Metal cluster chemistry: Structure and stereochemistry in the polynuclear rhodium hydrides H(n)Rh(n)[P(OR)(3)](2n)

Crystallographic analyses of x-ray and neutron diffraction data have provided a definitive structural representation of {HRh[P(O-i-C(3)H(7))(3)](2)}(2) and {HRh[P(OCH(3))(3)](2)}(3). These polynuclear hydrides are generated from square planar H(2)Rh[P(OR)(3)](2) units by edge (hydrogen atom) sharing and by vertex (hydrogen atom) sharing to form the dimeric and trimeric structures, respectively. The square-planar units are held together through four-center and three-center two-electron Rh-H-Rh bonds in the dimer and trimer, respectively. The dimer and trimer molecules each add one molecule of hydrogen to form H[(i-C(3)H(7)O)(3)P](2)RhH(3)Rh [P(O-i-C(3)H(7))(3)](2) and H(5)Rh(3)[P(OCH(3))(3)](6), respectively. NMR spectral information has served to define the stereochemical features of these polyhydrides. The significance of this chemistry in the metal cluster-metal surface analogy is described.

Selective potentiation of the metabotropic glutamate receptor subtype 2 blocks phencyclidine-induced hyperlocomotion and brain activation

Previous preclinical and clinical studies have demonstrated the efficacy of group II metabotropic glutamate receptor (mGluR) agonists as potential antipsychotics. Recent studies utilizing mGluR2-, mGluR3-, and double knockout mice support that the antipsychotic effects of those compounds are mediated by mGluR2. Indeed, biphenyl indanone-A (BINA), an allosteric potentiator of mGluR2, is effective in experimental models of psychosis, blocking phencyclidine (PCP)-induced hyperlocomotion and prepulse inhibition deficits in mice. In this study, we administered the NMDA receptor antagonist PCP (5.6 mg/kg i.p.) to rats, an established animal model predictive of schizophrenia. Here, we show that BINA (32 mg/kg i.p.) attenuated PCP-induced locomotor activity in rats. Using behaviorally relevant doses of BINA and PCP, we performed pharmacological magnetic resonance imaging (phMRI) to assess the specific brain regions that underlie the psychotomimetic effects of PCP, and examined how BINA modulated the PCP-induced functional changes in vivo. In anesthetized rats, acute administration of PCP produced robust, sustained blood oxygenation level-dependent (BOLD) activation in specific cortical, limbic, thalamic, and striatal regions. Pretreatment with BINA suppressed the amplitude of the BOLD response to PCP in the prefrontal cortex, caudaute-putamen, nucleus accumbens, and mediodorsal thalamus. Our results show key brain structures underlying PCP-induced behaviors in a preclinical model of schizophrenia, and, importantly, its reversal by potentiation of mGluR2 by BINA, revealing specific brain regions functionally involved in its pharmacological action. Finally, our findings bolster the growing body of evidence that mGluR2 is a viable target for the treatment of schizophrenia.

Lower quit rates among African American and Latino menthol cigarette smokers at a tobacco treatment clinic

BACKGROUND

Lower rates of smoking cessation and higher rates of lung cancer in African American (AA) smokers may be linked to their preference for mentholated cigarettes.

AIM

This study assessed the relationship between menthol smoking, race/ethnicity and smoking cessation among a diverse cohort of 1688 patients attending a specialist smoking cessation service.

RESULTS

46% of the patients smoked mentholated cigarettes, but significantly more AA (81%) and Latino (66%) patients than Whites (32%) smoked menthols. AA and Latino menthol smokers smoked significantly fewer cigarettes per day (CPD) than non-menthol smokers (15.7 vs. 20.3, for AA, and 17.0 vs. 22.1, for Latinos), with no differences among White menthol and non-menthol smokers. At 4-week follow up, AA, Latino and White non-menthol smokers had similar quit rates (54%, 50% and 50% respectively). In contrast, among menthol smokers, AAs and Latinos had lower quit rates (30% and 23% respectively) compared with Whites (43%, p < 0.001). AA and Latino menthol smokers had significantly lower odds of quitting [odds ratio (OR) = 0.34; 95% CI = 0.17, 0.69 for AA, and OR = 0.32; 95% CI = 0.16, 0.62 for Latinos] than their non-menthol counterparts. At 6-month follow up, a similar trend was observed for the race/ethnicity subgroups, with AA menthol smokers having half the odds of being abstinent compared with AA non-menthol smokers (OR = 0.48; 95% CI = 0.25, 0.9).

CONCLUSIONS

Despite smoking fewer CPD, AA and Latino menthol smokers experience reduced success in quitting as compared with non-menthol smokers within the same ethnic/racial groups.

Causes of death in the Kasekela chimpanzees of Gombe National Park, Tanzania

Understanding the rates and causes of mortality in wild chimpanzee populations has important implications for a variety of fields, including wildlife conservation and human evolution. Because chimpanzees are long-lived, accurate mortality data requires very long-term studies. Here, we analyze 47 years of data on the Kasekela community in Gombe National Park. Community size fluctuated between 38 and 60, containing 60 individuals in 2006. From records on 220 chimpanzees and 130 deaths, we found that the most important cause of mortality in the Kasekela community was illness (58% of deaths with known cause), followed by intraspecific aggression (20% of deaths with known cause). Previous studies at other sites also found that illness was the primary cause of mortality and that some epidemic disease could be traced to humans. As at other study sites, most deaths due to illness occurred during epidemics, and the most common category of disease was respiratory. Intraspecific lethal aggression occurred within the community, including the killing of infants by both males and females, and among adult males during the course of dominance-related aggression. Aggression between communities resulted in the deaths of at least five adult males and two adult females in the Kasekela and Kahama communities. The frequency of intercommunity violence appears to vary considerably among sites and over time. Intercommunity lethal aggression involving the Kasekela community was observed most frequently during two periods. Other less common causes of death included injury, loss of mother, maternal disability, and poaching.

The acute management of head injury

The management of traumatic brain injury has undergone extensive revision as the results of large collaborative outcome studies have cast doubt on many traditional 'common sense' practices. The primary goal of identifying and treating intracranial hypertension has given way to a focus on secondary brain ischemia, in which cerebral perfusion pressure and oxygen delivery have gained new importance. With the exception of impending herniation, the routine use of hyperventilation and high-dose barbiturates is no longer recommended. Hypertonic saline, given as intermittent boluses, has joined mannitol as an effective means of reducing cerebral edema. Preliminary results from a large multi-center study have cast doubt on the benefit of the broad application of hypothermia in improving outcome in traumatic brain injury.

Mannose-binding lectin gene polymorphisms in a cohort study of ANCA-associated small vessel vasculitis

OBJECTIVE

To investigate whether single nucleotide polymorphisms (SNPs) within the mannose-binding lectin (MBL) gene are associated with small vessel vasculitis (SVV) and are a risk factor for intercurrent infection, as described previously in other autoimmune diseases.

METHODS

Six SNPs in the MBL promoter and coding region were genotyped by sequence-specific polymerase chain reaction or restriction fragment length polymorphism assay in 170 white Caucasians with SVV and 372 ethnically matched controls in a case-control association study. Serum MBL levels were measured by ELISA. The genotype and protein concentrations were correlated to clinical details retrieved from hospital records.

RESULTS

No differences in allelic and genotypic frequencies were detected between patients with SVV and control subjects. MBL deficiency did not increase the susceptibility to infection (P = 0.6, Fisher's exact test) or the duration of hospital stay.

CONCLUSION

Our data suggest that MBL polymorphisms are not associated with SVV and do not influence the incidence of concomitant infections. These results raise doubts about the usefulness of MBL polymorphisms as a predictive marker for infection in SVV.

Elevations in Renal Interstitial Hydrostatic Pressure and 20-Hydroxyeicosatetraenoic Acid Contribute to Pressure Natriuresis

This study examined the role of changes in renal interstitial pressure on the renal levels of cytochrome P450 metabolites of arachidonic acid and compared the effects of inhibition of the formation of 20-hydroxyeicosatetraenoic acid (20-HETE) and epoxyeicosatrienoic acids with 1-aminobenzotriazole on the pressure-natriuretic response versus that seen after administration of HET0016, a more selective inhibitor of the formation of 20-HETE. Renal interstitial pressure rose by 3.4±0.3 mm Hg, and the levels of 20-HETE in renal cortical tissue doubled when renal perfusion pressure was increased from 100 to 160 mm Hg. Removal of the renal capsule prevented the increase in renal interstitial pressure and 20-HETE levels after an elevation in renal perfusion pressure. Urine flow and sodium excretion increased 5-fold when renal perfusion pressure was increased from 106 to 160 mm Hg. The administration of 1-aminobenzotriazole (50 mg/kg, IP) or HET0016 (10 mg/kg IV bolus plus 1 mg/kg per hour of infusion) decreased the pressure-natriuretic response by 50% and inhibited the renal formation of 20-HETE and epoxyeicosatrienoic acids by 90% and 50%, respectively. Administration of a lower dose of HET0016 (1 mg/kg per hour, IV) selectively reduced the formation of 20-HETE by 80% without inhibiting renal epoxygenase activity and blunted the pressure-natriuretic response by 42%. These results indicate that elevations in renal perfusion pressure increase 20-HETE levels in the kidney secondary to a rise in renal interstitial pressure. They also suggest that 20-HETE, rather than epoxyeicosatrienoic acids, modulates the pressure-natriuretic response, because selective blockade of the formation of 20-HETE with HET0016 blunts the response to the same extent as that seen after inhibition of the formation of 20-HETE and epoxyeicosatrienoic acids with 1-aminobenzotriazole.

Dopamine transporter activity mediates amphetamine-induced inhibition of Akt through a Ca2+/calmodulin-dependent kinase II-dependent mechanism

The primary mechanism for clearance of extracellular dopamine (DA) is uptake mediated by the dopamine transporter (DAT), which is governed, in part, by the number of functional DATs on the cell surface. Previous studies have shown that amphetamine (AMPH) decreases DAT cell surface expression, whereas insulin reverses this effect through the action of phosphatidylinositol 3-kinase (PI3K). Therefore, it is possible that AMPH causes DAT cell surface redistribution by inhibiting basal insulin signaling. Here, we show in a heterologous expression system and in murine striatal synaptosomes that AMPH causes a time-dependent decrease in the activity of Akt, a protein kinase immediately downstream of PI3K. This effect was blocked by the DAT inhibitor cocaine, suggesting that AMPH must interact with DAT to inhibit Akt. We also showed that AMPH is able to stimulate Ca2+/calmodulin-dependent kinase II (CaMKII) activity, both in the heterologous expression system as well as in murine striatal synaptosomes. The ability of AMPH to decrease Akt activity was blocked by the CaMKII inhibitor 2-[N-(2-hydroxyethyl)]-N-(4-methoxybenzenesulfonyl)]amino-N-(4-chlorocinnamyl)-N-methylbenzylamine (KN93), but not by its inactive analog 2-[N-(4-methoxybenzenesulfonyl)]amino-N-(4-chlorocinnamyl)-N-methylbenzylamine (KN92). Furthermore, preincubation with KN93 prevented the AMPH-induced decrease in DAT cell surface expression. Thus, AMPH, but not cocaine, decreases Akt activity through a CaMKII-dependent pathway, thereby providing a novel mechanism by which AMPH regulates insulin signaling and DAT trafficking.

Synergistic actions of enalapril and tempol during chronic angiotensin II-induced hypertension

Experiments were designed to test the hypothesis that antioxidant treatment would increase the anti-hypertensive actions of endogenous kinins during angiotensin converting enzyme (ACE) inhibition. Four groups of rats, all given angiotensin II (Ang II) for 2 weeks, were studied: 1) control, 2) enalapril, 3) tempol or 4) both tempol and enalapril. Ang II significantly increased systolic blood pressure (BP) when compared with the baseline (170+/-8 vs. 128+/-4 mm Hg, P<0.05). Neither enalapril nor tempol alone was able to attenuate the elevation in BP (165+/-7 and 164+/-6 mm Hg, respectively). In contrast, combined administration of tempol and enalapril prevented the increase in BP (137+/-5 mm Hg). Plasma 8-isoprostane increased in Ang II-infused rats when compared with control untreated rats (69+/-14 vs. 23+/-0.5 pg/ml, P<0.05). Tempol alone or tempol plus enalapril significantly attenuated the increase in plasma 8-isoprostane (29+/-6 and 34+/-7 pg/ml, respectively). In additional experiments, we used the bradykinin B(2) antagonist, icatibant to determine if increased B(2) receptor contributes to the anti-hypertensive effect of combined tempol and enalapril in Ang II-infused rats. Icatibant decreased the ability of this combination to lower arterial pressure. Additionally, a significant increase in B(1) receptor protein expression in renal cortex of Ang II-infused rats was observed compared to control suggesting that bradykinin receptor activation could account for the effect of enalapril to enhance the actions of tempol. These data support the hypothesis that combined reduction of superoxide along with enhanced endogenous kinins may facilitate blood pressure lowering in Ang II hypertension.

IL-18 is upregulated in the kidney and primes neutrophil responsiveness in ANCA-associated vasculitis

In antineutrophil cytoplasm autoantibody (ANCA)-associated systemic vasculitis (ASV), autoantibody-induced neutrophil activation is believed to cause organ damage. In vitro, tumor necrosis factor alpha (TNFalpha) primes neutrophils for ANCA stimulation and TNFalpha blockade has been successfully used to treat ASV. Nonetheless, irreversible organ damage can still occur, suggesting that other cytokines may circumvent TNFalpha blockade. We report that interleukin (IL)-18 deposition, as assessed by immunoperoxidase staining, is increased in renal biopsies from ASV patients. Immunofluorescence microscopy demonstrated that podocytes are the predominant glomerular IL-18-positive cell type, whereas in the interstitium, myofibroblasts, distal tubular epithelium, and infiltrating macrophages stained for IL-18. In vitro, IL-18 primed superoxide production by ANCA-activated neutrophils comparably to TNFalpha. IL-18-primed, ANCA-induced superoxide production was unaffected by anti-TNFalpha antibody, which abrogated TNFalpha priming. Furthermore, TNFalpha and IL-18 phosphorylated neutrophil p38 mitogen-activated protein kinase (MAPK), but IL-18-mediated p38 MAPK phosphorylation was unaffected by anti-TNFalpha antibody. The p38 MAPK inhibitor, SB20358, reduced IL-18-primed, ANCA-induced superoxide production in a concentration-dependent manner. ANCA-induced superoxide release was also sensitive to the Leukotriene B4 (LTB4) inhibitor MK-886. IL-18 priming was not associated with increased ANCA antigen expression on isolated neutrophils. We conclude that IL-18 is likely to be important for neutrophil recruitment and priming in ASV. Therapies targeting single priming agents may have limited efficacy in controlling disease.

The dopamine transporter: a vigilant border control for psychostimulant action

Neurotransmission within the mesocorticolimbic dopamine system has remained the central focus of investigation into the molecular, cellular and behavioral properties of psychostimulants for nearly three decades. The primary means by which dopamine transmission in the synapse is terminated is via the dopamine transporter (DAT), the presynaptic plasmalemmal protein that is responsible for the reuptake of released dopamine. Numerous abused as well as clinically important drugs have important pharmacological interactions with DAT. In general, these compounds fall into two categories: those that block dopamine transport (e.g., cocaine, methylphenidate) and those that serve as substrates for transport [e.g., dopamine, amphetamine and 3,4-methylenedioxymethamphetamine (MDMA or "ecstasy")]. Recent data from in vitro and in vivo studies have suggested that DAT, like other biogenic amine transporters, share several characteristics with classical ligand-gated ion channels. In addition, substrates for transport promote redistribution of DAT away from the plasma membrane, while transport inhibitors such as cocaine disrupt this process. In addition, presynaptic autoreceptors for dopamine have been implicated in the modulation of DAT surface expression and function. The present chapter summarizes some of the recent discoveries pertaining to the electrogenic properties of DAT and their potential relevance to the effects of amphetamine-like stimulants on DAT function. Although there are a number of intracellular and extracellular modulatory influences on dopamine clearance that may play particular roles in psychostimulant action, we specifically focus on the differential direct modulation of DAT function by transport substrates and inhibitors, and we also discusses the role of presynaptic D2 receptors in transport regulation.

Engineering craniofacial scaffolds

OBJECTIVE

To develop an integrated approach for engineering craniofacial scaffolds and to demonstrate that these engineered scaffolds would have mechanical properties in the range of craniofacial tissue and support bone regeneration for craniofacial reconstruction.

EXPERIMENTAL VARIABLE

Scaffold architecture designed to achieve desired elasticity and permeability. Scaffold external shape designed to match craniofacial anatomy.

OUTCOME MEASURE

Final fabricated biomaterial scaffolds. Compressive mechanical modulus and strength. Bone regeneration as measured by micro-CT scanning, mechanical testing and histology.

SETTING

Departments of Biomedical Engineering, Oral/Maxillofacial Surgery, and Oral Medicine, Pathology and Oncology at the University of Michigan.

RESULTS

Results showed that the design/fabrication approach could create scaffolds with designed porous architecture to match craniofacial anatomy. These scaffolds could be fabricated from a wide range of biomaterials, including titanium, degradable polymers, and degradable calcium phosphate ceramics. Mechanical tests showed that fabricated scaffolds had compressive modulus ranging 50 to 2900 MPa and compressive strength ranging from 2 to over 56 MPa, within the range of human craniofacial trabecular bone. In vivo testing of designed scaffolds showed that they could support bone regeneration via delivery of BMP-7 transduced human gingival fibroblasts in a mouse model. Designed hydroxyapatite scaffolds with pore diameters ranging from 400 to 1200 microns were implanted in minipig mandibular defects for 6 and 18 weeks. Results showed substantial bone ingrowth (between 40 and 50% at 6 weeks, between 70 and 80% at 18 weeks) for all scaffolds, with no significant difference based on pore diameter.

CONCLUSION

Integrated image-based design and solid free-form fabrication can create scaffolds that attain desired elasticity and permeability while fitting any 3D craniofacial defect. The scaffolds could be manufactured from degradable polymers, calcium phosphate ceramics and titanium. The designed scaffolds supported significant bone regeneration for all pore sizes ranging from 300 to 1200 microns. These results suggest that designed scaffolds are clinically applicable for complex craniofacial reconstruction.

Developmental differences in understanding the causes, controllability and chronicity of disabilities

OBJECTIVE

The present study explored typically developing children's (n = 77) understanding of the causes, controllability and chronicity of disabilities.

DESIGN

Children in each of four age groups (4-5 years, 6-7 years, 9-10 years and 11-12 years) were interviewed to explore their ideas about children with physical disabilities (minor: missing thumb; major: wheel-chair bound), sensory disabilities (blindness and hearing loss), learning disabilities (non-specific and Down syndrome) and emotional/behavioural difficulties (attention deficit hyperactivity disorder and lack of social skills).

RESULTS

Significant age differences were found in children's understandings of the causes, controllability and chronicity of disabilities. Furthermore, children showed a greater understanding of salient disabilities.

CONCLUSIONS

Findings are discussed in terms of developmental changes and the role of experience in shaping children's understanding of disabilities.

Anti-endothelial cell antibodies from lupus patients bind to apoptotic endothelial cells promoting macrophage phagocytosis but do not induce apoptosis

OBJECTIVE

Anti-endothelial cell antibodies (AECA) have been reported to induce apoptosis. We investigated the induction of apoptosis by these autoantibodies and their involvement in the removal of apoptotic cells.

METHODS

AECA isolated from patients with active systemic lupus erythematosus (SLE) were incubated with human umbilical vein endothelial cells (HUVECs). AECA-positive sera were identified using a cell-based ELISA. Apoptosis was measured by morphology and phosphatidylserine externalization using flow cytometry with fluorescein isothiocyanate (FITC)-conjugated annexin V. Flow cytometry was used to investigate AECA binding to apoptotic cells using FITC-conjugated anti-human immunoglobulin G (IgG). Apoptotic endothelial cells were stained with a red dye (PKH26) and co-cultured with macrophages, and phagocytosis was visualized under phase contrast microscopy.

RESULTS

AECA from patients with SLE did not induce apoptosis compared with normal IgG (nIgG) at any time point, as assessed by morphology (at 24 h, P = 0.167) or phosphatidylserine externalization (at 24 h, P = 0.098). However, there was increased binding of AECA to apoptotic endothelial cells (48.8 +/- 11.9 compared with 25.8 +/- 6.7% AECA binding to freshly isolated cells, P< 0.001). These opsonized endothelial cells showed greater phagocytosis by macrophages (mean phagocytic index 24.9 +/- 4.5%) when cells opsonized with nIgG were compared with AECA (34.8 +/- 3.4% n = 5, P = 0.01).

CONCLUSION

In conclusion, AECA bind to apoptotic endothelial cells but do not induce endothelial cell apoptosis. Macrophage phagocytosis is increased by opsonization of apoptotic endothelial cells by AECA, a proinflammatory mechanism of cell removal.

The importance of resolution of inflammation in the pathogenesis of ANCA-associated vasculitis

The primary small-vessel systemic vasculitides are disorders that target small blood vessels, inducing vessel wall inflammation, and are associated with the development of anti-neutrophil cytoplasmic antibodies. Multiple organs are attacked, including the lungs and kidneys. Increasing knowledge of pathogenesis suggests that the antibodies activate neutrophils inappropriately, leading to endothelial and vascular damage. Cytokines, such as tumour necrosis factor, can facilitate damage by priming the neutrophils and activating endothelial cells. Apoptosis of infiltrating neutrophils is also disrupted by anti-neutrophil cytoplasmic antibody activation, and removal of these effete cells occurs in a pro-inflammatory manner, promoting persistent inflammation. The autoimmune response may be promoted by aberrant phagocytosis of apoptotic neutrophils by dendritic cells. Understanding the pathogenesis can help to rationalize existing therapies and indicate new approaches to therapy.

Prevention of heterotopic ossification after spinal cord injury with COX-2 selective inhibitor (rofecoxib)

STUDY DESIGN

A randomized, prospective, double-blind, placebo-controlled clinical trial.

OBJECTIVES

To determine the effect of COX-2-selective inhibitor on the prevention of heterotopic ossification (HO) after spinal cord injury (SCI).

SETTING

County and University Teaching Hospital, Miami, FL, USA.

METHODS

A total of 76 patients were enrolled in the study. Among them, 39 patients received placebo, and 37 received COX-2-selective inhibitor rofecoxib 25 mg daily for a period of 4 weeks. Prevention was started 3 weeks after spinal cord injury (SCI). In both groups of patients there was similar age as well as the level of SCI and ASIA impairment scale. Two methods were used to diagnose early HO, clinical symptoms and bone scintigraphy. Radiography was used for diagnosis of late stages of HO development.

RESULTS

A significantly lower incidence of HO was found in the rofecoxib group (13.4%) than in the placebo group (33.3%: P<0.05). In patients receiving rofecoxib, there was a 2.5 times lower relative risk of developing HO than in the placebo group (95% CI, 2.3-6). There were no patients who discontinued the study due to adverse effects of medication.

CONCLUSION

Our data suggest that COX-2-selective inhibitor rofecoxib is an effective medication in prevention of HO after SCI.

Long-term regulation of N-methyl-D-aspartate receptor subunits and associated synaptic proteins following hippocampal synaptic plasticity

Synaptic plasticity in the dentate gyrus is dependent on activation of the N-methyl-D-aspartate (NMDA)-subtype of glutamate receptors. In this study, we show that synaptic plasticity in turn regulates NMDA receptors, since subunits of the NMDA receptor complex are bidirectionally and independently regulated in the dentate gyrus following activation of perforant synapses in awake animals. Low-frequency stimulation that produced a mild synaptic depression resulted in a decrease in the NMDA receptor subunits NR1 and NR2B 48 h following stimulation. High-frequency stimulation that produced long-term potentiation resulted in an increase in NR1 and NR2B at the same time point. Further investigations revealed that in contrast to NR2B, NR1 levels increased gradually after long-term potentiation induction, reaching a peak level at 48 h, and were insensitive to the competitive NMDA receptor antagonist 3-3(2-carboxypiperazin-4-yl) propyl-1-phosphate. The increased levels of NR1 and NR2B at 48 h were found associated with synaptic membranes and with increased NMDA receptor-associated proteins, postsynaptic density protein 95, neuronal nitric oxide synthase and Ca(2+)/calmodulin-dependent protein kinase II, alpha subunit. These data suggest that the persistence of long-term potentiation is associated with an increase in the number of NMDA receptor complexes, which may be indicative of an increase in synaptic contact area.

Stimulation-induced reset of hippocampal theta in the freely performing rat

Previous research has suggested that visual and auditory stimuli in a working memory task have the ability to reset hippocampal theta, perhaps allowing an organism to encode the incoming information optimally. The present study examined two possible neural pathways involved in theta resetting. Rats were trained on a visual discrimination task in an operant chamber. At the beginning of a trial, a light appeared over a centrally located lever that the rat was required to press to receive a water reward. There was a 30-s intertrial interval before the next light stimulus appeared. After learning the task, all rats received surgical implantation of stimulating electrodes in both the fornix and the perforant path and recording electrodes, bilaterally in the hippocampus. After surgery, theta was recorded before and after the light stimulus to determine whether resetting to the visual stimulus occurred. During the intertrial interval, rats received single-pulse electrical stimulation of either the fornix or perforant path. Theta was recorded both before and after the electrical stimulation to determine whether resetting occurred. In this experiment, hippocampal theta was reset after all three stimulus conditions (light, perforant path, and fornix stimulation), with the greatest degree of reset occurring after the fornix stimulation. The results suggest that activation of the perforant path and fornix may underlie theta reset and provide a mechanism by which the hippocampus may enhance cognitive processing.

ERK inhibition attenuates 5-HT-induced contractions in fetal and adult ovine carotid arteries

Growth and differentiation-related pathways are much more active in immature than in mature, fully differentiated smooth muscle. Because mitogen-activated protein kinases (MAPK) are intimately involved with growth and differentiation, and the extracellular signal-regulated kinase (ERK) subfamily of MAPKs are involved in some contractile responses, the present studies examined the hypothesis that ERKs play an important and age-dependent role in smooth muscle contraction. The MAPK inhibitors PD098059 and UO126 both inhibited serotonin (5-HT) concentration-response relations more effectively in carotid arteries from term fetal lambs, than in corresponding arteries from mature non-pregnant adult sheep. This inhibition involved significant decreases in both the pD2 (adult: 2-fold; fetus: 4- to 15-fold) and the maximum efficacy (adult: 15-19%; fetus: 34-39%) of 5-HT. Accompanying this age-dependent effect on contraction, quantitative Western blot assays revealed that ERK1 and ERK2 abundances were 39% and 164% greater, respectively, in fetal than in adult carotid arteries. The abundance of the putative ERK target, caldesmon, however, was about 7-fold greater in adult than in fetal arteries. Together, the present results support the view that ERK abundance and activity is upregulated in fetal relative to adult arteries, and that one consequence of this upregulation is that the contribution of ERKs to contraction, at least that initiated by 5-HT2a receptors, is greater in fetal than adult carotid arteries. Whereas the phosphorylation mechanisms through which ERKs augment contraction remain uncertain and controversial, the present results suggest that emphasis should be shifted away from caldesmon and toward other critical contractile proteins, and how these proteins may contribute differently to development of agonist-induced contractile force in immature and mature arteries.

The effects of hyaluronic acid on fibronectin fragment mediated cartilage chondrolysis in skeletally mature rabbits

OBJECTIVE

Intraarticular Na-Hyaluronate (HA) exerts a beneficial effect on adolescent rabbits after fibronectin fragment (Fn-f) mediated cartilage injury. We extended our studies to a population of rabbits which have reached full skeletal maturity.

DESIGN

Adult male NZW rabbits received an injury with Fn-f and no further treatment; an injection of HA followed by Fn-f injury, or Fn-f injury followed by a single or weekly intraarticular injection of HA. All animals were sacrificed 38 days after receiving the Fn-f injury. After sacrifice, proteoglycan (PG) content was determined from articular cartilage from the medial femoral condyles and tibial plateaus. The patellae were processed for histology.

RESULTS

Cartilage PG contents were significantly reduced after Fn-f injection (P=0.0167) and were only slightly improved with HA pre-treatment. However, post-treatment with HA resulted in significant improvements in cartilage PG content when compared to Fn-f only (single HA, P=0.01; weekly HA,P =0.01). Loss of Safranin-O staining, cell loss, osteophyte formation and inflammation were present in the patellae following Fn-f injection. Pre-treatment with HA reduced these changes. More significant protection of cartilage and restoration of Fn-f injury were noted in animals receiving post-treatment with HA.

CONCLUSIONS

These results suggest that 38 days after Fn-f injury the lost PG content induced by Fn-f injection is substantially restored by weekly post-treatment with intraarticular HA in rabbits that have reached full skeletal maturity.

Early alterations in the collagen meshwork and lesions in the ankles are associated with spontaneous osteoarthritis in guinea-pigs

OBJECTIVE

The purpose of this study was to evaluate matrix changes in knee cartilage prior to development of surface disruptions and to examine the ankle for evidence of osteoarthritis (OA)-like lesions.

DESIGN

Guinea-pig ankles and knees were examined histologically or viewed with polarization microscopy to reveal changes in orientation of the collagen fibers.

RESULTS

The medial femoral condyles were virtually free of histologic changes at 3 months of age. Changes were present by 6 months. Medial tibial plateau histologic changes were seen at 3 months which became more pronounced with age. Alterations in the collagen meshwork corresponding to areas of proteoglycan (PG) loss were noted in animals with an intact articular surface as early as 3 months. Histologic changes were noted in the ankles as early as 3 months of age which included surface disruptions, cell loss and loss of PG staining. Only knee joint composite histology scores were significantly elevated at 3 months while both knee and ankle scores were significantly elevated at 6 months. Knee and ankle joint scores were not different from each other at 6 months.

CONCLUSIONS

Alterations in the orientation of the collagen network of the cartilage correlated with Safranin-O loss suggesting that alterations in collagen:PG interactions play a role in the early phases of the OA process and precede frank histologic changes in the articular surface. The results in this study report for the first time OA-like lesions occurring spontaneously in articular cartilage of the ankle in the guinea-pig.