Type III units in the gerbil dorsal cochlear nucleus may be spectral notch detectors

Broadband sounds originating in the median plane are thought to be localized by neural processing of spectral notches introduced by the filtering action of the pinnae. Previous studies (Nelken, I., and E. D. Young. J. Neurophysiol. 71:2446-2462, 1994: Spirou, G. A., and E. D. Young. ibid. 66: 1750-1768. 1991) suggested that type IV units in decerebrate cat dorsal cochlear nucleus (DCN) are functional detectors of these spectral notches. Intracellular marking studies by Ding et al. (Ding, J., T. E. Benson, and H. F. Voigt. J. Neurophysiol. 82:3434-3457, 1999) have shown that type III units in gerbil arise from the DCN's principal output neurons, which are thought to have type IV unit properties in cat. A relative paucity of type IV units in the decerebrate gerbil (Davis. K. A., J. Ding, T. E. Benson, and H. F. Voigt. J. Neurophysiol. 75: 1411-1431, 1996) has motivated this study of spectral notch sensitivity in the gerbil DCN. Responses to notch noise stimuli were recorded from 15 gerbil type III units to investigate whether these units may function as spectral notch detectors. For narrow notch noise stimuli, all 15 units showed excitatory responses. For progressively wider notches, the discharge rate of 13/15 units became inhibited. As the maximum limits of notch width were approached, 11/15 units showed some degree of recovery from this inhibition. This response pattern in gerbil type III units possesses the salient features of notch noise responses in cat type IV units and implicates type III units in gerbilline spectral notch detection processes.

Influence of atrial fibrillation on outcome following mitral valve repair

BACKGROUND

To investigate the outcome of patients in atrial fibrillation (AF) following mitral valve repair, clinical and echocardiographic follow-up was undertaken in 400 consecutive patients who underwent mitral valvuloplasty from 1987 to 1999.

METHODS AND RESULTS

The main indications for surgery were degenerative (81.4%), endocarditis (7.1%), rheumatic (6.6%), ischemic (4.6%), and traumatic (0.3%) mitral valve disease. After excluding 6 paced patients and 1 patient in nodal rhythm, we compared the outcomes of 152 patients in AF against 241 patients in sinus rhythm. For patients in AF versus those in sinus rhythm, more AF patients were older (mean age 67.2+/-8.8 versus 61.9+/-11.8 years, respectively; P<0.001), more were assigned to a poorer New York Heart Association (NYHA) class (77.6% versus 66.0% in NYHA III/IV, respectively; P=0.01), and more demonstrated impaired ventricular function (78.9% versus 46.2% with moderate or severe impairment, respectively; P<0.001). For patients in AF versus those in sinus rhythm, there was no difference in 30-day mortality (2.0% versus 2.1%, respectively; P=0.95), repair failure (5.4% versus 3.6%, respectively; P=0.41), stroke (5.4% versus 2.2%, respectively; P=0.11), or endocarditis (2.3% versus 0.9%, respectively; P=0.27) on follow-up at a median of 2.8 years (interquartile range 1.1 to 6.0). On echocardiography, the proportion of patients with mild regurgitation or worse was 13.3% (AF patients) versus 10.8% (patients in sinus rhythm) (P=0.70). Patients in AF versus those in sinus rhythm had lower survival at 3 years (83% versus 93%, respectively) and 5 years (73% versus 88%, respectively). Univariate analysis identified factors affecting survival as AF (P=0.002), age >70 years (P=0.041), and poor ventricular function (P<0.001). However, by use of a multivariate model, only poor ventricular function remained significant (P=0.01).

CONCLUSIONS

AF does not affect early outcome or durability of mitral repair. The onset of AF may be indicative of disease progression because of its association with poor left ventricular function.

Non-thyphoidal salmonellosis in patients with systemic lupus erythematosus. A study of fifty patients and a review of the literature

The objective of this study was to characterize the clinical profile of lupus patients with non-typhoidal salmonellosis. A retrospective review of the clinical charts of lupus patients diagnosed with bacteriologically proven non-typhoidal salmonellosis over the last 20 y was undertaken, paying special attention to risk factors, clinical presentation and treatment outcome. Most episodes were bacteraemic without a localizing focus; and some patients were afebrile. They usually occurred in patients prone to opportunistic infections, and at times of increased immunosuppression given for lupus flares (especially nephritis). However, salmonellosis also occurred in some patients presenting with lupus. The C-reactive protein level was found to be significantly higher during the infective episodes compared to episodes of non-infective febrile lupus flare. All isolates were sensitive to the usual first-line antibiotics and eminently treatable with 3 weeks of appropriate antibiotics without recurrence/persistence or significant morbidity/mortality, the exceptions being spinal osteomyelitis and septic arthritis involving deformed joints requiring surgical debridement and prolonged antibiotic therapy for eradication. Mortality occurred in the setting of septic shock from mixed-microbial sepsis and major organ failure from active lupus. There is a high association of non-epidemic, non-typhoidal salmonellosis with SLE, especially in patients with active disease on intensified immunosuppression. The C-reactive protein value may be helpful in distinguishing between fever from a pure lupus flare and one complicated by infection.

Pervilleine A, a novel tropane alkaloid that reverses the multidrug-resistance phenotype

P-Glycoprotein-mediated drug efflux can yield a multidrug-resistance (MDR) phenotype that is associated with a poor response to cancer chemotherapy. Pervilleine A, a novel tropane alkaloid obtained from a chloroform extract of Erythroxylum pervillei as the result of bioactivity-guided fractionation, was found to restore the vinblastine sensitivity of cultured multidrug-resistant KB-V1 and CEM/VLB(100) cells, with IC(50) values of 0.36 and 0.02 microM, respectively. Similarly, the chemosensitivity of KB-8-5 cells to colchicine was restored with an IC(50) value of 0.61 microM. The mechanism of this response was evaluated with a number of model systems. First, incubation of multidrug-resistant KB-V1 and CEM/VLB(100) cells with up to 45 microM pervilleine A for 72 h did not significantly affect either the transcription of MDR1, as revealed by reverse transcriptional-PCR-based analysis of MDR1 mRNA, or levels of P-glycoprotein, as shown by Western blots. ATP-dependent binding of [(3)H]vinblastine observed with isolated multidrug-resistant KB-V1 cell membrane vesicles was inhibited by pervilleine A in a dose-dependent manner, and kinetic analysis indicted competitive inhibition with respect to vinblastine binding with a K(i) of 7.3 microM. Consistent with this effect, intracellular accumulation of [(3)H]vinblastine was increased from 0.18 pmol [(3)H]vinblastine/50 x 10(4) cells to approximately 5 pmol [(3)H]vinblastine/50 x 10(4) cells in the presence of 40 microM pervilleine A. To explore the potential relevance of these responses, KB-V1 or KB-8-5 cells were placed in hollow fibers and implanted into NCr nu/nu mice. Cell growth was not significantly inhibited when vinblastine or pervilleine A were administered as single agents, but when used in combination, inhibition of up to 75% was observed. Equimolar doses of verapamil were less effective. These data suggest that pervilleine A is an effective inhibitor of P-glycoprotein and should be further evaluated for clinical utility.

Restless legs syndrome in an Asian population: A study in Singapore

In face-to-face interviews, we examined 157 consecutive individuals aged 55 years and older, selected from the general population in Singapore, and 1,000 consecutive individuals aged 21 years and older, from a primary healthcare center. Based on the IRLSSG criteria, the prevalence of restless leg syndrome (RLS) was 0.6% and 0.1%, respectively.

Comparison of spinal myotatic reflexes in human adults investigated with cross-correlation and signal averaging methods

A cross-correlation method for recording spinal myotatic reflexes has been developed to meet the need for brief test periods in babies and children and subjects with central neurological pathology. In normal adult subjects the method has been validated by comparing excitatory and inhibitory reflexes obtained with cross-correlation with those obtained with conventional signal averaging. In the cross-correlation method a pseudo-random binary sequence of 64 brief tendon taps was delivered in <1.5 s, and in the averaging method 20-150 taps at one per second. The reflexes were expressed as unit impulse responses to enable direct, quantitative comparisons to be made. With cross-correlation the responses were slightly expanded in time, had lower peak amplitudes, and onset latencies advanced by 10 ms, the clock period of the pseudo-random binary sequence. The amplitude of biceps phasic stretch reflex increased with muscle contraction in a similar manner with both methods. In tests for stationarity the amplitude of biceps phasic stretch reflex varied <10% in the first six repeats of the pseudo-random binary sequence. The tap force required at threshold for cross-correlation was approximately half that for averaging, but with both methods the magnitude of biceps phasic stretch reflex varied linearly with tap force over the range of one to two times threshold. The validity of responses obtained with cross-correlation was assessed by a statistical procedure. In conclusion, the cross-correlation method is robust and gives similar results to those obtained with averaging.

Spinocerebellar ataxia in Singapore: predictive features of a positive DNA test?

Significant differences in frequency of the different spinocerebellar ataxia (SCA) subtypes have been described to occur in different populations. A 'blunderbuss' diagnostic DNA testing approach would entail unnecessary healthcare cost. In this study, we determine the prevalence of SCA subtypes and predictive features of a positive DNA test in consecutive clinically diagnosed SCA cases in Singapore. Twenty-one consecutive patients from 14 families were evaluated over a 3-year period. Thirteen patients (61.9%) from 6 families had a positive DNA test. Eleven of these (all ethnic Chinese) had SCA 3 (abnormal CAG size ranged from 61 to 71), and 2 ethnic Malays had SCA 2 (abnormal CAG size of 39). Clinical features which were highly predictive of a positive DNA SCA test in our population included presence of a positive family history, chorea and dystonia, muscle and tongue fasciculations, gaze-evoked nystagmus, and hypertonia. Our study draws attention to the observation that knowledge of relatively specific features of the most common SCA subtype in a local population can greatly enhance the practical accuracy of the choice of which SCA DNA test to order.

Dynamic helical computed tomography scan accurately detects hemorrhage in patients with pelvic fracture

BACKGROUND

The purpose of this study was to evaluate the use of dynamic helical computed tomography (CT) scan for screening patients with pelvic fractures and hemorrhage requiring angiographic embolization for control of bleeding.

METHODS

Patients admitted to the trauma service with pelvic fractures were identified from the trauma registry. Data retrieval included demographics, hemodynamic instability, Injury Severity Score, blood transfusion requirement, length of stay, and mortality. CT scans obtained during the initial evaluation were reviewed for the presence of contrast extravasation and correlated with angiographic findings. Data are reported as mean +/- SEM, with P<.05 considered significant.

RESULTS

Seven thousand seven hundred eighty-one patients were admitted from June 1994 to May 1999. A pelvic fracture was diagnosed in 660 (8.5%). Two hundred ninety (44.0%) dynamic helical CT scans were performed, of which 13 (4.5%) identified contrast extravasation. Nine (69%) were hemodynamically unstable and had pelvic arteriography performed. Arterial bleeding was confirmed in all and controlled by embolization. Patients with contrast extravasation had significantly greater Injury Severity Score, blood transfusion requirement and length of stay. Sensitivity, specificity, and accuracy of CT scan for identifying patients requiring embolization were 90.0%, 98.6%, and 98.3%, respectively.

CONCLUSIONS

Early use of dynamic helical CT scanning in the multiply injured patient with a pelvic fracture accurately identifies the need for emergent angiographic embolization.

The unusual mammographic appearance of breasts augmented by autologous fat injection

We report the case of a woman presenting to our centre with two breast lumps, 12 months after undergoing breast augmentation with autologous fat injection. Mammography showed a very unusual appearance, with most of the breast parenchyma displaced anteriorly by a large amount of fatty tissue. This was associated with extensive bizarre microcalcification, highlighting the difficulty in mammographic evaluation of this rare type of breast augmentation.

Nipah viral encephalitis or Japanese encephalitis? MR findings in a new zoonotic disease

BACKGROUND AND PURPOSE

An epidemic of suspected Japanese encephalitis occurred in Malaysia in 1998-1999 among pig farmers. In neighboring Singapore, an outbreak occurred among pig slaughterhouse workers. It was subsequently established that the causative agent in the outbreak was not the Japanese encephalitis virus but a previously unknown Hendra-like paramyxovirus named Nipah virus.

METHODS

The brain MR images of eight patients with Nipah virus infection were reviewed. All patients tested negative for acute Japanese encephalitis virus. Seven patients had contrast-enhanced studies and six had diffusion-weighted examinations.

RESULTS

All patients had multiple small bilateral foci of T2 prolongation within the subcortical and deep white matter. The periventricular region and corpus callosum were also involved. In addition to white matter disease, five patients had cortical lesions, three had brain stem involvement, and a single thalamic lesion was detected in one patient. All lesions were less than 1 cm in maximum diameter. In five patients, diffusion-weighted images showed increased signal. Four patients had leptomeningeal enhancement and four had enhancement of parenchymal lesions.

CONCLUSION

The brain MR findings in patients infected with the newly discovered Nipah paramyxovirus are different from those of patients with Japanese encephalitis. In a zoonotic epidemic, this striking difference in the appearance and distribution of lesions is useful in differentiating these diseases. Diffusion-weighted imaging was advantageous in increasing lesion conspicuity.

Outbreak of Nipah-virus infection among abattoir workers in Singapore

BACKGROUND

In March 1999, an outbreak of encephalitis and pneumonia occurred in workers at an abattoir in Singapore. We describe the clinical presentation and the results of investigations in these patients.

METHODS

Clinical and laboratory data were collected by systemic review of the case records. Serum and cerebrospinal fluid (CSF) samples were tested for IgM antibodies to Nipah virus with an IgM capture ELISA. Reverse-transcriptase PCR was done on the CSF and tissue samples from one patient who died.

FINDINGS

Eleven patients were confirmed to have acute Nipah-virus infection based on raised IgM in serum. Nipah virus was identified by reverse transcriptase PCR in the CSF and tissue of the patient who died. The patients were all men, with a median age of 44 years. The commonest presenting symptoms were fever, headache, and drowsiness. Eight patients presented with signs of encephalitis (decreased level of consciousness or focal neurological signs). Three patients presented with atypical pneumonia, but one later developed hallucinations and had evidence of encephalitis on CSF examination. Abnormal laboratory findings included a low lymphocyte count (nine patients), low platelet count, low serum sodium, and high aspartate aminostransferase concentration (each observed in five patients). The CSF protein was high in eight patients and white-blood-cell count was high in seven. Chest radiography showed mild interstitial shadowing in eight patients. Magnetic resonance imaging (MRI) showed focal areas of increased signal intensity in the cortical white marker in all eight patients who were scanned. The nine patients with encephalitis received empirical treatment with intravenous aciclovir and eight survived.

INTERPRETATION

Infection with Nipah virus caused an encephalitis illness with characteristic focal areas of increased intensity seen on MRI. Lung involvement was also common, and the disease may present as an atypical pneumonia.

Proliferation and collagen synthesis of human anterior cruciate ligament cells in vitro: effects of ascorbate-2-phosphate, dexamethasone and oxygen tension

Clinical and experimental studies demonstrate that injured anterior cruciate ligaments (ACL) do not usually heal and that autografts used to repair the ACL rapidly weaken in the early period and take a long time to regain strength. The aim of this study was to develop an in vitro culture system in which environmental and biochemical factors influencing the proliferation and matrix synthesis of cells derived from human anterior cruciate ligaments can be studied. Primary cultures of human ACL cells were obtained by outgrowth from explants of normal ACL obtained at knee replacement for osteoarthritis in Dulbecco's minimum essential medium (DMEM). The effects of the additives 100 microm L-ascorbic acid-2-phosphate (Asc-2-P) and 10 n m dexamethasone (dex) on proliferation and collagen synthesis were assessed after 4, 8 and 12 days in culture. Ligament cells were grown at 0, 5, 10 and 21%p O(2)in the presence of 100 microm asc-2-P and 10 n m dex. DNA content was assessed using the Hoechst dye method and collagen synthesis by the incorporation of 5 mCi/ml [(3)H]proline after 3, 6 and 12 days in culture. At 21%p O(2), the presence of asc-2-P and dex induced significantly greater (P< 0.01, ANOVA) cell proliferation than with either additives alone. Greatest percentage collagen to total protein synthesis was observed when cells were grown in the presence of asc-2-P only. Least proliferation and percentage collagen to total protein synthesis was seen when both additives were omitted. Greatest cell proliferation was seen when cells were grown in 10%p O(2)and 5%p O(2)was associated with increased collagen synthesis. These results suggest that it is possible to study the effects of environmental and biochemical factors on human ACL healing in vitro. Our data suggest oxygen can influence certain biosynthetic activities of ACL cells. Low oxygen tensions lead to an increase in collagen production by ACL cells. However early responses to injury require extensive cell proliferation which may be activated at higher p O(2). Variation of p O(2)in ligaments during healing may therefore be an important modulator of successful repair.

Effect of a 915-MHz simulated mobile phone signal on cognitive function in man

PURPOSE

To examine whether a simulated mobile telephone transmission at 915 MHz has an effect on cognitive function in man.

MATERIALS AND METHODS

Thirty-six subjects in two groups were each given two training sessions and then three test sessions in a randomized three-way cross-over design. About 1 W mean power at 915 MHz from a quarter-wave antenna mounted on a physical copy of an analogue phone, as a sine wave, or modulated at 217 Hz with 12.5% duty cycle, or no power, was applied to the left squamous temple region of the subjects while they undertook a series of cognitive function tests lasting approximately 25-30 min. The second group was investigated for sleep, consumption of alcohol and beverages, and any other substances that might affect performance.

RESULTS

In both groups, the only test affected was the choice reaction time and this showed as an increase in speed (a decrease in reaction time). There were no changes in word, number or picture recall, or in spatial memory. While an effect of visit-order was evident suggesting a learning effect of repeat tests, the design of the study allowed for this. Additionally, there was no systematic error introduced as a result of consumption of substances or sleep time.

CONCLUSIONS

There was evidence of an increase in responsiveness, strongly in the analogue and less in the digital simulation, in choice reaction time. This could be associated with an effect on the angular gyrus that acts as an interface between the visual and speech centres and which lies directly under and on the same side as the antenna. Such an effect could be consistent with mild localized heating, or possibly a non-thermal response, which is nevertheless power-dependent.

Effect of taurine supplementation on the lipid peroxide formation and the activities of glutathione-related enzymes in the liver and islet of type I and II diabetic model mice

Effects of taurine supplementation on lipid peroxide formation and the activities of glutathione (GSH) dependent enzymes in diabetic model mice were investigated. Type I diabetes mellitus was induced by injecting alloxan to ICR mice while type II diabetes mellitus was produced by high calorie diet feeding to genetically hyperglycemic KK mice. Taurine was given in drinking water at the level of 5% (w/v) for seven days. The malondialdehyde (MDA) levels of liver and the islets of type I diabetes were significantly increased compared to the control group but the levels were significantly decreased by taurine supplementation. In the type II diabetic model, the concentrations of MDA were not changed by taurine treatment. The activity of hepatic and islet GSH-peroxidase (GPX) was increased in the type I diabetic group, but in type II animals it was decreased. Hepatic GPX activity of both type I and II diabetics was not altered by taurine supplementation but was increased in the islets of the type II animals. No effect on the activity of GSH S-transferase (GST) was observed in both types of diabetes (I and II) following taurine supplementation. These results suggest that taurine supplementation protects type I diabetic mice from lipid peroxide formation.

A case of t(8;14) with total and partial trisomy 3 in Waldenstrom macroglobulinemia

A case of Waldenstrom macroglobulinemia with Burkitt-type t(8;14)(q24.1;q32) and total and partial trisomy 3 is reported. This is an unusual combination of chromosomal abnormalities in Waldenstrom macroglobulinemia.

Adult-onset Still's disease in an oriental population: manifestations, course and outcome in 16 patients

This retrospective descriptive study aims to characterise and compare the clinical manifestations, course and outcome of 16 Oriental patients with adult-onset Still's disease diagnosed in the last 4 years with published data based on Western populations and another Oriental (Japanese) series. Like the Japanese, we found a female preponderance, an older age at onset, and fewer patients with abdominal pain, myalgia, sore throat and serositis compared to the Western series. A longer delay in diagnosis occurred in patients lacking either arthritis or rash at presentation. Most patients had mild hyponatraemia and 2 patients had overt syndrome of inappropriate anti-diuretic hormone secretion. All patients showed a dissociation of elevated aldolase with normal to low creatine kinase levels. Over 50% relapsed within a year from diagnosis and needed slow-acting anti-rheumatic drugs as steroid-sparing agents. Two were given intravenous pulse cyclophosphamide therapy for progressive pneumonitis. Outcome was generally good with minimal functional impairment and no mortality.

The effect of early versus late fasciotomy in the management of extremity trauma

BACKGROUND

Recent reports have demonstrated an increase in the number of complications associated with delayed timing of fasciotomy for trauma. This study examines the effectiveness of early (less than 12 hours) versus late (more than 12 hours) fasciotomy in the injured extremity.

METHODS

This is a retrospective review of 88 patients undergoing fasciotomy for extremity trauma admitted to the University of Cincinnati from January 1990 through December 1995. Records were reviewed for demographics, compartment pressures, time and type of fasciotomy, complications, limb salvage, and mortality. Statistical analysis was determined with chi-squared, multivariant regression analysis, and Student's t test with significance at p less than 0.05.

RESULTS

Sixty-one (69%) patients had fasciotomy performed before 12 hours and twenty-seven (31%) after 12 hours. Although the rates of infection differed significantly between the two groups (7.3% for early versus 28% for late), the rates of limb salvage and neurologic sequelae were similar. Age, mechanism, shock, associated injuries, and time to fasciotomy were not predictive of complications.

CONCLUSIONS

Fasciotomy for trauma is most efficacious when performed early. However, when performed late, it results in similar rates of limb salvage as compared with early fasciotomy but at the increased risk of infection. These results support aggressive use of fasciotomy in extremity trauma regardless of time of diagnosis.

Calcineurin is required for virulence of Cryptococcus neoformans

Cyclosporin A (CsA) and FK506 are antimicrobial, immunosuppressive natural products that inhibit signal transduction. In T cells and Saccharomyces cerevisiae, CsA and FK506 bind to the immunophilins cyclophilin A and FKBP12 and the resulting complexes inhibit the Ca2+-regulated protein phosphatase calcineurin. We find that growth of the opportunistic fungal pathogen Cryptococcus neoformans is sensitive to CsA and FK506 at 37 degrees C but not at 24 degrees C, suggesting that CsA and FK506 inhibit a protein required for C. neoformans growth at elevated temperature. Genetic evidence supports a model in which immunophilin-drug complexes inhibit calcineurin to prevent growth at 37 degrees C. The gene encoding the C. neoformans calcineurin A catalytic subunit was cloned and disrupted by homologous recombination. Calcineurin mutant strains are viable but do not survive in vitro conditions that mimic the host environment (elevated temperature, 5% CO2 or alkaline pH) and are no longer pathogenic in an animal model of cryptococcal meningitis. Introduction of the wild-type calcineurin A gene complemented these growth defects and restored virulence. Our findings demonstrate that calcineurin is required for C. neoformans virulence and may define signal transduction elements required for fungal pathogenesis that could be targets for therapeutic intervention.

Mutations that perturb cyclophilin A ligand binding pocket confer cyclosporin A resistance in Saccharomyces cerevisiae

In complex with the peptidyl-prolyl isomerase cyclophilin A, the immunosuppressive antifungal drug cyclosporin A (CsA) inhibits a Ca2+/calmodulin-dependent protein phosphatase, calcineurin, which regulates signal transduction. We isolated and characterized cyclophilin A mutations that confer CsA resistance in a Saccharomyces cerevisiae strain whose growth is CsA-sensitive. Three mutations (G70S, H90Y, and G102A) alter single amino acids conserved between yeast and human cyclophilin A, which structural analyses implicate in CsA binding to human cyclophilin A. By Western analysis, all three mutant proteins are expressed in yeast. In vitro, two purified mutant cyclophilins (G70S, G102A) retain prolyl isomerase activity and have moderately reduced affinity for CsA and calcineurin but, when bound to CsA, do bind and inhibit calcineurin phosphatase activity. In contrast, the purified H90Y mutant cyclophilin is dramatically decreased in prolyl isomerase activity, CsA affinity, and calcineurin binding and inhibition. These studies identify conserved cyclophilin A residues that participate in CsA binding and catalysis.

Perforation of the sigmoid colon following ingestion of a dental plate

The authors report on the perforation of the sigmoid colon in a 48-year-old male following the accidental ingestion of a partial dental plate. Sharp, pointed objects may perforate the bowel and surgery should be considered. A review of the literature revealed no previously reported cases.

Gene disruption with PCR products in Saccharomyces cerevisiae

We describe here the generation of gene disruption constructs using PCR amplification of selectable markers with primers that provide homology to the target gene of interest. We find that regions of homology as short as 38 to 50 bp suffice to mediate homologous recombination in yeast. We describe applications of this technology to three specific yeast genes that would have been difficult to disrupt with current methods. By dispensing with the need to either clone the gene of interest or engineer a standard disruption construct, this method should facilitate analysis of sequenced genes of unknown function, which will soon include the entire yeast genome.

Directed tagging of the Arabidopsis FATTY ACID ELONGATION1 (FAE1) gene with the maize transposon activator

The FATTY ACID ELONGATION1 (FAE1) gene of Arabidopsis is required for the synthesis of very long chain fatty acids in the seed. The product of the FAE1 gene is presumed to be a condensing enzyme that extends the chain length of fatty acids from C18 to C20 and C22. We report here the cloning of FAE1 by directed transposon tagging with the maize element Activator (Ac). An unstable fae1 mutant was isolated in a line carrying Ac linked to the FAE1 locus on chromosome 4. Cosegregation and reversion analyses established that the new mutant was tagged by Ac. A DNA fragment flanking Ac was cloned by inverse polymerase chain reaction and used to isolate FAE1 genomic clones and a cDNA clone from a library made from immature siliques. The predicted amino acid sequence of the FAE1 protein shares homology with those of other condensing enzymes (chalcone synthase, stilbene synthases, and beta-ketoacyl-acyl carrier protein synthase III), supporting the notion that FAE1 is the structural gene for a synthase or condensing enzyme. FAE1 is expressed in developing seed, but not in leaves, as expected from the effect of the fae1 mutation on the fatty acid compositions of those tissues.