Design and Evaluation of [18F]CHDI-650 as a Positron Emission Tomography Ligand to Image Mutant Huntingtin Aggregates

Therapeutic interventions are being developed for Huntington's disease (HD), a hallmark of which is mutant huntingtin protein (mHTT) aggregates. Following the advancement to human testing of two [¹¹C]-PET ligands for aggregated mHTT, attributes for further optimization were identified. We replaced the pyridazinone ring of CHDI-180 with a pyrimidine ring and minimized off-target binding using brain homogenate derived from Alzheimer's disease patients. The major in vivo metabolic pathway via aldehyde oxidase was blocked with a 2-methyl group on the pyrimidine ring. A strategically placed ring-nitrogen on the benzoxazole core ensured high free fraction in the brain without introducing efflux. Replacing a methoxy pendant with a fluoro-ethoxy group and introducing deuterium atoms suppressed oxidative defluorination and accumulation of [¹⁸F]-signal in bones. The resulting PET ligand, CHDI-650, shows a rapid brain uptake and washout profile in non-human primates and is now being advanced to human testing.

Spirocycle MmpL3 Inhibitors with Improved hERG and Cytotoxicity Profiles as Inhibitors of Mycobacterium tuberculosis Growth

With the emergence of multi-drug-resistant strains of Mycobacterium tuberculosis, there is a pressing need for new oral drugs with novel mechanisms of action. A number of scaffolds with potent anti-tubercular in vitro activity have been identified from phenotypic screening that appear to target MmpL3. However, the scaffolds are typically lipophilic, which facilitates partitioning into hydrophobic membranes, and several contain basic amine groups. Highly lipophilic basic amines are typically cytotoxic against mammalian cell lines and have associated off-target risks, such as inhibition of human ether-à-go-go related gene (hERG) and IKr potassium current modulation. The spirocycle compound 3 was reported to target MmpL3 and displayed promising efficacy in a murine model of acute tuberculosis (TB) infection. However, this highly lipophilic monobasic amine was cytotoxic and inhibited the hERG ion channel. Herein, the related spirocycles (1-2) are described, which were identified following phenotypic screening of the Eli Lilly corporate library against M. tuberculosis. The novel N-alkylated pyrazole portion offered improved physicochemical properties, and optimization led to identification of a zwitterion series, exemplified by lead 29, with decreased HepG2 cytotoxicity as well as limited hERG ion channel inhibition. Strains with mutations in MmpL3 were resistant to 29, and under replicating conditions, 29 demonstrated bactericidal activity against M. tuberculosis. Unfortunately, compound 29 had no efficacy in an acute model of TB infection; this was most likely due to the in vivo exposure remaining above the minimal inhibitory concentration for only a limited time.

Essential but Not Vulnerable: Indazole Sulfonamides Targeting Inosine Monophosphate Dehydrogenase as Potential Leads against Mycobacterium tuberculosis

A potent, noncytotoxic indazole sulfonamide was identified by high-throughput screening of >100,000 synthetic compounds for activity against Mycobacterium tuberculosis (Mtb). This noncytotoxic compound did not directly inhibit cell wall biogenesis but triggered a slow lysis of Mtb cells as measured by release of intracellular green fluorescent protein (GFP). Isolation of resistant mutants followed by whole-genome sequencing showed an unusual gene amplification of a 40 gene region spanning from Rv3371 to Rv3411c and in one case a potential promoter mutation upstream of guaB2 (Rv3411c) encoding inosine monophosphate dehydrogenase (IMPDH). Subsequent biochemical validation confirmed direct inhibition of IMPDH by an uncompetitive mode of inhibition, and growth inhibition could be rescued by supplementation with guanine, a bypass mechanism for the IMPDH pathway. Beads containing immobilized indazole sulfonamides specifically interacted with IMPDH in cell lysates. X-ray crystallography of the IMPDH-IMP-inhibitor complex revealed that the primary interactions of these compounds with IMPDH were direct pi-pi interactions with the IMP substrate. Advanced lead compounds in this series with acceptable pharmacokinetic properties failed to show efficacy in acute or chronic murine models of tuberculosis (TB). Time-kill experiments in vitro suggest that sustained exposure to drug concentrations above the minimum inhibitory concentration (MIC) for 24 h were required for a cidal effect, levels that have been difficult to achieve in vivo. Direct measurement of guanine levels in resected lung tissue from tuberculosis-infected animals and patients revealed 0.5-2 mM concentrations in caseum and normal lung tissue. The high lesional levels of guanine and the slow lytic, growth-rate-dependent effect of IMPDH inhibition pose challenges to developing drugs against this target for use in treating TB.

A geostatistical approach to identify and mitigate agricultural nitrous oxide emission hotspots

Anthropogenic emissions of nitrous oxide (N₂O), a trace gas with severe environmental costs, are greatest from agricultural soils amended with nitrogen (N) fertilizer. However, accurate N₂O emission estimates at fine spatial scales are made difficult by their high variability, which represents a critical challenge for the management of N₂O emissions. Here, static chamber measurements (n=60) and soil samples (n=129) were collected at approximately weekly intervals (n=6) for 42-d immediately following the application of N in a southern Minnesota cornfield (15.6-ha), typical of the systems prevalent throughout the U.S. Corn Belt. These data were integrated into a geostatistical model that resolved N₂O emissions at a high spatial resolution (1-m). Field-scale N₂O emissions exhibited a high degree of spatial variability, and were partitioned into three classes of emission strength: hotspots, intermediate, and coldspots. Rates of emission from hotspots were 2-fold greater than non-hotspot locations. Consequently, 36% of the field-scale emissions could be attributed to hotspots, despite representing only 21% of the total field area. Variations in elevation caused hotspots to develop in predictable locations, which were prone to nutrient and moisture accumulation caused by terrain focusing. Because these features are relatively static, our data and analyses indicate that targeted management of hotspots could efficiently reduce field-scale emissions by as much 17%, a significant benefit considering the deleterious effects of atmospheric N₂O.

Characterizing the dielectric properties of human mesenchymal stem cells and the effects of charged elastin-like polypeptide copolymer treatment

HUMAN MESENCHYMAL STEM CELLS (HMSCS) HAVE THREE KEY PROPERTIES THAT MAKE THEM DESIRABLE FOR STEM CELL THERAPEUTICS: differentiation capacity, trophic activity, and ability to self-renew. However, current separation techniques are inefficient, time consuming, expensive, and, in some cases, alter hMSCs cellular function and viability. Dielectrophoresis (DEP) is a technique that uses alternating current electric fields to spatially separate biological cells based on the dielectric properties of their membrane and cytoplasm. This work implements the first steps toward the development of a continuous cell sorting microfluidic device by characterizing native hMSCs dielectric signatures and comparing them to hMSCs morphologically standardized with a polymer. A quadrapole Ti-Au electrode microdevice was used to observe hMSC DEP behaviors, and quantify frequency spectra and cross-over frequency of hMSCs from 0.010-35 MHz in dextrose buffer solutions (0.030 S/m and 0.10 S/m). This combined approach included a systematic parametric study to fit a core-shell model to the DEP spectra over the entire tested frequency range, adding robustness to the analysis technique. The membrane capacitance and permittivity were found to be 2.2 pF and 2.0 in 0.030 S/m and 4.5 pF and 4.1 in 0.10 S/m, respectively. Elastin-like polypeptide (ELP-) polyethyleneimine (PEI) copolymer was used to control hMSCs morphology to spheroidal cells and aggregates. Results demonstrated that ELP-PEI treatment controlled hMSCs morphology, increased experiment reproducibility, and concurrently increased hMSCs membrane permittivity to shift the cross-over frequency above 35 MHz. Therefore, ELP-PEI treatment may serve as a tool for the eventual determination of biosurface marker-dependent DEP signatures and hMSCs purification.

Sequential actions of BMP receptors control neural precursor cell production and fate

Bone morphogenetic proteins (BMPs) have diverse and sometimes paradoxical effects during embryonic development. To determine the mechanisms underlying BMP actions, we analyzed the expression and function of two BMP receptors, BMPR-IA and BMPR-IB, in neural precursor cells in vitro and in vivo. Neural precursor cells always express Bmpr-1a, but Bmpr-1b is not expressed until embryonic day 9 and is restricted to the dorsal neural tube surrounding the source of BMP ligands. BMPR-IA activation induces (and Sonic hedgehog prevents) expression of Bmpr-1b along with dorsal identity genes in precursor cells and promotes their proliferation. When BMPR-IB is activated, it limits precursor cell numbers by causing mitotic arrest. This results in apoptosis in early gestation embryos and terminal differentiation in mid-gestation embryos. Thus, BMP actions are first inducing (through BMPR-IA) and then terminating (through BMPR-IB), based on the accumulation of BMPR-IB relative to BMPR-IA. We describe a feed-forward mechanism to explain how the sequential actions of these receptors control the production and fate of dorsal precursor cells from neural stem cells.

Incidence and determinants of Pseudomonas aeruginosa infection among persons with HIV: association with hospital exposure

BACKGROUND

Little information exists on risk factors for Pseudomonas aeruginosa infection in persons with HIV. We assessed the incidence and factors associated with P aeruginosa among persons with HIV enrolled in a large observational cohort study in Los Angeles.

METHODS

Data were analyzed from 4825 persons aged > or =13 years with HIV infection enrolled from 4 outpatient facilities from 1990 to 1998. The association between P aeruginosa infection and demographic, risk behavior, and clinical factors was assessed.

RESULTS

P aeruginosa was diagnosed in 72 (1.5%) patients representing a crude incidence rate of 0.74 per 100 person-years. The most frequent site of infection was pulmonary (47%). In multivariate analysis, prior hospitalization (adjusted rate ratio = 7.9, 95% CI, 3.8-16.2), and both dapsone (adjusted rate ratio = 4.0, 95% CI, 2.2-7.4) and trimethoprim-sulfamethoxazole (adjusted rate ratio = 2.5, 95% CI, 1.2-5.3) use were independently associated with higher rates of infection. Increasing days of inpatient stay (P <.01) and decreasing CD4(+) counts (P <.01) were strongly associated with P aeruginosa. Azithromycin use decreased the risk of infection by nearly 70%.

CONCLUSION

Although the overall observed incidence of P aeruginosa was low, hospital exposure, declining CD4(+) levels, and the use of dapsone or trimethoprim-sulfamethoxazole increased the risk of P aeruginosa disease, and azithromycin use was protective in this population. These findings may assist in the early recognition and diagnosis of persons likely to be at increased risk of P aeruginosa infection.

POU transcription factors control expression of CNS stem cell-specific genes

Multipotential stem cells throughout the developing central nervous system have common properties. Among these is expression of the intermediate filament protein nestin and the brain fatty acid binding protein (B-FABP). To determine if common mechanisms control transcription in CNS stem cells, the regulatory elements of these two genes were mapped in transgenic mice. A 257 basepair enhancer of the rat nestin gene is sufficient for expression throughout the embryonic neuroepithelium. This enhancer contains two sites bound by the class III POU proteins Brn-1, Brn-2, Brn-4, and Tst-1. Only one of the two POU sites is required for CNS expression. An adjacent hormone response element is necessary for expression in the dorsal midbrain and forebrain. The regulatory sites of the B-FABP gene are strikingly similar to those of the nestin gene. A hybrid POU/Pbx binding site is recognized in vitro by Pbx-1, Brn-1 and Brn-2. This site is essential for expression in most of the CNS. In addition, a hormone response element is necessary for forebrain expression. Both the nestin and B-FABP genes therefore depend on POU binding sites for general CNS expression, with hormone response elements additionally required for activity in the anterior CNS. These data indicate that regulation by POU proteins and hormone receptors is a general mechanism for CNS stem cell-specific transcription.

Seasonality and factors associated with cryptosporidiosis among individuals with HIV infection

The seasonality and factors associated with Cryptosporidium infection were assessed in a cohort of HIV-infected patients in Los Angeles County to better define the epidemiology of cryptosporidiosis among individuals with HIV. Data were analysed from a cohort of 4247 patients > or = 13 years of age with HIV infection enrolled from four outpatient facilities in Los Angeles, 1990-6. Cryptosporidiosis was diagnosed in 120 (2.8%) patients. Among the 1296 individuals with complete follow-up until death, cryptosporidiosis occurred in 69 (5.3%). The seasonal rate of cryptosporidiosis showed a modest bimodal trend with the highest rates occurring in March-May and September-October. There was no difference in the rate of cryptosporidiosis for the periods of heaviest rainfall (December-March) and low rainfall (April-November). Infection rates were higher among males (1.59 per 100 person-years) than females (0.92) and lower in blacks (0.98) than other racial/ethnic groups (1.80). A significant trend of decreasing cryptosporidiosis was observed with increasing age, with the highest rate (2.34) in the 13-34 year age group. A strong association between cryptosporidiosis and CD4+ count was noted. These data suggest that cryptosporidiosis among HIV-infected individuals in Los Angeles County exhibits a modest spring and fall seasonality. This pattern of occurrence of cryptosporidiosis appears temporally unrelated to local rainfall patterns. Our findings suggest that HIV-infected men, individuals in younger age groups and those with CD4+ lymphocyte counts < 100 x 10(6)/l are at increased risk of cryptosporidiosis. Blacks with HIV infection appear less likely than other racial/ethnic groups to be diagnosed with Cryptosporidium infection. These results may provide insight into possible routes of transmission and sources of cryptosporidiosis infection in individuals with HIV.

A multidimensional scaling analysis of the techniques that physiotherapists use

Following the essentially 'hands-on' origin of the physiotherapy profession a century ago, the range of techniques available to practitioners has expanded considerably. While this expansion of techniques has been of research interest, the main focus has been upon individual techniques, thus neglecting the fundamental question of the use of techniques in combination. In addition, researchers have tended to treat the profession as homogeneous, thus overlooking possible differences in technique usage. The present study addressed these questions. It postulated that ordered combinations of techniques usage would be employed, and that a typology would exist that differentiates the profession according to patterns of use. The study comprised a questionnaire survey of 230 clinical physiotherapists in England. This sought information on the range and frequency of techniques used over the previous six months. Descriptive analysis indicated a high frequency of use of several techniques, notably exercise therapy, passive mobilisation techniques and ultrasound. A feature of the analysis was the use of two multivariate procedures, multidimensional scalogram analysis (MSA) and smallest space analysis (SSA). The SSAs revealed a clear structure concerning combinations of techniques used, and the MSAs provided a coherent typology based upon this usage. One feature of the techniques in combination that emerged was the frequent use of passive mobilising techniques, which was associated with equally frequent use of electrotherapy techniques. In contrast, respondents who employed neurological or respiratory techniques made little use of electrotherapy. Regarding the typology, differentiation of the profession according to use of particular combinations of techniques indicated probable specialisms. The specialist areas identified were neurological physiotherapy, respiratory physiotherapy and musculo-skeletal physiotherapy. The results reinforce the need for both future research and physiotherapy education to address the issue of techniques in combination. Finally, and on the basis of the analyses, elements of a theoretical model are advanced that may provide directions for future research.

The relationship between the density of Aedes vigilax (Diptera: Culicidae) eggshells and environmental factors on Kooragang Island, New South Wales, Australia

Knowledge of oviposition sites selected by wetland mosquitoes could improve mosquito control and guide wetland rehabilitation practices to avoid creating or exacerbating a mosquito problem. Two studies that enumerated Aedes vigilax eggshells found in salt marsh soil on the western portion of Kooragang Island in New South Wales, Australia, allowed an evaluation of oviposition sites. In one study, the density of eggshells found in samples collected from a large area was related to environmental factors, including distance from nearby drainage channels, vegetation cover, elevation, and terrain characteristics. Multiple-regression analysis suggested eggshell densities were positively correlated with the presence of depressions and ponds, vegetation cover, and distance from culverts, but negatively related to elevation. In another study, eggshell density was related to relative elevation and vegetation species within each of two 400-m2 plots on Kooragang Island. In all but one instance, samples from bare soil contained fewer eggshells than samples with vegetation cover at both plots. Eggshell density did not differ between the two dominant vegetation species, Sarcocornia quinqueflora and Sporobolus virginicus, although bare soil of one plot had a mean eggshell density similar to that of soil with S. quinqueflora cover. Eggshells were at highest density at intermediate elevations at one plot but at low elevations at the other.

Incidence and factors associated with extrapulmonary cryptococcosis among persons with HIV infection in Los Angeles County

OBJECTIVE

To determine the incidence and factors associated with extrapulmonary cryptococcosis among a cohort of persons with HIV in Los Angeles County.

DESIGN

Records-based cohort study.

METHODS

Data were analysed from a cohort of 3836 persons aged > or = 13 years with HIV infection enrolled from four outpatient facilities in Los Angeles from 1990 to 1995. The potential association between cryptococcosis and demographic risk behavior and clinical factors was assessed. Possible seasonal clustering was evaluated and an estimate of survival following cryptococcosis was calculated. Multivariate analysis was performed using a Cox proportional hazards approach.

RESULTS

Cryptococcosis was identified in 112 patients (2.9%) representing a crude incidence rate of 1.7 cases per 100 person-years experience. The rate of cryptococcosis was higher among men than women (1.9 and 0.6, respectively; P < 0.01) and in Hispanics than in whites (2.3 and 1.2, respectively, P < 0.01). A significant trend of decreasing cryptococcosis was observed with increasing age (P < 0.01). Cryptococcosis increased with declining CD4+ lymphocyte count, with risk being greatest at CD4+ cell counts below 100 x 10(6)/l (P < 0.001). In bivariate analysis persons with a history of antifungal medication had a marginally lower rate of cryptococcosis, but this difference was not statistically significant. The rate of cryptococcosis was significantly higher in fall and winter months [rate ratio (RR), 1.45; 95% confidence interval (CI), 1.0-2.3; P = 0.05]. After controlling for other variables, cryptococcosis was more common in men than women (adjusted RR, 3.2; 95% CI, 1.0-10.4) and in Hispanics than whites (adjusted RR, 1.6; 95% CI, 0.9-2.7). Both CD4+ count and age continued to be strongly associated with the occurrence of cryptococcosis. After controlling for other factors a substantial protective effect was observed for antifungal therapy (adjusted RR, 0.48; 95% CI, 0.29-0.79).

CONCLUSION

Our data suggest that HIV-infected men, Hispanics, persons aged under 45 years and those with CD4+ counts under 100 x 10(6)/l have an increased risk of extrapulmonary cryptococcosis. A fall-winter seasonality in the occurrence of cryptococcosis may exist. Significant primary protection against cryptococcal disease is afforded by antifungal therapy. These results may provide insight into possible routes of transmission and sources of cryptococcal infection and help guide both primary prophylaxis and early recognition and diagnosis in persons likely to be at increased risk.

Test of a mosquito eggshell isolation method and subsampling procedure

Production of Aedes vigilax, the common salt-marsh mosquito, can be assessed by determining eggshell densities found in soil. In this study, 14 field-collected eggshell samples were used to test a subsampling technique and compare eggshell counts obtained with a flotation method to those obtained by direct examination of sediment (DES). Relative precision of the subsampling technique was assessed by determining the minimum number of subsamples required to estimate the true mean and confidence interval of a sample at a predetermined confidence level. A regression line was fitted to cube-root transformed eggshell counts obtained from flotation and DES and found to be significant (P < 0.001, r2 = 0.97). The flotation method allowed processing of samples in about one-third of the time required by DES, but recovered an average of 44% of the eggshells present. Eggshells obtained with the flotation method can be used to predict those from DES using the following equation: DES count = [1.386 x (flotation count)0.33 - 0.01]3.

Emerging patterns of HIV transmission: the value of alternative surveillance methods

OBJECTIVE

To assess the current patterns of HIV transmission in Los Angeles County and determine if AIDS surveillance data accurately reflect these patterns.

DESIGN

Records-based cohort study.

METHODS

The demographic and HIV risk characteristics of persons considered to be recently infected with HIV (CD4+ count > 700 x 10(6)/l) were determined and compared with the characteristics of persons meeting the Centers for Disease Control and Prevention (CDC) 1993 AIDS case definition. Data were obtained for patients with HIV infection enrolled from four HIV outpatient clinics and analyzed between August 1991 and July 1993.

RESULTS

The patient cohort included 1857 persons with HIV infection; 1096 (59.1%) met the CDC 1993 AIDS case definition and 134 (7.2%) had a CD4+ lymphocyte count > 700 x 10(6)/l. The median CD4+ count for the group presumed to be recently infected was 809 x 10(6)/l. Persons considered recently infected with HIV were more likely than those meeting the AIDS case definition to be female (26.1 and 14.5%, respectively; P < 0.001), black (28.4 and 18.2%, respectively; P = 0.001), or male homosexual injecting drug users (IDU; 6.7 and 3.4%, respectively; P = 0.05). After controlling for confounding variables by logistic regression, persons recently infected were more likely to be female [adjusted odds ratio (OR), 3.4; 95% confidence interval (CI), 1.8-6.5; P < 0.001], black (adjusted OR, 1.6; 95% CI, 1.1-2.5; P = 0.02) or male homosexual IDU (adjusted OR, 2.4; 95% CI, 1.1-5.2; P = 0.02) than persons with AIDS.

CONCLUSIONS

Our results suggest that the HIV epidemic in Los Angeles County is currently advancing into different subpopulations and indicate that the current patterns of HIV transmission in the County are not fully reflected in standard AIDS surveillance activities. However, our data must be interpreted cautiously because of potential selection and misclassification biases. These findings illustrate the benefits of alternative surveillance mechanisms in detecting important changes in HIV transmission and defining groups at risk, especially in jurisdictions without HIV reporting.

Anal intercourse and disclosure of HIV infection among seropositive gay and bisexual men

Human immunodeficiency virus (HIV)-infected gay and bisexual men (n = 609) randomly selected from two HIV outpatient clinics in Los Angeles completed confidential, self-administered questionnaires at the clinics, reporting sexual activities and disclosure during the previous 2 months. Approximately 9% had engaged in unprotected insertive anal intercourse with one or more partners. This activity was 3.27 times more likely to have occurred with seropositive partners than with partners who were seronegative or whose serostatus was unknown. Fourteen men (2.3% of total sample) had engaged in unprotected insertive anal sex with 25 seronegative or unknown serostatus partners who were not informed of their risk of infection. Thirty-three men (5.4% of total sample) had engaged in this activity with 37 seropositive partners who were informed. Clinicians and other health professionals can play an important role in helping to control the HIV epidemic by discussing with seropositive patients the importance of using safer sex and informing sexual partners. Such discussion should include information about the potentially negative health effects of unprotected sex between seropositive persons.

Increased density of HLA-DR antigen on monocytes of patients infected with the human immunodeficiency virus

Monocytes and macrophages play an important role in the pathogenesis of the acquired immunodeficiency syndrome (AIDS). Dysfunction of these cells contributes to the immunocompromised state that characterizes AIDS, and they probably serve as a reservoir for the human immunodeficiency virus (HIV). HIV-infected macrophages may also be responsible for the infection of many CD4-positive lymphocytes by means of cell to cell contact during the initiation of immunological responses. The efficiency of this process would be enhanced by activation of the macrophages, since that is accompanied by increased expression of class II major histocompatibility (HLA-DR) antigen. Using a direct blood antibody marking procedure in conjunction with flow cytometry, we have analyzed the expression of HLA-DR antigen on the surfaces of monocytes present in the peripheral blood of HIV-infected patients. In contrast to the results reported by other investigators who purified the monocytes using Ficoll-Hypaque centrifugation prior to antibody marking, we found that the percentage of monocytes expressing HLA-DR antigen was identical in the patients and normal controls. However, a subpopulation of monocytes was detected in the blood of the majority of the patients that was expressing increased levels of HLA-DR antigen. It was also found that the proportion of monocytes with a high density of HLA-DR antigen on their surfaces negatively correlated with the absolute numbers of CD4-positive lymphocytes present in the peripheral blood of the patient. These findings support the postulated role of monocytes and macrophages in the HIV infection and ultimate destruction of CD4-positive lymphocytes.

Management of patients with glottic and subglottic stenosis resulting from thermal burns

A series of 11 laryngeal burn patients is reviewed. Various methods of laryngeal burn management are detailed, including steroid usage, laser therapy, and reconstruction with local flaps, grafts, and stents.

Does diazepam really reduce the cardiotoxic effects of intravenous bupivacaine?

The effect of diazepam on the cardiovascular toxicity of bupivacaine was investigated in a rat model. Under chloral hydrate (400 mg/kg intraperitoneal) anesthesia, unilateral femoral venous and bilateral femoral arterial cannulae were placed for administration of drugs, for blood sampling, and for continuous qualitative monitoring of arterial blood pressure. Lead II ECG was continuously recorded and a tracheostomy performed to increase FIO2 by use of a "T-piece." Four groups of 24 to 36 rats each were studied. All rats received IV bupivacaine 2 mg/kg, within 10 seconds. Group I, the control group, received only bupivacaine. Groups II and III received IV diazepam 0.2 mg/kg, or diazepam vehicle in an equivalent volume, respectively. Five minutes after this pretreatment, groups II and III received IV bupivacaine 2 mg/kg. Group IV was given diazepam, 0.2 mg/kg, 30 seconds after injection of 2 mg/kg bupivacaine. A marked respiratory and metabolic acidosis occurred in all rats but was significantly worse in groups II and III. No rat in the study became hypoxemic. Serious arrhythmias (ventricular or supraventricular tachycardia) were noted in all groups, but the incidence was significantly higher in the group of rats given diazepam pretreatment than in the other three groups. It is concluded that IV diazepam 0.2 mg/kg given 5 minutes before administration of IV bupivacaine 2 mg/kg increases the incidence of serious cardiac arrhythmias. Second, this increase is not solely due to increased acidosis, because the rats receiving the vehicle (group III) developed equivalent acidosis but did not develop increased arrhythmias.

Inverted papilloma

Two hundred twenty-three cases of inverted papilloma seen at this institution over a 35-year period were reviewed. The number of cases steadily increased over each 5-year period. Common presenting signs and symptoms, association with carcinoma, and results of surgical and radiographic treatment are presented. The pathologic controversy surrounding this disease is discussed, and an argument is made for including all pathologic subtypes and septal, lateral wall, or sinus cases in a common clinical grouping of inverted papilloma. Lateral rhinotomy was found to be associated with fewer recurrences and a better probability of cure than lesser procedures and is recommended as the standard surgical therapy. Radiotherapy was found to be a useful and effective adjunct in cases associated with malignancy or for multiply recurrent and inoperable benign inverted papillomas. Lifelong follow-up is urged.

The influence of diazepam on the pharmacokinetics of intravenous and epidural bupivacaine in the rhesus monkey

Pretreatment of patients with diazepam has been reported to reduce the plasma half-life of epidurally administered bupivacaine. The concentrations of bupivacaine used to estimate its plasma half-life may be influenced by input into the vascular system (rate and extent of absorption from the epidural space) and disposition (distribution and elimination). We conducted a study in Rhesus monkeys in which the input function was known and the influence of intravenous diazepam on the disposition of intravenous bupivacaine could be delineated. Results indicated no differences in the primary pharmacokinetic parameters (i.e., total clearance and volume of distribution) for the disposition of bupivacaine. To determine whether the apparent disparity between these results and a previous study might be due to a diazepam-induced alteration in the input function, the influence of intravenous diazepam or saline on the mean absorption time of epidurally administered bupivacaine was also studied in monkeys. Epidural bupivacaine was completely absorbed whether the animals received intravenous saline or intravenous diazepam. No significant differences in pharmacokinetic parameters were found between animals pretreated with intravenous saline or intravenous diazepam and receiving an epidural injection of bupivacaine. The mean residence time of bupivacaine in the body (P less than 0.01) and plasma elimination half-life (P less than 0.005) were significantly longer after epidural administration than after intravenous administration. Intravenous diazepam does not alter the pharmacokinetics of intravenously or epidurally administered bupivacaine.

Influence of cimetidine on bupivacaine disposition in rat and monkey

Recent reports have appeared describing a cimetidine-induced alteration in either the input or disposition function for many drugs. The total clearance component of the disposition function is the primary perturbation. In the present investigation, the influence of cimetidine on bupivacaine disposition was studied, using in vitro and in vivo models. Since the extraction ratio for bupivacaine is low, total clearance follows the capacity-limited theory. Hence, the influence of cimetidine on the intrinsic clearance of bupivacaine was assessed using microsome and hepatocyte models. Results for both systems are in excellent agreement and indicate a noncompetitive inhibition. Additionally, the influence of cimetidine on the protein-binding profile of bupivacaine was determined. In the presence of cimetidine, the these findings was assessed in vivo in rhesus monkeys. co-administration of cimetidine resulted in an increase in the volume of distribution at steady state and no change in the total clearance of bupivacaine.

Diagnosis and management of viral infections

With the introduction of new diagnostic techniques and the expanding choices of antiviral agents, clinical virology is rapidly becoming an important field in infectious diseases. While effective therapy for several respiratory viruses, cytomegalovirus, hepatitis B virus, and Epstein-Barr virus is not currently available, herpes simplex, varicella zoster, and influenza A associated diseases can be adequately treated in many cases at the present time. New agents such as interferon, other nucleoside analogues, and immunomodulators are being investigated for their role in the treatment of viral illnesses, and many such illnesses with high morbidity and mortality may soon have effective therapy.

Bupivacaine protein binding in the term parturient: effects of lactic acidosis

The effects of lactic acidosis on bupivacaine serum protein binding was studied in a group of term parturients and a group of nonpregnant female control subjects. Groups were matched in age and health. Distribution characteristics of bupivacaine in pregnancy were determined. Bupivacaine protein binding was best characterized by the model for two classes of binding sites in all studies. The parturients exhibited a lower capacity for the high-affinity, low-capacity (alpha 1-acid glycoprotein) site and higher affinity for the low-affinity, high-capacity (albumin) site. Lactic acidosis decreased the affinity constant for the high-affinity, low-capacity site in the control group but did not change binding characteristics in the parturients. Free concentration of bupivacaine (Cu) was elevated at low total bupivacaine concentrations (Ct) (less than 10 micrograms/ml). No differences in Cu were detected at concentrations in the cardiotoxic range (greater than 20 micrograms/ml). The Cu values predicted by the estimated binding parameters from in vitro experiments were compared with actual Cu measured in nine parturients at delivery; they correlated significantly (r = 0.94). Distribution changes for bupivacaine in the parturients were consistent with known physiologic changes in body composition associated with pregnancy. Alterations that occur in serum protein binding during pregnancy should not result in increased risk of central nervous system or cardiovascular system toxicity since these alterations do not increase free tissue concentration.

Pharmacokinetics and neural blockade after subarachnoid lidocaine in the rhesus monkey. III. Effects of phenylephrine

Using a rhesus monkey model, lidocaine (30 mg) in 7.5% dextrose was compared with lidocaine (30 mg) in 7.5% dextrose containing 1.5 mg of phenylephrine (Neosynephrine). Phenylephrine increased both duration of maximum motor block and time for complete motor recovery. A significantly higher sensory dermatome level and significantly longer time for complete sensory recovery was found when the lidocaine solution contained phenylephrine. Time for two-segment regression of sensory blockade was unaffected by phenylephrine. The slope of the regression phase for motor block was parallel for both treatments, suggesting differences in neural blockade were caused by a more profound initial block when phenylephrine was added. Pharmacokinetic analysis revealed identical absorption and elimination constants. Maximum plasma concentrations of lidocaine and time to reach maximum plasma concentrations were identical with and without phenylephrine. The systemic absorption (fraction of drug absorbed from the subarachnoid space) was complete with and without phenylephrine. No lag times for systemic absorption were found for either treatment. Our data demonstrate that there are no clinically significant differences between phenylephrine and epinephrine when added to lidocaine solutions for spinal anesthesia.

Comparison of neural blockade and pharmacokinetics after subarachnoid lidocaine in the rhesus monkey. II: Effects of volume, osmolality, and baricity

The effects of volume, osmolality, and baricity on lidocaine spinal anesthesia in the rhesus monkey were studied. Changes in neural blockade, physical properties of cerebrospinal fluid, and arterial pharmacokinetics associated with variations in injectate composition were assessed. Wide ranges of volume, baricity, and osmolality were studied using 1, 2, and 5% lidocaine prepared in either sterile water or 7.5% dextrose. Minimal changes in neural blockade were found in the ranges of osmolality and baricity studied, although 5% lidocaine in sterile water resulted in significantly shorter complete recovery times for both sensory and motor block when compared to other solutions. Samples of cerebrospinal fluid obtained after injection of lidocaine showed increases or decreases in specific gravity and osmolality depending on the physical properties of the solution injected. No differences in elimination phase pharmacokinetics were found with any of the lidocaine solutions. Rates of systemic absorption increased with decreasing osmolality. Osmotic potentiation of lidocaine spinal anesthesia could not be demonstrated.

Neural blockade and pharmacokinetics following subarachnoid lidocaine in the rhesus monkey. I. Effects of epinephrine

A sensitive and reliable animal model for the objective physiologic and pharmacokinetic evaluation of spinal anesthesia has been developed. Using this model, spinal anesthesia using lidocaine (30 mg) in 7.5% dextrose with and without epinephrine was compared. Epinephrine did not alter the degree or duration of time to achieve maximum motor block. However, epinephrine did significantly increase the time for complete motor recovery. A significantly higher dermatome level of sensory block was achieved in the epinephrine-containing solutions, as well as a significantly longer time for complete recovery. This reflects a latent effect of epinephrine, as the time for two-segment regression was independent of epinephrine. Pharmacokinetic analysis showed no effect of epinephrine on absorption and elimination constants. The maximum plasma concentration and time to reach maximum plasma concentration were equal with and without epinephrine.

A comparison of intravenous and subarachnoid lidocaine pharmacokinetics in the rhesus monkey

A comparative study between intravenous and subarachnoid lidocaine in the rhesus monkey was conducted in an effort to compare the kinetics of lidocaine in the monkey with reported intravenous human data, and to determine the rate and extent of systemic absorption of lidocaine following subarachnoid injection. Each animal received an intravenous and subarachnoid treatment in an effort to determine the fraction of drug absorbed. Pharmacokinetic parameters were calculated for each animal based on arterial blood concentrations of lidocaine. In the case of the intravenous data, a standard two-compartment model was used. Subarachnoid injections were evaluated by fitting data to an extravascular one-compartment model and by analog computer fitting of the blood level data to an extravascular two-compartment model. Data for both intravenous and subarachnoid injection were also analysed independent of compartment model. The intravascular parameters, alpha and beta, were in excellent agreement with those reported for man.