Theta and alpha oscillatory signatures of auditory sensory and cognitive loads during complex listening.

The neuronal signatures of sensory and cognitive load provide access to brain activities related to complex listening situations. Sensory and cognitive loads are typically reflected in measures like response time (RT) and event-related potentials (ERPs) components. It's, however, strenuous to distinguish the underlying brain processes solely from these measures. In this study, along with RT- and ERP-analysis, we performed time-frequency analysis and source localization of oscillatory activity in participants performing two different auditory tasks with varying degrees of complexity and related them to sensory and cognitive load. We studied neuronal oscillatory activity in both periods before the behavioral response (pre-response) and after it (post-response). Robust oscillatory activities were found in both periods and were differentially affected by sensory and cognitive load. Oscillatory activity under sensory load was characterized by decrease in pre-response (early) theta activity and increased alpha activity. Oscillatory activity under cognitive load was characterized by increased theta activity, mainly in post-response (late) time. Furthermore, source localization revealed specific brain regions responsible for processing these loads, such as temporal and frontal lobe, cingulate cortex and precuneus. The results provide evidence that in complex listening situations, the brain processes sensory and cognitive loads differently. These neural processes have specific oscillatory signatures and are long lasting, extending beyond the behavioral response.

[Surgical Treatment of Tuberculous Spondylodiscitis]. / Operacní lécba tuberkulózní spondylodiscitidy.

PURPOSE OF THE STUDY The paper presents a monocentric retrospective study of patients treated surgically for spinal tuberculosis. Clinical and radiological results are analysed, early and late complications are recorded. The study aims to answer the following questions. 1. Can we use instrumentation to restore the stability and alignment in the infected spinal focus? 2. Should we always perform radical anterior resection of TBC lesions? 3. What is the prognosis of surgical treatment of TBC patients with neurological deficit manifestation? MATERIAL AND METHODS Between 2010 and 2020, a total of 12 patients were treated for spinal tuberculosis at our department, of whom 9 patients (5 men, 4 women) with the mean age of 47.3 years (range 29 to 83 years) underwent a surgery. A total of three patients were operated on before the final confirmation of the TBC and treatment with antituberculosis medication, four patients in the initial therapy phase and two patients in the continuous phase. Two patients only underwent a non-instrumented decompression surgery followed by external support fixation. In the other seven patients, always with spinal deformity, instrumentation was used (3 cases of isolated posterior decompression, transpedicular fixation, posterior fusion, 4 cases of anteroposterior instrumented reconstruction). In 2 cases a structural bone graft and in 2 cases an expandable titanium cage were used for anterior column reconstruction. RESULTS Of the total number of patients, altogether eight patients were assessed at 1 year after surgery (one 83-year-old patient died from heart failure 4 months after surgery). Of the remaining eight patients, three patients exhibited a neurological deficit and postoperative regression of the finding. The McCormick score improved from the preoperative mean score of 3.25 to 1.62 at 1 year after surgery (p < 0.001). The clinical VAS score regressed from 5.75 to 1.63 at 1 year after surgery (p < 0.001). Radiographic healing of the anterior fusion was achieved in all patients, both after decompression and instrumented surgery. The initial mean kyphosis of 20.36 degrees of the operated segment measured by the mCobb angle was corrected to 14.6 degrees postoperatively, with a subsequent slight deterioration to 14.86 degrees (p < 0.05). The greatest correction was achieved in patients who had undergone a two-stage surgery with anterior resection and AP reconstruction. DISCUSSION In our cohort, titanium instrumentation was used in seven of nine patients. One patient only manifested persistent tuberculosis with nonspecific bacterial flora superinfection. Revision surgery with anterior radical debridement and subsequent treatment with antituberculotic drugs healed the patient. There were four patients with major preoperative neurological deficit persisting more than 2 weeks before the final treatment with subsequent improvement in all cases. These patients were treated with anteroposterior reconstruction and anterior radical debridement. CONCLUSIONS No increased risk of recurrent infection associated with the use of spinal instrumentation was found in the study. Anterior radical debridement is performed in patients with manifested kyphotic deformity and spinal canal compression, followed by reconstruction with a structural bone graft or a titanium cage. The other patients are treated based on the principle of "optimal" debridement with or without the use of transpedicular instrumentation. If adequate spinal canal decompression and stability are achieved, neurological improvement can be anticipated even in case of a major neurological deficit. Key words: spine tuberculosis, tuberculous spondylitis, Pott's disease, anterior debridement, spine instrumentation.

[Pathophysiology of hearing loss : Classification and treatment options]. / Pathophysiologie des Hörverlusts : Klassifikation und Therapieoptionen.

From the therapeutic perspective, the etiology and pathophysiology of hearing loss can be classified based on the extent of the primary cause. Hearing loss can have very different consequences for cell preservation in the organ of Corti and the spiral ganglion. These not only have implications for prosthetic therapy outcome, but may also influence the potential for future causal molecular therapies. Etiologies leading to deficits that are limited to one or a few molecules without having an effect on cell survival have the greatest potential for future causal therapy using molecular and cellular approaches. Preliminary success for molecular therapy was recently reported in animal experiments. Unfortunately, the incidence of these types of hearing loss is very low and in the future the therapy of hearing loss will therefore also require several different approaches. In addition to peripheral pathophysiology, hearing loss has consequences on the functioning of the brain, which can vary greatly due to individual adaptation to the situation without hearing. The authors therefore argue for individualization of the diagnostics and therapy that focus not only the symptom of hearing loss, but also the individual pathophysiology and consequences. Only with individualized therapy can the success of treating hearing disorders be significantly improved.

Extended boiling of peanut progressively reduces IgE allergenicity while retaining T cell reactivity.

BACKGROUND: Current peanut oral immunotherapy is hampered by frequent adverse events. It has been shown that boiling can reduce peanut allergenicity. Hypoallergenic peanut products have the potential to reduce treatment-related reactions during desensitization. OBJECTIVE: To show that extended boiling (for up to 12 h) can progressively reduce peanut allergenicity while retaining T cell reactivity. METHODS: Raw peanuts were boiled for half, 1, 2, 4 and 12 h in deionized water. After dehydration, boiled and raw peanuts were ground, defatted and soluble proteins extracted in PBS and cooking water (leachate) retained. SDS-PAGE, Western blot, inhibition ELISA, mass spectrometry and skin prick test were used to characterize changes to peanut allergens and human IgE reactivity. T cell responses to raw and boiled peanut extracts were determined by proliferation of CD4+/CD25+/CD134+ T cells in peanut-allergic and non-allergic individuals. RESULTS: Extended boiling progressively reduced peanut allergenicity through a combination of leaching of allergens into cooking water, fragmentation of allergens and denaturation of conformational epitopes. Two-hour boiling led to an eightfold reduction in IgE binding capacity of boiled peanuts as determined by inhibition ELISA, while 12-h boiling led to a 19-fold reduction. Mass spectrometry revealed an increasing number of unique allergen peptides with longer boiling times. Raw, 2- and 12-h boiled peanut extracts were equivalent in their ability to stimulate T cell activation and proliferation. CONCLUSION AND CLINICAL RELEVANCE: Progressive reduction in peanut allergenicity with extended boiling does not affect T cell reactivity. Boiled peanuts may be a candidate for oral immunotherapy.

Cystatin C Is Associated with the Extent and Characteristics of Coronary Atherosclerosis in Patients with Preserved Renal Function.

Cystatin C (CysC), an endogenous inhibitor of cysteine proteases and a sensitive and accurate marker of renal function, is associated with the severity of coronary atherosclerosis assessed by angiography and future cardiovascular events according to previous studies. We aimed to evaluate the association between CysC levels and coronary plaque volume, composition and phenotype assessed by intravascular ultrasound and intravascular ultrasound-derived virtual histology in patients with preserved renal function. Forty-four patients with angiographically documented coronary artery disease and complete intravascular imaging were included in the study. Patients were categorized into tertiles by CysC levels. Subjects in the high CysC tertile had significantly higher mean plaque burden (48.0 % ± 6.9 vs. 42.8 % ± 7.4, P = 0.029), lower mean lumen area (8.1 mm2 ± 1.7 vs. 9.9 mm2 ± 3.1, P = 0.044) and a higher number of 5-mm vessel segments with minimum lumen area < 4 mm2 (17.9 ± 18.9 vs. 6.8 ± 11.7, P = 0.021) compared to patients in the lower tertiles. In addition, CysC levels demonstrated significant positive correlation with the mean plaque burden (r = 0.35, P = 0.021). Neither relative, nor absolute plaque components differed significantly according to CysC tertiles. The Liverpool Active Plaque Score was significantly higher in the high CysC tertile patients (0.91 ± 1.0 vs. 0.18 ± 0.92, P = 0.02). In conclusion, our study demonstrated a significant association of increased CysC levels with more advanced coronary artery disease and higher risk plaque phenotype in patients with preserved renal function.

Prediction of coronary vessel involvement on the basis of atherosclerosis risk factor analysis.

The prediction of coronary vessel involvement by means of noninvasive tests is one of the fundamental objectives of preventive cardiology. This review describes the current possibilities of coronary vessel involvement prediction by means of ultrasonographic examination of carotid arteries, analysis of polymorphisms in the genes encoding enzymes responsible for production of nitric oxide and carbon monoxide and assessment of levels of certain proinflammatory cytokines. In the presented work these noninvasive markers are correlated with the extent of coronary vessel involvement as assessed by coronary angiography, intravascular ultrasound and virtual histology (Fig. 5, Ref. 40).

Development of brainstem-evoked responses in congenital auditory deprivation.

To compare the development of the auditory system in hearing and completely acoustically deprived animals, naive congenitally deaf white cats (CDCs) and hearing controls (HCs) were investigated at different developmental stages from birth till adulthood. The CDCs had no hearing experience before the acute experiment. In both groups of animals, responses to cochlear implant stimulation were acutely assessed. Electrically evoked auditory brainstem responses (E-ABRs) were recorded with monopolar stimulation at different current levels. CDCs demonstrated extensive development of E-ABRs, from first signs of responses at postnatal (p.n.) day 3 through appearance of all waves of brainstem response at day 8 p.n. to mature responses around day 90 p.n.. Wave I of E-ABRs could not be distinguished from the artifact in majority of CDCs, whereas in HCs, it was clearly separated from the stimulus artifact. Waves II, III, and IV demonstrated higher thresholds in CDCs, whereas this difference was not found for wave V. Amplitudes of wave III were significantly higher in HCs, whereas wave V amplitudes were significantly higher in CDCs. No differences in latencies were observed between the animal groups. These data demonstrate significant postnatal subcortical development in absence of hearing, and also divergent effects of deafness on early waves II-IV and wave V of the E-ABR.

Cortical representation of interaural time difference in congenital deafness.

Binaural cues are required for localization of sound sources. In the present paper, representation of binaural cues has been investigated in the adult auditory cortex. Hearing and congenitally deaf cats were stimulated through binaural cochlear implants and unit responses were collected in the subregion of field A1 showing the largest amplitudes of evoked local field potentials. Sensitivity to interaural time difference (ITD) in the range from -600 to 600 micros was tested at intensities of 0-10 dB above hearing threshold. Template ITD functions were fitted to the data and parameters of ITD functions were compared between deaf and hearing animals. In deaf animals, fewer units responded to binaural stimulation, and those that responded had smaller maximal evoked firing rate. The fit to the template ITD functions was significantly worse in deaf animals, and the modulation depth in ITD functions was smaller, demonstrating a decrease in ITD sensitivity. With increasing binaural levels, hearing controls demonstrated systematic changes in ITD functions not found in deaf animals. Bimodal responses, likely related to precedence effect, were rare in deaf animals. The data demonstrate that despite some rudimentary sensitivity to interaural timing, cortical representation of ITDs is substantially altered by congenital auditory deprivation.

Genetic variants in haem oxygenase-1 and endothelial nitric oxide synthase influence the extent and evolution of coronary artery atherosclerosis.

The genetic basis for atherosclerosis development and progression is poorly characterized. We aimed to assess the relationship between endothelial nitric oxide synthase (ENOS) 894 G/T, haem oxygenase-1 (HO1) dinucleotide-length promoter polymorphisms and coronary artery atherosclerotic invol vement and its changes during statin therapy. Coronary angiography, intravascular ultrasound (IVUS), IVUS-derived virtual histology (VH) and genetic polymorphism analysis were performed at study entry. Patients were randomized 1:1 to standard or aggressive hypolipidaemic treatment, and a follow-up evaluation was performed after twelve months. Plaque magnitude was significantly higher in carriers of HO1 risk variants when compared with carriers of the protective variants (< 25 GT repeats). Similarly, the total coronary atherosclerotic burden was significantly greater in HO1 risk variant carriers than in HO1 protective variant carriers. Both parameters did not differ with respect to the ENOS genotype. A higher prevalence of thin-cap fibroatheroma (TCFA) in HO1 risk variant carriers was observed, compared with the HO1 protective variant carriers. The prevalence of TCFA was not influenced by the ENOS genotype. Baseline plaque composition did not differ significantly with respect to both polymorphisms. Significant interactions between plaque composition changes and ENOS and HO1 genotypes were observed during statin treatment. In conclusion, the protective HO1 promoter polymorphism correlates with a lower coronary artery plaque burden, whereas the protective ENOS 894 G/T polymorphism seems to favourably influence changes of coronary artery plaque composition during statin therapy, but has no significant correlation to the magnitude of coronary atherosclerosis.

Recruitment of the auditory cortex in congenitally deaf cats by long-term cochlear electrostimulation.

In congenitally deaf cats, the central auditory system is deprived of acoustic input because of degeneration of the organ of Corti before the onset of hearing. Primary auditory afferents survive and can be stimulated electrically. By means of an intracochlear implant and an accompanying sound processor, congenitally deaf kittens were exposed to sounds and conditioned to respond to tones. After months of exposure to meaningful stimuli, the cortical activity in chronically implanted cats produced field potentials of higher amplitudes, expanded in area, developed long latency responses indicative of intracortical information processing, and showed more synaptic efficacy than in naïve, unstimulated deaf cats. The activity established by auditory experience resembles activity in hearing animals.

Results of open heart surgery in Jehovah's Witnesses patients.

AIM: The aim of this paper was to evaluate the results in patients from the religious community of Jehovah's Witnesses (JW) undergoing open heart surgery. METHODS: Between January 1998 and November 2007, 35 patients with a religious background of JW church underwent open heart surgery at the Department of Cardiothoracic Surgery, Medical University of Vienna (Austria). Eighteen patients underwent coronary artery bypass graft (CABG), 11 patients underwent valve surgery and 5 patients underwent combined procedures. One patient underwent isolated ascending aortic replacement. Five patients undergoing CABG were operated without cardiopulmonary bypass (CBP). RESULTS: Mean baseline hematocrit serum levels were 35.8+/-6.3%. The mean decrease of hematocrit serum levels was 20.0+/-21.1% after surgery. The mean decrease of hematocrit serum levels in patients undergoing CABG without CPB was 12.5+/-5.4% and 12.0+/-20.0% in patients after isolated valve replacement. One patient died during the operation. Four patients died in the postoperative period due to anemia. During follow-up, being 34.6+/-34.8 months to date, no cardiovascular related adverse event has been observed. CONCLUSIONS: The decrease of hematocrit serum levels is significantly characterizing the postoperative period of open heart surgery in JW. In patients undergoing CABG without CPB and in patients undergoing isolated valve replacement, decrease of hematocrit serum levels was lowest. Therefore, these techniques should be considered for first choice when appropriate. Furthermore, highly normal preoperative hematocrit serum levels and a meticulous surgical technique remain the mainstay of therapy in these patients.

[Early hearing experience and sensitive developmental periods]. / Frühe Hörerfahrung und sensible Entwicklungsphasen.

This article reviews the studies on functional deficits in the auditory cortex of congenitally deaf animals. It compares their results with psychophysical and imaging data obtained from prelingually deaf humans. The studies demonstrate that the development of the auditory cortex is affected by the absence of hearing experience. In humans, the restoration of hearing after congenital deafness shows a sensitive period of 4 years, whereas even within this sensitive period cortical plasticity is already decreasing with increasing age. The reasons for the sensitive period are developmental changes of synaptic plasticity, developmentally modified synaptogenesis and synaptic pruning as well as changes in connectivity of the auditory cortex. Absence of top-down interactions from higher order auditory areas is another cardinal reason for the sensitive period. All these mechanisms contribute to the decreasing capacity for cortical plasticity during postnatal development. From the developmental and neurophysiological point of view, an early identification of hearing loss is an important prerequisite for effective therapy.

The inverse relationship between chronic HBV and HCV infections among injection drug users is associated with decades of age and drug use.

Infection with hepatitis C virus (HCV) may suppress co-infection with hepatitis B virus (HBV) during acute or chronic HBV infection. We examined relationships between HBV infection, HCV infection and other factors among injection drug users (IDUs) with antibodies to both viruses. Participants enrolled in a cross-sectional study during 1998-2000 were considered to have been infected with HBV if they had core antibody, to be chronically infected if they had hepatitis B surface antigen (HBsAg), to have been infected with HCV if they had HCV antibody and to be chronically infected if they had HCV RNA. Among 1694 participants with antibody to both viruses, HBsAg prevalence decreased with increasing age among those positive for HCV RNA [from 4.55% in those 18-29 years to 1.03% in those >or=50 years old (P(trend) = 0.02)], but not among those who were negative for HCV RNA. Chronic HBV infection was less common overall among those with chronic HCV infection (odds ratio [OR], 0.25; P < 0.0001), but this inverse relationship was much stronger in the oldest (>50 years; OR = 0.15) than the youngest (18-29 years; OR = 0.81) participants (P(trend) = 0.03). Similar results were obtained when duration of injection drug use was substituted for age (P(trend) = 0.05). Among IDUs who have acquired both HBV and HCV, chronic HBV infection is much less common among those with chronic HCV infection, but this inverse relationship increases markedly with increasing years of age and injection drug use. Co-infection with HCV may enhance the resolution of HBsAg during the chronic phases of these infections.

Publisher Correction: Spiral Form of the Human Cochlea Results from Spatial Constraints.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

New thin-film surface electrode array enables brain mapping with high spatial acuity in rodents.

In neuroscience, single-shank penetrating multi-electrode arrays are standard for sequentially sampling several cortical sites with high spatial and temporal resolution, with the disadvantage of neuronal damage. Non-penetrating surface grids used in electrocorticography (ECoG) permit simultaneous recording of multiple cortical sites, with limited spatial resolution, due to distance to neuronal tissue, large contact size and high impedances. Here we compared new thin-film parylene C ECoG grids, covering the guinea pig primary auditory cortex, with simultaneous recordings from penetrating electrode array (PEAs), inserted through openings in the grid material. ECoG grid local field potentials (LFP) showed higher response thresholds and amplitudes compared to PEAs. They enabled, however, fast and reliable tonotopic mapping of the auditory cortex (place-frequency slope: 0.7 mm/octave), with tuning widths similar to PEAs. The ECoG signal correlated best with supragranular layers, exponentially decreasing with cortical depth. The grids also enabled recording of multi-unit activity (MUA), yielding several advantages over LFP recordings, including sharper frequency tunings. ECoG first spike latency showed highest similarity to superficial PEA contacts and MUA traces maximally correlated with PEA recordings from the granular layer. These results confirm high quality of the ECoG grid recordings and the possibility to collect LFP and MUA simultaneously.

Spiral Form of the Human Cochlea Results from Spatial Constraints.

The human inner ear has an intricate spiral shape often compared to shells of mollusks, particularly to the nautilus shell. It has inspired many functional hearing theories. The reasons for this complex geometry remain unresolved. We digitized 138 human cochleae at microscopic resolution and observed an astonishing interindividual variability in the shape. A 3D analytical cochlear model was developed that fits the analyzed data with high precision. The cochlear geometry neither matched a proposed function, namely sound focusing similar to a whispering gallery, nor did it have the form of a nautilus. Instead, the innate cochlear blueprint and its actual ontogenetic variants were determined by spatial constraints and resulted from an efficient packing of the cochlear duct within the petrous bone. The analytical model predicts well the individual 3D cochlear geometry from few clinical measures and represents a clinical tool for an individualized approach to neurosensory restoration with cochlear implants.

Encapsulated cell device approach for combined electrical stimulation and neurotrophic treatment of the deaf cochlea.

Profound hearing impairment can be overcome by electrical stimulation (ES) of spiral ganglion neurons (SGNs) via a cochlear implant (CI). Thus, SGN survival is critical for CI efficacy. Application of glial cell line-derived neurotrophic factor (GDNF) has been shown to reduce SGN degeneration following deafness. We tested a novel method for local, continuous GDNF-delivery in combination with ES via a CI. The encapsulated cell (EC) device contained a human ARPE-19 cell-line, genetically engineered for secretion of GDNF. In vitro, GDNF delivery was stable during ES delivered via a CI. In the chronic in vivo part, cats were systemically deafened and unilaterally implanted into the scala tympani with a CI and an EC device, which they wore for six months. The implantation of control devices (same cell-line not producing GDNF) had no negative effect on SGN survival. GDNF application without ES led to an unexpected reduction in SGN survival, however, the combination of GDNF with initial, short-term ES resulted in a significant protection of SGNs. A tight fibrous tissue formation in the scala tympani of the GDNF-only group is thought to be responsible for the increased SGN degeneration, due to mechanisms related to an aggravated foreign body response. Furthermore, the fibrotic encapsulation of the EC device led to cell death or cessation of GDNF release within the EC device during the six months in vivo. In both in vitro and in vivo, fibrosis was reduced by CI stimulation, enabling the neuroprotective effect of the combined treatment. Thus, fibrous tissue growth limits treatment possibilities with an EC device. For a stable and successful long-term neurotrophic treatment of the SGN via EC devices in human CI users, it would be necessary to make changes in the treatment approach (provision of anti-inflammatories), the EC device surface (reduced cell adhesion) and the ES (initiation prior to fibrosis formation).

Unmet need for recommended preventive health services among clients of California syringe exchange programs: implications for quality improvement.

BACKGROUND: Comprehensive preventive services are recommended for injection drug users (IDU), including screening tests, vaccinations, risk reduction counseling, and sterile syringes. Syringe exchange programs (SEP) may facilitate receipt of preventive services by IDUs, but whether SEP clients receive recommended preventive care is not known. We examined use of recommended preventive services by clients of 23 SEPs throughout California. METHODS: Five hundred and sixty SEP clients were recruited from 23 SEPs throughout California between March and September 2003. Receipt of 10 recommended preventive services and source of care (SEP versus non-SEP providers) was ascertained from client interviews. RESULTS: On average, SEP clients received only 13% of recommended preventive services and 49% of clients received none of the recommended services. Of services that were received, 76% were received from SEPs. In multivariate analysis, use of drug treatment and more frequent SEP visits were associated with receipt of recommended preventive services by clients. CONCLUSIONS: SEPs are often the only source of preventive care for their IDU clients. Still, SEP clients fail to receive most recommended preventive services. Interventions to increase use of preventive services and improve the quality of preventive care received by IDUs, such as increased access to drug treatment and SEPs, are needed.

Evaluation of farnesyl:protein transferase and geranylgeranyl:protein transferase inhibitor combinations in preclinical models.

Farnesyl:protein transferase (FPTase) inhibitors (FTIs) were originally developed as potential anticancer agents targeting the ras oncogene and are currently in clinical trials. Whereas FTIs inhibit the farnesylation of Ha-Ras, they do not completely inhibit the prenylation of Ki-Ras, the allele most frequently mutated in human cancers. Whereas farnesylation of Ki-Ras is blocked by FTIs, Ki-Ras remains prenylated in FTI-treated cells because of its modification by the related prenyltransferase, geranylgeranyl:protein transferase type I (GGPTase-I). Hence, cells transformed with Ki-ras tend to be more resistant to FTIs than Ha-ras-transformed cells. To determine whether Ki-ras-transformed cells can be targeted by combining an FTI with a GGPTase-I inhibitor (GGTI), we evaluated potent, selective FTIs, GGTIs, and dual prenylation inhibitors (DPIs) that have both FTI and GGTI activity. We find that in human PSN-1 pancreatic tumor cells, which harbor oncogenic Ki-ras, and in other tumor lines having either wild-type or oncogenic Ki-ras, treatment with an FTI/GGTI combination or with a DPI blocks Ki-Ras prenylation and induces markedly higher levels of apoptosis relative to FTI or GGTI alone. We demonstrate that these compounds can inhibit their enzyme targets in mice by monitoring pancreatic and tumor tissues from treated animals for inhibition of prenylation of Ki-Ras, HDJ2, a substrate specific for FPTase, and Rap1A, a substrate specific for GGPTase-I. Continuous infusion (72 h) of varying doses of GGTI in conjunction with a high, fixed dose of FTI causes a dose-dependent inhibition of Ki-Ras prenylation. However, a 72-h infusion of a GGTI, at a dose sufficient to inhibit Ki-Ras prenylation in the presence of an FTI, causes death within 2 weeks of the infusion when administered either as monotherapy or in combination with an FTI. DPIs are also lethal after a 72-h infusion at doses that inhibit Ki-Ras prenylation. Because 24 h infusion of a high dose of DPI is tolerated and inhibits Ki-Ras prenylation, we compared the antitumor efficacy from a 24-h FTI infusion to that of a DPI in a nude mouse/PSN-1 tumor cell xenograft model and in Ki-ras transgenic mice with mammary tumors. The FTI and DPI were dosed at a level that provided comparable inhibition of FPTase. The FTI and the DPI displayed comparable efficacy, causing a decrease in growth rate of the PSN-1 xenograft tumors and tumor regression in the transgenic model, but neither treatment regimen induced a statistically significant increase in tumor cell apoptosis. Although FTI/GGTI combinations elicit a greater apoptotic response than either agent alone in vitro, the toxicity associated with GGTI treatment in vivo limits the duration of treatment and, thus, may limit the therapeutic benefit that might be gained by inhibiting oncogenic Ki-Ras through dual prenyltransferase inhibitor therapy.