An analysis of clinical outcomes using color doppler testicular ultrasound for testicular torsion

OBJECTIVES

To delineate the clinical outcomes of color Doppler ultrasound (US) in the equivocal torsion patient.

METHODS

From 1992 to 1997, 130 patients (<23 years old) from 2 institutions underwent US imaging using a 7.5-mHz linear transducer to evaluate an acute scrotum equivocal, or of low suspicion, for torsion. The US reports and hospital charts of these patients were retrospectively reviewed.

RESULTS

After clinical and radiologic evaluation, torsion was excluded in 110 patients without surgical exploration. In 3 patients, intermittent testicular torsion was diagnosed and in 17 patients, emergent exploration was performed for US diagnosis of testicular torsion. Twenty-five patients (22.7%) were subsequently lost to follow-up. Follow-up of 85 patients with US negative for torsion (mean length of follow-up = 466.9 days) revealed no testicular atrophy in 83. Two patients underwent delayed orchiectomy/contralateral orchiopexy for missed testicular torsion. Of 17 patients with US positive for torsion, 9 underwent orchiectomy for a necrotic torsed testis, 7 viable torsed testes were found, and 1 torsed appendix testis was found. Therefore, color Doppler US for the equivocal acute scrotum yielded a 1% false-positive rate, sensitivity of 88.9%, and specificity of 98.8%.

CONCLUSION

When faced with ruling out testicular torsion, it is necessary to integrate the multiple pieces of patient data, knowing that each piece of data may have inaccuracies. With this in mind, this analysis of outcomes verifies that color Doppler US is an excellent adjunctive study in the clinically real situation in which the clinical evaluation is equivocal or low suspicion.

Recognition of tetrahedral 1,10-phenanthroline-cuprous chelates by transcriptionally active complexes does not depend on the sequence of the promoter

BACKGROUND

The open complex formed at the initiation site of transcription within the active site of RNA polymerase is unique to actively transcribing genes and is thus an ideal target for the design of transcription inhibitors. Many redoxactive tetrahedral cuprous chelates of 1,10-phenanthroline (OP) or derivatives cleave the single-stranded template, principally at sequence positions -7 to -3, whereas the redox-inactive tetrahedral cuprous chelate of 2, 9-dimethyl-OP (neocuproine) blocks transcription, but does not cleave. The octahedral (OP)3-Fe2+ chelate has no effect. Different promoters can give different cleavage patterns. We therefore searched for structural determinants of the open complex that are important in the cleavage reaction.

RESULTS

Using site-directed mutagenesis, we systematically altered the nucleotides at the cleavage sites of the Escherichia coli lac UV-5-RNA polymerase open complex (positions -6 to -4), which are highly variable in E. coli promoters. Surprisingly, these changes had little effect on catalytic activity, on transcription inhibition by the cuprous complex of neocuproine and on the cleavage patterns generated by the cuprous chelates of OP derivatives. The scission pattern of a lac UV-5 promoter mutant in which the cleavage sites have the sequence of the trp EDCBA promoter is that of the lac UV-5 promoter, not the trp EDCBA promoter.

CONCLUSIONS

Nucleotide-specific interactions are not responsible for the observed cleavage patterns. The recognition of the tetrahedral OP chelate must be due to a specific structure of the single-stranded regions, determined by RNA polymerase-DNA interactions in the upstream regulatory region.

Human immunodeficiency virus type 1 and 2 Tat proteins specifically interact with RNA polymerase II

The Tat-responsive region (TAR) element is a critical RNA regulatory element in the human immunodeficiency virus (HIV) long terminal repeat, which is required for activation of gene expression by the transactivator protein Tat. Recently, we demonstrated by gel-retardation analysis that RNA polymerase II binds to TAR RNA and that Tat prevents this binding even when Tat does not bind to TAR RNA. These results suggested that direct interactions between Tat and RNA polymerase II may prevent RNA polymerase II pausing and lead to Tat-mediated increases in transcriptional elongation. To test this possibility, we performed protein interaction studies with RNA polymerase II and both the HIV-1 and the closely related HIV-2 Tat protein. These studies indicated that both the HIV-1 and HIV-2 Tat proteins could specifically interact with RNA polymerase II. Mutagenesis of both HIV-1 and HIV-2 Tat demonstrated that the basic domains of both the HIV-1 and HIV-2 Tat proteins were required for this interaction. Furthermore, "far Western" analysis suggested that the largest subunit of RNA polymerase II was the site for interaction with Tat. The interactions between Tat and RNA polymerase II were of similar magnitude to those detected between RNA polymerase II and the cellular transcription factor RAP30, which stably associates with RNA polymerase II during transcriptional elongation. These studies are consistent with the model that RNA polymerase II is a cellular target for Tat resulting in Tat-mediated increases in transcriptional elongation from the HIV long terminal repeat.

Specific binding of RNA polymerase II to the human immunodeficiency virus trans-activating region RNA is regulated by cellular cofactors and Tat

The regulation of human immunodeficiency virus type 1 (HIV-1) gene expression in response to Tat is dependent on an element downstream of the HIV-1 transcriptional initiation site designated the trans-activating region (TAR). TAR forms a stable stem-loop RNA structure in which a 3-nt bulge structure and a 6-nt loop structure are important for Tat activation. In the absence of Tat, the HIV-1 promoter generates so-called short or nonprocessive transcripts terminating at +60, while in the presence of Tat the synthesis of these short transcripts is markedly decreased and transcripts that extend through the 9.0-kb HIV-1 genome are synthesized. Tat effects on transcriptional elongation are likely due to alterations in the elongation properties of RNA polymerase II. In this study we demonstrated that a set of cellular cofactors that modulate the binding of the cellular protein TRP-185 to the TAR RNA loop sequences also functioned to markedly stimulate the specific binding of hypophosphorylated (IIa) and hyperphosphorylated (IIo) RNA polymerase II to TAR RNA. The concentrations of RNA polymerase II required for this interaction with TAR RNA were similar to those required to initiate in vitro transcription from the HIV-1 long terminal repeat. RNA gel retardation analysis with wild-type and mutant TAR RNAs indicated that the TAR RNA loop and bulge sequences were critical for the binding of RNA polymerase II. The addition of wild-type but not mutant Tat protein to gel retardation analysis with TAR RNA and RNA polymerase II resulted in the loss of binding of RNA polymerase II binding to TAR RNA. These results suggest that Tat may function to alter RNA polymerase II, which is paused due to its binding to HIV-1 TAR RNA with resultant stimulation of its transcriptional elongation properties.

Structure of the Escherichia coli Fis-DNA complex probed by protein conjugated with 1,10-phenanthroline copper(I) complex

The Escherichia coli Fis (factor for inversion stimulation) protein functions in many diverse biological systems including recombination, transcription, and DNA replication. Although Fis is a site-specific DNA-binding protein, it lacks a well-defined consensus recognition sequence. The electrophoretic mobility of Fis-DNA complexes, along with considerations of the Fis crystal structure, indicates that significant deformation of DNA occurs upon Fis binding. To investigate the structure of Fis-DNA complexes, the chemical nuclease 1,10-phenanthroline-copper complex (OP-Cu) has been linked to four specific sites within the Fis DNA-binding domain. Two of these Fis-OP derivatives were active in cleaving DNA. The scission patterns obtained on four different Fis binding sites indicate that Fis positions itself on these highly divergent DNA sequences in a very similar fashion. The patterns of cleavage of a derivative at Asn-98 generally support a model of a Fis-DNA complex that contains specific bends within the core-recognition sequence. Data from a second Fis-OP derivative at Asn-73 provides evidence for greater wrapping of flanking DNA around the sides of the Fis protein than was previously postulated. The cleavage efficiency of flanking segments varies, suggesting that the extent of DNA wrapping is sequence dependent. Specific amino acids on Fis are implicated in promoting this DNA wrapping.

tat regulates binding of the human immunodeficiency virus trans-activating region RNA loop-binding protein TRP-185

The TAR element extending from -17 to +80 in the human immunodeficiency virus long terminal repeat (HIV LTR) is required for activation of gene expression by the tat trans-activator protein. TAR RNA forms a stable stem-loop structure, and mutagenesis studies indicate that the stem structure, the primary sequence of the loop, and the bulge element are the major determinants for tat activation. RNA gel retardation analysis demonstrates that both tat and cellular proteins bind to TAR RNA, but the mechanism by which these proteins increase HIV gene expression is unknown. We have fractionated HeLa cell nuclear extracts in an attempt to identify cellular proteins that bind to TAR RNA and are involved in regulating HIV gene expression. RNA gel retardation and UV cross-linking reveal that a cellular protein of 185 kD, which we designate TAR RNA-binding protein 185 (TRP-185), binds with both high affinity and marked specificity to TAR RNA. RNA gel retardation and competition analyses indicate that TRP-185 binding is strongly dependent on the TAR RNA loop sequences. The binding of TRP-185 is modulated by both a set of cellular cofactors and the tat protein. Highly purified preparations of TRP-185 are capable of activating in vitro transcription of wild-type, but not mutated, HIV LTR chloramphenicol acetyltransferase (CAT) constructs. These results characterize a positively acting cellular RNA-binding factor, TRP-185, which is involved in the regulation of HIV gene expression.

Immunoglobulin enhancer and promoter motifs 5' of the B29 B-cell-specific gene

B29 is a B-cell-specific member of the immunoglobulin gene superfamily that is expressed throughout B-cell development beginning with the earliest precursor B cells undergoing immunoglobulin heavy-chain gene segment rearrangements. We have analyzed the region upstream of the B29 gene to identify DNA sequences involved in transcriptional regulation of this gene. The B29 gene lacks a TATA box and transcription is initiated at multiple sites. The B29 gene sequence 5' of these transcription start sites contains six promoter and enhancer motifs known to control immunoglobulin gene transcription. The most notable is a perfect octamer (5'-ATTTGCAT-3'), which binds the Oct-2 B-cell-specific transcription factor and thereby can account for the tissue-specific expression of this gene.

Xeroradiography in the diagnosis of facial fractures

Xeroradiography, because of its unique phenomenon of "edge enhancement," has some advantages for assessing facial fractures. In 17 of the 19 patients in our pilot study group, this technique was as valuable as, or more so than, plain films. The xerogram done prior to laminagraphy is a useful "map" for the radiologist to use in planning laminagraphic cuts. For the surgeon this technique offers a relatively accurate diagnostic tool, useful early after the facial injury.