Search PubMed⌕ Search

Biomedical subjects

L Wikström

Publications and source records attributed to L Wikström.

At least 19 recordsLinked to original sources
PubMed2002

Glutamate-induced currents reveal three functionally distinct NMDA receptor populations in rat dorsal horn - effects of peripheral nerve lesion and inflammation.

The importance of the N-methyl-D-aspartate (NMDA) receptor in various painful conditions is well established. The effects of peripheral nerve lesion or joint inflammation, as models of different pain states, on NMDA receptor-mediated currents and NMDA receptor subunit mRNA expression were therefore studied in acutely dissociated neurones from the rat spinal cord dorsal horn. In the neuronal population from control rats, all four NR2 subunits and both NR1 splice variants assayed were detected. A majority of neurones expressed mRNA for more than one NR2 subunit, and some neurones expressed all four NR2 subunits as well as both NR1 splice variants. The NR2B subunit was the most commonly expressed, while the NR2C was the rarest. Following nerve lesion, fewer neurones expressed NR2A compared to the control. The dose-response curve for glutamate-evoked NMDA receptor-mediated currents in the neurones was best described by a three-component fit, suggesting that three functionally distinct NMDA receptor populations are present in the dorsal horn. Minor changes in the dose-response curve after nerve lesion could not be ascribed with certainty to the lesion. Changes in other parameters of NMDA receptor-mediated currents were observed neither after nerve lesion nor after joint inflammation. In summary, the present work demonstrates that single dorsal horn neurones express mRNA for several NMDA receptor subunits. The glutamate dose-response curves indicate that there are three major types of NMDA receptors present in dorsal horn neurones. We also report a reduced expression of NR2A following peripheral nerve lesion.

Animals↗
PubMed2001

Differential protein expression in rat trigeminal ganglia during inflammation.

A proteomics approach was used to investigate global protein changes in rat sensory ganglia exposed to pro-inflammatory stimuli. Inflammation was provoked in vivo by injecting selected facial areas with Freunds Complete Adjuvant (FCA), or by stimulating freshly isolated trigeminal ganglia ex vivo with pro-inflammatory mediators (interleukin-1 beta, tumor necrosis factor-alpha, interferon-gamma). Following two-dimensional gel electrophoresis, silver staining and mass spectrometry, a protein reference map and database was generated for rat trigeminal ganglia, which to our knowledge is the first to be reported. Sixty-seven out of 85 selected protein spots were successfully identified using matrix-assisted laser desorption/ionization mass spectrometry. This reference map was used to monitor changes in the ganglia proteome induced during inflammation in vivo and ex vivo. In vivo we found that FCA treatment specifically induced differential protein expression of two unidentified protein spots and, to a lower extent, of beta-tubulin. Image analysis of ganglia treated ex vivo with the cocktail of cytokines indicated that some of the changes in the protein population were also observed in vivo after FCA treatment. If the cytokine stimulation was performed in the presence of acetaminophen (paracetamol), the drug seemed to reverse the effects of cytokine treatment for at least some protein spots, restoring the same protein pattern observed in control samples.

Animals↗
PubMed2001

Scavenger treatment of free radical injury in familial amyloidotic polyneuropathy: a study on Swedish transplanted and non-transplanted patients.

Since oxidative stress has been implicated in amyloid diseases, a study of scavenger treatment of hereditary transthyretin amyloidosis was undertaken on 23 familial amyloidotic polyneuropathy (FAP) patients. Nine patients had undergone a liver transplantation for the disease. Twenty patients completed the 6-month study period of scavenger treatment (vitamin C, 1 g, three times daily, vitamin E, 0.1 g, three times daily and acetylcysteine, 0.2 g three times daily). They were evaluated clinically and by immunohistochemical measurement of hydroxynonenal (HNE), a product of lipid peroxidation, in biopsy specimens. For non-transplanted patients, no improvement was found for HNE in relation to the amyloid content in biopsy specimens, whereas a tendency to a decreased amount was noted for transplanted patients. Clinically, no differences were found for non-transplanted patients, but an increased nutritional status, measured by a modified body mass index (mBMI) was noted for transplanted patients. In summary, scavenger treatment with the drugs and doses used in the present study appears to be unable to decrease lipid peroxidation in amyloid-rich tissue in non-transplanted FAP patients. For transplanted patients, lipid peroxidation tended to decrease, and the nutritional status measured by mBMI improved, even though the findings may be explained by liver transplantation alone, scavenger treatment may facilitate recovery after transplantation.

Acetylcysteine↗
PubMed2000

Outcome of gastrointestinal complications after liver transplantation for familial amyloidotic polyneuropathy.

BACKGROUND: Gastrointestinal disturbances are important prognostic factors for mortality and morbidity after liver transplantation for familial amyloidotic polyneuropathy (FAP). However, the impact of liver transplantation on malabsorption and bacterial small-bowel contamination has not been evaluated. METHODS: Twenty-three FAP patients were available for the study. They were examined for gastrointestinal disturbances as a part of the evaluation for liver transplantation for FAP. Bile acid malabsorption was diagnosed with the [75Se]-homocholic acid taurate (SeHCAT) test; fat malabsorption by measuring faecal fat excretion; and bacterial small-bowel contamination with the hydrogen breath test (HBT). RESULTS: No significant improvement of malabsorption test results were noted from the pre-transplant evaluation 8 months (range, 2-20 months) before transplantation to the post-transplant evaluation performed a median of 20 months (range, 9-62 months) after the procedure. The SeHCAT test result became abnormal in two patients and normal in one, and changes in the test correlated with the time the patients were waiting for transplantation. Faecal fat excretion after transplantation correlated with duration of the disease and with fat excretion before transplantation. A significantly increased fat excretion was noted at the post-transplant evaluation. A change in HBT result was noted in only one patient, in whom the test result became normal; pre-transplant values correlated with those obtained after transplantation. CONCLUSION: For most FAP patients no improvement in gastrointestinal function was found after transplantation. The finding underlines the importance of an early transplantation before the patients have developed gastrointestinal dysfunction.

Adult↗
PubMed2000

Effects of thyroid hormone receptor gene disruption on myosin isoform expression in mouse skeletal muscles.

Skeletal muscle is known to be a target for the active metabolite of thyroid hormone, i.e., 3,5,3'-triiodothyronine (T(3)). T(3) acts by repressing or activating genes coding for different myosin heavy chain (MHC) isoforms via T(3) receptors (TRs). The diverse function of T(3) is presumed to be mediated by TR-alpha(1) and TR-beta, but the function of specific TRs in regulating MHC isoform expression has remained undefined. In this study, TR-deficient mice were used to expand our knowledge of the mechanisms by which T(3) regulates the expression of specific MHC isoforms via distinct TRs. In fast-twitch extensor digitorum longus (EDL) muscle, TR-alpha(1)-, TR-beta-, or TR-alpha(1)beta-deficient mice showed a small but statistically significant decrease (P < 0.05) of type IIB MHC content and an increased number of type I fibers. In the slow-twitch soleus, the beta/slow MHC (type I) isoform was significantly (P < 0. 001) upregulated in the TR-deficient mice, but this effect was highly dependent on the type of receptor deleted. The lack of TR-beta had no significant effect on the expression of MHC isoforms. An increase (P < 0.05) of type I MHC was observed in the TR-alpha(1)-deficient muscle. A dramatic overexpression (P < 0.001) of the slow type I MHC and a corresponding downregulation of the fast type IIA MHC (P < 0.001) was observed in TR-alpha(1)beta-deficient mice. The muscle- and fiber-specific differences in MHC isoform expression in the TR-alpha(1)beta-deficient mice resembled the MHC isoform transitions reported in hypothyroid animals, i.e., a mild MHC transition in the EDL, a dramatic but not complete upregulation of the beta/slow MHC isoform in the soleus, and a variable response to TR deficiency in different soleus muscle fibers. Thus the consequences on muscle are similar in the absence of thyroid hormone or absence of thyroid hormone receptors, indicating that TR-alpha(1) and TR-beta together mediate the known actions of T(3). However, it remains unknown how thyroid hormone exerts muscle- and muscle fiber-specific effects in its action. Finally, although developmental MHC transitions were not studied specifically in this study, the absence of embryonic and fetal MHC isoforms in the TR-deficient mice indicates that ultimately the transition to the adult MHC isoforms is not solely mediated by TRs.

Adenosine Triphosphatases↗
PubMed1998

Abnormal heart rate and body temperature in mice lacking thyroid hormone receptor alpha 1.

Thyroid hormone, acting through several nuclear hormone receptors, plays important roles in thermogenesis, lipogenesis and maturation of the neonatal brain. The receptor specificity for mediating these effects is largely unknown, and to determine this we developed mice lacking the thyroid hormone receptor TR alpha 1. The mice have an average heart rate 20% lower than that of control animals, both under normal conditions and after thyroid hormone stimulation. Electrocardiograms show that the mice also have prolonged QRS- and QTend-durations. The mice have a body temperature 0.5 degrees C lower than normal and exhibit a mild hypothyroidism, whereas their overall behavior and reproduction are normal. The results identify specific and important roles for TR alpha 1 in regulation of tightly controlled physiological functions, such as cardiac pacemaking, ventricular repolarisation and control of body temperature.

Animals↗
PubMed1998

Liver transplantation in familial amyloidotic polyneuropathy (FAP). A comparative study of transplanted and non-transplanted patient's survival.

The purpose of the present study was to evaluate the impact of liver transplantation on familial amyloidotic polyneuropathy (FAP met-30) patients' survival. Forty-five FAP patients were involved in the study; 15 non-transplanted FAP patients and 30 liver-transplanted patients. All patients' records were scrutinised for information on disease duration. Preoperative nutritional status was evaluated in all patients. No difference in survival was observed for transplanted patients overall compared to historical controls. However, for cases in good nutritional status, an increased survival can be expected as a significantly increased mortality rate for malnourished patients was observed (P < 0.05). Increased survival has so far not been found for transplanted FAP patients. However, none of the transplanted cases has yet reached the expected survival time for nontransplanted FAP control patients. which is 14 years. A high fatality rate of malnourished patients transplanted late in the course of the disease contributed significantly to the mortality among transplanted patients.

Adult↗
PubMed1997

Processing and membrane topology of the spike proteins G1 and G2 of Uukuniemi virus.

The membrane glycoproteins G1 and G2 of the members of the Bunyaviridae family are synthesized as a precursor from a single open reading frame. Here, we have analyzed the processing and membrane insertion of G1 and G2 of a member of the Phlebovirus genus, Uukuniemi virus. By expressing C-terminally truncated forms of the p10 precursor containing the whole of G1 and decreasing portions of G2, we found that processing in BHK21 cells occurred with an efficiency of about 50% if G1 was followed by 50 residues of G2, while complete processing occurred if 98, 150, or 200 residues of G2 were present. Surprisingly, processing of all truncated G2 forms was less efficient in HeLa cells. Proteinase K treatment of microsomes isolated from infected cells indicated that the C terminus of G1 is exposed on the cytoplasmic face. Using G1 tail peptide antisera, the tail was likewise found by immunofluorescence to be exposed on the cytoplasmic face in streptolysin O-permeabilized cells. By introducing stop codons at various positions of the G1 tail and at the natural cleavage site between G1 and G2 and expressing these mutants in BHK cells, we found that no further processing of the G1 C terminus occurred following cleavage of G2 by the signal peptidase. This was also supported by the finding that an antiserum raised against a peptide corresponding to the region immediately upstream from the G2 signal sequence reacted in immunoblotting with G1 from virions. Finally, we show that both G1 and G2 are palmitylated. Taken together, these results show that processing of p10 of Uukuniemi virus occurs cotranslationally at only one site, i.e., downstream of the internal G2 signal sequence. G1 and G2 are inserted as type I proteins into the lipid bilayer, leaving the G1 tail exposed on the cytoplasmic face of the membrane. Since the G2 tail is only 5 residues long, the G1 tail is likely to be responsible for the interaction with the nucleoproteins during the budding process, in addition to harboring a Golgi localization signal.

Amino Acid Sequence↗
PubMed1995

Liver transplantation in familial amyloidotic polyneuropathy. Follow-up of the first 20 Swedish patients.

Familial amyloidotic polyneuropathy (FAP) is an inherited fatal form of amyloidosis caused by mutant transthyretin. The disease is characterized by progressive peripheral and autonomic neuropathy. Most of the transthyretin is produced by the liver, and we have shown previously that the metabolic deficiency can be corrected by liver transplantation. In the present study, the clinical results from the first 20 patients who underwent liver transplantation for FAP in Sweden are evaluated. Three of the patients suffered from renal failure and underwent a simultaneous kidney transplantation. Fourteen of the 20 patients (70%) are alive 10-52 months after transplantation. The patients' nutritional status at the time of transplantation had a significant impact on mortality and morbidity (P < 0.007). Long-standing disease was another negative prognostic factor (P < 0.02). One year after transplantation, the nutritional status had improved (P < 0.02). Improvements were also noted in walking capacity and for gastrointestinal and urogenital symptoms. The results show that liver transplantation offers an effective means to treat patients with FAP. The procedure should preferably be performed before the nutritional status is poor and advanced organ dysfunction has developed.

Adult↗
PubMed1994

Secretory pattern of vasopressin in plasma and cerebrospinal fluid of patients with dementia and of two control groups.

Since the description of its antidiuretic effect in 1913, a variety of functions have been attributed to vasopressin, one of the most controversial throughout the years probably being its effect on memory processes. In an attempt to study the actual secretory rhythm of vasopressin in humans with demonstrated impaired memory, the plasma and cerebrospinal fluid levels of the peptide have been examined during 24 h in a group of patients with dementia, and their values compared with two healthy control groups of young and elderly volunteers. Patients with dementia had higher circulating levels of vasopressin in plasma than the healthy participants and the differences were statistically significant when compared with the healthy elderly (p = 0.003). This difference is not age-related because both groups were in the same age range. A possible explanation could be the higher plasma osmolality measured in the patients with dementia, despite the fact that their levels were within the normal ranges. The different results could not be attributed to changes in electrolytes or blood pressure because these parameters were similar in all groups (p = NS). But more interesting, perhaps, is the secretory pattern found in all three groups. The pattern is biphasic, with two significant peaks: at 16.00 h (p = 0.032) and at night (p = 0.002). This pattern was similar in all cases and in all groups. The total nocturnal secretion of vasopressin is higher than the diurnal secretion (p = 0.02) only in the plasma because the cerebrospinal fluid values were higher during the day.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Once hypertensive, always hypertensive? A three year follow-up after stopping medication.

OBJECTIVE: To verify the existence of hypertension in a group of long-term pharmacologically treated hypertensives and to evaluate the possibility of discontinuing their medication. DESIGN: The diagnosis of hypertension was established when after a wash-out period (one month) the blood pressure measured at three consecutive examinations, with at least one week interval between them, was always higher than WHO's reference levels for the diagnosis of hypertension. Those who did not fulfil these criteria would continue, with regular controls, without medication as long as clinically indicated. The final evaluation was done after a three year follow-up. SETTING: The out-patient Hypertensive Unit of the Department of Geriatrics, Skellefteå Hospital, Sweden. PARTICIPANTS: 86 out-patients (33 males and 53 females) aged 68 to 82 years (mean 74) with long-term hypertension sent to our unit by general practitioners in our health district (population 80,000). RESULTS: 34 of the initial 86 patients required medication by the end of the wash-out period. The remaining 52, 16 males and 36 females, continued without medication and after the three year follow up 14 of them were still without it. There was a striking difference between males and females since a significantly higher number of males than females were free of medication at the end of the period (p < 0.001). In those who restarted pharmacological therapy, the period without medication lasted no longer than five months. CONCLUSIONS: Arterial hypertension can easily be over-represented as a diagnosis if not revised when clinically advisable or if established without accurate criteria. The possibility of stopping the antihypertensive medication in old patients is worth considering, particularly in male patients. The dangers of such strategy are practically minimal when regular controls are undertaken during the attempt.

Aged↗
PubMed1993

Unfolded H2b asialoglycoprotein receptor subunit polypeptides are selectively degraded within the endoplasmic reticulum.

When expressed alone in fibroblasts, approximately 80% of newly made H2b subunits of the human asialoglycoprotein receptor are retained and degraded in the endoplasmic reticulum (ER), whereas about 20% reaches the plasma membrane (1). Thapsigargin, an inhibitor of the ER Ca2+ ATPase, blocks ER folding of the H1 (2) as well as of the H2b subunit, prevents maturation of H2b, and accelerates ER degradation of newly made H2b. The secretory pathway is normal in thapsigargin-treated cells, as monitored by maturation of the vesicular stomatitis virus G protein. The protease inhibitors TLCK and TPCK block the first step in ER degradation of H2, an endoproteolytic cleavage just exoplasmic to the membrane-spanning domain. In protease inhibitor-treated cells, the approximately 80% of H2b that would normally be degraded remains in the ER; as judged by migration on nonreducing SDS-polyacrylamide gel electrophoresis this H2b is improperly folded. Thus, incorrectly folded H2b is normally subjected to ER degradation. In the presence of thapsigargin H2b cannot fold properly and is degraded within the ER. The preferential ER degradation of misfolded or unfolded membrane proteins demonstrated here, functions as a step in ER quality control.

3T3 Cells↗
PubMed1993

Intermediates in degradation of the erythropoietin receptor accumulate and are degraded in lysosomes.

The erythropoietin receptor (EPO-R) is synthesized in transfected Ba/F3 cells as a major 64-kDa endoglycosidase H (Endo H)-sensitive species, with a single N-linked oligosaccharide, and a minor 62-kDa unglycosylated form. Approximately half of the newly made EPO-R is processed to a mature 66-kDa form with a Golgi-processed Endo H-resistant oligosaccharide, of which only a minor fraction is expressed at the cell surface. Both the Endo H-sensitive and the Endo H-resistant forms of the receptor have a half-life of 45-60 min (Yoshimura, A., D'Andrea, A. D., and Lodish, H. F. (1990) Proc. Natl. Acad. Sci. U. S. A. 87, 4139-4143). The mature, Endo H-resistant form of the EPO-R appears to be degraded in lysosomes or in other acidic organelles, since receptor degradation is blocked by treatment with NH4Cl, chloroquine, or leupeptin. A fraction of the Endo H-resistant EPO-R molecules is cleaved, generating two fragments of 46 and 39 kDa. The sizes of these fragments and their reactivities with carboxyl-terminal-specific antibodies indicate that the receptor is cleaved at two sites in the exoplasmic domain, 7 kDa apart, and carboxyl-terminal to the N-glycosylation site. Both fragments are membrane anchored and are probably formed in a late or post-Golgi compartment, since their formation is blocked by incubation of cells at 20 degrees C or by incubation with brefeldin A. These membrane-anchored COOH-terminal fragments are probably degraded in lysosomes or in other acidic vesicles as cell fractionation demonstrates that they colocalize with lysosomes, and similar to the intact EPO-R, their degradation is inhibited by NH4Cl. Finally, double labeling immunofluorescence experiments demonstrate that in NH4Cl-treated cells both intact mature EPO-R and the 46- and 39-kDa fragments accumulate in lysosomes and presumably are normally degraded there. The sensitivity of the EPO-R to endoproteolytic cleavages in its exoplasmic domain may relate to its low surface expression and to its extreme metabolic instability.

3T3 Cells↗
PubMed1992

Calcium is required for folding of newly made subunits of the asialoglycoprotein receptor within the endoplasmic reticulum.

By resolving immunoprecipitates on nonreducing sodium dodecyl sulfate gels, we have detected several disulfide-bonded intermediates in folding within the endoplasmic reticulum of newly made H1 subunits of the asialoglycoprotein receptor. H1 in the endoplasmic reticulum (ER) can be partially unfolded by treatment of cells with dithiothreitol, but H1 in Golgi or post-Golgi organelles is resistant to such unfolding. This defines a late step in H1 folding that occurs just prior to exit from the ER. Depletion of calcium from the endoplasmic reticulum, either by treatment with A23187 or thapsigargin, has no effect on folding or secretion of newly made albumin, but totally blocks H1 maturation from the ER. No ER intermediates in H1 folding are formed in cells treated with A23187 or thapsigargin, indicating that at least an early step in H1 folding requires a high Ca2+ concentration in the ER lumen. As judged by cross-linking experiments, formation of H1 dimers and trimers occurs immediately after biosynthesis of the peptide chain, before monomer folding, and occurs normally in cells in which ER Ca2+ is reduced and where the monomer never folds properly. Calcium is essential for the asialoglycoprotein receptor to bind galactose, and our results suggest that Ca2+ is also essential for the receptor polypeptides to fold in the ER.

Albumins↗
PubMed1992

Endoplasmic reticulum degradation of a subunit of the asialoglycoprotein receptor in vitro. Vesicular transport from endoplasmic reticulum is unnecessary.

The H2a subunit of the human asialoglycoprotein receptor is rapidly degraded from the endoplasmic reticulum (ER) when expressed in CHO15B cells. We have reconstituted ER degradation of H2a in semipermeable cells. At least the initial step in degradation (a proteolytic cleavage inhibited by N alpha-p-tosyl-L-lysine chloromethyl ketone and L-1-tosylamido-2-phenylethyl chloromethyl ketone) can occur in vitro in the presence of guanosine 5'-3-O-(thio)triphosphate or in the absence of ATP and postnuclear supernatant, conditions that do not allow vesicular transport of subunit H1 from the ER to the Golgi. We conclude that vesicular transport from the ER is not required for ER degradation of H2a to occur and thus that it takes place in the ER itself.

Asialoglycoprotein Receptor↗
PubMed1991

Nonlysosomal, pre-Golgi degradation of unassembled asialoglycoprotein receptor subunits: a TLCK- and TPCK-sensitive cleavage within the ER.

The human asialoglycoprotein receptor subunit H2a is cotranslationally inserted into the ER membrane. When expressed together with subunit H1 in mouse fibroblasts part forms a hetero-oligomer that is transported to the cell surface, but when expressed alone it is all rapidly degraded. Degradation is insensitive to lysosomotropic agents and the undegraded precursor is last detected in the ER region of the cell. Small amounts of an intermediate 35-kD degradation product can be detected (Amara, J. F., G. Lederkremer, and H. F. Lodish. 1989. J. Cell Biol. 109:3315). We show here that the oligosaccharides on both precursor H2a and the 35-kD fragment are Man6-9GlcNAc2, structures typically found in pre-Golgi compartments. Subcellular fractionation shows that the intermediate degradation product does not cofractionate with the lysosomal enzyme beta-galactosidase, but is found in a part of the ER that contains ribosomes. Thus the intermediate degradation product is localized in the ER, indicating that the initial degradation event does take place in the ER. All degradation of H2a, including the initial endoproteolytic cleavage generating the 35-kD intermediate, is blocked by the protease inhibitors N-tosyl-L-lysine chloromethyl ketone and N-tosyl-L-phenylalanine chloromethyl ketone. These drugs do not inhibit ER-to-Golgi transport of H1. Depleting the cells of ATP or inhibiting protein synthesis allows the initial endoproteolytic cleavage to occur, but blocks further degradation of the 35-kD intermediate; thus we can convert all cellular H2 into the 35-kD intermediate. Approximately 50% of H2b, a splicing variant differing from H2a by a five amino acid deletion, can be transported to the cell surface, and the rest appears to be degraded by the same pathway as H2a, both when expressed alone in fibroblasts and together with H1 in HepG2 cells. Addition of N-tosyl-L-lysine chloromethyl ketone or N-tosyl-L-phenylalanine chloromethyl ketone blocks degradation of the approximately 50% that is not transported, but does not affect the fraction of H2b that moves to the Golgi region. Thus, a protein destined for degradation will not be transported to the Golgi region if degradation is inhibited.

2,4-Dinitrophenol↗
PubMed1988

Concanavalin A-induced redistribution of surface receptors in Acanthamoeba castellanii at different growth phases.

Concanavalin A (ConA)-induced redistribution of surface receptors has been studied in Acanthamoeba castellanii at different growth phases utilizing double fluorescent techniques and transmission electron microscopy. When the amoebae were incubated with 2 micrograms and 10 micrograms tetramethylrhodamine isothiocyanate (TRITC)-ConA/ml for 4 min and 15 min at 28 degrees C the staining pattern was characterized by various numbers of scattered aggregates of fluorescent ConA. Double labeling of the amoebae showed that the fluorescent aggregates represented internalized label, and the internalization was not preceded by any aggregation of ConA receptors on the cell surface as visualized by incubating with anti-ConA serum followed by fluorescein isothiocyanate-conjugated anti-IgG. Following exposure of the amoebae to 10 micrograms TRITC-ConA/ml for 4 min and 15 min at 28 degrees C intracellular accumulation of some of the fluorescent aggregates in cap-like structures occurred at the logarithmic and postlogarithmic growth phases but not at the early stationary growth phase. Electron microscopic observation of amoebae labeled with ferritin-conjugated ConA at 28 degrees C revealed a uniform surface labeling and an intracellular accumulation of the label in vesicular and tubular structures, and occasionally in cap-like structures. Surface capping of ConA receptors in Acanthamoeba was induced by treating the amoebae with ConA and anti-ConA serum at 0 degrees C followed by incubation at 28 degrees C. The formation of surface caps in Acanthamoeba showed growth-phase dependency, too. The visualization of the surface caps at the electron microscopic level was performed by indirect staining utilizing protein A-colloidal gold.(ABSTRACT TRUNCATED AT 250 WORDS)

Acanthamoeba↗