Detection of Borrelia burgdorferi antigens in cerebrospinal fluid

We examined CSF for Borrelia burgdorferi antigens using antigen-capture ELISA and Western (immuno) blot. Antigen-capture ELISA was positive in 38 of 77 (49%) CSF samples obtained from neurologic patients with presumed B burgdorferi infection, compared with one of 34 (3%) CSF samples obtained from other neurologic disease controls who came from a region endemic for Lyme disease. Western immunoblot was positive for B burgdorferi antigens in 12 of 22 (55%) CSF samples from the B burgdorferi infected groups, compared with none of 11 CSF samples from the control group. CSF antigen detection should prove helpful in evaluating patients for suspected neurologic Lyme disease.

Cloning and characterization of a mouse 3-methyladenine/7-methyl-guanine/3-methylguanine DNA glycosylase cDNA whose gene maps to chromosome 11

In Escherichia coli, the repair of 3-methyladenine (3MeA) DNA lesions by DNA glycosylases prevents alkylation induced cell death. We described previously the isolation of a human 3MeA DNA glycosylase (AAG) cDNA that maps to chromosome 16 and hybridizes to specific genomic DNA fragments from a number of mammals, including mouse. As a first step in the generation of a 3MeA DNA glycosylase deficient mouse by homologous replacement in embryonic stem cells, we have cloned the mouse 3MeA DNA glycosylase cDNA. The cloned 1095 base pair cDNA contains a complete 333 amino acid open reading frame that predicts a 36.5 kDa protein and hybridizes to a 1.5 kb mRNA transcript. Mouse 3MeA DNA glycosylase (Aag) transcript levels vary by up to 21 fold among tissues, being highest in the testes and lowest in the heart. The Aag cDNA encodes a glycosylase able to release 3MeA, 7-methylguanine (7MeG) and 3-methylguanine (3MeG) from alkylated DNA. The expression of Aag in E. coli provides substantial resistance against killing by methylating agents, but, unlike its E. coli counterparts, the Aag glycosylase fails to protect against killing by ethylating and propylating agents. A 232 amino acid stretch of the predicted mouse protein shares extensive amino acid identity with rat (93%) and human (83%) 3MeA DNA glycosylases and we observe that all three mammalian glycosylases have a bipartite nuclear localization signal. The Aag gene maps to mouse chromosome 11, suggesting a segment of conserved synteny between mouse chromosome 11 and human chromosome 16, which bears the human 3MeA DNA glycosylase gene. Cloning the mouse 3MeA DNA glycosylase cDNA is a step toward understanding the role of this DNA repair enzyme in mammals.

[The growth pattern of atherosclerotic rabbit aortic smooth muscle cells in culture]

Rabbit aortic smooth muscle cells (SMCs) both from normal and atherosclerotic (AS) animals were cultured for study on their growth activities and the relation to the cell cycle kinetics. The growth activities of different cell populations were compared by measuring cell doubling time, labelling index and mitosis index. For cell cycle analysis, 3H-TdR flash labelling method was employed. The results showed that SMCs derived from atherosclerotic rabbits grew more rapidly in culture than those from normal animals, the cell doubling time in the AS group was shorter than normal, 28.8 hrs versus 40.8 hrs, while the labelling and mitosis index in the AS group were higher. SMC cell cycle analysis showed that their generation time was 9.6-9.9 hrs and there was no significant difference of the distribution of cell cycle phases and their generation time between SMCs from AS and control group. The results indicate that the increased proliferative activities of atherosclerotic SMCs are not due to the change of their cell cycle kinetics, but having more cells emerging from G0/G1 phase into S phase.

Site-specific degradation of Streptomyces lividans DNA during electrophoresis in buffers contaminated with ferrous iron

Streptomyces lividans DNA contains a modification which makes it susceptible to double-strand cleavage during electrophoresis in buffers contaminated with ferrous iron (which may be present in some batches of EDTA). The cleavage of the DNA is site-specific and the average fragment size resulting from limit digestion of total S. lividans DNA is about 6kb. DNA from Streptomyces coelicolor A3(2) and several other Streptomyces strains, and from E. coli, is not cleaved under the same conditions. A S. lividans mutant has been isolated which lacks the DNA modification. We suspect that many reports of "poor" preparations of S. lividans plasmids may be due to the above effect.

Infections caused by Penicillium marneffei in China and Southeast Asia: review of eighteen published cases and report of four more Chinese cases

One accidental and 17 natural human infections caused by Penicillium marneffei have been reported in the literature. The accidental infection, in Paris, followed inoculation of a culture from a Vietnamese bamboo rat into the finger of a mycologist. All patients with natural infections had lived or traveled in the Far East. Nine of these patients were Chinese, all from Guangxi Zhuang Autonomous Region. The four additional infections from Guangxi reported herein bring the total to 21 natural infections. P. marneffei is a primary pathogen of humans, causing two clinical types of disease: focal infection and fatal, progressive, disseminated infection. There are three histopathologic reactions: (1) granulomatous; (2) suppurative; and (3) anergic and necrotizing. The first two reactions are seen in patients with "normal" immunity and the third in patients with compromised immunity. P. marneffei is unique among species of Penicillium because of its thermal dimorphism, its recognized ecologic niche (restricted to the Far East), and its propensity to infect the lungs and the reticuloendothelial system and to proliferate within histiocytes.

Hemodynamic influences on sinus node recovery time: effects of autonomic blockade

Ten patients with normal sinus node function were evaluated prospectively, to determine whether the decrease in blood pressure during rapid atrial pacing shortens the corrected sinus node recovery time. All patients had 30 seconds of atrial pacing at cycle lengths from 600 to 300 ms, with continuous arterial pressure monitoring, before and after intravenous administration of propranolol (0.2 mg/kg body weight) and atropine (0.04 mg/kg). In the control state, a decrease in corrected sinus node recovery time was recorded with faster atrial pacing rates, which was significantly related to the initial drop in systolic blood pressure at the onset of atrial pacing. Specifically, as the initial pressure drop increased from 15 mm Hg or less to 16 to 45 and 45 to 100 mm Hg, corrected sinus node recovery time decreased from 272 +/- 79 to 205 +/- 70 ms (p less than 0.04) and to 134 +/- 120 ms (p less than 0.04), respectively. In contrast, after autonomic blockade, the corrected sinus node recovery time was prolonged, in a near linear fashion, as atrial pacing rates increased. The magnitude of blood pressure drop with atrial pacing did not differ significantly from that in the control state at similar pacing rates. These findings suggest that hypotension during rapid atrial pacing activates autonomic reflexes that significantly shorten the corrected sinus node recovery time. Autonomic blockade negates this effect and the corrected sinus node recovery time prolongs with faster atrial pacing.

Wide QRS tachycardia due to AV nodal reentry and a "bystander" bypass tract with slow conduction properties

An unusual mechanism for recurrent, wide QRS complex supraventricular tachycardia is described in this report. A 25-year-old man with normal PR and QRS intervals during sinus rhythm was shown to have preexcitation with a left bundle branch block pattern during tachycardia and during atrial pacing. Electrophysiologic studies demonstrated slow and decremental conduction properties in an accessory "bystander" AV pathway utilized for antegrade conduction during AV nodal reciprocating tachycardia. The differential diagnosis of this tachycardia is discussed in detail.

Expression of a Streptomyces plasmid promoter in Escherichia coli

A 166-bp DNA fragment from the Streptomyces multicopy plasmid pIJ101 with in vivo promoter activity both in Streptomyces lividans and in Escherichia coli was isolated. The start point of the RNA transcribed from this fragment, determined by high resolution S1 nuclease mapping, was the same in S. lividans and in E. coli. This suggests that the E. coli RNA polymerase recognizes the same sequence determinants and chooses the point of initiation of RNA synthesis in the same way as the corresponding S. lividans enzyme. The putative promoter sequence shows good homology to the E. coli promoter consensus sequence in the '-35' region but poor homology in the '-10' region.