A novel nucleolar G-protein conserved in eukaryotes

We describe here a novel, evolutionarily conserved set of predicted G-proteins. The founding member of this family, TbNOG1, was identified in a two-hybrid screen as a protein that interacts with NOPP44/46, a nucleolar phosphoprotein of Trypanosoma brucei. The biological relevance of the interaction was verified by co-localization and co-immunoprecipitation. TbNOG1 localized to the trypanosome nucleolus and interacted with domains of NOPP44/46 that are found in several other nucleolar proteins. Genes encoding proteins highly related to TbNOG1 are present in yeast and metazoa, and related G domains are found in bacteria. We show that NOG1 proteins in humans and Saccharomyces cerevisae are also nucleolar. The S. cerevisae NOG1 gene is essential for cell viability, and mutations in the predicted G motifs abrogate function. Together these data suggest that NOG1 may play an important role in nucleolar functions. The GTP-binding region of TbNOG1 is similar to those of Obg and DRG proteins, which, together with NOG, form a newly recognized family of G-proteins, herein named ODN. The ODN family differs significantly from other G-protein families, and shows several diagnostic sequence characteristics. All organisms appear to possess an ODN gene, pointing to the biological significance of this family of G-proteins.

Analysis of targeting sequences demonstrates that trafficking to the Toxoplasma gondii plastid branches off the secretory system

Apicomplexan parasites possess a plastid-like organelle called the apicoplast. Most proteins in the Toxoplasma gondii apicoplast are encoded in the nucleus and imported post-translationally. T. gondii apicoplast proteins often have a long N-terminal extension that directs the protein to the apicoplast. It can be modeled as a bipartite targeting sequence that contains a signal sequence and a plastid transit peptide. We identified two nuclearly encoded predicted plastid proteins and made fusions with green fluorescent protein to study protein domains required for apicoplast targeting. The N-terminal 42 amino acids of the apicoplast ribosomal protein S9 directs secretion of green fluorescent protein, indicating that targeting to the apicoplast proceeds through the secretory system. Large sections of the S9 predicted transit sequence can be deleted with no apparent impact on the ability to direct green fluorescent protein to the apicoplast. The predicted transit peptide domain of the S9 targeting sequence directs protein to the mitochondrion in vivo. The transit peptide can also direct import of green fluorescent protein into chloroplasts in vitro. These data substantiate the model that protein targeting to the apicoplast involves two distinct mechanisms: the first involving the secretory system and the second sharing features with typical chloroplast protein import.

Angiopoietin-1 is an antipermeability and anti-inflammatory agent in vitro and targets cell junctions

Inflammation is a basic pathological mechanism that underlies many diseases. An important component of the inflammatory response is the passage of plasma components and leukocytes from the blood vessel into the tissues. The endothelial monolayer lining blood vessels reacts to stimuli such as thrombin or vascular endothelial growth factor by changes in cell-cell junctions, an increase in permeability, and the leakage of plasma components into tissues. Other stimuli, such as tumor necrosis factor-alpha (TNF-alpha), are responsible for stimulating the transmigration of leukocytes. Here we show that angiopoietin-1, a cytokine essential in fetal angiogenesis, not only supports the localization of proteins such as platelet endothelial cell adhesion molecule-1 (PECAM-1) into junctions between endothelial cells and decreases the phosphorylation of PECAM-1 and vascular endothelial cadherin, but it also strengthens these junctions, as evidenced by a decrease in basal permeability and inhibition of permeability responses to thrombin and vascular endothelial growth factor. Furthermore, angiopoietin-1 inhibits TNF-alpha-stimulated leukocyte transmigration. Angiopoietin-1 may thus have a major role in maintaining the integrity of endothelial monolayers.

Improving nursing care through mentored research: a paper within a paper

In 1995 Western Sydney Area Health Service (WSAHS) and University of Western Sydney Nepean (UWSN) entered a strategic alliance to develop a nursing research culture in Western Sydney. As a result, the WSAHS/UWSN Professorial Nursing Unit (PNU) was established in 1996: Its mandate was to develop a variety of strategies to promote a nursing research culture in the area. One of these strategies was to encourage mentored research projects between personnel in the PNU and inexperienced clinical nurses. This paper describes one such project. In addition, it contextualizes the study in relevant literature relating to mentored research and outlines both the issues and the benefits associated with such projects.

Diurnal changes in plasma prolactin during the last one third of pregnancy in the baboon

Previous studies in our laboratory revealed that daily plasma prolactin (Prl) levels were higher in the evening than in the morning in the pregnant baboon suggesting a diurnal variation. The goal of this study was to examine in more detail the diurnal alterations in plasma Prl levels. A tethered pregnant baboon model was utilized for these studies. Hourly venous blood samples were taken from 0700 to 2400 hr (n=10) or until 0700 hr the following day (n=5). The studies were performed at various days of pregnancy from day 135 until delivery. Plasma samples were analyzed for Prl by radioimmunoassay. A surge in plasma Prl was detected, starting around 1500 to 1600 hr and lasting for 3 to 5 hr. The surge occurred before the lights went off in the colony (1800 hr). Baseline Prl levels were higher in animals < 15 days before delivery compared to those > 15 days before delivery (P < 0.05). In contrast, no differences were found in the average peak Prl values between these two groups of animals. In summary, in the pregnant baboon during the last one-third of pregnancy plasma Prl surges, beginning around 1500 to 1600 hr and lasting for 3 to 5 hr. Less than 15 days before delivery the mean baseline Prl levels are higher compared to animals greater than 15 days before delivery.

A guide to the use of focus groups in health care research: Part 1

Focus group interviewing is becoming a popular research method among nurses as well as allied health professionals. Prior to performing a focus group interview a novice must first search the literature to gain an understanding of the function, uses, preparation, conduct and analysis of this form of methodology. This paper has been compiled in an attempt to synthesise, condense and simplify the information from an extremely wide and varied focus group literature and provide a comprehensive review to assist nurses who are considering utilising this methodology in their research studies. The purpose of this paper was stimulated by one of the author's (MP) own experience learning about focus group methodology before commencing her first focus group.

A guide to the use of focus groups in health care research: Part 2

In this paper, the second in a two part series on focus groups, a comprehensive overview of the literature concerning the interviewing process, methodology and analysis is provided. We discuss the characteristics of the moderator and the way in which a focus group is conducted (the who, where, and how of the focus group process), the participants, the process, and the analysis. Nursing staff and allied health professionals, especially those contemplating using focus groups for the first time, will be able to gain an understanding of the conduct of focus groups from this one source. The comprehensive reference list will provide a wealth of primary sources for further reading.

Isolation and characterization of Leishmania mutants defective in glycosomal protein import

Kinetoplastid parasites contain a unique microbody organelle called the glycosome. Several important metabolic pathways found in the cytoplasm of higher eukaryotes are compartmentalized within the glycosome in these pathogens. This fundamental difference between the host and parasite has led to consideration of the glycosome as a potential chemotherapeutic target. The genetic basis of glycosome biogenesis is therefore of great interest. This report describes the isolation of multiple Leishmania mutant cell lines defective in glycosomal protein import, and the detailed characterization of three such lines. The mutants examined partially mislocalize a subset of glycosomal proteins to the cytosol yet retain wild-type numbers of glycosomes. One of the mutants has a mutation in the previously identified LdPEX2 (GIM1) gene. The other two mutants are demonstrated to contain cell-specific lesions in one or more genes distinct from PEX2. The identification of multiple genetically distinct mutants with defects in glycosome import provides an important genetic tool to facilitate the identification of genes involved in glycosome biogenesis.

Role clarity, organizational commitment, and job satisfaction during hospital reengineering

This study investigated the relationships among role conflict, role ambiguity, organizational commitment, and job satisfaction experienced by clinical team members in a hospital undergoing reengineering. The sample consisted of 409 registered nurses (RNs) and 278 non-RNs. Participants who experienced much role conflict and ambiguity exhibited less organizational commitment and job satisfaction. RNs had more role conflict and ambiguity than non-RNs. No significant differences in role conflict and role ambiguity, organizational commitment, and job satisfaction were observed between RNs working on medical-surgical units and those on specialty units. Strategies that reduce role conflict and role ambiguity to increase organizational commitment and job satisfaction are discussed.

Sexuality and perversion a hundred years on: discovering what Freud discovered

The author considers how Freud's original formulation of the sexual drive may be understood in contemporary terms. Parallels between psychoanalysis, art history and the social and natural sciences underline the idea of sexuality as a construct that can be revisited. The nature of sexuality depends on how its irreducible biological basis is interpreted by a particular society at a particular time. The importance of revisiting is illustrated by Klein's concept of a position, which revisits the theoretical construct of a developmental stage. Freud's own construction of sexuality is based on his view of drive as comprising source, aim and object. Freud, in the Darwinian climate of his time, considered the object in terms of whether it served the fulfillment of the aim, but his paradigm can today be understood more broadly than Freud himself was able to. A discussion of perversion shows that psychoanalysis has moved from seeing it as defensive against instinctual derivatives to seeing it as defensive against object-relatedness. This reflects a shift in the analytic conceptualization of sexuality in general. Freud's paradigm for the sexual drive can be reconceived in terms of source, aim and quality of relatedness to object. Such a view of sexuality also has implications for gender issues, for the comparison of male and female perversion, and for the relation between sexuality and love.

Pathways involved in environmental sensing in trypanosomatids

Digenetic parasites, such as those of the order Kinetoplastida, must respond to extracellular and intracellular signals as they adapt to new environments within their different hosts. Evidence for signal transduction has been obtained for Trypanosoma brucei, T. cruzi and Leishmania, as reviewed here by Marilyn Parsons and Larry Ruben. Although the broad picture suggests similarities with the mammalian host, there are large gaps in our understanding of these processes; this probably contributes to a perception of differences. Nonetheless, current evidence suggests that the trypanosomatids might lack certain classes of signalling molecules found in other organisms.

Echoplanar magnetic resonance imaging in acute stroke

Echoplanar magnetic resonance imaging (EPI) enables rapid, non-invasive imaging and analysis of cerebral pathophysiology in acute stroke. It represents an important clinical advance over computed tomography (CT) and conventional magnetic resonance (MR) scanning. It can rapidly delineate infarcted cerebral tissue and distinguish acute from chronic stroke. In addition, EPI has the potential to quickly determine the presence and degree of potentially viable brain tissue in the ischaemic penumbra. Thrombolysis is thought to reperfuse the penumbra and hence reduce infarct size. The thrombolytic agent tissue plasminogen activator (t-PA) improves outcome in ischaemic stroke when administered within the first 3 hours of onset. However, there is a significant risk of haemorrhage, and the time window for benefit may well exceed 3 hours in some patients. Hence, by facilitating diagnosis of 'at-risk' tissue in the ischaemic penumbra, a major clinical role of EPI may well become the rational selection of patients for acute interventional stroke therapy.

Chest pain in children: diagnosis through history and physical examination

INTRODUCTION

Chest pain is a common complaint in the pediatric age group and can be a physically and emotionally distressing symptom. Although chest pain in children rarely indicates serious cardiac problems, chest pain is perceived as "heart pain" to most children and their families and presents a diagnostic challenge to health care providers.

METHODS

A prospective study was conducted to identify specific factors in history taking and physical examination that permit accurate diagnosis of the cause of pediatric chest pain. Fifty children (ages 5-21 years; mean, 13 years), referred to the cardiology clinic with the chief complaint of chest pain, underwent systematic history taking, physical examination, and electrocardiogram testing.

RESULTS

The following diagnoses were made: 38 children (76%) had musculoskeletal/costochondral chest pain, 6 children (12%) had exercise-induced asthma, 4 children (8%) had chest pain resulting from gastrointestinal causes, and 2 children (4%) had chest pain resulting from psychogenic causes.

DISCUSSION

All the children in this study had noncardiac causes of their chest pain. This finding supports previous research suggesting that chest pain in children is rarely of cardiac origin. This article reviews the causes of pediatric chest pain and suggests an approach to its evaluation and management.

Mast cell tryptase stimulates human lung fibroblast proliferation via protease-activated receptor-2

Mast cells play a potentially important role in fibroproliferative diseases, releasing mediators including tryptase that are capable of stimulating fibroblast proliferation and procollagen synthesis. The mechanism by which tryptase stimulates fibroblast proliferation is unclear, although recent studies suggest it can activate protease-activated receptor (PAR)-2. We therefore investigated the role of PAR-2 in tryptase-induced proliferation of human fetal lung and adult lung parenchymal and airway fibroblasts and, for comparative purposes, adult dermal fibroblasts. Tryptase (0.7-70 mU/ml) induced concentration-dependent increases in proliferation of all fibroblasts studied. Antipain, bis(5-amidino-2-benzimidazolyl)methane, and benzamidine inhibited tryptase-induced fibroblast proliferation, demonstrating that proteolytic activity is required for the proliferative effects of tryptase. RT-PCR demonstrated the presence of PAR-2 mRNA, and immunohistochemical staining localized PAR-2 to the cell surface of lung fibroblasts. In addition, specific PAR-2 activating peptides, SLIGKV and SLIGRL, mimicked the proliferative effects of tryptase. In contrast, human dermal fibroblasts only weakly stained with the PAR-2 antibody, PAR-2 mRNA was almost undetectable, and fibroblasts did not respond to PAR-2 activating peptides. These results suggest that tryptase induces lung, but not dermal, fibroblast proliferation via activation of PAR-2 and are consistent with the hypothesis that the release of tryptase from activated mast cells may play an important role in the fibroproliferative response observed in asthma, chronic obstructive pulmonary disease, and patients with pulmonary fibrosis.

Mechanical load enhances procollagen processing in dermal fibroblasts by regulating levels of procollagen C-proteinase

Mechanical forces are emerging as key regulators of cell function. We hypothesize that mechanical load may influence dermal fibroblast activity. We assessed the direct effects of mechanical load on human dermal fibroblast procollagen synthesis and processing in vitro. Cells were loaded in a biaxial loading system (Flexercell 3000). Hydroxyproline levels were measured in the medium and cell layer as an estimate of procollagen synthesis and processing to insoluble collagen. Mechanical load (in the presence of serum or TGF-beta) enhanced procollagen synthesis by 45 +/- 3% (P < 0.001), and 38 +/- 4% (P < 0.001), respectively, over unloaded growth factor controls after 48 h. Insoluble collagen deposition was enhanced in the same cultures by 115 +/- 8% (P < 0.01) and 72% +/- 9% (P < 0.01), respectively. This effect was inhibited using l-arginine suggesting that procollagen C-proteinase, the enzyme which directly cleaves the C-terminal propeptide of procollagen to form insoluble collagen, is required for the fiber formation observed. Procollagen mRNA levels in loaded samples increased by more than two-fold in both serum and TGF-beta-treated cultures at 48 h. Procollagen C-proteinase mRNA levels were also enhanced by a similar magnitude, although the increase was observed at 24 h. Procollagen C-proteinase protein levels were also increased at this time. Protein and mRNA levels of the procollagen C-proteinase enhancer protein, which binds the C-terminal propeptide of procollagen to enhance the rate of peptide cleavage, were unaffected by mechanical load. This study demonstrates that mechanical load promotes procollagen synthesis in dermal fibroblasts by enhancing gene expression and posttranslational processing of procollagen.

Mechanical load enhances procollagen processing in dermal fibroblasts by regulating levels of procollagen C-proteinase

Mechanical forces are emerging as key regulators of cell function. We hypothesize that mechanical load may influence dermal fibroblast activity. We assessed the direct effects of mechanical load on human dermal fibroblast procollagen synthesis and processing in vitro. Cells were loaded in a biaxial loading system (Flexercell 3000). Hydroxyproline levels were measured in the medium and cell layer as an estimate of procollagen synthesis and processing to insoluble collagen. Mechanical load (in the presence of serum or TGF-beta) enhanced procollagen synthesis by 45 +/- 3% (P < 0.001), and 38 +/- 4% (P < 0.001), respectively, over unloaded growth factor controls after 48 h. Insoluble collagen deposition was enhanced in the same cultures by 115 +/- 8% (P < 0.01) and 72% +/- 9% (P < 0.01), respectively. This effect was inhibited using l-arginine suggesting that procollagen C-proteinase, the enzyme which directly cleaves the C-terminal propeptide of procollagen to form insoluble collagen, is required for the fiber formation observed. Procollagen mRNA levels in loaded samples increased by more than two-fold in both serum and TGF-beta-treated cultures at 48 h. Procollagen C-proteinase mRNA levels were also enhanced by a similar magnitude, although the increase was observed at 24 h. Procollagen C-proteinase protein levels were also increased at this time. Protein and mRNA levels of the procollagen C-proteinase enhancer protein, which binds the C-terminal propeptide of procollagen to enhance the rate of peptide cleavage, were unaffected by mechanical load. This study demonstrates that mechanical load promotes procollagen synthesis in dermal fibroblasts by enhancing gene expression and posttranslational processing of procollagen.

The logic of play in psychoanalysis

The paper puts forward the idea that play is at work all the time in psychoanalysis. The play element functions continuously to sustain a paradoxical reality where things may be real and not real at the same time. This paradox is what allows the work of psychoanalysis to take place. The concept of play covers different activities with complex interrelations, and general definitions may be misleading. The essential element is the framework that makes the paradoxical reality possible. The logical structure of the play framework is investigated, and the paper clarifies the relations between the play frame, transference and enactment. Play and humour are compared. Spontaneity is the essence of both, and the criterion for analytic validity in both cases is whether they deepen the analytic process. The tragic and ironic aspects of psychoanalysis are related to the intrinsic connection between play and loss. The relation between play and games is discussed. The rule-bound quality of games can block more exploratory kinds of play, but it may be necessary to accept this, in order for analysis to feel safe enough. Clinical material illustrates the importance of the play framework, both in a case marked by prolonged hostile and negative states of mind, and in others where more straightforward playfulness was possible.

Pathophysiological topography of acute ischemia by combined diffusion-weighted and perfusion MRI

BACKGROUND AND PURPOSE

Combined echoplanar MRI diffusion-weighted imaging (DWI), perfusion imaging (PI), and magnetic resonance angiography (MRA) can be used to visualize acute brain ischemia and predict lesion evolution and functional outcome. The appearance of a larger lesion by PI than by DWI quantitatively defines a mismatch of potential clinical importance. Qualitative lesion variations exist in the topographic concordance of this mismatch. We examined both the topographic heterogeneity and relative frequency of mismatched patterns in acute stroke using these MRI techniques.

METHODS

Acute DWI, PI, and MRA studies of 34 prospectively recruited patients with supratentorial ischemic lesions scanned within 24 hours of stroke onset (range 2.5 to 23.3 hours, 12 patients <6 hours) were analyzed.

RESULTS

Ischemic lesions were predominantly in the middle cerebral artery (MCA) territory (94%), with DWI lesions most commonly affecting the insular region. Mismatched patterns with PI lesion larger than DWI lesion occurred in 21 patients (62% overall), in all 4 patients imaged within 3 hours, and in 44% of patients imaged after 18 hours. A patient with a large PI but no DWI lesion and severe clinical deficit at 2.5 hours after stroke onset recovered completely. Regional variations in DWI and PI lesion loci were found, inferring site of proximal MCA occlusion, embolic pathogenesis, and regional arterial reperfusion.

CONCLUSIONS

Analysis of the topographic concordance of PI and DWI lesions in acute stroke reveals regional PI lesions without concomitant DWI lesions, which do not necessarily progress to infarction but may suggest stroke pathogenesis and site of current arterial occlusion. Location of DWI lesions may suggest an earlier site of arterial occlusion and regions of maximal perfusion deficit.

Raspberry leaf and its effect on labour: safety and efficacy

The purpose of this study was to examine the safety and efficacy of raspberry leaf products consumed by a group of mothers during their pregnancy, by comparison with a group of mothers who did not. A retrospective observational design was used. Subjects were women who birth their babies at Westmead Hospital between January 1998-July 1998. The sample consisted of 108 mothers; 57 (52.8%) consumed raspberry leaf products while 51 (47.2%) were in the control group. The findings suggest that the raspberry leaf herb can be consumed by women during their pregnancy for the purpose for which it is taken, that is, to shorten labour with no identified side effects for the women or their babies. The findings also suggest ingestion of the drug might decrease the likelihood of pre and post-term gestation. An unexpected finding in this study seems to indicate that women who ingest raspberry leaf might be less likely to receive an artificial rupture of their membranes, or require a caesarean section, forceps or vacuum birth than the women in the control group.

Distal external iliac lymph nodes in early cervical cancer

OBJECTIVE

To evaluate the utility of the deep circumflex iliac vein as a landmark for the caudal limit of external iliac lymphadenectomy for early cervical cancer.

METHODS

During dissection of the distal (caudal), anterior (ventral) aspect of the external iliac vessels in conjunction with radical hysterectomy for carcinoma of the cervix, a careful search was made for the deep circumflex iliac vein. Lymph nodes immediately above this vein were sent as adjacent and lymph nodes caudal to the vein were sent as distal. The distance from the vein to the femoral canal was measured.

RESULTS

Seventy-one women were studied over 40 months. Fifty-five had squamous cell carcinoma, 15 had adenocarcinoma, and one had adenosquamous carcinoma. The mean distance from the deep circumflex iliac vein to the femoral canal was 16 mm. Sixty-three patients had dissections distal to identified deep circumflex iliac veins and 49 (77%) of these had distal lymph nodes removed. The median number of pelvic lymph nodes removed was 24 (range nine to 68), and the median number of distal lymph nodes removed was 1.0 from each side. Lymph node metastases were found in 13 women (18%). One subject with multiple macroscopically positive nodes had a single positive distal lymph node. Thus, a small number of distal lymph nodes were found in most women with early invasive cervical cancer, and 8% of those with positive nodes had involvement of this nodal group.

CONCLUSION

The deep circumflex iliac vein was an appropriate landmark for the caudal limit of external iliac lymphadenectomy.

Performance of a reagent strip device for quantitation of the urine albumin: creatinine ratio in a point of care setting

AIM

We have evaluated the performance of a reagent strip (Clinitek, Bayer plc, Newbury) incorporating a novel dip and read device for the quantitation of the albumin: creatinine ratio together with their individual concentrations in urine.

METHODS

The performance was compared with that of a lateral flow device for the semi-quantitation of albumin (Micral II, Roche Diagnostics, Lewes) and also a laboratory based procedure. The device employs novel methods for both analytes, using a sulphonephthalein dye binding at pH 1.5 for albumin and the peroxidase-like activity of copper creatinine complexes. The color yields of the separate reaction pads are monitored with the Clinitek 50TM bench top urine chemistry analyzer and compared to a pre-programmed calibration algorithm.

RESULTS

The imprecision of the device was assessed by observing the discrepancy between duplicates in a total of 144 urine samples collected from patients with diabetes and/or renal disease; there were 10 discrepancies in the case of the albumin estimation (6.9%), 12 in the case of the creatinine estimation (12.5%) and 23 in the case of the albumin: creatinine ratio (16.0%). In the case of the Micral II, where 96 of the urines were analyzed there were 12 discrepancies (12.5%). When considered as a two-class test for albumin with a cut off of 20 mg/L the Clinitek gave a sensitivity of 95.4% with specificity of 78.9% and a positive predictive value of 87.4%. When analyzing four urines (two controls, two patient pools) with replicate analysis on the Clinitek system we found 100% agreement for the albumin estimation, 95% for creatinine and 96.7% for the albumin: creatinine for 60 analysis within a day and 100, 95 and 97.5% on single analyses each day for 20 days for the two urine controls. The discrepant results were always within one color block. When considering the albumin: creatinine ratio with a cut off of < 30 mg/g the Clinitek gave a sensitivity of 76.3% with a specificity of 89.1% and a positive predictive value of 89.7%.

CONCLUSION

The Clinitek system provides a reliable means to screen for microalbuminuria with the opportunity of a semi-quantitative assessment when microalbuminuria is found.

Lateral microscopic extension of squamous cell carcinoma of the vulva

PURPOSE

The aim of this study was to measure the radial occult microscopic spread of tumor in patients with invasive squamous cell carcinoma of the vulva.

MATERIALS AND METHODS

In the operating room the gross tumor border was marked. The pathologist took a radial section in each quadrant and measured the distance of occult lateral spread of the tumor.

RESULTS

From 7/01/93 to 6/30/96, 24 tumors from 21 patients were studied. The mean maximum tumor diameter was 3. 2 cm (0.5-7.0) and the mean depth of invasion was 9.1 mm (1.1-28.0). The gross and microscopic extent correlated in 20 tumors. Maximum lateral microscopic extent of the other 4 tumors was 3.5, 5 (to the margin), 10, and 16 mm. These 4 tumors were ulcerative and infiltrative and arose from or involved mucosa.

CONCLUSION

The gross and microscopic periphery of most invasive squamous vulvar cancers are approximately the same. Ulcerative tumors with an infiltrative pattern of invasion which involve mucosal epithelium may be more likely to extend beyond what is grossly apparent. Measurement of the tumor-free margin should be included in future studies.

A dominant negative mutation in the GIM1 gene of Leishmania donovani is responsible for defects in glycosomal protein localization

Kinetoplastid protozoa contain a unique microbody organelle called the glycosome. Several important metabolic pathways are compartmentalized within the glycosome that are found in the cytoplasm of higher eukaryotes. We have previously reported the identification of a Leishmania donovani cell line called gim1-1, in which several normally glycosomal proteins are partially mislocalized to the cytoplasm. The GIM1 gene complements the defect and restores import of proteins to the glycosome. Here we demonstrate that GIM1 encodes an integral membrane protein of the glycosome. We also report that the mutant gim1-1 allele behaves as a dominant negative mutation. Introducing the gim1-1 allele extrachromasomally led to mislocalization of a glycosomal reporter protein even in wild-type cells. Gene disruption experiments in heterozygous GIM1/gim1-1 cells showed that when the mutant gim1-1 allele was lost, cells re-established normal glycosomal protein localization. Interestingly, no disruptions of the wild-type allele were obtained. These data indicate that a dominant negative mutation in the GIM1 gene is the sole genetic lesion responsible for the glycosomal defects in gim1-1, and suggest that GIM1 is an essential gene in Leishmania.