AMPA receptor antagonist, YM90K, reduces infarct volume in thrombotic distal middle cerebral artery occlusion in spontaneously hypertensive rats

We examined the effects of a potent and selective antagonist of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) subtype of glutamate receptor, YM90K, on brain infarction using a newly developed stroke model of thrombotic distal middle cerebral artery occlusion. Male spontaneously hypertensive rats (5-7 months old) were subjected to photochemically-induced distal middle cerebral artery occlusion as previously described [Stroke 26 (1996) 333-336]. Intravenous infusion of YM90K (n = 8) (5 mg/kg per h for 1 h) or the same amount of vehicle (n = 8) (alkaline saline) was started 5 min after distal middle cerebral artery occlusion. Penumbral cerebral blood flow was determined with laser-Doppler flowmetry. Three days after the ischemic insult, brains were stained with 2,3,5-triphenyltetrazolium chloride and infarct volumes were determined. One hour infusion of YM90K significantly reduced infarct volume by 34% (93 +/- 23 mm3 in control group vs. 61 +/- 25 mm3 in YM90K-treated group, P = 0.017). There were no significant differences in the degrees of cerebral blood flow reduction after distal middle cerebral artery occlusion between the YM90K treated and control groups. YM90K reduces infarct volume in experimental ischemia produced by photothrombotic distal middle cerebral artery occlusion in rats. The present results demonstrated beneficial effects of AMPA receptor blockade on acute ischemic stroke.

cAMP activates MAP kinase and Elk-1 through a B-Raf- and Rap1-dependent pathway

Cyclic adenosine monophosphate (cAMP) has tissue-specific effects on growth, differentiation, and gene expression. We show here that cAMP can activate the transcription factor Elk-1 and induce neuronal differentiation of PC12 cells via its activation of the MAP kinase cascade. These cell type-specific actions of cAMP require the expression of the serine/threonine kinase B-Raf and activation of the small G protein Rap1. Rap1, activated by mutation or by the cAMP-dependent protein kinase PKA, is a selective activator of B-Raf and an inhibitor of Raf-1. Therefore, in B-Raf-expressing cells, the activation of Rap1 provides a mechanism for tissue-specific regulation of cell growth and differentiation via MAP kinase.

Age-related changes in the DNA and RNA content of the brain in spontaneously hypertensive rats

To elucidate the effects of aging accompanied with hypertension on brain nucleic acid, we measured both the DNA and RNA contents of six specific brain regions in adult (5-6 months old) and aged (18-22 months old) female spontaneously hypertensive rats (SHRs). Although no statistical difference was observed in the RNA content, the DNA content did tend to increase in the hippocampal CA1 of aged SHR (4.24 +/- 0.55 ng/microgram protein, mean +/- SD, n = 6) in comparison to that of adult SHR (3.21 +/- 0.71 ng/microgram protein, n = 4). Hence, aged SHRs showed a significant decrease in the RNA to DNA ratio in the CA1 subfield of the hippocampus (3.79 +/- 0.61) compared to adult SHR (5.27 +/- 0.81). On the other hand, no other regions, except for the dorsolateral region of the striatum, showed any difference in the RNA/DNA ratio between aged and adult SHR. We therefore conclude that subtle changes in the nucleic acid occur in vulnerable regions of the brain in aged SHRs.

[CT for diagnosis of parathyroid adenoma]

We analyzed Ct findings of 10 cases with parathyroid adenoma which had been verified by surgery and pathologic section. The correct localization of 9 adenomas was made by CT preoperatively. The method of CT scanning of parathyroid adenoma were elucidated. The results showed that most adenomas were located in the groove between trachea and esophagus. The contour of tumors was oval, the edge was smooth and regular. Enhancement CT images were helpful for differentiating the tumor from blood vessel. It is indicated that CT scanning is a good method for localizing the parathyroid adenoma.

Mutant presenilins of Alzheimer's disease increase production of 42-residue amyloid beta-protein in both transfected cells and transgenic mice

The mechanism by which mutations in the presenilin (PS) genes cause the most aggressive form of early-onset Alzheimer's disease (AD) is unknown, but fibroblasts from mutation carriers secrete increased levels of the amyloidogenic A beta 42 peptide, the main component of AD plaques. We established transfected cell and transgenic mouse models that coexpress human PS and amyloid beta-protein precursor (APP) genes and analyzed quantitatively the effects of PS expression on APP processing. In both models, expression of wild-type PS genes did not alter APP levels, alpha- and beta-secretase activity and A beta production. In the transfected cells, PS1 and PS2 mutations caused a highly significant increase in A beta 42 secretion in all mutant clones. Likewise, mutant but not wildtype PS1 transgenic mice showed significant overproduction of A beta 42 in the brain, and this effect was detectable as early as 2-4 months of age. Different PS mutations had differential effects on A beta generation. The extent of A beta 42 increase did not correlate with presenilin expression levels. Our data demonstrate that the presenilin mutations cause a dominant gain of function and may induce AD by enhancing A beta 42 production, thus promoting cerebral beta-amyloidosis.

Diversity associated with the second expressed HLA-DRB locus in the human population

Although diversity within the HLA-DRB region is predominantly focused in the DRB1 gene, the second expressed DRB loci, DRB3, DRB4, and DRB5, also exhibit variation. Within DRB1(*)15 or DRB1(*)16 haplotypes, four new variants were identified: 1) two new DRB5 alleles, DRB5*0104 and DRB5*0204, 2) a haplotype carrying a DRB1(*)15 or *16 allele without the usual accompanying DRB5 allele, and 3) a haplotype carrying a DRB5(*)0101 allele without a DRB1(*)15 or *16 allele. The evolutionary origins of these haplotypes were postulated based on their associations with the DRB6 pseudogene. Within HLA haplotypes which carry DRB3, a new DRB3(*)0205 allele and one unusual DRB3 association were identified. Finally, two new null DRB4 alleles are described: DRB4(*)0201N, which exhibits a deletion in the second exon, and a second allele, DRB4(*)null, which lacks the second exon completely. Gene conversion-like events and variation in the number of functional genes through reciprocal recombination and inactivation contribute to the diversity observed in the second expressed HLA-DRB loci.

Mitogen-activated protein kinase phosphatase 1 is overexpressed in prostate cancers and is inversely related to apoptosis

Several oncogenes involved in prostate carcinogenesis activate mitogen-activated protein (MAP) kinases, which can relay both proliferative (via extracellular regulated kinases (ERK)) and apoptotic signals (via jun N-terminal protein kinases (JNK)) to the nucleus. Mitogen-activated protein kinase phosphatase 1 (MKP-1) is induced by several oncogenes in the ras-dependent pathway and can inactivate both MAP kinase pathways. The role of MKP-1 in proliferation and apoptosis is, however, still controversial. A series of 51 prostate cancers, including a subset (n = 13) that had been previously treated by androgen ablation, was used to examine whether MKP-1 mRNA and protein expression correlated with that of ERK-1, JNK-1, bcl-2, which confers resistance to apoptosis, and apoptotic index measured by in situ end-labeling of fragmented DNA. In a subset of tumors, MKP-1 expression was assessed by semiquantitative RT-PCR and was compared with both ERK-1 and JNK-1 enzymatic activity. In cases not treated by androgen ablation, MKP-1 was overexpressed in the preinvasive stage of prostate cancer, but its expression decreased with higher histologic grade and advanced disease stage. There was coexpression of MKP-1, ERK-1, and JNK-1 proteins. In addition, MKP-1 expression was inversely correlated to JNK-1 but not to ERK-1 enzymatic activity. Finally, MKP-1 and bcl-2 were inversely related to apoptotic indices. In cases treated by total androgen ablation, MKP-1 and bcl-2 were both down-regulated, whereas JNK-1 was up-regulated. Subpopulations of cells that did not undergo apoptosis maintained expression of both MKP-1 and bcl-2. These results suggest that MKP-1 overexpression is associated with the early phases of neoplastic transformation in prostate tissue. The enzymatic data on MKP-1 kinase substrates and the inverse correlation between MKP-1 and parameters of programmed cell death support the hypothesis that MKP-1 inhibits apoptosis in human prostate tumors, perhaps through the JNK pathway.

Expression of mitogen-activated protein kinase phosphatase-1 in the early phases of human epithelial carcinogenesis

Many mitogens and human oncogenes activate extracellular regulated kinases (ERKs), which in turn convey proliferation signals. ERKs or mitogen-activated protein (MAP) kinases are inactivated in vitro by MAP kinase phosphatases (MKPs). The gene encoding one of these MKPs, MKP-1, is a serum-inducible gene and is transcriptionally activated by mitogenic signals in cultured cells. As MKP-1 has been shown to block DNA synthesis by inhibiting ERKs when expressed at elevated levels in cultured cells, it has been suggested that it may act as a tumor suppressor. MKP-1 mRNA and MAP kinase (ERK-1 and -2) protein expression was assessed in 164 human epithelial tumors of diverse tissue origin by in situ hybridization and immunohistochemistry. MKP-1 was overexpressed in the early phases of prostate, colon, and bladder carcinogenesis, with progressive loss of expression with higher histological grade and in metastases. In contrast, breast carcinomas showed significant MKP-1 expression even when poorly differentiated or in late stages of the disease. MKP-1, ERK-1, and ERK-2 were co-expressed in most tumors examined. In a subset of 15 tumors, ERK-1 enzymatic activity as well as structural alterations that might be responsible for loss of function of MKP-1 during tumor progression, were examined. ERK-1 enzymatic activity was found to be elevated despite MKP-1 overexpression. No loss of 5q35-ter (containing the MKP-1 locus) was detected by polymerase chain reaction in metastases compared with primary tumors. Finally, no mutations were found in the catalytic domain of MKP-1. These data indicate that MKP-1 is an early marker for a wide range of human epithelial tumors and suggest that MKP-1 does not behave as a tumor suppressor in epithelial tumors.

Amlodipine, a Ca2+ channel antagonist, modifies cerebral blood flow autoregulation in hypertensive rats

We measured the cerebral blood flow at rest and during hemorrhagic hypotension in 7 rats of each group using laser-Doppler flowmetry. Simultaneously, the absolute baseline cerebral blood flow values in the parietal cortex were quantified with the hydrogen clearance method. Baseline mean arterial pressure was significantly lowered, by 29 mm Hg, in the amlodipine-treated group, while the baseline cerebral blood flow was 36 +/- 4 ml/100 g/min (mean +/- S.D.) which was almost the same as the 40 +/- 5 in the control group. The lower limits of the cerebral blood flow autoregulation, defined as the mean arterial pressure at which the cerebral blood flow decreased by 10% of the baseline value, were shifted to a lower level of 107 +/- 9 mm Hg in the treated group compared with 133 +/- 5 mm Hg in the control (P < 0.001). The results demonstrated that, in hypertensive rats with amlodipine treatment, cerebral perfusion was preserved at a lower blood pressure level, which is advantageous under hypotensive conditions.

L-arginine does not improve cortical perfusion or histopathological outcome in spontaneously hypertensive rats subjected to distal middle cerebral artery photothrombotic occlusion

The potential of nitric oxide (NO) to influence positively or negatively the outcome of mechanically induced focal cerebral ischemia is still controversial. Recent evidence suggests that NO of vascular origin, whether synthesized from exogenously administered L-arginine (L-Arg) or from NO donor compounds, is beneficial but that of neuronal origin is not. However, the therapeutic potential of NO to ameliorate stroke induced by arterial thrombosis has not been reported. We assessed the therapeutic effect of L-Arg administration in spontaneously hypertensive rats (SHR) subjected to permanent photothrombotic occlusion of the distal middle cerebral artery (dMCA). The ipsilateral carotid artery was left unligated to enhance L-Arg delivery into the putative penumbral region. Local CBF (LCBF) was assessed at 30 min by the [14C]iodoantipyrine technique (n = 9), while histological infarct volumes and index of peripheral ischemic cell change were determined at 3 days (n = 7). Rats (n = 9) given 300 mg/kg L-Arg at 18 and 3 h before photothrombotic dMCA occlusion and at 5 min afterward displayed no significant differences in LCBF compared with animals (n = 8) injected with water (the carrier vehicle) and similarly irradiated. Infarct volumes were also similar, being 37.0 +/- 9.7 mm3 (SD) in the vehicle-treated and 49.1 +/- 17.2 mm3 (SD) in the L-Arg-treated groups (both n = 7), as were assessments of ischemic neuronal density in the penumbra. In contrast, L-Arg administered intravenously in a dose of 300 mg/kg to nonischemic SHR (n = 5) increased cortical CBF by approximately 75% during a 70-min observation period. We conclude that thrombotic processes superimposed upon cerebral ischemia may facilitate tissue reactions that offset the potentially beneficial effect of L-Arg, and this caveat must be considered when proposing L-Arg for clinical treatment of focal thrombotic stroke.

Metabolically programmed polyamine analogue antidiarrheals

The design, synthesis, and testing of a novel class of antidiarrheal drugs based on a tetraamine pharmacophore are reported. While N1,N14-diethylhomospermine (DEHSPM) (5 mg/kg) completely prevents diarrhea in rodents, tissue distribution studies demonstrated that the principal metabolite of DEHSPM, homospermine (HSPM), accumulates and persists in tissues for a protracted period of time. This accumulation accounts for a large part of the chronic toxicity of DEHSPM. Thus a major objective was to develop a metabolically labile analogue of DEHSPM which retained the desirable biological properties of the parent drug. Hydroxyl groups, sites vulnerable to further metabolic transformation, were introduced into the external aminobutyl segments providing N1,N14-diethyl-(3R),(12R)-dihydroxyhomospermine [(HO)2-DEHSPM]. The design concept was assisted by molecular modeling, which predicted that (HO)2DEHSPM would have a Ki for polyamine transport essentially identical with that of DEHSPM. The experimentally measured Ki and also the observed values of other biological properties of (HO)2DEHSPM were in fact identical with those of DEHSPM, including IC50 against L1210 cells, impact on the NMDA receptor, and impact on L1210 native polyamine pools. Most significantly, however, there was no accumulation of the dideethylated metabolite in tissues from mice treated chronically with (HO)2DEHSPM, and (HO)2DEHSPM was 3-fold less toxic than DEHSPM. Finally, (HO)2DEHSPM completely prevented diarrhea in the castor oil-treated rat model at a dose of 5 mg/kg, just as did DEHSPM.

Diagnosis and treatment of nephrotic syndrome during pregnancy

OBJECTIVE

To set forth the methods of diagnosis and treatment of nephrotic syndrome during pregnancy (NSP) so as to decrease perinatal mortality.

MATERIALS AND METHODS

Forty cases of NSP including 5 twins in Tianjin Central Hospital of Obstetrics and Gynecology in the past 13 years have been reviewed, and the diagnosis and treatment were compared between group A (1979-1990, 23 cases) and group B (1991-1992, 17 cases).

RESULTS

NSP occurred before the 20th gestational week in 15% of cases and the patient's condition was serious. Clinically, NSP was classified into three types: simple, nephritis and pregnancy induced hypertension (PIH) type. The perinatal maternal and fetal prognosis was poor. Complications occurred in 27.5% of patients. One patient died from eclampsia and disseminated intravascular coagulation (DIC). The total perinatal mortality was 42.22%, with group A (27 babies including 4 twins), 51.86% (14/27), and group B (18 babies including 1 twin), 27.78% (5/18) (P < 0.01).

CONCLUSIONS

NSP is a result of reproductive immunology and belongs to type III allergic reaction in terms of immunology. Early diagnosis, early treatment and timely termination of pregnancy may improve the outcome.

Detection of PML-RAR alpha in patients with APL during follow-up period

OBJECTIVE

To evaluate the significance of PML-RAR alpha transcripts in patients with acute promyelocytic leukemia (APL) during remission period and to follow up the patients through monitoring aberrant gene expression.

PATIENTS AND METHODS

This study included 17 patients with APL (5 females and 12 males). Another 19 APL patients during relapse served as control. RNA extraction was obtained through the single-step method. By means of reverse transcriptase polymerase chain reaction (PCR), the PML-RAR alpha was detected in the sample mRNA.

RESULTS

Nine out of 10 patients with complete remission (CR) duration shorter than 3 years were positive. Four cases became negative and three remained positive among 7 cases in a long remission of over 3 years. The difference of the positive rate of PML-RAR alpha transcripts between the 2 groups was significant (P < 0.05). Four among 12 positive cases relapsed. No evidence of relapse was present in the 5 negative patients after 9.6 +/- 3.9-month follow-up. Further treatment was therefore given to the 4 positive patients whose treatment was already ceased at that time. By this management they were all in CR during the following 10-month observation.

CONCLUSIONS

RT-PCR detection for PML-RAR alpha transcripts was useful in monitoring MRD and guiding further treatment to obtain a long remission. Persistently positive transcripts were closely associated with the relapse.

Simplified model of krypton laser-induced thrombotic distal middle cerebral artery occlusion in spontaneously hypertensive rats

BACKGROUND AND PURPOSE

The effects of thrombotic occlusion of the middle cerebral artery on compromised ischemic tissue may be different from and more severe than those of cerebral ischemia induced by mechanical occlusion of the artery. Photothrombosis, which is based on photochemical damage to the endothelium and subsequent platelet aggregation, is an efficient method to induce thrombosis in vivo. This study aimed to improve and simplify this unique method for an ischemia model of middle cerebral artery occlusion in rats.

METHODS

Male spontaneously hypertensive rats (5 to 6 months old, 300 to 450 g) were anesthetized with halothane, endotracheally intubated, and mechanically ventilated. A krypton laser operating at 568 nm was used to irradiate the exposed distal middle cerebral artery with an intact dura above the rhinal fissure. The photosensitizing dye rose bengal (20 mg/kg body wt) was administered intravenously over 90 seconds starting simultaneously with 4 minutes of laser irradiation at a power of 20 mW to cause thrombotic occlusion of this artery.

RESULTS

The irradiated middle cerebral artery was completely occluded by intraluminal thrombi within 3 minutes after simultaneous laser irradiation and rose bengal infusion. Thrombosed materials were not stained by phosphotungstic acid-hematoxylin stain (ie, aggregated platelets lacked apparent fibrin). The mean volume of 3-day-old infarction, indicated by the lack of staining with 2,3,5-triphenyltetrazolium chloride, was 84.8 +/- 17.4 mm3 (mean +/- SD, n = 6).

CONCLUSIONS

We demonstrated a reproducible and minimally traumatic model of brain infarction induced by the thrombotic distal middle cerebral artery occlusion in rats.

The alpha 1-adrenoceptor antagonist, doxazosin, modulates the lower limit of autoregulation of cerebral blood flow during hemorrhagic hypotension in anesthetized hypertensive rats

The objective of the present study was to examine the effects of administration of an alpha 1-adrenoceptor antagonist, doxazosin, for 7 days on cerebral blood flow and the autoregulatory response to hypotension in anesthetized spontaneously hypertensive rats. We determined the cerebral blood flow at rest and during hemorrhagic hypotension in 14 rats of each group using laser-Doppler flowmetry, and at the same time, the absolute baseline cerebral blood flow values at the parietal cortex were also quantified in some of the rats with the hydrogen clearance method. Baseline mean arterial pressure was significantly lowered, by 41 mm Hg, in the doxazosin-treated group, while the baseline cerebral blood flow was 31 +/- 4 ml/100 g/min(mean +/- S.D.) which was almost the same as the 32 +/- 5 ml/100 G/min in the control group. The lower limits of cerebral blood flow autoregulation were 139 +/- 9 mm Hg in the control group and 96 +/- 12 mm Hg in the treated group; the difference was significant (P < 0.001). The present results demonstrated that the lower limit of cerebral blood flow autoregulation shifts to a lower level after chronic treatment with doxazosin, an effect which is favorable for the maintenance of cerebral blood flow under hypotensive conditions.

Cyclic adenosine monophosphate can convert epidermal growth factor into a differentiating factor in neuronal cells

The rat pheochromocytoma (PC12) cell line is a model for studying the mechanism of growth factor action. Both epidermal growth factor and nerve growth factor stimulate mitogen-activated protein (MAP) kinase in these cells. Recent data suggest that the transient activation of MAP kinase may trigger proliferation, whereas sustained activation triggers differentiation in these cells. We have tested this model by asking whether agents that stimulate MAP kinase without inducing differentiation can act additively to trigger differentiation. Neither forskolin nor epidermal growth factor can stimulate differentiation, yet both activate MAP kinase in these cells. Together, their actions on MAP kinase are synergistic. Cells treated with both agents differentiate, measured morphologically and by the induction of neural-specific genes. We propose that cellular responses to growth factor action are dependent not only on the activation of growth factor receptors by specific growth factors but on synchronous signals that may elevate MAP kinase levels within the same cells.