Long-term photoreceptor transplants in dystrophic and normal mouse retina

PURPOSE

To determine the long-term status of transgenic photoreceptors transplanted to the subretinal space of both rd mutant (receptorless) and normal mouse retina.

METHODS

Microaggregates of neural retina from transgenic mice containing lacZ-labeled photoreceptors were transplanted to the subretinal space of adult rd mutant and normal mice. The transplant site was examined by light and electron microscopy at monthly intervals up to 9 months after transplantation surgery.

RESULTS

Photoreceptors develop and survive well if transplanted with the proper orientation to the retinal pigment epithelium (RPE). The status of the photoreceptors, including outer segments and synaptic terminals, appear normal for at least 9 months after transplantation; they continue to express the lacZ reporter gene. Cones survive as well as rods. Transplants to the normal mouse develop normally, whereas the host photoreceptors displaced from the RPE degenerate. A barrier, formed by Müller cell processes, develops after photoreceptor degeneration in both normal and rd mouse retina and demarcates host from transplant tissue. Areas can be found in which neural processes have penetrated this barrier. There is no evidence of host-graft rejection.

CONCLUSION

Transplanted progenitor photoreceptors develop and survive well for long periods of time in either the rd mutant or normal retina if they are properly positioned. In the former, they reconstitute a photoreceptor layer; in the latter, they replace the host photoreceptor layer, which degenerates after being displaced from the RPE. Areas of potential contact between donor and host neurons exist in these transplants.

[Comparison of corneal topography and keratometer in patients with cataract preoperatively and postoperatively]

The comparison of corneal topography with keratometer in 200 patients (278 eyes) was made. The results revealed that Sim K values of corneal topography were 44.22D and 44.26D, mean diopters of keratometer were 44.16D and 44.23D in 150 eyes of 116 patients with cataract preoperatively. There was no significant difference between Sim K values of topography and diopters of keratometer (P > 0.05). The Sim K values of the topography were 46.37D and 43.06D and diopters of keratometer were 46.09D and 42.88D in 90 eyes of 67 patients who received cataract extraction with IOL implantation or second IOL implantation. No significance was found in results between Sim K values and diopters of keratometer in patients postoperatively (P > 0.05). Our investigation demonstrated that Sim K values of corneal topography were in agreements with diopters of keratometer in patients with cataracts preoperatively or postoperatively. However, corneal topography has great values in diagnosis of corneal diseases, traumatic astigmatism, severe non-rule stigmatisms, in which keratometer is often useless.

Water volume and osmotic behaviour of mouse spermatozoa determined by electron paramagnetic resonance

Experiments were conducted to determine the water volume and osmotic behaviour of mouse spermatozoa using an electron paramagnetic resonance technique using the spin label tempone, and the broadening agent potassium chromium oxalate. After a swim-up procedure, an average water volume of 43.3 micron3 of individual spermatozoa was obtained at 290 mosmol. If a water compartment of 59% is assumed, the total volume of mouse spermatozoa is 73.4 micron3. A plot of the relative water volume of mouse spermatozoa versus the reciprocal of buffer osmolality (Boyle van't Hoff plot) is linear in the range 250-900 mosmol of sodium chloride solutions (r2 = -.96). The Boyle van't Hoff plot intercept indicates that 13% of the spin-label accessible isotonic water is osmotically inactive.

Enhanced brain delivery of an anti-HIV nucleoside 2'-F-ara-ddI by xanthine oxidase mediated biotransformation

In order to enhance the brain delivery of 2'-F-ara-ddI,2'-F-ara-ddP 6 was synthesized and its in vitro and in vivo bioconversion reaction studied. For the study, a new efficient synthetic method for 2'-F-ara-ddP 6 was developed from 5-benzoyl-1,2-O-isopropylidene-3-deoxyribose 1. For in vitro study 2'-F-ara-ddP was incubated in pH 2, mouse liver homogenate, and mouse serum at 37 degrees C. No degradation was observed in pH 2 and serum, while in liver homogenate 2'-F-ara-ddP was almost completely converted to 2'-F-ara-ddI within 20 min (t1/2 = 3.54 min). In order to determine the role of xanthine oxidase in the conversion of 2'-F-ara-ddP to 2'-F-ara-ddI, in vitro studies were conducted in phosphate buffer (pH 7.4) in the presence or absence of allopurinol, in which the half-lives of 2'-F-ara-ddP were 7.4 and 3.4 h, respectively, indicating the conversions were catalyzed by the xanthine oxidase. A similar experiment with aldehyde oxidase isolated from the human liver did not affect the biotransformation. The biotransformation was also detected in the brain homogenate, although the rate of conversion was low and incomplete. In order to assess the bioconversion in vivo, pharmacokinetic studies of 2'-F-ara-ddP and 2'-F-ara-ddI were conducted in mice. The maximum serum concentrations of 2'-F-ara-ddI administered itself and as 2'-F-ara-ddP reached 48.1 +/- 10.00 and 89.3 +/- 26.0 microM and were observed in 1 and 0.25 h, respectively. The data indicate that 2'-F-ara-ddI is absorbed at a slower rate than that of 2'-F-raa-ddP. The bioavailability of the prodrug after oral administration was 60.7%. The concentration of 2'-F-ara-ddI following oral administration of 2'-ara-ddI was close to the detection limits while 2'-F-ara-ddI was detected at significantly higher concentrations in the brain after oral administration of 2'-F-ara-ddP. From this study, we have administered the enhanced brain delivery of anti-HIV nucleoside utilizing an in vivo biotransformation system.

[Effect of indomethacin on H+ transportation of pig gastric H+/K(+)-ATPase]

As a noncompetitive inhibitor of pig gastric H+/K(+)-ATPase, indomethacin inhibited the H+ transportation function of the enzyme, leading to not only the obvious dissipation of H+/K(+)-ATPase-generated H+ gradients, but also the decreasing of the H+ gradient formation ability of the enzyme. 4% of indomethacin was able to penetrate into the lipid bilayer of H+/K(+)-ATPase vesicles at 0.15 mg/ml protein concentration, which showed an influence of indomethacin to the membrane. Indomethacin reduced the membrane fluidity of H+/K(+)-ATPase vesicles significantly. It also damaged the conformation of membrane protein extraordinarily, which was evidenced by decreasing the intrinsic fluorescence of H+/K(+)-ATPase. From the results, we suggest that the effect of indomethacin on H+/K(+)-ATPase is taken place by its inhibition on H+/K(+)-ATPase protein, as well as by its influence on the membrane lipid bilayer of H+/K(+)-ATPase vesicles.

Determination of boar spermatozoa water volume and osmotic response

Boar spermatozoa water volume and osmotic response were determined by a shapeindependent method for measuring cellular volume, electron paramagnetic resonance (EPR), employing the spin label, tempone, and the broadening agent, potassium chromium oxalate (CrOx). A water volume of 18.4 +/- 1.6 mum(3) (X +/- SD) was obtained for individual boar spermatozoa at 290 milliosmolar (mOsm) which, after correction for the presence of cytoplasmic droplets, yields a boar sperm water volume of 13.0 to 15.0 mum(3). Assuming 59% of the total cell volume is water, the total cell volume of boar spermatozoa is 22.0 to 25.4 mum(3). In addition, the experiment indicated that the relative water volume versus the reciprocal of the external osmolality (Boyle van't Hoff plot) was linear over the range of 210 to 1500 mOsm of sodium chloride (r(2) = 0.996), supporting the hypothesis that boar spermatozoa act as ideal osmometers. A non-zero y axis intercept of 0.23 from the Boyle van't Hoff plot indicated a 23% spin label accessible, but osmotically inactive water component.

Assessment of the acrosomal status and viability of human spermatozoa simultaneously using flow cytometry

Acrosomal status and viability were evaluated simultaneously on human spermatozoa using flow cytometry. Samples were divided into three aliquots and randomly assigned to one of three treatments: (i) cryopreservation; (ii) 10 microM calcium ionophore [A23187 in dimethylsulphoxide (DMSO)] or (iii) DMSO alone (control). Acrosomal status was evaluated using monoclonal antibodies recognizing MH61 and CD46, respectively. Fluorescein-conjugated goat anti-mouse immunoglobulin (IgG) was used as a second antibody. Sperm viability was assessed using Hoechst 33258 (H258) exclusion. The following factors were analysed: (i) the specificity of the monoclonal antibodies for the human acrosome; (ii) the relative effectiveness of flow cytometry and direct fluorescent microscopy scoring and (iii) the acrosomal status and viability of the control, ionophore-treated, and cryopreserved spermatozoa. Across all treatments, the MH61 and CD46 monoclonal antibodies resulted in acrosomal status values (acrosome-reacted/viable spermatozoa) which were not significantly different (P > 0.05): control, 1.0 +/- 0.3% and 1.5 +/- 0.6% (mean +/- SEM); A23187, 42.8 +/- 3.5% and 38.1 +/- 3.5%; cryopreserved, 8.2 +/- 2.0% and 9.9 +/- 1.3%; respectively. However, acrosomal status among treatments differed significantly (P < 0.01). Flow cytometric and direct fluorescent microscopy assessments were significantly correlated (r2 = 0.96, P < 0.01). These results indicate that flow cytometry, using an acrosome-specific monoclonal antibody and a supravital dye, provides an objective and efficient method to evaluate human sperm acrosomal and viability status simultaneously.

Retinal pigment epithelial transplants and retinal function in RCS rats

PURPOSE

To determine if retinal pigment epithelium (RPE) transplantation maintains visual function in Royal College of Surgeons (RCS) strain of rats.

METHODS

Twelve RCS rats received RPE transplants at 16 to 20 days after birth. The retinas were studied electrophysiologically and histologically from 3 to 10 months after transplantation and compared with 11 RCS controls and 11 normal rats of comparable ages. A microelectrode was guided to the transplant site visible by its pigmentation in the albinotic RCS retina to detect responses.

RESULTS

Spontaneous ganglion cell activity was present in all retinas. Ganglion cell responses to light were detected in 9 of the 12 transplant eyes but not in any of the 11 controls. 96, 44, 140 units were encountered and 30%, 0%, 97% were driven by light respectively in transplant, control, and normal retinas. In transplants 36%, 29%, and 28% were driven at 3 to 4, 6 to 7, and 10 months after transplantation, respectively. Intraretinal ERGs with both a- and b-waves were recorded in 5 of the 8 transplants studied. None of the RCS controls studied had an IERG. The average IERG was 2.5 microV (SD = 1.9) in transplants and 59 microV (SD = 19) in normal retinas. The electrode track was traced to the transplant site in six of the seven retinas that were responsive to light and examined histologically.

CONCLUSION

RPE transplants to RCS rats maintain retinal function in the transplant site for long periods of time.

Effect of receiver fluid pH on in vitro skin flux of weakly ionizable drugs

In in vitro skin permeation experiments, the pH of viable epidermis is readily conditioned by the receiver fluid. For weakly ionizable compounds, the flux determined experimentally thus depends on the receiver fluid pH. The purpose of the present work is to characterize this pH effect, since nonphysiological conditions have often been used in the receiver fluid to enhance the solubility of the subject compounds. A transport model was developed to analyze the above-mentioned pH effect of the receiver fluid on the steady state flux of weakly ionizable drugs. The results showed that the skin flux had a strong dependence on pH for those compounds with high intrinsic partition coefficients. Experimentally, this pH effect was observed with a model acid and a model base. The skin flux was found to have a profound dependence on the receiver fluid pH. This dependence also correlates with the octanol/water partition coefficient of the molecule. It was concluded that the use of a physiological receiver fluid would be crucial for a realistic estimation of transdermal potential. The results also suggested that, for weakly ionizable compounds with high partition coefficients, the viable epidermis could be a significant transport barrier for systemic absorption.

Autocrine, endocrine and paracrine regulation of growth abnormalities in autosomal dominant polycystic kidney disease

Genetic polycystic kidney disease (ADPKD) is an autosomal dominant trait in man, the phenotypic expression of which is characterized by enormous cystic enlargement of renal tubules. Since this is, in part, a result of aberrant epithelial cell proliferation, the nature of this defect has been characterized by comparison of growth factor action on defined epithelial primary monolayer cultures derived from individually microdissected normal human renal proximal and distal tubules and ADPKD cyst-lining epithelia. Mitogenic assays showed an increased sensitivity of ADPKD epithelia to stimulation by the combination of the endocrine factors hydrocortisone (dexamethasone) and insulin, and Northern analysis suggested increased levels of insulin receptor steady state mRNA. The most potent, single mitogen was epidermal growth factor (EGF), and hypersensitivity to EGF in ADPKD epithelia was correlated with increased mRNA levels for EGF receptor in ADPKD kidneys. The localization in vivo of EGF immunoreactivity in ADPKD cyst-lining epithelia and in (apical) cyst fluids and the demonstration of EGF-receptor immunostaining and specific [125I]EGF binding to apical cell surfaces suggested an autocrine mechanism of growth stimulation by EGF in ADPKD epithelia. Transforming growth factor beta was an inhibitor of normal renal tubule proliferation but was unable to completely inhibit EGF stimulation in ADPKD cultures. Platelet-derived growth factor (PDGF) immunoreactivity which was also seen in ADPKD cyst epithelia, was not mitogenic to ADPKD epithelia but did stimulate division in ADPKD fibroblasts in vitro. This suggested a paracrine regulation of the observed fibrosis in ADPKD.

Measurement of human sperm intracellular water volume by electron spin resonance

An electron spin resonance technique using the spin label tempone and the broadening agent potassium chromium oxalate was used to measure the water volume of human sperm. The toxicity of tempone (5 mmol/L) and potassium chromium oxalate (50 mmol/L) to sperm was measured over a time span of 120 minutes using computer-assisted semen analysis. Tempone had no effect on any computer-assisted semen analysis parameters, including motility. Potassium chromium oxalate reduced sperm motility by an average of 24% during the first 30 minutes of exposure. After selection by swim-up and correction for the presence of dead cells and cytoplasmic droplets, a water volume of 20.0 +/- 2.9 microns3 was obtained. This yields a total volume of 33.9 microns3 if a water compartment of 59% by volume is assumed. These results are consistent with other shape-independent techniques for measuring volume, but larger than the generally accepted optical and electronic particle counter sizes.

Reconstruction of degenerate rd mouse retina by transplantation of transgenic photoreceptors

Photoreceptors from neonatal transgenic mice with normally developing retinas were transplanted to the subretinal spaces of 2-3-month-old rd mutant mice that lack photoreceptors. The transgenic mouse photoreceptors express high levels of the lac Z reporter gene product, beta-galactosidase, which facilitated tracking the transplanted cells. Two sources were used for these cells: (1) dissection of retinal microaggregates containing photoreceptors and (2) papain-dissociated photoreceptors. Host retinas were examined after transplantation. Both methods led to survival of photoreceptors for at least 2 mo after transplantation. Relatively mature outer segments were found only in transplanted microaggregates; this occurred optimally when the cells were adjacent to the retinal pigment epithelium (RPE). beta-galactosidase-labeled outer segments associated closely with the apical processes of the host RPE, which, together with labeled phagosomes in the RPE cells, suggested functional interaction between the transplanted photoreceptors and the host RPE. This study is the first to the authors' knowledge to show electron microscopically that a morphologically normal-appearing photoreceptor layer can be reconstructed in an otherwise photoreceptorless retina.

[Chemical constituents of the leaves of Acanthopanax trifoliatus (Linn) Merr]

Nevadensin (A), kaur-16-en-19-oic acid (B), taraxerol (C) and taraxerol-acetate (D) were isolated from the leaves of Acanthopanax trifoliatus. A and B were isolated for the first time. Pharmacological experiments have shown that nevadensin possesses expectorant and antitussive actions.

[Effect of Chinese-made vesnarinone on experimental heart failure of dog]

Intravenous drip of sodium pentobarbital 6 mg/kg per min induced obvious heart failure of anesthetic dogs (n = 11) followed by an infusion of 0.25 mg/kg per min to maintain the heart failure state. The Chinese-made vesnarinone 3 mg/kg was injected, followed by an infusion of 0.1 mg/kg per min, or the solvent in the same volume, for 30 min. Vesnarinone increased significantly and instantly the cardiac output and left ventricular maximum + dp/dt, which almost recovered to normal at the end of the infusion and also significantly increased 30 min after administration. The positive inotropic effect of vesnarinone was not accompanied by an increase in the heart rate and the blood pressure. The results of our experiment reveal that the Chinese-made vesnarinone has a potent and relatively selective positive action on heart failure of dogs.

Experimental studies of pancreatic transplantation after freezing and thawing

The successful rat pancreatic transplantation, after 30 minutes cryopreservation at -80 degrees C, is presented with the normal graft function till the 6th postoperative day maximum. The freezing device used by the authors is shortly described. The choice of optimal freezing and thawing parameters is discussed. Organ freezing is a hopeful method which could serve to preserve the solid organs for a long period of time. Our former experimental research showed that slow freezing (1-2 degrees C/min) and fast thawing (> 100 degrees C/min) had produced less damage to the pancreas of the rat [1]. Recently we performed rat pancreatic transplantation after freezing and thawing the donor pancreas with the parameters mentioned above.

Alterations of spinal dorsal horn substance P following electroacupuncture analgesia--a study of the formalin test with immunohistochemistry and densitometry

Substance P (SP), released from thin afferent terminals, is believed to be a neurotransmitter for pain transmission in the spinal dorsal horn. It has been demonstrated that in addition to analgesia, morphine increases the accumulation of SP possibly due to the inhibition of its release. The present work investigated the level of spinal SP like immunoreactivity (SPLI) following electroacupuncture analgesia in rats using immunohistochemistry and image analysis. Experiment results revealed that formalin injected into the hind paw elicited marked pain response and accumulation of SP in the spinal dorsal horn. Electroacupuncture of Tsu-San-Li could depress the pain response, however increasing further the SP accumulation. It is thus suggested that pain stimulation itself may activate the endogenous opioid mechanism to inhibit SP release and acupuncture is able to enhance the process. This may be one mechanism of acupuncture analgesia.

Monitoring photoreceptor transplants with nuclear and cytoplasmic markers

Two methods are described for identifying transplanted photoreceptors in a foreign host retina. One involves the use of [3H]thymidine to label the nuclei of photoreceptors which are dividing for 1 week after birth in myomorphic retina. These photoreceptors can be identified by autoradiography. The second involves the use of a transgenic mouse carrying a bovine rhodopsin promoter in tandem with the bacterial LacZ gene. These mice express beta-galactosidase in their rods. X-gal reaction allows these rods to be identified by routine light and electron microscopy. These methods have been used to follow photoreceptor transplants in adult Royal College of Surgeons strain rat and C3H mouse mutants which have lost virtually all their photoreceptors. Dissociated photoreceptors transplanted to the subretinal space of these animals survive for at least 3 months. The inner segment, cell body, and synaptic terminal of these transplanted photoreceptors remain morphologically normal; the outer segment, however, becomes rudimentary.

[Hypocrellin A induced photodamage to the fluidity of human erythrocyte membranes and membranes of some phospholipid liposomes]

In this paper, the photodamage of Hypocrellin A to the fluidity of human erythrocyte membranes and some kinds of membranes of phospholipid liposomes was investigated by measuring the changes in fluorescence polarization of the membranes. The results showed that the photosensitization effect of HA caused the decrease of membrane fluidity of the phospholipid (DPPC, DPPC/DPPE, phospholipid of erythrocyte membranes) liposomes. The DPPC and DPPC/DPPE liposomes were more sensitive to the damage than the phospholipid liposomes of erythrocyte membranes. To human erythrocyte membranes, the photodamage effect of HA caused its fluidity first increased and then, with the increment of illumination time, decreased. To spectrin-depleted and trypsin-treated erythrocyte membranes, this kind of change in fluidity was inhibited. All of the results indicated that phospholipids and proteins play different roles in the photodamage of HA to the fluidity of membranes. Membrane proteins, especially spectrin, were the key factor involved in the changes of the fluidity.

Transplanted photoreceptors identified in dystrophic mouse retina by a transgenic reporter gene

Dissociated photoreceptor cells from a transgenic strain of mice, containing a bovine promoter lac Z gene construct, were transplanted to the dystrophic retinas of a strain of mice (C3H, rd/rd) without obvious photoreceptors. The transgenic photoreceptor cells expressed beta-galactosidase and were distinguishable from the host retinal cells by light and electron microscopy after the 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside histochemical reaction. These results showed that transplanted transgenic photoreceptor cells survived at least 1 month in the host retina and had a primitive outer segment and a well-developed synaptic terminal.

[Preliminary studies on subtypes of respiratory syncytial virus in China]

An analysis of subtypes of 9 respiratory syncytial (RS) viruses isolated from Guangzhou and Nanjing areas of china was carried out with eight Sweden RS-subtype specific monoclonal antibodies (MAbs) and 7 internal anti-RS MAbs. All these MAbs directed against respectively the large Glycoprotein (G), fusion protein (F), nucleoprotein (NP), and phosphoprotein (P) components of the prototype Long strain of RS virus. The patterns of the reactions of these MAbs to the nine isolated strains of RS virus were compared with indirect immunofluorescence assay (IFA), alkaline phosphoesterase-anti alkaline phosphoesterase (APAAP) enzyme-linked assay and Western blotting. The antigenic variations were founded among the strains of RS virus, and two subtypes allocated to the subtype A and B of RS virus by using the eight RS-subtype specific MAbs. Seven out of the 9 isolated strains of RS virus belonged to the subtype A, and two were being to the subtype B. The antigenic diversities were also founded within the same subtype, and the main pronounced difference were observed on the G glycoprotein by using the internal anti-RS MAbs. These findings are potentially important both for vaccine development and for the understanding of clinical and epidemiological characteristics of RS virus.

[The effect of hypocrellin A on the lipid bilayer of erythrocyte membrane]

In this paper, using human erythrocyte membrane, the effect of Hypocrellin A on the lipid bilayer of the membrane was studied by measuring the change of the fluidity of the membrane, the energy transfer of the fluorescent probes, the shift of the fluorescent emission peaks, and the split of band-a of Hypocrellin A. The results showed that in the presence of HA, the fluidity of erythrocyte membrane was increased, the fluorescence intensity of the probes was decreased, and the fluorescence peaks shifted blue. These phenomena took place more seriously with the increment of HA concentration. Meanwhile, the band-a of HA excitation spectra was splitted. It was suggested from all of the results that HA could significantly perturb the lipid bilayer of erythrocyte membrane, there were interactions existing between the Hypocrellin A and the membrane. The HA was mainly located in the middle range of the membrane lipid bilayer when in high concentration (mainly to the 12-16 positions of the long chain fatty acid).

Transplantation of photoreceptors labeled with tritiated thymidine into RCS rats

Tritiated thymidine was administered to newborn rats to label photoreceptors, about 50% of which are still dividing. These photoreceptors were enzymatically dissociated and separated from the remainder of the retina after the infant rat matured. These labeled photoreceptors were then transplanted into a foreign host retina in the region of the outer nuclear layer. The hosts were ocular, albinotic, Royal College of Surgeons (RCS) rats, congenic to the normal donors and at least 4 months old, a time when virtually all the photoreceptors have degenerated from their retinas. The transplant site was examined at various times after transplantation by light microscope autoradiography. Labeled photoreceptor cell bodies were found in clusters in the outer nuclear layer region for as long as 3 months after transplantation surgery.

Reversed polarity of Na(+) -K(+) -ATPase: mislocation to apical plasma membranes in polycystic kidney disease epithelia

Autosomal dominant polycystic kidney disease (ADPKD) is a genetic disorder in which renal tubules become enormously enlarged due to fluid accumulation. Na(+) -K(+) -ATPase was compared in normal and cystic regions of whole kidneys and in confluent primary cultures of microdissected renal tubule and cyst-lining epithelia. Immunostaining with antibodies directed against the Na(+) -K(+) -ATPase catalytic alpha-subunit was confined to apical, luminal plasma membranes of ADPKD epithelia, which was a complete reversal of the normal renal tubule polarized location in basolateral membranes. Mislocated Na(+) -K(+) -ATPase was shown to be functionally active, because identical intense apical staining was observed by use of a cytochemical assay. In addition, biochemical assays showed a significant increase in these ouabain-inhibitable Na(+) -K(+) -ATPase specific activity levels in ADPKD kidneys compared with age-matched normal kidneys. Specific binding of [3H] ouabain was not only increased but also confined to the apical membrane vesicles prepared from cystic regions of ADPKD kidneys compared with normal age-matched controls, in which binding was confined to basolateral membrane vesicles. Although steady-state levels of Na(+) -K(+) -ATPase alpha- and beta-subunit in mRNAs were increased somewhat in ADPKD kidneys, this alone was not sufficient to account for the observed activation. Confluent ADPKD epithelia grown on dual-chamber, permeable membrane supports also showed reversed polarity of 22NaCl vectorial transport, because this was from basal to apical media compartments. Because this transport could also be blocked by ouabain, this suggested apical Na(+) -K(+) -ATPase was responsible and implicated altered polarity of Na(+) -K(+) -ATPase and resultant Na+ secretion as a mechanism for cyst formation in ADPKD. Because no reversal of polarity of other basolateral or apical membrane proteins was detected, an intracellular sorting defect specific for Na(+) -K(+) -ATPase is proposed.

Survival and synapse formation of transplanted rat rods

Isolated rods enzymatically removed from normal adult rat retina have been transplanted to the subretinal space of adult rats with a retinal dystrophy which has destroyed almost all the photoreceptors. These transplanted rods survive for months after transplantation during which time they form synapses with other retinal cells. Rod spherules with large amounts of synaptic vesicles and synaptic ribbons are found forming discreet contacts with pre- and post-synaptic densities in arrangements closely resembling those seen in the normal retina.