Requirement of hydD, hydE, hypC and hypE genes for hydrogenase activity in Helicobacter pylori

Helicobacter pylori possesses a membrane-bound, nickel containing, hydrogen uptake hydrogenase enzyme; its synthesis requires structural as well as accessory proteins, the latter needed for the complete maturation of the enzyme. Our lab previously characterized mutants in the accessory hyp genes, hypA, hypB, hypD and hypF that were all severely affected for hydrogenase activity, and in some cases (hypA and hypB mutants) also affected for urease activity. This finding prompted us to disrupt the two remaining unstudied hyp genes of H. pylori, hypC and hypE, in order to see if the same pleiotropic effect would be observed. In both mutants hydrogenase activity was abolished but urease activity remained unaffected. Addition of 5 microM nickel into the growth medium partially restored the hydrogenase activity in the hypE mutant and to a lesser extent in the hypC mutant. In addition, we also disrupted the genes HP0634 (referred as hydD in the H. pylori 26695 genome database) and HP0635 (whose function was unknown, referred to here as hydE) to address their possible roles in the hydrogenase synthesis/maturation process. In both cases, hydrogenase activities were abolished and addition of nickel could not restore the activity, suggesting that these proteins are involved in the hydrogenase synthesis process rather than in nickel mobilization/insertion steps.

Roles of conserved nucleotide-binding domains in accessory proteins, HypB and UreG, in the maturation of nickel-enzymes required for efficient Helicobacter pylori colonization

Helicobacter pylori synthesizes two nickel-containing enzymes (urease and hydrogenase), both of which are important pathogenesis factors. Among the many accessory proteins needed for maturation of these Ni-enzymes, are two proteins, HypB and UreG, each of which contain a conserved nucleotide-binding domain (GSGKT). To address the role of this domain in the maturation process, site-directed mutations were introduced in both hypB and ureG. The hypB site-directed mutant strain (Lys59 to Ala59) lacked hydrogenase activity and had less than 1% of the parental urease activity. Hydrogenase activity was partially, and urease activity was fully restored in the hypB mutant strain when grown on nickel supplemented media. The hydrogenase activity of the ureG site-directed mutant strain (Lys14 to Ala14) was comparable to that of the parental strain. However, the ureG mutant strain lacked urease activity, and this deficiency could not be suppressed even when the strain was grown on nickel supplemented media. The expression of immunologically detectable HypB and UreG in the mutants was similar to the parental strain. Expression of the UreA and UreB subunits of urease in both the mutants was also normal. Purified UreG parental and mutant (Lys14 to Ala14) proteins had molecular masses of 27 kDa, but possessed negligible GTP hydrolyzing activity.

Characterization of Helicobacter pylori nickel metabolism accessory proteins needed for maturation of both urease and hydrogenase

Previous studies demonstrated that two accessory proteins, HypA and HypB, play a role in nickel-dependent maturation of both hydrogenase and urease in Helicobacter pylori. Here, the two proteins were purified and characterized. HypA bound two Ni(2+) ions per dimer with positive cooperativity (Hill coefficient, approximately 2.0). The dissociation constants K(1) and K(2) for Ni(2+) were 58 and 1.3 microM, respectively. Studies on purified site-directed mutant proteins in each of the five histidine residues within HypA, revealed that only one histidine residue (His2) is vital for nickel binding. Nuclear magnetic resonance analysis showed that this purified mutant version (H2A) was similar in structure to that of the wild-type HypA protein. A chromosomal site-directed mutant of hypA (in the codon for His2) lacked hydrogenase activity and possessed only 2% of the wild-type urease activity. Purified HypB had a GTPase activity of 5 nmol of GTP hydrolyzed per nmol of HypB per min. Site-directed mutagenesis within the lysine residue in the conserved GTP-binding motif of HypB (Lys59) nearly abolished the GTPase activity of the mutant protein (K59A). In native solution, both HypA and HypB exist as homodimers with molecular masses of 25.8 and 52.4 kDa, respectively. However, a 1:1 molar mixture of HypA plus HypB gave rise to a 43.6-kDa species composed of both proteins. A 43-kDa heterodimeric HypA-HypB complex was also detected by cross-linking. The cross-linked adduct was still observed in the presence of 0.5 mM GTP or 1 microM nickel or when the mutant version of HypA (altered in His2) and HypB (altered in Lys59) were tested. Individually, HypA and HypB formed homodimeric cross-linked adducts. An interaction between HypA and the Hp0868 protein (encoded by the gene downstream of hypA) could not be detected via cross-linking, although such an interaction was predicted by yeast two-hybrid studies. In addition, the phenotype of an insertional mutation within the Hp0868 gene indicated that its presence is not critical for either the urease or the hydrogenase activity.

Ending a nurse practitioner-patient relationship: uncovering patients' perceptions

DATA SOURCES

Seventy-nine patients assigned to the care of a nurse practitioner (NP) were interviewed to explore reactions to ending a yearlong therapeutic relationship at the conclusion of a clinical trial. Three researchers identified, reviewed and

CONCLUSIONS

Of the total 79 patients, 22 (28%) spontaneously discussed perceptions and feelings about the termination of their relationship with the NP, Qualitative analysis of their statements identified future concerns about continuity of care and emotional themes ranging from gratitude, regret, and anxiety to grief.

IMPLICATIONS FOR PRACTICE

Changes in health care coverage often result in abrupt termination of patient-provider relationships. The involuntary termination of a patient-provider relationship may have significant negative consequences on patients with substantial influence on physical and emotional health. Awareness and anticipatory counseling may be useful in stemming these effects.

Effect of various alkyl and unsaturated substituents on the mutagenicity of some nitrophenyl thioethers

A variety of nitro-substituted phenyl alkyl/aryl thioethers and nitroso-substituted phenyl alkyl/aryl thioethers have been synthesized and tested for their mutagenicity towards Salmonella typhimurium strain TA100, TA98, TA98NR and TA98/1,8-DNP(6) in the absence of S9 mix. The relative order of mutagenicity in TA98 and TA100 among p-nitrophenyl thioethers having alkyl or aryl substituents is allyl>phenyl>benzyl>butyl>propyl>ethyl>methyl. Compounds having an alkyl chain C(6) to C(12) were found to be non-mutagenic. Among the various positional isomers (ortho, meta and para) of nitro-substituted diphenyl thioethers only the compounds having the -NO(2) function at the para position is mutagenic, whereas compounds having a -NO(2) function at ortho and meta are non-mutagenic. However, the reduced intermediate, ortho-nitroso derivative was found to be mutagenic in all the four strains but the meta-nitroso derivative was found to be non-mutagenic. All mutagens were found to be non-mutagenic when tested in nitroreductase deficient strain TA98NR, whereas their nitroso intermediates are found to be mutagenic. A substantial fall in the mutagenic activity is observed when some mutagens are tested in O-acetyltransferase deficient strain TA98/1,8-DNP(6).

Twenty-nine years after carbon monoxide intoxication

Carbon monoxide (CO) is a worldwide environmental toxin and a leading cause of deliberate or accidental poisoning. There is an extensive literature devoted to the clinical features and treatment of those victims who have survived acute CO poisoning for a short length of time. The long-term sequelae of non-fatal poisoning have received scanty references, and the prospects for the long-lasting survivors of acute CO intoxication are less clear. Literature review uncovered reports of only three patients who were followed for a considerable period of time. We present a case of CO poisoning with progressive neurological and psychological deterioration that began 17 years after recovery from a severe, accidental CO asphyxia. The patient was examined in the neurology out patient clinic 29 years after the initial CO intoxication. We believe the unique status of this patient, her similarity to one other case in the literature and the circumstances allowing correlation of the clinical picture to the CO poisoning warrants emphasis.

Mandibular deviations in TMD and non-TMD groups related to eye dominance and head posture

This study was designed to determine whether eye-dominance affects head posture (rotation) and in turn, whether head posture is associated with mandibular frenum midline deviation, in both TMJ and control subjects. Eye dominance was determined using three tests: Porta, Hole, Point tests. Natural head posture was evaluated using the Arthrodial protractor. Mandibular frenum deviation was recorded as left, right or no deviation. Fifty female subjects were included in the study, 25 TMJ patients attending the Gelb Craniomandibular Pain Center and 25 non-TMJ control subjects. The findings indicate that eye dominance and direction of head rotation are strongly associated in both TMJ and control subjects. Further, in TMJ subjects mandibular deviation occurred in greater frequency than in controls and tends to occur in the contra lateral direction of head rotation.

Comparison of the effects of a cell saver and low-dose aprotinin on blood loss and homologous blood usage in patients undergoing valve surgery

OBJECTIVE

To compare 2 important techniques of blood conservation, use of a cell saver and low-dose aprotinin, in terms of blood loss and homologous blood usage in patients undergoing cardiac valve surgery.

DESIGN

Prospective, randomized.

SETTING

Tertiary care hospital.

PARTICIPANTS

Sixty adult patients undergoing elective valve surgery.

INTERVENTIONS

The patients were divided into 3 groups of 20 each. In group 1, aprotinin in the dose of 30,000 KIU/kg was added to the pump prime, with a further dose of 15,000 KIU/kg added at the end of each hour of cardiopulmonary bypass. In group 2, a cell-saver system was used to collect all blood at the operation site for processing in preparation for subsequent reinfusion. Group 3 patients acted as a control group and underwent routine management, which included collection of autologous blood during the pre-cardiopulmonary bypass period. A hemoglobin of <8 g/dL was considered as an indication for bank blood transfusion in the postoperative period.

MEASUREMENTS AND MAIN RESULTS

The chest tube drainage was significantly less in group 1 compared with groups 2 and 3, with total drainage (median [interquartile range]) amounting to 250 mL [105 to 325 mL] vs. 700 mL [525 to 910 mL] in group 2 and 800 mL [650 to 880 mL] in group 3 (p < 0.001). The patients in groups 1 and 2 required significantly less bank blood (median [interquartile range]) as compared with group 3 (350 mL [0 to 525 mL], 350 mL [0 to 350 mL], and 1050 mL [875 to 1050 mL]; p < 0.001), respectively. Cell saver provided 410 +/- 130 mL of hemoconcentrated blood in group 2. The average preoperative hemoglobin concentration was 11.3 g/dL, and it was around 9 g/dL on the 7th postoperative day. The hemoglobin concentration at various stages during hospitalization in all 3 groups was similar.

CONCLUSIONS

Low-dose aprotinin and a cell saver are effective and comparable methods of blood conservation. Aprotinin helps by decreasing the postoperative drainage, and a cell saver helps by making the patient's own blood available for transfusion.

Finding evidence-based answers to clinical questions online

You can find evidence-based answers to clinical questions quickly by searching online medical databases. The key is to be selective, on the basis of the type of information you need. Online textbooks, consensus guidelines systematic reviews, and MEDLINE are all available.

Directed evolution of a new catalytic site in 2-keto-3-deoxy-6-phosphogluconate aldolase from Escherichia coli

BACKGROUND

Aldolases are carbon bond-forming enzymes that have long been identified as useful tools for the organic chemist. However, their utility is limited in part by their narrow substrate utilization. Site-directed mutagenesis of various enzymes to alter their specificity has been performed for many years, typically without the desired effect. More recently directed evolution has been employed to engineer new activities onto existing scaffoldings. This approach allows random mutation of the gene and then selects for fitness to purpose those proteins with the desired activity. To date such approaches have furnished novel activities through multiple mutations of residues involved in recognition; in no instance has a key catalytic residue been altered while activity is retained.

RESULTS

We report a double mutant of E. coli 2-keto-3-deoxy-6-phosphogluconate aldolase with reduced but measurable enzyme activity and a synthetically useful substrate profile. The mutant was identified from directed-evolution experiments. Modification of substrate specificity is achieved by altering the position of the active site lysine from one beta strand to a neighboring strand rather than by modification of the substrate recognition site. The new enzyme is different to all other existing aldolases with respect to the location of its active site to secondary structure. The new enzyme still displays enantiofacial discrimination during aldol addition. We have determined the crystal structure of the wild-type enzyme (by multiple wavelength methods) to 2.17 A and the double mutant enzyme to 2.7 A resolution.

CONCLUSIONS

These results suggest that the scope of directed evolution is substantially larger than previously envisioned in that it is possible to perturb the active site residues themselves as well as surrounding loops to alter specificity. The structure of the double mutant shows how catalytic competency is maintained despite spatial reorganization of the active site with respect to substrate.

Mutagenicity studies of FAVOR PAC

A series of in vitro and in vivo assays have been conducted using FAVOR PAC (CAS Registry No. 9003-04-7), a cross-linked sodium polyacrylate polymer, to test its ability to induce mutations. FAVOR PAC is a member of the FAVOR family of superabsorbent polymers (SAPs) developed by Stockhausen GmbH & Co KG (Krefeld, Germany). These SAPs are known for their ability to retain large volumes of fluid, even against pressure. The genotoxic potential of FAVOR PAC and its extracts was examined in the following five standard mutagenicity assays: the Salmonella typhimurium and Escherichia coli reverse mutation assay, the mouse lymphoma fluctuation assay, the mouse lymphoma forward mutation assay, the in vivo mouse micronucleus assay, and an in vitro rat DNA synthesis assay. Based on the results of these assays, it was concluded that FAVOR PAC was clearly not genotoxic under any of the conditions of the mutagenicity assays performed.

Disposable versus reusable biopsy forceps for colorectal epithelial cell proliferation in humans

The performance of various measures of rectal mucosal proliferation has been evaluated in the literature, but the performance of the forceps used to obtain the tissue has received little attention. We used data from two large studies of proliferation at a single institution to compare reusable and disposable endoscopic forceps. Endoscopic pinch biopsies were taken 10 cm from the anal verge using either reusable or disposable, oval-cupped, sheathed forceps. The specimens were fixed, embedded, and sectioned, taking care to orient the specimens longitudinally. Five sections were placed on each slide. We determined how many slides did not contain eight scorable crypts (inadequate) and how many sections were necessary to identify eight complete crypts. There were 395 subjects who had biopsies taken with reusable forceps and 185 subjects who had biopsies taken with disposable forceps. The specimens were inadequate in 27.6% of the reusable forceps specimens versus 2.7% of the disposable forceps (P < 0.0001). The mean number of tissue sections necessary to identify eight scorable crypts for the reusable forceps was 3.82 (SD, 0.87) compared with 3.17 (SD, 0.83) for disposable forceps (P = 0.0001). The specimens taken with the disposable forceps were better, probably because the forceps were sharper. We believe that the better quality of the specimens and the sterility justify the higher cost of disposable forceps. We would urge investigators in proliferation studies to evaluate the biopsy equipment as carefully as they evaluate other aspects of their methods.

Management and prevention of meningococcal disease

While many other illnesses affecting children have been contained or even eliminated, meningococcal disease has become a leading infectious cause of death. The major management challenge may be increased intracranial pressure or toxic shock, depending on whether meningitis or septicemia predominates. A new protein-conjugated group C vaccine is expected to reduce deaths by as much as 40%.

Growth in human milk-Fed very low birth weight infants receiving a new human milk fortifier

BACKGROUND/AIMS

Human milk fortification has been advocated to enhance premature infants' growth. We, therefore, undertook this study of a new human milk fortifier containing more protein than a reference one.

METHODS

Open, randomized, controlled, multiclinic trial, with weekly growth parameters and safety evaluations in premature infants <1,500 g.

RESULTS

The 2 groups did not differ in demographic and baseline characteristics. The adjusted daily milk intake was significantly higher in the infants fed reference human milk fortifier (n = 29; 154.2 +/- 2.1 vs. 144.4 +/- 2.5 ml/kg/day, mean +/- SE; p < 0.05). Both human milk fortifiers produced increases over baseline in weight, length, and head circumference, with greater gains observed in the new human milk fortifier-fed infants for the former two parameters (weight gain 26.8 +/- 1.3 and 20.4 +/- 1.2 g/day, p < 0.05; head circumference 1.0 +/- 0.1 and 0.8 +/- 0.1 cm/week; length 0.9 +/- 0.1 and 0.8 +/- 0.1 cm/week, respectively). Serum chemistries were normal and acceptable for age. Study events were typical for premature infants and similar in both groups.

CONCLUSIONS

This new human milk fortifier had comparable safety to the reference human milk fortifier and promoted faster weight gain and head circumference growth.

Pancreaticoduodenectomy for metastatic renal cell carcinoma: report of a case

Metastasis to the pancreas from a distant primary cancer is uncommon, most cases being detected in the advanced stages of disease, often multiple in number, and diffusely displayed beyond surgical salvage. A solitary metastasis in the head of the pancreas is rarely encountered and although potentially amenable to surgical resection, surgeons are hesitant to perform pancreaticoduodenectomy for metastatic disease. Renal cell carcinoma is one malignancy with a propensity to metastasize to the pancreas. We report herein the case of a solitary pancreatic metastasis from renal cell carcinoma successfully treated by pancreaticoduodenectomy in a middle-aged man. A discussion on the indications and effectiveness of performing pancreaticoduodenectomy for metastatic renal cell carcinoma is also presented.

Antisense-induced reduction of presenilin 1 expression selectively increases the production of amyloid beta42 in transfected cells

Autosomal dominant mutations in the presenilin 1 (PS1) gene are associated with familial, early-onset Alzheimer's disease. Although the pathogenic mechanism of these mutations is unclear, their common feature is that they lead to an increased concentration of amyloid beta-peptide (Abeta) 42 in the plasma of early-onset patients, in the conditioned media of transfected cells, and in the brains of transgenic mice that overexpress mutant PS1. To address the mechanism(s) by which the pathogenic PS1 mutations increase Abeta42, we constructed human cell lines expressing a doxycyclin (dox)-inducible antisense PS1 RNA and measured its effects on the levels of PS1, amyloid precursor protein (APP), and Abeta. In time course experiments, we observed a statistically significant (p = 0.0038) more than twofold elevation in secreted Abeta42 as early as 12 days after addition of dox. This correlated with an 80% decrease in the 46-kDa PS1 holoprotein and a 30% decrease in the 26-kDa N-terminal fragment (NTF). Furthermore, there was a significant fivefold (p = 0.002) increase in Abeta42 after 14-day dox treatment; this correlated with a >90% decrease in PS1 holoprotein and 60% decrease in NTF. At no time point did we observe significant changes in Abeta40, APP holoprotein, presenilin 2, or tubulin. Ten days after the removal of dox, we observed a return to constitutive levels for Abeta42, PS1 holoprotein, and NTF. These results suggest that in human cell lines, the reduction of normal PS1 activity results in the increased production of Abeta42. Furthermore, our results are consistent with a loss of function or dominant negative mechanism for the pathogenic PS1 mutations.

Initiating a structural study of 2-keto-3-deoxy-6-phosphogluconate aldolase from Escherichia coli

2-Keto-3-deoxy-6-phosphogluconate aldolase (KDPG aldolase, E.C. 4.1. 2.14) is a member of the pyruvate/phosphoenolpyruvate aldolase family. It is also a synthetically useful enzyme, capable of catalyzing the stereoselective aldol addition of pyruvate to a range of unnatural electrophilic substrates. The recombinant protein was purified by a two-step HPLC protocol involving anion-exchange and hydrophobic chromatography. Dynamic light-scattering experiments indicated the protein to be monodisperse. Crystals were obtained using the sitting-drop vapour-diffusion method, with PEG 6K as precipitant. Diffraction data were collected on a frozen crystal to a resolution of 2.26 A on station PX9.6 at the Daresbury synchrotron. The crystal belongs to space group P2(1)2(1)2(1), with unit-cell parameters a = 53.2, b = 77.9, c = 146.8 A.

Searching the Internet for medical information: practical tips

The Internet can be useful for physicians, but beginning users are apt to encounter two problems: too much irrelevant information, and difficulty finding the desired information. This paper offers some practical tips that can prevent frustration and wasted time when searching for medical information on the Internet.

Widespread alterations of alpha-synuclein in multiple system atrophy

Glial cytoplasmic inclusions (GCI) are the hallmark of multiple system atrophy (MSA), a rare movement disorder frequently associated with autonomic dysfunction. In this study of 21 cases of MSA, GCI were consistently immunoreactive for alpha-synuclein and double-immunostained for ubiquitin and oligodendroglial markers, but not glial fibrillary acidic protein. No statistically significant difference was found in the density of GCI in various brain regions in the two forms of MSA, striatonigral degeneration (SND) and olivopontocerebellar atrophy (OPCA). Postmortem brain samples from 9 cases of MSA were fractionated according to solubility in buffer, Triton-X 100, sodium dodecyl sulfate (SDS), and formic acid, and alpha-synuclein immunoreactivity was measured in Western blots. Total alpha-synuclein immunoreactivity was increased in MSA compared to controls, with no statistically significant difference between SND and OPCA. Most of the increase was due to alpha-synuclein in SDS fractions. In controls this fraction had little or no immunoreactivity. In 7 cases and 4 controls correlations were investigated between quantitative neuropathology and biochemical properties of alpha-synuclein. Surprisingly, the amount of SDS-soluble alpha-synuclein correlated poorly with the number of GCI in adjacent sections. Furthermore, areas with few or no GCI unexpectedly had abundant SDS-soluble alpha-synuclein. These findings provide evidence that modifications of alpha-synuclein in MSA may be more widespread than obvious histopathology. Moreover, these alterations may constitute a biochemical signature for the synucleinopathies.

Posttraumatic gustatory neuralgia: a clinical model of trigeminal neuropathic pain

Six cases are reported in which the primary complaint was episodic, recurrent facial pain that was triggered by a taste stimulus. The pain first occurred days to weeks after head and neck surgery. Patients reported that a food stimulus placed in the mouth evoked episodic, electric shock-like pain in a preauricular location on the surgical side. The smell of food or, less reliably, emotional excitement could also trigger pain. Mandibular movement did not evoke the pain, and between lancinating attacks there was either no pain or only mild discomfort. Following an episode of pain, there was a refractory period during which the pain could not be elicited. Physical examination demonstrated a preauricular sensory loss of variable distribution. No abnormal sweating or vasomotor findings were clinically apparent. No odontogenic, muscular, salivary gland, neurologic, or psychologic pathology was found to explain the clinical symptoms. The pain was not relieved with standard doses of anticonvulsants that are commonly used to treat trigeminal neuralgia. The duration of the recurrent pain symptoms in this group was 8 to 132 months without remission. Gustatory neuralgia may be a discrete syndrome that results from abnormal interactions between salivary efferent fibers and trigeminal sensory afferent fibers in the injured auriculotemporal nerve. The unique features of the disorder make it a potentially useful clinical model for the investigation of autonomic/sensory interactions in neuropathic pain.

alpha-Synuclein shares physical and functional homology with 14-3-3 proteins

alpha-Synuclein has been implicated in the pathophysiology of many neurodegenerative diseases, including Parkinson's disease (PD) and Alzheimer's disease. Mutations in alpha-synuclein cause some cases of familial PD (Polymeropoulos et al., 1997; Kruger et al., 1998). In addition, many neurodegenerative diseases show accumulation of alpha-synuclein in dystrophic neurites and in Lewy bodies (Spillantini et al., 1998). Here, we show that alpha-synuclein shares physical and functional homology with 14-3-3 proteins, which are a family of ubiquitous cytoplasmic chaperones. Regions of alpha-synuclein and 14-3-3 proteins share over 40% homology. In addition, alpha-synuclein binds to 14-3-3 proteins, as well as some proteins known to associate with 14-3-3, including protein kinase C, BAD, and extracellular regulated kinase, but not Raf-1. We also show that overexpression of alpha-synuclein inhibits protein kinase C activity. The association of alpha-synuclein with BAD and inhibition of protein kinase C suggests that increased expression of alpha-synuclein could be harmful. Consistent with this hypothesis, we observed that overexpression of wild-type alpha-synuclein is toxic, and overexpression of alpha-synuclein containing the A53T or A30P mutations exhibits even greater toxicity. The activity and binding profile of alpha-synuclein suggests that it might act as a protein chaperone and that accumulation of alpha-synuclein could contribute to cell death in neurodegenerative diseases.

AsGM1+ NK cells prevent metastasis of invading LD-MCA-38 tumor cells in the nude mouse

BACKGROUND

Although the liver is a potent tumor cell killing organ it is frequently the site of lethal metastases often signifying the endstage for patients with colorectal cancers. Enhancing hepatic-associated immunity remains elusive until the interactions among hepatic nonparenchymal cells (NPC) are deciphered. We sought to modulate the cellular components of the hepatic immune system of mice with anti-NK and anti-T-cell-neutralizing antibodies in order to determine the cell type most efficacious in preventing liver metastasis.

MATERIALS AND METHODS

Liver-derived murine colon adenocarcinoma (LD-MCA-38) cells were injected into the ileocolic vein (ICV) of immunocompetent and immunodeficient C57BL/6 mice. Mice were pretreated 1 day prior to tumor cell injection with one of three antibodies: anti-AsGM1, Anti-NK1.1, or Anti-Thy1.2. On Day 21 laparotomy was performed to determine the extent of hepatic tumor foci. The number of hepatic tumor foci was recorded and compared by the Wilcoxon rank sum test.

RESULTS

Mice pretreated with anti-AsGM1 or Anti-NK1.1 developed a massive increase in the number of hepatic tumor foci and decreased survival compared to the control treated mice. Pretreatment with anti-Thy1.2 antibody resulted in a significant decrease in the number of hepatic tumor foci. LD-MCA-38 tumor cells were unable to colonize the liver of C57BL/6 athymic nude mice; however, anti-AsGM1 antibody abolished this antimetastatic effect. There was no difference in the extent of hepatic metastasis and survival between immunodeficient C57BL/6 bg/bg and their conventional littermates bg/+.

CONCLUSION

AsGM1+ NK cells exhibit a significant antitumor response in the absence of T-cells. The concept of stimulating NK cell activity and suppressing T-cell function may enhance liver-associated immunity and serve as a deterrent for blood-borne tumor cells metastasizing to the liver.

The incidence and nature of fibrous continuity between the sphenomandibular ligament and the anterior malleolar ligament of the middle ear

The purpose of this study was to determine the structural interrelationship between the temporomandibular joint (TMJ) and the middle ear, in terms of fibrous continuity between the sphenomandibular ligament (SML) of the mandible and the anterior malleolar ligament (AML) of the middle ear. Thirty-seven specimens of the TMJ and middle ear were obtained from adult human cadavers. The temporal bone, petrotympanic fissure, mandibular fossa, and middle ear were dissected en bloc, fixed, sectioned, stained, and observed microscopically. Of the 37 specimens, 67.6% had a continuity of the SML through the fissure passing near the malleus of the middle ear. The AML was present at the fissure in 64.9% of the specimens, with 58.3% passing through and not stopping at the fissure. Results indicated a fibrous continuity between the SML and the AML. Structural differences between the two ligaments were also noted. The SML contained randomly arranged fibrous connective tissue with numerous interposed blood vessels. The AML had a smooth arrangement of fibers within the connective tissue, and few blood vessels were apparent. The clear anatomic relationship observed strongly supports the contention of a functional interrelationship between the TMJ and the middle ear.

Control of tachycardia and hypertension following coronary artery bypass graft surgery: efficacy and haemodynamic effects of esmolol

Hypertension following coronary artery bypass grafting is not uncommon, especially in patients having good left ventricular function. It is often accompanied by tachycardia. The purpose of this study is to determine the efficacy of esmolol in the treatment of tachycardia and hypertension immediately following cardiopulmonary bypass and to study other haemodynamic effects of esmolol. Thirty patients undergoing elective [corrected] coronary artery bypass grafting were included in this prospective study. Morphine-based anaesthetic technique along-with standard bypass techniques were used in all the patients. The study was performed in the operating room about 30-45 minutes after the termination of cardiopulmonary bypass. Patients having a heart rate of more than 90 bpm and systolic blood pressure of more than 130 mm Hg without any inotropic support were included and randomly assigned to esmolol or control group. Esmolol was administered in a bolus dose of 500 micrograms/kg followed by infusion of upto 100 micrograms/kg/min. The patients in the control group were administered comparable volumes of normal saline. Baseline haemodynamic measurements were obtained just before the administration of esmolol or normal saline and were repeated after 5, 10, 15, 30 and 45 min. The baseline measurement in both the groups showed that patients were maintaining a state of hyperdynamic circulation with high systolic blood pressure (esmolol group 148 +/- 15 mm Hg, control group 140 +/- 8 mm Hg; p = NS), heart rate (esmolol group 128 +/- 17 bpm, control group 127 +/- 17 bpm; p = NS) and cardiac index (esmolol group 3.1 +/- 1 L/min/m2, control group 3.3 +/- 0.5 L/min/m2; p = NS). Esmolol decreased systolic blood pressure (p < 0.001), heart rate (p < 0.01) and cardiac index (p < 0.05) at five minutes. These changes persisted throughout the study period. The left ventricular stroke work index decreased at five minutes (p < 0.05) and remained so till 30 minutes. The maximum fall in heart rate (15%) and systolic blood pressure (16%) was observed at 45 minutes. There were no haemodynamic changes in the control group except that cardiac index, stroke volume and left ventricular stroke work index increased at five minutes. We conclude that esmolol lowers the indices of cardiovascular work in patients who demonstrated hyperdynamic circulation. This was achieved by decreasing the heart rate and systolic blood pressure which was accompanied by decrease in cardiac index and left ventricular stroke work index.

Changes in adult zebra finch song require a forebrain nucleus that is not necessary for song production

Male zebra finches normally crystallize song at approximately 90 days and do not show vocal plasticity as adults. However, changes to adult song do occur after unilateral tracheosyringeal (ts) nerve injury, which denervates one side of the vocal organ. We examined the effect of placing bilateral lesions in LMAN (a nucleus required for song development but not for song maintenance in adults) upon the song plasticity that is induced by ts nerve injury in adults. The songs of birds that received bilateral lesions within LMAN followed by right ts nerve injury silenced, on average, 0.25 syllables, and added 0.125 syllables (for an average turnover of 0.375 syllables), and changed neither the frequency with which individual syllables occurred within songs nor the motif types they used most often. In contrast, the songs of birds that received sham lesions followed by ts nerve injury lost, on average, 1.625 syllables, silenced 0.125 syllables, and added 0.75 syllables, turning over an average of 2.5 syllables. They also significantly changed both the frequency with which individual syllables were included in songs and the motif variants used. Thus, song plasticity induced in adult zebra finches with crystallized songs requires the presence of LMAN, a nucleus which had been thought to play a role in vocal production only during song learning. Although the changes to adult songs induced by nerve transection are more limited than those that arise during song development, the same circuitry appears to underlie both types of plasticity.

Characteristics and identification of sites of chagasic ventricular tachycardia by endocardial mapping

OBJECTIVE

To study electrophysiological characteristics that enable the identification and ablation of sites of chagasic tachycardia.

METHODS

Thirty-one patients with chronic Chagas' heart disease and sustained ventricular tachycardia (SVT) underwent electrophysiological study to map and ablate that arrhythmia. Fifteen patients had hemodynamically stable SVT reproducible by programmed ventricular stimulation, 9 men and 6 women with ages ranging from 37 to 67 years and ejection fraction varying from 0.17 to 0.64. Endocardial mapping was performed during SVT in all patients. Radiofrequency (RF) current was applied to sites of presystolic activity of at least 30 ms. Entrainment was used to identify reentrant circuits. In both successful and unsuccessful sites of RF current application, electrogram and entrainment were analyzed.

RESULTS

Entrainment was obtained during all mapped SVT. In 70.5% of the sites we observed concealed entrainment and ventricular tachycardia termination in the first 15 seconds of RF current application. In the unsuccessful sites, significantly earlier electrical activity was seen than in the successful ones. Concealed entrainment was significantly associated with ventricular tachycardia termination. Bystander areas were not observed.

CONCLUSION

The reentrant mechanism was responsible for the genesis of all tachycardias. In 70.5% of the studied sites, the endocardial participation of the slow conducting zone of reentrant circuits was shown. Concealed entrainment was the main electrophysiological parameter associated with successful RF current application. There was no electrophysiological evidence of bystander regions in the mapped circuits of SVT.

Combination of chemotherapy with interleukin-2 and interferon alfa for the treatment of metastatic melanoma

PURPOSE

The primary objective of this clinical study was to assess the feasibility of administering recombinant interleukin-2 and recombinant interferon alfa-2a before and after combination cytotoxic chemotherapy. After encouraging initial responses, the study was expanded to further evaluate the therapeutic potential, clarify the toxicities of this regimen, and explore any associated immunologic changes.

PATIENTS AND METHODS

Eighty-four patients with metastatic melanoma, including patients with brain metastases, were treated on this 6-week protocol. Patients received combination cisplatin (25 mg/m2/d) and dacarbazine (220 mg/m2/d) on days 1 through 3 and 22 through 24 plus carmustine (150 mg/m2) on day 1. Interleukin 2 (13.5 million IU/m2/d) and interferon alfa (6 MU/m2/d) were administered on days 4 through 8 and 17 through 21.

RESULTS

Among 83 patients assessable for response, 12 complete and 34 partial responses were documented (55% response rate). The median time to disease progression was 7 months, the median survival from study entry was 12.2 months, and the median survival from diagnosis of metastatic disease was 15.5 months. Although patients were hospitalized to receive treatment, intensive care unit support generally was not needed. Dose-limiting toxicities were related to elevations in serum bilirubin and serum creatinine levels. No patient developed a grade 4 clinical toxicity. Treatment produced a skin depigmentation, which was associated with prolonged survival.

CONCLUSION

A plateau in both the survival and time to progression curves beyond 2 years (15% of the patients) and a greater than 10% disease-free survival beyond 4 years indicate that there may be a long-term benefit for some patients. The limited toxicity of this regimen should permit its use in most oncology settings. A randomized trial of chemoimmunotherapy versus chemotherapy should be performed to establish the value of chemoimmunotherapy for melanoma.

Adjustments in energy expenditure and substrate utilization during late pregnancy and lactation

BACKGROUND

Metabolic adjustments occur during pregnancy and lactation to support fetal growth and milk synthesis; however, the effect of body composition and hormonal milieu on these changes is poorly understood.

OBJECTIVE

We hypothesized that energy metabolism changes during pregnancy and lactation to support fetal growth and milk synthesis, and that body composition and hormonal milieu influence these alterations.

DESIGN

We measured energy expenditure, body composition, and hormone, metabolite, and catecholamine concentrations in 76 women (40 lactating, 36 nonlactating) at 37 wk gestation and 3 and 6 mo postpartum. Total energy expenditure (TEE), basal metabolic rate (BMR), sleeping metabolic rate (SMR), and minimal SMR (MSMR) were measured with room calorimetry. Fat-free mass (FFM) and fat mass were estimated with a 4-component model.

RESULTS

TEE, BMR, SMR, and MSMR were 15-26% higher during pregnancy than postpartum after being adjusted for FFM, fat mass, and energy balance. TEE, SMR, and MSMR were higher in lactating than in nonlactating women. Fasting serum insulin, insulin-like growth factor I, fatty acids, and leptin, and 24-h urinary free norepinephrine, epinephrine, and dopamine correlated positively with TEE, BMR, SMR, and MSMR. In nonlactating women, the respiratory quotient decreased over time, carbohydrate oxidation decreased, and fat oxidation increased. Substrate utilization was not influenced by body composition, fasting serum hormones, or 24-h urinary catecholamines.

CONCLUSIONS

These results indicate increased energy expenditure and preferential use of carbohydrates during pregnancy and lactation. Elevated respiratory quotient and carbohydrate utilization during pregnancy continue during lactation, consistent with preferential use of glucose by the fetus and mammary gland.

Noninvasive rejection monitoring of cardiac transplants using high resolution intramyocardial electrograms: initial US multicenter experience

Endomyocardial biopsy (EMB) remains the mainstay for the diagnosis of acute cellular rejection in cardiac transplant patients. A noninvasive alternative that would supplant or reduce the number of EMBs would be a highly desirable and cost-effective tool. To evaluate one potential alternative, a pacemaker with high resolution telemetry capabilities and two fractally coated epimyocardial leads were implanted in 30 patients at five transplant centers during the heart transplant procedure. Ventricular electrograms were recorded during intrinsic and paced activity and digitized to a laptop-based data acquisition device. Electrograms were recorded at frequent intervals and systematically on days when EMBs were performed. The electrogram data were then transferred via the Internet to a central data processing site. Clinical patient management was blinded to the electrogram results and varied considerably among the five centers. Using EMB together with clinical assessment of the transplant revealed 18 cases of clinically significant rejection beyond postoperative day 27 that required antirejection therapy. The normalized parameter values extracted from the electrogram recordings during pacing (the ventricular evoked response) that were associated with significant rejection were statistically lower (86% +/- 16% versus 96% +/- 22%, P < 0.005). The application of a single-threshold diagnosis model to the parameter values allowed detection of significant rejection with a negative predictive value of 98%. This analysis also showed that as many as 55% of the routine surveillance EMBs could have been eliminated had the pacemaker monitoring technique been used as a screening tool prior to EMB. A prospective study should further define the role of this technique in the detection and management of cardiac transplant patients.

Truncated presenilin 2 derived from differentially spliced mRNA does not affect the ratio of amyloid beta-peptide 1-42/1-40

Numerous mutations in the presenilin (PS) genes cause early onset familial Alzheimer's disease (FAD). Here we characterize the expression of two naturally occurring alternative PS2 transcripts which lack either exons 3 and 4 (PS2 deltaexon3,4) or exons 3, 4, and 8 (PS2 deltaexon3,4,8). These transcripts do not contain the natural initiation codon within exon 3. The transcripts are efficiently translated as N-terminal truncated proteins. These deleted proteins are still able to regulate formation of endogenous PS fragments, indicating that the C-terminal half of the PS2 protein is sufficient for this phenomenon. Although approximately 50% of the PS1 and both PS2 mutations occur within the N-terminal region lacking in the PS2 deltaexon3,4 and PS2 deltaexon3,4,8 proteins, expression of these truncated proteins does not affect pathological generation of amyloid beta-peptide (Abeta). This suggests that point mutations causing AD are gain of function mutations.

Low density lipoproteins and Lovastatin modulate the organ-specific transendothelial migration of primary and metastatic human colon adenocarcinoma cell lines in vitro

Tumor cell arrest and tumor migration are two of the critical steps in the metastatic cascade. We hypothesized that these steps may be facilitated by the low density lipoprotein (LDL)-induced activation of microvessel endothelial cells (MVEC). The purpose of our study was to investigate the biological effects of an LDL-enriched milieu and the effects of the anticholesterol drug Lovastatin on metastatic behavior. The SW480 and SW620 are primary and metastatic human colonic adenocarcinoma cell lines derived from the same patient. We investigated the effect of LDL on adhesion and migration of the two tumor cell lines across human brain, lung, liver and dermal endothelial monolayers. Adhesion and migration assays were done before and after pretreatment of the MVEC or tumor cells with LDL (100 microg/ml) for 24 h. Although metastatic SW620 cells were more adherent to MVEC compared with primary SW480 cells, LDL pretreatment of SW480 and SW620 cells did not affect tumor cell adhesion to MVEC. In contrast, tumor cell migration was significantly increased across endothelial monolayers when MVEC were pretreated with LDL. Transendothelial cell migration was not significantly affected by pretreatment of the tumor cells with LDL. Lovastatin is an inhibitor of HMG-CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis. It has been shown to have anti-tumor activity in vitro. We investigated the effect of Lovastatin on tumor cell kinetics and tumor cell migration across MVEC. Growth curves and migration assays were done before and after pretreatment of the tumor cells with Lovastatin (30 microg/ml). Migration assays were also done after treatment of unstimulated or LDL-stimulated MVEC (100 microg/ml) for 24 h with Lovastatin. Lovastatin inhibited the in vitro growth of the metastatic SW620 cell line to a greater extent than the invasive SW480E cell line. On the other hand, pretreatment of tumor cells with Lovastatin (30 microg/ml) did not suppress transendothelial tumor cell migration of tumor cells. Finally, Lovastatin given to mice effectively suppressed the number of MCA-26 tumor colonies in the liver of Balb/c mice compared with untreated mice.

Congenital tuberculosis

Congenital tuberculosis is a rare disease. The non-specific nature of presenting signs and symptoms (because of the lack of host response) and the fatal outcome in the absence of early therapy all underscore the importance of early diagnosis and treatment in infants. Recognition requires awareness that tuberculosis at this age has manifestations not found in older children. Here a case of congenital tuberculosis is presented, where changes were confined only to the thorax. Tuberculosis in the mother could be diagnosed only retrospectively.

Prevalence and predictors of the prone sleep position among inner-city infants

CONTEXT

The prone sleep position is associated with an increased risk of sudden infant death syndrome (SIDS), but few studies have assessed factors associated with the choice of infant sleep position.

OBJECTIVES

To describe infant sleep position in a cohort of infants born to predominantly low-income, inner-city mothers and to identify predictors of the prone sleep position in this population.

DESIGN

Prospective birth cohort study.

PATIENTS AND SETTING

Three hundred ninety-four mother-infant dyads, systematically selected from 3 District of Columbia hospitals between August 1995 and September 1996. Mothers were interviewed shortly after delivery and again at 3 to 7 months postpartum.

MAIN OUTCOME MEASURES

Position in which infants were placed for sleep on the night prior to the 3- to 7-month interview.

RESULTS

At 3 to 7 months of age, 157 infants (40%) were placed for sleep in the prone position. Independent predictors of prone sleep position included poverty (odds ratio [OR], 1.81; 95% confidence interval [CI], 1.10-2.99), black race (OR, 2.06; 95% CI, 1.05-4.04), presence of infant's grandmother in the home (OR, 1.83; 95% CI, 1.11-3.00), and intent, as measured shortly after delivery, to place the infant in the prone position (OR, 2.28; 95% CI, 1.44-3.60). Importantly, of the 43 mothers who observed their infants in the prone sleep position while in the hospital, 40 (93%) intended to place their infants prone at home.

CONCLUSIONS

A substantial proportion of infants in this predominantly low-income population were placed in the prone sleep position. Educational efforts should address both initial intentions and reinforcement of the correct sleep position, once initiated. Hospitals should ensure that healthy newborn infants are placed in the supine sleep position during the postpartum hospital stay.

Emergency mitral valve replacement for traumatic mitral insufficiency following balloon mitral valvotomy: an early haemodynamic study

Acute severe mitral insufficiency may occur during percutaneous transvenous balloon mitarl valvotomy. Urgent surgical intervention in the form of mitral valve repair or replacement may be necessary in these patients. The haemodynamic measurements at various stages in these patients were obtained and compared with those of patients undergoing elective mitral valve replacement for chronic mitral regurgitation. Between September 1995 and December 1947, urgent mitral valve replacement was performed in 14 patients out of a total of 1688 patients who underwent balloon mitral valvotomy. Haemodynamic measurements could be obtained in 7 of these patients and they constituted group I. Eight other patients undergoing elective mitral valve replacement during the same period for chronic mitral regurgitation constituted group II. Standard haemodynamic measurements were obtained at the following stages: (1) Baseline- 20-30 min after endotracheal intubation; (2) stage 1- 20-30 min after termination of the cardiopulmonary bypass: (3) stage 2- four hours after the patient was transferred to ICU and (4) stage 3-30 min after extubation. All the patients were suffering from severe pulmonary hypertension. However, the indices of pulmonary artery hypertension such as mean pulmonary artery pressure, pulmonary capillary wedge pressure, pulmonary vascular resistance as well as right ventricular systolic and end-diastolic pressures did not decrease after surgery in group I. In contrast, in group II, there was significant decrease in mean pulmonary artery pressure (p<0.05), pulmonary capillary wedge pressure (p<0.05), right ventricular systolic (p<0.001) and end-diastolic pressures (p<0.05) at stage 1. These changes persisted throughout the study period. Pulmonary vascular resistance showed a decreasing trend, but attained statistical significance at stage 1 only. Two patients died; one of intractable cardiac failure and another from septicaemia and multiple organ failure in group I, but there were no deaths in group II. Reactive pulmonary hypertension secondary to acute mitral regurgitation may not recover immediately following mitral valve replacement and may be responsible for poor outcome in these patients.

Post-cardiotomy intra-aortic balloon counter pulsation: application and prognostic evaluation

Cardiac assistance by intra-aortic balloon counter pulsation was studied in 113 cardiac surgical cases comprising 91 male and 22 female patients. This included 82 percent of patients having coronary artery bypass surgery, while 18 percent were operated for valvular lesions. It was observed that the time of institution of cardiac assistance by intra-aortic balloon counter pulsation, following cardiac surgery, was of prime importance to decrease patient mortality. It was lowest (16%) when the balloon was inserted for assistance before termination and highest (50%) when there was delay of more than 15 minutes following termination of cardiopulmonary bypass. Early balloon assistance significantly lowered the pulmonary capillary wedge pressure and usually 1:2 augmentation was more effective, probably because of existing tachycardia in most patients. Advances in catheter technology have reduced the vascular complication at the insertion site. Percutaneous insertion had less local complications (13.3%) than open arteriotomy technique (31.2%). Similarly with sheathless insertion, complications were less (6.6%) in comparison to sheathed insertion (21.7%). Proper placement of balloon avoided position-related complications and there was no compromise of blood flow through left internal mammary artery as noticed in our series.

Cloning and characterization of the presenilin-2 gene promoter

Mutations in the presenilin-2 (PS-2) have been shown to cause early onset Alzheimer's disease (AD) in a series of families known as the Volga Germans and in an unrelated Italian kindred. Expression of the PS-2 gene is regulated during AD, aging, development and brain injury. Although expressed primarily in neurons, enhanced levels of PS-2 have been reported in astrocytes activated by neuronal damage. Understanding the regulation of the PS-2 gene may thus provide an insight into its role in AD. We have isolated a 3635 bp DNA fragment that contains 2934 bp of DNA sequence upstream from the PS-2 gene. Primer extension analysis was used to map three major transcriptional start sites within the PS-2 gene. The promoter sequence, upstream of each transcriptional start site, does not contain TATA or CAAT boxes but does contain several GC rich sites (Sp-1 and AP-2). A reporter gene construct containing the PS-2 promoter (PS2P, -2934 to +702) transfected into M17 cells drives basal transcription to 20% of the levels of the SV-40 viral promoter. Addition of NGF to PC-12 cells was found to upregulate the PS2P promoter and an NGF-responsive element was localized by deletional analysis between -403 and +13 within the promoter. Since the PS-2 gene has multiple start sites and the upstream sequence is GC rich with no TATA box, the PS-2 promoter is consistent with the GC class of 'housekeeping' genes.

A variant of Alzheimer's disease with spastic paraparesis and unusual plaques due to deletion of exon 9 of presenilin 1

We describe a novel variant of Alzheimer's disease (AD) in a Finnish pedigree with 17 affected individuals of both sexes in three generations. The disease is characterized by progressive dementia which is, in most cases, preceded by spastic paraparesis. Neuropathological investigations revealed numerous, distinct, large, round and eosinophilic plaques as well as neurofibrillary tangles and amyloid angiopathy throughout the cerebral cortex. The predominant plaques resembled cotton wool balls and were immunoreactive for Abeta but lacked a congophilic dense core or marked plaque-related neuritic pathology. Molecular genetic analysis revealed that the disease was caused by a deletion of exon 9 (delta9) of the presenilin 1 (PS1) gene from the mRNA: unlike previous examples of the delta9 variant, the deletion was not caused by a splice acceptor site mutation.