Ligand binding and covalent structure of an oxygen-binding heme protein from Rhodobacter sphaeroides, a representative of a new structural family of c-type cytochromes

The amino acid sequence of an oxygen-binding heme protein (SHP) from Rhodobacter sphaeroides has been determined. The cysteines, which bind the single heme group in the 112-residue protein, are located at positions 43 and 46. SHP is similar in size to the large membrane-bound form of the class I cytochrome c5 of Azotobacter vinelandii (116 residues) and in the location of the heme binding site at positions 48 and 51. Two extra cysteines in SHP (residues 89 and 97) are located in positions similar to those of cytochrome c5 (residues 98 and 101) and form a disulfide bridge in both proteins. In total, four regions of alpha-helix are predicted, covering 46% of the protein, which is comparable to that in other small cytochromes. SHP is thus distantly related to small class I c-type cytochromes but is representative of a distinct family by virtue of its high-spin nature, the lack of a strong sixth ligand, and its capacity to bind oxygen. Potentially, the most important characteristic of SHP is its ability to transiently bind oxygen during autoxidation, which occurs with a half-life of 3 min with a 4-fold excess of O2. SHP also binds carbon monoxide, azide, and cyanide. The kinetics of reduction by free flavins indicate that SHP is less reactive than other class I cytochromes c and that the heme is less accessible to solvent. There is localized positive charge (+3) at the site of reduction of SHP, although the overall protein charge is -2. This may account in part for the ability of SHP to bind anions.     

Disruption of cellular translational control by a viral truncated eukaryotic translation initiation factor 2alpha kinase homolog

Phosphorylation of eukaryotic translation initiation factor 2alpha (eIF2alpha) is a common cellular mechanism to limit protein synthesis in stress conditions. Baculovirus PK2, which resembles the C-terminal half of a protein kinase domain, was found to inhibit both human and yeast eIF2alpha kinases. Insect cells infected with wild-type, but not pk2-deleted, baculovirus exhibited reduced eIF2alpha phosphorylation and increased translational activity. The negative regulatory effect of human protein kinase RNA-regulated (PKR), an eIF2alpha kinase, on virus production was counteracted by PK2, indicating that baculoviruses have evolved a unique strategy for disrupting a host stress response. PK2 was found in complex with PKR and blocked kinase autophosphorylation in vivo, suggesting a mechanism of kinase inhibition mediated by interaction between truncated and intact kinase domains.     

Islet amyloid polypeptide in patients with pancreatic cancer and diabetes

Population-based psychiatric admission rates vary across geographic areas, but reasons for this variation are unknown. Insofar as Community Mental Health Centers (CMHCs) provide outpatient services that may deter the need for hospitalization, the presence and structural characteristics of CMHCs may have an impact on a population's psychiatric admission rates. This study uses small area analysis to examine how general hospital psychiatric admission rates are associated with CMHC characteristics. Based on a survey of all CMHCs in Iowa and corresponding small area variation data, it was found that population admission rates were higher in areas closer to the CMHC and lower in outlying catchment areas, adjusting for age, sex, and urban/rural differences in populations. There was little evidence that differences in staffing and service variables influenced admission rates, although greater CMHC staff coverage by social workers and psychiatric residents was associated with lower admission rates. The results suggest that CMHCs do not lower an area's hospitalization rate, and in fact, the presence of CMHCs may promote a "supplier-induced demand" phenomenon of higher admissions.     

Time-dependent effects of repeated amphetamine treatment on norepinephrine in the hypothalamus and hippocampus assessed with in vivo microdialysis

The effects of repeated amphetamine (AMPH) pretreatment on norepinephrine (NE) neurotransmission in the hypothalamus and hippocampus were assessed using in vivo microdialysis. Rats were pretreated with either saline or an escalating-dose AMPH regimen (1-->10 mg/kg) over 10 consecutive days, and then were withdrawn from AMPH for either 1 day or 30 days, at which time the animals underwent two consecutive days of testing. As expected, repeated treatment with AMPH resulted in time-dependent changes in both spontaneous locomotor activity and in the psychomotor response to a subsequent challenge injection of AMPH. In addition, repeated exposure to AMPH resulted in time-dependent and regionally-specific changes in the basal concentrations of NE in dialysate, and in the NE response to an AMPH challenge. For example, AMPH pretreatment produced a persistent (at least one month) increase in the basal concentration of NE in the hippocampus, but not the hypothalamus, although the response to an AMPH challenge was altered in both structures. It is suggested that AMPH treatment produces adaptations in NE systems that far outlast the acute effects of the drug, and that these may contribute to both transient and more persistent behavioral sequelae associated with the discontinuation of chronic AMPH use.     

Dopamine D3 receptor mutant mice exhibit increased behavioral sensitivity to concurrent stimulation of D1 and D2 receptors

The dopamine D3 receptor is expressed primarily in regions of the brain that are thought to influence motivation and motor functions. To specify in vivo D3 receptor function, we generated mutant mice lacking this receptor. Our analysis indicates that in a novel environment, D3 mutant mice are transiently more active than wild-type mice, an effect not associated with anxiety state. Moreover, D3 mutant mice exhibit enhanced behavioral sensitivity to combined injections of D1 and D2 class receptor agonists, cocaine and amphetamine. However, the combined electrophysiological effects of the same D1 and D2 agonists on single neurons within the nucleus accumbens were not altered by the D3 receptor mutation. We conclude that one function of the D3 receptor is to modulate behaviors by inhibiting the cooperative effects of postsynaptic D1 and other D2 class receptors at systems level.     

Joint loading with valgus bracing in patients with varus gonarthrosis

The purpose of this study was to determine whether a brace designed to unload varus degenerative knees actually alters medial compartment loads by decreasing the adduction moment. Eleven patients who had arthrosis confined to the medial compartment were fitted with a valgus brace and tested before and after brace wear with pain and function scoring instruments and by automated gait analysis. The biomechanical data from these patients were compared with those from 11 healthy control subjects. Scores from an analog pain scale decreased 48% with brace wear, and function with activities of daily living increased 79%. Mean adduction moment without the brace measured 4.0 +/- 0.8% body weight times height versus 3.6 +/- 0.8% body weight times height when wearing the brace (10% decrease). The mean adduction moment for control subjects was 3.5 +/- 0.6% body weight times height. Thus, the mean adduction moment decreased from approximately one standard deviation from the normal mean to a value that is similar to the control value. Nine of 11 patients had a decrease in the adduction moment with the brace, five of 11 patients had a reduction higher than 10%, and decreases in this moment were as high as 32%. This study shows that pain, function, and biomechanical knee loading can be altered by a brace designed to unload the medial compartment of the knee.     

P2Y2 nucleotide receptors expressed heterologously in sympathetic neurons inhibit both N-type Ca2+ and M-type K+ currents

The P2Y2 receptor is a uridine/adenosine triphosphate (UTP/ATP)-sensitive G-protein-linked nucleotide receptor that previously has been reported to stimulate the phosphoinositide signaling pathway. Messenger RNA for this receptor has been detected in brain tissue. We have investigated the coupling of the molecularly defined rat P2Y2 receptor to neuronal N-type Ca2+ channels and to M-type K+ channels by heterologous expression in rat superior cervical sympathetic (SCG) neurons. After the injection of P2Y2 cRNA, UTP inhibited the currents carried by both types of ion channel. As previously reported [Filippov AK, Webb TE, Barnard EA, Brown DA (1997) Inhibition by heterologously expressed P2Y2 nuerones. Br J Pharmacol 121:849-851], UTP inhibited the Ca2+ current (ICa(N)) by up to 64%, with an IC50 of approximately 0.5 microM. We now find that UTP also inhibited the K+M current (IK(M)) by up to 61%, with an IC50 of approximately 1.5 microM. UTP had no effect on either current in neurons not injected with P2Y2 cRNA. Structure-activity relations for the inhibition of ICa(N) and IK(M) in P2Y2 cRNA-injected neurons were similar, with UTP >/= ATP > ITP > GTP,UDP. However, coupling to these two channels involved different G-proteins: pretreatment with Pertussis toxin (PTX) did not affect UTP-induced inhibition of IK(M) but reduced inhibition of ICa(N) by approximately 60% and abolished the voltage-dependent component of this inhibition. In unclamped neurons, UTP greatly facilitated depolarization-induced action potential discharges. Thus, the single P2Y2 receptor can couple to at least two G-proteins to inhibit both Ca2+N and K+M channels with near-equal facility. This implies that the P2Y2 receptor may induce a broad range of effector responses in the nervous system.     

Hepatic hemangioma. Analysis of 103 cases. Clinical considerations and imaging methods

Hemangiomas are the most common benign vascular tumor found in the liver. In this study, 103 cases of hepatic hemangiomas were analysed in a retrospective manner. Image aspects such as those seen in ultrassonography, computed tomography, nuclear magnetic resonance and arteriography are discussed. The incidence was higher amongst the female sex, between individuals from 40 to 60 years old, which presented predominantly without symptoms (66%) and localized mainly in the right hepatic lobe (74%). The meaning of those aspects, when adopted, permits the clinicians to differentiate benign from malignant nodular lesions in the liver.     

District sputum smear microscopy services in Malawi

SETTING: Government hospitals and health centres in 23 districts in Malawi. OBJECTIVE: To determine 1) the number and smear-positivity rate of sputum samples submitted at health centres and hospitals, and 2) the time for sputum samples to get from health centres to smear examination. DESIGN: Prospective data collection on sputum specimens coming from health centres to hospital laboratories, and over the equivalent time period, retrospective data collection from laboratory sputum registers. RESULTS: Information was collected over a period of 5.6 months during 1997. Of 21 527 patients submitting sputum samples, 16995 (79%) were from within the hospital and 4532 (21%) were from health centres. Of 15 833 new TB suspects, 12 804 (81%) submitted sputum within the hospital and 3029 (19%) were from health centres. The overall smear-positivity rate was 11.9%: the proportion of new suspects who were smear-positive was significantly higher in health centres (14.1%) compared with hospital-based patients (11.4%, P < 0.05); 27% of all sputum specimens from health centres took 8 days or longer to get to smear examination. Sputum smears were positive from 1-30 days between submission and laboratory examination. CONCLUSION: Fewer sputum samples are submitted at health centres compared with hospitals, and there may be long delays between sputum submission and smear examination. The precise reasons are unclear, but health centre staff need training about the importance of timely case finding procedures.     

The readability of currently used surgical/procedure consent forms in the United States

We report a patient diagnosed prenatally on routine fetal ultrasound, at 30 weeks' gestation, with subdural haemorrhage. The mother had suffered a mild abdominal trauma and had Factor XI deficiency; however, both were felt to be aetiologically insignificant. Prenatal follow-up showed a complete resolution of the haematoma and no postnatal sequelae have been noted to date. The aetiologies and outcomes in the few previously reported cases are reviewed and compared with our case.