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B Lichardus

Publications and source records attributed to B Lichardus.

At least 37 records · Page 2Linked to original sources
PubMed1990

[Present state and perspectives of endocrinology in Czechoslovakia].

The contemporary state of the sub-discipline of endocrinology within the framework of internal medicine is generally considered rather desolate, but so far actual data were lacking. Based on an analysis of data provided by regional specialists in the Czech Republic and by regional (district) specialists in internal medicine in Slovak republic it may be said that in the majority of health institutions the number of endocrinologists does not reach even the unsatisfactory standard (i. e. 1 endocrinologist per 150 to 250,000 population), that specialized training of endocrinologists, specialists in internal medicine and other specialist is not ensured, that there are not adequate numbers of community doctors and factory medical officers, that there are not adequate capacities of specialized laboratory examinations and that adequate collaboration with other disciplines is not ensured (the position is in particular alarming as regards immunological methods and cytological processing of specimens obtained by aspiration biopsy from the thyroid gland. With regard to these data the authors recommend to raise the numbers of endocrinologists so that in institutions corresponding to hospitals with policlinics type II there will be one endocrinologist per 50-100,000 population, to improve the standard and availability of auxiliary examinations, to ensure endocrinological in-patient care at the level of hospitals with policlinics type III and to create specialized centres within the framework of the research base or university hospitals. It is important to resolve the link between endocrinology and other disciplines (paediatrics, gynaecology etc). It is also essential to coordinate closely therapy, education and research, Federal coordination is essential.

Czechoslovakia↗
PubMed1990

Suppression of natriferic activity of the vasopressin molecule by modifications in positions 1, 2 and 4.

The capacity of five synthetic analogs of [8-arginine] vasopressin (AVP) to stimulate frog skin sodium transport (natriferic activity) was characterized electrophysiologically using the method of short-circuit current, and compared to that of synthetic AVP. The analogs used were [8-arginine] vasopressins modified in positions 1 and 2: [1-(1-mercapto-4-tert-butylcyclohexaneacetic acid)] AVP (I); [1-(1-mercapto-4-methylcyclohexaneacetic acid)] AVP (II); [1-(1-mercapto-4-methylcyclohexaneacetic acid)-2-O-methyltyrosine] AVP (III); and in position 4: [1-(1-mercaptocyclohexaneacetic acid)-4-arginine] AVP (IV); [1-(2-mercaptopropionic acid)-4-arginine] AVP (V). The addition of synthetic vasopressins I, II and V to the frog skin resulted in a weaker stimulation of the skin sodium transport, measured as the level of the short-circuit current (Isc), as compared to that induced by synthetic AVP. In relation to natriferic activity, analogs III and IV did not change the electrical parameters of the skin. It is concluded that introduction of cyclic structure at the beta-carbon in position 1 of the vasopressin molecule decreased its natriferic activity by about 70%. The same reduction of the activity was caused by the replacement of the glutamine residue in position 4 with arginine, and deamination in position 1. Cyclic structure bound in position 1 together with methylation of tyrosine in position 2 resulted in a full suppression of natriferic activity. Similarly, introduction of cyclic group in position 1 in combination with substitution of glutamine in position 4 with arginine totally abolished natriferic activity.

Amino Acid Sequence↗
PubMed1990

Endogenous digoxin-like substance in the urine of newborns and children.

Endogenous digoxin-like substance (EDLS) in urine has been considered to be the representative of the natriuretic hormone, the endogenous inhibitor of the sodium pump (the sodium-potassium transporting enzyme Na, K-ATPase). Its site of production remains unknown, and so does its chemical nature. It has been suggested however that EDLS and the atrial natriuretic factor represent two distinct natriuretic system. Although the present work does not provide evidence for EDLS to be a natriuretic hormone, it nevertheless supplies data in support of this hypothesis. In preterm neonates, the decreased sodium excretion during the first days of life is accompanied by a parallel decrease in urinary EDLS excretion. The same was observed in a group of children from the infant period through the age of 12-14 years. Both parameters showed in parallel the lowest values in the oldest children examined. Children aged 8-12 years also showed parallel excretion of sodium and ELDS, even if natriuresis was induced in recumbent position and antinatriuresis in upright position. When the children remained recumbent for 24 h there were no differences in sodium and EDLS excretion between daytime and night. Children involved in adequate physical activities during daytime excreted less sodium and EDLS during the day than at night.

Adolescent↗
PubMed1990

Stimulation of the sodium transport across the frog skin by three N-terminally extended arginine-vasopressins.

The standard Ussing method was used to electrophysiologically characterize the effects of three analogs of arginine-vasopressin (AVP) on the frog skin, a model Na-transporting epithelium. The analogs tested were N-terminally extended Arg8-vasopressins: Ala-AVP, Ser-Ala-AVP and Thr-Ser-Ala-AVP; synthetic Arg8-AVP was used as the reference agent. The vasopressins were applied to the basolateral side of the frog skin in concentrations ranging between 10(-8) to 10(-5) mol.l-1. All the three analogs increased both the short-circuit current (Isc) and the open-circuit transepithelial potential (Voc), and decreased the transepithelial d.c. resistance (Rt) similarly as did synthetic Arg8-AVP. The results show that N-terminal extension of the Arg8-AVP did not alter the natriferic properties of AVP.

Animals↗
PubMed1990

Comparison of the effects of dDAVP and AVP on the sodium transport in the frog skin.

The effect of 1-deamino-8-D-arginine-vasopressin, dDAVP, the synthetic analogue of vasopressin, upon the active sodium transport across the frog skin was studied using standard microelectrode technique and compared with the effect of synthetic arginine-vasopressin, AVP. dDAVP applied to the basolateral side of the epithelium stimulated the active sodium transport as reflected by the increase of short-circuit current, Isc, and transepithelial electrical potential difference, Voc. Potential difference across both the apical, Vo, and the basolateral, Vi, cell membranes decreased. The driving force of transepithelial sodium transport, ENa, did not change. The transepithelial electrical resistance, Rt, ohmic resistance of the active sodium transport, RNa, and apical cell membrane resistance, Ro, rapidly decreased, while the resistance of the basolateral cell membrane, Ri, and the resistance of the shunt pathway, Rs, remained unchanged. It is concluded that dDAVP primarily increases sodium permeability of the apical cell membrane which subsequently stimulates sodium pump activity. This action is similar to that of AVP.

Animals↗
PubMed1989

Bilateral acute heart atrial auriectomy reduced diuresis and natriuresis following hypertonic sodium load in anaesthetized dogs.

Anaesthetized dogs were deprived of a portion of the atrial natriuretic factor producing tissue by bilateral acute heart atrial auriectomy. Their ability to respond by diuresis and natriuresis either to the expansion of extracellular fluid volume with isotonic saline (3% b.w.) or to hyperosmolality induced by hypertonic saline loading (0.13% b.w. of 20% NaCl solution) was subsequently reduced by about 50%. It is thus suggested that atrial natriuretic system may also play a role in osmoregulation by taking part in the promotion of renal sodium excretion.

Animals↗
PubMed1989

Microelectrode study of insulin effect on apical and basolateral cell membrane of frog skin: comparison with the effect of 1-deamino-8-D-arginine-vasopressin (dDAVP).

The standard microelectrode technique was used to electrophysiologically characterize the effect of insulin on both apical and basolateral cell membranes of the frog skin, a model Na-transporting epithelium. Insulin applied to the basolateral side of the epithelium stimulated the sodium transport as shown by both increased short-circuit current, Isc, (P less than 0.02) and transepithelial potential difference, Voc, (P less than 0.002). Potential difference across the apical cell membrane, Vo, decreased (P less than 0.002) as did the apical cell membrane resistance, Ro, (P less than 0.05). The driving force of sodium ions, ENa, increased after insulin (P less than 0.005). These findings confirm that insulin acts both to increase the apical cell membrane permeability for ions and to stimulate the sodium pump in the basolateral membrane. The effects of insulin were compared with those of a vasopressin analog (dDAVP), known to stimulate transepithelial sodium transport by increasing the permeability of the apical cell membrane for sodium ions. dDAVP applied at the height of insulin effect further stimulated transepithelial transport, but insulin applied at the height of dDAVP action did not. It is concluded that the direct stimulation of the sodium pump by insulin may not represent a decisive component in the stimulation of transepithelial transport across the frog skin. A more potent stimulus for sodium transport is obviously the increased permeability of the apical membrane for ions.

Animals↗
PubMed1989

[Endogenous digoxin-like substance (nonspecific interference or a new hormone?)].

The authors assessed changes of the serum level and urinary excretion of an endogenous digoxin-like substance in healthy neonates and parturient women who did not have digitalis therapy. Higher concentrations of the endogenous digoxin-like substance (ESPD) found in the umbilical blood, as compared with parallel samples of venous blood of the mothers (n = 13; p less than 0.01), provide indirect evidence of the secretory autonomy of the neonatal organism. The highest ESPD concentrations in umbilical blood were found in neonates born before the 34th week of gestation (0.5-1.0 ng/ml), whereby with advancing gestational age the ESPD level declined significantly (n = 21; r = 0.62; p less than 0.01). This fact along with the positive correlation between the excretory fraction of sodium and renal ESPD excretion in the group of healthy 1-5-week-old premature babies (n = 10, r = 0.53; p less than 0.01) is consistent with the view on the identity of ESPD and the assumed natriuretic hormone, the circulating endogenous inhibitor of Na+, K+-ATPase.

Blood Proteins↗
PubMed1988

Vasopressin and 1-deamino-8-D-arginine-vasopressin (DDAVP) reduce elevated plasma catecholamine levels in rats with hypothalamic deafferentation.

1. Anterolateral cut (ALC) of the medial basal hypothalamus (MBH) in rats produces an elevation of plasma catecholamine levels, especially of norepinephrine (NE), in unstressed animals and a more pronounced rise of plasma NE levels in response to immobilization (IMO). Animals with ALC have a destroyed corresponding vasopressin (AVP) and other peptides containing innervation of the median eminence and the posterior pituitary, resulting in the prevention of increased AVP secretion during the early intervals of IMO. 2. The administration of AVP (Pitressin, 7 days, 1 IU per rat i.m.) or of 1-deamino-8-D-arginine-vasopressin (DDAVP), an AVP analogue without pressoric activity, taken in drinking water (about 100 micrograms per day) was almost equally potent in decreasing the elevated water consumption and plasma NE levels in unstressed rats with ALC. However, the stress-induced potentiation of plasma NE levels in rats with ALC was not influenced by AVP substitution and only partly reduced by DDAVP in the late IMO intervals. 3. The lack of circulating vasopressin is the main factor in the mechanism of increased activity of the sympathoadrenal system induced by ALC in unstressed rats. 4. The regulation of sympathoadrenal activity by vasopressin and DDAVP in rats with ALC seems to be mediated predominantly by V2-subtype receptors. 5. In stressed rats with ALC the potentiation of plasma NE levels was not reduced after AVP or DDAVP administration, suggesting that some addition regulatory mechanisms were involved.

Afferent Pathways↗
PubMed1988

Effect of acute and repeated immobilization stress on food and water intake, urine output and vasopressin changes in rats.

In several experiments the rats were subjected to immobilization stress (IMO) for 150 min daily for 7 to 38 days and after each IMO they were placed into individual metabolism cages. A considerable decrease of food and water intake was found even after the first IMO and lasted up to the 7th IMO. This resulted in a decrease of body weight and of diurnal urine output, while the osmolality of urine increased. However, the expected corresponding increase in urinary excretion of vasopressin (AVP) did not occur. In contrast, AVP excretion after 6th and 7th IMO decreased by about 50 per cent. In some experiments the urine was collected during the period of IMO. It was found that the total urine output sharply increased and its osmolality decreased. Moreover, the excretion of AVP decreased and the excretion of calcium and Na :K ratio in urine were elevated. After repeated IMO (i. e. after 7th, 16th and 38th IMO) all mentioned changes were still more expressed. Thus, the urine output increased more than two fold. However, the administration of dDAVP (synthetic analogue of AVP) prior to IMO resulted either in the normalization of urine output or anuria, respectively, depending on the dose administered. When 30 min portions of urine excreted during 150 min IMO were collected, it was found that during the first period, when the level of AVP in plasma was increased, the urine output was almost zero. During the second period of IMO the level of AVP in plasma decreased even bellow the control values which was accompanied by water diuresis. Similar biphasic changes were found even previously. It is suggested that the increased AVP release during the first period might be due to the physical stress stimuli (manual squeezing of animals, pain etc.), while the inhibition of AVP release during the second period may be caused by a simultaneous activation of other endocrine mechanisms (endogenous opioids, steroids, catecholamines, atrial natriuretic peptides etc.).

Animals↗