Cycloidal-spiral sampling for three-modal x-ray CT flyscans with two-dimensional phase sensitivity

We present a flyscan compatible acquisition scheme for three-modal X-Ray Computed Tomography (CT) with two-dimensional phase sensitivity. Our approach is demonstrated using a "beam tracking" setup, through which a sample's attenuation, phase (refraction) and scattering properties can be measured from a single frame, providing three complementary contrast channels. Up to now, such setups required the sample to be stepped at each rotation angle to sample signals at an adequate rate, to prevent resolution losses, anisotropic resolution, and under-sampling artefacts. However, the need for stepping necessitated a step-and-shoot implementation, which is affected by motors' overheads and increases the total scan time. By contrast, our proposed scheme, by which continuous horizontal and vertical translations of the sample are integrated with its rotation (leading to a "cycloidal-spiral" trajectory), is fully compatible with continuous scanning (flyscans). This leads to greatly reduced scan times while largely preserving image quality and isotropic resolution.

Coronavirus Disease 2019 (COVID-19) Vaccination for Children: Position Statement of Indian Academy of Pediatrics Advisory Committee on Vaccination and Immunization Practices

JUSTIFICATION

Data generated after the first wave has revealed that some children with coronavirus 19 (COVID-19) can become seriously ill. Multi-inflammatory syndrome in children (MIS-C) and long COVID cause significant morbidity in children. Prolonged school closures and quarantine have played havoc with the psychosocial health of children. Many countries in the world have issued emergency use authorisation (EUA) of selected Covid-19 vaccines for use in children. In India, a Subject Expert Committee (SEC) has recommended the use of Covaxin (Bharat Biotech) for children from the ages of 2-18 years. The recommendation has been given to the Drugs Controller General of India (DCGI) for final approval.

OBJECTIVE

To provide an evidence-based document to guide the pediatricians on the recommendation to administer COVID vaccines to children, as and when they are available for use.

PROCESS

Formulation of key questions was done by the committee, followed by review of literature on epidemiology and burden of Covid-19 in children, review of the studies on COVID vaccines in children, and the IAP stand on Covid-19 vaccination in children. The available data was discussed in the ACVIP focused WhatsApp group followed by an online meeting on 24 October, 2021, wherein the document was discussed in detail and finalized.

RECOMMENDATIONS

The IAP supports the Government of India's decision to extend the COVID-19 vaccination program to children between 2-18 years of age. Children with high-risk conditions may be immunized on a priority basis. The IAP and its members should be a partner with the Government of India, in the implementation of this program and the surveillance that is necessary following the roll-out.

Coronavirus Disease 2019 (COVID-19) Vaccination for Children: Position Statement of Indian Academy of Pediatrics Advisory Committee on Vaccination and Immunization Practices

Justification

Data generated after the first wave has revealed that some children with Coronavirus 19 (COVID-19) can become seriously ill. Multi-inflammatory syndrome in children (MIS-C) and long COVID cause significant morbidity in children. Prolonged school closures and quarantine have played havoc with the psychosocial health of children. Many countries in the world have issued emergency use authorisation (EUA) of selected COVID-19 vaccines for use in children. In India, a Subject Expert Committee (SEC) has recommended the use of Covaxin (Bharat Biotech) for children from the ages of 2–18 years. The recommendation has been given to the Drugs Controller General of India (DCGI) for final approval.

Objective

To provide an evidence-based document to guide the pediatricians on the recommendation to administer COVID vaccines to children, as and when they are available for use.

Process

Formulation of key questions was done by the committee, followed by review of literature on epidemiology and burden of COVID-19 in children, review of the studies on COVID vaccines in children, and the IAP stand on COVID-19 vaccination in children. The available data was discussed in the ACVIP focused WhatsApp group followed by an online meeting on 24 October, 2021, wherein the document was discussed in detail and finalized.

Recommendations

The IAP supports the Government of India’s decision to extend the COVID-19 vaccination program to children between 2–18 years of age. Children with high-risk conditions may be immunized on a priority basis. The IAP and its members should be a partner with the Government of India, in the implementation of this program and the surveillance that is necessary following the roll-out.

Breastfeeding and Coronavirus Disease 2019 (COVID-19) Vaccination: Position Statement of Indian Academy of Pediatrics Advisory Committee on Vaccination and Immunization Practices

Justification

In India, till recently, breastfeeding women have been excluded from the coronavirus disease (COVID-19) vaccination program, rendering a significant population of the country, including frontline workers, ineligible to derive the benefits of the COVID-19 vaccine rollout.

Objective

The objective of this recommendation is production of an evidence-based document to guide the pediatricians to give advice to breastfeeding mothers regarding the safety of COVID-19 vaccines in lactating women.

Process

Formulation of key question was done under the chairmanship of president of the IAP. It was followed by review of literature regarding efficacy and safety of COVID-19 vaccines in breastfeeding women. The recommendations of other international and national professional bodies were also deliberated in detail. The available data was discussed in the ACVIP focused WhatsApp group. Opinion of all members was taken and the final document was prepared after achieving consensus.

Recommendations

The IAP/ACVIP recommends the administration of COVID-19 vaccines to all breastfeeding women. The IAP/ACVIP endorses the recent recommendation of the Government of India, to consider all breastfeeding women as eligible for COVID-19 vaccination.

Revealing NOTCH-dependencies in synaptic targets associated with Alzheimer's disease

Recent studies have identified NOTCH signaling as a contributor of neurodegeneration including Alzheimer's disease' (AD) pathophysiology. As part of the efforts to understand molecular mechanisms and players involved in neurodegenerative dementia, we employed transgenic mouse models with Notch1 and Rbpjk loss of function (LOF) mutation in pyramidal neurons of the CA fields. Using RNA-seq, we have investigated the differential expression of NOTCH-dependent genes either upon environmental enrichment (EE) or upon kainic acid (KA) injury. We found a substantial genetic diversity in absence of both NOTCH1 receptor or RBPJK transcriptional activator. Among differentially expressed genes, we observed a significant upregulation of Gabra2a in both knockout models, suggesting a role for NOTCH signaling in the modulation of E/I balance. Upon excitotoxic stimulation, loss of RBPJK results in decreased expression of synaptic proteins with neuroprotective effects. We confirmed Nptx2, Npy, Pdch8, TncC as direct NOTCH1/RBPJK targets and Bdnf and Scg2 as indirect targets. Finally, we translate these findings into human entorhinal cortex containing the hippocampal region from AD patients performing targeted transcripts analysis. We observe an increased trend for RBPJK and the ligand DNER starting in the mild-moderate stage of the disease with no change of NOTCH1 expression. Alongside, expression of the Notch targets Hes5 and Hey1 tend to rise in the intermediate stage of the disease and drop in severe AD. Similarly the newly discovered NOTCH targets, NPTX2, NPY, BDNF show an up-warding tendency during the mild-moderate stage, and decline in the severe phase of the disease. This study identifies NOTCH as a central signaling cascade capable of modulating synaptic transmission in response to excitatory insult through the activation of neuroprotective genes that have been associated to AD.

Breastfeeding and Coronavirus Disease 2019 (COVID-19) Vaccination: Position Statement of Indian Academy of Pediatrics Advisory Committee on Vaccination and Immunization Practices

JUSTIFICATION

In India, till recently, breastfeeding women have been excluded from the coronavirus disease (COVID-19) vaccination program, rendering a significant population of the country, including frontline workers, ineligible to derive the benefits of the COVID-19 vaccine rollout.

OBJECTIVE

The objective of this recommendation is production of an evidence-based document to guide the pediatricians to give advice to breastfeeding mothers regarding the safety of COVID-19 vaccines in lactating women.

PROCESS

Formulation of key question was done under the chairmanship of president of the IAP. It was followed by review of literature regarding efficacy and safety of COVID-19 vaccines in breastfeeding women. The recommendations of other international and national professional bodies were also deliberated in detail. The available data was discussed in the ACVIP focused WhatsApp group. Opinion of all members was taken and the final document was prepared after achieving consensus.

RECOMMENDATIONS

The IAP/ACVIP recommends the administration of COVID-19 vaccines to all breastfeeding women. The IAP/ACVIP endorses the recent recommendation of the Government of India, to consider all breastfeeding women as eligible for COVID-19 vaccination.

Indian Academy of Pediatrics (IAP) Advisory Committee on Vaccines and Immunization Practices (ACVIP): Recommended Immunization Schedule (2020-21) and Update on Immunization for Children Aged 0 Through 18 Years

JUSTIFICATION

In view of new developments in vaccinology and the availability of new vaccines, there is a need to revise/review the existing immunization recommendations.

PROCESS

Advisory Committee on Vaccines and Immunization Practices (ACVIP) of Indian Academy of Pediatrics (IAP) had a physical meeting in March, 2020 followed by online meetings (September-October, 2020), to discuss the updates and new recommendations. Opinion of each member was sought on the various recommendations and updates, following which an evidence-based consensus was reached.

OBJECTIVES

To review and revise the IAP recommendations for 2020-21 and issue recommendations on existing and new vaccines.

RECOMMENDATIONS

The major changes include recommendation of a booster dose of injectable polio vaccine (IPV) at 4-6 years for children who have received the initial IPV doses as per the ACVIP/IAP schedule, re-emphasis on the importance of IPV in the primary immunization schedule, preferred timing of second dose of varicella vaccine at 3-6 months after the first dose, and uniform dosing recommendation of 0.5 mL (15 µg HA) for inactivated influenza vaccines.

Immunization During the COVID-19 Pandemic: Recommendations From Indian Academy of Pediatrics Advisory Committee on Vaccines and Immunization Practices

During the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, immunization practices of all age groups, especially routine childhood vaccines, have been interrupted. Immunization is considered an essential health activity, which needs to be resumed as early as possible. This pandemic has created several unique issues related to routine immunization of individual children at clinics, which needs to be addressed. In this communication, the Advisory Committee on Vaccines and Immunization Practices (ACVIP) of Indian Academy of Pediatrics addresses the common questions and issues related to SARS-CoV-2 and routine immunization services. This also includes the recommendations for routine immunization of SARS-CoV-2 suspect and positive children, and for the logistics to be followed for immunization services.

Notch signaling in response to excitotoxicity induces neurodegeneration via erroneous cell cycle reentry

Neurological disorders such as Alzheimer's disease, stroke and epilepsy are currently marred by the lack of effective treatments to prevent neuronal death. Erroneous cell cycle reentry (CCR) is hypothesized to have a causative role in neurodegeneration. We show that forcing S-phase reentry in cultured hippocampal neurons is sufficient to induce neurodegeneration. We found that kainic-acid treatment in vivo induces erroneous CCR and neuronal death through a Notch-dependent mechanism. Ablating Notch signaling in neurons provides neuroprotection against kainic acid-induced neuronal death. We further show that kainic-acid treatment activates Notch signaling, which increases the bioavailability of CyclinD1 through Akt/GSK3β pathway, leading to aberrant CCR via activation of CyclinD1-Rb-E2F1 axis. In addition, pharmacological blockade of this pathway at critical steps is sufficient to confer resistance to kainic acid-induced neurotoxicity in mice. Taken together, our results demonstrate that excitotoxicity leads to neuronal death in a Notch-dependent manner through erroneous CCR.

Breast gangrene in an HIV-positive patient

INTRODUCTION

Breast gangrene has been reported as a complication following puerperal sepsis, breast surgery, nipple piercings, warfarin toxicity, etc. We report a case of primary breast gangrene in an HIV-positive individual which, to the best of our knowledge, is the first of its kind.

CASE REPORT

A 40-year-old previously healthy woman presented with fulminating left breast gangrene. She was detected to be HIV positive. Mastectomy was performed. The detailed management of the condition is discussed.

CONCLUSION

Severe necrotising infections may be initial manifestations of HIV infection and patients with such infections should be screened for HIV.

Juvenile hyaline fibromatosis: a case report

Juvenile hyalinefibromatosis (JHF) is a rare autosomal recessive (4q21) genodermatosis characterized by a triad of cephalic fibrous outgrowths, gingival hypertrophy and flexion contractures. This paper presents a case report of juvenile hyaline fibromatosis.

Non seminomatous germ cell tumour of a solitary testis in a 70-year-old man: a rare case

We report a rare case of a 70-year-old patient who presented with undifferentiated malignant teratoma arising from a solitary testis. The literature review highlights the rarity of such tumour in this age group, and this may represent the oldest reported patient with non seminomatous germ cell tumour of testicle.

Thermo-expandable Intra-prostatic Stent in the Treatment of Acute Urinary Retention in Elderly Patients with Significant Co-morbidities

We assess the use of thermo-expandable intra-prostatic stent (Memokath, Engineers and Doctors A/S, Denmark) for the treatment of acute urinary retention (AUR) in men with significant co-morbidities for transurethral resection of prostate (TURP). We evaluate the pre- and post-operative complications, duration of stents in-situ and patients quality of life after the stent insertion. Patients with significant co-morbidities presenting with AUR were selected, who were unfit for TURP. The co-morbidities included ischaemic heart disease, congestive heart failure, and chronic obstructive pulmonary disease. The exclusion criteria were bladder tumour and atonic bladder. The Memokath stents were inserted using a flexible cystoscope under local anaesthesia. The patients were followed up at 3 and 6 months after the procedure and the ones who remained alive were asked to complete self-administered questionnaires and IPSS scores. Fifteen men with acute urinary retention were recruited for stent insertion with the mean age of 87 years. No peri-operative complications were recorded. Three patients died after the insertion with functional Memokath in-situ. Nine patients had good functioning stents post-operatively, and remain catheter free up to 30 months after the procedure. The mean duration of stent life was 18 months. Three long-term complications were detected, including stent migration and prostate overgrowth. The Memokath is a good option for frail elderly patients presenting with AUR. The procedure is safe and has minimal long term complications. The stent also provides a sustained good quality of life for patients and avoids the necessity of long term catheterisation.

Therapeutic potential of yoga practices in modifying cardiovascular risk profile in middle aged men and women

AIMS OF STUDY

To study effect of yoga on the physiological, psychological well being, psychomotor parameter and modifying cardiovascular risk factors in mild to moderate hypertensive patients.

METHODS

Twenty patients (16 males, 4 females) in the age group of 35 to 55 years with mild to moderate essential hypertension underwent yogic practices daily for one hour for three months. Biochemical, physiological and psychological parameters were studied prior and following period of three months of yoga practices, biochemical parameters included, blood glucose, lipid profile, catecholmines, MDA, Vit. C cholinesterase and urinary VMA. Psychological evaluation was done by using personal orientation inventory and subjective well being.

RESULTS

Results showed decrease in blood pressure and drug score modifying risk factors, i.e. blood glucose, cholesterol and triglycerides decreased overall improvement in subjective well being and quality of life. There was decrease in VMA catecholamine, and decrease MDA level suggestive decrease sympathetic activity and oxidant stress.

CONCLUSION

Yoga can play an important role in risk modification for cardiovascular diseases in mild to moderate hypertension.

Sphingomyelinase converts lipoproteins from apolipoprotein E knockout mice into potent inducers of macrophage foam cell formation

The apoE knockout (E0) mouse is one of the most widely used animal models of atherosclerosis, and there may be similarities to chylomicron remnant-induced atherosclerosis in humans. Although the lesions of these mice contain large numbers of cholesteryl ester (CE)-laden macrophages (foam cells), E0 plasma lipoproteins are relatively weak inducers of cholesterol esterification in macrophages. Previous in vivo work has suggested that arterial wall sphingomyelinase (SMase) may promote atherogenesis in the E0 mouse, perhaps by inducing subendothelial lipoprotein aggregation and subsequent foam cell formation. The goal of the present study was to test the hypothesis that the modification of E0 lipoproteins by SMase converts these lipoproteins into potent inducers of macrophage foam cell formation. When d<1.063 E0 lipoproteins were pretreated with SMase and then incubated with E0 macrophages, cellular CE mass and stimulation of the cholesterol esterification pathway were increased approximately 5-fold compared with untreated lipoproteins. SMase-treated E0 lipoproteins were more potent stimulators of cholesterol esterification than either E0 lipoproteins in the presence of lipoprotein lipases or oxidized E0 lipoproteins. The uptake and degradation of SMase-treated E0 lipoproteins by macrophages were saturable and specific and substantially inhibited by partial proteolysis of cell-surface proteins. Uptake and degradation were diminished by an anti-apoB antibody and by competition with human S(f) 100-400 hypertriglyceridemic VLDL, raising the possibility that a receptor that recognizes apoB-48 might be involved. In conclusion, SMase-modification of E0 lipoproteins, a process previously shown to occur in lesions, may be an important mechanism for foam cell formation in this widely studied model of atherosclerosis. Moreover, the findings in this report may provide important clues regarding the atherogenicity of chylomicron remnants in humans.

Creation of a mouse model for non-neurological (type B) Niemann-Pick disease by stable, low level expression of lysosomal sphingomyelinase in the absence of secretory sphingomyelinase: relationship between brain intra-lysosomal enzyme activity and central nervous system function

Most lysosomal storage diseases result in neurodegeneration, but deficiencies in the same enzymes can also lead to syndromes without neurologic manifestations. The hypothesis that low levels of residual, intra-lysosomal enzymatic activities in the central nervous system (CNS) are protective has been difficult to prove because of inconsistencies in assays of tissue samples. Experimental correction of lysosomal enzyme deficiencies in animal models suggests that low-level enzymatic activity may reduce CNS pathology, but these results are difficult to interpret owing to the partial and transient nature of the improvements, the presence of secretory hydrolases, and other confounding factors. Using a novel transgenic/knockout strategy to manipulate the intracellular targeting of a hydrolase, we created a mouse that stably expresses low levels of lysosomal sphingomyelinase (L-SMase) in the complete absence of secretory sphingomyelinase (S-SMase). The brains of these mice exhibited 11.5-18.2% of wild-type L-SMase activity, but the cerebellar Purkinje cell layer, which is lost by 4 months of age in mice completely lacking L- and S-SMase, was preserved for at least 8 months. The L-SMase activities in other organs were 1-14% of wild-type levels, and by 8 months of age all peripheral organs had accumulated sphingomyelin and demonstrated pathological intracellular inclusions. Most importantly, L-SMase-expressing mice showed no signs of the severe neurologic disease observed in completely deficient mice, and their life span and general health were essentially normal. These findings show that stable, continuous, low-level expression of intra-lysosomal enzyme activity in the brain can preserve CNS function in the absence of secretory enzyme or other confounding factors.

Acute systemic inflammation up-regulates secretory sphingomyelinase in vivo: a possible link between inflammatory cytokines and atherogenesis

Inflammation plays a critical role in atherogenesis, yet the mediators linking inflammation to specific atherogenic processes remain to be elucidated. One such mediator may be secretory sphingomyelinase (S-SMase), a product of the acid sphingomyelinase gene. The secretion of S-SMase by cultured endothelial cells is induced by inflammatory cytokines, and in vivo data have implicated S-SMase in subendothelial lipoprotein aggregation, macrophage foam cell formation, and possibly other atherogenic processes. Thus, the goal of this study was to seek evidence for S-SMase regulation in vivo during a physiologically relevant inflammatory response. First, wild-type mice were injected with saline or lipopolysaccharide (LPS) as a model of acute systemic inflammation. Serum S-SMase activity 3 h postinjection was increased 2- to 2.5-fold by LPS (P < 0.01). To determine the role of IL-1 in the LPS response, we used IL-1 converting enzyme knockout mice, which exhibit deficient IL-1 bioactivity. The level of serum S-SMase activity in LPS-injected IL-1 converting enzyme knockout mice was approximately 35% less than that in identically treated wild-type mice (P < 0.01). In LPS-injected IL-1-receptor antagonist knockout mice, which have an enhanced response to IL-1, serum S-SMase activity was increased 1. 8-fold compared with LPS-injected wild-type mice (P < 0.01). Finally, when wild-type mice were injected directly with IL-1beta, tumor necrosis factor alpha, or both, serum S-SMase activity increased 1. 6-, 2.3-, and 2.9-fold, respectively (P < 0.01). These data show regulation of S-SMase activity in vivo and they raise the possibility that local stimulation of S-SMase may contribute to the effects of inflammatory cytokines in atherosclerosis.

Sphingomyelinase, an enzyme implicated in atherogenesis, is present in atherosclerotic lesions and binds to specific components of the subendothelial extracellular matrix

Atherosclerotic lesions contain an extracellular sphingomyelinase (SMase) activity that hydrolyzes the sphingomyelin of subendothelial low density lipoprotein (LDL). This SMase activity may promote atherosclerosis by enhancing subendothelial LDL retention and aggregation, foam cell formation, and possibly other atherogenic processes. The results of recent cell-culture studies have led to the hypothesis that a specific molecule called secretory SMase (S-SMase) is responsible for the SMase activity known to be in lesions, although its presence in atheromata had not been examined directly. Herein we provide immunohistochemical and biochemical support for this hypothesis. First, 2 different antibodies against S-SMase detected extracellular immunoreactive protein in the intima of mouse, rabbit, and human atherosclerotic lesions. Much of this material in lesions appeared in association with the subendothelial matrix. Second, binding studies in vitro demonstrated that (125)I-S-SMase adheres to the extracellular matrix of cultured aortic smooth muscle and endothelial cells, specifically to the laminin and collagen components. Third, in its bound state, S-SMase retains substantial enzymatic activity against lipoprotein substrates. Overall, these data support the hypothesis that S-SMase is an extracellular arterial wall SMase that contributes to the hydrolysis of the sphingomyelin of subendothelial LDL. S-SMase may therefore be an important participant in atherogenesis through local enzymatic effects that stimulate subendothelial retention and aggregation of atherogenic lipoproteins.

Multiple forms of arginase are differentially expressed from a single locus in Neurospora crassa

The Neurospora crassa catabolic enzyme, arginase (L-arginine amidinohydrolase, EC 3.5.3.1), exists in multiple forms. Multiple forms of arginase are found in many vertebrates, but this is the only reported example in a microbial organism. The two major forms are structurally similar with subunit sizes of 36 and 41 kDa, respectively. The larger form is produced by mycelia growing in arginine-supplemented medium. Both forms are localized in the cytosol. The structural gene for arginase, aga, has been cloned and sequenced; it contains a 358-codon open reading frame with three in-frame ATGs at the amino terminus. Mutagenesis of these ATGs revealed that the first ATG initiates the 41-kDa protein and the third ATG initiates the 36-kDa protein. Mutation of the second ATG has no effect on translation. Northern analysis demonstrated that a 1.4-kilobase (kb) transcript is synthesized in minimal medium and both a 1.4- and 1.7-kb transcript are produced in arginine-supplemented medium. Primer extension identified the 5' ends of each transcript and demonstrated that the first and third ATG of the open reading frame are the initial AUGs of the 1.7- and 1. 4-kb mRNA, respectively. The results suggest that a basal promoter produces the 1.4-kb transcript and an arginine "activated" promoter is responsible for the 1.7-kb transcript. Tandem promoters are rare in eukaryotic organisms, and they often regulate developmental or tissue-specific gene expression. The possibility that arginase has a role in differentiation in N. crassa is being investigated.

Human vascular endothelial cells are a rich and regulatable source of secretory sphingomyelinase. Implications for early atherogenesis and ceramide-mediated cell signaling

We recently reported that macrophages and fibroblasts secrete a Zn2+-dependent sphingomyelinase (S-SMase), which, like lysosomal SMase, is a product of the acid SMase gene. S-SMase may cause subendothelial retention and aggregation of lipoproteins during atherogenesis, and the acid SMase gene has been implicated in ceramide-mediated cell signaling, especially involving apoptosis of endothelial cells. Because of the central importance of the endothelium in each of these processes, we now sought to examine the secretion and regulation of S-SMase by vascular endothelial cells. Herein we show that cultured human coronary artery and umbilical vein endothelial cells secrete massive amounts of S-SMase (up to 20-fold more than macrophages). Moreover, whereas S-SMase secreted by macrophages and fibroblasts is almost totally dependent on the addition of exogenous Zn2+, endothelium-derived S-SMase was partially active even in the absence of added Zn2+. Secretion of S-SMase by endothelial cells occurred both apically and basolaterally, suggesting an endothelial contribution to both serum and arterial wall SMase. When endothelial cells were incubated with inflammatory cytokines, such as interleukin-1beta and interferon-gamma, S-SMase secretion by endothelial cells was increased 2-3-fold above the already high level of basal secretion, whereas lysosomal SMase activity was decreased. The mechanism of interleukin-1beta-stimulated secretion appears to be through increased routing of a SMase precursor protein through the secretory pathway. In summary, endothelial cells are a rich and regulatable source of enzymatically active S-SMase, suggesting physiologic and pathophysiologic roles for this enzyme.

Evidence that the initial up-regulation of phosphatidylcholine biosynthesis in free cholesterol-loaded macrophages is an adaptive response that prevents cholesterol-induced cellular necrosis. Proposed role of an eventual failure of this response in foam cell necrosis in advanced atherosclerosis

Macrophages in atherosclerotic lesions accumulate free cholesterol (FC) as well as cholesteryl ester and appear to have high rates of phospholipid (PL) synthesis and increased PL mass. Previous short term (i.e. </=24 h) studies with cultured macrophages have shown that these cells respond to FC loading by up-regulating phosphatidylcholine biosynthesis. We propose that this response is adaptive by keeping the FC:PL ratio in the macrophages from reaching toxic levels. We further propose that one cause of macrophage necrosis, a prominent and important event in atherosclerosis, is an eventual decrease of this adaptive response. To explore these ideas, cultured macrophages were loaded with FC for up to 4 days and assayed for phosphatidylcholine biosynthesis, FC and PL mass, and cytotoxicity. For the first 24 h, cellular phosphatidylcholine biosynthesis and FC and PL mass increased 3-4-fold, and thus the FC:PL molar ratio was prevented from reaching very high levels; at this point, there were no overt signs of cytotoxicity. Over the next 24-48 h, however, phosphatidylcholine biosynthesis, and then phosphatidylcholine mass, began to decrease. Initially, the macrophages remained healthy and continued to accumulate FC, but eventually these macrophages, but not unloaded macrophages, became necrotic (swollen organelles and disrupted membranes). Lipoprotein dose studies indicated a close relationship between the onset of macrophage necrosis and the FC:PL ratio. To test further the causal nature of these relationships, cellular FC and PL mass were independently manipulated by using high density lipoprotein3 (HDL3) to decrease cellular FC and choline depletion to decrease cellular PC. As predicted by our hypotheses, HDL3 protected FC-loaded macrophages from necrosis, whereas choline depletion accelerated cytotoxic changes. These findings support the idea that the initial increase in phosphatidylcholine biosynthesis in FC-loaded macrophages is an adaptive response that prevents cholesterol-induced macrophage necrosis. We propose that an eventual failure of the PL response in foam cells may represent one cause of macrophage necrosis in advanced atherosclerotic lesions.

Duplication-induced mutation of a new Neurospora gene required for acetate utilization: properties of the mutant and predicted amino acid sequence of the protein product

A cloned Neurospora crassa genomic sequence, selected as preferentially transcribed when acetate was the sole carbon source, was introduced in extra copies at ectopic loci by transformation. Sexual crossing of transformants yielded acetate nonutilizing mutants with methylation and restriction site changes within both the ectopic DNA and the normally located gene. Such changes are typical of the duplication-induced premeiotic disruption (the RIP effect) first described by Selker et al. (E. U. Selker, E. B. Cambareri, B. C. Jensen, and K. R. Haack, Cell 51:741-752, 1987). The mutants had the unusual phenotype of growth on ethanol but not on acetate as the carbon source. In a cross to the wild type of a mutant strain in which the original ectopic gene sequence had been removed by segregation, the acetate nonutilizing phenotype invariably segregated together with a RIP-induced EcoRI site at the normal locus. This mutant was transformed to the ability to use acetate by the cloned sequence. The locus of the mutation, designated acu-8, was mapped between trp-3 and un-15 on linkage group 2. The transcribed portion of the clone, identified by probing with cDNA, was sequenced, and a putative 525-codon open reading frame with two introns was identified. The codon usage was found to be strongly biased in a way typical of most Neurospora genes sequenced so far. The predicted amino acid sequence shows no significant resemblance to anything previously recorded. These results provide a first example of the use of the RIP effect to obtain a mutant phenotype for a gene previously known only as a transcribed wild-type DNA sequence.