Amyloid beta peptide-induced cerebral endothelial cell death involves mitochondrial dysfunction and caspase activation

Amyloid beta peptide (A beta), a 39 to 43 amino acid fragment of the beta-amyloid precursor protein (betaAPP), forms insoluble fibrillar accumulation in neurofibrillary tangles and vascular plaques. A beta has been implicated in neuronal and vascular degeneration in brain regions susceptible to plaque formation because of its cytotoxic effect on neurons and endothelial cells (ECs). The authors used a murine cerebral endothelial cell (CEC) line and primary cultures of bovine CECs to explore the cytotoxic mechanism of A beta. A beta 1-40 and A beta 25-35 peptides caused cell death in a dose-dependent and time-dependent manner. Exposure to either A beta 25-35 or A beta 1-40 at 10 micromol/L for 48 hours caused at least 40% cell death. Cerebral endothelial cell death was characterized by nuclear condensation, mitochondrial dysfunction, and nuclear and mitochondrial DNA damage. A beta 25-35 activated both caspase-8 and caspase-3 in murine CECs. zVAD-fmk, a broad-spectrum caspase inhibitor, prevented A beta 25-35-induced increase in caspase-3 activity and CEC death. N-acetyl-cysteine, an antioxidant, also prevented A beta-induced cell death. Together, these findings indicate that A beta-mediated CEC death is an apoptotic process that is characterized by increased oxidative stress, caspase activation, mitochondrial dysfunction, and nuclear and mitochondrial DNA damage.

High-fat hypocaloric diet modifies carbohydrate utilization of obese rats during weight loss

The effects of fat content in the hypocaloric diet on whole body glucose oxidation and adipocyte glucose transport were investigated in two animal-feeding experiments. Diet-induced obese rats were food restricted to 75% of their previous energy intakes with either a high (45% by calorie) or a low (12% by calorie) corn oil diet for 9 wk (experiment 1) or 10 days (experiment 2). The losses of body weight (P < 0.05) and adipose depot weight (P < 0.05) were less in the 45% compared with the 12% fat group. During the dynamic phase of weight loss (day 10 of food restriction), plasma glucose and insulin concentrations were higher (P < 0.05) in the 45% than those in the 12% fat group. Whole body carbohydrate oxidation rate in response to an oral load of glucose was increased (P < 0.001) by food restriction in both dietary groups; however, carbohydrate oxidation rates were lower (P < 0.01) in the 45% than in the 12% fat-fed rats during the weight loss period. Adipocyte glucose transport was greater (P < 0.02) in the 45% than in the 12% fat group in an intra-abdominal adipose depot but not in subcutaneous fat. These data suggest that dietary fat content modifies whole body glucose oxidation and intra-abdominal adipocyte glucose uptake during weight loss.

Building a generic architecture for medical information exchange among healthcare providers

Due to the inability to exchange clinical information among hospitals, continuity of care cannot be maintained and a tremendous amount of medical resource has been wasted. This paper describes an architecture that would facilitate exchange of clinical information among heterogeneous hospital information systems. It is dubbed 'Medical Information Exchange Center' or MIEC as part of a six-year Health Information Network Project hosted by the Department of Health. MIEC was designed so that it is innovative yet technically feasible today. It is convenient for authorized users yet secure enough so people can trust and has minimal impact to participated hospitals. Authorized users will be able to access information through two web-based interfaces directed to physician and non-physician users respectively. Hospitals are connected through a virtual private network to exchange patient information and users need to obtain a private key from the certificate authority in order to securely connect to MIEC. A pilot project was conducted to demonstrate the feasibility of this architecture and the problems encountered were discussed.

Diagnosis and treatment of lipomas of the internal auditory canal

A Chinese woman came to the otolaryngology department with a complaint of a longstanding progressive left hearing loss and intractable tinnitus. A finding of asymmetry on sensorineural hearing loss and auditory brainstem response testing provided evidence of a retrocochlear lesion on the left side. Computed tomography and magnetic resonance imaging detected a tumor in the left internal auditory canal (IAC). In addition to these radiologic features, our suspicion of the possibility of an IAC lipoma was raised by the observation of multiple lipomas over the patient's trunk and limbs. The patient underwent a complete tumor resection via the translabyrinthine approach, Pathology confirmed the diagnosis of an IAC lipoma. Although we were not able to preserve the hearing in her left ear, the patient was satisfied that we had relieved her constant tinnitus. In this article, we review the particulars of this case and discuss the clinical, radiologic, and pathologic features of IAC lipomas.

Cellular localization of tumor necrosis factor-alpha following acute spinal cord injury in adult rats

Posttraumatic inflammatory reaction may contribute to secondary injury after traumatic spinal cord injury (SCI). Expression of tumor necrosis factor-alpha (TNF-alpha), a key inflammatory mediator, has been demonstrated in the injured cord. However, the specific cell types that are responsible for TNF-alpha expression after SCI remain to be identified. In the present study, cellular sources of TNF-alpha were examined in rats that received a spinal cord impact injury at the 9th thoracic (T9) level. Here we demonstrate that, within hours after SCI, increased TNF-alpha immunoreactivity was localized in neurons, glial cells (including astrocytes, oligodendrocytes, and microglia), and endothelial cells in areas of the spinal cord adjacent to the lesion site. Myelin breakdown was noted in oligodendrocytes that are immunopositive for TNF-alpha. In sham-operated controls, a low level of TNF-alpha immunoreactivity was detected. In antigen-absorption experiments, no TNF-alpha immunoreactivity was detected, indicating the specificity of TNF-alpha immunocytochemistry in the present study. Results suggest that various cell types, including neurons, glial cells, and vascular endothelial cells, contribute to TNF-alpha production in the injured cord.

iNOS and nitrotyrosine expression after spinal cord injury

Secondary tissue damage after spinal cord injury (SCI) may be due to inflammatory mediators. After SCI, the nuclear factor-kappaB (NF-kappaB) transcription factor can activate many pro-inflammatory genes, one of which is inducible nitric oxide synthase (iNOS). iNOS catalyzes the synthesis of nitric oxide (NO), a key inflammatory mediator, which in turn reacts with superoxide to generate peroxynitrite. Peroxynitrite is a strong oxidant that can damage cellular enzymes, membranes, and subcellular organelles through the nitration of tyrosine residues on proteins. The presence of nitrotyrosine (NT) is an indirect chemical indicator of toxic NO and peroxynitrite-induced cellular damage. Using a New York University (NYU) impactor to induce SCI in adult rats, we examined the temporal and cellular expression of iNOS and NT. We observed a progressive increase in iNOS expression in the injured cord starting at day 1 with maximal expression occurring at day 7, as determined by Western blot analysis. iNOS expression corresponded temporally to an increase in iNOS enzyme activity after SCI. In parallel with the progressive increase in iNOS activity, NT expression also increased with time after SCI. The iNOS and NT immunoreactivity was localized in neurons, astrocytes, endothelial cells and ependymal cells at the epicenter and adjacent to the region of spinal cord impact and injury. Results from the present study suggest that increased iNOS and peroxynitrite anion, as reflected by the progressive accumulation of NT in the injured impacted spinal cord, may contribute to the secondary injury process after SCI.

Tie-1 tyrosine kinase is an independent prognostic indicator for invasive breast cancer

Receptor tyrosine kinases are known to be involved in the growth, progression and metastasis of solid tumors. We investigated the relationship between tie-1 expression and progression of invasive ductal breast carcinoma with immunohistochemical analysis. Tie-1 protein was detected in the microvessel endothelial cells and cytoplasm of tumor cells. The tumor size and stage were significantly associated with the expression of tie-1, which portends a worse 5-year disease-free status (39.3% v 59.2%, p = 0.07) and overall survival rate (67.3% v 93%, p = 0.02) than those without tie-1 expression. Multivariate analysis demonstrated that larger tumor size, presence of lymph node metastasis and tie-1 expression were independent prognostic parameters, both in 5-year disease-free survival and overall survival. Patients with lymph node metastases and tie-1 expression had the worst 5-year disease-free survival (0%) and overall survival (42.4%) compared to those without tie-1 expression (50.2%, 85%). In lymph node negative patients, those without tie-1 expression had better 5-year disease-free survival and overall survival (72.9%, 100%) compared to those with tie-1 expression (65.5%, 87.7%). We conclude that tie-1 expression is an independent prognostic factor for invasive ductal breast carcinoma, adversely affecting survival of breast cancer patients with positive nodes to a significant extent.

Magnetic resonance imaging findings in patients with delusional disorder due to diffuse cerebrovascular disease: a report of seven cases

Delusions associated with cerebrovascular diseases have been sporadically reported. Although both psychiatrists and neurologists attempted to link delusions with anatomical locations of the brain lesion, comorbid psychiatric and neurological disorders make the interpretation of delusions difficult. The purpose of the present paper is to report the clinical features and magnetic resonance imaging (MRI) characteristics in patients with delusional disorder due to diffuse cerebrovascular diseases, and to redefine the concept of 'vascular delusion'. The clinical features and MRI findings were reviewed retrospectively in a series of seven patients with 'delusional disorder due to cerebrovascular disease' as defined in Diagnostic and Statistical Manual of Mental Disorders (DSMIV). The average age of onset is 64. No patient had a prior personal or family history of major psychiatric illness. The illness is presented as acute, subacute or stepwise course. Hypertension was present in all patients. Two had diabetes mellitus, and one had atrial fibrillation. Three had clinical evidence of previous cerebrovascular attacks, only one showed minor neurological deficits. Three had diffuse cortical slow wave in electroencephalogram. No patient had significant cognitive impairment but had multiple cortical and subcortical cerebrovascular lesions in MRI, with white-matter lesions (WML) in bilateral frontal areas. Delusional disorder due to diffuse cerebrovascular change is characterized by late-onset, stepwise course, and comorbid medical and neurological diseases. The results of vascular changes in the present study did not establish a cause-effect relationship and should be considered as multifactorial in pathogenesis. The findings suggested the hypothesis of neural circuit theory. Further studies in larger numbers of patients and newer neuroimaging techniques are needed to expand the knowledge learned from these findings.

Surgical treatment for concomitant fractures of the femoral neck and diaphysis: a treatment protocol

Concomitant ipsilateral femoral shaft and neck fractures are difficult to treat. The standard protocol in our hospital is plates for diaphyseal fractures and lag screws or dynamic hip screws (DHS) fixations for the femoral neck fractures. We treated 21 patients with these complex fractures between 1988 and 1998 with this protocol. All patients were injured from high-energy trauma. There were 15 males and 6 females with an average age of 44 years. The average follow-up period is 50 months. All except one patient united well. During the follow-up period, neither non-union of the femoral neck fracture nor osteonecrosis of the femoral head was noted. There was also no malunion. There were twenty good results and one poor functional result. We conclude that plate on the shaft and sliding hip screws or separate screws in the hip are a reliable method for concomitant ipsilateral femoral neck and shaft fractures.

Endoscopic sinus surgery for the treatment of chronic sinusitis in geriatric patients

Although endoscopic sinus surgery is a well-documented procedure for the treatment of chronic sinusitis in children and adults, no study has been conducted to specifically investigate its application in a geriatric population. We undertook to fill this void by analyzing the records of 1,112 patients who had undergone endoscopic sinus surgery for chronic sinusitis in our department between April 1988 and March 1998. We categorized these patients by age. There were 171 patients (15.4%) in the geriatric group (age: > or = 65 yr), 837 patients (75.3%) in the adult group (age: 17 to 64), and 104 patients (9.4%) in the pediatric group (age: < or = 16 yr). We found that the geriatric group experienced a disproportionately larger share of operative complications, but most of them were minor. Outcomes were similar in all three groups. We conclude that endoscopic sinus surgery is a safe and effective treatment for older patients with chronic sinusitis.

Inducible nitric oxide synthase neutralizes carbamoylating potential of 1,3-bis(2-chloroethyl)-1-nitrosourea in c6 glioma cells

Expression of iNOS in glioma and other tumors has been extensively documented but the effects of NO derived from iNOS on tumor-killing mechanisms of chemotherapy drugs remain to be fully defined. We note that increased NO synthesis by cytokine exposure or iNOS overexpression neutralized the cytotoxicity of 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU), but not cisplatin, in rat C6 glioma cells. Suppression of BCNU cytotoxicity associated with iNOS overexpression could be abolished by pharmacological inhibition of NOS or coexpression of an antisense RNA against iNOS. Both BCNU and CCNU are chloroethylnitrosoureas that kill tumor cells via carbamoylating and alkylating actions. Further studies using compounds that each carry these different activities indicate that iNOS neutralized carbamoylating, but not alkylating, action of chloroethylnitrosoureas. Temozolomide, a novel chemotherapy drug recently available for treating brain tumors, carries only alkylating, but not carbamoylating, action. Overexpression of iNOS in C6 cells failed to neutralize temozolomide cytotoxicity. Results from the present study demonstrate the ability of iNOS-derived NO to confer chemoresistance against the carbamoylating potential of chloroethylnitrosoureas in vitro. Further investigation is needed to test whether iNOS expression, frequently noted in malignant brain tumors, also enhances chemoresistance against chloroethylnitrosoureas in vivo.

Delayed glial cell death following wallerian degeneration in white matter tracts after spinal cord dorsal column cordotomy in adult rats

The devastating consequences of spinal cord injury (SCI) result primarily from damage to long tracts in the spinal white matter. To elucidate the secondary injury processes occurring after SCI, we investigated the relationship between apoptosis and Wallerian degeneration in spinal white matter tracts. In the rat spinal cord, the corticospinal tract (CST) and the dorsal ascending tract (DAT) are separated from each other in the dorsal column and relay information in opposite directions. A dorsal column cordotomy at the eighth thoracic (T8) level simultaneously induces Wallerian degeneration in the CST caudal to and in the DAT rostral to the injury. Using the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method, we demonstrate that apoptosis occurred in areas of Wallerian degeneration in both tracts throughout the length of the cord segments studied (from T3 to T12). This delayed cell death, more apparent in the DAT, began at 7 days after injury and peaked at 14 days for the DAT and 28 days for the CST. Although a few TUNEL+ cells, slightly above the noninjury control level, were found in intact areas of both tracts, statistically significant differences in the number of TUNEL+ cells were found between the intact and the lesioned tract segments (CST, F < 0.01; DAT, F < 0.001). Within a particular spinal segment, a mean number of 64 and 939 TUNEL+ cells in the degenerating CST and DAT, respectively, were estimated stereologically at 14 days postinjury. TUNEL+ cells in degenerating tracts outnumber their intact counterparts by 3.8:1 in the CST and 4.1:1 in the DAT, although a statistically significant difference between the two was only found in the DAT at this time point (P < 0.05). Finally, we demonstrated that oligodendrocytes, the myelin-forming cells in the central nervous system, constitute at least a portion of the cells undergoing apoptosis within areas of Wallerian degeneration.

Spinal fractures and pseudoarthrosis complicating ankylosing spondylitis: MRI manifestation and clinical significance

PURPOSE

To analyze magnetic resonance (MR) patterns of fractures and pseudoarthrosis of the ankylosing spondylitic spine, and related changes in the dura and adjacent soft tissue.

MATERIALS AND METHODS

Sixteen patients with radiographically evident fractures or pseudoarthrosis of the spine were included. Each underwent MR studies. Ten patients among them underwent surgical operations.

RESULTS

Both transdiscal (n = 12) and transvertebral (n = 4) fractures were identified. The levels were located from T9 to L3. Five of 16 patients had pseudoarthrosis. The fractures or pseudoarthrosis had two patterns: low signal on T1-and high signal on T2-weighted images, and low signal on both T1-and T2-weighted images. Disruption of anterior longitudinal ligament (ALL) was identified in 14 patients. Seven patients had vertebral translation, all had disruption of the ALL. Dural adhesions were noted in five patients and manifested as linear epidural enhancements with triangular blunt edges.

CONCLUSION

MR patterns of ankylosing spondylitis are important in evaluating complications of fractures or pseudoarthrosis, as well as changes in dura, soft tissue, and ligaments.

Relationship between hematocrit and renal function in men and women

BACKGROUND

Anemia is a known complication of renal insufficiency, but the relationship between level of renal function and magnitude of reduction in hematocrit is not well defined. Men have higher hematocrit and absolute glomerular filtration rate (GFR) than women; however, it is unknown whether the level of clearance associated with decreased hematocrit is the same in men and women.

METHODS

We conducted a cross-sectional study of 12,055 adult ambulatory patients. General linear models were used to analyze the relationship between hematocrit and Cockcroft-Gault equation estimated creatinine clearance (C(Cr); mL/min) and Modification of Diet in Renal Disease (MDRD) formula estimated the GFR indexed to body surface area (mL/min/1.73 m(2)).

RESULTS

The hematocrit decreased progressively below estimated C(Cr) 60 mL/min in men and 40 mL/min in women. Compared with subjects with C(Cr)> 80 mL/min, men with C(Cr) 60 to 50 mL/min, 50 to 40 mL/min, 40 to 30 mL/min, 30 to 20 mL/min, and < or =20 mL/min had mean hematocrits that were lower by 1.0, 2.4, 3.7, 3.5, and 10.0%, respectively; the corresponding reductions in women with C(Cr) 40 to 30 mL/min, 30 to 20 mL/min, and < or =20 mL/min were 1.7, 2.9, and 6.3% (all P < 0.05). This between-sex difference diminished when renal function measurement was indexed to body size. Compared with subjects with GFR> 80 mL/min/1.73 m(2), men with GFR 50 to 40 mL/min/1.73 m(2), 40 to 30 mL/min/1.73 m(2), 30 to 20 mL/min/1.73 m(2), and < or =20 mL/min/1.73 m(2) had mean hematocrits that were lower by 2.0, 4.4, 5.3, and 9.4%; the corresponding reductions in women with GFR 50 to 40 mL/min/1.73 m(2), 40 to 30 mL/min/1.73 m(2), 30 to 20 mL/min/1.73 m(2) and < or =20 mL/min/1.73 m(2) were 0.6, 1.6, 3.8, and 5.3% (all P < 0.05).

CONCLUSIONS

A decrease in hematocrit is apparent even among patients with mild to moderate renal insufficiency. At any given level of renal function below estimated C(Cr) 60 mL/min, men have a larger decrease in hematocrit than women.

Does treatment of non-malignant hypertension reduce the incidence of renal dysfunction? A meta-analysis of 10 randomised, controlled trials

OBJECTIVE

It remains controversial whether non-malignant 'benign' hypertension causes renal dysfunction. The effect of lowering blood pressure on the incidence of renal dysfunction among patients with non-malignant hypertension is not clear. This meta-analysis was conducted to determine whether antihypertensive drug therapy reduces the incidence of renal dysfunction in patients with non-malignant hypertension.

METHODS

Randomised, controlled trials of antihypertensive drug therapy of more than 1 year duration that reported renal dysfunction as an outcome were identified through MEDLINE search and literature review. A random effects model was used to obtain summary estimates.

RESULTS

Ten trials were identified, involving 26, 521 individuals and 114 000 person-years. All excluded subjects with advanced baseline renal disease. Definition of renal dysfunction outcome varied among trials but within each trial was applied similarly to both treatment and control groups. Drug treatment consisted mostly of diuretics and adrenergic blockers. Overall, treated patients had lower blood pressure and fewer cardiovascular events. There were a total of 317 cases of renal dysfunction. Patients randomised to antihypertensive therapy (or more intensive therapy) did not have a significant reduction in their risk of developing renal dysfunction (relative risk = 0.97; 95% confidence interval (CI) 0.78-1.21; P = 0.77).

CONCLUSIONS

Among patients with non-malignant hypertension enrolled in randomised trials, treated patients did not have a lower risk of renal dysfunction. The 95% CI suggests that a 25% or more true protective effect of antihypertensive drugs is unlikely.

Glucocorticoid receptor-mediated suppression of activator protein-1 activation and matrix metalloproteinase expression after spinal cord injury

Post-traumatic inflammatory reaction may contribute to progressive tissue damage after spinal cord injury (SCI). Two key transcription factors, nuclear factor kappaB (NF-kappaB) and activator protein-1 (AP-1), are activated in inflammation. An increase in NF-kappaB binding activity has been shown in the injured spinal cord. We report activation of AP-1 after SCI. Electrophoretic mobility shift assay showed that AP-1 binding activity increased after SCI, starting at 1 hr, peaking at 8 hr, and declining to basal levels by 7 d. Methylprednisolone (MP) is the only therapeutic agent approved by the Food and Drug Administration for treating patients with acute traumatic SCI. MP reduced post-traumatic AP-1 activation. RU486, a glucocorticoid receptor (GR) antagonist, reversed MP inhibition of AP-1 activation. Immunostaining showed an increase in the expression of the Fos-B and c-Jun components of AP-1 in the injured cord. A c-fos antisense oligodeoxynucleotide (ODN) inhibited AP-1, but not NF-kappaB, activation after SCI. AP-1 and NF-kappaB can transactivate genes encoding matrix metalloproteinase-1 (MMP-1) and MMP-9. Western blotting and immunostaining show increased expression of MMP-1 and MMP-9 in the injured cord. MP inhibited MMP-1 and MMP-9 expression after SCI. RU486 reversed this MP effect. The c-fos antisense ODN, however, failed to suppress MMP-1 or MMP-9 expression. These findings demonstrate that MP may suppress post-traumatic inflammatory reaction by inhibiting both the AP-1 and NF-kappaB transcription cascades via a GR mechanism. Expression of inflammatory genes such as MMP-1 and MMP-9 that are transactivated jointly by AP-1 and NF-kappaB may not be suppressed by inhibiting only AP-1 activity.

Amyloid-beta peptides are cytotoxic to oligodendrocytes

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive dementia. Amyloid-beta peptide (Abeta), a 39-43 amino acid peptide derived from beta-amyloid precursor protein, forms insoluble fibrillar aggregates that have been linked to neuronal and vascular degeneration in AD and cerebral amyloid angiopathy. Here we demonstrate that Abeta 1-40 and a truncated fragment, Abeta 25-35, induced death of oligodendrocytes (OLGs) in vitro in a dose-dependent manner with similar potencies. Abeta-induced OLG death was accompanied by nuclear DNA fragmentation, mitochondrial dysfunction, and cytoskeletal disintegration. Abeta activation of redox-sensitive transcription factors NF-kappaB and AP-1 and antioxidant prevention of Abeta-mediated OLG death suggest that oxidative injury contributes to Abeta cytotoxicity in OLGs. Recent demonstration of Abeta deposition and white matter abnormalities in AD implies a potential pathophysiological role for Abeta-mediated cytotoxicity of OLGs in this neurodegenerative disease.

iNOS expression inhibits hypoxia-inducible factor-1 activity

Hypoxia-inducible factor-1 (HIF-1) activates genes important in vascular function such as vascular endothelial growth factor (VEGF), erythropoietin (EPO), and inducible nitric oxide synthase (iNOS). iNOS catalyzes the synthesis of nitric oxide (NO), a free radical gas that mediates a number of cellular processes, including regulation of gene expression, vasodilatation, and neurotransmission. Here we demonstrate that iNOS expression inhibits HIF-1 activity under hypoxia in C6 glioma cells transfected with an iNOS gene and a VEGF promoter-driven luciferase gene. HIF-1 induction of VEGF-luciferase activity in C6 cell is also inhibited by sodium nitroprusside (SNP). Furthermore, pretreatment of C6 cells with N-acetyl-l-cysteine (NAC), an antioxidant, nullified the inhibitory effect of iNOS on HIF-1 binding. These results demonstrate that NO generated by iNOS expression inhibits HIF-1 activity in hypoxic C6 cells and suggest a negative feedback loop in the HIF-1 --> iNOS cascade.

Functional endoscopic sinus surgery in children and adults

Functional endoscopic sinus surgery (FESS) has become a popular procedure for the treatment of adults with chronic sinusitis. Recently, it has also been applied in the pediatric population. It has been used to treat chronic sinusitis in our department since April 1988. As of March 1998, 1,112 patients were available for analysis by file and questionnaire review. Of the 1,112 patients, 104 patients (9.4%) who were 16 years of age or younger at the time they first underwent FESS in our department were included in the pediatric endoscopic sinus surgery (PESS) group. The other 1,008 patients (90.6%) were included in the ordinary FESS group. In total, 121 PESS and 1,106 (adult) FESS operations were performed on these patients. Operative complications occurred in 5 PESS operations (4.1%) and 116 FESS operations (10.5%). The postoperative improvement rate was 84% in PESS and 77.1% in FESS. We conclude that PESS can be applied to treat chronic sinusitis effectively in the pediatric population and with less morbidity than FESS.

The therapeutic time window—Theoretical and practical considerations

The length of time during which neuroprotectants can be expected to be effective is likely to vary from drug to drug and depends on an individual drug's specific mechanism of action. Glutamate-induced toxicity is a very early event during the acute phase of ischemic stroke, which means that glutamate antagonists are likely to be effective as neuroprotectants for only a short time (perhaps as little as 1 to 2 hours). Neurotrophic growth factors, however, begin to appear a few hours after the onset of ischemia, and their production may continue for weeks. Drugs aimed at protecting neurons against reperfusion injury, however, may need to be given for 1 to 2 days. Similarly, caspases, the key enzymes in apoptosis, reach a peak 1 to 2 days after the onset of ischemia. Consequently, caspase inhibitors would need to be given for at least 2 days. Drugs with very short therapeutic time windows will be difficult to examine in phase III clinical trials because of the difficulty in completing the formalities for entry to the trial. There is also a potential problem in achieving adequate concentrations of the drug in the brain if the time window is short, especially if the drug enters the central nervous system slowly. One factor that determines the way in which the drug will be used is the slope of the dose-response curve. If the curve is steep, it is easy to undershoot or overshoot the target plasma concentration. Another practical consideration is controlling physiologic and biochemical parameters. The effects of drugs that alter blood pressure or blood glucose, for example, will need to be taken into account in developing treatment regimens. Short durations of treatment are simpler to administer. Drugs or regimens that increase the level of nursing care will require changes to management practices-for example, checking that an infusion is running properly or that a large fluid load has not triggered congestive heart failure. If a treatment requires the patient to be immobile for a prolonged period, the risk of venous thrombosis, for example, will increase. Such risks will have to be balanced against the benefit the drug provides. In general, the magnitude of benefit will tend to diminish with time after the onset of stroke, whereas the risk of adverse phenomena increases with time. The utility of the drug will therefore change with the length of time the treatment needs to be given.

Differences in vulnerability to permanent focal cerebral ischemia among 3 common mouse strains

BACKGROUND AND PURPOSE

Genetically engineered mice are used to study the role of single genes in cerebral ischemia, but inherent, strain-dependent differences in neuronal vulnerability may affect experimental end points. To examine this possibility, tissue injury resulting from focal ischemia and its relationship to cerebral hemodynamics were determined in 3 common mutant mouse strains.

METHODS

Permanent middle cerebral artery ligation was performed in male C57BL/6J, Balb/C, and 129X1/SvJ mice. Mean arterial blood pressure, blood gases, basal and postischemic cortical blood flow ([(14)C]iodoantipyrine autoradiography and laser-Doppler flowmetry), posterior communicating artery patency, and infarct size were determined.

RESULTS

Basal cortical blood flow did not differ among strains. Ten minutes after middle cerebral artery ligation, relative red cell flow in the ischemic cortex was 6% to 7% of preischemic flow in every strain. Despite similar hemodynamics, cortical infarcts in Balb/C mice were 3-fold larger than those in 129X1/SvJ and C57BL/6J mice; infarct size in the latter 2 strains was not significantly different. The posterior communicating artery was either poorly developed or absent in >90% of the Balb/C and C57BL/6J but in <50% of the 129X1/SvJ mice.

CONCLUSIONS

The extent of ischemic injury differed markedly between the 3 strains. The presence and patency of posterior communicating arteries, although variable among strains, did not affect preischemic or postischemic cortical blood flow or bear any relationship to ischemic injury. Therefore, intrinsic factors, other than hemodynamic variability, may contribute to the differences in ischemic vulnerability among strains. These findings underscore the importance of selecting genetically matched wild-type controls.

Over-expression of nucleophosmin/B23 decreases the susceptibility of human leukemia HL-60 cells to retinoic acid-induced differentiation and apoptosis

Stable clones of HL-60 cells in which nucleophosmin/B23 was over-expressed were established. Less percentages (4-20%) of nucleophosmin/B23 over-expressed (pCR3-B23) cells exhibited the morphological characteristic of apoptosis as compared with control vector-transfected (pCR3) cells (6-53%) during the 10 microM RA treatment for 1-4 days. In flow cytometry analysis, a block in the G1 phase was noted in all the pCR3-B23 and pCR3 cells after 2 days of 10 microM RA treatment and continued to be observed at all times measured up to 6 days. Smaller peaks of apoptotic cells with less than G1 DNA content were observed in pCR3-B23 as compared with pCR3 cells after 4-6 days of 10 microM RA treatment. As measured by expressions of differentiation markers and the functional assessment of the ability to reduce nitroblue-tetrazolium, our results further showed that over-expression of nucleophosmin/B23 decreased the response of the cells to RA-induced differentiation. Less cleavage of PARP and in vitro caspase-3 activity were observed in PCR3-B23 cells as compared with pCR3 cells treated with 10 microM RA for 3-4 days. IRF-1 was induced after 6 hr of 10 microM RA treatment in the pCR3-B23 and pCR3 cells. Significantly more nucleophosmin/B23 was co-immunoprecipitated with IRF-1 from pCR3-B23 cells than from pCR3 cells during RA treatment (10 microM; 24 hr, 96 hr). The IRF-1 transcriptional activity was found to be attenuated in pCR3-B23 cells as compared with pCR3 cells during the treatment of cells with RA. Nucleophosmin/B23, through interacting with IRF-1, plays an important role in the control of the susceptibility of cells to RA-induced differentiation and apoptosis.

Effects of low-energy CO2 laser irradiation and the organic matrix on inhibition of enamel demineralization

In the past two decades, accumulated evidence has clearly demonstrated the inhibitory effects of laser irradiation on enamel demineralization, but the exact mechanisms of these effects remain unclear. The purpose of this study was to investigate the effects of low-energy CO2 laser irradiation on demineralization of both normal human enamel and human enamel with its organic matrix removed. Twenty-four human molars were collected, cleaned, and cut into two halves. One half of each tooth was randomly selected and its lipid and protein content extracted. The other half of each tooth was used as the matched control. Each tooth half had two window areas. All the left windows were treated with a low-energy laser irradiation, whereas the right windows served as the non-laser controls. After caries-like lesion formation in a pH-cycling environment, microradiographs of tooth sections were taken for quantification of demineralization. The mean mineral losses (with standard deviation) of the enamel control, the lased enamel, the non-organic enamel control, and the lased non-organic enamel subgroups were 3955 (1191), 52(49), 4565(1311), and 1191 (940), respectively. A factorial ANOVA showed significant effects of laser irradiation (p = 0.0001), organic matrix (p = 0.0125), and the laser-organic matrix interaction (p = 0.0377). The laser irradiation resulted in a greater than 98% reduction in mineral loss, but the laser effect dropped to about 70% when the organic matrix in the enamel was removed. The results suggest that clinically applicable CO2 laser irradiation may cause an almost complete inhibition of enamel demineralization.

Diabetes, hemoglobin A(1c), cholesterol, and the risk of moderate chronic renal insufficiency in an ambulatory population

Moderate chronic renal insufficiency is common, with 12.5 million individuals in the United States estimated to have a creatinine clearance less than 50 mL/min/1.73 m(2). Little is known about the risk factors for moderate chronic renal insufficiency. We studied 1, 428 subjects with Cockcroft-Gault-estimated creatinine clearances greater than 70 mL/min in a hospital-based ambulatory population. Over a mean of 5.7 +/- 1.3 years, 86 subjects developed moderate chronic renal insufficiency, defined as a decrease in creatinine clearance to less than 60 mL/min (1.1 case/100 person-years). Risk factors for moderate chronic renal insufficiency were identified using a proportional hazards model controlling for age, sex, race, systolic blood pressure, and angiotensin-converting enzyme (ACE) inhibitor use. The risk for developing moderate chronic renal insufficiency was associated with diabetes mellitus (relative risk, 2.1; 95% confidence interval [CI], 1.3 to 3.3) and elevated hemoglobin A(1c) levels. Compared with subjects with normoglycemia (hemoglobin A(1c) </= 5.7%), the relative risk for moderate chronic renal insufficiency for patients in the upper quartile of hemoglobin A(1c) (>9.0%) was 2.7 (95% CI, 1.4 to 5.1). The development of moderate chronic renal insufficiency was also independently predicted by elevated maximum serum cholesterol level. Compared with subjects with maximum cholesterol levels of 250 mg/dL or less, the relative risk for those with maximum cholesterol levels greater than 350 mg/dL was 2.4 (95% CI, 1.1 to 5.2). Similar relative risks were obtained when moderate chronic renal insufficiency was defined by the development of an increase in serum creatinine level. Hypercholesterolemia was also associated with moderate chronic renal insufficiency among persons without diabetes. In conclusion, the risk for developing moderate chronic renal insufficiency is increased by diabetes and elevated hemoglobin A(1c) and serum cholesterol levels. Modification of these risk factors may decrease the incidence of moderate chronic renal insufficiency.

Chronic renal confusion: insufficiency, failure, dysfunction, or disease

The terms routinely used to describe states of reduced glomerular filtration rate (GFR) not requiring renal replacement therapy are poorly defined. With increasing interest in the epidemiology of chronic renal insufficiency and the timing of initiation of dialysis, terms such as "pre-ESRD" and "pre-dialysis" have been popularized, again without clear definition. Unambiguous terminology should be adopted. The authors favor using the term chronic renal insufficiency to describe states of reduced GFR not severe enough to require dialysis or transplantation. The authors propose classifying patients with GFR of 60 to 41 mL/min, 40 to 21 mL/min, and 20 mL/min or below as having mild, moderate, and advanced degrees of chronic renal insufficiency, respectively. The use of this terminology will facilitate communication among nephrologists and other physicians and provide a framework for comparison of populations across cohort studies and clinical trials.