Patterns of effective connectivity during memory encoding and retrieval differ between patients with mild cognitive impairment and healthy older adults

Previous research has shown that there is considerable overlap in the neural networks mediating successful memory encoding and retrieval. However, little is known about how the relevant human brain regions interact during these distinct phases of memory or how such interactions are affected by memory deficits that characterize mild cognitive impairment (MCI), a condition that often precedes dementia due to Alzheimer's disease. Here we employed multivariate Granger causality analysis using autoregressive modeling of inferred neuronal time series obtained by deconvolving the hemodynamic response function from measured blood oxygenation level-dependent (BOLD) time series data, in order to examine the effective connectivity between brain regions during successful encoding and/or retrieval of object location associations in MCI patients and comparable healthy older adults. During encoding, healthy older adults demonstrated a left hemisphere dominant pattern where the inferior frontal junction, anterior intraparietal sulcus (likely involving the parietal eye fields), and posterior cingulate cortex drove activation in most left hemisphere regions and virtually every right hemisphere region tested. These regions are part of a frontoparietal network that mediates top-down cognitive control and is implicated in successful memory formation. In contrast, in the MCI patients, the right frontal eye field drove activation in every left hemisphere region examined, suggesting reliance on more basic visual search processes. Retrieval in the healthy older adults was primarily driven by the right hippocampus with lesser contributions of the right anterior thalamic nuclei and right inferior frontal sulcus, consistent with theoretical models holding the hippocampus as critical for the successful retrieval of memories. The pattern differed in MCI patients, in whom the right inferior frontal junction and right anterior thalamus drove successful memory retrieval, reflecting the characteristic hippocampal dysfunction of these patients. These findings demonstrate that neural network interactions differ markedly between MCI patients and healthy older adults. Future efforts will investigate the impact of cognitive rehabilitation of memory on these connectivity patterns.

Tumor Thickness: A predictor of nodal disease in early squamous cell carcinomas of buccal mucosa

Squamous cell carcinomas of buccal mucosa is one the highest number of malignancies seen in the Southeast Asian region. It is related to chewing a combination of tobacco mixed with betel leaves, areca nut, and lime shell called quid. As it is most commonly due to substance abuse and affects younger population, it has tremendous economical and social consequences. Surgery is the most successful modality of management in these patients. The surgery involves wide excision of the diseased mucosa and neck dissection. Neck dissection is associated with certain morbidities, but is routinely practiced in some centers like ours. We have attempted to evaluate the occurrence of the nodal disease in relation to the thickness of the tumor in cases of early cancers of buccal mucosa (stage I and II). We have used ultrasound of the lesion as our modality to assess the tumor thickness preoperatively. AJCC 7th edition was used to assess the clinical and pathological stage of the disease. We have studied 52 patients of early buccal mucosal squamous cell carcinoma, and we observed that tumors thicker than 7mm (p-0.05) have highest co-relation with nodal metastases. This study also recommends that neck dissection should be prophylactically performed for tumors thicker than 4mm. Tumor characteristics such as grade, perineural invasion, and lymphatic invasion should be considered as predictors for early nodal involvement.

Probiotics for preterm neonates: what will it take to change clinical practice?

Necrotizing enterocolitis (NEC) is a major cause of mortality (25%) and morbidity including recurrent sepsis, dependence on parenteral nutrition, need for surgery, and survival with short bowel syndrome in preterm very low birth weight infants. Mortality (45-100%) and morbidity including the risk of long-term neurodevelopmental impairment are higher in extremely preterm infants needing surgery for NEC. Systematic reviews of randomized controlled trials (RCT) indicate that probiotics significantly reduce the risk of NEC (RR 0.39; 95% CI 0.29-0.52; p < 0.00001) and all-cause mortality (RR 0.52; 95% CI 0.40-0.69; p < 0.00001) while facilitating enteral feeds in preterm infants. At present, data from 25 RCT (∼5,000 neonates) and reports on routine use (∼3,000 neonates) indicates that significant adverse effects of probiotics are rare. Despite the robust evidence, there is still reluctance in incorporating routine probiotic prophylaxis in clinical practice. If the goal is to have zero tolerance for NEC, then probiotic prophylaxis must be adopted as soon as possible. Current gaps in knowledge can be addressed by continued research while providing routine probiotic supplementation. We believe that the concept of evidence-based practice of medicine has been stretched too far in this case. Trial sequential analysis has already shown that the evidence for probiotic supplementation was conclusive after 10 trials. Results of the ongoing trials are unlikely to change the conclusions of the systematic reviews significantly. Currently we are at trial number 25; how many more trials do we need? What will it take to change clinical practice?

Benign esophagorespiratory fistula: a case series and a novel technique of definitive management

Benign esophagorespiratory fistula is a relatively rare condition in adults that poses a technical challenge to manage. This case series describes our experience in the treatment of benign esophagorespiratory fistula in 12 adults. A retrospective review of case records of 12 patients with benign esophagorespiratory fistula was done. There were eight tracheoesophageal fistulae and four bronchoesophageal fistulae. Among them, four fistulae were congenital, one was secondary to corrosive injury, three were due to foreign body (dentures), one was secondary to erosion because of prolonged endotracheal intubation, one was secondary to penetrating trauma, and two were infective in etiology. Of the 12 patients, there were nine males and three females. The mean age of presentation was 30.16 years (range 15-53 years). Nine patients had a definitive surgical intervention. The esophageal end of the fistula was managed by primary closure of the esophageal defect and reinforcement with pleural or intercostal muscle flap or a subtotal esophagectomy. The respiratory end of the fistula was dealt with by primary closure of the defect or by a novel technique of neomembranous airway formation, whereby the tracheal defect was closed with the help of a vascularized patch of the esophageal wall. The technique of this neomembranous airway formation is described in detail, and to our knowledge, this is the first time that this technique is being reported in the English literature. This technique is a novel method for definitive repair and can be considered as an option for repair of esophagorespiratory fistula with large defects.

Sudden cardiac arrest in a neonate with congenital adrenal hyperplasia

We describe a 6-day-old male who developed cardiac arrest due to hyperkalemia secondary to congenital adrenal hyperplasia and was successfully resuscitated. This case illustrates the importance of considering congenital adrenal hyperplasia as one of the causes of sudden cardiac arrest in a neonate. A literature review revealed only one similar case in a 3-month-old with a fatal outcome.

Uraemia suppresses central dopaminergic metabolism and impairs motor activity in rats

OBJECTIVE

Uraemia often provokes various neurological disorders, such as mental changes, malperception, confusion, seizures and coma. Since changes in neurotransmissions induce neurological symptoms, we investigated changes in the monoamine metabolism and motor activity in uraemic rats.

DESIGN

Prospective, randomised, controlled animal study.

SUBJECTS

Male Wistar rats.

INTERVENTIONS

Acute renal failure was induced by occlusion of bilateral renal arteries for 60 min, and the motor activity and brain monoamine turnover were examined 48 h later. The brain monoamine turnover was evaluated by the depletion of norepinephrine (NE) and dopamine (DA) induced by alpha-methyl-p-tyrosine (alpha-MT), or the accumulation of 5-hydroxyindoleacetic acid (5-HIAA) induced by probenecid.

MEASUREMENTS AND RESULTS

Marked damage in renal function was found in animals subjected to renal ischaemia 48 h after the operation. The motor activity of the uraemic rats was impaired. The turnover of DA in the striatum, mesencephalon and hypothalamus was decreased in these rats. The turnover of NE and 5-hydroxytryptamine (5-HT) was unchanged in all regions examined.

CONCLUSIONS

Suppression of the central DA turnover appears to be involved in the impairment of motor activity in uraemic rats.

Hedgehog signaling in germ cell migration

The primitive gonad of the Drosophila embryo is formed from two cell types, the somatic gonad precursor cells (SGPs) and the germ cells, which originate at distant sites. To reach the SGPs the germ cells must undergo a complex series of cell movements. While there is evidence that attractive and repulsive signals guide germ cell migration through the embryo, the molecular identity of these instructive molecules has remained elusive. Here, we present evidence suggesting that hedgehog (hh) may serve as such an attractive guidance cue. Misexpression of hh in the soma induces germ cells to migrate to inappropriate locations. Conversely, cell-autonomous components of the hh pathway appear to be required in the germline for proper germ cell migration.

In vitro and ex vivo hydrolysis rates of ethacrynate esters and their relationship to intraocular pressure in the rabbit eye

Esters of ethacrynic acid and partial structural analogs were synthesized and evaluated for topical antiglaucoma activity in rabbits. Maximum activity was shown by analogs 2 and 6 (34% and 30% reduction in intraocular pressure recovery rate, respectively). Among the esters, only the ethyl ester (2) was found to be active; the methyl and n-propyl esters (1 and 3) were inactive. Analogs 1-3 were subjected to an estimation of physicochemical properties and chemical stability. However, no correlation was found to exist between the biological activity/inactivity and the physicochemical properties of the analogs. The analogs were evaluated for ex vivo hydrolysis using rabbit aqueous humor (AH), corneal (C) homogenate and iris-ciliary body (ICB) homogenate. For all tissues, the rate of enzymatic hydrolysis increased significantly with an increasing ester chain length. The ICB-mediated hydrolysis was the fastest among the three tissues for all of the analogs. The relationship between the rate constants for the tissue-mediated hydrolyses were: analog 1, ICB>C>AH; analog 2, ICB>C=AH and analog 3, ICB>AH>C. Apparent Michaelis-Menten kinetic parameters were determined for the three analogs using corneal homogenate. Analog 2 showed the highest v0 for all substrate concentrations studied. The conventional Michaelis-Menten equation did not fit the data as well as a sigmoidal model. Both fits of the data showed the fastest enzyme-mediated hydrolysis for analog 2. The parameters of the sigmoidal fit of the data correlated with the activity/inactivity of the analogs. The data indicate that the major factors responsible for the observed activity/inactivity are the differences in the corneal enzymatic hydrolysis of the esters in conjunction with the rapid dynamics of ocular prodrug absorption.

Repeat charcoal hemoperfusion treatments in life threatening carbamazepine overdose

A 16-month-old female experienced a massive carbamazepine ingestion resulting in a peak serum carbamazepine concentration of 55 microg/ml. Clinical manifestations included generalized seizures, coma, shock, and gastrointestinal hypomotility. Gut decontamination was attempted using multiple-dose activated charcoal and cathartics. Because of the severity of illness, charcoal hemoperfusion was initiated. The patient underwent three sessions of charcoal hemoperfusion, each utilizing a fresh cartridge, with one session immediately following the other. Serum carbamazepine and carbamazepine-10,11-epoxide concentrations decreased from 54 microg/ml to 23 microg/ml, and 30 microg/ml to 17 microg/ml, respectively, during charcoal hemoperfusion. There were no complications. The patient recovered completely and was discharged on the 4th hospital day. Charcoal hemoperfusion should be considered for life-threatening carbamazepine intoxication, especially when drug-induced gastrointestinal hypomotility prevents elimination via the gut.

Novel functions of nanos in downregulating mitosis and transcription during the development of the Drosophila germline

It has previously been shown that germ cells in embryos derived from nos mutant mothers do not migrate to the primitive gonad and prematurely express several germline-specific markers. In the studies reported here, we have traced these defects back to the syncytial blastoderm stage. We show that pole cells in nos embryos fail to establish/maintain transcriptional quiescence; the sex determination gene Sex-lethal (Sxl) and the segmentation genes fushi tarazu and even-skipped are ectopically activated in nos- germ cells. We show that nos- germ cells are unable to attenuate the cell cycle and instead continue dividing. Unexpectedly, removal of the Sxl gene in the zygote mitigates both the migration and mitotic defects of nos- germ cells. Supporting the conclusion that Sxl is an important target for nos repression, ectopic, premature expression of Sxl protein in germ cells disrupts migration and stimulates mitotic activity.

The N-terminal domain of Sxl protein disrupts Sxl autoregulation in females and promotes female-specific splicing of tra in males

Sex determination in Drosophila depends upon the post-transcriptional regulatory activities of the Sex-lethal (Sxl) gene. Sxl maintains the female determined state and activates female differentiation pathways by directing the female-specific splicing of Sxl and tra pre-mRNAs. While there is compelling evidence that Sxl proteins regulate splicing by directly binding to target RNAs, previous studies indicate that the two Sxl RNA-binding domains are not in themselves sufficient for biological activity and that an intact N-terminal domain is also critical for splicing function. To further investigate the functions of the Sxl N terminus, we ectopically expressed a chimeric protein consisting of the N-terminal 99 amino acids fused to ss-galactosidase. The Nss-gal fusion protein behaves like a dominant negative, interfering with the Sxl autoregulatory feedback loop and killing females. This dominant negative activity can be attributed to the recruitment of the fusion protein into the large Sxl:Snf splicing complexes that are found in vivo and the consequent disruption of these complexes. In addition to the dominant negative activity, the Nss-gal fusion protein has a novel gain-of-function activity in males: it promotes the female-specific processing of tra pre-mRNAs. This novel activity is discussed in light of the blockage model for the tra splicing regulation.

An N-terminal truncation uncouples the sex-transforming and dosage compensation functions of sex-lethal

In Drosophila melanogaster, Sex-lethal (Sxl) controls autoregulation and sexual differentiation by alternative splicing but regulates dosage compensation by translational repression. To elucidate how Sxl functions in splicing and translational regulation, we have ectopically expressed a full-length Sxl protein (Sx.FL) and a protein lacking the N-terminal 40 amino acids (Sx-N). The Sx.FL protein recapitulates the activity of Sxl gain-of-function mutations, as it is both sex transforming and lethal in males. In contrast, the Sx-N protein unlinks the sex-transforming and male-lethal effects of Sxl. The Sx-N proteins are compromised in splicing functions required for sexual differentiation, displaying only partial autoregulatory activity and almost no sex-transforming activity. On the other hand, the Sx-N protein does retain substantial dosage compensation function and kills males almost as effectively as the Sx.FL protein. In the course of our analysis of the Sx.FL and Sx-N transgenes, we have also uncovered a novel, negative autoregulatory activity, in which Sxl proteins bind to the 3' untranslated region of Sxl mRNAs and decrease Sxl protein expression. This negative autoregulatory activity may be a homeostasis mechanism.

Removal of non-transferrin-bound iron from blood with iron overload using a device with immobilized desferrioxamine

An extracorporeal hollow-fiber device with immobilized desferrioxamine (DFO) was developed for the removal of nontransferrin-bound iron (NTBI) from blood, without the toxicity of parenteral chelation. When blood circulates through the fibers having pores with 30 kD cut-off, non-transferrin-bound-iron (NTBI) crosses the fiber pores and is chelated by the immobilized desferrioxamine. Removal of circulating iron stimulates iron release from larger proteins and tissue stores, establishing continuous iron flow to the immobilized chelator. During in vitro circulation through a device, iron removed from blood of hemodialysis or sickle cell patients was proportional to, but always in less than 50% of the initial iron level. We attribute the inability to remove more serum iron to irreversible iron binding by transferrin. To investigate where removable and fixed iron was bound, iron binding proteins were analyzed in sera from six patients with genetic anemias and iron overload. Sera separated by sieving chromatography contained 1-14% of the iron in the < 30 kD protein pool, 26-48% was in the combined non-transferrin pools. Sera from hemochromatosis patients without iron overload did not contain NTBI. Circulation of hemochromatosis blood through the device removed one third of the iron, this came from all molecular weight fractions. Iron removal by the device from the < 30 kD pool appears to establish a disequilibrium, that stimulates continuous iron release from ligands with low iron affinity, renewing the pool in the < 30 kD range, which includes potentially toxic NTBI. Therapy with the chelator device having immobilized desferrioxamine should be beneficial for treatment of patients with iron overload.

Activities of the Sex-lethal protein in RNA binding and protein:protein interactions

The Drosophila sex determination gene Sex-lethal (Sxl) controls its own expression, and the expression of downstream target genes such as transformer , by regulating pre-mRNA splicing and mRNA translation. Sxl codes an RNA-binding protein that consists of an N-terminus of approximately 100 amino acids, two 90 amino acid RRM domains, R1 and R2, and an 80 amino acid C-terminus. In the studies reported here we have examined the functional properties of the different Sxl protein domains in RNA binding and in protein:protein interactions. The two RRM domains are responsible for RNA binding. Specificity in the recognition of target RNAs requires both RRM domains, and proteins which consist of the single domains or duplicated domains have anomalous RNA recognition properties. Moreover, the length of the linker between domains can affect RNA recognition properties. Our results indicate that the two RRM domains mediate Sxl:Sxl protein interactions, and that these interactions probably occur both in cis and trans. We speculate that cis interactions between R1 and R2 play a role in RNA recognition by the Sxl protein, while trans interactions stabilize complex formation on target RNAs that contain two or more closely spaced binding sites. Finally, we show that the interaction of Sxl with the snRNP protein Snf is mediated by the R1 RRM domain.

Sex-lethal interacts with splicing factors in vitro and in vivo

The Drosophila sex determination gene Sex-lethal controls its own expression and the expression of downstream target genes such as transformer by regulating RNA splicing. Genetic and molecular studies have established that Sxl requires the product of another gene, snf, to autoregulate the splicing of its own transcripts. snf has recently been shown to encode a Drosophila U1 and U2 small nuclear ribonucleoprotein particle protein. In the work reported here, we demonstrate that the Sxl and Snf proteins can interact directly in vitro and that these two proteins are part of an RNase-sensitive complex in vivo which can be immunoprecipitated with the Sxl antibody. Unlike bulk Snf protein, which sediments slowly in sucrose gradients, the Snf protein associated with Sxl is in a large, rapidly sedimenting complex. Detailed characterization of the Sxl-Snf complexes from cross-linked extracts indicates that these complexes contain additional small nuclear ribonucleoprotein particle proteins and the U1 and U2 small nuclear RNAs. Finally, consistent with the RNase sensitivity of the Sxl-Snf complexes, Sxl transcripts can also be immunoprecipitated by Sxl antibodies. On the basis of the physical interactions between Sxl and Snf, we present a model for Sxl splicing regulation. This model helps explain how the Sxl protein is able to promote the sex-specific splicing of Sxl transcripts, utilizing target sequences that are distant from the regulated splice sites.

scute (sis-b) function in Drosophila sex determination

The primary sex determination signal, the X chromosome-to-autosome (X/A) ratio, controls the choice of sexual identity in the Drosophila melanogaster embryo by regulating the activity of the early promoter of the Sex-lethal gene, Sxl-Pe. This promoter is activated in females (2X/2A), while it remains off in males (1X/2A). Promoter activation in females is dependent upon X-linked numerator genes. One of these genes, sisterless-b (sis-b), corresponds to the scute (sc) locus of the achaete-scute complex, and it encodes a helix-loop-helix transcription factor. In the studies reported here we have used monoclonal antibodies to study the expression and functioning of the sc(sis-b) protein. Sc is first detected at nuclear cycle 6 to 7, well before Sxl-Pe is first active. At this stage, the protein is in the cytoplasm, not the nucleus. Only after the formation of the syncytial blastoderm, at nuclear cycle 10 to 11, does a substantial fraction of the protein enter the nucleus, and this nuclear import closely coincides with the initial activation of Sxl-Pe. Consistent with the idea that the dose of sc(sis-b) is critical for its function as an X-chromosome counting element, wild-type syncytial blastoderm embryos could be grouped into two classes based on the level of protein. Western blot (immunoblot) analysis demonstrates that this difference in protein level correlates directly with the activity state of the Sxl gene. Finally, we provide the first direct evidence that Sc forms heteromeric complexes in vivo in early embryos with the maternally derived helix-loop-helix protein Daughterless. This in vivo complex is likely to be critical for Sc function in Sxl-Pe activation.

Rearrangement and overexpression of the gene coding for tumor antigen p53 in a rat histiocytoma AK-5

The gene coding for the cellular tumor antigen p53 is rearranged and overexpressed in a rat histiocytoma, AK-5. The protein coded by the gene was detected by immunofluorescence and its full size was confirmed by immunoprecipitation using monoclonal antibodies against p53. Southern hybridizations with a full length cDNA probe specific for p53 indicated rearrangement of the gene. Alterations in the upstream region, which probably disrupt the normal regulatory control are suggested by the pattern obtained using a 5'-specific p53 probe in Southern hybridization.

Renal and Auditory toxic effects of amikacin in children with cancer

Amikacin sulfate was given to 21 febrile children with neutropenia and cancer for 9 +/- 3 days. Peak serum amikacin levels ranged between 13 and 32 microgram/mL, and trough levels were consistently less than 2 microgram/mL. Renal toxic effects were detected in two children (9.5%) and were extremely mild. Two additional children (16.5%) experienced mild, transient, unilateral, high-frequency hearing losses. The lack of serious renal and auditory impairment suggests that children are at less risk than adults from aminoglycoside therapy.

Improved method for determining erythrocyte creatine by the diacetyl-alpha-naphthol reaction: elimination of endogenous glutathione interference

We describe a simple, accurate, and reproducible method for determining erythrocyte creatine. The method is free from glutathione inhibition and is adaptable to use with standard spectrophotometers as well as centrifugal analyzers. A clear filtrate, essentially free of protein, hemoglobin, and glutathione, is prepared from 0.1 mL of packed erythrocytes by treatment with Ba(OH)2 and ZnSO4, then reacted with diacetyl-alpha-naphthol. The standard curve for this method is linear from 10 to 500 mg/L. We show that endogenous sulfhydryl species such as erythrocyte glutathione will interfere with the creatine-diacetyl-alpha-naphthol reaction. This observation confirmed a suspicion of underestimation of erythrocyte creatine by the method of Griffiths (Clin. Chim. Acta 9: 210, 1964). Added p-chloromercuribenzoic acid did not completely eliminate this inhibition. In the present method these interfering sulfhydryl species are eliminated from the reaction mixture, thus obviating the need for p-chloromercuribenzoic acid and dialysis. The reference interval for this method is 42-80 mg/L.

Improved method for determining erythrocyte creatine by the diacetyl-alpha-naphthol reaction: elimination of endogenous glutathione interference

We describe a simple, accurate, and reproducible method for determining erythrocyte creatine. The method is free from glutathione inhibition and is adaptable to use with standard spectrophotometers as well as centrifugal analyzers. A clear filtrate, essentially free of protein, hemoglobin, and glutathione, is prepared from 0.1 mL of packed erythrocytes by treatment with Ba(OH)2 and ZnSO4, then reacted with diacetyl-alpha-naphthol. The standard curve for this method is linear from 10 to 500 mg/L. We show that endogenous sulfhydryl species such as erythrocyte glutathione will interfere with the creatine-diacetyl-alpha-naphthol reaction. This observation confirmed a suspicion of underestimation of erythrocyte creatine by the method of Griffiths (Clin. Chim. Acta 9: 210, 1964). Added p-chloromercuribenzoic acid did not completely eliminate this inhibition. In the present method these interfering sulfhydryl species are eliminated from the reaction mixture, thus obviating the need for p-chloromercuribenzoic acid and dialysis. The reference interval for this method is 42-80 mg/L.