Wales Infants' and childreN's Genome Service (WINGS): providing rapid genetic diagnoses for unwell children

INTRODUCTION

This study reviews the first 3 years of delivery of the first National Health Service (NHS)-commissioned trio rapid whole genome sequencing (rWGS) service for acutely unwell infants and children in Wales.

METHODS

Demographic and phenotypic data were prospectively collected as patients and their families were enrolled in the Wales Infants' and childreN's Genome Service (WINGS). These data were reviewed alongside trio rWGS results.

RESULTS

From April 2020 to March 2023, 82 families underwent WINGS, with a diagnostic yield of 34.1%. The highest diagnostic yields were noted in skeletal dysplasias, neurological or metabolic phenotypes. Mean time to reporting was 9 days.

CONCLUSION

This study demonstrates that trio rWGS is having a positive impact on the care of acutely unwell infants and children in an NHS setting. In particular, the study shows that rWGS can be applied in an NHS setting, achieving a diagnostic yield comparable with the previously published diagnostic yields achieved in research settings, while also helping to improve patient care and management.

Börjeson-Forssman-Lehmann syndrome: delineating the clinical and allelic spectrum in 14 new families

Börjeson-Forssman-Lehmann syndrome (BFLS) is an X-linked intellectual disability syndrome caused by variants in the PHF6 gene. We ascertained 19 individuals from 15 families with likely pathogenic or pathogenic PHF6 variants (11 males and 8 females). One family had previously been reported. Six variants were novel. We analysed the clinical and genetic findings in our series and compared them with reported BFLS patients. Affected males had classic features of BFLS including intellectual disability, distinctive facies, large ears, gynaecomastia, hypogonadism and truncal obesity. Carrier female relatives of affected males were unaffected or had only mild symptoms. The phenotype of affected females with de novo variants overlapped with the males but included linear skin hyperpigmentation and a higher frequency of dental, retinal and cortical brain anomalies. Complications observed in our series included keloid scarring, digital fibromas, absent vaginal orifice, neuropathy, umbilical hernias, and talipes. Our analysis highlighted sex-specific differences in PHF6 variant types and locations. Affected males often have missense variants or small in-frame deletions while affected females tend to have truncating variants or large deletions/duplications. Missense variants were found in a minority of affected females and clustered in the highly constrained PHD2 domain of PHF6. We propose recommendations for the evaluation and management of BFLS patients. These results further delineate and extend the genetic and phenotypic spectrum of BFLS.

POU3F3-related disorder: Defining the phenotype and expanding the molecular spectrum

POU3F3 variants cause developmental delay, behavioral problems, hypotonia and dysmorphic features. We investigated the phenotypic and genetic landscape, and genotype-phenotype correlations in individuals with POU3F3-related disorders. We recruited unpublished individuals with POU3F3 variants through international collaborations and obtained updated clinical data on previously published individuals. Trio exome sequencing or single exome sequencing followed by segregation analysis were performed in the novel cohort. Functional effects of missense variants were investigated with 3D protein modeling. We included 28 individuals (5 previously published) from 26 families carrying POU3F3 variants; 23 de novo and one inherited from an affected parent. Median age at study inclusion was 7.4 years. All had developmental delay mainly affecting speech, behavioral difficulties, psychiatric comorbidities and dysmorphisms. Additional features included gastrointestinal comorbidities, hearing loss, ophthalmological anomalies, epilepsy, sleep disturbances and joint hypermobility. Autism, hearing and eye comorbidities, dysmorphisms were more common in individuals with truncating variants, whereas epilepsy was only associated with missense variants. In silico structural modeling predicted that all (likely) pathogenic variants destabilize the DNA-binding region of POU3F3. Our study refined the phenotypic and genetic landscape of POU3F3-related disorders, it reports the functional properties of the identified pathogenic variants, and delineates some genotype-phenotype correlations.

Further delineation of the clinical spectrum of White-Sutton syndrome: 12 new individuals and a review of the literature

White-Sutton syndrome (WHSUS) is a neurodevelopmental disorder caused by heterozygous loss-of-function variants in POGZ. Through the Deciphering Developmental Disorders study and clinical testing, we identified 12 individuals from 10 families with pathogenic or likely pathogenic variants in POGZ (eight de novo and two inherited). Most individuals had delayed development and/or intellectual disability. We analyzed the clinical findings in our series and combined it with data from 89 previously reported individuals. The results demonstrate WHSUS is associated with variable developmental delay or intellectual disability, increased risk of obesity, visual defects, craniofacial dysmorphism, sensorineural hearing loss, feeding problems, seizures, and structural brain malformations. Our series includes further individuals with rod-cone dystrophy, cleft lip and palate, congenital diaphragmatic hernia, and duplicated renal drainage system, suggesting these are rare complications of WHSUS. In addition, we describe an individual with a novel, de novo missense variant in POGZ and features of WHSUS. Our work further delineates the phenotypic spectrum of WHSUS highlighting the variable severity of this disorder and the observation of familial pathogenic POGZ variants.

A mild case of acromesomelic dysplasia, type Maroteaux with novel natriuretic peptide receptor B (NPR2) variants

Acromesomelic dysplasia, type Maroteaux is caused by variants in NPR2. It is a severe chondrodysplasia resulting in shortening of the middle and distal segments of the limbs. Limb length at birth may be normal but decreased growth becomes obvious in the first 2 years of life. Here we present an 11-year-old male with mild but typical skeletal features of acromesomelic dysplasia, type Maroteaux. Whole exome sequencing has identified two likely pathogenic variants in NPR2 which have not previously been reported in individuals with acromesomelic dysplasia, type Maroteaux. Given these findings, a diagnosis of AMDM should be considered in individuals with characteristic radiological findings, even if stature is only modestly affected.

BRCA gene testing in women with high-grade serous ovarian carcinoma

The objective of this study was to compare the pick-up rate of pathogenic BRCA variants in those with a high-grade serous ovarian carcinoma (HGSOC) undergoing oncology-led testing with the traditional genetics family history-based testing model. With novel therapies, BRCA status can affect treatment. Welsh oncologists are now testing all women with HGSOC at diagnosis rather than referring to genetics, where family history is required for testing. The records of 332 women who underwent testing via oncology were analysed. The outcome measures were; percentage of women with a pathogenic BRCA variant and the difference in identification of pathogenic BRCA variants between the oncology-led and traditional genetics testing models. Of the 332 women, 25 women (7.5%) tested positive for a pathogenic BRCA variant. This was slightly lower than the detection rate of 9.8% for patients tested via the genetics service over the same period. Testing through genetics, using family history criteria would have identified only 19 (76%) of those with pathogenic variants in the oncology cohort. Since women with a pathogenic BRCA variant can be offered life-extending targeted treatment and a significant proportion of these women would be missed if testing was offered based on family history criteria alone, universal BRCA testing of all women with HGSOC is justified.Impact statement:What is already known on this subject? It is well established that individuals with a strong family history of breast and ovarian cancer are more likely to carry a pathogenic BRCA gene variant. With the use of tools such as the Manchester scoring system women are often invited for testing through clinical genetics services. Until recently there was no clinical impact for those already diagnosed with ovarian cancer.What do the results of this study add? Our study has shown that the diagnosis of high grade serious ovarian carcinoma alone without the need for any family history leads to a similar rate of detection of pathogenic BRCA variants as traditional methods. With the advent of targeted treatments such as olaparib, women with a pathogenic BRCA variant can access different life extending treatment options. With comparable pick-up rates to traditional family history based scoring systems, oncologists can now arrange BRCA gene testing directly.What are the implications of these findings for clinical practice and/or further research? Our study shows universal genetic testing of those with high-grade serious ovarian carcinoma by oncologists allows more women to access life extending treatment in a shorter timeframe compared to the traditional testing model used by clinical genetics services. We hope that other centres, both in the UK and beyond, will adopt this approach.

Muramyl dipeptide enhances the response to endotoxin to cause multiple organ injury in the anesthetized rat

Nucleotide oligomerization domain (NOD) proteins recognize peptidoglycan fragments, resulting in up-regulation of transcription factors, and may enhance the inflammatory response to infection. Specifically, NOD2 has been shown to sense muramyl dipeptide (MDP), which is released during bacterial cell growth and replication. Activation of NOD2 by MDP enhances the inflammatory response caused by LPS (endotoxin). Here, we investigated the effects of MDP on the organ injury/dysfunction caused by systemic administration of a low dose of LPS. Male Wistar rats were coadministered with either MDP (1 - 10 mg kg(-1), i.v.) or vehicle (0.5 mL kg(-1) saline, i.v.), and a low dose of LPS (1 mg kg(-1), i.v.) or vehicle (1 mL kg(-1), saline, i.v.). MAP and heart rate were continuously monitored for 6 h. Markers of organ dysfunction/injury, plasma cytokine levels, and lung myeloperoxidase activity were measured 6 h after MDP and LPS coadministration. In a separate study, MDP (3 or 10 mg kg(-1), i.v.) or vehicle (0.5 mL kg(-1) saline, i.v.) was administered 24 h before LPS infusion. When compared with animals receiving low-dose LPS alone, coadministration of MDP (10 mg kg(-1), i.v.) and LPS, or administration of MDP (10 mg kg(-1), i.v.) 24 h before LPS resulted in a significant increase in the degree of organ injury, cytokine release, and lung injury caused by LPS alone. Thus, our results demonstrate that the two bacterial wall components MDP and LPS work in concert to cause multiple organ injury and systemic inflammation. We hope that our results stimulate other studies designed to evaluate the effects of NOD ligands in animal models of inflammation.

Selective NOD1 agonists cause shock and organ injury/dysfunction in vivo

RATIONALE

NLRs (nucleotide oligomerisation domain [NOD] proteins containing a leucine-rich repeat) are cytosolic pattern recognition receptors. NOD1 senses diaminopimelic acid-containing peptidoglycan present in gram-negative bacteria, whereas NOD2 senses the muramyl dipeptide (MDP) present in most organisms. Bacteria are the most common cause of septic shock, which is characterized clinically by hypotension resistant to vasopressor agents. In animal models, gram-negative septic shock is mimicked by lipopolysaccharide (LPS), which signals through Toll-like receptor 4 (TLR4) and its adaptor MyD88. The role of NLRs in the pathophysiology of septic shock is not known.

OBJECTIVES

To compare the effects of selective NOD1 agonists with LPS in vivo.

METHODS

Vascular smooth muscle cells or whole aortas from wild-type or genetically modified mice were stimulated in vitro with agonists of NOD1 (FK565) or NOD2 (MDP). Vasoconstriction was measured using wire myography. Nitric oxide (NO) formation was measured using Griess reaction and NO synthase-II protein by Western blotting. In vivo, blood pressure, heart rate, and urine output were measured in sham-, LPS-, or FK565-treated animals. Biomarkers of end-organ injury, coagulation activation, NO, and cytokines were measured in plasma.

MAIN RESULTS

FK565, but not MDP, induced NO synthase-II protein/activity in vascular smooth muscle and vascular hyporeactivity to pressor agents. FK565 had no effect on vessels from NOD1(-/-) mice, but was active in vessels from TLR4(-/-), TLR2(-/-), or MyD88(-/-) mice. FK565 induced hypotension, increased heart rate, and caused multiple (renal, liver) injury and dysfunction in vivo.

CONCLUSIONS

Activation of NOD1 induces shock and multiple organ injury/dysfunction.

LYSOPHOSPHATIDIC ACID REDUCES THE ORGAN INJURY CAUSED BY ENDOTOXEMIA-A ROLE FOR G-PROTEIN-COUPLED RECEPTORS AND PEROXISOME PROLIFERATOR-ACTIVATED RECEPTOR-γ

Exogenous lysophosphatidic acid (LPA) has been shown to beneficial in renal ischemia/reperfusion injury, wound healing and colitis. LPA acts via specific G-protein-coupled receptors and also peroxisome proliferator-activated receptor-gamma (PPAR-gamma). However, activation of PPAR-gamma is dependent on the presence of an unsaturated acyl chain. Here we investigate the effects of saturated LPA (18:0) and unsaturated LPA (18:1) on the organ injury associated with endotoxemia and the receptors mediating LPA activity. Male Wistar rats received either lipopolysaccharide (LPS, 6 mg/kg i.v.) or vehicle. The PPAR-gamma antagonist GW9662 (1 mg/kg i.v.), the LPA receptor antagonist Ki16425 (0.5 mg/kg i.v.) or vehicle was administered 30 min after LPS. LPA 18:0 or LPA 18:1 (1 mg/kg i.v.) or vehicle was administered 1 h after injection of LPS. Endotoxemia for 6 h resulted in an increase in serum levels of aspartate aminotransferase, alanine aminotransferase and creatine kinase. Therapeutic administration of LPA 18:0 or 18:1 reduced the organ injury caused by LPS. LPA 18:0 also attenuated the increase in plasma IL-1beta caused by LPS. Ki16425, but not GW9662, attenuated the beneficial effects of LPA 18:0, however, Ki16425 and GW9662 attenuated the beneficial effects of 18:1. In conclusion, LPA reduces the organ injury caused by endotoxemia in the rat. Thus, LPA may be useful in the treatment of shock of various aetiologies. The mechanism of action is related to acyl chain saturation, with LPA 18:0 acting via G-protein-coupled receptors and LPA 18:1 acting via G-protein-coupled receptors and PPAR-gamma.

Inhibition of endogenous hydrogen sulfide formation reduces the organ injury caused by endotoxemia

Hydrogen sulfide (H2S) is a naturally occurring gaseous transmitter, which may play important roles in normal physiology and disease. Here, we investigated the role of H2S in the organ injury caused by severe endotoxemia in the rat. Male Wistar rats were subjected to acute endotoxemia (Escherichia coli lipopolysaccharide (LPS) 6 mg kg(-1) intravenously (i.v.) for 6 h) and treated with vehicle (saline, 1 ml kg(-1) i.v.) or DL-propargylglycine (PAG, 10-100 mg kg(-1) i.v.), an inhibitor of the H2S-synthesizing enzyme cystathionine-gamma-lyase (CSE). PAG was administered either 30 min prior to or 60 min after the induction of endotoxemia. Endotoxemia resulted in circulatory failure (hypotension and tachycardia) and an increase in serum levels of alanine aminotransferase and aspartate aminotransferase (markers for hepatic injury), lipase (indicator of pancreatic injury) and creatine kinase (indicator of neuromuscular injury). In the liver, endotoxemia induced a significant increase in the myeloperoxidase (MPO) activity, and in the expression and activity of the H2S-synthesizing enzymes CSE and cystathionine-beta-synthase. Administration of PAG either prior to or after the injection of LPS dose-dependently reduced the hepatocellular, pancreatic and neuromuscular injury caused by endotoxemia, but not the circulatory failure. Pretreatment of rats with PAG abolished the LPS-induced increase in the MPO activity and in the formation of H2S and in the liver. These findings support the view that an enhanced formation of H2S contributes to the pathophysiology of the organ injury in endotoxemia. We propose that inhibition of H2S synthesis may be a useful therapeutic strategy against the organ injury associated with sepsis and shock.

Lipoproteins in inflammation and sepsis. I. Basic science

BACKGROUND

High-density lipoproteins (HDL) have been shown to bind and neutralize lipopolysaccharide (LPS) and are regarded as possible therapeutic agents for sepsis and conditions associated with local or systemic inflammation. However, in recent years, a multitude of possible immunomodulatory properties other than LPS neutralization have become evident.

DISCUSSION

This review highlights the advances in the understanding of how HDL is protective in both in vitro and in vivo inflammatory settings, including the ability of HDL to modulate adhesion molecule expression, upregulate endothelial nitric oxide synthase and counteract oxidative stress. Also, the active components of HDL and the recent discovery of novel lipid modulators of inflammation are discussed.

Glycogen synthase kinase-3beta inhibitors protect against the organ injury and dysfunction caused by hemorrhage and resuscitation

Glycogen synthase kinase 3beta (GSK-3beta) is a serine/threonine protein kinase that has recently emerged as a key regulatory switch in the modulation of the inflammatory response. Dysregulation of GSK-3beta has been implicated in the pathogenesis of several diseases including sepsis. Here we investigate the effects of 2 chemically distinct inhibitors of GSK-3beta, TDZD-8 and SB216763, on the circulatory failure and the organ injury and dysfunction associated with hemorrhagic shock. Male Wistar rats were subjected to hemorrhage (sufficient to lower mean arterial blood pressure to 35 mmHg for 90 min) and subsequently resuscitated with shed blood for 4 h. Hemorrhage and resuscitation resulted in an increase in serum levels of (a) creatinine and, hence, renal dysfunction, and (b) alanine aminotransferase and aspartate aminotransferase and, hence, hepatic injury. Treatment of rats with either TDZD-8 (1 mg/kg, i.v.) or SB216763 (0.6 mg/kg, i.v.) 5 min before resuscitation abolished the renal dysfunction and liver injury caused by hemorrhagic shock. In addition, TDZD-8, but not SB216763, attenuated the increase caused by hemorrhage and resuscitation in plasma levels of the proinflammatory cytokine interleukin 6 and also of the anti-inflammatory cytokine interleukin 10. Neither of the GSK-3beta inhibitors however affected the delayed fall in blood pressure caused by hemorrhagic shock. Thus, we propose that inhibition of GSK-3beta may represent a novel therapeutic approach in the therapy of hemorrhagic shock.

Lysophosphatidylcholine reduces the organ injury and dysfunction in rodent models of gram-negative and gram-positive shock

1. Lysophosphatidylcholine (LPC) modulates the inflammatory response and reduces mortality in animal models of sepsis. Here, we investigate the effects of LPC from synthetic (sLPC) and natural, soy bean derived LPC, (nLPC) sources on the organ injury/dysfunction caused by systemic administration of lipopolysaccharide (LPS) or peptidoglycan (PepG) and lipoteichoic acid (LTA). 2. Rats were subjected to (i) endotoxaemia (LPS 6 mg kg(-1) i.v.) and treated with sLPC (1-100 mg kg(-1)), (ii) endotoxaemia and treated with nLPC (10 mg kg(-1)) or (iii) gram-positive shock (PepG 10 mg kg(-1) and LTA 3 mg kg(-1) i.v.) and treated with sLPC (10 mg kg(-1)). 3. Endotoxaemia or gram-positive shock for 6 h resulted in increases in serum makers of renal dysfunction and liver, pancreatic and neuromuscular injury. 4. Administration of sLPC, at 1 or 2 h after LPS, dose dependently (1-10 mg kg(-1)) reduced the organ injury/dysfunction. High doses of sLPC (30 and 100 mg kg(-1)) were shown to be detrimental in endotoxaemia. sLPC also afforded protection against the organ injury/dysfunction caused by gram-positive shock. nLPC was found to be protective in endotoxaemic animals. 5. The beneficial effects of sLPC were associated with an attenuation in circulating levels of interleukin-1beta (IL-1beta). 6. In conclusion, LPC dose and time dependently reduces the organ injury and circulating IL-1beta levels caused by gram-negative or gram-positive shock in the rat. Thus, we speculate that appropriate doses of LPC may be useful in reducing the degree of organ injury and dysfunction associated with shock of various aetiologies.

Peroxisome proliferator-activated receptor-gamma antagonists GW9662 and T0070907 reduce the protective effects of lipopolysaccharide preconditioning against organ failure caused by endotoxemia

OBJECTIVE

There is evidence that a) ligands of the nuclear receptor peroxisome proliferator-activated receptor (PPAR)-gamma and b) lipopolysaccharide preconditioning protect the organs against the multiple organ injury and dysfunction caused by endotoxemia. Here we investigate the hypothesis that the protective effects of lipopolysaccharide preconditioning are due to an enhanced formation of endogenous ligands of PPAR-gamma.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Ninety-nine anesthetized male Wistar rats.

INTERVENTIONS

Rats were pretreated with low-dose lipopolysaccharide (1 mg/kg intraperitoneally, 24 hrs before induction of endotoxemia) in the absence or presence of the selective PPAR-gamma antagonists GW9662 (1 mg/kg intraperitoneally) or T0070907 (1 mg/kg intraperitoneally) or the selective cyclooxygenase-2 inhibitor parecoxib (20 mg/kg intraperitoneally). At 24 hrs after preconditioning with low-dose lipopolysaccharide, the rats were subjected to acute severe endotoxemia (lipopolysaccharide 6 mg/kg intravenously).

MEASUREMENTS AND MAIN RESULTS

Lipopolysaccharide preconditioning significantly attenuated the development of renal dysfunction (serum creatinine), hepatocellular injury (serum alanine aminotransferase and aspartate aminotransferase), and circulatory failure (hypotension) as well as the increase in the plasma levels of interleukin-1beta caused by severe endotoxemia. All of these beneficial effects afforded by preconditioning with lipopolysaccharide were attenuated by the specific PPAR-gamma antagonists used. In contrast, the cyclooxygenase-2 inhibitor parecoxib did not affect the beneficial effects afforded by preconditioning with lipopolysaccharide.

CONCLUSIONS

We propose that endogenous ligands of PPAR-gamma contribute to the protection afforded by lipopolysaccharide preconditioning against the organ injury and dysfunction associated with severe endotoxemia in the rat.

Insulin reduces the multiple organ injury and dysfunction caused by coadministration of lipopolysaccharide and peptidoglycan independently of blood glucose: role of glycogen synthase kinase-3beta inhibition

OBJECTIVE

Insulin reduces morbidity and mortality among critically ill patients, but the molecular mechanisms of its effect remain unknown. Insulin is a well-known inhibitor of glycogen synthase kinase-3, which may play an important role in systemic inflammation and shock. Here we investigate the role of blood glucose and glycogen synthase kinase-3beta inhibition in the protective effect of insulin on the organ injury/dysfunction associated with excessive systemic inflammation.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Eighty-five anesthetized Wistar rats.

INTERVENTIONS

Rats received Escherichia coli lipopolysaccharide (1 mg/kg) and Staphylococcus aureus peptidoglycan (0.3 mg/kg) or vehicle intravenously. Insulin (1.4 units/kg intravenously) was administered in the absence or presence of continuous glucose administration (4.5 mg/kg/hr intravenously) either prophylactically or therapeutically. The potent and selective glycogen synthase kinase-3beta inhibitor TDZD-8 (1 mg/kg intravenously) or vehicle (10% dimethyl sulfoxide) was administered either prophylactically or therapeutically.

MEASUREMENTS AND MAIN RESULTS

Coadministration of lipopolysaccharide and peptidoglycan resulted in increases in the serum levels of creatinine (indicator of renal dysfunction), alanine aminotransferase, and aspartate aminotransferase (indicators of liver injury) at 6 hrs. Insulin or TDZD-8 similarly attenuated the organ injury/dysfunction caused by lipopolysaccharide and peptidoglycan when given either prophylactically or therapeutically. Continuous glucose administration had no effect on blood glucose levels or organ injury/dysfunction at 6 hrs. Treatment with insulin or TDZD-8 reduced the plasma levels of the proinflammatory cytokine interleukin-1beta. In vitro, insulin or TDZD-8 caused similar reductions in the nuclear factor-kappaB p65 activity and similar increases in the phosphorylation of Ser9 of glycogen synthase kinase-3beta.

CONCLUSIONS

Therapy with insulin or the potent and selective glycogen synthase kinase-3beta inhibitor TDZD-8 reduced the organ injury/dysfunction caused by lipopolysaccharide and peptidoglycan in the rat. We propose that the inhibitory effect of insulin on the activity of glycogen synthase kinase-3beta contributes to the protective effect of insulin against the organ injury/dysfunction caused by excessive systemic inflammation independently of any effects on blood glucose.

Serum concentrations of trimethoprim and sulfadiazine following oral paste administration to the horse

Two fasted and 2 fed horses were dosed orally with a combined trimethoprim and sulfadiazine paste formulation at a dose of 35 mg (1:5 combined active ingredients)/kg. Serum concentrations of each drug were determined periodically for 3 consecutive days for the 4 horses. The extent and rate of absorption for trimethoprim were variable, but peak serum concentrations occurred generally within 3 hours; sulfadiazine absorption was slower, reaching peak concentrations by 6 hours. Fasting did not have a consistent effect on the serum concentration profiles for either drug. Both drugs achieved serum concentrations that equaled or exceeded the minimum inhibitory concentrations necessary to inhibit the growth of certain pathogens common to the horse. Thus, the paste formulation provides an effective means of dose administration of horses.

Experimental induction of Proteus mirabilis cystitis in the pony and evaluation of therapy with trimethoprim-sulfadiazine

Proteus mirabilis cystitis was induced in 9 ponies by chemically eroding the bladder mucosa before the organism was inoculated. Comparisons were made in the treatment of P mirabilis cystitis between ponies treated daily for 13 days with a trimethoprim-sulfadiazine (TMP-SDZ) paste and both positive and negative controls. Urine cultures from ponies treated with TMP-SDZ became negative for P mirabilis between days 3 and 9 after the start of the treatment, whereas positive controls remained infected until day 13. Urine cultures from all ponies were negative for P mirabilis on day 28. Urine concentrations of TMP and SDZ were relatively high after day 1 of therapy.

Thin layer chromatographic screening method for sulfadiazine residues in calf tissues, plasma, and urine

Because of the lack of specificity of the Bratton-Marshall procedure for assaying sulfonamides, a sensitive, specific tissue residue assay for sulfadiazine (SDZ) was developed. The methodology has been extended to provide a highly sensitive screen for sulfonamide residues, which employs 2-dimensional thin layer chromatography in conjunction with fluorescamine derivatization. The procedure described, which has been developed for SDZ in calf tissues, involves direct ethyl acetate extraction of tissue homogenates. Following evaporation of the organic phase, a portion of the residue is spotted on a 20 X 20 cm silica gel 60 plate, which is then developed in 2 dimensions with solvent systems devised to separate SDZ from endogenous substances as well as from 12 other sulfonamides that might be present in calf tissues. The presence of SDZ at a concentration of 0.1 ppm or its absence is easily demonstrated in calf kidney, liver, muscle, plasma, and urine. The basic method can be modified for a particular sulfonamide in a target tissue and can be used as a quantitative assay for sulfonamide residues.

Thin Layer Chromatographic Screening Method for Sulfadiazine Residues in Calf Tissues, Plasma, and Urine

Because of the lack of specificity of the Bratton-Marshall procedure for assaying sulfonamides, a sensitive, specific tissue residue assay for sulfadiazine (SDZ) was developed. The methodology has been extended to provide a highly sensitive screen for sulfonamide residues, which employs 2-dimensional thin layer chromatography in conjunction with fluorescamine derivatization. The procedure described, which has been developed for SDZ in calf tissues, involves direct ethyl acetate extraction of tissue homogenates. Following evaporation of the organic phase, a portion of the residue is spotted on a 20x20 cm silica gel 60 plate, which is then developed in 2 dimensions with solvent systems devised to separate SDZ from endogenous substances as well as from 12 other sulfonamides that might be present in calf tissues. The presence of SDZ at a concentration of 0.1 ppm or its absence is easily demonstrated in calf kidney, liver, muscle, plasma, and urine. The basic method can be modified for a particular sulfonamide in a target tissue and can be used as a quantitative assay for sulfonamide residues.