Biomedical subjects

N C Vrabchev

Publications and source records attributed to N C Vrabchev.

4 recordsLinked to original sources

PubMed1989

A program package for self-assessment and examination in biochemistry.

A BASIC program has been developed for self-evaluation and testing of an individual's knowledge of main categories in biochemistry. The computer tests permit sequential or random distribution of items, random distribution of answers in each item at each new run, effective feedback control with the student, use of a program clock to determine different time allowance, precise and quick analysis and grading of student's answer thus saving the time and labour of examiners. Editing, deleting and appending of new items is easily achieved. Information is obtained for verifying the quality of the test itself. Examination versions of tests in ten categories have been combined into an annual computer test in biochemistry.

Algorithms↗

PubMed1988

Effect of bevelling on C1-selective microelectrodes: experimental and model study.

Bevelling of the ultra-fine tips of C1-selective microelectrodes (ME) based on liquid ion-exchanger Corning 477913 caused significant decrease in ME resistivity, increase in sensitivity dependent on its initial value and decrease in selectivity constant for bicarbonates (KC1,HCO3) from 10:1 to approximately 8:1. Bevelling did not affect KC1,NO3 which had value below 1 due to higher selectivity of the ion-exchanger for nitrates. The observed experimental alterations in ME behavior after bevelling were in agreement with those predicted by a relatively simple electrical model comprising of two conductive pathways in parallel having opposite in sign sensitivities.

Chlorides↗

PubMed1986

Suprachiasmatic nuclei lesions do not eliminate the circadian rhythms of electrolyte excretion in the rat.

The 24-hour variations in 2-hour diuretic and saluretic action of furosemide (4 mg/kg) given at 8, 12, 16, 20, 24 or 4 hr and the circadian rhythms of food and water intake, urine and electrolyte excretion followed for two consecutive days at 4-hour intervals were investigated in suprachiasmatic nuclei (SCN)-lesioned or sham-operated male Wistar rats. The results showed that: a distinct 24-hour rhythm in furosemide-induced urine, sodium and chloride excretion persisted after SCN lesions, and the lesions abolished the circadian rhythms of food and water intake but only desynchronized the individual 24-hour variations in electrolyte excretion. We concluded that SCN play a role as a central synchronizer but not as a major oscillator of the circadian rhythms of electrolyte excretion in the rat.

Animals↗

PubMed1985

Circadian rhythms of food and 1% NaCl intake, urine and electrolyte excretion, plasma renin activity and insulin concentration in adrenalectomized rats.

The circadian rhythms of food and 1% NaCl intake, and urine, Na+, Cl- and K+ excretion were followed up in male Wistar rats before and one week after bilateral adrenalectomy at 4-hour intervals during two consecutive days. The circadian rhythms of plasma renin activity (PRA) and plasma immunoreactive insulin (IRI) were evaluated after decapitation of both intact and adrenalectomized rats at 08, 16 and 24 h. To all rats 1% NaCl was offered instead of drinking water. Adrenalectomy did not cause any significant phase shift in the cosine curves approximating the data collected at 4-hour intervals. The circadian rhythms showed the same relationships before and after the operation: the rhythms of food intake, K+ excretion and saline intake preceded significantly the rhythms of urine, Na+ and Cl- excretion. Adrenalectomy induced an increase in mean PRA and shifted its minimal value from 08 to 24 h. After the operation mean IRI decreased and the minimal value shifted from 16 to 24 h. It was concluded that adrenal glands do not play an important role in the synchronization of the circadian rhythms of food and 1% NaCl intake, urine and synchronization of the circadian rhythms of food and 1% NaCl intake, urine and electrolyte excretion with the illumination cycle, but play a relevant role in the synchronization of the circadian rhythms of PRA and IRI in the rat.

Adrenalectomy↗