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Biomedical subjects

J Weber

Publications and source records attributed to J Weber.

At least 469 records · Page 26Linked to original sources
PubMed1989

Fidelity of human immunodeficiency virus type I reverse transcriptase in copying natural DNA.

Reverse transcriptase from the human immunodeficiency virus type I (HIV-1) was expressed in E. coli and purified to near homogeneity. The enzyme was shown to contain reverse transcriptase, DNA polymerase and ribonuclease H activities. The DNA polymerase activity converted singly-primed phi X174 (+) DNA into the double-stranded form. Two third of the replication product is ligatable to covalently closed circular DNA (RFIV-form DNA) indicating that DNA synthesis by HIV reverse transcriptase can proceed until the enzyme matches the 5'-end of a pre-existing primer molecule. The in vitro accuracy of HIV reverse transcriptase was measured with the phi X174am16 reversion assay to be 1/7,400. Reversion rates for the individual mispairs were determined from pool bias studies to be 1/8,000 for the dGMP:T template mismatch, 1/35,000 for the dGMP:A template mismatch, 1/45,000 for the dAMP:G template mismatch, 1/73,000 for the dCMP:T template mispair, 1/140,000 for the dCMP:A template mispair, and 1/180,000 for the dGMP:G template mismatch. The dTMP:T template mispair was below the detection limit of the assay indicating a reversion rate of less than 1/300,000 for this particular mispair.

Cloning, Molecular↗
PubMed1989

HIV-1 infection among intravenous drug users in Manhattan, New York City, from 1977 through 1987.

Intravenous drug users are the second largest group to develop the acquired immunodeficiency syndrome, and they are the primary source for heterosexual and perinatal transmission in the United States and Europe. Understanding long-term trends in the spread of human immunodeficiency virus among intravenous drug users is critical to controlling the acquired immunodeficiency syndrome epidemic. Acquired immunodeficiency syndrome surveillance data and seroprevalence studies of drug treatment program entrants are used to trace seroprevalence trends among intravenous drug users in the borough of Manhattan. The virus entered this drug-using group during the mid-1970s and spread rapidly in 1979 through 1983. From 1984 through 1987, the seroprevalence rate stabilized between 55% and 60%--well below hepatitis B seroprevalence rates. This relatively constant rate is attributed to new infections, new seronegative persons beginning drug injection, seropositive persons leaving drug injection, and increasing conscious risk reduction.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Effect of timolol on the amplitude and dynamics of accommodation.

There is still debate about whether the ciliary muscle is innervated by the sympathetic nervous system. We investigated the amplitude and the dynamics of accommodation under influence of the non-selective beta-blocker timolol. For this purpose the variations in thickness of the human lens during step-like changes in accommodation were measured with high-resolution A-scan echography. Results showed that the dynamics of accommodation, expressed in the time constants of the response, were affected as well as the amplitude.

Accommodation, Ocular↗
PubMed1989

Motor abnormalities of digestive and urinary tracts in patients on ventilator for acute exacerbation of chronic obstructive pulmonary disease.

The frequency of digestive motor abnormalities was evaluated in 30 consecutive patients ventilated for acute exacerbation of chronic obstructive pulmonary disease. Total and segmental colonic transit times were investigated by radiopaque marker transit time in all patients. Eleven patients also had rectoanal and esophageal manometries, combined with urodynamic study in eight cases. The results show that total radiopaque marker transit time was increased, 201 +/- 14 hr (mean +/- SE), with two main regions of decreased transit rates: the right colon (42% of global transit time) and the rectosigmoid (36%). Delayed transit of radiopaque markers in nine of 11 cases was combined with esophageal motor dysfunction and absence of rectoanal inhibitory reflex. In three of eight cases there was disinhibition of urinary bladder contraction, and micturition was impossible in two of eight cases. We conclude that patients on ventilator for exacerbation of chronic obstructive pulmonary disease always have a delayed colonic transit time with diffuse digestive and bladder motor dysfunction.

Acute Disease↗
PubMed1989

The visual field in advanced glaucoma.

For analysis of the morphology of the visual field in advanced glaucoma, we tested 62 eyes of 54 late stage glaucoma patients using program 10-2 on the Humphrey Field Analyzer. The fields, which were already reduced to a small central isle, had mostly typical, asymmetric borders with their largest extend to the temporal lower quadrant and their smallest extend to the upper nasal quadrant. An upper nasal step was very frequent. The boundaries are equivalent to the retinal nerve fiber lines. Actually, the glaucomatous isle is a 'centro-coecal isle', representing a remnant of intact maculo-papillary nerve fiber bundles. A test with a 2 degrees spacing like the Humphrey program 10-2 proved to be useful for routine perimetry in these cases.

Adolescent↗
PubMed1989

Graphical analysis of topographical trends (GATT) in automated perimetry.

The assessment of change in analysis of visual fields is one of the most difficult tasks in automated perimetry. A new, computerized method shows the original fields and the topographic trends in one easy graphic display. This new way of analysis the 'GATT' superimposes the grayscale maps of two fields with a simple logic, producing the following patterns: all stable, unchanged areas are displayed normally; in changed areas, the grayscale of the first and the second field are mixed in the form of stripes. The contrast between the stripes indicates the amount of change. The orientation of the stripes depends on the direction of change: horizontal stripes mean deterioration, vertical stripes mean improvement. The GATT is also able to compare 4 fields, using the same patterns. In addition, a scatterboard without stripes indicates areas of high fluctuation, but without a significant change in the course of the 4 fields. The GATT enables a quick, quantitative judgement of the trends of visual fields.

Computer Graphics↗
PubMed1989

Hemolytic and toxic properties of Hydra attenuata nematocysts.

Crude extract prepared from isolated and purified nematocysts (stenoteles, desmonemes, isorhizas) of Hydra attenuata Pall. (Cnidaria, Hydrozoa) contains two main toxic proteins. The first is a hemolysin (100-200,000 mol.wt) which also causes initial spasmodic contractions in larval and adult specimens of Drosophila. Both, hemolytic and neurotoxic activities are inhibited by low concentrations of Triton X-100. The second protein (30-100,000 mol.wt), which is not susceptible to Triton causes long lasting paralysis leading to death of the test animals (LD50 approximately 5 mg crude nematocyst extract per kg). Neither of the toxins is identical with the previously described phospholipase.

Animals↗
PubMed1989

Multifactorial genesis of enhanced platelet aggregability in patients with nephrotic syndrome.

Platelet aggregation, beta-thromboglobulin (beta-TG) and platelet factor 4 (PF 4) release and thromboxane B2 (TxB2) formation in stimulated platelet-rich plasma were investigated in 13 patients with nephrotic syndrome who had normal serum creatinine levels (creatinine clearance greater than 70 ml/min/1.73 m2). In contrast to 13 sex- and age-matched controls, spontaneous platelet aggregation only occurred in patients with nephrotic syndrome with correlation to serum albumin and plasma fibrinogen levels. The EC50 (estimated concentration of aggregating agent to cause half maximum velocity of primary aggregation) for ADP and collagen and threshold concentration of arachidonic acid (threshold AA) were decreased in patients with nephrotic syndrome, reflecting a hyperaggregable state. In patients with nephrotic syndrome EC50 ADP values were significantly correlated to serum albumin, serum cholesterol and plasma fibrinogen, however, EC50 collagen or threshold AA did not correlate to these parameters. Plasma beta-TG levels were increased in patients, whereas plasma PF 4 levels were not significantly changed in patients compared to controls. In vitro TxB2 formation was elevated in patients only after stimulation with AA. Nevertheless, after stimulation with collagen and ADP, TxB2 formation was unchanged in patients compared to controls. Platelet hyperaggregability in nephrotic patients was confirmed in our study. However, unchanged thromboxane B2 formation after collagen stimulus as well as missing correlations between EC50 collagen or threshold AA and serum albumin were contradictory to the hypothesis that enhanced AA availability due to hypoalbuminemia is responsible for platelet hyperaggregability. Platelet hyperaggregability in terms of EC50 ADP being associated with serum albumin levels as well as to serum cholesterol and plasma fibrinogen indicate a multifactorial genesis.

Female↗
PubMed1989

Successful piezoelectric lithotripsy of a common bile duct stone.

The "problematic common bile duct stone", which cannot be extracted primarily by routine endoscopic methods is one of the indications for extracorporeal shock wave lithotripsy (ESWL). We report on the successful piezoelectric lithotripsy of a large common bile duct stone in an 86-year-old patient. Focusing was achieved by ultrasound without problems; the resulting fragments were extracted endoscopically without difficulty. No side effects were observed in this painless piezoelectric lithotripsy.

Aged↗
PubMed1989

[Graphic analysis of topographic trends in perimetry follow-up of glaucoma].

GATT is a new, graphic method of showing the development of visual fields in glaucoma and other diseases. The grayscale maps of a series of two or four fields are superimposed with a simple logic, producing the following pattern: all stable areas are displayed in the usual way, thus giving defects a typical appearance. Changed areas appear as stripes, alternately showing the grayscale of the two fields. The orientation of the stripes is vertical in zones of improvement and horizontal in areas of deterioration. The level of contrast indicates the amount of change. The authors examined the development of the visual fields in 30 glaucomatous eyes. With the help of GATT it was established that areas of change were close to existing defects. Second, most of the changes were at the periphery. GATT is not only proving to be a method for perimetric follow-up in glaucoma cases that furnishes much useful information, but is also raising hopes of new findings concerning the course of glaucoma.

Computer Graphics↗
PubMed1989

The biology and epidemiology of HIV infections.

The world now has a pandemic of infection by the human immunodeficiency virus type I (HIV-1). More recently, a focus of epidemic HIV-2 infection in West Africa has been noted and this too is spreading internationally. HIV-2 closely resembles a simian lentivirus, SIV; SIV isolates have now been made from African (but not Asian) old world monkeys and SIV infection in macaques may provide the best animal model for HIV. All of these viruses share a tropism for the CD4 molecule, which is intimately involved in their pathogenesis. The immune response to these viruses has yet to demonstrate any protective immunity.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Accommodation used to determine ultrasound velocity in the human lens.

Intraocular distances can be measured by echography. In this determination the velocity of sound in the various media is assumed to be constant and equal to the velocity found by in vitro measurements. However, interindividual variability causes an inaccurate determination of these distances. We present a method to determine the velocity of ultrasound in the lens "in vivo." For this purpose continuous registrations of the transit times for the anterior chamber, lens, and vitreous were made during accommodation. Regression analysis of the variation of transit times provides the velocity of ultrasound in the lens with an accuracy of about +/- 3 m/s.

Accommodation, Ocular↗
PubMed1989

Infection of brain cells by diverse human immunodeficiency virus isolates: role of CD4 as receptor.

Cell lines originally derived from malignant tumours of the brain were infected by diverse human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2) isolates. By surface immunofluorescence it was shown that susceptible cells did not bear the CD4 antigen. They were also non-permissive for the formation of plaques by vesicular stomatitis virus pseudotypes and did not form syncytia with HIV-producing cells. Virus production was of low titre, and reverse transcriptase and the p24 antigen were consistently undetectable in the culture supernatants. Output virus could be detected by cocultivation with a sensitive T cell line, C8166, by the culture of supernatant medium with T cells and by detection of proviral HIV DNA after amplification. A higher multiplicity of input virus was required to establish a brain cell infection than was required for T lymphocytes or monocytes. Some HIV-susceptible brain cells contained mRNA for CD4 but infection was not blocked by anti-CD4 antibodies. Apparently HIV infection of these cells does not involve CD4 as the cellular receptor.

Antibodies, Viral↗