Divergent evolution of the activity and regulation of the glutamate decarboxylase systems in Listeria monocytogenes EGD-e and 10403S : roles in virulence and acid tolerance

The glutamate decarboxylase (GAD) system has been shown to be important for the survival of Listeria monocytogenes in low pH environments. The bacterium can use this faculty to maintain pH homeostasis under acidic conditions. The accepted model for the GAD system proposes that the antiport of glutamate into the bacterial cell in exchange for γ-aminobutyric acid (GABA) is coupled to an intracellular decarboxylation reaction of glutamate into GABA that consumes protons and therefore facilitates pH homeostasis. Most strains of L. monocytogenes possess three decarboxylase genes (gadD1, D2 & D3) and two antiporter genes (gadT1 & gadT2). Here, we confirm that the gadD3 encodes a glutamate decarboxylase dedicated to the intracellular GAD system (GADi), which produces GABA from cytoplasmic glutamate in the absence of antiport activity. We also compare the functionality of the GAD system between two commonly studied reference strains, EGD-e and 10403S with differences in terms of acid resistance. Through functional genomics we show that EGD-e is unable to export GABA and relies exclusively in the GADi system, which is driven primarily by GadD3 in this strain. In contrast 10403S relies upon GadD2 to maintain both an intracellular and extracellular GAD system (GADi/GADe). Through experiments with a murinised variant of EGD-e (EGDm) in mice, we found that the GAD system plays a significant role in the overall virulence of this strain. Double mutants lacking either gadD1D3 or gadD2D3 of the GAD system displayed reduced acid tolerance and were significantly affected in their ability to cause infection following oral inoculation. Since EGDm exploits GADi but not GADe the results indicate that the GADi system makes a contribution to virulence within the mouse. Furthermore, we also provide evidence that there might be a separate line of evolution in the GAD system between two commonly used reference strains

Striatal interneurons in dissociated cell culture

In addition to the well-characterized direct and indirect projection neurons there are four major interneuron types in the striatum. Three contain GABA and either parvalbumin, calretinin or NOS/NPY/somatostatin. The fourth is cholinergic. It might be assumed that dissociated cell cultures of striatum (typically from embryonic day E18.5 in rat and E14.5 for mouse) contain each of these neuronal types. However, in dissociated rat striatal (caudate/putamen, CPu) cultures arguably the most important interneuron, the giant aspiny cholinergic neuron, is not present. When dissociated striatal neurons from E14.5 Sprague–Dawley rats were mixed with those from E18.5 rats, combined cultures from these two gestational periods yielded surviving cholinergic interneurons and representative populations of the other interneuron types at 5 weeks in vitro. Neurons from E12.5 CD-1 mice were combined with CPu neurons from E14.5 mice and the characteristics of striatal interneurons after 5 weeks in vitro were determined. All four major classes of interneurons were identified in these cultures as well as rare tyrosine hydroxylase positive interneurons. However, E14.5 mouse CPu cultures contained relatively few cholinergic interneurons rather than the nearly total absence seen in the rat. A later dissection day (E16.5) was required to obtain mouse CPu cultures totally lacking the cholinergic interneuron. We show that these cultures generated from two gestational age cells have much more nearly normal proportions of interneurons than the more common organotypic cultures of striatum. Interneurons are generated from both ages of embryos except for the cholinergic interneurons that originate from the medial ganglionic eminence of younger embryos. Study of these cultures should more accurately reflect neuronal processing as it occurs in the striatum in vivo. Furthermore, these results reveal a procedure for parallel culture of striatum and cholinergic depleted striatum that can be used to examine the function of the cholinergic interneuron in striatal networks

Total Hip Arthroplasty in the Setting of Post-Traumatic Arthritis Following Acetabular Fracture: A Systematic Review

Background: Acetabular fractures are frequently associated with post-traumatic arthritis (PTA), for which total hip arthroplasty (THA) has emerged as the established procedure. The purpose of this systematic review is to report the patient outcomes, complications, and implant survival of delayed THA for patients with PTA following acetabular fracture. Methods: A systematic review was performed in December 2021 as per Preferred Reporting Items for Systematic Review and Meta-Analysis Guidelines to identify all studies reporting outcomes of delayed THA performed for PTA with a history of acetabular fracture. From an initial screen of 893 studies, 29 studies which met defined inclusion criteria including minimum 12 months of follow-up and minimum 10 THA were included in the final review. Results: A total of 1220 THA were reported across 29 studies, with 1174 THA completing a minimum of 1-year follow-up at a mean of 86 months. All 29 studies reported upon complications, with a control included in 6 for comparison. Higher complication rates were observed both in patients who had prior open reduction internal fixation and conservative treatment, most notably infection which was observed following 3.6% THA. The total joint revision rate was 9.7%. An improvement was noted in all 25 studies which recorded patient-reported outcomes, with a mean rise in the Harris hip score from 45 to 86 across 18 studies. Conclusions: THA may reduce reported pain levels and improve functional outcomes in selected patients experiencing PTA following acetabular fractures. There is an increased risk of complications, necessitating careful consideration when planning the operation and open discussion with prospective patients and caregivers

Effects of home-based resistance training and neuromuscular electrical stimulation in knee osteoarthritis: a randomized controlled trial

<p>Abstract</p> <p>Background</p> <p>Quadriceps femoris muscle (QFM) weakness is a feature of knee osteoarthritis (OA) and exercise programs that strengthen this muscle group can improve function, disability and pain. Traditional supervised resistance exercise is however resource intensive and dependent on good adherence which can be challenging to achieve in patients with significant knee OA. Because of the limitations of traditional exercise programs, interest has been shown in the use of neuromuscular electrical stimulation (NMES) to strengthen the QFM. We conducted a single-blind, prospective randomized controlled study to compare the effects of home-based resistance training (RT) and NMES on patients with moderate to severe knee OA.</p> <p>Methods</p> <p>41 patients aged 55 to 75 years were randomised to 6 week programs of RT, NMES or a control group receiving standard care. The primary outcome was functional capacity measured using a walk test, stair climb test and chair rise test. Additional outcomes were self-reported disability, quadriceps strength and cross-sectional area. Outcomes were assessed pre- and post-intervention and at 6 weeks post-intervention (weeks 1, 8 and 14 respectively).</p> <p>Results</p> <p>There were similar, significant improvements in functional capacity for the RT and NMES groups at week 8 compared to week 1 (p≤0.001) and compared to the control group (p < 0.005), and the improvements were maintained at week 14 (p≤0.001). Cross sectional area of the QFM increased in both training groups (NMES: +5.4%; RT: +4.3%; p = 0.404). Adherence was 91% and 83% in the NMES and RT groups respectively (p = 0.324).</p> <p>Conclusions</p> <p>Home-based NMES is an acceptable alternative to exercise therapy in the management of knee OA, producing similar improvements in functional capacity. Trial registration: Current Controlled Trials ISRCTN85231954</p

Taurine Fails to Protect Against 1-methyl-4-phenyl-1,2,3,6- Tetrahydropyridine-Induced Striatal Dopamine Depletion in Mice

The potent parkinsonian neurotoxin, 1-methyl-4-phenyl- 1,2,3,6-tetrahydropyridine (MPTP) through its oxidized metabolite, 1-methyl-4-phenylpyridinium (MPPþ) causes lesion specifically to the dopaminergic system of the substantia nigra pars compacta (SNpc) of the brain (Burns et al., 1983). This ability of MPTP and MPPþ has been exploited to develop animal models for Parkinson’s disease (PD). MPTP crosses the blood–brain barrier, gets converted to its neurotoxically active metabolite MPPþ by monoamine oxidase-B in astrocytes and is selectively taken up into dopaminergic neurons by dopamine (DA) transporters (Javitch et al., 1985; Ransom et al., 1987), where it is sequestered into the mitochondria (Ramsay and Singer, 1986). MPPþ causes mitochondrial complex I inhibition, leading to an out surge of free radical species as the lethal process in the neuronal death (Tieu et al., 2003)

Self-reported prior lung diseases as risk factors for non-small cell lung cancer in Mexican Americans

This study was conducted to assess the association between prior history of respiratory disease and lung cancer among Mexican Americans using data from a multi-racial/ethnic lung cancer case-control study. Cases (n = 204) were patients with previously untreated lung cancer. Healthy control participants (n = 325) were recruited from a large physician group practice. Demographics, cigarette use, and history of respiratory disease were collected. Multivariable logistic regression models were used to estimate relative risk. Prior history of COPD (OR = 2.0; 95 % CI 1.2-3.3) and pneumonia (OR = 2.2; 95 % CI 1.3-3.6) were associated with an increased risk of lung cancer. These findings illustrate that prior COPD and pneumonia are associated with an increased risk of lung cancer among Mexican Americans. To our knowledge, this is one of largest case-control analyses assessing the role of respiratory disease and lung cancer risk specifically among Mexican-Americans