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Biomedical subjects

R J Swanson

Publications and source records attributed to R J Swanson.

At least 19 recordsLinked to original sources
PubMed2003

Intermittent hypoxia: mechanisms of action and some applications to bronchial asthma treatment.

Being essentially cut off from the global scientific community, Ukrainian and Russian scientists have developed a new concept for the beneficial use of adaptation to artificial intermittent hypoxia in treating of many diseases. The basic mechanisms underlying intermittent hypoxic training were elaborated mainly in three areas: regulation of respiration, free radical production and mitochondrial respiration. Twenty-year experience of the application of intermittent hypoxic therapy for the treatment of chronic obstructive bronchitis and bronchial asthma allows affirming that the adaptation to this kind of hypoxia causes a significant improvement of the clinical picture or even a complete recovery. The absence of negative side effects, typically observed during drug therapy, and the stimulation of organism's general, nonspecific resistance, makes the hypoxic therapy a treatment with a future. A special note is devoted to the use of intermittent hypoxic training in industrial health care for the purpose of prophylaxis and treatment of professional diseases.

Animals↗
PubMed2000

Mechanisms of taurine antihypoxic and antioxidant action.

The study was undertaken to elucidate the effects of taurine on lipid peroxidation (LP) intensity and membrane Na+, K+-ATPase activity in a hypoxic rat model. It was shown that 3 intraperitoneal (i.p.) injections of 200 mg/kg of taurine prevented hypoxia-induced lactate accumulation and LP in brain, liver, and heart tissues and prevented the decrease of Na+, K+-ATPase activity in the liver. It is suggested that the effect of taurine on LP could be due to the taurine antiacidotic action as well as to its membrane stabilizing activity.

Animals↗
PubMed2000

Geriatric men at altitude: hypoxic ventilatory sensitivity and blood dopamine changes.

BACKGROUND: Short-term exposure to high-altitude hypoxia increases hypoxic ventilatory sensitivity (HVS) in healthy humans. Dopamine (DA) is the implicated neurotransmitter in carotid body (CB) chemoreceptor response, and the microenvironmental conditions in CB tissue are comparable to blood. Continuous DA infusion affected ventilation in animals and humans. Age-related oscillations in blood DA levels may influence peripheral chemoreflexes. OBJECTIVE: Hypoxic ventilatory responses (HVR) relative to blood DA concentration and its precursor, dihydroxyphenylalanine (DOPA) was measured in young and elderly men during short-term altitude adaptation. METHODS: Nine elderly climbers (group 1:61+/-1.4 years) and 7 young healthy subjects (group 2: 23+/-2 years) were tested at sea level on day 0, on day 3 after passive transport to 2,200 m, and on day 14 after climbing to 4,200 and 5,642 m. RESULTS: Sea level HVR in group 1 was 47% lower than in group 2, accompanied by higher blood DOPA (300%) and DA (37%) content. Initial DA and DOPA concentrations showed a negative correlation with initial HVR but a positive correlation with age. Passive transport to middle altitude (2,200 m) increased HVS, doubling HVR slopes in groups 1 and 2 and producing increased maximum expired minute ventilation during isocapnic rebreathing (29 and 28%, respectively). Day 3 2,200-meter blood DOPA content decreased by 22% in group 1 and increased by 300% in group 2. DA increased in both groups. CONCLUSION: The relationship between HVR and the reciprocal DA and DOPA values seen in both groups is associated with age, producing decreased DA receptor sensitivity and enhanced DA reuptake during adaptation to high altitude.

Adaptation, Physiological↗
PubMed1999

Human hypoxic ventilatory response with blood dopamine content under intermittent hypoxic training.

Adaptation to intermittent hypoxia can enhance a hypoxic ventilatory response (HVR) in healthy humans. Naturally occurring oscillations in blood dopamine (DA) level may modulate these responses. We have measured ventilatory response to hypoxia relative to blood DA concentration and its precursor DOPA before and after a 2-week course of intermittent hypoxic training (IHT). Eighteen healthy male subjects (mean 22.8+/-2.1 years old) participated in the study. HVRs to isocapnic, progressive, hypoxic rebreathing were recorded and analyzed using piecewise linear approximation. Rebreathing lasted for 5-6 min until inspired O2 reached 8 to 7%. IHT consisted of three identical daily rebreathing sessions separated by 5-min breaks for 14 consecutive days. Before and after the 2-week course of IHT, blood was sampled from the antecubital vein to measure DA and DOPA content. The investigation associated pretraining high blood DA and DOPA values with low HVR (r = -0.66 and -0.75, respectively), elevated tidal volume (r = 0.58 and 0.37) and vital capacity (r = 0.69 and 0.58), and reduced respiratory frequency (r = -0.89 and -0.82). IHT produced no significant change in ventilatory responses to mild hypoxic challenge (Peto2 from 110 to 70-80 mm Hg; 1 mm Hg = 133.3 Pa) but elicited a 96% increase in ventilatory response to severe hypoxia (from 70-80 to 45 mm Hg). Changes in HVRs were not accompanied by statistically significant shifts in blood DA content (24% change), although a twofold increase in DOPA concentration was observed. Individual subject's changes in DA and DOPA content were not correlated with HVR changes when these two parameters were evaluated in relation to the IHT. We hypothesize that DA flowing to the carotid body through the blood may provoke DA autoreceptor-mediated inhibition of endogenous DA synthesis-release, as shown in our baseline data.

Adaptation, Physiological↗
PubMed1999

Intermittent hypoxia alters hypoxic ventilatory responses.

Intermittent hypoxic training (IHT) shows promise for prevention and treatment of some diseases and efficiently produces great advancement in athletic training. We studied (1) hypoxic ventilatory responses (HVR) in supine and sitting positions during normobaric, isocapnic, progressive hypoxia (rebreathing technique) and (2) lung ventilation and gas exchange while breathing ambient air at rest and during 5 min of breathing 11% O2. Duel measurements were made pre- and post-15-day IHT regimen on 12 (experimental) healthy males (24.6 y.o. +/- 1.9 y.o.) and on 6 (control) healthy males (24.2 y.o. +/- 2.3 y.o.) given pseudo-IHT (p-IHT) without decreasing PiO2. IHT involved rebreathing eucapnic (chemically absorbed) air as P(ET)O2 decreased to 35 mmHg, three 6-7 min sessions, three times a day, with 10 min breaks between each session over a 15 day training period. Without IHT, HVRs were the same in sitting and supine positions at low levels of hypoxic challenge (slope one--S1: P(ET)O2 from 110-60 mm Hg) and significantly higher (by 45%) during severe hypoxia (slope two--S2: P(ET)O2 from 60-35 mm Hg). IHT caused an increase in HVR in both sitting and supine positions: S1 by 70 and 100%, S2 by 158 and 200%, maximal lung ventilation by 35 and 78%, respectively. There were no significant changes in the p-IHT group. IHT also caused enhanced respiratory reactions during sustained hypoxia (lung and alveolar ventilation increased by 36 and 22%, respectively). A striking hypoxic ventilatory sensitivity was noted in subjects with hyper-reactive breathing patterns.

Adult↗
PubMed1994

Sperm morphology as diagnosed by strict criteria: probing the impact of teratozoospermia on fertilization rate and pregnancy outcome in a large in vitro fertilization population.

OBJECTIVE: To investigate the predictive value of sperm morphology assessed by strict criteria on IVF outcome. DESIGN: Retrospective analysis of all IVF cycles (January 1987 to December 1992). MAIN OUTCOME MEASURES: All patients were assigned to one of three groups based on sperm morphology: P-pattern (< 4% normal forms), G-pattern (4% to 14% normal forms), and N-pattern (> 14% normal forms). Morphology pattern was related to other semen characteristics and IVF outcome. RESULTS: Despite corrective measures at oocyte insemination, the fertilization rate was significantly different among the three morphology groups, P < G < N. N-pattern sperm produced a mean fertilization rate over 85% regardless of low motility or concentration. In a cohort study, P-pattern cycles produced a lower implantation rate and lower ongoing pregnancy rate, independent of the lower fertilization rate. CONCLUSIONS: Strict morphology is an excellent biomarker of sperm fertilizing capacity, independent of motility and concentration. P-pattern sperm may denote a poorer prognosis for establishing a pregnancy, even after a satisfactory fertilization rate is achieved.

Adult↗
PubMed1992

The YAG laser used in micromanipulation to transect the zona pellucida of hamster oocytes.

PROBLEM: Since there has been no reported use of the YAG laser to micromanipulate oocytes, our purpose was to study whether (1) a YAG laser could be used to open the zona pellucida of hamster oocytes; (2) human sperm could reach the ooplasm and (3) under sperm penetration assay conditions, sperm would bind and penetrate the ooplasm. RESULTS: A YAG 100 laser was used at 10 W and 0.4-sec pulse width to open eight of eight ooplasm oocytes. The opening in the zonae was 0.25 to 1.0 rad (10 to 40 microns). For the initial eight oocytes and two parallel controls, the coarse appearance of the ooplasm was unchanged after 3 days. Next, in 11 of 12 manipulated oocytes, the sperm clustered at the opening of the zona. When 16 more oocytes were opened and exposed to sperm in sperm penetration assay conditions, each ooplasm bound sperm. There was no penetration noted. Each manipulation time was < 1 min. To clarify the laser effect, oocytes were exposed to laser energy then utilized as the interactive surface in the sperm penetration assay. It was found that only 20% bound sperm with no penetration. CONCLUSION: While the time factor compares favourably with other methods of zona opening, further study needs to be performed to minimize effect to the exposed oocyte.

Animals↗
PubMed1992

Fertilization and mouse embryo development in the presence of midazolam.

Mouse embryo in vitro development elucidates the effect of a pharmacologic agent on cellular differentiation. Midazolam provides conscious sedation for patients undergoing egg retrieval for in vitro fertilization and is found in patient follicular fluid. Mouse preimplantation embryo formation and development were evaluated in the presence of midazolam. Midazolam was cocultured with two-cell mouse preimplantation embryos over 72 h and injected systemically just before ovulation and coitus. Concentrations to 12.5 micrograms/mL displayed no significant toxic effects on in vitro two-cell-to-blastocyst development. Doses to 35.0 mg/kg did not prevent or impair in vivo fertilization. Midazolam has no adverse effect on in vitro development of two-cell-to-blastocyst-stage embryos nor on in vivo fertilization and cell division at concentrations approximating and exceeding those that ova are exposed to during clinical anesthesia. Midazolam is recommended for use to induce sedation in human in vitro fertilization where association with gametes and zygotes is probable.

Animals↗
PubMed1989

Hypoosmotic swelling test in the prediction of male fertility.

The hypoosmotic swelling test (HOS) is a simple test to measure the functional competence of human sperm membranes. The question is, does a relationship exist between this competence and the fertilization potential of human spermatozoa? In this study the strongest correlation (r = 0.76) was obtained between sperm swelling and sperm viability (supravital staining). Only a moderate correlation (r = 0.50) was obtained with normal sperm morphology; weaker correlations were also obtained with the sperm penetration assay (r = 0.42) and human IVF (r = 0.24). The results, therefore, indicate that the HOS test has a limited predictive value. Notwithstanding this low concordance between sperm swelling and fertilizing potential, a less than 50% HOS test threshold was seen to be a definite indicator of a male factor.

Cell Survival↗
PubMed1989

Usefulness of sperm penetration assay in fertility predictions.

The competence of the sperm penetration assay (SPA) to predict male fertility, as determined by normal sperm morphology and the fertilizing potential, as shown by human in vitro fertilization (IVF), was investigated. A significant correlation was obtained between normal sperm morphology and the SPA (phi = 0.623). A weaker correlation was however obtained with human IVF (phi = 0.397). Notwithstanding this weak association, a positive SPA (greater than 10%) was highly predictive (95%) of human IVF success. In contrast, a negative SPA (less than or equal to 10%) was associated with a high rate of false-negatives (65%). The SPA does however warn that a male factor may be present, as the mean fertilization rate of this group of patients was markedly reduced. The preincubation period for the spermatozoa did not play a major role in the predictive ability of a SPA outcome.

Female↗
PubMed1988

Extravasation. A serious complication of the split-sheath introducer technique for venous access.

The use of split-sheath introducers to place venous access catheters results in the potential for subcutaneous extravasation and tissue injury or necrosis. We present six cases that demonstrate this complication and illustrate the probable mechanism. The safe use of these catheters requires verification that blood can be aspirated from the catheter and a high index of suspicion for extravasation when symptoms develop.

Adult↗
PubMed1988

Mouse embryo quality control for toxicity determination in the Norfolk in vitro fertilization program.

Ongoing quality control is necessary as part of the maintenance and improvement of a successful human in vitro fertilization (IVF) program. Using a mouse quality-control culture system, several instrument preparation protocols were reevaluated to determine their efficiency in the control or elimination of potential toxicity. Dilute concentrations of urine and endometrial fluid were also tested. Medium rinsed through laparoscope and aspiration needles failed to support embryo development. This effect was reversed in needles that were pretreated with rinses of Dulbecco's phosphate-buffered saline. Endometrial fluid demonstrated no obvious toxic effect, but urine-exposed embryos arrested in the two-cell state. The importance of periodic evaluation of materials and their pretreatment before use in in vitro fertilization of human oocytes is essential to ensure control of potentially toxic substances.

Animals↗
PubMed1988

Predictive value of abnormal sperm morphology in in vitro fertilization.

In patients with acceptable sperm count and motility, two patterns of abnormal morphology, judged with strict criteria, were identified and described. Patients with less than 4% normal forms and less than 30% morphology index (summation of normal and slightly amorphous forms) had a fertilization rate of 7.6% of the oocytes (P pattern, poor prognosis). Patients with normal morphology between 4 and 14% had a significantly better fertilization rate of 63.9% of the oocytes (P less than 0.0001). Cases with greater than 14% normal forms fertilized within the normal range for the laboratory. By evaluating sperm morphology with the proposed strict criteria, its predictive value in in vitro fertilization is enhanced.

Female↗
PubMed1988

Corrective measures and pregnancy outcome in in vitro fertilization in patients with severe sperm morphology abnormalities.

Sperm morphology evaluated by new, strict criteria is a good predictor of outcome in in vitro fertilization (IVF). This study aimed (1) to determine whether the fertilization rate of preovulatory oocytes in patients with abnormal morphology can be improved by increasing insemination concentration at the time of IVF and (2) to evaluate the pregnancy outcome in patients with abnormal sperm morphology. Three groups were studied: (1) normal morphology, (2) good prognosis pattern, and (3) poor prognosis pattern. All other sperm parameters were normal. Group 3 had a lower overall fertilization rate, lower pregnancy rate/cycle, and lower ongoing pregnancy rate/cycle. Groups 2 and 3 showed a higher miscarriage rate, although not significantly different from group 1. By increasing insemination concentration from 2- to 10-fold, the fertilization rate in group 3 increased from 14.5% to 62.6%. However, pregnancy outcome did not improve. We conclude that patients with severe sperm head abnormalities have a lower ability to establish successful pregnancies, even though fertilization may be achieved.

Abortion, Spontaneous↗
PubMed1988

Abnormal sperm morphology and other semen parameters related to the outcome of the hamster oocyte human sperm penetration assay.

A new method for evaluation of sperm morphology using strict criteria is currently used in the andrology laboratory at the Eastern Virginia Medical School. A prospective study was designed to evaluate the following semen parameters in samples of all patients over a set period of time: sperm concentration and motility, and normal sperm morphology. These factors were correlated with results of the hamster zona-free oocyte/human sperm penetration assay (SPA). One hundred patients with a sperm concentration ranging from 2 to 219 X 10(6)/ml, a motile sperm fraction ranging from 6.9 to 87%, and normal sperm morphology ranging from 1 to 39%, were evaluated. The statistical analysis system general linear model was used to judge the influence of the different variables. There was a statistically significant relationship between the per cent of sperm with normal morphology and penetration rate in the SPA (P = 0.001). Outcome of the SPA was also correlated with in vitro fertilization, retrospectively, in 84 patients. Thirty-eight patients had an SPA less than 10%, with no fertilization in vitro in 13 patients (33.3%) and fertilization in 25 (66.7%). Forty-five had an SPA greater than 10% with fertilization in 37 (82.2%) and no fertilization in eight (17.8%) patients.

Animals↗
PubMed1988

Correlation between sperm morphology, acrosin, and fertilization in an IVF program.

Acrosin, a neutral proteinase, is located within the acrosome. The aim of this study was to evaluate acrosin concentrations in patients with severe damage of the sperm head and to determine whether acrosin concentration could predict the chances of fertilization in an IVF program. Sixty patients were accepted into this study, prospectively. The patients were divided into two groups, those with a normal morphology of less than 14% (group I, n = 33) and those with normal morphology less than 14% (group II, n = 27). All patients had a sperm concentration of less than 20 million sperm/ml and less than 30% progressively motile sperm. The acrosin assays were performed on the semen sample obtained on the day of IVF. Routine IVF insemination procedures were used, and only mature oocytes were considered. The only factor that showed a significant correlation of fertilization was normal morphology (p less that 0.01). The mean acrosin level was 73.4 /+- 38.6 mED/10 million sperm in group I and 70.9 /+- 42.7 mIU/10 million sperm in group II (no significant difference). The fertilization rate in group I was 45.4% and in group II, 77.7% p less than 0.002). Acrosin levels were not significantly different in patients with and without fertilization (72.0 /+- 42.1 and 73.6 /+- mIU/10 million sperm, respectively).

Acrosin↗