Compare the Efficacy and Safety of Modified Combined Short and Long Axis Method versus Oblique Axis Method for Right Internal Jugular Vein Catheterization in Adult Patients (The MCSLOA Trial): Study Protocol of a Randomized Controlled Trial

Background

Ultrasound-guided internal jugular vein (IJV) catheterization has become a standard procedure as it yields a higher success rate and fewer mechanical complications compared with an anatomical landmark technique. There are several common methods for ultrasound guidance IJV catheterization, such as short-axis out-of-plane, long-axis in-plane and oblique axis in-plane, but these technologies are still developing. It is important to further study the application of different ultrasound-guided IJV puncture techniques and find an effective and safe ultrasound-guided puncture technique.

Methods

A China randomized, open-label, parallel, single center, positive-controlled, non-inferiority clinical trial will evaluate 190 adult patients undergoing elective surgery and need right jugular vein catheterization. Study participants randomized in a 1:1 ratio into control and experimental groups. The control group will take the oblique axis in-plane method for IJV catheterization. The experimental group will take the Modified combined short and long axis method. The primary endpoint of the trial is the rate of one-time successful guidewire insertion without posterior wall puncture (PWP). Secondary endpoints are the number of needle insertion attempts, the total success rate, the procedure time, and mechanical complications.

Conclusion

This randomized controlled trial will evaluate the effectiveness and safety of Modified combined short and long axis method and oblique axis in-plane method for right IJV catheterization in adult patients.

Asymptomatic carbon dioxide embolism during transoral vestibular thyroidectomy: A case report

BACKGROUND

Endoscopic thyroidectomy has obvious advantages over conventional surgical techniques in terms of postoperative cosmetic outcome. Although the incidence of carbon dioxide embolism (CDE) during endoscopic thyroidectomy is very low, it is potentially fatal. The clinical manifestations of CDE vary, and more attention should be paid to this disorder.

CASE SUMMARY

A 27-year-old man was scheduled for thyroidectomy by the transoral vestibular approach. The patient had no other diseases or surgical history. During the operation, he developed a CDE following inadvertent injury of the anterior jugular vein. The clinical manifestation in this patient was a transient sharp rise in end-tidal carbon dioxide, and his remaining vital signs were stable. In addition, loud coarse systolic and diastolic murmurs were heard over the precordium. The patient was discharged on day 4 after surgery without complications.

CONCLUSION

A transient sharp rise in end-tidal carbon dioxide is considered a helpful early sign of CDE during endoscopic thyroidectomy.

Aspiration pneumonia during general anesthesia induction after esophagectomy: A case report

BACKGROUND

Esophageal cancer is a common malignant tumor of the digestive system. At present, surgery is the most important treatment strategy. After esophagectomy and gastric esophagoplasty, the patients are prone to regurgitation. However, these patients currently do not receive much attention, especially from anesthesiologists.

CASE SUMMARY

A 55-year-old woman was scheduled for right lower lung lobectomy. The patient had undergone radical surgery for esophageal cancer under general anesthesia 6 mo prior. Although the patient had fasted for > 17 h, unexpected aspiration still occurred during induction of general anesthesia. Throughout the operation, oxygen saturation was 98%-100%, but the airway pressure was high (35 cmH₂O at double lung ventilation). The patient was sent to the intensive care unit after surgery. Bedside chest radiography was performed, which showed exudative lesions in both lungs compared with the preoperative image. After surgery, antibiotics were given to prevent lung infection. On day 2 in the intensive care unit, the patient was extubated and discharged on postoperative day 7 without complications related to aspiration pneumonia.

CONCLUSION

After esophagectomy, patients are prone to regurgitation. We recommend nasogastric tube placement followed by rapid sequence induction or conscious intubation.

Two-beam combined 3.36 J, 100 Hz diode-pumped high beam quality Nd:YAG laser system

In this paper, we develop a diode-pumped all-solid-state high-energy and high beam quality Nd:YAG laser system. A master oscillator power amplifier structure is used to provide a high pulse energy laser output with a high repetition rate. In order to decrease the amplifier working current so as to reduce the impact of the thermal effect on the beam quality, a beam splitting-amplifying-combining scheme is adopted. The energy extraction efficiency of the laser system is 50.68%. We achieve 3.36 J pulse energy at a 100 Hz repetition rate with a pulse duration of 7.1 ns, a far-field beam spot 1.71 times the diffraction limit, and 1.07% energy stability (RMS).

Association among EPHB2, TrkA, and MYCN expression in low-stage neuroblastomas

BACKGROUND

The EPH family is the largest subfamily of receptor protein-tyrosine kinases, consisting of EPHA and EPHB subgroups. Ligands of EPH family receptors are called ephrins, which include ephrin-A and ephrin-B subgroups. We recently found that transcripts encoding the EPHB subgroup (EPHB) and the ephrin-B subgroup (EFNB) were expressed together in neuroblastoma (NB) cell lines.

PROCEDURE

In this study, we examined the expression of EPHB and EFNB transcripts in 24 NB specimens representing all clinical stages. We found that several EPHB and EFNB transcripts were expressed together in all NBs examined.

RESULTS

Among the transcripts examined, EPHB6 expression was most significantly associated with low stage tumors (stages 1, 2, and 4S; P = 0.0048). TrkA expression was significantly correlated with EPHB6, EFNB2, and EFNB3 expression (P < 0.01 in each case). Taken together, these data indicate that the expression of EPHB6, EFNB2, and EFNB3 may serve as prognostic indicators of favorable NBs. In the low-stage NBs without MYCN amplification, EPHB2 expression was correlated both with MYCN expression and with TrkA expression (P < 0.01 in each case). Moreover, MYCN expression was correlated with TrkA expression (P < 0.01) in the low-stage NBs.

CONCLUSIONS

This observation points to the possibility that MYCN expression might contribute to favorable outcome of low-stage NBs.

Prognostic significance of EPHB6, EFNB2, and EFNB3 expressions in neuroblastoma

BACKGROUND

EPH family receptor tyrosine kinases and their ligand ephrins play pivotal roles in development. High-level expression of transcripts encoding EPHB6 receptors (EPHB6), its ligands ephrin-B2 and ephrin-B3 (EFNB2, EFNB3) is predictive of favorable disease outcome of neuroblastoma (NB). When combined with TrkA expression, the expression of EPHB6, EFNB2, or EFNB3 predicts more accurately the disease outcome than each of the four variables alone.

PROCEDURE

Cox regression and Kaplan-Meier analyses were used to assess the prognostic significance of EPHB6, EFNB2, EFNB3, and TrkA expressions in NB without MYCN amplification.

RESULTS

High-level expression of EFNB3 or TrkA predicted favorable NB outcome of NB without MYCN amplification (p < 0.03). As found in the general NB population, EPHB6, EFNB2, or EFNB3 expression in combination with TrkA expression was significantly predictive of the disease outcome of normal MYCN NB (p < 0.01).

CONCLUSIONS

EPHB6, EFNB2, and EFNB3 expressions may permit further refinement of the prognostic stratification of NB into favorable and unfavorable groups.

Implications of EPHB6, EFNB2, and EFNB3 expressions in human neuroblastoma

Neuroblastoma (NB) is a common pediatric tumor that exhibits a wide range of biological and clinical heterogeneity. EPH (erythropoietin-producing hepatoma amplified sequence) family receptor tyrosine kinases and ligand ephrins play pivotal roles in neural and cardiovascular development. High-level expression of transcripts encoding EPHB6 receptors (EPHB6) and its ligands ephrin-B2 and ephrin-B3 (EFNB2, EFNB3) is associated with low-stage NB (stages 1, 2, and 4S) and high TrkA expression. In this study, we showed that EFNB2 and TrkA expressions were associated with both tumor stage and age, whereas EPHB6 and EFNB3 expressions were solely associated with tumor stage, suggesting that these genes were expressed in distinct subsets of NB. Kaplan-Meier and Cox regression analyses revealed that high-level expression of EPHB6, EFNB2, and EFNB3 predicted favorable NB outcome (P<0.005), and their expression combined with TrkA expression predicted the disease outcome more accurately than each variable alone (P<0.00005). Interestingly, if any one of the four genes (EPHB6, EFNB2, EFNB3, or TrkA) was expressed at high levels in NB, the patient survival was excellent (>90%). To address whether a good disease outcome of NB was a consequence of high-level expression of a "favorable NB gene," we examined the effect of EPHB6 on NB cell lines. Transfection of EPHB6 cDNA into IMR5 and SY5Y expressing little endogenous EPHB6 resulted in inhibition of their clonogenicity in culture. Furthermore, transfection of EPHB6 suppressed the tumorigenicity of SY5Y in a mouse xenograft model, demonstrating that high-level expressions of favorable NB genes, such as EPHB6, can in fact suppress malignant phenotype of unfavorable NB.

High-level expression of EPHB6, EFNB2, and EFNB3 is associated with low tumor stage and high TrkA expression in human neuroblastomas

Neuroblastoma (NB) is a common pediatric tumor of neural crest origin that is biologically and clinically heterogeneous. EPH family receptor tyrosine kinases and ephrin ligands play fundamental roles in neurodevelopmental processes. Recently, we found that NB cell lines expressed several EPHB and EFNB transcripts, which encode EPHB subgroup receptors and ephrin-B subgroup ligands, respectively. To explore the role of EPHB receptors and ephrin-B ligands in the biology of NB, we examined the expression of EPHB and EFNB transcripts in 47 primary NB specimens. Multiple EPHB and EFNB transcripts were expressed in all of the NB tumors examined, suggesting the involvement of these transcripts in modulating the biological behavior of NB. Higher levels of EPHB6, EFNB2, and EFNB3 expression were found in low-stage tumors (stage 1, 2, and 4S) than in advanced-stage tumors (stage 3 and 4; P = 0.0013, P = 0.0048, and P = 0.027, respectively). Expression of TrkA, a well-established prognostic marker of favorable NB, was positively correlated with EPHB6, EFNB2, and EFNB3 expression (P < 0.0001, P = 0.0019, and P = 0.0001, respectively). MYCN-amplified tumors expressed lower levels of EPHB6, EFNB2, EFNB3, and TrkA transcripts compared to nonamplified tumors (P = 0.0006, P = 0.0023, P = 0.0048, and P = 0.0001, respectively). These data suggest that high-level expression of EPHB6, EFNB2, and EFNB3 is associated with favorable NB and that low-level expression of EPHB6, EFNB2, and EFNB3 correlates with aggressive MYCN-amplified NB. Thus, EPHB6, EFNB2, and EFNB3 may have biological relevance in NB. Further investigation on the biology of these genes may help provide insight into the treatment of NB.

Coexpression of transcripts encoding EPHB receptor protein tyrosine kinases and their ephrin-B ligands in human small cell lung carcinoma

The EPH family is the largest subfamily of receptor protein tyrosine kinases, consisting of the EPHA and EPHB subgroups. Ephrin-B1, ephrin-B2, and ephrin-B3 are ligands of the EPHB subgroup and are encoded by the EFNB1, EFNB2, and EFNB3 genes, respectively. We have shown previously that EPHB2 transcripts are expressed in six small cell lung carcinoma (SCLC) cell lines. In this study, we examined the expression of EPHB1, EPHB2, EPHB3, EPHB4, and EPHB6 in 4 SCLC tumor specimens and 14 cell lines including 3 cell lines derived from these tumor specimens. To investigate whether potential autocrine loops of EPHB receptors and ephrin-B ligands exist in SCLC, the expression of EFNB1, EFNB2, and EFNB3 was also examined. Our data show that transcripts encoding multiple members of the EPHB subgroup and the ephrin-B subgroup are coexpressed in SCLC cell lines and tumors. These results suggest that the EPHB subgroup receptor kinases may modulate the biological behavior of SCLC through autocrine and/or juxtacrine activation by ephrin-B ligands that are expressed in the same or neighboring cells.

A variant transcript encoding an isoform of the human protein tyrosine kinase EPHB2 is generated by alternative splicing and alternative use of polyadenylation signals

We previously isolated and characterized cDNA clones of DRT (EPHB2), encoding a receptor protein-tyrosine kinase of the EPH family. Northern blot analysis showed that EPHB2 transcripts are expressed in three sizes of approximately 4, 5, and 11 kb, suggesting that these transcripts are generated by alternative splicing and/or alternative use of polyadenylation sites. To explore this possibility, we isolated additional EPHB2 cDNA clones, including clone 5K-1, by re-screening the human fetal brain cDNA library. Nucleotide sequence analysis of clone 5K-1 revealed that it represents a variant transcript of EPHB2 (EPHB2v). Relative to the EPHB2 cDNA sequence previously reported, clone 5K-1 has two coding region deletions of 3 and 93 nucleotides. Nucleotide sequence analyses of EPHB2 genomic DNA fragments corresponding to these deletions suggest that the EPHB2v transcript is generated by alternative splicing. The 3' end of clone 5K-1 contains a polyadenosine stretch preceded by a potential polyadenylation signal, which is not used to generate the EPHB2 transcript. Taken together, these data indicate that EPHB2v is generated by both alternative splicing and alternative use of polyadenylation sites. The EPHB2v protein lacks one arginine residue that resides immediately following the EPHB2 transmembrane domain. In contrast, as a result of the frame shift caused by the 93 nucleotide deletion, the C-terminus of the EPHB2v protein is longer by 70 amino acids than that of EPHB2. We also show that the human neuroblastoma cell line SY5Y and NTera-2N neurons express high levels of EPHB2 and lower levels of EPHB2v. These structural variations found between the EPHB2 and EPHB2v proteins may reflect functional heterogeneity of EPHB2.

cDNA cloning, chromosomal localization, and expression pattern of EPLG8, a new member of the EPLG gene family encoding ligands of EPH-related protein-tyrosine kinase receptors

By screening a human fetal brain cDNA library under low stringency using cDNA encoding the mouse ligand of Cek5 as a probe, we have isolated a novel cDNA belonging to the EPLG gene family. This family encodes ligands of EPH-related tyrosine kinase receptors. Since the novel gene is the eighth member of the EPLG gene family, it is designated EPLG8. The deduced amino acid sequence of EPLG8 suggests that it encodes a transmembrane protein that is most related to those encoded by EPLG2 and EPLG5. We mapped the EPLG8 gene to human chromosome 17p11.2-p13.1 by PCR screening of human-rodent somatic cell hybrid panels. In the midterm fetus, EPLG8 mRNA is expressed at the highest level in brain, followed by heart, kidney, and lung. In the adult, EPLG8 mRNA expression is restricted to brain. These data suggest that LERK-8, the protein encoded by EPLG8, is important in brain development as well as in its maintenance. Moreover, since levels of EPLG8 expression were particularly high in several forebrain subregions compared to other brain subregions, LERK-8 may play a pivotal role in forebrain function.

ECK, a human EPH-related gene, maps to 1p36.1, a common region of alteration in human cancers

Mouse eck, a member of the EPH gene family, has been mapped to mouse chromosome 4. The syntenic relationship between this chromosome and human chromosome 1 suggests that the human ECK gene maps to the distal short arm of human chromosome 1 (1p). Since this region is frequently deleted or altered in certain tumors of neuroectodermal origin, it is important to define the specific chromosomal localization of the human ECK gene. PCR screening of a rodent-human somatic cell hybrid panel by ECK-specific primers showed that ECK is indeed localized to human chromosome 1. Additional PCR screening of a regional screening panel for chromosome 1p indicated that ECK is localized to 1p36, distal to FUCA1. Furthermore, fluorescence in situ hybridization analysis with an ECK-specific P1 clone showed that ECK maps proximal to genetic marker D1S228. Taken together, the data suggest that ECK maps to 1p36.1, a region that is frequently deleted in neuroblastoma, melanoma, and other neuroectodermal tumors.

Identification of epitope recognized by an anti-c-myc monoclonal antibody that cross-reacts with E. coli sigma factor using phage display libraries

BACKGROUND

During the epitope mapping of monoclonal antibodies specific for myc proteins, two E. coli proteins cross-reactive with an anti-c-myc monoclonal antibody (MYC-X-5/1) were identified. One of the proteins is approximately 90 kDa and the other is over 150 kDa in apparent molecular mass. The molecular masses of these cross-reactive proteins suggested that they may be subunits of E. coli RNA polymerase.

OBJECTIVES

We have investigated whether or not the proteins cross-reactive with MYC-X-5/1 are subunits of E. coli RNA polymerase. In addition, we have attempted to determine the epitope of MYC-X-5/1.

STUDY DESIGN

The reactivity of MYC-X-5/1 antibody was tested against highly purified E. coli RNA polymerase holo-enzyme preparations and the cell lysate made from E. coli carrying a multi-copy plasmid with an insert of the rpoD gene, the structural gene for the E. coli sigma subunit. The epitope of MYC-X-5/1 was determined by use of phage display of random peptide libraries.

RESULTS

On immunoblotting assays, MYC-X-5/1 reacted with the 90-kDa protein in the E. coli RNA polymerase preparations and with the 90-kDa protein over-expressed in E. coli carrying the plasmid with the rpoD insert. In addition, we have deduced the epitope of the MYC-X-5/1 antibody to be residues 235-245 of the human c-myc protein. A highly similar sequence to this was also identified in residues 62-72 of the sigma subunit of E. coli RNA polymerase.

CONCLUSION

These data demonstrated that the 90-kDa protein cross-reactive with MYC-X-5/1 is the sigma subunit of E. coli RNA polymerase. Furthermore, this study shows that random peptide libraries displayed on filamentous phage are useful tools for epitope mapping and defining cross-reactivities of monoclonal antibodies.

Molecular characterization and chromosomal localization of DRT (EPHT3): a developmentally regulated human protein-tyrosine kinase gene of the EPH family

By screening a human fetal brain cDNA expression library using a monoclonal antiphosphotyrosine antibody and by 5' RACE procedures, we have isolated overlapping cDNAs encoding a receptor-type tyrosine kinase belonging to the EPH family, DRT (Developmentally Regulated EPH-related Tyrosine kinase gene). The DRT gene is expressed in three different size transcripts (i.e. 4, 5 and 11 kb). DRT transcripts are expressed in human brain and several other tissues, including heart, lung, kidney, placenta, pancreas, liver and skeletal muscle, but the 11 kb DRT transcript is preferentially expressed in fetal brain. Steady-state levels of DRT mRNA in several tissues, including brain, heart, lung and kidney, are greater in the midterm fetus than those in the adult. DRT transcripts are detectable at low levels in a human teratocarcinoma cell line (NTera-2), but its expression is greatly increased after the NTera-2 cells are induced to become postmitotic neurons (NTera-2N) by retinoic acid treatment. These data suggest that DRT plays a part in human neurogenesis. A large number of tumor cell lines derived from neuroectoderm express DRT transcripts, including 12 neuroblastomas, two medulloblastomas, one primitive neuroectodermal tumor and six small cell lung carcinomas (SCLC). Interestingly, several neuroblastoma cell lines with 1p deletion and one SCLC cell line express DRT transcripts of aberrant size (i.e. 3, 6 and 8 kb) in addition to those found in normal tissues. We mapped the DRT gene to human chromosome 1p35-1p36.1 by PCR screening of human-rodent somatic cell hybrid panels and by fluorescence in situ hybridization. As the distal end of chromosome 1p is often deleted in neuroblastomas and altered in some cases in SCLCs, these chromosomal abnormalities may have resulted in the generation of aberrant size transcripts. Thus, the DRT gene may play a part in neuroblastoma and SCLC tumorigenesis.

cDNA cloning, molecular characterization, and chromosomal localization of NET(EPHT2), a human EPH-related receptor protein-tyrosine kinase gene preferentially expressed in brain

By screening a human fetal brain cDNA expression library using a monoclonal anti-phosphotyrosine antibody, we have isolated a cDNA clone encoding a receptor type protein-tyrosine kinase belonging to the EPH family, NET (neuronally expressed EPH-related tyrosine kinase). NET shows 87% homology in nucleotide sequence and 99% homology in the deduced amino acid sequence to rat elk, suggesting that NET is the human homologue of elk. The NET gene is mapped to human chromosome 3q21-q23 by PCR screening of a human-rodent somatic cell hybrid panel and by fluorescence in situ hybridization. Examination of NET mRNA expression in several human tissues has shown that the NET gene is expressed preferentially in brain as a 5-kb transcript. Steady-state levels of NET mRNA in human brain are greater in the midterm fetus than in the adult. Lower levels of NET mRNA are found in fetal kidney and adult skeletal muscle. The expression pattern of NET mRNA thus differs from that of elk, suggesting that these two gene products may perform distinct roles in human and rat. NET transcripts are detected in human NTera-2 teratocarcinoma cells after retinoic acid-induced neuronal differentiation. Several human tumor cell lines derived from neuroectoderm including primitive neuroectodermal tumor, small cell lung carcinoma, and neuroblastoma also express NET transcripts. Since the NET mRNA expression in human brain is developmentally regulated and is induced during neuronal differentiation, NET potentially plays important roles in human neurogenesis.

An alternative view of T-cell receptor-MHC interaction: T-cell receptor binds transversally to the alpha-helices of the MHC molecule

We have attempted to elucidate the relative orientation of the T-cell receptor (TCR) to the major histocompatibility complex (MHC)-antigen complex during antigen recognition, using the T-cell response to B10.A (I-Ek) and B10.A(5R) (I-Eb) mice to the 1-23(H) peptide derived from glycoprotein D of the herpes simplex virus. The 1-23(H)-specific T-cells derived from both B10.A and B10.A(5R) mice use the same set of V alpha genes and a different array of V beta genes. The CDR1s of these TCR beta chains share residues at particular positions. The CDR2s of the TCR beta chains have a negative charge, which correlates with I-Eb reactivity and with the positively charged polymorphic residues residing at the C-terminal end of the alpha-helix of the I-Eb beta chain of the class II molecule. Taken together, the data suggest that the TCR beta chain interacts with both the alpha and beta chains of the MHC class II molecule, as does the TCR alpha chain.

T cells from unprimed mice respond to the self antigen heme, in a class II restricted manner, at a frequency similar to alloresponses

Heme is a non-protein autoantigen which stimulates potent proliferative responses by T cells from unprimed mice of some strains. These studies show that T cells responding to heme in primary responses are predominantly CD4+, classically I-A restricted, and use diverse TCR characterized by the expression of distinct V, D and J gene segments. These characteristics distinguish heme from superantigens and mitogens which exhibit degenerate MHC restriction and, in the case of superantigens, restricted V gene usage. Using limiting dilution analysis these studies also show that the potent primary response of H-2s mice reflects a high frequency (0.26-0.45%) of heme responsive T cells in the periphery, comparable to the frequency of alloresponsive T cells reported by others in primary mixed lymphocyte reactions. In contrast, heme responsive T cells occur at -10-fold lower frequency in unprimed H-2d mice (0.03%). To determine the antigen recognized by heme reactive T cells, the mass spectra of peptides eluted from the high responder haplotype, I-A(s), were examined. These indicated a markedly different molecular weight distribution of peptides isolated from cells grown in the presence of heme, compared with those from cells grown in its absence. This suggests that heme mediates the expansion of diverse T cells in the peripheral repertoire by a mechanism similar to that for allogeneic responses in which the profile of naturally processed peptides bound to the MHC class II molecule is changed.

[Assessment of fiberoptic bronchoscopic examination in inhalation injury--analysis of 32 cases]

68 times of fiberoptic bronchoscopic serial examinations in 32 patients with inhalation injury were performed at early stage after injury. Bronchoscopic abnormalities including congestion, erythema, edema and necrosis were observed. Patients were divided into three groups according to the degree of damage: mild, moderate and severe. 8 patients with mild inhalation injury, their bronchoscopic abnormalities included slight congestion and edema, these changes extended to the carina with disappearance of the trachea rings, airway lumen was slight narrowed, carina was blunted, these lesions were resolved within one week after injury. The fiberoptic bronchoscopy of patients with moderate injury showed moderate congestion and edema of mucosa of the trachea, disappearance of the trachea rings, the lumen was more narrowed as compared with mild injury. The blunted carina widen to 0.5 cm due to swelling, the mucosa of primary bronchus showed slight congestion and edema. These lesions were resolved 2 weeks after injury. The fiberoptic bronchoscopic abnormalities of 13 patients with severe inhalation injury were extreme congestion and edema of the trachea mucosa with necrosis; hemorrhage and ulceration of the mucosa were seen. The trachea lumen was significantly narrowed, the carina widened to 1 cm, and even the primary bronchus mucosa manifested moderate congestion and edema with necrosis. However, secondary bronchus mucosa was only slightly damaged. All lesions resolved about three weeks after injury. The results of the fiberoptic bronchoscopy correlated with the clinical course, blood gas analysis, as well as the prognosis.

Affinity of anti-peptide antibodies measured by resonance energy transfer

Because of the increasing use of monoclonal anti-peptide antibodies we have undertaken to formulate a general method for the measurement of intrinsic association constants characterizing complex formation between peptide and antibody. The method is based on the phenomenon of resonance energy transfer between tryptophan-excited antibody and an appropriate fluorophor conjugated to the amino terminus of the peptide. The fluorophor we have employed is 8-(2-N-succinylaminoethylamino)-1-naphthalene-sulfonic acid with an absorption maximum at 344 nm and an emission maximum at 500 nm. The model peptide used was the sequence corresponding to residues 48-60 of the regulatory subunit of aspartyltranscarbamoylase. Three IgG and two IgM affinity-purified monoclonal anti-peptide antibodies were used in the fluorescence titration experiments. A maximum value of 2.1 X 10(6) M-1 was found for the IgG antibodies and a maximum of 2.7 X 10(4) M-1 for the IgM antibodies. These limited results suggest similar behavior for the anti-peptide B cell response with respect to affinity maturation as observed for other specificities. In particular it is likely that the IgM affinities are restricted to the potential available in the germline repertoire of variable region genes and, therefore, express only germline affinities.