The scid recombination-inducible cell line: a model to study DNA-PK-independent V(D)J recombination

To investigate the molecular mechanisms of the variable (diversity) joining (V(D)J) recombination process at an endogenous gene locus, recombination-inducible cell lines were made from both bcl-2-bearing severe combined immune deficiency (scid) homozygous and scid heterozyous (s/ + ) mice by transforming pre-B cells with the temperature-sensitive Abelson murine leukemia virus (ts-Ab-MLV). These transformants can be induced to undergo immunoglobulin light-chain gene rearrangements by incubating them at the non-permissive temperature. In the case of transformed scid cells, a significant amount of hairpin coding ends are accumulated during recombination induction, but few coding joints are generated. After being shifted to the permissive temperature. however, these cells are capable of opening hairpin ends and forming coding joints. Thus, ts-Ab-MLV transformed scid cells can be readily manipulated for both recombination cleavage and end resolution. However, unlike the rapid coding joint formation in s/ + cells that have the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), the process for resolving coding ends in scid cells is slow and error prone, and also appears to be correlated with a reduction in the RAG1/2 expression. Apparently, this process is mediated by a DNA-PK-independent pathway. The fact that the activity of this pathway can be manipulated in vitro makes it possible to delineate the mechanisms in end opening, processing and joining. Therefore, these ts-Ab-MLV transformed scid cell lines offer a model to study the molecular nature as well as the regulation of the DNA-PK-independent pathway in coding end resolution.

Activation of V(D)J recombination induces the formation of interlocus joints and hybrid joints in scid pre-B-cell lines

V(D)J recombination is the mechanism by which antigen receptor genes are assembled. The site-specific cleavage mediated by RAG1 and RAG2 proteins generates two types of double-strand DNA breaks: blunt signal ends and covalently sealed hairpin coding ends. Although these DNA breaks are mainly resolved into coding joints and signal joints, they can participate in a nonstandard joining process, forming hybrid and open/shut joints that link coding ends to signal ends. In addition, the broken DNA molecules excised from different receptor gene loci could potentially be joined to generate interlocus joints. The interlocus recombination process may contribute to the translocation between antigen receptor genes and oncogenes, leading to malignant transformation of lymphocytes. To investigate the underlying mechanisms of these nonstandard recombination events, we took advantage of recombination-inducible cell lines derived from scid homozygous (s/s) and scid heterozygous (s/+) mice by transforming B-cell precursors with a temperature-sensitive Abelson murine leukemia virus mutant (ts-Ab-MLV). We can manipulate the level of recombination cleavage and end resolution by altering the cell culture temperature. By analyzing various recombination products in scid and s/+ ts-Ab-MLV transformants, we report in this study that scid cells make higher levels of interlocus and hybrid joints than their normal counterparts. These joints arise concurrently with the formation of intralocus joints, as well as with the appearance of opened coding ends. The junctions of these joining products exhibit excessive nucleotide deletions, a characteristic of scid coding joints. These data suggest that an inability of scid cells to promptly resolve their recombination ends exposes the ends to a random joining process, which can conceivably lead to chromosomal translocations.

The effects of polar and/or ionizable residues in the core and flanking regions of hydrophobic helices on transmembrane conformation and oligomerization

To explore the influence of amino acid composition on the behavior of membrane-inserted alpha-helices, we examined the behavior of Lys-flanked polyleucyl (pLeu) helices containing a single polar/ionizable residue within their hydrophobic core. To evaluate the location of the helices within the membrane by fluorescence, each contained a Trp residue at the center of the sequence. When incorporated into dioleoylphosphatidylcholine (DOPC) model membrane vesicles, pLeu helices with or without a single Ser, Asn, Lys, or Asp residue in the hydrophobic core maintained a transmembrane state (named the N state) at neutral and acidic pH. In this state, the central Trp exhibited highly blue-shifted fluorescence, and fluorescence quenching by nitroxide-labeled lipids showed it located at the bilayer center. A state in which Trp fluorescence red-shifted by several nanometers (named the B state) was observed above pH 10-11. B state formation appears to result from deprotonation of the flanking Lys residues. Despite the red shift in Trp emission, fluorescence quenching showed that in the B state the Trp at most is only slightly shallower than in the N state, suggesting the B state also is a transmembrane or near-transmembrane structure. The B state is characterized by increased helix oligomerization, as shown by the dependence of Trp lambda(max) on the concentration of the peptide within the bilayer at high pH. The pLeu peptide with a Asp residue in the core underwent a pH-dependent transition at a lower pH than the other peptides (pH 8-9). At high pH, it exhibited both a more highly red-shifted fluorescence and shallower Trp location than the other peptides. This state (named the S state) did not exhibit a concentration-dependent Trp lambda(max). We attribute S state behavior to the formation of a charged Asp residue at high pH, and a consequent movement of the Asp toward the membrane surface, resulting in the formation of a nontransmembrane state. We conclude that a polar or ionizable residue can readily be tolerated in a single transmembrane helix, but that the charges on ionizable residues in the core and regions flanking the helix significantly modulate the stability of transmembrane insertion and/or helix-helix association.

Brain tumor invasion rate measured in vitro does not correlate with Ki-67 expression

The need for more accurate prediction of the biological behavior of brain tumors has lead to the use of immunohistochemical methods for assessment of proliferating cell nuclear antigens such as Ki-67. There is a variable association of glioma Ki-67 labeling index with patient survival. Brain invasion by individual tumor cells also defines biological aggressiveness, and can be assessed in vitro. Further, proliferation and migration seem to be mutually exclusive behaviors for a given cell at a point in time. We studied the relationship between Ki-67 labeling index and invasion rate in a group of 10 gliomas, and 2 meningiomas. Human tumor spheroids obtained from operative specimen were co-cultured with fetal rat brain aggregates, and invasion rate was measured by confocal microscopic observation. There was no correlation between two measures of invasion and Ki-67 labeling. This finding supports the dichotomous nature of glioma proliferation and invasion, and may in part explain the limited usefulness of proliferation marker labeling.

The value of sonohysterography combined with cytological analysis of the fluid retrieved from the endometrial cavity in predicting histological diagnosis

OBJECTIVE

The purpose of the study was to assess the efficacy of sonohysterography combined with cytological analysis of the fluid retrieved from the endometrial cavity in predicting histological diagnosis.

STUDY DESIGN

A prospective study was conducted comparing sonohysterography combined with endometrial washings for cytology with histological evaluation after surgical procedures. Of 152 patients referred for sonohysterography, 87 were premenopausal and 65 were postmenopausal. Some of the injected fluid was aspirated for cytological analysis. Sixty-one patients (40%) underwent surgical hysteroscopy and eight (5%) had dilatation and curettage as a result of the sonohysterographic findings. Histological diagnoses were compared with the sonohysterographic and cytological findings.

RESULTS

In 99 (65%) patients, sonohysterography demonstrated endometrial polypoid lesions. Only 54 endometrial cavitary lesions were confirmed pathologically. Epithelial cells with atypia were more often found in patients without (five of 53) than in those with (two of 99) an endometrial polyp (p < 0.05). Only one out of nine cases of histological diagnosis of hyperplasia was predicted cytologically.

CONCLUSIONS

The addition of cytological analysis of the fluid retrieved from the endometrial cavity during sonohysterography did not contribute to the prediction of benign histological diagnosis of endometrial hyperplasia.

Control of the transmembrane orientation and interhelical interactions within membranes by hydrophobic helix length

We examined the effect of the length of the hydrophobic core of Lys-flanked poly(Leu) peptides on their behavior when inserted into model membranes. Peptide structure and membrane location were assessed by the fluorescence emission lambdamax of a Trp residue in the center of the peptide sequence, the quenching of Trp fluorescence by nitroxide-labeled lipids (parallax analysis), and circular dichroism. Peptides in which the hydrophobic core varied in length from 11 to 23 residues were found to be largely alpha-helical when inserted into the bilayer. In dioleoylphosphatidylcholine (diC18:1PC) bilayers, a peptide with a 19-residue hydrophobic core exhibited highly blue-shifted fluorescence, an indication of Trp location in a nonpolar environment, and quenching localized the Trp to the bilayer center, an indication of transmembrane structure. A peptide with an 11-residue hydrophobic core exhibited emission that was red-shifted, suggesting a more polar Trp environment, and quenching showed the Trp was significantly displaced from the bilayer center, indicating that this peptide formed a nontransmembranous structure. A peptide with a 23-residue hydrophobic core gave somewhat red-shifted fluorescence, but quenching demonstrated the Trp was still close to the bilayer center, consistent with a transmembrane structure. Analogous behavior was observed when the behavior of individual peptides was examined in model membranes with various bilayer widths. Other experiments demonstrated that in diC18:1PC bilayers the dilution of the membrane concentration of the peptide with a 23-residue hydrophobic core resulted in a blue shift of fluorescence, suggesting the red-shifted fluorescence at higher peptide concentrations was due to helix oligomerization. The intermolecular self-quenching of rhodamine observed when the peptide was rhodamine-labeled, and the concentration dependence of self-quenching, supported this conclusion. These studies indicate that the mismatch between helix length and bilayer width can control membrane location, orientation, and helix-helix interactions, and thus may mismatch control both membrane protein folding and the interactions between membrane proteins.

Morphometric studies of secretory granule formation in mouse pancreatic acinar cells. Dissecting the early structural changes following pilocarpine injection

Secretory granule formation in pancreatic acinar cells is known to involve massive membrane flow. In previous studies we have undertaken morphometry of the regranulation mechanism in these cells and in mast cells as a model for cellular membrane movement. In our current work, electron micrographs of pancreatic acinar cells from ICR mice were taken at several time points after extensive degranulation induced by pilocarpine injection in order to investigate the volume changes of rough endoplasmic reticulum (RER), nucleus, mitochondria and autophagosomes. At 2-4 h after stimulation, when the pancreatic cells demonstrated a complete loss of granules, this was accompanied by an increased proportion of autophagosomal activity. This change primarily reflected a greatly increased proportion of profiles retaining autophagic vacuoles containing recognisable cytoplasmic structures such as mitochondria, granule profiles and fragments of RER. The mitochondrial structures reached a significant maximal size 4 h following injection (before degranulation 0.178 +/- 0.028 microm3; at 4 h peak value, 0.535 +/- 0.109 microm3). Nucleus size showed an early volume increase approaching a maximum value 2 h following degranulation. The regranulation span was thus divided into 3 stages. The first was the membrane remodelling stage (0-2 h). During this period the volume of the RER and secretory granules was greatly decreased. At the intermediate stage (2-4 h) a significant increase of the synthesis zone was observed within the nucleus. The volume of the mitochondria was increasing. At the last step, the major finding was a significant granule accumulation in parallel with an active Golgi zone.

A 30s PAS stain for frozen section analysis of surgical margins of vulvectomy in Paget's disease

Application of a modified periodic-acid Schiff's procedure (PAS) technique in frozen section analysis of surgical margins of vulvectomy specimen in Paget's disease is described. The reaction obtained using a microwave procedure takes only 30 seconds. This method was found to be useful in identifying Paget cells on the margins thought to be free of disease by conventional histological evaluation.

Transmembrane orientation of hydrophobic alpha-helices is regulated both by the relationship of helix length to bilayer thickness and by the cholesterol concentration

A fluorescence-based approach to evaluate the regulation of transmembrane orientation of alpha-helices has been developed to examine the behavior of a membrane-inserted alpha-helical peptide with a 19 residue hydrophobic sequence. The emission lambdamax of a Trp residue in the helix was used to determine its location in the bilayer. To calibrate this method, Trp lambdamax and depth (determined by parallax analysis of fluorescence quenching) were measured for transmembrane peptides with Trp at different positions. Transmembrane orientation of the alpha-helix was found to be destabilized by differences between the width of the bilayer and the length of the hydrophobic sequence (i.e., hydrophobic mismatch). When bilayer width exceeded the length of the hydrophobic segment, mismatch induced formation of a nontransmembraneous orientation close to the polar/hydrocarbon interface. By manipulation of bilayer width in situ, it was found that the transmembrane and nontransmembrane orientations could interconvert. Cholesterol altered the transmembrane/nontransmembrane equilibrium to a degree consistent with its tendency to increase bilayer thickness. Evaluation of the energetics of transmembrane vs nontransmembrane insertion showed increased mismatch of a helix with bilayer width by the equivalent of just one hydrophobic residue can destabilize transmembrane orientation by roughly 0.5 kcal/mol. Inclusion of 30 mol % cholesterol in a bilayer can alter transmembrane insertion stability by 3-5 kcal/mol. Thus, physiologically relevant variations in both the hydrophobic helix length/membrane thickness ratio and the cholesterol levels influence transmembrane insertion significantly.

Mucosal addressin cell adhesion molecule-1: a structural and functional analysis demarcates the integrin binding motif

The leukocyte integrin receptor, alpha 4 beta 7, and the mucosal addressin cell adhesion molecule-1 (MAdCAM-1) are postulated to be important in regulating lymphocyte trafficking to normal intestine. Here we provide the first description of MAdCAM-1 expression in inflamed intestine. Using mouse models of experimentally induced colitis, we show a concordant increase in MAdCAM-1 expression associated with increased cellular infiltrates in areas of intestinal inflammation. To understand more of the molecular nature of the interactions between MAdCAM-1 and its leukocyte ligand, the alpha 4 beta 7 integrin receptor, we have analyzed the structural and functional properties of chimeric recombinant MAdCAM-1 proteins in vitro. Using site-directed mutagenesis and molecular modeling, we demarcate the alpha 4 beta 7 binding motif as three linear residues within the C-D loop in the first domain of MAdCAM-1. Mutation of residue L40, D41, or T42 in the first domain completely abrogates alpha 4 beta 7+ cell binding and cellular activation. Mutagenesis of other residues in the first domain do not impact these functions. We have modeled peptides based on the predicted structure of the alpha 4 beta 7 integrin binding motif on MAdCAM-1 and are able to show specific and selective blocking of cell binding. These observations suggest that the amino acid residues LDT on MAdCAM-1 play a role in the interaction with alpha 4 beta 7 in cell adherence and cell activation.

Mucosal addressin cell adhesion molecule-1: a structural and functional analysis demarcates the integrin binding motif

The leukocyte integrin receptor, alpha 4 beta 7, and the mucosal addressin cell adhesion molecule-1 (MAdCAM-1) are postulated to be important in regulating lymphocyte trafficking to normal intestine. Here we provide the first description of MAdCAM-1 expression in inflamed intestine. Using mouse models of experimentally induced colitis, we show a concordant increase in MAdCAM-1 expression associated with increased cellular infiltrates in areas of intestinal inflammation. To understand more of the molecular nature of the interactions between MAdCAM-1 and its leukocyte ligand, the alpha 4 beta 7 integrin receptor, we have analyzed the structural and functional properties of chimeric recombinant MAdCAM-1 proteins in vitro. Using site-directed mutagenesis and molecular modeling, we demarcate the alpha 4 beta 7 binding motif as three linear residues within the C-D loop in the first domain of MAdCAM-1. Mutation of residue L40, D41, or T42 in the first domain completely abrogates alpha 4 beta 7+ cell binding and cellular activation. Mutagenesis of other residues in the first domain do not impact these functions. We have modeled peptides based on the predicted structure of the alpha 4 beta 7 integrin binding motif on MAdCAM-1 and are able to show specific and selective blocking of cell binding. These observations suggest that the amino acid residues LDT on MAdCAM-1 play a role in the interaction with alpha 4 beta 7 in cell adherence and cell activation.

The efficacy of brief group counseling in HIV risk reduction among homosexual Asian and Pacific Islander men

OBJECTIVES

The incidence of AIDS is increasing at a higher rate among homosexual Asian and Pacific Islanders (API) than white homosexual men in the United States. The number of homosexual API men engaging in unsafe sex is increasing at an alarming rate. HIV risk reduction is urgently needed in this population.

SUBJECTS AND METHODS

We developed and evaluated culturally appropriate brief group counseling with 329 self-identified homosexual API recruited in San Francisco between 1992 and 1994. Participants were randomized into a single, 3-h skills training group or a wait-list control group. The intervention consisted of four components: (1) development of positive self-identity and social support, (2) safer sex education, (3) eroticizing safer sex, and (4) negotiating safer sex. Data were collected at baseline and 3 months after the intervention.

RESULTS

Significant reductions in number of sexual partners were observed among all treatment subjects, regardless of ethnicity (P = 0.003). Treatment decreased the number of partners reported at 3-month follow-up by 46% [95% confidence interval (CI), 28-77]. Chinese and Filipino men further benefited from the intervention: treatment subjects from these two ethnic groups reduced unprotected anal intercourse at follow-up by more than half when compared to their counterparts (odds ratio = 0.41; 95% CI, 0.19-0.89; P = 0.024).

CONCLUSIONS

We demonstrated the efficacy of brief group counseling in reducing HIV risk among homosexual API. Cities with significant API populations should adopt culturally tailored skills training as part of HIV prevention strategies for this group of homosexual men.

Prostaglandin E2 production by chronic graft-versus-host disease dermal fibroblasts

Chronic graft versus host disease (cGVHD) across minor histocompatibility barriers is associated with the development of cutaneous fibrosis, disappearance of mast cells and immunosuppression. The idea, which has been the basis of our previous and present studies, is that fibroblasts are not only a target for modulation in cGVHD, but also have effector roles in this condition. In the present study we investigated the production of prostaglandin E2 (PGE2) and of collagen by cultured dermal fibroblasts obtained from cGVHD and control mice. Early in the development of the disease (Day 8) cGVHD fibroblasts generated constitutively more PGE2 (3-fold) than did control fibroblasts. Thereafter, PGE2 production declined to near normal levels by Day 20 post cGVHD induction. On the other hand, at this time point cGVHD fibroblasts displayed an enhanced synthesis of collagen as compared to the control fibroblasts and to earlier time points. Therefore, PGE2 synthesis appears to inversely correlate with collagen synthesis by cGVHD fibroblasts. We propose that fibroblasts may contribute to the development of immunosuppression, which characterizes the early phase of cGVHD.

Ovarian endometrioid carcinoma and endometriosis developing in a postmenopausal breast cancer patient during tamoxifen therapy: a case report and review of the literature

We present the first case of ovarian endometrioid carcinoma and endometriosis in a postmenopausal patient who was treated with tamoxifen for breast cancer. The association with prolonged unopposed estrogen-like stimulation with tamoxifen as a possible factor in the development of ovarian endometrioid carcinoma is discussed.

Cytoplasmic granule formation in mouse pancreatic acinar cells. Evidence for formation of immature granules (condensing vacuoles) by aggregation and fusion of progranules of unit size, and for reductions in membrane surface area and immature granule volume during granule maturation

We used a computer-assisted morphometry approach to analyze quantitatively the process of cytoplasmic granule formation in mouse pancreatic acinar cells stimulated with pilocarpine to induce secretion. Our findings suggest that each condensing vacuole/immature granule of pancreatic acinar cells is formed by the progressive aggregation of 106 to 128 "unit progranules" of narrowly fixed volume, define a range of 7.7 to 9.2 for the factor of volume condensation between the largest immature granules and the mature unit granule, and predict that the formation of a single mature unit granule by the aggregation and fusion of unit progranules involves a net reduction of at least 95% in the amount of membrane surface area associated with these structures.

Triple approach in the diagnosis of dominant breast masses: combined physical examination, mammography, and fine-needle aspiration

In an attempt to reduce the number of breast biopsies done for benign breast disease in patients with breast lumps, we evaluated prospectively the sensitivity and specificity of the combination of three diagnostic modalities: clinical examination, mammography, and fine-needle aspiration cytologic examination (FNA). A total of 234 patients with a breast mass had a physical examination, a mammogram, and FNA, and were listed as malignant/suspicious or benign. All patients underwent a subsequent biopsy: 110 were found to have breast cancer, and 124 had a benign lesion. The sensitivity and specificity of the individual tests were as follows: 89% and 73%, respectively, for mammographic examination; 93% and 97% for FNA cytologic examination; and 89% and 60% for physical examination. For the combined triad of tests, the sensitivity was 100% and specificity 57%. All patients who had breast cancer had positive findings for malignancy in one or more of the diagnostic tests, i.e., 100% sensitively. All patients who had negative findings for malignancy in all three diagnostic tests had benign lesions, i.e., a negative predictive value of 100%. We conclude that breast masses can be diagnosed with a high degree of accuracy by combined physical, mammographic, and fine-needle aspiration cytologic examination. Patients in whom physical examination, mammography, and FNA were negative for malignancy can be safely observed, obviating the need for an open biopsy.

Measurement of kinetic parameters for urea in end-stage renal disease patients using a two-compartment model

Urea kinetic modeling depends critically on the parameters of the model used. When urea is removed during hemodialysis, the kinetic model is quite complex. This experiment describes for the first time the use of injected stable isotope-labeled urea to define kinetics in ESRD patients and compares the magnitude of the two urea compartments in these patients with those of control subjects. Such an experimental approach provides the kinetic data in the most direct manner. A gas chromatograph/mass spectrometer-based assay provided quantitation to as little as 0.2 mol% excess urea. The rapidly equilibrating fraction of the two urea compartments is quantified as 41.2% in ESRD patients and 33.4% in controls (P = 0.24). The rest is in a more slowly equilibrating pool. The urea clearances between these two compartments were near 1 L/min for both sets of subjects. The elimination of urea was due to the metabolic removal of the 15N label in both groups of subjects as well as renal elimination in the controls. The nearly threefold larger clearance (Cl) of labeled urea removal in controls (Cl = 74.6 mL/min) than in ESRD patients (Cl = 25.4 mL/min; P = 0.015) shows the extent to which renal clearance is more important than metabolism. These direct analyses of the fractional volumes and intercompartmental clearances for urea agree closely with previous measurements during high-efficiency hemodialysis and indicate that ESRD patients do not differ significantly from control subjects in these parameters.

Preoperative chemotherapy in the management of intracaval extension of Wilms' tumor

Extension of Wilms' tumor into the renal vein and vena cava complicates the operative treatment of a small but significant number of patients. Two children presented with Wilms' tumor and intracaval tumor extension. After biopsy, both children were given chemotherapy. In one case the tumor completely disappeared from the vena cava, and in the other the tumor regressed substantially, and proximal control became possible at the level of the infrahepatic vena cava. Both children then had an uneventful nephrectomy that was greatly simplified. We conclude that preoperative chemotherapy can induce resolution of intravascular tumor, and may be a useful option in cases of extension of Wilms' tumor into the vena cava.