The overall impact of recently developed foods on the dietary habits of adolescents.
Explore the source record for details and available documents.
Adolescent↗
Biomedical subjects
J M Rees
Publications and source records attributed to J M Rees.
Weight gain in adolescents during pregnancy: rate related to birth-weight outcome.
This study of 459 subjects from prenatal clinics for teenagers at three universities across the United States, addresses questions about gestational weight gain in adolescents raised by the 1990 Institute of Medicine Report. Rate and pattern of gain, independent of pregravid weight, are based on serial measures of mothers with favorable and unfavorable outcomes. Rate of gain (determined by using regression statistics) from weeks 15 to 40 was 0.588, 0.510, and 0.488 kg/wk for mothers of term infants weighing 3000-4000 g, term infants weighing < 3000 g, and preterm infants, respectively. The significantly lower percentage of infants weighing 3000-4000 g vs < 3000 g needing intensive care at birth (6% vs 15%, respectively, P < 0.05) further indicates the superior outcome among mothers with higher rates of gain. Rate of gain of mothers of infants weighing 3000-4000 g (favorable outcome) equaled the highest amount provisionally recommended, suggesting that restricting natural gain of adolescents to recommended rates may result in smaller than optimal infants.
Adolescent↗
The yield, motility and performance in the hamster egg test of human spermatozoa prepared from cryopreserved semen by four different methods.
Different procedures were investigated for the dilution of human cryopreserved semen and the preparation of an enriched population of motile spermatozoa for assisted reproduction. The dilution of a 0.25 ml straw of cryopreserved human semen by addition of 2.0 ml Ham's F-10 buffer in one step caused a large decrease in the proportion of motile spermatozoa. This was due to osmotic stress because many of the diluted spermatozoa exhibited swollen tails. To a large extent the damage could be avoided by adding the buffer in 0.10-ml aliquots at 30-s intervals. Spermatozoa obtained after such dilution of cryopreserved human semen were subjected to the swim-up procedure, to centrifugation on two-step gradients of Nycodenz or Percoll, or to filtration through glass fibre paper and compared with respect to yield, motility parameters and penetrating ability in the hamster egg test. The swim-up procedure yielded spermatozoa with excellent motility but only 12% of the available motile spermatozoa were recovered. On both Nycodenz and Percoll gradients, greater than 40% of the available motile spermatozoa were recovered and the average velocity of the spermatozoa was not significantly less than for the swim-up technique. When A23187 was used to promote acrosome reactions in the hamster egg test, Percoll-prepared spermatozoa achieved an average of 8.6 decondensed sperm heads/egg compared to 1.9 for Nycodenz and 1.3 for the swim-up procedure. The yield from glass fibre paper filtration was only 12% and the velocity of the spermatozoa and their performance in the hamster egg test was significantly poorer than in all the other methods.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Controlling the swimming speed of human sperm by varying the incubation temperature and its effect on cervical mucus penetration.
The objective of the present experiments was to study the effect of sperm velocity as a single variable on the ability of sperm to penetrate cervical mucus in a modified Kremer test. Sperm incubated at 13, 22 and 37 degrees C exhibited progressive velocities of 25 +/- 1.7, 40 +/- 2.1 and 56 +/- 2.1 microns sec-1 (mean +/- SEM, n = 6) respectively, but the percentage of progressively motile sperm, their lateral head displacement and the viscoelastic properties of cervical mucus remained comparatively unchanged over this temperature range. The number of sperm which penetrated the mucus and the percentage of successful collisions were correlated strongly with the average velocity of the sperm population (r = 0.82 and r = 0.72 respectively). It is concluded that sperm velocity has an important influence on the penetration of cervical mucus because it governs the frequency of collisions with the mucus interface and is determined by the thrust generated by the flagellum which also determines the ability of the sperm to traverse the mucus interface.
Cervix Uteri↗
The cost of burn care and the federal government's response in the 1990s.
This article attempts to predict the federal government's response to the cost of burn care in the 1990s by examining the explosive growth of health care costs in the 1980s and the impact that this had on hospitals with burn centers. The Prospective Payment System (PPS) was enacted in 1983, which limited the government's liability to hospitals by effectively capping the amount of federal dollars in the system. The inequities of the classification of burn patients by the PPS is discussed and a proposal for modification is outlined.
Burn Units↗
The effect of A23187 concentration and exposure time on the outcome of the hamster egg penetration test.
We investigated the conditions required to enhance the performance of human sperm in the hamster egg penetration test with the free acid form of A23187. The best performance was observed after stimulation with 2 microM A23187 for 1 h when the median penetration rate with sperm from fertile donors was 100% of eggs with 5.8 decondensed sperm heads/egg. Extending the stimulation period with 2 microM A23187 to 2 or 3 h, resulted in a progressive decrease in the penetration rate. In the absence of A23187, the penetration rate was lower (0.7 decondensed sperm heads/egg after 1 h) but increased with stimulation time. A similar picture was observed with sperm from patients taken for an IVF programme. For a pool of cryopreserved semen, the coefficient of variation of the penetration rate after stimulation with 2 microM A23187 for 1 h, expressed as decondensed sperm heads/egg, was 11% within and 20% between assays. There was no correlation between the outcome of the hamster egg penetration test and the percentage motility, velocity or lateral head displacement of the sperm measured after the same stimulation regime. However, in IVF patients the initial velocity and lateral head displacement of the sperm (zero time) were correlated with the best result from the hamster egg penetration test (r = 0.62 and 0.57 respectively). No motility changes characteristic of capacitation were detected. We conclude that stimulation with 2 microM A23187 (free acid) for 1 h prior to the addition of the zona free hamster eggs can produce a high penetration rate with fertile samples and provides a convenient and robust protocol for the assay. However, when carried out in this way the test does not assess the ability of the sperm to capacitate.
Acrosome↗
Management of obesity in adolescence.
A great deal of the discouragement about treating adolescents who are obese is related to the traditional treatment approaches. Obesity is a complex problem needing comprehensive treatment. Focusing on weight loss as a short-term goal is unreasonable because of individual variation in the physiologic potential to lose weight. Short-term goals and rewards are related to adopting daily habits that will lead to a decrease in energy storage in the long term. Support for changing habits and improving psychosocial adjustment is a necessary component of effective treatment, enabling patients and their families to make changes.
Adolescent↗
Effect of caffeine and of pentoxifylline on the motility and metabolism of human spermatozoa.
Human spermatozoa were washed and incubated with 6 mM-caffeine or 0.15-1.2 mM-pentoxifylline. Sperm motility was measured by time-lapse photography, the rate of glycolysis by the release of tritiated water from 1 mM-[3-3H]D-glucose and the rate of mitochondrial respiration by the release of 14CO2 from 1 mM-[U-14C]-L-lactate or 1 mM-[2-14C]pyruvate. Caffeine stimulated the majority of spermatozoa to convert from the 'rolling' to the 'yawing' mode of progression with a concomitant increase in lateral head displacement from 4.1 +/- 0.09 microns (343) to 6.7 +/- 0.25 microns (105) (mean +/- s.e.m. (number of spermatozoa)). There was a 45% decline in the percentage of progressively motile spermatozoa and a very small decrease in their velocity. Pentoxifylline had only a slight effect on lateral head displacement or percentage motility but produced a significant increase in velocity. Both compounds increased the rate of glycolysis by greater than 40% but elevated the rate of 14CO2 production to a smaller extent. The concentrations of ATP and ADP changed very little. We conclude that the glycolytic pathway in human spermatozoa can respond efficiently to changes in energy demand.
Adenosine Diphosphate↗
An evaluation of the role of relaxin in the penetration of cervical mucus by spermatozoa.
Relaxin-like immunoreactivity was measured in seminal plasma from men who were separated into two groups, on the basis of a previous positive or negative result in a postcoital cervical mucus penetration test. There was no difference in the relaxin concentration between the groups. The effect of exogenous porcine relaxin (0, 10 or 100 ng/ml) on human cervical mucus penetration in vitro by washed human spermatozoa was studied using a capillary tube preparation. In the positive postcoital test group the highest relaxin concentration (100 ng/ml) tended to inhibit cervical mucus penetration, although this effect was only significant for one of the parameters measured (number of spermatozoa penetrating to the 10-mm mark). The same trend was apparent for the negative postcoital test group, but no differences were significant. The results are in direct contrast to previous reports that relaxin can stimulate human spermatozoa motility and cervical mucus penetration.
Cervix Mucus↗
Identification of relaxin in the placenta of the ewe.
Sheep placentomes were collected at the abattoir and the stage of gestation was estimated from the crown-rump length and appearance of the fetus. Samples were extracted and either freeze dried (crude extracts) or fractionated on Sephadex G-50 and CM-cellulose. Relaxin immunoreactivity (RXN-IR) was detected in all samples by a pig relaxin RIA and diluted in parallel with the standard curve. Two patterns of RXN-IR were seen after Sephadex G50 purification: (a) a single main peak of RXN-IR eluting at a position similar to pig relaxin; or (b) a 3-peak pattern with additional higher (void volume) and lower (approximately 1000) molecular weight peaks. These peaks were all found with 4 different and specific antisera. The 6000 molecular weight peak eluted at a similar position to pig relaxin on CM cellulose and inhibited electrically stimulated rat uterine contractions in vitro. The amount of relaxin measured in crude extracts of placentomes from different ewes was very variable. Most samples were within the range 0.05-11.2 ng/g wet weight of tissue (3.0 +/- 0.45 (s.e.m.), n = 44) but a few contained much higher concentrations (25.5-61.4 ng/g, n = 3). There was no obvious variation in concentration with stage of pregnancy (20 days to term). Samples of intercotyledonary endometrium, allantochorion and whole ovaries from pregnant ewes were also extracted. All contained low concentrations of RXN-IR (0.6 +/- 0.13 ng/g, n = 4; 0.6 +/- 0.29 ng/g, n = 3; 1.0 +/- 0.66 ng/g, n = 7, respectively). We conclude that relaxin-like peptides are present in the pregnant ewe and that, as the placentomes are the largest component by weight, they represent the major source.
Animals↗
The role of mean corpuscular haemoglobin concentration in limiting the storage life of human blood.
Human erythrocytes stored for more than 21 days in citrate phosphate dextrose with adenine (CPDA-1) at +4 degrees C had a decreased cell volume, an increased cell density, an elevated mean corpuscular haemoglobin concentration (MCHC) and hence an elevated internal viscosity. These changes are normally masked by the reversible cell swelling which accompanies storage in CPDA-1. Incubation of stored cells for 24 h at 37 degrees C in fresh autologous plasma mimics the effects of reinfusion and causes the artificially swollen cells to shrink to their true volume. Thus, incubated cells which had been stored in CPDA-1 for more than 21 days exhibited a decreased filterability through Nuclepore membranes in vitro, which is apparently correlated with a decreased survival time in vivo.
Adenine↗
The use of nystatin to restore the flow properties of time-expired stored erythrocytes.
Human erythrocytes stored for more than 21 days in citrate phosphate dextrose with adenine (CPDA-1) exhibited a marked reduction in volume following incubation for 24 h at 37 degrees C in fresh autologous plasma. This incubation apparently mimics the effects of reinfusion of the stored cells in vivo. These shrunken stored cells have a decreased filterability as measured by their increased transit times through a 5-microns diameter Nuclepore filter. The polyene antifungal agent nystatin was used to reinflate these shrunken cells with different concentrations of potassium ions. A concentration of 90 mM potassium chloride was found to reinflate the shrunken stored cells so that their mean cell volume, mean corpuscular haemoglobin concentration and average densities were the same as those of fresh cells. This reinflation also restored the filterability of the shrunken stored cells so as to be similar to that of fresh cells.
Adenine↗
The effects of reinflation on the survival of time-expired stored rabbit erythrocytes in vivo.
Rabbit blood cells stored for prolonged periods in citrate phosphate dextrose with adenine (CPDA-1) at +4 degrees C show the same decreased volume, increased cell density and decreased filterability as human cells stored under similar conditions. As with human erythrocytes, the stored rabbit cells had to be incubated with autologous fresh plasma for 24 h at 37 degrees C before these changes could be observed (this incubation process apparently mimics the effects of reinfusion). These shrunken stored rabbit cells could also be reinflated using nystatin, so that their mean cell volume, mean corpuscular haemoglobin concentration, average cell densities and filterabilities were restored to normal values. This in vitro reinflation of the stored cells significantly prolonged their in vivo survival rate as determined by radiochromium labelling studies. This reinflation technique may therefore have an application in the prolongation of the useful storage life of human blood.
Adenine↗
Health, developmental, and nutritional status of adolescent alcohol and marijuana abusers.
The impact of alcohol and marijuana abuse on the physical health and nutritional status of adolescents has not been well documented. The health consequences of alcoholism and chemical abuse in adults may not relate to the pediatric population. Forty-nine adolescent boys (mean age 15.8 years) with varying degrees of alcohol and marijuana use by self-report were evaluated as to their general health, pubertal development and nutritional status using health and dietary history, physical examination, anthropometrics, and biochemical assays of liver function and tissue nutrients. Thirteen (27%) were alcohol and marijuana abusers, 20 (41%) marijuana abusers, and 16 (32%) nonusers. There were significant differences between alcohol and marijuana abusers and marijuana abusers compared to nonusers with respect to endorsing symptoms of nutritional deficiency (muscle weakness, bleeding gums, tiredness, etc) (P less than .001). There were no significant differences between subgroups in other nutritional measures except plasma zinc concentration which was low in marijuana abusers (mean 85 micrograms/dL). All adolescents reported consuming adequate nutrients, although alcohol and marijuana abusers reported eating more snack foods and less fruit, vegetables, and milk than other groups. There were no significant differences in hematologic status (complete blood cell count, transferrin, folate), liver function (gamma-glutamyltranspeptidase), or anthropometric and sexual maturational indices of growth. There were no chronic signs of chemical abuse by physical examinations. It appears that health and nutritional disability from chemical abuse in adolescents relates more to poor dietary habits and symptomatic deterioration in general health than to specific effects on growth or nutritional status. Studies with larger numbers of subjects need to document these findings.
Adolescent↗
Identification of relaxin immunoreactivity in human follicular fluid.
Relaxin immunoreactivity has been found in samples of human follicular fluid collected from artificially stimulated pre-ovulatory follicles. The crude extract caused a reduction in the height of the contractions in a rat uterine strip bioassay. The reactive material eluted from Sephadex G50 in two major peaks. The first contained approximately 60% of the immunoreactivity and had an elution position corresponding to that of porcine relaxin, indicating a mol. wt of approximately 6000 daltons. The second peak was of a lower mol. wt, but its exact size and significance are unknown. A possible role for relaxin in the process of follicular rupture is suggested.
Biological Assay↗
The effects of 50 Hz magnetic fields on opioid peptide mediated inhibition of guinea pig ileum.
Strips of guinea pig ileum were mounted in a tissue bath within the poles of a magnet capable of generating a 50 Hz field of intensity up to 1 mT. In the absence of magnetic field the preparations were stimulated transmurally at tetanic frequency (10 Hz). The post-tetanic inhibition was antagonised by naloxone. When this inhibitory phase was repeated in the presence of a magnetic field of 0.5 mT there was a small but significant increase in the inhibition when compared with paired controls.
Animals↗
Changes in plasma opioid concentrations after physiotherapeutic exercises for arthritic patients.
Plasma concentrations of [met]enkephalin (ME) and beta-endorphin (beta E) were measured in samples obtained immediately before and after physiotherapeutic exercises for patients with ankylosing spondylitis (AS), osteoarthritis (OA), or knee injuries. Correlations were sought between opioid peptide concentrations or changes therein, and nature, severity and duration of disease, age, severity of pain reported and pain threshold. No correlation was found with any of the pain parameters. However, there was a possible relationship between age or duration of disease and changes in ME concentrations.
Adult↗