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Biomedical subjects

B J Rogers

Publications and source records attributed to B J Rogers.

At least 55 records · Page 3Linked to original sources
PubMed1989

The appearance of surfaces specified by motion parallax and binocular disparity.

The experiments reported in this paper were designed to investigate how depth information from binocular disparity and motion parallax cues is integrated in the human visual system. Observers viewed simulated 3-D corrugated surfaces that translated to and fro across their line of sight. The depth of the corrugations was specified by either motion parallax, or binocular disparities, or some combination of the two. The amount of perceived depth in the corrugations was measured using a matching technique. A monocularly viewed surface specified by parallax alone was seen as a rigid, corrugated surface translating along a fronto-parallel path. The perceived depth of the corrugations increased monotonically with the amount of parallax motion, just as if observers were viewing an equivalent real surface that produced the same parallax transformation. With binocular viewing and zero disparities between the images seen by the two eyes, the perceived depth was only about half of that predicted by the monocular cue. In addition, this binocularly viewed surface appeared to rotate about a vertical axis as it translated to and fro. With other combinations of motion parallax and binocular disparity, parallax only affected the perceived depth when the disparity gradients of the corrugations were shallow. The discrepancy between the parallax and disparity signals was typically resolved by an apparent rotation of the surface as it translated to and fro. The results are consistent with the idea that the visual system attempts to minimize the discrepancies between (1) the depth signalled by disparity and that required by a particular interpretation of the parallax transformation and (2) the amount of rotation required by that interpretation and the amount of rotation signalled by other cues in the display.

Attention↗
PubMed1989

Concurrent validation of Hutt's Bender Gestalt screening method for schizophrenia, depression, and brain damage.

The effectiveness of Hutt's Bender Gestalt scoring system in screening for schizophrenia, depression, and brain damage was investigated in a sample of mixed, psychiatric inpatients. Fifteen patients represented each diagnostic category. After an examination of each patient's Bender Gestalt protocol according to Hutt's criteria, it was found that the true positive and true negative success rates of the screening procedures for depression and brain damage were significantly higher than corresponding base rates. The Lacks Bender Gestalt screening method for brain damage was no more successful than the Hutt method in identifying true positives and true negatives. With the brain-damaged patients excluded, Hutt's screening procedures for both depression and schizophrenia resulted in significantly high rates of successful identification of true positives and true negatives. Moreover, these rates did not significantly differ from those determined by patients' Minnesota Multiphasic Personality Inventory (MMPI) T scores on corresponding scales.

Adult↗
PubMed1989

Examination of data from programs of in vitro fertilization in relation to sperm integrity and reproductive success.

This paper reviews the work of 11 different in vitro fertilization (IVF) groups from around the world in an effort to determine the effectiveness of IVF as a therapy for male factor infertility as well as threshold values for semen parameters that are synonymous with success. Two key questions that are asked are: 1) What fertilization rate is expected for male factor patients and 2) Can we predict which patients will fertilize. The immediate problem which arises in attempting to compare results from various groups is that there is no standardization in male factor criteria. This lack of agreement in what constitutes an abnormal semen sample is also reflected in the fertilization rates and threshold values. The first group reviewed (Mahadevan, 1983) suggest greater than 20% motile in the initial semen sample as a threshold value required for success while the second group (Cohen, 1985) presents 6 couples with less than 20% motility achieving pregnancy. Such inconsistencies in results are typical of this confusing and controversial area. Fertilization in IVF has been achieved with as few as 2 x 10(6) sperm/ml or as low as only 2% motility in the initial semen sample. It appears that most workers would agree that the lower limits of traditional semen parameters that are compatible with success are not well defined. Consensus might also be reached on the fact that fertilization rates are usually significantly lower in male factor cases than in normal semen parameters coupled with tubal infertility. Beyond those two factors, little agreement is found in the literature. The spectrum of methodology for semen processing is very broad and often not clearly detailed. In addition to the additional semen parameters of count, motility, and morphology, attempts have been made to establish other prognostic tests such as the sperm penetration assay (SPA), acrosome reaction determinations, and motility parameters such as velocity, linearity and lateral head displacement. Controversy abounds concerning the value of these newer tests. Threshold values for acrosome reaction and motility parameters have not been established. The SPA is believed to be highly predictive by some and unreliable by others. The one redeeming feature of this IVF male factor area is that it seems to be one of the most effect treatments for male factor infertility.

Evaluation Studies as Topic↗
PubMed1988

Use of the SPA in assessing toxic effects on male fertilizing potential.

The sperm penetration assay (SPA), which involves the use of zona-free hamster eggs to assess fertilizing potential of human spermatozoa, has the capability of evaluating the functional capacity of sperm. If men are exposed to a toxic insult that could result in impaired fertility, this has been monitored historically by determining the routine semen parameters of concentration, motility, and morphology. The lack of availability of the SPA for evaluating toxic exposure in field studies has hampered its utilization. The purpose of this article is to illustrate the use of the SPA in a specific field study and to describe two recent innovations in the SPA that make its use more accessible for field studies. These two innovations are shipping semen samples in TEST-yolk buffer by overnight express to a central laboratory for testing and using frozen hamster eggs in the test. The report is divided into the following three major sections: I. Kunia study; II. TEST-yolk buffer modifications of SPA; and III. Use of frozen eggs in SPA.

Animals↗
PubMed1988

Dynamic occlusion and motion parallax in depth perception.

Random-dot techniques were used to examine the interactions between the depth cues of dynamic occlusion and motion parallax in the perception of three-dimensional (3-D) structures, in two different situations: (a) when an observer moved laterally with respect to a rigid 3-D structure, and (b) when surfaces at different distances moved with respect to a stationary observer. In condition (a), the extent of accretion/deletion (dynamic occlusion) and the amount of relative motion (motion parallax) were both linked to the motion of the observer. When the two cues specified opposite, and therefore contradictory, depth orders, the perceived order in depth of the simulated surfaces was dependent on the magnitude of the depth separation. For small depth separations, motion parallax determined the perceived order, whereas for large separations it was determined by dynamic occlusion. In condition (b), where the motion parallax cues for depth order were inherently ambiguous, depth order was determined principally by the unambiguous occlusion information.

Attention↗
PubMed1987

Ethanol inhibits human and hamster sperm penetration of eggs.

The effect of alcohol on the fertilizing ability of both human and hamster spermatozoa was examined by an in vitro fertilization assay using hamster ova. Spermatozoa were incubated in capacitating media for 3 hr (hamster sperm) and 4 hr (human sperm). Hamster ova were inseminated with preincubated sperm and were examined after 2 to 3 hr. Ethanol was added to the capacitating media at concentrations of 25, 50, 100, 200, and 400 mg%. Fertilization of zona-free hamster eggs by human spermatozoa was reduced from 49.6% in no alcohol to 16.7% in 400 mg% ethanol. Fertilization of hamster eggs by hamster sperm revealed a reduction from 63.6% to 33.7% in cumulus-intact eggs and from 65.8% to 10.8% in cumulus-free eggs in the presence of ethanol at 400 mg%. Hamster sperm acrosome reaction was reduced from 47% to 12%. When these hamster sperm with reduced acrosome reaction were placed with zona-free hamster eggs, the 100% fertilization rate was not reduced; however, the fertilization index, which reflects the number of swelling sperm heads per egg, was reduced from 8.5 to 1.8. This suggests that as little as 12% of the sperm with an acrosome reaction is sufficient to fertilize 100% of the zona-free eggs. If ethanol was added to the insemination media only, there was no inhibition of fertilization by human sperm or hamster sperm that had been previously capacitated in an ethanol-free media. Removal of the ethanol from the preincubated sperm produced fertilization at control levels; thus the inhibitory effect is reversible. These results indicate that ethanol may affect fertilization by an inhibition of the capacitation and/or acrosome reaction process.

Acrosome↗
PubMed1987

Combination clomiphene citrate/human menopausal gonadotropin stimulation protocols for in vitro fertilization-embryo transfer.

Various protocols have been utilized for stimulation of multiple ovarian follicles in patients undergoing in vitro fertilization-embryo transfer (IVF-ET). Previous studies have suggested that the combination of clomiphene citrate (CC) and human menopausal gonadotropins (hMG) is superior to either CC or hMG alone in terms of follicular development, oocyte recovery, and embryo transfer. However, no significant increase in viable pregnancy rates has been reported with any of the protocols. This report examines five different CC/hMG protocols. While differences were seen in terms of serum estradiol response and fertilization rates of mature oocytes among the various protocols, no significant differences were found in terms of follicular development, oocyte recovery, embryo transfer, or pregnancy. The pregnancy rate in IVF-ET appears unaffected by variations in the dose and timing of CC and hMG in a combination protocol.

Adult↗
PubMed1987

Effects of photoperiod on androgen-binding protein and sperm fertilizing ability in the hamster.

Androgen binding protein (ABP) was detected in both the testis and epididymis of golden hamsters exposed to a long photoperiod (16L:8D). The concentration of ABP in the testis rose from 0.1 pmol/g testis in 2-week-old animals to attain maximum values (3.9 pmol/g testis) at 6-7 weeks, then declined to adult values (1.8 +/- 0.4 pmol/g testis) after 10-11 weeks of age. In contrast, the ABP concentration of the caput epididymidis reached maximum values at 4-7 weeks of age (14 pmol/g tissue) and declined to adult values (4.8 +/- 1.5 pmol/g tissue) by 10-11 weeks of age. ABP content of the corpus epididymidis was maximal (1.0 pmol/g tissue) at 2 weeks of age and thereafter declined to below detectable levels by 10-11 weeks. No ABP could be detected in the cauda epididymidis from animals of any age examined. Hamster ABP analysed by steady-state polyacrylamide gel electrophoresis had a relative mobility (Rf) of 0.33 compared to 0.41 for rabbit ABP. Sucrose gradient analysis of hamster ABP indicated a sedimentation coefficient of about 4 S. The binding of [3H]5 alpha-dihydrotestosterone [( 3H]5 alpha-DHT) to hamster ABP was very rapid with equilibrium occurring within 10 min. The dissociation of [3H]5 alpha-DHT from hamster ABP was also rapid (t1/2 = 2.77 min). Saturation analysis of ABP from mature animals yielded an apparent dissociation constant of 6.4 nM and an ABP concentration of 1.2 +/- 0.2 pmol/mg protein. The binding of [3H]5 alpha-DHT to hamster ABP was inhibited by 5 alpha-DHT greater than testosterone greater than greater than greater than oestradiol greater than cyproterone acetate. Exposure of mature hamsters to a short photoperiod (8L:16D) for 3 weeks resulted in a 42% drop in epididymal ABP levels (10.3 to 4.3 pmol/g tissue). Epididymal ABP further declined so that after 15 weeks in a short photoperiod it was 4% (0.4 pmol/g) of initial values. Accompanying this decrease in epididymal ABP concentrations was a decline in the fertilizing ability of spermatozoa from the distal cauda. When hamsters were transferred from a short to a long photoperiod (16L:8D), epididymal ABP content returned to about 50% of control values within 3 weeks. However, the fertilizing ability of spermatozoa from the cauda epididymidis of these animals did not return to control values after a 9-week exposure to a stimulatory photoperiod.

Androgen-Binding Protein↗
PubMed1987

Direct effects of sulfonylurea agents on glucose transport in the BC3H-1 myocyte.

The actions of sulfonylurea agents to increase peripheral glucose disposal have been classically ascribed to an ability to potentiate insulin action. However, in the BC3H-1 cultured muscle cell, tolbutamide, glipizide, and glyburide directly provoked more than a twofold increase in 2-deoxyglucose (2-DG) uptake in a dose-dependent manner in the absence of insulin. Tolbutamide (3 mM) enhanced 2-DG uptake by 130% in the presence or absence of insulin and did not significantly change insulin binding or the sensitivity of the insulin response. The onset of tolbutamide-stimulated hexose transport was seen after 30 min and reached a plateau after 12 h. Tolbutamide-stimulated glucose transport was associated with a twofold increase in the Vmax of 2-DG uptake and was completely blocked by 50 microM cytochalasin B, indicating that this action is mediated by increase in cell membrane glucose transporters. We show that sulfonylureas at therapeutic concentrations directly increase glucose transport into muscle cells. Because muscle is the major peripheral target tissue for glucose disposal, these results provide the basis for the therapeutic effect of these agents in improving peripheral glucose disposal in insulin-resistant type II (non-insulin-dependent) diabetes mellitus.

Animals↗
PubMed1986

Comparison of human menopausal gonadotropin, clomiphene citrate, and combined human menopausal gonadotropin-clomiphene citrate stimulation protocols for in vitro fertilization.

Human menopausal gonadotropins (hMG) and clomiphene citrate (CC), either alone or in combination, are frequently used for in vitro fertilization (IVF) in an attempt to maximize the number of oocytes recovered and the number of embryos transferred. However, direct comparison of the relative efficacy of these protocols in the same institution has been limited. To evaluate this question, the authors examined the outcome of 304 consecutive women attempting IVF. One hundred eighty-one women received hMG, 42 received CC, and 81 received combination hMG/CC. The percentages of women undergoing laparoscopy were not different among the groups (69%, 71%, and 74%, respectively), nor were the rates of oocyte recovery (94%, 100%, and 100%). However, the percentage of women achieving oocyte fertilization (77%, 83%, and 93%) and embryo transfer (73%, 83%, and 90%) were significantly greater among those who had received hMG/CC stimulation. A comparison of hMG/CC with hMG and CC cycles revealed a statistically significant increase in the total number of developing follicles (4.5 +/- 0.3, 3.3 +/- 0.2, and 3.1 +/- 0.3, respectively; P = 0.0137), total oocytes recovered (4.1 +/- 0.3, 3.2 +/- 0.2, and 2.5 +/- 0.2; P = 0.0011), and embryos transferred (2.2 +/- 0.2, 1.4 +/- 0.2, and 1.4 +/- 0.2; P = 0.0013). However, there was no significant difference in the occurrence of ongoing pregnancies. Thus, in terms of the per-patient number of follicles, oocytes, and embryo transfers, combined hMG/CC stimulation appears to be superior to either hMG or CC alone. However, to date the combined regimen has not improved pregnancy rates.

Clomiphene↗
PubMed1986

Illusory continuous motion from oscillating positive-negative patterns: implications for motion perception.

A black and white (positive) grating pattern was superimposed in exact register on its own photographic negative. Four operations were repetitively applied to this positive pattern so that it moved fractionally to the right, grew dimmer, moved back to the left, and grew brighter again. This sequence produced a strong illusion of continuous apparent motion to the right for as long as the cycle was repeated. The small relative motion between the two patterns generated two new illusory effects: enhanced real movement (ERM) and reversed real movement (RRM). The dimming and brightening phases gave rise to reversed apparent movement (RAM). All three effects are attributed to spatial filtering by neural mechanisms, which shifts the effective position of the positive-negative contours.

Color Perception↗
PubMed1985

Selection of superior stimulation protocols for follicular development in a program for in vitro fertilization.

Classification of stimulated controlled follicular development cycles in programs for in vitro fertilization by the likelihood of culminating in a pregnancy would allow for increased efficacy in patient management and the distribution of care provider services. Analysis of human menopausal gonadotropin stimulations by the estradiol (E2) patterns identified trends suggesting superiority of one pattern, but no statistically significant difference was identified. Similarly, trends were identified in the Norfolk data for the height and pattern of E2 response, but no statistical significance was identified. While these observations may become significant with larger numbers, until that time, criteria for altering patient management based on the rise of follicular phase E2 levels should be reconsidered.

Chorionic Gonadotropin↗
PubMed1985

Polyspermy: effect of varying stimulation protocols and inseminating sperm concentrations.

Results from 198 cycles of in vitro fertilization (IVF) were examined to identify factors in the subsequent development of polyspermy. Polyspermy occurred in 24 of 235 fertilized oocytes and was equally likely in mature and immature oocytes. No significant difference in polyspermy was demonstrated between the stimulation protocol using human menopausal gonadotropin (hMG) and those using clomiphene citrate (CC) or combined hMG/CC. The incidence of polyspermy was no different after insemination of oocytes with concentrations of progressively motile sperm ranging from 250,000 to 500,000. Although polyspermy continues to be a problem in IVF, we have been unable to identify possible predisposing mechanisms for its development.

Clomiphene↗
PubMed1985

Effect of the number of inseminating sperm and the follicular stimulation protocol on in vitro fertilization of human oocytes in male factor and non-male factor couples.

The effect of sperm concentration and follicular stimulation protocol on in vitro fertilization of human oocytes is not well established. Comparison was made of three inseminating concentrations (250,000, 375,000, and 500,000 progressively motile sperm/oocyte) and three protocols (human menopausal gonadotropin [hMG], clomiphene citrate [CC], and combination hMG/CC) on the fertilization rate of mature and immature oocytes in couples with male factor and non-male factor infertility. In non-male factor couples, total fertilization rates for CC, hMG, and hMG/CC were 70.3%, 54.5%, and 68.8%, respectively, while total fertilization rates at the varying number of inseminating sperm were not significantly different. Mature oocytes were more likely than immature oocytes to fertilize. Among semen male factor couples, there was no difference in fertilization by stimulation protocol; however, insemination with the higher number of inseminating sperm resulted in an increased fertilization rate.

Clomiphene↗