Cold-induced microtubule disruption and relocalization of membrane proteins in kidney epithelial cells

Cold preservation of kidneys is commonly used in human transplantation and in vitro studies. However, although disruption of the cytoskeleton by cold has been demonstrated in cultured cells, the effect of cold treatment on intact kidney is poorly understood. In this study, specific antibodies were used to examine the effect of hypothermia on the cytoskeletal network and the trafficking of some membrane proteins in the urinary tubule. Rat kidneys were cut into thin slices (approximately 0.5 mm) that were divided into several groups: (1) some were immediately fixed in paraformaldehyde, sodium periodate, and lysine (PLP); (2) some were stored at 4 degrees C for 15 min or 4 h before being fixed in cold PLP; or (3) after 4 h cold treatment, some slices were rewarmed to 37 degrees C for 15, 30, and 60 min in a physiologic solution, pH 7.4, and were then fixed in warm PLP. Immunofluorescence staining revealed an almost complete disruption of the microtubule network in proximal tubules after 15 min cold treatment, whereas microtubules in other segments were affected after 4 h. A partial recovery of the microtubule network was observed after 60 min rewarming. In contrast, actin filaments seemed to be resistant to cold treatment. gp330, aquaporin-2, H+ ATPase, and the AE1 anion exchanger were all relocated into numerous vesicles that were distributed throughout the cytoplasm after hypothermia followed by rewarming, whereas Na-K-ATPase retained its basolateral localization. The vasopressin-stimulated insertion of aquaporin-2 water channels into the apical membrane was inhibited during the initial rewarming period after cold exposure. Thus, cold preservation of tissues might impair, at least transiently, the polarized membrane expression and function of some transport proteins in renal epithelial cells.

Influence of GB virus C viraemia on the clinical, virological and histological features of early hepatitis C-related hepatic disease

BACKGROUND/AIMS

GB virus C is a newly described RNA virus. The aims of this study were to determine the prevalence of GB virus C infection in patients with chronic type C hepatitis and to examine the clinical, virological and histological features in hepatitis C and GB virus C co-infected patients.

METHODS/RESULTS

One hundred and sixty patients with hepatitis C infection were studied. GBV-C RNA was detected in 33/160 (20.6%) patients; co-infected patients with hepatitis C and GB virus C infection were significantly younger (p=0.04). No difference was found between the two groups according to gender and biochemical parameters. Seventy-two of the 160 patients, for whom a liver tissue specimen taken simultaneously with the serum was available and who had compensated liver disease, were studied separately. The source of infection, duration of infection, HCV genotype and HCV RNA concentrations did not differ between 15/72 patients with dual infection and 57/72 with hepatitis C infection alone. Patients with co-infection had significantly higher degrees of portal and periportal inflammation (p=0.0006 and 0.01, respectively). No difference was observed in parenchymal activity score or extent of fibrosis.

CONCLUSIONS

These results indicate a relatively high prevalence of GB virus C infection in younger patients with chronic hepatitis C, suggesting a common route of transmission. Although GB virus C co-infection does not alter the biochemical and virological profile of patients with HCV hepatitis, there is an association between GB virus C and hepatitis C viraemia and portal and periportal inflammation.

Basolateral distribution of caveolin-1 in the kidney. Absence from H+-atpase-coated endocytic vesicles in intercalated cells

In kidney epithelial cells, a variety of physiological processes are dependent on the active recycling of membrane proteins between intracellular vesicles and the cell surface. Although clathrin-mediated endocytosis occurs in several renal cell types, endocytosis can also occur by non-clathrin-coated vesicles, including pinocytotic structures known as caveolae that contain a novel coat protein, caveolin. Exo- and endocytosis of a vacuolar H+-ATPase in intercalated cells also occurs via specialized "coated" vesicles that do not contain clathrin. The aim of this study was to localize caveolin in the kidney and, in addition, to determine whether it could be a component of the H+-ATPase recycling process. Using an antibody against the alpha- and beta-isoforms of caveolin-1, our immunocytochemical data show a marked heterogeneity in the cellular expression of this isoform of caveolin in kidney. In contrast, caveolin-3 was not detectable in renal epithelial cells. Caveolin-1 was abundant in endothelial cells and smooth muscle cells and was present in the parietal cells of Bowman's capsule. Distal tubule cells, connecting tubule cells, and collecting duct principal cells exhibited marked punctate basolateral staining, corresponding to the presence of caveolae detected by electron microscopy, whereas all intercalated cells were negative in both cortex and medulla. These data indicate that although caveolin-1 may participate in basolateral events in some kidney epithelial cell types, it does not appear to be involved in the regulated recycling of H+-ATPase in intercalated cells. Therefore, these cells recycle H+-ATPase by a mechanism that involves neither clathrin nor caveolin-1.

Absence of anti-envelope antibodies and clearance of hepatitis C virus in a cohort of Irish women infected in 1977

The presence or absence of antibodies to the second envelope protein (anti-E2) of hepatitis C virus (HCV) was determined in stored sera taken from a cohort of 87 Irish women with antibodies to HCV (anti-HCV) who were all infected by HCV genotype 1b from contaminated anti-D immunoglobulin given in 1977. Anti-E2 was found in 16 patients (100%) who were HCV RNA positive but only in 31 of 50 patients (62%) who were HCV antibody positive by recombinant immunoblot assay (RIBA) but HCV RNA negative. In the remaining 21 sera taken from women who had indeterminate recombinant immunoblot assays and who were repeatedly negative on testing for HCV RNA, anti-E2 was found in only three cases (14%). This suggests that loss or absence of anti-E2 may be useful in confirming clearance of HCV.

Diagnosis of neonatal congenital heart defects by remote consultation using a low-cost telemedicine link

To determine whether telemedicine could assist in the earlier diagnosis of neonates with congenital heart disease (CHD) in an area hospital remote from a paediatric cardiologist, we established a low-cost telemedicine link between the neonatal unit of a district general hospital and the regional paediatric cardiology unit. Realtime ultrasound images of babies suspected of having CHD were obtained by a paediatrician and transmitted for realtime interpretation by a paediatric cardiologist. In a four-month pilot study, 10 neonates were studied in this way. In eight of the ten cases, the diagnosis made over the telemedicine link was confirmed subsequently in a direct examination at the regional unit. In one case the patient died before the direct examination was possible. In one case two small muscular ventricular septal defects were missed on the remote examination. Our early experience suggests that, with realtime guidance by a paediatric cardiologist, transmitted images of sufficient quality to allow confirmation or exclusion of major cardiac defects can be obtained. This form of remote consultation should improve morbidity and mortality rates by reducing the waiting time for specialist diagnosis and treatment.

Imaging soft X-rays with opaque spheres

Images of small fluorescence X-ray sources obtained by diffraction with opaque spheres were recorded with a flow-proportional counter and on X-ray sensitive film. Image fluxes and intensities obtained experimentally were compared with theoretical estimates made using analytical expressions derived from the sphere's point-source imaging properties.

Ophthalmoplegic migraine: reversible enhancement and thickening of the cisternal segment of the oculomotor nerve on contrast-enhanced MR images

BACKGROUND AND PURPOSE

Ophthalmoplegic migraine is a rare condition characterized by the association of headaches and an oculomotor nerve palsy. We report six patients with typical clinical features of this disorder in whom enhancement of the cisternal segment of the oculomotor nerve developed during the acute phase, followed by resolution of enhancement over several weeks as the symptoms resolved.

METHODS

Six patients, ages 3 to 27 years, underwent MR imaging during the acute phase of ophthalmoplegic migraine and at the time of recovery several weeks later. The MR studies, performed on a 1.5-T MR unit, included noncontrast and contrast-enhanced axial and coronal T1-weighted sequences. Sagittal images were obtained in two patients, with and without contrast enhancement.

RESULTS

Enhancement of the cisternal segment of the oculomotor nerve was seen in all patients at initial presentation. Contrast-enhanced studies also showed focal thickening at the exit of the nerve in the interpeduncular cistern in five of six patients. No patient had enhancement of the cavernous sinus or adjacent dura. Enhancement was almost completely resolved on follow-up studies 7 to 9 weeks later.

CONCLUSION

Our findings confirm an intrinsic transient abnormality in the cisternal segment of the third nerve in patients with a typical clinical presentation of ophthalmoplegic migraine.

The status of indirect restorative dental materials

The ideal restorative material should enable restoration of teeth that have either suffered trauma or have been prepared during the removal of caries to their original function and appearance. At the same time a seal should develop between the material and the tooth to prevent bacteria-laden fluids from permeating the dentine and reaching the pulp. Few, if any, of the available materials fulfil these requirements. This, the second of a short series, considers the status of indirect restorative materials as the millennium approaches. In this review indirect restorative materials are regarded as those which call not only upon the dexterity and judgement of the dental practitioner, but also upon the skills of the dental technician and techniques of construction that are suitable for use only in a laboratory. Included in this group are the dental casting and bonding alloys, dental ceramics and those resin composites that are shaped, cured and finished in the laboratory.

Polarized expression of membrane proteins in renal epithelial cells: involvement of specialized transport vesicles and intracellular pathways

The polarized insertion of membrane proteins in epithelial cells is a highly regulated process that involves the coordinated interaction of many subsets of intracellular proteins. Thus, like cog-wheels in a complex machine, the different parts of the trafficking pathway must work together to ensure the correct functioning of an individual cell and of the entire epithelium in which it resides. The individual portions of the trafficking pathway include (1) sorting of membrane proteins into the correct apically or basolaterally targeted vesicles at the level of the trans-Golgi network; (2) delivery of these vesicles to their correct membrane destination by the microtubular (and probably the actin) cytoskeleton; (3) fusion of the vesicles with the appropriate membrane domain via a complex set of fusion proteins. This review has briefly outlined some of these processes and has used examples from the kidney to illustrate their importance to normal renal function.

Localization of pH regulating proteins H+ATPase and Cl-/HCO3- exchanger in the guinea pig inner ear

Mechanisms that regulate endolymphatic pH are unknown. It has long been recognized that, because of the large positive endolymphatic potential in the cochlea, a passive movement of protons would be directed out of endolymph leading to endolymphatic alkalization. However, endolymphatic pH is close to that of blood, suggesting that H+ is being secreted into endolymph. Since the kidney and the inner ear are both actively engaged in fluid and electrolyte regulation, we attempted to determine whether proteins responsible for acid secretion in the kidney also exist in the guinea pig inner ear. To that end, a monoclonal antibody against a 31 kDa subunit of a vacuolar vH+ATPase and a polyclonal, affinity purified antibody against the AE2 Cl-/HCO3- exchanger (which can also recognize AE1 under some conditions) were used. In the cochlea, the strongest immunoreactivity for the vH+ATPase was found in apical plasma membranes and apical cytoplasm of strial marginal cells. These cells were negative for the Cl-/HCO3- exchanger. Certain cells of the inner ear demonstrated both apical staining for vH+ATPase and basolateral staining for the Cl-/HCO3- exchanger; these included interdental cells and epithelial cells of the endolymphatic sac. Cochlear cell types with diffuse cytoplasmic staining for vH+ATPase and a basolaterally localized Cl-/HCO3- exchanger included inner hair cells, root cells and a subset of supporting cells in the organ of Corti. Hair cells of the utricle, saccule and cristae ampullaris also expressed both vH+ATPase and the Cl-/HCO3- exchanger, but immunostaining for the vH+ATPase was less intense and less polarized than in the cochlea. These immunocytochemical results support a role for the vH+ATPase and Cl-/HCO3- exchanger in the regulation of endolymphatic pH and suggest that certain cells (including strial marginal cells and epithelial cells of the endolymphatic sac) may be specialized for this regulation.

Slit diaphragm-reactive nephritogenic MAb 5-1-6 alters expression of ZO-1 in rat podocytes

Monoclonal antibody (MAb) 5-1-6 identifies a 51-kDa protein (p51) on rat podocyte foot processes and causes severe complement- and leukocyte-independent proteinuria when injected into rats. In the studies reported here, we used various immunohistological techniques to define the precise location of p51 and its relationship to ZO-1, a known component of the podocyte slit diaphragm in adult rat glomeruli. Our results demonstrate that p51 and ZO-1 lie close to each other on opposite sides of the podocyte plasma membrane at the point of insertion of the slit diaphragm: ZO-1 on the cytoplasmic face and p51 on the slit diaphragm and adjoining outer leaflet of the plasma membrane bordering the filtration slits. In addition to their geographic proximity, there appears to be a relationship between p51 and ZO-1. After MAb 5-1-6 injection, there was a progressive decline in stainable ZO-1 in the podocytes of heavily proteinuric rats. In addition, Western blot analysis of glomerular lysates showed that the decline in staining was due to a loss of immunoreactive ZO-1 rather than redistribution or diffusion of the protein. Simultaneously, the distribution of glomerular-bound MAb 5-1-6 became more clumped, apparently because of partial endocytosis into a lysosomal compartment, while the slit diaphragms remained morphologically intact. These findings suggest that MAb 5-1-6 alters the molecular composition of the slit diaphragm and thereby affects the glomerular permeability barrier.

Redistribution of villin to proximal tubule basolateral membranes after ischemia and reperfusion

After ischemia and reperfusion, severe alterations in the cytoskeletal organization of renal tubular epithelial cells have been reported. These effects, accompanied by a modification in the polarized distribution of some membrane transport proteins, are especially evident in the proximal tubule. In normal proximal tubule cells, actin is concentrated in apical brush border microvilli, along with the actin-binding protein villin. Because villin plays an important role in actin bundling and in microvillar assembly but can also act as an actin-fragmenting protein at higher calcium concentrations, we examined the effects of ischemic injury and reperfusion on the distribution of villin and actin in proximal tubule cells of rat kidney. Using specific antibodies against villin and actin, we show that these proteins redistribute in parallel from the apical to the basolateral plasma membrane within 1 h of reperfusion after ischemia. Ischemia alone had no effect on the staining pattern. Repolarization of villin to the apical membrane begins within hours after reperfusion with enhanced apical localization over time during the period of regeneration. This apical repolarization of villin is accompanied by the migration of actin back to the apical membrane. These results show not only that villin may be involved in the initial disruption of the actin cytoskeleton during reperfusion injury but also that its migration back to the apical domain of these cells accompanies the reestablishment of a normal actin distribution in the brush border.

Localization of the high-affinity glutamate transporter EAAC1 in rat kidney

Most amino acids filtered by the glomerulus are reabsorbed in the kidney via specialized transport systems. Recently, the cDNA encoding a high-affinity glutamate transporter, EAAC1, has been isolated and shown to be expressed at high levels in the kidney. To determine the potential role of EAAC1 in renal acidic amino acid reabsorption, the distribution of EAAC1 mRNA and protein in rat kidney was examined. In situ hybridization revealed that EAAC1 mRNA is expressed predominantly in S2 and S3 segments of the proximal tubules and at low levels in the inner stripe of outer medulla and inner medulla. Polyclonal antibodies raised against the carboxy terminus of EAAC1 recognized a single band of approximately 70 kDa on Western blots of membrane protein from kidney cortex and medulla. Immunofluorescence microscopy revealed intense signals in the luminal membrane of S2 and S3 segments and weaker signals in S1 segments, descending thin limbs of long-loop nephrons, medullary thick ascending limbs, and distal convoluted tubules. These results are consistent with EAAC1 encoding the previously described apical high-affinity glutamate transporter in the kidney that mediates reabsorption of acidic amino acids in tubules beyond early proximal tubule S1 segments. Potential additional roles of EAAC1 in acid/base balance, cell volume regulation, and amino acid metabolism are discussed.

The status of restorative dental materials

The ideal restorative material should enable teeth which have suffered trauma or have been damaged during the removal of caries, to be restored to their original function and appearance. At the same time a seal should develop between the material and the tooth such that bacteria-laden fluids cannot permeate the dentine and reach the pulp. Few, if any, of the materials currently available fulfil these requirements. This short series will consider the current status of each.

Prostaglandin F2alpha-induced nest-building in pseudopregnant pigs. II. Space restriction stress does not influence secretion of oxytocin, prolactin, oestradiol or progesterone

We have previously shown that prostaglandin F2alpha (PG) is capable of inducing nest-building behaviour in pseudopregnant gilts and established a protocol. This experiment examined which reproductive endocrine systems might mediate these behavioural responses, in the presence or absence of a space restriction stress. Pseudopregnancy was induced with 5 mg/day i.m. (intramuscular) injections of oestradiol valerate (OV) on Days 11-15 of the oestrous cycle, jugular vein catheters were placed on Day 39 of pseudopregnancy, and blood samples were collected daily from Day 40 to Day 48. On Day 42, gilts were either space restricted to farrowing crates 1.6 x 0.6 m (C: n = 11) or left in pens 2.8 x 1.74 m (P: n = 11). On Day 47, blood samples were collected from all animals every 15 min from 90 min prior to a single i.m. injection of 15 mg of prostaglandin F2alpha (PG: Lutalyse, Upjohn, Crowley, West Sussex) to 120 min post-PG and then hourly for 4 h and assayed for oxytocin, prolactin, progesterone, and oestradiol. Results showed that mean daily concentrations of prolactin and progesterone were significantly lower (p < 0.05 respectively) in C than P gilts from Day 42 to Day 46 of pseudopregnancy. There were no significant differences in mean daily concentrations of oxytocin and oestradiol between C and P gilts during this time. For both groups, oxytocin, prolactin, and progesterone concentrations increased significantly (p < 0.05) post-PG when compared to their respective pre-PG values. However, for both groups, oestradiol concentrations were unaffected by PG injection. The prostaglandin-induced increases in oxytocin, prolactin, and progesterone concentrations did not differ between groups. We conclude that coincident changes in oestradiol secretion does not influence nesting behaviour and that space restriction stress associated with nest-building does not influence secretion of oxytocin, prolactin, oestradiol, or progesterone.

Long-chain polyunsaturated fatty acid transport across the perfused human placenta

The role of the placenta in controlling the supply of fatty acids to the fetus was investigated in term placentae (n = 9) from normal pregnancies. The maternal side was perfused ex vivo for 90 min with a modified Krebs Ringer solution containing a physiological mixture of fatty acids and ratio of fatty acid to human albumin. There was no evidence of chain elongation and desaturation of the essential fatty acids. Relative to the value for oleic acid, the rate of transfer to the fetal circulation was: 1.30 +/- 0.02 (P < 0.001) for linoleic acid, 1.61 +/- 0.09 (P = 0.002) for alpha-linolenic acid, 0.67 +/- 0.10 (P = 0.033) for arachidonic acid and 2.10 +/- 0.16 (P = 0.003) for docosahexaenoic acid. For tissue accumulation the values were 1.47 +/- 0.39 (P < 0.001) for linoleic acid, 2.24 +/- 0.37 (P = 0.027) for alpha-linolenic acid, 9.84 +/- 1.03 (P = 0.001) for arachidonic acid, and 3.01 +/- 0.79 (P = 0.064) for docosahexaenoic acid. The order of selectivity for transfer from the maternal to the fetal circulation was docosahexaenoic > alpha-linolenic > linoleic > oleic > arachidonic acid. Such a mechanism would allow the preferential transfer of docosahexaenoic acid and the essential fatty acids to the fetal circulation, thereby protecting the polyunsaturated fatty acid supply to the fetus during a critical period of development.

Response to measles revaccination among Bolivian school-aged children

The response to measles revaccination was evaluated in 1994 among 202 Bolivian school-aged children whose antibody levels were below 200 miu (milli-international units) by haemagglutination inhibition (HI) in a large-scale serosurvey conducted in Santa Cruz one year earlier. Of the 202 revaccinated children, 164 (82%) had seroconverted between the 1993 serosurvey and the pre-revaccination blood sample. A measles outbreak occurred in Santa Cruz 6 months before the revaccination. Among the seroconvertors, only 6% gave a history of measles, and 15% a history of contact with a case of measles. All 20 children with undetectable HI antibody pre-revaccination, and all 6 children with levels below 100 miu, seroconverted after revaccination. The geometric mean titres by HI at 4 weeks after revaccination were 2018 miu (95% confidence limits [95% CL] 1143, 3564) and 398 miu (95% CL 254, 625) in the 2 groups, respectively. Six of 9 children with pre-revaccination antibody titres of 100-199 miu also seroconverted. No child demonstrated a measles-specific immunoglobulin M response. Among the 29 children who seroconverted and were followed up at one year after revaccination, 15(52%) showed a fourfold or greater decline in antibody levels, which in 8 fell to levels below 200 miu. This study confirmed the observation that revaccination is successful in producing an antibody response in children with low or undetectable pre-revaccination titres, but it also confirmed that vaccine-induced immunity wanes rapidly.

Prostaglandin F2alpha-induced nest-building in pseudopregnant pigs. I. Effects of environment on behaviour and cortisol secretion

Pigs may be susceptible to stress when they are strongly motivated to nest-build in a space-restricted environment. This study aimed to explore whether nest-building behaviour could be induced by prostaglandin F2alpha (PG) administration to pseudopregnant gilts and to determine whether induced behaviour and cortisol output differed between animals chronically placed in either farrowing crates or pens. Jugular vein catheters were placed on Day 39 of pseudopregnancy and blood samples collected daily from Day 40 to Day 48. On Day 42, gilts were either restricted to farrowing crates 1.6 x 0.6 m with no straw (C: n = 11) or left in pens 2.8 x 1.74 m with straw (P: n = 11). On Day 47, blood and behaviour sampling was from 90 min pre-PG (Dinoprost; Lutalyse, Upjohn, Kalamazoo, MI) to 6 h post-PG. PG injection successfully induced nest-building behaviour in P gilts within 15 min of injection. Penned gilts engaged in more straw/floor-directed behaviour than C gilts (p < 0.01), whereas attempts in C gilts seemed partial or incomplete. Conversely, C gilts showed increased (p < 0.05) amounts of fixture-directed behaviour, whereas P gilts did not post-PG. For both groups, cortisol increased significantly (p < 0.05) post-PG compared to pre-PG values. Cortisol concentrations in C gilts were significantly greater than in P gilts prior to and after PG (p < 0.05) on Day 47, whereas there were no significant differences in concentrations of cortisol between C and P on other days. These results demonstrate that PG can induce nest-building behaviour in the absence of foetal signals. Whereas the pseudopregnant gilt seemed to chronically adapt to the imposition of a farrowing crate, gilts subsequently attempting to nest-build showed increases in cortisol output when compared to their penned counterparts, suggesting that a stress was imposed by the space-restricted environment.