A 10-year experience with anastomotic leaks in upper gastrointestinal surgery-Retrospective cohort study

BACKGROUND

Anastomotic leak (AL) in upper gastrointestinal (UGI) surgery continues to be a diagnostic challenge. We seek to identify clinical parameters that predict AL and examine the effectiveness of investigations in evaluating AL following UGI surgeries.

METHODS

592 patients underwent UGI surgeries with an anastomosis between January 2011 and January 2021. Data on patient characteristics, surgery, postoperative investigations and outcomes were prospectively collected and analysed.

RESULTS

The overall occurrence of AL was 6.4 %. Tachycardia >120 BPM (OR 6.959, 95 % CI 1.856-26.100, p = 0.004) and leukocyte count >19 × 109/L (OR 3.327, 95 % CI 1.009-10.967, p = 0.048) were independent predictors of AL. On multivariate analysis, patients whose anastomosis was deemed high risk and had pre-emptive investigation done postoperatively to exclude a leak were less likely to require intervention and were more likely to be managed conservatively (66.7 % vs 14.3 %, p = 0.025). Methylene blue test, oral contrast study and Computed Tomography scan with intravenous and oral contrast had 50.0 %, 20.0 % and 9.1 % false negative results, while esophagogastroduodenoscopy had none. There was no misdiagnosed AL when more than 1 investigation (n = 15, 39.5 %) were performed.

CONCLUSION

Our study demonstrates that the presence of a triad including desaturation, tachycardia and leucocytosis predicts for AL following UGI surgery and for confirmation of a leak, evaluation with 2 or more investigation is needed. A practice of evaluating high risk anastomosis prior to commencement of feeding decreased the need for surgical intervention and improves success of conservative treatment.

Alterations in colorectal cancer virome and its persistence after surgery

Viruses are a key component of the colon microbiome, but the relationship between virome and colorectal cancer (CRC) remains poorly understood. We seek to identify alterations in the viral community that is characteristic of CRC and examine if they persist after surgery. Forty-nine fecal samples from 25 non-cancer (NC) individuals and 12 CRC patients, before and 6-months after surgery, were collected for metagenomic analysis. The fecal virome of CRC patients demonstrated an increased network connectivity as compared to NC individuals. Co-exclusion of influential viruses to bacterial species associated with healthy gut status was observed in CRC, suggesting an altered virome induced a change in the healthy gut bacteriome. Network analysis revealed lower connectivity within the virome and trans-kingdom interactions in NC. After surgery, the number of strong correlations decreased for trans-kingdom and within the bacteria and virome networks, indicating lower connectivity within the microbiome. Some co-occurrence patterns between dominant viruses and bacteria were also lost after surgery, suggesting a possible return to the healthy state of gut microbiome. Microbial signatures characteristic of CRC include an altered virome besides an altered bacterial composition. Elevated viral correlations and network connectivity were observed in CRC patients relative to healthy individuals, alongside distinct changes in the cross-kingdom correlation network unique to CRC patients. Some patterns of dysbiosis persist after surgery. Future studies should seek to verify if dysbiosis truly persists after surgery in a larger sample size with microbiome data collected at various time points after surgery to explore if there is field-change in the remaining colon, as well as to examine if persistent dysbiosis correlates with patient outcomes.

Preoperative Quality of Life and Mental Health Can Predict Postoperative Outcomes and Quality of Life after Colorectal Cancer Surgery

Background and Objectives: It remains unclear which domains of preoperative health-related quality of life (HRQOL) and mental health are predictive of postoperative clinical and patient-reported outcomes in colorectal cancer (CRC) patients. Materials and Methods: A prospective cohort of 78 CRC patients undergoing elective curative surgery was recruited. The EORTC QLQ-C30 and HADS questionnaires were administered preoperatively and one month after surgery. Results: Preoperative cognitive functioning scores (95% CI 0.131-1.158, p = 0.015) and low anterior resection (95% CI 14.861-63.260, p = 0.002) independently predicted poorer 1-month postoperative global QOL. When postoperative complications were represented using the comprehensive complication index (CCI), poorer preoperative physical function scores were associated with higher CCI scores (B = -0.277, p = 0.014). Preoperative social function score (OR = 0.925, 95% CI 0.87 to 0.99; p = 0.019) was an independent predictor for 30-day readmission, while physical functioning score (OR = -0.620, 95% CI -1.073--0.167, p = 0.008) was inversely related to the length of hospitalization. The overall regressions for 1-month postoperative global QOL (R²: 0.546, F: 1.961, p = 0.023) and 30-day readmission (R²: 0.322, χ2: 13.129, p < 0.001) were statistically significant. Conclusions: Various QLQ-C30 domains were found to be predictive of postoperative outcomes, including complications, readmission, and length of hospitalization. Preoperative cognitive dysfunction and low AR were independent predictors of poorer postoperative global QOL. Future research should seek to examine the efficacy of targeting specific baseline QOL domains in improving clinical as well as patient-reported outcomes after CRC surgery.

Safely Implementing a Program of Pure Laparoscopic Donor Right Hepatectomy: The Experience From a Southeast Asian Center

Laparoscopic donor right hepatectomy (LDRH) is a technically challenging procedure. There is increasing evidence demonstrating the safety of LDRH in high-volume expert centers. We report our center's experience in implementing an LDRH program in a small- to medium-sized transplantation program.

Methods

Our center systematically introduced a laparoscopic hepatectomy program in 2006. We started with minor wedge resections followed by major hepatectomies with increasing complexities. In 2017, we performed our first laparoscopic living donor left lateral sectionectomy. Since 2018, we have performed 8 cases of right lobe living donor hepatectomy (laparoscopy-assisted: 4 and pure laparoscopic: 4).

Results

The median operative time was 418 (298-540) min, whereas the median blood loss was 300 (150-900) mL. Two patients (25%) had surgical drain placed intraoperatively. The median length of stay was 5 (3-8) d, and the median time to return to work was 55 (24-90) d. None of the donors sustained any long-term morbidity or mortality.

Conclusions

Small- to medium-sized transplant programs face unique challenges in adopting LDRH. Progressive introduction of complex laparoscopic surgery, a mature living donor liver transplantation program, appropriate patient selection, and the invitation of an expert to proctor the LDRH are necessary to ensure success.

Alterations in co-abundant bacteriome in colorectal cancer and its persistence after surgery: a pilot study

There is growing interest in the role of gut microbiome in colorectal cancer (CRC), ranging from screening to disease recurrence. Our study aims to identify microbial markers characteristic of CRC and to examine if changes in bacteriome persist after surgery. Forty-nine fecal samples from 25 non-cancer (NC) individuals and 12 CRC patients, before and 6-months after surgery, were collected for analysis by bacterial 16S rRNA gene sequencing. Bacterial richness and diversity were reduced, while pro-carcinogenic bacteria such as Bacteroides fragilis and Odoribacter splanchnicus were increased in CRC patients compared to NC group. These differences were no longer observed after surgery. Comparison between pre-op and post-op CRC showed increased abundance of probiotic bacteria after surgery. Concomitantly, bacteria associated with CRC progression were observed to have increased after surgery, implying persistent dysbiosis. In addition, functional pathway predictions based on the bacterial 16S rRNA gene data showed that various pathways were differentially enriched in CRC compared to NC. Microbiome signatures characteristic of CRC comprise altered bacterial composition. Elements of these dysbiotic signatures persists even after surgery, suggesting possible field-change in remnant non-diseased colon. Future studies should involve a larger sample size with microbiome data collected at multiple time points after surgery to examine if these dysbiotic patterns truly persist and also correlate with disease outcomes.

A phase I study of binimetinib (MEK 162), a MEK inhibitor, plus carboplatin and pemetrexed chemotherapy in non-squamous non-small cell lung cancer

INTRODUCTION

MEK inhibition is a potential therapeutic strategy in non-small cell lung cancer (NSCLC). This phase I study evaluates the MEK inhibitor binimetinib plus carboplatin and pemetrexed in stage IV non-squamous NSCLC patients (NCT02185690).

METHODS

A standard 3 + 3 dose-escalation design was used. Binimetinib 30 mg BID (dose level 1 [DL1]) or 45 mg BID (dose level 2 [DL2]) was given with standard doses of carboplatin and pemetrexed using an intermittent dosing schedule. The primary outcome was determination of the recommended phase II dose (RP2D) and safety of binimetinib. Secondary outcomes included efficacy, pharmacokinetics, and an exploratory analysis of response based on mutation subtype.

RESULTS

Thirteen patients (6 DL1, 7 DL2) were enrolled: 7 KRAS, 5 EGFR, and 1 NRAS mutation. The RP2D was binimetinib 30 mg BID. Eight patients (61.5%) had grade 3/4 adverse events, with dose limiting toxicities in 2 patients at DL2. Twelve patients were evaluated for response, with an investigator-assessed objective response rate (ORR) of 50% (95% CI 21.1%-78.9%; ORR 33.3% by independent-review, IR), and disease control rate 83.3% (95% CI 51.6%-97.9%). Median progression free survival (PFS) was 4.5 months (95% CI 2.6 months-NA), with a 6-month and 12-month PFS rate of 38.5% (95% CI 19.3%-76.5%) and 25.6% (95% CI 8.9%-73.6%), respectively. In an exploratory analysis, KRAS/NRAS-mutated patients had an ORR of 62.5% (ORR 37.5% by IR) vs. 25% in KRAS/NRAS wild-type patients. In MAP2K1-mutated patients, the ORR was 42.8%.

CONCLUSION

The addition of binimetinib to carboplatin and pemetrexed appears to have manageable toxicity with evidence of activity in advanced non-squamous NSCLC.

295 Radiotherapy for Curative-intent Metastatic Rectal Cancer: A Systematic Review and Meta-Analysis

Introduction

The role and optimal regimen of radiotherapy in curative-intent treatment of metastatic rectal cancer is unclear and hence a single arm meta-analysis was performed.

Method

Medline, Embase and Cochrane Library databases were searched up to 16 May 2020. A Meta-analysis of binomial data was performed using a Freeman-Tukey double arcsine transformation, and pooled estimates were used to construct risk ratios and confidence intervals via the Katz-logarithmic method. Additionally, comparative meta-analysis was performed with the Mantel Haenszel model.

Results

18 studies were included. Rectal pathological complete response (pCR) was observed in 14% of tumours treated with radiotherapy (n = 57/388, CI 0.07 to 0.23). Comparative meta-analysis of cohort studies showed that treatment regimens including radiotherapy were associated with higher pT1 tumour and better oncological outcomes compared to regimens without radiotherapy. Katz-logarithmic method showed that neoadjuvant radiotherapy had a higher proportion of pN0 staging (RR = 1.81, 95% CI 1.06 to 3.09, p = 0.029) and better oncological outcomes compared to adjuvant radiotherapy, and that short course radiotherapy (SCRT) had a lower proportion of pT3 tumours (RR = 0.778, 95% CI 0.609 to 0.994, p = 0.044) and similar oncological outcomes compared to long course radiotherapy (LCRT).

Conclusions

This study supports the evidence that radiotherapy should be used in curative intent metastatic rectal cancer.

Young colorectal cancer patients often present too late

PURPOSE

Current screening and health education strategies on colorectal cancer (CRC) remain focused on individuals >50 years old. However, CRC in young adults is not uncommon. This paper aims to explore how CRC presents in young adults and their clinical outcomes.

METHODS

All patients aged <50 years diagnosed with CRC from January 2007 to December 2015 were reviewed. Patient demographics, clinical symptoms, and outcomes of treatment were collected.

RESULTS

Of 1367 patients diagnosed with CRC, 154 (11.6%) were aged <50 years. The median age of diagnosis was 45 years (range, 19-49). The majority (61%) of the patients presented acutely via the emergency department and the three most common presenting symptoms were abdominal pain (n = 94; 61.0%), change in bowel habits (n = 74; 48.1%), and per rectal bleeding (n = 69; 44.8%). Most of the primary cancers were left sided (n = 122, 79.2%) in location and 33 (21.4%) patients had metastatic disease on presentation. 138 (89.6%) patients were treated with curative intent, including 17 (51.5%) with metastatic disease on presentation. There were 31 (22.5%) patients who developed disease recurrence at a median duration of 10.0 (range, 0.5-94.0) months. The younger group (<45 years old) were more likely to present acutely and had more aggressive tumor biology.

CONCLUSIONS

The majority of young CRC patients present acutely and their presenting symptoms are often vague. There is a need to educate young adults on the possibility of harboring CRC and its typical presenting symptoms to enable earlier detection.

Palliative surgical intervention in metastatic colorectal carcinoma: a prospective analysis of quality of life

AIM

Quality of life (QOL) was assessed after palliative surgery for incurable metastatic colorectal cancer (CRC).

METHOD

Newly diagnosed patients with incurable metastatic CRC who were offered elective palliative surgical intervention were included. The European Organization for Research and Treatment of Cancer QLQ-C30 and QLQ-CR29 questionnaire was used for the assessment of QOL at baseline and at 3 and 6 months after surgery. Generalized estimating equations were used to estimate the mean change in the QOL score from baseline.

RESULTS

Twenty-four patients formed the study group. Sixteen underwent resection of the primary tumour and eight had a proximal diversion or bypass. The Global Health (GH) score and Social Functioning (SF) score improved at 3 and 6 months after intervention respectively (GH +11, P = 0.021; SF +15, P = 0.005). Mean anxiety scores were markedly improved from the baseline of 51 to 71 (P = 0.004, 3 months) and 76 (P = 0.002, 6 months). Weight concerns also improved significantly when compared with baseline (3 months, +20, P < 0.001; 6 months, +14, P = 0.012). Symptoms of diarrhoea (3 months, --17, P = 0.007; 6 months,--16, P = 0.008) and nausea (--8, P = 0.032) improved.

CONCLUSION

In patients with incurable metastatic CRC, surgery improved QOL.

Juvenile hormone-binding protein from the cytosol of Drosophila Kc cells

Insect cells of an established line, Drosophila Kc cells, take up and metabolize juvenile hormone (JH). The cytoplasm of these cells contains a protein that binds JH with specificity, saturability, and high affinity (K(d) = 1.56 x 10(-8) M). The kinetics for the specific binding and dissociation of JH I were independently measured, and the rate constants were found to be k(a) = 1.3 x 10(6) M(-1) min(-1), k(d) = 1.3 x 10(-2) min(-1), respectively. All three juvenile hormones bind to the protein with comparable affinities; the corresponding acid or diol metabolites of JH I are not bound. About 2500 hormone-binding protein molecules are present per cell. The protein has a molecular weight of 80,000 as estimated by gel permeation chromatography and by sucrose gradient sedimentation. The properties of this protein suggest that it functions as a cytoplasmic receptor for juvenile hormone.

The Juvenile Hormone Binding Protein in the Hemolymph of Manduca sexta Johannson (Lepidoptera: Sphingidae)

C(18):juvenile hormone is quite soluble in water, yielding a monomeric solution greater than 10(-5) M. In vivo injection or addition of aqueous juvenile hormone to the hemolymph in vitro shows the complexation of juvenile hormone to a protein, as demonstrated by gel permeation chromatography and disc-gel electrophoresis. The protein has an apparent molecular weight of 3.4 x 10(4) and is present in the hemolymph at a concentration in the micromolar range. The binding of the hormone to the protein can be described as a simple thermodynamic equilibrium with a dissociation constant of 3 x 10(-7) M, and the protein has a much higher affinity for the hormone than for the hydrolysis products.

SYNTHESIS AND DEGRADATION OF POLY-beta-HYDROXYBUTYRIC ACID IN CONNECTION WITH SPORULATION OF BACILLUS MEGATERIUM

Slepecky, Ralph A. (Northwestern University, Evanston, Ill.), and John H. Law. Synthesis and degradation of poly-beta-hydroxybutyric acid in connection with sporulation of Bacillus megaterium. J. Bacteriol. 82:37-42. 1961.-The production of poly-beta-hydroxybutyrate has been followed in Bacillus megaterium, a sporulating strain, and B. megaterium strain KM, a nonsporulating strain, by an improved assay procedure and by the use of C(14)-acetate. The production of polymer in the KM strain follows the growth curve very slowly and reaches a peak at the time the cells are entering the stationary phase of growth. Slow utilization of polymer follows. When the sporulating strain is grown under conditions favorable for polymer production, no spores are formed; polymer production and utilization follow kinetics similar to those observed with asporogenous strains. When the sporulating strain is grown under conditions unfavorable for polymer production but favorable for sporulation, less polymer is produced and peak production occurs during the log phase of growth. Rapid utilization of the polymer precedes sporulation. If the medium is made favorable for polymer production by the addition of glucose and acetate and vigorous aeration conditions are used, sporulation can be obtained after good polymer production and subsequent utilization.

Aedes aegypti transferrin. Gene structure, expression pattern, and regulation

Mosquitoes and all other insects so far examined have an abundant haemolymph transferrin (Tsf). The exact function of these proteins has not been determined, but they may be involved in iron transport, in oogenesis and in innate immune defence against parasites and pathogens. The Tsf gene of Aedes aegypti has been cloned and sequenced. It contains a single small intron, which contrasts it to vertebrate Tsf genes that contain up to sixteen introns. The promoter region of the gene is rich in putative NF-kappaB binding sites, which is consistent with the postulated role of Tsf in insect innate immunity. Tsf message levels are very low in embryos and early larvae, but high in late larvae, pupae and adults. Western blotting experiments revealed high levels of Tsf protein in pupae and adults. Late larvae and ovaries of blood-fed mosquitoes have little intact protein, but two prominent proteolytic degradation products. These may represent biologically active peptides, as has been shown for other organisms. Tsf message is down-regulated by inorganic iron in the diet or environment, but up-regulated by a blood meal in the adult female. The up-regulation following a blood meal may, in part, be due to the decrease in juvenile hormone (JH) that is known to follow blood feeding. Treatment of blood-fed females with methoprene, an analogue of JH, resulted in decrease of the Tsf message.

On the biosynthesis of Rhodnius prolixus heme-binding protein

The biosynthesis of Rhodnius prolixus heme-binding protein (RHBP), which is present in the hemolymph and oocytes of Rhodnius prolixus, was investigated. Fat bodies of female insects incubated in vitro with 14C-leucine were able to synthesize and secrete 14C-RHBP to the culture medium. Titrtion of synthesized RHBP with hemin showed that the protein secreted by the fat bodies is bound to heme, despite the presence of apo-RHBP in the hemolymph. The sequence of the RHBP cDNA encodes a pre-protein of 128 amino acids with no significant homology to any known protein. Northern-blot assays revealed that RHBP expression was limited to fat bodies. The levels of both RHBP mRNA and secreted protein increased in response to blood meal. In addition, the time-course of RHBP secretion in vitro paralleled mRNA accumulation observed in vivo. The inhibition of the de novo heme biosynthesis by treatment of fat bodies with succinyl acetone (SA), an irreversible inhibitor of delta-aminolevulinic acid-dehydratase, led to a significant decrease of heme-RHBP secretion. Nevertheless, the levels of RHBP mRNA were not modified by SA treatment, suggesting that the heme availability is involved in a post-transcriptional control of the RHBP synthesis.

Drosophila melanogaster ferritin: cDNA encoding a light chain homologue, temporal and tissue specific expression of both subunit types

Drosophila melanogaster secreted ferritin like the cytosolic ferritins of other organisms is composed of two subunits, a heavy chain homologue (HCH) and a light chain homologue (LCH). We report the cloning of a cDNA encoding the ferritin LCH of this insect. As predicted from the gene sequence, it contains no iron responsive element (IRE). Northern blot analysis reveals two mRNAs that differ in length due to the choice of polyadenylation signals. Message levels vary through the life cycle of the fly and are markedly increased by high levels of dietary iron. The gut is the main site of increased message synthesis and iron preferentially increases the amount of shorter messages. Western blotting reveals that LCH is the predominant ferritin subunit in all life stages. The amount of LCH protein corresponds well with the message levels in control animals, while in iron-fed animals LCH does not increase proportionally with the message levels. In contrast, the amount of HCH is less than that would be predicted from message levels in control animals, but corresponds well in iron-fed animals. Ferritin is abundant in gut and hemolymph of larvae and adults and in ovaries of adult flies. At pupariation, ferritin becomes more abundant in hemolymph than in other tissues.

Transcriptional control is relevant in the modulation of mosquito ferritin synthesis by iron

In yellow fever mosquito cells (Aag2 clone), iron treatment induces a threefold increase in ferritin message (fer mRNA) and protein (ferritin) by 16 h. These data contrast with work in mammalian hepatocytes and fibroblasts in which fer mRNA levels do not change with iron stimulation, but ferritin levels increase 50-fold. Pretreatment of the Aag2 cells with actinomycin D blocks induction of fer mRNA and reduces the ferritin subunit synthesis, suggesting that iron induction of ferritin subunit synthesis is subjected to transcriptional control. A putative iron-regulatory protein has also been identified in cytoplasmic extracts from Aag2 cells.

A novel lipoprotein from the hemolymph of the cochineal insect, Dactylopius confusus

A new type of insect lipoprotein was isolated from the hemolymph of the female cochineal insect Dactylopius confusus. The lipoprotein from the cochineal insect hemolymph was found to have a relative molecular mass of 450 000. It contains 48% lipid, mostly diacylglycerol, phospholipids and hydrocarbons. The protein moiety of the lipoprotein consists of two apoproteins of approximately 25 and 22 kDa, both of which are glycosylated. Both apolipoproteins are also found free in the hemolymph, unassociated with any lipid. Purified cochineal apolipoproteins can combine with Manduca sexta lipophorin, if injected together with adipokinetic hormone into M. sexta. This could indicate that the cochineal lipoprotein can function as a lipid shuttle similar to lipophorins of other insects, and that the cochineal insect apolipoproteins have an overall structure similar to insect apolipophorin-III.

Iron availability dramatically alters the distribution of ferritin subunit messages in Drosophila melanogaster

Insect ferritins have subunits homologous to the heavy and light chains of vertebrate ferritins. Cloning and sequence of the heavy chain homologue (HCH) of Drosophila melanogaster ferritin subunit have been reported earlier. When Northern blots of D. melanogaster RNA were probed with a cDNA for this HCH, three bands were observed. It was shown that these represented at least four classes of mRNA of various lengths. The polymorphism results from alternative splicing of an intron in the 5' untranslated region (UTR) that contains the iron-responsive element (IRE) and from two alternative polyadenylation sites in the 3' UTR. This has also been reported by others [Lind, M. I., Ekengren, S., Melefors, O. & Söderhäll, K. (1998) FEBS Lett. 436, 476-482]. By hybridizing Northern blots with specific probes, it has been shown that the relative proportions of the messages vary with the life stage and especially with iron supplementation of the diet. Iron significantly increases the amount of ferritin HCH messages and dramatically shifts the balance toward those messages that lack an IRE and/or have a short 3' UTR. In the larvae this change takes place in the gut, but not in the fat body. We speculate that this dramatic shift in message distribution may result from an effect of iron on the rate of transcription or message degradation, or from an effect on the splicing process itself. Synthesis of ferritin HCH subunit mRNAs that lack an IRE may be important under conditions of iron overload.

Drosophila melanogaster transferrin. Cloning, deduced protein sequence, expression during the life cycle, gene localization and up-regulation on bacterial infection

Drosophila melanogaster transferrin cDNA was cloned from an ovarian cDNA library by using a PCR fragment amplified by two primers designed from other dipteran transferrin sequences. The clone (2035 bp) encodes a protein of 641 amino acids containing a signal peptide of 29 amino acids. Like other insect transferrins, Drosophila transferrin appears to have a functional iron-binding site only in the N-terminal lobe. The C-terminal lobe lacks iron-binding residues found in other transferrins, and has large deletions which make it much smaller than functional C-terminal lobes in other transferrins. In-situ hybridization using a digoxigenin labeled transferrin cDNA probe revealed that the gene is located at position 17B1-2 on the X chromosome. Northern blot analysis showed that transferrin mRNA was present in the larval, pupal and adult stages, but was not detectable in the embryo. Iron supplementation of the diet resulted in lower levels of transferrin mRNA. When adult flies were inoculated with bacteria (Escherichia coli), transferrin mRNA synthesis was markedly increased relative to controls.

Mosquito transferrin, an acute-phase protein that is up-regulated upon infection

When treated with heat-killed bacterial cells, mosquito cells in culture respond by up-regulating several proteins. Among these is a 66-kDa protein (p66) that is secreted from cells derived from both Aedes aegypti and Aedes albopictus. p66 was degraded by proteolysis and gave a virtually identical pattern of peptide products for each mosquito species. The sequence of one peptide (31 amino acids) was determined and found to have similarity to insect transferrins. By using conserved regions of insect transferrin sequences, degenerate oligonucleotide PCR primers were designed and used to isolate a cDNA clone encoding an A. aegypti transferrin. The encoded protein contained a signal sequence that, when cleaved, would yield a mature protein of 68 kDa. It contained the 31-amino acid peptide, and the 3' end exactly matched a cDNA encoding a polypeptide that is up-regulated when A. aegypti encapsulates filarial worms [Beerntsen, B. T., Severson, D. W. & Christensen, B. M. (1994) Exp. Parasitol. 79, 312-321]. This transferrin, like those of two other insect species, has conserved iron-binding residues in the N-terminal lobe but not in the C-terminal lobe, which also has large deletions in the polypeptide chain, compared with transferrins with functional C-terminal lobes. The hypothesis is developed that this transferrin plays a role similar to vertebrate lactoferrin in sequestering iron from invading organisms and that degradation of the structure of the C-terminal lobe might be a mechanism for evading pathogens that elaborate transferrin receptors to tap sequestered iron.

Isolation and properties of Drosophila melanogaster ferritin--molecular cloning of a cDNA that encodes one subunit, and localization of the gene on the third chromosome

Ferritin was purified from iron-fed Drosophila melanogaster extracts by centrifugation in a gradient of potassium bromide. On polyacrylamide gel electrophoresis, the product showed two protein bands corresponding to the ferritin monomer and dimer. Electrophoresis following dissociation with SDS and 2-mercaptoethanol revealed three strong bands of approximately 25, 26, and 28 kDa. N-terminal amino acid sequences were identical for the 25-kDa and 26-kDa subunits, but different for the 28-kDa subunit. Conserved ferritin PCR primers were used to amplify a 360-bp cDNA product, which was used to isolate a clone from a D. melanogaster cDNA library that contained the complete coding sequence for a ferritin subunit. Additional 5' sequence obtained by the RACE method revealed the presence of a putative iron regulatory element. The PCR product was also used to locate the position of the ferritin subunit gene at region 99F on the right arm of the third chromosome. The deduced amino acid sequence of the D. melanogaster ferritin subunit contained a signal sequence and resembled most closely ferritin of the mosquito Aedes aegypti. The evolution of ferritin sequences is discussed.

Characterization of the solubilized oocyte membrane receptor for insecticyanin, a biliprotein of the hawkmoth, Manduca sexta

We report the solubilization and characterization of the oocyte membrane receptor for insecticyanin, a blue biliprotein of the hawkmoth Manduca sexta. The insecticyanin receptor was solubilized using 40 mM CHAPS. Strong binding affinity of [125I]insecticyanin to its solubilized receptor was demonstrated to be heat-labile, pH-dependent, Ca2+-dependent, and saturable. The binding was inhibited by excess unlabeled insecticyanin, but not by two other major hemolymph and oocyte proteins, vitellogenin and lipophorin. The receptor for insecticyanin showed tissue specificity: it was present only in oocyte membranes, not in membranes of fat body, midgut or ovariole sheath. The equilibrium data for the solubilized receptor, K(d) and B(max), were estimated to be 17 nM and 11.4 pmol/mg solubilized proteins, respectively. The results from co-immunoprecipitation showed that the apparent molecular mass for the insecticyanin receptor is approximately 185 kDa while chemical crosslinking of the insecticyanin-receptor complex revealed a product with a molecular mass near 10(3) kDa. This suggests that the insecticyanin receptor has a multimeric structure, or that four receptor molecules can bind to one insecticyanin tetramer.

Comparative nutrition of iron and copper

The suggestion from nutritional studies with mammals of a link between iron and copper metabolism has been reinforced by recent investigations with yeast cells. Iron must be in the reduced ferrous (FeII) state for uptake by yeast cells, and reoxidation to ferric (FeIII) by a copper oxidase is part of the transport process. Thus, yeast cells deficient in copper are unable to absorb iron. In an analogous way, animals deficient in copper appear to be unable to move FeII out of cells, probably because it cannot be oxidized to FeIII. Invertebrate animals use copper and iron in ways very similar to vertebrates, with some notable exceptions. In the cases where vertebrates and invertebrates are similar, the latter may be useful models for vertebrate metabolism. In cases where they differ (e.g. predominance of serum ferritin in insects, oxygen transport by a copper protein in many arthropods, central importance of phenoloxidase, a copper enzyme in arthropods), the differences may represent processes that are exaggerated in invertebrates and thus more amenable to study in these organisms. On the other hand, they may represent processes unique to invertebrates, thus providing novel information on species diversity.

Cockroach transferrin closely resembles vertebrate transferrins in its metal ion-binding properties: a spectroscopic study

The optical and electron paramagnetic resonance (EPR) spectroscopic properties of a transferrin from the cockroach Blaberus discoidalis have been investigated to determine the relation of this protein to vertebrate transferrins. Difference spectrophotometry substantiates the involvement of tyrosyl residues in iron binding, and confirms the specific binding of two equivalents of iron per molecule. The far-UV CD spectrum also indicates a secondary structure with marked similarity to those of vertebrate transferrins. EPR studies show a dependence of iron binding on (bi)carbonate, consistent with the absolute requirement of transferrins for a synergistic anion in binding iron. Continuous wave (CW) and pulsed EPR studies of the cupric complex of the protein implicate a histidyl nitrogen ligand in metal coordination, as in human transferrin. Additional studies establish that the pH-dependent release of iron is similar to that of human serum transferrin. The present data confirm cockroach transferrin as an authentic member of the transferrin superfamily, thereby suggesting an ancestral relationship of insect to vertebrate transferrins.

Purification of an expressed insect transferrin from cell culture media using high-capacity Ni(2+)-dipicolylamine gel

Vertebrate transferrin is a well characterized iron transport protein. In contrast, little is known concerning the role of transferrin in insects. Yet, study of iron metabolism in insects could give insights into strategies for insect control, particularly for insects that transmit disease.

Purification and cDNA cloning of ferritin from the hepatopancreas of the freshwater crayfish Pacifastacus leniusculus

Ferritin was purified from the hepatopancreas of the freshwater crayfish Pacifastacus leniusculus after injection of iron. It has the same size as horse spleen ferritin (440 kDa) and migrates as two bands, 19 kDa and 20 kDa, respectively, in SDS/PAGE under reducing conditions. Crayfish ferritin (20 kDa) was cloned from a hepatopancreas cDNA library. The deduced amino acid sequence of the crayfish ferritin shows a closer relationship to vertebrate ferritin heavy chains than to insect ferritin and contains the conserved H-specific residues for the ferroxidase centre found in vertebrate ferritin heavy chain. An IRE(iron-responsive element)-like sequence with a predicted stem-loop structure was present in the 5' untranslated region of the crayfish ferritin mRNA. Crayfish ferritin does not share the atypical properties of insect ferritins, such as high molecular mass of intact protein, abundance in hemolymph, and export into vacuoles. We suggest that there are two different types of ferritins distributed in different species: insect-type or secretory ferritins which are predominant in the snail oocyte and insects, and vertebrate (crustacean)-type or cytosolic ferritins which are predominant in vertebrates and crustacea.

Purification of recombinant insect transferrin from large volumes of cell culture medium using high capacity Ni(2+)-dipicolylamine gel

We report the purification of secreted recombinant Manduca sexta transferrin from Spodoptera frugiperda (Sf9) cell culture medium in a single step using high capacity Ni(2+)-dipicolylamine (DPA)-Novarose gel. Although the original sample was highly diluted (approximately 10 micrograms transferrin/ml medium) and the cell culture medium contained 10% surfactant (Pluronic F68) and a lipid emulsion, we were able to recover the recombinant transferrin (1 mg protein/100 ml) under gentle elution conditions with 70% yield at > 90% homogeneity. This work demonstrates the versatility of immobilized metal ion affinity chromatography using a high metal ion capacity gel to purify a recombinant protein and illustrates the potential of this affinity technique for protein separations from large volumes of cell culture media that contain surfactants.

Cloning and sequence analysis of the cDNA for a protein from Coccidioides immitis with immunogenic potential

We have cloned and sequenced the cDNA encoding an immunoreactive protein from the pathogenic fungus Coccidioides immitis which stimulates human T cells and has been associated with protective vaccines in mice. The transcript contained an open reading frame encoding 194 amino acids with a calculated molecular weight of 19.5 kDa, a 151 base 5' untranslated region (UTR), and a 468 base 3'UTR. A four member repeat motif, usually thr-ala-glu-pro, exists for amino acids 98 through 141. Deduced amino acid sequence derived from the cDNA was identical with previously determined internal amino acid sequence from the native protein, and goat antiserum raised against the purified fungal protein reacted with an inducible fusion protein translated from this cDNA. Using this cDNA to produce recombinant protein will allow direct testing of its role in human immunity to coccidioidomycosis and may lead to new diagnostic tests.

Manduca sexta lipid transfer particle: synthesis by fat body and occurrence in hemolymph

Lipid transfer particle (LTP) is present in hemolymph of the tobacco hornworm Manduca sexta. Biosynthesis of LTP, occurrence in hemolymph, and the role of LTP-apoproteins in the lipid transfer reaction were investigated using antibodies specific for LTP or for each of the apoproteins. In vitro protein synthesis followed by immunoprecipitation demonstrated that LTP is synthesized by the fat body and secreted into the medium. In contrast to apolipophorin III, an exchangeable apoprotein of lipophorin (the major lipid transport protein in hemolymph), apoLTP-III could not be detected free in hemolymph. LTP concentrations in the hemolymph were measured by a sandwich ELISA using a mouse monoclonal antibody against apoLTP-III as capturing antibody and rabbit polyclonal antibody against apoLTP-I as detecting antibody. LTP concentration increased during the late fifth instar larval stage, followed by a decrease in the wandering stage. Subsequently, LTP concentrations were strongly increased in hemolymph of adult moths. The role of the three apoproteins of LTP in the lipid transfer reaction was analyzed using apoprotein-specific antibodies. All three, apoLTP-I, -II, and -III, appeared to be important for lipid transfer activity, as shown by inhibition of lipid transfer by antibodies specific for each of the three apoproteins.

Proenzyme of Manduca sexta phenol oxidase: purification, activation, substrate specificity of the active enzyme, and molecular cloning

Phenol oxidase (PO) was isolated as a proenzyme (pro-phenol oxidase, pro-PO) from the hemolymph of Manduca sexta larvae and purified to homogeneity. Pro-PO exhibits a M(r) of 130,000 on gel filtration and two bands with an apparent M(r) of approximately 100,000 on SDS/PAGE, as well as size-exclusion HPLC. Activation of pro-PO was achieved either by specific proteolysis by a cuticular protease or by the detergent cetylpyridinium chloride at a concentration below the critical micellar concentration. A cDNA clone for M. sexta pro-PO was obtained from a larval hemocyte cDNA library. The clone encodes a polypeptide of approximately 80,000 Da that contains two copper-binding sites and shows high sequence similarity to POs, hemocyanins, and storage proteins of arthropods. The M. Sexta pro-PO, together with other arthropod pro-POs, contains a short stretch of amino acids with sequence similarity to the thiol ester region of alpha-macroglobulins and complement proteins C3 and C4.

Sequestration of insecticyanin, a blue hemolymph protein, into the egg of the hawkmoth Manduca sexta. Evidence for receptor-mediated endocytosis

Sequestration of the blue biliprotein, insecticyanin, into developing oocytes of the hawkmoth, Manduca sexta was investigated. Immunodiffusion assays revealed that insecticyanin concentration in mature eggs (29.6 microM) is slightly higher than that in hemolymph (25.8 microM). The endocytotic uptake of insecticyanin was visualized at the light microscopic level using autoradiography. Uptake of 125I-insecticyanin by isolated oocytes was saturable. Analysis of in vitro uptake data estimated that the value of K(uptake) (insecticyanin concentration at half-maximal uptake rate) is 4.2 microM and that the Vmax (maximum rate of uptake) is 1 pmol follicle-1 h-1. Labeled insecticyanin was shown to bind to sonicated follicle membranes with high specificity and affinity. The KD (equilibrium dissociation constant) and the Bm (total number of binding sites per follicle), were estimated as 4 x 10(-8) M and 8 x 10(7) respectively. Competition studies showed that binding of labeled insecticyanin to oocyte membranes was blocked by excess amounts of unlabeled insecticyanin but not by lipophorin and vitellogenin of M. sexta. Additional membrane binding experiments demonstrated that receptors for insecticyanin are only present in the oocytes membranes, not in fat body or gut tissue.

Rapid and efficient isolation of transferrin and ferritin from Manduca sexta

We report methods for the rapid purification of two iron-binding proteins from larval hemolymph of Manduca sexta. Ferritin was purified in two steps by density gradient ultracentrifugation. To accomplish this, we utilized the relatively high level of ferritin present in the hemolymph of this animal and augmented the density of the protein in vivo by injection of iron sulfate. Nitrocellulose blots analyzed by laser densitometry showed hemolymph from iron-injected insects contained about 0.4 mg of ferritin per ml (approximately 0.7% of total hemolymph protein); of this, 62% was found as pure ferritin in the pellet formed during ultracentrifugation. Following the density ultracentrifugation, we purified transferrin from the hemolymph subphase by immobilized metal ion affinity chromatography using a new gel, Novarose-SE1000/40 coupled to dipicolylamine (DPA) chelated with nickel. Higher capacity Ni2+DPA-gel permitted good resolution of transferrin in the first chromatography; a lower capacity of the same gel allowed purification of transferrin in a second step. Overall transferrin recovery was 52%. Larval hemolymph contained 0.770 mg transferrin/ml, representing about 1.3% of the total protein.

Isolation, cloning and deduced amino acid sequence of a novel glycoprotein from the haemolymph of the hawkmoth Manduca sexta

A low-abundance haemolymph protein from adult male Manduca sexta was purified to homogeneity. The 29,000 Da glycoprotein is synthesized in the fat body, is present in both male and female, and is present during all stages of development. Antiserum against the 29 kDa protein was raised in a rabbit and used to screen an M. sexta larval fat body cDNA library. An 880 base pair clone was isolated and found to contain the full-length transcript. Sequencing of the cDNA revealed an open reading frame of 699 bases beginning from the possible translation initiation site. The deduced 233-amino acid polypeptide contains an apparent 17-amino acid signal peptide and three potential N-glycosylation sites. The function of the 29 kDa protein is unknown.

Evidence that MIF plays a role in the development of pigmentation patterns in the frog

A ventrally localized melanization-inhibiting factor (MIF) may play an important role in the expression of dorsal-ventral pigment patterns of amphibians. In efforts to purify this putative MIF, ventral skin conditioned medium (VCM) from Rana forreri was partially fractionated and used to immunize mice. A monoclonal antibody that has the ability to block the activity of MIF was isolated, and an immunoaffinity matrix was prepared by cross-linking the antibody to protein G-Sepharose. The fraction of VCM that bound to the affinity matrix decreased the number of melanized cells in the Xenopus laevis neural tube explant assay, but did not reduce significantly the number of cells that emigrated. The monoclonal antibody was used for immunohistochemical studies on R. pipiens skin. Strong staining with the antibody was observed beneath the basement membrane, in mucous glands, and in the subcutaneous tissue of the ventral skin. A weak staining was also observed in the ground substances of both ventral and dorsal skin. These results confirm that a monoclonal antibody has been secured against at least one of the MIF constituents and that it is useful as a probe in detecting the distribution of MIF in tissues. The results of its use in this study support the hypothesis that MIF plays a role in the expression, development, and maintenance of the dorsal-ventral pigmentation patterns of frogs.

Isolation and characterization of mosquito ferritin and cloning of a cDNA that encodes one subunit

Ferritin, an iron storage protein, was isolated from larvae and pupae of Aedes aegypti grown in an iron-rich medium. Mosquito ferritin is a high molecular weight protein composed of several different, relatively small, subunits. Subunits of molecular mass 24, 26, and 28 kDa are equally abundant, while that of 30 kDa is present only in small amounts. The N-terminal sequence of the 24 and 26 kDa subunits are identical for the first 30 amino acids, while that of the 28 kDa subunit differs. Studies using antiserum raised against a subunit mixture showed that the ferritin subunit were present in larvae, pupae, and adult females, and were increased in animals exposed to excess iron. The antiserum also was used to screen a cDNA library from unfed adult female mosquitoes. Nine clones were obtained that differed only in a 27 bp insertion in the 3' end. Rapid amplification of cDNA ends (RACE) was used to obtain the complete protein coding sequence. A putative iron-responsive element (IRE) is present in the 5'-untranslated region. The deduced amino acid sequence shows a typical leader sequence, consistent with the fact that most insect ferritins are secreted, rather than cytoplasmic proteins. The sequence encodes a mature polypeptide of 20,566 molecular weight, smaller than the estimated size of any of the subunits. However, the sequence exactly matches the N-terminal sequences of the 24 and 26 kDa subunits as determined by Edman degradation. Of the known ferritin sequences, that of the mosquito is most similar to that of somatic cells of a snail.

Immunocytochemical localization of a follicle specific protein of the hawkmoth Manduca sexta

A follicle specific protein (FSP-I) from the hawkmoth Manduca sexta, has been localized in developing follicles by immuno-fluorescence and immuno-gold labeling techniques. At the light microscopical level, the protein was demonstrated to be present in both the basolateral and apical parts of follicular epithelial cells, as well as in clearly defined, spherical compartments in the cortex of the developing oocyte. Immuno-gold labeling at the electron microscopical level revealed the localization of FSP-I in endoplasmic compartments of the follicular epithelial cells, in the extracellular matrix of the follicle and in endocytic compartments of the oocyte. Our results indicate that M. sexta FSP-I is synthetized and secreted by the follicular epithelial cells, after which it is taken up by the developing oocyte through endocytic routes.

Increased frequency of obstructive airway abnormalities with long-term tracheostomy

Eighty-one patients with long-term tracheostomy tubes (mean duration, 4.9 months) were examined via fiberoptic bronchoscopy prior to decannulation. Obstructive airway lesions were observed in 54 patients (67 percent). All tracheal lesions were anatomically located proximal to the stoma. No cuff lesions were observed. The two most commonly observed lesions were tracheal granuloma (60 percent) and tracheomalacia (29 percent). Less frequently observed lesions were tracheostenosis (14 percent) and vocal cord and laryngeal dysfunction (8 percent). As a result of the high frequency of tracheal abnormalities, especially that for tracheal granuloma which has not been previously reported (to our knowledge), we recommend that all decannulation candidates undergo anatomic examination of the airways.

Protein and lipoprotein uptake by developing oocytes of the hawkmoth Manduca sexta. An ultrastructural and immunocytochemical study

The ultrastructure of developing Manduca sexta oocytes is described with respect to the endocytic pathway for protein incorporation. Three major (lipo) protein components of mature M. sexta eggs, lipophorin, vitellogenin and microvitellogenin, were localized along this pathway by immuno-fluorescence and immuno-gold labeling techniques. Labeling of the antigens was observed in the extracellular spaces of the follicle. In those cases where fixation and en bloc staining procedures did not destroy antigenicity, antigens were detected in coated pits and coated vesicles near the plasma membrane of the oocyte. All three antigens were demonstrated to be present in endosomes in the cortex of the oocyte. Both the morphology and the labeling pattern of the endosomes indicate that this organelle is a compartment of uncoupling of receptor and ligand. Tubular elements at the surface of the endosome, interpreted to be involved in the recycling of receptors and membrane to the oocyte surface, were not labeled. Strong labeling of lipophorin, vitellogenin and microvitellogenin was observed in the developing yolk bodies, the main protein storage compartment of the oocyte. The uptake and storage of hemolymph proteins and lipoproteins by M. sexta oocytes is discussed in comparison with other insect and vertebrate endocytic systems.

Transferrin in a cockroach: molecular cloning, characterization, and suppression by juvenile hormone

In a study of juvenile hormone-regulated gene expression, we isolated an anonymous cDNA representing a message that was strongly suppressed by juvenile hormone in the fat body of the cockroach Blaberus discoidalis. The protein deduced from the cDNA sequence showed compelling resemblance in sequence to the transferrins, a superfamily of internally duplicated, 80-kDa iron-binding/transport proteins characterized from several vertebrates and, to date, one insect (the tobacco hornworm, Manduca sexta). We isolated a 78-kDa protein from cockroach hemolymph, verified its congruence with the cloned cDNA, and found that it did bind iron. The cockroach protein is a member of the transferrin superfamily based on several features, including 32-46% amino acid positional identity with transferrins whose sequences are known, internal homology, positioning of cysteine residues, and iron binding. Whereas the previously characterized insect transferrin binds one atom of iron per protein molecule, B. discoidalis transferrin binds two iron atoms as do the vertebrate transferrins. The diferric property of cockroach transferrin is consistent with presence of two sets of residues positioned appropriately for iron binding. Juvenile hormone suppressed transferrin mRNA levels drastically in the adult female cockroach.

Molecular cloning and sequence of a novel ommochrome-binding protein cDNA from an insect, Manduca sexta

An ommochrome-binding protein (OBP) from the hemolymph of Manduca sexta has recently been purified and characterized. A cDNA clone was isolated from a fifth instar larval cDNA expression library utilizing antiserum against OBP. Northern blot analysis of total fat body RNA detected a transcript of approximately 1.2 kilobases in fifth instar wandering larvae RNA. The complete nucleotide sequence of the 905-base pair cDNA insert was determined by the dideoxy chain termination method. The OBP cDNA encodes a polypeptide of 274 residues with a predicted molecular weight of 30,580 and with one consensus N-linked glycosylation site. Comparison of the NH2-terminal sequence of the mature protein and the cDNA sequence revealed a typical signal peptide of 18 amino acids. In wandering stage larvae, the OBP transcript appeared to be at least 250-fold less abundant than ribosomal RNA.

Preliminary biological characterization of a melanization stimulating factor (MSF) from the dorsal skin of the channel catfish, Ictalurus punctatus

A two step fractionation of conditioned media made from the darkly pigmented dorsal skin of the channel catfish, Ictalurus punctatus, has produced fractions that contain a melanization stimulating factor (MSF). Isolated neural tubes of Xenopus laevis embryos exposed to conditioned media and to specific fractions exhibit greater melanization (increased numbers of melanized cells and elevated percentages of melanized cells), a greater number of dendrites per melanized cell, and a greater number of emigrated neural crest cells than control neural tubes. The presence of MSF activity in the darkly pigmented dorsal integument suggests a role for a molecule or molecules in the development and maintenance of the dorsal/ventral pigment pattern of this piscine species and possibly of other vertebrates.

Purification and properties of an ommochrome-binding protein from the hemolymph of the tobacco hornworm, Manduca sexta

A yellow-colored protein (YCP) was isolated from the hemolymph (i.e. blood) of fifth instar wandering stage larvae of Manduca sexta. The molecular mass of YCP was 31 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Gel filtration chromatography suggested that native YCP was a monomer. The absorbance spectrum of YCP revealed maxima at 278 and 405 nm. Chromophore was released from YCP through denaturation of the protein with methanol and chloroform. In neutral solution and in acid, the released chromophore showed the absorbance characteristics of an ommochrome: ommatin D. In addition, the chromophore was sensitive to treatment with arylsulfatase as would be expected for ommatin D. The amino acid composition and the N-terminal sequence of YCP were determined. The YCP polypeptide chain was found to be glycosylated. Carbohydrate analysis suggested that Man and GlcNAc were present in a 3:1 ratio. Circular dichroism indicated that YCP consisted of 68% beta-pleated sheet with no alpha-helices being detected. An in vitro incubation of larval fat body in the presence of [35S]methionine indicated that this organ was the site of synthesis. Ommochromes arise in insects as end products of the metabolism of tryptophan. It is well-documented that ommochromes occur in both the tissues and the excreta of insects. We propose that in M. sexta, one such tryptophan metabolite is found in the hemolymph associated with a specific protein.

Lipophorin structure analyzed by in vitro treatment with lipases

Adult Manduca sexta high density lipophorin (HDLp-A) is composed of three apolipoproteins (apoLp-I, -II, and -III) and 52% lipid. The flight-specific low density lipophorin (LDLp) contains 62% lipid and is associated with several additional molecules of apoLp-III. The amount of phospholipid remains constant in lipophorin (140 mol/mol of lipophorin), while the diacylglycerol content varies between different lipophorin species (310 mol/mol HDLp up to 1160 mol/mol LDLp). Both lipophorin particles were enzymatically depleted of phospholipid or diacylglycerol by in vitro incubation with either phospholipase A2 or triacylglycerol lipase. Albumin was used to remove free fatty acids generated during the reaction. Treatment with phospholipase A2 removed all phospholipids (except sphingomyelin) and the resulting particles were stable. Triacylglycerol lipase hydrolyzed large fractions of diacylglycerol. The resulting particles were smaller in size, higher in density, and devoid of apoLp-III. The particles retained apoLp-I and -II and the other lipid components, including a substantial amount of diacylglycerol. Structural integrity of diacylglycerol-depleted lipophorin was confirmed by electron microscopical analysis. When treated with both phospholipase A2 and triacylglycerol lipase, lipophorin precipitated. From these results we conclude that: 1) all phospholipid and apoLp-III are located at the surface of lipophorin, whereas diacylglycerol is partitioned between the sublayers and the surface of the particle; 2) both diacylglycerol and phospholipid play a role in stabilizing lipophorin in the aqueous medium; and 3) lipophorin can be extensively unloaded and still retain its basic structure, a necessary feature for its function as a reusable lipid shuttle.

In vivo and in vitro loading of lipid by artificially lipid-depleted lipophorins: evidence for the role of lipophorin as a reusable lipid shuttle

Lipid transport in the hemolymph of Manduca sexta is facilitated by a high density lipophorin in the resting adult insect (HDLp-A, d approximately 1.109 g/ml) and by a low density lipophorin during flight (LDLp, d approximately 1.060 g/ml). Lipophorin presumably shuttles different lipids between sites of uptake or storage, and sites of utilization. In order to shuttle lipid, a lipid-depleted lipophorin should be able to reload with lipid. To test this hypothesis, we used HDLp-A particles that were artificially depleted of either phospholipid (d approximately 1.118 g/ml) or diacylglycerol (d approximately 1.187 g/ml) and subsequently radiolabeled in their protein moiety. Upon injection into adult moths, both particles shifted their density to that of native HDLp-A, indicating lipid loading. Also, upon subsequent injection of adipokinetic hormone, both particles shifted to a lower density (d approximately 1.060 g/ml) indicating diacylglycerol loading and conversion to LDLp. Both phospholipid and diacylglycerol loading were also studied using an in vitro system. The lipid-depleted particles were incubated with fat body that had been radiolabeled in either the phospholipid or the triacylglycerol fraction. Transfer of radiolabeled phospholipid and diacylglycerol from fat body to lipophorin was observed. During diacylglycerol loading, apoLp-III associated with lipophorin, whereas phospholipid loading occurred in the absence of apoLp-III. The results show the ability of lipid-depleted lipophorins to reload with lipid and therefore reaffirm the role of lipophorin as a reusable lipid shuttle.

An immunoreactive apoglycoprotein purified from Coccidioides immitis

Deglycosylation of glycoproteins in a lysate of spherules of Coccidioides immitis has permitted purification and partial characterization of a proline-rich pronase-sensitive antigen. Moreover, soluble antigen specifically stimulated lymphocytes from persons with dermal delayed-type hypersensitivity to coccidioidal antigens. When related to reference coccidioidin by tandem two-dimensional immunoelectrophoresis, the antigen fused in the anodal region with a specific reference antigen (antigen 2). It did not show identity with coccidioidal antigens used in conventional serologic assays. Although immunoblots of the purified protein with monospecific rabbit antiserum showed a single antigen at 33 kDa, the parent spherule lysate bound the same antibody in a broad band between 70 and greater than 200 kDa, which could be explained by microheterogeneity of glycosylation. Immunoelectron microscopy using affinity-purified human antibodies localized the antigen to the cell wall and internal septa of spherules. These findings suggest that the apoglycoprotein may be important in human immune responses to coccidioidal infection.