A laboratory study of spontaneous platelet aggregation

During studies on platelet aggregation using the EEL platelet aggregation meter, 8% of the individuals tested were found to have platelets which aggregated spontaneously when citrated, platelet-rich plasma was stirred at 37 degrees C. The EEL aggregation meter differs from other machines in that it incorporates a vertical stirrer which subjects platelets to greater mechanical force. When using this machine it is suggested that spontaneous platelet aggregation is related to increased mechanical fragility of the platelets and low levels of plasma ADP-inhibitor.     

Characterization of BrkA Expression in Bordetella bronchiseptica

BrkA confers resistance to killing by complement in Bordetella pertussis. Complement resistance in Bordetella bronchiseptica was examined. Four B. bronchiseptica strains possessed the brkA gene; however, only three expressed the protein. Only the strain lacking BrkA was susceptible to complement. Introduction of the B. pertussis brkA gene restored BrkA expression to this strain but did not confer resistance. brkA was mutated in the strains that naturally expressed BrkA, and loss of BrkA did not confer sensitivity to complement. As a species, B. bronchiseptica is more resistant to complement than B. pertussis, and BrkA does not mediate resistance.     

A computer protocol to predict myocardial infarction in emergency department patients with chest pain

To achieve more appropriate triage to the coronary care unit of patients presenting with acute chest pain, we used clinical data on 1379 patients at two hospitals to construct a simple computer protocol to predict the presence of myocardial infarction. When we tested this protocol prospectively in 4770 patients at two university hospitals and four community hospitals, the computer-derived protocol had a significantly higher specificity (74 vs. 71 percent) in predicting the absence of infarction than physicians deciding whether to admit patients to the coronary care unit, and it had a similar sensitivity in detecting the presence of infarction (88.0 vs. 87.8 percent). Decisions based solely on the computer protocol would have reduced the admission of patients without infarction to the coronary care unit by 11.5 percent without adversely affecting the admission of patients in whom emergent complications developed that required intensive care. Although this protocol should not be used to override careful clinical judgment in individual cases, the computer protocol for the most part yields accurate estimates of the probability of myocardial infarction. Decisions about admission to the coronary care unit based on the protocol would have been as effective as those actually made by the unaided physicians who cared for the patients, and less costly. Whether physicians who are aided by the protocol perform better than unaided physicians cannot be determined without further study.     

Alpha 1-antitrypsin deficiency and anti-proteinase 3 antibodies in anti-neutrophil cytoplasmic antibody (ANCA)-associated systemic vasculitis.

alpha 1-antitrypsin (alpha 1-AT) is a naturally occurring inhibitor of proteinase 3 (PR3) and elastase, two of the target antigens of anti-neutrophil cytoplasmic antibodies (ANCA). An increased incidence of alpha 1-AT phenotypes associated with dysfunctional alpha 1-AT or low serum levels has been reported in patients with anti-PR3 antibodies. We have studied the relationship between ANCA, and phenotypes and serum levels of alpha 1-AT. Phenotypes usually associated with a moderate or severe reduction in alpha 1-AT serum levels or in dysfunctional activity were found more often in individuals with anti-PR3 antibodies than in the general population: four of the 31 patients (13%) with anti-PR3 antibodies had phenotypes MZ (n = 2), S (n = 1) or Z (n = 1) (P < 0.05). However, the corresponding alpha 1-AT serum levels were normal (n = 3) or elevated (n = 1). None of the 31 sera with anti-PR3 antibodies had low levels of alpha 1-AT. No abnormal alpha 1-AT phenotype was demonstrated in seven patients with anti-elastase antibodies, despite a low level of alpha 1-AT in one serum. Anti-myeloperoxidase antibodies are common in patients with ANCA, but no abnormal phenotype or low serum alpha 1-AT level was demonstrated in any of 29 sera containing these antibodies. Finally anti-glomerular basement membrane (GBM) antibodies occur occasionally in patients with ANCA-associated diseases, but again none of 10 sera had an abnormal alpha 1-AT phenotype or low serum level. ANCA were not demonstrated by indirect immunofluorescence in any serum from 73 patients with abnormal alpha 1-AT phenotypes. These results confirm that patients with anti-PR3 antibodies often have alpha 1-AT phenotypes that are usually associated with low serum levels of alpha 1-AT or with dysfunctional protein. Nevertheless, the incidence of anti-PR3 antibodies in patients with abnormal alpha 1-AT phenotypes is very low. This probably reflects the rarity of Wegener's granulomatosis, the major disease associated with anti-PR3 antibodies, and the relative frequency of abnormal alpha 1-AT phenotypes. The mechanism for the development of anti-PR3 antibodies in patients with abnormal alpha 1-AT phenotypes is not clear, but may relate to the increased propensity of unbound and uninhibited PR3 to stimulate autoantibody production.     

Sedative but not anxiolytic properties of benzodiazepines are mediated by the GABA(A) receptor alpha1 subtype

Inhibitory neurotransmission in the brain is largely mediated by GABA(A) receptors. Potentiation of GABA receptor activation through an allosteric benzodiazepine (BZ) site produces the sedative, anxiolytic, muscle relaxant, anticonvulsant and cognition-impairing effects of clinically used BZs such as diazepam. We created genetically modified mice (alpha1 H101R) with a diazepam-insensitive alpha1 subtype and a selective BZ site ligand, L-838,417, to explore GABA(A) receptor subtypes mediating specific physiological effects. These two complimentary approaches revealed that the alpha1 subtype mediated the sedative, but not the anxiolytic effects of benzodiazepines. This finding suggests ways to improve anxiolytics and to develop drugs for other neurological disorders based on their specificity for GABA(A) receptor subtypes in distinct neuronal circuits.     

Sequences of two kinetoplast minicircle DNAs of Trypanosoma (Nannomonas) congolense

Random minicircle DNA molecules were released from isolated kinetoplast network DNA of Trypanosoma congolense by BamHI digestion and cloned into plasmid pUC19. The sequences of two cloned minicircles (958 bp and 964 bp) were determined. Both minicircles contain the 13 bp sequence, 5'-GGGGTTGGTGTAA-3', thought to be the replication origin of minicircles in other trypanosomatids. The two minicircles have extensive homology in the 120 bp preceeding, and the 20 bp following, this 13-mer but only scattered homology elsewhere. Both possess tandem repeats downstream of the 13-mer. Comparison of these minicircles with minicircle sequences from other trypanosomatids reveals that they have the same general sequence organization as the others although only the 13-mer and its flanking regions are homologous.     

Growth, morbidity, and mortality in a cohort of institutionalized HIV-1-infected African children

OBJECTIVE: As a result of the HIV epidemic in Africa, much debate exists on whether institutionalized compared with community-based care provides optimum management of infected children. Previous reports calculated 89% mortality by age 3 years among outpatients in Malawi. No similar data are available for infected children in institutionalized care. We characterized patterns of morbidity and mortality among HIV-1-infected children residing at an orphanage in Nairobi. METHODS: Medical records for 174 children followed over 5 years were reviewed. Mortality was analyzed by Kaplan-Meier methods with adjustment to account for survival in the community before admission. Anthropometric indices were calculated to include mean z scores for weight for length and length for age. Low indices reflected wasting and stunting. Opportunistic infections were documented. RESULTS: Of 174 children, 64 had died. Survival was 70% at age 3 years. Morbidity included recurrent respiratory tract infections, gastroenteritis, parotitis, and lymphoid interstitial pneumonitis. No new cases of tuberculosis disease were noted after admission. Mean z scores for length for age suggested overall stunting (z = -1.65). Wasting was not observed (z = -0.39). CONCLUSION: The optimal form of care for HIV-infected children in resource-poor settings may be the development of similar homes. Absence of tuberculosis disease in long-standing residents may have contributed to improved survival. Stunting in the absence of wasting implied that growth was compromised by opportunistic infections and other cofactors.     

Development of Na+-dependent hexose transport in a cultured line of porcine kidney cells

LLC-PK1 cells in culture do not concentrate alpha-methylglucoside (alpha-meG) during their early growth phase but develop the capacity to concentrate this hexose as the growth rate decreases in confluent cultures. The concentrating ability is dependent on the Na+ electrochemical gradient and is inhibited by phlorizin with KI,0.5 approximately 0.2 microM. The development of the concentrative capacity can be accelerated by the Friend cell inducer hexamethylene bisacetamide (HMBA) and by the phosphodiesterase inhibitors dibutyryl cAMP, theophylline, and 1-methyl-3-isobutylxanthine (MIX). In cultures treated with any of these differentiation-accelerating chemicals, the development of alpha-meG concentrating capacity is severely inhibited by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) but not by inactive (in tumor promotion) analogs of TPA. In all cases, an early event in the development of alpha-meG accumulating capacity is an elevated intracellular cAMP concentration; however the results suggest that this increase in cAMP may be necessary but not sufficient to induce the differentiated hexose-accumulating capacity.     

Longitudinal studies on the egg drop syndrome 1976 (eds-76) in the fowl following experimental infection at 1-day-old

Following oral infection of 1-day-old chicks with egg drop syndrome - 1976 (EDS-76) virus (strain D61) lateral transmission of the virus was demonstrated throughout the rearing period. At point of lay, pullets previously infected at 1-day-old responded to EDS-76 inactivated vaccine given intramuscularly with a pronounced rise in haemagglutination inhibition antibody titre, but failed to respond to oral challenge with live virus. Egg production and shell quality were not affected following EDS-76 infection at 1-day-old, but egg weight was reduced and internal egg quality adversely affected.     

Marek's disease as a model for the Landry--Guillain--Barré syndrome: latent viral infection in nonneuronal cells accompanied by specific immune responses to peripheral nerve and myelin.

In the chicken, Marek's disease virus (MDV) induces a demyelinating peripheral neuropathy that, early in the course of the disease, is histopathologically indistinguishable from that seen in the Landry--Guillain--Barré syndrome in man. A continuing role for a productive infection in the pathogenesis of this disease is unlikely, since neither MDV nor MDV antigens can be characteristically detected in nerves or spinal ganglia examined at necropsy. The authors investigated the possible role of a latent viral infection by explanting and maintaining in vitro the sciatic nerves and spinal ganglia from diseased birds. In these tissues, viral specific products were induced and detected by immunofluorescence and ultrastructural methods early after explanation in well-isolated Schwann cells, satellite cells, and lymphocytes. Later, virus was detected in fibroblasts, macrophages, and neoplastic lymphoblastoid cells. Neurons and myelinating Schwann cells, in contrast, did not replicate the agent. Specific cell-mediated and humoral immune responses to chicken peripheral nerve and peripheral nerve myelin were demonstrated early in the course of the disease. When considered relative to potential pathogenetic mechanisms, these results suggest that Marek's disease neuropathy is initiated by the establishment of a latent viral infection in neuronal supporting cells. A specific immune response to viral-induced antigens on these cells could, in turn, result in subsequent demyelination.