Syntheses of (Z)-and (E)-4-amino-2-(trifluoromethyl)-2-butenoic acid and their inactivation of gamma-aminobutyric acid aminotransferase.

(Z)- and (E)-4-amino-2-(trifluoromethyl)-2-butenoic acid (4 and 5, respectively) were synthesized and investigated as potential mechanism-based inactivators of gamma-aminobutyric acid aminotransferase (GABA-AT) in a continuing effort to map the active site of this enzyme. The core alpha-trifluoromethyl-alpha,beta-unsaturated ester moiety was prepared via a Reformatsky/reductive elimination coupling of the key intermediates tert-butyl 2,2-dichloro-3,3,3-trifluoropropionate and N,N-bis(tert-butoxy-carbonyl)glycinal. Both 4 and 5 inhibited GABA-AT in a time-dependent manner, but displayed non-pseudo-first-order inactivation kinetics; initially, the inactivation rate increased with time. Further investigation demonstrated that the actual inactivator is generated enzymatically from 4 or 5. This inactivating species is released from the active site prior to inactivation, and as a result, 4 and 5 cannot be defined as mechanism-based inactivators. Furthermore, 4 and 5 are alternate substrates for GABA-AT, transaminated by the enzyme with Km values of 0.74 and 20.5 mM, respectively. Transamination occurs approximately 276 and 305 times per inactivation event for 4 and 5, respectively. The enzyme also catalyzes the elimination of the fluoride ion from 4 and 5. A mechanism to account for these observations is proposed.     

A novel method for the evaluation of proximal tubule epithelial cellular necrosis in the intact rat kidney using ethidium homodimer

Background  

Ethidium homodimer is a cell-membrane impermeant nuclear fluorochrome that has been widely used to identify necrotic cells in culture. Here, we describe a novel technique for evaluating necrosis of epithelial cells in the proximal tubule that involves perfusing ethidium homodimer through the intact rat kidney. As a positive control for inducing necrosis, rats were treated with 3.5, 1.75, 0.87 and 0.43 mg/kg mercuric chloride (Hg²⁺, intraperitoneal), treatments which have previously been shown to rapidly cause dose-dependent necrosis of the proximal tubule. Twenty-four h after the administration of Hg²⁺, ethidium homodimer (5 μM) was perfused through the intact left kidney while the animal was anesthetized. The kidney was then removed, placed in embedding medium, frozen and cryosectioned at a thickness of 5 μm. Sections were permeabilized with -20°C methanol and then stained with 4',6-diamidino-2-phenylindole (DAPI) to label total nuclei. Total cell number was determined from the DAPI staining in random microscopic fields and the number of necrotic cells in the same field was determined by ethidium homodimer labeling.     

Diminished Reovirus Capsid Stability Alters Disease Pathogenesis and Littermate Transmission

Reovirus is a nonenveloped mammalian virus that provides a useful model system for studies of viral infections in the young. Following internalization into host cells, the outermost capsid of reovirus virions is removed by endosomal cathepsin proteases. Determinants of capsid disassembly kinetics reside in the viral σ3 protein. However, the contribution of capsid stability to reovirus-induced disease is unknown. In this study, we found that mice inoculated intramuscularly with a serotype 3 reovirus containing σ3-Y354H, a mutation that reduces viral capsid stability, succumbed at a higher rate than those infected with wild-type virus. At early times after inoculation, σ3-Y354H virus reached higher titers than wild-type virus at several sites within the host. Animals inoculated perorally with a serotype 1 reassortant reovirus containing σ3-Y354H developed exaggerated myocarditis accompanied by elaboration of pro-inflammatory cytokines. Surprisingly, unchallenged littermates of mice infected with σ3-Y354H virus displayed higher titers in the intestine, heart, and brain than littermates of mice inoculated with wild-type virus. Together, these findings suggest that diminished capsid stability enhances reovirus replication, dissemination, lethality, and host-to-host spread, establishing a new virulence determinant for nonenveloped viruses.     

Treatment of methanol poisoning with ethanol and hemodialysis.

Twelve cases of methanol poisoning are reviewed. The clinical presentation and biochemical features are described and the results of treatment with alkali, ethanol and dialysis reported. The outcome of methanol poisoning appears to be related more to the interval between the time of ingestion and the start of therapy and to the degree of acidosis than to the initial serum methanol level. Therefore, early and aggressive treatment with bicarbonate and ethanol and subsequent institution of hemodialysis are strongly recommended whenever methanol can be detected in the blood, especially when metabolic acidosis of the anion-gap type is present, when mental or visual disturbances are present, or when more than 30 ml of absolute methanol has been consumed.     

Analytical errors in measuring radioactivity in cell proteins and their effect on estimates of protein turnover in L cells.

Previous studies from this laboratory on protein turnover in 3H-labelled L-cell cultures have shown recovery of total 3H at the end of a 3-day experiment to be always significantly in excess of the 3H recovered at the beginning of the experiment. In this study we have critically reviewed a number of possible sources for this error in measuring radioactivity in cell proteins. 3H-labelled proteins, when dissolved in 0.3 M-NaOH and counted for radioactivity in a liquid-scintillation spectrometer, showed losses of 30-40% of the radioactivity; neither external or internal standardization compensated for this loss. Hydrolysis of these proteins with either Pronase or concentrated HCl significantly increased the measured radioactivity. In addition, approx. 5-10% of the cell protein is left on the plastic culture dish when cells are recovered in phosphate-buffered saline. To aggravate this latter loss further, this surface-adherent protein, after pulse labelling, contains proteins of high radioactivity that turn over rapidly and make a major contribution to the accumulating radioactivity in the medium. These combined errors can account for up to 60% of the total radioactivity in the cell culture. Similar analytical errors have been found in studies of other cell cultures. The effect of these analytical errors on estimates of protein turnover in cell cultures is discussed.     

Messy eaters: Swabbing prey DNA from the exterior of inconspicuous predators when foraging cannot be observed

Complex coevolutionary relationships among competitors, predators, and prey have shaped taxa diversity, life history strategies, and even the avian migratory patterns we see today. Consequently, accurate documentation of prey selection is often critical for understanding these ecological and evolutionary processes. Conventional diet study methods lack the ability to document the diet of inconspicuous or difficult‐to‐study predators, such as those with large home ranges and those that move vast distances over short amounts of time, leaving gaps in our knowledge of trophic interactions in many systems. Migratory raptors represent one such group of predators where detailed diet studies have been logistically challenging. To address knowledge gaps in the foraging ecology of migrant raptors and provide a broadly applicable tool for the study of enigmatic predators, we developed a minimally invasive method to collect dietary information by swabbing beaks and talons of raptors to collect trace prey DNA. Using previously published COI primers, we were able to isolate and reference gene sequences in an open‐access barcode database to identify prey to species. This method creates a novel avenue to use trace molecular evidence to study prey selection of migrating raptors and will ultimately lead to a better understanding of raptor migration ecology. In addition, this technique has broad applicability and can be used with any wildlife species where even trace amounts of prey debris remain on the exterior of the predator after feeding.     

Fine needle aspiration cytology of neoplasms metastatic to the breast

The fine needle aspiration (FNA) cytologic findings in 18 cases of metastatic neoplasms of the breast are reported. The cases were encountered in a combined series of 2,529 FNA breast biopsies, of which 666 were malignant; the metastatic neoplasms of the breast thus constituted 2.7% of all the malignant breast tumors. The series consists of 15 women and 3 men, with a mean age of 48 years (range of 11 to 73 years). Sixteen biopsies confirmed metastatic malignancy in patients with known extramammary primaries; the prebiopsy clinical diagnoses in six of the patients were benign breast lesions. In eight patients, the clinical differential diagnosis was either a benign or malignant primary breast lesion versus a metastatic malignancy. In two additional patients, the FNA biopsy identified metastatic neoplasms from unsuspected extramammary primaries. The metastatic neoplasms included three small-cell carcinomas of the lung, one squamous-cell carcinoma of the lung, two malignant melanomas, three ovarian malignancies, including a dysgerminoma, and one each of carcinoma of the fallopian tube, endometrial carcinoma, transitional-cell carcinoma of the urinary bladder, prostatic carcinoma, acute granulocytic leukemia, lymphoma, mycosis fungoides, hepatoma and neuroblastoma of the retroperitoneum. Recognition of unusual cytologic patterns raised the suspicion of, or confirmed the diagnosis of, malignancy in all cases, with no false-negative diagnoses. None of the cases were cytologically interpreted as a primary breast malignancy. Ancillary studies performed on the FNA material, including immunocytochemistry, contributed to a definitive diagnosis in three cases. FNA diagnosis of metastatic malignancy of the breast is essential in order to avoid unnecessary mastectomy and to ensure appropriate chemotherapy and/or irradiation treatment.     

Deletion of the Nuclear Localization Sequences and C-Terminus of PTHrP Impairs Embryonic Mammary Development but also Inhibits PTHrP Production

Parathyroid hormone-related protein (PTHrP) can be secreted from cells and interact with its receptor, the Type 1 PTH/PTHrP Receptor (PTHR1) in an autocrine, paracrine or endocrine fashion. PTHrP can also remain inside cells and be transported into the nucleus, where its functions are unclear, although recent experiments suggest that it may broadly regulate cell survival and senescence. Disruption of either the PTHrP or PTHR1 gene results in many abnormalities including a failure of embryonic mammary gland development in mice and in humans. In order to examine the potential functions of nuclear PTHrP in the breast, we examined mammary gland development in PTHrP (1–84) knock-in mice, which express a mutant form of PTHrP that lacks the C-terminus and nuclear localization signals and which can be secreted but cannot enter the nucleus. Interestingly, we found that PTHrP (1–84) knock-in mice had defects in mammary mesenchyme differentiation and mammary duct outgrowth that were nearly identical to those previously described in PTHrP^−/− and PTHR1^−/− mice. However, the mammary buds in PTHrP (1–84) knock-in mice had severe reductions in mutant PTHrP mRNA levels, suggesting that the developmental defects were due to insufficient production of PTHrP by mammary epithelial cells and not loss of PTHrP nuclear function. Examination of the effects of nuclear PTHrP in the mammary gland in vivo will require the development of alternative animal models.