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Biomedical subjects

B J Rogers

Publications and source records attributed to B J Rogers.

At least 37 records · Page 2Linked to original sources
PubMed1994

Mutagenicity of o-anisidine to the bladder of lacI- transgenic B6C3F1 mice: absence of 14C or 32P bladder DNA adduction.

Earlier studies have established that the rodent bladder carcinogen o-anisidine (OA) gives negative results in all of the standard rodent genetic toxicity assays. In the present study, a single oral administration of the maximum tolerated dose level (750 mg/kg) of OA to B6C3F1 mice yielded negative results in 32P-post-labelling assays of bladder and liver DNA (24 h after dosing). Likewise, 14C-ring-labelled OA administered orally to B6C3F1 mice gave no evidence of DNA binding 6, 12 or 24 h later. Administration of OA (750 mg/kg) to transgenic lacI- mice (Big Blue) led to a small increase in mutation frequency (MF) in the bladder, but not in the liver. Increased MFs were observed in the bladder following 1, 3 or 10 daily doses with sampling times of 1 or 2 weeks after the final dose. However, statistical significance (P < 0.01) was only reached 2 weeks after either 3 or 10 daily administrations of OA. The positive control chemical (dimethylnitrosamine) gave a positive result (P < 0.01) in the liver, but not the bladder, 7 days after a single administration of 10 mg/kg. The possibility that OA is mutagenic and carcinogenic to the rodent bladder via formation of radical species is suggested.

Aniline Compounds↗
PubMed1993

Vertical disparities, differential perspective and binocular stereopsis.

To calculate the depth difference between a pair of points on a three-dimensional surface from binocular disparities, it is necessary to know the absolute distance to the surface. Traditionally, it has been assumed that this information is derived from non-visual sources such as the vergence angle of the eyes. It has been shown that the horizontal gradient of vertical disparity between the images in the two eyes also contains information about the fixation distance. Recent results, however indicated that manipulations of the vertical disparity gradient have no effect on either the perceived shape or the perceived depth of surfaces defined by horizontal disparities. Following the reasoning of Longuet-Higgins and Tyler, we suggest that vertical disparities are best understood as a consequence of perspective viewing from two different vantage points and the results we report here show that the human visual system is able to exploit vertical disparities and use them to scale the perceived depth and size of stereoscopic surfaces, if the field of view is sufficiently large.

Depth Perception↗
PubMed1993

Transgenic systems for in vivo mutation analysis.

Transgenic mice carrying shuttle vectors containing the lacI gene as the target permit the in vivo measurement of mutations in multiple tissues and have been used to test the mutagenic effects of several compounds. Tissue-specific and time-dependent responses have been observed, and the spectrum of mutations determined by sequencing allows analysis of the role of expression time in mutagenesis. The results obtained from sequencing analysis have demonstrated spectra paralleling those observed in alternative in vivo assays. In addition to color screening, modifications to this system have permitted direct selection for mutations in the lacI target by a variety of methods. Transgenic rats containing the same lambda/lacI shuttle vector have been developed for inter-species comparison of mutagenesis testing results, which may offer a better understanding of the specific mechanisms involved in mutagenesis at the molecular level in vivo.

Animals↗
PubMed1993

Anisotropies in the perception of stereoscopic surfaces: the role of orientation disparity.

We measured stereoscopic slant detection thresholds for surfaces slanting about a horizontal or a vertical axis. For random-dot covered surfaces, 1.25 deg of slant was required to detect slant about a horizontal axis, whereas 2.1 deg of slant was required to detect slant about a vertical axis. This anisotropy could be due to the fact that orientation disparities, which contain information about surface slant, are generally smaller for surfaces slanting about a vertical axis. To test this possibility, slant thresholds were measured for surfaces whose orientation disparity content was manipulated independently of the other slant information present. When the magnitude of orientation disparity was the same for surfaces slanting about a horizontal and a vertical axis, both surface orientations required about 1.5 deg of slant to be detected; thus the anisotropy became negligible. In contrast, when the orientation disparity content of a surface slanting about a vertical axis was zero, 3-4 deg of slant was required for detection; thus the anisotropy became larger. Under the conditions of these experiments, it appears that the visual system utilizes orientation disparities.

Depth Perception↗
PubMed1993

New depth to the Müller-Lyer illusion.

It is demonstrated that when the two halves of the Müller-Lyer illusion are shown separately to the two eyes this can result in a perception of the binocularly viewed shaft as slanted in depth. For short fin lengths, the magnitude of this slant can be predicted by the extent of the ordinary two-dimensional illusion. This result is discussed in relation to Julesz's claim that stereoscopic matching of the images in the two eyes must precede whatever process is responsible for the Müller-Lyer illusion (whereas the reported illusion seems to imply the reverse). The cyclopean Müller-Lyer demonstration on which Julesz's argument is based is reexamined. It is suggested that the matching of coarse-scale features in the images in the two eyes may help to explain both the cyclopean and the reported three-dimensional Müller-Lyer illusion.

Depth Perception↗
PubMed1993

The relationship of psychological adjustment to perceived family functioning among African-American adolescents.

The Family-of-Origin Scale for adolescents (FOS) is a 40-item ten subscale instrument designed to assess perceived psychological health in the respondent's family. To date, the FOS has been used exclusively with white adolescents. The FOS was administered concurrently with the Langner Symptom Survey (LSS), a measure of adjustment, to 135 African-American adolescents. The LSS exhibited moderate, yet significant, correlations with the FOS: A total score, two superordinate dimensions, and six subscales. The results lend modest support for the construct validity of the FOS.

Adaptation, Psychological↗
PubMed1992

Visual and nonvisual information disambiguate surfaces specified by motion parallax.

Motion parallax has been shown to be an effective and unambiguous source of information about the structure of three-dimensional (3-D) surfaces, both when an observer makes lateral movements with respect to a stationary surface and when the surface translates with respect to a stationary observer (Rogers & Graham, 1979). When the same pattern of relative motions among parts of the simulated surface is presented to a stationary observer on an unmoving monitor, the perceived corrugations are unstable with respect to the direction of the peaks and troughs. The lack of ambiguity in the original demonstrations could be due to the presence of (1) non-visual information (proprioceptive and vestibular signals) produced when the observer moves or tracks a moving surface, and/or (2) additional optic flow information available in the whole array. To distinguish between these two possibilities, we measured perceived ambiguity in simulated 3-D surfaces in situations where either nonvisual information or one of four kinds of visual information was present. Both visual and nonvisual information were effective in disambiguating the direction of depth within the simulated surface. Real perspective shape transformations affecting the elements of the display were most effective in disambiguating the display.

Adult↗
PubMed1991

Combined administration of a gonadotropin-releasing hormone antagonist and testosterone in men induces reversible azoospermia without loss of libido.

GnRH antagonists suppress pituitary and gonadal function by competing with endogenous GnRH for binding to receptors on pituitary gonadotrophs. We studied the effects of GnRH antagonist administration to men in a protocol simulating a likely male contraceptive regimen combined with a low dose of testosterone. The GnRH antagonist Nal-Glu was given daily (10 mg, sc) for 20 weeks to eight normal men, and a low dose of testosterone enanthate (25 mg, sc) was given every week. Sperm counts started declining during week 4, and complete azoospermia was reached within 6-12 weeks in six of the eight subjects. Subjects 7 and 8, whose sperm counts and serum gonadotropin levels were not suppressed after 10 weeks, were given 20 mg Nal-Glu starting at week 10. One became azoospermic at week 16, while the other's total sperm counts continued declining and reached a nadir of 1.4 million by week 20. Sperm motility and viability in this subject were completely suppressed after week 14. Sperm counts returned to baseline levels 12-14 weeks after the end of Nal-Glu administration. The mean serum LH level of the first six subjects decreased from 3 +/- 03. U/L at baseline to less than 0.1 U/L until week 20, and then levels returned to baseline. FSH levels similarly decreased from a combined mean of 3.6 +/- 0.9 U/L at baseline to below 0.3 U/L after 4 weeks of Nal-Glu administration. Serum mean testosterone levels between weekly injections of testosterone enanthate ranged from 27.4 +/- 5.9 to 4.8 +/- 1.4 nmol/L, but remained in the hypogonadal range (less than 10 nmol/L) for 4 of the 7 days. None of the subjects, however, complained of decreased libido or potency, as assessed by a questionnaire. No systemic or significant local side-effects were observed, other than a minimal reaction at the injection site. These data suggest that complete sustained azoospermia can be achieved in man, without loss of libido, by chronic administration of a GnRH antagonist plus testosterone.

Adult↗
PubMed1990

Prediction of human sperm penetrating ability using computerized motion parameters.

The sperm penetration assay (SPA) is used to assess male fertilizing potential but it is tedious and costly. Computer analysis could replace the need for the SPA in some cases, if computerized sperm motility parameters are highly predictive of SPA performance. The objective of this study was to determine whether computerized motility parameters from fresh semen samples could be used to predict SPA performance. Computer automated semen analysis (CASA; CellSoft, Cryo Resources) was used to quantitate sperm concentration (CONC), percent motility (MOT), curvilinear velocity (VEL), linearity of swimming trajectory (LIN), mean amplitude of lateral head displacement (ALH), and beat/cross frequency (B/CF). The SPA was performed using either Biggers, Whitten, and Whittingham's medium (BWW) or TEST-yolk buffer (TYB). Patients were divided into three groups depending on SPA performance: group 1, BWW-treated, 0% versus greater than 0% penetration; group 2, TYB-treated, 0% versus greater than 0% penetration; and group 3, TYB-treated, less than 20% versus less than or equal to 20% penetration. SPA performance was highly correlated with CONC, MOT, VEL, and B/CF. CONC, MOT, VEL, and B/CF were significantly higher for patients who penetrated in the SPA than for those who failed to penetrate. Discriminant function analysis (DFA) successfully classified 76% of all patients treated with TYB (group 2) who penetrated and 86% of nonpenetrators based on their computerized motility parameters. For group 2 DFA predicted that 93 men would penetrate in the SPA with TYB. Of these, 90 (97%) successfully penetrated at least one egg.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

The use of gonadotropin releasing hormone agonist (GnRHa) in good responders undergoing repeat in vitro fertilization/embryo transfer (IVF/ET).

The use of gonadotropin releasing hormone agonists (Gn-RHa) has been shown to improve the response in patients classified as "poor responders" undergoing ovarian stimulation for in vitro fertilization/embryo transfer (IVF/ET). This study sought to determine whether GnRHa therapy would benefit patients undergoing IVF/ET who had been classified as "good responders" in prior attempts. Twenty-three patients who had completed a prior IVF/ET attempt but who failed to conceive underwent ovarian stimulation using a combination of GnRHa and human menopausal gonadotropin (hMG). Each patient's prior stimulation served as her control and consisted of clomiphene citrate (CC)/hMG in 18 patients and follicle stimulating hormone (FSH) and/or hMG in 5 patients. The numbers of oocytes retrieved, oocytes fertilized, embryos cleaved, and embryos transferred were all significantly greater in cycles treated with GnRHa/hMG compared to control cycles. The clinical pregnancy rate was 39% and the ongoing pregnancy rate was 26% during the cycle when GnRHa pretreatment was utilized. These data suggest that GnRHa therapy is of benefit even to those patients previously classified as "good responders" undergoing ovarian stimulation for IVF/ET.

Adult↗
PubMed1990

The efficacy of cryopreserved hamster ova in the sperm penetration assay.

To solve the logistical problems of the sperm penetration assay (SPA) to provide just a sufficient number of hamster ova exactly when they are needed, a new method to cryopreserve the ova has been devised. The ova, suspended in a 1.5 M solution of propylene glycol as a cryoprotectant in an isotonic salt solution, were frozen in 1/4 mL plastic straws. Included in each straw was a sucrose solution, isosmotic to the propylene glycol solution, to serve as an osmotic buffer during dilution of the cryoprotectant out of the ova. This one-step method of dilution permitted the ova to be recovered and diluted out of the cryoprotectant within the straw in which they had been originally frozen. A total of 547 cryopreserved ova were thawed, 504 (92.1%) of which were morphologically normal after they had been incubated at 37 degrees C for 3 hours. After removal of the zonae, the frozen-thawed ova were compared with fresh, control ova in SPAs of donor and patient semen that had been capacitated in TEST-yolk buffer. The percent penetration and penetration index of fresh versus cryopreserved ova did not differ significantly for either donor or patient semen.

Analysis of Variance↗
PubMed1990

Establishment of TEST-yolk buffer enhanced sperm penetration assay limits for fertile males.

TEST-yolk buffer has been shown to enhance sperm penetration of zona-free hamster eggs. Review of sperm penetration assay (SPA) data from a fertile population was undertaken to determine a normal range for SPA with TEST-yolk buffer enhancement. Thirty-eight intrauterine insemination patients and 4 artificial insemination donors who had successfully initiated a pregnancy within 18 months of SPA analysis were examined. All 42 enhanced SPAs demonstrated penetration of greater than 10%, and 37 of these (88%) yielded SPA values of greater than or equal to 20%. Thirty-three percent (14/42) of these individuals achieved 0% penetration in the SPA without TEST-yolk buffer. The SPA performed with the TEST-yolk modification has fewer false negatives than the assay done with the original methodology.

Animals↗
PubMed1990

Importance of glycolysable substrates for in vitro capacitation of human spermatozoa.

To investigate the importance of glycolysable substrate for supporting the ability of human sperm to capacitate and penetrate oocytes in vitro, washed spermatozoa were incubated with or without various sugars in BWW culture medium containing pyruvate and lactate. Sperm penetration was assayed using zona-free hamster oocytes. After an 18-h preincubation, glucose (1 mg/ml) supported higher penetration of sperm into oocytes than either mannose or fructose (60.7% vs. 28.2% or 21.5%, respectively) at the same concentration. Penetration was even lower when medium contained the nonmetabolizable sugar galactose (2.1% at 1 mg/ml). On the other hand, higher concentrations (5 or 10 mg/ml) of glucose, but not fructose, suppressed penetration, provided the glucose was present throughout the 18-h preincubation. When caffeine, a stimulant of glycolysis in human sperm, was present along with glucose, sperm penetration was enhanced, but only after 6 h of sperm preincubation. This effect was not observed in glucose-free medium, however, where penetration remained low over a 10-h incubation period. In these experiments, the percentage of motile sperm was unaffected by treatment, but the quality of motility was diminished in the absence of glucose. We conclude that stimulation of glycolysis may promote capacitation of human spermatozoa in vitro and that optimization of penetrating ability of sperm is dependent upon both the type and concentration of glycolysable sugar present.

Animals↗
PubMed1989

Luteinizing hormone and ovulation timing in a therapeutic donor insemination program using frozen semen.

A series of 110 therapeutic donor insemination cycles was analyzed to determine the impact on fecundity when a urinary luteinizing hormone detection kit was used to plan inseminations. To prevent the transmission of human immunodeficiency virus, frozen semen, thawed after a 90-day quarantine, was used. The minimum standard for insemination with cryopreserved semen was a total of 24 x 10(6) motile sperm per milliliter after thawing. Fecundity was 0.12 when insemination timing was based on cervical mucus evaluation and basal body temperature charts and 0.13 when a urinary luteinizing hormone kit was also used to predict ovulation. Life table analysis with the log rank test showed no statistically significant difference in the number of cycles required to achieve conception between the group of patients using conventional methods of ovulation timing and the group of patients using the urinary luteinizing hormone kit. Urinary luteinizing hormone testing offers no advantage over conventional methods, such as cervical mucus examination and evaluation of basal body temperature, when ovulation is being timed for insemination with frozen donor semen.

Acquired Immunodeficiency Syndrome↗
PubMed1989

The human blastocyst produces a soluble factor(s) that interferes with lymphocyte proliferation.

Animal studies have reported that the blastocyst produces immunosuppressive factors that are critical to successful implantation. The production of such factor(s) by the human blastocyst has not yet been described. To test that hypothesis, the spent media of 67 human embryos developed in vitro was evaluated using either the allogeneic one-way mixed lymphocyte response (MLR) or the concanavalin A (Con-A) stimulated lymphocyte response (SLR). Conditioned embryo media was obtained at in vitro fertilization (IVF) in aliquots of (A) the first 24 hours in vitro, (B) the second 24 hours in vitro, and (C) from 24 hours until development of the blastocyst stage. Control media consisted of Ham's F-10 medium (Gibco, Grand Island, NY) with identical maternal serum concentration to test media. Conditioned media (either A, B, or C) or control media was added to 200-microL wells containing lymphocytes in either the MLR or SLR. A significant suppressive effect of 25% to 60% was observed in seven of nine samples of blastocyst-conditioned media (P less than 0.05). No significant suppressive effect was found in the earlier embryo media (A or B) in either the MLR or the SLR. These data suggest that the human blastocyst produces a factor(s) that interferes with lymphocyte proliferation.

Blastocyst↗
PubMed1989

The influence of oocyte maturity and embryo quality on pregnancy rate in a program for in vitro fertilization-embryo transfer.

An important factor influencing the pregnancy rate after in vitro fertilization-embryo transfer (IVF-ET) appears to be the number of embryos transferred to the uterus. In this study, the influence of oocyte maturity and embryo quality on pregnancy rate was assessed in patients undergoing IVF-ET. Ovarian hyperstimulation was performed by human menopausal gonadotropin (hMG [n = 29]), clomiphene citrate (CC)/hMG (n = 81), and hMG/follicle-stimulating hormone (FSH [n = 13]) protocols. Oocyte maturity was graded on a scale from 1 to 5 based on the morphology of the ooplasm, cumulus mass, corona radiata, and membrana granulosa cells. Embryos were graded according to the symmetry of the blastomeres and the presence or absence of fragmentation. Mature preovulatory oocytes yielded the highest fertilization rates. No differences were found among the protocols in terms of fertilization rate, embryo quality, or pregnancy rate. When all protocols were combined, patients who conceived had a significantly higher number of embryos transferred than those who did not conceive (3.6 +/- 0.1 [mean = SEM] versus 2.7 +/- 0.1). When embryo quality was compared, there was no difference in the number of "B" embryos transferred between patients who conceived and those who did not (1.2 +/- 0.2 versus 1.2 +/- 0.1), but the patients who conceived had significantly more "A" embryos transferred (1.6 +/- 0.3 versus 0.8 +/- 0.1). These data suggest that the treatment protocol did not determine embryo quality. Furthermore, the increase in pregnancy rates seen with an increase in embryos transferred is the result of the transfer of more "A" embryos.

Blastomeres↗