Biomedical subjects

A D Smith

Publications and source records attributed to A D Smith.

At least 109 records · Page 6Linked to original sources

PubMed1999

Heightened suspicion and rapid evaluation with CT for early diagnosis of partial renal infarction.

BACKGROUND AND OBJECTIVE: Although renal infarction has been well studied and clearly defined, it remains greatly underdiagnosed, resulting in significant morbidity. Acute segmental renal infarction is a diagnosis even more problematic, as the problem can appear insidiously and masquerade as other entities including stone, infection, and even tumor. The clinical manifestations and evaluation of partial renal infarction in our patients were reviewed. PATIENTS AND METHODS: Seven patients presenting to the emergency department who were subsequently found to have partial renal infarction were identified from the 5-year records of a single institution. Patients were evaluated for presenting complaints, physical findings, temperature, and blood pressure. Laboratory analysis consisted of a complete blood count (CBC); measurements of creatinine, lactate dehydrogenase (LDH), aspartate transaminase/alanine transaminase (AST/ALT), and alkaline phosphatase; and urinalysis. The sequence of the work-up was recorded, as well as time to diagnosis. The etiology of infarction was identified for all patients. RESULTS: All seven patients were eventually discovered to have partial renal infarction as a result of dysrhythmia (N = 4), mural thrombus (N = 2), or septic emboli (N = 1). The average time to diagnosis was 65.2 hours with a range of 9.5 to 168 hours. The chief complaint was flank pain (N = 3), nonspecific abdominal pain (N = 2), left lower-quadrant pain (N = 1), and mental status change (N = 1). The presenting signs and symptoms included abdominal tenderness (N = 4), nausea and vomiting (N = 4), temperature >100.5 degrees F (N = 3), and hypertension (N = 3). Laboratory studies revealed a white cell count >11,000/microL in six, microhematuria in four, proteinuria in four, elevated LDH in all patients, elevated AST/ALT in two, and elevated alkaline phosphatase in one. The work-up varied by presentation, but definitive diagnosis was made by CT in all five patients scanned and by angiography in two. Angiography confirmed the CT findings in four of the five patients. CONCLUSION: In evaluating partial renal infarction, a strong clinical suspicion is necessary. We found a history of dysrhythmia or other cardiac disease, the presence of abdominal or flank pain, fever with an elevated white cell count, and an elevated LDH to be clinically significant, and their presence should alert the clinician to the possibility of renal infarction. Once a degree of suspicion exists, early evaluation with CT should speed the diagnosis and effect decreased morbidity.

Adolescent↗

PubMed1999

Acute ureteral elongation in two animal models using a balloon expander.

BACKGROUND AND OBJECTIVE: Repair of ureteral injuries and strictures often necessitates a major reconstructive procedure such as a psoas hitch, Boari flap, renal mobilization, ileal interposition, or autotransplantation. Tissue expanders have been used to elongate nerves and arteries. We examined the effects of acute ureteral elongation in two animal models. MATERIALS AND METHODS: In eight female rabbits, we exposed the left ureter through a midline incision and placed a Ruiz-Cohen balloon beneath the undermined portion. The expander was then inflated until the ureter was tightly stretched across it. After deflation, the expanded segment was measured in situ and compared with its original length. Follow-up urography was performed, and the tissue was harvested and examined by a pathologist. The same procedure was performed in five pigs; however, in these animals, a segment of ureter was excised, and a ureteroureterostomy was performed, after the acute expansion. RESULTS: We were able to achieve acute elongation of the expanded ureteral segment. The mean elongation was 31.3% in the rabbits and 32.0% in the pigs. An intravenous urogram (IVU) 6 weeks after the elongation showed a functioning kidney and a patent ureter. Histologic examination of the ureter within 24 hours after the expansion revealed that all segments were viable, the luminal epithelium was intact, and the muscular layers appeared normal. At 6 weeks, the expanded segment showed mild inflammatory changes, but the overall morphology, size, and cytology findings were similar to those of a normal control. CONCLUSIONS: Acute ureteral elongation using a tissue expander is a new method of increasing ureteral length. It may be useful to cover defects that would need major operations with greater morbidity.

Anastomosis, Surgical↗

PubMed1999

Percutaneous nephrolithotomy with renal angiomyolipomas: a rare challenge.

Renal angiomyolipomas (AML) are vascular tumors associated with a risk of spontaneous bleeding. Renal trauma may also initiate such hemorrhage. We present a case in which we initially avoided direct puncture and the possible risk of bleeding through extensive renal AMLs and then subsequently performed a direct puncture through the tumors. A 21-year-old obese male patient with tuberous sclerosis and mental retardation presented to our institution with left renal colic and was found to have a staghorn calculus. A CT scan revealed extensive bilateral renal AMLs. The patient had previously undergone renal angioinfarction for an enlarging right-sided AML, and nuclear renography demonstrated 70% function from the left side. The patient had a nephrostomy access created on the morning of a scheduled percutaneous nephrolithotomy under three-dimensional CT guidance. There was no clinically significant bleeding. Intraoperatively, a second access site was required in order to render the patient stone free. This was done using standard biplanar fluoroscopic technique and traversed an AML. Both tracts were balloon dilated prior to placement of a 34F Amplatz sheath. Postoperatively, the patient had an uneventful recovery. A CT scan performed 1 day postoperatively revealed no retroperitoneal collection. This case demonstrates that renal access can be achieved with remarkable accuracy using 3D CT imaging. Furthermore, although this approach seems most prudent in the case of extensive renal AMLs, fluoroscopically guided renal access and dilation to 34F was not associated with bleeding in this patient.

Adult↗

PubMed1999

Escherichia coli promotes macrophage apoptosis.

BACKGROUND: Escherichia coli is the bacterium most commonly isolated from the urine of patients with urinary tract infection (UTI). Recurrent episodes of UTI lead to renal interstitial scarring. In interstitial fibrosis and scarring, infiltration of mononuclear cells has been reported to play a key role. MATERIALS AND METHODS: We evaluated the effect of two strains of E. coli--the pathogenic BH-5 and the plasmidless, nonfimbriated HB-101-on human monocyte and murine macrophage apoptosis. RESULTS: E. coli BH-5 enhanced apoptosis in a time- and dose-dependent manner. It also promoted necrosis in a time- and dose-dependent manner. Strain HB-101 promoted monocyte apoptosis in a dose-dependent manner. However, the magnitude of HB-101-induced monocyte apoptosis was lower than BH-5-induced macrophage apoptosis. CONCLUSION: The ability of E. coli to induce apoptosis may contribute to its virulence and play a role in renal interstitial scarring.

Animals↗

PubMed1999

13-year survival comparison of percutaneous and open nephroureterectomy approaches for management of transitional cell carcinoma of renal collecting system: equivalent outcomes.

BACKGROUND AND OBJECTIVE: Transitional cell carcinoma (TCC) of the renal collecting system traditionally has been managed by open nephroureterectomy with en bloc resection of a bladder cuff. However, for a select patient population with a solitary kidney or bilateral disease, the morbidity and mortality associated with chronic renal insufficiency and dialysis is deterring. In these situations, a more conservative approach such as antegrade percutaneous resection should be considered. The long-term disease-free outcome of percutaneous management in comparison with open nephroureterectomy has not been previously reported. We evaluated our experience with two surgical approaches to treat upper tract TCC: percutaneous resection and nephroureterectomy/nephrectomy to assess the clinical efficacy of these surgical modalities. PATIENTS AND METHODS: We retrospectively identified 162 patients who had clinically localized TCC of the upper urinary tract. Records were reviewed to identify those with 13-year follow-up (N = 110) in respect to tumor grade, stage, disease-free status, length of cancer-specific survival, and overall survival. Statistical analysis of the results of open nephroureterectomy/nephrectomy (N = 60) and percutaneous resection (N = 50) was performed using Kaplan-Meier survival curves and Student's t-test. RESULTS: All patients had disease in clinical stage Ta through T3. During a mean follow-up of 46.6 (range 6-150) months, grade 1 disease demonstrated little invasive potential. Of the disease-specific deaths, 60% (17/26) were of patients with grade 3 lesions, with a mean cancer survival period of 15.2 months after the initial procedure. Disease-specific survival rates after open and percutaneous approaches for grade 2 disease were 53.8 and 53.3 months, respectively (P > 0.05). CONCLUSIONS: Tumor grade appeared to be the most important prognostic indicator in patients with renal TCC regardless of the surgical approach. Grade 3 tumors were more aggressive, presenting in an advanced stage with invasion, and recurrences were usually associated with metastasis. In this population, nephroureterectomy is warranted if the patient is a surgical candidate. The percutaneous option for grade 1 or 2 disease may be extended beyond the population with solitary kidneys and a risk of chronic renal failure to be offered to healthy individuals with normal contralateral kidneys who are willing to abide by a strict and lengthy follow-up.

Adult↗

PubMed1999

Failed endopyelotomy: low expression of TGF beta regardless of the presence or absence of crossing vessels.

BACKGROUND AND OBJECTIVE: Endopyelotomy relies on Davis' intubated ureterotomy principle of healing by secondary intention and smooth-muscle regeneration. Approximately 15% of endopyelotomies fail, and the restrictured segment almost always shows evidence of reactive fibrosis with little smooth-muscle regeneration. Previous data suggests that an elevation of TGF beta in obstructed ureteropelvic junctures may be necessary for successful tissue repair following endopyelotomy. The role of crossing vessels in endopyelotomy failure is very controversial. To better understand the pathophysiology of endopyelotomy failure, the expression of transforming growth factor-beta (TBG beta) in patients with a failed endopyelotomy and crossing vessels was compared with that in patients without crossing vessels, as well as those having primary pyeloplasty or a normal ureteropelvic junction (UPJ). MATERIALS AND METHODS: The expression of TGF beta was detected immunohistochemically in slide-mounted thin sections (4 microns) cut from paraffin-blocked adult UPJ segments obtained during primary pyeloplasty (N = 11), secondary pyeloplasty after failed endopyelotomy with documented crossing vessels (N = 10), secondary pyeloplasty after failed endopyelotomy without crossing vessels (N = 11), and normal UPJs removed during nephrectomy for purposes unrelated to obstruction (N = 11). Expression was graded on a scale of 0 to 4. RESULTS: The combined failed endopyelotomy group had a significantly (P < 0.05) lower level of TGF beta (1.9 +/- 0.7) than did primary obstructed UPJs (2.6 +/- 0.7). The TGF beta level in the crossing vessels group (1.9 +/- 0.7) did not differ from that in the group without crossing vessels (1.8 +/- 0.7), nor did it differ from that in the group with normal UPJs (1.6 +/- 0.7). As expected, primary obstructed UPJs had a significantly higher level of TGF beta than normal ones (P < 0.02). CONCLUSIONS: Obstructed UPJs that had failed endopyelotomy had a similarly reduced level of TGF beta whether or not crossing vessels were present. These data suggest that an elevation of TGF beta in obstructed UPJs may be necessary for successful tissue repair after endopyelotomy and that the presence of crossing vessels is probably not relevant.

Adult↗

PubMed1999

Secret patterns: validation of a screening tool to detect bulimia.

We prospectively validated a two-item screening tool for bulimia. Subjects recruited from a women's health practice completed the previously developed two-item screening tool ("Do you ever eat in secret?" and "Are you satisfied with your eating patterns?") at their initial office visit. This was validated against a telephone interview with a licensed psychologist. The prevalence of current bulimia was 16% in 75 subjects, determined by psychologists' assessment (sensitivity 75%, specificity 49%) and 4% by DSM-III-R criteria. The positive and negative predictive values of one screening question positive were 22% and 91%, respectively, when compared with the psychologists' assessments as the gold standard. This screening tool allows physicians to identify patients who warrant further valuation for bulimia.

Adolescent↗

PubMed1999

Aurothioglucose inhibits murine thioredoxin reductase activity in vivo.

Gold (I)-containing compounds, including aurothioglucose (ATG), are potent in vitro inhibitors of several selenocysteine-containing enzymes. Gold compounds have also been shown to potentiate the virulence of several viruses in mice, including coxsackievirus, implicated as a possible infectious agent in Keshan disease. One possible mechanism by which gold compounds may be increasing the virulence of viral infections in mice is by acting as a selenium antagonist in vivo and inducing oxidative stress. To investigate the possible role of gold compounds in inducing oxidative stress in mice, we assessed the ability of ATG administered in vivo to inhibit the activity of the selenocysteine-containing enzymes thioredoxin reductase (TR) and glutathione peroxidase (GPX1). Doses as low as 0. 025 mg ATG/g body weight caused significant and prolonged inhibition of TR activity in all tissues examined. No such inhibition of GPX1 activity was seen, indicating differential in vivo sensitivity of the enzymes to inhibition by ATG. In liver and heart, some recovery of TR activity was observed after a 7-d period, but no recovery was observed in pancreas or kidney. Because TR is involved in several important cellular redox functions, its inhibition most likely will affect multiple cellular processes. These results indicate that in vivo administration of ATG results in significant and long-lasting inhibition of TR activity. Such inhibition of TR could lead to increased levels of oxidative stress in vivo, thereby increasing the virulence of several viruses including the coxsackievirus.

Animals↗

PubMed1999

Dyspepsia on withdrawal of ranitidine in previously asymptomatic volunteers.

OBJECTIVE: H2 receptor antagonist therapy has been shown to produce rebound acid hypersecretion. The clinical significance of this phenomenon is not known. We performed this study to determine whether withdrawal of H2 receptor antagonist therapy results in dyspepsia in previously asymptomatic volunteers. METHODS: Thirty-five Helicobacter pylori-positive asymptomatic volunteers were randomized in double-blind fashion to receive 2 months' treatment with either ranitidine 300 mg nocte or placebo. Dyspeptic symptoms were measured before starting treatment and over the course of 10 days after stopping treatment by means of a validated questionnaire. RESULTS: Thirty-one subjects completed the study; 17 were randomized to ranitidine. The pretreatment median aggregate dyspepsia score of the placebo group was 0 (0-4), as was that of the ranitidine group (0-8) (N.S.). During the 10 days after completion of ranitidine, the median aggregate dyspepsia score was 1.4 (0-30), compared with 0 (0-6.3) after placebo (p < 0.01). Of those given ranitidine, 59% experienced dyspepsia after treatment, compared with only 14% who took placebo. In the subgroup that developed dyspepsia after active therapy, the median duration of symptoms was 2 days, symptom severity being maximal on the second day after completion of the tablets. On the days when dyspepsia was experienced, the median daily dyspepsia score was 5 (range, 2-10), which was similar to that of a control group with active duodenal ulcer disease (5; range, 0-11). CONCLUSIONS: Withdrawal of a 2-month course of ranitidine 300 mg nocte results in the development of dyspeptic symptoms in a proportion of previously asymptomatic subjects. Patients receiving ranitidine should be warned about this rebound dyspepsia and advised not to immediately resume treatment, as rebound symptoms are likely to improve within a few days.

Adult↗

PubMed1999

Serious sex offending against women by men with schizophrenia. Relationship of illness and psychotic symptoms to offending.

BACKGROUND: Little is known about men who commit sex offences in the context of psychosis. AIMS: To examine the relationship of illness and psychotic symptoms to sex offending in men with schizophrenia. METHOD: A search of Home Office records was completed for all 84 male restricted hospital order in-patients with schizophrenia, resident in any hospital in England and Wales during May 1997, with an index conviction for a contact sex offence against a woman. RESULTS: At the time of their index offences 80 men were psychotic and half of them had delusions or hallucinations related to the offences. Specific delusional or hallucinatory drive was pertinent in only 18 men but the majority of men committed their first sex offence after onset of schizophrenia. Exclusive sex offending was uncommon. CONCLUSIONS: When a man with schizophrenia commits a serious sex offence the illness is, more commonly than not, relevant to that offence even though a direct symptom relationship may be relatively unusual.

Adolescent↗

PubMed1999

A disulfide-bound HIV-1 V3 loop sequence on the surface of human rhinovirus 14 induces neutralizing responses against HIV-1.

An immunogenic sequence from the V3 loop of the MN isolate of human immunodeficiency virus type 1 (HIV-1), His-Ile-Gly-Pro-Gly-Arg-Ala-Phe, was transplanted onto a surface loop of the VP2 capsid protein of human rhinovirus 14. To optimize for virus viability and immunogenicity of the transplanted sequence, the HIV sequence was flanked by (1) a cysteine residue that could form a disulfide bond and (2) randomized amino acids (in either of two arrangements) to generate numerous presentations of the Cys-Cys loop. The location for engineering in VP2 was chosen by searching the geometries of disulfide-bound loops in known protein structures. A model for the structure of the transplanted V3 loop sequence was developed using molecular dynamics and energy minimization calculations. Proteolytic digestion with and without reducing agent demonstrated the presence of the disulfide bond in the chimeric virus examined. Monoclonal and polyclonal antibodies directed against the V3 region of the HIV-1MN strain potently neutralized two chimeric viruses. Guinea pig antisera against two chimeric viruses were able to neutralize HIV-1MN and HIV-1ALA-1 in cell culture. The ability of chimeric viruses to elicit antibodies capable of neutralizing the source of the transplanted sequence could be favorable for vaccine development.

Animals↗

PubMed1999

Ethanol exposure differentially alters central monoamine neurotransmission in alcohol-preferring versus -nonpreferring rats.

Individual differences in ethanol preference may be linked to differences in the functional activity of forebrain monoamine systems or their sensitivity to modification by ethanol. To test this hypothesis, basal extracellular concentrations of dopamine (DA) and serotonin (5-HT) in the nucleus accumbens as well as the effects of repeated ethanol pretreatment on the basal release of these transmitters were examined in alcohol-preferring (P), alcohol-nonpreferring (NP), and genetically heterogeneous Wistar rats. All animals received i.p. injections of ethanol (1.0 g/kg) or saline for 5 consecutive days. Fifteen hours after the final pretreatment, basal extracellular concentrations and "in vivo extraction fraction" values for DA and 5-HT were determined by no-net-flux in vivo microdialysis. In ethanol-naive rats, significant line differences were observed with high basal 5-HT release in P rats, low 5-HT release in NP rats, and intermediate 5-HT levels in Wistar rats. No differences among groups were noted in basal DA release. Ethanol pretreatment decreased basal extracellular 5-HT levels in P rats whereas increasing 5-HT efflux was seen in the Wistar and NP lines. In addition, ethanol pretreatment increased extracellular DA concentrations in Wistar and P rats, but not in NP rats. The results confirm a relationship between the functional status of forebrain DA and 5-HT systems and ethanol preference or aversion. Moreover, the data suggest that ethanol exposure can alter basal DA and 5-HT in the nucleus accumbens and that vulnerability to ethanol-induced changes in monoamine neurotransmission may be a factor in genetically determined ethanol preference.

Alcohol Drinking↗

PubMed1999

Complete renal embolization as an alternative to nephrectomy.

PURPOSE: Simple nephrectomy is technically demanding in patients with recurrent inflammation or bleeding. It is also unwise to subject patients in poor health to the rigors of an extensive operative procedure. We report our experience with complete renal embolization as a safe and reliable alternative to surgical nephrectomy. MATERIALS AND METHODS: Eight patients underwent complete renal embolization as an alternative to nephrectomy. Patients were given antibiotics intravenously before and after embolization. Six patients with indwelling nephrostomy tubes received post-embolization instillation of 80 mg. gentamicin before tube removal. Narcotic analgesics were also given as needed for pain control. Post-embolization hospital course was noted. RESULTS: The indications for embolization included hydronephrotic, poorly functioning kidneys with pain in 5 cases, and recurrent bleeding from angiomyolipoma, bleeding after percutaneous resection of renal pelvic transitional cell carcinoma with metastases and spontaneous renal bleeding after hemodialysis in 1 each. Embolization was successful in 4 men and 4 women with a mean age of 58.8 years. In 6 patients severe flank pain required narcotic analgesics. One patient complained of nausea, 6 had fever and 6 had leukocytosis. In 1 case thrombosis of a limb of an aortobifemoral bypass graft required thrombectomy. Median hospital stay was 2.5 days. At a mean followup of 30.6 months presenting symptoms had resolved in all cases without hypertension, renal failure or abscess. CONCLUSIONS: Complete renal embolization is a viable alternative to nephrectomy in patients with poorly functioning kidneys who present with pain or bleeding and in those who are poor operative candidates. This procedure is safe, reliable and minimally invasive with few long-term sequelae, and it is well tolerated.

Adolescent↗

PubMed1999

Endopyelotomy review.

UNLABELLED: Open pyeloplasty remained the standard treatment until the mid-1980s. The advantages of the open pyeloplasty include mucosa-to-mucosa anastomosis and excision of redundant renal pelvis and diseased ureter. Over the past decade, antegrade endopyelotomy has evolved as the treatment of choice for obstructions of the UPJ. Further experience has shown that primary UPJ obstruction responded equally well, with long-term success rates for both groups of patients approaching 85%. Endopyelotomy results in significantly less morbidity, and should this technique fail, subsequent open pyeloplasty is no more difficult than had it been performed initially. A 20% incidence of stones associated with UPJ obstruction has been reported. Antegrade endopyelotomy can treat these patients simultaneously. Our series of more than 400 endopyelotomies showed that success was based on the degree of preoperative hydronephrosis and renal function. The presence of massive hydronephrosis had a pejorative influence on endopyelotomy, lowering the success rate from 96% to 50%. Similarly poor renal function (less than 25% of total function) reduced the success rate from 92% to 54%. Although not as extensively reported in the urologic literature, indeed fewer patients with fewer follow-ups have undergone a ureteroscopic endopyelotomy compared with an antegrade endopyelotomy, success rates have ranged between 79% and 94%. Nephrectomy was required in 2.5% for bleeding and 5% for poor renal function. In patients with primary UPJ obstruction, Acucise has a success rate that is 15% lower than antegrade endopyelotomy. Acucise endopyelotomy is a blind procedure, with 1.5% of bleeding reported requiring transfusion and 3% has undergone postoperative embolization. Laparoscopic pyeloplasty is also a relatively new technique which has only been reported with some extensive experience in two institutions, although the success rate has been extremely high, despite a short follow-up. Overall, the incidence of crossing vessels at the UPJ is approximately 50%. The greatest problem lies in determining whether a crossing vessel is etiologically or clinically significant. Thus, the presence of a crossing vessel was potentially causally related to endopyelotomy failure in 4% of the patients. Our overall success rate of 78% for endopyelotomy is comparable and sometimes higher than the reported success rate for open pyeloplasty for horseshoe kidneys, which ranged from 55 to 80%. However, endopyelotomy has become an established treatment modality in the adult, with a decreased morbidity in comparison with open pyeloplasty. The benefits of endourologic management of pediatric UPJ obstruction are less well established. CONCLUSIONS: Endopyelotomy is a safe and effective treatment for primary and secondary UPJ obstruction for most patients. The biggest experience with better results has been reported with antegrade endopyelotomy, which permits the treatment of associated stones. Laparoscopic pyeloplasty, which is technically demanding, may be considered the best treatment in patients with severe hydronephrosis and poor renal function, which resulted in a success rate of only 38% and 57%, respectively, with endopyelotomy. If we are going to minimize morbidity for our patients, open pyeloplasty is only the first choice for neonates and younger children, and should be considered in patients after failed endopyelotomy.

Adult↗

PubMed1999

An unusual Ca(2+) entry pathway activated by protein kinase C in dog splenic artery.

The characteristics of the Ca(2+) entry pathways that are activated by protein kinase C (PKC) in canine splenic artery were investigated. Phorbol 12, 13-dibutyrate (PDB) contracted tissues and increased Ca(2+) influx. PDB-induced contraction was reduced by preincubation of tissues in Ca(2+)-free Krebs' solution (1 mM EGTA) but was unaffected when Ca(2+)-free solution was applied after contraction was initiated with PDB. In contrast, (45)Ca influx and contraction induced by PDB were resistant to nifedipine, Cd(2+), Gd(3+), La(3+), or Ni(2+) whether added before or during exposure to PDB. Indeed, Cd(2+) reduced (45)Ca(2+) efflux and potentiated Ca(2+) influx, but not PDB-induced contraction. Norepinephrine (NE)-induced contractions were inhibited by preincubation in Ca(2+)-free Krebs' solution (1 mM EGTA). Nifedipine (10 microM) led to a small reduction in the NE-induced contraction but was without effect on (45)Ca(2+) influx. Pretreatment for 16 min with Cd(2+), Gd(3+), or La(3+) (each 1 mM) reduced or abolished NE-induced contraction and Ca(2+) influx. Application of these cations after exposure to NE did not affect (45)Ca(2+) influx but reduced tension. The Q(10) for the increase in (45)Ca(2+) influx was approximately 2 for high K(+) and NE, but 4 for PDB. The results suggest that stimulation of PKC in dog splenic artery activates a Ca(2+) entry pathway that is resistant to di- and trivalent cations. The inhibition of Ca(2+) influx by preincubating with cations during short-term exposure to NE may represent an action on Ca(2+) turnover that precedes activation of PKC.

Animals↗

PubMed1999

Self-organizing map (SOM) of space acceleration measurement system (SAMS) data.

In this paper, space acceleration measurement system (SAMS) data have been classified using self-organizing map (SOM) networks without any supervision; i.e., no a priori knowledge is assumed regarding input patterns belonging to a certain class. Input patterns are created on the basis of power spectral densities of SAMS data. Results for SAMS data from STS-50 and STS-57 missions are presented. Following issues are discussed in details: impact of number of neurons, global ordering of SOM weight vectors, effectiveness of a SOM in data classification, and effects of shifting time windows in the generation of input patterns. The concept of 'cascade of SOM networks' is also developed and tested. It has been found that a SOM network can successfully classify SAMS data obtained during STS-50 and STS-57 missions.

Acceleration↗

PubMed1999

Unsupervised classification of Space Acceleration Measurement System (SAMS) data using ART2-A.

The Space Acceleration Measurement System (SAMS) has been developed by NASA to monitor the microgravity acceleration environment aboard the space shuttle. The amount of data collected by a SAMS unit during a shuttle mission is in the several gigabytes range. Adaptive Resonance Theory 2-A (ART2-A), an unsupervised neural network, has been used to cluster these data and to develop cause and effect relationships among disturbances and the acceleration environment. Using input patterns formed on the basis of power spectral densities (psd), data collected from two missions, STS-050 and STS-057, have been clustered.

Acceleration↗

PubMed1998

Abnormal function of potassium channels in platelets of patients with Alzheimer's disease.

BACKGROUND: Reports of abnormalities of potassium-channel function in various cultured cells of Alzheimer's disease patients led us to attempt to characterise the pharmacological characteristics of the abnormal channel. METHODS: We studied platelets from 14 patients with Alzheimer-type dementia and 14 non-demented controls matched for age and sex. The effects of specific inhibitors of K+ channels on the efflux of rubidium-86 ions, a radioactive analogue of K+, from the platelets were measured. FINDINGS: Normal platelets contain three types of K+ channel, sensitive to the inhibitory actions of apamin (small-conductance calcium-dependent potassium channels), charybdotoxin (of less specificity, but probably intermediate-conductance calcium-dependent K+ channels), and alpha-dendrotoxin (voltage-sensitive K+ channels). However, 8Rb+ efflux from the platelets of patients with Alzheimer-type dementia was not inhibited by either apamin or charybdotoxin. By contrast, inhibition by alpha-dendrotoxin did occur. INTERPRETATION: Our results suggest that calcium-dependent K+ channels in platelets are selectively impaired in Alzheimer's disease. A similar abnormality in neurons could contribute to the pathophysiology of the disorder.

Aged↗