Development and Validation of a UPLC-MS/MS Method to Monitor Cephapirin Excretion in Dairy Cows following Intramammary Infusion

Cephapirin, a cephalosporin antibiotic, is used by the majority of dairy farms in the US. Fecal and urinary excretion of cephapirin could introduce this compound into the environment when manure is land applied as fertilizer, and may cause development of bacterial resistance to antibiotics critical for human health. The environmental loading of cephapirin by the livestock industry remains un-assessed, largely due to a lack of appropriate analytical methods. Therefore, this study aimed to develop and validate a cephapirin quantification method to capture the temporal pattern of cephapirin excretion in dairy cows following intramammary infusion. The method includes an extraction with phosphate buffer and methanol, solid-phase extraction (SPE) clean-up, and quantification using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The LOQ values of the developed method were 4.02 µg kg⁻¹ and 0.96 µg L⁻¹ for feces and urine, respectively. This robust method recovered >60% and >80% cephapirin from spiked blank fecal and urine samples, respectively, with acceptable intra- and inter-day variation (<10%). Using this method, we detected trace amounts (µg kg⁻¹) of cephapirin in dairy cow feces, and cephapirin in urine was detected at very high concentrations (133 to 480 µg L⁻¹). Cephapirin was primarily excreted via urine and its urinary excretion was influenced by day (P = 0.03). Peak excretion (2.69 mg) was on day 1 following intramammary infusion and decreased sharply thereafter (0.19, 0.19, 0.08, and 0.17 mg on day 2, 3, 4, and 5, respectively) reflecting a quadratic pattern of excretion (Quadratic: P = 0.03). The described method for quantification of cephapirin in bovine feces and urine is sensitive, accurate, and robust and allowed to monitor the pattern of cephapirin excretion in dairy cows. This data will help develop manure segregation and treatment methods to minimize the risk of antibiotic loading to the environment from dairy farms.     

The Cold Box stem-loop proximal to the 5'-end of the Escherichia coli cspA gene stabilizes its mRNA at low temperature.

The 5'-end region of cspA mRNA contains a Cold Box sequence conserved among several cold-shock mRNAs. This region forms a stable stem-loop structure followed by an AU-rich sequence. Here we show that the Cold Box region is essential for the normal scale of cspA mRNA induction after cold shock because a deletion of the stem-loop significantly destabilizes the mRNA and reduces the cold shock-induced cspA mRNA amount by approximately 50%. The AU-rich track, however, slightly destabilizes the mRNA. The integrity of the stem is essential for the stabilizing function, whereas that of the loop sequence is less important. Overexpression of a mutant cspA mRNA devoid of both the AUG initiation codon and the coding sequence results in a severe growth inhibition at low temperature along with a derepression of the chromosomal cspA expression. Furthermore, the overexpressed RNA is stably associated with the 30 S and 70 S ribosomes. Our results demonstrate that the AUG initiation codon and the coding region containing the downstream box are not required for cspA mRNA to bind ribosomes and that the 5'-untranslated region by itself has a remarkable affinity to ribosomes at low temperature.     

Computational and Experimental Investigation of the Antimicrobial Peptide Cecropin XJ and its Ligands as the Impact Factors of Antibacterial Activity

Cecropin XJ, as a heat stable antimicrobial peptide (AMP), displayed broad bacteriostatic activities, effectively inhibited proliferation of cancer cells and induced cell apoptosis in vitro. However, it exhibited little hemolytic activity and very low cytotoxicity to erythrocytes and normal cells. Although exerts multiple remarkable bioactivities, the refined molecular conformation of native Cecropin XJ remains unsolved. The aim of the present study is to comprehensively investigate the physicochemical characteristics and structure-function relationship of this antimicrobial peptide by using a series of bioinformatics and experimental approaches. In this study, we revealed that the mature Cecropin XJ consists of 41 amino acids, containing two α-helical structures from Lys⁷ to Lys²⁵ and from Ala²⁹ to Ile³⁹. The phylogenetic tree indicated that Cecropin XJ belongs to the Class I AMPs of cecropin family. Hydrophobic analysis showed Cecropin XJ is a typical amphiphilic molecule. The surface of Cecropin XJ was found to have a much wide range of electrostatic potential from ?83.243 to +83.243. The amphipathicity and surface potential of Cecropin XJ partially supported the AMP pore-forming hypothesis. Scanning electron microscopy experimentally confirmed the damages of Cecropin XJ to microbial membrane. Four predicted docking sites respectively for magnesium ion (Mg²⁺), adenosine diphosphate (ADP), bacteriopheophytin (BPH), and guanosine triphosphate (GTP) were found on the surface of Cecropin XJ. Thereinto, Mg²⁺ was experimentally proved to suppress the antibacterial activity of Cecropin XJ; both GTP and ADP enhanced the bactericidal activities to varying degrees. The present study provides a foundation for further investigation of molecular evolution, structural modification, and functional mechanisms of Cecropin XJ.     

Bayesian Quantile Regression for Longitudinal Studies with Nonignorable Missing Data

Summary .  We study quantile regression (QR) for longitudinal measurements with nonignorable intermittent missing data and dropout. Compared to conventional mean regression, quantile regression can characterize the entire conditional distribution of the outcome variable, and is more robust to outliers and misspecification of the error distribution. We account for the within-subject correlation by introducing a   ℓ₂   penalty in the usual QR check function to shrink the subject-specific intercepts and slopes toward the common population values. The informative missing data are assumed to be related to the longitudinal outcome process through the shared latent random effects. We assess the performance of the proposed method using simulation studies, and illustrate it with data from a pediatric AIDS clinical trial.     

Identity between the novel integrin beta 7 subunit and an antigen found highly expressed on intraepithelial lymphocytes in the small intestine.

A cDNA clone encoding the N-terminal sequence of the murine integrin beta 7 subunit, a novel member of the leukocyte cell adhesion molecule subset (Leu-CAM), has been isolated. An N-terminal region of 13 contiguous amino acids deduced from the cDNA shows complete identity with the N-terminus of the 120 kDa subunit of the M290 antigen, a surface molecule found highly expressed on mouse intestinal intraepithelial lymphocytes (IEL). This unexpected result focuses two previously unconnected areas of research and suggests that integrins may have a special role to play in the defence of the gut mucosa.     

Effect of a Low-Protein Diet Supplemented with Ketoacids on Skeletal Muscle Atrophy and Autophagy in Rats with Type 2 Diabetic Nephropathy

A low-protein diet supplemented with ketoacids maintains nutritional status in patients with diabetic nephropathy. The activation of autophagy has been shown in the skeletal muscle of diabetic and uremic rats. This study aimed to determine whether a low-protein diet supplemented with ketoacids improves muscle atrophy and decreases the increased autophagy observed in rats with type 2 diabetic nephropathy. In this study, 24-week-old Goto-Kakizaki male rats were randomly divided into groups that received either a normal protein diet (NPD group), a low-protein diet (LPD group) or a low-protein diet supplemented with ketoacids (LPD+KA group) for 24 weeks. Age- and weight-matched Wistar rats served as control animals and received a normal protein diet (control group). We found that protein restriction attenuated proteinuria and decreased blood urea nitrogen and serum creatinine levels. Compared with the NPD and LPD groups, the LPD+KA group showed a delay in body weight loss, an attenuation in soleus muscle mass loss and a decrease of the mean cross-sectional area of soleus muscle fibers. The mRNA and protein expression of autophagy-related genes, such as Beclin-1, LC3B, Bnip3, p62 and Cathepsin L, were increased in the soleus muscle of GK rats fed with NPD compared to Wistar rats. Importantly, LPD resulted in a slight reduction in the expression of autophagy-related genes; however, these differences were not statistically significant. In addition, LPD+KA abolished the upregulation of autophagy-related gene expression. Furthermore, the activation of autophagy in the NPD and LPD groups was confirmed by the appearance of autophagosomes or autolysosomes using electron microscopy, when compared with the Control and LPD+KA groups. Our results showed that LPD+KA abolished the activation of autophagy in skeletal muscle and decreased muscle loss in rats with type 2 diabetic nephropathy.