MHC recognition in thymic development: distinct, parallel pathways for survival and lineage commitment

The molecular events triggered by MHC recognition and how they lead to the emergence of mature CD4 and CD8 lineage thymocytes are not yet understood. To address these questions, we have examined what signals are necessary to drive the development of CD8 lineage thymocytes in TCRalpha(-) mice in which TCR/MHC engagement cannot occur. We find that the combination of constitutive Notch activity and constitutive Bcl-2 expression are necessary and sufficient to allow the appearance of mature CD8 lineage thymocytes in TCRalpha(-) mice. In addition, Notch activity alone in TCRalpha(-) mice can induce the up-regulation of HES1, suggesting that thymocytes are competent to respond to Notch signaling in the absence of MHC recognition. These data indicate that survival and lineage commitment represent distinct, parallel pathways that occur as a consequence of MHC recognition, both of which are necessary for the development of mature CD8 lineage T cells.

Complications of the laparoscopic Roux-en-Y gastric bypass: 1,040 patients--what have we learned?

BACKGROUND

The Roux-en-Y gastric bypass (RYGBP) is one of the most common operations for morbid obesity. Laparoscopic techniques have been reported, but suffer from small numbers of patients, longer operative times and seemingly higher initial complication rates as compared to the traditional "open" procedure. The minimally invasive approach continues to be a challenge even to the most experienced laparoscopic surgeons. The purpose of this study is to describe our experience and complications of the laparoscopic Roux-en-Y gastric bypass with a totally hand-sewn gastrojejunostomy.

METHODS

1,040 consecutive laparoscopic procedures were evaluated prospectively. Only patients who had a previous open gastric procedure were excluded initially. Eventually, even patients with failed "open" bariatric procedures and other gastric procedures were revised laparoscopically to the RYGBP. All patients met NIH criteria for consideration for weight reductive surgery.

RESULTS

There were no anastomotic leaks from the hand-sewn gastrojejunostomy. Early complications and open conversions were related to sub-optimal exposure and bowel fixation techniques. Several staple failures were attributed to a manufacturer redesign of an instrument. Average hospital stay was 1.9 days for all patients and 1.5 days for patients without complications. Operative times consistently approach 60 minutes. Average excess weight loss was 70% at 12 months. There were 5 deaths: perioperative pulmonary embolism (1), late pulmonary embolism (2), asthma (1), and suicide (1).

CONCLUSIONS

The laparoscopic Roux-en-Y gastric bypass for morbid obesity with a totally hand-sewn gastrojejunostomy can be safely performed by the bariatric surgeon with advanced laparoscopic skills in the community setting. Fixation and closure of all potential hernia sites with non-absorbable sutures is essential. Stenosis of the hand-sewn gastrojejunal anastomosis is amenable to endoscopic balloon dilation. Meticulous attention must be paid to the operative and perioperative care of the patient.

Laparoscopic Roux-en-Y gastric bypass for morbid obesity: technique and preliminary results of our first 400 patients

HYPOTHESIS

A technique of the laparoscopic Roux-en-Y gastric bypass can be developed that is safe, effective, and practical in the community setting.

DESIGN

A case series of 400 morbidly obese and superobese individuals who underwent the laparoscopic Roux-en-Y gastric bypass over a 22-month period.

SETTING

Community private practice in Fresno, Calif.

PATIENTS

A consecutive sample of 400 patients (70 males and 330 females) who met National Institutes of Health criteria for recommendation of a bariatric procedure. Only patients who had a previous gastric or bariatric procedure were excluded from this sample.

INTERVENTION

Laparoscopic Roux-en-Y gastric bypass with a hand-sewn gastrojejunal anastomosis.

MAIN OUTCOME MEASURES

Weight loss, complications, length of hospital stay, successful completion of the operation, and operative times were measured.

RESULTS

Open conversion was required in 12 patients (6 males and 6 females) and a secondary operation for incomplete division of the stomach was required in 2 patients early in the case series. Alternative exposure and fixation techniques greatly reduced these occurrences. There were 6 staple-line failures owing to a change in the manufacture of the instrument. There were no leaks at the gastrojejunal anastomosis, but 21 patients required endoscopic balloon dilation for significant stenosis. The average hospital stay was 1.6 days for the patients who underwent laparoscopy and 2.7 days for patients requiring open conversion. Average excessive weight loss was 69% at 12 months. Operative times are between 60 and 90 minutes. Other complications are described.

CONCLUSION

The Roux-en-Y gastric bypass can be safely and effectively performed in the community setting using advanced laparoscopic techniques.

Calcium channel agonists and dystonia in the mouse

Systemic administration of the L-type calcium channel agonists +/-Bay K 8644 or FPL 64176 causes a characteristic pattern of motor dysfunction in normal C57BL/6J mice that resembles generalized dystonia. There is no associated change in the electroencephalogram, confirming that the motor disorder does not reflect epileptic seizures. However, the electromyogram reveals an increase in baseline motor unit activity with prolonged phasic discharges consistent with dystonia. The duration and severity of dystonia is dependent on the dose administered and the age of the animal at testing. The effects are transient, with the return of normal motor behavior 1-4 hours after treatment. Similar effects can be provoked by intracerebral administration of small amounts of the drugs, indicating a centrally mediated response. Dystonia can be attenuated by co-administration of dihydropyridine L-type calcium channel antagonists (nifedipine, nimodipine, and nitrendipine) but not by non-dihydropyridine antagonists (diltiazem, verapamil, and flunarizine). These results implicate abnormal function of L-type calcium channels in the expression of dystonia in this model.

Hepatocyte growth factor: a regulator of extracellular matrix genes in mouse mesangial cells

The potential role of hepatocyte growth factor (HGF) in regulating extracellular matrix in mouse mesangial cells (MMC) was evaluated. Functional HGF receptors were deed in MMC by HGF-induced extracellular acidification, a response that was inhibited by the HGF inhibitor HGF/NK2, a splice variant expressing the N-terminal domain through the second kringle domain HGF also increased fibronectin and collagen alpha1 (IV) mRNA levels in these cells; the increases were associated with a concentration-dependent increase in transcriptional activity of the collagen alpha1 (IV) gene. HGF also stimulated fibronectin and collagen alpha1 (IV) mRNA levels in primary rabbit proximal tubule epithelial cells To evaluate the potential consequences of chronic elevation of HGF on renal fuction, HGF was administered continuously for 18 days to normal and diabetic C57BLKS/J lepr(db) mice. In the diabetic mice, HGF reduced creatinine clearance and increased microalbuminuria, indicating that chronic exposure to HGF impairs renal function. Thus, chronically elevated HGF may contribute to the progression of chronic renal disease in diabetes by decreasing the glomerular filtration rate and possibly promoting the accumulation of extracellular matrix.

Guillain-Barré syndrome

The concepts of Guillain-Barré syndrome have changed substantially over the last 10 years, and the last 2 years have been no exception. Guillain-Barré syndrome is now recognized as a heterogeneous disorder with many clinical manifestations. Most current investigations are centered on the hypothesis of molecular mimicry. The major challenge now is to identify the precise mechanisms of nerve fiber injury and to determine how to prevent immune injury.

Ganglioside GM1 mimicry in Campylobacter strains from sporadic infections in the United States

To determine whether GM1-like epitopes in Campylobacter species are specific to O serotypes associated with Guillain-Barré syndrome (GBS) or whether they are frequent among random Campylobacter isolates causing enteritis, 275 random enteritis-associated isolates of Campylobacter jejuni were analyzed. To determine whether GM1-like epitopes in Campylobacter species are specific to O serotypes associated with Guillan-Barre syndrome (GBS) or whether they are frequent among random Campylobacter isolates causing enteritis, 275 enteritis-associated isolates, randomly collected in the United States, were analyzed using a cholera-toxin binding assay [corrected]. Overall, 26.2% of the isolates were positive for the GM1-like epitope. Of the 36 different O serotypes in the sample, 21 (58.3%) contained no strains positive for GM1, whereas in 6 serotypes (16.7%), >50% of isolates were positive for GM1. GBS-associated serotypes were more likely to contain strains positive for GM1 than were non-GBS-associated serotypes (37.8% vs. 15.1%, P=.0116). The results suggest that humans are frequently exposed to strains exhibiting GM1-like mimicry and, while certain serotypes may be more likely to possess GM1-like epitopes, the presence of GM1-like epitopes on Campylobacter strains does not itself trigger GBS.

Pneumoperitoneum from an eroded T-fastener

We present a case of late gastric perforation caused by retained T-fasteners after removal of a percutaneous endoscopic gastrostomy tube. We emphasize that timely removal of these fasteners is important in preventing this complication.

Some characteristics of a cellular receptor for virulent infectious bursal disease virus by using flow cytometry

A flow cytometric virus binding assay that directly visualizes the binding of infectious bursal disease virus (IBDV) to its target cells was established. The chicken B lymphoblastoid cell line, LSCC-BK3, which is permissive for IBDV infection, bound high levels of the virus. Another B lymphoblastoid cell line, LSCC-1104-B1, bound low levels of the virus, although it was nonpermissive. No virus binding was detected in nonpermissive T lymphoblastoid cell lines. In the binding assay to heterogeneous cell populations of chicken lymphocytes, IBDV (a highly virulent OKYM strain) bound to 94% cells in the lymphocytes prepared from the bursa of Fabricius, 37% cells in those prepared from the spleen, 3% cells in those prepared from the thymus, and 21% cells in those prepared from the blood. Most of the cells, which bound the virus, were surface immunoglobulin M (SIgM)-positive, but a small number of them were SIgM-negative. Additionally, the binding of IBDV to the LSCC-BK3 cells was affected by treatment of the cells with proteases and N-glycosylation inhibitors. These findings may indicate that the IBDV host range is mainly controlled by the presence of a virus receptor composed of N-glycosylated protein associated with the subtle differentiation stage of B-lymphocytes represented mostly by SIgM-bearing cells.

Glaucoma pattern amongst the elderly Chinese in Singapore

Glaucoma is a major blinding condition and is more prevalent amongst the elderly. A population study of 479 elderly Chinese aged 60 years and older, and residing in Singapore was carried out to determine the prevalence of glaucoma. The overall glaucoma prevalence was 4.8% with normal tension glaucoma (61%) and primary angle closure glaucoma (26%) being the most prevalent forms of glaucoma. All cases were silent in presentation with 97% of cases previously undiagnosed. With the greying population in Singapore, the issue of screening the elderly for glaucoma should be considered.

Evaluation of a recombinant 27-kDa outer membrane protein of Coxiella burnetii as an immunodiagnostic reagent

The 27-kDa outer membrane protein from eight strains of Coxiella burnetii was expressed in the pET-21c protein expression system. Two fusion proteins with molecular masses of 30 and 32 kDa were evident in all eight of the recombinants by SDS-PAGE and immunoblotting. A protein having an approximate size of 30 kDa was purified from the Escherichia coli lysates by one-step affinity purification. The utility of the purified recombinant protein in ELISA was also evaluated by testing its reactivity with human sera and comparing this reactivity with that of Nine Mile phase II antigen. All of the 40 IF-positive serum samples were ELISA-positive for both the Nine Mile phase II and recombinant antigens, and negative serum controls were negative for both antigens. These results suggest that ELISA with the 27-kDa recombinant antigen is a sensitive and specific method for detecting anti-C. burnetii antibodies in human sera.

Human FGF-1 gene delivery protects against quinolinate-induced striatal and hippocampal injury in neonatal rats

Fibroblast growth factors (FGFs) are cell mitogens and differentiating factors with neuroprotective properties in the CNS. We have already shown that endothelial cells genetically engineered to secrete human FGF-1 (RBEZ-FGF) survive implantation to neonatal rat brain (Johnston et al. (1996) J. Neurochem. 67, 1643-1652]. In this study, the effects of cell-based FGF-1 gene delivery on quinolinate-induced neurotoxicity in the developing rat brain were examined. Control endothelial cells (RBE4), and RBEZ-FGF cells were implanted into right striatum at post-natal day (PND) 7. On PND 10, quinolinate (150 nmol), an endogenous N-methyl-d-aspartate (NMDA) receptor agonist, or vehicle alone was injected into striatum ipsilateral to cell implantation. Injury was quantified in coronal sections obtained from PND 17 animals by comparing striatal and hippocampal volumes ipsilateral and contralateral to the site of quinolinate injection. Human FGF-1 specific transgene expression in vivo was shown by Northern blot and RT-PCR up to 14 days after cell implantation in control animals, and up to 4 days after quinolinate exposure. Quinolinate reduced the size of ipsilateral striatum by 37% and hippocampus by 38% in animals preimplanted with control endothelial cells. In contrast, quinolinate reduced the size of striatum by only 14% and had no effect on hippocampal size in animals preimplanted with RBEZ-FGF cells. Thus, FGF-1 gene delivery protected the developing striatum and hippocampus from quinolinate-induced volume loss by 62% and 100%, respectively. Intrastriatal quinolinate resulted in a significant decrease in density of NOS+ CA3 hippocampal neurons (-38%) without affecting the density of NOS+ neurons in hippocampal regions CA1, dentate gyrus or striatum. This response of CA3 NOS+ neurons appeared to be only partially reversed by FGF-1 gene delivery. Our results show that intracerebral FGF-1 gene expression within the developing brain can protect striatum and hippocampus from quinolinate-mediated injury.

Direct identification of Coxiella burnetii plasmids in human sera by nested PCR

Nested PCR assays were used for the direct identification of Coxiella burnetii plasmids in human sera. A total of 81 serum samples from 81 patients with Q fever were tested by nested PCR with four sets of primers. The first set of primers was used to detect the genomic sequences. The second set of primers was used to detect the conserved sequences of the plasmids. Another two sets of primers were used to identify the QpH1 and QpRS plasmids. QpH1 and QpRS plasmid-specific sequences were identified in 40 (49.4%) and 24 (29.6%) of the serum samples, respectively. Both of the QpH1 and QpRS plasmid-specific sequences were detected in 5 (8.6%) of the serum samples but were not found in 12 (20.7%) of the serum samples. Furthermore, all of the 23 acute-phase serum samples were positive for the QpH1 plasmid and negative for the QpRS plasmid. Nested PCR with plasmid-specific primers appears to be a useful method for the direct typing of C. burnetii plasmids in human sera.

Evidence for gene silencing by endogenous DNA methylation

Transformed cells can spontaneously silence genes by de novo methylation, and it is generally assumed that this is due to DNA methyltransferase activity. We have tested the alternative hypothesis that gene silencing could be due to the uptake of 5-methyl-dCMP into DNA, via the di- and triphosphonucleotides. 5-Methyl-dCMP would be present in cells from the ongoing repair of DNA. We have isolated a strain of Chinese hamster ovary (CHO) cells, designated HAM-, which spontaneously silences two tested genes at a very high frequency. We have shown that this strain incorporates 5-[3H]methyldeoxycytidine into 5-methylcytosine and thymine in DNA. It also has low 5-methyl-dCMP deaminase activity. Another HAM+ strain has high deaminase activity and a very low frequency of gene silencing. The starting strain, CHO K1, has a phenotype intermediate between HAM- and HAM+.

Campylobacter species and Guillain-Barré syndrome

Since the eradication of polio in most parts of the world, Guillain-Barré syndrome (GBS) has become the most common cause of acute flaccid paralysis. GBS is an autoimmune disorder of the peripheral nervous system characterized by weakness, usually symmetrical, evolving over a period of several days or more. Since laboratories began to isolate Campylobacter species from stool specimens some 20 years ago, there have been many reports of GBS following Campylobacter infection. Only during the past few years has strong evidence supporting this association developed. Campylobacter infection is now known as the single most identifiable antecedent infection associated with the development of GBS. Campylobacter is thought to cause this autoimmune disease through a mechanism called molecular mimicry, whereby Campylobacter contains ganglioside-like epitopes in the lipopolysaccharide moiety that elicit autoantibodies reacting with peripheral nerve targets. Campylobacter is associated with several pathologic forms of GBS, including the demyelinating (acute inflammatory demyelinating polyneuropathy) and axonal (acute motor axonal neuropathy) forms. Different strains of Campylobacter as well as host factors likely play an important role in determining who develops GBS as well as the nerve targets for the host immune attack of peripheral nerves. The purpose of this review is to summarize our current knowledge about the clinical, epidemiological, pathogenetic, and laboratory aspects of campylobacter-associated GBS.

Gene silencing by DNA methylation and dual inheritance in Chinese hamster ovary cells

Chinese hamster ovary (CHO) cells strain D422, which has one copy of the adenine phosphoribosyl transferase (APRT) gene, were permeabilized by electroporation and treated with 5-methyl deoxycytidine triphosphate. Cells with a silenced APRT gene were selected on 2, 6-diaminopurine. Colonies were isolated and shown to be reactivated to APRT+ by 5-aza-cytidine and by selection in medium containing adenine, aminopterin and thymidine. Genomic DNA was prepared from eight isolates of independent origin and subjected to bisulphite treatment. This deaminates cytosine to uracil in single-stranded DNA but does not deaminate 5-methyl cytosine. PCR, cloning and sequencing revealed the methylation pattern of CpG doublets in the promoter region of the APRT- gene, whereas the active APRT gene had nonmethylated DNA. CHO strain K1, which has two copies of the APRT+ gene, could also be silenced by the same procedure but at a lower frequency. The availability of the 5-methyl dCTP-induced silencing, 5-aza-CR and a standard mutagen, ethyl methane sulphonate, makes it possible to follow concomitantly the inheritance of active, mutant or silenced gene copies. This analysis demonstrates "dual inheritance" at the APRT locus in CHO cells.

Gene silencing and endogenous DNA methylation in mammalian cells

It is known that transformed mammalian cells can spontaneously inactivate genes at low frequency by the de novo methylation of promoter sequences. It is usually assumed that this is due to DNA methyl transferase activity, but an alternative possibility is that 5-methyldCTP is present in these cells and can be directly incorporated into DNA. The ongoing repair of DNA containing 5-methylcytosine will produce 5-methyldeoxycytidine monophosphate (5-methyldCMP), so the question arises whether this can be phosphorylated to 5-methyldCTP. We have tested this using three strains of CHO cells with different levels of 5-methyldCMP deaminase activity. That with the lowest enzyme activity, designated HAM-, has previously been shown to incorporate tritium labelled 5-methyldeoxycytidine into 5-methylcytosine in DNA, with a greater amount of label in thymine. This strain is phenotypically unstable producing cells resistant to bromodeoxyuridine (BrdU) and 6-thioguanine (6-TG) at high frequency. In contrast, the strain with the highest 5-methyldCMP deaminase, designated HAM+, is extremely stable, and the starting strain K1 HAMsl is intermediate between the HAM- and HAM+ phenotypes. We have also shown that human diploid fibroblast strain MRC-5 has a phenotype like HAM+, whereas its SV40 transformed derivative, MRC-5V2 resembles HAM- in having low 5-methyl dCMP deaminase activity, and is phenotypically unstable with regard to 6-TG resistance. It seems that 5-methyldCMP deaminase can be down-regulated in transformed cells, and this can promote de novo methylation by incorporation of 5-methyldCTP derived from 5-methyldCMP.

Comparison of laparoscopic and open adrenalectomy

This review compares the outcomes of patients who have undergone laparoscopic and open adrenalectomy. Records of all patients who underwent adrenalectomy between January 1993 and December 1996 at Cedars-Sinai Medical Center, Los Angeles, were reviewed. Ten patients underwent laparoscopic, and ten patients underwent open adrenalectomy. The average age in the laparoscopic group (LA) was 48 years (range, 23-64) and 47 years (range, 28-79) in the open group (OA). The LA had smaller tumor size (2.9 +/- 2.0 versus 6.1 +/- 2.8 cm; P = 0.01), longer operative times (164 +/- 47 versus 124 +/- 29 minutes; P = 0.03), shorter length of postsurgical stay (4.1 +/- 2.5 versus 5.9 +/- 1.1 days; P = 0.05), and fewer days of parenteral pain medication (1.9 +/- 1.8 versus 3.4 +/- 1.0 days; P = 0.04). Although the differences did not reach statistical significance, LA also had lower estimated blood loss (118 +/- 158 versus 210 +/- 172 cc; P = 0.23), less time to oral intake (1.8 +/- 2.2 versus 2.8 +/- 1.3 days; P = 0.24), and less direct cost ($3645 +/- 1502 versus $5752 +/- 2948; P = 0.07). Complications of LA included one patient who had a prolonged ileus and adrenal insufficiency and another patient who required readmission for adrenal insufficiency. Complications of OA included one patient who had a prolonged ileus and one patient who had a 20 per cent pneumothorax. Laparoscopic adrenalectomy is the preferred technique in nonmalignant adrenal lesions less than 6 cm in size.

Identification of new autolytic sites of recombinant truncated mature human fibroblast stromelysin by mass spectrometry

Stromelysin has been proposed to play a major role in the pathologic degradation of diseased cartilage of osteoarthritis and rheumatoid arthritis patients. A truncated, recombinant form of this enzyme, with the sequence Phe83 to Thr260 (mSL-t), has been expressed and purified from E. coli to investigate its biochemical and biophysical properties, and to develop inhibitors for arthritis treatment. LC/ESI-MS technique was utilized for the characterization of mSL-t. The mass spectra of mSL-t showed the presence of a number of different protein components in addition to the full-length mSL-t form. We have demonstrated that protein degradation arose from autolysis. Molecular weights determined by LC/ESI-MS of these autolysis products allowed for the identification of new autolytic sites in mSL-t. Furthermore, two strategies were undertaken to prepare mSL-t free of degradation products. These include preparation of a mutant form of the enzyme in which Arg163 was substituted for Leu163 and purification of mSL-t using affinity chromatography. The LC/ESI-MS data of the mutant protein confirmed the Leu to Arg mutation. The affinity-purified material showed only one LC peak in the LC/MS chromatograms, and the mass spectrum of the peak identified only the intact protein, demonstrating that the full-length protein has been successfully separated from the autodegradation products and further autolysis of the enzyme has been prevented.

Eye diseases in the elderly in Singapore

OBJECTIVE

The study was conducted to determine the prevalence rates of blindness and visual impairment in those aged 60 years and above in Singapore and to determine the pickup rate of undiagnosed eye diseases through an active screening programme.

METHOD

A random frame of 3,000 elderly persons aged 60 years and above was obtained from the Ministry of Home Affairs in Singapore. They were invited by mail to attend eye screening at Hougang Senior Citizens' Health Care Centre. The eye screening was in two parts: the first part by a trained registered nurse or therapy aide and the second part by the ophthalmologist. For each respondent, autorefraction, tonometry, retinal photography and visual field analysis were done. Examination criteria and disease classification were modelled after the Framingham Eye Study.

RESULTS

574 subjects attended the screening, giving a response rate of 22.2%. The prevalence rates for blindness and visual impairment in the elderly screened were 3.0% and 15.2% respectively. The prevalence rates for cataract, age-related macular degeneration, glaucoma and diabetic retinopathy were 78.6%, 27.0%, 5.7% and 5.1% respectively. For every person known to have cataract, 2 were unknown; for every person with age-related macular degeneration, 154 were unknown. None of the 29 persons with diabetic retinopathy was diagnosed previously.

CONCLUSION

Almost 1 in 5 of the elderly screened had some degree of visual disability. The rates of visual impairment and blindness were similar to those reported in other studies and indicate a significant burden of visually impairing diseases in the community.