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To cause infection, bacterial pathogens must overcome host immune factors and barriers to nutrient acquisition. Reproducing these aspects of host physiology in vitro has shown great promise for antibacterial drug discovery. When used as a bacterial growth medium, human serum replicates several aspects of the host environment, including innate immunity and iron limitation. We previously reported that a high-throughput chemical screen using serum as the growth medium enabled the discovery of novel growth inhibitors overlooked by conventional screens. Here, we report that a subset of compounds from this high-throughput serum screen display an unexpected growth enhancing phenotype and are enriched for synthetic siderophores. We selected 35 compounds of diverse chemical structure and quantified their ability to enhance bacterial growth in human serum. We show that many of these compounds chelate iron, suggesting they were acting as siderophores and providing iron to the bacteria. For two different pharmacophores represented among these synthetic siderophores, conjugation to the β-lactam antibiotic ampicillin imparted iron-dependent enhancement in antibacterial activity. Conjugation of the most potent growth-enhancing synthetic siderophore with the monobactam aztreonam produced MLEB-22043, a broad-spectrum antibiotic with significantly improved activity against Klebsiella pneumoniae , Escherichia coli , Acinetobacter baumannii , and Pseudomonas aeruginosa . This synthetic siderophore-monobactam conjugate uses multiple TonB-dependent transporters for uptake into P. aeruginosa . Like aztreonam, MLEB-22043 demonstrated activity against metallo-β-lactamase expressing bacteria, and, when combined with the β-lactamase inhibitor avibactam, was active against clinical strains coexpressing the NDM-1 metallo-β-lactamase and serine β-lactamases. Our work shows that human serum is an effective bacterial growth medium for the high-throughput discovery of synthetic siderophores, enabling the development of novel Trojan Horse antibiotics.

There exists a gap in existing patient education resources for children with chronic conditions. This pilot study assesses large language models' (LLMs) capacity to deliver developmentally appropriate explanations of chronic conditions to pediatric patients. Two commonly used LLMs generated responses that accurately, appropriately, and effectively communicate complex medical information, making them a potentially valuable tool for enhancing patient understanding and engagement in clinical settings., Competing Interests: Conflicts of Interest: The authors have no relevant financial or non-financial interests to disclose.

Low- and middle-income countries face limited critical care capacity due to constraints in staffing, resources, and technology. "Smart ICUs" that integrate telehealth to augment care delivery, communication, and data integration have the potential to bridge these gaps and reduce preventable morbidity and mortality. While their efficacy has been well validated in adult populations, applications of Smart-ICU services in the neonatal population have not been studied. Neonatal intensive care units (NICUs) in India using a common Smart-NICU platform, developed by CloudPhysician, utilize a hub-and-spokes framework along with locally designed technology to facilitate remote patient care in collaboration with local health systems. In this article, we investigate the operational characteristics and performance outcomes for Smart-NICU deployment from the 18 NICUs and 214 beds deployed to date. These findings highlight the potential impact of Smart-NICUs and establish generalizable principles for implementation in low-resource settings., Competing Interests: Declaration of Conflicting InterestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Herein we report on the development and application of chemoenzymatic Dynamic Kinetic Asymmetric Transformation (DYKAT) of α-substituted β-hydroxyketones (β-HKs), using Candida antartica lipase B (CALB) as transesterification catalyst and a ruthenium complex as epimerization catalyst. An operationally simple protocol allows for an efficient preparation of highly enantiomerically enriched α-substituted β-oxoacetates. The products were obtained in yields up to 95 % with good diastereomeric ratios., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Background: Individuals with panic disorder (PD) exhibit a hypersensitivity to inhaled carbon dioxide, possibly reflecting a lowered threshold for sensing signals of suffocation. Animal studies have shown that carbon dioxide-mediated fear behavior depends on chemosensing of acidosis in the amygdala via the acid-sensing ion channel ASIC1a. We examined whether the human ortholog of the ASIC1a gene, ACCN2, is associated with the presence of PD and with amygdala structure and function., Methods: We conducted a case-control analysis (n = 414 PD cases and 846 healthy controls) of ACCN2 single nucleotide polymorphisms and PD. We then tested whether variants showing significant association with PD are also associated with amygdala volume (n = 1048) or task-evoked reactivity to emotional stimuli (n = 103) in healthy individuals., Results: Two single nucleotide polymorphisms at the ACCN2 locus showed evidence of association with PD: rs685012 (odds ratio = 1.32, gene-wise corrected p = .011) and rs10875995 (odds ratio = 1.26, gene-wise corrected p = .046). The association appeared to be stronger when early-onset (age ≤ 20 years) PD cases and when PD cases with prominent respiratory symptoms were compared with controls. The PD risk allele at rs10875995 was associated with increased amygdala volume (p = .035) as well as task-evoked amygdala reactivity to fearful and angry faces (p = .0048)., Conclusions: Genetic variation at ACCN2 appears to be associated with PD and with amygdala phenotypes that have been linked to proneness to anxiety. These results support the possibility that modulation of acid-sensing ion channels may have therapeutic potential for PD., (Copyright © 2014 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Parathyroid hormone-related peptide (PTHrP) has substantial homology with both human and rat parathyroid hormone (66% and 73%, respectively) in the first 15 amino acids. PTHrP (1-34) stimulates cyclic adenosine monophosphate (cAMP) release in bone and kidney, and these effects are felt to occur through interaction with the parathyroid hormone (PTH) receptor. Differences in the biologic potency between rat PTH(1-34) and human PTH(1-34)--and between PTHrP and PTH--have been described in a variety of experimental systems. In this study, we compared the bioactivity of these three amino-terminal synthetic fragments on the stimulation of cAMP formation in an isolated perfused rat femur preparation. Dose-response experiments demonstrated that PTHrP(1-34) was more potent in stimulating cAMP release than human PTH(1-34), whereas PTHrP(1-34) and rat PTH(1-34) were equipotent. Despite the fact that the extraction of immunoreactive rat PTH(1-34) and human PTH(1-34) was the same, rat PTH(1-34) was more potent in stimulating adenylate cyclase activity than human PTH(1-34). These data show that the isolated perfused rat femur preparation is an effective method for evaluation of the effects of PTH and PTHrP. Despite significant structural differences in the binding domain between rat PTH(1-34) and PTHrP(1-34), the effects of rat PTH(1-34) and PTHrP(1-34) are similar. Because the structure of rat PTHrP(1-34) and human PTHrP(1-34) are identical, and because it is desirable to utilize homologous systems to study the potency and effects of test peptides, it would appear that rat PTH(1-34) is the most appropriate peptide for comparison with PTHrP in rat-based experimental systems.

1,25-Dihydroxyvitamin D3 (1,25D) regulates its own levels in circulation by affecting its rates of synthesis and degradation, 22-Oxacalcitriol (OCT), a vitamin D analog with low calcemic activity, decreases circulating PTH levels, one of the regulators of renal 1 alpha-hydroxylase, and stimulates vitamin D degradation in vitro. The purpose of this study was to examine the effects of OCT administration on serum levels of 1,25D. In normal rats, OCT administration (4-200 ng, ip, daily for 5 days) caused a dose-dependent reduction in serum calcitriol levels. At a dose of 200 ng, OCT reduced serum 1,25D from 34.5 +/- 2.7 to 10.9 +/- 0.7 pg/ml (P less than or equal to 0.01) without significant changes in ionized Ca or phosphorus levels. The contribution of the suppression of PTH by OCT to the reduction of serum 1,25D was examined by administering OCT to parathyroidectomized (PTX) rats. Two hundred nanograms of OCT, ip, daily for 5 days significantly reduced serum calcitriol from 29.7 +/- 7.6 to 9.1 +/- 0.5 pg/ml (P less than or equal to 0.01) in rats fed a normal calcium diet. Because OCT increased total calcium (TCa) in this group from 7.4 +/- 0.1 to 9.5 +/- 0.3 mg/dl, similar doses of OCT were given to PTX rats fed a calcium-deficient diet. OCT decreased 1,25D from 58.9 +/- 8.9 to 10.3 +/- 0.4 pg/ml and increased TCa from 4.8 +/- 0.2 to 7.4 +/- 0.1 mg/dl. Comparison of serum 1,25D for identical TCa levels in PTX rats (normal calcium diet controls vs. calcium-deficient diet, OCT-treated) clearly indicates that OCT per se reduced serum 1,25D. Further support for a direct effect of OCT was provided by studies in PTX rats fed a low phosphorus diet. OCT decreased serum 1,25D from 125.8 +/- 15.6 to 10.9 +/- 0.6 pg/ml without significant changes in TCa. To further characterize the mechanisms involved in this effect, similar studies were performed in six normal dogs. Intravenous administration of 0.75 micrograms OCT every other day for 1 week decreased serum calcitriol from 25.4 +/- 3.2 to 12.2 +/- 1.3 pg/ml (P less than or equal to 0.002). Ionized Ca and phosphorus remained unchanged. Despite the short half-life of OCT in the circulation, 1,25D levels returned to basal concentrations 96 h after the last dose of OCT.(ABSTRACT TRUNCATED AT 400 WORDS)

A variety of analogs of 1,25-(OH)2D3 with less calcemic activity and lower receptor binding affinity than 1,25-(OH)2D3 have been developed. However, these compounds have equal or greater ability to differentiate leukemia cells and psoriatic fibroblasts and to suppress PTH synthesis and secretion. The mechanism for this selectivity has not been elucidated. Because the lower potency of ergocalciferol compared to cholecalciferol in preventing or curing rickets in chicks was associated with a lower affinity of the avian vitamin D binding protein (DBP) for vitamin D2, we tested five analogs with low calcemic activity including 22-oxa-1,25-(OH)2D3 (OCT), MC903, 1,25-(OH)2-16 ene-23-yne D3, 1,25-(OH)2-26,27 dihomo-22-ene-D3, and 1,25-(OH)2-24-trihomo-22-ene-D3 for their affinity for rat serum DBP. All analogs had a low affinity for DBP, ranging from 50-3000 times less than that of 1,25-(OH)2D3. OCT also bound with low affinity to dog and human serum DBP. We tested with OCT the possible consequences of its low affinity for serum DBP. One of the functions of DBP is to prolong the lifetime of 1,25-(OH)2D3 in circulation. Quantification of the metabolic clearance rate (MCR) of OCT in 8 normal dogs using a single bolus injection technique showed that OCT was cleared at a rate of 48.2 +/- 7.5 ml/min, approximately 6-7 times more rapidly than 1,25-(OH)2D3 (6.8 +/- 0.4 ml/min). The estimated half-life of OCT in the circulation was 2.5 +/- 0.3 h compared to 7.0 +/- 0.6; n = 7 for 1,25-(OH)2D3. As our primary interest is the potential of OCT in treating the secondary hyperparathyroidism of CRF, we also measured the MCR of OCT in 5/6 nephrectomized dogs. Uremia does not affect the rate of clearance of OCT from the circulation (MCR: 56.8 +/- 4.5; t1/2 = 2.1 +/- 0.2 n = 4). Despite its shorter half-life, OCT suppressed PTH secretion in vivo in uremic dogs. The effects of low binding to DBP on the percentage uremic dogs. The effects of low binding to DBP on the percentage of free sterol were determined using an ultrafiltration procedure. We compared the proportion of free (unbound) OCT and 1,25-(OH)2D3 in 0.1% BSA-PBS with concentrations of human serum ranging from 0-25%. The proportion of OCT in the free form was significantly higher than that of 1,25-(OH)2D3 for every serum concentration tested. The physiological relevance of a higher percentage of free OCT was tested in normal human macrophages.(ABSTRACT TRUNCATED AT 400 WORDS)

OCT, a non-calcemic analogue of 1,25(OH)2D3 has been found to have a more potent activity than that of 1,25(OH)2D3 regarding cell differentiation and immunopotentiation activity, and to prolong the average life span of MRL/l mice. Recently, we found that OCT effectively suppressed the secretion and synthesis of PTH without inducing hypercalcemia. In primary cultures of bovine parathyroid cells, OCT was capable of suppressing PTH release in a dose-dependent manner. OCT was also active in vivo, and, like 1,25(OH)2D3, decreased the pre-pro(PTH) mRNA levels. In a group of rats with CRF, daily administration of OCT, 8 ng i.p. for 2 weeks returned PTH levels to normal without changes in serum calcium. Preliminary results in dogs with CRF indicated that after the administration of OCT 5 micrograms i.v., N-terminal PTH decreased by 76% without changes in Ca. In conclusion, OCT may provide a unique contribution to the treatment of secondary hyperparathyroidism.

Phosphorus is a well-known modulator of renal 1 alpha-hydroxylase activity. In early and moderate renal failure it is proposed that dietary Pi reduction ameliorates secondary hyperparathyroidism through increased circulating levels of calcitriol (i.e, 1 alpha, 25-dihydroxycholecalciferol). To gain further insight into the mechanisms by which a low-Pi diet ameliorates secondary hyperparathyroidism in advanced renal insufficiency, studies were performed in five dogs before and 6 mo after the induction of uremia by 5/6 nephrectomy. Glomerular filtration rate decreased from 69.0 +/- 2.3 to 10.5 +/- 0.5 ml/min, immunoreactive parathyroid hormone (irPTH) increased from 66.0 +/- 8.8 to 321.0 +/- 46 pg/ml, and calcitriol decreased from 39.0 +/- 10.4 to 27.0 +/- 6.2 pg/ml. Thereafter, dietary Pi was decreased gradually every 2 wk from 0.95% to 0.6, 0.45, and 0.3%, respectively. Dietary Ca was reduced from 1.6 to 0.6% to prevent development of hypercalcemia. Ionized Ca (ICa) decreased from 5.4 +/- 0.04 to 5.2 +/- 0.05 mg/dl (P less than 0.02), and plasma Pi decreased from 6.3 +/- 0.7 to 4.7 +/- 0.2 mg/dl (P less than 0.05). Calcitriol remained low (23.3 +/- 4.7 pg/ml). However, irPTH gradually decreased from 321.0 +/- 46.0 to 94.7 +/- 22.9 pg/ml (P less than 0.005). These studies indicate that a decrease in dietary Pi from 0.95 to 0.3% suppressed irPTH by approximately 70%. Reduction of irPTH was observed in the absence of a concomitant increase in levels of ICa or calcitriol. These studies suggest that reduction in dietary Pi in advanced renal insufficiency improves secondary hyperparathyroidism by a mechanism that is independent of the levels of calcitriol or plasma ICa.

Under normal circumstances extrarenal sources of calcitriol probably constitutes a microendocrine system involved in cell differentiation and local intercellular communication with no influence on systemic calcium homeostasis. Under pathological conditions such as chronic renal failure, extrarenal sources have the potential to normalize serum calcitriol after adequate stimulation (such as, 25(OH)D administration). Extrarenal 1,25-(OH)2D3 synthesis is controlled by physiological levels of calcitriol. However, in sarcoidosis and other granulomatous diseases, 1,25-(OH)2D3 production by macrophages is deregulated, causing severe alterations in systemic calcium homeostasis.

In conclusion, a number vitamin D analogues have been developed that have very low calcemic activity but retain several other properties of 1,25-(OH)2D3, including the ability to differentiate leukemia and skin cells, to enhance the immune response, and to suppress parathyroid hormone levels. Although the mechanism of this selective activity is not yet clear, these analogues may provide new insights into the differences in action of 1,25-(OH)2D3 in various target tissues. Most importantly, the selective action of these analogues may be exploited for the treatment of diseases such as leukemia, psoriasis and hyperparathyroidism.

Hypocalcemia is the main factor responsible for the genesis of secondary hyperparathyroidism in chronic renal disease. Studies with parathyroid cells obtained from uremic patients indicate that there is a shift in the set point for calcium-regulated hormone (parathyroid hormone [PTH] secretion. Studies were performed in dogs to further clarify this new potential mechanism. Hypocalcemia was prevented in uremic dogs by the administration of a high calcium diet. Initially, ionized calcium was 4.79 +/- 0.09 mg/dl and gradually increased up to 5.30 +/- 0.05 mg/dl. Despite a moderate increase in ionized calcium, immunoreactive PTH (iPTH) increased from 64 +/- 7.7 to 118 +/- 21 pg/ml. Serum 1,25(OH)2D3 decreased from 25.4 +/- 3.8 to 12.2 +/- 3.6 pg/ml. Further studies were performed in two other groups of dogs. One group received 150-200 ng and the second group 75-100 ng of 1,25(OH)2D3 twice daily. The levels of 1,25(OH)2D3 increased from 32.8 +/- 3.5 to a maximum of 69.6 +/- 4.4 pg/ml. In the second group the levels of serum 1,25(OH)2D3 after nephrectomy remained normal during the study. Amino-terminal iPTH did not increase in either of the two groups treated with 1,25(OH)2D3. In summary, the dogs at no time developed hypocalcemia; however, there was an 84% increase in iPTH levels, suggesting that hypocalcemia, per se, may not be the only factor responsible for the genesis of secondary hyperparathyroidism.

We have previously demonstrated that while both normal humans and dogs tightly control serum calcitriol levels after 25(OH)D administration, anephric humans and 5/6 nephrectomized dogs significantly increase circulating 1,25(OH)2D when supraphysiological concentrations of 25(OH)D are reached in serum. Plasma 1,25(OH)2D level is determined not only by its rate of production but also by its rate of degradation. To further characterize the mechanisms involved in the responses to 25(OH)D therapy in normal circumstances and in chronic uremia, we measured metabolic clearance rate (MCR) and production rate (PR) of 1,25(OH)2D in normal dogs and in dogs with moderate and severe renal failure, at normal and supraphysiological serum concentrations of 25(OH)D. Basal MCR in uremic dogs, either with moderate or with severe renal failure, did not differ significantly from normals (6.7 +/- 0.7, 6.8 +/- 0.4 and 6.8 +/- 0.3 ml/min, respectively). Oral 25(OH)D administration for two weeks did not affect MCR either in normal animals or in both groups of uremic dogs. 25(OH)D treatment did not affect production rates in normal dogs and in animals with moderate renal failure (with normal basal values of 1,25(OH)2D), but significantly increased 1,25(OH)2D production from 0.13 +/- 0.01 to 0.25 +/- 0.04 micrograms/day (P less than 0.05) in dogs with severe renal insufficiency. These data suggest that it is the basal level of 1,25(OH)2D which regulates the synthesis of 1,25(OH)2D in response to 25(OH)D administration in normal and uremic animals.

Renal 1-alpha-hydroxylase activity is tightly regulated in normal humans and intact animals. No significant changes in serum 1,25(OH)2D levels occur in response to vitamin D challenge. However, conflicting reports have appeared in the literature with regard to stimulation of 1,25(OH)2D production after 25(OH)D administration in uremia. To provide further insight into this issue, 25(OH)D at a dose of 100 micrograms every other day for two weeks followed by 50 micrograms every other day for the next two weeks was given orally to seven uremic mongrel dogs. After two weeks of 25(OH)D therapy, 1,25(OH)2D levels increased from 16.4 +/- 0.9 to 28.0 +/- 1.9 pg/ml (P less than 0.001) in parallel with a fourfold increase in 25(OH)D concentrations from a basal of 50.1 +/- 6.5 to 203.2 +/- 18.1 ng/ml. No significant changes in serum i-PTH, ICa or P were observed. Linear regression analysis of the relationship between serum concentrations of 1,25(OH)2D versus 25(OH)D, for each dog during this period, showed highly significant correlation coefficients. To evaluate the possibility that extra-renal sites contribute to the described enhanced 1,25(OH)2D net synthesis after 25(OH)D treatment, similar studies were performed in four anephric patients undergoing hemodialysis. Basal serum 1,25(OH)2D levels were 5.5 +/- 2.4 pg/ml and increased to 19.6 +/- 5.0 pg/ml after 25(OH)D administration. A significant correlation was also found for the relationship between serum levels of 1,25(OH)2D and 25(OH)D in anephrics (r = 0.72, P less than 0.001). The same therapy in four normal volunteers showed no significant changes in serum 1,25(OH)2D concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)

1,25-(OH)2D has been shown to suppress the synthesis and secretion of parathyroid hormone in vivo and in dispersed parathyroid cell cultures. Control of transcription by 1,25-(OH)2D is believed to be mediated by interaction of this hormone with a specific receptor within target cells. We have examined the 1,25-(OH)2D receptor in parathyroid glands from normal dogs and chronic renal failure dogs. The levels of receptor were fourfold lower in parathyroid extracts from these uremic dogs than in those from normal dogs (109 +/- 11 vs. 446 +/- 61 fmol/mg protein). No differences were observed in the binding affinity for 1,25-(OH)2D or in the sedimentation in sucrose density gradients. Since this receptor has been shown to be upregulated by 1,25-(OH)2D, our findings of lower levels of receptor could be attributed to decreased serum concentrations of 1,25-(OH)2D in chronically uremic animals. Regression analysis of log serum 1,25-(OH)2D versus log receptor content yielded a correlation coefficient of 0.62 with P less than 0.02. Decreased receptor content showed a negative correlation with serum N-terminal PTH (r = 0.71 and P less than 0.01). It is likely that this reduced 1,25-(OH)2D receptor number in the parathyroid glands of chronically uremic animals renders the glands less responsive to the inhibitory action of 1,25-(OH)2D on the synthesis and secretion of PTH, and may contribute to the hyperparathyroidism associated with chronic renal failure.

Phosphate binders that contain aluminum are frequently prescribed to treat hyperphosphatemia in patients with chronic renal failure, but an accumulation of aluminum can lead to osteomalacia. To evaluate the efficacy of calcium carbonate as an alternative phosphate binder, we studied 20 patients maintained on dialysis during three consecutive periods. In period 1, the patients took aluminum hydroxide for a month (mean dose, 5.6 g per day; range, 1.5 to 14.0). In period 2, they took no phosphate binders for a month, and in period 3, they took calcium carbonate (Os-Cal) for two months (mean dose, 8.5 g per day; range, 2.5 to 17). The mean (+/- SE) serum calcium level during period 1 was 9.6 +/- 0.2 mg per deciliter; this decreased slightly (to 9.3 +/- 0.1) during period 2 and increased to 10.0 +/- 0.2 during period 3. The mean (+/- SE) serum phosphorus level during period 1 was 4.8 +/- 0.1 mg per deciliter; this increased to 7.3 +/- 0.3 during period 2, but returned to the control value (4.8 +/- 0.2) during period 3. Six of the 20 patients continued to need aluminum hydroxide during period 3 for satisfactory control of hyperphosphatemia. Calcium carbonate successfully lowered serum phosphorus levels and raised serum calcium levels in the majority of our patients, thereby confirming that this agent may be a satisfactory substitute for traditional phosphate binders that contain aluminum. The possibility that long-term treatment could cause such side effects as metastatic calcification will require further investigation.