Biomedical subjects

D Rose

Publications and source records attributed to D Rose.

At least 127 records · Page 7Linked to original sources

PubMed1992

Properties of cyclopean motion perception.

This study investigated the ability of human observers to discriminate the direction of laterally-moving cyclopean stimuli, in order to assess some of the properties of stereoscopic mechanisms that mediate the perception of cyclopean motion (motion existing at levels of binocular integration). The stimuli were moving grating patterns created from dynamic random-dot stereograms. Experiment 1 showed that duration thresholds for discrimination decrease with velocity; they are not governed by temporal frequency nor a constant spatial displacement. Experiment 2 revealed that discrimination thresholds increase with disparity magnitude, for both the crossed and uncrossed disparity directions equally. Experiment 3 showed that the rate of temporal variation at and above which direction discrimination fails (cyclopean upper limit of temporal resolution) is 8 Hz. Our results indicate that a mechanism for motion perception exists at binocular-integration levels of the visual system, which supports a model of motion perception that posits the existence of first-order and second-order processes.

Depth Perception↗

PubMed1992

A square root law for adaptation to contrast?

Several characteristic of aftereffects (especially the motion aftereffect) depend upon the square root of the time spent adapting. The same parameters are here examined for the contrast threshold elevation aftereffect. The time taken to recover is shown to be well predicted by root adaptation time (beyond a minimum duration), but the amount of threshold elevation, the rate of recovery and the integrated recovery phase cannot be so predicted.

Adaptation, Ocular↗

PubMed1992

[Eye diseases and visual disability in extremely low birth weight infants].

79 consecutively treated very low birth weight newborns (less than 1000 g) were systematically examined in the postpartal period and after a follow-up of 2 to 5.5 years. Retinopathy of prematurity was found in 19 eyes of 10 children (maximum stage III-IV). At a minimum age of 2 and maximum age of 6 years, when 42 of these children could be reexamined, including all children with earlier retinopathy of prematurity, 10 children suffered from minimal to moderate retinal pathology due to inactive retinopathy of prematurity (4 eyes with dragging of vessels and macula), but 9 children exhibited a minor visual disability due to strabism, higher ametropia, anisometropia, and amblyopia. This stresses the need for opthalmological follow-up in low birth weight babies with 6 months and 3-4 years of age.

Child, Preschool↗

PubMed1992

On the variety of percepts associated with dichoptic viewing of dissimilar monocular stimuli.

Upon dichoptic viewing of dissimilar patterns, several distinct perceptual states may be experienced over time. One state is exclusive monocular dominance, wherein the view of only one eye is seen in its entirety for some period of time. Another state is characterized by a mosaic-like college consisting of portions of the view of each eye. Two other states involve simultaneous perception of both monocular images in their entirety. In one of these states, the two monocular stimuli appear to be superimposed without depth (a phenomenon we shall term 'superimposition'). In the other state, the two monocular stimuli appear to be located at different depth planes (which we shall term 'transparency'). This paper documents the stimulus conditions favoring these various perceptual states. Exclusive monocular dominance occurs most often when the two eyes view dissimilar patterns with the same spatial-frequency content, particularly when both patterns consist of low spatial frequencies. Superimposition also occurs most often when the two eyes view the same spatial frequencies, but predominantly when those spatial frequencies are high. Transparency is favored when the spatial-frequency difference between the eyes is great, particularly when the view of one eye consists of high spatial-frequency information.

Depth Perception↗

PubMed1992

Stimulus mislocalization depends on spatial frequency.

It was previously reported that briefly presented peripheral stimuli are perceived closer to fixation than continuously presented stimuli at the same eccentricity; this effect has, however, not proved consistently replicable. In this study it was investigated whether the misperception of location might depend upon the spatial frequency content of the stimulus. Spatial-frequency-filtered vertical bars were displayed briefly and their locations were judged relative to continuously visible comparison spots. For monocular stimuli, a significant foveopetal mislocalization of the bar was obtained that increased in size as spatial frequency was lowered. Even larger mislocalizations were obtained for dichoptically presented horizontally disparate pairs of bars, and this effect also increased at low spatial frequencies. Possible underlying mechanisms are discussed, and spatial frequency is suggested to have been the confounding factor in previous studies.

Eye Movements↗

PubMed1992

Minimized surgery for retinal detachments with segmental buckling and nondrainage. An 11-year follow-up.

A prospective study was conducted of 107 retinal detachments operated on between August 1979 and January 1980, with a complete follow-up period ranging from 11 years to 11.5 years. Proliferative vitreoretinopathy (PVR) stage C1 or C2 was seen in 16 detachments. Surgery consisted of cryopexy and segmental buckling (limited to the area of breaks) with nondrainage. Of the surgical procedures, 71% were radial buckles, 19% circumferential, and 10% radial combined with circumferential buckles. The primary reattachment rate was 92.6%, and 97% after reoperation. During the long-term follow-up period, redetachment occurred in 12.1% of the eyes: 5.6% were classified as early redetachments (between 2 and 4 months), and 6.5% as late redetachments (between 3 and 7 years). Early redetachment was caused by PVR, and late redetachment by new holes. After reoperation, reattachment occurred in 92.6% of the eyes. The predominant cause of final failure was PVR (3.7%). Only one eye had two reoperations. There was a highly significant (P less than 0.001) improvement between preoperative visual function (mean 0.32) and postoperative visual function (mean 0.56) in all 99 reattached eyes during the follow-up period (Mann-Whitney U test).

Adolescent↗

PubMed1992

Detection and characterization of T-cell leukemia virus-like proviral sequences in PBL and tissues of baboons by PCR.

The "high lymphoma-prone" baboon stock (Papio hamadryas) of the Sukhumi Primate Center colony is characterized by a high prevalence of antibodies to the STLV-I/HTLV-I type of retrovirus and a high manifestation of human ATL-type (adult T-cell leukemia/lymphoma) malignancies (Yakovleva et al., this symposium). This is in contrast to other primate colonies and wild monkeys, which have low seroprevalence and very few if any ATL-type T-cell malignancies. To characterize the type of T-cell lymphoma retrovirus involved in the Sukhumi disease, a PCR (polymerase chain reaction) DNA analysis of peripheral blood lymphocytes (PBL) and of various tissues of healthy "at-risk", or ill baboons was performed. Proviral STLV/HTLV sequences were detected in all monkeys with symptoms of T-cell malignancy and/or antibodies to STLV-I/HTLV-I. For precise identification and characterization of the Sukhumi T-cell lymphoma virus, parts of the virus genome were mapped and sequenced from PCR derived fragments. A 420 nucleotide fragment of the env (gp 46) gene (analysed from 3 different DNA's) revealed 16.2% nucleotide divergence to the Japanese strain of HTLV-I and 14.8% to the Japanese strain of STLV-I including one deletion of a triplet. On the level of amino acid (a.a) sequence this revealed an exchange of 6 a.a. to STLV-I (4.3%), but only of 4 a.a. to HTLV-I (2.8%). The analysis of 120 nucleotides of the tax sequence (identical in 6 different DNAs) resulted in 5% nucleotide divergence to the HTLV-I (2.4% on the a.a. level) and 10% (7.3% a.a.) to the STLV-1. These results indicate that the Sukhumi T-cell lymphoma virus is a representative of the T-cell leukemia/lymphoma virus family, apparently more closely related to HTLV-I than to STLV-I genome. Furthermore, the infected monkeys from Sukhumi develop at a high rate a T-cell malignancy not observed among other baboons carrying STLV.

Amino Acid Sequence↗

PubMed1992

Demographic and economic factors associated with dietary quality for adults in the 1987-88 Nationwide Food Consumption Survey.

Data for 5,884 adults (19 years of age and older) who participated in the 1987-88 Nationwide Food Consumption Survey (1987-88 NFCS) were used to investigate demographic and economic factors associated with dietary quality. Although the low response rate for the 1987-88 NFCS has raised concerns about possible bias, it is appropriate to use this extensive data set for analyses that do not attempt to generalize the results to the US population as a whole. Two aspects of quality were calculated for the mean of the 3-day reported intakes: number of nutrients below two thirds of the 1989 Recommended Dietary Allowance (RDA) (low-intake nutrients) and percent of energy from fat. Few adults reported mean intakes that met suggested guidelines: 22% of diets were above two thirds of the RDA for all 15 nutrients and 14% were below 30% fat, but only 2% met both criteria. Energy intake was a strong negative predictor of number of low-intake nutrients and a weak positive predictor of percent of energy from fat. Results of multivariate regression analyses identified few demographic or economic predictors of either the number of low-intake nutrients or percent of energy from fat. According to these data, diets of most adults do not conform to current dietary guidelines. Nutrition education efforts should be directed to all adults, and research should be undertaken to determine more effective ways to help adults improve their overall dietary quality.

Adult↗

PubMed1991

Postnatal development of small and large dorsal root ganglion neurons in the cat. A study on cervical levels (C5-C6) and on phrenic afferents.

During feline postnatal development, the size of phrenic afferent neurons labelled by horseradish peroxidase was evaluated in comparison to that of the bulk of counterstained neurons located in the same cervical dorsal root ganglia (DRG) (C5-C6). From age 1 week to maturity, small and large cell components were individualized from experimental size distributions using a mathematical approach. The analysis of data in adult indicated a close correspondence between small cells and unmyelinated afferents and between large cells and myelinated afferents, respectively. From age 1 week to adulthood, mean increases in cell diameter ranged between 10 microns (small cells from phrenic afferents) and 29.5 microns (large counterstained cells). In each population, the ratio of small/large cells remained constant during growth. In contrast to data in adults, at 1 week, large phrenic neurons were bigger than the counterstained ones. At 19 weeks, the cat DRG cells had not yet reached their adult size.

Animals↗

PubMed1991

The value of postoperative ultrasound examination after laparoscopic laser cholecystectomy surgery.

Laparoscopic cholecystectomy surgery is rapidly becoming the procedure of choice for patients undergoing gallbladder removal. For the patient, this new minimally invasive surgery allows shorter hospitalization and faster recuperation than traditional open cholecystectomy surgery. Examinations were performed to determine the value of ultrasound in predicting morbidity of patients undergoing the laparoscopic cholecystectomy procedure. Examinations were performed immediately and 6-8 weeks postlaparoscopic surgery on 24 patients with acute or chronic gallbladder disease. All patients had ultrasound examinations prior to surgery. Of the 24 patients studied, 6 patients (25%) developed small fluid accumulations immediately postsurgery. All patients were asymptomatic clinically and remained asymptomatic 6-8 weeks after surgery. The fluid accumulation was thought to be insignificant on the immediate postsurgical studies. This percentage equals that found in open cholecystectomy surgeries. On the delayed ultrasound studies, no fluid deposits or other abnormalities were seen. Ultrasound examination of the asymptomatic patient postlaparoscopic cholecystectomy surgery is not of value for predicting complications in patients undergoing this procedure. Furthermore, immediately postlaparoscopic cholecystectomy surgery, 25% of patients will have small fluid collections, but will not develop complications.

Abdomen↗

PubMed1991

Optimization of human endothelial cell attachment to vascular graft polymers.

Endothelial cells (EC) covering the blood-contacting surface of a prosthetic material could potentially enhance the subsequent nonthrombogenicity of the surface. In order to create such a surface, the EC must become attached to the surface, spread and ultimately form a monolayer. In this study we examined several factors that influence these processes. On ePTFE surfaces, surface pretreatment with human serum for 30 minutes at a concentration of 1.4 gm percent protein resulted in significantly more attached EC when compared to other concentrations or when compared to fetal calf serum or human serum albumin. The rate of EC spreading was strongly influenced by temperature, with a maximum occurring at 37 degrees C. During real-time video microscopy, it was noted that the rate of EC attachment and spreading was primarily dependent on arrival of the EC to the surface rather than attachment and spreading. Thus as a method of increasing EC delivery, the concept of filtering EC onto the graft lumenal surface was tested by pressurizing the graft lumen to speed EC delivery to the surface. This technique produced a 2 to 5-fold increase in EC attachment when compared to gravity forced cell deposition. We conclude that an ePTFE graft can be rapidly endothelialized using these simple measures.

Biocompatible Materials↗

PubMed1991

Complement depletion in vitro limits monoclonal antibody 6-19-dependent complement-mediated killing of tumor cells in bone marrow.

Selective killing of nonhematopoietic tumor cells in bone marrow harvested for autologous bone marrow transplantation was studied using cultured neuroblastoma cells, monoclonal antibody 6-19, and baby rabbit serum as a source of complement. Monoclonal antibody 6-19, a murine IgG2a antibody, was selected for binding to a cell surface antigen on cultured human neuroblastoma cells that is not expressed by hematopoietic cells. The antigen is an 80-kd sialoglycoprotein present on a wide variety of nonhematopoietic tumors, and it is expressed by normal fibroblast and endothelial cells. The effect of the presence or absence of bone marrow mononuclear cells on target cell survival was evaluated using Hoechst 33342-stained neuroblastoma cells, trypan blue exclusion, and fluorescence microscopy. More than 4 logs of neuroblastoma cells were destroyed in the presence of a more than tenfold excess of bone marrow cells following two incubations with monoclonal antibody 6-19 and complement for 30 min at 37 degrees C. Monoclonal antibody concentrations greater than 5-10 micrograms/ml did not increase cell lysis. The destruction of tumor cells was limited by depletion of complement activity. Tumor cell killing increased with complement concentration and incubation duration but there was no additional cell lysis with incubations greater than 30 min. The percentage of target cells killed was significantly decreased when the target cells were treated in the presence of increasing concentrations of bone marrow mononuclear cells. This decrease in target cell destruction is a result of additional depletion of complement activity by bone marrow mononuclear cells. These results suggest that optimal purging of tumor cells by antibody and complement will be achieved following multiple brief incubations with fresh antibody and complement.

Antibodies, Monoclonal↗

PubMed1990

Structure of yeast triosephosphate isomerase at 1.9-A resolution.

The structure of yeast triosephosphate isomerase (TIM) has been solved at 3.0-A resolution and refined at 1.9-A resolution to an R factor of 21.0%. The final model consists of all non-hydrogen atoms in the polypeptide chain and 119 water molecules, a number of which are found in the interior of the protein. The structure of the active site clearly indicates that the carboxylate of the catalytic base, Glu 165, is involved in a hydrogen-bonding interaction with the hydroxyl of Ser 96. In addition, the interactions of the other active site residues, Lys 12 and His 95, are also discussed. For the first time in any TIM structure, the "flexible loop" has well-defined density; the conformation of the loop in this structure is stabilized by a crystal contact. Analysis of the subunit interface of this dimeric enzyme hints at the source of the specificity of one subunit for another and allows us to estimate an association constant of 10(14)-10(16) M-1 for the two monomers. The analysis also suggests that the interface may be a particularly good target for drug design. The conserved positions (20%) among sequences from 13 sources ranging on the evolutionary scale from Escherichia coli to humans reveal the intense pressure to maintain the active site structure.

Amino Acid Sequence↗

PubMed1990

Segregation of recombined chromosomes in meiosis I requires DNA topoisomerase II.

To understand better the similarities and differences between meiosis and mitosis, we examined the meiotic role of DNA topoisomerase II, an enzyme that is required mitotically to disentangle sister chromatids at the time of chromosome segregation. In meiosis, we found that topoisomerase II is required only at the time of nuclear division. When cold-sensitive top2 mutants are induced to sporulate at the restrictive temperature, they undergo premeiotic DNA synthesis and commitment to meiotic levels of recombination but fail to complete the first meiotic nuclear division. The introduction of a mutation blocking recombination relieves the requirement for topoisomerase II in meiosis I. These results suggest that topoisomerase II is required at the time of chromosome segregation in meiosis I for the resolution of recombined chromosomes.

Cell Nucleus↗

PubMed1990

The cat cervical dorsal root ganglia: general cell-size characteristics and comparative study of neck muscle, neck cutaneous and phrenic afferents.

Sizes of neuronal somata in the cat cervical dorsal root ganglia were determined at different levels (C1-C8). The average value and class distribution of mean cell diameter were analyzed. The ganglia from C1 to C5 could be clearly distinguished from those at levels of brachial plexus afferents (C6-C8) with respect to cell size range, distribution and average. The size distribution, most often limited to 70 microns from C1 to C5, skewed to more than 90 microns from C6 to C8. Cells in the 35-50 microns range of diameter constituted the main portion of the cell population (49-52%) at the C1-C5 levels, whereas from C6 to C8 51-77% of the ganglion cell bodies were more than 50 microns in diameter. The cell size distribution of afferents projecting from C1 to C5 and supplying different muscle or cutaneous targets was studied following retrograde labeling with horseradish peroxidase conjugated to wheatgerm agglutinin. Sizes of cell bodies of biventer cervicis (postural muscle), phrenic (purely respiratory muscle) and cutaneous afferents were all similar. The labelled cell bodies were in the majority (51-64%) less than 35 microns in diameter and ranged towards smaller diameters than counterstained cells in the corresponding ganglia. In spite of similarities in cell size distribution it was estimated from the fiber caliber spectra of the labelled afferents that both unmyelinated and myelinated cutaneous afferents originate from larger cell bodies than muscle afferents in the same diameter range.

Adolescent↗

PubMed1990

An improved method for localizing electric brain dipoles.

Methods for localizing electrical dipolar sources in the brain differ from one another by the models they use to represent the head, the specific formulas used in the calculation of the scalp potentials, the way that the reference electrode is treated, and by the algorithm employed to find the least-squares fit between the measured and calculated EEG potentials. The model presented here is based on some of the most advanced features found in other models, and on some improvements. The head is represented by a three-layer spherical model. The potential on any point on the scalp due to any source is found by a closed formula, which is not based on matrix rotations. The formulas will accept any surface electrode as the reference electrode. The least-squares procedure is based on optimal dipoles, reducing the number of unknowns in the iterations from six to three. The new method was evaluated by localizing five implanted dipolar sources in human sensorimotor cortex. The distances between the locations of the sources as calculated by the method, and the actual locations were between 0.4 and 2.0 cm. The sensitivity of the method to uncertainties encountered whenever a real head has to be modeled by a three-layer model has also been assessed.

Adult↗

PubMed1990

[Young and economically precarious: an analysis of the situation of couples].

Changes in the economic status of young married and unmarried couples in Canada are examined for the period 1960-1989. The impact of the economic recession created by the restructuring of the economy in the early 1980s on the income of the young is analyzed. The authors investigate the impoverishment of young couples and compare it "with the evolution of income among older couples and analyze the impact of various factors, [such] as job stability, wage level and relative contribution of both partners." (SUMMARY IN ENG AND SPA)

Age Factors↗

PubMed1990

[Studies on the composite joint in Cerec inlays].

In an in vitro study 32 ceramic restorations were constructed using the Cerec system and adhesively fixed in cavities prepared in extracted teeth with Dual Cement according to the supplier's instructions. The restored teeth were then histologically prepared and the joints between cement and inlay morphometrically evaluated at eight defined sites. The measurements showed average values of 118 microns with a standard deviation of 53 microns. It is particularly interesting to note the extremely great range of variation between the lowest and the highest value. The measured widths of the joints must be considered as a weakness of the system, because clinically they may result in wash-outs and material collapses in the long run. So far, no long-term studies have been conducted yet to investigate this effect.

Composite Resins↗