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Biomedical subjects

R B Mandell

Publications and source records attributed to R B Mandell.

At least 19 recordsLinked to original sources
PubMed1992

The effect of carboxyl-terminal deletions on the nuclear transport rate of rat hsc70.

Rat brain hsc70 is a constitutively expressed member of the 70-kDa family of heat shock proteins that is capable of bidirectional transport across the nuclear envelope when microinjected into Xenopus oocytes [1]. The objective of this study was to identify domains involved in its bidirectional transport. Limited proteolytic digestion with chymotrypsin generated three major truncated proteins of approximately 67.5, 59.5, and 56.5 kDa. Reactivity with NH2-terminal-specific antibodies showed that carboxyl-terminal fragments were removed. Nuclear uptake studies were performed by microinjecting 125I-labeled proteins into the cytoplasm and determining their subsequent nucleocytoplasmic distribution. The accumulation rates, while faster than bovine serum albumin controls, were inversely related to the size of the truncated proteins and greatly reduced compared to undigested hsc70. Nuclear efflux was assayed by microinjecting labeled proteins directly into oocyte nuclei. The relative efflux rates of the truncated polypeptides were less than the undigested protein, and, as observed for uptake, were inversely related to size. These results indicate that the carboxyl-terminal domain of hsc70 is involved in its bidirectional exchange.

Amino Acid Sequence↗
PubMed1991

Corneal trauma from overnight wear of rigid or soft contact lenses.

To evaluate the mechanical or biochemical insult to the cornea induced by overnight rigid gas permeable (RGP) or soft contact lens (SCL) wear, punctate, stipple staining and corneal blotting were evaluated by biomicroscopy in a group of 23 subjects who participated in a single overnight in-laboratory test session. The soft lens-wearing corneas typically showed greater area of staining along with corneal blotting in comparison to RGP-wearing corneas which showed smaller areas of corneal staining, even in the presence of RGP adherence, and no corneal blotting. We investigated the effect of hypoxia on corneal staining by having subjects wear an RGP lens of Dk = 150 on one eye and a soft lens of Dk = 9 on the fellow eye. Pachometry measurements immediately following eye opening showed an average central corneal swelling of 5 percent for the RGP lens-wearing eye and an average of 11 percent for the SCL-wearing eye. It is likely that the differences in corneal effects of RGP and SCL overnight lens wear are the result of differences in the nature of rigid versus soft contact lens adherence.

Adult↗
PubMed1991

Protein accumulation on disposable extended wear lenses.

We investigated protein accumulation on disposable extended wear contact lenses. Fifteen volunteers were fit with one low water content, non-ionic lens (Bausch & Lomb's SeeQuence) randomly assigned to one eye and a high water content ionic lens (Vistakon's Acuvue) assigned to the fellow eye. During the first 7 weeks of extended wear the lenses were removed weekly for sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis of protein deposition, and replacement lenses were inserted. Four subjects completed additional test sessions of 1 minute, 15 minutes, 24 hours, and 1 week extended wear. Lysozyme accumulation, as measured by SDS-PAGE, increased with wearing times up to one week on all Acuvue lenses, but after 24 hours wear lysozyme accumulation did not increase on the SeeQuence lens. Proteins falling into the reported molecular weight ranges of albumin, PMFA, IgG, IgA (sec), lactoferrin and subunits of protein G were evident on all gels at 1 minute of wear, but these protein groups did not have a detectable increase in deposition after 24 hours wear for either the SeeQuence or the Acuvue lenses. In most cases, the protein accumulation evident from SDS-PAGE analysis was not observable by biomicroscopy using standard clinical methods. A few patients reported preference for the initial comfort and vision achieved by the Acuvue lens, but no preference was found after adaptation.

Adult↗
PubMed1990

Identification of two HSP70-related Xenopus oocyte proteins that are capable of recycling across the nuclear envelope.

Two 70-kD polypeptides, B3 and B4, are present in equivalent concentrations in the nucleus and cytoplasm of Xenopus oocytes. The objectives of this study were to determine if they (a) are members of the 70-kD family of heat shock proteins, and (b) recycle between the nuclear and cytoplasmic compartments. Evidence based on high-affinity binding to ATP, cross-reactivity of B3/B4-specific antibodies with rat hsc70, and a comparison of cyanogen bromide cleavage peptide maps with hsc70, verified that B3 and B4 are members of the 70-kD family of heat-shock proteins. Nuclear uptake studies were performed by microinjecting 125I-labeled B3/B4, rat hsc70, and BSA into the cytoplasm of oocytes, and examining their subsequent intracellular distributions. By 6 h postinjection, the nuclear concentration of B3/B4 and hsc70 were approximately 24-fold greater than BSA controls. It was also found that B3/B4-coated gold particles as large as 120A in diameter were able to enter the nucleus by passing through the pores. Nuclear efflux was analyzed by microinjecting the iodinated proteins directly into the oocyte nuclei. 2 h after nuclear injection, at least 46% of the B3/B4 and 60% of the hsc70 were found in the cytoplasmic fractions, compared with less than 10% for the BSA controls. Cell fusion experiments, in which labeled, anucleate oocyte vegetal hemispheres were fused, under oil, with nucleate unlabeled animal hemispheres, demonstrated that cytoplasmic B3 and B4 could enter the nucleus after equilibration was reached, arguing against the existence of separate nuclear and cytoplasmic populations. Collectively, these results show that B3, B4, and rat hsc70 are transported across the nuclear envelope and recycle between the nucleus and cytoplasm.

Amino Acid Sequence↗
PubMed1990

Initial in vivo tear protein deposition on individual hydrogel contact lenses.

We investigated and compared the initial composition, morphology, and time course of deposits on individual soft contact lenses of different water contents and surface charges in order to evaluate the potential for antigenic reactions and to predict the optimal frequency of lens replacement. Newly manufactured lenses were worn for graduated periods of time from 1 min to 8 h by subjects who were first adapted to daily wear soft lenses. The morphology and composition of the deposits were analyzed by histological staining, light microscopy, scanning electron microscopy (SEM), sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) with silver nitrate staining, and immunofluorescence microscopy. The protein bands of the acrylamide gels were divided according to their molecular weights into six groups which have been defined in the literature from tear analyses by electrophoretic techniques and include lysozyme, proteins migrating faster than albumin (PMFA), protein G, albumin, lactoferrin, and other proteins heavier than albumin such as Ig-G and secretory Ig-A. Specific proteins (lysozyme, PMFA, and protein G) were detected on individual lenses after as little as 1 min of wear. There was an increasing amount of protein deposited as the wearing time increased. Differences in the rates and amounts of deposition were more dependent on lens water content and ionic characteristics than on intersubject differences. Such early significant protein deposition may occur in wearers of disposable lenses as well as in those subject to complications due to accumulation of protein.

Adolescent↗
PubMed1990

Humidity effects on corneal hydration.

Overall corneal hydration control expressed as the percent recovery per hour (PRPH) can be assessed with an exponential model that uses data derived from two kinds of corneal thickness measurements; one from monitoring recovery after inducing corneal swelling, and the other from measurements made after the eye has been open long enough to reach its open-eye steady-state (OESS) corneal thickness. Up to now these thickness measurements have been made without controlling the ambient humidity. It is possible that changes in relative humidity may effect tear film osmolarity sufficiently to change the state of corneal hydration. To evaluate the effects of humidity on hydration control, the OESS and PRPH were determined under several humidity levels. For both the OESS and the PRPH, two substudies were conducted. For the OESS, substudy 1 consisted of measuring corneal thickness when humidity was changed from 30% (ambient) to 52 or 97% controlled humidity. This resulted in mean +/- standard deviation (SD) changes in OESS thickness amounting to -0.33 +/- 3.5 microns and 2.6 +/- 3.4 microns, respectively, with a differential change of 2.94 +/- 3.04 microns (95% confidence interval [CI] from 0.77 to 5.11 microns). Corresponding results for substudy 2 connected with changes from 43% (ambient) to 12 or 97% controlled humidity were -2.4 +/- 2.7 microns and -0.3 +/- 1.9 microns, respectively, with a differential change of 2.1 +/- 1.8 microns (95% CI from 0.9 to 3.4 microns).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

The spore coat of a fucosylation mutant in Dictyostelium discoideum.

Strain HL250 of Dictyostelium discoideum cannot convert GDP-mannose to GDP-fucose, resulting in an inability to fucosylate protein. This affects a group of proteins which are normally fucosylated intracellularly and then secreted via prespore vesicles to become part of the outer lamina of the spore coat. We have found that strain HL250 nevertheless accumulates typical amounts of these proteins, stores them normally in prespore vesicles, and secretes them normally to become a part of the spore coat. However, affected proteins are proteolyzed after germination, the spore coat is more accessible to penetration by a macromolecular probe, and germination is inefficient in older spores. These findings can be explained by a dependence of the integrity of the outer layer of the spore coat on protein-linked fucose.

Antibodies, Monoclonal↗
PubMed1989

The effect of time, patching, and lens flexibility on RGP lens adherence.

The effects of time, eye patching, and lens flexibility on rigid lens adherence was evaluated in five overnight, in-laboratory test sessions. Patching was investigated with a group of 11 subjects in two overnight test sessions. Sleep time and lens flexibility were investigated in three separate overnight test sessions with two groups of subjects wearing two lens types of fluorosilicone materials (Dk 92 and 60). Adherence occurred in a significant portion of eyes within a 2-hour time period, and the incidence increased throughout the night. There was no significant difference between the incidence of adherence for lenses of a flexible material compared to lenses of a more rigid material (p greater than 0.6, X2 test), nor did patching have a significant influence on the incidence of adherence. The mechanism of lens adherence may be related to several factors including arbitrary lens movement to a peripheral corneal position, the creation of a geometric spacing between the lens and the eye, lid forces producing a negative pressure, and an increase in tear viscosity throughout the night.

Adhesiveness↗
PubMed1989

Corneal hydration control in Fuchs' dystrophy.

Corneal hydration control was tested in 22 patients with Fuchs' dystrophy, and eight subjects of similar age without the disease, by measuring the corneal thickness recovery from swelling induced by hypoxia or following overnight sleep. Measurement precision was enhanced by using a modified optical pachometer and conducting two test procedures which were analyzed by a coupled exponential model. We have identified three parameters of the recovery from corneal swelling which may be used to describe hydration control: percent recovery per hour (PRPH) (mean 25.4% for Fuchs' and 34.2% for normals), time for 95% of corneal thickness recovery (mean 10.2 hr for Fuchs' and 7.1 hr for normals), and the open-eye steady-state thickness (mean 562 microns for Fuchs' and 537 microns for normals.) A PRPH of 17.1%/hr was identified as the minimum below which the cornea could not regain its open-eye steady state during the entire day and approaches decompensation. Our test procedure quantifies the corneal hydration control mechanism and may provide a test of endothelial function which can be used to monitor the progression of Fuchs' disease and guide decisions related to corneal surgery.

Aged↗
PubMed1988

Rigid contact lens area and corneal oxygenation.

The corneal area covered by a rigid contact lens under static conditions was calculated for various combinations of lens and corneal diameters. The lens was then assumed to move to various positions on the cornea to find the lens overlap of the corneal area originally covered by the lens. For most clinically practical dimensions, when the contact lens moves to the corneal limbus, a small area of lens overlap remains. This corneal area receives no direct exposure to the external atmosphere and must derive its oxygen via a tear-pumping action by the lens. A method for the calculation of this area is presented. The model is used to explain the appearance of central corneal clouding (CCC), the function of the contact lens peripheral curve, and a possible mechanism for corneal oxygenation during extended wear.

Contact Lenses↗
PubMed1988

Rigid contact lens adherence: incidence, severity and recovery.

The incidence of rigid lens adherence in one eye of 25 subjects was compared to the results for the fellow eye wearing a soft lens of nearly equal permeability in an in-laboratory overnight study. A 48% incidence of adherence was found for both extended wear modalities, which demonstrates the high frequency of this problem. Adherence of both rigid and soft lenses caused epithelial breakdown and corneal distortion, but these sequelae were generally more severe with rigid lenses. Recovery data on nine subjects whose rigid lenses adhered show that positive signs of adherence often disappear within 1 hour, demonstrating the need for early morning examinations. Practical considerations for the detection of rigid lens adherence and the possible consequences of failure to diagnose this condition are discussed.

Adhesiveness↗
PubMed1987

Differential antigen presentation by heat-treated peripheral blood mononuclear cells and Epstein-Barr virus-transformed lymphoblastoid cell lines (EBV-LCL): heated EBV-LCL present alloantigen and soluble antigen but are deficient in the stimulation of autologous EBV-LCL primed T cells.

Heat-treated PBM (1 hr at 45 degrees C) cannot present soluble Candida albicans antigens (CAN) or stimulate in the mixed lymphocyte culture (MLC) reaction. This is despite their continued expression of serologically defined class II MHC antigens. In contrast, heat-treated EBV-LCL present soluble CAN and stimulate allogeneic T cells in the MLC. Heated EBV-LCL stimulate strong secondary responses from allogeneic alloprimed T-cell lines in the primed lymphocyte test (PLT), while heated PBM stimulate only weak secondary allogeneic responses. To test whether this difference was due to a subtle difference in the thermal stability of the functional expression of class II MHC antigens on PBM and EBV-LCL cells, the EBV-LCL cells were heated for 1 hr at temperatures from 45 degrees C to 60 degrees C. Even after treatment at 60 degrees C, the heated EBV-LCL strongly stimulated alloreactive T cells in MLC and PLT reactions. Heated EBV-LCL are not nonspecifically mitogenic, as they do not stimulate autologous T-cell lines primed to alloantigens. However, the weak response of alloprimed T-cell lines to heated allogeneic PBM can be augmented by coculturing with autologous heated EBV-LCL, suggesting heated EBV-LCL maintain a metabolic activity necessary for allogeneic stimulation that is deficient in heated PBM. While heated EBV-LCL stimulate allogeneic alloprimed T-cell lines, they no longer stimulate autologous EBV-LCL primed T-cell lines; irradiated EBV-LCL stimulate both strongly. This suggests the involvement of a heat labile antigenic or metabolic factor in the T-cell recognition of autologous but not allogenic EBV-LCL.

Antigen-Presenting Cells↗
PubMed1987

Slit lamp classification system.

A slit lamp classification system is presented which follows the same divisions as the FDA Slit Lamp Classification System but expands the number of categories. It also differs in that there is an orderly progression of the various findings and a numbering system which allows for easy statistical analysis. In this way, the incidence of findings may be grouped according to degree of severity, and may be easily compared across different categories.

Conjunctival Diseases↗
PubMed1976

Etiology of corneal striae accompanying hydrogel lens wear.

Vertical striae in the posterior cornea were produced experimentally in ten human subjects by depriving the anterior corneal surface of its normal oxygen supply and inducing corneal edema. These striae were similar in appearance and time of occurrence to those observed in gel lens wearers. Three subjects also wore gel lenses and developed vertical striae while wearing their lenses. These striae were eliminated by increasing the oxygen concentration at the anterior lens surface. The data confirm many clinical observations which have suggested that verical striae are caused by corneal edema accompanying gel lens wear.

Adult↗
PubMed1975

Corneal thickness changes from bathing solutions.

Corneal thickness changes were measured after bathing the outer corneal surface with sodium chloride solutions of various concentrations. Bathing was accomplished by total immersion in the solution in a goggle or by the application of drops for a period of 20 minutes. A nearly linear relationship was found between hypotonicity and the degree of corneal swelling.

Cornea↗