Biological responses to extreme weather events are detectable but difficult to formally attribute to anthropogenic climate change.

As the frequency and intensity of extreme events such as droughts, heatwaves and floods have increased over recent decades, more extreme biological responses are being reported, and there is widespread interest in attributing such responses to anthropogenic climate change. However, the formal detection and attribution of biological responses to climate change is associated with many challenges. We illustrate these challenges with data from the Elbe River floodplain, Germany. Using community turnover and stability indices, we show that responses in plant, carabid and mollusc communities are detectable following extreme events. Community composition and species dominance changed following the extreme flood and summer heatwave of 2002/2003 (all taxa); the 2006 flood and heatwave (molluscs); and after the recurring floods and heatwave of 2010 and the 2013 flood (plants). Nevertheless, our ability to attribute these responses to anthropogenic climate change is limited by high natural variability in climate and biological data; lack of long-term data and replication, and the effects of multiple events. Without better understanding of the mechanisms behind change and the interactions, feedbacks and potentially lagged responses, multiple-driver attribution is unlikely. We discuss whether formal detection and/or attribution is necessary and suggest ways in which understanding of biological responses to extreme events could progress.

Modelling nitrogen retention in floodplains with different degrees of degradation for three large rivers in Germany.

Floodplains perform a variety of ecosystem functions and services - more than many other ecosystems. One of these ecosystem services is the reduction in nitrogen (N) loads and a subsequent improvement to the water quality. Since diffuse and also point nitrogen sources continue to cause a variety of problems in rivers and floodplains, inundated floodplains could act as net sinks for N and are therefore of great importance throughout Germany and Europe. This study analyses the effects of riparian floodplains on N-retention on the landscape scale for three large river systems with different degrees of degradation. Two approaches, differing in terms of the complexity of their respective input data and methods, were applied under wet and dry conditions. Whereas the proxy-based approach considers proxy values for N-retention, the model-based approach accounts for event-driven dynamic input data such as the extent of the inundated floodplain and incoming loads. Comparing the results of the two approaches it can be observed that floodplains of the near-natural river can retain up to 4% of the river load under wet conditions. During such conditions N-retention in floodplains is similar to that of rivers. For the two other floodplains, the results of the two approaches were quite different, showing lower N-retention capacities. However, for these floodplains as well, both approaches are suitable for calculating measurable N-retention rates, which is an important result because it also suggests that even degraded floodplains still preserve this particular ecosystem function and therefore still contribute to improving the quality of river water.

The tales of two geckos: does dispersal prevent extinction in recently fragmented populations?

Although habitat loss and fragmentation threaten species throughout the world and are a major threat to biodiversity, it is apparent that some species are at greater risk of extinction in fragmented landscapes than others. Identification of these species and the characteristics that make them sensitive to habitat fragmentation has important implications for conservation management. Here, we present a comparative study of the population genetic structure of two arboreal gecko species (Oedura reticulata and Gehyra variegata) in fragmented and continuous woodlands. The species differ in their level of persistence in remnant vegetation patches (the former exhibiting a higher extinction rate than the latter). Previous demographic and modelling studies of these two species have suggested that their difference in persistence levels may be due, in part, to differences in dispersal abilities with G. variegata expected to have higher dispersal rates than O. reticulata. We tested this hypothesis and genotyped a total of 345 O. reticulata from 12 sites and 353 G. variegata from 13 sites at nine microsatellite loci. We showed that O. reticulata exhibits elevated levels of structure (FST=0.102 vs. 0.044), lower levels of genetic diversity (HE=0.79 vs. 0.88), and fewer misassignments (20% vs. 30%) than similarly fragmented populations of G. variegata, while all these parameters were fairly similar for the two species in the continuous forest populations (FST=0.003 vs. 0.004, HE=0.89 vs. 0.89, misassignments: 58% vs. 53%, respectively). For both species, genetic structure was higher and genetic diversity was lower among fragmented populations than among those in the nature reserves. In addition, assignment tests and spatial autocorrelation revealed that small distances of about 500 m through fragmented landscapes are a barrier to O. reticulata but not for G. variegata. These data support our hypothesis that G. variegata disperse more readily and more frequently than O. reticulata and that dispersal and habitat specialization are critical factors in the persistence of species in habitat remnants.

The impact of a cancer education program on the knowledge base of participating students.

BACKGROUND: Partners in Research is a ten-week summer elective designed to provide cancer-related educational activities. This study was undertaken to evaluate the impact of the program on the general cancer knowledge of medical students, pharmacy students, and undergraduate biology majors. METHODS: The 24 students enrolled in 1999 were evaluated using a pretest and post-test with 75 multiple-choice questions. RESULTS: The mean test score increased significantly from 46.6% to 53.0% (p = 0.001). Improvements were significant for general cancer knowledge and three specific disease categories (breast, gastrointestinal, and skin cancers). CONCLUSIONS: The results indicate that the program does increase the cancer-related knowledge of students.

Stress proteins and glycoproteins (Review).

Proteins represent both structural and functional elements of biological organisms, however, their structural and catalytic function is directly linked to the acquisition and maintenance of a complex three-dimensional conformation. A molecular machinery to accomplish protein folding and maintenance in vivo is provided by a variety of molecular chaperones that include both heat shock proteins (Hsps), glucose-regulated proteins (Grps), and a separate class of stress glycoproteins (S-Gps). Different chaperones associate to form functional complexes (chaperone) and work coordinately to accomplish specific functions during the folding of particular proteins. In this review, we will summarize recently acquired new insights into the complexities of chaperones, the current state of S-Gps and their interactions with Hsps, and of specific chaperones that appear to be designed for the folding of cellular glycoproteins. Finally, we discuss the physiological role of chaperones by examining their function in specific cellular processes, namely tumor/host interactions and diseases associated with aberrant prion protein folding.

Laparoscopic appendectomy does not change the incidence of postoperative infectious complications.

BACKGROUND: It is not clear whether the laparoscopic approach does decrease the incidence of postoperative infectious complications after appendectomy. METHODS: One hundred sixty-nine patients were randomized, 87 with laparoscopic (LA) and 82 with open appendectomy (OA). Patients in the OA group had a McBurney incision; LA was performed in the lithotomy position. RESULTS: Acute appendicitis was confirmed in 75% of patients. The appendix was perforated in 5 patients of the LA versus 2 patients of the OA group. No conversion to the open procedure was necessary. The median operating time was 35 minutes in the LA group and 31 minutes in the open group (P = 0.58). The median postoperative hospital stay was shorter after laparoscopic than after open surgery (3 days versus 4 days, P = 0.026), whereas the time required for return to work was not significantly different (14 versus 15 days). There were 5 (6%) patients with superficial wound infection following LA and 6 (7%) after OA (P = 0.67). Intra-abdominal fluid collections were found in 2 (2%) patients following LA and 3 (4%) patients following OA (P = 0.60). In the LA group, 3 patients presented with intra-abdominal hemorrhage and another 3 developed a paralytic ileus that was treated conservatively. CONCLUSIONS: Laparoscopic appendectomy is as safe and as effective as the open procedure; however, it does not decrease the rate of postoperative infectious complications.

Interaction of heat stress glycoprotein GP50 with classical heat-shock proteins.

Cellular stress conditions are known to elevate heat-shock protein (HSP) synthesis and protein glycosylation, leading to the development of cellular thermotolerance. In the present study, we investigated the interaction of a major stress glycoprotein, GP50, with other cellular proteins during recovery from heat stress, using' mostly immunoprecipitation techniques. Parallel studies of heat-stressed CHO and M21 cells showed that both glycosylated and unglycosylated forms of GP50 interact with several members of the classical HSP families (e.g., HSP70 and HSP90) in an ATP-dependent manner. The specificity of HSP-stress glycoprotein interactions was confirmed by chemical crosslinking with a homobifunctional agent, 3,3'-dithiobis (succinimidyl propionate). Interaction of GP50 with denatured proteins was also demonstrated through binding to gelatin. Protein complexes formed between stress glycoproteins and HSPs were further characterized by gel filtration and showed an average molecular mass between 400 and 600 kDa. Overall, the consistent association of stress glycoproteins with nonglycosylated HSPs suggests a structural/functional role for protein chaperone complexes that consist of denatured proteins and the glycone/aglycone elements of cellular stress response.

Calreticulin associates with stress proteins: implications for chaperone function during heat stress.

Acute heat stress leads to the glycosylation of a "prompt" stress glycoprotein, P-SG67/64, identified as calreticulin. In the present study, we used immunoprecipitation to investigate the interactions of P-SG/calreticulin with other proteins during cellular recovery from heat stress. In heat-stressed CHO and M21 cells, both glycosylated and unglycosylated P-SGs interact with HSP90, GRP94, GRP78, and the other prompt stress glycoprotein, P-SG50, in an ATP-independent manner. Specificity of HSP-P-SG interactions was determined by chemical cross-linking with the homo-bifunctional agent DSP (3,3'-dithiobis[succinimidyl propionate]). Characterization of the cross-linked complexes involving calreticulin and heat shock proteins (HSPs) showed an average mass of 400-600 kDa by gel filtration chromatography. Overall, the consistent association of glycosylated and unglycosylated calreticulin with P-SG50 and unglycosylated HSPs suggests that P-SG/calreticulin is an active member of the cast of glycone/aglycone chaperones that cooperate to achieve cellular recovery from acute heat stress.

Stress response in a leporine renal cell model.

It is well established that renal proximal tubule (RPT) cells grown under standard in vitro conditions attenuate many of their in vivo properties and functions. Thus, the study of renal stress response mechanisms requires an appropriate cell culture model. In the present study, we compared the heat stress (10 min, 45 degrees C) response of freshly isolated RPT cells with that of RPT cells grown in vitro for 6 days under two different culture conditions: (1) SHAKE conditions, where oxygen levels and physiological functions are maintained via continuous media motion [Nowak G, Schnellmann RG: Am J Physiol 1996;271:C2072-2080] and (2) STILL conditions, involving standard cell culture which leads to partial hypoxia and a marked reduction in physiological functions. The freshly isolated RPT cells progressively synthesized heat shock proteins (HSPs) and stress glycoproteins (SGs) during a 3-hour culture period in vitro. Under these conditions, heat stress did not further increase HSP and SG synthesis. In RPT cells grown under SHAKE conditions, HSP70 synthesis was detected 1 h after heat stress and decreased below detection by 3 h. In contrast, the uptake of radiolabeled mannose into (glycoprotein) GP62 (Mr 62,000), GP50, and GP38 was observed in control SHAKE cultures and was not further increased after heat stress. These results are consistent with immunohistochemistry studies, where similar changes in HSP70 and GP50 expression were noted. RPT cells grown under STILL conditions showed both increased synthesis of HSP70 and increased glycosylation of GP62, GP50, and GP38 as early as 1 h after heat stress, but in contrast to SHAKE conditions, this heat-induced stress response further intensified at 3 h after heat stress. By 7 h after heating, HSP synthesis returned to control levels, while glycosylation of GP62 and GP50 remained elevated. Based on our results, we conclude that freshly isolated RPT cells exhibit a stress response that may be caused by acute cell isolation/culture stress. While this stress response unfolds, freshly isolated RPT cells appear unable to respond to additional heat stress. RPT cells grown under SHAKE and STILL conditions exhibit high rates of SG glycosylation, especially that of GP62, possibly reflecting a 'stress' condition associated with growth on plastic substrate. Concurrently, RPT cells from STILL cultures show a higher capacity for responding to acute heat stress than SHAKE cultures, evidenced by the transiently increased HSP synthetic rates. The interpretation of the renal stress response capacity, therefore, must be linked to a specific culture condition.

Intracellular distribution of stress glycoproteins in a heat-resistant cell model expressing human HSP70.

Heat stress results in the cellular accumulation of heat-shock proteins (HSP) and increased protein glycosylation. Among known stress glycoproteins, GP50 and GP62 are associated with the expression of thermotolerance. In the present study, we characterized subcellular localization and redistribution of GP62 and GP50 in a rodent cell line, M21, before and after cellular heat-stress. M21 cells are heat-resistant cells that overexpress human HSP70 and also have concomitantly high GP62 levels. Cellular fractionation by differential centrifugation showed that GP62 and GP50 was present in each subcellular fraction. However, each stress glycoprotein exhibited a characteristic kinetic pattern of redistribution during cellular recovery after heat stress. For example, glycosylated GP62 was seen predominantly in the mitochondria before heat-stress. Immediately after heat-stress, its presence in the mitochondrial fraction was dramatically reduced, while it increased in lysosomes, microsomes and cytosol. By 1 h after heat stress, it had largely disappeared from microsomal and cytosolic fractions. After 24 h, all subcellular fractions showed only trace amounts of residual GP62. By comparison, GP50 was also highest in the mitochondrial fraction before heat-stress, redistributed like GP62 immediately after heat stress, but remained relatively unchanged thereafter. In contrast to GP62, GP50 showed little redistribution during 24 h after heat-stress and remained at high concentrations in all cell fractions, including microsomes. Distribution of GP50 and GP62 before and after heat stress, based on differential centrifugation, was consistent with immunolocalization data. Following heat stress, both GP50 and GP62 showed a partial overlap in distribution with HSP70. The above results indicate that each stress glycoprotein has a specific subcellular location, both before and after heat stress. The presence of GP62 in virtually all cell fractions is consistent with a multifunctional role for GP62 in the cellular stress response.

Intracellular distribution of heat-induced stress glycoproteins.

Cellular heat stress results in elevated heat-shock protein (HSP) synthesis and in thermotolerance development. Recently, we demonstrated that protein glycosylation is also an integral part of the stress response with the identification of two major stress glycoproteins, GP50, associated with thermotolerance, and P-SG67, the "prompt" stress glycoprotein induced immediately during acute heat stress. In the present study, we characterized the subcellular location and redistribution of these proteins during the cellular injury and recovery phase. In unheated and heated CHO cells, both stress glycoproteins were present in each subcellular fraction isolated by differential centrifugation. However, the subcellular redistribution in the course of cellular recovery after heat stress was specific for each stress glycoprotein. GP50 was present in all subcellular fractions before heat stress, but showed relatively little redistribution after heat stress. By 24 h of recovery following stress, GP50 showed partial depletion from lysosomes and microsomes, and was mainly present in the mitochondria. Glycosylated P-SG67 was redistributed in a more complex fashion. It was seen predominantly in the lysosomes and microsomes immediately following heat-stress, but after 6 h of recovery following heat stress, it largely disappeared from the microsomes and was present mainly in the cytosol. By 24 h of recovery following heat stress, it was found predominantly in the nucleus-rich fraction and mitochondria. The localization of GP50 and P-SG67 by subcellular fractionation is consistent with immunolocalization studies and contrasts with the translocation of HSP70 after heat stress from cytosol to nuclei and nucleoli. These results reflect a characteristic distribution for each stress glycoprotein; their presence in virtually all subcellular fractions suggests multifunctional roles for the various stress glycoproteins in the cellular heat stress response.

Partial homology of stress glycoprotein GP62 with HSP70.

Thermotolerance and heat resistance are often associated with elevated levels of heat shock proteins (HSPs) and a selective increase in protein glycosylation. In the present study, we have characterized heat stress-induced protein glycosylation in M21 cells, derived from the rat fibroblast line, Rat-1. M21 cells are characterized by constitutive overexpression of human HSP70 gene and show increased heat resistance without loss of its normal capacity for thermotolerance development after heat conditioning (Li et al., 1991, Proc. Natl. Acad. Sci. USA 88, 1681-1685). The data presented here show that the elevated heat resistance in these cells is associated not only with the constitutive overexpression of human HSP70, but also with increased glycosylation of a major stress glycoprotein, GP62 (Mr of 62,000). We further purified GP62 by sequential preparative isoelectric focusing and two-dimensional isoelectric focusing/SDS-polyacrylamide gel electrophoresis. The purified protein was digested and partially characterized by microsequencing of two peptide fragments, comprising of 14-15 amino acids each. These fragments had a 100% sequence homology with HSP70 and a 71-100% sequence homology with HSC70 from various species. Western blotting using both HSP70 and HSC70 antibodies showed positive reactivity of GP62 with HSP70. Affinity characterizations showed strong binding of GP62 to wheat germ agglutinin and concanavalin A, consistent with the presence of both alpha-D-mannosyl/glucosyl and N-acetyl-beta-D-glucosylaminyl/glucosamine oligomer residues in GP62. These data confirm the glycosylated status of GP62 and indicate that GP62 is a heat stress-induced glycoprotein with partial homology to HSP70.

Protein glycosylation in a heat-resistant rat fibroblast cell model expressing human HSP70.

Thermotolerance and heat resistance are frequently associated with elevated levels of heat shock proteins (HSPs). Elevated heat resistance is also found to be associated with the overexpression of high levels of HSP70, as seen in M21 cells, derived from the Rat-1 line. In the present study, we report that M21 cells also feature an increase in general protein glycosylation and specific expression of the stress glycoprotein, GP62, both of which correlate with cellular heat resistance. The expression of GP50, a major stress glycoprotein in cell lines such as CHO, however, did not correlate with cellular heat resistance in M21 cells. Protein glycosylation that occurs during acute heat stress ("prompt" glycosylation) was associated with the glycosylation of a major "prompt" stress glycoprotein, P-SG64 (M(r) of 64,000), that was identified by immunoblotting as a glycosylated form of calreticulin. The higher level of protein glycosylation in M21 cells correlated well with increased D-[2-3H]mannose incorporation into precursor pools of dolichyl phosphomannose and dolichyl pyrophosphoryl oligosaccharides and into glycoproteins. Thus, heat resistance in M21 cells is associated not only with expression of high levels of HSP70, but also with a concomitant increase in protein glycosylation. These data support the hypothesis that stress-induced protein glycosylation is a component of cellular stress response, either in association with HSPs or as an independent mechanism.

Protein glycosylation in rat fibroblast cells expressing deletion variants of the human hsp70 gene.

Elevated heat resistance is often associated with high cellular levels of hsp70. In the rat cell line, M21, increased heat resistance is associated with both the expression of an intact exogenous human hsp70 gene, and of an exogenous stress glycoprotein, GP62. In this study, we examined heat-stress induced alterations in protein glycosylation in two variant lines of M21 that contain specific deletions in the exogenous human hsp70 gene. The deletion mutant, MVH delta Sm, lacks the nucleolar localization sequence for human hsp70 gene, whereas the other mutant, MVH delta Bg, is characterized by deletion of the ATP binding domain in the human hsp70 gene. After heat induction, the MVH delta Sm mutants exhibited constitutive and heat-induced endogenous hsp70 mRNA levels, protein glycosylation, as well as hsp70 and GP62 protein levels comparable to those in the parent cell line, Rat-1. Cellular heat sensitivity of MVH delta Sm mutants was also similar to that of Rat-1 cells, although the mutant cells had a reduced capacity for thermotolerance development. On the other hand, MVH delta Bg mutants before thermotolerance induction, exhibited constitutive endogenous and human exogenous hsp70 mRNA levels similar to those in MVH delta Sm mutants. However, after thermotolerance induction, MVH delta Bg mutants showed lower levels of heat-induced endogenous hsp70 mRNA than MVH delta Sm mutants, an overall reduction in protein glycosylation, low hsp70 and GP62 levels, and increased heat sensitivity when compared to the parent Rat-1 cell line. Incorporation of D-[2-3H]mannose into oligosaccharide precursor pools and glycoproteins was consistent with protein glycosylation pattern for each cell line. Acute heat stress resulted in the selective glycosylation of the 'prompt' glycoprotein, P-SG64, in the two deletion mutants, similar to that in M21 cells expressing the intact human hsp70 gene. The data indicate that both protein glycosylation and hsp70 expression generally correlate with cellular heat resistance and thermotolerance expression. The presence of full or partially deleted copies of human hsp70 modulates thermotolerance and protein glycosylation in a complex manner that is not yet fully understood.

[Laparoscopic versus conventional appendectomy: a prospective randomized study]. / Laparoskopische versus konventionelle Appendektomie: eine prospektive, randomisierte Studie.

The discussion about laparoscopic appendectomy has increased since the introduction of this method. Randomized comparisons are still feasible, whereas this cannot be stated for other laparoscopic procedures (e.g., laparoscopic cholecystectomy). This randomized controlled trial included 170 patients. Open appendectomy was employed in 83 patients, and 87 were treated laparoscopically. The treatment groups were comparable regarding age, sex, Broca index, ASA classification, preliminary operations, and preoperative leucocytes. No statistically significant differences could be found with respect to surgical and general complications, operating time, consumption of analgesics and antibiotics, and return to work. The analysis revealed a statistically significant shorter hospital stay, a shorter time until return to normal physical activity, and a shorter duration of complaints for the laparoscopic group. We were unable to demonstrate any statistically significant advantage in using the open procedure.

[Laparoscopy-assisted colon surgery--overview and personal experiences with 64 patients]. / Laparoskopisch assistierte Kolonchirurgie--Ubersicht und eigene Erfahrungen bei 64 Patienten.

The number of laparoscopic or laparoscopic-assisted operations in abdominal surgery constantly increases. 64 patients between February 1992 and November 1993 underwent a laparoscopic assisted colorectal procedure. In 5 cases laparotomy was necessary. There were only 4 complications: one subileus treated conservatively and one peritoneal abscess was drained successfully under sonographic guidance; furthermore there were a postoperative pneumonia and a prolapse of the greater omentum in the area pierced by a 10 mm-trocar. The oncologic criteria for the resection of malignant tumours can be fulfilled in laparoscopic surgery. Our first experiences indicate that the advantages for the patient in laparoscopic procedures of the colon/rectum are the same as have been reported in laparoscopic cholecystectomy.

Partial characterization of a Cisplatin-resistant subline of murine rif-1 tumor-cells.

We have developed a drug-resistant cell line (RIF/Ptr1) (R) from the murine radiation-induced fibrosarcoma (RIF-1) also designated Pts or (S). This subline has been characterized previously by an increased resistance to cisplatin (cis-diamminedichloroplatinum(II) or CDDP), lowered intracellular CDDP concentrations, and elevated intracellular glutathione (GSH) levels (1.4-2.5-fold) but unaltered formation of CDDP-DNA interstrand cross-links. In this work, we have shown that RIF/Ptr1 cells were also resistant to carmustine (BCNU) and X-irradiation. Neither cell line had P-glycoprotein 170. The intrastrand CDDP-DNA adduct level was proportional to the concentration of intracellular CDDP. The oxygen consumption, ATP level, and glycolysis were similar in both cell lines. The cisplatin influx and efflux showed that the RIF/Ptr1 cells had lower drug influx and higher drug efflux compared to RIF-1. We conclude that the major difference between the cisplatin sensitive and cisplatin-resistant cells in this model is the regulation of cisplatin transport probably at the cell membrane level suggesting that a membrane active transport system other than P-glycoprotein 170 is involved. Whether glutathione is linked to the putative membrane transporter needs further investigation.

Prompt glycosylation of calreticulin is independent of Ca2+ homeostasis.

Selective glycosylation of "prompt" stress glycoproteins (P-SG), mainly P-SG67 and P-SG64 (M(r) of 64,000, pI = 5.1), occurs immediately during acute heat-stress. In the present study, P-SG64 was purified by sequential gel filtration, anion-exchange, affinity chromatography, and two-dimensional isoelectric focusing/SDS-PAGE. Purified P-SG64 was further characterized by microsequencing of a peptide fragment, PT-61, which showed a 100% sequence homology with calreticulin, suggesting that P-SG64 is identical to calreticulin. PT-61 also showed 55%, 58% and 63% sequence homologies with calnexin, HIV-1 gp120 and HIV-2 envelope polyprotein, respectively. 45Ca2+ overlay studies confirmed Ca(2+)-binding of P-SG64. P-SG67 was also recently identified as calreticulin (8), which suggests that CHO cells either have two isoforms of calreticulin or express variable states of calreticulin glycosylation during acute heat stress. The role of intracellular Ca2+ ([Ca2+]i) during heat-induced "prompt" glycosylation was also examined and indicated an 8-fold increase in [Ca2+]i. Chelation of this increased cytoplasmic Ca2+ by BAPTA reduced glycosylation of P-SG67/P-SG64/calreticulin only by approximately 20%. This observation suggests that altered [Ca2+]i homeostasis is not directly linked to calreticulin glycosylation, instead, heat-induced calreticulin glycosylation is a Ca(2+)-independent effect.

Heat shock-induced prompt glycosylation. Identification of P-SG67 as calreticulin.

Acute heat shock initiates the phenomenon of "prompt" glycosylation, which is characterized by selective glycosylation of specific cellular proteins called the prompt stress glycoproteins (P-SG). Prompt glycosylation rapidly occurs even during short heating periods, e.g. 10 min at 45 degrees C, and is not affected by the presence of cycloheximide (Henle, K. J., Kaushal, G. P., Nagle, W. A., and Nolen, G. T. (1993) Exp. Cell Res. 207, 245-251). The major P-SG in Chinese hamster ovary cells, P-SG67, was characterized by an M(r) of 67,000 and a pI = 5.1. In the present study, we purified P-SG67 by sequential gel filtration, anion exchange, affinity chromatography with concanavalin A-Sepharose, and two-dimensional isoelectric focusing/SDS-polyacrylamide gel electrophoresis. The purified protein was digested and partially characterized by microsequencing of three major peptide fragments. The fragments, comprising a total of 46 amino acid residues, had an almost 100% sequence homology with calreticulin and partial homology with calnexin. Calcium binding studies with 45Ca2+ overlay confirmed that P-SG67 is a Ca(2+)-binding protein. These observations support the notion that P-SG67 is identical to calreticulin and that the glycosylation status of calreticulin can respond to environmental stress conditions.