 60 years) and the decline in specific force was more gradual, reaching the level seen in post-menopausal women after the age of 75 years. 4. The protective effect of hormone replacement therapy on muscle strength is likely to be an important contributory factor to its proven action in preventing osteoporotic fractures. The dramatic peri-menopausal decline in muscle strength is a likely explanation for the known increases in falls and Colles' fractures around the time of the menopause.

Factors influencing HIV-1 banding patterns in miniaturized western blot testing of dried blood spot specimens.

In the HIV Seroprevalence Survey among Childbearing Women (SCBW), antibodies to human immunodeficiency virus type 1 are detected using enzyme immunoassays (EIA) and Western blot (WB) methods modified to accommodate samples of blood dried on special collection paper. Dried blood spot (DBS) eluates positive by EIA are tested by one of two WB methods, the miniblot technique using equipment from Immunetics Corporation and the PBS Integra assay (pageblot) from Genetic Systems. In this report we compared the performance of the two WB methods. The identity and position of the viral proteins on the WB were identified using monoclonal antibodies and monospecific antisera. The blots differed substantially in their composition and concentration of viral glycoproteins. Performance of the WB assays with DBS elution buffers from different EIA kits was equivalent except for samples eluted in the Abbott buffer, which reduced detection of antibodies to the p31, p51, p55, and p66 viral proteins. Case classification of DBS, positive sera, dilution curve samples, and seroconversion panels was equivalent by both tests in the presence of all elution buffers. Proficiency evaluation panels sent to SCBW participating laboratories over a 3-year period were used to note the differences between the two WB methods in detection of antibodies to the viral glycoproteins.

A comparison of isometric force, maximum power and isometric heat rate as a function of sarcomere length in mouse skeletal muscle.

The isometric force, maximum power and isometric heat rate have been measured at different sarcomere lengths (SL) between 1.40 and 3.63 microns in two types of mouse muscle, soleus and omohyoideus, at 25 degrees C. The SL force relationship is different in the two muscles. At a SL above optimum filament overlap, 2.44 microns in omohyoideus muscles, maximum power declined while isometric force remained high. In soleus muscles this occurred above a SL of 2.33 microns. In parallel experiments, the isometric heat rate declined linearly with increasing SL above 2.33 microns in soleus muscles, while isometric force remained closer to its maximum. At short SL, between 2.33-1.75 microns in soleus and 2.44-2.15 microns in omohyoideus, maximum power remained at or near its maximum value as did heat rate (soleus) while isometric force fell. In both muscles at SL greater than optimum for force development maximum power output (unlike force) is proportional to filament overlap. The variation in heat rate over this SL range can be described as the sum of constant rate and a rate proportional to filament overlap. These observations are compatible with the idea that maximum power and heat rate are less affected by non-uniformities in SL than is force.

The weakness of old age is not due to failure of muscle activation.

Maximum voluntary force and cross-sectional area (MVF and CSA) of the human adductor pollicis muscle were compared in groups of young (19-55 years, mean = 28, n = 53) and elderly (74-90 years, mean = 80, n = 39) subjects, of both sexes. Despite the elderly subjects being in good health and active outdoors, they were considerably weaker than the young subjects, their MVF/CSA being 26 +/- 3% (mean +/- SEM) lower. It was found that both young and elderly subjects could fully activate their muscles. Therefore the muscle weakness of old age does not appear to be due to reduced activation and must be caused by another mechanism, possibly biochemical in nature.

In mice, the muscle weakness due to age is absent during stretching.

1. The contractile force was compared in isolated soleus muscles from young (2.5-8 months old) and aged (28-31 months old) mice. Force was measured at 25 degrees C during isometric tetanic contractions during isovelocity stretching and shortening contractions. 2. The normalized isometric force was lower by 13.3% in muscles from aged mice. Muscles from young and aged mice produced 0.951 +/- 0.031 N mg-1 (n = 12) and 0.824 +/- 0.048 N mg-1 (n = 9) respectively. The relaxation time, from 90 to 10% of the tetanic force, of muscles from aged mice was 102.1 +/- 3.7 ms (n = 6), which was longer than that for muscles from young mice, 84.4 +/- 3.8 ms (n = 6) (means +/- S.E.M.). 3. The force during shortening was also reduced in muscles from aged animals by the same proportion as the isometric force. Therefore the force during shortening relative to the isometric force was the same in muscles from young and aged mice. 4. During rapid stretching soleus muscles from aged mice produced a similar force to those from young mice. Therefore stretch can remove the weakness in muscles of aged mice. 5. These changes in muscles from aged mice are similar to those produced when inorganic phosphate (Pi) levels are raised, in skinned rabbit psoas fibres, or during fatigue or with low intracellular pH (pHi), in frog muscle. It is possible therefore that the force loss due to ageing may be due to a higher Pi level or a lower pHi.

Micromethod for assaying reverse transcriptase of human T-cell lymphotropic virus type III/lymphadenopathy-associated virus.

A micromethod for assaying the reverse transcriptase enzyme of human T-cell lymphotropic virus type III/lymphadenopathy-associated virus in cocultures of clinical specimens for viral isolation was developed and compared with the macromethod in use. Ultracentrifuged, pelleted, and solubilized viral culture supernatants were transferred into either tubes (macromethod) or microtiter plates (micromethod) and incubated with tritiated enzyme substrate. Trichloroacetic acid-precipitated DNA was collected on individual filter papers with a Millipore filtration manifold (macromethod) or on filter sheets using a semiautomated cell harvester (micromethod). Filters were then placed in scintillation fluid and counted on a beta scintillation counter. Results of the micromethod significantly correlated to those of the macromethod, with a linear relationship between the two. The cutoffs for positivity based on the mean + 2 standard deviations for a set of known negative specimens (n = 19) was 4,973 cpm for the micromethod compared with 5,336 for the macromethod. The intrarun and interrun variations were comparable for both methods. There was a 67% increase in the maximal daily number of specimens which could be run (100 versus 60) as well as a reduction in reagent use. In summary, the micromethod utilizing a semiautomated cell harvester is comparable to the existing macromethod in accuracy and is an improvement due to savings in time and reagents.