Preventative and therapeutic potential of nutrition for inflammatory bowel diseases: A narrative review

Diet strongly shapes the gut microbiome and metabolome, which in turn influence intestinal inflammation in patients with inflammatory bowel disease (IBD). Separate from inflammation and malnutrition, diet's direct interactions with the gastrointestinal system can also provoke or attenuate a host of nonspecific gastrointestinal symptoms. Given these multifaceted effects of diet on inflammation and symptoms, nutrition has been investigated for its potential roles in the prevention and treatment of IBD. This review presents epidemiological, observational cohort, and clinical trial evidence that underlie our current understanding of nutrition for prevention and treatment of IBD.

Penning-Trap Mass Measurement of Helium-4

Light-ion trap (LIONTRAP), a high-precision Penning-trap mass spectrometer, was used to determine the atomic mass of ^{4}He. Here, we report a 12 parts-per-trillion measurement of the mass of a ^{4}He^{2+} ion, m(^{4}He^{2+})=4.001 506 179 651(48)  u. From this, the atomic mass of the neutral atom can be determined without loss of precision: m(^{4}He)=4.002 603 254 653(48)  u. This result is slightly more precise than the current CODATA18 literature value but deviates by 6.6 standard deviations.

Biopsy-Derived Oral Keratinocytes – a Model to Potentially Test for Oral Mucosa Radiation Sensitivity

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Human oral keratinocytes – the key players in radiation mucositis in head and neck cancer treatment – are established ex vivo from patient-derived micro-biopsies.

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Individual radiosensitivity of primary oral keratinocytes is measured by a novel assay for cellular proliferation and spreading.

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The keratinocyte model also supports classical functional assays such as clonogenic survival and DNA double strand repair.

Purpose

To establish stable in vitro growth of keratinocytes from very small biopsy specimens and successfully apply new test systems to determine their radiosensitivity.

Materials and Methods

Oral mucosa biopsies (diameter: 1.7 mm) from 15 subjects were immobilized with custom-made cups onto culture plates. Outgrowing cells were tested for cytokeratin 5/14 and Ki67, expanded, radiated at different doses, and seeded onto circumscribed areas before being allowed to spread centrifugally. In this newly developed spreading assay, cell-covered areas were measured by image analysis. For statistical analysis, a linear mixed regression model was used; additionally, results were correlated to the radiation dose applied. Colony forming efficiency (CFE) was used to validate the results. DNA damage repair was analysed by gammaH2AX and 53BP1 foci quantification using immunofluorescence microscopy 24 h and 96 h after irradiation.

Results

Stable keratinocyte growth continued for up to 7 weeks in 14 biopsies. Cells spread reliably from an initial 16.6 mm² up to a median of 119.2 mm² (range: 54.4–290). Radiated cells spread to only 100.7 mm² (2 Gy; range: 55.3–266.7); 73.2 mm² (4 Gy; 15–240.4); 47 mm² (6 Gy; 2–111.9), and 22.7 mm² (8 Gy; 0–80). Similarly, CFE decreased from 0.223 (0 Gy) to 0.0028 (8 Gy). Using an individual donor as a random factor, cell spread correlated with CFE, where radiation dose was the main driver (decrease by 0.50, adjusted for area). Upon irradiation with 6 Gy, radiation-induced DNA damage was increased after 24 h in all samples, and even after 96 h in 5 out of 7 samples, as detected by a higher number of gammaH2AX/53BP1 foci in irradiated cells (mean 3.7 for 24 h; mean 0.6 for 96 h).

Conclusion

In vitro propagation of keratinocytes derived from a small biopsy is feasible. Radiation impairs cellular migration and proliferation, and the newly described spreading assay allows ranking for cellular radioresistance. The keratinocyte model also supports classical functional assays such as clonogenic survival and DNA double strand repair. The clinical relevance awaits upcoming investigations.

DNA-damage repair deficiency (dDDR) and response to nanoliposomal irinotecan (nal-IRI) in metastatic pancreatic ductal adenocarcinoma (mPDAC)

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Background: Chemotherapy is the standard of care for patients with mPDAC but there are no biomarkers to aid in treatment selection. Nal-IRI with 5-fluorouracil/folinic acid (FUFA) improves survival over FUFA in the second-line treatment of mPDAC. Nal-IRI is a topoisomerase inhibitor and its action produces DNA damage leading to cell death. We hypothesize that tumors with dDDR, a process that is altered in a subset of patients with PDAC, may be more sensitive to the effects of nal-IRI. Methods: Utilizing the IRB-approved pancreas cancer databases at the University of Miami and Wake Forest University, we identified patients with mPDAC treated with nal-IRI and FUFA who had germline and/or somatic mutation testing. We conducted a retrospective chart review to extract demographic and clinical characteristics including treatments received, response, and survival. Results: Among 31 patients identified, the median age was 66y and 47% were female. Nine patients had a DDR mutation; 6 germline and 3 somatic. Median progression-free survival (PFS) in patients with any germline or somatic DDR mutation was 3.2m vs 3.9m for those without (log-rank p = 0.7). When restricted to germline DDR mutations only, the median PFS was not reached with germline dDDR vs 4m for those without (log-rank p = 0.22). Presence of dDDR was associated with a higher clinical benefit rate (CBR = partial response + stable disease); a DDR mutation was present in 36% of patients who showed clinical benefit vs 15% in those without clinical benefit (p = 0.21). Conclusions: DDR mutations appear to define a subset of patients with mPDAC who may be more sensitive to nal-IRI and FUFA. The PFS and CBR were numerically but not statistically superior, especially in patients with germline DDR mutations. Larger data sets and longer follow-up are needed to confirm this trend.

g Factor of Lithiumlike Silicon: New Challenge to Bound-State QED

The recently established agreement between experiment and theory for the g factors of lithiumlike silicon and calcium ions manifests the most stringent test of the many-electron bound-state quantum electrodynamics (QED) effects in the presence of a magnetic field. In this Letter, we present a significant simultaneous improvement of both theoretical g_{th}=2.000 889 894 4 (34) and experimental g_{exp}=2.000 889 888 45 (14) values of the g factor of lithiumlike silicon ^{28}Si^{11+}. The theoretical precision now is limited by the many-electron two-loop contributions of the bound-state QED. The experimental value is accurate enough to test these contributions on a few percent level.

Colorectal Cancer Screening Among South Asians: Focus Group Findings on Attitudes, Knowledge, Barriers and Facilitators

BACKGROUND

Colorectal cancer (CRC) screening rates are low among South Asians. Understanding barriers and facilitators about CRC screening among South Asians may inform effective messaging and interventions.

METHODS

We conducted eight focus groups (FGs) among South Asians to gather contextual information about CRC causes, screening barriers and facilitators, and cultural factors affecting screening.

FINDINGS

An overarching sentiment across Asian Indian and Bangladeshi FGs was that cancer is considered a death sentence. However, many participants were unaware that CRC was a problem in their communities, and considered CRC screening as a low priority. Women often thought of CRC as mostly affecting men. Physician influence on screening decisions was most frequently discussed among Bangladeshis, as were sentiments of shame and modesty that may prevent screening.

CONCLUSION

Findings highlight that physicians should provide culturally-appropriate CRC information for South Asian patients, and the importance of access to CRC screening for South Asians.

Schilddrüsenwerterhöhungen bei einem Hund infolge eines Dachsbisses

Gegenstand und Ziel: Untersuchung einer Schilddrüsenwerterhöhung in Zusammenhang mit einer entzündeten Dachsbissverletzung. Diskussion der klinischen Befunde. Material und Methode: Fallbericht einer acht Jahre alten Dackelhündin, die nach einem Biss in den Hals veränderte Werte der Schilddrüsenparamter aufwies. Ergebnisse: Das Tier zeigte erhöhte Werte an Thyroxin (T4) und freiem Thyroxin (fT4) sowie eine erniedrigte cTSH-Konzentration, die mittels Sonographie und Szintigraphie hinsichtlich des hormonproduzierenden Gewebes abgeklärt wurden. Vorberichtlich war ein noch sichtbarer Dachsbiss mit Abszedierung im Kehlbereich bekannt. Sonographisch fiel eine schlechte Abgrenzbarkeit des Lobus dexter der Schilddrüse zum umgebenden Gewebe auf. Die Szintigraphie ließ eine normale Anreicherung im Bereich der Schilddrüse ohne versprengtes aktives Gewebe erkennen. Bei einer Kontrolle der Schilddrüsenwerte 14 Tage nach der ersten Untersuchung lagen diese wieder im Referenzbereich. Schlussfolgerungen: Die transient erhöhten Werte der Schilddrüsenhormone wurden bei diesem Patienten sehr wahrscheinlich durch eine möglicherweise infektionsbedingte Thyreoiditis oder Perithyreoididtis infolge eines Dachsbisses hervorgerufen. Die Möglichkeit, dass durch Bildung von Thyroxin-Autoantikörpern nach verletzungsbedingtem Austritt von T3/T4 in das umliegende Gewebe falsch hohe Schilddrüsenhormonkonzentrationen gemessen wurden, lässt sich nicht komplett ausschließen. Klinische Relevanz: Die Ergebnisse der Untersuchungen decken sich mit den Befunden humanmedizinischer Fallberichte über nicht autoimmun bedingte Schilddrüsenentzündungen. Differenzialdiagnostisch sollte bei erhöhten Schilddrüsenhormonwerten des Hundes auch an eine Entzündung der Thyreoidea gedacht werden.

High-Precision Measurement of the Proton's Atomic Mass

We report on the precise measurement of the atomic mass of a single proton with a purpose-built Penning-trap system. With a precision of 32 parts per trillion our result not only improves on the current CODATA literature value by a factor of 3, but also disagrees with it at a level of about 3 standard deviations.

Geographical differences in survival of dogs with non-Hodgkin lymphoma treated with a CHOP based chemotherapy protocol

BACKGROUND

In humans geographical differences in the incidence and presentation of various cancers have been reported. However, much of this information has not been collected in veterinary oncology.

AIM

The purpose of this study was to determine if a geographic difference in progression free survival exists for dogs with lymphoma treated within the US.

MATERIALS AND METHODS

Medical records of 775 cases of canine lymphoma from 3 US regions (west, south and north), treated with CHOP chemotherapy, were retrospectively evaluated. Cases were collected from referral institutions and were required to have received at least one doxorubicin treatment and have follow up information regarding time to progression.

RESULTS

Significant differences in sex (p = 0.05), weight (p = 0.049), stage (p < 0.001), immunophenotype (p = <0.001), and number of doxorubicin doses (p = 0.001) were seen between regions. Upon univariate analysis, progression free survival (PFS) differed by region (p = 0.006), stage (p = 0.009), sub-stage (p = 0.0005), and immunophenotype (p = 0.001). A multivariable Cox regression model showed that dogs in the western region had a significantly shorter PFS when compared to the south and east.

CONCLUSION

PFS was significantly affected by stage, sub-stage and phenotype.

Structural and reactivity insights into covalently linked Cu(i) complex-Anderson polyoxometalates

Synthesis, single-crystal X-ray diffraction structures and reactivity information is reported for covalently linked photoactive metal complex – polyoxometalate aggregates.

A supramolecular H-bond driven light switch sensor for small anions

A cationic iridium complex with a 2,2'-bibenzimidazole ligand can act as a luminescent sensor for various anions. Strong H-bond supported ion pair bonding with an electron accepting dinitro-benzoate anion switches the luminescence "off". The luminescence of the sensor is switched back "on" when benzoate is replaced by competing H-bonded small anions, therefore leading to an enhanced sensitivity of the sensor system.

“CLICKable” azide-functionalized phosphonates for the surface-modification of molecular and solid-state metal oxides

A bifunctional phosphonate azide tether is reported which enables surface modification of molecular and solid state metal oxides as well as subsequent modification by CLICK chemistry.

Optimized synthesis of a tert-butyl-phenyl-substituted tetrapyridophenazine ligand and its Ru(ii) complexes and determination of dimerization behaviour of the complexes through supramolecular “Fingerhakel”

A high dimerization constant of a ruthenium complex is observed with the aid of ¹H-NMR spectroscopy. The solid state molecular structure indicates that multiple π-interactions are the reason for strong dimerization.

Single incision laparoscopic cholecystectomy

BACKGROUND

As surgeons embrace the concept of increasingly less invasive surgery, techniques using only a single small incision have begun to gain traction. Multiple case series managed by a single-incision laparoscopic cholecystectomy (SILC) have been published. The objective of this study is to describe the short-term outcomes of SILC in our institution.

METHODS

A retrospective review was done for 51 patients who underwent SILC between 2009-2012. The operative time, surgical technique, conversion rate, and postoperative complications were reported.

RESULTS

SILC was performed for 51 patients, all women, with a mean age of 35.6 years (range=19-62). Their body mass index(BMI) ranged from 16.8-35.6 kg m2 with a mean of 20.4. Twelve patients (23.52 %) had acute cholecystitis. The mean operating time was 58.6 minutes (range=45-95 min). Incidents were encountered in 6 patients (11.76%) and were related to intraoperative bleeding. There was a single conversion to the standard laparoscopic procedure (1.9%) and in 5 cases an accessory needle grasp was used (9.8%). Two patients (3.9%)presented postoperative complications (wound infections) and the mean hospital stay was 1.6 days.

CONCLUSIONS

SILC is feasible and provides a promising alternative to natural orifice transluminal endoscopic surgery for scarless laparoscopic cholecystectomy. However, routine application of this novel technique requires an evaluation of its safety and cost effectiveness in larger studies.

Perforation of Meckel's diverticulum by foreign body, a rare complication

Meckel's diverticulum is a congenital disorder that results from an incomplete obliteration of the vitelline duct. Meckel's diverticulum may give rise to bleeding, intestinal obstruction and inflammation; however, its perforation by a foreign body is an extremely rare life-threatening complication. We report ona 37-year-old male presenting symptoms and signs of acute abdomen with an initial suspicion of acute appendicitis.However, the right diagnosis was made only during exploratory laparoscopy when the appendix was found to be normal,whereas Meckel's diverticulum was found to be inflamed and perforated by a chicken bone. The patient was treated successfully with laparoscopic resection of the diverticulum, and had an uncomplicated postoperative course.

[Severe maternal hepatopathies in the peripartum period--a case series with review of the literature focusing on pathogenesis and differential diagnosis]

BACKGROUND

A severe hepatopathy constitutes a serious threat during pregnancy and poses considerable challenges to the treating physicians. A broad spectrum of pregnancy-dependent or independent diseases like HELLP-syndrome, liver infection or acute fatty liver of pregnancy (AFLP) is characterized by these affections of the liver. In this study, we present a series of 3 cases with life-threatening hepatopathies and discuss the current state of the literature. A special focus is placed on pathogenesis and differential diagnosis.

METHODOLOGY

Pathological, radiological and gynaecological/surgical procedures were performed according to the current German guidelines. Laboratory tests were conducted in the clinics' routine diagnostics section. The existing literature was reviewed via the US National Library of Medicine database “PubMed.gov”.

RESULTS

The first patient had been afflicted by a fulminant HELLP syndrome causing delivery after 32 weeks of pregnancy. Consecutively, she suffered a sub-total liver infarction followed by a severe coagulopathy and septic peritonitis. The second patient was diagnosed with HELLP syndrome at 36 weeks of pregnancy. The initially mild syndrome exacerbated after delivery leading to haemorrhagic shock and acute renal failure. In the third case, a woman with asymptomatic hepatitis B delivered in the 36th week of pregnancy. Post partum, her pre-existing condition worsened fulminantly resulting in sub-acute liver dystrophy and massive coagulopathy.

DISCUSSION AND CONCLUSION

Whenever a hepatopathy occurs during pregnancy, several divergent diagnoses with severe implications and different aetiopathologies have to be considered. Diagnostic and therapeutic strategies have to be weighed quickly to enable a fast, interdisciplinary cooperation in order to prevent fatal outcomes.

Cutaneous vasculitis after renal transplantation: a case report

BACKGROUND

Cutaneous vasculitis is a rare symptom after renal transplantation. With a broad spectrum of differential diagnosis, the new appearance of a skin rash in transplanted patients can be challenging.

CASE REPORT

We present the case of a 69-year-old man with palpable purpura, skin ulcerations, and diffuse arthralgias. He had a history of cadaveric renal transplantation owing to biopsy-proven isolated immunoglobulin (Ig)A nephropathy and never suffered from any skin manifestation before. Skin biopsy confirmed Henoch-Schoenlein purpura (HSP), which developed under maintenance immunsuppressive therapy with tacrolimus and mycophenolate mofetil. Renal biopsy showed recurrent IgA nephropathy with positive mesangial and capillary IgA staining.

DISCUSSION

This is the first case to describe a new manifestation of HSP following renal transplantation owing to isolated IgA nephropathy. Here, we summarize the differential diagnosis of cutaneous vasculitis following renal transplantation. Moreover we give a short review of the recurrence of IgA nephropathy and HSP after renal transplantation followed by possible strategies for prevention and therapy of recurrent disease.

Recurrent metastasi zing neuroendocrine tumor of paranasal sinuses

Neuroendocrine tumours- their rare occurrence and propensity for recurrences can undoubtedly pose as a diagnostic and therapeutic dilemma. A case report of one such case with recurrence and bony metastasis is presented.

Expression of the multidrug resistance proteins MRP2 and MRP3 in human cholangiocellular carcinomas

BACKGROUND

Cholangiocellular carcinomas and gallbladder carcinomas are highly aggressive tumours with a poor prognosis and are generally regarded as chemoresistant tumours. Overexpression of ATP-binding cassette transporters of the multidrug resistance protein (MDR) and multidrug resistance-related protein (MRP) family in cancer cells is a major cause for the multidrug resistance phenotype in vitro and in vivo. To further define the role of MRP family members in biliary tract cancer, we studied the expression and localization of MRP2 and MRP3 in cholangiocellular carcinomas and gallbladder carcinomas.

MATERIALS AND METHODS

The expression and cellular localization of the multidrug resistance proteins MRP2 and MRP3 in human cholangiocellular carcinomas and gallbladder carcinomas were analysed by immunohistochemistry using isoform-specific antibodies. Expression of MRP isoforms was studied in vitro in Mz-ChA-1 cells derived from gallbladder adenocarcinoma by reverse transcription-polymerase chain reaction (RT-PCR), immunoblotting and immunofluorescence microscopy.

RESULTS

Mz-ChA-1 cells constitutively expressed MDR P-glycoproteins, MRP1, MRP2 and MRP3 by RT-PCR, immunoblotting and immunofluorescence microscopy. MRP2 and MRP3 are expressed in the respective apical and basolateral membrane domains. MRP3 was the predominant MRP isoform in gallbladder carcinomas (93%) and cholangiocellular carcinomas (57%), whereas MRP2 expression was detected in only 29% of gallbladder carcinomas and was undetectable in cholangiocellular carcinomas.

CONCLUSIONS

Our findings suggest that the intrinsic multidrug resistance of cholangiocellular and gallbladder carcinomas seems to be independent of MRP2 expression while the expression of MRP3 may contribute to the MDR phenotype.

Reproducibility of activations in Broca area with two language tasks: a functional MR imaging study

BACKGROUND AND PURPOSE

Functional MR imaging (fMRI) is rapidly evolving and claims to complement or even substitute intraoperative mapping (IOM) of language functions. However, little is known about the reproducibility of imaging data in the language domain. The aim of our study was to assess the reproducibility of activations for 2 widely used paradigms: naming and word generation. Individual analysis was focused on the Broca area and the left insula.

MATERIALS AND METHODS

We examined 13 healthy right-handed subjects in 3 sessions with fMRI. Two conditions were assessed: overt naming and overt naming plus noun generation. The same stimuli were used in all of the sessions. A random-effects analysis was performed to analyze whole-brain activation on a group level. For the regions of interest, the number of voxels classified as active were counted for each subject, and individual reproducibility coefficients were calculated over sessions.

RESULTS

For the naming condition, the random-effects analysis did not reveal significant activations in the specified regions; small individual activations were not reproducible. For the combined task, all of the subjects showed activations in the Broca area that were more extensive and reproducible than in the naming task. Activations in the insula were only poorly reproducible.

CONCLUSION

Naming is an approved task in IOM but does not identify the Broca area with fMRI in a reproducible way. Priming may have affected our results, but the use of a combined task, in which naming is paired with noun generation, improves the reproducibility of activations and is also suitable for IOM.

Effect of dexamethasone on voltage-gated Ca2+ channels and cytosolic Ca2+ in rat chromaffin cells

The present study examined whether the synthetic glucocorticoid dexamethasone (DEX) can modulate voltage-gated Ca2+ channel (VGCC) activity, and as a consequence agonist-induced increases in cytosolic Ca2+, in cultured rat adrenal medullary chromaffin (RAMC) cells. Exposure to 1 microM DEX for 48 h significantly increased peak VGCC current (delta +140%). DEX treatment also significantly potentiated the increases in cytosolic Ca2+ in response to submaximal stimulatory concentrations of KCl (delta +64%) and nicotine (delta +32%). The Ca2+ channel agonist BAY K-8644 increased both VGCC current (delta +109%) and potentiated the KCl-stimulated increase in cytosolic Ca2+ (delta +35%) to a comparable extent to that seen with DEX. These data suggest that DEX treatment increases VGCC activity, and that this increased Ca2+ influx leads to potentiation of agonist-induced increases in cytosolic Ca2+ in RAMC cells.

Treatment of lumbar disc herniation in the second decade of life

Lumbar disc herniation is rare in patients under the age of 20 years. In the department of orthopaedic surgery of the University Hospital of Frankfurt, 33 patients below the age of 20 with lumbar disc herniation were treated over a period of 10 years. Eighteen were managed conservatively and 15 surgically. The purpose of this study is to report on the long-term outcome of these patients and to compare the results of conservative and surgical treatment. We analysed information obtained from the medical records, and for the long-term follow-up we prepared a questionnaire. The questionnaire was composed of general questions about the patients' lifestyle and their ability to return to a normal life and activity after treatment, together with a request for them to score their pain level and remaining symptoms. We found that the longest duration of symptoms before diagnosis was 72 months, with a mean duration of 11.1 months. Low back pain and monoradicular sciatica were the main complaints, but findings of neurological deficits were rare. Lasegue's sign and tight hamstrings seemed to be strong diagnostic signs in this age group. On the day of discharge, 94% of patients reported excellent or good results. The outcomes after a mean follow-up period of 5.4 years were similar in both treatment groups. Almost all patients were able to attain a normal activity level and few reported restrictions on their daily life. Only 14% complained of permanent pain and 7% reported poor results regarding their activity capabilities. In conclusion, we believe that in all cases of lumbar disc herniation in the second decade of life, conservative treatment should be pursued as a mainstay of treatment. Only after a certain time, if conservative treatment is ineffective, should surgical treatment be considered.

[Keratoconus in Mulvihill-Smith syndrome]

BACKGROUND

The Mulvihill-Smith syndrome consists of a large number of stigmata. A few of them are also seen in the LEOPARD syndrome. In both syndromes keratoconus has not yet been reported.

PATIENT

We present a twenty-year-old male patient suffering from keratoconus in connection with a Mulvihill-Smith syndrome. A keratoplasty à chaud was done after perforation of the corneal ulcer.

CONCLUSION

As a major complication corneal graft rejection is known after keratoplasty à chaud. However, in our patient immunological graft failure may be prevented by the T-cell defect.

Glycosylation pattern and processing of envelope gene products encoded by glycosylation mutants of Friend spleen focus-forming virus

The protein encoded by the envelope gene of Friend spleen focus-forming virus is responsible for the acute leukaemogenicity of this virus. In order to correlate glycosylation and intracellular processing of this protein with viral pathogenicity, envelope gene products of pathogenic and apathogenic glycosylation mutants were expressed in Rat-1 cells and metabolically labelled with [6-3H]glucosamine. Following immunoprecipitation, primary and secondary gene products (gp55, gp65) were separated by preparative polyacrylamide gel electrophoresis. Oligosaccharides were released from tryptic glycopeptides by treatment with endo-beta-N-acetylglucosaminidase H (gp55), peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F (gp65) or by reductive beta-elimination. Resulting glycans were characterized by co-chromatography with authentic oligosaccharide standards using different HPLC systems and digestion with exoglycosidases. The results revealed that the primary envelope gene products of pathogenic glycosylation mutants were, in part, further processed in Rat-1 cells similar to wild-type glycoprotein, resulting in polypeptides carrying complex-type N-glycans as well as partially sialylated O-linked oligosaccharides. In contrast, corresponding glycoproteins encoded by apathogenic mutants were found to remain at the level of the primary translation product exclusively comprising high-mannose-type N-glycans. Hence, intracellular maturation of the envelope gene products in this model cell line seems to correlate with the in vivo pathogenicity of the glycosylation mutants studied.

The role of gp55 N-glycosylation in pathogenesis of Friend spleen focus-forming virus

The product of the envelope gene (gp55) of Friend spleen focus-forming virus is responsible for the acute form of erythroleukaemia caused by this virus. In order to investigate the role that the four known N-linked carbohydrate side-chains of gp55 play in pathogenesis, we have inactivated the four N-glycosylation signals by mutating the asparagine residues of these four sites into serine. When glycosylation sites 1 and/or 2 were altered, the viruses remained fully pathogenic. However, mutation at either of glycosylation sites 3 or 4 rendered the virus apathogenic, independent of mutations at other sites. Furthermore, when site 3 was changed, a new product appeared which seemed to have acquired a carbohydrate chain at a position normally not glycosylated, presumably at position Asn378.