Hepatic transcatheter arterial chemoembolization alternating with systemic protracted continuous infusion 5-fluorouracil for gastrointestinal malignancies metastatic to liver: a phase II trial of the Puget Sound Oncology Consortium (PSOC 1104)

We assessed a regimen of alternating regional and systemic therapy in patients with gastrointestinal malignancies with liver-dominant metastases for feasibility, toxicity, response rate, response duration, patterns of progression, and progression-free and overall survival. Regional therapy comprised selective hepatic transcatheter arterial chemoembolization (TACE) using a suspension of cisplatin and particulate polyvinyl alcohol. This procedure was delivered between cycles of protracted continuous infusion 5-fluorouracil (PCI-5FU) as systemic chemotherapy. Patient eligibility criteria included: (a) having histologically documented adenocarcinoma arising from a gastrointestinal primary site with unresectable liver metastases bidimensionally measurable on computerized tomography scan; (b) age greater than 18 years; and (c) performance status 0-2 (Zubrod). PCI-5FU (250 mg/m2/day) was administered i.v. for 28 days, followed by the first TACE (TACE 1) delivered to the hepatic artery supplying the lobe with the greatest tumor burden. Restaging was performed before TACE 2 and TACE 3, which followed at monthly intervals. PCI-5FU for 21 days was sandwiched between each of the TACE treatments. After the final TACE, maintenance PCI-5FU was given for 28 days of each 35-day cycle until toxicity or progression. Between December 23, 1991, and January 19, 1995, 32 patients were registered in this trial, of whom 27 were eligible; 20 completed one or more treatment cycles and were evaluable for radiographic response. Patients with colorectal liver metastases predominated (74%). Twelve (44%) of 27 patients had failed one or more prior treatment regimens. There were no treatment-related deaths, and hematological and hepatic toxicities were generally manageable and reversible. Two patients, however, developed hepatic abscesses requiring drainage, and one patient developed an infarcted gallbladder, which necessitated cholecystectomy. There were no patients with complete responses; there were 8 (40%) with partial responses, 4 (20%) with minor responses, 2 (10%) with stable disease, and 6 (30%) who progressed on the treatment. The median duration of response for partial responders was 4.2 months (127 days; range, 56-245 days). The median reduction in carcinoembryonic antigen for responders was 87.5%. Two patients underwent subsequent resection of residual metastases; one of them is still alive at 58.4 months follow-up. The predominant site of disease progression was the liver; 25% of the patients progressed in extrahepatic sites. The median overall survival for the whole group is 14.3 months (95% confidence interval, 7.2-16.2). Actuarial overall survival for the whole group at 1 year and 2 years is 57 and 19%, respectively. Alternating systemic PCI-5FU and regional TACE (cisplatin/polyvinyl alcohol) is an active and feasible regimen with manageable toxicities in patients with metastatic gastrointestinal malignancies with liver-dominant disease and merits further investigation. The complications seen were in line with those reported at other specialized centers.

Treatment of inferior vena cava anastomotic stenoses with the Wallstent endoprosthesis after orthotopic liver transplantation

PURPOSE

To evaluate the efficacy of the Wallstent endoprosthesis for treatment of stenotic or occlusive inferior vena cava (IVC) lesions refractory to balloon angioplasty in patients after orthotopic liver transplantation.

MATERIALS AND METHODS

Wallstent endoprostheses were implanted in six patients with IVC anastomotic stenoses or occlusions that were refractory to balloon angioplasty. Follow-up included both duplex ultrasound (US) and clinical evaluations.

RESULTS

Ten stents were successfully implanted in six patients. Five of six patients (83%) demonstrated primary patency on duplex US for a mean period of 11 months (range, 4-17 months). One patient's symptoms recurred within 3 weeks after intervention. This patient underwent repeated stent placement. Follow-up duplex US in this patient demonstrated primary assisted patency at 7 months. Mean clinical follow-up was 12 months (range, 7-18 months). Other than the previously described case, no patient developed recurrent symptoms of IVC stenosis or occlusion. Two patients who experienced hemorrhagic complications secondary to anticoagulation were treated successfully.

CONCLUSIONS

The Wallstent endoprosthesis is a useful adjunct for treatment of IVC stenosis or occlusions in patients who have undergone orthotopic liver transplantation when these lesions are refractory to simple balloon angioplasty.

Current status of transjugular intrahepatic portosystemic shunts

The use of the transjugular intrahepatic portosystemic shunt (TIPS) has emerged as an important nonoperative modality for variceal bleeding, intractable ascites, and for selected cases of hepatic venous obstruction. We believe that TIPS should be viewed as a 'bridge' to liver transplantation and should be carried out only in experienced centres. The adverse haemodynamic changes on the cardiopulmonary system after TIPS should be borne in mind. Prospective trials to evaluate the role of TIPS versus sclerotherapy in variceal bleeding will be watched with interest. There is, however, an urgent need to improve long-term results of TIPS as stent thrombosis and stenosis occur frequently. We advocate routine surveillance to detect these problems at an early stage.

Imaging of acute thoracic aortic injury due to blunt trauma: a review

Much recent work on the use of computed tomography (CT) and transesophageal echocardiography in screening for and facilitating the diagnosis of acute thoracic aortic injury in the patient with blunt chest trauma has shown favorable results. This has led some physicians to question whether conventional thoracic aortography is still the reference standard. The purpose of this review article is to summarize the epidemiology and pathophysiology of acute thoracic aortic injury, the current status of the individual imaging modalities in use, and the surgeon's perspective. Despite a burgeoning literature and a confounding array of clinical and imaging advances, timely diagnosis of acute thoracic aortic injury remains a challenge. To overcome this problem, some trauma centers have used CT, transesophageal echocardiography, or both, in their diagnostic algorithm for acute thoracic aortic injury. These diagnostic algorithms are individually tailored by each institution and are still under investigation; therefore, no definite conclusions can be reached.

Carbon dioxide angiography of the transplanted kidney: technical considerations and imaging findings

OBJECTIVE

We evaluated the usefulness of carbon dioxide as the primary contrast material for renal transplant arteriography.

CONCLUSION

Carbon dioxide accurately showed artery pathology including anastomotic and intrarenal stenoses, arteriovenous shunting, and diffuse arterial disease from chronic transplant rejection. Using carbon dioxide as a contrast agent reduced the volume of iodinated contrast material that needed to be used. There was no procedure-associated nephrotoxicity.

Gadolinium-enhanced three-dimensional MR angiography of the aorta and peripheral arteries: evaluation of a multistation examination using two gadopentetate dimeglumine infusions

OBJECTIVE

Three-dimensional gadolinium-enhanced MR angiography is a rapid and accurate method that can at times image only a limited amount of anatomy during an examination. We evaluated a technique that doubled the anatomy imaged by obtaining two separate gadolinium-enhanced MR angiograms during a single examination.

MATERIALS AND METHODS

Twenty-three patients referred for MR evaluation of aortic or peripheral vascular disease underwent two successive gadolinium-enhanced three-dimensional MR angiographic examinations during a single MR examination. An injection of 15 ml of gadopentetate dimeglumine was used for the first MR angiogram, and 25 ml was used for the second MR angiogram. The angiograms were quantitatively and qualitatively evaluated to determine the effect of residual gadolinium from the initial MR angiogram on the second angiogram.

RESULTS

The two studies depicted either the entire aorta to the femoral arteries (n = 10) or the distal aorta to the popliteal arteries (n = 13). The total mean gadolinium dose was 0.245 mmol/kg per patient. An average of 15 min elapsed between injections. The value of arterial signal-to-noise ratio (mean, 48.8 versus 56.4) and artery-to-vein contrast-to-noise ratio (mean, 45.5 versus 49.0) increased between the first and second angiograms, respectively. Residual gadolinium elevated the values for venous signal-to-noise ratio (mean, 2.3 versus 7.2) and background-to-muscle signal-to-noise ratio (mean, 5.5 versus 10.1) on the second MR angiogram. Qualitative evaluation by three observers showed no significant differences in diagnostic usefulness or overall image quality between the first and second MR angiograms.

CONCLUSION

The use of two low-dose gadolinium-enhanced three-dimensional MR angiograms during a single examination is a feasible approach to increase anatomic coverage when performing gadolinium-enhanced three-dimensional MR angiography of the aorta and peripheral vessels. Although background enhancement is slightly elevated on the second angiogram, such enhancement does not significantly change diagnostic usefulness or overall image quality.

Catheter-directed thrombolysis in the treatment of phlegmasia cerulea dolens

Phlegmasia cerulea dolens is a potentially devastating complication of extensive deep venous thrombosis for which there is currently no consensus for treatment. Heparin anticoagulation, surgical thrombectomy, thrombolytic therapy, fasciotomy, and amputation have each been advocated. We present two cases of phlegmasia cerulea dolens successfully treated with catheter-directed venous thrombolytic therapy.

Evolution of the interaction between Hox genes and a downstream target

Segmental identities along the insect body depend on the activities of Hox genes [1,2]. In Drosophila melanogaster, one well-studied Hox regulatory target is Distal-less (Dll), which is required for the development of distal limb structures [3]. In abdominal segments, Dll transcription is prevented when Hox proteins of the Bithorax Complex (BX-C) bind to cis-regulatory elements upstream of the Dll transcription start site [4,5]. Previous evolutionary comparisons of gene expression patterns suggest that this direct repression is conserved between Diptera and Lepidoptera, but is absent in the Crustacea [6,7]. We examined gene expression patterns in three orders of hexapods, all of which develop abdominal appendages, in order to determine when the strong repressive interaction between BX-C proteins and Dll appeared during evolution. In each of the species examined, Dll expression was initiated in abdominal cells despite the presence of high levels of BX-C proteins. It appears that the strong repressive effects of BX-C proteins on Dll expression arose relatively late in insect evolution. We suggest that the regulatory interaction between the BX-C genes and Dll has evolved within the hexapods in a complex, segment-specific manner.

Functional analysis of eve stripe 2 enhancer evolution in Drosophila: rules governing conservation and change

Experimental investigations of eukaryotic enhancers suggest that multiple binding sites and trans-acting regulatory factors are often required for wild-type enhancer function. Genetic analysis of the stripe 2 enhancer of even-skipped (eve), an important developmental gene in Drosophila, provides support for this view. Given the importance of even-skipped expression in early Drosophila development, it might be predicted that many structural features of the stripe 2 enhancer will be evolutionarily conserved, including the DNA sequences of protein binding sites and the spacing between them. To test this hypothesis, we compared sequences of the stripe 2 enhancer between four species of Drosophila: D. melanogaster, D. yakuba, D. erecta and D. pseudoobscura. Our analysis revealed a large number of nucleotide substitutions in regulatory protein binding sites for bicoid, hunchback, Kruppel and giant, as well as a systematic change in the size of the enhancer. Some of the binding sites in D. melanogaster are either absent or modified in other species. One functionally important bicoid-binding site in D. melanogaster appears to be recently evolved. We, therefore, investigated possible functional consequences of sequence differences among these stripe 2 enhancers by P-element-mediated transformation. This analysis revealed that the eve stripe 2 enhancer from each of the four species drove reporter gene expression at the identical time and location in D. melanogaster embryos. Double staining of native eve protein and transgene mRNA in early embryos showed that the reporter gene mimicked native eve expression and, in every case, produced sharply defined stripes at the blastoderm stage that were coincident with eve stripe 2 protein. We argue that stripe 2 eve expression in Drosophila evolution can be viewed as being under constant stabilizing selection with respect to the location of the anterior and posterior borders of the stripe. We further hypothesize that the stripe 2 enhancer is functionally robust, so that its evolution may be governed by the fixation of both slightly deleterious and adaptive mutations in regulatory protein binding sites as well as in the spacing between binding sites. This view allows for a slow but continual turnover of functionally important changes in the stripe 2 enhancer.

Effects of transjugular intrahepatic portosystemic shunts on hepatic metabolic function determined with serial monitoring of arterial ketone bodies

PURPOSE

To investigate the effects of transjugular intrahepatic portosystemic shunt (TIPS) on hepatic metabolic function by measuring serial arterial ketone body ratio (acetoacetate/-hydroxybutyrate; AKBR).

MATERIAL AND METHODS

The arterial blood of 30 TIPS patients was assayed before TIPS, 30 minutes after TIPS, and 24 hours after TIPS for acetoacetate, beta-hydroxybutyrate, and glucose. The authors compared the AKBR values to clinical outcome stratified by Child class, emergent versus elective TIPS, and before-TIPS AKBR value < or = 0.5 versus before-TIPS AKBR value > 0.5.

RESULTS

A significant change was noted between the AKBR values obtained before TIPS and values 30 minutes after TIPS (0.76 +/- 0.09 vs 0.61 +/- 0.05, P < .05) and between 30 minutes and 24 hours after TIPS (0.81 +/- 0.10, P < .001), but not between the value obtained before TIPS and that obtained 24 hours after TIPS. The 30-day mortality rate in emergency TIPS patients was 50% compared to 7% in the elective TIPS patients (P < .01). The pre-TIPS AKBR values were significantly suppressed in the emergency TIPS patients compared to the elective TIPS patients (0.56 +/- 0.04 vs 0.99 +/- 0.17, P < .005). The 30-day mortality rate in patients with a pre-TIPS AKBR value < or = 0.5 was 75%, which was significantly higher than the 14% rate in patients with a pre-TIPS AKBR value > 0.5 (P < .01).

CONCLUSION

A low pre-TIPS AKBR may be predictive of poor outcome after TIPS. Furthermore, AKBR may be of value in determining the timing for performing an elective TIPS.

Rotational imaging of complex acetabular fractures

Understanding complex acetabular fractures is difficult and may require three-dimensional reformatted computed tomographic (CT) images. This paper evaluates a technique, digital rotational imaging (DRI), that displays multiple oblique images of the pelvis and acetabulum. When viewed statically, DRI provides optimal iliac and obturator oblique projections, often differing in obliquity from the conventional 45-degree orthogonal views. Dynamic DRI viewing in rapid sequence provides a three-dimensional effect that improves perception of acetabular fracture relationships.

Renal artery origins: best angiographic projection angles

PURPOSE

To determine the best projection angles for imaging the renal artery origins in profile.

MATERIALS AND METHODS

A mathematical model of the anatomy at the renal artery origins in the transverse plane was used to analyze the amount of aortic lumen that projects over the renal artery origins at various projection angles. Computed tomographic (CT) angiographic data about the location of 400 renal artery origins in 200 patients were statistically analyzed.

RESULTS

In patients with an abdominal aortic diameter no larger than 3.0 cm, approximately 0.5 mm of the proximal part of the renal artery and origin may be hidden from view if there is a projection error of +/-10 degrees from the ideal image. A combination of anteroposterior and 20 degrees and 40 degrees left anterior oblique projections resulted in a 92% yield of images that adequately profiled the renal artery origins. Right anterior oblique projections resulted in the least useful images.

CONCLUSION

An error in projection angle of +/-10 degrees is acceptable for angiographic imaging of the renal artery origins. Patients sex, site of interest (left or right artery), and local diameter of the abdominal aorta are important factors to consider.

Crustacean appendage evolution associated with changes in Hox gene expression

Homeotic (Hox) genes specify the differential identity of segments along the body axis of insects. Changes in the segmental organization of arthropod bodies may therefore be driven by changes in the function of Hox genes, but so far this has been difficult to demonstrate. We show here that changes in the expression pattern of the Hox genes Ubx and AbdA in different crustaceans correlate well with the modification of their anterior thoracic limbs into feeding appendages (maxillipeds). Our observations provide direct evidence that major morphological changes in arthropod body plans are associated with changes in Hox gene regulation. They suggest that homeotic changes may play a role in the normal process of adaptive evolutionary change.

Genetic separation of the neural and cuticular patterning functions of gooseberry

In addition to their role in the specification of the epidermal pattern in each segment, several segment polarity genes, including gooseberry (gsb), specify cell fate in the Drosophila central nervous system (CNS). Analyses of the gsb CNS phenotype have been complicated by the fact that the previously available gsb mutants, all caused by cytologically visible deficiencies, have severe segmentation defects and also lack a number of additional genes. We have characterized two novel gsb mutants which, due to their hypomorphic nature, have CNS defects, but have only weak or no segmentation defects. These gsb alleles, as well as gsb rescue experiments, have allowed us to determine which aspects of the deficiency mutant phenotypes can be attributed to loss of gsb. gsb mutants lack U and CQ neurons, have duplicated RP2 neurons, and display posterior commissure defects. gsb neural defects, as well as the gsb cuticle defect, are differentially sensitive to the level of functional Gsb. We have used one of the novel gsb alleles in order to understand the genetic interactions between gsb, wingless (wg), and patched (ptc) during the patterning of the ventral neuroectoderm. In contrast to epidermal patterning, where Gsb is required to maintain wg transcription, we find that Gsb antagonizes the Wg signal that confers neuroblast (NB) 4–2 fate.

Krüppel, a Drosophila segmentation gene, participates in the specification of neurons and glial cells

We report that the Drosophila segmentation gene Krüppel (Kr) is expressed in neural precursor cells, neurons and glial cells at different stages of neurogenesis and that Kr mutants develop aberrant peripheral (PNS) and central (CNS) nervous systems. Expression derived from a Kr minigene rescues the segmentation defects but these embryos continue to lack most of the neural Kr activity. Phenotypic analysis of the rescued embryos indicates that, in addition to overall effects on the PNS and CNS structure via its segmentation role, Kr expression in the nervous system is functionally required for establishing particular neural and glial fates.

Neo-Darwinian developmental evolution: can we bridge the gap between pattern and process?

In the past decade, there has been a surge of renewed interest in the study of developmental evolution. One approach that has been taken is to examine the expression patterns of a candidate gene in divergent taxa and to use these results to infer which aspects of a particular genetic pathway are either conserved or altered. Here we consider this approach from the perspective of the neo-Darwinian paradigm for evolutionary change. If adaptations are typically composed of large numbers of gene substitutions that are of small effect individually, then the candidate gene approach is unlikely to bridge the gap between developmental pattern and evolutionary process: changes in gene expression patterns may identify the steps in developmental pathways that have been altered during evolution but fail to identify the actual genetic changes that have occurred. On the other hand, there is growing support for the view that adaptations often involve large-effect genes; fortunately, the candidate gene approach is well suited to this type of genetic architecture.

Imaging of complications in liver transplantation

Hepatic transplantations are being performed with increasing frequency, leading to greater demand for accurate evaluation of related complications. Ultrasonography (US) is the primary screening technique for detection of vascular complications of hepatic transplantation: angiography is used to confirm the US findings or when the US study is suboptimal. Hepatic artery thrombosis, the most common (as high as 42% of pediatric cases; 4%-12% of adult cases) and important vascular complication, may be associated with bilomas, infarcts, or abscesses at gray-scale US and absence of proper hepatic and intrahepatic arterial flow at Doppler analysis. Hepatic artery stenosis (seen in 11% of cases) is suspected if a focal accelerated velocity of greater than 2-3 m/sec with turbulence is seen at or distal to the stenosis or if a tardus parvus pattern of intrahepatic arterial flow is seen. In cases of inferior vena cava thrombosis and stenosis, US may show echogenic thrombus or obvious narrowing, with a substantially increased flow velocity through the stenosis or reversal of flow in the hepatic veins. Biliary complications occur relatively often (13%-25% of cases) after liver transplantation; bile leakage and biliary stricture, the most common biliary complications, are seen as a fluid collection and a stricture, respectively. Although acute rejection is one of the most serious complications affecting graft survival, it cannot be reliably detected with available diagnostic tests or radiologic methods.

Posttraumatic Budd-Chiari syndrome treated with thrombolytic therapy and angioplasty

Injury of the hepatic veins or suprahepatic inferior vena cava is a rare cause of Budd-Chiari syndrome. Treatment of this syndrome has primarily involved hepatic venous decompression with a variety of portosystemic shunts. We report a case of thrombosis of the inferior vena cava after blunt injury managed with interventional radiologic techniques.

Digital subtraction rotational angiography for aneurysms of the intracranial anterior circulation: injection method and optimization

PURPOSE

To optimize parameters of rotational angiography for examination of the internal carotid circulation; to compare rotational angiography with standard digital subtraction angiography (DSA) in the evaluation of aneurysms of the intracranial internal carotid circulation; and to determine tolerance and safety limits of prolonged internal carotid injection angiography.

METHODS

Rotational angiograms were obtained during injection of the internal carotid circulation as part of the clinical angiographic evaluation of aneurysms in 41 patients. Injection rates, X-ray delays, and fields of view were studied retrospectively. Findings at rotational angiography and standard DSA were compared. Nonionic contrast material was injected over 6 seconds, and patients were studied before and after prolonged injection angiography by physical and laboratory examination, including measurement of blood pressure, pulse, and intracranial pressure.

RESULTS

Vascular conspicuity was equivalent at carotid injection rates of 4 and 5 mL/s delivered over 6 seconds. At 3 mL/s, more image manipulation was required to see small vascular structures. One-second X-ray delay combined with 6-second injection duration provided the best arterial depiction of intracranial vessels from start to end of rotational angiography. Maximal rotational resolution was with a 17-cm field of view. Identification of aneurysms and small vessels was equivalent at all injection rates. Aneurysm detection was equivalent with rotational angiography and DSA. In 9 of 31 aneurysms, the neck was defined more clearly with rotational angiography than with DSA, compared with 2 of 31 that were seen better with DSA. Aneurysms of the intracranial internal carotid circulation were seen with rotational angiography and not DSA in 12 of 41 cases. No change was noted in clinical or laboratory findings.

CONCLUSION

Rotational angiography provided better definition of the aneurysmal neck and greater clarity of aneurysms than did DSA; it also improved the level of confidence in predicting the presence or absence of aneurysms, especially in the anterior communicating artery; however, in our small series it did not significantly increase the detection of aneurysms. Prolonged injection angiography was well tolerated in all patients.

Sequence and expression of grasshopper antennapedia: comparison to Drosophila

We have cloned and characterized the Antennapedia (Antp) gene from the grasshopper Schistocerca americana. The Antennapedia protein contains seven blocks of sequence, including the homeodomain, that are conserved in the homologous proteins of other insects, interspersed with (usually repetitive) sequences unique to each species. There is no similarity between 1.8 kb of 3' untranslated sequence in grasshopper and Drosophila. We examined Antennapedia protein expression in grasshopper using an antibody raised against a grasshopper fusion protein and reexamined its expression in Drosophila using several different antibodies. Early patterns of expression in the two insects are quite different, reflecting differing modes of early development. However, by the germband stage, expression patterns are quite similar, with relatively uniform epithelial expression throughout the thoracic and abdominal segments which later retracts to the thorax. Expression is observed in muscle pioneers, the peripheral nervous system, and the central nervous system (CNS). In the CNS expression is initially limited to a few neurons, but eventually becomes widespread. Both insects show strong expression in certain homologous identified neurons and similar temporal modulation of expression.

The meaning of a nonspecific abdominal gas pattern

RATIONALE AND OBJECTIVES

The radiology report is the primary means of communication between the radiologist and the referring physician. A lack of precision in this report may adversely affect patient care. We examined how radiologists would define "nonspecific abdominal gas pattern" and how referring physicians would perceive the meaning.

METHODS

A questionnaire was distributed to radiologists and referring physicians in Flint, Michigan. They were asked to categorize their definition or interpretation, respectively, of "nonspecific abdominal gas pattern" into "normal"; "either normal or abnormal"; or "abnormal, representing either mechanical obstruction or adynamic ileus."

RESULTS

Thirty-three radiologists responded, 23 (69.7%) of whom used the term. One hundred fifty-seven referring physicians responded, 127 of whom assigned a specific definition to the term. Using a 2 x 3 chi-square test (df = 2), we found a statistically significant difference (p < .03) between the distribution of the meaning of the term between radiologists and their referring physicians.

CONCLUSION

The term "nonspecific abdominal gas pattern" should be abandoned because it may signify a normal condition or a pathologic state. We found the definition to be dichotomous and asynchronous between radiologists and their referring physicians.

Scintigraphic detection of sequential symmetrical metatarsal stress fractures

A patient with complaints of right foot pain and previous normal radiographs had an abnormal three-phase bone scan consistent with a second metatarsal stress fracture. Subsequent radiographs confirmed this diagnosis. Two months later, the patient developed pain in his left foot, and again initial radiographs were noncontributory. A later bone scan revealed a left second metatarsal stress fracture. The results in this case reemphasize the value of bone scintigraphy in patients with foot pain and no bone abnormalities on plain radiographs.

The novel homeodomain gene buttonless specifies differentiation and axonal guidance functions of Drosophila dorsal median cells

We have identified a novel homeodomain gene, buttonless (btn), that is specifically expressed in 20 cells of a single type during Drosophila embryonic development. These cells, the dorsal median (DM) cells, are arranged as a single pair within each segment along the dorsal midline of the CNS. Distinctive features of the DM cells include a large cell body and a long thick process extending laterally to the muscle attachment site. In the absence of btn gene function the initial commitment to the DM cell fate is made but differentiation fails to occur and the DM cells are lost. The btn mutation thus specifically eliminates the DM cells, and this genetic ablation in turn reveals a requirement for DM cells as cellular cues for axonal guidance during transverse nerve outgrowth and bifurcation of the median nerve.

Developmental evolution: insights from studies of insect segmentation

Rapid advances have been made in the understanding of the genetic basis of development and pattern formation in a variety of model systems. By examining the extent to which these developmental systems are conserved or altered between different organisms, insight can be gained into the evolutionary events that have generated the diversity of organisms around us. The molecular and genetic basis of early pattern formation in Drosophila melanogaster has been particularly well studied, and comparisons to other insects have revealed conservation of some aspects of development, as well as differences that may explain variations in early patterning events.

Serially homologous engrailed stripes are generated via different cell lineages in the germ band of amphipod crustaceans (Malacostraca, Peracarida)

A monoclonal antibody (mAb 4D9) was used to analyze engrailed expression in amphipod embryos. As in other arthropods, engrailed is expressed in iterated transverse stripes in the germ band. In the anterior region these stripes are generated without a recognizable division pattern, and their appearance and formation show some irregularities. In the posterior region of the germ band, engrailed expression is correlated with a stereotyped cell division pattern resulting in a highly ordered formation and array of stripes. The engrailed positive cells mark the anterior border of genealogical units, which therefore can be compared with parasegments in Drosophila. Expression starts in the mandibular segment and proceeds first anteriorly and subsequently in a posterior direction. Initial stripes are one cell wide. The widening of stripes is caused by both division of engrailed positive cells and recruitment of new cells that did not previously express engrailed. The widening process is related to segment formation as the intersegmental furrows are established behind the engrailed expressing cells, which are restricted to the posterior portion of the forming segments. A comparison of the modes of engrailed expression in different segments suggests that initial engrailed expression is independent of a certain cell lineage or division pattern. The comparison of the development of the early engrailed stripes in different insects and crustaceans reveals some similarities which show that early engrailed expression is not necessarily clonally inherited.

Engrailed controls glial/neuronal cell fate decisions at the midline of the central nervous system

The molecular mechanisms involved in glial/neuronal fate decisions during embryonic development are largely unknown. Here we show that the segment-polarity gene engrailed, which encodes a homeodomain protein, controls these decisions within an insect CNS lineage. The grasshopper median neuroblast (MNB) generates both neurons and midline glia in distinct temporal phases. engrailed expression in MNB progeny can be inhibited by injection of antisense oligodeoxynucleotides into the MNB nucleus. This produces a phenotype in which the midline glia do not develop and extra midline neurons are generated. In the absence of engrailed function, midline glial precursors are apparently converted into neuronal precursors. Thus, engrailed is required for execution of the decision between the glial and neuronal fates.

repo encodes a glial-specific homeo domain protein required in the Drosophila nervous system

We report the identification of a Drosophila locus, reversed polarity (repo). Weak repo alleles were viable but affected glia in the optic lobe, resulting in a reversal in polarity of the electrophysiological to light in the adult. Strong repo alleles caused defects in embryonic glia and resulted in embryonic lethality. Expression of repo appeared to be specific to glia throughout development. In the adult visual system, repo was expressed in laminal glia, medullar glia, and subretinal cells; in the embryo, repo was expressed in nearly all of the identified glia in the central and peripheral nervous systems except midline glia. The repo gene encoded a homeo domain protein suggesting that it might be a transcriptional regulator of genes required for glial development.

Pair-rule expression patterns of even-skipped are found in both short- and long-germ beetles

Now that the genes controlling embryonic patterning have been identified in several model organisms, long-standing questions concerning the evolution of developmental systems are open to investigation. Examination of the expression of even-skipped in a variety of insects reveals that Insect germ-type designations apparently do not reflect the variations in the mechanisms of segmentation evident throughout insect phylogeny.

Multidrug resistance in cancer chemotherapy

Resistance to chemotherapy is the single most important reason for treatment failure in cancer patients. Over the past 15 years, we have gained significant insight into one of the mechanisms responsible for this process: multidrug resistance (MDR). Far from being a phenomenon limited to the laboratory, multidrug resistance has been identified in a wide variety of newly diagnosed and recurrent human tumors. A number of compounds can block p-glycoprotein and overcome MDR in vitro and in vivo. Current strategies to block MDR are discussed in this review. Future research in this area will focus on the identification of more selective and potent MDR reversing agents and the development of entirely new approaches to overcoming multidrug resistance such as monoclonal antibodies, immunotoxins, and gene therapy.

Embryonic expression of the single Tribolium engrailed homolog

We have cloned and sequenced the single Tribolium homolog of the Drosophila engrailed gene. The predicted protein contains a homeobox and several domains conserved among all engrailed genes identified to date. In addition it contains several features specific to the invected homologs of Bombyx and Drosophila, indicating that these features most likely were present in the ancestral gene in the common ancestor of holometobolous insects. We used the cross-reacting monoclonal antibody, 4D9, to follow the expression of the Engrailed protein during segmentation in Tribolium embryos. As in other insects, Engrailed accumulates in the nuclei of cells along the posterior margin of each segment. The first Engrailed stripe appears as the embryonic rudiment condenses. Then as the rudiment elongates into a germ band, Engrailed stripes appear in an anterior to posterior progression, just prior to morphological evidence of the formation of each segment. As in Drosophila (a long germ insect), expression of engrailed in Tribolium (classified as a short germ insect) is preceded by the expression of several homologous segmentation genes, suggesting that similar genetic regulatory mechanisms are shared by diverse developmental types.

Analysis of the gooseberry locus in Drosophila embryos: gooseberry determines the cuticular pattern and activates gooseberry neuro

The segment-polarity class of segmentation genes in Drosophila are primarily involved in the specification of sub-segmental units. In addition, some of the segment-polarity genes have been shown to specify cell fates within the central nervous system. One of these loci, gooseberry, consists of two divergently transcribed genes, gooseberry and gooseberry neuro, which share a paired box as well as a paired-type homebox. Here, the expression patterns of the two gooseberry gene products are described in detail. The gooseberry protein appears in a characteristic segment-polarity pattern of stripes at gastrulation and persists until head involution. It is initially restricted to the ectodermal and neuroectodermal germ layer, but is later detected in mesodermal and neuronal cells as well. The gooseberry neuro protein first appears during germ band extension in cells of the central nervous system and also, much later, in epidermal stripes and in a small number of muscle cells. P-element-mediated transformation with the gooseberry gene has been used to demonstrate that gooseberry transactivates gooseberry neuro and is sufficient to rescue the gooseberry cuticular phenotype in the absence of gooseberry neuro.

Fasciclin IV: sequence, expression, and function during growth cone guidance in the grasshopper embryo

Monoclonal antibody 6F8 was used to characterize and clone fasciclin IV, a new axonal glycoprotein in the grasshopper, and to study its function during growth cone guidance. Fasciclin IV is dynamically expressed on a subset of axon pathways in the developing CNS and on circumferential bands of epithelial cells in developing limb buds. One of these bands corresponds to the location where the growth cones of the Ti1 pioneer neurons make a characteristic turn while extending toward the CNS. Embryos cultured in the 6F8 antibody or Fab exhibit aberrant formation of this axon pathway. cDNA sequence analysis suggests that fasciclin IV has a signal sequence; long extracellular, transmembrane, and short cytoplasmic domains; and shows no homology with any protein in the available data bases. Thus, fasciclin IV appears to be a novel integral membrane protein that functions in growth cone guidance.

Changing role of even-skipped during the evolution of insect pattern formation

The development of Drosophila is typical of the so-called long germband mode of insect development, in which the pattern of segments is established by the end of the blastoderm stage. Short germband insects, such as the grasshopper Schistocerca americana, by contrast, generate all or most of their metameric pattern after the blastoderm stage by the sequential addition of segments during caudal elongation. This difference is discernible at the molecular level in the pattern of initiation of the segment polarity gene engrailed, and the homeotic gene abdominal-A (ref. 5). For example, in both types of insects, engrailed is expressed by the highly conserved germband stage in a pattern of regularly spaced stripes, one stripe per segment. In Drosophila, the complete pattern is visible by the end of the blastoderm stage, although engrailed appears initially in alternate segments in a pair-rule pattern that reflects its known control by pair-rule genes such as even-skipped. In contrast, in the grasshopper, the engrailed stripes appear one at a time after the blastoderm stage as the embryo elongates. To address the molecular basis for this difference, we have cloned the grasshopper homologue of the Drosophila pair-rule gene even-skipped and show that it does not serve a pair-rule function in early development, although it does have a similar function in both insects during neurogenesis later in development.

Drosophila neurotactin, a surface glycoprotein with homology to serine esterases, is dynamically expressed during embryogenesis

Drosophila neurotactin is a transmembrane glycoprotein with an apparent molecular mass of 135 × 10(3). Neurotactin is regionally expressed at the cellular blastoderm stage; later in embryogenesis the expression of the protein becomes restricted to cells of the peripheral and central nervous system. Immunocytochemical localization shows neurotactin protein at points of cell-cell contact. Using the anti-neurotactin monoclonal antibody BP-106, a neurotactin cDNA was isolated that encodes a 846 residue polypeptide. The chromosomal location of the neurotactin gene is 73C. The extracellular domain at the carboxyterminal end of the neurotactin protein shows a strong structural and sequence homology to serine esterases without retaining the amino acids forming the active center. Neurotactin therefore belongs to a growing group of proteins including Drosophila glutactin and thyroglobulins that are known to share this serine esterase protein domain motif without retaining the active center of the enzyme.

Differential splicing generates a nervous system-specific form of Drosophila neuroglian

We recently described the characterization and cloning of Drosophila neuroglian, a member of the immunoglobulin superfamily. Neuroglian contains six immunoglobulin-like domains and five fibronectin type III domains and shows strong sequence homology to the mouse neural cell adhesion molecule L1. Here we show that the neuroglian gene generates at least two different protein products by tissue-specific alternative splicing. The two protein forms differ in their cytoplasmic domains. The long form is restricted to the surface of neurons in the CNS and neurons and some support cells in the PNS; in contrast, the short form is expressed on a wide range of other cells and tissues. Thus, whereas the mouse L1 gene appears to encode only one protein that functions largely as a neural cell adhesion molecule, its Drosophila homolog, the neuroglian gene, encodes at least two protein forms that may play two different roles, one as a neural cell adhesion molecule and the other as a more general cell adhesion molecule involved in other tissues and imaginal disc morphogenesis.

Drosophila neuroglian: a member of the immunoglobulin superfamily with extensive homology to the vertebrate neural adhesion molecule L1

Drosophila neuroglian is an integral membrane glycoprotein that is expressed on a variety of cell types in the Drosophila embryo, including expression on a large subset of glial and neuronal cell bodies in the central and peripheral nervous systems and on the fasciculating axons that extend along them. Neuroglian cDNA clones were isolated by expression cloning. cDNA sequence analysis reveals that neuroglian is a member of the immunoglobulin superfamily. The extracellular portion of the protein consists of six immunoglobulin C2-type domains followed by five fibronectin type III domains. Neuroglian is closely related to the immunoglobulin-like vertebrate neural adhesion molecules and, among them, shows most extensive homology to mouse L1. Its homology to L1 and its embryonic localization suggest that neuroglian may play a role in neural and glial cell adhesion in the developing Drosophila embryo. We report here on the identification of a lethal mutation in the neuroglian gene.

Expression of engrailed during segmentation in grasshopper and crayfish

We have used a monoclonal antibody that recognizes engrailed proteins to compare the process of segmentation in grasshopper, crayfish, and Drosophila. Drosophila embryos rapidly generate metameres during an embryonic stage characterized by the absence of cell division. In contrast, many other arthropod embryos, such as those of more primitive insects and crustaceans, generate metameres gradually and sequentially, as cell proliferation causes caudal elongation. In all three organisms, the pattern of engrailed expression at the segmented germ band stage is similar, and the parasegments are the first metameres to form. Nevertheless, the way in which the engrailed pattern is generated differs and reflects the differences in how these organisms generate their metameres. These differences call into question what role homologues of the Drosophila pair-rule segmentation genes might play in other arthropods that generate metameres sequentially.