The Neisseria type 2 IgA1 protease cleaves LAMP1 and promotes survival of bacteria within epithelial cells

Infection of human epithelial cells by Neisseria meningitidis (MC) and Neisseria gonorrhoeae (GC) increases the rate of degradation of LAMP1, a major integral membrane glycoprotein of late endosomes and lysosomes. Several lines of evidence indicate that the neisserial IgA1 protease is directly responsible for this LAMP1 degradation. LAMP1 contains an IgA1-like hinge region with potential cleavage sites for the neisserial type 1 and type 2 IgA1 proteases. Neisserial type 2 IgA1 protease cleaves purified LAMP1 in vitro. Unlike its wild-type isogenic parent, an iga mutant of N. gonorrhoeae cannot affect LAMP1 turnover and its growth in epithelial cells is dramatically reduced. Thus, IgA1 protease cleavage of LAMP1 promotes intracellular survival of pathogenic Neisseria spp.

Cloning and characterization of the Neisseria meningitidis rfaC gene encoding alpha-1,5 heptosyltransferase I

We cloned and characterized the Neisseria meningitidis rfaC gene which encodes an enzyme, alpha-1,5 heptosyltransferase I, involved in the synthesis of the deep-core of the lipooligosaccharide. The N. meningitidis rfaC mutant, obtained by an allelic exchange, produced lipooligosaccharide which migrated faster in sodium dodecyl sulfate-polyacrylamide gel electrophoresis than the lipooligosaccharide isolated from the wild-type N. meningitidis. The N. meningitidis rfaC mutant was not affected by growth in a rich microbiological medium and did not show any defect in adhesion to epithelial cell lines. Conversely, the rfaC mutant was attenuated in the infant rat model of meningococcemia, thus confirming the importance of intact lipooligosaccharide in the virulence of N. meningitidis.

Comparison of the effects of an ampakine with those of methamphetamine on aggregate neuronal activity in cortex versus striatum

The present study used in situ hybridization to c-fos mRNA to compare the effects of an 'ampakine' (a positive modulator of AMPA type glutamate receptors) with those of methamphetamine on the balance of aggregate neuronal activity in the cortex versus striatum. Methamphetamine (n = 11) induced a marked increase in c-fos mRNA in the dorsomedial quadrant of the striatum and a 21% smaller, but still reliable, increase in the ventrolateral quadrant. The drug also elevated c-fos mRNA levels in the ventral and medial segments of the orbitofrontal cortex but had no detectable effects in motor and somatosensory neocortices. The ampakine (n = 11) caused a near inverse pattern of changes; i.e. a sizable increase in somatosensory labeling and a significant decrease in striatal labeling with statistically insignificant effects in motor and orbitofrontal cortex. Within-rat cortical and striatal values were correlated in both the vehicle (n = 11) and ampakine groups, and appropriate comparisons established that the ampakine caused 27-55% increases in the ratio of cortical to striatal labeling. These results are in accord with the idea that facilitation of glutamatergic transmission has 'network level' effects that are opposite in nature to those resulting from enhanced dopaminergic transmission. The potential relevance of ampakines alone or in conjunction with dopamine antagonists for the treatment of schizophrenia is discussed.

Rumination and psychological distress among bereaved partners

Recently bereaved men who evidenced more negative ruminative thoughts in free-response interviews showed greater psychological distress on several outcome measures both 1 month and 12 months after their loss and less increase in positive morale over this 12-month period. Men who engaged in more analysis of themselves and the meaning of their loss reported greater positive morale 1 month after their loss but showed more persistent depression and absence of positive states of mind over the 12 months following their loss. Finally, men who reported more social friction also evidenced more enduring depressive symptoms over the year than did men who reported less social friction. These results are generally consistent with other studies that have shown that self-reflective, ruminative coping with negative emotions and social friction are associated with longer and more severe periods of depressed mood following stressful events.

Rumination and psychological distress among bereaved partners

Recently bereaved men who evidenced more negative ruminative thoughts in free-response interviews showed greater psychological distress on several outcome measures both 1 month and 12 months after their loss and less increase in positive morale over this 12-month period. Men who engaged in more analysis of themselves and the meaning of their loss reported greater positive morale 1 month after their loss but showed more persistent depression and absence of positive states of mind over the 12 months following their loss. Finally, men who reported more social friction also evidenced more enduring depressive symptoms over the year than did men who reported less social friction. These results are generally consistent with other studies that have shown that self-reflective, ruminative coping with negative emotions and social friction are associated with longer and more severe periods of depressed mood following stressful events.

Sentinel node dissection in the treatment of melanoma. Report of three cases and review of the literature

BACKGROUND

Elective lymph node dissection for treatment of cutaneous malignant melanoma is controversial. Sentinel node dissection involves removing the primary lymph node in a nodal basin that drains a particular cutaneous lesion. Theoretically, this node would collect regional metastases first. Therefore, if this node is negative, the chances are low that the melanoma would have spread either systemically or to other nodes within this basin. Removing one node would decrease the morbidity associated with radical lymph node dissection. However, the actual risk of widespread metastases in sentinel node-negative patients is yet to be determined, pending results of large, multicenter studies currently under investigation.

OBJECTIVE

To present three cases of intermediate thickness cutaneous melanoma treated with selective lymph node dissection and to review the techniques of selective lymphadenectomy and lymphoscintigraphy.

METHODS

In a nonrandomized prospective evaluation, patients with intermediate depth melanomas or in transit metastases without signs of systemic disease were given the opportunity for further investigation by sentinel node dissection to determine if additional lymph node dissection or adjunctive therapies would be advantageous.

RESULTS

All three patients had negative sentinel node examinations. Two are without visceral or nodal metastases 1 year after the procedure. The third had in-transit metastases from the outset, had in-transit metastases on sentinel node/lymphatic examination, and now has systemic cutaneous metastases. Complications of sentinel node dissection were limited to transient postoperative lymphedema of the extremities and transient seroma formation. No postoperative wound infections or permanent nerve damage were noted.

CONCLUSIONS

Our preliminary findings in this limited series suggests that sentinel node dissection appears to be a procedure of low morbidity and relatively high predictive value.

Effects of an AMPA receptor modulator on methamphetamine-induced hyperactivity in rats

The present study tested if a positive modulator of AMPA-type glutamate receptors would counteract the behavioral effects of a drug that enhances the release of dopamine. BDP-29, a compound shown to increase AMPA receptor-mediated synaptic responses in hippocampal slices, markedly attenuated the amount of stereotypic rearings seen in rats after methamphetamine injections. These results suggest that AMPA receptor modulators ameliorate certain aberrant, dopamine-related behaviors and hence may be of interest with regard to schizophrenia.

Effects of pharmacologically facilitating glutamatergic transmission in the trisynaptic intrahippocampal circuit

The effects of a recently synthesized benzoyl-piperidine drug that enhances currents mediated by alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)-type glutamate receptors were tested on monosynaptic and polysynaptic responses in hippocampal slices of the rat. Stimulation of perforant path inputs to the dentate gyrus evoked extracellular responses in field CA1 that had latencies and laminar profiles indicating that they were relayed through the trisynaptic intrahippocampal circuit. Under control conditions, trisynaptic field excitatory postsynaptic potentials did not show larger paired-pulse facilitation than monosynaptic responses and failed to exhibit frequency facilitation. Low concentrations of picrotoxin greatly enhanced trisynaptic responses and, under these conditions, frequency facilitation was obtained. Benzoyl-piperidine-12 (250 microM) had a three-fold greater effect on the amplitude of trisynaptic responses than on monosynaptic field excitatory postsynaptic potentials, indicating that the drug's effect is amplified across the successive stages of a polysynaptic circuit. The AMPA receptor modulator did not change the frequency characteristics of monosynaptic potentials and had only a modest influence on those of the trisynaptic response. The effect of benzoyl-piperidine-12 on trisynaptic responses was significantly greater when GABAergic inhibition was partially blocked with picrotoxin; the GABA blocker did not alter the effects of benzoyl-piperidine-12 on monosynaptic responses. These results indicate that centrally active AMPA receptor modulators are likely to have a greater influence on brain operations involving long chains of connections than on those mediated by simple reflex-like circuits, and will vary markedly in their effects depending upon the excitability of local interneurons.

HmbR outer membrane receptors of pathogenic Neisseria spp.: iron-regulated, hemoglobin-binding proteins with a high level of primary structure conservation

We have recently cloned and characterized the hemoglobin receptor gene from Neisseria meningitidis serogroup C. N. meningitidis cells expressing HmbR protein were able to bind biotinylated hemoglobin, and the binding was specifically inhibited by unlabeled hemoglobin and not heme. The HmbR-mediated hemoglobin binding activity of N. meningitidis cells was shown to be iron regulated. The presence of hemoglobin but not heme in the growth medium stimulated HmbR-mediated hemoglobin binding activity. The efficiency of utilization of different hemoglobins by the HmbR-expressing N. meningitidis cells was shown to be species specific; human hemoglobin was the best source of iron, followed by horse, rat, turkey, dog, mouse, and sheep hemoglobins, The phenotypic characterization of HmbR mutants of some clinical strains of N. meningitidis suggested the existence of two unrelated hemoglobin receptors. The HmbR-unrelated hemoglobin receptor was shown to be identical to Hpu, the hemoglobin-haptoglobin receptor of N. meningitidis. The Hpu-dependent hemoglobin utilization system was not able to distinguish between different sources of hemoglobin; all animal hemoglobins were utilized equally well. HmbR-like genes are also present in N. meningitidis serogroups A and B, Neisseria gonorrhoeae MS11 and FA19, Neisseria perflava, and Neisseria polysaccharea. The hemoglobin receptor genes from N. meningitidis serogroups A and B and N. gonorrhoeae MS11 were cloned, and their nucleotide sequences were determined. The nucleotide sequence identity ranged between 86.5% (for N. meningitidis serogroup B hmbR and MS11 hmbR) and 93.4% (for N. meningitidis serogroup B hmbR and N. meningitidis serogroup C hmbR). The deduced amino acid sequences of these neisserial hemoglobin receptors were also highly related, with overall 84.7% conserved amino acid residues. A stop codon was found in the hmbR gene of N. gonorrhoeae MS11. This strain was still able to use hemoglobin and hemoglobin-haptoglobin complexes as iron sources, indicating that some gonococci may express only the HmbR-independent hemoglobin utilization system.

The meaning of equivocal pancreatic cytology in patients thought to have pancreatic cancer

INTRODUCTION

Fine needle aspirations (FNAs) and endoscopic retrograde cholangiopancreatography (ERCP)-guided brushings (BRUSH) are useful tools in the differentiation between malignant and benign disease of the pancreas. Once the decision to obtain a cytologic confirmation of one's clinical suspicion is made, the interpretation of the findings, especially an equivocal or negative cytology finding, can be unclear. This study seeks to evaluate the utility of cytologic studies in the evaluation of a patient with suspected pancreatic malignancy.

METHODS

A retrospective review of 224 cytologic reports, including 174 FNAs and 50 BRUSHs, from all pancreatic FNAs and BRUSHs performed between January 1989 and June 1995, was performed. Subsequent confirmation of the cytologic diagnosis was made either by histologic or strict clinical criteria.

RESULTS

Forty-three percent of the cytologic reports were read as malignant, all others reported as suspicious, atypical, or negative. All cytology studies read as malignant and all FNAs reported as suspicious were histologically or clinically confirmed to be malignant. Of those reported as atypical or negative, 55% and 49% were confirmed to be malignant. Both FNA and BRUSH were 100% specific, 75% sensitive, and 80% accurate.

CONCLUSIONS

We conclude that a cytological diagnosis of malignant or suspicious is reliable and useful for further therapy planning in the patient suspected to have a pancreatic malignancy. The reason for the cytologic tests was a strong clinical suspicion, therefore, a high incidence of cancer was found in the patients with atypical or negative readings. A diagnosis of atypical or negative is equivocal and requires further diagnostic maneuvers, frequently including surgery, to make the definitive diagnosis.

Facilitation of olfactory learning by a modulator of AMPA receptors

The effects of a benzoyl-piperidine drug (BDP) that facilitates AMPA receptor-mediated synaptic responses were tested on the acquisition and retention of long-term memory at dosages that had no detectable effects on a variety of performance measures. BDP-12 produced a dose-dependent suppression of exploratory activity in rats with statistically reliable effects occurring at 50 mg/kg (i.p.). The drug had no effects on balance beam performance at 30 mg/kg but at 45 mg/kg reduced the number of crossings made within a session; it did not, however, affect the time required to perform a traversal. The performance of well-trained rats presented with a familiar pair of odors (correct and incorrect) was not not detectably altered by BDP-12 at 30 mg/kg; however, the number of correct responses made in a five-trial test was reduced at 45 mg/kg. These results indicate that the AMPA receptor modulator at 30 mg/kg has little influence on arousal, motivation, sensori-motor processing, and attention; higher dosages cause a depression of learned and unlearned prepotent responses. The effects of the lower concentration were tested on two-odor discrimination learning in rats that had extensive training on the task. The animals (n = 20) were given three or five acquisition trials with novel odor pairs immediately after an injection of drug or vehicle and then tested 1-3 d later for retention in five unrewarded probe trials. Retention performance was not significantly better than chance 52.6 +/- 4.5% correct) for odors learned on vehicle injection days but was well above chance for odors learned on drug injection days (70.6 +/- 4.2% correct). Within-subject comparisons confirmed the memory enhancing effect of BDP-12 (p < 0.01). Analyses of performance during five training trials indicated that the rats made more correct responses on days on which they were given the drug than on days on which they were injected with vehicle (p < 0.02). Within-subject differences in acquisition were correlated with differences in retention (r = 0.70). There were no evident effects of the drug on response latencies during acquisition. These results suggest that AMPA receptor modulators reduce the amount of training needed for the formation of long-term memory and do so at dosages which have little effect on variables that secondarily influence acquisition. Possible reasons for this selectivity are discussed.

Comparison of long-term potentiation in the proximal versus distal stratum radiatum of hippocampal field CA1

Recent studies indicate that long-term potentiation is accompanied by changes in the waveform of field excitatory postsynaptic potentials in the CA1 field of disinhibited hippocampal slices, suggesting that long-term potentiation alters the kinetics of the glutamate receptor channels that mediate excitatory synaptic responses. The present study examined the effects of stimulating and recording location within stratum radiatum on the magnitude of long-term potentiation and the associated waveform changes. Stimulation of stratum radiatum proximal to the cell body layer evoked field excitatory postsynaptic potentials in proximal stratum radiatum that had decay phases well-fit by single exponentials; long-term potentiation reduced the decay time constant of these potentials, as reported previously. Stimulation of distal stratum radiatum evoked field excitatory postsynaptic potentials in distal stratum radiatum that were contaminated by positive after-potentials; meaningful estimates of decay time constants for these responses could not be obtained. Long-term potentiation of distal responses tended to be smaller than that obtained proximally. Comparisons were also made between responses recorded distally and proximally for either distal or proximal stimulation. For both stimulation loci, the distally-recorded responses had positive after-potentials and the proximally-recorded responses did not. The decay time constants for proximally-recorded responses to distal stimulation decreased significantly after long-term potentiation. Proximal and distal stimulation both produced greater long-term potentiation recorded proximally than distally and the difference was significantly greater for proximal stimulation. When long-term potentiation was induced by stimulation of proximal and distal sites simultaneously, the difference between proximally- and distally-recorded long-term potentiation was significantly reduced. Paired-pulse facilitation was greater when recorded proximally but the variation in facilitation with stimulation and recording position was different from that obtained for long-term potentiation. Paired-pulse facilitation of response amplitude was slightly reduced after long-term potentiation, but the change did not depend on the stimulation-recording arrangement; facilitation of response slope was not reliably affected by long-term potentiation. These results indicate that the shape of the dendritic field excitatory postsynaptic potential is influenced by the relative position of recording electrodes in stratum radiatum; when the position is such that after-potentials are minimized, long-term potentiation produces a decrease in the decay time constant of the synaptic field potential.(ABSTRACT TRUNCATED AT 400 WORDS)

Further characteristics of long-term potentiation in piriform cortex

Mechanisms for the induction and expression of long-term potentiation (LTP) were studied in slices of piriform cortex. Cooperativity among afferent inputs as a controlling factor for induction of LTP was tested by pairing stimulation of one input that normally does not induce LTP with stimulation of another input. Combined stimulation, given either to two weak inputs with simultaneous bursts or by pairing single pulses with bursts, did effectively induce LTP. Tests for expression of LTP by NMDA vs. non-NMDA receptors indicated that non-NMDA receptor-mediated responses expressed much greater LTP than NMDA receptor-mediated responses. Ratios for paired-pulse facilitation and depression were not altered after induction of LTP. These characteristics are comparable to those exhibited by synapses in the CA1 field of hippocampus.

Non-Hebbian properties of long-term potentiation enable high-capacity encoding of temporal sequences

A hypothesis commonly found in biological and computational studies of synaptic plasticity embodies a version of the 1949 postulate of Hebb that coactivity of pre- and postsynaptic elements results in increased efficacy of their synaptic contacts. This general proposal presaged the identification of the first and still only known long-lasting synaptic plasticity mechanism, long-term potentiation (LTP). Yet the detailed physiology of LTP induction and expression differs in many specifics from Hebb's rule. Incorporation of these physiological LTP constraints into a simple non-Hebbian network model enabled development of "sequence detectors" that respond preferentially to the sequences on which they were trained. The network was found to have unexpected capacity (e.g., 50 x 10(6) random sequences in a network of 10(5) cells), which scales linearly with network size, thereby addressing the question of memory capacity in brain circuitry of realistic size.

Cholestatic jaundice due to ackee fruit poisoning

A 27-yr-old Jamaican male presented with a 2-month history of jaundice, pruritus, intermittent diarrhea, and right upper quadrant abdominal pain. Over the next month, his abdominal pain and diarrhea improved, but his jaundice and pruritus worsened. He was afebrile and profoundly jaundice, with a benign abdominal examination. Medical workup included a normal abdominal ultrasound, iron studies, ceruloplasm, and serum electrophoresis. Negative viral (Epstein-Barr virus, cytomegalovirus, mononucleosis, hepatitis A, B, C) studies, ANA, AMA, ASMA, RPR were noted. He denied any alcohol, drug, or toxin exposure. Liver tests revealed total bilirubin of 25.6 mg/dl, direct bilirubin of 13.9 mg/dl, alkaline phosphatase 278 IU/L, AST 45 IU/L, and ALT 71 IU/L. Liver biopsy demonstrated centrilobular zonal necrosis and cholestasis most consistent with a toxic reaction. The patient was again interviewed regarding potential toxins, and he admitted to the ingestion of ackee fruit, a native Jamaican fruit that is illegal in the United States. Shortly after he had ceased intake of the fruit, his symptoms resolved and his liver function tests returned to normal. We present a case of chronic ackee fruit ingestion that led to cholestatic jaundice, vomiting, and abdominal pain.

Ruminative coping with depressed mood following loss

In a longitudinal study of 253 bereaved adults, people with poorer social support, more concurrent stressors, and higher levels of postloss depression reported more rumination than people with better social support, fewer stressors, and lower initial depression levels. Women reported more rumination than men. People with a ruminative style at 1 month were more likely to have a pessimistic outlook at 1 month, which was associated with higher depression levels at 6 months. People with a more ruminative style were more depressed at 6 months, even after controlling for initial depression levels, social support, concurrent stressors, gender, and pessimism. Additional stressors and high depression scores at 1 month were also associated with higher levels of depression at 6 months.

Effects of cyclothiazide on synaptic responses in slices of adult and neonatal rat hippocampus

The effects of cyclothiazide, a drug that blocks AMPA receptor desensitization, on synaptic responses were studied in field CA1 of hippocampal slices from adult and neonatal rats. Cyclothiazide (100 microM) reliably increased AMPA receptor-mediated field EPSP decay times in adult slices but only after prolonged (60-120 min) applications. In neonatal slices, 30 min applications of cyclothiazide were sufficient to produce large and long-lasting increases in response decay times. Since the effects of cyclothiazide on AMPA receptor binding properties were similar in adult and neonatal forebrain membranes, the data indicate that the slow action of the drug in adult slices is probably due to diffusion barriers. The prolongation of EPSP decay by cyclothiazide suggests that AMPA receptor-mediated synaptic responses in hippocampus are terminated by receptor desensitization.

Waveform analysis suggests that LTP alters the kinetics of synaptic receptor channels

The waveform of an isolated excitatory monosynaptic response reflects the kinetics of transmitter release, the kinetics of synaptic receptor channels and the filtering properties of neurons. Results reported here indicate that long-term potentiation (LTP) causes correlated decreases in the rise time and decay time constant of synaptic potentials recorded in hippocampal slices in which inhibitory currents and post-synaptic spiking were suppressed. Statistical comparisons of waveforms revealed that the distortions introduced by LTP could be corrected by stretching the time-scale of potentiated responses according to the percent change in the decay time constant. The LTP associated decrease in the decay time constant also obtained in slices from immature hippocampus which contain spines and dendrites greatly simplified from those of the adult. Hence, filtering properties of spines are not likely involved in the effect. Paired-pulse facilitation (PPF), a transient increase in transmitter release, did not reproduce the waveform effects of LTP but did cause a slight leftward shift of the response. These results suggest that LTP modifies the kinetics of receptor channels, and that PPF accelerates release.