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L Lowenstein

Publications and source records attributed to L Lowenstein.

At least 19 recordsLinked to original sources
PubMed1999

Rapid estimation of the accuracy of automatic blood pressure measuring devices (READ).

We propose a rapid method for the evaluation of automatic blood pressure measurement devices (READ) in response to the claim to simplify the validation of those devices. The READ is based on numerous blood pressure (BP) measurements at rest and during a standardised postural challenge in a small number of subjects who exhibit a wide range of BPs. Automatic (AU) and mercury sphygmomanometric (MS) brachial BP were measured simultaneously in a blinded manner. An average of 30 measurements per patient were done in 10-min while in a supine position, followed by 30 min in head-up tilt and again supine for 10 min. Two Collin-8800 automated oscillometric devices were tested with the aid of the READ in 15 adults. The consistency of the MS standard was demonstrated by duplicate MS measurements showing minimal inter-observer differences consistent with class A of the British Hypertension Society (BHS) grading system. AU-to-MS differences of 447 measurements were mean systolic deltaBP = 1.1 +/- 11.4 mm Hg and mean diastolic deltaBP = -13.36 +/- 8.9 mm Hg, classifying into category D of the BHS. Both tested instruments, each subject, each phase of the tilt test (supine I, tilt, supine II) and each mode of measurement (at 5-min intervals or continuously) equally qualified as 'D'. We conclude that the READ permitted us to identify quickly and at low expense a grossly inaccurate automatic BP measuring device. Further studies will show whether the READ can be efficient as a pre-validation test, post-validation test, and for assessment of ambulatory BP measuring devices.

Adult↗
PubMed1979

Evolution of polypyrimidines in Drosophila.

We surveyed 101 different Drosophila species for the presence of a particular highly repetitive DNA sequence containing long tracts of polypyrimidine/polypurine DNA, first found in D. melanogaster. Out of 55 tested species in the melanogaster group, only the sibling species D. simulans and D. mauritiana, as well as one distant relative in the ananassae subgroup, D. varians, contained the same sequence. All four of these species have long pyrimidine tracts as shown by acid hydrolysis of labelled DNA. All four species have the same sequence, bu the amount of this polypyrimidine/polypurine DNA varies greatly. Four other species in the hydei subgroup were found to contain a polypyrimidine/polpurine sequence, with an oligonucleotide composition different from that of D. melanogaster. This polypyrimidine DNA varies from as much as 10% of the total DNA in D. nigrohydei, to as little as 0.4% in D. neohydei. The long pyrimidine tracts in the hydei subgroup are often more than a thousand nucleotides in length, representing exceedingly homogeneous repetitious sequences.--These results show a rapid but discontinuous pattern of evolution for polypyrimidine/polypurine DNA . These sequences are not species specific, yet closely related species have greatly different amounts of polypyrimidines. Drastic changes occur in the amounts of these satellite type DNA sequences, as if the sequence had no continuous selective advantage in evolution. The implications of these results with regard to the general function and evolution of satellite DNA are discussed.

Animals↗
PubMed1975

Polypyrimidine segments in Drosophila melanogaster DNA: II. Chromosome location and nucleotide sequence.

Long pyrimidine tracts, purified from Drosophila melanogaster DNA after treatment with formic acid-diphenylamine, were used as template for E. coli RNA polymerase to produce a polynucleotide containing only purines. This polypurine RNA hybridized specifically to D. melanogaster DNA with high efficiency at low Cot values. The resulting hybrid showed high thermal stability. When polypurine RNA was subjected to complete hydrolysis with ribonuclease T1, over 90% of the nucleotide products were ApGp and ApApGp. Partial hydrolysis yielded a distinct additional component, ApApGpApGp + ApGpApApGp. We conclude that the major sequence in the polypurine transcript is (ApGpApApGp)n. In situ hybridization to salivary gland polytene chromosomes and to metaphase chromosomes from neural ganglia indicated that polypyrimidines complementary to polypurine RNA are located in heterochromatin. In femal cells, the predominant labeling was on centromeric heterochromatin of the 2nd chromosome. We have verified the location of polypyrimidines in neural ganglion cells, by using a cytological marker of chromosomes 2. In male cells, hybrid was also found on the Y chromosome.

Adenosine Triphosphate↗
PubMed1975

Acid treatment of Drosophila deoxyribonucleic acid.

In cytologic preparations of chromosomes, acid-treated deoxyribonucleic acid (DNA) is found largely in the native state. However, acid treatments widely used for chromosome preparations produce significant amounts of depurination in DNA. DNA is similarly sensitive to depurination in intact cells or as purified DNA. If treated with alkali, these apurinic gaps can be converted to single strand breaks. Acid treatment has widely different effects on specific fractions of DNA. In Drosophila melanogaster 3% of the DNA is composed of very long tracts of pyrimidines (polypyrimidines) which are resistant to acid hydrolysis. The implications of these results for molecular cytogenetics are discussed.

Acetates↗