In vivo biocompatibility of a new cyanine dye for ILM peeling

PURPOSE

To investigate the biocompatibility of the new cyanine dye: 3,3'-Di-(4-sulfobutyl)-1,1,1',1'-tetramethyl-di-1H-benz[e]indocarbocyanine (DSS) as a vital dye for intraocular application in an in vivo rat model and to evaluate the effects of this dye on retinal structure and function.

METHODS

DSS at a concentration of 0.5% was applied via intravitreal injections to adult Brown Norway rats with BSS serving as a control. Retinal toxicity was assessed 7 days later by means of retinal ganglion cell (RGC) counts, light microscopy, optical coherence tomography (OCT), and electroretinography (ERG).

RESULTS

No significant decrease in RGC numbers was observed. No structural changes of the central retina were observed either in vivo (OCT) or under light microscopy. ERGs detected a temporary reduction of retinal function 7 days after injection; this was no longer evident 14 days after injection.

CONCLUSIONS

DSS showed good biocompatibility in a well-established experimental in vivo setting and may be usable for intraocular surgery as an alternative to other cyanine dyes. In contrast to indocyanine green, it additionally offers fluorescence in the visual spectrum. Further studies with other animal models are needed before translation into clinical application.

Merkel cell distribution in the human eyelid

Although Merkel cell carcinoma of the eyelid is reported frequently in the literature, only limited information exists about the distribution of Merkel cells in this tissue. Therefore, serial sections of 18 human cadaver eyelids (donors ages ranging between 63 and 97 years) were stained for cytokeratin 20 in various planes. The overall appearance of Merkel cells in these samples was low and mainly located in the outer root layer of the cilia hair follicles. Merkel cells were more frequent in the middle, and almost not detectable at the nasal and temporal edges. The localization is in accordance with that of Merkel cell carcinoma, but concerning the scarce appearance within this adulthood group, a specific physiological role of these cells in the eyelid is difficult to establish.

An in vivo evaluation of Brilliant Blue G in animals and humans

BACKGROUND/AIMS

To evaluate the retinal toxicity of Brilliant Blue G (BBG) following intravitreal injection in rat eyes and examine the biocompatibility and the staining properties in humans.

METHODS

BBG was injected into the 11 rat eyes to evaluate toxic effects with balanced salt solution (BSS) serving as control. Retinal toxicity was assessed by retinal ganglion cell (RGC) counts and by light microscopy 7 days later. In addition, BBG was applied during vitrectomy for macular hole (MH) (n = 15) or epiretinal membranes (ERM) (n = 3) in a prospective, non-comparative consecutive series of patients. Before and after surgery, all patients underwent a complete clinical examination including measurement of best corrected visual acuity (VA) and intraocular pressure, perimetry, fundus photography and optical coherence tomography. Patients were seen 1 day before surgery and then in approximately four weeks intervals.

RESULTS

No significant reduction in RGC numbers and no morphological alterations were noted. A sufficient staining of the internal limiting membrane (ILM) was seen in patients with MH, while the staining pattern in ERM cases was patchy, indicating that parts of the ILM were peeled off along with the ERM in a variable extent. All MHs could be closed successfully. VA improved in 10 eyes (56%; 8/15 MH patients, 2/3 ERM patients), was unchanged in four eyes (22%; all MH patients) and was reduced in four eyes (22%; 3/15 MH, 1/3 ERM). No toxic effects attributable to the dye were noted during patient follow-up. The ultrastructure of tissue harvested during surgery was unremarkable.

CONCLUSION

Brilliant Blue provides a sufficient and selective staining of the ILM. No retinal toxicity or adverse effects related to the dye were observed in animal and human studies. The long-term safety of this novel dye will have to be evaluated in larger patient series and a longer follow-up.

Staining and peeling of the internal limiting membrane using a fluorescent dye (Rhodamine 6 G)

AIM

To assess whether low concentrations of a fluorescent dye such as Rhodamine 6G would help the unaided human eye visualise the vitreous and the internal limiting membrane (ILM) under standard halogen illumination.

MATERIAL/METHODS

The UV/Vis absorption (E) and fluorescence (I) spectra of Rhodamine 6G in water were measured and compared with Indocyanine Green (ICG). Surgery was performed in two rhesus monkeys and consisted of standard pars plana vitrectomy with halogen light source used for illumination. Rhodamine 6G was diluted in balanced salt solution (BSS). A few drops of the dye in a concentration of 0.1% (307 mOsm) were applied over the posterior pole in the air-filled globe and washed out by irrigation after 1 min. Immediately after surgery, the globes were enucleated, fixated and prepared for histological evaluation.

RESULTS

In contrast to ICG, both the maximum of the absorption and emission of Rhodamin 6G are very much within the spectral sensitivity of the human eye. The Rhodamine 6G-BSS itself appears red in colour. Using a dye concentration of 0.1%, there was no visible red-staining of the ILM as such. As the dye was irrigated out with BSS, a marked green fluorescence of the fluid within the vitreous cavity was noted. With halogen illumination through a standard 20-gauge light pipe, the dye provided a sufficient green fluorescence to identify and safely remove the ILM and to clearly differentiate areas of peeled from non-peeled ILM. During light microscopy, eyes revealed a peeled ILM demarcation with no signs of acute retinal toxicity.

CONCLUSION

The findings indicate that a fluorescent dye can be used for ILM peeling. Assuming that the fluorophore provides a high enough fluorescence quantum yield after adsorption to the ILM, much lower dye concentrations could be used compared with absorbent dyes, thereby minimising toxic effects.

Proteins with an endostatin-like domain in a mouse model of oxygen-induced retinopathy

Neovascularization in the retinopathy of prematurity (ROP) mouse eye is a self-limiting phenomenon. Free endostatin is known to be anti-angiogenic. In this study, we identified the localization of endostatin-like protein (ELP) sequences and investigated their possible role in this process. ROP was induced in C57Bl/6 mice and the eyes observed 1-11 days after termination of high oxygen supply (P13-P21). Sagittal sections and retinal flatmounts were double-stained with antibodies against a protein-sequence of endostatin, vascular endothelial growth factor (VEGF), lectin, and smooth-muscle alpha actin. The fluorescence was visualized by traditional and confocal microscopy. Intense staining for VEGF in the inner retina was limited to the early stages of neovascularization and diminished at P19-P21. In contrast, staining for ELPs appeared at P15 around the newly formed vessels and remained even after degeneration of their endothelial cells. Staining of the inner retinal vasculature for ELPs was restricted to P17-P19, the known maximum of the neovascular response. Outer retinal vessels did not show presence of ELPs at any time. Our study demonstrates that ELPs, absent at the beginning of neovascular sprouting, increases with the amount of neovascularization and thus, varies reciprocally to VEGF in the time period investigated. ELPs remain during the regression of the vessels and might therefore play an important role in the self-limiting process of ROP neovascularization.

Role of tissue growth factors in aqueous humor homeostasis

The aqueous humor supplies nutrients to the nonvascularized cornea, lens, and trabecular meshwork. A number of tissue growth factors have been detected in this fluid. The composition of these proteins changes dramatically with different ocular conditions, such as inflammation and glaucoma. In this review, an overview of new findings regarding effects of aqueous humor growth factors is given. Our main emphasis is on the regulation of the avascular anterior eye compartment, the possible role of growth factors in the pathogenesis of glaucoma, and the importance of growth factors for the special immunosuppressive status of the anterior chamber.

Molecular methods for the detection of mutations

We report the results of a collaborative study aimed at developing reliable, direct assays for mutation in human cells. The project used common lymphoblastoid cell lines, both with and without mutagen treatment, as a shared resource to validate the development of new molecular methods for the detection of low-level mutations in the presence of a large excess of normal alleles. As the "gold standard, " hprt mutation frequencies were also measured on the same samples. The methods under development included i) the restriction site mutation (RSM) assay, in which mutations lead to the destruction of a restriction site; ii) minisatellite length-change mutation, in which mutations lead to alleles containing new numbers of tandem repeat units; iii) loss of heterozygosity for HLA epitopes, in which antibodies can be used to direct selection for mutant cells; iv) multiple fluorescence-based long linker arm nucleotides assay (mf-LLA) technology, for the detection of substitutional mutations; v) detection of alterations in the TP53 locus using a (CA) array as the target for the screening; and vi) PCR analysis of lymphocytes for the presence of the BCL2 t(14:18) translocation. The relative merits of these molecular methods are discussed, and a comparison made with more "traditional" methods.

Evaluation of the rhodopsin knockout mouse as a model of pure cone function

PURPOSE

To determine a time window in the rhodopsin knockout (Rho(-/-)) mouse during which retinal function is already sufficiently developed but cone degeneration is not yet substantial, thus representing an all-cone retina.

METHODS

Electroretinograms (ERGs) were obtained from 14 homozygous Rho(-/-) mice and eight C57Bl/6 control mice. The same individuals were tested every 7 days, beginning as early as postnatal day (P)14. The ERG protocols included flash and flicker stimuli, both under photopic and scotopic conditions. Retinal and choroidal morphology was observed in animals of comparable age.

RESULTS

Functionally, the developmental phase lasted until postnatal week (PW)3 in both the Rho(-/-) mice and the control animals. During PW4 to 6, the Rho(-/-) mice showed a plateau in ERG parameters with normal or even supernormal cone responses and complete absence of rod contributions. At PW7, there was a marked onset of degeneration, which progressed so that no ERG signals were left at PW13, when the control eyes still had normal ERG responses. Microscopically, cone degeneration paralleled the functional changes, beginning at approximately PW6 and almost complete at PW13, whereas retinal pigment epithelium (RPE) and choroid did not show any abnormalities.

CONCLUSIONS

From PW4 to 6, Rho(-/-) mice appear to have normal cone and no rod function. Despite the missing rod outer segment (OS), the structure of retina, RPE, and choroid remained unchanged. Therefore, the Rho(-/-) mice can serve during this age period as a model for pure cone function. Such a model is particularly useful to evaluate rod-cone interaction and to dissect rod- from cone-mediated signaling pathways in vivo.

Integrated analysis of sequence evolution and population history using hypervariable compound haplotypes

We have examined compound haplotypes from a highly informative region of human chromosome 16, in which information from the rapid evolution of a highly unstable minisatellite is integrated with data on the longer-term evolution of this segment from 10 flanking substitutional polymorphisms. Combined with sequence data from non-human primates, analysis of relationships between these compound haplotypes allows the reconstruction of a rooted network of the evolutionary pathways between them. Most relationships can be explained via simple substitutional mutations, although the origins of some haplotypes involve recurrent events at a hotspot for substitutional mutation and/or gene conversion. For compound haplotypes including the minisatellite array, the network found in a range of world-wide populations constitutes a highly informative data set for the analysis of population history (437 different compound haplotypes were discriminated among 658 studied). Since the mutation rates and processes of the minisatellite array are known from direct studies, ages for individual lineages have been estimated using associated minisatellite diversity. These analyses suggest that the higher information content and sampling depth of these compound haplotypes may allow more precise calibration of lineage ages than is possible using coalescent analysis of DNA sequence. Using this method we have dated the oldest Eurasian lineage as 52,000-66,000 years and the oldest European specific lineage as 37,600-56,200 years.

Changes in choroidal innervation in Royal College of Surgeons rats with hereditary retinal degeneration

In Royal College of Surgeons (RCS) rats with hereditary retinal degeneration loss of retinal pigmented epithelium (RPE) and choriocapillaris is most pronounced in the upper-temporal quadrant. To investigate whether changes in choroidal vasodilative innervation might be involved in the RPE degeneration, we analyzed whole mount preparations of the retina and choroid stained for nitric oxide synthase and for NADPH-diaphorase (d) of 19 dystrophic RCS rats and 24 age-matched congenic controls of different age groups. Density of NADPH-d-positive nerve fibers was quantitatively evaluated in the upper-temporal and lower-nasal quadrant. Our results revealed that even in control animals there were much less positively stained nerve fibers in the upper-temporal than in the lower-nasal quadrant. Nerve fiber density in both quadrants increased for up to 3 months and remained nearly constant throughout life. In the dystrophic animals up to 3 months of age nerve fiber density was similar to that seen in the controls. In dystrophic animals older than 3 months nerve fiber density in the upper-temporal quadrant decreased significantly, whereas density in the lower-nasal quadrant revealed nearly the same values as in the age-matched controls. Decrease of NADPH-d stained nerve fibers in this quadrant occurred prior to the vascular changes in the choriocapillaris. In the retina of RCS dystrophic rats an increase of NADPH-d-positive amacrine cells was found only in 3-month-old animals. Most of these cells were located in the vicinity of irregularly arranged branches of the central retinal artery. In animals 5 months of age and older the number of cells decreased to the same values found in controls, so that we assume that increase of NADPH-d-positive amacrine cells is involved in capillary degeneration or sprouting.

Minisatellite mutation frequency in human sperm following radiotherapy

Screening pedigrees for inherited minisatellite length changes provides an efficient means of monitoring repeat DNA instability but has given rise to apparently contradictory results regarding the effects of radiation on the human germline. To explore this further in individuals with known radiation doses and to potentially gain information on the timing of mutation induction, we have used an extremely sensitive single molecule approach to quantify the frequencies of mutation at the hypervariable minisatellites B6.7 and CEB1 in the sperm of three seminoma patients following hemipelvic radiotherapy. Scattered radiation doses to the testicles were monitored and pre-treatment sperm DNA was compared with sperm derived from irradiated pre-meiotic, meiotic and post-meiotic cells. We show no evidence for mutation induction in any of the patients and discuss this finding in the context of previous population studies using minisatellites as reporter systems, one of which provided evidence for radiation-induced germline mutation.

AlphaB-crystallin in lacrimal gland duct and tears

PURPOSE

To investigate alphaB-Crystallin expression and localization in the lacrimal gland and tear fluid.

METHODS

Mouse, rat, porcine, monkey and human lacrimal gland samples were immuno-histochemically and immuno-electron-microscopically stained with various antibodies against alphaB-crystallin. Western- and Northern-blotting was performed to demonstrate the presence of alphaB-crystallin mRNA and protein. Human tear fluid was analyzed for the presence of alphaB-crystallin using dot blotting.

RESULTS

alphaB-Crystallin is located in the lacrimal gland duct cells but not in the acini. Electron microscopically, the protein was frequently found in apical electron-dense granules of lacrimal duct cells, occasionally also in the duct lumina. Western blotting confirmed the presence of alphaB-crystallin in the lacrimal gland, Northern blot samples revealed the presence of alphaB-crystallin mRNA. In the human tear fluid, alphaB-crystallin was present in all samples investigated.

CONCLUSIONS

We demonstrate for the first time that alphaB-crystallin is present in the lacrimal gland. Presence of the protein in apical secretory granules as well as presence in the tear fluid might indicate secretion of alphaB-crystallin into the tear fluid.

Induction of tissue transglutaminase in the trabecular meshwork by TGF-beta1 and TGF-beta2

PURPOSE

To study whether human trabecular meshwork (HTM) cells are capable of expressing and secreting tissue transglutaminase (tTgase), an enzyme cross-linking extracellular matrix (ECM) proteins, and whether tTgase and synthesis of cross-linked fibronectin are increased after treatment of HTM cells with transforming growth factor (TGF)-beta1 or -beta2.

METHODS

Anterior segments of six normal human eyes were stained with antibodies to tTgase. Tissues from three eyes were analyzed for tTgase using Western blot analysis. Monolayer cultures of HTM cells from eyes of five human donors were treated with 1.0 ng/ml TGF-beta1, -beta2, or 5 X 10(-7) M dexamethasone (DEX) for 12 to 96 hours. Induction of tTgase was investigated by Western and Northern blot analysis. External tTgase activity was measured by the ability to form polymerized fibronectin and the incorporation of biotinylated cadaverine into fibronectin.

RESULTS

Labeling for tTgase was observed throughout the entire HTM. Cultured HTM cells expressed tTgase intra- and extracellularly. Treatment of cultured HTM cells with TGF-beta1 and -beta2 increased the tTgase mRNA and protein levels, whereas DEX had no effect. TGF-beta-treated HTM cells showed a significant increase in polymerized and unpolymerized fibronectin. Incorporation of biotinylated cadaverine was markedly increased when HTM cells were treated with TGF-beta for 24 hours before seeding.

CONCLUSIONS

The enzyme tTgase is expressed in the HTM and is inducible by TGF-beta1 or -beta2 in cultured HTM cells. Extracellular tTgase is able to polymerize fibronectin. Increased levels of TGF-beta2 in the aqueous humor may lead to an increase of tTgase expression and activity in the HTM, causing an increase of irreversibly cross-linked ECM proteins. This mechanism might play a role for the increased outflow resistance seen in glaucomatous eyes.

Vascular and glial changes in the retrolaminar optic nerve in glaucomatous monkey eyes

Vascular and glial changes of the retrolaminar optic nerve were studied in monkey eyes with increased intraocular pressure (IOP) from 1 to 4 years and with different stages of optic nerve atrophy. In histological cross-sections of retrolaminar optic nerves of 11 rhesus and 6 cynomolgus monkeys the entire area, number of axons and vessels and area of pial septa were quantitated and three different kinds of nerve degeneration classified. Ultrathin sections of these different stages were performed and the number of open and occluded vessels was determined. In addition, in cynomolgus monkey optic nerves immunohistochemical staining for alphaB-crystallin, glial fibrillary acidic protein (GFAP) and vimentin was performed. Even in animals with the same duration of glaucoma and comparable mean IOP values the axon degeneration varied considerably. Independently of axon loss the number of capillaries in the rhesus monkeys remained constant, whereas there was a slight decrease in the cynomolgus monkeys. Some of the vessels, especially in the most severely damaged regions, were occluded. The density of glial cells increased whereas the total number remained nearly constant. In control sections all astrocytes stained for GFAP and alphaB-crystallin. In the glaucomatous optic nerves the density of alphaB-crystallin- and GFAP-positive cells was significantly increased. The vascular reaction in the retrolaminar glaucomatous optic nerves differs from that described in the prelaminar region. We assume that in the postlaminar region in areas with diminished nutritional needs vessels occlude and finally degenerate.

Alpha-B-crystallin expression in tissues derived from different species in different age groups

alphaB-Crystallin is constitutively expressed in a variety of tissues including the nervous system, the eye, heart and striated muscles and the kidney. The functional significance of the protein in the different cell populations is not yet known. Experimental data indicate that mechanical stress to the cells might play a role but that there is also a close correlation with markers of oxidative activity. Increased expression of alphaB-crystallin is seen in a number of age-related degenerative diseases. Whether aging per se induces expression of the protein has not been investigated yet. In this study tissue samples of the anterior eye segment, optic nerve, heart muscle and thyroid gland from mouse, rat, pig, cow and human donors of different age groups were investigated with immunohistochemical methods. alphaB-Crystallin levels in heart muscle and optic nerve samples from different species and different age groups were investigated using protein immunoblotting (dot blot) and the mRNA levels using semiquantitative PCR methods. The results showed that neither in heart muscle known to show constitutively high amounts of the protein nor in nonlenticular eye tissues with variations in staining intensity of different cell populations or in glandular cells studied for the first time, there were significant age-related staining differences. Dot blot methods as a quantitative evaluation method gave similar results. There were, however, species differences. In the eye these differences could be due to functional differences related to the development of a fovea centralis and an accommodative system in primates. In addition, in all mouse tissues there was less protein expression than in the other species. Differences in the absolute life span might be a factor involved in alphaB-crystallin expression. In summary the findings show that an increase in alphaB-crystallin with age may occur but is not a general phenomenon in tissues constitutively expressing this protein.

Mast cell heterogeneity in the human uvea

To identify chymase- and tryptase-positive mast cells in the human uvea, and to study their associations with different types of resident uveal cells, uveal specimens from 24 human donor eyes were cryosectioned in sagittal and tangential planes. Enzyme histochemical staining of chymase was combined with immunohistochemical staining for tryptase, detected with the APAAP method. Fluorescence immunohistochemistry was performed with antibodies against c-kit, alpha smooth muscle actin, protein gene product (PGP) 9.5, CD45, and HLA-DR. In different uveal compartments, the total amounts of mast cells were calculated and the distributions of chymase and tryptase were quantified. All uveal mast cells were c-kit and CD45 positive and HLA-DR negative. No association existed between mast cells and actin-containing cells. Only a few mast cells were in close association with PGP 9.5-labeled nerve fibers. In the choroid, most mast cells were located in the inner central part (mean density = 48.9/mm(2)), and contained both chymase and tryptase (96%). The ciliary muscle contained numerous mast cells (mean density = 33.7/mm(2)), many of them tryptase positive but chymase negative (63%). In the pars plana, a high number of chymase-positive, tryptase-negative mast cells were found (20%). In the iris only a few mast cells were present. Although the choroid contains the most common subtype of mast cells, a unique situation concerning the distribution of chymase and tryptase is present in the anterior uveal tissues. A possible role for these cells in the special immunological situation of the anterior eye chamber merits further investigation.

AlphaB-crystallin in the trabecular meshwork is inducible by transforming growth factor-beta

PURPOSE

Because in glaucomatous eyes transforming growth factor-beta (TGF-beta) and alphaB-crystallin are increased in the anterior eye segment, the effect of TGF-beta1 and TGF-beta2 on the expression of alphaB-crystallin and its corresponding mRNA was studied in human trabecular meshwork (TM) cells.

METHODS

Monolayer cultures of "cribriform" and "corneoscleral" TM cells of 5 human donors (12-73 years of age) were treated with either 1.0 ng/ml TGF-beta1, TGF-alpha2, or 5 X 10(-7) dexamethasone (DEX) for 12 to 96 hours. Induction of alphaB-crystallin and the related mRNA was investigated by western and northern blot analyses. For comparison, human foreskin fibroblasts (HFF) and NIH 3T3 cells were treated in the same way as the TM cells.

RESULTS

An increase of alphaB-crystallin mRNA was observed after treatment of TM cells with TGF-beta1 and TGF-beta2, whereas DEX had no effect. In the cribriform TM cells with a high basal level, the enhancement ranged between 2 and 3 times; whereas in the corneoscleral TM cells alphaB-crystallin mRNA increased between 5 and 6 times. Using western blot analysis, the increase of alphaB-crystallin expression in the cribriform TM cells was only small compared with the significant increase in the corneoscleral TM cells. Treatment of HFF and NIH 3T3 cells with TGF-beta did not induce alphaB-crystallin mRNA.

CONCLUSIONS

This is the first time to show that alphaB-crystallin is not only induced by stress factors but also by TGF-beta in TM cell cultures. The difference in induction of mRNA and protein seems to be dependent on alphaB-crystallin concentration before treatment.

Human minisatellites, repeat DNA instability and meiotic recombination

Minisatellites include some of the most variable loci in the human genome and are superb for dissecting processes of tandem repeat DNA instability. Single DNA molecule analysis has revealed different mutation processes operating in the soma and germline. Low-level somatic instability results in simple intra-allelic rearrangements. In contrast, high frequency germline instability involves complex gene conversions and is therefore recombinational in nature, almost certainly occurring at meiosis. To determine whether true meiotic crossovers occur at human minisatellites, we have used polymorphisms near the repeat array to recover recombinant DNA molecules directly from sperm DNA. Analysis of minisatellite MS32 has revealed an intense and highly localised meiotic crossover hotspot centred upstream of the array, the first example of a human hotspot defined at the molecular level. This hotspot extends into the beginning of the repeat array, resulting in unequal and equal crossovers. Array crossovers occur much less frequently than array conversions but appear to arise by a common process, most likely by alternative processing of a recombination initiation complex. The location of MS32 at the boundary of a recombination hotspot suggests that this locus has evolved as a by-product of localised meiotic recombination activity, and that minisatellites might in general mark recombinationally proficient hotspots or hot domains in the genome. Finally, sperm crossover analysis makes it possible to explore the molecular rules that govern human meiotic recombination, and to detect phenomena such as meiotic drive that could provide a possible connection between recombination and DNA sequence diversity itself.

Cis-regulation of inter-allelic exchanges in mutation at human minisatellite MS205 in yeast

Tandemly repeated DNA is a major component of the human genome, and includes loci contributing to human disease. Minisatellites include the most variable human loci described to date, and the mechanisms by which this variation is generated in humans have been studied in detail. Integration of human minisatellites into yeast not only provides a model for further dissecting the molecular basis of length change mutation at these loci, but also more generally allows the study of complex recombinational events in yeast. We have used human minisatellite MS205 integrated into yeast to study the structural details of length change mutations. Apart from showing that mutation at this locus in yeast has features similar to those observed at some minisatellites in humans, including meiosis-specificity, and polarity, in which exchange events are localised to one extremity of the array, we here, for the first time, directly demonstrate that a flanking element in yeast regulates the mutation process. The results therefore support the hypothesis that flanking initiators are involved in minisatellite mutation in humans. Furthermore, mutant alleles showed more complex rearrangements in one orientation than the other. The data also suggest that the mutational pathway for deletions might be different from the pathway generating inter-allelic exchanges and duplications.

Extremely complex repeat shuffling during germline mutation at human minisatellite B6.7

Human minisatellite B6.7 is a highly variable locus showing extensive heterozygosity with alleles ranging from six to >500 repeat units. Paternal and maternal mutation rates to new length alleles were estimated from pedigrees at 7.0 and 3.9% per gamete, respectively, indicating that B6.7 is one of the most unstable minisatellites isolated to date. Mutation at this locus was also analysed by small pool PCR of sperm and blood DNA. Male germline instability varied from <0.8 to 14% per allele and increased with tandem array size. In contrast, the frequency of mutants in somatic (blood) DNA was far lower (<0.5%), consistent with a meiotic origin of germline mutants. Sperm mutants were further characterized by minisatellite variant repeat mapping using four major polymorphic sites within the B6.7 repeats. This highly informative system revealed a wide variety of changes in allele structure, including simple intra-allelic duplications and deletions and more complicated inter- and intra-allelic transfers of repeat blocks, as seen at other human minisatellites. The main mode of sperm mutation, however, resulted in extremely complex allele reorganization with evidence of inter-allelic transfer plus the generation of novel repeats by rearrangement at the sub-repeat level, suggesting that recombinational instability at B6.7 is a complex multistep process.

Isolation of Helicobacter pylori genes that modulate urease activity

Helicobacter pylori urease, a nickel-requiring metalloenzyme, hydrolyzes urea to NH3 and CO2. We sought to identify H. pylori genes that modulate urease activity by constructing pHP8080, a plasmid which encodes both H. pylori urease and the NixA nickel transporter. Escherichia coli SE5000 and DH5alpha transformed with pHP8080 resulted in a high-level urease producer and a low-level urease producer, respectively. An H. pylori DNA library was cotransformed into SE5000 (pHP8080) and DH5alpha (pHP8080) and was screened for cotransformants expressing either lowered or heightened urease activity, respectively. Among the clones carrying urease-enhancing factors, 21 of 23 contained hp0548, a gene that potentially encodes a DNA helicase found within the cag pathogenicity island, and hp0511, a gene that potentially encodes a lipoprotein. Each of these genes, when subcloned, conferred a urease-enhancing activity in E. coli (pHP8080) compared with the vector control. Among clones carrying urease-decreasing factors, 11 of 13 clones contained the flbA (also known as flhA) flagellar biosynthesis/regulatory gene (hp1041), an lcrD homolog. The LcrD protein family is involved in type III secretion and flagellar secretion in pathogenic bacteria. Almost no urease activity was detected in E. coli (pHP8080) containing the subcloned flbA gene. Furthermore, there was significantly reduced synthesis of the urease structural subunits in E. coli (pHP8080) containing the flbA gene, as determined by Western blot analysis with UreA and UreB antiserum. Thus, flagellar biosynthesis and urease activity may be linked in H. pylori. These results suggest that H. pylori genes may modulate urease activity.

Morphological changes of retinal pigment epithelium and choroid in rd-mice

The sequence of degenerative changes in the retinal pigment epithelium (RPE) and the choroid of retinal degeneration (rd)-mice was studied in correlation with photoreceptor changes. Three weeks to 26-month-old animals were investigated using light and transmission electron microscopy, enzyme histochemistry and quantitative morphology. Changes in the choriocapillaris (CC) were additionally studied by scanning electron microscopy of corrosion cast preparations. In 3-week-old mice, in which most of the outer segments of photoreceptors in the central portion of the retina had disappeared but remnants of the cells were still present, the RPE was enlarged and showed elongated microvilli. In 8-week-old animals, the photoreceptors were completely absent in large areas of the posterior pole region. In these areas the RPE was also completely lost. Quantitative evaluation performed in histological serial sections showed that loss of RPE measured as length of RPE-free Bruch's membrane, continuously increased up to the age of 20 months. In 8-week-old animals, CC adjacent to degenerating RPE showed loss of fenestration. In 10-week-old animals, the CC disappeared in those areas where the RPE was already lacking. The loss of CC increased with increasing age and in 20-month-old animals 5-10% of the entire CC was lacking. Loss of the related arterioles and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d)-positive nerve fibers occurred only in approximately 2-year-old rd-mice. Compared to other animal models, RPE and CC defects in rd-mice are relatively large. The rd-mice might therefore provide a good tool to study factors involved in CC degeneration.

Retinal vasculature changes in Norrie disease mice

PURPOSE

To correlate morphologic changes in the retinal vasculature with degenerative changes in the neuronal retina of mice lacking 56 amino acids from the N-terminus of the Norrie disease (ND) gene product.

METHODS

Posterior eye segments of ND mice of different age groups were investigated by light and electron microscopy (EM) and scanning EM of vascular corrosion cast preparations. The results were qualitatively and quantitatively compared with those obtained in age-matched littermate control mice and C57B1/6 mice.

RESULTS

Quantitative evaluation revealed an increase in the number of blood vessels in the interface of the ganglion cell layer and the nerve fiber layer and a decrease in the inner and outer plexiform layers in ND mice older than 9 days compared with control mice. Vessels were also seen adjacent to the vitreous surface of the inner limiting membrane. Most of these vessels showed fenestrations and occasionally penetrated the inner limiting membrane. Hyaloid vessels were still present in the vitreous. The abnormal vascularization pattern was found in the entire retina and occurred in addition to the previously described alterations of the neuronal retina.

CONCLUSIONS

There is a malformation of the retinal vasculature and a persistence of hyaloid vessels in the vitreous of ND mice. It is assumed that the ND gene product is required for normal vascularization of the inner retinal layers and for atrophy of hyaloid vessels.

Alpha B-crystallin in the mammalian inner ear

To study the distribution of alpha B-crystallin, formalin-fixed preparations of the inner ear of the rat, cynomolgus monkey, rhesus monkey and human were stained immunohistochemically for alpha B-crystallin. In all cochleae investigated, intense staining for alpha B-crystallin was found in the inner and outer pillars as well as in the cells of Hensen and Claudius. In the primate inner ear, alpha B-crystallin was also present in the polygonal epithelial cells of Reissner's membrane, the interdental cells and some fibrocytes of the spiral limbus, epithelial cells of the outer spiral sulcus and the Schwann cells of the 8th nerve. In the primate stria vascularis, alpha B-crystallin was mainly seen in the basal cell layer and the adjacent cells of the connective tissue layer. alpha B-crystallin was found to be present in a large variety of cells in the inner ear surrounding the scala media.

Localization of the stress proteins alpha B-crystallin and trabecular meshwork inducible glucocorticoid response protein in normal and glaucomatous trabecular meshwork

PURPOSE

To examine the differential staining of two potential stress-response markers, alpha B-crystallin and the trabecular meshwork inducible glucocorticoid response protein (TIGR), in meshwork from normal and glaucomatous human eyes.

METHODS

Trabecular meshwork from 35 eyes from 23 donors with either primary open-angle glaucoma, pseudoexfoliative glaucoma, or low-tension glaucoma, and from age-matched normal eyes, was examined. Sagittal and tangential frozen sections were stained with polyclonal antibodies to alpha B-crystallin or TIGR and then by a fluorescent secondary antibody.

RESULTS

In normal eyes, labeling for alpha B-crystallin occurred in the subendothelial region of Schlemm's canal and outer corneoscleral regions, whereas TIGR labeling was found in the inner uveal meshwork region and the anterior portion of the meshwork. In contrast, in many glaucomatous eyes, labeling for alpha B-crystallin and TIGR occurred in more regions of the meshwork and appeared more intense than in normal eyes, regardless of the type or clinical severity of glaucoma.

CONCLUSIONS

The differences in localization of alpha B-crystallin and TIGR may relate to functional specialization within meshwork tissues. The increase in the staining for these proteins in glaucomatous eyes could involve environmental and genetic factors in the disease processes.

Description and function of the ciliary nerves--some historical remarks on choroidal innervation

The earliest accounts of the eye recognized its main function as providing vision, but the mechanism of how the eye functioned remained obscure for many centuries. The aim of the following work is to outline these changes in the understanding of a particular structure and function of the human body, namely, the ciliary nerves supplying the uveoscleral part of the eye. In the extensive study on the history of ophthalmology by Hirschberg (published between 1899 and 1918), the ciliary nerves and choroidal innervation are only sparsely mentioned.

Choroidal ganglion cell plexus and retinal vasculature in monkeys with laser-induced glaucoma

The choroid of primates possesses an elaborate nitrergic nerve fiber plexus containing a great number of ganglion cells. Postganglionic nerve fibers innervate mainly the choroidal vasculature. In addition, the choroid contains an elastic muscular system closely associated to the vasculature. The goal of the present investigation was to analyze how sustained IOP elevation would affect the choroidal vasculature with its specialized innervation and the adjacent retina. For this purpose the posterior eye segment of 15 rhesus monkeys which after laser coagulation of the trabecular meshwork developed elevated IOP up to 4 years were studied using immunohistochemical and histochemical methods, and scanning electron microscopy of corrosion casts. The most striking finding was a significant reduction of choroidal thickness and loss of choroidal ganglion cells and nerve fibers, especially in the central portion of the choroid. Corrosion casts of the choroidal vasculature showed a slight decrease in capillary density and a decrease in length of the arterioles in glaucomatous eyes. Whole mount preparations of the retina stained for NADPH diaphorase revealed a significant reduction in positively stained amacrine cells, reduction in diameter of arterioles and changes in the staining pattern of the retinal vasculature, particularly in the perimacular region.

Mutation rate heterogeneity and the generation of allele diversity at the human minisatellite MS205 (D16S309)

Many tandemly repeated minisatellite loci display extreme levels of length variation as a consequence of high rates of spontaneous germline mutation altering repeat copy number. Direct screening for new allele lengths by small-pool PCR has shown that instability at the human minisatellite locus MS205 (D16S309) is largely germline specific and usually results in the gain or loss of just a few repeat units. Structural analysis of the order of variant repeats has shown that these events occur preferentially at one end of the tandem array and can result in complex rearrangements including the inter-allelic transfer of repeat units. In contrast, putative mutants recovered from somatic DNA occur at a substantially lower rate and are simple and non-polar in nature. Germline mutation rates vary considerably between alleles, consistent with regulation occurring in cis. Although examination of DNA sequence polymorphisms immediately flanking the minisatellite reveals no definitive associations with germline mutation rate variation, differences in rate may be paralleled by changes in mutation spectrum. These findings help to explain the diversity of MS205 allele structures in modern humans and suggest a common mutation pathway with some other minisatellites.

alpha B-crystallin in the primate ciliary muscle and trabecular meshwork

The presence of alpha B-crystallin, a protein with heat-shock protein-like properties, has been demonstrated in ciliary muscle and trabecular meshwork derived from human and monkey eyes using immunohistochemical and polymerase chain reaction methods. Both frozen sections and cultured cells have been analyzed. In the ciliary muscle, alpha B-crystallin staining is localized in the region of the dense bands, in the cytoplasm of the muscle cells and in the Schwann cells of the nerves supplying the muscle. In the trabecular meshwork, two cell types could be distinguished on the basis of alpha B-crystallin occurrence. Whereas the trabecular cells covering the lamellae were virtually devoid of the protein, the subendothelial or cribriform cells contained relatively large amounts in parallel with a higher alpha B-crystallin mRNA level.

Quantitative and morphological changes of the choroid vasculature in RCS rats and their congenic controls

In Royal College of Surgeons (RCS) rats the outer retina degenerates owing to a phagocytic defect of the retinal pigmented epithelium (RPE). To analyse whether the choriocapillaris also undergoes degenerative changes, corrosion casts of choroidal vessels of ten RCS rats and 12 age-matched controls of different age groups were investigated by scanning electron microscopy. The pattern of the ciliary arteries was analysed qualitatively and the areas covered by capillaries in the different quadrants and regions of the choroid were evaluated quantitatively. In both RCS rats and their congenic controls the choroid was supplied by only three ciliary arteries. A separate artery supplying the upper quadrant in other rat strains was lacking. The quantitative evaluation revealed that in controls the capillary density decreased from the central to the peripheral regions. In addition there were slightly fewer capillaries in the upper temporal quadrant compared to other quadrants. In RCS rats older than 6 months, all parts of the choroid displayed a decrease in the number of capillaries of about 10-15% compared to the controls. Most prominent loss of capillaries was found in the upper temporal quadrant. Electron-microscopical investigation of the upper temporal quadrant showed that loss of choriocapillaris was directly correlated with degeneration of the adjacent retinal pigmented epithelium (RPE).

Minisatellite diversity supports a recent African origin for modern humans

In a study of human diversity at a highly variable locus, we have mapped the internal structures of tandem-repetitive alleles from different populations at the minisatellite MS205 (D16S309). The results give an unusually detailed view of the different allelic structures represented on modern human chromosomes, and of the ancestral relationships between them. There was a clear difference in allelic diversity between African and non-African populations. A restricted set of allele families was found in non-African populations, and formed a subset of the much greater diversity seen on African chromosomes. The data strongly support a recent African origin for modern human diversity at this locus.

Presence of a contractile cell network in the human choroid

Immunohistochemical staining of choroidal whole mounts as well as serial tangential sections and electron-microscopic investigation of 21 human donor eyes revealed a network of nonvascular alpha-smooth-muscle-actin-positive cells (NVSMC) in the entire choroid most densely arranged in the posterior part of the suprachoroid of the submacular region. Ultrastructurally these cells present the typical structure of myofibroblasts. Double labeling with desmin and smooth muscle myosin showed a positive reaction only in few of these cells. Posteriorly the NVSMC net reaches the optic nerve, anteriorly it ends in the region of the vortex veins but does not continue into the ciliary muscle. In places, intimate contact between the contractile cells and the elastic fiber network of the choroidal stroma and the perivascular sheaths is seen. The elastic net of the choroid is firmly connected with the posterior elastic tendons of the ciliary muscle. In the course of accommodation, the ciliary muscle pulls this net foreward presumably influencing position and diameter of the choroidal vessels. We assume that the network of NVSMC of the choroid counteracts the ciliary body movements during accommodation, thus guaranteeing the three-dimensional architecture of the choroid and the position of the retina, particularly in the macular region.

Mutation processes at human minisatellites

Minisatellites provide one of the most experimentally tractable systems for studying tandem repeat instability in man. Analysis of mutation processes has been greatly aided by the development of single molecule methods for recovering de novo mutants, and of techniques for exploring allele structure in detail. Application of these approaches to man has shown that minisatellites do not primarily mutate by processes such as replication slippage and unequal crossover intrinsic to the tandem repeat array. Instead, germline repeat instability is largely regulated by cis-acting elements near the array and involves unexpectedly complex processes of gene conversion, of potential relevance to the biology of meiosis. These processes can be explored both in humans and, in principle, in transgenic mouse models of human repeat instability.

Charomid cloning vectors meet the pedipalpal chelae: single-locus minisatellite DNA probes for paternity assignment in the harlequin beetle-riding pseudoscorpion

We describe the first application of the charomid-cloning method for developing single-locus minisatellite DNA probes in a terrestrial arthropod. From a genomic library of the neotropical pseudoscorpion, Cordylochernes scorpioides, we have isolated two probes with heterozygosities exceeding 95%. These probes yielded single-locus patterns after only low stringency washing and in the absence of genomic competitor DNA. Analysis of three pedigrees indicated germline stability and showed no evidence of linkage between the loci. Patterns of allelic transmission generally conformed closely to Mendelian expectations but large offspring numbers did enable detection of one example of significant bias in allele inheritance. Two test cases are presented to illustrate the clarity and power with which these probes can establish paternity: (i) a female mated to three unrelated males, and (ii) a female mated to two of her brothers. In both cases, a single probe could be used to assign the paternity of all offspring.

Nitric oxide inhibits resting sphincter of Oddi activity

The sphincter of Oddi has basal myogenic phasic activity that is modulated by neural and hormonal pathways. Stimulatory innervation to this organ is cholinergic, whereas the inhibitory pathways are unknown. Nitric oxide (NO), generated from L-arginine, relaxes gastrointestinal smooth muscle in vitro. We, therefore, hypothesized that resting sphincter of Oddi and duodenal motilities are regulated by a NO-mediated inhibitory pathway. In 23 anesthetized prairie dogs, systemic blood pressure and sphincter of Oddi and duodenal motilities were monitored during systemic infusion of N omega-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthase. L-NAME was infused alone and simultaneously with excess D- and L-arginine. L-NAME alone and L-NAME with D-arginine produced hypertension and increased sphincter of Oddi and duodenal motilities. L-arginine blocked these increases, suggesting that baseline sphincter of Oddi and duodenal motility regulation involves the generation of NO from L-arginine. We conclude that baseline sphincter of Oddi phasic activity is regulated by cholinergic stimulatory and NO-mediated inhibitory neural pathways.

DNA fingerprinting by specific priming of concatenated oligonucleotides

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The effect of calcium on gallbladder absorption

The absorption of water and electrolytes is an important physiologic function of the gallbladder which is altered during gallstone formation. Extracellular calcium and calcium channel antagonists are known to affect intestinal absorption, yet their effect on gallbladder absorption is less well defined. We, therefore, tested the hypothesis that changes in extracellular calcium or in calcium channels would alter gallbladder absorption. New Zealand white rabbit gallbladders were removed, filled with a modified Krebs buffer (Ca2+ = 0.7 mM), and suspended in an oxygenated bath of the same buffer. Water absorption was determined gravimetrically by obtaining serial gallbladder weights at 10-min intervals. After a 40-min control period, the serosal bathing solution was changed to one of four experimental solutions (n = 6 for each group): Ca2+ = 0.25, 0.7, or 1.2 mM or Ca2+ = 0.7 mM plus 0.1 mM verapamil. Absorption was determined during an 80-min experimental period with results expressed as the percentage change in gallbladder absorption compared to that of the control period. The 0.25, 0.7, and 1.2 mM Ca2+ groups did not show a significant change in absorption rate from their respective control rates. However, the verapamil group did demonstrate a significant (P less than 0.05) decrease in absorption rate of -69 +/- 8% by the end of the experimental period. These data demonstrate that verapamil inhibits gallbladder absorption while changes in serosal calcium concentration have no effect. We conclude that calcium channels and intracellular calcium may play an important role in modulating gallbladder absorption.

Treatment of adrenocortical carcinoma: a case report and review of the literature

A case report of adrenocortical carcinoma is presented, and its natural history and treatment are discussed. Adrenocortical carcinoma is a rare malignant disease. The mean survival time for untreated patients is less than three months. The tumor is classified as functioning or nonfunctioning depending on biochemical and clinical evidence of steroid overproduction. Surgical resection of the tumor is the primary treatment. Chemotherapy is indicated for antitumor and antihormonal effects. Mitotane is a direct adrenolytic, and is the only drug currently available that has extended survival in patients with this disease. Its clinical usefulness is limited by its gastrointestinal and neurological toxicity. Aminoglutethimide inhibits steroid synthesis by blocking the conversion of cholesterol to pregnenolone. It has no antitumor effect in adrenocortical carcinoma, but is effective in relieving the signs and symptoms of excessive hormone production in functioning tumors. Both mitotane and aminoglutethimide have complex mechanisms of action. Their combined use in the treatment of adrenocortical carcinoma requires a complete understanding of their individual actions and awareness of the potential for additive effects, both therapeutic and toxic.

Methyldopa does not alter the disposition of digoxin

To investigate whether methyldopa alters digoxin disposition, eight healthy subjects received methyldopa titrated to 250 mg t.i.d. or placebo in a double-blind, cross-over manner for 16 consecutive days, with 0.25 mg intravenous digoxin coadministered on day 5 and 0.25 mg oral digoxin on days 9 to 16. Digoxin concentrations in plasma and urine were measured by RIA. Although assay sensitivity did not allow an adequate assessment of serum AUC(0-infinity) after intravenous administration, mean digoxin AUC(0-24) was 10.2 +/- 3.5 and 10.0 +/- 1.8 ng/ml X hr with placebo and methyldopa, respectively (P greater than 0.05). Mean urinary excretion after digoxin with or without methyldopa treatment was 0.204 +/- 0.34 and 0.197 +/- 0.38 mg, respectively. The mean steady-state serum concentrations of oral digoxin (AUC(0-24)/zeta) with and without methyldopa were 0.65 +/- 0.2 and 0.62 +/- 0.3 ng/ml, respectively. These data revealed no significant differences (P greater than 0.05) for various parameters with power of greater than 0.8 to detect meaningful differences of approximately 30 per cent. Thus, methyldopa did not alter digoxin disposition in healthy subjects, and a pharmacokinetic interaction in patients is unlikely.

Prediction of steady-state concentrations of valproic acid as determined from single plasma concentrations after the first dose

A mathematical equation that predicts the maintenance dose needed to achieve a desired steady-state plasma concentration (Css) for first-order drugs from a single plasma concentration drawn after a single dose was tested for valproic acid. Six healthy volunteers received a single oral 500-mg dose of valproic acid and plasma concentrations were determined at 0, 1, 2, 4, 6, 8, 10, 24, and 32 hours. Each subject then received 750 mg of valproic acid daily in three divided doses for four days and a Css was determined. The equation was rearranged to predict the Css of valproic acid from plasma concentrations drawn at 1, 2, 4, 6, 8, and 10 hours after the single dose of valproic acid, using individually determined and mean terminal rate constant (k) values. The predicted Css were then compared with the actual Css. There was no difference in the predicted and actual Css using plasma concentrations collected at 6, 8, or 10 hours regardless of the derivation of the k values. The four-hour concentration predicted a lower Css if the mean (rather than the individual) k values were used. The one- and two-hour concentrations were not accurate predictors. While a 6-, 8-, or 10-hour plasma concentration would be adequate for predicting the Css, the 10-hour concentration had the least difference between the predicted and actual values. The time and cost of titrating valproic acid to a desired Css may be decreased by using this mathematical equation to predict the necessary maintenance dose.

Effects of three antacids on the bioavailability of valproic acid

The effects of three antacid products on the bioavailability of valproic acid were evaluated. Each of seven normal, healthy volunteers received a 500-mg dose of valproic acid alone on one occasion and then with each of three commonly used antacids. Specifically, equal neutralizing capacity doses of 160 meq of Maalox (62 ml), Trisogel (97 ml), or Titralac (42 ml) were administered one and three hours after meals and at bedtime on the same day. Blood samples were obtained at 0, 1, 2, 4, 6, 8, 10, 24, and 32 hours and analyzed for valproic acid by gas liquid chromatography. There was a significant increase in total area under the curve (AUC) (range 3% to 28%, mean 12%) when valproic acid was administered with Maalox (p = 0.026 for total AUC and p = 0.009 for AUC to 32 hours). There was an insignificant trend toward an increase in AUC when valproic acid was administered with the other two antacids. No differences were observed in time to peak serum concentration, height of peak serum concentration, volume of distribution, half-life, or first order elimination rate constant. Caution should be exercised if valproic acid and antacids are administered concomitantly.